Ultrasonic probe

Abstract

To reduce intensity of a grating beam without reducing a transducer pitch of a transducer array or reducing a transmission frequency of ultrasonic waves.SOLUTION: An ultrasonic probe includes a transducer array 10 consisting of a plurality of transducers 12 arranged in an array direction. Each transducer 12 is virtually divided into a first virtual part 12a and a second virtual part 12b by a straight line 22 passing through a center of gravity 20 of the transducer 12 and extending in the array direction. The transducer 12 has such a shape that a first virtual center of gravity 24a, the center of gravity of the first virtual part 12a, and a second virtual center of gravity 24b, the center of gravity of the second virtual part 12b, are located at different positions in the array direction.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] This specification discloses an improvement to an ultrasound probe. [Background technology]

[0002] There is known an ultrasound diagnostic device that can form ultrasound tomographic images representing cross sections in an ultrasound scanning plane and perform various measurements based on waves reflected from a subject when ultrasound is transmitted to the subject. The ultrasound diagnostic device is equipped with an ultrasound probe that is brought into contact with the subject and transmits and receives ultrasound waves to the subject. The ultrasound probe is equipped with multiple transducer elements, and ultrasound waves are transmitted from the transducer elements toward the subject by supplying transmission signals to each of the transducer elements from the ultrasound diagnostic device main body. The transducer elements also receive reflected waves from the subject, convert the reflected waves into electrical signals, and transmit the received signals to the device main body.

[0003] Various improvements have been proposed for ultrasonic probes, particularly for the arrangement of multiple transducer elements. For example, Patent Document 1 discloses an ultrasonic probe in which transducer elements are arranged in a one-dimensional direction (array direction) to obtain two-dimensional and three-dimensional images in real time. Patent Document 2 also discloses a cylindrical ultrasonic transducer in which the transducer elements are arranged inclined relative to the circumferential direction. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 10-62396 [Patent Document 2] Japanese Patent Application Publication No. 11-64492 Summary of the Invention [Problem to be solved by the invention]

[0005] However, there are cases where a virtual image appears in an ultrasonic tomographic image formed by an ultrasonic diagnostic device. Such a virtual image is also called an artifact. One cause of the artifact is a grating beam. Grating beams will be described with reference to Figs. 45 to 48.

[0006] Fig. 45 is a plan view of a transducer element array PEA provided in a conventional ultrasonic probe, and Fig. 46 is a side view of the conventional transducer element array PEA. In this specification, a plan view means a view from the depth direction, and a side view means a view from the elevation direction. In addition, in this specification, the arrangement direction of multiple transducer elements PE is called the array direction, the direction parallel to the transducer element surface (the same plane) and perpendicular to the array direction is called the elevation direction, and the direction perpendicular to the array direction and the elevation direction is called the depth direction.

[0007] As shown in FIG. 45, a conventional transducer element PE is assumed to have a substantially rectangular shape extending in the elevation direction. When a transmission signal is supplied to each transducer element PE, ultrasonic waves are output from each transducer element PE. In FIG. 46, the wavefront WF of the ultrasonic waves output from each transducer element PE is represented by an arc centered on each transducer element PE. The wavefronts WF from each transducer element PE are combined to form a composite wavefront CWFm, and the ultrasonic waves have the properties of a beam. The direction indicated by the arrow Dm perpendicular to the composite wavefront CWFm is the transmission direction of the ultrasonic beam. The intended (target) ultrasonic beam to be output is called the main beam. As shown in FIG. 46, if ultrasonic waves are output simultaneously from each transducer element PE, the direction of the main beam will be parallel to the depth direction. However, the direction of the main beam can be controlled by controlling the output timing of the ultrasonic waves from each transducer element PE.

[0008] Here, an ultrasonic beam (called a grating beam) may be formed in a direction different from the main beam. For example, as shown in Figure 46, consider a case where ultrasonic waves are output simultaneously from each transducer element PE and the direction of the main beam is set parallel to the depth direction. Each transducer element PE repeatedly outputs ultrasonic waves based on the transmission frequency, and a grating beam is formed by combining a wavefront WF output from a certain transducer element PE and a wavefront WF output from a transducer element PE adjacent to the certain transducer element PE, which is shifted by one period from the wavefront WF.

[0009] Figure 47 is a diagram showing the principle of generation of a grating beam. First, a wavefront WFa is output from transducer element PEa. At this time, wavefronts are also output from other transducer elements PE, including transducer elements PEb and PEc, but these wavefronts are not shown in Figure 47. One period later (1 / f [s] later if the transmission frequency is f), a wavefront WFb is output from transducer element PEb. Wavefronts output from transducer elements PE other than transducer element PEb at this time are also not shown. After another period, a wavefront WFc is output from transducer element PEc. Wavefronts output from transducer elements PE other than transducer element PEc at this time are also not shown.

[0010] Then, the wavefronts WFa, WFb, and WFc are combined to form a composite wavefront CWF g is formed, which also has the properties of a beam. This is a grating beam, and the transmission direction of the grating beam is the direction indicated by the arrow Dg, which is perpendicular to the composite wavefront CWFg.

[0011] Fig. 48 is a diagram for explaining the generation conditions of a grating beam. In Fig. 48, the pitch between transducer elements PE in the transducer element array PEA (referred to as transducer element pitch in this specification) is indicated by P, and the angle of the main beam direction (direction of arrow Dm) with respect to the depth direction is indicated by θm. When multiple transducer elements PE are arranged on a plane, the generation conditions of a grating beam are expressed by the following equation 1. P>λ / (1+sinθm) Equation 1 In Equation 1, λ is the wavelength of the ultrasonic wave output from each transducer element PE, and is the reciprocal of the transmission frequency of the ultrasonic wave.

