There are three common types of fingerprint sensors on smartphones.
1. Optical scanner
2. Capacitive scanner
3. Ultrasonic scanner
Today I will discuss how these three scanners work.
Optical scanner
This fingerprint scanner is the oldest method of fingerprint read and recognition. These scanners basically create an optical image or photograph of your finger. After creating the image, this scanner detects the unique features at your fingertips with its own algorithm. Such as the special curves, folds, lines, etc. of your fingers. Basically these are detected by comparing the light and dark areas of the captured image. Like smartphone cameras, these scanners can have their own resolutions, and just like smartphone cameras, the higher the resolution, the more detailed the image will be, and the faster the fingerprint recognition will be, the faster and more secure it will be.
The second time you place your finger on the fingerprint scanner, the scanner matches your fingerprint with the previously created optical image and lets you unlock your phone only if it is successful to match. But these scanners have some drawbacks. First, since this scanner only works with an optical image of your fingerprint and unlocks your phone depending on the image, it is much easier to fool these scanners than other scanners. If you can get a perfect photograph that is small in your fingerprint, it is possible to make a fool of this scanner by using it. So these fingerprint scanners are no longer used in high end and mid end smartphones. Nowadays you will see this type of scanner only in very low priced smartphones. Let us know,
Capacitive scanner
You will find these capacitive scanners in a lot of high end or flagship smartphones starting from upper midrange smartphones. The difference with an optical scanner is that this scanner works on a small electric component called a capacitor. Instead of creating a traditional image of your fingerprint, these fingerprint scanners use some small capacitor circuits to collect Anaf data about your fingerprint. Since capacitors can store electric charge, it is possible to collect the details of your fingerprint by placing these capacitors on the conductive plate on the surface of the scanner. When your finger is placed on top of this scanner, the charges on this capacitor will change slightly. And the air gap between your fingerprint and the scanner will cause the charges to fall almost unchanged on these capacitors. These changes are then tracked using an integrator circuit and saved using an analog-digital converter. These saved data are then analyzed to extract the unique features and attributes of the fingerprint which are then saved again for further reliable fingerprint scanning. The benefit of this is that it is much harder to fool this saved fingerprint pattern with an image as it will create another type of charge on the capacitor of a different material scanner that will never match the previously saved pattern. In this case, the more capacitors there are in the scanner, the more accurately the fingerprint can be recorded and the faster and more responsive the fingerprint recognition will be. Since these scanners have to hold thousands of tiny capacitors, these scanners are a little more expensive than the optical scanners made. And that is why these fingerprint scanners are not used in cheap smartphones.
Ultrasonic scanner
This technology is new to fingerprint scanning and much more advanced than others. This fingerprint scanner was first used on (Leeco Le Max Pro smartphones) Qualcomm and its Sense ID technology are also a major design element of this fingerprint scanner. Fingerprint capture and recognition of these scanners is quite simple and straight forward. This scanner basically uses an ultrasonic transmitter and a receiver to scan fingerprints. The finger that is place on top of this scanner transmits a kind of ultrasonic pulse as opposed to that finger or fingerprint. Some of these pulses is absorbed by the fingers and some this sent back to the scanner depending on the curves, folds and depth of the lines of your fingers. Those that this sent back to receiveing by the receiver.
By receiving these returned pulses, the scanner receives a fairly accurate amount of data at your fingertips, which it then uses to recognize fingerprints again. These data are unique to each finger. And since this scanner is also generating data based on the depth of the fingerprint, what it finally gets is a 3D scanning that is almost accurate of your fingerprint. As a result, it is almost impossible to fool these scanners.
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