Line-focused ultrasonic transducer

Abstract

A line-focused ultrasonic transducer is provided. A line-focused ultrasonic transducer according to one embodiment of the present invention is a line-focused ultrasonic transducer including a piezoelectric element for focusing ultrasonic waves onto a linear focal point extending in a predetermined first direction, wherein the piezoelectric element includes a curved surface having a predetermined first radius of curvature with respect to the linear focal point, a projection obtained by projecting the curved surface of the piezoelectric element onto a plane perpendicular to the normal direction from the center of the piezoelectric element is formed to have a planar length extending in the first direction and a planar width in a second direction perpendicular to the first direction, a first reduction portion having a width in the second direction that decreases toward one end in the first direction is formed at one end portion in the first direction, and a second reduction portion having a width in the second direction that decreases toward the other end in the first direction is formed at the other end portion in the first direction.

Description

Focused ultrasound transducer

[0001] The present invention relates to a linear focused ultrasonic transducer.

[0002] An ultrasonic transducer is a device that converts electrical signals and sound waves, performing the conversion process between electrical signals and sound waves using a piezoelectric element formed of a piezoelectric material.

[0003] In this case, the ultrasound transducer can non-invasively treat diseased tissues within the body through High-Intensity Focused Ultrasound (HIFU) technology, which precisely focuses ultrasound energy to a specific depth within the body to generate thermal or mechanical energy.

[0004] At this time, the area where the focus is formed reaches a temperature of tens of degrees or more, forming microscopic thermal coagulation points that induce tissue regeneration or necrosis, while the energy is dispersed from the skin surface or surrounding tissues away from the focus, preventing damage.

[0005] Thanks to these characteristics, ultrasonic transducers are widely used as an effective treatment method in various medical and cosmetic fields, such as skin lifting and tumor treatment.

[0006] Figure 1 is a diagram showing energy focused on the skin using a conventional ultrasonic transducer and a graph of the sound pressure distribution at that time.

[0007] In the past, a hemispherical ultrasound transducer (1'') that collects energy into a single point shape was mainly used, but it had the disadvantage of being inefficient relative to the treatment area and taking a long time to treat.

[0008] To improve this, a method of forming energy into a linear focus with a predetermined length has been proposed, which can deliver energy to a wide area simultaneously with a single irradiation, thereby dramatically increasing the speed and efficiency of the procedure.

[0009] However, conventional cylindrical elements used to form a linear focus suffer from a structural vulnerability where sound pressure is formed irregularly within the focus region due to the limitations of their geometric shape.

[0010] Referring to FIG. 1, a conventional cylindrical ultrasonic transducer (1') is formed to have a rectangular planar projection shape, which has a problem of strongly generating edge diffraction waves during ultrasonic radiation by having physically sharp right-angled corners and straight outer boundary lines.

[0011] The diffracted waves generated at this time interfere with the main sound waves radiated from the center of the element, and as a result, the sound pressure is not maintained at a constant level within the linear focal point (3) section inside the skin (2), causing a beading phenomenon in which energy is irregularly clustered.

[0012] In particular, this non-uniformity of negative pressure causes serious technical contradictions in establishing standards for appropriate output during procedures and becomes a fatal factor that threatens patient safety.

[0013] Points where negative pressure is abnormally high within the linear focus (3) section are the direct cause of excessive heat energy being concentrated in the skin (2) tissue, resulting in burns or unbearable pain.

[0014] Conversely, if the device output is limited to the high-pressure point to prevent such risks, energy transfer in the remaining low-pressure range fails to reach the minimum level required for tissue degeneration, resulting in minimal treatment efficacy.

[0015] In such a state where the sound pressure distribution is uneven, it is very difficult to set an appropriate output value that can simultaneously achieve the conflicting objectives of ensuring safety and maximizing effectiveness.

[0016] In addition, some existing high-performance devices have adopted methods to suppress this non-uniformity by dividing the electrodes on the surface of the piezoelectric element into complex patterns or coating the area in a limited manner to adjust weighting for each region.

[0017] However, this method has economic disadvantages, as it necessitates the addition of precision machining processes to implement fine electrode patterns, which increases manufacturing costs and lowers production yield.

[0018] Above all, since electrical control methods alone cannot completely block the inherent diffraction phenomenon occurring at the physical boundary of the device, they reveal clear limitations in terms of durability and stability, such as the sound pressure uniformity easily deteriorating due to device degradation or electrical interference during long-term use.

[0019] Therefore, there is a critical need for a new level of design that can effectively suppress edge diffraction by optimizing only the mechanical shape of the piezoelectric element body without complex electrode pattern design or separate control circuit, and secure extreme sound pressure uniformity (e.g., a variation rate of 1 decibel (dB) or less) over the entire linear focus (3).

[0020] The present invention aims to solve the aforementioned problems, and the objective of the present invention is to provide a linearly focused ultrasonic transducer capable of effectively suppressing edge diffracted waves and ensuring sound pressure uniformity across the entire linear focus range.

[0021] Another objective of the present invention is to provide a focused ultrasound transducer capable of ensuring high safety and maximizing the treatment effect by stably setting an appropriate output value.

[0022] The problems of the present invention are not limited to those mentioned above, and other unmentioned problems will be clearly understood by a person skilled in the art to which the present invention pertains from the description below.

[0023] According to one aspect of the present invention, a linear focusing ultrasonic transducer is provided, comprising a piezoelectric element that focuses ultrasonic waves into a linear focus extending along a predetermined first direction, wherein the piezoelectric element comprises a curved surface having a predetermined first radius of curvature centered on the linear focus, and the projection shape formed by projecting the curved surface of the piezoelectric element onto a plane perpendicular to the normal direction at the center of the piezoelectric element is formed to have a plane length extending along the first direction and a plane width in a second direction perpendicular to the first direction, wherein a first reduction portion is formed at one end of the first direction side such that the width in the second direction side decreases as it moves toward the one end of the first direction side, and a second reduction portion is formed at the other end of the first direction side such that the width in the second direction side decreases as it moves toward the other end of the first direction side.

[0024] At this time, the edge of the first reduction part may be formed in a shape corresponding to a first curve in which the center of curvature is located within the projection shape, and the edge of the second reduction part may be formed in a shape corresponding to a second curve in which the center of curvature is located within the projection shape.

[0025] At this time, the projection shape may be formed in a shape corresponding to a third area in which a virtual first area in the shape of a rectangle having the plane length along the first direction and the plane width along the second direction can overlap with a second area according to [Equation 1] in a coordinate system with the center of the first area as the origin.

