EP0134346B1 - Ultraschallwandler - Google Patents

Ultraschallwandler Download PDF

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Publication number
EP0134346B1
EP0134346B1 EP19830304934 EP83304934A EP0134346B1 EP 0134346 B1 EP0134346 B1 EP 0134346B1 EP 19830304934 EP19830304934 EP 19830304934 EP 83304934 A EP83304934 A EP 83304934A EP 0134346 B1 EP0134346 B1 EP 0134346B1
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EP
European Patent Office
Prior art keywords
piezoelectric
section
transducer according
transducer
spiral
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
EP19830304934
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English (en)
French (fr)
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EP0134346A1 (de
Inventor
Henry Peter Beerman
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Analogic Corp
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Analogic Corp
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Filing date
Publication date
Application filed by Analogic Corp filed Critical Analogic Corp
Priority to EP19830304934 priority Critical patent/EP0134346B1/de
Priority to DE8383304934T priority patent/DE3379990D1/de
Publication of EP0134346A1 publication Critical patent/EP0134346A1/de
Application granted granted Critical
Publication of EP0134346B1 publication Critical patent/EP0134346B1/de
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B06—GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS IN GENERAL
    • B06B—METHODS OR APPARATUS FOR GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS OF INFRASONIC, SONIC, OR ULTRASONIC FREQUENCY, e.g. FOR PERFORMING MECHANICAL WORK IN GENERAL
    • B06B1/00—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency
    • B06B1/02—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy
    • B06B1/06—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy operating with piezoelectric effect or with electrostriction
    • B06B1/0688—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy operating with piezoelectric effect or with electrostriction with foil-type piezoelectric elements, e.g. PVDF
    • B06B1/0692—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy operating with piezoelectric effect or with electrostriction with foil-type piezoelectric elements, e.g. PVDF with a continuous electrode on one side and a plurality of electrodes on the other side
    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
    • G10K11/00—Methods or devices for transmitting, conducting or directing sound in general; Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
    • G10K11/18—Methods or devices for transmitting, conducting or directing sound
    • G10K11/26—Sound-focusing or directing, e.g. scanning
    • G10K11/32—Sound-focusing or directing, e.g. scanning characterised by the shape of the source

