{Disarmed} What is the UD fingerprint scanner, the biometric technique of the new POCO F4

What is the UD fingerprint scanner, the biometric technique of the new POCO F4

The new POCO F4 , or Redmi K50 as it is still known, has not yet been seen but it already points in a couple of clear directions: the commitment to the latest innovations in 120W fast charging , new generation Snapdragon 898 processors and a novelty that dates back to the Mi 5, the UD (ultrasonic) fingerprint scanner.

This ultrasonic fingerprint system hidden under the screen seems to also be one of the novelties in biometrics of the Xiaomi 12 , as we discussed yesterday . And what is it about? We tell you in depth, going back to his first patents.

UD fingerprint scanner in the new POCO F4

Let's start from the information we have. The first leak targeting this feature, the UD finger scanner in the new POCO F4, comes from Weibo , from a major insider . Traditional media such as MyDrivers echoed the news, but it is still convenient to take it with a grain of salt .

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Let's talk about our footprints. You have to understand that at a microscopic level our fingerprint is not only unique, but impossible to imitate. Its orography makes up an imaginary country that is only in you: its ridges and valleys and sweaty density are not replicated in anyone else.

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So well, we know that fingerprints have unique details in each person and that fingerprint sensors can recreate an image using optical, capacitive or acoustic techniques. Now, what is an ultrasonic fingerprint scanner ? A scan using pulses of ultrasonic light that virtualizes our footprint, generating a 3D model on the fly and comparing it with previously recorded information.

A much more advanced methodology than capacitive reading , with lower resolution, or the technique using PMUT (micromachined piezoelectric ultrasonic transducers).

Fingerprint 1 1
Differences between an optical, capacitive and ultrasonic fingerprint scanner schematic model.

Finger scanning has obviously evolved over time. Early scanners used absorbed refraction on a glass prism - that prism could be a lens hidden on the surface shield of the screen. That is, every time you touch the screen with your fingerprint, the LED light illuminates the area and, depending on the result, the total reflection, whether or not the system is unlocked.

In short, the reader recognizes the amount of light absorbed, so to speak. This is what is known as contact reflection.

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With this simple trick you can solve possible blockages of the fingerprint sensor of your Xiaomi phone

As is evident, there are many other methodologies to map, analyze and virtualize the grooves of our fingerprints: by OCT or optical coherence tomography , for example, or by pulses of a certain frequency - we recommend reading this patent -, in the same way that thousands of wearables "read" our heart rate or blood oxygen saturation level.

Redmi K40 Pro

And what is special about the UD finger scanner? The reflection factor is different between glass and skin than between glass and air , so the transducers must be able to read the differences. And those differences are subtle but essential to fine-tune the reading.

As we already mentioned, this technique is based on reflected acoustic waves . The impedance mismatch between the emitted and the reflected quantity defines the shape and density of the barrier against which it collides. A barrier that in this case are the furrows of our skin.

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The best tricks for your Xiaomi with on-screen fingerprint sensor

This method has shown greater efficiency, a reduction in false positives that, ultimately, guarantee greater security in the biometric protection of our mobile.

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The news What is the UD fingerprint scanner, the biometric technique of the new POCO F4 was originally published on xiaomist by Isra Fdez .

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