Ultrasonic transceiving method and ultrasonic transceiver

Abstract

To provide an ultrasonic transceiving method and an ultrasonic transceiver, capable of transmitting an ultrasonic wave without using a contact medium and receiving a further excellent reception signal.SOLUTION: An ultrasonic transceiving method includes: a first transmitting step of transmitting a first ultrasonic wave having a first frequency to a subject by a first focus type electromagnetic ultrasonic transducer having a first focus; a second transmitting step of transmitting a second ultrasonic wave having a second frequency to the subject by a second focus type electromagnetic ultrasonic transducer having a second focus so that a corresponding position corresponding to the first focus in the subject becomes the second focus; and a receiving step of performing the first and second transmitting steps so that the first ultrasonic wave of the first focus type electromagnetic ultrasonic transducer and the second ultrasonic wave of the second focus type electromagnetic ultrasonic transducer generate a non-linear third wave interaction in the ultrasonic wave at a corresponding position (S5) to receive the third ultrasonic wave generated by the non-linear third wave interaction by a third ultrasonic wave transduce (S6).SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to an ultrasonic transmission / reception method and an ultrasonic transmission / reception device that utilize nonlinear three-wave interaction in ultrasonic waves. [Background technology]

[0002] Ultrasound is used in various fields because it can detect properties (cavities (cracks), tissue changes, etc.) in a specimen non-destructively. One such method is to utilize nonlinear three-wave interaction in ultrasound, which is disclosed in, for example, Non-Patent Document 1.

[0003] The method disclosed in Non-Patent Document 1 involves placing first and second wedge-shaped ultrasonic transducers on the surface of a subject at a predetermined distance apart, and using a third ultrasonic transducer placed on the surface of the subject at a central position between the first and second ultrasonic transducers, to receive a third ultrasonic transducer generated by nonlinear three-wave interaction in the subject below the central position between the first and second ultrasonic transducers transmitted from the first and second ultrasonic transducers, respectively. [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] Anthony J. Croxford, Paul D. Wilcox, and Bruce W. Drinkwater, “The use of non-collinear mixing for nonlinear ultrasonic detection of plasticity and fatigue”, J.Acoust.Soc.Am.126(5), November 2009 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the first and second ultrasonic transducers disclosed in the above-mentioned non-patent document 1 are contact type, and are brought into contact with the specimen directly or through a contact medium. Therefore, the received signal is easily affected by the contact state between the specimen and the first and second ultrasonic transducers, respectively, and there is a problem with the reproducibility. Furthermore, there is also a problem that the contact type ultrasonic transducer is difficult to apply to a specimen with a relatively high temperature.

[0006] The present invention has been made in consideration of the above-mentioned circumstances, and an object of the present invention is to provide an ultrasonic transmission / reception method and an ultrasonic transmission / reception device that can transmit ultrasonic waves without using a contact medium and receive a better reception signal. [Means for solving the problem]

[0007] As a result of various studies, the inventors of the present invention have found that the above object can be achieved by the present invention described below. That is, an ultrasonic transmission / reception method according to one aspect of the present invention includes a first transmission step of transmitting a first ultrasonic wave of a first frequency to a test object by a first-focus electromagnetic ultrasonic transducer at a first focus, a second transmission step of transmitting a second ultrasonic wave of a second frequency different from the first frequency to the test object by a second-focus electromagnetic ultrasonic transducer at a second focus so that a corresponding position corresponding to the first focus in the test object becomes the second focus, and a receiving step of receiving a third ultrasonic wave generated by the nonlinear three-wave interaction by a third ultrasonic transducer by performing the first and second transmission steps so that the first ultrasonic wave of the first-focus electromagnetic ultrasonic transducer and the second ultrasonic wave of the second-focus electromagnetic ultrasonic transducer generate a nonlinear three-wave interaction in ultrasonic waves at the corresponding position. Another aspect of the present invention provides an ultrasonic transmission / reception device comprising: a first focused electromagnetic ultrasonic transducer at a first focus that transmits a first ultrasonic wave of a first frequency to a subject; a second focused electromagnetic ultrasonic transducer at a second focus that transmits a second ultrasonic wave of a second frequency different from the first frequency to the subject; a third ultrasonic transducer; and a transmission control unit that controls the transmission of each of the first and second focused electromagnetic ultrasonic transducers, wherein each of the first and second focused electromagnetic ultrasonic transducers is arranged so that a corresponding position corresponding to the first focus on the subject is the second focus, and the transmission control unit controls the transmission of each of the first and second focused electromagnetic ultrasonic transducers so that the first ultrasonic wave of the first focused electromagnetic ultrasonic transducer and the second ultrasonic wave of the second focused electromagnetic ultrasonic transducer generate a nonlinear three-wave interaction in ultrasonic waves at the corresponding position, and the third ultrasonic transducer is arranged to receive the third ultrasonic wave generated by the nonlinear three-wave interaction.

[0008] Although an electromagnetic ultrasonic transducer can transmit and receive ultrasonic waves without contacting a subject, it is generally not suitable for nonlinear three-wave interaction because the transmission and reception efficiency (transmission efficiency) between the subject and the transducer is not large. The ultrasonic transmission and reception method and ultrasonic transmission and reception device described above use a focused type electromagnetic ultrasonic transducer, and can transmit ultrasonic waves by concentrating them at the focal position, which enables nonlinear three-wave interaction, and can transmit the first and second ultrasonic waves without using a contact medium and receive a better reception signal for the third ultrasonic wave.

