Fabrication and test of SiC convex aspheric mirror

Abstract

In order to satisfy all-frequency error quality controlling and high-precision test during the process of the convex asphere,double laps with polar coordinate polishing technique and the measuring poles method used for the alignment of Hindle test are proposed.Firstly,the double laps with polar coordinate polishing technique for manufacturing the aspheric mirror and the numerical control machine for processing aspheric surface are presented.Then,the measuring poles method used to control the distances between vertex of the standard sphere and the vertex and focus of the tested asphere is introduced,and the controlling precision is analyzed.Finally,for a convex asphere with the aperture of Φ158 mm,the test results and precision of the Hindle test are described.The results indicate that the double laps polishing technique can make the low-frequency surface error convergence quickly,and the mid-frequency surface error is restrained at the same time.The controlling precision of the low-frequency surface error is about λ /30(λ = 633 nm).The limit error using the measuring poles to control the distance is ± 0.065 mm,and the tolerances of the two space parameters are ± 0.22 mm and ± 0.30 mm,respectively.The fast manufacture and all-frequency controlling of the convexasphere are realized by the double laps with polar coordinate polishing technique,and the test result of lowfrequency surface error is 0.022λ(RMS,@ 633 nm) in the Hindle test,which satisfies the specification requirements of the optical design.