Ultrasonic transmission and reception method and apparatus

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] This invention relates to an ultrasonic transmission and reception method and an ultrasonic transmission and reception apparatus that utilize nonlinear three-wave interaction in ultrasound. [Background technology]

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

[0003] The method disclosed in Non-Patent Document 1 involves placing wedge-shaped first and second ultrasonic transducers on the surface of a subject at a predetermined interval, and receiving a third ultrasonic transducer, which is placed on the surface of the subject at a central position between the first and second ultrasonic transducers, and which generates a third ultrasonic wave produced by the nonlinear three-wave interaction of the first and second ultrasonic waves transmitted from each of the first and second ultrasonic transducers in the subject below the central position. [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 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] Incidentally, the first and second ultrasonic transducers disclosed in Non-Patent Document 1 are of the contact type and are in contact with the subject directly or via a coupling medium. Therefore, the received signal is easily affected by the contact state between the subject and the first and second ultrasonic transducers, respectively, and there are issues with reproducibility. Furthermore, contact-type ultrasonic transducers also have the problem of being difficult to apply to subjects that are relatively hot.

[0006] The present invention was made in view of the above circumstances, and its purpose is to provide an ultrasonic transmitting and receiving method and an ultrasonic transmitting and receiving device that can transmit ultrasonic waves without using a coupling medium and receive a better received signal. [Means for solving the problem]

[0007] As a result of various studies, the inventors have found that the above objective can be achieved by the present invention as described below. That is, an ultrasonic transmission and reception method according to one aspect of the present invention comprises: a first transmission step of transmitting a first ultrasonic wave of a first frequency to a subject using a first-focus type electromagnetic ultrasonic transducer with a first focal point; a second transmission step of transmitting a second ultrasonic wave of a second frequency different from the first frequency to the subject using a second-focus type electromagnetic ultrasonic transducer with a second focal point such that the corresponding position on the subject corresponding to the first focal point becomes the second focal point; 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 such 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 nonlinear three-wave interaction in the ultrasonic wave at the corresponding position. Another aspect of the present invention provides an ultrasonic transmitting and receiving device comprising: a first-focus type electromagnetic ultrasonic transducer with a first focus that transmits a first ultrasonic wave of a first frequency to a subject; a second-focus type electromagnetic ultrasonic transducer with 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 the first and second-focus type electromagnetic ultrasonic transducers, respectively, wherein the first and second-focus type electromagnetic ultrasonic transducers are arranged such that the corresponding position on the subject corresponding to the first focus becomes the second focus; the transmission control unit controls the transmission of the first and second-focus type electromagnetic ultrasonic transducers such 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 produce a nonlinear three-wave interaction in the ultrasonic wave at the corresponding position; and the third ultrasonic transducer is arranged to receive the third ultrasonic wave produced by the nonlinear three-wave interaction.

[0008] Electromagnetic ultrasonic transducers can transmit and receive ultrasound non-contact with a subject, but their transmission efficiency is not high, making them generally unsuitable for nonlinear three-wave interaction. The above-described ultrasonic transmission and reception method and ultrasonic transmission and reception device use a focused electromagnetic ultrasonic transducer, allowing ultrasound to be focused at the focal point. This enables nonlinear three-wave interaction, allowing the transmission of the first and second ultrasounds without the use of a coupling medium, and enabling the reception of a better received signal for the third ultrasound.

[0009] In another embodiment, the ultrasonic transmission and reception method described above further comprises: a first transmission and reception step of transmitting the first ultrasonic wave to the subject using the first focused electromagnetic ultrasonic transducer and receiving it with the third ultrasonic transducer; a second transmission and reception step of transmitting the second ultrasonic wave to the subject using the second focused electromagnetic ultrasonic transducer and receiving it with the third ultrasonic transducer; and an extraction step of extracting the waveform of the third ultrasonic wave generated by the nonlinear three-wave interaction, which is included in the third received waveform, based on a first frequency spectrum which is the sum of the first received waveform received in the first transmission and reception step and the second received waveform received in the second transmission and reception step, and the second frequency spectrum of the third received waveform received in the reception step. In another embodiment, in the ultrasonic transmitting and receiving device described above, the transmitting 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, which is included 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 the third received waveform received by the third ultrasonic transducer from the third ultrasonic interaction.

[0010] The third ultrasonic transducer actually receives not only the third ultrasonic wave generated by the nonlinear three-wave interaction, but also ultrasonic waves originating from the first and second ultrasonic waves, respectively, 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, which is the sum of the first received waveform and the second received waveform, 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 embodiment, in the ultrasonic transmitting and receiving method and ultrasonic transmitting and receiving apparatus described above, the third ultrasonic transducer is pin-type or non-contact type.

