Assessing surface imperfections of freeforms using a robotic light scattering sensor

Light scattering-based characterization techniques are fast, sensitive, and robust, which can be exploited for roughness measurements or homogeneity and defect assessment. However, only compact scattering instruments enable even large freeform surfaces to be inspected close to fabrication or even within fabrication processes. The combination of a light scattering sensor with an industrial robot, as well as its application for full surface evaluation of aspheriscal and freeform surfaces, is addressed. In addition to the technical considerations regarding the sensor, the robotic handling system, or the sample curvature, examples of application to different optical components fabricated at the Fraunhofer Institute for Applied Optics and Precision Engineering using state-of-the-art techniques are presented. The results include the discussion of anisotropic surface structures induced by diamond turning or polishing as well as the analysis of the influence of a protection layer.