大口径折反式中波红外衍射望远镜系统设计

Design of catadioptric middle infrared diffractive telescope system with large aperture

为实现空间红外望远镜的高分辨率探测,基于Schupmann消色差理论,开展了大口径折反式中波红外衍射望远镜系统的设计及消热差模型研究。设计了口径1 m、F数为2、全视场0.12°、波段3.8μm~4.2μm的折反式中波红外衍射望远镜系统,其主镜及校正镜均为平面衍射透镜,中继系统采用卡塞格林折反式结构,再聚焦及三次成像系统均为折射式结构,对系统进行了公差、鬼像及冷反射分析。设计结果表明:在-20℃~60℃温度下,系统的MTF在16.7 lp/mm范围内均大于0.7,接近衍射极限,且具有100%冷屏效率,公差满足现有加工装配水平;鬼像能量为0.1%,对目标信号的影响较小;冷反射等效温差(NITD)随温度的变化量小于探测器噪声等效温差(NETD)。该系统可为更大口径红外衍射望远镜系统的设计提供参考。

To achieve the high-resolution detection of space infrared telescopes,based on the Schupmann ach-romatic theory,the design and athermalization model of catadioptric middle infrared diffractive telescope system with large aperture were studied.An optical system which had an aperture of 1 m,F-number of 2,full field of view of 0.12°,waveband of 3.8μm~4.2μm was designed,the primary mirror and correction mirror were plane diffractive lenses,the relay system adopted catadioptric Cassegrain structure,and the refocusing and three times imaging systems used refractive structure,then the tolerance,ghost image and cold reflection of the system were analyzed.The design results show that at the temperature of-20℃~60℃,the MTF of the system is greater than 0.7 in the range of 16.7 lp/mm,close to the diffraction limit,and has 100%cold shield efficiency.The tolerance of system satisfies requirements of fabrication,the ghost image energy is 0.1%,which has little influence on the target signal,and the Narcissus induced equivalent temperature difference(NITD)value of cold reflection with temperature is less than noise equivalent temperature difference(NETD).The system can provide reference for the design of larger aperture infrared diffractive telescope system.