Choosing laser eyewear works differently from all other eye protection: darker does not mean safer. Protection is tied to a specific wavelength — a filter that stops 1064 nm may be completely transparent at 532 nm.
Marking
An EN 207 marking is made up of a mode letter, a wavelength range and an L-number — D 315-532 L5, for example. The L-number, from 1 to 10, gives the attenuation, each step being a factor of ten.
- D
- Continuous wave (>0.25 s)
- I
- Pulsed mode (1 μs – 0.25 s)
- R
- Giant pulsed mode (1 ns – 1 μs)
- M
- Mode-locked (<1 ns)
Note that an EN 207 filter must withstand a direct hit for at least 5 s or 50 pulses without failing. Selection must always be based on the laser's data sheet — wavelength, power, pulse duration and beam diameter.