Definitions

  • This invention relates to ultrasonic transducers.
  • Ultrasonic transducers employed for example for medical diagnostic purposes, are known in which the transducer is focussed for an intended focal length.
  • Such transducers generally include a spherically curved ceramic piezoelectric element supported on an acoustic backing material, or a flat piezoelectric element supported on an acoustic backing material with an acoustic lens disposed on the front surface of the flat element to provide the intended focussing.
  • These known transducers are operative for only a single focal length, and a different transducer must be constructed for each focal length of interest.
  • a known ultrasonic transducer is described in FR-A-2316608 and GB­ A­1539569.
  • the transducer comprises a plurality of piezoelectric ultrasonic transducer elements distributed in circular formation on an arcuate support member.
  • the transducer elements may have flat or curved radiation surfaces.
  • the target point is positioned at the centre of a circle along an arc of which the transducers are arranged in succession.
  • an ultrasonic transducer comprising a plurality of piezoelectric sections disposed along a portion of a cylindrical concave surface, rear electrode- means on the rear surface of the piezoelectric means and front electrode means on the front surface of the piezoelectric means, and means for supporting the piezoelectric sections, characterised in that the concavity of the cylindrical concave surface is in the form of a spiral of length L and in that each piezoelectric section has along the spiral a different focal length.
  • the transducer thus comprises a piezoelectric element having a cylindrical spiral or generally cylindrical spiral surface with respective sections or zones of the cylindrical spiral providing respective different focal lengths.
  • the piezoelectric element is a plastic piezoelectric film, such as polyvinylidene fluoride (PVF 2 ), disposed on a support member providing the cylindrical spiral surface.
  • the sections may each have a corresponding focus lying in a common plane disposed transversely to the spiral surface.
  • the curved surface of the spiral provides focussing in one dimension, along the length of the spiral.
  • Focussing in the orthogonal dimension may be provided by a Fresnel zone pattern on the front surface of each section of the piezoelectric film.
  • the zone pattern is formed by electrodes on the front surface of the film extending across the width of the film.
  • the front electrodes of the several sections are electrically connected in series or parallel, or in a series-parallel combination, depending upon the capacitance and reaction required for specific applications.
  • the electrode pattern for each section terminates in a respective electrical terminal for coupling to excitation or reception circuitry.
  • a rear electrode is provided on the back surface of the film, typically in the form of a continuous conductive layer with a common terminal for all sections.
  • the Fresnel pattern can be eliminated and replaced by a continuous electrode for each zone on the front surface of the spiral film in applications where ultrasonic focussing is desired in only one dimension in order to provide a line focus.
  • an ultrasonic transducer constructed in accordance with the invention, which comprises a piezoelectric film 10 supported on a support or backing 12 of acoustic damping material and having a concave surface 14 of varying radius of curvature and uniform width and length.
  • a filler maetrial 16 for acoustic damping is disposed rearwardly of support 12, the entire assembly being contained within a housing 18.
  • the piezoelectric film 10 is divided into adjacent sections which are formed by strips of substantially constant width along the length, L, of the concave surface 14, each section having a different respective focal length.
  • section 10a has a focus at 0 1
  • section 10b has a focus at O2
  • section 10c has a focus at 0 3
  • section 10d has a focus at 0 4 .
  • the focal points 0 1 to 0 4 lie along an axis 20 which is the optical axis of the transducer.
  • the sections can have continuously increasing radius of curvature to provide part of a true spiral, or each section can have constant or substantially constant radius of curvature to approximate a spiral path.
  • Each section of the film 10 has a Fresnel zone pattern thereon across the width, w, of the film surface to provide focussing in the width dimension as shown in Figures 1 and 3. Focussing in the longitudinal direction of the spiral is provided by the curved surfaces of the sections.
  • the Fresnel zone pattern for each section is slightly different to that of the others to account for the different focal lengths.
  • the Fresnel pattern for each section is provided by conductive strips 22 formed on the front surface of the film 10, the front electrodes being electrically interconnected to provide an intended capacitance and reactance.
  • a rear electrode 24 is provided on the rear surface of the film 10 in the form of a continuous conductive layer providing a common electrode for the sections.
  • the Fresnel zone pattern for one section is illustrated in Figure 5.
  • the pattern includes a plurality of electrode areas symmetrically disposed about a centre line, each of the electrode areas being of predetermined width and spaced from adjacent electrode areas by a predetermined distance.
