Rapid calibration of a TOF system uses a stationary target object and electrically introduces phase shift into the TOF system to emulate target object relocation. Relatively few parameters suffice to model a parameterized mathematical representation of the transfer function between measured phase and Z distance. The phase-vs-distance model is directly evaluated during actual run-time operation of the TOF system. Preferably modeling includes two components: electrical modeling of phase-vs-distance characteristics that depend upon electrical rather than geometric characteristics of the sensing system, and elliptical modeling that phase-vs-distance characteristics that depending upon geometric rather than electrical characteristics of the sensing system.

Three-dimensional (3D) cameras (or sensors) based on time-of-flight (TOF) principle acquire distance information from object(s) in a scene being imaged. Distance information is produced independently at each pixel of the camera's sensor. Exemplary such systems are described in U.S. Pat. No. 6,323,942 "CMOS-Compatible Three-Dimensional Image Sensor IC" (2001), and U.S. Pat. No. 6,515,740 "Methods for CMOS-Compatible Three-Dimensional Image Sensing Using Quantum Efficiency Modulation" 2003, which patents are assigned to Canesta, Inc., presently of Sunnyvale, Calif.
As described in U.S. Pat. No. 6,323,942, a TOF system emits optical energy and determines how long it takes until at least some of that energy reflected by a target object arrives back at the system to be detected. Emitted optical energy traversing to more distant surface regions of a target object before being reflected back toward the system will define a longer TOF than if the target object were closer to the system. If the roundtrip TOF time is denoted t1, then the distance between target object and the TOF system is Z1, where Z1=t1·C/2, where C is velocity of light. Such systems can acquire both luminosity date (signal amplitude) and TOF distance, and can realize three-dimensional images of a target object in real time.
A more sophisticated TOF system is described in U.S. Pat. No. 6,515,740, wherein TOF is determined by examining relative phase shift between transmitted light signals and light signals reflected from a target object. FIG. 1A depicts an exemplary phase-shift detection system 100 according to the '740 patent. Detection of the reflected light signals over multiple locations in the system pixel array results in measurement signals that are referred to as depth images. The depth images represent a three-dimensional image of the target object surface.
Referring to FIG. 1A, TOF system 100 includes a two-dimensional array 130 of pixel detectors 140, each of which has dedicated circuitry 150 for processing detection charge output by the associated detector. In a typical application, array 130 might include 100×100 pixels 230, and thus include 100×100 processing circuits 150. IC 110 may also include a microprocessor or microcontroller unit 160, memory 170 (which preferably includes random access memory or RAM and read-only memory or ROM), a high speed distributable clock 180, and various computing and input/output (I/O) circuitry 190. Among other functions, controller unit 160 may perform distance to object and object velocity calculations.
Under control of microprocessor 160, a source of optical energy 120 is periodically energized via exciter 115, and emits optical energy via lens 125 toward an object target 20. Typically the optical energy is light, for example emitted by a laser diode, VCSEL (vertical-cavity surface emitting laser) or LED device 120. Some of the optical energy emitted from device 120 will be reflected off the surface of target object 20, and will pass through an aperture field stop and lens, collectively 135, and will fall upon two-dimensional array 130 of pixel detectors 140 where an image is formed. In some implementations, each imaging pixel detector 140 captures time-of-flight (TOF) required for optical energy transmitted by emitter 120 to reach target object 20 and be reflected back for detection by two-dimensional sensor array 130. Using this TOF information, distances Z can be determined. Advantageously system 100 can be implemented on a single IC 110, without moving parts and with relatively few off-chip components.
Typically optical energy source 20 emits preferably low power (e.g., perhaps 1 W peak) periodic waveforms, producing optical energy emissions of known frequency (perhaps 30 MHz to a many hundred MHz) for a time period known as the shutter time (perhaps 10 ms). Optical energy from emitter 120 and detected optical energy signals within pixel detectors 140 are synchronous to each other such that phase difference and thus distance Z can be measured for each pixel detector. The detection method used is referred to as homodyne detection in the '740 and '496 patents. Phase-based homodyne detection TOF systems are also described in U.S. Pat. No. 6,906,793, Methods and Devices for Charge Management for Three-Dimensional Sensing, assigned to Canesta, Inc., assignee herein.
The optical energy detected by the two-dimensional imaging sensor array 130 will include light source amplitude or intensity information, denoted as "A", as well as phase shift information, denoted as φ. As depicted in exemplary waveforms in FIGS. 1B and 1C, the received phase shift information (FIG. 1C) varies with TOF and can be processed to yield Z data. For each pulse train of optical energy transmitted by emitter 120, a three-dimensional image of the visible portion of target object 20 is acquired, from which intensity and Z data is obtained (DATA). As described in U.S. Pat. Nos. 6,515,740 and 6,580,496 obtaining depth information Z requires acquiring at least two samples of the target object (or scene) 20 with 90° phase shift between emitted optical energy and the pixel detected signals. While two samples is a minimum figure, preferably four samples, 90° apart in phase, are acquired to permit detection error reduction due to mismatches in pixel detector performance, mismatches in associated electronic implementations, and other errors. On a per pixel detector basis, the measured four sample data are combined to produce actual Z depth information data. Further details as to implementation of various embodiments of phase shift systems may be found in U.S. Pat. Nos. 6,515,740 and 6,580,496.
FIG. 1D is similar to what is described with respect to the fixed phase delay embodiment of FIG. 10 in U.S. Pat. No. 6,580,496, entitled Systems for CMOS-Compatible Three-Dimensional Image Sensing Using Quantum Efficiency Modulation, or in U.S. Pat. No. 7,906,793, entitled Methods and Devices for Charge Management for Three-Dimensional Sensing, both patents assigned to Canesta, Inc., assignee herein. In FIG. 1D, generated photocurrent from each quantum efficiency modulated differential pixel detector, e.g., 140-1, is differentially detected (DIF. DETECT) and differentially amplified (AMP) to yield signals B·cos(φ), B·sin(φ), where B is a brightness coefficient.
During normal run-time operation of the TOF system, a fixed 0° or 90° phase shift delay (DELAY) is switchably insertable responsive to a phase select control signal (PHASE SELECT). Homodyne mixing occurs using quantum efficiency modulation to derive phase difference between transmitted and received signals (see FIGS. 1B, 1C), and to derive TOF, among other data. A more detailed description of homodyne detection in phase-based TOF systems is found in the '496 patent. Although sinusoidal type periodic waveforms are indicated in FIG. 1D, non-sinusoidal waveforms may instead be used. As described later herein, the detection circuitry of FIG. 1D may be used with embodiments of the present invention.
In many applications it is advantageous to have geometric information as such information makes it easier to perceive and interact with the real world. As noted, three-dimensional TOF camera systems including exemplary system 100 in FIG. 1A accomplish this task using a modulated light source 120 (e.g., an LED, a laser, a VCSEL, etc.) to illuminate a scene containing a target object 20. The light reflected from the scene is processed in the camera's sensor pixels to determine the phase delay (φ) between the transmitted light and reflected light. Phase delay (or simply phase herein) is proportional to the (Z) distance between the sensor and the target. However phase delay is a relative quantity and is not per se equal to Z distance. For example as Z increases, phase φ increases, but after an increase of 360°, the phase folds-over and further increases in Z will produce further increases in φ, again starting from 0°. It is thus necessary to disambiguate or de-alias the phase data to obtain a true measure of Z.
Furthermore, the sensor's pixels measure phase delay along a certain radial angle that is different for each pixel 140 in array 130. However many applications prefer using Cartesian (or real world X,Y,Z) coordinates instead of radial information. A mechanism is needed to establish correspondence or mapping between phase and real world coordinates. Such a mechanism is obtained through a calibration process.
Thus, one function of calibration may be defined as creating a mapping from the sensor 140 response to geometrical coordinates, which are X, Y, and Z information with respect to a known reference. As used herein, X and Y coordinates are the horizontal and vertical offsets from the optical axis of the system, and Z is the perpendicular distance between the sensor and the target object (e.g., object in a scene). Typically the calibration process includes several steps, where each step creates one kind of mapping. For instance, the mapping for real-world Z coordinates is done by a step called Z (distance or depth) calibration, while the mapping for real-world X,Y coordinates is done by another step called XY calibration.
In addition to geometrical calibration, one must perform other types of calibration to account for certain environmental factors, including without limitation temperature and ambient lighting conditions. For example, temperature changes in sensor array 130 can increase so-called dark current in pixels 140, which dark current can in turn change measured phase φ. Ambient light can interfere with system-emitted light from source 120, and can result in phase errors. A complete calibration procedure preferably will include steps to model the effects of such environmental changes. So doing can allow these effects to be removed dynamically during run-time operation, when the environmental conditions may change.
Consider for example distance (Z) calibration techniques, according to the prior art. One known calibration method for a three-dimensional system captures sensor phase response for a number of known Z distance values as the target object is successively moved or relocated in the XY plane. This prior art calibration method will be referred to herein as the "by-example" method. Using this method sensor data from array 130 are captured for each target object location and stored in memory. The resultant phase-vs.-distance curve is constructed as a calibration table of sensor response-distance pairs that is sampled at several values of distance. During actual run-time operation of the TOF system so calibrated, perhaps system 100, the stored calibration table data is interpolated and bracketed to determine Z distance for a given sensor phase response. Thus, a given phase response from the sensor array is converted to distance by interpolating the values stored in the calibration table. However the phase-vs-distance transfer function curve contains harmonics and sufficient data points must be stored in the calibration table to model these harmonics to avoid loss of accuracy due to insufficient sampling. There is also interpolation error that can only be reduced by increasing the size of the table.
Although the "by-example" method is straightforward to implement with relatively fast run-time processing, it has several disadvantages. Taking a subset of the operating range and subsequent interpolation results in errors that can be several cm in magnitude. Further, as the operating range of the sensor is increased, more data must be stored in the calibration table to maintain accuracy. This generates larger calibration tables, requiring more storage, as well as longer interpolation times. Storage can be on the order of several MB, e.g., very large for use with embedded systems. Another problem from a practical standpoint is the large physical space needed to capture data from the sensor for large field of view (FOV) and operating ranges as the target object is repositioned. For example, a sensor with a 100° FOV and 5 m operating range requires a target object of approximately 12 m×12 m, which target object must be moved between 0 and 5 m during calibration. Given enough physical space for target object relocation during calibration, and given enough time for the calibration procedure, such prior art "by example" calibration can be carried out. But such prior art calibration procedure has high costs and is not very suitable for calibrating a high-volume product.
What is needed are more efficient methods and systems to implement detected phase to distance calibration for three-dimensional camera systems. Such methods and systems should require less time and smaller physical space to be carried out, and the calibration data should require less space for storage for use during system run-time operation. Preferably such calibration should provide a first model that depends upon electrical rather than physical characteristics of the sensors in the system under calibration, and should provide a second model that depends upon physical rather than electrical characteristics of the sensors.
The present invention provides such methods and systems.

