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The influence of contaminated mirror on the flux distributions of stray radiation of infrared telescope systems

The existence of contaminated mirror in infrared telescope system not only reduces the contrast between objects and background, but also leads to the nonuniformity of the flux distribution of stray radiation on detector, resulting in great difficulty in obtaining and analyzing the target signal. In this paper, taking Cassegrain telescope as a typical example and using the optical analysis software, i.e., ASAP, the three-dimensional simulation model has also been built up. The self-generated thermal radiation flux and the flux distributions of stray radiation on the image plane have been simulated when the primary mirror under two cases, i.e., clean and local area contaminated. The influence of the size and position of the contaminated area on the uniformity of the flux distributions of stray radiation has been focused on discussion. The radiation flux and the flux distributions of stray radiation have been employed to evaluate the stray radiation performance of the system. The results indicate that the local area contamination on mirrors could change the uniformity of the flux distributions on the image plane and also degrade the stray radiation performance of the system, resulting in the influence on the detection and identification of the target. Consequently, it is of critical importance to keep the surface of optical elements clean, especially to avoid local area contamination on optics.