Info.

LED lamp is a new type of light source after incandescent lamp, fluorescent lamp and energy-saving lamp. It has high luminous efficiency, but many people don't understand its light-emitting principle and spectral characteristics. It is inevitable that it will not damage the eyes.

Spectrally, the light emitted by LEDs is very different from that of traditional incandescent lamps and fluorescent lamps. The so-called "spectrum" means that the light emitted by an object has a "rainbow". The light of traditional incandescent lamps and fluorescent lamps has the same seven colors of "red orange, yellow, green, blue, and purple" as sunlight.

However, the general LED emits only three colors of "RGB", where R is red, which means red light; G means green, which is green light; and B means blue, which is blue light. These three color LEDs are the most important and most basic of the "blue LED" between 400nm and 500nm. Blue LED technology once won the Nobel Prize in Physics

The blue LED technology was developed in 1998, and the technology won the 2014 Nobel Prize in Physics. It appears that the tall blue LED is made by encapsulating a GaN chip and yttrium aluminum garnet (YAG). The GaN chip emits blue light with a wavelength λ equal to 465 nm and a wavelength bandwidth of approximately 30 nm.

How does a white LED emit white light?

So, how does the white LED of the household produce white light? As already mentioned above, the energy of the blue photon is high, so it can be used to excite the fluorescent light. Generally, the blue light generated by the blue LED is used to generate yellow light on the fluorescent powder (similar to the principle of the fluorescent lamp, the fluorescent light is emitted by the ultraviolet light on the fluorescent powder on the inner wall of the fluorescent tube). After the yellow light is excited by the blue light, they are shot together from the LED. We will feel as if we have seen the white light. In fact, this is just a combination of blue and yellow colors. Let's take an analogy. Blu-ray is the "mother" and Huang Guang is the "son". Their mother and son form a single-parent family of "white light".

Because of this principle, many manufacturers in order to improve the brightness of white LEDs, directly increase the intensity of blue light, so the yellow light will increase accordingly, and the brightness of the resulting white light will increase, but this will cause us to Explain the "over blue light" problem. The tissue used to receive light in the human eye is called the retina. If the brightness of the 400–500 nm blue light band in the light source is too high, the eye may cause photochemical damage to the retina after long-term direct view of the light source. The damage is mainly divided into two categories: damage caused by direct reaction of blue light with visual pigment in visual photoreceptor cells, and damage caused by reaction of blue light with lipofuscin in retinal pigment epithelial cells. These photochemical reactions produce large amounts of cytotoxic free radicals that disrupt the normal growth and function of retinal cells.

We can also consider the harmfulness of blue light from another angle. Why can't people's eyes accept the "excessive blue light" from blue LEDs? Because humans evolved in the solar system, according to the Wien displacement law of blackbody radiation, we can calculate the center wavelength of sunlight at around 550 nm through the temperature of the sun's surface, while the blue LED center wavelength is 465 nm, which deviates from the sun. The central wavelength of light, so from an evolutionary perspective, our human eyes cannot accept "excessive" blue light.