[0012] Such ultrasonic transmission and reception methods and ultrasonic transmission and reception devices do not require a coupling medium for reception by the third ultrasonic transducer, as they use either a pin-type or non-contact type third ultrasonic transducer. When using a non-contact type, the ultrasonic transmission and reception methods and ultrasonic transmission and reception devices can be applied to subjects with relatively high temperatures. [Effects of the Invention]

[0013] The ultrasonic transmission and reception method and ultrasonic transmission and reception apparatus according to the present invention can transmit ultrasonic waves without using a coupling medium and can receive a better received signal. [Brief explanation of the drawing]

[0014] [Figure 1] This is a block diagram showing the configuration of an ultrasonic transceiver in an embodiment. [Figure 2] This is a schematic diagram illustrating the focused electromagnetic ultrasonic transducer in the aforementioned ultrasonic transmitting and receiving device. [Figure 3] This is a schematic diagram illustrating the meandering coil in the aforementioned focused electromagnetic ultrasonic transducer. [Figure 4]It is a schematic diagram for explaining the arrangement position of the third ultrasonic transducer in the ultrasonic transmitting and receiving device. [Figure 5] It is a flowchart showing the operation of the ultrasonic transmitting and receiving device. [Figure 6] As an example, it is a schematic diagram for explaining the arrangement positions of the subject and the first to third ultrasonic transducers in one embodiment. [Figure 7] In the above-mentioned one embodiment, it is a diagram showing the first and second received waveforms and their sum. [Figure 8] In the above-mentioned one embodiment, it is a diagram showing the third received waveform. [Figure 9] In the above-mentioned one embodiment, it 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. [Figure 10] In the above-mentioned one embodiment, it is a diagram showing the difference spectrum which is the difference between the first and second frequency spectra. [Figure 11] In the above-mentioned one embodiment, it is a diagram showing the ratio spectrum which is the ratio of the first and second frequency spectra. [Figure 12] In the above-mentioned one embodiment, it is a diagram showing the normalized spectrum in which the difference between the first and second frequency spectra is normalized by the first frequency spectrum.

Embodiments for Carrying Out the Invention

[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 each figure, components denoted by the same reference numerals are the same components, and the description thereof will be omitted as appropriate. In this specification, when referring to components in general, reference numerals without subscripts are used, and when referring to individual components, reference numerals with subscripts are used.

[0016] The ultrasonic transmission and reception method in this embodiment includes: a first transmission step of transmitting a first ultrasonic wave of a first frequency to a subject using a first-focus type electromagnetic ultrasonic transducer with a first focal point; a second transmission step of transmitting a second ultrasonic wave of a second frequency different from the first frequency to the subject using a second-focus type electromagnetic ultrasonic transducer with a second focal point, such that the corresponding position on the subject corresponding to the first focal point becomes the second focal point; and a receiving step of receiving a third ultrasonic wave generated by the nonlinear three-wave interaction by performing the first and second transmission steps such that the first ultrasonic wave from the first-focus type electromagnetic ultrasonic transducer and the second ultrasonic wave from the second-focus type electromagnetic ultrasonic transducer generate a nonlinear three-wave interaction in the ultrasonic wave at the corresponding position, with the third ultrasonic wave being received by the third ultrasonic transducer. The ultrasonic transmission and reception method and apparatus described herein will be explained in more detail below using an ultrasonic transmission and reception apparatus that implements the ultrasonic transmission and reception method.

[0017] Figure 1 is a block diagram showing the configuration of an ultrasonic transceiver in an embodiment. Figure 2 is a schematic diagram illustrating a focused electromagnetic ultrasonic transducer in the ultrasonic transceiver. Figure 2A is a perspective view of the focused electromagnetic ultrasonic transducer with the permanent magnet 11(21) shown by a dashed line, and Figure 2B is a cross-sectional view of the focused electromagnetic ultrasonic transducer including the subject Ob. Figure 3 is a schematic diagram illustrating a meandering coil in the focused electromagnetic ultrasonic transducer. Figure 3A is a top view of the meandering coil 12(22), and Figure 3B is a cross-sectional view of the meandering coil 12(22). Figure 4 is a schematic diagram illustrating the arrangement position of the third ultrasonic transducer in the ultrasonic transceiver. Figure 4A shows the arrangement position in the first embodiment, Figure 4B shows the arrangement position in the second embodiment, and Figure 4C shows the arrangement position in the third embodiment.

[0018] The ultrasonic transmitting and receiving device 1000 in the embodiment includes, for example, a first-focus type electromagnetic ultrasonic transducer 1, a second-focus type electromagnetic ultrasonic transducer 1, an ultrasonic transducer 3, a control processing unit 4, and a storage unit 8, as shown in Figures 1 to 4. In the example shown in Figure 1, it further includes an input unit 5, an output unit 6, and an interface unit (IF unit) 7.

