Investigation of the partially coherent effects in a 2D Talbot interferometer
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The recent use of a one-dimensional (1D) X-ray Talbot interferometer has triggered great interest in X-ray differential phase contrast imaging. As an improved version of a 1D interferometer, the development of two-dimensional (2D) grating interferometry strongly stimulated applications of grating-based imaging. In the framework of Fresnel diffraction theory, we investigated the self-image of 2D-phase gratings under partially coherent illumination. The fringe visibility of the self-image has been analyzed as a function of the spatial coherence length. From the viewpoint of self-image visibility, it is possible to find the optimal 2D grid for 2D X-ray grating interferometer imaging. Numerical simulations have been also carried out for quantitative evaluation. Results, in good agreement with theoretical analysis, indicate the spatial coherence requirements of the radiation illuminating a 2D grating interferometer. Moreover, our results can be used to optimize performances of a 2D grating interferometer and for further theoretical and experimental research on grating-based imaging systems.
KeywordsX-ray phase contrast 2D Talbot interferometer Partially coherent illumination Visibility
We would like to gratefully acknowledge Dr. Augusto Marcelli for fruitful discussions. This work was partly supported by the National Outstanding Youth Fund (Project No. 10125523 to ZW), the Knowledge Innovation Program of the Chinese Academy of Sciences (KJCX2-YW-N42), the Key Important Project of the National Natural Science Foundation of China (10734070), the National Natural Science Foundation of China (NSFC 10774144 and 10979055), and the National Basic Research Program of China (2009CB930804).
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