EP0033071A1 - Ultrasonic transducer - Google Patents

Ultrasonic transducer Download PDF

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Publication number
EP0033071A1
EP0033071A1 EP81100120A EP81100120A EP0033071A1 EP 0033071 A1 EP0033071 A1 EP 0033071A1 EP 81100120 A EP81100120 A EP 81100120A EP 81100120 A EP81100120 A EP 81100120A EP 0033071 A1 EP0033071 A1 EP 0033071A1
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EP
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Prior art keywords
ultrasonic transducer
lead section
workpiece
transducer
curved
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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.)
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EP81100120A
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German (de)
French (fr)
Inventor
Michael Vieth
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Siemens AG
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Siemens AG
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Publication date
Application filed by Siemens AG filed Critical Siemens AG
Publication of EP0033071A1 publication Critical patent/EP0033071A1/en
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    • 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
    • G10K11/30—Sound-focusing or directing, e.g. scanning using refraction, e.g. acoustic lenses

Definitions

  • the invention relates to an ultrasonic transducer with a curved piezoelectric oscillator body, which is polarized in the direction of its thickness and the flat sides of which are each provided with an electrically conductive surface layer.
  • ultrasonic technology requires constricted sound fields in many applications. This focus of the sound beam is used in non-destructive material testing, in medicine and, for example, when cleaning and welding with ultrasound.
  • the transducer is arranged in a container with acoustic transmission fluid, which is provided with an acoustically transparent window, which is used for coupling to the body to be examined.
  • the two flat sides of the piezoelectric vibrating body are each provided with an electrically conductive surface layer and connected to electrodes.
  • the surface of the vibrating body facing the body to be examined can be concavely curved (DE-OS 27 10 038).
  • Focusing in the case of planar piezoelectric transducer bodies is also obtained by means of a spherical lens placed directly on the planar transducer.
  • this focusing lens is still one preferably changeable lead section made of a material suitable as an adapter body, whose surface facing the vibrating body of the focusing lens is adapted and whose opposite surface is adapted to the surface of the body to be examined, the transducer can also be placed directly on the surface of the object to be examined.
  • a liquid film for example made of oil, is then generally used for the coupling.
  • the focusing effect of this ultrasonic transducer with a flat transducer body is less than the focusing with a curved transducer body.
  • additional false echoes are obtained at the interface between the focusing lens and the lead section ("Material Institute" 19 (1977), No. 10, pages 441 to 444).
  • the invention is therefore based on the object of improving an ultrasonic transducer of the type mentioned, in particular it should be usable for direct testing with a large signal-to-noise ratio.
  • a lens is assigned to the curved vibrating body as a leading section, the convex surface of which is adapted to the curvature of the vibrating body and the opposite surface of which can be acoustically coupled to the surface shape of an object to be examined.
  • the height of the lens is preferably selected so that expected signal echoes from the focus area and false echoes from the interface between the lens and the test specimen are recorded by the transducer body after different transit times.
  • a fixed lead section is thus assigned to the curved vibrating body.
  • the transducer can be adapted to different surface shapes, for example different radii of curvature, of the workpiece to be examined by means of an exchangeable lead section.
  • the distance between the vibrating body and the surface of the workpiece and thus the position of the focal point within the body to be examined can be changed.
  • the oscillating body forming a spherical cap and, if appropriate, also the leading section can be divided into two equal halves to avoid acoustic coupling.
  • one half of the transducer body can be used as a transmitter and the other as a receiver.
  • a curved oscillating body 2 made of piezoelectric material is provided on its flat side with a surface layer 4 or 6 made of electrically conductive material, which are connected to electrical connection conductors, not shown in the figure.
  • the concave flat side of the membrane 2 is connected to a lead section 8, the surface of which facing the vibrating body 2 is adapted to the curvature of the vibrating body and its opposite surface is adapted to the surface of a workpiece 10, which is shown flat in the figure.
  • the position of the focal point Fp in the workpiece 10 to be examined can be determined by the frequency f and the diameter D and the radius of curvature R of the oscillator body 2 and can be changed by the distance L of the vibrating body 2 from the surface of the workpiece 10 and by the ratio of the speed of sound c 1 of the material of the lead section 8 to the speed of sound c 2 of the material of the workpiece 10 to be examined.
  • the lead section 8 made of solid material allows a better acoustic adaptation to a metallic workpiece 10 than a liquid.
  • the transducer can also be coupled to a sound-absorbing medium, for example the human body, with a lead section 8 made of polymethyl methacrylate (plexiglass).
  • a lead section is provided whose surface facing the body 10 to be examined has this radius of curvature.
  • the lead section 8 of the converter can preferably be exchangeable.
  • a protective layer is generally provided between the metal layer 6 and the lead section 8, which can also be designed as an adaptation layer.
  • the vibrating body 2 with the lead section 8 can be divided into two halves, for example with a cut along the rotation axis 12 indicated by dash-dotted lines, one of which is then used as the transmitter and the other as the receiver can be.
  • a curved oscillating body 2 which forms a spherical cap.
  • the transducer can also contain a cylindrical oscillator body, which is part of a hollow cylinder. Instead of a focal point, this oscillator body forms a focal line parallel to the cylinder axis.

