Annular array ultrasonic transducers
AssigneeTechnicare Corporation
InventorDennis R. Dietz
Life of this patent
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Abstract
An annular array ultrasonic transducer is provided which comprises a plurality of concentric rings of piezoelectric material having widths chosen for operation at different depths of focus. The total aperture of the transducer is divided into a plurality of contiguous focal depths. In the near field only the inner element or elements are activated, and rings of increasing radius are added as the depth of focus is increased. The widths of the rings are chosen to keep phase errors across each ring within acceptable limits over the depth of field for which they are energized. The transition depths at which the aperture is changed are chosen to allow rings of manufacturable widths to be employed while maintaining aperture transitions which prevent banding in the ultrasonic image.
Claims10
A selectable focus annular array ultrasonic transducer comprising a concave of piezoelectric material which is separated into a plurality of concentric rings including a central disc-shaped element and capable of being selectively focused over consecutive regions of a given depth of field by activating rings of increasing radii in combination with said disc-shaped element and rings activated in shorter field regions, if any, as the transducer is focused at increasing depths of field;
- each ring exhibiting a width selected in accordance with a predetermined phase criterion such that the received signal phase error across the ring width does not exceed a given signal phase change for signals received from the nearest field point at which the ring is initially activated.
A selectable focus annular array ultrasonic transducer comprising a concave surface of piezoelectric material which is separated into a central disc region and a plurality of concentric rings surrounding said central disc and capable of being selectively focused over consecutive regions of a given depth of field by activating different ring combinations of increasing radii in regions of increasing depth of field;
- said rings each having a width exhibiting a phase change thereacross which does not exceed a given predetermined signal phase change for signals received from the nearest field for which they are activated;
- and at least one of said rings radially remote from said disc exhibiting a greater width than at least one of said rings which is radially less remote from said disc.
A selectable focus annular array ultrasonic transducer comprising a concave surface of piezoelectric material which is separated into a central disc region and a plurality of concentric rings surrounding said central disc, and capable of being selectively focused over consecutive regions of a given depth of field by activating different ring combinations of increasing radii in regions of increasing depth of field;
- said concave surface exhibiting a curvature which provides a geometric focal point such that the phase error for received signals across the transducer aperture is substantially the same magnitude but of opposite sign at approximately the minimal and maximal limits of said depth of field;
- said rings each exhibiting a width providing a phase error thereacross when activated which does not exceed .pi./1.1 degrees for a received ultrasonic signal.
Dependencies are inferred from the claim text.