Hughes Aircraft Company

Raytheon Company

Carl G Pfeiffer

Cheng-Chih Tsai

Richard L Hedden

Danny D Nguyen

D Spyro Gumas

Edward L Gussin

J Brian Murphy

Christopher Calingaert

Richard E Burney

A computationally efficient missile detection and tracking system, operating on data samples from a focal plane assembly (FPA) of an electro-optical sensor which is observing the earth and space, detects missiles, aircraft, resident space objects or other objects in the presence of background clutter, determines missile types and estimates missile position and velocity components in an inertial reference frame. Digitized samples from an array of electro-optical detectors which are viewing the earth and/or space are processed to detect and track missiles, aircraft and resident space objects. Streak detection is used for this purpose, where the target is separated from a background scene by exploiting target motion relative to the background scene. This processing system provides superior performance and simplified implementation as compared to conventional methods. The weight and power of a computer which can implement the processing system is much reduced as compared to conventional implementation.

Background adaptive target detection and tracking with multiple

An integrating circuit (12) includes a capacitor (22) which charges at a rate proportional to the instantaneous amplitude of an input signal V.sub.IN generated by a photosensor (14) to produce an integrated output signal V.sub.OUT. The input signal V.sub.IN is proportional to the photon rate upon the photosensor (14), which is the quantity of interest. The output signal V.sub.OUT is non-destructively oversampled at a rate which is much higher than the Nyquist rate of the input signal V.sub.IN to produce sample signals V.sub.S1 which are differenced and later recombined to produce a replica of the output signal V.sub.OUT. The capacitor (22) is discharged and the output signal V.sub.OUT thereby reset to zero whenever the amplitude of the output signal V.sub.OUT reaches a predetermined maximum value V.sub.RESET. The output signal V.sub.OUT is thereby 'folded' into a sawtooth waveform, which has a dynamic range of V.sub.RESET divided by a minimum value. The photon rates of large amplitude signals, which can cause several resets during the observation period, are later reconstructed by averaging the slopes of the sawtooth waveform. The photon rates of small amplitude signals are later reconstructed by summing the differenced outputs during a Nyquist sample interval. Anomalous sample signals V.sub.S1 with very large amplitudes corresponding to short duration 'gamma' events such as nuclear radiation are detected, deleted and replaced with sample signals having amplitudes interpolated from the amplitudes of adjacent sample signals.

Photosensor readout detector having dynamic reset rate

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. A threshold band comparison and time-out logic circuit 21 within background subtractor stage 20 controls the operation of recursive filter stage 18 in order to suppress signals due to sensed radiation bursts and to eliminate the unwanted, dynamically varying background radiation portion of the signal present at node 17b. A processed output signal present at node 20i is then passed to a target detection processor (not shown).

Extremely high speed, real-time background filter for radiation detectors

Growing community of inventors

Hermosa Beach, CA, United States of America

Carl G Pfeiffer