• 정보저장시스템학회:학술대회논문집
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• 2005.10a
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• pp.151-152
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• 2005

Blu-ray 디스크에서는 NA=0.85 의 높은 개구수를 채용함으로써 디스크 보호층의 두께 변동에 따른 구면수차 발생량이 매우 커지는 문제가 발생하게 된다. 따라서 디스크 두께 공차 $3{\mu}m$에서 Blu-ray 시스템의 수차 발생 허용수준을 초과한다. 그리고 Multi-layer 디스크의 경우 각 층의 간격이 $25{\mu}m$ 정도의 간격을 두고 배치되어 있어 기록층 사이에서 발생하는 구면수차의 보정이 필요하며, 종래의 기술은 보상범위가 $3{\mu}m$로 한정되어 사용이 불가능하며 또한 대물렌즈 조립공차가 엄격히 관리되어야 하는 문제점을 안고 있었다. 본 연구에서는 액정렌즈에 의한 구면수차 보정으로 이러한 문제점들을 해결하고자 하였다. 액정렌즈는 오목렌즈 액정소자와 볼록렌즈 액정소자로 구성되며 픽업 광학계 내에 조합하여 설계함으로써 Multi-layer 디스크의 두께 변동에 따라 발생하는 구면수차를 보정하고 대물렌즈 조립공차 문제를 해결할 수 있다.

• Current Optics and Photonics
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• v.5 no.4
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• pp.391-401
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• 2021

In the present study, a hyperelastic constitutive model is built by complying with a simplified hyperelastic strain energy function, which yields the numerical solution for a deformed polydimethylsiloxane (PDMS) membrane in the case of axisymmetric hydraulic pressure. Moreover, a nonlinear equilibrium model is deduced to accurately express the deformation of the membrane, laying a basis for precise analysis of the optical transfer function. Comparison to experimental and simulated data suggests that the model is capable of accurately characterizing the deformation behavior of the membrane. Furthermore, the stretch ratio derived from the model applies to the geometrical optimization of the deformed membrane.

• Proceedings of the IEEK Conference
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• 1999.11a
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• pp.921-924
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• 1999

By controlling the pixels of a liquid crystal display (LCD) electronically, we fabricated a real-time moving window on a LCD, through which light passes. Using the moving window and hi-focusing lens, we suggested a non-mechanical spatio-angular multiplexed holographic memory system and demonstrated its feasibility through optical experiments. The principle of the proposed method and optical experimental results are also presented.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.05a
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• pp.241-244
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• 2004

Microlens patterned micro-mold fabrication method for Light Guiding Plate(LGP), kernel part of LCD-BLU(Back Light Unit), was presented. Instead of erosion dot pattern for LCP optical design, microlens pattern, fabricated by LIGA-reflow process, was applied. Optical pattern design method was also developed not only for negative pattern LGP, but also positive pattern LGP. In order to achieve flow balance during the micro-injection molding process and dimensional accuracy, two LGP pattern was made in one micro-mold.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.34D no.9
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• pp.64-71
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• 1997

A new etching technique of meltback was investigated for GaAs lensed optical devices with selective windows opending in the LPE (liquid phase epitaxy) system. In the meltback process, the etch depth and the etch shape were controlled by the degree of under-saturation, etch time and other parameters. A GaAs/AlGaAs DH layer was grown on the selectively etched hemispherical well for optical device application such as lensed surface emitting LED. The regrowth process were related with the coolin grate and the well to well spacing. A novel surface emitting LED with hemispherical AlGaAs lens was fabricated using the meltbakc and regrowth as the key process for AlaAs lens array. The light emitting efficiency of the LED was upto three times higher than the similar structure LED without lens. The meltback and regrowth technique was applicable to manufacture the optical device in LPE.

