Real-time underwater polarization imaging without relying on background

Abstract

Polarization imaging has excellent potential for use in underwater application scenarios due to efficient elimination of backscattered light. In most studies, two images that contain the maximum and minimum visible backscatter are obtained by finding the brightest and darkest moments during the rotation of the polarizer. In addition, the background region must be included in the image. To prevent these limitations, this study directly generates the optimal image pair via the Stokes vector. These images are then transformed into the frequency domain, and the global distribution of the degree of polarization of backscattered light is obtained using low-pass filtering. Recovery of the clear scene requires neither relying on background nor a search for the brightest and darkest images, significantly enhancing the real-time characteristics of the imaging process. Because of this, imaging of moving targets comes true. Additionally, experimental results at continuously varying distances verify the effectiveness of the proposed method for targets with different polarization properties. Especially, the imaging distance can be increased by 30% compared to the conventional active polarization imaging model at the same level of contrast.