JPS6352054A - Array type ultrasonic probe - Google Patents

Abstract

PURPOSE:To realize wide band characteristics and to obtain high distance resolution by making the curvature of an acoustic matching layer less than the curvature of a vibrator so that the thickness of the acoustic matching layer is about 1/4 as large as wavelength over the entire surface. CONSTITUTION:The vibrator 1 is a rectangular vibrator which has a concave surface of curvature R1 as a radiation surface for an ultrasonic wave and a plane surface as a back surface where a packing material 2 is provided. This vibrator is obtained by working only the surface of a rectangular ceramic substrate into the concave surface, and providing an electrode and then performing polarization. Then the vibrator is adhered to the packing material 2 and then cut into a rectangular vibrator with specific width, thereby obtaining an array type probe. For example, when epoxy resin of, for example, 2,900m/s in acoustic speed is used for the acoustic matching layer 3, the 1/4-wavelength acoustic matching layer 3 needs to be about 0.11mm thick at the center part and about 0.21mm thick at the end arts. For the purpose, the curvature of the matching layer 3 is about 50mm. Consequently, the 1/4-wavelength acoustic matching layer 3 is obtained over the entire surface, the wide range characteristics are realized, and the high distance resolution is obtained.

Description

[Detailed description of the invention] [Purpose of the invention] (Industrial application field) This invention relates to an ultrasonic probe.

(Prior Art) As an important characteristic of an ultrasonic probe, distance resolution, which represents resolution in the propagation direction of ultrasonic waves, is evaluated.

The resolution of an ultrasonic probe is determined by its three main components: a transducer made of piezoelectric material such as piezoelectric ceramic that emits ultrasonic waves; Backing material for suppressing Q.
Further, the radiation surface of the vibrator includes an acoustic matching layer for acoustic matching with the subject. Generally, one way to improve the resolution of an ultrasonic probe is to increase the acoustic impedance of the backing material. This is a method of lowering the Q of the vibrator using the high acoustic impedance of the backing material and achieving high resolution by providing broadband frequency characteristics. The acoustic impedance of this backing material is 0.5 of the acoustic impedance of the piezoelectric vibrator.
Acoustic impedance of ~0.8 times is required, and it must also be excellent in absorbing ultrasonic waves.
Composite materials made by mixing and molding resin and metal powder are conceivable as backing materials that satisfy these requirements, but it is not easy to create materials that meet these requirements.

On the other hand, since the frequency of ultrasonic waves is determined by the thickness of the transducer, there are transducers that aim to include many frequencies, that is, to widen the band, by making one transducer non-uniform in thickness. As an example of this, by making the ultrasonic emission surface of the transducer concave and the back surface flat, it is possible to achieve a wider band and higher resolution.Also, since the ultrasonic emission surface is concave, it is possible to increase the ultrasonic beam. Although distance resolution and azimuth resolution can be improved like 9 and above, which have the feature of focusing, the effect of the acoustic matching layer is small because it uses an acoustic matching layer of a certain thickness. There were drawbacks.

(Problems to be solved by the invention) Conventional acoustic matching layers used plastic films with a certain thickness, so it was not possible to obtain an acoustic matching effect corresponding to a wide range of frequencies, and a sufficiently wide band could not be obtained. An object of the present invention is to provide an array type ultrasonic probe having high distance resolution by configuring an acoustic matching layer with a thickness of 1/4 wavelength corresponding to a wide frequency band.

[Structure of the invention]

(Means for Solving the Problems) The ceramic resonator used in the present invention has a flat back surface and a concave surface having a curvature R1, so that the frequency is highest at the thinner center part, and the frequency at the end part is the highest. The frequency has a characteristic of decreasing as it reaches .

The 1/4 wavelength acoustic matching layer suitable for this concave resonator should be thinnest at the center where the J#I wave number is high, and as the frequency decreases towards the ends, it needs to be thicker than the center. In the present invention, the thickness of the acoustic matching layer is approximately 174 wavelengths over the entire surface, and the curvature R2 of the acoustic matching layer is smaller than the curvature R8 of the vibrator.

(Function) According to such a configuration, 17
It is possible to form a four-wavelength acoustic matching layer, achieve broader band characteristics, and obtain high distance resolution.

(Example) Figure 1 shows a cross-sectional view of an array probe.
This is a rectangular vibrator whose ultrasonic wave emission surface is a concave surface with a curvature RL and whose back surface is flat and has a backing material (2). This resonator is manufactured by processing only the surface of a rectangular ceramic substrate into a concave surface, providing electrodes, and then bonding it to a zero-order backing material ■ that performs polarization, and then forming a rectangular resonator with a predetermined width. Cut to obtain an array type probe. Width: 1.5 m, length: 12
-m, curvature R1 = 70m, thickness at the center is 0.35m,
For a rectangular vibrator with an end thickness of 0.62 m, approximately 3.5
~6.5 M) lz. *e
The speed of sound in the matching layer is 2900! When using a l/S epoxy resin, the 1/4 wavelength acoustic matching layer is required to have a thickness of about 0.11 mm at the center and about 0.21 mm at the edges. The curvature of the matching layer to obtain this thickness is approximately 501, and if the thickness at the center is 0.11 m, the thickness at the end is approximately 0.21 m, and the curvature is approximately 17 mm over the entire surface.
An example of the manufacturing method will be described with reference to FIG. 2, in which a four-wavelength acoustic matching layer (1) is obtained. First, Figure 2 (a)
As shown in the figure, a concave rectangular vibrator is formed on a backing material (22), and then a liquid epoxy resin (23) is applied. After defoaming the epoxy resin, as shown in FIG. 2(b), a semi-cylindrical jig (25) having a curvature R□=50+rn is pressed from above, and the resin is cured to a predetermined thickness.
Acoustic matching M(24) of 74 wavelengths is obtained. At this time, if a fluororesin film (24) is used between the jig (25) and the acoustic matching layer (26), the jig (25) and the acoustic matching layer can be easily removed. Also, instead of fluororesin film, other plastic films,
For example, if a polyethylene or polyester film is used, it can be combined with the acoustic matching layer (23) to form a two-layer acoustic matching layer.

[Effects of the Invention] According to the above-described probe of the present invention, the thickness of the acoustic matching layer is thin at the center and becomes thicker toward the ends, so that an acoustic matching layer of approximately 174 wavelengths can be formed over the entire surface. Therefore, good acoustic matching can be obtained on the entire surface,
Broadband characteristics can be achieved and high distance resolution can be obtained.

[Brief explanation of drawings]

1I 121 is a perspective view for explaining the present invention in detail, and FIG. 2 is a sectional view for explaining the manufacturing method of the embodiment of the present invention. 1... Concave rectangular vibrator 2... Backing material 3... Acoustic matching layer. Agent Patent Attorney Nori Chika Ken Tama Takehana Kakuo Figure 1 (αn(b@2)

Claims (1)

[Claims] In an array type ultrasound probe configured by arranging a plurality of rectangular transducers each having a flat back surface and a concave surface, the acoustic matching layer has a concave surface with a curvature smaller than the curvature of the rectangular transducer having a concave surface. An array type ultrasonic probe characterized in that an acoustic matching layer of approximately 1/4 wavelength can be formed over the entire surface.