Sangeetha Pulapaka

Did you mean to ask how a fingerprint scanner works? If yes, then here goes....

Everyone’s fingerprint is unique, even for identical twins.

3 major types of fingerprints include:

Arch: Only a few, that is close to 5% have this type of fingerprint. An arch doesn’t have any delta, lines, or cores.

Whorl: 25-35% of fingerprint patterns are whorls. Whorls have at least two deltas and a core. Any fingerprint pattern that contains equal or more than 2 deltas will be a whorl pattern.

Loop: 60-70% of fingerprints patterns are loops. These are the most common fingerprint pattern. Loops pattern must have one delta and one core.

Fingerprints consist of a unique pattern of ridges and valleys on the surface of the skin, improving the capability to grip objects. The pattern develops in the womb and is influenced by a range of environmental factors as well as genetics.

Optical fingerprint scanners use a charge couple device, or CCD, similar to those found in a digital camera, to generate an image of your fingerprint. To scan your fingerprint, you place your finger on a sheet of glass covering the CCD. Light emitting diodes illuminate your finger, and light sensitive diodes on the surface of the CCD measure the intensity of the reflected light at many points. An analog-to-digital converter then converts the analog light levels from the photo diodes to digital data. One disadvantage of optical scanners is that they may have problems reading fingerprints from dirty or marked fingers, which will falsely alter the light and dark patterns.

Capacitive fingerprint scanners use electrical current to form an impression of the ridges and valleys making up a fingerprint. A series of metal plates form capacitors, which are connected together by ridges in the skin, and untouched by valleys. By measuring the capacitance of the plates, the pattern of the ridges and valleys on the finger can be determined. Capacitive scanners are harder to trick than optical scanners, as they require a finger substitute that alters the capacitance in the same way as a human finger.

Ultrasonic fingerprint scanners use imaging devices found in hospitals and medical centers. Piezoelectric transducers generate high-frequency sound waves, directed at the finger, which penetrate into the skin. Ultrasonic sensors measure the reflected energy and can determine the locations of ridges and valleys by the different reflections returned. As the ultrasonic waves penetrate through the top layers of skin, these scanners offer the most accurate results as dirt on the finger

or reader does not affect the scan.

Vivekanand Vellanki

The finger print scanner does not need to know which finger's print it is taking.

For comparison, it compares against the prints of all 5 fingers and declares a match if any of the prints match.

Usually, the print of the index finger is used for verification. However, in cases where the print of the index finger is not good, the print of any other finger can be used for verification.