Experimental demonstration of Fresnel zone plate lens for robust subwavelength focusing at mega hertz

Pan, Xiao; Zeng, Long-Sheng; Li, Yong; Zhu, Xuefeng; Jin, Yabin

doi:10.1016/j.ultras.2022.106876

Cited by 10 publications

(2 citation statements)

References 57 publications

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“…Conventional focusing transducers primarily use several passive focusing methods concerning acoustic concave lenses [16,17], Fresnel zone plates [18,19], or off-axis parabolic reflectors [20] to enhance the lateral resolution of transducers. However, these approaches have a significant problem, which is the loss of sensitivity of transducers [21].…”

Section: Introductionmentioning

confidence: 99%

Investigation of an Active Focusing Planar Piezoelectric Ultrasonic Transducer

Wu,

You,

Zhang

et al. 2024

Sensors

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Ultrasonic focusing transducers have broad prospects in advanced ultrasonic non-destructive testing fields. However, conventional focusing methods that use acoustic concave lenses can disrupt the acoustic impedance matching condition, thereby adversely affecting the sensitivity of the transducers. In this paper, an active focusing planar ultrasonic transducer is designed and presented to achieve a focusing effect with a higher sensitivity. An electrode pattern consisting of multiple concentric rings is designed, which is inspired by the structure of Fresnel Zone Plates (FZP). The structural parameters are optimized using finite element simulation methods. A prototype of the transducer is manufactured with electrode patterns made of conductive silver paste using silk screen-printing technology. Conventional focusing transducers using an acoustic lens and an FZP baffle are also manufactured, and their focusing performances are comparatively tested. The experimental results show that our novel transducer has a focal length of 16 mm and a center frequency of 1.16 MHz, and that the sensitivity is improved by 23.3% compared with the conventional focusing transducers. This research provides a new approach for the design of focusing transducers.

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Section: Introductionmentioning

confidence: 99%

Investigation of an Active Focusing Planar Piezoelectric Ultrasonic Transducer

Wu,

You,

Zhang

et al. 2024

Sensors

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“…Thereafter, the concept of photonic crystals was further extended to acoustic/elastic waves, known as phononic crystals (PCs), which were exploited for negative refraction and subwavelength imaging of acoustic 8 – 15 /elastic 16 – 18 waves. Besides PCs, metasurfaces were also exploited for acoustic/elastic wave focusing and subwavelength imaging due to their ability to control incident wavefront with a gradient phase profile realized using subwavelength structural units 19 – 22 . Unlike negative refraction in PCs, the subwavelength resolution in metasurfaces is achieved because of the near-field interference of waves after diffracting through an array of subwavelength units.…”

Section: Introductionmentioning

confidence: 99%

Broadband subwavelength imaging of flexural elastic waves in flat phononic crystal lenses

Danawe

Tol

2023

Sci Rep

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Subwavelength imaging of elastic/acoustic waves using phononic crystals (PCs) is limited to a narrow frequency range via the two existing mechanisms that utilize either the intense Bragg scattering in the first phonon band or negative effective properties (left-handed material) in the second (or higher) phonon band. In the first phonon band, the imaging phenomenon can only exist at frequencies closer to the first Bragg band gap where the equal frequency contours (EFCs) are convex. Whereas, for the left-handed materials, the subwavelength imaging is restricted to a narrow frequency region where wave vectors in PC and background material are close to each other, which is essential for single-point image formation. In this work, we propose a PC lens for broadband subwavelength imaging of flexural waves in plates exploiting the second phonon band and the anisotropy of a PC lattice for the first time. Using a square lattice design with square-shaped EFCs, we enable the group velocity vector to always be perpendicular to the lens interface irrespective of the frequency and incidence angle; thus, resulting in a broadband imaging capability. We numerically and experimentally demonstrate subwavelength imaging using this concept over a significantly broadband frequency range.

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