Pencil beam generation from a focused tranducer
conference paper
Scanning using a focused transducer gives a narrow focus depth, although locally there is a high resolution. Because the focal point can be considered as a second source, the wavefield can be split in its causal and anticausal parts. Imaging can be performed efficiently with a mapping algorithm in the wavenumber domain (f-k or Stolt migration), achieving a pencil beam. This work investigates the potential of this mapping algorithm on simulated and experimentally obtained pulseecho data of a line of point deflectors (pins) mounted in a water tank. The simulated dataset was created using an in-house implementation of a wavefield extrapolation algorithm, and the experimental dataset was obtained using an xyz-system. A 1MHz transducer was used with diameter 1.5’’ and focal distance 3’’. The aforementioned concept is illustrated on simulated data, where the - 6dB lateral point spread functions (PSF) were improved by 91.3%, 0% and 90.5% in the near-field (2.5cm), focus (7.4cm) and far-field (13.5cm), respectively. Measurements confirm this pattern, and showed improvements in the PSFs by 86.8%, 0% and 60.0% at the same distances. The resolution enhancement, produced by the mapping algorithm, is such that effectively a pencil beam is obtained in both the simulations and experiments.
TNO Identifier
954462
ISSN
0094243X
ISBN
9780735411296
Publisher
American Institute of Physics AIP
Source title
39th Annual Review of Progress in Quantitative Nondestructive Evaluation, QNDE 2012, 15-20 July 2012
Editor(s)
Thompson, D.E.
Chimenti, D.O.
Chimenti, D.O.
Collation
9 p.
Pages
924-931
Files
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