Color filters, also known as "color filters", are colored transparent sheets that have the functions of absorbing, reflecting and transmitting colored light. Color filters are optical elements that selectively allow light of a certain wavelength to pass through, and are usually made of colored optical or colored chemical films.

Color filters have a simple structure and are widely used. When used, they are installed in front of or behind the lens to adjust the tone and contrast of the scene, so that the tone of the scene captured by the lens is similar to the degree perceived by the human eye. Color filters can also be used to obtain certain specific artistic effects.

Color filters are widely used in photography creation, printing plate making and various scientific and technological photography. Color filters are divided into three primary color filters of red, green and blue and three complementary color filters of yellow, magenta and cyan. In map re-photography, color filters are used to separate and photograph multi-color original images. According to the type, they can be divided into four types: colloid, glass, glass and colloid synthesis, and glass and liquid synthesis. Generally, red, yellow, blue, purple and other colors are used as a set. Commonly used ones include protective filters, compensation filters, color separation filters and interference filters.

Filters are auxiliary components of microscopes. Reasonable selection can improve the image quality. Color filters have the following main functions:

1. Use yellow-green filters with achromatic objectives to correct aberrations.

2. For apochromatic objectives, blue filters can be used; since the wavelength of blue light is shorter than that of yellow-green light, the resolution of the objective can be improved.

3. Reduce the intensity of the light source. In addition to the commonly used yellow-green filters, the new microscope also has one or more gray neutral density filters, which can be used to reduce the intensity of the incident light without changing other characteristics of the incident light. This kind of filter is preferably made of alloy to form an evaporation precipitation film on the glass, and can be made into filters with different light transmittances according to needs, and its transmittance can range from 80% to 0.001%.