Single-exposure x-ray dark-field imaging via a dual-energy propagation-based setup

X-ray dark-field imaging visualizes scattering from sample microstructure and has found application in medical and security contexts. While most x-ray dark-field imaging techniques rely on masks, gratings, or crystals, recent work on the Fokker-Planck model of diffusive imaging has enabled dark-field imaging in the propagation-based geometry. Images captured at multiple propagation distances or x-ray energies can be used to reconstruct dark-field from propagation-based images but have previously required multiple exposures. Here, we show single-exposure dark-field imaging by exploiting the harmonic content in a monochromatized synchrotron beam and utilizing an energy-discriminating photon-counting detector to capture dual-energy propagation-based images. The method is validated by filming time-varying samples, showing the advantage of the dark-field contrast in analyzing dynamic evolution. We measure and adjust for the impact of detector charge-sharing on the images. This work opens the way for dynamic dark-field x-ray imaging without the need for a high-stability setup and precision optics.