Optical Density, commonly abbreviated as OD, is one of the most important specifications found on laser safety glasses. It describes the ability of a lens to attenuate laser radiation at a particular wavelength.

In simple terms, a higher OD rating means the filter blocks more laser energy. For example, OD 5 attenuates significantly more radiation than OD 3, while OD 7 provides even greater attenuation.

OD values are wavelength specific. A lens may provide OD 7 protection at one wavelength but offer lower protection at another wavelength. This is why laser safety glasses must always be matched to the laser system being used.

Manufacturers typically publish wavelength protection charts that show the optical density provided across different wavelength ranges.

OD ratings are often used alongside other technical specifications such as EN207 L-ratings, Visible Light Transmission (VLT), and laser wavelength compatibility.

Understanding optical density can help users interpret laser safety specifications and select eyewear appropriate for their workplace requirements.