• Title/Summary/Keyword: Fringe Pattern

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Strain analysis of cantilever beam under eccentric force using holographic interferometry (홀로그래픽 간섭법을 이용한 편심하중에 의한 외팔보의 변형률분포 해석)

  • 박승옥;김홍석;권혁홍;조동현
    • Korean Journal of Optics and Photonics
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    • v.8 no.1
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    • pp.14-18
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    • 1997
  • Using holographic interferometry, strain distributions for a cantilever beam subjected to the eccentric force can be analysed. Holographic fringe pattern shows inclined straight lines for the composite deformation of bending and torsion. Using these inclinations of the fringe pattern, 3rd order polynomial of plane displacements can be determined without difficulty. As the result, both of axial and shear strain distribution can be obtained from the second partial derivatives of this polynomial. These results agree well with FEM.

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Vibration Analysis of Loudspeaker by Using Electronic Speckle Pattern interferometry (전자 스페클 간섭계에 의한 스피커 진동 해석)

  • 강영준
    • Journal of the Korean Society of Manufacturing Technology Engineers
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    • v.6 no.1
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    • pp.92-99
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    • 1997
  • Nowadays, Electronic Speckle Pattern Interferometry is a well-established measuring technique with a wide range of industrial applications, particularly in the fields of deformation measurement and vibration analysis. Comparing with holographic interferometry, it has some attractive features, which are rapid recording and reconstruction, satisfiable automation etc. The Time-Average ESPI is used to provide vibration mode shape of an object whose vibration amplitude is given as a fringe pattern. Its merit is rapid and simple measurement for vibrating object. However, it is not possible to determine the direction of motions of a point on the object at any given time, because it does not give any information about the phase of vibration. But, Stroboscopic ESPI can measure the amplitude and phase of vibrating surface. In this paper, loudspeakers were tested by these two methods. As a result, we can assume that these techniques will be applied directly in the loudspeaker industry.

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Surface contouring using Electronic Speckle Pattern Interferometry (전자 스페클 패턴 간섭계를 이용한 형상 측정)

  • 김계성;유원재;강영준
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 1995.10a
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    • pp.397-401
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    • 1995
  • ESPI(Electronic Speckle Pattern Interfermetry) is an optical technique to measure surface deforamtion of engineering components and materials in industrial ares. This optical method is capable of providing full-field results with high spatial resolution, high speed and is the non-contact technique. One of important application aspects using electronic speckle pattern interferometry is to generate contours of a diffuse object in order to provide data for 3-D shape analysis and topography measurement. The contouring method by modified dual-beam speckle pattern interferometry is proposed. We introduce a shift of the illumination beams through optical fiber in order to obtain the contour fringe patterns. The speckle pattern correlation technique is suitable for providing measurement range from millimeters to several centimeters. The complete geometric analysis of the contoretical and experimental results are obtained.

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A Study on the Measurement of 3-D object, make use of grid fringe generator (피치가변격자를 이용한 자유곡선 형상측정에 관한 연구)

  • 박윤창;정경민;박경근;장석준
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2000.11a
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    • pp.19-22
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    • 2000
  • Noncontact measuring methodology of 3-dimensional profile using CCD camera are very attractive because of it's high measuring speed and its's high sensitivity. Especially, when projecting a grid pattern over the object the captured image have 3 dimensional information of the object. Projection moire extract 3-D information with another grid pattern in front of CCD camera. However phase measuring profilometry(PMP) obtain similar results without additional grid pattern. In this paper, new method for grid pattern generation system by polygonal mirror and Laser Diode. This system is applied the projection moire and the PMP.

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A Study on the Strain Measuring of Structure Object (전자처리 및 Laser 간섭에 의한 구조물의 Strain측정에 관한 연구)

  • 김경석;최형철;양승필;정현철;김정호
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 1993.10a
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    • pp.267-272
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    • 1993
  • This paper presents the performance and problems in analysis method and testing system of Electronic Speckle Pattern Interferometry (ESPI) method, in measuring two-dimensional in-plane displacement. The anyalysis result of measurement by ESPI is quite comparable to that of measurement by strain gauge method. This implieds that the method of ESPI is a very effective tool in non-contact two-dimensional in-planc strain analysis. But there is a controversal point,measurment error. This error is discussed to be affected not by ESPI method itseif, but by its analysis scheme of the interference fringe,where the first-order interpolation has been applied to the points of strain measured. In this case, it is turned out that the more errors would be occured in the large interval of fringe. so, this paper describes a computer method for drawing when the height is available only for some arbitary collection of points, the method is based on a distance-weighted, least-squares approximation technique, with the weight varying with the distance of the data points.

