DE3002663A1 - ULTRASONIC transducer - Google Patents

Description

The invention relates to an ultrasonic transducer with a curved piezoelectric oscillator body, which is polarized in the direction of its thickness and its flat sides each with an electrically conductive surface layer are provided.

To increase the intensity or to increase the resolution are sound fields with constriction in many applications within ultrasound technology necessary. This focusing of the sound beam is used in non-destructive material testing, in medicine as well as, for example, cleaning and welding with ultrasound. In a known device For examining tissues with ultrasound, the transducer is in a container with acoustic transmission fluid arranged, which is provided with an acoustically transparent window for coupling on the body to be examined. The two flat sides of the piezoelectric oscillator body are each with an electrically conductive surface layer provided and connected to electrodes. To focus the sound bundle, the to be examined can Body facing surface of the oscillating body be concave curved (DE-OS 27 10 038).

A focusing in the case of flat piezoelectric oscillating bodies is also obtained by directing one to the spherical lens attached to the flat transducer. If this focusing lens is also provided with a preferably

Kin 2 Koe / January 15, 1980

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VPA 80 P 7 5 O 7 1> ε assigned to an exchangeable feed path made of a material suitable as an adaptation body, whose surface facing the oscillating body is adapted to the focusing lens and whose opposite surface is adapted to the surface of the body to be examined _? so 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 coupling in fetal examinations. However, the focusing effect of this ultrasonic transducer with a flat sciminger body is less than the focusing effect with a curved oscillator body. In addition, additional false echoes are obtained at the interface between the focusing lens and the advance path (^ Materialprüfung ⁰³ 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 at the beginning, in particular, it should be used with a large signal-to-noise ratio be usable for a direct test.

This object ^ ■ d.rd achieved according to the invention in that A lens © is assigned to the curved oscillating body as a forward path, "whose convex surface of the Curvature of the oscillator body is adapted and its opposite surface to the surface shape an object to be examined can be coupled acoustically. At this time, the height of the lens is preferably so '30 selected j that expected signal echoes from the focus area and interference echoes from the interface between lenses © and test body from the Schvfinger body according to different Runtimes are included. The curved transducer body is thus a solid © flow stream © assigned. By reducing the number of interfaces, there are clearer echo displays and thus better measurement results.

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The converter can different surface shapes, for example different radii of curvature, of the workpiece to be examined be adjusted. In addition, the distance between the oscillator body and the surface of the workpiece can thus be reduced and thus the position of the focal point within the body to be examined can be changed.

In a special embodiment of the ultrasonic transducer the oscillating body forming a spherical cap and possibly also the feed path to the Avoid acoustic cross-coupling, be divided into two equal halves. In this embodiment can one half of the transducer body can be used as a transmitter and the other half as a receiver.

To further explain the invention, reference is made to the drawing, in which one embodiment an ultrasonic transducer according to the invention is illustrated schematically.

A curved oscillator body 2 made of piezoelectric material has a surface layer on its flat side 4 and 6 made of electrically conductive material, which are not shown in the figure electrical connection conductors are connected. The concave flat side of the membrane 2 has a feed path 8 connected, whose surface facing the oscillator body 2 of the curvature of the oscillator body and whose opposite surface is adapted to the surface of a workpiece 10, which is flat in the figure is shown.

The position of the focal point F in the workpiece to be examined 10 can by the frequency f and the diameter D and the radius of curvature R of the oscillator body 2 and

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by the distance L of the oscillating body 2 from the surface of the workpiece 10 and by the ratio of Speed of sound c, of the material of the delay line 8 to the speed of sound c ^ of the material of the workpiece 10 to be examined changed v / ground.

Brass, ceramic or ceramic glass (Macor), for example, are used as the material for the feed line 8 Polymethyl methacrylate (plexiglass) suitable. The lead section 8 made of solid material has a better acoustic Adaptation to a metallic workpiece 10 as a liquid. Even on a sound-soft medium, For example, the human body, the transducer can be connected to a feed line 8 made of polymethyl methacrylate (Plexiglas).

Should the ultrasonic transducer be used to examine a workpiece 10 are used with a curved surface, so icLrd provided a delay line whose the surface facing the body 10 to be examined has this radius of curvature.

The initial path 8 of the converter can preferably be interchangeable. In this embodiment, there is generally between the metal layer 6 and the lead-in section 8 a protective layer, not shown in the figure, is also provided, which also acts as an adaptation layer can be executed.

If, in a special embodiment of an ultrasonic transducer, the transmitter and receiver are to be grounded separately, the transducer body 2 with the feed path 8 can be divided into two halves, for example with a section along the axis of rotation © 12 indicated by dash-dotted lines, of which one is the transmitter and the other can be used as a receiver.

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In the exemplary embodiment, a curved oscillating body 2 is assumed, which forms a spherical cap. Of the However, instead of the spherically curved oscillator body, the transducer can also have a cylindrical oscillator body included, which is part of a hollow cylinder. This oscillating body forms instead of one Focus point a focus line parallel to the cylinder axis.

4 claims
1 figure

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Claims (1)

Claims ψ 7 5 0 7 \ Λ * jUltraschallXiandler with a curved piezoelectric oscillating body that extends in the direction of its thickness
is polarized and its flat sides are each provided with an electrically conductive surface layer "
characterized in that the curved oscillating body (2) is used as a leading stretch © (8)
a lens is assigned whose convex surface is adapted to the curvature of the oscillating body (2) and whose opposite surface can be acoustically coupled to the surface of a workpiece (10) to be examined, 2 ο ultrasonic transducer according to claim 1, characterized
characterized in that the height (L) of the
Forward path (8) is chosen so that signal echoes from the area of the focal point (F) and interference echoes from the interface between the forward path (8) and workpiece (10) are picked up by the sciminger body (2) after different transit times » 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 ο 4. Ultrasonic transducer according to one of claims 1 to 3, characterized in that the leading section (8) is exchangeable. 1 30031/0285 BATH ORIGINAL