Optical coating refers to the process of coating one or more metal thin films on the surface of optical parts by means of vacuum sputtering. The purpose of coating the surface of optical parts is to change the reflection and transmission characteristics of the material surface. Today we will talk about optical coating.
The common method of optical thin film technology is to coat a thin film on a glass substrate by means of vacuum sputtering, which is generally used to control the reflectance and transmittance of the substrate to the incident beam to meet different needs. In order to eliminate the reflection loss on the surface of optical parts and improve the image quality, for various application needs, the use of highly reflective films to manufacture polarized reflective films, color splitting films, cold light films and interference filters, etc.
After the surface of the optical parts is coated, the light is reflected and transmitted multiple times on the coating to form multi-beam interference. By controlling the refractive index and thickness of the coating, different intensity distributions can be obtained. This is the basic principle of interference coating.
The optical film needs to be realized in a high-vacuum coating chamber. Conventional coating processes require raising the substrate temperature (usually about 300°C); while more advanced technologies, such as IAD, can be performed at room temperature. The IAD process not only produces films with better physical properties than conventional coating processes, but also can be applied to substrates made of plastic. Such as glasses lenses.
Common optical coating materials are as follows:
1.Magnesium fluoride
Material characteristics: Colorless tetragonal crystal powder with high purity. The optical coating can be prepared by using it to increase the transmittance without breaking point.
2.Silica
Material characteristics: Colorless and transparent crystal, high melting point, high hardness and good chemical stability. With high purity, high-quality SiO2 coating can be prepared by using it, with good evaporation state and no collapse points. Divided into ultraviolet, infrared and visible light according to the requirements.
3.Zirconia
Material characteristics: White heavy crystalline state, with high refractive index and high temperature resistance, stable chemical properties, high purity, it is used to prepare high-quality zirconia coating without collapse.
The following introduces several widely used optical coating technologies, such as plasma sputtering and evaporation deposition.
Plasma sputtering
Plasma sputtering includes a series of known technologies, including advanced plasma sputtering and magnetron sputtering. The general concept comes from the generation of plasma. The ions in the plasma then accelerate into the source material, collide with loose high-energy ions, and then sputter onto the target optical element. Although each type of plasma sputtering has its unique characteristics, advantages and disadvantages, because they have a common operating concept, these technologies are combined.
Vacuum evaporation
In the vacuum evaporation process, the source material in the vacuum chamber evaporates by heating or electron beam bombardment. During evaporation, the steam condenses onto the optical surface and precisely controls heating, vacuum pressure, substrate positioning and rotation, so that the optical coating of a given design thickness remains uniform. vacuum evaporation can accommodate larger machine sizes and is usually more cost effective than the other techniques.
The main system for vacuum pumping equipment is composed of vacuum acquisition equipment (oil diffusion pump, cryogenic pump, molecular pump), electron beam evaporation, light control, heater control, vacuum control and automatic process control integrated the whole coating machine.
Shanghai EVP Vacuum Technology Co., Ltd. provides vacuum pump equipment in the field of coating has a very good application, can meet your different needs.
FB Turbo Molecular pump, the ultimate vacuum is from 10-6Pa to 10-8Pa, and the capacity is 8m3/h-300m3/h.
For over 25 years, EVP has provided the optical coating with cost-effective vacuum pumps and vacuum systems. Our products require minimal maintenance to keep your processes running smoothly even under the industry’s demanding conditions. We will continue to offer innovative solutions that further improve reliability while increasing your energy efficiency and profitability.
Do you need more reliable performance and energy savings? You need EVP.
EVP Vacuum has extensive experience in the optical coating industry, please feel free to communicate any questions.
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