If we want to protect the eyes from laser radiation, so-called “full protection glasses" (EN 207) are needed. Filters as well as frames have to be selected to match the maximum power and beam size of the laser in order to make sure that the amount of radiation that advances to the eye behind the glasses, is below the MPE-values (MPE = maximum permissible exposure). This is the same limit which applies to
lasers in class 1.
Lasers which emit light in the visible range of the spectrum and which are used for aiming or alignment purposes, can only be used safely when the power of the laser is low enough. This means, that natural protection mechanisms (blink reflex, reflex to turn away) must be sufficient to make sure that the radiation reaching the eye is below the damage threshold. The limits for this radiation are given for laser classes 2 and 2M. If due to the application higher power lasers are required so-called alignment filters are needed. Such glasses reduce the radiation which can reach the eye, below the limits of a class 2 laser.
Additionally, combination glasses for full protection with an additional alignment function are possible. In this case, the filters act different for different wavelengths (e.g. works as full protection in the near infrared and has an alignment function in the visible). These glasses are designed for alignment purposes only. When working with laser generating visible light for longer periods of time, full protection glasses are necessary and recommended.
