How an ultrasonic fingerprint scanner works

This is not the first time Samsung has adopted an in-screen ultrasonic fingerprint scanner in its smartphones. Of course, in general, the technology is cool and it needs to be developed, but at this stage the company has too many haters because of this decision. The main criticism is that the scanner is very slow. Other manufacturers have found a way to make it much faster and more reliable. Personally, I expect that something will change in the new generation of the Galaxy S line, and the company will either accelerate the existing scanner or start using a new one. In the meantime, let's figure out what is the peculiarity of ultrasonic fingerprint scanning technology, because questions still remain.

On-screen fingerprint scanner

Such a fingerprint scanner raises some questions.

When did the ultrasonic fingerprint scanner appear?

Aside from the path that ultrasound fingerprint scanning technology has gone through in labs, it began in December 2018. At this time, Qualcomm announced its 3D in-screen fingerprint scanner. It could work with devices based on Snapdragon 855. Manufacturers themselves decided whether to use it or not, but like any other technology, it had its pros and cons.

How the in-screen fingerprint scanner works

Qualcomm's 3D Ultrasonic Fingerprint Scanner is based on what was formerly called Sense ID. Unlike optical and capacitive fingerprint scanners, the solution, which was new at that time, was based on ultrasound. These are waves of sound that are beyond the reach of human hearing. Therefore, we do not hear them, but in many cases they help. In this case, they allow you to build a detailed picture of a person's finger drawing. You just need to touch the phone screen and it will unlock.

To capture the details of a fingerprint, the hardware consists of a transmitter and a receiver. An ultrasonic pulse is transmitted to the finger, which is located above the scanner. Some of this pulse is absorbed and some is reflected back to the sensor, depending on the protrusions, pores and other details unique to each person.

How an ultrasonic fingerprint scanner works

Fingerprints are unique to each person. No two are the same.

These return signals are used to calculate the intensity of the reflected ultrasound pulse at different points in the scanner. Scanning for longer periods of time allows for the collection of additional depth data, resulting in highly detailed 3D finger-drawing.

There is no recent information on technology updates and the time it takes to unlock, but Qualcomm initially said the latency was 250 milliseconds and the error rate was 1 percent. On paper, this is comparable to other types of scanners, but in practice, the response speed of an ultrasound scanner is much slower. Considering how we are used to the high-speed performance of smartphones, the difference is really felt – especially in top-end devices.

Benefits of an ultrasonic fingerprint scanner

As we have already determined, ultrasonic technology works in a completely different way than capacitive technology. The first one can build a three-dimensional model of a finger, and the second one only two-dimensional. Naturally, the 3D model is much more difficult to fake and trick the scanning system. When compared with an optical scanner, the advantage will also be on the side of the ultrasonic one.


At the moment, there are only two normal ways to identify a user: fingerprint and face scan. The rest is self-indulgence.

If the display has a built-in fingerprint reader, this is not necessarily an ultrasonic option. For example, the OnePlus 6T and Huawei Mate 20 Pro use optical scanner technology.

An important feature of an ultrasound scanner from a manufacturer's perspective is that it works great through thin materials like glass, plastic or even aluminum. The sensor is only 0.15 mm thick and can “punch” up to 800 µm glass and 650 µm aluminum. Thus, the scanner can be built into many more parts of the smartphone body, while remaining efficient. This is why sweat and moisture on your finger does not interfere with the scanning process, as is the case with capacitive or optical sensors.

Such a sensor also has additional features that can also be used if desired. For example, it allows you to track the parameters of a person's health, including heart rate and pulse.

Pulse on smartphone

An ultrasound scanner can even detect a person's pulse. And not only.

Of course, scanning a finger with any sensor is only half the battle. In addition, complex algorithms for information processing and additional degrees of protection must be built into the smartphone itself, which will not allow hacking the system and gaining access to the user's personal data. They even use cryptographic accelerators and a hardware isolation system.

What's wrong with an ultrasonic fingerprint scanner

Considering that modern people unlock their smartphone up to a hundred times a day (they simply do not notice it), the fingerprint scanner should work quickly and identify its owner from the first time, without confusing him with someone else. That is why the fingerprint scanner must be fast, and this is currently the main problem at the current stage of development of ultrasound scanning technology.

Finger scanner

In the future, we will have cool new user identification systems, but the fingerprint will forever remain in our hearts.

Even the Samsung Galaxy S20 Ultra, which I used for a long time, often annoyed me with its slowness and the fact that sometimes I had to put my finger twice. Scanning a face with a mask during the quarantine period worked so-so, so it was the finger that had to be scanned. If it worked faster, everything would be fine, but so far it is clearly not finalizing.

This is why many people – including me – want Samsung to move away from this in the next generation. Let it be used and refined in other smartphones, and leave the flagships with their speed. Well, or just increase it for an ultrasound scanner, but I don't believe in the possibility of this yet.

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