Hands-free multi-type character text entry in virtual reality

Multi-type characters, including uppercase and lowercase letters, symbols, and numbers, are essential in text entry activities. Although multi-type characters are used in passwords, instant messages, and document composition, there has been limited exploration of multi-character text entry for virtual reality head-mounted displays (VR HMDs). Typically, multi-type character entry requires four kinds of keyboards between which users need to switch. In this research, we explore hands-free approaches for rapid multi-type character entry. Our work explores two efficient and usable hands-free approaches for character selection: eye blinks and dwell. To enable quick switching between keyboards, we leverage the usability and efficiency of continuous head motions in the form of cross-based activation. In a pilot study, we explored the usability and efficiency of four locations of the switch keys, the two hands-free selection mechanisms, and crossing-based switching. In the main experiment, we evaluated four user-inspired layouts designed according to the findings from the pilot study. Results show that both blinking and dwell can work well with crossing-based switching and could lead to a relatively fast text entry rate (5.64 words-per-minute (WPM) with blinking and 5.42 WPM with dwell) with low errors (lower than 3% not corrected error rate (NCER)) for complex 8-digit passwords with upper/lowercase letters, symbols, and numbers. For sentences derived from the Brown Corpus, participants can reach 8.48 WPM with blinking and 7.78 WPM with dwell. Overall, as a first exploration, our results show that it is usable and efficient to perform hands-free text entry in VR using either eye blinks or dwell for character selection and crossing for mode switching.