Coded-aperture based imaging is a non-interferometric X-ray phase contrast imaging technique, which is based on the edge illumination principle. It enhances the image contrast and relaxes the requirements on experimental conditions, such as source sizes and detectors. Quantitative phase and absorption information can be retrieved by two opposite acquisitions. However, the retrieving accuracy and sensitivity depend on source conditions and experimental setups. In this paper, we present a new derivation for the laboratory-based retrieving method by using the slope at the center of the standard illumination curve. By analyzing the beam distribution on the detector with different source conditions, several corresponding extracting formulae are derived. Simulation results suggest that our extracting formulae can extract a relatively stable and accurate result of refraction angle with different X-ray sources. The sensitivity to refraction angle decreases with the increase of source size, its maximum value is determined by the sample aperture. Furtherly, sensitivity will be decreased when the detector aperture is small, because the edges of the beam are blocked by the detector mask. This work helps to choose the X-ray sources and to optimize the experimental setups, moreover, to improve the quantitative extracting accuracy of the refraction angle.
Source size and temporal coherence requirements of coded aperture type x-ray phase contrast imaging systems