Shfting Gears - Acoustic Interactive Surfaces

Acoustic Sensors Make Surfaces Interactive

14:22 28 November 2006
NewScientist.com news service
Tom Simonite

A series of acoustic sensors that turn any surface into a touch-sensitive computer interface have been developed by European researchers.

Two or more sensors are attached around the edges of the surface. These pinpoint the position of a finger, or another touching object, by tracking minute vibrations. This allows them to create a virtual touchpad, or keyboard, on any table or wall.

The system, called Tai-Chi (Tangible Acoustic Interfaces for Computer-Human Interaction), was developed by researchers from Switzerland, Italy, Germany, France and the UK. "We have made a system that can give any object, even a 3D one, a sense of touch," says Ming Yang, an engineer at Cardiff University, UK, who is coordinating the project.

A video produced by the researchers shows four sensors attached to a flat, vertical surface, being used to trace a researcher's finger (4.6MB, wmv format). Another video shows a simple interactive instrument developed using the system. The sensors were also used to create an interactive globe that accesses geographical information on a computer screen when the user touches different regions.

'Sonar' Tracking

"One advantage of the system is that for little cost you can have a much larger touch-sensitive area," says Yang. "The whole surface of your desk could become your keyboard and mouse-pad."

Tai-Chi uses tiny piezoelectric sensors to sense surface vibrations. The sensors are connected to a desktop computer loaded with software developed by the team and the system can track up to two objects at once, in one of two ways.

One method involves measuring differences in the amount of time vibrations take to arrive at two or three different sensors – a similar approach to sonar. Using this method any surface can be made touch sensitive simply by attaching the sensors.

The other method requires just one sensor and can actually be more accurate – to within just a few millimetres. But this method requires the calibration of the system beforehand, so that it recognises the vibrations caused by contact at different points on the surface. It then uses a database of vibration "fingerprints" to identify the point of contact.

Hygiene

Workplaces in which hygiene is critical, such as hospitals, could particularly benefit from Tai-Chi, says Wang. "Keyboards are very difficult to keep clean and can harbour infection," he explains. "We could have a keyboard drawn onto the desks that would work perfectly and could be disinfected much more easily."

William Harwin, a haptic interfaces researcher at Reading University, UK, thinks Tai-Chi has promise. "It is a very clever idea," he told New Scientist. "The technology is a neat and relatively simple solution to making ordinary objects touch sensitive."

But Harwin adds that users might not find it easy to switch from a normal keyboard to simply tapping on their desk. "People expect a degree of feedback from pushing buttons and switches," Harwin explains. "It is important in giving people a sense of quality."