Contrast threshold measurements of peripheral targets in night-time driving images

Properly defining the visual adaptation field in night-time driving conditions is important in order to implement the CIE 191 system of mesopic photometry. In night-time driving, visual scenes include several objects with different luminances. The luminance distribution affects visual performance. In this study, contrast threshold measurements were conducted using simulated night-time driving images taken from a street illuminated by LED light sources. A large screen illuminated by three projectors, providing a visual field subtending 180° ×44°, was used to provide the background and target. Ten subjects (mean age 30 years) participated in the experiment. The subjects were asked to detect the targets appearing at different eccentricities (from '60° to 60°). The results indicate that the target luminance and luminance distribution of the surrounding area affects peripheral target detection. Under similar luminance distributions, the contrast threshold values did not differ between circular 10° and 20° fields of view. The results support the importance of the area surrounding the road for the visual adaptation field.