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Fourier-transform Ghost Imaging for pure phase object based on Compressive Sampling algorithm
A special algorithm for the Fourier-transform Ghost Imaging (GI) scheme is discussed based on the Compressive Sampling (CS) theory. Though developed mostly in real space, CS algorithm could also be used for the Fourier spectrum reconstruction of pure phase object by setting a proper sensing matrix. This could find its application in diffraction imaging of X-ray, neutron and electron with higher efficiency and resolution. Simulation and experiment results are also presented to prove the feasibility.
Hui Wang; Shensheng Han
We present a novel image hiding method based on phase retrieval algorithm under the framework of nonlinear double random phase encoding in fractional Fourier domain. Two phase-only masks (POMs) are efficiently determined by using the phase retrieval algorithm, in which two cascaded phase-truncated fractional Fourier transforms (FrFTs) are involved. No undesired information disclosure, post-processing of the POMs or digital inverse computation appears in our proposed method. In order to achieve the reduction in key transmission, a modified image hiding method based on the modified phase retrieval algorithm and logistic map is further proposed in this paper, in which the fractional orders and the parameters with respect to the logistic map are regarded as encryption keys. Numerical results have demonstrated the feasibility and effectiveness of the proposed algorithms. PMID:25321769
Wang, Xiaogang; Chen, Wen; Chen, Xudong
Imaging Fourier transform spectrometer
This invention is comprised of an imaging Fourier transform spectrometer having a Fourier transform infrared spectrometer providing a series of images to a focal plane array camera. The focal plane array camera is clocked to a multiple of zero crossing occurrences as caused by a moving mirror of the Fourier transform infrared spectrometer and as detected by a laser detector such that the frame capture rate of the focal plane array camera corresponds to a multiple of the zero crossing rate of the Fourier transform infrared spectrometer. The images are transmitted to a computer for processing such that representations of the images as viewed in the light of an arbitrary spectral ``fingerprint`` pattern can be displayed on a monitor or otherwise stored and manipulated by the computer.
Bennett, C.L.
Presents a new method to match a 2D image to a translated, rotated and scaled reference image. The approach consists of two steps: the calculation of a Fourier-Mellin invariant (FMI) descriptor for each image to be matched, and the matching of the FMI descriptors. The FMI descriptor is translation invariant, and represents rotation and scaling as translations in parameter space.
Qin-sheng Chen; Michel Defrise; Frank Deconinck
A solid state laser is frequency tripled to 0.3 {micro}m. A small portion of the laser is split off and generates a Stokes seed in a low power oscillator. The low power output passes through a mask with the appropriate hole pattern. Meanwhile, the bulk of the laser output is focused into a larger stimulated Brillouin scattering (SBS) amplifier. The low power beam is directed through the same cell in the opposite direction. The majority of the amplification takes place at the focus which is the fourier transform plane of the mask image. The small holes occupy large area at the focus and thus are preferentially amplified. The amplified output is now imaged onto the multichip module where the holes are drilled. Because of the fourier plane amplifier, only about 1/10th the power of a competitive system is needed. This concept allows less expensive masks to be used in the process and requires much less laser power. 1 fig.
Hackel, L.A.; Hermann, M.R.; Dane, C.B.; Tiszauer, D.H.
A solid state laser is frequency tripled to 0.3 .mu.m. A small portion of the laser is split off and generates a Stokes seed in a low power oscillator. The low power output passes through a mask with the appropriate hole pattern. Meanwhile, the bulk of the laser output is focused into a larger stimulated Brillouin scattering (SBS) amplifier. The low power beam is directed through the same cell in the opposite direction. The majority of the amplification takes place at the focus which is the fourier transform plane of the mask image. The small holes occupy large area at the focus and thus are preferentially amplified. The amplified output is now imaged onto the multichip module where the holes are drilled. Because of the fourier plane amplifier, only .about.1/10th the power of a competitive system is needed. This concept allows less expensive masks to be used in the process and requires much less laser power.
Hackel, Lloyd A. (Livermore, CA); Hermann, Mark R. (San Ramon, CA); Dane, C. Brent (Livermore, CA); Tiszauer, Detlev H. (Tracy, CA)
Imaging Fourier Transform Spectrometer
The operating principles of an Imaging Fourier Transform Spectrometer (IFTS) are discussed. The advantages and disadvantages of such instruments with respect to alternative imaging spectrometers are discussed. The primary advantages of the IFTS are the capacity to acquire more than an order of magnitude more spectral channels than alternative systems with more than an order of magnitude greater etendue than for alternative systems. The primary disadvantage of IFTS, or FTS in general, is the sensitivity to temporal fluctuations, either random or periodic. Data from the IRIFTS (ir IFTS) prototype instrument, sensitive in the infrared, are presented having a spectral sensitivity of 0.01 absorbance units, a spectral resolution of 6 cm{sup {minus}1} over the range 0 to 7899 cm{sup {minus}1}, and a spatial resolution of 2.5 mr.
Bennett, C.L.; Carter, M.R.; Fields, D.J.; Hernandez, J.
NASA Astrophysics Data System (ADS)
Based on the two-step phase-shifting interference (PSI) technique in fractional Fourier transform (FRT) domain and random mixed encoding, we present a new scheme for double image encryption. In the proposed scheme, information of each primitive image is recorded in two intensity interference patterns of FRT spectra by PSI technique, from which an encrypted image for each primitive image can be digitally derived. Random mixed encoding is then employed to divide and recombine both encrypted images into a single synthetic encrypted image. During the mixed encoding process, repositioning operations based on shift-variance of FRT are performed on the encrypted images to realize the spatial separation of decoded results in the output plane. By inverse FRT with correct fractional order, any of the primitive images can be easily retrieved directly from the synthetic encoded image with the corresponding phase encoding key. Crosstalk effect due to the overlapping of decoded images is alleviated for their spatial separation. Computer simulation and experimental results are presented to verify the validity and efficiency of our scheme.
Wang, Qu; Guo, Qing; Lei, Liang; Zhou, Jinyun
NASA Astrophysics Data System (ADS)
The classical double random phase encoding technique (DRPE) is vulnerable to chosen ciphertext attacks, known-plaintext attacks and chosen-plaintext attacks for its linearity. In order to avoid the disadvantages originated from the linearity and symmetric, an improved method for multiple-image encryption based on nonlinear operations in Fourier domain is proposed. The random phase masks (RPMs) for encryption and additive keys which are determined by the original images and generated by the nonlinear operations in encryption process, are necessary for image decoding. As a result of the nonlinear operations, the increase in the number of keys, removal of linearity and high robustness could be achieved in this cryptosystem. Computer simulations are presented to demonstrate its good performance, and the security is analyzed as well.
Wang, Xiaogang; Zhao, Daomu
Electro-optic imaging Fourier transform spectrometer
NASA Technical Reports Server (NTRS)
An Electro-Optic Imaging Fourier Transform Spectrometer (EOIFTS) for Hyperspectral Imaging is described. The EOIFTS includes an input polarizer, an output polarizer, and a plurality of birefringent phase elements. The relative orientations of the polarizers and birefringent phase elements can be changed mechanically or via a controller, using ferroelectric liquid crystals, to substantially measure the spectral Fourier components of light propagating through the EIOFTS. When achromatic switches are used as an integral part of the birefringent phase elements, the EIOFTS becomes suitable for broadband applications, with over 1 micron infrared bandwidth.
Chao, Tien-Hsin (Inventor); Znod, Hanying (Inventor)
Electro-optic Imaging Fourier Transform Spectrometer
NASA Technical Reports Server (NTRS)
JPL is developing an innovative compact, low mass, Electro-Optic Imaging Fourier Transform Spectrometer (E-0IFTS) for hyperspectral imaging applications. The spectral region of this spectrometer will be 1 - 2.5 pm (1000 -4000 cm-') to allow high-resolution, high-speed hyperspectral imaging applications [l-51. One application will be theremote sensing of the measurement of a large number of different atmospheric gases simultaneously in the sameairmass. Due to the use of a combination of birefiingent phase retarders and multiple achromatic phase switches toachieve phase delay, this spectrometer is capable of hyperspectral measurements similar to that of the conventionalFourier transform spectrometer but without any moving parts. In this paper, the principle of operations, systemarchitecture and recent experimental progress will be presen.
Chao, Tien-Hsin
Electro-optic Imaging Fourier Transform Spectrometer
NASA Technical Reports Server (NTRS)
JPL is developing an innovative compact, low mass, Electro-Optic Imaging Fourier Transform Spectrometer (E-O IFTS) for hyperspectral imaging applications. The spectral region of this spectrometer will be 1 - 2.5 micron (1000-4000/cm) to allow high-resolution, high-speed hyperspectral imaging applications. One application will be the remote sensing of the measurement of a large number of different atmospheric gases simultaneously in the same airmass. Due to the use of a combination of birefringent phase retarders and multiple achromatic phase switches to achieve phase delay, this spectrometer is capable of hyperspectral measurements similar to that of the conventional Fourier transform spectrometer but without any moving parts. In this paper, the principle of operations, system architecture and recent experimental progress will be presented.
Chao, Tien-Hsin
Laser Field Imaging Through Fourier Transform Heterodyne
The authors present a detection process capable of directly imaging the transverse amplitude, phase, and Doppler shift of coherent electromagnetic fields. Based on coherent detection principles governing conventional heterodyned RADAR/LADAR systems, Fourier Transform Heterodyne incorporates transverse spatial encoding of the reference local oscillator for image capture. Appropriate selection of spatial encoding functions allows image retrieval by way of classic Fourier manipulations. Of practical interest: (1) imaging may be accomplished with a single element detector/sensor requiring no additional scanning or moving components, (2) as detection is governed by heterodyne principles, near quantum limited performance is achievable, (3) a wide variety of appropriate spatial encoding functions exist that may be adaptively configured in real-time for applications requiring optimal detection, and (4) the concept is general with the applicable electromagnetic spectrum encompassing the RF through optical.
Cooke, B.J.; Laubscher, B.E.; Olivas, N.L.; Galbraith, A.E.; Strauss, C.E.; Grubler, A.C.
Birefringent Fourier-transform imaging spectrometer
Birefringent Fourier-transform imaging spectrometer Andrew Robert Harvey and David William firstname.lastname@example.com http://www.ece.eps.hw.ac.uk/~arharvey Abstract: Fourier-transform imaging spectrometers offer important, for application in harsh environments, deployment of Fourier-transform instruments based on traditional moving
Harvey, Andy
Efficient image processing in Fourier holography for moving images
For still images, diffraction-based beam-forming of laser light is a well-known task in optics called Fourier holography. Using a phase-only diffractive optical element (DOE) which displays a computer-generated hologram (CGH) very efficient beam forming is realized. The drawbacks of this technique are massive computation costs for phase-only holograms. In this paper, we briefly describe this diffraction-based technology. Then, we depict
Marc Bernau
Coherent electromagnetic field imaging through Fourier transform heterodyne
The authors present a detection process capable of directly imaging the transverse amplitude, phase, and if desired, Doppler shift of coherent electromagnetic fields. Based on coherent detection principles governing conventional heterodyned RADAR\\/LIDAR systems, Fourier Transform Heterodyne (FTH) incorporates transverse spatial encoding of the local oscillator for image capture. Appropriate selection of spatial encoding functions, or basis set, allows image retrieval
B. J. Cooke; B. E. Laubscher; N. L. Olivas; R. M. Goeller; M. Cafferty; S. D. Briles; A. E. Galbraith; A. C. Grubler
Fourier Transform and Reflective Imaging Pyrometry
A stationary Fourier transform pyrometer was used to record mid-wavelength IR spectra in dynamic shock experiments. The gated-IR camera used with this system was also used to record images of light produced and light reflected from shocked metals in order to constrain the dynamic emissivity and provide temperature estimates. This technique will be referred to as reflective imaging pyrometry.
Stevens, G. D.
An Imaging Fourier Transform Spectrometer for NGST
Due to its simultaneous deep imaging and integral field spectroscopic capability, an Imaging Fourier Transform Spectrograph (IFTS) is ideally suited to the Next Generation Space Telescope (NGST) mission, and offers opportunities for tremendous scientific return in many fields of astrophysical inquiry. We describe the operation and quantify the advantages of an IFTS for space applications. The conceptual design of the Integral Field Infrared Spectrograph (IFIRS) is a wide field (5'.3 x 5'.3) four-port imaging Michelson interferometer.
James R. Graham
Lensless Fourier-transform ghost imaging with classical incoherent light
The Fourier-transform ghost imaging of both amplitude-only and pure-phase objects was experimentally observed with classical incoherent light at Fresnel distance by a lensless scheme. The experimental results are in good agreement with the standard Fourier transform of the corresponding objects. This scheme provides a route toward aberration-free diffraction-limited three-dimensional images with classically incoherent thermal light (or neutrons), which have no resolution and depth-of-field limitations of lens-based tomographic systems.
Zhang, Minghui; Wei, Qing; Shen, Xia; Liu, Yongfeng; Liu, Honglin; Cheng, Jing; Han, Shensheng [Key Laboratory for Quantum Optics and Center for Cold Atom Physics, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800 (China)
Lensless Fourier-Transform Ghost Imaging with Classical Incoherent Light
The Fourier-Transform ghost imaging of both amplitude-only and pure-phase objects was experimentally observed with classical incoherent light at Fresnel distance by a new lensless scheme. The experimental results are in good agreement with the standard Fourier-transform of the corresponding objects. This scheme provides a new route towards aberration-free diffraction-limited 3D images with classically incoherent thermal light, which have no resolution and depth-of-field limitations of lens-based tomographic systems.
Minghui Zhang; Qing Wei; Xia Shen; Yongfeng Liu; Honglin Liu; Jing Cheng; Shensheng Han
Fourier analysis of blood plasma laser images phase maps in the diagnosis of cancer in human organs
NASA Astrophysics Data System (ADS)
A method of polarization mapping of the optico-anisotropic polycrystalline networks of the blood plasma albumin and globulin proteins with adjusted spatial-frequency filtering of the coordinate distributions of the azimuth and ellipticity of the polarization of laser radiation in the Fourier plane is proposed and substantiated. Comparative studies of the effectiveness of direct methods of mapping and a spatial-frequency selection in differentiating polarization azimuth and ellipticity maps of the field of laser radiation converted by the networks of albumin - globulin crystals of the blood plasma in healthy people and patients with prostate cancer have been carried out.
Angelsky, P. O.; Kushnerick, L. Ya.; Bachinskiy, V. T.; Vanchuliak, O. Ya.; Garazdiuk, M.; Pashkovska, N. V.; Andriychuk, D.
NASA Astrophysics Data System (ADS)
A technique for simultaneous encryption of a color and a gray-scale image is proposed, using single-channel double random-phase encoding in the fractional Fourier domain. Prior to the encryption, the segregated red, green, and blue components of the color image and the gray-scale image are encoded into a single image after changing their bit formats. The format of the encoded image is such that it cannot be perceived by the human eye. The fractional orders of the fractional Fourier transform and two random-phase masks act as key parameters for the encryption. Performance of the scheme is verified against chosen plain-text and known plain-text attacks, respectively. The effect of noise on the performance of the proposed technique is analyzed.
Joshi, Madhusudan; Singh, Kehar
Fourier phase analysis in radio-interferometry
Most statistical tools used to characterize the complex structures of the interstellar medium can be related to the power spectrum, and therefore to the Fourier amplitudes of the observed fields. To tap into the vast amount of information contained in the Fourier phases, one may consider the probability distribution function (PDF) of phase increments, and the related concepts of phase entropy and phase structure quantity. We use these ideas here with the purpose of assessing the ability of radio-interferometers to detect and recover this information. By comparing current arrays such as the VLA and Plateau de Bure to the future ALMA instrument, we show that the latter is definitely needed to achieve significant detection of phase structure, and that it will do so even in the presence of a fair amount of atmospheric phase fluctuations. We also show that ALMA will be able to recover the actual "amount'' of phase structure in the noise-free case, if multiple configurations are used.
Francois Levrier; Edith Falgarone; Francois Viallefond
Phase information in coherent Fourier scatterometry
NASA Astrophysics Data System (ADS)
Incoherent Optical Scatterometry (IOS) is widely used in semiconductor industry in applications related to optical metrology particularly in grating reconstruction. Recently, Coherent Fourier Scatterometry (CFS) has emerged as a strong alternative to the traditional IOS under suitable condition. When available, phase information is an added advantage in CFS to complement the intensity data. Phase information in the scattered far field is dependent on the structure and the composition of the grating. We derive and discuss the phase information accessible through the CFS. Phase difference between the diffracted orders is computed and the polarization dependent phase sensitivity of the grating parameters are discussed. The results are rigorously simulated and an experimental implementation of CFS demonstrates the functionality of the method.
Kumar, N.; El Gawhary, O.; Roy, S.; Pereira, S. F.; Urbach, H. P.
Imaging sensor for the Geosynchronous Imaging Fourier Transform Spectrometer (GIFTS)
NASA Astrophysics Data System (ADS)
Accurate high resolution temperature sounding through our atmosphere is paramount to improving our weather forecasting, monitoring, and analysis capability. From the vantagepoint of earth Orbit, remote temperature sounding is becoming a reality and its accuracy is bolstered by recent advances in infrared hyper-spectral sensor capability. One promising approach takes advantage of a two-dimensional, imaging Fourier transform spectrometer to obtain a data cube with the field of view along one plane and multiple IR spectra (one for every FPA pixel) along the orthogonal axis. The spatial resolution is limited only by the pixel pitch in the imaging focal plane and the optics used to collect the data. The maximum optical path difference in the Michelson FTS defines the spectral resolution and dictates the number of path-length interferogram samples (FPA frames required per cube. This paper discusses the unique challenges placed on the focal plane by the Geosynchronous Imaging Fourier Transform Spectrometer (GIFTS) approach and how advanced focal plane technology is applied to satisfy these challenges. Two focal planes are required to provide spectral coverage from 4.4 to 6.1um and 8.85-14.6um. Currently, the GIFT"s LWIR focal plane is the longest wavelength two-dimensional PV HgCdTe array of this size (128 square on 60 um centers) planned for space deployment. The paper presents performance data of Liquid Phase Epitaxy (LPE) fabricated HgCdTe detectors and design details of the advanced readout integrated circuit necessary to meet the demanding requirements of the imaging sensor for the GIFTS instrument.
Stobie, James A.; Hairston, Allen W.; Tobin, Stephen P.; Huppi, Ronald J.; Huppi, Ray
Ubung 2. Fast Fourier Transform in image April 27, 2005
Ubung 2. Fast Fourier Transform in image processing April 27, 2005 1 Background Fourier Transform, the contribution of Fourier Transformation states that any function can be expressed as the integral of sines and in a Fourier transform, can be reconstructed (recovered) completely via an inverse process. This important
Kjellström, Hedvig
Spinor Fourier Transform for Image Processing Thomas Batard, Michel Berthier
1 Spinor Fourier Transform for Image Processing Thomas Batard, Michel Berthier Abstract--We propose in this paper to introduce a new spinor Fourier transform for both grey-level and color image processing. Our Fourier transform may be used to perform frequency filtering that takes into account the Riemannian
Paris-Sud XI, Université de
Fourier transform digital holographic adaptive optics imaging system
A Fourier transform digital holographic adaptive optics imaging system and its basic principles are proposed. The CCD is put at the exact Fourier transform plane of the pupil of the eye lens. The spherical curvature introduced by the optics except the eye lens itself is eliminated. The CCD is also at image plane of the target. The point-spread function of the system is directly recorded, making it easier to determine the correct guide-star hologram. Also, the light signal will be stronger at the CCD, especially for phase-aberration sensing. Numerical propagation is avoided. The sensor aperture has nothing to do with the resolution and the possibility of using low coherence or incoherent illumination is opened. The system becomes more efficient and flexible. Although it is intended for ophthalmic use, it also shows potential application in microscopy. The robustness and feasibility of this compact system are demonstrated by simulations and experiments using scattering objects. PMID:23262541
Liu, Changgeng; Yu, Xiao; Kim, Myung K.
Fourier Analysis and Structure Determination. Part II: Pulse NMR and NMR Imaging.
ERIC Educational Resources Information Center
Uses simple pulse NMR experiments to discuss Fourier transforms. Studies the generation of spin echoes used in the imaging procedure. Shows that pulse NMR experiments give signals that are additions of sinusoids of differing amplitudes, frequencies, and phases. (MVL)
Chesick, John P.
Interferometric SAR image coregistration based on the Fourier-Mellin invariant descriptor
The problem of interferometric SAR image coregistartion is addressed. For classical images, the application of the Symmetric Phase Only Matching Filtering (SPOMF) to the Fourier-Mellin Invariant (FMI) descriptors allows an accurate and efficient registration of translated, rotated and scaled images. This paper discusses an extension of the technique to cover the FMI descriptors of two interferometric SAR images. This method
R. Abdelfattah; J. M. Nicolas; F. Tupin
Single beam Fourier transform digital holographic quantitative phase microscopy
NASA Astrophysics Data System (ADS)
Quantitative phase contrast microscopy reveals thickness or height information of a biological or technical micro-object under investigation. The information obtained from this process provides a means to study their dynamics. Digital holographic (DH) microscopy is one of the most used, state of the art single-shot quantitative techniques for three dimensional imaging of living cells. Conventional off axis DH microscopy directly provides phase contrast images of the objects. However, this process requires two separate beams and their ratio adjustment for high contrast interference fringes. Also the use of two separate beams may make the system more vulnerable to vibrations. Single beam techniques can overcome these hurdles while remaining compact as well. Here, we describe the development of a single beam DH microscope providing whole field imaging of micro-objects. A hologram of the magnified object projected on to a diffuser co-located with a pinhole is recorded with the use of a commercially available diode laser and an arrayed sensor. A Fourier transform of the recorded hologram directly yields the complex amplitude at the image plane. The method proposed was investigated using various phase objects. It was also used to image the dynamics of human red blood cells in which sub-micrometer level thickness variation were measurable.
Anand, A.; Faridian, A.; Chhaniwal, V. K.; Mahajan, S.; Trivedi, V.; Dubey, S. K.; Pedrini, G.; Osten, W.; Javidi, B.
A two-dimensional (2D) Fourier transform algorithm for the image reconstruction of synthetic-aperture imaging ladar (SAIL) collected data is suggested. This algorithm consists of quadratic phase compensation in azimuth direction and 2D fast Fourier transform. Based on this algorithm and the parallel 2D Fourier transform capability of spherical lens, an optical principle scheme that processes the SAIL data is proposed. The basic principle, design equations, and necessary analysis are presented. To verify this principle scheme, an experimental optical SAIL processor setup is constructed. The imaging results of SAIL data obtained by our SAIL demonstrator are presented. The optical processor is compact, lightweight, and consumes low power. This optical processor can also provide inherent parallel and speed-of-light computing capability, and thus has potential applications in on-board and satellite-borne SAIL systems. PMID:24663462
Sun, Zhiwei; Hou, Peipei; Zhi, Ya'nan; Sun, Jianfeng; Zhou, Yu; Xu, Qian; Lu, Zhiyong; Liu, Liren
Imaging Fourier transform spectrometry of chemical plumes
NASA Astrophysics Data System (ADS)
A midwave infrared (MWIR) imaging Fourier transform spectrometer (FTS), the Telops FIRST-MWE (Field-portable Imaging Radiometric Spectrometer Technology - Midwave Extended) has been utilized for the standoff detection and characterization of chemical plumes. Successful collection and analysis of MWIR hyperspectral imagery of jet engine exhaust has allowed us to produce spatial profiles of both temperature and chemical constituent concentrations of exhaust plumes. Successful characterization of this high temperature combustion event has led to the collection and analysis of hyperspectral imagery of lower temperature emissions from industrial smokestacks. This paper presents MWIR data from remote collection of hyperspectral imagery of methyl salicilate (MeS), a chemical warfare agent simulant, during the Chemical Biological Distributed Early Warning System (CBDEWS) test at Dugway Proving Grounds, UT in 2008. The data did not contain spectral lines associated with emission of MeS. However, a few broad spectral features were present in the background-subtracted plume spectra. Further analysis will be required to assign these features, and determine the utility of MWIR hyperspectral imagery for analysis of chemical warfare agent plumes.
Bradley, Kenneth C.; Gross, Kevin C.; Perram, Glen P.
Fourier Phase Domain Steganography: Phase Bin Encoding Via Interpolation
NASA Astrophysics Data System (ADS)
In recent years there has been an increased interest in audio steganography and watermarking. This is due primarily to two reasons. First, an acute need to improve our national security capabilities in light of terrorist and criminal activity has driven new ideas and experimentation. Secondly, the explosive proliferation of digital media has forced the music industry to rethink how they will protect their intellectual property. Various techniques have been implemented but the phase domain remains a fertile ground for improvement due to the relative robustness to many types of distortion and immunity to the Human Auditory System. A new method for embedding data in the phase domain of the Discrete Fourier Transform of an audio signal is proposed. Focus is given to robustness and low perceptibility, while maintaining a relatively high capacity rate of up to 172 bits/s.
Rivas, Edward
Calibration of the Geostationary Imaging Fourier Transform Spectrometer (GIFTS)
NASA Astrophysics Data System (ADS)
The NASA New Millennium Program's Geostationary Imaging Fourier Transform Spectrometer (GIFTS) requires highly accurate radiometric and spectral calibration in order to carry out its mission to provide water vapor, wind, temperature, and trace gas profiling from geostationary orbit. A calibration concept has bene developed for the GIFTS Phase A instrument design. The in-flight calibration is performed using views of two on-board blackbody sources along with cold space. A radiometric calibration uncertainty analysis has been developed and used to show that the expected performance for GIFTS exceeds its top level requirement to measure brightness temperature to better than 1 K. For the Phase A GIFTS design, the spectral calibration is established by the highly stable diode laser used as the reference for interferogram sampling, and verified with comparisons to atmospheric calculations.
Best, Fred A.; Revercomb, Henry E.; Bingham, Gail E.; Knuteson, Robert O.; Tobin, David C.; LaPorte, Daniel D.; Smith, William L.
Calibration of the Geostationary Imaging Fourier Transform Spectrometer (GIFTS)
NASA Technical Reports Server (NTRS)
The NASA New Millennium Program's Geostationary Imaging Fourier Transform Spectrometer (GIFTS) requires highly accurate radiometric and spectral calibration in order to carry out its mission to provide water vapor, wind, temperature, and trace gas profiling from geostationary orbit. A calibration concept has been developed for the GIFTS Phase A instrument design. The in-flight calibration is performed using views of two on-board blackbody sources along with cold space. A radiometric calibration uncertainty analysis has been developed and used to show that the expected performance for GIFTS exceeds its top level requirement to measure brightness temperature to better than 1 K. For the Phase A GIFTS design, the spectral calibration is established by the highly stable diode laser used as the reference for interferogram sampling, and verified with comparisons to atmospheric calculations.
Best, F. A.; Revercomb, H. E.; Bingham, G. E.; Knuteson, R. O.; Tobin, D. C.; LaPorte, D. D.; Smith, W. L.
Fourier-transform ghost imaging with pure far-field correlated thermal light
Pure far-field correlated thermal light beams are created with phase grating, and Fourier-transform ghost imaging depending only on the far-field correlation is demonstrated experimentally. Theoretical analysis and the results of experimental investigation of this pure far-field correlated thermal light are presented. Applications which may be exploited with this imaging scheme are discussed.
Liu Honglin; Shen Xia; Han Shensheng [Key Laboratory for Quantum Optics and the Center for Cold Atom Physics of CAS, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, P.O. Box 800-211, Shanghai, 201800 (China); Zhu Daming [University of Science and Technology of China, Hefei, 230027 (China); University of Missouri-Kansas City, Kansas City, Missouri 64110 (United States)
Ultrahigh speed spectral / Fourier domain ophthalmic OCT imaging
Ultrahigh speed spectral / Fourier domain optical coherence tomography (OCT) imaging using a CMOS line scan camera with acquisition rates of 70,000 - 312,500 axial scans per second is investigated. Several design configurations ...
Chen, Yueli
InSAR image co-registration using the Fourier-Mellin transform
The problem of interferometric SAR (InSAR) image co?registration is addressed. Classical InSAR matching considers only the translation shift between two complex images. However, for accurate radar image matching (different swaths, paths, or aspects angles), other shift parameters would be useful. For two?dimensional images, the application of the Symmetric Phase Only Matching Filtering (SPOMF) to the Fourier�Mellin Invariant (FMI) descriptors allows
R. Abdelfattah; J. M. Nicolas
Fourier amplitude and phase analysis in the clinical evaluation of patients with cardiomyopathy
Fifty-four patients with a cardiomyopathy were studied by Radionuclide Cardangiography (RNCA) and Fourier amplitude and phase image analysis. The study group included patients with ischemic cardiomyopathy (27) and an equal number of patients with a primary cardiomyopathy: drug-induced (22), idiopathic (three), radiation-induced (one), and amyloidosis (one). Twenty-eight patients had rest studies alone and 26 had both rest and stress studies (80 total). The mean rest LVEF in the ischemic group was 27.9%, in the drug-induced group 36.5%, and in the idiopathic group 30%. The stress LVEF decreased in 92% of patients with ischemic cardiomyopathy and 45% of patients with primary (drug-induced) cardiomyopathy. Fourier amplitude and phase images were generated for each study. Amplitude and phase images were abnormal in all patients with an ischemic cardiomyopathy. LV amplitude abnormalities were regional and phase was directional. A zone of dysynergy on phase analysis was present in 44% of patients with ischemic cardiomyopathy. In the drug-induced primary cardiomyopathy group, all patients had abnormal amplitude and 86% had abnormal phase. Amplitude abnormalities were global rather than regional and phase patterns were nondirectional. Only one patient had a zone of dysynergy on the phase image. We conclude that the stress LVEF alone cannot consistently differentiate between ischemic and primary cardiomyopathies and that Fourier amplitude and phase analysis may be useful in determining the etiology of a cardiomyopathy (ischemic vs primary).
Alcan, K.E.; Robeson, W.; Graham, M.C.; Palestro, C.; Oliver, F.H.; Benua, R.S.
Gray-level image reconstruction using Bessel-Fourier moments
NASA Astrophysics Data System (ADS)
In this work, we reconstruct discrete image functions by means Bessel-Fourier polynomials. To measure the image reconstruction we use the Normalized image reconstruction error between the input and reconstructed images. We show that, a good reconstruction performance is found to be available for gray-level images. The reconstruction algorithm is implemented using the first forty zeros of the Bessel functions of the first kind. Experimental results are presented.
Toxqui-Quitl, C.; Guti�rrez-Lazcano, L.; Padilla-Vivanco, A.; Camacho-Bello, C.
Fractional Fourier transform in temporal ghost imaging with classical light
We investigate temporal, second-order classical ghost imaging with long, incoherent, scalar plane-wave pulses. We prove that in rather general conditions, the intensity correlation function at the output of the setup is given by the fractional Fourier transform of the temporal object. In special cases, the correlation function is shown to reduce to the ordinary Fourier transform and the temporal image of the object. Effects influencing the visibility and the resolution are considered. This work extends certain known results on spatial ghost imaging into the time domain and could find applications in temporal tomography of pulses.
Setaelae, Tero [Department of Applied Physics, Aalto University, P.O. Box 13500, FI-00076 Aalto (Finland); Shirai, Tomohiro [Photonics Research Institute, National Institute of Advanced Industrial Science and Technology, 1-2-1 Namiki, Tsukuba 305-8564 (Japan); Friberg, Ari T. [Department of Applied Physics, Aalto University, P.O. Box 13500, FI-00076 Aalto (Finland); Department of Physics and Mathematics, University of Eastern Finland, P.O. Box 111, FI-80101 Joensuu (Finland)
Geosynchronous Imaging Fourier Transform Spectrometer (GIFTS): Imaging and Tracking Capability
NASA Technical Reports Server (NTRS)
The geosynchronous-imaging Fourier transform spectrometer (GIFTS) engineering demonstration unit (EDU) is an imaging infrared spectrometer designed for atmospheric soundings. It measures the infrared spectrum in two spectral bands (14.6 to 8.8 microns, 6.0 to 4.4 microns) using two 128 128 detector arrays with a spectral resolution of 0.57/cm with a scan duration of approx. 11 seconds. From a geosynchronous orbit, the instrument will have the capability of taking successive measurements of such data to scan desired regions of the globe, from which atmospheric status, cloud parameters, wind field profiles, and other derived products can be retrieved. The GIFTS EDU provides a flexible and accurate testbed for the new challenges of the emerging hyperspectral era. The EDU ground-based measurement experiment, held in Logan, Utah during September 2006, demonstrated its extensive capabilities and potential for geosynchronous and other applications (e.g., Earth observing environmental measurements). This paper addresses the experiment objectives and overall performance of the sensor system with a focus on the GIFTS EDU imaging capability and proof of the GIFTS measurement concept.
Zhou, D. K.; Larar, A. M.; Liu, Xu; Reisse, R. A.; Smith, W. L.; Revercomb, H. E.; Bingham, G. E.; Zollinger, L. J.; Tansock, J. J.; Huppi, Ronald J.
Electro-Optical Imaging Fourier-Transform Spectrometer
NASA Technical Reports Server (NTRS)
An electro-optical (E-O) imaging Fourier-transform spectrometer (IFTS), now under development, is a prototype of improved imaging spectrometers to be used for hyperspectral imaging, especially in the infrared spectral region. Unlike both imaging and non-imaging traditional Fourier-transform spectrometers, the E-O IFTS does not contain any moving parts. Elimination of the moving parts and the associated actuator mechanisms and supporting structures would increase reliability while enabling reductions in size and mass, relative to traditional Fourier-transform spectrometers that offer equivalent capabilities. Elimination of moving parts would also eliminate the vibrations caused by the motions of those parts. Figure 1 schematically depicts a traditional Fourier-transform spectrometer, wherein a critical time delay is varied by translating one the mirrors of a Michelson interferometer. The time-dependent optical output is a periodic representation of the input spectrum. Data characterizing the input spectrum are generated through fast-Fourier-transform (FFT) post-processing of the output in conjunction with the varying time delay.
Chao, Tien-Hsin; Zhou, Hanying
NASA Astrophysics Data System (ADS)
We present a full-range Fourier domain polarization-sensitive optical coherence tomography technique which is able to obtain images of retardance, fast optical axis and intensity of sample. In this technique, the sinusoidal phase modulation is introduced into the spectral interferograms while the probe beam scans over the sample (B-scan). Then the complex horizontal and vertical signals are reconstructed by demodulation. By the Fourier transformation of the two interferograms, the full range images are obtained. Herein, the typical linear phase modulation is modified to sinusoidal phase modulation, which improves the system tolerance of sample movements and avoids sensitivity fall-off along the transverse scan. Furthermore, the images are obtained through the recombination of the horizontal and vertical polarization beam components acquired by a single camera, which avoids the problems of synchronous control and alignments in the situation of two cameras.
Chen, Yan; Wang, Xiangzhao; Li, Zhongliang; Nan, Nan; Guo, Xin
SU(3) phase states and finite Fourier transform
We describe the construction of SU(3) phase operators using Fourier-like transform on a hexagonal lattice. The advantages and disadvantages of this approach are contrasted with other results, in particular with the more traditional approach based on polar decomposition of operators.
Brandon Zanette; Hubert de Guise
Note: Phase sensitive detection of photoluminescence with Fourier transform spectroscopy.
Although known for more than twenty years, there is limited information in the literature regarding the experimental parameters of lock-in based phase sensitive emission detection in conjunction with Fourier spectrometers. For this technique - also known as double modulation spectroscopy - we present a guideline for parameter optimization by measuring the photoluminescence of InSb:Te at cryogenic temperatures. PMID:22300001
Ullrich, B; Brown, G J
Aperture-scanning Fourier ptychography for 3D refocusing and super-resolution macroscopic imaging.
We report an imaging scheme, termed aperture-scanning Fourier ptychography, for 3D refocusing and super-resolution macroscopic imaging. The reported scheme scans an aperture at the Fourier plane of an optical system and acquires the corresponding intensity images of the object. The acquired images are then synthesized in the frequency domain to recover a high-resolution complex sample wavefront; no phase information is needed in the recovery process. We demonstrate two applications of the reported scheme. In the first example, we use an aperture-scanning Fourier ptychography platform to recover the complex hologram of extended objects. The recovered hologram is then digitally propagated into different planes along the optical axis to examine the 3D structure of the object. We also demonstrate a reconstruction resolution better than the detector pixel limit (i.e., pixel super-resolution). In the second example, we develop a camera-scanning Fourier ptychography platform for super-resolution macroscopic imaging. By simply scanning the camera over different positions, we bypass the diffraction limit of the photographic lens and recover a super-resolution image of an object placed at the far field. This platform's maximum achievable resolution is ultimately determined by the camera's traveling range, not the aperture size of the lens. The FP scheme reported in this work may find applications in 3D object tracking, synthetic aperture imaging, remote sensing, and optical/electron/X-ray microscopy. PMID:24921553
Dong, Siyuan; Horstmeyer, Roarke; Shiradkar, Radhika; Guo, Kaikai; Ou, Xiaoze; Bian, Zichao; Xin, Huolin; Zheng, Guoan
Visible-NIR imaging optics for a Fourier transform spectrometer
NASA Astrophysics Data System (ADS)
We present details of optical design, opto-mechanical design and testing of a visible-NIR imaging optical system for a Fourier transform spectrometer dedicated to astronomical application at the Mont M�gantic Observatory (Observatoire du Mont M�gantic, OMM, located south Qu�bec city, Canada). Design considerations as well as testing and experimental results are presented.
Thibault, Simon; Reecht, J�r�me; Lavigne, Jean-Fran�ois; Desnoyers, Nichola
Medical image processing using transient Fourier holography in bacteriorhodopsin films
processing is demonstrated by recording and reconstructing the transient photoisomerizative grating formedMedical image processing using transient Fourier holography in bacteriorhodopsin films Sri of the technique is the ability to transient display of selected spatial frequencies in the reconstructing process
Rao, D.V.G.L.N.
Scanning plasmonic microscopy by image reconstruction from the Fourier space.
We demonstrate a simple scheme for high-resolution imaging of nanoplasmonic structures that basically removes most of the resolution limiting allowed light usually transmitted to the far field. This is achieved by implementing a Fourier lens in a near-field scanning optical microscope (NSOM) operating in the leakage-radiation microscopy (LRM) mode. The method consists of reconstructing optical images solely from the plasmonic 'forbidden' light collected in the Fourier space. It is demonstrated by using a point-like nanodiamond-based tip that illuminates a thin gold film patterned with a sub-wavelength annular slit. The reconstructed image of the slit shows a spatial resolution enhanced by a factor ~/= 4 compared to NSOM images acquired directly in the real space. PMID:23263132
Mollet, Oriane; Huant, Serge; Drezet, Aur�lien
Canning plasmonic microscopy by image reconstruction from the Fourier space
We demonstrate a simple scheme for high-resolution imaging of nanoplasmonic structures that basically removes most of the resolution limiting allowed light usually transmitted to the far field. This is achieved by implementing a Fourier lens in a near-field scanning optical microscope (NSOM) operating in the leakage-radiation microscopy (LRM) mode. The method consists of reconstructing optical images solely from the plasmonic `forbidden' light collected in the Fourier space. It is demonstrated by using a point-like nanodiamond-based tip that illuminates a thin gold film patterned with a sub-wavelength annular slit. The reconstructed image of the slit shows a spatial resolution enhanced by a factor $\\simeq 4$ compared to NSOM images acquired directly in the real space.
Mollet, O; Drezet, A
In-orbit performance of the Herschel/SPIRE imaging Fourier transform spectrometer
NASA Astrophysics Data System (ADS)
The Spectral and Photometric Imaging Receiver (SPIRE) is one of three scientific instruments onboard the European Space Agency's Herschel Space Observatory launched on 14 May 2009. The low to medium resolution spectroscopic capability of SPIRE is provided by an imaging Fourier transform spectrometer of the Mach-Zehnder configuration. Results from the in flight performance verification phase of the SPIRE spectrometer are presented and conformance with the instrument design specifications is reviewed.
Naylor, David A.; Baluteau, Jean-Paul; Barlow, Mike J.; Benielli, Dominique; Ferlet, Marc; Fulton, Trevor R.; Griffin, Matthew J.; Grundy, Timothy; Imhof, Peter; Jones, Scott; King, Ken; Leeks, Sarah J.; Lim, Tanya L.; Lu, Nanyao; Makiwa, Gibion; Polehampton, Edward T.; Savini, Giorgio; Sidher, Sunil D.; Spencer, Locke D.; Surace, Christian; Swinyard, Bruce M.; Wesson, Roger
NASA Astrophysics Data System (ADS)
It has been shown that biometric information can be used as a cipher key for binary data encryption by applying double random phase encoding. In such methods, binary data are encoded in a bit pattern image, and the decrypted image becomes a plain image when the key is genuine; otherwise, decrypted images become random images. In some cases, images decrypted by imposters may not be fully random, such that the blurred bit pattern can be partially observed. In this paper, we propose a novel bit coding method based on a Fourier transform hologram, which makes images decrypted by imposters more random. Computer experiments confirm that the method increases the randomness of images decrypted by imposters while keeping the false rejection rate as low as in the conventional method.
Takeda, Masafumi; Nakano, Kazuya; Suzuki, Hiroyuki; Yamaguchi, Masahiro
Infrared small target enhancement via phase spectrum of Quaternion Fourier Transform
NASA Astrophysics Data System (ADS)
Small target enhancement is one of the crucial stages in infrared small target detection. In this paper, we propose a new method using phase spectrum of Quaternion Fourier Transform to enhance small targets while suppressing backgrounds for infrared images. This is inspired by the property that regularly Gaussian-like shape small targets could be considered as attractively salient signal in infrared images and the location information of such signal is implicitly contained in the phase spectrum from frequency domain. Formally, in the proposed method, we adopt the phase spectrum of Quaternion Fourier Transform instead of using traditional Fourier Transform to enhance the targets since the quaternion provides at most four data channels than only one for the latter, which could be helpful to broad types of background clutters by adding more information. For the construction of the quaternion, we present a second-order directional derivative filter via facet model to compute four second order directional derivative maps from four directions respectively as the four data channels. This filter is used to suppress noises and distinguish the targets and backgrounds into separably different textures so that it would boost the robustness of small target enhancement. In experiments, some typical infrared images with various scenes are tested to validate the effectiveness of the proposed method. The results demonstrate that our method actually has good performance and outperforms several state-of-the-art methods, which can be further used for infrared small target detection and tracking.
Qi, Shengxiang; Ma, Jie; Li, Hang; Zhang, Shuiping; Tian, Jinwen
An update on the imaging Fourier transform spectrometer for Brad G. Gom and David A. Naylor*
An update on the imaging Fourier transform spectrometer for SCUBA-2 Brad G. Gom and David A. Naylor and current design and of an imaging Fourier transform spectrometer (IFTS) for use with SCUBA-2, the second. Keywords: Imaging, Fourier, Transform, Spectrometer, SCUBA-2, Submillimetre 1. INTRODUCTION SCUBA-2
Naylor, David A.
NASA Astrophysics Data System (ADS)
A multiple-image encryption scheme is proposed based on the asymmetric technique, in which the encryption keys are not identical to the decryption ones. First, each plain image is scrambled based on a sequence of chaotic pairs generated with a system of two symmetrically coupled identical logistic maps. Then, the phase-only function of each scrambled image is retrieved with an iterative phase retrieval process in the fractional Fourier transform domain. Second, all phase-only functions are modulated into an interim, which is encrypted into the ciphertext with stationary white noise distribution by using the fractional Fourier transform and chaotic diffusion. In the encryption process, three random phase functions are used as encryption keys to retrieve the phase-only functions of plain images. Simultaneously, three decryption keys are generated in the encryption process, which make the proposed encryption scheme has high security against various attacks, such as chosen plaintext attack. The peak signal-to-noise is used to evaluate the quality of the decrypted image, which shows that the encryption capacity of the proposed scheme is enhanced considerably. Numerical simulations demonstrate the validity and efficiency of the proposed method.
Sui, Liansheng; Duan, Kuaikuai; Liang, Junli; Zhang, Zhiqiang; Meng, Haining
Detecting correlation functions of ultracold atoms through Fourier sampling of time-of-flight images
We propose a detection method for ultracold atoms which allows reconstruction of the full one-particle and two-particle correlation functions from the measurements. The method is based on Fourier sampling of the time-of-flight images through two consecutive impulsive Raman pulses. For applications of this method, we discuss a few examples, including detection of phase separation between superfluid and Mott insulators, various types of spin or superfluid orders, entanglement, exotic or fluctuating orders.
L. -M. Duan
NASA Astrophysics Data System (ADS)
An image hiding method based on cascaded iterative Fourier transform and public-key encryption algorithm was proposed. Firstly, the original secret image was encrypted into two phase-only masks M1 and M2 via cascaded iterative Fourier transform (CIFT) algorithm. Then, the public-key encryption algorithm RSA was adopted to encrypt M2 into M2' . Finally, a host image was enlarged by extending one pixel into 2�2 pixels and each element in M1 and M2' was multiplied with a superimposition coefficient and added to or subtracted from two different elements in the 2�2 pixels of the enlarged host image. To recover the secret image from the stego-image, the two masks were extracted from the stego-image without the original host image. By applying public-key encryption algorithm, the key distribution was facilitated, and also compared with the image hiding method based on optical interference, the proposed method may reach higher robustness by employing the characteristics of the CIFT algorithm. Computer simulations show that this method has good robustness against image processing.
Zhang, B.; Sang, Jun; Alam, Mohammad S.
Fourier-processed images of dynamic lung function from list-mode data
Time and volume correlated amplitude and phase images are computed from nuclear medical ventilation studies and for dynamic transmission scans of the lungs. This is made possible by a hardware interface and data acquisition system, developed in-house, allowing camera events and multiple ancillary physiological signals (including lung volume) to be acquired simultaneously in list mode. The first harmonic amplitude and phase images are constructed on an event by event basis. These are computed for both equal time and equal lung volume increments. Time and volume correlated Fourier images for ventilation studies have shown details and functional structures not usually seen in conventional imaging techniques. Processed transmission scans show similar results compared to ventilation images.
Zubal, I.G.; Rowe, R.W.; Bizais, Y.; Susskind, H.; Bennett, G.W.; Brill, A.B.
Ghost imaging of phase objects with classical incoherent light
We describe an optical setup for performing spatial Fourier filtering in ghost imaging with classical incoherent light. This is achieved by a modification of the conventional geometry for lensless ghost imaging. It is shown on the basis of classical coherence theory that with this technique one can realize what we call phase-contrast ghost imaging to visualize pure phase objects.
Shirai, Tomohiro [Electronics and Photonics Research Institute, National Institute of Advanced Industrial Science and Technology, 1-2-1 Namiki, Tsukuba 305-8564 (Japan); Setaelae, Tero [Department of Applied Physics, Aalto University, P.O. Box 13500, FI-00076 Aalto (Finland); Friberg, Ari T. [Department of Applied Physics, Aalto University, P.O. Box 13500, FI-00076 Aalto (Finland); Department of Physics and Mathematics, University of Eastern Finland, P.O. Box 111, FI-80101 Joensuu (Finland); Department of Microelectronics and Applied Physics, Royal Institute of Technology, Electrum 229, SE-164 40 Kista (Sweden)
Imaging Fourier transform spectrometer (IFTS): parametric sensitivity analysis
NASA Astrophysics Data System (ADS)
Imaging Fourier transform spectrometers (IFTS) allow for very high spectral resolution hyperspectral imaging while using moderate size 2D focal plane arrays in a staring mode. This is not the case for slit scanning dispersive imaging spectrometers where spectral sampling is related to the focal plane pixel count along the spectral dimension of the 2D focal plane used in such an instrument. This can become a major issue in the longwave infrared (LWIR) where the operability and yield of highly sensitivity arrays (i.e.HgCdTe) of large dimension are generally poor. However using an IFTS introduces its own unique set of issues and tradeoffs. In this paper we develop simplified equations for describing the sensitivity of an IFTS, including the effects of data windowing. These equations provide useful insights into the optical, focal plane and operational design trade space that must be considered when examining IFTS concepts aimed at a specific sensitivity and spectral resolution application. The approach is illustrated by computing the LWIR noise-equivalent spectral radiance (NESR) corresponding to the NASA Geosynchronous Imaging Fourier Transform Spectrometer (GIFTS) concept assuming a proven and reasonable noise-equivalent irradiance (NEI) capability for the focal plane.
Keller, Robert A.; Lomheim, Terrence S.
Reconstruction of multispectral image cubes from multiple- telescope array Fourier transform objects is more difficult, since the multispectral image cube is missing low spatial frequency information will present results for the simultaneous reconstruction of a multispectral image cube using simulated data
Fienup, James R.
