High precision measurements of the free form mirror geometries

Denis Dontsov; Ilko Rahneberg; Wolfgang Pöschel; Walter Schott

doi:10.1117/12.2275266

15 June 2017 High precision measurements of the free form mirror geometries

Denis Dontsov, Ilko Rahneberg, Wolfgang Pöschel, Walter Schott

Proceedings Volume 10326, Fourth European Seminar on Precision Optics Manufacturing; 103260U (2017) https://doi.org/10.1117/12.2275266
Event: Fourth European Seminar on Precision Optics Manufacturing, 2017, Teisnach, Germany

Abstract

There are many established technologies for precise characterization of the mirror geometries available. The paper presents a high precision measuring setup based on a single beam homodyne laser interferometer. The single beam interferometer is moved by a linear stage between the reference and measuring surfaces and delivers the differences between them. The reference mirror defines an absolute accuracy of the method. This point based method allows a high spatial resolution of the mirror shape and is suitable for measurements of the free form mirror geometries as long as the radius of curvature does not exceed the maximal toleranced tilt.

The measuring results have been obtained for optics with dimensions of up to 50 mm and have been verified both for plan mirrors and for mirrors with radii of curvature in the range between 6 m and 10 m. A repeatability of the measuring results in sub-nanometer range can be shown.

Especially for mirrors with a very big radius of curvature the knowledge of the exact position of the each measuring point on the surface is important for minimizing the errors of the mathematical fitting algorithms. Therefore a triple beam interferometer has been used for measurements of the stage position. The tight synchronization between all interferometer channels of 0.1 ns allows very fast “on-the-fly” scans of the surface.

Citation Download Citation

Denis Dontsov, Ilko Rahneberg, Wolfgang Pöschel, and Walter Schott "High precision measurements of the free form mirror geometries", Proc. SPIE 10326, Fourth European Seminar on Precision Optics Manufacturing, 103260U (15 June 2017); https://doi.org/10.1117/12.2275266

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