• Journal of Biomedical Engineering Research
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• v.21 no.3 s.61
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• pp.233-237
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• 2000

In general. fiber-optic medical endoscopes are made from glass step index (SI) fibers. These endoscopes have limitations in both image quality and mechanical properties. In particular. the image resolution of the SI endoscopes is limited to about 5$\mu$m. In this study the image resolution of plastic graded index (GRIN) super-resolution image guides with pixel sizes from 7 to 2.5 $\mu$m were measured and compared with those of 91ass SI image guides. There is an improvement in resolution of the plastic GRIN image guides as the microfiber diameter is reduced from 7 $\mu$m to 2.5 $\mu$m. The measured resolution of plastic GRIN image guide with 2.5 $\mu$m microfibers is more than a factor of two higher than that of g1ass SI image guide with 5$\mu$m microfibers. This new design of optical systems could have a major impact on a wide array of future optical systems used in defense. industrial, and medical applications.

• Journal of Korean Ophthalmic Optics Society
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• v.13 no.3
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• pp.61-64
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• 2008

Purpose: The analysis of individual eye model designed from clinical demonstration about emmetropia shows that the aberration would be changed by the wave change. Method: The model on the basis of clinical demonstration of eye ball is designed in a form of having 4 refraction surfaces and a constant refractive index. We analyzed designed twelve individual eye model into aberrations changes, as giving changes Fraunhofer lines's six wavelengths. Result: About individual eye model, change in the wavelength of the wavefront aberrations analysis using the Zernike coefficient. This data indicate that the shorter wave is, the more defocus increases and the deviation value of spherical aberration and RMS are widened. Conclusion: As quantity of defocus according to result wavelength change is shorter and shorter, inclination which is similar twelve individual eye model is bigger and bigger and individual eye model majority of cases, little change, and change is shown in part individual eye model is a significant performance degradation can be raised.

• 한국어정보학회:학술대회논문집
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• 2016.10a
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• pp.285-290
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• 2016

한국어는 형태론적으로 굴절어에 속하는 언어로서, 어휘의 형태가 문장 속에서 문법적인 기능을 하게 되고, 형태론적으로 풍부한 언어라는 특징 때문에 조사나 어미와 같은 기능어들이 다양하게 내용어들과 결합한다. 이와 같은 특징들은 한국어를 대상으로 하는 구 기반 통계적 기계번역 시스템에서 데이터 부족문제(Data Sparseness problem)를 더욱 크게 부각시킨다. 하지만, 한국어의 몇몇 조사와 어미는 함께 결합되는 내용어에 따라 의미는 같지만 두 가지의 형태를 가지는 이형태로 존재한다. 따라서 본 논문에서 이러한 이형태들을 하나로 표준화하여 데이터부족 문제를 완화하고, 베트남-한국어 통계적 기계 번역에서 성능이 개선됨을 보였다.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.474-474
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• 2013

PDMS는 미세패턴을 위해 소프트 리소그래피 널리 활용되어질 뿐만 아니라, 재질이 투명하고 탄성과 강한 내구성을 갖고 있어 유연한 광학 및 전자소자에 이용될 수 있다. 최근에는, 이러한 PDMS를 서브파장구조(subwavelength grating structure)를 형성하거나 텍스쳐(texture)표면구조를 이용한 효과적인 반사방지막(antireflection coating)기판을 제작하여 태양전지 및 디스플레이 소자의 성능을 발전시키는 연구가 활발히 진행되고 있다. 한편, 수열합성법(hydrothermal method)이나 전기화학증착법(electrodeposition method)으로 비교적 간단한 공정을 통해서 다양한 기판위에 산화아연(ZnO) 나노막대(nanorod)를 수직정렬로 성장시킬 수 있는데, 이러한 구조는 반사방지특성의 유효 굴절률 분포(effective refractive index profile)를 갖고 있기 때문에 LED나 태양전지에 성능을 개선할 수 있다. 이에 본 연구에서는 수열합성법을 통해 성장된 수직 정렬된 산화아연 나노막대를 이용한 PDMS 표면의 미세패턴 형성하여 광학적 특성을 분석하였다. 실험을 위해, 스퍼터링을 통해서 산화아연 시드층을 형성한 후, 질산아연헥사수화물과 헥사메틸렌테트라민을 수용액에 담가두어 산화아연 나노막대를 성장시켰으며, PDMS의 베이스와 경화제의 질량비를 10：1으로 용액을 준비하여 수직 정렬된 산화아연 나노막대 표면을 casting method으로 코팅하여 열경화 처리하였다. 제작된 샘플의 형태, 구조 광특성을 관찰하기 위해서 전계방출형전자현미경, X선 회절 분석기, 분광 광도계를 이용하였다.

• Journal of the Korean Society for Railway
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• v.12 no.1
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• pp.122-128
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• 2009

A bimodal low-floor tram is designed to provide the flexibility of bus and the punctuality of trains together to the passengers. The propulsion equipment of the bimodal tram is a series hybrid type using a set of CNG engine generator and Li-polymer battery. The present paper describes the specifications of the propulsion system in the bimodal tram which was drawn by a desirable driving cycle. In addition, it shows how the propulsion system of the bimodal tram can be controlled. With using a computer simulation tool of hybrid vehicles, ADVISOR, the performance of the bimodal tram was verified.

