JP3558494B2 - Acoustic transducer for living body - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an acoustic transducer for a living body measurement device that superimposes and transmits a sound wave having an audio frequency band or less and an ultrasonic pulse from the surface of a living body to a body, and receives a reflected wave thereof. Can be transmitted to a shallow site.
[0002]
[Prior art]
The acoustic transducer for measuring a living body transmits a sound wave from the surface of the living body toward the inside of the body, and receives the reflected wave. By analyzing the acoustic information thus obtained, the state in the living body can be detected.
[0003]
This acoustic transducer is of a type called a two-frequency acoustic transducer, which simultaneously injects a sound wave below the audible frequency band and an ultrasonic pulse of about several megahertz into the body. A large displacement is given to the body by a sound wave of a frequency, and the state of the displacement can be detected by an ultrasonic pulse.
[0004]
As this two-frequency acoustic transducer, one described in Japanese Patent Publication No. 5-87249 is known. As shown in FIGS. 5A and 5B, this acoustic transducer includes a ring-shaped low-frequency vibrator 52 and a disk-shaped high-frequency vibrator 51, which form a coaxial structure. As described above, the high-frequency vibrator 51 is arranged in the ring of the low-frequency vibrator 52. The low-frequency vibrator 52 transmits a sound wave of an audible frequency band or less in the axial direction to receive a reflected wave, and the high-frequency vibrator 51 transmits an ultrasonic wave in the axial direction and receives a reflected wave.
[0005]
This conventional acoustic transducer is intended for use in a deep part of a living body. Therefore, the high-frequency vibrator 51 has a high-sensitivity high-frequency thickness mode vibrator made of piezoelectric ceramics (that is, expands and contracts in the thickness direction orthogonal to the sound wave radiation surface) so that high-frequency sound waves can be transmitted and received efficiently. The low-frequency vibrator 52 is a relatively large-diameter low-frequency vibrator made of piezoelectric ceramics so that low-frequency sound waves can be transmitted deep into the body. A thickness mode annular vibrator is used.
[0006]
As described above, since both the high-frequency vibrator 51 and the low-frequency vibrator 52 are thickness mode vibrators, the high-frequency vibrator 51 is arranged so as not to overlap the sound wave radiation surface of the low-frequency vibrator 52. .
[0007]
[Problems to be solved by the invention]
However, in this conventional acoustic transducer, the position where the low-frequency sound wave is generated and the position where the high-frequency sound wave are generated are distant, so that the emitted low-frequency sound wave and high-frequency sound wave must be kept at a certain distance from the acoustic transducer. If they do not overlap. Therefore, it is difficult to superimpose a high-frequency sound wave and a low-frequency sound wave on a shallow part of a living body, and for example, it has not been possible to obtain acoustic information on a sound wave superimposed on a wrist artery.
[0008]
The present invention solves such a conventional problem, and provides a living body acoustic transducer capable of superposing and injecting high-frequency ultrasonic waves and low-frequency sound waves even in a shallow part of a living body. It is aimed at.
[0009]
[Means for Solving the Problems]
Therefore, in the acoustic transducer for living body of the present invention, the bending mode vibrator that sends out low-frequency sound waves (that is, the piezoelectric body expands and contracts in a direction parallel to the sound wave emitting surface, and the sound wave emitting surface bends in an arc shape). A thickness mode vibrator for transmitting a high-frequency sound wave is provided on the sound wave emitting surface side of the vibrator).
[0010]
This acoustic transducer can generate high-frequency ultrasonic waves and low-frequency ultrasonic waves in a superimposed manner, and injects the high-frequency ultrasonic waves and low-frequency ultrasonic waves into a shallow part of a living body in a superimposed state, and outputs acoustic waves from the supersonic waves. Information can be obtained.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
The invention according to claim 1 of the present invention is directed to a biological acoustic transducer for transmitting and receiving a low-frequency sound wave and a high-frequency sound wave, wherein a bending mode vibrator and a thickness mode are provided at a position on the sound wave radiation surface side of the bending mode vibrator. A low-frequency sound wave is output from the bending mode vibrator, and a high-frequency sound wave is output from the thickness mode vibrator, so that the low-frequency sound wave and the high-frequency sound wave can be superimposed from the generation stage. it can.
