LAS VEGAS—Dear old fingerprint sensors, your days are numbered.

At CES here, a Chinese vendor is showing off a smartphone built with a fingerprint reader that's hidden behind the display.

The Vivo smartphone is using an optical sensor from California-based Synaptics. The fingerprint reader itself is about the size of a small coin and works by scanning your finger through the tiny gaps found along the phone's pixels. PCMag tried it out, and came away impressed. Even though the sensor is hidden from view, it's still able to read your fingerprint in less than a second—0.7 seconds to be exact, Synaptics said.

The technology is production-ready, according to Synaptics, which said it's been talking to vendors across the smartphone industry. Like other new smartphone features, the fingerprint reader will first be offered in premium smartphones, in part because the scanner only works with OLED displays, at least for now.

But the company expects the tech to eventually become standard. Gone will be the days when smartphone vendors have to choose between placing the fingerprint reader in the home button, behind the phone, or ditching it altogether for facial ID as Apple has done.

Setting up the fingerprint reader is also easy. The process itself is no different from other smartphones, where you repeatedly let your phone scan your finger. The whole setup process took about a minute, and the phone read my fingerprint easily.

Interested buyers can expect the fingerprint reader to be featured in Vivo's next phone, which will be announced early this year.

In the future, Synaptics wants to make the phone's entire screen a fingerprint sensor. That way, you'll be able to place your fingers anywhere to unlock the phone. However, the technology is still a few years out.

Synaptics is not the first company to experiment with this, of course. Last year, Qualcomm unveiled an ultrasonic scanner that can read fingerprints through water, a device's screen, and even thin layers of aluminum. A year earlier, LG showed off similar concept technology.