Abstract

An ultrasonic transducer having a curved piezoelectric oscillator element. In accordance with the invention, the spherically or cylindrically concavely curved oscillator element (2) is assigned as delay path a convex lens (8) whose convex surface is matched to the curvature of the oscillator element (2) and whose opposite surface can be coupled acoustically to the surface of a workpiece (10) to be investigated. This transducer provides good focusing and only small unwanted echoes. <IMAGE>

Description

Die Erfindung bezieht sich auf einen Ultraschallwandler mit einem gekrümmten piezoelektrischen Schwingerkörper, der in Richtung seiner Dicke polarisiert ist und dessen Flachseiten jeweils mit einer elektrisch leitenden Oberflächenschicht versehen sind.The invention relates to an ultrasonic transducer with a curved piezoelectric oscillator body, which is polarized in the direction of its thickness and the flat sides of which are each provided with an electrically conductive surface layer.

Zur Erhöhung der Intensität oder zur Erhöhung des Auflösungsvermögen sind innerhalb der Ultraschalltechnik bei vielen Anwendungsfällen Schallfelder mit Einschnü- .rung erforderlich. Man benutzt diese Fokussierung des Schallbündels in der zerstörungsfreien Werkstoffprüfung, in der Medizin sowie beispielsweise auch beim Reinigen und Schweißen mit Ultraschall. In einer bekannten Vorrichtung zur Untersuchung von Geweben mit Ultraschall ist der Wandler in einem Behälter mit akustischer Übertragungsflüssigkeit angeordnet, der mit einem akustisch transparenten Fenster versehen ist, das zur Ankopplung an den zu untersuchenden Körper dient. Die beiden Flachseiten des piezoelektrischen Schwingerkörpers sind jeweils mit einer elektrisch leitenden Oberflächenschicht versehen und mit Elektroden verbunden. Zur Fokussierung des Schallbündels kann die dem zu untersuchenden Körper zugewandte Oberfläche des Schwingerkörpers konkav gekrümmt sein (DE-OS 27 10 038).To increase the intensity or to increase the resolving power, ultrasonic technology requires constricted sound fields in many applications. This focus of the sound beam is used in non-destructive material testing, in medicine and, for example, when cleaning and welding with ultrasound. In a known device for examining tissues with ultrasound, the transducer is arranged in a container with acoustic transmission fluid, which is provided with an acoustically transparent window, which is used for coupling to the body to be examined. The two flat sides of the piezoelectric vibrating body are each provided with an electrically conductive surface layer and connected to electrodes. To focus the sound bundle, the surface of the vibrating body facing the body to be examined can be concavely curved (DE-OS 27 10 038).

Eine Fokussierung bei ebenen piezoelektrischen Schwingerkörpern erhält man ferner durch eine unmittelbar auf den ebenen Schwinger aufgesetzte sphärische Linse. Wird dieser Fokussierungslinse noch eine vorzugsweise auswechselbare Vorlaufstrecke aus einem als Anpassungskörper geeigneten Material zugeordnet, deren dem Schwingerkörper zugewandte Oberfläche der Fokussierungslinse angepaßt ist und deren gegenüberliegende Oberfläche der Oberfläche des zu untersuchenden Körpers angepaßt ist, so kann der Wandler auch direkt auf die Oberfläche des zu untersuchenden Objektes aufgesetzt werden. Zur Ankopplung dient dann bei Materialuntersuchungen im allgemeinen noch ein Flüssigkeitsfilm, beispielsweise aus Öl. Die fokussierende Wirkung dieses Ultraschallwandlers mit flachem Schwingerkörper ist jedoch geringer als die Fokussierung mit einem gekrümmten Schwingerkörper. Ferner erhält man an der Grenzfläche zwischen der Fokussierungslinse und der Vorlaufstrecke zusätzliche Störechos ("Materialprüfung" 19 (1977), Nr. 10, Seiten 441 bis 444).Focusing in the case of planar piezoelectric transducer bodies is also obtained by means of a spherical lens placed directly on the planar transducer. If this focusing lens is still one preferably changeable lead section made of a material suitable as an adapter body, whose surface facing the vibrating body of the focusing lens is adapted and whose opposite surface is adapted to the surface of the body to be examined, the transducer can also be placed directly on the surface of the object to be examined. In the case of material examinations, a liquid film, for example made of oil, is then generally used for the coupling. However, the focusing effect of this ultrasonic transducer with a flat transducer body is less than the focusing with a curved transducer body. Furthermore, additional false echoes are obtained at the interface between the focusing lens and the lead section ("Materialprüfung" 19 (1977), No. 10, pages 441 to 444).

