Influence of acousto-optic interactions on the determination of the diffracted field by an array obtained from displacement measurements

Certon, Dominique; Férin, Guillaume; Matar, Olivier Bou; Guyonvarch, J.; Remeniéras, Jean-Pierre; Patat, F.

doi:10.1016/j.ultras.2003.12.035

Cited by 19 publications

(12 citation statements)

References 6 publications

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“…Nichols "postulated" that the acoustic wave transmitted over the surface of the baffle, encountering a rapid change in impedance at the edge, gave rise to secondary radiation. Certon et al 36 have observed similar radiation from unbaffled underwater transducers.…”

Section: B Limitationsmentioning

confidence: 80%

“…34 It became the basis of a primary calibration method for high-frequency hydrophones. 8,35,36 A second method uses a laser Doppler vibrometer to detect and measure the velocity of a pellicle or transducer surface. 9,33,37 These two interferometric methods involve phase and frequency modulation.…”

Section: B Acoustic Field Projection and Measurement Methodsmentioning

confidence: 99%

“…Previously, the acousto-optic effect has been modeled vis-a-vis optical determination of pellicle motion, both by homodyne laser interferometric determination of displacement 31,34,36 and by heterodyne laser interferometric determination of velocity. 9,10,42 It has also been modeled for crossbeam measurement of the acoustic field in a plane parallel with that of the radiating transducer 9,39,43 or crosswise to the beam axis in the case of a focusing transducer.…”

Section: Modeling the Acousto-optic Effectmentioning

confidence: 99%

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Acousto-optic effect compensation for optical determination of the normal velocity distribution associated with acoustic transducer radiation

Foote

Theobald

2015

The Journal of the Acoustical Society of America

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The acousto-optic effect, in which an acoustic wave causes variations in the optical index of refraction, imposes a fundamental limitation on the determination of the normal velocity, or normal displacement, distribution on the surface of an acoustic transducer or optically reflecting pellicle by a scanning heterodyne, or homodyne, laser interferometer. A general method of compensation is developed for a pulsed harmonic pressure field, transmitted by an acoustic transducer, in which the laser beam can transit the transducer nearfield. By representing the pressure field by the Rayleigh integral, the basic equation for the unknown normal velocity on the surface of the transducer or pellicle is transformed into a Fredholm equation of the second kind. A numerical solution is immediate when the scanned points on the surface correspond to those of the surface area discretization. Compensation is also made for oblique angles of incidence by the scanning laser beam. The present compensation method neglects edge waves, or those due to boundary diffraction, as well as effects due to baffles, if present. By allowing measurement in the nearfield of the radiating transducer, the method can enable quantification of edge-wave and baffle effects on transducer radiation. A verification experiment has been designed. [http://dx

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Section: B Limitationsmentioning

confidence: 80%

Section: B Acoustic Field Projection and Measurement Methodsmentioning

confidence: 99%

Section: Modeling the Acousto-optic Effectmentioning

confidence: 99%

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Acousto-optic effect compensation for optical determination of the normal velocity distribution associated with acoustic transducer radiation

Foote

Theobald

2015

The Journal of the Acoustical Society of America

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“…We compensated for the index of refraction of oil, 1.47 [25], to calculate the displacement of the membrane surface. We assumed this index of refraction was constant since acousto-optical effects were shown to be negligible in this setup [25], [26], and the maximum pressure output of the transducer never exceeded 500 kPa peak to peak.…”

Section: Methodsmentioning

confidence: 99%

Evaluation of wafer bonded CMUTs with rectangular membranes featuring high fill factor

Wong

Kupnik

Zhuang

et al. 2008

IEEE Trans. Ultrason., Ferroelect., Freq. Contr.

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Increasing fill factor is one design approach used to increase average output displacement, output pressure, and sensitivity of capacitive micromachined ultrasonic transducers (CMUTs). For rectangular cells, the cell-to-cell spacing and the aspect ratio determine the fill factor. In this paper, we explore the effects of these parameters on performance, in particular the nonuniformity of collapse voltage between neighboring cells and presence of higher order modes in air or immersed operation. We used a white light interferometer to measure nonuniformity in deflection between neighboring cells. We found that reducing the cell-to-cell spacing could cause bending of the center support post, which amplifies nonuniformities in collapse voltage to 18.4% between neighboring cells. Using a 2-D finite element model (FEM), we found that for our designs, increasing the support post width to 1.67 times the membrane thickness alleviated the post bending problem. Using impedance and interferometer measurements to observe the effects of aspect ratio on higher order modes, we found that the (1,3) modal frequency approached the (1,1) modal frequency as the aspect ratio of the rectangles increased. In air operation, under continuous wave (CW) excitation at the center frequency, the rectangular cells behaved in the (1,1) mode. In immersion, because of dispersive guided modes, these cells operated in a higher order mode when excited with a CW signal at the center frequency. This contributed to a loss of output pressure; for this reason our rectangular design was unsuitable for CW operation in immersion.

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“…The experimental angular directivity pattern was obtained from the measured particle velocity field thanks to the Rayleigh integral formulation in which the acoustic optic interaction effects were corrected [21]. The two angular directivity spectra are presented in Fig.…”

Section: B Measurement Of Directivity Patternmentioning

confidence: 99%

Two-dimensional electroacoustic model of transducer array based on 1-3 piezocomposite materials

Certon

Guyonvarch

Férin³

et al. 2006

IEEE Trans. Ultrason., Ferroelect., Freq. Contr.

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An analytical model is presented to achieve simultaneous prediction of the elementary electroacoustic response and directivity pattern of a one-dimensional (1-D) piezocomposite array. The theoretical approach was based on guided wave theory in a multilayered structure in which the 1-3 piezocomposite material is considered as a homogeneous piezoelectric plate. A matrix method was applied to simulate the displacement fields generated at the surface of the array when one element was excited with an electrical pulse. A test device was manufactured, then characterized through measurements of displacement performed with an interferometric laser probe when the array vibrated in air and in water. The experimental results are presented and compared with theory.

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Influence of acousto-optic interactions on the determination of the diffracted field by an array obtained from displacement measurements

Cited by 19 publications

References 6 publications

Acousto-optic effect compensation for optical determination of the normal velocity distribution associated with acoustic transducer radiation

Acousto-optic effect compensation for optical determination of the normal velocity distribution associated with acoustic transducer radiation

Evaluation of wafer bonded CMUTs with rectangular membranes featuring high fill factor

Two-dimensional electroacoustic model of transducer array based on 1-3 piezocomposite materials

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