This patent is subject to a terminal disclaimer.

Method and system for fast calibration of three-dimensional (3D) sensors


A thermal-type infrared radiation detector cell includes a diaphragm structural body that forms a gap of a predetermined width over a semiconductor substrate. The diaphragm structural body is capable of either providing metal wiring films that doubles as an infrared radiation reflector film or providing a high refractive index film having a thickness set to satisfy the expression d=xcexxc3x97{1/(4xc3x97n)}, where n is the refractive index of the high refractive index film, and xcex is the wavelengths of infrared rays. As a result, in the former option, no separate infrared radiation reflector film is required, whilst in the latter no separate infrared radiation absorption layer is required. This facilitates the manufacturing process and improves the sensitivity in infrared radiation detection.

The present invention relates to infrared radiation detector cells for detecting infrared radiation, in particular, to thermal-type infrared radiation detector cells for detecting infrared radiation by converting it to heat, and further relates to image capture devices incorporating such thermal-type infrared radiation detector cells. Specifically, the present invention relates to thermal-type infrared radiation detector cells with an increased infrared radiation absorption rate and reduced irregularities in detection sensitivity, and further relates to image capture devices incorporating such thermal-type infrared radiation detector cells.
Conventionally, there are a large variety of infrared radiation detection methods being developed based on different principles and adopted in the working of various types of infrared radiation detector cells for detecting infrared radiation. Typically used among these methods is to convert infrared radiation energy into electrical signals by means of a band gap of semiconductor materials, i.e., to exploit photon effects of infrared radiation energy, because the method exhibits high sensitivity and quick response. Infrared radiation detector cells incorporating the method is called a quantum type.
Despite these advantages, the quantum-type infrared radiation detector cell is only capable of detecting a limited range of wavelengths. To detect those infrared rays with very low infrared radiation energy, e.g., those with long wavelengths, semiconductor materials used for the detection of infrared radiation need to be kept at an extremely low temperature. For example, in the quantum-type infrared radiation detector cell, the semiconductor material needs to be kept around 77K, that is, approximately xe2x88x92196xc2x0 C., using liquid nitrogen. This requirement makes infrared radiation detector devices cumbersome to handle and difficult to make smaller due to the use of liquid nitrogen for cooling.
Another type of infrared radiation detector cells developed based on different principles to detect infrared radiation is of thermal types that do so by converting infrared radiation energy into heat. In a thermal-type infrared radiation detector cell, as a detector cell material absorbs infrared radiation energy and converts it to heat, the detector cell material heats up and thus changes its physical properties (electrical resistance, pyroelectricity, etc.). By means of the detection of these changes, the infrared radiation is detected.
Accordingly, in the thermal-type infrared radiation detector cell, unlike in its quantum-type counterpart, there is no need for semiconductor materials used for the detection of infrared radiation to be kept at extremely low temperatures. Thus, the thermal-type infrared radiation detector cell can be used at room temperature and offers room for possible reduction in size through the omission of cooling means, thereby getting wide attention for its practical performance in recent years.
However, some objects generate so little heat in the thermal-type infrared radiation detector cell that the resultant temperature elevation is as small as 0.01xc2x0 C. or even smaller, making it difficult for the thermal-type infrared radiation detector cell to detect infrared radiation. To solve this problem, some thermal-type infrared radiation detector cells incorporate such a structure that exhibits an increased infrared radiation absorption rate, and thus increase the elevation in their temperature and enhance the sensitivity in detecting infrared radiation to a greatest extent possible.
To solve these problems, the typical thermal-type infrared radiation detector cell typically including a diaphragm structure in which a diaphragm structural body for detecting infrared radiation is separated by a predetermined gap from a semiconductor substrate on which there is provided an integrated circuit (or a signal integrated circuit) electrically connected to the diaphragm structural body by metal wiring. The structure enhances the thermal insulation between the diaphragm structural body (infrared radiation receiving section, or sensor section) for detecting infrared radiation and the semiconductor substrate with an integrated circuit, thereby successfully achieving high sensitivity in the detection of infrared radiation.
To further improve on the infrared radiation absorption rate, the thermal-type infrared radiation detector cell incorporating the diaphragm structure normally employs one of two techniques: namely, (a) the selective use of substance exhibiting high infrared radiation absorption, and (2) the adoption of multiple reflection of infrared rays. According to technique (1), arrangement (a) is employed whereby a thin film (infrared radiation absorbing film) composed of a material exhibiting a high infrared radiation absorption rate is provided on the surface of the diaphragm structure. According to technique (2), arrangement (b) is employed whereby, in addition to arrangement (a), an infrared radiation reflector film is provided on the semiconductor substrate below the diaphragm structure.
FIGS. 15(a) and 15(b) show an example of arrangement. (a) adopted in a thermal-type infrared radiation detector cell incorporating technique (1). A diaphragm structural body 101a is positioned over a semiconductor substrate 108 on top of which there is provided an integrated circuit (not shown), so as to be separated from the semiconductor substrate 108 by a predetermined gap. An infrared radiation absorbing film 107a is also provided on the surface of the diaphragm structural body 101a (arrangement (a)).
FIGS. 16(a) and 16(b) show an example of arrangement (b) adopted in a thermal-type infrared radiation detector cell incorporating technique (2). Arrangement (b) is basically identical to arrangement (a) employed in the thermal-type infrared radiation detector cell shown in FIGS. 15(a) and 15(b), except that arrangement (b) additionally includes an infrared radiation reflector film 106 on the surface of the semiconductor substrate 108.
The arrangements employed in the thermal-type infrared radiation detector cell will be briefly discussed below. The diaphragm structural body 101a or 101b are each constituted by a second silicon oxide film 102, a thermally variable resistor film 103 and a metal wiring film 104 provided on the second silicon oxide film 102 in a predetermined pattern, and a third silicon oxide film 105 covering these films. Infrared radiation absorbing films 107a and 107b composed of a material processing a high infrared radiation absorption rate are provided on the third silicon oxide film 105 according to techniques (1) and (2) respectively (arrangement (a)).
A first silicon oxide film 109 is provided on the semiconductor substrate 108 on top of which there is provided an integrated circuit (not shown). According to technique (2), an infrared radiation reflector film 106 composed of a substance capable of substantially entirely reflecting infrared rays is provided on the first silicon oxide film 109 so as to oppositely face the diaphragm structural body 101b (arrangement (b)).
It should be noted that as shown in FIG. 15 (a) and FIG. 16(a), both diaphragm structural bodies 101a and 101b are supported by legs 110 and electrically connected to the semiconductor substrate 108 via the metal wiring film 104 contained in the legs 110. As shown in FIG. 15(a) and FIG. 16(a), almost all of the surfaces of the diaphragm structural bodies 101a and 101b serve as first infrared radiation receiving areas (enclosed by broken lines).
In the thermal-type infrared radiation detector cells including arrangement (a) and (b), incident infrared rays shine down on the infrared radiation absorbing films 107a and 107b in the first infrared radiation receiving areas of the diaphragm structural bodies 101a and 101b respectively. Under these conditions, in technique (1), infrared rays are substantially entirely absorbed by the infrared radiation absorbing film 107a of a sufficiently increased thickness.
In technique (2), the infrared rays are partly reflected by, and partly pass through, the infrared radiation absorbing film 107b, with the rest of the infrared rays being converted to Joule heat by the electrical resistance of, and subsequently absorbed by, the infrared radiation absorbing film 107b. Having passed through the infrared radiation absorbing film 107b, the infrared rays pass through the diaphragm structural body 101b, that is, through the third silicon oxide film 105, the thermally variable resistor film 103, and the second silicon oxide film 102, and reach the infrared radiation reflector film 106.
The infrared rays are then entirely reflected back toward the diaphragm structural body 101b from the infrared radiation reflector film 106 with a phase delay of xcfx80, because the infrared radiation reflector film 106 is a low-resistance complete reflection film composed with a metal with a sheet resistance not exceeding a few xcexa9/xe2x96xa1. The reflected infrared rays take the path in reverse direction, passing through the diaphragm structural body 101b. As having reached the infrared radiation absorbing film 107b disposed on the top of the diaphragm structural body 101b, the infrared rays are again reflected, passed, and absorbed by the infrared radiation absorbing film 107b.
As detailed above, the incident infrared rays entering the diaphragm structural body 101b are repeatedly reflected in the diaphragm structural body 101b and do not leak out, effectively improving the infrared radiation absorption rate of the thermal-type infrared radiation detector cell. In a thermal-type infrared radiation detector cell incorporating the diaphragm structural body 101b, that is, employing technique (2), the infrared radiation absorption rate per unit area is determined by the relationships among the reflection, passage, and absorption of infrared rays in the diaphragm structural body 101b.
A specific example of technique (2) is disclosed in Japanese Laid-Open Patent Application No. 10-111178/1998. In this example, the infrared radiation absorbing film is separated from a reflector film by a predetermined distance by means of the interposition of one or more intermediate films of a predetermined thickens between the infrared radiation absorbing film and the reflector film underneath. In this example the predetermined distance, d, is defined as follows:
d=(2Nxe2x88x921)xc3x97xcex/(4n)
wherein N is a positive integer, xcex is the wavelengths of infrared rays detected, and n is the refractive index of the film with a predetermined thickness.
The arrangement enables the distance by which the reflector film is separated from the infrared radiation absorbing film to be maintained at a fixed value, and improves sensitivity by reducing the thickness of the diaphragm structural body 101b, since an increase in the refractive index of the intermediate film allows a reduction in the predetermined distance.