[0012]
According to a second aspect of the present invention, the bending mode vibrator is formed of a monomorph vibrator made of a piezoelectric body and a metal plate, and the thickness mode vibrator is formed of a flexible piezoelectric material. A metal plate is used as a back body of the thickness mode oscillator, and the thickness mode oscillator having flexibility generates high-frequency sound waves without being affected by the vibration of the bending mode oscillator, and The low-frequency vibration of the bending mode vibrator is radiated through the thickness mode vibrator.
[0013]
According to a third aspect of the present invention, there is provided the acoustic transducer for a living body according to the second aspect, wherein a piezoelectric ceramic is used for a piezoelectric body of the monomorph oscillator, and a polymer piezoelectric body is used for a flexible piezoelectric material. It is possible to superimpose acoustic vibrations in the audible frequency band and the several megahertz band.
[0014]
According to a fourth aspect of the present invention, there is provided a low frequency signal generating means for generating a low frequency signal to be supplied to the bending mode vibrator, and a high frequency signal generating means for generating a high frequency signal to be supplied to the thickness mode vibrator. The signal is generated in synchronization with two positive and negative peaks in the cycle of the low-frequency signal, and by generating a high-frequency pulse on the peak of the low-frequency sound wave, the sound pressure is reduced. Dependent non-linear phenomena of a living body can be detected with a high-frequency pulse.
[0015]
According to a fifth aspect of the present invention, in the acoustic transducer of the fourth aspect, a negative pulse is generated as a high frequency signal when the low frequency signal has a positive peak, and a positive pulse is generated as the high frequency signal when the low frequency signal has a negative peak. In this case, a safety pulse is generated, and the absolute value of the peak voltage can be reduced to enhance safety.
[0016]
According to a sixth aspect of the present invention, a high-frequency signal is input to the back side of the thickness mode vibrator, and the low-frequency signal is grounded by an electrode on the sound wave emitting surface side of the bending mode vibrator. Leakage of low-frequency signals to the living body on the surface side can be suppressed, and safety can be improved.
[0017]
According to a seventh aspect of the present invention, a blocking coil for blocking a high frequency signal is connected to a supply line of a low frequency signal to the bending mode vibrator, and a high frequency signal is supplied to a low frequency signal generating means. Can be blocked.
[0018]
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0019]
(1st Embodiment)
As shown in FIG. 1A (longitudinal sectional view) and FIG. 1B (top view), the acoustic transducer for living body according to the first embodiment transmits high-frequency sound waves such as ultrasonic waves by thickness mode vibration. A piezoelectric vibrator (thickness mode vibrator) 1 for transmission / reception, a metal plate 2 acting as a back body of the thickness mode vibrator 1, and bonded to the metal plate 2 to perform bending mode vibration to generate sound waves in an audible frequency band. The case includes a piezoelectric vibrator 3 and a case 5 that supports the metal plate 2 via an adhesive portion 6.
[0020]
The thickness mode vibrator 1 is made of a material such as a polymer piezoelectric resin.
[0021]
The metal plate 2 functions as a back body of the thickness mode vibrator 1 and forms a monomorph vibrator together with the bonded piezoelectric vibrator 3 to be a bending mode vibrator 4.
[0022]
Next, the operation will be described.
[0023]
First, when an electric signal is applied to the bending mode vibrator 4, the metal plate 2 and the piezoelectric vibrator 3 perform bending vibration. At this time, since the peripheral portion of the metal plate 2 is bonded and supported to the case 5 via the bonding portion 6, the vibration at the central portion increases. The bending vibration of the metal plate 2 passes through the thickness mode vibrator 1 and is injected into the living body existing on the sound wave emitting surface side.
