Laser Safety Standards

In the US, laser safety falls under the ANSI Z136.1 standard, while in europe, it is regulated by the EN207, EN208, and IEC 60825 standards.

Lasers are classified under the ANSI Z136.1 standard into various general categories. Note: classification alone is not enough to determine whether eye protection is needed or which type of laser safety eyewear is required.

Class Definition Pulse Length
1 Non-hazardous Eyewear not required.
1M Eye safe visible laser (400-700nm) if used without magnifying optics. Eyewear not required unless used with magnifying optics.
2 Eye safe visible laser (400-700nm) (safe within the blink reflex of 0.25s). Eyewear not required.
2M Eye safe visible laser (400-700nm) (safe within the blink reflex of 0.25s) if used without magnifying optics. Eyewear recommended.
3R Likely unsafe for intrabeam viewing. Maximum Permissible Exposure (MPE) is up to 5 times class 2 limit for visible lasers of 5 times class 1 limit for invisible lasers. Eye hazard; eyewear is recommended.
3B Eye hazardous for intrabeam viewing. Limited diffuse hazard. Eye hazard; eyewear is recommended.
4 Eye and skin hazard for direct and diffuse exposure. Fire and burn hazard. Eye protection and other personal safety equipment is required.

 

ANZI Z136.1 mandates that laser safety eyewear be specified based on optical density (OD) and allows for the calculation of a nominal hazard zone (NHZ), beyond which diffuse viewing eyewear may be used.

Optical Density (OD) represents the reduction of laser energy as it passes through a filter. a higher OD value indicates greater attenuation, providing stronger protection. in simple terms, OD measures how much laser energy is blocked by the filter.

OD is mathematically defined as the logarithmic reciprocal of transmittance, expressed as:  D? = -log10 t ?, where T represents transmittance.

OD (Optical Density) Transmission in % Attenuation Factor
0 100% 1
1 10% 10
2 1% 100
3 0.1% 1,000
4 0.01% 10,000
5 0.001% 100,000
6 0.0001% 1,000,000
7 0.00001% 10,000,000


European Laser Safety Standards EN207/208/60825

European laser safety regulations EN207/EN208 take into account both optical density (OD) and the power/energy density of the laser (measured as power over time and area) when defining safety requirements. similar to ANZI Z136.1, laser safety eyewear must have an adequate optical density to reduce the laser's power to at or below the maximum permissible exposure (MPE) levels. however, EN207 also requires that eyewear provides damage threshold protection, meaning it must withstand direct laser exposure for a specific duration and energy level.  Under EN207, laser safety goggles must protect against direct intrabeam exposure.

The EN207 standard mandates that laser safety eyewear be labeled with its protection level, indicating its damage threshold. for example, a marking such as 10600 D L5 means that the eyewear can withstand a 100 Megawatt/m² power density for 10 seconds at a 10,600 nm wavelength.

EN207 L-ratings specify the damage threshold of the eyewear material, detailing the maximum power density the lenses can handle. this standard also requires laser stability testing, ensuring eyewear can endure at least 10 seconds of continuous wave (cw) exposure or 100 pulses in pulsed mode.

Modes of Operation

Various modes of laser operation have different power density characteristics and often different eyewear requirements.

Mode Definition Pulse Length
D Continuous Wave (cw) with consistent average power greater than 0.25 second
I Pulsed: short single or periodic energy emission > 1 µs to 0.25 s
R Giant Pulsed: very short single or periodic energy emission 1 µs to 1 ns
M Mode Locked < 1 ns (pico and femtosecond)