However, generally, a structure with high infrared radiation absorption and a manufacturing process to incorporate such a structure in the thermal-type infrared radiation detector cell are so complex to reduce the yields and increase cost. Both techniques (1) and (2) suffer these problems.
In addition to these problems, thermal-type infrared radiation detector cells fabricated by technique (1) entail slow response due to its enlarged size and hence increased thermal capacity. As a result, an infrared radiation image capture device incorporating such a thermal-type infrared radiation detector cell fails to produce a satisfactory level of performance.
Specifically, according to technique (1), the infrared radiation absorbing film 107a including arrangement (a) should be composed of material capable of absorbing infrared radiation efficiently, such as gold black and organic materials; however, it is difficult to fabricate a thin film from the material. Contradictory to the requirement to reduce the film thickness made of the material, the infrared radiation absorbing film 107a needs to have a thickness of at least a few xcexcm to exhibit an infrared radiation absorption rate of 80% or greater. The thickness imparts too large thermal capacity for the infrared radiation detector cell to produce quick response, which presents an obstacle in high speed imaging. For these reasons, the thermal-type infrared radiation detector cell incorporating technique (1) is rarely applied in infrared radiation image capture elements.
According to technique (2), the diaphragm structural body 101b including arrangement (b) produces internal multiple reflection and thereby does not allow infrared rays to leak out. This allows the infrared radiation absorbing film 107b incorporating arrangement (a) to have a reduced thickness as small as a few hundred nm and hence to have a reduced thermal capacity. Further, theoretically, the infrared radiation absorption rate reaches almost 100% if the distance by which the diaphragm structural body 101b incorporating arrangement (a) is separated from the semiconductor substrate 108 incorporating arrangement (b) is equal to xc2xcn times the wavelength of the infrared rays absorbed, and the sheet resistance of the infrared radiation absorbing film 107b incorporating arrangement (a) is equal to 377 xcexa9.
However, technique (2) entails three major structural problems caused by (i) the metal wiring film 104, (ii) the infrared radiation reflector film 106, and (iii) the control of the distance between the infrared radiation absorbing film 107b and the infrared radiation reflector film 106. These problems are discussed in detail in the following.
(i) Problems Arising from the Metal Wiring Film 104
As shown in FIG. 16(a), in the thermal-type infrared radiation detector cell, a metal wiring film 104 is formed along each side of the thermally variable resistor film 103 to measure the resistance of the thermally variable resistor film 103. The metal wiring film 104 is typically composed of aluminum, and thus cause undesired reflection of infrared rays.
In other words, the diaphragm structural body 101b is designed so that the infrared radiation reflector film 106 reflects infrared rays in such a manner that the infrared rays are ultimately absorbed. Meanwhile, the metal wiring film 104 reflects infrared rays in such a manner that none of the infrared rays are absorbed. So, the parts of the thermally variable resistor film 103 covered with the metal wiring films 104 absorb almost no infrared rays.
The net infrared radiation absorption by the thermal-type infrared radiation detector cell is determined by the infrared radiation absorption rate in the infrared radiation receiving area I multiplied by the infrared radiation absorption area ratio. The infrared radiation absorption area ratio is defined as the ratio (fill factor) of the infrared radiation receiving area I to the size (cell size) of the thermal-type infrared radiation detector cell. For example, the thermal-type infrared radiation detector cell shown in FIG. 16(a) has a fill factor of about 0.5, and the infrared radiation absorption rate in the infrared radiation receiving area I is 80%. Accordingly, the net infrared radiation absorption by the thermal-type infrared radiation detector cell is given by:
80%xc3x970.5=40%
The figure indicates that about 40% of incident infrared rays is absorbed.
ii) Problems Caused by the Infrared Radiation Reflector Film 106
The infrared radiation reflector film (low-resistance complete reflection film) 106 capable of reflecting the infrared rays having passed through the diaphragm structural body 101b is formed on a top surface of a first silicon oxide film 109, serving as a protection film, formed on the semiconductor substrate 108 on which there is provided an integrated circuit. Therefore, a separate step is necessary to fabricate the infrared radiation reflector film 106, which adds to the time required for the whole manufacturing process. Besides, the step to form the infrared radiation reflector film 106 must include alignment and etching, which adds to the total cost.
(iii) Problems in the Control of the Distance Between the Infrared Radiation Absorbing Film 107b and the Infrared Radiation Reflector Film 106
According to the principles based on which the infrared radiation absorbing film 107b absorb infrared rays, the infrared radiation absorption rate is influenced by the distance between the infrared radiation absorbing film 107b (arrangement (a)) and the infrared radiation reflector film 106 (arrangement (b)). Thus, the control of the distance between these thin films is essential. However, the stress of the thin films are extremely difficult to control, compared to the thicknesses of the thin films. Therefore, the thicknesses can be successfully controlled to form desirably thin films, whereas the control of the stress is likely to fail. This causes warping of the diaphragm structural body 101b and hence irregular distance. The resultant, actual infrared radiation absorption rate is thus inferior to that originally designed. For example, a thermal-type infrared radiation detector cell designed to absorb infrared rays of wavelengths in a range from 8 xcexcm to 12 xcexcm is. theoretically capable of achieving a 100% infrared radiation absorption rate, but in practical use exhibits only an unimpressive rate of about 80%.
Besides, the distance becomes irregular at any given point in a chip matrix. Therefore, when applied in an infrared radiation image capture element, the thermal-type infrared radiation detector cells incorporating technique (2) entail another problem of irregularities in in-plane angles, which negatively affects image quality.
A further problem is found in Tokukaihei 10-111178 which is an example of technique (2). According to the disclosure, the infrared radiation absorbing film is separated from the reflector film by a predetermined distance, d, by means of the interposition of one or more intermediate films. This structure does enable the distance by which the reflector film is separated from the infrared radiation absorbing film to be maintained at a fixed value. However, at least three different kinds of films (namely, the infrared radiation absorbing film, the reflector film, and the intermediate film) need to be formed, and the thicknesses of all of them need to be controlled as detailed in the foregoing. These requirements add to the number of steps and cost required in the manufacture.
In view of the above problems, the present invention has an object to present thermal-type infrared radiation detector cells capable of achieving increased infrared radiation absorption and being manufactured in fewer and simpler steps.
Another object of the present invention is to present thermal-type infrared radiation detector cells including a diaphragm structure of a small thermal capacity, capable of achieving an increased infrared radiation absorption rate and reduced irregularities in sensitivity without adding largely to the number of steps in manufacturing process.
A thermal-type infrared radiation detector cell in accordance with the present invention has a diaphragmatic structure constituted by:
a semiconductor substrate on which there is provided an integrated circuit; and
a diaphragm structural body electrically connected to, and separated by a predetermined gap from, the semiconductor substrate,
wherein the diaphragm structural body includes at least:
a thermally variable resistor film changing resistance thereof upon reception of infrared rays; and
metal wiring films electrically connected to the thermally variable resistor film and also to a terminal section in the substrate,
wherein the metal wiring films are formed so as to constitute an infrared radiation reflector film for reflecting incident infrared rays so that the thermally variable resistor film can receive the reflected infrared rays in the diaphragm structural body.
According to the arrangement, the metal wiring films are constituted by an infrared radiation reflector film capable of reflecting infrared rays; therefore, unlike prior art, the metal wiring films in the diaphragm structural body do not interrupt the infrared rays entering the infrared radiation reflector film placed on a side of the diaphragm structural body opposite to the substrate, and thereby provides an increased effective absorption area where the diaphragm structural body can absorb infrared rays. Further, since the metal wiring film doubles as the infrared radiation reflector film, no separate step is necessary to fabricate a infrared radiation reflector film, facilitating the manufacturing process of the cell.
In the thermal-type infrared radiation detector cell arranged in this manner, it is preferable if the metal wiring films are formed so as to cover a substantial entirety of either a top surface or a bottom surface of the thermally variable resistor film.
According to the arrangement, after being reflected by the metal wiring films, the infrared rays having passed through the diaphragm structural body interferes with reflected light from the surface of the high refractive index film (dielectric film) at this surface, having its reflection substantially offset. The infrared rays are therefore efficiently absorbed by reflection and interference in the diaphragm structural body, and the diaphragm structural body greatly increases its absorption of infrared rays.
It is preferable if the metal wiring films are composed of a material capable of reflecting 95% or more of incident infrared rays entering the infrared radiation receiving section. Titanium and aluminum are good examples.
In the thermal-type infrared radiation detector cell arranged in this manner, it is preferable if the diaphragm structural body has such a substantially planar shape to provide a two-dimensionally spreading infrared radiation receiving area where infrared rays are received; and the metal wiring films are formed so as to two-dimensionally spread substantially corresponding to the infrared radiation receiving area.
This structure further ensures the function of the metal wiring films as an infrared radiation reflector film. The thermally variable resistor film may be provided on the metal wiring films, either on their top or bottom surface.
It is preferable if the thermal-type infrared radiation detector cell arranged in this manner further includes an insulating layer interposed between the thermally variable resistor film and the metal wiring films. A suitable insulating layer is primarily composed of silicon oxide.
