X-ray dark-field imaging can provide inaccessible and complementary information compared to conventional absorption contrast imaging. However, extraction of the dark-field signal is difficult, and sophisticated optics are often required. In this Letter, we report a novel approach to generate high-quality dark-field images using a simple membrane. The dark-field image is extracted from the maximum correlation coefficient by applying a cross-correlation algorithm to a stack of speckle images collected by scanning a membrane in a transverse direction to the incident x-ray beam. The new method can also provide directional dark-field information, which is extremely useful for the study of strongly ordered systems. The potential of the proposed technique for nondestructive x-ray imaging is demonstrated by imaging representative samples.
Wang, H., Kashyap, Y., & Sawhney, K. (2015). Hard-X-ray directional dark-field imaging using the speckle scanning technique. Physical Review Letters, 114(10). https://doi.org/10.1103/PhysRevLett.114.103901