本文選題：非均勻性校正 + FPGA��； 參考：《西安電子科技大學(xué)》2015年碩士論文

【摘要】：紅外焦平面陣列作為凝視型紅外成像系統(tǒng)的核心組件,是最具發(fā)展?jié)摿Φ囊环N紅外探測(cè)器,但是由于傳感器材料和制造工藝、信號(hào)處理系統(tǒng)暗電流噪聲以及工作環(huán)境等因素的影響,探測(cè)器各個(gè)單元的響應(yīng)之間存在非均勻性,從而在所輸出的圖像序列中產(chǎn)生固定圖案的噪聲。紅外成像的非均勻性不僅嚴(yán)重降低了系統(tǒng)的成像質(zhì)量,而且會(huì)對(duì)圖像的后續(xù)處理產(chǎn)生干擾,因此改善紅外成像的非均勻性顯得十分有必要,目前采用的最有效的方法是基于數(shù)字圖像處理的非均勻性校正技術(shù)。本文的目的在于研究一種基于場(chǎng)景的紅外成像非均勻性自適應(yīng)校正算法,并對(duì)其進(jìn)行硬件實(shí)現(xiàn),從而設(shè)計(jì)一種紅外成像非均勻性實(shí)時(shí)校正系統(tǒng)。本文研究了基于神經(jīng)網(wǎng)絡(luò)的非均勻性校正算法,并分析了算法中存在的缺陷及其產(chǎn)生的原因。在此基礎(chǔ)上,對(duì)神經(jīng)網(wǎng)絡(luò)法做出如下改進(jìn):一方面采用引導(dǎo)濾波計(jì)算預(yù)測(cè)圖像,在對(duì)圖像起到平滑作用的同時(shí)保留圖像中的邊緣信息,從而在提高校正效果的同時(shí)有效抑制“鬼影”現(xiàn)象的產(chǎn)生;另一方面使用投影法估計(jì)場(chǎng)景中的運(yùn)動(dòng)情況,并只在場(chǎng)景運(yùn)動(dòng)比較充足的情況下對(duì)校正參數(shù)進(jìn)行更新,從而避免了場(chǎng)景靜止時(shí)因參數(shù)重復(fù)迭代更新造成的圖像模糊。針對(duì)上述改進(jìn)算法,本文使用兩組具有代表性的紅外圖像序列進(jìn)行仿真并觀察校正效果,同時(shí)結(jié)合圖像粗糙度、均方誤差和信噪比等評(píng)價(jià)指標(biāo)對(duì)校正結(jié)果進(jìn)行定量分析,最終說(shuō)明所提出的改進(jìn)算法相對(duì)于傳統(tǒng)神經(jīng)網(wǎng)絡(luò)法具有明顯的優(yōu)勢(shì)。另外,本文以FPGA為核心處理器構(gòu)建硬件平臺(tái),充分利用FPGA可編程性強(qiáng)和并行計(jì)算的特點(diǎn),對(duì)改進(jìn)的神經(jīng)網(wǎng)絡(luò)非均勻性校正算法進(jìn)行硬件實(shí)現(xiàn),設(shè)計(jì)了一種基于FPGA的紅外成像非均勻性自適應(yīng)校正系統(tǒng),能夠?qū)?56×256像素的圖像序列以每秒25幀的速度進(jìn)行實(shí)時(shí)校正。文中根據(jù)自頂向下的層次化設(shè)計(jì)思想詳細(xì)描述了系統(tǒng)的實(shí)現(xiàn)方式,包括FPGA的頂層設(shè)計(jì)和模塊劃分,以及各個(gè)功能模塊之間的數(shù)據(jù)流向,并詳細(xì)描述了各個(gè)子模塊的設(shè)計(jì)細(xì)節(jié)。最后,通過(guò)仿真和測(cè)試驗(yàn)證了系統(tǒng)的功能,并從FPGA資源占用和系統(tǒng)運(yùn)算速度兩方面分析了系統(tǒng)的性能。最終證明,本文給出的硬件系統(tǒng)能夠?qū)t外圖像中的非均勻性進(jìn)行實(shí)時(shí)的自適應(yīng)校正,并有效防止“鬼影”和模糊現(xiàn)象的產(chǎn)生。
[Abstract]:As the core component of staring infrared imaging system, infrared focal plane array (IRFPA) is one of the most promising infrared detectors. However, due to sensor materials and manufacturing technology, Due to the influence of dark current noise and working environment in the signal processing system, the response of each unit of the detector is non-uniform, which produces the fixed pattern noise in the output image sequence. The nonuniformity of infrared imaging not only seriously reduces the imaging quality of the system, but also interferes with the subsequent processing of the image, so it is necessary to improve the non-uniformity of infrared imaging. The most effective method used at present is non-uniformity correction based on digital image processing. The purpose of this paper is to study a scene based adaptive correction algorithm for nonuniformity of infrared imaging and implement it in hardware, and then design a real-time correction system for nonuniformity of infrared imaging. In this paper, the nonuniformity correction algorithm based on neural network is studied, and the defects in the algorithm and its causes are analyzed. On the basis of this, the neural network method is improved as follows: on the one hand, the guided filter is used to calculate the predicted image, which can smooth the image while preserving the edge information of the image. On the other hand, the projection method is used to estimate the motion of the scene and update the correction parameters only when the scene motion is sufficient. Thus the image blur caused by repeated iterative updating of parameters when the scene is still is avoided. In view of the above improved algorithm, two groups of representative infrared image sequences are used to simulate and observe the correction effect. At the same time, the correction results are quantitatively analyzed by combining the evaluation indexes such as image roughness, mean square error and signal-to-noise ratio. Finally, it is shown that the proposed improved algorithm has obvious advantages over the traditional neural network method. In addition, this paper takes FPGA as the core processor to build the hardware platform, makes full use of the characteristics of FPGA programmable and parallel computing, implements the improved neural network nonuniformity correction algorithm in hardware. An adaptive infrared imaging nonuniformity correction system based on FPGA is designed, which can correct 256x25pixels image sequences at a speed of 25 frames per second. According to the top-down hierarchical design idea, this paper describes the implementation of the system in detail, including the top-level design and module partition of FPGA, as well as the data flow direction between each functional module, and describes the design details of each sub-module in detail. Finally, the function of the system is verified by simulation and test, and the performance of the system is analyzed from the aspects of FPGA resource occupation and system operation speed. Finally, it is proved that the hardware system presented in this paper can correct the nonuniformity of infrared image in real time and effectively prevent "ghost" and blur.
【學(xué)位授予單位】：西安電子科技大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：TN215;TP391.41;TN791

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