• Proceedings of the Optical Society of Korea Conference
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• 한국광학회 2001년도 제12회 정기총회 및 01년도 동계학술발표회
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• pp.140-141
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• 2001

반사형 STN-LCD (supertwisted nematic liquid crystal display) 는 많은 display에서 사용되고 있는 LCD mode 중의 하나이다. 그러나 현재 많이 사용되는 반사형 STN-LCD는 그림 1과 같이 한 장의 polarizer와 두장의 retardation film을 사용하는 구조이므로 각각의 component에 대한 parameter들에 의해 display의 표시 성능이 좌우된다. 먼저 Reflective STN-LCD의 보상에 필요한 parameter를 살펴보면, 그림 1과 같이 5개 ( $\alpha$, ø$_1$, ø$_2$, 각 retarder의 retardation : Δnd$_1$, Δnd$_2$)의 parameter의 결정이 필요하다. (중략)

• Proceedings of the Optical Society of Korea Conference
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• 한국광학회 1989년도 제4회 파동 및 레이저 학술발표회 4th Conference on Waves and lasers 논문집 - 한국광학회
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• pp.157-160
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• 1989

The most serious difficulty in using the finite element method is the appearance of the so-called spurious, nonphysical modes. We have proposed the finite element formulation of the variational expression in the three-component magnetic field based on Galerkin's method. In this approach, the divergence relation H is satisfied and spurious modes does not appear and finite-element solutions agree with the exact solutions.

• The Journal of Korean Academy of Prosthodontics
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• 제50권1호
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• pp.53-60
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• 2012

Purpose: The purpose of this study was to compare Ni-Cr alloy property of gas-oxygen torch soldering and infrared welding using optical microscope and Electron Probe Micro Analyzer (EPMA). Materials and methods: Ni-Cr alloys were casted for specimens. Specimens had 3.0 mm diameter, 30.0 mm length and were divided into two groups. Each group had 4 specimens. One group was for gas-oxygen torch soldering and the other was infrared welding. Specimens were cut with low-speed disc and soldered each other with gas-oxygen torch and infrared machine. After soldering and polishing, specimens were observed at 3 points (soldering point, 5 mm distance point, 10 mm distance point) with optical microscope and analyzed 3 points (soldering point, 5 mm distance point, 10 mm distance point with EPMA. Results: The results of this study were as follows: 1. The observation of gas-oxygen torch soldering at 10 mm distance point under the optical microscope was not founded any specific surface properties, but some crack lines were observed at 5 mm distance and soldering point. 2. There were no crack lines were founded at the observation of infrared welding at 10 mm distance and 5 mm distance points under the optical microscope. However, at the 5 mm distance, the surface was not smooth enough compared with at 10 mm distance point. Some crack lines were observed at the welding point as well. 3. In the EPMA analysis of the gas-oxygen torch soldering, the component of Ni was increased by 4.5%, Cr was increased by 7.5% than that of the Ni-Cr alloy at the 10.0 mm distance. At the 5 mm distance, the component of Ni was decreased by 6.1%, Mo was increased by 9.0% than that of the Ni-Cr alloy but Cr was equally shown at the 5.0 mm distance. Only Ni was shown at the soldering point. 4. In the EPMA analysis of the infrared welding, the component of Ni was increased by 9.1%, Cr was increased by 0.4% than that of the Ni-Cr alloy but Al was equal at the 10.0 mm distance. At the 5 mm distance, the component of Ni was increased by 4.7%, Cr was increased by 4.7% and Al was increased by 0.1% than that of the Ni-Cr alloy. At the welding point, the component of Ni was increased by 8.8%, Cr was increased by 8.2% than that of the Ni-Cr alloy. Conclusion: From these results, at the 5 mm distance from the soldering point, the surface of the infrared welding was more smoother than that of the gas-oxygen torch soldering. On the EPMA analysis, the component of the specimens with infrared welding was more similar than that of the gas-oxygen torch soldering compared with the component of the Ni-Cr alloy.

• Journal of the Optical Society of Korea
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• 제12권1호
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• pp.25-30
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• 2008

The optical performances of 15-inch edge-lit backlight were simulated by using a Monte Carlo ray-tracing technique. The backlight model was built by combining a wedge-type light guide plate, a diffuser sheet, a tubular fluorescent lamp with a lamp reflector, and two crossed prism sheets. Angular distributions of the luminance on each optical component obtained from simulation were consistent with those obtained from experiments on a real 15-inch backlight. The constructed backlight model was used to evaluate the optical performances of a micro-pyramid film. It was found that the on-axis luminance gain on the pyramid film is higher than that on one prism film but much lower than that on the two crossed prism films. These results suggest that a reliable simulation model can be used to develop new hybrid films and to optimize the optical structure of edge-lit backlight in order to reduce the developmental period.

