X射线源透射式工业计算机断层扫描成像技术在复合材料工件检测中的散射修正

在X射线源透射式工业计算机断层扫描成像技术（X-TICT）中，X射线透射物质时，发生了Compton光子散射现象，有用信息连同散射光子一起进入探头形成伪影。因此，必须进行散射修正。利用X射线透射物质时X光子散射遵循的Compton散射强度方程，结合X射线与物质相互作用的特性，建立了有效去除X—TICT在复合材料工件检测中光子散射问题造成的图像伪影的散射修正模型。探头的总计数减去散射光子数，即可有效去除X-TICT在复合材料工件检测中散射光子造成的伪影。     

连续谱X射线在ICT中的散射修正

在X射线工业计算机断层扫描成像技术（ICT）中，连续谱X射线透射物质时，发生了光子散射现象，有用信息连同散射光子一起进入探头形成伪影。如未修正，必引起赝像。利用X射线透射物质时的X光子散射遵循的Compton散射强度方程，建立了连续谱X射线完整精确的散射修正模型及其修正方法。为有效去除连续谱X光子的散射造成的图像伪影提供比较完善精确的修正模型和修正方法。     

基于独立分量分析的X射线图像增强方法

为了改善由于散射造成的X射线检测图像对比度低,被测工件细节不易显示等缺点。针对退化图像中散射的分离,提出一种盲参数估计分离散射算法,该算法在假定图像由独立散射光谱组成的基础上,通过对散射偏振分析建立盲分离模型,来实现X射线图像的增强。采用小波变换得到图像子带图像,对盲参数间接估计。理论分析和实验结果表明,该算法在抑制散射的基础上有效的提高了图像的对比度和清晰度。     

康普顿散射层析的一些结果和应用考虑

报告康普顿散射层析(CST)的一些结果和应用设想。提出利用聚焦准直器代替单个准直器以达到增大探测器接收到的散射光子通量的目的。     

平板工件中射线束散射比的一般表述式

射线束在被检工件内的散射,常常使射线底片对比度降低.对于这个现象,文献[1]已做了较好的分析,并且给出了一定条件下的散射比与工件板厚之间的实验线性回归关系.本人认为除工件厚度外,影响散射比的因素还有很多,如焦距、射线照射场大小和X射线线质等,我们应试图找出一种能较全面反映这些因素的一般表述式.     

聚苯乙烯微球的Mie散射特性分析

应用Mie散射理论针对聚苯乙烯微球的光散射特性进行了研究,分析了入射光波长、偏振角和微粒直径对散射光强的影响。结果表明：进行聚苯乙烯微球粒子散射方面的研究,应该选择可见光波段中波长较短的作为光源;在其它条件不变的情况下,波长越短散射光强集中分布的角度越小,粒子直径越大散射光强越集中分布在小角度内;球形粒子的散射光强与散射角的变化关系,不仅与入射光波长有关,而且与散射颗粒与周围介质的相对折射率m有关。     

金属材料X射线散射比的测定

通过实验对铁、铝材料经X线射透照时产生的散射X射线进行了测量,得出了透照焦距与散射比的关系曲线,管电压和散射比、板厚与散射比的关系曲线。最后提出了在实际探伤时散射X射线的防护措施。     

关于康普顿效应的两个问题

众所周知,在射线探伤的能量范围内,康普顿效应是射线与工件作用的主要效应。然而对这一主要效应在理论上至今还有两方面的分歧: (1)产生康普顿效应时,入射光子的作用对象。 (2)康普顿散射的线衰减系数fc与物质原子序数Z的关系。 笔者想就以上问题阐述自己的观点,并讨论影响吼的因素。     

射线检测在复合材料无损检测中的应用

随着新型复合材料的迅速开发和应用，其制造过程监测、产品缺陷检测及质量评价等已成为不可缺少的环节。射线检测技术在复合材料无损评价中占有极其重要的地位。对现有的主要射线检测方法，包括X射线照相法、X射线实时成像法、射线计算机断层扫描法、射线断层形貌成像法、康普顿散射法及中子照相法等在复合材料质量评价中的应用状况进行了简要的评述，并指出复合材料射线检测的发展趋势。     

使用X射线康普顿散射的在线密度测量系统

建立了一个基于X射线康普顿散射的密度测量系统,安装在工业生产线使用。这个计算机控制系统自动无损测量粉末冶金中间产品(未烧结状态)的局部密度(几个立方毫米)。对密度范围在6～7.3g·cm~(-3)的铁粉压制产品,用工业X射线管和多孔准直器测量系统在40s内可得到精度优于1％的密度测量。     

