Ever wondered how a fingerprint scanner works?
- Abhishek
- Dec 19, 2017
- 2 min read
A smartphone's fingerprint scanner - THE MOST USED FINGERPRINT SCANNER.. Isn't it ? But how does it identifies you and prevent others from taking a sneak peak of your personal information?
Here's how a fingerprint scanner works -
The scanning process begins at the very moment when your finger is placed on the scanner . As the finger is placed ,it is illuminated by a bright beam of light generally by the use of an array of light emitting diodes and then a CCD (charge coupled device) camera takes a picture. It is the same light sensor system used in digital cameras and camcorders.
This system actually generates an inverted image with darker areas representing more reflected light (the ridges of the finger) and lighter areas representing less reflected light (the valleys between the ridges).
But before the processor compares the generated image to the saved one ,it makes sure that a nice and crisp image is captured by a system of check which checks its average pixel darkness. If the generated image is rejected ,the scanner adjusts the exposure time to let in more or less light, and then tries the scan again. Once the image generated is crisp and clear ,the scanner processor compares the captured fingerprint with fingerprints on file and acts accordingly.
BUT WE DON'T OBSERVE ANY KIND OF ILLUMINATION AS YOU MENTIONED, WHEN WE USE THE FINGERPRINT SCANNER ON OUR SMARTPHONES AND SEVERAL OTHER DEVICES TOO......
You are indeed correct my friend because the fingerprint scanner present in most of the portable devices are CAPACITIVE FINGERPRINT SCANNERS.
Till now you were reading about an OPTICAL FINGERPRINT SCANNER..
So,what's the difference?
A capacitive scanner also generates an image of the ridges and valleys that make up a fingerprint. However ,unlike the optical fingerprint scanner they use electrical current for the same.
Instead of creating a traditional image of a fingerprint, capacitive fingerprint scanners use arrays of tiny capacitor circuits to collect data about a fingerprint. As capacitors can store electrical charge, connecting them up to conductive plates on the surface of the scanner allows them to be used to track the details of a fingerprint. The charge stored in the capacitor will be changed slightly when a finger’s ridge is placed over the conductive plates, while an air gap will leave the charge at the capacitor relatively unchanged. An op-amp integrator circuit is used to track these changes, which can then be recorded by an analogue-to-digital converter and then this digital data can be analysed to look for distinctive and unique fingerprint attributes.
The best part about this type of fingerprint scanner is that it is much tougher to fool than an optical scanner.The results can’t be replicated with an image and thus it is tough as hell to fool them.The only way they can be fooled is by some sort of software or hardware hacking..
However they are also pricey as compared to the optical ones because of the complex circuit it uses.
That's all for this article if you want me to publish an article about a topic you want, you can send me your tech topics of interest through the contact section of my page .
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