将衍射结构视为折射率无限大的薄透镜，研究了衍射透镜高折射率表示的折衍混合复消色差望远物镜设计的PWC方法；设计了焦距为2000mm、相对孔径为1／15的双片型折衍混合复消色差望远物镜，并与常规三片型纯折射复消色差望远物镜进行了比较，结果表明双片型折衍混合复消色差望远物镜具有更好的二级光谱校正能力，色球差更小，因此具有更好的成像质量．

The secondary spectrum is a main factor debasing image quality in telescope objectives that have long focal length and large relative aperture. Recently,the special dispersion character of the diffractive structure has been applied to correct secondary spectrum with ordinary material and simple construction. In this paper,a diffractive optical element is equivalent to a thin lens with infinite refractive index. Based on this ultra-high index model,the PWC method has been investigated to design hybrid diffractiverefractive (HDR) apochromatic telescope objectives. A HDR doublet apochromatic telescope objective with a focal length of 2000 mm and a relative aperture of 1/15 has been designed. Compared with conventional triplet design,it is shown that hybrid objective is better to correct secondary spectrum and spherochromatic aberration,so has better image quality.