Influence of workpiece orientation for multimaterial measurements in dimensional computed tomography

Abstract

Computed tomography (CT) is a flexible measurement method for a variety of metrological tasks. However, to achieve reliable and accurate measurements, interrelated setting parameters must be chosen. The workpiece orientation is one of such parameters, especially for multimaterials. Current approaches to support optimal orientation do not adequately consider the effect on accuracy in complex measurement tasks. Additionally, only few experimental studies provide the therefore necessary insights. Consequently, this study aimed to investigate the influence of orientation of a multimaterial workpiece on the subsequent evaluation and measurement process. For this purpose, a workpiece containing multiple features was scanned in a total of 14 orientation configurations and the resulting effects on both image (based on contrast-to-noise-ratio) and measurement quality (based on measurement accuracy) were investigated. It was shown that components measurable in the medium power range of a CT system have a wide range of optimal angles for optimal orientation. The image quality is suited for its identification.

Performance parameters for evaluating pore detection ability of computed tomography systems

“…For quantifying global image quality, the histogram-based contrast-to-noise ratio (CNR) was used. It was assessed via the grey-value distributions of the histograms of the reconstruction and calculated using the method presented in [13].…”

“…voxels in the background. [13] The calculation was carried out to the following equation: Besides CNR, image sharpness S was determined as a generalization of the MTF assessment method [14] (cf. Section 4.3.2 and 4.3.3).…”