CT for industrial metrology - Accuracy and Structural Resolution of CT Dimensional Measurements

Verification of dimensional measurement accuracy and other metrological characteristics of X-ray Computed Tomography (CT) systems is necessary both for establishing traceability of CT dimensional measurements and for achieving comparability of CT to other dimensional measuring techniques used in industrial metrology. This paper summarizes the state of the art in accuracy evaluation of CT dimensional measurements, discussing methods for metrological performances verification and traceability establishment. The work is based on experimental results obtained both from (i) the first international interlaboratory comparison on CT dimensional metrology and from (ii) additional CT measurements performed at University of Padova specifically for a more in depth examination of specific metrological characteristics. Particular attention is given to the evaluation of a specific metrological characteristic that too often is neglected when testing CT systems: the structural resolution for dimensional measurements. After discussing possible methods for determining the structural resolution, a new method is proposed, based on a novel calibrated reference standard that has been developed expressly for facilitating the evaluation of structural resolution. Preliminary results of an experimental investigation are discussed and conclusions are reported.