[0012] From Equation 1, it can be seen that the lower the transmission frequency of the ultrasound (the longer the wavelength), the more difficult it is to generate a grating beam, but from the perspective of improving the image quality of ultrasonic tomographic images, it may not be appropriate to lower the transmission frequency of the ultrasound. Also, from Equation 1, it can be seen that the smaller the transducer element pitch, the more difficult it is to generate a grating beam, but there are limits to how small the transducer element pitch can be due to cost and manufacturing issues.

[0013] The ultrasonic probe disclosed in this specification aims to reduce the intensity of the grating beam without reducing the transducer element pitch of the transducer element array and without reducing the transmission frequency of the ultrasonic waves. [Means for solving the problem]

[0014] The ultrasonic probe disclosed in this specification is an ultrasonic probe having a transducer element array consisting of a plurality of transducer elements arranged in an array direction, wherein when the transducer elements are virtually divided into a first virtual portion and a second virtual portion by a straight line passing through the center of gravity of the transducer elements and extending in the array direction, each of the transducer elements has a shape such that a first virtual center of gravity, which is the center of gravity of the first virtual portion, and a second virtual center of gravity, which is the center of gravity of the second virtual portion, are located at different positions in the array direction, and due to the shape, the grating beam output from the first virtual portion and the grating beam output from the second virtual portion cancel each other out due to a phase shift, thereby reducing the intensity of the grating beam output from each of the transducer elements.

[0015] In a plan view seen from the depth direction, the shape of the vibration element may be a polygon having five or more sides, or at least one side of the vibration element may be curved.

[0016] In a plan view seen from the depth direction, the shape of the first imaginary portion and the shape of the second imaginary portion may be in a point-asymmetric relationship with respect to the center of gravity of the vibration element.

[0017] A virtual center-of-gravity distance, which is a distance between the first virtual center of gravity and the second virtual center of gravity in the array direction, may be less than a pitch of transducer elements in the transducer element array.

[0018] When the plurality of vibration elements are arranged on a plane, the distance between the virtual centers of gravity may be half the pitch of the vibration elements.

[0019] When the plurality of vibration elements are arranged on a curved surface, the distance between the virtual centers of gravity is preferably half the virtual pitch P' between the vibration elements. Here, the virtual pitch P' is P'=Psinθg / sin(θg-β) β=(N / 4)*α where P is the transducer element pitch, θg is the beam angle of the grating beam, N is the number of aperture transducer elements, and α is the angle pitch between the transducer elements. [Effects of the Invention]

[0020] According to the ultrasonic probe disclosed in this specification, the intensity of the grating beam can be reduced without reducing the transducer element pitch of the transducer element array and without reducing the transmission frequency of the ultrasonic waves. [Brief explanation of the drawings]

