Statistical Theory of X-ray Diffraction Phase Contrast Formation

A successive consideration of the formation of X-ray diffraction phase contrast of weakly absorbing noncrystalline objects with statistically distributed small-scale density inhomogeneities has been performed. It was assumed that the incident X-ray beam has an arbitrary degree of spatial coherence, and the changes in the statistical characteristics of this radiation during Bragg diffraction reflection from the monochromator and analyzer were taken into account. The phenomena of the increase and/or decrease in the phase contrast from regions with randomly distributed microcalcifications, in dependence of their rms sizes, relative refractive index decrement, and the lengths of spatial coherence of radiation and phase correlation as a result of diffraction-enhanced diffuse scattering are explained.