Taking on Mother Nature at the Fingerprint Scanner

April 26, 2006
New fingerprint reader solves Achilles heel of fingerprint biometrics: very dry fingers

If you live in a dry environment, you know what it’s like to watch all the ridges in your fingers turn white from lack of moisture. Your skin might crack, or catch on your clothes, or flake. It might also stop a fingerprint reader from recognizing you.

Dry fingers, as well as wet fingers, dirty fingers and skin damage, have traditionally caused problems for fingerprint readers in the field because the affected surface layer of skin is the layer being read. For example, optical readers scanning dry fingers may create a light image not suitable for identification. Capacitance readers have the same problem, since very dry fingers don’t conduct electric current. In either case, the poor image may result in a false rejection of the user.

“So far there has been no one sensor that works for all skin types,” said Harry R. Smith, president of consultancy HRS Technologies LLC. “You might have one that works well for you, but then maybe Harry puts his finger on it and it doesn’t like it very well, and he has to try again. There is quite a number of variations in the technology of the scanners, and the technology behind them works differently for one finger type than another. A number of sensors may champion wet finger reading, but the dry finger is a real issue in a number of environments nationally and internationally.”

This week at GovSec in Washington, DC, Silex Technology America (booth 1749) is introducing a PC access fingerprint reader that is designed to defeat dry finger and other surface-layer problems. The S1 USB-interface reader uses radio frequency technology to read below the surface layer of skin to the corium—the inner layer—so that surface abnormalities don’t affect the scan.

“As opposed to using conventional capacitor sensor approaches, this goes down and reads inside the fingerprint surface, so it takes a truer image of the fingerprint,” said Gary Bradt, vice president of Silex’s biometric division. And because the reader uses RF technology, Bradt said, the finger doesn’t need to touch the sensor silicon die. The user touches a plastic shell covering the die instead of the sensor components themselves, reducing wear on the sensor. The plastic covering also protects it from spills and dirt damage, and it gives the reader a higher immunity to electrostatic discharge, according to HRS Technologies’ Smith, who has been testing a beta of the S1.

“I call the S1 the iPod of fingerprint readers,” said Smith. “It’s rugged, it’s sleek, and anyone can use it.”