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.
, Machkour-Deshayes, N.
, Kim, B.
, Wang, Q.
and Assoufid, L.
Uncertainties in Aspheric Profile Measurements with the Geometry Measuring Machine at NIST, SPIE - Optics and Photonics, San Diego, CA
(Accessed February 22, 2024)