Abstract: A method of forming a transducer device having integral transducer and impedance matching portions includes forming grooves partially through a thickness of a piezoelectric member. A groove volume fraction at the impedance matching portion controls the electrical impedance. The impedance matching portion may be at either or both of the front and rear surfaces of the transducer portion, which generates acoustic wave energy in response to application of a drive signal. The drive signal is introduced by electrodes. In one embodiment, the electrode at the impedance matching portion extends into the grooves, but preferably a filler material is selected and deposited to allow use of a planar electrode. An alternative embodiment to fabricating the transducer device is to assemble piezoelectric material. For example, an integral transducer and impedance matching portions may be formed by using molding techniques or by stacking dimensionally different thin piezoelectric layers.

Abstract: A method of forming an impedance matching layer of an acoustic transducer includes geometrically patterning impedance matching material directly onto a radiating surface of piezoelectric substrate. In one embodiment, the matching layer is deposited onto the piezoelectric substrate and photolithographic techniques are utilized to pattern the matching layer to provide posts tailored to better match the piezoelectric substrate to a medium into which acoustic waves are to be transmitted. A nominal layer of metal between the posts and the piezoelectric substrate improves the attachment of the matching material to the substrate. The nominal layer may be chrome-gold and the matching material may be copper. Typically, the radiating surface is the substrate front surface from which acoustic waves are directed into a medium of interest, e.g., water or human tissue.

Abstract: A transducer device includes delay sections for creating a phase differential of acoustic waves. The delay sections are spaced apart by sections having an absence of delay. In a preferred embodiment, the phase differential is 180.degree., so that constructive and destructive interference of pressure waves function occurs to reduce the ringdown time of the transducer device. In the preferred embodiment, the array of delay sections is at the back surface of a piezoelectric element. However, delay sections may be at the front, radiating surface of the piezoelectric element for control of the shape of emitted pulses. Vectorial summation of wave energy cancels unwanted energy that is present as a result of reverberations within the transducer device. Alternative delay structures or multiple delay sections can be used to control the transducer impulse response.

Abstract: An ultrasound system and method for intravascular ultrasonic imaging includes an array of beacons that are fixed to direct ultrasonic energy toward an imaging transducer, with individual beacons being identifiable in order to determine the angular position of the imaging transducer. Based upon the data related to beacon identification, operation of the imaging device is adaptively adjusted in order to compensate for variations in angular velocity of the transducer. Adaptive compensation may be performed by adjusting the pulse repetition rate of transmitted ultrasonic energy, by adjusting the scan conversion algorithm or mapping reflected ultrasonic energy, or by varying control of the drive structure for rotating the transducer. The beacons are preferably piezoelectrically active, but passive beacons may also be used. Position identification may be performed by techniques including amplitude sensing, phase sensing, pulse length sensing, and frequency sensing.

Abstract: A tunable ultrasonic probe of the that provides efficient electrical coupling of probe control lines to imaging system components and further provides for variable control over size of an effective acoustic aperture of the probe. The ultrasonic probe includes a body of a piezoelectric material that has a first surface and an opposing surface. A first set of electrodes is coupled with the first surface of the body. A second set of electrodes is also coupled with the first surface of the body and arranged so that each electrode of the second set substantially overlaps at least a respective one electrode of the first set. A third set of electrodes is coupled with the opposing surface of the body. At least one bias voltage source is coupled with the electrodes for substantially polarizing ceramic material within selected regions of the body. Switches are coupled with the first and second set of electrodes for changing an acoustic aperture of the probe by varying size of the selected polarized regions.

Abstract: A method and apparatus for three dimensional ultrasonic scanning with reduced electronic switching and cabling requirements. The invention includes a body including a relaxor ferroelectric ceramic material and electrodes coupled to opposing surfaces of the body. Electronic switches select electrodes so as to select column regions of the body that are arranged adjacent to one another in a row extending radially outward from a central axis of the body. A bias voltage source is coupled with the electronic switches for substantially polarizing ceramic material within the selected column regions of the body. A sector controller dynamically configures the electronic switches to rotationally vary a position of the row arrangement of selected column regions. An oscillating voltage source excites the row of selected column regions to emit an acoustic beam, so that the beam rotationally scans the medium as the sector controller rotationally varies the position of the row arrangement.

Abstract: A tunable ultrasonic probe includes a body of a first piezoelectric material acoustically coupled in series with a body of a second piezoelectric material. The second piezoelectric material has a Curie temperature that is substantially different than that of the first piezoelectric material. Preferably, the first piezoelectric material is a conventional piezoelectric ceramic, such as lead zirconate titanate, while the second piezoelectric material is a relaxor ferroelectric ceramic, such as lead magnesium niobate. At an operating temperature of the probe, the first piezoelectric material has a fixed polarization. In contrast, the second piezoelectric material has a polarization that is variable relative to the fixed polarization of the first piezoelectric material. A preferred novel arrangement of electrodes electrically couples the bodies in parallel with one another. An oscillating voltage for exciting the acoustic signals in the probe is coupled with the electrodes.

Abstract: An ultrasonic probe for providing efficient and controlled acoustic coupling to a desired medium under examination by the probe. The ultrasonic probe of the present invention employs one or more ultrasonic transducers substantially surrounded by a fluid. The ultrasonic transducer is acoustically coupled to the fluid for transmitting the beam of acoustic signals therethrough. A housing that is acoustically coupled with the fluid substantially encloses the fluid and the transducer. The housing comprises a layer portion of a material contiguous with a bulk remainder portion of the material. Additionally, an impedance matching means is integral with the housing for controlling an acoustic impedance of the layer portion of the housing.

Abstract: An ultrasonic transducer for controlling an elevation aperture utilizes the electric field-induced polarization properties of relaxor ferroelectric materials. The Curie temperature of the material is typically close to room temperature, so that the application of a bias voltage provides piezoelectric activity. By varying the thickness of a dielectric layer that spaces apart the relaxor ferroelectric material from an electrode or providing the bias voltage, the piezoelectric activity can be tailored. That is, degrees of polarization of the relaxor ferroelectric material are varied spatially in correspondence with changes in thickness of the dielectric layer. The effective elevation aperture of the transducer can be varied by adjusting the bias voltage.