A novel calibration method for the photometric stereo system with non-isotropic LED lamps

This paper presents a new calibration method of photometric stereo system which works under near-field lighting condition and with non-isotropic light sources. To estimate the position of light source, a multiple-sphere-based approach is introduced. According to the axial symmetry property of the lighting field, we show that there exists a unique brightest point which locates on the symmetry axis. By the using of a reference plane and detecting the brightest image point, principle optical axis of light source can be precisely calculated. By considering the radiance model of light source, lighting condition for each surface point can be accurately represented. Both planar and free-form surfaces are used for the experiments. And the results show that, high-quality 3D reconstruction results can be obtained by the proposed calibration approach in comparison with conventional methods.