Ultra-precision finishing of optical mold by magnetorheological polishing using a cylindrical permanent magnet

摘要

A magnetorheological polishing was proposed to be used for optical glass mold finishing, aiming at suppressing middle spatial frequency errors from ultra-precision grinding while improving surface roughness. A small polishing head, with a cylindrical permanent magnet enveloped by a nonmagnetic outer shell, was also developed. Polishing experiments were performed on concave aspheric tungsten carbide molds. The results demonstrated the developed magnetorheological polishing successfully suppressed the middle spatial frequency errors on the optical mold by decreasing amplitude to 1 nm, while improving overall surface finish to 1 nm in R (a) .