How does fingerprint scanners work?

     Nowadays fingerprint scanners are used in almost all mobile phones. It makes unlocking of mobile easier and faster. Everyday fingerprint technology is getting better and better.  Have you ever wondered how it is working? If so, then this is the right place. Let's get started.

     There are three types of fingerprint scanners;

• Optical Scanners
• Capacitive Scanners
• Ultrasonic Scanners

OPTICAL SCANNERS

     Optical fingerprint scanners are the oldest method of capturing and comparing the fingerprints. It captures an optical image and uses algorithms to detect a unique pattern in ridges and unique marks by analyzing the dark and light area.

     These scanners take high contrast images. It has a number of diodes per inch to capture the details very close and accurate. If we place our finger over the scanner, there won't be any light to capture the image. So led is used as the light source behind our finger. This design makes the component bulkier.

credits: slideshare

     One of the major drawbacks of the optical scanner is that it can be fooled very easily. It can capture a 2D image only. So if you have a high contrast image of the fingerprint, then it can be used to fool the scanner.

     Optical scanners are not much used in devices because of low security. Smartphones are coming out with the bezel-less display, so they use an optical fingerprint scanner inside the display. OnePlus 6T uses the optical fingerprint scanner as the in-display fingerprint scanner.

Capacitive Scanners

     As the name suggests, the main component used here is an electronic component ie; capacitors. This method uses the capacitor circuit to collect the details of the fingerprint. Capacitor store charges. The charge stored in the capacitor varies when the ridges touch the conductive plate which is placed above and is connected to the capacitor. The air gap in the fingerprint will leave the charge in the capacitor unchanged. An op-amp circuit is used to track the changes. Then the analog-to-digital circuit is used to store and analyze the data captured.

     It is not easy to fool this type of fingerprint scanner. Each material store different charges. A 2D image cannot be used to fool this scanner. The only security risk is by hardware or software hacking.

     Due to a large number of capacitors cost is high. To overcome this 'swipe' scanner is used which captures and refresh the data when the finger is swiped over it. Many users complain about its working that it fails to recognize most of the times.

     Nowadays tap and hold type scanners are used in most of the mobiles which use the same mechanism of capacitive scanners.

Ultrasonic Scanner

    An ultrasonic scanner is the latest fingerprint technology to enter the market. To capture the details in hardware it uses an ultrasonic transmitter and receiver. An ultrasonic pulse is transmitted against the finger. Some of the signals are absorbed and some are bounced back according to the ridges and pattern of the finger. These signals are sensed by the mechanical stress sensor. 

     This type of scanner produces a 3D image of the fingerprint and can be used for future detection. These scanners are very tough to be fooled. 

     

     This type of scanner is used in the latest Samsung Galaxy S10.

     So, that's all about the different types of fingerprint scanners and its working. Thanks for reading. For more technology posts stay connected. Subscribe to blog.