Abstract: A reflectance-outcoupled laser resonator 10 with an improved electro-optical Q-switch 13, 18,19, 21 is disclosed which is alignment stable. The laser performance is insensitive to angular movements of the resonator elements. This resonator requires fewer optical components and lower total cost than other resonators which are designed to perform similar functions. The invention includes a laser medium 12, two prisms 13, 21, a polarizer 18, an electro-optic crystal 19, and an alignment wedge 20. A polarization preserving folding prism 13 allows great flexibility in resonator design by passing any arbitrary polarization state without change. A double end-reflector prism 21 serves as both cavity end reflectors of the resonator and also serves as a component of the Q-switch 13, 18, 19, 21.

Abstract: Apparatus is disclosed for protecting delicate sensor optics from the damaging effects of unwanted powerful laser radiation. A thin-film reflective pellicle 14 is placed in the light path of a sensor telescope. Incident light 10 is focused by some combination of optical elements 12 onto the reflective surface 28 of the laser hazard protector 14. The reflected light 10 is then imaged by further optics 16 onto a detector array 18. Should a signal too strong for the detector enter the sensor aperture with the incident light 10, the focused power at the surface of the pellicle 28 will ablate the carbon and metallic film, burning a hole in the pellicle, and the high-power light 11 will be deflected from the detector array and be absorbed instead by the beam dump 20. A power meter within the beam dump determines when the laser threat has stopped and signals the turning mechanisms 15a and 15b to turn the pellicle reflector to a fresh position at which point normal sensor operations may resume.

Abstract: A new technique, and output encoding circuits using that technique, are disclosed for interfacing between a semiconductor IR detector 23 and associated output electronics 24, 25, 26 which technique and circuits transfer a charge packet onto a sense capacitor 22 that previously stored a reset level signal. The resulting stepped signal change, or delta, in the voltage present on that capacitor 22 is employed as the output signal.

Abstract: An enhanced quadrature notch filter which is capable of rejecting an undesired signal component of an input signal, generally comprising a quadrature phase splitter for producing first and second reference signals which have substantially the same frequency as the undesired signal component but which are 90.degree. out of phase with each other, a pair of amplitude control loops for adding the first and second reference signals to the input signal in amplitudes which will cancel the undesired signal component, and a phase locked loop circuit for maintaining a predetermined phase relationship between the undesired signal component and one of the first and second reference signals.

Abstract: Method and apparatus for testing photodiode arrays using an electron beam. The diodes are charged at successive intervals over the RC time constant curve to develop successively increasing voltages at the ends of succeeding time intervals. Diode voltage and current are measured at the end of each interval and the resulting data are used to develop a current-voltage characteristic for each diode.

Abstract: A transresistance amplifier particularly adapted for use in a radiation detection system. The amplifier includes a feedback gain stage with a switched capacitor load. The amplifier is arranged to provide an average detector voltage approximating zero thus substantially reducing detector noise and also providing a low equivalent input impedance for increasing injection efficiency. A switched capacitor output load is also provided which allows the total transresistance to be determined by simply selecting an appropriate capacitance value.

Abstract: An adaptive laser system (10) includes an adaptable laser (12), a waveform sensor (14), an amplitude distribution sensor (16), and a processor (18) for converting data from the sensors into commands for controlling the waveform of a laser beam. Amplitude distribution data is to weight waveform data as the processor determines actuator commands for deforming the laser's main mirror (22). Amplitude weighting permits more accurate determination of the waveform sensor-to-actuator-coupling matrix and more precise optimization of the on-axis intensity of the laser beam across the laser aperture.

Abstract: An improved driver circuit for an integrated gate circuit using Gallium Arsenide direct coupled FET logic. The push-pull driver circuit generally comprises an enhancement mode voltage follower transistor for driving a load during a first logic transition, and an enhancement mode pull-down transistor for driving this load during a second logic transition. Since only one of these transistors are conductive during these logic transitions (i.e., LO to HI, and HI to LO), little or no static current flows through these transistor means during steady state conditions. Thus, particularly for large capacitive loads, the driver circuit will be considerably faster than conventional DCFL technology, while not causing a significant increase in the power consumed by the push-pull driver circuit.

Abstract: An apparatus for mounting a device used for detecting infrared signals is disclosed. The apparatus includes a housing and an expander upon which the device is mounted. An insulating material comprising polymeric foam is disposed between the expander and the housing which allows the apparatus to be cooled without requiring evacuation of the apparatus.

Abstract: An imaging system incorporating a scanned array of infrared detectors for a presentation of scene data on a display includes gain normalization circuitry coupled to individual ones of the detectors of the detector array. The normalization circuitry is structured as a feedback loop introducing equality between the magnitude of an average value of a detector signal and a reference signal. The imaging system comprises a set of channels connecting with respective ones of the detectors, each channel having adaptive gain control circuitry. A common value of the reference signal is applied to each channel for uniformity in a displayed image. The averaging time is several times greater than the duration of a single scan in the scanning of the detector array so that the display is relatively free of nonuniformities associated with differing responsivities of the detectors to infrared radiation.

Abstract: Target or scene tracking capability is provided by a dual mode video tracker which includes both a correlation processor (30) and a centroid processor (32) for processing incoming video signals representing the target scene (20) and for generating tracking error signals over an entire video frame or a selected mode thereof. A microcomputer (26) controls the operation of the correlation and centroid processors, as well as a preprocessor (28) which preconditions the incoming video signals. The tracker operates in any of several modes in which the correlation and centroid processors function either independently or cooperatively with each other. The correlation processor generates a reference map in pixel format which is used to produce azimuth and elevation optimal weighting values for each pixel in the field-of-view. The reference map is recursively updated. The track gate for the correlation processor is automatically sized using a gradient function derived from the optimal weighting values.

