Fingerprint recognition

A fingerprint scanner that reads from a finger using a scanner to digitize the fingerprint.

Purpose

With a fingerprint scanner, the identity of a person can be matched with the data contained in a database or on a card. This scanner is the access, such as a safe, granted or denied. Compared with a password, which offers similar advantages, a fingerprint is harder to steal and hard to guess. However, the test finger, eg in case of an injury not readily be changed by someone else, as is often the case with a password.

Liveness detection

Traces of fingerprints, so-called latency fingerprints are time- independent point left when smooth surfaces are touched with the fingers. An attacker could gain the marks of third parties with the methods known from the field of criminology, make copies and start with this one overcoming attempt against the fingerprint recognition. Therefore, it is necessary for safety-related applications, to distinguish genuine fingerprints of copies. There are various methods of liveness detection, where the scanners capture certain characteristics such as pulse, blood circulation, thermal imaging or 3D depth model for this purpose.

Designs

We distinguish between the following types of fingerprint scanners:

• Resting fingerprint scanner. With them you have to drag your finger over a narrow scanning area. They are of poor quality, but also cheaper. The image of the finger is not as good as you may not be pulling the finger evenly on the scanner surface.
• Moving fingerprint scanner. With him, you put your finger on a surface and the scanner goes through under the surface. The moving is qualitatively better than the stationary fingerprint scanner, as it 's uniformly over the finger, but it is also more expensive.

Operation

There are optical ( infrared ) method, capacitive method and ultra -sonic methods. A simple liveness detection is possible with infrared light because it absorbs mostly dead tissue; oxygen saturation can also be measured capacitively. The fingerprint is usually taken as a whole (such as CCD camera or special components, the electrical charge between the measurement points (usually about 500dpi ) and the corresponding points of the finger measured ). There are also semi - automatic devices that are reliant on the scanned fingerprint is moved with almost uniform speed on the scanner line.