JPS6365200B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ultrasonic probe, and more particularly to an ultrasonic probe that has dedicated transducers for transmission and reception, and is suitable for use as a phased array.

Ultrasonic probes with transducer bodies made of piezoelectric ceramics have traditionally been used as electroacoustic transducers in various ultrasonic devices that use ultrasonic waves for diagnosis, flaw detection, measurement, etc. . However, although this piezoelectric ceramic vibrator has a high conversion efficiency, it has poor acoustic matching with the human body or water, and therefore has the disadvantage of a narrow frequency bandwidth.

On the other hand, an ultrasonic probe having a transducer body made of a polymeric piezoelectric material is also used as an electroacoustic transducer. Although this product has broadband characteristics, the electroacoustic conversion efficiency is low, and it can only be manufactured with a thin thickness. The drawback is that it can only be used in the high frequency range of approximately 10MHz or higher. In order to use this in a practical low frequency region of several MHz, conventionally, as illustrated in FIG.
The main body 2 of the vibrator was formed by overlapping them and adhering them to each other. In this main body 2, pairs of electrodes 3 facing each other in the thickness direction are arranged at a predetermined arrangement pitch in the width direction, that is, in the direction X of the stretching axis of the element 1, and spaced apart from each other. There is. In the figure, 4 is a front plate, and 5 is a back plate. It is configured to utilize the vibration mode in the polarization direction Y, that is, the thickness vibration mode. In addition,
The vibrator main body 2 may be divided in the stretching axis direction X. However, in the conventional probe configured as described above, the transducer body 2 is formed by laminating and bonding a plurality of elements 1, so the electroacoustic mutual conversion efficiency is higher than that of a single layer. There is a drawback that it is further reduced.

The present invention has been made under the above circumstances, and aims to provide a phased array type that has high electroacoustic mutual conversion efficiency, good acoustic matching with the human body and water, and is easy to manufacture. An object of the present invention is to provide an ultrasonic probe suitable for use as an ultrasonic probe.

Hereinafter, the present invention will be described with reference to an illustrated embodiment. In Fig. 2, 10... indicates a plurality of composite oscillators (the figure shows a case of four), and these composite oscillators 1
0... each have a first transducer 11 for transmission and a second transducer 12 for reception, which are arranged in the horizontal direction at a predetermined arrangement pitch d.

The first vibrator 11 includes a main body 13 made of piezoelectric ceramics, which is formed into a rectangular parallelepiped shape with a thickness of T in the front-rear direction and a width of W in the lateral direction, and electrodes disposed at both ends of the main body 13 in the front-rear direction. 14 and 15. These electrodes 14 and 15 are formed of a conductive material in the form of a thin film, and are attached to the main body 13 by means such as vapor deposition or baking.
The first vibrators 11 are fixed to each other via an electrically insulating filler 16 filled between them. Further, the front electrodes 14... are grounded, and the rear electrodes 15... are connected to an appropriate transmitter (not shown), and these electrodes 14, 15...
The structure is such that a sound field of ultrasonic pulses can be generated in front by applying a pulse voltage E _t between them. The general configuration as described above regarding the first vibrators 11 may be the same as in the conventional device.

The second vibrator 12 is the first vibrator 11
In the illustrated example, two sets of vibrator bodies 17a and 17b are located opposite to and in front of this.
, an intermediate electrode 18 interposed between the main bodies 17a and 17b, and end electrodes 19 and 19 disposed on mutually opposite end surfaces. The main body 17
a and 17b are made of a polymeric piezoelectric material (for example, PVDF, etc.), and are formed in the shape of a rectangular parallelepiped with a length l in the stretching axis direction x and a thickness t in the polarization direction Y, so that the stretching axis direction X forms the front-back direction. They are arranged in the polarization direction Y and face each other so that their polarization directions are opposite to each other. The electrodes 18 and 19, 19 are formed in the form of a thin film from a conductive material,
For example, it is attached to the main bodies 17a, 17b by suitable means such as vapor deposition or baking. Also,
The end electrodes 19, 19 located opposite to each other in the intermediate portions of the adjacent composite vibrators 10, 10 may be provided separately from each other, or may be provided integrally as shown in the figure. By grounding the end electrodes 19, 19 and connecting the intermediate electrode 18 to an appropriate receiver (not shown), the two main bodies 17a, 17b are integrally operated in the same phase. It is composed of

