Zhang Haijun: Lighting white light should be equal to light efficiency and color rendering index

The white light of the illumination must have a color rendering index and a comfortable color temperature. Both natural light and incandescent light are endowed by nature, and are the goal pursued by humans to create artificial light sources. They represent the ideal light source with a color temperature index close to 100 for high color temperature (above 5000K) and low color temperature (below 3000K). Up to now, artificial light sources have almost no such good color rendering source other than incandescent lamps (low color temperature) and xenon lamps (high color temperature).
In all the current lighting applications, it is not necessary to achieve a color rendering of the light source of 100. Fluorescent lamps with a color rendering index of only 50 calcium halophosphate phosphors have been used for more than half a century; high-pressure sodium lamps with a color rendering of only about 20 have been applied on the road for nearly half a century. Therefore, it cannot be generalized. The boundary between the light source and the use of the light source must be drawn according to the surrounding environment and the conditions of use.

Now, color rendering has gained more and more attention. Light sources with poor color rendering are often not available or recommended in many applications. The most typical example is the low-pressure sodium lamp, although the luminous efficiency is close to 200 lm / W, but the monochromatic yellow light makes it only used for road lighting and rarely other occasions. For indoor environments with a larger audience, the required color rendering is higher.

The trend of replacing traditional light sources with LEDs has become clear. High light efficiency and not too low color rendering index have emerged in some indoor and outdoor lighting, showing good results and strong development momentum. When looking at the light effect of LED, we must pay attention to its color rendering index, only the light effect, no color rendering index is not practical. White light with high luminous efficiency and high color rendering index and meeting the lighting environment or lighting work is the best white light. There are many requirements in indoor lighting. For example, the color rendering index in the home environment is above 80, which has become a customary requirement. Therefore, higher efficiency than conventional light sources (or made lamps with higher light output than conventional lamps) and a color rendering index greater than 80 should be a yardstick for measuring white LEDs for indoor lighting.