Real time passive imaging at 250GHz for security: Technology and phenomenology

This paper describes a new imaging platform that has been commercially developed for security applications. The primary goal of this approach is to reveal objects that may be concealed under a persons clothing using natural light, i.e., the imagery is essentially passive and so no external illumination of the subject is involved. A second goal is to be able to carry out such security screening in a discrete manner on moving people often at a distance of 10 metres or more. In order to achieve these goals the imaging wavelength selected was 1.2 mm or a frequency of approximately 250 GHz. At this band width good penetration of clothing is still possible whilst still the use of relatively small optical systems. During a talk an overview of the systems will be given in conjunction with the achieved performance. Imaging at this wavelength provides a new way of looking looking at the natural world and has uncovered some interesting phenomenology that will also be described. Examples of typical real time imagery in a variety of situations will be given.