JPS5811851A - Ultrasonic probe - Google Patents

Abstract

PURPOSE:To prevent a decrease in mutual electroacoustic transducing efficiency by arranging the electrode in a polarizing direction, and utilizing oscillation mode of a main body in the elongating direction. CONSTITUTION:An oscillator 10 consists of a main body 11 and electrodes 12. The main body 11 is made of a high polymer piezoelectric material, and each electrode 12 is made of a thin film of a conductive material. The oscillators 10 are arrayed at prescribed pitch in a polarizing direction and gaps 15 are formed between adjacent oscillators 10 and 10. A front surface plate 13 serves as at least one of a protective layer for the oscillators 10, an acoustic matching layer, and an acoustic lens. A rear plate 14 serves as at least one of a backing layer for the oscillators 10, an acoustic absorbing layer, and an acoustic matching layer. The phase of an electrode potential difference and amplitude of each oscillator are controlled to obtain the operation as a phased array which utilizes an oscillation mode in the elongation-axis direction.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ultrasonic probe, and more particularly to an ultrasonic probe having a transducer body made of a polymeric piezoelectric material.

2. Description of the Related Art Ultrasonic probes having piezoelectric ceramic vibrator bodies have been used as electroacoustic transducing means in various ultrasonic devices that use ultrasonic waves for diagnosis, flaw detection, measurement, and the like. Although this ceramic resonator is sensitive, its bandwidth is narrow, and the shape ratio (width/thickness at the smallest cross section when formed into a rectangular parallelepiped shape) is sufficiently small compared to the wavelength, making it difficult to hear. Therefore, it has the disadvantage that it is not suitable for phased arrays used at high frequencies of approximately 5 MHz or higher. In other words, when performing fan-shaped scanning using an array type ultrasound probe in an ultrasound diagnostic device, etc., the second
'In order to prevent the generation of false images due to viewing poles, the wavelength V (oscillator array pitch) must exceed a predetermined value determined in relation to the coverage area of beam scanning. For phased array probes using ceramic resonators, the plate-shaped resonator glued to the backing material was cut and divided into multiple pieces, so cutting the resonator and adhesive was necessary. Because the resistance is weak, it is difficult to make the width of the vibrator sufficiently narrow, and because there is a limit to the blade thickness of the cutter, it is difficult to make the width of the cutting groove, that is, the distance between the vibrators, narrow enough. As a result, it has been virtually impossible to make the arrangement pitch of the vibrators sufficiently small.

On the other hand, a vibrator made of a polymer piezoelectric material has broadband characteristics, but has low sensitivity and a thickness of 9 to 30 μm.
Since it is possible to manufacture only about m, there is a drawback that as it is, it can only be used in a high frequency range of about 1QMHz or more.

In order to use this in a practical low-threat region, conventionally, as illustrated in the first factor, a plurality of elements (three in the figure) are connected in the thickness direction, that is, in the polarization direction (Y). The vibrator main body 2 was formed by polymerizing and adhering each other. This main body 2 has a pair of IT electrodes facing each other in the thickness direction, that is, in the width direction, that is, the element 1.
... are arranged at a predetermined array pitch and interval in the direction of the stretching axis (X). In the figure, 4 is an 11-sided plate, and 5 is a back plate. And, it is configured to utilize the vibration mode in the polarization direction (1). Note that the vibrator 2 may be divided in the direction of the stretching axis.

However, in the conventional probe configured as described above, the transducer body 2 is formed by laminating and bonding a plurality of single vibrating elements, which results in poor electrical-acoustic mutual conversion efficiency. Not only that, but also because the piezoelectric d constant of main body 2 is small? The air → sound conversion efficiency is poor, and the acoustic impedance of the main body 2 is approximately 4 x 106 f/m, so it cannot be used with the human body, water, etc. (acoustic impedance of approximately 1.5 x 10 f/m).
'Qf/m2s), the problem is that the acoustic matching is poor.

The present invention has been made based on the above circumstances, and an object of the present invention is to have a vibrator main body made of a polymeric piezoelectric material, and to have a high electricity-acoustic mutual conversion efficiency, so that it can absorb the sounds of the human body, water, etc. An object of the present invention is to provide an ultrasonic probe that has good consistency and can be used as a high-frequency phased array.

