Magnetorheological finishing (MRF) is a subaperture lap, deterministic process developed at the Center for Optics Manufacturing (COM). MRF can remove subsurface damage from an optical component while correcting figure errors and smoothing small scale microroughness. The "standard" magetorheological (MR) fluid for finishing of optical glasses consists of magnetic carbonyl iran and nonmagnetic cerium oxide particles in water. This composition works well for a variety of soft and hard glass types, but it does not perform adequately for certain single crystal material and polycrystalline compounds used in IR applications. in this paper, we describe modifications to MRF and finishing experiments for LiF, ZnSe, CaF2, AMTIR-1, ZnS, MgF2, sapphire, and CVD diamond.

Magnetorheological finishing (MRF) is a subaperture lap, deterministic process developed at the Center for Optics Manufacturing. MRF can remove subsurface damage from an optical component while correcting figure errors and smoothing small scale microroughness. The 'standard' magnetorheological fluid for finishing of optical glasses consists of magnetic carbonyl iron and nonmagnetic cerium oxide particles in water. This composition works well for a variety of soft and hard glass types, but it does not perform adequately for certain single crystal materials and polycrystalline compounds used in IR applications. In this paper, we describe modifications to MRF and finishing experiments for LiF, ZnSe, CaF2, AMTIR-1, ZnS, MgF2, sapphire, and CVD diamond.

Several in-house bound abrasive polisher compositions have been developed which remove subsurface damage (SSD) and reduce the rms microroughness of a variety of optical glass types to ≤10 Å in a 30 minute polishing cycle. The polisher manufacturing method is consistent and reproducible.1 The majority of the work to date has been done on a single spindle machine by polishing flat optical glass parts against a molded pellet lap using deionized water as the coolant.1,2 Recently, the Opticam®SX machining center at the Center for Optics Manufacturing (COM) became a second experimental testbed for evaluating polisher performance. The machine was utilized for evaluating polishers of the same composition as the molded pellet polishers, but in the ring tool configuration. Surface microroughnesses of <10 Å rms were obtained on BK7 glass. A new polisher formulation also removed the cutter marks which are typically introduced during the grinding cycle. The ring tool polisher was used as the last tool in a series of automated tools for final finishing of a microground lens surface.