In thermal-type infrared radiation detector cell arranged in this manner, it is preferable if the diaphragm structure is provided with an infrared ray entry surface separated from the surfaces of the metal wiring films by a distance substantially equal to xc2xcn times the wavelengths of incident infrared rays, where n is the refractive index of a substance interposed between the infrared ray entry surface and the surfaces of the metal wiring films.
According to the arrangement, the infrared rays reflected by the metal wiring films interferes with reflected light from the surface of the high refractive index film at this surface, having its reflection substantially offset and being absorbed by the infrared radiation absorbing film. This ensures the absorption of infrared rays by means of reflection and interference within the diaphragm structural body, and the diaphragm structural body greatly increases its absorption of infrared rays.
Another thermal-type infrared radiation detector cell in accordance with the present invention has a diaphragm structure constituted by
a semiconductor substrate on which there is provided an integrated circuit; and
a diaphragm structural body electrically connected to, and separated by a predetermined gap from, the semiconductor substrate,
wherein the diaphragm structure further includes a high refractive index film and an infrared radiation reflector film provided beneath the high refractive index, and
the high refractive index film has a thickness, d, given approximately by
d=xcexxc3x97{1/(4xc3x97n)}
where n is a refractive index of the high refractive index film and xcex is the wavelengths of infrared rays absorbed.
According to the arrangement, the adoption of a diaphragm structure keeps the thermal conductance low with the equation being substantially satisfied in the diaphragm structure. Therefore, the diaphragm structure does not allow Joule heat produced by infrared rays to escape therefrom, and the reflection of infrared rays by the surface of the diaphragm structure is offset by interference effects. Thus, infrared rays are not allowed to escape from the diaphragm structure. The distance separating the high refractive index film from the reflector film, which influence interference effects greatly, is controlled by means of the thickness of the high refractive index film, and therefore is constant.
For these reasons, the thermal-type infrared radiation detector cell exhibits much higher and constant infrared radiation absorption rate than conventional counterparts, and thereby achieves more constant sensitivity The use of a high refractive index film enables the diaphragm structure to have a greatly reduced thickness, preventing increase in the thermal capacity of the thermal-type infrared radiation detector cell. In other words, the thermal capacity of the diaphragm structure can be greatly reduced compared to conventional technologies. As a result, an element can be prepared with a better sensitivity and shorter response time than those of conventional technologies.
Further, according to the arrangement, no infrared radiation absorbing film needs to be formed, and an increase in efficiency in infrared radiation absorption can be achieved structurally through control of the thickness of the high refractive index film alone. So, no additional steps are required in the manufacturing process. Rather, the manufacturing process can be simplified and the manufacturing cost is reduced, due to the fact that no infrared radiation absorbing film needs to be formed. The thermal-type infrared radiation detector cell thereby boasts excellent performance and are prepared at a reduced cost.
In the thermal-type infrared radiation detector cell arranged in the above manner, it is preferable if the diaphragm structural body further includes a thermally variable resistor film that changes its electric resistance with temperature variations and metal wiring films electrically connected to the thermally variable resistor film.
According to the arrangement, the infrared radiation absorption by the high refractive index film increases temperature. The rise in temperature then changes the electric conductance, hence resistance, of the thermally variable resistor film changes accordingly. As a result, infrared rays absorbed by the high refractive index film are converted to electric signals, passed through the metal wiring films electrically connected the thermally variable resistor film, and detected efficiently. Therefore, it is better ensured that infrared rays are detected.
In the thermal-type infrared radiation detector cell arranged in the above manner, it is preferable if there is provided an insulating layer between the infrared radiation reflector film and the thermally variable resistor film.
According to the arrangement, the provision of an insulating layer between the infrared radiation reflector film and the thermally variable resistor film prevents heat, which is intended to heat the thermally variable resistor film, from flowing through the highly heat conductive infrared radiation reflector film. Thus the thermally variable resistor film is efficiently heated. As a result, the thermal-type infrared radiation detector cell has improved sensitivity.
In the thermal-type infrared radiation detector cell arranged in the above manner, it is preferable if there is provided at least a thermally variable resistor film between the high refractive index film and the infrared radiation reflector film.
According to the arrangement, the thermally variable resistor film is placed closely to the high refractive index film producing heat by means of infrared radiation absorption. Therefore, the heat from the high refractive index film is prevented from flowing into the infrared radiation reflector film before reaching the thermally variable resistor film. Thus the thermally variable resistor film is efficiently heated. As a result, the thermal-type infrared radiation detector cell has improved sensitivity.
In the thermal-type infrared radiation detector cell arranged in the above manner, it is preferable if the infrared radiation reflector film doubles as the metal wiring films.
According to the arrangement, the metal wiring films double as the infrared radiation reflector film; therefore, no step is required to deposit an infrared radiation reflector film and fabricate it into a predetermined shape. Thus the thermal-type infrared radiation detector cell has a simplified structure, and is manufactured at a further reduced cost.
In the thermal-type infrared radiation detector cell arranged in the above manner, it is preferable if there is provided an insulating layer between the high refractive index film and the infrared radiation reflector film.
According to the arrangement, the high refractive index film is insulated from the infrared radiation reflector film; therefore, no sense current branches out from the thermally variable resistor film to the high refractive index film. Thus, changes in the resistance of the thermally variable resistor film caused by infrared radiation absorption can be efficiently detected, and the thermal-type infrared radiation detector cell has further improved sensitivity.
Besides, according to the arrangement, no sense current branches out to the high refractive index film; therefore, the heat resistance variation of the thermally variable resistor film can be increased by increasing its resistivity. As a result, the thermal-type infrared radiation detector cell has further improved sensitivity. Further, since no sense current branches out to the high refractive index film, the high refractive index film itself can have a reduced resistivity. Therefore, the high refractive index film can have an increased refractive index, and thus reduced thickness. As a result, the thermal-type infrared radiation detector cell has improved time resolution.
In the thermal-type infrared radiation detector cell arranged in the above manner, it is preferable if the diaphragm structure includes a supporting member for supporting the diaphragm structural body over the semiconductor substrate while maintaining a predetermined gap therebetween, wherein
the metal wiring films are provided on the supporting member, and there is provided an insulating layer to cover the metal wiring films formed on at least the supporting member.
According to the arrangement, the insulating layer covers the metal wiring films on the supporting member, and thereby provides protection to the normally exposed metal wiring films on the supporting member. As a result, the thermal-type infrared radiation detector cell has improved environmental insusceptibility.
In the thermal-type infrared radiation detector cell arranged in the above manner, it is preferable if the high refractive index film is primarily composed of either silicon or germanium.
In the thermal-type infrared radiation detector cell arranged in the above manner, the high refractive index film may double as the thermally variable resistor film.
According to the arrangement, the dues role of the high refractive index film as the thermally variable resistor film enables omission of the step to deposit an infrared radiation reflector film and fabricate it into a predetermined shape. Thus the thermal-type infrared radiation detector cell has a simplified structure, and is manufactured at a further reduced cost. In the arrangement, the high refractive index film is, suitably, composed primarily of silicon.
Another thermal-type infrared radiation detector cell in accordance with the present invention includes:
a semiconductor substrate on which there is provided an integrated circuit; and
a substantially planar diaphragm structural body electrically connected to, and separated by a predetermined gap, from the semiconductor substrate,
wherein the diaphragm structural body is provided with at least: an infrared ray entry surface through which infrared rays enter; and an infrared radiation reflector surface by which infrared rays having entered the diaphragm structural body are reflected, the infrared radiation reflector surface being disposed beneath the infrared ray entry surface, and
the infrared ray entry surface is separated from the infrared radiation reflector surface by a distance specified substantially equal to xc2xcn times the wavelengths of incident infrared rays, where n is a refractive index of a substance interposed between the infrared ray entry surface and the infrared radiation reflector surface.
According to the arrangement, with respect to the infrared rays having been reflected either by the metal wiring films or by infrared radiation reflector film, the reflection by the infrared ray entry surface is substantially offset. Therefore, infrared rays are absorbed by means of reflection and interference in the infrared radiation receiving section, and no separate infrared radiation absorbing film needs to be formed. As a result, the thermal-type infrared radiation detector cell absorbs a greater amount of infrared rays, thus improves sensitivity in detecting infrared rays, and has a simplified structure.
An image capture device in accordance with the present invention incorporates a thermal-type infrared radiation detector cell arranged in one of the above manners. According to the arrangement, thermal-type infrared radiation detector cells arranged in one of the above manners is used to constitute image capture elements; therefore, pixels exhibit infrared radiation absorption rates that are far more constant in the infrared radiation image capture element than in the image capture device incorporating conventional infrared radiation detector cells. Consequently, the image capture device in accordance with the present invention has sensitivity that varies less from pixel to pixel, and capable of capture higher quality images than conventional counterparts.
For a fuller understanding of the nature and advantages of the invention, reference should be made to the ensuing detailed description taken in conjunction with the accompanying drawings.