[0009] In another aspect, the above-mentioned ultrasonic transmission / reception method further includes a first transmission / reception step of transmitting the first ultrasonic wave to the subject using the first focused electromagnetic ultrasonic transducer and receiving it using the third ultrasonic transducer, a second transmission / reception step of transmitting the second ultrasonic wave to the subject using the second focused electromagnetic ultrasonic transducer and receiving it using the third ultrasonic transducer, and an extraction step of extracting the waveform of a third ultrasonic wave generated by the nonlinear three-wave interaction contained in the third received waveform based on a first frequency spectrum of the sum of the first received waveform received in the first transmission / reception step and the second received waveform received in the second transmission / reception step, and a second frequency spectrum of the third received waveform received in the receiving step. In another aspect, in the above-mentioned ultrasonic transmission / reception device, the transmission control unit further controls the transmission of the first focused electromagnetic ultrasonic transducer to transmit the first ultrasonic wave to the subject, controls the transmission of the second focused electromagnetic ultrasonic transducer to transmit the second ultrasonic wave to the subject, and further includes an extraction unit that extracts the waveform of the third ultrasonic wave generated by the nonlinear three-wave interaction contained in the third received waveform based on a first frequency spectrum of the sum of a first received waveform received by the third ultrasonic transducer when the first focused electromagnetic ultrasonic transducer transmits the first ultrasonic wave to the subject and a second received waveform received by the third ultrasonic transducer when the second focused electromagnetic ultrasonic transducer transmits the second ultrasonic wave to the subject, and a second frequency spectrum of a third received waveform of the third ultrasonic wave generated by the nonlinear three-wave interaction received by the third ultrasonic transducer.

[0010] The third ultrasonic transducer actually receives not only the third ultrasonic wave generated by the nonlinear three-wave interaction, but also ultrasonic waves caused by each of the first and second ultrasonic waves, and the third received waveform received by the third ultrasonic transducer includes ultrasonic waves other than the third ultrasonic wave. The ultrasonic transmission and reception method and ultrasonic transmission and reception device use the first frequency spectrum of the sum of the first and second received waveforms for the second frequency spectrum of the third received waveform, so that the waveform of the third ultrasonic wave generated by the nonlinear three-wave interaction can be extracted with high accuracy.

[0011] In another aspect, in the ultrasonic transmission / reception method and the ultrasonic transmission / reception device described above, the third ultrasonic transducer is of a pin type or a non-contact type.

[0012] In the ultrasonic transmission and reception method and the ultrasonic transmission and reception device, a pin type or a non-contact type is used for the third ultrasonic transducer, so that a contact medium is not required for reception of the third ultrasonic transducer. When a non-contact type is used, the ultrasonic transmission and reception method and the ultrasonic transmission and reception device can be applied to a subject having a relatively high temperature. Effect of the Invention

[0013] The ultrasonic transmission / reception method and ultrasonic transmission / reception device according to the present invention can transmit ultrasonic waves without using a contact medium and can receive a better reception signal. [Brief description of the drawings]

[0014] [Figure 1] 1 is a block diagram showing a configuration of an ultrasonic transmitting / receiving device according to an embodiment. [Diagram 2] 3 is a schematic diagram for explaining a focused electromagnetic ultrasonic transducer in the ultrasonic transmitting / receiving device. FIG. [Diagram 3] FIG. 2 is a schematic diagram for explaining a meandering coil in the focused electromagnetic ultrasonic transducer. [Figure 4]4 is a schematic diagram for explaining the position of a third ultrasonic transducer in the ultrasonic transmitting / receiving device. FIG. [Diagram 5] 4 is a flowchart showing an operation of the ultrasonic transmitting and receiving device. [Figure 6] FIG. 2 is a schematic diagram for explaining, as an example, the positions of a subject and first to third ultrasonic transducers in one embodiment. [Figure 7] FIG. 4 is a diagram showing first and second received waveforms and their sum in the embodiment. [Figure 8] FIG. 11 is a diagram showing a third received waveform in the embodiment. [Figure 9] FIG. 4 is a diagram showing a first frequency spectrum of the sum of the first and second received waveforms and a second frequency spectrum of the third received waveform in the embodiment. [Figure 10] FIG. 4 is a diagram showing a difference spectrum which is a difference between a first and a second frequency spectrum in the embodiment. [Figure 11] FIG. 4 is a diagram showing a ratio spectrum, which is a ratio between a first and a second frequency spectrum, in the embodiment. [Figure 12] FIG. 4 is a diagram showing a normalized spectrum obtained by normalizing a difference between a first and second frequency spectrum by the first frequency spectrum in the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, one or more embodiments of the present invention will be described with reference to the drawings. However, the scope of the invention is not limited to the disclosed embodiments. In addition, configurations with the same reference numerals in each drawing indicate that they are the same configurations, and their description will be omitted as appropriate. In this specification, when referring to a general term, a reference numeral without a subscript is used, and when referring to an individual configuration, a reference numeral with a subscript is used.

[0016] The ultrasonic transmission and reception method in the embodiment includes a first transmission step of transmitting a first ultrasonic wave of a first frequency to a test object by a first-focused electromagnetic ultrasonic transducer at a first focus, a second transmission step of transmitting a second ultrasonic wave of a second frequency different from the first frequency to the test object by a second-focused electromagnetic ultrasonic transducer at a second focus so that a corresponding position corresponding to the first focus in the test object becomes the second focus, and a receiving step of receiving a third ultrasonic wave generated by the nonlinear three-wave interaction by a third ultrasonic transducer by performing the first and second transmission steps so that the first ultrasonic wave of the first-focused electromagnetic ultrasonic transducer and the second ultrasonic wave of the second-focused electromagnetic ultrasonic transducer generate a nonlinear three-wave interaction in ultrasonic waves at the corresponding position. Hereinafter, such an ultrasonic transmission and reception method and the device will be described in more detail using an ultrasonic transmission and reception device that implements the ultrasonic transmission and reception method.

[0017] FIG. 1 is a block diagram showing the configuration of an ultrasonic transmission / reception device in an embodiment. FIG. 2 is a schematic diagram for explaining a focused electromagnetic ultrasonic transducer in the ultrasonic transmission / reception device. FIG. 2A is a perspective view of the focused electromagnetic ultrasonic transducer with a permanent magnet 11 (21) shown by a broken line, and FIG. 2B is a cross-sectional view of the focused electromagnetic ultrasonic transducer including an object Ob. FIG. 3 is a schematic diagram for explaining a meandering coil in the focused electromagnetic ultrasonic transducer. FIG. 3A is a top view of the meandering coil 12 (22), and FIG. 3B is a cross-sectional view of the meandering coil 12 (22). FIG. 4 is a schematic diagram for explaining the arrangement position of a third ultrasonic transducer in the ultrasonic transmission / reception device. FIG. 4A shows the arrangement position in a first mode, FIG. 4B shows the arrangement position in a second mode, and FIG. 4C shows the arrangement position in a third mode.

