Highly efficient deterministic polishing using a semirigid bonnet

This paper presents a semirigid (SR) bonnet tool which has the advantages of high efficiency and determinacy for material removal on optical elements and also has the potential to be used on aspheric optics. It consists of three layers: a metal sheet, a rubber membrane, and a polishing pad, from inside to outside. It inherits the flexibility of a normal bonnet but has a higher stiffness. Finite element analysis was performed to determine that the stainless steel is the best-suited material for use as the metal sheet. An SR bonnet with a stainless-steel metal sheet was fabricated and tested. Its tool influence function (TIF) is Gaussian-like, and the TIF stability is more than 90%. The peak-to-valley of its uniform removal area is less than 0.1 lambda. Tool ripples are highly depressed and the surface profile is well preserved in the prepolishing test. In 12 min, similar to 36 mm(3) of material is removed. (C) The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.