Rogers, TW;
Ollier, J;
Morton, EJ;
Griffin, LD;
(2017)
Measuring and correcting wobble in large-scale transmission radiography.
Journal of X-ray Science and Technology
, 25
(1)
pp. 57-77.
10.3233/XST-160607.
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Abstract
BACKGROUND: Large-scale transmission radiography scanners are used to image vehicles and cargo containers. Acquired images are inspected for threats by a human operator or a computer algorithm. To make accurate detections, it is important that image values are precise. However, due to the scale (∼5 m tall) of such systems, they can be mechanically unstable, causing the imaging array to wobble during a scan. This leads to an effective loss of precision in the captured image. OBJECTIVE: We consider the measurement of wobble and amelioration of the consequent loss of image precision. METHODS: Following our previous work, we use Beam Position Detectors (BPDs) to measure the cross-sectional profile of the X-ray beam, allowing for estimation, and thus correction, of wobble. We propose: (i) a model of image formation with a wobbling detector array; (ii) a method of wobble correction derived from this model; (iii) methods for calibrating sensor sensitivities and relative offsets; (iv) a Random Regression Forest based method for instantaneous estimation of detector wobble; and (v) using these estimates to apply corrections to captured images of difficult scenes. RESULTS: We show that these methods are able to correct for 87% of image error due wobble, and when applied to difficult images, a significant visible improvement in the intensity-windowed image quality is observed. CONCLUSIONS: The method improves the precision of wobble affected images, which should help improve detection of threats and the identification of different materials in the image.
| Type: | Article |
|---|---|
| Title: | Measuring and correcting wobble in large-scale transmission radiography |
| Open access status: | An open access version is available from UCL Discovery |
| DOI: | 10.3233/XST-160607 |
| Publisher version: | http://doi.org/10.3233/XST-160607 |
| Language: | English |
| Additional information: | This version is the author accepted manuscript. For information on re-use, please refer to the publisher’s terms and conditions. |
| Keywords: | Science & Technology, Technology, Physical Sciences, Instruments & Instrumentation, Optics, Physics, Applied, Physics, Image correction, wobble artefact, X-ray imaging, transmission radiography, security screening, RAY, TECHNOLOGY, CONTAINERS, INSPECTION, SEARCH, SYSTEM, GANTRY |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > Dept of Computer Science |
| URI: | https://discovery.ucl.ac.uk/id/eprint/1550381 |
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