[0018] The ultrasonic transmission / reception device 1000 in the embodiment includes, for example, a first focused electromagnetic ultrasonic transducer 1, a second focused electromagnetic ultrasonic transducer 1, an ultrasonic transducer 3, a control processing unit 4, and a memory unit 8, as shown in Figures 1 to 4, and further includes an input unit 5, an output unit 6, and an interface unit (IF unit) 7 in the example shown in Figure 1.

[0019] The first focused electromagnetic ultrasonic transducer 1 is an electromagnetic ultrasonic transducer that is connected to a control processing unit 4 and transmits ultrasonic waves (first ultrasonic waves) of a predetermined frequency (first frequency) to an object Ob so as to be focused at a focal point (first focal point) FC1 under the control of the control processing unit 4. The object Ob may be any member capable of generating electromagnetic ultrasonic waves, for example, a member made of a metal (including an alloy). The member may be a substantially flat plate-like member, or may be a cylindrical member having a curved surface because a magnet that follows the curved surface (curvature) may be used. In one example, the object Ob is a steel plate or steel pipe to be inspected that has been manufactured through a plurality of processes, or a steel plate or steel pipe that is relatively hot during manufacturing.

[0020] The second focused electromagnetic ultrasonic transducer 2 is an electromagnetic ultrasonic transducer that is connected to a control processing unit 4 and transmits ultrasonic waves (second ultrasonic waves) of a second frequency different from the first frequency to the subject Ob in such a manner that the ultrasonic waves are focused at a focal point (second focal point) FC2 in accordance with the control of the control processing unit 4.

[0021] The first and second focused electromagnetic ultrasonic transducers 1, 2 are each positioned so that a corresponding position PT corresponding to a first focus FC1 on the subject Ob is the second focus FC2, and a first ultrasonic wave α1 of a first frequency f1 is transmitted to the subject Ob from the first focused electromagnetic ultrasonic transducer 1 at the first focus FC1, and a second ultrasonic wave α2 of a second frequency f2 is transmitted to the subject Ob from the second focused electromagnetic ultrasonic transducer 2 at the second focus FC2, so that a corresponding position PT corresponding to the first focus FC1 on the subject Ob is the second focus FC2. When the first focal point FC1 and the second focal point FC2 coincide with each other, the placement position (first placement position) of the first focused electromagnetic ultrasonic transducer 1 as seen from the first focal point FC1 (= second focal point FC2) and the placement position (first placement position) of the second focused electromagnetic ultrasonic transducer 2 as seen from the first focal point FC1 (= second focal point FC2) may or may not be placed at symmetrical positions with a plane passing through the first focal point FC1 (= second focal point FC2) and having a line segment connecting the first and second placement positions as its normal as the target plane.

[0022] In this embodiment, the first and second focused electromagnetic ultrasonic transducers 1 and 2 have different first and second frequencies f1 and f2, so the arc intervals designed as described below are different between the first focused electromagnetic ultrasonic transducer 1 and the second focused electromagnetic ultrasonic transducer 2, but since they have similar configurations, they will be described below together using Figures 2 and 3. In the following description of the focused electromagnetic ultrasonic transducers, in Figures 2 and 3, the symbol of the second focused electromagnetic ultrasonic transducer 2 is shown in parentheses following the symbol of the first focused electromagnetic ultrasonic transducer 1.

[0023] An electromagnetic acoustic transducer (abbreviated as "EMAT") is a probe that generates a sound source directly in a test object by electromagnetic action and transmits and receives ultrasonic waves. No contact medium is required for transmitting and receiving ultrasonic waves, and non-contact measurement is possible. There are Lorentz type and magnetostrictive type EMATs, both of which are composed of a magnet and a coil. A Lorentz type EMAT has a magnet that forms a static magnetic field in a metal and a coil that generates eddy currents in the metal by high-frequency current, and generates ultrasonic waves by generating a Lorentz force in the metal through the interaction between the static magnetic field and the eddy current, and receives ultrasonic waves propagating through the metal by the reverse action. On the other hand, a magnetostrictive EMAT is applicable only to magnetic materials, and transmits and receives ultrasonic waves by utilizing the magnetostrictive effect of a magnetic material. A magnetostrictive EMAT is preferably used when the test object Ob is a magnetic material, and a Lorentz type EMAT is preferably used when the test object Ob is a non-magnetic material. There are various types of EMATs, but in this embodiment, they are point-focused electromagnetic acoustic transducers (abbreviated as "PF-EMAT" as appropriate) that focus ultrasonic waves at one point. For example, PF-EMAT1 (2) shown in FIG. 2 and FIG. 3 is used as the first and second focused electromagnetic acoustic transducers 1 and 2, respectively.

[0024] The PF-EMAT1(2) shown in Fig. 2 and Fig. 3 includes a substantially rectangular parallelepiped permanent magnet 11(21) that forms a static magnetic field, and a planar meandering coil 12(22) that forms a variable magnetic field and has a substantially sector-shaped outer shape. The meandering coil 12(22) is a coil that includes a plurality of conductor wires of arc portions extending in the circumferential direction, arranged in a zigzag pattern in the radial direction. The conductor wires of these arc portions are arranged in parallel to each other at a predetermined interval (arc interval) so as to be concentric. The meandering coil 12(22) is arranged with its coil surface spaced apart from the surface of the subject Ob, and the permanent magnet 11(21) is arranged on the meandering coil 12(22).

[0025] In such a PF-EMAT1(2), the permanent magnet 11(21) forms a static magnetic field in the depth direction of the object Ob. When a burst-shaped high-frequency current is applied to the meandering coil 12(22), an eddy current flows near the surface of the object Ob due to electromagnetic induction, and the interaction between this eddy current and the static magnetic field generated by the permanent magnet 11(21) generates a Lorentz force. In the conductor wires of the adjacent arc portions of the meandering coil 12(22), currents flow in opposite directions, as shown by × in a circle or · in a circle in FIG. 2B. Therefore, near the surface of the object Ob under each of the conductor wires of the adjacent arc portions, shear deformation occurs in opposite directions due to the Lorentz force, as shown by → in FIG. 2B, and each sound source of the SV wave is formed, and an ultrasonic wave is generated in the object Ob. With this mechanism, the PF-EMAT1(2) can transmit ultrasonic waves to the object Ob in a non-contact manner without using a contact medium. In the case of reception, the PF-EMATs 1 and 2 can receive ultrasonic waves from the object Ob by the reverse mechanism, but in this embodiment, ultrasonic waves are received from the object Ob by the third ultrasonic transducer 3, as described later.

