Certified Laser Safety Glasses
Optical Density (OD) Comparison
- Hardened Polycarbonate Lenses (Resistant to Breaking)
- Absorptive Dye Encapsulated in Polycarbonate
- Surface Scratches Do Not Reduce the Optical Density of the Lenses
- Protection Lasts for a Minimum of 10 seconds at Maximum EN 207 Rated Exposure (See Specs Tutorial Tab)
- Top and Side Shield Protection
- Comfortable Frame Style can be used over Prescription Glasses
- All Models Except for LG14 are CE Certified EN 207 Compliant (See Specs Tutorial Tab)
- LG13 and LG14 are CE Certified for Laser Alignment (EN 208)
The LG series of laser safety glasses provide CE certified laser radiation protection. The comfortable frame style can be used over the top of prescription lenses and has top and side shields to protect the user's eyes from peripheral laser radiation. The interior dimensions of the LG series of laser goggles are 145 mm x 53 mm and have a 140 mm temple. The lenses have a diagonal length of 68 mm. Each pair of laser safety glasses comes with a protective storage case, a slip-on neck strap, and a cleaning cloth.
When not being used, the laser safety glasses should be stored in their protective case and in an area where the temperature does not exceed 80 °F (26.6 °C). The laser safety glasses can be cleaned using 91% isopropyl alcohol and wiped with a cotton swab.
Picking the Appropriate Laser Safety Glasses
Since the correct choice of laser safety eyewear depends upon many local factors that cannot be evaluated remotely, including the beam path, laser parameters, and lab environment, Thorlabs cannot recommend specific eyewear for your application. We would recommend discussing your needs with your organization's laser safety officer.
OD to % Transmittance Conversions
OD = Optical Density
T = Transmittance (decimal)
*** This guide is not intended as a substitute for reading and understanding the ANSI Z136 or EN 207 or EN 208 Laser Safety Standards. It is only meant to provide an introductory overview to understanding the markings on the lenses of the LG series of laser glasses. ***
Indelibly printed on the laser safety glasses are two sets of numbers: Optical Density (OD) and L-Rating, which are both used to indicate the level of protection provided for specific wavelength ranges. The OD numbers indelibly printed on the laser safety glasses can be used to determine if the glasses meet the ANSI Z136 standards of laser safety protection for a given laser product. In addition, the OD can be used to calculate the transmittance (T) of light through the laser safety glasses.
Optical Density = Log10 (1/T) or T = 10-OD.
The European EN 207 standard for laser safety glasses requires that the protective eyewear be labeled with the CE mark and that the L-Rating specifications are indelibly printed on the lens. In addition, the lenses and frames must be able to provide the stated level of protection for 10 seconds or 100 pulses depending on the mode of the laser. The L-Rating is composed of 3 components: a wavelength range, a laser mode designation, and a scale number. The wavelength range engraved on the laser safety glasses is given in nm and is extremely important since the level of protection provided by the laser safety glasses is wavelength dependent. The laser mode designation is based on the duration of laser pulse emitted by the laser.
Laser Mode Designation
|Laser Mode||Engraved Symbol||Pulse Duration|
|Continuous Wave (CW)||D||>0.25 s|
|Pulsed Mode||I||>1 µs - 0.25 s |
|Giant Pulsed Mode||R||1 ns - 1 µs|
|Mode Locked||M||< 1ns|
|Please refer to the official EN 207 standard that can be purchased from BSI.|
The scale number (Ln) is intended to be used in conjunction with the wavelength range and the laser mode designation in order to determine if the laser safety glasses meets the minimum required level of protection for a given laser; see the table below. If one component of the L-Rating is shared, a plus sign is used to separate multiple wavelength ranges or laser modes and scale numbers in order to save space. In addition, a greater than, >, sign preceding a wavelength range indicates that the mode and scale number ratings for that wavelength range are valid for wavelengths of light greater than the bottom number in the range up to and including the top number in the range. For example, if the glasses were rated as 330-370 D L2 and >370-500 D L3 then at 370 nm the rating would be D L2 and for all wavelengths greater than 370 nm up to and including 500 nm would be rated at D L3.
