Light is diffracted when passing through a perforated object, resulting in a spatial distribution of light intensity that depends on the size and form of the aperture and the wavelength of light. Analysis of this diffraction can be used to estimate the inclination of the surface. However, because of distortions in the image acquisition process, these estimations are not very precise when using standard CCD- cameras. In order to increase accuracy and solve ambiguities, polarization analysis is added as an additional source of information. Polarized light is used as source of illumination. Due to interaction with the matter of the aperture the light is partly depolarized, hence we get a spacial distribution of the degree of polarization. The measurements of the degree of polarization are not based on absolute light intensity and thus much more robust. For irregularly shaped objects with a large number of apertures methods for shape estimation are presented. Reasonable assumptions of the surface structure are introduced to reduce the number of degrees of freedom. Possible applications of the proposed method are discussed and we show relations of optical and mechanical quantities such as traction.

Date Published: 16 September 1999
PDF: 8 pages
Proc. SPIE 3826, Polarization and Color Techniques in Industrial Inspection, (16 September 1999); doi: 10.1117/12.364316

Published in SPIE Proceedings Vol. 3826:
Polarization and Color Techniques in Industrial Inspection
Elzbieta A. Marszalec; Emanuele Trucco, Editor(s)