Thermal-type infrared radiation detector cell and image capture device incorporating the same


A superachromatic focusing objective lens which focuses wavelengths extending between the ultraviolet and the visible wavelength spectrum and is able to achieve superachromatic correction for three wavelengths within the visible spectrum is disclosed. The present objective lens includes an achromatic lens to assist in the correction spherical and coma aberration, a modified gauss for minimizing spherochromatism, a reversed modified gauss for adding symmetry to aid in the correction of coma, distortion and lateral color aberrations, and a stop located between the modified gauss and the reverse modified gauss. A glass plate is provided for forming a splatter shield to protect the lens from debris, and may be used to define one wall of a vacuum chamber. The elements of the objective lens may be made from various glasses to include calcium fluoride, quartz, and barium fluoride.

Objective lenses are well known and provide the final focusing element in an optical train of components in an optical system such as a micro-machining apparatus for using a laser beam to micro-machine a workpiece. Achromatic objectives which focus only two wavelengths at the same point are known. Apochromatic objectives which focus three wavelengths of light at the same point are also known. The lens disclosed in IBM Technical Disclosure Bulletin, Vol. 33, No. 04, September 1990, Eximer Laser Lens, pages 206-207 is apochromatic between the ultraviolet and the visible wavelengths of light, however only achieves achromatic correction for two wavelengths in the visible band.

Superachromatic UV and visible focusing objective lens

International Business Machines Corporation


A polyimide film-laminated body is composed of a metal layer and an aromatic polyimide layer formed by casting a polyamic acid solution composition, comprising 3,3′,4,4′-biphenyltetracarboxylic dianhydride as an essential tetracarboxylic dianhydride component and with introduction of a specific diamine component, onto a metal foil. The polyimide film-laminated body has an excellent gas permeation rate and moisture permeation rate, with heat resistance, a high elastic modulus and a low linear expansion coefficient, and with reduced foaming and delamination during the high-temperature steps for formation of the laminated body.

Polyimides derived from 3,3′,4,4′-biphenyltetracarboxylic dianhydride, which produces heat resistant polyimides, are usually polyimides obtained using 3,3′,4,4′-biphenyltetracarboxylic dianhydride and paraphenylenediamine as the starting acid dianhydride component and starting diamine component, respectively, and these are known to yield polyimides with low linear thermal expansion coefficients and high elastic moduli.
Because films composed of such polyimides have excellent thermal and electrical properties, they are widely used in electronic devices. However, it is not possible to achieve high adhesive strength with adhesives that are usually used in the field of electronics, while laminated bodies comprising metal layers formed by metal vapor deposition or sputtering have relatively low peel strength.
The polyimide films also have low saturated absorption percentages and low hygroscopic expansion coefficients, and therefore provide an advantage of dimensional stability against environmental changes. Yet their relatively low moisture permeation rates tend to result in foaming or delamination at the metal-polyimide interfaces of laminated bodies manufactured by casting methods.
Conventional polyimide laminated bodies made of aromatic polyimide film layers and metal material layers, and processes for their manufacture, are described or suggested in Japanese Examined Patent Publication No. 59-18221, Japanese Unexamined Patent Publication No. 57-181857, Japanese Unexamined Patent Publication No. 62-212140 and Japanese Examined Patent Publication No. 1-52843.
There has also been proposed a polyimide composite sheet comprising a metal film layer and an aromatic polyimide film layer formed by casting an aromatic polyamic acid solution composition, obtained by polymerizing an aromatic tetracarboxylic acid component composed of a biphenyltetracarboxylic anhydride and a pyromellitic anhydride, and an aromatic diamine component composed of a phenylenediamine and a diaminodiphenyl ether, onto a metal thin-film and drying the film while accomplishing imidization at high temperature (see Japanese Unexamined Patent Publication No. 61-111359).
There has also been proposed a printed wiring substrate comprising a metal film layer and an aromatic polyimide film layer formed by casting an aromatic polyamic acid solution composition, obtained by polymerizing an aromatic tetracarboxylic acid component composed of a biphenyltetracarboxylic anhydride and a pyromellitic anhydride, and an aromatic diamine component composed of a phenylenediamine and a diaminodiphenyl ether, onto an alkali-etchable metal substrate, performing imidization and then etching the metal substrate (see Japanese Unexamined Patent Publication No. 3-85789).
In addition, a flexible printed wiring substrate has been proposed which comprises a metal film layer and a polyimide film layer formed by casting a polyamic acid solution composition obtained by polymerizing components containing an aliphatic tetracarboxylic anhydride and a diamine onto a metal substrate and imidizing it (see Japanese Unexamined Patent Publication No. 2004-358961), but excessive time is required for drying and imidization, and this results in poor productivity.


A low-cost, reference grade pyranometer responsive to radiation in a band such as ultraviolet-B embodies unexpected and efficient construction. Large arrays or other multisensor systems are consequently available to a greater range of users. A dome constructed of UV-transmissive material has mounted therein a UV-pass "black glass" filter which transmits UV-B to a phosphor layer. The phosphor absorbs UV-B and re-emits it as predominantly green visible light. A green filter, which is "solar blind," i.e. non-transmissive to reds in the solar spectrum, transmits light to a solid state photodiode. The solid state photodiode has peak sensitivity in the green portion of the spectrum and rejects substantially all red leakage. Critical parameters such as the density and thickness of the phosphor and temperature compensation of the pyranometer combine to provide for a simplified pyranometer having great precision in measuring bands such as UV-B compared to the prior art.