[0021] [Figure 1] FIG. 1 is a first diagram for explaining the conditions for canceling out grating beams. [Figure 2] FIG. 10 is a second diagram for explaining the cancellation conditions of the grating beams. [Figure 3] FIG. 2 is a side view of the transducer element array of the ultrasonic probe according to the first embodiment. [Figure 4] FIG. 2 is a plan view of a transducer element array of the ultrasonic probe according to the first embodiment. [Figure 5] FIG. 2 is an enlarged plan view of the vibration element. [Figure 6] FIG. 5 is a diagram showing a grating beam generated in a conventional linear array at the elevation position indicated by A in FIG. 4. [Figure 7] 5 is a diagram showing a grating beam generated in the transducer element array according to the first embodiment at a position in the elevation direction indicated by A in FIG. 4. FIG. [Figure 8] FIG. 5 is a diagram showing a grating beam generated in a conventional linear array at the elevation position indicated by B in FIG. 4. [Figure 9] 5 is a diagram showing a grating beam generated in the transducer element array according to the first embodiment at the position in the elevation direction indicated by B in FIG. 4. FIG. [Figure 10] FIG. 5 is a diagram showing a grating beam generated in a conventional linear array at the elevation position indicated by C in FIG. 4. [Figure 11] 5 is a diagram showing a grating beam generated in the transducer element array according to the first embodiment at a position in the elevation direction indicated by C in FIG. 4. FIG. [Figure 12] FIG. 5 is a diagram showing a grating beam generated in a conventional linear array at the elevation position indicated by D in FIG. 4. [Figure 13] 5 is a diagram showing a grating beam generated in the transducer element array according to the first embodiment at a position in the elevation direction indicated by D in FIG. 4. FIG. [Figure 14] FIG. 5 is a diagram showing a grating beam generated in a conventional linear array at the elevation position indicated by E in FIG. 4. [Figure 15]5 is a diagram showing a grating beam generated in the transducer element array according to the first embodiment at a position in the elevation direction indicated by E in FIG. 4. FIG. [Figure 16] FIG. 1 shows a grating beam at a given depth for a conventional linear array in two-dimensional space in the array and elevation directions. [Figure 17] 10A and 10B are diagrams showing grating beams at a predetermined depth for the transducer element array according to the first embodiment in a two-dimensional space in the array direction and elevation direction at the predetermined depth. [Figure 18] FIG. 1 shows the grating beams generated in a conventional linear array across the elevation direction. [Figure 19] 10A and 10B are diagrams showing grating beams generated in the transducer element array according to the first embodiment in the entire elevation direction. [Figure 20] 4 is a graph showing the relationship between signal intensity and beam angle at a predetermined depth in the first embodiment. [Figure 21] 10 is a graph showing the relationship between the grating level and the virtual center-of-gravity distance at the beam angle at which the intensity of the grating beam reaches its peak in the first embodiment. [Figure 22] FIG. 10 is a first diagram for explaining an appropriate upper limit of the distance between virtual centers of gravity. [Figure 23] FIG. 10 is a second diagram for explaining an appropriate upper limit of the distance between virtual centers of gravity. [Figure 24] FIG. 10 is a diagram showing a modified example of the vibration element. [Figure 25] FIG. 10 is a side view of a transducer element array of an ultrasonic probe according to a second embodiment. [Figure 26] FIG. 5 is a diagram showing a grating beam generated in a conventional curved array at the elevation position indicated by A in FIG. 4. [Figure 27] 5 is a diagram showing a grating beam generated in the transducer element array according to the second embodiment at the position in the elevation direction indicated by A in FIG. 4. FIG. [Figure 28]FIG. 5 is a diagram showing a grating beam generated in a conventional curved array at the elevation position indicated by B in FIG. 4. [Figure 29] 5 is a diagram showing a grating beam generated in the transducer element array according to the second embodiment at the position in the elevation direction indicated by B in FIG. 4. FIG. [Figure 30] FIG. 5 is a diagram showing a grating beam generated in a conventional curved array at the elevation position indicated by C in FIG. 4. [Figure 31] 5 is a diagram showing a grating beam generated in the transducer element array according to the second embodiment at the position in the elevation direction indicated by C in FIG. 4. FIG. [Figure 32] FIG. 5 is a diagram showing a grating beam generated in a conventional curved array at the elevation position indicated by D in FIG. 4. [Figure 33] 5 is a diagram showing a grating beam generated in the transducer element array according to the second embodiment at the position in the elevation direction indicated by D in FIG. 4. FIG. [Figure 34] FIG. 5 is a diagram showing a grating beam generated in a conventional curved array at the elevation position indicated by E in FIG. 4. [Figure 35] 5 is a diagram showing a grating beam generated in the transducer element array according to the second embodiment at a position in the elevation direction indicated by E in FIG. 4. FIG. [Figure 36] FIG. 1 shows a grating beam at a given depth for a conventional curved array in two-dimensional space in the array and elevation directions. [Figure 37] 10A and 10B are diagrams showing grating beams at a predetermined depth for a transducer element array according to a second embodiment in a two-dimensional space in the array direction and elevation direction at the predetermined depth. [Figure 38] FIG. 1 illustrates the grating beams generated in a conventional curved array across the elevation direction. [Figure 39]10A and 10B are diagrams showing grating beams generated in the transducer element array according to the second embodiment in the entire elevation direction. [Figure 40] 10 is a graph showing the relationship between signal intensity and beam angle at a predetermined depth in the second embodiment. [Figure 41] 10 is a graph showing the relationship between the grating level and the virtual center-of-gravity distance at the beam angle at which the intensity of the grating beam reaches its peak in the second embodiment. [Figure 42] FIG. 1 is a first diagram for explaining a method for calculating a virtual pitch. [Figure 43] FIG. 10 is a second diagram for explaining a method for calculating a virtual pitch. [Figure 44] 10 is a graph showing the relationship between the main beam width and the virtual center-of-gravity distance. [Figure 45] FIG. 1 is a plan view of a transducer array provided in a conventional ultrasound probe. [Figure 46] FIG. 1 is a side view of a conventional vibration element array. [Figure 47] A diagram showing the principle of generating a grating beam. [Figure 48] FIG. 10 is a diagram for explaining the conditions for generating a grating beam. DETAILED DESCRIPTION OF THE INVENTION

[0022] <Grating beam cancellation conditions> Before describing the first embodiment, the cancellation conditions of the grating beam will be described. Figures 1 and 2 are diagrams for explaining the cancellation conditions of the grating beam. Figure 1 is a plan view of a transducer element array PEA in which each transducer element PE has a substantially rectangular shape extending in the elevation direction.

[0023] The transducer element pitch of the transducer element array PEA shown in Fig. 1 is assumed to be p0. Here, p0, together with the wavelength λ of the ultrasonic waves output from each transducer element PE, satisfies the above-mentioned conditions for generating a grating beam. In other words, when ultrasonic waves are output from each transducer element PE included in the transducer element array PEA, a grating beam is generated.

[0024] Here, consider the case where the transducer element pitch is p0 / 2, that is, half the transducer element pitch that satisfies the grating beam generation condition, as in the transducer element array PEA' shown in Figure 2. In the transducer element array PEA', multiple transducer elements PE are arranged in the array direction, just like in Figure 1, but conceptually, the transducer element array PEA' can be seen as having shaded transducer elements PE'x and white transducer elements PE'y arranged alternately.

[0025] In the transducer array PEA', when viewed in the transmission direction of the grating beam, the grating beam formed by the ultrasonic waves output from the transducer element PE'x and the grating beam formed by the ultrasonic waves output from the transducer element PE'y adjacent to the transducer element PE'x have opposite phases, so the two grating beams cancel each other out. Therefore, by setting the transducer pitch P to half of p0, which satisfies the grating beam generation condition, the strength of the grating beam can be reduced.

[0026] In the embodiments disclosed herein, the grating beam cancellation condition described above is utilized to reduce the intensity of the grating beam.

