A method of examining thin layer structures on a surface for differences in respect of optical thickness, which method comprises the steps of: irradiating the surface with light so that the light is internally or externally reflected at the surface; imaging the reflected light on a first two-dimensional detector; sequentially or continuously scanning the incident angle and/or wavelength of the light over an angular and/or wavelength range; measuring the intensities of light reflected from different parts of the surface and impinging on different parts of the detector, at at least a number of incident angles and/or wavelengths, the intensity of light reflected from each part of the surface for each angle and/or wavelength depending on the optical thickness of the thin layer structure thereon; and determining from the detected light intensities at the different light incident angles and/or wavelengths an optical thickness image of the thin layer structures on the surface. According to the invention, part of the light reflected at said surface is detected on a second detector to determine the incident angle or wavelength of the polarized light irradiating the surface. An apparatus for carrying out the method is also disclosed.

The present invention relates to a method and an apparatus for optical surface analysis of a sample area on a sensor surface.
The interest for surface sensitive measuring techniques has increased markedly recently as several optical techniques have been developed for identifying and quantifying molecular interactions. which techniques do not require labelling. The most used optical technique so far is based on surface plasmon resonance. hereinafter frequently referred to as SPR.
The phenomenon of surface plasmon resonance, or SPR, is well known. In brief, SPR is observed as a dip in intensity of light for a specific wavelength reflected at a specific angle (as measured by, e.g., a photodetector) from the interface between an optically transparent material, e.g. glass, and a thin metal film, usually silver or gold. and depends on among other factors the refractive index of the medium (e g., a sample solution) close to the metal surface. A change of the real part of the complex refractive index at the metal surface, such as by the adsorption or binding of material thereto. will cause a corresponding shift in the angle at which SPR occurs. the so-called SPR-angle. For a specific angle of incidence, the SPR is observed as a dip in intensity of light at a specific wavelength, a change in the real part of the refractive index causing a corresponding shift in the wavelength at which SPR occurs.
To couple the light to the interface such that SPR arises, three alternative arrangements may be used, viz. either a metallized diffraction grating (see H. Raether in xe2x80x9cSurface Polaritonsxe2x80x9d, Eds. Agranovich and Mills, North Holland Pubi. Comp., Amsterdam, 1982), a metallized glass prism (Kretschmann configuration) or a prism in close contact with a metallized surface on a glass substrate (Otto configuration). In a SPR-based assay, for example, a ligand is bound to the metal surface, and the interaction of this sensing surface with an analyte in a solution in contact with the surface is monitored.
Originally, collimated light was used for measuring the SPR-angle, the sensing area being restricted to the intersection of the collimated light beam and the metal surface. The apparatus used was based on mechanical goniometry with two movable mechanical axes carrying the illumination and detecting components, the rotational center of which was placed in the center of the sensor area, i.e., one axis for the incident light and another axis for the reflected light which was detected by a single photodetector. A plane-sided coupling prism at total internal reflection condition was used to preserve the collimated beam inside the prism, which, however, introduced a refraction at non-orthogonal incidence at the prism, thereby introducing a beam-walk at the metal surface. A half-cylindrical coupling lens with orthogonal incidence of the optical axis of the light gave a fixed sensor area, however, introduced a beam-convergency, i.e., a noncollimated or quasi-collimated beam inside the prism.
In a development, the movable opto-mechanical axis on the illumination side was eliminated by using a focused incident beam, so-called focused attenuated total reflection (focused ATR), as described by Kretschmann, Optics Comm. 26 (1978) 41-44, the whole angular range simultaneously illuminating a focal line or point of a given sensing surface. The use of a detector matrix for detecting the reflected light eliminated the movable opto-mechanical axis also on the reflectance side, providing a faster SPR-detection than that of the prior art. Such systems are described in, e.g., EP-A-305 109 and WO 90/05295. In the latter, light beams reflected from a specific sub-zone at the sensor area are imaged anamorphically so that beams in one plane (the sagittal plane) create a real image on a specific detector-pixel row of a matrix detector, permitting the occurrence of a local surface binding reaction to be identified, while quantification of the reaction is obtained via angular data for a reflectance curve measured along the same pixel row, where the reflectance curve is created by beams in a plane (the meridian plane) normal to the first-mentioned plane. Thus, one dimension of the matrix detector is used for real imaging simultaneously as the other dimension is used for only angular measurement. This permits only sub-zones arranged in a row to be simultaneously monitored and imaged.
In a variation of goniometry, the bulky mechanical axes were replaced by rotating or vibrating mirrors, respectively. A disadvantage of that approach is, however, that when scanning the incident angle by means of a plane mirror, the point where the light beam hits the sensor surface will move along the internal reflection surface of the prism. This problem was avoided by using a combination of rotating mirror and focused SPR, e.g., as described by Oda, K., Optics Comm. 59 (1986) 361. In this construction, a first collimated beam of about 1 mm diameter impinges on the rotational center of a rotating mirror placed at the focal length of a focusing lens, thus producing a second quasi-collimated beam, the distance of which to the optical axis depends on the reflecting angle of the mirror. The second collimated beam is focused by a second focusing lens onto a prism base at total internal reflection conditions. During the rotation of the mirror, the angle of incidence at the approximately fixed sensor area is scanned for the quasi-collimated beam.
Another approach to obtain a fixed and also enlarged sample spot is proposed by Lenferink et al., xe2x80x9cAn improved optical method for surface plasmon resonance experimentsxe2x80x9d, Sensors and Actuators B, vol. 3 (1991) 261-265. This technique uses the combination of a collimated light beam illuminating a plane rotating mirror, a focusing cylindrical (convex) lens after the mirror and a half-cylinder lens for coupling the light to the sensing surface. By making the cylindrical lens focus the light on the focal surface of the coupling half-cylinder, using a relatively complex lens system, a collimated beam is obtained inside the coupling prism.
Other optical techniques similar to SPR are Brewster angle reflectometry (BAR) and critical angle reflectometry (CAR).
When light is incident at the boundary between two different transparent dielectric media, from the higher to the lower refractive index medium, the internal reflectance varies with angle of incidence for both the s- and p-polarized components. The reflected s-polarized component increases with the angle of incidence, and the p-polarized component shows a minimum reflectance at a specific angle, the Brewster angle. The angle at which both s- and p-polarized light is totally internally reflected is defined as the critical angle. For all angles of incidence greater than the critical angle, total internal reflection (TIR) occurs.
Schaaf et al., Langmuir, vol. 3 (1987) describes Brewster angle reflectometry using a micro-controlled rotation table and a movable detector in scanning angle reflectometry around the internal Brewster angle to study a protein (fibrinogen) at a silica/solution interface. The use of movable optomechanical axes and a rotation table gives a slow measuring procedure, and the sensor area is restricted to the cross-section of the collimated light beam with the sensor surface being limited by the need for non-beam-walking.
A focusing critical angle refractometer, based on a wedge of incident light which strikes the line of measurement, including the critical angular interval to be measured, and which measures the one-dimensional refractive index profile along a focused line immediately adjacent to the glass wall of a liquid container is described by Beach, K. W., et al., xe2x80x9cA one-dimensional focusing critical angle refractometer for mass transfer studiesxe2x80x9d Rev. Sci. Instrum., vol. 43, 1972. This technique is limited in that it enables only a one-dimensional sensor area, which is restricted to the cross-section of the light line with the sensor area.
In all the above described prior art methods for reflectometric measurements, the reflectometric signal obtained represents an average value for the sensor surface and the size of the sensor surface is restricted, or minimized, to the extension of the collimated or quasi-collimated narrow beam, or focusing point or line. Therefore, such SPR-based methods used to measure, for example, inter alia protein interactions are limited to quantitative information for sensing areas localized in one spot or one row of spots on the surface where a specific interaction takes place. Approaches to monitor a two-dimensional interaction pattern have been made for both macroscopic and microscopic SPR-based imaging of a sensing surface.
Thus, EP-A-341 928 discloses a method for monitoring a large SPR sensor area in real-time by scanning a small focused beam, of, e.g., 10 xcexcm, as a measuring sensing surface successively over the large area, more specifically a DNA sequencing gel, for example 20xc3x9720 cm2, thereby making it possible to build up an image or picture of the sample distribution within the sequencing gel by means of a photodetector array. This method requires, however, the use of scanning mirrors for both addressing the sensor zones and scanning the angle and complex and expensive processing of angular and positional data from the mirror-scanners and photodetectors, which limits the detection rate.
Yeatman and Ash, Electronic Letters 23 (1987) 1091-1092, and SPIE 897 (1988) 100-107 disclose microscopic real imaging of the sensing surface, so called surface plasmon microscopy, or SPM. This was achieved by the use of SPR in the Kretschmann configuration with a triangular prism for imaging dielectric patterns deposited on a silver film with a lateral resolution of about 25 xcexcm, utilizing a focused beam in the form of a line scanned along the sensor surface. Also described is the use of an expanded laser beam at the resonance angle to illuminate a larger area and make a photograph of such an image by a positive lens in front of the photodetector. The illuminating beam is collimated and the angle of incidence is adjusted by rotating the triangular prism. The method is proposed to be used for the examination of metal films. biological and other superimposed monolayers.
Image processing methods for such SPM using a collimated beam and a lens inserted into the reflected beam to create an image of the sample distribution at the prism base are discussed by Yeatman and Ash in xe2x80x9cComputerized Surface Plasmon Microscopyxe2x80x9d, SPIE, Vol. 1028 (1988) 231.
Okamoto and Yamaguchi have described a SPR-microscope wherein the position of a collimated beam, SPIE vol. 1319 (1990) 472-473, or a focused beam, Optics Communications 93 (1992) 265-270, is scanned across the sample surface in a Kretschmann configuration, the assembled point-SPR data thereby creating an image. In the focused beam alternative, a linear photodiode array is used for detection of the SPR-angle, in accordance with the principle of focused ATR as described earlier by Kretschmann, supra.
Drawbacks with mechanically scanned SPR-sampling includes that a high lateral resolution and high speed for xe2x80x9creal time monitoringxe2x80x9d demands a complex and expensive scanning mechanics (due to the bulkiness of the illumination and detection device).
EP-A-469377 describes an analytical system and method for the determination of an analyte in a-liquid sample based on surface plasmon imaging. Surface plasmon images as a function of the angle of incidence are monitored by a CCD-camera and analyzed by an image-software. Algorithms are used for comparing the measured SPR-angle for different areas of the sensor surface for the purpose of eliminating the contribution from a non-specific binding, and for calibration of the response curve.
Rothenhausler and Knoll, Nature, 332 (1988) 615-617, demonstrates surface plasmon microscopy on organic films (a multilayer cadmium arachidate), based on SPR in a Kretschmann configuration. A simple lens is used to form an image of the sample/metal interface. A collimated beam (plane waves) illumination and a movable bulky optomechanical axis are used to change the angle of incidence.
In the above prior art arrangements for SPM, the angle of incidence is varied by the use of goniometry, either in a form where one or both optomechanical axes are moved (scanned) in relation to a fixed prism, or in a form using a movable optomechanical axis in combination with a rotating prism, the common rotation point being in the center of the prism sensor surface. and the angle of incidence being derived from the change in position or rotation of the mechanical axis through mechanical, electronic, electromagnetic or optical means. It is readily understood that such variation of the incident angle based on rotation of the mechanical axis carrying illuminating, imaging and detector modules is rather slow and inaccurate if not a complex and expensive design is provided.
Another approach is disclosed by Kooyman and Krull, Langmuir 7 (1991) 1506-15094, namely SPM using a small vibrating mirror in combination with a Kretschmann configuration to adjust the angle of incidence. A disadvantage is, however, that the probed spot is not stationary during the angular scan, i.e., all sites within a sensing area are not probed by light at an equal angle of incidence range, unless bulky optics is covering the sensing area at an excess.
Also microscopy based on Brewster angle measurements has been described. Hxc3xa8non and Meunier, Rev. Sci. Instum., vol. 62 (1978) 936-939 discloses the use of a microscope at the Brewster angle for direct observation of first-order phase transitions in monolayers. In this case, external Brewster angle is measured, ie., no internal reflection and no coupling prism, the camera plane being parallel with the sensor surface.
Similarly, Hxc3x6nig and Mobius, J. Phys. Chem., vol. 95 (1991) 4590-4592 describes the use of Brewster angle microscopy to study the air-water interface. Objects of about 3 xcexcm diameter could be visualized by video recording of p-polarized light reflected under a fixed Brewster angle for the pure water surface.
A microscopic imaging ellipsometer has been described by Beaglehole, D., Rev. Sci. Instrum., 59 (12) (1988) 2557-2559.
Multiple-angle evanescent wave ellipsometry, in the form of using rotating optical means and a rotating prism for the variation of incident angle, and a phase-modulated ellipsometer, has been used for studying the polymer (polystyrene) concentration profile near a prism/liquid interface; see Kim, M. W., Macromolecules, 22, (1989) 2682-2685. Furthermore, total internal reflection ellipsometry in the form of stationary optical means at a single angle of incidence has been suggested for quantification of immunological reactions; see EP-A1-0 067 921 (1981), and EP-A1-0 278 577 (1988).
Azzam, R. M. A., Surface Science 56 (1976) 126-133, describes a use of evanescent wave ellipsometry, wherein both the intensity and polarization ellipse of the reflected beam can be monitored as functions of the angle of incidence, wavelength or time. Under steady state conditions, measurements as a function of wavelength and angle of incidence can provide basic information on the molecular composition and organization of the (biological) cell periphery. In a dynamic time-varying situation, measurements as a function of time can resolve the kinetics of certain surface changes.
Abelxc3xa8s, F. et al., in Polaritons, Editor E. Burstein and F. De Martini, Pergamon Press, Inc., New York, 1974, 241-246, shows how extremely sensitive surface plasmons are to very fine modifications of the surface, and the advantage of then measuring not only the reflected amplitude, but also the ellipsometric parameters, amplitude and phase, of the reflected wave.
