title: A simulation-based study on the influence of beam hardening in X-ray computed tomography for dimensional metrology.
abstract: X-ray computed tomography (CT) is a radiographic scanning technique for visualising cross-sectional images of an object non-destructively. From these cross-sectional images it is possible to evaluate internal dimensional features of a workpiece which may otherwise be inaccessible to tactile and optical instruments. Beam hardening is a physical process that degrades the quality of CT images and has previously been suggested to influence dimensional measurements. Using a validated simulation tool, the influence of spectrum pre-filtration and beam hardening correction are evaluated for internal and external dimensional measurements. Beam hardening is shown to influence internal and external dimensions in opposition, and to have a greater influence on outer dimensions compared to inner dimensions. The results suggest the combination of spectrum pre-filtration and a local gradient-based surface determination method are able to greatly reduce the influence of beam hardening in X-ray CT for dimensional metrology.
authors.affiliation: Electro-Mechanical Engineering Group, The University of Southampton, Southampton, UK.
authors.forename: Joseph J
authors.initials: JJ
authors.lastname: Lifton
authors.affiliation: Singapore Institute of Manufacturing Technology, Precision Measurements Group, Singapore.
authors.forename: Andrew A
authors.initials: AA
authors.lastname: Malcolm
authors.affiliation: Electro-Mechanical Engineering Group, The University of Southampton, Southampton, UK.
authors.forename: John W
authors.initials: JW
authors.lastname: McBride
mesh_terms: D000465:Algorithms; D003198:Computer Simulation; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008954:Models, Biological; D011856:Radiographic Image Enhancement / Q000379:methods; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000379:methods*
keywords: Computed tomography; ISO50; X-ray spectrum estimation; beam hardening; dimensional metrology; surface determination