Hughes Aircraft Company

Raytheon Company

Hughes Electronics Corporation

Michael Y Pines

J Steve Anderson

James S Duncan

Kapriel V Krikorian

Colin G Whitney

Robert D Schaefer

Dale G Maeding

N John Koda

Donald F King

Dwight J Mellema

Robert L Sendall

Yifal J Shaham

Israel D Levy

Themi H Demas

Daniel F Murphy

A radar on a moving platform for three dimensional target recognition of a target on a flat or sloping terrain is described. The target is illuminated from a plurality of locations to generate images at many aspect angles. The radar is positioned at a low grazing angle with respect to the target for generating a shadow of the target on the flat or sloping terrain for each aspect angle of the plurality of aspect angles. The radar comprises an analog to digital converter for converting reflections from the target induced by radar illumination into target digital data and for converting reflections induced by the illumination from the flat or sloping terrain into terrain digital data. The radar further comprises a computer for extracting radar images of the target and its shadow(s) at the plurality of aspect angles at low grazing angles; computing the slope of the terrain from the terrain digital data; correlating a plurality of the radar images to compute a three dimensional image of the target from the shadow of the target upon the flat or sloping terrain; and classifying the three dimensional image for target recognition using a target recognition algorithm.

Technique for low grazing angle 3D SAR target recognition

A small, compact optical scanning system with small aperture size requirements, wide field-of-regard and minimal color dispersion characteristics. The inventive scanning system and method provides for optical beam steering over a broad spectral band and over a wide field-of-regard. The inventive system includes a novel device for receiving an input wavefront of electromagnetic energy along a first axis and refracting the wavefront as an output wavefront along a second axis. The device is a unique form of a multi-channel liquid crystal array in which each channel has a length parallel to the first axis. By applying signals to change the refractive index of each channel, the incident wavefront can be steered at an angle with respect to the first axis and otherwise manipulated according to the index variant pattern induced in the array. Accordingly, the output beam is steered in response to the applied signals.

Broadband optical beam steering system and device

A small,compact optical scanning system with small aperture size requirements, wide field-of-regard and minimal color dispersion characteristics. The inventive scanning system and method provides for optical beam steering over a broad spectral band and over a wide field-of-regard. The inventive system includes a novel device for receiving an input wavefront of electromagnetic energy along a first axis and refracting the wavefront as an output wavefront along a second axis. The device is a unique form of a liquid crystal array which can be electrically manipulated to change the effective refractive index of each pixel. The index of refraction of the device varies in response to an applied voltage. The voltage is supplied by a microprocessor and/or a servo-control system. By changing the index, the incident phase front can be steered at an angle with respect to the first axis and otherwise manipulated according to the index variant pattern induced in the array. Accordingly, the output beam is steered in response to the applied voltage.

Broadband optical beam steering system and method

An imaging device (10) includes an array (18) of picture elements (16) or pixels, each of which is responsive to incident radiant energy to provide an output signal. The array (18) consists of pixels (16) in adjacent horizontal rows, each row having a certain pitch (P) or center-to-center distance between pixels. Each alternate row is horizontally offset by a distance equal to one-half of a row pitch from each adjacent row to form a 'brick wall' or quincunx pattern. An azimuthal traverse of the quincunx focal plane array (18) provides twice the azimuthal resolution and approximately 140 percent of the minimum resolvable temperature measurement capability of conventional focal plane arrays.

Quincunx sampling grid for staring array

A multispectral imaging sensor. The inventive sensor (10) includes a broadband detector (30) capable of sensing electromagnetic energy across a spectra of interest. A filter arrangement (20) is mounted within the sensor in alignment with the detector (30). The sensor arrangement (20) includes a first filter (24) with a first passband, a second filter (26) with a second passband, and a mechanism for selectively positioning either the first filter (24) or the second filter (26) in optical alignment with the detector (30). In a specific embodiment, infrared and visible light are directed to the filter arrangement by a reflective optical arrangement (16, 18, 19). The positioning arrangement includes a turntable (22) on which the first filter (24) and second filter (24) are disposed. A motor (27) activates the turntable (220 from a first position at which the first filter (24) is in alignment with the detector (30) and the reflective optical arrangement (16, 18, 19) to a second position at which the second filter (26) is in alignment with the detector (30) and the optical arrangement (16, 18, 19). Multispectral imaging sensing is effected by simply switching the appropriate filter into the optical path of the detector (30).

Multispectral-staring sensor

A pyroelectric detector using electronic chopping of the detector bias signal to reset the detector. The detector is preferably operated slightly above or below its Curie temperature. Multiplexing of a plurality of electronically-reset detectors is also disclosed.

Pyroelectric detector using electronic chopping

Images of two fields of view of one or two scenes in a radiation sensor are generated by use of a single detector and common signal process circuitry. The two imaged fields of view, typically a narrow view and a wide view, are provided by two independent telescopes (18, 20), and are combined by use of a field-of-view switch (32) comprising a chopper wheel (34) or an optical switch in synchronized operation with a mirror scanner (22). The same field-of-view switch is employed in performing detector non-uniformity correction functions, such as automatic responsivity control and direct current restoration. Folding optics couples scanned radiation from the scanner to the switch. An additional field of view may be introduced by displacing a folding mirror of the folding optics. Also, a portion of a reflecting surface of the switch may be tilted to admit a reference beam of radiation useful in performing the functions of responsivity control and D.C. restoration.

Multiple field of view sensor

A pyroelectric focal plane array useful for thermal imaging applications comprises a detector (10), comprises a reticulated and aluminized pyroelectric chip (12) interfaced with a signal processor chip (14) by thermally insulating bumps (30) coated with a thin conductive layer (38) to form a plurality of thermally insulative and electronically conductive interconnections (16) between detector chips (12) and processor chip (14).

