Simulation-based investigation of the metrological interface structural resolution capability of X-ray computed tomography scanners

The miniaturisation of components leads to new demands onmeasurement systems. One of these is the resolution. As a volumetric analysismethod and method of non-destructive testing, industrial X-ray computedtomography (XCT) has the ability to measure geometrical features and theircorresponding dimensions without destroying them and can therefore be used forquality assurance. However, the concept of resolution is not trivial for XCTand has not yet been finally clarified. In particular, the interface structuralresolution, the detectability of two surfaces facing each other aftersurface segmentation, faces a lack of a test specimen, a correspondingmeasurand and a reliable method. Simulation-based XCT investigations of amethod to determine this type of resolution are presented in this articleusing the geometry of a test specimen that contains several radiallyarranged holes of the same size. The borehole diameters correspond to thedistance between the holes to investigate the resolvability of surfaces andinterfaces. The evaluation is based on mean and extreme values of grey valueprofiles between the individual boreholes of the reconstructed volume. It isshown that the geometrical detectability of the test specimen surface andinterface can be extended by a reasonable choice of the threshold value forsurface segmentation within a defined interval. With regard to the resolvingcapability, a distinction is made between assured detectability and possibledetectability, as well as the threshold value used when using the ISO50threshold for surface segmentation and measurement chain completion.