• Korean Journal of Optics and Photonics
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• v.14 no.5
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• pp.498-503
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• 2003

We analyze the electro-optic polarization transmission characteristics of liquid crystal cells in the Poincare sphere representation. We determine fundamental conditions on maximizing of brightness and contrast ratio of liquid crystal display devices for polychromatic light by use of retardation films. For optimizing two colors, at least two properly designed retardation films are needed, and for three wavelengths, either it can be approximated to the two-color case or three retardation films are needed.

• Journal of the Optical Society of Korea
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• v.15 no.4
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• pp.345-351
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• 2011

We present a novel approach to the holographic three-dimensional display using a liquid crystal shutter for binocular display applications. One of the difficult problems in implementing a binocular holographic three-dimensional display is the extremely narrow viewing angle. This problem is attributed to the spatial light modulator pixel number which restricts the maximum spatial bandwidth of the spatial light modulator. In our proposed method, a beam splitter and liquid crystal shutter are used to present two holograms of a three-dimensional scene to the corresponding eyes. The combination of holographic display and liquid crystal shutter can overcome the problem of the extremely narrow viewing angle, presenting threedimensional images to both eyes with correct accommodation depth cues.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.10
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• pp.902-908
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• 2002

Homogeneously aligned nematic liquid crystal displays (LCDs) driven by in-plane or fringe field were known to exhibit wide viewing angle and appeared to be black in the off state. However, the existence of spacers inside the cell causes the deformation of the liquid crystal molecules. Such a deformation of the liquid crystal causes light-leakage in the dark state, which lowers contrast ratio of the display. We found that the light-leakage due to deformation of the LC director near the spacer mainly depends on the dielectric anisotropy and the ratio of elastic constants of the LC. In this paper, the mechanism on deformation of the LC near spacer is investigated by optical polarizing microscopy.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.05a
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• pp.150-152
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• 2004

We have studied contrast ratio of a homogeneously aligned nematic liquid crystal (LC) display as a function of the angle between the polarizer axis and LC director. The results show that a cell configuration in which a polarizer axis facing a light source coincides with a short LC axis has a better process margin in terms of high contrast ratio than that of the cell coinciding with a long LC axis.

• Journal of the Korean Society of Visualization
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• v.7 no.1
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• pp.21-28
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• 2009

The study of swirling flow is of technical and scientific interest because it has an internal recirculation field, and its tangential velocity is related to the curvature of streamline. The fluid flow for tubes and elbow of heat exchangers has been studied largely through experiments and numerical methods, but studies about swirling flow have been insufficient. Using the particle image velocimetry(PTV) method, this study found the time averaged velocity distribution with swirl and without swirl along longitude sections and the results appear to be physically reasonable. In addition, streamwise mean velocity distribution was compares with that of other. Furthermore, other experimental investigation was performed to study the characteristics of turbulent water flow in a horizontal circular tube by using liquid crystal. 2D PIV technique is employed for velocity measurement and liquid crystal is used for heat transfer experiments in water. Temperature visualization was made quantitatively by calibrating the colour of the liquid crystal versus temperature using various approaches.

• Korean Journal of Optics and Photonics
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• v.10 no.6
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• pp.494-499
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• 1999

We report on the results of holographic transmission grating that can be controlled by the applied AC electric field. We have fabricated a polymer-dispersed liquid crystal material that composed of multifunctional acrylate monomer blended with the liquid crystal mixture E7. To investigate an electro-optic properties of fabricated HPDLC, diffraction efficienties (DE) are measured as a fuction of applied electric field and density of liquid crystal. Maximum DE of about 70% is obtained about 30 wt% of LC concentration at a zero field. We have also shown that optical image was recorded in the tllm, and then the reconstructive image was switchable with the applied electric fields. ields.

• Journal of the Korean Society of Industry Convergence
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• v.6 no.4
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• pp.373-378
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• 2003

An experimental investigation was performed to study the characteristics of laminar water flow in a horizontal circular tube by using liquid crystal. A simultaneous measurement technique has been employed to measure the temperature field in a two-dimensional cross section of fluid flow. This study found the temperature distribution for Re =900~1,500 along longitudinal sections and the results appear to be physically reasonable. To determine some characteristics of the laminar flow, 2D PIV technique is employed for temperature measurement and liquid crystal is used for heat transfer experiments in water. The experimental rig was manufactured from an acryle tube. The test tube diameter of 25mm, and a length of 1200mm. The used algorithm is the gray level cross-correlation method by using Kimura et al. in 1986.

• 한국정보디스플레이학회:학술대회논문집
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• 2002.08a
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• pp.427-429
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• 2002

In this paper, we investigated dynamic behaviors of liquid crystal director profiles by simulating two different modeling equations based on vectorial and tensorial approaches. By performing 3-dimensional simulation for a unit pixel, we found that the simulation results from the each of modeling equations lead to different motional behaviors of liquid crystal directors around the disclination line. This is due to the fact that the vectorial approach has a physically meaningless sign of liquid crystal director ${\overline{n}}$. Consequently, it is clarified that the tensorial approach gives more realistic behaviors for the rotation of the directors around the disclination line when the voltages were removed since it maintains nematic symmetry that gives an equivalence of ${\overline{n}}$ and its opposite - ${\overline{n}}$.

• Journal of Information Display
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• v.8 no.4
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• pp.1-4
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• 2007

In the present study, we propose Monte Carlo simulation that takes into consideration the interface phenomena between liquid crystal and substrate. We use rigid model molecules of liquid crystal and substrate. Interface is generated using potential field that induces decomposition of molecules. We use hard spherocylinders as model liquid crystal molecules. Substrate is modeled as region composed of shorter spherocylinders. Our results show that there is a case in which nematic order is reinforced in the vicinity of rubbed substrate.

• Journal of the Korean Society of Industry Convergence
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• v.7 no.1
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• pp.19-24
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• 2004

An experimental investigation was performed to study the characteristics of laminar water flow in a horizontal circular tube by using liquid crystal. A simultaneous measurement technique has been employed to measure the velocity field in a two-dimensional cross section of fluid flow. This study found the velocity distributions for Re = 1,594 ~ 2,510 along longitudinal sections and the results appear to be physically reasonable. To determine some characteristics of the laminar flow, 2D PIV technique is employed for velocity measurement by using liquid crystal in water. The experimental rig was manufactured from an acryle tube. The test tube diameter of 25mm, and a length of 1200mm. The used algorithm is the gray level cross-correlation method by using Kimura et al. in 1986.