DE19928765A1 - Ultrasonic transducer for multi-frequency, multi-layer test head can transmit different frequencies and receive frequency selectively over wide band with higher sensitivity than conventional arrangements - Google Patents

Abstract

The arrangement has at least two oscillation layers arranged one after the other in the radiation direction and which can be driven individually or as a group (G1,G2). At least two groups can be operated at different frequencies and at least one group can be operated as a transmitter and at least one group as a receiver. The group operated as a transmitter is different from the group operated as a receiver.

Description

The invention is in the field of ultrasound technology.

The invention relates to an ultrasonic transducer arrangement at least two, one behind the other, seen in a radiation direction other arranged vibrating layers, individually or in Combination can be controlled to form a group, whereby to be at least two groups with different frequencies are drivable and control at least one group as a transmitter is cash.

It also relates to a method for ultrasonic testing, whereby at least two, one behind the other, seen in a radiation direction other vibration layers individually or in combination a group can be controlled, at least two Groups are operated with different frequencies and at least one group is controlled as a transmitter.

From European patent specification EP 0 667 978 B1 is a Ultrasonic test head known, the one in a common Housing arranged ultrasonic transducer arrangement with little at least one ultrasonic transducer array and at least two aku S / E ultrasound transducers separated from each other. The ultrasound transducer array is in pulse-echo mode drivable and the two S / E ultrasound arranged next to it converters can be operated in the transmit / receive mode. That im pulse-echo mode operated ultrasonic transducer array is used Detect surface defects in the workpiece. On the other hand is the pulse-echo mode, in which the sending and receiving against the ultrasonic waves in one and the same transducer detects defects close to the surface in the workpiece not suitable as a converter active for sending for a certain period of time after the transmission for those from the error  signals reflected back in the workpiece is practically blind ("Ringing"). For detection of near-surface defects the ultrasound probe described in EP 0 667 978 B1 the two separate S / E ultrasound transducers, one of which one is operated as a transmitter and the other as a receiver. The advantages of the Im are indeed in this ultrasonic test head pulse echo mode as well as the advantages of the transmit-receive mo dus united, but such an ultrasound test is required head due to the lateral arrangement of the S / E ultrasound transducer next to the ultrasound transducer array a large ankop surface and is therefore not suitable for numerous test tasks sufficiently compact to look at.

At the Internet address http://www.ultrasonic.de/article/splitt/splitt.htm was created on 07.02.1996 at 3:26 p.m. a technical article by G. Splitt with the Title "Probes with composite transducers - a milestone for ultrasound testing ". There is a Transducer material described in the case of parallel aligned Ceramic sticks are embedded in an epoxy resin matrix.

From European patent specification EP 0 451 984 B1 is a Ultrasonic probe system with a large number of stacked pie known zoelectric layers. Are between layers Electrodes arranged with a polarization reversal circuit are connected. As a result, neighboring piezoelectric trical layers optionally with essentially opposite sets directional electric fields or with in the same Chen direction directed electric fields bar. The polarization reversal ensures that with the Ultrasonic probe system Ultrasonic waves with a variety of different frequencies are broadcast. The stacked piezoelectric layers have the same thickness.

A disadvantage of the ultrasound probe system described in EP 0 451 984 B1 is that the polarity of at least one of the piezoelectric layers must be changed before each frequency change. Therefore, with this ultrasonic probe system, the frequencies cannot be changed quickly. In the German patent DE 29 49 991 C3, a device for ultrasound scanning is disclosed which comprises a plurality of layers of oscillating material arranged one behind the other as seen in a sound direction, which, individually or in summary, represent the transmitters for selected frequency bands of a transmission frequency spectrum. In order to receive reflected portions of all ultrasonic waves transmitted at different frequencies, the device has a separate PVF ₂ film which acts as a sound absorber. This PVF ₂ film must be irradiated by an emitted ultrasound wave before the ultrasound wave can be coupled into the test specimen. This disadvantageously results in runtime losses when the device is operated in pulse-echo mode. Another disadvantage of the separate PVF ₂ film is that between the PVF ₂ film and the vibrating layers serving as transmitters, a matching layer is required to adapt the acoustic impedance of the PVF ₂ film to the vibrating layers, in order to avoid excessive reflection losses of the emitted ultrasonic wave to avoid. Such an adaptation layer can always be optimally dimensioned for only a few or a few frequencies. Another disadvantage of the device of DE 29 49 991 C3 is that - in order to be sensitive to all ultrasound frequencies emitted by the vibrating layers - the PVF ₂ film must be very broadband. This results in a poor signal-to-noise ratio.

The invention is therefore based on the object, an ul specify transducer arrangement, with the ultrasound wel len different frequencies are broadcast. In doing so Ultrasonic waves also in a wide frequency band fre can be received with a selective frequency and with higher sensitivity be than in the known devices. To this end  it is also an object of the invention to provide a method for ultra to specify sound test.

