Fast Reconstruction of the Ultrasonic Bessel Transducer Field by Using Schlieren Techniques

Ultrasonic transducers uniformly poled have been used for clinical diagnostic applications, and usually medical imaging use focused beams that present a short depth of ultrasonic field.

With ultrasonic transducers that produce limited diffraction beams (Bessel transducers), high-resolution images can be achieved over a large depth of field compared with the focused beams.

In this paper we use the Schlieren method in order to obtain a 2-dimensional image of the acoustic field. By assuming axi-symmetrical proprieties of the field, we develop a fast algorithm that allows as reconstructing the 3-dimensional field of acoustical power. We compare its diffraction field with one emitted by a piston-like transducer with the same diameter and excited with the same frequency. We see that the diffraction effect in the last transducer produces a power spread greater than the Bessel one.

Keywords:

• Ultrasonic transducers
• acoustic field image

Acknowledgments

The authors would like to thank to PEDECIBA (Uruguayan agency) and CLAF for financial support.

Paper originally presented at IMF-11, Iguassu Falls, Brazil, September 5–9, 2005;