硬X射线位相衬度成象

常规X射线成象技术是建立在吸收衬度和几何光学基础上.介绍了“in-line”位相衬度成象 技术和成象理论.以生物样品为例,说明常规X射线吸收衬底成象与位相衬度成象的差别,并 对X射线源尺寸对成象衬度的影响进行了研究.此外,对吸收衬底象和位相衬度象的关键参量 进行了计算模拟和讨论.关键词：位相衬度成象硬X射线     

Effect of transverse object position on the reconstructed image of an aperture-limited in-line hologram

It is experimentally demonstrated that the image resolution from an in-line Fraunhofer hologram degrades appreciably when the centre of the diffraction pattern from a 5-bar resolution target is located asymmetrically in the hologram aperture. This effect is confirmed and analysed using calculated and experimentally measured images from holograms of a one-dimensional wire. Increasing asymmetry results in an increasing error in the measured linewidth, and a reduction of image resolution. A simple model based on average fringe contrast is used to predict this decrease in resolution with transverse object position.     

微粒场远场同轴全息术

本文从一般模型出发,导出了微粒场远场同轴全息图和再现实象面上的光强分布的普遍表达式.给出了全息图条纹对比度、记录介质的分辨率要求和可允许的微粒最大位移的普遍公式.完善和普遍化了微粒场同轴全息术的理论体系.     

Study of in-line single-mode optical fiber polarizer

The theoretical calculation method of multilayer metal-clad planar optical waveguide presented by Y. YAMAMOTO is greatly improved and transplant into the optical fiber and a suitable waveguide model of in-line single-mode optical fiber polarizer is set up to study its characteristics, the theorical analyses are in accordance with the experimental re suits. The polarizer whose extinction ratio is more than 30 dB at 0.633μm wavelength with an insertion loss of 0.5 dB is formed by grinding off the cladding on one side of a single-mode fibre and evaporating metal onto the polished durface in our Lab.     

Visibility in differential phase-contrast imaging with partial coherence source

This paper gives theoretical analysis of visibility of fringes, which is influenced by distances, temporal and spatial coherence of source, in hard x-ray differential phase-contrast imaging with microfocus x-ray source. According to the character of longitudinal periodicity of the interferogram, the setup is insensitive to mechanical drift and vibrations. The effect of temporal coherence of x-ray source is investigated and its related bandwidth is derived. Based on the theory of partially coherent light, it shows that the requirement for the spatial coherence of x-ray source is not strict and can be met by the general microfocus x-ray tube for x-ray differential phase-contrast imaging.     

Propagation based X-ray phase-contrast imaging technique for the microstructure analysis of biological soft tissues

X-ray phase-contrast imaging (PCI) technique is an emerging method for the study of the biological soft tissues, carbon composite materials, polymers, low-Z material science, etc. We have set up an experimental facility using a combination of X-ray CCD detector and a microfocus X-ray source. We demonstrate that sufficient contrast and intensity can be achieved for biological soft tissues with the X-ray source in the standard operation mode. Based on the cylindrical fiber and pigeon feathers imaging experiments, the boundary information was observed successfully in the light element materials and extremely low absorption material. This shows that X-ray phase-contrast imaging in this area will have a brilliant future.     

Magnetic resonance measurement of blood flow in peripheral vessels after acute exercise

Velocity-encoded Cine magnetic resonance imaging (MRI) was used to measure blood flow in the anterior tibial artery (AT), posterior tibial artery (PT), and popliteal artery of adult human subjects (mean age 29 yr) before and after 90 s of ankle dorsiflexion exercise. Before exercise, mean flow, peak systolic velocity, and end-diastolic velocity in AT were 8.1 ± 1.6 (SE, n = 6) ml/min, 26.9 ± 2.6 cm/s, and −0.6 ± 0.4 cm/s, respectively. After exercise, mean flow and peak systolic velocity in AT increased by 19-fold and 3-fold, respectively, and end-diastolic velocity increased to 8.7 ± 1.1 cm/s. Flow in popliteal artery above its bifurcation was similar to the sum of flows in AT and PT, both before and after exercise. Flow in AT declined exponentially after exercise with a mean half-time of 4 min. The results demonstrate the utility of MR phase-encoded flow-velocity measurements for physiological studies of peripheral vascular dynamics after exercise.     

