Freeform Optics Post-Processing using Pseudo-Random Orbiting Stroke

Abstract

In addition to achieving a desired freeform profile, ensuring superb micro-roughness finish is a key factor for a successful freeform optics manufacturing. We present a Pseudo-random Orbiting Stroke (PROS)-based post-processing technique that maintains freeform optics forms while improving small-scale surface quality. The full aperture tool can avoid subaperture effects, and the small stroke pseudo-random 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 (MRF)-polished BK7 glass, single-point diamond-turned (SPDT) polymethylmethacrylate (PMMA), 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 post-processing technology. Surface roughness measurement highlights improvements in local surface roughness and periodic tool mark errors left by the previous polishing method.