Another Dimension in Mobile Displays
By David Pescovitz, Thu Mar 10 08:45:00 GMT 2005

A look deep into the future of 3D displays for mobile devices, no glasses required.

In 1953, moviegoers experienced a new dimension in fear, or at least campy horror, with the release of House of Wax. The Vincent Price shockfest was the first 3D feature produced by a major film studio. Unfortunately though, director André de Toth couldn't fully enjoy his own creation. The 3D illusion depended on binocular vision, but de Toth only had one eye.

In some ways today, we're all faced with the same problem. Mobile devices are now equipped with 3D graphics chips to bring a heightened sense of realism to the small screen. Videogame designers are cranking out dazzling 3D experiences that will soon put the playpower of a console in our pockets. The rub, though, is that the vast majority of our displays are stranded in flatland.

"Most games and many other applications are written in 3D although the final image is shown in 2D," says Ian Thompson, director of business development at Sharp Laboratories of Europe. "In nature humans see the world in 3D and yet we have become accustomed to seeing flat images"

That may be true today, but researchers in many laboratories, including Sharp's, have their eyes set on the next generation of 3D technology. If mobile displays are necessarily limited by length and width, the only option is to increase their depth. And unlike the 3D movies of yesterday (and even today), the new 3D displays don't require any special eyewear. Sharp is leading the charge, having supplied mobile phones equipped with "glasses-free" 3D displays to NTT DoCoMo for two years. The company claims that their first 3D handset "sold over 1.5 million units in the first 6 months of sales, more than all previous 3D products combined." Of course, Sharp is not the only one convinced that mobile 3D is ready for prime time.

At the end of last year, South Korea's Samsung SDI announced the first 3D display for mobile phones that can be viewed from any angle. (Sharp's display requires relatively careful alignment of the eyes with the screen to appreciate the 3D effect.) Samsung believes the 3D display market will grow from $300 million to $2 billion between 2007 and 2010. They expect their new 3D display to hit the market later this year.

All 3D displays exploit our binocular vision system. The spacing between our eyes means that we see two different perspectives of the world around us at the same time. The brain uses these two images to calculate depth and combine the two viewpoints into a 3D representation of whatever we're looking at. Three-dimensional displays deliver a slightly different image of the same scene to each eye to create the illusion of depth. In a movie theater, special glasses control which image enters each eye by either filtering out certain colors or electronically blocking one lens and then the other in succession too fast for you to notice.

Glasses-free 3D displays, known as autostereoscopic displays, use the screen itself to deliver a specific image to each eye. The most common kind of autostereoscopic displays are the 3D photographs and kitschy postcards and available in souvenir shops. The textured surface of the image is actually an array of lenses that provide each eye with its own view.

Sharp's 3D display is obviously higher-tech, but not much. Their device employs a "parallax barrier," electronically-controllable LCD columns aligned with the columns of pixels in the display. When switched on, the parallax barrier divides the image and controls the direction that the light leaves the display and hits your eyes. The beauty of the Sharp technology, Thompson explains, is that the parallax barrier can be instantly switched off for 2D content.

Right now, research at Sharp is focused on making the displays brighter, less power-hungry and also expanding the viewing angle. While novelty may initially drive sales of the devices -- current applications are limited to the likes of games and screensavers -- Thompson envisions myriad applications that would be enhanced through 3D.

"If a phone is used to view a map for a location-based service, a 3D display will make it much clearer," he says. "For the corporate user, complex financial data can be displayed in 3D."

Several months ago, NEC reported that their latest prototype 3D LCD provides the world's highest resolution images at 235 pixels per inch. In traditional autostereoscopic 3D displays, the horizontal resolution is cut in half right out of the gate because every pixel in a standard image now requires two adjacent pixels, one for each eye. NEC claims to have solved this problem by shifting the shape of the pixels from square to rectangular. Each pixel is then divided horizontally into sub-pixels to provide double the resolution and the ability to display 2D and 3D images simultaneously. NEC described the technology at a scientific display research conference but did not predict when it would emerge from the laboratory.

While the applications for desktop 3D displays are clear -- from medical visualizations to teleconferencing -- the killer app for mobile 3D remains to be seen. That means that a low price is key for the technology to have value beyond its wow appeal.

Keigo Iizuka, a professor of engineering at the University of Toronto, recently discovered that a penny sheet of standard cellophane is better than commercial optical materials for rotating the polarization of light emitted by the phone to deliver separate images to each eye. While his approach requires the user to don 3D glasses, or mount the cellophane in a bulky cover so that the "display screen wears the glasses," Iizuka says that the polarization technique beats the image quality of parallax barrier approaches like Sharp's. Iizuka he says he has no plans to commercially pursue 3D mobile displays, instead furthering his efforts to design cameras and displays for the holy grail in three-dimensional display technology, 3D TV.

Eventually, Iizuka says his optical innovations might be integrated into a projection system that bounces the image off a polarizing screen to generate the 3D effect on a wall. Combine that technology with the "pocket projectors" now emerging from various labs, and the famous 3D projection of Princess Leia from Star Wars moves into the realm of possibility.

According to the description of a tiny digital video projector system recently developed at the University of Cambridge, "while this is some way away yet, the (projection) technology could bring the holographic video displays of science fiction one step closer to reality."