A focusing critical angle refractometer for measuring a one-dimensional refractive index profile being displayed in a graphic image for mass transfer studies has been described by Beach, K. W., The Review of Scientific Instruments, 43, No. 6 (1972) 925-928. Since this apparatus uses one dimension in the image plane for a real image, and the other dimension for projecting the reflectance versus angle of incidence, it could not, however, provide a two-dimensional image of the refractive index distribution.
The prior art microscopy systems described above do not permit a sufficiently rapid, sensitive and accurate scanning and measurement of the incident angle to permit highly quantitative multi-site real-time monitoring of a sensor surface. Further, they are only suitable for imaging a limited sensor area of up to about 1xc3x971 mm2. They are also too laborative and operator-dependent to be used in a commercial analytical instrument.
More particularly, the prior art apparatuses and systems for SPR microscopy and Brewster angle microscopy use either a high inertia scanner in the form of a goniometer where one or both mechanical axes for the illumination side and the imaging side, respectively, are rotated in relation to a fixed prism, or a movable mechanical axis in combination with a rotating prism for scanning the optical axis, i.e., the angle of incidence. In case the illumination consists of a collimated beam of light, the incident angle is measured directly on the angle steering signal without using the incident light, e.g., on the control signal to the rotor-driving motor of a mirror, or by an electronic or optoelectronic angle sensor placed on or at the rotated axis. Alternatively, a galvanometric or resonant low inertia scanner is used to drive a vibrating mirror to oscillate within a given calibrated angular range, determined by a given drive current, without monitoring the actual incident angle of the light.
The necessary high refractometric sensitivity for determining the refractive index of the sensor surface with an apparatus constructed according to the above prior art in a long-term accurate commercial analytical instrument could therefore only be achieved with a very complex and expensive design.
It is an object of the present invention to overcome the above disadvantages and provide an optical method and apparatus that permits microscopic as well as large area analysis of the sensing surface of a sensor chip or plate with a high refractometric sensitivity and accuracy at high spatial resolution.
According to the present invention, the above object is obtained in a large area or microscopy analytical apparatus of the above described types, as well as in others, by using part of the angular or wavelength-scanned light that illuminates the sensor chip for monitoring and determining the momentary incident angle or wavelength of the light.
As will be further explained below, this enables an improved quantitative measuring precision, accuracy and speed in the determination of the angle of incidence (alternatively wavelength) corresponding to the local reflection curve parameters, e.g., reflectance minimum, at the surface structures on the sensor surface, such as surface-distributed reaction sites.
In one aspect, the present invention provides a method of examining thin layer structures on a surface for differences in respect of optical thickness, which method comprises:
irradiating the surface with light so that the light is internally or externally reflected at the surface,
imaging the reflected light on a first two-dimensional detector, sequentially or continuously scanning the incident angle and/or wavelength of the light over an angular and/or wavelength range,
measuring the intensities of light reflected from different parts of the surface and impinging on different parts of the detector, at at least a number of incident angles and/or wavelengths, the intensity of light reflected from each part of the surface for each angle and/or wavelength depending on the optical thickness of the thin layer structure thereon,
and determining from the detected light intensities at each of the different light incident angles and/or wavelengths an optical thickness image of the thin layer structures on the surface,
which method is characterized in that part of the light reflected at the surface is detected on a second detector to determine the incident angle or wavelength of the light irradiating the surface
In another aspect, the present invention provides an apparatus for examining thin layer structures on a surface for differences in respect of optical thickness, comprising:
a sensor unit having a sensing surface with a number of zones capable of exhibiting thin layer structures of varying optical thickness, particularly as the result of contact with a sample,
a light source for emitting a beam of light,
optical means for coupling said light beam to said sensor unit,
first photodetector means,
means for sequentially or continuously scanning said light incident at said sensor surface over a range of incident angles and/or wavelengths,
means for imaging light reflected from said different parts of the sensor surface onto said first photodetector means for detecting the intensities of the reflected light,
means for determining each said angle and/or wavelength of light impinging on said sensing surface,
evaluation means for determining from the relationship between detected intensity of the reflected light and incident light angle and/or wavelength, the optical thickness of each zone of said sensor surface to thereby produce and monitor a morphometric image of the optical thickness of the sensor surface,
which apparatus is characterized in that it comprises second photodetector means, and that said means for determining said light angles and/or wavelengths comprise means for focusing a part of said light reflected at the sensing surface onto said second photodetector means, wherein each position of said focused light on said second photodetector means is related to a specific angle and/or wavelength of the light incident at the sensing surface.
The term xe2x80x9coptical thicknessxe2x80x9d as used herein defines a composite optical property of a material which is a function of both its physical thickness and its refractive index.
The term xe2x80x9csurface structuresxe2x80x9d as used herein means any chemical, physical, biophysical and/or biochemical structures of thin or other type on a sensor surface, especially structures produced via chemical or biochemical interactions with species immobilized on the sensor surface.
It is understood that in accordance with the present invention, a series of images of a sensor surface are created, one image for each specific incident angle or wavelength. A part of the imaging detector, or a separate detector, is used for measuring the incident angle or wavelength. This will be described in more detail further below.
The light is usually polarized prior to hitting the photodetector. This may be accomplished by using a light source which emits polarized light or by placing a polarizer between the light source and the detector.
In one basic embodiment of the invention, monochromatic angularly scanned light is used, and a main first part of the reflected collimated beam is used to produce a real image on a first main area of the matrix photodetector, while a second part of the reflected collimated beam is focused into a sharp line on a second specific minor linear area of the matrix photodetector. During the angular scan of the collimated beam the change in angle of incidence is determined through the change in position of either the maximum, or the centroid of the focused light intensity detected by the detector elements along the linear detector area by use of an intensity-curve analysis algorithm.
In another basic embodiment of the invention, a scanned monochromatic light at a fixed angle of incidence is used, and the second part of the reflected fixed collimated beam passes a wavelength dispersive element, and is then focused into a sharp point or line on a second specific minor linear area of said matrix detector. During the wavelength scan of the beam the change in wavelength is determined through the change in position of either the maximum, or the centroid of the focused light intensity detected by the detector elements along the linear detector area by use of an intensity-curve analysis algorithm.
In a preferred embodiment, the present invention provides an improved reflectometric performance for an imaging method based on total internal reflection, such as e.g., surface plasmon resonance (SPR), or external reflection, such as external Brewster angle spectroscopy or ellipsometry, by the use of a novel optical design which will be further described below and comprises a bifocal imaging system enabling simultaneous sensor zone resolution and projection of rays for measurement of the angle of incidence, and of the wavelength, on the same matrix photodetector array, and a low inertia mirror scanner system for a mainly stationary illuminated area of the sensor chip in combination with a total internal reflection element, or a grating, for coupling an evanescent wave to the sensor surface.
More particularly, such an apparatus may comprise an imaging system having two different focal lengths in the same plane of projection (meridian plane), together with an identical focal length for the sagittal plane and the dominating part of the meridian plane, and a common photodetector matrix array for image and angle monitoring. Preferably, the main part of the detector array lies in the real image plane of the imaging system, while a minor part of the detector matrix array lies in the back focal plane of the imaging system. Detector elements within the real image plane monitor light intensity originating from specific local spots at microscopic lateral resolution, while other detector elements within the back focal plane detect the position of the focused line, i e., the angle of incidence.
In an alternative form, the bifocal imaging enables detector elements within the real image plane to monitor light intensity originating from a specific local spot at microscopic lateral resolution, while other detector elements within the back focal plane detect the position of the focused line corresponding to the wavelength.
The reflected light intensity varies with the angle of incidence, mainly due to the angle dependent reflection coefficient, but may also vary due to a movement of the illuminated area if the light intensity across the illuminating beam is not constant. By use of an approximately stationary illuminated sensor area, together with an image-intensity normalization algorithm, a highly resolved light intensity of the local reflectance curves may be detected, which enables a high resolution in the determined angle/wavelength at the corresponding reflectance minima or maxima or centroid.
While it is preferred that the same detector array component is used for both image detection and angle or wavelength detection, separate detectors may, of course, also be used.
When both incident angle and wavelength of the light are to be measured, the detector may be divided into two (smaller) parts, and a larger part, wherein one of the smaller parts is used for detection of the incident angle, and the other smaller part is used for detection of the wavelength, and the larger detector part is used for imaging.
As stated above, the present invention is characterized by an integral detection of both image and incident light angle and/or wavelength to obtain a better accuracy and sensitivity in the multi-zone reflectometry and a faster analysis procedure than those obtained in the prior art. Thus, according to the present invention, the same collimated light is used (i) to illuminate each point on the sensor surface with a practically identical angle of the incident light, permitting a minimum deviation (a maximum deviation of 0.002xc2x0) within the whole sensor area for a large angular/refractometric dynamic range, and (ii) to measure changes in this angle for each zone with a resolution of the order of 0.0001xc2x0.
Thus, by integrating into the structure (i) a detector for a highly resolved image of, for example, a multi-zone sensor surface, and (ii) a detector for the angle and/or wavelength, respectively of the incident light, and thereby reduce the sources of error for the measurement of angle and wavelength, respectively, and their relation to a specific sensor subzone representation on the photodetector matrix, the following advantages may be obtained in relation to the prior art apparatus constructions:
A higher resolution of absolute and relative reflectance minimum angle,
a higher resolution of absolute and relative reflectance minimum wavelength,
a higher image contrast and resolution of image contrast,
a higher frequency for reflectance image data detection,
a higher optomechanical robustness (less wear, lower maintenance cost),
a smaller total volume for the optomechanical apparatus, which permits an improved (cheaper, quicker) thermostatting, and thereby improved measuring system performance.
The apparatus according to the invention may use any of a number of optical principles for the scanning of the angle of incidence of the collimated beam, known to those skilled in art, including the principles described above in the description of the prior art, as long as the beam deflecting principle selected provides an angularly scanned collimated beam incident on a sensor surface at total internal reflection conditions, in either a Kretschmann or Otto prism configuration, or a grating coupling configuration, during the probing of a mainly stationary area.
Exemplary such scanning principles are reflective beam steering through mirrors or reflection diffraction gratings, and transmissive beam steering through refracting scanners, or through transmission diffraction gratings or transient gratings (acousto-optical scanning). These beam-steering principles may be combined into suitable scanner configurations known to a person skilled in the art.
Likewise, the optical system principle for the determination of reflection versus angle and/or wavelength of incidence may be selected from a number of optical principles known to a person skilled in art, including those described above in the description of the prior art. Exemplary such optical principles are surface plasmon resonance (SPR), Brewster angle (both internal and external), ellipsometry angle (both internal and external), critical angle, and frustrated total reflection waveguide resonance.
In the case of also an evanescent wave absorbing sample interaction with the sensing zone, the change in the complex refractive index corresponds not only to a shift in the SPR-angle or SPR-wavelength (related to the changed real part of the complex refractive index) but also to a shift in depth of the intensity at the resonance.
For sensor applications involving absorbance, the apparatus according to the invention may operate for reflectance-absorption imaging.
In the case of the incident light being coherent, a spatially heterogeneous sensing surface in terms of optical thickness or refractive index modulates the relative phase of the evanescent wave, creating a stationary interference pattern in the image or real image obtained. The incident light may after the total internal reflection interfere with light partially reflected at another interface of the sensor unit, e.g., on the opposite side to the sensor surface substrate interface on the substrate. When, for example, a sample molecule is specifically bound to certain areas within this sensing surface, the interference fringes move into new positions. By tracking the position of specific fringes by use of image process software, in relation to the scanned angle or wavelength of incidence, the local surface concentration changes may be interferometrically monitored by the apparatus according to the invention. The interferometric feature of phase-sensitive evanescent wave detection may increase the refractometric sensitivity in, for example, interferometric surface plasmon resonance image analysis. or interferometric Brewster angle and critical angle image analysis.
Generally, the present invention creates an optically densitometrically (refractometrically) quantitated image of a sensing surface pattern in approximative real-time by momentarily detecting the polarized light reflectance of the sensing surface. While the reflectance in the sensing surface preferably is internal, i.e., the light enters from a dielectric medium of a higher refractive index towards a dielectric medium of a lower refractive index, the reflectance may also be external, i.e., the probing light passes through a layer, such as a sample layer, to be probed on the sensor surface, e.g., external Brewster angle reflectometry and external ellipsometry.
Hereinafter, the present invention will be described in more detail, by way of example only, with regard to some embodiments of the invention. Reference is made to the accompanying drawings, wherein identical parts throughout the Figures are indicated by the same reference designations.


