A comparative evaluation of sliding contact tactile systems displaying braille and raised print.

This article focuses on evaluating the optimal inter-character spacing (ICS) for embossed characters on a sliding contact tactile display designed for blind and visually impaired (BVI) users. Two discs with ICS of 6.5 mm and 8 mm, each embossed with 40 braille characters on one side and raised print on the other, were tested by visually impaired participants reading MNREAD sentences. Results showed that an ICS of 8 mm enabled accurate braille reading with a low error rate (6.4%) and supported both Grade 1 and Grade 2 braille, while the smaller 6.5 mm spacing resulted in higher errors. However, raised print reading was less accurate at both spacings, indicating that larger spacing (around 10 mm) and greater character height are necessary for tactile perception of raised print. These findings contribute to the design of cost-effective, single-actuator sliding contact tactile displays that balance accuracy and device size for BVI users.