optical filter
Optical filters are waveguide components used in optical networks and in photography. They can be used to filter out individual wavelengths or planes of polarization from a mixture of wavelengths.
Examples of optical filters used in optical networks include dichroic filters and Bragg gratings, arrayed waveguide gratings( AWG), thin film filters, and phase arrays( PHASAR). Optical filters used in photography and optics include interference filters, IR filters and UV filters, primary color filters, complementary color filters, and polarizing filters. In digital photography, people use primary color filters such as the Bayer filter and strip filters the color separation. They block two-thirds of the incident light because, for example, a green filter filters out the primary colorsred and blue, whereas complementary color filters filter out only one- third of the spectral range. Edge filters and graduated filters are used in image processing.
Several filter techniques use thin-film technology with cascaded interference filters through which the respective wavelengths are decoupled. However, cascading increases the insertion losses of such filters when the number of channels is high. Planar filters such as the PHASAR work with doped silicon oxide (SiO), which must be specially structured for the wavelengths. In addition, there are optical color filters for photography. They filter certain wavelengths from the light spectrum to create higher contrast photos or those with fewer reflections. These filters include interference filters, IR filters and UV filters, and polarizing filters. Polarizing filters, UV and IR filters are also used in optics, allowing daylight to pass through and blocking infrared light or UV light or both.
Digital cameraimage sensors create color separation with Bayer filters or strip filters located just in front of the image sensor. And in image processing, edge filters and graduated filters are used to detect jumpy transitions or for continuously adjustable attenuations.