THE BASICS OF FINGERPRINT ANALYSIS

Fingerprint-analysis algorithms used by scanner systems are designed to capture and recognize the same basic features that have been employed by fingerprint-analysis experts for decades. At its core, fingerprint analysis seeks to identify specific minute features (minutiae) within the fingerprint structure and compare them to others in a database. Digital fingerprint scanners can also add other information, such as specific distances between minutiae and the direction of whorls in the fingerprint structure, to further increase the uniqueness of the measurement and thereby decrease FAR and FRR numbers.

In both the classic “ink” type of fingerprint recording and in the digital capture of a fingerprint using one of the technologies listed above, the fingerprint friction ridge, the raised portion that contacts the glass surface of the scanner, is recorded as black, and the fingerprint valley, which is filled with air, is recorded as white. Keeping these in mind, fingerprint experts have developed a list of minutiae that can be found in most fingerprints. The primary minutiae that are employed in fingerprint characterization include.

Iris scanners capture the minute patterns in the iris, the colored region between the pupil and the sclera, and compare these patterns to previously stored iris scans. Iris scans have the advantage that eyeglasses and contact lenses need not be removed for the system to operate properly.

The first step in the process is the isolated capture of the iris, without the sclera, pupil, and any light reflections that might be present. This is usually accomplished by smoothing (averaging) the picture so that the disk of the pupil can be more easily identified by software. Next, software locates the best fit circle that just inscribes the pupil and the best circle that captures the outer edge of the iris.

In the 1930s, Simon and Goldstein published a paper in which they reported that the pattern of minute blood vessels in the retina of the eye is unique and could be used as the basis for identifying a person. The eye is protected from the external environment much as the brain is and, as a critical sensory organ, is also protected carefully against injury throughout a person's lifetime. In a subsequent study performed by Dr. Paul Tower in 1955, it was shown that these retinal blood vessels unique, even in the specific case of identical twins, where such a difference is least likely to occur. In fact, Tower showed that, of all the factors that he compared between identical twins, these retinal blood vessels showed the least similarity.