Figuring of fused silica optical surface with thin parts by plasma chemical vaporization machining

Abstract

Our previously developed plasma chemical vaporization machining (CVM) does not apply a load to the surface to be figured during its process. Thus, plasma CVM is expected to be able to process lightweight mirrors having a surface with thin parts supported by ribs with high accuracy. In this study, we investigated the removal characteristics of plasma CVM for fused silica workpieces having thin and thick parts simulating a lightweight mirror. The experimental results showed that such workpieces were processed with a uniform removal depth by placing a fused silica column at the back of the thin part. Moreover, a flat surface having a thin part of 0.6 mm thickness was figured by plasma CVM, where a column was placed in the thin part in the same way as in the fundamental study. As a result, we successfully demonstrated that plasma CVM enables the figuring of an optical surface with thin parts.