Ultra Sonic Fingerprint scanner

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How ultrasonic fingerprint scanners work

Qualcomm’s 3D in-display ultrasonic fingerprint scanner is based on what used to be called Sense ID. Rather than existing photographic or capacitive-based fingerprint scanners, ultrasonic fingerprint scanners make use of very high-frequency ultrasonic sound. You can’t hear it, but these waves are used to map out the details of the user’s fingerprint. Fortunately, there’s no need to swipe, just touch the finger to the sensor like the top of the line capacitive fingerprint .

To actually capture the details of a fingerprint, the hardware consists of both a transmitter and a receiver. An ultrasonic pulse is transmitted against the finger that is placed over the scanner. Some of this pulse’s pressure is absorbed and some of it is bounced back to the sensor, depending upon the ridges, pores and other details that are unique to each fingerprint.

There isn’t a microphone listening out for these returning signals. Instead, a sensor that can detect mechanical stress is used to calculate the intensity of the returning ultrasonic pulse at different points on the scanner. Scanning for longer periods of time allows for additional depth data to be captured, resulting in a highly detailed 3D reproduction of the scanned fingerprint.

Qualcomm notes that there’s about a 250-millisecond latency for unlocking, roughly equivalent to capacitive fingerprint scanners. The sensor has about a 1 percent error rate, which again is pretty comparable to other scanners.

Of course, there’s still plenty to be done with this fingerprint data and keeping it secure is an equally important part of the system.

As will all biometric security systems, processing and security highly sensitive personal information security are key. Qualcomm’s processors are built with dedicated security tools, including Cryptographic Accelerators, Key Provisioning Security, and a Trusted Execution Environment. This ensures that the processing and storage of sensitive data are kept well away from malicious applications. Other Arm-based processors offer TrustZone hardware isolation for similar levels of protection.

Qualcomm’s setup is also designed to support the Fast Identity Online (FIDO) Alliance protocols, which can be used for online password-less authentication. FIDO does this without transferring any of the confidential fingerprint information to the cloud or through networks that could be compromised.

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Ultrasonic fingerprint scanners certainly have a number of advantages of existing capacitive implementations and given the prevalence of Qualcomm processors in mobile products.