How Sunglasses Reduce Light Radiation

u003cbru003eIn addition to reducing the radiation intensity of visible light, glasses.com/sunglasses-1.html' target='_blank'>sunglasses can also reduce ultraviolet and infrared radiation. The basic requirements for sunglasses are: eliminate unnecessary radiation bands that may damage the eyes; reduce the intensity of ambient light entering the eyes, provide clear and comfortable functional vision; maintain normal color vision, which is reflected in the rapid and accurate identification Traffic signal lights; maintain the amount of dark adaptation or night vision; good impact resistance and abrasion resistance. This article introduces the ways in which sunglasses can reduce light radiation. Sunglasses reduce light radiation mainly through the absorption and surface reflection of the lens material: 1. Absorbing glass is to evenly distribute the coloring agent into the lens material during the production process. The purpose of radiation protection is usually achieved by adding metal oxides to the lenses. Adding iron oxide to glass can absorb 95% of UV and IR radiation. The addition of metal oxides usually changes the color of the lens. For example, cobalt oxide appears blue, chromium oxide appears green, and copper oxide appears blue. Adding silicic acid and boric acid to the glass will increase the UV transmittance. Absorbent resin lenses are organic pigments added to the lens during the lens production process or after the surface processing and edge cutting are completed. Color absorption filters can be used to improve visual function. What the filter actually changes is the contrast between the object and the background. However, it is not appropriate to judge its radiation protection function based on the color or dyeing of the lens. For example, gray or neutral glass sheets can usually transmit ultraviolet and infrared rays, and are not suitable for professional UV and IR protective glasses, but because they do not affect Color vision, so it can be used as ordinary sunglasses. 2. Absorbing resin refers to immersing the resin material or mirror into the dye, and the dye can penetrate 1 mm below the surface. CR39 can only absorb ultraviolet and visible light, and the absorption of infrared rays will deform the lens. PC material can absorb infrared. But the color of the resin filter does not explain its light transmission characteristics. 3. Reflective filter, a thin metal film is plated on the back surface of the lens in a vacuum environment to increase the reflection of the surface. Reflective lenses provide radiation protection by reflecting excess radiation. Since the back surface of the film is in direct contact with the air, it will cause a high proportion of reflection. Usually, a layer of magnesium fluoride (anti-reflection film) is coated on it to reduce excessive back surface reflection light from entering the eyes. Reflective filter with reflective film on the surface. Reflective lenses are mainly coated with a vacuum metal film on the surface of the lens, which can transmit visible light and reflect infrared rays, but the ability to absorb ultraviolet rays is not very strong. 4. Gradient dyeing, that is, the depth of dyeing changes continuously on the surface of the lens. It is usually used for resin lenses. 5. Polarizing filter. In addition to absorbing excessive radiation, this kind of lens can also absorb plane-polarized light generated by each reflective surface. The reflected light is completely plane-polarized, and the vibrating surface is parallel to the reflecting surface (horizontal direction). If the polarization axis of the filter polarization lens is set to the vertical direction, the reflected light will be absorbed. In this way, the polarizing filter can filter the reflected glare light so that the eyes can see the object illuminated by the non-polarized light. The polarized light transmitted by the polarizer is approximately 32% of the incident light. 6. Interference filter. It is composed of a multi-layer electrical insulating film that allows the spectra of specific wavelengths to pass. The wavelength of light passing through can be changed by controlling the material of the film layer (ie, controlling the refractive index). Interferometers are more sensitive to changes in the angle of incidence and temperature. Changing the angle of incidence and temperature will change the interference of waves, thereby changing the wavelength of the transmitted light. In addition to polarizers, sunglasses generally do not eliminate glare, nor do they change contrast. Sunglasses just reduce the glare to an intensity level that the eyes can tolerate. Ordinary sunglasses absorb the illumination intensity from the object and its background in the same proportion, so the contrast does not change. Special-purpose sunglasses can absorb the light from the object and the background in different proportions, thereby changing the contrast. The transmittance of spectacle lenses must be below 4096 to be used as protective sunglasses. Colored sunglasses can change the ability of the eyes to distinguish colors, so sunglasses are generally not suitable for driving at night. The difference in the light transmittance of the two spectacle lenses will affect the perception of depth. Poor surface processing quality of sunglasses lens can cause visual distortion, headaches, eye fatigue and other symptoms.
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