[0019] The first-focus type electromagnetic ultrasonic transducer 1 is connected to the control processing unit 4 and, in accordance with the control processing unit 4, transmits ultrasonic waves (first ultrasonic waves) of a predetermined frequency (first frequency) to the object Ob so as to be focused on the focal point (first focal point) FC1. The object Ob can be any material capable of generating electromagnetic ultrasonic waves, for example, a material made of metal (including alloys). The material may be a substantially flat plate, or it may be a curved cylindrical shape as long as a magnet that follows the curved surface (curvature) is used. In one example, the object Ob may be a steel plate or steel pipe that is subject to inspection after being manufactured through multiple processes, or a steel plate or steel pipe that is relatively hot during manufacturing.

[0020] The second-focus type electromagnetic ultrasonic transducer 2 is connected to the control processing unit 4 and, in accordance with the control of the control processing unit 4, transmits ultrasonic waves of a second frequency (second ultrasonic waves) different from the first frequency to the subject Ob, focusing them on the focal point (second focal point) FC2.

[0021] The first and second focus type electromagnetic ultrasonic transducers 1 and 2 are positioned such that the corresponding position PT on the subject Ob, which corresponds to the first focus FC1, becomes the second focus FC2. The first focus type electromagnetic ultrasonic transducer 1 at the first focus FC1 transmits a first ultrasound α1 with a first frequency f1 to the subject Ob, and the second focus type electromagnetic ultrasonic transducer 2 at the second focus FC2 transmits a second ultrasound α2 with a second frequency f2 to the subject Ob, such that the corresponding position PT on the subject Ob, which corresponds to the first focus FC1, becomes the second focus FC2. When the first focus FC1 and the second focus FC2 coincide, the placement position of the first focus type electromagnetic ultrasonic transducer 1 as seen from the first focus FC1 (= second focus FC2) (first placement position) and the placement position of the second focus type electromagnetic ultrasonic transducer 2 as seen from the first focus FC1 (= second focus FC2) (first placement position) may or may not be placed at positions symmetrical with respect to a plane whose normal is the line segment passing through the first focus FC1 (= second focus FC2) and connecting the first and second placement positions.

[0022] In this embodiment, the first and second focal-type electromagnetic ultrasonic transducers 1 and 2 have different first and second frequencies f1 and f2, and therefore the arc spacing designed for them differs between the first focal-type electromagnetic ultrasonic transducer 1 and the second focal-type electromagnetic ultrasonic transducer 2, as described later. However, they have similar configurations, so they will be explained below in detail using Figures 2 and 3. In the following description of the focal-type electromagnetic ultrasonic transducers, and in Figures 2 and 3, the reference numeral for the second focal-type electromagnetic ultrasonic transducer 2 is shown in parentheses following the reference numeral for the first focal-type electromagnetic ultrasonic transducer 1.

[0023] An electromagnetic acoustic transducer (EMAT) is a probe that generates a sound source directly within a sample through electromagnetic action and transmits and receives ultrasonic waves. It does not require a coupling medium for transmitting and receiving ultrasonic waves, enabling non-contact measurement. There are two types of EMATs: Lorentz type and magnetostrictive type, both of which consist of a magnet and a coil. A Lorentz type EMAT comprises a magnet that forms a static magnetic field in a metal and a coil that generates eddy currents in the metal using a high-frequency current. The interaction between the static magnetic field and the eddy currents generates a Lorentz force in the metal, thereby generating ultrasonic waves, and the reverse action receives the ultrasonic waves propagating through the metal. On the other hand, a magnetostrictive type EMAT is applicable only to magnetic materials and transmits and receives ultrasonic waves by utilizing the magnetostrictive effect of the magnetic material. A magnetostrictive type EMAT is preferably used when the sample Ob is a magnetic material, while a Lorentz type EMAT is preferably used when the sample Ob is a non-magnetic material. While there are various types of EMATs, in this embodiment, it is a point-focusing electromagnetic acoustic transducer (PF-EMAT) that focuses ultrasound waves to a single point. For example, the PF-EMAT1(2) shown in Figures 2 and 3 are used as the first and second focus-type electromagnetic acoustic transducers 1 and 2, respectively.

[0024] The PF-EMAT1(2) shown in Figures 2 and 3 comprises a substantially rectangular parallelepiped permanent magnet 11(21) that forms a static magnetic field, and a planar serpentine coil 12(22) with a substantially fan-shaped outer form that forms a fluctuating magnetic field. The serpentine coil 12(22) is a coil having multiple conductor wires in the radial direction, which are bent in a zigzag pattern into circumferential arc portions. Each of these conductor wires in the arc portions is arranged parallel to each other at a predetermined interval (arc spacing) so as to be concentric. The serpentine coil 12(22) is positioned with its coil surface separated from the surface of the specimen Ob, and the permanent magnet 11(21) is placed on the serpentine coil 12(22).

