JPH029520B2 - - Google Patents

Description

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

Conventional ultrasonic probes of this type, for example,
As shown in the figure, using one ultrasonic transducer 1,
A backing material 3 was provided on one acoustic radiation surface 2 of the ultrasonic transducer 1, and an acoustic impedance modification layer 4 was provided on the other acoustic radiation surface 2.
5 is a lead wire.

In nondestructive testing and medical diagnosis, the acoustic propagation characteristics of a subject may be frequency dependent. 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 is composed of only one ultrasonic transducer 1, bucking material 3, and acoustic impedance transformation layer 4, so there is freedom in controlling the above-mentioned constants. The frequency is small, and this has the disadvantage that it is sometimes difficult to achieve the required frequency characteristics.

This invention solves the above-mentioned drawbacks by stacking a plurality of ultrasonic transducers 1 with different acoustic radiation areas with a delay material 6 in between. This will be explained in detail using examples.

FIG. 2 shows an embodiment of the ultrasonic probe according to the present invention, in which a plurality of ultrasonic transducers 1 having different acoustic radiation areas are stacked with a delay material 6 in between. It consists of 7 is an ultrasonic propagation medium. 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, when the ultrasonic probe shown in Fig. 2 is subjected to impulse excitation using an electric circuit similar to the conventional one, the ultrasonic transducer 1, which has a large acoustic radiation area, is excited with an ultrasonic pulse having a large amplitude level, and the acoustic radiation is emitted. In the ultrasonic transducer 1 having a small area, ultrasonic pulses having a small amplitude level are excited. This is because the capacitance of the ultrasonic transducer 1 is proportional to the acoustic radiation area, which is generally known in this type of technical field, but the acoustic radiation resistance is inversely proportional to the capacitance, and normally the acoustic The value of the radiation resistance is about several kΩ to several tens of kΩ. Therefore, if the acoustic radiation area doubles, for example, the acoustic radiation resistance will decrease by half, and the matching with the power supply resistance of the electric circuit (usually several tens to hundreds of ohms) will not be perfect. is correspondingly better, so that the effective power supply from the power source increases, ie, ultrasonic pulses with higher amplitude levels are excited. Furthermore, the time for the ultrasonic waves excited by each ultrasonic transducer 1 to reach the surface of the test material is delayed as the ultrasonic transducer 1 is located closer to the bucking material 3. Therefore, in the ultrasonic probe shown in FIG. 2, the ultrasonic pulses transmitted to the test material are the same as those excited by each ultrasonic transducer 1 at the above-mentioned amplitude level and time delay. The waveform is synthesized by taking into account the following, and the waveform is as shown in FIG. 3, for example. The first pulse in the figure is excited by the lower ultrasonic transducer in Fig. 2, the second pulse is excited by the central ultrasonic transducer in Fig. The third pulse corresponds to that excited by the upper ultrasonic transducer in FIG. Note that the temporal relationship between these pulses is determined by the delay material 6 shown in FIG. Further, the Fourier transform of the waveform shown in FIG. 3 is the frequency characteristic, and the waveform shown in FIG. 3 can be controlled by changing the acoustic radiation area of each ultrasonic transducer 1. Therefore, the ultrasonic probe according to the present invention has an advantage in that the degree of freedom of the constants that can control the frequency characteristics is greater than in the past, and required frequency characteristics can be achieved more easily than in the past. The above explained the case of transmitting ultrasonic waves, but
The above also applies to the case of receiving ultrasonic waves.

Although the above description has been made regarding the case of the embodiment shown in FIG. 2, the present invention is not limited to this. It is clear that if the thickness of the delay material 6 is also controlled, an ultrasonic probe that can meet more diverse requirements can be constructed. 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, by stacking a plurality of ultrasonic transducers 1 with different acoustic radiation areas with the delay material 6 in between,
This has the advantage that the frequency characteristics of the ultrasonic probe can be controlled with a greater degree of freedom than in the past.

[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, 3 is a backing material, 4 is an acoustic impedance modification layer, 5 is a lead wire, 6 is a delay material, and 7 is an ultrasonic propagation medium. In the drawings, the same or corresponding parts are denoted by the same reference numerals.

Claims (1)

[Claims] 1. An ultrasonic probe characterized in that a plurality of ultrasonic transducers with different acoustic radiation areas are stacked with a delay material sandwiched between them so that the frequency characteristics of transmitted and received ultrasonic pulses can be controlled.