Study on dichromatism's color appearance to LED lights

In recent years, with the utilization of blue Light Emitting Diode, the Light Emitting Diode element is beginning to be actively used in various scenes, and Light Emitting Diode is used even for traffic light now. The Light Emitting Diode traffic signal light has little power consumption as compared with the traffic signal light using the conventional electric bulb, and spreads to progress increasingly from now on. Because the discernment of the yellow of a signal light and red is difficult for sense-of-color unusual person, in the present signal light system, yellow signal light color is made somewhat brighter than red signal light. The aim of the present study is to collect the fundamental data for the display of the traffic signal light, which is easy to be recognized also by sense-of-color unusual persons. The results revealed that the optimal brightness of the yellow light from which a sense-of-color unusual person can distinguish the difference between yellow and red, i.e., "visual barrier-free domain", is the area where yellow light is 2.8 times brightness of the red light.