Overcoming Shadows in 3-Source Photometric Stereo

• Published in: IEEE transactions on pattern analysis and machine intelligence Vol. 33; no. 2; pp. 419 - 426
• Main Authors: Hernández, Carlos, Vogiatzis, G, Cipolla, R
• Format: Journal Article
• Language: English
• Published: Los Alamitos, CA IEEE 01-02-2011; IEEE Computer Society; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Algorithms; Ambiguity; Applied sciences; Artificial intelligence; Computer science; control theory; systems; Equations; Exact sciences and technology; Image color analysis; Image reconstruction; Intelligence; Light sources; Noise; Occlusion; Orientation; Pattern analysis; Pattern recognition. Digital image processing. Computational geometry; Photometric stereo; Pixel; Pixels; shadows; Shape; Studies; Three dimensional displays; Occlusion; Computer vision; Integrability; Shadow; Orientation; Shadow region; Photometric stereo; shadows; Ill posed problem; Stereopsis; Occultation; Photometry; Numerical algorithm; Ambiguity
• ISSN: 0162-8828; 1939-3539
• DOI: 10.1109/TPAMI.2010.181

Light occlusions are one of the most significant difficulties of photometric stereo methods. When three or more images are available without occlusion, the local surface orientation is overdetermined so that shape can be computed and the shadowed pixels can be discarded. In this paper, we look at the challenging case when only two images are available without occlusion, leading to a one degree of freedom ambiguity per pixel in the local orientation. We show that, in the presence of noise, integrability alone cannot resolve this ambiguity and reconstruct the geometry in the shadowed regions. As the problem is ill-posed in the presence of noise, we describe two regularization schemes that improve the numerical performance of the algorithm while preserving the data. Finally, the paper describes how this theory applies in the framework of color photometric stereo where one is restricted to only three images and light occlusions are common. Experiments on synthetic and real image sequences are presented.