大相对口径轻量化卡塞格林系统主镜的加工检验

介绍了卡塞格林系统的焦距为6000 mm,系统的相对口径为1/10,主镜的口径为600 mm,主镜相对口径为1/1.2,主镜的材料是微晶玻璃,背面打有盲孔,质量为原来的50%.由于主镜的相对口径比较大,而且经过轻量化,因此加工难度比较大,在加工过程中在传统方法的基础上对工艺加以改进,采用三点扩九点的支撑方法和四点夹持的方法,最终将主镜加工到了很高的精度.主次镜组合系统的弥散圆直径小于0.02 mm,用干涉仪检验卡塞格林系统主镜的峰值(PV)为1.23λ,均方根(RMS)为0.18λ.

Manufacture and Test of Cassegrain System's Primary Mirror with Large Relative Diameter and Lightweight

The Cassegrain system is manufactured with focal length of 6000 mm, and relative diameter of 1/10. The diameter of the primary mirror is 600 mm with its relative diameter of 1/1.2 and the material of the primary mirror is crystallitic glass. Because of even holes on the back of the primary mirror, the lightweight ratio of the primary mirror is 50%. For the reason of large relative diameter and light weight the manufacture of the system is difficult. In the course of the manufacture new methods are developed based on the traditional methods. The support of nine points is used based on the support of three points and finally the primary mirror is made with a high precision. The diameter of dispersion circular of the Cassegrain system is less than 0.02 mm, peak value (PV) of Cassegrain system is 1.23λ (λ=0.6328μm), and the root-mean-square (RMS) value of system is 0.18λ.