Figure 4

Directional dark-field images of the dark-field phantom at a sample-to-detector distance of 3.5 m retrieved from the uncorrected (A) and corrected (B–D) data. Regions of reference-only and sample-and-reference images used to retrieve these are shown in Fig. 3, with the region shown highlighted by the green box in (D). Edge artefacts are shown in (A) around the metal aperture and plastic tubes (green arrows) as well as a directional signal from the microspheres (red arrow) and noisy texture in the signal retrieved from the carbon fibres (blue arrow). The artefacts seen in (A) are significantly reduced in (B), (C), and (D). The edge artefacts from the plastic tube are removed completely in all corrected images and the microspheres appear more white indicating isometric scattering as expected. The noisy texture seen in the carbon fibres is reduced most in (B) and (D) where the sample-only image is removed. All of the directional dark-field images have brightness scaled between zero and the maximum dark-field strength \(\Theta _{RMS}\) of 13.8 \(\upmu\)rad.