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Non-contact object localisation for automated 'on-belt- tomosynthesis

22 February 2012

Selina Kolokytha

Security screening technology, the part of aviation security focused on the detection of explosives and illicit materials, is both challenging and a costly. This report presents a study aiming to advance the potential of ‘On-belt’ Tomosynthesis (ObT), a fully automated pseudo-3D imaging system developed by Reid et al. (2010), as a post check-in baggage screening system with the implementation of close-range photogrammetry for accurate non-contact determination of the object location.

For this, two sets of x-ray image acquisition are made of a baggage phantom using the novel ObT technique. The algorithm developed to reconstruct 2D slice-images of the phantom requires three inputs, the x-ray images, the phantom location measurements and the phantom orientation values corresponding to each acquisition. Images are reconstructed twice, first using object localisation measurements produced manually and second produced using close-range photogrammetry.

The reconstructed images produced from each method are compared to each other for consistency. In addition, the phantom location and orientation measurements produced by each method are also compared. The correlation of all values for both acquisition sets shows the differences between the two methods are insignificant. The photogrammetrically-resulting reconstructed images are compared to the manually-resulting ones, which are taken as the “gold standard”, by means of subtracting the sequential reconstructed images. If two images are identical the result would be a 100% black image.

This study finds that the difference of the two produces on average 99.9% black images for both sets. This study demonstrates the feasibility of implementing close-range photogrammetry to a potential ObT system, for accurate non-contact determination of object location. However, there are several considerations which would enable this system to become a good-quality cost-effective post check-in baggage screening system in airports.