Development of a non-contact center thickness optical metrology system

Michael J. Thorpe; Jason K. Brasseur; Peter A. Roos

doi:10.1117/12.2190163

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1 September 2015 Development of a non-contact center thickness optical metrology system

Michael J. Thorpe, Jason K. Brasseur, Peter A. Roos

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Proceedings Volume 9576, Applied Advanced Optical Metrology Solutions; 95760I (2015) https://doi.org/10.1117/12.2190163
Event: SPIE Optical Engineering + Applications, 2015, San Diego, California, United States

Abstract

The last place an optics manufacturer wants to physically touch a lens is at the center. However, this is precisely what is currently done to measure center thickness of lenses. Using contact methods, the question is not whether the optic is damaged, it is whether the resulting damage is acceptably low. At Bridger Photonics, we have proven the feasibility of a non-contact center thickness metrology system to address this need. The apparatus uses a technique similar to swept-frequency optical coherence tomography to measure both physical thickness and optical thickness. From these measurements, the group index of refraction can also be determined. Moreover, the phase index can be determined, given the Sellmeier coefficients. In this presentation, we will report our demonstrated measurement range of 75 mm optical thickness (larger possible), as low as 20 nm precision, and group index of refraction determined to better than 5 parts is 10⁵. We believe the metrology system resulting from these proof-of-principle demonstrations will be a valuable tool for precision optics manufacturing.

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Michael J. Thorpe, Jason K. Brasseur, and Peter A. Roos "Development of a non-contact center thickness optical metrology system", Proc. SPIE 9576, Applied Advanced Optical Metrology Solutions, 95760I (1 September 2015); https://doi.org/10.1117/12.2190163

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