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Proceedings Paper

Parametric optical surface roughness measurement by means of polychromatic speckle autocorrelation
Author(s): Stefan Patzelt; Andreas Ciossek; Peter Lehmann; Armin Schoene
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Paper Abstract

A method for determining surface roughness of engineering surfaces that is applicable to in-process measurements under harsh circumstances of industrial production plants (e.g. vibrations, humidity) is introduced. The rough surface is illuminated with polychromatic laser light. The angular distribution of scattered light intensities, i.e. a polychromatic speckle pattern, is the result of an incoherent superposition of monochromatic speckle intensities. The angular dispersion leads to increasing speckle widths with an increasing distance to the optical axis an effect called speckle elongation. This gives rise to a radial structure of the speckle pattern. However, with increasing surface roughness the radial structure vanishes because of a decreasing similarity of the monochromatic speckle patterns of the different wavelengths. The markedness of this effect is analyzed by digital image processing algorithms, e.g. the procedure of polychromatic speckle autocorrelation. The latest approach to an in-process roughness measurement device was made by the use of singlemode fiber-pigtailed laser diodes in order to supply a trichromatic, temporally partially coherent laser beam. A brief introduction to the theoretical background is followed by the presentation of the experimental setup. The image processing algorithms for calculating an optical roughness measure from digitalized speckle patterns are explained, and first results of surface roughness determination are presented.

Paper Details

Date Published: 30 October 1998
PDF: 10 pages
Proc. SPIE 3426, Scattering and Surface Roughness II, (30 October 1998); doi: 10.1117/12.328446
Show Author Affiliations
Stefan Patzelt, Univ. of Bremen (Germany)
Andreas Ciossek, Univ. of Bremen (Germany)
Peter Lehmann, Univ. of Bremen (Germany)
Armin Schoene, Friedrich-Wilhelm-Bessel-Institut (Germany)

Published in SPIE Proceedings Vol. 3426:
Scattering and Surface Roughness II
Zu-Han Gu; Alexei A. Maradudin, Editor(s)

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