An internal combustion engine with multiple cylinders and injection valves that are provided for the cylinders and that meter fuel also comprises an exhaust gas tract in which an exhaust gas catalytic converter is arranged. A characteristic value (OSC) of an oxygen storage capacity of the exhaust gas catalytic converter is determined. In accordance with the characteristic value (OSC), a heating measure (HM) for heating the exhaust gas catalytic converter is carried out.

Increasingly stringent statutory regulations governing permissible polluting emissions in motor vehicles in which internal combustion engines are disposed make it necessary to limit the polluting emissions to an absolute minimum during the operation of an internal combustion engine. This can be accomplished on the one hand by a reduction in the polluting emissions that are produced during the combustion of the air/fuel mixture in the respective cylinder of the internal combustion engine. On the other hand exhaust gas aftertreatment systems are employed in internal combustion engines in order to convert the polluting emissions produced during the combustion process of the air/fuel mixture in the respective cylinder into harmless substances. In spark ignition engines in particular, three-way catalytic converters are used as exhaust gas catalyzers for this purpose, for example. A precisely adjusted air/fuel ratio in the cylinders is a prerequisite in order to achieve a high degree of efficiency in the conversion of polluting emissions such as e.g. carbon monoxide, hydrocarbons and nitrogen oxides. Furthermore the mixture upstream of the exhaust gas catalytic converter must also exhibit a predefined variation, that is, for example, alternating operation of the internal combustion engine in excess air mode and air deficiency mode, in order to effect a replenishment and depletion of the oxygen store of the exhaust gas catalytic converter. When oxygen is stored, the nitrogen oxides in particular are reduced, whereas when the store is emptied the oxidation process is assisted and in addition stored oxygen molecules are prevented from deactivating subsections of the exhaust gas catalytic converter.
A particularly relevant proportion of the polluting emissions normally occurs after the internal combustion engine is started and before the exhaust gas catalytic converter has reached a state of operational readiness. Heating measures which can include, for example, an injection of secondary air are known for bringing about the operational readiness of the exhaust gas catalytic converter in the swiftest possible manner.

