Posted on

Laser Standards

Laser Safety falls under the ANSI 136.1 standard in the United States and the EN207/EN208/EC60825 standard in Europe.

Lasers are categorized by the ANSI Z136.1 standard into the following general categories. NOTE: Category alone is not sufficient to determine if or which eye protection is required.

ClassDefinitionPulse Length
1Non-hazardousEyewear not required.
1MEye safe visible laser (400-700nm) if used without magnifying optics.Eyewear not required unless used with magnifying optics.
2Eye safe visible laser (400-700nm) (safe within the blink reflex of 0.25s).Eyewear not required.
2MEye safe visible laser (400-700nm) (safe within the blink reflex of 0.25s) if used without magnifying optics.Eyewear recommended.
3RLikely 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.
3BEye hazardous for intrabeam viewing. Limited diffuse hazard.Eye hazard; eyewear is recommended.
4Eye and skin hazard for direct and diffuse exposure. Fire and burn hazard.Eye protection and other personal safety equipment is required.

ANSI Z136.1 requires specification of laser safety eyewear according to optical densities (OD), and allows a Nominal Hazard Zone (NHZ) to be calculated, outside which diffuse viewing eyewear is allowed.

  • Optical Density (OD) is a measure of the attenuation of energy passing through a filter. The higher the OD value, the higher the attenuation and the greater the protection level. In other words, OD is a measure of the laser energy that will pass through a filter.
  • OD is the logarithmic reciprocal of transmittance, expressed by the following: D? = -log10 T ?, where T is transmittance.
OD (Optical Density)Transmission in %Attenuation Factor
0100%1
110%10
21%100
30.1%1,000
40.01%10,000
50.001%100,000
60.0001%1,000,000
70.00001%10,000,000

European Laser Safety Standards EN207/208/60825

European laser safety regulations EN 207/EN208 consider Optical Density and also the power/energy density (power over time over area) of the laser when determining laser safety requirements. Like ANSI Z136.1, laser safety eyewear must provide sufficient optical density to reduce the power of a laser to be equal or less than the Maximum Permissible Exposure levels (MPE), but it must also provide damage threshold protection (direct hit over a given amount of time/energy). Under EN207, Laser safety goggles must protect against direct intrabeam exposure to the laser.

The EN207 standard requires that eyewear is labeled to with protection levels that detail their damage thresholds, (e.g. 10600 D L5 (where L5 reflects a power density of 100 MegaWatt/m2 during a 10 seconds direct hit test at 10,600nm).

  • EN207 L- ratings account for the damage threshold of the eyewear material, i.e., the power density eyewear will withstand, and requires actual laser stability testing for at least 10 seconds (cw) or 100 pulses (pulsed modes).

euro_lasersafety

Modes of Operation

Lasers operating at different modes have different power density characteristics and often different eyewear requirements.

ModeDefinitionPulse Length
DContinuous Wave (cw) with consistent average powergreater than 0.25 second
IPulsed: short single or periodic energy emission.> 1 µs to 0.25 s
RGiant Pulsed: very short single or periodic energy emission.1 µs to 1 ns
MMode Locked< 1 ns (pico and femtosecond)

Leave a Reply