Photometric stereo allows us to estimate the surface normal of an object based on its shading. In uncalibrated photometric stereo, the light source direction is unknown; thus, both the light source direction and surface normal should be estimated, which establishes an ill-posed problem with ambiguity in its solution. Consequently, assumptions should be made to uniquely determine the solution; however, assumptions are not always satisfied in practice, which results in an estimated surface normal that differs from the true surface normal. To improve surface normal estimation, we analyze the polarization state of reflected light considering that polarization can constrain the possible orientation of the surface normal. Thereafter, through extensive experimental evaluations, we demonstrate that polarization effectively improves uncalibrated photometric stereo.
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