MRF fabricates 'perfectly bad' surfaces

摘要

Magnetorheological finishing (MRF) can be used to modify and characterize a surface in an optical system so that it is "perfectly bad," or precisely compensating for all other system wavefront errors. The final finishing step in any optical-component manufacturing process has always been associated with improving the surface or wavefront. Magnetorheological finishing (MRF) and its deterministic polishing approach is well known for the benefits it brings to this important step. This approach is, of course, fine when the desired result is a flatter or more spherical (or conventional aspheric) surface, even when such a surface is expected to be λ/10 peak-to-valley or better. What is one to do, however, when simply making the surface flatter or more spherical isn't enough, or when the desired shape is something other than a "perfect" plano or spherical surface? Certain components and applications require optical surfaces and wavefronts that deviate in a very specific way from the flat or spherical surfaces described above. We have chosen to call these "perfectly bad" surfaces, in that they are designed with the same or even tighter figure tolerances than their more mundane counterparts and yet have the added requirement that the residual error be of a very specific nature.