射线实时成像检测图像质量的改进方法

研究了射线实时成像检测时改进图像质量的方法。采用外加磁场的方法矫正钢管剩磁,可克服由钢管剩磁引起的X射线图像畸变。在射线源上方附近及图像增强器输入屏处放置铅板,可减小由射线散射引起的图像噪声。采用独立电源和图像增强器单独接地等手段,可降低设备干扰引起的X射线图像噪声。通过合理选择射线源焦点、焦距和图像放大倍数,减少了X射线实时成像检测图像的不清晰度。     

A study of multiple scattering background in Compton scatter imaging

The multiple scattering background in Compton scatter imaging at 662 keV is studied, both experimentally and by Monte Carlo radiation transport calculations, as a function of the scattering angle, scattering material (aluminium, brass and tin) and object thickness. A double-peak structure was observed in the pulse-height distribution for the thicker brass and tin objects and at the larger scattering angles (90° and 120°). In addition to the Compton peak, a second peak appeared at a higher energy. Monte Carlo transport simulations have revealed the origin of the second peak: photons that have scattered exactly twice before reaching the detector. The ratio of the multiple-scattered radiation to the total radiation detected was calculated as a function of the energy-window width around the Compton peak and scattering angle. The results of this study may help in the design of future Compton scatter imaging apparatus.     

Rayleigh to Compton ratio computed tomography using synchrotron radiation

The detection of X-ray photons scattered through a sample by the Rayleigh and Compton processes is used to perform tomographic images. In the present paper, we describe a new experimental arrangement and the corresponding reconstruction method. The scanning method is similar to the one used for first generation tomographs. A standard reconstruction algorithm gives two intermediate images, corresponding to the Compton and Rayleigh contributions. Quantitative comparisons are made with the aim to explain the difference of sensitivity between each scattering process. On both images artifacts are present, due to photon attenuation. Computing the ratio between those two images produces a map, free from artifacts, which represents the atomic number Z. Differentiation between polyethylene and an aqueous solution containing a low concentration of iodine (0.5 g l⁻¹) is easily performed. The experiments were carried out at the European Synchrotron Radiation Facility (ESRF), in Grenoble (France), on line ID15 B. As a result of the very high photon flux, short measurement times (about five seconds per point) are allowed, as well as a good spatial resolution. The voxel size is 1×1 mm² in the plane of the slice and 0.3 mm in the third direction.     

空心叶片残留型芯影像的射线照相对比度

从型芯影像射线照相对比度的角度分析了残芯在叶片中的可检性。通过推导的残芯影像对比度公式,分析了影像对比度的各种影响因素,并在理论上进行了计算。从试验与理论计算相比较的结果表明,通过改善梯度和散射能有效地提高型芯影像的对比度。得出型芯在叶片材料上的最小可检厚度。     

Influence of electronic structure on Compton scattering through comparing Cu-Ni alloys with Cu-Ni powder mixtures

The application fields of Compton scattering have been further broadened through the studies of theories and experiments as well as the electronic structure of the scatters. The relationship between the contents of binary alloys (also binary powder mixtures) and the number of Compton scattered photons has been thoroughly examined. The linear expression of the relationship has been obtained approximately according to the Compton scattering theory. And the relationship has been validated well through the Compton scattering experiments with the scatters of Cu-Ni binary alloys or Cu-Ni binary powder mixtures. Furthermore, it is found that the slope of Cu-Ni powder mixture series is steeper than that of Cu-Ni alloy series, and through the pseudopotential plane wave theory of DFT the microscopic principles of Compton scattering of Cu-Ni alloy and Cu-Ni powder mixture series have been discussed and compared with each other. The results show that the electronic structure is the main reason for the difference of the linear slopes, and the line slope of Cu-Ni powder mixtures series is steeper than that of Cu-Ni alloy series.     

不等厚板搭接焊缝缺陷数字X射线检测

在不等厚钢板搭接焊缝X射线检测图像中,由于工件及焊缝厚度变化带来的图像背景灰度差异、焊缝区灰度连续变化等,给基于图像处理的缺陷自动识别带来困难.同时,被检测焊缝装卡的空间位置具有不确定性,垂直布置的焊缝和重力方向存在一定角度,不便于缺陷自动识别及定位.文中给出一种基于不变矩的X射线图像校正方法,解决焊缝图像倾斜问题;在此基础上,给出一种图像噪声抑制、背景去除、图像分割及数学形态学相结合的缺陷识别方法.结果表明,所提方法能有效识别不等厚搭接焊缝中的气孔类缺陷,适用于自动检测.