[0027] First Embodiment FIG. 3 is a side view of the transducer element array 10 of the ultrasound probe according to the first embodiment, and FIG. 4 is a plan view of the transducer element array 10 of the ultrasound probe according to the first embodiment. The ultrasound probe is connected to an ultrasound diagnostic device body for use. The ultrasound probe has a transducer element array 10 made up of a plurality of transducer elements 12. When a transmission signal, which is an electrical signal, is supplied from the ultrasound diagnostic device body to each transducer element 12, each transducer element 12 outputs an ultrasound wave of a transmission frequency (or wavelength) corresponding to the transmission signal. Each transducer element 12 also receives a reflected wave of the output ultrasound from the subject and outputs a received signal, which is an electrical signal, to the ultrasound diagnostic device body. Based on the received signal, the ultrasound diagnostic device body performs various processes, such as forming an ultrasound image (ultrasonic tomographic image or Doppler image) and performing various measurements.

[0028] As shown in Fig. 3, the vibration element array 10 according to the first embodiment is composed of a plurality of vibration elements 12 arranged on a plane. In this specification, a vibration element array composed of a plurality of vibration elements 12 arranged on a plane in this manner is called a linear array. In other words, the vibration element array 10 according to the first embodiment is a linear array. Furthermore, as shown in Figs. 3 and 4, the vibration element pitch in the vibration element array 10 is represented by P.

[0029] The dashed lines in Fig. 4 represent conventional vibration elements whose extension direction is parallel to the elevation direction, as shown in Fig. 45, for example. As shown in Fig. 4, each vibration element 12 included in the vibration element array 10 according to the first embodiment has a shape different from the shape of the conventional vibration element shown by the dashed lines. Hereinafter, the shape of the vibration element 12 according to the first embodiment will be described in detail with reference to Fig. 5.

[0030] Fig. 5 is an enlarged plan view of a vibration element 12. Here, the vibration element 12 is virtually (ideally) divided into two parts by a straight line 22 that passes through the center of gravity 20 of the vibration element 12 and extends in the array direction. In this specification, the part above the line 22 in Fig. 5 (the shaded part) is referred to as a first virtual part 12a, and the part below the line 22 (the open part) is referred to as a second virtual part 12b. Fig. 5 shows a first virtual center of gravity 24a that is the center of gravity of the first virtual part 12a, and a second virtual center of gravity 24b that is the center of gravity of the second virtual part 12b.

[0031] The transducer element 12 has a shape in which a first virtual center of gravity 24a and a second virtual center of gravity 24b are located at different positions in the array direction. In Fig. 5, the first virtual center of gravity 24a is shifted to the left in the array direction with respect to the center of gravity 20, and the second virtual center of gravity 24b is shifted to the right in the array direction with respect to the center of gravity 20. As a result, the first virtual center of gravity 24a and the second virtual center of gravity 24b are shifted by ΔG in the array direction. In this specification, the distance in the array direction between the first virtual center of gravity 24a and the second virtual center of gravity 24b is referred to as the virtual center-of-gravity distance ΔG, and the virtual center-of-gravity distance ΔG is expressed in units of the transducer element pitch P (for example, 0.5P).

[0032] As an example of a shape in which the first virtual center of gravity 24a and the second virtual center of gravity 24b are at different positions in the array direction, the vibration element 12 may have a shape in which the shape of the first virtual portion 12a and the shape of the second virtual portion 12b are point-symmetrical about the center of gravity 20 of the vibration element 12 in a plan view seen from the depth direction. In the example of FIG. 5, the vibration element 12 is a quadrangle (particularly a parallelogram). When the vibration element 12 is a parallelogram, the first virtual center of gravity 24a and the second virtual center of gravity 24b are at different positions in the array direction, so that the extension direction of the vibration element 12 is not parallel to the elevation direction but extends obliquely from top to bottom in FIG. 5 with respect to the elevation direction.

[0033] The effect of the transducer element 12 having the above-described shape will be described below. The ultrasonic wave transmitting / receiving surface of the transducer element 12 has a certain area, and ultrasonic waves are actually output from the entire ultrasonic wave transmitting / receiving surface. However, for simplicity, it is assumed here that ultrasonic waves are output from the first virtual center of gravity 24a for the first virtual portion 12a and the second virtual center of gravity 24b for the second virtual portion 12b. Since the first virtual center of gravity 24a and the second virtual center of gravity 24b are located at different positions (shifted) from each other in the array direction, as described with reference to FIGS. 1 and 2, the grating beam formed by the ultrasonic waves output from the first virtual center of gravity 24a and the grating beam formed by the ultrasonic waves output from the second virtual center of gravity 24b are shifted in phase, and this phase shift causes the two grating beams to cancel each other out. This reduces the intensity of the grating beams. In particular, when the virtual center-of-gravity distance ΔG is set to P / 2, that is, half the transducer element pitch, the phases of the grating beam formed by the ultrasonic waves output from the first virtual center-of-gravity 24a and the grating beam formed by the ultrasonic waves output from the second virtual center-of-gravity 24b are inverted to each other, so that the two grating beams cancel each other out and the intensity of the grating beam is reduced to the minimum. In other words, the optimal value for the virtual center-of-gravity distance ΔG is P / 2.

[0034] 6 to 20, the following describes the results of examining the intensity of the grating beam when the virtual center-of-gravity distance ΔG is set to P / 2. In the following examination, the intensity of the grating beam is examined when the direction of the main beam is set parallel to the depth direction.