The arrangement-related task is done with an ultrasound converter arrangement of the type mentioned in the Erfin tion solved in that at least one group as a recipient is operable.

It can e.g. B. at least

• - a first group at a first frequency and
• - a second group at a ver of the first frequency be different second frequency operable.

The first and optionally the second group can be used as Be controllable transmitter. The first group can e.g. B. also as Receiver can be operated at the first frequency.

According to a preferred development, the is on as a transmitter controllable group from the group that can be operated as a receiver different.

For example, the second group is the recipient of the second frequency operable.

Each vibrating layer is preferably both as a transmitter and can also be controlled as a receiver.

The vibrating layers are preferably made of a piezoceramic manufactured. An ultra made from a piezoceramic sound receiver creates a special when receiving sound high signal amplitude.

The groups, which comprise one or more jointly controlled oscillator layers and can be operated as receivers, can advantageously be operated selectively at their respective frequency, ie in particular for the first or second frequency, as a sensitive receiver with a good signal-to-noise ratio. Here are z. B. the first and the second frequency largely selectable within a broad frequency band

• a) Choice of suitable thicknesses of the vibrating layers, whereby the Resonance frequency of the relevant vibrating layer affected is flowable, and / or
• b) Combination of certain vibration layers into one common sam controllable group.

The fact that in the ultrasonic transducer arrangement according to the Er Finding individual vibration layers both as transmitters and the ultrasonic wall can also be operated as a receiver The arrangement is particularly simple and compact, and can be constructed also prone to interference. When operating in pulse-echo mode there is also no annoying loss of runtime because sending and receiving essentially the same spatial place takes place.

The frequency assigned to a group is either in one Frequency band around the resonance frequency of an individually controlled or a frequency band around one "Sum resonance frequency" of combined in combination controlled vibratory layers. The combination is preferred formed by adjacent vibration layers. These will for example, driven in combination by a tax voltage in the direction of radiation over that from the two single NEN thicknesses of the vibrating layers formed total thickness is switched.

According to another preferred development, the Ultra sound transducer arrangement at least three vibration layers on that can be controlled such that at least four groups can be formed with different frequencies.

Can between two adjacent vibrating layers an electrode film may be attached.  

The groups are preferably driven with the same polarity conceivable.

For example, electrode films are used for this purpose apply an electric field to the vibrating layers are beatable in or against the direction of radiation with egg larger electrical potential can be applied than the previous electrode film. In other words: The potential is released from electrode film to electrode film neither smaller or larger. At a such control of the vibrating layers or the group pen is used to generate different transmission frequencies Change in polarity of an emitting oscillating layer not required so that e.g. B. the change from the first Frequency to the second frequency can be carried out particularly quickly is.

A first of the vibrating layers preferably has one of the thickness of the second vibration layer different thickness on. This advantageously allows many different ones Set frequencies for sending and / or receiving.

According to a particularly preferred embodiment, at least one of the transducer layers as a composite transducer builds. There are small ceramic parts in a composite transducer embedded in a matrix, for example made of epoxy resin, and it can be about the fill level of the matrix, i.e. H. in particular about the quantitative ratio of ceramic to epoxy resin, a ge lower acoustic impedance than with a pure piezoceramic can be set so that the acoustic impedance of the Schwingers z. B. to that of a steel test object or one Leader body made of plexiglass approximates. This will make him is sufficient that no separate adaptation layer is necessary, which in broadband in the way already described would limit ultrasound reception.  

According to another preferred embodiment, the electrode film is formed between two adjacent oscillating layers

• - A first electrically conductive coating on one the vibrating layers,
• - A second electrically conductive coating on the other vibrating layer as well
• - An electrically conductive connecting the coatings against adhesive layer.

Such an arrangement is particularly easy to manufacture.

In this context, coating is generally used Apply a firmly adhering layer of shapeless material understood on a workpiece, the substance in particular from the gas, vapor, powder or ionized state is applied.

In a preferred development, the ultrasonic transducer order protrudes one of the vibrating layers bil dend in a direction deviating from the direction of radiation beyond an adjacent vibrating layer, and a second adjacent vibrating layers of attached electro the film extends to the top.

The electrode film extending to the protrusion advantageously offers an easy way to an electrical line, for example, the electrode film by soldering or bonding. Over the line can to the electrode film for sending a vibrating layer required electrical potential can be applied. The Electrical conduction can also serve to receive a signal to feed one of the vibrating layers to an evaluation unit ren.

The protrusion protrudes laterally over a neighboring bearded vibrating layer beyond.  

The electrode film is preferably in contact on the projection animals.

