Views: 130 Author: Site Editor Publish Time: 2020-08-14 Origin: Site
Anti blue light reading glasses have become a necessity for many people. A pair of glasses consists of a spectacle frame and spectacle lenses. A good pair of glasses can correct vision and bring convenience to life. Let me tell you how to choose spectacle lenses.
The refractive index of the lens is determined by the material used for the lens. Under the condition that the center thickness and the size of the lens are completely the same, the edge of the lens with high refractive index is thinner than that with low refractive index.
With the same brand and the same series, the price of the lens can be estimated by the refractive index. Basically, the higher the refractive index, the higher the price. Compared with different brands or different series of the same brand, because the basic optical indicators such as effective light transmittance, wear resistance, anti pollution are very different, there is no significance for comparison.
Simply comparing the price and ignoring the huge gap in quality are the common ways used by marketers. The quality of the lens material, the quality of the lens mold, the level of coating and production technology, the quality control ability and quality stability of lens manufacturing have a huge gap among all brands. It is more important to choose the lens of the professional optical lens manufacturer's own brand than to choose the refractive index. It is worth noting that from the perspective of visual perception, the lower the refractive index, the better (except 1.56).
Spherical lens refers to a lens with a convex or concave shape cut out from a sphere. Due to the inevitable occurrence of aberrations and other phenomena in spherical lenses, aspheric lenses appear to correct the shortcomings of spherical lenses. Aspheric lens refers to the rotating surface with the same non-circular cross section on all meridians. The biggest advantage is that there is no object distortion in the edge field of view, and the edge of the lens is about 1 / 3 thinner than that of the ordinary spherical lens.
At present, the aspheric lens is indeed closer to the naked eye vision, the lens edge deformation is smaller, the field of vision is larger, and it has been the mainstream configuration. But not everyone can adapt. Some people's eyes can only adapt to spherical lenses.
Non-abrasion resistance is the biggest drawback of resin lenses. To address this shortcoming, brand manufacturers have hardened the surface of the lenses. The surface hardness of the original ordinary resin lens is 2 to 3H. After the hardening process, the hardness reaches 6 to 7H. The addition of hard film improves the disadvantage of the lens being not wear-resistant. With the continuous progress of technology, it will be closer to the surface hardness of glass lenses.
Light transmittance refers to the total amount of light that passes through the lens and is not reflected or absorbed. Higher light transmittance means higher definition. In general, the light transmittance of a lens is related to the refractive index of the lens. The higher the refractive index, the lower the light transmittance. This is mainly because lenses with high refractive index have higher reflection and refractive index, which reduces the amount of effective light entering the eye and affects the clarity of the lens. After coating a multi-layer anti-reflection film on the surface of the lens, the reflected light ratio can be reduced and the light transmittance can be improved. Therefore, when choosing a lens, the refractive index cannot be used to judge the light transmittance, and it is necessary to evaluate the other parameters of the lens comprehensively.
The Abbe number is the dispersion coefficient, which is an important indicator to measure the imaging clarity of the lens. The larger the Abbe number, the smaller the dispersion and the better the sharpness of its imaging. The Abbe number of the lens has a certain relationship with the refractive index. However, when choosing glasses, it is necessary to consider comprehensively according to our own vision, personal visual sensitivity, eye demand, frame size, frame material, frame structure, which is the most important thing for a specific individual.
The anti radiation effect of the anti radiation lens is only the scope of the lens. While the electromagnetic wave is not completely straight-line propagation and the harm of the electromagnetic wave to the human body also needs accurate quantitative analysis. Ordinary optical lenses have anti-ultraviolet function, not to mention UV protection sunglasses, because the anti-ultraviolet index is one of many optical indicators. The main function of the anti blue reading glasses is to reduce the visual fatigue caused by the electronic display screen. There is no further evidence to prove that the blue light filter reading glasses can effectively improve the sore eyes, dry eyes, decreased vision, and fundus lesions. Therefore, the main selling points of anti-radiation, anti-ultraviolet and anti-blue light just are usually marketing methods.
In short, choosing lenses is an easy thing to underestimate but extremely important. It involves a wide range of aspects, but it can be summed up in three aspects, professionalism, comfort and fashion. Consumers can choose the blue filter reading glasses or uv400 protective sunglasses with high popularity and the quality will be guaranteed.
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