Ultrasonic transducer array with apodized elevation focus

An ultrasonic transducer array for imaging a target by scanning a narrow beam of ultrasonic energy in an imaging plane, the narrow beam having associated side lobes on both sides of a main lobe that extend in elevation away from the imaging plane, the transducer array comprising:

• a plurality of transducer elements aligned along an array axis in the imaging plane, each of the plurality of transducer elements including
• a piezoelectric substrate having a front surface and a rear surface,
• a front electrode overlaying selected portions of the front surface of the piezoelectric substrate, such selected portions being less than the entire front surface,
• a rear electrode overlaying the rear surface of the piezoelectric substrate, and
• a first acoustic matching layer overlaying the front electrode and conducting electrical signals to the front electrode,
• wherein the front electrode is configured to approximate a predetermined weighting function, so that the transducer element produces an apodized beam of ultrasonic energy directed toward the target and focused in the elevation plane, with the beam's side lobes having a lower magnitude than the side lobes that would be emitted by a piezoelectric element having a uniform front electrode.

A method for ultrasonic imaging, comprising:

• providing a plurality of piezoelectric transducer elements aligned along an array axis in an imaging plane, each piezoelectric transducer element including
• a piezoelectric substrate having a front surface and a rear surface,
• a patterned front electrode overlaying selected portions of the front surface of the piezoelectric substrate, such selected portions being less than the entire front surface and providing a predetermined tapered weighting function distributed along an elevation axis oriented perpendicular to the imaging plane,
• a rear electrode overlaying the rear surface of the piezoelectric substrate;
• and
• a first acoustic matching layer overlaying the front electrode and conducting electrical signals to the front electrode;
• and
• exciting each transducer element with an excitation signal applied between the rear electrode and the first acoustic matching layer, to cause those portions of the front surface of the piezoelectric substrate overlaid by the patterned front electrode to emit an ultrasonic beam toward a target, wherein the patterned front electrode is configured to provide an ultrasonic beam that is apodized in the elevation plane.