Theory and experiment of in-line phase contrast imaging on non-uniformly distributed source

In-line phase contrast imaging has been discussed in both plane wave and point source condition in many works. For source with finite size and non-uniform distribution, however, it is not easy to obtain images with high contrast. In this work, we propose a new theoretical method to improve image contrast on this type of source. For a non-uniformly distributed source based on a simple cylinder model, we discuss the dependence of the contrast on the experimental conditions, i.e., the radius of the cylinder, the distance between the detector and the object, the difference of the refractive index, and the spatial coherence of the source. Optimal parameters for different samples and sources, which are meaningful for a non-uniformly distributed source, are presented and discussed. A series of experimental results are presented to confirm the theoretical framework.