The Study On Spectral Optimization Of White LED With Specific Color Temperature Under Mesopic Vision

The white LED has a range of applications for mesopic vision.In this paper,we study the spectrum optimization of white LED with specific color temperature for three kinds of practical applications range of road,residential and commercial lighting under mesopic vision.In this experiment,the average value of the limited mesopic luminous efficacy which is called LLE_m,ave,ave for mesopic vision is optimized for the spectrum optimization under mesopic vision.We classify the three applications based on their brightness:the application for road lighting is divided into 4 levels which are 0.5cd/m²,0.8cd/m²,1.25cd/m²,1.75cd/m²;the application for residential lighting is divided into 3 levels which are 0.35cd/m²,0.525cd/m²,0.7cd/m²;the applications for commercial lighting is divided into 3 levels which are 0.7 cd/m²,1.05cd/m²,1.4cd/m².We establish the theoretical and practical spectral models of three kinds white LEDs which are white LED with phosphors and blue chip?pc-W LED?,with phosphors,blue and red chips?pc/R LED?and with blue chip and quantum dots phosphors?QD LED?.We regard the LLE_m,ave,ave which is the average value of the limited mesopic luminous efficacy?LLE_m?for different brightness levels of road,residential or commercial lighting by white LED as the target optimized under mesopic vision.Under conditions of color rendering index?CRI?which is 70,80 and 90,we obtain the best theoretical and practical spectral distribution,peak wavelength,full-width at half maximum and the percentage of blue,green and red light of photometric and colorimetric performance for 8specific color temperatures which is range from 2700K to 6500K for three kinds of applications of three kinds of white LEDs under mesopic vision.Under the condition of same application,same CRI,same temperature and same type of white LED,we compare the theoretical LLE_m,ave with practical LLE_m,ave and discovery that all of the theoretical LLE_m,ave are larger than practical LLE_m,ave.So the data of the theoretical spectrum we obtain can direct the research about LED chips and phosphors materials.Uuder the condition of t same application,same color temperature and same type of white LED,when CRI=70,the LLE_m,ave is the largest;when CRI=90,the LLE_m,ave is the lowest;when CRI=80,the LLE_m,ave is during CRI=70 and CRI=90.Under the condition of same application,same CRI,same temperature,we find that the LLE_m,ave of pc/R LED is obviously larger than QD LED and pc-W LED,the LLE_m,ave of QD LED is larger than pc-W LED.So according to the results of experiment,we suggest that when design white LED for mesopic vision,the pc/R LED is the best solution.