Touchscreen-Based Haptic Information Access for Assisting Blind and Visually-Impaired Users: Perceptual Parameters and Design Guidelines

Touchscreen-based smart devices, such as smartphones and tablets, offer great promise for providing blind and visually-impaired (BVI) users with a means for accessing graphics non-visually. However, they also offer novel challenges as they were primarily developed for use as a visual interface. This paper studies key usability parameters governing accurate rendering of haptically-perceivable graphical materials. Three psychophysically-motivated usability studies, incorporating 46 BVI participants, were conducted that identified three key parameters for accurate rendering of vibrotactile lines. Results suggested that the best performance and greatest perceptual salience is obtained with vibrotactile feedback based on: (1) a minimum width of 1 mm for detecting lines, (2) a minimum gap of 4 mm for discriminating lines rendered parallel to each other, and (3) a minimum angular separation (i.e., cord length) of 4 mm for discriminating oriented lines. Findings provide foundational guidelines for converting/rendering visual graphical materials on touchscreen-based interfaces for supporting haptic/vibrotactile information access.