• Title/Summary/Keyword: Image-crystal

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Characteristics of Optical Phase Conjugate Wave Generated by Self-Pumping in Photorefractive $BaTiO_3$ Single Crystal ($BaTiO_3$ 광굴절 결정에서 자기 펌핑에 의해 발생되는 위상공액파의 특성)

  • 이장두
    • Proceedings of the Optical Society of Korea Conference
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    • 1990.02a
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    • pp.157-161
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    • 1990
  • Self-pumped phase conjugation(SPPC) in BaTiO3 single crystal is experimentally investigated at a wavelength of 514.5nm from an Ar+ laser. The incident Gaussian beam enters the crystal as an extraordinary ray. The maximum SPPC reflectivity of 48% is obtained at incident angle 80 degree. the SPPC wave demonstrates good image reconstruction. The response time (r) of SPPC wave as a function of incident intensity is measured to be r=36$\times$I-0.79sec.

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Viewing angle controllable liquid crystal display using fringe-field switching mode with high aperture ratio characteristic (고투과율 특성을 갖는 FFS 모드의 시야각 스위칭)

  • Kim, Jin-Ho;Her, Jung-Hwa;Chin, Mi-Hyung;Lim, Young-Jin;Jin, Hyun-Suk;Kim, Byeong-Koo;Lee, Seung-Hee
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2009.06a
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    • pp.32-33
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    • 2009
  • We propose viewing angle switchable liquid crystal display(LCD) associated with fringe-field switching (FFS) mode with high aperture ratio characteristic. This device is composed of R(red), G(green), B(blue), pixel and W(white) pixel in which R,G,B pixel shows image and white pixel for both viewing angle control and image. Conventional viewing angle controllable liquid crystal display has not transmittance because the liquid crystal only tilts up without rotates in viewing angle control region. In this paper, we suggested that the device has high transmittance characteristic because the LC directors are rotated in which viewing angle control region are generated fringe electric field.

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Antiferroelectric Liquid Crystal Display with High Image Quality

  • Chang, Young-Joo;Yu, Jeong-Seon;Yoo, Jeong-Geun;Jeong, Dong-Jin;Park, Sung-Chon;Chae, Su-Yong;Yang, Hong-Geun
    • Journal of Information Display
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    • v.3 no.4
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    • pp.1-3
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    • 2002
  • The antiferroelectric liquid crystal display (AFLCD) is a unique display that can at demonstrate a moving image perfectly the passive matrix driving scheme. We optimised driving the waveform and introduced a dual-driving method. Also, by improving this driving method and using line inversion method, we realize the AFLC display of high image quality with $160(RGB){\times}240$, 32768 colors, crosstalk free and flicker free contrast ratio is greater than 60:1, and the brightness is above 200 $cd/m^2$.

An Experimental Investigation of Unsteady Mixed Convection in a Horizontal Channel with Cavity Using Thermo-Sensitive Liquid Crystals

  • Bae, Dae-Seok;Cai, Long-Ji;Kim, Eun-Pil
    • Journal of Advanced Marine Engineering and Technology
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    • v.33 no.7
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    • pp.987-993
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    • 2009
  • An experimental study is performed to investigate unsteady mixed convection in a horizontal channel with a heat source. Particle image velocimetry (PIV) with thermo-sensitive liquid crystal (TLC) tracers is used for visualization and analysis. This method allows simultaneous measurement of velocity and temperature fields at a given instant of time. Quantitative data of the temperature and velocity are obtained by applying the color-image processing to a visualized image, and neural network is applied to the color-to-temperature calibration. It is found that the periodic flow of mixed convection in a cavity appears at very low Reynolds numbers (Re<0.4), and the period decreases with increasing Reynolds numbers and increases with increasing aspect ratio.

Antiferroelectric Liquid Crystal Display with High Image Quality

  • Yu, Jeong-Seon;Chang, Young-Joo;Yoo, Jeong-Geun;Jeong, Dong-Jin;Park, Sung-Chon;Chae, Su-Yong;Yang, Hong-Geun
    • 한국정보디스플레이학회:학술대회논문집
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    • 2002.08a
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    • pp.545-547
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    • 2002
  • The antiferroelectric liquid crystal display (AFLCD) is unique display that can show the perfect moving image using the passive matrix driving scheme. We optimized the driving waveform and introduced the dual driving method. Also, by improving this driving method and using line inversion method, we realized AFLC display with high image quality, which has 160(RGB)${\times}$240, 32768colors, crosstalk free and flicker free. The contrast ratio is greater than 60:1, and the brightness is above 200cd/$m^2$.