The present invention relates to ultraviolet radiation measuring means responsive to radiation in a selected ultraviolet band, and more particularly to a pyranometer for measuring ultraviolet-B in solar radiation.
Measurement of solar radiation may be made within particular bands with the ultraviolet spectrum, such as ultraviolet-A or ultraviolet-B. Measurement of solar ultraviolet-B radiation is a distinguishable endeavor from ultraviolet radiation measurement in general. Ultraviolet-B radiation, also referred to in the art as UV-B, is the radiation in the range of 280-320 nm. It is this portion of the UV spectrum that is associated with erythmal damage, for example sunburn. Prior art monitors for measuring outputs of ultraviolet lamps are, of course, well-known. They will have some utility in measuring ultraviolet radiation. However, the solar spectrum differs from that produced by common prior art electrical ultraviolet radiation sources.
It is for this reason that the present invention is characterized as a pyranometer rather than broadly as ultraviolet measuring apparatus. The "pyra" root refers to early forms of such apparatus in which heating on blackened metal strips due to solar radiation was measured. The present invention will provide for accuracy of UV-B measurement in ways not contemplated in the design of apparatus for measuring the output of artificial sources. The monitors for electrical sources do not address concerns uniquely associated with precise measurement of solar UV-B.
In accordance with the present invention, it is desired to provide a reference grade instrument useful for measurement of environmental UV-B, or other ultraviolet band such as UV-A. The need for measurement of UV-C with the present invention is not contemplated to be as great, Reference grade instruments are well-known in the art. However, as described below, there are significant applications of pyranometers that require their use in large numbers. Embodying such an instrument in a relatively low-cost form greatly increases its accessibility to users.
Measurement of solar UV-B is an important concern due to the scientific and environmental issues concerning depletion of the earth's stratospheric ozone layer. Stratospheric ozone attenuates UV-B. There is concern that people on the earth's surface will be exposed to undue risks of erythmal damage due to increased exposure to UV-B resulting from depletion of the ozone layer. Substantial depletions of the Antarctic stratospheric ozone layer was documented in J. C. Farman, B. G. Gardiner and J. D. Shanklin: Large losses of total ozone in Antarctica reveal seasonal ClO.sub.x /NO.sub.x interaction. Nature, 315(6016), 207-210, (1985). In M. Blumenthaler and W. Ambach: Measurements of the temperature coefficient of the Robertson-Berger sunburn meters and the Eppley UV Radiometer. Arch. Meteorol. Geophys. Bioclim., B36, 357-363, (1986), it is reported that UV-B flux has increased about 1% per year in the Swiss Alps. Consequently, there is a need for global monitoring of ultraviolet radiation levels in solar radiation reaching the earth's surface.
Measurement of UV-B flux due to solar radiation in urban areas is difficult due to presence of UV-B absorbers such as aerosols and pollution-caused ozone in the troposphere. Consequently, there is a need for establishment of an improved measuring technology and for an efficiently produced apparatus suitable for use in widespread UV-B monitoring networks. Existence of large-scale, geographically extensive networks is a prerequisite for establishing a complete and accurate UV-B climatology of the earth.
Measurement of solar UV-B can be done with primary spectroradiometers, which serve as reference instruments and provide baseline data. However, their expense and complexity makes them impractical for widespread use. Conventional secondary optical detection schemes, e.g. silicon detectors, are not really suited to this task since the amount of energy present in the ultraviolet-B spectrum is only a small fraction of the total amount of energy available in the visible portion of the spectrum. Rejection of response to visible portions of the spectrum is very important. Even if a detector converts only a very small percentage of visible radiation into a signal supposedly indicative of UV-B, its utility for indicating slight increases in UV-B flux over a period of time will be totally compromised.
Current ultraviolet-B radiation detectors are further embodiments of a scheme for detecting UV-B described in D. F. Robertson: Solar ultraviolet radiation in relation to human sunburn and skin cancer. Ph.D. thesis, University of Queensland, Australia, (1972). This basic for of measurement was improved by Berger, as described in, D.S. Berger: The sunburning ultraviolet meter: design and performance. Photochem. Photobiol., 24, 587-593 (1976). Present versions of these instruments are often referred to as Robertson-Berger meters, or R-B meters.
In the general scheme of an R-B meter, radiation is directed to a phosphor which is excited by UV-B and re-emits at another wavelength. In this manner, a detector can be used which is nominally insensitive to red visible radiation, and response to UV-B is provided while visible radiation is desired to be rejected. Robertson uses a photomultiplier to sense radiation intensity emitted by the phosphor. An updated version using a solid state radiation detector rather than a photomultiplier is disclosed in U.S. Pat. No. 4,348,664 issued Sep. 7, 1982 and assigned to Elder pharmaceuticals. While this system is nominally insensitive to red radiation, it is utilized to measure the output of UV lamps to assure uniform dosage therefrom. However, this apparatus is not intended for use with the sun as a source. It would be imprecise for the reasons discussed above if used in the context of solar radiation. Gaseous ultraviolet lamps have a significantly lower "red" component in their output spectrum than solar radiation. Even a small fraction of the visible component of sunlight can contain more power than the UV-B component. Consequently, precision can be destroyed if even a small portion of the sunlight is not rejected. The apparatus as disclosed in the patent nominally rejects "red" response from an artificial source, but may not be operative to reject "red" at the levels received from solar radiation.
It is important to be able to provide a pyranometer for solar UV-B measurement since there is a need to perform solar measurement that is not addressed by instruments designed to monitor the output of UV lamps, and because it requires only a limited degree of imprecision in the output of the pyranometer to render it inoperative for meeting the objectives of the present invention.

Reference grade solar ultraviolet band pyranometer


A disk drive connected to a host computer compatible with a plurality of computer hardware types can automatically transmit one desired control signal to the host computer, the desired control signal corresponding to a computer hardware type which is being used for the host computer. The disk drive may use a signal transmitted from the host computer which represents a storage capacity of a disk used for the disk drive.

The present invention relates generally to a signal selecting circuit, provided in a disk drive, which outputs a predetermined signal to a host computer and the disk drive having such a signal selecting circuit, and more particularly to a signal selecting circuit which selectively outputs a predetermined signal to a host computer compatible with a plurality of computer hardware types and a disk drive having such a signal selecting circuit.
In a conventional computer system comprising a so-called floppy disk drive (abbreviated FDD hereinafter), an interface connected to the FDD, and a host computer connected to the interface, the host computer judges if it can access the FDD by means of detecting either a ready signal (abbreviated RDY signal hereinafter) or a disk change signal (abbreviated DC signal hereinafter). Hereupon, the term "RDY signal", as used herein, means a signal representing a floppy disk is loaded into the FDD and thus information can be recorded thereon and/or reproduced therefrom. On the other hand, the term "DC signal", as used herein, means a signal representing the floppy disk is ejected from the FDD. Whether the host computer detects the RDY signal or the DC signal is predetermined by a hardware type of the host computer. For example, an NEC PC9801 detects the RDY signal, and an IBM PC/AT detects the DC signal. Jumper lines or short bars (strap pins) are provided in the FDD, and consequently the FDD outputs the signal corresponding to the hardware type of the host computer thereto via the jumper line (or the short bar) and the interface.
A storage capacity of a floppy disk used in the FDD is also predetermined by the hardware used in the host computer. For example, a high density type (2HD) disk having a storage capacity of 1.6 MB and/or a normal density type (2DD) disk having a storage capacity of 1.0 MB, before the disk is formatted, is used for the host computer if it is the NEC PC9801. On the other hand, a high density type (2HD) disk having a storage capacity of 2.0 MB and/or a normal density type (2DD) disk having a storage capacity of 1.0 MB, before the disk is formatted, is used for the host computer if it is the IBM PC/AT. Incidentally, if the FDD uses the 2.0 MB disk, the FDD is set in a 2.0 mode. Likewise, if the FDD uses the 1.6 MB disk, the FDD is set in a 1.6 mode, and if the FDD uses the 1.0 MB disk, the FDD is set in a 1.0 mode. In addition, for example, a term "2.0/1.0MB" means that the FDD has two modes so that it can be selectively set in the 2.0 mode or the 1.0 mode.
However, a host computer compatible with a plurality of computer hardware types, such as the NEC PC9801 and the IBM PC/AT, has been increasingly required. The FDD which can only output the RDY signal or the DC signal cannot be used for such a host computer. Additionally, a "2.0/1.6/1.0 MB" FDD which can be selectively set in one of the three modes is necessary. Although the 2.0/1.6/1.0 MB FDD has been already on sale, the FDD which has a signal selecting circuit which selectively outputs the RDY signal or the DC signal has not been developed yet. In a 2.0/1.6/1.0 MB FDD, the 2HD mode and the 2DD mode are switched by detecting the presence of a discriminating hole in the disk. Moreover, the 2.0 mode and the 1.6 mode are switched based on an external signal suppled from the host computer. However, since the FDD can only output the RDY signal, it cannot communicate with a host computer using a IBM PC/AT type. On the other hand, a computer system in which the FDD simultaneously outputs both the RDY signal and the DC signal to the host computer and the host computer selects either signal has been proposed. However, this computer system also has a disadvantage in that, since it is generally necessary to provide an extra output terminal for the FDD so as to simultaneously output both RDY signal and DC signal, the FDD cannot be compatible with the conventional interface. As a result, the computer system is made expensive and has complicated hardware.

