JPS6133511B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ultrasonic probe, and particularly to an ultrasonic probe that transmits and receives an ultrasonic pulse beam.

Emit an ultrasonic beam in a pulsed manner in a predetermined direction,
Ultrasonic probes that receive reflected echoes from objects are used for various measurements, and are suitable for flaw detection, depth sounding, distance measurement, etc. It is used in ultrasonic diagnostic equipment that non-invasively displays images of internal organs and other organs by emitting radiation.

Conventional ultrasonic probes use ceramic piezoelectric materials such as PZT as transducers, but these conventional probes have had the problem of not necessarily achieving satisfactory ultrasonic beam transmission and reception effects.

FIG. 1 schematically shows a conventional ultrasonic probe, in which excitation electrodes 12 and 14 are attached or fixed by baking to both sides of a ceramic piezoelectric body 10.

In this type of conventional probe, since the acoustic impedance of the ceramic piezoelectric body 10 is large, an impedance mismatch occurs between the probe and an object with a small acoustic impedance, such as a subject in ultrasound diagnosis. However, there is a problem in that the efficiency of transmitting and receiving ultrasonic beams decreases. For this purpose, in the conventional apparatus, as shown in FIG. 1, a matching layer 16 made of epoxy or other polymeric material is provided on the ultrasonic beam emitting surface side of the ceramic piezoelectric body 10, and the matching layer 16 is made of epoxy or other polymeric material. Impedance matching is achieved.

Furthermore, in ultrasonic diagnostic equipment that displays images using reflected echoes of ultrasonic pulse beams, in order to increase the resolution in the distance direction, it is usually better to shorten the vibration time of the ultrasonic pulse; As the number increases, the resolution decreases and it becomes difficult to obtain clear images. For this purpose, piezoelectric body 1
0, an excitation signal with a short pulse width is applied via the excitation electrodes 12 and 14, but as is well known, due to the mechanical free vibration of the piezoelectric body 10, the actual vibration waveform is as shown in FIG. It is known that the pulse width T becomes longer. In the conventional device, a sound wave absorbing material 18 is attached to the back side of the ceramic piezoelectric body 10, as shown in FIG. 1, in order to damp the mechanical free vibration. Sound wave absorber 1
8, the mechanical free vibration of the piezoelectric body 10 is damped to some extent, and as shown in FIG. 3, it becomes possible to reduce the pulse width T compared to FIG. 2. However, even in the probe having this sound wave absorbing material 18, the ceramic piezoelectric material 10
whose acoustic impedance is 5 of the sound wave absorbing material 18
Since it is ~10 times larger, a large reflection occurs at the interface between the two, and the vibration waveform shown in FIG. 3 still has a long pulse width, which has the disadvantage that the resolution cannot be sufficiently improved.

The present invention has been made in view of the above-mentioned conventional problems, and an object thereof is to provide an ultrasonic probe with significantly improved ultrasonic transmission and reception characteristics by shortening the transmitted ultrasonic pulse width.

In order to achieve the above object, the present invention provides a ceramic piezoelectric material that emits an ultrasonic pulse beam by application of an excitation signal, and a radiation surface between the ceramic piezoelectric material and a subject on the radiation surface side of the ceramic piezoelectric material. A cancellation excitation signal delayed for a certain period of time is transmitted to the polymer piezoelectric film so as to cancel the rear end waveform of the ultrasonic pulse waveform obtained by the polymer piezoelectric film disposed as a matching layer for impedance matching and the ceramic piezoelectric material. The present invention is characterized by comprising a canceling excitation signal supplying means for supplying the film to the film.

Hereinafter, preferred embodiments of the present invention will be described based on the drawings.

FIG. 4 shows a schematic configuration of an ultrasonic probe according to the present invention, and the same members as those of the conventional device shown in FIG.

A characteristic feature of the present invention is that a polymer piezoelectric film 20 is attached to the ultrasonic beam emitting surface side of the ceramic piezoelectric body 10 so as to double as a matching layer, and the polymer piezoelectric film 20 has a shortened ultrasonic pulse width. In this embodiment, one end surface of a piezoelectric film 20 is attached to the electrode 12. Suitable examples of the polymer piezoelectric film 20 in the examples include polyvinylidene fluoride, polyvinyl fluoride, etc., copolymers containing these as main components, and piezoelectric materials mixed with inorganic powder such as ceramic. The film 20 has a smaller acoustic impedance than the ceramic piezoelectric material 10, and its value is approximately the same as that of the subject. According to the present invention, this polymeric piezoelectric film 20 is used in place of the conventional matching layer 16. It becomes possible to use it. Unlike the conventional polymer matching layer 16, this polymer piezoelectric film has good flexibility. By exposing the molecular piezoelectric film 20 and bringing it into close contact with the subject, it is possible to improve familiarity between the two and reduce attenuation of the ultrasound beam.

In the embodiment shown in FIG. 4, since the polymer piezoelectric film 20 is used for receiving reflected echoes, an excitation electrode 22 is provided on the radiation surface side of the piezoelectric film 20. Further, in the embodiment, an acoustic lens 24 is disposed on the radiation surface side of the polymer piezoelectric film 20 to protect the probe, focus the beam, and perform other functions. In the example, the acoustic impedance of the ceramic piezoelectric material 10, the polymer piezoelectric film 20, and the acoustic lens 24 is 30×10 ⁶ Kg/m ² s, 4×10 ⁶ Kg/m ² s, and 4 to 1.5.
×10 ⁶ Kg/m ² s.

