This Is How In-Display Fingerprint Sensors Actually Work

Rumors and prototypes were here for years, an in-display fingerprint reader is finally shipping in a major phone from a major company. Like the international Vivo X21 model marks the first place to use this technology, and as well as the first time it’s been a standard feature anywhere in the world.

In-display fingerprint scanners is such a technology which allow for smartphones with thin bezels and high screen-to-body ratios by integrating biometric authentication into the display itself.

How it works? For instance, you could just put the in-display fingerprint scanner on the back of the phone, as companies like Samsung, Google, and LG have done for years, but that’s less convenient in many situations. Where now comes to other Chinese manufacturers, this similar technology is used on their smartphones, too.

You might not be familiar with Vivo, and the US soccer team’s unexpected absence from the World Cup means that the company’s tie-in sponsorship blitz won’t penetrate America as much as might have been hoped. In other parts of the world, including India, it’s a huge brand with big shares of the Chinese and Indian smartphone markets in particular.

Vivo isn’t the only company selling phones with this technmology; Xiaomi and Huawei both have recently announced top-tier versions of their high-end flagships that use similar scanners. Where Vivo is, however, pushing this tech a lot more than anyone else.

The Synaptics prototype we saw at CES this year eventually got released in China as the X20 UD, a special edition version of the company’s last flagship, while the impressive Apex concept with a larger finger-scanning area found its place at MWC.

The X21, then, represents the first mainstream test run of the technology, using a sensor component from Goodix. It’s not a prototype or a limited edition, rather it’s just a phone. And it works perfectly well.

The Vivo X21 is a dream to unlock

When compared X21’s design, things are very difficult in this post-iPhone X world. Like most other Android powered flagships this year, the X21 has a notched display with a tall aspect ratio and a slight chin bezel at the bottom. The screen dimensions are also very similar to the OnePlus 6. And the screen isn’t only thing the X21 has in common with the OnePlus 6, both shares the presence of a glass back and lack wireless charging capabilities.

The X21 is using a midrange Qualcomm’s Snapdragon 660 processor, lower-end cameras, and micro-USB charging. Then, the OnePlus 6 along with almost every other 2018 Android phones – has a fingerprint sensor on the back.

The X21, by contrast, has no visible fingerprint sensor at all, at least until you pick it up. The in-display scanning technology only works with OLED screens, which it has to be able to light up your finger, and an LCD’s backlight would get in the way – which otherwise allows Vivo to pull off some heat tricks to highlight the sensor. When you pick it up, it automatically lights up a stylized fingerprint icon over the sensor area. If you wake it up by pressing the sleep button, that same icon will be brighter than the rest of the screen.

Once your finger is registered, you unlock the phone the same way you would on any other. For that, just hold your thumb down and wait. It’s a bit slower than more recent fingerprint scanners, to be sure. You can’t unlock the phone just by tapping the icon as if it were a button. Instead, you’ll have to wait half a second or so as a techy animation spreads across the screen.

iPhone 8 Plus (left) vs. Vivo X21 (right).

The X21 does also offer face unlocking, which won’t be as secure as Face ID but worked well enough for many. By default, face unlocking only triggers when you press the wake button, so it doesn’t override the fingerprint scanner if you just pick up the phone.

Overall, the scanner used in the Vivo X21 is a success. Would you like a hypothetical Android phone to have thin bezels? Yes. Would you prefer it to have fingerprint unlock over face unlock? Yes. Would you prefer that this fingerprint sensor was on the front of the phone, even a slightly slower one? Definitely.

Finally, thanks to The Verge to explain about Vivo X21’s in-display fingerprint scanning technology, in real-world use it’s remarkably good.

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