• Journal of the Korean Society for Nondestructive Testing
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• v.27 no.6
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• pp.556-562
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• 2007

This paper presents the use of a novel fiber optic accelerometer system to monitor ambient vibration (both wind-induced one and vehicle-induced) of a real bridge structure. This sensor system integrates the $Moir\'{e}$ fringe phenomenon with fiber optics to achieve accurate and reliable measurements. A low-cost signal processing unit implements unique algorithms to further enhance the resolution and increase the dynamic bandwidth of the sensors. The fiber optic accelerometer has two major benefits in using this fiber optic accelerometer system for monitoring civil engineering structures. One is its immunity to electromagnetic (EM) interference making it suitable for difficult applications in such environments involving strong EM fields, electrical spark-induced explosion risks, and cabling problems, prohibiting the use of conventional electromagnetic accelerometers. The other is its ability to measure both low- and high-amplitude vibrations with a constantly high resolution without pre-setting a gain level, as usually required in a conventional accelerometer. The second benefit makes the sensor system particularly useful for real-time measurement of both ambient vibration (that is often used for structural health monitoring) and strong motion such as earthquake. Especially, the semi-strong motion and the small ambient one are successfully simulated and measured by using the new fiber optic accelerometer in the experiment of the structural health monitoring of a real bridge.

• Journal of the Korean Society for Nondestructive Testing
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• v.26 no.6
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• pp.373-379
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• 2006

Vibration-based structural health monitoring is one of non-destructive evaluation (NDE) techniques for civil infrastructures. This paper presents a novel fiber optic accelerometer system to monitor civil engineering structures and a successful application of the novel sensor system for measuring ambient vibration of a real building structure. This sensor system integrates the Moire fringe phenomenon with fiber optics to achieve accurate and reliable measurements. The sensor system is immune to electromagnetic (EM) interference making it suitable for difficult applications in such environments involving strong EM fields, electrical spark-induced explosion risks, and cabling problems, prohibiting the use of conventional electromagnetic accelerometers. A prototype sensor system has been developed, together with a signal processing software. The experimental studies demonstrated the high-performance of the fiber optic sensor system. Especially, the sensor was successfully used for monitoring a real building on UCI (University of California Irvine, USA).

• The Journal of Korean Institute of Communications and Information Sciences
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• v.11 no.1
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• pp.1-15
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• 1986

Optic flow is 2D velocity projected on the image plane of 3D velocity of a moving surface element. In this paper, we survey techniques computing optic flows from an image time sequence of moving objects and techniques determining 3D velocities and surface structures of the moving objects from the optic flows determined.

• 제어로봇시스템학회:학술대회논문집
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• 1996.10b
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• pp.1149-1152
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• 1996

Recently visual servo control is an important feature of an intelligent robot system. In this paper, we presents a Kalman filter approach for estimation of the linear optic flow model which is utilized in the visual servoing of a mobile robot. The proposed method is also compared with the conventional least mean square method via computer simulation.

• Journal of Biomedical Engineering Research
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• v.16 no.1
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• pp.43-48
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• 1995

A high speed optic scanner capable of 16 frames/sec imaging has been developed for the realization of the infrared thermal Imaging system with a single element infrared sensor. The high speed optic scanner is composed of a rotating polygon mirror for horizontal scanning, a flat mirror mounted on a galvanometer for vertical scanning, and a spherical mirror. It has been experimentally found that the optic scanner is capable of 16 framesllsec imaging with the frame matrix size of 256 x 64.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.10a
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• pp.717-723
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• 2002

Recently, the interest in safety assessment of civil infrastructures is increasing in Korea. Especially, as bridge structures become large-scale, it is necessary to monitor and maintain the safety state of bridges, which requires the monitoring system that can make a long-term measurement during the service time of bridge. In this paper, advanced fiber optic sensors for long-term measurement, setup techniques of bridge monitoring system and the assessment of measured data are introduced. Attached or embedded optical fiber sensors to structural members of small and big structures including Sung San Bridge are surveyed. For the Sung San Bridge, the responses of the fiber optic sensors by 30 ton weigh truck loads with various speeds ate measured. Monitoring system is also applied to the mock-up of bridges. The monitoring capability of the advanced fiber optic sensor system was confirmed.

• Journal of Biomedical Engineering Research
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• v.15 no.1
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• pp.97-104
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• 1994

In the conventional infrared imaging system, complex infrared lens systems are usually used for directing collimated narrow infrared beams into the high speed 2-dimensional optic scanner. In this paper, a simple reflective infrared optic system with a 2-dimensionaloptic scanner is proposed for the realization of medical infrared thermography system. It has been experimentally proven that the infrared thermography system composed ofthe proposed optic system has the temperature resolution of $0.1{\circ}C$ under the spatial resolution of 1mrad, the image matrix size of $256{\times}240$, and the imaging time of 4 seconds.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.21 no.6
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• pp.1596-1603
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• 1996

A single body type of fiber-optic current and voltae sensor using a rare earth doped YIG and a bismuth silicon oxide single crystsl is proposed, which is used for simultaneous measurement of the AC electric current and AC electric voltage over the trasmission lines. Experimental results showed that the fiber-optic current sensor has the maximum 7.5% error within the current range of 0A to 400A, and the fiber-optic voltage sensor has the maximum 0.87% error within the current range of 0V to 400V. The output waveforms of proposed fiber-optic sensor system has a good agreement with output waveforms of conductor current and voltage. Experimental results proved that the output of fiber-optic current sensor is not affected by the electric voltage applied to the fiber-optic voltage sensor, and also, that the output of fiber-optic voltage sensor is not affected by the electric current applied to the fiber-optic current sensor.

• Proceedings of the KIEE Conference
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• 1998.07e
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• pp.1843-1845
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• 1998

Gyroscope is a very important core sensor as a rotation sensor in inertial space, in inertial guidance and navigation system on aeronautics. Plane, vessel and so on for civilian and millitary applications. Research and development of fiber optic gyroscope began in 1976 and focused on improving the gyroscope's sensitivity to rotation. bias performance and reducing noise. We have developed a Interferometric Fiber Optic' Gyroscope using a integrated-optic-circuit (IOC), which is operating with closed-loop electronic circuit. This paper describes the scheme of optical part and electronic part and also test results of this fiber optic gyroscope using a integrated-optic-circuit (IOC). The performance have been achieved as long-term bias drift of $1.73^{\circ}/h$.

• Journal of the Korean Society for Nondestructive Testing
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• v.28 no.2
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• pp.157-163
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• 2008

This paper presents a novel fiber optic tiltmeter system for the health monitoring of large-size structures. The system is composed of a sensor head, a light control unit and a signal processing unit. The sensing mechanism of the sensor head is based on a novel integration of the moire fringe phenomenon with fiber optics to achieve a robust performance in addition to its immunity to EM interference, easy ratting, and low cost. In this paper, a prototype of the fiber optic tiltmeter system has been developed successfully. A low-cost light control unit has been developed to drive the system's optic and electronic components. From an experimental test, the fiber optic tiltmeter is proven to be a prospective sensor for the monitoring of the tilting angle of civil structure with a good linearity. Finally, the test also successfully demonstrates the performance and the potential of the novel fiber optic tiltmeter system to monitor the health of civil infrastructures.