Proposition and experimental evaluation of a point-based compensation approach to reduce systematic errors in CT measurements

Industrial applications of computed tomography (CT) for dimensional metrology have increased steadily over the last few years, despite the fact that the measurement uncertainty has rarely been evaluated and reported. Despite being an important prerequisite of any scientific or industrial measurement, the complex CT measurement chain and the numerous influencing quantities involved in the measurement process mean that the problem of evaluating the uncertainty and tracing the dimensional measurement results back to the unit of length remains an unsolved issue. In this paper, the use of master part reference measurements for later point-based compensation of CT datasets is proposed to correct known systematic effects and reduce the measurement uncertainty down to the level of the CT measurement process repeatability, for part features that can be accessed and calibrated using a reference coordinate measuring system (R-CMS). The point-based compensation approach is described, experimentally tested using a prismatic part and is discussed for several geometrical tolerance verification cases.