[0026] [Mathematical Formula 1]

[0027]

[0028] At this time, in the above [Mathematical Formula 1], the value of m and the value of n may be the same.

[0029] At this time, in the above [Mathematical Formula 1], the values ​​of m and n can be 2.

[0030] At this time, in the above [Mathematical Formula 1], the value of b may be at least 1 time and no more than 10 times the width of the plane.

[0031] At this time, the first curve includes the boundary line of the second region, and the end of the first curve may be connected to the boundary line of the first region, and in [Equation 1], when the value of b exceeds the plane width, the first curve is corrected so that the position of the end of the first curve is spaced a predetermined distance from the intersection point where the first region and the second region intersect and passes through the connection point where the first curve and the first region are connected, and the slope of the tangent of the first curve at the connection point may match the slope of the boundary line of the first region.

[0032] At this time, the second curve includes the boundary line of the second region, and the end of the second curve may be connected to the boundary line of the first region, and in [Equation 1], when the value of b exceeds the plane width, the second curve is corrected so that the position of the end of the second curve is spaced a predetermined distance from the intersection point where the first region and the second region intersect and passes through the connection point where the second curve and the first region are connected, and the slope of the tangent of the second curve at the connection point may match the slope of the boundary line of the first region.

[0033] At this time, the projection shape may be formed in a shape including a first length portion that can be formed as a part of a pair of boundary lines extending along the first direction among the boundary lines of the first region, a first curve connected to one end of the first length portion, and a second curve connected to the other end of the first length portion.

[0034] At this time, the second region may be formed as a region with a boundary of a virtual curve located within a range that is expanded or contracted by 10% or less from the origin of the coordinate system, which is the virtual region formed according to [Equation 1].

[0035] At this time, the first curve and the second curve may be formed in a shape that is symmetrical to each other with respect to the center of the projection shape.

[0036] At this time, the projection shape may have a length that is the plane length minus a predetermined curvature reference length along the first direction, and may be formed in a shape corresponding to a sixth region in which a virtual fourth region having the plane width along the second direction and a fifth region according to [Equation 2] below can be combined along a coordinate system with the center of the fourth region as the origin.

[0037] [Mathematical Formula 2]

[0038]

[0039] At this time, in the above [Equation 2], the values ​​of m and n may be the same.

[0040] At this time, in the above [Equation 2], the values ​​of m and n can be 2.

[0041] At this time, the projection shape may be formed in a shape including a first length portion that can be formed as a part of a pair of boundary lines extending along the first direction among the boundary lines of the fourth region, a first curve connected to one end of the first length portion, and a second curve connected to the other end of the first length portion.

[0042] At this time, the fifth region may be formed as a region with a boundary of a virtual curve located within a range that is expanded or contracted by 10% or less from the origin of the coordinate system, which is the virtual region formed according to [Equation 2].

[0043] At this time, a continuous electrode having a shape corresponding to the projection shape may be formed on the surface of the piezoelectric element.

[0044] At this time, a sound-absorbing member may be formed at the boundary surface of the first reduction part and the second reduction part of the projection shape of the piezoelectric element, which absorbs edge diffraction waves generated at the boundary surface and can reduce the longitudinal sound pressure deviation of the linear focus.

[0045] At this time, the edge of the first reduction part may be formed in a triangular or trapezoidal shape such that as it moves toward one end of the first direction side, both ends of the second direction side become closer to the center of the second direction side, and the edge of the second reduction part may be formed in a triangular or trapezoidal shape such that as it moves toward the other end of the first direction side, both ends of the second direction side become closer to the center of the second direction side.

[0046] At this time, the projection shape is formed in a shape including a first length portion formed as a part of a pair of boundary lines extending along the first direction, a first reduction portion connected to one end of the first length portion, and a reduction portion connected to the other end of the first length portion, wherein the portion in contact with the first reduction portion or the second reduction portion of the projection shape of the piezoelectric element and the first length portion may be formed in a curve shape in which the center of curvature is located within the projection shape.

[0047] According to the above configuration, a linear focused ultrasonic transducer according to one aspect of the present invention can effectively suppress edge diffracted waves and ensure extreme sound pressure uniformity over the entire linear focus range.

[0048] According to the above configuration, the linear focused ultrasound transducer according to another aspect of the present invention can ensure high safety and maximize the treatment effect by stably setting an appropriate output value.

[0049] The effects of the present invention are not limited to the effects described above, and should be understood to include all effects that can be inferred from the configuration of the invention described in the detailed description or claims of the present invention.

[0050] Figure 1 is a diagram showing energy focused on the skin using a conventional ultrasonic transducer and a graph of the sound pressure distribution at that time.

[0051] FIG. 2 is a perspective view of a linearly focused ultrasonic transducer according to one embodiment of the present invention.

[0052] FIG. 3 is a perspective view of a piezoelectric element of a linear focused ultrasonic transducer according to one embodiment of the present invention.

[0053] FIG. 4 is a cross-sectional view of a piezoelectric element of a linear focused ultrasonic transducer according to one embodiment of the present invention.

[0054] FIG. 5 is a drawing showing the projection shape of a piezoelectric element of a linear focused ultrasonic transducer according to one embodiment of the present invention projected onto a plane.

[0055] FIG. 6 is an xy-plane diagram for defining the shape of a projection shape according to one embodiment of the present invention.

[0056] Figure 7 is an enlarged view of part A of Figure 6.

[0057] FIG. 8 is a drawing showing the projection shape of a piezoelectric element of a linear focused ultrasonic transducer according to another embodiment of the present invention projected onto a plane.

[0058] FIG. 9 is an xy-plane diagram for defining the shape of a projection shape according to another embodiment of the present invention.

[0059] FIG. 10 is a table showing the sound pressure fluctuation rate according to design specification variables of a linear focused ultrasonic transducer according to another embodiment of the present invention.

[0060] Figures 11 and 12 illustrate graphs of the sound pressure distribution of a conventional cylindrical ultrasonic transducer.

[0061] FIGS. 13 and 14 are graphs illustrating the sound pressure distribution of a linear focused ultrasonic transducer according to one embodiment of the present invention.

[0062] FIGS. 15 and 16 are graphs illustrating the sound pressure distribution of a linear focused ultrasonic transducer according to another embodiment of the present invention.

[0063] FIG. 17 is a graph showing the sound pressure distribution of a linear focused ultrasonic transducer according to one embodiment of the present invention.

