Optical film technology Interference with light, optical film material

The optical film is formed by plating a specific film quality on an optical element to change the characteristics of light wave transmission and the effect of interference light. The role of optical films in optical systems:

First, improve optical efficiency, reduce stray light, such as mirror coating optical film, improve or reduce the reflection of light. The high-reflection mirror only takes the reflected light to minimize the transmitted light; the anti-reflection mirror reduces the emitted light on the surface of the optical component and improves the transmitted light.

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Second, to achieve beam adjustment or redistribution, such as the application of dichroic mirrors, spectroscopes. The beam splitter has a neutral beam splitter, a two-color beam splitter, a polarizing beam splitter, etc., and the light transmission, reflection, and refraction are changed by the characteristics of the optical film.

Third, through the selective transmission of wavelength to improve the signal-to-noise ratio of the system, such as bandpass filters, cut-off filters. A bandpass filter is a filter with a high transmittance in a certain band and a very low transmittance on both sides. An optical device in which the cut-off filter is opaque in one band and has a high transmittance in another adjacent band.

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The optical film can be deplated by an optical coater, and the plating technique includes a gas film forming method and a liquid film forming method. The gaseous film formation method can be divided into chemical vapor deposition (CPV) and physical gas deposition (PVD); liquid film formation method is chemical or electrochemical.

The so-called film must control the thickness of the film layer. Generally, the film thickness can be monitored by visual inspection (by human eye recognition), quartz crystal monitoring method (detected by quartz crystal oscillator), and optical monitoring method (by analysis of the entire optical system. ).

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Optical film materials: Common optical film materials are chemically divided into oxides, fluorides and alloys. Each of the three materials has advantages and disadvantages. The oxide has the characteristics of high melting point, large specific gravity, high mechanical and high refractive index, and hard texture of the film layer; fluoride has low melting point, small specific gravity, low refractive index, soft film and water The characteristics of the alloy; the alloy has strong reflective and light absorbing properties.