Experimental investigations on the structural resolution in metrological computed tomography

In the recent years, X-ray computed tomography (CT) has been successfully applied as an innovative coordinate measurement technology in industrial metrology. An important metrological characteristic to be assessed during CT performance verification is the metrological structural resolution (MSR) for dimensional measurements, which describes the size of the smallest structure that can still be measured within error limits to be specified, as defined in the guideline VDI/VDE 2630-1.3. The MSR statement provides important information, especially when measuring small geometries or microstructures. The ‘Hourglass’ method, developed at the University of Padova, allows testing the MSR by using a simple geometry consisting of two touching spheres with the same diameter. In this work, latest findings are presented, based on the implementation of two different strategies for applying the ‘Hourglass’ method. Advantages in using this method are also discussed in comparison with other existing proposals and a selection of factors influencing the method were evaluated through experimental analyses.