The development of an 'on-belt tomosynthesis' system for cost-effective (3D) baggage screening.

This study describes a cost-effective check-in baggage screening system, based on 'on-belt tomosynthesis' (ObT) and close-range photogrammetry, which is designed to address the limitations of the most common method of baggage screening, conventional projection radiography. The latter's limitations can lead to loss of information and an increase in baggage handling time, as baggage is manually searched or screened with more advanced systems. This project proposes a system that overcomes such limitations creating a cost-effective automated pseudo-3D imaging system, by combining x-ray and optical imaging to form digital tomograms. Tomosynthesis is the creation of pseudo-3D images from a number of 2D projections which are acquired at a range of orientations around a static object. In the ObT system, instead of moving the source and detectors around the object, as in conventional CT, the movement of bags around bends in the baggage transport system provides the required relative motion between source, object and a fan configuration of strip-detectors. For image reconstruction it is necessary to accurately establish the sequential position and orientation of each bag as it is imaged. For this, a low-cost photogrammetric solution is used, based on geometrically calibrated web-cameras positioned around the bends where the bags are imaged. This paper describes a study demonstrating the feasibility of implementing close-range photogrammetry to a potential ObT system, for accurate determination of the object location. After this, an optimum ObT system is designed and built, the process of which is presented in this paper.