Grating-based X-ray InterferometryGrating-based X-ray interferometry has ventured into many areas of X-ray Imaging, since its first demonstration by LMN researchers over a decade ago .
Our current research in grating interferometry includes the areas of
- Differential phase contrast and dark-field imaging
- Metrology applications at synchrotron and XFELs
- Grating fabrication
A typical grating interferometer consists of a phase shifting grating G1 (Figure 1) made made of silicon which diffracts the incident radiation mainly into a first and minus first diffraction order that propagate at angles +θ and -θ with respect to their original direction of propagation. These two orders interfere at a distance d downstream, forming a periodic interference pattern that can be analyzed by an absorbing grating G2 made of gold and a camera. Any refracting object in the beam, such as the wedge shown in Figure 1, a biomedical or material science sample in imaging or an X-ray optical element in metrology, leads to a locally modified propagation direction of the X-ray beam. This beam angle α leads to a local lateral shift of the interference pattern that can be detected by the combination of analyzer grating and camera. From this shift, the refraction angle α can be quantitatively determined.
Figure 1: Grating interferometer working principle
- C. David, B. Nöhammer, H. H. Solak, E. Ziegler Differential phase-contrast imaging using a grating interferometer, Applied Physics Letters 81 (2002), 3287. DOI: 10.1063/1.1516611