Method and device for operating an internal combustion engine


A molding apparatus is provided which comprises a lower mold portion and an upper mold portion movable into engagement with the lower portion. A movable spray head is disposed on a traversing rack mounted within a retractable coating box. The coating box upper surface contains a first opening corresponding in size and shape to the outer periphery of the mold cavity of the upper mold and a second opening which corresponds in size and shape to the opening of an overspray recovery transition piece disposed at a position adjacent the fully disengaged upper mold portion. Prior to a molding operation, the coating box engages the upper mold permitting both the transition piece opening and cavity opening in the top surface of the box to align with the transition piece and cavity, respectively. The spray heads and drive of the traversing rack are activated and the overspray recovery transition piece fluidly communicates with an evacuated recovery booth, thereby causing the cavity of the upper mold to be coated and the overspray to be withdrawn into the recovery booth.

The present invention relates generally to a molding apparatus which includes apparatus for coating the inner surface of a mold with a fluidized coating and recovering overspray prior to a molding operation.
Molded parts are readily manufactured from sheet molding compound ("SMC") which is molded into the desired shape within a pressurized mold. Such parts often exhibit poor surface quality (e.g., porosity, waviness, pits, etc.) and typically require special treatments with paint or liquid, in-mold coatings in the event colored surfaces are desired. Accordingly, significant expense may be incurred in improving the surface quality and painting or otherwise coating the surface of the parts.
One approach to eliminating costly post-molding treatments of a molded part is disclosed in U.S. Pat. No. Re 28,068 to Lemelson. This patent discloses an apparatus for selectively depositing a particulate coating against the surface of a mold. When the mold is subsequently filled with a molding material, the coating and the molding material fuse so as to form an integral structure.
U.S. Pat No. 4,205,028 discloses an apparatus for coating the interior surface of a mold with a coating which forms a surface coating on a product molded from sheet molding compound. The coating is an electrostatically charged powdered thermosetting resin which is sprayed onto the heated interior surface of the mold before the mold is filled. The mold is grounded so that the electrical charge on the powdered resin causes the powder to stick to the surface of the mold. The heat of the mold melts the powder and causes it to flow and cure. Sheet molding compound is added to the mold and the mold is heated to cure the SMC resin. The coating and the SMC resin cure so as to form an integral product having a smooth outer surface.
A significant problem associated with the coating of a mold inner surface is that of overspray. The practice of applying an electrostatic charge to the powder as it emerges from a spray gun and grounding the mold surface increases the amount of sprayed powder which adheres to the mold surface. However, even when an electrostatic charge is applied to the powder, very substantial amounts of powder fail to adhere to the mold and are lost as overspray. This overspray must then be collected and reused in order to reduce the cost of the coating process. Whether the powder is reused or not, it must be contained and collected in order to prevent contamination of the surrounding atmosphere. The cost of containing the powder in a spraying room and the cost of collecting the oversprayed powder can be very significant.
U.S. Pat. No. 4,472,451 to Mulder discloses an apparatus for powder coating the interior surface of a heated mold cavity whereby electrostatically charged powder is sprayed onto the surface of the mold which is surrounded by a mask. The mask includes a shield positioned adjacent the shear edge of the mold and vacuum conduits are disposed beneath the shield which engage with vacuum ducts to draw off overspray. The combination of the shield and vacuum conduits are intended to prevent the build-up of the powder on hot surfaces of the mold external of the mold cavity. The overspray recovery apparatus consists of a set of pipes which provide limited evacuation capability and which are susceptible to blockage and associated problems.


An esterase isolated from Aspergillus oryzae is capable of stereoselective hydrolysis of chiral esters and also has arylesterase activity (EC 3.1.1.2) and feruloyl esterase activity (EC 3.1.1.73). The esterase has only a limited homology to known amino acid sequences.

It is known to prepare chiral esters of high optical purities by asymmetric hydrolysis with enzymes. Thus, U.S. Pat. No. 4,587,462 discloses asymmetric hydrolysis of lower alkyl esters of naproxen with a microbial enzyme, particularly a specific splitting esterase from Aspergillus oryzae DSM 2808 (ATCC 11492). U.S. Pat. No. 5,155,028 discloses enzymatic stereoselective ester cleavage using lipases, esterases or proteases, e.g. lipases or esterases from Aspergillus or proteases from Aspergillus oryzae. JP 7-206756 A discloses use of an enzyme to prepare optically active compounds. The enzyme may be a protease or esterase produced by Aspergillus, e.g. from A. oryzae.
Enzymes with ferulic acid esterase activity are known, e.g., from Aspergillus oryzae. M. Tenkanen, Biotechnology and Applied Biochemistry, 27 (1), 19–24 (1998)); M. Tenkanen et al., J. Biotechnol., 18 (1–2), 69–84 (1991).
U.S. Pat. No. 5,516,679 discloses a penicillin V amidohydrolase from Fusarium oxysporum.


An improved machine for insolating photopolymer plates and comprising a device secured sidewise onto the frame and delivering a flow of cooling air tangentially to the top part of the frame of the machine to avoid the formation of defects on the photosensitive polymer plate disposed upon the top part of the frame, in view of the energy radiated by the ultraviolet source insolating the plate, the machine permitting the insolation of photopolymer plates for flexographic printing.

The present invention relates essentially to an improved machine for insolating photopolymer plates for flexographic printing.
There has already been proposed machines suitable for carrying out the insolation of photopolymer plates with the assistance of a source of ultraviolet light.
In a general manner these machines comprise a frame above which is arranged at least one bank or row of ultraviolet lamps.
Upon the upper part of the frame underneath the bank of ultraviolet lamps one places a photopolymer plate which is insolated by the lamps through a negative film placed on the plate. The film-plate assembly is held under vacuum on the upper portion of the frame of the machine with the assistance of a transparent membrane.
It has now been found that the energy of the ultraviolet lamps heats the space defined by the transparent membrane and the upper portion of the frame of the machine, i.e. the space containing the negative film and the flexographic plate.
It results therefrom that in spite of the vacuum provided in that space, the latter forms a gas pocket which results in the separation or disconnection of the flexographic plate from the negative film.
One therefore is subjected to bad insolation conditions so that one eventually obtains a printing plate which is fuzzy.
More specifically after the insolation of the plate under the bad conditions stated hereinabove and after washing of this insolated plate with a solvent, it appears that there is a bad definition or resolution of the relief of the plate produced by the ultraviolet light which either travels through the transparent zones of the negative film or is stopped by the opaque zones of this film, so that the printing provided by this plate after inking thereof will be fuzzy.
Therefore the object of the present invention is to remedy these inconveniences by providing an improved machine owing to which the flexographic plate to be insolated will not undergo any disturbance or trouble due to the heat of the ultraviolet light lamps.

Machine for insulating and cooling photopolymer plates for flexographic printing


Ground bounce noise in a digital system is evaluated using a weighted average simultaneous switching output (“WASSO”) on an I/O bank of a digital switching device, such as a field programmable gate array (“FPGA”). The WASSO allows a designer to normalize output drivers having different characteristics on a single I/O bank. In a further embodiment, a simultaneous switching output allowance (“SSO allowance”) is calculated using scaling factors derived from values assumed in the creation of published SSO information and predicted actual values of the device in a digital system that are not represented in tables of published SSO guidelines. The SSO allowance is used in conjunction with WASSO values of adjacent I/O banks to evaluate ground bounce for adjacent I/O banks.

