Miyoshi AYAMA, Hiroyasu UJIKE¹, Wataru IWAI², Masami FUNAKAWA³, and Katsunori OKAJIMA⁴

Department of Information and Control Systems Science, Graduate School of Engineering, Utsunomiya University, 7-1-2 Yoto, Utsunomiya 321-8585, Japan
¹Institute for Human Science and Biomedical Engineering, National Institute of Advanced Industrial Science and Technology, 1-1-1 Higashi, Tsukuba 305-8566, Japan
²Matsushita Electric Works, Ltd., 1048 Oaza Kadoma, Kadoma, Osaka 571-8686, Japan
³Nissan Research Center, Nissan Motor Co., Ltd., 1 Natsushima-cho, Yokosuka, Kanagawa 237-8523, Japan
⁴Graduate School of Environment and Information Sciences, Yokohama National University, 79-7 Tokiwa-dai, Hodogaya-ku, Yokohama 240-8501, Japan

(Received March 20, 2006; Accepted August 4, 2006)

We examined effects of contrast and character size upon legibility of Japanese text stimuli presented on visual display terminal (VDT). In the experiment, three different character sizes were employed and the text stimulus was presented under a variety of conditions where contrast between the text and the background changed. Reading speed and the rate of readable characters were measured. Subjective rating for legibility was also evaluated. Results showed that legibility increases with luminance contrast for all character sizes examined here. A strong correlation was found between the subjective rating index and reading speed.

Key words: legibility, character size, luminance contrast, VDT, reading speed, subjective rating