Infrared Digital Image Detail Enhancement Technology Based On FPGA

Infrared imaging system occupies a large number of markets in many fields because of its successful development and extensive application.The main factor restricted its development is that the output infrared image has low spatial resolution and low temperature resolution.With the increasing development of infrared focal plane arrays(IRFPA)manufacturing technology,large-scale detection arrays and high AD sampling applications,the infrared image contains lots of detail information,and its dynamic range is also growing.But the range of the ordinary monitor can only display image which gray level is between 0 to 255,and the sensitive gray level of human is from 0 to 127.IRFPA obtains a high dynamic range of data,while the display device and the human eye sensitive area is low dynamic range data.In order to solve the contradiction,the study of efficient infrared image dynamic range compression and enhancement algorithm is of great significance to the development and application of infrared imaging system.In this paper,the compression and detail enhancement algorithms of high dynamic infrared images commonly used are studied,and the linear and nonlinear compression algorithms are simulated and compared.The new compression algorithm based on optimization curve is introduced,and its application field is analyzed.The commonly used histogram equalization and the enhancement algorithm based on histogram expansion are briefly described,and their advantages and disadvantages are analyzed in this paper.The enhancement algorithm based on multi-scale decomposition is introduced.And the fundamental multi-scale decomposition methods include Gaussian filtering,bilateral filtering and guided filtering.And some simulation experiments are performed.In this paper,a new enhancement algorithm by combining the guided filtering and SLIC super pixel segmentation is proposed.Firstly,the SLIC is used to segment the entire image.Secondly,the guided filtering is used to get the details of the image.Then,the gain coefficient is calculated by the mean value of the local area,which can adjust brightness of the different area of the image.Finally,the output image is synthesized by local sub-region.The simulation results show that the enhancement effect is obvious.Aiming at the application of the specific infrared alarm system,the hardware system based on FPGA + DSP architecture is designed,and the main hardware structure and function are elaborated.The enhancement and compression of the segmented linear infrared image are realized in FPGA,and the discontinuity of the infrared image is solved.And the enhancement algorithm based on Gaussian hierarchical principle is realized in FPGA too.The hardware realization of super pixel segmentation process is introduced in detail in this paper.The result has shown that the piecewise liner compression is realized in real time,and the output video has good continuity and ideal visual effect.