Abstract

In an underwater imaging system, a refractive interface is introduced when a camera looks into the water-based environment, re- sulting in distorted images due to refraction. Simply ignoring the re- fraction effect or using the lens radial distortion model causes erroneous 3D reconstruction. This paper deals with a general underwater imaging setup using two cameras, of which each camera is placed in a separate waterproof housing with a flat window. The impact of refraction is explic- itly modeled in the refractive camera model. Based on two new concepts, namely the Ellipse of Refrax (EoR) and Refractive Depth (RD) of a scene point, we show that provably optimal underwater structure and motion under L? -norm can be estimated given known rotation. The constraint of known rotation is further relaxed by incorporating two-view geometry estimation into a new hybrid optimization framework. The experimental results using both synthetic and real images demonstrate that the pro- posed method can significantly improve the accuracy of camera motion and 3D structure estimation for underwater applications.