Evaluation of Easily Identifiable Dot Distance and Line Distance for Concave Lines Used in Braille Publications

: In addition to convex dots and lines, concave dots and lines are used for ruled lines in figures and graphs in Braille publications such as in books and textbooks. However, no academic basis for the ease of distinguishing concave dots and lines in Braille publications. Therefore, quantitative guidelines of easy-to-identify concave dots and lines for people with visual impairments are required. In this study, we focused on ruled lines consisting of concave dots and lines, often used in Braille publications, and evaluated dot and line distances to quantitatively determine the identification of concave ruled lines. We found that a narrower concave point interval, such as 2 mm, was more easily identified. Conversely, narrow concave lines, with a line distance of approximately 4–7 mm, were more difficult to identify.