Types of optical filters and how they work

A custom optical filter is an optical device used to select the desired radiation band and filter out the wavelengths of light that are not needed. Thus, it achieves the filtering processing of light.

Types and the working principle

The working principle of the filter is mainly based on optical phenomena such as light absorption, interference and diffraction.

1.Absorbent filter

Use the light absorption characteristics of a specific material to achieve filtering. When light passes through the filter, the material inside absorbs some wavelengths of light while allowing others to pass through. Filter out other unwanted light by selective absorption, allowing only specific wavelengths of light to pass through.

2. Interference filter

It uses the optical interference effect of multi-layer film to make specific wavelengths of light reflect and refract several times in the film, so as to achieve selective filtering of light.When the light passes by, the light of different wavelengths is reflected and refracted several times between the films, resulting in interference. By precisely controlling the thickness and refractive index of the film, it is possible to make specific wavelengths of light enhance each other during the interference process, and other wavelengths of light cancel each other, so as to achieve a specific band of filtering. This principle makes the interference filter have the characteristics of high transmittance, high blocking degree and wide wavelength range.

3. Diffracted filters

use the diffraction principle of light to work. By marking a specific pattern or structure on the surface of the filter, the light is diffracted when passing, and the selection of a specific wavelength is realized. Such filters typically have extremely high wavelength resolution and flexibility, enabling precise control of light.

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