• 한국광학회:학술대회논문집
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• 한국광학회 2002년도 하계학술발표회
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• pp.56-57
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• 2002

일정한 파장 간격을 가지는 다파장 광원은 WDM 시스템에서 중요한 소자중의 하나로 부각되고 있다. 다파장 광원에서 요구되는 주요 특징은 넓은 파장대역과 많은 수의 채널이며 각 채널들의 출력이 크고 균일해야 할 필요가 있다. 또한 각 채널의 파장이 ITU frequency grid와 일치해야 한다. 반도체 레이저와 광섬유레이저를 이용하여 이런 요구들을 만족하는 다파장 광원에 대한 다양한 연구들이 이루어져 왔다. (중략)

• 대한전기학회:학술대회논문집
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• 대한전기학회 1989년도 하계종합학술대회 논문집
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• pp.409-410
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• 1989

Discharge characteristics of a commercial made Xe-flashlamp have been studied for the pumping source of dye Lasers. The rise-time, FWHM, intensity and energy of pumping light pulses of the lamp were measured as functions of the serial resistor and applied voltage. The grid effects of the lamp on pre-discharge and the spectrum of light pulses also have been investigated.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
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• pp.247.1-247.1
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• 2016

Low-cost, high efficiency solar cells are tremendous interests for the realization of a renewable and clean energy source. ZnTe based solar cells have a possibility of high efficiency with formation of an intermediated energy band structure by impurity doping. In this work, ZnO/ZnTe:Cr and ZnO/i-ZnTe structures were fabricated by pulsed laser deposition (PLD) technique. A pulsed (10 Hz) Nd:YAG laser operating at a wavelength of 266 nm was used to produce a plasma plume from an ablated a ZnTe target, whose density of laser energy was 10 J/cm2. The base pressure of the chamber was kept at approximately $4{\times}10-7Torr$. ZnTe:Cr and i-ZnTe thin films with thickness of 210 nm were grown on p-Si substrate, respectively, and then ZnO thin films with thickness of 150 nm were grown on ZnTe:Cr layer under oxygen partial pressure of 3 mTorr. Growth temperature of all the films was set to $250^{\circ}C$. For fabricating ZnO/i-ZnTe and ZnO/ZnTe:Cr solar cells, indium metal and Ti/Au grid patterns were deposited on back and front side of the solar cells by using thermal evaporator, respectively. From the fabricated ZnO/ZnTe:Cr and ZnO/i-ZnTe solar cell, dark currents were measured by using Keithley 2600. Solar cell parameters were obtained under Air Mass 1.5 Global solar simulator with an irradiation intensity of 100 mW/cm2, and then the photoelectric conversion efficiency values of ZnO/ZnTe:Cr and ZnO/i-ZnTe solar cells were measured at 1.5 % and 0.3 %, respectively.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2003년도 ICCAS
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• pp.174-179
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• 2003

Through the simultaneous localization and map building (SLAM) technique, a robot can create maps about its unknown environment while it continuously localizes its position. Grid maps and feature maps have been widely used for SLAM together with application of probability methods and POMDP (partially observed Markov decision process). But this approach based on grid maps suffers from enormous computational burden. Topological maps, however, have drawn more attention these days because they are compact, provide natural interfaces, and are easily applicable to path planning in comparison with grid maps. Some topological SLAM techniques like GVG (generalized Voronoi diagram) were introduced, but it enables the robot to decide only whether the current position is part of GVG branch or not in the GVG algorithm. In this paper, therefore, to overcome these problems, we present a method for updating a global topological map from the local topological maps. These local topological maps are created through a labeled Voronoi diagram algorithm from the local grid map built based on the sensor information at the current robot position. And the nodes of a local topological map can be utilized as the features of the environment because it is robust in light of visibility problem. The geometric information of the feature is applied to the extended Kalman filter and the SLAM in the indoor environment is accomplished. A series of simulations have been conducted using a two-wheeled mobile robot equipped with a laser scanner. It is shown that the proposed scheme can be applied relatively well.

• 한국측량학회지
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• 제30권4호
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• pp.335-342
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• 2012

건축, 토목, 의료, 컴퓨터 그래픽스 분야 등 다양한 분야에서 이용되는 3D point cloud는 최근 레이저 스캐너의 발달로 인해 그 용량이 점점 커지게 되었다. 컴퓨터 메모리의 용량을 넘어서서 모든 데이터를 한 번에 처리할 수 없는 대용량 3D point cloud를 가시화하고 편집하기 위해 여러 전처리 및 가시화 방법들이 소개되었고 본 논문에서 비교한 QSplat의 경우 3D 모델의 형상 확인과 용량 감소를 목적으로 원본 좌표를 손실 압축하여 저장하였다. 본 논문에서 제시하는 방법은 3D point cloud를 정육면체 격자로 분할하고 center sampling을 통해 가상점 집합을 생성하며 가시화 과정에서 격자에 저장된 point 집합 취득을 통한 빠른 렌더링이 가능하다. 홍익대학교 인근 지역을 측정한 약 1억 2천만 개 point의 대용량 3D point cloud를 QSplat과 다단계 정육면체 격자 기반 방법으로 비교한 결과 전처리 과정에서는 QSplat이, 가시화 과정에서는 다단계 정육면체 격자 기반 방법이 빠른 속도를 보여주었다. 또한 다단계 정육면체 격자 기반 방법은 point의 원본 좌표를 저장하기에 추후 가시화 외에 편집, segmentation 등의 작업을 고려하여 고안되었다.

