Touch Screens for Many Fingers

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Han's touch display is made of clear acrylic with light-emitting diodes attached to the edges, illuminating the six-millimeter-thick acrylic piece with infrared light. Normally, the light from the diodes reflects along predictable paths within the acrylic, a physical phenomenon called total internal reflection. However, once a finger or other object touches the acrylic, the internally reflecting light diffuses at the point of contact, scattering outside the surface. Behind the acrylic surface, there is a camera that captures this light. Using simple image-processing software, the captured scattering is interpreted in real time as discrete touches and strokes.

Many researchers who've been working for decades on touch technology are excited to see these developments. "For almost two decades, we've been trapped by the tyranny of the screen, the mouse, and the keyboard," says Don Norman, professor at Northwestern University, in Chicago, and author of The Design of Future Things, to be published in October. "It's nice to think we're breaking away from that and going toward touch-screen manipulation in the real physical world."

Some researchers are even developing touchable displays that can touch back. The emerging technology that enables this is called haptics. (See "The Cutting Edge of Haptics.") One type of haptics technology involves a surface that senses when it's touched and then vibrates at various frequencies, depending on the placement of one's fingers. This sort of technology could be useful for the touch keyboard on Apple's iPhone, says Scott Klemmer, professor of computer science at Stanford University. "You wouldn't get the tactile feel of real buttons, but [because of the vibrations] you can tell you've touched a real button."