Ground bounce can occur with high-speed digital integrated circuits ("ICs") when multiple outputs change states simultaneously. Ground bounce can cause several undesired effects, both on the output of the switching device and on the receiving logic device. In order to avoid problems associated with ground bounce, manufacturers of ICs publish tables of guidelines for the maximum number of simultaneous switching outputs ("SSOs") that each power/ground pair (driver) of an IC can provide without violating a specified ground bounce limit.
Ground bounce is primarily due to current changes in the combined inductance from ground pins, bond wires, and ground metallization. The internal ground level of the IC deviates from the external system ground level for a short duration (typically a few nanoseconds) after multiple outputs change state simultaneously.
The switching output is supposed to provide a logical "1" or logical "0". Ground bounce can affect whether the switching output is properly read by receiving logic because the logical state is typically derived by comparing an incoming signal to the internal ground of the switching device. Noise on the signal and/or ground can alter the logical state read by the receiving logic and cause erroneous operation of the system if the ground bounce amplitude exceeds the instantaneous noise margin. For example, ground bounce noise on a non-changing input that raises the internal ground level above the instantaneous noise margin might unintentionally toggle the logical state of a receiving logic input. In other words, the ground bounce can be interpreted as a switched signal on an input that isn't being switched.
The ground bounce limit is set according to the most sensitive input driven by the switching device. Given a ground bounce limit, the number of SSOs ("drivers") allowed on a power/ground pair is set according to several assumptions. Manufacturers print tables of SSO guidelines for various types of logic, drivers, and packages. The SSO guidelines assume various values for parameters that affect ground bounce voltage.
Table 1, which is merely exemplary, is a table of the maximum number of SSOs per power/ground pair published by XILINX, INC. of San Jose, Calif. for using a VIRTEX™ FPGA in a digital switching system. The first column refers to the logic standard, such as whether the receiving logic is low-voltage complimentary metal-oxide-semiconductor, second generation ("LVCMOS2") or low-voltage transistor—transistor logic ("LVTTL"), which can have a fast slew rate or a slow slew rate. The recommended maximum number of SSOs depends on many factors, such as how much current is drawn by the loads, the total input capacitance of the loads being driven, and the type of package the FPGA will be housed in, such as a ball grid array ("BGA") package, a high-heat dissipation quad flat package ("HQ"), or a plastic quad flat package ("PQ"). For example, in the first row of Table 1 the number "10" relates to the "Package Type" "BGA" and indicates that no more than 10 LVCMOS2-type SSOs are recommended for the FPGA when it is in a BGA package. Similarly, the number "7" relates to the "Package Type" "HQ" and indicates that no more than 7 LVCMOS2-type SSOs are recommended for the FPGA when it is in a HQ package. And the number "5" relates to the "Package Type" "PQ" and indicates that no more than 7 LVCMOS2-type SSOs are recommended for the FPGA when it is in a PQ package.
TABLE 1Maximum Number of Recommended Simultaneous SwitchingOutputsReceiving Logic StandardPackage TypeBGAHQPQLVCMOS21075LVTTL, Fast Slew Rate, 8 mA drive13107LVTTL, Fast Slew Rate, 12 mA drive1075LVTTL, Fast Slew Rate, 24 mA drive543LVTTL, Slow Slew Rate, 8 mA drive221712LVTTL, Slow Slew Rate, 12 mA drive17129LVTTL, Slow Slew Rate, 24 mA drive975
Table 1 is a small subset of the type of SSO guideline tables typically published by a device manufacturer for use as an engineering design tool. Such tables often include many more types of receiving logic standards, package types, and loads. The drivers in the FPGA are configurable, and are selectively programmed to provide the proper drive characteristics for the intended receiving logic. Typical SSO guideline tables frequently include several hundred entries.
A design engineer using Table 1 would see that a power/ground pair of the FPGA could accommodate 13 8 mA LVTTL fast-slew loads when the FPGA is in a BGA package, or 22 8 mA LVTTL slow-slew loads. Fewer SSOs are recommended as the slew rate increases, and fewer SSOs are recommended as the driver current increases; however, these are merely general trends.
The SSO design tables are generated using circuit-simulation software. A circuit model of the switching device, receiving logic, package, and PWB is created. A simulator is used to iteratively determine how many SSOs may be driven before a specified noise voltage limit is exceeded. The parameters are varied one-by-one to obtain the table entries. The process of generating a complete SSO guideline table is long and tedious. To complicate matters, several values that affect the SSO guidelines are assumed during the simulation, such as the inductance of vias in a PWB, or of a trace in a package. Packing and PWBs continue to change, which changes the actual inductance from that which was assumed when generating the SSO guideline table. Similarly, the maximum allowable ground bounce voltage is not the same for all receiving logic, and new types of receiving logic may have a lower ground bounce voltage specification.
For example, LVTTL-type drivers can have as much as 800 mV of ground bounce noise before tripping an input-low threshold. Digital switching devices having an assumed ground bounce specification of ±600 mV when used with a PWB having an inductance to ground of 1 nH should work with the LVTTL driver if the SSO guidelines (which assumed a 1 nH board-level inductance) are followed. However, advances in PWB manufacturing have increased actual board-level inductance to 2–3 nH, and actual ground bounce voltage for the digital switching device might exceed the 800 mV threshold of the LVTTL-type driver when used on a newer PWB. Similarly, as the supply voltage level of logic devices decreases, components generally tolerate less ground bounce noise. Some new receiving logic devices tolerate as little as 400 mV undershoot at the input, and might not operate correctly if a SSO guideline table assuming a maximum of ±600 mV was used to design the interface between the switching device (e.g. FPGA) and the receiving logic.
It is desirable to provide guidance for managing ground bounce at the package level for a digital switching device without having to re-establish and re-publish SSO guideline tables. It is further desirable to provide flexibility in determining the maximum number of SSOs to account for different types of output drivers on a single I/O bank of a digital switching device. It is also desirable to be able to analyze ground bounce voltage for an entire digital switching device.

Method for calculating weighted average ground bounce noise generated by simultaneous switching outputs in a digital system


A torque screwdriver structure that has a positioning bar, a fixing ring, fixing balls, a sliding tube, a spring and a torque adjusting tuber providing strong mechanism between clutch and torque-adjusting button and being easy in use and simple in assembly when manufacturing.

In prior art, its holder has a torque-setting mechanism inside, which is triggered through an torque-adjusting button that can move the operational bar vertically to depress or stretch the spring set between supporting ring and torque-adjusting nut. However, the mechanism between the clutch and the torque-adjusting button is weak, so the operational bar, clutch, spring, and the torque-adjusting nut would move synchronously when the torque-adjusting button is turned, making it unable to use.


A method of producing copper compounds involves contacting metallic copper with oxygen or an oxygen-containing gas, with an aqueous solution consisting essentially of water in solution in which is a soluble ammonium salt NH.sub.4 X, where X is the anion of the salt, and with ammonia in an amount such that the solution is initially alkaline. As a result of such contact the metallic copper is initially dissolved to form a copper ammine Cu(NH.sub.3).sub.4 X and the formation of the ammine continues until the saturation concentration of the ammine is reached. Subsequently, the ammine continuously breaks down to form 3Cu(OH).sub.2.CuX.sub.2 and the water soluble products of the ammine decomposition continuously reform the amine by further reaction with the metallic copper and the oxygen on oxygen-containing gas.

