Photoacoustic inspection of matching layers of ultrasonic air-coupled transducers

Stor-Pellinen, Jyrki; Okasanen, M.; Vuohelainen, R.; Rantala, Jukka; Hartikainen, J.; Luukkala, M.

doi:10.1109/ultsym.1989.67068

Cited by 2 publications

(2 citation statements)

References 5 publications

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“…One of the main difficulties has been the provision of low-loss matching layers with the required acoustic impedance, as few materials will suffice for the purpose. In Manuscript received November 24, 1993; revised April 29, 1994; accepted July 11, 1994 this regard, numerous options have been investigated, such as cork [7], balsa wood [7], [8], silicone rubber [7], foam plastics [9], aerogels [8], [10], multi-horns [11], and even multiple matching layers [12], [13]. Additional work has focused upon reducing the impedance of the active element through the use of 1-3 connectivity composite elements [4], [6], which leads to an increase in bandwidth and sensitivity.…”

Section: Introductionmentioning

confidence: 99%

The design and characterization of micromachined air-coupled capacitance transducers

Schindel

Hutchins

Zou

et al. 1995

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

271

104

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Air-coupled capacitance transducers have been manufactured using anisotropically etched silicon backplates and commercially available dielectric films (Kapton and Mylar). The small backplate pits which result from etching, provide well ordered and highly uniform air layers between the backplate surface and thin dielectric film. Such uniformity allows the transducers to be manufactured with reproducible characteristics (a property difficult to achieve through conventional manufacturing). Impulse response studies in generation and detection, have indicated well-damped, wideband behavior, with bandwidths extending from <100 kHz to 2.3 MHz (at the 06 dB points). These bandwidths are investigated as a function of excitation pulse width, applied bias potential, and dielectric film thickness. An estimate of detection sensitivity is also provided by comparison with a calibrated laser interferometer.

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Section: Introductionmentioning

confidence: 99%

The design and characterization of micromachined air-coupled capacitance transducers

Schindel

Hutchins

Zou

et al. 1995

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

271

104

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“…The impedance of a plate with holes thus can be modeled as parallel connection of two impedances Z inp in (9) and Z inh in (10):…”

Section: B Thick Plate With Many Small Holesmentioning

confidence: 99%

New type of matching layer for air-coupled ultrasonic transducers

Toda¹

2002

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

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This paper presents a new concept in the design of an impedance matching structure for air coupled ultrasonic transducers. A reflective layer structure is inserted between the transducer and propagation medium with a small air space. Adjusting the air space and the reflectivity of the inserted structure causes the transducer impedance to match with the impedance of the propagation medium. Two such structures were investigated as a reflector: a polymer thin film and a thick plate with many holes. Wave impedance theory was applied to these reflecting structures, and the impedance of a thin film layer at the incident surface was calculated using boundary conditions. Impedance of holed plate is calculated in a similar fashion. It was found that the calculated impedance of these structures approximately matched the impedance of the PZT air transducer (40 KHz). The acoustic pressure output was maximized by adjusting the position of the matching structure. A theoretical gain of up to 10 dB in the acoustic pressure was predicted under ideal circumstances, and the experimental observations showed a gain of 9.5 dB in the acoustic pressure for a 12 m polyethylene film placed at a distance of 0.1 mm from the transducer's surface. The increase was 9.8 dB for a polyvinylidene fluoride (PVDF) film and 9.7 dB for a 1.5 mm printed circuit board with many holes at a distance of 25 m from the transducer's surface.

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Photoacoustic inspection of matching layers of ultrasonic air-coupled transducers

Cited by 2 publications

References 5 publications

The design and characterization of micromachined air-coupled capacitance transducers

The design and characterization of micromachined air-coupled capacitance transducers

New type of matching layer for air-coupled ultrasonic transducers

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