Thursday, May 29, 2008

A Low-Cost Multitouch Screen

A new system from Microsoft turns virtually any surface into a multitouch display.

By Kate Greene

The multitouch screen is certainly having its day in the sun. Apple's iPhone and iPod and Microsoft's touch-screen table, called Surface, all illustrate the concept in slick ways. And at a recent conference, Bill Gates and Steve Ballmer showed off Windows 7, a forthcoming operating system that supports multitouch. But the capabilities of today's multitouch software are still somewhat limited, and researchers and engineers aren't yet sure how best to exploit large displays. Recently, however, Microsoft introduced a new multitouch platform, called LaserTouch, which includes hardware that's cheap enough to retrofit any display into a touch screen. The software giant believes that by providing inexpensive multitouch hardware, researchers will be more inclined to experiment with different form factors and develop interesting software.

LaserTouch is a system built on the cheap: the hardware only costs a couple hundred dollars, excluding the display--which can be a plasma television or overhead projector, for instance--and the computer that runs the software. Unlike Surface, which uses a camera within the table to detect touch and a rear-projection system to create the images, LaserTouch uses a camera that's mounted on top of the display. Two infrared lasers, with beams spread wide, are affixed at the corners, essentially creating sheets of invisible light. When a person's finger touches the screen, it breaks the plane of light--an action that's detected by the camera above.

One of the main differences between Surface and LaserTouch, says Andy Wilson, one of Surface's developers, is that you can use LaserTouch on high-resolution displays. These displays lend themselves nicely to graphics applications, such as photo and video editing. And since LaserTouch can be fitted to any type of display, Wilson adds, it could be used for office applications such as presentations.

While multitouch interfaces have gotten a significant amount of attention recently, it's certainly not new technology. Researchers have been playing around with touch screens in labs for decades. But only when the iPhone illustrated a practical use for the technology did excitement build, says Scott Hudson, a professor of computer science at Carnegie Mellon University. "The iPhone has given [multitouch] a whole lot of visibility at present," he says. "I think it's reached the level of general public interest so that a lot of manufacturers are thinking that it has potential."

Cheap trick: Andy Wilson, a Microsoft researcher responsible for developing Surface, shows off LaserTouch, a low-cost multitouch system that can transform any display into a touch screen.
Credit: Microsoft

To be sure, Microsoft isn't the only company building large touch displays. Mitsubishi Electric Research Laboratories has built DiamondTouch, a touch table for business collaborations. Perceptive Pixel, a startup based in New York that was founded by Jeff Han, a research scientist at New York University, is currently selling giant, wall-sized touch screens that support multiple inputs. And kits that allow a person to assemble her own open-source touch-screen tables are currently available to the general public.

At a Microsoft Research demonstration last week, Wilson showed off some of the software that the company is trying to develop. Some of the more whimsical applications included a chess game that could be played with a virtual partner, and an application that lets people virtually "pick up" objects on the screen. (When a person makes a scooping gesture with his hand, a virtual hand appears on the screen, holding the object that was scooped.)

Wilson also demonstrated new presentation software designed for the touch screen that allowed him to easily flick through slides, resize objects, and navigate through components of his presentation. Presentations call out for touch-screen interaction, he says, because swooping gestures on a large screen provide theatrics that can make a talk engaging.

Microsoft has no plans to commercialize LaserTouch but still hopes that the approach can help spread the development of multitouch applications within the research community.

"It definitely helps everyone to make the hardware as cheap as possible, especially for larger form factors," says Han. However, he notes that the fidelity of the system needs to be maintained in order to make these new applications practical, and LaserTouch has the potential for errors. "It's quite easy for fingers and hands to block the sensing mechanism," Han says. "There's a real danger of vendors out there rushing to land-grab part of this hot multitouch space with substandard solutions which fall short of the potential of these interfaces."