Stereoscopic dual-energy X-ray imaging for target materials identification

An experimental stereoscopic dual-energy X-ray imaging system is employed to extract the effective atomic number from a target layer of multiple layers of different materials. Further work investigated utilising stereoscopic parallax data to calculate layer thickness which, when combined with dual-energy data, enables the mass density of the target to be established. The research is part of an ongoing programme of work in collaboration with the UK Home Office to discriminate and identify substances in X-ray security screening applications. Initial work utilised a basis materials decomposition (BMD) technique to compute the characteristic angle, an indicator of atomic composition. The problem of overlapping materials masking a target was solved by further refinement of the BMD method, which can also be used determine mass density when layer thickness is known. The empirical investigation concentrated on computing the characteristic angle for different target materials in various overlapping arrangements. Also, the results from employing manually extracted parallax data to calculate the thickness of a target material are presented together with the resultant estimation of the targets´ mass density.