Copper sulphate (CuSO.sub.4.5H.sub.2 O) is a compound used extensively in such areas as agriculture (as a soil additive in pesticides and as a feed additive), medicine, electric batteries, steel manufacture and the petroleum industry.
The difficulty in providing a starting point for manufacture of copper chemicals has always been the relative inactivity of the metal. The metal can be oxidised by heating in air, but this is expensive and slow, and the resultant oxide is not satisfactory as a source of cupric salts.
Traditionally, copper sulphate has been manufactured by reacting copper metal, usually copper scraps, with dilute (25%) sulphuric acid, in the presence of excess air, utilising the reaction: EQU Cu+H.sub.2 SO.sub.4 +1/2O.sub.2 .fwdarw.CuSO.sub.4 +H.sub.2 O (1)
The reaction is endothermic and will not proceed at a satisfactory rate unless the temperature of the solution is maintained at a minimum of 70.degree. C., and usually at more than 80.degree., for example to a temperature in the range 80.degree. C. to 90.degree. C.
An external heat source is required for this reaction, and steam is commonly used for this purpose.
The reaction is usually carried out by pumping the acid through towers packed with scrap copper, through which air is blown, or in submerged reactors, where the acid is agitated in a tank packed with scrap, and air is introduced by submerged aerators.
Air addition rates are usually required to be 7 to 10 times the stoichiometric amount, based on its oxygen content, giving an oxygen level of 7 times the stoichiometric amount.
The reaction is usually conducted batchwise, and is complete when the residual acid level falls to an acceptable level.
With such a process, production rates of 0.1 t/hour/m.sup.3 of reactor volume are rarely exceeded.
The resultant copper sulphate solution is cooled and the copper sulphate crystallises out and subsequently removed, usually by centrifuge. The crystals are dried and packed and the mother liquid is usually returned after acid enrichment, to the next batch.
This traditional method has several problems:
(a) Capital and maintenance costs must take into account the highly corrosive nature of aerated 25% hot sulphuric acid.
(b) The endothermic nature of the reaction, combined with the heat removal resulting from the high air flows required, result in the need for external heating either by steam or some other means.
(c) The process is non-selective in that metals other than copper in scrap, that will dissolve in hot sulphuric acid, can contaminate the product.
(d) The reaction rate is not fast, and production rates of 0.05 t/hour/m.sup.3 of reactor volume are common.
(e) The air effluent can contain sulphur dioxide, acid droplets and copper sulphate mist, and must be treated in some way.
(f) The necessity to recycle mother liquor leads to build-up of contaminants which must be removed by some method.
As a result of at least some of the above problems, energy costs may amount to in excess of $50/t of product.
It has also been long known that solutions of ammonia salts, or various combinations of them, will also attack copper metal, gain in the presence of oxygen. Copper ammines are produced, according to the equations: EQU Cu+1/2O.sub.2 +4NH.sub.3 +H.sub.2 O.fwdarw.Cu(NH.sub.3).sub.4 (OH).sub.2 (2)
and EQU Cu+1/2O.sub.2 +2NH.sub.3 +2NH.sub.4 X.fwdarw.Cu(NH.sub.3).sub.4 X.sub.2 +H.sub.2 O (3)
or EQU Cu+1/2O.sub.2 +2NH.sub.3 +(NH.sub.4).sub.2 Y.fwdarw.Cu(NH.sub.3).sub.4 Y H.sub.2 O (4)
in the case of dibasic acid salts.
U.S. Pat. No. 3,760,070 discloses a process in which a reaction according to equation 3 is carried out. The copper ammine solution is then heated to produce copper oxide, and the ammonia and ammonium salt are recycled.
One major disadvantage of the process of U.S. Pat. No. 3,760,070 is the energy costs associated with the heating step.
An alternative ammonia/ammonium salt process uses organic strippers.
In this process copper scrap is reacted with a solution containing ammonia and ammonium carbonate, with aeration, under agitation. This solution rapidly dissolves copper up to a concentration of 30 g/l. The pregnant solution is then removed from the reactor and mixed with a proprietary organic liquid (for example one known as LIX54) which although immiscible with the aqueous ammine solution, has the power of stripping the pregnant solution of the contained copper, while leaving the NH.sub.3 and Cu.sub.3.sup.= in the aqueous phase. The stripped aqueous phase is then recycled to the reactor, while the separated organic layer, containing the copper ions, is reacted with dilute sulphuric acid, which forms copper sulphate. This migrates to the aqueous phase, leaving the organic layer stripped of copper.
The organic layer is then separated for re-use, while the aqueous phase is evaporated, cooled, and the copper sulphate recovered in the usual way.
This method has the following advantages:
(a) Maintenance costs are lower because the reacting medium is alkaline.
(b) The reaction is exothermic, and is therefore self-sustaining, energy wise.
(c) The process is selective, as only those metals soluble in ammonia are attached.
(d) The reaction rate is quite fast and rates of 0.1-0.2 t/hr/m.sup.3 of reactor volume are common. but also has the following disadvantages:
(a) Capital costs for machinery are reasonable, but the cost of the organic stripper can be as high as $20,000 m.sup.3 of reactor volume.
(b) Losses of organic stripper can usually be reckoned to be in the order of $10 to 50 per tonne of copper sulphate product.
(c) The organic stripper is prone to what is known as "crudding up" due to impurities, leading to even higher losses.
(d) Ammonia recovery systems are required to recover expensive ammonia from the effluent gas and solid residues.
Generally all except very large producers have remained with the "lesser of the two evils" and have used the acid route.
Various organic strippers have also been developed for stripping copper ions out of acid copper sulphate solution, but these also suffer from the problem of reagent loss and "crudding" referred to above.
It is an object of this invention to provide an improved process for producing copper compounds.
The invention provides, a method of producing copper compounds, including the step of contacting metallic copper with oxygen or an oxygen-containing gas, and an aqueous solution consisting essentially of water in solution in which, to a concentration up to the limit of solubility thereof, is a soluble ammonium salt NH.sub.4 X, where X is the anion of said salt, together with ammonia in an amount such that initially said solution is alkaline, whereby as a result of said contact said metallic copper is initially dissolved to form a copper ammine Cu(NH.sub.3).sub.4 X said ammine formation proceeding until the saturation concentration of said ammine is reached, whereafter said ammine continuously breaks down to form the water insoluble tribasic salt 3Cu(OH).sub.2.CuX.sub.2, and the water-soluble products of the decomposition of said ammine continuously reform the said ammine by further reaction with said metallic copper and said oxygen or oxygen-containing gas until said solution becomes exhausted of the said anion.
The invention also provides apparatus for carrying out a method of producing copper compounds, including
a cylindrical reaction tank fitted with a circular screen such that copper metal is confined to the area between the screen and the tank walls, and having a bladed agitator located inside the screen driven at a minimum tip speed of 500 meters/minute, and also providing for the introduction of an oxygen containing gas at or near the agitator blades;
said tank being provided with means of adding acid at a controlled rate; and
said tank being fitted with a solids removal system such that the said water insoluble tribasic copper salt is removed from the reacting solution at a controlled rate.
It has been discovered that if an aqueous solution of an ammonium salt of any of the common acids (for example sulphuric, hydrochloric or nitric) is prepared at any strength up to saturation level, and this solution is made alkaline with aqueous ammonia, preferably to a pH of 7.0 to 8.0, and this solution is then allowed to react with copper metal in the presence of oxygen, then an aqueous medium is produced, which is capable of rapid conversion of copper metal, in the presence of oxygen, into the insoluble tribasic salt, under certain minimum conditions of agitation and aeration, until all the acid ions contained in the original aqueous solution are exhausted.
Furthermore, if the acid ions removed from the original solution, by formation of the insoluble tribasic salt, are replaced by addition of the relevant acid to the aqueous medium at an equivalent rate, after the formation of the tribasic salt has begun to occur, and if the resultant solid tribasic salt is removed from the aqueous medium by, for example, filtration, then a continuous cyclic reaction occurs where copper ammine is continuously formed from the copper metal, and is continuously decomposed to the tribasic salt, at a rapid rate.
The nett effect is a continuous process for conversion of copper metal into solid 3Cu(OH).sub.2.CuSO.sub.4 (Brochantite) in the case of ammonium sulphate, 3Cu(OH).sub.2.CuCl.sub.2 (Atacamite or copper oxychloride) in the case of ammonium chloride, or 3Cu(OH).sub.2.Cu(NO.sub.3).sub.2 in the case of ammonium nitrate.
These tribasic salts can easily be converted into the relevant acid salt by addition of a stoichiometric quantity of the relevant acid, according to the equation EQU 3Cu(OH).sub.2 CuX.sub.2 +6HX.fwdarw.4CuX.sub.2 +6H.sub.2 O (5)
or EQU 3Cu(OH).sub.2 CuY+3H.sub.2 Y.fwdarw.4CuY+6H.sub.2 O (6)
in the case of a dibasic acid.
This process can be controlled, if necessary, to produce direct crystalline salts, by use of the acid in concentrated form.
Equally, the tribasic salt can easily be converted to copper hydroxide by addition of a stoichiometric quantity of an alkali such as sodium hydroxide, according to the equation EQU 3Cu(OH).sub.2 CuX.sub.2 +2NaOH.fwdarw.4Cu(OH).sub.2 +2NaX (7)
and EQU 3Cu(OH).sub.2 CuY.sub.2 +2NaOH.fwdarw.4Cu(OH).sub.2 +2NaY (8)
the insoluble hydroxide can be recovered by filtration and washing.
However, it should be noted that the tribasic salts themselves, particularly the sulphate and chloride, find direct application as fungicides. The invention thus also provides a direct method for the manufacture of such tribasic salts.
The reaction mechanism appears to involve initial formation of copper ammine, according to the equation EQU Cu+1/2O.sub.2 +4NH.sub.4.sup.+ .fwdarw.Cu(NH.sub.3).sub.4.sup.++ +H.sub.2 O+2H.sup.+ ( 9)
This reaction proceeds until the copper content of the solution approaches 28 g/l. At this point the ammine decomposes according to the equation EQU 4Cu(NH.sub.3).sub.4.sup.++ +8X.sup.- +6H.sub.2 O.fwdarw.3Cu(OH).sub.2.CuX.sub.2 +10NH.sub.3 +6NH.sub.4.sup.+ +6X.sup.-( 10)
in the case of a monobasic acid salt, or EQU 4Cu(NH.sub.3).sub.4.sup.++ +4Y.sup.- +6H.sub.2 O.fwdarw.3Cu(OH).sub.2.CuY+10NH.sub.3 +6NH.sub.4.sup.+ +6Y.sup.-( 11)
in the case of a dibasic acid salt.
This results in the formation of the tribasic salt, accompanied by the release of all of the contained ammonia and most of the contained acid anions, which are then available for the formation of further copper ammine.
Thus the reaction continues to produce tribasic copper salt, while maintaining the copper ammine level in the reaction liquor at the saturation concentration.
The reaction can plainly be seen to only continue whilst sufficient acid anions are available for formation of the tribasic salt, because only 75% of the anion is released.


A method to provide a highly intelligent, automated diagnostic system that identifies the need to replace specific parts to minimize machine downtime rather than require extensive service troubleshooting. In particular, a systematic, logical test analysis scheme to assess machine operation from a simple sensor system and to be able to pinpoint parts and components needing replacement is provided by a series of first level of tests by the control to monitor components for receiving a first level of data and by a series of second level of tests by the control to monitor components for receiving a second level of data. Each of the first level tests and first level data is capable of identifying a first level of part failure independent of any other test. Each of the second level tests and second level data is a combination of first level tests and first level data or a combination of a first level test and first level data and a third level test and third level data. The second level tests and second level data are capable of identifying second and third levels of part failure. Codes are stored and displayed to manifest specific part failures.

