Catadioptric projectors

We present a catadioptric projector analogous to a catadioptric camera by combining a commodity digital projector with additional optical units. We show that, by using specially shaped reflectors/refractors, catadioptric projectors can offer an unprecedented level of flexibility in aspect ratio, size, and field of view. We also present efficient algorithms to reduce projection artifacts in catadioptric projectors, such as distortions, scattering, and defocusing. Instead of recovering the reflector/refractor geometry, our approach directly models the light transport between the projector and the viewpoint using the light transport matrix (LTM). We show how to efficiently approximate the pseudo inverse of the LTM and apply it to find the optimal input image that produces least projection distortions. Furthermore, we present a projection defocus analysis for reflector and thin refractor based catadioptric projectors. We show that defocus blur can be interpreted as spatially-varying Gaussian blurs on the input image. We then measure the kernels directly from the LTM and apply deconvolution to optimize the input image. We demonstrate the practical uses of catadioptric projectors in panoramic and omni-directional projections. Our new system achieves much wider field-of-view projection while maintaining sharpness and low geometric and photometric distortions.