Pseudorandom orbiting stroke for freeform optics postprocessing

Abstract

In addition to achieving a desired freeform profile, ensuring a superb micro-roughness finish is a key factor for successful freeform optics manufacturing. We present a pseudorandom orbiting stroke-based postprocessing technique that maintains freeform optic forms, while improving small-scale surface quality. The fullaperture tool can avoid subaperture effects, and the small stroke pseudorandom tool path guarantees the match of freeform profiles while preventing the directionality of the final surface profiles. Three independent experimental studies are designed, conducted, and presented for a wide range of optics, including magnetorheological finishing-polished BK7 glass, single-point diamond turned (SPDT) poly(methyl methacrylate), and SPDT Al6061 optics. The comparison of direct measured maps on the initial and final smoothed optics verifies the form maintenance capability of the freeform optics postprocessing technology. Surface roughness measurement highlights improvements in local surface roughness and periodic toolmark errors left by the previous polishing method.