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Ultrasonic fingerprint reader for smartphones: what it is and how it works



Ultrasonic fingerprint reader for smartphones: what it is and how it works


For several years now, smartphones, whether Android or iOS, have offered several authentication methods for access. These are essential, given that all of our personal information is now within mobile devices. Furthermore, these authentication methods are used by Android as well as iOS to access payment services, digital identity and more. From here we understand how important it is that these authentication methods are secure.

Among the most recent authentication methods we find the ultrasonic fingerprint reader. The fingerprint reading is conceptually the authentication method arrived first on smartphones, and the ultrasonic one represents its latest evolution. To clarify immediately, the ultrasonic fingerprint reader corresponds to the component used to make the in-display fingerprint sensorsor those integrated under the smartphone display.

So let’s see what its functioning consists of, how it is widespread in the current market and what are the main differences compared to other authentication methods.

Index

Operation of an ultrasonic fingerprint reader

Ultrasonic fingerprint sensors are based on information decoding technology via ultrasound. Ultrasounds are sound waves that are found at frequencies that are not audible to the human ear. The ultrasound technique is used a lot in the medical and industrial sector, such as in ultrasound where ultrasounds are used to build two-dimensional images or three-dimensional of the investigated site.

In imaging technique, the ultrasound technique involves sending sound waves to the site to be mapped and analyzed as they are reflected or refracted by the same site being analyzed. On the basis of the reflected and refracted waves, a two-dimensional representation of the analyzed structure will be obtained. In the case of finger scanners, the structure to be analyzed corresponds to fingerprint profile.

Therefore such sensors provide a transmitter and a receiver to decode the ultrasounds under examination. Clearly, some time is required for the emitted ultrasounds to be reflected and analyzed. Qualcomm, which is one of the most active companies in the production of these components, quantifies a delay of about 250 ms between the sending of the ultrasonic pulse and the response of the sensor.

It should be emphasized that, in the case of ultrasonic fingerprint readers, the mapping of the structure, or the profile of the users’ finger, can take place in three dimensions. This adds a significant degree of safety to the technology used.

Smartphone with ultrasonic fingerprint reader

As just mentioned, Qualcomm is one of the companies that has worked the most on the development of ultrasonic fingerprint sensors. The US company made one of the first ultrasonic sensors for the consumer market in 2018, compatible with the Snapdragon 855 processor.

The first models with ultrasonic fingerprint sensor to arrive on the market are the Galaxy S10 And S10 Plus by Samsung. These were followed by the models of the Galaxy S20 series, while with the Galaxy S21 series came the second generation of ultrasonic fingerprint sensors made by Qualcomm. This would have increased the speed of fingerprint recognition, which for some users was not particularly fast in previous models. Even on the current top of the range, the Galaxy S22, we find this type of sensor.

Among the latest innovations with ultrasonic fingerprint sensor we find the new Vivo X80 Pro. The device of the Chinese company, just presented in Europe, has a new generation ultrasonic sensor with a larger surface. These improvements should lead to greater speed and accuracy of the sensor itself.

The other smartphone manufacturers seem not to want to embrace the path of the ultrasonic fingerprint sensor. Some of these, the majority, opt for fingerprint sensors in the display opticiansthat is, based on a two-dimensional mapping of the footprint. Among the most recent models with this technology we find for example the Google Pixel 6. The sensors capacitivethat is, those that cannot be integrated under the display, we find them on older smartphone models or in the medium and medium-low range.

Safety

Ultrasonic fingerprint sensors are a great advantage for those who intend to have a certain degree of safety and no rear / side fingerprint sensor on your smartphone. The safety of ultrasonic sensors is higher than optical ones. The mapping of the footprint takes place in three dimensions, while with the optical ones there is a two-dimensional structure.

Ultrasonic sensors typically have a thickness of just 0.15mm and can scan up to 800 µm of glass and up to 650 µm of aluminum. This makes them fully compatible with the integration under the display of smartphones.

The technical conformation of an ultrasonic sensor also implies one greater resistance to external agents: it is difficult to tamper with, as well as it is resistant to sweat and humidity, factors that can be frequent in daily use on smartphones.

From the point of view of security, the ultrasonic solutions that we find for the smartphone market, such as the Qualcomm sensors that we find purely in the Samsung models, provide cryptography for information processing. Among these are highly personal ones, such as the biometric structure of the fingerprint.

The ultrasonic sensors developed by Samsung also offer support to online authentication without a password through the Fast Identity Online (FIDO) Alliance protocol. This constitutes a further aspect in favor of this sensor technology, compared to the optical ones that we find on the smartphone market.