Foreword
LED industry technology is developing rapidly, and the product with luminous efficiency of 160lm/w has been put on the market. High-quality white light - CRI with color rendering index of 90 or above, color temperature of 3000K, 100lm/w or more has been mass-produced, and LED enters functional lighting. The times have come.
LED high color saturation characteristics, digital, intelligent, networked multi-spectral combination control, to meet the needs of different visual operations and functional lighting. The international standards of illumination based on the traditional Planck blackbody radiation theory, such as color temperature, color rendering index, and chromatic aberration correction, are quite different from the visual cognition and non-visual perception effects of high-color saturated LED combined light source. Practice has shown that this causes a widening gap between physical photometry, physical colorimetry and visual photometry, and visual colorimetry. It also makes photometrics, colorimetry, surveying, color engineering and other serious challenges, leading to innovation in lighting theory. The following is a question that we have raised the international controversy caused by high color saturation LED color light combination illumination. It is discussed that high color saturation LED combination lighting will become a new bright spot and new hot spot of lighting.
First, the understanding of the nature of lighting
Artificial lighting is the combined effect of the combination of the light source system, the illuminated object and the observer. The LED light source emits monochromatic light with high color saturation. The combination of multiple color lights makes the illuminated object more vivid and eye-catching, and has an extraordinary impact on human physiology and psychology. We believe that lighting is a systematic project with multiple disciplines and technologies. The interpretation of matter is science, the expression of emotion is art, the combination of emotion and reason is psychology, and the essence of illumination is the combination of matter, reason and emotion, as shown in Figure 1.
At present, all lighting theories and standards are mostly limited and positioned in the visual requirements, and there are not many effects on the biological and psychological effects and requirements. The colorful LED lighting system makes the proposition of "light and health" more active. There have been many high-level seminars in the world, including medical scientists, architects and lighting experts to discuss the potential of LED lighting systems.
Figure 1. The essence of lighting is the combination of things, reason and emotion.
In short, human visual cognition and non-visual perception determine the quality and quantity requirements of the lighting. In addition to satisfying the functional requirements of people's visual operations, artificial lighting must also meet the physiological and psychological needs of people and meet the requirements of people's comfortable, healthy and safe lighting. People-oriented, people need to live in a harmonious light environment.
Second, LED light source coloration caused international controversy
1. The CRI test value of the LED light source is very different from the visual effect.
In the past 40 years, the color of the illumination source has been evaluated by the CRI of the color rendering index. However, when many RGB trichromatic LED sources are mixed into white light, the visual effect is very good, but the CRI value is less than 30. As shown in Figure 2, the 3500K RGB trichromatic LED source has a CRI value of only 27.
Figure 2.3500K RGB three primary color LED spectrum and CRI values
Experiments have shown that there is no intrinsic link between the CRI index value of the LED and the visual effect. CIE (TC1-62) Technical Report 177:2007 proposes that in a series of light source comparisons, the technical committee concluded that "CIE's CRI does not apply to the color rendering range of white LED sources." There is no intrinsic link between CRI index values ​​and human visual effects. CIE recommends quantitative evaluation of the color rendering of light sources. It is a "color measurement method" revised in 1974. It specifies two standard illuminants and 14 test color samples. One to eight test samples are selected to calculate the general color rendering index CRI. Samples are samples of medium lightness and medium color saturation, as shown in Figure 3. There are too many limitations on the source and sample specifications, especially the high-color saturation source (combination) for high-color saturation object illumination.
Figure 3. Eight test samples for CRI calculations