Signal selecting circuit which selectively outputs predetermined signal to host computer compatible with plurality of computer hardware types and disk drive having such signal selecting circuit


A digital camera system is composed of a digital camera and a lens unit detachable to this digital camera. The digital camera includes a first taking lens and a first CCD image sensor to convert subject light into image data. The first taking lens is surrounded by a detachable decorative ring. When a hook release button is pressed to detach the decorative ring, a camera-side mount appears. The lens unit is attached to this camera-side mount, and photographing can be performed with a second taking lens and a second CCD image sensor in the lens unit.

Digital cameras have been popular for years, which convert subject light through a taking lens into an electrical signal using an image sensor, and produce image data from this electrical signal, and then store the image data in such a recording medium as a memory card.
Since the image sensors are getting smaller and less expensive these days, some of the digital cameras are composed of a lens unit having the image sensor in a lens barrel, and a camera body to which the lens unit is attached detachably (see, Japanese Patent Laid-open publication No. 08-172561). In this type of digital camera, the electrical signal from the lens unit is converted to the image data at the camera body, and stored in the recording medium. This configuration allows for selective use of various lens units in a single digital camera.
It is also planed, on the other front, to provide the camera body with another pair of the taking lens and the image sensor, so that photography can be carried out without the lens unit. However, with this configuration, a lens unit mount appears on the camera body when the taking lens of the camera body is used, and the overall appearance of the digital camera is therefore spoiled.

Digital camera, digital camera system, and control program for digital camera system


A feed wheel (10) for tree trunks, with rows of drive teeth (30) protruding from extended supports (20) united with a peripheral surface (18) of the wheel. In order to make the spaces between the supports (20) more self-clearing, supports (20) that are neighbours extend mutually divergently throughout the complete sideways direction of the peripheral surface (18) (at an angle α).

A common problem with feed wheels for tree trunks is that bark and wood material from the trunks collects and becomes fixed to the periphery of the wheel in the spaces between the rows of drive teeth. The normally means that the depth of penetration of the drive teeth is reduced, such that the feed wheels acquire a poorer feed capacity, and this in turn means that the contact pressure of the feed wheels must be increased, leading to the wheels and tree trunks being subject to greater wear and damage. The accumulation of this material on the periphery of the rollers also causes their effective rolling diameter to vary in an unpredictable manner. If they are then used for the measurement of timber from processed tree trunks, as is common in, for example, single-grip harvesters, unreliable measurement results are obtained. It is thus strongly desired to prevent the accumulation of bark and wood material on the feed wheels.
Many attempts have been previously made to solve this problem. The teeth in one known type of feed wheel have such a large height that the accumulation of a certain amount of material on the wheels is permitted, and the self-cleaning properties of the tops of the teeth are relied on, in that the outermost layer of foreign material is relatively easily torn off from an underlying material layer. Such high teeth, however, can cause damage to the tree trunks. It is also known to make the supports spring-loaded against springs of, for example, a rubber material at the peripheral surface of the wheel, whereby the spring movements of the supports have a certain self-clearing influence on the collected bark and wood material. Such wheels, however, have relatively high maintenance costs due to the fact that the springs have a limited lifetime. The bases of the teeth in a further type of feed wheel are arranged elevated onto a plateau of the support above the periphery of the feed wheel. The plateau can be considered to be similar to a protective ring—such as that on a ski pole—that partially prevents the teeth sinking too deeply into the softer bark material, and in this way partially prevents the material falling down into the spaces between the supports.


A developer can express the logic offered by a Web service, or other network accessible service, using a standard programming language augmented with declarative annotations specifying preferences for exposing that logic as a Web service. At compile time, an enhanced compiler can analyze the annotated source file and automatically generate the mechanisms required to expose its functionality as a Web service or network accessible service.

There is a rapidly expanding industry emerging around Web services, a term loosely defined as the ability to share software as a service using network protocols. Web services and other network accessible software services require significant time. As the Web service infrastructure evolves, it is becoming increasingly complicated, requiring more time, skill, knowledge and ultimately money to create Web services. Consequently, the generation and deployment of Web services is increasingly tedious and unnecessarily complicated for the average developer. Currently, in addition to developing the software logic offered via the Web service, developers are also required to address a number of tedious and complex issues involving Web service generation and deployment. Examples of such issues include but are not limited to, security, reliable messaging and message pre/post processors (a.k.a. interceptors).
It is not uncommon for Web services to require several forms of security simultaneously. The creation and deployment of secure Web services and other software services made available over networks is a complex and time consuming process for both software developers and system managers.
Reliable messaging is often required for Web services, but yet is not inherent in the protocols typically used. Reliable messaging is implemented on both the client and the server and will generally support a callback path, used in the event of a failure. Thus, developers require considerable specialized knowledge and time to develop, test, and deploy reliable messaging schemes.
In many practical Web services implementations and system integrations, it is necessary to manipulate both incoming and outgoing network messages with message pre/post processors. These manipulations can include transformation of message headers and contents, logging, auditing, message redirection, and protocol conversions.

Systems and methods for creating network-based software services using source code annotations


The present invention relates to a sliding-frequency guiding filter which is capable of guiding soliton pulses to hundreds of different resonant frequencies by designing the device so that the filter can automatically offset its peak resonant frequency from the frequency of incoming soliton pulses. The sliding-frequency guiding filter comprises the followings: a coupler to tap some of incoming soliton signals; a wafer whose one half is coated by multilayered dielectric on both sides while leaving the other half uncoated, where the soliton signals tapped through the coupler is directed to coated half and uncoated half of the wafer, respectively; and, a thermoelectric cooler attached to the coated side of the wafer. The sliding-frequency guiding filter, made of the same design, can be applied throughout the soliton transmission line instead of the numerous filters all operating at different resonant frequencies. Accordingly, the sliding-frequency guiding filter can be practically used in ultralong distance soliton transmission system.

Soliton is a unique pulse which can be transmitted over long distance in its characteristic form by compensating the color dispersion effect of optic fiber through non-linear formation. The soliton has been used for ultralong distance transmission regardless of the color dispersion limitation, by employing an optical amplifier in the soliton transmission to compensate the loss caused by optic fiber. However, accumulation of amplified spontaneous emission ("ASE") noise, caused by the optical amplifiers which are distributed at periodic intervals to compensate the loss by optical fiber, could impose a significant limitation on the maximum transmission distance (which is known as "Gorden-Haus effect").
Recently, in order to avoid Gorden-Haus effect, a sliding-frequency guiding filter (hereinafter referred to as "SFG filter") has been suggested in the art (see: L. F. Mollenauer et al., Optics Lett., 17(22);1575-1577(1992)). In this filter, bandpass filters with slightly different resonant frequency are distributed along the optical amplifiers to prevent the ASE noise accumulation, grounded on a fact that: soliton, a non-linear wave, can be guided along the resonant frequency of the filter, while ASE noise cannot be guided. SFG filter can increase the soliton transmission capacity, by reducing the limitation of transmission distance caused by Gordon-Haus effect and by decreasing the interaction of soliton signals. Also, application of wavelength division multiplexing (WDM) system in the soliton control in a frequency domain allows more channels to be used, since the interaction with soliton signals from different channels can be reduced (see: U.S. Pat. No. 5,357,364).
However, the conventional SFG filter, though it can be realized easily by employing simple Fabry-Perot filter, has not been practically applied in the art because hundreds of these filters operating at slightly different resonant frequencies from each other are required in the long distance soliton transmission system. For example, for the transoceanic soliton transmission system applied to a distance of about 10,000 km over the Pacific ocean, approximately 300 SFG filters, under a consideration of an optical amplification distance of 30 to 50 km, are required and each filter should be designed, manufactured and implemented in a separate manner.
Accordingly, there are strong reasons for exploring and developing an improved SFG filter in order to solve the said problems in the art.

Sliding-frequency guiding filter for soliton transmission

Korea Advanced Institute of Science and Technology


The improved thermal head comprises heating elements which were provided with heating histories to previously change their resistance values by predetermined values; and a carbon-based protective layer which was formed after the heating elements were provided with the heating histories. The invention provides the thermal head in which corrosion and wear of the protective film, and the resistance variation of the heating elements due to thermal recording were significantly reduced, and which has a sufficient durability and stability with the passage of time to perform thermal recording of high-quality images in a consistent manner over an extended period of operation.

