Graphic Display for Ultrasonic Nondestructive Testing

Abstract

Acoustical holography can present a “complete” image of three-dimensional ultrasonic field. Because of this capability, its application to nondestructive testing, biomedical examination and especially underwater acoustics seems promising. Although there are several two-dimensional sensors, such as liquid surface or Polhman cell, which are able to directly make a hologram, their sensitivity is rather low. An ultimate sensitivity has been so far obtained by the scanning transducer method. In this method, a transducer is scanned over the aperture of the hologram and its output is recorded in a two-dimensional form. The reconstruction of image is done by either analog processing by coherent optics or digital processing by computer. The latter processing becomes increasingly popular because of its flexibility. The cost of digital processing is also decreasing due to the recent development of integrated circuits.