Modern Fingerprint Scanner

Modern Fingerprint Scanner Types

These days, cellphones mostly use capacitive, optical, and ultrasonic scanners. Each of them has pros and limitations, and they each have a different method of obtaining the picture.

First, each time, the user uses a different placement for their finger on the scanner. Additionally, depending on how hard the finger is placed on the scanner, the sensor may only be able to capture a very small portion of the finger. Additionally, minor cuts or other wounds could slightly change the scene as a whole. The smartphone is nonetheless successfully unlocked.

Example of a fingerprint

On the print, as you can see, some lines branch out, others are broken up, and yet others appear to be tiny islands. All of this can be represented schematically as follows:

The smartphone searches for these exact details, or minutiae, in each unique fingerprint. A unique defeatured one print called a minutia can have upwards of 70 minutiae.

Accordingly, the more times a user scans the same fingerprint while slightly shifting the finger to the sides and the greater the scan quality, the more information the smartphone collects for future analysis. Instead of prints, these distinctive characteristics are frequently what is kept.

The method by which they acquire a fingerprint for further processing is the key distinction between several types of fingerprint scanners:

For this, a capacitive scanner needs electricity.

Sound is used by the ultrasonic scanner.

Light is used by an optical scanner to capture images.

fingerprint scanner with capacitance

The lines of a fingerprint pattern are thinner than the many tiny electrically conducting plates that make up this scanner. These leaves create capacitors that can hold a certain charge.

Our bodies are capable of carrying current, thus when a finger touches the scanner’s surface, the capacitor’s charge changes. Additionally, the skin will occasionally come into contact with the scanner and occasionally not. After all, the ridges and depressions between them make up the papillary pattern of the print. As a result, it will produce varying capacitance capacities depending on where micro gaps between the scanner and the finger arise and where the print pattern directly contacts the scanner with its protrusions:

The smartphone analyses each cell and uses voltage to identify whether there was a groove (void) or protrusion near each capacitor and whether the skin was in touch with the scanner surface. This is how the print’s general composition is put together.

Why capacitive fingerprint scanners are advantageous

In terms of the full range of features, these scanners are the best. They are easy to produce, and the technology is well-established and relatively old. These scanners scan a three-dimensional object, taking into consideration the protrusions and indentations on the finger, rather than only taking a two-dimensional (flat) image.

High-speed capacitive scanners exist. The Touch ID scanner operates instantaneously on identical iPhones. The delay can’t even be felt. It is challenging to trick such scanners. The finger does not need to be particularly clean and dry because of the high level of stability. What is wrong with them, then? Why are these scanners only included on entry-level Android smartphones?

fingerprint scanner with optical

Scanners that use light operate entirely differently. When your finger touches the display, an optical scanner—a black-and-white camera buried behind the screen—takes a photo of your fingerprint. Therefore, it stands to reason that you must only touch that specific area of the screen, which is where the “hidden camera” lies.

Since these displays are translucent, they can accommodate any type of sensor behind them, including proximity/lighting sensors, selfie cameras, and finger scanners, so they can only be used to apply this technology on screens.

If backlighting weren’t required, the IPS matrices might be covered with something as they are translucent. The truth is that when electricity is applied to a dot (or pixel), it automatically emits light. Additionally, a pixel in an IPS display is essentially a cyclopedia through which outside light must travel.

Optical fingerprint scanners have advantages.

An optical scanner’s key benefit is that it may be positioned beneath the screen. However, the matrix resolution and glass transparency affect scanning quality and speed (coating quality, etc.).

An illustration of how an optical scanner works

The same lighting may be thought of as an optical scanner’s drawback. When the finger is not completely covering the sensor at night, the bright green light can be uncomfortable since it irritates the eyes.

The final flaw with optical scanners is how unpredictable they are when it comes to safety glasses. The stability and speed of fingerprint recognition can be impacted by the thickness and materials of protective coatings and eyewear.

Fingerprint Ultrasonic Scanner

Extremely high-frequency sound is used in ultrasonic fingerprint scanners. The user’s fingerprint is traced in depth using the waves. A receiver and a transmitter make up the entire set. As a result, some of the pulse pressure is absorbed and interest is reflected off the sensor when a user scans their finger across the glass. Each fingerprint has its own set of ridges, pores, and other details.



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