New signal extraction method in x-ray differential phase contrast imaging with a tilted collinear analyzer grating

摘要

In a grating interferometer-based x-ray differential phase contrast (DPC) imaging system, an analyzer grating (i.e. a G2 grating) is typically used to record the refraction information in conjunction with the use of a phase stepping technique. This method requires a sequential mechanical movement of the grating or object, as a result, the data acquisition time of the conventional DPC imaging can be prohibitively long. To eliminate the mechanical phase stepping procedure, a novel local moire fringe analysis method was developed to achieve single-shot exposure imaging using a conventional collinear G2 grating. A relative rotation between the G1 and G2 gratings was introduced to generate the needed moire fringes on the detector plane. Initial experiments have demonstrated that this new signal extraction method is able to generate signals with the following three contrast mechanisms: absorption, differential phase, and the dark field.