EN 207 is a European norm for laser safety eyewear (now superseded, together with the EN 208, by the ISO 19818:2021 standard [1] ). Any laser eye protection sold within the European Community must be certified and labeled with the CE mark. According to this standard, laser safety glasses should not only absorb laser light of a given wavelength, but they should also be able to withstand a direct hit from the laser without breaking or melting, both the filter and the frame. In this respect, the European norm is more strict than the American norm (ANSI Z 136) that only regulates the required optical density. More precisely, the safety glasses should be able to withstand a continuous wave laser for 5 seconds, or 50 pulses for a pulsed laser (EN 207:2017). [2]
An EN 207 specification might read IR 315–532 LB6. Here, the letters IR indicate the laser working mode, in this case a pulsed mode. The range 315–532 indicates the wavelength range in nanometers. Finally, the scale number LB6 indicates a lower limit for the optical density, i.e. the transmittance within this wavelength range is less than 10−6.
EN 207 specifies four laser working modes:
Working mode | Letter | Pulse length |
---|---|---|
Continuous wave | D | > 0.25 s |
Pulsed mode | I | > 1 μs–0.25 s |
Giant pulsed mode | R | > 1 ns–1 μs |
Modelocked | M | < 1 ns |
The scale numbers range from LB1 to LB10, where the number is a lower limit for the optical density, i.e. LBn means that OD > n, or , where T is the transmittance. The minimum scale number for a given laser with a beam diameter of 1 mm depends on the working mode and the wavelength as follows (EN 207:2017):
Working mode | Wavelength range | Maximum laser power density | Minimum protection level for given power* |
---|---|---|---|
D (continuous) | 180–315 nm | 1×10n−3 W/m2 | log(P) + 3 |
>315–1400 nm | 1×10n+1 W/m2 | log(P) − 1 | |
>1400 nm–1000 μm | 1×10n+3 W/m2 | log(P) − 3 | |
I,R (pulsed) | 180–315 nm | 3×10n+1 J/m2 | log(E/3) − 1 |
>315–1400 nm | 5×10n−3 J/m2 | log(E/5) + 3 | |
>1400 nm–1000 μm | 1×10n+2 J/m2 | log(E) − 2 | |
M (ultrashort pulses) | 180–315 nm | 3×10n+10 W/m2 | log(P/3) − 10 |
>315–1400 nm | 1.5×10n−4 J/m2 | log(E/1.5) + 4 | |
>1400 nm–1000 μm | 1×10n+11 W/m2 | log(P) − 11 | |
*P in W/m2, E in J/m2. Level numbers should be rounded upwards. |
If the beam diameter differs from 1 mm a correction factor, depending on the material of the filter and frame, must be applied. Another correction factor must be used for pulsed lasers in case of repeated pulses for wavelengths above 400 nm.
From the scale it can be inferred that the power densities that correspond to are considered safe without protective eyewear.
A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The word laser is an anacronym that originated as an acronym for light amplification by stimulated emission of radiation. The first laser was built in 1960 by Theodore Maiman at Hughes Research Laboratories, based on theoretical work by Charles H. Townes and Arthur Leonard Schawlow.
Microscopy is the technical field of using microscopes to view objects and areas of objects that cannot be seen with the naked eye. There are three well-known branches of microscopy: optical, electron, and scanning probe microscopy, along with the emerging field of X-ray microscopy.
Raman spectroscopy is a spectroscopic technique typically used to determine vibrational modes of molecules, although rotational and other low-frequency modes of systems may also be observed. Raman spectroscopy is commonly used in chemistry to provide a structural fingerprint by which molecules can be identified.
Sunglasses or sun glasses are a form of protective eyewear designed primarily to prevent bright sunlight and high-energy visible light from damaging or discomforting the eyes. They can sometimes also function as a visual aid, as variously termed spectacles or glasses exist, featuring lenses that are colored, polarized or darkened. In the early 20th century, they were also known as sun cheaters.
