临床X射线成像所使用的X射线源实际上都是部分相干的,由部分相干源在一定距离内所成的像一般既有吸收衬度又有相位衬度。本文根据Fresnel-Kirchhoff衍射理论的基本思想,导出X射线相位衬度成像的理论公式,着重对其衬度进行分析,并与实验作了比照,结果与预期的相符。 X-ray sources used in clinical X-ray imaging are in fact all partially coherent, with the partial coherence source formed at a distance as generally both absorbing and phase contrast. Based on the basic idea of ​​Fresnel-Kirchhoff diffraction theory, the theoretical formula of X-ray phase contrast imaging is derived in this paper. The contrast of the contrast is emphatically analyzed and compared with the experiment. The result is consistent with the expectation.