Comparison of metrology techniques for off-axis and freeform optical surfaces

Christopher Hall; Johnathan Davis

doi:10.1117/12.2602827

28 October 2021 Comparison of metrology techniques for off-axis and freeform optical surfaces

Christopher Hall, Johnathan Davis

Author Affiliations +

Proceedings Volume 11889, Optifab 2021; 118891H (2021) https://doi.org/10.1117/12.2602827
Event: SPIE Optifab, 2021, Rochester, New York, United States

Abstract

Modern optical fabrication techniques have grown progressively more complex to reflect the broadening design space of optical systems. Rotationally symmetric aspheric surfaces have been joined by off-axis and freeform designs, and the demands made of the “simpler” designs are continuously pushing the limits of the current “state of the art.” As a result the metrology needed to support the fabrication of such components has become increasingly complex. Both in-process testing and final performance certification require metrology that can report surface performance as a function of alignment to reference datums. The metrology requirements for the various process steps are often differentiated by the resolution requirements. As the processing progresses away from full aperture tooling, the opportunity to address and/or impart higher order content increases. The resolution of the test setup must correspondingly increase to provide a way to measure and mitigate any of this content deemed undesirable. Simply specifying a low-order figure tolerance is no longer sufficient. As system requirements have changed designers have become more aware of the issues associated with these higher order errors. Surface error specifications now often span a specific range of spatial frequencies and therefore require a corresponding range of instruments to characterize as well. This paper will compare the various metrology techniques employed by the team at QED Optics and discuss how they enable specific aspects of the manufacturing process.

Conference Presentation

Citation Download Citation

Christopher Hall and Johnathan Davis "Comparison of metrology techniques for off-axis and freeform optical surfaces", Proc. SPIE 11889, Optifab 2021, 118891H (28 October 2021); https://doi.org/10.1117/12.2602827

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