A front plate 20 that can perform at least one of the functions of a protective layer, an acoustic matching layer, and an acoustic lens for these vibrators 10 is provided at the front end of the composite vibrator 10. is provided with a back plate 21 that can function as at least one of a backing layer, an acoustic absorption layer, and an acoustic matching layer.

According to the above configuration, while controlling the phase and amplitude of the potential E _t applied to each rear electrode 15 of the first vibrator 11 as appropriate, the second vibrator 1
By providing a control circuit for appropriately controlling the phase and amplitude of the generated potential E _r between each intermediate electrode 18 of 2... and the input end of the receiver, it can be used as a phased array probe. I can do it.

Furthermore, the acoustic impedance of the first vibrator 11 can be set to be larger or close to that of the second vibrator 12 and the back plate 21 which are connected to both the front and rear ends of the first vibrator 11, so that half-wavelength resonant operation can be achieved. can be done. On the other hand, since the second vibrator 12 can be set to have an acoustic impedance close to that of the front plate 20 connected to the front end and significantly larger than that of the first vibrator 11 connected to the rear end, the 1/4 wave type It is possible to perform the following actions. Therefore,
By setting the operating center frequencies of the first vibrator 11 and the second vibrator 12 to match,
The second vibrator 12 can have the function of a quarter wavelength matching layer for the operation of the first vibrator 11.

Furthermore, since the first vibrator 11 having the main body 13 made of piezoelectric ceramics is used when transmitting, the efficiency of electrical to acoustic conversion is good, and when receiving, the main body 17 is made of a polymeric piezoelectric material.
Since the second vibrator 12 having the transducers a and 17b is used, the acoustic to electrical conversion characteristics can be made to have a wide band. Moreover, in the first vibrator 11, the piezoelectric d
Since the constant is larger than the piezoelectric g constant, the conversion efficiency during transmission (electrical → acoustic conversion) is better than during reception (acoustic → electrical conversion), and the second vibrator 1
In No. 2, the piezoelectric g constant is larger than the piezoelectric d constant, so the conversion efficiency is better during reception than during transmission. Therefore, compared to the case where only a conventional vibrator having a main body made of piezoelectric ceramics is used, the conversion efficiency at the time of transmission is the same, the conversion efficiency at the time of reception is excellent, and the bandwidth is much wider. I can do it.

In addition, since the second vibrator 12 uses the vibration mode in the stretching axis direction X, the length l of the vibrator bodies 17a and 17b in the vibration direction
can be easily formed to match the desired frequency by simply cutting the material. Therefore, there is no need to laminate and bond a plurality of elements 1 (FIG. 1) in the vibration direction as in conventional devices.
There will be no reduction in acoustic to electrical conversion efficiency. Moreover, in the polymer piezoelectric material, the acoustic impedance in the stretching axis direction X has a value closer to that of the human body, water, etc. than in the polarization direction Y, so that the acoustic matching for these can also be improved.

Furthermore, a main body 17 constituting the second vibrator 12
a and 17b are arranged so that the directions of polarization Y are opposite to each other, so that the adjacent composite oscillators 1
End electrodes 19 facing each other at 0,10,
19 can be integrally formed and shared. Therefore, regardless of the number of main bodies 17..., the number of electrodes need only be one more than the main bodies, and the number of electrodes and conductive wires connected to them can be reduced compared to the case where each main body has two electrodes. Great savings can be made, and the overall structure is simplified, making it easy to manufacture.

