When using lasers in industrial applications, risks are a constant presence. Risks of eye damage go hand in hand with humans working near lasers. Because of this, all lasers fall into a certain laser class after testing. The classes are according to potential risks and in descending order for eye safety, so: the higher the laser class, the lower the safety. In other words: the higher the laser class, the higher the potential risk!
Which laser classes are there?
The lasers and laser sensors are classified based on the risks that they impose. The different classes are categorized by the maximum power rate and beam size of the laser. These laser classes are defined by the harmonized IEC EN 60825-1 standard. The classification consists of the following classes: 1, 1M, 2, 2M, 3R, 3B and 4.
Laser safety class 1
Laser light that belongs to this class is safe at all times in all circumstances. Even with the use of optical instruments it imposes no risk to nearby persons. These lasers do not exceed the maximum tolerated exposure values. So, there is no damage to the eyes. Lasers in this class are LAM distance sensors, for example. This is relatively the safest laser class.
Laser safety class 1M
A Class 1M laser is safe in all circumstances, even with direct irradiation into the eye, except for when the beam goes through an optical instrument like a lens. Then a direct irradiation is dangerous. Direct and collimating beams are especially dangerous with direct irradiation. An example of such laser is the Z1M18B-F-635-lg90 that is used in applications like the positioning of a saw on a saw table.
Laser safety class 2
A Class 2 laser is considered safe at direct irradiation into the eye, except when the laser light is within the visible spectrum and has an optical output of up to 1 mW. Under normal circumstances the human eye is capable of shutting the eyelid within 250 ms. This way eye damage is prevented. This class is only applicable to light within visible wavelengths and an optical output of up to 1mW. A good example is the Z1D-635-pe-24, a red dot laser that is used for positioning in the textile industry.
Laser safety class 2M
Laser light in this class is safe because of the reflex time of the eyes with which they shut the eyelids during exposure. The definitions are identical to Class 2 , except for the prerequisite of not using an optical instrument. Lasers in Class 2M also have a higly divergent or wide beam diameter. A laser in this class is the ZLP1 laser projector from Z-Laser that is used in many logistic applications like pick-and-place.
Laser safety class 3R
Lasers in the class 3R have a continuous beam and an optical power between 1 and 5 MW. Within the wavelength range between 400 and 700 nm, a maximum AEL (Accessible Emission Limit) is five times that of a laser in class 2. For full-spectrum lasers from 302.5 nm, a maximum of five times the AEL of a class 1 laser. Direct radiation from these lasers is considered dangerous, reflections do not have to be considered dangerous under normal circumstances. Using optical instruments makes this laser dangerous at all times. Think of the Z5M18B-F-635-pe point projection laser.
Laser safety class 3B
A class 3B laser beam is dangerous for the eye at all times, as well in the visible as the invisible ranges. Even irradiation from reflections into the eyes can cause damage. Normally, an exposure to a reflection from a distance of 13 cm with a duration of up to 10 seconds is not considered dangerous. The maximum optical output in Class 3B is 500 mW for lasers with a continuous beam. For pulsated lasers a maximum optical output for each pulse has to be smaller than 105 J.m-2 per pulse per surface. Factories that make use of Class 3B lasers have to meet extra precautionary measures, in comparison to aforementioned classes, for the protection of their personnel that works near these lasers.
Laser safety class 4
This is the highest and most dangerous laser class. Class 4 lasers consist of lasers with an optical output over 500 mW. Direct irradiation as well as that of reflections are dangerous at all times under all circumstances. These lasers can also ignite a surface or atmosphere which can lead to a fire or an explosion. Laser beams in this class can burn the skin and even permanently damage the eyes with direct, diverted or indirect exposure. For a Class 4 laser a NOHA (Nominal Ocular Hazard Area) and an NOHD (Nominal Ocular Hazard Distance) have to be considered. The areas in which these lasers can be equipped with a key switch or a safety interlock, from Haake for example. This way no people can enter the area with a Class 4 laser while it is operating.
The classes that are mentioned are in effect on the laser itself. The class can change in a different application. This means that the same laser with class 1, for example, might not have the same class in every area of application. When this laser is applied in an application where an operator has to look directly into the laser, the laser is classified as a class 2 laser.
Another exceptional application is the use of two lasers with class 1. When these lasers are aimed at the same point, it makes for a higher laser class than the initial one of the used lasers.