  In recent years, a novel x-ray imaging modality has emerged that reveals
unresolved sample microstructure via a "dark-field image", which provides
complementary information to conventional "bright-field" images, such as
attenuation and phase-contrast modalities. This x-ray dark-field signal is
produced by unresolved microstructures scattering the x-ray beam resulting in
localised image blur. Dark-field retrieval techniques extract this blur to
reconstruct a dark-field image. Unfortunately, the presence of non-dark-field
blur such as source-size blur or the detector point-spread-function can affect
the dark-field retrieval as they also blur the experimental image. In addition,
dark-field images can be degraded by the artefacts induced by large intensity
gradients from attenuation and propagation-based phase contrast, particularly
around sample edges. By measuring any non-dark-field blurring across the image
plane and removing it from experimental images, as well as removing attenuation
and propagation-based phase contrast, we show that a directional dark-field
image can be retrieved with fewer artefacts and more consistent quantitative
measures. We present the details of these corrections and provide "before and
after" directional dark-field images of samples imaged at a synchrotron source.
This paper utilises single-grid directional dark-field imaging, but these
corrections have the potential to be broadly applied to other x-ray imaging
techniques.