[0035] FIG. 6 is a diagram showing a grating beam generated in a conventional linear array (shown by a dashed line in FIG. 4) at the elevation direction position shown by A in FIG. 4 (one end of the transducer element 12 in the elevation direction). FIG. 7 is a diagram showing a grating beam generated in the transducer element array 10 at the elevation direction position shown by A in FIG. 4. FIG. 8 is a diagram showing a grating beam generated in the conventional linear array at the elevation direction position shown by B in FIG. 4. FIG. 9 is a diagram showing a grating beam generated in the transducer element array 10 at the elevation direction position shown by B in FIG. 4. FIG. 10 is a diagram showing a grating beam generated in the conventional linear array at the elevation direction position shown by C in FIG. 4 (the center of the transducer element 12 in the elevation direction). FIG. 11 is a diagram showing a grating beam generated in the transducer element array 10 at the elevation direction position shown by C in FIG. 4. FIG. 12 is a diagram showing a grating beam generated in the conventional linear array at the elevation direction position shown by D in FIG. 4. Fig. 13 is a diagram showing a grating beam generated in the transducer element array 10 at the elevation direction position indicated by D in Fig. 4. Fig. 14 is a diagram showing a grating beam generated in a conventional linear array at the elevation direction position indicated by E in Fig. 4 (the other end of the transducer element 12 in the elevation direction). Fig. 15 is a diagram showing a grating beam generated in the transducer element array 10 at the elevation direction position indicated by E in Fig. 4.

[0036] In Fig. 6, the portion with high signal intensity extending in the depth direction at the center of the array direction represents the main beam MB, and the portion with slightly high signal intensity extending radially at a predetermined beam angle from depth 0 at the center of the array direction represents the grating beam GB. While Fig. 6 representatively shows the beam directions of the main beam MB and grating beam GB, the directions of the main beam and grating beam are the same in Figs. 7 to 15 and Figs. 18 to 19.

[0037] 6 and 7, 8 and 9, 10 and 11, 12 and 13, and 14 and 15, it can be seen that the intensity of the grating beam GB is reduced by the transducer element array 10 according to the first embodiment. The intensity of the grating beam is particularly reduced at the center in the elevation direction (FIGS. 10 and 11). On the other hand, at the ends in the elevation direction (FIGS. 6 and 7, and 14 and 15), the reduction in the grating beam intensity is smaller on one side of the main beam (the left side of the main beam in FIG. 7, and the right side of the main beam in FIG. 15).

[0038] Fig. 16 is a diagram showing a grating beam at a predetermined depth for a conventional linear array in two-dimensional space in the array direction and elevation direction. Fig. 17 is a diagram showing a grating beam at a predetermined depth for a transducer element array 10 in two-dimensional space in the array direction and elevation direction. In the transducer element array 10, the extension direction of each transducer element 12 extends obliquely with respect to the elevation direction, so the direction in which the grating beam is generated is also inclined, as shown by the straight line L in Fig. 17.

[0039] FIG. 18 is a diagram showing grating beams generated in a conventional linear array over the entire elevation direction. FIG. 19 is a diagram showing grating beams generated in the transducer element array 10 over the entire elevation direction. While FIGS. 6 to 15 compare grating beams at each position in the elevation direction, FIGS. 18 and 19 are diagrams obtained by averaging the signal strength at each elevation position. Comparing FIGS. 18 and 19, it can be seen that grating beams are significantly reduced over the entire elevation direction, i.e., over the entire transducer element array 10.

[0040] 20 is a graph showing the relationship between signal intensity and beam angle at a predetermined depth. In FIG. 20, the dashed line graph is a graph for a conventional transducer element whose extension direction is parallel to the elevation direction, and the solid line graph is a graph for the transducer element array 10 according to the first embodiment. In the dashed line graph, the grating peak is at a beam angle of ±57 degrees, and the intensity of the grating beam is significantly increased, while in the solid line graph, it can be seen that the grating beam is significantly reduced.

[0041] FIG. 21 is a graph showing the relationship between the grating level and the virtual center-of-gravity distance ΔG at the beam angle at which the intensity of the grating beam peaks. In the graph of FIG. 21, when the virtual center-of-gravity distance ΔG is 0 (the left end of the graph), the element has the same shape as a conventional transducer element in which the extension direction is parallel to the elevation direction. It can be seen that within the range of the virtual center-of-gravity distance ΔG shown in FIG. 21, the grating level is reduced at least compared to when the virtual center-of-gravity distance ΔG is 0 (conventional). Also, as mentioned above, the grating level is reduced most when the virtual center-of-gravity distance ΔG is P / 2.

[0042] In this way, by configuring the shape of the transducer element 12 so that the first virtual center of gravity 24a and the second virtual center of gravity 24b are positioned at different positions in the array direction, the grating level can be reduced regardless of the virtual center-of-gravity distance ΔG. However, from the viewpoint other than reducing the intensity of the grating level (particularly from the viewpoint of performance degradation of the main beam), there is an appropriate range (appropriate upper limit) for the virtual center-of-gravity distance ΔG.

[0043] 22 and 23 are diagrams illustrating an appropriate upper limit of the virtual center-of-gravity distance ΔG. As described above, the output timing of ultrasonic waves from each transducer element 12 is controlled to control the direction of the main beam. That is, a different delay amount is set for each transducer element 12, and each transducer element 12 outputs ultrasonic waves at a timing corresponding to the delay amount. To suitably control the direction of the main beam (in other words, to output a main beam with a strong signal strength at a desired beam angle), it is essential that ultrasonic waves are output with an appropriate delay amount from each position (each sound source) in the array direction. As shown by the dashed lines in FIGS. 22 and 23, in conventional transducer elements whose extension direction is parallel to the elevation direction, the extension direction is parallel to the elevation direction, and therefore the transducer elements 12, which are sound sources, are aligned in the array direction. Therefore, by setting different delay amounts for each transducer element 12, the direction of the main beam can be suitably controlled.

