Design of a compact infrared catadioptric system

The design method of a compact infrared catadioptric system is proposed. In the design, the metal mirrors are adopted for the primary and secondary mirrors in the system, and the IR transmission material is used for the rear set of lenses. The ratio of total length and focus length is 0.55. The temperature effects of the system were analyzed during the design process and an effective measure was taken for the purpose of making the system quasi-athermalized. The parasitic light in the system was also analyzed. A scheme to suppress the parasitic light is given. The analysis result shows that the stray light on the image plane of the system is less than 0.5%, the expansion coefficients of optical material and structural material are proper for their match, and the thermal effect of the system is verified.