Thermally insulative and electrically conductive interconnect and

The charge coupled device focal zoom of the present invention is used in connection with a time delay and integration charge coupled device imager in which a plurality of detectors is scanned at an angular rate .omega. across a field of view subtended by a scanning angle .alpha., wherein output charge from the detector array is clocked through associated charge coupled device registers at a clock frequency f.sub.ccd in synchronism with the scanning motion. A video display receiving the signal from the charge coupled device register may zoom in on a small portion of the field of view subtended by a reduced angle .alpha./n. This is accomplished by restricting the scanning angle to the reduced angle .alpha./n and simultaneously reducing the CCD clocking frequency to f.sub.ccd /n and the scanning rate to .omega./n. The resolution of the image is enhanced because the sampling time T is increased while at the same time the synchronism between charge transfer and scanning movement is maintained for all values of n. A frequency converter is provided at the output of the serial registers which periodically integrates output charge packets from the registers at a constant rate so that a video signal having a constant frequency is output to video display electronics even though the zoom magnification factor n is varied.

Charge coupled device focal zoom

An automatic responsivity control (ARC) circuit compensates for the nonuniform deviation .DELTA.R in the average responsivity R of a column of photodetectors from a nominal responsivity R.sub.0 which is uniform from column to column. The ARC circuit first establishes a reference level by subtracting two known calibration signals occurring during optical retracing and then multiplies the reference level by each image signal occurring during optical scanning. The resulting product contains undesirable signal components or terms which are algebraic functions of .DELTA.R.sup.2 and other terms which are algebraic functions of .DELTA.R. The terms in .DELTA.R.sup.2 are ignored because .DELTA.R is significantly less than R.sub.0. The terms in .DELTA.R are eliminated by establishing a second reference level, which itself includes terms in .DELTA.R, and then subtracting the foregoing product from the second reference level. If the bias voltages applied to the ARC circuit are adjusted according to a formula discussed in the detailed description, this second subtraction results in a cancellation of all terms in .DELTA.R. The resulting output signal therefore contains only terms in .DELTA.R.sup.2 which are negligible, and thus the output signal is substantially free of distortion due to responsivity deviations.

Automatic responsivity control for a CCD imager

As CCD circuit for restoring to a common DC level, data received from a plurality of detector channels of a scanned array so as to overcome the effect of variations in detector parameters and other non-uniformities in the circuit. The DC correction value is established during retrace time by storing a representative time integrated data charge packet when energy from a cold reference surface is being applied to the detectors. During the scan time of the field of view by the detectors the representative charge packet is utilized to provide a DC restoration or correction charge to each data charge packet received from the detectors. The system thus standardizes to a common DC level, the output data from a plurality of channels.

DC Restore circuit for charge coupled devices

An optically scanned monolithic focal plane array includes an on-chip aperture corrector interposed between the photodetector output register and the multiplexer, thereby providing data to the aperture corrector in an order parallel to the direction of optical scan, advantageously eliminating any requirement of additional hardware for demultiplexing, memory or timing functions. The desired transfer function is achieved by providing a supplementary source of charge flow in addition to the photodetector signal, the supplementary charge flow being reduced in response to each signal charge packet at first and second intervals which are advanced and delayed respectively with reference to each corresponding signal charge packet by a selected interval. This reduction is proportional to a portion p of the signal charge packet which is determined by adjustment of bias voltages controlling injection of supplementary charge without requiring a charge splitting mechanism. The resulting transfer function boosts the high frequency response of the system, thereby providing aperture correction to compensate for high frequency attenuation.

Charge summing filter aperture corrector

An optically scanned monolithic focal plane array includes an on-chip aperture corrector interposed between the photodetector output register and the multiplexer, thereby providing data to the aperture corrector in an order parallel to the direction of optical scan, advantageously eliminating any requirement for additional hardware for demultiplexing, memory or timing functions. The desired transfer function is achieved by providing a supplementary source of charge flow in addition to the photodetector signal, the supplementary charge flow being reduced in response to each signal charge packet at first and second intervals which are advanced and delayed respectively with reference to each corresponding signal charge packet by a selected interval. This reduction is proportional to a portion P of the signal charge packet which is determined by a charge splitting mechanism. The resulting transfer function boosts the high frequency response of the system, thereby providing aperture correction to compensate for high frequency attenuation.

Monolithic focal plane array having on-chip aperture corrector

There is disclosed an all silicon monolithic focal plane array of variable size infrared detectors for image detection. The structure comprises two epitaxial layers grown on an extrinsically doped silicon substrate. The detectors are formed in and extend through the substrate, the material of which is sensitive to specific wavelength infrared signals according to the dopant used in the substrate. The collection of charges takes place on a first buried layer formed around a portion of the first epitaxial layer-substrate interface, and the charges are then transferred through a third buried layer of the same conductivity type to a conducting surface layer on the upper portion of the second epitaxial layer. A second buried layer in a second portion of the epitaxial layer-substrate interface connected through a fourth buried layer to a surface layer provides a means for controlling the size of the detector region. The signal readout function is performed by a charge coupled device shift register constructed in the second epitaxial layer and includes selectively spaced electrodes in an insulating layer. Carriers generated in the detector by incident infrared radiation are collected into the first buried layer and then pass through the third buried layer to the surface layer and they are injected therefrom into the CCD shift register and are detected at the output.

Growing community of inventors

Los Angeles, CA, United States of America

Michael Y Pines