Optical Density (OD) is one of the most important specifications when selecting laser safety glasses. It describes how effectively a lens reduces the intensity of laser radiation.

Optical density is measured on a logarithmic scale. Each increase in OD represents a tenfold reduction in transmitted laser energy. For example, an OD 4 filter reduces laser energy by a factor of ten thousand.

Higher optical density values provide stronger attenuation, which may be necessary for high-power laser systems. However, higher OD lenses can sometimes reduce visible light transmission, which may affect brightness.

Selecting the appropriate OD depends on several factors including laser power, wavelength, and exposure conditions. Laser safety standards and workplace safety guidelines often determine the recommended OD level.

Lens markings typically list the wavelength range alongside the optical density value, allowing users to verify compatibility.

Understanding optical density helps ensure protective eyewear provides the required level of laser attenuation.