[0025] In this PF-EMAT1(2), a static magnetic field is formed in the depth direction of the subject Ob by the permanent magnet 11(21). When a burst-like high-frequency current is passed through the meandering coil 12(22), eddy currents flow near the surface of the subject Ob due to electromagnetic induction, and a Lorentz force is generated by the interaction of these eddy currents with the static magnetic field from the permanent magnet 11(21). In the zigzag meandering coil 12(22), currents flow in opposite directions in each conductor wire of adjacent arc portions, as shown by the circles with ×s and circles with ·s in Figure 2B. Therefore, near the surface of the subject Ob under each conductor wire of adjacent arc portions, shear deformation occurs in opposite directions due to the Lorentz force, as shown by the arrows in Figure 2B, forming SV wave sound sources and generating ultrasound in the subject Ob. Through this mechanism, PF-EMAT1(2) can transmit ultrasound to the subject Ob non-contact without using a coupling medium. In the case of reception, the PF-EMAT1 and PF-EMAT2 can receive ultrasound from the subject Ob through the reverse mechanism. In this embodiment, as described later, the ultrasound is received from the subject Ob by the third ultrasound transducer 3.

[0026] In PF-EMAT1(2), a large displacement of ultrasound can be generated at focal point FC1(FC2) by designing (setting) the arc spacing between each conductor wire in adjacent arc portions so that the ultrasound waves generated from each sound source overlap in phase at focal point FC1(FC2). More specifically, since ultrasound waves with opposite phases are generated from adjacent sound sources, the propagation distance from each sound source to focal point FC1(FC2) is designed to increase monotonically by half a wavelength from the center outward in the radial direction. That is, as shown in Figures 3A and 3B, the center of each conductor wire in the arc portion of the meandering coil 12(22) (center of the concentric circle) is set as the coordinate origin (0,0), and an rZ orthogonal coordinate system is set with the r axis along the radial direction within the coil plane and the Z axis along the depth direction from the coil plane, and the propagation distance from the sound source corresponding to the i-th arc portion to focal point FC1(FC2) is R i Let C be the speed of sound, and f be the frequency of the high-frequency current (the driving frequency of the meandering coil 12 (22)). Then R i+1 -R iEach arc interval (=r i+1 -r i ) is designed to satisfy =C / (2f) (=half wavelength). 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 , and when the depth of the focal point FC1 (FC2) is Z F , R i 2 =r i 2 +Z F 2 From R i , R i+1 can be represented by r i , r i+1 .

[0027] The third ultrasonic transducer 3 is connected to the control processing unit 4 and receives ultrasonic waves from the subject Ob according to the control of the control processing unit 4. From the viewpoint of not using a coupling 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, in which a conical frustum-shaped aluminum needle is attached to the piezoelectric element with an adhesive, and the tip of the conical frustum is directly contacted (dry contact) with the subject Ob to receive ultrasonic waves from the subject Ob. The non-contact type ultrasonic transducer is, for example, a so-called ultrasonic sensor that receives ultrasonic waves from the subject Ob through air, a laser ultrasonic transducer that receives ultrasonic waves from the subject Ob by detecting minute vibrations caused by ultrasonic waves on the surface of the subject Ob with a laser interferometer, an electromagnetic ultrasonic transducer, or the like. Although a coupling medium will be 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 arranged to receive the third ultrasonic wave generated by the non-linear three-wave interaction between the first ultrasonic wave of the first PF-ENAT1 and the second ultrasonic wave of the second PF-EMAT2.

[0029] Nonlinear three-wave interaction is a phenomenon in which, when two first and second ultrasonic waves α1 and α2 intersect in a material, a third ultrasonic wave β with 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 intersection region due to the nonlinearity of the material caused by anharmonicity of interatomic potentials, dislocations, and microcracks in the intersection region. In this embodiment, the first and second PF-EMAT1 and 2 are arranged such that the corresponding position PT corresponding to the first focal point FC1 in the subject Ob becomes the second focal point FC2, and since nonlinear three-wave interaction occurs in the intersection region, the intersection region in which nonlinear three-wave interaction occurs is the corresponding position PT (=(first focal point FC1 in the subject)=(second focal point FC2 in the subject)). The generation of nonlinear three-wave interaction requires first and second ultrasonic waves α1 and α2 with relatively large amplitudes. In this embodiment, point-focus type first and second PF-EMAT1 and 2 are used to generate the first and second ultrasonic waves α1 and α2, so that nonlinear three-wave interaction can be generated at the corresponding position PT.

