• 제목/요약/키워드: Focusing Element

검색결과 448건 처리시간 0.031초

초음파 영상에서 Multi-element Receive Synthetic Focusing을 이용한 그레이팅 로브 감축 (A Reduction of Grating Lobe By Using the Multi-element Receive Synthetic Focusing In Ultrasonic Image)

  • 이종석;안영복
    • 대한의용생체공학회:학술대회논문집
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    • 대한의용생체공학회 1997년도 추계학술대회
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    • pp.559-562
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    • 1997
  • In this paper, we propose the method that reduce the grating lobe in the ultrasound synthetic focusing images. synthetic focusing images have more larger and closer grating lobe than conventional phased array images and more lower signal to noise ratio. so, we represent the method that reduce the grating lobe by using multi element receive focusing. experimental results are showed that the proposed multi element receiving method reduce the grating lobe and increase the signal to noise ratio.

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유한요소법을 통한 판에서 시간반전 램파의 공간집속성능 규명 (Investigating the Spatial Focusing Performance of Time Reversal Lamb Waves on a Plate through the Finite Element Method)

  • 최정희;이해성;박현우
    • 한국소음진동공학회논문집
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    • 제21권12호
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    • pp.1120-1131
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    • 2011
  • Researches using time reversal acoustics(TRA) for impact localization have been paid attention to recently. Dispersion characteristics of Lamb waves, which restrict the utility of classical nondestructive evaluation based on time-of-flight information, can be compensated through the application of TRA to Lamb waves on a plate. This study investigates the spatial focusing performance of time reversal Lamb waves on a plate using finite element analysis. In particular, the virtual sensor effect caused by multiple wave reflections at the boundaries of a plate is shown to enable the spatial focusing of Lamb waves though a very small number of surface-bonded piezoelectric(PZT) sensors are available. The time window size of forward response signals, are normalized with respect to the number of virtual active sensors. Then their effects on the spatial focusing performance of Lamb waves are investigated.

유한요소법과 하이브리드형 무한요소법을 이용한 초음파 집속변환자의 음장 해석 (Acoustic Field Analysis of Ultrasonic Focusing Transducer by Using Finite Element. Method and Hybrid Type Infinite Element Method)

  • 박순종;윤종락;하강열;김천덕
    • 한국음향학회지
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    • 제14권5호
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    • pp.36-43
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    • 1995
  • 본 논문에서는 유한요소법과 하이브리드형 무한요소법을 사용하여 전기계$\cdot$기계계$\cdot$음향계로 결합된 초음파 집속변환자의 집속특성과 시간 응답을 구하였다. 초음파 집속변환자의 촛점거리, 분해능 특성들을 구하였고, 댐퍼가 부가된 경우 방사면상의 변위분포가 안정되어 분해능이 개선된다는 것을 집속특성과 시간 응답으로부터 해석하였다. 해석의 결과는 초음파 집속변환자의 설계나 성능해석에 응용될 수 있을 것이다.

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초음파 영상 시스템의 Synthetic Focusing을 위한 구면파 발생 방법 (Method Generating Circular Wave for Synthetic Focusing)

  • 오진식;김정준;송태경;안영복
    • 대한의용생체공학회:학술대회논문집
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    • 대한의용생체공학회 1998년도 추계학술대회
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    • pp.215-216
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    • 1998
  • The ultrasonic imaging systems using synthetic aperture beamforming has been formed in the way that one element transmits and then receives a pulse. Because the amplitude of a pulse from one element is too small to propagate a long distance, the SNR(Signal to Noise Ratio)is low. This paper proposes the method to make a circular wave almost equal to one generated by one element using several elements. The amplitude of the wave made up of several elements is much larger than that of one element. And we can improve the SNR.

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초음파 영상 시스템에서 합성 집속을 위한 새로운 구면파 발생 방법 (New Circular Wave Generation Method for Synthetic Focusing in Ultrasonic Imaging Systems)

  • 안영복
    • 대한의용생체공학회:의공학회지
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    • 제28권6호
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    • pp.798-802
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    • 2007
  • The synthetic focusing in the ultrasonic imaging systems has been formed in the way that one element transmits a circular wave and receives an echo signal. The amplitude of the signal transmitted from one element is too small to propagate a long distance so that the SNR(Signal to Noise Ratio) is very low in an image obtained by the synthetic focusing. To solve this problem, a defocusing method which uses several elements has been proposed. In this method, the SNR is improved due to using several elements to transmit the circular wave. But if the number of transmitting elements increases, the phase distortion is severe in the defocusing method. In this paper, we propose a new method that can generate a circular wave using a lot of elements without phase distortion. At first, we generate limited plane waves with different propagation angles and then superpose them to make a circular wave. We show that the circular wave can be used to improve SNR in the real-time 3D ultrasonic imaging as well as the synthetic focusing through computer simulation and experiments.

