<title>The effect of illumination volume in underwater camera image</title>

Abstract

Video cameras are standard equipment on, practically, all of today's underwater robotics vehicles. As a part of a camera system setting, the arrangement of active illumination affects the quality of acquisition, particularly in turbid water environment. Large illumination volume helps to increase image brightness but depresses modulated contrast. This paper elaborates on the effects of illumination volume due to the forward and backward scattering progresses. An intensity model is proposed to include the geometrical parameters of the illumination setup. This model is based on the volume scattering function (VSF) and Lambertian reflection effects. The distribution of scattering noise in the image is predicted for different size of light beam. Experiments were conducted in a short water tank using a continuous wave, 532nm laser light source with an adjustable parallel beam output. In application, as laser beam scanning is a well-known method to improve underwater visibility, the theoretical model helps in determining the optimum illumination setting in different water conditions, and accordingly reducing the time of photomosaicing.