|Protection filter for:||Diode-HeNe|
Laser safety eyewear usually consists of two components: the frame - also known as the support body - and the filters. Since it is difficult and expensive to integrate a corrective effect into the filter, there are basket frames for spectacle wearers, which can also be worn over corrective glasses. So that the sides of the corrective glasses do not conflict with the basket frame, basket frames are held in place by an elastic headband like diving goggles. Glasses with sides, on the other hand, are only suitable for people who do not also need corrective glasses.
It was shown early on that the appropriate attenuation of laser safety goggles - the optical density - is not enough for adequate eye protection for the wearer. This is reflected in the European standard EN 207. The laser safety goggles must also have a minimum time of 5 seconds against this radiation, which should allow the wearer to withdraw from the beam path in time in the event of an accidental hit before the glasses fail. The combination of both criteria is expressed by the protection level. It can have values from 1 to 10, which can be different for the various operating modes D, I, R and M.
There are four different laser operating modes: continuous wave D, pulse I, giant pulse R and ultra-short pulse M. The distinction is made by the duration of the radiation and the pulse duration. The reason for the distinction is that the interaction between laser radiation and matter depends not only on the wavelength, but also on the irradiance and the duration of action.
A laser is an arrangement in which a so-called pump delivers energy to the laser medium so that its electrons are transported to a higher energy level and the increase in energy can be called up again in a targeted manner. If the electrons fall back in an orderly manner to a lower energy level, the energy difference can be released in the form of photons. If this process is implemented in a resonator as an amplification process, the photon stream can achieve very high power densities. The laser is often referred to as an overdriven amplifier, which turns it into a transmitter; hence the name laser oscillator.
As part of a research project initiated by the BAuA (unfortunately only available in German, see https://www.baua.de/DE/Angebote/Publikationen/Berichte/F2442.html), laser safety goggles up to 20 years old were examined . Signs of aging that impair eye protection were not found, neither in products with mineral filters nor with plastic filters.
Laser safety glasses are regulated by the European standard EN 207. They have to limit the irradiance of the laser to the limit value of laser class 1. Laser adjustment glasses are regulated by the European standard EN 208. They only have to limit the irradiance of the laser to the limit value of laser class 2. This means that there is still the chance of being able to detect the laser beam while maintaining eye safety.
The HeNe laser is a gas laser in which the laser medium consists of neon (Ne) to which helium (He) is added. It is pumped by an electrical discharge and emits mainly the wavelength 632.8 nm.
The heart of the diode laser consists of two different semiconductor crystals. If electrical current flows through the arrangement, photons can be generated at the interface between the two semiconductors, which can be released as laser radiation.
With the CE mark, the manufacturer declares that his product has been tested in accordance with the relevant European standards; in the case of laser eye protection, these are EN 207 or EN 208. Since fraud is still possible here, information on the EU type certificate must also be included in the accompanying documents.
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