| This thesis explores eyes-free text entry solutions for mobile devices. For devices with physical buttons, a wheel-based technique is proposed, with a focus on visually impaired users. The technique, called LetterScroll , uses a mouse wheel to manoeuvre a cursor across a linear sequence of characters. Text input is accompanied by speech feedback. Similarly for touch sensitive devices, a stroke-based input technique is presented. Entry progresses by inking Graffiti strokes with a finger. The strokes are accompanied by speech and non-speech sounds. Three user studies assess the value of both techniques. In particular, various aspects of the interaction are measured such as speed and accuracy. The results suggest that eyes-free text entry is possible on both classes of hardware. Although throughput rates for LetterScroll are not as high as expected, they are within the range of those found for visually impaired persons. The stroke-based technique was able to reach entry rates equal to those found for walk-up Graffiti use (7.0 wpm). Results from this evaluation were used to develop an enhanced version of the technique that incorporated an error correction algorithm. A follow up study found entry rates averaging 10.0 wpm with an overall accuracy of 95.7%. |
