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How to select the right laser safety glasses. On this page, we explain the various aspects.
In an area where a class 4 laser is used, wearing laser safety glasses is an absolute requirement. Because laser light does not diverge, the intensity of the laser beam remains dangerous to the eye over long distances.
Direct exposure of the eye to the laser welding equipment is virtually impossible under normal circumstances. During welding, only a portion of the laser light will be absorbed and converted into heat. Another part of the light will reflect. Depending on the surface and material type, this reflection can be either specular or diffused.
In both cases, the risk of eye damage remains. The use of laser safety glasses is therefore always necessary (mandatory) in the vicinity of a laser welding machine.
For more information regarding the risks, please refer to this link.
Laser safety glasses are designed for a specific type of laser. Not every pair of glasses is suitable for all types of laser light. To select the right laser glasses, consider:
The pulse length is important for the intensity of the laser and is crucial for selecting the right laser safety glasses. The classification is shown in the table below. For laser welding, we always consider D or I.
| Mode | Letter | Pulse lengte |
|---|---|---|
| Continuous Wave | D | >0,25s |
| Pulsed | I | 1µs – 0,25s |
| Giant Pulsed | R | 1ns – 1µs |
| Mode-Locked | M | <1µs |
The attenuation level of the laser safety glasses is indicated by the LB or OD value marked on the glasses. According to NEN-EN 207, the protective value of the glasses must apply to both the lens and the frame of the glasses. This concerns the LB value indicated on the glasses. The OD value (Optical Density) indicates the attenuation level of the lens.
In some cases, the OD value is higher than the LB value indicated. In this case, the lens in the frame has a higher protective value than the frame.
The attenuation level of the lens is structured as follows:
| OD Factor | Power Attenuation | Power Transmission |
|---|---|---|
| OD1 | 0 | 100% |
| OD1 | 1/10 | 10% |
| OD2 | 1/100 | 1% |
| OD3 | 1/1000 | 0,1% |
| OD4 | 1/10.000 | 0,001% |
| OD5 | 1/100.000 | 0,0001% |
| OD6 | 1/1.000.000 | 0,000001% |
| OD7 | 1/10.000.000 | 0,0000001% |
| OD8 | 1/100.000.000 | 0,00000001% |
| OD9 | 1/1.000.000.000 | 0,000000001% |
Different materials absorb light colors or wavelengths to a greater or lesser extent. This also applies to the materials used in laser safety glasses. For this reason, the glasses should indicate the attenuation level applicable to a specific wavelength.
Laser safety glasses typically provide protection against a specific wavelength range of light. The glasses will indicate for which wavelength the protection is provided.
An example of how the marking on a laser safety glasses is indicated is:
800 – 1100 nm DIR LB5
In this case, the laser safety glasses provide protection in the wavelength range of 800 to 1100 nm. This protection is provided for lasers operating with a pulse duration between 1 nanosecond to 0.25 seconds.
In laser safety products, traditional welding color codes we are familiar with, such as DIN color codes 7 to 13, do not apply. These color codes cannot be translated into values known in laser safety products.
For all laser safety products, such as laser glasses and laser safety glasses, the Visual Light Transmission value is also indicated. This value indicates to what extent visible light is transmitted through the laser safety glasses. A higher value allows more light to pass through than a lower value.
