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Home > Laser Safety

Laser Safety

In most cases, a laser emits light in the form of a laser beam. This means that the light dominantly propagates in a certain direction, typically with most of the optical power concentrated to a small area. This characteristic combined with spatial coherence i.e. a fixed phase relationship between the electric field values at different locations, has as result that the power of laser is independent of the distance to the radiation source.

The most recent classification norms (EN60825-1) have catalogued lasers into several hazard classes, depending on the Accessible Emission Limits. AELs are defined as the exposure levels which are inherently safe for the eye; the classification scheme is a measure of the laser system to produce injures to the personnel.

ClassConceptComment
1The radiation emitted by this laser is not dangerousNo need for protection equipment
1MEye safe when used without optical instruments, may not be safe when optical instruments are usedNo need for protection equipment, if used without optical instruments
2Eye safe by aversion responses including the blink reflex.No need for protection equipment
2MThe light that can hit the eye has the values of a class 2 laser, depending on a divergent or widened beam, it may not be safe when optical instruments are usedNo need for protection equipment, if used without optical instruments
3RThe radiation from this laser exceeds the MPE values (MPE: maximum permissible exposure). The radiation is max. 5 x AELs of class 1 (invisible) or 5 x of class 2 (visible). The risk is slightly lower than that of class 3BDangerous to the eyes, safety glasses are recommended
3BOld class 3B without 3R.
The view into the laser is dangerous. Diffuse reflections are not considered as dangerous.
Dangerous to the eyes, safety glasses are obligatory
5Old class 4
Even scattered radiation can be dangerous, also danger of fire and danger to the skin
Personal safety equipment is necessary (glasses, screens)

Laser safety regulations have the purpose of defining the necessary guidelines to every operator working with lasers. Most of the existing norms are for the major part intended to deal with eye protection, being this the most critical organ in relation to laser injury.

The current European norm - EN 60825 - requires that laser safety eyewear provide sufficient optical density to reduce the power of a given laser to equal to or less than the listed Maximum Permissible Exposure levels (MPE).

EN 207 contains the specifications that eye protection equipment shall have to be safe for the laser operator: requirements related to optical density (OD) and to stability to laser radiation.

Duration of test for filters and eye protectors against laser radiation.
Testing conditions for laser typeTypical laser typePulse length (s)Number of pulses
Dcontinuous wave laser51
Ipulsed laser10-4 to -150
RQ-Switched pulsed laser10-9 to 10-750
Mmode-locked pulsed laser<10-9 50
Reference: EN 207

According to this norm, protection due to optical density alone is not sufficient when the material of the eyewear cannot withstand a direct hit. Filter and frame must be able to resist a direct hit from the laser for which they have been selected for at least 5 seconds (CW) or 50 pulses (pulsed mode).

Scale numberMaximum spectral trasmittance for laser wavelength
τ (λ)
Power and energy density (E, H) for testing the protective effort and stability to laser radiation in the wavelength range
180 nm to 315 nm>315 nm to 1400 nm>1400 nm to 1000 µm
For test condition
D
>3·104
I, R
10-9 to
3·104
M
<10-9
D
>5·10-4
I, R
10-9 to
5·10-4
M
<10-9
D
>0,1
I, R
10-9 to 0,1
M
<10-9
ED
W/m2
HI/R
J/m2
EM
W/m2
ED
W/m2
HI/R
J/m2
HM
W/m2
ED
W/m2
HI/R
J/m2
EM
W/m2
LB110-10,013·1023·10111020,051,5·10-31041031012
LB210-20,13·1033·10121030,51,5·10-21051041013
LB310-313·1043·101310450,151061051014
LB410-4103·1053·1014105501,51071061015
LB510-51023·1063·10151065·102151081071016
LB610-61033·1073·10161075·1031,5·1021091081017
LB710-71043·1083·10171085·1041,5·10310101091018
LB810-81053·1093·10181095·1051,5·104101110101019
LB910-91063·10103·101910105·1061,5·105101210111020
LB1010-101073·10113·102010115·1071,5·106101310121021
Reference: EN 207

EN 208 refers to glasses for laser alignment: these glasses allow the user to see the beam spot while aligning the laser. Alignment glasses must be able to limit the incident power to the power of a class II laser and to withstand a direct hit.

Scale NumberCW lasers and pulsed lasers with pulse length of >2·10-4 s
Max. laser power in W
Pulsed lasers with a pulse length >10-9 to 2·10-4 s
Max. pulse energy in J
RB10.01 W2·10-6
RB20.1 W2·10-5
RB31 W2·10-4
RB410 W2·10-3
RB5100 W2·10-2
Reference: EN 208