Passive and active imaging of humans for contraband detection at 640 GHz

Submillimeter wave images of a human subject have been obtained at 640 GHz using a scanned single pixel Schottky diode mixer operating at room temperature. A metal object hidden under cotton fabric could be detected passively due to the contrast between the body temperature and the reflections of the environment. Additionally, it was demonstrated that the high receiver sensitivity allows a commercially available ceramic heat lamp to be used as a modulated illumination source, so that reflective materials such as metal can be actively detected. This means that it should be possible to construct an imaging instrument that combines a passive detection mode with an active mode using a thermal emitter in a single instrument. If a large number of channels (pixels) could be included in such an instrument, it could even operate at or near video speed frame rates (30 Hz), which would make it extremely useful for contraband detection.