Direct Ion Beam Figuring Process and Rotational Measurement Method for Ultra-smooth Aspherical Surfaces of a 46.5 nm Telescope  

作　　者：Weichen Gu Jun Yu Pengfeng Sheng Qiaoyu Wu Qiushi Huang Zhanshan Wang 

机构地区：[1]Key Laboratory of Advanced Micro-structured Materials,Ministry of Education,Tongji University,Shanghai 200092,China [2]Institute of Precision Optical Engineering,School of Physics Science and Engineering,Tongji University,Shanghai 200092,China

出　　处：《Research in Astronomy and Astrophysics》2023年第11期136-149,共14页天文和天体物理学研究（英文版）

基　　金：funded by the National Key R&D Program of China (2022YFF0709101);the National Natural Science Foundation of China (NSFC) under Nos. 62105244 and 61621001。

摘　　要：This paper describes a fabrication process for the hyperboloidal concave mirror of a 46.5 nm telescope. The180 mm aperture hyperboloidal concave mirror and 70 mm aperture compensator are machined directly from chemical mechanical polishing of a spherical surface to a high-accuracy aspherical surface by ion beam figuring.The aspherical measurement method is the Dall null test. To minimize system errors in the measurement process,the rotational measurement method with six rotations is used in the null test. The results of the analysis for the ME(first solve the machined surface profile, then solve the system errors) and EM(first solve the system errors, then solve the machined surface profile) methods of calculation in the measurement are given. The ME method is a more accurate rotational test method, and the six rotations are appropriate for rotational measurements. After the figuring process, the hyperboloidal concave mirror surface profile reached 8.27 nm rms and the compensator surface profile is approximately 4 nm rms. The roughness of the hyperboloidal concave mirror is smooth to0.160 nm rms.

关 键 词：Astronomical Instrumentation Methods and Techniques instrumentation:high angular resolution telescopes 

分 类 号：P111[天文地球—天文学]