[0064] Hereinafter, embodiments of the present invention are described in detail with reference to the attached drawings so that those skilled in the art can easily implement the present invention. The present invention may be embodied in various different forms and is not limited to the embodiments described herein. To clearly explain the present invention, parts unrelated to the description in the drawings have been omitted, and the same reference numerals have been used throughout the specification for identical or similar components.

[0065] The words and terms used in this specification and claims are not limited to their ordinary or dictionary meanings, but should be interpreted in a meaning and concept consistent with the technical spirit of the invention in accordance with the principles by which the inventor defines terms and concepts to best describe his invention.

[0066] In this specification, terms such as "comprising" or "having" are intended to describe the existence of the features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, and should not be understood as precluding the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof.

[0067] In describing the drawings below, each direction is defined and described based on the coordinate axes shown in FIG. 2. More specifically, the positive direction of the z-axis is defined as the upward side and the negative direction of the z-axis is defined as the downward side. The positive direction of the y-axis is defined as the right side and the negative direction of the y-axis is defined as the left side. The positive direction of the x-axis is defined as the forward side and the negative direction of the x-axis is defined as the rear side.

[0068] Thickness or size has been exaggerated in the drawings to clearly express the characteristics of the configuration, and the thickness or size of the configuration shown in the drawings is not necessarily the same as the actual value.

[0069] Therefore, the embodiments described in this specification and the configurations illustrated in the drawings correspond to preferred embodiments of the present invention and do not represent all technical ideas of the present invention; thus, various equivalents and modifications that may replace such configurations may exist at the time of filing the present invention.

[0070] In the following description, descriptions of some components may be omitted to clarify the features of the present invention.

[0071] FIG. 2 is a perspective view of a linearly focused ultrasonic transducer according to one embodiment of the present invention.

[0072] A linear focused ultrasonic transducer (1) according to one embodiment of the present invention may include a piezoelectric element (10) and a housing (30).

[0073] The housing (30) can form a predetermined receiving space inside and can stably support the piezoelectric element (10). Accordingly, the housing (30) can guide the ultrasonic waves emitted from the piezoelectric element (10) to maintain a state aligned in a predetermined direction toward the skin (2).

[0074] However, the shape or material of the housing (30) according to one embodiment of the present invention does not necessarily have to be limited to the form shown in the drawing, and it may be sufficient if it is a configuration that can stably accommodate the piezoelectric element (10) and protect it from external impact.

[0075] The piezoelectric element (10) can be placed inside the housing (30). The piezoelectric element (10) can be formed of a piezoelectric material and can generate ultrasound by converting an electrical signal applied from the outside into mechanical vibration.

[0076] A linear focused ultrasound transducer (1) according to one embodiment of the present invention can operate based on high-intensity focused ultrasound (HIFU) technology.

[0077] More specifically, ultrasonic energy generated from the piezoelectric element (10) can be precisely focused at a linear focus (3) located at a specific depth inside the skin (2) and extending along a predetermined first direction.

[0078] Accordingly, high-temperature thermal energy is concentrated in the area where the focus (3) is formed, and fine thermal coagulation points can be formed, thereby inducing tissue regeneration or necrosis.

[0079] At this time, since the ultrasonic energy is focused to form a linear focus (3), the treatment can be performed on a relatively wide area inside the skin (2) with only one irradiation compared to a method of gathering energy in a point shape.

[0080] As a result, the focused ultrasound transducer (1) according to one embodiment of the present invention can improve the efficiency of the procedure and reduce the time required for the procedure.

[0081] FIG. 3 is a perspective view of a piezoelectric element of a linear focused ultrasonic transducer according to one embodiment of the present invention. FIG. 4 is a cross-sectional view of a piezoelectric element of a linear focused ultrasonic transducer according to one embodiment of the present invention.

[0082] A piezoelectric element (10) according to one embodiment of the present invention may include a curved surface having a predetermined first radius of curvature (R). The curved surface of the piezoelectric element (10) may be formed around a linear focus (3), and ultrasonic waves emitted from the piezoelectric element (10) can be precisely focused to the linear focus (3).

[0083] The piezoelectric element (10) can be formed to have a predetermined thickness.

[0084] At this time, the thickness of the piezoelectric element (10) can be determined in correspondence with the target driving frequency of the transducer and can be formed with a thickness that can optimize the vibration efficiency of the piezoelectric material.

[0085] Electrodes can be formed on the surface of the piezoelectric element (10).

[0086] More specifically, the electrodes can be formed on the upper side or the lower side of the curved surface of the piezoelectric element (10), respectively, and can transmit an external electrical signal to the piezoelectric material to induce mechanical vibration.

[0087] An electrode according to one embodiment of the present invention may be formed as a continuous electrode having a shape corresponding to the projection shape (20) of the piezoelectric element (10) to be described later.

[0088] The continuous electrode can be formed integrally on the surface of the piezoelectric element (10) without interruption. Accordingly, the process of etching or dividing the electrode into a complex pattern to ensure sound pressure uniformity can be eliminated, thereby simplifying the manufacturing process and improving production yield.

[0089] In addition, this continuous electrode structure can be combined with the geometric outer shape design of the piezoelectric element (10) to help form a uniform sound field over the entire linear focus (3) without a separate electrical weighting control circuit or complex control.

[0090] However, the material of the piezoelectric element (10) or the material of the electrode according to one embodiment of the present invention does not necessarily have to be limited to a specific one, and various known materials capable of radiating ultrasound and transmitting electrical signals may be adopted.

[0091] FIG. 5 is a drawing showing the projection shape of a piezoelectric element of a linear focused ultrasonic transducer according to one embodiment of the present invention projected onto a plane.

[0092] In order to clearly explain the shape of the piezoelectric element (10) of the linear focused ultrasonic transducer (1) according to the present invention, the shape of the curved surface of the piezoelectric element (10) projected onto a plane perpendicular to the normal direction at the center of the piezoelectric element can be defined as the projection shape (20).

[0093] A piezoelectric element (10) of a linear focused ultrasonic transducer (1) according to one embodiment of the present invention may be formed such that each part as a three-dimensional structure and each part on a projection shape (20) when the three-dimensional structure is unfolded on a plane correspond to each other in a one-to-one manner.

[0094] Referring to FIG. 5, the projection shape (20) may have a planar length (a) extending along a predetermined first direction and a planar width (d) along a second direction perpendicular to the first direction.