[0024]
Since the thickness mode vibrator 1 is made of a polymer piezoelectric resin, the thickness mode vibrator 1 has greater flexibility than the metal plate 2 and has less influence on the vibration of the metal plate 2. The thickness mode vibrator 1 vibrates at several megahertz in a direction perpendicular to the metal plate 2 to generate ultrasonic waves. The thickness of the thickness mode vibrator 1 can be set to 0.1 mm or less. Therefore, the vibration in the audible frequency band generated in the metal plate 2 can be transmitted through the thickness mode vibrator 1 almost without being affected by the thickness mode vibrator 1.
[0025]
As a result, it is possible to superimpose the sound wave in the audible frequency band and the ultrasonic wave of several megahertz on the surface of the living body in contact with the thickness mode vibrator 1. When the living body is irradiated with such superimposed sound waves, a large displacement is given to the body by a low-frequency signal, and the state of the displacement is detected by a high-frequency pulse, whereby the acoustic characteristics of the living body can be measured.
[0026]
As described above, in the acoustic transducer of this embodiment, by arranging the thickness mode oscillator on the sound wave emitting surface side of the bending mode oscillator, the acoustic vibration in the audible frequency band and the several megahertz band can be efficiently superimposed. , Can be injected into a living body.
[0027]
In addition, as a constituent material of the thickness mode vibrator 1, not only a polymer piezoelectric resin but also a composite piezoelectric material made of a resin and a piezoelectric ceramic has a greater flexibility than the metal plate 2 and is a desirable material. is there.
[0028]
(Second embodiment)
In the second embodiment, a drive system in the biological acoustic transducer according to the first embodiment will be described.
[0029]
As shown in FIG. 2, a biological acoustic transducer having this drive system includes a thickness mode vibrator 1 composed of an electrode 8, a piezoelectric material 9, and an electrode 10, a metal plate 2, an electrode 11, a piezoelectric material 12, and an electrode 13. A high-frequency drive unit 17 that generates a high-frequency pulse 19 to be supplied to the thickness-mode vibrator 1, and a low-frequency drive unit 16 that generates a low-frequency signal 20 to be supplied to the bending-mode vibrator 4. A control unit 18 for controlling the low-frequency drive unit 16 and the high-frequency drive unit 17, a blocking coil 15 for preventing the high-frequency pulse 19 from flowing into the low-frequency drive unit 16, and a low-frequency And a grounding coil 14 for passing only the frequency signal 20 and grounding.
[0030]
The grounding coil 14 and the blocking coil 15 block the passage of the high-frequency pulse 19 generated by the high-frequency driver 17, but pass the low-frequency signal generated by the low-frequency driver 16 well.
[0031]
Next, the operation will be described.
[0032]
First, the low-frequency driving unit 16 generates a low-frequency signal 20 under the control of the control unit 18 and supplies the low-frequency signal to the electrode 11 of the bending mode vibrator 4 via the blocking coil 15. The blocking coil 15 has a low impedance with respect to the low frequency signal, and can pass the low frequency signal 20.
[0033]
The low-frequency signal 20 causes the bending oscillator 4 to vibrate and is grounded from the electrode 13 via the grounding coil 14.
[0034]
At this time, the low-frequency signal 20 supplied to the electrode 11 also reaches the electrode 10 via the metal plate 2 and excites the thickness mode oscillator 1, but its displacement is smaller than that of the bending mode oscillator 4. . The low-frequency signal 20 that has reached the electrode 10 also reaches the high-frequency driver 17, but the high-frequency driver 17 is provided with a low-capacity output capacitor, and the low-frequency signal 20 is absorbed by the high-frequency driver 17. The rate at which it is done is small.
[0035]
On the other hand, the high-frequency driving unit 17 generates a high-frequency pulse 19 at a timing controlled by the control unit 18 and supplies the high-frequency pulse 19 to the electrode 10 to excite the thickness mode vibrator 1.
