The cut-off band of a filter is adjacent to both sides of the transmission band of the spectral characteristic curve, which is called Bandpass filter. Bandpass filters can be roughly divided into broadband filters and narrowband filters according to their spectral characteristics. But there is no clear boundary for this division. The two kinds of filters are usually combined. It applies the principle of light wave interference. Bandpass filters are widely used in various fields.
The spectral transmission area near the wavelength is called the pass band of the filter. Usually, there are cut-off areas on both sides, and there may be bypass bands around the cut-off area, which can be eliminated by the Colored Glass, absorbing films, or cut-off filter.
Bandpass filters can be used in cable TV upgrade equipment, wireless transmission equipment, mobile phone barcode scanning, infrared electronic whiteboard, infrared camera, infrared touch screen, iris recognition, infrared medical equipment, infrared ink recognition, red film recognition, face recognition sensor system , hand-held infrared laser rangefinders, optical instruments, medical and health equipment and testing instruments.