[0026] In the PF-EMAT1(2), the arc interval between the conductor wires of the adjacent arc portions is designed (set) so that the ultrasonic waves generated from the sound sources overlap in the same phase at the focal point FC1(FC2), thereby allowing a large displacement of the ultrasonic waves to be generated at the focal point FC1(FC2). More specifically, since the adjacent sound sources generate ultrasonic waves of opposite phases, the sound sources are designed so that the propagation distance from each sound source to the focal point FC1(FC2) increases monotonically from the center side to the outside in the radial direction by half wavelengths. That is, as shown in FIG. 3A and FIG. 3B, an rZ orthogonal coordinate system is set with the center (center of the concentric circle) of each conductor wire of the arc portion of the meandering coil 12(22) as the coordinate origin (0, 0), an r axis along the radial direction within the coil surface, and a Z axis along the depth direction from the coil surface, and the propagation distance from the sound source corresponding to the i-th arc portion to the focal point FC1(FC2) is set as R i If the speed of sound is C and the frequency of the high-frequency current (the driving frequency of the meandering coil 12 (22)) is f, then R i+1 -R i= C / (2f) (= half wavelength) so that the arc interval (= r i+1 -r i ) is designed. Here, the distance from the center (0, 0) of each conductor line to the conductor line of the i-th arc portion is r i Let the depth of the focus FC1 (FC2) be Z F In this case, R i 2 =r i 2 +Z F 2 From R i , R i+1 is r i , r i+1 It can be expressed as:

[0027] The third ultrasonic transducer 3 is connected to the control processing unit 4 and receives ultrasonic waves from the object Ob under the control of the control processing unit 4. From the viewpoint of not using a contact medium, the third ultrasonic transducer 3 is preferably a pin type or a non-contact type. The pin type ultrasonic transducer is, for example, an ultrasonic probe using a piezoelectric element, an aluminum needle of a truncated cone is attached to the piezoelectric element with an adhesive, and the tip of the truncated cone is directly contacted (dry contacted) with the object Ob to receive ultrasonic waves from the object Ob. The non-contact type ultrasonic transducer is, for example, a so-called ultrasonic sensor that receives ultrasonic waves from the object Ob through the air, a laser ultrasonic transducer that receives ultrasonic waves from the object Ob by detecting minute vibrations caused by ultrasonic waves on the surface of the object Ob with a laser interferometer, an electromagnetic ultrasonic transducer, etc. It should be noted that, although a contact medium is used, an ultrasonic probe using a piezoelectric element with excellent reception sensitivity may be used as the third ultrasonic transducer 3.

[0028] The third ultrasonic transducer 3 is disposed to receive a third ultrasonic wave generated by a nonlinear three-wave interaction between the first ultrasonic wave of the first PF-ENAT 1 and the second ultrasonic wave of the second PF-EMAT 2 .

[0029] The nonlinear three-wave interaction is a phenomenon in which, when two first and second ultrasonic waves α1 and α2 cross each other in a material, a third ultrasonic wave β having a frequency f1±f2 equal to the sum and difference of the first and second frequencies f1 and f2 of the two first and second ultrasonic waves α1 and α2 is generated in the crossing region due to the nonlinearity of the material caused by the anharmonicity of the interatomic potential, dislocations, and microcracks in the crossing region. In this embodiment, the first and second PF-EMAT1 and 2 are arranged so that the corresponding position PT corresponding to the first focal point FC1 in the object Ob is the second focal point FC2, and the nonlinear three-wave interaction occurs in the crossing region, so that the crossing region where the nonlinear three-wave interaction occurs is the corresponding position PT (=(first focal point FC1 in the object)=(second focal point FC2 in the object)). To generate a nonlinear three-wave interaction, first and second ultrasonic waves α1, α2 of relatively large amplitude are required. In this embodiment, however, point-focus type first and second PF-EMAT1, 2 are used to generate the first and second ultrasonic waves α1, α2, so that a nonlinear three-wave interaction can occur at the corresponding position PT.

[0030] This nonlinear three-wave interaction is excellent in terms of spatial selectivity, that is, limited to the intersection region where the two first and second ultrasonic waves α1 and α2 intersect, and in terms of frequency selectivity, that is, the frequency f1±f2 in the third ultrasonic wave β is easily separated from the harmonics in the two first and second ultrasonic waves α1 and α2, and the nonlinearity of the material can be selectively evaluated. In terms of the frequency selectivity, for example, when the first frequency f1=2[MHz] of the first ultrasonic wave α1 and the second frequency f2=2.75[MHz] of the second ultrasonic wave α2, the frequency f3 (=f1±f2) in the third ultrasonic wave β is 4.75[MHz] and 0.75[MHz]. On the other hand, the harmonics of the first ultrasonic wave α1 are 4[MHz], 6[MHz], 8[MHz], and the harmonics of the second ultrasonic wave α2 are 5.5[MHz], 8.25[MHz], 11[MHz], and the like. For this reason, the third ultrasonic wave β is easily separated from the first ultrasonic wave α1 and its harmonics, and the second ultrasonic wave α2 and its harmonics.

[0031] The third ultrasonic transducer 3 is arranged at a position (directly below the corresponding position PT) that intersects with a normal to the surface of the object Ob passing through the corresponding position PT on the back surface of the object Ob on which the first and second PF-EMATs 1 and 2 are arranged in a non-contact manner so as to receive the third ultrasonic wave β generated by the nonlinear three-wave interaction between the first ultrasonic wave α1 and the second ultrasonic wave α2 when the object Ob is a plate-shaped member, as shown in Fig. 4A. Alternatively, for example, the third ultrasonic transducer 3 is arranged at a position (directly above the corresponding position PT) that intersects with a normal to the surface of the object Ob passing through the corresponding position PT on the back surface of the object Ob on which the first and second PF-EMATs 1 and 2 are arranged in a non-contact manner so as to receive the third ultrasonic wave β generated by the nonlinear three-wave interaction between the first ultrasonic wave α1 and the second ultrasonic wave α2 when the object Ob is a plate-shaped member, as shown in Fig. 4B. Alternatively, for example, as shown in FIG. 4C, an echo of the third ultrasonic wave β reflected from the rear surface may be received by a third ultrasonic transducer 3 disposed at a position directly above the corresponding position PT.

