How does a fingerprint reader work?

Fingerprint scanning is a form of physiological biometrics that analyzes your physical characteristics in order to authenticate your identity. Basically, it recognizes that your fingerprint belongs to you and no one else.

Everyone has unique, identifying marks on their fingers which are used to create a fingerprint. These cannot be changed or removed and so are a preferred indicator of identity for security procedures.

You may have come across a fingerprint reader before. They are often used in border control, at the police station, on the latest smartphone handsets and in many security companies. Fingerprint readers can protect against fraud and identity theft and are a more reliable authenticator of identity than the traditional pin and password method.

So, how do they work?

Fingerprint readers can rely on different technologies to capture the unique features in your prints. The most common fingerprint reader will fall under optical scanners, which use lenses to reflect lights onto complementary metal oxide semiconductor (CMOS) sensors which then convert light into electronic signals.

Other readers capture prints using capacitive sensors. Fingerprint ridges and valleys create different electric currents at different areas of the finger. Each fingerprint reader uses the electric current to create a picture of your print.

Each of your finger’s ridges and valleys act as insulators, restricting the flow of current produced by the reader. As this happens, the scanner can use this data to generate a clear picture of the individuality of your finger, or a ‘Biometric Identifier’.

See the image below for a simple example of how this works:


Fingerprint reader


Once these details are stored, each time your fingerprint is scanned, it can authenticate your identity. Matching your print to you. To build a more complete and accurate image of your fingerprints, the scanner often requests to take multiple prints from the same finger.

To find out more about biometrics, read our posts here and here.

If you have any questions about fingerprint scanning, let us know in the comment section below or by tweeting to us at @JustAskGemalto.