Absolute pose for cameras under flat refractive interfaces

This paper studies the problem of determining the absolute pose of a perspective camera observing a scene through a known refractive plane, the flat boundary between transparent media with different refractive indices. Efficient minimal solvers are developed for the 2D, known orientation and known rotation axis cases, and near-minimal solvers for the general calibrated and unknown focal length cases. We show that ambiguities in the equations of Snell's law give rise to a large number of false solutions, increasing the complexity of the problem. Evaluation of the solvers on both synthetic and real data show excellent numerical performance, and the necessity of explicitly modelling refraction to obtain accurate pose estimates.