Absorption is a physical parameter for the optical density and describes the absorption of energy from a wave by the medium to be passed through. Absorption leads to a weakening of the intensity of the light along the path, proportional to the absorption coefficient. The absorption is strongly dependent on frequency. This is due to the band structure of the medium to be crossed. Photons of certain energy excite atoms and molecules that have quantum transitions with exactly this energy difference in the electron shell or in their molecular vibrations. When light is absorbed, the absorbed energy is mostly lost as entropy.

The norm DIN EN 12254 defines AB protection levels for laser protection shields. The protection levels are based on the maximum spectral transmittance (τ) at the corresponding laser wavelength (λ). The maximum power density (E) or energy density (H) depending on the wavelength range and operating mode of the laser (D, I, R, M). The levels are additionally divided into 4 wavelength ranges, the UV-A and UV-B range (180-315 nm), the UV-C, the visible range, the NIR range (315-1050 nm), especially the near infrared range from 1050 - 1400 nm and the far infrared range (FIR) from 1400 nm. An additional factor for defining a protection level is the maximum spectral transmission.

Reference: Screens for laser working places - Safety requirements and testing; German version EN 12254:2010 + AC:2011

Accredited bodies of the European Union are private inspection bodies (auditors and certifiers) which are appointed and supervised by the state. Accredited bodies are commissioned by manufacturers to control and certify the conformity assessment of manufactured industrial products of various kinds. These bodies hereby exercise an "indirect state administration".

Accredited bodies have the task of certifying the products of the manufacturer under competent surveillance authorities of the contracting states of the European Economic Area. Both, in the compliance with "essential requirements" for the product quality and the compliance with the applicable harmonisation directive of the applicable conformity assessment procedure. They thus authorise the commissioned manufacturer to issue a declaration of conformity and to affix a CE marking if the requirements are met.

Cooperation with accredited bodies

DIN CERTCO (Notified Body 0196)
DIN CERTCO GESELLSCHAFT FÜR KONFORMITÄTSBEWERTUNG MBH
Albinostraße 56
12103 Berlin

ECS (Notified Body 1883)
ECS European Certification Service GmbH
Hüttfeldstraße 50
73430 Aalen

The smallest accessible beam diameter must be used. For the calculation it is assumed, that this beam diameter contains 63% of the total laser energy.

Laser radiation is coherent radiation. Coherent radiation is electromagnetic waves which have a fixed phase relationship in their spatial and temporal propagation.

If you have not found a suitable product for your highly specialised application in our product portfolio, it is possible to create and certify a special filter according to your protection requirements from two already certified glass filters.  The custom filter individual approval is limited to 10 glasses.

According to DIN EN 207, the actual beam area (the area of the smallest circle containing 63 % of the laser intensity or laser energy) should be used for all calculations of energy and power density. For beam diameters with a different shape, a similar procedure should be applied and the smallest accessible rectangle/ellipse containing 63 % of the laser power or laser energy should be used.

Dielectric filters are used in laser protection. The technology of the dielectric filter makes it possible to additionally equip absorbing glass laser safety filters with reflective layers. Here, multiple layers with different refractive indices are combined with each other in a complex process, whereby the wave resistance changes and certain wavelengths and wavelength ranges can be reflected.

A very high protection level better visibility and colour accuracy can be realisied with the dilectric layers in comparison to standard absorption filters.

The extremely thin layers are extremely sensitive and lose their effect when damaged, such as scratches or impacts.

The smaller the divergence of a laser beam, the more parallel it will propagate. A small divergence will state, that the cross section of the laser beam will widen less over distance than a laser beam with a higher divergence.

The smallest accessible beam diameter must be used. For the calculation it is assumed, that this beam diameter contains 63% of the total laser energy.

The full angle is defined by the divergence. It results from the trigonometric relationship between the central of the beam and the alteration in cross-section over the distance.

The half angle is defined by the divergence. It results from the trigonometric relationship between the central axis of the beam and the alteration in cross-section over the distance.