[0030] This nonlinear three-wave interaction is superior in terms of spatial selectivity, being limited to the intersection region where the two first and second ultrasonic waves α1 and α2 intersect, and in terms of frequency selectivity, as the frequencies f1±f2 of the third ultrasonic wave β are easily separated from the harmonics of the two first and second ultrasonic waves α1 and α2, allowing for selective evaluation of the nonlinearity of the material. Regarding the aforementioned frequency selectivity, for example, if the first frequency f1 of the first ultrasonic wave α1 is 2 [MHz] and the second frequency f2 of the second ultrasonic wave α2 is 2.75 [MHz], then the frequencies f3 (=f1±f2) of the third ultrasonic wave β will be 4.75 [MHz] and 0.75 [MHz]. On the other hand, the harmonics of the first ultrasonic wave α1 will be 4 [MHz], 6 [MHz], 8 [MHz], ... and the harmonics of the second ultrasonic wave α2 will be 5.5 [MHz], 8.25 [MHz], 11 [MHz], ... Therefore, the third ultrasonic wave β is easily separated from the first ultrasonic wave α1 and its harmonics, as well as the second ultrasonic wave α2 and its harmonics.

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

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

[0033] Returning to Figure 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 instruct the start of ultrasound transmission and reception, and various data necessary for operating the ultrasound transmission and reception device 1000, such as the name of the subject Ob and the date of the procedure. Examples of input units include a keyboard, mouse, and multiple input switches assigned to predetermined functions. 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, as well as waveforms related to the third ultrasound β, in accordance with the control of the control processing unit 4. Examples of output units include display devices such as CRT displays, LCDs (liquid crystal displays), and organic EL displays, and printing devices such as printers.

[0034] The input unit 5 and output unit 6 may be configured as touch panels. In this configuration, the input unit 5 is a position input device that detects and inputs the operating position, such as a resistive or capacitive touchscreen, 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 candidate input contents that can be input to the display device are displayed. When the user touches the display position that displays the input content they want to input, the position input device detects that position, and the display content displayed at the detected position is input to the ultrasonic transceiver 1000 as the user's operation input. With such a touch panel, the user can easily understand the input operation intuitively, thus providing an ultrasonic transceiver 1000 that is easy for the user to use.

[0035] The IF unit 7 is connected to the control processing unit 4 and, in accordance with the control of the control processing unit 4, is a circuit that inputs and outputs data to and from external devices, for example. Examples include an RS-232C serial communication interface circuit, an interface circuit using the Bluetooth® standard, and an interface circuit using the USB standard. Alternatively, the IF unit 7 may be a communication interface circuit that sends and receives communication signals to and from external devices, such as a data communication card or a communication interface circuit conforming to the IEEE 802.11 standard.

[0036] The memory unit 8 is connected to the control processing unit 4 and is a circuit that stores various predetermined programs and various predetermined data in accordance with 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 parts 1 to 3 and 5 to 8 of the ultrasonic transceiver 1000 according to the function of each part. The transmission control program is a program that controls the transmission of the first and second focus-type electromagnetic ultrasonic transducers, respectively. 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 include, for example, data such as the name of the subject Ob and the date of implementation, which are necessary for executing each of these programs.

[0037] Such a storage unit 8 may include, for example, a non-volatile memory element such as ROM (Read Only Memory) or a rewritable non-volatile memory element such as EEPROM (Electrically Erasable Programmable Read Only Memory). Furthermore, the storage unit 8 may include a RAM (Random Access Memory) or the like, which serves as the working memory of the control processing unit 4 for storing data generated during the execution of the predetermined program. The storage unit 8 may also be configured to include a hard disk drive with a relatively large storage capacity.

[0038] The control processing unit 4 is a circuit that controls each of the parts 1-3 and 5-8 of the ultrasonic transceiver 1000 according to the function of each part, and transmits and receives ultrasound to the subject Ob. The control processing unit 4 is configured, for example, with a CPU (Central Processing Unit) and its peripheral circuits. When the control processing program is executed, the control unit 41, the transmission control unit 42, and the extraction unit 43 are functionally configured in the control processing unit 4.

[0039] The control unit 41 controls each of the parts 1-3 and 5-8 of the ultrasonic transceiver 1000 according to the function of each part, and is in charge of controlling the entire ultrasonic transceiver 1000.

[0040] The transmission control unit 42 controls the transmission of the first and second focused electromagnetic ultrasonic transducers 1 and 2, respectively. More specifically, the transmission control unit 42 controls the transmission of the first and second focused electromagnetic ultrasonic transducers 1 and 2, respectively, 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 produce a nonlinear three-wave interaction in the ultrasonic waves at the corresponding position PT. As a result, the first and second ultrasonic waves α1 and α2 converge and intersect at the corresponding position PT, causing a nonlinear three-wave interaction and generating a third ultrasonic wave β.

