Three-dimensional X-ray Imaging for Security Screening

Abstract

The X-ray screening of luggage by aviation security personnel may be badly hindered by the lack of visual cues to depth in an image that has been produced by transmitted radiation. The standard procedures in use today employ two-dimensional ‘shadowgraphs’, with ‘organic’ and ‘metallic’ objects encoded using two different colours (usually orange and blue). In the context of luggage-screening there are no reliable cues to depth present in individual shadowgraph X-ray images. Therefore, the screener is required to convert the ‘zero depth resolution’ shadowgraph into a three-dimensional mental picture to be able to interpret the relative spatial relationship of the objects under inspection. Consequently, additional cognitive processing is required, eg integration, inference and memory. However, these processes can lead to serious misinterpretations of the actual physical structure being examined. This paper describes the development of a stereoscopic imaging technique which enables the screener to utilise binocular stereopsis to enhance interpretation of the actual nature of the objects under examination.