Cascade Talbot–Lau interferometers for x-ray differential phase-contrast imaging

X-ray Talbot-Lau interferometer (TLI)-based differential phase-contrast imaging (DPCI), owing to its potential capability of multiple contrast mechanisms and adaptability for variety of samples, has attracted wide spread attention in the last decade. However, the fabrication of the absorption grating, an indispensable element in a conventional TLI, presents a significant challenge for practical applications. Here, we report on a cascaded TLI (CTLI) configuration for DPCI, i.e. a TLI followed by an inverse TLI (ITLI), through which the small-period high-aspect-ratio (HAR) absorption gratings (analyzer gratings and source gratings in the conventional TLI and ITLI, respectively) could be omitted. Instead, the large- period absorption gratings (generally tens of microns) are allowed to be employed, which significantly relieves the grating fabrication difficulties, especially for the large-area ones. The success of our CTLI configuration is validated by the observation of moire fringes, and the resulting phase-contrast and visibility-contrast images for DPCI. Moreover, our CTLI configuration is promising to yield magnified interference fringes capable of being detected directly by commonly used large-area detectors.