A study of vision ergonomic of LED display signs on different environment illuminance

Abstract

The LED (light emitting diode, also referred to as LED) have already been used widely. However, despite the high visibility of LED with high brightness performance, it also leads to a glare problem, which generates a direct security issue in applying to traffics. Therefore, this research aimed to study how to make the LED display sign be more legible under high illuminative environments and to avoid the observers feeling dazzling glare under low illuminative environments. This research firstly studied the literatures to explore the drivers of visual ergonomic as well as the optical properties of LED, and investigated the relatively existing norms for engineering vehicle LED display signs. Three variables were set in this study: three kinds of ambient illumination, four kinds of luminance contrast and two kinds of character form. In the first phase of the experiment, subjects observed LED display signs in both near and distant locations and filled out the SWN scale (Subjective Well-being under Neuroleptics), and in the second phase, subjects were then asked to moved forward and recorded their perceptions of comfort and glare to distance range. The findings demonstrated that, there was no variation in subjective evaluation to display signs with no backgrounds either in the near or distant locations, while to display signs with backgrounds, the subjects perceptions were the farther the distance, the clearer the legibility; higher ambient illumination could effectively reduce observers of glare perception to LED display signs; display signs with backgrounds at the luminance contrast of 3:1 (L max = 3100, L min = 1033 cd / m2) showed the lowest uncomfortable and glare level to observers. The two forms of character showed no significant variation in affecting observers in terms of the comfort and glare perception. © 2011 Springer-Verlag Berlin Heidelberg.