Imaging the sun in hard x rays using Fourier telescopes
NASA Technical Reports Server (NTRS)
For several years, solar flares have been observed with a variety of instruments confirming that tremendous amounts of energy are locally stored in the solar magnetic field and then rapidly released during the life of the flare. In concert with observations, theorists have attempted to describe the means by which these energetic events occur and evolve. Two competing theories have emerged and have stood the test of time. One theory describes the flare in terms of nonthermal, electron beam injection into a thick target while the other uses a thermal approach. Both theories provide results which are reasonably consistent with current observations; but to date, none have been able to provide conclusive evidence as to the validity of either model. Imaging on short time scales (1 s) and/or small size scales (1 arc s) should give definitive answers to these questions. In order to test whether a realistic telescope can indeed discriminate between models, we construct model sources based upon the thermal and the nonthermal models and calculate the emission as a function of time and energy in the range from 10 to 100 keV. In addition, we construct model telescopes representing both the spatial modulation collimator (SMC) and the rotating modulation collimator (RMC) techniques of observation using random photon counting statistics. With these two types of telescopes we numerically simulate the instrument response to the above two model flares to see if there are distinct x-ray signatures which may be discernable. We find that theoretical descriptions of the primary models of solar flares do indeed predict different hard x-ray signatures for 1 sec time scales and at 1-5 arc sec spatial resolution. However, these distinguishing signatures can best be observed early in the impulsive phase and from a position perpendicular to the plane of the loop. Furthermore, we find that Fourier telescopes with reasonable and currently attainable design characteristics can image these signatures and that the same sensitive areas and short temporal integration times relative to source evolution (i.e., 1 s), the RMC and the SMC will both provide about the same performance.
Campbell, J. W.
The artefact-free reconstruction of structured illumination microscopy images requires precise knowledge of the pattern phases in the raw images. If this parameter cannot be controlled precisely enough in an experimental setup, the phases have to be determined a posteriori from the acquired data. While an iterative optimisation based on cross-correlations between individual Fourier images yields accurate results, it is rather time-consuming. Here I present a fast non-iterative technique which determines each pattern phase from an auto-correlation of the respective Fourier image. In addition to improving the speed of the reconstruction, simulations show that this method is also more robust, yielding errors of typically less than ?/500 under realistic signal-to-noise levels. PMID:24150313
Wicker, Kai
High throughput full Stokes Fourier transform imaging spectropolarimetry.
A complete full Stokes imaging spectropolarimeter is proposed. Four separate polarized spectra are fed into the Sagnac Fourier transform spectrometer without slit using different angle combinations of the polarized elements. The four polarized spectra are separated without spatial aliasing. And the system has a good performance to resist the instrument noise due to its high light throughput. The mathematical model for the approach is derived and an optimization of the retardance is discussed. For acquiring the four spectra simultaneously, an improved robust polarization modulator using aperture division is outlined. Then the system is discussed in detail including the imaging principle and spectral resolution. Lastly, two proven experiments are carried out and the experimental results in visible light are outlined. PMID:24514802
Meng, Xin; Li, Jianxin; Xu, Tingting; Liu, Defang; Zhu, Rihong
Registration of Translated and Rotated Images Using Finite Fourier Transforms
A well-known method for image registration is based on a conventional correlation between phase-only, or whitened, versions of the two images to be realigned. The method, covering rigid translational movements, is characterized by an outstanding robustness against correlated noise and disturbances, such as those encountered with nonuniform, time varying illumination. This correspondence discusses an extension of the method to cover
E. De Castro; C. Morandi
Fourier transform infrared phase shift cavity ring down spectrometer
NASA Astrophysics Data System (ADS)
OPTRA has developed a Fourier transform infrared phase shift cavity ring down spectrometer (FTIR-PS-CRDS) system under a U.S. EPA SBIR contract. This system uses the inherent wavelength-dependent modulation imposed by the FTIR on a broadband thermal source for the phase shift measurement. This spectrally-dependent phase shift is proportional to the spectrally-dependent ring down time. The spectral dependence of both of these values is introduced by the losses of the cavity including those due to the molecular absorption of the sample. OPTRA's approach allows broadband detection of chemicals across the feature-rich fingerprint region of the long-wave infrared. This represents a broadband and spectral range enhancement to conventional CRDS which is typically done at a single wavelength in the near IR; at the same time the approach is a sensitivity enhancement to traditional FTIR, owing to the long effective path of the resonant cavity. In previous papers1,2, OPTRA has presented a breadboard system aimed at demonstrating the feasibility of the approach and a prototype design implementing performance enhancements based on the results of breadboard testing. In this final paper in the series, we will present test results illustrating the realized performance of the fully assembled and integrated breadboard, thereby demonstrating the utility of the approach.
Schundler, Elizabeth; Mansur, David J.; Vaillancourt, Robert; Benedict-Gill, Ryan; Newbry, Scott P.; Engel, James R.; Dupuis, Julia Rentz
Clifford Fourier Transform for Color Image Thomas Batard, Michel Berthier and Christophe Saint-Jean
Clifford Fourier Transform for Color Image Processing Thomas Batard, Michel Berthier and Christophe Saint-Jean Abstract The aim of this paper is to define a Clifford Fourier transform that is suit- able to generalize the classical approach of scalar signal processing with the Fourier transform to higher dimen
Paris-Sud XI, Université de
An Accurate Discrete Fourier Transform for Image Processing Normand Beaudoin' and Steven S . Beauchernint Abstract The classical method of numerically computing the Fourier transform of digitizedfunctions in one or in d- dimensions is the so-called discrete Fourier transform (DFT),efficiently implemented
Beauchemin, Steven S.
Clifford Fourier Transform for Color Image Thomas Batard, Michel Berthier and Christophe Saint-Jean
Clifford Fourier Transform for Color Image Processing Thomas Batard, Michel Berthier and Christophe Saint-Jean Abstract The aim of this paper is to define a Clifford Fourier transform that is suit- able the classical approach of scalar signal processing with the Fourier transform to higher dimen- sional signals
Objective Current imaging techniques are often sub-optimal for the detection of mandibular invasion by squamous cell carcinoma. The aim of this study was to determine the feasibility of a magnetic resonance imaging (MRI) based technique known as Sweep Imaging with Fourier Transform (SWIFT) to visualize the structural changes of intra-mandibular anatomy during invasion. Design Descriptive case study Setting Tertiary academic institution Method Two specimens from patients with oral carcinoma who underwent segmental mandibulectomy were imaged using a 9.4 Tesla Varian MRI system. The SWIFT images were correlated with histological sections. Results The SWIFT technique with in vitro specimens produced images with sufficient resolution (156�273) and contrast to allow accurate depiction of tumor invasion of cortical and medullary bone. Both specimens had histopathological evidence of mandibular invasion with tumor. A high degree of correlation was found between MR images and histopathologic findings. Conclusion SWIFT MRI offers three-dimensional assessment of cortical and medullary bone in fine detail with excellent qualitative agreement with histopathology. MR imaging with the SWIFT technique demonstrates great potential to identify mandibular invasion by oral carcinoma. PMID:21930980
Kendi, Ayse Tuba Karagulle; Khariwala, Samir S.; Zhang, Jinjin; Idiyatullin, Djaudat S.; Corum, Curtis A.; Michaeli, Shalom; Pambuccian, Stefan E.; Garwood, Michael; Yueh, Bevan
Ultrasonic reflection imaging has the potential to produce higher image resolution than transmission tomography, but imaging resolution and quality still need to be further improved for early cancer detection and diagnosis. We present an ultrasound reflection image reconstruction method using the split-step Fourier propagator. It is based on recursive inward continuation of ultrasonic wavefields in the frequency-space and frequency-wavenumber domains. The inward continuation within each extrapolation interval consists of two steps. In the first step, a phase-shift term is applied to the data in the frequency-wavenumber domain for propagation in a reference medium. The second step consists of applying another phase-shift term to data in the frequency-space domain to approximately compensate for ultrasonic scattering effects of heterogeneities within the breast. We use synthetic ultrasound pulse-echo data recorded around a ring for heterogeneous, computer-generated numerical breast phantoms to study the imaging capability of the method. The phantoms are derived from an experimental breast phantom and a sound-speed tomography image of an in-vivo ultrasound breast data collected usi ng a ring array. The heterogeneous sound-speed models used for pulse-echo imaging are obtained using a computationally efficient, first-arrival-time (time-of-flight) transmission tomography method. Our studies demonstrate that reflection image reconstruction using the split-step Fourier propagator with heterogeneous sound-speed models significantly improves image quality and resolution. We also numerically verify the spatial sampling criterion of wavefields for a ring transducer array.
HUANG, LIANJIE [Los Alamos National Laboratory; QUAN, YOULI [Los Alamos National Laboratory
The Geosynchronous Imaging Fourier Transform Spectrometer (GIFTS): noise performance
NASA Astrophysics Data System (ADS)
The NASA New Millennium Program (NMP) Geosynchronous Imaging Fourier Transform Spectrometer (GIFTS) instrument was designed to demonstrate new and emerging technologies and provide immense improvements in satellite based remote sensing of the atmosphere from a geostationary orbit [1]. Combining a Fourier Transform Spectrometer (FTS) and Large Area Focal Plane Arrays, GIFTS measures incident infrared radiance with an extraordinary combination of spectral, temporal, and spatial resolution and coverage. Thermal vacuum testing of the GIFTS Engineering Development Unit (EDU) was performed at the Space Dynamics Laboratory and completed in May 2006 [2,3]. The GIFTS noise performance measured during EDU thermal vacuum testing indicates that threshold performance has been realized, and that goal performance (or better) has been achieved over much of both the Longwave Infrared (LWIR) and Short/Midwave Infrared (SMWIR) detector bands. An organizational structure for the division of the noise sources and effects for the GIFTS instrument is presented. To comprehensively characterize and predict the effects of measurement noise on expected instrument performance, the noise sources are categorically divided and a method of combining the independent effects is defined. Within this architecture, the total noise is principally decomposed into spectrally correlated noise and random (spectrally uncorrelated) noise. The characterization of the spectrally correlated noise sources specified within the structure is presented in detail.
Taylor, Joe K.; Revercomb, Henry E.; Tobin, David C.; Best, Fred A.; Knuteson, Robert O.; Elwell, John D.; Cantwell, Gregory W.; Scott, Deron K.; Bingham, Gail E.; Smith, William L.; Zhou, Daniel K.; Reisse, Robert A.
Amplitude and phase fourier correlation of ``twin'' GC-spectra of fatty acids from sheep dairy
NASA Astrophysics Data System (ADS)
Authors present the discrimination performances of amplitude and phase-only Fourier correlation over the "twin" typed GC-spectra of sheep milk and ripened cheese. Therefore, in order to assess the most robust Fourier correlation method for the "twin" GC-spectra discrimination, the correlation matrix is built up over 17 analyzed GC-spectra in both amplitude and phase domains.
Teusdea, Alin C.; Gabor, Gianina; Hilma, Elena
Opto-digital image encryption by using Baker mapping and 1-D fractional Fourier transform
NASA Astrophysics Data System (ADS)
We present an optical encryption method based on the Baker mapping in one-dimensional fractional Fourier transform (1D FrFT) domains. A thin cylinder lens is controlled by computer for implementing 1D FrFT at horizontal direction or vertical direction. The Baker mapping is introduced to scramble the amplitude distribution of complex function. The amplitude and phase of the output of encryption system are regarded as encrypted image and key. Numerical simulation has been performed for testing the validity of this encryption scheme.
Liu, Zhengjun; Li, She; Liu, Wei; Liu, Shutian
NASA Astrophysics Data System (ADS)
In this paper, digital holography based on two-step phase shifting interference (PSI) was applied to realize the iterative partial phase encoding with joint fractional transform correlator (JFTC). By this security system, the primitive image is encoded in two joint fractional power spectra (JFPS) corresponding to different phase-shifting values. The encrypted image can be deduced directly from the JFPSs by digital means, thus eliminating the noise interference of dc and conjugate terms. JFTC not only relaxes the alignment requirement but also avoids the beam splitting required by traditional holography. In the iterative partial phase encoding, the random phase masks (RPMs) are generated by chaotic mapping, and encoding areas are confined by a sequence of random binary masks. To recover the primitive image, decipher must regenerate the partial RPMs with correct chaotic conditions and perform inverse fractional Fourier transforms with correct orders. The decryption process can be realized by JFTC or by totally digital means. Simulation and experimental results have been presented to test security level and feasibility of the scheme.
Wang, Qu; Guo, Qing; Lei, Liang; Zhou, Jinyun
Methods for enhancing ultrasonic reflection imaging are taught utilizing a split-step Fourier propagator in which the reconstruction is based on recursive inward continuation of ultrasonic wavefields in the frequency-space and frequency-wave number domains. The inward continuation within each extrapolation interval consists of two steps. In the first step, a phase-shift term is applied to the data in the frequency-wave number domain for propagation in a reference medium. The second step consists of applying another phase-shift term to data in the frequency-space domain to approximately compensate for ultrasonic scattering effects of heterogeneities within the tissue being imaged (e.g., breast tissue). Results from various data input to the method indicate significant improvements are provided in both image quality and resolution.
Huang, Lianjie
In-orbit performance of the Herschel/SPIRE imaging Fourier transform spectrometer: lessons learned
NASA Astrophysics Data System (ADS)
The Spectral and Photometric Imaging Receiver (SPIRE) is one of three scientific instruments on board the European Space Agency's Herschel Space Observatory which ended its operational phase on 29 April 2013. The low to medium resolution spectroscopic capability of SPIRE is provided by an imaging Fourier transform spectrometer (iFTS) of the Mach-Zehnder configuration. With their high throughput, broad spectral coverage, and variable resolution, coupled with their well-defined instrumental line shape and intrinsic wavelength and intensity calibration, iFTS are becoming increasingly common in far-infrared space astronomy missions. The performance of the SPIRE imaging spectrometer will be reviewed and example results presented. The lessons learned from the measured performance of the spectrometer as they apply to future missions will be discussed.
Naylor, David A.; Baluteau, Jean-Paul; Bendo, George J.; Benielli, Dominique; Fulton, Trevor R.; Gom, Brad G.; Griffin, Matthew J.; Hopwood, Rosalind; Imhof, Peter; Lim, Tanya L.; Lu, Nanyao; Makiwa, Gibion; Marchili, Nicola; Orton, Glenn S.; Papageorgiou, Andreas; Pearson, Chris; Polehampton, Edward T.; Schulz, Bernhard; Spencer, Locke D.; Swinyard, Bruce M.; Valtchanov, Ivan; van der Wiel, Matthijs H. D.; Veenendaal, Ian T.; Wu, Ronin
Fourier-transform evaluation of phase data in spatially phase-biased TV holograms.
TV holograms for spatial phase stepping are formed with a small angular offset between the object and the reference beams to give a spatial frequency bias to the pattern recorded by the TV camera. It is common to set the bias so that there is a 90� or 120�phase shift between adjacent pixels and to use the irradiance of three or more adjacent pixels to evaluate the phase of the interference. We report the Fourier-transform evaluation of such recordings to obtain their phase data. We also demonstrate the direct calculation of the phase difference between successive recordings without intermediate calculation of the random phase of each hologram. This technique is proposed as an approach to pulsed TV holography. PMID:21069016
Saldner, H O; Molin, N E; Stetson, K A
Discovering Ordered Phases of Block Copolymers: New Results from a Generic Fourier-Space Approach
A generic Fourier-space approach to solve the self-consistent field theory of block copolymers is developed. This approach is based on the fact that, for any computational box with periodic boundary conditions, all spatially varying functions are spanned by the Fourier series determined by the size and shape of the box. The method reproduces all known diblock copolymer phases. The application
Zuojun Guo; Guojie Zhang; Feng Qiu; Hongdong Zhang; Yuliang Yang; An-Chang Shi
Rotational-translational fourier imaging system requiring only one grid pair
NASA Technical Reports Server (NTRS)
The sky contains many active sources that emit X-rays, gamma rays, and neutrons. Unfortunately hard X-rays, gamma rays, and neutrons cannot be imaged by conventional optics. This obstacle led to the development of Fourier imaging systems. In early approaches, multiple grid pairs were necessary in order to create rudimentary Fourier imaging systems. At least one set of grid pairs was required to provide multiple real components of a Fourier derived image, and another set was required to provide multiple imaginary components of the image. It has long been recognized that the expense associated with the physical production of the numerous grid pairs required for Fourier imaging was a drawback. Herein one grid pair (two grids), with accompanying rotation and translation, can be used if one grid has one more slit than the other grid, and if the detector is modified.
Campbell, Jonathan W. (Inventor)
Terahertz phase contrast imaging
NASA Astrophysics Data System (ADS)
Terahertz imaging is presently in its exploratory stage. Although plots of time versus terahertz amplitude, and frequency versus terahertz magnitude are some of the most common ways of analyzing terahertz data, no standard rendering technique has been established. While existing methods are indispensable, improvements to how terahertz data is rendered and analyzed should be explored so that new techniques can complement existing ones and/or provide a means of displaying new information that existing methods cannot. This paper reports on one solution to terahertz imaging: an implementation of a new form of phase contrast imaging, which is based on a well-established technique for optical microscopy. This will provide us with a further way of interpreting information from terahertz imaging systems.
Png, Gretel M.; Mickan, Samuel P.; Rainsford, Tamath J.; Abbott, Derek
Vector power multiple-parameter fractional Fourier transform of image encryption algorithm
NASA Astrophysics Data System (ADS)
In this paper, we propose a multiple-parameter fractional Fourier transform with its transform order being a real vector, based on which a high-security image encryption scheme is also given. This novel fractional Fourier transform has removed the restriction on the dimension of transform order and highly enhances the security of image encryption scheme proposed in this paper without increasing the computational complexity and hardware cost. The numerical results verify the efficacy and security of this image encryption method. The vector power multi-parameter fractional Fourier transform is a generalized form of the classical fractional Fourier transform with all the previous fractional Fourier transform as its special cases and has theoretical significance in information processing and information security.
Ran, Qiwen; Zhao, Tieyu; Yuan, Lin; Wang, Jian; Xu, Lei
The spatio-temporal Fourier transform is usually applied to determine the velocity of an object from a series of standard light intensity frames. In this paper the technique has been extended to determine the object acceleration. The techniques for velocity and acceleration determination based on the spatio-temporal Fourier transform have been applied to experimental low light level images. Under these conditions,
Manuel P. Cagigal; Pedro M. Prieto
Geostationary Imaging Fourier Transform Spectrometer (GIFTS): science applications
NASA Astrophysics Data System (ADS)
A revolutionary satellite weather forecasting instrument, called the "GIFTS" which stands for the "Geostationary Imaging Fourier Transform Spectrometer", was recently completed and successfully tested in a space chamber at the Utah State University's Space Dynamics Laboratory. The GIFTS was originally proposed by the NASA Langley Research Center, the University of Wisconsin, and the Utah State University and selected for flight demonstration as NASA's New Millennium Program (NMP) Earth Observing-3 (EO-3) mission, which was unfortunately cancelled in 2004. GIFTS is like a digital 3-d movie camera that, when mounted on a geostationary satellite, would provide from space a revolutionary four-dimensional view of the Earth's atmosphere. GIFTS will measure the distribution, change, and movement of atmospheric moisture, temperature, and certain pollutant gases, such as carbon monoxide and ozone. The observation of the convergence of invisible water vapor, and the change of atmospheric temperature, provides meteorologists with the observations needed to predict where, and when, severe thunderstorms, and possibly tornados, would occur, before they are visible on radar or in satellite cloud imagery. The ability of GIFTS to observe the motion of moisture and clouds at different altitudes enables atmospheric winds to be observed over vast, and otherwise data sparse, oceanic regions of the globe. These wind observations would provide the means to greatly improve the forecast of where tropical storms and hurricanes will move and where and when they will come ashore (i.e., their landfall position and time). GIFTS, if flown into geostationary orbit, would provide about 80,000 vertical profiles per minute, each one like a low vertical resolution (1-2km) weather balloon sounding, but with a spacing of 4 km. GIFTS is a revolutionary atmospheric sensing tool. A glimpse of the science measurement capabilities of GIFTS is provided through airborne measurements with the NPOESS Airborne Sounding Testbed - Interferometer (NAST-I).
Smith, W. L.; Revercomb, H. E.; Zhou, D. K.; Bingham, G. E.; Feltz, W. F.; Huang, H. L.; Knuteson, R. O.; Larar, A. M.; Liu, X.; Reisse, R.; Tobin, D. C.
This paper addresses two fundamental issues involved in the reconstruction of a multidimensional sequence from either the phase or magnitude of its Fourier transform. The first issue relates to the uniqueness of a multidimensional sequence in terms of its phase or magnitude. Although phase or magnitude information alone is not sufficient, in general, to uniquely specify a sequence, a large
M. Hayes
Complete fourier direct magnetic resonance imaging (CFD-MRI) for diffusion MRI
The foundation for an accurate and unifying Fourier-based theory of diffusion weighted magnetic resonance imaging (DW�MRI) is constructed by carefully re-examining the first principles of DW�MRI signal formation and deriving its mathematical model from scratch. The derivations are specifically obtained for DW�MRI signal by including all of its elements (e.g., imaging gradients) using complex values. Particle methods are utilized in contrast to conventional partial differential equations approach. The signal is shown to be the Fourier transform of the joint distribution of number of the magnetic moments (at a given location at the initial time) and magnetic moment displacement integrals. In effect, the k-space is augmented by three more dimensions, corresponding to the frequency variables dual to displacement integral vectors. The joint distribution function is recovered by applying the Fourier transform to the complete high-dimensional data set. In the process, to obtain a physically meaningful real valued distribution function, phase corrections are applied for the re-establishment of Hermitian symmetry in the signal. Consequently, the method is fully unconstrained and directly presents the distribution of displacement integrals without any assumptions such as symmetry or Markovian property. The joint distribution function is visualized with isosurfaces, which describe the displacement integrals, overlaid on the distribution map of the number of magnetic moments with low mobility. The model provides an accurate description of the molecular motion measurements via DW�MRI. The improvement of the characterization of tissue microstructure leads to a better localization, detection and assessment of biological properties such as white matter integrity. The results are demonstrated on the experimental data obtained from an ex vivo baboon brain. PMID:23596401
Ozcan, Alpay
Directional Wavelet Analysis with Fourier-type Bases for Image Processing
and image compression. The idea that biological visual systems might analyse image along dimensions. To refine these models, multiscale edge representations using wavelet maxima [29] or an edge of multiscale trigonometric bases for image processing using Fourier-type constructions, namely, the multiscale
Rajpoot, Nasir
Synthetic quadrature phase detector/demodulator for Fourier transform spectrometers.
A method is developed to demodulate (velocity correct) Fourier transform spectrometer data that are taken with an analog to digital converter that digitizes equally spaced in time. This method makes it possible to use simple low-cost, high-resolution audio digitizers to record high-quality data without the need for an event timer or quadrature laser hardware and makes it possible to use a metrology laser of any wavelength. The reduced parts count and simple implementation make it an attractive alternative in space-based applications when compared to previous methods such as the Brault algorithm. PMID:19104542
Campbell, Joel
Discovering ordered phases of block copolymers: new results from a generic Fourier-space approach.
A generic Fourier-space approach to solve the self-consistent field theory of block copolymers is developed. This approach is based on the fact that, for any computational box with periodic boundary conditions, all spatially varying functions are spanned by the Fourier series determined by the size and shape of the box. The method reproduces all known diblock copolymer phases. The application of this method to a model "frustrated" triblock copolymer leads to a phase diagram with a number of new phases. Furthermore, the capability of the method to reproduce experimentally observed structures is demonstrated using the knitting pattern of triblock copolymers. PMID:18764231
Guo, Zuojun; Zhang, Guojie; Qiu, Feng; Zhang, Hongdong; Yang, Yuliang; Shi, An-Chang
Discovering Ordered Phases of Block Copolymers: New Results from a Generic Fourier-Space Approach
NASA Astrophysics Data System (ADS)
A generic Fourier-space approach to solve the self-consistent field theory of block copolymers is developed. This approach is based on the fact that, for any computational box with periodic boundary conditions, all spatially varying functions are spanned by the Fourier series determined by the size and shape of the box. The method reproduces all known diblock copolymer phases. The application of this method to a model �frustrated� triblock copolymer leads to a phase diagram with a number of new phases. Furthermore, the capability of the method to reproduce experimentally observed structures is demonstrated using the knitting pattern of triblock copolymers.
Guo, Zuojun; Zhang, Guojie; Qiu, Feng; Zhang, Hongdong; Yang, Yuliang; Shi, An-Chang
Purpose: To describe the limitations of Fourier-domain optical coherence tomography (OCT) in imaging common conjunctival and corneal pathology. Materials and Methods: Retrospective, single-center case series of 40 patients with conjunctival and cornea pathology. Results: Fourier-domain OCT imaged laser in situ keratomileusis (LASIK) flaps in detail, including its relation to other corneal structures and abnormalities. Similarly, in infectious or degenerative corneal disorders, Fourier-domain OCT successfully showed the extent of infiltration or material deposition, which appeared as hyper-reflective areas. In cases with pterygium, the underlying cornea could not be imaged. All cases of common conjunctival pathologies, such as nevus or pinguecula, were successfully imaged in detail. Nevi, scleritis, pterygium, pinguecula, and subconjunctival hemorrhage were hyper-reflective lesions, while cysts and lymphangiectasia were hyporeflective. The details of the underlying sclera were not uniformly imaged in conjunctival pathologies. Fourier-domain OCT imaged the trabeculectomy bleb in detail, whereas the details of structures of the anterior chamber angle were not routinely visualized in all cases. Conclusions: Light scatter through vascularized, densely inflamed, or thick lesions limits the imaging capabilities of Fourier-domain anterior segment OCT. PMID:25100905
Demirci, Hakan; Steen, Daniel W.
Cardiac motion tracking using CINE harmonic phase (HARP) magnetic resonance imaging
This article introduces a new image processing technique for rapid analysis of tagged cardiac magnetic resonance image sequences. The method uses isolated spectral peaks in SPAMM- tagged magnetic resonance images, which contain information about cardiac motion. The inverse Fourier transform of a spectral peak is a complex image whose calculated angle is called a harmonic phase (HARP) image. It is
Nael F. Osman; William S. Kerwin; Elliot R. McVeigh; Jerry L. Prince
A Highly Efficient Lucky Imaging Algorithm: Image Synthesis Based on Fourier Amplitude Selection
NASA Astrophysics Data System (ADS)
We propose a new algorithm dramatically enhancing the efficiency of the lucky imaging technique for AO-corrected images in the visible range. It is achieved by a selection based on the relative strength of signal for each spatial frequency in the Fourier domain, making a more efficient use of information contained in each frame. Realistic simulations show that our algorithm allows us to reach the diffraction limit in the visible range on an AO-equipped 8 m telescope and enhances the Strehl ratio of an AO long exposure by a factor of up to 4. It outperforms the lucky imaging technique at an equivalent selection ratio. The fraction of selected data in simulation is also boosted from two to eight times for a given Strehl-ratio performance.
Garrel, Vincent; Guyon, Olivier; Baudoz, Pierre
The transport of intensity equation (TIE) has long been recognized as a quantitative method for phase retrieval and phase contrast imaging. However, it is shown that the most widely accepted fast Fourier transform (FFT) based solutions do not provide an exact solution to the TIE in general. The root of the problem lies in the so-called "Teague's assumption" that the transverse flux is considered to be a conservative field, which cannot be satisfied for a general object. In this work, we present the theoretical analysis of the phase discrepancy owing to the Teague's assumption, and derive the necessary and sufficient conditions for the FFT-based solution to coincide with the exact phase. An iterative algorithm is then proposed aiming to compensate such phase discrepancy in a simple yet effective manner. PMID:25090531
Zuo, Chao; Chen, Qian; Huang, Lei; Asundi, Anand
The Fourier series approach to investigate phase-locking behaviors of the sinoatrial node cell
NASA Astrophysics Data System (ADS)
Phase-locking behaviors are closely relevant to arrhythmias. The traditional approach to investigate the subject is the phase resetting map, which interprets phase-locking via the view point of nonlinear mapping dynamics. In the present paper, the Fourier series approach is developed. By decomposing the traces of the transmembrane voltage and total ionic current into Fourier series, the effect of the stimulations on the oscillation period could be revealed analytically. The following well-studied problems are reinvestigated: i) the phase resetting property of the cell; ii) the bifurcations between phase-locking zones; iii) phase-locking behaviors of a pair of coupled cells, which is relevant to behaviors of the sinoatrial node tissue. The work may provide a deeper insight into the subject and a simple method to predict sinoatrial node phase-locking dynamics.
Huang, X.; Liu, X.; Mi, Y.
Differential phase contrast tomosynthesis imaging
NASA Astrophysics Data System (ADS)
The development of differential phase contrast imaging using conventional x-ray tubes has spurred great interest in the medical imaging community. It has been shown to provide higher contrast than absorption imaging in some cases, and in this work we translate these advantages to tomosynthesis imaging. A general framework for reconstruction of images from differential phase contrast projection data has been proposed and implemented using data from a grating-based x-ray phase contrast tomosynthesis system. Reconstructed tomosynthesis images from differential phase contrast data are shown, using both a direct backprojection (BP) technique and a filtered backprojection (FBP) reconstruction method. From the results it is seen that phase contrast tomosynthesis can separate superimposed phase objects while providing complementary information to absorption tomosynthesis.
Li, Ke; Bevins, Nicholas; Zambelli, Joseph; Chen, Guang-Hong
One consequence of the self-amplified stimulated emission process used to generate x rays in free electron lasers (FELs) is the intrinsic shot-to-shot variance in the wavelength and temporal coherence. In order to optimize the results from diffractive imaging experiments at FEL sources, it will be advantageous to acquire a means of collecting coherence and spectral information simultaneously with the diffraction pattern from the sample we wish to study. We present a holographic mask geometry, including a grating structure, which can be used to extract both temporal and spatial coherence information alongside the sample scatter from each individual FEL shot and also allows for the real space reconstruction of the sample using either Fourier transform holography or iterative phase retrieval.
Flewett, Samuel; Eisebitt, Stefan
The data processing pipelines for the Herschel/SPIRE imaging Fourier transform spectrometer
NASA Astrophysics Data System (ADS)
We present an update to the data processing pipelines that generate calibrated spectral data products from the Spectral and Photometric Imaging Receiver (SPIRE), one of three scientific instruments onboard the European Space Agency's Herschel Space Observatory launched on 14 May 2009. The pipelines process telemetry from SPIRE's imaging Fourier Transform Spectrometer (FTS) taken in point source, jiggle- and raster-map observing modes, producing calibrated spectra in low-, medium-, high-, and mixed low- and high-spectral resolution. While the order and algorithms of the data processing modules in the spectrometer pipelines remain for the most part unchanged compared to their pre-launch status, some improvements and optimizations have been realized through the analysis of data from the performance verification and science demonstration phases of the mission. The data processing pipelines for the SPIRE FTS as of the beginning of the routine phase of the Herschel mission are presented in their entirety, with more detailed descriptions reserved for those elements that have changed since launch, in particular the first- and second-level correction steps for glitches, the step that corrects for clipped samples, and the process by which Level-1 spectral data are converted to Level-2 products. In addition, we discuss some of the challenging aspects still faced by the automated processing pipelines, such as the removal of the contributions from the Herschel telescope and SPIRE instrument, and the relative spectral response correction and flux conversion steps.
Fulton, Trevor R.; Baluteau, Jean-Paul; Bendo, George; Benielli, Dominique; Gastaud, Rene; Griffin, Matt; Guest, Steve; Imhof, Peter; Lim, Tanya L.; Lu, Nanyao; Naylor, David A.; Panuzzo, Pasquale; Polehampton, Edward; Schwartz, Arnold; Surace, Christian; Swinyard, Bruce M.; Xu, Kevin
An Effective Approach for Iris Recognition Using Phase-Based Image Matching
This paper presents an efficient algorithm for iris recognition using phase-based image matching - an image matching technique using phase components in 2D discrete Fourier transforms (DFTs) of given images. Experimental evaluation using the CASIA iris image databases (versions 1.0 and 2.0) and Iris challenge evaluation (ICE) 2005 database clearly demonstrates that the use of phase components of iris images
Kazuyuki Miyazawa; Koichi Ito; Takafumi Aoki; Koji Kobayashi; Hiroshi Nakajima
Reducing Number of Elements of Transducer Arrays in Fourier Image ConstructionMethod
Reducing Number of Elements of Transducer Arrays in Fourier Image ConstructionMethod Jian-yu Lu- lationship between the quality of images constructed with the Founer method and the element spacing of array trans- ducers. In the study, two linear arrays were used. Effec- tive larger element spaclngs were
Lu, Jian-yu
The data processing pipelines for the Herschel\\/SPIRE imaging Fourier transform spectrometer
We present an update to the data processing pipelines that generate calibrated spectral data products from the Spectral and Photometric Imaging Receiver (SPIRE), one of three scientific instruments onboard the European Space Agency's Herschel Space Observatory launched on 14 May 2009. The pipelines process telemetry from SPIRE's imaging Fourier Transform Spectrometer (FTS) taken in point source, jiggle- and raster-map observing
Trevor R. Fulton; Jean-Paul Baluteau; Dominique Benielli; Peter Davis-Imhof; Bruce M. Swinyard; Steve Guest; Christian Surace; Dave Clements; Pasquale Panuzzo; David A. Naylor; Edward Polehampton; Arnold Schwartz; Kevin Xu
The data processing pipeline for the Herschel\\/SPIRE Imaging Fourier Transform Spectrometer
We present the data processing pipeline to generate calibrated data products from the Spectral and Photometric Imaging Receiver (SPIRE) imaging Fourier Transform Spectrometer. The pipeline processes telemetry from SPIRE point source, jiggle- and raster-map observations, producing calibrated spectra in low-, medium-, high-, and mixed low- and high- resolution modes. The spectrometer pipeline shares some elements with the SPIRE photometer pipeline,
Trevor R. Fultona; David A. Naylorb; Peter Davis-Imhofa; M. Swinyarde; Tanya L. Lime; Nanyao Luh; France Marseille
Compressive Sensing Ensemble Average Propagator Estimation via 1 Spherical Polar Fourier Imaging
a dense 3D sampling. Q-Ball Imaging (QBI) [16, 9] and Diffusion Orientation Transform (DOT) [13] are firstname.lastname@example.com Abstract. In diffusion MRI (dMRI) domain, many High Angular Resolution Diffusion Imaging (HARDI) methods) was proposed to represent diffusion signal using Spherical Polar Fourier (SPF) ba- sis without specific
Boyer, Edmond
To simplify the reconstruction calculation of a large-aperture digital hologram we propose a novel Fourier-transformation reconstruction algorithm. When the reconstructed wave is the same as or similar to the reference wave, the higher-order phase term of reconstruction can be compensated for. For example, the variation between the higher-order phase term and the aperture angle with a different field of view in in-line phase-shifting digital holography is analyzed. PMID:15035488
Lu, Xiaoxu; Zhang, Yimo; Zhong, Liyun; Luo, Yinlong; She, Canling
Pfaff equation and Fourier analysis to phase extraction from an interferogram with carrier frequency
NASA Astrophysics Data System (ADS)
In the phase extraction techniques, one of the steps most used is to calculate the phase unwrapping from the wrapped phase, which is generally obtained via the inverse tangent function. With the idea to avoid this process, in the present manuscript a method based in the solution of the Pfaff equations is proposed. It is shown that the Pfaff equation is formed with the phase gradient and an auxiliary vector. The phase gradient is obtained from an interference patron with carrier frequency by applying the Fourier transform method and the partial derivatives. In the present manuscript, mathematical analysis, numerical simulation, and the phase extraction of some experimental interferograms are shown.
Lara-Cortez, Francisco; Meneses-Fabian, Cruz; Rodriguez-Zurita, Gustavo
Alpha-rooting method of color image enhancement by discrete quaternion Fourier transform
NASA Astrophysics Data System (ADS)
This paper presents a novel method for color image enhancement based on the discrete quaternion Fourier transform. We choose the quaternion Fourier transform, because it well-suited for color image processing applications, it processes all 3 color components (R,G,B) simultaneously, it capture the inherent correlation between the components, it does not generate color artifacts or blending , finally it does not need an additional color restoration process. Also we introduce a new CEME measure to evaluate the quality of the enhanced color images. Preliminary results show that the ?-rooting based on the quaternion Fourier transform enhancement method out-performs other enhancement methods such as the Fourier transform based ?-rooting algorithm and the Multi scale Retinex. On top, the new method not only provides true color fidelity for poor quality images but also averages the color components to gray value for balancing colors. It can be used to enhance edge information and sharp features in images, as well as for enhancing even low contrast images. The proposed algorithms are simple to apply and design, which makes them very practical in image enhancement.
Grigoryan, Artyom M.; Agaian, Sos S.
Phase-sensitive swept source OCT imaging of the human retina with a VCSEL light source
Despite the challenges in achieving high phase stability, Doppler swept source / Fourier domain OCT has advantages of less fringe washout and faster imaging speeds compared to spectral / Fourier domain detection. This manuscript demonstrates swept source OCT with a VCSEL light source at 400kHz sweep rate for phase-sensitive Doppler imaging, measuring pulsatile total retinal blood flow with high sensitivity and phase stability. A robust, simple, and computationally efficient phase stabilization approach for phase-sensitive swept source imaging is also presented. PMID:23381430
Choi, WooJhon; Potsaid, Benjamin; Jayaraman, Vijaysekhar; Baumann, Bernhard; Grulkowski, Ireneusz; Liu, Jonathan J.; Lu, Chen D.; Cable, Alex E.; Huang, David; Duker, Jay S.; Fujimoto, James G.
Spectrum multiplexing and coherent-state decomposition in Fourier ptychographic imaging
Information multiplexing is important for biomedical imaging and chemical sensing. In this paper, we report a microscopy imaging technique, termed state-multiplexed Fourier ptychography (FP), for information multiplexing and coherent-state decomposition. Similar to a typical Fourier ptychographic setting, we use an array of light sources to illuminate the sample from different incident angles and acquire corresponding low-resolution images using a monochromatic camera. In the reported technique, however, multiple light sources are lit up simultaneously for information multiplexing, and the acquired images thus represent incoherent summations of the sample transmission profiles corresponding to different coherent states. We show that, by using the state-multiplexed FP recovery routine, we can decompose the incoherent mixture of the FP acquisitions to recover a high-resolution sample image. We also show that, color-multiplexed imaging can be performed by simultaneously turning on R/G/B LEDs for data acquisition...
Dong, Siyuan; Nanda, Pariksheet; Zheng, Guoan
Optically-detected magnetic resonance using Nitrogen Vacancy (NV) color centres in diamond is a leading modality for nanoscale magnetic field imaging, as it provides single electron spin sensitivity, three-dimensional resolution better than 1 nm, and applicability to a wide range of physical and biological samples under ambient conditions. To date, however, NV-diamond magnetic imaging has been performed using real space techniques, which are either limited by optical diffraction to 250 nm resolution or require slow, point-by-point scanning for nanoscale resolution, e.g., using an atomic force microscope, magnetic tip, or super-resolution optical imaging. Here we introduce an alternative technique of Fourier magnetic imaging using NV-diamond. In analogy with conventional magnetic resonance imaging (MRI), we employ pulsed magnetic field gradients to phase-encode spatial information on NV electronic spins in wavenumber or k-space followed by a fast Fourier transform to yield real-space images with nanoscale resolution, wide field-of-view (FOV), and compressed sensing speed-up.
K. Arai; C. Belthangady; H. Zhang; N. Bar-Gill; S. J. DeVience; P. Cappellaro; A. Yacoby; R. L. Walsworth
Data processing pipeline for a time-sampled imaging Fourier transform spectrometer
ABSTRACT Imaging Fourier transform spectrometers ,(IFTS) are becoming ,the preferred systems ,for remote ,sensing spectral imaging applications because of their ability to provide, simultaneously, both high spatial and spectral resolution images ofa scene. IFTS can be operated in either step-and-integrate or rapid-scan modes, where it is common practice to sample interferograms at equal optical path difference intervals. The step-and-integrate mode
David A. Naylor; Trevor R. Fulton; Peter W. Davis; Ian M. Chapman; Brad G. Gom; D Locke; John V. Lindner; Nathan E. Nelson-fitzpatrick; Margaret K. Tahic; Gary R. Davis
An Imaging Fourier Transform Spectrometer for the Next Generation Space Telescope
Due to its simultaneous deep imaging and integral field spectroscopic capability, an Imaging Fourier Transform Spectrograph (IFTS) is ideally suited to the Next Generation Space Telescope (NGST) mission, and offers opportunities for tremendous scientific return in many fields of astrophysical inquiry. We describe the operation and quantify the advantages of an IFTS for space applications. The conceptual design of the Integral Field Infrared Spectrograph (IFIRS) is a wide field (5'.3 x 5'.3) four-port imaging Michelson interferometer.
James R. Graham
Phase correction in piezoelectric photoacoustic Fourier transform infrared spectroscopy of mica
Piezoelectric photoacoustic IR spectra of mica are obtained using a Fourier transform IR spectrometer and lead zirconate titanate (PZT) as a detector. The spectra exhibit negative intensities and transmission like bands, instead of more conventional absorption bands generally observed with a gas- microphone cell. Correct spectra of mica\\/PZT are calculated only when the interferogram phase is constrained to the first
S. L. Zhang; Kirk H. Michaelian; James A. Burt
Estimation of motions in color image sequences using hypercomplex fourier transforms.
Although the motion estimation problem has been extensively studied, most of the proposed estimation approaches deal mainly with monochrome videos. The most usual way to apply them also in color image sequences is to process each color channel separately. A different, more sophisticated approach is to process the color channels in a "holistic" manner using quaternions, as proposed by Ell and Sangwine. In this paper, we extend standard spatiotemporal Fourier-based approaches to handle color image sequences, using the hypercomplex Fourier transform. We show that translational motions are manifested as energy concentration along planes in the hypercomplex 3-D Fourier domain and we describe a methodology to estimate the motions, based on this property. Furthermore, we compare the three-channels-separately approach with our approach and we show that the computational effort can be reduced by a factor of 1/3, using the hypercomplex Fourier transform. Also, we propose a simple, accompanying method to extract the moving objects in the hypercomplex Fourier domain. Our experimental results on synthetic and natural images verify our arguments throughout the paper. PMID:19095528
Alexiadis, Dimitrios S; Sergiadis, George D
Estimation of phase derivatives using discrete chirp-Fourier-transform-based method.
Estimation of phase derivatives is an important task in many interferometric measurements in optical metrology. This Letter introduces a method based on discrete chirp-Fourier transform for accurate and direct estimation of phase derivatives, even in the presence of noise. The method is introduced in the context of the analysis of reconstructed interference fields in digital holographic interferometry. We present simulation and experimental results demonstrating the utility of the proposed method. PMID:19684794
Gorthi, Sai Siva; Rastogi, Pramod
Terahertz holography for imaging amplitude and phase objects.
A non-monochromatic THz Quantum Cascade Laser and an uncooled micro-bolometer array detector with VGA resolution are used in a beam-splitter free holographic set-up to measure amplitude and phase objects in transmission. Phase maps of the diffraction pattern are retrieved using the Fourier transform carrier fringe method; while a Fresnel-Kirchhoff back propagation algorithm is used to reconstruct the complex object image. A lateral resolution of 280 �m and a relative phase sensitivity of about 0.5 rad are estimated from reconstructed images of a metallic Siemens star and a polypropylene test structure, respectively. Simulations corroborate the experimental results. PMID:24977861
Hack, Erwin; Zolliker, Peter
Several factors, including spatial and temporal coherence of the electron microscope, specimen movement, recording medium, and scanner optics, contribute to the decay of the measured Fourier amplitude in electron image intensities. We approximate the combination of these factors as a single Gaussian envelope function, the width of which is described by a single experimental B-factor. We present an improved method
Ali Saad; Steven J. Ludtke; Joanita Jakana; Frazer J. Rixon; Hiro Tsuruta; Wah Chiu
NASA Astrophysics Data System (ADS)
In this work, we developed a full-range Fourier domain optical coherence tomography (FD-OCT) imaging probe with a magnetic-driven resonant fiber cantilever. A galvanometer-driven reference mirror provides a linear phase modulation to each M-scan/B-scan frame to enable complex conjugate-free, full-range FD-OCT imaging. A fiber cantilever inside the probe is driven by a low-voltage miniature magnetic transducer. The fiber cantilever scans at its resonant frequency synchronized to the phase modulation induced by the reference mirror. Using a CCD line-scan camera-based spectrometer, we demonstrated real-time full-range FD-OCT at 34 frame/s (1024 pixel lateral � 2048 pixel axial).
Zhang, Kang; Huang, Yong; Kang, Jin U.
Gaseous effluent monitoring and identification using an imaging Fourier transform spectrometer
We are developing an imaging Fourier transform spectrometer for chemical effluent monitoring. The system consists of a 2-D infrared imaging array in the focal plane of a Michelson interferometer. Individual images are coordinated with the positioning of a moving mirror in the Michelson interferometer. A three dimensional data cube with two spatial dimensions and one interferogram dimension is then Fourier transformed to produce a hyperspectral data cube with one spectral dimension and two spatial dimensions. The spectral range of the instrument is determined by the choice of optical components and the spectral range of the focal plane array. Measurements in the near UV, visible, near IR, and mid-IR ranges are possible with the existing instrument. Gaseous effluent monitoring and identification measurements will be primarily in the ``fingerprint`` region of the spectrum, ({lambda} = 8 to 12 {mu}m). Initial measurements of effluent using this imaging interferometer in the mid-IR will be presented.
Carter, M.R.; Bennett, C.L.; Fields, D.J.; Hernandez, J.
Phase imaging of buried structures
We report magnetic and electrostatic phase imaging of micron-scale metallic lines covered with 525nm of SiO2. Magnetic force microscopy (MFM) has been used to image a buried current-carrying line, to resolve its micron-scale defects, and characterize current crowding around those defects. The MFM phase signal from this structure compares quantitatively to the MFM signal from the same structure, taken prior
R. Yongsunthon; P. J. Rous; A. Stanishevsky; K. Siegrist; E. D. Williams
Image Stability Requirements For a Geostationary Imaging Fourier Transform Spectrometer (GIFTS)
NASA Technical Reports Server (NTRS)
A Geostationary Imaging Fourier Transform Spectrometer (GIFTS) has been selected for the NASA New Millennium Program (NMP) Earth Observing-3 (EO-3) mission. Our paper will discuss one of the key GIFTS measurement requirements, Field of View (FOV) stability, and its impact on required system performance. The GIFTS NMP mission is designed to demonstrate new and emerging sensor and data processing technologies with the goal of making revolutionary improvements in meteorological observational capability and forecasting accuracy. The GIFTS payload is a versatile imaging FTS with programmable spectral resolution and spatial scene selection that allows radiometric accuracy and atmospheric sounding precision to be traded in near real time for area coverage. The GIFTS sensor combines high sensitivity with a massively parallel spatial data collection scheme to allow high spatial resolution measurement of the Earth's atmosphere and rapid broad area coverage. An objective of the GIFTS mission is to demonstrate the advantages of high spatial resolution (4 km ground sample distance - gsd) on temperature and water vapor retrieval by allowing sampling in broken cloud regions. This small gsd, combined with the relatively long scan time required (approximately 10 s) to collect high resolution spectra from geostationary (GEO) orbit, may require extremely good pointing control. This paper discusses the analysis of this requirement.
Bingham, G. E.; Cantwell, G.; Robinson, R. C.; Revercomb, H. E.; Smith, W. L.
Image stability requirements for a Geostationary Imaging Fourier Transform Spectrometer (GIFTS)
NASA Astrophysics Data System (ADS)
A geostationary Imaging Fourier Transform Spectrometer (GIFTS) has been selected for the NASA New Millennium Program (NMP) Earth Observing-3 (EO-3) mission. Our paper will discuss one of the key GIFTS NMP mission is designed to demonstrate new and emerging sensor and data processing technologies with the goal of making revolutionary improvements in meteorological observational capability and forecasting accuracy. The GIFTS payload is a versatile imaging FTS with programmable spectral resolution and spatial scene selection that allows radiometric accuracy and atmospheric sounding precision to be traded in near real time for area coverage. The GIFTS sensor combines high sensitivity with a massively parallel spatial data collection scheme to allow high spatial resolution measurement of the Earth's atmosphere and rapid broad area coverage. An objective of the GIFTS mission is to demonstrate the advantages of high spatial resolution on temperature and water vapor retrieval by allowing sampling in broken cloud regions. This small gsd, may require extremely good pointing control. This paper discusses the analysis of this requirement.
Bingham, Gail E.; Cantwell, G.; Robinson, Richard C.; Revercomb, Henry E.; Smith, William L.
