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Through its ability to measure otherwise inaccessible internal structures, x-ray computed tomography (CT) has become a useful tool in the field of dimensional metrology. However, the lack of international standards for performance verification and the determination of metrological characteristics has so far prevented it from becoming a standardized measurement technology. This paper considers how a test object comprising a dismantleable tetrahedral assembly of four calibrated alumina spheres can be employed to assess the metrological performance of an industrial-type CT system. The measurement accuracy was characterized in terms of sphere size, separation and form errors. In all cases, sub-voxel accuracy was achieved, with errors as small as 1/10 of a voxel being obtained. Good measurement repeatability was demonstrated even upon dismantling and reconstructing the reference object. The tetrahedral test object offers a simple robust solution for the verification of metrological performance with great versatility and adaptability. © 2014 IOP Publishing Ltd.
- coordinate measuring machine (CMM)
- coordinate metrology
- dimensional metrology
- x-ray tomography