• Proceedings of the Korean Geotechical Society Conference
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• 2000.11b
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• pp.223-232
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• 2000

Optical fibre sensors have shown a potential to serve real time health monitoring of the structures. They can be easily embedded or attached to the structures and are not affected by the electro-magnetic field. Furthermore, they have the flexibility of the sensor size and very highly sensitive. In this study, we conducted several laboratory and field tests using a novel optical sensor based on Brillouin scattering. One of the advantages of this technique is that the bare fibre itself acts as sensing element without any special fibre processing or preparation. Test results have shown that BOTDR can be a great solution for sensor systems of Civil Engineering Smart Structures.

• Journal of ILASS-Korea
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• v.10 no.3
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• pp.17-28
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• 2005

The Holographic Particle Velocimetry system can be a promising optical tool for the measurements of three dimensional particle velocities. In this study, diffused illumination holographic system to measure the sizes and 3D velocities of moving particles based on automatic image processing was developed. First of all basic optical systems for pulse laser recording, continuous laser reconstruction, and image acquisition, were constructed. To determine the position of particles in the optical axis, new three auto-focusing parameters(AEP), namely, Correlation Coefficient, Sharpness Index, and Depth Intensity were introduced and verified. The developed system was applied to spray droplets to validate the capability of the system. Three dimensional positions of particles viewed from two sides were decided using AFP and then 3D velocities of Particles were extracted by particle tracking algorithm. Comparison of measurement results of sizes and 3D velocities of particles with those obtained by laser instrument, PDPA, showed good consistency of the developed holographic system.

• Proceedings of the Optical Society of Korea Conference
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• 2008.02a
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• pp.427-428
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• 2008

In this paper, we propose an BRDF measurement method based on laser light scattering, which is very effective for roughness measurement. The measurement setup has a very simple configuration, which consists of a collimated green laser, a detector. The experimental tests show that the BRDF measurement has difference between good Au Pad and bad Au Pad.

• The Magazine of the IEIE
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• v.38 no.1
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• pp.44-49
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• 2011

다중채널 압축센싱(multi-channel compressive sensing) 문제는 0이 아닌 성분이 공통된 위치에 분포하는 벡터들을 복원하는 방법을 다루는 문제이며 레이다의 도착방향 추정 문제, 역산란 문제, 산란광 단층촬영과 같은 많은 실용적인 문제에 응용될 수 있다. 압축 센싱 문제는 성긴(sparse) 속성을 갖는 벡터를 상당히 높은 확률로 복원시킬 수 있음이 밝혀져 있다. 이로 인해 기존의 압축 센싱 방법이 다중채널 압축센싱에서도 많이 활용되어 왔으며, 측정 벡터의 개수가 적을 때에도 높은 확률로 입력 신호를 복원할 수 있다. 그러나, 측정 벡터의 개수가 많아질수록, 기존의 압축센싱 알고리즘을 이용했을 때의 성능은 복수신호분리 (MUSIC) 알고리즘과 같이 배열신호처리(array signal processing)에서 활용되는 방법을 적용했을 때보다 더 나쁜 특성을 보인다. 이러한 기존 방법의 문제점으로 인해 우리는 새로운 다중채널 압축센싱 알고리즘을 제시하고자 하며, 이는 기존의 압축센싱 이론과 배열 신호처리 알고리즘을 개별적으로 적용할 때 가지는 한계를 극복할 수 있게 해준다.

