ANSI Z136 standard requires specification according to optical densities (OD) only. The Optical Density (OD or D(λ)) is the attenuation of light that passes through an optical filter. The higher the OD value, the higher the attenuation. ANSI also allows a Nominal Hazard Zone (NHZ) to be determined by the laser safety officer (LSO). Outside of the NHZ, diffuse viewing eyewear is allowed. Most Asian countries refer to these ANSI regulations. Australia has adopted new laser safety regulations that are based on the European laser safety regulations (EN 207/EN208).
The World of Laser Safety in Europe (EN207/208/60825)
In Europe there is a second criteria to be taken into consideration which is the power/energy density (i.e. the power/energy per area= per beam area). "Diffuse viewing" is not allowed, laser safety glasses have to protect against a direct hit. Protection with Optical Density alone is not sufficient when the material of the eyewear will not be able to withstand a direct hit. The followingregulations are called the "norm", but in fact they are legal requirements and enforceable. Other legal requirements(e.g. the regulations for industrial safety as well as the medical equipment regulations) refer to them as well.
