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) for admitting IR from a scene and a dewar (4A) that contains a coldshield (3) that encloses a cooled IR detector (2) disposed at an image plane (2A). The dewar includes a dewar window (4), and an optical axis of the IR imaging system passes through the dewar window and the image plane. The IR imaging system further includes a plurality of uncooled optical elements (22, 24, 26, 28) disposed along the optical axis between the entrance aperture and the dewar window, and a plurality of generally annular reflector segments (18A, 18B) disposed around the optical axis betwen the dewar window and the entrance aperture. Each of the reflector segments has a reflective surface that faces the dewar window. An opening through an outermost reflector segment furthest from 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 the reflector segments (18A) that is located nearer to the dewar window. In the preferred embodiment the at least one optical element, and the reflector segment that is located nearer to the dewar window, are comprised of a single monolithic body (31) that has a compound optical surface.