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In view of the problem that the imaging quality of the large-aperture and long-focal length infrared optical system is sensitive to temperature changes. In this paper, we propose an idea of combining athermalization design with catadioptric optical system, and a large-aperture long-focal length catadioptric infrared optical system is designed by this idea. According to the influence of each parameter by environmental changes, the system optical power is allocated reasonably. Select the appropriate infrared lens material and reflector base material for the system so that the image plane deviation caused by the environmental changes of the components cancel each other out. The design method and idea proposed in this paper have important reference value for the realization of heat dissipation of catadioptric optical system. The working band of the system is 8~14μⅿ,the focal length is 250ⅿⅿ, F-number is 1, and the three infrared materials used in the system are HWS2, HWS9 and IRG22. The design results show that the system can maintain high imaging quality in the temperature range of -40°C~+60°C, with the modulation transfer function (MTF) curves close to the diffraction limit at the cutoff frequency. The design methods and ideas proposed in this paper have significant reference value for realizing athermalization of catadioptric optical systems.
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