The photochromic lenses photochromic phenomenon

Is mainly introduced in this paper the photochromic lenses of photochromic phenomenon. Darker/fade under the condition of complete illumination, photochromic materials from a very small amount of residual impression ( Light transmittance about 90%, can satisfy most people normal indoor vision) , and then according to their composition, change to dark. Incident lens is the type of radiation and the surrounding temperature influence the degree of lens darker two complex factors. Much darker effect is due to the effect of ultraviolet rather than visible light, and with the temperature change and the performance is different. Heat can cause bleaching photochromic materials, so in the summer, darker effect tend to weaken. Lens manufacturers also have been trying to solve this contradiction, developed in recent years the photochromic materials have been able to reduce the temperature dependence. Discoloration rate variable depth rate: dark rate depends mainly on the lens material of optical density, usually from a few seconds to several minutes from big light transmittance is very little light transmittance. Fading rate: fade rate depending on the composition of the lens and the discoloration of heat treatment. It also takes a few seconds to several minutes from light transmittance is great to light transmittance. Photochromic materials darker and fading rate is very important. The product color is very fast, but the lens color changing too fast is not good, may even be dangerous. Drive with the lens if it is instantly change color, is not ideal. Our eyes need a few seconds of time to completely adapt to the change of illumination conditions, if the lens darker time with the eyes to adapt to changes in illumination time close to, is the ideal ratio. Lens bleaching rate or fade rate are also important, enter indoor Dai Jingzhe won't fade hope the lens to a comfortable state of time is too long. Any color lens should be able to fade back to 60% in a few seconds 70% of light transmittance, in about 15 ~ 20 min 85% light transmittance. The change of the temperature effect on rate of optical density and temperature. In the process of color darker, under the high temperature of heat treatment can have high light transmittance, whereas under the heat treatment of low temperature will have a lower light transmittance. Fading rate of acceleration or with additional heat than make exposure of longer wavelength light lens color burn. Color lenses are usually under the uv rays and violet light transmittance is low, and there is higher under the red light and infrared light transmittance.