Dirt: A Fingerprint's Weakest Link

Ultrasonic fingerprint scanning and matching solutions may soon make biometric access control applications practical and effective for the security industry.

Fingerprinting has always tantalized security officials searching for accurate and difficult-to-defeat biometric access control methods. But acquiring and matching fingerprints has proved problematic when dealing with large populations.

Until recently, acquiring fingerprints required ink or optical live-scan technology, which essentially snaps photographs of fingerprints. For security directors, acquiring fingerprints with ink requires too much care and time, and it leaves employees' fingers covered with ink.

Optical fingerprinting technology, which came on the scene 20 years ago, seemed to solve the problems connected with ink by snapping a picture of an enrollee's finger. In practice, however, dirty fingers alter fingerprint images in ways that make it difficult for software systems to find accurate matches, thus making them unreliable.

Optical system providers have addressed this difficulty in two ways: by urging security directors to make sure employees wash their hands and by tweaking the software that matches fingerprints to adjust to inconsistencies created by dirt and grease on the fingerprint image.

Unfortunately, employees don't always wash up prior to fingerprinting and judgments made by software can reduce matching accuracy.

In 1996, a company called Ultra-Scan introduced an ultrasonic fingerprint scanner, calling it a major breakthrough in the field of biometrics. The research community agreed and recognized the company with the R&D Top 100 Award for innovative products. Since then, Ultra-Scan has improved its technology and developed hardware and software systems applying the technology to access control needs.

Ultra-Scan uses sound waves to scan fingerprints. "It is the same technology used in the medical arena to scan pregnant women," says Dr. John K. Schneider, founder and chief technology officer of the Amherst, N.Y.-based Ultra-Scan. "Sound waves penetrate dirt, grease, and other contamination on the finger and create an accurate image of the fingerprint ridge structure."

Fingerprints created with ultrasonic imaging bring three benefits to biometric access control systems, Schneider says. First, ultrasonic images make it possible to enroll all employees. Optical systems fail about 10 percent of the time. Next, employees find ultrasonic systems easy to use. Optical scanners at access points must be kept perfectly clean, and entering employees must scan clean fingers. Ultrasonic access readers require no special maintenance and are not affected by dirty fingers. Third, the Ultra-Scan software that matches prints of entering employees with prints stored in the database, called automatic fingerprint identification systems or AFIS, delivers a level of accuracy at nearly 100 percent.

According to Schneider, software designed to match optically scanned fingerprints cannot reach that level of performance. "It's important to ask for data on accuracy from a third-party tester when evaluating fingerprint biometric systems," he says. "We have that data, and that is what distinguishes Ultra-Scan from other players."

Ultra-Scan is currently conducting beta tests of its biometric access control system at three U.S. airports to control access of airport employees to airside locations. Additional beta tests are in the works at several hospitals, to control patients' access to methadone. "Over the past year, we've done over 140,000 patient identifications in these trials and had no medication errors due to misidentification," Schneider says.

In addition to airport and healthcare applications for government, Ultra-Scan says its biometric fingerprint technology can control access in government buildings and secure areas, border crossings, vehicles and fleets and correctional facilities.

Ultra-Scan does not manufacture systems for sale. Instead it licenses its technology to hardware and software providers who, in turn, deliver systems to customers.