X-ray flat-panel detector geometry correction to improve dimensional computed tomography measurements

To improve the accuracy of dimensional X-ray computed tomography (CT), error sources have to be characterised and accounted for. A variety of error sources was comprehensively described in literature. However, the influence of the geometrical distortion of the flat-panel detector was rarely considered. In this paper, the deviation from nominal geometry of a flatpanel X-ray detector was characterised using a calibrated ball plate. In-plane deviations were separated from the detector topography by varying the source-detector distance, resulting in a three-dimensional detector geometry. A correction model for arbitrary source-detector distances was developed, which reduced the maximum errors of sphere centre-to-centre distances from scale corrected CT measurements from ±3.9 μm to below ±0.8 μm. This fivefold improvement emphasises the importance of such correction for dimensional CT.