[0095] A first reduction portion (21) may be formed at one end of the first direction side of the projection shape (20), and a second reduction portion (22) may be formed at the other end of the first direction side.

[0096] The first reduction section (21) may be formed such that the width of the second direction side decreases as it moves toward one end of the first direction side. Similarly, the second reduction section (22) may be formed such that the width of the second direction side decreases as it moves toward the other end of the first direction side.

[0097] A central part (23) may be located between the first reduction part (21) and the second reduction part (22), with the width maintained at a constant plane width (d).

[0098] The first reduction section (21) and the second reduction section (22) can gradually reduce the ultrasonic radiation area as it approaches the end of the element.

[0099] Accordingly, a physical weight adjustment effect (Apodization) can be induced by mitigating the rapid phase change occurring at the outer boundary of the piezoelectric element (10).

[0100] As a result, the linear focused ultrasonic transducer (1) according to one embodiment of the present invention can effectively suppress edge diffraction waves that occur in conventional rectangular elements and can minimize sound pressure deviation along the length direction of the linear focus (3).

[0101] However, the specific boundary shape of the first reduction part (21) and the second reduction part (22) may be formed in various forms including curves or straight lines, as described later, and is not necessarily limited to a specific curvature or shape.

[0102] In addition, the overall ratio or size of the projection shape (20) can be varied depending on the use and design specifications of the transducer.

[0103] Meanwhile, the first reduction part (11), the second reduction part (12), and the center (13) of the piezoelectric element (10) illustrated in FIG. 3 may represent each actual part of the piezoelectric element (10) in a bent state having a predetermined first radius of curvature (R) to form a linear focus (3).

[0104] Accordingly, the first reduction part (21), the second reduction part (22), and the center (23) of the projection shape (20) shown in FIG. 5 may represent each region of the shape that appears when the curved surface of the piezoelectric element (10) is geometrically projected onto a plane.

[0105] At this time, the first reduction part (21) of the projection shape (20) may correspond to the first reduction part (11) of the piezoelectric element (10), the second reduction part (22) of the projection shape (20) may correspond to the second reduction part (12) of the piezoelectric element (10), and the center (23) of the projection shape (20) may correspond to the center (13) of the piezoelectric element (10).

[0106] That is, the outer boundary design of the piezoelectric element (10) according to the present invention can be mathematically defined based on the first reduction part (21) and the second reduction part (22) of the projection shape (20) in a planar state, and the first reduction part (11) and the second reduction part (12) of the final piezoelectric element (10) can be completed by implementing this planar design in three dimensions.

[0107] FIG. 6 is an xy-plane diagram for defining the shape of a projection shape according to an embodiment of the present invention. FIG. 7 is an enlarged view of portion A of FIG. 6.

[0108] The projection shape (20) of a piezoelectric element (10) according to one embodiment of the present invention may have its boundary shape defined based on a predetermined mathematical formula.

[0109] Referring to FIG. 6, a coordinate system can be established with the center of the projection shape (20) as the origin to define the shape of the projection shape (20).

[0110] The projection shape (20) can be formed in a shape corresponding to a third area (S3) where a virtual first area (S1) and a second area (S2) according to mathematical formula 1 overlap.

[0111] At this time, the first region (S1) can be defined as a rectangular region having a planar length (a) along the first direction and a planar width (d) along the second direction.

[0112] [Mathematical Formula 1]

[0113]

[0114] The second region (S2) according to [Mathematical Formula 1] may have a so-called Lame curve or super-ellipse shape.

[0115] At this time, the rate of change of curvature of the projection shape (20) can be determined according to the values ​​of m and n, and the degree of expansion toward the second direction of the corresponding lame curve or hyperellipse can be determined according to the value of b.

[0116] In one embodiment of the present invention, the values ​​of m and n may be 2, in which case the second region (S2) may have an elliptical shape. Additionally, the value of b may have a range of 1 to 10 times the plane width (d).

[0117] However, the shape of the curve forming the boundary of the second region (S2) according to one embodiment of the present invention is not necessarily limited to [Equation 1], and is not limited to a curve approximated by [Equation 1], for example, a modified curve designed to follow the trajectory of [Equation 1] with a correlation coefficient of 90% or more.

[0118] At this time, a deformation curve that is tracked with a correlation coefficient of 90% or more is sufficient if it is a curve located within a range that is expanded or contracted by 10% or less relative to the origin of the area defined by [Equation 2] above.

[0119] Referring to FIG. 7, the first curve (211) forming the edge of the first reduction portion (21) may include the boundary line of the second region (S2).

[0120] At this time, if the value of b is set to exceed the plane width (d), an intersection point (24') where the first curve (211) and the first region (S1) intersect can be formed.

[0121] When the above [Equation 1] defining the second region (S2) is differentiated with respect to the x value at the intersection point (24'), if the b value is greater than the plane width, the derivative value may have a value other than 0.

[0122] Accordingly, at the intersection (24'), the first region (S1) and the second region (S2) may not be smoothly connected.

[0123] However, if such a part is included in the shape of the piezoelectric element (10), discontinuity in acoustic impedance may occur at the mechanical boundary.

[0124] In order to prevent this, a linear focused ultrasonic transducer (1) according to one embodiment of the present invention may be formed such that the slope of the tangent of the first curve (211) matches the slope of the boundary line of the first region (S1).

[0125] Accordingly, the end of the first curve (211) is corrected from the boundary line of the second region (S2) so that the end of the first curve (211) is formed to pass through a connection point (24) spaced a predetermined distance from the intersection point (24') rather than the intersection point (24') between the first region (S1) and the second region (S2).

[0126] At this time, the connection point (24) between the first curve (211) and the first length portion (231) of the center (23) on the first curve (211) can be formed as a differentiable portion.

[0127] That is, a straight section where the planar width (d) is maintained and a curved section where the width decreases can be smoothly connected at the connection point (24) so ​​as to be differentiable.

[0128] Similarly, the second curve forming the edge of the second reduction section (22) can also be formed so that the slope of the tangent at the connection point (24) on the other end side matches.

[0129] This differentiable connection structure can eliminate abrupt discontinuities in acoustic impedance that may occur at the mechanical boundaries of the piezoelectric element (10).

[0130] Accordingly, unintended scattering or phase distortion of ultrasound can be prevented at the boundary connection point, and a more uniform sound pressure distribution can be secured along the length direction of the linear focus (3).

