• Journal of the Korean Vacuum Society
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• v.20 no.1
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• pp.30-34
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• 2011

We investigated the structural, electrical and optical characteristics of thin films with ITO deposited by a low temperature RF reactive magnetron sputtering. The deposited thin films were annealed for 2 hours at various temperatures of $50^{\circ}C$, $100^{\circ}C$, $150^{\circ}C$, $200^{\circ}C$ and $250^{\circ}C$ and were analyzed by using X-ray diffractometer, scanning electron microscopy and 4 point probe. The films annealed at temperatures higher than $150^{\circ}C$ were found to be crystallized and their electrical resistance were decreased from $40{\Omega}cm$to $18{\Omega}cm$. The optical transmittance of the film annealed at $150^{\circ}C$ was increased by over 87% in the 450 nm ~ 900 nm wavelength range. Our results indicate that the films with ITO deposited at even a low temperature can show better optical and electrical properties through a proper heat treatment.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.7
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• pp.205-215
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• 2013

In digital imaging system, Bayer pattern is widely used and the observed image is degraded by optical blur during image acquisition process. Generally, demosaicing and deblurring process are separately performed in order to convert a blurred Bayer image to a high resolution color image. However, the demosaicing process often generates visible artifacts such as zipper effect and Moire artifacts when performing interpolation across edge direction in Bayer pattern image. These artifacts are emphasized by the deblurring process. In order to solve this problem, this paper proposes a deblurring algorithm combined with edge directional color demosaicing method. The proposed method is consisted of interpolation step and region classification step. Interpolation and deblurring are simultaneously performed according to horizontal and vertical directions, respectively during the interpolation step. In the region classification step, characteristics of local regions are determined at each pixel position and the directionally obtained values are region adaptively fused. Also, the proposed method uses blur model based on wave optics and deblurring filter is calculated by using estimated characteristics of local regions. The simulation results show that the proposed deblurring algorithm prevents the boosting of artifacts and outperforms conventional approaches in both objective and subjective terms.

• Proceedings of the Korean Vacuum Society Conference
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• 1999.07a
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• pp.93-93
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• 1999

양자점(Quantum dot : QD)를 이용한 소자를 만들기 위해서는 수직방향으로의 적층이 필수적이다. 양자점의 적층은 수직적으로 같은 위치에 정렬하므로, 고려되어야 할 요소로는 양자점간의 파동함수의 중첩(coupling)에 의한 특성변화, 적층의 진행에 따른 변형(strain)의 증가로 기인되는 volcano 모양으로 나타나는 결함등이 있다. 이러한 결함은 nonradiative recombination center로 작용하여 오히려 효율이 떨어지게 되는 현상이 발생하게 되므로 본 연구에서는 적층횟수에 따른 발광효율의 변화를 조사하여 소자응용에 적절한 적층 조건을 조사하였다. 시료성장은 molecular beam epitaxy (MBE) 장치를 이용하여 GAs(100) 기판위에 GaAs buffer를 58$0^{\circ}C$에서 150nm 성장후 InAs/GaAs 양자점과 50$0^{\circ}C$에서 적층회수 1, 3, 6, 10, 15, 20회로 하였으며 적층성장 이후 GaAs cap layer를 성장하였다. GaAs spacing과 cap layer의 성장온도 역시 50$0^{\circ}C$이며 시료의 분석은 photoluminescence (PL)과 scanning transmission electron microscope (STEM)으로 하였다. 적층횟수를 바꾸어 시료를 성장하기 전에 적층횟수를 10회로 고정하고 spacing 두께를 2.8nm, 5.6nm, 11.2nm로 바꾸어 성장하여 PL 특성을 관찰하여본 결과 spacing이 2.8nm인 경우 수직적으로 정렬된 양자점 간에 coupling이 매우 커서 single layer QD의 PL peak에 비해 약 100nm 정도 파장이 증가하였고, spacing의 두께가 11.2nm 일 경우는 single layer QD와 거의 같은 파장의 빛을 방출하여 중첩이 거의 일어나지 않지만 두꺼운 spacing때문에 PL세기가 감소하였다. 한편, 적층회수에 따른 광학적 특성을 PL로 조사하여 본 결과 peak 파장은 적층횟수가 1회에서 3회로 증가했을 때는 blue shift 하다가 이후 적층이 증가함에 따라 red shift 하였다. 그리고 10층 이상의 적층에서는 excited state에서 기인된 peak이 검출되었다. 이렇나 원인은 적층수가 증가함에 따라 carrier life time이 증가하여 exciter state에 carrier가 존재할 확률이 증가하기 때문으로 생각된다. 또한 PL 세기가 다소 증가하다가 10층 이상의 경우는 다시 감소함을 알 수 있었다. 반치폭도 3층과 6층에서 가장 적은 값을 보였다. 이와 같은 결과는 결함생성과 관련하여 STEM 분석으로 해석되어질 수 있는데 6층 적층시는 양자점이 수직적으로 정렬되어 잘 형성됨을 관찰할 수 있었고 적층에 따른 크기 변화도 거의 나타나지 않았다. 그러나 10층 15층 적층시 몇가지 결함이 형성됨을 볼수 있었고 양자점의 정렬도 완전하게 이루어지지 않음을 볼 수 있었다. 그러므로 수직적층된 InAs 양자점의 광학적 특성은 성장조건에 따른 결함생성과 밀접한 관련이 있으며 상세한 논의가 이루어질 것이다.

