Roughness Metrology of Aspheres & Freeforms

The measurement of surface texture can be critical to ensuring optimal performance in an imaging system. Standard aspheric surface fabrication techniques including, diamond turning and sub-aperture polishing, can leave traces of the cutting process on the final product. Issues with surface texture on a lens can lead to a lack of image uniformity, scattered light, and even diffraction in the final image. Zygo 3D systems can quickly detect surface texture issues using full area, high resolution optical metrology.

A typical surface texture application includes analyzing results such as Sa and Sq to determine the roughness of the lens over the entire optical area. Surface texture analysis can also identify localized defects on the surface due to damage or contamination. A more advanced surface texture application might include analyzing the uniformity or period of turning marks on the lens. In all cases, surface texture can be useful for identifying problem areas in the molding, polishing, or coating process.