• Journal of the Semiconductor & Display Technology
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• v.9 no.4
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• pp.31-37
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• 2010

In this paper, optical deflection of laser scattering has been investigated based on Rayleigh criterion for crystalline silicon wafer in solar cell. A laser scattering mechanism is newly designed using light scattering properties in silicon wafer. Intensity distributions of laser scattering are different, depending on the incident angle of laser computed from Rayleigh criterion. In case of the incident angle satisfied with the criterion, they are asymmetric. Also, their specular reflection angle is shifted to unpredicted ones. These phenomena are in accordance with previous theories of laser scattering. The optical deflection of laser scattering is experimentally identified with the designed laser scattering mechanism. Its mathematical model is presented from the geometric relationship of laser scattering. It is shown that the optical deflection of laser scattering agree with the presented model, exclusive of grazing angles which is satisfied with Rayleigh criterion.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.2
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• pp.267-280
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• 1992

This paper describes a numerical analysis of the light scattering patterns of roughness profiles. This analysis was based upon the light scattering theory developed by Beckmann. In the analysis, the roughness profile was regarded as a profile whose irregularities depend on the production process and the shape of cutting tool. Generally, waviness of an actual surface seriously distorts the scattered pattern of roughness profile. In order to avoid the effects of waviness of actual surfaces, several theoretically calculated scattering patterns, instead of actual scattering patterns, were used to analyze the scattering patterns of typical engineering roughness profiles. The characteristics of the light scattering patterns for five model surfaces were studied.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.1558-1559
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• 2007

This study is an application field by using optical fiber. The system to measure sBs from optical fiber is designed, So it can be used as a temperature sensor. by using frequency shift, resulting from temperature changes. the frequency shift is checked by changing temperature from $25^{\circ}C$ to $69^{\circ}C$ with chamber in the laboratory and using 40Km optical fiber. It's also measured by varying the length of optical fiber The program to do the real-time monitoring and analyze the measured data is created to find accurate frequency. It can be used as an optical fiber sensor, which is capable of measuring temperature and distance by using sBs.

• Korean Journal of Optics and Photonics
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• v.3 no.3
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• pp.167-171
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• 1992

We present the static and dynamic light scattering results of the salt induced restructured colloidal silica aggregates. We also report the results from the transmission electron micrographs which confirms the individual sizes of the particles and the local structure of the ramified aggregates. The fractal dimensions of the restructuring silica aggregates are considerably different with in-situ light scattering measurements. The measured fractal dimensions, $D_{F}$, is 2.21 for the 0.5 wt.% concentration of the salt induced Ludox-AM. The Rayleigh linewidth for 0.1 wt.% concentration of Ludox-AM is discussed.

• Korean Journal of Optics and Photonics
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• v.9 no.1
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• pp.31-37
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• 1998

We fabricated acrylamie photopolymer holographic recording materials by photopolymerization of acrylamide, and described hologram formation process. Light absorption and phtobleaching process by MB(methylene blue) dye and radical polymerization process due to TEA(triethanolamind) are explained in detail. We adopted the Beer-lambert law in order to explain the photobleaching kinetics. Dependencies of diffraction efficiency of the hologram on monomer amout and the exposure are investigated. The scattering effect caused by grain of polymer crystal, and fixing method are also illustrated.

• Proceedings of the Optical Society of Korea Conference
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• 2003.07a
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• pp.278-279
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• 2003

광도의 기본 단위인 칸델라(Candela) 눈금은 물론 복사조도(irradiance), 조명도(illuminance)와 같은 유도 단위를 실현하기 위해서는 검출기의 시야를 한정하는 개구면적의 정밀한 측정이 필요하다. 여기에서는 가장자리의 광학적 검출방법에 의한 개구면적의 산출방식을 소개하고, 가우시안광에 의한 면적 측정법의 측정값과도 비교하여 그 결과를 보여준다. 기존의 개구 면적 측정방식으로 한가지 방법은 탐촉자를 물리적으로 접촉시켜서 개구의 가장자리를 결정하고, 개구의 기하학적 모양을 원으로 가정하여 면적을 산출하는 방식이 있는데, 이 방법을 사용하면 기계적인 접촉에 의하여 칼날과 같았던 개구의 가장자리가 손상을 입게 되기 때문에 측정이 잘못되는 것은 물론이고, 이렇게 측정된 개구를 사용하게되면 손상된 부위에 의한 면적의 변화와 이로 인한 산란이 증가하게 된다. (중략)