• Progress in Medical Physics
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• v.12 no.1
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• pp.79-94
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• 2001

The fluorescence emanating from a biological tissue contains information about scattering, absorption and the intrinsic fluorescence (fluorescence only due to fluorophores). Becaue fluorescence spectra of biological tissue are often significantly affected by the presence of tissue absorbers and scatterers, the measured tissue fluorescence cannot be interpreted as a linear combination of intrinsic fluorescence spectra of different tissue biochemical. We conducted experiments to examine the influence of scattering and absorption on the experimentally measured fluorescence of a turbid medium such as biological tissue. Therefore, we acquired fluorescence and reflectance spectra of tissue phantoms with a wide range of scatterer and absorber concentrations. By applying a photon migration model, which uses the scattering and absorption information contained in reflectance spectra to remove their distortion also present in fluorescence spectra, we extract the intrinsic fluorescence of these tissue models. We achieved excellent agreement between modeled and actual intrinsic fluorescence spectra. The motivation for this research is that intrinsic fluorescence spectra are expected to change with progression of disease in human tissue, due to changes in the tissue biochemical composition. It is not possible to distinguish the two tissue types by using only the measured fluorescence, however clear separation can be achieved with the intrinsic fluorescence in real time optical biopsy.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.305-305
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• 2014

양자점(Quantum dots)은 3차원적 운반자 구속과 낮은 전류와 높은 온도에서 작동하는 나노 크기의 전기적, 광학적 소자로 응용이 적합하기 때문에 그 특성을 이용한 단전자 트랜지스터, 적외선 검출기, 레이저, LED, 태양전지 등 반도체 소자로의 응용연구가 활발히 진행되고 있다. 특히 양자점의 낮은 임계전류밀도와 높은 차동 이득(differential gain), 그리고 고온에서 작동이 용이하여 양자점 레이저로 활용되고 있다. 이러한 분야에 양자점을 응용하기 위해서는 양자점의 운반자 동역학을 이해하고 양자점의 모양, 크기, 크기 분포와 같은 특성 조절이 필요하다. 또한 기존의 연구들은 III-V족 화합물 반도체 양자점에 대한 연구가 대부분이며, II-VI족으로 구성된 연구가 미흡한 상황이기 때문에 II-VI족 화합물 반도체 양자점에 대한 많은 연구가 필요한 상황이다. II-VI 족 화합물 반도체 양자점은 기존의 III-V 족 양자점보다 더 큰 엑시톤 결합에너지(exciton binding energy)를 가지고 있으며, 이러한 특성을 가지는 II-VI 족 화합물 반도체 양자점 중에서도 CdTe 양자점은 높은 엑시톤 결합에너지와 녹색 스펙트럼 영역을 필요로 하는 광학적 장치들에 응용 가능성이 높기 때문에 더욱 주목받고 있다. 본 연구에서는 분자 선속 에피 성장법(Molecular Beam Epitaxy; MBE)과 원자 층 교대 성장법(Atomic Layer Epitaxy; ALE)으로 CdTe/ZnTe 나노구조에서 ZnTe 완충층의 두께에 따른 운반자 동역학 및 광학적 특성을 연구 하였다. 저온 광루미네센스 측정(Photoluminescence; PL) 을 통하여 ZnTe 완충층 두께가 증가할수록 양자점의 광루미네센스 피크가 낮은 에너지로 이동함을 알 수 있었는데, 이는 ZnTe 완충층의 두께가 증가할수록 ZnTe 완충층과 CdTe 양자점의 격자 불일치(lattice mismatch)로 인한 구조 변형력이 감소하고 이에 따라 CdTe 양자점으로 가해지는 변형(Strain)이 감소하여 CdTe 양자점의 크기가 증가했기 때문이다. 그리고 ZnTe 완충층의 두께가 증가할수록 PL 세기가 증가함을 알 수 있었는데, 이는 ZnTe 완충층의 두께가 증가할수록 양자 구속 효과로부터 electronic state와 conduction band edge 사이의 에너지 차이의 증가 때문이다. 또한 시분해 광루미네센스 측정 결과 ZnTe의 두께가 증가할수록 양자점의 소멸 시간이 더 길게 측정되었는데, 이는 더 큰 양자점 일수록 엑시톤 오실레이터 강도가 감소하기 때문에 더 긴 소멸 시간을 나타내는 것을 확인할 수 있었다. 결과적으로 본 연구는 ZnTe 두께 변화를 통해 양자점의 에너지 밴드를 제어할 수 있으며, 양자점의 효율 향상을 할 수 있는 좋은 방법임을 제시하고 있다.

