改进的离轴三反光学系统的设计

摘要

基于离轴三反光学系统(TMA)的一般设计方法,总结了设计要点.以两个基于三反光学系统的设计为实例,阐述了通过合理地安排光学结构、将次镜设计为球面反射镜、主镜和三镜在球面基础上改变高次非球面系数等,可使离轴三反光学系统的设计结果接近衍射极限,传递函数在50 lp/mm时都接近0.6,Strehl率由通常的0.91提高到0.93.与传统离轴三反系统相比,相机加工公差和面形加工公差从原来的λ/50放宽到λ/40,主、次、三镜的装调公差放宽了4倍.文中的设计降低了相机的加工及装调难度,有助于系统光学特性实现衍射极限,为三反光学系统的广泛应用提供了借鉴和实用参考.%The key design of off-axial Three-mirror Anastigmat (TMA) systems was summarized, and an improved design of the off-axial TMA optical systems was proposed with a new optical structure. By taking two designed systems for examples, the optical elements of the TMA system were reasonably arranged, the secondary mirror was designed as a spherical surface, and the primary and the third mirrors were optimized with high-order aspheric coefficients. Obtained results show that the Modulation Transform Function(MTF) curve of the designed system approaches to the optical diffraction limit with an improved value of 0. 6 at the spatial frequency of 50 pl/mm. Compared with the common off-axial TMA optical system, the Strehl ratio can be increased from 0. 91 to 0. 93. The surface tolerance is relaxed from λ/50 to λ/40, and the assembling tolerances of the primary mirror, second mirror and the third mirror can be relaxed by a factor of 4. The improved design makes the manufacture and assembly of the off-axial TMA optical system much easier, and helps the system to achieve excellent performance in the level of optical diffraction limit. These are beneficial to the popularization of off-axial TMA optical systems.