Published online 10 June 2005 | Nature | doi:10.1038/news050606-17

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Foggy screen points the way

Display made from curtain of mist lets users click in mid-air.

No such thing as look but don't touch for the FogScreen.No such thing as "look but don't touch" for the FogScreen.© FogScreen Inc.

Forget plasma screens, here's one made out of nothing but water. Inventors have fashioned an interactive computer display from a curtain of fog.

The FogScreen uses ceiling-mounted air jets to create a vertical, turbulence-free slice of air a few centimetres thick, into which a fine mist of water is pumped. An ordinary projector can be used to display images on the resulting wall of fog.

The idea works on a similar principle to that of public lightshow displays, in which a beam or sheet of laser light is shone through a diffuse cloud of fog. But in this case the fog is in a sheet, rather than the light.

“It would regenerate itself in a matter of seconds.”

Mika Herpiö
FogScreen Inc.

When the projector is hooked up to a normal computer, the FogScreen can function much like the large display from a desktop in a lecture theatre. But, with the help of a laser-scanning system, the FogScreen also allows users to click on the watery screen itself.

Poke a finger at the screen, and the laser beams scanning the surface of the fog are interrupted, allowing the system to detect where you have 'clicked'.

High-tech theatre

The gadget's most obvious applications are for splashy displays at high-tech events, says Mika Herpiö, chief executive of FogScreen, the Finnish company that created the device. Giant screens could be created that allow participants to walk straight through them, for example. Although their hair might be ruffled by a quick blast of wind and they might get a tiny bit damp, the screen itself would refill with fog in just a few seconds.

It looks high-tech, but the FogScreen relies on fairly simple technologies. Ceiling-mounted blowers create vertical sheets of non-turbulent air that flow side-by-side without mixing. High-frequency ultrasound vibrations vaporize water into tiny droplets that are pumped between air flows.

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Such airstreams are notoriously unstable, says Marcel Escudier, who studies fluid mechanics at the University of Liverpool, UK. But he adds that the presence of the mist, which is denser than the surrounding air, could help to stabilize the system.

The screen will, of course, be disturbed as people walk through it. But Herpiö says this will not affect picture quality, because fog is constantly pumped in to the airstream. "It reforms itself all the time," he says.

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FogScreen Inc.