Abstract: A single integrated source of infrared and ultraviolet energy with minimal visible radiation therein. The invention (10) includes a first source of infrared and visible radiation (12) and a second source of ultraviolet and visible radiation (14). In a specific implementation, visible radiation from the infrared source (12) is eliminated by a filter (20) comprising a germanium substrate coated with a thin film multilayer stack. The filtered infrared beam and the ultraviolet beam are combined by a set of mirrors. A cold first mirror (30) directs the ultraviolet energy to a cold second mirror (22) which then transmits infrared energy and reflects ultraviolet energy. The visible radiation from the ultraviolet source is eliminated by transmission through the first cold mirror. The first and second mirrors provide a composite output beam which is collimated by a third mirror (36) and output as a single beam. For safety, a shutter (24) is provided in front of the ultraviolet source (14).

Abstract: An adaptive dynamic range control circuit architecture is disclosed that enables an IR-FPA (10) to achieve a higher dynamic range. The circuit architecture significantly reduces a resolution required for an analog-to-digital converter (ADC 24) that converts the analog output signals of the IR-FPA to a digital representation. In a preferred embodiment of this invention a column CTIA readout integrated circuit architecture is used in conjunction with the adaptive feedback circuitry of this invention to provide pedestal suppression on a per-pixel basis for the IR-FPA. The use of the circuitry of this invention modifies the conventional column CTIA amplifier configuration to a configuration having an auto-zeroed charge ratioed gain stage (50). One advantage to this technique is that by suppressing the charge pedestal, the usable signal output from the IR-FPA can be brought off-chip to the readout integrated circuit at a much higher gain.

Abstract: An improved multiquantum well superlattice photodetector (10) for detecting long wavelength infrared radiation. Electron transport in a first excited energy state is enhanced in barrier layers (20) of the superlattice (16) by lowering the potential energy barriers of the barrier layers (20) to a predetermined level below the first excited energy state. The tunneling component of the dark current in a multiquantum well photodetector (10) may be substantially eliminated by placing a blocking layer (22) at one end of the superlattice (16). The thickness of the blocking layer (22) is also substantially greater than that of the barrier layers (20) of the superlattice (16) to prevent charge carriers which tunnel through the superlattice (16) from reaching the collector contact. The blocking layer (22) also has a potential energy barrier having a height at a level higher than that of the barrier layers (20) of the superlattice (16).

Abstract: Two dichroic mirrors (26, 30) and a dichroic beamsplitter (36) are introduced into the conventional Michelson Fourier transform spectrometer to accommodate two spectral bands. A conventional Michelson Fourier transform spectrometer (FTS) uses two mirrors (20, 22), one fixed (20) and the other moving (22). The present invention replaces each of the two mirrors (20, 22) with a pair of mirrors, one of which is a dichroic mirror (26, 30). The present invention involves inserting the first dichroic mirror (26) fixed in position between the beamsplitter (12) and the first plane mirror (20) and inserting a second dichroic minor (30), which can be moved in a direction normal to the plane surface, between the beamsplitter (12) and the second plane mirror (22). The first dichroic mirror (26) and second dichroic mirror (30) transmit long wavelength radiation and reflect short wavelength radiation.

Abstract: A radiation detector (1) unit cell (10) includes an n-p+ LWIR photodiode that is vertically integrated with a p+-n MWIR photodiode in a n-p+-n structure. Electrical contact is made separately to each of these layers in order to simultaneously detect both the LWIR and MWIR bands. The electrical contact is made via indium bump interconnections (23, 25, 27) enabling the unit cell to be subsequently hybridized with a topside mounted electronic readout integrated circuit (30). The n-p+-n structure in a given pixel of an array of radiation detector pixels is electrically isolated from all neighboring pixels by a trench (28) that is etched into an underlying substrate (12). To compensate for a reduction in the optically sensitive area due to the placement of the electrical contacts and the presence of the pixel isolation trench, a microlens (34) may be provided within, upon, or adjacent to the backside, radiation receiving surface of the substrate in registration with the unit cell.

