JPS5875056A - Probe - Google Patents

Abstract

PURPOSE:To obtain a probe which makes the effective sound field constant independently of frequency, by making a transmittable or receivable ultrasonic frequency in the side of the aperture end lower than that in the side of the center of the aperture face. CONSTITUTION:A piezoelectric element 2 consists of a disc-shaped element, which is provided in the center, and a torus-shaped element which is provided around this disc-shaped element in a shape like a concentric ring, and the whole of a transducer is formed so as to have a concave in the center for the purpose of forming a focus. A disc-shaped electrode 6 and a ring-shaped electrode 7 are formed on the back of the disc-shaped piezoelectric element in the center, and an earth electrode 5 is formed on all of the surface of this element. Ring-shaped electrodes 8-13 arranged on concentric circles are formed on the back of the ring-shaped piezoelectric element, and the earth electrode 5 is formed on all of the surface of this element. A back absorbing layer 4 is provided on the back of the whole of the transducer. The thickness of the piezoelectric element or a matching layer 3 is adjusted for every element to make the shape of the long- distance transmission sound field constant throughout a desired frequency band.

Description

[Detailed description of the invention] This invention uses ultrasonic waves to scoop and inspect media.

The present invention relates to a probe used in an ultrasonic measuring device for diagnosis, etc., and particularly to a probe that can improve the shape of the effective sound field in the far-field noise field κ.

Conventionally, ultrasound user-side constant value IT. using ultrasound transmission, reflection scattering, etc. For example, ultrasound camera, hologram, reflection imaging device, OT! % when busy with installation/aperture synthesis equipment, etc.
It is designed to use a slow aR medium pulse wave of a predetermined frequency a (including frequency band).An ultrasonic transducer for such a device uses a single ultrasonic transducer.
- those with a sa element (e.g. disc number)
or.

4x several elements (such as the Ayu Ue-to Array, the Linear Takiguchi Synthesis Array, etc.) are used. And in the latter case,
Send each element simultaneously, sequentially, or further.
The reception time phase is being changed.

However, gl
It becomes as shown in the figure. The transmitting sound field of a disk-shaped ultrasonic transducer with diameter D in the direction of force I117j is as follows:
At nine o'clock.

is given by D12) in the distance and is given by the beam diameter %7 at a long distance.

Therefore, the transmitted sound field created by the ultrasonic transducer is approximately determined by the frequency and the geometry of the transducer. Same}? In the case of using a speed ether, the frequency will be different for every 4 frequencies. This #f is naturally a sound field diffusion type, and 4. Even if it is a convergent form, the size of the transducer is the same unless it is infinitely small or infinitely large.

In the case of a wide frequency bandwidth such as a pulse, the transmitting sound field shape is centered at W49, and the transmitting sound field shape is set at the upper limit or lower frequency within the above-mentioned circumferential range. becomes a different one. For this reason, even when measuring the shape of [13 constant value using ultrasonic waves, for example, {III-fixed-fix-Zhao will be introduced. Mafc
In order to measure the material temporality of each part, for example, the tissue characteristics of each part in a living body, the 9I number wave number (
The interaction of the ultrasonic waves with substances and tissues causes an effect on the frequency. However, there are efforts being made to utilize different things. In the case of this type of usage layer, the original measured value of each circumference ms is either due to ζ and κ, whose interactions with substances and tissues vary depending on the frequency, or because the effective sound field shape is constant with frequency. I don't know if this is due to the difference. , will introduce a fatal boss into the lilJ fixed result.

The present invention aims to solve the above points,
To provide a middle probe that can keep the effective sound field constant regardless of frequency. ◎And for that purpose, the probe of the present invention has a predetermined opening surface.

In a probe that transmits or receives ultrasonic waves to or from a medium, if the probe is placed at the aperture a- from the center of the aperture surface, the frequency of the ultrasonic waves that can be received by It is characterized by a low peripheral RFC number on the center side.

In addition, in the present invention, the phrase "effective sound field" is used in the furnace, and the phrase can be considered to be a general term for each of the following fields, for example. That is.

(A) Transmission sound field (actual sound field) Ultrasonic transducer refers to the field of ultrasound output actually emitted as ultrasound, and includes diffused waves in ultrasound optical cameras, holograms, aperture synthesis, etc. (II plane・
Beam-shaped focused wave by concave transducer, (ji
It means a sound field actually formed inside the body to be measured by focusing or coordinating the lt array elements by time-phase control.

(B) Receiving sound field (decreased receiving sensitivity) The ultrasonic waves generated from the coordinate points inside the body to be measured due to transmission, refraction, reflection, scattering, etc. are converted into ultrasonic detectors. means the field of spatial distribution of sensitivity when +
1) Directivity of transducer) Focusing s 1111
1st grade II! Sensitivity - means a field of receiving sensitivity formed in the same manner.