• Journal of the Korean Chemical Society
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• v.36 no.6
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• pp.879-888
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• 1992

Separation of the optical isomers of free amino acids by a reversed phase high performance liquid chromatography has been studied by adding a copper(II) complex of L-proline or L-proline derivatives (hydroxy-L-proline, N-benzyl-L-proline, p-xylenyl-L-proline, p-xylenyl-hydroxy-L-proline) in the mobile phase. An OPA postcolumn detection system was used for the detection of amino acids. The chromatographic properties for the free amino acids were discussed in terms of the pH, the kinds and concentration of chelate or organic modifier. The retention behaviors of the free amino acids were considerably different from, those of DNS-amino acids or DABS-amino acids. The enantioselectivity of the free amino acids was better than that of derivatized amino acids. The enantioselectivity between the optical isomers observed by use of the Cu(II)-p-xylenyl-L-proline chiral cheleate was the best among the several copper(II) chelate. A separation mechanism could be illustrated not only by the hydrophobic interaction of the diastereomer with stationary phase but also by the steric effect of the ligand exchange reaction between the free-amino acids and copper chelate.

• Korean Journal of Optics and Photonics
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• v.26 no.1
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• pp.23-29
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• 2015

In this paper, we propose a microscope system for detecting both a tumor and blood vessels in brain tumor surgery as fluorescence images by using multiple light sources and a beam-splitter module. The proposed method displays fluorescent images of the tumor and blood vessels on the same display device and also provides accurate information about them to the operator. To acquire a fluorescence image, we utilized 5-ALA (5-aminolevulinic acid) for the tumor and ICG (Indocyanine green) for blood vessels, and we used a beam-splitter module combined with a microscope for simultaneous detection of both. The beam-splitter module showed the best performance at 600 nm for 5-ALA and above 800 nm for ICG. The beam-splitter is flexible to enable diverse objective setups and designed to mount a filter easily, so beam-splitter and filter can be changed as needed, and other fluorescent dyes besides 5-ALA and ICG are available. The fluorescent images of the tumor and the blood vessels can be displayed on the same monitor through the beam-splitter module with a CCD camera. For ICG, a CCD that can detect the near-infrared region is needed. This system provides the acquired fluorescent image to an operator in real time, matching it to the original image through a similarity transform.

