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.

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.

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†For maxmimum protection, our laser safety glasses should not be used more than five years from the production date. All of our laser safety glasses except for the LG11 and LG11A are inscribed with a production date code on the bottom-right corner of the right lens, as can be seen here. The date code is represented as a five-digit number, with the first two digits defining the year and the last three defining the day of the year. Thorlabs will not ship glasses with less than three years of usable life remaining.

*** 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. ***

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Sport StyleThe Sport Style glasses have a compact (134 mm x 48 mm) frame designed for full laser safety coverage without the need for side shields and provide the user with a wide field of view. Glasses with this frame style have arms that feature adjustable lengths and an adjustable joint (seen by clicking on the image to the right) to customize the fit for different head shapes and sizes. These sport style glasses cannot be worn over prescription glasses and do not include inserts for prescription lenses. Laser safety ratings are indelibly printed on the lenses to indicate the level of protection provided for specific wavelength ranges.

The optical density (OD) and LB-Rating for specific wavelength ranges are indelibly printed on the lens or frame for permanent identification without blocking the field of view†. For a complete list of optical densities and LB-Ratings, please click on the row corresponding to each item # in the selection guide to the right.

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:

The scale number (LBn) 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 LB-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.

Each pair of laser safety glasses comes with a protective storage case, cleaning cloth, and adjustable neck strap. However, the Modern Goggle style does not come with the separate neck strap as the neckstrap for the Modern Goggles is built in.

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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 LBn=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.

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Example 1: The LG3 laser safety glasses have an LB-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 LB4 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.

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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.

These Laser Safety Glasses provide CE certified laser radiation protection. The lenses of all glasses except for the LG11 series are made from absorptive dye encapsulated in hardened polycarbonate, which provides superior resistance to breakage and prevents minor scratches from affecting laser protection. The LG11(A) Laser Safety glasses use a Schott glass substrate.*

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Care InstructionsWhen 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 cleaning cloth included with each pair of laser safety glasses can be used for removing dust from the surface of the lens. Products used for cleaning prescription eyeglasses are safe to use with our laser safety glasses. For disinfection of the glasses, we recommend mild detergent or soap and hot water or a dilution of isopropyl alcohol (up to 70% solution). We do not recommend any highly caustic solutions. The laser safety rating will not be affected by any of the above cleaning procedures.

Picking the Appropriate Laser Safety GlassesSince 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.

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Comfort StyleComfort Style glasses feature a medium (145 mm x 47 mm) frame with solid side shields for full protection from peripheral laser radiation. While these laser safety glasses cannot be worn over prescription glasses, each pair includes a detachable insert for prescription lenses (seen by clicking on the the image to the right). Contact your doctor to fit lenses for the inserts. These frames are equipped with an extended nosepiece that allows the glasses to sit more comfortably on the noses of users who have a low nose bridge. Laser safety ratings are indelibly printed on the lenses (LG11A laser ratings are printed on the frame) to indicate the level of protection provided for specific wavelength ranges.

Universal StyleUniversal Style laser safety glasses feature a large (145 mm x 53 mm) frame that can be worn comfortably on top of prescription glasses. They are equipped with lensed side shields and solid top shields to protect the user's eyes from laser radiation while maintaining peripheral vision. The frame has adjustable arm lengths to accommodate different temple sizes. Laser safety ratings are indelibly printed on the lenses to indicate the level of protection provided for specific wavelength ranges.

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The LG13 and LG14 series of 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.

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*The LG11 and LG11A are made using Schott glass, and therefore use a different frame design than our other Universal style laser glasses. Fit over prescription glasses may be affected (see the Frame Styles tab for details). To ensure CE compliance, only two styles are offered. OD and LB-Rating specifications for the LG11 and LG11A are printed on the frame.

Note: The LG11 and LG11A are made using Schott glass, and therefore use a different frame design than our other Universal style laser glasses. Fit over prescription glasses may be affected (see the Frame Styles tab for details). To ensure CE compliance, only two styles are offered. OD and LB-Rating specifications for the LG11 and LG11A are printed on the frame.

The LG11 is composed of a Schott Glass substrate, and 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 may not fit over prescription glasses. Laser ratings on the LG11 are indelibly printed on the left side shield, not on the lenses.

Modern Goggle StyleThe Modern Goggle Style features an adjustable strap, a gasket to create a seal around the eyes, as well as vents to prevent fogging. The interior dimensions of these laser goggles are 133 mm x 51 mm. The lenses have a diagonal length of 66 mm. Laser Safety Goggles are equipped with detachable inserts for prescription lenses (please consult your doctor to fit prescription lenses for the insert). Laser safety ratings are indelibly printed on the lenses to indicate the level of protection provided for specific wavelength ranges.

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.

The European EN 207 standard for laser safety glasses requires that the protective eyewear be labeled with the CE mark and that the LB-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 LB-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.

Indelibly printed on the laser safety glasses are two sets of numbers: Optical Density (OD) and LB-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 transmission (T) of light through the laser safety glasses.