Optical filters are inseparable from our lives. Today, the editor of Gengxu Optoelectronics will take a look at the optical filters that exist in life and where are they all? For example, there are anti-reflection filters on myopia for correcting vision, high reflection filters on car mirrors, and the core components of projectors that are widely used in business offices integrate a variety of filters. Go to the hospital for physical examination. Many of the monochromators, one of the core components of biochemical detectors, use narrow-band filters. Digital cameras use long-pass filters, short-pass filters, various optical instruments, liquid crystal displays, anti-counterfeiting technology, optical communications, laser technology, etc., are inseparable from the development of filter technology. It can be said that without the development of filter technology as a basis, many modern and modern emerging technologies are difficult to achieve current achievements.

Optical filter refers to coating one or more layers of dielectric film or metal film on optical elements or independent substrates to change the characteristics of light wave transmission. Utilize the characteristic change phenomena of light waves in the transmission of these films, such as transmission, absorption, scattering, reflection, polarization, phase change, etc., and then design and manufacture various filter products to achieve scientific and engineering application purposes. Manufacturing filter technology is a complex engineering technology, involving many professional technical fields, including vacuum acquisition technology, vacuum measurement technology, computer-aided design technology, optical characteristic testing technology, electronic circuit technology, material characteristic testing and preparation Technology etc.

is used to select the optical device of the required radiation band. Divided into two categories: color filters, which are flat glass or gelatin films of various colors with a transmission bandwidth of hundreds of angstroms. They are mostly used in broadband photometry or installed in stellar spectrographs to isolate overlapping spectral orders. Its main feature is that the size can be made quite large. Thin film filters are divided into thin film absorption filters and thin film interference filters. The former is based on a specific material, using chemical etching to make the absorption line exactly at the desired wavelength.

Generally, the transmitted wavelength is longer, and it is mostly used as an infrared filter. The latter is to alternately form metal-medium-metal films with a certain thickness of high refractive index or low refractive index or all dielectric films on a certain substrate by vacuum coating to form a low-order, multi-stage series-connected solid Interferometer. The choice of film material, thickness and series connection mode is determined by the required center wavelength and transmission bandwidth λ.

Various interference filters with any wavelength from ultraviolet to infrared and λ ranging from 1 to 500 angstroms are currently available. The peak transmittance of the metal-dielectric film filter is not as high as that of the full-dielectric film, but the second peak and sideband problems of the latter are more serious. 

There is also a circular or long strip variable interference filter in the thin film interference filter, which is suitable for space astronomical measurement. In addition, there is a two-color filter, which is placed at an angle of 45° to the incident beam, and can split the beam into two different colors of light with directions perpendicular to each other with high and uniform reflection and transmittance. It is suitable for multi-channel and multi-channel light. Color metering. Interference filters generally require vertical incidence, and when the angle of incidence increases, they move in the direction of shortwaves. This feature can be used to align the center wavelength within a certain range.