Instead of extra face furniture (never fun for those of us already wearing glasses) or complex hardware to create holograms, the Media Lab system uses layers of liquid-crystal displays (LCDs). The result is a convincing 3D illusion that requires a refresh rate of about 360 times per second (360 hertz).
Sounds like hard work, but this type of display might not be so far off. LCD TVs with 240 hertz refresh rates are already on the market.
“Holography works, it’s beautiful, nothing can touch its quality,” says Douglas Lanman, a postdoc at the Media Lab. “The problem, of course, is that holograms don’t move. To make them move, you need to create a hologram in real-time, and to do that, you need … little tiny pixels, smaller than anything we can build at large volume at low-cost. So the question is, what do we have now? We have LCDs. They’re incredibly mature, and they’re cheap.”
Though you may not think this technology is available, you might have already held something similar in your hands. The Nintendo 3DS uses two layered LCD screens to produce the illusion of depth, with the bottom screen simply displaying alternating dark and light bands.
According to MIT, this technology is already more than a century old and it produces a stereoscopic image.
Lanman, graduate student Matthew Hirsch and professor Ramesh Raskar, who leads the Camera Culture group, reasoned that by tailoring the patterns displayed on the top and bottom screens to each other, they could filter the light emitted by the display in more sophisticated ways, creating an image that would change with varying perspectives.
In a project they dubbed HR3D, they developed algorithms for generating the top and bottom patterns as well as a prototype display, which they presented at Siggraph Asia in 2010.
The problem is that, whereas a stereoscopic system such as a 3D movie projector or the 3DS needs to display only two perspectives on a visual scene, one for each eye, the system the Media Lab researchers envisioned had to display hundreds of perspectives in order to accommodate a moving viewer.
That was too much information to display at once, so for every frame of 3D video, the HR3D screen in fact flickered 10 times, displaying slightly different patterns each time. With this approach, however, producing a convincing 3D illusion would require displays with a 1,000-hertz refresh rate.
To get the refresh rate down to 360 hertz, the researchers added another LCD screen, which displays yet another pattern. That makes the problem of calculating the patterns exponentially more complex, however. In solving that problem, Raskar, Lanman and Hirsch were joined by Gordon Wetzstein, a new postdoc in the Camera Culture group.
Three panels coming to Siggraph
At the Siggraph conference, the Media Lab researchers will demonstrate a prototype display that uses three LCD panels. They’ve also developed another prototype that uses only two panels, but between the panels they introduce a sheet of lenses that refract light left and right.
The lenses were actually developed for stereoscopic display systems. An LCD panel beneath the lenses alternately displays one image intended for the left eye, which is diffracted to the left, and another for the right eye, which is diffracted to the right.
This might sound technical, but the upshot is something that we could be enjoying each day in our living rooms. 3D displays of moving images or even 3D TV are still seen as quirky or are only used in specific situations.
Being able to turn something like this on when you feel like it because the technology is lighter and more accessible? That’s the future we like to think about. Holograms at home sound cool.