How fingerprint scanner work: Capacitive, Optical and Ultrasonic Method

How fingerprint scanner work: Capacitive, Optical and Ultrasonic Method

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Optical Scanner
Optical Scanner

How fingerprint scanner work: Capacitive, Optical and Ultrasonic Method: With the increase in the demand for security of gadgets, the system of fingerprint security has also increased by a great extent. Fingerprint scanners have become common in smartphones and gadgets and here we have explained the working of the latest scanners and the differences between each one of them.

How fingerprint scanner work: Capacitive, Optical and Ultrasonic Method

Optical Scanner

This is one of the oldest methods of fingerprint scanning. Optical scanners captures an optical image of the finger and then with the help of algorithms it identifies the unique features on the surface, like the ridges, marks or curves, by examining the lightest and darkest areas.

Optical Scanner
Optical Scanner

These scanners work like a camera and therefore they have finite resolution and the higher the resolution the better would be its performance. But unlike regular cameras, these sensors capture higher contrast images and to get a detailed picture they have high diodes per inch. Optical Scanner also has its own LED which works as a flash to illuminate the image.

The disadvantage of using the Optical Scanner as the fingerprint sensor is, it has a bulky design which is not suitable for the slim smartphones, it only captures 2D pictures and therefore it can easily be fooled. Therefore, Optical Scanner does not provide a superior level security and are hence used less in today’s time.

Capacitive Scanners

As the name suggests, this scanner uses capacitor and it is one of the most widely used fingerprint scanner of today’s time. The Capacitive Scanner uses a range of small capacitor circuit to collect information about a fingerprint. When these capacitors are connected to conductive plates on the surface of the scanner they track the details of the fingerprint. The capacitors store electrical charge and when the finger is placed on the surface this stored electric charge changes slightly. This change is traced by an op-amp integrator circuit and then these tracings are recorded by an analogue-to-digital converter.

Capacitive Scanners
Capacitive Scanners

After the fingerprint is captured, its unique attributes are saved for comparison. The best thing about this scanner is that it cannot be fooled easily with a replicated image or through prosthetics because different materials will result in different changes in charge at the capacitor.

As was the case with the Optical Scanner same is with this one, a large number of capacitors will result in a more finite image of the fingerprint and therefore better security. But the disadvantage is that these capacitors increase the price of the scanner.

Ultrasonic Scanner

Ultrasonic scanners are the most latest scanning technology and one of the most reliable scanners of the recent time. These were first introduced in the Le Max Pro smartphone. This hardware consists of an ultrasonic transmitter and a receiver. When a finger is placed on the scanner an ultrasonic pulse is transmitted against it. Some of this pulse is absorbed while the rest of it bounces back to the sensor as a result of ridges, pores and other details of the finger.

A sensor detects the mechanical stress and it calculates the intensity of the returning pulse. This scanner produces a 3D result of the fingerprint which cannot be replicated easily and therefore this is the safest means of scanning.