Metrology of Visibly Transparent Large Aspheric Optics

Optimax has made great progress in advanced manufacturing techniques by implementing deterministic robotic polishing for the production of freeform optics. However, one of the last key steps necessary for efficient manufacturing is to integrate onboard metrology into this closed loop process. In traditional optics manufacturing, the default ‘go-to’ test is wavefront phase-shifting interferometry, capable of sub-nanometer accuracy. Interferometry is limited in the types of optical surface shapes and sizes it can measure. Interferometry of freeform optics requires using costly computer generated holograms (CGH) which are difficult to align and can only be used for one specific optical design. Also they require large setup fixtures, and the equipment itself is expensive and disruptive to the manufacturing flow. Fringe reflection measurement addresses these pitfalls of interferometry and is more compatible with closed loop manufacturing. We propose to complete the manufacturing process loop by fully integrating fringe reflection measurement onto the robotic polishing platform and to measure parts in-situ. Integrating metrology onto the manufacturing platform will also solve the issues of physically moving large conformal windows and the associated time, cost and safety issues of repeatable moving large, heavy optics.