판의 충격위치 추정을 위한 시간반전 램파의 공간모임성능 규명 (Investigating the Spatial Focusing Performance of Time Reversal Lamb waves for Impact Localization on a Plate)

  • 박현우
    • 한국소음진동공학회:학술대회논문집
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    • 한국소음진동공학회 2011년도 추계학술대회 논문집
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    • pp.418-429
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    • 2011
  • Researches using time reversal acoustics (TRA) for impact localization have been paid attention to recently. Dispersion characteristics of Lamb waves, which restrict the utility of classical nondestructive evaluation based on time-of-flight information, can be compensated through the application of TRA to Lamb waves on a plate. This study investigates the spatial focusing performance of time reversal Lamb waves on a plate using finite element analysis. In particular, the virtual sensor effect caused by multiple wave reflections at the boundaries of the plate is shown to enable the spatial focusing of Lamb waves though a very small number of surface-bonded piezoelectric (PZT) sensors are available. The time window size of forward response signals, are normalized with respect to the number of virtual active sensors. Then their effects on the spatial focusing performance of Lamb waves are investigated.

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A Synthetic Aperture Focusing Method for Three-way Dynamic Focusing

  • Kim Jung-Jun;Chang Jin-Ho;Song Tai-Kyong
    • 대한의용생체공학회:의공학회지
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    • 제26권1호
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    • pp.31-35
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    • 2005
  • A novel synthetic aperture method for real-time three-way dynamic focusing is proposed, which provides lateral beam patterns represented as the product of Fourier transforms of transmit subaperture, receive subaperture, and a synthetic window function. In the proposed method, all array elements are fired individually and for each firing echo signals are recorded from all elements of a receive subaperture moving along an array with the transmit element. The three-way dynamic focusing is then achieved by employing a synthetic aperture algorithm for two-way dynamic focusing and a synthetic focusing method for transmit dynamic focusing. Both theoretical analysis and computer simulation results show that the proposed method produces ultrasound beams with improved lateral resolution at all depths compared to the conventional phased array imaging and synthetic aperture focusing methods.

페이즈드 어레이 트랜스듀서에 있어서 구성 압전소자의 간격 변화에 따른 초음파 빔 전파 특성 해석 (Analysis of the Ultrasonic Beam Profile Due to Variation of the Inter-Element Spacing for the Phased Array Transducer)

  • 최상우;이준현
    • 대한기계학회논문집A
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    • 제24권4호
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    • pp.972-981
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    • 2000
  • The phased array transducer has two distinct advantages. One is rapid scanning comparing with the conventional mechanical or manual scanning system. Therefore, output image is represented in real-time. The other is the dynamic focusing and the dynamic steering of ultrasonic beam. Only the delay times that are controlled electrically are used to focus and to steer beam without any lenses or wedges. In this study, the profile of the ultrasonic beam for the phased array transducer has been simulated in the Huygens principle with varying the inter-element spacing of the linear phased array transducer. From the result of this study, it was found that the ultrasonic beam spread wider as the inter-element spacing was decreased. However, the focusing effect was improved, even when the number of the element was not big. In addition, there was grating lobes that are constructed when the inter-element spacing is more than half wavelength. However, this grating lobe has lower amplitude than the main lobe.

공기 중 휘발성 유기화합물의 측정을 위한 열탈착-분석시스템의 구성 및 평가 (Composition and Evaluation of the Thermal Desorption-Gas Chromatographic System for the Measurement of Volatile Organic Compounds in Air)

  • 이수형;송희남;김희갑
    • Environmental Analysis Health and Toxicology
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    • 제17권1호
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    • pp.63-71
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    • 2002
  • The thermal desorption-gas chromatographic (TD-GC) system has been constructed for the measurement of volatile organic compounds. The thermal desortion unit is composed of four major parts: 1) the control part; 2) the thermal desorption part; 3) the focusing part; and 4) the injection part. The peltier element was introduced to the focusing part for the temperature of the focusing tube to reach-35$^{\circ}C$. The system was tested for the linearity of the calibration curves and reproducibility of instrumental analyses using some disinfection by-products (DBPs) and BTXs (benzene, toluene and p-xylene). The coefficients of determination (r$^2$) for all the calibration curves made were higher than 0.998, and the coefficients of variation (CV) for triplicate measurements were all within 10%. The system also has been tested for field applicability. The analysis of field samples showed that there was no breakthrough problem in the sampling system and that the system could be applied to field measurements.

HYPERSPECTRAL IMAGING SPECTROMETER WITH A NOVEL ZOOMING FUNCTION

  • Choi Jin;Kim Tae Hyung;Kong Hong Jin;Lee Jong-Ung
    • 대한원격탐사학회:학술대회논문집
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    • 대한원격탐사학회 2005년도 Proceedings of ISRS 2005
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    • pp.213-216
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    • 2005
  • A novel hyperspectral imaging spectrometer controlling spatial and spectral resolution individually has been proposed. This imaging spectrometer uses a zoom lens as a telescope and a focusing element. It can change the spatial resolution fixing the spectral resolution or the spectral resolution fixing the spatial resolution. Here, we report the concept of the hyperspectral imaging spectrometer with the novel zooming function and the optical design of a zoom lens as the focusing element. By using lens module and third-order aberration theory, we have presented the initial design of four-group zoom lens with external entrance pupil. And the optimized zoom lens with a focal length of 50 to 150 mm is obtained from the initial design by the optical design software. As a result, the designed zoom lens shows satisfactory performances in wavelength range of 450 to 900 nm as a focusing element in an imaging spectrometer. Furthermore, the collimator lens of the imaging spectrometer is designed through the third-order aberration correction by using an iterative process.

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