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Intelligent Machines

New Display Technology Lets LCDs Produce Princess Leia-Style Holograms

Startup aims to give mobile devices the power to display full-color holographic images and video.

Relatively recent advances in the ability to control light at the nanoscale open new possibilities for display technology.

During a famous scene in Star Wars, Princess Leia has R2D2 play a holographic video message in midair in which she pleads for help from Obi-Wan Kenobi. In the near future, smartphones and other mobile devices will have the ability to show something similar, according to David Fattal.

A two-by-two-inch “holomodule” will be Leia’s first product.

Fattal’s company, appropriately named Leia, will demonstrate a prototype of its new 3-D display next week at Mobile World Congress in Barcelona. Later this year it plans to release a small display module capable of producing full-color 3-D images and videos that are visible—with no special glasses—from 64 different viewpoints.

Key to Leia’s technology is an invention by Fattal that takes advantage of advances in the ability to control the paths light takes at the nanoscale. He first revealed the concept, which Leia calls a “multiview backlight,” in a Nature paper published two years ago (see “35 Innovators Under 35: David Fattal”). At the time, Fattal was a researcher at HP Labs and his work applied to optical interconnects, which allow computers to exchange information encoded in light. But he realized that the idea could also be used to display holographic images, and he left Hewlett-Packard to pursue that idea.

Optical interconnects rely on nanoscale structures called diffraction gratings, which cause the light rays that hit them to travel in precise directions depending on the angle at which they arrive. It occurred to Fattal that rather than using gratings to send light through a cable to transmit data, he could engineer them to send light in prescribed directions in space, and that could be the basis of a holographic 3-D display.

Leia has refined Fattal’s initial design to improve the image quality and has also developed a way to make the holograms come out of a conventional liquid crystal display (LCD). That’s impressive because it means the technology is ready to be commercialized, says Gordon Wetzstein, a professor of electrical engineering at Stanford University who studies next-generation display technologies.

Every standard LCD display has a component called a backlight, which is made of two parts: a light source and an attached “light guide,” made of plastic. The light guide directs the light toward the display’s pixels; images appear on the screen as the LCD selectively blocks varying amounts of light at each pixel.

Leia essentially replaced the standard light guide with a much more sophisticated one that has nanoscale gratings. The new light guide has much more control over the direction that light travels before it reaches the pixel array. Instead of simply guiding all the light in a uniform way, as in a conventional display, it can direct a single ray of light to a single given pixel on the display. Leia sets up the LCD to send 64 different images, each produced by 1/64th of the available pixels, and blend those images together in a way that makes the viewer’s brain perceive a seamless hologram. The process sacrifices some resolution, which may make it challenging to apply to larger screens, but today’s mobile devices have such high resolution that viewers won’t notice, says Wetzstein.

The company tentatively plans to release a small display module in an Asian market, with an eye toward early adopters who could begin developing new applications and content.

The biggest question facing all 3-D displays, especially after the failure of the recent wave of 3-D televisions, is what it will take to convince people to spend money on them. Mobile gaming seems like an obvious opportunity.

Leia has built an online resource that developers can use to convert existing 3-D graphics and animations into content compatible with its backlight. A content creator can import a 3-D graphic or animation already used on the Web or in a game, and Leia’s tool automatically breaks it into the 64 images necessary to generate a hologram.

Holographic video that is more like Princess Leia’s is not yet possible. Whereas the image of her appeared to be visible from all sides, Fattal’s technology makes it possible to see the hologram within a 60° arc, and even that requires 64 cameras positioned precisely. At Mobile World Congress, Fattal plans to demonstrate real-time video chat, which will require a bulky camera array. He imagines that eventually this setup could be streamlined by a dedicated device, such as a set of cameras arranged in the back of a TV set that would record images of a person looking at the screen and send them over the Internet to another screen where they would make up a hologram. “That’s something that’s completely doable in the not-so-distant future,” he says.

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