Incoherent radiation is non-directional optical radiation emitted by, for example, incandescent lamps, fluorescent lamps, LEDs, gas lamps, metal and glass melts, welding arcs, medical flash lamps, melting furnaces and also the sun. Incoherent radiation is often emitted as a by-product of working with lasers.

This radiation can also be dangerous and is also subject to Directive 2006/25/EC "Minimum health and safety requirements regarding the exposure of workers to the risks arising from physical agents (artificial and optical radiation).

This high-energy pulsed light is used in dermatology and hair removal. A flash time of 20-100 milliseconds and an irradiation intensity of 5-30 joules/cm² can cause irreversible injuries to the eyes. The wavelength range for IPL is 380-1400 nm. The thermal effects of an IPL flash can affect the calcium concentration in the tissue to be treated and thus influence the expression of certain proteins.

Ionising radiation is a term for particles or electromagnetic radiation that is able to remove electrons from atoms, leaving behind positively charged ions. Laser protection products offer no protection against ionising radiation, with the exception of the UV-A range.  In the electromagnetic spectrum, this is referred to as wavelengths of less than 250 nm. Examples are X-rays, radioactive radiation and ultraviolet radiation. If overdosed, this radiation can damage organic life.

Laser adjustment glasses can be used for the adjustment of lasers within the visible wavelength range (400-700 nm). The maximal laser output is 100W.

The energy of the laser is lowered to a level below 1 mW (continuous wave laser)/ <0,2 μJ (pulsed laser) (0,12 μJ at 2 seconds), corresponding to the exposure value limit of laser class 2.
A damage of the eyes is prevented by the natural eyelid closure reflex. By definition, the ray may hit the eye for .25 seconds, for not causing any damage. The maximum beam diameter is 7 mm. Laser adjustment goggles are classified by RB protection levels.

Laser Class 1

Lasers of laser class 1 do not have a potential hazard when used in a foreseeable manner, even in interaction with optical devices such as magnifying glasses or microscopes. Lasers of laser class 1 must be protected against manipulation. Industrial laser systems are usually shielded in such a way that no radiation greater than that of laser class 1 occurs outside the shielding. This is important, as laser radiation in the non-visible range is normally used here.

Laser Class 1M

Accessible laser rays in a spectral range from 302,5 and 4000 nm, proceeding divergent and widened are defined as Laser Class 1M. The complete ray is limited to a power of .5 Watt, the defined limit value of Laser Class 3B.

In the spectral range of 400-1400 nm the ray is naturally by the pupil, and merely a part of the ray will penetrate the inner eye, which will not go pass the level of Laser Class 1.

A hazard potential arises when the class 1M laser beam is viewed through an optical instrument such as a microscope or binoculars. In this case, corrective glasses should not be seen as a hazardous instrument, as they merely establish the correct field of vision for the eye.

The manufacturer must specify which optical instruments pose a hazard potential with a class 1M laser beam.

Laser Class 1C

With the revision of the norm, published in July 2015, this class has been defined for devices which are intended for the contact with a target object, such as the skin.
This class holds lasers which are used for cosmetical applications, like hair removal, skin tightening, acne treatment or tattoo removal. The class is also applicable for laser devices intended for the use at home. The passing of the energy values of Laser Class 1 has to be prevented. This is normally solved with the use of contact switches, which are designed to prevent human errors and the potential exposure passing the limit values of Laser Class 1.

Laser Class 2

Lasers within the definition of Laser Class 2 exclusively emit in the visible part of the spectral range, which is, defined by law, from 400-700 nm. The power is limited to 1 mW. A direct hit of the laser ray to the eye, even trough an optical instrument may lead to dazzling, but not to an irreversible damage. Still the intended look into the laser ray should be avoided.

