High precision interferometric measurement of freeform surfaces from the well-defined sub-aperture surface profiles

Sangwon Hyun; Soonkyu Je; Geon-Hee Kim

doi:10.1117/12.2536867

15 November 2019 High precision interferometric measurement of freeform surfaces from the well-defined sub-aperture surface profiles

Sangwon Hyun, Soonkyu Je, Geon-Hee Kim

Author Affiliations +

Proceedings Volume 11175, Optifab 2019; 111752B (2019) https://doi.org/10.1117/12.2536867
Event: SPIE Optifab, 2019, Rochester, New York, United States

Abstract

We report an interferometric method for smooth freeform optics from the amount of sub-aperture surface profiles. The overall experimental system is composed of a 5-axis precision stage and a sub-aperture measuring interferometer, which is carefully calibrated to achieve 2 nmRMS precision. The sub-aperture interferometer adopts a broadband source in order to maximize the reliability of profile measurement, and a preliminary assumption of the overall surface is derived from the measured local 2nd derivatives which is robust to tip/tilt alignment errors during the sub-aperture acquisition. The optical surface of a 200 mm diameter 2D polynomial freeform mirror is measured based on this system and traditional contact surface profiler for the cross-validation. The experiment shows the effectiveness of the system that the mismatch against a commercial interferometer is less than 20 nmRMS.

Citation Download Citation

Sangwon Hyun, Soonkyu Je, and Geon-Hee Kim "High precision interferometric measurement of freeform surfaces from the well-defined sub-aperture surface profiles", Proc. SPIE 11175, Optifab 2019, 111752B (15 November 2019); https://doi.org/10.1117/12.2536867

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