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一、引言 在彩色电视广播中,光学成象是非常重要的,就是说在播送节目之前必须产生一个理想的影象,因此要求摄象机要有一个性能特别好的光学系统。这个系统是由外部光学和内部光学组成的,前者是变焦距物镜和扩展镜(或倍率镜),后者是指分色棱镜、滤光片、背景光路和测试卡投影系统。这两部分之间有紧密的关系,设计时必须统一考虑,例如为了能容纳由分色棱镜和各种滤光片所组成的复杂光路,就要求变焦距物镜有足够长的后工作距离。为了减小分色棱镜的色偏移现象,要求物镜出瞳是远心的,即使设计有困难,也应使出瞳尽量远离象面。同样,为了避免轴外象场的色偏移,需尽可能
I. INTRODUCTION In color television broadcasting, optical imaging is very important. That is to say, an ideal image must be produced before the program can be broadcasted. Therefore, it is required that the camera have an optical system with particularly good performance. The system consists of external optics and internal optics, the former being a zoom objective and an expander (or magnification mirror) and the latter being a dichroic prism, a filter, a backlight and a test-card projection system. There is a close relationship between these two parts and must be considered in the design. For example, in order to accommodate the complicated optical path formed by the dichroic prism and the various filters, the focal length of the zoom lens is required to be long enough for the rear working distance. In order to reduce the color shift of the dichroic prism, it is required that the exit pupil of the objective lens is telecentric, and even if the design is difficult, the exit pupil should be made as far as possible from the image plane. Also, in order to avoid the color shift of the off-axis image field, it should be as possible