[0131] However, each parameter of [Equation 1] can be appropriately adjusted within the above range depending on the focal length of the transducer or the required sound field characteristics, and is not necessarily fixed at a specific value.

[0132] FIG. 8 is a drawing illustrating a projection shape of a piezoelectric element of a linearly focused ultrasonic transducer according to another embodiment of the present invention projected onto a plane. FIG. 9 is an xy-plane drawing for defining the shape of the projection shape according to another embodiment of the present invention.

[0133] According to another embodiment of the present invention, the projection shape (20) of the piezoelectric element (10) may have a track shape in which the width of the center (23) is maintained at a constant level and then converges into a curve at both ends.

[0134] Referring to FIG. 9, in order to strictly define the shape of the projection shape (20), a coordinate system can be established with the geometric center of the projection shape (20) as the origin.

[0135] At this time, the projection shape (20) can be formed in a shape corresponding to the sixth region (S6) formed by combining the virtual fourth region (S4) and fifth region (S5).

[0136] The fourth region (S4) may have a length equal to the plane length (a) minus a predetermined curvature reference length (c) along the first direction, and may be defined as a rectangular region having a plane width (d) along the second direction.

[0137] This fourth region (S4) may correspond to the center (23) of the piezoelectric element (10) and may provide a main ultrasonic radiation area for forming a linear focus (3).

[0138] The fifth region (S5) can be connected to the first direction-side end and the other end, respectively, of the fourth region (S4). The outer boundary line of the fifth region (S5) may include a trajectory defined by the following [Equation 2].

[0139] [Mathematical Formula 2]

[0140]

[0141] However, the shape of the curve forming the boundary of the fifth region (S5) according to one embodiment of the present invention is not necessarily limited to [Equation 2], and is not limited to a curve approximated by [Equation 2], for example, a modified curve designed to follow the trajectory of [Equation 2] with a correlation coefficient of 90% or more.

[0142] At this time, a deformation curve that is tracked with a correlation coefficient of 90% or more is sufficient if it is a curve located within a range that is expanded or contracted by 10% or less relative to the origin of the area defined by [Equation 2] above.

[0143] Referring to [Equation 2], a double absolute value symbol can be applied to the variable in the x-axis direction. Accordingly, the fifth region (S5) can be formed with a structure that is perfectly symmetrical left-right and up-down with respect to the origin.

[0144] This symmetrical structure can uniformly control the phase of the diffracted waves generated at both ends of the piezoelectric element (10) and prevent the sound pressure distribution from being deflected with respect to the center of the linear focus (3).

[0145] In this case, the curvature reference length (c) may be a design variable that determines the proportion of the curved reduction portion within the total planar length (a).

[0146] The curvature reference length (c) may have a range of 0.02 times or more and 1 time or less of the planar length (a). In particular, when the curvature reference length (c) is set to a range of 0.4 times or more and 0.5 times or less of the planar length (a), an optimal apodization effect can be obtained that minimizes the longitudinal sound pressure fluctuation rate of the linear focus (3).

[0147] More specifically, as the curvature reference length (c) increases, the slope of the first reduction part (11) and the second reduction part (12) at both ends of the piezoelectric element (10) is formed more gently, which is advantageous for preventing sudden fluctuations in sound pressure.

[0148] However, if the curvature reference length (c) exceeds 0.5 times the plane length (a), on the projection shape (20), a virtual shape of an ellipse or hyperellipse formed including the first reduction part (21) and a virtual shape of an ellipse or hyperellipse formed including the second reduction part (22) partially overlap at the center (23).

[0149] Accordingly, the shapes of the first reduction part (11) and the second reduction part (12) formed at both ends of the piezoelectric element (10) can interact again at the center (23) to cause fluctuations in sound pressure.

[0150] Referring to the illustration in Fig. 10, it can be seen that when the elliptical R value corresponding to half of the curvature reference length (c) does not exceed 1 / 4 of the 25mm corresponding to the planar length (a), i.e., when the elliptical R value is 6.0mm, the sound pressure fluctuation rate is 4.14%, whereas when the elliptical R value is 6.5mm, which exceeds 1 / 4 of the 25mm corresponding to the planar length (a), the sound pressure fluctuation rate increases again to 4.31%.

[0151] However, even in cases where the sound pressure fluctuation rate is 4.31%, it is a case where the sound pressure fluctuation rate is significantly improved compared to 25.1% measured in an ultrasonic transducer with a structure similar to the conventional technology, so the curvature reference length (c) is not necessarily limited to 0.5 times or less of the planar length (a).

[0152] Meanwhile, the values ​​of m and n can define the rate of change of curvature of the fifth region (S5), and in another embodiment of the present invention, the values ​​of m and n can be 2.

[0153] When the value of n is 2, both ends of the fifth region (S5) may have a shape corresponding to a part of an ellipse, which ensures ease of processing during the manufacturing process and effectively suppresses sound wave scattering at mechanical boundaries.

[0154] The projection shape (20) may include a first length portion (232) formed as part of a pair of boundary lines extending along the first direction of the boundary lines of the fourth region (S4).

[0155] The first length portion (232) can form a section in which the width of the second direction side is maintained constant at the center (23) of the piezoelectric element (10).

[0156] At both ends of the first length portion (232), the first curve and the second curve, which are the boundary lines of the fifth region (S5), can be connected respectively, and the connection portion can be smoothly connected so as to be differentiable as described above.

[0157] A track-shaped piezoelectric element (10) according to another embodiment of the present invention can concentrate sufficient energy at the center of the linear focus (3) through the fourth region (S4), which is a central straight section, while attenuating edge diffracted waves through the fifth region (S5) at both ends. Accordingly, a uniform sound field without beading can be formed along the length direction while maintaining a constant overall sound pressure intensity of the linear focus (3).

[0158] However, each parameter and numerical range of the above [Equation 2] may be flexibly changed according to the frequency band of the transducer or the target penetration depth into the skin (2), and is not necessarily limited to the above numerical values ​​as long as it is within a range that can optimize the performance of the piezoelectric element (10).

[0159] FIG. 10 is a table showing the sound pressure fluctuation rate according to design specification variables of a linear focused ultrasonic transducer according to another embodiment of the present invention.

[0160] FIG. 10 is a table showing the sound pressure fluctuation rate according to the design specification variables of a linear focused ultrasonic transducer (1) according to embodiments of the present invention.

