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• Liquid_crystal_tunable_filter abstract "Liquid crystal tunable filters (LCTFs) are optical filters that use electronically controlled liquid crystal (LC) elements to transmit a selectable wavelength of light and exclude others. Often, the basic working principle is based on the Lyot filter but many other designs can be used. The main difference with the original Lyot filter is that the fixed wave plates are replaced by switchable liquid crystal wave plates. LCTFs are known for very high image quality and relatively easy integration with regard to optical system design and software control but relatively low peak transmission values due to the use of multiple polarizing elements. This can be mitigated in some instances by using wider bandpass designs, since a wider bandpass results in more light traveling through the filter. Some LCTFs are designed to tune to a limited number of fixed wavelengths such as the red, green, and blue (RGB) colors while others can be tuned in small increments over a wide range of wavelengths such as the visible or near-infrared spectrum from 400 to the current limit of 2450 nm. The tuning speed of LCTFs varies by manufacturer and design, but is generally several tens of milliseconds, mainly determined by the switching speed of the liquid crystal devices. Higher temperatures can decrease the transition time for the molecules of the liquid crystal material to align themselves and for the filter to tune to a particular wavelength. Lower temperatures increase the viscosity of the liquid crystal material and increase the tuning time of the filter.LCTFs are often used in multispectral imaging or hyperspectral imaging systems because of their high image quality and rapid tuning over a broad spectral range. Multiple LCTFs can be used in optical designs when the required wavelength range exceeds the capabilities of a single filter, such as in astronomy applications.Another type of solid-state tunable filter is the Acousto Optic Tunable Filter (AOTF), based on the principles of the acousto-optic modulator. In comparison to LCTFs, AOTFs enjoy a much faster tuning speed (microseconds versus milliseconds) and broader wavelength ranges. However, since they rely on the acousto-optic effect of sound waves to diffract and shift the frequency of light, imaging quality is comparatively poor, and the optical design requirements are more stringent. Indeed, LCTFs are capable of diffraction-limited imaging onto high-resolution imaging sensors. AOTFs have smaller apertures and have narrower angle-of-acceptance specifications compared with LCTFs which can have working aperture sizes exceeding 22 mm and can be placed into positions where light rays travel through the filter at angles up to 15 degrees from the normal.LCTFs have been utilized for space and airborne imaging. Their light weight and low power requirements make them good candidates for remote-sensing applications. They can be found integrated into compact but high-performance scientific digital imaging cameras as well as industrial- and military-grade instruments (multispectral and high-resolution color imaging systems). LCTFs can have a long lifespan, usually many years. Environmental factors that can ‘age’ filters are extended exposure to high heat and humidity, thermal and/or mechanical shock (most, but not all, LCTFs utilize glass as the principal base material), and long-term exposure to high photonic energy such as ultraviolet light which can photobleach some of the materials used to construct the filters.Recent advances in miniaturized electronic driver circuitry have reduced the size requirement of LCTF enclosures without sacrificing large working aperture sizes. In addition, new materials have allowed the effective wavelength range to be extended to 2450 nm.".
• Liquid_crystal_tunable_filter thumbnail LCTF_New_and_Old_VariSpec.jpg?width=300.
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• Liquid_crystal_tunable_filter hasPhotoCollection Liquid_crystal_tunable_filter.
• Liquid_crystal_tunable_filter subject Category:Liquid_crystals.
• Liquid_crystal_tunable_filter subject Category:Optical_filters.
• Liquid_crystal_tunable_filter type Artifact100021939.
• Liquid_crystal_tunable_filter type Device103183080.
• Liquid_crystal_tunable_filter type Filter103339643.
• Liquid_crystal_tunable_filter type Instrumentality103575240.
• Liquid_crystal_tunable_filter type Object100002684.
• Liquid_crystal_tunable_filter type OpticalFilters.
• Liquid_crystal_tunable_filter type PhysicalEntity100001930.
• Liquid_crystal_tunable_filter type Whole100003553.
• Liquid_crystal_tunable_filter comment "Liquid crystal tunable filters (LCTFs) are optical filters that use electronically controlled liquid crystal (LC) elements to transmit a selectable wavelength of light and exclude others. Often, the basic working principle is based on the Lyot filter but many other designs can be used. The main difference with the original Lyot filter is that the fixed wave plates are replaced by switchable liquid crystal wave plates.".
• Liquid_crystal_tunable_filter label "Liquid crystal tunable filter".
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• Liquid_crystal_tunable_filter sameAs Q6557432.
• Liquid_crystal_tunable_filter sameAs Q6557432.
• Liquid_crystal_tunable_filter sameAs Liquid_crystal_tunable_filter.
• Liquid_crystal_tunable_filter wasDerivedFrom Liquid_crystal_tunable_filter?oldid=569276088.
• Liquid_crystal_tunable_filter depiction LCTF_New_and_Old_VariSpec.jpg.
• Liquid_crystal_tunable_filter isPrimaryTopicOf Liquid_crystal_tunable_filter.