The invention relates to analysis of xerographic processes, and more particularly, to the precise determination of failed parts within the xerographic process.
As reproduction machines such as copiers and printers become more complex and versatile, the interface between the machine and the service representative must necessarily be expanded if full and efficient trouble shooting of the machine is to be realized. A suitable interface must not only provide the controls, displays, fault codes, and fault histories necessary to monitor and maintain the machine, but must do so in an efficient, relatively simple, and straightforward way. In addition, the machine must be capable of in depth self analysis and either automatic correction or specific identification of part failure to minimize service time.
Diagnostic methods often require that a service representative perform an analysis of the problem. For example, problems with paper movement in a machine can occur in different locations and occur because of various machine conditions or failure of various components. In the prior art, this analysis by the service representative has been assisted by recording fault histories in the machine control to be available for readout and analysis. For example, U.S. Pat. No. 5,023,817, assigned to the same assignee as the present invention, discloses a method for recording and displaying in a finite buffer, called a last 50 fault list, machine faults as well as fault trends or near fault conditions. This data is helpful in diagnosing a machine. It is also known in the prior art, to provide a much larger data log, known as an occurrence log, to record a variety of machine events.
In addition U.S. Pat. No. 5,023,817, assigned to the same assignee as the present invention, discloses a technique to diagnose a declared machine fault or a suspected machine fault by access to a library of fault analysis information and the option to enter fault codes to display potential machine defects related to the fault codes. It is also known, as disclosed in U.S. Pat. No. 5,533,193 to save data related to given machine events by selectively setting the control to respond to the occurrence of a given machine fault or event, monitoring the operation of the machine for the occurrence of the given machine event, and initiating the transfer of the data in a buffer to a non-volatile memory.
It is also known to be able to monitor the operation of a machine from a remote source by use of a powerful host computer having advanced, high level diagnostic capabilities. These systems have the capability to interact remotely with the machines being monitored to receive automatically initiated or user initiated requests for diagnosis and to interact with the requesting machine to receive stored data to enable higher level diagnostic analysis. Such systems are shown in U.S. Pat. Nos. 5,038,319, and 5,057,866 owned by the assignee of the present invention. These systems employ Remote Interactive Communications to enable transfer of selected machine operating data (referred to as machine physical data) to the remote site at which the host computer is located, through a suitable communication channel. The machine physical data may be transmitted from a monitored document system to the remote site automatically at predetermined times and/or response to a specific request from the host computer.
The host computer may include a compiler to allow communication with a plurality of different types of machines and an expert diagnostic system that performs higher level analysis of the machine physical data than is available from the diagnostic system in the machine. After analysis, the expert system can provide an instruction message which can be utilized by the machine operator at the site of the document system to overcome a fault. Alternatively, if the expert system determines that more serious repair is necessary or a preventive repair is desirable, a message can be sent to a local field office giving a indication of the type of service action required.
Also, U.S. Pat. No. 5,636,008, assigned to the same assignee as the present invention, discloses a technique for remote access and diagnostic manipulation of a machine for improved preparation before making a service call.
It is expected that future office products could be serviced by a variety of individuals that could include the customer, representative of product manufactures, or third party service organizations. The service may include parts repair or replacements, adjustments or software updates and should be made as conveniently and readily available as possible. In order to meet this new level of convenient service in an ever complex set of products, it is necessary to provide rapid, easily interpretable information on the status of the machines, to those that are likely to service the product.
The use of expert systems discussed above, are also well known in the art. For example, it is known to provide a computer controlled diagnostic apparatus for industrial or other types of operating systems. A rule base pertinent to the particular operating system being diagnosed is stored in memory. The rule base is established by experts in the field to which the diagnosis pertains. Sensors monitor operating parameters of the system and provide output signals which are fed to the diagnostic apparatus. Indications of the overall "health" of the operating system in general and of its components in particular are provided to the user via a display. In addition, U.S. Pat. No. 5,138,377 discloses an internal expert system to aid in servicing which monitors predetermined status conditions of the machine for automatic correction or for communication to the user.
A difficulty with prior art diagnostic services is the inability to easily and automatically pinpoint the precise parts or subsystems in a machine causing a malfunction or deteriorating condition. It would be much more economical to be able to simply replace a part than to exert significant time and effort trying to correct or repair the part. This is the trend in today's high tech system environment. It would be desirable, therefore, to provide a highly intelligent, automated diagnostic system that provides an indication of the need to replace specific parts or subsystems rather than the need for extensive service troubleshooting to minimize machine downtime.
In copying or printing systems, such as a xerographic copier, laser printer, or ink-jet printer, a common technique for monitoring the quality of prints is to artificially create a "test patch" of a predetermined desired density. The actual density of the printing material (toner or ink) in the test patch can then be optically measured to determine the effectiveness of the printing process in placing this printing material on the print sheet.
In the case of xerographic devices, such as a laser printer, the surface that is typically of most interest in determining the density of printing material thereon is the charge-retentive surface or photoreceptor, on which the electrostatic latent image is formed and subsequently, developed by causing toner particles to adhere to areas thereof that are charged in a particular way. In such a case, the optical device for determining the density of toner on the test patch, which is often referred to as a toner area coverage sensor or "densitometer", is disposed along the path of the photoreceptor, directly downstream of the development of the development unit. There is typically a routine within the operating system of the printer to periodically create test patches of a desired density at predetermined locations on the photoreceptor by deliberately causing the exposure system thereof to charge or discharge as necessary the surface at the location to a predetermined extent.
The test patch is then moved past the developer unit and the toner particles within the developer unit are caused to adhere to the test patch electrostatically. The denser the toner on the test patch, the darker the test patch will appear in optical testing. The developed test patch is moved past a densitometer disposed along the path of the photoreceptor, and the light absorption of the test patch is tested; the more light that is absorbed by the test patch, the denser the toner on the test patch. Xerographic test patches are traditionally printed in the interdocument zones on the photoreceptor. Generally each patch is about an inch square that is printed as a uniform solid half tone or background area. Thus, the traditional method of process controls involves scheduling solid area, uniform halftones or background in a test patch. Some of the high quality printers contain many test patches.
It would be desirable, therefore, to be able to use a simple toner area coverage sensor rather than a complex sensor system to provide machine data to be able to diagnose a machine and identify specific part or subsystem failures or malfunctions. It would also be desirable to provide a systematic, logical test analysis scheme to assess machine operation from a simple sensor system and to be able to pinpoint parts, components, and subsystems needing replacement.
It is an object of the present invention, therefore, to determine an unacceptable degree of machine contamination by determining the existence of any defective areas of the photoreceptor surface by monitoring the reflectance of a bare photoreceptor surface in a series of segment readings, calculating an overall clean belt uniformity measurement, determining the variance of each of the segment readings from the belt uniformity measurement, and finding a uniformity factor for each segment reading. Still another object of the present invention is to provide a highly intelligent, automated diagnostic system that identifies the need to replace specific parts rather than the need for extensive service troubleshooting to minimize machine downtime.. It is still another object of the present invention to provide a systematic, logical test analysis scheme to assess machine operation from a simple sensor system and to be able to pinpoint parts and components needing replacement.
Other advantages of the present invention will become apparent as the following description proceeds, and the features characterizing the invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

P/R process control patch uniformity analyzer


A filter having a thin-film resonator fabricated on a semiconductor substrate and a method of making the same are disclosed. The filter has a bonding pad connected to the resonator and in contact with the substrate to form a Schottky diode with the substrate to protect the resonator from electrostatic discharges.

The present invention relates to acoustic resonators, and more particularly, to resonators that may be used as filters for electronic circuits.
The need to reduce the cost and size of electronic equipment has led to a continuing need for ever-smaller electronic filter elements. Consumer electronics such as cellular telephones and miniature radios place severe limitations on both the size and cost of the components contained therein. Further, many such devices utilize electronic filters that must be tuned to precise frequencies. Filters select those frequency components of electrical signals that lie within a desired frequency range to pass while eliminating or attenuating those frequency components that lie outside the desired frequency range.
One class of electronic filters that has the potential for meeting these needs is constructed from thin film bulk acoustic resonators (FBARs). These devices use bulk longitudinal acoustic waves in thin film piezoelectric (PZ) material. In one simple configuration, a layer of PZ material is sandwiched between two metal electrodes. The sandwich structure is preferably suspended in air. A sample configuration of an apparatus 10 having a resonator 12 (for example, an FBAR) is illustrated in FIGS. 1A and 1B. FIG. 1A illustrates a top view of the apparatus 10 while FIG. 1B illustrates a side view of the apparatus 10 along line A—A of FIG. 1A. The resonator 12 is fabricated above a substrate 14. Deposited and etched on the substrate 14 are, in order, a bottom electrode layer 15, piezoelectric layer 17, and a top electrode layer 19. Portions (as indicated by brackets 12) of these layers—15, 17, and 19—that overlap and are fabricated over a cavity 22 constitute the resonator 12. These portions are referred to as a bottom electrode 16, piezoelectric portion 18, and a top electrode 20. In the resonator 12, the bottom electrode 16 and the top electrode 20 sandwiches the PZ portion 18. The electrodes 14 and 20 are conductors while the PZ portion 18 is typically crystal such as Aluminum Nitride (AlN).
When electric field is applied between the metal electrodes 16 and 20, the PZ portion 18 converts some of the electrical energy into mechanical energy in the form of mechanical waves. The mechanical waves propagate in the same direction as the electric field and reflect off of the electrode/air interface.
At a resonant frequency, the resonator 12 acts as an electronic resonator. The resonant frequency is the frequency for which the half wavelength of the mechanical waves propagating in the device is determined by many factors including the total thickness of the resonator 12 for a given phase velocity of the mechanical wave in the material. Since the velocity of the mechanical wave is four orders of magnitude smaller than the velocity of light, the resulting resonator can be quite compact. Resonators for applications in the GHz range may be constructed with physical dimensions on the order of less than 100 microns in lateral extent and a few microns in total thickness. In implementation, for example, the resonator 12 is fabricated using known semiconductor fabrication processes and is combined with electronic components and other resonators to form electronic filters for electrical signals.
The use and the fabrication technologies for various designs of FBARs for electronic filters are known in the art and a number of patents have been granted. For example, U.S. Pat. No. 6,262,637 granted to Paul D. Bradley et al. discloses a duplexer incorporating thin-film bulk acoustic resonators (FBARs). Various methods for fabricating FBARs also have been patented, for example, U.S. Pat. No. 6,060,181 granted to Richard C. Ruby et al. discloses various structures and methods of fabricating resonators, and U.S. Pat. No. 6,239,536 granted to Kenneth M. Lakin discloses method for fabricating enclosed thin-film resonators.
However, the continuing drive to increase the quality and reliability of the FBARs presents challenges requiring even better resonator quality, designs, and methods of fabrication. For example, one such challenge is to eliminate or alleviate susceptibility of the FBARs from damages from electrostatic discharges and voltage spikes from surrounding circuits. Another challenge is to eliminate or alleviate susceptibility of the resonator from frequency drifts due to interaction with its environment such as air or moisture.

Electrostatic discharge protection of thin-film resonators

Avago Technologies Wireless IP (Singapore) Pte. Ltd.


An electrically switchable optical modulator for modulating an optical wavefront transmitted therethrough, comprising a birefringent first optical element and a birefringent second optical element each having respective ordinary and extraordinary refractive indices. A birefringent liquid crystal material is sandwiched between the first and second optical elements. The extraordinary refractive index of the liquid crystal material is electrically switchable between: a first state in which it has a first value; and, a second state in which it has a second value different from the first value. One or both of the first value and the second value is un-matched to the extraordinary refractive index of the first optical element in respect of light polarised in a first direction of linear polarisation, and is un-matched to the extraordinary refractive index of the second optical element in respect of light polarised in a second direction of linear polarisation orthogonal to the first direction. This switchably renders a relative contrast in extraordinary refractive index as between the liquid crystal material and the first and second optical elements for modulating said wavefront.

