Soccer team in a huddle

Touchscreen with Fingerprint Sensor

April 4, 2014 by Nicolas Zeitler

Johanna Wanka, Germany’s Federal Minister of Education and Research, was quite happy to let Sven Köhler take her fingerprints at the recent CeBIT trade fair in Hanover.  The government minister was visiting 23-year-old Sven, a computer science student from the Hasso Plattner Institute (HPI), to find out more about the “Fiberio” touchscreen that he has helped develop. In recognition of their achievements, CeBIT and the German Ministry of Education and Research subsequently presented Sven and his fellow student Christian Holz with this year’s CeBIT Innovation Award for Visionary Ideas, worth €20,000.

What makes Fiberio unique is that it can identify different users by their fingerprints within fractions of a second as they tap and swipe the device’s multi-touch screen. And even if several different people use the touchscreen simultaneously, there is no need for them to log on separately, because fingerprint recognition technology ensures that each person can only access the applications that he or she is authorized to use.

Materials research breakthrough

The Fiberio prototype that Sven presented to Germany’s research and education minister is mounted on a hip-height stand. The touchscreen is roughly the size of a sheet of A3/ledger paper.  On a shelf below the screen are a projector that throws the image onto the touchscreen and a sensor for identifying fingerprints.

One of the challenges of developing Fiberio was to find a surface material for the touchscreen that would enable both of these functions simultaneously, which was more of a material research challenge than an IT one.  It was also the subject of the doctoral thesis that Christian Holz wrote under the supervision of HPI professor Patrick Baudisch. “For the projected image to be displayed, the surface needs to be matt and slightly milky.  At the same time, it needs to be transparent enough to allow fingerprints to be read when a finger is pressed against the screen,” explains Sven.

Christian eventually found a material from the medical technology industry that offers both characteristics and is usually used in X-ray equipment. Thanks to this material, the glass-fiber Fiberio touchscreen is able to diffuse the light that hits it to create the display – and simultaneously to reflect the light rays from a finger that is touching the surface back to the camera.

Recognizing fingerprints in fractions of a second

But discovering this material was by no means the end of the story.  The next challenge was to find a way of identifying users by their fingerprints almost instantly. “Fingerprint scanners have been around for years, but there can be anything up to a half-second delay in identifying fingerprints by this method,” says Sven.  This is no use for a device that is supposed to recognize users while they are actually using it. So Sven developed his own applications for this part of the solution. He wrote software that runs directly on the Fiberio graphics card and that analyses who is currently working on the touchscreen based on the hills and valleys in the fingerprint.

The Fiberio system could prove practical for groups of people who want to work on the same document. Co-workers could take turns to edit a text, for example, and fingerprint recognition would make it easy to track who made which changes and when without each person having to log on and off separately each time. Fiberio could also “remove the barriers,” as Sven puts it, at meetings between, say, service personnel and their customers.  The service provider and the customer could even work on the same display. There would be no danger of the customer inadvertently gaining access to confidential data by touching the screen, even within a single application, because only the service provider whose fingerprint is identified would be able to access the elements shown on the screen.

“Our aim with Fiberio is to turn mobile devices, such as tablets, into truly multi-user devices,” says Sven.  For example, a family could buy one tablet PC for all the family members to use. User profiles would be created for mom, dad, and the two kids and linked to each one’s fingerprints. Each member of the family could then use the device whenever they wanted to without having to log on and off separately. If mom taps the e-mail app symbol, her inbox opens.  If she puts the device down to go and do something else and her 12-year-old daughter picks it up, she will be directed to her own inbox – not her mom’s – when she taps the e-mail symbol.  “This will make the process of logging on and off obsolete,” says Sven.  Which, in his view, will also make devices more secure. In the past, people have often not bothered with passwords because the whole rigmarole of logging on, logging off, preventing timeouts, and locking the device was too inconvenient. Fiberio, says Sven, shifts responsibility for security away from the user and back into the system.

From Fiberio prototype to tablet: still a long way to go

Nevertheless, according to Sven, it will “take quite a while” for this vision to become reality. The Fiberio that Sven and Christian presented at CeBIT was constructed using a laser cutter and aluminum profiles from a hardware store.  It current uses a bulky projector – like the ones people have attached to the ceiling to create a home cinema – to project images upwards onto the display. And the equipment for identifying fingerprints consists of an equally cumbersome infrared light and high-resolution camera. These components will need to become a whole lot smaller before they can be integrated into the surfaces used in smartphones and tablets.

Sven says that at least some of the prize money from the CeBIT Innovation Award will go into developing Fiberio further. His partner Christian, who has now completed his PhD, and Professor Patrick Baudisch have applied to have their development patented. And what about Sven himself?  He has just finished the first semester of a masters’ study program. “I could really see myself entering the academic world when I’ve finished my studies,” says the talented young researcher.

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