Abstract
Previous studies on edge illumination (EI) X-ray phase-contrast imaging (XPCi) have investigated the nature and amplitude of the signal provided by this technique. However, the response of the imaging system to different object spatial frequencies was never explicitly considered and studied. This is required in order to predict the performance of a given EI setup for different classes of objects. To this scope, in the present work we derive analytical expressions for the contrast transfer function of an EI imaging system, using the approximation of near-field regime, and study its dependence upon the main experimental parameters. We then exploit these results to compare the frequency response of an EI system with respect of that of a free-space propagation XPCi one. The results achieved in this work can be useful for predicting the signals obtainable for different types of objects and also as a basis for new retrieval methods.
Highlights
Edge illumination (EI) X-ray phase-contrast imaging (XPCi) has been developed and investigated during recent years at University College London [1,2,3,4]
It is worth mentioning that a procedure similar to dithering in EI could be adapted to the case of free-space propagation (FSP), whereby the sample is scanned in sub-pixel steps and multiple images are acquired and combined
We have developed the concept of a contrast transfer function for EI XPCi, under the geometrical optics approximation
Summary
Edge illumination (EI) X-ray phase-contrast imaging (XPCi) has been developed and investigated during recent years at University College London [1,2,3,4]. A formalism based on the contrast transfer function (CTF), which describes how efficiently each object frequency is transferred to the image, is naturally suited to this scope. We demonstrate that, under the approximation of near-field regime, a CTF can be defined and calculated for EI. We exploit this formalism to compare EI with a wellknown XPCi technique, free-space propagation (FSP) [14,15,16,17], which is currently widely used at both SR facilities and in laboratory setups with microfocal sources.
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