Fabrication and testing of aspheric silicon carbide mirror

In order to manufacture a precise aspheric silicon carbide (SiC) mirror, the fabrication and testing technologies for the substrate of the SiC mirror and the surface of the modified SiC mirror were studied. The technique of the computer-controlled optical surfacing for manufacturing aspheric mirror and the FSGJ-2 numerically-controlled machine for processing aspheric surface are introduced. The methods of contour testing and null testing were adopted respectively to measure the surface accuracy of aspheric mirror while SiC mirrors were grinded and polished. The surface profile and roughness of the final aspheric SiC mirror were tested with null testing and surface roughness tester. The testing results indicate that all the specifications meet the requirements of design. The surface profile accuracy of the aspheric SiC mirror is 0.016λ RMS and the surface roughness of the mirror is 0.85nm RMS.