为了提高远距离红外目标的探测能力, 针对640 pixel×512 pixel红外CCD探测器, 分析温度变化对光学系统的影响, 设计出一种波长范围为8 μm~12 μm红外摄远物镜。系统采用折衍混合结构形式, 焦距为200 mm, 相对孔径为1: 2.2, 视场角为7°, 具有体积小, 结构紧凑的优点。仅使用硫化锌、硒化锌和锗3种材料以及4片透镜实现了无热化设计。应用Zemax对设计结果进行像质评价, 在-40 ℃~+60 ℃工作温度范围内, 截止频率为17 lp/mm时各视场调制传递函数值超过0.4, 达到衍射极限, 像面稳定, 80%的能量集中在1个像元内, 满足光学系统的设计要求。

In order to improve target detection ability of IR images in long range effectively, an infrared telephoto objective for 8 μm~12 μm wave-band is designed for 640 pixel×512 pixel infrared CCD detector. Effects of surrounding environmental temperature are analyzed and refractive diffractive hybrid thermal compensation is discussed. Focal length of the system is 200 mm, relative aperture is 1: 2.2 and field of view is 7°. Infrared telephoto system with small volume and compact structure is designed in a large range of temperature. The system is composed of four lenses with only three materials of zinc sulfide, zinc selenide and germanium to compensate for the temperature. Image quality of the system is evaluated by ZEMAX optical design software. Results show that modulation transfer function (MTF) for each field of view at cut-off frequency of 17 lp/mm is greater than 0.4 which approaches diffraction limit. Root mean square radius of spot diagram for each field of view is close to Airy disk radius. Telephoto objective has favorable performance at working temperature of -40 ℃~+60 ℃. The system meets the requirements of technical specification.