• 한국생산제조학회지
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• 제21권5호
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• pp.773-777
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• 2012

Recently UV laser micromachining processes is widely introduced to meet the needs of advanced components of IT, BT and ET industries. Due to the characteristics of non-contact and high-speed laser processing, UV laser micromachining is applied to manufacture very thin substrate such as polymer, metals and composite. These minimum line width obtained by UV laser micromachining is generally determined from laser wavelength, optical lens and its numerical aperture. In this paper we will show the lens effect of water droplet on the surface of workpiece to reduce the line width when UV laser light is irradiated and focused through the water droplet. Because of the refraction effect generated by the semi-spherical or spherical shape of water droplet, we can find smaller line width. And water droplet could not only protect thermal deformation, but also carry away burr around micro dent. Firstly fundamental theory of minimum line width was derived from relationship between the geometry of water droplet and laser light trace, and then experimental and simulation results will be finally compared to verify the effectiveness of water droplet lens effect of UV laser micromachining process.

• Journal of the Optical Society of Korea
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• 제17권3호
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• pp.269-274
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• 2013

The effect of diffusing substrate and pillow lenses on the outcoupling efficiency of organic light-emitting diodes (OLEDs) was studied by optical simulation based on the point-dipole model. The diffusing substrate included Mie scatterers by which the condition of total internal reflection could be broken. The finite-difference time-domain method was used to obtain the intensity distribution on the transparent electrode of an OLED, which was used as a light source to carry out a ray-tracing simulation of the OLED and the diffusing substrate. It was found that the outcoupling efficiency of the OLED was sensitive to the thickness of organic layers and could be increased by 21.0% by adopting a diffusing substrate in which Mie scatterers whose radius was $2.0{\mu}m$ were included at the density of $10^7mm^{-3}$ and by 65.5% by forming one pillow lens with the radius of 2 mm on the front surface of the glass substrate. This study revealed that the outcoupling efficiency could be improved by adopting diffusing substrate and pillow lenses along with the optimization of the thickness of each layer in the OLED.

• 한국광학회지
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• 제8권5호
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• pp.431-437
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• 1997

광신호 상호연결 및 입력물체의 결상을 위한 기존의 평판광학계에서는 굴절률이 일정한 유리기판을 광신호 전달매체로 사용하였는데 반하여, 본 연구에서는 물매-굴절률(gradient-index) 분포를 갖는 기판을 사용하는 새로운 개념의 평판광학계를 제안하였다. 물매기판에 의한 결상특성을 근축광선 추적에 의해 분석하였으며, 입력 광신호의 위치에 따라 결상된 위치가 변하는 실험결과로부터 새로운 결상광학계로의 응용 가능성을 검증하였다. 그리고, 물매기판을 이용한 평판광학계가 하나의 입력신호를 여러 출력면으로 동시에 분배할 수 있는 광신호처리계로도 응용될 수 있음을 제시하였다.

• 한국통신학회논문지
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• 제17권4호
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• pp.371-378
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• 1992

본 논문에서는 Y-cut $LiNbO_3$ 기판 위에 TIPE 방식을 이용하여 평면 광도파로 렌즈를 제작하고 그 특성을 측정하였다. Ti 내부확산 평면광도파로 및 TIPE 평면 광도파로 제작하고, 프리즘 결합으로 굴절율을 측정하였다. 측정한 기본파 유효굴절율로부터 평면 광도파로 렌즈의 궤적을 구하여, 사진식각법과 lift-off기법을 이용하여 TIPE 평면 광도파로 렌즈를 제작하였다. 도파로를 따라 도파되던 광이 평면 광도파로 렌즈에 의하여 접속되는 현상을 관측하였고 측정한 결과와 컴퓨터 시뮬레이션의 결과가 잘 일치함을 알 수 있었다. 관측한 초점의 위치 및 크기가 설계한 값과 잘 일치하였다.

• 한국레이저가공학회지
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• 제11권2호
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• pp.26-32
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• 2008

Micro lens array (MLA) is widely used in information technology (IT) industry fields, for examples such as a projection display, an optical power regulator, a micro mass spectrometer and for medical appliances. Recently, MLA have been fabricated and developed by using a reflow method, micro etching, electroplating, micromachining and laser local heating. Laser local thermal-expansion (LLTE) technology demonstrates the formation of microdots on the surface of polymer substrate, in this paper. We have also investigated the new direct fabrication method of placing the MLA on the surface of a SU-8 photoresist layer. We have obtained the 3D shape of the micro lens processed by UV laser irradiation and have experimentally verified the optimal process conditions.