[0044] If the first virtual center of gravity 24a and the second virtual center of gravity 24b are positioned differently in the array direction, the first virtual portion 12a and the second virtual portion 12b are actually one transducer element 12, and therefore the first virtual center of gravity 24a and the second virtual center of gravity 24b output ultrasonic waves with the same delay amount (at the same timing) even though they are positioned differently in the array direction. In reality, ultrasonic waves output from the shaded area in Fig. 22 are ultrasonic waves output at a timing different from the desired delay amount. This causes a deterioration in the accuracy of directional control of the main beam.

[0045] As shown in FIG. 23, the larger the virtual center-of-gravity distance ΔG (in the example shown in FIG. 23, the virtual center-of-gravity distance ΔG is 1 pitch), the larger the shaded area, i.e., the area where ultrasonic waves are output at a timing different from the desired delay amount. In other words, the larger the virtual center-of-gravity distance ΔG, the more the accuracy of the directional control of the main beam deteriorates. Since there is a trade-off between the directional control of the main beam and the reduction of the grating level, it is preferable to determine the virtual center-of-gravity distance ΔG within a range where the two are well balanced. Generally, when the virtual center-of-gravity distance ΔG is 1 pitch or more, more than half of the transducer elements 12 fall within the shaded area, and the performance of the main beam deteriorates. Therefore, it is preferable that the virtual center-of-gravity distance ΔG is less than the transducer element pitch in the transducer element array 10.

[0046] In the examples of FIGS. 4 and 5 , the vibration element 12 has a parallelogram shape. However, the shape of the vibration element 12 may be other shapes as long as the first virtual center of gravity 24 a and the second virtual center of gravity 24 b are at different positions in the array direction. For example, the shape of the vibration element 12 may be a polygon with five or more sides in a plan view from the depth direction. Alternatively, as in the vibration element 12-2 shown in FIG. 24 , at least one of the sides of the vibration element 12-2 in a plan view may be curved. Furthermore, in the examples of FIGS. 4 and 5 , the shape of the first virtual portion 12 a and the shape of the second virtual portion 12 b of the vibration element 12 are point-symmetric about the center of gravity 20 of the vibration element 12 in a plan view from the depth direction. However, the shape of the first virtual portion 12 a and the shape of the second virtual portion 12 b of the vibration element 12 may be point-asymmetric about the center of gravity 20 of the vibration element 12 in a plan view from the depth direction.

[0047] Second Embodiment FIG. 25 is a side view of a transducer element array 10-2 of an ultrasonic probe according to the second embodiment. As shown in FIG. 25, the transducer element array 10-2 according to the second embodiment is configured with a plurality of transducer elements 12 arranged on a curved surface. In this specification, a transducer element array configured with a plurality of transducer elements 12 arranged on a curved surface is referred to as a curved array. In other words, the transducer element array 10-2 according to the second embodiment is a curved array. As shown in FIG. 25, the transducer element pitch in the transducer element array 10-2 is also represented by P. In a curved array, the transducer element pitch is represented by the radial distance between the centers of gravity of adjacent transducer elements 12-2. In a curved array, the array direction is a curve, so in this specification, the direction perpendicular to the depth direction is referred to as the lateral direction. Note that in a curved array, the normals of the ultrasonic wave transmitting and receiving surfaces of the transducer elements 12 face in different directions, so the depth direction and lateral direction differ for each transducer element.

[0048] In the second embodiment, as in the first embodiment, each transducer element 12 has a shape in which the first virtual center of gravity 24a and the second virtual center of gravity 24b are located at different positions in the array direction in a plan view seen from the depth direction, as shown in Figures 4 and 5. This reduces the intensity of the grating beam output from the transducer element array 10-2 by the same principle as in the first embodiment.

[0049] 26 to 40, the verification results of the intensity of the grating beam when the virtual center-of-gravity distance ΔG is set to P / 2 will be described below. In the following verification, the intensity of the grating beam is verified when the direction of the main beam is set to be parallel to the depth direction of one vibration element 12.

[0050] FIG. 26 is a diagram showing a grating beam generated in a conventional curved array (shown by a dashed line in FIG. 4) at a position in the elevation direction shown by A in FIG. 4 (one end of the transducer element 12 in the elevation direction). FIG. 27 is a diagram showing a grating beam generated in the transducer element array 10-2 at a position in the elevation direction shown by A in FIG. 4. FIG. 28 is a diagram showing a grating beam generated in a conventional curved array at a position in the elevation direction shown by B in FIG. 4. FIG. 29 is a diagram showing a grating beam generated in the transducer element array 10-2 at a position in the elevation direction shown by B in FIG. 4. FIG. 30 is a diagram showing a grating beam generated in a conventional curved array at a position in the elevation direction shown by C in FIG. 4 (the center of the transducer element 12 in the elevation direction). FIG. 31 is a diagram showing a grating beam generated in the transducer element array 10-2 at a position in the elevation direction shown by C in FIG. 4. Fig. 32 is a diagram showing a grating beam generated in a conventional curved array at a position in the elevation direction indicated by D in Fig. 4. Fig. 33 is a diagram showing a grating beam generated in the transducer element array 10-2 at a position in the elevation direction indicated by D in Fig. 4. Fig. 34 is a diagram showing a grating beam generated in a conventional curved array at a position in the elevation direction indicated by E in Fig. 4 (the other end of the transducer element 12 in the elevation direction). Fig. 35 is a diagram showing a grating beam generated in the transducer element array 10-2 at a position in the elevation direction indicated by E in Fig. 4.