[0041] Then, in order to obtain the received waveform (first received waveform) at the third ultrasonic transducer 3 when the first focused electromagnetic ultrasonic transducer 1 transmits only the first ultrasonic α1 to the subject Ob, the transmission control unit 42 controls the transmission of the first focused electromagnetic ultrasonic transducer 1 to transmit the first ultrasonic α1 to the subject Ob. More specifically, the transmission control unit 42 controls the first focused electromagnetic ultrasonic transducer 1 to flow a burst-type high-frequency current from the high-frequency power supply. Similarly, in order to obtain the received waveform (second received waveform) at the third ultrasonic transducer 3 when the second focused electromagnetic ultrasonic transducer 2 transmits only the second ultrasonic α2 to the subject Ob, the transmission control unit 42 controls the transmission of the second focused electromagnetic ultrasonic transducer 2 to transmit the second ultrasonic α2 to the subject Ob. More specifically, the transmission control unit 42 controls the second focused electromagnetic ultrasonic transducer 2 to flow a burst-type high-frequency current from the high-frequency power supply.

[0042] The extraction unit 43 extracts the waveform of the third ultrasonic wave generated by the nonlinear three-wave interaction, which is included in the third received waveform, based on the first frequency spectrum, which is 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 subject 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 subject Ob, and the second frequency spectrum, which is the received waveform (third received waveform) received by the third ultrasonic transducer 3 from the third ultrasonic wave β generated by the nonlinear three-wave interaction. More specifically, for example, the extraction unit 43 extracts the waveform of the third ultrasonic wave generated by the nonlinear three-wave interaction, which is included 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 can be obtained 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, which is included in the third received waveform, by determining the ratio of the first and second frequency spectra. For example, the ratio of the first frequency spectrum to the second frequency spectrum is determined for each frequency ((second frequency spectrum) / (first frequency spectrum)). Alternatively, for example, the ratio of the first and second frequency spectra is determined for each frequency by dividing the result of subtracting the first frequency spectrum from the second frequency spectrum 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 transceiver 1000 can be configured by a computer, such as a desktop or notebook computer.

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

[0045] When the ultrasonic transceiver 1000 with this configuration is powered on, it performs the necessary initialization of each part and starts operating. The control processing unit 4 is functionally configured with a control unit 41, a transmission control unit 42, and an extraction unit 43 through the execution of its control processing program.

[0046] When the ultrasonic transceiver 1000 is set on the subject Ob, and for example the operator (user) instructs it to start, in Figure 5, first, the ultrasonic transceiver 1000, through the transmission control unit 42 of the control processing unit 4, transmits a first ultrasonic wave α1 of a first frequency f1 to the subject Ob using the first PF-EMAT1 (S1), and the control unit 41 of the control processing unit 4 receives the ultrasonic waves caused by this transmitted first ultrasonic wave α1 from the subject Ob using the third ultrasonic transducer 3 (S2, first transmission / reception process).

[0047] In one example, as shown in Figure 6, a 30 mm thick aluminum plate-shaped member is used as the subject Ob, and the first and second PF-EMAT1 and 2 are set on the surface of the subject Ob, such that the position directly below the center of the first and second PF-EMAT1 and 2 on the back surface of the subject Ob is the corresponding position PT. The voltage in 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-EMAT1 and 2 is approximately 14 to 36°, and a pin-type third ultrasonic transducer 3 is used. When the first PF-EMAT1 transmits the first ultrasonic wave α1 to the subject Ob at a first frequency f1 = 2 MHz, for example, the first received waveform shown in Figure 7A is obtained.

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

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

[0050] Next, the ultrasonic transceiver 1000, via the transmission control unit 42, transmits first and second ultrasonic waves α1 and α2 of the first and second PF-EMAT1 and PF-EMAT2 respectively to the subject Ob with first and second frequencies f1 and f2, so that the first ultrasonic wave α1 of the first PF-EMAT1 and the second ultrasonic wave α2 of the second PF-EMAT2 produce a nonlinear three-wave interaction in the ultrasonic waves at the corresponding position PT (S5, execution of the first and second transmission steps). The third ultrasonic wave generated by the nonlinear three-wave interaction is then received by the third ultrasonic transducer 3 (S6, reception step).

