A Camera-Aided Legibility Assessment Protocol of Displays for Enhanced Human-Computer Interaction

Legible text and graphics presented on computer displays and projection screens are essential for benefit of human-computer interaction. Legibility of characters depends on the display brightness, luminance contrast of characters, character size, font types, color, viewing distance and angle, and observer’s acuity level. In sign and display industry, a legibility index, defined as the viewing distance divided by the character height, has been widely used for legibility evaluation. However, this index fails to examine all major factors other than geometry. To enhance human-computer interaction, a quantitative legibility evaluation method, which takes into account all major affecting factors, is needed for quick and reliable guidance, goal of this study. This study thus developed a legibility assessment protocol based on a redefined legibility index as the inverse square root of the solid angle subtended by the target, a legibility equation, and innovative camera-aided high dynamic range photogrammetric techniques the author recently developed.