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1
Content available remote Design and simulation of single-electrode liquid crystal phased arrays
100%
Bellini B. , Geday M. A. , Bennis N. , Spadło A. , Quintana X. , Otón J. M. , Dąbrowski R.
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tom Vol. 14, No. 4
269-273
EN
Liquid crystal (LC) phased arrays and gratings have been employed in optical switching and routing [1]. These diffractive optic elements are of great interest because they can be scaled up to a large number of elements and their optical properties can be electrically addressed with a low driving voltage. LC phase gratings have been achieved either by periodic addressing of pixels or by using periodically-modified structures. The latter approach leads to less reconfigurable devices but the addressing is simpler. In this paper we focus on optical phased arrays where the phase is varied either continuously or discretely and where the periodicity is induced by electrode configuration. We first describe a possible structure based on a conductive silicon wafer. We argue that this structure can induce either continuously or discretely varying arrays while applying single voltage to the array. In the second part we simulate the behaviour of such arrays. We base the simulation on a LC synthesized at the Military University of Technology, this high-birefringence nematic LC shows in a 4-µm thick cell a linear phase shift range of more than 3600 between 1.2 V and 1.8 V. We calculate the distribution of the LC molecule director and assess the performance of the array with respect to the applied voltage. Finally, the relevance of such technology for switchable phased arrays is discussed.
2
Content available remote Antiferroelectric liquid crystal displays
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Otón J. M. , Quintana X. , Castillo P. L. , Lara A. , Urruchi V. , Bennis N.
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tom Vol. 12, No. 3
263-269
EN
In the last few years, the unique features of antiferroelectric liquid crystals (AFLCs) have been explored to develop high-end displays. A number of passive- and active-matrix prototypes have been presented. However, although their use in a number of application areas has been suggested, no commercial products have been announced yet. This work reviews the state of the art of AFLC displays, the reasons for their present low incidence in display markets, and the latest developments aiming to overcome the main shortcomings that hinder their development. V-shape smectic displays are also included in this study. Although not considered strictly antiferroelectrics nowadays, V-shape materials behaviour and scope are similar to traditional AFLCs.
3
Content available remote Video-rate multiplexed driving scheme for passive antiferroelectric liquid crystal displays
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Quintana X. , Castillo P. L. , Otón J. M. , Bennis N. , Lara A. , Urruchi V. , Dąbrowski R.
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tom Vol. 12, No. 3
291-297
EN
Antiferroelectric liquid crystals have been applied to high-end multiplexed displays. The interest on these materials chiefly comes up from their capability of being multiplex addressed with no need of active matrices. Antiferroelectric grey levels arise from a double symmetric hysteresis loop that can be stabilized by a constant holding voltage. Driving schemes are compatible with passive multiplexing, but limitations appear when the multiplexing rate increases. To avoid these limitations, new driving schemes for high multiplexing level at video rate have been designed. The problem of accumulated voltage on bias level arising from data voltages is tackled as well.
4
Content available remote Lenticular arrays based on liquid crystals
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Urruchi Del Pozo V. , Algorri Genaro J. F. , Sánchez-Pena J. M. , Geday M. A. , Arregui X. Q. , Bennis N.
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2012
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tom Vol. 20, No. 3
260-266
EN
Lenticular array products have experienced a growing interest in the last decade due to the very wide range of applications they can cover. Indeed, this kind of lenses can create different effects on a viewing image such as 3D, flips, zoom, etc. In this sense, lenticular based on liquid crystals (LC) technology is being developed with the aim of tuning the lens profiles simply by controlling the birefringence electrically. In this work, a LC lenticular lens array has been proposed to mimic a GRIN lenticular lens array but adding the capability of tuning their lens profiles. Comb control electrodes have been designed as pattern masks for the ITO on the upper substrate. Suitable high resistivity layers have been chosen to be deposited on the control electrode generating an electric field gradient between teeth of the same electrode. Test measurements have allowed us to demonstrate that values of phase retardations and focal lengths, for an optimal driving waveform, are fairly in agreement. In addition, results of focusing power of tuneable lenses were compared to those of conventional lenses. The behaviour of both kinds of lenses has revealed to be mutually similar for focusing collimated light and for refracting images.
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Content available remote Comparative electrooptic study of new orthoconic liquid crystals with fluorinated alkoxy terminal chains
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Spadło A. , Otón E. , Dąbrowski R. , Żurowska M. , Otón J. M. , Bennis N.
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tom Vol. 18, No. 2
219-222
EN
Electrooptical properties of several new orthoconic antiferroelectric liquid crystal mixtures with partially fluorinated alkoxyalkoxy terminal chains have been investigated in order to select the best mixture for display applications. Electrooptical studies have been performed on these orthoconic materials aiming at evaluating their static and dynamic performance under passive multiplexing conditions. A number of parameters have been evaluated, static and dynamic contrast, driving scheme for passive multiplexing, rise and fall response times, dynamic range, and dynamic greyscale.
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Content available remote Real time phase modulation measurements in liquid crystals
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Bennis N. , Merta I. , Kalbarczyk A. , Maciejewski M. , Marc P. , Spadlo A. , Jaroszewicz L. R.
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tom Vol. 25, No. 2
69--73
EN
We propose real time phase measurements in liquid crystals cells using Young’s interferometer constructed with a new principle with possibility to control the distance between two point sources. The optical interference optical pattern is detected by a bicell photo-detector in a back Fourier focal plane. A phase modulation controlled by a mono pixel liquid crystals’ cell placed in a reference arm of interferometer is observed as a dynamic shift of the fringes’ pattern in spatial domain. Concept of signals’ demodulation in the Fourier focal plane will be described using a new approach to the demodulation signals. In this work we evaluate the demodulation condition of our setup and we present measurements of a dynamic phase response for nematic liquid crystals and antiferroelectric liquid crystals cells.
7
Content available remote Synthesis and properties of high tilted antiferroelectric esters with partially fluorinated alkoxyalkoxy terminal chains
84%
Żurowska M. , Dąbrowski R. , Dziaduszek J. , Czupryński K. , Skrzypek K. , Filipowicz M. , Bennis N. , Otón J. M.
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2008
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tom Vol. 16, No. 3
251-256
EN
Novel chiral esters with partially fluorinated alkoxyalkoxy terminal chains are described. Their phase transition temperatures, enthalpies, and electrooptical properties are reported. A helical pitch in pure compounds and their mixtures based on selective reflection of light is also characterized.
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Content available remote Low threshold voltage asymmetric antiferroelectric liquid crystal cells
84%
Bennis N. , Spadło A. , Dąbrowski R. , Martinelli E. , Galli G. , Quintana X. , Otón J. M. , Geday M. A.
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tom Vol. 14, No. 4
281-285
EN
Asymmetric antiferroelectric liquid crystal displays (AAFLCD) are attractive since they show a very well defined off state and fast switching time. Moreover, they can be driven by a simple biasless DC compensated waveform. The electrooptical response of an AAFLCD allows for new addressing modes, including quasi-static intermediate greyscales maintained without applying a field and passively addressed multiplexed high-frequency displays and spatial light modulators. A new kind of asymmetric cells have been obtained by using fluorinated block copolymer (FBC) alignment, which enhances surface segregation and provides a low energy surface. In this work we combine FBC alignment with antiferroelectric liquid crystal mixtures containing strongly electronegative fluorinated components. Threshold voltages for the antiferroelectric-ferroelectric phase transition as low as 3 volts are observed. We report the time evolution of the shift of the electro-optical response.
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