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Certified Laser Safety Glasses
Universal Style: Can be Worn with or without Prescription Glasses
These Laser Safety Glasses provide ANSI Z136 compliant and CE certified laser radiation protection. The lenses are made from absorptive dye encapsulated in hardened polycarbonate, which provides superior resistance to breaking and prevents minor scratches from affecting laser protection. The optical density (OD) and L-Rating for specific wavelength ranges are indelibly printed on the lens or frame for permanent identification without blocking the field of view. Each pair of laser safety glasses comes with a protective storage case, a slip-on neck strap, and a cleaning cloth.
Thorlabs offers laser safety glasses in up to three different frame styles (see the Frame Styles tab for details). The universal style frame (except LG11) can be worn over prescription glasses and features side and top shield protection from peripheral laser radiation. The comfort style frame features detachable inserts for prescription lenses (please consult your doctor to fit lenses for the inserts) and an extended nose piece that may be more comfortable for users who have a low nose bridge. Finally, the sport style frame is designed to wrap around the user's face, providing full laser protection with a continuous field of view.
Picking the Appropriate Laser Safety Glasses
OD to % Transmittance Conversions
OD = Optical Density
T = Transmittance (decimal)
LG1 Universal Style Laser Glasses on 1 x 1 cm Grid for Measuring Interior Dimensions
The LG11 uses a different frame than other universal style laser glasses that features side shields made from solid plastic providing full laser protection but at the expense of peripheral vision. These laser glasses do not fit over prescription glasses. Laser ratings on the LG11 are indelibly printed on the left side shield, not on the lenses.
*** 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. ***
ANSI Z136 and EN 207 Standards
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
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 LB2 and >370-500 D LB3 then at 370 nm the rating would be D LB2 and for all wavelengths greater than 370 nm up to and including 500 nm would be rated at D LB3.
European Norm for the Selection of Laser Safety Glasses
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 LB7 + IR LB4". 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(A)(B) and LG14(A)(B) 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
P(mW) = Power in mW
Light Exiting a Fiber
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
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:
Note: The LG11 uses a different frame than our other Universal style laser glasses and do not fit over prescription lenses (see the Frame Styles tab for details).