The unique pattern of ridges, valleys, and swirls that make up fingerprints has been studied in huge detail. There are three basic defined patterns:
- Arch. The ridges start at one side of the print, rise up in the center to form an arch, and continue to the other side of the print.
- Loop. The ridges start at one side of the print, curve around in the centre, and finish on the same side of the print.
- Whorl. The ridges form concentric circles around a middle point on the print.
In addition to these basic patterns, fingerprints consist of minutiae: tiny features of the fingerprint ridges themselves that contribute to the uniqueness of each print’s patterns. These include a Y-shaped bifurcation of a ridge, an ‘island’ ridge that is a small line or dot between two other ridges, and a ‘bridge’ that runs between two parallel ridges.
How do fingerprint sensors work?
When fingerprint scanners are presented with a subject’s finger, they identify the patterns and minutiae on the print, then check them against their database to see if they match a registered user. There are a wide range of different technologies available for scanning fingerprints, including:
- Optical sensors which use a digital camera.
- Capacitive/CMOS sensors which use electrical currents.
- Ultrasound sensors which use high frequency sound waves.
- Thermal sensors which use differences in surface temperature between the ridges and valleys of the print.