Brightness Evaluation for White LED Light Sources with Different Packaging Density

Abstract

Light-emitting diode (LED) light sources are increasingly being used. One LED light source is composed of many small LED chips, so the luminance distribution varies depending on the number and arrangement of the LED chips. Quantitative relationships between non-uniform light sources, such as LEDs, and discomfort glare rating have been widely reported, but the relationship between the non-uniform light sources and the perception of brightness has not been clarified.

In this paper, a brightness matching experiment was performed to study the effects of non-uniform spatial luminance distribution on perception of brightness. The results show that non-uniform light sources are perceived to be brighter than uniform ones when they have the same average luminance. Brightness sensitivity and discomfort glare rating were also compared. The results show that both the brightness and discomfort glare for non-uniform and/or uniform light sources can be evaluated with the effective glare luminance, which is the index of the discomfort glare rating.