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The difference between different material lenses and fluorite lens making materials
1. Natural material-crystal lens
The main component of this material is silicon dioxide, which is usually divided into two types: colorless and brown. The material is not easy to wear, and the coefficient of thermal expansion is small. Due to its unique transparency to ultraviolet rays, it is easy to cause visual fatigue when worn. In addition, due to the uneven density of the crystal material, the lens often contains impurities, which is prone to birefringence during use.
Second, glass lens
is the main material for the production of lenses, which can be divided into the following five types:
This kind of lens is also called white support, white film, optical white film, its basic ingredients It is sodium titanium silicate, colorless and transparent, with high clarity, and can absorb ultraviolet rays from optical lenses below 330A. Adding Ceo2 and Tio2 to the white support sheet can prevent ultraviolet rays below 346A, so it is also called UV white sheet. The visible light transmittance is 91-92%, and the refractive index is 1.523.
Commonly known as , the light transmittance is 87%. This kind of lens has a two-color effect, it is light blue under sunlight (so it is also called blue film), light red under incandescent lamp (because it contains metal element neodymium), it can absorb ultraviolet light below 340A, part of infrared light and yellow of 580A Visible light.
Commonly known as kesai film, add Ceo2 and Mno2 to the white support lens material, which can be Improve UV absorption capacity. This kind of optical lens lens is light red under sunlight and incandescent lamp, so it is also called red film. It can absorb ultraviolet rays below 350A, and the light transmittance is above 88%.
Super thin sheet
This kind of lens has Tio2 and Pbo added to the raw material to increase the refractive index to 1.70. Its surface reflectivity is high, which is about 1/3 thinner than ordinary one-diopter white or red films. It is suitable for high myopia wear and has a beautiful appearance. In addition, due to the low Abbe number and large chromatic aberrations, the ultra-thin sheet is likely to cause a decrease in peripheral vision, and colors will appear when the lines are curved.
1.60 glass lens
The refractive index of this kind of lens is 1.60, which is thinner than ordinary glass lens (1.523). The ultra-thin lens (focusing lens 1.70) has a smaller specific gravity, so it is very light and very suitable for moderate wearers. Some manufacturers call it ultra-light ultra-thin lens.
Fluorite is formed from calcium fluoride (CaF2) crystals. Its obvious characteristics are extremely low refractive index and dispersion, and good transmittance to infrared and ultraviolet rays. But there is another point worth paying attention to: it also has bright and delicate description performance that ordinary optical glass can't achieve. Because the focus deviation caused by light passing through a general lens will cause color divergence, which will reduce the sharpness of the captured image, we call it chromatic aberration. Fluorite lens has very little light dispersion and almost no chromatic aberration, so it is the most suitable lens for photography. But in nature, there is almost no fluorite as large as an aspheric lens that can be used in SLR camera lenses, so it can be said that people have long wished to make artificially generated fluorite lenses.
Fluorite lens making material
Fluorite lens making material is fluorite, also known as fluorite , Is a mineral whose main component is calcium fluoride (CaF2), which contains many impurities. Ca is often replaced by rare earth elements such as Y and Ce. In addition, it also contains a small amount of Fe2O3, SiO2 and trace amounts of Cl, O3, He, etc. . Fluorite in nature often shows bright colors, and its hardness is lower than that of a knife. Fluorite is an excellent optical material. Lenses made of fluorite have very excellent optical qualities, especially in terms of anti-dispersion properties, far exceeding all other optical materials.