Three-dimensional television displays have been around for a couple of years now, but what we're all really waiting for is a holographic display — a la Princess Leia in Star Wars.

At Imec, a research lab in Leuven, Belgium, one team of engineers and scientists came up with a holographic display that works by shining lasers onto microscopic mirrors. The mirrors are so small, that each one represents a pixel of light in a moving image. And each mirror moves up and down like a piston when a specific voltage is applied to it. The light bounces off the edges of the pixels around it. At that scale, the waves of light interfere with each other and create an interference pattern that produces a three-dimensional image. The whole contraption is called a micro-electromechanical system — or MEMS for short.

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There are good reasons to move to holographic images. Many people who watch conventional 3-D movies get headaches. That’s because when watching a 3-D film the brain is trying to focus on the screen a certain distance away, while the eyes insist that the image is at some other distance, either closer or further. Watching Avatar without needing an aspirin would be a big plus for many. 

But getting from a 3-D holographic display to a moving image won’t be easy. The MEMS structures have to bounce up and down many times per second to create the illusion of movement. On top of that, they have to be small –- to get the diffraction patterns they each have to be comparable in size to the wavelength of light, which is measured in nanometers. And such a display would be expensive. That said, Imec said it hopes to have a proof-of-concept model out by early in 2012.

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There have been other attempts at holographic imaging. The MIT Media Lab built a system for holographic imaging that could produce movies at about 15 frames per second using off-the-shelf parts. (And yes, they tried duplicating the Princess Leia scene). Two months earlier, at the University of Arizona, another group also got a crude movie working. Perhaps the most impressive and market-ready version is from Innovision Labs USA, which has a product called HoloAD. But that requires a lot more space than a television, and doesn’t have the frame rate necessary for true video; it's better suited to advertising and displays.

With all these groups working on the problem, it seems only a matter of time before there really is a true holographic illusion that displays in the air — and Leia’s message won’t be science fiction anymore.

Via IEEE Spectrum

Image: Imec