How does it work? | Fingerprint scanner

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2017-06-22 17:00:07

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How does it work? | Fingerprint scanner

Identification of the fingerprint — one of the most reliable ways to confirm the identity of the person. On the accuracy of this method is second only to the retinal scan and DNA analysis. Fingerprint — it's nothing like papillary patterns on the skin that are unique to each person and are formed in the fetus after 12 week simultaneously with the nervous system. Thus the patterns affect the genetic code of the child, the position of the fetus in the uterus, the nutrition of the mother during pregnancy, the environment and other random factors. In simple language, papillary patterns — the projections and recesses on the skin, forming a one of a kind figure. Even if the damage of the epidermis over time, the pattern is restored, it is only a matter of time and, of course, the extent of damage. How does the fingerprint scanner of a modern smartphone — this was in today's issue.

Any fingerprint scanner has two functions: to obtain the fingerprint image, and check its pattern matches other patterns in the database. Modern smartphones use optical scanners. They work on the same principle as the small digital cameras. The is done using a chip consisting of light-sensitive photodiodes and Autonomous source of light — matrix LEDs, which illuminates the patterns on the finger.

When exposed to light photodiodes produce electric charge, capturing individual pixel in the future picture. Depending on the amount of available light, the intensity of pixel color changes. A set of pixels of different intensities and forms on the scanner the fingerprint. Before you start to verify the fingerprint scanner checks the quality of the image, namely its brightness and clarity. If the picture is too bright or dark, adjusting exposure time of the scanner, and the process repeats again.

After the print is received, it is analyzed using special software. To determine the characteristics of papillary patterns ON uses complex algorithms. Only there are three types of patterns: arc, loop and a. Identifying the type of pattern, the scanner identificeret the line end patterns, for example, breaks and split — called minutiae. They are unique and enable a fingerprint to identify the owner. The scanner determines the position of the minutia relative to each other in every picture: he breaks the mark on a block of 9x9 pixels, each of which contains a certain number of minutia. The coordinates of the detected minutia and the orientation angles are recorded in the vector. Then identical blocks with scanner and images from the database are compared, and if the patterns are identical, the fingerprints belong to the same owner. It should be noted that the scanners do not analyze each line of the pattern: they find the same patterns only in a small number of blocks and it set the similarity.

There are two basic types of optical scanners. The first makes the desired area of the finger touching the scanner. This type is used in smartphones Apple, starting with iPhone 5s.

The second type of optical scanner involves holding your finger on it. He takes a series of shots and the software combines them together. This scanner has also found its application in Samsung Galaxy S5. But in later models it was replaced by the first type, which is more convenient, but more expensive because of the need for using a larger matrix.

A Common drawback of optical scanners is the susceptibility to contamination and scratches. In addition, this scanner can be fooled with the impression of the finger.

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