NASA Astrophysics Data System (ADS)
Optical coherence tomography (OCT) is a noninvasive imaging modality generating cross sectional and volumetric images of translucent samples. In Fourier domain OCT (FD OCT), the depth profile is calculated by a fast Fourier transformation of the interference spectrum, providing speed and SNR advantage and thus making FD OCT well suitable in biomedical applications. The interference spectrum can be acquired spectrally resolved in spectral domain OCT or time-resolved in optical frequency domain imaging (OFDI). Since OCT images still suffer from motion artifacts, especially under in vivo conditions, increased depth scan rates are required. Therefor, the principle of Fourier domain mode locking has been presented by R. Huber et al. circumventing the speed limitations of conventional FD OCT systems. In FDML lasers, a long single mode fiber is inserted in the ring resonator of the laser resulting in an optical round trip time of a few microseconds. Sweeping the wavelength synchronously by a tunable Fabry-Perot filter can provide wavelength sweeps with repetition rates up to a few MHz used for OFDI. Imaging of subpleural lung tissue for investigation of lung dynamics and its elastic properties is a further biomedical application demanding high-speed OCT imaging techniques. For the first time, the visualization of subpleural alveolar structures of a rabbit lung is presented by the use of an FDML-based OCT system enabling repetition rates of 49.5 kHz and 122.6 kHz, respectively.
Kirsten, Lars; Walther, Julia; Cimalla, Peter; Gaertner, Maria; Meissner, Sven; Koch, Edmund
High-resolution fluorescence imaging via pattern-illuminated Fourier ptychography.
Fluorescence microscopy plays a vital role in modern biological research and clinical diagnosis. Here, we report an imaging approach, termed pattern-illuminated Fourier ptychography (FP), for fluorescence imaging beyond the diffraction limit of the employed optics. This approach iteratively recovers a high-resolution fluorescence image from many pattern-illuminated low-resolution intensity measurements. The recovery process starts with one low-resolution measurement as the initial guess. This initial guess is then sequentially updated by other measurements, both in the spatial and Fourier domains. In the spatial domain, we use the pattern-illuminated low-resolution images as intensity constraints for the sample estimate. In the Fourier domain, we use the incoherent optical-transfer-function of the objective lens as the object support constraint for the solution. The sequential updating process is then repeated until the sample estimate converges, typically for 5-20 times. Different from the conventional structured illumination microscopy, any unknown pattern can be used for sample illumination in the reported framework. In particular, we are able to recover both the high-resolution sample image and the unknown illumination pattern at the same time. As a demonstration, we improved the resolution of a conventional fluorescence microscope beyond the diffraction limit of the employed optics. The reported approach may provide an alternative solution for structure illumination microscopy and find applications in wide-field, high-resolution fluorescence imaging. PMID:25321288
Dong, Siyuan; Nanda, Pariksheet; Shiradkar, Radhika; Guo, Kaikai; Zheng, Guoan
We present a numerical approach to extract the dispersion mismatch in ultrahigh-resolution Fourier domain optical coherence tomography (OCT) imaging of the retina. The method draws upon an analogy with a Shack-Hartmann wavefront sensor. By exploiting mathematical similarities between the expressions for aberration in optical imaging and dispersion mismatch in spectral / Fourier domain OCT, Shack-Hartmann principles can be extended from the two-dimensional paraxial wavevector space (or the x-y plane in the spatial domain) to the one-dimensional wavenumber space (or the z-axis in the spatial domain). For OCT imaging of the retina, different retinal layers, such as the retinal nerve fiber layer (RNFL), the photoreceptor inner and outer segment junction (IS/OS), or all the retinal layers near the retinal pigment epithelium (RPE) can be used as point source beacons in the axial direction, analogous to point source beacons used in conventional two-dimensional Shack-Hartman wavefront sensors for aberration characterization. Subtleties regarding speckle phenomena in optical imaging, which affect the Shack-Hartmann wavefront sensor used in adaptive optics, also occur analogously in this application. Using this approach and carefully suppressing speckle, the dispersion mismatch in spectral / Fourier domain OCT retinal imaging can be successfully extracted numerically and used for numerical dispersion compensation to generate sharper, ultrahigh-resolution OCT images. PMID:23187353
Choi, WooJhon; Baumann, Bernhard; Swanson, Eric A.; Fujimoto, James G.
Fourier-domain beamforming: the path to compressed ultrasound imaging.
Sonography techniques use multiple transducer elements for tissue visualization. Signals received at each element are sampled before digital beamforming. The sampling rates required to perform high-resolution digital beamforming are significantly higher than the Nyquist rate of the signal and result in considerable amount of data that must be stored and processed. A recently developed technique, compressed beamforming, based on the finite rate of innovation model, compressed sensing (CS), and Xampling ideas, allows a reduction in the number of samples needed to reconstruct an image comprised of strong reflectors. A drawback of this method is its inability to treat speckle, which is of significant importance in medical imaging. Here, we build on previous work and extend it to a general concept of beamforming in frequency. This allows exploitation of the low bandwidth of the ultrasound signal and bypassing of the oversampling dictated by digital implementation of beamforming in time. By using beamforming in frequency, the same image quality is obtained from far fewer samples. We next present a CS technique that allows for further rate reduction, using only a portion of the beamformed signal's bandwidth. We demonstrate our methods on in vivo cardiac data and show that reductions up to 1/28 of the standard beamforming rates are possible. Finally, we present an implementation on an ultrasound machine using sub-Nyquist sampling and processing. Our results prove that the concept of sub-Nyquist processing is feasible for medical ultrasound, leading to the potential of considerable reduction in future ultrasound machines' size, power consumption, and cost. PMID:25073133
Chernyakova, Tanya; Eldar, Yonina
Sub-wavelength Coherent Imaging of a Pure-Phase Object with Thermal Light
We report, for the first time, the observation of sub-wavelength coherent image of a pure phase object with thermal light,which represents an accurate Fourier transform. We demonstrate that ghost-imaging scheme (GI) retrieves amplitude transmittance knowledge of objects rather than the transmitted intensities as the HBT-type imaging scheme does.
Minghui Zhang; Qing Wei; Xia Shen; Yongfeng Liu; Honglin Liu; Yanfeng Bai; Shensheng Han
[The meteorological satellite spectral image registration based on Fourier-Mellin transform].
The meteorological satellite spectral image is an effective tool for researches on meteorological science and environmental remote sensing science. Image registration is the basis for the application of the meteorological satellite spectral image data. In order to realize the registration of the satellite image and the template image, a new registration method based on the Fourier-Mellin transform is presented in this paper. Firstly, we use the global coastline vector map data to build a landmark template, which is a reference for the meteorological satellite spectral image registration. Secondly, we choose infrared sub-image of no cloud according to the cloud channel data, and extract the edges of the infrared image by Sobel operator. Finally, the affine transform model parameters between the landmark template and the satellite image are determined by the Fourier-Mellin transform, and thus the registration is realized. The proposed method is based on the curve matching in essence. It needs no feature point extraction, and can greatly simplify the process of registration. The experimental results using the infrared spectral data of the FY-2D meteorological satellite show that the method is robust and can reach a high speed and high accuracy. PMID:23705469
Wang, Liang; Liu, Rong; Zhang, Li; Duan, Fu-Qing; L�, Ke
NASA Astrophysics Data System (ADS)
Large-aperture segmented primary mirror will be widely used in next-generation space-based and ground-based telescopes. The effects of intersegment gaps, obstructions, position and figure errors of segments, which are all involved in the pupil plane, on the image quality metric should be analyzed using diffractive imaging theory. Traditional Fast Fourier Transform (FFT) method is very time-consuming and costs a lot of memory especially in dealing with large pupil-sampling matrix. A Partial Fourier Transform (PFT) method is first proposed to substantially speed up the computation and reduce memory usage for diffractive imaging analysis. Diffraction effects of a 6-meter segmented mirror including 18 hexagonal segments are simulated and analyzed using PFT method. The influence of intersegment gaps and position errors of segments on Strehl ratio is quantitatively analyzed by computing the Point Spread Function (PSF). By comparing simulation results with theoretical results, the correctness and feasibility of PFT method is confirmed.
Dong, Bing; Qin, Shun; Hu, Xinqi
Novel Algorithm for Polar and Spherical Fourier Analysis on Two and Three Dimensional Images
NASA Astrophysics Data System (ADS)
Polar and Spherical Fourier analysis can be used to extract rotation invariant features for image retrieval and pattern recognition tasks. They are demonstrated to show superiorities comparing with other methods on describing rotation invariant features of two and three dimensional images. Based on mathematical properties of trigonometric functions and associated Legendre polynomials, fast algorithms are proposed for multimedia applications like real time systems and large multimedia databases in order to increase the computation speed. The symmetric points are computed simultaneously. Inspired by relative prime number theory, systematic analysis are given in this paper. Novel algorithm is deduced that provide even faster speed. Proposed method are 9-15% faster than previous work. The experimental results on two and three dimensional images are given to illustrate the effectiveness of the proposed method. Multimedia signal processing applications that need real time polar and spherical Fourier analysis can be benefit from this work.
Yang, Zhuo; Kamata, Sei-Ichiro
Phase correction in piezoelectric photoacoustic Fourier transform infrared spectroscopy of mica
NASA Astrophysics Data System (ADS)
Piezoelectric photoacoustic IR spectra of mica are obtained using a Fourier transform IR spectrometer and lead zirconate titanate (PZT) as a detector. The spectra exhibit negative intensities and transmission like bands, instead of more conventional absorption bands generally observed with a gas- microphone cell. Correct spectra of mica/PZT are calculated only when the interferogram phase is constrained to the first and fourth quadrants, similar to the case in differential spectroscopy where negative intensities occur.
Zhang, S. L.; Michaelian, Kirk H.; Burt, James A.
Implementation of the digital phase vocoder using the fast Fourier transform
This paper discusses a digital formulation of the phase vocoder, an analysis-synthesis system providing a parametric representation of a speech waveform by its short-time Fourier transform. Such a system is of interest both for data-rate reduction and for manipulating basic speech parameters. The system is designed to be an identity system in the absence of any parameter modifications. Computational efficiency
M. Portnoff
Instrumental phase-based method for Fourier transform spectrometer measurements processing.
Phase correction is a critical procedure for most space-borne Fourier transform spectrometers (FTSs) whose accuracy (owing to often poor signal-to-noise ratio, SNR) can be jeopardized from many uncontrollable environmental conditions. This work considers the phase correction in an FTS working under significant temperature change during the measurement and affected by mechanical disturbances. The implemented method is based on the identification of an instrumental phase that is dependent on the interferometer temperature and on the extraction of a linear phase component through a least-squares approach. The use of an instrumental phase parameterized with the interferometer temperature eases the determination of the linear phase that can be extracted using only a narrow spectral region selected to be immune from disturbances. The procedure, in this way, is made robust against phase errors arising from instrumental effects, a key feature to reduce the disturbances through spectra averaging. The method was specifically developed for the Mars IR Mapper spectrometer, that was designed for operation onboard a rover on the Mars surface; the validation was performed using ground and in-flight measurements of the Fourier transform IR spectrometer planetary Fourier spectrometer, onboard the MarsExpress mission. The symmetrization has been exploited also for the spectra calibration, highlighting the issues deriving from the cases of relevant beamsplitter emission. The applicability of this procedure to other instruments is conditional to the presence in the spectra of at least one spectral region with a large SNR along with a negligible (or known) beamsplitter emission. For the PFS instrument, the processing of data with relevant beamsplitter emission has been performed exploiting the absorption carbon dioxide bands present in Martian spectra. PMID:21509063
Saggin, Bortolino; Scaccabarozzi, Diego; Tarabini, Marco
Among several techniques, phase shifting interferometry can be implemented with a grating used as a beam divider to attain several interference patterns around each diffraction order. Because each pattern has to show a different phase-shift, a suitable shifting technique must be employed. Phase gratings are attractive to perform the former task due to their higher diffraction efficiencies. But as is very well known, the Fourier coefficients of only-phase gratings are integer order Bessel functions of the first kind. The values of these real-valued functions oscillate around zero, so they can adopt negative values, thereby introducing phase shifts of pi at certain diffraction orders. Because this almost trivial fact seems to have been overlooked in the literature regarding its practical implications, in this communication such phase shifts are stressed in the description of interference patterns obtained with grating interferometers. These patterns are obtained by placing two windows in the object plane of a 4f system with a sinusoidal grating/grid in the Fourier plane. It is shown that the corresponding experimental observations of the fringe modulation, as well as the corresponding phase measurements, are all in agreement with the proposed description. A one-shot phase shifting interferometer is finally proposed taking into account these properties after proper incorporation of modulation of polarization. PMID:19582027
Toto-Arellano, Noel-Ivan; Rodriguez-Zurita, Gustavo; Meneses-Fabian, Cruz; Vazquez-Castillo, Jose F
Remote Fourier transform-infrared spectral imaging system with hollow-optical fiber bundle.
A spectral imaging system consisting of a Fourier transform-infrared spectrometer, a high-speed infrared camera, and a bundle of hollow-optical fibers transmitting infrared radiation images was constructed. Infrared transmission spectra were obtained by carefully processing multiple interferograms taken by high-speed photography. Infrared spectral images of a variety of samples captured by the system were measured. We successfully detected existence maps of the oil and fat of biological samples by mapping the transmission of specific wavelengths in the spectrum. PMID:23052066
Huang, Chenhui; Kino, Saiko; Katagiri, Takashi; Matsuura, Yuji
A LABORATORY DEMONSTRATION OF HIGH-RESOLUTION HARD X-RAY AND GAMMA-RAY IMAGING USING FOURIER-TRANSFORM A laboratory imaging system has been developed to study the use of Fourier-transform techniques in high. We discuss considerations for the design of a Fourier-transform imager and describe
Prince, Thomas A.
Identification of Earthquake Induced Damage Areas Using Fourier Transform and SPOT HRVIR Pan Images.
A devastating earthquake with a magnitude of Mw 7.4 occurred on the North Anatolian Fault Zone (NAFZ) of Turkey on August 17, 1999 at 00:01:39 UTC (3:01 a.m. local time). The aim of this study is to propose a new approach to automatically identify earthquake induced damage areas which can provide valuable information to support emergency response and recovery assessment procedures. This research was conducted in the Adapazari inner city, covering a 3 � 3 km area, where 11,373 buildings collapsed as a result of the earthquake. SPOT high resolution visible infrared (HRVIR) Pan images obtained before (25 June 1999) and after (4 October 1999) the earthquake were used in the study. Five steps were employed to conduct the research and these are: (i) geometric and radiometric correction of satellite images, (ii) Fast Fourier Transform (FFT) of pre- and post-earthquake images and filtering the images in frequency domain, (iii) generating difference image using Inverse Fast Fourier Transform (IFFT) pre- and post- earthquake images, (iv) application of level slicing to difference image to identify the earthquake-induced damages, (v) accuracy assessment of the method using ground truth obtained from a 1/5,000 scale damage map. The total accuracy obtained in the research is 80.19 %, illustrating that the proposed method can be successfully used to automatically identify earthquake-induced damage areas. PMID:22573966
Sertel, Elif
The work presented in this paper details the design and performance characteristics of a new hyperspectral visible imaging technique. Rather than using optical filters or a dispersing element, this design implements Fourier transform spectroscopy to achieve spectral discrimination. One potentially powerful application of this new technology is the non-destructive analysis and authentication of written and printed documents. Document samples were prepared using red, blue, and black inks. The samples were later altered using a different ink of the same color. While the alterations are undetectable to the naked eye, the alterations involving the blue and black inks were easily detected when the spectrally resolved images were viewed. Analysis of the sample using the red inks was unsuccessful. A 2004 series 20 US dollars bill was imaged to demonstrate the application to document authentication. The results argue that counterfeit detection and quality control during printing are plausible applications of Fourier transform hyperspectral visible imaging. All of the images were subjected to fuzzy c-means cluster analysis in an effort to objectively analyze and automate image analysis. Our results show that cluster analysis can distinguish image features that have remarkably similar visible transmission spectra. PMID:16925917
Brauns, Eric B; Dyer, R Brian
Identification of Earthquake Induced Damage Areas Using Fourier Transform and SPOT HRVIR Pan Images
A devastating earthquake with a magnitude of Mw 7.4 occurred on the North Anatolian Fault Zone (NAFZ) of Turkey on August 17, 1999 at 00:01:39 UTC (3:01 a.m. local time). The aim of this study is to propose a new approach to automatically identify earthquake induced damage areas which can provide valuable information to support emergency response and recovery assessment procedures. This research was conducted in the Adapazari inner city, covering a 3 � 3 km area, where 11,373 buildings collapsed as a result of the earthquake. SPOT high resolution visible infrared (HRVIR) Pan images obtained before (25 June 1999) and after (4 October 1999) the earthquake were used in the study. Five steps were employed to conduct the research and these are: (i) geometric and radiometric correction of satellite images, (ii) Fast Fourier Transform (FFT) of pre- and post-earthquake images and filtering the images in frequency domain, (iii) generating difference image using Inverse Fast Fourier Transform (IFFT) pre- and post- earthquake images, (iv) application of level slicing to difference image to identify the earthquake-induced damages, (v) accuracy assessment of the method using ground truth obtained from a 1/5,000 scale damage map. The total accuracy obtained in the research is 80.19 %, illustrating that the proposed method can be successfully used to automatically identify earthquake-induced damage areas. PMID:22573966
Sertel, Elif
Quantum Pseudo-fractional Fourier Transform and its application to quantum phase estimation
- In this paper we present a method to compute the coefficients of the fractional Fourier transform (FrFT) on a quantum computer using quantum gates of polynomial complexity of the order O(n^3). The FrFt, a generalization of the DFT, has wide applications in signal processing and is particularly useful to implement the Pseudopolar and Radon transforms. Even though the FrFT is a non-unitary operation, to develop its quantum counterpart, we develop a unitary operator called the quantum Pseudo-fraction Fourier Transform (QPFrFT) in a higher-dimensional Hilbert space, in order to computer the coefficients of the FrFT. In this process we develop a unitary operator denoted U by which is an essential step to implement the QPFrFT. We then show the application of the operator U in the problem of quantum phase estimation.
Srinivas V. Parasa; K. Eswaran
A truncated gaussian method based on Fourier transforms is proposed to generate periodic 3D porous structure from a 2D image of the sample. This technique improves a previous method developed by Quiblier [Quiblier, J.A., 1984. A new three-dimensional modeling technique for studying porous media. J. Colloid Interface Sci 98, 84�102] and Adler et al. [Adler, P.M., Jacquin, C.G., Quiblier, J.A.,
Z. R. Liang; C. P. Fernandes; F. S. Magnani; P. C. Philippi
Effect of the fringe visibility on spectrum SNR of Fourier transform imaging spectrometer
NASA Astrophysics Data System (ADS)
The principle of Fourier transform spectrometer is based on the relationship of Fourier-Transform between interferogram and spectrum. The spectral information of Fourier transform imaging spectrometer (FTIS) reconstructed from raw interferogram by data processing. So there are two kinds of signal-to-noise ratio (SNR) to evaluate instrument performance, one regarding interferogram and the other regarding reconstructed spectrum. Because the raw interferogram is intuitive, the interferogram SNR is studied usually. On the contrary, the spectrum SNR is studied less because of the complexity of the data processing from interferogram to spectrum. The research about the effect of the interference fringe visibility on the spectrum SNR is especially few. This paper present a research work on the relations between the interference fringe visibility and the spectrum SNR. Firstly, the reduction of fringe visibility caused by imaging lens defocus was analyzed. Secondly, the changes of the average spectrum signal and noise caused by the reduction of fringe visibility were calculated. For average spectrum signal, the math deductions are done base on Fourier transform theory. The average noise with different input signal optic-electrons number are simulated. the results show that the average spectrum signal is directly proportional to the fringe visibility, and the effect of fringe visibility on the noise related to signal can be ignorable. Finally, In order to demonstrate above results, the imaging experiment was done with white-light source, using LASIS (Large aperture static imaging spectrometer) based on Sagnac Interferometer. The average spectrum SNRs under different fringe visibility are calculated and analyzed. The experimental results show that: the average spectrum SNRs increase from 42.7 to 62.4.along with the fringe visibility increasing from 0.5051 to 0.687. the reconstructed spectrum SNR is directly proportional to the fringe visibility. As a result, the interferogram fringe visibility can be used to estimate the reconstructed spectrum SNR, and evaluate the performance of FTIS before data processing.
Wang, Shuang; Bin, Xiangli; Jing, Juanjuan; Pi, Haifeng
NASA Technical Reports Server (NTRS)
Examples are presented of applications of a fast Fourier transform algorithm to analyze time series of images of Normalized Difference Vegetation Index values. The results obtained for a case study on Zambia indicated that differences in vegetation development among map units of an existing agroclimatic map were not significant, while reliable differences were observed among the map units obtained using the Fourier analysis.
Menenti, M.; Azzali, S.; Verhoef, W.; Van Swol, R.
Fourier transform imaging of impurities in the unit cells of crystals: Mn in GaAs
NASA Astrophysics Data System (ADS)
The lattice sites of Mn in ferromagnetic (Ga,Mn)As thin films were imaged using the x-ray standing wave technique. The model-free images, obtained straightforwardly by Fourier inversion, disclose immediately that the Mn mostly substitutes the Ga with a small fraction residing on minority sites. The images further reveal variations in the Mn concentrations of the different sites upon post-growth treatments. Subsequent model refinement based on the directly reconstructed images resolves with high precision the complete Mn site distributions. It is found that post-growth annealing increases the fraction of substitutional Mn at the expense of interstitial Mn whereas hydrogenation has little influence on the Mn site distribution. Our study offers an element-specific high-resolution imaging approach for accurately determining the detailed site distributions of dilute concentrations of atoms in crystals.
Lee, T.-L.; Bihler, C.; Schoch, W.; Limmer, W.; Daeubler, J.; Thie�, S.; Brandt, M. S.; Zegenhagen, J.
A depth resolved hyperspectral imaging spectrometer can provide depth resolved imaging both in the spatial and the spectral domain. Images acquired through a standard imaging Fourier transform spectrometer do not have the depth-resolution. By post processing the spectral cubes (x, y, ?) obtained through a Sagnac interferometer under uniform illumination and structured illumination, spectrally resolved images with depth resolution can be recovered using structured light illumination algorithms such as the HiLo method. The proposed scheme is validated with in vitro specimens including fluorescent solution and fluorescent beads with known spectra. The system is further demonstrated in quantifying spectra from 3D resolved features in biological specimens. The system has demonstrated depth resolution of 1.8 ?m and spectral resolution of 7 nm respectively. PMID:25360367
Choi, Heejin; Wadduwage, Dushan; Matsudaira, Paul T; So, Peter T C
A depth resolved hyperspectral imaging spectrometer can provide depth resolved imaging both in the spatial and the spectral domain. Images acquired through a standard imaging Fourier transform spectrometer do not have the depth-resolution. By post processing the spectral cubes (x, y, ?) obtained through a Sagnac interferometer under uniform illumination and structured illumination, spectrally resolved images with depth resolution can be recovered using structured light illumination algorithms such as the HiLo method. The proposed scheme is validated with in vitro specimens including fluorescent solution and fluorescent beads with known spectra. The system is further demonstrated in quantifying spectra from 3D resolved features in biological specimens. The system has demonstrated depth resolution of 1.8 ?m and spectral resolution of 7 nm respectively. PMID:25360367
Choi, Heejin; Wadduwage, Dushan; Matsudaira, Paul T.; So, Peter T.C.
High-resolution Fourier-transform infrared chemical imaging with multiple synchrotron beams
Conventional Fourier-transform infrared (FTIR) microspectroscopic systems are limited by an inevitable trade-off between spatial resolution, acquisition time, signal-to-noise ratio (SNR) and sample coverage. We present an FTIR imaging approach that substantially extends current capabilities by combining multiple synchrotron beams with wide-field detection. This advance allows truly diffraction-limited high-resolution imaging over the entire mid-infrared spectrum with high chemical sensitivity and fast acquisition speed while maintaining high-quality SNR. PMID:21423192
Nasse, Michael J; Walsh, Michael J; Mattson, Eric C; Reininger, Ruben; Kajdacsy-Balla, Andre; Macias, Virgilia; Bhargava, Rohit; Hirschmugl, Carol J
This invention permits retinal images to be acquired at high speed and with unprecedented resolution in three dimensions (4.times.4.times.6 .mu.m). The instrument achieves high lateral resolution by using adaptive optics to correct optical aberrations of the human eye in real time. High axial resolution and high speed are made possible by the use of Fourier-domain optical coherence tomography. Using this system, we have demonstrated the ability to image microscopic blood vessels and the cone photoreceptor mosaic.
Olivier, Scot S. (Livermore, CA); Werner, John S. (Davis, CA); Zawadzki, Robert J. (Sacramento, CA); Laut, Sophie P. (Pasedena, CA); Jones, Steven M. (Livermore, CA)
Realization of Fourier transform imaging spectrometer based on all-reflective optics
NASA Astrophysics Data System (ADS)
We present our latest research development of the all-reflective Fourier transform imaging spectrometer based on the principle of wavefront-splitting interference. The optical configuration of this system includes a set of Fresnel's double mirrors and a number of other reflective telescopes or mirrors. The major advantages of this system includs higher optical throughput, larger spectral bandwidth, and less chromatic aberration as compared with conventinal chromatic-despersion imaging spectrometer . In this paper ,the optical principle and the prototype device of our system are introduced, and the latest experimental results from our prototype device are presented.
Liao, Ningfang; Wu, Wenmin; Cui, Deqi; Tian, Lixun; Tan, Boneng
NASA Astrophysics Data System (ADS)
This paper addresses the problem of multidimensional signal reconstruction from generalized samples in fractional Fourier domain including the deterministic case and the stochastic case. The generalized sampling expansion is investigated for the case where the fractional bandlimited input depends on N real variable, i.e., f(t)=f(t1,⋯,tN) and is used as a common input to a parallel bank of m independent N dimensional linear fractional Fourier filters H?,k(u), k=1,⋯,m. For the deterministic input, the input is assumed to have its N dimensional fractional Fourier transform bandlimited to the frequency rang |ui|??i, for i=1,⋯,N. If m, the number of fractional Fourier filters, is written as a product of positive integers in the form m=m1m2⋯mN, and if the fractional bandlimited input f(t) is processed by fractional Fourier filter H?,k(u)resulting m outputs gk(t), then f(t) can be reconstructed in terms of the samples gk(nT), each output being sampled at the identical rates of ?1 csc ?/m1?, ?2 csc ?/m2?,⋯, ?N csc ?/mN? samples/second in t1,⋯,tN respectively. This contrasts with the rates of ?1 csc ?/?, ?2 csc ?/?,⋯, ?N csc ?/? in t1,⋯,tN needed for reconstruction of the unfiltered input f(t). Input sampling expansions in terms of samples of the output filters are given for both deterministic and stochastic inputs, the generalized sampling expansion for random input having the same form as for the deterministic case but interpreted in the mean-square sense. Our formulation and results are general and include derivative sampling and periodic nonuniform sampling in the fractional Fourier domain for multidimensional signals as special case. Finally, the potensional application of the multidimensional generalized sampling is presented to show the advantage of the theory. Especially, the application of multidimensional generalized sampling in the context of the image scaling about image super-resolution is also discussed. The simulation results of image scaling are also presented.
Wei, Deyun; Li, Yuanmin
NASA Astrophysics Data System (ADS)
The high-energy laser (HEL) lethality community needs for enhanced laser weapons systems requires a better understanding of a wide variety of emerging threats. In order to reduce the dimensionality of laser-materials interaction it is necessary to develop novel predictive capabilities of these events. The objective is to better understand the fundamentals of laser lethality testing by developing empirical models from hyperspectral imagery, enabling a robust library of experiments for vulnerability assessments. Emissive plumes from laser irradiated fiberglass reinforced polymers (FRP), poly(methyl methacrylate) (PMMA) and porous graphite targets were investigated primarily using a mid-wave infrared (MWIR) imaging Fourier transform spectrometer (FTS). Polymer and graphite targets were irradiated with a continuous wave (cw) fiber lasers. Data was acquired with a spectral resolution of 2 cm-1 and spatial resolution as high as 0.52 mm2 per pixel. Strong emission from H2O, CO, CO2 and hydrocarbons were observed in the MWIR between 1900-4000 cm-1. A single-layer radiative transfer model was developed to estimate spatial maps of temperature and column densities of CO and CO2 from the hyperspectral imagery of the boundary layer plume. The spectral model was used to compute the absorption cross sections of CO and CO2, using spectral line parameters from the high temperature extension of the HITRAN. Also, spatial maps of gas-phase temperature and methyl methacrylate (MMA) concentration were developed from laser irradiated carbon black-pigmented PMMA at irradiances of 4-22 W/cm2. Global kinetics interplay between heterogeneous and homogeneous combustion kinetics are shown from experimental observations at high spatial resolutions. Overall the boundary layer profile at steady-state is consistent with CO being mainly produced at the surface by heterogeneous reactions followed by a rapid homogeneous combustion in the boundary layer towards buoyancy.
Acosta, Roberto I.
Holographic image encryption using random phase mask
NASA Astrophysics Data System (ADS)
Random phase mask has been widely used for increasing security of holographic image encryption. This works study effect of random phase mask on quality of decrypted images through computer simulations. The results show that the image quality depends of the position of the phase mask with respect to the input image.
Widjaja, Joewono
Universal and special keys based on phase-truncated Fourier transform
We propose a novel optical asymmetric cryptosystem based on a phase-truncated Fourier transform. Two decryption keys independent of each other are generated. They are referred to as universal key and special key, respectively. Each of them can be used for decryption independently in absence of the other. The universal key is applicable to decrypt any ciphertext encoded by the same encryption key, but with poor legibility. On the contrary, the special key is adequate for legible decryption, but only valid for one ciphertext corresponding to the specified plaintext. A set of simulation results show the interesting performance of two types of de cryption keys. PMID:25339784
Qin, Wan; Peng, Xiang; Meng, Xiangfeng; Gao, Bruce
Manipulating stored images with phase imprinting at low light levels.
Coherent manipulation of stored images is performed at low light levels based on enhanced cross-Kerr nonlinearity in a four-level N-type electromagnetically induced transparency (EIT) system. Using intensity masks in the signal pulse, quadratic phase shifts with low nonlinear absorption can be efficiently imprinted on the Fraunhofer diffraction patterns already stored in the EIT system. Fast-Fourier-transform-based numerical simulations clearly demonstrate that the far-field images of the retrieved probe light can be flexibly modulated by applying different signal fields. Our studies could help advance the goals of nonlinear all-optical processing for spatial information coherently stored in EIT systems. PMID:22825156
Zhao, L; Yang, Guojian; Duan, Wenhui
NASA Astrophysics Data System (ADS)
Polarization properties of anterior segment disorders of the eyes were evaluated using a fiber-based polarization-sensitive Fourier-domain optical coherence tomography (PS-FD-OCT). The light source is a superluminescent diode with a central wavelength of 840 nm, and bandwidth of 50 nm. Synchronized two line-CCD cameras allow high-speed measurement of birefringence of retina (line rate 27.7 kHz), and the sensitivity of the system is 100.7 dB. Birefringence of the optical fiber was compensated with the surface reflection. Phase retardation and orientation of the birefringence were measured with a Jones matrix based algorithm. The phase retardation map of the anterior segment was visualized as a depth-resolved three-dimensional image in addition to the conventional cross sectional OCT image. In the polarization image of the normal eye, striking polarization change was observed at the sclera. In the eyes with necrotizing scleritis, abnormal thinning of the sclera could be confirmed. In the eyes after filtering glaucoma surgery, polarization change in the conjunctiva due to the abnormal fibrosis after surgery could be observed. PS-FD-OCT is an effective tool to understand the polarization properties of different types of pathological changes in the anterior segment of the eye.
Miura, Masahiro; Yamanari, Masahiro; Watabnabe, Yuji; Mori, Hideki; Iwasaki, Takuya; Elsner, Ann E.; Kawana, Keisuke; Oshika, Tetsuro; Yatagai, Toyohiko; Yasuno, Yoshiaki
Iterative Image Reconstruction for PROPELLER-MRI using the NonUniform Fast Fourier Transform
Purpose To investigate an iterative image reconstruction algorithm using the non-uniform fast Fourier transform (NUFFT) for PROPELLER (Periodically Rotated Overlapping parallEL Lines with Enhanced Reconstruction) MRI. Materials and Methods Numerical simulations, as well as experiments on a phantom and a healthy human subject were used to evaluate the performance of the iterative image reconstruction algorithm for PROPELLER, and compare it to that of conventional gridding. The trade-off between spatial resolution, signal to noise ratio, and image artifacts, was investigated for different values of the regularization parameter. The performance of the iterative image reconstruction algorithm in the presence of motion was also evaluated. Results It was demonstrated that, for a certain range of values of the regularization parameter, iterative reconstruction produced images with significantly increased SNR, reduced artifacts, for similar spatial resolution, compared to gridding. Furthermore, the ability to reduce the effects of motion in PROPELLER-MRI was maintained when using the iterative reconstruction approach. Conclusion An iterative image reconstruction technique based on the NUFFT was investigated for PROPELLER MRI. For a certain range of values of the regularization parameter the new reconstruction technique may provide PROPELLER images with improved image quality compared to conventional gridding. PMID:20578028
Tamhane, Ashish A.; Anastasio, Mark A.; Gui, Minzhi; Arfanakis, Konstantinos
Higher-dimensional phase imaging
NASA Astrophysics Data System (ADS)
Traditional full-field interferometric techniques (speckle, moir�, holography etc) provide 2-D phase images, which encode the surface deformation state of the object under test. Over the past 15 years, the use of additional spatial or temporal dimensions has been investigated by a number of research groups. Early examples include the measurement of 3-D surface profiles by temporally-varying projected fringe patterns, and dynamic speckle interferometry. More recently (the past 5 years) a family of related techniques (Wavelength Scanning Interferometry, Phase Contrast Spectral Optical Coherence Tomography (OCT), and Tilt Scanning Interferometry) has emerged that provides the volume deformation state of the object. The techniques can be thought of as a marriage between the phase sensing capabilities of Phase Shifting Interferometry and the depth-sensing capabilities of OCT. Finally, in the past 12 months a technique called Hyperspectral Interferometry has been proposed in which absolute optical path distributions are obtained in a single shot through the spectral decomposition of a white light interferogram, and for which the additional dimension therefore corresponds to the illumination wavenumber. An overview of these developments, and the related issue of robust phase unwrapping of noisy 3-D wrapped phase volumes, is presented in this paper.
Huntley, Jonathan M.
Optical phase imaging using a synthetic aperture phase retrieval technique.
Optical phase imaging enables visualization of transparent samples, numerical refocusing, and other computational processing. Typically phase is measured quantitatively using interferometric techniques such as digital holography. Researchers have demonstrated image enhancement by synthetic aperture imaging based on digital holography. In this work we introduce a novel imaging technique that implements synthetic aperture imaging using phase retrieval, a non-interferometric technique. Unlike digital holography, phase retrieval obviates the need for a reference arm and provides a more compact, less expensive, and more stable experimental setup. We call this technique synthetic aperture phase retrieval. PMID:24787826
Lee, Dennis J; Weiner, Andrew M
Imaging phased telescope array study
NASA Technical Reports Server (NTRS)
The problems encountered in obtaining a wide field-of-view with large, space-based direct imaging phased telescope arrays were considered. After defining some of the critical systems issues, previous relevant work in the literature was reviewed and summarized. An extensive list was made of potential error sources and the error sources were categorized in the form of an error budget tree including optical design errors, optical fabrication errors, assembly and alignment errors, and environmental errors. After choosing a top level image quality requirment as a goal, a preliminary tops-down error budget allocation was performed; then, based upon engineering experience, detailed analysis, or data from the literature, a bottoms-up error budget reallocation was performed in an attempt to achieve an equitable distribution of difficulty in satisfying the various allocations. This exercise provided a realistic allocation for residual off-axis optical design errors in the presence of state-of-the-art optical fabrication and alignment errors. Three different computational techniques were developed for computing the image degradation of phased telescope arrays due to aberrations of the individual telescopes. Parametric studies and sensitivity analyses were then performed for a variety of subaperture configurations and telescope design parameters in an attempt to determine how the off-axis performance of a phased telescope array varies as the telescopes are scaled up in size. The Air Force Weapons Laboratory (AFWL) multipurpose telescope testbed (MMTT) configuration was analyzed in detail with regard to image degradation due to field curvature and distortion of the individual telescopes as they are scaled up in size.
Harvey, James E.
NASA Astrophysics Data System (ADS)
Measuring retinal hemodynamics in response to flicker stimulus is important for investigating pathophysiology in small animal models of diabetic retinopathy, because a reduction in the hyperemic response is thought to be one of the earliest changes in diabetic retinopathy. In this study, we investigated functional imaging of retinal hemodynamics in response to flicker stimulus in the rat retina using an ultrahigh speed spectral / Fourier domain OCT system at 840nm with an axial scan rate of 244kHz. At 244kHz the nominal axial velocity range that could be measured without phase wrapping was +/-37.7mm/s. Pulsatile total retinal arterial blood flow as a function of time was measured using an en face Doppler approach where a 200?m � 200?m area centered at the central retinal artery was repeatedly raster scanned at a volume acquisition rate of 55Hz. Three-dimensional capillary imaging was performed using speckle decorrelation which has minimal angle dependency compared to other angiography techniques based on OCT phase information. During OCT imaging, a flicker stimulus could be applied to the retina synchronously by inserting a dichroic mirror in the imaging interface. An acute transient increase in total retinal blood flow could be detected. At the capillary level, an increase in the degree of speckle decorrelation in capillary OCT angiography images could also be observed, which indicates an increase in the velocity of blood at the capillary level. This method promises to be useful for the investigation of small animal models of ocular diseases.
Choi, WooJhon; Baumann, Bernhard; Clermont, Allen C.; Feener, Edward P.; Boas, David A.; Fujimoto, James G.
Slit Function Measurement of An Imaging Spectrograph Using Fourier Transform Techniques
NASA Technical Reports Server (NTRS)
Knowledge of a spectrograph slit function is necessary to interpret the unresolved lines in an observed spectrum. A theoretical slit function can be calculated from the sizes of the entrance slit, the detector aperture when it functions as an exit slit, the dispersion characteristic of the disperser, and the point spread function of the spectrograph. A measured slit function is preferred to the theoretical one for the correct interpretation of the spectral data. In a scanning spectrometer with a single exit slit, the slit function is easily measured. In a fixed grating/or disperser spectrograph, illuminating the entrance slit with a near monochromatic light from a pre-monochrmator or a tunable laser and varying the wavelength of the incident light can measure the slit function. Even though the latter technique had been used successfully for the slit function measurements, it had been very laborious and it would be prohibitive to an imaging spectrograph or a multi-object spectrograph that has a large field of view. We explore an alternative technique that is manageable for the measurements. In the proposed technique, the imaging spectrograph is used as a detector of a Fourier transform spectrometer. This method can be applied not only to an IR spectrograph but also has a potential to a visible/UV spectrograph including a wedge filter spectrograph. This technique will require a blackbody source of known temperature and a bolometer to characterize the interferometer part of the Fourier Transform spectrometer. This pa?er will describe the alternative slit function measurement technique using a Fourier transform spectrometer.
Park, Hongwoo; Swimyard, Bruce; Jakobsen, Peter; Moseley, Harvey; Greenhouse, Matthew
NASA Astrophysics Data System (ADS)
Conventional FTIR spectroscopy and microscopy has been widely used in forensic science. New opportunities exist to obtain rapid chemical images and to enhance the sensitivity of detection of trace materials using attenuated total reflection (ATR) Fourier transform infrared (FTIR) spectroscopy coupled with a focal-plane array (FPA) detector. In this work, the sensitivity of ATR-FTIR spectroscopic imaging using three different kinds of ATR crystals (Ge coupled with an infrared microscope, ZnSe and diamond) and resulting in three different optical arrangements for the detection of model drug particles is discussed. Model systems of ibuprofen and paracetamol particles having a size below 32 micrometers have been prepared by sieving. The sensitivity level in the three different approaches has been compared and it has been found that both micro and macro-ATR imaging methods have proven to be a promising techniques for the identification of concealed drug particles. To demonstrate the power and applicability of FTIR chemical imaging to forensic research, various examples are discussed. This includes investigation of the changes of chemical nature of latent fingerprint residue under controlled conditions of humidity and temperature studied by ATR-FTIR imaging. This study demonstrates the potential of spectroscopic imaging for visualizing the chemical changes of fingerprints.
Ricci, Camilla; Chan, K. L. Andrew; Kazarian, Sergei G.
NASA Astrophysics Data System (ADS)
Image restoration using Wiener and geometric mean filtering is one of the commonly used techniques in image processing applications. In this paper we propose the use of discrete fractional Fourier transform in place of conventional discrete Fourier transform (DFT) in the Wiener and geometric mean filters. The use of discrete fractional Fourier transform (DFrFT) provides us additional degree of freedom in terms of the angle parameter of the transforms which can be exploited for the purpose of image restoration. The proposed restoration filters are applied on both colored and grey images and the simulation results of the proposed technique are presented. The effect of variation of parameters of the transforms and filters are also studied under the presence of noise. It is observed that the results of the conventional Wiener and geometric mean filters are better than the filters using DFrFT except for a specific value of the angle parameter about 0.8.
Sharma, K. K.; Mittal, Priya
The objective of this study was to evaluate the application of Fourier transform infrared (FTIR) spectroscopy for detecting diffuse axonal injury (DAI) in a mouse model. Brain tissues from DAI mouse model were prepared with H&E, silver, and ?-amyloid precursor protein (?-APP) immunohistochemistry stains and were also studied with FTIR. The infrared spectrum images showed high absorption of amide II in the subcortical white matter of the experimental mouse brain, while there was no obvious expression of amide II in the control mouse brain. The areas with high absorption of amide II were in the same distribution as the DAI region confirmed by the silver and ?-APP studies. The result suggests that high absorption of amide II correlates with axonal injury. The use of FTIR imaging allows the biochemical changes associated with DAI pathologies to be detected in the tissues, thus providing an important adjunct method to the current conventional pathological diagnostic techniques. PMID:24147828
Yang, Tiantong; He, Guanglong; Zhang, Xiang; Chang, Lin; Zhang, Haidong; Ripple, Mary G; Fowler, David R; Li, Ling
4D imaging of embryonic chick hearts by streak-mode Fourier domain optical coherence tomography
NASA Astrophysics Data System (ADS)
Recently, we developed the streak-mode Fourier domain optical coherence tomography (OCT) technique in which an area-scan camera is used in a streak-mode to record the OCT spectrum. Here we report the application of this technique to in ovo imaging HH18 embryonic chick hearts with an ultrahigh speed of 1,016,000 axial scans per second. The high-scan rate enables the acquisition of high temporal resolution 2D datasets (1,000 frames per second or 1 ms between frames) and 3D datasets (10 volumes per second), without use of prospective or retrospective gating technique. This marks the first time that the embryonic animal heart has been 4D imaged using a megahertz OCT.
Wang, Rui; Yun, Julie X.; Goodwin, Richard; Markwald, Roger; Borg, Thomas K.; Runyan, Raymond B.; Gao, Bruce
NASA Astrophysics Data System (ADS)
SSG Precision Optronics, Inc. has delivered a silicon carbide (SiC) pointing mirror and telescope for NASA's Geostationary Imaging Fourier Transform Spectrometer (GIFTS) project. The 28 x 45 cm SiC pointing mirror is part of SSG's two-axis gimbaled mirror assembly that will provide object-space pointing and jitter control. The 24 cm aperture telescope is an off-axis afocal three mirror anastigmat that is the collection aperture for the GIFTS instrument. Silicon carbide was selected for the GIFTS pointing mirror and telescope in order to minimize weight, provide athermal optical performance from room temperature to 190 Kelvin, and maintain image quality and line-of-sight stability in the presence of partial or full solar loading (minimizing solar outages). Both subsystems were successfully designed, fabricated, and subjected to testing prior to being delivered to Utah State University's Space Dynamics Laboratory for integration. This paper describes the pointing mirror and telescope design and hardware results.
Schwalm, Mark; Dibiase, Dan; Landry, Dave; Rider, Brian; Ugolini, Virginia
Discovering Ordered Phases of Block Copolymers: A New Fourier-space Approach
NASA Astrophysics Data System (ADS)
A new method to solve the self-consistent field theory of block copolymers is developed. This method is based on the fact that, for any computational boxes with periodic boundary conditions, all spatially varying functions are spanned by the Fourier series determined by the size and shape of the box. This method is well suited for the discovery of ordered structures of block copolymer systems. The symmetry of the ordered structures emerges from the minimization of the free energy density. Application of the technique to diblock copolymers recovers all the previously known ordered structures plus a few new metastable ones. As an example of application, the method is used to construct a phase diagram for a model of frustrated triblock copolymers. A variety of stable or metastable three-dimensional ordered structures are discovered. Furthermore, the capability of the method to reproduce experimentally observed structures is demonstrated by the knitting pattern in triblock copolymers.
Qiu, Feng; Shi, An-Chang; Guo, Zuojun; Zhang, Hongdong; Yang, Yuliang
Group Fourier transform and the phase space path integral for finite dimensional Lie groups
We formulate a notion of group Fourier transform for a finite dimensional Lie group. The transform provides a unitary map from square integrable functions on the group to square integrable functions on a non-commutative dual space. We then derive the first order phase space path integral for quantum mechanics on the group by using a non-commutative dual space representation obtained through the transform. Possible advantages of the formalism include: (1) The transform provides an alternative to the spectral decomposition via representation theory of Lie groups and the use of special functions. (2) The non-commutative dual variables are physically more intuitive, since despite the non-commutativity they are analogous to the corresponding classical variables. The work is expected, among other possible applications, to allow for the metric representation of Lorentzian spin foam models in the context of quantum gravity.
Matti Raasakka
A viscoplastic approach using the Fast Fourier Transform (FFT) method for obtaining local mechanical response is utilized to study microstructure-property relationships in composite materials. Specifically, three-dimensional, two-phase digital materials containing isotropically coarsened particles surrounded by a matrix phase, generated through a Kinetic Monte Carlo Potts model for Ostwald ripening, are used as instantiations in order to calculate the stress and strain rate fields under uniaxial tension. The effects of the morphology of the matrix phase, the volume fraction and the contiguity of particles, and the polycrystallinity of matrix phase, on the stress and strain rate fields under uniaxial tension are examined. It is found that the first moments of the stress and strain rate fields have a different dependence on the particle volume fraction and the particle contiguity from their second moments. The average stresses and average strain rates of both phases and of the overall composite have rather simple relationships with the particle volume fraction whereas their standard deviations vary strongly, especially when the particle volume fraction is high, and the contiguity of particles has a noticeable effect on the mechanical response. It is also found that the shape of stress distribution in the BCC hard particle phase evolves as the volume fraction of particles in the composite varies, such that it agrees with the stress field in the BCC polycrystal as the volume of particles approaches unity. Finally, it is observed that the stress and strain rate fields in the microstructures with a polycrystalline matrix are less sensitive to changes in volume fraction and contiguity of particles.
Lebensohn, Ricardo A [Los Alamos National Laboratory; Lee, Sukbin [CMU; Rollett, Anthony D [CMU
NASA Astrophysics Data System (ADS)
As a solution to iterative CT image reconstruction, first-order methods are prominent for the large-scale capability and the fast convergence rate {O}(1/k^2). In practice, the CT system matrix with a large condition number may lead to slow convergence speed despite the theoretically promising upper bound. The aim of this study is to develop a Fourier-based scaling technique to enhance the convergence speed of first-order methods applied to CT image reconstruction. Instead of working in the projection domain, we transform the projection data and construct a data fidelity model in Fourier space. Inspired by the filtered backprojection formalism, the data are appropriately weighted in Fourier space. We formulate an optimization problem based on weighted least-squares in the Fourier space and total-variation (TV) regularization in image space for parallel-beam, fan-beam and cone-beam CT geometry. To achieve the maximum computational speed, the optimization problem is solved using a fast iterative shrinkage-thresholding algorithm with backtracking line search and GPU implementation of projection/backprojection. The performance of the proposed algorithm is demonstrated through a series of digital simulation and experimental phantom studies. The results are compared with the existing TV regularized techniques based on statistics-based weighted least-squares as well as basic algebraic reconstruction technique. The proposed Fourier-based compressed sensing (CS) method significantly improves both the image quality and the convergence rate compared to the existing CS techniques.
