The Experts below are selected from a list of 13203 Experts worldwide ranked by ideXlab platform
Tae-hoon Yoon - One of the best experts on this subject based on the ideXlab platform.
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Optical Compensation for Elimination of Off-Axis Light Leakage in a Homogeneously-Aligned Liquid Crystal Cell
Molecular Crystals and Liquid Crystals, 2015Co-Authors: Tae-hoon YoonAbstract:We propose an achromatic optical compensation method using uniaxial films to eliminate the off-axis Light Leakage in a homogeneously-aligned liquid crystal cell. In this technique, four uniaxial films with complementary dispersion characteristics are used to compensate for one another, resulting in achromatic effective phase retardation for off-axis angles. The retardation values are optimized with the aid of the Poincare sphere and through numerical research. The contrast ratio of the proposed configuration for white Light is higher than 2400:1 at a polar angle of ±60°, irrespective of the azimuthal angle.
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Elimination of off-axis Light Leakage in a homogeneously aligned liquid crystal cell
Proceedings of SPIE, 2015Co-Authors: Byung Wok Park, Tae-hoon YoonAbstract:Among various liquid crystal display modes, the in-plane switching mode exhibits the widest viewing angle because the liquid crystals are homogeneously-aligned initially and rotate within a plane parallel to the substrates when an in-plane field is applied. However, further improvement is still needed for viewing high-quality dark images from the bisector direction of the crossed polarizers. Several compensation schemes have been proposed to eliminate the off-axis Light Leakage in a homogeneously-aligned liquid crystal cell. Although a 100:1 iso-contrast contour at an wavelength of 550 nm can cover the entire viewing cone, Light Leakage at other wavelengths still remains very severe. In this paper we introduce achromatic optical compensation methods using uniaxial films to eliminate the off-axis Light Leakage at the dark state in homogeneously-aligned liquid crystal cell.Uniaxial films with different dispersion characteristics are used so that they can compensate one another to achieve achromatic optical compensation. The retardation values are optimized through numerical research with the aid of the Poincare sphere.
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optical compensation methods for the elimination of off axis Light Leakage in an in plane switching liquid crystal display
Journal of information display, 2015Co-Authors: Seungwon Oh, Byung Wok Park, Tae-hoon YoonAbstract:Optical compensation to improve the wide-viewing-angle characteristics in a liquid crystal display (LCD) is essential for high-quality dark images, especially from the bisector direction of the crossed polarizers. This paper reviews optical compensation schemes for the elimination of off-axis Light Leakage in an in-plane-switching LCD. A uniaxial film with normal dispersion commonly increases the dark-state Light Leakage, but it can be used in the opposite manner to remove the dark-state Light Leakage at off-axis viewing angles. Using symmetrical rotation of the polarization state on the Poincare sphere, the dark-state Light Leakage over the entire viewing cone for white Light can be effectively eliminated.
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Elimination of Light Leakage over the entire viewing cone in a homogeneously-aligned liquid crystal cell.
Optics Express, 2014Co-Authors: Tae-hoon YoonAbstract:We propose an optical compensation scheme that uses uniaxial films for perfect elimination of Light Leakage over the entire viewing cone in a homogeneously-aligned liquid crystal cell. Uniaxial films with different dispersion characteristics are used so that they can compensate one another to achieve achromatic optical compensation. Owing to the rotational symmetry of the polarization change on the S2–S3 plane of the Poincare sphere, we can eliminate the Light Leakage at all azimuth angles. The contrast ratio of the proposed configuration for white Light is higher than 3000:1 at a polar angle of ± 85°, irrespective of the azimuth angle.
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achromatic optical compensation using dispersion of uniaxial films for elimination of off axis Light Leakage in a liquid crystal cell
Applied Optics, 2013Co-Authors: Seungwon Oh, Byung Wok Park, Tae-hoon YoonAbstract:We propose an achromatic optical-compensation method using uniaxial films to eliminate the off-axis Light Leakage at the dark state in a homogeneously aligned liquid crystal cell. Three uniaxial films with different dispersion characteristics are used so that they can compensate each other to achieve achromatic effective phase retardation at off-axis. The retardation values are optimized with the aid of the Poincare sphere and through numerical research. A contrast ratio of higher than 2000∶1 is predicted over the entire ±60° viewing cone for a homogeneously aligned LC cell with zero pretilt angle.
Shin-tson Wu - One of the best experts on this subject based on the ideXlab platform.
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Compensation Film Designs for High Contrast Wide-View Blue Phase Liquid Crystal Displays
Journal of Display Technology, 2014Co-Authors: Yifan Liu, Qi Hong, Yi-fen Lan, Shin-tson WuAbstract:The polarization rotation effect of blue phase liquid crystal (BPLC) composite causes Light Leakage in the dark state, which in turn degrades the contrast ratio. We propose three approaches to compensate the Light Leakage and thereby improve the contrast ratio and widen the viewing angle of a BPLC display. The merit and drawback of each design are also discussed.
