Hughes Aircraft Company

Hughes Electronics Corporation

He Holdings, Inc.

Stephen J Herbst

Kenneth E Prager

Weston K Furukawa

Jeffrey E Orr

Jerry N Sisneros

John J Wootan

Douglas M Gleichman

Weston Furukawa

A system for correcting detector array channel signal output level non-uniformities in a thermal imaging system. The non-uniformity correction system includes a target scene detector (27) having an array of detector elements (26a, 26b) responsive to energy from a detected target scene (14) and including a plurality of associated output channels (31, 32). The system includes a memory (62) for storing non-uniformity correction commands and a processor (82) operative to implement the non-uniformity commands in response to detected non-uniformities in the output channels signal. The system also includes a non-uniformity corrector (60) for adjusting the level of the output channels in response to commands from the processor (82).

System with motion detection scene-based non-uniformity correction

A system for producing a high quality scene image in a thermal imaging system by electronically compensating for variations in the imaging system imager focal length. The system includes optics (16, 18) for detecting a scene (14), a detector assembly (27) being responsive to energy from the detected scene; and an imager (25) for imaging the energy from the detected scene onto the detector assembly (27). The imager (25) includes a temperature sensor (25b) for sensing imager lens temperature. The detector assembly (27) outputs electric signals in response to the energy from the detected scene at a first clock sample rate. The system further includes a processor (84) for controlling the first clock sample rate of the detector assembly to maximize detected scene image quality through variation of the first clock sample rate to automatically compensate for imager lens focal length variation due to ambient temperature changes in the imager lens (25a) and due to inherent manufacturing tolerances.

Electronic effective focal length compensator

A scene based nonuniformity correction method (40) that computes and applies offset correction errors to a video signal corresponding to an image derived from a imaging sensor (11). A video signal derived from the sensor (11) is processed such that a vector representing offset correction terms is formed, and this vector is initially set to zero. Each element in this vector represents a correction term for a particular detector of the sensor (11). The vector is applied to each pixel of the image by a processor (13) as the pixels are read from the sensor (11). To measure the offset error, the image is separated into vertically oriented regions, each comprising a plurality of channels. The average of each channel within a region is computed (42), and a set of region vectors is foraged, such that there is one region vector for each region. Each region vector is then globally high-pass filtered and then edges larger than a predefined threshold are detected (43), and marked (44). Then, each region vector is further separated into sub-regions (45). The isolated sub-regions are locally high-pass filtered. In one embodiment, the correction terms for each vertical region vector are averaged together, resulting in a single correction vector (48). The correction terms calculated for each vertical region may also be applied individually to each detector of the sensor (11). In this second embodiment, the offset level error in each region for each channel is calculated (49), wherein the offset level error at boundary edges is undefined. The correction terms corresponding to a region are applied as the detector (11) scans the scene and views a portion corresponding to that particular region. The correction terms are smoothed at region boundaries to eliminate noise due to boundary transitions.

Nonuniformity correction of an imaging sensor using region-based

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Redondo Beach, CA, United States of America

Stephen J Herbst