Choi, Kihwan; Li, Ruijiang; Nam, Haewon; Xing, Lei
As a solution to iterative CT image reconstruction, first-order methods are prominent for the large-scale capability and the fast convergence rate [Formula: see text]. In practice, the CT system matrix with a large condition number may lead to slow convergence speed despite the theoretically promising upper bound. The aim of this study is to develop a Fourier-based scaling technique to enhance the convergence speed of first-order methods applied to CT image reconstruction. Instead of working in the projection domain, we transform the projection data and construct a data fidelity model in Fourier space. Inspired by the filtered backprojection formalism, the data are appropriately weighted in Fourier space. We formulate an optimization problem based on weighted least-squares in the Fourier space and total-variation (TV) regularization in image space for parallel-beam, fan-beam and cone-beam CT geometry. To achieve the maximum computational speed, the optimization problem is solved using a fast iterative shrinkage-thresholding algorithm with backtracking line search and GPU implementation of projection/backprojection. The performance of the proposed algorithm is demonstrated through a series of digital simulation and experimental phantom studies. The results are compared with the existing TV regularized techniques based on statistics-based weighted least-squares as well as basic algebraic reconstruction technique. The proposed Fourier-based compressed sensing (CS) method significantly improves both the image quality and the convergence rate compared to the existing CS techniques. PMID:24840019
Choi, Kihwan; Li, Ruijiang; Nam, Haewon; Xing, Lei
NASA Astrophysics Data System (ADS)
An anti-noise subpixel algorithm of phase-shifting of fundamental frequency was presented based on the phase-shifting of Fourier transform and the anti-noise characteristics of low-frequency part of the phase spectrum of the image. The essence of the algorithm is that the displacement caculation of the image is replaced by the movement caculation of the coordinate, which makes the phase of the fundamental frequency zero under different coordninates when image position changes. Under the circumstances that the image of the CCD autocollimator is polluted by the noises caused by tempreture, the measuring accuracies of the normally-used barycenter, edge detection, Gaussian fitting algorithm and the algorithm presented in this paper were compared. Experiment results show, the subpixel algorithm demonstrated here has the advantages of strong anti-noise ability and high precision. The reliability of the algorithm is also disproved by the peak location of the reconstructed image after the removal of higher harmonics. When applied to the one-dimensional CCD photoelectric autocaollimator used in field conditions, fine linearity and +/-3// measurement accuracy were simutaneously obtained in the whole +/-3600// measurement range when the temperature varies between -400C-600C.
Gao, Min; Bian, Zhenglan; Dong, Zuoren; Ye, Qing; Fang, Zujie; Qu, Ronghui
Conventional histologic methods provide valuable information regarding the physical nature of damage in fatigue-loaded tendons, limited to thin, two-dimensional sections. We introduce an imaging method that characterizes tendon microstructure three-dimensionally and develop quantitative, spatial measures of damage formation within tendons. Rat patellar tendons were fatigue loaded in vivo to low, moderate, and high damage levels. Tendon microstructure was characterized using multiphoton microscopy by capturing second harmonic generation signals. Image stacks were analyzed using Fourier transform-derived computations to assess frequency-based properties of damage. Results showed 3D microstructure with progressively increased density and variety of damage patterns, characterized by kinked deformations at low, fiber dissociation at moderate, and fiber thinning and out-of-plane discontinuities at high damage levels. Image analysis generated radial distributions of power spectral gradients, establishing a "fingerprint" of tendon damage. Additionally, matrix damage was mapped using local, discretized orientation vectors. The frequency distribution of vector angles, a measure of damage content, differed from one damage level to the next. This study established an objective 3D imaging and analysis method for tendon microstructure, which characterizes directionality and anisotropy of the tendon microstructure and quantitative measures of damage that will advance investigations of the microstructural basis of degradation that precedes overuse injuries. PMID:20232150
Fung, David T; Sereysky, Jedd B; Basta-Pljakic, Jelena; Laudier, Damien M; Huq, Rumana; Jepsen, Karl J; Schaffler, Mitchell B; Flatow, Evan L
Discrimination of paper-based kraft tapes using Fourier transform of transmitted light images.
This study focused on two-dimensional fast Fourier transform (2D-FFT) as a new technique for the discrimination of kraft tapes, which is a kind of adhesive packing tape. The 2D power spectrum (2D-PS) obtained by applying 2D-FFT to an image enables us to obtain information about the spatial periodicity, even if the periodicity is invisible within the image. However, in the case of kraft tape, peaks in the 2D-PS are too unclear to determine its periodicity. We developed novel analytical image processes combined with 2D-FFT. 2D-FFT was applied to 50 randomly selected areas in a transmitted light image of kraft tape. The 2D-PSs were calculated from each area without applying a logarithmic transformation, accumulated, and processed by the removal of the area surrounding the center, and finally normalized for visualization. These processes enhanced the peaks and eliminated local variations. Through an intra-roll comparison, the 2D-PSs collected from a roll were similar in the location of the peaks and in their patterns at low frequency area. Using an inter-roll comparison, the 2D-PSs from 50 commercially available brand-name products were classified into 26 groups based on these peaks and patterns. All results demonstrate that this method, which is convenient, rapid, and non-destructive, could be a valuable tool for the identification of kraft tapes. PMID:22341568
Sasaoka, Sara; Saito, Koichi; Higashi, Kenjirou; Limwikrant, Waree; Moribe, Kunikazu; Suzuki, Shinichi; Yamamoto, Keiji
Conventional Fourier transform infrared (FT-IR) spectroscopy and microscopy have been widely used in forensic science. New opportunities exist to obtain chemical images and to enhance the spatial resolution using attenuated total reflection (ATR) FT-IR spectroscopy coupled with a focal-plane array (FPA) detector. In this paper, the sensitivity limits of FT-IR imaging using three different ATR crystals (Ge, ZnSe, and diamond) in three different optical arrangements for the detection of model particles is discussed. Model systems of ibuprofen and paracetamol particles having sizes below 32 mum were studied. The collection of drug particles was achieved with the aid of two different tapes: common adhesive tape and a film of polydimethylsiloxane (PDMS). The surface of the film with collected particles was measured directly via ATR-FT-IR imaging. Since the removal of tape from porous surfaces can be difficult, the application of micro ATR-FT-IR imaging directly to the surface of a newspaper contaminated with particles of model drugs is also discussed. In order to assess the feasibility of the chosen method in a forensic case study, the detection of diacetylmorphine hydrochloride traces in PDMS matrix and the finger surface is investigated. The scenarios considered were that of the detection of evidence collected at a crime scene with the tape lift method and the analysis of the finger of an individual after drug handling. The results show broad implications in the detection of drugs of abuse. PMID:17002827
Ricci, Camilla; Chan, K L Andrew; Kazarian, Sergei G
NASA Astrophysics Data System (ADS)
The Geosynchronous Imaging Fourier Transform Spectrometer (GIFTS) represents a revolutionary step in satellite based remote sensing of atmospheric parameters. Using the combination of a Fourier Transform Spectrometer and Large Area Focal Plane Arrays, GIFTS measures incident infrared radiance with an unprecedented combination of spectral, temporal, and spatial resolution and coverage. In its regional sounding mode, it measures the infrared spectrum every 11 seconds at a spectral resolution of ~0.6 cm-1 in two spectral bands (14.6 to 8.8 ?m, 6.0 to 4.4 ?m) using two 128 � 128 detector arrays. From a geosynchronous orbit, the instrument will have the capability of taking successive measurements of such data to scan desired regions of the globe, from which thermal and gaseous concentration profiles, cloud properties, wind field profiles, and other derived products can be retrieved. Thermal vacuum testing of the GIFTS Engineering Development Unit (EDU) was performed at the Space Dynamics Laboratory in Logan Utah and completed in September 2006. With a focus on spectral characterization of the sensor, analyses of selected thermal vacuum tests are presented here.
Tobin, David C.; Revercomb, Henry E.; Taylor, Joe K.; Best, Fred A.; Knuteson, Robert O.; Smith, William L.; Elwell, John; Cantwell, Greg; Bingham, Gail; Tansock, Joe; Reisse, Robert A.; Zhou, Daniel K.
An approach to the interface of a reverse-phase high-performance liquid chromatograph and a Fourier transform infrared spectrometer has been developed in which the solutes eluting from the column are continuously extracted into dichloromethane. The application of both flow cell a...
NASA Astrophysics Data System (ADS)
We present new data obtained with SpIOMM, the imaging Fourier transform spectrometer attached to the 1.6-m telescope of the Observatoire du Mont-Megantic in Qu�bec. Recent technical and data reduction improvements have significantly increased SpIOMM's capabilities to observe fainter objects or weaker nebular lines, as well as continuum sources and absorption lines, and to increase its modulation efficiency in the near ultraviolet. To illustrate these improvements, we present data on the supernova remnant Cas A, planetary nebulae M27 and M97, the Wolf-Rayet ring nebula M1-67, spiral galaxies M63 and NGC 3344, as well as the interacting pair of galaxies Arp 84.
Drissen, L.; Alarie, A.; Martin, T.; Lagrois, D.; Rousseau-Nepton, L.; Bilodeau, A.; Robert, C.; Joncas, G.; Iglesias-P�ramo, J.
Fast Fourier transforms (FFT) is a basic approach to remote sensing image processing. With the improvement of capacity of remote sensing image capture with the features of hyperspectrum, high spatial resolution and high temporal resolution, how to use FFT technology to efficiently process huge remote sensing image becomes the critical step and research hot spot of current image processing technology. FFT algorithm, one of the basic algorithms of image processing, can be used for stripe noise removal, image compression, image registration, etc. in processing remote sensing image. CUFFT function library is the FFT algorithm library based on CPU and FFTW. FFTW is a FFT algorithm developed based on CPU in PC platform, and is currently the fastest CPU based FFT algorithm function library. However there is a common problem that once the available memory or memory is less than the capacity of image, there will be out of memory or memory overflow when using the above two methods to realize image FFT arithmetic. To address this problem, a CPU and partitioning technology based Huge Remote Fast Fourier Transform (HRFFT) algorithm is proposed in this paper. By improving the FFT algorithm in CUFFT function library, the problem of out of memory and memory overflow is solved. Moreover, this method is proved rational by experiment combined with the CCD image of HJ-1A satellite. When applied to practical image processing, it improves effect of the image processing, speeds up the processing, which saves the time of computation and achieves sound result. PMID:24822428
Yang, Xue; Li, Xue-You; Li, Jia-Guo; Ma, Jun; Zhang, Li; Yang, Jan; Du, Quan-Ye
Effect of transmitting beam position error on the imaging quality of a Fourier telescope
NASA Astrophysics Data System (ADS)
The effect of beam position error on the imaging quality of a Fourier telescope is analyzed in this paper. First, the origin of the transmitting beam position error and the error types are discussed. Second, a numerical analysis is performed. To focus on the transmitting beam position error, other noise sources exclusive of the reconstruction process are neglected. The Strehl ratio is set to be the objective function and the transfer function of the position error is constructed. Based on the numerical model, the features of Strehl ratio reduction caused by position error are deduced. Third, simulations are performed to study the position error effect on the imaging quality. A plot of the Strehl ratio versus the different levels of position errors is obtained and the simulation results validate the numerical model to a certain extent. According to the simulation results, a high value of the transmitting beam position error obviously degrades the imaging quality of the system; thus, it is essential to contain the position error within a relatively low level.
Zhou, Zhi-sheng; Bin, Xiang-Li; Zhang, Wen-xi; Li, Yang; Kong, Xin-xin; Lv, Xiao-yu
NASA Astrophysics Data System (ADS)
Spectral calibration and radiometric calibration is an important part in the data processing of the windowing Fourier transform imaging spectrometer, it can ensure that the spectral curve output from spectrometer are more closely to target spectrum. The main idea of spectral calibration is using a monochromatic source whose wavelength is known, in the same way, radiometric calibration can be achieved by using radiation source whose radiation characteristic is known. In this paper, we propose a set of methods of spectral calibration and radiometric calibration. In order to carry out spectral calibration, we use monocharomator to scan several sample points near the position of every spectral channel of imaging spectrometer, and then we employ Gaussian fitting function to determine the central wavelength and bandwidth of every spectral channel. In order to carry out radiometric calibration, we employ panchromatic light source and integrating sphere, at the position of every spectral channel of imaging spectrometer, we measure the response ability of spectrometer to radiation. The calibration accuracy is carefully analyzed. Experimental results show that calibration accuracy meet the given requirements.
Zhang, Lei; Gao, Jiao Bo; Zhao, Yu Jie; Luo, Yan Ling; Xiao, Xiang Guo; Zhang, Fang
We carry out a comparative analysis on a viewing angle change in Fresnel and Fourier holographic images reconstructed by a tilted plane wave. A tilted plane wave illuminating an on-axis hologram generates a diffractive wave carrying the holographic image in a paraxial region of a new diffraction axis. The reconstructed image in the Fresnel hologram is deformed along the new viewing direction, which is well described as Affine transformation. In the Fourier holographic image, the replica of the image is formed without its deformation when the hologram is placed in the front focal plane of the lens, whereas in the case of a hologram that is located at a distance different from a focal length, image deformation arises. This property is investigated through numerical simulation based on a wide-angle diffraction phenomenon. We also perform a similar interpretation for high-order diffraction images appearing in the sampled Fourier hologram and discuss a method for enlarging the viewing angle of the holographic image. PMID:24922205
Chae, Byung Gyu
NASA Technical Reports Server (NTRS)
Microstructural images may be tone pulse encoded and subsequently Fourier transformed to determine the two-dimensional density of frequency components. A theory is developed relating the density of frequency components to the density of length components. The density of length components corresponds directly to the actual grain size distribution function from which the mean grain shape, size, and orientation can be obtained.
Generazio, E. R.
Despite the challenges in achieving high phase stability, Doppler swept-source/Fourier-domain optical coherence tomography (OCT) has advantages of less fringe washout and faster imaging speeds compared to spectral/Fourier-domain detection. This Letter demonstrates swept-source OCT with a vertical cavity surface-emitting laser light source at 400 kHz sweep rate for phase-sensitive Doppler imaging, measuring pulsatile total retinal blood flow with high sensitivity and phase stability. A robust, simple, and computationally efficient phase stabilization approach for phase-sensitive swept-source imaging is also presented. PMID:23381430
Choi, WooJhon; Potsaid, Benjamin; Jayaraman, Vijaysekhar; Baumann, Bernhard; Grulkowski, Ireneusz; Liu, Jonathan J; Lu, Chen D; Cable, Alex E; Huang, David; Duker, Jay S; Fujimoto, James G
We demonstrate ultrahigh speed swept source/Fourier domain ophthalmic OCT imaging using a short cavity swept laser at 100,000 � 400,000 axial scan rates. Several design configurations illustrate tradeoffs in imaging speed, ...
Potsaid, Benjamin M.
The study of a single BGC823 cell using Fourier transform infrared microspectroscopic imaging
NASA Astrophysics Data System (ADS)
In order to investigate gastric cancer at cellular and sub-cellular level, a single human gastric adenocarcinoma BGC823 cell was studied by an infrared microscope equipped with a focal plane array (FPA) detector. The spectra showed difference between the nucleus and the endoplasmic reticulum (ER) of the BGC823 cell. The peak of v asPO 2- was shifted to a higher wavenumber at the nucleus compared with that at the ER. The height ratios of 2954 cm -1/2922 cm -1 (CH 3/CH 2) and 1088 cm -1/1539 cm -1 (DNA/amide II) of the nucleus were significantly higher than those of the ER. Furthermore, chemical images reveal the intensity distributions of lipids, proteins and DNA of the single BGC823 cell, and the intense absorptions of proteins and DNA were observed in the nuclear region of the cell while the intense absorption of lipids was found in the ER region of the cell. The Fourier transform infrared (FTIR) microspectroscopic imaging result indicates the study of the single gastric cancer cell at sub-cellular level can be beneficial for knowing gastric cancer more which will be of great importance for the study and diagnosis of gastric cancer. The result also suggests that FPA is a useful tool in the study of a single cell and may be a powerful tool for study and diagnosis of gastric cancer.
Wang, Xin; Qi, Zeming; Wang, Shengyi; Liu, Gang; Gao, Helong; Tian, Yangchao
This document is the final report on work performed at Sandia National Laboratories during FY 1992 and 1993 for a Laboratory Directed Research and Development (LDRD) program to look at problems associated with the design and long term operation of a short wavelength imaging Fourier Transform (FT) spectrometer for use in space. In attempts to answer two fundamental questions: is a FT spectrometer with a resolution of 1 cm{sup {minus}1} covering the silicon detector wavelength range of 0.4 to 1.1 microns feasible in a long life space instrument and, if so, is it the best method of obtaining the desired information? Emphasis has been on identifying methods which minimize reliance on precision mechanical alignment and precise velocity control. An important consideration has also been to develop methods which will be compatible with a variety of self-scanning solid state imaging devices. A breadboard instrument was constructed using cube corner retroreflectors and a laser diode position reference. Some preliminary results are reported. This work is primarily intended to act as an aid to engineers at Sandia who wish to pursue the fabrication of a flight qualified instrument. The theoretical parts are intended to be somewhat tutorial in nature to aid the engineer who is not familiar with FT spectroscopy.
Abbink, R.E.
NASA Astrophysics Data System (ADS)
The design and implementation of a compact multiple-image Fourier transform spectrometer (FTS) is presented. Based on the multiple-image FTS originally developed by A. Hirai, the presented device offers significant advantages over his original implementation. Namely, its birefringent nature results in a common-path interferometer which makes the spectrometer insensitive to vibration. Furthermore, it enables the potential of making the instrument ultra-compact, thereby improving the portability of the sensor. The theory of the birefringent FTS is provided, followed by details of its specific embodiment. A laboratory proof of concept of the sensor, designed and developed at the Optical Detection Lab, is also presented. Spectral measurements of laboratory sources are provided, including measurements of light-emitting diodes and gas-discharge lamps. These spectra are verified against a calibrated Ocean Optics USB2000 spectrometer. Other data were collected outdoors and of a rat esophagus, demonstrating the sensor's ability to resolve spectral signatures in both standard outdoor lighting and environmental conditions, as well as in fluorescence spectroscopy.
Kudenov, Michael W.; Banerjee, Bhaskar; Chan, Victoria C.; Dereniak, Eustace L.
Modeled vs. actual performance of the Geosynchronous Imaging Fourier Transform Spectrometer (GIFTS)
NASA Astrophysics Data System (ADS)
The NASA Geosynchronous Imaging Fourier Transform Spectrometer (GIFTS) has been completed as an Engineering Demonstration Unit (EDU) and has recently finished thermal vacuum testing and calibration. The GIFTS EDU was designed to demonstrate new and emerging sensor and data processing technologies with the goal of making revolutionary improvements in meteorological observational capability and forecasting accuracy. The GIFTS EDU includes a cooled (150 K), imaging FTS designed to provide the radiometric accuracy and atmospheric sounding precision required to meet the next generation GOES sounder requirements. This paper discusses a GIFTS sensor response model and its validation during thermal vacuum testing and calibration. The GIFTS sensor response model presented here is a component-based simulation written in IDL with the model component characteristics updated as actual hardware has become available. We discuss our calibration approach, calibration hardware used, and preliminary system performance, including NESR, spectral radiance responsivity, and instrument line shape. A comparison of the model predictions and hardware performance provides useful insight into the fidelity of the design approach.
Cantwell, Gregory W.; Elwell, John D.; Esplin, Roy W.; Esplin, Mark P.; Scott, Deron K.; Zollinger, Lorin J.; Bingham, Gail E.; Revercomb, Henry E.; Smith, William L.; Reisse, Robert A.
NASA Astrophysics Data System (ADS)
The Geosynchronous Imaging Fourier Transform Spectrometer (GIFTS), developed for the NASA New Millennium Program (NMP) Earth Observing-3 (EO-3) mission, has recently completed a series of uplooking atmospheric measurements. The GIFTS development demonstrates a series of new sensor and data processing technologies that can significantly expand geostationary meteorological observational capability. The resulting increase in forecasting accuracy and atmospheric model development utilizing this hyperspectral data is demonstrated by the uplooking data. The GIFTS sensor is an imaging FTS with programmable spectral resolution and spatial scene selection, allowing spectral resolution and area coverage to be traded in near-real time. Due to funding limitations, the GIFTS sensor module was completed as an engineering demonstration unit that can be upgraded to flight quality. This paper reviews the GIFTS system design considerations and the technology utilized to enable a nearly two order performance increase over the existing GOES sounder and shows its capability. While not designed as an operational sensor, GIFTS EDU provides a flexible and accurate testbed for the new products the hyperspectral era will bring. Efforts to find funding to upgrade and demonstrate this amazing sensor in space are continuing.
Bingham, G. E.; Anderson, R. E.; Cantwell, G. W.; Zhou, D. K.; Scott, D. K.; Esplin, R. W.; Hansen, G. B.; Jensen, S. M.; Jensen, M. D.; Brown, S. B.; Zollinger, L. J.; Thurgood, V. A.; Esplin, M. P.; Huppi, R. J.; Revercomb, H. E.; Best, F. A.; Tobin, D. C.; Taylor, J. K.; Knuteson, R. O.; Smith, W. L.; Reisse, R. A.; Hooker, R.
a CW Phased Array Ultrasonic Imaging System
The goal of this work was to build a digitally scanned and focused ultrasonic phased array imaging system. The system was to consist of two piezoelectric transducer arrays containing 128 elements, transmitting and receiving analog electronics, digital phase controllers, system control electronics, external RF signal processing and a computer to be used for control of the imaging system and the
Kenneth Alan Fesler
Phase conjugating lens for image manipulation
In this paper, for the first time, image manipulation using a dual- sided phase conjugated lens is discussed. We demonstrate the ability of the lens to magnify and de-magnify images by changing the frequency of the pump wave. In addition we demonstrate the focusing and displacement capabilities of the lens due to amplitude or phase control of the transmitted field.
Oleksandr Malyuskin; Vincent Fusco
NASA Astrophysics Data System (ADS)
A blue white He-Cd laser composed of three R/G/B component beams in place of He-Ne laser is directly applied to fabricate the optical Fourier transform hologram (OFTH) using the red sensitive silver halide material (SO-253 film) for holography. As a result, the red beams play an important role as the coherent beams in the fabrication of OFTH. A green solid state laser is applied to fabricate the OFTH using the same film for holography. The visual appearance of reconstruted color images caused by He-Cd laser is discussed in contrast to that of an ordinary OFTH which can be made using the He-Ne laser and solid state laser. The visual color effect using the He-Cd laser is checked from the viewpoint of the relative real size and its place in the OFTH, and the visual depth sensation of overlapped ghost images called cross-talk in the Fresnel hologram. The purpose using a commercially available software such as HSL color model is to carry out the intuitive modification of overlapped and deteriorated color images in the digital reconstruction of OFTH and Fresnel hologram.
Iizuka, Masayuki; Kariya, Makoto; Uehara, Shinobu; Nakashima, Yoshio; Takamatsu, Mamoru
We lay the foundations for the construction of analytic expressions for Fourier-domain gravitational waveforms produced by eccentric, inspiraling compact binaries in a post-circular or small-eccentricity approximation. The time-dependent, 'plus' and 'cross' polarizations are expanded in Bessel functions, which are then self-consistently reexpanded in a power series about zero initial eccentricity to eighth order. The stationary-phase approximation is then employed to obtain explicit analytic expressions for the Fourier transform of the post-circular expanded, time-domain signal. We exemplify this framework by considering Newtonian-accurate waveforms, which in the post-circular scheme give rise to higher harmonics of the orbital phase and to amplitude corrections of the Fourier-domain waveform. Such higher harmonics lead to an effective increase in the inspiral mass reach of a detector as a function of the binary's eccentricity e{sub 0} at the time when the binary enters the detector sensitivity band. Using the largest initial eccentricity allowed by our approximations (e{sub 0}<0.4), the mass reach is found to be enhanced up to factors of approximately 5 relative to that of circular binaries for Advanced LIGO, LISA, and the proposed Einstein Telescope at a signal-to-noise ratio of ten. A post-Newtonian generalization of the post-circular scheme is also discussed, which holds the promise to provide 'ready-to-use' Fourier-domain waveforms for data analysis of eccentric inspirals.
Yunes, Nicolas [Department of Physics, Princeton University, Princeton, New Jersey 08544 (United States); Arun, K. G. [McDonnell Center for the Space Sciences, Department of Physics, Washington University, St. Louis, Missouri 63130 (United States); GReCO, Institut d'Astrophysique de Paris, CNRS, Universite Pierre et Marie Curie, 98 bis Boulevard Arago, 75014 Paris (France); LAL, Universite Paris Sud, IN2P3/CNRS, Orsay (France); Berti, Emanuele [Department of Physics and Astronomy, The University of Mississippi, University, Mississippi 38677-1848 (United States); Theoretical Astrophysics 130-33, California Institute of Technology, Pasadena, California 91125 (United States); Will, Clifford M. [McDonnell Center for the Space Sciences, Department of Physics, Washington University, St. Louis, Missouri 63130 (United States); GReCO, Institut d'Astrophysique de Paris, CNRS, Universite Pierre et Marie Curie, 98 bis Boulevard Arago, 75014 Paris (France)
NASA Astrophysics Data System (ADS)
We lay the foundations for the construction of analytic expressions for Fourier-domain gravitational waveforms produced by eccentric, inspiraling compact binaries in a post-circular or small-eccentricity approximation. The time-dependent, �plus� and �cross� polarizations are expanded in Bessel functions, which are then self-consistently reexpanded in a power series about zero initial eccentricity to eighth order. The stationary-phase approximation is then employed to obtain explicit analytic expressions for the Fourier transform of the post-circular expanded, time-domain signal. We exemplify this framework by considering Newtonian-accurate waveforms, which in the post-circular scheme give rise to higher harmonics of the orbital phase and to amplitude corrections of the Fourier-domain waveform. Such higher harmonics lead to an effective increase in the inspiral mass reach of a detector as a function of the binary�s eccentricity e0 at the time when the binary enters the detector sensitivity band. Using the largest initial eccentricity allowed by our approximations (e0<0.4), the mass reach is found to be enhanced up to factors of approximately 5 relative to that of circular binaries for Advanced LIGO, LISA, and the proposed Einstein Telescope at a signal-to-noise ratio of ten. A post-Newtonian generalization of the post-circular scheme is also discussed, which holds the promise to provide �ready-to-use� Fourier-domain waveforms for data analysis of eccentric inspirals.
Yunes, Nicolas; Arun, K. G.; Berti, Emanuele; Will, Clifford M.
Phase Tomography Using Diffraction-Enhanced Imaging
Phase tomography using diffraction-enhanced imaging (DEI) is presented with the observation of a phantom consisting of polyvinyl-chloride tubes and water. The boundary between the tube and water was successfully differentiated in a resultant tomographic image obtained with 0.06-nm synchrotron X rays. The sensitivity of this method is discussed in comparison with an image obtained by conventional X-ray tomography. The spatial and density resolutions achieved by the phase tomography are also discussed.
Koyama, I.; Momose, A. [Department of Advanced Materials Science, Graduate School of Frontier Sciences, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Hamaishi, Y. [Department of Applied Physics, School of Engineering, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan)
NASA Astrophysics Data System (ADS)
The Navy Indian Ocean METOC Imaging (IOMI) mission for the Geostationary Imaging Fourier Transform Spectrometer (GIFTS) will begin in early 2006 for a period of five years. The IOMI-GIFTS will measure Earth's outgoing infrared radiation with spatial (~4 km), temporal (~half hour), and spectral (~0.625 cm-1) resolutions and spectral coverages from longwave (LW, 685 - 1150 cm-1) for temperature profiles and short midwave (SMW, 1650 - 2250 cm-1) for moisture profiles. Retrieval of boundary layer moisture from IOMI-GIFTS with high vertical resolution and accuracy, is a special interest of the Navy, can provide water vapor wind information over the ocean. The characteristics of boundary layer moisture retrievals from IOMI-GIFTS are demonstrated. Both theoretical analysis and a simulation study with a GIFTS forward model developed at UW-Madison show that the contrast between surface air temperature and surface skin temperature has significant impact on the accuracy of boundary layer moisture retrievals. A large contrast (> 5 K) will result in noticeable boundary layer moisture improvement over that with less contrast.
Li, Jun; Huang, Hung-Lung
NASA Astrophysics Data System (ADS)
Myocardial infarction often leads to an increase in deposition of fibrillar collagen. Detection and characterization of this cardiac fibrosis is of great interest to investigators and clinicians. Motivated by the significant limitations of conventional staining techniques to visualize collagen deposition in cardiac tissue sections, we have developed a Fourier transform infrared imaging spectroscopy (FT-IRIS) methodology for collagen assessment. The infrared absorbance band centered at 1338 cm-1, which arises from collagen amino acid side chain vibrations, was used to map collagen deposition across heart tissue sections of a rat model of myocardial infarction, and was compared to conventional staining techniques. Comparison of the size of the collagen scar in heart tissue sections as measured with this methodology and that of trichrome staining showed a strong correlation (R=0.93). A Pearson correlation model between local intensity values in FT-IRIS and immuno-histochemical staining of collagen type I also showed a strong correlation (R=0.86). We demonstrate that FT-IRIS methodology can be utilized to visualize cardiac collagen deposition. In addition, given that vibrational spectroscopic data on proteins reflect molecular features, it also has the potential to provide additional information about the molecular structure of cardiac extracellular matrix proteins and their alterations.
Cheheltani, Rabee; Rosano, Jenna M.; Wang, Bin; Sabri, Abdel Karim; Pleshko, Nancy; Kiani, Mohammad F.
Calibration of the AKARI Far-Infrared Imaging Fourier Transform Spectrometer
The Far-Infrared Surveyor (FIS) onboard the AKARI satellite has a spectroscopic capability provided by a Fourier transform spectrometer (FIS-FTS). FIS-FTS is the first space-borne imaging FTS dedicated to far-infrared astronomical observations. We describe the calibration process of the FIS-FTS and discuss its accuracy and reliability. The calibration is based on the observational data of bright astronomical sources as well as two instrumental sources. We have compared the FIS-FTS spectra with the spectra obtained from the Long Wavelength Spectrometer (LWS) of the Infrared Space Observatory (ISO) having a similar spectral coverage. The present calibration method accurately reproduces the spectra of several solar system objects having a reliable spectral model. Under this condition the relative uncertainty of the calibration of the continuum is estimated to be $\\pm$ 15% for SW, $\\pm$ 10% for 70-85 cm^(-1) of LW, and $\\pm$ 20% for 60-70 cm^(-1) of LW; and the absolute uncertainty is estimated to be +35/-55% for...
Murakami, Noriko; Takahashi, Hidenori; Okada, Yoko; Yasuda, Akiko; Ootsubo, Takafumi; Kaneda, Hidehiro; Matsuo, Hiroshi; Baluteau, Jean-Paul; Davis-Imhof, Peter; Gom, Brad G; Naylor, David A; Zavagno, Annie; Yamamura, Issei; Matsuura, Shuji; Shirahata, Mai; Doi, Yasuo; Nakagawa, Takao; Shibai, Hiroshi
On-orbit calibration of the Geosynchronous Imaging Fourier Transform Spectrometer (GIFTS)
NASA Astrophysics Data System (ADS)
The Geosynchronous Imaging Fourier Transform Spectrometer (GIFTS) sensor has been designed to provide highly accurate radiometric and spectral radiances in order to meet the requirements of remote sensing of atmospheric motion from a geostationary orbit. The GIFTS sensor was developed under NASA New Millenium Program funding to demonstrate the tracking of infrared water vapor features in the atmosphere with high vertical resolution. A calibration concept has been developed for the GIFTS instrument design which meets the top level requirement to measure brightness temperature to better than 1 K. The in-flight radiometric calibration is performed using views of two on-board blackbody sources along with cold space. For the GIFTS design, the spectral calibration is established by the highly stable diode laser used as the reference for interferogram sampling, and verified with comparisons to atmospheric absorption line positions. The status of the GIFTS on-orbit calibration approach is described and accuracy estimates are provided. GIFTS is a collaborative activity among NASA Langley Research Center, Utah State Space Dynamics Laboratory, and the University of Wisconsin Space Science and Engineering Center.
Knuteson, Robert O.; Best, Fred A.; Bingham, Gail E.; Elwell, John D.; Revercomb, Henry E.; Tobin, David C.; Scott, Deron K.; Taylor, Joseph K.; Smith, William L., Sr.
Fuzzy Logic Classification of Imaging Laser Desorption Fourier Transform Mass Spectrometry Data
The fuzzy logic method is applied to classification of mass spectra obtained with an imaging internal source Fourier transform mass spectrometer (I2LD-FTMS). Traditionally, an operator uses the relative abundance of ions with specific mass-to-charge (m/z) ratios to categorize spectra. An operator does this by comparing the spectrum of m/z versus abundance of an unknown sample against a library of spectra from known samples. Automated positioning and acquisition allow the I2LD-FTMS to acquire data from very large grids, which would require classification of up to 3600 spectra per hour to keep pace with the acquisition. The tedious job of classifying numerous spectra generated in an I2LD-FTMS imaging application can be replaced by a fuzzy rule base if the cues an operator uses can be encapsulated. Appropriate methods for assigning fuzzy membership values for inputs (e.g., mass spectrum abundances) and choice of fuzzy inference operators to translate linguistic antecedent into confidence values for the consequence (or in this case the classification) is followed by using the maximum confidence and a necessary minimum threshold for making a crisp decision. This paper also describes a method for gathering statistics on ions, which are not currently used in the rule base, but which may be candidates for making the rule base more accurate and complete or to form new rule bases based on data obtained from known samples. A spatial method for classifying spectra with low membership values, based on neighboring sample classifications, is also presented.
Timothy R. McJunkin; Jill R. Scott
NASA Astrophysics Data System (ADS)
The ultimate remote sensing benefits of the high resolution Infrared radiance spectrometers will be realized with their geostationary satellite implementation in the form of imaging spectrometers. This will enable dynamic features of the atmosphere's thermodynamic fields and pollutant and greenhouse gas constituents to be observed for revolutionary improvements in weather forecasts and more accurate air quality and climate predictions. As an important step toward realizing this application objective, the Geostationary Imaging Fourier Transform Spectrometer (GIFTS) Engineering Demonstration Unit (EDU) was successfully developed under the NASA New Millennium Program, 2000-2006. The GIFTS-EDU instrument employs three focal plane arrays (FPAs), which gather measurements across the long-wave IR (LWIR), short/mid-wave IR (SMWIR), and visible spectral bands. The GIFTS calibration is achieved using internal blackbody calibration references at ambient (260 K) and hot (286 K) temperatures. In this paper, we introduce a refined calibration technique that utilizes Principle Component (PC) analysis to compensate for instrument distortions and artifacts, therefore, enhancing the absolute calibration accuracy. This method is applied to data collected during the GIFTS Ground Based Measurement (GBM) experiment, together with simultaneous observations by the accurately calibrated AERI (Atmospheric Emitted Radiance Interferometer), both simultaneously zenith viewing the sky through the same external scene mirror at ten-minute intervals throughout a cloudless day at Logan Utah on September 13, 2006. The accurately calibrated GIFTS radiances are produced using the first four PC scores in the GIFTS-AERI regression model. Temperature and moisture profiles retrieved from the PC-calibrated GIFTS radiances are verified against radiosonde measurements collected throughout the GIFTS sky measurement period. Using the GIFTS GBM calibration model, we compute the calibrated radiances from data collected during the moon tracking and viewing experiment events. From which, we derive the lunar surface temperature and emissivity associated with the moon viewing measurements.
Tian, Jialin; Smith, William L.; Gazarik, Michael J.
NASA Astrophysics Data System (ADS)
Using numerical simulations, we investigate the realization of self-focusing media using two-dimensional graded photonic crystals and their applications for imaging and non-imaging purposes. The two-dimensional graded photonic crystals consist of spatially varying cylindrical holes drilled in a dielectric host. By controlling the gradient of the refractive index and the thickness of the self-focusing medium, it is possible to obtain either a focusing lens with Fourier transforming capabilities or an imaging lens, which produces inverted images. Non-imaging applications include a simple antenna for directive emission obtained from the focusing lens, whereas a directional cloak is obtained by modifying the imaging lens. Graded photonic crystal based devices work well up to the Bragg frequencies. They are compact, made from lossless dielectrics, and compatible with planar lithographic techniques, so they can find applications in a broad frequency range, even at the optical frequencies.
Vasi?, Borislav; Gaji?, Rado�
Robust phase sensitive inversion recovery imaging
, the acquired complex image is modulated by a spatially varying background phase which makes the retrieval of polarity information non-trivial. Many commercial MR scanners perform magnitude-only reconstruction which, due to loss of polarity information, reduces...
Garach, Ravindra Mahendrakumar
Nonlinear Ultrasonic Phased Array Imaging
NASA Astrophysics Data System (ADS)
This Letter reports a technique for the imaging of acoustic nonlinearity. By contrasting the energy of the diffuse field produced through the focusing of an ultrasonic array by delayed parallel element transmission with that produced by postprocessing of sequential transmission data, acoustic nonlinearity local to the focal point is measured. Spatially isolated wave distortion is inferred without requiring interrogation of the wave at the inspection point, thereby allowing nonlinear imaging through depth.
Potter, J. N.; Croxford, A. J.; Wilcox, P. D.
Imaging of weak phase objects by a Zernike phase plate.
Analysis of the imaging of some simple distributions of object phase by a phase plate of Zernike type shows that sharp transitions in the object phase are well transmitted. The low-frequency components of the complete object function are attenuated by the plate. The behaviour can be characterised by a cut-on parameter defined as the product of the cut-on frequency of the plate and a characteristic dimension of the object. When this parameter exceeds a value of the order of unity, a sharp boundary in the object is imaged by a Zernike plate as a dark lining inside the boundary with a white outline or halo outside the boundary, in agreement with reported observations. The maximum diameter of objects that can be imaged accurately is inversely proportional to the diameter of the hole for beam transmission in the phase plate. PMID:24184389
Edgcombe, C J
Phase contrast portal imaging using synchrotron radiation.
Microbeam radiation therapy is an experimental form of radiation treatment with great potential to improve the treatment of many types of cancer. We applied a synchrotron radiation phase contrast technique to portal imaging to improve targeting accuracy for microbeam radiation therapy in experiments using small animals. An X-ray imaging detector was installed 6.0 m downstream from an object to produce a high-contrast edge enhancement effect in propagation-based phase contrast imaging. Images of a mouse head sample were obtained using therapeutic white synchrotron radiation with a mean beam energy of 130 keV. Compared to conventional portal images, remarkably clear images of bones surrounding the cerebrum were acquired in an air environment for positioning brain lesions with respect to the skull structure without confusion with overlapping surface structures. PMID:25085143
Umetani, K; Kondoh, T
Phase contrast portal imaging using synchrotron radiation
NASA Astrophysics Data System (ADS)
Microbeam radiation therapy is an experimental form of radiation treatment with great potential to improve the treatment of many types of cancer. We applied a synchrotron radiation phase contrast technique to portal imaging to improve targeting accuracy for microbeam radiation therapy in experiments using small animals. An X-ray imaging detector was installed 6.0 m downstream from an object to produce a high-contrast edge enhancement effect in propagation-based phase contrast imaging. Images of a mouse head sample were obtained using therapeutic white synchrotron radiation with a mean beam energy of 130 keV. Compared to conventional portal images, remarkably clear images of bones surrounding the cerebrum were acquired in an air environment for positioning brain lesions with respect to the skull structure without confusion with overlapping surface structures.
Umetani, K.; Kondoh, T.
Phase calibration for synthetic aperture imaging
High-resolution imaging can be achieved by optical aperture synthesis. Using a sparse array of smaller aperture, one can synthesize an aperture with the resolution of the equivalent filled aperture while reducing the size and weight of system. The environment and vibration factors of synthetic aperture arrays lead to errors in phase measurement and cause a severe degradation in the image
Changwei Wang; Yuesong Jiang; Yuntao He; Li Liu
NASA Astrophysics Data System (ADS)
The NASA New Millennium Program's Geosynchronous Imaging Fourier Transform Spectrometer (GIFTS) instrument provides enormous advances in water vapor, wind, temperature, and trace gas profiling from geostationary orbit. The top-level instrument calibration requirement is to measure brightness temperature to better than 1 K (3 sigma) over a broad range of atmospheric brightness temperatures, with a reproducibility of +/-0.2 K. For in-flight radiometric calibration, GIFTS uses views of two on-board blackbody sources (290 K and 255 K) along with cold space, sequenced at regular programmable intervals. The blackbody references are cavities that follow the UW Atmospheric Emitted Radiance Interferometer (AERI) design, scaled to the GIFTS beam size. The cavity spectral emissivity is better than 0.998 with an absolute uncertainty of less than 0.001. Absolute blackbody temperature uncertainties are estimated at 0.07 K. This paper describes the detailed design of the GIFTS on-board calibration system that recently underwent its Critical Design Review. The blackbody cavities use ultra-stable thermistors to measure temperature, and are coated with high emissivity black paint. Monte Carlo modeling has been performed to calculate the cavity emissivity. Both absolute temperature and emissivity measurements are traceable to NIST, and detailed uncertainty budgets have been developed and used to show the overall system meets accuracy requirements. The blackbody controller is housed on a single electronics board and provides precise selectable set point temperature control, thermistor resistance measurement, and the digital interface to the GIFTS instrument. Plans for the NIST traceable ground calibration of the on-board blackbody system have also been developed and are presented in this paper.
Best, Fred A.; Revercomb, Henry E.; Knuteson, Robert O.; Tobin, David C.; Ellington, Scott D.; Werner, Mark W.; Adler, Douglas P.; Garcia, Raymond K.; Taylor, Joseph K.; Ciganovich, Nick N.; Smith, William L., Sr.; Bingham, Gail E.; Elwell, John D.; Scott, Deron K.
NASA Astrophysics Data System (ADS)
The NASA New Millennium Program's Geosynchronous Imaging Fourier Transform Spectrometer (GIFTS) instrument was designed to provide enormous advances in water vapor, wind, temperature, and trace gas profiling from geostationary orbit. The top-level instrument calibration requirement is to measure brightness temperature to better than 1 K (3 sigma) over a broad range of atmospheric brightness temperatures, with a reproducibility of +/-0.2 K. For the onboard calibration approach used by GIFTS that employs two internal blackbody sources (290 K and 255 K) plus a space view sequenced at regular programmable intervals, this instrument level requirement places tight requirements on the blackbody temperature uncertainty (0.1 K) and emissivity uncertainty (0.001). The blackbody references are cavities that follow the UW Atmospheric Emitted Radiance Interferometer (AERI) design, scaled to the GIFTS beam size. The engineering model blackbody system was completed and fully calibrated at the University of Wisconsin and delivered for integration into the GIFTS Engineering Development Unit (EDU) at the Utah State Space Dynamics Laboratory. This paper presents a detailed description of the methodology used to establish the required temperature and emissivity performance, with emphasis on the traceability to NIST standards. In addition, blackbody temperature data are presented from the GIFTS EDU thermal vacuum tests that indicate excellent temperature stability. The delivered on-board blackbody calibration system exceeds performance goals - the cavity spectral emissivity is better than 0.998 with an absolute uncertainty of less than 0.001, and the absolute blackbody temperature uncertainty is better than 0.06 K.
Best, Fred A.; Revercomb, Henry E.; Tobin, David C.; Knuteson, Robert O.; Taylor, Joseph K.; Thielman, Donald J.; Adler, Douglas P.; Werner, Mark W.; Ellington, Scott D.; Elwell, John D.; Scott, Deron K.; Cantwell, Gregory W.; Bingham, Gail E.; Smith, William L.
NASA Astrophysics Data System (ADS)
The Geostationary Imaging Fourier Transform Spectrometer (GIFTS), as part of NASA's New Millennium Program, is an advanced instrument to provide high-temporal-resolution measurements of atmospheric temperature and water vapor, which will greatly facilitate the detection of rapid atmospheric changes associated with destructive weather events, including tornadoes, severe thunderstorms, flash floods, and hurricanes. The Committee on Earth Science and Applications from Space under the National Academy of Sciences recommended that NASA and NOAA complete the fabrication, testing, and space qualification of the GIFTS instrument and that they support the international effort to launch GIFTS by 2008. Lossless data compression is critical for the overall success of the GIFTS experiment, or any other very high data rate experiment where the data is to be disseminated to the user community in real-time and archived for scientific studies and climate assessment. In general, lossless data compression is needed for high data rate hyperspectral sounding instruments such as GIFTS for (1) transmitting the data down to the ground within the bandwidth capabilities of the satellite transmitter and ground station receiving system, (2) compressing the data at the ground station for distribution to the user community (as is traditionally performed with GOES data via satellite rebroadcast), and (3) archival of the data without loss of any information content so that it can be used in scientific studies and climate assessment for many years after the date of the measurements. In this paper we study lossless compression of GIFTS data that has been collected as part of the calibration or ground based tests that were conducted in 2006. The predictive partitioned vector quantization (PPVQ) is investigated for higher lossless compression performance. PPVQ consists of linear prediction, channel partitioning and vector quantization. It yields an average compression ratio of 4.65 on the GIFTS test data, which significantly outperforms the standard compression methods such as JPEG-2000, JPEG-LS, and CCSDS IDC 9/7M & 5/3.
Huang, Bormin; Wei, Shih-Chieh; Huang, Allen H.-L.; Smuga-Otto, Maciek; Knuteson, Robert; Revercomb, Henry E.; Smith, William L., Sr.
Discovering Ordered Phases of Block Copolymers: A New Fourier-space Approach
A new method to solve the self-consistent field theory of block copolymers is developed. This method is based on the fact that, for any computational boxes with periodic boundary conditions, all spatially varying functions are spanned by the Fourier series determined by the size and shape of the box. This method is well suited for the discovery of ordered structures
Feng Qiu; An-Chang Shi; Zuojun Guo; Hongdong Zhang; Yuliang Yang
Background: Real-time myocardial contrast echocardiography (MCE) is increasingly used to assess myocardial perfusion. However, objective methods for evaluating MCE are not yet widely available. We sought to validate the ability of Fourier analysis applied to MCE to assess serial changes in microvascular perfusion during coronary occlusion and reperfusion. Methods: Six pigs underwent 45 min of left anterior descending coronary artery
Alexander Hansen; Raffi Bekeredjian; Grigorious Korosoglou; David Wolf; Arthur Filusch; Helmut F. Kuecherer
The spatial characteristics of letters and their influence on readability and letter identification have been intensely studied during the last decades. There have been few studies, however, on statistical image properties that reflect more global aspects of text, for example properties that may relate to its aesthetic appeal. It has been shown that natural scenes and a large variety of visual artworks possess a scale-invariant Fourier power spectrum that falls off linearly with increasing frequency in log-log plots. We asked whether images of text share this property. As expected, the Fourier spectrum of images of regular typed or handwritten text is highly anisotropic, i.e., the spectral image properties in vertical, horizontal, and oblique orientations differ. Moreover, the spatial frequency spectra of text images are not scale-invariant in any direction. The decline is shallower in the low-frequency part of the spectrum for text than for aesthetic artworks, whereas, in the high-frequency part, it is steeper. These results indicate that, in general, images of regular text contain less global structure (low spatial frequencies) relative to fine detail (high spatial frequencies) than images of aesthetics artworks. Moreover, we studied images of text with artistic claim (ornate print and calligraphy) and ornamental art. For some measures, these images assume average values intermediate between regular text and aesthetic artworks. Finally, to answer the question of whether the statistical properties measured by us are universal amongst humans or are subject to intercultural differences, we compared images from three different cultural backgrounds (Western, East Asian, and Arabic). Results for different categories (regular text, aesthetic writing, ornamental art, and fine art) were similar across cultures. PMID:23554592
Melmer, Tamara; Amirshahi, Seyed A; Koch, Michael; Denzler, Joachim; Redies, Christoph
Synchronous Phase-Resolving Flash Range Imaging
NASA Technical Reports Server (NTRS)
An apparatus, now undergoing development, for range imaging based on measurement of the round-trip phase delay of a pulsed laser beam is described. The apparatus would operate in a staring mode. A pulsed laser would illuminate a target. Laser light reflected from the target would be imaged on a verylarge- scale integrated (VLSI)-circuit image detector, each pixel of which would contain a photodetector and a phase-measuring circuit. The round-trip travel time for the reflected laser light incident on each pixel, and thus the distance to the portion of the target imaged in that pixel, would be measured in terms of the phase difference between (1) the photodetector output pulse and (2) a local-oscillator signal that would have a frequency between 10 and 20 MHz and that would be synchronized with the laser-pulse-triggering signal.
Pain, Bedabrata; Hancock, Bruce
Cardiac phase-correlated image reconstruction and advanced image processing in pulmonary CT imaging
Image quality in pulmonary CT imaging is commonly degraded by cardiac motion artifacts. Phase-correlated image reconstruction\\u000a algorithms known from cardiac imaging can reduce motion artifacts but increase image noise and conventionally require a concurrently\\u000a acquired ECG signal for synchronization. Techniques are presented to overcome these limitations. Based on standard and phase-correlated\\u000a images that are reconstructed using a raw data-derived synchronization
Robert M. Lapp; Marc Kachelrie�; Dirk Ertel; Yiannis Kyriakou; Willi A. Kalender
NASA Astrophysics Data System (ADS)
This paper proposes a new Fourier-type phase estimation method (FPEM) for estimating the rotor phase in the sensorless drives of salient-pole permanent-magnet synchronous motors. The method involves the use of a stator current induced by high-frequency voltage injection. The proposed FPEM has the following characteristics: 1) it is versatile, i.e., it can be applied to almost all voltage injections, 2) it does not require band-pass filters that extract the high-frequency component from the stator current, 3) it could have the potential to enhance the positive correlation between the rotor phase and high-frequency current, 4) it does not require redesigning of the integrated PLL when the amplitude and/or frequency of the injected high-frequency voltage is changed. The usefulness of the proposed method is verified through extensive experiments.
