• Journal of the Korea Convergence Society
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• v.6 no.1
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• pp.43-48
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• 2015

We studied on the injection molding conditions of defect-free PMMA lens for surgical light. When the heat temperature of mold is low, more imperfect molding or weldlines and flow marks have showed. A defective lens depends on low fluidity of the PMMA resin and its temperature is high, a flexural strain has occurred. The longer cooling time of specimens, the more cracks have occurred due to resin crystallization. In this study, optimal molding conditions for defect-free PMMA lens is as follows. The heat temperature of core mold was 110 [$^{\circ}C$] and also the cooling time was 25 [sec]. PMMA materials can realized low expense to produce plastic optical lens and applications.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.4
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• pp.929-934
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• 2010

Improvements in characteristics of a single junction AlGaAs/GaAs solar cell are observed by capping a PMMA lens on it. In order to show the effect of the lens, characteristics of a single junction AlGaAs/GaAs solar cell before and after the lens formation are compared under the one-sun illumination condition ($100mW/cm^2$). Characteristics of the solar cell under very weak illumination condition (about 1200 lux) is also measured with the lighting of a fluorescent desk lamp. About 5% of cell efficiency is improved after the capping of PMMA lens on the single junction AlGaAs solar cell and $83\;{\mu}m/cm^2$ of electrical power was generated with the lighting of a desk lamp.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.1511-1512
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• 2011

마이크로 렌즈를 제작하기 위해 PMMA 몰드를 PMMA 용액을 MEMS 기술을 이용하여 제작한 실리콘 마이크로 홀 어레이에 PMMA 용액을 스핀 코팅하여 제작하였다. PMMA 몰드에 PDMS 용액을 코팅하여 OLED 광추출 향상용 마이크로 렌즈를 제작하였다.

• Proceedings of the KAIS Fall Conference
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• 2001.05a
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• pp.298-299
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• 2001

안경렌즈는 유리를 연마하여 제작하거나 단량체를 세라믹 금형에 넣어 캐스팅공법으로 플라스틱 렌즈를 만드는 것이 일반적인 방법이었다. 한편 사출성형에 의한 렌즈 및 안경의 제작은 광학적으로 우수한 재료 및 금형을 개발하지 못하여 국내에서는 시도조차 못하는 형편이다. 구미나 유럽의 일부 국가는 PMMA 및 PC를 이용하여 안경 및 안경렌즈를 개발하고 있으며, 이는 공정을 대폭 줄이기 때문에 대량 생산 및 원가 절감을 이룩할 수 있다. 본 연구에서는 PMMA 및 PC를 이용하여 그동안 성형할 때에 가장 문제가 되었던 오목 렌즈를 제작하기 위한 근본적인 금형 설계의 문제점 해결과 이를 이용한 일체형 안경과 고강도 렌즈의 제작을 고찰하였다.

• Proceedings of the Optical Society of Korea Conference
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• 2000.02a
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• pp.190-191
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• 2000

미세가공 기술을 이용한 초소형 렌즈의 제작 및 연구가 매우 활발히 진행되고 있다. 초소형렌즈의 응용 분야는 바코더 스캐너, 레이저 프린터, 프로젝터, 광 기록 장치, 광섬유를 이용한 광통신 등이 있으며 앞으로도 더 많은 응용 분야를 위한 광범위한 설계와 제작 공정들이 연구되어 갈 것이다. 본 논문에서는 아크릴 레진을 이용하여 초소형 렌즈를 제작하는 공정을 개발하여 새로운 재료와 공정에 대한 가능성을 확인한다. (중략)

• Clean Technology
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• v.11 no.4
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• pp.205-211
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• 2005

There have been many technologies and materials proposed for realizing microlens array, and plastic injection is recognized as the most promising one because of several merits such as optical properties, impact resistance, formability, lightening and environmental adaptability. Since PR reflow for injection template fabrication enables the lens shape control easier, and the sample technology more effective for mass production, it lowers the cost, enhances integration, and reduces process steps, which leads to be environmentally benign. However injection of polymers may face the difficulty of formability depending on their properties. In order to overcome the difficulty, fast heating/cooling technology was introduced in this study, and microlenses were fabricated and evaluated. template obtained by PR reflow method was heated and cooled fast during injection to fabricate microlens array. PC and PMMA polymer materials were compared, and it was realized that PMMA showed much better formability due to its lower melting temperature. Injection parameters of pressures and velocities were driven out for injection optimization.

• Journal of Korean Ophthalmic Optics Society
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• v.12 no.4
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• pp.29-35
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• 2007

This study was conducted to measure the central corneal thickness(CTT) changes associated with kinds of wearing contact lens. The CCT was measured using ultrasonic pachymeter in three hundred four subjects in their 20s and 30s. Although the CCT of Group 1 who had never worn any kinds of contact lens had no differences between left and right eye as well as between genders, the CCT tended to become thinner depending on the increment in refractive error. In Group 2 wearing only soft contact lens, the CCT was thinner depending on wearing period, and subjects wearing for more than 10 years had significantly thin CCT comparing with subjects wearing for less than 4 years. There was no significant difference in the CCT between Group 3 wearing only RGP lens and Group 2 for less than 4 years. Furthermore, when comparing the CCT between the Group 2 and Group 4 changing to RGP lens after wearing soft contact lens, there was no statistically significant change in the CCT. However, the CCT was significantly thinner in Group 5 changing to soft contact lens after wearing PMMA(polymethyl methacrylate) hard lens compared with Group 2.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.11
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• pp.2450-2456
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• 2002

Microlenses and microlens arrays are fabricated using a novel fabrication technology based on the exposure of a resist (usually PMMA) to deep X-rays and subsequent thermal treatment. The fabrication technology is very simple and produces microlenses and microlens arrays with good surface roughness (less than 1 nm). The molecular weight and glass transition temperature of PMMA is reduced when it is irradiated with deep X-rays. The microlenses is produced through the effects of volume change, surface tension, and reflow during thermal treatment of irradiated PMMA. The geometry of the microlens is determined by parameters such as the X-ray dose applied to the PMMA, the diameter of the microlens, along with the heating temperature, heating time, and cooling rate in the thermal treatment. Microlenses are produced with diameters ranging from 30 to 1500 ${\mu}{\textrm}{m}$. The modified LIGA process is used not only to construct hemispherical microlenses but also structures that are rectangular-shaped, star-shaped, etc.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.228-232
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• 2003

Mircolens and microlens arrays are realized using a novel fabrication technology based on the exposure of a resist, usually PMMA, to deep X-rays and subsequent thermal treatment. Hot embossing process is also studied for mass production. The fabrication technology is very simple and produces microlenses and microlens arrays with good surface roughness of several nm. The molecular weight and glass transition temperature of PMMA is reduced when it is irradiated with deep X-rays. The microlenses were produced through the effects of volume change, surface tension. and reflow during thermal treatment of irradiated PMMA. A hot embossing machine is designed and manufactured with a servo motor transfer system. The hot embossing process follows the steps of heating mold to the desired temperature, embossing a mold insert on substrate. cooling mold to the de-embossing temperature. and de-embossing. Microlenses were produced with diameters ranging from 30 to 1500 ${\mu}{\textrm}{m}$. The surface X-ray mask is also fabricated to realize microlens arrays on PMMA sheet with a large area.

• 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.