Pub Date : 2002-10-08DOI: 10.1109/ULTSYM.2002.1193434
S. Kakio, Y. Shimatai, Y. Nakagawa
In this paper, the propagation characteristics of two modes of surface acoustic waves (SAWs) on ST quartz with a tantalum pentoxide (Ta/sub 2/O/sub 5/) thin film are investigated theoretically and experimentally. One is the pure shear-horizontal (SH) wave and the another is the Love-wave-type SAW converted from the leaky SAW (LSAW). For these SAWs, stronger energy trapping effects on the surface can be expected by loading the substrate with the TA/sub 2/O/sub 5/ thin film, because this film has a relatively high density. In fact, the film thickness of the Ta/sub 2/O/sub 5/ film required to obtain the minimum insertion loss and the maximum K/sup 2/ for the SH wave on ST-90/spl deg/X quartz is around 0.01 /spl lambda/, which is approximately one-fourth of that reported for silicon dioxide film. Furthermore, the attenuation of the LSAW on ST quartz was reduced by loading with the Ta/sub 2/O/sub 5/ film because the LSAW becomes the Love-wave-type SAW without attenuation.
{"title":"Shear-horizontal-type surface acoustic waves on quartz with Ta/sub 2/O/sub 5/ thin film","authors":"S. Kakio, Y. Shimatai, Y. Nakagawa","doi":"10.1109/ULTSYM.2002.1193434","DOIUrl":"https://doi.org/10.1109/ULTSYM.2002.1193434","url":null,"abstract":"In this paper, the propagation characteristics of two modes of surface acoustic waves (SAWs) on ST quartz with a tantalum pentoxide (Ta/sub 2/O/sub 5/) thin film are investigated theoretically and experimentally. One is the pure shear-horizontal (SH) wave and the another is the Love-wave-type SAW converted from the leaky SAW (LSAW). For these SAWs, stronger energy trapping effects on the surface can be expected by loading the substrate with the TA/sub 2/O/sub 5/ thin film, because this film has a relatively high density. In fact, the film thickness of the Ta/sub 2/O/sub 5/ film required to obtain the minimum insertion loss and the maximum K/sup 2/ for the SH wave on ST-90/spl deg/X quartz is around 0.01 /spl lambda/, which is approximately one-fourth of that reported for silicon dioxide film. Furthermore, the attenuation of the LSAW on ST quartz was reduced by loading with the Ta/sub 2/O/sub 5/ film because the LSAW becomes the Love-wave-type SAW without attenuation.","PeriodicalId":378705,"journal":{"name":"2002 IEEE Ultrasonics Symposium, 2002. Proceedings.","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125878613","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 : 2002-10-08DOI: 10.1109/ULTSYM.2002.1193457
Paul D Fox
A procedure is provided for decomposing the linear field of flat pulsed wave annular arrays into an equivalent set of known limited diffraction Bessel beams. Each Bessel beam propagates with known characteristics, enabling good insight into the propagation of annular fields to be obtained. Numerical examples are given in the context of a 10-ring annular array operating at a central frequency of 2.5 MHz in water.
