Comparison of low-scatter-mirror PSD derived from multiple-wavelength BRDFs and WYKO profilometer data

Wallace K. Wong; Dexter Wang; Robert T. Benoit; Peter Barthol

doi:10.1117/12.50499

1 December 1991 Comparison of low-scatter-mirror PSD derived from multiple-wavelength BRDFs and WYKO profilometer data

Wallace K. Wong, Dexter Wang, Robert T. Benoit, Peter Barthol

Proceedings Volume 1530, Optical Scatter: Applications, Measurement, and Theory; (1991) https://doi.org/10.1117/12.50499
Event: San Diego, '91, 1991, San Diego, CA, United States

Abstract

An electroless nickel plated over aluminum mirror was tested for BRDF and surface profiles at two stages: First, after a standard polish for optical figure, and second, after a `super finishing process' which is designed to minimize optical scatter. BRDF measurements corresponding to spatial frequency range between .0016 micrometers -1 to 1 micrometers -1 were obtained using 0.633 micrometers , 1.06 micrometers , 3.39 micrometers and 10.6 micrometers lasers. The conversion formula used to derive PSD2D from BRDF data is based on the Rayleigh-Rice vector theory. Measurements of the same spots by an optical profilometer (WYKO TOPO-2D) with several objectives were used to cover similar spatial frequency limits. The surface finish statistics, extracted from the profile data, was processed to produce PSD1D. Then, composite PSD1d were fitted to an analytic function for PSD1D using the K- correlation model approach. The derived PSD2D from profile data was readily determined from the A,B,C coefficients associated with the K-correlation model. The derived PSD2D from BRDF and profile measurements were compared to quantify the difference in surface finish statistics between the standard polished mirror and the same mirror after `super finishing.' Good correlation is found for the standard polished surface. This corroborates the `topographic scatter' behavior for the clean, standard polished nickel surface which promise useful interpolation of BRDF values to wavelengths at which direct BRDF data is unavailable. Correlation for the `super finished' surface is worse, probably due to unplanned surface contamination between tests.

Citation Download Citation

Wallace K. Wong, Dexter Wang, Robert T. Benoit, and Peter Barthol "Comparison of low-scatter-mirror PSD derived from multiple-wavelength BRDFs and WYKO profilometer data", Proc. SPIE 1530, Optical Scatter: Applications, Measurement, and Theory, (1 December 1991); https://doi.org/10.1117/12.50499

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