A new kind of three-dimensional display developed at HP Labs plays
hologram-like videos without the need for any moving parts or glasses.
Videos displayed on the HP system hover above the screen, and viewers
can walk around them and experience an image or video from as many 200
different viewpoints—like walking around a real object.
The screen
is made by modifying a conventional liquid-crystal display (LCD), the
same kind of display found in most phones, laptops, tablets, and
televisions. Researchers hope these 3-D systems will enable new kinds of
user interfaces for portable electronics, gaming, and data
visualization. The work, carried out at HP Labs in Palo Alto,
California, relies on complex physics to make 3-D displays that are as
thin as half a millimeter.
Conventional 3-D—the type found in
movie theaters—provides the viewer with only one perspective. The key to
making a multiview 3-D display is reproducing all the light rays
reflecting off an object from every angle and to get a different image
to the left and right eye of the viewer. Some systems for producing
multiview 3-D images require rapidly spinning mirrors; others use
systems of lasers and multiple graphics processors. The HP display uses nanopatterned grooves, which HP researcher David Fattal,
who led the work, calls “directional pixels,” to send light off in
different directions. This requires no new moving parts, and the
patterns are built into an existing display component, the backlight.
A
conventional LCD uses a sheet of plastic or glass that’s covered in
bumps that scatter white light and direct it through the display’s color
filters, polarizers, and shutters to the viewer. The new 3-D display
builds on optics research demonstrating how the path, color, and other
properties of light can be manipulated by passing it through materials
patterned at the nanoscale.
The
HP display replaces the randomly scattering bumps in a normal LCD with
deliberately patterned grooves. Each “directional pixel” has three sets
of grooves that direct red, green, and blue light in one particular
direction. The number of directional pixels determines the number of
viewpoints the display can produce. Light from the pixels then passes
through a conventional array of liquid crystal shutters that pass or
block the light to make a moving image—just like in a conventional LCD. The
HP researchers showed that they could make static images with 200
viewpoints, or videos with 64 viewpoints and 30 frames per second—so
far. The number of viewpoints in the video system has been limited by
their ability to put the backlight together with the nanopatterned
liquid-crystal shutters in the lab. Fattal says the system should
ultimately be easy to manufacture, because it’s a modified LCD. The work
is described today in the journal Nature. Science
fiction has provided no shortage of visions of futuristic computer
interfaces that allow people to manipulate data, images, and maps by
waving their hands through streams of holograms. The technology for
tracking gestures is pretty well developed, says Fattal—systems like
Microsoft’s Kinect are available off the shelf. All that’s lacking, he
says, are practical systems for producing high-quality 3-D images that
can be viewed from multiple positions around a screen. There has been very little innovation in the basic physics for making 3-D images since early in the 20th century, says Gordon Wetzstein, a researcher at the MIT Media Lab’s Camera Culture
group. Wetzstein was not involved with the work. Most 3-D televisions
and other systems on the market use old optical tricks—special glasses
to filter part of the image for the left or right eye, for example—to
create the illusion of depth. He says the new display “is transforming a
technology that’s been around for 100 years.” Fattal acknowledges
that producing content for the new display requires 200 different
images. Some of this image data can be reconstructed digitally—it’s not
necessary to have 200 cameras—but for the foreseeable future, the most
promising applications for the displays will be in showing
computer-generated images. “A 3-D interface for a cell phone or laptop
might display different windows next to each other, or architects could
use a tablet to show a 3-D model to a customer, instead of building a
physical model,” Fattal says. “Or you might use a smart watch to view
Google Maps in 3-D.” David Krum, codirector of the University of Southern California’s Mixed Reality Lab,
says many computer scientists are now working on content development
for 3-D systems. Part of the challenge, he says, is understanding human
perception and which light rays can be left out while still creating the
perception of a 3-D image for the viewer. Without addressing this,
mobile 3-D will create big bandwidth and data-storage burdens, he says.http://www.technologyreview.com/news/512716/new-3-d-display-could-let-phones-and-tablets-produce-holograms
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