Pub Date : 2002-12-01DOI: 10.1109/ULTSYM.2002.1193370
K. Uehara, H. Nakamura, H. Nakase, K. Tsubouchi
We have successfully developed (00/spl middot/1) AlN film with atomically flat surface on (00/spl middot/1) sapphire substrate using metalorganic chemical vapor deposition (MO-CVD) method. The atomically flat surface of less than Ra=2/spl Aring/, Ra means mean roughness measured by atomic force microscope (AFM), within the thickness of 1.7 /spl mu/m has been achieved, whose conditions are high substrate temperature of 1200/spl deg/C, low pressure of 30Torr, low V-III ratio of 500 and the numerous flow rate of trimethylaluminum (TMA)-back-up H/sub 2/ gas of 5.0slm The temperature-coefficient-of-delay (TCD) of the fabricated surface-acoustic-wave (SAW) device on (00/spl middot/1)AlN/ (00/spl middot/1) Al/sub 2/O/sub 3/ combination with atomically flat surface are found to be 44.5 ppm//spl deg/C at kH=2.25 and 28.5 ppm//spl deg/C at kH=3.32, where kH is the normalized thickness by wave number, k is wave number and H is AlN film thickness. These measured TCD are agreed with simulated curve. AlN/Al/sub 2/O/sub 3/ combination with atomically flat surface has a potential for zero-TCD at kH=4.5.
{"title":"AlN epitaxial film with atomically flat surface for GHz-band SAW devices","authors":"K. Uehara, H. Nakamura, H. Nakase, K. Tsubouchi","doi":"10.1109/ULTSYM.2002.1193370","DOIUrl":"https://doi.org/10.1109/ULTSYM.2002.1193370","url":null,"abstract":"We have successfully developed (00/spl middot/1) AlN film with atomically flat surface on (00/spl middot/1) sapphire substrate using metalorganic chemical vapor deposition (MO-CVD) method. The atomically flat surface of less than Ra=2/spl Aring/, Ra means mean roughness measured by atomic force microscope (AFM), within the thickness of 1.7 /spl mu/m has been achieved, whose conditions are high substrate temperature of 1200/spl deg/C, low pressure of 30Torr, low V-III ratio of 500 and the numerous flow rate of trimethylaluminum (TMA)-back-up H/sub 2/ gas of 5.0slm The temperature-coefficient-of-delay (TCD) of the fabricated surface-acoustic-wave (SAW) device on (00/spl middot/1)AlN/ (00/spl middot/1) Al/sub 2/O/sub 3/ combination with atomically flat surface are found to be 44.5 ppm//spl deg/C at kH=2.25 and 28.5 ppm//spl deg/C at kH=3.32, where kH is the normalized thickness by wave number, k is wave number and H is AlN film thickness. These measured TCD are agreed with simulated curve. AlN/Al/sub 2/O/sub 3/ combination with atomically flat surface has a potential for zero-TCD at kH=4.5.","PeriodicalId":378705,"journal":{"name":"2002 IEEE Ultrasonics Symposium, 2002. Proceedings.","volume":"2 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132677756","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-12-01DOI: 10.1109/ULTSYM.2002.1192629
S. Umemura, T. Azuma, Y. Miwa, K. Sasaki, T. Sugiyama, T. Hayashi, H. Kuribara
In imaging with a microbubble contrast agent, which tends to make irreversible changes by transmission even at a low intensity, both transmission beamwidth and number of transmission per frame must be minimized. A transmission focusing technique based on a noncylindrical delay, which is applicable to a one-dimensional array, is proposed. Unlike X waves, the main beam propagates always coherently with the waves transmitted from the central part of the aperture. The non-cylindrical focusing delay was calculated by assuming a local focal length along the aperture, which increases gradually as the distance from the center increases. Numerical simulation of wave propagation predicted a large depth of field for a reasonably narrow main beam having longitudinally uniform intensity. The noncylindrical focusing was employed in a prototype beamformer, and the large depth of transmission field was confirmed with Shrielen measurements.
