Abstract
We focused on near point distance as a metrics of eye fatigue at reading task for the purpose of getting an objective scale for seeking readable Electronic Paper. Near point distance can be measured both procedures by approaching and by extending a target mark, which is tried to be focused by subjects. Correlation between the increase of the near point distance and subjective answers were evaluated in reading tasks of 120 minutes by using each procedure of the near point measurements. The approaching procedure of the near point measurement showed superior correlation coefficient : it was regarded as an enough value for using a quantitative index of eye fatigue. This approaching method was then applied for measurements of eye fatigue with reading task of 270 minutes on various mediums : paper, electronic paper (book reader using electrophoretic display), and conventional display (LCD). Measured results of near point distance showed increase only for LCD. No increase of the near point distance was shown for electronic paper and paper. These results suggest that the electronic paper used in this study is superior than conventional display with regards to avoiding fatigue in reading tasks
