The Study Of Spectral Optimization Of White LED For Mesopic Vision

Color rendering property and luminous efficacy are important factors to evaluate the quality of LED white-light source. The design of white light LED for mesopic vision is to realize the maximization of mesopic luminous efficacy under the condition of a certain color temperature and color rendering index. We use the simulation program to study white LED for mesopic vision. In order to get better simulation results, we put forward a new objective function, the average limited mesopic luminous efficacy(mLLE), to optimize spectra of a white LED for mesopic vision.We studied three kinds of white LED, which are white LED with phosphors and blue chip p-W LED,with phosphors, blue and red chips(PC/R LED) and with blue chip and quantum dots phosphors(QD WLED), under the condition of CRI ≥ 70 by maximizing the average limited mesopic luminous efficacy(mLLE) or S/P value. The results show that the average limit mesopic luminous efficacy(mLLE) as an objective function is better choice for spectral optimization of white LED under mesopic vision.For p-W LED with CRI ≥ 70, under CCTs of 2700 – 6500 K, themLLE of optimal theoretical spectra reached the highest of 459 lm/W at 6500 K, and the LLEm of optimal real spectra reached the highest of 428 lm/W at 6500 K. For p-W LED without CRI requirement, the mLLE of optimal theoretical spectra reached the highest of 499 lm/W at 6500 K. For PC/R LED with CRI ≥ 70, under CCTs of 2700 – 6500 K, themLLE of optimal theoretical spectra reached the highest of 508 lm/W at 6500 K, and the LLEm of optimal real spectra reached the highest of510 lm/W at 6500 K. For PC/R LED without CRI requirement, themLLE of optimal theoretical spectra reached the highest of 554 lm/W at 6500 K. For QD LED with CRI ≥ 70, under CCTs of2700 – 6500 K, themLLE of optimal theoretical spectra reached the highest of 472 lm/W at 6500 K. For QD LED without CRI requirement, themLLE of optimal theoretical spectra reached the highest of 517 lm/W at 6500 K. By comparison of p-W LED、PC/R LED and QD LED, the PC/R LED can achieve the highestmLLE, so it is suggested that the PC/R LED scenario is adopted in the design of white LED for mesopic vision.For four mesopic road lighting standards, the LLEms of optimal theoretical spectra p-W LEDs with CRI ≥ 70 reached the highest of 365.8 lm/W at CCT = 5000 K for mesopic luminance(Lmes)of 0.50 cd/m2, 348.9 lm/W at CCT = 5000 K for Lmes of 0.80 cd/m2, 336.7 lm/W at CCT = 3500 K for Lmes of 1.25 cd/m2, and 329.6 lm/W at CCT = 3500 K for Lmes of 1.75 cd/m2. The LLEms ofoptimal theoretical spectra PC/R LEDs with CRI ≥ 70 reached the highest of 421.7 lm/W at CCT= 3000 K for mesopic luminance(Lmes) of 0.50 cd/m2, 412.5 lm/W at CCT = 3000 K for Lmes of0.80 cd/m2, 406.0 lm/W at CCT = 2700 K for Lmes of 1.25 cd/m2, and 401.8 lm/W at CCT = 2700 K for Lmes of 1.75 cd/m2. The LLEms of optimal theoretical spectra QD LEDs with CRI ≥ 70 reached the highest of 379.3 lm/W at CCT = 5000 K for mesopic luminance(Lmes) of 0.50 cd/m2,364.0 lm/W at CCT = 3500 K for Lmes of 0.80 cd/m2, 354.4 lm/W at CCT = 3000 K for Lmes of1.25 cd/m2, and 348.9 lm/W at CCT = 3000 K for Lmes of 1.75 cd/m2. The LLEms of optimal theoretical spectra QD LEDs with CRI ≥ 85 and CQS ≥ 85 reached the highest of 366.1 lm/W at CCT = 5000 K for mesopic luminance(Lmes) of 0.50 cd/m2, 350.8 lm/W at CCT = 5000 K for Lmes of 0.80 cd/m2, 339.3 lm/W at CCT = 3500 K for Lmes of 1.25 cd/m2, and 333.6 lm/W at CCT =3500 K for Lmes of 1.75 cd/m2.