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Precise System Models using Crystal Penetration Error Compensation for Iterative Image Reconstruction of Preclinical Quad-Head PET

  • Lee, Sooyoung;Bae, Seungbin;Lee, Hakjae;Kim, Kwangdon;Lee, Kisung;Kim, Kyeong-Min;Bae, Jaekeon
    • Journal of the Korean Physical Society
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    • v.73 no.11
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    • pp.1764-1773
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    • 2018
  • A-PET is a quad-head PET scanner developed for use in small-animal imaging. The dimensions of its volumetric field of view (FOV) are $46.1{\times}46.1{\times}46.1mm^3$ and the gap between the detector modules has been minimized in order to provide a highly sensitive system. However, such a small FOV together with the quad-head geometry causes image quality degradation. The main factor related to image degradation for the quad-head PET is the mispositioning of events caused by the penetration effect in the detector. In this paper, we propose a precise method for modelling the system at the high spatial resolution of the A-PET using a LOR (line of response) based ML-EM (maximum likelihood expectation maximization) that allows for penetration effects. The proposed system model provides the detection probability of every possible ray-path via crystal sampling methods. For the ray-path sampling, the sub-LORs are defined by connecting the sampling points of the crystal pair. We incorporate the detection probability of each sub-LOR into the model by calculating the penetration effect. For comparison, we used a standard LOR-based model and a Monte Carlo-based modeling approach, and evaluated the reconstructed images using both the National Electrical Manufacturers Association NU 4-2008 standards and the Geant4 Application for Tomographic Emission simulation toolkit (GATE). An average full width at half maximum (FWHM) at different locations of 1.77 mm and 1.79 mm are obtained using the proposed system model and standard LOR system model, which does not include penetration effects, respectively. The standard deviation of the uniform region in the NEMA image quality phantom is 2.14% for the proposed method and 14.3% for the LOR system model, indicating that the proposed model out-performs the standard LOR-based model.

Optical Simulation of Viewing Angle Property of Biaxial Nematic Bent-Core Liquid Crystal

  • Yang, Seungbin;Lee, Ji-Hoon
    • Journal of the Optical Society of Korea
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    • v.20 no.4
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    • pp.510-514
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    • 2016
  • The conventional liquid crystal displays (LCDs) have been using optically uniaxial liquid crystal (LC) medium and this often causes a significant image change at oblique viewing angles. We simulated the viewing angle properties of the biaxial nematic (Nb) phase of a bent-core liquid crystal (BLC) and compared the results with the vertically aligned (VA)- and the in-plane switching (IPS)-LCDs. The Nb phase of the BLC showed a smaller transmittance at the dark state as well as a greater contrast ratio at wide viewing angle. The viewing angle property of the Nb-mode without any compensation film was slightly superior to the IPS-mode with the compensation films eliminating the decross of the polarizers at oblique viewing angle.

Optical Properties of Ga2O3 Single Crystal by Floating Zone Method (부유대역법을 이용한 단결정Ga2O3의 광학적 특성)

  • Gim, JinGi;Kim, Jongsu;Kim, Gwangchul
    • Journal of the Semiconductor & Display Technology
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    • v.20 no.4
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    • pp.78-82
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    • 2021
  • The Ga2O3 single crystal was grown through a floating zone method, and its structural and optical properties were instigated. It has a monoclinic crystal structure with a (100) crystal orientation and an optical band gap energy of 4.6 eV. It showed an average transmittance of 70% in the visible region. At room temperature, its photoluminescent spectrum showed three different peaks: the ultraviolet at 360 nm, the blue-green at 500 nm, and the red peaks at 700 nm. Especially, at liquid nitrogen temperature, the ultraviolet peak was optically active while the others were quenched.

A Study on the Analysis of Temperature Field of Bubbly Flow Using Thermo-sensitive Liquid Crystals (감온액정을 이용한 기포유동의 온도장 해석에 관한 연구)

  • Bae, Dae-Seok
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.27 no.11
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    • pp.1572-1578
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    • 2003
  • Particle Image Thermometry(PIT) with liquid crystal tracers is used for visualizing and analysis of the bubbly flow in a vertical temperature gradient. Quantitative data of the temperature were obtained by applying the color-image processing to a visualized image, and neural-network was applied to the color-to-temperature calibration. This paper describes the method, and presents the transient mixing temperature patterns of the bubbly flow.