Focussing of ultrasonic waves in air using a micromachined Fresnel zone-plate

Schindel, D.W.; Bashford, A.G.; Hutchins, David A.

doi:10.1016/s0041-624x(97)00011-5

Cited by 38 publications

(20 citation statements)

References 14 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In the present work, a cylindrically symmetric micromachined Fresnel zone plate was used, which had been developed previously by the authors as a means of focusing the fields of the capacitance transducer in air at high frequencies [37]. As seen in Fig.…”

Section: B Annular and Zone Plate Transducersmentioning

confidence: 99%

Micromachined ultrasonic capacitance transducers for immersion applications

Bashford

Schindel

Hutchins

1998

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

Self Cite

View full text Add to dashboard Cite

Investigations into the characteristics of water-coupled ultrasonic capacitance transducers have been undertaken for a range of transducer configurations. The radiated fields have been scanned in water using a miniature hydrophone detector, and the results compared to theory based on a plane piston approach. Micromachined backplates in conjunction with thin Mylar and mica membranes have been investigated, together with aperture modifications such as an annulus and Fresnel zone plate. The measured results agree well with theory, thus demonstrating that wideband predictable performance (>8 MHz) is obtainable with such transducers. Additionally, pulse-echo C-scans of a Plexiglas plate containing an artificial defect have been undertaken with the capacitance transducer, in order to demonstrate that the capacitance transducer has sufficient sensitivity to allow routine nondestructive testing within immersion applications.

show abstract

Section: B Annular and Zone Plate Transducersmentioning

confidence: 99%

Micromachined ultrasonic capacitance transducers for immersion applications

Bashford

Schindel

Hutchins

1998

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

Self Cite

View full text Add to dashboard Cite

show abstract

“…By shaping the pump ultrasound field launched with a focused air-coupled transducer, and also with acoustic masks, focusing mirrors, [9][10][11] and Fresnel plates [11][12][13] ), the radiation pattern (i.e., spatial distribution of I) can be manipulated at the air/medium interface. In addition, ultrasound arrays can electronically scan the pump field across the interface.…”

mentioning

confidence: 99%

Air-coupled acoustic radiation force for non-contact generation of broadband mechanical waves in soft media

Ambroziński

Pelivanov

Song

et al. 2016

Applied Physics Letters

View full text Add to dashboard Cite

A non-contact method for efficient, non-invasive excitation of mechanical waves in soft media is proposed, in which we focus an ultrasound (US) signal through air onto the surface of a medium under study. The US wave reflected from the air/medium interface provides radiation force to the medium surface that launches a transient mechanical wave in the transverse (lateral) direction. The type of mechanical wave is determined by boundary conditions. To prove this concept, a homemade 1 MHz piezo-ceramic transducer with a matching layer to air sends a chirped US signal centered at 1 MHz to a 1.6 mm thick gelatin phantom mimicking soft biological tissue. A phasesensitive (PhS)-optical coherence tomography system is used to track/image the mechanical wave. The reconstructed transient displacement of the mechanical wave in space and time demonstrates highly efficient generation, thus offering great promise for non-contact, non-invasive characterization of soft media, in general, and for elasticity measurements in delicate soft tissues and organs in bio-medicine, in particular. Published by AIP Publishing. [http://dx.doi.org/10.1063/1.4959827] Acoustic radiation force (ARF) is commonly used in ultrasound (US)-based elastography to remotely generate shear waves deep within tissue. 1-3 Detection of shear waves can be performed with a conventional ultrasound (US) imaging probe or with another imaging method, e.g., optical coherence tomography (OCT). The combination of ARF with high frame rate OCT can produce quantitative crosssectional maps of the shear modulus in soft tissues. 4 For many clinical applications, however, a totally non-contact system for generation/detection of mechanical waves is desirable and, in some cases (for instance, the eye), is necessary. OCT is an ideal approach for these applications if an efficient and robust non-contact generation technology can be developed.Generation of mechanical waves with an air puff was used in Ref. 5 to produce very narrow bandwidth displacements in the cornea, which may not be able to characterize corneal elasticity at the spatial resolution required for clinical decision making. Our group has recently demonstrated non-contact generation using absorption of pulsed UV laser light. 6 Although UV generation can provide the bandwidth required for high spatial resolution maps of corneal elasticity, it is not clear at this point whether the required UV energy levels will meet the safety requirement for routine clinical use.Here we propose a fully non-contact and non-invasive US technique to create efficient localized wideband mechanical waves in soft tissue. The method utilizes US launched with an air-coupled transducer (i.e., through air) to the air/ medium interface. The US wave reflected from this interface provides radiation force to the medium surface, which induces a transient displacement at that surface, ultimately generating a propagating shear/guided/interface/Lamb wave (wave type determined by boundary conditions). We will call this the mechanical wave to maintain ge...

show abstract

“…The major characterization methods include: Schlieren imaging [3], ball reflector [4], cone transducer [5], micro-electromechanical sensors [6], hydrophones, membrane interferometry [7], and capacitive based sensors [8]. Relative to the requirements of 100 kHz, 0.2 mm spatial sensitivity, 1-10 mPa pressure sensitivity, and air coupled ultrasound only capacitive sensors and membrane interferometry were found to be promising candidates.…”

Section: State Of the Artmentioning

confidence: 99%