Computer Controlled Polishing of the Off-axis Aspheric Mirrors

In this paper, the manufacturing and testing procedures to make large off-axis aspherical mirrors are presented. The difficulties in polishing and testing for both circular-aperture and rectangular-aperture mirrors are previewed, and a possible solution is given. The two mirrors have been polished by means of CCOS, and the final accuracy is 25nm rms for 770mm×210mm rectangular mirror and 20nm rms for φ600mm circular mirror. These results just meet the optical tolerances specified by the designer, and the manufacturing and testing procedures presented here show good ability to make the large off-axis aspherical mirrors.