[0032] The intensity (amplitude) and propagation direction of the third ultrasonic wave β generated by the nonlinear three-wave interaction depend on the nonlinearity in the crossing region, and by evaluating this third ultrasonic wave β, it becomes possible to evaluate the nonlinearity of the object Ob caused by anharmonicity, dislocations, microcracks, etc. The larger the amplitude (intensity) of the third ultrasonic wave β, the greater the nonlinearity.

[0033] 1, the input unit 5 is connected to the control processing unit 4 and is a device that inputs various commands such as a command to start transmitting and receiving ultrasound, and various data required for operating the ultrasound transmitting and receiving device 1000, such as the name of the subject Ob and the implementation date, to the ultrasound transmitting and receiving device 1000, and is, for example, a keyboard, a mouse, and a plurality of input switches to which predetermined functions are assigned. The output unit 6 is connected to the control processing unit 4 and is a device that outputs commands and data input from the input unit 5 and waveforms related to the third ultrasound β under the control of the control processing unit 4, and is, for example, a display device such as a CRT display, an LCD (liquid crystal display device), or an organic EL display, or a printing device such as a printer.

[0034] The input unit 5 and the output unit 6 may be configured as a touch panel. In the case of configuring this touch panel, the input unit 5 is a position input device that detects and inputs an operation position, for example, a resistive film type or a capacitive type, and the output unit 6 is a display device. In this touch panel, a position input device is provided on the display surface of the display device, and one or more input content candidates that can be input to the display device are displayed. When a user touches a display position that displays the input content that the user wants to input, the position is detected by the position input device, and the display content displayed at the detected position is input to the ultrasonic transmission / reception device 1000 as the user's operation input content. In such a touch panel, the user can easily intuitively understand the input operation, and therefore an ultrasonic transmission / reception device 1000 that is easy for the user to handle is provided.

[0035] The IF unit 7 is connected to the control processing unit 4 and is a circuit that inputs and outputs data to and from, for example, an external device under the control of the control processing unit 4, and is, for example, an interface circuit of RS-232C, which is a serial communication method, an interface circuit using the Bluetooth (registered trademark) standard, an interface circuit using the USB standard, etc. The IF unit 7 may also be, for example, a communication interface circuit that transmits and receives communication signals to and from an external device, such as a data communication card or a communication interface circuit conforming to the IEEE802.11 standard, etc.

[0036] The storage unit 8 is connected to the control processing unit 4 and is a circuit that stores various predetermined programs and various predetermined data under the control of the control processing unit 4. The various predetermined programs include, for example, a control processing program, and the control processing program includes, for example, a control program, a transmission control program, and an extraction program. The control program is a program that controls each of the units 1 to 3 and 5 to 8 of the ultrasonic transmitting / receiving device 1000 according to the function of each unit. The transmission control program is a program that controls the transmission of each of the first and second focused electromagnetic ultrasonic transducers. The extraction program is a program that extracts the waveform of the third ultrasonic wave β generated by the nonlinear three-wave interaction, which is included in the third received waveform received by the third ultrasonic transducer 3. The various predetermined data includes data necessary for executing each of these programs, such as the name of the subject Ob and the date of implementation.

[0037] Such a storage unit 8 includes, for example, a ROM (Read Only Memory) which is a nonvolatile storage element, an EEPROM (Electrically Erasable Programmable Read Only Memory) which is a rewritable nonvolatile storage element, etc. The storage unit 8 also includes a RAM (Random Access Memory) which serves as a so-called working memory of the control processing unit 4 for storing data generated during execution of the predetermined program, etc. The storage unit 8 may also be configured to include a hard disk device with a relatively large storage capacity.

[0038] The control processing unit 4 is a circuit for controlling each of the units 1-3, 5-8 of the ultrasonic transmitting / receiving device 1000 according to the function of each unit, and transmitting and receiving ultrasonic waves to and from the subject Ob. The control processing unit 4 is configured, for example, with a CPU (Central Processing Unit) and its peripheral circuits. In the control processing unit 4, a control unit 41, a transmission control unit 42, and an extraction unit 43 are functionally configured by executing the control processing program.

[0039] The control unit 41 controls each of the units 1 to 3 and 5 to 8 of the ultrasonic transmitting / receiving device 1000 in accordance with the function of each unit, and is responsible for controlling the ultrasonic transmitting / receiving device 1000 as a whole.

[0040] The transmission control unit 42 controls the transmission of each of the first and second focused electromagnetic ultrasonic transducers 1 and 2. More specifically, the transmission control unit 42 controls the transmission of each of the first and second focused electromagnetic ultrasonic transducers 1 and 2 so that the first ultrasonic wave α1 of the first focused electromagnetic ultrasonic transducer 1 and the second ultrasonic wave α2 of the second focused electromagnetic ultrasonic transducer 2 generate a nonlinear three-wave interaction in ultrasonic waves at the corresponding position PT. As a result, the first and second ultrasonic waves α1 and α2 are focused and cross each other at the corresponding position PT, a nonlinear three-wave interaction occurs, and a third ultrasonic wave β is generated.

[0041] Then, in order to obtain a reception waveform (first reception waveform) at the third ultrasonic transducer 3 when only the first ultrasonic wave α1 is transmitted to the object Ob by the first focused electromagnetic ultrasonic transducer 1, the transmission control unit 42 controls the transmission of the first focused electromagnetic ultrasonic transducer 1 so as to transmit the first ultrasonic wave α1 to the object Ob. More specifically, the transmission control unit 42 controls the first focused electromagnetic ultrasonic transducer 1 to pass a burst-shaped high-frequency current from the high-frequency power source to the first focused electromagnetic ultrasonic transducer 1. Similarly, in order to obtain a reception waveform (second reception waveform) at the third ultrasonic transducer 3 when only the second ultrasonic wave α2 is transmitted to the object Ob by the second focused electromagnetic ultrasonic transducer 2, the transmission control unit 42 controls the second focused electromagnetic ultrasonic transducer 2 to pass the second ultrasonic wave α2 to the object Ob. More specifically, the transmission control unit 42 controls the second focused electromagnetic ultrasonic transducer 2 to pass a burst-shaped high-frequency current from the high-frequency power source to the second focused electromagnetic ultrasonic transducer 2.

