The Study On CCOS Of Large-diameter SiC Mirrors

In recent years, the material properties of traditional mirror materials cannot meet the requirements of space-based optical system. Space-technology researchers have focused on silicon carbide (SiC) for its high elastic modulus, low density and thermal expansion, high thermal conductivity, and so on. But the optical surfacing on SiC mirrors is extremely difficult because of its high hardness and elastic modulus. So it's very important for the manufacture of space-based optical system to master the computer controlled optical surfacing (CCOS) technology of SiC mirror. In this thesis, the key technology to manufacture the SiC mirror applying CCOS was studied.1. InstrumentThe optical surfacing instrument, FSGJ- II aspheric computer controlled manufacturing center, was introduced briefly.2. CCOS grindingThe mechanism of grinding on SiC mirror was studied, and Preston Function was proved to be true in the grinding on SiC mirror. And the key factors affect the SiC CCOS grinding, such as tools, abrasives, load, speed, were studied and chosen.3. CCOS polishingThe mechanism of polishing on SiC mirror was studied. And the key factors affect the SiC CCOS polishing, such as tools, abrasives, load, speed and slurry PH were studied and chosen. Surface roughness and optical properties of the SiC mirrors were also tested.4. Optical film claddingThe improvement upon the mirror surficial qualities after film cladding was discussed. And the adhesive strength and the thermal stability of the film were tested.5. An exampleComputer controlled optical surfacing and testing process of a 480×280mmflat RB-SiC mirror are mentioned. It's showed that the surface figure( RMS ) is 0.050 wavelength( A =632.8nm ).