Measuring large aspherics using a commercially available 3D-coordinate measuring machine

Wolfgang Otto; Axel Matthes; Heinz Schiehle

doi:10.1117/12.391498

20 July 2000 Measuring large aspherics using a commercially available 3D-coordinate measuring machine

Wolfgang Otto, Axel Matthes, Heinz Schiehle

Proceedings Volume 4003, Optical Design, Materials, Fabrication, and Maintenance; (2000) https://doi.org/10.1117/12.391498
Event: Astronomical Telescopes and Instrumentation, 2000, Munich, Germany

Abstract

A CNC-controlled precision measuring machine is a very powerful tool in the optical shop not only to determine the surface figure, but also to qualify the radius of curvature and conic constant of aspherics. We used a commercially available 3D-coordinate measuring machine (CMM, ZEISS UPMC 850 CARAT S-ACC) to measure the shape of the GEMINI 1-m convex secondary mirrors at different lapping and polishing stages. To determine the measuring accuracy we compared the mechanical measurements with the results achieved by means of an interferometrical test setup. The data obtained in an early stage of polishing were evaluated in Zernike polynomials which show a very good agreement. The deviation concerning long wave rotational symmetrical errors was 20 nm rms, whereas the accuracy measuring of mid spatial frequency deviations was limited to about 100 nm rms.

Citation Download Citation

Wolfgang Otto, Axel Matthes, and Heinz Schiehle "Measuring large aspherics using a commercially available 3D-coordinate measuring machine", Proc. SPIE 4003, Optical Design, Materials, Fabrication, and Maintenance, (20 July 2000); https://doi.org/10.1117/12.391498

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