• The Bulletin of The Korean Astronomical Society
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• v.39 no.2
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• pp.121.2-121.2
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• 2014

2013년 설립된 부산일과학고등학교 천문대는 교육 및 연구목적으로 12인치 굴절망원경, 16인치 반사망원경 및 다수의 소형망원경들이 설치되어 있다. 우리는 본격적인 관측, 연구를 수행하기에 앞서 망원경의 다양한 성능을 검증하여 향후 연구 활동에 기초자료로 사용하고자 한다. 본 연구에서는 망원경에 4K CCD 및 DSLR을 장착하여 얻은 관측 영상으로부터 망원경의 추적 특성, 지향정밀도, 광학적 특성을 고찰하고, Landolt (1992)의 표준성을 이용한 BV측광을 수행하여 표준계변환의 특성을 조사하였다. 또한 산개성단의 BV관측을 통해 한계등급을 측정하였다. 이 연구결과로부터 향후 부산일과학고등학교 천문대에서 수행할 수 있는 적합한 관측 연구의 방향을 제시한다.

• Annual Conference on Human and Language Technology
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• 2016.10a
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• pp.285-290
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• 2016

한국어는 형태론적으로 굴절어에 속하는 언어로서, 어휘의 형태가 문장 속에서 문법적인 기능을 하게 되고, 형태론적으로 풍부한 언어라는 특징 때문에 조사나 어미와 같은 기능어들이 다양하게 내용어들과 결합한다. 이와 같은 특징들은 한국어를 대상으로 하는 구 기반 통계적 기계번역 시스템에서 데이터 부족 문제(Data Sparseness problem)를 더욱 크게 부각시킨다. 하지만, 한국어의 몇몇 조사와 어미는 함께 결합되는 내용어에 따라 의미는 같지만 두 가지의 형태를 가지는 이형태로 존재한다. 따라서 본 논문에서 이러한 이형태들을 하나로 표준화하여 데이터부족 문제를 완화하고, 베트남-한국어 통계적 기계 번역에서 성능이 개선됨을 보였다.

• Journal of the Institute of Convergence Signal Processing
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• v.6 no.2
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• pp.59-66
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• 2005

Accuracy of current measurement in fiber optic current sensor(FOCS), especially, unidirectional polarimetric fiber optic current sensor(PFOCS) is affected by the environment perturbations such as acoustic vibrations changes to the sensing fiber, and intrinsic perturbations such as the bending fiber that the sensing fiber wound around a current carrying wire. The perturbations affect the birefringence properties of sensing fiber in sensor head and cause false current readings. Thus, using compensation technique, reciprocal PFOCS, for unidirectional PFOCS the perturbations are suppressed. In this paper, we carried out the numerical analysis of performance in reciprocal PFOCS including the degree of polarization error, and false current of environmental and intrinsic perturbations on the sensing fiber. Also, we compared the effect of mirror with the faraday rotation mirror(FRM) in reciprocal PFOCS configuration. And the different optical source's wavelengths, 633nm and 1300nm is used. In the results, at 633nm, using mirror and FRM, the degree of polarization error is calculated to $2.3\%$ and $0.0196\%$, respectively. At $1300{\cal}nm$ using mirror and FRM the degree of polarization error is calculated to $9.97\%$ and $0.0196\%$, respectively. Also, compared with false current, the results is calculated to $9.82{\times}10^{-9}A$ and $1.4{\times}10^{-17}A$, respectively, and show that the reciprocal PFOCS is more robust configuration than unidiretionnal PFOCS for environmental and intrinsic perturbations.

• Korean Journal of Optics and Photonics
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• v.26 no.2
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• pp.88-97
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• 2015

An omnidirectional optical system can be described as a special optical system that images in real time a panoramic image with an azimuthal angle of $360^{\circ}$ and the altitude angle corresponding to the upper and lower fields of view from the horizon line. In this paper, for easy fabrication and compact size, we designed and fabricated a catadioptric omnidirectional optical system consisting of the mirror part of a spherical mirror with a central hole (that is, obscuration), a plane mirror, the imaging lens part of 3 single spherical lenses, and a spherical doublet in the visible light spectrum. We evaluated its image performance by measuring the cut-off spatial frequency using automobile license plates, and the vertical field of view using an ISO 12233 chart. We achieved a catadioptric omnidirectional optical system with vertical field of view from $+53^{\circ}$ to $-17^{\circ}$ and an azimuthal angle of $360^{\circ}$. This optical system cleaniy imaged letters on a car's front license plate at the object distance of 3 meters, which corresponds to a cut-off spatial frequency of 135 lp/mm.

• Korean Journal of Optics and Photonics
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• v.32 no.2
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• pp.68-78
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• 2021

A subminiature catadioptric omnidirectional optical system (SCOOS) with 2 mirrors, 6 plastic aspherical lenses, and an illumination system of 6 light emitting diodes, to observe the 360° panoramic image of the inner intestine, is optically designed and evaluated for a capsule endoscope. The total length, overall length, half field of view (HFOV), and F-number of the SCOOS are 14.3 mm, 8.93 mm, 51°~120°, and 3.5, respectively. The optical system has a complementary metal-oxide-semiconductor sensor with 0.1 megapixels, and an illumination system of 6 light-emitting diodes (LEDs) with 0.25 lm to illuminate on the 360° side view of the intestine along the optical axis. As a result, the spatial frequency at the modulation transfer function (MTF) of 0.3, the depth of focus, and the cumulative probability of tolerance at the Nyquist frequency of 44 lp/mm and MTF of 0.3 of the optimized optical system are obtained as 130 lp/mm, -0.097 mm to +0.076 mm, and 90.5%, respectively. Additionally, the simulated illuminance of the LED illumination system at the inner surface of the intestine within HFOV, at a distance of 15.0 mm from the optical axis, is from a minimum of 315 lx to a maximum of 725 lx, which is a sufficient illumination and visibility.