Foggy Image Enhancement Method Research And Fpga Implenations

Due to the effect of suspended particle scattering, video image captured by imaging tracking module of target tracking system always shows low visibility and low contrast in foggy situation. The shell target may be extremely difficult for military personnel to track the target accurately. In order to solve this problem, the paper with Xilinx’s Spartan 3AN series of low-cost FPGA chip as the core design the real-time image enhancement system. The main work is as follows:(1) The theoretical research of mainstream image enhancement algorithms based on Retinex and histogram equalization are researched. Low contrast images under different scene are selected as material, and the algorithms are analazed and simulated in Matlab software. The simulation result is used to subjective observation and analysing merits and faults of the algorithms. On this basis, objective parameters and amount of calculation of the algorithms based on histogram equalization are estimated. The contrast limited adaptive histogram equalization algorithm is defined in this paper.(2) System hardware platform is designed, and primary work includes the selection of FPGA and digital camera and PCB circuit design. Then welding and debugging the hardware platform are accomplished. Meanwhile, the image acquisition and display control program are compiled by using Verilog language in ISE software.(3) CLAHE image enhancement algorithm implementation processe is improved. The method of histogram redistribution and computing histogram equalization and pixel reconstruction are optimized. The CLAHE algorithm is realized in the FPGA, and simulated in Moselsim software. Then FPGA program is downloaded to the hardware platform for the fog image real-time enhancement system test, and the experimental results are analyzed.Many experimental results show that the design of real-time image enhancement system in this paper greatly enhances the low-contrast video images and the target in these images can be clearly identified. Besides military field, this system can be used in medical image strengthening, traffic detecting, aeronautics, astronautics and other fields which hashigh practical value.