Image enhancement of underwater target detection by inhomogeneous illumination

For underwater target detection by homogeneous illumination or laser, the strong backscattering is mainly generated at the range close to the detector, yielding low visibility. Therefore, we build the underwater imaging system based on inhomogeneous illumination field, which intensity distribution relates to the attenuation pattern of light transmission with an inverse form. It is shown via pool and sea experiments to be effective in decreasing backscattering within a wide field-of-view (FOV), which improves image contrast. For human viewers and/or further automated image processing, this paper compares image enhancement methods based on histogram, sharpening, as well as partial differential equation (PDE). The experiments show the results of the underwater image enhancement methods.