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How optical fingerprint scanners work

Author: huifan   Time: 2019-09-05

The fingerprint scanner system has two basic tasks: one is to obtain an image of the finger, and the other is to determine whether the lines and troughs in the image match the lines and troughs in the previously scanned image.

 

There are several ways to get a person's fingerprint image. The most common methods nowadays are optical scanning and capacitive scanning. These two scanning methods work in a completely different way, but all get the same image. The following mainly talk about the working principle of the optical fingerprint scanner.

 

The core component of the optical scanner is the charge coupled device (CCD), which is identical to the closed sensor system used in digital cameras and cameras. A CCD is nothing more than a group of photodiodes (called photosensors) that generate electrical signals under the action of photons. Each photosensor records one pixel, a tiny dot representing the beam hitting that point. The light and dark pixels together form an image of a scanned scene (eg, a finger). Typically, there is an analog to digital converter in the scanner system that processes the analog electronic signals to produce a digital representation of the image.

 

HF4000 Optical USB Fingerpirnt Scanner

China optical fingerpirnt scanner manufacturer

 

It has below advantages:

Optical fingerpirnt scanner support USB Interface。

Optical fingerprint scanner support OS, Android, Linux System.

Optical fingerprint scanner has 17*19mm window area.

Optical fingerprint scanner image format support WSQ, BMP and etc.

 

The scanner is equipped with a light source, usually a set of light-emitting diodes, to illuminate the lines of the fingers. When you put your finger on the glass, the scanning process begins and the CCD camera takes a photo of the fingerprint. In fact, the CCD system produces an inverted image of the finger, the darker area represents more reflected light (the pattern of the finger), and the brighter area represents the smaller reflected light (the valley of the finger).

 

Before comparing fingerprints with stored data, the scanner processor ensures that the CCD captures a sharp image. It checks the average of the darkness of the pixel or the overall value of a small sample if the image is too dark or too bright overall. The scan will be abandoned. The scanner then adjusts the exposure time to allow more or less light to enter, once in the scan.

If the darkness is appropriate, the scanner system will continue to check the sharpness of the image (sharpness of the fingerprint scan). The processor will look at several lines that move vertically and horizontally across the image. If the line perpendicular to the texture consists of very dark pixels and very bright pixels, it means that the fingerprint image has good clarity.

 

When the processor finds that the image is clear and the exposure is correct, it continues to compare the captured fingerprint to the fingerprint on the file. We will soon understand this process, but first let's take a look at another major scanning technology, the capacitive fingerprint scanner.

 

For other systems, there are many advantages. E.g:
Forging physical features is much harder than forging identity cards.
It is impossible to guess the fingerprint pattern like guessing the password.
It won't lose fingerprints, irises or sounds like losing a card.
It don't forget my fingerprint like I forgot my password.
 capacitive fingerpirnt china manufacturer
A good way to make these security systems more reliable is to combine traditional authentication methods such as passwords (like ATMs with bank cards and PIN numbers) with biological analysis. But if you lose your credit card or inadvertently tell someone your secret PIN number, you can still apply for a new card or change your password. But if someone steals your fingerprint, the rest of your life is really unfortunate. You can't get a new fingerprint. Therefore, unless you are absolutely certain that all copies have been destroyed, you will no longer be able to use fingerprints as an identification form.
 

HF7000 Bluetooth USB Capacitive Fingerprint Scanner

 
 capacitive fingerpirnt china manufacturer
 
Despite some shortcomings, fingerprint scanners and biosecurity systems are still an excellent way to identify themselves. In the future, they are likely to become a necessary part of everyone's daily life, just like today's keys, ATM cards and passwords. In movies, automated fingerprint analyzers often overlay different fingerprint images together to find matching images. This is not a practical way to compare fingerprints. In fact, this approach rarely results in perfect image overlap, and stains can make the two images of the same fingerprint look very different. In addition, comparing and analyzing whether the entire fingerprint image is matched often wastes a lot of processing power, and it is also easier to steal fingerprint data.
 
The scanner system software uses highly sophisticated algorithms to identify and analyze these small patterns. The basic idea is to measure the relative position of the small patterns, which is the same as the way to identify a part of the sky by the relative position of the stars. A simple way to think about it is to look at the shape of the various small patterns as you draw a straight line between the small patterns. If two fingerprint images have three textured ends and two intersections that form the same shape on the same scale, they are likely to be the same fingerprint image. To get a match, the scanner system does not have to look at all the small patterns of the fingerprint image in the sample and record, just confirm that there are enough numbers of the same small pattern in the two fingerprint images. The exact number varies depending on the scanner program.
 
 

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