• Proceedings of the KSME Conference
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• 2001.06d
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• pp.497-502
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• 2001

Three-dimensional natural convection from a discrete flush-mounted circular heat source on the bottom of a cubic enclosure was studied by using a holographic interferometric tomography. The heat source was located at the off-center of the bottom plate so that three-dimensional temperature field can be achieved. A set of multidirectional holographic interferogram was recorded by employing a double-reference beam, double-exposure holographic technique in order to eventually reconstruct the temperature fields. The recorded interferometric data appear good enough to be further processed to extract optical pathlength data from them and finally reconstruct the temperature fields. A complete analysis of the temperature fields including the field reconstructions and comparison with thermocouple measurements is underway and will be reported shortly.

• Journal of the Korean Society for Precision Engineering
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• v.15 no.12
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• pp.113-119
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• 1998

Recently Electronic Speckle Pattern Interferometry(ESPI) has been studied because it has the advantages to be able to measure the whole-field surface deformations of engineering components and materials in industrial areas with noncontact. The speckle patterns to be formed with interference phenomena of scattering light from rough surfaces illuminated by laser light have phase informations of surface deformations. In this study we used this interference phenomena and the phase shifting method to measure the inplane deformations, together with the use of digital image equipment to process the informations contained in the speckle pattern and to display consequent interferograms on TV monitor. FEA was performed before experiments and we obtained good agreement between the experimental results and FEA.

• Journal of the Semiconductor & Display Technology
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• v.4 no.1 s.10
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• pp.17-21
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• 2005

We presented a new method to obtain four speckle interferograms with relative phase shift of $\pi$/2 by passive devices such as waveplate and polarizer, calculate the phase at each point of the speckle interferogram in shearography using Wollaston prism, which can be applied to the deformation evaluation of semiconductor devices, and theoretically demonstrated the feasibility of the proposed method by Jones matrix.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.239-242
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• 2001

Electronic Speckle Pattern Interferometry(ESPI) was proposed in the 1970's as a method of producing the interferogram without using traditional holographic technique. ESPI is more faster than Holography method, because the interferometric image is recorded and updated by the video camera every 1/30 second and whold-field inspection possibly. In this study using a non-contact optical technique that is suited for in-plane and out-of-plane deformation measurement. Thin plate with crack was analyzed by ESPI to determine the characteristics of vibration mode shape and natural frequency. Also, results of the experiment were compared with Finite Element Method(FEM).

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.04a
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• pp.91-95
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• 1997

ESPI(Electronic Speckle Pattern Interferometry) is new optical measuring method to be able to measure the surface deformations of engineering components and materials in industrial areas. Conventional measuring method of surface deformation such as the strain gauge have many demerits because it is contact and point-to-point measuring one. But ESPI that is non-contact, whole field measuring method can overcome previous disadvantages. The speckle pattern to be formed with interference phenomena of scattering light from rough surfaces illuminated by laser light have phase information of surface In this study we used this interference phenomena and the phase shifting method to measure the in- plane deformation, together with the use of digital equipment to process the information contained in the speckle pattern and to display consequent inter ferograms. Finally we obtained good agreement between the experimenta results and those of FEM..

• Proceedings of the Optical Society of Korea Conference
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• 2007.07a
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• pp.307-308
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• 2007

We present a novel chromatic dispersion measurement method using a spectral domain interferometer for single mode optical fiber over a wide spectral range (200 nm). This technique is based on the Mach-Zehnder interferometer using a white light source and spectrometer. A phase was directly retrieved from a measured spectral interferogram to obtain relative group velocity, chromatic dispersion and dispersion slope. The measured results with the proposed method were compared with those obtained using a conventional measurement method. Those results have good agreement with each other. Our proposed method can simply, accurately, and quickly (< 500 ms) measure chromatic information for a short length of optical fiber as well as optical device.

• Journal of the Optical Society of Korea
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• v.15 no.2
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• pp.111-117
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• 2011

Full-range spectral domain optical coherence tomography (SD-OCT) with a 1-${\mu}m$ band light source is shown here. The phase of the reference beam is continuously stepped while the probing beam scans the sample laterally (B-scan). The two dimensional spectral interferogram obtained is processed by a Fourier transform method to obtain a complex spectrum leading to a full-range OCT image. A detailed mathematical explanation of the complex conjugate resolving method utilized is provided. The system's measurement speed was 7.96 kHz, the measured axial resolution was $9.6{\mu}m$ in air and the maximum sensitivity 99.4 dB. To demonstrate the effect of mirror image elimination, In vivo human eye pathology was measured.

• Journal of Astronomy and Space Sciences
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• v.14 no.1
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• pp.117-125
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• 1997

A Fabry-Perot interferometer has a very high (~1,000,000) resolution, so recently this has been widely used for many fields of space science. To understand the working principle of this a mathematical modeling is needed, and to analyze the interferogram it is essential to know the precise instrument function. The spectrum from the interferometer is mixed with a true signal from the light source and the instrument function through convolution. The true signal has the information about the quantum state of mo lecules, temperature and bulk motion of the gas. Therefore if we model the signal and convolve this with the theoretical instrument function we can predict the spectrum for the real case.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.18 no.6
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• pp.8-13
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• 2004

We presented the method to obtain four speckle interferograms with relative phase shift of $\pi$/2 by passive devices such as waveplate and polarizer, calculate the phase at each point of the speckle interferogram in shearography using Wollaston prism, and theoretically demonstrated the feasibility of the unposed method by Jones matrix.

• Proceedings of the KSRS Conference
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• 2000.04a
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• pp.91-95
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• 2000

위성영상을 이용한 해안선의 추출은 연안 지형의 변화감지의 조간대의 DEM 생성 등 지구과학적인 활용 외에도 지형도와 해도의 수정에도 활용될 수 있다. 바람이 세거나 파랑이 높을 때 돌아오는 레이다의 신호는 육지와 구별이 어렵고 또한 speckle 잡음으로 인하여 SAR를 이용한 해안선 추출은 광학자료에서 사용하는 thresholding 방법이나 간단한 edge detector 등의 방법을 적용하여 좋은 결과를 얻는데 어려움이 있다. 본 연구에서는 SAR 자료를 이용하여 빠르고 정확하게 해안선을 추출할 수 있는 ratio에 기초한 해안선 추출 방법인 MSP-PoA(Maximum Stregth Edged Pruning Ratio of Average)을 경남 낙동강 하구지역의 인공해안선에 대해 적용하여 결과를 분석하였다. 그 결과는 매우 만족할 만 하나, 육지와 해수의 점이적인 특성을 나타내는 조간대가 분포하는 전남 곰소만 지역에서는 SAR intensity의 변화가 크지 않아서 만족할 만한 결과를 얻을 수 없었다. 이러한 지역에 대해서는 SAR의 위상정보를 이용하는 interferogram의 정확도를 정량적으로 평가하는데 사용되는 coherence map을 구하여 해안선을 추출하고자 한다.