The iPhone may be getting lots of attention, but Steve Jobs has no corner on “multi-touch” displays, which allow a person to use multiple fingers to do things like zoom in and out of pictures. At New York University’s Courant Institute of Mathematical Sciences, research scientist Jeff Han has developed an effective way to make large, very high-­resolution screens that accommodate 10, 20, or even more fingers. Applications could include interactive white boards, touch-screen tables, and digital walls.

In Han’s setup, a digital projector shines an image on a six-­millimeter-thick clear acrylic screen. Touch sensitivity comes from infrared light-emitting diodes attached to the edges of the screen. Normally, the diodes’ light reflects internally and stays trapped within the acrylic. Once fingers or other objects touch the acrylic, though, the light diffuses at the point of contact and scatters outside the surface. A camera behind the screen detects these changes. Simple image-processing software can interpret the scattering, in real time, as discrete touches and strokes.

“The new iPhone is too small to be a very interesting multi-touch device,” says Han. With larger screens, multiple users could collabo­rate–in brainstorming sessions that use networked, interactive white boards, for instance, or animation sessions joined by many artists.

Versions of multi-touch technology have been around since the 1980s, but they never took off commercially. Multi-touch screens “never completely went away, but they’re coming back in different ways,” says Bill ­Buxton, principal researcher at Microsoft Research. Han’s company, Perceptive Pixel, shipped its first wall-size screen to an undisclosed U.S. military customer this winter.