Paper Abstract
Ten-finger surface typing promises a portable alternative to physical keyboards and touchscreens, making it well-suited for mobile scenarios, but remains challenging to balance sensing cost with input performance. We ask whether it can be enabled with two IMU rings, without relying on bulky wearables or continuous vision processing. We first present TypeRingIMU, which detects rapid ten-finger touches and identities with an F1-score of 98.4%, enabling efficient ten-finger typing on any flat surface using only two IMU rings. We further enhance it via optical-inertial fusion that opportunistically detects touch positions from IMU-triggered touch events, leveraging the front-facing camera already available on mobile devices, namely TypeRing. It removes fingering constraints, thus improving input naturalness and accuracy. Our method achieves 28.6 WPM input speed (63.5% of physical keyboards), with top-1 and top-12 accuracies of 88.5% and 98.1%, significantly outperforming current methods and demonstrating strong potential for efficient, convenient, and user-friendly mobile text input.