• 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.

• 한국결정성장학회지
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• 제2권1호
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• pp.43-50
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• 1992

인상속도를 변수로 Czochralski법을 이용하여 $ LiNbO_3$결정들을 성장시켰다. 성장된 단결정에 균열, 기포, 셀 구조 등의 결함들이 관찰되었다. 균열들은 인상속도와 냉각속도에 매우 민감하였는데 6~7mm/h의 인상속도와 20^{circ}C/h의 냉각속도가 직경 15mm정도의 결정성장에 적당한 조건임을 알 수 있었다. 소자응용에 필요한 유전적 성질 및 광학적 성질 등을 알아보기 위하여 a축, c축방향에 따라 절삭된 시편을 온도를 변화시켜가며 측정하였다.

• ETRI Journal
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• 제28권6호
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• pp.739-744
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• 2006

In this paper, we report numerically calculated results of testing a temperature-insensitive refractive sensor based on a planar-type long-period waveguide grating (LPWG). The LPWG consists of properly chosen polymer materials with an optimized thermo-optic coefficient for the core layer in a four-layer waveguide structure. The resonant wavelength shift below the spectral resolution of the conventional optical spectrum analyzer is obtained accurately over a temperature change of ${\pm}7.5^{\circ}C$ even without any temperature control. The refractive index sensitivity of the proposed grating scheme is about 0.004 per resonant wavelength shift of 0.1 nm for an optimized thermo-optic coefficient.

• 대한기계학회논문집
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• 제18권4호
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• pp.1064-1071
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• 1994

There are three active radicals which become to the scale of flame diagnostics at the flame front. They are OH, CH and $C_2$ radical. For this, optical measurement system which could monitor simultaneously the luminous waves of three radicals, was constructed. These were analyzed statistically into the cross correlation, coherence and phase. Through such an statistical treatment, combustion characteristics was investigated at the primary zone of gas turbine combustor. The local equivalence ratio was predicted with the ratio of luminuous intensity between CH and $C_2$ radical. This result was matched up to the equivalence ratio calculated from gas composition within 5% error. In general, equivalence ratio was said to be 1.0 at flame front, but it could be increased up to about 1.2 depending on the degree of swirl intensity in case of changing properly the air amount of primary zone.

• 한국정밀공학회지
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• 제30권12호
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• pp.1273-1279
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• 2013

We propose a dual grating alignment technique for roll-to-roll positioning which allows achieving nanometer scale alignment by using micro-size marks. The high precision alignment system were designed and manufactured. It was confirmed that the optical system was properly adjusted and fully aligned with the dual gratings. The experiment and computer simulation results were presented. Alignment accuracy below 50 nm was achieved.

• 천문학논총
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• 제19권1호
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• pp.47-54
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• 2004

We present the detailed description on the fiber techniques adopted in the BOES: the design concepts and manufacturing of the v grooves, the procedures of the fiber polishing, adhering of the fibers to the v grooves, and the axis alignment of the fiber input and exit. The high efficiency and throughput of the BOES imply that the adopted fiber arts and the other optical components were well designed and properly treated. We learned that the relatively low efficiency of the 80 micron fiber comparing with the 200 and 300 micron fibers comes from the seeing and the guiding effects not from the poor fiber handling.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 1995년도 춘계학술대회 논문집
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• pp.40-62
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• 1995

A micro positioning system using piezoelectric actuators have very wide application region such as ultra-precision machine tool optical device measurement system. In order to keep a high precision displacement resolution it to useful to take a position sensor and feedback of the error. From the practical point of view high-resolution displacement sensor systems are very expensive and it is difficult to make such a sensitive sensor work properly in a poor operational environment of industry. In this study a piezo-electric micro-depth control system which does not require position sensor but piezoelectric voltage feedback has been developed. It is driven by hysteresis-considering reference input voltage calculated in advance and actuator/sensor characteristics of piezoelectric materials. From the result of experiments a fast and stable response of micro-depth control system has been achieved and an efficient technique to control the piezoelectric actuator suggested.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1996년도 추계학술대회 논문집
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• pp.195-198
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• 1996

In conducting systems based on LB films, TCNQ derivatives have been extensively studied as electron acceptor molecules. We have investigated the optical, electrical, and magnetic properties of Viologen-(TCNQ￣)$_2$LB films. In UV/visible absorption measurements, we have observed TCNQ￣ peak at 380 nm and dimer peak at 620 nm. The electron spin resonance measurements infer that Viologen-(TCNQ￣)$_2$LB film exhibits anisotropic properly. In other words, the LB film shows angular dependence. Iodine doping affects the degree of charge transfer and the conductivity of the films. The UV/visible absorption spectra of the LB film doped with I$_2$show peaks at near 400~430 nm and there is no dimer absorption peak. The in-plane electrical conductivity of the undoped film is approximately 4.2$\times$10$^{-6}$ S/cm.

• 대한전자공학회논문지
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• 제24권3호
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• pp.510-516
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• 1987

An analysis and numerical computations relating to the coupling of optical modes between two neighboring waveguides are discussed. The waveguides are fabricated with Lithium Niobate as guide 1 and Vanadium Oxide as guide 2. In a wave guide system that incorporates two lossless guides, a complete transfer of power from one guide to another can occur when the waveguides are (1) identical or (2) the modes in each guide have identical phase constants. Here we discuss the coupling effects when the guides are dissimilar with respect to both geometry and losses. In thers results, we show that power transfer can occur between the two guides, one lossy and the other lossless, provided the phase matched condition is satisfied. When properly coupled, the power attenuation varies according to the amount of coupling.

• 한국광학회지
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• 제3권4호
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• pp.266-272
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• 1992

화염내부의 온도분포를 측정하기 위하여 코헤런트 라만분광 기술을 연구하였다. 측정의 공간분해능을 높이기 위하여 상자형 위상정합 방법을 사용하여 CARS 신호를 측정하였다. 측정된 CARS신호를 이용하여 화염의 온도를 계산하는 프로그램을 연구하였다. 섭동이론을 이용하여 에너지 간격법칙으로 기술되는 질소 분자의 라만 Q-가지 분광선의 선폭확대 효과를 온도계산 프로그램에 삽입하였다. 에너지 간격법칙을 이용하여 계산된 화염내부의 온도 분포가 열전대로 측정된 오도와 계산에 의해 구해진 단열 화염 온도와 적절히 일치함을 확인하였다.