Low- and mid-spatial frequency components measurement for aspheres

摘要

The Large Area Curvature Scanning (LACS) method for measuring all types of surfaces including aspheres is based on scanning the surface at discrete lateral coordinate positions, but the amount of information captured during measurement is much greater. The Extended LACS (ELACS) method will be presented that uses this information to evaluate also the mid-spatial frequency components of the surface. An examples of measurement for a surface showing a relatively high mid-spatial frequency content is given and ELACS is compared to other methods. These are various methods subsumed under the term "stitching," especially stitching interferometry. Different mathematical concepts for these methods are briefly discussed and a novel approach is presented and analyzed with special emphasis being laid on the uncertainty which can be achieved with stitching methods.