Freeform non-contact surface metrology with UltraSurf

Abstract

Freeform optics are gaining popularity and the industry is adapting to meet the challenges. Datum surfaces are generally required for proper tolerancing of freeform surfaces due to the possible lack of symmetry. Complex rotationally symmetric surfaces such as high departure aspheres are becoming more commonplace. Metrology systems must now be able to handle large spherical departures, curvature inflections, vertical or steep datum features, and varying surface texture. The UltraSurf was created to address many of these challenges. It is a 5-axis non-contact metrology system. It employs various optical point sensors that can handle rough surface textures such as ground glass as well as highly reflective optical and surfaces. The combination of five motion axes allow for the scanning of standard aspheric optical shapes as well as freeform optics and associated datum structures. UltraSurf can scan freeform windows to gather form error on both primary surfaces as well as thickness and wedge when paired with a low-coherence interferometry probe. UltraSurf was designed from the ground up to have flexible software that can enable a user to input these complex freeform surfaces and address the upcoming challenges. Examples of freeform and steep complex surface metrology will be presented along with how the UltraSurf can streamline the process.