[0036]
At this time, the high-frequency pulse 19 supplied to the electrode 10 also reaches the electrode 11 via the metal plate 2. The high-frequency pulse 19 reaching the electrode 11 is blocked by the blocking coil 15, and few reach the low-frequency drive unit 16. The high-frequency pulse 19 arriving at the electrode 11 passes through the piezoelectric material 12 and reaches the electrode 13, but is shielded by the grounding coil 14, and the ratio of grounding is small. The grounding coil 15 has a high impedance with respect to the high-frequency pulse, and cannot pass the high-frequency pulse.
[0037]
In this manner, the low-frequency signal 20 or the high-frequency pulse 19 can be applied to each of the bending mode oscillator and the thickness mode oscillator.
[0038]
FIG. 3 shows an example of the waveform of the high-frequency pulse 19 and the low-frequency signal 20 applied to each of the bending mode oscillator and the thickness mode oscillator. Here, the high-frequency pulse 19 is generated in synchronization with the peak position of the voltage of the low-frequency signal 20. When the voltage of the low-frequency signal 20 has a positive peak, the high-frequency pulse 19 has a negative polarity, and the low-frequency signal 20 has a negative polarity. Is high, the high-frequency pulse 19 is generated twice in one cycle of the low-frequency signal 20 so that the high-frequency pulse 19 has a positive polarity.
[0039]
By synchronizing the drive signals in this way, it becomes possible to superimpose the ultrasonic wave at the positive and negative peak positions of the sound pressure of the low-frequency sound wave generated by the polar-mode vibrator 4, which is particularly dependent on the sound pressure. Non-linear phenomena of a living body can be detected by an ultrasonic pulse.
[0040]
Also, by reversing the positive and negative polarities of the peak voltage of the low frequency signal 20 and the positive and negative polarities of the high frequency pulse 19, the absolute value of the peak voltage on the metal plate 2 to which the high frequency pulse 19 and the low frequency signal 20 are added Can be reduced, and safety can be improved.
[0041]
As described above, in the biological acoustic transducer of this embodiment, it is possible to apply a low-frequency signal and a high-frequency pulse to each of the bending mode oscillator and the thickness mode oscillator, and the sound wave in the audible frequency band. And a high-frequency ultrasonic pulse can be superimposed. Further, by controlling the polarity of the high-frequency pulse according to the sign of the voltage of the low-frequency signal, it is possible to reduce the absolute value of the peak voltage.
[0042]
(Third embodiment)
In the acoustic transducer for living body of the third embodiment, the metal plate constituting the bending mode vibrator is grounded to completely prevent the leakage of the low frequency signal to the living body.
[0043]
In this acoustic transducer for a living body, as shown in FIG. 4, a low-frequency signal generated by the low-frequency driving unit 16 is supplied to the electrode 13 of the bending mode vibrator 4 via the blocking coil 15, The electrode 11 side of the bending mode vibrator 4 is grounded via a grounding coil 14. Further, a high-frequency amplifier 25 for amplifying a reception signal received by the thickness mode vibrator 1 is provided. Other configurations are the same as those of the second embodiment.
[0044]
Next, the operation will be described.
[0045]
First, the low-frequency driver 16 generates a low-frequency signal and supplies it to the electrode 13 via the blocking coil 15. This low-frequency signal causes the bending mode vibrator 4 to vibrate, and is grounded via the electrode 11 and the grounding coil 14. Therefore, no low-frequency signal appears on the metal plate 2.
[0046]
The high-frequency driving unit 17 generates a high-frequency pulse and supplies it to the electrode 10 to excite the thickness mode vibrator 1. The high-frequency pulse supplied to the electrode 10 reaches the electrode 11 via the metal plate 2. Of the high-frequency pulses 19 that have reached the electrodes 11, only a few pass through the grounding coil 14. The high-frequency pulse arriving at the electrode 11 is directed to the blocking coil 15 via the pole mode oscillator 4, but only a small amount passes through the blocking coil 15 and is absorbed by the low-frequency driving unit 16. There are few things.
