Directional Trimming of Radiated Ultrasonic Beam Using Decentered Annular Transducer Array

Masuyama, Hiroyuki; Mizutani, Koichi; Nagai, Keinosuke

doi:10.1143/jjap.44.4311

Cited by 7 publications

(12 citation statements)

References 15 publications

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“…In the measurement of sound fields, the advantage of an optical probe is that it exerts no physical influence on sound fields. 10) Therefore, it can be expected that optical sensing is widely applied to the calibration of microphones, the performance evaluation of transducers, 11,12) and the observation of microbubbles, 13) among others.…”

Section: Introductionmentioning

confidence: 99%

Optical Computerized Tomography for Visualization of Ultrasonic Fields Using Michelson Interferometer

Obuchi

Masuyama

Mizutani

et al. 2006

jjap

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We propose a method for the noncontact visualization of ultrasonic fields using the Michelson interferometer and optical computerized tomography (O-CT). The light source of the interferometer is a He–Ne laser. The test light passing through radiated sound fields is interfered by the reference light. Therefore, the index of refraction gradient including sound pressure information is transformed into the intensity of the interference light that can be electrically acquired by an avalanche photo-diode. Projection data along the optical axis is obtained by single linear scanning in the range of ±32 mm and electronically quadrature-detected as complex amplitude. Thirty-six projections are acquired in the range of 0≤θ<π (rad), and complex sound fields are reconstructed in a region of 64×64 mm2 by CT. The experimental results are in agreement with the numerical results.

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Section: Introductionmentioning

confidence: 99%

Optical Computerized Tomography for Visualization of Ultrasonic Fields Using Michelson Interferometer

Obuchi

Masuyama

Mizutani

et al. 2006

jjap

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“…Acoustic Bessel beams have been excited using acoustical axicons [8], in analogy with the optical case. However, the most convenient way to form acoustic Bessel beams is by using annular transducer arrays [13]. Related theoretical studies include the scattering of Bessel beams by spheres [14], non-diffracting bulk-acoustic X waves [15] or non-linearly generated Bessel beams of higher harmonics [16,17].…”

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confidence: 99%

Acoustic Bessel-like beam formation by an axisymmetric grating

Jiménez¹,

Romero‐García²,

Picó³

et al. 2014

EPL

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We report Bessel-like beam formation of acoustic waves by means of an axisymmetric grating of rigid tori. The results show that the generated beam pattern is similar to that of Bessel beams, characterized by elongated non-diffracting focal spots. A multiple foci structure is observed, due to the finite size of the lens. The dependence of the focal distance on the frequency is also discussed, on the basis of an extended grating theory. Experimental validation of acoustic Bessel-like beam formation is also reported for sound waves. The results can be generalized to wave beams of different nature, as optical or matter waves. PACS numbers: 43.20.Mv, 43.20.Hq,43.20.Fn Bessel beams, originally proposed in optics 1,2 , are now at the basis of many applications due to their unusual propagation properties 3-8 . The most celebrated property of a Bessel beam is that, in the ideal case, the field propagates invariantly, i.e. without any diffracting broadening, in contrast to the other canonical case, the Gaussian beam, where the beam experiences diffractive broadening in free space propagation. As a consequence, the field pattern in a Bessel beam possesses an infinitely extended focal line.Strictly speaking, Bessel beam is a solution of the wave equation in the form of a monochromatic wave with a transverse profile given by a Bessel function of the first kind, which by definition presents an infinite spatial extension. This ideal case cannot be realized in practice (in the same way as ideal, infinitely extended plane waves cannot exist). However, approximate or imperfect Bessel beams of finite transverse extent can be excited by different means, displaying not an infinite but an extremely elongated focal line.In optics, Bessel-like beams are usually formed by focusing a Gaussian beam by an axicon 9 , a transparent refractive element of conical shape, as shown in Fig. 1(a). The beam in propagation through the axicon acquires linearly tilted (conical) wave-fronts, which results in an elongated focus behind the axicon. As the axicon is not infinitely extended in transverse space, the resulting Bessel beam is not perfect, and displays a focal line of finite extent. Optical Bessel beams have been also obtained by acoustic gradient index lenses 10 . In electromagnetism, Bessel-like beams have been generated from a subwavelength aperture by adding a metallic circular grating structure in front of the aperture 11 . Such imperfect Bessel beams find multiple applications, e.g. in optics for laser inscription of patterns deep into transpar-m=1 m=2 m=3 M (a) (b) f(r)| n=2 f(r)| n=1 a n=2 n=1 FIG. 1. (Color online) (a) Illustration of the formation of Bessel beam by an axicon resulting in imperfect Bessel beam showing a focus-line of finite extent; (b) Illustration of the formation of Bessel-like beams by a plane of concentric rings, where converging diffracted waves result in two elongated foci.ent materials, or for etching of deep narrow holes in laser manufacturing of opaque materials, among others 3,4,6 . In acoustics, Bessel beam...

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“…However, since the introduction of the optical method of forming nondiffracting beams by Durnin, 6,7) the acoustic method of forming such nondiffracting beams with sharp profiles has been widely studied. [8][9][10][11][12][13] A sound source using an equiamplitude-driven annular transducer array 14,15) has a simple structure, and it can become a useful means of forming the nondiffracting beam. Additionally, an array of this type has a feature that there exists a separation between neighboring elements.…”

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confidence: 99%

“…Utilizing this separation in order to decenter array elements, it becomes possible to change and trim the radiation direction of the beam, and to scan the beam. [16][17][18][19][20] In the production of the sound source, it is considered that it is necessary to ensure sufficient accuracy in forming the narrow beam. Meanwhile, in the actual production of the sound source, it is desirable that the process be simple, insofar as a problem does not occur in use.…”

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confidence: 99%

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Direction-Variable Beam by Decentered Annular Array Sound Source with Rounded Width of Elements

Masuyama¹,

Mizutani

2008

jjap

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In this paper, we describe an examination of a direction-variable beam generated by a sound source that causes the decentering operation of the equiamplitude-driven annular array. In the presented method, we apply a rounding operation for the width of each annular array element. From results of the calculations carried out for examining the effect on the shape of the radiated sound beams, it is shown that the beam profiles exhibit no marked turbulence in comparison with the profile in which the rounding operation is not applied, as long as the number of array elements and the central radius of the outermost element satisfy the desired value. It is expected that these results will enable the simplification of the process for forming the array element, in the actual production of sound sources.

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Directional Trimming of Radiated Ultrasonic Beam Using Decentered Annular Transducer Array

Cited by 7 publications

References 15 publications

Optical Computerized Tomography for Visualization of Ultrasonic Fields Using Michelson Interferometer

Optical Computerized Tomography for Visualization of Ultrasonic Fields Using Michelson Interferometer

Acoustic Bessel-like beam formation by an axisymmetric grating

Direction-Variable Beam by Decentered Annular Array Sound Source with Rounded Width of Elements

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