基于中波红外320 pixel×256 pixel制冷型探测器，采用机械正组补偿方式，并采用折叠光路，实现大变倍比中波红外变焦光学系统的设计。该系统由变焦物镜系统和二次成像系统组成，包括7片透镜和2个反射镜，并引入3个非球面。介绍了该光学系统结构参数的求解过程，并用Zemax光学软件进行了设计。对设计结果进行了像质评价、凸轮曲线求解和冷反射分析。设计与分析结果表明，该系统在3.7~4.8 μm波段实现了18~360 mm连续变焦，满足100%冷阑匹配，在空间频率16 lp/mm处调制传递函数(MTF)值均大于0.5，冷反射可忽略不计。该系统具有变倍比大、分辨率高、结构紧凑和变焦曲线平滑等特点，可应用于机载光电侦察设备中。

For a cool 320 pixel×256 pixel detector with staring focal plane array, an infrared continuous zoom optical system using mechanical compensation and folding beam path for middle wavelength infrared (MWIR) is designed. The system is composed of a zoom system and a secondary imaging system, including seven lenses, two reflectors and three even aspheres. The computing process is introduced to obtain structural parameters of the optical system, and then optimization is applied by Zemax. Image evaluation, cam curve and cold reflection are listed. The design results show that the system which works at 3.7~4.8 μm has achieved the zoom of 18~360 mm, and satisfied 100% cold shield efficiency. The modulation transfer function is always bigger than 0.5 at the spatial frequency of 16 lp/mm. The system can be used for airborne optical-electronic detection.