In another extremely advantageous further development the protruding vibrating layer on the electrode back of the film facing away from a groove that extends along an egg ner edge of the adjacent vibrating layer extends. By the groove is achieved that the - for sending and / or receiving gene activated - transducer cross-sectional area in the neighboring beard vibrating layers is identical. The one acoustic Separating groove prevents the protrusion of a protruding vibrating layer not for sending and / or Receive is activated. By an identical active Cross-sectional area of the transducer of adjacent vibration layers is achieved when different Schwin the transmission or reception characteristics, at for example the sound field propagation, each unchanged remains. In addition, there are annoying echoes on the protrusions avoided.

When viewed in the direction of radiation, the groove preferably covers the edge or is flush with the edge.

In another, contact-related training manure has one of the vibrating layers on the edge of an Aus recording, and one between neighboring vibrating layers attached electrode film extends to the Ausneh mung. This training also offers the advantage of a times contacting the electrode film. Besides, that is Transducer cross activated for sending and / or receiving intersection in the neighboring vibrating layers in the we somewhat the same since the recess is the size of a Soldering point can be limited.

The electrode film is preferably in contact in the recess animals.  

According to another preferred development, at least one of the vibrating layers is configured as an array.

This has the advantage that the radiation direction, for. B. defined by the insonification angle or a squint angle, is pivotable. Furthermore, the focus depth and the near field length can be set by switching individual array elements on and off. With the art further developed ultrasound transducer arrangement according to the invention, it is therefore possible to carry out a particularly large number of test functions in each case at different frequencies with one and the same test head, for. B.

• a) the insonification angles 45 ° and 60 ° with a transverse wave,
• b) the insonification angles 70 ° and 0 ° with a longitudinal wave,
• c) as well as the wave conversion technology in pulse-echo mode and
• d) negative and positive squint angles.

The ultrasound wall further developed in the mentioned manner The arrangement is therefore space-saving, compact and with Small coupling area can be built up and is therefore particularly versatile applicable.

Two oscillator layers are preferably arranged as an array oscillator trained layer, the radiation directions in particular at least with one component in different, not parallel planes are pivotable.

For example, one of the array vibrating layers is in the Operate transmit-receive mode, i. H. some of their array elements elements are used as transmitters and other array elements as receivers controllable. For example, one of the array is Schwin layers can be operated in impulse-echo mode. The combination a transmit-receive mode and a pulse-echo mode in one ner stack-like operable at different frequencies Ultrasonic transducer arrangement allows an extremely large number of tests functions with minimal space requirements.  

The task of specifying a procedure is related to the initially mentioned method according to the invention thereby ge resolves that a first group as a recipient at a first Frequency is operated.

For example, the first group is also used as a broadcaster at first frequency operated.

The method according to the invention is particularly advantageous with the ultrasonic transducer arrangement according to the invention feasible. The advantages mentioned in this regard apply to the Procedure accordingly.

A second group and optionally more are preferred Groups as receivers at a second frequency or wide Ren frequencies operated. In particular, the second group different from the first group.

For example, the second group is also used as a broadcaster at the second frequency operated.

The groups are preferably indicated with the same polarity controls.

The vibrating layers can - viewed in the direction of radiation tet - each on its front and back with an elec Trodenfilm be contacted. By applying a voltage between two of these electrode films, the between the vibrating layer located on the electrode films or the there forming a group between the oscillating layers as Controlled transmitter or receiver.

For example, ultrasonic waves are different Frequencies sent and / or received by at least three Vibrating layers can be controlled in groups, whereby a first group from several neighboring Schwingerschich ten is formed and various other groups  one layer or several adjacent vibration layers are formed.

According to a preferred further development of the method the groups are controlled sequentially. This will advantageously a timed or timed tete received and / or transmit bandwidth achieved ("gate").

The first group is preferred as the recipient at the first frequency and then the second group as the receiver with a second Fre. different from the first frequency quenz operated.

The method is particularly advantageously designed such that that first a group as a transmitter at a transmission frequency and then the first after completing the broadcast activity Group as a receiver at a ver of the transmission frequency different first frequency is operated.

This is a particularly advantageous transmit / receive operation possible, the transmitter and receiver have the same sound level point of entry since they are viewed in the direction of radiation are arranged one behind the other. Sender and receiver are there at operated at different frequencies.

One or more others will be optional after sending Groups as receivers at different from the transmission frequency Frequencies operated. For example, with a large band broad sent and then at different frequencies received within the transmission frequency band. With that you can especially good cracks in a workpiece (test object) decorate or evaluate, because when excited with a wide fre quenzband different zones of a crack with under radiate different frequencies.

According to another preferred further development of the process two of the groups each comprise an array transducer  layer, and the radiation directions of the two groups are at least with one component in different, not parallel planes pivoted, the two groups as Transmitter can be operated at different frequencies.

The planes are preferably perpendicular to one another.

One of the groups in the transmission-reception Mode operated. The direction of radiation of this group can be pivoted art that the squint angle of the abge radiated ultrasonic wave is varied ("Horizontal swivel ").

