<title>Computer-controlled polishing of aspheric surfaces</title>

Abstract

From the option's viewpoint, aspheric surfaces are usually the most difficult surfaces to fabricate accurately. For this reason, the cost of aspheric elements which are figured by hand is high. In this paper, a computer controlled generation of rotation— ally symmetric aspheric surfaces is presented, which accurately predicts material removal rates with a X—Y type computer—controlled polishing system and a small polishing tool. In according to theoretical calculation,300mm spheric surface (r=2090) is figured into a 300mm f/3.5 parabolic surface along 10 concentric circle areas in 30.8 hrs. The surface accuracy of A./8(RMS) can be obtained,by testing tower including CQG—1 digital interferometer. After analysis of the technique methods and experiment results, we come to the conclusion that the double rotation tool polishing removal profile is the key parame— ter,To insure the optical surface quality, the different polishing paths, optimized operating parameters and adequate detecting system are required in polishing of different aspheric surfaces. A computer model of the polishing process was developed and used to investigate the removal profile of various tool shapes and different polishing parameters from the model. Software was developed to control the X—Y stepmotors, monitor the process, calculating material removal profiles and surface testing data. Some unsolved problems and other possible uses are discussed in this CCP system. Finally, the development of the X—Y polishing machine and the necessary software of IBM/PC microcomputer to implement the process are also discussed.