变焦系统可在大范围内快速寻找、搜索目标, 同时能在小范围内对目标物体进行更加细致的观察。因此红外变焦光学系统在**、工业等领域的应用与需求不断增长。对连续变焦镜头的设计理论、设计方法进行介绍, 利用Zemax软件设计了一款连续变焦的红外镜头, 变焦范围为30 mm~110 mm, 工作波段在8 μm ~12 μm, F#为1.0, 配合一款320像素×240像素的非制冷探测器使用, 探测器像元尺寸为25 μm×25 μm, 光学系统的总长小于230 mm, 整个系统由7片透镜组成, 并且只使用了锗一种材料, 所有表面均为球面。实验结果表明: 在短焦30 mm时, 系统MTF值在20 lp/mm处均大于0.3; 长焦110 mm时, 系统MTF值在20 lp/mm处大于0.317 4。最后对红外变焦系统进行了容差分析, 得出一组较为宽松的公差。

Zoom system can quickly find and search for the target in a wide range,while more detailed information of the object can be observed in a small range of view.Therefore the application and demand of infrared zoom system in defense, industrial, military and other fields have been growing.We introduced the theory and methods for designing continuous zoom lens,and completed the design of a continuous zoom infrared lens with focal length range of 30mm~110mm, working wavelength of 8 μm~12 μm and F number of 1.0,which was used in conjunction with a 320×240 pixel uncooled detector with the pixel size of 25 μm×25 μm.The total length of the optical system is less than 230 mm, the entire system consists of 7 lenses, and only uses the germanium material, all surfaces are spherical. Finally,we conducted the tolerance analysis the infrared zoom system, and obtained a set of loose machining tolerance.The results show that in the short focus of 30 mm, the modulation transfer function (MTF) value of system is greater than 0.3 at 20 lp/mm,while it is greater than 0.317 4 at 20 lp/mm in the long focus of 110 mm.