LED road lighting should be used in the evaluation of the visual way

To determine the lighting evaluation system and method has a decisive influence on the selection of light source and lighting effect. For a long period of time, only the use of visual and dark visual evaluation system in the world, the fact shows that the visual curve does not take into account all the visual cells of the human eye, especially the blue cone cells. The defects of the visual curve are as follows: the brightness value measured by the bright visual curve does not represent the visible brightness of the human eye, and can not evaluate the visual effects of different groups of people. As a matter of fact, people of different ages have different perception of light, and the spectral transmission rate decreases with age. For 1.5% of the proportion of people with color blindness, visual curve can not reflect the visual perception. For a long period of time, the intermediate visual curve is in the missing state.

To establish effective mesopic photometry system has been concern in the international lighting industry seminar. The 2010 International Lighting Commission (CIE) issued a recommendation system for mesopic photometry. The lighting system that based on the visual luminosity bring challenges and impact, and as the future development and application of LED light source has great influence. Associate professor of Fudan University School of Information Engineering Department of electric light source and lighting research Dr. Lin Yandan pointed out that the "middle vision photometry for a defined period of existence, the intermediate visual curve is a necessary supplement to improve the photometric evaluation, intermediate vision covers all the range of road lighting. Pan Jiangen, chairman of Hangzhou far optical Touchplus information Corp also believes that the road lighting standards will enter the era of evaluation of intermediate vision. The new CIE-MES2 system (0.005-5cd/m2) is the most perfect intermediate vision system. "But there are still a lot of research work to be done to improve the system," he added. "

Then the intermediate visual index system for lighting applications of various light sources will produce what kind of impact? Application of mesopic vision photometric periods need background luminance and spectral data obtained from the source S/P value as the input, the S/P value is a scotopic light output and light output of the photopic ratio of light source S/P the higher the value, the light effect in the middle of the visual design of the more high. The measurement of the light output of the lamp will be changed by using the intermediate vision system, and the light efficiency level of the lamp can be changed. Mesopic photometry favor high S/P value of the Bai Guangyuan LED, compared to the traditional light source is the high S/P value of Bai Guangyuan, the introduction of intermediate visual evaluation system for LED manufacturers to provide the basis according to the development of low brightness lighting applications optimized for LED, is expected to white LED applied to the outdoor lighting field further pave the way.

Lin Yandan introduced to the middle vision raises an important exploration, which could reduce the brightness of the white light of road lighting. And thus lead to two key issues, as the luminance decreased, visual effect decreased? S/P value decreased significantly and improve the color index of the extent to which can make up for the visual effects? To explore these issues, do a lot of experiments on the international. The experimental results show that for the central target, especially the color of the central target, the brightness is reduced, the visual effect will be reduced; the light effect of the 2cd/m2 can reach the brightness of the 10cd/m2 effect of the high pressure sodium lamp. The effect of 0.1cd/m2 on the color of the metal halide lamp is similar to that of the high pressure sodium lamp 1cd/m2; the brightness of different light sources to achieve the same visual effect is different, and the light intensity of the metal halide lamp is lower than that of the high-pressure sodium lamp. Britain and Italy and other countries in the relevant provisions, the use of high color light source, in the same grade road lighting, illumination can reduce a grade. Shanghai Lighting Association chapter HAICONG special tips, the provisions of the British standard BS5489-1:2003, the color index of street lighting light source (Ra = 60), the illuminance reduced by half, but need to pay attention to the provisions of the conditions of use, "the lighting level branch (pedestrians and bicyclists)" at present, the results will be extended to all kinds of road work is still too early, still need further study before make a decision.

MES2 system is of intermediate visual luminosity, but it is not the whole content of mesopic vision. Need to consider a variety of specific environmental factors. The "middle visual assessment is a comprehensive system engineering, is a comprehensive assessment of the visual LED pedestrians and drivers of different visual tasks at the same time also need to consider the method, comprehensive evaluation of visual intermediate LED while studying brightness, spectrum and environment constraint method. "The forest is summed up.