Photobiological safety Testing of Lamps and Lamp Systems

With the popularity of LED lighting, the photobiological safety testing issues caused by its light radiation have attracted public attention, the most important of which is the blue light hazard. Optical radiation not only adversely affects the human retina, but may also harm the cornea, conjunctiva, lens and skin of our eyes. This paper intends to analyze and elaborate on photobiosafety from the concept, types, measurement methods, influencing factors, and actual effects of photobiosafety, and strive to trace the origin and eliminate some inherent impressions caused by excessive publicity.

1. Photobiosafety
The concept of photobiological safety, in a narrow sense, refers to the safety problems caused by the radiation effect of light, and in a broad sense, it refers to the safety problems caused by optical radiation to human health, including the visual effects of light, Non-visual effects of light, radiative effects of light.

In the existing photobiological safety research system, the research object of photobiological safety is lighting or display equipment, and the object of photobiological safety is the human body’s eyes or skin and other organs, which are expressed as some physiological parameters such as body temperature, pupil Changes in diameter, etc. The research on photobiological safety mainly focuses on three major directions: the measurement and evaluation of photobiological safety radiation generated by light sources, the quantitative relationship between optical radiation and human response, the limit standards and protection methods for photobiological safety radiation research.

The optical radiation generated by different light sources has differences in the intensity, spatial distribution and spectrum of the optical radiation. With the development of lighting materials and smart lighting technology, new smart 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, the new smart light source has stronger radiation energy and higher spectral specificity. Optical radiation of different wavelengths acts on different human organs or tissues, resulting in different physiological responses. Since the human body is a complex system, the quantitative description of the relationship between optical radiation and human response is also one of the frontier directions of photobiosafety research, such as the impact of light on human circadian rhythm and its application research, triggering non-visual Effect of light intensity dose issues and so on.

The purpose of research on photobiological safety is to prevent the human body from being harmed by light radiation. Therefore, according to the research results of the photobiological safety and photobiological 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 frontier directions of photobiological safety research. Design of healthy lighting system for human spacecraft, research on healthy lighting and display system, research on light health and light safety application technology of blue light protective film, etc.

2. Photobiosafety bands and mechanisms
The optical radiation band range involved in photobiological safety is mainly electromagnetic waves from 200nm to 3000nm. Ultraviolet radiation refers to electromagnetic radiation with a wavelength of 100nm-400nm. Human eyes cannot perceive the existence of ultraviolet radiation, but ultraviolet radiation has a great impact on human physiology. When UV rays irradiate the skin, it can cause dilation of blood vessels and erythema, and prolonged exposure can cause dryness, loss of elasticity and aging of the skin. When ultraviolet rays irradiate the eyes, it may cause keratitis, conjunctivitis, cataracts, etc., and cause damage to the eyes. It is generally believed that there are two main forms of photobiological mechanism: photochemical mechanism and thermal radiation mechanism.

Visible light radiation, usually refers to electromagnetic waves with a wavelength of 380-780nm. The physiological effects of visible light on the human body mainly include burns to the skin, erythema, and damage to the eyes such as thermal damage and solar retinitis. Especially the high-energy blue light of 400nm-500nm can cause photochemical damage to the retina and accelerate the oxidation of cells in the macular area. Therefore, blue light is generally considered to be the most harmful visible light.

Infrared radiation refers to electromagnetic radiation with a wavelength of 700nm-1mm. The human eye also cannot perceive the presence of infrared radiation, but infrared radiation can affect the human body through thermal effects. When infrared rays are irradiated on the skin, they will be absorbed by the subcutaneous tissue and locally heated, causing acute skin burns. When the irradiation area is large and the time is long, the human body will have systemic symptoms due to overheating, and even heatstroke will occur. Infrared irradiation of the human eye can cause damage to the cornea and pupillary sphincter, causing eye discomfort or pain.

3. Types of Photobiosafety
The narrow sense of “photobiological safety” refers to the safety of the radiation effect of light, focusing on the light radiation hazards caused by light sources and lamps, mainly involving the 200nm-3000nm band. Light radiation hazards can be divided into hazards to the anterior surface of the eye (cornea, conjunctiva and lens), retina and skin according to the site of action on the human body. The hazards to the front surface of the eyes mainly involve actinic UV hazards, near-ultraviolet hazards to the eyes, and infrared radiation hazards to the eyes.

4. Photobiosafety hazard assessment
The evaluation of the photobiological safety of a light source or luminaire is to measure the relevant indicators of various photobiological safety hazards. By comparing the measurement results with the exposure limit, the lamps and lamp systems are divided into different levels.

Based on the ICNIRP Guidelines for Incoherent Light Sources, lamps and lamp systems are classified as Exempt, Hazard Class 1 (Low Hazard), Hazard Class 2 (Moderate Hazard), Hazard Class 3 (High Hazard).

If the measurement result is below the exempt emission limit, it is exempt class; if the measurement result is between the exempt emission limit and the low hazard emission limit, it is classified as hazard class 1; if the measurement result is between the low hazard emission limit and the moderate hazard emission limit , it is a hazard level 2; if the measurement result is greater than the medium hazard emission limit, it is a hazard class 3.

5. The actual effect of photobiosafety
Photobiological safety testing has been included in the category of mandatory testing in 2018. Therefore, for the manufacturers of lamps, in terms of photobiological safety, it is necessary to pay more attention to the design and manufacture.

In the issue of photobiological safety, there is usually no need to pay special attention to the effect of thermal radiation, because according to common sense, when the human body is exposed to excessive thermal radiation, it can be sensed, and the human body will naturally escape from this environment. . For photochemical action, because it is an effect on cells, the human body cannot perceive the damage during the accumulation of harm, so it is necessary to do a good job of protection.

However, whether it is a traditional lighting source, a new type of light source such as LED, or even a variety of electronic display devices, the photobiological safety problems that can be caused are difficult to reach the level of harm. In fact, studies have shown that the photobiological safety problems that various artificial light sources can bring will not exceed the impact of the sun, so in most cases, it is not necessary to do special protection for photobiological safety problems.

To protect the photobiological safety, in fact, reduce the dose of photobiological safety. The way to protect photobiological safety is very simple. First, use protective clothing or protective glasses to block light if necessary. Second, if there is no condition to block light, you should try to reduce the time in this light environment. Simply put, if you want to protect your eyes from photobiological safety, avoid looking directly at strong light sources with the naked eye.

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