1. Photobiological effect
To discuss the issue of photobiological safety, the first step is to clarify the photobiological effects. Different scholars have different definitions of the connotation of photobiological effects, which can refer to various interactions between light and living organisms. In this article, we only discuss the physiological reactions of the human body caused by light.
The impact of photobiological effects on the human body is multifaceted. According to the different mechanisms and results of photobiological effects, they can be roughly divided into three categories: visual effects of light, non visual effects of light, and radiation effects of light.
The visual effect of light refers to the effect of light on vision, which is the most fundamental effect of light. Visual health is the most fundamental requirement for lighting. The factors that affect the visual effects of light include brightness, spatial distribution, color rendering, glare, color characteristics, flicker characteristics, etc., which can cause eye fatigue, blurred vision, and decreased efficiency in visual related tasks
The non visual effects of light refer to the physiological and psychological reactions of the human body caused by light, which are related to people’s work efficiency, sense of security, comfort, physiological and emotional health. The research on non visual effects of light started relatively late, but has developed rapidly. In today’s lighting quality evaluation system, the non visual effects of light have become an important factor that cannot be ignored.
The radiation effect of light refers to the damage caused to human tissues by the effects of different wavelengths of light radiation on the skin, cornea, lens, retina, and other parts of the body. The radiation effect of light can be divided into two categories based on its mechanism of action: photochemical damage and thermal radiation damage. Specifically, it includes various hazards such as UV chemical hazards from light sources, retinal blue light hazards, and skin thermal hazards.
The human body can to some extent resist or repair the effects of these injuries, but when the light radiation effect reaches a certain limit, the body’s self repair ability is insufficient to repair these injuries, and the damage will accumulate, resulting in irreversible effects such as vision loss, retinal lesions, skin damage, etc.
Overall, there are complex multi factor interactions and positive and negative feedback mechanisms between human health and the light environment. The effects of light on organisms, especially on the human body, are related to various factors such as the wavelength, intensity, operating conditions, and state of the organism.
The purpose of studying the effects of photobiology is to explore the related factors between the results of photobiology and the light environment and biological state, identify the risk factors that can harm health and the favorable aspects that can be applied, seek benefits and avoid harm, and enable the deep integration of optics and life sciences.

2. Photobiosafety
The concept of photobiosafety can be understood in two ways: narrow and broad. Narrowly defined, “photobiosafety” refers to the safety issues caused by the radiation effects of light, while broadly defined, “photobiosafety” refers to the safety issues caused by light radiation on human health, including visual effects of light, non visual effects of light, and radiation effects of light.
In the existing research system of photobiosafety, the research object of photobiosafety is lighting or display devices, and the target of photobiosafety is organs such as the eyes or skin of the human body, manifested as changes in physiological parameters such as body temperature and pupil diameter. The research on photobiosafety mainly focuses on three major directions: measurement and evaluation of photobiosafety radiation generated by light sources, quantitative relationship between photoradiation and human response, and limitations and protection methods for photobiosafety radiation.
The light radiation generated by different light sources varies in intensity, spatial distribution, and spectrum. With the development of lighting materials and intelligent lighting technology, new intelligent light sources such as LED light sources, OLED light sources, and laser light sources will gradually be applied in home, commercial, medical, office, or special lighting scenarios. Compared with traditional light sources, new intelligent light sources have stronger radiation energy and higher spectral specificity. Therefore, one of the forefront directions in the research of photobiological safety is the study of measurement or evaluation methods for the photobiological safety of new light sources, such as the study of biological safety of automotive laser headlights and the evaluation system of human health and comfort of semiconductor lighting products.
The physiological reactions caused by different wavelengths of light radiation acting on different human organs or tissues also vary. As the human body is a complex system, quantitatively describing the relationship between light radiation and human response is also one of the cutting-edge directions in photobiosafety research, such as the impact and application of light on human physiological rhythms, and the issue of light intensity dose triggering non visual effects.
The purpose of conducting research on photobiological safety is to avoid the harm caused by human exposure to light radiation. Therefore, based on the research results on the photo biological safety and photo biological effects of light sources, corresponding lighting standards and protection methods are proposed, and safe and healthy lighting product design schemes are proposed, which is also one of the forefront directions of photo biological safety research, such as the design of health lighting systems for large manned spacecraft, research on health lighting and display systems, and research on the application technology of blue light protective films for light health and light safety.

3. Photobiosafety bands and mechanisms
The range of light radiation bands involved in photobiological safety mainly includes electromagnetic waves ranging from 200nm to 3000nm. According to wavelength classification, optical radiation can be mainly divided into ultraviolet radiation, visible light radiation, and infrared radiation. The physiological effects produced by electromagnetic radiation of different wavelengths are not entirely the same.
Ultraviolet radiation refers to electromagnetic radiation with a wavelength of 100nm-400nm. The human eye cannot perceive the presence of ultraviolet radiation, but ultraviolet radiation has a significant impact on human physiology. When ultraviolet radiation is applied to the skin, it can cause vasodilation, resulting in redness. Prolonged exposure can cause dryness, loss of elasticity, and aging of the skin. When ultraviolet radiation is applied to the eyes, it may cause keratitis, conjunctivitis, cataracts, etc., causing damage to the eyes.
Visible light radiation typically refers to electromagnetic waves with wavelengths ranging from 380-780nm. The physiological effects of visible light on the human body mainly include skin burns, erythema, and eye damage such as thermal injury and retinitis caused by sunlight. Especially high-energy blue light ranging from 400nm to 500nm can cause photochemical damage to the retina and accelerate the oxidation of cells in the macular area. Therefore, it is generally believed that blue light is the most harmful visible light.