Importance

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Abstract

A thermal or infrared imaging system having an optical barrel, an external stop formed by a mirror, a dewar, a cold shield, a focal plane array, and multiple retroreflectors. The cold shield and focal plane array are located inside the dewar. The mirror directs desired light bundles at the focal plane array. The retroreflectors are attached to the inside of the optical barrel. The retroreflectors are arranged such that the retroreflectors exist in all lines of sight of the focal plane array, except those lines of sight associated with the external stop. Consequently, the retroreflectors do not interfere with the desired light bundles which are focused onto the focal plane array. However, all light outside of that which is focused is prevented from reaching the focal plane array by the retroreflectors. The retroreflectors are infrared retroreflectors arranged in a matrix. Each of the retroreflectors is a 'concave' corner cube having low emissivity reflecting facets. The corner cubes reflect incoming rays by 180 degrees relative to input angles of the incoming rays. Thus, the focal plane array sees only cold outside of the desired light bundles.

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First Claim