The Feature: The Eyes Have It

Tomorrow's mobile-phone displays may project the wireless Web right onto your eyeballs.

The mobile Internet suffers from scarcities. Wireless bandwidth is too low. Radio spectrum is in short supply. Batteries don't last long enough. Screens are too small. The first three challenges are non-trivial, but solutions are already emerging. Display size is a bit trickier though. New applications for mobile devices have led to a run on screen real estate and there's not much room for expansion inside your pocket. However, in the next five to ten years, virtual retina displays will change the way we look at our mobile devices.



On first glance, the virtual retinal display (VRD) developed at Washington University's Human Interface Technology Laboratory resembles a traditional heads-up display, a tiny monitor mounted just inches from your eyeball. In fact, earlier this month Mitsubishi announced an inexpensive heads-up display called SCOPO. What makes the VRD so unique is that there is no screen. The device literally paints a video image onto your eyeball with a laser beam. The picture is crisper and brighter than any competing heads-up display and doesn't guzzle power like postage-stamp LCD or LED screens.



Professor Thomas Furness, director of the Human Interfaces Laboratory, has focused much of his research on the VRD since the idea was just a twinkle in his eye more than a decade ago.



"The small screens and narrow fields of view of mobile devices don't work well with the human vision system," Furness says. "When we first started talking about VRD, the idea was to create a system that requires very little power but can be connected to a PDA or cell phone to deliver a wide field of view with high brightness. For mobile computing applications where you want to overlay digital information on top of what you see, you need the luminance to compete with the outside world."



That vision is called "augmented reality," superimposing useful computer-generated data on top of the real world. Imagine walking around a new city and location-based information about the buildings you pass appears in front of you. Or perhaps you've forgotten where you parked in a huge lot. Wouldn't it be helpful if a tiny red bullseye appeared to lead you to your vehicle? Driven by the promise of augmented reality applications, Furness succeeded in building two prototypes of the VRD. One of the systems, mounted on a laboratory table, displays a full color VGA image on the retina. It's anything but portable though.



"The challenge is taking something off an optical bench and shrinking it to the point where it can be worn like eyeglasses," Furness says.



Redmond, Washington-based Microvision did just that. Sort of. The company licensed Furness's technology and developed the Nomad Expert Technician System. Announced this year, the Wi-Fi-equipped system enables automobile technicians, for example, to see repair diagrams superimposed over the engines they're tinkering with.



Microvision shrank Furness's original system by building their own "retinal scanning engine," a thumb-sized device containing the key components of the VRD. Inside the engine, a tiny laser diode produces the beam while a microscopic mirror reflects it. Tiny actuators - -fabricated the same way microchips are manufactured -- steer the mirror, sweeping the beam across your retina at incredibly high speeds to produce what appears to be a solid image.



"With other head-mounted displays, you're looking at a real image," Furness says. "But the VRD doesn't have discrete cells or pixels, so the resolution is almost unlimited. Also, the photons are beamed right onto the retina so the image is incredibly vibrant."



The rub is that Nomad only displays images in bright red. It also costs approximately $4000, chump change for a car company but completely impractical for the average smartphone-toting consumer.



Color will come in time, Furness says. The first generation VRDs, he explains, leveraged the semiconductor industry's investment in red laser diode development for optical communications applications. While blue and green laser diodes have a huge potential market in optical storage, the technology is not yet mature enough for a wearable VRD, he says.



In the meantime, Furness is exploring a method to simplify the VRD and help bring costs down. His latest design dispenses with the mirror entirely. Instead, the tip of a single fiber-optic strand is pointed at the retina and mechanically bent back and forth at very high rates. Essentially, you're staring right down the beam instead of at its reflection. The stripped-down scanner, he says, may not only be less expensive to produce but also paints a prettier picture.

"We could make the image as big as we want and display a huge gamut of a colors," Furness says. "It would be like wearing an IMAX theater in a pair of eyeglasses."