The application field of Anti-Reflection coating involves medical military space exploration
In optical components, light energy is lost due to the reflection on the surface of the component. In order to reduce the reflection loss on the surface of the component, a transparent medium film is often coated on the surface of the optical component. This film is called an Anti-Reflection coating. It is possible to increase the transmission of the Anti-Reflection coating from the perspective of energy conservation.
The principle is qualitatively analyzed; according to the Fresnel formula and the law of refraction, the principle of increasing the transmission of the AR coating is given a quantitative explanation; the principle of increasing the transmission of the AR coating is given theoretical explanation using the electromagnetic theory of electrodynamics.
Anti-reflection coating for glass and plastic substrates
In many optical systems, a very important component is the coating that can reduce reflection on the lens. In many application fields, Anti-Reflection coatings are indispensable, otherwise, the application requirements cannot be met.
Take a 35mm auto-zoom camera composed of 18 lenses, assuming that each glass and air interface has 4% reflection, the light transmittance of the lens without Anti-Reflection is 27%, and it is coated with a layer of film ( The light transmittance of the lens is 66% for the remaining reflection (1.3%), and 85% for the multi-layer coating (the remaining reflection is 0.5%).
Is there anything I should pay attention to in optical coating processing? When light enters different transmission materials (such as air enters glass), about 5% will be reflected off. There are many lenses and refractors in the optical sight, and the total can make the incident light loss up to 30% to 40% . Modern optical lenses are usually coated with a single-layer or multiple-layer Anti-Reflection coating of magnesium fluoride. A single-layer Anti-Reflection coating can reduce the reflection to 1.5%, and a multilayer Anti-Reflection coating can reduce the reflection to 0.25%, so the entire aim If the mirror is properly coated, the light penetration rate can reach 95%. Lenses coated with a single-layer anti-reflection coating are usually blue-violet or red, while lenses coated with a multi-layer anti-reflection coating are light green or dark purple.
The essence of the Anti-Reflection coating to increase the intensity of the transmitted light is that during the propagation of the electromagnetic wave, at the interface of different media, the energy distribution is changed due to the different boundary conditions. For a single-layer film, when the media on both sides of the Anti-Reflection coating are 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) (respectively medium 1 , 2 refractive index), so that all incident light can pass through the medium. General optical lenses are used in the air. For optical glass with a general refractive index of about 1.5, in order to achieve a 100% anti-reflection effect of a single-layer film, n1=1.23, or close to 1.23; also an anti-reflection film The thickness = (2k+1) times a quarter wavelength. The single-layer film only provides anti-reflection to the electromagnetic wave of a certain wavelength. In order to realize the anti-reflection in a larger range and more wavelengths, people use multi-layer coating to realize the anti-reflection.
People have a lot of experience in the use of anti-reflection coatings, and have discovered many materials that can be used as anti-reflection coatings. At the same time, they have also mastered many advanced coating technologies. Therefore, the application of anti-reflection coatings involves medicine, military, space exploration, etc. All walks of life have made significant contributions to the advancement of human science and technology.
