Characteristics of bandpass filters:By using optical evaporation coating to allow specific light waves to pass through, unwanted background light sources and light wave noise in applications can be eliminated, and the signal-to-noise ratio can be improved.

According to the working wavelength, it can be divided into:UV bandpass filter, visible bandpass filter, infrared bandpass filter.

Bandpass filters are mainly used in anti-counterfeiting recognition, fluorescence microscopes, laser radar modules, night vision devices, industrial cameras, laser ranging, barcode scanning, facial recognition, fingerprint recognition, human-computer interaction devices, medical equipment, and so on.

Spectral description of bandpass filter

λa，λb——The wavelengths on both sides corresponding to half of the maximum transmittance

CWL——Center wavelength, also known as peak wavelength

Tmax——Center wavelength transmittance, or peak transmittance

FWHM——Transmittance is the wavelength width that is half the peak transmittance, i.e. bandwidth

Cut off band——Acceptable minimum unwanted wavelength range

Deadline rate（OD）——OD=log-10（1/Maximum transmittance corresponding to the cut-off range）