• Title/Summary/Keyword: Speckle size

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An Adaptive Pseudomedian Filter for the Ultrasound Medical Image Processing (진단 초음파 영상 처리를 위한 적응 Pseudomedian 필터)

  • Eo, Jin-Woo;Hur, Eun-Seok
    • Journal of IKEEE
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    • v.7 no.2 s.13
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    • pp.271-280
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    • 2003
  • This paper presents an effective method to segment objects from the ultrasound medical image which is inherently corrupted by speckle noise. In order to reduce the speckle noise morphological opening was used as preprocessing. For the preprocessed image, sample variance of neighborhood pixels is to be computed to classify where the pixel is located on the edge region or homogeneous region. Then pseudomedian filtering with different window size is taken according to the region classified, named adaptive pseudomedian filter. Various experimental results were presented to prove superiority of the proposed filter.

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Measurement of 3-D Deformation by Using Holospeckle Interferometry (홀로스펙클 간섭법을 이용한 3차원 변형측정 연구)

  • 박승옥;권영하;유성규
    • Korean Journal of Optics and Photonics
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    • v.1 no.1
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    • pp.12-15
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    • 1990
  • Holospeckle interferometry, the combined technique of holographic interferometry and speckle photography, was applied to the measurement of 3-D contact deformation created by an indentor. This new tech$.$ nique makes possible to measure both in-plane and out-of-plane displacements from one photographic plate. In this study, the optical system based on image holography was set up. In order to enhance the size and the contrast of the speckle, a proper magnification and a low reference beam ratio was used as compared with the conventional holographic interferometry technique. This system shows the magnified and clear holographic interference fringe as well as Young's fringe patterns.tterns.

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Mean time delay variation performane of DTTL bit synchronizer (DTTL 비트동기장치의 평균시간지연 편차 성능에 관한 연구)

  • 김관옥
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.22 no.11
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    • pp.2401-2408
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    • 1997
  • The measured pulse shapes provided in the given data package demonstrated pulse distortions due to laser speckle. the distorted pulse shapes were carefully analyzed, modeled, and then applied to the DTTL(Digital-data Transition Tracking Loop)[1] bit synchronizer simulator to measure the mean time delay and its delay variation performance. The result showed that the maximum mean time delay variation with the modeled data was 12.5% when window size equals 1. All the data given were located within this modeled boundary and the maximum eman time delay variation was 7% in this case. The mean time delay variation was known to be smaller by reducing the window size [2][5][6]. The mitigated delay variation was 2.5% in the modeled case and 1.4% in the data set given when the windown size equals 0.1. With the digital DTTL insteal of analog DTTL, similar results was obtained.

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The analysis of interferometry fringe pattern under shearing quantity and inside pressure change for inspect inside defects using by digital shearography (Digital shearography를 이용한 내부결함 검출에 있어서 전단량과 내부압력 변화에 따른 간섭줄무늬 패턴 분석)

  • 김형택;김경석;홍진후;강기수
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2001.04a
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    • pp.140-143
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    • 2001
  • Digital shearography, a speckle pattern method is based on the superposition of two laterally sheared images. Therefore, object points which are positioned in some distance from each other are superposed in the image plane. This shearography, one of NDT methods without contact, is able to inspect defects in pipelines and pressure vessels that are used in nuclear power plants. This is can inspect whole fields and has a low sensitivity to environmental noise. Because optical setting is very simple, it has a little exhaustion of time, cost and man power. And also it can find a defect position through real time monitoring of a part. This paper, finds out the relationship among shearing quantity image quality and defect size with this method.

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Speckle Interferometric Detection of Defects on the backside of steel plate (스페클 간섭계를 이용한 평판 이면결함의 검출 특성)

  • 김동한;장석원;장경영
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2001.04a
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    • pp.195-198
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    • 2001
  • Backside defect of plate structure may grow due to fatigue or overload to cause critical failure during operation, so it is important to detect this kind of defect in line. For this purpose, nondestructive, non-contact and highly sensitive method is required. ESPI and Shearography are considered as useful method to satisfy these requirements. In this paper, the possibility of application of ESPI and Shearography to detect the backside defect of steel plate and to quantify the defect size was tested. For the experiment, some steel plates with defect on the backside were prepared. Experimental results for these plates showed that location and size of defect could be detected correctly by both of ESPI and Shearography.

