Abstract: A method of visually aligning an optical instrument (10, 26, 28) that simultaneously operates at two different wavelengths where the first wavelength is in the visible photopic electromagnetic spectral region and the second wavelength is outside the visible photopic electromagnetic spectral region. The method for visually aligning the optical instrument (10, 26, 28) includes employing an aiming reticle (12) located at the eyepiece (18) of the optical instrument (10, 26, 28), this first reticle (12) having a reticle pattern (64) which is in focus when viewed through the eyepiece (18), and a plate (44) with a second reticle pattern (62) on one side. The second reticle pattern (62) is positioned in the optical system such that when this second reticle pattern (62) is illuminated (58) with light of the first wavelength, then this second reticle pattern (62) will be in focus and superimposed on the first reticle pattern (64) when viewed through the eyepiece (18).

Abstract: A three terminal solid-state ionizing radiation detector (10) includes a first layer (18) of a substantially intrinsic Group II-VI compound semiconductor material, such as CdZnTe. The first layer is responsive to incident ionizing radiation for generating electron-hole pairs. The detector further includes a second layer (24) of Group II-VI compound semiconductor material and a third layer (20) of Group II-VI compound semiconductor material that is interposed between first surfaces of the first layer and the second layer. The third layer functions as a grid layer. A first electrical contact (12, 17) is coupled to a second surface of the first layer, a second electrical contact (29, 30) is coupled to a second surface of the second layer, and a third electrical contact (22) is coupled to the third layer for connecting the detector to an external circuit that establishes an electric field across the detector.

Abstract: A differential spectrometry system detects very narrow-band spectral features, while providing much higher optical transmittance and signal-to-noise ratios than prior optical-filter-based spectrometer systems. A plurality of light detectors (10a, 10b) detect light that falls within respective wide wavebands. The wide wavebands have overlapping and non-overlapping portions, one of which is the desired narrow waveband. The detector outputs are operated upon to produce an output signal (22) which includes substantially only the desired narrow waveband. In the preferred embodiment, the light detectors (10a, 10b) are implemented with a pair of optical detectors (30a, 30b) and respective optical interference filters (24a, 24b). The filters have substantially identical cut-off wavelengths (.lambda..sub.2) and cut-on wavelengths that are shifted by .DELTA..lambda. with respect to each other (.lambda..sub.1 and (.lambda..sub.1 +.DELTA..lambda.), respectively).

Abstract: Gamma ray detectors (20, 130) are provided with a detector layer (30) that is formed of Hg.sub.x Cd.sub.1-x-y Zn.sub.y Te, wherein 0<x<0.05 and 0.ltoreq.y<0.5. The Hg percentage in the group II sublattice of this detector layer is limited to replace Cd vacancies. These Cd vacancies are native point defects which degrade the resolution of gamma ray detectors because they facilitate early electron-hole recombination and time delays of current carriers.

Abstract: A system and technique for measuring the thickness of an optical element. A first energy signal of a first phase is transmitted into the element. The first signal reflects off of a distal surface of the element and is detected as a return signal. The phase of the reflected signal is compared to the phase of the transmitted signal and the frequency varied to extract a third signal representing a desired phase difference therebetween. Corresponding frequency data are processed to determine the thickness of the element at the point of transmission of the first signal.

Abstract: An array (10) of diode lasers (12) is comprised of a substrate (22) having a plurality of electrically conductive surface areas (24, 24a, 24b, 24c) and a plurality of diode laser subassemblies (20) individual ones of which are conductively coupled to one of the plurality of surface areas (24a). Each of the diode laser subassemblies includes a diode laser (12), preferably a SE-DFB diode laser, that is conductively coupled to and mounted upon a first surface of an electrically conductive body or submount (14). The submount has a second opposite surface that is electrically coupled to and mounted upon one of the electrically conductive areas, preferably with a layer (25) of compliant, deformable material such as indium foil or an indium alloy. The individual diode lasers are preferably electrically connected in a series, voltage adding configuration.

