Wavelength Wednesday Focus on Safety Eye Wear

Posted by William Burgess on Jan 6, 2016 12:39:37 PM

When we ride our Harleys, we wear a helmet. But when we fire up a Class 3B or Class 4 laser, safety eyewear is often overlooked. Proper selection of eyewear sometimes presents some challenges. All laser safety eyewear is not the same. Eyewear that works well for a CO2 laser is not appropriate for a Nd:YAG laser.


There are many important factors that need to evaluated when selecting the safest possible eyewear. We will discuss the two most important factors. The first is the wavelength coverage of the eyewear. It is marked on the lens and is typically given as a range of wavelengths (i.e. 635nm – 685nm). It is important to select eyewear that  matches the laser in use. When grabbing eyewear from the storage cabinet, don’t become overly reliant on the color of the lenses. Always read the markings!

The other factor that needs to be evaluated is the level of protection. This is also written on the lens and is marked in units labeled OD (Optical Density) as defined by ANSI Z136. There is a number that follows the letters OD. This denotes the strength of the protection. The higher the number the better the protection.

OD to % Transmittance Conversions

OD Transmittance
0 1
1 0.1
2 0.01
3 0.001
4 0.0001
5 0.00001
6 0.000001
7 0.0000001
8 0.00000001
9 0.000000001

The European standard EN 207 uses an L-Rating Spec instead of OD. That is a topic for another day… 

 Laser Safety Eyewear is available from Power Technology. No matter where you bought your laser, we will be happy to help you select the appropriate eyewear for your specific laser.

 By William Burgess, Member ANSI Z136, Z136.1, and Z136.10.

 Would you like to learn more about laser safety eye wear?

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Topics: Laser Safety, wavelength wednesday

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