{"title":"Limited diffraction maps for pulsed wave annular arrays","authors":"Paul D Fox","doi":"10.1109/ULTSYM.2002.1193457","DOIUrl":"https://doi.org/10.1109/ULTSYM.2002.1193457","url":null,"abstract":"A procedure is provided for decomposing the linear field of flat pulsed wave annular arrays into an equivalent set of known limited diffraction Bessel beams. Each Bessel beam propagates with known characteristics, enabling good insight into the propagation of annular fields to be obtained. Numerical examples are given in the context of a 10-ring annular array operating at a central frequency of 2.5 MHz in water.","PeriodicalId":378705,"journal":{"name":"2002 IEEE Ultrasonics Symposium, 2002. Proceedings.","volume":"20 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125298503","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 : 2002-10-08DOI: 10.1109/ULTSYM.2002.1192651
M. Fink, L. Sandrin, M. Tanter, S. Catheline, S. Chaffai, J. Bercoff, J. Gennisson
Ultrafast ultrasonic imaging seems to have a strong potential for medical imaging applications. During the past five years, it has been applied successfully to quantitative assessment of soft tissues elasticity. An ultrafast ultrasonic scanner was built in our lab for quantitatively mapping the shear elasticity of soft tissues. The ultrafast Scanner provides images of the echogenecity of tissues similar to a standard echographic device but with a 200 times higher a frame rate. It allows to detect fast tissue motion induced by low frequency shear waves inside the body. From these displacements, a shear elasticity map is constructed using inverse problem algorithms. Preliminary in vivo results in breast demonstrate that this technique, known as transient elastography, is very sensitive to the presence of hard tumors. The same technique can also be combined with remote palpation induced par ultrasonic radiation pressure to replace the usual external vibrating system The same probe allows both to generate and detect shear waves propagation by using an unusual emission-reception sequence.
{"title":"Ultra high speed imaging of elasticity","authors":"M. Fink, L. Sandrin, M. Tanter, S. Catheline, S. Chaffai, J. Bercoff, J. Gennisson","doi":"10.1109/ULTSYM.2002.1192651","DOIUrl":"https://doi.org/10.1109/ULTSYM.2002.1192651","url":null,"abstract":"Ultrafast ultrasonic imaging seems to have a strong potential for medical imaging applications. During the past five years, it has been applied successfully to quantitative assessment of soft tissues elasticity. An ultrafast ultrasonic scanner was built in our lab for quantitatively mapping the shear elasticity of soft tissues. The ultrafast Scanner provides images of the echogenecity of tissues similar to a standard echographic device but with a 200 times higher a frame rate. It allows to detect fast tissue motion induced by low frequency shear waves inside the body. From these displacements, a shear elasticity map is constructed using inverse problem algorithms. Preliminary in vivo results in breast demonstrate that this technique, known as transient elastography, is very sensitive to the presence of hard tumors. The same technique can also be combined with remote palpation induced par ultrasonic radiation pressure to replace the usual external vibrating system The same probe allows both to generate and detect shear waves propagation by using an unusual emission-reception sequence.","PeriodicalId":378705,"journal":{"name":"2002 IEEE Ultrasonics Symposium, 2002. Proceedings.","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125409546","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 : 2002-10-08DOI: 10.1109/ULTSYM.2002.1192674
R. Baldewsing, C. D. de Korte, F. Mastik, J. Schaar, A. V. D. van der Steen
Knowledge of the Young's modulus distribution of an atherosclerotic artery allows for differentiation between its components. Intravascular elastography generates an artifactual image of this Young's modulus distribution. A finite element model (FEM) can assist in interpreting the elastogram and give its Young's modulus distribution by inverse problem solution. Intravascular ultrasound (IVUS) measurements were performed on a hard phantom with soft eccentric plaque and an atherosclerotic coronary artery. The complex FEM geometry and Young's modulus distribution were defined using a custom-made graphical user interface. Next elastograms were calculated from IVUS data and compared with FEM elastograms. IVUS and FEM elastograms showed excellent agreement in case of the phantom and a similar pattern in case of the artery. Strain values in the FEM elastogram appeared highly sensitive for variations in the Young's modulus but not in the Poisson's ratio.