Abstract: Apparatus is disclosed for protecting delicate sensor optics frm the damaging effects of unwanted powerful laser radiation. A thin-film reflective pellicle 14 is placed in the light path of a sensor telescope. Incident light 10 is focused by some combination of optical elements 12 onto the reflective surface 28 of the pellicle laser power limiter 14. The reflected light 10 is then imaged by further optics 16 onto a detector array 18. Should a signal too strong for the detector to enter the sensor aperture with the incident light 10, the focused power at the surface of the pellicle 28 will oblate the plastic and metallic film, burning a hole in the pellicle, and the high-power light 11 will be deflected from the detector array and instead will be absorbed by the beam dump 20. A power meter within the beam dump determines when the laser threat has stopped and signals the turning machanisms 15a and 15b to turn the pellicle reflector to a fresh position at which point normal sensor operations may resume.

Abstract: An optical receiver system operative to allow a set of fixed positioned detectors in the same Dewar to be optically directed to concurrently sense any subset of a known set of spectral lines. The system also has a transmitter mode that allows a group of radiation sources having a subset of a possible set of spectral lines to be relatively optically overlapped at the transmitter aperture.

Abstract: A five stage background filter circuit 10 is disclosed which is capable of responding to background radiation changes at speeds which are from one to two orders of magnitude faster than conventional prior filters. The invention utilizes a cross scan multiplexing technique in combination with filter circuitry depicted in schematic overview in FIG. 1. Circuit 10 includes a differential amplifier 12, a sample and hold device 14, a responsivity corrector 16, a recursive filter 18, and a background subtractor 20. Output signals 11 from a focal plane array of detectors (shown in FIG. 3) are passed through impedance matching input resistors 12a,b to an amplifier. A sample and hold circuit 14a cyclically selects and stores a signal received from first stage 12. The detector outputs are then normalized by responsivity corrector stage 16 which employs a digital-to-analog converter 16a and random access memory 16c.

Abstract: An infrared imaging system includes a scanner of infrared radiation emanating from a subject, the radiation being scanned past an array of radiation detectors disposed on a common substrate. A set of amplifiers connecting with a multiplexer is built upon the array of detectors, individual ones of the amplifiers connecting with respective ones of the detectors. Each amplifier is composed of a structure having the components of a charge-coupled device and includes circuitry for pulsing a charge-coupled device repetitively. A transistor switching circuit interconnects a detector with its corresponding charge-coupled device for modulating the magnitude of charge in each charge packet propagating through the device. A pair of integrators is disposed on the common substrate, and a steering circuit steers modulated and unmodulated pulses to alternate ones of the integrators.

Abstract: Apparatus is disclosed for providing microelectronic, intra-chip and chip-to-chip interconnections in an ultra-dense integrated circuit configuration. Compressive pedestals 20 are used to form spring-loaded electrical and mechanical interconnections to conductive terminals on a chip interface mesa and chip assembly 28 in order to form a large multi-chip array 23 on an interconnection substrate 24. Methods are also disclosed for fabricating the compressive pedestals 20.

Abstract: Retroreflector (10) has a base (12) with an even back surface (24) and an uneven forward surface (14). The uneven forward surface is illustrated as grooved with one of the grooves shown at (22) with groove sides (30) and (32). The uneven forward surface (14) is coated with retroreflector elements (16) so that incident light from almost 90.degree. to the normal is retroreflected.

Abstract: A DC restoration circuit for a video imaging system having a detector array and AC coupled amplifiers is disclosed. The DC restoration circuit includes circuitry (15) for providing a difference signal indicative of the difference between a first scan line video signal and a second scan line video signal; a histogram circuit (20) responsive to the difference signal for generating histogram data indicative of the number of occurrences of difference values of the difference signal; a dominant shift detector circuit (30) responsive to the histogram data for determining a representative difference signal value and for providing a video correction signal which is based on the representative difference signal value; and correction circuitry (13, 17) responsive to the second scan line video signal and the video correction signal for providing a corrected video signal.

Abstract: A method and apparatus for determining the junction-to-case thermal resistance, .theta..sub.jc, of a solid-state hybrid circuit element 38. First, the temperature coefficient, T.sub.c, of the voltage across the junction is determined with a small calibration current flowing through the junction. Digital multimeters 12 and 28 are used to measure the junction voltage and current, respectively. Next, more power is applied and the total power, P.sub.T, dissipated by the hybrid circuit element 38 is determined from values of the applied voltage and current measured with digital multimeters 12 and 14. The case of the hybrid element is kept at a constant temperature by a heat sink arrangement and the junction is allowed to reach thermal equilibrium at the higher power level. Finally, the increase in power to the hybrid element is removed and the change in junction voltage drop, .DELTA.V.sub.BE, between low-power operation and high-power operation is determined using a storage oscilloscope 30.

Abstract: An imaging system incorporating a scanned array of infrared detectors for presentation of scene data on a display includes gain normalization circuitry coupled to individual ones of the detectors of the detector array. The normalization circuitry is structured as a feedback loop introducing euality between the magnitude of an average value of a detector signal and a reference signal. The imaging system comprises a set of channels connecting with respective ones of the detectors, each channel having adaptive gain control circuitry. A common value of the reference signal is applied to each channel for uniformity in a displayed image. The averaging time is several times greater than the duration of a single scan in the scanning of the detector array so as the display is relatively free of nonuniformities associated with differing responsivities of the detectors to infrared radiation. A nonlinear gain function is produced by connection of multipliers and/or logarithmic circuitry in a forward branch of the loop.