  • the centre line of each electrode area lies at a distance d from the centre line of the Fresnel pattern and can be found by where n is an integer 0, 1, 2, etc. for each successful electrode area; a is the mean focal length for the particular section of the curved surface; and A is the wavelength per cycle.
  • each electrode area Ad can be obtained by substituting n ⁇ 0.25 for the integer n in equation 1.
  • the centre of each area between the electrode areas can be found by substituting (2n+1)/2 for the integer n in equation 1.
  • equation 1 reduces to
  • the section is considered as having a constant radius, and therefore constant focal length, throughout its extent. Since the surface is actually a portion of a cylindrical spiral which has a slightly varying focal length throughout its zone length, the location of the electrode areas should be calculated for the mean focal length for the zone. Alternatively, the electrode areas can be calculated separately for the end portions of a zone to accommodate the focal length variations.
  • the electrode areas are electrically connected in series or parallel, or in a series-parallel combination to provide an intended capacitance to achieve a reactance of predetermined value, typically in the range of 25-50 ohms.
  • Each section has a respective electrical terminal 25 ( Figure 5) for connection to electronic circuitry for energizing the transducer for transmission for receiving and processing signals produced in response to received ultrasonic energy.
  • the rear electrode is common to all sections and has a common terminal which serves as the second terminal for all sections.
  • the piezoelectric film is polyvinylidene fluoride (PVF 2 ), and the electrodes are formed of a nickel-chrome alloy. The electrodes are provided on the film in any known manner, such as by vacuum sputtering.
  • the polyvinylidene fluoride has a broadband frequency response, and therefore the thickness of the film is not as critical as with typical PZT materials which have a much narrower band frequency response.
  • the film operative at 1 MHz can have a thickness of about 250-500 microns.
  • K dielectric constant 13
  • the capacitance C for each square centimetre of the electrode area of a Fresnel pattern is where e' is the permittivity of free space (0.088x 10-'2) and where t is the film thickness in centimetre.
  • the capacitance C is equal to 46 picofarads per square centimetre.
  • the capacitance is For each section or zone in which the electrode areas are connected in parallel, the total electrode area is 3185 picofarads/46 picofarads per square centimetre, which equals 69 square centimetres.
  • the Fresnel pattern can be eliminated, and the front electrode provided by a continuous electrode film formed on each section of the front surface of the piezoelectric material, each front electrode having a respective electrical terminal.
  • a line focus would be provided by each section of the spiral surface, as distinguished from a point focus provided in the embodiment described above.
  • FIG. 6 Another embodiment is shown in Figure 6 in which a piezoelectric film 10 is supported on a ceramic piezoelectric material 30 such as PZT (lead zirconate titanate). Both piezoelectric materials are disposed in a portion of a cylindrical spiral path, as in the above embodiment.
  • This dual layer structure is supported on an acoustic damping backing material, as in the above embodiment, and can otherwise be similarly housed.
  • the PZT material 30 is bent into the spiral configuration while in its plastic state prior to firing, and after firing, it will retain its spiral shape.
  • the piezoelectric film 10 can then be bonded to the PZT material.
  • Front and rear electrodes are provided for each piezoelectric layer, the electrode areas being connected to respective terminals.
  • each piezoelectric layer can have the Fresnel pattern for each zone on its front surface, and a rear electrode on its rear surface, with an electrically insulating spacer provided between the front electrodes of the PZT material and the rear electrode of the film material to maintain electrical isolation between the two transducers.
  • the polyvinylidene fluoride film is more effective for ultrasonic reception than for transmission, while the PZT material is superior for transmission rather than reception.
  • the PZT layer is energized with an appropriate driving signal for transmitting ultrasonic energy in a focussed manner to an object under study, and the film layer is operative to receive energy preferentially focussed onto the respective section or zone of the film to generate output signals representative of received ultrasonic energy.
  • the novel transducer finds particular application as an immersion transducer for medical diagnostic purposes.
  • the immersion transducer is placed in a vessel containing water or other liquid, the transducer being spaced from the subject by the interposed liquid.
  • Ultrasonic energy is coupled via the liquid from the transducer to the subject, which is also immersed in the liquid.
  • a thin layer of liquid or gel can be employed to couple the transducer directly to living tissue.
  • the transducer can be employed for sonar, in which case the transducer dimensions would be appropriately scaled up to accommodate the lower frequencies employed for sonar work.
  • frequencies are typically in the range of 1-10 MHz, while sonar is operative at about 30 KHz.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Acoustics & Sound (AREA)
  • Multimedia (AREA)
  • Transducers For Ultrasonic Waves (AREA)

