How fingerprint scanner works: optical, Capacitive & ultrasonic

The fingerprint scanner on the phone is no longer a new technology in the mobile world, but it has become very old. Earlier, where we used the PIN password pattern for security in the phone, most mobile users use the fingerprint sensor to unlock the lock.

Due to the fingerprint touch sensor, the lock of the phone opens in a few moments.

You must have thought at some time when we use our finger, the phone is unlocked and when we use the finger of another, the phone is not unlocked. How does this happen?

I’ll tell you how this happens but before that let’s understand the structure of our fingers.

There are 2 main things that make patterns in our fingers one is ridges and another one is valleys.

Ridges are the Bulge that you see in your fingers and valleys are the canyons due to these ridges.

As you can see in this image the dark part of this sample fingerprint are ridges and the white part of the fingerprint are valleys.

Now, let’s see the types of fingerprint scanners. Which will make it easier to understand how the fingerprint sensor works.

Fingerprint touch sensors are of generally of three types, which are as follows.

  1. Optical Fingerprint Scanner
  2. Capacitive Fingerprint Scanner
  3. Ultrasonic Fingerprint Scanner

Table of Contents

Optical fingerprint scanner:

Optical Fingerprint sensor  

Source: ResearchGate

This technique is although the oldest kind of fingerprint scanner. In this technique, there are light sensors in the scanner that takes photographs of your finger from different angles and stores as a map in its database.

Now, when you touch the scanner next time, it again takes the photograph and tries to match with the map in the database. And if it matches, your device is unlocked.

It does not verify if the goods do not come to comprehend with the fingerprint saved earlier.

Fingerprint verification by an optical fingerprint sensor takes a few seconds and this technology is old technology. This technology is not used in Mobiles.

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Capacitive Fingerprint Scanner

This type of touch sensor is used in phones nowadays. This is a quite advanced technology in which capacitive plates and capacitors are used instead of image sensors.

In this fingerprint scanning technology, there are capacitors installed on the scanner. When you place your finger on the sensor capacitors of the part of the finger that touches the sensor is activated. And this way it creates a map of the finger from different angles.

Now, rest process is pretty similar to the optical scanners, next time when you place your fingers it matches with the fingerprint map. If the match meets then you are in and if doesn’t meet then you’re out.

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Such fingerprint sensors have a large number of capacitors installed for better performance. So that it has good performance and reduces the time to unlock the phone, that is, the phone is unlocked in a few moments. This also increases the security of the phone.

Ultrasonic Fingerprint Scanner:

This is the latest technology in the fingerprint scanning technology and is used in very few flagship smartphones.

This technology was first introduced in Le Max Pro smartphone. It is a 3D fingerprint technology. This technology is made by Qualcomm Snapdragon Company.

In this technology, the hardware consists of an ultrasonic transmitter and receiver. The Ultrasonic transmitter sends some signal when you place your finger on the scanner. Which touches your finger, some of which is left on the finger and the remaining Signal is returned and the receiver receives the returned signal and creates a 3D image from it. In this way, you have your fingerprint store and verification in your mobile and after that, your phone is unlocked.


Earlier in the past, we used to have patterns, PIN, and password for security locks. These are still in use but are a little bit slow. new security locks like fingerprint sensors, face lock, voice lock are replacing this traditional locking system. New technologies are not only secure but also faster than traditional security locks.

In Smartphones, capacitive fingerprint sensors are the most popular. Ultrasonic sensors for on-screen fingerprint lock system are still in the development period.

Ultrasonic sensors are expensive and that’s why we see this technology in flagship phones. Was it helpful? Tell me in comments with Yes or No.