X射线同轴轮廓成像中影响成像质量的若干因素研究

采用数字模拟方法较为系统地研究了光子能量、样品直径和散射强度对成像质量的影响，克服了已有实验结果的局限性.研究得到成像质量随光子能量的变化关系，模拟结果与已有实验结果相符.研究发现，当其他成像参数不变时，同一样品存在多个光子能量可实现相近的成像质量，且成像质量都较好，这可用于定量相衬成像中多图重构时图像的选择，也为对辐射剂量有要求的样品提供理论依据.得到了不同直径样品在成像质量最佳时所对应的样品到探测器距离，发现这一距离随样品直径的增加而增加.研究了样品厚度或折射率变化导致的散射X射线对成像质量的影响，发 关键词： X射线同轴轮廓成像 成像质量 X射线散射

Effect of some factors on imaging quality of X-ray in-line outline imaging

The imaging quality of X-ray in-line outline imaging(XIOI)is mainly related to the size of samples, X-ray photon energy, X-ray scattering, distance from sample to detector D_sd and also distance from source to sample for point X-ray source and so on. To maximize the resolution of the image under the practical limitations of laboratorial equipment in distance from sample to detector and range of adjustable photon energy etc., the present paper studies the effect of the above factors on the imaging quality using numeral simulation. We obtained the relationship between imaging quality and photon energy, and not only found that there are certain X-ray photon energies which are equally well suitable for imaging but also found that we can get some high quality images for phase retrieval through which we can get the exact phase and absorption information. We have determined the precice D_sd values at which the imaging quality is the best for samples of different size, and found that D_sd is propertional to the sample size and determined the factor of proportionality. Though the diffuse scattering of X-ray reduces the contrast of images, we can still have good contrast when the variation in thickness is the order of the sample size when the scattering are only caused by the variation in thickness. So under these unfavorable conditions XIOI still performs effectively.