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An image is shown on a table-top screen. Lift a piece of paper over the table, however, and another, related image appears on it; move the paper and the image changes again. That鈥檚 the intriguing essence of a low-cost system designed by and 鈥榮 team at the University of Magdeburg in Germany to explore new ways of interacting with computers.

The team鈥檚 new system consists of a ceiling-mounted projector and infrared camera positioned directly above a horizontal screen, which displays an image of interest to the user. Several more projected images related to the one on display can be 鈥渟tacked鈥� in the 3D space above the table.

The trick is that the paper 鈥� dubbed a Paperlens 鈥� carries infrared-reflecting markers. The ceiling-mounted camera tracks those markers and a computer calculates the Paperlens鈥檚 position and orientation to an accuracy of 1聽centimetre in all directions.

The positional data is sent to the projector, which then projects an image onto the Paperlens. This enables the Paperlens to provide additional information relating to the main image displayed on the table-top screen, and the image will change depending on where the Paperlens is held.

Table-top competition

Dachselt鈥檚 team has demonstrated a number of applications for their Paperlens system, including using it as a magnifying glass or as an aid for investigating 3D medical scans (see video above).

Several other research groups have produced similar devices. For example, Microsoft is developing a similar table-top system, called Secondlight, which projects images onto a surface held above a screen. But this system cannot 鈥渟tack鈥� images.

And Dachselt thinks his group is the first to think seriously about potential applications for this kind of technology in an affordable and simple-to-set-up system. 鈥淭he most important contribution from our point of view is not the technology itself but the systematic usage of the space above the table top,鈥� he says.

at Queen鈥檚 University in Kingston, Ontario, Canada, has seen the Paperlens system in action. He says it is one of a number of research projects that are taking computers beyond traditional desktop designs and will deliver a 鈥渘ew way of computing鈥�.

鈥淭he notion is that the computing display will be much thinner and the hardware removed from sight,鈥� he adds.

Flexible friends

Many of these other projects, unlike Paperlens, employ flexible displays, where images are projected on surfaces which are not flat, Vertegaal says. Although they use projection systems similar to Paperlens, ultimately these could be replaced with flexible screens, eliminating the need for tracking and projection systems. 鈥淥cclusion is a problem [with projector systems]; it鈥檚 easy to create unwanted shadows,鈥� he says.

Dachselt agrees that self-powered screens have advantages over projector systems. 鈥淲e expect the passive 鈥榣enses鈥� to be replaced by active organic light-emitting diode 鈥榣enses鈥� in some nearer future,鈥� he says.

Nevertheless Vertegaal thinks that projector displays like this will be useful in some situations. 鈥淭his has obvious advantages if the technology is used to operate on patients,鈥� he says. 鈥淵ou can project information directly onto the patient 鈥� you can鈥檛 do that using a flexible screen.鈥�

Dachselt鈥檚 team presented their work at the conference in Banff, Alberta, Canada, last week.