Photorebiological safety issues include the damage of ultraviolet, visible and infrared radiation to human eyes and skin.
The human eye is very complex in structure and has weak repair ability. It is the most sensitive to light radiation and vulnerable to injury.
At present, the main technological way to make white LED is to use the blue light emitted by LED chip to excite the yellow phosphor coating on its surface and mix it to form white light.
According to the reports at home and abroad and the experimental research and hazard assessment of LED products on the market, the light radiation of existing LED lighting products is not enough to cause ultraviolet damage to the skin and eyes, near-ultraviolet damage to the eyes and thermal damage to the retina.
Current studies and IEC 62471 international standards suggest that 200 ~ 400nm blue light has the most significant effect on the photochemical reaction of the retina of the human eye. Obviously, the photobiosafety hazard of LED lights is mainly manifested as blue light.
With the continuous breakthrough of LED technology, the greatly reduced cost of LED products, and the rapid promotion of LED lamp use, the problem of LED light biosafety must be paid attention to and studied.
At present, LED lighting products for indoor lighting mainly include desk lamp, bulb lamp, ceiling lamp (flat-panel lamp), tube lamp and beam lamp (PAR lamp), etc. This paper takes these products as research objects, analyzes the influencing factors of photobiosafety, and carries out a prospective analysis on the photorebiological risk of LED products by designing different research schemes.
1) the photorebiological safety testing system used for the analysis is shown in FIG. 1, including the following main equipment: retinal radiance luminometer, radiation safety measurement spectral radiance analyzer, distributed photometer, full-digital illuminometer, etc.
2) 10 samples of five products were collected from the manufacturing enterprises and the market for the detection of photobiosafety, of which the bulb lamp usage was the largest, 20 samples were collected and tested according to the Chinese photobiosafety standard.
The distribution of photobiosafety was found through the detection of five products.
The amount of samples of products with significant photorefractive safety risks was further expanded and the severity of photorefractive safety of these products was found.
3) conduct data test with the test method specified in IEC 62471 "light biological safety of lamp and lamp system" and GB/T 20145-2006 "light biological safety of lamp and lamp system", and analyze various optical factors that affect the light biological risk value, such as color temperature, beam Angle and lamp transmission cover, and propose product use and improvement Suggestions.
4) optimize the existing test methods, design a test and analysis scheme with reference to the distance between human body and LED based on the actual use environment of the LED lamp, and conduct a more rigorous analysis of the biological safety risk of LED lighting.
Photobiosecurity of different LED indoor lighting products
2.1 test results of biosafety of five types of products (table 1)
It can be seen from the test results that the indoor lighting products, such as LED bulb lamp, LED table lamp and LED panel lamp, have good results in the light biological safety test, all of which are of no danger level.
Photorebiological safety 1 type of hazards mainly occur in LED tube lamps and spotlights.
However, due to the small number of samples, it is difficult to obtain reliable statistical conclusions, so we increased the sample number of LED downlight and downlight to conduct supplementary tests.
2.2 analysis of photorebiological safety of spotlights and downlights
According to the above test results, increase the sampling rate of samples for testing and statistics. The results are shown in table 2:
According to the test results, the damage ratio of LED lamp sample is 65%, and the damage ratio of LED lamp sample is 35%.
According to the light biological safety standard and method of the lamps currently in use in China, the harm level of LED emitting lamp and tube lamp is more significant in various experimental samples.
Influence factors of blue light hazard of spotlights and down lamps
Down lamps and downlights usually have the function of decoration and modification in lighting occasions. For the consideration of beauty and specific lighting direction, these two types of lamps generally have the following characteristics in the process: the lamp passes through secondary light distribution, and different types of light transmission covers are needed at the front end of the light source;
Rich in color, white light has a high degree of discrimination, including multiple color temperature intervals between 3000K and 6500K.
According to these characteristics, the photorebiological safety analysis was carried out from the aspects of color temperature, half peak beam Angle and light transmittance mask.
3.1 relationship between color temperature and blue light damage
It can be seen from table 3 that when the color temperature is lower than 5000K, 90% of LED downlamps and 90% of LED lighting biosafety grade are harmless.
