Abstract

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Title:: Cramér-Rao lower bound of dark-field imaging using a grating interferometer

Author(s):: LIU Bo; CHEN Zihan; GU Yao; CHEN Heng; WANG Zhili; Department of Optical Engineering, School of Physics, Hefei University of Technology, Hefei 230009, China

Keywords:: Keywords: dark-field imaging grating interferometer Cramér-Rao lower bound visibility

Abstract:: Abstract: In grating-based phase contrast imaging, the phase stepping technique is commonly utilized for data acquisition and signal retrieval from acquired intensity data. However, the algorithm efficiency with respect to the dark-field retrieval has yet to be sufficiently evaluated. Herein the algorithm efficiency of dark-field retrieval based on Cramér-Rao lower bound is evaluated. The theoretical analysis and numerical results demonstrates that fully efficient algorithm is currently available only for 3-step phase stepping technique, and other techniques with more phase steps are all sub-optimal. Quantitatively, the dependence of the algorithm efficiency on the phase step number and the visibility is investigated. It is shown that the phase stepping technique can nearly approach its theoretical optimal efficiency in the case of a low visibility. With a phase step greater than 5, the algorithm efficiency is only 77.4% in the case of a high visibility. The study can provide some reference for signal-to-noise ratio improvement and potential dose optimization in X-ray and neutron grating-based dark-field imaging.