Figure Correction of a Quartz Sub-Mirror for a Transmissive Diffractive Segmented Telescope by Reactive Ion Figuring

Abstract

A quartz sub-mirror was figure-corrected in a parallel removal process for the first time. An Reactive Ion Figuring (RIF) process with a simple and universal masking method was demonstrated, and the 350-mm quartz sub-mirror was figure-corrected from the initial figure error of ~23 nm RMS to the final figure error of ~8 nm RMS in total effective figuring time of ~52 minutes after 4 iterations, which exhibited the actual potential of RIF on the figure-correction of quartz optical elements and the possibility on applying RIF to meet the requirement of mass production for sub-mirrors of transmissive diffractive segmented telescopes.

Plasma Figure Correction Method Based on Multiple Distributed Material Removal Functions

“…This is similar to the calculation and acquisition of dwell time in other polishing methods. In addition, unlike our previous attempts to perform reactive ion etching for fast figure-correction of transmission wave-front error on lightweight thin film diffraction elements and a quartz sub-mirror [ 25 , 30 ], an inkjet printer was used to print the UV-curable ink masking layers on the non-etching area MReg i ( x , y ) to protect the surface material. During each figuring cycle, when etching was completed, the masking layers were stripped using hydrogen peroxide, alcohol, and acetone, and the mirror was cleaned with deionized water.…”