Today give you first introduce several common optical filter in our life, such as vision correction of myopia have minus reflection filter on the mirror, car mirrors with high reflection filter, widely used in the business office projector core components but also brings together a variety of filters, went to the hospital to check body using biochemical detector is one of the core parts of monochromator many are using narrowband filter, digital camera is used in the long wave pass filter, short wave pass filter, all kinds of optical instruments, liquid crystal displays and anti-counterfeiting technology, optical communication, laser technology and so on all is closely connected with the development of filter technology. It can be said that without the development of the filter technology as a foundation, many modern and emerging technologies could not achieve the current achievements, so who can say that optical filters are not important? Not integrated into our lives?

Filter refers to a layer or multiple layers of dielectric film or metal film on the optical element or independent substrate to change the characteristics of light wave transmission. In order to achieve scientific and engineering applications, various kinds of filters are designed and manufactured by using the characteristics of transmission, absorption, scattering, reflection, polarization and phase change of light waves in the transmission of these films. The production of filter technology is a complex engineering technology, involving many technical fields, including vacuum acquisition technology, vacuum measurement technology, computer aided design technology, optical property detection technology, electronic circuit technology, material property detection and preparation technology, etc..

An optical device used to select the desired radiation band. It is divided into two categories: color filters, which are flat glass or gelatin of various colors with a transmission bandwidth of several hundred angstroms. They are often used in broadband photometry or installed in stellar spectrographs to isolate overlapping spectral levels. Its dimensions can be made quite large. Thin film filter is divided into two kinds: thin film absorption filter and thin film interference filter. The former is on a specific material substrate, using chemical etching so that the absorption line is exactly at the desired wavelength.

Generally through the longer wavelength, more used as infrared filters. The latter is to form metal-dielectric-metal films with a certain thickness of high or low refractive index alternately by vacuum coating method on a certain substrate, or all medium films, to form a low grade, multi-stage series solid interferometer. The selection of the material, thickness and series mode of the film is determined by the required central wavelength and transmission bandwidth λ.

At present, it can be used in any wavelength from ultraviolet to infrared, λ is 1 ~ 500 angstroms of various interference filters. The peak transmittance of metal-dielectric membrane filter is not as high as that of all-dielectric membrane, but the problems of sub-peak and side-band are more serious in the latter. There is also a circular or long variable interference filter in the thin film interference filter, which is suitable for space astronomical measurement. In addition, there is a dual-color filter, which is placed at an Angle of 45° with the incident beam, and can decompose the beam into two different colors of light with high and uniform reflection and transmittance, which is suitable for multi-channel multicolor metering. Interference filters generally require vertical incidence, as the incidence Angle increases, to the short-wave direction of movement. This feature can be used to adjust the central wavelength within a certain range.