Scattering Effects From Residual Optical Fabrication Errors

Scattering effects from residual optical fabrication errors limit the optical performance of many imaging systems. Residual surface roughness over a broad range of relevant spatial frequencies must be specified and controlled for many applications of interest. Wide-angle scatter from surface microroughness severely reduces contrast in extended images. However, small-angle scatter from `mid\u27 spatial frequency surface irregularities that span the gap between the `figure\u27 and `finish\u27 errors will degrade the achievable resolution. Specifying the traditional surface `figure\u27 and `finish\u27 is thus inadequate for high resolution imaging systems or for optical elements fabricated by new automated optical manufacturing processes. A linear systems treatment of surface scatter theory will be presented and its implementation in a computer code for modeling the image degradation effects of residual surface irregularities over the entire range of relevant spatial frequencies will be demonstrated. Parametric performance predictions can then be used to determine realistic optical fabrication tolerances for a variety of applications