Wave front related surface form tolerances for manufacturing higher grade optical components

Abstract

For about 200 years surface shape specification for optical components always had one goal only, to make an individual optical component comparable with other pieces of the same type. If the specification is met, the component should fulfill the requested behavior in the related optical system. Nomenclature of specification did not differ in dependence on the components different position in the system or on different used beam diameters vs. components clear aperture. With increasing performance of designed optical systems, surface shape tolerances of components became tighter more and more. Such requirements either lead to inadequate expenses or to the absence of equipment to manufacture and test them in a controlled process. But in reality, only a small part of optical system components are used as they are measured - within full clear aperture. Moreover, the light beam has a significant smaller diameter than the clear aperture has. Typically, this kind of components we find in scanning systems and lenses with large Field of View (FOV). As far as designed surface shape tolerances are derived from maximal acceptable wave front deviation for individual light beams passing through the system, the related method for optical components acceptance test procedures is to analyze wave front deviation in sub apertures caused by surface shape deviation. In this case designed values and manufactured results are comparable to each other. To get the comparable values, surface shape analysis must be done in a gliding sub-aperture area instead of analysing full clear aperture. We show how sophisticated optical systems components may be specified, manufactured and tested in gliding subaperture areas for any term described in normative papers, such as ISO 10110-Part 5 Surface Form Tolerances, to assure the final function in system. The chosen examples correspond with classic specified optical component surface shapes down to 3/ - (0.02)@546nm.