• 한국인쇄학회지
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• 제29권3호
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• pp.105-124
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• 2011

TFT-LCD consists of LCD panel on the top, circuit unit on the side and BLU on the bottom. The recent development issues of BLU-dependent TFT-LCD have been power consumption minimization, slimmerization and size maximization. As a result of this trend, LED is adopted as BLU instead of CCFL to increase brightness and to reduce thickness. In liquid crystal displays, the light efficiency is below 10% due to the loss of light in the path from a light source to an LCD panel and presence of absorptive polarizer. This low efficiency results in low brightness and high power consumption. One way to circumvent this situation is to use a reflective polarizer between backlight units and LCD panels. Since a nano-wire grid polarizer has been known as a reflective polarizer, an idea was proposed that it can be used for the enhancement of the brightness of LCD. The use of reflective polarizing film is increasing as edge type LED TV and 3D TV markets are growing. This study has been carried out to fabrication of the nano-wire grid polarizer(NWGP) and investigated the brightness enhancement of LCD through polarization recycling by placing a NWGP between an c and a backlight unit. NWGPs with a pitch of 200nm were fabricated using laser interference lithography and aluminum sputtering and wet etching. And The NWGP fabrication process was using by the UV imprinting and was applied to plastic PET film. In this case, the brightness of an LCD with NWGPs was 1.21 times higher than that without NWGPs due to polarization recycling.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
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• pp.306.1-306.1
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• 2016

ZnO semiconductor material has been widely utilized in various applications in semiconductor device technology owing to its unique electrical and optical features. It is a promising as solar cell material, because of its low cost, n-type conductivity and wide direct band gap. In this work ZnO/Si heterojunctions were fabricated by using pulsed laser deposition. Vacuum chamber was evacuated to a base pressure of approximately $2{\times}10^{-6}Torr$. ZnO thin films were grown on p-Si (100) substrate at oxygen partial pressure from 5mTorr to 40mTorr. Growth temperature of ZnO thin films was set to 773K. A pulsed (10 Hz) Nd:YAG laser operating at a wavelength of 266 nm was used to produce a plasma plume from an ablated a ZnO target, whose density of laser energy was $10J/cm^2$. Thickness of all the thin films of ZnO was about 300nm. The optical property was characterized by photoluminescence and crystallinity of ZnO was analyzed by X-ray diffraction. For fabrication ZnO/Si heterojunction diodes, indium metal and Al grid patterns were deposited on back and front side of the solar cells by using thermal evaporator, respectively. Finally, current-voltage characteristics of the ZnO/Si structure were studied by using Keithly 2600. Under Air Mass 1.5 Global solar simulator with an irradiation intensity of $100mW/cm^2$, the electrical properties of ZnO/Si heterojunction photovoltaic devices were analyzed.

• 제어로봇시스템학회논문지
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• 제21권10호
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• pp.965-971
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• 2015

This paper suggests a feature point-based Iterative Closest Point (ICP) algorithm to compensate for the disparity error in building a two-dimensional map. The ICP algorithm is a typical algorithm for matching a common object in two different images. In the process of building a two-dimensional map using the laser scanner data, warping and distortions exist in the map because of the disparity between the two sensor values. The ICP algorithm has been utilized to reduce the disparity error in matching the scanned line data. For this matching process in the conventional ICP algorithm, pre-known reference data are required. Since the proposed algorithm extracts characteristic points from laser-scanned data, reference data are not required for the matching. The laser scanner starts from the right side of the mobile robot and ends at the left side, which causes disparity in the scanned line data. By finding the matching points between two consecutive frame images, the motion vector of the mobile robot can be obtained. Therefore, the disparity error can be minimized by compensating for the motion vector caused by the mobile robot motion. The validity of the proposed algorithm has been verified by comparing the proposed algorithm in terms of map-building accuracy to conventional ICP algorithm real experiments.

• 한국지리정보학회지
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• 제6권3호
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• pp.33-42
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• 2003

최근 높은 수직정확도를 갖는 항공레이저측량 기술이 개발됨에 따라 이를 이용한 DEM(digital elevation model) 생성, 건물추출, 홍수위험지도 제작, 3차원 도시모델 구축 등의 다양한 연구가 활발하게 수행되고 있다. 본 연구에서는 항공레이저측량으로부터 취득한 원시자료로부터 생성한 해상도별 DEM의 표준편차를 계산하기 위해 점비교법, 등고선비교법 그리고 1/5,000 수치지형도를 활용하였다. 비교결과 점비교법이 등고선비교법보다 낮은 DEM 표준오차를 나타냈으며, 이것은 등고선비교법이 점비교법에 비해 조밀한 격자 연산이 이루어지지 않은 것이 원인으로 파악되었다. 또한 1/5,000 수치지형도는 평균수평거리인 25.4m 이하에서는 점비교법과 등고선비교법에 비해 높은 오차를 보였으며, 25.4m 이상에서는 등고선비교법과 유사한 결과를 나타냄을 알 수 있었다.

• 태양에너지
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• 제17권3호
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• pp.59-66
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• 1997

본 연구에서는 PTV기법에 의해 속도를 계측하였으며 계측시스템은 레이저를 이용한 시이트라이트와 이미지보오드를 내장한 퍼스널컴퓨터 그리고 관련 소프트웨어로 구성하였다. 속도벡터는 PTV 시스템에 의해 구하였으며 그 결과를 압력에 관한 프와송방정식에 적용하여 전유동장의 압력을 구하였다. 이때의 경계조건으로서는 벽면에서는 부착조건을 부여하였고 구동류가 흐르는 캐비티의 상부에서는 내부의 속도 값을 외삽하였다. 압력계산에 있어서 격자의 해상도는 $40{\times}40$이며 등간격의 엇갈림격자를 사용하였다. 계측결과는 유동장의 속도 및 압력분포를 잘 나타내었다.