[0047]
With such a configuration, it is possible to drive the pole mode oscillator 4 with a low frequency signal generated by the low frequency drive unit 16 and drive the thickness mode oscillator 1 with a high frequency pulse generated by the high frequency drive unit 17. is there. In particular, since the low-frequency signal can be grounded in the metal plate 2, it is possible to completely prevent the low-frequency signal from leaking to the living body on the sound wave emitting surface side.
[0048]
As described above, in the acoustic transducer for living body of this embodiment, the low-frequency signal and the high-frequency pulse can be respectively applied to each of the bending mode oscillator and the thickness mode oscillator, and the acoustic wave in the audible frequency band can be applied. And a high-frequency ultrasonic pulse can be superimposed. Further, the low-frequency signal can be grounded in the metal plate 2, so that the safety of the living body on the sound wave emitting surface side can be further improved.
[0049]
【The invention's effect】
As is clear from the above description, the biological acoustic transducer of the present invention can generate a sound wave in an audible frequency band and an ultrasonic pulse in a superimposed state. Therefore, this superimposed sound wave can be injected into a shallow part of a living body, and acoustic information can be obtained therefrom.
[Brief description of the drawings]
FIG. 1 is a longitudinal side view (a) and a top view (b) showing a configuration of a biological acoustic transducer according to a first embodiment of the present invention;
FIG. 2 is a cross-sectional view and a block diagram illustrating a configuration of a biological acoustic transducer according to a second embodiment of the present invention;
FIG. 3 is a waveform diagram of a low-frequency signal and a high-frequency pulse used in the biological acoustic transducer according to the second embodiment;
FIG. 4 is a sectional view and a block diagram showing a configuration of a biological acoustic transducer according to a third embodiment of the present invention;
5A and 5B are a cross-sectional view and a top view, respectively, showing a configuration of a conventional acoustic transducer for a living body.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Thickness mode oscillator 2 Metal plate 3 Piezoelectric oscillator 4 Bending mode oscillator 5 Case 6 Adhesion parts 8, 10, 11, 13 Electrodes 9, 12 Piezoelectric material 14 Grounding coil 15 Blocking coil 16 Low frequency driving part 17 High-frequency driver 18 Controller 25 High-frequency amplifier

Claims (7)

A biological acoustic transducer that transmits and receives low-frequency sound waves and high-frequency sound waves,
A bending mode oscillator,
And a thickness mode vibrator arranged on the sound wave radiation surface side of the bending mode vibrator. The bending mode vibrator is a monomorph vibrator including a piezoelectric body and a metal plate, and the thickness mode vibrator is formed of a flexible piezoelectric material, and the metal plate is a back body. The acoustic transducer for a living body according to claim 1, wherein The acoustic transducer according to claim 2, wherein a piezoelectric ceramic is used as a piezoelectric body of the monomorph vibrator, and a polymer piezoelectric body is used as the flexible piezoelectric material. A low-frequency signal generating unit that generates a low-frequency signal supplied to the bending mode vibrator, and a high-frequency signal generating unit that generates a high-frequency signal supplied to the thickness mode vibrator; The acoustic transducer for living body according to claim 1, wherein the acoustic transducer is generated in synchronization with two positive and negative peaks in a cycle of the low frequency signal. 5. A negative pulse is generated as the high frequency signal at a positive peak of the low frequency signal, and a positive pulse is generated as the high frequency signal at a negative peak of the low frequency signal. The acoustic transducer for living body according to claim 1. 2. The bio-acoustic according to claim 1, wherein a high-frequency signal is input to a rear side of the thickness mode oscillator, and a low-frequency signal is grounded by an electrode on a sound wave emitting surface of the bending mode oscillator. 3. converter. The bioacoustic transducer according to claim 1, wherein a blocking coil for blocking a high-frequency signal is connected to a supply line of a low-frequency signal to the bending mode vibrator.

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