Der Erfindung liegt deshalb die Aufgabe zugrunde, einen Ultraschallwandler der eingangs genannten Art zu verbessern, insbesondere soll er bei großem Signal-Rausch--abstand für eine Direktprüfung verwendbar sein.The invention is therefore based on the object of improving an ultrasonic transducer of the type mentioned, in particular it should be usable for direct testing with a large signal-to-noise ratio.

Diese Aufgabe wird erfindungsgemäß dadurch gelöst, daß dem gekrümmten Schwingerkörper als Vorlaufstrecke eine Linse zugeordnet ist, deren konvexe Oberfläche der Krümmung des Schwingerkörpers angepaßt ist und deren gegenüberliegende Oberfläche an die Oberflächenform eines zu untersuchenden Objekts akustisch ankoppelbar ist. Dabei wird die Höhe der Linse vorzugsweise so gewählt, daß zu erwartende Signalechos aus dem Fokusbereich und Störechos von der Grenzfläche zwischen Linse und Prüfkörper vom Schwingerkörper nach unterschiedlichen Laufzeiten aufgenommen werden. Dem gekrümmten Schwingerkörper ist somit eine feste Vorlaufstrecke zugeordnet. Durch Verminderung der Grenzflächenzahl ergeben sich übersichtlichere Echoanzeigen und damit bessere Meßergebnisse.This object is achieved in that a lens is assigned to the curved vibrating body as a leading section, the convex surface of which is adapted to the curvature of the vibrating body and the opposite surface of which can be acoustically coupled to the surface shape of an object to be examined. The height of the lens is preferably selected so that expected signal echoes from the focus area and false echoes from the interface between the lens and the test specimen are recorded by the transducer body after different transit times. A fixed lead section is thus assigned to the curved vibrating body. By reducing the number of interfaces, there are clearer echo displays and thus better measurement results.

Durch eine auswechselbare Vorlaufstrecke kann der Wandler verschiedenen Oberflächenformen, beispielsweise verschiedenen Krümmungsradien, des zu untersuchenden Werkstücks angepaßt werden. Außerdem kann damit der Abstand des Schwingerkörpers von der Oberfläche des Werkstücks und damit die Lage des Fokuspunktes innerhalb des zu untersuchenden Körpers geändert werden.The transducer can be adapted to different surface shapes, for example different radii of curvature, of the workpiece to be examined by means of an exchangeable lead section. In addition, the distance between the vibrating body and the surface of the workpiece and thus the position of the focal point within the body to be examined can be changed.

In einer besonderen Ausführungsform des Ultraschallwandlers können der eine Kugelkalotte bildende Schwingerkörper und gegebenenfalls auch die Vorlaufstrecke zur Vermeidung akustischer Überkopplung in zwei gleiche Hälften aufgeteilt sein. In dieser Ausführungsform kann eine Hälfte des Schwingerkörpers als Sender und die andere als Empfänger verwendet werden.In a special embodiment of the ultrasound transducer, the oscillating body forming a spherical cap and, if appropriate, also the leading section can be divided into two equal halves to avoid acoustic coupling. In this embodiment, one half of the transducer body can be used as a transmitter and the other as a receiver.

Zur weiteren Erläuterung der Erfindung wird auf die Zeichnung Bezug genommen, in der eine Ausführungsform eines Ultraschallwandlers nach der Erfindung schematisch veranschaulicht ist.To further explain the invention, reference is made to the drawing, in which an embodiment of an ultrasonic transducer according to the invention is schematically illustrated.