{"title":"Non-cylindrical transmission focusing for large depth of field","authors":"S. Umemura, T. Azuma, Y. Miwa, K. Sasaki, T. Sugiyama, T. Hayashi, H. Kuribara","doi":"10.1109/ULTSYM.2002.1192629","DOIUrl":"https://doi.org/10.1109/ULTSYM.2002.1192629","url":null,"abstract":"In imaging with a microbubble contrast agent, which tends to make irreversible changes by transmission even at a low intensity, both transmission beamwidth and number of transmission per frame must be minimized. A transmission focusing technique based on a noncylindrical delay, which is applicable to a one-dimensional array, is proposed. Unlike X waves, the main beam propagates always coherently with the waves transmitted from the central part of the aperture. The non-cylindrical focusing delay was calculated by assuming a local focal length along the aperture, which increases gradually as the distance from the center increases. Numerical simulation of wave propagation predicted a large depth of field for a reasonably narrow main beam having longitudinally uniform intensity. The noncylindrical focusing was employed in a prototype beamformer, and the large depth of transmission field was confirmed with Shrielen measurements.","PeriodicalId":378705,"journal":{"name":"2002 IEEE Ultrasonics Symposium, 2002. Proceedings.","volume":"270 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"120895211","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-12-01DOI: 10.1109/ULTSYM.2002.1192518
A. Hladky-Hennion, D. Markley, R. Newnham, R. Meyer, W. Hughes
This paper describes the design and the development of transducer arrays fabricated from miniature piezoceramic hollow spheres, the BBs. After the presentation of the fabrication procedure of the transducers, it presents the numerical tools used to model 2/spl times/2 and 4/spl times/4 transducer arrays in water. Numerical calculations give good agreement with the experimental results and provide physical insight for understanding the acoustic observations.
{"title":"Analysis of transducers arrays from piezoelectric hollow spheres","authors":"A. Hladky-Hennion, D. Markley, R. Newnham, R. Meyer, W. Hughes","doi":"10.1109/ULTSYM.2002.1192518","DOIUrl":"https://doi.org/10.1109/ULTSYM.2002.1192518","url":null,"abstract":"This paper describes the design and the development of transducer arrays fabricated from miniature piezoceramic hollow spheres, the BBs. After the presentation of the fabrication procedure of the transducers, it presents the numerical tools used to model 2/spl times/2 and 4/spl times/4 transducer arrays in water. Numerical calculations give good agreement with the experimental results and provide physical insight for understanding the acoustic observations.","PeriodicalId":378705,"journal":{"name":"2002 IEEE Ultrasonics Symposium, 2002. Proceedings.","volume":"33 3","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"113974329","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-12-01DOI: 10.1109/ULTSYM.2002.1192597
Z. M. Benenson, A. B. Elizarov, T. Yakovleva, W. O’Brien
A technique is proposed that generates a depth-independent and narrow beamwidth 3D ultrasonic image. A high-frequency, wide-bandwidth spherical transducer is scanned in 2D along Cartesian coordinates. The received wideband ultrasonic pulses are dynamically focused by means of correcting the spatial spectrum of signals for various temporal frequencies. The main procedures of the algorithm consist in the direct and inverse fast Fourier transforms by time and by two spatial Cartesian coordinates.
{"title":"Depth-independent narrow beamwidth 3D ultrasonic image formation technique","authors":"Z. M. Benenson, A. B. Elizarov, T. Yakovleva, W. O’Brien","doi":"10.1109/ULTSYM.2002.1192597","DOIUrl":"https://doi.org/10.1109/ULTSYM.2002.1192597","url":null,"abstract":"A technique is proposed that generates a depth-independent and narrow beamwidth 3D ultrasonic image. A high-frequency, wide-bandwidth spherical transducer is scanned in 2D along Cartesian coordinates. The received wideband ultrasonic pulses are dynamically focused by means of correcting the spatial spectrum of signals for various temporal frequencies. The main procedures of the algorithm consist in the direct and inverse fast Fourier transforms by time and by two spatial Cartesian coordinates.","PeriodicalId":378705,"journal":{"name":"2002 IEEE Ultrasonics Symposium, 2002. Proceedings.","volume":"21 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134569736","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-12-01DOI: 10.1109/ULTSYM.2002.1192686
Y. Yamakoshi, Y. Ozawa, N. Masuda
When the micro-bubble oscillates under the ultrasonic wave, the bubble radiates secondary waves around it. This wave generates secondary Bjerknes force between the neighboring bubbles and the force assists inherent bubble movements such as bubble aggregation inside the ultrasonic wave field. In this paper, a novel technique to characterize the secondary ultrasonic wave from the bubbles is proposed. This method is based on the observation of fringe like pattern produced around the bubble of interest. This pattern is produced by micro bubbles which are trapped inside the interference wave field of incident wave and the secondary wave. The experiments are carried out by an ultrasonic wave contrast agent "Levovist" (SCHERING A.G. Germany). The fringe like patterns are observed for relative large aggregated bubbles.
