中波红外三视场变焦光学系统设计

三视场变焦光学系统相对于其他形式的变焦系统具有机械结构简单、可靠性高、变焦时间短等优点。采用320240分辨率、像元尺寸30 m30 m制冷型探测器，二次成像方式设计了一种工作于3～5 m中波制冷型三视场红外光学系统，系统视场角1.4～23.8，F数为４，可实现焦距为30mm/100mm/500mm。设计中采用了硅和锗两种材料校正谱段内色差，采用了一个非球面校正系统球差，两个反射镜折转光路的方式实现系统轴向尺寸的缩减，整个系统外形尺寸小于210 mm160 mm120 mm，系统具有外形尺寸小、变焦结构简单、成像质量高等特点，在空间频率17 lp/mm处，系统调制传递函数（MTF）均在0.5以上，能量集中度大于70%。

Design of three-field middle-wave infrared zoom system

Three-field zoom system has advantages of simple mechanical structure, better reliability, short time of changing focal relative to other pattern zoom systems. Using 320240 resolution cooled detector with 30 m30 m pixel dimension, a middle-wave three-field optical system was designed by secondary imaging way. The system's F number is 4, FOV range is 1.4-23.8, it can realize 30 mm/100 mm/500 mm three position focal length. In designing process, the Germanium material and Silicon material were adopted to balance chromatic aberration, introducing one asphere to balance sphere aberration. The system use two mirrors reducing the axis dimension. The dimension of system better than 210 mm160 mm120 mm, it has characteristics of small dimension, simple zoom structure, good image quality etc. The modulation transfer function(MTF) is above 0.5 at spatial frequency of 17 lp/mm and energy concentration ratio is greater than 70% within the sensing element of the detector.