ABSTRACT:According to the changing external environment, or night fog cases collected a blurry image. In this paper, the conventional histogram equalization algorithm is optimized and improved, as well as an adaptive histogram equalization algorithm is proposed, which can effectively control the contrast ratio. To convert images from the RGB space to HSI space, and then to HSI space of luminance component (I) of gray histogram for optimization of the algorithm, and then convert to RGB space. The realization of the algorithm by FPGA, image recognition degree enhanced obviously, improve the quality of the image, the actual application effect is superior.