US 4,902,893 AGranted

Passive infrared radiation scanning system

OwnerGordon J. Burrerinventor

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Abstract

A radiation scanning system comprises scan mirrors optically coupled together by means of a spherical reflector to relay the scan mirror pupils through the optical path with minimal pupil shift for both wide and narrow field-of-view applications. The mirrors may oscillate at a predetermined fundamental frequency and a hamonic thereof to achieve near linear line scans or both line scan mirrors may oscillate at the predetermined fundamental frequency to achieve wider scan angles. In another embodiment, a line scan mirror is mounted on a multi-mode resonant scanner and phase lock oscillated at multiple frequencies while a second scan mirror functions as the field or line scanning element. In yet another embodiment, one line scan mirror is mounted on a non-turnable resonant scanner while a second scan mirror functions as the field scanning element. General compatibility with TV formatted systems can be achieved through self resonance or by controlling the fundamental line scan frequency through an external master clock. The line scan mirrors can operate at a predetermined fundamental frequency which is a fraction of the standard TV line frequency. System scanners may be passive, active or combinations thereof, and can operate in the ultraviolet, visible, or infrared spectrums.

A passive infrared scanning system having high optical throughput for detecting infrared radiation emanating from an object field and providing an output compatible with video display systems, comprising:

spherical reflecting means for optically relaying pupils along an optical path of said passive infrared scanning system with minimal pupil shift, said spherical reflecting means including a spherical reflecting surface, an optical axis, a predetermined radius of curvature, and a predetermined intermediate focal line;
second scanning means for coupling radiation emanating from the object field onto said spherical reflecting surface of said spherical reflecting means, said second scanning means including a second rotational axis and an essentially flat reflecting surface adjacent said second rotational axis for oscillatory movement thereabout, and wherein said second scanning means is positioned a distance from said spherical reflecting surface equal to said predetermined radius of curvature;
wherein the radiation reflected from said spherical reflecting surface converges at said predetermined intermediate focal line and diverges therefrom;
radiometric reference source means disposed at ends of said predetermined intermediate focal line for calibrating the radiation converging at said predetermined intermediate focal line;
first scanning means operative for line scanning by intercepting and reflecting the radiation diverging from said predetermined intermediate focal line, said first scanning means including a first rotational axis and an essentially flat reflecting surface adjacent said first rotational axis for oscillatory movement thereabout, and wherein said first scanning means is positioned a distance from said spherical reflecting surface equal to said predetermined radius of curvature;
and
detection means for coupling the divergent radiation reflected from said first scanning means to focalize for detection.

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Abstract

Claims20