A phase demodulation method for two-dimensional grating-based X-ray interferometry

This paper presents a novel approach to achieving high spatial resolution in the demodulation of images produced by a two-dimensional X-ray Talbot interferometry (XTI) system. Currently, demodulation of XTI images is mainly performed by either phase-stepping (PS) or Fourier transform (FT) methods. However, the PS method for two-dimensional XTI demodulation requires a larger number of exposures and a more complex grating control process than that of one-dimensional XTI. On the other hand, although the FT method uses only a single-fringe image, it gives lower spatial resolution than the PS method. For practical application of two-dimensional XTI, a simpler exposure process with high spatial resolution is required. In this paper, we introduce a hybrid method combining the PS and FT methods. This method simplifies the exposure process in comparison with the PS method required in two-dimensional XTI while achieving higher spatial resolution than the FT method in the demodulation of images. The method works by using additional exposures to eliminate unnecessary spectral components that appear in the FT method. Furthermore, the proposed method is demonstrated by using actual two-dimensional XTI data and shown to achieve high spatial resolution in the demodulation of images for both the x- and y-differential phase components.