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New fingerprint sensor could expand your phone's display

By hiding the Synaptics optical sensor beneath the display, phone makers could get rid of home buttons and lengthen screens by a half inch.

Would you rather see pixels than a big circular button on your phone's fingerprint sensor?

Sarah Tew/CNET

A new fingerprint sensor has just arrived that could make your next phone's screen significantly bigger without making the phone itself larger.

Touch-tech expert Synaptics announced the new fingerprint sensor on Tuesday, an optical model that fits under a phone screen's cover glass. That contrasts with today's capacitive models that need dedicated territory, like the circular home button at the bottom of Apple iPhones.

The company's first-generation models still need an area that can't be part of the display. But phase two for the company will embed the fingerprint sensor under the display -- technology the company will demonstrate at the massive CES show in Las Vegas in January.

Getting rid of the dedicated home button on an iPhone screen could make it about a half inch longer. That's a lot of space for a small device -- though it might be harder to figure out where exactly to place your thumb over the 10x4mm sensor.

Some Android phones already use an on-screen home button that doesn't take up any physical space, but that doesn't work with today's fingerprint sensors. Google's flagship Pixel phone puts the fingerprint sensor on the back of the phone, an approach that works when fishing for your phone in your pocket but that's awkward when it's resting face-up on your desk.

Samsung, though, puts its home screen and fingerprint unlock button on the front of its flagship phones, and the upcoming Galaxy S8 is rumored to have an under-glass fingerprint reader.

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Spoof-proof?

Synaptics' sensor is designed to ensure nobody will unlock your phone with a fake fingertip. Specifically, the company's SentryPoint technology uses "liveness" detection to make sure it's looking at a real finger. One part of the technology, called PurePrint, uses artificial intelligence technology to block spoofing attempts.

Fake fingers may sound more like a James Bond movie than reality, but it's a serious concern -- especially if you're among the 1 million people whose fingerprint data was stolen in a 2015 hack attack on the US government's Office of Personnel Management.

Synaptics says its optical fingerprint reader isn't fooled by fakes like this cast made with wood glue and coated with graphite.

Synaptics

And making a fake finger isn't necessarily rocket science. You can do it with ordinary materials like scanners, printers and Play-Doh, Synaptics warns in a look at the technology (PDF).

It's not clear how much the optical sensors will cost, but Synaptics said it'll be competitive with old-style capacitive fingerprint sensors. The company is a major player for sensors, supplying Samsung, Lenovo, Asus, HP and others.

Another advantage of the optical approach is that it'll work better when wet. A sensor fully covered by glass is also protected from electrostatic discharge -- the electric zap you sometimes get when touching a doorknob after walking across a carpet.

First published December 13, 11:45 a.m. PT.
Update, 12:34 p.m.: Adds further details on optical fingerprint readers.