JPH0251149B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ultrasonic probe used for nondestructive testing and medical diagnosis.

For example, as shown in FIG. 1, a conventional ultrasonic probe of this type uses one ultrasonic transducer 1 and has a backing material 3 on one acoustic radiation surface 2 of the ultrasonic transducer 1. and an acoustic impedance changing layer 4 on the other acoustic radiation surface 2. 5
is the lead wire.

In non-destructive testing and medical diagnosis, the acoustic propagation characteristics of a test material may have frequency dependence. When inspecting a subject with such characteristics, the frequency characteristics of the transmitted ultrasonic pulses are measured in advance, the frequency characteristics of the received pulses from inside the subject are analyzed, and differences between the two frequency characteristics are detected. Therefore, methods for obtaining information inside the subject are being applied. Therefore, if the frequency characteristics of the transmitted ultrasonic pulse can be controlled, the amount of information can be further increased.

Now, the frequency characteristics of the above transmitted ultrasonic pulse are:
It is determined by the combination of the ultrasonic probe and the electric circuit that excites it. However, the above electric circuit usually has an output impedance of 50Ω,
The excitation waveform of an ultrasonic probe is an extremely narrow pulse that can almost be considered an impulse.
Therefore, in order to change the frequency characteristics of the transmitted ultrasound pulse, it is necessary to change the constants of the ultrasound probe. However, as mentioned above, the conventional ultrasonic probe of this type was composed of only one ultrasonic transducer 1, bucking material 3, and acoustic impedance transformation layer 4, so the degree of freedom in controlling the above-mentioned constants was However, there are disadvantages in that it is difficult to achieve the desired frequency characteristics.

In this invention, a plurality of ultrasonic transducers 1 are stacked with delay materials 6 in between, and the excitation amplitude of each ultrasonic transducer 1 is controlled to control the frequency characteristics of the transmitted ultrasonic pulse. The above-mentioned drawbacks are solved by configuring the ultrasonic probe with
A detailed explanation will be given below using an example shown in FIG.

FIG. 2 shows an embodiment of the ultrasonic probe according to the present invention, which is constructed by laminating a plurality of ultrasonic transducers 1 with a delay material 6 interposed therebetween. Reference numeral 7 denotes an external electric circuit consisting of, for example, a resistor, which is provided for each ultrasonic transducer 1. 5 is a lead wire, and as shown in FIG. 2, it is connected so that the ultrasonic transducer 1 is excited at the same time.

Now, let us consider the operation of the ultrasonic probe shown in FIG. 2 when it is subjected to impulse excitation using a conventional electric circuit. In FIG. 2, it is assumed that the polarization directions of all three ultrasonic transducers 1 face downward in the figure. The lead wires 5 from each ultrasonic transducer 1 are connected so that the direction of the electric field applied to each ultrasonic transducer 1 also faces downward in the figure. This case will be explained below, but even if all three ultrasonic transducers 1 face upward in the figure, the polarization direction is
The purpose and effect of this invention remain essentially the same. This will be explained later.

Since the three ultrasonic transducers 1 are excited by electrical impulses, each of the three ultrasonic transducers 1 generates an ultrasonic pulse with a short pulse width. Let us consider the phase relationship between these three ultrasonic pulses generated from each ultrasonic transducer 1. For the sake of explanation, the ultrasonic transducers 1 are numbered serially from the bottom to the top in the figure, and the first, second, and third ultrasonic transducers 1 are numbered sequentially from the bottom to the top.
I will call it. Furthermore, for the sake of explanation, the first
The ultrasonic pulses generated from the second and third ultrasonic transducers 1 are also given serial numbers and will be referred to as first, second, and third ultrasonic pulses, respectively. In the first, second, and third ultrasonic transducers 1, the polarization direction and the electric field direction match. Therefore, the first, second, and third ultrasonic pulses generated from these three ultrasonic transducers 1 are in phase. Three ultrasonic pulses with such a phase relationship are generated simultaneously from the three ultrasonic transducers 1 and transmitted to the test material, but at one point (observation point) within the test material,
Suppose that we have observed what kind of ultrasonic pulses have been transmitted from the ultrasonic probe as a whole. Since the first ultrasonic transducer 1 is located closest to the specimen,
The first ultrasonic pulse generated from the first ultrasonic transducer 1 reaches the observation point earliest. Next, since the distance of the second and third ultrasonic transducers 1 is increasing in order through the delay material 6, the observation point is delayed in accordance with the order of the second and third ultrasonic pulses. is reached.

