Research On The Low Light Level Image Enhanced Technology Based On FPGA

With the progress of science and technology and the development of society,the monitoring system has been applied to various fields and assumed more and more important roles.From troops to prison,from banking to shopping,from school to the residential area,and even every street for the increasing demand of the monitoring system,and the definition of the monitoring system,real-time,and even light performance requirements more and more is also high.With the increase of people's nocturnal activity time,the information reflected in low illumination and even light environment is becoming more and more important,and the low-light image in many places is very important.The main features of lowlight level vision images are: 1.Low mean value,low signal-to-noise ratio and low contrast,it is difficult for the naked eye to identify the targets in the scene.2.The image gray level distribution is relatively concentrated,and the whole frame image is usually concentrated in the gray level of tens to hundreds,which means less means to improve the image quality.Based on the analysis of the characteristics of night vision image,this paper designs a lowlight level image enhancement system,which integrates CMOS imaging unit,processing unit and output unit,with small size,low power consumption and good night vision.The lowlight level image is low contrast,and the image is mixed with a lot of isolated noise,and the first of this is to process the image through the median filter,Gaussian filter,and the filter of the image,to remove the isolated noise from the dark current and image transmissions;In view of the image grey value on the grayscale distribution side of the problem,this paper designed the children histogram equalization image enhancement algorithm,through the study of the histogram of the image partition,dynamic range adjustment,make night vision image distribution more uniform,still can keep the original image details;The gray level probability of histogram is adjusted and normalized,so that the night vision image will not be enhanced after enhancement,and better image quality will be improved.In this paper,a variety of image quality evaluation methods are proposed.Based on FPGA,the lowlight level image image enhancement system is built,and the virtex-5 series XC5VSX50 T FPGA core processing chip produced by Xilinx company has strong logic programming ability.At the end of this paper,the system level test and result analysis are carried out,and the evaluation indexes such as information entropy,contrast and SNR are used to evaluate the enhanced image quality,and verify the effectiveness of the algorithm and the real-time performance of the lowlight level image enhancement system.