[0042] The extraction unit 43 extracts the waveform of the third ultrasonic wave generated by the nonlinear three-wave interaction contained in the third received waveform based on a first frequency spectrum of the sum of the first received waveform received by the third ultrasonic transducer 3 when the first focused electromagnetic ultrasonic transducer 1 transmits the first ultrasonic wave α1 to the object Ob and the second received waveform received by the third ultrasonic transducer 3 when the second focused electromagnetic ultrasonic transducer 2 transmits the second ultrasonic wave α2 to the object Ob, and a second frequency spectrum of the received waveform (third received waveform) of the third ultrasonic wave β generated by the nonlinear three-wave interaction received by the third ultrasonic transducer 3. More specifically, for example, the extraction unit 43 extracts the waveform of the third ultrasonic wave generated by the nonlinear three-wave interaction contained in the third received waveform by calculating the difference between the first and second frequency spectra. For example, the difference between the first and second frequency spectra is calculated by subtracting the first frequency spectrum from the second frequency spectrum for each frequency ((second frequency spectrum)-(first frequency spectrum)). Alternatively, for example, the extraction unit 43 extracts the waveform of the third ultrasonic wave generated by the nonlinear three-wave interaction included in the third received waveform by obtaining a ratio between the first and second frequency spectra. For example, the ratio of the first frequency spectrum to the second frequency spectrum is obtained for each frequency ((second frequency spectrum) / (first frequency spectrum)). Alternatively, for example, the ratio of the first and second frequency spectra is obtained by subtracting the first frequency spectrum from the second frequency spectrum for each frequency and dividing the result by the first frequency spectrum (((second frequency spectrum)-(first frequency spectrum)) / (first frequency spectrum)).

[0043] The control processing unit 4, input unit 5, output unit 6, IF unit 7 and storage unit 8 in such an ultrasonic transmitting / receiving device 1000 can be configured by, for example, a desktop or notebook computer.

[0044] Next, the operation of this embodiment will be described. FIG. 5 is a flowchart showing the operation of the ultrasonic transmitting / receiving device. FIG. 6 is a schematic diagram for explaining the positions of the subject and the first to third ultrasonic transducers in one embodiment as an example. FIG. 7 is a diagram showing the first and second received waveforms and their sum in the one embodiment. FIG. 7A shows the first received waveform, FIG. 7B shows the second received waveform, and FIG. 7C shows the sum of the first and second received waveforms. In FIGS. 7A to 7C, the horizontal axis indicates time (elapsed time) [μs], and the vertical axis indicates amplitude (intensity) [V]. FIG. 8 is a diagram showing the third received waveform in the one embodiment. The horizontal axis of FIG. 8 is time (elapsed time) [μs], and the vertical axis is amplitude (intensity) [V]. FIG. 9 is a diagram showing the first frequency spectrum of the sum of the first and second received waveforms and the second frequency spectrum of the third received waveform in the one embodiment. The horizontal axis of FIG. 9 is frequency [MHz], and the vertical axis is amplitude (intensity). FIG. 10 is a diagram showing a difference spectrum which is a difference between the first and second frequency spectra in the embodiment. The horizontal axis of FIG. 10 is frequency [MHz], and the vertical axis is the difference between the first and second frequency spectra (amplitude difference (intensity difference)). FIG. 11 is a diagram showing a ratio spectrum which is a ratio between the first and second frequency spectra in the embodiment. The horizontal axis of FIG. 11 is frequency [MHz], and the vertical axis is the ratio between the first and second frequency spectra (amplitude ratio (intensity ratio)). FIG. 12 is a diagram showing a normalized spectrum in which the difference between the first and second frequency spectra is normalized by the first frequency spectrum in the embodiment. The horizontal axis of FIG. 11 is frequency [MHz], and the vertical axis is the ratio between the first and second frequency spectra (amplitude ratio (intensity ratio)) obtained by dividing the difference between the first and second frequency spectra by the first frequency spectrum.

[0045] When the ultrasonic transmitting / receiving device 1000 having such a configuration is powered on, it initializes each required unit and starts its operation. In the control processing unit 4, a control unit 41, a transmission control unit 42, and an extraction unit 43 are functionally configured by executing a control processing program.

[0046] When the ultrasonic transmission / reception device 1000 is set on the subject Ob and, for example, an operator (user) issues a command to start, in FIG. 5, first, the ultrasonic transmission / reception device 1000 transmits a first ultrasonic wave α1 of a first frequency f1 to the subject Ob using the first PF-EMAT1 via the transmission control unit 42 of the control processing unit 4 (S1), and then receives the ultrasonic wave resulting from the transmitted first ultrasonic wave α1 from the subject Ob using the third ultrasonic transducer 3 via the control unit 41 of the control processing unit 4 (S2, first transmission / reception process).

[0047] In one example, as shown in FIG. 6, a plate-shaped aluminum member having a thickness of 30 [mm] is used as the object Ob, and the first and second PF-EMATs 1 and 2 are set on the surface of the object Ob so that the position directly below the center position of the first and second PF-EMATs 1 and 2 on the back surface of the object Ob becomes the corresponding position PT. The voltage of the burst-like high-frequency current is 2000 [V] (peak-to-peak), and the number of burst cycles is 10. The incidence angle of the SV wave in the first and second ultrasonic waves α1 and α2 excited by the first and second PF-EMATs 1 and 2 is about 14 to 36 [°], and a pin type is used as the third ultrasonic transducer 3. Then, when the first PF-EMAT1 transmits the first ultrasonic wave α1 to the object Ob at the first frequency f1=2 [MHz], for example, the first reception waveform shown in FIG. 7A is obtained.

[0048] Next, the ultrasonic transmission / reception device 1000 transmits a second ultrasonic wave α2 of a second frequency f2 to the subject Ob using the second PF-EMAT2 via the transmission control unit 42 (S3), and receives the ultrasonic wave resulting from the transmitted second ultrasonic wave α2 from the subject Ob using the third ultrasonic transducer 3 via the control unit 41 (S4, second transmission / reception process).