Abstract: A method and apparatus are provided to eliminate spectral interference variation contained in optical signals transmitted to an optical detector or array of optical detectors, the spectral variation deriving from the presence of a layer deposited on the detector having a different index of refraction from the detector. The practice of the invention involves optically coupling a plate to the layer using an adhesive, with the proviso that the plate, layer and adhesive have substantially the same index of refraction so that a composite thickness with the refractive index of the layer is formed. Given the inverse relationship between thickness of the layer and period of the interference in wavenumber, the effective increase in thickness of the layer yields a corresponding decrease in the period.

Abstract: A method is disclosed for grinding and polishing a substrate (20). An abrasive slurry (26) is applied to the surface (22) of the substrate (20). A lap (28) is moved across, and in engagement with, the surface of the substrate (20) in the medium of the abrasive slurry (26). Ultrasonic energy is mechanically applied to the surface (24) of the substrate such that half wave resonance occurs substantially at the surface (22) of the substrate (20). In this manner, a thickness of material is removed at an enhanced rate from the surface (22) of the substrate (20).

Abstract: An optical beam homogenizer includes an entrance pupil through which a non-uniform optical beam propagates. A first optical component having plural flat surfaces receives the input beam. The flat surfaces of the first optical component effectively segment the entrance pupil by dividing the input beam into plural beamlets, one beamlet for each pupil segment and flat surface. The beamlets are received by a second optical component which also has multiple flat surfaces, each flat surface receiving a beamlet. The second optical component directs the beamlets toward each other such that they overlap at an exit pupil of the system. The second optical component also focuses the beamlets such that an image of each entrance pupil segment is formed at the exit pupil. The images of the individual entrance pupil segments are superimposed upon each other at the exit pupil to form a uniform optical output beam.

Abstract: Optical immersion of a semiconductor photodetector to a plano-convex lens is obtained with a spring arranged to urge the photodetector to abut the lens. To facilitate alignment of the detector and the lens, the spring defines, in one embodiment, a convex surface to abut a substrate that carries the detector. In another embodiment, alignment is facilitated by a ball positioned between the spring and the substrate. Optical noise is reduced by a dielectric between the detector and the lens, with the dielectric thickness less than 1/10 of any radiation wavelength of interest.

Abstract: An in-situe chemical gas or fluid analyzer for vehicles, industrial, environmental and process control applications. As applied to a vehicle (1) having an internal combustion engine, the analyzer includes: (i) a source of electromagnetic radiation (14, 16); and (ii) a sampling cell (12) which collects emission gases of interest and which is capable of withstanding hostile environments while preserving a "clear" optical path between the sensor sampling cell and the source of radiation. The analyzer further includes: (iii) a solid state sensor (24, 26, 28, 30, 32 ) of monolithic construction which selectively detects electromagnetic radiation that is absorbed or emitted by one or more chemical species of interest, that compensates for temporal and spatial variations in illumination level provided by the source, and that provides an electrical signal output, in either analog or digital format, that is related to the measured concentrations.

Abstract: An optical spectrometer system that includes an optical element having a two-dimensional, curved, reflective, low emissivity slit body, or surround, in which an imaging slit is formed. The optical spectrometer system includes a detector, such as an infrared detector, for example, disposed in a cavity at a focal plane thereof, an optical system in the cavity for focusing radiation onto the detector, and an entrance pupil disposed in the cavity. The curved slit body effectively and substantially eliminates out-of-field radiation from impinging upon the slit body, and its low emissivity greatly reduces self-emission from the slit body. The reflective slit body is a low emissivity element that images the detector back upon itself and passes background energy that falls within a cone defined by the entrance pupil. By using the two-dimensional curved slit body, a relatively small detector dewar or focal plane cooler may be employed in the optical spectrometer system to cool the detector.

Abstract: A deformable mirror device which includes a deformable face plate, a backing plate spaced from the deformable face plate, and at least one axially movable actuator which extends between the face plate and the backing plate. The actuator is fixed adjacent a first end to the backing plate and adjacent a second end, which is opposed to the first end, to the deformable face plate in a kinematic joint by reason of which no forces are transmitted in an ideal mating of the two components. At least a portion of the actuator may be disconnected and removed from the first end, and replaced by another actuator. The kinematic joint includes a high temperature, permanent, joint and a pair of spaced apart, low temperature, temporary joints. The high temperature joint is defined by a ball segment affixed to the deformable face plate as by frit. One of the low temperature joints is defined by an epoxy connection between the actuator at its first end and the backing plate.