• Journal of Digital Contents Society
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• v.10 no.2
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• pp.199-207
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• 2009

The Q-switching the shutter or the different optical science element puts in within the laser light resonator and the storehouse departs from the within the resonator it loses the mortar and the reversal distribution which when is sufficient creates from within the active medium, opens the shutter instantaneously and it is to do to be made to emit with the light where the energy which is accumulated within the resonator is strong very. Like this Q-switching of laser resonator--It decreases factor increasing suddenly to make. To method of Laser Q-switching mechanical switching methods, electro-optic switching methods and switching by saturable absorber methods, acousto-optic switching method etc. 4 kind are being used on a large scale. In these people the conversion which is electric in compliance with the effect which is electrooptics is widely being used the Q-switching pulse of short pulse width because being it will be able to create. Consequently, Pockel cell where it has the quality of electrooptics effect) the Q-it is become known that it is suitable it uses with switch. From the research which it sees FET and one-chip microprocessor where it is a switching element and pulse transfomer to plan and produce pockel cell Q-switch driving gears, pulse style Nd: It applied in YAG Laser system and it investigated and researched the operating characteristic of the Q-switch. Also, the Q-switch leads and Nd where it is output: YAG with forecast in compliance with a theoretical calculation it comes to buy laser beam side politics it compared and laser beam qualities which had become Q-switching it analyzed.

• Korean Journal of Optics and Photonics
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• v.28 no.3
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• pp.116-121
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• 2017

In this paper, a Raman spectrometer is designed to detect chemicals contaminating the ground. The system is based on Raman spectroscopy, which is spectral analysis of scattered light from chemicals, induced by a laser. The system consists of a transmitting-optics module with a laser to induce Raman-scattered light from the sample, a receiving-optics module to collect the scattered light, and a spectrograph to separate the collected light into a wavelength spectrum. The telescope, a part of the receiving-optics module, is designed to produce a focal spot in the same position for variable measurement distances using the code V simulator, considering the distance change between the system and the road. The Raman spectra of 12 chemicals on a glass surface and on a concrete sample were measured. Intensity differences between the Raman spectra acquired on a glass surface and on a concrete sample were observed, but the characteristics of the spectra according to the chemicals on them were similar. Additionally, the Raman spectrum of PTFE (polytetrafluoroethylene) was measured at various distances. The measured and simulated optical throughputs were similar. In conclusion, it is confirmed that with this system the Raman spectrum can be measured, irrespective of the distance change.

• Journal of the Korea Society of Computer and Information
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• v.26 no.4
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• pp.11-19
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• 2021

An abnormal object refers to a person, an object, or a mechanical device that performs abnormal and unusual behavior and needs observation or supervision. In order to detect this through artificial intelligence algorithm without continuous human intervention, a method of observing the specificity of temporal features using optical flow technique is widely used. In this study, an abnormal situation is identified by learning an algorithm that translates an input image frame to an optical flow image using a Generative Adversarial Network (GAN). In particular, we propose a technique that improves the pre-processing process to exclude unnecessary outliers and the post-processing process to increase the accuracy of identification in the test dataset after learning to improve the performance of the model's abnormal behavior identification. UCSD Pedestrian and UMN Unusual Crowd Activity were used as training datasets to detect abnormal behavior. For the proposed method, the frame-level AUC 0.9450 and EER 0.1317 were shown in the UCSD Ped2 dataset, which shows performance improvement compared to the models in the previous studies.