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Look ma, no specs. A 3D HP logo created with the new technology.

Kar Han Tan

3D TV, Without the Glasses

If you've pondered whether to sink a cool couple of grand into a fancy new three-dimensional TV but didn't want to mess around with those dorky glasses, you may want to sit tight for a few more years. Researchers at Hewlett Packard (HP) Laboratories in Palo Alto, California, report that they've come up with a new 3D technology that not only doesn't require viewers to wear special glasses, but it also can be viewed from a wide variety of angles. The advance could propel the development of mobile 3D devices as well as TVs.

Our eyes and brains visualize our world in its full 3D glory with seeming ease, thanks to what's known as parallax. Our eyes are several centimeters apart and thus perceive slightly different—yet overlapping—images when looking at an object. Our brains stitch the two views together into a single coherent image. But because TVs present images on 2D screens, this task is much harder to pull off. To allow us to see in three dimensions, imaging technologies must present slightly different images to each of our eyes.

Numerous technologies have been invented over the years to carry this out. Perhaps the most familiar is the one that requires moviegoers to wear red and green glasses. In this case, the visual information for full 3D images is sent out in all directions, and the glasses filter out unwanted portions for each eye. To display 3D images without special glasses, engineers must control how light is directed from each pixel of the display so that different light patterns reach the viewer's eyes. (The strategy for more modern 3D glasses is largely the same.)

Today, the gold standard in providing that control is holography, which can project specified colors in any direction. But holography is expensive and practical only for displaying still images rather than full-motion video. In recent years, researchers have come up with several alternatives. One family of techniques, known as autostereoscopic multiview 3D displays, projects multiple different images on a single screen. But such approaches have tended to reduce resolution or permit the ideal 3D images to be seen in only a few spots where viewers are the right distance from the screen and oriented at the correct angle, muting interest among consumers.

To get around these limitations, the HP Labs team, led by physicist David Fattal, used standard computer chip manufacturing techniques to create an array of optical elements called diffraction gratings that precisely control the direction in which light emerges from each pixel in the display. The researchers then used other standard optical devices called waveguides to steer light toward the diffraction grating in each pixel, as well as liquid crystals to modulate which colors of light are sent out from each spot. The result was a high-resolution video display that allowed viewers to see full 3D images from 14 different viewing zones, the researchers report online today in Nature. The HP team believes that it should be able to increase the number of viewing zones to 64, enough to convince our eyes that they are seeing a seamless 3D image even if we walk around the room. In addition, because the technology uses conventional chip-patterning techniques, the new diffraction gratings should be cheap to make and already offer a resolution that is potentially higher than current displays.

Still, the novel displays aren't a shoo-in for commercial success, notes Neil Dodgson, a computer scientist at the University of Cambridge in the United Kingdom. In a commentary in Nature, Dodgson writes that the novel displays must still leap a series of manufacturing hurdles, and that engineers must come up with cameras that can capture 14 to 64 different images that would then be projected through the 3D TV. "If the authors can solve the practical problems, then they have a compelling alternative to existing 3D display technology," Dodgson says. That might also give them a raft of customers ready to put down those 3D glasses.