Anti-reflection film application field involves medical military space exploration
In the optical element, light energy is lost due to the reflection of the surface of the element. In order to reduce the reflection loss on the surface of the element, a transparent dielectric film is often plated on the surface of the optical element. This film is called an anti-reflection film. Qualitative analysis can be given to the principle of increasing transmission of antireflection film from the perspective of energy conservation; quantitative explanation can be given to the principle of increasing transmission of antireflection film according to Fresnel formula and refraction law; increase of antireflection film by electrodynamic electromagnetic theory The principle of transmission gives a theoretical explanation.
AR coating for glass and plastic substrates
A significant component of many optical systems is the coating on the lens that reduces reflection. In many applications, AR coatings are indispensable, otherwise they will not meet the requirements of the application.
Taking a 35mm auto-zoom camera consisting of 18 lenses, it is assumed that each glass and air interface has 4% reflection, and the lens that has no antireflection has a light transmittance of 27%, coated with a film ( The remaining light transmittance of the lens was 1.3%, and the multilayer film (the remaining reflection was 0.5%) was 85%.
Do you have any attention in optical coating? When light enters different transfer materials (such as air into the glass), about 5% will be reflected off. There are many lenses and refractors in the optical sight, which together add up to 30% to 40% of incident light. . Modern optical lenses are usually coated with a single or multiple layers of magnesium fluoride anti-reflection film, a single anti-reflection coating reduces reflection by 1.5%, and a multilayer anti-reflection coating reduces reflection to 0.25%, so the entire aiming If the mirror is properly coated, the light transmission rate can reach 95%. Lenses coated with a single antireflection coating are usually blue-violet or red, and those coated with multi-layer antireflection coatings are either pale green or dark purple.
The anti-reflection film increases the intensity of the transmitted light. The optical wave as the electromagnetic wave is in the process of propagation. At the interface of different media, the energy distribution is changed due to the different boundary conditions. For a single-layer film, when the medium on both sides of the anti-reflection film is different, the film thickness is an odd multiple of 1/4 wavelength and the refractive index of the film is n=(n1*n2)^(1/2) (media 1 respectively) The refractive index of 2, the incident light can be transmitted through the medium. Generally, the optical lens is used in air. For an optical glass with a general refractive index of about 1.5, in order to achieve a 100% anti-reflection effect of the single-layer film, n1=1.23, or close to 1.23; Thickness = (2k + 1) times a quarter of a wavelength. Single-layer films are only transparent to electromagnetic waves of a specific wavelength, and in order to achieve anti-reflection in a wider range and more wavelengths, one is realized by using a multi-layered film.
People have a lot of experience in the use of anti-reflection coatings, and found a lot of materials that can be used as anti-reflection coatings. At the same time, they have mastered many advanced coating technologies. Therefore, the application of anti-reflection coatings involves medical, military, space exploration, etc. All walks of life have made significant contributions to the advancement of human science and technology.
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