Phase-Contrast and Dark-Field Imaging

Abstract

Phase-contrast and dark-field imaging have been quickly-growing topics in the field of X-ray imaging for the past 15 years, both in medical and in materials communities. More than one hundred X-ray laboratories, and many synchrotron beamlines, are, today, equipped with Talbot-interferometers, Lau-interferometers or Talbot-Lau setups. However, new setups emerge every day, e.g., based on the far-field moiré effect or on transmission X-ray microscopy. Both grating-based differential phase-contrast and dark-field image contrast have been shown to provide answers to formerly unsolvable questions in the field of medical and material imaging, e.g., imaging human lung tissue at the micrometer level or calculating local fiber orientation in carbon fiber composite automotive parts. Meanwhile, tomographic reconstruction and signal processing for these new contrast modes have become vivid fields of research in mathematics and computer science. Optimizing a grating-interferometer for a given task is not an easy task and requires detailed knowledge, both of the imaging physics and of the signal response from the specimen. Furthermore, the production processes for high-aspect optical gratings are presently at their technological limits, which will have to be overcome using entirely new approaches, if we want use DPC and DIC to inspect larger parts, e.g., from aircrafts and cars.