Scattering Effects Of Machined Optical Surfaces

Recent progress in the machining of optical surfaces promises to significantly reduce the time and cost of manufacturing optical elements. Specific reference is made to a new kind of machining process called deterministic microgrinding. Optical surfaces made by machining processes like single-point diamond turning, or deterministic microgrinding exhibit residual cutting tool marks that result in scattering effects which can significantly degrade optical performance. However, for some infrared applications, post-polishing may not be required and thus resulting in substantial cost savings. In this paper surface scattering theory has been implemented to model the image degradation effects of residual surface irregularities for optical surfaces exhibiting: i) azimuthal tool marks (diamond turning), ii) radial tool marks (deterministic microgrinding) and, iii) random roughness caused by conventional grinding and polishing. Intercomparison of these three processes provides new insight into the scattering behavior and fabrication tolerances for these very different manufacturing processes