Geometric errors of CT scanners and their estimation by imaging a reference object

Abstract

Computed Tomography (CT) has been included in the routine of the dimensional quality loop of manufactured products over the past two decades. Characterized by a complex measurement chain, many influence factors may affect the accuracy of CT measurements. Misalignments stemming from imperfections of the components of the CT metrology instrument exemplify an influence factor over which the user may have no control. In this regard, this paper describes the experimental study of the geometric errors of a CT instrument using an image-based method to map them. The experiments were designed with the purposes of understanding the time-related variation pattern of the geometric errors and assessing the actual measurement capability of the image-based method itself to discriminate the geometric errors. The experimental findings can contribute to an optimized use of the CT technology for dimensional measurements, for example, by assisting the proper actions to be taken by the user for error correction.