Optimization of parameters for bonnet polishing based on the minimum residual error method

Chunjin Wang,Yinbiao Guo,Qiao Xu,Bo Zhong,Wei Yang,Shiwei Ye,Zhenzhong Wang

doi:10.1117/1.oe.53.7.075108

Abstract

For extremely high accuracy optical elements, the residual error induced by the superposition of the tool influence function cannot be ignored and leads to medium-high frequency errors. Even though the continuous computer-controlled optical surfacing process is better than the discrete one, which can decrease this error to a certain degree, the error still exists in scanning directions when adopting the raster path. The purpose of this paper is to optimize the parameters used in bonnet polishing to restrain this error. The formation of this error was theoretically demonstrated and will also be further experimentally presented using our newly designed prototype. Orthogonal simulation experiments were designed for the following five major operating parameters (some of them are normalized) at four levels: inner pressure, z offset, raster distance, H-axis speed, and precession angle. The minimum residual error method was used to evaluate the simulations. The results showed the impact of the evaluated parameters on the residual error. The parameters in descending order of impact are as follows: raster distance, z offset, inner pressure, H-axis speed, and precession angle. An optimal combination of these five parameters among the four levels considered, based on the minimum residual error method, was determined.

Highlights

The development of optical technology has increased the requirements for high-precision optical elements, especially aspheric optics
This paper reported that the residual error occurs because of the superposition of the tool influence function (TIF) in the bonnet polishing process
Practical bonnet polishing experiments are not appropriate for this purpose, because the residual error could be disturbed by conditions, such as initial surface profile error, instability of the TIF, and holding an error of the work-piece

Summary

Introduction

The development of optical technology has increased the requirements for high-precision optical elements, especially aspheric optics. The polishing procedure is vital for acquiring high-accuracy aspheric optics during the manufacturing process. Various computer-controlled optical surfacing (CCOS) processes have been developed in recent decades.[2,3,4,5,6] CCOS adopting a small-pitch tool was first developed by Jones,[2] and it has been successfully used for polishing various types of optical elements.[7,8] Its form correction efficiency is much higher than the artisanal processes. There is a mismatch between the pitch tool and the work-piece surface when polishing the aspheric optics. The bonnet polishing technology was first developed by Zeeko, Ltd. (Leicestershire, United Kingdom) in collaboration with the Optical Science Laboratory at the University College London and Loh Optikmaschinen.[17,18] This technology

Objectives

Methods

Discussion

Conclusion