在电视制导中,当目标捕获时希望用短焦距、大视场光学系统,当目标跟踪时希望用长焦距、小视场光学系统。传统方法是设计两档或三档变倍光学系统,但在换档过程中目标易丢失,而采用连续变焦系统,可兼顾系统对目标的捕获与跟踪。文中介绍了变焦光学系统的原理及其参数确定方法,并设计了一种焦距为20~100mm,视场角为1.8°×1.38°~9°×6.8°的可见光连续变焦电视光学系统,试验结果表明系统像质良好,长焦时能对远距离点目标高精度跟踪,短焦时能快速捕获和观察目标。

In the television-guided system, a short focal length lens with wide field of view is hoped when target recognition, however, a long focal length lens with narrow field of view is hoped when target tracking. The traditional method is to design a switch-zoom optical system, which is subject to losing target in the course of shifting, but a mechanical-compensated zoom lens can be a good balance between target acquisition and tracking. The principle of zoom lens and the optical parameters determination are described in the thesis, and a focal length from 20 to 100mm visible video zoom lens is designed, that field of view is 1.8°×1.38°~9°×6.8°. The results of experiments show the system has good image quality, and it not only can accurately track far spot target in the case of long focal length, but also can fast recognize and observe target in the case of short focal length.