Object-based 3D X-ray imaging for second-line security screening

X-rays in 1, 2 or 3 orthogonal views are excellent for first-line security screening. If any doubt remains after such 1st.-line inspection, the relevant item of luggage or container is normally unpacked. Here we propose an X-ray technique creating a precise 3D model of any object under suspicion - and characterising its material - thus giving the benefit of unpacking without the inconvenience. Indeed, we can use the computer thus to examine in detail anything embedded inside an object. One approach to such 3D information might be computed tomography (CT), where a fan-beam source and a line array of sensors rotate in the plane of a desired image slice. However, CT entails very high X-ray exposures and imposes a heavy computational load. Whilst it produces excellent 2D images, the third dimension depends on interpolation between some tens of slices. Our method restricts radiation primarily to the object of interest. It uses the information in a novel way, for the precise 3D reconstruction of objects.