硬x射线同轴相衬成像的相位恢复

基于角谱的概念,分析了硬x射线同轴相衬成像过程,在传统相位恢复算法GS算法的基础上 ,提出了基于角谱传播的相位恢复算法——迭代角谱法（IASA）,并利用数值法模拟研究了 相衬成像和相位恢复过程,从理论上验证了这一相位恢复算法.关键词：相位恢复相位衬度角谱硬x射线     

相衬照相法检测聚苯乙烯微球气泡缺陷

利用较高能量的X射线对聚苯乙烯（PS）微球进行离焦相衬成像,球壁内密度变化较大的微小气泡的边缘衬度得到有效增强,从而在灰度变化较平滑的微球整体图像中凸显出来,分析了衬度来源及相关因素。实验采用微焦斑的X射线管及CCD作为光源及探测器,图像分辨力约为2 μm,在能量为20～30 keV时,实现了PS微球缺陷快速检测,为微球制备工艺的改善和提高提供了快速有效的监测手段。     

北京同步辐射装置上的位相衬度成像

在北京同步辐射装置上首次用位相衬度成像方法对生物样品和复合材料进行研究,得到了非常清晰而精细的材料内部细观结构.其图像的清晰度和分辨率明显地优于吸收衬度成像关键词：位相衬度成像相干光源同步辐射硬X射线     

数字像面全息与同轴全息实验研究

通过采用数字像面全息与同轴全息技术拍摄透明物体以及不透明物体的全息图,并在计算机上再现。结果表明,当记录较小物体的全息图像时像面全息技术更加合适。     

相衬照相法检测聚苯乙烯微球气泡缺陷

 利用较高能量的X射线对聚苯乙烯（PS）微球进行离焦相衬成像,球壁内密度变化较大的微小气泡的边缘衬度得到有效增强,从而在灰度变化较平滑的微球整体图像中凸显出来,分析了衬度来源及相关因素。实验采用微焦斑的X射线管及CCD作为光源及探测器,图像分辨力约为2 μm,在能量为20～30 keV时,实现了PS微球缺陷快速检测,为微球制备工艺的改善和提高提供了快速有效的监测手段。     

X射线相衬成像光子筛

基于 Zernike相衬成像原理和光瞳切趾原理,提出一种将相位板和切趾光子筛集成为一个相衬显微物镜的 X射线相衬成像光子筛的设计方法.这种 X射线相衬成像物镜可以实现生物体组织或者其他弱吸收材料的高分辨率和高衬度成像.通过优化光子筛透镜的衍射结构,可以抑制成像系统的点扩展函数的旁瓣和消除高阶衍射焦点,从而提高成像分辨率;另外,将光子筛透镜和变相板合为一体,克服了成像透镜和变相板难以对准的缺陷.以高斯切趾光子筛为例,实验验证了设计方法的可行性.关键词：X射线显微技术相衬成像光瞳切趾光子筛     

同步辐射相位衬度成像医学应用初探

近年来,相位衬度成像技术医学领域应用的发展引人瞩目.同步辐射相位衬度成像无须使用对比剂就能显示传统X射线无法显示的肌腱、软骨、韧带、脂肪、血管及神经等软组织.文章作者应用包括类同轴相衬成像和衍射增强成像在内的相位衬度成像技术进行了肝胆、肺脏、肾脏、胃肠道、心脏、血管、骨关节组织与肿瘤成像,证实了同步辐射相位衬度成像较传统X射线成像图像清晰,分辩率明显提高,特别适用于软组织、血管等的成像.     

一种具有多种成像倍率的电视跟踪测量物镜

在飞行试验中,采用直接成像的电视跟踪系统对飞行目标进行自动跟踪和测量,不仅观察方便,而且更适合于对视频信号数字化和图像处理。电视系统要执行在作用距离内对飞行目标的搜索、跟踪和测量等功能,单靠一种固定焦距的电视物镜显然是不够的。介绍了一种具有三种成像倍率的变焦距电视物镜,着重描述了其结构组成、技术性能及特点。借助于三种成像倍率的变化,系统得以实现形心跟踪、边缘跟踪和相关跟踪等多种跟踪方式,从而完成地多种成像状态下对飞行目标的自动跟踪和测量,如远距离的点目标,近距离体目标的某部位以及复杂背景中的动目标等。     

用高速摄影和脉冲同轴全息照相联合诊断微射流

针对强冲击载荷下金属材料的微物质喷射中微射流的实验研究,提出了高速摄影与脉冲同轴全息照相联合诊断的测试方案,并组建了由微射流产生装置、高速摄影系统、脉冲同轴全息照相系统和高精度时序控制同步系统组成的测试系统。动态实验结果表明,高速摄影和脉冲同轴全息照相联合诊断微射流能在一次实验获得微射流的发展图像和微射流头部低动态模糊图像。