Conventional TV and computer displays huff and puff to form an image--usually on a screen or monitor--and then your eyes take it in. Tom Furness has chosen a slightly more aggressive strategy. Why not skip the peripheral dribbling and passing, he wondered, and slam-dunk the imaging signal directly into your eyeballs with lasers?
"For 23 years," says Furness, "I worked at Wright-Patterson Air Force Base on virtual cockpits for fighter pilots." Since pilots need to process visual information quickly, projecting instrument readings, maps, and so forth onto the plane's windshield seemed like a good idea. This wasn't easy to do because competing with the bright views blasting directly into the pilots' eyes required a very high luminance. "It was clear to me," Furness says, "that we had to have some kind of paradigm shift." After moving to the University of Washington in 1989, Furness teamed up with engineer Joel Kollin and tried using tiny, harmless lasers--about as bright as daylight--to scan virtual images, line by line, directly onto the retina. "A lot of people said it wouldn't work," he recalls. They didn't think that the illusion of whole images would persist. But it did persist.
The real challenge was packaging the technology--how to make the lasers, and the mechanical scanners that point them, small and precise. In 1993 the university received funding from Microvision, a Seattle corporation, in return for a license to develop the technology. The latest hardware package is the size of a thimble. At its heart is a fast, minuscule oscillating mirror that reflects red, green, and blue laser beams into the eyes. Clipped onto glasses, the device gives you virtual color images that seem to hover at arm's length. By adjusting the brightness, you can make this display look like a transparent overlay on reality, or you can make it obliterate the boring real world. Last November, Microvision delivered retinal displays to the Air Force and two aerospace companies, and it has a contract to make a helmet-mounted version for helicopter pilots. Similar hands-free devices could show, say, a patient's ghostly, transparent X-rays to operating surgeons, or float diagrams from a repair manual in front of greasy-handed mechanics, or lay X-marks-the-spot virtual maps of a minefield in front of soldiers' footsteps. For now, at a cost of $400,000 and more, these displays are beyond the grasp of ordinary consumers, but Microvision's zealous engineers are working on ways to mass-produce them.
