Infrared Image Enhancement Algorithm Based On Atmospheric Scattering Physical Model And FPGA Implementation

Infrared imaging technology is widely used in military and civil fields because of its advantages of all-weather working,high precision,good concealment and strong anti-interference ability.However,due to the effects of the higher temperature of earth'surface and target than background,infrared radiation isotropic diffusion,water vapor absorption,atmospheric scattering and so on,the infrared images is generally low contrast and fuzzy.In order to remove the isotropic heat radiation causing the infrared image to be blurred and to highlight the specificity of the target and the background,This theis focuses on the development of the infrared image enhancement algorithm based on the atmospheric scattering physical model Thenan infrared image enhancement system built upon the Xilinx Spartan-6 FPGA chip is designed and implemented.The main works of this thesis are listed as follows:1.Several typical infrared image enhancement algorithms are briefly reviewed.review of.Based on the introduction of the features of infrared images,this thesis discusses three categories of infrared image enhancement algorithms,including dual-platform histogram equalization,unsharp masking and Retinex algorithms.In order to facilitate the comparison and analysis of the enhancement quality,the sharpness evaluation index,details enhancement evaluation index,contrast evaluation index are proposed as the objective evalutation metrics.The performance metrics of the three typical algorithms are shown and discussed.2.An infrared image enhancement algorithm based on atmospheric scattering physics model is improved.In the infrared image enhancement algorithm based on the physical model of atmospheric scattering,we have to estimate the atmospheric light and transmittance.However,due to the large amount of calculation and time-consuming of atmospheric transmittance with the widely-used soft matting method,it is not appropriate to be implemented on the FPGA hardware.Therefore,we propose to utilize the guided filter to refine the rough transmittance.To avoid the tow brightness of the infrared image after removing blur,the Gamma correction method is applied to increase brightness.Simulation experinents compares the performance of the proposed algorithm with the dual-platform histogram equalization,unsharp masking and Retinex algorithms.The results show that the proposed algorithm is effective toimprove the contrast of the infrared images and rich the details of information.3.Design and implementation of an infrared image enhancement system based on the proposed algorithm.The system mainly includes an infrared detector for acquisitiing real-time infrared video image,a video decoder chip(TVP5150),a video encoder chip(TFP410),FPGA chip and a HDMI high definition display.Taking advantage of the parallel processing characteristics of FPGA,the modules such as pseudo-dark primary color,atmospheric light value calculation,transmittance calculation,guided filtering,Gamma correction and so on are implemented,and the TVP5150 and TFP410 are configured tihrough I2C bus to reali'ze the ffunction of infrared video data acquisition and HDMI high-definition video output.Finally,the proposed infrared image enhancement algorithm is implemented on the FPGA platform.4.Experimental evaluation of the desgined infrared image enhaixcement system.The experimental results show that the developed system can achieve the enhancement of the video images with a frame rate of 25 frames per second and a resolution of 720*576 in real-time.The enhanced images have higher contrast,richer detail information and better visiual quality,which demonstrates the effectiveness of the designed system...