水下距离选通降质图像的增强

针对水下距离选通成像所得图像的噪声大、照度不均匀、对比度差的问题，提出一种二次图像增强方法.首先，对图像采用全局二维双平台直方图均衡化，实现目标、背景、边界信息分别增强的目标，解决直方图均衡化带来的背景噪声提升、灰度简并的孤立性问题；然后，在非迭代引导滤波的框架下用带有估计误差抑制的Retinex算法二次增强图像，实现抑制背景噪声，平衡图像亮度的功能.以图像信息熵、统计评价指标进行对比实验，实验结果表明，该方法信息熵评价指标提升15%，统计评价指标提升28%，噪声抑制指标提升12%，增强效果明显，满足应用要求. 

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.