• Journal of IKEEE
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• 제2권2호
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• pp.178-184
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• 1998

Optical fiber coupler is a crucial optical passive component for optical transmission systems. In this paper, we fabricate wavelength insensitive optical coupler(WIC), of two types for which the processing procedures are complicate and difficult. These couplers are fabricated by two optical fibers having either different fiber parameters or different cladding diameters. To clarify the validity, we measure the optical characteritics and compare to the data of theoretical simulation. The experiment results ref#eat that it has uniformity of about 1.0 dB and excess loss of less than 0.1 dB in the range of $1310{\pm}40nm\;and\;1550{\pm}40nm$.

• Korean Journal of Optics and Photonics
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• 제15권5호
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• pp.449-454
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• 2004

The optical limiter is an optical component which reduces laser beam intensity for the protection of eyes and light sensors. Carbon nanotube is now known as a highly efficient optical limiting material. Optical limiting effect of the multi-walled carbon nanotube suspensions, in several kinds of solvents such as distilled water, chloroform, ethanol and ethylene glycol, were measured in the range from room temperature to near to the boiling points of the solvents. The pulsed Nd:YAG laser whose wavelength is 1064 nm and pulse duration is 6 ns was used as a light source. The experimental result shows that the limiting efficiency was reduced as the temperature increased, and the suspension which has lower boiling point, viscosity and surface tension has highest efficiency.

• Journal of the Korean Society of Manufacturing Process Engineers
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• 제9권5호
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• pp.57-63
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• 2010

Tolerance analysis is one of the most important processes to improve the image quality of products. High resolution camera module for mobile phones needs precision assembly technology since the module becomes smaller and thinner. This paper will focus on the unit tolerance and the assembly tolerance which can affect the performance of the module. Lens shading and relative illumination were used to evaluate the optical axis scatter for each component on camera and estimate the assembly yield rate based on the evaluation result. A program was developed to analyze the impact on optical axis by each module, then to optimize the dimensions and tolerance for reducing the scatter of optical axis assembly. Through the simulation, though a rate of relative illumination was declined in where optical axis is displaced $100{\mu}m$ from sensor center, MTF performance is not influenced by increasing in optical axis displacement. It was seen that assembly yield was improved in result of simulation after correcting optical axis tolerance.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 한국소성가공학회 2008년도 춘계학술대회 논문집
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• pp.269-272
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• 2008

LGP is a key component of LCD back light unit because it determines the brightness and sharpness of display image. Usually, it has optical patterns fabricated on the bottom surface. In the present paper the LiGA-reflow method was applied to fabricate the LGP mold. Furthermore, the optical simulation considering the replication ratio of pattern height was applied to the pattern design. The optical simulation through systematic correction scheme helped find the optimum distribution of pattern density. Finally, the stamper fabricated by this method was installed in the mold and LGP was produced by injection molding. As a result of luminance measurement for the final product, the average luminance and luminance uniformity was measured 3,180 nit and 84%, respectively. Consequently, the mold fabrication method using the LiGA-reflow and optical simulation(CAE) can save the expense and time compared with the existing fabrication methods(laser ablation and chemical etching).

• Smart Structures and Systems
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• 제18권3호
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• pp.471-484
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• 2016

Optical fiber sensors have been proven that they have the potential to detect high-frequency ultrasonic signals, in structural health monitoring field which generally refers to acoustic emission signals from active structural damages and guided waves excited by ultrasonic actuators and propagating in waveguide. In this work, the sensing properties of optical fiber sensors based on Mach-Zehnder interferometer were investigated in the metal plate. Analytical formulas were conducted first to explore the parameters affecting its sensing performances. Due to the simple and definable frequency component, the Lamb wave excited by the piezoelectric wafer was employed to study the sensitivity of the proposed optical fiber sensors with respect to the frequency, rather than the acoustic emission signals. In the experiments, according to above investigations, spiral shape optical fiber sensors with different size were selected to increase their sensitivity. Lamb waves were excited by a circular piezoelectric wafer, while another piezoelectric wafer was used to compare their voltage responses. Furthermore, by changing the excitation frequency, the tuning frequency characteristic of the proposed optical fiber sensor was also investigated experimentally.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 한국공작기계학회 2002년도 춘계학술대회 논문집
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• pp.167-172
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• 2002

Recent years, optical components'are widely used in optical communication industry for high speed and mass storage data processing. Micro grooving of planar lightwave circuit and glass, those are widely used in optical component, are realized by polycrystalline diamond tool with ultrasonic vibration. To know the characteristics of brittle materials cutting, ultrasonic vibration cutting tool and machining system are built for the experiment. Grooving on planar lightwave circuit and glass experiments are performed and their shape are measured by photograph with microscope. It reveals that better groove shape with low chipping of planar lightwave circuit and glass are obtained by micro grooving machining with ultrasonic vibration. These experiments are considered as a possibility to the micro grooving of optical communication components.