一、 Protective glasses - absorption filter
1. Sunshade glasses, also known as Sunglasses: the transmittance of visible light is about 20%, and the absorption of ultraviolet and infrared rays is good. There are light green, light gray, light tea and other colors, which are used to make sun shading and snow work protective glasses. The light gray lens has the least influence on color recognition; Light tea glasses make the blue sky look darker and reduce the transmission of green light; The light green lens reduces the transmission of red light.
2. Protective glasses for gas welding: the colorants used in this kind of lens are mainly iron oxide and cobalt oxide, which are yellow green, and can fully absorb light waves with wavelengths below 500 urn. The transmittance of visible light is below 1%, and only a small amount of infrared can pass through. This kind of glasses is specially used for gas welding operation.
3. Protective glasses for electric welding: the ultraviolet light generated by electric welding will cause damage to the cornea and conjunctiva of the eye (the most serious is 28nm light). The strong infrared ray produced is easy to cause ocular lens opacity. Goggles for electric welding can well block the above infrared and ultraviolet rays. The lens is based on optical glass and uses colorants such as iron oxide, cobalt oxide and chromium oxide. In addition, a certain amount of cerium oxide is added to increase the absorption of ultraviolet rays. The appearance is green or yellowish green. It can block all ultraviolet rays. The infrared transmittance is less than 5% and the visible light transmittance is about 0.1%.
4. There are two kinds of blue protective glasses. One is colored with iron oxide and cobalt oxide, which makes the filament purplish red. The other is colored with copper oxide and manganese oxide, which makes the filament white. They can all absorb the dazzling glare in the band of 500-600 nm (visible light sensitive area of human eyes). The light transmittance at 400 nm is less than 12% and can also absorb ultraviolet rays. They are suitable for operators in front of various industrial high-temperature furnaces.
5. Dark red glass glasses: this kind of glasses lens is a kind of dark red glass colored with cadmium sulfide and cadmium selenide. It can absorb all light with a wavelength below 600nm. It can be used as goggles for medical or industrial personnel when operating X-ray fluoroscopy equipment.
6. Laser protective glasses: there are two types of glasses, namely reflection type and absorption type. The surface of the former is coated with a metal film by vacuum coating method, and the reflectivity of 532nm, 694nm and 1060nm laser bands is greater than 99.5%; The latter lens can fully absorb the 1060nm laser band. The lens must be equipped with a closed or semi closed frame to prevent the laser from entering the eye around the lens. It can be used as protective glasses for laser operators.
7. Microwave protective glasses: microwave is an electromagnetic wave with a wavelength of about 1nm LM. It can also cause harm to people, especially eyes. Under the action of strong microwave, it can cause eye fatigue, dry eyes and dizziness, and even lead to lens opacity, cataract and retinal damage. Its protection is to spray tin tetrachloride and metal compounds that can improve the conductivity on the surface of the lens to form a multilayer conductive film on the surface of the lens, which plays the role of shielding microwave. Because the microwave can bypass the lens and enter the eye, the frame should also be shielded to prevent the damage of microwave to the eye.
二、 Protective glasses - reflective filters
Absorption filter uses the lens to absorb some wavelengths of light to reduce the light intensity into the eye. However, because the lens absorbs some light, it becomes heat emission, especially infrared and other long wave light, which makes the eyes feel very uncomfortable due to the accumulation of heat. If protective glasses and reflective filters are used, this problem can be solved well. As mentioned in the front coated glasses, if a layer of material film with higher refractive index than the lens itself is coated on the lens surface, it will increase the reflection of light and reduce the transmission intensity of light, so as to protect the eyes from strong light and harmful rays.
In actual work and life, many cases are used by the combination of absorption and reflection, that is, a layer of high reflection film is plated on the colored lens to make the filter function stronger, such as glasses worn by operators such as electric welding, chlorine arc welding and plasma cutting.