{"title":"Comparison of finite elements model elastograms and IVUS elastograms acquired from phantoms and arteries","authors":"R. Baldewsing, C. D. de Korte, F. Mastik, J. Schaar, A. V. D. van der Steen","doi":"10.1109/ULTSYM.2002.1192674","DOIUrl":"https://doi.org/10.1109/ULTSYM.2002.1192674","url":null,"abstract":"Knowledge of the Young's modulus distribution of an atherosclerotic artery allows for differentiation between its components. Intravascular elastography generates an artifactual image of this Young's modulus distribution. A finite element model (FEM) can assist in interpreting the elastogram and give its Young's modulus distribution by inverse problem solution. Intravascular ultrasound (IVUS) measurements were performed on a hard phantom with soft eccentric plaque and an atherosclerotic coronary artery. The complex FEM geometry and Young's modulus distribution were defined using a custom-made graphical user interface. Next elastograms were calculated from IVUS data and compared with FEM elastograms. IVUS and FEM elastograms showed excellent agreement in case of the phantom and a similar pattern in case of the artery. Strain values in the FEM elastogram appeared highly sensitive for variations in the Young's modulus but not in the Poisson's ratio.","PeriodicalId":378705,"journal":{"name":"2002 IEEE Ultrasonics Symposium, 2002. Proceedings.","volume":"57 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115065878","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 : 2002-10-08DOI: 10.1109/ULTSYM.2002.1193538
O. Matar, S. D. Santos, Michel Vila, F. Meulen
In this work, a new method to measure in contact the nonlinearity parameter /spl beta/ of solid plates is presented. This method is based on an idea developed by Barriere and Royer (2001) to measure the nonlinearity parameter in liquids. A high frequency (HF) tone-burst signal of 20 MHz is inserted in the material by a contact-transducer (with a suitable coupling). A low frequency (LF) pulse (2.5 MHz) is applied to the other face, in the opposite direction, such that the nonlinear interaction of the two waves takes place during the back propagation toward the HF transducer. This collinear interaction creates a phase modulation of the HF tone-burst which is directly proportional to the /spl beta/ coefficient and the particle velocity of the LF wave. To determine this particle velocity a self reciprocity calibration of the contact LF transducer is used, as proposed by Dace et al. (1991). A numeric phase demodulation has been performed, giving the beta coefficient of the sample. The proposed method is validated by nonlinearity parameter measurements in Fused Silica.
{"title":"Acoustic nonlinear parameter measurement in solid with a contact phase modulation method","authors":"O. Matar, S. D. Santos, Michel Vila, F. Meulen","doi":"10.1109/ULTSYM.2002.1193538","DOIUrl":"https://doi.org/10.1109/ULTSYM.2002.1193538","url":null,"abstract":"In this work, a new method to measure in contact the nonlinearity parameter /spl beta/ of solid plates is presented. This method is based on an idea developed by Barriere and Royer (2001) to measure the nonlinearity parameter in liquids. A high frequency (HF) tone-burst signal of 20 MHz is inserted in the material by a contact-transducer (with a suitable coupling). A low frequency (LF) pulse (2.5 MHz) is applied to the other face, in the opposite direction, such that the nonlinear interaction of the two waves takes place during the back propagation toward the HF transducer. This collinear interaction creates a phase modulation of the HF tone-burst which is directly proportional to the /spl beta/ coefficient and the particle velocity of the LF wave. To determine this particle velocity a self reciprocity calibration of the contact LF transducer is used, as proposed by Dace et al. (1991). A numeric phase demodulation has been performed, giving the beta coefficient of the sample. The proposed method is validated by nonlinearity parameter measurements in Fused Silica.","PeriodicalId":378705,"journal":{"name":"2002 IEEE Ultrasonics Symposium, 2002. Proceedings.","volume":"41 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116005470","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 : 2002-10-08DOI: 10.1109/ULTSYM.2002.1193480
C. Fournier, S. Bridal, A. Coron, P. Laugier
This in vitro study investigates the role of skin-collagen in the variation of the integrated backscatter coefficient (IBS) and the frequency dependence of backscatter (n). IBS and n (11-27 MHz) were estimated from spectral analysis of radio frequency (RF) signals acquired in 31 human skin specimens of abdomen and breast dermis at depths of 370, 620 and 880 /spl mu/m beneath the skin surface. Microscopic morphometrical analysis was applied at matched depths of histologic sections from each specimen to estimate mean thickness of collagen bundles (TH), mean space between bundles (SP) and percent fractional-area occupied by the collagen (%A). Both IBS and n decreased with depth of the measurement region beneath the skin surface and were significantly different for abdomen and breast. For abdomen specimens, n was inversely correlated to TH and %A in the most superficial depth. IBS was inversely correlated to %A in the most superficial depth. For breast samples, IBS significantly decreased as SP increased at all three depths. Knowledge of the relationship between dermal collagen distribution and acoustic properties should aid interpretation of in vivo ultrasound measurements.