Qi Hong - One of the best experts on this subject based on the ideXlab platform.
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Compensation Film Designs for High Contrast Wide-View Blue Phase Liquid Crystal Displays
Journal of Display Technology, 2014Co-Authors: Yifan Liu, Qi Hong, Yi-fen Lan, Shin-tson WuAbstract:The polarization rotation effect of blue phase liquid crystal (BPLC) composite causes Light Leakage in the dark state, which in turn degrades the contrast ratio. We propose three approaches to compensate the Light Leakage and thereby improve the contrast ratio and widen the viewing angle of a BPLC display. The merit and drawback of each design are also discussed.
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An O-plate compensated in-plane switching liquid crystal display
IEEE\ OSA Journal of Display Technology, 2006Co-Authors: Qi HongAbstract:Pretilt angle effect on the dark-state Light Leakage and viewing angle of in-plane switching (IPS) liquid crystal display is investigated. As the liquid crystal (LC) pretilt angle increases, the Light Leakage becomes more severe and the off-axis Light Leakage from the out-of-plane LC directors cannot be neglected. Introducing an oblique compensation plate (O-plate) reduces the off-axis Light Leakages from the crossed linear polarizers and the anisotropic LC media simultaneously which, in turn, improves the viewing angle of the IPS LCD
Yuka Utsumi - One of the best experts on this subject based on the ideXlab platform.
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Quantitative Analysis Method for Measuring Light Leakage Intensity of Three Primary Color Filters Placed between Crossed Polarizers
Japanese Journal of Applied Physics, 2008Co-Authors: Yuka Utsumi, Ikuo Hiyama, Yasushi Tomioka, Kikuo OnoAbstract:We investigated the Light Leakage properties of three-primary-color filters placed between crossed polarizers. Although Light Leakage is caused by Light scattering due to pigment cohesion in the filter layers of a color filter, the detectability of this intensity is strongly related to the spectral properties of polarizers. We have developed a quantitative analysis method for measuring Light Leakage intensity using the degree of imperfection, derived from the depolarization index. The degree of imperfection is an intrinsic property of the color of the filters.
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11.2: Improved Contrast Ratio in IPS-Pro LCD TV by Using Quantitative Analysis of Depolarized Light Leakage from Component Materials
SID Symposium Digest of Technical Papers, 2008Co-Authors: Yuka Utsumi, Shintaro Takeda, Ikuo Hiyama, Yasushi Tomioka, Masahiro Ishii, Hiroyuki Kagawa, Daisuke Kajita, Toshiki Asakura, Masato Shimura, Kaori MiyazakiAbstract:The degree of imperfection was defined as the independent intrinsic index of the degree of degraded contrast ratio for each component. The scattering index of liquid crystal layer gives an effective guideline for reducing Light Leakage intensity. By using this guideline, we have made an IPS-Pro LCD with a uniform contrast ratio of 1500:1 within ±16.5° of polar angle.
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Light Leakage Behaviors of Homogenously Aligned Liquid Crystal Layers Placed between Crossed Polarizers
Japanese Journal of Applied Physics, 2008Co-Authors: Yuka Utsumi, Shintaro Takeda, Ikuo Hiyama, Yasushi Tomioka, Masahiro Ishii, Kikuo OnoAbstract:We investigated the Light Leakage behaviors homogeneously aligned liquid crystal layers placed between crossed polarizers using a backLight unit with diffused Light to reduce the transmittance in the black state in in-plane liquid crystal displays. The Light Leakage intensity was clearly proportional to a specific variable (Scell) consisting of the ordinary refractive index no, the extraordinary refractive index ne, their difference Δn, the elastic constant K, and the thickness of the liquid crystal layers d. A high elastic constant and a low Δn can result in a low Light Leakage intensity.
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Analysis of Light Leakage Caused by Color Filter between Crossed Polarizers
Japanese Journal of Applied Physics, 2007Co-Authors: Yuka Utsumi, Ikuo Hiyama, Yasushi Tomioka, Katsumi Kondo, Shigeru MatsuyamaAbstract:The Light Leakage caused by color filters between crossed polarizers was analyzed in terms of Light scattering due to pigments inside color filter layers. Localized pigment particles in the color filter layers used in devices were observed with a scanning transmission electron microscope. The direct observation of the scattering Light revealed that the pigment particles cause Rayleigh scattering. We found that the depolarized Light Leakage by color filters between crossed polarizers is governed by Light scattering.
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Depolarized Light scattering from liquid crystals as a factor for black level Light Leakage in liquid-crystal displays
Journal of Applied Physics, 2005Co-Authors: Makoto Yoneya, Yuka Utsumi, Yoshiyuki UmedaAbstract:Depolarized Light scattering due to thermally excited orientational fluctuations of liquid-crystal directors was investigated in the context of the black level Light Leakage in liquid-crystal displays. Particular attention was given on the comparison between homogeneous and homeotropic liquid-crystal alignments which are both used as black states of liquid-crystal displays. The homeotropic alignment was found to have lower Light-scattering intensity and less Light Leakage than the homogeneous alignment in the small scattering angle regions. The dependency of the scattering intensity on the cell gap and the extrapolation length was also evaluated. The cell gap and the extrapolation length were found to have a large influence.
