<title>Super-smooth surface polishing on aspherical optics</title>

Abstract

The study of microscopes for shortwave light such as X rays has made much progress in recent years. Accordingly, the demand for a super-smooth aspherical optical element is increasing. The purpose of this research is to achieve a 0.08 p m or less surface figure error (relative accuracy 1O),and a 0.2 nm rms or less surface roughness on freeform surface optical elements of 500 mm in diameter or more. In order to improve the degree of surface roughness, we used a local pitch polishing method that had a profile generation possibility. A surface roughness of less than O.O6nm rms was achieved in the end of 1990 using the fused silica. In order to improve figure accuracy and ripple, we developed the Canon Super Smooth Polisher (CSSP)(Fig.1) which corrects the figure error by an on-machine measurement and developed a profile generating algorithm by early 1991. In this paper, we describe the results of studies on super-smooth polishing methods and the evaluation results of the CSSP system.