折反式中波红外双视场变焦系统无热化设计

利用折/衍混合透镜实现了宽温度范围双视场变焦系统的光学被动无热设计。系统工作波段为3～5 m，使用320240红外制冷探测器，像元大小为30 m30 m，焦距为400 mm和800 mm两档，F数分别为2和4。两系统通过机械结构改变冷光栏大小分别实现100%冷光栏效率。在两档共用组份采用一片折衍混合透镜，对双视场系统两焦距位置消热差，实现了一个衍射面对两档系统的无热化设计，结构简单。设计结果表明:在-40 ～60 ℃温度范围内，空间频率18 lp/mm处系统MTF值接近衍射极限，成像质量良好，实现了双视场变焦系统的无热化设计。

Athermalization design of catadioptric middle infrared dual field zoom system

Hybrid refractive-diffractive design offers a new approach for athermalization design in wide temperature range. In this paper, working wavelength is in 3-5 m. For cool 320240 infrared detector, pixel size 30 m30 m, this system can realize 400 mm and 800 mm dual filed-of-view and the F-number of 2/4 respectively. Two systems both can obtain the cold shield efficiency of 100% though controlling machine structure. A diffractive surface was introduced in the shared part of two different focal length position. It achieve the athermal design using only one diffractive surface. The evolution of the system was given in the temperature range -40-60℃. The results show that at the spatial frequency of 18 lp/mm the MTF approach to the diffractive limitation.