Abstract: A hinge (20) includes two hinge plates (22, 24) and a connecting hinge pin (32). A coil spring (48) supported on a bushing (44) overlies the hinge pin (32), which is free to move along its longitudinal axis (30). A cam follower (42) on the hinge pin (32) engages a cam (32) mounted to one of the hinge plates (22), so that the hinge pin (32) slides longitudinally as the hinge plates (22, 24) pivot relative to each other about the hinge pin (32). As the hinge pin (32) slides longitudinally, it axially compresses or decompresses the spring (48). The cam (32) is oriented such that pivoting of the hinge plates (22, 24) in either direction from an open position compresses the spring (48), providing a restoring force which tends to retain the hinge plates (22, 24) in the open position.

Abstract: A Compressing Capacitively Coupled Transimpedance Amplifier (CCTIA) circuit (10) has an amplifier (AMP) with a variable capacitance feedback network (C1, C2, C3, Q1, Q2) coupled between a current receiving amplifier input node and an amplifier output node. The output node outputs a voltage in response to a received current. The variable capacitance feedback network is responsive to the output voltage for establishing one of a plurality of different transimpedance values for the circuit such that the circuit exhibits a greatest transimpedance value for an input current having a magnitude below a threshold magnitude, and a lesser transimpedance value for an input current having a magnitude equal to or above the threshold magnitude.

Abstract: A microbolometer detector element includes an optically absorptive material structure that absorbs a portion of incident radiation, and has a plurality of openings that diffract other portions of the incident radiation. The absorptive structure has an electrical resistivity that varies as a function of its temperature. An optical radiation director re-directs the diffracted optical radiation back to the absorptive structure. The distance between the radiation director and the absorptive structure is tuned so that, for a predetermined design wavelength, optical radiation that is re-directed back to the absorptive structure constructively interferes with incident optical radiation that is not reflected by the absorptive structure. The constructive interference causes the absorptive structure to absorb substantially more optical radiation at the design wavelength than at other wavelengths.

Abstract: A lower vacuum housing (34) of a sensor dewar (26) is fabricated in a single brazing operation from ceramic and metallic components. The components are assembled with ceramic-to-metal interfaces and metal-to-metal interfaces. Brazing is accomplished by active brazing of the ceramic-to-metal interfaces and non-active brazing of the metal-to-metal interfaces. Specific combinations of active braze alloys and non-active braze alloys are provided for various combinations of dewar materials.

Abstract: A feedthrough (34) is formed of a feedthrough plate (44) having at least one bore (46) therethrough and a feedthrough pin (48) hermetically sealed into the bore (46). The feedthrough pin (48) includes an elongated pin (50) having an axis of elongation (52), a recess (54) in at least one end of the pin (50), the recess (54) extending parallel to the axis of elongation (52), and a gold coating (56) within the recess (54). There are preferably a plurality of bores (46) in the feedthrough plate (48) and a corresponding plurality of the feedthrough pins (48). The gold coatings (56) at the ends of the feedthrough pins (48) are desirably lapped to ensure coplanarity and a smooth surface finish especially suited for wire bonding or tab bonding.

Abstract: An optical radar system includes a laser diode and an external cavity formed by a partial reflector for reflecting a first portion of the laser beam back into the diode. A second portion of the beam is passed out of the external cavity for backscatter thereof from a target back into the diode. The emission thereby has a beat frequency related to the velocity of the target. A frequency chirp is introduced by mechanically oscillating the partial reflector longitudinally resulting in a modulation frequency in the emission corresponding to the range of the target. A photodetector and processor are used to determine the velocity and range.

Abstract: A microelectronic device is fabricated by furnishing a first substrate (40) having a silicon etchable layer (42), a silicon dioxide etch-stop layer (44) overlying the silicon layer (42), and a single-crystal silicon wafer (46) overlying the etch-stop layer (44), the wafer (46) having a front surface (52) not contacting the etch stop layer (44). A microelectronic circuit element (50) is formed in the single-crystal silicon wafer (46). The method further includes attaching the front surface (52) of the single-crystal silicon wafer (46) to a second substrate (58), and etching away the silicon layer (42) of the first substrate (40) down to the etch-stop layer (44). The second substrate (58) may also have a microelectronic circuit element (58') therein that can be electrically interconnected to the microelectronic circuit element (50).

