A test object with parallel grooves for calibration and accuracy assessment of industrial computed tomography (CT) metrology

While computed tomography (CT) has long been used for medical applications and material inspection, its application field has recently been broadened to include industrial dimensional metrology. However, the accuracy of CT-based measurements remains yet largely uncertain. Not only are the measurements influenced by a number of factors and parameters like e.g. workpiece orientation, magnification, edge detection and so on, but also the calibration method matters greatly. This paper investigates the influence of these factors and parameters and the calibration method (rescaling and correction) on accuracy and repeatability of the measurements, using a test object with parallel grooves. The test object is also used to illustrate how more accurate CMM measurements can be used to calibrate CT measurements and to compare different calibration and compensation strategies.