[0049] In the above-described example shown in FIG. 6, when the second PF-EMAT2 transmits a second ultrasonic wave α2 to the object Ob at the second frequency f1=2.75 [MHz], for example, a second received waveform shown in FIG. 7B is obtained.

[0050] Next, the ultrasonic transmission / reception device 1000 transmits first and second ultrasonic waves α1, α2 of first and second frequencies f1, f2 from the first and second PF-EMAT1, 2, respectively, to the subject Ob so that the first ultrasonic wave α1 of the first PF-EMAT1 and the second ultrasonic wave α2 of the second PF-EMAT2 generate a nonlinear three-wave interaction in ultrasonic waves at the corresponding position PT by the transmission control unit 42 (S5, performing the first and second transmission steps), and receives the third ultrasonic wave generated by the nonlinear three-wave interaction by the third ultrasonic transducer 3 (S6, receiving step).

[0051] In the above-mentioned example shown in FIG. 6, when the first PF-EMAT1 transmits a first ultrasonic wave α1 to the object Ob at a first frequency f1=2 [MHz] and the second PF-EMAT2 transmits a second ultrasonic wave α2 to the object Ob at a second frequency f1=2.75 [MHz], for example, a third received waveform shown in FIG. 8 is obtained.

[0052] Next, the ultrasonic transmission / reception device 1000 extracts, by the extraction unit 43 of the control processing unit 4, the waveform of a third ultrasonic wave generated by the nonlinear three-wave interaction contained in the third received waveform based on a first frequency spectrum of the sum of the first received waveform received in process S2 and the second received waveform received in process S4, and the second frequency spectrum of the third received waveform received in process S6 (S7, extraction step).

[0053] In the above example shown in FIG. 6, the sum of the amplitudes is calculated for each frequency, and the waveform (sum operation waveform) shown in FIG. 7C is obtained as the sum of the first reception waveform shown in FIG. 7A and the second reception waveform shown in FIG. 7B. When the time range from about 12 [μs] to about 19 [μs] is set as the FFT gate and the sum operation waveform shown in FIG. 7C in this time range is fast Fourier transformed, the first frequency spectrum SP1 shown in FIG. 9 is obtained. When the third reception waveform shown in FIG. 8 in the time range is fast Fourier transformed, as shown in FIG. 9, in the first frequency spectrum SP1, no peak is recognized at the sum of the first and second frequencies 4.75 [MHz] and the difference 0.75 [MHz], but in the second frequency spectrum SP2, a peak can be recognized at the sum of the first and second frequencies 4.75 [MHz] and the difference 0.75 [MHz]. There are easily recognizable differences between the first and second frequency spectra SP1 and SP2. These peaks are caused by nonlinear three-wave interaction in ultrasound. Then, for example, by subtracting the first frequency spectrum SP1 from the second frequency spectrum SP2 for each frequency, the difference between the first and second frequency spectra SP1, SP2 shown in Fig. 10 is obtained. Alternatively, for example, by dividing the second frequency spectrum SP2 by the first frequency spectrum SP1 for each frequency, the ratio between the first and second frequency spectra SP1, SP2 shown in Fig. 11 is obtained. Alternatively, for example, by dividing the result of subtracting the first frequency spectrum SP1 from the second frequency spectrum SP2 for each frequency by the first frequency spectrum SP1, the ratio between the first and second frequency spectra SP1, SP2 shown in Fig. 12 is obtained. As can be seen from Figures 10 to 12, by performing an extraction step of processing the third received waveform received when a nonlinear three-wave interaction is caused by the first and second ultrasonic waves α1, α2 based on the first and second received waveforms received when the first and second ultrasonic waves α1, α2 are transmitted individually to the subject Ob, other signal components such as the first and second ultrasonic waves α1, α2 and their harmonics and noise are reduced or removed, and the waveform of the third ultrasonic wave caused by the nonlinear three-wave interaction can be clearly extracted.By measuring the amplitude (intensity) of a peak in the waveform of the third ultrasonic wave generated by the nonlinear three-wave interaction, the nonlinearity in the object Ob can be evaluated.

[0054] Here, in the above description, the difference between the first and second frequency spectra SP1 and SP2 and the ratio between the first and second frequency spectra SP1 and SP2 are obtained, but the sum of the received waveform when only the first frequency is excited and the received waveform when only the second frequency is excited may be divided from the received waveform when the first and second frequencies are excited simultaneously, and the waveform resulting from the subtraction may be subjected to fast Fourier transform. Even with this processing result, the peaks shown in Figures 10 to 12 above can be obtained.

[0055] Then, the ultrasonic transmitting / receiving device 1000 causes the control unit 41 of the control processing unit 4 to output the extraction results obtained in process S7 to the output unit 6 (S8), and ends this process. For example, the extraction results shown in Fig. 10 to Fig. 12 are output to the output unit 6. Note that the control unit 41 may output the extraction results to an external device via the IF unit 7 as necessary.

[0056] Although an electromagnetic ultrasonic transducer can transmit and receive ultrasonic waves without contact with a subject, it is generally not suitable for nonlinear three-wave interaction because the transmission and reception efficiency (transmission efficiency) between the subject and the subject is not large. The ultrasonic transmission and reception method in the embodiment and the ultrasonic transmission and reception device 1000 that implements the same use focused electromagnetic ultrasonic transducers 1 and 2, and can transmit ultrasonic waves focused at the focal position, making nonlinear three-wave interaction possible, and can transmit the first and second ultrasonic waves α1 and α2 without using a contact medium and receive a better reception signal for the third ultrasonic wave β.

[0057] The third ultrasonic transducer 3 actually receives not only the third ultrasonic wave β generated by the nonlinear three-wave interaction, but also ultrasonic waves caused by the first and second ultrasonic waves α1 and α2, and the third received waveform received by the third ultrasonic transducer 3 includes ultrasonic waves other than the third ultrasonic wave β. The ultrasonic transmission and reception method and ultrasonic transmission and reception device 1000 use the first frequency spectrum SP1, which is the sum of the first and second received waveforms, for the second frequency spectrum SP2 of the third received waveform, and therefore can accurately extract the waveform of the third ultrasonic wave β generated by the nonlinear three-wave interaction.

