With the health concerns and awareness of the effects of photobioradiation, the focus on photobioradiation safety of lighting products that are closely related to our daily lives has been high. A large number of photobiology and medical researches around the world have shown that modern lighting sources have inconsistent and disharmonious effects on human biological characteristics, posing a new threat to human health. Children with myopia, vision deterioration, poor night vision, insomnia, obesity, decreased hormones, reproductive dysfunction, breast cancer, hair loss, depression, etc., are closely related to the use of "light." At the same time, with the dual promotion of industrial capital and government subsidy policies, LED lighting products have been rapidly developed with their characteristics of energy saving, environmental protection, long life and small size, and gradually began to enter indoor lighting.
In this context, people's attention and attention to the photo-radiation effect of LED lighting products has reached an unprecedented height. So, what kind of damage will LED lighting products cause to the human body?
Blue light biological effect
The blue light hazard is a photochemical action caused by radiation with wavelengths between 300 nm and 700 nm, and there is usually a potential for damage to the retina. If the irradiation time exceeds l〇S, this damage mechanism plays a major role and is several times the mechanism of thermal damage.
1.1 LED blue light generation
White LED technology can be realized in a variety of ways (as shown in Figure 1). There are two main types: one is to use blue light technology to form white light with yellow phosphor; the other is to mix white light to obtain white light. Since the driving voltage, the light-emitting output, the temperature characteristics and the lifetime of different color LEDs are different, the multi-color hybrid white light LED is complicated in production and high in cost. Manufacturers generally use the first technology.
Figure 1 white LED technology
At present, the mainstream GaN chip has a center wavelength of the radiation spectrum of 450 nm to 470 nm, and a half width of the radiation band of 30 nm. When the emission spectrum excites the YAG yellow phosphor and the blue light is mixed, a typical white LED spectrum as shown in Fig. 2 is formed. As can be seen from Figure 2, the emission spectra of the different color temperature LEDs are different from the ratio of the luminescence spectra of the excited yellow phosphors. In the high color temperature LED spectrum, the proportion of blue light is significantly higher than that of the low color temperature LED. At present, it is generally believed that the color temperature white LED above 4000K will cause potential danger to photobiological radiation of the human body. Especially when LEDs are used for indoor lighting, it is recommended to use low color temperature LEDs with 2700K~3000K and color rendering index of 80 or more due to the long contact time with the human body. However, the efficacy of low color temperature LEDs is low. Therefore, in order to pursue the light effect and color rendering index, the lighting product manufacturer will increase the color temperature of the product, resulting in more high color temperature and color rendering index products in the market. At the same time, in order to pursue high-utilization LED products, more and more high-power, high-brightness LED products have emerged. These products increase the power and brightness of the light source by adding secondary optical design components, but the narrower beam angles and increasingly brighter LEDs also increase the potential for photobioradiation.
Figure 2 Typical white LED spectrum
2.2 Blu-ray and human health
As an indispensable component of white LEDs, blue light can penetrate the lens of the human eye to reach the retina and cause photochemical damage to the retina. Japanese studies have found that all blue light radiation greater than 20_hcm-2 can cause significant fundus changes. Moreover, the lens of the human eye begins to form and gradually develops with the age of the person. Therefore, the greatest risk of blue light hazard occurs in infants and young children. At this time, the well-developed human eye lens has a high transmittance for short-wavelength spectral radiation, which is several times that of an adult's eye. Short-wave blue light is more likely to reach the retina through the lens of such a person, thereby accelerating the macular area of ​​the retina. Oxidation of cells. Although the adult lens has a low transmittance to blue light, long-term exposure to blue light will cause degeneration of the retina and form photoretinitis.
Evaluation and measurement of blue radiation safety
The International Organization for Standardization IECTC76 in 2006 based on the CIES: 009 technical report, developed the IEC62471 "Light and Light System Photobiosafety" international standard, which specifies the photochemical damage of retinal blue light. The IEC subsequently developed a technical report on the ffiC62778 for the blue light hazard of lamps and light sources. China has also completed the development of requirements and grade classification methods and test method standards for devices and modules for semiconductor light-emitting diodes. The standard is divided into four grades according to the degree of hazard, RGO "exemption class", RG1 "low risk", RG2 "moderate risk" and RG3 "high risk". For LED products that reach the RGO "exemption class", normal human eyes can be directly viewed for a long time (10000 seconds) without causing retinal photochemical damage.
