SBIR Phase II: High Dynamic, Alignment Free Metrological Method for 3D Shape Measurement of Optical Surfaces Based on Polarization

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This Small Business Innovation Research Phase II proposal aims at developing a new alignment-free metrological turn-key system dedicated to the measurement of optical surfaces with high measurement speed and high dynamic range. Next generation optical surfaces will need to be mass-produced with high departure from spherical shapes and high numerical aperture (Aspheric). Manufacturing these optical components is challenging because of today's limited metrology methods: contact sensors are too slow to be used in-process whereas interferometers and wavefront sensors have a small limited dynamic range and require careful alignment. The research objective is to design a prototype of a polarization based method and to evaluate its performances; speed, dynamic range, accuracy, insensitivity to alignment. The proposed approach combines an innovative polarization camera, a specific illumination, and a novel algorithm for automatic 3D shape extraction. The result of this research is to demonstrate that the proposed approach leads to very low sensitivity to alignment, fast measurement time, high dynamic range, and uncertainty smaller than current manufacturing tolerances. Preliminary simulations show that 2" diameter aspheric lens can be measured in 40 ms, with a resolution of 10,000 points, a dynamic range of 20 mm and an accuracy of 0.25 micron root-mean-square (RMS). The broader impact/commercial potential of this project will address the growing manufacturing of aspheric optical components used for various applications: concentrating photovoltaics (CPV) for solar power generation, optical instruments, ophthalmic lenses and consumer electronics (cameras, phones). Controlling aspheric optical surfaces using current metrology tools is a time consuming process. Contact sensors are too slow and interferometers have tight alignment requirements and low dynamic range. The commercial potential of a system insensitive to alignment, performing fast measurements, with high dynamic range and good accuracy is extremely valuable for the following reasons. The system would allow mass production of high quality aspheric lenses with systematic inspection of each manufactured component. High numerical aperture lenses would also be measured easily in-process which will drastically increase productivity. This will translate into the faster deployment of cheaper, more efficient solar power production, lighter optical systems, and better corrected contact lenses. The present project will also have the broader impact of opening the door to a new kind of metrology based on polarization sensing, which could also be applied to many other industries such as plastics, steel, glass, automotive, robotics, surveillance and medical industries in the future.