Interferometric and deflectometric flatness metrology with nanometre measurement uncertainties for optics up to 1 metre at PTB

G. Ehret; H. Reinsch; M. Schulz

doi:10.1117/12.2538872

18 November 2019 Interferometric and deflectometric flatness metrology with nanometre measurement uncertainties for optics up to 1 metre at PTB

G. Ehret, H. Reinsch, M. Schulz

Author Affiliations +

Proceedings Volume 11189, Optical Metrology and Inspection for Industrial Applications VI; 1118905 (2019) https://doi.org/10.1117/12.2538872
Event: SPIE/COS Photonics Asia, 2019, Hangzhou, China

Abstract

High-precision topography measurements of nearly flat specimens with nanometre uncertainty are still demanding. They are needed for synchrotron or other high-quality optical mirrors. At the Physikalisch-Technische Bundesanstalt (PTB), we operate an interferometric setup and a small-angle deflectometric setup for flatness measurement. We present both systems, show the measurement uncertainties and discuss the pros and cons of interferometric and gradient based measurement systems. To achieve the nanometre level in flatness metrology, the environmental conditions and the holder of the specimen are very important. We show measurements of topography changes due to delayed elasticity effects. We demonstrate current developments with the small-angle deflectometer, especially to improve the lateral resolution.

Citation Download Citation

G. Ehret, H. Reinsch, and M. Schulz "Interferometric and deflectometric flatness metrology with nanometre measurement uncertainties for optics up to 1 metre at PTB", Proc. SPIE 11189, Optical Metrology and Inspection for Industrial Applications VI, 1118905 (18 November 2019); https://doi.org/10.1117/12.2538872

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