Shinnaka, Shinji
NASA Astrophysics Data System (ADS)
This paper summarizes the design and development of the Panchromatic Imaging Fourier Transform Spectrometer (PanFTS) for the NASA Geostationary Coastal and Air Pollution Events (GEO-CAPE) Mission. The PanFTS instrument will advance the understanding of the global climate and atmospheric chemistry by measuring spectrally resolved outgoing thermal and reflected solar radiation. With continuous spectral coverage from the near-ultraviolet through the thermal infrared, this instrument is designed to measure pollutants, greenhouse gases, and aerosols as called for by the U.S. National Research Council Decadal Survey; Earth Science and Applications from Space: National Imperatives for the Next Decade and Beyond1. The PanFTS instrument is a hybrid based on spectrometers like the Tropospheric Emissions Spectrometer (TES) that measures thermal emission, and those like the Orbiting Carbon Observatory (OCO), and the Ozone Monitoring Instrument (OMI) that measure scattered solar radiation. Simultaneous measurements over the broad spectral range from IR to UV is accomplished by a two sided interferometer with separate optical trains and detectors for the UV-visible and IR spectral domains. This allows each side of the instrument to be independently optimized for its respective spectral domain. The overall interferometer design is compact because the two sides share a single high precision cryogenic optical path difference mechanism (OPDM) and metrology laser as well as a number of other instrument systems including the line-of-sight pointing mirror, the data management system, thermal control system, electrical system, and the mechanical structure. The PanFTS breadboard instrument has been tested in the laboratory and demonstrated the basic functionality for simultaneous measurements in the visible and IR. It is set to begin operations in the field at the California Laboratory for Atmospheric Remote Sensing (CLARS) observatory on Mt. Wilson measuring the atmospheric chemistry across the Los Angeles basin. Development has begun on a flight size PanFTS engineering model (EM) that addresses all critical scaling issues and demonstrates operation over the full spectral range of the flight instrument which will show the PanFTS instrument design is mature.
Wu, Yen-Hung; Key, Richard; Sander, Stanley; Blavier, Jean-Francois; Rider, David
Cluster analysis and artificial neural networks (ANNs) are applied to the automated assessment of disease state in Fourier transform infrared microscopic imaging measurements of normal and carcinomatous immortalized human breast cell lines. K-means clustering is used to implement an automated algorithm for the assignment of pixels in the image to cell and non-cell categories. Cell pixels are subsequently classified into carcinoma and normal categories through the use of a feed-forward ANN computed with the Broyden-Fletcher-Goldfarb-Shanno training algorithm. Inputs to the ANN consist of principal component scores computed from Fourier filtered absorbance data. A grid search optimization procedure is used to identify the optimal network architecture and filter frequency response. Data from three images corresponding to normal cells, carcinoma cells, and a mixture of normal and carcinoma cells are used to build and test the classification methodology. A successful classifier is developed through this work, although differences in the spectral backgrounds between the three images are observed to complicate the classification problem. The robustness of the final classifier is improved through the use of a rejection threshold procedure to prevent classification of outlying pixels. PMID:14610931
Zhang, Lin; Small, Gary W; Haka, Abigail S; Kidder, Linda H; Lewis, E Neil
A Synthetic Quadrature Phase Detector/Demodulator for Fourier Transform Transform Spectrometers
NASA Technical Reports Server (NTRS)
A method is developed to demodulate (velocity correct) Fourier transform spectrometer (FTS) data that is taken with an analog to digital converter that digitizes equally spaced in time. This method makes it possible to use simple low cost, high resolution audio digitizers to record high quality data without the need for an event timer or quadrature laser hardware, and makes it possible to use a metrology laser of any wavelength. The reduced parts count and simplicity implementation makes it an attractive alternative in space based applications when compared to previous methods such as the Brault algorithm.
Campbell, Joel
Imaging IR spectrometer, phase 2
NASA Technical Reports Server (NTRS)
The development is examined of a prototype multi-channel infrared imaging spectrometer. The design, construction and preliminary performance is described. This instrument is intended for use with JPL Table Mountain telescope as well as the 88 inch UH telescope on Mauna Kea. The instrument is capable of sampling simultaneously the spectral region of 0.9 to 2.6 um at an average spectral resolution of 1 percent using a cooled (77 K) optical bench, a concave holographic grating and a special order sorting filter to allow the acquisition of the full spectral range on a 128 x 128 HgCdTe infrared detector array. The field of view of the spectrometer is 0.5 arcsec/pixel in mapping mode and designed to be 5 arcsec/pixel in spot mode. The innovative optical design has resulted in a small, transportable spectrometer, capable of remote operation. Commercial applications of this spectrometer design include remote sensing from both space and aircraft platforms as well as groundbased astronomical observations.
Gradie, Jonathan; Lewis, Ralph; Lundeen, Thomas; Wang, Shu-I
NASA Astrophysics Data System (ADS)
A blue white He-Cd laser composed of three R/G/B component beams is directly applied to fabricate the optical Fourier transform hologram (OFTH). The visual appearance of reconstructed color hologram images is discussed in contrast to that of an ordinary OFTH which is fabricated using a monochromatic He-Ne laser and diode-pumped solid state(Nd:YAG)laser. The characteristic of He-Cd laser is checked from the viewpoint of the visual size and its place of reconstructed color ghost image called cross talk in the reconstruction process. The visual effect of reconstructed hologram ghost image which can be digitally modified and emphasized by means of commercially available software is discussed through this study.
Kariya, M.; Iizuka, M.; Ookuma, Y.; Nakashima, Y.; Takamatsu, M.
NASA Astrophysics Data System (ADS)
The Gimballed Limb Observer for Radiance Imaging of the Atmosphere (GLORIA) is an imaging Fourier transform spectrometer that is capable of operating on various high altitude research aircraft. It measures the atmospheric emission in the thermal infrared spectral region in limb and nadir geometry. GLORIA consists of a classical Michelson interferometer combined with an infrared camera. The infrared detector has a usable range of 128 � 128 pixels, measuring up to 16 384 interferograms simultaneously. Imaging Fourier transform spectrometers impose a number of challenges with respect to instrument calibration and algorithm development. The innovative optical setup with extremely high optical throughput requires the development of new methods and algorithms for spectral and radiometric calibration. Due to the vast amount of data there is a high demand for scientifically intelligent optimisation of the data processing. This paper outlines the characterisation and processing steps required for the generation of radiometrically and spectrally calibrated spectra. Methods for performance optimisation of the processing algorithm are presented. The performance of the data processing and the quality of the calibrated spectra are demonstrated for measurements collected during the first deployments of GLORIA on aircraft.
Kleinert, A.; Friedl-Vallon, F.; Guggenmoser, T.; H�pfner, M.; Neubert, T.; Ribalda, R.; Sha, M. K.; Ungermann, J.; Blank, J.; Ebersoldt, A.; Kretschmer, E.; Latzko, T.; Oelhaf, H.; Olschewski, F.; Preusse, P.
Ultrahigh-speed imaging of the rat retina using ultrahigh-resolution spectral/Fourier domain OCT
NASA Astrophysics Data System (ADS)
We performed OCT imaging of the rat retina at 70,000 axial scans per second with ~3 ?m axial resolution. Three-dimensional OCT (3D-OCT) data sets of the rat retina were acquired. The high speed and high density data sets enable improved en face visualization by reducing eye motion artifacts and improve Doppler OCT measurements. Minimal motion artifacts were visible and the OCT fundus images offer more precise registration of individual OCT images to retinal fundus features. Projection OCT fundus images show features such as the nerve fiber layer, retinal capillary networks and choroidal vasculature. Doppler OCT images and quantitative measurements show pulsatility in retinal blood vessels. Doppler OCT provides noninvasive in vivo quantitative measurements of retinal blood flow properties and may benefit studies of diseases such as glaucoma and diabetic retinopathy. Ultrahigh speed imaging using ultrahigh resolution spectral / Fourier domain OCT promises to enable novel protocols for measuring small animal retinal structure and retinal blood flow. This non-invasive imaging technology is a promising tool for monitoring disease progression in rat and mouse models to assess ocular disease pathogenesis and response to treatment.
Liu, Jonathan J.; Potsaid, Benjamin; Chen, Yueli; Gorczynska, Iwona; Srinivasan, Vivek J.; Duker, Jay S.; Fujimoto, James G.
Applications of Fourier Domain Mode Locked lasers for optical coherence tomography imaging
Optical coherence tomography (OCT) is a micrometer-resolution imaging technique that produces cross-sectional images of sample microstructure by measuring the amplitude and echo time delay of backscattered light. OCT imaging ...
Adler, Desmond Christopher, 1978-
X-Ray Imaging with Phase Contrast
NASA Astrophysics Data System (ADS)
The easiest way to obtain X-ray images of the internal structure of condensed objects is to register projections on an area detector like a photographic plate or a CCD and analyze the intensity of the transmitted beam. In such an arrangement the main cause of structures seen on the image is usually absorption contrast which scales with Z(Z/E)m where Z is atomic number, E is X-ray energy, and m ~ 2.5 to 3.5. Hence for light elements (which often are of main importance in the medical field) absorption contrast is quite small and sometimes unspecific compared to contrast caused by X-ray phase shift which scales with Z/E. In recent years various methods capable of registering X-ray phase shift have been developed, which include double crystal topography, X-ray interferometry, in-line phase-contrast imaging, the use of Talbot-mode grid devices, and others. A survey of existing approaches and examples of recent results will be given. -An important aspect in the application of X-ray imaging in the medical field is the amount of unavoidable irradiation dose to be applied to the patient under investigation. There is some hope that in the future, with a suitable phase-contrast method, the dose can be lowered.
Bonse, Ulrich; Beckmann, Felix
The Pacific Northwest National Laboratory is developing a range of technologies to broaden the field of explosives detection. Phased contrast X-ray imaging, which uses silicon gratings to detect distortions in the X-ray wave front, may be applicable to mail or luggage scanning for explosives; it can also be used in detecting other contraband, small-parts inspection, or materials characterization.
Erin Miller
Phase object imaging inside the airy disc
NASA Astrophysics Data System (ADS)
The possibility of phase objects superresoluton imaging is theoretically justifieth The measurements with CPM " AIRYSCAN" showed the reality of O structures observations when the Airy disc di ameter i s 0 86 j. . m SUMMARY It has been known that the amount of information contained in the image of any object is mostly determined by the number of points measured i ndependentl y or by spati al resol uti on of the system. From the classic theory of the optical systems it follows that for noncoherent sources the -spatial resolution is limited by the aperture dd 6LX/N. A. ( Rayleigh criterion where X is wave length NA numerical aperture. ) The use of this criterion is equivalent tO the statement that any object inside the Airy disc of radius d that is the difraction image of a point is practical ly unresolved. However at the coherent illumination the intensity distribution in the image plane depends also upon the phase iq (r) of the wave scattered by the object and this is the basis of the Zernike method of phasecontrast microscopy differential interference contrast (DIC) and computer phase microscopy ( CPM ). In theoretical foundation of these methods there was no doubt in the correctness of Rayleigh criterion since the phase information is derived out of intensity distribution and as we know there were no experiments that disproved this
Tychinsky, Vladimir P.
Quantitative phase imaging with partially coherent illumination.
In this Letter, we formulate a mathematical model for predicting experimental outcomes in quantitative phase imaging (QPI) when the illumination field is partially spatially coherent. We derive formulae that apply to QPI and discuss expected results for two classes of QPI experiments: common path and traditional interferometry, under varying degrees of spatial coherence. In particular, our results describe the physical relationship between the spatial coherence of the illuminating field and the halo effect, which is well known in phase-contrast microscopy. We performed experiments relevant to this common situation and found that our theory is in excellent agreement with the data. With this new understanding of the effects of spatial coherence, our formulae offer an avenue for removing halo artifacts from phase images. PMID:25360915
Nguyen, T H; Edwards, C; Goddard, L L; Popescu, G
Quantitative Fourier transform infrared analysis of gas phase cigarette smoke and other gas mixtures
A new method for the analysis of selected components in complex gas mixtures has been developed utilizing a relatively inexpensive Fourier transform infrared spectrometer and a continuous flow gas cell. The method was used to monitor nitric oxide and nitrogen dioxide concentrations in cigarette smoke with time. Using multivariate least-square regression analysis, it is possible to simultaneously quantitate both NO and NO{sub 2}, even in the presence of overlapping peaks. Using this method, the oxidation of nitric oxide in the presence of isoprene in cigarette smoke and in a model system was followed with time. The method also can be applied to other compounds in smoke or to any other gaseous mixture.
Cueto, R.; Church, D.F.; Pryor, W.A. (Louisiana State Univ., Baton Rouge (USA))
Phase and amplitude phase restoration in synthetic aperture radar imaging.
Methods for addressing two types of multiplicative noise in synthetic aperture radar (SAR) imaging are presented. The authors consider a multiplicative noise with a real phase (i.e. the SAR signal's phase is contaminated but its amplitude is uncorrupted) that possesses unknown functional characteristics with respect to the radar signal's temporal frequencies. A perturbation solution for phase reconstruction from amplitude is developed from a wave equation governing the SAR signal and a Riccati equation that relates the amplitude and phase functions of the SAR signal. This solution is converted into a noniterative analytical solution in terms of the moments and powers of the log amplitude function. Next, the authors consider a multiplicative noise with a complex phase (i.e. both the amplitude and phase of the SAR signal are contaminated) that varies linearly with respect to the radar signal's temporal frequencies. The two wave equations governing the SAR signal at two temporal frequencies of the radar signal are combined to derive a method to reconstruct the complex phase error function. PMID:18296157
Soumekh, M; Choi, J H
The pericardial effusion pattern on phase images
The effect of pericardial effusion on phase images of gated studies was investigated. Twenty-six patients with suspected or known pericardial effusion were correlated with echocardiography and/or clinical and other laboratory data to ascertain the presence and size of effusion. The phase image pattern and parameters were compared to the results previously obtained in seven normal patients, and in 26 patients with documented regional wall motion abnormalities but no evidence of pericardial effusion. The phase pattern was graded into five categories: typical (IV) (wide histogram, well defined concentric convex pattern, progressive delay toward the inferolateral area, identifiable also over the right ventricle); less pronounced (III); atypical (II); ill defined changes (I); and normal (0). Results: Group L (large pericardial effusion): four of six had pattern (IV) and the left ventricular histogram showed abnormal parameters. These patients had large free effusions in the pericardial sac and none had regional wall motion abnormalities. Two of six had pattern (III) and (II) but also had ancillary pericardial pathology and/or decreased ejection fraction. Group M (moderate pericardial effusion), S (small pericardial effusion), and A (absent pericardial effusion, but not normal) had variable phase images and numeric parameters. After therapeutic drainage of pericardial fluid two patients changed pattern from IV and III to 0 and a third from III to I. Category IV pattern is 100% specific for pericardial effusion; the combination of category IV or III is 87.5% specific and 61% sensitive for large and moderate pericardial effusion.
Pavel, C.M.; Kahn, J.; Rich, S.; Gonzalez, P.; Turner, S.; Pavel, D.G.
NASA Astrophysics Data System (ADS)
Waveguiding of surface plasmon polaritons by dielectric-loaded metal structures is studied in detail by combining numerical simulations and leakage radiation microscopy. These types of waveguides are first numerically investigated using the effective index model and the differential method. We analyzed systematically the influence of the ridge width and thickness of the waveguide on the properties of the surface plasmon guided modes. In particular we investigated the confinement factor of the modes and their associated propagation lengths. These two parameters can be optimized by adjusting the thickness of the dielectric layer. Waveguides loaded with thick and thin dielectric ridges are then optically characterized by leakage radiation microscopy. The mode propagation distance is measured by direct-space imaging and the propagation constants are evaluated by Fourier imaging and analysis. Good agreements are found between theoretical and experimental data.
Grandidier, J.; Massenot, S.; Des Francs, G. Colas; Bouhelier, A.; Weeber, J.-C.; Markey, L.; Dereux, A.; Renger, J.; Gonz�lez, M. U.; Quidant, R.
We evaluate the temporal partial coherence of transmission electron microscopy (TEM) using the three-dimensional (3D) Fourier transform (FT) of through-focus images. Young's fringe method often indicates the unexpected high-frequency information due to non-linear imaging terms. We have already used the 3D FT of axial (non-tilted) through-focus images to reduce the effect of non-linear terms on the linear imaging term, and demonstrated the improvement of monochromated lower-voltage TEM performance [Kimoto et al., Ultramicroscopy 121 (2012) 31-39]. Here we apply the 3D FT method with intentionally tilted incidence to normalize various factors associated with a TEM specimen and an imaging device. The temporal partial coherence of two microscopes operated at 30, 60 and 80 kV is evaluated. Our method is applicable to such cases where the non-linear terms become more significant in lower acceleration voltage or aberration-corrected high spatial resolution TEM. PMID:23834771
Kimoto, Koji; Sawada, Hidetaka; Sasaki, Takeo; Sato, Yuta; Nagai, Takuro; Ohwada, Megumi; Suenaga, Kazu; Ishizuka, Kazuo
Optical Coherence Tomography (OCT) is an emerging optical biomedical imaging technology that enables cross-sectional imaging of scattering tissue with high sensitivity and micron-scale resolution. In conventional OCT, the ...
Srinivasan, Vivek Jay
The combination of massively parallel spatial sampling and accurate spectral radiometry offered by imaging FTS makes it extremely attractive for earth and planetary remote sensing. We constructed a breadboard instrument to help assess the potential for planetary applications of small imaging FTS instruments in the 1-5 micrometers range. The results also support definition of the NASA Geostationary Imaging FTS instrument
Henry E. Revercomb; Lawrence A. Sromovsky; Patrick M. Fry; Fred A. Best; Daniel D. LaPorte
Geometric Analysis and Symbol Calculus: Fourier Transform Magnetic Resonance Imaging and Wavelets
Due to its unequalled advantages, the magnetic resonance imaging (MRI) modality has truly revolutionized the diagnosis and evaluation of pathology. Because many morphological anatomic details that may not be visualized by other high tech imaging methods can now be readily shown by diagnostic MRI, it has already become the standard modality by which all other clinical imaging techniques are measured.
Walter Schempp
Bispectra and Phase Correlations for Chaotic Dynamical Systems.
National Technical Information Service (NTIS)
The bispectrum is the natural third-order generalization of the power spectrum. It provides information about correlations between different Fourier components of a signal or image, and about the statistics of Fourier phase. A number of numerical and expe...
A. K. Evans, M. D. London, S. J. Nimmo
Multiple template-based image matching using alpha-rooted quaternion phase correlation
NASA Astrophysics Data System (ADS)
In computer vision applications, image matching performed on quality-degraded imagery is difficult due to image content distortion and noise effects. State-of-the art keypoint based matchers, such as SURF and SIFT, work very well on clean imagery. However, performance can degrade significantly in the presence of high noise and clutter levels. Noise and clutter cause the formation of false features which can degrade recognition performance. To address this problem, previously we developed an extension to the classical amplitude and phase correlation forms, which provides improved robustness and tolerance to image geometric misalignments and noise. This extension, called Alpha-Rooted Phase Correlation (ARPC), combines Fourier domain-based alpha-rooting enhancement with classical phase correlation. ARPC provides tunable parameters to control the alpha-rooting enhancement. These parameter values can be optimized to tradeoff between high narrow correlation peaks, and more robust wider, but smaller peaks. Previously, we applied ARPC in the radon transform domain for logo image recognition in the presence of rotational image misalignments. In this paper, we extend ARPC to incorporate quaternion Fourier transforms, thereby creating Alpha-Rooted Quaternion Phase Correlation (ARQPC). We apply ARQPC to the logo image recognition problem. We use ARQPC to perform multiple-reference logo template matching by representing multiple same-class reference templates as quaternion-valued images. We generate recognition performance results on publicly-available logo imagery, and compare recognition results to results generated from standard approaches. We show that small deviations in reference templates of sameclass logos can lead to improved recognition performance using the joint matching inherent in ARQPC.
DelMarco, Stephen
Application of fourier method in energetics, for root-mean-square value and phase shift measurement
Recorded information about transmission system faults or disturbances is essential for determining the performance of system components and to analyze the nature and cause of a disturbance in energetics. The systems for disturbance recording perform the monitoring and analysis of different events specific to energetic systems. The root-mean-square (RMS) values and phase shifts of voltages and currents are widely used
D. M. Purcaru; I. Purcaru; C. Gordan; E. Niculescu; S. D. Nedelcut
Synthetic phase holograms for auto-stereoscopic image displays using a modified IFTA.
A Fourier-transformed synthetic phase hologram for an auto-stereoscopic image display system is proposed and implemented. The system uses a phase-only spatial light modulator and a simple projection lens module. A modified iterative Fresnel transform algorithm method, for the reconstruction of gray-level quantized stereo images with fast convergence, high diffraction efficiency and large signal-to-noise ratio is also described. Using this method, it is possible to obtain a high diffraction efficiency(~90%), an excellent signal-to-noise ratio(> 9.6dB), and a short calculation time(~3min). Experimentally, the proposed auto-stereoscopic display system was able to generate stereoscopic 3D images very well. PMID:19475082
Choi, Kyongsik; Kim, Hwi; Lee, Byoungho
Determination of senescent spotting in banana ( Musa cavendish) using fractal texture Fourier image
The analysis of fractal texture reflects a change in pixel intensity, and this might contain information about the structure of objects since a great change in intensity might usually indicate changes in the object. In the images of banana surfaces, the texture image can, to some extent, reflect changes and thus it can be used as an indicator of the
R. Quevedo; F. Mendoza; J. M. Aguilera; J. Chanona; G. Guti�rrez-L�pez
Coupling Fourier transform infrared spectroscopy with focal plane array detectors at synchrotron radiation sources (SR-FTIR-FPA) has provided a rapid method to simultaneously image numerous biochemical markers in situ at diffraction limited resolution. Since cells and nuclei are well resolved at this spatial resolution, a direct comparison can be made between FTIR functional group images and the histology of the same section. To allow histological analysis of the same section analyzed with infrared imaging, unfixed air-dried tissue sections are typically fixed (after infrared spectroscopic analysis is completed) via immersion fixation. This post fixation process is essential to allow histological staining of the tissue section. Although immersion fixation is a common practice in this filed, the initial rehydration of the dehydrated unfixed tissue can result in distortion of subcellular morphology and confound correlation between infrared images and histology. In this study, vapor fixation, a common choice in other research fields where postfixation of unfixed tissue sections is required, was employed in place of immersion fixation post spectroscopic analysis. This method provided more accurate histology with reduced distortions as the dehydrated tissue section is fixed in vapor rather than during rehydration in an aqueous fixation medium. With this approach, accurate correlation between infrared images and histology of the same section revealed that Purkinje neurons in the cerebellum are rich in cytosolic proteins and not depleted as once thought. In addition, we provide the first direct evidence of intracellular lactate within Purkinje neurons. This highlights the significant potential for future applications of SR-FTIR-FPA imaging to investigate cellular lactate under conditions of altered metabolic demand such as increased brain activity and hypoxia or ischemia. PMID:23638613
NASA Astrophysics Data System (ADS)
Fourier transform infrared imaging (FTIRI) combining with principal component regression (PCR) analysis were used to determine the reduction of proteoglycan (PG) in articular cartilage after the transection of the anterior cruciate ligament (ACL). A number of canine knee cartilage sections were harvested from the meniscus-covered and meniscus-uncovered medial tibial locations from the control joints, the ACL joints at three time points after the surgery, and their contralateral joints. The PG loss in the ACL cartilage was related positively to the durations after the surgery. The PG loss in the contralateral knees was less than that of the ACL knees. The PG loss in the meniscus-covered cartilage was less than that of the meniscus-uncovered tissue in both ACL and contralateral knees. The quantitative mapping of PG loss could monitor the disease progression and repair processes in arthritis.
Yin, Jianhua; Xia, Yang
Fourier optical cryptosystem using complex spatial modulation
NASA Astrophysics Data System (ADS)
Our goal is to enhance the security level of a Fourier optical encryption system. Therefore we propose a Mach�Zehnder interferometer based encryption setup. The input data is organized in a binary array, and it is encoded in the two wave fronts propagated in the arms of the interferometer. Both input wave fronts are independently encrypted by Fourier systems, hence the proposed method has two encryption keys. During decryption, the encrypted wave fronts are propagated through the interferometer setup. The interference pattern of the output shows the reconstructed data in cases where the correct decryption Fourier keys are used. We propose a novel input image modulation method with a user defined phase parameter. We show that the security level of the proposed cryptosystem can be enhanced by an optimally chosen phase parameter.
Sarkadi, T.; Koppa, P.
Phase imaging of EUV masks using a lensless EUV microscope
NASA Astrophysics Data System (ADS)
In extreme ultraviolet (EUV) lithography, controlling the reflection phase of the mask pattern is important for enlarging the process window and for compensating for phase defects. And, there are shadowing effect owing to the oblique illumination which modifies reflection phase of absorber patterns. A phase imaging microscope is required to determine this actinic phase distribution. To this end, we have developed a coherent EUV scatterometry microscope (CSM) based on coherent diffraction imaging (CDI). The CSM consists of a coherent EUV source and a charge-coupled device (CCD) camera, which records the diffraction images from the mask pattern directly. The system is lensless and makes use of the inverse computations based on the intensity of the scattered radiation, instead of the image-forming optics, to retrieve the frequency-space phase data. This allows the aerial-image phase data to also be reconstructed. Using the CSM system, one can obtain the intensity and phase images of the sample pattern. In this study, we also reconstructed the phase images of line-and-space patterns that were free of the shadowing effect as well as of patterns in which shadowing occurred. In the case of the latter, shadowing could be observed clearly in the phase image. Finally, the phase image of a programmed phase defect was also reconstructed and its phase value evaluated quantitatively. Thus, the CSM system is powerful tool for developing phase-controlled masks.
Harada, Tetsuo; Nakasuji, Masato; Nagata, Yutaka; Watanabe, Takeo; Kinoshita, Hiroo
Feasibility of differential phase contrast CT for whole body imaging
NASA Astrophysics Data System (ADS)
Phase contrast based imaging techniques have shown improved contrast in certain biological materials. This has led to an increased interest for the potential of preclinical and clinical imaging systems that incorporate phase sensitive imaging techniques. However, the interplay between the phase contrast mechanism and the so-called small-angle scattering or dark-field mechanism is often not considered. In this work we explore the potential for phase-sensitive whole body imaging by imaging a freshly euthanized specimen. The results suggest that when extrapolating phantom and ex vivo results to whole body imaging, one must consider the complex anatomy of the entire body and its effect on each contrast mechanism.
Li, Ke; Bevins, Nicholas B.; Zambelli, Joseph N.; Chen, Guang-Hong
NASA Technical Reports Server (NTRS)
The geosynchronous-imaging Fourier transform spectrometer (GIFTS) engineering demonstration unit (EDU) is an imaging infrared spectrometer designed for atmospheric soundings. It measures the infrared spectrum in two spectral bands (14.6 to 8.8 microns, 6.0 to 4.4 microns) using two 128 x 128 detector arrays with a spectral resolution of 0.57 cm(exp -1) with a scan duration of approximately 11 seconds. From a geosynchronous orbit, the instrument will have the capability of taking successive measurements of such data to scan desired regions of the globe, from which atmospheric status, cloud parameters, wind field profiles, and other derived products can be retrieved. The GIFTS EDU provides a flexible and accurate testbed for the new challenges of the emerging hyperspectral era. The EDU ground-based measurement experiment, held in Logan, Utah during September 2006, demonstrated its extensive capabilities and potential for geosynchronous and other applications (e.g., Earth observing environmental measurements). This paper addresses the experiment objectives and overall performance of the sensor system with a focus on the GIFTS EDU imaging capability and proof of the GIFTS measurement concept.
Zhou, Daniel K.; Smith, William L.; Bingham, Gail E.; Huppi, Ronald J.; Revercomb, Henry E.; Zollinger, Lori J.; Larar, Allen M.; Liu, Xu; Tansock, Joseph J.; Reisse, Robert A.; Hooker, Ronald
NASA Astrophysics Data System (ADS)
Fourier transform infrared imaging (FTIRI) combined with chemometrics can be used to detect the structure of bio-macromolecule, measure the concentrations of some components, and so on. In this study, FTIRI with Partial Least-Squares (PLS) regression was applied to study the concentration of two main components in bovine nasal cartilage (BNC), collagen and proteoglycan. An infrared spectrum library was built by mixing the collagen and chondroitin 6-sulfate (main of proteoglycan) at different ratios. Some pretreatments are needed for building PLS model. FTIR images were collected from BNC sections at 6.25?m and 25?m pixel size. The spectra extracted from BNC-FTIR images were imported into the PLS regression program to predict the concentrations of collagen and proteoglycan. These PLS-determined concentrations are agreed with the result in our previous work and biochemical analytical results. The prediction shows that the concentrations of collagen and proteoglycan in BNC are comparative on the whole. However, the concentration of proteoglycan is a litter higher than that of collagen, to some extent.
Zhang, Xuexi; Xiao, Zhi-Yan; Yin, Jianhua; Xia, Yang
NASA Astrophysics Data System (ADS)
The Geosynchronous Imaging Fourier Transform Spectrometer (GIFTS) was developed for the NASA New Millennium Program (NMP) Earth Observing-3 (EO-3) mission. This paper discusses the GIFTS measurement requirements and the technology utilized by the GIFTS sensor to provide the required system performance. Also presented are preliminary results from the recently completed calibration of the instrument. The GIFTS NMP mission challenge was to demonstrate new and emerging sensor and data processing technologies to make revolutionary improvements in meteorological observational capability and forecasting accuracy using atmospheric imaging and hyperspectral sounding methods. The GIFTS sensor is an imaging FTS with programmable spectral resolution and spatial scene selection, allowing radiometric accuracy and atmospheric sounding precision to be traded in near-real time for area coverage. System sensitivity is achieved through the use of a cryogenic Michelson interferometer and two large-area, IR focal plane detector arrays. Due to funding limitations, the GIFTS sensor module was completed as an engineering demonstration unit, which can be upgraded for flight qualification. Capability to meet the next generation geosynchronous sounding requirements has been successfully demonstrated through thermal vacuum testing and rigorous IR calibration activities.
Elwell, J. D.; Cantwell, G. W.; Scott, D. K.; Esplin, R. W.; Hansen, G. B.; Jensen, S. M.; Jensen, M. D.; Brown, S. B.; Zollinger, L. J.; Thurgood, V. A.; Esplin, M. P.; Huppi, R. J.; Bingham, G. E.; Revercomb, H. E.; Best, F. A.; Tobin, D. C.; Taylor, J. K.; Knuteson, R. O.; Smith, W. L.; Reisse, R. A.; Hooker, R.
Quantitative Fourier Domain Optical Coherence Tomography Imaging of the Ocular Anterior Segment
NASA Astrophysics Data System (ADS)
Clinical imaging within ophthalmology has had transformative effects on ocular health over the last century. Imaging has guided clinicians in their pharmaceutical and surgical treatments of macular degeneration, glaucoma, cataracts and numerous other pathologies. Many of the imaging techniques currently used are photography based and are limited to imaging the surface of ocular structures. This limitation forces clinicians to make assumptions about the underlying tissue which may reduce the efficacy of their diagnoses. Optical coherence tomography (OCT) is a non-invasive, non-ionizing imaging modality that has been widely adopted within the field of ophthalmology in the last 15 years. As an optical imaging technique, OCT utilizes low-coherence interferometry to produce micron-scale three-dimensional datasets of a tissue's structure. Much of the human body consists of tissues that significantly scatter and attenuate optical signals limiting the imaging depth of OCT in those tissues to only 1-2mm. However, the ocular anterior segment is unique among human tissue in that it is primarily transparent or translucent. This allows for relatively deep imaging of tissue structure with OCT and is no longer limited by the optical scattering properties of the tissue. This goal of this work is to develop methods utilizing OCT that offer the potential to reduce the assumptions made by clinicians in their evaluations of their patients' ocular anterior segments. We achieved this by first developing a method to reduce the effects of patient motion during OCT volume acquisitions allowing for accurate, three dimensional measurements of corneal shape. Having accurate corneal shape measurements then allowed us to determine corneal spherical and astigmatic refractive contribution in a given individual. This was then validated in a clinical study that showed OCT better measured refractive change due to surgery than other clinical devices. Additionally, a method was developed to combine the clinical evaluation of the iridocorneal angle through gonioscopy with OCT.
McNabb, Ryan Palmer
The overall objective of Phase II is the development of an FT-IR instrument for the rapid and automated determination of char, soot, ash and gas temperatures and concentrations, and char and ash particle sizes in practical combustion devices. The technique employs measurements made at more than 1000 frequencies in the mid IR (400-6500/cm). Both emission and transmission measurements are made for temperature determinations, and the technique is referred to as the E/T technique. The large amount of information in the complete spectrum permits the elimination of some of the assumptions normally made in color-temperature measurements and permits monitoring of several phases. During the program, these capabilities of the FT-IR were demonstrated in the laboratory. In addition, an instrument capable of being operated in the more severe environment of process monitoring was selected and modified for the E/T measurements. Two successful field tests were made of the instrument demonstrating on-line and in-situ capabilities.
Solomon, P.R.; Chien, P.L.; Best, P.E.
Phased Contrast X-Ray Imaging (Image of Erin Miller, Ph.D.)
Transcript Phased Contrast X-Ray Imaging 1 TRANSCRIPT (Image of Erin Miller, Ph.D.) Erin A. Miller Contrast X-Ray Imaging; we're hoping to use it for enhanced explosives detection. (Images of empty airport security checkpoint, screenshot of Phased Contrast X-ray image, cardboard shipping boxes, suitcases, vials
Analysis of hyper-spectral data derived from an imaging Fourier transform: A statistical perspective
Fourier transform spectrometers (FTS) using optical sensors are increasingly being used in various branches of science. Typically, a FTS generates a three-dimensional data cube with two spatial dimensions and one frequency/wavelength dimension. The number of frequency dimensions in such data cubes is generally very large, often in the hundreds, making data analytical procedures extremely complex. In the present report, the problem is viewed from a statistical perspective. A set of procedures based on the high degree of inter-channel correlation structure often present in such hyper-spectral data, has been identified and applied to an example data set of dimension 100 x 128 x 128 comprising 128 spectral bands. It is shown that in this case, the special eigen-structure of the correlation matrix has allowed the authors to extract just a few linear combinations of the channels (the significant principal vectors) that effectively contain almost all of the spectral information contained in the data set analyzed. This in turn, enables them to segment the objects in the given spatial frame using, in a parsimonious yet highly effective way, most of the information contained in the data set.
Sengupta, S.K.; Clark, G.A.; Fields, D.J.
NASA Technical Reports Server (NTRS)
The combination of massively parallel spatial sampling and accurate spectral radiometry offered by imaging FTS makes it extremely attractive for earth and planetary remote sensing. We constructed a breadboard instrument to help assess the potential for planetary applications of small imaging FTS instruments in the 1 - 5 micrometer range. The results also support definition of the NASA Geostationary Imaging FTS (GIFTS) instrument that will make key meteorological and climate observations from geostationary earth orbit. The Planetary Imaging FTS (PIFTS) breadboard is based on a custom miniaturized Bomen interferometer that uses corner cube reflectors, a wishbone pivoting voice-coil delay scan mechanism, and a laser diode metrology system. The interferometer optical output is measured by a commercial infrared camera procured from Santa Barbara Focalplane. It uses an InSb 128x128 detector array that covers the entire FOV of the instrument when coupled with a 25 mm focal length commercial camera lens. With appropriate lenses and cold filters the instrument can be used from the visible to 5 micrometers. The delay scan is continuous, but slow, covering the maximum range of +/- 0.4 cm in 37.56 sec at a rate of 500 image frames per second. Image exposures are timed to be centered around predicted zero crossings. The design allows for prediction algorithms that account for the most recent fringe rate so that timing jitter produced by scan speed variations can be minimized. Response to a fixed source is linear with exposure time nearly to the point of saturation. Linearity with respect to input variations was demonstrated to within 0.16% using a 3-point blackbody calibration. Imaging of external complex scenes was carried out at low and high spectral resolution. These require full complex calibration to remove background contributions that vary dramatically over the instrument FOV. Testing is continuing to demonstrate the precise radiometric accuracy and noise characteristics.
Revercomb, Henry E.; Sromovsky, Lawrence A.; Fry, Patrick M.; Best, Fred A.; LaPorte, Daniel D.
NASA Astrophysics Data System (ADS)
Polarized infrared (IR) absorbance of carbonyl groups in the electrically unwound SC/* phase in planar aligned cells are studied as a function of IR polarizer rotation angle and the sign of the applied electric field for several ferroelectric liquid crystals. The various absorbance profiles under the electric field are analyzed using newly derived general formulas for polarized IR absorption. We report four different IR experiments. First, we study the biased rotational motion of the carbonyl groups, and there are no significant differences correlated with their positions in the molecules. The various carbonyl group absorbance profiles are described in terms of two moments
Jang, Won Gun
Implementation of image encryption using the phase-contrast technique
NASA Astrophysics Data System (ADS)
An image encoding scheme using the phase-contrast technique and a random phase distribution is proposed to encrypt images in phase masks. The robustness of the encoding is assured by the non-linearities intrinsic to the phase-contrast technique and the bandwidth of the random phase distribution. The advantage of this method, compared to the previous methods proposed, is the direct encoding of the image without any iterative calculation to generate the phase mask. This approach permits practical applications since the final phase mask could be implemented using thermoplastic plates and spatial light modulators (Slims).
Neto, Luiz G.
NASA Astrophysics Data System (ADS)
The combination of massively parallel spatial sampling and accurate spectral radiometry offered by imaging FTS makes it extremely attractive for earth and planetary remote sensing. We constructed a breadboard instrument to help assess the potential for planetary applications of small imaging FTS instruments in the 1-5 micrometers range. The results also support definition of the NASA Geostationary Imaging FTS instrument that will make key meteorological and climate observations from geostationary earth orbit. The PIFTS pivoting voice- coil delay scan mechanism, and laser diode metrology system. The interferometer optical output is measured by a commercial IR camera procured from Santa Barbara Focal plane. It uses an InSb 128 by 128 detector array that covers the entire FOV of the instrument when coupled with a 25-mm focal length commercial camera lens. With appropriate lenses and cold filters the instrument can be used from the visible to 5 micrometers . The delay scan is continuos, but slow, covering the maximum range of +/- 0.4 cm in 37.56 sec at a rate of 500 image frames per second. Image exposures are timed to be centered around predicted zero crossings. The design allows for prediction algorithms that account for the most recent fringe rate so that timing jitter produced by scan speed variations can be minimized. Response to a fixed source is linear with exposure time nearly to the point of saturation. Linearity with respect to input variations was demonstrated to within 0.16 percent using a 3-point blackbody calibration. Imaging of external complex scenes was carried out at low and high spectral resolution. These require full complex calibration to remove background contributions that vary dramatically over the instrument FOV. Testing is continuing to demonstrate the precise radiometric accuracy and noise characteristics.
Revercomb, Henry E.; Sromovsky, Lawrence A.; Fry, Patrick M.; Best, Fred A.; LaPorte, Daniel D.
Phase-contrast imaging of thin biomaterials.
The necessity of information about the inner microscopical features of low absorbing materials is one of the most important goals in the structural research field. So far, non destructive analysis have been performed using contact radiography giving the scope for great advances in the production and application of new materials. However, the nature of interaction, namely X-ray absorption, limited the observations only to materials having sufficient heavy elements content. The adoption of a different X-ray interaction with matter which involves refractive properties of materials is at the basis of phase-contrast imaging. The novel method allows the use of high X-ray energies, for a deeper penetration and a lower released dose, without losing any information on the nature of the sample. A demonstration study, performed at the third generation European Synchrotron Radiation Facility (ESRF)-Grenoble, to show the potential of the new technique applied to biomaterials characterization is presented here. The test samples are a commercial matrix barrier (GUIDOR) intended to aid the healing process after periodontal surgery and a hydroxyapatite thin slab originally deposited by plasma spray technique on a TA6V alloy substrate. Phase-contrast images showed significant advantages revealing features that have negligible absorption contrast. The technique can be successfully used for the characterization of biomaterials. PMID:11374450
Baruchel, J; Lodini, A; Romanzetti, S; Rustichelli, F; Scrivani, A
Ultrahigh Speed Imaging of the Rat Retina Using Ultrahigh Resolution Spectral/Fourier Domain OCT
We performed OCT imaging of the rat retina at 70,000 axial scans per second with ~3 ?m axial resolution. Three-dimensional OCT (3D-OCT) data sets of the rat retina were acquired. The high speed and high density data sets ...
Liu, Jonathan Jaoshin
Fourier cross-sectional profile for vessel detection on retinal images
Retinal blood vessels are important objects in ophthalmologic images. In spite of many attempts for vessel detection, it appears that existing methodologies are based on edge detection or modeling of vessel cross-sectional profiles in intensity. The application of these methodologies is hampered by the presence of a wide range of retinal vessels. In this paper we define a universal representation
Tao Zhu
For dynamic samples and/or for simple ease-of-use experiments, single-image phase contrast tomography is a very effective method for the 3D visualization of materials which would otherwise be indiscernible in attenuation based x-ray imaging. With binary samples (e.g. air-material) and monochromatic wavefields a transport-of-intensity (TIE)-based phase retrieval algorithm is known to retrieve accurate quantitative maps of the phase distribution. For mixed material samples and/or white beam radiation the algorithm can still produce useful qualitative tomographic reconstructions with significantly improved area contrast. The stability of the algorithm comes with a recognized associated loss of spatial resolution due to its essential behaviour as a low-pass filter. One possible answer to this is an image fusion technique that merges the slices reconstructed from raw phase contrast images and those after phase retrieval, where the improved contrast may be acquired without the associated loss of high-frequency information. We present this technique as a simple few-parameter Fourier method, which is easily tunable and highly compatible with current reconstruction steps. PMID:25401876
Irvine, S; Mokso, R; Modregger, P; Wang, Z; Marone, F; Stampanoni, M
NASA Technical Reports Server (NTRS)
The Fourier Imaging X-ray Spectrometer (FIXS) is one of four instruments on SAC-1, the Argentinian satellite being proposed for launch by NASA on a Scout rocket in 1992/3. The FIXS is designed to provide solar flare images at X-ray energies between 5 and 35 keV. Observations will be made on arcsecond size scales and subsecond time scales of the processes that modify the electron spectrum and the thermal distribution in flaring magnetic structures.
Dennis, Brian R.; Crannell, Carol JO; Desai, Upendra D.; Orwig, Larry E.; Kiplinger, Alan L.; Schwartz, Richard A.; Hurford, Gordon J.; Emslie, A. Gordon; Machado, Marcos; Wood, Kent
The high mass accuracy and resolving power of Fourier transform ion cyclotron resonance mass spectrometers (FT-ICR MS) make them ideal mass detectors for mass spectrometry imaging (MSI), promising to provide unmatched molecular resolution capabilities. The intrinsic low tolerance of FT-ICR MS to RF interference, however, along with typically vertical positioning of the sample, and MSI acquisition speed requirements present numerous engineering challenges in creating robotics capable of achieving the spatial resolution to match. This work discusses a two-dimensional positioning stage designed to address these issues. The stage is capable of operating in ?1 � 10�8 mbar vacuum. The range of motion is set to 100 mm � 100 mm to accommodate large samples, while the positioning accuracy is demonstrated to be less than 0.4 micron in both directions under vertical load over the entire range. This device was integrated into three different matrix assisted laser desorption/ionization (MALDI) FT-ICR instruments and showed no detectable RF noise. The �oversampling� MALDI-MSI experiments, under which the sample is completely ablated at each position, followed by the target movement of the distance smaller than the laser beam, conducted on the custom-built 7T FT-ICR MS demonstrate the stability and positional accuracy of the stage robotics which delivers high spatial resolution mass spectral images at a fraction of the laser spot diameter. PMID:21639522
Aizikov, Konstantin; Smith, Donald F.; Chargin, David A.; Ivanov, Sergei; Lin, Tzu-Yung; Heeren, Ron M. A.; O'Connor, Peter B.
Dispersion control with a Fourier-domain optical delay line in a fiber-optic imaging interferometer.
Recently, Fourier-domain (FD) optical delay lines (ODLs) were introduced for high-speed scanning and dispersion compensation in imaging interferometry. We investigate the effect of first- and second-order dispersion on the photocurrent signal associated with an optical coherence imaging system implemented with a single-mode fiber, a superluminescent diode centered at 950 nm +/- 35 nm, a FD ODL, a mirror, and a layered LiTAO3 that has suitable dispersion characteristics to model a skin specimen. We present a practical and useful method to minimize the effect of dispersion through the interferometer and the specimen combined, as well as to quantify the results using two general metrics for resolution. Theoretical and associated experimental results show that, under the optimum solution, the maximum broadening of the point-spread function through a 1-mm-deep specimen is limited to 57% of its original rms width value (i.e., 8.1 microm optimal, 12.7 microm at maximum broadening) compared with approximately 110% when compensation is performed without the specimen taken into account. PMID:16004048
Lee, Kye-Sung; Akcay, A Ceyhun; Delemos, Tony; Clarkson, Eric; Rolland, Jannick P
It is important to develop rapid and sensitive screening assays to assess the biological effects of emerging contaminants. In this contribution, the ability to determine the molecular level effects of 17?-estradiol on single MCF-7 cells using Fourier transform infrared imaging spectroscopy (FT-IRIS) was investigated. The use of FT-IRIS enabled subcellular imaging of the cells and determination of a dose dependent response in mucin concentration at 24 and 48 h of incubation. The 48 h increase in mucin was comparable to increases in cellular proliferation (Pearson R = 0.978). The EC50 values for the E-screen and FT-IRIS assays were 2.29 and 2.56 ppt, respectively, indicating that the molecular changes, which are observed at the single cell level using FT-IRIS, are reflective of physiological changes that are observed as the cell population responds to 17�-estradiol. The FT-IRIS method, when combined with principal component analysis, enabled differentiation and grouping of cells exposed to varying concentrations of 17�-estradiol. The FT-IRIS method shows potential to be used as a rapid and sensitive screening technique for the detection of biological responses to different emerging contaminants in relevant cells or tissues. PMID:24650306
Johnson, Candice M; Pleshko, Nancy; Achary, Mohan; Suri, Rominder P S
NASA Astrophysics Data System (ADS)
Hepatocellular carcinoma (HCC) is the most common form of primary hepatic carcinoma. HCC ranks the fourth most prevalent malignant tumor and the third leading cause of cancer related death in the world. Hepatocellular carcinoma develops in the context of chronic liver disease and its evolution is characterized by progression through intermediate stages to advanced disease and possibly even death. The primary sequence of hepatocarcinogenesis includes the development of cirrhosis, followed by dysplasia, and hepatocellular carcinoma.1 We addressed the utility of Fourier Transform Infrared (FT-IR) spectroscopic imaging, both as a diagnostic tool of the different stages of the disease and to gain insight into the biochemical process associated with disease progression. Tissue microarrays were obtained from the University of Illinois at Chicago tissue bank consisting of liver explants from 12 transplant patients. Tissue core biopsies were obtained from each explant targeting regions of normal, liver cell dysplasia including large cell change and small cell change, and hepatocellular carcinoma. We obtained FT-IR images of these tissues using a modified FT-IR system with high definition capabilities. Firstly, a supervised spectral classifier was built to discriminate between normal and cancerous hepatocytes. Secondly, an expanded classifier was built to discriminate small cell and large cell changes in liver disease. With the emerging advances in FT-IR instrumentation and computation there is a strong drive to develop this technology as a powerful adjunct to current histopathology approaches to improve disease diagnosis and prognosis.
Sreedhar, Hari; Pant, Mamta; Ronquillo, Nemencio R.; Davidson, Bennett; Nguyen, Peter; Chennuri, Rohini; Choi, Jacqueline; Herrera, Joaquin A.; Hinojosa, Ana C.; Jin, Ming; Kajdacsy-Balla, Andre; Guzman, Grace; Walsh, Michael J.
NASA Astrophysics Data System (ADS)
The NASA Geostationary Imaging Fourier Transform Spectrometer (GIFTS) represents a revolutionary step in remote sensing of Earth's atmosphere that will demonstrate the technology and measurement concepts for future NOAA geostationary operational environmental satellites (GOES). GIFTS consists of a 128 x 128 large focal plane array (LFPA) imaging FTS with the spectral coverage from 685 to 1130 cm -1 and 1650 to 2250 cm -1. GIFTS was selected for flight demonstration on NASA's New Millennium Program (NMP) Earth Observing 3 (EO-3) Satellite Mission. GIFTS provides full disk global coverage obtained within an hour at moderate spectral resolutions (e.g. 1.2 cm -1) as well as regional sounding of atmospheric temperature and absorbing gas profiles at high spectral resolution (e.g. 0.6 cm -1). Given the unprecedented data volume produced by GIFTS, lossless data compression is critical for the overall success of the GIFTS experiment where the data is to be disseminated to the user community in real-time and archived for scientific studies and climate assessment. In this paper we will study lossless compression of GIFTS data that has been collected as part of the calibration or Ground Based Tests that were conducted in 2006. Standard compression methods JPEG-2000, JPEG-LS, and CCSDS IDC 9/7M & 5/3 are investigated for compression benchmarks. The bias-adjusted reordering (BAR) preprocessing scheme is also investigated to improve their performance on GIFTS data compression.