Laser Class 2M

Just as Laser Class 2, the lasers classified as Laser Class 2M are within the, defined by law, visible spectral range of 400-700 nm. The ray is either widened of divergent.
The power of the complete ray is limited to .5 W, similar to the limit value of Laser Class 3B. Within the spectral range of 400-1400 nm, the ray is naturally absorbed by the pupil, and merely a fraction of the ray, below the limit value, defined by Laser Class 1 can penetrate the inner eye.
A potential hazard will only occur, should the ray be observed through an optical instrument.

Laser Class 3R

Lasers defined as Laser Class 3R are similar to lasers defined as Laser Class 2, with a 5 times higher power (400-700 nm; 5 mW). Outside the visible spectral range, the value of 5 times the value limit of Laser Class 1 must not be exceeded, unless widened, by the laser ray. A direct exposure of the eye is to be avoided. Lasers defined as Laser Class 3R are mostly used as show lasers.

Laser Class 3B

Lasers defined as Laser Class 3B have their energy value limit at 0,5 W in continuous wave mode. The observation of the incoming laser ray through a diffuse reflection (p.e. a non-reflecting surface) will not cause damage to the eye. The norm defines the minimum distance from the point of impact as 13 cm and the maximum observation time as 10 seconds.

The direct look into the source of the radiation may lead to irreversible eye damage. Therefore, the norm demands the use of a laser safety google, certified by DIN EN 207.

Laser Class 4

Every laser not classified into the previously named Laser Classes, is classified as Laser Class 4. Ray and also the reflection may cause irreversible damage to eyes and skin.
A laser safety goggle, certified after the norm DIN EN 207 has to be worn. Furthermore, the wearing of laser protective clothing is highly advised.

Lasers classified as Laser Class 4 may cause combustion and explosions, therefore, the necessary prevention to ensure the safety must be executed.

The pulse duration of a continuous wave (CW) laser is over 0.25 seconds.
The pulse duration of a pulse laser is greater than one microsecond, but not greater than 0.25 seconds.
The pulse duration of a Q-switched laser is between one nanosecond and one microsecond.
The pulse duration of a mode-locked laser is, by definition, less than one nanosecond.

Millisecond [ms]= one thousandth of a second [10^-3 s].
Microsecond [µs]= one millionth of a second [10^-6 s].
Nanosecond [ns]= one billionth of a second [10^-9 s].

For the certification of laser safety products according to EN 207, EN208 and EN 12254, laser stress tests are mandatory. In contrast to the OD-values, which are given outside the European Union, considered sufficient by the ANSI-Norm and measured by spectral photometers, the European norms demand the products to be actually shot by lasers. These tests are done by accredited testing institutes. The goal of these tests is to define the resistance time against laser stress, to make a valid statement about the laser protective properties of the product. The required resistance times for the protection levels are defined by the norms. PROTECT- Laserschutz determines the values in the pre-test, which are later confirmed by the accredited bodies.

For certifications according to EN 60825-4, the resistance times (10 s; 100 s; 30.000 s) are as well defined as an important factor.

The DIN EN 207 norm specifies LB protection levels for laser safety eyewear. The protection levels are based on the maximum spectral transmittance (τ) at the corresponding laser wavelength (λ). The maximum power density (E) or energy density (H) depending on the wavelength range and operating mode of the laser (D, I, R, M) (insert link). The specifications are additionally divided into 3 wavelength ranges, the UV-A and UV-B range (180-315 nm), the UV-C to NIR range (315-1400 nm) and the far infrared range (FIR) from 1400 nm.

Reference: Personal eye-protection equipment - Filters and eye-protectors against laser radiation (laser eye-protectors); German version EN 207:2009 + AC:2011

Since the 80's, liquid crystal display technology has been used for glare protection. This technology is used in medical technology, for example in IPL applications and in welding protection. The LCD shutters can be adapted to the respective protection requirements of the application. In welding protection, these filters are additionally provided with an infrared coating.

The orientation of the liquid crystals is influenced by electrical signals and thus the darkening stage of the optical filter is controlled. The emission of the electrical signals is triggered by light-sensitive sensors. With the help of this technology, the residual daylight transmission (VLT) can be adaptively adjusted to the protection requirements of the respective light emission and the required protection level can be established. This technology can also be used in shutter glasses, which are used in medicine and welding protection.

