Japan's cloak of almost invisibility

By Richard Taylor Editor, BBC Click Online

Ever so occasionally we decide to look beyond the technology of today and tomorrow, and look at stuff that most of us would think is pure fantasy. Richard Taylor has been to Japan to see if it really could be possible to vanish into thin air.

The cloak is made up of tiny beads of a retro-reflective material

The aura of invisibility has long fired the popular imagination.

It may be straightforward for the likes of Harry Potter, who has a magic cloak, but we muggles have had to contend with merely fictionalizing such a fantastical state.

At Tokyo University, researchers have moved the ideas of science fiction one step closer to reality by developing an optical camouflage system.

The idea is simple. A camera behind the wearer is linked through a computer to a projector which displays the image of the background onto a coat.

Impressive

It is no ordinary coat though.

This "invisibility cloak" is made up of thousands of tiny beads of a retro-reflective material, which shines the light straight back in the direction it came from.

The effect is pretty impressive.

The purpose of our study is not to create the invisible man Susumu Tachi

But, as yet, this invisibility cloak is an optical illusion that would not really fool anyone.

And, even for this rather crude incarnation, the conditions have to be just right.

Not only is there lots of equipment involved, but any movement in perspective behind the camera soon gives the game away, as does a change in angle by the viewer.

The cloak's inventor, Susumu Tachi, says all that is by the by.

"The purpose of our study is not to create the invisible man. That's just a by-product. Our real purpose is to establish augmented reality technology."

Augmented reality is basically a way of transforming real objects into virtual ones.

This could prove a useful tool for surgeons hoping to pinpoint where to operate, so as to minimise invasive surgery.

For example, instead of projecting an image of the background onto the person, an x-ray of the inside of the person could be projected onto the retro-reflective material.

Using the same projection principle you can make inanimate objects appear invisible as well.

For example, pilots could project an image of the landscape beneath them onto the cockpit floor, helping them to accurately judge landing distances.

Battlefield

Invisibility would bring incalculable advantages on the battlefield.

Imagine replacing a soldier's camouflage with one which actually adapts to the environment, or perhaps concealing a top-secret military facility.

Amazingly, several patents along these lines have already been filed.

To make the object appear invisible it would be blanketed with lots of flat screen display panels, each containing optical sensors which act as miniature cameras.

The sensors would take an image of their surroundings and transfer it to a display on the opposite side of the object, thereby creating the illusion.

These are hugely ambitious ideas and, even though the US military is said to be actively considering some of them, it will be years before they make it off the drawing board and into the real world.

The technology just is not advanced enough yet.

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