Design, implementation and evaluation of a dynamic layout of a vision based virtual keyboard

Abstract

A hands-free text entry system is needed when the typical text entry with hands is not feasible due to the user's physical disability or other limitations. Use of head/face tracking is one of the options to interact with virtual keyboards for hands-free text entry. Performance and usability impacts of the layout of the virtual keyboard used with such hands-free text entry systems have not been studied enough. This thesis introduced a novice layout design of virtual keyboard to be used with face/head input. The aim of this thesis was to check if the performance of the new and traditional layouts will be any different. The new layout was inspired by Fitts law. In the new layout, the size of each key was calculated dynamically in proportion to its distance from the last pressed key. The performance of the new layout was tested against the traditional static QWERTY layout in a user experiment with 16 able bodied participants where each user entered 8 text phrases of approximately 30 characters with each layout. Face tracking was used to control the cursor movement and a key from the physical keyboard was used to enter the selected character. Text entry speed was 5.03 and 5.14 words per minute, error rate was 0.83% and 1.28% for dynamic and static layouts, correspondently. Keystrokes per character was 1.05 with both layouts. Statistical analysis did not show significant differences in the performance of these two layouts. The subjective rating revealed that the participants liked both layouts equally but felt that the dynamic layout requires more mental effort and is less accurate than the static layout. Directions for further improvement of the dynamic layout are suggested as a future work.