• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.05a
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• pp.378-380
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• 2002

There has been lower the tilt margin by the increase of coma aberration due to the reduction of wave-length and the increase of numerical aperture for high density recording. The RF signal degradation is increased as the decrease of tilt margin. To compensate the tilt margin, the optical pick-up actuator for high-speed CD/DVD re-writable system should be able to drive the radial-tilt motion. We announce that the 3-axis drive actuator for high-speed CD/DVD rewritable system. And what was more, the DC/AC sensitivities of this actuator are suitable fur the low-speed playability, the high-speed readability and the high-speed rewritability.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.46 no.7
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• pp.15-21
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• 2009

We proposed a fusion splicing method for low splicing loss between a single-mode fiber(SMF) and two different photonic crystal fibers(PCFs) such as a photonic bandgap fiber(PBGF) and highly nonlinear photonic crystal fiber(NL-PCF). The splicing loss between the SMF and PBGF is affected by air-hole collapse. Therefore, we optimized fusion splicer and reduced a splicing loss below 1.22 dB. We also inserted a Intra High Numerical Aperture(UHNA) fiber between the SMF and NL-PCF to achieve a splicing loss of below 2.59 dB.

• Current Optics and Photonics
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• v.7 no.5
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• pp.537-544
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• 2023

Differential phase contrast (DPC) microscopy, a central quantitative phase imaging (QPI) technique in cell biology, facilitates label-free, real-time monitoring of intrinsic optical phase variations in biological samples. The existing DPC imaging theory, while important for QPI, is grounded in paraxial diffraction theory. However, this theory lacks accuracy when applied to high numerical aperture (NA) systems that are vital for high-resolution cellular studies. To tackle this limitation, we have, for the first time, formulated a nonparaxial DPC imaging equation with a transmission cross-coefficient (TCC) for high NA DPC microscopy. Our theoretical framework incorporates the apodization of the high NA objective lens, nonparaxial light propagation, and the angular distribution of source intensity or detector sensitivity. Thus, our TCC model deviates significantly from traditional paraxial TCCs, influenced by both NA and the angular variation of illumination or detection. Our nonparaxial imaging theory could enhance phase retrieval accuracy in QPI based on high NA DPC imaging.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.11a
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• pp.226-233
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• 2003

There are many researches going on to develop the information storage devices using Blue-ray disc and DVD as a demand for high-density information storage devices is highly increasing. This high-density information storage device requires a short-wave laser and objective lens of high numerical aperture set in fer its operation. And, that brings out rapid decrease of tilt tolerance. Therefore, it is necessary that an actuator should control tilt motions to get a stable signal. In this paper, a new mathematical form of 3-D.O.F coupled model is formulated and magnetic circuit in constraints is most effectively designed with the use of the moving coil type actuator in higher sensitivity. Further, this paper presents a tilt coil whose rotational center point is put on that of the lens through the variation of tilt coil and proposes a 3-axis actuator with high sensitivity improved in its dynamic property through its structure analysis.

• Tunnel and Underground Space
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• v.17 no.2 s.67
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• pp.109-118
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• 2007

The excavation damaged zone (EDZ) is an area around an excavation where in situ rock mass properties, stress condition. displacement. groundwater flow conditions have been altered due to the excavation. Various studies have been carried out on EDZ, but most studies have been focused on the mechanical bahavior of EDZ by in situ experiment. Even though the EDZ could potentially form a high permeable pathway of groundwater flow, only a few studies were performed on the analysis of groundwater flow in EDZ. In this study, the' hydraulic EDZ' was defined as the rock Lone adjacent to the excavation where the hydraulic aperture has been changed due to the excavation. And hydraulic EDZ (hydraulic aperture changed zone) estimated by two-dimensional DEM program was considered in three-dimensional DFN model. From this approach the groundwater flow characteristics corresponding to hydraulic aperture change were examined. Together. a parametric study was performed to examine the boundary conditions that frequently used in DFN analysis such as constant head or constant flux condition. According to the numerical analysis, hydraulic aperture change induced by the hydraulic-mechanical interaction becomes one of the most important factors Influencing the hydraulic behavior of jointed rock masses. And also from this study, we suggest the proper boundary condition in three-dimensional DFN model.

• Transactions of the Society of Information Storage Systems
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• v.3 no.3
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• pp.123-125
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• 2007

We report the readout stability improvement results of super-resolution near field structure (Super-RENS) writeonce read-many (WORM) disk at a blue laser optical system. (Laser wavelength 405nm, numerical aperture 0.85) By using diffusion barrier structure (GeSbTe sandwiched by GeN) and high transition temperature recording material ($BaTiO_3$), material diffusion of phase change layer and recording mark degradation were greatly improved during high power (Pr=2.0mW) readout process up to $1{\times}10^5$ times.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.05a
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• pp.195-199
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• 2004

Recently, optical disc drives are required to have high density and capacity in according with development of high definition images and rapid increase of various informations. Consequently, the numerical aperture becomes larger, the wavelength of laser is coming to be short. However, it deteriorates rolling mode effect on an optical pickup actuator. Therefore, this paper proposes new design and optimization of tracking coils for reducing it. First, we verify that discord between the center of force and the center of mass by restrictions of design condition is an important factor of rolling mode effect. Then, in order to reduce it, we propose new design parameters of tracking coils. Finally, we reduce rolling mode effect through optimization of tracking coils using Taguchi method and response surface method.

• 정보저장시스템학회:학술대회논문집
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• 2005.10a
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• pp.42-43
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• 2005

Higher density in the holographic storage can be obtained by using shorter wavelength laser and higher numerical aperture (NA). In this paper, we adopted a blue laser diode with a wavelength of 405nm and high NA object lens. And the phase conjugation method is applied to prevent image distortion due to high NA. The performance of the system has been shown experimentally.

• Proceedings of the Optical Society of Korea Conference
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• 2003.02a
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• pp.258-259
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• 2003

보호층 0.1mm두께의 20GB이상의 광디스크를 기록·재생하는 High Density Optical System에서는 Blue-violet laser와 NA(Numerical Aperture)0.85의 High NA의 대물렌즈를 사용한 Optical Pick Up이 필요로 된다. 종래의 대물렌즈는 glass 또는 plastic제의 2매 조합 대물렌즈가 많이 사용되어지고 있는데, 이는 두 렌즈간의 거리를 일정하게 유지시키기 위한 홀더 조립시의 공차가 엄격히 요구되며, 2매 조합 대물렌즈를 구동시키기 위한 actuator의 부피와 무게를 증가시킴으로서 구동감도를 감소시키는 단점이 있다. (중략)

• 한국태양에너지학회:학술대회논문집
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• 2011.04a
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• pp.144-149
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• 2011

This study aims to evaluate performance of ventilation and thermal about breathing wall by flowing air to indoor on appropriate conditions that is effective aperture area in the Central region(20, 50, $80cm^2/m^2$). The result is as follows : 1) Sectional temperature distribution of inflow and outflow out under the constant ventilation was reviewed. In the case of inflow, outside temperature increase effect was confirmed. 2) The more differences of temperature between outdoor and indraft of air was high, the more heat recovery was high.