跳至主要内容

When you buy glasses, how to choose the lens ? (1)


t0124aa0ad3b1e92b05




When refer to how to choose the lens. we will talk about the refractive index, coefficient of wear resistance, spherical selection, Abbe number, anti-fouling ability, brand selection, and functional choice.





   1.Refractive index
The refractive index of the lens is determined by the material of lens.
In the case of the same thickness of the center, the lens of the same degree and the same material, a thinner edge of the lens has a higher refractive index; when the brand is the same, the refractive index means the different usage of the material, and the price of the lens can also be judged. The higher the refractive index, the higher the price.
Refractive index selection reference: (For reference only, do not completely follow it)
1.56: 0 — 400° (-4.00D)
1.60: 300° (-3.00D) — 600° (-6.00D)
1.67: 400° (-4.00D) — 800° (-8.00D)
1.74: 800° (-8.00D) or above2.
t015960dd159d00466b
  1. Wear resistance coefficient
The reason why the wear resistance coefficient is mentioned is that the resin lens is not wear-resistant when it enters the market, and it is basically worn after wearing the lens for half a year. However, with the development of the technology, the surface hardness of the ordinary resin lens is 2-3H, and after enhancing its hardness, its hardness reaches 4-5H.Now the hardness of the resin lens has exceeded 6-7H. Adding a hard film solves the disadvantage that the lens is not wear resistant.
It hardness can not be compared with the glass sheet. But the glass sheet are mainly used to provide high refractive index, such as: 1.8, 1.9, the refractive index.
By the way, talk about PC tablets.
Light, tough and not easy to break are significant advantages of PC tablets.
Teach you a skill to identify the hardness of the lens, you can use the same material to circle  on the sample back and forth. According to the depth and thickness of the scratch, you can roughly detect the surface hardness of the lens.
t01845027beaa1b803d
  1. Spherical and aspherical surface
Cutting a part of a lens with a convex or concave shape from a sphere is called a spherical lens.
Since the spherical lens is difficult to avoid aberrations (especially astigmatic aberrations, such as bending aberrations), there are lenses that correct the disadvantages of spherical lenses, that is, aspherical surfaces (usually referred to as single-sided aspherical lenses).
Aspherical lens: refers to a rotating surface (such as a parabola) 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 the ordinary spherical lens, so the price will be relatively higher. There are double-sided aspherical lenses on the market. Its view is clearer and the imaging effect is better. Of course, the price is also very expensive.

  1. Abbe number
Abbe number is the dispersion coefficient, which is an important indicator to measure the clarity of lens imaging.
The smaller the Abbe number, the greater the dispersion and the worse the clarity of the image. The Abbe number of the lens has a certain relationship with the refractive index. The larger the refractive index of the material, the more the dispersion, that is, the lower the Abbe number.
Therefore, for this single indicator, the lower the refractive index, the better. But how to judge it is be based on the overall situation of vision. Which is the most factor is whether it is appropriate, and it can not be mechanically limited to the Abbe number.
标签：

评论

发表评论

此博客中的热门博文

How Often should you replace glasses?

Many of us go for years at a time without considering changing out our glasses because we doggedly believe that we can still see perfectly with our old lenses. While you may not have noticed or realized it, your old eyeglasses may be working against you, causing undue eyestrain or fatigue. But how often should we replace our glasses, and why? Listen to the Advice of Your Optometrist Your glasses should be replaced when your optometrist recommends that they should be. This usually will occur in tandem with your regular eye exam. The American Optometric Association recommends that non-senior adults and children over age 6 have regular eye exams a minimum of once every two years if they do not have risk factors for poor vision. Seniors over age 60 and individuals with risk factors should have an eye exam every year, or more frequently if recommended by their doctor. During this regular eye exam, you will need to ask your optometrist whether or not you need to replace your glasses w...
发表评论
阅读全文

 Have you chosen the right glasses?

With the development of science and technology and the popularity of digital products, more and more people wear glasses for myopia. Previously, people wear glasses only as a way to correct their poor vision. Now glasses are not only used correct myopia, but also as a very important decoration for people. If your glasses are not match with your style, the glasses will have bad influence on your image. How do you match your own glasses with your style? Here's how to choose the right eye for you. 1. Choose according to your face type How to identify your face: Give yourself a face contour and pick up your forehead to reveal the hairline. Take a frontal photo of yourself with a camera or mobile phone, pass it to the computer, use the drawing tools to trace the outline of the face, and the face map is done. Compare the face classification to find out your face shape. Various face types  round face suitable for the water chest or rectangula...
发表评论
阅读全文

How to choose the frames? (2)

3, On the logo - look at the material. Many frames will be framed on the temples, especially the precious metal frames of gold and titanium. Let's take a brief look at their logo. (1) GF/GP: GF is a gold-clad frame, which is a frame obtained by welding thin gold sheets on other metal substrates; GP is a gold-plated frame, that is, gold is plated on other metals. (2) Ti-P/Ti-C: Ti is a mark containing a titanium material, Ti-P represents pure titanium, and Ti-C represents a titanium alloy or the like. By the way, what is the difference between titanium, titanium alloy, beta titanium, and memory alloy? A. Pure titanium. Titanium metal materials with a purity of more than 99% of titanium can be used as pure titanium glasses. The frame made of pure titanium material has excellent characteristics such as high melting point, light material, strong corrosion resistance and firm plating layer, which can ensure the two important performances of the eyeglass frame beautiful and durabl...
发表评论
阅读全文