| 摘要 |
A system for material identification in radiographic imaging for large sized objects combines binocular stereoscopic and multi-energy transmission imaging techniques. The method first creates template depth planes of objects along the depth direction in a detection space by means of the binocular stereoscopic technique. Depth plane grey images of the objects are then reconstructed (grey reconstruction) from the transmission image. Finally the multi-energy technique is applied to identify the materials of the objects for which the reconstruction of corresponding grey images in depth plane succeeded. The method comprises the following steps: causing two angled x-ray beams to penetrate through objects under examination so as to obtain data of left and right transmission images, segmenting said left and right transmission images and matching the results of said segmentation; creating a template depth plane along the depth direction of the transmission images; reconstructing a depth plane grey image from the transmission images; repeating the above process on transmission images of variation energy to obtain a template depth plane of each depth plane for the variation energy; merging the template planes for different energy levels at the same depth to obtain a template depth plane for each depth plane and energy of a predetermined group of energy levels; identifying the material of the objects for each of which the grey reconstruction in depth plane succeeds. With the method, any obstacle that dominates the ray absorption can be peeled off from the objects that overlap in the direction of a ray beam. The object that is unobvious due to a relatively small amount of ray absorption will thus stand out, and the material property of the object, such as organic, mixture, metal and the like can be identified. This method lays a fundament for automatic identification of harmful objects, such as explosive, drugs, etc., concealed in a freight container. |