{"title":"Relationship between skin-collagen micro-architecture and ultrasonic backscatter parameters at 20 MHz","authors":"C. Fournier, S. Bridal, A. Coron, P. Laugier","doi":"10.1109/ULTSYM.2002.1193480","DOIUrl":"https://doi.org/10.1109/ULTSYM.2002.1193480","url":null,"abstract":"This in vitro study investigates the role of skin-collagen in the variation of the integrated backscatter coefficient (IBS) and the frequency dependence of backscatter (n). IBS and n (11-27 MHz) were estimated from spectral analysis of radio frequency (RF) signals acquired in 31 human skin specimens of abdomen and breast dermis at depths of 370, 620 and 880 /spl mu/m beneath the skin surface. Microscopic morphometrical analysis was applied at matched depths of histologic sections from each specimen to estimate mean thickness of collagen bundles (TH), mean space between bundles (SP) and percent fractional-area occupied by the collagen (%A). Both IBS and n decreased with depth of the measurement region beneath the skin surface and were significantly different for abdomen and breast. For abdomen specimens, n was inversely correlated to TH and %A in the most superficial depth. IBS was inversely correlated to %A in the most superficial depth. For breast samples, IBS significantly decreased as SP increased at all three depths. Knowledge of the relationship between dermal collagen distribution and acoustic properties should aid interpretation of in vivo ultrasound measurements.","PeriodicalId":378705,"journal":{"name":"2002 IEEE Ultrasonics Symposium, 2002. Proceedings.","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116111700","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 : 2002-10-08DOI: 10.1109/ULTSYM.2002.1193478
J. Stitt, R. Tutwiler, K. Shung
An improved analog beamformer is described that is used to process the data from a high frequency linear array. This unit is a part of a test system, which has the capability to characterize ultrasound transducer arrays up to 128 elements. Improvements include increasing the accuracy of the dynamic focusing capability and an increased bandwidth of the summing circuit.
{"title":"An improved four-focal zone high-frequency ultrasound analog beamformer","authors":"J. Stitt, R. Tutwiler, K. Shung","doi":"10.1109/ULTSYM.2002.1193478","DOIUrl":"https://doi.org/10.1109/ULTSYM.2002.1193478","url":null,"abstract":"An improved analog beamformer is described that is used to process the data from a high frequency linear array. This unit is a part of a test system, which has the capability to characterize ultrasound transducer arrays up to 128 elements. Improvements include increasing the accuracy of the dynamic focusing capability and an increased bandwidth of the summing circuit.","PeriodicalId":378705,"journal":{"name":"2002 IEEE Ultrasonics Symposium, 2002. Proceedings.","volume":"23 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122780413","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 : 2002-10-08DOI: 10.1109/ULTSYM.2002.1193534
T. Gómez, B. González, F. Montero
Measurements of different types of paper (surface density from 80 gr/m/sup 2/ to 300 gr/m/sup 2/) using air-coupled, wide frequency band ultrasound and analysis in the frequency domain is presented. The working frequency range is 0.6-2.2 MHz. At normal incidence, thickness resonances in the paper samples are excited and sensed. From the analysis in the frequency domain, of such resonances, density, longitudinal velocity and attenuation of sound waves in the paper samples are obtained. At oblique incidence, Lamb waves are observed by use of Cremer's coincidence rule. The velocity of different Lamb modes is measured.
