Multiview x-ray based system for detecting contraband such as in baggage

Abstract

A multiview X-ray based inspection system detects contraband such as explosives, weapons, drugs and money in packages such as baggage. Each bag moves through at least three stationary, fan-shaped beams of x-rays that are in parallel planes spaced from each other in the direction of bag travel, to produce three projection views of the bag taken from different angles. These projection views are processed to extract two-dimensional outlines of likely individual objects in the bag, and the two-dimensional outlines are matched between different projection views to extract three-dimensional outlines of likely objects in the bag. The system uses these three-dimensional outlines to estimate effective atomic numbers and mass densities of material in these objects, and then to determine the presence of likely contraband in the baggage by testing these estimates against windows in a multi-dimensional space in which one dimension is effective atomic number and another is mass density. The typical windows correspond to known contraband materials. The system can derive measurements from additional modalities such as nuclear quadrupole resonance (NQR) for use in conjunction with the x-ray measurements in finding likely contraband.