• Proceedings of the KIEE Conference
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• 1999.07g
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• pp.3316-3318
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• 1999

PMMA(poly-methyl methacrylate) microlens array is fabricated using transparent acrylic resin. PMMA is commonly used material for plastic lens due to its excellent visibility larger than 90% and other optical characteristics so much close to those of glass. Orthodontic resin (DENTSPLY International Inc.), commonly used in dentistry, is an transparent acrylic resin kit including MMA liquid and polymerization powder. Their mixture results in PMMA through polymerization. Using the resin PMMA layer is formed on the substrate through spin-coating. Designed pattern of lens structure is transferred to PMMA layer by RIE (Reactive Ion Etching) with oxygen plasma. Final lens shape is formed by thermal treatment that causes PMMA to reflow, The thickness of PMMA spun on the substrate is $17{\mu}m$ that is also final sag of microlens, Designed diameters of the microlenses are $200{\mu}m$, $300{\mu}m$,and $500{\mu}m$, respectively.

• Design & Manufacturing
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• v.7 no.1
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• pp.55-59
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• 2013

A Light Emitting Diode(LED) is a semiconductor device which converts electricity into light. LEDs are widely used in a field of illumination, LCD(Liquid Crystal Display) backlight, mobile signals because they have several merits, such as low power consumption, long lifetime, high brightness, fast response, environment friendly. In general, LEDs production does die bonding and wire bonding on board, and do silicon and phosphor dispensing to protect LED chip and improve brightness. Then lens molding process is performed using mixed liquid silicon rubber(LSR) by resin and hardener. A mixture of resin and hardener affect the optical characteristics of the LED lens. In this paper, computational design of static mixer was performed for mixing of liquid silicon. To evaluate characteristic of mixing efficiency, finite element model of static mixer was generated, and fluidic analysis was performed according to length of mixing element. Finally, optimal condition of length of mixing element was applied to static mixer from result of fluidic analysis.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.10
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• pp.1370-1376
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• 2003

The investigation of liquid fuel film on the cylinder liner is an essential to understand the engine-out hydrocarbon emissions formation in SI engines. In this research, two-dimensional visualization was carried out to investigate the liquid fuel film on the quartz liner in the optical engine. For this, the optical engine with hydraulic system was designed based on the commercial SI engine. The visualization was based on the laser-induced fluorescence with total reflection technique. Using a quartz liner and a special lens, only the liquid fuel film on the liner was visualized. With using this technique, the distribution of the fuel film on the cylinder liner was measured for different engine conditions and injection timing in the optical engine.

• Transactions of the Korean Society of Automotive Engineers
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• v.10 no.5
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• pp.90-97
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• 2002

The interaction between airflow and liquid phase LfG (Liquefied Petroleum Gas) sprays was investigated in a steady flow system embodied in a wind tunnel to simulate the variety of flow inside intake port of LPG engines with liquid injection system. The spray developments in flowing fields with the mean velocities of 5.4, 21.5 and 42.4m/s were identified by spray visualization techniques such as Mie scattering and shadowgraph. The microscopic visualization using a telescopic lens system was performed to investigate the shape and size of liquid droplets in the spray. PDA measurement was used to get 1-dimensional velocity and diameter of liquid droplets. The fast co-flows make the spray field be compact and be lead upward to the injection direction. SMD of the spray was smaller at the fast flowing field. Spray width got bigger and SMD of the spray was smaller with higher injection pressure.

• 한국정보디스플레이학회:학술대회논문집
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• 2005.07a
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• pp.528-530
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• 2005

In this paper, we present a new and practical method for achieving real-time wavefront measurement, dramatically increasing the resolution, dynamic range of Shack-Hartmann wavefront sensor and improving the wavefront reconstruction quality. In proposal method, a liquid crystal display panel (LCD) for the generation of an array of Fresnel microlenses is use instead of the static microlens array of the conventional Shack-Hartmann type sensor. An off-axis holographic microlens array is designed instead of the normal microlens array to increase the effective array and then the dynamic range. The focus properties of the off-axis lens are studied.