In addition, one of the groups, in particular one, is preferred other than the above group, be in pulse echo mode drove. For example, the direction of radiation of this Group pivoted such that the angle of incidence of this group emitted ultrasonic wave is varied ("Vertical swivel).

Embodiments of the ultrasonic transducer arrangement according to the invention are explained in more detail with reference to FIGS. 1 to 13. The figures, some of which have only a schematic character, also serve to explain the method according to the invention. Show it:

Fig. 1 shows a first embodiment of an ultrasonic transducer arrangement according to the invention,

Fig. 2 shows the ultrasonic transducer assembly of FIG. 1 in egg nem coupled to a device under test state,

Fig. 3 shows a second embodiment of an ultrasonic transducer arrangement according to the invention,

Fig. 4 shows an enlarged detail from Fig. 3, in which an electrode film of the ultrasound transducer assembly is shown in FIG. 3 in detail,

Fig. 5 shows a third embodiment of an ultrasonic transducer arrangement according to the invention,

Fig. 6 shows a fourth embodiment of an ultrasonic transducer arrangement according to the invention,

Fig. 7 shows a fifth embodiment of an ultrasonic transducer arrangement according to the invention,

Fig. 8 shows a detail of the frequency characteristic of the ultrasonic transducer assembly of FIG. 3,

Fig. 9 shows a sixth embodiment of an ultrasonic transducer arrangement according to the invention formed as an array transducer layers,

Fig. 10, the ultrasonic transducer assembly of FIG. 9 at loading operating in a first transmission-reception mode,

Fig. 11, the ultrasonic transducer assembly of FIG. 9 at loading operating in a second transmission-reception mode,

Fig. 12, the ultrasonic transducer assembly of FIG. 9 when operating in a first pulse-echo mode, and

Fig. 13, the ultrasonic transducer assembly of Fig. 9 when operating in a second pulse-echo mode.

Fig. 1 shows an ultrasonic transducer arrangement with a he most vibrating layer 1 and a second vibrating layer 3 , which are designed as piezoelectric composite transducers with an acoustic impedance of approximately 8 to 10. The first vibrating layer 1 has a thin first electrode film 5 on its rear side. The two vibrating layers 1 , 3 are connected to one another via a thin second electrode film 7 , which acts as an adhesive connection. At the front of the second vibrating layer 3 , a thin third electrode film 9 is applied. The electrode films 5 , 7 , 9 he extend perpendicular to the plane of the drawing over the entire width of the vibrating layers 1 , 3rd

The first layer thickness d _{1 of} the first oscillation layer 1 and the second layer thickness d _{2 of} the second oscillation layer 3 are different. Due to the layer thicknesses d ₁ , d ₂ , the resonance frequencies f ₁ , f _{2 of} the oscillating layers 1 , 3 are given. The first resonance frequency f _{1 of} the first vibrating layer 1 is approximately:

f ₁ = c / (2.d ₁ )

The second resonance frequency f _{2 of} the second oscillation layer 3 is:

f ₂ = c / (2.d ₂ )

C denotes the speed of sound.

The electrode films 5 , 7 , 9 are in contact via a first line 5 A, a second line 7 A and a third line 9 A. Thereby, among other voltages V _1, V ₂ to the vibrator layers 1, 3, applied for driving the vibrator layers 1, 3 for transmitting ultrasonic waves. Received signals can also be dissipated via the lines 5 A, 7 A, 9 A.

Between the first vibrator layer 1 enclosing electrode films 5, 7 is a first voltage V ₁ and between the second oscillator layer 3 inclusive electrode film 7, a second voltage V applied 9 ₂ in such a way that the two transducer layers 1, 3 in the same direction elec trically be polarized. In other words: the second electrode film 7 is an anode for the first oscillation layer 1 and cathode for the second oscillation layer 3 .

By applying a third voltage V ₃ between the first electrode film 5 and the third electrode film 9, there is also a total oscillation layer formed by the first oscillation layer 1 and the second oscillation layer 3 with a layer thickness formed from the sum of the first layer thickness d ₁ and the second layer thickness d ₂ d ₁ + d _{2 can} be controlled as an ultrasound transducer.

The third voltage V ₃ is identical in magnitude and polarity to the first voltage V ₁ and the second voltage V ₂ .

Also in the overall oscillation layer, the electrical polarization generated by the third voltage V ₃ is directed in the same direction as the polarization directions generated in the individual oscillation layers 1 , 3 when activated with the first voltage V ₁ or the second voltage V ₂ .

A control unit 8 is provided for control, e.g. B. a SAPHIR device or a multi-channel control unit capable of group emitters.

