Title :
A circularly focused and scanned acoustic scanner
Author_Institution :
Minist. of Transp. & Commun., Taipei, Taiwan
Abstract :
This paper describes a new type of electronically scanned and focused acoustic imaging device called the cylindrical grating acoustic scanner. With this device, a new transducer called the circular-edge-bonded transducer (CEBT) is devised that is bonded on one end of a cylindrical substrate and can generate a surface acoustic wave propagating along the cylindrical surface of the substrate. An array of grooves is fabricated on the cylindrical surface of the substrate to serve as a scattering grating. The periodical grooves scatter a chirped surface-wave pulse coherently into a focused bulk-wave "ring" that scans at the surface-wave velocity. The focal length and resolution can be adjusted by changing the chirp rate and time-bandwidth product of the chirp, respectively. A 2.3-MHz circular scanner with 25-cm field of view and 2.6-mm resolution has been constructed and studied. Acoustic image of an artificial defect in an aluminum pipe is obtained.
Keywords :
image scanners; surface acoustic wave transducers; ultrasonic imaging; ultrasonic materials testing; 2.3 MHz; CEBT; acoustic imaging device; artificial defect; chirp rate; chirped surface-wave pulse; circular-edge-bonded transducer; circularly focused acoustic scanner; circularly scanned acoustic scanner; cylindrical grating acoustic scanner; focal length; periodical grooves; resolution; scattering grating; surface acoustic wave; time-bandwidth product; Acoustic devices; Acoustic imaging; Acoustic scattering; Acoustic transducers; Bonding; Chirp; Focusing; Gratings; Surface acoustic wave devices; Surface acoustic waves;
Journal_Title :
Ultrasonics, Ferroelectrics, and Frequency Control, IEEE Transactions on
