Filter products are mainly classified by spectral band, spectral characteristics, film material, application characteristics, etc. There are mainly medical equipment filters, beauty equipment filters, photography filters, WeChat projection filters, infrared induction filters, thermometer filters, far-infrared filters, narrow-band filters, AR Filters (Antireflection), etc.

Spectral band: UV filter, visible filter, infrared filter;

Spectral characteristics: bandpass filter, cut-off filter, spectral filter, neutral density filter, reflection filter;

Film material: soft film filter, hard film filter;

The hard-coated filter not only refers to the hardness of the film, but also its laser damage threshold, so it is widely used in laser systems, while the soft-coated filter is mainly used in biochemical analyzers.

Bandpass type: Light in the selected band is passed, and light outside the passband is cut off. Its optical indicators are mainly the central wavelength and half bandwidth. Divided into narrowband and broadband. such as narrowband filters.

Short-pass type (also called low-pass): Light shorter than the selected wavelength passes through, and light longer than the wavelength is cut off. Such as infrared cut filter.

Long-pass type (also called high-pass): Light longer than the selected wavelength passes through, and light shorter than the wavelength is cut off, such as an infrared-transmitting filter.

Filters do a great job. Widely used in the photography world. In the landscape paintings taken by some photographers, why the main scene is always so prominent and how to do it? This uses a filter. For example, if you want to shoot a yellow flower with the camera, the background is blue sky and green leaves. If you shoot as usual, you cannot highlight the theme of "yellow flower", because the image of the yellow flower is not prominent enough. However, if you put a yellow filter in front of the lens to block some of the green light scattered by the green leaves and the blue light scattered by the blue sky, while allowing a large amount of yellow light scattered by the yellow flowers to pass through, the yellow flowers will appear very obvious and stand out. "Yellow Flower" theme.