Precise Modeling And Its Application Of Phosphor Coating For White LED Based On Bidirectional Scattering Distribution Function

Light-Emitting Diode(LED),also known as semiconductor light source,has attracted great attention due to its advantages of high luminous efficiency,environmental protection and long service life.In recent years,it has become a research and application hotspot in the world.With the development of technology and the market,our requirements for LED quality are increasing.Simulation process is usually required during the design of LED to verify and optimize its optical performance.However,the optical simulation models for the white LED phosphor coating at present have a certain limitations.In this paper,we establish a more accurate and general simulation model for the phosphor coating in the white LED,based on its BSDF(Bidirectional Scattering Distribution Function)characteristic.The specific research contents are as follows:(1)First,a BSDF automatic measurement system was designed to measure the BSDF characteristics of the phosphor coating.The automatic control system and measurement program of the measuring system are designed and developed,and a complete BSDF automatic measurement system is set up.Thereby The BSDF data of the phosphor coating can be measured automatically and efficiently.(2)We fabricated a serie of YAG phosphor coating films with different parameters(density ranging from 10% to 60% and thicknesses ranging from 0.1mm to 1.3mm)by simple mold injection molding method.Then the BSDF data were measured and analyzed statistically.A BSDF curve calculation model of arbitrary density and thickness parameters was established,and a complete model of the BSDF characteristic of the phosphor coating was accomplished.The model can be used to obtain the accurate light power and its angular distribution in the optical simulation.(3)The variety rule of the spectral distribution curve of the white LED is analyzed using the integrating sphere spectrum testing system.The fitting model of the LED spectrum is established by Gaussian function,Lorentz function and Sigmoid function.Once acquiring the power of blue and yellow light,we are able to calculate the spectral distribution curve of the white LED.(4)We designed a remote phosphor white LED downlight lamp.The phosphor coating BSDF model and spectral unfolding model were applied to the warm white,neutral white and cool white lamps with different color temperatures.After simulating in TracePro,we acquired the output flux,chromaticity coordinates,color temperature and other major parameters of the lamps.Compared with the measured value,the error of the luminous flux is less than 4%,the chromaticity coordinate error is less than 3-order MacAdam ellipse and the color temperature deviation is less than 3%,which proves the accuracy and reliability of our modeling method.