Laser Alignment (Adjustment Eyewear)

European Standard EN 208

EN 208 applies to Visible lasers only (ie 400 - 700 nm wavelength range).

Standard protective eyewear generally has a high Optical Density (OD), for example OD 6 or higher is common, giving an attenuation factor 1,000,000 or more. The result is that even visible laser beams become invisible and we cannot see at what point the beam is landing.

From the point of view of safety it is better if we can tell where the beam is, since we are then less likely to expose ourselves to it. Also sometimes it is necessary to be able to see where the beam is for purposes of alignment.

Alignment eyewear:

Balances the Optical Density between protection and visibility of the beam

Protects against the beam in the case of accidental direct exposure to the eye

Allows the wearer to see the spot from the beam

Reduces the power of the laser beam to below the Class 2 limit (ie 1 mW for CW lasers)

Is not designed for intentional direct viewing of the beam

EN 208 (Personal eye-protection. Eye-protectors for adjustment work on lasers and laser systems (laser adjustment eye-protectors)) specifies testing and markings for laser alignment eyewear. To calculate the required eyewear specification for alignment eyewear for your laser, do the following:

For CW lasers (and pulsed lasers with pulse durations greater than 0.2 ms)

Take the CW (or average) power of the laser (if the beam is larger than 7 mm take only the power which can pass through a 7 mm diameter aperture)

Look up the specification from table B1.

For Pulsed lasers (with pulse durations between 1 ns and 0.2 ms)

Take the Energy per pulse (for beams exceeding 7 mm take the Energy passing through a 7 mm diameter aperture)

Multiply by correction factor N1/4 (where N is the number of pulses in 10 s)

Look up specification from table B1 below.

Scale               Maximum Power                 Maximum Energy
Number           (Duration > 2 x 10-4 s)      (Pulses 10-9 to 2 x 10-4 s)
                        W                                       J
R1                    0.01                                   2 x 10-6

R2                    0.1                                     2 x 10-5

R3                    1                                        2 x 10-4

R4                    10                                      2 x 10-3

R5                    100                                    2 x 10-2

Hence eyewear is marked as follows:

Eg. 532 0,1 W 2 x 10-5 J R2

It is important not to confuse R2 EN208 marking with R L2 EN207 marking etc. (see article on EN 207)

Eyewear with EN208 markings will have an Optical Density at the specified wavelengths, as shown in this table:

Scale         Optical

Number     Density

R1             1 > OD < 2

R2             2 > OD < 3

R3             3 > OD < 4

R4             4 > OD < 5

R5             5 > OD < 6

EN208 specifies an extensive list of testing similar to EN207. In Particular the damage threshold testing is carried out using a beam size of 1 mm2, ie 10-6 m2)

See our range of Alignment Eyewear


 PI 0615243617656


Via N. Tommaseo, 3

00100 Campagnano di Roma- Italia

Tel +39 06 9041786

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Laser Optronic Srl


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20139 Milano - Italia

Tel +39 02 574651

Fax +39 02 57410127

Classificazione Laser EN 207 Laser Safety Standards EN 208