[0161] In order to maximize the sound pressure uniformity of the linear focus (3) in the piezoelectric element (10) according to the present invention, design variables such as planar length (a), curvature reference length (c), planar width (d), and first radius of curvature (R) can be mutually and organically optimized.

[0162] The planar width (d) of the piezoelectric element (10) according to the present invention may have a range of at least 1.1 times and no more than 1.4 times the radius of curvature (R).

[0163] For example, when the first radius of curvature (R) is 16 mm, the planar width (d) can be set to 20 mm, and the ratio can be approximately 1.25 times. Within this numerical range, the piezoelectric element (10) can secure an appropriate aperture angle to form a linear focus (3) while simultaneously maximizing the forming effect of the reduction part described later.

[0164] In addition, in the case of the second embodiment having a track shape, the sound pressure fluctuation rate can change sensitively according to the ratio of the curvature reference length (c) to the total planar length (a).

[0165] According to the simulation results of FIG. 10, when the curvature reference length (c) is 12 mm (approx. 0.48 times) under the condition that the planar length (a) is 25 mm, the sound pressure fluctuation rate can be measured as approximately -0.375 dB (approx. 4.14%). This may be a further improved figure compared to the sound pressure fluctuation rate of approximately -0.741 dB (approx. 8.2%) of the elliptical shape (c=a=25 mm) according to the first embodiment.

[0166] In particular, the curvature reference length (c) can be set to a range of 0.4 times or more and 0.5 times or less of the planar length (a). In this case, the piezoelectric element (10) can effectively control edge diffraction waves through changes in curvature of the reduction portions at both ends while maintaining a sufficient effective radiation area at the center (23).

[0167] Accordingly, a critical effect can be obtained in which the sound pressure fluctuation rate within the effective range of the linear focus (3) is reduced to an extreme range of 1 decibel (dB) or less, more specifically to 0.5 decibels (dB) or less.

[0168] When examining the sensitivity according to changes in the m and n values, when the m and n values ​​are 2, the mechanical processability of the piezoelectric element (10) is excellent, and a smooth apodization curve can be formed.

[0169] If the value of n approaches 1 or becomes excessively large, the change in slope at the curve connection point may become steep or gradual, which may cause a peak in the sound pressure or reduce uniformity.

[0170] In this way, the linear focused ultrasonic transducer (1) according to the present invention can achieve the target sound pressure uniformity by optimizing the main design parameters of the piezoelectric element (10) within the numerical range without complex electrode patterns or electrical control.

[0171] As a result, the linear focused ultrasound transducer (1) according to the present invention can secure a safe output standard that prevents the risk of burns during the procedure and can induce a consistent procedure effect throughout the entire linear focus range.

[0172] However, the specific numerical values ​​shown in Figure 10 above are merely examples based on a driving frequency of 4 MHz, and the optimal numerical range may vary depending on the frequency characteristics of the transducer or the type of piezoelectric material.

[0173] Therefore, the scope of the present invention should be understood not as being limited to the specific numerical values ​​mentioned above, but as encompassing the entire design concept of controlling the correlation between numerical variables to suppress edge diffraction.

[0174] A linear focused ultrasonic transducer (1) according to one embodiment of the present invention may further include a sound-absorbing member for controlling residual diffracted waves generated at the outer boundary of a piezoelectric element (10).

[0175] The sound-absorbing member may be formed on the boundary surface of the first reduction part (21) and the boundary surface of the second reduction part (22) among the projection shape (20) of the piezoelectric element (10).

[0176] More specifically, the sound-absorbing member may be arranged to wrap around or cover the side of the piezoelectric material along the edges of the first reduction part (21) and the second reduction part (22).

[0177] These sound-absorbing members can physically absorb and attenuate diffracted waves that are finely residual at the interface and can affect the entire sound field among the edge diffracted waves that are primarily suppressed through the geometric shape optimization of the piezoelectric element (10).

[0178] Accordingly, the sound-absorbing member can additionally block residual diffracted waves from interfering with the main sound waves radiated from the center of the element, and can more precisely fine-tune the sound pressure deviation along the length direction of the linear focus (3).

[0179] That is, by forming a dual defense structure that combines mechanical diffraction suppression through the shape design of the piezoelectric element (10) and physical diffraction absorption through the sound-absorbing member, extreme sound pressure uniformity can be secured throughout the entire linear focus (3).

[0180] As a result, the sound-absorbing member can compensate for minute sound pressure spikes that may occur due to shape processing errors or changes in the operating environment, and can improve the performance stability of the transducer.

[0181] However, the material of the sound-absorbing member according to one embodiment of the present invention does not necessarily have to be limited to a specific material, and various known materials capable of effectively absorbing or scattering and attenuating ultrasonic energy, such as rubber, polymers, resins, and porous materials, may be adopted.

[0182] In addition, the method of attaching or applying the sound-absorbing material to the boundary surface of the piezoelectric element (10) and the thickness thereof can be appropriately changed according to the output specifications of the transducer or the target sound pressure fluctuation rate.

[0183] FIGS. 11 and 12 illustrate sound pressure distribution graphs of a conventional cylindrical ultrasonic transducer. FIGS. 13 and 14 illustrate sound pressure distribution graphs of a linear focused ultrasonic transducer according to one embodiment of the present invention. FIGS. 15 and 16 illustrate sound pressure distribution graphs of a linear focused ultrasonic transducer according to another embodiment of the present invention.

[0184] In order to objectively verify the effect of the linear focused ultrasonic transducer (1) according to the present invention, a numerical analysis simulation can be performed under driving frequency conditions of 4 megahertz (MHz).

[0185] At this time, in order to evaluate the sound pressure uniformity within the acoustic field, the areas of the 6-decibel (dB) sound field, the 2-decibel (dB) sound field, and the 1-decibel (dB) sound field can be calculated, respectively.

[0186] Referring to FIG. 11, in the case of a conventional cylindrical ultrasonic transducer (1'), it can be seen that a beading phenomenon occurs in which the sound pressure fluctuates rapidly within a linear focus (3) section along the first direction.

[0187] This is due to interference of diffracted waves occurring at the edge boundaries of the rectangular element, and the sound pressure fluctuation rate can be very large at the center of the linear focus (3).

[0188] In the 6-decibel sound field area, a portion where the sound pressure is about half or more of the peak sound pressure is displayed, in the 2-decibel sound field area, a portion where the sound pressure is about 80% or more of the peak sound pressure is displayed, and in the 1-decibel sound field area, a portion where the sound pressure is about 90% or more of the peak sound pressure is displayed.

