SUB-SURFACE DAMAGE EVALUATION IN GRINDING OF LARGE OPTICS

摘要

This paper shows results obtained when grinding optical materials using the BoX~® grinding system. An efficient process has been developed for precision grinding large optics. Total grinding process time to remove 0.5 mm from a pre-shaped 1 metre optical blank is 10. hours.rnOn Zerodur~®, the surface roughness (R_a) and subsurface damage level obtained are 247 nm and 4 μm respectively. On ULE~®, R_a and SSD level obtained are 191 nm and 8 μm respectively. The difference of subsurface damage can be related to relative material brittleness. No significant connection was seen between surface roughness and subsurface damage using the BoX~® grinding mode. Further work will be carried out regarding the influence of grinding machine dynamics and induced subsurface damage levels in optical surfaces.