OPTICAL SYSTEM FOR A WIDE FIELD OF VIEW STARING INFRARED SENSOR HAVING IMPROVED OPTICAL SYMMETRY

摘要

A wide-angle IR imaging system (1A) has an entrance aperture (40) foradmitting IR from a scene and a dewar (4A) that contains a coldshield (3) thatencloses a cooled IR detector (2) disposed at an image plane (2A). The dewarincludes a dewar window (4), and an optical axis of the IR imaging systempasses through the dewar window and the image plane. The IR imaging systemfurther includes a plurality of uncooled optical elements (22, 24, 26, 28)disposed along the optical axis between the entrance aperture and the dewarwindow, and a plurality of generally annular reflector segments (18A, 18B)disposed around the optical axis betwen the dewar window and the entranceaperture. Each of the reflector segments has a reflective surface that facesthe dewar window. An opening through an outermost reflector segment furthestfrom the dewar window defines an effective cooled aperture stop, or warm stop(20A) of the IR imaging system, and at least one of the optical elements (22)is disposed between the effective cooled aperture stop and another one of thereflector segments (18A) that is located nearer to the dewar window. In thepreferred embodiment the at least one optical element, and the reflectorsegment that is located nearer to the dewar window, are comprised of a singlemonolithic body (31) that has a compound optical surface.