The anti-reflection principle of the anti-reflection film
Anti-reflection Coating, known as anti-reflection membrane, is called anti-reflection coating in English, or AR membrane for short. The basis of anti-reflection is the wave and interference of light. The principle is: Two light waves with the same amplitude and the same wavelength are superimposed, then the light wave amplitude is enhanced. The two wavelengths and amplitudes are the same, but the superposition of wavelengths with different wave paths (similar to dislocation) cancels each other out. Therefore, the anti-reflection film plated on the surface of the lens uses this principle to make the reflected light generated by the front and rear surfaces of the film layer interfere with each other, thus canceling each other and achieving the effect of reducing reflection.
What color coating is good?
The purpose of plating anti-reflection film is to reduce the reflection of light. But because it is impossible to be completely free of reflected light, there will always be some residual reflection on the surface of the lens that causes the visible color. Someone asks which kind of these residual color is best. It does not have a standard actually. It is mainly based on a personal preference for color. More on the market at present is green color. However, these residual colors can initially help us to judge the thickness of the film: when the film is thin (the thickness is less than 139nm), the reflected light will show light yellow, and when the film is thick (the thickness is more than 139nm), it will show blue-green. The current multi-layer anti-reflection film thickness is about 0.3μm.
Why the lens coating is not uniform?
Sometimes we find differences in the color between the convex and concave surfaces, between the center and the edge of the lens, and the anti-reflection effect between the convex and concave surfaces. his is mainly because the lens coating is that it is plated on one surface and then turned over to another surface. And Areas with small curvature changes are easy to coat. So the center of the lens has reached the desired thickness of the film but the edge has not. At the same time, the different curvature of the convex surface and concave surface causes the different coating speed. So the surface of the lens will show green in the center and lavender red or some other color at the edges.
What material is the lens coating used?
The anti-reflection film material of glass lenses is usually magnesium fluoride. Because the coating process of magnesium fluoride must be carried out at more than 200℃, otherwise it cannot be attached to the surface of the lens. The resin sheet is not used. Since the 1990s, with the development of vacuum coating technology, the combined effect of film and lens has been improved. At the same time, high purity metal oxide materials like titanium oxide and zirconia can be deposited on the surface of the resin sheet through the evaporation process to achieve a good anti-reflection effect.
About the early domestic anti-reflection coating lens
Chinese coated lenses appeared in the mid-1980s. At that time, Europe (such as France and Germany) and Asia (such as Japan, Singapore, and Taiwan) had already launched coated lenses to the market, and the grade of lenses was evaluated based on the quality of the anti-reflection effect. Among them, Germany and France were the two leading countries in technology. Technically, the use of French original film material (referred to as H2) can reduce the effect by 99.98% (refers to the light transmittance, the same below). Almost you can not see the reflection, but the material is expensive. Therefore, the coating lens which is currently used in the world is born. The anti-reflection effect is controlled at about 98%, so the coating cost is greatly reduced. And it is accepted by consumers because it presents various colors, especially green. At the same time, because at the same time, it can be easily distinguished from non-coated lenses. It can reflect the high-grade film lens, and it is accepted by the sales staff.