针对三组式伸缩型结构高倍率变焦距镜头设计进行了研究。对含中间固定组的三组式结构高斯光学进行了讨论, 给出了高倍率设计的高斯解范围和选取原则, 并编制了可视化辅助设计软件, 为高斯参数的最优化选取提供条件。采用这种结构设计了一套焦距12~600 mm、变倍比50倍、视场角0.85°~41.2°的伸缩型变焦距镜头, 短焦时前片至像面175 mm、长焦时为309 mm, 长焦端远摄比达0.51; 各焦距位置在100 lp/mm处轴上视场调制传递函数(MTF)大于0.3, 边缘视场MTF大于0.2, 同时系统具有小型、便携的特点。

High ratio zoom lens design using three-group flexible structure is researched. The Guassian optics for three-group structure with fixed middle group is discussed. The range of Guassian parameters and principle of selection for high ratio design are presented. The visible assist design software for Guassian parameters selection is developed. A flexible zoom lens with ratio 50×, focal length 12~600 mm, and field of view 0.85°~41.2° is designed. The optical total length is 175 mm for short focal length, 309 mm for long focal length, and the telephoto ratio of long focal length is 0.51. The modulation transfer function (MTF) at 100 lp/mm for each focal length is higher than 0.3 at center field, and higher than 0.2 at edge field. The system possesses the characters of miniature and portable.