Absolute interferometric tests of spherical surfaces based on rotational and translational shears
Johannes A. Soons, Ulf Griesmann
Traceability of interferometric form measurements requires characterization of the reference wavefront. We investigate absolute tests for spherical surfaces where the form errors of both reference and test surface are estimated by minimizing the difference in measurements obtained at various positions and orientations of the test surface. This approach yields an estimate for the test surface errors without changing experimental settings, such as cavity length, that may affect the apparent reference errors. The method requires at least one translation of the test surface in the field of view and one rotation. Additional measurements provide redundancies to improve and characterize measurement uncertainties. The errors of the reference and test surface are estimated with pixel-level spatial resolution without assuming an underlying error model, such as a representation based on Zernike polynomials. The estimation algorithm consists of an iterative sequence of stitching steps, with the role of reference and test surface reversed for each step. Measurement uncertainties are evaluated using Monte-Carlo procedures and analysis of residual errors for experiments with redundant measurements. Key sources of measurement uncertainty are spatially correlated measurement errors resulting from errors in test surface location, image distortion, and environmental effects. Experimental results are presented comparing the method to a random ball test.
Interferometry XVI: Techniques and Analysis, Proceedings of SPIE Volume 8493.
and Griesmann, U.
Absolute interferometric tests of spherical surfaces based on rotational and translational shears, Interferometry XVI: Techniques and Analysis, Proceedings of SPIE Volume 8493.
, San Diego, CA, [online], https://doi.org/10.1117/12.930030
(Accessed November 29, 2023)