{"title":"Holographic visualization of secondary ultrasonic waves radiated from micro-bubbles","authors":"Y. Yamakoshi, Y. Ozawa, N. Masuda","doi":"10.1109/ULTSYM.2002.1192686","DOIUrl":"https://doi.org/10.1109/ULTSYM.2002.1192686","url":null,"abstract":"When the micro-bubble oscillates under the ultrasonic wave, the bubble radiates secondary waves around it. This wave generates secondary Bjerknes force between the neighboring bubbles and the force assists inherent bubble movements such as bubble aggregation inside the ultrasonic wave field. In this paper, a novel technique to characterize the secondary ultrasonic wave from the bubbles is proposed. This method is based on the observation of fringe like pattern produced around the bubble of interest. This pattern is produced by micro bubbles which are trapped inside the interference wave field of incident wave and the secondary wave. The experiments are carried out by an ultrasonic wave contrast agent \"Levovist\" (SCHERING A.G. Germany). The fringe like patterns are observed for relative large aggregated bubbles.","PeriodicalId":378705,"journal":{"name":"2002 IEEE Ultrasonics Symposium, 2002. Proceedings.","volume":"75 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132460529","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-12-01DOI: 10.1109/ULTSYM.2002.1192566
H. Yao, P. Phukpattaranont, E. Ebbini
It has long been recognized that thermal lesions formed using high-intensity focused ultrasound (HIFU) exhibit nonlinear behavior that can be detected in pulse-echo ultrasound. Second harmonic imaging of freshly formed thermal lesions have consistently shown significant enhancement in their visualization confirming this nonlinear behavior. In this paper, we describe a post-beamforming nonlinear filtering algorithm based on a second-order Volterra filter (SVF) model that separates the linear and quadratic components of the echo signal leading to significant enhancement of lesion visualization. Images from ex vivo tissue samples are shown to demonstrate the level of contrast enhancement achieved with the SVF-based quadratic filter compared with standard echo and 2nd harmonic imaging results.
{"title":"Detection and mapping of thermal lesions using dual-mode ultrasound phased arrays","authors":"H. Yao, P. Phukpattaranont, E. Ebbini","doi":"10.1109/ULTSYM.2002.1192566","DOIUrl":"https://doi.org/10.1109/ULTSYM.2002.1192566","url":null,"abstract":"It has long been recognized that thermal lesions formed using high-intensity focused ultrasound (HIFU) exhibit nonlinear behavior that can be detected in pulse-echo ultrasound. Second harmonic imaging of freshly formed thermal lesions have consistently shown significant enhancement in their visualization confirming this nonlinear behavior. In this paper, we describe a post-beamforming nonlinear filtering algorithm based on a second-order Volterra filter (SVF) model that separates the linear and quadratic components of the echo signal leading to significant enhancement of lesion visualization. Images from ex vivo tissue samples are shown to demonstrate the level of contrast enhancement achieved with the SVF-based quadratic filter compared with standard echo and 2nd harmonic imaging results.","PeriodicalId":378705,"journal":{"name":"2002 IEEE Ultrasonics Symposium, 2002. Proceedings.","volume":"7 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121205284","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-12-01DOI: 10.1109/ULTSYM.2002.1192555
T. Bigelow, W. O’Brien
Due to regulatory reasons, the output levels of ultrasound sources for use in medical applications must be known. Currently, this is done by making focal pressure measurements for a very large number of drive voltage amplitudes and then linearly derating the measured pressure levels. In order to reduce calibration times, some have proposed to linearly extrapolate pressures rather than perform direct measurements. However, nonlinear propagation effects corrupt the linear extrapolation and derating procedure. Thus, a reliable indicator of nonlinearity is needed to identify when linear extrapolation/derating would be valid. In this study, eight different nonlinearity indicators were evaluated experimentally in terms of their correspondence to the linear extrapolation error. Spherically focused ultrasound transducers were selected and excited to test the indicators sensitivity to frequency (3 - 8 MHz), f/# (1 and 2), transducer diameter (1.905 and 5.08 cm), pulse duration (1 and 3 cycles), and pulse phase (0/spl deg/ and 180/spl deg/). None of the eight nonlinearity indicators yielded consistent results. The lack of consistency resulted from the competing effects of nonlinear absorption and asymmetric distortion, which have yet to be combined into a unified theory.