Claims (12)

1. Ultraschallwandler, mit mehreren piezoelektrischen Abschnitten (10a, 10b, 10c, 10d; 30), die entlang einem Teil einer zylindrischen konkaven Fläche (14) angeordnet sind, einer Einrichtung (12) zum Lagern der piezoelektrischen Abschnitte, einer auf den Rückseiten der piezoelektrischen Abschnitte gelegenen rückwärtigen Elektrodenanordnung (24) und einer an den Vorderseiten der piezoelektrischen Abschnitte gelegenen vorderen Elektrodenanordnung (22), dadurch gekennzeichnet, daß die Konkavität der zylindrischen konkaven Fläche die Form einer Spirale der Länge L hat, und daß jeder piezoelektrische Abschnitt entlang der Spirale eine unterschiedliche Brennweite besitzt.
2. Wandler nach Anspruch 1, bei dem die Brennpunkte (01, O2,...04) der piezoelektrischen Abschnitte an der Vorderseite der konkaven Seite des Wandlers entlang einer gemeinsamen Achse angeordnet sind.
3. Wandler nach Anspruch 2, bei dem die vordere Elektrodenanordnung (22) für jeden pizeoelektrischen Abschnitt eine Fresnelmusterzone über der Spiralfläche darstellt, wobei die Länge jeder Zone wesentlich größer ist als ihre Breite, die sich entlang der Länge L der Spiralfläche mißt, und wobei jeder Abschnitt (10a...10d) eine Fresnelmusterzonen-Brennweite aufweist, die der Brennweite des zugehörigen Abschnitts (10a...10d) der Spiralfläche (10) entspricht.
4. Wandler nach Anspruch 3, bei dem die vordere Elektrodenanordnung (22) für jeden Abschnitt ein Feld aus beabstandeten Elektrodenflächen aufweist.
5. Wandler nach Anspruch 4, bei der die Elektrodenflächen jedes Abschnitts elektrisch verbunden sind, um eine vorbestimmte Kapazität und Reaktanz zu bilden.
6. Wandler nach Anspruch 5, bei dem das Fresnelzonenmuster für jeden Abschnitt unterschiedliche Breite und unterschiedlichen Abstand aufweist, um eine eigene Brennweite zu bilden.
7. Wandler nach einem der Ansprüche 3 bis 6, bei dem das Fresnelzonenmuster für jeden Abschnitt symmetrisch bezüglich der Längs-Mittellinie des Teils der zylindrischen Spiralfläche angeordnet ist.
8. Wandler nach jedem der vorhergehenden Ansprüche, bei dem die piezoelektrische Einrichtung ein piezoelektrischer Film ist.
9. Wandler nach Anspruch 8, bei dem der piezoelektrische Film aus Polyvinyliden-Fluorid gebildet ist.
10. Wandler nach jedem der vorhergehenden Ansprüche bei dem die Lagerungseinrichtung (12) ein akustisch dämpfendes Material (16) enthält.
11. Wandler nach Anspruch 10, bei dem die Lagerungseinrichtung (12) eine gekrümmte Oberfläche aufweist, auf der die piezoelektrische Einrichtung angeordnet ist, und die mit der Krummung der piezoelektrischen Einrichtung (10) konform ist.
12. Wandler nach Anspruch 11, bei dem die piezoelektrische Einrichtung (10) über die Länge das Teils der zylindrischen Spiralfläche eine gleichmäßige Breite besitzt.
EP19830304934 1983-08-25 1983-08-25 Ultraschallwandler Expired EP0134346B1 (de)

Priority Applications (2)

Application Number Priority Date Filing Date Title
EP19830304934 EP0134346B1 (de) 1983-08-25 1983-08-25 Ultraschallwandler
DE8383304934T DE3379990D1 (en) 1983-08-25 1983-08-25 Ultrasonic transducers

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
EP19830304934 EP0134346B1 (de) 1983-08-25 1983-08-25 Ultraschallwandler

Publications (2)

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EP0134346A1 EP0134346A1 (de) 1985-03-20
EP0134346B1 true EP0134346B1 (de) 1989-05-31

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20110028867A1 (en) * 2009-07-29 2011-02-03 Seh-Eun Choo Apparatus and method for non-invasive delivery and tracking of focused ultrasound generated from transducer

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2570837B1 (fr) * 1984-09-25 1987-11-20 Cgr Ultrasonic Sonde a ultrasons pour balayage sectoriel electronique et echographe incorporant une telle sonde
US5412854A (en) * 1993-06-18 1995-05-09 Humphrey Instruments, Inc. Method of making a high frequency focused transducer
KR20080093281A (ko) * 2007-04-16 2008-10-21 주식회사 메디슨 초음파 진단용 프로브
US20230038081A1 (en) * 2021-08-05 2023-02-09 University Of Washington Non-planar holographic beam shaping lenses for acoustics

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3924453A (en) * 1973-05-04 1975-12-09 United States Steel Corp Ultrasonic testing of tubing employing a spiral wave generator
JPS5550438B2 (de) * 1974-11-25 1980-12-18
FR2292978A1 (fr) * 1974-11-28 1976-06-25 Anvar Perfectionnements aux dispositifs de sondage par ultra-sons
DE2529112C3 (de) * 1975-06-30 1978-03-23 Siemens Ag, 1000 Berlin Und 8000 Muenchen Ultraschall-Applikator für die zeilenweise Ultraschallabtastung von Körpern
US4395652A (en) * 1979-09-13 1983-07-26 Toray Industries, Inc. Ultrasonic transducer element

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20110028867A1 (en) * 2009-07-29 2011-02-03 Seh-Eun Choo Apparatus and method for non-invasive delivery and tracking of focused ultrasound generated from transducer

Also Published As

Publication number Publication date
EP0134346A1 (de) 1985-03-20
DE3379990D1 (en) 1989-07-06

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