Annular Array Search Units and Their Potential Application in Conventional Ultrasonic Testing Systems
This paper is based on a program to investigate the potential of multi-element annular arrays for practical application in ultrasonic testing systems. The annular array is comprised of coaxially-located, ring-shaped piezoelectric elements. By providing excitation pulses in a spherical time relationship, the transmitted beam may be focused at a specific range. By electronic switching, the focal point can be placed at various distances in the material under examination, Of particular interest is the length over which the beam can be held in collimation. Fabrication methods, delayed excitation techniques, and beam patterns in water and steel are described,
A New Ultrasound Imaging Technique Employing Two-Dimensional Electronic Beam Steering
In recent years, ultrasound imaging based on B-mode echosonography has become an accepted and useful technique in medical diagnosis. However, the application of this technique has been limited by the time required to obtain an adequate image, the resolution that can be obtained in the image and problems related to the dynamic range of the echo information. A new ultrasound imaging system which removes or substantially reduces many of these limitations has been developed in the hope that ultrasound tomography may find even more widespread application and greater diagnostic value.
A Study of Near Field Ultrasonic Beam Patterns from a Pulsed Linear Array
A major advantage of pulse-echo imaging in the near-field of an acoustic array is the improved lateral resolution that focusing makes possible. Usually, equivalence is tacitly assumed between a lateral beam dimension for continuous wave excitation and a lateral pulse dimension for the same geometry. Although distinctions certainly exist between the lateral dimensions in these two cases, it is convenient in dealing with pulsed ultrasound to speak of a “beam” or “beams” of ultrasonic energy. By analogy to the continuous wave case, such a beam may be defined as the envelope of a pulse dimension. This dimension may be specified by some absolute or r.m.s. pressure magnitude criterion (e.g., the distance to a point at which the absolute pressure is down “n” dB from the maximum value in the field).