More than a decade ago, most people would not have thought that lighting and health would be related. After more than a decade of development, the LED lighting industry has increased from the pursuit of light efficiency, energy saving and cost to the demand for light quality, light health, light biosafety and light environment. Especially in recent years, the problems of blue light harm, human rhythm disorder and human retinal damage caused by LED are becoming more and more obvious, which makes the industry realize that the popularization of healthy lighting is urgent.

Biological basis of health lighting

Generally speaking, health lighting is to improve and improve people’s working, learning and living conditions and quality through LED lighting, so as to promote psychological and physical health.

The biological effects of light on human beings can be divided into visual effects and non visual effects.

(1) Visual effects of light:

Visible light passes through the cornea of the eye and is imaged on the retina through the lens. It is transformed into physiological signals by photoreceptor cells. After receiving it, the optic nerve generates vision, so as to judge the color, shape and distance of objects in space. Vision can also cause people’s psychological mechanism reaction, which is the psychological effect of vision.

There are two types of visual cells: one is cone cells, which sense light and color; The second type is rod-shaped cells, which can only sense luminosity, but the sensitivity is 10000 times that of the former.

Many phenomena in daily life belong to the visual effect of light:

Bedroom, dining room, coffee shop, warm color light (such as pink and light purple) makes the whole space have a warm and relaxed atmosphere, and makes people’s skin and face look healthier at the same time.

In summer, blue and green light will make people feel cool; In winter, red makes people feel warm.

Strong colorful lighting can make the atmosphere active and vivid, and increase the bustling festive atmosphere.

Modern family rooms also often use some red and green decorative lights to decorate the living room and restaurant to increase the happy atmosphere.

Some restaurants have neither overall lighting nor chandeliers on the table. They only use weak candle lighting to set off the atmosphere.

(2) Non visual effects of light, the discovery of iprgc:

There is a third type of photoreceptor cells in the human retina – intrinsic photosensitive retinal ganglion cells, which are responsible for regulating non visual effects outside the body’s vision, such as the function of managing time, coordinating and controlling people’s activity rhythm and amplitude in different periods of time.

This non visual effect is also called sichen visual effect, which was discovered by Berson, Dunn and Takao of Brown University in mammals in 2002. It is one of the top ten discoveries in the world in 2002.

Studies have shown that the non visual effect of house mice is 465nm, but for humans, genetic studies show that it should be 480 ~ 485nm (the peaks of cone cells and rod cells are 555nm and 507nm, respectively).

(3) Principle of iprgc controlling biological clock:

Iprgc has its own neural transmission network in human brain, which is very different from visual neural transmission network. After receiving light, iprgc generates bioelectric signals, which are transmitted to the hypothalamus (RHT), and then enter the suprachiasmatic nucleus (SCN) and extracerebral nerve nucleus (PVN) to reach the pineal gland.

The pineal gland is the center of the brain’s biological clock. It secretes melatonin. Melatonin is synthesized and stored in the pineal gland. Sympathetic excitation innervates pineal cells to release melatonin into flowing blood and induce natural sleep. Therefore, it is an important hormone to regulate physiological rhythm.

The secretion of melatonin has an obvious circadian rhythm, which is inhibited during the day and active at night. However, the excitability of sympathetic nerve is closely related to the energy and color of light reaching the pineal gland. Light color and light intensity will affect the secretion and release of melatonin.

In addition to regulating the biological clock, iprgc has an impact on human heart rate, blood pressure, alertness and vitality, all of which belong to the non visual effect of light. In addition, the physiological damage caused by light should also be attributed to the non visual effect of light.