Virtual keyboard for head mounted display-based wearable devices

Wearable devices eliminate the need of physically taking out a mobile device before operating on it and are emerging as the next wave of mobile systems. Head-mounted display (HMD) is a key building block of wearable devices, and offers users immediate access to relevant information in a glance. However, most existing user input mechanisms accompanying HMDs are designed for interactive information exploration rather than for extended text entry. This paper describes the design, implementation and evaluation of a text input system for HMDs called Air Typing, which requires only a standard camera and is shown to be comparable in effectiveness to single-hand text input on tablet computers in a lab setting. Air Typing features a novel two-level virtual keyword layout, which substantially improves the typing speed by cutting down unnecessary hand movements during typing and greatly simplifies the associated image processing task by doing away with fine-grained matching between fingertips and keys. The current Air Typing prototype incorporates an OpenCV-based virtual key press detection algorithm that runs on the featured two-level virtual keyboard. In our tests, an experienced user´s typing speeds of one-hand text input and of two-hand text input under Air Typing are 13 and 15 words per minute (WPM), respectively.