For X-ray protection, lead equivalents are given, the indication of a lead equivalent is a comparative indication, for the product used for protection and its shielding effect against ionising radiation, compared to the shielding effect of a pure lead layer. PROTECT- Laser Protection offers X-ray protection glasses with a lead equivalent value of 0.75 mm Pb.  The decisive factor here is the density of the material, which allows conclusions to be drawn about the distances between the atoms inside atomic lattices. The equivalent lead layer thickness [mm] is calculated according to an equation described in the DIN 6812 standard. (Pb = lead)

Both the waist radius [W₀] and the divergence angle [θ] of a real laser beam are increased by a factor of M compared to the basic mode. From this, the beam parameter product is calculated by multiplying the divergence angle by the waist radius. This corresponds to the product of the beam quality factor/diffraction coefficient and the wavelength [λ] divided by the factor π. To estimate the real ray data, this is multiplied by the diffraction coefficient of the laser used.

 The numerical aperture is used as a non-dimensional parameter for the boundary of light-rays in optical systems, which defines the luminous intensity and the resolution of objects.  By definition, the numerical aperture is a parameter for the beam limitation and refers to the boundary rays. The value is calculated using the sine of half the angle of propagation of the cut-off wavelength.

The optical density, p.ex. OD8+ indicates that a light ray of the defined wavelength spectrum is reduced by 10 to the power of the factor of the optical density, in this example, the light ray would be reduced by the factor of 10 to the power of 8, or the 10 millionth part of the energy would penetrate the material, while the rest of the energy is absorbed into the material. The optical density is calculated by the decadic logarithm of the quotient of incoming to outgoing radiation.

A marking about the optical density is not sufficient for the European market, as it does not contain any information about the permissible irradiance.

The DIN EN 208 norm defines RB protection levels. RB protection levels are assigned on the basis of a time base of 0.25 seconds, or 2 seconds. They are based on the maximum power of the laser for this time base. For continuous wave lasers the power is given in watts, for pulsed lasers the maximum energy is given in joules. An additional factor to define a protection level is the maximum spectral transmission.

Reference: Personal eye-protection - Eye-protectors for adjustment work on lasers and laser systems (laser adjustment eye-protectors); German version EN 208:2009

The smallest accessible beam diameter must be used. For the calculation it is assumed that this beam diameter contains 63% of the total laser energy.

Reflection or mirroring of light rays at an interface can be observed on metallic surfaces but also on glass panes and other dielectric interfaces. The best example of (almost) total reflection is a commercially available mirror. They normally consist of a thin glass pane coated with aluminium or silver. However, a dielectric multilayer mirror is usually used to reflect laser radiation.

Both the waist radius [W₀] and the divergence angle [θ] of a real laser beam are increased by a factor of M compared to the basic mode. From this, the beam parameter product is calculated by multiplying the divergence angle by the waist radius. This corresponds to the product of the beam quality factor/diffraction coefficient and the wavelength [λ] divided by the factor π. To estimate the real ray data, this is multiplied by the diffraction coefficient of the laser used.

VLT as a percentage is an indication of how much of the brightness of daylight or lighting in the visible range (380-780 nm) is still visible to the observer. DIN EN 207:2017 stipulates that for wearers of laser safety spectacles, if light transmission is below 20 %, based on standard illuminant D65, defined by ISO 11664-2:2007, a recommendation must be made to raise illuminance at the workplace concerned.

The wavelength is the distance between two points of a periodic wave which are in the same phase. PROTECT laser protection offers protection in the wavelength range from 180-11000 nm. The corresponding protection of the products can be found in the product information and certified protection levels.

The wavelength λ is calculated from the product of the phase velocity and the sweep fraction of the frequency of the wave.

If a laser with a frequency > 25 Hz is used during a test, a Y protection level is assigned.