Lighting science: very good, why can't most of the white LED display white

On the international research on light source for white color very much, but everyone still don't understand. Then, white color is going on? Why can't most of the white LED good shows white?

the main reason is the ordinary white LED in the color of white, there are a lot of defects.

us most of the white object, such as white paper, shirt, even our teeth contain fluorescent whitening agent. The manufacturer by adjusting the content of fluorescent whitening agent to adjust the whiteness of these objects. Figure under ultraviolet light

the fluorescent whitening agent containing fluorescent whitening agent napkin the work principle of phosphors is familiar with us, it can absorb ultraviolet and light purple, then this part of the energy is transformed into the blue light. And our human eye within limits, white with a little more white than pure white to blue.

figure, the working principle of fluorescent whitening agent

because most of the white object containing fluorescent whitening agent, so we are very familiar with these after fluorescent whitening agent to adjust the whiteness of the object.

for traditional light source, whether of incandescent lamp, fluorescent lamp, HID all contain a certain wavelength ultraviolet radiation or short purple light, they can bring the effect of fluorescent whitening agent to improve the whiteness, and with the uv radiation is due to the luminous principle of the light source, is not you deliberately add ultraviolet or violet light.

figure as shown in the left side of the grey area above, incandescent lamp, daylight and fluorescent lamp contains 380 - 430 nm shortwave violet light and ultraviolet components, by blue light stimulates the yellow phosphor white light LED the lack of the spectral composition of the band.

our side now commonly used white LED is blue leds and a phosphor, their basic does not contain any ultraviolet light and short wavelength violet light. It is because of this reason, the LED can't stimulate white objects contain fluorescent whitening agent, so the white object under the irradiation of the LED is no longer so white.

figure two LED lamps and lanterns, CRI is above 80, the following can properly show different whiteness, the above can't. Reason is that after a spectrum of design, the following LED with accurate content of purple light can stimulate the fluorescent whitening agent.

it should be pointed out that, is not to say that we can add a uv light simple in white LED can solve this problem. We have been through the experimental results show that the existence of people dialogue degrees also have a preference, the white object is not as white as possible. White LED by carefully spectrum adjustment is needed to accurately display the whiteness of white object.

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