Estimating Light Sources

Maneesh Kumar Singh and Narendra Ahuja

In this paper, we propose an algorithm for the estimation of extended light sources illuminating a scene. We assume that the light sources are located at infinity, they are themselves not visible to the camera, and there are no interreflections. Such an estimation from images of the scene under consideration is difficult because the images depend on surface shapes, surface reflectances and the camera (sensor) response functions, in addition to the illumination pattern. We simplify the problem by using a probe, a sphere of known size and lambertian reflectance function, and show that it is possible to recover the illumination pattern from images of this probe. A system of equations involving unknown light sources is obtained and solved using projection onto convex sets method. We present results of simulations involving synthesized light sources.

Keywords: light sources, estimation, shift-variant deblurring, POCS

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