A new biometric touch screen that identities people by their fingerprints could provide a new way of allowing people to securely interact with computers in public places.

Fiberio, developed by Christian Holz and Patrick Baudisch of the Hasso Plattner Institute in Potsdam, Germany, is the first touch-controlled tabletop computer that can identify multiple users from their fingerprints each time they interact with it.

The researchers say that a major drawback with current displays is that they emit light but cannot sense it.

This flaw makes it impossible for the screen itself to recognise a user via their fingerprint, unless a separate sensor is set up beside the screen.

"Fiberio is a touchscreen that simultaneously displays images and scans user's fingerprints on the very same surface," Holz told Techworld.

In order to reveal fingerprints, the screen has to produce contrast between the ridges and valleys of the fingertip.

This requires a 'specular' screen surface that reflects light like a mirror, said Holz.

In order for the screen to be used as a display, it also has to allow light from a projector to produce a visible image.

This requires the screen material to be 'diffuse' so the light can spread, said Holz.

"Unfortunately, specular and diffuse are contradictory requirements for such a surface. Fiberio now resolves this contradiction. The key that allows Fiberio to display an image and sense fingerprints at the same time is its screen material: a fibre optic plate," said Holz.

The fibre optic plate is comprised entirely of millions of 3mm-long optical fibres bundled together vertically.

Each fibre emits rays of visible light from an image projector placed below the glass. At the same time, infrared light from a source adjacent to the projector bounces off the fingerprints and back down to an infrared camera below.

Overcoming Security

Security is one of the main issues around deploying public computers and the researchers addressed this by implementing an additional security layer, which authenticates users every time they try and do something to verify if the respective user has the authority to perform the task they are trying to complete.

"While previous systems can only authenticate users across an entire session (such as when logging in), Fiberio authenticates on a per-input-event level," said Holz. "As such, Fiberio authenticates every single interaction, which makes it a lot more secure than existing systems."

The researchers envision Fiberio being used as a large, shareable, interactive tabletop device in coffee shops or lobbies, allowing people to work or browse the internet on instead of having to bring in a laptop or tablet computer. Or customers at a bank could pass secure e-documents across a table and discuss them with a clerk.

The human computer interaction researchers built the screen in one and a half years with off-the-shelf components.