When the color temperature is higher than 7000K, about 65% LED downlights and lighting biosafety level reach 1 kind of hazard.
The statistical results show that blue-ray hazard is more likely to occur in LED products with higher color temperature.
3.2 relationship between half-peak beam Angle and blue light hazard
At present, the commonly used LED lights have many types of beam angles: some are narrow-beam LED lamps with secondary light distribution design, while some are lambert-body light distribution (large beam Angle)LED lamps with no secondary optical design.
These leds of different types of beam angles differ in light intensity distribution and blue light risk level, and it is only through statistics that they can be found to be correlated.
Half-peak beam angles of LED tube lights and spotlights were tested with a distributed photometer, and the beam angles and blue light risk levels of 40 samples were counted (as shown in figure 2).
Figure 2 shows that the blu-ray risk level has the following characteristics: 1 # ~ 17 # sample sample beam Angle acuity 50 °, but the level of biological safety are almost no danger, 18 # # ~ 40 samples of beam Angle at 40 °, 15 ° - 23 samples there are 19 samples (82%) of the light of biosafety level 1 class.
The data sufficiently indicate that under the same conditions, the smaller the beam Angle of LED downlight and spotlight products, the greater the possibility of blue light hazard.
3.3 influence of light transmittance mask on the harm of blue light
The commonly used light transmission covers of LED tube lamp and shooting lamp are: condensing lens lamp shade, frosted lamp shade, transparent lamp shade, etc., its essence is the optical element of second light distribution of light source.
We tested the radiative brightness of 40 downlight and downlight samples respectively, and the results are shown in table 4.
As can be seen from table 4, there is no blue light hazard after removing the light transmission cover.
The reason for the reduction of biohazards in the sample of concentrated lens from class 1 to class 1 is that the beam Angle becomes larger, the light becomes divergent from convergence, and the radiance value decreases.
However, after the removal of the sand type lampshade, the blue light risk of the light source did not reach a higher level of hazard level despite the increase of radiative brightness.
Therefore, the LED light transmittance cover is an important factor that causes or strengthens the risk degree of photobiosecurity in lamps. If the LED light transmission cover can be used rationally, the risk of blue light can be controlled in the level of no risk.
Comparison of results of different detection methods
All the previous data tests in this paper are based on the detection method of GB/t20145-2006 "light biological safety of lamp and lamp system".
This method requires the measurement of all optical parameters under the reference condition of illumination of 5001x.
In fact, indoor household lighting products cannot guarantee this condition. What can be determined indoors is only the installation height of lighting products, usually 2.5m ~ 2.7m. However, the damage of testing light on human body, especially the retina of human eyes, will be analyzed more strictly by the distance from human eyes to light.
In recent years, the iec has conducted a supplementary study on the specific test methods. The iec has proposed a test and judgment view combining brightness and illumination.
Based on the simulated LED lamp's actual use environment for human (that is, the vertical distance from human eyes to lamps is about 1.1m), we designed an analysis scheme to measure the distance to a fixed value and carried out experimental analysis.
In the experiment, the parameters of photobiosecurity were measured under the condition that the distance between the lamp and the detector was 1m, and the results were shown in table 5.
Can be seen from the measured results, the results different measuring conditions, which LED to shoot the light reaches 1 class hazard ratio from 30% to 50%, LED canister light reaches 1 class hazard ratio from 20% to 30%, which based on the value of the measured distance light the harm results of biological safety test analysis scheme is higher than the current standard method, the optical biological safety level analysis is more conservative, light biological safety requirements more stringent.
Analysis in this paper shows that:
1) the higher the color temperature of LED lamp, the greater the possibility of blue light damage, and it is impossible to develop high luminous efficiency products at the expense of human safety by improving the color temperature;
2) the beam Angle is directly related to the blue light hazard of LED products. Reasonable optical design should be adopted to reduce the photobiological hazard level of the products, so as to balance the beauty effect of LED lights and human health needs.
3) for indoor lighting LED products, the photobiosecurity level is measured by equidistant method. The evaluation results are more rigorous than current methods of isoillumination testing, which is conducive to more prospective research on the biosecurity of LED lighting.