This invention relates to the art of thermal heads for thermal recording which are used in various types of printers, plotters, facsimile, recorders and the like as recording means.
Thermal materials comprising a thermal recording layer on a substrate of a film or the like are commonly used to record images produced in diagnosis by ultrasonic scanning (sonography).
This recording method, also referred to as thermal recording, eliminates the need for wet processing and offers several advantages including convenience in handling. Hence in recent years, the use of the thermal recording system is not limited to small-scale applications such as diagnosis by ultrasonic scanning and an extension to those areas of medical diagnoses such as CT, MRI and X-ray photography where large and high-quality images are required is under review.
As is well known, thermal recording involves the use of a thermal head having a heater (glaze), in which heating elements comprising heat-generating resistors and electrodes, used for heating the thermal recording layer of a thermal material to record an image are arranged in one direction (main scanning direction) and, with the glaze urged at small pressure against the thermal material (thermal recording layer), the two members are moved relative to each other in the auxiliary scanning direction perpendicular to the main scanning direction, and the heating elements of the respective pixels on the glaze are heated by energy application in accordance with image data to be recorded which were supplied from an image data supply source such as MRI or CT in order to heat the thermal recording layer of the thermal material and form color, thereby accomplishing image reproduction.
In thermal recording, density unevenness on the recorded image brings about a reduction in the quality of the finished image, which may cause an important problem in applications requiring high quality image recording. Especially the aforementioned medical application requires high quality images. Density unevenness also prevents image observation which will cause an important problem leading to an erroneous diagnosis. It is thus required that the thermal head is capable of recording high quality thermal images without density unevenness and having a reduced deterioration with the passage of time over an extended period of time.
Primary causes of the deterioration of the thermal head with the passage of time include variation in the properties of heating elements due to heat generation, and wear and corrosion (or wear due to corrosion) of the glaze.
A heating element of the thermal head usually comprises a heat-generating resistor and a pair of electrodes which energize the heat-generating resistor. The resistance value of the heating element varies with the time for heat generation and the energy for heat generation. Hence, the more the resistance value decreases, the more the amount of heat generation increases. The temperature of the heating element associated with the supplied energy for heat generation increases by the reduced resistance value, which brings about an increase in the image density.
The heating history which shows the total amount of heat generation, or the ratio of heat generation for the image recording performed is inherently different in each of the heating elements of the thermal head mounted in the thermal recording apparatus. Then, the amount of resistance variation is also different in each of the heating elements. Therefore, in the course of image recording, differences in the amount of resistance variation are produced among the respective heating elements, which gives rise to density unevenness on the recorded image in association with the differences.
The thermal head and the thermal material are moved relative to each other to perform recording, with the glaze thereon urged at small pressure against the thermal material. A protective film is formed on the surface of the glaze of the thermal head in order to protect the heating elements and other components. It is this protective film that contacts the thermal material during thermal recording and the heat-generating resistors heat the thermal material through this protective film so as to perform thermal recording.
The protective film is usually made of wear-resistant ceramics; however, during thermal recording, the surface of the protective film is heated and kept in sliding contact with the thermal material, so it will gradually wear and deteriorate upon repeated recording.
If the wear of the protective film progresses, density unevenness will occur on the thermal image or a desired protective strength can not be maintained and, hence, the ability of the film to protect the heaters is impaired to such an extent that the intended image recording is no longer possible (the head has lost its function).
Particularly in the applications such as the aforementioned medical use which require multiple gradation images of high quality, the trend is toward adopting thermal films with highly rigid substrates such as polyester films and also increasing the setting values of recording temperature and of the pressure at which the thermal head is urged against the thermal material. Under these circumstances, as compared with the conventional thermal recording, a greater force and more heat are exerted on the protective film of the thermal head, making wear and corrosion (or wear due to corrosion) more likely to progress.
With a view to preventing the wear of the protective film on the thermal head so as to improve its durability, a number of techniques have been considered in order to improve the performance of the protective film. Among others, a carbon-based protective film (hereinafter referred to as a carbon protective layer) is known as a protective film excellent in resistance to wear and corrosion.
Thus, Examined Published Japanese Patent Application (KOKOKU) No. 61-53955 discloses a thermal head excellent in wear resistance and response obtained by forming a very thin carbon protective layer having a Vickers hardness of 4500 kg/mm.sup.2 or more as the protective film of the thermal head.
Moreover, Unexamined Published Japanese Patent Application (KOKAI) No. 7-132628 discloses a thermal head which has a dual protective film comprising a lower silicon-based compound layer and an overlying diamond-like carbon layer, whereby the potential wear and breakage of the protective film are significantly reduced to ensure that high-quality image can be recorded over an extended period of time.
These carbon protective layers have a very high hardness and chemical stability, hence they exhibit sufficiently excellent properties to prevent wear and corrosion which may be caused by the sliding contact with thermal materials.
However, the carbon protective layers are not enough to resolve the aforementioned recording unevenness due to the resistance variation of the heating elements with the passage of time. It is also important the carbon protective layers have excellent properties in order to record high quality thermal images having a reduced deterioration with the passage of time over an extended period of time.


A cotton packager for mounting on a chassis of a cotton harvester interchangeably with a cotton basket, allowing for pivotal movement of the packager between an operating position and a tilted unloading position. The packager includes a pivotable fluid cylinder which attaches to the chassis in place of a fixed front lift cylinder of the basket, and a rear pivot which attaches to the chassis in place of a rear lift cylinder. As a result, a rear open end of the packager can be lowered closer to a surface onto which cotton is to be unloaded, and drivers for an unloader door of the packager can be subjected to less damaging loads.

Cotton packagers, also commonly referred to as cotton module builders, and cotton receiving baskets, are structures commonly utilized on cotton harvesters for receiving and holding harvested cotton. A cotton packager will typically compact and package the cotton in a unitary body which will retain its shape once removed from the packager so as to be transportable in that form to a gin for processing or other location. A cotton basket, in contrast, may compact the cotton to increase the capacity of the basket, but when unloaded, typically dispenses the cotton in a less, or not at all, cohesive form. As another difference, it is typically desirable for a cotton packager to be tilted while remaining at the chassis level for unloading a completed unitary cotton package or module therefrom through a rear opening. The module is unloaded onto a ramp or other structure for conveying the package or module intact onto the ground or another surface lower than a floor of the packager. Therefore, the packager is typically supported and connected to the chassis at the front by at least one fluid cylinder and at the rear by a hinge or pivot. A cotton basket, on the other hand, is typically lifted in a horizontal orientation a substantial distance above the chassis using fluid cylinders located front and rear, and then the cotton unloaded therefrom either by tilting the basket in the elevated position, or by conveying the cotton through an open side door, into another basket or a module builder disposed beside the harvester or onto the ground or another surface. The basket is thus supported and connected to the chassis by two or more fluid cylinders, front and rear.
It is anticipated that some cotton producers will continue to utilize cotton baskets, which is an older technology, for economic reasons, preferences, and a possible lack of capability of transporting and handling cotton modules. Cotton packagers, which are newer, are expected to increase in popularity. However, presently, manufacturers of cotton harvesters desire to have the capability to produce harvesters having baskets or packagers. Cotton harvesters are produced on a relatively low volume basis. Therefore, for reasons including economic reasons and versatility of manufacturing, it would be desirable to use the same chassis configuration interchangeably with either a cotton packager or a basket.
It would also be advantageous when unloading, for the tilting movement of the packager to exert forces against an unloader door of the packager for urging it toward an unfolded unloading position, while reducing or minimizing occurrences of applying possibly damaging loads against components of the door, particularly extended fluid cylinders for unfolding the door.
It would also be desirable when the packager is tilted for unloading, for the rear end of the floor to be as closer to the ground or other surface below onto which the cotton module is to be unloaded. This is because the closer the rear end of the floor is to the ground when in the tilted unloading position, the shorter the doors need to be when unfolded to reach the ground for unloading the cotton module. This will also be an advantage in that the doors when folded in the closed position are below the height that would require their removal for shipping or transport.
Still further, compacting cotton into a unitary compacted module requires stronger and heavier apparatus compared to the apparatus for compacting cotton to the extent required in a basket. However, when the cotton is unloaded from the basket, it is moved out onto the unloading door and is cantilevered out from the lift cylinders. This produces combined torsion and bending loads in the lift cylinders, which requires them to be larger with larger rod ends and cylinder walls. By tilting the heavier structure of the packager, the loading is a less severe shear or direct compressive load.
Thus, what is sought is a cotton packager and unloader door configuration which is substantially interchangeable with a cotton basket for mounting on a chassis of a cotton harvester, and which provides enhanced unloading operability, and overcomes one or more of the problems or shortcomings set forth above.

Cotton packager and unloader door arrangement for mounting on a chassis of a cotton harvester