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Optical Engineering

Polarization imaging for material classification
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Paper Abstract

A simple and stable method is proposed for distinguishing dielectric and metal material surfaces from the polarization images captured by a vision system consisting of a linear polarizer and a digital camera. The polarization state is determined by the transmitted light intensity through the polarizer as a function of polarizing orientation. The degree of polarization (DOP) is estimated from the image intensities through the polarizer. The DOP map is quite effective for material classification around specular highlight on an object surface. We prove that the DOP map is convex for a dielectric surface and concave for a metal surface. The problem of material classification is then reduced to a simple judgment of the convexity of the DOP map obtained around the highlight peak. The proposed method is not a pixelwise local method based on thresholding the Fresnel ratio computed at each pixel but an area-based method based on the DOP map in a highlight area. The feasibility of the method is confirmed in experiments under a variety of conditions.

Paper Details

Date Published: 1 December 2008
PDF: 14 pages
Opt. Eng. 47(12) 123201 doi: 10.1117/1.3041770
Published in: Optical Engineering Volume 47, Issue 12
Show Author Affiliations
Shoji Tominaga, Chiba Univ. (Japan)
Akira Kimachi, Osaka Electro-Communication Univ. (Japan)

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