Restoring Polarization Angle Map for High-Fidelity Underwater Imaging

Abstract

Obtaining polarization information enables researchers to enhance underwater imaging quality by removing backscattering effect and to distinguish targets of different materials. However, due to the simplified assumption of unpolarized target light, most of the existing underwater polarimetric methods lose part of the polarization information, resulting in degraded imaging quality. In this work, a novel underwater polarimetric method is reported, which obtains the angle of polarization (AOP) map to improve imaging quality. Specifically, the Stokes vectors were exploited to remove the backscattering effect by obtaining two pairs of orthogonal polarization sub-images of the underwater scene. The target reflected light and the angle between the polarization directions of the target reflected light and the backscattered light were computed through the two groups of the orthogonal polarized sub-images. The AOP map of the target light could be derived from the Stokes vectors. Then, the transmission map of the target light was estimated by using the non-local color priorly combined with the properties of light propagating underwater. Experiments show that the reported technique enables distinguishing different targets when the colors are similar. The quantitative metrics validate that the reported technique produces state-of-the-art performance for underwater imaging.

Keywords

underwater imaging / polarization / angle of polarization (AOP) / Stokes vector