Fingerprint recognition is one of the most widely used biometrics in the access control industry.This is because fingerprints are one of the oldest forms of personal identification, inexpensive to collect and analyze, and they are stable. Biometric fingerprint access control applications use one or both of two fingerprint characteristics: ridge patterns and minutiae details, which are unique features found within the patterns. Some extremely hi-tech biometric fingerprint scanners not only require a fingerprint to match, but they employ temperature and humidity monitors to ensure that a live finger is being scanned.
There are three basic patterns, of fingerprint recognition ridges: the arch, loop, and whorl.
- The arch is made up of ridges lying one above the other in a general arching formation.
- The loop is made up of ridges that enter from one side of the finger, form a curve, and then exit on the same side.
- The whorl is made up of ridges that form a circular pattern around a central point.
- Minutiae recognition, as seen in Figure 3-19, is the most common form of biometric access control fingerprint identification. Minutiae include the discontinuities that interrupt the otherwise smooth flow of fingerprint ridges and the abrupt ridge endings and bifurcations. The major minutia features of fingerprints are bifurcation, dots, and ridge endings.
- Bifurcations are the points where one ridge divides into another.
- Dots are very small ridges, no longer than the width of adjacent ridges.
- Ridge ending is the point where a ridge terminates.
- The ridge patterns and minutiae are important in fingerprint analysis since no two fingerprints are identical.
Operation
A fingerprint recognition sensor is a device used to capture a digital image of a fingerprint. There are several commercially available sensor technologies for electronically collecting fingerprints, including optical, silicon, ultrasound, and light emitting.
Optical technology is the oldest and most widely used collection method. For optical collection, the finger is placed on a proprietary, coated platen. A charged coupled device (CCD) converts the image of the fingerprint, dark ridges and light valleys, into a digital format. Optical devices can withstand temperature fluctuations, are inexpensive, and provide resolution typically ranging from 500 to 1,000 dots per inch (dpi). Drawbacks of optical technology primarily relate to the requirement to make contact with the reading device’s surface. Users leave residual fingerprints, grease, dirt, and other materials that interfere with the reader’s performance and cause the reading surface to wear. Some of the new contactless optical fingerprinting detectors eliminate these deficiencies.
Silicon chip technology, or capacitance technology, has gained considerable acceptance since its introduction to the marketplace in the 1990s. In most chip systems, the sensor acts as one plate of a capacitor and the finger acts as the other. The capacitance between the detector and the finger is converted into an 8-bit grayscale digital image. Silicon generally produces better image quality with less surface area than optical technology. Silicon-based equipment can be much smaller than optical devices. The primary drawbacks are a shorter track record for durability in suboptimal environments compared to optical technology, the smaller scanning surfaces, and issues relating to the requirement to touch the reader’s surface.
Ultrasound technology has only recently been introduced to the biometric market, thus it is not widely used.
For more information please visit our website: Myengineerings.com