(0) Transmitting/receiving field (actual mgi sound field') The above receiving sound field is superimposed on the transmitting sound field actually formed inside the body to be measured, resulting in the actual receiving 11! Santa II! Becomes No. 1. Therefore, in the case of the above-mentioned zero-reflection method in which the transmitting sound field and the receiving sound field are spatially and temporally superimposed to form the actual receiving signal sound field, separate transducers for transmitting and receiving are used. During aperture synthesis, an appropriate IP transmitting/receiving transducer arrangement is taken for an acousto-optical camera, hologram, etc.

However, in any case, the above transmission sound field and reception
Sound fields are superimposed spatially and temporally, giving a characteristic sound field including transmission and reception, and the transmission and reception fields refer to this sound field.

(D) fI sound field The calculation process fMt'' may be applied to the received sound field. For example, deconvolution calculation using a despreading function or lli image processing for the focused sound field. In the aperture synthesis for the Mayu diffused sound field, calculation processing may be performed for the filf1 issue.By performing these processes, the apparent convergence level for the filf1 is increased. It is possible to sharpen the spatial resolution K and virtually sharpen the sound field.The sound field is a virtual sound field or processing given by such a relief field. The sound field is the result of the process being carried out.

This will be explained below with reference to the drawings.

Figure 3 shows the principle of an embodiment of the present invention. In the figure, l is the transducer, δ is the central axis, 10 is the opening center%, 1m is the predetermined position, and the weight is the thickness at the opening center. %T
is the thickness of the transducer at position fi1m.

It is generally known that the resonance w8 wave number f of a piezoelectric element can be expressed by the following equation, where V is the sound velocity within the vibrating element and t is the thickness.

If the ratio of D and wavelength λ is kept constant, the shape in the far-field sound field is the same for any shoulder*a. Therefore, the shape of the swth
The shape of the ultrasonic wave emitted from center position lo and position l- shown in AK in the far-field sound field is as follows: f
If o=fm and the aperture diameter at each position is DosDa, then it can be generally set to satisfy the following equation.

10xDom/axDa +6) Therefore, the following equation can be derived as a function representing the thickness at the 1 m position of Equation 1) and Equation (6).

T.

Te na□　DI　’’　　　　　　　　+7)D.

It can be done.

Also, in order to focus the ultrasonic waves transmitted from the transducer 1, there is a method in which the line surface lb having the center of curvature is curved at a predetermined position of the medium Al4IO in the figure.

It is generally known that when the surface 1b is curved, the curve dglct is formed by a function in which the n function wt shown in equation (8) is superimposed.

In this way, the position thickness of the opening of the transformer l is set to #I
(By setting to satisfy formula 81.

Every cycle tI1.
It is possible to match the actual sound field shape at the far front jiiK with respect to the ultrasonic waves at llL.

Fig. 8 (M) * (B) J'f An embodiment of the present invention, and Fig. 4 (M) - (B) are respectively shown in Fig. 8. Modification Example 111 (M) is a front view of an ultrasonic transducer according to an embodiment of the present invention, and mawJ (B) is 1181g (A)
-X' cross-sectional view is shown. 8 in the figure is a piezoelectric element made of PZT, etc., S is an acoustic impedance matching layer, 4 is a back rIn absorption layer, 5 is a ground electrode, and 6
1 to 18 are annular electrodes, and 14 is a small St that can be provided as necessary to reduce the OI4 force joint t.
Express it.

In the illustrated case, the piezoelectric element 3 is a disk-shaped element provided in the center and its jiIIIllll! The entire transducer is formed with a concave portion in the center to form a focal point. A circular electrode 6 and an annular electrode 7 are formed on the back side of the central disc-shaped piezoelectric element, and a ground electrode 5 is formed on the entire mall 1.

Further, on the back surface of the annular piezoelectric element, there are annular electrodes 4Ii8 and -L1g# arranged concentrically, and a ground electrode device is formed on the entire @ surface side. A #c//i back absorption layer 4 on the back side of the entire transducer is also formed.

In this specification, the phrase "ultrasonic transducer element" is used, but when the above-mentioned pair of ground electrodes are provided opposite to each other on the front and back sides of the piezoelectric element S, 1 Two piezoelectric elements S, K11la's super 1fII! It is assumed that a transducer element exists.

Of course, the piezoelectric elements are divided into four parts for each element.
In the illustrated embodiment, the thickness of the piezoelectric element and/or the matching layer may be 8 thickness is adjusted for each element. For example, the element corresponding to the electrode 6 is adjusted to have high i efficiency for the desired upper limit frequency and still have a predetermined efficiency for the lower limit frequency, and the element corresponding to the electrode 18 is adjusted to have a high i efficiency for the desired upper limit frequency, and the element corresponding to the electrode 18 is adjusted to The KFJ4 is arranged so that it has a high efficiency for higher frequencies, but has an efficiency of almost 1 or a lower efficiency for higher frequencies, and the elements corresponding to each electrode 1s of those cabinets are between the above two elements. O g I IIi! I e '41 Explained with reference to figure t.
As (, there is no dependence on the number of units, and at a long distance, λ・Z/D
Therefore, in order to eliminate the frequency dependence of the shape of the long-distance transmission sound field mentioned above, the wavelength λ should be increased so that the above-mentioned λ/D is 1 meter. As the diameter becomes larger, the diameter Dt shown in FIG. 1 can be increased.