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Study on an Image Reconstruction Algorithm for 3D Cartilage OCT Images (A Preliminary Study) (3차원 연골 광간섭 단층촬영 이미지들에 대한 영상 재구성 알고리듬 연구)

  • Ho, Dong-Su;Kim, Ee-Hwa;Kim, Yong-Min;Kim, Beop-Min
    • Progress in Medical Physics
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    • v.20 no.2
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    • pp.62-71
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    • 2009
  • Recently, optical coherence tomography (OCT) has demonstrated considerable promise for the noninvasive assessment of biological tissues. However, OCT images difficult to analyze due to speckle noise. In this paper, we tested various image processing techniques for speckle removal of human and rabbit cartilage OCT images. Also, we distinguished the images which get with methods of image segmentation for OCT images, and found the most suitable method for segmenting an image. And, we selected image segmentation suitable for OCT before image reconstruction. OCT was a weak point to system design and image processing. It was a limit owing to measure small a distance and depth size. So, good edge matching algorithms are important for image reconstruction. This paper presents such an algorithm, the chamfer matching algorithm. It is made of background for 3D image reconstruction. The purpose of this paper is to describe good image processing techniques for speckle removal, image segmentation, and the 3D reconstruction of cartilage OCT images.

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A Study on the Measurement of Elastic-Plastic Zone at the Crack Tip under Cyclic Loading using ESPI System (전자스패클패턴 간섭시스템을 이용한 피로하중을 받는 균열선단에서 탄소성 영역 측정에 관한 연구)

  • 김경수;심천식
    • Journal of Ocean Engineering and Technology
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    • v.16 no.4
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    • pp.13-18
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    • 2002
  • The magnitude of the plastic zone around the crack tip of DENT(Double Edge Notched Tension) specimen and the crack growth length under cyclic loading were measured by ESPI(Electronic Speckle Pattern Interferometry) system. The measured magnitude of plastic zone was compared with the equations proposed by Irwin and calculated by a nonlinear static method of MSC/NASTRAN. The measured crack growth length by ESPI system was also compared with the obtained data by the image analysis system. From the study, it is confirmed that the plastic zone and crack growth length can be measured accurately with the high-tech equipment.

Strain Analysis by Dual-beam Shearography (미소변형 해석을 위한 Dual-beam Shearography)

  • 김경석;최태호;김성식;최정석
    • Proceedings of the Korean Society of Machine Tool Engineers Conference
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    • 2003.04a
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    • pp.251-254
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    • 2003
  • In recent years, shearogrpahy has significantly improved capabilities In the areas of unbend and separation detection in tires. Although shearography has many advantages fur qualitative evaluation, the technique remains the problem of quantitative analysis of inside defects, because shearography needs several effective factors including the amount of shearing, shearine direction and induced load, which exist as barrier for the quantitative analysis of inside defects. Since the factors are highly dependent on inspectors skill and also affect the in-situ workability. The factors were optimized and the size of cracks inside of pipeline and tire has been quantitatively determined.

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Welding Characteristics of Inconel 600 using a high power CW Nd:YAG Laser (고출력 CW Nd:YAG 레이저를 이용한 인코넬 600의 용접 특성)

  • Yoo Young-Tae;Shin Ho-Jun;Lim Kie-Gon
    • Transactions of the Korean Society of Machine Tool Engineers
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    • v.13 no.6
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    • pp.119-126
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    • 2004
  • The welding characteristics of Inconel 600 Alloy using a continuous wave Nd:YAG laser are experimentally investigated. The major process parameters studied in the present laser welding experiment were the positions of focus, laser power and travel speed of laser bean We measured the fusion zone size and its shape using an optical microscope for the observation of cross-sectional area. We performed two tests regarding the tension and the micro hardness for welding quality estimation. Then we measured residual stress in welds by electronic speckle pattern interferometry(ESPI). In conclusion the optimum butt welding process parameters were 0.5mm focus position, 1.6kW laser power, 1m/min travel speed and 5.5$\ell$/min assist gas discharge.

Development of tiny green laser for mobile projectors

  • Yu, N.E.;Jung, C.;Yu, B.;Lee, Y.L.;Kim, I.S.;Choi, J.W.;Ko, D.K.
    • 한국정보디스플레이학회:학술대회논문집
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    • 2009.10a
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    • pp.476-477
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    • 2009
  • The smallest green laser containing a built-in temperature controlling unit has been demonstrated. The device volume was just 0.5 cubic centimeters, which is nearly the same size as existing red and blue diode lasers, has an electrical-to-optical conversion efficiency of 10% and 150 mW power output. Furthermore as an alternative approach for compact green laser development, a quasi-phase matching method with wide spectral bandwidth for the reduction of speckle noise will be presented.

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