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Optical Engineering

Topography and reflectance analysis of paper surfaces using a photometric stereo method
Author(s): Peter Hansson; Per-Ake Johansson
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Paper Abstract

This paper describes a fast photometric stereo method, useful for the determination of surface-topography and reflectance. First we show how the irradiance in two images of a surface, illuminated from the left and right, respectively, can be used to determine the inclination of the surface elements. This requires a model for the light scattering properties of the surface. The model used divides the scattered light into a bulk-scattered, Lambertian part and a surface-scattered, specular part. The specular part is eliminated with the help of crossed polarizers. The inclinations are integrated to give a surface height function with the help of a Wiener filter, which suppresses frequencies with an expected poor signal-to-noise ratio. Profiles measured with this method show good agreement with profiles obtained both with optical and mechanical scanning methods. The standard deviation between surface height measured with the different methods was about 1 ?m. The ability of this method to study reflectance and topography at the same time makes it suitable for studies of the coupling between print result and surface topography. As an example, a gravure-printed paper surface with missing dots has been studied. It was found that missing dots occur at depressions, or pores, in the surface.

Paper Details

Date Published: 1 September 2000
PDF: 7 pages
Opt. Eng. 39(9) doi: 10.1117/1.1287261
Published in: Optical Engineering Volume 39, Issue 9
Show Author Affiliations
Peter Hansson, Optronic Consult (Sweden)
Per-Ake Johansson, STFI, Swedish Pulp & Paper Research Institute (Sweden)

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