A scanning system inspired by bats could spell the end of airport metal detectors, according to the European Space Agency.

It is based on the principles of echolocation, the technique bats use to hunt in the dark. Named Tadar, after the Brazilian Tadarida bat, it uses millimetre waves to scan for concealed weapons, and can detect non metallic objects as easily as metallic ones.

The company behind the scanner, Farran Systems, explains that the technology was originally developed for ESA's space systems.

The scanner uses 3mm microwaves to scan people as they walk through a booth. Its sensors detect thermal energy emitted by the body as well as microwaves being reflected from objects.

Clothes become transparent, but denser objects, such as plastic explosives or other weapons, show up clearly against the background thermal image of the body. Everyday items like door keys and money will also be clearly visible as will liquids and non metallic items.

Different materials reflect the microwaves at different frequencies, and will show up in different representative colours. This will give the scan operators an idea of what kinds of materials they are dealing with.

The system can operate in both passive and active modes. When it is in passive mode, people would need to stand still to be scanned, but in active mode, it can produce a three dimensional map of a scene from a distance of up to 50m.

Tadar is being demonstrated at this week's Inter Airport Europe Exhibition in Munich. ®

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