With the development and application of laser technology, laser safety protection products are widely known and used by people. According to the protection principle, laser protection products can be divided into: reflection type, absorption type, photoelectric switch type, grating type, etc. Among them, the photoelectric switch type and the grating type are difficult to be widely adopted due to slow response time and inconvenience to wear. Nowadays, reflective and absorptive laser protective glasses are more common on the market.
So, briefly introduce the protection technology and principle of these two kinds of goggles.
Reflective laser protective glasses were developed and applied in the 1970s. The principle is to coat the surface of the lens with a light reflective film of the corresponding laser wavelength, and reflect the incident light through the reflective properties of the material to achieve protection. Absorptive laser protective glasses appeared in the late 1980s. The principle is to add a light absorber of a specific wavelength to the lens material, and use the light absorption performance of the absorber to absorb and protect the light of the corresponding wavelength.
Reflective goggles have a high visible light transmittance due to the principle of coating a reflective optical film, which can reach VLT ≥ 80%, and the light transmission color (the color of the lens) is relatively light, so the visual impact on the human eye is very small. But the reflective film has a big weakness, that is, its protective effect depends on the angle of the incident light source. When the light source enters another medium from one medium, if the incident angle is greater than a certain critical angle, total reflection will occur, otherwise part of the light will "escape". This is what we said, the reflective film has a certain selectivity to the incident light source. At the same time, the protective film layer is easy to fall off due to the influence of environmental humidity, temperature, and time extension. Therefore, its protective capacity has certain limitations.
As for the absorptive goggles, because the principle is to add a light absorber of a specific wavelength to the material, the color of the absorber will affect the visible light transmittance and visual effect of the absorptive goggles. This is reflected in the absorption of protective goggles on the market lenses will have very obvious blue, red, green, etc., and some wearers will also experience color fatigue and mild dazzling due to color cast. But compared to reflective protective goggles, the biggest advantage of the absorptive type is that it has no selectivity to the incident light source. The incident light at any angle will be quickly absorbed as long as it reaches the surface of the lens. At the same time, its optical density value is very high, the OD value can reach 10 and above (but the visible light transmittance will be correspondingly lower). The absorption type is not easily affected by changes in the environment and has a high degree of damage resistance. Even if the lens surface is scratched or scratched, it will not affect the protective effect of the product, while the reflective film will lose its protective effect due to slight damage. Therefore, combining the above advantages and disadvantages, absorption protection is currently the most widely used laser protective goggles technology.
