At MWC Shanghai, Qualcomm announced its latest ultrasonic fingerprint solution, with the new highlights being its integration underneath OLED displays (up to 1.2mm-thick), as well as working fine even when the device is immersed in water
Ultrasonic fingerprint sensor
Let’s take a closer look at how this technology works and what sort of advantages it has to offer over current fingerprint scanning technologies on the market.
Rather than existing photographic or capacitive based fingerprint scanners, Qualcomm’s Sense ID makes use of ultrasonic sound, as the name implies, in order 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 scanners.
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 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
This is considerably different to even the best capacitive fingerprint scanners on the market at the moment, which are only able to reproduce 2D images. 3D details are much more difficult to forge or fool than 2D versions of the technology, potentially making the ultrasonic system much more secure.
Another added perk of this ultrasonic fingerprint scanner technology is that it allows the fingerprint scanner to still operate through thin materials, such as a smartphone case built from glass, aluminium or plastic. Therefore, the scanner can be embedded under the case, allowing for a more discrete look. Additionally, there’s less chance of damaging the sensor or exposing it to external tampering, and sweat or moisture on the finger won’t interfere with the scanning process either.
The demo started off with a familiar fingerprint registration process, except I had to place my finger on a marked area on the screen, which was just above the old fingerprint button. Once done, I was able to unlock the phone by touching that same spot using my registered finger; and just to be sure, I tried with my other fingers which fortunately failed to unlock the device.
Vivo smartphone with under display fingerprint sensor
While the solution seemed to work as advertised, I found the fingerprint recognition speed to be noticeably slower -- about one second between first touch and entering home screen -- than the near-instantaneous unlock that I'm used to on most recent smartphones. I was also slightly disappointed by how small the recognition area was. That said, Vivo's demonstrators told me that in theory, the same sensing technology could be applied across the entire screen, but that would significantly increase production cost; instead, Vivo might eventually cover just the bottom half of the screen, which would still be better than what the demo offered.
In another demo, the company applied the same ultrasonic tech to a spot on the back of the phone's metallic body, thus allowing the phone to be unlocked even when placed in water. Since this unlock method could be associated with the camera app, this could come in handy for those moments when you want to take underwater photos or videos while in shallow water. But of course, other companies have solved this use case with a physical shutter button (Sony) or squeeze detection (HTC).
The Vivo reps couldn't provide a timeline as to when we'll start seeing this tech on their devices, but according to Qualcomm, its solution will come in two waves. "Qualcomm Fingerprint Sensors for Glass and Metal" can be integrated into devices powered by Snapdragon 660 and 630, and it'll start shipping to OEMs this month. As for the more advanced "Qualcomm Fingerprint Sensors for Display," it'll work with future Snapdragon platforms as well as non-Snapdragon platforms, and it'll only start commercial sampling in Q4 this year.