{"title":"Experimental evaluation of some possible nonlinearity indicators","authors":"T. Bigelow, W. O’Brien","doi":"10.1109/ULTSYM.2002.1192555","DOIUrl":"https://doi.org/10.1109/ULTSYM.2002.1192555","url":null,"abstract":"Due to regulatory reasons, the output levels of ultrasound sources for use in medical applications must be known. Currently, this is done by making focal pressure measurements for a very large number of drive voltage amplitudes and then linearly derating the measured pressure levels. In order to reduce calibration times, some have proposed to linearly extrapolate pressures rather than perform direct measurements. However, nonlinear propagation effects corrupt the linear extrapolation and derating procedure. Thus, a reliable indicator of nonlinearity is needed to identify when linear extrapolation/derating would be valid. In this study, eight different nonlinearity indicators were evaluated experimentally in terms of their correspondence to the linear extrapolation error. Spherically focused ultrasound transducers were selected and excited to test the indicators sensitivity to frequency (3 - 8 MHz), f/# (1 and 2), transducer diameter (1.905 and 5.08 cm), pulse duration (1 and 3 cycles), and pulse phase (0/spl deg/ and 180/spl deg/). None of the eight nonlinearity indicators yielded consistent results. The lack of consistency resulted from the competing effects of nonlinear absorption and asymmetric distortion, which have yet to be combined into a unified theory.","PeriodicalId":378705,"journal":{"name":"2002 IEEE Ultrasonics Symposium, 2002. Proceedings.","volume":"59 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133945198","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-12-01DOI: 10.1109/ULTSYM.2002.1193564
Y. Yong, J. Vig, A. Ballato
An analytical technique for designing high Q, thickness shear micro electromechanical, ring electroded mesa quartz resonators is proposed. The method is demonstrated using two-dimensional straight crested wave analysis. The design method is based on the two characteristics of a stable resonator: (a) The mode is energy trapped and relatively isolated from its supports, and (b) the motional impedance of the mode is low. The root mean squares of vibration displacements are employed to characterize the modes of vibration, and the thickness shear mode has a large rms u/sub 1/ displacement in the x/sub 1/ direction (diagonal axis). The rms displacement is used to compare the energy trapping of the thickness shear mode as a function of the electrode and plate geometry. For each mode of vibration, the electric flux density D/sub 2/ is calculated at the quartz to electrode interface to yield the electric current at the electrodes. Given a constant driving voltage, the magnitude of the electric current is inversely proportional to the motional impedance. Hence the electric current for a mode as a function of the electrode and plate geometry is employed as a further means for comparing the merits of different resonator designs. Results are shown for a 1 GHz inverted mesa AT-cut resonator.
{"title":"Straight crested wave analysis of quartz MEMS ring electroded mesa resonators","authors":"Y. Yong, J. Vig, A. Ballato","doi":"10.1109/ULTSYM.2002.1193564","DOIUrl":"https://doi.org/10.1109/ULTSYM.2002.1193564","url":null,"abstract":"An analytical technique for designing high Q, thickness shear micro electromechanical, ring electroded mesa quartz resonators is proposed. The method is demonstrated using two-dimensional straight crested wave analysis. The design method is based on the two characteristics of a stable resonator: (a) The mode is energy trapped and relatively isolated from its supports, and (b) the motional impedance of the mode is low. The root mean squares of vibration displacements are employed to characterize the modes of vibration, and the thickness shear mode has a large rms u/sub 1/ displacement in the x/sub 1/ direction (diagonal axis). The rms displacement is used to compare the energy trapping of the thickness shear mode as a function of the electrode and plate geometry. For each mode of vibration, the electric flux density D/sub 2/ is calculated at the quartz to electrode interface to yield the electric current at the electrodes. Given a constant driving voltage, the magnitude of the electric current is inversely proportional to the motional impedance. Hence the electric current for a mode as a function of the electrode and plate geometry is employed as a further means for comparing the merits of different resonator designs. Results are shown for a 1 GHz inverted mesa AT-cut resonator.","PeriodicalId":378705,"journal":{"name":"2002 IEEE Ultrasonics Symposium, 2002. Proceedings.","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129161424","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-12-01DOI: 10.1109/ULTSYM.2002.1193458
Y. Koike, T. Tsuyoshi, H. Kikura, M. Aritomi, M. Mori
The current principle of the flow velocity measurement method is based on the detection of the echoes of ultrasonic pulse Doppler method (UDM). However, in some applications, for example, a flow rate measurement in clean water, any particle does not exist in the flow and hence, the conventional UDM cannot be applied. The authors group proposed to employ the ultrasonic cavitation bubbles as reflectors in the flow measurement by UDM. The low frequency Langevin transducer attached to the outside wall of the pipe produces the cavitation bubbles in the flow. Therefore, UDM can be applied to the flow rate measurement without any suspending particle tracers. In this report, applicability and accuracy of the flow rate measurement are investigated in the case of the cavitations bubbles as reflectors. The measurement system with the cavitation production system is also designed and fabricated.
