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Dual Detector Differential Infrared Scanning Instrument

IP.com Disclosure Number: IPCOM000087078D
Original Publication Date: 1976-Dec-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 2 page(s) / 33K

Publishing Venue

IBM

Related People

Lukianoff, GV: AUTHOR [+2]

Abstract

In a scanning infrared instrument used in applications where it is desired to selectively enhance higher-temperature areas relative to a lower temperature background, two detectors are used. One detector is sensitive to shorter infrared wavelengths than the other. The signal from one of the detectors (e.g., the longer wavelength detector) is inverted and mixed with the uninverted signal from the other detector. This results in partial cancellation of the two signals, such that higher-temperature areas are enhanced in the resultant image. A differential amplifier may be used instead of separate inverting and mixing circuits, as shown in the drawing.

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Dual Detector Differential Infrared Scanning Instrument

In a scanning infrared instrument used in applications where it is desired to selectively enhance higher-temperature areas relative to a lower temperature background, two detectors are used. One detector is sensitive to shorter infrared wavelengths than the other. The signal from one of the detectors (e.g., the longer wavelength detector) is inverted and mixed with the uninverted signal from the other detector. This results in partial cancellation of the two signals, such that higher-temperature areas are enhanced in the resultant image. A differential amplifier may be used instead of separate inverting and mixing circuits, as shown in the drawing.

Further enhancement may be obtained by filtering one of the two signal channels selectively: e.g., inserting a low pass filter in the signal path from the longer wavelength detector.

In one arrangement, the two detectors are concentric. One detector has an annular shape and surrounds the other detector.

In a preferred arrangement, the two detectors have the same size and shape and are disposed side by side along a center line parallel to the line-scan direction of the scanning system. The signal from one of the detectors is delayed by a time interval corresponding to the relation between the line-scan rate and the distance between the centers of the two detectors. Thus, the timing of signals arriving at the mixer can be arranged to synchronize separate signals ari...