Instead, it relies on an ultrasonic distance sensor to detect a hand (or foot) waved in front of the door. An Arduino Leonardo runs the show, sounding a buzzer when the ultrasonic sensor is triggered.

A new ultrasonic fingerprint sensor measures 3-D image of your finger's surface and the tissue beneath it -- enhancing biometrics and information security for smartphones and other devices ...

Qualcomm has partnered with Katouzian to announce the world's first 3D ultrasonic in-display fingerprint sensor for mobile devices. Here's what you need to know!