European Norm for the Selection of Laser Safety Glasses
|Wavelength Range||Laser Mode||Maximum Power Density (P)|
Maximum Energy Density (E)
|Minimum Scale Number (Ln)|
|180 - 315 nm||D||1x10n-3 W/m2||log10(P)+3|
|I and R||3x10n+1 J/m2||log10(E/3)-1|
|315 - 1400 nm||D||1x10n+1 W/m2||log10(P)-1|
|I and R||5x10n-3 J/m2||log10(E/5)+3|
|1400 - 1000000 nm||D||1x10n+3 W/m2||log10(P)-3|
|I and R||1x10n+2 J/m2||log10(E)-2|
|Please refer to the official EN 207 standard that can be purchased from BSI.|
There are two ways to use the table above: start with the scale number and calculate the maximum safe power density or start with a power density and calculate the minimum safe scale number. This is demonstrated by the two examples below.
Example 1: The LG3 laser safety glasses have an L-Rating line that reads "180-315 D L7 + IR L4". So if the LG3 glasses are being used with a 10 µs pulsed 280 nm light source the table above can be referenced to find that, E=3x10n+1 J/m2, where in this example the scale number is L4 so n=4. As a result, when the LG3 laser safety glasses are being used in this situation the maximum power density of the light source should not exceed 3x105 J/m2.
Example2: A CW Krypton Ion laser lasing at 647.1 nm has a maximum power density of 2.2x104 W/m2. Using the table above, the scale number can be calculated using Ln=log10(P)-1, which results in a rounded up scale number of 4. The LG4 laser safety glasses meet the safety specifications of the European EN 207 standard for this example.
Alignment Rating (EN 208)
The LG13 and LG14 glasses are rated for laser alignment applications. This rating allows the lens to transmit a portion of the light for alignment purposes, while attenuating the light to eye-safe power levels in the event of accidental direct exposure to a beam. The rating is given as RB# where # is replaced by the minimum optical density at the specified wavelength or wavelength range (in nm). Along with this RB value is the maximum allowable power and energy of the laser over a Ø7 mm aperture. Power is given for pulses greater than 0.2 ms, while energy is specified for pulses from 1 ns to 0.2 ms. When using a pulsed laser, a correction factor of N1/4 must be multiplied by the maximum energy rating, replacing N with the number of pulses the laser produces in a 10 s interval.
Example: The LG14 laser safety glasses have an alignment rating of 1 W 2 x 10-4 J 532 RB3. At 532 nm, the glasses will have an optical density between 3 and 4, correlating to transmission between 0.1% and 0.01%. The maximum power/energy over a Ø7 mm aperture that these glasses can be used with at 532 nm is 1 W for CW or pulses greater than 0.2 ms, and 2 x 10-4 J for pulses from 1 ns to 0.2 ms.
Please refer to the official EN 208 standard that can be purchased from BSI.
dBm to mW Power Conversions
|4.0||2.5119||30.0||1,000.0000 (1 W)|
|6.0||3.9811||40.0||10,000.0000 (10 W)|
|8.0||6.3096||50.0||100,000.0000 (100 W)|
P(mW) = Power in mW
Light Exiting a Fiber
|NA||Divergence Half Angle, Θ||Beam Area|
@ 25.4 mm (1") From Fiber
Note: The values in this table are rounded down to provide conservative beam areas.
When working with fiber optics, light emitted directly from the endface of a fiber is diverging. Thus, the power density is decreasing as the beam spreads and the danger of damage to the eye decreases. The table to the left lists the beam area created by light exiting a fiber for fibers with numerical apertures (NA) between 0.10 and 0.50. If you know the total power emitted from the fiber, you can calculate the power density at 25.4 mm (1") from the fiber tip. This power density will allow you to determine the safe fiber-tip viewing distances.
Laser Safety and Classification
Safe practices and proper usage of safety equipment should be taken into consideration when operating lasers. The eye is susceptible to injury, even from very low levels of laser light. Thorlabs offers a range of laser safety accessories that can be used to reduce the risk of accidents or injuries. Laser emission in the visible and near infrared spectral ranges has the greatest potential for retinal injury, as the cornea and lens are transparent to those wavelengths, and the lens can focus the laser energy onto the retina.
