Optical  filter, also known as "color filter", is a colored transparent sheet that has the function of absorbing, reflecting and transmitting colored light. Color filter is an optical element that selectively allows light of a certain wavelength to pass through, usually made of colored optical or colored chemical film. Color filter has a simple structure and is widely used. When used, it is 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. It can also be used to obtain a certain specific artistic effect.

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

1. Using yellow-green Optical  filter with achromatic objectives can 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 color filters, new microscopes also have 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 type 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%.

In short, Optical  filters are auxiliary components of microscopes, and reasonable selection can improve imaging quality.