For the measurement of blue light hazard, it is usually implemented by measuring the radiance of the sample to be tested. When the sample to be tested is a small light source (with a side angle of less than 0.011 radians), an alternative method of measuring illuminance can be used. The radiance is typically measured using a point imaging radiance meter and a surface imaging radiance meter (such as a CCD camera). In the newly developed semiconductor light-emitting diode test method, it is recommended to use the spectral radiance method for measurement. The spectral range of the radiance luminance meter should cover 300 nm to 700 nm. If the CCD surface imaging radiance measurement method is used, the radiance value needs to be corrected by the spectral coefficient. When measuring with different exposure times, the linearity of the response needs to be corrected. At the same time, the measurement field of view of the imaging radiance meter should be consistent with the angle of view corresponding to the classification level of the radiation hazard (eg, 1 〇〇 milliradians, H milliradians, etc.), and the receiving aperture is 7 mm. The field of view and the receiving aperture of the imaging radiance meter should remain constant for measurements at different distances.
Blu-ray hazard research experiment
3.1 Experimental samples and devices
Through the supermarket, market, online shopping and other ways, a total of 9 commercially available LED lamp samples of common types and specifications were randomly selected, and the blue light radiation measurement and evaluation of the samples were carried out. The test samples are shown in Table 1.
Table 1 experimental samples
The experimental device uses a photobiosafety radiation test system produced by Hangzhou Zheda Tricolor Instrument Co., Ltd. The system is mainly composed of a spectral radiation analyzer, a retinal brightness meter and a calibration source, and the structure is shown in FIG. In order to effectively measure the potential hazard of the test sample to the human eye, the retinal brightness meter used in the experiment uses a measurement structure that completely simulates the human eye optical system, including a small 7mm pupil that simulates the pupil of the human eye, and 2 million simulated retinal imaging. Pixel CCD camera. At the same time, the field angle changes of 1.7mrad, llmrad and 100mrad corresponding to different durations of the human eye are effectively simulated, and the measured field angle is kept constant M during the measurement distance change.
Figure 3 Structure of photobioradiation safety experimental device
3.2 Experimental results
According to the test method and safety class classification method defined by the IEC62471 standard, nine tested parts were tested separately, and the hazard level of photobioradiation safety was classified according to the test results. The results are shown in Table 2.
Table 2 sample test results and hazard classification
In the photobioradiation safety test, the final hazard level of the sample to be tested is based on the highest hazard level of all hazard types. For samples No. 24 and No. 25, although the risk level of the other five hazard types is RG0, since the blue light hazard is RG2, the final hazard level of the tested sample will still be classified as RG2.
It can be seen from Table 1 and Table 2 that among the 9 LED lamps tested, LED bulbs , LEDPAR lamps, LED tubes , LED wall lamps and downlights are classified as non-hazardous levels; LED floodlights and LED shots The lights are classified as low risk; 2 LED flashlights are classified as moderate hazard levels. The potential hazard of blue light hazard causes the final hazard level of the tested samples of fis, £UVA, iR, all at a non-hazard level to be assessed as low or moderate. This indicates that blue light hazards are critical to the assessment of the photobiosafety hazard level of LED products. At the same time, the risk of blue light hazard may increase as the beam angle of the sample decreases.
in conclusion
Blu-ray hazards have become a lighting safety issue that people are increasingly concerned about. The commercially available LED products of this survey also cover the commonly used indoor lighting products. From the test results, the LED products on the market at this stage are generally in line with the photobiosafety standards.
However, the current LED products have not yet formed a standardized and orderly market order, and the products that are mixed and shoddy still exist. In order to promote the further development and upgrading of the LED lighting industry, it is necessary to improve standards as soon as possible, develop and improve LED lighting technology, and standardize the LED market. At the same time, the LED product manufacturer also has the responsibility to guide the user to use the lighting products correctly. For example, the shape and structure of the product cannot be changed, the accessories and covers of the lamps are removed, and their use cannot be changed. Requires to install the luminaire. For narrow-beam LED products, there should be a warning that the light source cannot be viewed directly with the eye. Lighting product manufacturers must strictly implement the requirements marked in the standard, and provide warning signs or reminders for some products that need to be marked.
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