Abstract: A method and apparatus for protecting metal bumped chips during processing and for providing mechanical support to interconnected chips. A protective adhesive stop is affixed to a metal bumped chip so that the height of the stop is at least as high as the metal bump. The stop protects the metal bump during routine handling. When the chip is interconnected to another bumped chip by cold welding their respective metal bumps, the stop contacts the face of the second chip and provides mechanical support. The stop is preferably a thermoplastic that is heated to adhere it to the second chip. The addition of the protective stop facilitates automated processing of metal bumped chips, and provides stronger, faster, and lower power chips.

Abstract: A rugate filter (10) having suppressed harmonics includes a layer (18) of material disposed on a surface (14) of an optical substrate (12) having an index of refraction versus thickness profile that is the superposition of a principle sinusoid and a secondary sinusoid. The secondary sinusoid being superimposed about -90 degrees out of phase with the principle sinusoid.

Abstract: An apparatus (10) for characterizing an optic (14) includes a light source (20) adapted to direct a light beam into an optic (14) such that total internal reflection of the light beam occurs. A light detector (38) is disposed to detect light exiting the optic (14). The apparatus (10) also includes a reservoir for holding and dispensing an index of refraction matching fluid between the optic (14) and the light detector (38) to enable light to exit the optic (14) toward the light detector (38) such that the material of the optic (14) is characterized rather than merely the surface thereof.

Abstract: An apparatus (10) for correcting for changes in the charge transfer efficiency of a charge coupled device (12) includes a light source (38) for providing synthetic reference images to a preselected portion (26) of the image array (16) of the charge coupled device (12). The initial synthetic reference image is compared with subsequent synthetic references images to determine the changes in the charge transfer efficiency of the charge coupled device (12). The changes are used to correct images form the image array (16).

Abstract: A transparent chuck is used to force a semiconductor wafer to take a prescribed shape. Any gap which is formed between the chuck and the wafer can be imaged through the transparent chuck. An interferometer is used to illuminate the gap with a narrow band illumination to create interference fringes in the gap. The fringes can be electronically imaged to create a digital input to a computer. Merit functions corresponding to the total volume of fringes in the gap or to the summation of nearest neighbor slopes of such fringes provide a measure of the thickness of such gap.

Abstract: A method for fabricating a two layer epitaxial structure by a liquid phase epitaxy (LPE) process, the structure being comprised of a Group II-VI semiconductor material. The method includes the steps of providing an LPE growth chamber that contains a molten Group II-VI semiconductor material 24, the molten Group II-VI semiconductor material having a first temperature (T.sub.1); growing, at the first temperature, a base layer (22) from the molten Group II-VI semiconductor material, the base layer being grown to have a first bandgap energy; employing a shutter mechanism (30) to isolate the base layer from the molten Group II-VI semiconductor material without removing the base layer from the growth chamber; reducing the first temperature of the molten Group II-VI semiconductor material to a second temperature (T.sub.

Abstract: A method is disclosed for specifying the ratios of three or more coating materials so as to specify and control the index of refraction profile, stress profile, and/or the coefficient of thermal expansion of an optical coating. Also disclosed is a coating deposition chamber (10) that includes an in-situ stress monitor (12) for measuring a stress within a coating (20). The output of the monitor is compared to predicted profiles and appropriate corrections are made to chamber constants. In a presently preferred embodiment, the in-situ stress monitor includes an interferometer having a sample beam (28a) that reflects from a surface of a substrate (22) upon which the coating is being formed. A change in the optical path length is indicative of a direction and magnitude of a substrate flexure due to stress induced in the coating. Responsive to the determined stress, coating chamber operating parameters are varied, if required, to maintain the stress at a desired magnitude and type.

Abstract: A focal plane array (10) of radiation detectors (10b) has all features inclined with respect to an illuminating beam of radiation. That is, all features that would be orthogonally disposed with respect to an incoming wavefront are instead inclined to the incoming wavefront, an arrangement referred to as compound tipping. The disclosed embodiments of the invention create a compound tipping of the focal plane array such that there are no features of the array, such as mesa edges and sidewalls, that lie in the plane of the incoming wavefront. As a result, only a small amount of scattered light is observed, and the optical signature is significantly reduced. The invention substantially eliminates the optical signature by simultaneously tipping the focal plane features (optically and/or mechanically) in both major array axes, without degrading the imaging performance of the detective assembly.