Research On The Evaluation Of Color Rendering Property And Its Application To White-light LED

After the incandescent lights and fluorescent lights,as the main force of the third generation of the general lighting,white LED lighting gradually replace the traditional lighting because of its high luminous efficiency,long life and other advantages.CRI(Color Rendering index),as an index to evaluate on the quality of lighting sources has many problems when evaluating white LED lighting sources.Based on the common white LED light sources and traditional light sources,this article analyzes the differences and problems existing in the existing evaluation methods,and then comes up with a new method for evaluating the visual similarity of the light source spectrum to evaluate the color differences of lighting sources,which is based on the wavelength resolution of human eyes.The evaluation method is applied to the designing of high quality color white LED light sources.The main research contents and conclusions are as follows:Firstly,we analyzed the difference of the Color Rendering Index(CRI)and Color Quality Scale(CQS)when we evaluate the color rendering of light sources.10 kinds of fluorescent,7 kinds of RGB LED and 25 kinds of Phosphor white LED which are common in the market were calculated for the value of the corresponding CRI(aR)and CQS(aQ).The relationship between the two indexes was analyzed through the correlation,the chromatic aberration and the difference ratio,respectively.The results show that when we evaluated the light sources with extremely low color temperatures,high color saturation,poor color rendering and RGB LED light sources,the difference between CRI and CQS which was modified was great.The overall trend of the difference ratio between CQS and CRI was lower when CRI was higher through the difference analysis.And the difference Ratio between them is close to 0 when CRIaR was above 90.Secondly,a method for evaluating the color rendering of light sources by using spectral visual similarity parameter was studied.And a visual similarity model of test light source spectra and reference light source spectra was established based on the spectral luminous efficiency,the color-resolution function and the spectral response function.The calculation formula of spectral visual similarity parameter,VR,was also given.The spectral similarity and spectral visual similarity of several CIE standard light sources and the equal energy white light,E,were calculated.The results show that the spectral visual similarity was very high(VR(29)97),although the spectral similarity was low,which demonstrating thatVR is of representative significance when evaluating the high color rendering light sources.When evaluating the actual light sources,we still use the CIE standard light source spectrum as the reference light source spectrum.The spectra of white-light LED,incandescent bulb,trichromatic fluorescent and natural-light LED lamps tested in the experiment were used to calculate their responding spectral visual similarity parameterVR,respectively.The results showed that spectral visual similarity parameterVR of white-light LED and the natural light LED lamps was higher than that of the incandescent bulb and three-color fluorescent,which was in agreement with the experimental results.Finally,we applied the spectral visual similarity parameterVR to designing high light-color property of LED synthetic light sources.Using the D50,the standard light source recommended by CIE,as the reference light,we calculated the each number of combination mixed with cold white LED,warm white LED,red,green,cyan and blue LED.According to the requirement ofVR(29)96,it turned out that the color temperature Range of LED synthetic light source was between 4000 K ~ 7000 K,and the general color rendering index 95aR(29),which is accordant with the requirements of high light-color property in illumination light sources.The calculation program of the spectral visual similarity parameterVR is much easier when compared with the color rendering indexaR.The two index have great correlation when evaluating the high color rendering light sources,although they have poor correlation when evaluating the low color rendering light sources,The VR can better reflect the spectral similarity of the measured light sources and the reference light sources and the color similarity of the illuminated object,which has the reference value.