Seung Hee Lee - One of the best experts on this subject based on the ideXlab platform.
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Helical pitch-dependent electro-optics of optically high transparent nano-phase separated liquid crystals.
Optics Express, 2018Co-Authors: Srinivas Pagidi, Yi-hsin Lin, Ramesh Manda, Young Jin Lim, Seong Min Song, Hyesun Yoo, Jong Hoon Woo, Seung Hee LeeAbstract:Feeble Light Leakage in a dark state of conventional optically isotropic liquid crystal (OILC) device has a strong impact on the contrast ratio of a liquid crystal (LC) device. In order to overcome such intrinsic problem, we proposed an OILC in which the LC directors inside droplets are twisted by introducing chirality. The Light Leakage is effectively suppressed by matching the refractive indices between LC and polymer matrix; consequently, we achieved a high contrast ratio, 1:1401. Interestingly, the on-state transmittance is enhanced by ~49% compared to conventional OILC. The response time was also improved and the hysteresis was suppressed to be negligible. The improved electro-optic performances of the proposed OILC device would give diverse applications in upcoming flexible display and various photonic devices.
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Suppressing pretilt angle for enhancing black quality in diagonal viewing angle of homogenously aligned liquid crystal display
Liquid Crystals, 2017Co-Authors: Tae Rim Lee, Seung Hee Lee, Jin Ho Kim, Myung Chul Jun, Hong Koo BaikAbstract:ABSTRACTThe diagonal viewing angle Light Leakage in a black state of in-plane switching (IPS) liquid crystal display (LCD) associated with pretilt angle has been investigated. The mechanical rubbing process with a cloth causes relatively high pretilt angle in the homogenously aligned liquid crystals (LCs) so that the tilted LC director results in increase of a Light Leakage in a black state at diagonal viewing angles. In this study, we theoretically estimated using classical optic theory how the Light Leakage in a black state at diagonal viewing angle is associated with the pretilt angle and also proposed an effective method to reduce the pretilt angle from 1.5° to 0° in rubbed IPS LCD by utilising polymer stabilisation. With this approach, we could successfully acquire a better black quality in all viewing angles as compared with normal IPS LCD.
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Optimisation of alignment materials for minimising residual retardation in in-plane switching liquid crystal display
Liquid Crystals, 2016Co-Authors: Lee Tae Rim, Seung Hee Lee, Jin Ho Kim, Myung Chul Jun, Hong Koo BaikAbstract:ABSTRACTThe Light Leakage in a black state of in-plane switching (IPS) liquid crystal display (LCD) associated with rubbing process has been investigated. The mechanical rubbing process with a cloth caused orientation disorders in the liquid crystal directors and these partial orientation disorders result in residual retardations of the IPS LCD, causing the Light Leakages at the black state. In this study, we theoretically estimated how the Light Leakage is associated with the rubbing uniformity using 2 × 2 Jones matrix equation and also experimentally confirmed how it is associated with structural properties of the alignment layer. The Light Leakage was clearly reduced in the alignment layer with reduced crystallinity and flexibility.
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Study on the Light Leakage mechanism of a blue phase liquid crystal cell with oblique interfaces
Journal of Physics D, 2012Co-Authors: Sukin Yoon, Heon Jeong, Gyu Hyung Yang, Prasenjit Nayek, Seung Hee Lee, Seung Ho Hong, Hyeok Jin Lee, Sung-tae ShinAbstract:The mechanism of Light Leakage in the dark state of a blue phase liquid crystal display cell which has protruded electrodes was investigated. We have performed a hybrid numerical simulation by combining the geometrical optics with the extended Jones matrix method. The Light Leakage in the cell was caused by changes in the polarization state which has been explained by the asymmetric amplitude change of transverse electric and transverse magnetic fields at the oblique interface and the change in an effective angle between crossed polarizers by the Light path refraction. Based on our analysis, Light Leakage can be suppressed by the matching of the refractive indices of adjacent materials to the interface of the protruded electrodes whose surfaces are not parallel to the substrate.
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Reduction of Light Leakage in protruded electrode by refractive index matching between protrusion and blue phase liquid crystal
Photomedicine and Laser Surgery, 2011Co-Authors: Heon Jeong, Sukin Yoon, Gyu Hyung Yang, Prasenjit Nayek, Nam Ho Cho, Seung Hee Lee, Seung Ho Hong, Hyeok Jin Lee, Sung-tae ShinAbstract:We have studied the Light Leakage mechanism of the protruded electrode used for blue phase LCD. According to our study, the Light Leakage can be reduced by identical refractive indices of the protrusion and BPLC.