Huang, Bormin; Wei, Shih-Chieh; Huang, Allen H.-L.; Smuga-Otto, Maciek; Knuteson, Robert; Revercomb, Henry E.; Smith, William L., Sr.
Implementation of image encryption using the phase-contrast technique
An image encoding scheme using the phase-contrast technique and a random phase distribution is proposed to encrypt images in phase masks. The robustness of the encoding is assured by the non-linearities intrinsic to the phase-contrast technique and the bandwidth of the random phase distribution. The advantage of this method, compared to the previous methods proposed, is the direct encoding of
Luiz G. Neto
Calibration and performance of the airborne fourier transform visible hyperspectral imager (FTVHSI)
A new hyperspectral imager has recently been developed by Kestrel Corporation for use in light aircraft platforms. The instrument provides 256 spectral channels with 87 cm{sup -1} spectral bandwidth over the 350 nm to 1050 nm portion of the spectrum. Operated as a pushbroom imager, the FTVHSI has been shown to have a IFOV of 0.75 mrad, and a FOV of 0.23 rad. The sensor includes an internal spectral/radiometric calibration source, a self contained spectrally resolved downwelling sensor, and complete line of sight and GPS positioning information. The instrument is now completing an extensive set of calibration and performance measurements and is operating from a Cessan TU-206 single engine aircraft. It is anticipated that the sensor will be placed into service in the Spring of 1996. 5 refs., 12 figs., 2 tabs.
Otten, L.J. III; Meigs, A.D. [Kestrel Corp., Albuquerque, NM (United States); Sellar, R.G
NASA Astrophysics Data System (ADS)
Particles in the atmosphere influence visibility, climate, and human health. Secondary organic aerosols (SOA) formed from chemical reactions in the atmosphere constitute a portion of total organic particle mass. Most research on SOA has focused on gas phase reactions; however, reactions taking place in cloud and fog drops may be significant. One group of water-soluble compounds that participate in these reactions is phenols. Phenols, emitted from biomass burning, react in the aqueous phase to form low-volatility SOA products. The products formed from these reactions are currently poorly characterized. In order to characterize laboratory-generated samples, we are developing an attenuated total reflectance-Fourier transform infrared spectroscopic (ATR-FTIR) technique to identify and quantify organic functional groups in SOA. Aqueous SOA is made in the laboratory by illuminating solutions of phenolic compounds with an oxidant. The illuminated solution is then blown to dryness in order to determine the mass of SOA produced. The dry SOA is reconstituted in water and drops of this solution are placed onto a single-reflection ATR accessory. In order to identify and quantify functional groups in the complex SOA samples, it is necessary to calibrate with compounds and mixtures of compounds containing bond types similar to those found in the laboratory-generated SOA. Initially, focus has been placed on multiple peaks located in the region between 1800 cm-1 and 800 cm-1, including peaks for C=O and C-O. We distinguish between characteristic absorbances to begin determining the organic functional group composition of the SOA samples. This ATR-FTIR technique complements information from mass spectrometry measurements and allows us to quantify organic mass for non-volatile SOA products.
George, K.; Ruthenburg, T. C.; Smith, J.; Anastasio, C.; Dillner, A. M.
Phase Retrieval Using a Genetic Algorithm on the Systematic Image-Based Optical Alignment Testbed
NASA Technical Reports Server (NTRS)
NASA s Marshall Space Flight Center s Systematic Image-Based Optical Alignment (SIBOA) Testbed was developed to test phase retrieval algorithms and hardware techniques. Individuals working with the facility developed the idea of implementing phase retrieval by breaking the determination of the tip/tilt of each mirror apart from the piston motion (or translation) of each mirror. Presented in this report is an algorithm that determines the optimal phase correction associated only with the piston motion of the mirrors. A description of the Phase Retrieval problem is first presented. The Systematic Image-Based Optical Alignment (SIBOA) Testbeb is then described. A Discrete Fourier Transform (DFT) is necessary to transfer the incoming wavefront (or estimate of phase error) into the spatial frequency domain to compare it with the image. A method for reducing the DFT to seven scalar/matrix multiplications is presented. A genetic algorithm is then used to search for the phase error. The results of this new algorithm on a test problem are presented.
Taylor, Jaime R.
Quantitative assessment of effects of phase aberration and noise on high-frame-rate imaging.
The goal of this paper is to quantitatively study effects of phase aberration and noise on high-frame-rate (HFR) imaging using a set of traditional and new parameters. These parameters include the traditional -6-dB lateral resolution, and new parameters called the energy ratio (ER) and the sidelobe ratio (SR). ER is the ratio between the total energy of sidelobe and the total energy of mainlobe of a point spread function (PSF) of an imaging system. SR is the ratio between the peak value of the sidelobe and the peak value of the mainlobe of the PSF. In the paper, both simulation and experiment are conducted for a quantitative assessment and comparison of the effects of phase aberration and noise on the HFR and the conventional delay-and-sum (D&S) imaging methods with the set of parameters. In the HFR imaging method, steered plane waves (SPWs) and limited-diffraction beams (LDBs) are used in transmission, and received signals are processed with the Fast Fourier Transform to reconstruct images. In the D&S imaging method, beams focused at a fixed depth are used in transmission and dynamically focused beams are used in reception for image reconstruction. The simulation results show that the average differences between the -6-dB lateral beam widths of the HFR imaging and the D&S imaging methods are -0.1337mm for SPW and -0.1481mm for LDB, which means that the HFR imaging method has a higher lateral image resolution than the D&S imaging method since the values are negative. In experiments, the average differences are also negative, i.e., -0.2804mm for SPW and -0.3365mm for LDB. The results for the changes of ER and SR between the HFR and the D&S imaging methods have negative values, too. After introducing phase aberration and noise, both simulations and experiments show that the HFR imaging method has also less change in the -6-dB lateral resolution, ER, and SR as compared to the conventional D&S imaging method. This means that the HFR imaging method is less sensitive to the phase aberration and noise. Based on the study of the new parameters on the HFR and the D&S imaging methods, it is expected that the new parameters can also be applied to assess quality of other imaging methods. PMID:22546551
Chen, Hong; Lu, Jian-yu
Fast Two-Phase Image Deblurring Under Impulse Noise
In this note, we propose a two-phase approach to restore images corrupted by blur and impulse noise. In the first phase, we identify the outlier candidates �the pixels that are likely to be corrupted by impulse noise. We consider that the remaining data pixels are essentially free of outliers. Then in the second phase, the image is deblurred and denoised
Jian-Feng Cai; Raymond H. Chan; Mila Nikolova
NSDL National Science Digital Library
The Fourier program displays the Fourier transform of a user-defined complex spatial function of position. The default spatial function is a complex Gaussian. Additional parameters can be specified using the Display | Switch GUI menu item. Fourier is an Open Source Physics program written for the teaching of mathematical methods in the sciences. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the math_fourier.jar file will run the program if Java is installed. Other mathematical methods programs are also available. They can be found by searching ComPADRE for Open Source Physics, OSP, or Math.
Christian, Wolfgang
Structured illumination microscopy (SIM) is an established microscopy technique typically used to image samples at resolutions beyond the diffraction limit. Until now, however, achieving sub-diffraction resolution has predominantly been limited to intensity-based imaging modalities. Here, we introduce an analogue to conventional SIM that allows sub-diffraction resolution, quantitative phase-contrast imaging of optically transparent objects. We demonstrate sub-diffraction resolution amplitude and quantitative-phase imaging of phantom targets and enhanced resolution quantitative-phase imaging of cells. We report a phase accuracy to within 5% and phase noise of 0.06 rad. PMID:24156044
Chowdhury, Shwetadwip; Izatt, Joseph
Real-time measurement of alveolar size and population using phase contrast x-ray imaging
Herein a propagation-based phase contrast x-ray imaging technique for measuring particle size and number is presented. This is achieved with an algorithm that utilizes the Fourier space signature of the speckle pattern associated with the images of particles. We validate this algorithm using soda-lime glass particles, demonstrating its effectiveness on random and non-randomly packed particles. This technique is then applied to characterise lung alveoli, which are difficult to measure dynamically in vivo with current imaging modalities due to inadequate temporal resolution and/or depth of penetration and field-of-view. We obtain an important result in that our algorithm is able to measure changes in alveolar size on the micron scale during ventilation and shows the presence of alveolar recruitment/de-recruitment in newborn rabbit kittens. This technique will be useful for ventilation management and lung diagnostic procedures.
Leong, Andrew F.T.; Buckley, Genevieve A.; Paganin, David M.; Hooper, Stuart B.; Wallace, Megan J.; Kitchen, Marcus J.
Generalized fiber Fourier optics.
A twofold generalization of the optical schemes that perform the discrete Fourier transform (DFT) is given: new passive planar architectures are presented where the 2 � 2 3 dB couplers are replaced by M � M hybrids, reducing the number of required connections and phase shifters. Furthermore, the planar implementation of the discrete fractional Fourier transform (DFrFT) is also described, with a waveguide grating router (WGR) configuration and a properly modified slab coupler. PMID:21686007
Cincotti, Gabriella
X-ray phase imaging with a paper analyzer
We present a simple x-ray phase imaging method that utilizes the sample-induced distortion of a high contrast random intensity pattern to quantitatively retrieve the two-dimensional phase map at the exit surface of a coherently illuminated sample. This reference pattern is created by placing a sheet of sandpaper in the x-ray beam, with the sample-induced distortion observed after propagation to the detector, a meter downstream. Correlation analysis comparing a single ''sample and sandpaper'' image to a reference ''sandpaper only'' image produces two sensitive differential phase contrast images, giving the sample phase gradient in vertical and horizontal directions. These images are then integrated to recover the projected phase depth of the sample. The simple experimental set-up, retention of flux, and the need for only a single sample image per reconstruction suggest that this method is of value in imaging a range of dynamic processes at both synchrotron and laboratory x-ray sources.
Morgan, Kaye S.; Paganin, David M. [School of Physics, Monash University, Victoria 3800 (Australia); Siu, Karen K. W. [Monash Biomedical Imaging, Monash University, Victoria 3800 (Australia); Australian Synchrotron, Victoria 3168 (Australia)
NASA Astrophysics Data System (ADS)
Dual excitation fluorescence imaging has been used as a first step towards multi-wavelength excitation/emission fluorescence spectral imaging. Target cells are transformed keratinocytes, and other osteosarcoma, human breast and color cancer cells. Mitochondrial membrane potential probes, e.g. TMRM (tetramethylrhodamine methyl ester), Mitotracker Green (Molecular Probes, Inc., Eugene OR,USA; a recently synthesized mitochondrial oxygen probe, [PRE,P1"- pyrene butyl)-2-rhodamine ester] allow dual excitation in the UV plus in teh blue-green spectral regions. Also, using the natural endogenous probe NAD(P)H, preliminary results indicate mitochondrial responses to metabolic challenges (e.g. glucose addition), plus changes in mitochonrial distribution and morphology. In terms of application to biomedicine (for diagnostiscs, prognostsics and drug trials) three parameters have been selected in addition to the natural probe NAD(P)H, i.e. vital fluorescence probing of mitochondria, lysosomes and Golgi apparatus. It is hoped that such a multiparameter approach will allow malignant cell characterization and grading. A new area being introduced is the use of similar methodology for biotechnical applications such as the study of the hydrogen-producing alga Chlamydomonas Reinhardtii, and possible agricultural applications, such as Saccharomyces yeast for oenology. Complementation by Photoacoustic Microscopy is also contemplated, to study the internal conversion component which follows the excitation by photons.
Kohen, Elli; Hirschberg, Joseph G.; Berry, John P.; Ozkutuk, Nuri; Ornek, Ceren; Monti, Marco; Leblanc, Roger M.; Schachtschabel, Dietrich O.; Haroon, Sumaira
Multifocus Image Fusion Using Local Phase Coherence Measurement
Multifocus Image Fusion Using Local Phase Coherence Measurement Rania Hassen, Zhou Wang, and email@example.com Abstract. Image fusion is the task of enhancing the perception of a scene by combining information captured by different imaging sensors. A critical issue in the design of image fusion algorithms is to define activ- ity
Wang, Zhou
Techniques on Analysis of Photo Phase Shift Imaging
. Real-time MRI temperature mapping was evaluated using the magnitude and phase difference DICOM images. To reduce noise on the temperature maps, a mask was created using the magnitude images and eliminating pixel values greater than a set threshold...
Terry, Robin 1990-
The application of Fourier transform ion cyclotron resonance (FTICR) mass spectrometry to the quantitative study of molecular recognition in the gas phase is reviewed. Because most quantitative measurements are dependent on accurate determination of the pressure of a neutral reagent, methods for accurate pressure measurement in FTICR, including gauge calibration using a reaction with known rate constants (the traditional method), exothermic proton transfer rate measurement (often the best method when accurate neutral pressures in the trapping cell are desired), and linewidth measurement (a little-used, but generally applicable method) are discussed. The use of rate constant measurements in molecular recognition is illustrated with examples employing natural abundance isotopic labeling to study self-exchange and 2 : 1 ligand:metal complex formation kinetics in crown ether-alkali cation systems. Self-exchange rates do not correlate with alkali cation/crown cavity size relationships, whereas 2 : 1 complex formation kinetics correlate strongly with size relationships. The use of exchange equilibrium constant measurements to characterize molecular recognition is illustrated by alkali cation exchanges between 18-crown-6 and the isomers of dicyclohexano-18-crown-6. These experiments show that the alkyl-substituted ligand binds alkali cations better than unsubstituted 18-crown-6 in the gas phase, in accordance with expectations based on the higher polarizability of the alkyl-substituted ligand. Further, the metal binding thermochemistry differs for the two dicyclohexano-18-crown-6 isomers, with the bowl-shaped cis-syn-cis isomer binding all the alkali cations more strongly than the cis-anti-cis isomer. The measurement of entropies and enthalpies associated with one of the most subtle forms of molecular recognition, enantiomeric discrimination, is illustrated by studies of the discrimination between enantiomers of chiral amines by dimethyldiketopyridino-18-crown-6. This chiral ligand binds chiral primary ammonium cations that have the opposite absolute configuration at their stereocenter more strongly than the enantiomer with the same absolute configuration. Gas-phase studies show that this enantiomeric discrimination is enthalpic in origin, likely related to more favorable pi-pi stacking for the preferred enantiomer. Entropy disfavors binding of the preferred enantiomer. PMID:11599077
Dearden, D V; Liang, Y; Nicoll, J B; Kellersberger, K A
Ultrasonic backscatter imaging by shear-wave-induced echo phase encoding of target locations.
We present a novel method for ultrasound backscatter image formation wherein lateral resolution of the target is obtained by using traveling shear waves to encode the lateral position of targets in the phase of the received echo. We demonstrate that the phase modulation as a function of shear wavenumber can be expressed in terms of a Fourier transform of the lateral component of the target echogenicity. The inverse transform, obtained by measurements of the phase modulation over a range of shear wave spatial frequencies, yields the lateral scatterer distribution. Range data are recovered from time of flight as in conventional ultrasound, yielding a B-mode-like image. In contrast to conventional ultrasound imaging, where mechanical or electronic focusing is used and lateral resolution is determined by aperture size and wavelength, we demonstrate that lateral resolution using the proposed method is independent of the properties of the aperture. Lateral resolution of the target is achieved using a stationary, unfocused, single-element transducer. We present simulated images of targets of uniform and non-uniform shear modulus. Compounding for speckle reduction is demonstrated. Finally, we demonstrate image formation with an unfocused transducer in gelatin phantoms of uniform shear modulus. PMID:21244978
McAleavey, Stephen
Ultrasonic Backscatter Imaging by Shear-Wave-Induced Echo Phase Encoding of Target Locations
We present a novel method for ultrasound backscatter image formation wherein lateral resolution of the target is obtained by using traveling shear waves to encode the lateral position of targets in the phase of the received echo. We demonstrate that the phase modulation as a function of shear wavenumber can be expressed in terms of a Fourier transform of the lateral component of the target echogenicity. The inverse transform, obtained by measurements of the phase modulation over a range of shear wave spatial frequencies, yields the lateral scatterer distribution. Range data are recovered from time of flight as in conventional ultrasound, yielding a B-mode-like image. In contrast to conventional ultrasound imaging, where mechanical or electronic focusing is used and lateral resolution is determined by aperture size and wavelength, we demonstrate that lateral resolution using the proposed method is independent of the properties of the aperture. Lateral resolution of the target is achieved using a stationary, unfocused, single-element transducer. We present simulated images of targets of uniform and non-uniform shear modulus. Compounding for speckle reduction is demonstrated. Finally, we demonstrate image formation with an unfocused transducer in gelatin phantoms of uniform shear modulus. PMID:21244978
McAleavey, Stephen
B0 insensitive multiple-quantum resolved sodium imaging using a phase-rotation scheme
NASA Astrophysics Data System (ADS)
Triple-quantum filtering has been suggested as a mechanism to differentiate signals from different physiological compartments. However, the filtering method is sensitive to static field inhomogeneities because different coherence pathways may interfere destructively. Previously suggested methods employed additional phase-cycles to separately acquire pathways. Whilst this removes the signal dropouts, it reduces the signal-to-noise per unit time. In this work we suggest the use of a phase-rotation scheme to simultaneously acquire all coherence pathways and then separate them via Fourier transform. Hence the method yields single-, double- and triple-quantum filtered images. The phase-rotation requires a minimum of 36 instead of six cycling steps. However, destructive interference is circumvented whilst maintaining full signal-to-noise efficiency for all coherences.
Fiege, Daniel P.; Romanzetti, Sandro; Tse, Desmond H. Y.; Brenner, Daniel; Celik, Avdo; Felder, J�rg; Jon Shah, N.
Phase noise analysis of two wavelength coherent imaging system.
Two wavelength coherent imaging is a digital holographic technique that offers several advantages over conventional coherent imaging. One of the most significant advantages is the ability to extract 3D target information from the phase contrast image at a known difference frequency. However, phase noise detracts from the accuracy at which the target can be faithfully identified. We therefore describe a method for relating phase noise to the correlation of the image planes corresponding to each wavelength, among other parameters. The prediction of the phase noise spectrum of a scene will aid in determining our ability to reconstruct the target. PMID:24514640
Dapore, Benjamin R; Rabb, David J; Haus, Joseph W
We have investigated the spatial distribution of molecular changes associated with C6 glioma progression using Fourier transform infrared (FT-IR) microspectro-imaging in order to determine spectroscopic markers for early diagnosis of tumor growth. Our results showed that at day 7 after tumor implantation, FTIR investigations displayed a very small abnormal zone associated with the proliferation of C6 cells in the caudate putamen. From this day, rats developed solid and well-circumscribed tumors and invasive areas. The volume of peritumoral areas increased rapidly until day 19. The maturation of the tumor was accompanied by a diminution in its proliferative and invasive area. The presence of necrotic areas was visible from day 15. A non-negative least-squares algorithm was used to quantify spatial distribution of molecular changes in tissues (lipids, nucleic acids, and proteins) associated with glioma progression. Compared to those in normal brain, statistical tests on fit coefficients showed that the concentrations of sphingomyelin (SMY), nucleic acids, phosphatidylserine (PS), and galactocerebroside (GalC) were significantly affected during C6 glioma development. These constituents can be used as spectroscopic markers for C6 glioma progression. Indeed, the concentration of DNA decreased significantly from tumor to invasion, to normal brain tissues, the necrotic area has higher concentrations of the Galc than other areas. The PS content was significantly higher in the peritumoral zone and decreased in the tumor zones matter. PMID:19824663
Beljebbar, Abdelilah; Dukic, Sylvain; Amharref, Nadia; Bellefqih, Salima; Manfait, Michel
We report detailed studies of the dynamics of the mitochondrial reticulum in live cells using two independent experimental techniques: Fourier imaging correlation spectroscopy and digital video fluorescence microscopy. When both methods are used to study the same system, it is possible to directly compare measurements of preaveraged statistical dynamical quantities with their microscopic counterparts. This approach allows the underlying mechanism of the observed rates to be determined. Our results indicate that the dynamics of the reticulum structure is composed of two independent contributions, each important on very different time and length scales. During short time intervals (1-15 sec), local regions of the reticulum primarily undergo constrained thermally activated motion. During long time intervals (>15 sec), local regions of the reticulum undergo long-range "jump" motions that are associated with the action of cytoskeletal filaments. Although the frequency of the jumps depend on the physiological state of the cells, the average jump distance ( approximately 0.8 microm) is unaffected by metabolic activity. During short time intervals, the dynamics appear to be spatially heterogeneous, whereas the cumulative effect of the infrequent jumps leads to the appearance of diffusive motion in the limit of long time intervals. PMID:11023889
Margineantu, D; Capaldi, R A; Marcus, A H
We have developed an imaging Fourier transform spectrometer (FTS) for space-based far-infrared astronomical observations. The FTS employs a newly developed photoconductive detector arrays with a capacitive trans-impedance amplifier, which makes the FTS a completely unique instrument. The FTS was installed as a function of the far-infrared instrument (FIS: Far-Infrared Surveyor) on the Japanese astronomical satellite, AKARI, which was launched on February 21, 2006 (UT) from the Uchinoura Space Center. The FIS-FTS had been operated for more than one year before liquid helium ran out on August 26, 2007. The FIS-FTS was operated nearly six hundreds times, which corresponds to more than one hundred hours of astronomical observations and almost the same amount of time for calibrations. As expected from laboratory measurements, the FIS-FTS performed well and has produced a large set of astronomical data for valuable objects. Meanwhile, it becomes clear that the detector transient effect is a considerable factor for FTSs with photoconductive detectors. In this paper, the instrumentation of the FIS-FTS and interesting phenomena related to FTS using photoconductive detectors are described, and future applications of this kind of FTS system are discussed.
Mitsunobu Kawada; Hidenori Takahashi; Noriko Murakami; Hiroshi Matsuo; Yoko Okada; Akiko Yasuda; Shuji Matsuura; Mai Shirahata; Yasuo Doi; Hidehiro Kaneda; Takafumi Ootsubo; Takao Nakagawa; Hiroshi Shibai
- gle discrete Fourier Transform. Watermark casting is per- formed by estimating the Just-Chromatic Discrete Fourier Trans- form (SCDFT) for data embedding. Of the particular rele- vance is the theory that each pair of fre- quency values results in rainbow gratings of different fre- quency and orientation
Zhang, Xiao-Ping
NASA Technical Reports Server (NTRS)
The ultimate remote sensing benefits of the high resolution Infrared radiance spectrometers will be realized with their geostationary satellite implementation in the form of imaging spectrometers. This will enable dynamic features of the atmosphere s thermodynamic fields and pollutant and greenhouse gas constituents to be observed for revolutionary improvements in weather forecasts and more accurate air quality and climate predictions. As an important step toward realizing this application objective, the Geostationary Imaging Fourier Transform Spectrometer (GIFTS) Engineering Demonstration Unit (EDU) was successfully developed under the NASA New Millennium Program, 2000-2006. The GIFTS-EDU instrument employs three focal plane arrays (FPAs), which gather measurements across the long-wave IR (LWIR), short/mid-wave IR (SMWIR), and visible spectral bands. The GIFTS calibration is achieved using internal blackbody calibration references at ambient (260 K) and hot (286 K) temperatures. In this paper, we introduce a refined calibration technique that utilizes Principle Component (PC) analysis to compensate for instrument distortions and artifacts, therefore, enhancing the absolute calibration accuracy. This method is applied to data collected during the GIFTS Ground Based Measurement (GBM) experiment, together with simultaneous observations by the accurately calibrated AERI (Atmospheric Emitted Radiance Interferometer), both simultaneously zenith viewing the sky through the same external scene mirror at ten-minute intervals throughout a cloudless day at Logan Utah on September 13, 2006. The accurately calibrated GIFTS radiances are produced using the first four PC scores in the GIFTS-AERI regression model. Temperature and moisture profiles retrieved from the PC-calibrated GIFTS radiances are verified against radiosonde measurements collected throughout the GIFTS sky measurement period. Using the GIFTS GBM calibration model, we compute the calibrated radiances from data collected during the moon tracking and viewing experiment events. From which, we derive the lunar surface temperature and emissivity associated with the moon viewing measurements.
Tian, Jialin; Smith, William L.; Gazarik, Michael J.
Computational phase imaging based on intensity transport
Light is a wave, having both an amplitude and a phase. However, optical frequencies are too high to allow direct detection of phase; thus, our eyes and cameras see only real values - intensity. Phase carries important ...
Waller, Laura A. (Laura Ann)
High density image-storage holograms by a random phase sampling method.
The random phase sampling method that has been proposed to make high quality and high storage density holograms capable of storing image information is described and discussed from the aspect of the quantitative characteristics of its reconstructed image. The method enables the uniform distribution of light energy over the hologram area made on the exact Fourier transformed plane. The details of the characteristics of the method are investigated, especially with respect to the luminance tone linearity, the signal-to-noise ratio, and the resolution to give good agreement with the results of a calculation. In the experiment, reconstructed images with high quality were obtained from holograms of 2-mm diam, which were made by 10(6) sampling and random phase shifting. By using the random phase sampling medthod, an image retrievel model system storing twenty kinds information was developed. This system holds promise of being used in various practical applications such as holographic ultramicrofilm system or a holographic videopackage system. PMID:20134626
Tsunoda, Y; Takeda, Y
Image quality and dose efficiency of high energy phase sensitive x-ray imaging: Phantom studies
The goal of this preliminary study was to perform an image quality comparison of high energy phase sensitive imaging with low energy conventional imaging at similar radiation doses. The comparison was performed with the following phantoms: American College of Radiology (ACR), contrast-detail (CD), acrylic edge and tissue-equivalent. Visual comparison of the phantom images indicated comparable or improved image quality for all phantoms. Quantitative comparisons were performed through ACR and CD observer studies, both of which indicated higher image quality in the high energy phase sensitive images. The results of this study demonstrate the ability of high energy phase sensitive imaging to overcome existing challenges with the clinical implementation of phase contrast imaging and improve the image quality for a similar radiation dose as compared to conventional imaging near typical mammography energies. In addition, the results illustrate the capability of phase sensitive imaging to sustain the image quality improvement at high x-ray energies and for � breast � simulating phantoms, both of which indicate the potential to benefit fields such as mammography. Future studies will continue to investigate the potential for dose reduction and image quality improvement provided by high energy phase sensitive contrast imaging. PMID:24865208
Wong, Molly Donovan; Wu, Xizeng; Liu, Hong
Phase contrast portal imaging for image-guided microbeam radiation therapy
NASA Astrophysics Data System (ADS)
High-dose synchrotron microbeam radiation therapy is a unique treatment technique used to destroy tumors without severely affecting circumjacent healthy tissue. We applied a phase contrast technique to portal imaging in preclinical microbeam radiation therapy experiments. Phase contrast portal imaging is expected to enable us to obtain higherresolution X-ray images at therapeutic X-ray energies compared to conventional portal imaging. Frontal view images of a mouse head sample were acquired in propagation-based phase contrast imaging. The phase contrast images depicted edge-enhanced fine structures of the parietal bones surrounding the cerebrum. The phase contrast technique is expected to be effective in bony-landmark-based verification for image-guided radiation therapy.
Umetani, Keiji; Kondoh, Takeshi
Multi-phase image segmentation using level sets
NASA Astrophysics Data System (ADS)
A hierarchical multi-phase image segmentation using the original and a modified Chan-Vese 2-phase method is considered. A method of capturing features inside a pre-selected region of interest (ROI) is proposed that effectively restricts the segmentation operation to the ROI. At the first step, a modified image is created by setting the portion of the image outside the ROI to a uniform intensity equal to the mean image intensity inside the ROI. Effectively, this procedure partitions the initial image into two phases, in such a way that the ROI effectively becomes a 'segmented' feature. At the second step, the segmentation procedure is applied to the modified image, partitioning the image in two phases - object and background - inside the ROI. By confining segmentation to the ROI, it is shown, using an artificial image, that objects can be discriminated that could not have been found if segmentation had been performed on the entire image. If necessary, this second step can be repeated to further segment features of interest within the ROI, thereby providing a multi-phase segmentation procedure. ROI placement around features of interest requires prior knowledge, and may be derived from an atlas or manually prescribed by the operator. In this way, segmentation is possible on low-contrast features of interest, while ignoring features irrelevant for a particular application. Examples are provided for segmentation of several 2D/3D images performed both on entire images and inside a ROI.
Zhilkin, Peter; Alexander, Murray
Schlieren confocal microscopy for phase-relief imaging.
We demonstrate a simple phase-sensitive microscopic technique capable of imaging the phase gradient of a transparent specimen, based on the Schlieren modulation and confocal laser scanning microscopy (CLSM). The incident laser is refracted by the phase gradient of the specimen and excites a fluorescence plate behind the specimen to create a secondary illumination; then the fluoresence is modulated by a partial obstructor before entering the confocal pinhole. The quantitative relationship between the image intensity and the sample phase gradient can be derived. This setup is very easy to be adapted to current confocal setups, so that multimodality fluorescence/structure images can be obtained within a single system. PMID:24690716
Xie, Hao; Jin, Dayong; Yu, Junjie; Peng, Tong; Ding, Yichen; Zhou, Changhe; Xi, Peng
Full range polarization-sensitive Fourier domain optical coherence tomography
A swept source based polarization-sensitive Fourier domain optical coherence tomography (FDOCT) system was developed that can acquire the Stokes vectors, polarization diversity intensity and birefringence images in biological tissue by reconstruction of both the amplitude and phase terms of the interference signal. The Stokes vectors of the reflected and backscattered light from the sample were determined by processing the analytical
Jun Zhang; J. Stuart Nelson; Woonggyu Jung; Zhongping Chen
Phase based level set segmentation of ultrasound images
Ultrasound images segmentation is a difficult problem due to speckle noise, low contrast and local changes of intensity. Intensity based methods do not perform particularly well on ultrasound images. However, it has been previously shown that these images respond well to local phase-based methods which are theoretically intensity-invariant. Here, we use level set propagation to capture the left ventricle boundaries.
A. Belaid; D. Boukerroui; Y. Maingourd; J.-F. Lerallut
Phase-Based Level Set Segmentation of Ultrasound Images
Ultrasonic image segmentation is a difficult problem due to speckle noise, low contrast, and local changes of intensity. Intensity-based methods do not perform particularly well on ul- trasound images. However, it has been previously shown that these images respond well to local phase-based methods which are the- oretically intensity invariant. Here, we use level set propagation to capture the left
Ahror Belaid; Djamal Boukerroui; Yves Maingourd; Jean-Fran�ois Lerallut
Reversible ischemia in myocardial segments with severe hypoperfusion ({le}50% of normal activity) on stress Tc-99m-Sestamibi (MIBI) images was assessed with ECG-gated tomographic (GSPECT) indices of myocardial thickening, as reflected by an increase in regional count density during systole. GSPECT bullseye plots were generated for each of 8 frames acquired after stress MIBI injection in 39 patients with coronary artery disease and at least one severe perfusion defect on summed SPECT images. Using first harmonic Fourier amplitude (AMP) and AMP to perfusion ratio (APR) images, regional myocardial systolic thickening was assessed using a 5-segment model, scored 0 to 3, for absent, minimal, mildly reduced or normal thickening. These data were regionally compared with defect reversibility assessed using a separate-day or a preceding same-day resting MIBI injection images, in which these segments were scored from 0 to 3 for absent, minimal, partial or complete defect reversibility. Of 91 severe stress defects, 16 showed absent, 18 minimal, 43 partial, and 14 complete reversibility on resting images. Both AMP and APR scores were in statistically significant agreement (p=.0218 and .0006) with resting image reversibility grades, with 79% (p=.0324) and 86% (p=.0001) agreement on the presence of reversibility on resting imaging, respectively. AMP correctly identified 89% of the reversibility defects on rest images, while the APR identified 99% (p=.0248 vs. AMP). On analysis of segment scores, the AMP slightly underestimated the degree of rest image reversibility (p=.0235), while APR images indicated more reversibility thin did resting images (p=.0092). In conclusion, GSPECT MIBI bullseye Fourier AMP images correlate well with the pattern of reversibility on resting MIBI in severe stress perfusion defects. When indexed for the degree of hypoperfusion, the Fourier images depict a greater degree of defect reversibility than resting MIBI images.
Williams, K.A.; Taillon, L.A. [Univ. of Chicago, IL (United States)
Quantitative phase from defocused intensity by image deconvolution
NASA Astrophysics Data System (ADS)
We present a method for quantitative phase recovery using the axially defocused intensity information based on the phase optical transfer function in defocused situation. The image formation process is linearized by subtraction of two intensity images with equal and opposite defocus distances and quantitative phase information is separated and extracted by solving an inverse problem with Wiener filtering. Experiments confirm the accuracy and stability of the proposed method outperforms the transport-of-intensity reconstruction method.
Zuo, Chao; Chen, Qian; Asundi, Anand
A direct method for retrieval of the projected potential from a single HREM image of a thin sample is presented. Both out-of-focus and astigmatic images can be restored. The defocus and astigmatism values are first determined from the Fourier transform of the digitised HREM image. Then a filter is applied which reverts the phases of those Fourier components which have
Xiaodong Zou; Margareta Sundberg; Maxim Larine; Sven Hovm�ller
Effect of coherence loss in differential phase contrast imaging
NASA Astrophysics Data System (ADS)
Coherence property of x-rays is critical in the grating-based differential phase contrast (DPC) imaging because it is the physical foundation that makes any form of phase contrast imaging possible. Loss of coherence is an important experimental issue, which results in increased image noise and reduced object contrast in DPC images and DPC cone beam CT (DPC-CBCT) reconstructions. In this study, experimental results are investigated to characterize the visibility loss (a measurement of coherence loss) in several different applications, including different-sized phantom imaging, specimen imaging and small animal imaging. Key measurements include coherence loss (relative intensity changes in the area of interest in phase-stepping images), contrast and noise level in retrieved DPC images, and contrast and noise level in reconstructed DPC-CBCT images. The influence of size and composition of imaged object (uniform object, bones, skin hairs, tissues, and etc) will be quantified. The same investigation is also applied for moir� pattern-based DPC-CBCT imaging with the same exposure dose. A theoretical model is established to relate coherence loss, noise level in phase stepping images (or moir� images), and the contrast and noise in the retrieved DPC images. Experiment results show that uniform objects lead to a small coherence loss even when the attenuation is higher, while objects with large amount of small structures result in huge coherence loss even when the attenuation is small. The theoretical model predicts the noise level in retrieved DPC images, and it also suggests a minimum dose required for DPC imaging to compensate for coherence loss.
Cai, Weixing; Ning, Ruola; Liu, Jiangkun
Relationships between smooth- and small-phase conditions in X-ray phase-contrast imaging.
We analyze some relationships between the small- and smooth-phase conditions in propagation-based X-ray phase-contrast imaging. Although these conditions are generally well-understood, our analysis yields the identification of physical conditions under which they are mathematically equivalent. We also demonstrate that the smooth-phase condition depends not only on the imaging system resolution and object-to-detector distance, but also on the topography of the wavefield phase function. PMID:19933011
Shi, Daxin; Anastasio, Mark A
Phase-retrieval ghost imaging of complex-valued objects
An imaging approach, based on ghost imaging, is reported to recover a pure-phase object or a complex-valued object. Our analytical results, which are backed up by numerical simulations, demonstrate that both the complex-valued object and its amplitude-dependent part can be separately and nonlocally reconstructed using this approach. Both effects influencing the quality of reconstructed images and methods to further improve the imaging quality are also discussed.
Gong Wenlin; Han Shensheng [Key Laboratory for Quantum Optics and Center for Cold Atom Physics of the Chinese Academy of Sciences, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800 (China)
Development of neutron tomography and phase contrast imaging technique
NASA Astrophysics Data System (ADS)
This paper presents design and development of a state of art neutron imaging technique at CIRUS reactor with special reference for techniques adopted for tomography and phase contrast imaging applications. Different components of the beamline such as collimator, shielding, sample manipulator, digital imaging system were designed keeping in mind the requirements of data acquisition time and resolution. The collimator was designed in such a way that conventional and phase contrast imaging can be done using same collimator housing. We have done characterization of fuel pins, study of hydride blisters in pressure tubes hydrogen based cells, two phase flow visualization, and online study of locomotive parts etc. using neutron tomography and radiography technique. We have also done some studies using neutron phase contrast imaging technique on this beamline.
Kashyap, Y. S.; Agrawal, Ashish; Sarkar, P. S.; Shukla, Mayank; Sinha, Amar
Development of neutron tomography and phase contrast imaging technique
This paper presents design and development of a state of art neutron imaging technique at CIRUS reactor with special reference for techniques adopted for tomography and phase contrast imaging applications. Different components of the beamline such as collimator, shielding, sample manipulator, digital imaging system were designed keeping in mind the requirements of data acquisition time and resolution. The collimator was designed in such a way that conventional and phase contrast imaging can be done using same collimator housing. We have done characterization of fuel pins, study of hydride blisters in pressure tubes hydrogen based cells, two phase flow visualization, and online study of locomotive parts etc. using neutron tomography and radiography technique. We have also done some studies using neutron phase contrast imaging technique on this beamline.
Kashyap, Y. S.; Agrawal, Ashish; Sarkar, P. S.; Shukla, Mayank; Sinha, Amar [Neutron and X-ray Physics Facilities, Bhabha Atomic Research Centre, Mumbai-400085 (India)
Fast volumetric phase-gradient imaging in thick samples.
Oblique back-illumination microscopy (OBM) provides high resolution, sub-surface phase-gradient images from arbitrarily thick samples. We present an image formation theory for OBM and demonstrate that OBM lends itself to volumetric imaging because of its capacity for optical sectioning. In particular, OBM can provide extended depth of field (EDOF) images from single exposures, by rapidly scanning the focal plane with an electrically tunable lens. These EDOF images can be further enhanced by deconvolution. We corroborate our theory with experimental volumetric images obtained from transparent bead samples and mouse cortical brain slices. PMID:24515075
David Giese, J; Ford, Tim N; Mertz, Jerome
Adaptive optics and phase diversity imaging for responsive space applications.
The combination of phase diversity and adaptive optics offers great flexibility. Phase diverse images can be used to diagnose aberrations and then provide feedback control to the optics to correct the aberrations. Alternatively, phase diversity can be used to partially compensate for aberrations during post-detection image processing. The adaptive optic can produce simple defocus or more complex types of phase diversity. This report presents an analysis, based on numerical simulations, of the efficiency of different modes of phase diversity with respect to compensating for specific aberrations during post-processing. It also comments on the efficiency of post-processing versus direct aberration correction. The construction of a bench top optical system that uses a membrane mirror as an active optic is described. The results of characterization tests performed on the bench top optical system are presented. The work described in this report was conducted to explore the use of adaptive optics and phase diversity imaging for responsive space applications.
Smith, Mark William; Wick, David Victor
We demonstrate ultrahigh speed swept source/Fourier domain ophthalmic OCT imaging using a short cavity swept laser at 100,000�400,000 axial scan rates. Several design configurations illustrate tradeoffs in imaging speed, sensitivity, axial resolution, and imaging depth. Variable rate A/D optical clocking is used to acquire linear-in-k OCT fringe data at 100kHz axial scan rate with 5.3um axial resolution in tissue. Fixed rate sampling at 1 GSPS achieves a 7.5mm imaging range in tissue with 6.0um axial resolution at 100kHz axial scan rate. A 200kHz axial scan rate with 5.3um axial resolution over 4mm imaging range is achieved by buffering the laser sweep. Dual spot OCT using two parallel interferometers achieves 400kHz axial scan rate, almost 2X faster than previous 1050nm ophthalmic results and 20X faster than current commercial instruments. Superior sensitivity roll-off performance is shown. Imaging is demonstrated in the human retina and anterior segment. Wide field 12�12mm data sets include the macula and optic nerve head. Small area, high density imaging shows individual cone photoreceptors. The 7.5mm imaging range configuration can show the cornea, iris, and anterior lens in a single image. These improvements in imaging speed and depth range provide important advantages for ophthalmic imaging. The ability to rapidly acquire 3D-OCT data over a wide field of view promises to simplify examination protocols. The ability to image fine structures can provide detailed information on focal pathologies. The large imaging range and improved image penetration at 1050nm wavelengths promises to improve performance for instrumentation which images both the retina and anterior eye. These advantages suggest that swept source OCT at 1050nm wavelengths will play an important role in future ophthalmic instrumentation. PMID:20940894
Potsaid, Benjamin; Baumann, Bernhard; Huang, David; Barry, Scott; Cable, Alex E.; Schuman, Joel S.; Duker, Jay S.; Fujimoto, James G.
Fourier-domain biophotoacoustic subsurface depth selective amplitude and phase imaging of
- phasize the operating energy conversion mechanism of bio- logical tissues has received significant to the frequency spectrum of the detected acoustic response and of a narrow signal detection bandwidth to improve of breast and brain tumors.13 Detection of laser-induced acoustic waves reveals localized increase
Mandelis, Andreas
Single Cancer Cells from Human tumors are being detected and imaged by Fourier Transform Infrared (FT-IR), Fourier Transform Near Infrared (FT-NIR)Hyperspectral Imaging and Fluorescence Correlation Microspectroscopy. The first FT-NIR chemical, microscopic images of biological systems approaching one micron resolution are here reported. Chemical images obtained by FT-NIR and FT-IR Microspectroscopy are also presented for oil in soybean seeds and somatic embryos under physiological conditions. FT-NIR spectra of oil and proteins were obtained for volumes as small as two cubic microns. Related, HR-NMR analyses of oil contents in somatic embryos as well as 99% accurate calibrations are also presented here with nanoliter precision. Such high-resolution, 400 MHz H-1 NMR analyses allowed the selection of mutagenized embryos with higher oil content (e.g. >~20%) compared to the average levels in non-mutagenized control embryos. Moreover, developmental changes in single soybean seeds and/or somatic embryos may be monito...
Baianu,I C; Hofmann, N E; Korban, S S; Lozano, P; You, T
Multilayer phased microcoil array for magnetic resonance imaging
We present for the first time wirebonded microcoils arranged in a planar phased-array configuration for large field of view (FOV) microscale magnetic resonance imaging (MRI) of 2D samples. The phased array consists of seven microcoils providing a sensitive area of 18.3 mm 2 . We demonstrate successful high-resolution imaging of a water phantom with 16 x 16 ?? m 2
O. G. Gruschke; L. Clad; N. Baxan; K. Kratt; M. Mohmmadzadeh; D. von Elverfeldt; A. Peter; J. Hennig; V. Badilita; U. Wallrabe; J. G. Korvink
Phase Sensitive X-Ray Imaging: Towards its Interdisciplinary Applications
NASA Astrophysics Data System (ADS)
X-ray phase imaging including phase tomography has been attracting increasing attention during the past few decades. The advantage of X-ray phase imaging is that an extremely high sensitivity is achieved for weakly absorbing materials, such as biological soft tissues, which generate a poor contrast by conventional schemes. Especially for such living samples, where the reduction of the applied dose is of paramount interest, phase sensitive measurements schemes have an inherent potential for a significant dose reduction combined with an image quality enhancement. Several methods have been invented for x-ray phase contrast imaging that either use an approach based on interferometry, diffraction or wave-field propagation. Some of these techniques have a potential for commercial applications, such as in medicine, non-destructive testing, security and inspection. The scope of this manuscript thus deals with one particular such technique that measures the diffraction caused by the specimen by means of a grating interferometer. Examples of measurements are shown that depict the potential of phase contrast imaging for future commercial applications, such as in medical imaging, non-destructive testing and inspection for quality control. The current state of the technology is briefly reviewed as well as its shortcomings to be overcome with regard to the applications.
Kottler, C.; Revol, V.; Kaufmann, R.; Urban, C.; Knop, K.; Sennhauser, U.; Jerjen, I.; L�thi, T.; Cardot, F.; Niedermann, P.; Morel, J.-P.; Maake, C.; Walt, H.; Knop, E.; Blanc, N.
ATMOSPHERIC PHASE NOISE AND APERTURE SYNTHESIS IMAGING AT MILLIMETER WAVELENGTHS M. C. H. Wright wavelength aperture synthesis images is limited by atmospheric turbulence. Observing techniques and data of observations of astronomical sources. At optical wavelengths, the seeing is limited by tropospheric density
Militzer, Burkhard
Computer simulation of synthesizing images by digital phased arrays
A method of synthesizing images by digital phased arrays is proposed. Following this method a numerical experiment of image synthesis is conducted to simulate arrays of 64 � 64 by computer. Each array element is assigned a binary digit, that is, it is either excited or nonexcited.
Y. Aoki
X-ray phase sensitive wave-front sensor techniques are detailed that are capable of measuring the entire two-dimensional x-ray electric field, both the amplitude and phase, with a single measurement. These Hartmann sensing and 2-D Shear interferometry wave-front sensors do not require a temporally coherent source and are therefore compatible with x-ray tubes and also with laser-produced or x-pinch x-ray sources.
Baker, Kevin Louis
Motionless phase stepping in X-ray phase contrast imaging with a compact source
X-ray phase contrast imaging offers a way to visualize the internal structures of an object without the need to deposit significant radiation, and thereby alleviate the main concern in X-ray diagnostic imaging procedures today. Grating-based differential phase contrast imaging techniques are compatible with compact X-ray sources, which is a key requirement for the majority of clinical X-ray modalities. However, these methods are substantially limited by the need for mechanical phase stepping. We describe an electromagnetic phase-stepping method that eliminates mechanical motion, thus removing the constraints in speed, accuracy, and flexibility. The method is broadly applicable to both projection and tomography imaging modes. The transition from mechanical to electromagnetic scanning should greatly facilitate the translation of X-ray phase contrast techniques into mainstream applications. PMID:24218599
Miao, Houxun; Chen, Lei; Bennett, Eric E.; Adamo, Nick M.; Gomella, Andrew A.; DeLuca, Alexa M.; Patel, Ajay; Morgan, Nicole Y.; Wen, Han
Phase Contrast Neutron Imaging using Single and Multiple Pinhole Apertures
NASA Astrophysics Data System (ADS)
In the present work phase contrast neutron imaging at low/medium intensity neutron sources using single and multiple pinhole apertures has been investigated. Phase contrast techniques utilize the wave nature of neutrons (along with the particle nature used by conventional neutron imaging) to enhance the material edge contrast in the object image. The technique benefits from differences in the coherent scattering length densities of different materials in the sample. The performed investigation included multiple aspects related to the theoretical understanding, simulation techniques, experimental feasibility at the PULSTAR imaging facility, and image processing/reconstruction pertaining to these techniques. The theoretical aspects include the physical understanding of phase contrast as well as multi-pinhole imaging. The theory for the image intensity variation for mixed phase-amplitude objects was developed. Presence of an additional interaction term, quantified by the scalar product of the gradient of real and imaginary parts of the transmission function of the object, was found in the neutron intensity expression. Further, a theoretical understanding of the image formation process using multi-pinhole masks was also developed. It was shown that the formed image of the object from a multiple pinhole aperture can be written as a convolution of the source mask image at the detector with the object image obtained through a single pinhole. The theoretical work performed above was used to develop simulation and design methodologies. An image simulation technique was developed to simulate phase contrast images of specified objects using the phase-amplitude formulation. Demonstration of the technique was performed using various designed phantoms. The simulation technique can act as a tool for assessing the usefulness of phase contrast imaging as an edge enhancement method for a particular sample. Performance of phase contrast neutron imaging requires a spatially coherent beam. Spatial coherence of the beam can be increased by increasing the L d ratio and the average wavelength of the neutron beam. These methods of improving the spatial coherence lead to a significant reduction in the neutron intensity available to image the object, thereby favoring its implementation at high intensity neutron sources. However, in order to harness the potential of this technique, its usability needs to be expanded to low/medium intensity neutron sources that are more common worldwide. In the present work experimental demonstration of the technique was performed at the 1MWth PULSTAR reactor, which represents a medium intensity neutron source. This required meticulous design to maximize the spatial coherence of the beam while maintaining the neutron intensity at the image plane. Twelve inches of single crystal sapphire was used to filter out fast neutrons to lower the average energy of the neutron beam. A 500mum gadolinium foil with a 0.5mm diameter pinhole was used as the aperture following which, a 0.6o beam divergence was provided using borated polyethylene discs with holes of increasing diameter. In order to improve the SNR in the image multiple pinhole apertures were explored. Uncoded masks were considered for this purpose. A collimator with seven pinholes was designed to perform the imaging. Masks with greater number of pinholes were studied using simulations but could not be explored experimentally due to space restrictions at the facility. The image reconstruction of the raw data was performed using a least square de-convolution technique. Tikhonov regularization was investigated in this regard to make the convolution matrices well behaved wherever required. Also, various de-noising techniques like median filtering, Wiener filtering and soft thresholding using Symlets were explored to improve the reconstructed image. It was concluded that the choice of the de-noising techniques depends upon the properties desired in the reconstructed image like smoothness, blockiness etc. Thus, in the present work two of the comparatively new neutron imagin
Mishra, Kaushal Kishor
Four-dimensional (4D) imaging during structural changes are reported here using ultrafast electron microscopy (UEM). For nanostructures, the phase transition in the strongly correlated material vanadium dioxide is our case study. The transition is initiated and probed in situ, in the microscope, by a femtosecond near-infrared and electron pulses (at 120 keV). Real-space imaging and Fourier-space diffraction patterns show that the transition from the monoclinic (P21/c) to tetragonal (P42/mnm) structure is induced in 3 +/- 1 ps, but there exists a nonequilibrium (metastable) structure whose nature is determined by electronic, carrier-induced, structural changes. For the particles studied, the subsequent recovery occurs in about 1 ns. Because of the selectivity of excitation from the 3d parallel-band, and the relatively low fluence used, these results show the critical role of carriers in weakening the V4+-V4+ bonding in the monoclinic phase and the origin of the nonequilibrium phase. A theoretical two-dimensional (2D) diffusion model for nanoscale materials is presented, and its results account for the observed behavior. PMID:17622175
Lobastov, Vladimir A; Weissenrieder, Jonas; Tang, Jau; Zewail, Ahmed H
Water is ubiquitous in the mouths of healthy individuals and is a major interfering factor in the development of a durable seal between the tooth and composite restoration. Water leads to the formation of a variety of defects in dentin adhesives; these defects undermine the tooth-composite bond. Our group recently analyzed phase partitioning of dentin adhesives using high-performance liquid chromatography (HPLC). The concentration measurements provided by HPLC offered a more thorough representation of current adhesive performance and elucidated directions to be taken for further improvement. The sample preparation and instrument analysis using HPLC are, however, time-consuming and labor-intensive. The objective of this work was to develop a methodology for rapid, reliable, and accurate quantitative analysis of near-equilibrium phase partitioning in adhesives exposed to conditions simulating the wet oral environment. Analysis by Fourier transform infrared (FT-IR) spectroscopy in combination with multivariate statistical methods, including partial least squares (PLS) regression and principal component regression (PCR), were used for multivariate calibration to quantify the compositions in separated phases. Excellent predictions were achieved when either the hydrophobic-rich phase or the hydrophilic-rich phase mixtures were analyzed. These results indicate that FT-IR spectroscopy has excellent potential as a rapid method of detection and quantification of dentin adhesives that experience phase separation under conditions that simulate the wet oral environment. PMID:24359662
Ye, Qiang; Parthasarathy, Ranganathan; Abedin, Farhana; Laurence, Jennifer S.; Misra, Anil; Spencer, Paulette
Fourier transform infrared spectroscopy has been used in conjunction with differential scanning calorimetric measurements to investigate the nature of molecular degradation and its effect on the phase transition temperatures in irradiated polytetrafluoroethylene (PTFE). Both the 19 and 30/sup 0/C transitions are observed to exhibit similar shifts to low temperatures upon irradiation. Infrared absorbance subtraction data from irradiated PTFE indicate a continual decrease in sample crystallinity accompanied by an increase in the number of free and bonded - COOH groups with increasing dose consistent with molecular degradation by chain scission. By comparing infrared band intensities on a number of irradiated PTFE samples with those from short chain perfluoro n-alkanes, it was determined that the overall reduction in chain length caused by irradiation was primarily responsible for the observed reduction in both phase transition temperatures.
