Underwater Mueller matrix de-scattering imaging under the influence of natural light

Underwater polarization imaging in real-world marine conditions is influenced by both active polarization illumination and unpolarized natural light, a factor often overlooked in existing research. This paper presents three polarization de-scattering approaches aimed at optimizing the image model, suppressing background light, and enhancing image contrast. We investigated the effectiveness of these methods under various scattering conditions, particularly focusing on the impact of natural light on active polarization illumination measurements. The experimental results indicate that the presence of natural light causes the degree of circular polarization to be slightly higher than the degree of linear polarization. Consequently, the same de-scattering effect can be achieved using either linearly polarized or circularly polarized detection within the image model-based approach. The method of suppressing background light is not effective when the background light is significantly uneven and has a small degree of polarization. Our proposed method for enhancing image contrast does not require estimating any parameters or variables about objects and background, making it adaptable to underwater images with non-uniform illumination. This research provides a foundation for selecting appropriate measurement and analysis schemes for underwater imaging in real-world environments.