Construction of Visibility Evaluation Model in a Practical Environment

Visibility is a psychophysical characteristic obtained from our visual senses. This is a feature based on the physical properties of mediums such as paper and electronic device. So far, we have used novel photometric equipment: a charge-coupled device sensor that can measure the distribution of luminance and measured luminance distribution of papers printed on a specific striped pattern with predetermined spatial frequency and contrast. We have proposed parameterization method of luminance distribution and constructed a model to predict the visibility level from optical properties in viewing distance 3m that conforms to the U.S. patent; but it has not been examined practically in environments, such as reading. In this study, to construct the visibility evaluation model in a more practical environment, we measured the optical properties with novel photometric equipment and the visibility with sensory test in viewing distance 0.5m. We also compared the visibility evaluation model in viewing distance 3m and 0.5m. As a result, contrast Lcon, spatial frequency cpd, reflection efficiency rho was selected as explanatory variables in the 3m visibility evaluation model. On the other hand, contrast Lcon and space frequency Cpd were selected as explanatory variables in the 0.5m visibility evaluation model. It is for this reason that the effects of the spatial frequency Cpd were increased and the contrast Lcon and reflection efficiency rho were decreased.