For example, assume that the vibration durations of the first, second, and third ultrasonic pulses are each one cycle. Furthermore, assume that the thickness of the delay material 6 is set so that the time required for the ultrasonic wave to propagate between the centers of vertically adjacent ultrasonic transducers 1 is equivalent to one cycle. .
Furthermore, by changing the value of the external electric circuit 7 consisting of a resistor, for example, for each ultrasonic transducer 1, the second ultrasonic pulse has the largest amplitude, then the third ultrasonic pulse, and then the first ultrasonic pulse. Assume that the setting is made so that the amplitude becomes smaller in accordance with the order of the ultrasonic pulses.

At this time, if we consider the ultrasonic pulse that reaches the observation point as a whole, this ultrasonic pulse is the sum of the above three ultrasonic pulses taking into account the above time delay. As a result, the overall ultrasonic pulse becomes as shown in FIG. In FIG. 3, the first one cycle is the first ultrasonic pulse, the next one cycle is the second ultrasonic pulse,
The last one cycle corresponds to the third ultrasonic pulse.

If the constant value of the external electric circuit 7 is changed for each ultrasonic transducer 1 to take a different value from the above, the overall waveform of the ultrasonic pulse will be different from that shown in FIG. For example, if the amplitudes of the first and third ultrasonic pulses are set to be large and the amplitude of the second ultrasonic pulse is small, the overall shape of the ultrasonic pulse envelope will be concave in the center. It will look like this. The frequency characteristics of such a waveform are of course different from the frequency characteristics of the waveform shown in FIG.

That is, the ultrasonic probe according to the present invention has the function and effect of being able to meet a request for a specific transmission waveform depending on the properties of the material being tested. On the contrary, it is an object of the present invention to meet such demands.

In addition, in FIG. 2, if the polarization direction of the ultrasonic transducer 1 is all directed upward in the figure, the third
A signal with the phase of the signal shown in the figure as a whole is inverted by 180 degrees will be generated. However, in many cases, an overall 180 degree phase reversal is not a problem with an ultrasonic probe, so it can be assumed that this case essentially has the same purpose and effect as described above. .

In addition, the thickness of the delay material 6 is determined so that the time required for the ultrasonic wave to propagate between the centers of the vertically adjacent ultrasonic transducers 1 is determined by the thickness of the ultrasonic pulse generated from each ultrasonic transducer 1. It is not necessarily necessary to select it so that it matches the vibration duration time. The vibration portions of the ultrasonic pulses generated from each ultrasonic transducer 1 may be selected so that they do not overlap with each other, or conversely, they may be selected so that they overlap. In short,
It is only necessary to select it so that the desired waveform can be realized. The delay material 6 has the purpose and effect of transmitting the ultrasonic pulses generated from each ultrasonic transducer 1 for a required time so that a desired waveform can be obtained. Further, the purpose and effect of providing the external electric circuit 7 for each ultrasonic transducer 1 is to make it possible to realize a desired waveform by combining it with the delay time obtained by the delay material 6.

Furthermore, the polarization direction does not need to be oriented in the same direction for all the ultrasonic transducers 1. if,
In Fig. 2, if the polarization direction of any ultrasonic transducer 1 is opposite to that of the others, the ultrasonic pulse generated from that ultrasonic transducer 1 will be polarized in the opposite direction to that of the others. Become a phase. Utilizing this has the advantage of being able to meet more diverse requirements for transmission waveforms.

Next, let's consider the case of receiving ultrasonic waves. Assume that an acoustic impulse is applied to the ultrasonic probe shown in FIG. Since acoustic impulses are input, electric pulses with short pulse widths are received from each of the three ultrasonic transducers 1. Let us consider the phase relationship of these three electric pulses received from each ultrasonic transducer 1. For explanation, first, second, and third ultrasonic transducers 1
A serial number is also assigned to the electrical pulses received from the
They will be referred to as first, second, and third electrical pulses, respectively. 1st, 2nd, and 3rd
When the polarization direction and electric field direction of all three ultrasonic transducers 1 match, the first, second, and third electric pulses received from these three ultrasonic transducers 1 are in phase. Become.

