OptiRing: Low-Resolution Optical Sensing for Subtle Thumb-to-Index Input

We present OptiRing, a ring-based wearable device that enables subtle single-handed micro-interactions using low-resolution camera-based sensing. We demonstrate that our approach can work with ultra-low image resolutions (e.g., 5x5 pixels), which is instrumental in addressing privacy concerns and reducing computational needs. Using a miniature camera, OptiRing supports thumb-to-index finger gestures, such as stateful pinch and left/right swipes, as well as continuous 1-DOF input. We present a modeling approach that uses heuristic-based methods to identify interactions and machine learning for input gating, generalizing recognition across users and sessions. We assess this technique's capabilities, accuracy, and limitations through a user study with 15 participants. OptiRing achieved 93.1% accuracy in gesture recognition, 99.8% accuracy for stateful pinch gestures, and a minimal number of false positives. Further, we validate OptiRing's ability to handle continuous 1D input in a Fitts' law study. We discuss these findings, the tradeoff between resolution and interaction accuracy, and the potential of this technology, which can help address challenges associated with optical sensing for input.