轻小型长波红外光学系统的设计及实现

无人机载光电吊舱对其载荷体积重量的要求苛刻，为了满足8～12.5 μm红外探测需求，设计并实现了一种轻巧紧凑的长波红外光学系统。系统F数为2，口径为150 mm，总视场为2.34°。光学系统采用二次成像折反射式结构，将常用的卡式主系统简化为折叠牛顿式主系统，将球面次镜简化为平面镜折叠光路，轴外像差通过非球面校正镜组校正。主系统采用全铝光机结构，结合后光路的光机材料匹配，在工作环境温度范围内，光学设计传函高于0.41@17 lp/mm，具有100%冷屏效率，而体积仅为Φ152 mm×125 mm。整机装调后，全视场传函高于0.24@17 lp/mm，像质清晰，满足预期。光学系统设计巧妙、结构轻小紧凑、加工装调成本低。设计思路和研制方法可为类似应用的无人机载光电吊舱长波红外仪器的光学系统提供参考。

Design and realization of light and small long-wave infrared optical system

The requirements on its load volume and weight are strict for unmanned airborne photoelectric pod. In order to meet the needs of 8-12.5 μm infrared detection, a lightweight and compact long-wave infrared optical system was designed and realized. The F number of the system was 2, the diameter was 150 mm, and the total field of view was 2.34 °. A twice focusing reflection-refraction structure was used as the optical system structure. It simplified the commonly used Cassegrain-type main system into a folded Newton-type main system, and simplified the spherical secondary into a plane mirror folding optical path. The off-axis aberrations were corrected by the aspherical correction lens group. An all-aluminum optical-mechanical structure was designed for the main system, combined with the optical-mechanical material matching of the rear optical path. In the temperature range of the working environment, the designed MTF of the system was more than 0.41@17 lp/mm, with 100% cold stop efficiency, and the volume was only Φ152 mm×125 mm. After final alignment, the MTF of the instrument was more than 0.24@17 lp/mm, and the image quality was clear and met expectations. The optical system was smartly designed, so the structure was light and compact, and the cost of manufacture and alignment was low. The design ideas and development methods can provide a reference for the optical systems of long-wave infrared instruments of unmanned airborne photoelectric pods for similar applications.