u003cbru003eIn addition to reducing the radiation intensity of visible light, sun
glasses can also reduce ultraviolet and infrared radiation. Polarized
sunglasses can also be used to eliminate horizontal reflections on water, snow, and gravel roads. Sun
glasses are more fashionable. But the fundamental role of
sunglasses is to provide radiation protection for the eyes. The basic requirements for
sunglasses are: eliminate unnecessary radiation bands that may be harmful to 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 wear resistance. This article mainly introduces the principle of optical radiation protection in the basic knowledge of sunglasses. 1. The principle of optical radiation protection The damage to eye tissues caused by radiation may be immediate or cumulative. The general principle of radiation protection is 'prevent trouble before it happens.' The following are several indicators used to assess whether environmental radiation has reached the level of protection required: (1) Safety exposure duration (SED) is the ratio between the tissue radiation exposure threshold and the intensity of the light source. SED can be used to calculate UV, VIS and IR protection. The light source can be long-wavelength or short-wavelength, as long as the tissue exposure threshold and the intensity of the light source are within the same wavelength range. SED can also be used to evaluate the protection provided by filters. (2) The ratio between the radiation intensity threshold of the tissue damage caused by the protection factor (PF) and the radiation intensity of the light source. It can be used to calculate the damage of electromagnetic radiation in UV, VIS and IR bands. (3) Relative effectiveness (RE) is the relative weight coefficient of different wavelengths that can cause damages such as photosensitive keratitis, cataract, etc. in the ultraviolet range of 200 nm to 320 nm, with 270 nm as high as 1.00.
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