[0051] In Fig. 26, the portion with high signal intensity extending in the depth direction at the center of the array direction represents the main beam MB, and the portion with slightly high signal intensity extending radially at a predetermined beam angle from depth 0 at the center of the array direction represents the grating beam GB. While Fig. 26 representatively shows the beam directions of the main beam MB and grating beam GB, the directions of the main beam and grating beam are the same in Figs. 27 to 35 and Figs. 38 to 39.

[0052] 26 and 27, 28 and 29, 30 and 31, 32 and 33, and 34 and 35, it can be seen that the intensity of the grating beam GB is also reduced by the transducer element array 10-2 according to the second embodiment. As in the first embodiment, in the second embodiment, the intensity of the grating beam is particularly reduced at the center in the elevation direction (FIGS. 30 and 31). On the other hand, at the ends in the elevation direction (FIGS. 26 and 27, and 34 and 35), the reduction in the grating beam intensity is smaller on one side of the main beam (the left side of the main beam in FIG. 27, and the right side of the main beam in FIG. 35).

[0053] Fig. 36 is a diagram showing a grating beam at a predetermined depth for a conventional curved array in two-dimensional space in the horizontal and elevation directions. Fig. 37 is a diagram showing a grating beam at a predetermined depth for the transducer element array 10-2 in two-dimensional space in the horizontal and elevation directions. As in the first embodiment, in the transducer element array 10-2, the extension direction of each transducer element 12 extends obliquely with respect to the elevation direction, so the direction in which the grating beam is generated is also inclined, as shown by the straight line L in Fig. 37.

[0054] FIG. 38 is a diagram showing grating beams generated in a conventional curved array over the entire elevation direction. FIG. 39 is a diagram showing grating beams generated in the transducer element array 10-2 over the entire elevation direction. While FIGS. 26 to 35 compare grating beams at each position in the elevation direction, FIGS. 38 and 39 are diagrams obtained by averaging the signal strength at each elevation position. Comparing FIGS. 38 and 39, it can be seen that grating beams are significantly reduced over the entire elevation direction, that is, over the transducer element array 10-2 as a whole.

[0055] 40 is a graph showing the relationship between signal intensity and beam angle at a predetermined depth. In FIG. 40, the dashed line graph is a graph for a conventional transducer element whose extension direction is parallel to the elevation direction, and the solid line graph is a graph for the transducer element array 10-2 according to the second embodiment. In the dashed line graph, the grating peak is at a beam angle of approximately ±60 degrees, and the intensity of the grating beam is significantly increased, while in the solid line graph, it can be seen that the grating beam is significantly reduced.

[0056] Fig. 41 is a graph showing the relationship between the grating level and the virtual center-of-gravity distance ΔG at the beam angle at which the intensity of the grating beam peaks. In the graph of Fig. 41, when the virtual center-of-gravity distance ΔG is 0 (the left end of the graph), the element has the same shape as a conventional transducer element in which the extension direction is parallel to the elevation direction. It can be seen that within the range of the virtual center-of-gravity distance ΔG shown in Fig. 41, the grating level is reduced at least compared to when the virtual center-of-gravity distance ΔG is 0 (the conventional case).

[0057] In the first embodiment (linear array), the grating level was reduced most when the virtual center-of-gravity distance ΔG was P / 2, but in the second embodiment (curved array), the grating level was reduced most when the virtual center-of-gravity distance ΔG was about 0.75 pitch instead of P / 2 (0.5 pitch), as shown in Fig. 41. Hereinafter, with reference to Figs. 42 and 43, a method for determining the optimal virtual center-of-gravity distance ΔG from the viewpoint of reducing the grating level in the transducer element array 10-2, which is a curved array, will be described.

[0058] Fig. 42 is a side view of the transducer element array 10-2. In Fig. 42, each transducer element 12 is simply represented by a black circle indicating its center of gravity. In the following description, as shown in Fig. 42, the radius of curvature of the curved surface on which the transducer elements 12 are arranged is r (the center of which is point O), the angular pitch between the transducer elements 12 is α, the number of aperture transducer elements used during transmission or reception of the transducer element array 10-2 is N, and the direction perpendicular to the virtual line VL from the transducer element 12x (directly upward in Fig. 42) is set as the direction of the main beam, and the beam angle of the grating beam with respect to the direction of the main beam is θg.

[0059] The transducer element array 10-2 is a curved array, and the transducer elements 12 are arranged on a curved surface, so it is difficult to obtain the optimum virtual center-of-gravity distance ΔG as is. Therefore, in this embodiment, as shown in Fig. 43, the transducer elements 12 arranged on the curved surface are converted into a virtual linear array (virtual linear array), and the optimum virtual center-of-gravity distance ΔG is obtained using the transducer element pitch in the virtual linear array (referred to as the virtual pitch in this specification).

[0060] Specifically, a virtual straight line VL is assumed to pass through one transducer element 12 (e.g., transducer element 12x in FIG. 42) and be a tangent to the curved surface on which the transducer elements 12 are arranged. The transducer elements 12 other than transducer element 12x are virtually rotated as indicated by arrow AR and virtually moved along the virtual straight line VL to form a virtual linear array. The rotation angle of each transducer element 12 can be approximately the average angle of the rotation angles of transducer elements 12 that are half the diameter of the transducer element array 10-2. If this average angle is β, then β can be expressed by the following equation 2: β=(N / 4)*α Equation 2 That is, by rotating each transducer element 12 by an angle β, a virtual linear array can be formed in which the transducer elements 12 are virtually aligned on a virtual straight line VL.