Ein gekrümmter Schwingerkörper 2 aus piezoelektrischem Material ist an seiner Flachseite jeweils mit einer Oberflächenschicht 4 bzw. 6 aus elektrisch leitendem Material versehen, die mit in der Figur nicht dargestellten elektrischen AnschluBleitern verbunden sind. Die konkave Flachseite der Membran 2 ist mit einer Vorlaufstrecke 8 verbunden, deren dem Schwingerkörper 2 zugewandte Oberfläche der Krümmung des Schwingerkörpers und -deren gegenüberliegende Oberfläche der Oberfläche eines Werkstücks 10 angepaßt ist, das in der Figur flach dargestellt ist.A curved oscillating body 2 made of piezoelectric material is provided on its flat side with a surface layer 4 or 6 made of electrically conductive material, which are connected to electrical connection conductors, not shown in the figure. The concave flat side of the membrane 2 is connected to a lead section 8, the surface of which facing the vibrating body 2 is adapted to the curvature of the vibrating body and its opposite surface is adapted to the surface of a workpiece 10, which is shown flat in the figure.

Die Lage des Fokuspunktes Fp im zu untersuchenden Werkstück 10 kann durch die Frequenz f und den Durchmesser D sowie den Krümmungsradius R des Schwingerkörpers 2 und durch den Abstand L des Schwingerkörpers 2 von der Oberfläche des Werkstücks 10 sowie durch das Verhältnis der Schallgeschwindigkeit c1 des Materials der Vorlaufstrecke 8 zur Schallgeschwindigkeit c2 des Materials des zu untersuchenden Werkstücks 10 verändert werden.The position of the focal point Fp in the workpiece 10 to be examined can be determined by the frequency f and the diameter D and the radius of curvature R of the oscillator body 2 and can be changed by the distance L of the vibrating body 2 from the surface of the workpiece 10 and by the ratio of the speed of sound c 1 of the material of the lead section 8 to the speed of sound c 2 of the material of the workpiece 10 to be examined.

Als Material für die Vorlaufstrecke 8 ist beispielsweise Messing, Keramik oder keramisches Glas (Macor) sowie Polymethylmetacrylat (Plexiglas) geeignet. Die Vorlaufstrecke 8 aus festem Material läßt eine bessere akustische Anpassung an ein metallisches Werkstück 10 zu als eine Flüssigkeit. Auch an ein schallweiches Medium, beispielsweise den menschlichen Körper, läßt sich der Wandler mit einer Vorlaufstrecke 8 aus Polymethylmetacrylat (Plexiglas) ankoppeln.For example, brass, ceramic or ceramic glass (Macor) and polymethyl methacrylate (Plexiglas) are suitable as materials for the lead section 8. The lead section 8 made of solid material allows a better acoustic adaptation to a metallic workpiece 10 than a liquid. The transducer can also be coupled to a sound-absorbing medium, for example the human body, with a lead section 8 made of polymethyl methacrylate (plexiglass).

Soll der Ultraschallwandler zur Untersuchung eines Werkstücks 10 mit einer gekrümmten Oberfläche verwendet werden, so wird eine Vorlaufstrecke vorgesehen, deren dem zu untersuchenden Körper 10 zugewandte Oberfläche diesen Krümmungsradius hat.If the ultrasound transducer is to be used to examine a workpiece 10 with a curved surface, a lead section is provided whose surface facing the body 10 to be examined has this radius of curvature.

Die Vorlaufstrecke 8 des Wandlers kann vorzugsweise auswechselbar sein. In dieser Ausführungsform wird im allgemeinen zwischen der Metallschicht 6 und der Vorlaufstrecke 8 noch eine in der Figur nicht dargestellte Schutzschicht vorgesehen, die auch als Anpassungsschicht ausgeführt sein kann.The lead section 8 of the converter can preferably be exchangeable. In this embodiment, a protective layer, not shown in the figure, is generally provided between the metal layer 6 and the lead section 8, which can also be designed as an adaptation layer.

Sollen in einer besonderen Ausführungsform eines Ultraschallwandlers Sender und Empfänger getrennt werden, so kann der Schwingerkörper 2 mit der Vorlaufstrecke 8 beispielsweise mit einem Schnitt längs der strichpunktiert angedeuteten Rotationsachse 12 in zwei Hälften aufgeteilt werden, von denen dann einer als Sender und der andere als Empfänger verwendet werden kann.If, in a special embodiment of an ultrasound transducer, the transmitter and receiver are to be separated, the vibrating body 2 with the lead section 8 can be divided into two halves, for example with a cut along the rotation axis 12 indicated by dash-dotted lines, one of which is then used as the transmitter and the other as the receiver can be.

