• 한국조명전기설비학회지:조명전기설비
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• 제5권2호
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• pp.84-95
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• 1991

Mostly, phase control method is used to control the single phase AC power. The phase control method has some advantages such as ease to control and simple configuration. But the retardation of firing angle causes a lagging current even if load is purely resistive. So phase control causes a lagging power factor and a low efficiency at the input side in comparing with the system without switching device. A new PWM control method which can improve these defects for single phase AC power control circuit is proposed in this paper. The performances of the single phase AC power control circuit using the proposed method was investigated theoretically. Both power factor and waveform of load current can be improved better than those of the conventional methods.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2009년도 9th International Meeting on Information Display
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• pp.942-944
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• 2009

Blue phase shows several different reflection colors from the randomly oriented domains and crystal direction. Also there are variations in the size of domains. The domain size is dependent on the temperature gradient. With smaller cooling rate of temperature, the domain size was increased compared with rapid cooling. With injection of light of specific wavelength, we find that the diffraction patterns were occurred around the light spot in the cell of blue phase. It was supposed to be from the matching of the phase retardation and domain size. However, actually the diffraction pattern is reflecting the lattice structure in double twist of the blue phase. The lattice constant from the radius of diffraction patterns shows very similar one from the reflection spectrum, which indicates the internal lattice constant in double twist of the blues phase.

• 한국광학회:학술대회논문집
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• 한국광학회 2008년도 하계학술발표회 논문집
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• pp.453-454
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• 2008

• 한국광학회지
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• 제3권3호
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• pp.155-160
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• 1992

평행한 단색광이 회절격자에 입사하면 회절격자의 뒷쪽 공간의 특정한 위치마다 반복하여 격자선 무늬를 본뜬 그림자가 생기는 지점이 나타난다. 빛의 회절로 인하여 렌즈없이도 격자선의 상이 만들어지는 이 현상은 흥미로울뿐만 아니라 회절격자를 사용한 미소거리의 측정에 응용될 수 있다. 본 연구에서는 간단한 Fraunhofer 근사를 사용해도 이러한 현상을 해석할 수 있음을 보였고 실험을 통하여 예측한 대로 특정한 영역에서 격자선 복제가 일어나는 것을 확인하였다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 하계학술대회 논문집
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• pp.271-272
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• 2009

We fabricated a hybrid aligned film using reactive rod-like mesogen to reduce light leakage of twisted nematic(TN) cell in off-axis of the dark state. We proved that the fabricated compensation film has hybrid alignment by changing phase retardation according to polar angle. In this paper, we confirmed characteristics of compensation film through simulation results and found the matching factor of simulation results and experimental result. In result, the maximum pretilt angle of hybrid compensated film is $19^{\circ}$ which has phase retardation 0.1445.

• 조명전기설비학회논문지
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• 제27권11호
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• pp.1-6
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• 2013

It is introduced the phase error sources of a incoherent hologram in incoherent triangular holography and derived the reconstruction image of point-source including the phase error in the lateral direction. From the reconstruction image of point-source, we analyzed the effect of phase error on the lateral resolution. When the phase retardation errors and azimuth angle error of a wave plate and a polarizer range from 0 to $2{\pi}/15$, the normalized intensities of reconstructed images are down by about 0.1% and 2.3%, respectively.

• 한국광학회지
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• 제4권1호
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• pp.22-27
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• 1993

개구상에서 위상을 변조하였을 때에 국산 쌍안경 대물경계의 OTF에 미치는 영향을 살펴보았다. 설계 data로부터 유한광선추적을 하여 파면수차를 계산하고 수치적으로 시계각 $0^{\circ}$와 에 대하여 OTF를 계산하였다. 위상변조는 개구상에 아눌라 형태로 위한을 $\pi$만큼 지연하는 것이다. 위상형태에 따라서 OTF값이 변화하는 것을 위상변조하지 않은 경우와 비교하였다. 결과적으로 시계각이 $0^{\circ}$일 때는 낮은 값을 보이나 $1.5^{\circ}$일 경우에는 특정한 주파수 영역에서 높은 값을 보여주고 있다. 따라서 적절한 위상변조에 의해 OTF값을 증진할 수가 있다.

• Current Optics and Photonics
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• 제4권2호
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• pp.115-120
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• 2020

A novel method is proposed for controlling the distance of an image plane in Fourier holograms using varifocal electric-field-driven liquid-crystal (ELC) lenses. Phase Fresnel lenses are employed to reduce the thickness and response time of the ELC lenses. The voltages applied to the electrodes of the ELC Fresnel lens are adjusted so that the lens has the same retardation distribution as an ideal lens. The focal length can be controlled by changing the retardation distribution with the applied voltages. Simulations were conducted for the image reconstruction of Fourier holograms with various focal lengths of the ELC Fresnel lenses. The simulation results indicate that the distance of the image plane can be properly controlled with the varifocal ELC Fresnel lens.

• 한국광학회지
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• 제20권5호
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• pp.281-287
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• 2009

편광법을 사용하여 패턴이 있는 LCD 유리기층위에 놓여 있는 러빙된 PI(polyimide)의 광학이방성을 분석하였다. 투과형 편광계를 사용하여 0.4 nm 이하의 극히 작은 위상지연의 크기와 광축의 방향을 정밀하게 측정하였다. 온도에 따르는 광학이방성의 미세변화를 위상지연의 크기 및 광축 방향의 변화곡선으로 나타내고 간단한 광학모델을 사용하여 설명하였다.

• Journal of Information Display
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• 제7권1호
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• pp.7-11
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• 2006

In this paper, we report the fabrication of high quality polymer walls by using a monomer containing fluorine (F-monomer). Polymer walls with no phase retardation were fabricated by using photo-polymerization induced anisotropic phase separation of the mixture composed of liquid crystal (LC) and F-monomer. Thanks to the immiscibility of fluoride, we could form high quality polymer walls with no light leakage. We measured electro-optic characteristics of a twisted-nematic (TN) LC cell whose polymer walls were fabricated by using the F-monomer, and the measurements were compared with that fabricated by using the monomer without fluorine.