Technology on Fabrication of Precise SiC Aspherical Mirror

This paper represents a technique to produce the large size optical aspherical mirror by using reaction-bonded silicon carbide to meet the material requirements of the space used mirrors, based on the characters comparison of all types mirror material. Techniques are described in this paper, including the bonding procedure of silicon carbide to form a mirror shape, the CCOM technology for aspheric grinding, polishing on a home-developed tool –FSGJ-2, and the aspheric profilometry. A specialized Offner Null lens is also developed to measure the aspherical mirror with laser interferometer. With the technology depicted in the paper, a 502mm x 298 mm off-axis SiC aspherical mirror is successfully made with a surface accuracy better than 1/50λrms, the final result meets the design requirement.