Abstract: A light source radiates an infrared beam that passes through a chopper, a calibration cell and the exhaust plume of a motor vehicle passing in front of the source. A photosensor assembly includes a plurality of photodetectors which are spaced closely adjacent to each other and simultaneously sense the beam after it propagates through the plume. An optical beam homogenizer or integrator disposed between the plume and the photosensor unit causes the light incident on the photodetectors to have uniform intensity. The photodetectors are sensitive to different wavelengths corresponding to spectral absorption peaks of constituents of the composition of the plume, including carbon monoxide (CO), carbon dioxide (CO.sub.2), hydrocarbon (HC), water vapor (H.sub.2 O) and nitric oxide (NO). A computer computes the composition of the plume as the percentages of the constituents based on the sensed transmittances of the respective wavelengths through the plume.

Abstract: An improved system for acquiring and tracking an optical beam. In the illustrative application, the inventive system is used to facilitate optical communication between two satellites and provides an improved technique for acquiring and tracking two optical beams. The illustrative embodiment includes an optical transmitter (26) mounted on the first satellite for transmitting a first optical beam. The beam is scanned over a predetermined area in a predetermined pattern at a predetermined rate. When the beam is detected at the second satellite, the receiver at the second satellite generates a signal indicative of the time at which the beam is detected. This signal is used to modulate a second beam transmitted by the second satellite. The second beam is scanned over a predetermined area in a predetermined pattern at a predetermined rate.

Abstract: A thinned backside illuminated charge-coupled imaging device has improved quantum efficiency by providing a sharp ion implant distribution profile (20) disposed at the rear surface (22) of the device. The sharp ion implant distribution profile (20) is formed using ion implantation at a beam energy potential of between 100-150 keV, which forms an electric field beneath the surface of the device. The ion distribution profile (20) is brought to the surface (22) of the device by removing silicon (18) from the rear surface (22), using a polishing technique wherein the device is lapped with colloidal silica abrasive to controllably remove silicon down to the level of the ion implantation profile (20).

Abstract: An array of dual-band HgCdTe radiation detectors (10) wherein individual detectors include a first layer (14) having a first type of electrical conductivity and a bandgap selected for absorbing radiation within a first spectral band. The radiation detectors also each include a second layer (16) overlying the first layer. The second layer has a second type of electrical conductivity that is opposite the first type of electrical conductivity. Each radiation detector further includes a third layer (18) overlying the second layer, the third layer having the first type of electrical conductivity and a bandgap selected for absorbing radiation within a second spectral band. The first and second spectral bands are selected from SWIR, MWIR, LWIR, and VLWIR. The first, second and third layers are contained within at least one mesa structure (10a, 10b) that supports on a top surface thereof a first electrical contact (24) to the first layer and a second electrical contact (28) to the third layer.

Abstract: A system for receiving electromagnetic energy with reduced signal aliasing in the cross-scan direction. The system is adapted to be mounted on a spacecraft or an aircraft for movement over a surface in the cross-scan direction and has a sensor for receiving electromagnetic energy. The invention (10) includes an arrangement for directing energy to the sensor which has an astigmatic blur in the cross-scan direction which is effective to reduce aliasing of a signal transmitted or received by the system in the cross-scan direction of movement. In the illustrative embodiment, the invention (10) includes an array (20) of radiometric detectors. A reflective optical arrangement directs energy from a surface to the detector array. The optical arrangement includes at least one mirror (16) which has a small controlled cylindrical surface perturbation which introduces an astigmatic blur into the received image which reduces aliasing of the signal in the cross-scan direction.

Abstract: A method and apparatus for reducing electromagnetic scatter is disclosed in which a step discontinuity is formed at the interface between two media having different surface impedances.

Abstract: A photovoltaic diode unit cell (10) includes a first layer (14) having a first type of electrical conductivity and a second layer (16) of Group II-VI material having a second type of electrical conductivity that differs from the first type. The first layer and the second layer are coupled together so as to form a photovoltaic junction (15) therebetween. The photovoltaic junction is coupled via electrical interconnects (18, 20, 22) to a readout 24 and collects first charge carriers resulting from an absorption of IR radiation within the layer 14. The junction also collects second charge carriers resulting from the absorption of visible light in a region of highly graded crystal potential formed, in a Liquid Phase Epitaxy (LPE)-grown embodiment of this invention, at an interface of a substrate and the first layer. The substrate is subsequently removed, preferably by a mechanical operation followed by a wet chemical etch, to expose the region of highly graded crystal potential.