Fabrication, Surface Shape Detection and System Error Correction of Precise Large Diameter Convex Aspheric Surface

Abstract

Convex aspheric mirrors are core optical elements in space optical systems, and their surface shape errors directly affect the imaging quality of the system. In order to improve the surface accuracy of large diameter convex aspheric mirrors, the high-precision fabrication and testing techniques of large diameter convex aspheric mirrors are studied. With an off-axis three mirror optical system secondary mirror as the optical parameters of convex aspheric mirror, use high precision aspheric surface milling-robot grinding and polishing process-ion beam polishing as machining method. In the grinding stage, the surface shape is measured by three-coordinate measuring instrument, in the polishing stage, the surface shape is measured by meniscus lens with interferometer, the calibration and correction of the meniscus are carried out by using standard spherical mirror. Based on the theoretical analysis of the detection method of aspheric surface, combined with experiments, extracted the error factor. Through the process method, the error parameter of high sensitivity are controlled, and the perfect large aperture convex aspheric test error separation is constructed. The system error is calibrated and the surface distribution of the real aspheric optical component is calibrated. The testing result indicate that the surface figure accuracy are 0.017λRMS. Through this measuring method, full aperture testing of optical aspheric can be realized. All the specifications of the convex aspheric mirror can meet the requirements of the optical design.