[0189] Accordingly, referring to Fig. 11, it can be seen that even in the 6-decibel sound field region, the sound pressure distribution is concentrated only at both ends along the linear focus line, and there are places along the linear focus line where the focus is not well captured.

[0190] In addition, in the 2-decibel sound field range, it can be seen that focus is achieved smoothly only at both ends of the linear focus line, and focus is not achieved smoothly in most other parts.

[0191] In addition, it can be observed that in the 1-decibel sound field range, the focus is mostly not captured except at both ends of the linear focus line.

[0192] Also, referring to FIG. 12, it can be seen that in the case of a conventional ultrasonic transducer (1'), the sound pressure fluctuation rate relative to the peak sound pressure is approximately -2.51135 decibels (approx. 25%).

[0193] On the other hand, referring to FIG. 13, in the case of a linear focused ultrasonic transducer (1) according to one embodiment of the present invention, it can be seen that not only a 6-decibel sound field region but also a 2-decibel sound field region and a 1-decibel sound field region are formed continuously along a linear focus (3) line.

[0194] In particular, a 1-decibel sound field region where energy of more than 90% of the peak sound pressure is concentrated is continuously formed along a linear focus line (3), so that the intensity of the sound pressure can be maintained very uniformly within that section.

[0195] Also, referring to FIG. 14, the sound pressure fluctuation rate relative to the peak sound pressure according to one embodiment of the present invention may be approximately -0.741 decibels (approx. 8.2%).

[0196] This is a value in which the deviation of sound pressure is significantly reduced compared to the fluctuation rate of about 25% shown by the conventional transducer (1'), and it can be proven that the energy clustering phenomenon caused by diffraction is effectively controlled in forming a linear focus (3).

[0197] Referring to FIG. 15, in the case of a track-shaped piezoelectric element (10) according to another embodiment of the present invention, it can be seen that a 1-decibel sound field region is formed stably and uniformly along a linear focus line (3).

[0198] This may be the result of securing a sufficient ultrasonic radiation area through the central straight section while effectively suppressing diffracted waves through the curved shaping of both ends.

[0199] Accordingly, the effect of maintaining acoustic energy consistently without discontinuous interruption within the uniform sound pressure range effective for the procedure can be achieved.

[0200] Referring to FIG. 16, the sound pressure fluctuation rate relative to the peak sound pressure according to another embodiment of the present invention can be measured as approximately -0.36425 decibels (approx. 4.14%).

[0201] This is a value in which the deviation of sound pressure is significantly reduced compared to the fluctuation rate of about 25% shown by the conventional transducer (1'), and it can be confirmed that the ultrasonic transducer (1) according to the present invention can achieve an extremely precise sound pressure uniformity of less than 1 decibel.

[0202] These numerical results can show that the geometric structure of the track shape is optimized to evenly distribute acoustic energy over the entire length of the linear focus (3).

[0203] These simulation results can serve as a basis for fundamentally resolving the technical contradictions described in the background technology.

[0204] More specifically, the sound pressure fluctuation rate is maintained uniformly within 1 decibel (dB) throughout the entire linear focus (3), thereby preventing the risk of skin (2) burns or pain caused by energy concentration at a specific point during the procedure.

[0205] At the same time, even in the section where the negative pressure is low, energy exceeding the threshold required for the procedure can be stably delivered, thereby forming a uniform and consistent thermal coagulation point at the target depth inside the skin (2).

[0206] As a result, the linear focused ultrasound transducer (1) according to the present invention can provide a reliable energy distribution so that the operator can stably set an appropriate output value, and can simultaneously improve the predictability of the procedure and the safety of the patient.

[0207] FIG. 17 is a graph showing the sound pressure distribution of a linear focused ultrasonic transducer according to one embodiment of the present invention.

[0208] Referring to FIG. 17, in another embodiment of the present invention, the edges of the first reduction portion (21) and the second reduction portion (22) of the piezoelectric element (10) may be formed in a straight line shape having a predetermined slope.

[0209] Specifically, the edge of the first reduction portion (21) may be formed in a triangular or trapezoidal shape such that as it moves toward one end of the first direction side, both ends of the second direction side become closer to the center of the second direction side.

[0210] Similarly, the edge of the second reduction portion (22) may be formed in a triangular or trapezoidal shape such that as it moves toward the other end of the first direction side, both ends of the second direction side become closer to the center of the second direction side.

[0211] This straight edge structure can have the effect of lowering the processing difficulty compared to curve processing and improving manufacturing efficiency in the process of cutting the outer edge of the piezoelectric element (10).

[0212] At this time, the center (23) of the piezoelectric element (10), which maintains a width of planar width (d), can be in contact between the first reduction part (21) and the second reduction part (22).

[0213] At this time, the center (23) may be formed in a shape including a first length portion (232) formed as a part of a pair of boundary lines extending along the first direction of the boundary lines.

[0214] The first length portion (232) can form a section in which the width of the second direction side is maintained constant at the center (23) of the piezoelectric element (10).

[0215] At this time, the portion where the first reduction portion (21) or the second reduction portion (22) and the center (23) of the piezoelectric element (10) come into contact with each other may include a curved connecting portion (14).

[0216] A first reduction section (21) and a second reduction section (22) may be connected to each end of the first length section (232), and the connection portion may be smoothly connected so as to be differentiateable as described above.

[0217] The connecting part (14) can be formed so that the center of curvature is located inside the projection shape (20). That is, at the inflection point where the width begins to decrease, the straight lines are not connected in an angular manner, but can be smoothly connected through the connecting part (14) having a predetermined curvature.

[0218] In this way, by treating the point where the straight section and the center (23) meet as a curve, discontinuity in acoustic impedance due to abrupt shape changes at the mechanical boundary can be suppressed.

[0219] Accordingly, unintended edge diffraction waves that may occur at that point can be effectively controlled, and the peak phenomenon in which the sound pressure at the linear focus (3) rises sharply at a specific point can be prevented.

[0220] As a result, while adopting a straight-shaped reduction section that is easy to process, the sound pressure uniformity in the entire linear focus (3) section can be maintained at a level above a certain level through the curved forming of the connecting section (14).

[0221] However, the angle of the straight line shape or the specific trapezoidal ratio according to one embodiment of the present invention does not necessarily need to be limited to a specific numerical value, and it is sufficient if the connection part with the center (23) is rounded into a curve while maintaining a shape in which the overall width decreases.

