The bandpass filter is the filter that faces the cut-off band on both sides of the transmission band of the spectral characteristic curve. According to the spectral characteristics, the bandpass filter is roughly divided into two types: broadband filter and narrowband filter. The two types of filters are usually combined. The band-pass filter is prepared by the principle of light wave interference, and the band-pass filter has been widely used in various fields. Band-pass filter is a kind of important optical thin film element. It has been widely used in chemical spectroscopy, laser, astrophysics, optical fiber communication biology and other fields. The spectral curve and wavelength of the band-pass filter prepared by the principle of light wave interference λ The spectral transmission area near 0 is called the passband of the filter. Generally, there are cut-off zones on both sides, and there may be bypass zones around the cut-off zone. Generally, colored glass absorption film or cut-off filter is required to eliminate the bypass zone. Generally, the six kings with a relative half-width of not less than 20% are called broadband filters.
Broadband filters can usually be combined with short and long wave pass filters. Considering the absorption characteristics of the film, some short or long wave pass filters can be used as broadband filters themselves. Even if the exiles mode is on different substrates again, several cut-off filters with different cut-off wavelengths can form a set of broadband filters with different half-width peak wavelengths. In order to eliminate ghost images, the whole film filter must be coated on the same side of the substrate to reduce the temperature. The design method is still to use symmetrical periodic film system. The narrow-band filter in the band-pass filter needs to be synthesized with long-wave pass and short-wave pass filters. The processing process is very difficult because the cut-off wavelength, central wavelength and half-width of the grindstone are difficult to control.
In the practical application of band-pass filters in optical engineering, not all places that need band-pass filters hope that the narrower the passband is, the better. There is also a need for broadband filters. For example, the automatic dimming mask used for welding protection requires the use of a band-pass filter that is transparent to visible light and controlled by infrared depth. Color visible light transparent band with transmittance of visible light transparency center not less than 50%. Among them, narrowband filter can be used in the dense wavelength division multiplexer technology for ultra-narrow optical fiber communication system. The band filter must have good thermal stability and low insertion loss. In addition to the characteristics of small polarization related loss, in order to correctly extract each carrier from a beam of light containing multiple wavelengths at the transmission light terminal, there is no crosstalk. There are also optical comb filters.
Hanzhong Borisun Optics Co., Ltd. specializes in the production of various filters, filter processing, filter manufacturing and research and development. The main products are: narrow band filter, band pass filter, long wave pass filter, short wave pass filter, neutral density filter, splitter, dichroic mirror, infrared cut-off filter, interference filter, reflector, laser protection lens, infrared transparent acrylic plate and various optical film lenses.
