High power laser pointers and laser modules are both entertaining and widely used for a large number of applications. There is just one serious problem though with the spread of high power lasers. High power lasers can cause serious and permanent damage to your eyes in less time than it takes to blink. Governments and health organizations are aware of this and use and ownership of lasers is becoming increasingly regulated to reduce the dangers of lasers.
The best solution though to the danger of high powered lasers is laser safety glasses or goggle for eye protection.
Laser safety goggles work by using a polymer containing dyes that block light over a specific range of colors or wavelengths. For example some safety glasses will block light with a wavelength of 500nm to 540nm which provides protection from green lasers.
With laser safety goggles, quality depends on two points. How well they block light at a certain wavelength and how much visibility they provide. The ability to block light is determined by optical density or OD for short. The higher the OD, the more light that is blocked.
For most applications the preferred OD is from 3 to 4. If the OD is lower than 3, not enough of the laser beams energy is blocked. If the OD higher than 4, visibility while wearing the safety glasses will be too impaired.
Safety glasses are designed to protect users from accidental exposure to laser beams not deliberate extended exposure. After several seconds exposure to a laser beam, the dyes in the glasses will be destroyed and the glasses will no longer provide protection.