[0058] The ultrasonic transmission and reception method and the ultrasonic transmission and reception device 1000 use a pin type or a non-contact type for the third ultrasonic transducer 3, and therefore do not require a contact medium for reception by the third ultrasonic transducer 3. When a non-contact type is used, the ultrasonic transmission and reception method and the ultrasonic transmission and reception device 1000 can be applied to a subject having a relatively high temperature.

[0059] In order to express the present invention, the present invention has been described adequately and sufficiently through the embodiments with reference to the drawings in the above description, but it should be recognized that those skilled in the art can easily change and / or improve the above-mentioned embodiments. Therefore, unless the changes or improvements made by those skilled in the art are at a level that departs from the scope of the claims described in the claims, the changes or improvements are interpreted as being included in the scope of the claims.

[0060] In the above embodiment, the transmission control unit 42 may further control the frequencies f1 and f2 of the first and second ultrasonic waves α1 and α2. This allows the first and second focal points, i.e., the ultrasonic transmitting / receiving device 1000, to change (control) the corresponding position PT on the Z axis shown in Fig. 3B. For example, the lower the frequencies f1 and f2 of the first and second ultrasonic waves α1 and α2, the closer the corresponding point position PT is to the front surface of the object Ob, and the higher the frequencies f1 and f2 of the first and second ultrasonic waves α1 and α2, the closer the corresponding point position PT is to the rear surface of the object Ob. In other words, if the frequencies f1, f2 of the first and second ultrasonic waves α1, α2 at which the corresponding point position PT is near the surface of the object Ob are f10, f20, respectively, then as the frequencies f1, f2 of the first and second ultrasonic waves α1, α2 are increased from the frequencies f10, f20 of the first and second ultrasonic waves α1, α2, the corresponding point position PT moves away from the surface of the object Ob and closer to the back surface of the object Ob.

[0061] In addition, in the above-mentioned embodiment, a point-focused electromagnetic ultrasonic transducer that is relatively easy to generate a large signal intensity at the focus is used as the focused electromagnetic ultrasonic transducer 1, but a line-focused electromagnetic ultrasonic transducer may be used as the focused electromagnetic ultrasonic transducer 1 as long as a signal intensity that generates a nonlinear three-wave interaction can be obtained. [Explanation of symbols]

[0062] 1000 Ultrasonic transmitter / receiver 1. First focused electromagnetic ultrasonic transducer (First PF-EMAT) 2. Second focused electromagnetic ultrasonic transducer (second PF-EMAT) 3. Third ultrasonic transducer 4. Control Processing Section 8 Memory section 41 Control section 42 Transmission control section 43 Extraction part

Claims

1. a first transmission step of transmitting a first ultrasonic wave of a first frequency to a subject by a first-focused electromagnetic ultrasonic transducer at a first focus; a second transmission step of transmitting a second ultrasonic wave having a second frequency different from the first frequency to the subject by a second-focus type electromagnetic ultrasonic transducer at a second focus so that a corresponding position on the subject corresponding to the first focus becomes the second focus; and a receiving step of receiving a third ultrasonic wave generated by the nonlinear three-wave interaction at a third ultrasonic transducer by performing the first and second transmitting steps so that the first ultrasonic wave of the first focused electromagnetic ultrasonic transducer and the second ultrasonic wave of the second focused electromagnetic ultrasonic transducer generate a nonlinear three-wave interaction in ultrasonic waves at the corresponding positions. Ultrasonic transmission and reception method.

2. a first transmitting / receiving step of transmitting the first ultrasonic wave to the subject by the first focused electromagnetic ultrasonic transducer and receiving the first ultrasonic wave by the third ultrasonic transducer; a second transmission / reception step of transmitting the second ultrasonic wave to the subject by the second focused electromagnetic ultrasonic transducer and receiving the second ultrasonic wave by the third ultrasonic transducer; and an extraction step of extracting a waveform of a third ultrasonic wave generated by the nonlinear three-wave interaction, which is included in the third received waveform, based on a first frequency spectrum of a sum of the first received waveform received in the first transmission / reception step and the second received waveform received in the second transmission / reception step, and a second frequency spectrum of the third received waveform received in the receiving step. The ultrasonic transmission / reception method according to claim 1 .

3. The third ultrasonic transducer is a pin type or a non-contact type. The ultrasonic transmission / reception method according to claim 1 .

4. a first-focus electromagnetic ultrasonic transducer at a first focus for transmitting a first ultrasonic wave of a first frequency to a subject; a second focus type electromagnetic ultrasonic transducer at a second focus for transmitting a second ultrasonic wave having a second frequency different from the first frequency to the subject; A third ultrasonic transducer; a transmission control unit that controls transmission from each of the first and second focused electromagnetic ultrasonic transducers, The first and second focal electromagnetic ultrasonic transducers are each disposed such that a corresponding position on the subject that corresponds to the first focal point is the second focal point, The transmission control unit controls the transmission of each of the first and second focused electromagnetic ultrasonic transducers so that the first ultrasonic wave of the first focused electromagnetic ultrasonic transducer and the second ultrasonic wave of the second focused electromagnetic ultrasonic transducer generate nonlinear three-wave interaction in ultrasonic waves at the corresponding positions, The third ultrasonic transducer is disposed to receive a third ultrasonic wave generated by the nonlinear three-wave interaction. Ultrasonic transmitting and receiving device.

5. The transmission control unit further controls the transmission of the first focused electromagnetic ultrasonic transducer to transmit the first ultrasonic wave to the subject, and controls the transmission of the second focused electromagnetic ultrasonic transducer to transmit the second ultrasonic wave to the subject, The apparatus further includes an extracting unit that extracts a waveform of a third ultrasonic wave generated by the nonlinear three-wave interaction contained in the third received waveform based on a first frequency spectrum of a sum of a first received waveform received by the third ultrasonic transducer when the first focused electromagnetic ultrasonic transducer transmits the first ultrasonic wave to the subject and a second received waveform received by the third ultrasonic transducer when the second focused electromagnetic ultrasonic transducer transmits the second ultrasonic wave to the subject, and a second frequency spectrum of a third received waveform of the third ultrasonic wave generated by the nonlinear three-wave interaction received by the third ultrasonic transducer.

5. The ultrasonic transmitting / receiving device according to claim 4.

6. The third ultrasonic transducer is a pin type or a non-contact type.

5. The ultrasonic transmitting / receiving device according to claim 4.

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