With the ultrasound transducer arrangement shown in FIG. 1 and made up of two oscillating layers 1 , 3 , a total of three groups with different frequencies can be formed:

• 1. a first group G1, which is formed solely by driving the first oscillation layer 1 , and which can be operated at a first frequency F ₁ in the frequency band around the first resonance frequency f ₁ ≈ 2 MHz of the first oscillation layer 1 ,
• 2. a second group G2, which is formed by driving only the second oscillation layer 3 , and at a second frequency F ₂ in the vicinity of the second resonance frequency f ₂ ≈ 3 MHz of the second oscillation layer 3 , and
• 3. a third group G3, which is formed by combined actuation of the first vibrating layer 1 and the second vibrating layer 3 , and which can be operated at a third frequency F ₃ in the vicinity of a "total resonance frequency" of the total vibrating layer. The following applies to the third frequency F ₃ :
  1 / F ₃ = 1 / f ₁ + 1 / f ₂ ; F ₃ ≈ 1.2 MHz

The three groups G1, G2, G3 can be operated both as a transmitter with a radiation direction 11 and as a receiver with a reception direction 10 .

For example, the first group G1 is transmitted and the second group G2 receives a portion reflected back. In such a transmit-receive operation of the ultrasonic transducer arrangement according to the invention with different frequencies F ₁ , F ₂ , the transmitter and receiver have advantageously the same sound entry or exit point.

In Fig. 2, the ultrasonic transducer arrangement of FIG. 1 is shown acoustically coupled via a lead wedge 12 to a test specimen or a workpiece 14 .

The embodiment shown in Fig. 3 of an ultrasonic transducer arrangement according to the invention comprises a total of five vibrating layers 1 , 3 , 25 , 27 , 29 , each of which can be operated both as a transmitter and as a receiver. The vibrating layers 1 , 3 , 25 , 27 , 29 are stacked, as seen in the radiation direction 11 , one behind the other. They have at the end or between two respective Schwingerschich th thin, large-area electrode films 5 , 7 , 9 , 31 , 33 , 35 , which are electrically contacted via lines 5 A, 7 A, 9 A, 31 A, 33 A, 35 A. . The oscillating layers 1 , 3 , 25 , 27 , 29 have different resonance frequencies f ₁ , f ₂ , f ₃ , f ₄ , f ₅ . By applying an electrical voltage (not shown) between each two of the electrode films 5 , 7 , 9 , 31 , 33 , 35 , the vibrating layers arranged between these electrically applied electrode films can be controlled as a group. For example, a total of four groups G1, G2, G3, G4 are shown in FIG. 3 from a large number of possible groups. These are in detail:

• 1. a first group G1, which is formed by joint control of the first vibrating layer 1 and the second vibrating layer 3 , and which is operated at a first frequency F ₁ , for which:
  1 / F ₁ = 1 / f ₁ + 1 / f ₂
• 2. a second group G2, which is formed by driving the first oscillation layer 1 and which can be operated at a second frequency F ₂ , for which the following applies:
  F ₂ ≈ f ₁
• 3. a third group G3, formed by common control of the first vibrating layer 1 , the second vibrating layer 3 and the third vibrating layer 25 , and can be operated at a frequency F ₃ :
  1 / F ₃ = 1 / f ₁ + 1 / f ₂ + 1 / f ₃
• 4. a fourth group G4, formed by common control of the third vibrating layer 25 , the fourth vibrating layer 27 and the fifth vibrating layer 29 , and operated at a frequency F ₄ :
  1 / F ₄ = 1 / f ₃ + 1 / f ₄ + 1 / f _5.

In addition, the second oscillation layer 3 (second resonance frequency f ₂ ) and the third oscillation layer 25 (third resonance frequency f ₃ ) could be operated as a fifth or sixth group (not shown).

In Fig. 4, the electrode films 7 , 9 , 31 , 33 arranged between two oscillator layers 1 , 3 , 25 , 27 , 29 are shown in greater detail in the example of the electrode film 7 between the first oscillator layer 1 and the second oscillator layer 3 . The second electrode film 7 is formed from a first electrically conductive coating 41 , which was applied to the first vibrating layer 1 , and from a second electrically conductive coating 43 , which was applied to the second vibrating layer 3 . The second electrode film 7 is further formed from an electrically conductive adhesive layer 45 connecting the coatings 41 , 43 . The thickness of the adhesive layer 45 is preferably less than λ / 10, so that no annoying reflections arise. Here λ is based on the smallest ultrasound wavelength that occurs.

In the third exemplary embodiment of an ultrasonic transducer arrangement according to the invention shown in FIG. 5, a total of four oscillator layers 1 , 3 , 25 , 27 are arranged in a stack, as seen in the radiation direction 11 . The first vibrating layer 1 and the third vibrating layer 25 protrude laterally, ie in a direction 54 perpendicular to the radiation direction 11 , beyond the second vibrating layer 3 and the fourth vibrating layer 27 , as a result of which a first projection 51 on the first vibrating layer 1 and on the third vibrating layer 25 a second projection 53 is formed. The second electrode film 7 and the fourth electrode film 31 extend to the protrusions 51 and 53, respectively. They are electrically connected to lines 7 A and 31 A via solder joints 7 B and 31 B, respectively.

