A kind of image real-time enhance processing technology of visible light with low contrast

The effective distance of the optical imaging system based on CCD/CMOS is affected strongly by fog or haze on the border less travelled by or the sea level, so this paper aims to adopt an effective method to use near-infrared filter and digital image processing to increase the system effective distance. Firstly, this paper analyzes theoretically that the system has a longer visual distance in the near-infrared than that in the visible light in the low visibility condition, and makes clear that the visual distance of the system will increase to about 1.5 times as much as before. Secondly, given the border/ coastal surveillance having the characteristics of broad visual angle and the large distance between the observed targets, this paper works out a partially overlapped sub-block local histogram equalization algorithm, which will achieve the real-time image enhancement processing of beyond visual range optical imaging on the condition of enhancing the contrast and maintaining the image specifics. Thirdly, it has developed a real-time enhancement image processing system of beyond visual range photoelectric image with high-performance DSP and FPGA. And the observed distance of the system can realize more than two times as much as the visibility in the weather condition with the visibility is about 7 KM.