In the case shown in Figure 8, an element with high efficiency t for high frequencies exists in the center, and elements whose efficiency gradually decreases Y for high frequencies are arranged toward the periphery. The size of the desired aperture is changed in proportion to the size of the aperture, and it is possible to make the shape of the long-distance inertia field the same across the above range. , some trout have multiple small elm 4
In order to simplify the Ichisei which has been reduced to the number of elements a1 in the figure, even if 14 are added, the number of elements in the figure is reduced to a1. can be integrated into one electrode.
In the case shown in Fig. g4, the piezoelectric elements S and /17t are constructed in such a way that the thickness of the matching layer opening is gradually reduced, as in the case of t shown in Fig. 3. In the case shown in FIG. 4(A), electrodes 6 and 7.8 iυ011 to 1 m or -rL1
') K aggregate nmjl! In the case shown in Fig. 4 (CB), electrodes 6 and 7.8, Zl and 11 are each 1'':) K aggregated, and in the case shown in Fig. 4 (0), electrodes 6 to 9, and 10 to 18 are It is summarized in one thing.

As described above, when operating the t-type transformers shown in FIG. 1-4411ii3, they are driven simultaneously.

In addition, from each position of the workpiece 9, an ultrasonic wave signal having a center frequency component uniquely determined by the meshwork at each position and occupying a predetermined frequency band is transmitted.

Then, when the thickness is adjusted as in the present invention, each station #! from each position. The actual sound field shape of several ultrasonic waves is the far sound field Ki
? The present invention has the effect of minimizing the difference in entertainment due to the difference in the shape of the f-bridge.

In addition, in the embodiments described above, the relationship between each of the frequency bands that can be transmitted from each position is not explained in detail, but regardless of the 5Aj1ii example of the antenna, it is possible to The super 1ttIIL Shuhanmin Teijo who can send with 1
41 is preferably configured to include a frequency band of ultrasonic waves that can be transmitted at a position located on the side of the field mouth.

This is 1m if the band that can be transmitted on the aperture center side includes the band that can be transmitted closer to the aperture end and transmitted at 4 AI castles.
Regarding the band that can be transmitted from the end of the mouth, it will be transmitted at a cliff where the center part of the opening does not exist, and the ultra f of that band will be transmitted.
This is because it is expected to have an adverse effect on the directivity of waves, etc. As explained above, according to the present invention, the shape of the ultrasonic beam transmitted from the probe can be
They can be made into the same shape even if they are different.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram illustrating the first question from this paper. The cocoon S diagram is an explanatory diagram of the principle, and Figures 8 (A) and (B) are one example of the present invention.
0) are diagrams each showing a modification of the illustrated transducer. In the diagram, 1el is a piezoelectric element, S is an acoustic intensity matching layer, 4 is an absorption layer, and S is a ground voltage a. 6 to 18 are electrodes, respectively. Shin 11v-Applicant ・rIJNa, Fujika Co., Ltd. Mimi 1
1! ]. Bu 40

Claims (1)

[Claims] 0) A probe that has a predetermined aperture surface and transmits or receives ultrasonic waves to or from a medium, the probe having a predetermined aperture surface that is located closer to the aperture end than the center of the rupture surface. A probe characterized in that the frequency of ultrasonic waves that can be transmitted or received is lower on the center side of the aperture surface (2) The probe has an ultrasonic vibrating element, The vibrator is configured so that the thickness on the open end side is thicker than the thickness on the center side, and the thickness of the vibrator at the center position is equal to the upper limit frequency band a of the frequency band in which the probe can operate. The thickness is such that the number of operating center stations rll at each position on the opening end side is in the frequency a band corresponding to each position, and the operating center network wave number is formed in such a thickness that the operating center frequency is ff described in claim 0)
l! Ugly child. (3) A probe according to claim (1) or (2), in which the value of the vibrator is divided by aK+ in the direction from the center of the aperture toward the aperture 4. (4)#
The probe includes an ultrasonic transducer having a predetermined common fRR wavenumber;
# A matching layer that matches the acoustic impedance of the ultrasonic transducer and the medium, and # The center station tILa at each position of the aperture is adjusted by the matching layer. Scope No. 11 or No. 1 Section or Collection (8)
XJ era probe B thing and 1
The probe according to claim 1, wherein the axillary acoustic matching layer and the backing layer align the central station *a at the open can position to v4. <<6>> The vibrator has a plane κ drive or a bond extracting electrode and a ground electrode that face each other.
At least % of the driving electric motor etc. should be divided into *a 4
#Characteristic tfClaim 41) or 7tFi 1st
2》 term or striped 《3》 term is good {4) Probe of product. <<7>> The frequency band of the ultrasonic waves transmitted from the predetermined position of the aperture of the probe includes the frequency band of the ultrasonic waves transmitted from the aperture positions outside the predetermined position. Characteristics of claim (1) e Jig 12
) term - stripe (3) term. Section <<4> s #I (Is) Section) Section (6>) Distributed probe ●