Often laser safety glasses are required to reduce the laser power to within an eye-safe limit while still allowing the laser beam or spot to be visible for alignment purposes. For example, you may have a 30mW 532nm laser that you need to align however want to ensure that it is still visible.
In normal indoor lighting if the laser is under 1mW in power, then it will still be visible. To achieve this, you need laser eyewear that will attenuate the laser beam by approximately 30X or to 1/30th of its original power.
Knowing you want to cut the laser down by around 30 times you then need to work out the optical density required for the glasses. Too high and it will cut the beam out entirely and too low will not provide adequate protection.
Optical density (OD) can simply be thought of as the number of zeros after the one that the laser eyewear will cut the laser power down by. An optical density of one is 10X attenuation, 2 is 100X attenuation, 3 is 1000X attenuation etc. Therefore simply put you are looking for an optical density between 1 & 2. To work out exactly what the attenuation of a pair of glasses is you can use a scientific calculator and enter the shift key and 10 to the power x and enter the OD, which will give you the corresponding attenuation factor. For example, an OD of 1.5 gives an attenuation of 31X. The OD 1.5 will cut the 30mW laser down to around 0.96mW, therefore, provides a good balance of visibility and protection.
If the laser is outdoors, then this needs to be also considered as in many situations under bright light laser power about 1mW maybe required.
If you have any questions regarding suitable laser glasses for your specific situation, please contact us on 1300 411 337 or email us at info@dioptika.com.
Belo provides like to some of the laser safety glasses we do with low optical densities for alignment applications.