Shape and curvature error estimation in polished surfaces of ground glass molds

In the fabrication process of aspheric glass lens and moulds, shape characterization is a fundamental task to control geometrical errors. Nevertheless, the more significant geometrical functional aspect related to the optical properties is the curvature, that is rarely investigated in the manufacturing process of lenses. In this paper, algorithms for the assessment of shape and curvature errors on aspheric surface profile are presented. The method has been investigated on profiles measured before and at different steps of the membrane polishing process. The results show how surface roughness, shape and curvature, change during the polishing process as a function of the machining time.