{"title":"Paper characterization by measurement of thickness and plate resonances using air-coupled ultrasound","authors":"T. Gómez, B. González, F. Montero","doi":"10.1109/ULTSYM.2002.1193534","DOIUrl":"https://doi.org/10.1109/ULTSYM.2002.1193534","url":null,"abstract":"Measurements of different types of paper (surface density from 80 gr/m/sup 2/ to 300 gr/m/sup 2/) using air-coupled, wide frequency band ultrasound and analysis in the frequency domain is presented. The working frequency range is 0.6-2.2 MHz. At normal incidence, thickness resonances in the paper samples are excited and sensed. From the analysis in the frequency domain, of such resonances, density, longitudinal velocity and attenuation of sound waves in the paper samples are obtained. At oblique incidence, Lamb waves are observed by use of Cremer's coincidence rule. The velocity of different Lamb modes is measured.","PeriodicalId":378705,"journal":{"name":"2002 IEEE Ultrasonics Symposium, 2002. Proceedings.","volume":"54 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122624861","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 : 2002-10-08DOI: 10.1109/ULTSYM.2002.1192604
P. Cao, K. Shung, N. Karkhanis, Wohsing Chen
A Field Programmable Gate Array (FPGA) based real time beamformer was developed for a six-ring annular array ultrasound transducer. Six analog to digital converters (AD9054, Analog Devices Inc.) were used to digitized the echoes at 200MHz. A Xilinx Virtex E FPGA chip which works at a 200MHz clock was used to delay the digitized echoes for beamforming. The delay for each channel was accomplished in two steps. A programmable FIFO was used for the delays of integer multiples of the clock period, a 4-tap Fractional Delay (FD) FIR filter was used for the delays less than one clock period. A high speed Cypress FIFO was used to transfer the summed beam to a DSP microprocessor (ADSP21065L). The DSP microprocessor completes envelope detection, imaging processing and transfers the image data to a computer for display through a PCI bus I/O card (PCI6534, National Instruments). The source codes for FPGA were written in VHDL language and schematic capture. A lookup table method based multiplier was designed to improve the speed of algorithm. The whole beamformer was designed in a pipeline structure; it is capable of working at 240MHz clock frequency after implemented in ISE Foundation 4.2i (Xilinx Inc). Using a Gaussian modulated sinusoidal pulse, with a 50MHz center frequency and a 50% bandwidth, the Matlab simulation study shows that the FD filter gave a maximal error of 11.2% in amplitude from the ideal waveform, and a 0.3% maximum mean square error when the required delay was 0.2 of the clock period.
针对六环环形超声换能器，研制了一种基于现场可编程门阵列(FPGA)的实时波束形成器。使用六个模数转换器(AD9054, analog Devices Inc.)对200MHz的回波进行数字化处理。采用工作频率为200MHz的Xilinx Virtex E FPGA芯片对数字化回波进行延迟，实现波束形成。每个通道的延迟分两个步骤完成。可编程FIFO用于时钟周期整数倍的延迟，4分路分数阶延迟(FD) FIR滤波器用于小于一个时钟周期的延迟。采用高速Cypress FIFO将求和光束传输到DSP微处理器(ADSP21065L)。DSP微处理器完成包络检测、成像处理，并通过PCI总线I/O卡(PCI6534, National Instruments)将图像数据传输到计算机显示。用VHDL语言编写了FPGA的源代码，并进行了原理图捕获。为了提高算法的速度，设计了一种基于查找表法的乘法器。整个波束形成器采用管道结构设计;在ISE Foundation 4.2i (Xilinx Inc .)中实现后，它能够在240MHz时钟频率下工作。采用高斯调制正弦脉冲，中心频率为50MHz，带宽为50%，Matlab仿真研究表明，当所需延迟为时钟周期的0.2时，FD滤波器与理想波形的幅值最大误差为11.2%，均方误差最大为0.3%。
{"title":"Design of a real time digital beamformer for a 50MHz annular array ultrasound transducer","authors":"P. Cao, K. Shung, N. Karkhanis, Wohsing Chen","doi":"10.1109/ULTSYM.2002.1192604","DOIUrl":"https://doi.org/10.1109/ULTSYM.2002.1192604","url":null,"abstract":"A Field Programmable Gate Array (FPGA) based real time beamformer was developed for a six-ring annular array ultrasound transducer. Six analog to digital converters (AD9054, Analog Devices Inc.) were used to digitized the echoes at 200MHz. A Xilinx Virtex E FPGA chip which works at a 200MHz clock was used to delay the digitized echoes for beamforming. The delay for each channel was accomplished in two steps. A programmable FIFO was used for the delays of integer multiples of the clock period, a 4-tap Fractional Delay (FD) FIR filter was used