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

[0052] Next, the ultrasonic transceiver 1000, using the extraction unit 43 of the control processing unit 4, extracts the waveform of the third ultrasonic wave generated by the nonlinear three-wave interaction, which is included in the third received waveform, based on the first frequency spectrum obtained by summing 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 example shown in Figure 6, by calculating the sum of each amplitude for each frequency, the waveform shown in Figure 7C (sum calculation waveform) is obtained as the sum of the first received waveform shown in Figure 7A and the second received waveform shown in Figure 7B. When the sum calculation waveform shown in Figure 7C in the time range of approximately 12 [μs] to approximately 19 [μs] is subjected to a Fast Fourier Transform, the first frequency spectrum SP1 shown in Figure 9 is obtained, using the FFT gate for this time range. When the third received waveform shown in Figure 8 in the same time range is subjected to a Fast Fourier Transform, as shown in Figure 9, no peak is recognized in the first frequency spectrum SP1 at the sum of the first and second frequencies of 4.75 [MHz] and the difference of 0.75 [MHz], but in the second frequency spectrum SP2, a peak can be recognized at the sum of the first and second frequencies of 4.75 [MHz] and the difference of 0.75 [MHz]. There is a noticeable difference between the first and second frequency spectra SP1 and SP2. These peaks are caused by the nonlinear three-wave interaction in ultrasound. For example, subtracting the first frequency spectrum SP1 from the second frequency spectrum SP2 for each frequency yields the difference between the first and second frequency spectra SP1 and SP2 shown in Figure 10. Alternatively, for example, dividing the second frequency spectrum SP2 by the first frequency spectrum SP1 for each frequency yields the ratio of the first and second frequency spectra SP1 and SP2 shown in Figure 11. Alternatively, for example, dividing the result of subtracting the first frequency spectrum SP1 from the second frequency spectrum SP2 by the first frequency spectrum SP1 for each frequency yields the ratio of the first and second frequency spectra SP1 and SP2 shown in Figure 12. As can be seen from Figures 10 to 12, by performing an extraction process that processes the third received waveform received when a nonlinear three-wave interaction is generated between the first and second ultrasonic waves α1 and α2, using the first and second received waveforms received when the first and second ultrasonic waves α1 and α2 are individually transmitted to the subject Ob as a reference, other signal components such as the first and second ultrasonic waves α1 and α2 and their harmonics and noise can be reduced or removed, and the waveform of the third ultrasonic wave generated by the nonlinear three-wave interaction can be clearly extracted.By measuring the amplitude (intensity) of the peak in the waveform of the third ultrasonic wave generated by the aforementioned nonlinear three-wave interaction, the nonlinearity in the subject Ob can be evaluated.

[0054] In the above, the difference between the first and second frequency spectra SP1 and SP2, or the ratio of the first and second frequency spectra SP1 and SP2, was calculated. However, the received waveform when the first and second frequencies are excited simultaneously may be divided by the sum of the received waveform when only the first frequency is excited and the received waveform when only the second frequency is excited, and the resulting waveform may be subjected to a Fast Fourier Transform. Even with such processing results, peaks as shown in Figures 10 to 12 above can be obtained.

[0055] Then, the ultrasonic transceiver 1000 outputs the extraction results obtained in process S7 to the output unit 6 (S8) via the control unit 41 of the control processing unit 4, and the process ends. For example, each extraction result shown in Figures 10 to 12 is output to the output unit 6. The control unit 41 may also output the extraction results to an external device via the IF unit 7 if necessary.

[0056] Electromagnetic ultrasonic transducers can transmit and receive ultrasound non-contact with a subject, but they are generally not suitable for nonlinear three-wave interaction because their transmission efficiency with the subject is not high. The ultrasonic transmission and reception method and the ultrasonic transmission and reception device 1000 implementing it in this embodiment use focal-type electromagnetic ultrasonic transducers 1 and 2, so that ultrasound can be focused and transmitted at the focal point, enabling nonlinear three-wave interaction. This allows for the transmission of first and second ultrasounds α1 and α2 without the use of a coupling medium, and enables the reception of a better received signal for the third ultrasound 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 originating from the first and second ultrasonic waves α1 and α2, respectively, 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 received waveform and the second received waveform, for the second frequency spectrum SP2 of the third received waveform, so that the waveform of the third ultrasonic wave β generated by the nonlinear three-wave interaction can be extracted with high accuracy.

[0058] The above-described ultrasonic transmission and reception method and ultrasonic transmission and reception device 1000 use either a pin-type or non-contact type third ultrasonic transducer 3, and therefore do not require a coupling medium for reception by the third ultrasonic transducer 3. When using a non-contact type, the above-described ultrasonic transmission and reception method and ultrasonic transmission and reception device 1000 can be applied to subjects with relatively high temperatures.

[0059] To illustrate the present invention, the embodiments have been adequately and fully described above with reference to the drawings. However, those skilled in the art should recognize that it is easy to modify and / or improve upon the embodiments described above. Therefore, unless such modifications or improvements implemented by those skilled in the art fall outside the scope of the claims, such modifications or improvements shall be considered to be included within the scope of the claims.