{"title":"Flow rate measurement using ultrasonic Doppler method with cavitation bubbles","authors":"Y. Koike, T. Tsuyoshi, H. Kikura, M. Aritomi, M. Mori","doi":"10.1109/ULTSYM.2002.1193458","DOIUrl":"https://doi.org/10.1109/ULTSYM.2002.1193458","url":null,"abstract":"The current principle of the flow velocity measurement method is based on the detection of the echoes of ultrasonic pulse Doppler method (UDM). However, in some applications, for example, a flow rate measurement in clean water, any particle does not exist in the flow and hence, the conventional UDM cannot be applied. The authors group proposed to employ the ultrasonic cavitation bubbles as reflectors in the flow measurement by UDM. The low frequency Langevin transducer attached to the outside wall of the pipe produces the cavitation bubbles in the flow. Therefore, UDM can be applied to the flow rate measurement without any suspending particle tracers. In this report, applicability and accuracy of the flow rate measurement are investigated in the case of the cavitations bubbles as reflectors. The measurement system with the cavitation production system is also designed and fabricated.","PeriodicalId":378705,"journal":{"name":"2002 IEEE Ultrasonics Symposium, 2002. Proceedings.","volume":"19 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128335403","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-12-01DOI: 10.1109/ULTSYM.2002.1193504
Xiangtao Yin, S. A. Morris, W. O’Brien
The ultrasonic pulse-echo Backscattered Amplitude Integral (BAI)-mode imaging technique [UFFC Trans, 45:30, 1998] has been developed to detect small channel defects in flexible food package seals. This technique detects 38-/spl mu/m-diameter channels reliably and 6-/spl mu/m-diameter channels occasionally using a 17.3-MHz focused transducer in water (20/spl deg/C, /spl lambda/ /spl ap/ 86 /spl mu/m, total sample thickness 22 /spl mu/m). However, interaction between ultrasound and sample microstructure - the underlying detection mechanism is poorly understood. Experimental evidence showed at the subwavelength channel was fused inside the two binding trilaminate plastic package films. Each trilaminate film a three sublayers. Package sample impedance profiles along the ultrasound beam axis were examined. Although identical in nominal impedance properties before sealing, the two binding films showed an asymmetric impedance profile after sealing. A generalized impedance profile model was proposed. The defect detection behavior of the echo signal was investigated by solving the 2D linear acoustic wave equations in fluid with finite-difference time-domain method and the perfectly matched layer absorbing boundary. The normalized correlation coefficients between the simulated and the measured RF echo waveforms were greater than 95% for this generalized model.
{"title":"Numerical evaluation of ultrasonic pulse-echo subwavelength defect detection","authors":"Xiangtao Yin, S. A. Morris, W. O’Brien","doi":"10.1109/ULTSYM.2002.1193504","DOIUrl":"https://doi.org/10.1109/ULTSYM.2002.1193504","url":null,"abstract":"The ultrasonic pulse-echo Backscattered Amplitude Integral (BAI)-mode imaging technique [UFFC Trans, 45:30, 1998] has been developed to detect small channel defects in flexible food package seals. This technique detects 38-/spl mu/m-diameter channels reliably and 6-/spl mu/m-diameter channels occasionally using a 17.3-MHz focused transducer in water (20/spl deg/C, /spl lambda/ /spl ap/ 86 /spl mu/m, total sample thickness 22 /spl mu/m). However, interaction between ultrasound and sample microstructure - the underlying detection mechanism is poorly understood. Experimental evidence showed at the subwavelength channel was fused inside the two binding trilaminate plastic package films. Each trilaminate film a three sublayers. Package sample impedance profiles along the ultrasound beam axis were examined. Although identical in nominal impedance properties before sealing, the two binding films showed an asymmetric impedance profile after sealing. A generalized impedance profile model was proposed. The defect detection behavior of the echo signal was investigated by solving the 2D linear acoustic wave equations in fluid with finite-difference time-domain method and the perfectly matched layer absorbing boundary. The normalized correlation coefficients between the simulated and the measured RF echo waveforms were greater than 95% for this generalized model.","PeriodicalId":378705,"journal":{"name":"2002 IEEE Ultrasonics Symposium, 2002. Proceedings.","volume":"11 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128412676","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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