Im Ausführungsbeispiel ist ein gekrümmter Schwingerkörper 2 angenommen, der eine Kugelkalotte bildet. Der Wandler kann jedoch statt des sphärisch gekrümmten Schwingerkörpers auch einen zylinderförmigen Schwingerkörper enthalten, der einen Teil eines Hohlzylinders darstellt. Dieser Schwingerkörper bildet anstelle eines Fokuspunktes eine Fokuslinie parallel zur Zylinderachse.In the exemplary embodiment, a curved oscillating body 2 is assumed, which forms a spherical cap. However, instead of the spherically curved oscillator body, the transducer can also contain a cylindrical oscillator body, which is part of a hollow cylinder. Instead of a focal point, this oscillator body forms a focal line parallel to the cylinder axis.

Claims (4)

1. Ultraschallwandler mit einem gekrümmten piezoelektrischen Schwingerkörper, der in Richtung seiner Dicke polarisiert ist und dessen Flachseiten jeweils mit einer elektrisch leitenden Oberflächenschicht versehen sind, dadurch gekennzeichnet , daß dem gekrümmten Schwingerkörper (2) als Vorlaufstrecke (8) eine Linse zugeordnet ist, deren konvexe Oberfläche der Krümmung des Schwingerkörpers (2) angepaßt ist und deren gegenüberliegende Oberfläche an die Oberfläche eines zu untersuchenden Werkstücks (10) akustisch ankoppelbar ist.1. Ultrasonic transducer with a curved piezoelectric transducer body, which is polarized in the direction of its thickness and the flat sides of which are each provided with an electrically conductive surface layer, characterized in that a lens is assigned to the curved transducer body (2) as a leading section (8), the convex of which Surface of the curvature of the vibrating body (2) is adapted and the opposite surface of which can be acoustically coupled to the surface of a workpiece (10) to be examined. 2. Ultraschallwandler nach Anspruch 1, dadurch gekennzeichnet , daß die Höhe (L) der Vorlaufstrecke (8) so gewählt wird, daß Signalechos aus dem Bereich des Fokuspunktes (Fp) und Störechos von der Grenzfläche zwischen Vorlaufstrecke (8) und Werkstück (10) vom Schwingerkörper (2) nach unterschiedlichen Laufzeiten aufgenommen werden.2. Ultrasonic transducer according to claim 1, characterized in that the height (L) of the lead section (8) is selected such that signal echoes from the area of the focal point (F p ) and false echoes from the interface between the lead section (8) and the workpiece (10 ) are picked up by the oscillator body (2) after different running times. 3. Ultraschallwandler nach Anspruch 1 oder 2, dadurch gekennzeichnet, daß der Schwingerkörper (2) in zwei Hälften aufgeteilt ist, von denen eine als Sender und die andere als Empfänger verwendbar ist.3. Ultrasonic transducer according to claim 1 or 2, characterized in that the oscillator body (2) is divided into two halves, one of which can be used as a transmitter and the other as a receiver. 4. Ultraschallwandler nach einem der Ansprüche 1 bis 3, dadurch gekennzeichnet , daß die Vorlaufstrecke (8) auswechselbar ist.4. Ultrasonic transducer according to one of claims 1 to 3, characterized in that the lead section (8) is interchangeable.
EP81100120A 1980-01-25 1981-01-09 Ultrasonic transducer Withdrawn EP0033071A1 (en)

Applications Claiming Priority (2)

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DE19803002663 DE3002663A1 (en) 1980-01-25 1980-01-25 ULTRASONIC transducer
DE3002663 1980-01-25

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0421286A2 (en) * 1989-10-03 1991-04-10 Richard Wolf GmbH Piezoelectric transducer
EP0606804A2 (en) 1992-12-30 1994-07-20 McGILL UNIVERSITY Marker for neurotensin receptor

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102008028200B4 (en) 2008-06-12 2013-01-31 Karlsruher Institut für Technologie Ultrasonic transducer with variable focus adjustment

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4205686A (en) * 1977-09-09 1980-06-03 Picker Corporation Ultrasonic transducer and examination method

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4205686A (en) * 1977-09-09 1980-06-03 Picker Corporation Ultrasonic transducer and examination method

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
SOVIET JOURNAL OF NONDESTRUCTIVE TESTING, Band 13, Nr. 3, 06-05-1977, New York, US A. VOPILKIN et al. "Ultrasonic wideband probes and their experimental analysis", Seiten 264-271. * Seiten 268, Zeile 6 - Seite 269, Zeile 6; Figur 8 IIIb * *

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0421286A2 (en) * 1989-10-03 1991-04-10 Richard Wolf GmbH Piezoelectric transducer
EP0421286A3 (en) * 1989-10-03 1992-06-03 Richard Wolf Gmbh Piezoelectric transducer
EP0606804A2 (en) 1992-12-30 1994-07-20 McGILL UNIVERSITY Marker for neurotensin receptor

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