Advances In Fingerprint Biometric Technology

For many years now, the promise of biometrics has not been fully realized in large part because performance in the lab is not representative of performance in the field. That’s the reason major locksmiths began shying away from biometrics. As one...


For many years now, the promise of biometrics has not been fully realized in large part because performance in the lab is not representative of performance in the field. That’s the reason major locksmiths began shying away from biometrics. As one recently said, “They’re 1 percent of my sales and 10 percent of my service calls.” Failure rates were running from 3 to 20 percent. In a 50-person firm, they could work around this. However, if hundreds of people are involved, the customer has a big mess which falls back on the locksmith.

The core problem is that conventional biometric technologies rely on unobstructed and complete contact between the fingerprint and the sensor, a condition that is elusive in the real world, a world that is wet, dry, or dirty. Users are not all young office workers with great skin who are experienced at using biometrics. Bottom line – good images give good results; bad images give bad results.

 

Wet or Dry Fingers May Fail

Wet conditions are notoriously difficult for both semiconductor and conventional optical fingerprint sensors to handle. And, yet, moisture is a fairly common real world condition. Some environments are naturally damp, due to climate (Oregon) or setting (a spa). Some people have moist hands. It is also typical for people going through security to be nervous — and to have sweaty hands.

Conventional optical technologies are often unable to produce images in wet conditions because excess moisture obscures fingerprint ridges, resulting in images of puddles, not fingerprints.

Has any other real world condition caused so much trouble in the biometrics industry? Dry fingertips are common, caused by anything from climate conditions and natural skin characteristics to frequent hand-washing and air travel. For instance, a high desert climate causes dry fingers in an entire population.

Most optical sensors are configured to look for the presence or absence of total internal reflectance (TIR), which is the phenomenon whereby the interface between glass and air acts like a mirror at certain angles. The contact between the skin and the platen defeats the TIR, allowing those points of contact between the finger and the sensor to be imaged. Thus, those points of contact must be complete and unobscured to enable the conventional sensor to collect a fingerprint image.

With dry fingers, this is simply not the case. Establishing firm and complete contact with the sensor is very difficult with dry fingers. There is not enough moisture in the skin nor is the skin pliable enough to facilitate the contact necessary for TIR imaging.

 

It’s a Dirty World Out There

The real world is a rough place and most of us are showing some wear and tear on our hands. Additionally, people don’t have time to wash and lotion their hands before they use a fingerprint sensor.

A construction site is an interesting case. Construction workers work with their hands and have the cuts and calluses to prove it. Additionally, the construction site is dirty so workers may have grime on their hands when they approach a fingerprint sensor. Altogether, this real world scenario is a nightmare for system administrators whose conventional fingerprint sensors depend on quality contact between the finger and the platen.

 

We’re All Different

Many people, both young and adult, have small or fine fingerprint features that can be difficult to image. If the sensor cannot differentiate between these fine characteristics, system performance will suffer.

Age is another physiological characteristic that can affect the ability of a sensor. One effect of aging is the loss of collagen in the skin; elderly fingers have soft fingerprint ridges that collapse into each other when the finger touches a surface. Because many sensor technologies depend on the quality of contact between the finger and the sensor to collect a good image, soft fingerprint ridges can be difficult.

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