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根据菲涅耳衍射积分理论,提出了X射线光栅相衬成像系统的仿真模型.以聚甲基丙烯酸甲酯(PMMA)小球作为成像物体模型,选取30 keV的X射线做模拟计算.通过仿真,得到了穿过球体和相位光栅的X射线波前的变化.采用多步位移法从模拟条纹图中恢复出了PMMA小球的相位信息,并分析了莫尔条纹对比度对成像质量的影响,为实际的实验提供可靠的参数选择.经过仿真得到的相移信息与通过实验得到一致,验证了仿真算法的正确性.“,”According to the Fresnel diffraction theory,a simulation model of grating-based X-ray differential phase contrast imaging system was established.A PMMA sphere was the image object and the level of X-ray was 30 keV. Through the simulation, the change of the wave front of the X-ray passing through the sphere and phase grating was gotten.In addition,the image of first-order derivative of object phase was extracted by the method of phase-stepping. Furthermore, the influence of Moire fringe contrast on image quality was analyzed. The optimization design of the parameters of the grating was discussed. The simulation results are helpful to optimize the experimental platform,and analyze the factors that affecting the image quality.