The profound influence of LED on illumination (three)

Three, LED visual science content needs to improve and supplement

As mentioned earlier, the broad range of disciplines in the light of the visual and non visual sciences. The flexibility of LED determines its wide application prospect, and expands the non visual part of the illumination discipline. On the other hand, LED will also promote the Visual Science in the lighting discipline. For example:

1, the subject of visual lighting lighting

Photometry and colorimetry are based on the traditional light source, because of the traditional light source includes the candle photometry and colorimetry of electric light source non thermal radiation source and gas discharge light sources when established, are basically stable, we call steady light source. But because of the short switching time and the dimming of the PWM, the LED switch is very convenient, which is equivalent to the LED in the case of non steady state. The direct question, then, is whether the lighting Science (Visual Science) established in steady-state light conditions is suitable for illumination under unsteady conditions At present there is no conclusion. If the final study found that the pulse light visual lighting has not the same phenomenon, it should at least be born "," pulse pulse photometry "colorimetry".

2, the evaluation method of color rendering

The general evaluation method for the color rendering of the light source is the color rendering index. According to the physical meaning of the color rendering index: the ability of the organism to produce the original color under the light source, the original object is the color of the sun or the standard blackbody. In the quantitative calculation, the color difference between the standard light source and the measured light source is calculated with 14 standard color plates to obtain the color rendering index. Before LED, the main electric light sources are incandescent lamp, fluorescent lamp, high pressure sodium lamp, metal halide lamp and so on. Although the spectra can be changed by changing the filling composition in the lamp, the spectral form is limited in general. Therefore, the empirical formula for calculating the color index is consistent with these light sources.

However, the emergence of LED will make this approximation characterization problem. Due to the flexibility of the LED spectrum, the spectrum can be assembled by a plurality of LED devices, and the light efficiency of the light source can be reduced to some extent. If humans can one day be able to properly reduce the efficiency, then the establishment of a "standard lamp index" or "solar spectrum index" may be the best way to characterize the color rendering.

3, review the evaluation index of visual lighting application

The development of lighting science is based on the light source of the material, and the characteristics of the light source can be used to determine the standard of lighting evaluation. For example, the color rendering index of high pressure sodium lamp is around 20, relatively good in light of traditional light sources, and roads and other outdoor lighting requirements are relatively low, therefore, we accept the road lighting color index is very low in fact. At the same time, LED in the scale space, spectral space, time and space infinite flexibility, can be said that "everything is possible", then, in the future we can accept the low color rendering index of road lighting standards? At present, thanks to the white LED mainstream blue light + yellow phosphor technical route, making the LED color index reached more than 70, the future of the road color rendering index is above 70.

However, with the green LED efficiency is greatly improved, RGB white way (which can be further extended for multi spectral color) unlimited may be greater efficiency and adjustment, color spectrum theory, the achievements of LED, so the white line of future technology will turn to RGB. At that time, the color rendering index and the efficiency of this pair of contradictions in the road lighting will be the color of the formation of indicators on the debate, that is, the high color rendering index is appropriate? I believe it will not be 20, it will not be 70. Due to the high degree of flexibility of LED, it is necessary to study and explore the illumination discipline in the future.