Pixel‐wise varifocal camera model for handling multilayer refractions

Abstract

When observing a scene by a perspective camera through multiple refractive planes (e.g. underwater imaging), distortions and illusions, mainly caused by the refractions occurring at the interfaces between the different mediums, will be brought into the imaging system. Traditional pin-hole camera model becomes invalid in handling such case. A novel general camera model is presented, which is in fact a virtual pixel-wise varifocal model and can be used to encode multilayer refractions effectively. The model is built up based on two important findings. One is that the air between the camera centre and the nearest layer can be modelled as an air layer. The other one is that a ray passing through the air layer and these multiple layers causes only lateral displacement without changing its direction. The proposed camera model guarantees fast calculation of the backward projection. The forward projection equation is also derived and an efficient solving algorithm is proposed. Synthetic and real experiments are designed to verify the effectiveness and efficiency of the proposed theory.