Hemispherical refraction and camera calibration in underwater vision

We examine the challenges to underwater vision that are caused by light refracting through both hemispherical and planar pressure housing interfaces. As light travels through water, into a pressure housing, and finally into a camera, it is bent according to Snell's law, rendering the typically-used perspective camera model invalid. Through numerical simulation, we examine the degree to which the incorrect perspective model results in 2-D image distortion, and errors in 3-D scene reconstruction computed using stereo vision or structure from motion. We focus on the use of hemispherical pressure housing interfaces with imperfectly mounted cameras, and include comparisons with cameras behind planar interfaces.We also address the problem of calibrating a camera model which takes into account the physical parameters of the pressure housing interface.