There are typically three different types of filters used in laser safety glasses.
Polycarbonate filters are the most popular as they are lightweight and more cost effective. They are made by injecting a specific dye into the polycarbonate that absorbs the specific wavelengths.
The next type of filter used in laser safety glasses is the filter glass lens. These typically use a mineral glass lens that absorbs and certain range of frequencies.
Lastly some laser glasses use dielectric coatings on the surface of a glass lens. These can provide narrow band protection and therefore can often appear clear where normal polycarbonate lenses would have colour.
For more information or if you have any questions feel free to contact us at email@example.com and one of our laser safety experts will be happy to help.