[0222] Although embodiments of the present invention have been described above, the spirit of the present invention is not limited to the embodiments presented in this specification. Those skilled in the art who understand the spirit of the present invention may easily propose other embodiments within the scope of the same spirit by adding, changing, deleting, or adding components, and such embodiments shall also be considered to fall within the scope of the spirit of the present invention.

Claims

1. A linear focusing ultrasonic transducer comprising a piezoelectric element that focuses ultrasonic waves into a linear focus extending along a predetermined first direction, The above piezoelectric element includes a curved surface having a predetermined first radius of curvature centered on the linear focus, and The projection shape obtained by projecting the curved surface of the above-mentioned piezoelectric element onto a plane perpendicular to the normal direction at the center of the above-mentioned piezoelectric element is, It is formed to have a planar length extending along the first direction and a planar width in a second direction perpendicular to the first direction, and A linearly focused ultrasonic transducer, wherein a first reduction portion is formed at the first direction-side end portion such that the width of the second direction-side portion decreases as it moves toward the first direction-side end portion, and a second reduction portion is formed at the other end portion such that the width of the second direction-side portion decreases as it moves toward the other end portion of the first direction-side portion.

2. In Paragraph 1, The edge of the first reduction portion is formed in a shape corresponding to a first curve in which the center of curvature is located within the projection shape, and A linear focused ultrasonic transducer, wherein the edge of the second reduction portion is formed in a shape corresponding to a second curve in which the center of curvature is located within the projection shape.

3. In Paragraph 2, The above projection shape is, A virtual first region in the shape of a rectangle having the planar length along the first direction and the planar width along the second direction, and A linear focused ultrasonic transducer formed in a shape corresponding to a third region that overlaps with a second region according to [Equation 1], following a coordinate system with the center of the first region as the origin. [Mathematical Formula 1] 4. In Paragraph 3, A linear focused ultrasonic transducer in which the m value and the n value are the same in the above [Mathematical Formula 1].

5. In Paragraph 4, A linear focused ultrasonic transducer in the above [Mathematical Formula 1], wherein the values ​​of m and n are 2.

6. In Paragraph 3, A linear focused ultrasonic transducer, wherein in the above [Mathematical Formula 1], the value of b is at least 1 time and no more than 10 times the plane width.

7. In Paragraph 3, The first curve includes the boundary line of the second region, and the end of the first curve is connected to the boundary line of the first region, wherein In the above [Mathematical Formula 1], if the value of b exceeds the plane width, The above first curve is, A line-focused ultrasonic transducer, wherein the position of the end of the first curve is offset by a predetermined distance from the intersection point where the first region and the second region intersect, and is corrected to pass through the connection point where the first curve and the first region are connected, and the slope of the tangent of the first curve at the connection point matches the slope of the boundary line of the first region.

8. In Paragraph 7, The second curve includes a boundary line of the second region, and the end of the second curve is connected to the boundary line of the first region, wherein In the above [Mathematical Formula 1], if the value of b exceeds the plane width, The above second curve is, A line-focused ultrasonic transducer, wherein the position of the end of the second curve is adjusted to be spaced a predetermined distance from the intersection point where the first region and the second region intersect, and passes through the connection point where the second curve and the first region are connected, and the slope of the tangent of the second curve at the connection point matches the slope of the boundary line of the first region.

9. In Paragraph 3, The above projection shape is, A first length portion formed as a part of a pair of boundary lines extending along the first direction among the boundary lines of the first region, and A linear focused ultrasonic transducer formed in a shape including a first curve connected to one end of the first length portion and a second curve connected to the other end of the first length portion.

10. In Paragraph 3, The above second region is, A linear focused ultrasound transducer formed by a region with a boundary of a virtual curve located within a range that is expanded or contracted by 10% or less from the origin of the coordinate system, according to the above [Mathematical Formula 1].

11. In Paragraph 2, A line-focused ultrasonic transducer in which the first curve and the second curve are formed in a shape symmetrical to each other with respect to the center of the projection shape.

12. In Paragraph 2, The above projection shape is, A virtual fourth region having a length obtained by subtracting a predetermined curvature reference length from the plane length along the first direction, and having the plane width along the second direction, and A linear focused ultrasonic transducer formed in a shape corresponding to a sixth region formed by combining a fifth region according to [Equation 2], following a coordinate system with the center of the fourth region as the origin. [Mathematical Formula 2] 13. In Paragraph 12, A linear focused ultrasonic transducer in which the values ​​of m and n are the same in the above [Mathematical Formula 2].

14. In Paragraph 13, A linear focused ultrasonic transducer in the above [Mathematical Formula 2], wherein the values ​​of m and n are 2.

15. In Paragraph 12, The above projection shape is, A first length portion formed as a part of a pair of boundary lines extending along the first direction among the boundary lines of the fourth region, and A linear focused ultrasonic transducer formed in a shape including a first curve connected to one end of the first length portion and a second curve connected to the other end of the first length portion.

16. In Paragraph 12, The above fifth region is, A linear focused ultrasound transducer formed by a region using a virtual curve as a boundary, located within a range that expands or contracts the virtual region formed according to [Mathematical Formula 2] to a range of 10% or less from the origin of the coordinate system.

17. In Paragraph 1, A linear focused ultrasonic transducer having a continuous electrode formed on the surface of the piezoelectric element having a shape corresponding to the projection shape.

18. In Paragraph 1, At the boundary surface of the first reduction part and the second reduction part of the projection shape of the above piezoelectric element, A linear focused ultrasonic transducer having a sound-absorbing member formed therein that absorbs edge diffraction waves generated at the above interface to reduce the longitudinal sound pressure deviation of the linear focus.

19. In Paragraph 1, The edge of the first reduction portion is formed in a triangular or trapezoidal shape such that as it approaches one end of the first direction side, both ends of the second direction side become closer to the center of the second direction side. A linear focused ultrasonic transducer, wherein the edge of the second reduction portion is formed in a triangular or trapezoidal shape such that as it moves toward the other end of the first direction side, both ends of the second direction side become closer to the center of the second direction side.

20. In Paragraph 19, The above projection shape is, A first length portion formed as a part of a pair of boundary lines extending along the first direction, and It is formed in a shape including a first reduction part connected to one end of the first length part and a reduction part connected to the other end of the first length part, The portion where the first reduction portion or the second reduction portion of the projection shape of the above piezoelectric element and the first length portion come into contact is A linear focused ultrasound transducer formed in a curved shape with the center of curvature located within the projection shape.

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