采取将变倍组、补偿组、后固定组分开进行联动的方式对传统光学补偿连续变焦中波红外光学系统进行改进,获得了超长焦距、超大视场、大变倍比、小型化的光学系统。推导了其数学模型,基于该模型采用640×512制冷型中波探测器,设计了焦距为11.56~982.6 mm、变倍比为85×的连续变焦光学系统,该光学系统的应用波段为3.6~4.9 μm,F数为5.5,冷屏效率为100%。设计结果显示,该光学系统的外形尺寸为333.5 mm×125 mm(局部直径为177.5 mm)×80 mm(局部直径为180 mm),结构紧凑,变焦过程中变倍补偿曲线平滑、像面稳定。从点列图、光学传递函数、畸变等方面对该光学系统的像质进行评价,结果表明,其像质优良,分辨率高,可满足热像仪整机使用要求。

The traditional optical compensated continuous zoom medium wave infrared optical system is improved by means of the combination of the zoom group, compensation group, and post-fixed group. The optical system with super-long focal length, super-large field of view, large zoom ratio, and small envelope is obtained. The mathematical model is deduced. Based on this model, a continuous zoom optical system with focal length of 11.56-982.6 mm and zoom ratio of 85× is designed by using 640×512 refrigerated medium wave detector. The application band of the optical system is 3.6-4.9 μm, the F number is 5.5,and the cold screen efficiency is 100%. The design results show that the envelope of the optical system is 333.5 mm×125 mm (local diameter of 177.5 mm)×80 mm (local diameter of 180 mm). The structure is compact, the zoom compensation curve is smooth, and the image plane is stable in zoom process. The image quality of the optical system is evaluated from the aspects of point diagram, optical transfer function, and distortion. The results show that the optical system has excellent image quality and high resolution, and meets the requirements of the thermal imager.