| abstract |
A detection system for detecting sheets of material includes a device for moving along a path a container which can harbor a sheet of material sought to be detected; an X-ray scanner having a beam for scanning across the path of the container through a predetermined angle and a device for moving the scanner to shift the origin of the scanning beam to align during at least a portion of the scan the scanning beam with the sheet for producing a high projected density contrasted with its surroundings. |