Large Area Multi-Functional Under-Display Ultrasound Sensor: Fingerprint, Passive Stylus, Heart Rate, Force Sensing, Contact Gesture

This paper reports the commercialized large area (20×30mm
²
), multi-functional, thin form-factor, ultrasound fingerprint technology for under display integration in mobile devices. This technology consists of a thin piezoelectric polymer ultrasonic transceiver layer deposited on highly scalable 2D pixel array fabricated using low temperature polysilicon (LTPS) thin film transistors (TFT) circuitry on glass substrate. The technology not only delivers a high quality under display fingerprint scanner for biometric authentication, but also enables multiple value-added features including heart rate monitor, ultrasound based passive stylus, force sensor, and a contact gesture sensor. The large sensing area removes the requirement for accurate finger placement and therefore provides a better user experience for fingerprint authentication. Larger sensing area is also used for multi-finger authentication for enhanced security. Furthermore, the integrated multifunctional sensing enriches the user experience in the scenarios of gaming, education, health indicator monitoring etc.