Laser safety FAQs

Common questions about laser safety products

Here's what our customers frequently ask about laser safety:

 

Common questions about laser safety eyewear, from LaserVision.

 

Do you have laser safety glasses with "Class 4"?

The term 'class 4' is the laser classification according to EN 60825-1 and ANSI Z136.1. Class 4 designation means that this is a dangerous laser and emitted radiation is an eye, skin and fire hazard. When you work with this laser, laser protective eyewear is essential. However, the laser classification does not include any information regarding the wavelengths or the required protection levels that the glasses must protect against. Please contact us for assistance in selecting the appropriate protection.

 

How long will my glasses protect me?

There is no simple answer to this question. Some glasses are worn-out after only one year, while others look like new after four years. This depends on several factors such as careful treatment, proper care, and environmental factors. A pair of glasses that are treated with care, cleaned according to instructions and used in a laboratory setting will certainly outlast a pair of glasses that are treated carelessly, or worn by several different people in a rough production environment. Glasses that show any damage (such as a damaged or scratched filter, colour changes in the filter, or damage to the metal reinforcement of the frames) should not be used. If you are in doubt, please contact us to arrange a safety inspection of your glasses.

 

What is the difference between glasses offered according to EN 207 and glasses offered according to EN 60825?

The difference is in the resistance time of the filter against a direct laser hit in relation to the specified protection level and the energy or power density of the laser. The European legislation (EN 207) requires that a filter must withstand a direct hit from the laser for which it was designed for under defined conditions for 5 seconds (continuous wave mode) or 50 pulses (pulsed mode). If there is no filter available that fulfils these requirements, we quote (based on the EN 60825) a filter that comes as close as possible to these requirements. This means that the Optical Density (OD) is always correct, but the resistance time of 5 seconds/50 pulses cannot be guaranteed.

 

Why is the beam diameter so important for the calculation of the protection level?

This has to do with the resistance time, over which a filter will withstand a direct hit. To know this, it is necessary to calculate the damage threshold. This is the highest value that the material can withstand. The unit is power or energy density - the power or energy per square metre. For this calculation, the beam area and the pulse energy or the average power of the laser is needed. Without the diameter, it is not possible to calculate the beam area, the energy or the power density. Therefore, without the beam diameter, it is impossible to know what the filter has to withstand in case of a direct laser hit.

 

Can I see the laser beam with the glasses?

Unless shone directly into the eye, a laser beam in the visible wavelength range is only seen when its light is scattered by dust in the air, or when it hits an object and appears as a beam spot.

Laser safety eyewear is usually designed as full protection eyewear (EN 207). Such filters protect against laser radiation of the specified wavelength or wavelengths ranges and absorb or reflect the beam completely. This means that the beam spot will not be visible. If it is still visible, then the protection level of the glasses is not high enough, or secondary radiation (a different wavelength) is generated.

Please check carefully whether the marking of the laser safety eyewear matches the requirements of the laser. The protection of carefully selected eyewear will remain stable when hit by the laser throughout a minimum period of 5 seconds and 50 pulses under standardised conditions. Nevertheless, it is not advisable to look into the beam directly under any circumstances.

 

What can I do when I have to align my visible laser?

Never put down your laser safety glasses when working with lasers above class II. There are alignment glasses available for this purpose, (acc. to EN 208 for 400 - 700 nm only). These filters are suitable for aligning lasers that emit dangerous radiation in the visible spectral range. Alignment filters do not absorb or reflect the laser radiation completely. The radiation is only reduced to values below 1 mW for continuous wave lasers (see laser class 2). You must take care that the average power of the laser does not exceed the power given on the glasses.

 

Can I look right into the laser beam with my laser safety glasses?

Laser safety glasses are designed to protect your eyes against an accidental direct hit of the laser beam. They are not designed for long-term or intra beam laser viewing conditions. A properly selected pair of glasses will protect you under standardised conditions against a direct look into the laser, but only for 5 seconds/50 pulses.

 

You have quoted red filters. Can I have the glasses with a different colour?

The colour of absorption filters cannot be chosen at random, but depends on the wavelength the filters protect against. To protect against wavelengths in the UV-region or the lower visible (blue radiation), a yellow or orange filter is usually offered. A red filter is usually used to protect against wavelengths in the green region. Please take into consideration that you cannot select glasses by the colour. Always make sure that the quoted or available pair of glasses matches the requirements of your laser. Pure coated filters (interference structure on clear substrates), do not affect the colour recognition and possess a high daylight transmission.

 

I have a pair of glasses (e.g. for a Nd:YAG Laser). Can I use them for my new laser as well?

Before this question can be answered, you must determine the specific requirements of your new laser (wavelength, operational parameters, viewing conditions, etc.) and calculate the protection level according to the EN 207/208 standard. When these parameters are known, verify that the marking on your existing pair of glasses matches these requirements. If you are not sure, please call us. We will carry out the calculation and check for you.

Please note: The thoughtless use of a pair of laser safety glasses for a different application (different wavelength or different power/energy than previously calculated) may cause the loss of your eyesight.

 

Why is there not a pair of glasses covering all my lasers?

The radiation that is visible to humans lies between 380 - 780 nm (the exact limits are different for each person). In order to cover all lasers, you would need a material that does not transmit any visible radiation, which means it would be completely black and you would be unable to see to work. If you have several visible lasers, then it is necessary to use several pairs of glasses.

However, even if you do not want to completely block all wavelengths or have a fairly small number of wavelengths to cover, the glasses may be too dark to work with. Usually the protection within a material slowly increases spectrally until it reaches the required protection level at a given wavelength. This means that it not only covers the required wavelength but also areas below and above it (with lower Optical Density). Therefore, if you want to cover several wavelengths in the visible spectrum the Optical Density curves will overlap resulting in dark filters or glasses.