Hereinafter, the present invention will be described with reference to an illustrated embodiment. Second
In the figure, a vibrator 1o includes a main body 11 and electrodes 12.12. The vibrator main body 11 is made of a polymeric piezoelectric material (for example, PVDF', etc.) and has a length in the stretching axis direction (3)! , is formed in the shape of a rectangular parallelepiped with a thickness t in the polarization direction. Electrode 1
2.12 is formed in the form of a thin film from a suitable conductive material, and is attached to the free surface of the main body 1 in the polarization direction by means such as vapor deposition or adhesion. Such a vibrator 10
are arranged at a predetermined arrangement pitch in the polarization direction 1, and a front plate 13 and a back plate 14 are provided at both ends in the stretching direction, and a gap 15 is formed between adjacent vibrators 10 and 10. ing. The front plate 13 is configured to function as at least one of a protection j-1 acoustic matching layer or an acoustic lens for the vibrators 10... It is configured to function as at least one of a backing layer, an acoustic absorption layer, and an acoustic matching layer.The gap 15 is filled with an electrically insulating material (for example, air). By appropriately controlling the phase and amplitude of the potential difference El between the electrodes 12 and 12 for each child 10..., it is possible to operate as a phased array using the vibration mode in the stretching axis direction (3). It is configured.

According to the above configuration, since both ends in the stretching direction are used, the length of the vibrator main body 11 in the vibration direction can be reduced! can be easily formed to match the desired frequency by simply cutting the composite material, thereby achieving a practically preferred frequency band (about 1 to 29 MHz).
can be covered. Therefore, unlike in the conventional device C2, there is no need to laminate a plurality of vibrator bodies in the thickness direction, that is, in the vibration direction f''11, so that there is no reduction in the electric-acoustic mutual conversion efficiency.

In addition, in the polymer piezoelectric material, the stretching axis direction (X)i=
The piezoelectric d constant in the polarization direction (approximately twice the value in Yl) is good, and the acoustic impedance in the stretching axis direction is closer to the value of the human body, water, etc. than in the polarization direction, so the acoustic matching for these is also improved. be done.

Furthermore, since the vibration mode in the stretching axis direction (■) is utilized as described above, the thickness t of the vibrator body 11 in the polarization direction
can be made sufficiently thin, and therefore the array pitch of the vibrators 10... can be made sufficiently small compared to conventional polymeric royal material vibrators (2), and can also be made thin enough by cutting ceramic vibrators. It is easy to reduce the size to 1/10 or less compared to the one formed using the same method, and in this case, it can be used for a phased array for high frequencies of 10 times or more.

Note that the present invention is not limited to the above-mentioned embodiments. For example, as shown in FIG. Alternatively, one unit of the vibrator 20 may be configured. A probe in which a plurality of units of such vibrators are arranged in the polarization direction can increase the gain when used in a relatively narrow angular range. Alternatively, as shown in FIG. 4, only one unit of the vibrator 21 may be provided, which is formed by layering a plurality of vibrator bodies 11 (18 in the figure) end layers in the polarization direction. . The probe configured in this manner can be used as a broadband probe in the same way as conventional probes used for nondestructive testing, flow measurement, and the like. Furthermore, in any of the above cases, an oily thin film such as silicone oil is interposed between the mutually adjacent vibrator bodies 11 and between the sensor 11 and the electrode 12, and the surface of this oily thin film is Adjacent two pieces may be pasted together using tension. With this configuration, the assembly work can be greatly simplified compared to the case of bonding with adhesive, and the suppressing effect against vibration in the extending axis direction of the vibrator body 11... Since the weight is much lighter than in the case of the conventional case, the electric to acoustic conversion efficiency can be improved.

The present invention has a vibrator body formed of a polymeric piezoelectric material as described above, and is characterized in that electrodes are disposed in the polarization direction of the vibrator body in order to utilize the vibration mode in the direction of the stretching axis of the body. It is something to do. Therefore, since the length in the vibration direction can be adjusted to match the desired frequency, there is no need to glue multiple bodies together in the thickness direction.
It is possible to prevent the deterioration of the electric-acoustic mutual conversion efficiency. In addition, since the piezoelectric constant is good and the acoustic impedance is closer to that of the human body or 7J (etc.), the acoustic matching to the human body, water, etc. can be improved. Since the thickness of the vibrator body in the direction may be thin, it is suitable for high frequency phased arrays.

In addition, by attaching the vibrator main body and the electrodes together with an oily thin film between them, the assembly work is simplified, and the vibration suppression effect is reduced to improve the electrical to acoustic conversion efficiency. be able to.

[Brief explanation of drawings]

Fig. 1 is a sectional view showing a conventional example, Fig. 2 is a sectional view showing an embodiment of the present invention, and Figs. 10.20.21... Vibrator, 11... Vibrator body, 12... Electrode, X... Extension axis direction, Y... Polarization direction.

Claims (2)

[Claims] (1) An ultrasonic probe having a vibrator body made of a polymeric piezoelectric material, characterized in that electrodes are arranged in the polarization direction to utilize the vibration mode in the direction of the stretching axis of the body. Child. (2) The ultrasonic probe according to claim 1, wherein the transducer main body and the electrode are bonded to each other with an oily thin film interposed between them.