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Goggles, or safety glasses, are forms of protective eyewear that usually enclose or protect the area surrounding the eye in order to prevent particulates, water or chemicals from striking the eyes. They are used in chemistry laboratories and in woodworking. They are often used in snow sports as well, and in swimming. Goggles are often worn when using power tools such as drills or chainsaws to prevent flying particles from damaging the eyes. Many types of goggles are available as prescription goggles for those with vision problems.
An optical filter is a device that selectively transmits light of different wavelengths, usually implemented as a glass plane or plastic device in the optical path, which are either dyed in the bulk or have interference coatings. The optical properties of filters are completely described by their frequency response, which specifies how the magnitude and phase of each frequency component of an incoming signal is modified by the filter.
Laser radiation safety is the safe design, use and implementation of lasers to minimize the risk of laser accidents, especially those involving eye injuries. Since even relatively small amounts of laser light can lead to permanent eye injuries, the sale and usage of lasers is typically subject to government regulations.
A laser pointer or laser pen is a small handheld device with a power source and a laser diode emitting a very narrow coherent low-powered laser beam of visible light, intended to be used to highlight something of interest by illuminating it with a small bright spot of colored light.
Eye protection is protective gear for the eyes, and sometimes face, designed to reduce the risk of injury. Examples of risks requiring eye protection can include: impact from particles or debris, light or radiation, wind blast, heat, sea spray or impact from some type of ball or puck used in sports.
In photography and optics, a neutral-density filter, or ND filter, is a filter that reduces or modifies the intensity of all wavelengths, or colors, of light equally, giving no changes in hue of color rendition. It can be a colorless (clear) or grey filter, and is denoted by Wratten number 96. The purpose of a standard photographic neutral-density filter is to reduce the amount of light entering the lens. Doing so allows the photographer to select combinations of aperture, exposure time and sensor sensitivity that would otherwise produce overexposed pictures. This is done to achieve effects such as a shallower depth of field or motion blur of a subject in a wider range of situations and atmospheric conditions.
The Shiva laser was a powerful 20-beam infrared neodymium glass laser built at Lawrence Livermore National Laboratory in 1977 for the study of inertial confinement fusion (ICF) and long-scale-length laser-plasma interactions. Presumably, the device was named after the multi-armed form of the Hindu god Shiva, due to the laser's multi-beamed structure. Shiva was instrumental in demonstrating a particular problem in compressing targets with lasers, leading to a major new device being constructed to address these problems, the Nova laser.
This is a list of acronyms and other initialisms used in laser physics and laser applications.
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An output coupler (OC) is the component of an optical resonator that allows the extraction of a portion of the light from the laser's intracavity beam. An output coupler most often consists of a partially reflective mirror, allowing a certain portion of the intracavity beam to transmit through. Other methods include the use of almost-totally reflective mirrors at each end of the cavity, emitting the beam either by focusing it into a small hole drilled in the center of one mirror, or by redirecting through the use of rotating mirrors, prisms, or other optical devices, causing the beam to bypass one of the end mirrors at a given time.
A photoionization mode is a mode of interaction between a laser beam and matter involving photoionization.
Volume holograms are holograms where the thickness of the recording material is much larger than the light wavelength used for recording. In this case diffraction of light from the hologram is possible only as Bragg diffraction, i.e., the light has to have the right wavelength (color) and the wave must have the right shape. Volume holograms are also called thick holograms or Bragg holograms.
A laser beam profiler captures, displays, and records the spatial intensity profile of a laser beam at a particular plane transverse to the beam propagation path. Since there are many types of lasers — ultraviolet, visible, infrared, continuous wave, pulsed, high-power, low-power — there is an assortment of instrumentation for measuring laser beam profiles. No single laser beam profiler can handle every power level, pulse duration, repetition rate, wavelength, and beam size.
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