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Passive Fibre Optic Devices
Published in Abdul Al-Azzawi, Photonics, 2017
Liquid crystal tunable filters (LCTFs) use electrically controlled liquid crystal elements, which select a specific visible wavelength of light for transmission through the filter. A typical wavelength-selective LCTFs is constructed from a stack of fixed filters that consist of interwoven birefringent crystal/liquid-crystal combinations and linear polarizers. The spectral region transmitted through an LCTF depends upon the choice of polarizers, optical coatings, and the liquid crystal characteristics (nematic, cholesteric, smectic, etc.). In general, visible-wavelength devices of this type usually perform in the range of 400–700 nm. This type of filter is ideal for use with electronic imaging devices, such as CCDs, because it offers excellent imaging quality with a simple optical pathway.
Passive Fibre Optic Devices
Published in Abdul Al-Azzawi, Fibre Optics, 2017
Liquid crystal tunable filters (LCTFs) use electrically controlled liquid crystal elements, which select a specific visible wavelength of light for transmission through the filter. A typical wave-length-selective LCTFs is constructed from a stack of fixed filters that consist of interwoven birefringent crystal/liquid-crystal combinations and linear polarizers. The spectral region transmitted through an LCTF depends upon the choice of polarizers, optical coatings, and the liquid crystal characteristics (nematic, cholesteric, smectic, etc.). In general, visible-wavelength devices of this type usually perform in the range of 400–700 nm. This type of filter is ideal for use with electronic imaging devices, such as CCDs, because it offers excellent imaging quality with a simple optical pathway.
The application of photography in investigating fraud
Published in The Imaging Science Journal, 2019
An optical filter called a liquid crystal tunable filter (LCTF), allows the transmission of either a selected wavelength of light to the exclusion of others, or the transmission of wide spectra from 400 nm to the current limit of 2450 nm. The images are coupled with a hypercube of data: a multidimensional array of data and a set of algorithms; to produce a detailed and accurate set of data and images, which can withstand repeated imaging and ultimately the legal scrutiny of the provenance of that data set.