[0061] On the other hand, the condition for generating a grating beam in a linear array can be expressed by the following equation 3. P sinθ=mλ Equation 3 In Equation 3, P is the transducer element pitch, θ is the beam angle of the grating beam, m is an integer, and λ is the wavelength of the ultrasonic wave. By transforming Equation 3, we obtain Equation 4 below. P=mλ / sinθ Equation 4

[0062] Equation 4 shows that, under the condition of generating a grating beam, as the beam angle θ of the grating beam becomes smaller, the transducer element pitch P becomes larger. As shown in Equation 2, it can be approximated that the grating angle becomes θg-β as each transducer element 12 is virtually rotated by an angle β to form a virtual linear array (see FIG. 43). Therefore, from Equation 3, if mλ is constant, P'sin(θ-β)=Psinθg...Equation 5 holds true. In Equation 5, P' is the pitch of the transducer elements in the virtual linear array, that is, the virtual pitch.

[0063] From Equation 5, the virtual pitch P' is expressed by Equation 6 below. P'=Psinθg / sin(θg-β)...Equation 6 Since the virtual pitch P' in the virtual linear array is calculated using Equation 6, as in the first embodiment, the intensity of the grating beam can be reduced most by setting the virtual center-of-gravity distance ΔG to half the virtual pitch P'.

[0064] In Equation 6, when the angle β is sufficiently larger than the angle θg, Equation 6 can be approximately expressed as Equation 7 below. P'=P / (1-β)...Equation 7 For the virtual pitch P', the optimum virtual center-of-gravity distance ΔG may be determined simply using Equation 7.

[0065] Fig. 44 is a graph showing the relationship between the main beam width and the virtual center-of-gravity distance ΔG in the transducer element array 10-2. The main beam width refers to the angular width of the beam at a signal strength that is a predetermined amount smaller than the maximum signal strength of the main beam, based on the beam angle at which the main beam has the maximum signal strength (see symbol BW in Fig. 40). It can be said that the smaller the main beam width BW, the better the performance of the main beam.

[0066] As shown in Figure 44, as the virtual center-of-gravity distance ΔG increases, the main beam width BW also increases. In other words, the performance of the main beam decreases. In other words, because there is a trade-off between the virtual center-of-gravity distance ΔG and the main beam width BW, it is best to determine the virtual center-of-gravity distance ΔG by considering the balance between the two. For example, comparing the virtual center-of-gravity distance ΔG of 0.5 pitch with the virtual center-of-gravity distance of 0.75 pitch, the intensity of the grating beam is reduced more when the virtual center-of-gravity distance ΔG is 0.75 pitch than when the virtual center-of-gravity distance ΔG is 0.5 pitch (see Figure 41), but the main beam width BW is larger. In this case, the virtual center-of-gravity distance ΔG may be set to 0.75 pitch to prioritize reducing the intensity of the grating beam, or the virtual center-of-gravity distance ΔG may be set to 0.5 pitch to prioritize the main beam width BW.

[0067] The above describes the inspection result display device for vibration elements according to the present disclosure, but the inspection result display device for vibration elements according to the present disclosure is not limited to the above embodiment, and various modifications are possible as long as they do not deviate from the spirit thereof. [Explanation of symbols]

[0068] 10, 10-2: Vibration element array, 12, 12-2, 12x: Vibration element, 12a: First virtual part, 12b: Second virtual part, 20: Center of gravity, 24a: First virtual center of gravity, 24b: Second virtual center of gravity, P: Vibration element pitch, ΔG: Distance between virtual centers of gravity, P': Virtual pitch.

Claims

1. An ultrasonic probe including a transducer array consisting of a plurality of transducer elements arranged in an array direction, When the vibration element is virtually divided into a first virtual portion and a second virtual portion by a straight line passing through a center of gravity of the vibration element and extending in the array direction, each of the vibration elements has a shape such that a first virtual center of gravity that is the center of gravity of the first virtual portion and a second virtual center of gravity that is the center of gravity of the second virtual portion are located at different positions in the array direction, Due to the shape, the grating beam output from the first virtual portion and the grating beam output from the second virtual portion cancel each other out due to a phase shift, thereby reducing the intensity of the grating beam output from each of the vibration elements. An ultrasonic probe characterized by:

2. In a plan view seen from the depth direction, the shape of the vibration element is a polygon having pentagons or more, or at least one side of the vibration element is curved.

2. The ultrasonic probe according to claim 1.

3. In a plan view seen from the depth direction, the shape of the first imaginary portion and the shape of the second imaginary portion are in a point-asymmetric relationship with respect to the center of gravity of the vibration element.

2. The ultrasonic probe according to claim 1.

4. a virtual center-of-gravity distance, which is a distance between the first virtual center of gravity and the second virtual center of gravity in the array direction, is less than a vibration element pitch in the vibration element array.

2. The ultrasonic probe according to claim 1.

5. When the plurality of vibration elements are arranged on a plane, the distance between the virtual centers of gravity is half the vibration element pitch.

5. The ultrasonic probe according to claim 4.

6. When the plurality of vibration elements are arranged on a curved surface, the distance between the virtual centers of gravity is half the virtual pitch P′ between the vibration elements.

5. The ultrasonic probe according to claim 4. Here, the virtual pitch P' is P'=Psinθg / sin(θg−β) β = (N / 4) * α where P is the pitch of the transducer elements, θg is the beam angle of the grating beam, N is the number of aperture transducer elements, and α is the angle pitch between the transducer elements.

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