Vanni, H.; Rabolt, J.F.
The Asymmetric Pupil Fourier Wavefront Sensor
NASA Astrophysics Data System (ADS)
This article introduces a novel wavefront sensing approach that relies on the Fourier analysis of a single conventional direct image. In the high Strehl ratio regime, the relation between the phase measured in the Fourier plane and the wavefront errors in the pupil can be linearized, as was shown in a previous work that introduced the notion of generalized closure-phase, or kernel-phase. The technique, to be usable as presented requires two conditions to be met: (1) the wavefront errors must be kept small (of the order of one radian or less), and (2) the pupil must include some asymmetry, which can be introduced with a mask, for the problem to become solvable. Simulations show that this asymmetric pupil Fourier wavefront sensing or APF-WFS technique can improve the Strehl ratio from 50% to over 90% in just a few iterations, with excellent photon noise sensitivity properties, suggesting that on-sky close loop APF-WFS is possible with an extreme adaptive optics system.
Martinache, Frantz
Phase retrieval for undersampled broadband images
to determine the aberrations of an optical system from system point-spread functions (blurred images of point, which employ analytic expressions for the gradient of an error metric, required narrow-band light a flexible description of the aberrations, are described in this study. © 1999 Optical Society of America [S
Fienup, James R.
Holographic nondestructive testing at the Fourier plane
A technique for the holographic nondestructive testing at the Fourier plane is proposed. An object's lateral and longitudinal rigid body translations are equivalent to linear and quadratic phase shifts in the object's Fourier spectrum. Thus a double-exposure hologram at the Fourier plane produces fringes on reconstruction which are straight for lateral and circular for longitudinal object translation. The fringes are
C. Roychoudhuri; R. Machorro
Phase Contrast Imaging of Biological Materials using LEBRA-PXR
NASA Astrophysics Data System (ADS)
Phase contrast x-ray imaging is an important technique for investigation of materials consisted of light atoms, such as soft biological tissues. The tunable monochromatic x-ray source based on Parametric X-ray Radiation (PXR), which was developed at Laboratory for Electron Beam Research and Application (LEBRA) in Nihon University, provides x-rays with a high spatial coherence which is an essential property required for phase contrast imaging. In preliminary experiment, refraction contrast images for leaf tissues of a tree and animal specimen have been obtained successfully with the LEBRA-PXR x-rays. In the imaging system, the x-ray that passed through the sample once reflects off the silicon perfect-crystal x-ray analyzer at the Bragg angle, and then enters the imaging plate. The bright-field and the dark-field phase contrast images have been obtained by infinitesimal rotations of the analyzer, showing the evidence of contrast reversal. Although the conventional radiograph by absorption contrast was also taken with the LEBRA-PXR, significant differences are found between the radiograph and the phase contrast images.
Kuwada, T.; Hayakawa, Y.; Nogami, K.; Sakai, T.; Tanaka, T.; Hayakawa, K.; Sato, I.
Self-imaging of transparent objects and structures in focusing of a spatially phase-modulated laser beam into an extended weakly absorbing medium is described. The laser power level that is necessary for effective imaging corresponds to the illuminating beam power when thermal self-defocusing starts evolving in the medium. The effect can be described in terms of the ideology of Zernike's classical phase-contrast method. Edge enhancement in visualised images of transparent objects is experimentally demonstrated. Self-imaging of a microscopic object in the form of transparent letters and long-lived refractive-index fluctuations in liquid glycerol is shown. Due to the adaptivity of the process under consideration, unlike the classical case, self-imaging occurs also in the situations where a beam is displaced (undergoes random walk) as a whole in the Fourier plane, for example, in the presence of thermal flows. (image processing)
Bubis, E L [Institute of Applied Physics, Russian Academy of Sciences, Nizhny Novgorod (Russian Federation)
Phase Preserving Dynamic Range Compression of Aeromagnetic Images
NASA Astrophysics Data System (ADS)
Geoscientific images with a high dynamic range, such as aeromagnetic images, are difficult to present in a manner that facilitates interpretation. The data values may range over 20000 nanoteslas or more but a computer monitor is typically designed to present input data constrained to 8 bit values. Standard photographic high dynamic range tonemapping algorithms may be unsuitable, or inapplicable to such data because they are have been developed on the basis of statistics of natural images, feature types found in natural images, and models of the human visual system. These algorithms may also require image segmentation and/or decomposition of the image into base and detail layers but these operations may have no meaning for geoscientific images. For geological and geophysical data high dynamic range images are often dealt with via histogram equalization. The problem with this approach is that the contrast stretch or compression applied to data values depends on how frequently the data values occur in the image and not on the magnitude of any data features themselves. This can lead to inappropriate distortions in the output. Other approaches include use of the Automatic Gain Control algorithm developed by Rajagopalan, or the tilt derivative. A difficulty with these approaches is that the signal can be over-normalized and perception of the overall variations in the signal can be lost. To overcome these problems a method is presented that compresses the dynamic range of an image while preserving local features. It makes no assumptions about the formation of the image, the feature types it contains, or its range of values. Thus, unlike algorithms designed for photographic images, this algorithm can be applied to a wide range of scientific images. The method is based on extracting local phase and amplitude values across the image using monogenic filters. The dynamic range of the image can then be reduced by applying a range reducing function to the amplitude values, for example taking the logarithm, and then reconstructing the image using the original phase values. An important attribute of this approach is that the local phase information is preserved, this is important for the human visual system in interpreting the image. The result is an image that retains the fidelity of its features within a greatly reduced dynamic range. An additional advantage of the method is that the range of spatial frequencies that are used to reconstruct the image can be chosen via high-pass filtering to control the scale of analysis. A relatively low cutoff frequency allows large overall trends in the data to be observed. As the spatial cutoff frequency is progressively increased the analysis becomes more localized and the relative magnitudes of features become more equal.
Kovesi, Peter
Perceived blur in naturally contoured images depends on phase.
Perceived blur is an important measure of image quality and clinical visual function. The magnitude of image blur varies across space and time under natural viewing conditions owing to changes in pupil size and accommodation. Blur is frequently studied in the laboratory with a variety of digital filters, without comparing how the choice of filter affects blur perception. We examine the perception of image blur in synthetic images composed of contours whose orientation and curvature spatial properties matched those of natural images but whose blur could be directly controlled. The images were blurred by manipulating the slope of the amplitude spectrum, Gaussian low-pass filtering or filtering with a Sinc function, which, unlike slope or Gaussian filtering, introduces periodic phase reversals similar to those in optically blurred images. For slope-filtered images, blur discrimination thresholds for over-sharpened images were extremely high and perceived blur could not be matched with either Gaussian or Sinc filtered images, suggesting that directly manipulating image slope does not simulate the perception of blur. For Gaussian- and Sinc-blurred images, blur discrimination thresholds were dipper-shaped and were well-fit with a simple variance discrimination model and with a contrast detection threshold model, but the latter required different contrast sensitivity functions for different types of blur. Blur matches between Gaussian- and Sinc-blurred images were used to test several models of blur perception and were in good agreement with models based on luminance slope, but not with spatial frequency based models. Collectively, these results show that the relative phases of image components, in addition to their relative amplitudes, determines perceived blur. PMID:21833246
Murray, Stephanie; Bex, Peter J
Overlapped Fourier coding for optical aberration removal.
We present an imaging procedure that simultaneously optimizes a camera's resolution and retrieves a sample's phase over a sequence of snapshots. The technique, termed overlapped Fourier coding (OFC), first digitally pans a small aperture across a camera's pupil plane with a spatial light modulator. At each aperture location, a unique image is acquired. The OFC algorithm then fuses these low-resolution images into a full-resolution estimate of the complex optical field incident upon the detector. Simultaneously, the algorithm utilizes redundancies within the acquired dataset to computationally estimate and remove unknown optical aberrations and system misalignments via simulated annealing. The result is an imaging system that can computationally overcome its optical imperfections to offer enhanced resolution, at the expense of taking multiple snapshots over time. PMID:25321982
Horstmeyer, Roarke; Ou, Xiaoze; Chung, Jaebum; Zheng, Guoan; Yang, Changhuei
Real-time quantitative phase imaging for cell studies
NASA Astrophysics Data System (ADS)
Most biological cells are not clearly visible with a bright field microscope. Several methods have been developed to improve contrast in cell imaging, including use of exogenous contrast agents such as fluorescence microscopy, as well as utilizing properties of light-specimen interaction for optics design, to reveal the endogenous contrast, such as phase contrast microscopy (PCM) and differential interference contrast (DIC) microscopy. Although PCM and DIC methods significantly improve the image contrast without the need for staining agents, they only provide qualitative information about the phase change induced by the cells as light passes through them. Quantitative phase imaging (QPI) has recently emerged as an effective imaging tool which provides not only better image contrast but also cell-induced phase shifts in the optical pathlength, thus allowing nanometer-scale measurements of structures and dynamics of the cells. Other important aspects of an imaging system are its imaging speed and throughput. High-throughput, high-speed, real-time quantitative phase imaging with high spatial and temporal sensitivity is highly desirable in many applications including applied physics and biomedicine. In this dissertation, to address this need, I discuss the development of such an imaging system that includes the white light diffraction phase microscopy (wDPM), a new optical imaging method, and image reconstruction/analysis algorithms using graphics processing units (GPUs). wDPM can measure optical pathlength changes at nanometer scale both spatially and temporally with single-shot image acquisition, enabling very fast imaging. I also exploit the broadband spectrum of white light used as the light source in wDPM to develop a system called spectroscopic diffraction phase microscopy (sDPM). This sDPM system allows QPI measurements at several wavelengths, which solves the problem of thickness and refractive index coupling in the phase shifts induced by the cell, and which also may help visualize more-complex cell structures. Owing to its high spatial and temporal sensitivity and single-shot acquisition, wDPM enables measurement of nanometer-scale dynamic processes of cells at very high rate and measurement of cell growth because of the linear relationship between a cell-induced phase shift and its dry mass. The parallel algorithms and software tools I developed allow real-time QPI imaging and online image analysis at frame rates of up to 40 megapixel-size images per second. This capability allows very high throughput of several thousands of cells in imaging mode and eliminates the need of storing the images since we only need to store processed data, which is much smaller in storage size. Finally, I present the capability of the system by showing an application in red blood cell screening, which can be used as a diagnostic tool in blood testing and may pave the way for digital hematology and remote diagnostics.
Pham, Hoa Vinh
A motion-compensated, hand-held, common-path, Fourier-domain optical coherence tomography imaging probe has been developed for image-guided intervention during microsurgery. A hand-held prototype instrument was achieved by integrating an imaging fiber probe inside a stainless steel needle and attached to the ceramic shaft of a piezoelectric motor housed in an aluminum handle. The fiber probe obtains A-scan images. The distance information was extracted from the A-scans to track the sample surface distance and a fixed distance was maintained by a feedback motor control which effectively compensated hand tremor and target movements in the axial direction. Real-time data acquisition, processing, motion compensation, and image visualization and saving were implemented on a custom CPU-GPU hybrid architecture. We performed 10� zero padding to the raw spectrum to obtain 0.16 �m position accuracy with a compensation rate of 460 Hz. The root-mean-square error of hand-held distance variation from target position was measured to be 2.93 �m. We used a cross-correlation maximization-based shift correction algorithm for topology correction. To validate the system, we performed free-hand OCT M-scan imaging using various samples. PMID:23243562
Huang, Yong; Liu, Xuan; Song, Cheol; Kang, Jin U
A motion-compensated, hand-held, common-path, Fourier-domain optical coherence tomography imaging probe has been developed for image-guided intervention during microsurgery. A hand-held prototype instrument was achieved by integrating an imaging fiber probe inside a stainless steel needle and attached to the ceramic shaft of a piezoelectric motor housed in an aluminum handle. The fiber probe obtains A-scan images. The distance information was extracted from the A-scans to track the sample surface distance and a fixed distance was maintained by a feedback motor control which effectively compensated hand tremor and target movements in the axial direction. Real-time data acquisition, processing, motion compensation, and image visualization and saving were implemented on a custom CPU-GPU hybrid architecture. We performed 10� zero padding to the raw spectrum to obtain 0.16 �m position accuracy with a compensation rate of 460 Hz. The root-mean-square error of hand-held distance variation from target position was measured to be 2.93 �m. We used a cross-correlation maximization-based shift correction algorithm for topology correction. To validate the system, we performed free-hand OCT M-scan imaging using various samples. PMID:23243562
Huang, Yong; Liu, Xuan; Song, Cheol; Kang, Jin U.
We introduce an efficient multielectron first-principles based electronic structure method, the two-electron Fourier-grid (2EFG) approach, that is particularly suited for use in mixed quantum/classical simulations of condensed-phase systems. The 2EFG method directly solves for the six-dimensional wave function of a two-electron Hamiltonian in a Fourier-grid representation such that the effects of electron correlation and exchange are treated exactly for both the ground and excited states. Due to the simplicity of a Fourier-grid representation, the 2EFG is readily parallelizable and we discuss its computational implementation in a distributed-memory parallel environment. We show our method is highly efficient, being able to find two-electron wave functions in approximately 20 s on a modern desktop computer for a calculation this is equivalent to full configuration interaction (FCI) in a basis of 17 million Slater determinants. We benchmark the accuracy of the 2EFG by applying it to two electronic structure test problems: the harmonium atom and the sodium dimer. We find that even with a modest grid basis size, our method converges to the analytically exact solutions of harmonium in both the weakly and strongly correlated electron regimes. Our method also reproduces the low-lying potential energy curves of the sodium dimer to a similar level of accuracy as a valence CI calculation, thus demonstrating its applicability to molecular systems. In the following paper [W. J. Glover, R. E. Larsen, and B. J. Schwartz, J. Chem. Phys. 132, 144102 (2010)], we use the 2EFG method to explore the nature of the electronic states that comprise the charge-transfer-to-solvent absorption band of sodium anions in liquid tetrahydrofuran. PMID:20405979
Glover, William J; Larsen, Ross E; Schwartz, Benjamin J
NASA Astrophysics Data System (ADS)
We introduce an efficient multielectron first-principles based electronic structure method, the two-electron Fourier-grid (2EFG) approach, that is particularly suited for use in mixed quantum/classical simulations of condensed-phase systems. The 2EFG method directly solves for the six-dimensional wave function of a two-electron Hamiltonian in a Fourier-grid representation such that the effects of electron correlation and exchange are treated exactly for both the ground and excited states. Due to the simplicity of a Fourier-grid representation, the 2EFG is readily parallelizable and we discuss its computational implementation in a distributed-memory parallel environment. We show our method is highly efficient, being able to find two-electron wave functions in ~20 s on a modern desktop computer for a calculation this is equivalent to full configuration interaction (FCI) in a basis of 17 million Slater determinants. We benchmark the accuracy of the 2EFG by applying it to two electronic structure test problems: the harmonium atom and the sodium dimer. We find that even with a modest grid basis size, our method converges to the analytically exact solutions of harmonium in both the weakly and strongly correlated electron regimes. Our method also reproduces the low-lying potential energy curves of the sodium dimer to a similar level of accuracy as a valence CI calculation, thus demonstrating its applicability to molecular systems. In the following paper [W. J. Glover, R. E. Larsen, and B. J. Schwartz, J. Chem. Phys. 132, 144102 (2010)], we use the 2EFG method to explore the nature of the electronic states that comprise the charge-transfer-to-solvent absorption band of sodium anions in liquid tetrahydrofuran.
Glover, William J.; Larsen, Ross E.; Schwartz, Benjamin J.
Analyser-based phase contrast image reconstruction using geometrical optics
NASA Astrophysics Data System (ADS)
Analyser-based phase contrast imaging can provide radiographs of exceptional contrast at high resolution (<100 �m), whilst quantitative phase and attenuation information can be extracted using just two images when the approximations of geometrical optics are satisfied. Analytical phase retrieval can be performed by fitting the analyser rocking curve with a symmetric Pearson type VII function. The Pearson VII function provided at least a 10% better fit to experimentally measured rocking curves than linear or Gaussian functions. A test phantom, a hollow nylon cylinder, was imaged at 20 keV using a Si(1 1 1) analyser at the ELETTRA synchrotron radiation facility. Our phase retrieval method yielded a more accurate object reconstruction than methods based on a linear fit to the rocking curve. Where reconstructions failed to map expected values, calculations of the Takagi number permitted distinction between the violation of the geometrical optics conditions and the failure of curve fitting procedures. The need for synchronized object/detector translation stages was removed by using a large, divergent beam and imaging the object in segments. Our image acquisition and reconstruction procedure enables quantitative phase retrieval for systems with a divergent source and accounts for imperfections in the analyser.
Kitchen, M. J.; Pavlov, K. M.; Siu, K. K. W.; Menk, R. H.; Tromba, G.; Lewis, R. A.
NASA Astrophysics Data System (ADS)
Phase unwrapping refers to the reconstruction process of a continuous phase distribution from a wrapped phase map in optical interferometers, fringe projection systems and synthetic aperture radars. Usually, phase unwrapping (PU) is challenging due to speckle noise, atmosphere interference, and long discontinuities. Two dimensional phase unwrapping algorithms have been developed for several decades including the classic path-following PU algorithm and path independent minimum-norm PU algorithms. Being one of the path-following algorithms, quality-guided phase unwrapping algorithm relies on a quality map to guide the integration path. Recently, quality-guided phase unwrapping algorithm along with WFF processing (WFF-QG) was developed. It can provide better quality map compared with commonly used phase derivative variance (PDV) and largely improve the reliability of quality guided phase unwrapping algorithm. However, the WFF-QG algorithms are computationally expensive, prohibiting it from real-time applications. In this paper, to realize real-time WFF-QG algorithm, we propose a pipelined heterogeneous system based on CPU and graphic processing unit. Using NVIDIA GTX285 graphics card and quad-core 2.5 GHz Intel(R) Xeon(R) CPU E5420, 2.15 frames per second (fps) can be achieved by WFF-QG algorithm for real-time continuous phase retrieval with size 256�256. Moreover, up to 62.3� speedup compared with the sequential codes in the same CPU has been achieved.
Gao, Wenjing; Kemao, Qian
Robustness of phase retrieval methods in x-ray phase contrast imaging: A comparison
Purpose: The robustness of the phase retrieval methods is of critical importance for limiting and reducing radiation doses involved in x-ray phase contrast imaging. This work is to compare the robustness of two phase retrieval methods by analyzing the phase maps retrieved from the experimental images of a phantom. Methods: Two phase retrieval methods were compared. One method is based on the transport of intensity equation (TIE) for phase contrast projections, and the TIE-based method is the most commonly used method for phase retrieval in the literature. The other is the recently developed attenuation-partition based (AP-based) phase retrieval method. The authors applied these two methods to experimental projection images of an air-bubble wrap phantom for retrieving the phase map of the bubble wrap. The retrieved phase maps obtained by using the two methods are compared. Results: In the wrap's phase map retrieved by using the TIE-based method, no bubble is recognizable, hence, this method failed completely for phase retrieval from these bubble wrap images. Even with the help of the Tikhonov regularization, the bubbles are still hardly visible and buried in the cluttered background in the retrieved phase map. The retrieved phase values with this method are grossly erroneous. In contrast, in the wrap's phase map retrieved by using the AP-based method, the bubbles are clearly recovered. The retrieved phase values with the AP-based method are reasonably close to the estimate based on the thickness-based measurement. The authors traced these stark performance differences of the two methods to their different techniques employed to deal with the singularity problem involved in the phase retrievals. Conclusions: This comparison shows that the conventional TIE-based phase retrieval method, regardless if Tikhonov regularization is used or not, is unstable against the noise in the wrap's projection images, while the AP-based phase retrieval method is shown in these experiments to be superior to the TIE-based method for the robustness in performing the phase retrieval.
Yan, Aimin; Wu, Xizeng; Liu, Hong [Department of Radiology, University of Alabama at Birmingham, Birmingham, Alabama 35233 (United States); Center for Bioengineering and School of Electrical and Computer Engineering, University of Oklahoma, Norman, Oklahoma 73019 (United States)
The ensemble average propagator (EAP) describes the 3D average diffusion process of water molecules, capturing both its radial and angular contents. The EAP can thus provide richer information about complex tissue microstructure properties than the orientation distribution function (ODF), an angular feature of the EAP. Recently, several analytical EAP reconstruction schemes for multiple q-shell acquisitions have been proposed, such as diffusion propagator imaging (DPI) and spherical polar Fourier imaging (SPFI). In this study, a new analytical EAP reconstruction method is proposed, called Bessel Fourier Orientation Reconstruction (BFOR), whose solution is based on heat equation estimation of the diffusion signal for each shell acquisition, and is validated on both synthetic and real datasets. A significant portion of the paper is dedicated to comparing BFOR, SPFI, and DPI using hybrid, non-Cartesian sampling for multiple b-value acquisitions. Ways to mitigate the effects of Gibbs ringing on EAP reconstruction are also explored. In addition to analytical EAP reconstruction, the aforementioned modeling bases can be used to obtain rotationally invariant q-space indices of potential clinical value, an avenue which has not yet been thoroughly explored. Three such measures are computed: zero-displacement probability (Po), mean squared displacement (MSD), and generalized fractional anisotropy (GFA). PMID:22963853
Hosseinbor, A Pasha; Chung, Moo K; Wu, Yu-Chien; Alexander, Andrew L
Grating based x-ray differential phase contrast imaging without mechanical phase stepping.
Grating-based x-ray differential phase contrast imaging (DPCI) often uses a phase stepping procedure to acquire data that enables the extraction of phase information. This method prolongs the time needed for data acquisition by several times compared with conventional x-ray absorption image acquisitions. A novel analyzer grating design was developed in this work to eliminate the additional data acquisition time needed to perform phase stepping in DPCI. The new analyzer grating was fabricated such that the linear grating structures are shifted from one detector row to the next; the amount of the lateral shift was equal to a fraction of the x-ray diffraction fringe pattern. The x-ray data from several neighboring detector rows were then combined to extract differential phase information. Initial experimental results have demonstrated that the new analyzer grating enables accurate DPCI signal acquisition from a single x-ray exposure like conventional x-ray absorption imaging. PMID:24977522
Ge, Yongshuai; Li, Ke; Garrett, John; Chen, Guang-Hong
Time-resolved Fourier transform near-infrared (FT-NIR) spectroscopic imaging was applied to the diffusion process of butanol(OD) into polyamide 11 (PA11) with a novel sheet-structured variable-temperature-controlled sample holder in order to demonstrate the significant differences of diffusion rate below and above the glass transition temperature of PA11. The diffusant butanol(OD) was chosen for two reasons: (1) it allows the diffusion front to be monitored by the intensity decrease of a NH-specific absorption band of PA11 due to the NH/ND isotope exchange and (2) under the measurement conditions the diffusion of butanol(OD) into PA11 takes place in an experimentally manageable time frame. Apart from the in situ visualization of the diffusion front in the time-resolved FT-NIR images, the type of diffusion and the diffusion coefficient of butanol(OD) into PA11 have been determined. PMID:21929860
Unger, Miriam; Ozaki, Yukihiro; Siesler, Heinz W
NSDL National Science Digital Library
This java applet simulates fourier approximations of sine, triangle, sawtooth and square waves, as well as noise, along with their phase terms and harmonics. The number of terms is adjustable, and the function can be played(in Windows), with adjustable frequency. The function can be resampled, quantized, rectified and full rectified. The applet can also simulate distortion. The page includes extensive instructions for the applet and source code.
Falstad, Paul
First Results from the Phase Contrast Imaging on Alcator C-Mod
NASA Astrophysics Data System (ADS)
A Phase Contrast Imaging (PCI) diagnostic was installed during the last campaign on the Alcator C-Mod tokamak. It measures the line-integrated electron density fluctuations in the frequency range 2-500 kHz and with sensitivity of about int tilde n dz >= 10^15 > m-2 M H z-1/2. A series of 12 vertical chords centered around the tokamak geometric axis is imaged on a 12-channel IR linear detector array. Fourier analysis of the detector signals provides information about characteristic frequencies and wavelengths of the density fluctuations. Two distinct modes have been observed. The first mode is quite coherent (? ? / ? ~ 0.2), exists only in H-mode and has the major radius component of its phase velocity ? / k_R ~ 1.5 > km/sec. Its frequency changes in the 60-150 kHz range with plasma conditions as the H-mode evolves. The second mode is a broadband turbulent one with ? / k_R ~ 4 > km/sec and it exists in a wide range of plasmas. Both modes have well defined dispersion relations. These and other results will be discussed in the poster, as well as future upgrades, calibration and computer simulation of the diagnostic optical design.
Mazurenko, A.; Porkolab, M.; Wukitch, S. J.; Hallock, G.; Shugart, A.
New Results from the Phase Contrast Imaging on Alcator C-Mod
NASA Astrophysics Data System (ADS)
A Phase Contrast Imaging (PCI) diagnostic has continued to operate on the Alcator C-Mod tokamak. It measures the line-integrated electron density fluctuations in the frequency range 2-500 kHz and with sensitivity of about int tilde n dz >= 10^15 > m-2. A series of 12 vertical chords centered around the plasma axis is imaged on a 12-channel IR linear detector array. Fourier analysis of the detector signals provides information about characteristic frequencies and wavelengths of the density fluctuations. Two distinct modes have been observed. The first mode is quite coherent (? ? / ? ~ 0.2), exists only in H-mode and has the major radius component of its phase velocity ? / k_R ~ 1.5 > km/sec. Its frequency changes in the 60-150 kHz range with plasma conditions as the H-mode evolves. The second mode is a broadband turbulent one with ? / k_R ~ 4 > km/sec and it exists in a wide range of plasmas. Both modes have well defined dispersion relations. Modulation of the beam near the RF frequency (80MHz) now allows heterodyne measurements of density fluctuations associated with propagating ICRF waves.
Mazurenko, A.; Porkolab, M.; Wukitch, S. J.; Hallock, G.; Shugart, A.
The purpose of this work was to validate ventilation-weighted (VW) and perfusion-weighted (QW) Fourier decomposition (FD) magnetic resonance imaging (MRI) with hyperpolarized (3)He MRI and dynamic contrast-enhanced perfusion (DCE) MRI in a controlled animal experiment. Three healthy pigs were studied on 1.5-T MR scanner. For FD MRI, the VW and QW images were obtained by postprocessing of time-resolved lung image sets. DCE acquisitions were performed immediately after contrast agent injection. (3)He MRI data were acquired following the administration of hyperpolarized helium and nitrogen mixture. After baseline MR scans, pulmonary embolism was artificially produced. FD MRI and DCE MRI perfusion measurements were repeated. Subsequently, atelectasis and air trapping were induced, which followed with FD MRI and (3)He MRI ventilation measurements. Distributions of signal intensities in healthy and pathologic lung tissue were compared by statistical analysis. Images acquired using FD, (3)He, and DCE MRI in all animals before the interventional procedure showed homogeneous ventilation and perfusion. Functional defects were detected by all MRI techniques at identical anatomical locations. Signal intensity in VW and QW images was significantly lower in pathological than in healthy lung parenchyma. The study has shown usefulness of FD MRI as an alternative, noninvasive, and easily implementable technique for the assessment of acute changes in lung function. PMID:22392633
Bauman, Grzegorz; Scholz, Alexander; Rivoire, Julien; Terekhov, Maxim; Friedrich, Janet; de Oliveira, Andre; Semmler, Wolfhard; Schreiber, Laura Maria; Puderbach, Michael
Phase contrast and darkfield imaging in x-ray microscopy
The transmission x-ray microscope has so far been used almost exclusively to form images with absorption contrast. Methods of forming phase contrast and darkfield images are considered, particularly in the scanning transmission x-ray microscope, and the advantages and disadvantages of these methods are reviewed, particularly in the context of the new generation of synchrotron x-ray sources that will be able
Graeme R. Morrison
Computation of component image velocity from local phase information
We present a technique for the computation of 2D component velocity from image sequences. Initially, the image sequence is represented by a family of spatiotemporal velocity-tuned linear filters. Component velocity, computed from spatiotemporal responses of identically tuned filters, is expressed in terms of the local first-order behavior of surfaces of constant phase. Justification for this definition is discussed from the
David J. Fleet; Allan D. Jepson
Phase space imaging in optical design
NASA Astrophysics Data System (ADS)
In the last years the requirement of special illumination optics increased in the course of developing specific optical systems for wide range of applications in industries and science. Standard components become continuously substituted by more complex freeform surfaces with higher efficiency. Therefore, other methods in evaluating optical systems are of special interest. In illumination design the classic way to check the performance of a system is to trace a huge number of rays through the system and analyze the radiance and irradiance distribution on the target surface. Another access to the most important illumination quantities like radiance is to look at the transformation of etendue in phase space. This offers a new perspective for the optical designer onto illumination systems. Another interesting aspect is the analysis of aberrations also for freeform elements where standard aberration theory for rotational symmetric systems fail.
Rausch, Denise; Herkommer, Alois
Dynamic quantitative phase imaging for biological objects using a pixelated phase mask.
This paper describes research in developing a dynamic quantitative phase imaging microscope providing instantaneous measurements of dynamic motions within and among live cells without labels or contrast agents. It utilizes a pixelated phase mask enabling simultaneous measurement of multiple interference patterns derived using the polarization properties of light to track dynamic motions and morphological changes. Optical path difference (OPD) and optical thickness (OT) data are obtained from phase images. Two different processing routines are presented to remove background surface shape to enable quantification of changes in cell position and volume over time. Data from a number of different moving biological organisms and cell cultures are presented. PMID:23162725
Creath, Katherine; Goldstein, Goldie
Dynamic quantitative phase imaging for biological objects using a pixelated phase mask
This paper describes research in developing a dynamic quantitative phase imaging microscope providing instantaneous measurements of dynamic motions within and among live cells without labels or contrast agents. It utilizes a pixelated phase mask enabling simultaneous measurement of multiple interference patterns derived using the polarization properties of light to track dynamic motions and morphological changes. Optical path difference (OPD) and optical thickness (OT) data are obtained from phase images. Two different processing routines are presented to remove background surface shape to enable quantification of changes in cell position and volume over time. Data from a number of different moving biological organisms and cell cultures are presented. PMID:23162725
Creath, Katherine; Goldstein, Goldie
Programs for high-speed Fourier, Mellin and Fourier-Bessel transforms
NASA Technical Reports Server (NTRS)
Several FORTRAN program modules for performing one-dimensional and two-dimensional discrete Fourier transforms, Mellin, and Fourier-Bessel transforms are described along with programs that realize the algebra of high speed Fourier transforms on a computer. The programs can perform numerical harmonic analysis of functions, synthesize complex optical filters on a computer, and model holographic image processing methods.
Ikhabisimov, D. K.; Debabov, A. S.; Kolosov, B. I.; Usikov, D. A.
Beyond the lateral resolution limit by phase imaging
NASA Astrophysics Data System (ADS)
We present a theory stating how to overcome the classical Rayleigh-resolution limit. It is based upon a new resolution criterion in phase of coherent imaging process and its spatial resolution is thought to be only SNR limited. Recently, the experimental observation of systematically occurring phase singularities in coherent imaging of sub-Rayleigh distanced objects has been reported.1 The phase resolution criterion relies on the unique occurrence of phase singularities. A priori, coherent imaging system's resolution can be extended to Abbe's limit.2 However, by introducing a known phase difference, the lateral as well as the longitudinal resolution can be tremendously enlarged. The experimental setup is based on Digital Holographic Microscopy (DHM), an interferometric method providing access to the complex wave front. In off-axis transmission configuration, sub-wavelength nano-metric holes on a metallic film acts as the customized high-resolution test target. The nano-metric apertures are drilled with focused ion beam (FIB) and controlled by scanning electron microscopy (SEM). In this manner, Rayleighs classical two-point resolution condition can be rebuilt by interfering complex fields emanated from multiple single circular apertures on an opaque metallic film. By introducing different offset phases, enhanced resolution is demonstrated. Furthermore, the measurements can be exploited analytically or within the post processing of sampling a synthetic complex transfer function (CTF).
Cotte, Y.; Toy, M. Fatih; Depeursinge, C.
Quantitative radiography of magnetic fields using neutron spin phase imaging.
We report on a novel neutron radiography technique that uses the Ramsey principle, a method similar to neutron spin echo. For the first time quantitative imaging measurements of magnetic objects and fields could be performed. The strength of the spin-dependent magnetic interaction is detected by a change in the Larmor precession frequency of the neutron spins. Hence, one obtains in addition to the normal attenuation radiography image a so-called neutron spin phase image, which provides a two-dimensional projection of the magnetic field integrated over the neutron flight path. PMID:19392450
Piegsa, F M; van den Brandt, B; Hautle, P; Kohlbrecher, J; Konter, J A
X-ray tomography can provide structural information of whole cells in close to their native state. Radiation-induced damage, however, imposes a practical limit to image resolution, and as such, a choice between damage, image contrast, and image resolution must be made. New coherent diffractive imaging techniques, such Fresnel Coherent Diffractive Imaging (FCDI), allows quantitative phase information with exceptional dose efficiency, high contrast, and nano-scale resolution. Here we present three-dimensional quantitative images of a whole eukaryotic cell by FCDI at a spatial resolution below 70?nm with sufficient phase contrast to distinguish major cellular components. From our data, we estimate that the minimum dose required for a similar resolution is close to that predicted by the Rose criterion, considerably below accepted estimates of the maximum dose a frozen-hydrated cell can tolerate. Based on the dose efficiency, contrast, and resolution achieved, we expect this technique will find immediate applications in tomographic cellular characterisation. PMID:23887204
Jones, Michael W. M.; van Riessen, Grant A.; Abbey, Brian; Putkunz, Corey T.; Junker, Mark D.; Balaur, Eugeniu; Vine, David J.; McNulty, Ian; Chen, Bo; Arhatari, Benedicta D.; Frankland, Sarah; Nugent, Keith A.; Tilley, Leann; Peele, Andrew G.
Phase relief imaging with confocal laser scanning system
NASA Astrophysics Data System (ADS)
Confocal laser scanning microscopy (CLSM) has become one of the most important biomedical research tools today due to its noninvasive and 3-D abilities. It enables imaging in living tissue with better resolution and contrast, and plays a growing role among microscopic techniques utilized for investigating numerous biological problems. In some cases, the sample was phase-sensitive, thus we introduce a novel method named laser oblique scanning optical microscopy (LOSOM) which could obtain a relief image in transparent sample directly. Through the LOSOM system, mouse kidney and HeLa cells sample were imaged and 10x, 20x and 40x magnify objective imaging results were realized respectively. Also, we compared the variation of pinhole size versus imaging result. One major parameters of LOSOM is the distance between fluorescence medium and the sample. Previously, this distance was set to 1.2 mm, which is the thickness of the slide. The experiment result showed that decreasing d can increase the signal level for LOSOM phase-relief imaging. We have also demonstrated the application of LOSOM in absorption imaging modality, when the specimen is non-transparent.
Peng, Tong; Xie, Hao; Ding, Yichen; Xi, Peng
Structured illumination microscopy (SIM) is an established technique that allows subdiffraction resolution imaging by heterodyning high sample frequencies into the system's passband via structured illumination. However, until now, SIM has been typically used to achieve subdiffraction resolution for intensity-based imaging. Here, we present a novel optical setup that uses structured illumination with a broadband light source to obtain noise-reduced, subdiffraction resolution, quantitative phase imaging (QPM) of cells. We compare this with a previous work for subdiffraction QPM imaging via SIM that used a laser source, and was thus still corrupted by coherent noise. PMID:24562266
Chowdhury, Shwetadwip; Izatt, Joseph
Wigner function for discrete phase space: exorcising ghost images
We construct, using simple geometrical arguments, a Wigner function defined on a discrete phase space of arbitrary integer Hilbert-space dimension that is free of redundancies. ``Ghost images'' plaguing other Wigner functions for discrete phase spaces are thus revealed as artifacts. It allows to devise a corresponding phase-space propagator in an unambiguous manner. We apply our definitions to eigenstates and propagator of the quantum baker map. Scars on unstable periodic points of the corresponding classical map become visible with unprecedented resolution.
Arturo Arg�elles; Thomas Dittrich
Discrete Fourier Series & Discrete Fourier Transform Chapter Intended Learning Outcomes
Discrete Fourier Series & Discrete Fourier Transform Chapter Intended Learning Outcomes (i) Understanding the relationships between the transform, discrete-time Fourier transform (DTFT), discrete Fourier series (DFS), discrete Fourier transform (DFT) and fast Fourier transform (FFT) (ii) Understanding
So, Hing-Cheung
Images reveal that atmospheric particles can undergo liquidliquid phase separations
, the scattering and absorption of solar radiation, and the reactive uptake of gas species on atmospheric particlesImages reveal that atmospheric particles can undergo liquidliquid phase separations Yuan Youa aerosol particles contains both organic material and inorganic salts. As the relative humidity cycles
An inexpensive imaging Instrument to quickly locate leaks of methane and other greenhouse and VOC gases would reduce the cost and effort expended by industry to comply with EPA regulations. In Phase I, of this WBIR program, a new gas leak visualization camera was demonstrated...
Phasing segmented mirrors using defocused images at visible wavelengths
Plans for future optical telescopes of diameter more than 10m are based on segmented mirrors, made up of hundreds or even thousands of segments. A challenge for these telescopes is the alignment in piston (cophasing) where phase differences between individual segments have to be reduced to a small fraction of the observing wavelength in order to avoid degradation of image
A. Schumacher; N. Devaney
Spatial frequency, phase, and the contrast of natural images
Spatial frequency, phase, and the contrast of natural images Peter J. Bex Institute of Ophthalmology, 11-43 Bath Street, London EC1V 9EL, UK Walter Makous Center for Visual Science, University, 2001; accepted November 28, 2001 We examined contrast sensitivity and suprathreshold apparent contrast
Makous, Walter
Phase-based level set segmentation of ultrasound images.
Ultrasonic image segmentation is a difficult problem due to speckle noise, low contrast, and local changes of intensity. Intensity-based methods do not perform particularly well on ultrasound images. However, it has been previously shown that these images respond well to local phase-based methods which are theoretically intensity invariant. Here, we use level set propagation to capture the left ventricle boundaries. The proposed approach uses a new speed term based on local phase and local orientation derived from the monogenic signal, which makes the algorithm robust to attenuation artifact. Furthermore, we use Cauchy kernels, as a better alternative to the commonly used log-Gabor, as pair of quadrature filters for the feature extraction. Results on synthetic and natural data show that the proposed method can robustly handle noise, and captures well the low contrast boundaries. PMID:21216695
Belaid, Ahror; Boukerroui, Djamal; Maingourd, Y; Lerallut, Jean-Francois
Para-Hydrogen-Enhanced Gas-Phase Magnetic Resonance Imaging
Herein, we demonstrate magnetic resonance imaging (MRI) inthe gas phase using para-hydrogen (p-H2)-induced polarization. A reactantmixture of H2 enriched in the paraspin state and propylene gas is flowedthrough a reactor cell containing a heterogenized catalyst, Wilkinson'scatalyst immobilized on modified silica gel. The hydrogenation product,propane gas, is transferred to the NMR magnet and is spin-polarized as aresult of the ALTADENA (adiabatic longitudinal transport and dissociationengenders net alignment) effect. A polarization enhancement factor of 300relative to thermally polarized gas was observed in 1D1H NMR spectra.Enhancement was also evident in the magnetic resonance images. This isthe first demonstration of imaging a hyperpolarized gaseous productformed in a hydrogenation reaction catalyzed by a supported catalyst.This result may lead to several important applications, includingflow-through porous materials, gas-phase reaction kinetics and adsorptionstudies, and MRI in low fields, all using catalyst-free polarizedfluids.
Bouchard, Louis-S.; Kovtunov, Kirill V.; Burt, Scott R.; Anwar,M. Sabieh; Koptyug, Igor V.; Sagdeev, Renad Z.; Pines, Alexander
Phase Effects on Mesoscale Object X-ray Absorption Images
At Lawrence Livermore National Laboratory particular emphasis is being placed on the nondestructive characterization (NDC) of 'mesoscale' objects.[Martz and Albrecht 2003] We define mesoscale objects as objects that have mm extent with {micro}m features. Here we confine our discussions to x-ray imaging methods applicable to mesoscale object characterization. The goal is object recovery algorithms including phase to enable emerging high-spatial resolution x-ray imaging methods to ''see'' inside or image mesoscale-size materials and objects. To be successful our imaging characterization effort must be able to recover the object function to one micrometer or better spatial resolution over a few millimeters field-of-view with very high contrast.
Martz, Jr., H E; Aufderheide, M B; Barty, A; Lehman, S K; Kozioziemski, B J; Schneberk, D J
NASA Astrophysics Data System (ADS)
Diffusion of two model drugs-benzyl nicotinate and ibuprofen-and the plasma macromolecule albumin across atherosclerotic rabbit aorta was studied ex vivo by attenuated total reflection-Fourier transform infrared (ATR-FTIR) imaging. Solutions of these molecules were applied to the endothelial surface of histological sections of the aortic wall that were sandwiched between two impermeable surfaces. An array of spectra, each corresponding to a specific location in the section, was obtained at various times during solute diffusion into the wall and revealed the distribution of the solutes within the tissue. Benzyl nicotinate in Ringer's solution showed higher affinity for atherosclerotic plaque than for apparently healthy tissue. Transmural concentration profiles for albumin demonstrated its permeation across the section and were consistent with a relatively low distribution volume for the macromolecule in the middle of the wall. The ability of albumin to act as a drug carrier for ibuprofen, otherwise undetected within the tissue, was demonstrated by multivariate subtraction image analysis. In conclusion, ATR-FTIR imaging can be used to study transport processes in tissue samples with high spatial and temporal resolution and without the need to label the solutes under study.
Palombo, Francesca; Danoux, Charl�ne B.; Weinberg, Peter D.; Kazarian, Sergei G.
Mass spectrometry imaging (MSI) determines the spatial localization and distribution patterns of compounds on the surface of a tissue section, mainly using MALDI (matrix�assisted laser desorption/ionization)-based analytical techniques. New matrices for small-molecule MSI, which can improve the analysis of low-molecular weight (MW) compounds, are needed. These matrices should provide increased analyte signals while decreasing MALDI background signals. In addition, the use of ultrahigh-resolution instruments, such as Fourier transform ion cyclotron resonance (FTICR) mass spectrometers, has�the ability to resolve analyte signals from matrix signals, and this can partially overcome many problems associated with the background originating from the MALDI matrix. The reduction in the intensities of the metastable matrix clusters by FTICR MS can also help to overcome some of the interferences associated with matrix peaks on other instruments. High-resolution instruments such as the FTICR mass spectrometers are advantageous as they can produce distribution patterns of many compounds simultaneously while still providing confidence in chemical identifications. Dithranol (DT; 1,8-dihydroxy-9,10-dihydroanthracen-9-one) has previously been reported as a MALDI matrix for tissue imaging. In this work, a protocol for the use of DT for MALDI imaging of endogenous lipids from the surfaces of mammalian tissue sections, by positive-ion MALDI-MS, on an ultrahigh-resolution hybrid quadrupole FTICR instrument has been provided. PMID:24300588
Le, Cuong H; Han, Jun; Borchers, Christoph H
Wavelength-multiplexing phase-sensitive surface plasmon imaging sensor.
A wavelength-multiplexing phase-sensitive surface plasmon resonance (SPR) imaging sensor offering wide dynamic detection range and microarray capability is reported. Phase detection is accomplished by performing self-interference between the s- and p- polarizations within the signal beam. A liquid crystal tunable filter is used to sequentially select the SPR excitation wavelength from a white light source. This wavelength-multiplexing approach enables fast detection of the sensor's SPR phase response over a wide range of wavelengths, thereby covering literally any regions of interest within the SPR dip and thus maintaining the highest sensitivity point at all times. The phase-sensitive approach is particularly important for imaging SPR sensing applications because of its less stringent requirements for intensity signal-to-noise ratio, which also means the possibility of using uncooled modest resolution analog-to-digital conversion imaging devices. Experimental results demonstrate a resolution of 2.7�10(-7) RIU with a dynamic range of 0.0138 RIU. PMID:23632487
Shao, Yonghong; Li, Yan; Gu, Dayong; Zhang, Kai; Qu, Junle; He, Jianan; Li, Xuejin; Wu, Shu-Yuen; Ho, Ho-Pui; Somekh, Michael G; Niu, Hanben
Dynamic phase imaging utilizing a 4-dimensional microscope system
NASA Astrophysics Data System (ADS)
This paper describes a new, novel interference Linnik microscope system and presents images and data of live biological samples. The specially designed optical system enables instantaneous 4-dimensional video measurements of dynamic motions within and among live cells without the need for contrast agents. This "label-free", vibration insensitive imaging system enables measurement of biological objects in reflection using harmless light levels with a variety of magnifications and wavelengths with fields of view from several hundred microns up to a millimeter. At the core of the instrument is a phase measurement camera (PMC) enabling simultaneous measurement of multiple interference patterns utilizing a pixelated phase mask taking advantage of the polarization properties of light. Utilizing this technology enables the creation of phase image movies in real time at video rates so that dynamic motions and volumetric changes can be tracked. Objects are placed on a reflective surface in liquid under a coverslip. Phase values are converted to optical thickness data enabling volumetric, motion and morphological studies. Data from a number of different organisms such as flagellates and rotifers will be presented, as will measurements of human breast cancer cells with the addition of various agents that break down the cells. These data highlight examples of monitoring different biological processes and motions.