for the delays less than one clock period. A high speed Cypress FIFO was used to transfer the summed beam to a DSP microprocessor (ADSP21065L). The DSP microprocessor completes envelope detection, imaging processing and transfers the image data to a computer for display through a PCI bus I/O card (PCI6534, National Instruments). The source codes for FPGA were written in VHDL language and schematic capture. A lookup table method based multiplier was designed to improve the speed of algorithm. The whole beamformer was designed in a pipeline structure; it is capable of working at 240MHz clock frequency after implemented in ISE Foundation 4.2i (Xilinx Inc). Using a Gaussian modulated sinusoidal pulse, with a 50MHz center frequency and a 50% bandwidth, the Matlab simulation study shows that the FD filter gave a maximal error of 11.2% in amplitude from the ideal waveform, and a 0.3% maximum mean square error when the required delay was 0.2 of the clock period.","PeriodicalId":378705,"journal":{"name":"2002 IEEE Ultrasonics Symposium, 2002. Proceedings.","volume":"3 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129517662","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 : 2002-10-08DOI: 10.1109/ULTSYM.2002.1193502
F. Lingvall, T. Stepinski
One of the fundamental requirements for the successful application of the classical synthetic aperture focusing technique (SAFT) is the use of a transducer that emits spherical (cylindrical) waves. For a planar transducer, the performance of the SAFT algorithm will deteriorate if its active area becomes too large comparing to the wavelength. This is due to the spatial impulse responses (SIRs) associated with the transducer that no longer resemble Dirac functions since the emitted waves is not spherical. Therefore, to achieve a high resolution or finite-sized transducers, the SIRs must be taken into consideration. Here, we propose a method that is based on a discrete linear model of the imaging system. The method uses a spatio-temporal deconvolution technique designed to minimize the mean squared reconstruction error of the imaging system. To demonstrate the performance of the proposed method we present experiments using a phased array for the inspection of a copper specimen. The results obtained using the deconvolution method for finite apertures are compared to those obtained with a time-domain SAFT algorithm and a focused phased array.
{"title":"Compensating transducer diffraction effects in synthetic aperture imaging for immersed solids","authors":"F. Lingvall, T. Stepinski","doi":"10.1109/ULTSYM.2002.1193502","DOIUrl":"https://doi.org/10.1109/ULTSYM.2002.1193502","url":null,"abstract":"One of the fundamental requirements for the successful application of the classical synthetic aperture focusing technique (SAFT) is the use of a transducer that emits spherical (cylindrical) waves. For a planar transducer, the performance of the SAFT algorithm will deteriorate if its active area becomes too large comparing to the wavelength. This is due to the spatial impulse responses (SIRs) associated with the transducer that no longer resemble Dirac functions since the emitted waves is not spherical. Therefore, to achieve a high resolution or finite-sized transducers, the SIRs must be taken into consideration. Here, we propose a method that is based on a discrete linear model of the imaging system. The method uses a spatio-temporal deconvolution technique designed to minimize the mean squared reconstruction error of the imaging system. To demonstrate the performance of the proposed method we present experiments using a phased array for the inspection of a copper specimen. The results obtained using the deconvolution method for finite apertures are compared to those obtained with a time-domain SAFT algorithm and a focused phased array.","PeriodicalId":378705,"journal":{"name":"2002 IEEE Ultrasonics Symposium, 2002. Proceedings.","volume":"65 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128295102","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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