Safe Practices and Light Safety Accessories
- Thorlabs recommends the use of safety eyewear whenever working with laser beams with non-negligible powers (i.e., > Class 1) since metallic tools such as screwdrivers can accidentally redirect a beam.
- Laser goggles designed for specific wavelengths should be clearly available near laser setups to protect the wearer from unintentional laser reflections.
- Goggles are marked with the wavelength range over which protection is afforded and the minimum optical density within that range.
- Laser Barriers and Blackout Materials can prevent direct or reflected light from leaving the experimental setup area.
- Thorlabs' Enclosure Systems can be used to contain optical setups to isolate or minimize laser hazards.
- A fiber-pigtailed laser should always be turned off before connecting it to or disconnecting it from another fiber, especially when the laser is at power levels above 10 mW.
- All beams should be terminated at the edge of the table, and laboratory doors should be closed whenever a laser is in use.
- Do not place laser beams at eye level.
- Carry out experiments on an optical table such that all laser beams travel horizontally.
- Remove unnecessary reflective items such as reflective jewelry (e.g., rings, watches, etc.) while working near the beam path.
- Be aware that lenses and other optical devices may reflect a portion of the incident beam from the front or rear surface.
- Operate a laser at the minimum power necessary for any operation.
- If possible, reduce the output power of a laser during alignment procedures.
- Use beam shutters and filters to reduce the beam power.
- Post appropriate warning signs or labels near laser setups or rooms.
- Use laser sign lightboxes if operating Class 3R or 4 lasers (i.e., lasers requiring the use of a safety interlock).
- Do not use Laser Viewing Cards in place of a proper Laser Barrier or Beam Trap.
Lasers are categorized into different classes according to their ability to cause eye and other damage. The International Electrotechnical Commission (IEC) is a global organization that prepares and publishes international standards for all electrical, electronic, and related technologies. The IEC document 60825-1 outlines the safety of laser products. A description of each class of laser is given below:
|1||This class of laser is safe under all conditions of normal use, including use with optical instruments for intrabeam viewing. Lasers in this class do not emit radiation at levels that may cause injury during normal operation, and therefore the maximum permissible exposure (MPE) cannot be exceeded. Class 1 lasers can also include enclosed, high-power lasers where exposure to the radiation is not possible without opening or shutting down the laser.|| |
|1M||Class 1M lasers are safe except when used in conjunction with optical components such as telescopes and microscopes. Lasers belonging to this class emit large-diameter or divergent beams, and the MPE cannot normally be exceeded unless focusing or imaging optics are used to narrow the beam. However, if the beam is refocused, the hazard may be increased and the class may be changed accordingly.|| |
|2||Class 2 lasers, which are limited to 1 mW of visible continuous-wave radiation, are safe because the blink reflex will limit the exposure in the eye to 0.25 seconds. This category only applies to visible radiation (400 - 700 nm).|| |
|2M||Because of the blink reflex, this class of laser is classified as safe as long as the beam is not viewed through optical instruments. This laser class also applies to larger-diameter or diverging laser beams.|| |
|3R||Lasers in this class are considered safe as long as they are handled with restricted beam viewing. The MPE can be exceeded with this class of laser, however, this presents a low risk level to injury. Visible, continuous-wave lasers are limited to 5 mW of output power in this class.|| |
|3B||Class 3B lasers are hazardous to the eye if exposed directly. However, diffuse reflections are not harmful. Safe handling of devices in this class includes wearing protective eyewear where direct viewing of the laser beam may occur. In addition, laser safety signs lightboxes should be used with lasers that require a safety interlock so that the laser cannot be used without the safety light turning on. Class-3B lasers must be equipped with a key switch and a safety interlock.|| |
|4||This class of laser may cause damage to the skin, and also to the eye, even from the viewing of diffuse reflections. These hazards may also apply to indirect or non-specular reflections of the beam, even from apparently matte surfaces. Great care must be taken when handling these lasers. They also represent a fire risk, because they may ignite combustible material. Class 4 lasers must be equipped with a key switch and a safety interlock.|| |
|All class 2 lasers (and higher) must display, in addition to the corresponding sign above, this triangular warning sign|| |