It is a logarithmic measure of how much light of a stated wavelength the lens blocks: each step blocks ten times more. It only applies at the wavelengths the marking names, so glasses are chosen by matching that range to the laser’s wavelength and the maker’s requirements.
Laser eyewear is chosen on two numbers printed on it, and both have to match the laser in use.
Wavelength range
The marking names the wavelengths the lens is made for, in nanometres. Hobby diode lasers often emit blue light, CO2 lasers emit far infrared, and fibre lasers emit near infrared. The laser’s manual or rating label states its wavelength, and the glasses must cover it.
Optical density
At those wavelengths the lens has an optical density (OD). The scale is logarithmic: each whole step reduces the transmitted light by a factor of ten. The density a laser requires depends on its power and class, and the laser maker’s instructions describe what protection to use.
The marking
Protective eyewear made to a recognised standard carries a marking stating its wavelength ranges and protection level. That marking is the evidence of what the filter does. A listing without one, or a lens chosen by colour, gives no such evidence.
Other points that matter
Side coverage, because reflections arrive from angles. Fit over prescription glasses, where needed. Visible light transmission, which decides how well the work can be seen through the lens.
What this site does not say
No pair is described here as safe for a given laser. Pages report the wavelength and optical density the marking states, and the laser maker’s instructions decide what protection is required.
If this page and the manufacturer’s manual disagree, follow the manual. Every laser power, speed, build volume, resolution, temperature and safety rating on this page is taken from the maker’s own documentation, with its unit as published and its source named — none of it is measured here. A figure is written the way the maker states it and is not converted into another convention, because the converted value would be a different number. And the limit this page does not cross: no enclosure, filter, extractor, pair of glasses or setting is described here as making a machine safe. The page reports what the maker supplies and what the markings state — a laser class, a filter type, an optical density at a stated wavelength — and the manufacturer’s instructions decide the rest, because the room, the material and the use are beyond what any listing can know.
Questions makers ask before buying
Can one pair of glasses cover every laser?
Not usually. Diode, CO2 and fibre lasers emit very different wavelengths, and a filter made for one may do little against another. The marking lists the ranges a pair covers.
Is a coloured lens enough?
No. Colour alone says nothing about protection at a given wavelength. The marking under a recognised standard is what states the filter’s performance.
Last reviewed 15 September 2026