According to the spectral characteristics of filters, filters can be divided into six categories:
Bandpass filter, cut-off filter, spectroscopic filter, neutral density filter, reflection filter and negative filter (notch filter);
Bandpass type: the light of the selected band passes through and the light outside the passband is cut off. Its optical indexes are mainly center wavelength (CWL) and half bandwidth (FWHM). It is divided into narrowband and broadband. For example, narrow band filter, nbf-808.
Short wave pass type (also known as low wave pass): light shorter than the selected wavelength passes through, and light longer than the wavelength is cut off. For example, infrared cut-off filter, ibg-650.
Long wave pass type (also known as high wave pass): light longer than the selected wavelength passes through, and light shorter than the wavelength is cut off, such as infrared transmission filter, ipg-800.
