Polishing of large-aperture reflective SiC mirror using computer-controlled optical surfacing

A 600 mm aperture SiC flat mirror was polished up to an aperture of 35 nm (RMS) with computer-controlled optical surfacing (CCOS) in a very short period. The SiC mirror structure, the choose of the diamond powder, and other procedures in CCOS are presented in the paper. The adjustment of the removal function in the polishing process was carefully performed in order to increase the polishing efficiency of the silicon material, and the efficiency in PV and RMS convergence was obtained according to the experiment results. In addition, the efficiency in polishing SiC material needs to be further analyzed to make sure that the batch production of this kind of hard material mirror is possible.