Liquid crystal tunable filters

EPE Eabry-Perot etalon LCTE liquid crystal tunable filter... 

Parameters FT System Dispersive Liquid Crystal Tunable Filter... 

Tunable filters in the form of AOTF devices, liquid crystal tunable filter (LCTF) and also tunable cavity Fabry-Perot etalon (FPE) devices have been considered in non-moving part instrument designs for many years. Today, the AOTF and the LCTF devices are used in the NIR spectral region.9,10 Originally, designs were also proposed for mid-IR AOTF devices, but these have not become available, mainly because of fabrication issues (cost and material purity). Tunable FPE devices, which are really just variable cavity interference filters, have been developed for the telecommunications industry. While these have been primarily used in the NIR, in most cases they can be fabricated to work also in the mid-IR, the latter being only an issue of material/substrate selection. 

Figure 11.20. Bright-field and Raman image of polystyrene beads 992 cm light was selected with a liquid crystal tunable filter. (Adapted from Reference 2.)...

Tunable single element bandpass filters have also been used as Raman monochromators. The most popular are acousto-optic tunable filters and liquid crystal tunable filters. These filters are electrically tunable and are well suited to Raman imaging. 

Liquid crystal tunable filter (LCTF) spectrometers may be... 

Liquid Crystai Tunabie Fiiters. The liquid crystal tunable filter (LCTF) has had considerable success in the visible region, with limited success in the near infrared. A LCTF element (shown in Fig. 4.1.1 lA) is a stack of retardation plates that becomes polarization sensitive (1,11). Specific regions of the NIR spectrum are determined by the number and thicknesses of the retardation plates (usually crystal quartz plates). 

Scientifle Solutions, Inc. (SSI) 55 Middlesex Street, Unit 210 North Chelmsford, MA 01863-1561 USA TEL 978-251-4554 FAX 978-251-8822 Email info sci-sol.com URL http //www.sci-sol.com/ Liquid crystal tunable filters (LCTF)... 

HR Morris, CC Hoyt, PJ Treado. Imaging spectrometers for fluorescence and Raman microscopy Acousto-optic and liquid crystal tunable filters. Appl Spectrosc 48 857-865, 1994. 

HR Morris, CC Hoyt, P Miller, PJ Treado. Liquid crystal tunable filter Raman chemical imaging. Appl Spectrosc 50 805-811, 1996. 

There are two types of spectrometers using optical filters. The first type is equipped with a number of optical filters transmitting NIR light of different wavelengths, which are used sequentially to transmit spectroscopic data. The other type applies wavelength-tunable Alters such as a liquid crystal tunable filter (LCTF) or a Fabry-Perot interferometer. 

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