There exists a need to provide polarisation independent switchable optical modulator devices, such as lenses, optical beam steerers and diffraction gratings or holograms. These would be highly desirable components for applications in smartphones, medical imaging, and photovoltaics. Desired properties are fast switching, polarisation independence, low power consumption and low cost scalable production potential. Polarisation independence enables an optical modulator to apply a desired optical modulation to unpolarised light which is insensitive to the inherent presence of two orthogonal polarisation components within all unpolarised light. That is to say, any unpolarised light may be decomposed in to two equal components of linearly polarised light, one component being polarised in a direction orthogonal to the other component or with the opposite handedness if circularly or elliptically polarised.
Existing approaches to try to provide polarisation independence in optical modulators include physically separating unpolarised light into its two polarised components, and then processing each component separately before returning the two processed components together again. Such methods often employ systems using two optical processing trains/devices arranged in parallel—one optical train/device for each respective one of the two orthogonal polarisation states of unpolarised light. This sort arrangement is often found in 3D displays and projectors whereby the two orthogonal polarisation components in a light beam are split using a polarisation beam-splitter (PBS) and directed on to separate optical processing devices arranged alongside each other, for parallel optical processing appropriate to the respective polarisation state, before being brought back together (e.g. on a screen).
Alternatively, two separate optical components, each operating on a respective one of the orthogonal polarisations, may be arranged in series. These may be mounted together and coupled using index matching fluid or adhesive. However, arrangements such as this suffer from issues with parallax, as between the two separate optical components, which is particularly important to avoid in lens systems. Such arrangements are not suitable for some applications, such as beam steerers etc. If other optical elements are needed in series, in order to mitigate these parallax issues, then this can quickly become an impractical arrangement.
These arrangements, whether parallel or series arrangements of optical elements, are expensive, complex and relatively bulky. They require duplication of components in order to duplicate optical processing upon each of the two orthogonal polarisation states of unpolarised light. The present invention provides an alternative.


A map file includes two-dimensional or three-dimensional geometric data items collectively representing layout of a building. The map file and parsed and the geometric data items analyzed to identify building elements including rooms, floors, and objects of the building, and to identify containment relationships between the elements. A space model having a space graph is constructed. The space graph includes nodes that correspond to the respective building elements and links forming relationships between nodes that correspond to the identified containment relationships. Each node may include node metadata, rules or code that operate on the metadata, and a node type that corresponds to a type of physical space. Some nodes may include user representations or device representations that represent physical sensors associated therewith. The representations may receive data from the respectively represented sensors, and the sensor data becomes available via the space model.

Recent advances in cloud technology and Internet of Things (IoT) hardware and software has made it inexpensive and convenient to put sensors in physical spaces and then collect information about the physical spaces. To provide information to a facility manager, sensors such as thermostats, lighting controls, motion sensors, etc. may be placed in a building's rooms and furniture. The facility manager may wish to see what rooms have what resources or see statistics about how the rooms or resources are being used. For large facilities with many sensors, this can be difficult. Furthermore, it can be difficult to meaningfully aggregate, synthesize, and analyze the information from the many sensors in a physical space such as a building. Consequently, a need has arisen for tools to model physical spaces and the devices and people within them. The information provided by a schematic or graph model of a space can allow new kinds of insights into the effectiveness of equipment, utilization of spaces, costs, efficiency, etc.
Cloud providers have developed complex space modeling tools for cloud tenants to use to schematically model physical spaces, people, devices, and their relationships. See, for instance, Azure Digital Twins™ available from Microsoft Corporation. A tenant may author a space model that models a physical space. The space model then facilitates integration of IoT devices with a cloud and synthesis of IoT sensor data. The space model may be executed and managed by the cloud and may have interfaces or facilities for communicating with IoT devices. The space model may model the locations of IoT devices within the corresponding physical space.
Space modeling techniques have been helpful for managing and organizing information about a physical space, synthesizing metadata about a physical space, providing the information about a physical space to other systems, etc. However, space models have been difficult to construct. Because a space model models logical relationships (e.g., containment) between elements and contents of a physical space or building, construction of the space model is challenging. Typically, a user will refer to a map of a physical space and attempt to visually discern the elements and relationships of the physical space. Depending on the type of map, this can be particularly difficult. If the map is a computer-assisted drawing (CAD) file, the map may have significant complexity and layers of information that are difficult to navigate and interpret. Just identifying the elements of a space, e.g., rooms and equipment, can be challenging. When an element such as a building floor has been identified, it may difficult to discern properties of that element. For example, it may not be easy to identify the name or type of an element (e.g., a room). In short, creating a space model has been a time-consuming and error-prone process.
Techniques related to constructing space models from map files and other information are discussed below.


An electrostatic microactuator comprising a substrate and at least one comb drive assembly having first and second comb drive members. Each of the first and second comb drive members is provided with comb drive fingers. The first comb drive member is mounted on the substrate. The at least one comb drive assembly is disposed between the first and second spaced-apart, beam-like spring members. The second comb drive member overlies the substrate. Each of the first and second beam-like members have a first end portion secured to the substrate and a second end portion secured to the second comb drive member for suspending the second comb drive member over the substrate. The second comb drive member is movable between a first position in which the comb drive fingers of the first and second comb drive members are spaced apart and a second position in which the comb drive fingers of the first and second comb drive members are interdigitated.

Microstructures fabricated using silicon integrated circuit processing techniques have been developed for a wide variety of sensing and actuation applications. Compared to conventional prior art implementations in these and other applications, micro-structures provide advantages in cost, reliability, and performance. Micro-machined pressure sensors is and accelerometers are now being manufactured in quantities of over 10 million per year for a variety of uses in the medical, automotive, industrial, and instrumentation fields.
However, existing microstructures are not practical for use in certain applications due to difficulties in achieving large forces and displacements from these small devices. Some developers have circumvented this problem by attaching external, conventional actuators such as solenoids, piezoelectric elements, or pneumatic sources to microstructures to provide the needed force or displacement. These external actuators are unattractive due to their large size, critical alignment, and large power requirements. Integrated actuators, that is, microstructures where the actuator is fabricated simultaneously with the mechanical structure, are advantageous from the standpoint of cost, reliability, and ease in assembly.
Various actuation methods have been used for integrated actuators for microstructures including electrostatic, electromagnetic, thermal and thermo-pneumatic. The thermal techniques tend to provide large force but with relatively slow response times. Electromagnetic techniques are complicated by the difficulty in providing coils with a sufficient number of turns in a planar structure and the high power dissipation caused by the high currents needed to produce the desired magnetic field. Electrostatic actuation becomes attractive on a small size scale because the forces increase as the gap between elements decrease. The power dissipated by electrostatic elements tends to be low and the operating speed is usually limited only by the mechanical response of the structure.
The driving forces in prior art electrostatic actuators have been typically created using only one of two types of driving electrodes: so-called comb drive fingers or parallel plates. Parallel plate capacitors generate a force that is proportional to the square of the drive voltage and inversely proportional to the square of the gap between the plates. This behavior limits the useful range of motion for such an actuator, as at large gaps the electrostatic force is unable to overcome the restoring spring force of the actuator supports, and at gaps less than about 2/3 of the initial gap, the actuator becomes unstable when the electrostatic force overwhelms the linear restoring force. For practical microstructure elements, the useful range of motion for parallel plate actuators is less than 10 microns. Comb drive actuators, such as described in U.S. Pat. No. 5,025,346, feature a series of interdigitated electrodes whose capacitance may be used to provide a motive force that is relatively constant over a range of motion roughly equal to the length of the comb fingers, which can be made greater than 100 microns. The force available from each finger is relatively small, so that practical comb drive actuators typically have between 10 and 200 fingers to produce adequate force for a microstructure device.
A serious difficulty with prior art comb drive devices is that the maximum motion of the device is limited by so-called electromechanical side instability. In the ideal case, the side forces on each finger are exactly balanced, however if the finger is not constrained to move down the precise center of the gap, a side force will be generated by the electrodes. While the forward motive force is nearly constant with incremental deflection, the side force increases rapidly with side deflection. The instability occurs when the derivative of the side force with respect to side displacement is larger than the lateral mechanical spring constant. If this derivative exceeds the side spring constant of the motor support structure, the comb drive will snap to the side, shorting out the drive electrodes and disrupting the forward motion of the actuator. This behavior for prior art devices is described in a paper entitled "Comb-drive actuators for large displacements" by Legtenberg, Groeneveld, and Elwenspoek, in J. Micromech. Microeng. 6 (1996) pages 320-329. Their designs have a maximum displacement of about 40 microns. The design techniques in the Legtenberg paper describe the maximum displacement for conventional comb drive actuators, but do not describe designs with substantially larger deflections.
The early comb drive actuators used thin polysilicon layers provided by the so-called surface micro-machining process to fabricate the comb fingers and the moveable, laterally-driven element. This polysilicon was typically 1-2 microns thick. Since the lateral feature size of these devices was comparable to the material thickness, the stiffness of the parts to out-of-plane deflections was very low. The advent of Deep Reactive Ion Etching (DRIE) has allowed similar structures to be fabricated in single crystal silicon with typical thicknesses of 100 microns. DRIE is described in a paper entitled, "Silicon Fusion Bonding And Deep Reactive Ion Etching; A New Technology For Microstructures" by Klassen, Petersen, Noworolski, Logan, Maluf, Brown, Storment, McCully, and Kovacs, in the Proceedings Of Transducers '95 (1995), pages 556-559. These thicker structures can provide larger vertical electrode areas and substantially higher stiffnesses out of the plane of deflection. Recently, other fabrication techniques, including thicker surface micro-machined polysilicon or plated metal structures made in photolithographically defined molds have been used to increase the thickness and thus the out-of-plane stiffness of comb drive structures. None of these fabrication techniques by themselves have been used to improve the limited deflection of prior art comb drive structures.
What is needed, therefore, is an improvement in the range of deflection and characteristics of prior art comb drive actuators.
Another object of the invention is to provide an electrostatic microactuator of the above character in which side instability forces in the comb drive assembly are minimized.
Another object of the invention is to provide an electrostatic microactuator of the above character in which means for attaching or coupling the actuator to external devices is provided.
Another object of the invention is to provide an electrostatic microactuator of the above character in which the resonant characteristics of the comb drive assembly are utilized to achieve large deflections.

Electrostatic microactuator and method for use thereof