[0060] In the above-described 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 transceiver 1000, to change (control) the corresponding position PT on the Z-axis shown in Figure 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 will be to the surface of the subject 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 will be to the back surface of the subject Ob. In other words, if the frequencies f1 and f2 of the first and second ultrasounds α1 and α2, respectively, are f10 and f20, respectively, when the corresponding point position PT is near the surface of the subject Ob, then the higher the frequencies f1 and f2 of the first and second ultrasounds α1 and α2 are compared to the frequencies f10 and f20 of the first and second ultrasounds α1 and α2, the further the corresponding point position PT moves away from the surface of the subject Ob and closer to the back surface of the subject Ob.

[0061] Furthermore, in the above-described embodiment, a point-focus type electromagnetic ultrasonic transducer, which is relatively easy to generate a large signal intensity at the focal point, was used as the focused electromagnetic ultrasonic transducer 1. However, if a signal intensity that generates a nonlinear three-wave interaction can be obtained, a line-focus type electromagnetic ultrasonic transducer may also be used as the focused electromagnetic ultrasonic transducer 1. [Explanation of Symbols]

[0062] 1000 Ultrasonic Transceiver 1. First Focus Type Electromagnetic Ultrasonic Transducer (First PF-EMAT) 2. Second Focus Type Electromagnetic Ultrasonic Transducer (2nd PF-EMAT) 3. Third ultrasonic transducer 4 Control Processing Unit 8 Memory section 41 Control Unit 42 Transmission Control Unit 43 Extraction part

Claims

1. A first transmission step involves transmitting a first ultrasonic wave of a first frequency to a subject using a first-focus type electromagnetic ultrasonic transducer at a first focus, A second transmission step in which a second focus type electromagnetic ultrasonic transducer with a second focus transmits a second ultrasonic wave of a second frequency different from the first frequency to the subject, such that the corresponding position on the subject corresponding to the first focus becomes the second focus. The first and second transmission steps are performed such that the first ultrasound of the first focused electromagnetic ultrasonic transducer and the second ultrasound of the second focused electromagnetic ultrasonic transducer generate a nonlinear three-wave interaction in the ultrasound at the corresponding position, and the third ultrasound generated by the nonlinear three-wave interaction is received by the third ultrasonic transducer. A first transmission / reception step in which the first focused electromagnetic ultrasonic transducer transmits the first ultrasonic wave to the subject and the third ultrasonic transducer receives it, A second transmission and reception step in which the second ultrasonic wave is transmitted to the subject by the second focused electromagnetic ultrasonic transducer and received by the third ultrasonic transducer, The system includes an extraction step for extracting the waveform of the third ultrasonic wave generated by the nonlinear three-wave interaction, which is included in the third received waveform, based on a first frequency spectrum obtained by summing the first received waveform received in the first transmission / reception step and the second received waveform received in the second transmission / reception step, and the second frequency spectrum of the third received waveform received in the reception step. Ultrasonic transmission and reception method.

2. The third ultrasonic transducer is either pin-type or non-contact-type. The ultrasonic transmission and reception method according to claim 1.

3. A first-focus type electromagnetic ultrasonic transducer with a first focus that transmits a first ultrasonic wave of a first frequency to a subject, A second-focus type electromagnetic ultrasonic transducer with a second focus that transmits a second ultrasonic wave of a second frequency different from the first frequency to the subject, Third ultrasonic transducer, The system comprises a transmission control unit that controls the transmission of the first and second focal-type electromagnetic ultrasonic transducers, Each of the first and second focal-type electromagnetic ultrasonic transducers is arranged such that the corresponding position in the subject corresponding to the first focal point becomes the second focal point. The transmission control unit controls the transmission of the first and second focus electromagnetic ultrasonic transducers such that the first ultrasonic wave of the first focus electromagnetic ultrasonic transducer and the second ultrasonic wave of the second focus electromagnetic ultrasonic transducer produce a nonlinear three-wave interaction in the ultrasonic waves at the corresponding position. The third ultrasonic transducer is arranged to receive the third ultrasonic wave generated by the nonlinear three-wave interaction, 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 system further includes an extraction unit that extracts the waveform of the third ultrasonic wave generated by the nonlinear three-wave interaction, which is included in the third received waveform, based on a first frequency spectrum obtained by 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 obtained by the third received waveform when the third ultrasonic transducer receives the third ultrasonic wave generated by the nonlinear three-wave interaction. Ultrasonic transmitting and receiving device.

4. The third ultrasonic transducer is either pin-type or non-contact-type. The ultrasonic transmitting and receiving device according to claim 3.

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