Source: AUDDI | Date of issue: 2022-05-11 10:23:06 | Views: 11870
Many people are confused about how to choose lenses.Dont worry. Xiaoxin teaches you some ways to choose lenses from the following five aspects. I hope it can help you.No. 1 selected refractive indexThe refractive index reflects the ability of the lens…
Many people are confused about how to choose lenses.
Don't worry. Xiaoxin teaches you some ways to choose lenses from the following five aspects. I hope it can help you.
The refractive index reflects the ability of the lens to refract light. Under the same conditions, the larger the refractive index, the thinner and more beautiful the lens is. Of course, the price is more expensive.
But remember that the thinner the lens, the better. Because there is a very related refractive index called Abbe number.
Abbe number refers to the dispersion coefficient, which is an important index to measure the imaging clarity of the lens. The higher the value, the clearer the image of the lens; The lower the value, the more blurred the image of the lens.
Abbe number and refractive index are relative and in the opposite development trend. As shown in the above figure, in this figure, the blue line represents the refractive index and the green line represents the Abbe number.
Generally speaking, the higher the refractive index of the lens, the lower the Abbe number. Therefore, high lightness and high clarity are the relationship between fish and bear's paw.
Therefore, it is generally recommended that you screen the lenses with corresponding refractive index according to your own degree. It is recommended to refer to the following:
Generally, it is recommended to select 1.56 below 200 degrees; 1.6 for 200 ~ 400; 1.67 for 400 ~ 700; 1.74 for more than 700; More than 1000 choose glass lens or high refractive index resin sheet. Please consult an optometrist for details.
A lens cut from a sphere with a convex or concave shape is called a spherical lens. Because spherical lens is difficult to avoid aberration, there is a lens to correct the shortcomings of spherical lens, that is, aspheric lens.
Aspherical lens refers to the rotating surface (such as parabola) with the same non-circular section on all meridians.
Its biggest advantage is that there is no image distortion in the edge field of vision, less visual deformation and more realistic visual objects. At the same time, the edge of the lens is about 1 / 3 thinner than the ordinary spherical lens.
Now the main products on the market are basically aspherical lenses, which is basically small. If you want to choose aspherical lenses, just choose aspherical lenses directly.
Lens prices range from tens to thousands or even tens of thousands of pieces. Where are your lenses? There may be differences in brand, material, technology and other aspects, and the biggest difference is the film.
Lens film is mainly used to reduce reflection, improve the clarity of the lens, waterproof and anti ultraviolet ability. The main optical films include hard film, antireflection film (antireflection film), antifouling film (waterproof film), anti radiation film, polarization film, anti fog film and light splitting film.
It is precisely because of the existence of these films that the clarity and comfort of different lenses are different. For example, for the lens with waterproof and antifouling film, each time you flush it with water, only a few drops of water will be left on the lens, and then suck it with a spectacle cloth, it will be very clean, and there will be no phenomenon that you can't wipe it clean.
You can choose lenses with different film layers according to your own needs.
Glass sheet: the clarity is slightly higher than that of resin. It is scratch resistant and wear-resistant than that of other materials. The lens is thin and has good optical performance. However, due to its heavy and fragile characteristics, the utilization rate is low, and the factory mainly focuses on high refractive index, such as refractive index of 1.8 and 1.9.
Resin sheet: it is the most mainstream material for glasses for myopia at present. It has the advantages of light weight, high temperature resistance, impact resistance, non fragile, safe use, and can effectively block ultraviolet rays.
PC film: also known as "space film" and "space film", it has the advantages of toughness, not easy to crack, impact resistance and so on. It is also the lightest material used for spectacle lenses at present.
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