• 한국세라믹학회지
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• 제51권6호
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• pp.533-538
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• 2014

Today, silicon and epoxy resin are used as materials of conversion lenses for white LEDs on the basis of their good bonding and transparency in LED packages. But these materials give rise to long-term performance problems such as reaction with water, yellowing transition, and shrinkage by heat. These problems are major factors underlying performance deterioration of LEDs. In this study, in order to address these problems, we fabricated a conversion lenses using glass, which has good chemical durability and is stable to heat. The fabricated conversion lenses were applied to a remote phosphor type. In this experiment, the conversion lens for white LED was coated on a glass substrate by a screen printing method using paste. The thickness of the coated conversion lens was controlled during 2 or 3 iterations of coating. The conversion lens fabricated under high heat treatment temperature and with a thin coating showed higher luminance efficiency and CCT closer to white light than fabricated lenses under low heat treatment temperature or a thick coating. The conversion lens with $32{\mu}m$ coating thickness showed the best optical properties: the measured values of the CCT, CRI, and luminance efficiency were 4468 K, 68, and 142.22 lm/w in 20 wt% glass frit, 80 wt% phosphor with sintering at $800^{\circ}C$.

• Journal of electromagnetic engineering and science
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• 제10권3호
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• pp.132-137
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• 2010

We present results of room-temperature characterization of lithographically manufactured antenna-coupled NbN micro-bolometers. The bolometers are assembled together with a hyper-hemispherical Si lens to couple the incident radiation to the bolometer from the back-side of the substrate. The bolometers are designed to operate at 300~1,000 GHz and they are characterized at 321~782 GHz. Radiation patterns are measured at 321 GHz, 400 GHz, 654 GHz, and at 782 GHz. The frequency dependency of the beamwidth is studied with several azimuthal beam profile measurements at 321~500 GHz.

• 한국기계가공학회지
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• 제8권3호
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• pp.62-67
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• 2009

Pt thin films on Cr or Ti interlayer were deposited onto a tungsten carbide(WC) substrate by the ion beam assisted DC magnetron sputtering. The various atomic percent of Cr and Ti underneath of the Pt films were prepared to examine the total thin film characteristics. The microstructure and surface analysis of the specimen were conducted by using the SEM, XRD and AFM. Mechanical properties such as hardness and adhesion strength of Pt thin film also were examined. The interlayer of pure Ti was formed with 40 nm thickness while that of pure Cr was done with 50 nm as standard reference. The growth rate of either Cr or Ti thin film was almost same under the same deposition conditions. The SEM images showed that anisotropic grain of Pt thin films consisting of dense columnar structures irrespectively grew from the different target compositions. The values of hardness and adhesion strength of Cr/Pt thin film coated on a WC substrate were higher than those of Ti/Pt thin film.

• 한국산학기술학회논문지
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• 제22권1호
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• pp.461-467
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• 2021

열경화성 소재를 이용하여 열경화방식의 웨이퍼 레벨 렌즈를 성형할 때 발생될 수 있는 불량요인 중 이형과정에서 성형 렌즈의 금형 고착문제는 웨이퍼 레벨에서 성형된 기판의 파손 및 기판의 변형으로 성형된 웨이퍼 기판의 적층시 웨이퍼 양면의 렌즈 형상 및 센터 정렬 오차에 영향을 미친다. 본 연구에서는 웨이퍼 레벨 렌즈 성형 공정에서 이형력에 영향을 미치는 인자를 검토하기 위한 실험을 수행하였다. 먼저 상·하 금형의 코팅 재질에 따른 이형력을 검토하기 위하여 금형 표면을 ITO 및 Ti로 표면처리 후 O2분위기에서 플라즈마 처리하였고, 또한 DLC 코팅도 진행하였으며 경화 및 이형성을 검토하였다. 그 결과를 바탕으로 pull-off 실험을 위한 코팅방법을 선정하였다. 또한 경화공정조건에 따른 이형력을 측정하기 위하여 압력을 유지하면서 경화시키는 방법과 일정한 간격을 유지하면서 경화시키는 방법을 실험적으로 적용하였다. 그 결과 Ti 코팅 후 O2 플라즈마 표면처리 방법이 이형력을 감소시키고 위치를 제어하면서 경화시킬 경우 경화수축에 의해 경화 중 계면의 접착에너지를 감소시켜 보다 나은 이형이 될 수 있음을 확인하였다.

• 한국광학회지
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• 제20권5호
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• pp.294-300
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• 2009

테라헤르츠 광원인 포토믹서의 출력을 향상시키기 위하여 강한 공진의 복사부와 안정적인 DC 급전부로 구성된 네잎클로버 형태의 새로운 안테나구조를 제안하였다. 먼저 복사환경을 단순화시킨 무한기판 위에서 제안한 안테나구조의 공진특성을 살펴보았고, 이를 바탕으로 제안한 구조가 확장형 반구렌즈 위에서 최대의 전체효율과 지향성을 지니도록 설계하였다. 기존의 전파장다이폴안테나와 비교한 결과, 제안한 구조는 공진주파수에서 6배 이상의 높은 입력임피던스 특성을 가짐으로써 포토믹서와의 부정합효율을 크게 개선시켰으며, 이로 인해 테라헤르츠 출력이 전파장 다이폴의 경우보다 2.7배 높게 예상되었다.