基于FPGA的辐射成像采集系统设计与实现

发布时间：2018-01-22 03:58

本文关键词： FPGA X射线辐射成像阵列探测器图像处理　出处：《东华理工大学》2017年硕士论文　论文类型：学位论文

【摘要】：目前,X射线辐射成像安全检查系统广泛应用于国内机场、铁路、海关、港口等场所中,应用需求量大,但国内自主研发的数字化辐射成像安全检查设备较少。作为重要的公共场所安全检查手段,基于FPGA的辐射成像采集系统利用X射线扫描成像技术快速扫描行李箱、集装箱内的物品,查出毒品、枪支、爆炸物等危险违禁物和走私货物,维护公民人身财产安全,保障社会和平与安宁。根据核脉冲信号的随机性和统计性的特点,本文重点研究了X射线与碘化铯晶体相互作用的机理,掌握了阵列探测器对核脉冲信号的处理方法。本文对X射线阵列探测器信号采集子系统的设计,完成了脉冲信号提取、积分放大、差值滤波、AD变换以及FPGA辐射成像数据采集板的设计与调试。使用嵌入式实验板搭建阵列探测器脉冲信号采集与测试平台,编写脉冲计数曲线绘制软件,利用数字示波器观察脉冲信号。采用理论方法定性分析了脉冲信号出现的“拖尾”现象,并对脉冲信号进行滤波成形、基线恢复和滑动均值滤波处理。针对FPGA数据采集与传输控制内核设计,本文完成了积分变换时序控制逻辑模块、LVDS数据传输模块、RAM存储模块、RAM读写时序控制模块、以及VGA时序控制模块的状态转移控制流程设计与Verilog HDL内核设计,并利用Signal Tap II逻辑分析仪对所设计的各个逻辑模块进行时序验证。针对X射线扇面束流强度的不均匀性和各个阵列探测器电路参数的不一致性导致图像存在明暗水平条纹和高频噪声,本文对其进行了图像处理算法研究,建立了线性插值算法数学模型,设计了线性插值算法软件,搭建了图像处理验证平台,并对图像处理效果进行了分析。论文研究结果表明,基于FPGA的辐射成像采集系统实现了X射线脉冲信号采集、数据传输、图像处理与VGA视频显示功能。使用了滤波成形处理方法后,阵列探测器信号输出的“拖尾”现象消失了,提高了脉冲计数容量。使用“极-零”相消处理方法后,脉冲信号的下冲现象也消失了,减小了对正电场信号的影响。通过系统验证和算法改进后,图像明暗水平条纹消失了,图像质量也得到了改善。基于FPGA的辐射成像采集系统在实际应用中基本满足了设计要求,具有很高的应用价值。
[Abstract]:At present, X-ray radiation imaging safety inspection system is widely used in domestic airports, railways, customs, ports and other places, the application of large demand. However, the digital radiation imaging safety inspection equipment developed independently in China is less. As an important means of public safety inspection. The radiation imaging acquisition system based on FPGA uses X-ray scanning imaging technology to quickly scan luggage, containers, and find dangerous and contraband goods such as drugs, guns, explosives and so on. According to the randomness and statistics of nuclear pulse signal, the mechanism of interaction between X-ray and cesium iodide crystal is studied in this paper. In this paper, the signal acquisition subsystem of X-ray array detector is designed, the pulse signal extraction, integral amplification, difference filtering are completed. Design and debug of AD transform and FPGA radiation imaging data acquisition board. Use embedded experiment board to build array detector pulse signal acquisition and test platform, write pulse count curve drawing software. The digital oscilloscope is used to observe the pulse signal. The phenomenon of "trailing" appears in the pulse signal is analyzed qualitatively by theoretical method, and the pulse signal is filtered and formed. Aiming at the design of FPGA data acquisition and transmission control kernel, this paper completes the integration transform timing control logic module and the LVDS data transmission module. The RAM memory module reads and writes the timing control module, and the state transition control flow of the VGA timing control module and the design of the Verilog HDL kernel. And using Signal Tap. The logic analyzer II verifies the timing of the designed logic modules. Aiming at the nonuniformity of the beam intensity in the X-ray sector and the inconsistency of the circuit parameters of each array detector, there are horizontal stripes of light and dark in the image. And high frequency noise. In this paper, the image processing algorithm is studied, the mathematical model of linear interpolation algorithm is established, the software of linear interpolation algorithm is designed, and the image processing verification platform is built. The research results show that X-ray pulse signal acquisition and data transmission are realized in the radiation imaging acquisition system based on FPGA. Image processing and VGA video display function. After using filter shaping method, the "tail" phenomenon of array detector signal output disappears. The pulse counting capacity is improved. After the "Pole-Zero" cancellation method is used, the impulse phenomenon of the pulse signal disappears, and the influence on the positive electric field signal is reduced. After the system verification and the algorithm improvement, the influence of the pulse signal on the positive electric field signal is reduced. The horizontal fringe of the image disappeared and the image quality was improved. The radiation imaging acquisition system based on FPGA basically meets the design requirements in practical application and has a high application value.
【学位授予单位】：东华理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O434.19;TP391.41

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