OPTIMIZATION OF TRICHROMATIC WHITE LED SPECTRUM FOR DIM LIGHTING CONDITIONS

Abstract

Most night-time outdoor and traffic lighting scenarios are in the mesopic range. Because colour gamut in the mesopic conditions is relatively narrow, the general colour rendering index is not suitable for evaluating colour fidelity. Therefore, an optimization of the white LED spectrum based on 3D colour gamut is essential to raise the ability of colour recognition under constant contrast condition for the lighting application. The optimal trichromatic white LED spectra can be obtained by investigating the variance of wavelength positions and peak power density ratios for 10 cd/m2 , 1 cd/m2 , 0.3 cd/m2 , and 0.1 cd/m2 . As a result, a trade-off between mesopic luminance and colour gamut is quite significant. According to the predicted photopic/mesopic luminance level and the gamut volume, the test spectra with the highest Lmes, largest gamut volume (GV), and highest (L mes+GV) are suggested as the optimal white LED spectra under a specific luminance level.