Abstract: An optical system for infrared detection in the 3 to 14 micrometer region comprising: a viewing aspheric corrector, a spherical mirror having a focal length, said spherical mirror being positioned to receive the light passed by said viewing aspheric corrector, a plurality of detector cells comprising an array thereof sufficient to vertically scan an image to provide high resolution and positioned to lie at the focal length of said optical system behind a narrow pass spectral filter, said detector cells being adapted to produce an electrical signal responsive to the infrared radiation detected thereby, means for moving the system field of view in azimuth, a multiplexer to scan the array of cells and deliver their signals sequentially to an image display, and a cryogenic cooling system for cooling the filter and the cells.

Abstract: Optical detectors are arranged along the focal length of a spherical mirr Signals passed by a lens and reflected by the mirror impinge on the detectors as the system scans the horizon. A reticle means is placed between the mirror and the detector to cause the optical system to discriminate against large radiating areas in the field of view of the lens. The reticle means may be straight or zig-zag opaque lines. The cross-sectional area of the lines and the area therebetween is such that radiation from point sources will impinge the detector in only one area at a time while radiation from large sources will overlap a plurality of areas. The output frequency from the detectors is indicative of the type of the radiation source.