Study On The Circadian Action Factor And Spectral Optimization Of Three-Primary LEDs

In today's society,people stay longer and longer under various light sources;The artificial lighting is able to make up the lack of natural light in the environment lighting.At the beginning of this century,based on the finding of third types of photoreceptor cells in the retina(intrinsically photosensitive ganglion cells-ipRGCs),the non-visual biological research has been carried out in-depth.People realize that light sources not only provide them with a bright environment,but also affect the secretion of melatonin,cortisol,and other hormones,and involving in the regulation of circadian rhythms.With the development of semiconductor lighting technology,in the field of lighting,white LEDs begin to replace traditional lamps,such as fluorescent lamps,incandescent lamps,and high-intensity discharge lamps,etc.White LEDs have shown several advantages,such as long lifespan,low power consumption,small size,fast response,color tunability,and so on.Therefore,this paper focuses on the research of non-visual biological effects of three-primary colored white LED:First,in the introduction chapter,we briefly describe non-visual biological effects,as well as existing research results.This dissertation introduces the development history of LED and the key points of white LEDs.In the second chapter,we introduce the structure of human eyes as well as the visual and non-visual channels,photometric and chromatic parameters of light source,and the evaluation system of non-visual biological effects.Then,in the third and fourth chapters,we tested the spectra of three-primary white LEDs under different working currents.The circadian rhythm factors(CAF)are calculated to study the relationship between circadian effects and working currents.We also compared these factors with the standard white light,find the method that by adjusting the current to change the.circadian rhythm factors and correlated colour temperature of the white light LED.Then we tested spectrum of natural light at different time in a sunny day,and test circadian rhythm factors,we found these factors are almost in about 0.9.By the mathematical model introduced in this paper obtain the currens of the LED similar to the natural light.The correctness of the mathematical model is verified by comparison between evaluation and experimen.In order to find a three-primary LEDs which similar to standard light on color rendering index(CRI),CAF,and color coordinates,we did spectrum optimization with diffierent the peak wavelength combinations(red,green and blue)of the LED.