How to measure the Mueller matrix of liquid-crystal cells
TL;DR: In this paper, a Mueller-matrix spectrometer was constructed to perform fast, dynamic measurements of the Mueller matrix of small areas of liquid-crystal cells throughout the visible range, which can be used for comparison with theoretical calculations, the determination of material parameters and modelling of the cell as an optical building block for technological use.
Abstract: The Mueller matrix is the transfer matrix in the Stokes algebra that describes the polarization of natural light. This matrix is very versatile for the task of characterizing the optical properties of liquid-crystal cells, since it can be used for comparison with theoretical calculations, the determination of material parameters and the modelling of the cell as an optical building block for technological use. We have constructed a Mueller-matrix spectrometer, with the ability to perform fast, dynamic measurements of the Mueller matrix of small areas of liquid-crystal cells throughout the visible range. To illustrate the potential of the instrument, dynamic measurements on a ferroelectric-liquid-crystal cell are presented and analysed. The optical measurements indicate that there is an asymmetry between the up and the down state, tilted smectic layers and polarization reversal initiated at the boundaries.
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TL;DR: An objective analysis is carried out of the matricial models representing the polarimetric properties of light and material media leading to the identification and definition of their corresponding physical quantities, using the concept of the coherency matrix, which constitutes a powerful tool for analyzing and exploiting experimental and industrial polarimetry.
Abstract: An objective analysis is carried out of the matricial models representing the polarimetric properties of light and material media leading to the identification and definition of their corresponding physical quantities, using the concept of the coherency matrix. For light, cases of homogeneous and inhomogeneous wavefront are analyzed, and a model for 3D polarimetric purity is constructed. For linear passive material media, a general model is developed on the basis that any physically realizable linear transformation of Stokes vectors is equivalent to an ensemble average of passive, deterministic nondepolarizing transformations. Through this framework, the relevant physical quantities, including indices of polarimetric purity, are identified and decoupled. Some decompositions of the whole system into a set of well-defined components are considered, as well as techniques for isolating the unknown components by means of new procedures for subtracting coherency matrices. These results and methods constitute a powerful tool for analyzing and exploiting experimental and industrial polarimetry. Some particular application examples are indicated.
239 citations
TL;DR: These signals are shown not to have a chiroptical origin but rather result from the interactions of linear anisotropies in polycrystalline bodies, which are comprehensible crystal-optical effects that serve to define mesoscale structure.
59 citations
TL;DR: This work proposes a simple method, based on the crystal rotation technique and heterodyne interferometry, to simultaneously determine the pretilt angle and cell gap of nematic liquid crystal cells, characterized by the advantages of simplicity of installation, ease of operation, high stability, high accuracy, and high resolution.
Abstract: This work proposes a simple method, based on the crystal rotation technique and heterodyne interferometry, to simultaneously determine the pretilt angle and cell gap of nematic liquid crystal cells. When heterodyne light passes through a nematic liquid crystal cell, the phase retardation given by the characteristic parameters of the cell can be measured accurately by heterodyne interferometry. This phase retardation relates to the pretilt angle, cell gap, and angle of incidence on the cell. By using the measured phase retardations at two incident angles, the pretilt angle and cell gap of the nematic liquid crystal cell can be estimated by numerical analysis. This method is feasible, requiring only two incident angles and prior knowledge of two characteristic parameters—extraordinary and ordinary refractive indices of the liquid crystal. It is characterized by the advantages of simplicity of installation, ease of operation, high stability, high accuracy, and high resolution.
30 citations
Patent•
09 Jun 2006
TL;DR: In this paper, a model of the polarization properties of an LCD cell is developed based on estimations of what the physical parameters of the LCD cell (30) are believed to be.
Abstract: Method and apparatus for testing of LCD panels is disclosed. An LCD panel under lest (30) may be mounted to a translatable table (40) between polarization state generator (10) and polarization state analyzer (16). For each location on cell (30) to be tested, a variety of known polarization states (22) are launched through the LCD cell (30) and detected by the polarization state analyzer (16). Electrical signals representative of polarization states are acquired by a computer. Within the computer, a model of polarization properties of the LCD cell (30) is developed based on estimations of what the physical parameters of the LCD cell (30) are believed to be. RMS differences between simulated polarization properties and measured polarization properties are minimized by iteratively refining the modeled physical cell properties, at which point cell thickness and other physical parameters of the LCD cell may be deduced.
30 citations
TL;DR: An experimental snapshot Mueller matrix polarimeter based on wavelength polarization coding is used to get a time-resolved description of electric-field-induced fast transition within a ferroelectric liquid-crystal cell.
Abstract: An experimental snapshot Mueller matrix polarimeter based on wavelength polarization coding is used to get a time-resolved description of electric-field-induced fast transition within a ferroelectric liquid-crystal cell. The parameters extracted from experimental Mueller matrices are linked to the molecule director distribution to further determine the average trajectory and the collective behavior of these molecules while they switch over to another state.
26 citations
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TL;DR: The surface-stabilized ferroelectric liquid crystal (SSFLC) as mentioned in this paper has been used in a variety of applications in the last few years, such as large and flat screen high definition television (HDTV).
Abstract: The discovery of ferroelectric liquid crystals (1974) together with the subsequent discovery of the surface-stabilized liquid crystals (1980) have enriched the family of ferroelectrics with a new, different and powerful member. At the same time it has considerably raised the performance level of liquid crystals as general electro-optic media and opened up new opportunities in domains where fast processing is necessary, for instance in optical computing. The last few years have seen an important development in the technology of surface-stabilized ferroelectric liquid crystal (SSFLC) devices, which today offers solutions for full dynamic grey scale, full color, high speed, high resolution and high information processing and storage. An example of a very demanding industrial application now attracting the SSFLC approach and where the full range of the SSFLC potential will be required, is the large and flat screen high definition television (HDTV). In this paper we review some key events in the resea...
61 citations
"How to measure the Mueller matrix o..." refers methods in this paper
...We could also rule out the chevron SSFLC cell configuration proposed by Lagerwall et al [12], which displays a strong splaying of the polarization, implying a twist of the principal optical axes....
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TL;DR: In this article, a broadband response that is almost independent of the wavelength can be obtained by using one or two static birefringent elements in conjunction with an FLC cell, and the influence of material characteristics on the results obtained with the two designs is discussed.
Abstract: While a single ferroelectric liquid-crystal (FLC) cell with a retardation of half a wave can be used as a switchable polarization rotator with monochromatic light, the variation of its retardation with wavelength results in a significant deterioration in its performance with white light. We show how a broadband response that is almost independent of the wavelength can be obtained by using one or two static birefringent elements in conjunction with an FLC cell. The influence of material characteristics on the results obtained with the two designs is discussed.
15 citations
"How to measure the Mueller matrix o..." refers background in this paper
...Two or three such plates can be combined in such a way that the combination is less wavelength-dependent than are the individual elements [8, 9]....
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