Citation

Cai H. Proc. Hum. Factors Ergon. Soc. Annu. Meet. 2011; 55(1): 1215-1219.

Copyright

(Copyright © 2011, Human Factors and Ergonomics Society, Publisher SAGE Publishing)

DOI

10.1177/1071181311551253

PMID

unavailable

Abstract

This study focused on developing a legibility index for text characters and its measurement technology in the field. This study first reviewed the conventional D/H ratio (LI = D/H, D is legibility distance, H is character height), and a recently redefined LI′ ( , ω is the solid angle subtended by the legible target). LI′ was aimed to replace the insufficient D/H ratio for common oblique viewing. Yet people's normal reading habit was not considered in LI′, which lowers their reading performance at large viewing angles. Direct measurement of solid angle is also inconvenient in the field. This study thus improved LI′, based on experimental data, as when 0° ≤ ξ < 66.8°; , when 66.8° ≤ ξ ≤ 82.8° (ξ is the incident angle). An objective protocol aided by innovative high dynamic range photogrammetric techniques was also proposed for quick and reliable measurement of LI″ in the field.

Language: en