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The physical properties of the lens and the optical properties of the lens
With the popularization of optical lenses, people's requirements for optical lenses are getting higher and higher. The quality of optical lenses is mainly determined by four aspects: surface (including visible internal flaws on the surface), optics, geometry and physics.
The inspection methods, conditions, devices, etc. of the first three have been clearly stipulated and have been popularized, but the equipment for testing the physical properties of resin lenses has not yet been popularized, so the general public Paying more attention to the quality of resin lenses is to pay more attention to its physical properties.
The physical properties of resin lenses mainly include:
1. Refractive index: It is the ratio of the sine of the incident light angle and the transmitted light angle of the lens. Its value is generally between 1.49-1.74. At the same power, the higher the refractive index, the thinner the lens. When we match glasses, the ultra-thin lenses that optical lenses often require are lenses with extremely high refractive index, but in general, the higher the refractive index of the material, the greater the dispersion.
2. Scratch resistance: refers to the degree of damage to the light transmittance of the lens surface under the action of external force. The scratch of the lens is an important factor that affects the service life and visual effect of the lens. The friction haze value (Hs) is commonly used in China, and its value is generally between 0.2-4.5, the lower the better. The BAYER method is commonly used abroad, and its value is between 0.8-4, the higher the better.
The hardened resin lens we usually refer to is better in scratch resistance than ordinary resin lenses. In daily life, we can rub two different lenses in pairs or test them with denim and 0000 steel wool to observe the scratches. Optical lens
3. UV cut-off rate: also known as UV value, which is an important indicator for evaluating the effective blocking of ultraviolet radiation by the lens. Its value must be greater than 315nm, generally greater than 350nm and less than 400nm. The UV400 lenses that we often hear in optical shops can effectively block UV radiation. We can do a simple experiment to check the UV radiation protection effect of the lens. Place the printed matter of the anti-counterfeiting mark (such as Renminbi) under the ultraviolet lamp, put the lens in the middle of the two, and observe whether there is purple light on the printed matter.
4. Light transmittance: refers to the ratio of the amount of light projected by the lens to the amount of incident light. The higher the light transmittance, the clearer the lens.
5. Abbe number: It is an inverse proportional index used to express the dispersion ability of transparent materials, and can be used to refer to the lens's ability to distinguish between the visible light of a focusable lens and the color. The value is between 32-60. The higher the Abbe number of the lens, the less distortion.
6. Impact resistance: refers to the mechanical strength of the lens to withstand impact. The impact resistance of resin lenses is stronger than that of glass lenses, and even some resin lenses are not broken.
7. Film firmness: It is an index used to refer to the film layer life of the coated lens. Nowadays, many consumers require lenses to be coated, and various films have different functions, and some lenses even add several kinds of films. The common ones are anti-reflection film, hard film (anti-wear film), and anti-UV film.
Optical properties of spectacle lenses
Spectacle lenses are one of the important components of spectacles, and spectacles must realize what they have The various functions of the aspherical lens are achieved through spectacle lenses. For example, ordinary glasses rely on lenses to correct various refractive errors and presbyopia; protective glasses must use lenses to block wind, light, and safety protection. It can be said that there are no glasses without lenses, but glasses without frames.
Modern spectacle lenses are a group of very complex optical systems, which are a combination of various materials and layers, and have certain characteristics. As one of the important components of the lens, the material of the spectacle lens is not only involved in the corrective function of the lens, but also the basis of the coating treatment of the lens system. The material of the lens is closely related to the coating layer.
The research purpose of spectacles is to make eyes with refractive errors clear by wearing corrective lenses. Therefore, when choosing lens materials, it is necessary to consider the influence of the refractive effect of the lenses. the elements of.