  In this work, a general theoretical framework is presented to explain the
formation of the phase signal in an X-ray microscope integrated with a grating
interferometer, which simultaneously enables the high spatial resolution
imaging and the improved image contrast. Using this theory, several key
parameters of phase contrast imaging can be predicted, for instance, the fringe
visibility and period, the conversion condition from the differential phase
imaging (DPI) to the phase difference imaging (PDI). Additionally, numerical
simulations are performed with certain X-ray optical components and imaging
geometry. Results demonstrate the accuracy of this developed quantitative
analysis method of X-ray phase-sensitive microscope imaging.
