A new approach of photometric stereo from linear image representation under close lighting

In this paper, we propose a novel method for shape from shading and representing intensity images of objects illuminated by near point light sources, where the distance between a light source and an object is small. Our image representation model is a linear model, and thus, the computational cost for analyzing intensity images is very small comparing with the non-linear model. We introduce an intensity projection matrix, and show that this matrix realizes the linear representation of near light source images. Furthermore, we propose a method for estimating the intensity projection matrices reliably. Finally, we derive a multilinear constraint from the intensity projection matrices, which enables us to generate images under arbitrary near light sources from 4 basis intensities linearly. The experimental results show that the proposed method can generate much more accurate images under near light sources than the traditional linear intensity model defined under infinite light source.