DIN-EN-62471: Photobiological safety of lamps and lamp systems
We cannot hold a direct view into the sun for long. If we look into a very bright light source we can observe the afterimage for a long time.
But - can the light harm the eyes? Can a look into a light source damage our retina?
There is no general answer to this question. If this can be excluded with a diffuse light source such as an LED panel, a laser, for example, is quite capable of damaging the retina.
The danger can be caused thermally as well as photochemically. In the case of a thermal hazard, the beam falling into the eye causes an increase in temperature at the affected area. This is caused by lasers, for example. In the case of photochemical hazards, the incident beam causes molecules to initiate a chemical reaction which can damage the affected tissue. This can occur, for example, when viewing the sun unprotected.
DIN EN 62471 offers help with classification, according to the criteria of which every illuminant and every luminaire must be tested for CE marking.
DIN-EN 62471
DIN or its equivalent, the European Directive 2006/25/EC, specifies the criteria according to which a light source must be evaluated and the resulting hazards.
Not only the light emitted is assessed.
It is not just the light emitted that is evaluated:
Possible retinal damage caused by light
Possible retinal damage especially by blue light
Possible damage by UV, UV-A and IR (infrared) light
Possible damage to the retina or skin by the heat radiated by the lamp
This standard covers lamps - including individual LEDs - and luminaires with integrated lamps. Once a light source has been tested, the luminaire in which it is used does not need to be tested again.
The hazard is assessed either from the distance at which the light source achieves 500 lux illuminance - or from a specified viewing distance of 200 millimetres.
Where an illuminant (e.g. LED) is installed in a luminaire, optics are usually installed in front of the lamp. This - and a generally higher viewing distance than 200 mm - drastically reduces the risk of damage (doubling the distance means four times less risk).
Risk groups (RG) Photobiological safety
For easy classification of the different illuminants, they are classified into 4 risk groups.
Risk group 0 (RG0)
There is no danger here. Even when looking directly into the light source for a longer period of time, the retina is not affected.
Risk group 1 (RG1)
There is a low risk here. Damage to the retina can be largely ruled out. Even with a longer but temporary view into the light source no damage occurs.
Risk group 2 (RG2)
There is a medium risk of damage in this group. Direct, prolonged exposure to the lamp should be avoided. This is where the aversion reaction occurs. The illuminant is so bright that an unconscious closing reaction of the eyelid is caused. We close our eyes and turn away. This reaction prevents damage to the retina. Only if this reaction is consciously prevented can damage of the retina be caused by prolonged staring into the light source.
Risk group 3 (RG3)
Here, damage to the retina can occur after just a short look into the light source. Here you will find e.g. very bright, directed light sources such as lasers etc.
Blue light hazard (Photoretinitis)
The light spectrum of a light source usually contains many different wavelengths. Particularly with LEDs, an increase in the blue wavelength range 400 nm to 500 nm can be observed in the distribution of the wavelengths in the spectrum due to technological reasons. High-energy blue visible light (maximum approx. 440 nm) can cause so-called photoretinis. This is a photochemical damage of the retina caused by oxidation. In this case, the size of the illuminant as well as the viewing distance and the luminance must be taken into account when assessing the risk.
With regard to the risk of blue light, it must also be ensured that blue ambient light does not cause retinal damage. Only a long, direct view into an illuminant with high luminance (strong light source) and a high blue light component can cause damage.
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