Expanding One-Handed Input Vocabulary for Smartphone Using In-Air Gesture of Index Finger Captured by Rear Camera

This paper presents an in-air gestural input method using the index finger of the hand gripping a smartphone. Our method allows the user to interact with the smartphone through a bending gesture and swiping gesture performed around the back of the device. Therefore, the user can interact with the smartphone without occluding the screen during one-handed use. Moreover, since our method uses the built-in rear camera, it can be easily introduced to off-the-shelf smartphones without additional sensors. To demonstrate our method, we built a prototype system using an off-the-shelf smartphone. In a pilot study to measure the gesture detection accuracy of our system, we obtained the total detection accuracy of 66.17%.