Creath, Katherine
A kind of phase-based image matching technique
NASA Astrophysics Data System (ADS)
Image matching is one of the most important techniques in intelligent systems and is widely applied in many fields. Firstly, based on integrated feature congruency, interesting target detection algorithm in complex natural backgrounds images is studied in this paper. By detecting the abrupt changes, we can detect interesting target areas. In this paper, the local image information is obtained by logGabor filter banks, and is represented by a collection of separate features. The integrated features consist of some separable significant features. The integrated feature congruency model is presented based on the integrated feature. We gain improved integrated feature congruency model by compensating noise. Then, we get a new kind of phase-based image matching method (PIM) by combining this model and Rotation Invariant Phase Only Correlation (RIPOC) algorithm. Experimental results show that the PIM algorithm is effective in detecting interesting targets and locating the matching targets exactly. This algorithm is invariant to image illumination, contrast, rotation and scaling. And this model is robust, general and accords with the human vision system (HVS) characteristics.
Xiao, Zhitao; Wu, Jun; Geng, Lei; Wang, Jianming; Xu, Nini
Parallel phase-sensitive three-dimensional imaging camera
An apparatus is disclosed for generating a three-dimensional (3-D) image of a scene illuminated by a pulsed light source (e.g. a laser or light-emitting diode). The apparatus, referred to as a phase-sensitive 3-D imaging camera utilizes a two-dimensional (2-D) array of photodetectors to receive light that is reflected or scattered from the scene and processes an electrical output signal from each photodetector in the 2-D array in parallel using multiple modulators, each having inputs of the photodetector output signal and a reference signal, with the reference signal provided to each modulator having a different phase delay. The output from each modulator is provided to a computational unit which can be used to generate intensity and range information for use in generating a 3-D image of the scene. The 3-D camera is capable of generating a 3-D image using a single pulse of light, or alternately can be used to generate subsequent 3-D images with each additional pulse of light.
Smithpeter, Colin L. (Albuquerque, NM); Hoover, Eddie R. (Sandia Park, NM); Pain, Bedabrata (Los Angeles, CA); Hancock, Bruce R. (Altadena, CA); Nellums, Robert O. (Albuquerque, NM)
A grating-based single-shot x-ray phase contrast and diffraction method for in vivo imaging
Purpose: The purpose of this study is to develop a single-shot version of the grating-based phase contrast x-ray imaging method and demonstrate its capability of in vivo animal imaging. Here, the authors describe the principle and experimental results. They show the source of artifacts in the phase contrast signal and optimal designs that minimize them. They also discuss its current limitations and ways to overcome them. Methods: A single lead grid was inserted midway between an x-ray tube and an x-ray camera in the planar radiography setting. The grid acted as a transmission grating and cast periodic dark fringes on the camera. The camera had sufficient spatial resolution to resolve the fringes. Refraction and diffraction in the imaged object manifested as position shifts and amplitude attenuation of the fringes, respectively. In order to quantify these changes precisely without imposing a fixed geometric relationship between the camera pixel array and the fringes, a spatial harmonic method in the Fourier domain was developed. The level of the differential phase (refraction) contrast as a function of hardware specifications and device geometry was derived and used to guide the optimal placement of the grid and object. Both ex vivo and in vivo images of rodent extremities were collected to demonstrate the capability of the method. The exposure time using a 50 W tube was 28 s. Results: Differential phase contrast images of glass beads acquired at various grid and object positions confirmed theoretical predictions of how phase contrast and extraneous artifacts vary with the device geometry. In anesthetized rats, a single exposure yielded artifact-free images of absorption, differential phase contrast, and diffraction. Differential phase contrast was strongest at bone-soft tissue interfaces, while diffraction was strongest in bone. Conclusions: The spatial harmonic method allowed us to obtain absorption, differential phase contrast, and diffraction images, all from a single raw image and is feasible in live animals. Because the sensitivity of the method scales with the density of the gratings, custom microfabricated gratings should be superior to off-the-shelf lead grids.
Bennett, Eric E.; Kopace, Rael; Stein, Ashley F.; Wen Han [National Heart, Lung, and Blood Institute, National Institutes of Health, Imaging Physics Section, Translational Medicine Branch, 10 Center Drive, MSC 1061, Bethesda, Maryland 20892 (United States)
NASA Astrophysics Data System (ADS)
Active pixel design using the complementary metal-oxide-semiconductor (CMOS) process is a compelling solution for use in X-ray imaging detectors because of its excellent electronic noise characteristics. We have investigated the imaging performance of a CMOS active pixel photodiode array coupled to a granular phosphor through a fiber-optic faceplate for mammographic applications. The imaging performance included the modulation-transfer function (MTF), noise-power spectrum (NPS), and detective quantum efficiency (DQE). Because we observed a nonlinear detector response at low exposures, we used the linearization method for the analysis of the DQE. The linearization method uses the images obtained at detector input, which are converted from those obtained at detector output by using the inverse of the detector response. Compared to the conventional method, the linearization method provided almost the same MTF and a slightly lower normalized NPS. However, the difference between the DQE results obtained by using the two methods was significant. We claim that the conventional DQE analysis of a detector having a nonlinear response characteristic can yield wrong results. Under the standard mammographic imaging condition, we obtained a DQE performance that was competitive with the performances of conventional flat-panel mammography detectors. We believe that the CMOS detector investigated in this study can be successfully used for mammography.
Han, Jong Chul; Yun, Seungman; Youn, Hanbean; Kam, Soohwa; Cho, Seungryong; Achterkirchen, Thorsten G.; Kim, Ho Kyung
Binary and phase-shifting image design for optical lithography
NASA Astrophysics Data System (ADS)
A number of pre-distorted mask design techniques for binary and phase-shifting masks are proposed. This approach is based on modeling the imaging mechanism of a stepper by the Hopkins equations and taking advantage of the photoresist nonlinear characteristics. Optimization techniques such as the branch and bound algorithm and simulated annealing algorithm are used to systematically design pre-distorted masks under incoherent and partially coherent illumination. Computer simulations are used to show that contour shapes of our designed mask patterns are sharper than those of conventional masks. The designed phase- shifting masks are shown to result in higher contrast as well as sharper contours than binary masks.
Liu, Yong; Zakhor, Avideh
Images of the Moon: Predicting Phases and Features
NSDL National Science Digital Library
This is an activity about investigating students' preconceptions of the Moon's appearance and its phases. Learners will first draw an image of how they think the Moon looks and then discuss as a group why the drawn pictures may vary. Then, learners will analyze a series of lunar phase photos, sorting them in the order they believe to be correct based on their experiences and ideas. This is Activity A-1 of Universe at Your Fingertips 2.0: A Collection of Activities and Resources for Teaching Astronomy DVD-ROM, which is available for purchase.
Quantitative phase imaging using a deep UV LED source.
We propose a method for high resolution phase imaging of biological and non-biological samples using an incoherent deep ultraviolet (DUV) LED source. The diffraction pattern of the object wave is recorded at different axial planes and the phase is retrieved by propagation of the angular spectrum. To maintain enough light intensity, we avoided using a pinhole or spectral filter for increasing the coherence of the DUV LED source. This makes the setup very simple and cost effective. The short wavelength (285�nm) of the DUV light, tuned to the absorption peak of the biological samples, allows simultaneously high resolution and high contrast images. The experimental results are presented to verify this principle. PMID:24978513
Singh, Alok Kumar; Faridian, Ahmad; Gao, Peng; Pedrini, Giancarlo; Osten, Wolfgang
Phase contrast in Simultaneous Topography and Recognition imaging.
The operation of a force microscope in Simultaneous Topography and Recognition (TREC) imaging mode is analyzed by means of numerical simulations. Both topography and recognition signals are analyzed by using a worm-like chain force as the specific interaction between the functionalized tip probe and the sample. The special feedback mechanism in this mode is shown to couple the phase signal to the presence of molecular recognition interactions even in absence of dissipation. PMID:19523768
Fuss, M C; Sahag�n, E; K�ber, M; Briones, F; Luna, M; S�enz, J J
Automatic detection of ridges in lunar images using phase symmetry and phase congruency
NASA Astrophysics Data System (ADS)
Lunar surface exploration is increasing rapidly. These exploring satellites provide a large number of high resolution images containing topographical information. The topographical information in lunar surface are craters, ridges, mountains and grabens. Extracting this topographical information manually is time-consuming. Hence, an automatic feature extraction is favored. This paper presents a novel approach using image processing techniques to automatically detect ridges in lunar images. The approaches adopted for this development includes phase symmetry, phase congruency and morphological operations to automatically detect significant ridges. The phase symmetry extracts symmetry features with discontinuities, phase congruency extracts features lying in low contrast regions and morphological operations such as thinning and pruning are used to obtain significant ridges. The proposed novel approach experiments on a test set of different regions. These different region images are obtained from different sensors (LROC, Selene and Clementine) having different spatial resolution and illumination variation. The results obtained are compared with the plan curvature method; and they are evaluated based on true and false detection of ridge pixels. Irrespective of illumination variation and spatial resolution, the proposed approach provides better results than the plan curvature method and its detection rate is approximately 92%.
Micheal, Anto A.; Vani, K.; Sanjeevi, S.
The variable of froth velocity is an effective flotation optimal control parameter in the machine vision based flotation monitoring and control, which closely related to the flotation performance indices. However, the bubble velocity extracted based on digital image processing is often difficult to accurately extract, due to the inevitable rotation, scaling and the collapse of the bubbles deformation and so
Mu Xue-min; Liu Jin-ping; Tang Zhao-hui; Gui Wei-hua; Yang Chun-hua
Lineshapes in phase-encoded spectroscopic imaging experiments
NASA Astrophysics Data System (ADS)
Two procedures for recording spectroscopic images with pure absorption mode lineshapes using phase-encoding pulsed field gradients are discussed and compared experimentally. Using a small phantom sample, both methods are shown to give significant improvements compared to the conventional absolute value display. It is found that the method based on the use of a symmetric data set is preferable to that based on a reversed precession experiment. To demonstrate its applicability to in vivo31P NMR, a surface coil placed over the scalp of a rabbit was used to record a one-dimensional phase-encoded spectrum. While the absolute value display of this data set contains overlap between the low-field ATP and the phosphocreatine resonances, these signals are completely resolved in the phase-sensitive spectrum.
Barker, P. B.; Ross, Brian D.
Infrared spectroscopy and imaging technology can provide new diagnostic capabilities for cancer research applications and to physicians directly involved in patient treatment. A methodology that permits the phenotypical description of cells and tissues is introduced, as well as a variety of new evaluation techniques that allow researchers and physicians to evaluate the infrared data at different levels of sophistication. The detection of cell alterations in the case of Chronic Lymphocytic Leukemia (CLL) demonstrates the capability of infrared spectroscopy to identify and stage this type of cancer, providing new prospects for diagnosis and treatment. The pathological study of oral tissue affected by Squamous Cell Carcinoma (SCC) illustrates the potential of Infrared Spectroscopy and Imaging for tissue diagnosis and cancer staging based in altered cell biochemistry, without using stains or any other marker technology. An example of combined fluid, cell and tissue analysis of thyroid cancers based on infrared technology is introduced to demonstrate the possibility of earlier detection of gland abnormalities and biochemical alterations in cell extracts using fine needle aspirates. Simple statistical techniques such as bivariate histogram analysis can distinguish between normal and altered cells and tissues when applied to infrared spectra and images. More complex mathematical techniques such as Principal Component Analysis (PCA) or Artificial Neural Networks (ANN) provide additional evaluation capabilities that can relate spectra of an unknown sample to an infrared reference database of known cell states. It is documented how this new infrared technology could enhance the diagnoses, treatment decisions and prognoses of patients in the field of cancer medicine. PMID:12622515
Schultz, Christian P
Fourier-Bessel rotational invariant eigenimages
We present an efficient and accurate algorithm for principal component analysis (PCA) of a large set of two-dimensional images and, for each image, the set of its uniform rotations in the plane and its reflection. The algorithm starts by expanding each image, originally given on a Cartesian grid, in the Fourier�Bessel basis for the disk. Because the images are essentially band limited in the Fourier domain, we use a sampling criterion to truncate the Fourier�Bessel expansion such that the maximum amount of information is preserved without the effect of aliasing. The constructed covariance matrix is invariant to rotation and reflection and has a special block diagonal structure. PCA is efficiently done for each block separately. This Fourier�Bessel-based PCA detects more meaningful eigenimages and has improved denoising capability compared to traditional PCA for a finite number of noisy images. PMID:23695317
Zhao, Zhizhen; Singer, Amit
Purpose. To demonstrate the application of phase-variance optical coherence tomography (pvOCT) for contrast agent�free in vivo imaging of volumetric retinal microcirculation in the human foveal region and for extraction of foveal avascular zone dimensions. Methods. A custom-built, high-speed Fourier-domain OCT retinal imaging system was used to image retinas of two healthy subjects and eight diabetic patients. Through the acquisition of multiple B-scans for each scan location, phase differences between consecutive scans were extracted and used for phase-variance contrast, identifying motion signals from within blood vessels and capillaries. The en face projection view of the inner retinal layers segmented out from volumetric pvOCT data sets allowed visualization of a perfusion network with the foveal avascular zone (FAZ). In addition, the authors presented 2D retinal perfusion maps with pseudo color-coded depth positions of capillaries. Results. Retinal vascular imaging with pvOCT provides accurate measurements of the FAZ area and its morphology and a volumetric perfusion map of microcapillaries. In this study using two images from each fundus fluorescein angiography (FA) and pvOCT, the measured average areas of the FAZ from two healthy subjects were below 0.22 mm2, and each of eight diabetic patients had an enlarged FAZ area, larger than 0.22 mm2. Moreover, the FAZ areas demonstrated a significant correlation (r = 0.91) between measurements from FA and pvOCT. Conclusions. The high-speed pvOCT allows contrast agent�free visualization of capillary networks in the human foveal region that is analogous to fundus FA imaging. This could allow for noninvasive diagnosis and progression monitoring of diabetic retinopathy in clinical settings. PMID:22125275
Fingler, Jeff; Zawadzki, Robert J.; Park, Susanna S.; Morse, Lawrence S.; Schwartz, Daniel M.; Fraser, Scott E.; Werner, John S.
Fourier transform channeled spectropolarimetry in the MWIR
forms of spectroscopic measurement, such as a diffraction grating spectrometer, in the MWIR. Luo, et al, "Polarization acquisition using a commercial Fourier transform spectrometer in the MWIR. Chapman et al, "Data processing pipeline for a time-sampled imaging Fourier transform spectrometer
Dereniak, Eustace L.
NASA Astrophysics Data System (ADS)
We propose a generalization of the encryption system based on double random phase encoding (DRPE) and a joint transform correlator (JTC), from the Fourier domain to the fractional Fourier domain (FrFD) by using the fractional Fourier operators, such as the fractional Fourier transform (FrFT), fractional traslation, fractional convolution and fractional correlation. Image encryption systems based on a JTC architecture in the FrFD usually produce low quality decrypted images. In this work, we present two approaches to improve the quality of the decrypted images, which are based on nonlinear processing applied to the encrypted function (that contains the joint fractional power spectrum, JFPS) and the nonzero-order JTC in the FrFD. When the two approaches are combined, the quality of the decrypted image is higher. In addition to the advantages introduced by the implementation of the DRPE using a JTC, we demonstrate that the proposed encryption system in the FrFD preserves the shift-invariance property of the JTC-based encryption system in the Fourier domain, with respect to the lateral displacement of both the key random mask in the decryption process and the retrieval of the primary image. The feasibility of this encryption system is verified and analyzed by computer simulations.
Vilardy, Juan M.; Torres, Yezid; Mill�n, Mar�a S.; P�rez-Cabr�, Elisabet
Phase-unwrapping algorithm for images with high noise content based on a local histogram
NASA Astrophysics Data System (ADS)
We present a robust algorithm of phase unwrapping that was designed for use on phase images with high noise content. We proceed with the algorithm by first identifying regions with continuous phase values placed between fringe boundaries in an image and then phase shifting the regions with respect to one another by multiples of 2pi to unwrap the phase. Image pixels are segmented between interfringe and fringe boundary areas by use of a local histogram of a wrapped phase. The algorithm has been used successfully to unwrap phase images generated in a three-dimensional shape measurement for noninvasive quantification of human skin structure in dermatology, cosmetology, and plastic surgery.
Meneses, Jaime; Gharbi, Tijani; Humbert, Philippe
NASA Astrophysics Data System (ADS)
The gradual transformation of a guided TM00 mode into an "intermediate" double mode by a splitting junction has been investigated with a phase-sensitive photon scanning tunneling microscope. Field profiles and wave vectors of the modes have been directly determined from the phase information. Via a Fourier analysis of the measured phase and amplitude maps the decay of the TM00 mode and buildup of the intermediate mode have been directly visualized. Phase singularities and phase jumps in the transition region underline the mode transformation process. Finally, a partial polarization conversion of the TM modes to TE-polarized modes has been observed.
Balistreri, M. L. M.; Korterik, J. P.; Kuipers, L.; van Hulst, N. F.
NASA Astrophysics Data System (ADS)
We propose a new out-of-plane vibration imaging technique for micro-structured solid-state devices such as MEMS (microelectro mechanical systems) microphones and resonators. This technique is based on the longitudinally scanning optical interferometry and an integrated image sensor device which we call the correlation image sensor (CIS). The CIS is able to extract an arbitrary frequency component from time-varying incident light and produce a complex correlation image including amplitude and phase in addition to a conventional intensity image. In heterodyne interferometry of vibrating objects, the vibration information is encoded in several frequency components generated by mutual modulation of longitudinal scan and vibration. In this paper, the combination of newly developed multi-channel CIS and the scanning heterodyne technique enable us to obtain the multiple frequency components simultaneously and reconstruct the vibration amplitude and phase distributions in real time. As an example, vibration modes of a MEMS acoustic sensor are shown to be rconstructed at video rate. A theoretical possiblitiy for the imaging of higher than GHz vibration combining other optical heterodyne techniques is also discussed.
Sato, Seichi; Kurihara, Toru; Ando, Shigeru
Stochastic optimal phase retrieval algorithm for high-contrast imaging
NASA Astrophysics Data System (ADS)
The Princeton University Terrestrial Planet Finder (TPF) has been working on a novel method for direct imaging of extra solar planets using a shaped-pupil coronagraph. The entrance pupil of the coronagraph is optimized to have a point spread function (PSF) that provides the suppression level needed at the angular separation required for detection of extra solar planets. When integration time is to be minimized, the photon count at the planet location in the image plane is a Poisson distributed random process. The ultimate limitation of these high-dynamic-range imaging systems comes from scattering due to imperfections in the optical surfaces of the collecting system. The first step in correcting the wavefront errors is the estimation of the phase aberrations. The phase aberration caused by these imperfections is assumed to be a sum of two-dimensional sinusoidal functions. Its parameters are estimated using a global search with a genetic algorithm and a local optimization with the BFGS quasi-Newton method with a mixed quadratic and cubic line search procedure.
Give'on, Amir; Kasdin, N. Jeremy; Vanderbei, Robert J.; Spergel, David N.; Littman, Michael G.; Gurfil, Pini
Fourier Transforms, Fourier Series and the FFT
NSDL National Science Digital Library
The goal of this module is to give students an understanding of the one-dimensional Fourier Transform, both mathematically and computationally, with a focus on finding periodicity in data. To motivate the study of the Fourier Transform, the students will be presented with certain application areas, such as searching for periodic patterns in CO2 data and differentiating between two sound signals using their power spectra. Students will explore some computational issues and challenges of the Discrete and Fast Fourier Transforms.
De Pillis, Lisette; Radunskaya, Ami
Relatively large values of objective-lens defocus must normally be used to produce detectable levels of image contrast for unstained biological specimens, which are generally weak phase objects. As a result, a subsequent restoration operation must be used to correct for oscillations in the contrast transfer function (CTF) at higher resolution. Currently used methods of CTF-correction assume the ideal case in which Friedel mates in the scattered wave have contributed pairs of Fourier components that overlap with one another in the image plane. This"ideal" situation may be only poorly satisfied, or not satisfied at all, as the particle size gets smaller, the defocus value gets larger, and the resolution gets higher. We have therefore investigated whether currently used methods of CTF correction are also effective in restoring the single-sideband image information that becomes displaced (delocalized) by half (or more) the diameter of a particle of finite size. Computer simulations are used to show that restoration either by"phase flipping" or by multiplying by the CTF recovers only about half of the delocalized information. The other half of the delocalized information goes into a doubly defocused"twin" image of the type produced during optical reconstruction of an in-line hologram. Restoration with a Wiener filter is effective in recovering the delocalized information only when the signal-to-noise ratio (S/N) is orders of magnitude higher than that which exists in low-dose images of biological specimens, in which case the Wiener filter approaches division by the CTF (i.e. the formal inverse). For realistic values of the S/N, however, the"twin image" problem seenwith a Wiener filter is very similar to that seen when either phase flipping or multiplying by the CTF are used for restoration. The results of these simulations suggest that CTF correction is a poor alternative to using a Zernike-type phase plate when imaging biological specimens, in which case the images can be recorded in a close-to-focus condition, and delocalization of high-resolution information is thus minimized.
Downing, Kenneth H.; Glaeser, Robert M.
Relatively large values of objective-lens defocus must normally be used to produce detectable levels of image contrast for unstained biological specimens, which are generally weak phase objects. As a result, a subsequent restoration operation must be used to correct for oscillations in the contrast transfer function (CTF) at higher resolution. Currently used methods of CTF-correction assume the ideal case in which Friedel mates in the scattered wave have contributed pairs of Fourier components that overlap with one another in the image plane. This �ideal� situation may be only poorly satisfied, or not satisfied at all, as the particle size gets smaller, the defocus value gets larger, and the resolution gets higher. We have therefore investigated whether currently used methods of CTF correction are also effective in restoring the single-sideband image information that becomes displaced (delocalized) by half (or more) the diameter of a particle of finite size. Computer simulations are used to show that restoration either by �phase flipping� or by multiplying by the CTF recovers only about half of the delocalized information. The other half of the delocalized information goes into a doubly defocused �twin� image of the type produced during optical reconstruction of an in-line hologram. Restoration with a Wiener filter is effective in recovering the delocalized information only when the signal-to-noise ratio (S/N) is orders of magnitude higher than that which exists in low-dose images of biological specimens, in which case the Wiener filter approaches division by the CTF (i.e. the formal inverse). For realistic values of the S/N, however, the �twin image� problem seen with a Wiener filter is very similar to that seen when either phase flipping or multiplying by the CTF are used for restoration. The results of these simulations suggest that CTF correction is a poor alternative to using a Zernike-type phase plate when imaging biological specimens, in which case the images can be recorded in a close-to-focus condition, and delocalization of high-resolution information is thus minimized. PMID:18508199
Downing, Kenneth H.; Glaeser, Robert M.
NASA Astrophysics Data System (ADS)
The NaNO3 droplets with sizes of 1-5?m generated from a nebulizer were deposited on a ZnSe substrate in a Fourier transform infrared attenuated total reflection (FTIR-ATR) chamber. After solidification of the droplets with dry N2 gas passing through the chamber, the solid NaNO3 particles were monitored by in situ FTIR-ATR spectra in cycles of deliquescence and efflorescence processes with varying relative humidities (RHs). With an increase in the RH, a dominant peak at �3539cm-1, together with three relatively weak peaks at �3400, �3272, and �3167cm-1, in the O-H stretching band of water was resolved by the high signal-to-noise ratio FTIR-ATR spectra. The dominant peak and the three relatively weak peaks were contributed by the water monomers and the aggregated water molecules adsorbed on the surfaces of solid NaNO3 particles, respectively. When the RH approached �72%, slightly lower than the deliquescence RH (74.5%), the band component at �3400cm-1 became the main peak, indicating that the water monomers and the aggregated water molecules aggregated to form a thin water layer on the surfaces of solid NaNO3 particles. A splitting of the ?3-NO3- band at 1363 and 1390cm-1 at the RH of �72%, instead of the single ?3-NO3- band at 1357cm-1 for the initial solid NaNO3, was observed. We suggested that this reflected a phase transition from the initial solid to a metastable solid phase of NaNO3. The metastable solid phase deliquesced completely in the region from �87% to �96% RH according to the fact that the ?3-NO3- band showed two overlapping peaks at 1348 and 1405cm-1 similar to those of bulk NaNO3 solutions. In the efflorescence process of the NaNO3 droplets, the ?1-NO3- band presented a continuous blueshift from 1049cm-1 at �77% RH to 1055cm-1 at �36% RH, indicating the formation of contact ion pairs between Na + and NO3-. Moreover, in the RH range from �53% down to �26%, two peaks at 836 and 829cm-1 were observed in the ?2-NO3- band region, demonstrating the coexistence of NaNO3 solid particles and droplets.
Lu, Pei-Dong; Wang, Feng; Zhao, Li-Jun; Li, Wen-Xue; Li, Xiao-Hong; Dong, Jin-Ling; Zhang, Yun-Hong; Lu, Gao-Qing
NASA Astrophysics Data System (ADS)
The objective of this study was to demonstrate the potential benefits of using high energy x-rays for phase sensitive breast imaging through a comparison with conventional mammography imaging. We compared images of a contrast-detail phantom acquired on a prototype phase sensitive x-ray imaging system with images acquired on a commercial flat panel digital mammography unit. The phase contrast images were acquired using a micro-focus x-ray source with a 50 �m focal spot at 120 kVp and 4.5 mAs, with a magnification factor of 2.46 and a 50 �m pixel pitch. A phase attenuation duality-based phase retrieval algorithm that requires only a single phase contrast image was applied. Conventional digital mammography images were acquired at 27 kVp, 131 mAs and 28 kVp, 54 mAs. For the same radiation dose, both the observer study and signal-to-noise ratio (SNR)/figure of merit comparisons indicated a large improvement by the phase retrieved image as compared to the clinical system for the larger disc sizes, but the improvement was not enough to detect the smallest discs. Compared to the double dose image acquired with the clinical system, the observer study also indicated that the phase retrieved image provided improved detection capabilities for all disc sizes except the smallest discs. Thus the SNR improvement provided by phase contrast imaging is not yet enough to offset the noise reduction provided by the clinical system at the doubled dose level. However, the potential demonstrated by this study for high energy phase sensitive x-ray imaging to improve lesion detection and reduce radiation dose in mammography warrants further investigation of this technique.
Donovan Wong, Molly; Yan, Aimin; Ghani, Muhammad; Li, Yuhua; Fajardo, Laurie; Wu, Xizeng; Liu, Hong
The objective of this study was to demonstrate the potential benefits of using high energy x-rays for phase sensitive breast imaging through a comparison with conventional mammography imaging. We compared images of a contrast-detail (CD) phantom acquired on a prototype phase sensitive x-ray imaging system with images acquired on a commercial flat panel digital mammography unit. The phase contrast images were acquired using a micro-focus x-ray source with a 50 ?m focal spot at 120 kVp and 4.5 mAs, with a magnification factor of 2.46 and a 50 ?m pixel pitch. A phase attenuation duality (PAD)-based phase retrieval algorithm that requires only a single phase contrast image was applied. Conventional digital mammography images were acquired at 27 kVp, 131 mAs and 28 kVp, 54 mAs. For the same radiation dose, both the observer study and SNR/FOM comparisons indicated a large improvement by the phase retrieved image as compared to the clinical system for the larger disk sizes, but the improvement was not enough to detect the smallest disks. Compared to the double dose image acquired with the clinical system, the observer study also indicated that the phase retrieved image provided improved detection capabilities for all disk sizes except the smallest disks. Thus the SNR improvement provided by phase contrast imaging is not yet enough to offset the noise reduction provided by the clinical system at the doubled dose level. However, the potential demonstrated by this study for high energy phase sensitive x-ray imaging to improve lesion detection and reduce radiation dose in mammography warrants further investigation of this technique. PMID:24732108
Wong, Molly Donovan; Yan, Aimin; Ghani, Muhammad; Li, Yuhua; Fajardo, Laurie; Wu, Xizeng; Liu, Hong
The objective of this study was to demonstrate the potential benefits of using high energy x-rays for phase sensitive breast imaging through a comparison with conventional mammography imaging. We compared images of a contrast-detail phantom acquired on a prototype phase sensitive x-ray imaging system with images acquired on a commercial flat panel digital mammography unit. The phase contrast images were acquired using a micro-focus x-ray source with a 50��m focal spot at 120 kVp and 4.5 mAs, with a magnification factor of 2.46 and a 50��m pixel pitch. A phase attenuation duality-based phase retrieval algorithm that requires only a single phase contrast image was applied. Conventional digital mammography images were acquired at 27 kVp, 131 mAs and 28 kVp, 54 mAs. For the same radiation dose, both the observer study and signal-to-noise ratio (SNR)/figure of merit comparisons indicated a large improvement by the phase retrieved image as compared to the clinical system for the larger disc sizes, but the improvement was not enough to detect the smallest discs. Compared to the double dose image acquired with the clinical system, the observer study also indicated that the phase retrieved image provided improved detection capabilities for all disc sizes except the smallest discs. Thus the SNR improvement provided by phase contrast imaging is not yet enough to offset the noise reduction provided by the clinical system at the doubled dose level. However, the potential demonstrated by this study for high energy phase sensitive x-ray imaging to improve lesion detection and reduce radiation dose in mammography warrants further investigation of this technique. PMID:24732108
Wong, Molly Donovan; Yan, Aimin; Ghani, Muhammad; Li, Yuhua; Fajardo, Laurie; Wu, Xizeng; Liu, Hong
X-ray phase imaging: from synchrotron to hospital
With the aim of clinical applications of X-ray phase imaging based on Talbot�Lau-type grating interferometry to joint diseases and breast cancer, machines employing a conventional X-ray generator have been developed and installed in hospitals. The machine operation especially for diagnosing rheumatoid arthritis is described, which relies on the fact that cartilage in finger joints can be depicted with a dose of several milligray. The palm of a volunteer observed with 19?s exposure (total scan time: 32?s) is reported with a depicted cartilage feature in joints. This machine is now dedicated for clinical research with patients. PMID:24470409
Momose, Atsushi; Yashiro, Wataru; Kido, Kazuhiro; Kiyohara, Junko; Makifuchi, Chiho; Ito, Tsukasa; Nagatsuka, Sumiya; Honda, Chika; Noda, Daiji; Hattori, Tadashi; Endo, Tokiko; Nagashima, Masabumi; Tanaka, Junji
Improved phase imaging from intensity measurements in multiple planes
Problems stemming from quantitative phase imaging from intensity measurements play a key role in many fields of physics. Techniques based on the transport of intensity equation require an estimate of the axial derivative of the intensity to invert the problem. Derivation formulas in two adjacent planes are commonly used to experimentally compute the derivative of the irradiance. Here we propose a formula that improves the estimate of the derivative by using a higher number of planes and taking the noisy nature of the measurements into account. We also establish an upper and lower limit for the estimate error and provide the distance between planes that optimizes the estimate of the derivative.
Soto, Marcos; Acosta, Eva
Development of a synthetic phase contrast imaging diagnostic
A ''synthetic diagnostic'' has been developed to calculate the expected experimental response of phase contrast imaging (PCI), a scattering diagnostic used to measure density fluctuations in laboratory plasmas, to a tokamak discharge modeled with the GYRO nonlinear gyrokinetic code [J. Candy and R. Waltz, J. Comput. Phys. 186, 545 (2003)]. The synthetic PCI includes the spatial response of the experimental diagnostic, primarily implemented as a line integral of plasma density along the beam path, and the minimum and maximum wavenumber response resulting from the detection scheme. The synthetic PCI can be used for comparisons between GYRO and experiment as well as studies of the PCI response.
Rost, J. C.; Lin, L.; Porkolab, M. [Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)
Development of a synthetic phase contrast imaging diagnostic
NASA Astrophysics Data System (ADS)
A "synthetic diagnostic" has been developed to calculate the expected experimental response of phase contrast imaging (PCI), a scattering diagnostic used to measure density fluctuations in laboratory plasmas, to a tokamak discharge modeled with the GYRO nonlinear gyrokinetic code [J. Candy and R. Waltz, J. Comput. Phys. 186, 545 (2003)]. The synthetic PCI includes the spatial response of the experimental diagnostic, primarily implemented as a line integral of plasma density along the beam path, and the minimum and maximum wavenumber response resulting from the detection scheme. The synthetic PCI can be used for comparisons between GYRO and experiment as well as studies of the PCI response.
Rost, J. C.; Lin, L.; Porkolab, M.
Spatiotemporal Characterization of a Fibrin Clot Using Quantitative Phase Imaging
Studying the dynamics of fibrin clot formation and its morphology is an important problem in biology and has significant impact for several scientific and clinical applications. We present a label-free technique based on quantitative phase imaging to address this problem. Using quantitative phase information, we characterized fibrin polymerization in real-time and present a mathematical model describing the transition from liquid to gel state. By exploiting the inherent optical sectioning capability of our instrument, we measured the three-dimensional structure of the fibrin clot. From this data, we evaluated the fractal nature of the fibrin network and extracted the fractal dimension. Our non-invasive and speckle-free approach analyzes the clotting process without the need for external contrast agents. PMID:25386701
Gannavarpu, Rajshekhar; Bhaduri, Basanta; Tangella, Krishnarao; Popescu, Gabriel
NASA Astrophysics Data System (ADS)
As part of NASA's New Millennium Program, the Geostationary Imaging Fourier Transform Spectrometer (GIFTS) is an advanced ultraspectral sounder with a 128x128 array of interferograms for the retrieval of such geophysical parameters as atmospheric temperature, moisture, and wind. With massive data volume that would be generated by future advanced satellite sensors such as GIFTS, chances are that even the state-of-the-art channel coding (e.g. Turbo codes, LDPC) with low BER might not correct all the errors. Due to the error-sensitive ill-posed nature of the retrieval problem, lossless compression with error resilience is desired for ultraspectral sounder data downlink and rebroadcast. Previously, we proposed the fast precomputed vector quantization (FPVQ) with arithmetic coding (AC) which can produce high compression gain for ground operation. In this paper we adopt FPVQ with the reversible variable-length coding (RVLC) to provide better resilience against satellite transmission errors remaining after channel decoding. The FPVQ-RVLC method is compared with the previous FPVQ-AC method for lossless compression of the GIFTS data. The experiment shows that the FPVQ-RVLC method is a significantly better tool for rebroadcast of massive ultraspectral sounder data.
Huang, Bormin; Wei, Shih-Chieh; Huang, Hung-Lung; Smith, William L.; Bloom, Hal J.
Diet-induced atherosclerotic lesions in the descending thoracic segment of rabbit aorta were analysed ex vivo by micro-attenuated total reflection (ATR)�Fourier transform infrared (FTIR) spectroscopic imaging. The distribution and chemical character of lipid deposits within the arterial wall near intercostal branch ostia were assessed in histological sections from immature and mature rabbits fed cholesterol with or without l-arginine supplements. Previous studies have shown that both these properties change with age in cholesterol-fed rabbits, putatively owing to changes in the synthesis of nitric oxide (NO) from l-arginine. Immature animals developed lesions at the downstream margin of the branch ostium, whereas lipid deposition was observed at the lateral margins in mature animals. Dietary l-arginine supplements had beneficial effects in mature rabbit aorta, with overall disappearance of the plaques; on the other hand, they caused only a slight decrease of the lipid load in lesions at the downstream margin of the ostium in immature rabbits. ATR�FTIR imaging enabled differences in the lipid to protein density ratio of atherosclerotic lesions caused by age and diet to be visualized. Lipid deposits in immature rabbits showed higher relative absorbance values of their characteristic spectral bands compared with those in immature l-arginine-fed rabbits and mature rabbits. The multivariate methods of principal component analysis (PCA) and factor analysis (FA) were employed, and relevant chemical and structural information were obtained. Two distinct protein constituents of the intima�media layer at different locations of the wall were identified using the method of FA. This approach provides a valuable means of investigating the structure and chemistry of complex heterogeneous systems. It has potential for in vivo diagnosis of pathology. PMID:18986964
Palombo, Francesca; Cremers, Stephanie G.; Weinberg, Peter D.; Kazarian, Sergei G.
Diet-induced atherosclerotic lesions in the descending thoracic segment of rabbit aorta were analysed ex vivo by micro-attenuated total reflection (ATR)-Fourier transform infrared (FTIR) spectroscopic imaging. The distribution and chemical character of lipid deposits within the arterial wall near intercostal branch ostia were assessed in histological sections from immature and mature rabbits fed cholesterol with or without l-arginine supplements. Previous studies have shown that both these properties change with age in cholesterol-fed rabbits, putatively owing to changes in the synthesis of nitric oxide (NO) from l-arginine. Immature animals developed lesions at the downstream margin of the branch ostium, whereas lipid deposition was observed at the lateral margins in mature animals. Dietary l-arginine supplements had beneficial effects in mature rabbit aorta, with overall disappearance of the plaques; on the other hand, they caused only a slight decrease of the lipid load in lesions at the downstream margin of the ostium in immature rabbits. ATR-FTIR imaging enabled differences in the lipid to protein density ratio of atherosclerotic lesions caused by age and diet to be visualized. Lipid deposits in immature rabbits showed higher relative absorbance values of their characteristic spectral bands compared with those in immature l-arginine-fed rabbits and mature rabbits. The multivariate methods of principal component analysis (PCA) and factor analysis (FA) were employed, and relevant chemical and structural information were obtained. Two distinct protein constituents of the intima-media layer at different locations of the wall were identified using the method of FA. This approach provides a valuable means of investigating the structure and chemistry of complex heterogeneous systems. It has potential for in vivo diagnosis of pathology. PMID:18986964
Palombo, Francesca; Cremers, Stephanie G; Weinberg, Peter D; Kazarian, Sergei G
NASA Astrophysics Data System (ADS)
We present a novel method for double image encryption that is based on amplitude-phase mixed encoding and multistage random phase encoding in gyrator transform (GT) domains. In the amplitude-phase mixed encoding operation, a random binary distribution matrix is defined to mixed encode two primitive images to a single complex-valued image, which is then encrypted into a stationary white noise distribution by the multistage phase encoding with GTs. Compared with the earlier methods that uses fully phase encoding, the proposed method reduces the difference between two primitive images in key space and sensitivity to the GT orders. The primitive images can be recovered exactly by applying correct keys with initial conditions of chaotic system, the GT orders and the pixel scrambling operation. Numerical simulations demonstrate that the proposed scheme has considerably high security level and certain robustness against data loss and noise disturbance.
Wang, Qu; Guo, Qing; Lei, Liang
Computational techniques in propagation-based x-ray phase imaging
NASA Astrophysics Data System (ADS)
X-ray phase imaging utilizes a variety of techniques to render phase information as intensity contrast and these intensity images can in some cases be processed to retrieve quantitative phase. A subset of these techniques use free space propagation to generate phase contrast and phase can be recovered by inverting differential equations governing propagation. Two techniques to generate quantitative phase reconstructions from a single phase contrast image are described in detail, along with regularization techniques to reduce the influence of noise. Lastly, a recently developed technique utilizing a binary-amplitude grid to enhance signal strength in propagation-based techniques is described.
Petruccelli, Jonathan C.; Tahir, Sajjad; Bashir, Sajid; Pan, Adam; Tian, Lei; Xu, Ling; MacDonald, C. A.; Barbastathis, George
Spacevariant Fourier Analysis: the Exponential Chirp Transform
of the fast exponential chirp algorithm on a database of images in a template matching task, and alsoVariant Image Processing, Fourier Analysis, NonUniform Sampling, RealTime Imaging, Warped Template Matching to the Mellin Transform) provides a fast exponential chirp transform. This provides size and rotation
Schwartz, Eric L.
Real Time Blood Testing Using Quantitative Phase Imaging
We demonstrate a real-time blood testing system that can provide remote diagnosis with minimal human intervention in economically challenged areas. Our instrument combines novel advances in label-free optical imaging with parallel computing. Specifically, we use quantitative phase imaging for extracting red blood cell morphology with nanoscale sensitivity and NVIDIA�s CUDA programming language to perform real time cellular-level analysis. While the blood smear is translated through focus, our system is able to segment and analyze all the cells in the one megapixel field of view, at a rate of 40 frames/s. The variety of diagnostic parameters measured from each cell (e.g., surface area, sphericity, and minimum cylindrical diameter) are currently not available with current state of the art clinical instruments. In addition, we show that our instrument correctly recovers the red blood cell volume distribution, as evidenced by the excellent agreement with the cell counter results obtained on normal patients and those with microcytic and macrocytic anemia. The final data outputted by our instrument represent arrays of numbers associated with these morphological parameters and not images. Thus, the memory necessary to store these data is of the order of kilobytes, which allows for their remote transmission via, for example, the cellular network. We envision that such a system will dramatically increase access for blood testing and furthermore, may pave the way to digital hematology. PMID:23405194
Pham, Hoa V.; Bhaduri, Basanta; Tangella, Krishnarao; Best-Popescu, Catherine; Popescu, Gabriel
Matrix phased array (MPA) imaging technology for resistance spot welds
NASA Astrophysics Data System (ADS)
A three-dimensional MPA probe has been incorporated with a high speed phased array electronic board to visualize nugget images of resistance spot welds. The primary application area of this battery operated portable MPA ultrasonic imaging system is in the automotive industry which a conventional destructive testing process is commonly adopted to check the quality of resistance spot welds in auto bodies. Considering an average of five-thousand spot welds in a medium size passenger vehicle, the amount of time and effort given to popping the welds and measuring nugget size are immeasurable in addition to the millions of dollars' worth of scrap metals recycled per plant per year. This wasteful labor intensive destructive testing process has become less reliable as auto body sheet metal has transitioned from thick and heavy mild steels to thin and light high strength steels. Consequently, the necessity of developing a non-destructive inspection methodology has become inevitable. In this paper, the fundamental aspects of the current 3-D probe design, data acquisition algorithms, and weld nugget imaging process are discussed.
Na, Jeong K.; Gleeson, Sean T.
Off-axis quantitative phase imaging processing using CUDA: toward real-time applications.
We demonstrate real time off-axis Quantitative Phase Imaging (QPI) using a phase reconstruction algorithm based on NVIDIA's CUDA programming model. The phase unwrapping component is based on Goldstein's algorithm. By mapping the process of extracting phase information and unwrapping to GPU, we are able to speed up the whole procedure by more than 18.8� with respect to CPU processing and ultimately achieve video rate for mega-pixel images. Our CUDA implementation also supports processing of multiple images simultaneously. This enables our imaging system to support high speed, high throughput, and real-time image acquisition and visualization. PMID:21750757
Pham, Hoa; Ding, Huafeng; Sobh, Nahil; Do, Minh; Patel, Sanjay; Popescu, Gabriel
A study on carrier phase distortion in phase measuring deflectometry with non-telecentric imaging.
In phase measuring deflectometry (PMD), the fringe pattern deformed according to slope deviation of a specular surface is digitized employing a phase-shift technique. Without height-angle ambiguity, carrier-removal process is adopted to evaluate the variation of surface slope from phase distribution when a quasi-plane is measured. However, the difficulty lies in the fact that the nonlinearity is generally contained in the carrier frequency due to the restrictions of system geometries. This paper investigates nonlinear carrier components introduced by the generalized imaging process in PMD. Furthermore, the analytical expression of carrier components in PMD is presented for the first time. The presented analytical form of carrier components can be extended to analyze and describe various effects of system parameters on carrier distortion. Assuming a pinhole perspective model, carrier phase distribution of arbitrary geometric arrangement is modeled as a function of spatial variables by exploring ray tracing method. As shown by simulation and experimental results, the carrier distortion is greatly affected by non-telecentric camera operation. Experimental results on the basis of reference subtraction technique further demonstrate that restrictions on reflection system geometry can be eliminated when the carrier phase is removed elaborately. PMID:23187214
Song, Lei; Yue, Huimin; Kim, Hanshin; Wu, Yuxiang; Liu, Yong; Liu, Yongzhi
Improved detection of anterior left ventricular aneurysm with multiharmonic fourier analysis
Single and multiharmonic Fourier analysis of LAO 30-45 degrees gated blood-pool studies were performed in a selected group of 30 patients with a left ventricular anterior aneurysm proven by contrast angiography. The sensitivity of the first harmonic phase image for the diagnosis of ventricular aneurysm was 80%. The clear phase shift (greater than 110 degrees) between the normal and the aneurysmal areas was missing in six patients. Peak acceleration images (negative maximum of the second derivative of the Fourier series) were calculated for each pixel with the analytical Fourier formula using two or three harmonics. A clear phase shift (greater than 126 degrees) than appeared in all the patients. This improvement was related to the increased weight of the second and third harmonics in the aneurysmal area when compared to control patients or to patients with dilative cardiomyopathy. Multiharmonic Fourier analysis clearly improved the sensitivity of the diagnosis of anterior left ventricular aneurysm on LAO 30 degrees-45 degrees gated blood-pool images.
Valette, H.B.; Bourguignon, M.H.; Merlet, P.; Gregoire, M.C.; Le Guludec, D.; Pascal, O.; Briandet, P.; Syrota, A.
Quality Factor Variation with Transform Order in Fractional Fourier Domain
Fractional Fourier Transform is a powerful tool, which is a generalization of the classical Fourier Transform. This paper provides a mathematical relation relating the span in Fractional Fourier domain with the amplitude and phase functions of the signal, which is further used to study the variation of quality factor with different values of the transform order. It is seen that
Sukrit Shankar; Chetana Shanta; K. Pardha Saradhi; Jaydev Sharma
Microscopic images of biological phase specimens of various optical thickness, acquired under off-axis illumination and apodized/conventional phase-contrast are compared. The luminance profiles in appropriately filtered apodized phase-contrast images compare well with those in the original off-axis illumination images. The two unfiltered image types also yield similar results in terms of quasi-three-dimensional surface (pseudo-relief) rendering, and thus are comparable in terms of the information contents (optical thickness map). However, the overall visual impression is very different as the visual cues to depth structure are present in the off-axis illumination images only. The comparison demonstrated in the present paper was made possible owing to apodization, which substantially reduces the "halo"/shade-off artifacts in the phase-contrast images. The results imply the possibility of combining the off-axis illumination and apodized phase-contrast imaging to examine specimens of medium optical thickness, in which the phase visualization capability of the two imaging modes substantially overlaps (e.g., larger cells or cell clusters). PMID:19021445
Pelc, Radek; Hostounsk�, Zdenek; Otaki, Tatsuro
Hierarchical security system using real-valued data and orthogonal code in Fourier domain
NASA Astrophysics Data System (ADS)
We propose a novel hierarchical encryption scheme using orthogonal code in Fourier domain and decryption based on interferometer system. The proposed system is composed of hierarchical ciphertexts with positive real values which can be applied for practical transmission such as Internet, and decryption keys with real valued function which has orthogonal characteristic in the decryption system. Since the original information is encrypted on the Fourier plane, the proposed encryption is more tolerant to loss of key information by scratching or cutting than encryption in a spatial domain. The resulting image using Fourier transform and an interferometer system with constant phase retarder is then decrypted by use of a ciphertext with different security level and each of decryption keys made from the multiplication of orthogonal code and random phase code in order to enhance the level of security. We demonstrate the efficiency of the proposed method and the fault-tolerance properties of data loss through several simulations.
Kim, Hyun-Jun; Seo, Dong-Hoan; Hwang, Kwang-Il; Lim, Tae-Woo
Nanoscale Imaging of Phase Transitions with Scanning Force Microscopy
NASA Astrophysics Data System (ADS)
Nanoscale imaging of materials through phase transitions can provide valuable insight into the local nature of the transition and the emergence of order. The scanning force microscope used in the studies presented here is an ideal instrument to investigate phase transitions with nanoscale spatial resolution. We study phase transitions in two different systems by operating in different modes: contact mode, in which we measure the local electronic properties of the sample; and non-contact mode, in which we probe the sample by monitoring the interaction between the sample and cantilever. We increased the versatility of this microscope by developing a method to control the quality factor Q of a conducting cantilever via capacitive coupling to the local environment. We show that Q may be reversibly tuned over a range of a factor of 260. We describe the underlying physics with a point-mass oscillator model. Tuning Q can enhance force-gradient sensitivity or scan speed, which we demonstrate with topographic scans of a VO2 acquired in high vacuum. Scanning in contact mode with a conductive cantilever, we study local electronic properties of a vanadium dioxide (VO2) thin film through an insulator to metal transition. At each point in the scan, we sweep the voltage applied to the sample, obtaining current versus voltage sweeps with nanoscale resolution while inducing the insulator to metal transition. In some VO2 grains, we see two electronic transitions, consistent with a locally stable intermediate insulating phase. We find large insulating state resistances and transition voltages at grain boundaries, underscoring the importance of Joule heating in triggering the transition in this type of measurement. Finally, we evaluate the conduction mechanism in the insulating regime, allowing the local determination of permittivity and temperature. We scan in non-contact mode with a magnetic tip to investigate the spin reorientation transition in single-crystal Nd2Fe14B. This ferromagnetic system undergoes the spin reorientation transition near 135 K. We achieve nanoscale magnetic resolution at both room temperature and at a variety of temperatures around the phase transition. We demonstrate the ability to resolve the magnetic domain structure and monitor its evolution through the phase transition.
Pivonka, Adam Edward