Expanding One-Handed Touch Input Vocabulary Using Index Finger on and Above Back-of-Device

This paper presents an input method to expand one-handed touch input vocabulary for smartphones using the index finger. To this end, our method combines thumb-based touch input and postures or gestures of the index finger on and above back-of-device. These postures and gestures are detected by three-dimensional directions or movements of the index finger. To enable this detection, users wear a ring-like device on the index finger. Moreover, our method includes a one-handed use detection system. Using this system, our method provides common input vocabulary for two-handed use and expands input vocabulary for one-handed use.