Three electrical pulses having such a phase relationship are received from each of the three ultrasound transducers 1, but let us consider what happens to the reception signal of the ultrasound probe as a whole. Since the first ultrasonic transducer 1 is located at the closest distance to the specimen, the first electric pulse from the first ultrasonic transducer 1 is received earliest. Next, since the distance between the second and third ultrasonic transducers 1 increases in order through the delay material 6,
The second and third electrical pulses are received with a delay according to the order of the pulses. The total received signal is obtained by adding these together on the time axis, taking into account time delays.

Now, for example, assume that the vibration durations of the first, second, and third electric pulses are each one cycle. Furthermore, assume that the thickness of the delay material 6 is set so that the time required for the ultrasonic wave to propagate between the centers of vertically adjacent ultrasonic transducers 1 is equivalent to one cycle. . Furthermore, by changing the value of the external electric circuit 7 for each ultrasonic transducer 1, the amplitude of the second electric pulse was the largest, followed by the third electric pulse, and then the first electric pulse. Assume that the settings are made so that the amplitude is received with a small amplitude. At this time, the overall received signal obtained is as shown in FIG. In Figure 3, the first cycle is the first cycle.
, the next one cycle corresponds to the second electric pulse, and the last one cycle corresponds to the third electric pulse.

That is, the ultrasonic probe shown in FIG. 2 has the effect and function of receiving an electrical signal having a desired waveform when an acoustic impulse is incident thereon. On the contrary, it is a second object of the present invention to receive such electrical signals.

By utilizing this, for example, it is possible to emphasize high frequency components or, conversely, to emphasize low frequency components. For example, when inspecting a test material with large attenuation, the attenuation increases as the frequency increases, so if the high frequency components are emphasized and received, it is possible to bring the received waveform closer to the transmitted waveform. In other words, it is possible to correct the attenuation of the test material and receive the signal. If this were to be done using an electric circuit, a Fourier transform circuit would be required, which would increase the circuit scale. Particularly when real-time processing is required, it is extremely difficult to realize this type of signal processing electrical circuit. The ultrasonic probe of the present invention has a simple configuration and has the ability to perform such processing.

Although the above description has been made regarding the case of one embodiment shown in FIG. It is clear that by controlling not only the thickness but also the acoustic radiation area of each ultrasonic transducer 1, an ultrasonic probe that can meet more diverse requirements can be constructed. Further, the external electric circuit 7 may be combined with a capacitor, a coil, or the like. Furthermore, this invention is applicable to an oblique ultrasonic probe that transmits and receives ultrasonic waves obliquely to the surface of a test material, and a surface wave type ultrasonic probe that transmits and receives ultrasound along the surface of a test material. You may. Further, the present invention may be applied to each element of an array type ultrasonic probe.

As described above, in the ultrasonic probe according to the present invention, a plurality of ultrasonic transducers 1 are stacked with the delay material 6 in between, and the excitation amplitude of each ultrasonic transducer 1 is controlled. , compared to the conventional method, has the advantage that the frequency characteristics of the ultrasonic probe can be controlled with a greater degree of freedom.

[Brief explanation of drawings]

Fig. 1 shows a conventional ultrasonic probe, Fig. 2 shows a conventional ultrasonic probe;
This figure shows an embodiment of the ultrasonic probe according to the present invention, and FIG. 3 is a diagram showing a waveform obtained by combining the outputs of the respective ultrasonic transducers shown in FIG. 2. In the figure, 1 is an ultrasonic transducer, 2 is an acoustic radiation surface, and 3
4 is a bucking material, 4 is an acoustic impedance change layer, 5 is a lead wire, 6 is a delay material, and 7 is an external electric circuit. In the drawings, the same or corresponding parts are denoted by the same reference numerals.

Claims (1)

[Claims] 1 A plurality of ultrasonic transducers are stacked with a delay material that delays the ultrasonic pulse of each ultrasonic transducer for a required period of time, and the amplitude of the pulse of one or more of the ultrasonic transducers is An ultrasonic probe characterized in that the plurality of ultrasonic transducers are connected via an external electric circuit that makes the pulse amplitude different from that of other ultrasonic transducers.