On the side facing away from the second electrode film 7 and the fourth electrode film 31 , the first vibrating layer 1 and the third vibrating layer 25 have a first groove 61 and a second groove 63, respectively. The grooves 61 , 63 first recur along the edge 71 of the second vibrating layer 3 .

The grooves 61 , 63 ensure that the protruding vibrating layers 1 , 25 with their projections 51 and 53 only send or receive within an active zone 100 , which largely coincides with the expansion of the non-protruding vibrating layers 3 , 27 .

The depth of the grooves is 50-70% of the thickness of the respective one Vibrating layer.

In the fourth exemplary embodiment shown in FIG. 6, a total of five oscillating layers 1 , 3 , 25 , 27 , 29 are stacked in a row in the radiation direction as viewed in a row. The vibrating layers 1 , 3 , 25 , 27 , 29 alternately protrude in opposite directions 54 , 58 since Lich beyond the respectively adjacent ultrasonic vibrating layer. In Fig. 6 thereby a he protrusion 51 and a second protrusion 53 and on the right side a third protrusion 55 and a fourth jump 57 are formed on the left side. The electrode films 7 , 9 , 31 , 33 erstrec ken up to the respective projection 51 , 53 , 55 and 57 and are there via solder joints 7 B, 9 B, 31 B, 33 B with electrical lines 7 A, 9 A , 31 A or 33 A connected.

On a side which is opposite to the side on which the adjacent electrode film extends to the respective projection, the respective vibrating layer has a groove 61 , 63 , 65 and 67 which extends along edges 71 of the vibrating layers 3 , 25 extend. The grooves 61 , 63 , 65 and 67 are largely flush with the edges 71 or cover in the radiation direction 11 considered the edges 71 . It is thereby achieved that the active zone 100 in al len vibrating layers 1 , 3 , 25 , 27 , 29 is largely identical.

In the fifth embodiment shown in FIG. 7, in contrast to the embodiment shown in FIG. 5, no projections are present. Instead, the three lowest arranged vibrating layers 1 , 3 , 25 are each provided at one corner with a recess 69 , in which the lines 7 A, 9 A and 31 A are attached to the electrode films 7 , 9 and 31 at the solder joints . The solder joints are completely arranged in the recesses 69 , so that the vibrating layers 1 , 3 , 25 , 27 are flush at the aforementioned corner and without a projection. Such a stacked arrangement of vibrating layers is particularly robust and resistant.

In Fig. 8, the frequency characteristic of the ultrasonic transducer arrangement shown in Fig. 3 is shown in part Darge. The normalized (transmit and / or sensitivity) amplitude A of individual groups and oscillator layers is plotted against the (transmit or receive) frequency f in a semi-logarithmic representation. With a tolerated deviation of 3 dB from the respective maximum value of the transmission or sensitivity curve of a single group or vibrating layer, a frequency band results for the entire ultrasound transducer arrangement that extends from the third resonance frequency f ₃ down to the third frequency F ₃ and above is also sufficient, and in which both the transmission and the reception of ultrasonic waves is possible without gaps by selective control of groups or individual oscillator layers with different frequencies.

In the illustrated in Fig. 9 sixth embodiment, a first vibrator layer A 1 and a second carrier layer oscillations 3 A as an array formed. These are linear ultrasound transducer arrays, each with six line-shaped transducer elements or array lines, the array lines being arranged crossed to one another. For reasons of clarity, only six array rows are shown in each case. In practice, e.g. B. 16 array lines before each.

The first array oscillator layer 1 A is the first group G1 at a first frequency F ₁ of z. B. approximately 2 MHz and the second array oscillator layer 3 A as a second group G2 at egg ner different second frequency F ₂ of z. B. operated about 1.5 MHz. To this end, the thicknesses of the array transducer are layers 1 A, 3 A different from each other. Instead of or in addition to the second group G2, the first array oscillator layer 1 A can also be operated together with the second array oscillator layer 3 A as a third group G3. The statements made below regarding the second group G2 also apply to the third group G3.

The first array oscillator layer 1 A and the second array oscillator layer 3 A are acoustically coupled to the test object 14 via a lead wedge. The lead wedge is formed by a first part wedge 12-1 and a second part wedge 12-2 . The two partial wedges 12-1 and 12-2 are arranged to cover the first array vibrating layer 1 A, which has a first electrode film 5 on its underside.

The formation of the leading wedge as two partial wedges 12-1 , 12-2 serves to carry out a transmit-receive mode, wherein transducer elements of an array oscillating layer as a transmitter with the first partial wedge 12-1 and other transducer elements of the same array oscillating layer as a receiver are used of the second partial wedge 12-2 are controlled (see FIGS . 10 and 11).

The two wedges 12-1 , 12-2 are acoustically decoupled via an acoustic separating layer 110 .

