HYBRID GAZE TRACKING SYSTEM

Various implementations disclosed herein include devices, systems, and methods that perform gaze tracking using combinations of ultrasound and imaging data. Some implementations detect a first attribute of an eye using imaging measurements in a first image of the eye, and a first location associated with the first attribute is determined in a 3D coordinate system based on depth information. A second attribute of the eye is detected based on depth information from ultrasound based measurements of the eye, and a second location associated with the second attribute is determined in the 3D coordinate system based on the depth information and a 3D model of a portion of the eye. A gaze direction in the 3D coordinate system is determined based on the first location and the second location. In some implementations. user characteristics are identified (e.g., authentication) using ultrasonic biometric characteristics with imaging biometrics.