Robin McKie, science editor
Sunday June 13, 2004
The Observer
They are the ultimate form of camouflage. Put one on, and you disappear from view. One saved Harry Potter from many tight scrapes, and in the film Die Another Day the technology provided James Bond with the ultimate escape vehicle, an invisible car.
But now Japanese scientists have turned fantasy into reality by creating an invisibility cloak that makes it possible to see straight through its wearer. He, or she, simply vanishes from view.
The garment - demonstrated last week at Nextfest, an exhibition of emerging technologies in San Francisco - is the work of Japanese inventor Susumu Tachi, a professor of computer science and physics at the University of Tokyo. 'It's a kind of augmented reality,' he said of his device.
In reality, the 'optical camouflage' cloak is anything but invisible. It is made up of 'retro-reflective material' coated with tiny light-reflective beads that cover its entire length. The cloak is also fitted with cameras that project what is at the back of the wearer on to the front, and vice versa. The effect, as the Japanese team demonstrated last week, is to make the wearer blend with his background.
The material was used to coat a ball, a brick and a cloak. In each case, it appeared as if the viewer could see through each item as it was moved about by a human operator to the back of the room.
The effect was not total, but it was sufficient to demonstrate that optical camouflage is technically possible, though one expert - writing in Wired magazine recently - pointed out that, for an invisibility cloak to work, it would have to have six stereoscopic cameras built into it, be covered with 11.6 million 'hyperpixels', each consisting of a very bright electronic display, and be controlled by a super-fast computer that would run on a power source that could be built into the cloak.
In short, a little more work will be needed before invisibility technology becomes reality, and certainly has some way to go before it reaches the effectiveness of Harry Potter's invisibility cloak. This originally belonged to his wizard father, James, and is used in Harry Potter and the Prisoner of Azkaban to let Harry move around the wizard village of Hogsmeade unnoticed.
The device is attracting serious attention from military experts keen to exploit a technology that could help troops move into action without being spotted. Nor does the potential end there, says Tachi's colleague, Naoki Kawakami. 'It could be used to help pilots see through the floor of the cockpit at a runway below, or for drivers trying to see through a fender to park a car.'
And, of course, there is also the prospect for mischievous, or even dangerous, misuse, from sneaking Celtic fans into the Glasgow Rangers end at Ibrox to wandering into changing rooms unseen. As one expert said: 'This technology has an awful lot of potential.'
Now you see it, now you don't: cloaking device is not just sci-fi
Ian Sample, science correspondent
Wednesday May 3, 2006
The Guardian
It's been the curse of the USS Enterprise and the Klingons' favoured weapon. But back on Earth, mathematicians claim to have worked out how to make a cloaking device to render objects invisible.
An outline for the device is described in a scientific paper published today in which the authors reveal how objects placed close to a material called a superlens appear to vanish.
Even in the world of science fiction, the technology is not perfect, and nor is the device proposed by Graeme Milton at Utah University and Nicolae-Alexandru Nicorovici at Sydney University of Technology. According to their calculations, the device would only work at certain frequencies of light, and only if the object is within close range of the superlens.
The cloaking device relies on recently discovered materials used to make superlenses that make light behave in a highly unusual way. Instead of having a positive refractive index - the property which makes light bend as it passes through a prism or water - the materials have a negative refractive index, which effectively makes light travel backwards. It's light, but not as we know it.
Prof Milton's team calculated that when certain objects are placed next to superlenses, the light bouncing off them is essentially erased by light reflecting off the superlens, making the object invisible.
The calculations show that while the device could be used to obscure almost any shape of object, it only works over a short range of wavelengths, so if used to hide objects from human vision, they might only partially disappear.
Sir John Pendry, a theoretical physicist at Imperial College London who invented superlenses, said: "Effectively, they are making a piece of space seem to disappear, at least as far as light is concerned."
The research appears in the journal Proceedings of the Royal Society today. Prof Pendry said the technology has great potential for hiding objects from radar or cloaking electronic instruments so they can be used in strong electromagnetic fields, such as those produced by hospital MRI brain scanners. "The secret is having the cloak itself be invisible and if you can do that cheaply and efficiently and it doesn't need to be metres thick, it would be extremely valuable for stealth. Even if you could cloak a single frequency, it would be very useful. The military is extremely interested in this."
So far the researchers have only worked through the mathematics to prove that the device is plausible. The practicalities of making one have yet to be solved.
Cool
I shudder to think where that would lead.
