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Uncertainties in Aspheric Profile Measurements with the Geometry Measuring Machine at NIST



Ulf Griesmann, Nadia Machkour-Deshayes, Byoung C. Kim, Quandou (. Wang, Lahsen Assoufid


The Geometry Measuring Machine (GEMM) of the National Institute of Standards and Technology (NIST) is a profilometer for free-form surfaces. A profile is reconstructed from local curvature of a test part surface, measured at several locations along a line. For profile measurements of free-form surfaces, methods based on local part curvature sensing have strong appeal. Unlike full-aperture interferometry they do not require customized null optics. The uncertainty of a reconstructed profile is critically dependent upon the uncertainty of the curvature measurement and on curvature sensor positioning. For an instrument of the GEMM type, we evaluate the measurement uncertainties for a curvature sensor based on a small aperture interferometer and then estimate the uncertainty in the reconstructed profile that can be achieved. In addition, profile measurements of a free-form mirror, made with GEMM, are compared with measurements using a long-trace profiler and subaperture-stitching interferometry.
Proceedings Title
SPIE - Optics and Photonics
Conference Dates
July 31-August 4, 2005
Conference Location
San Diego, CA
Conference Title


aspheric surface profile, profilometer, surface curvature


Griesmann, U. , Machkour-Deshayes, N. , Kim, B. , Wang, Q. and Assoufid, L. (2005), Uncertainties in Aspheric Profile Measurements with the Geometry Measuring Machine at NIST, SPIE - Optics and Photonics, San Diego, CA (Accessed June 16, 2024)


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Created July 31, 2005, Updated February 19, 2017