Ultrasonic tomography using scanned contact transducers

Tomographic images have been obtained from objects of rectangular cross section by scanning contact transducers across the sample faces. On each face, a piezoelectric transducer was set in a spring-loaded mount that forced it against the surface, and a stepper motor moved it to the desired scan position. Hemispherical brass caps were placed on each transducer to facilitate sliding along the surface. Waveforms from receiving transducers were captured on a four-channel digital oscilloscope and transferred to computer for storage and later analysis. The complete system was under the control of a microcomputer, resulting in an entirely automatic data collection system. Examples of images created from this system for objects with and without anomalies present illustrate the system´s use