Who should we trust about the dangers of LED blue light?

- Jul 17, 2019-

  With the progress of science and technology, various lighting sources keep emerging. These lighting sources can not only enrich lighting products and meet people's needs, but also cause harm to people due to improper use. Blue light hazards, since the first exposure has continued to cause considerable repercussions in the lighting industry. Recently, more medical experts worry that LED blue light can cause damage to the retina, even blindness. The news has attracted wide attention and a lot of comments on the Internet, as well as attention from experts on light sources.

  "Blue light" refers to the part of visible light closest to ultraviolet light. The frequency of these wavelengths in the range of 400-500 nanometers is slightly lower than ultraviolet light, which is the highest energy part of visible light. The colors are blue and purple, so it is commonly known as "blue light".

  The so-called harm of blue light refers to the damage to human eyes in a relatively short time or instant when the brightness of blue light reaches the 2 or 3 categories specified in the standard. It is based on GB/T 20145-2006 / CIE S009 / E: 2002 and the determination is based on the ctl-0744_2009-laser resolution.

  So how exactly does blue light harm human eyes? First, we need to understand the structure and visual function of human eyes.

  The path of light into the human eye is: light along the optic axis, through the cornea, pupil, lens, vitreous body to the retina. At the end of the optic axis of the retina, there is a shallow funnel-shaped small depression called macular fovea. Fovea is the most acute place of vision, which is rich in visual cells.

  The human eye has about 120 million columnar cells and 8 million cone cells. Visual cells cannot regenerate after death. Therefore, visual cells of human eyes are the most precious non-renewable resources of human body. Columnar cells can only sense the brightness of light. Cone cells generate bright vision under normal lighting (brightness value is greater than 3CD per square meter). Cone cells sense the color of light.

  Cone cells are divided into three types: cone cells that sense red light, cone cells that sense green light, and cone cells that sense blue light. Cone cells sensing red light are most sensitive to wavelengths of 650-680nm; cone cells sensing green light are most sensitive to wavelengths of 560-570nm; and cone cells sensing blue light are most sensitive to wavelengths of 440-450nm. This is close to the wavelength of white LED chip, which is also the reason why LED lighting source has blue light hazard.

  The scientific community is divided over the dangers of LED blue light. One of them is in line with the medical experts above. Light entering the human eye has two visual channels, one is the imaging visual channel, and the other is the non-imaging visual channel of biological clock and time. They believe that blue light from LED lamps in the imaging visual channel may cause visual harm to the retina. In non-imaging channels, blue light from LED fixtures may affect circadian rhythms.

  At present, the lighting LED in the market is basically all white LED, which stimulates yellow phosphor powder and forms white light through blue chip. Although this method can obtain white light at the lowest cost, due to the use of blue light pump, it inevitably contains too much blue light, the higher the color temperature, the more. Although the country recently issued some standards for the harm of LED blue light, these standards are for adults, not necessarily for teenagers.

  For blue leds can enter the classroom this problem, used to work at harvard medical school in the United States, the current college students in zhongshan institute professor doctoral tutor professor wen-liang zhou said, "if you want to use auxiliary illuminant, at present the most LED lights market single blue light is too strong, from the perspective of protecting teenagers eyes, personally, I temporarily not recommended to use in the classroom."

  Professor zhou wenliang said that the white LED used in the color temperature range defined by the national standard is safe for adults through the blue light hazard assessment in strict accordance with the national standard. The rapid development of white LED in the past few years has strongly promoted the great development of the semiconductor lighting industry. But white LED is only one kind of semiconductor lighting, has outstanding advantages, used for general indoor lighting is very good. But for children and adolescents, the risks are there, especially in classrooms where students are kept for longer periods of time. Too much blue light can cause retinal damage and disruption to the body's birth rhythms.