Bandpass filters transmit only one wavelength band and block other wavelength bands. The width of this filter is expressed in the wavelength range it allows to pass, and can be any value from much less than angstroms to hundreds of nanometers. This filter can be made by combining an LP filter and an SP filter.

It can be made in many ways. The filter is one of them. Light filters can also be made of gas or solution. Filter is a commonly used filter, which is divided into passband filter and cut-off filter according to spectral characteristics; Spectral analysis is divided into absorption filters and interference filters. It is mainly used as an auxiliary dispersion device, such as a spectral level separator in grating spectrometers, to eliminate low-level spectral overlap. Monochromators use interference filters to separate light in an extremely narrow band range.