Note that the present invention is not limited to the above embodiments. For example, the composite vibrator 10 may be a single one, or the second
The vibrator 12 has a set of main body 17 and end electrode 19,
19. If necessary, the main bodies 17a and 17b of the second vibrator 12 may each be formed from a plurality of elements, and in this case, the elements constituting one set of main bodies have the same polarization direction and are arranged in the polarization direction. It is assumed that it has been polymerized. Furthermore, in particular, the length l in the direction of the stretching axis
In the case of a low-frequency vibrator body with a long length, the bodies 17a, 17b and the electrodes 18, 19, etc. (or between these elements if the body is made up of multiple elements) are coated with silicone oil, for example. They may be bonded together by the surface tension of a thin film made of an insulating liquid such as . With this configuration, the degree of freedom of the vibrator body in the stretching axis direction X is greater than in the case of vapor deposition, baking, or bonding with an adhesive, etc., which further improves the electrical to acoustic conversion efficiency and significantly reduces the manufacturing work. It can be simplified to In addition, various modifications and applications are possible within the scope of the gist of the present invention.

As described above, the present invention is provided with a vibrator (first vibrator) having a main body made of piezoelectric ceramics, in which a polymeric material is placed opposite to the vibrator and in front of the vibrator in the direction of the sound field. A second vibrator, which has a main body made of a piezoelectric material and electrodes arranged in the polarization direction of the main body, and utilizes a vibration mode in the direction of the elongated axis, is arranged such that the elongated axis direction is in the sound field direction. It is characterized by being arranged parallel to the Therefore, by using the first transducer for transmitting and the second transducer for receiving, it is possible to construct a probe with good electroacoustic mutual conversion efficiency and broadband characteristics.
In addition, since the second vibrator uses the vibration mode in the direction of the stretching axis, it is easier to manufacture than the conventional vibrator that uses the vibration mode in the polarization direction, and it also improves the acoustic to electrical conversion efficiency and the human body. Acoustic matching against water and the like can be improved. Furthermore, by using the first and second oscillators so that their operating center frequencies match, the second oscillator can function as a 1/4 wavelength matching layer for the first oscillator. can do. A phased array probe can be constructed by arranging a desired number of composite vibrators having the first and second vibrators.

Further, by configuring the second vibrator to have two sets of bodies arranged in the polarization direction with different directions of polarization, and an intermediate electrode interposed between these bodies, Particularly in the case of a phased array type, the structure can be simplified and manufacturing work can be facilitated. In this case, the electroacoustic conversion efficiency and workability can be further improved by bonding the vibrator main body and the electrode to each other by the surface tension of a thin film made of an insulating liquid interposed therebetween.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram schematically showing a conventional example, and FIG. 2 is an explanatory diagram schematically showing an embodiment of the present invention. 10... Composite vibrator, 11... First vibrator, 12
...Second vibrator, 13, 17a, 17b...Main body,
14, 15...Electrode, 18...Intermediate electrode, 19...End electrode, X...Stretching axis direction, Y...Polarization direction.

Claims (1)

[Claims] 1. A first transducer for transmitting which has electrodes at both ends of a main body made of piezoelectric ceramics and generates a sound field in the direction of polarization; It has a main body made of a polymeric piezoelectric material and an electrode arranged in a direction perpendicular to the direction of the stretching axis of the main body, and is arranged so that the direction of the stretching axis is parallel to the sound field direction, and vibrates in the direction of the stretching axis. An ultrasonic probe characterized by comprising a second transducer for reception that utilizes a mode. 2. The second vibrator has two sets of bodies arranged in the polarization direction with different polarization directions, and an intermediate electrode interposed between these bodies. An ultrasonic probe according to claim 1, characterized in that: 3. The second vibrator is characterized in that the main body and the electrode are bonded to each other by the surface tension of a thin film made of an insulating liquid interposed between them. Ultrasonic probe.