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Ideal Phase map Extraction Method and Filtering of Electronic Speckle Pattern Interferometry (ESPI 에서의 이상적인 위상도 추출과 필터링 방법)

  • 유원재;이주성;강영준;채희창
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2001.04a
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    • pp.235-238
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    • 2001
  • Deformation phase can be obtained by using Least-Square Fitting. In extraction of phase values, Least-Square Fitting is superior to usual method like as 2, 3, 4-Bucket Algorithm. That can extract almost noise-free phase and retain 2$\pi$discontinuities. But more fringe in phase map, 2$\pi$ discontinuities is destroyed when that is filtered and reconstruction of deformation is not reliable. So, we adapted Least-Square Fitting using an isotropic window in dense fringe. using Sine-Cosine filter give us perfect 2$\pi$discontinuities information. We showed the process and result of extraction of phase map and filtering in this paper.

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Ray tracing simulation of SCOTS test for GMT secondary mirror

  • Kim, Ki-Won;Kim, Sug-Whan;Kim, Young-Soo
    • The Bulletin of The Korean Astronomical Society
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    • v.37 no.2
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    • pp.204.1-204.1
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    • 2012
  • We present SCOTS test simulation for on axis segment of the GMT secondary mirror that is ellipsoidal shape surface of 1.064m in diameter, 4.166747m in radius of curvature, -0.7154 in conic constant and $18.023{\mu}m$ P-V in asphericity. SCOTS test comprises a screen(diffusing sinusoidal fringe source), test surface(GMT secondary mirror), and a camera(CCD detector). We report ray tracing simulation result that is distorted sinusoidal fringe pattern detected at the camera. This simulation is to be used for analysis of experimental design, sensitivity from uncertainty, errors on fabrication and design.

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New Iterative Filter for Fringe Adjustment of Joint Transform Correlator

  • Jeong, Man-Ho
    • Journal of the Optical Society of Korea
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    • v.14 no.1
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    • pp.33-37
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    • 2010
  • The joint transform correlator (JTC) has been the best known technique for pattern recognition and identification. The JTC optically compares the reference image with the sample image then examines match or non-match by acquiring a correlation peak. However, the JTC technique has some problems such as weak correlation discrimination and noise which originates from the interference fringes in the Fourier transform plane. In order to solve these problems, this paper proposes a new technique of modifications of the interference fringes by adopting special iterative filters. Experimental results are presented to show that the proposed technique can successfully improve the correlation peaks and the level of discrimination.

Real-time 3-D shape measurement system using harmonics error removed digital fringe projection (하모닉스 에러가 제거된 디지털 프린지 투영을 사용한 실시간 3차원 형태 측정시스템)

  • Park, Won-Kyu;Kim, Byoung-Jin;Koh, Kwang-Sik
    • Proceedings of the Korea Information Processing Society Conference
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    • 2010.11a
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    • pp.629-632
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    • 2010
  • 본 논문에서는 Fringe Pattern profilometry(FPP)을 이용한 높이 측정 시스템을 구현하고, R, G, B 각 컬러 채널별로 위상이 다른 파형을 인가함으로써 Phase shifting 방법을 이용한 실시간 위상 정보를 획득할 수 있게 한다. 디지털 프로젝터의 비선형성으로 인해 필연적으로 발생하는 하모닉스 성분을 근사화된 정현파를 인가함으로써 높이 정보에서 가장 큰 문제를 발생하는 2차 하모닉스 성분을 줄인다. 이렇게 구한 위상 값을 Digital Phase Loop Lock(DPLL)회로에 인가함으로써 3차원 모양 정보를 실시간으로 획득 가능하게 한다.

A 3D measurement system based on a double frequency method using Fourier transform profilometry (FTP를 이용한 이중 파장법에 의한 3차원 형상 측정)

  • Koo, Ja-myoung;Cho, Tai-hoon
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.19 no.6
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    • pp.1485-1492
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    • 2015
  • This paper proposes a double frequency method using FTP(Fourier Transform Profilometry) in fringe projection techniques for 3D measurement systems. In fringe projection techniques, fringe pattern images are projected and captured, and then object is measured by analysing phase. PMP(Phase Measuring Profilometry) for analysing phase provides high-resolution and is robust to object's reflection and background intensities. However, the measurement range is narrow due to 2π ambiguity. In order to overcome this problem, a double frequency method is often used. This method can widen the range of measurement while maintaining the high-resolution, but the measurement time is taken about twice due to grab 2 times number of images. The proposed double frequency method using FTP requires an additional image for resolving 2π ambiguity. The proposed method effectively reduces the measurement time while maintaining the same accuracy.