Enhancement of the Underwater Range-Gated Degraded Image

A new twice image enhancement method was proposed to solve the problems of large noise, uneven illumination and poor contrast in the underwater range-gated image. Firstly, the problems of background noise's over enhancement and the gray level isolated degeneracy in the normal histogram equalization method were focused. Based on the improved image's global two-dimensional histogram transformation, the double platforms histogram equalization was added to achieve the goals that all the object, background, and boundary information were enhanced respectively. A custom suppressed estimated deviation parameter was appended to enhance the image twice in the framework of non-iterative Retinex transformation using the guided-filter to suppress the background noise and balance the image brightness. Simulation experiments' results show that the entropy index is increased by 15%, the statistical evaluation index is improved by 28%, and the noise suppression index is improved by 12% comparing with various algorithms. The effect of underwater range-gated image enhancement method is obvious and can reach the application requirement.