On its upper side, the first array vibrating layer 1 A has six longitudinal electrodes 7-1 , 7-2 , oriented in the direction of the separating layer 110 . , , 7-6 on. Through these longitudinal electrodes 7-1 . 7-2,. , , 7-6 , the regions of the piezoelectric material arranged between them and the first electrode film 5 can be activated as line-like transducer elements (array lines).

Associated electrical connecting cables are for the sake of Clarity not drawn.

Over the longitudinal electrodes 7-1 , 7-2 ,. , , 7-6 , the second Ar ray oscillator layer 3 A is acoustically coupled, which in turn has transverse electrodes 9-1 , 9-2 , on the upper side. , , 9-6 , which is perpendicular to the longitudinal electrodes 7-1 , 7-2 ,. , , 7-6 are arranged. Through the transverse electrodes 9-1 , 9-2 ,. , , 9-6 line-like converter elements (array lines) can also be activated.

Between adjacent longitudinal electrodes 7-1 , 7-2 ,. , , 7-6 and be adjacent cross electrodes 9-1 , 9-2 ,. , , 9-6 are each sawn or milled through which the respective activatable line-like transducer elements are acoustically partially separated from an adjacent transducer element.

The radiation direction of the first array oscillator layer 1 A can be pivoted in a first plane E ₁ and the radiation direction of the second array oscillation layer 3 A in a second plane E ₂ perpendicular to it. In the case of the ultrasonic transducer arrangement shown in FIG. 9, this means that a so-called "horizontal swivel" can be carried out with the first array oscillator layer 1 A, in which the squint angle γ, γ ₁ , γ ₂ (see FIGS. 10 to 12) of the emitted ultrasonic wave is changeable. A so-called "vertical swivel" can be carried out with the second array oscillator layer 3 A, the sound angle α (see FIG. 2) of the emitted ultrasound wave being variable with respect to the incident perpendicular.

Fig. 10 shows the first group G1 of the ultrasonic transducer arrangement of FIG. 9 in the transmit-receive operation at a sen-side squint angle γ ₁ of + 10 ° and a reception-side squint angle γ ₂ of -10 °. The ultrasonic wall leranordnung of FIG. 8 in a plan view, and the second group G2 forming second array transducer layer 3 A for reasons of clarity not Darge provides.

FIG. 11 shows the first group G1 of the ultrasonic transducer arrangement of FIG. 9 in a transceiver operation with a transmission-side squint angle γ ₁ of approximately 30 °. The side squint angle γ ₂ is z. B. approx. 25 °. The Schielwin angle γ ₁ , γ ₂ can be varied from -30 ° to + 30 °.

In the in Figs. 10 and 11 shown transmit Emp fangs operating three juxtaposed are respectively operated array lines of the first array transducer layer 1 A as a transmitter, namely from the left longitudinal electrodes 7-4. , , 7-6 activatable array lines. The remaining three array lines, which are from the right longitudinal electrodes 7-1 ,. , , 7-3 that can be activated are operated as receivers. For the sake of simplicity, only three array rows are shown.

When in Fig. 12, the illustrated operating a total of six array rows of the first array transducer layer 1 A, that is, the group G1, in pulse-echo mode Betrie ben. The squint angle γ is varied from -30 ° to + 30 °.

In Figs. 10 to 12 of the angle of incidence is α (see Fig. 2) approximately 70 ° and there will be a longitudinal wave insonified. The sound angle α depends on the wedge angle β (see FIG. 2).

FIG. 13 shows the group G2 of the ultrasound transducer arrangement of FIG. 9, which is formed by the second array oscillator layer 3 A. The second group G2 performs a "vertical swivel" in pulse-echo mode. The sound angle α (see FIG. 2) is varied from 0 ° to 70 °. A longitudinal or transverse wave is irradiated and received. The ultrasonic transducer arrangement can also be operated with wave conversion (LLT technology).

Claims (23)

