Optical trickery lets a modified LCD produce hologram-like still images and videos at 127 dots per inch and appears to be a path to practical nearterm commercial 3D displays

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.

Nature – A multi-directional backlight for a wide-angle, glasses-free three-dimensional display

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.

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.

A roll-to-roll imprint process that can be used for the mass-production of static 3D backlight patterns.

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.”

ABSTRACT

Multiview three-dimensional (3D) displays can project the correct perspectives of a 3D image in many spatial directions simultaneously. They provide a 3D stereoscopic experience to many viewers at the same time with full motion parallax and do not require special glasses or eye tracking. None of the leading multiview 3D solutions is particularly well suited to mobile devices (watches, mobile phones or tablets), which require the combination of a thin, portable form factor, a high spatial resolution and a wide full-parallax view zone (for short viewing distance from potentially steep angles). Here we introduce a multi-directional diffractive backlight technology that permits the rendering of high-resolution, full-parallax 3D images in a very wide view zone (up to 180 degrees in principle) at an observation distance of up to a metre. The key to our design is a guided-wave illumination technique based on light-emitting diodes that produces wide-angle multiview images in colour from a thin planar transparent lightguide. Pixels associated with different views or colours are spatially multiplexed and can be independently addressed and modulated at video rate using an external shutter plane. To illustrate the capabilities of this technology, we use simple ink masks or a high-resolution commercial liquid-crystal display unit to demonstrate passive and active (30 frames per second) modulation of a 64-view backlight, producing 3D images with a spatial resolution of 88 pixels per inch and full-motion parallax in an unprecedented view zone of 90 degrees. We also present several transparent hand-held prototypes showing animated sequences of up to six different 200-view images at a resolution of 127 pixels per inch.

SOURCES- Technology Review, Nature

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