The embodiment of the present invention has the above configuration, and as described above, the polymer piezoelectric film 20 provided on the radiation surface side of the ceramic piezoelectric body 10 is connected to the ceramic piezoelectric body 10 and the object to be examined (acoustic impedance 1.5×10 ⁶
Since it has an acoustic impedance value intermediate between Kg/m ² s), it acts as a good impedance matching layer for the ceramic piezoelectric body 10, and can significantly improve the transmission and reception efficiency of ultrasonic beams.

In the present invention, the ultrasonic beam is also transmitted using a ceramic piezoelectric material 10 that is well matched with the transmitting circuit.
5A, which is similar to that shown in FIG. 3 described above, and the pulse width T of the waveform shown in FIG. In the present invention, a canceling excitation signal having the waveform shown in FIG. 5B is supplied between the electrodes 12 and 22 at the same time as the transmission excitation signal is applied between the excitation electrodes 12 and 14, or after a certain period of delay. , which acts to shorten the vibration pulse width of the ceramic piezoelectric body 10. That is, the canceling excitation signal shown in FIG. 5B is supplied between the electrodes 12 and 22 with a slight delay from the excitation signal shown in FIG. It will be appreciated that the signal has a waveform whose pulse width T is significantly reduced, as shown in FIG. 5C. That is, the signal waveform at the rear end, which is the mechanically free vibration part of a normal excitation signal, is transferred to the polymer piezoelectric film 2.
As a result, it is possible to obtain an excitation signal with a short pulse width.

FIG. 6 shows a preferred embodiment circuit for supplying the excitation signal and the canceling excitation signal to the ceramic piezoelectric body 10 and the polymeric piezoelectric film 20, respectively, in response to a trigger signal from a trigger generator 26. By operating the main transmitting circuit 28 and supplying the excitation signal of the main transmitting circuit 28 to the electrode 14, the ceramic piezoelectric body 10 can be excited and driven.
On the other hand, the trigger signal of the trigger generator 26 is transmitted to the delay line 3
0 to the auxiliary transmitting circuit 32, and the delay line 30 and the auxiliary transmitting circuit 32 constitute canceling excitation signal supply means. Therefore, the auxiliary transmitting circuit 3
By supplying two delayed canceling excitation signals to the electrodes 22, the polymer piezoelectric film 20 can be excited and driven.

As described above, according to the present invention, it is possible to display a high-resolution image using an ultrasonic beam with a short pulse width using a polymer piezoelectric film attached to a ceramic piezoelectric body.

Furthermore, in the present invention, by using the polymer piezoelectric film 20, unlike the conventional method, when receiving the reflected echo of the probe, extremely good reception characteristics can be obtained. That is, when receiving a reflected echo, the polymer piezoelectric film 20 acts as a receiving vibrator, and an electrical signal corresponding to the reflected echo can be extracted from between the electrodes 12 and 22.
That is, the polymer piezoelectric film 2 in the present invention
Since the acoustic impedance of 0 is close to that of the subject, its Q value can be set to about 1 or less, and it has an extremely wide frequency characteristic and is characterized by a rapid decrease in free vibration. It is possible to faithfully convert ultrasound reflected echoes into electrical signals. That is, the polymer piezoelectric film 20 has extremely superior fidelity than the conventional ceramic piezoelectric material 10 when receiving reflected echoes.

Figure 7 shows the received waveform of the reflected echo;
The figure shows a case where a conventional ceramic piezoelectric body 10 is used, and FIG. 7B shows a case where a polymer piezoelectric film 20 according to the present invention is used.

As is clear from FIG. 7, when the conventional ceramic piezoelectric body 10 is used for reception, the reception pulse width increases more than necessary, and the resolution during reception deteriorates significantly. By using the polymer piezoelectric film 10 of the invention, it is possible to easily improve this receiving characteristic. Since the polymer piezoelectric film 20 has an acoustic impedance close to that of the subject, it has the advantage that, unlike the ceramic piezoelectric material 10, it does not require any impedance matching layer during reception.

As explained above, according to the present invention, it is possible to remove pulses caused by mechanical free vibration and obtain good ultrasonic transmission and reception characteristics by using a polymer piezoelectric film provided on the radiation surface side of a conventional ceramic piezoelectric material. This allows you to obtain clear images with high resolution.

Further, since the polymer piezoelectric film of the present invention serves as a matching layer, it is possible to exhibit excellent characteristics in a compact, low-cost ultrasonic probe.

[Brief explanation of the drawing]

Fig. 1 is a schematic explanatory diagram showing a conventional ultrasonic probe, Figs. 2 and 3 are excitation signal waveform diagrams of the probe in Fig. 1, and Fig. 4 is an ultrasonic probe according to the present invention. A schematic explanatory diagram showing a preferred embodiment of the child, FIG.
FIG. 6 is an excitation waveform diagram in the embodiment shown in the figure, FIG. 6 is an excitation circuit diagram at the time of transmission in FIG. 4, and FIG. 7 is a waveform diagram showing the operation of the present invention. 10...Ceramic piezoelectric material, 20...Polymer piezoelectric film.

Claims (1)

[Claims] 1. A ceramic piezoelectric body that emits an ultrasonic pulse beam by applying an excitation signal, and a matching device that matches impedance between the ceramic piezoelectric body and a subject on the radiation surface side of the ceramic piezoelectric body. A cancellation method that supplies a cancellation excitation signal delayed for a certain period of time to the polymer piezoelectric film so as to cancel the rear end waveform of the ultrasonic pulse waveform obtained by the polymer piezoelectric film arranged as a layer and the ceramic piezoelectric material. An ultrasonic probe comprising: excitation signal supply means. 2. The ultrasonic probe according to claim 1, wherein the ceramic piezoelectric material is used for transmitting an ultrasonic beam, and the polymer piezoelectric film is used for receiving reflected echoes.