1. Ultrasonic transducer arrangement with at least two oscillator layers ( 1 , 3 , 25 , 27 , 29 ; 1 A, 3 A) arranged one behind the other as seen in a radiation direction ( 11 ), which, individually or in combination, form a group (G1, G2, G3, G4 ) are controllable, at least two groups with different frequencies (F ₁ , F ₂ , F ₃ , F ₄ ) can be operated and at least one group can be controlled as a transmitter, characterized in that at least one group can be operated as a receiver . 2. Ultrasonic transducer arrangement according to claim 1, characterized in that the as Sender controllable group of the operable as a receiver Group is different. 3. Ultrasonic transducer arrangement according to claim 1 or 2, characterized by at least three oscillator layers ( 1 , 3 , 25 , 27 , 29 ; 1 A, 3 A) which can be controlled such that at least four groups (G1, G2, G3, G4 ) with different frequencies (F ₁ , F ₂ , F ₃ , F ₄ ) can be formed. 4. Ultrasonic transducer arrangement according to one of claims 1 to 3, characterized in that the groups (G1, G2, G3, G4) can be controlled with the same polarity. 5. Ultrasonic transducer arrangement according to one of claims 1 to 4, characterized in that a first of the vibrating layers ( 1 ) has a thickness (d ₂ ) of a second vibrating layer ( 3 ) different thickness (d ₁ ). 6. Ultrasonic transducer arrangement according to one of claims 1 to 5, characterized in that at least one of the oscillator layers ( 1 , 3 , 25 , 27 , 29 ) is constructed as a composite oscillator. 7. Ultrasonic transducer arrangement according to one of claims 1 to 6, characterized in that one of the oscillating layers ( 1 , 25 or 3 , 27 ) forming a projection ( 51 , 53 or 55 , 57 ) in a deviating from the radiation direction ( 11 ) Direction ( 54 or 58 ) extends beyond an adjacent vibrating layer ( 3 , 27 or 25 , 29 ), and that an electrode film is applied between adjacent vibrating layers ( 1-3 , 25-27 or 3-25 , 27-29 ) ( 7 , 31 and 9 , 33 ) to the projection ( 51 , 53 and 55 , 57 ) he stretches. 8. Ultrasonic transducer arrangement according to claim 7, characterized in that the electro denfilm ( 7 , 31 or 9 , 33 ) on the projection ( 51 , 53 or 55 , 57 ) is contacted. 9. Ultrasonic transducer arrangement according to claim 7 or 8, characterized in that the protruding oscillating layer ( 1 , 25 or 3 , 27 ) on its the electrode film ( 7 , 31 or 9 , 33 ) facing away from a groove ( 61 , 63 or . 65 , 67 ) which extends along an edge ( 71 ) of the adjacent vibrating layer ( 3 , 27 and 25 , 29 ). 10. Ultrasonic transducer arrangement according to claim 9, characterized in that viewed in the radiation direction ( 11 ), the groove ( 61 , 63 or 65 , 67 ) covers the edge ( 71 ) or closes flush with the edge ( 71 ). 11. Ultrasonic transducer arrangement according to one of claims 1 to 10, characterized in that one of the vibrating layers ( 1 , 3 , 25 ) has a recess ( 69 ) on the edge, and that one between adjacent vibrating layers ( 1-3 , 3-25 , 25-27 ) attached electrode film ( 7 , 9 , 31 ) extends to the recess ( 69 ). 12. Ultrasonic transducer arrangement according to claim 11, characterized in that the electro denfilm ( 7 , 9 , 31 ) in the recess ( 69 ) is contacted. 13. Ultrasonic transducer arrangement according to one of claims 1 to 12, characterized in that at least one of the oscillating layers ( 1 A, 3 A) is designed as an array. 14. A method for ultrasonic testing, wherein seen at least two in an emission direction (11) one behind the other preferred transducer layers (1, 3, 25, 27, 29; 1 A, 3 A), individually or in combination is a group (G1, G2, G3, G4 ) are controlled forming, at least two groups with different frequencies (F ₁ , F ₂ , F ₃ , F ₄ ) being operated and at least one group being controlled as a transmitter, characterized in that a first group (G1) as a receiver at a first frequency (F ₁ ) be operated. 15. The method according to claim 14, characterized in that a second group (G2) and optionally further groups (G3, G4) are operated as receivers at a second frequency (F ₂ ) or further frequencies (F ₃ , F ₄ ) /become. 16. The method according to claim 14 or 15, characterized in that the groups (G1, G2, G3, G4) can be controlled with the same polarity. 17. The method according to any one of claims 14 to 16, characterized in that the groups (G1, G2, G3, G4) can be controlled sequentially. 18. The method according to any one of claims 15 to 17, characterized in that first the first group (G1) as a receiver at the first frequency (F ₁ ) and then the second group (G2) as a receiver at one of the first frequency (F ₁ ) different second frequency (F ₂ ) is operated. 19. The method according to any one of claims 14 to 18, characterized in that first a group (G2) as a transmitter at a transmission frequency (F ₂ ) and then after completion of the transmission activity, the first group (G1) as a receiver at one of the transmission frequency ( F ₂ ) different first frequency (F ₁ ) is operated. 20. The method according to any one of claims 14 to 19, characterized in

• 1. that two of the groups (G1, G2) each comprise an array oscillator layer ( 1 A, 3 A), and
• 2. that the radiation directions of the two groups (G1, G2) are pivoted with at least one component in different, non-parallel planes (E ₁ , E ₂ ),
• 3. the two groups (G1, G2) being operated as transmitters at different frequencies (F ₁ , F ₂ ).

21. The method according to claim 20, characterized in that the planes (E ₁ , E ₂ ) are perpendicular to each other. 22. The method according to claim 20 or 21, characterized in that one of the Groups (G1) is operated in the transmit-receive mode. 23. The method according to any one of claims 20 to 22, characterized in that one of the Groups (G2) is operated in pulse echo mode.