Laser safety goggles and laser safety windows are very important laser protection accessory parts, especially for operation of high powered lasers. Before making decision of selecting laser safety goggles or windows, users should know factors as below:

1. Laser features: laser output power, wavelength and power density
2. Optical density (OD): laser safety glass or windows get larger OD value, can make even stronger protection of laser radiation and laser reflection.
3. Visible light transmittance (VLT): VLT value is below 20%, need to use in well lighting environments.
4. Laser safety goggles frame: whether to wear glasses, facial contours.

Laser standards:

1. US laser safety standard ANSI Z136.1: by optical density (OD, Optical Density) to measure
OD (Optical density) logical related with transmittance
T:D= D=-log10 T
2. European laser safety standard EN207/EN207: Consider optical density (OD) and damage threshold.
According to US Standard ANSI Z136.1 and European standards EN207 / EN208, lasers can be classified as below:
OD Specs (ANSI Z136) L-Rating Specs (EN 207)a
190 to 400 nm, OD = 5+ 808 to 840 nm (DIRM LB4)
808 to 840 nm, OD = 4+
>840 to 950 nm & >1080 to 1090 nm (DIRM LB5)
>840 to 950 nm, OD = 5+ >950 to 1080 nm (D LB6)
>950 to 1080 nm, OD = 7+ >950 to 1080 nm (IRM LB7)b
>1080 to 1090 nm, OD = 5+

There are two permanent digitals shown on both laser safety goggles and laser safety windows: optical density (OD) and L grade. Both are used to indicate that a given level of protection within the wavelength range. OD number printed on laser safety goggles or windows can be used to determine the lens for a give laser products, compliance with ANSI Z136 laser safety standards.

In addition, OD can be used to calculated laser safety glasses transmittance (T). The optical density (OD) = Log10 (1 / T) or T = 10-OD.

European EN207 laser safety goggles and laser safety windows standards require CE mark printed on protective glasses and windows, L grade specification printed on the lens. Further, according to laser mode, laser goggles and frames must reach up 10s or 100 nominal pulse level of protection.

L grade consists of three parts: wavelength range, laser mode name and ratio. Wavelength range in nm, engraved on laser safety goggles or windows. It is very important factors since laser safety level is closely concern with laser wavelength. Laser mode name is basing on emitted laser pulsed duration.

Laser Mode                           Engraved Mark                   Pulse Duration
Continuous wave (CW)           D                                       > 0.25sec
Pulse mode                           I                                        > 1 microsecond -0.25 sec
Giant-pulse mode                   R                                       1 ns -1 microsecond
Clamping                               M                                      <1 ns

Ratio number (Ln), wavelength range and laser mode name commonly used to determine whether laser safety goggles or laser safety windows achieve a given laser minimum level of protection requirement.

●"+". If an L level element is segmented, the plus sign "+" is used for the plurality of wavelength range, or the ratio number of separate laser mode, thus saves space.
●">". Wavelength range is greater than the number o previous models and show that ratio number of wavelength longer than the applicable minimum wavelength range, the range is less than or equal to the maximum wavelength of laser light.
For example, if laser glasses grade labeled: 330-370 D L2 + > 370-500 D L3, then at 370 nm rating of D L2, for wavelengths greater than 370 nm less than or equal to 500 nm class D L3.

Laser safety and laser classification

Laser operation should pay attention to safety measures and proper use of laser protective devices. Low intensity laser radiation has potential eye injury. A series of laser safety goggles or laser safety windows can reduce the risk of accidents and injuries.

Visible laser and near-infrared spectral range laser are mostly likely to cause retinal damage, since cornea and crystal can absorb these wavelengths laser radiations. Laser radiations energy focuses on retina.

Recommended that operation power of laser beam cannot be ignored (ie,> 1) at any time in the use of laser safety goggles, because the metal tool such as a screwdriver can change the beam direction unexpectedly.

1. designed for a specific wavelength laser goggles should be placed in a prominent positioning near the laser devices, to protect wearer from harm inadvertently reflected beam.
2. laser safety goggles, marked with the wavelength range of protection and minimum optical density within the range.
3. laser safety window can prevent direct or reflected laser light from experimental setup area or the exit.
4. the pigtailed laser only connect or disconnect fiber optic connectors need to be closed, especially above 10mW laser output power.
5. all laser beams should be terminated at the edge of working platform. Laser operation should close the laboratory door.
6. Do not place laser beam at eye level line.
7. Do not work close to the line when worn unnecessary reflective items such as reflective jewelry, rings, watches etc.
8. Note lens and other optical components may reflect from the front surface or the rear surface portion of the light.
9. run laser devices on any applications under the required minimum optical power. If possible, reduce the output power in the process of adjusting the optical path.
10. Place an appropriate warning signs or labels near laser devices or laboratories. Operating Class IIIR or Class 4 laser (ie, lasers requiring the use of safety interlock), use of laser safety signs light box.