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Development of a 20 MHz annular-array - a balancing act between optimized design and technological opportunities

: Juhrig, Andre; Schmidt, Ulrike; Wolf, Mario; Kühnicke, Elfgard; Günther, Paul A.; Gebhardt, Sylvia


Cochran, Sandy (General Co-Chair) ; Institute of Electrical and Electronics Engineers -IEEE-; IEEE Ultrasonics, Ferroelectrics, and Frequency Control Society:
IEEE International Ultrasonics Symposium, IUS 2019 : October 6 - 9, 2019, Glasgow, Scotland
Piscataway, NJ: IEEE, 2019
ISBN: 978-1-7281-4595-2
ISBN: 978-1-7281-4596-9
ISBN: 978-1-7281-4597-6
International Ultrasonics Symposium (IUS) <2019, Glasgow>
Fraunhofer IKTS ()
annular-array; microscopy; transducer

Scanning Acoustic Microscopes for nondestructive imaging commonly use strong focusing single element probes with center frequencies up to 230 MHz. Depending on the test scenario and the materials a resolution down to 10 mu m is reachable. This high resolution means a small extension of the sensitivity zone in lateral and axial direction and leads to the necessity of multiple C-Scans for the inspection of a volume. Using an annular-array transducer, the focal point can be shifted in axial direction. Thus, multiple scans in different depth can be replaced by a single scan. To achieve a comparable resolution to strong focused single element transducers it is necessary to increase the center frequency of annular-array transducers. So we present a prototype of a probe, that contains a planar annular-array transducer with a center frequency of 20 MHz and an aperture of 5.4 mm, separated into four quartered rings (16 elements). The characterization of the sound field, using a spherical reflector, shows a sensitivity zone with a lateral extension of 300 mu m for focusing without a lens.