chapter  29
24 Pages

Applications to Nonionizing Radiation Protection

ByJi Chen, Wolfgang Kainz, Dagang Wu

Walk-through metal detectors (WTMDs) are integral parts of the security surveillance systems found in airports and government buildings. Most of these metal detectors use electromagnetic signal variations to detect metallic objects. A pair or pairs of transmitter/ receiver coils is embedded in the frames of the WTMDs. A metal object between the transmitter/receiver pairs varies the electromagnetic signals, and if the signal variation exceeds a certain threshold, a metal object is detected. In principle, a stronger electromagnetic emission will lead to a higher signal-to-noise ratio and consequently produce more accurate results in metal detection. However, the electromagnetic emission used to detect metal objects also causes undesired electromagnetic energy depositions within humans.