Mm... Seen You Naked

As super powers go, X-ray vision ain't bad. Until you realise that all you get to see is a bunch of bones. But once mm-wave specs start selling, we'll all be blushing. So says Leila Sattary.

There's no doubt you’ve heard of microwaves and radio waves, and probably infrared and UV light, but even most scientists haven’t come across mm-waves. Inhabiting a relatively unknown region of the light spectrum (round about here) between microwaves and far infrared, they are imaginatively named ‘millimetre-waves’ because their wavelengths are between 1 and 10mm. And although you may be completely unaware of it, mm-waves are sneaking into everyday devices - and under you clothes.

What makes mm-waves so great?

Mm-waves biggest advantage is that they can “see through” a lot of things that other types of light can’t. Fog, smoke, dust and rain are all invisible to these mysterious waves.

Normally, small particles in the atmosphere cause scattering of light - this is the same effect that makes the sky blue. Unlike infrared and visible light, however, mm-waves aren't affected by these particles, making them extremely useful for outdoor imaging. Not only can mm-waves pass through fog, they can see through everything from clothes to plasterboard.

X-ray specs might be consigned to the realms of science fiction (and would in any case only show up your bones and ionise you to death), but mm-waves really can pass through clothes. They bounce off skin and can take a “naked” photo without any dangerous side effects.

Seeing through clothes
Metal detectors have traditionally been used to identify objects about a person and rely on detection of a mass of metal. What they can't do, unfortunately, is tell the difference between a gun and a belt and, as most of us are well aware, this can really slow down the flow of people through a security gate.

Check out the knife he's holding behind his newspaper. All down to the mms.

The increased threat of terrorism and the fact that modern weapons include plastic or ceramic guns, and plastic and liquid explosives, all of which cannot be detected with conventional metal detectors, means that more effective security scanners are needed.

This, of course, is where millimetre-waves come in. They pass through clothing but are partially reflected by the human body, as well as metals and plastics, all at different intensities. In other words, they can see through clothes, but metals and plastics show up against a dim body reflection.

Mm-wave scanners are already being tested in UK airports and are inevitably causing the public some concern. Luckily, however, millimetre-waves produce pixelated images and so do not reveal the naked body in too much detail. So there's no need to wax. Scientists are also developing scanners so that a computer can automatically identify guns, which means, hopefully, that nobody will get to sit behind the screen and perv at you.

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