Visibility Estimation Method Considering Disability Glare Using Contrast-Average Graph

The authors have proposed a visibility estimation method using Contrast-Average (C-A) graphs based on the contrast profile method. C-A graphs can express three factors (luminance contrast, adaptation luminance, and object size) necessary for visibility estimations from luminance images. The objective of this study is to propose a visibility estimation method considering disability glare (impaired visibility caused by high luminance light sources in the visual field) using C-A graphs. Visibility evaluation experiments were conducted under various conditions with high luminance light sources presented in the visual field. In experiments, the changes of visibility threshold C values were examined. Estimations of visibility threshold C values were attempted by using the ‘equivalent veiling luminance’ of past studies. However, it was confirmed that the estimation method has limitations in its applicable range. Therefore, by focusing on increments of C values, a visibility estimation equation was established from the multiple regression analyses of increments of C values and the illuminance received from each of the segmented visual fields. In this study, the estimation equation was established from experimental results that used circular objects with a 20-minute diameter.