Imaging in multiplexed illumination
Yoav Y. Schechner, Shree K. Nayar, Peter N. Belhumeur, Harish S. Peri · Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE · 2004
Lighting plays an important role in many applications of computer vision, machine vision and computer graphics. Often, an object needs to be photographed multiple times, in each of which lighting comes from a different direction. Lighting which uses a single source per image is prone to dynamic range problems, especially in dark areas and in specular highlights. In addition, it becomes a practical problem to use an increasingly larger number of discrete sources (say, hundreds). To counter these problems we develop a novel illumination strategy. In each image, multiple light sources irradiate the scene simultaneously. The set of light sources is different in each image, but not mutually exclusive. Then, the contribution of each individual source is extracted in computational post-processing. The number of acquired images using this approach is the same as the number used in single-source images. However, thanks to the multiplexing of light in the raw images, more light is used from a variety of directions, diminishing problems of dynamic range. We derive the optimal illumination multiplexing scheme, which increases the SNR of the images by (√n}/2, where {n} is the number of sources. This lighting strategy is complemented by a novel illumination setup. The setup is easily built and scaled to a huge number of sources, and is controllable by the computer. These advantages are obtained since the apparatus is based on indirect lighting originating from an LCD projector.