Image processing device having a piezoelectric transceiver

Abstract

To provide a micromachined ultrasonic transducer (MUT) including an electrode designed to improve both acoustical and electrical performances of the transducer.SOLUTION: A micromachined ultrasonic transducer (MUT) (720) includes a substrate; a membrane suspending from the substrate; a bottom electrode disposed on the membrane; a piezoelectric layer disposed on the bottom electrode, and an asymmetric top electrode (722) disposed on the piezoelectric layer. The areal density distribution of the asymmetric electrode (722) along an axis (742) has a plurality of local maxima, and locations of the plurality of local maxima coincide with locations (726) (728) where a plurality of anti-nodal points at a vibrational resonance frequency is located.SELECTED DRAWING: Figure 7B

Description

[Technical field]

[0001] The present invention relates to an image processing device, and more particularly to an image processing device having a micromachined ultrasonic transducer (MUT). [Background technology]

[0002] A non-invasive imaging system for imaging internal organs of the human body and displaying images of the internal organs transmits signals into the body and receives reflected signals from the organs. Typically, the transducers used in the imaging system, such as capacitive MUTs (cMUTs) or piezoelectric MUTs (pMUTs), are called transceivers, some of which are based on photoacoustic or ultrasound effects.

[0003] Generally, MUTs include two or more electrodes, and the topology of the electrodes affects the electrical and acoustic performance of the MUT. For example, as the size of the electrodes increases, the amplitude of the sound pressure generated by the pMUT increases, thereby improving the acoustic performance of the pMUT. However, as the size of the electrodes increases, the capacitance also increases, which reduces the electrical performance of the pMUT. In another example, the amplitude of the sound pressure at the vibration resonance frequency of the pMUT is affected by the geometry of the electrodes. Therefore, a method is needed to design electrodes to improve both the acoustic and electrical performance of the transducer. Summary of the Invention

[0004] In an embodiment, a micromachined ultrasonic transducer (MUT) includes an asymmetric top electrode, the areal density distribution of the asymmetric electrode along an axis having multiple maxima, where the locations of multiple maxima coincide with the locations of multiple antinodes at vibration resonance frequencies.

[0005] In an embodiment, a micromachined ultrasonic transducer (MUT) includes a symmetric top electrode, the areal density distribution of the symmetric electrode along an axis having multiple maxima, where the locations of multiple maxima coincide with the locations of multiple antinodes at vibration resonance frequencies.

[0006] In an embodiment, the transducer array comprises a number of micromachined ultrasonic transducers (MUTs), each of the plurality of MUTs comprising an asymmetric top electrode.

[0007] In an embodiment, the imaging device includes a transducer array having a number of micromachined ultrasonic transducers (MUTs), each of the MUTs having a symmetric upper electrode, the areal density distribution of the symmetric electrodes along an axis having a number of maxima, where the locations of the maxima coincide with the locations of the antinodes at the vibration resonance frequency. [Brief description of the drawings]

[0008] Reference will now be made to embodiments of the invention, examples of which are illustrated in the accompanying drawings. These drawings are intended as illustrative of the invention, but not limiting, and while the invention is generally described in the context of these embodiments, it will be understood that it is not intended to limit the scope of the invention to these specific embodiments. [Figure 1] FIG. 1 illustrates an image processing system according to an embodiment of the present disclosure. [Diagram 2] FIG. 2 shows a schematic diagram of an imaging device according to an embodiment of the present disclosure. [Figure 3A] FIG. 3A illustrates a side view of a transceiver array according to an embodiment of the present disclosure. [Figure 3B] FIG. 3B illustrates a top view of a transceiver tile according to an embodiment of the disclosure. [Figure 4A] FIG. 4A illustrates a plan view of a MUT according to an embodiment of the present disclosure. [Figure 4B] FIG. 4B shows a cross-sectional view of an MUT according to an embodiment of the present disclosure taken along line 4-4 in FIG. 4A. [Figure 5A] FIG. 5A illustrates vibration mode shapes of a MUT according to an embodiment of the present disclosure. [Figure 5B]FIG. 5B illustrates vibration mode shapes of the MUT according to an embodiment of the present disclosure. [Figure 5C] FIG. 5C illustrates vibration mode shapes of a MUT according to an embodiment of the present disclosure. [Figure 5D] FIG. 5D illustrates vibration mode shapes of a MUT according to an embodiment of the present disclosure. [Figure 5E] FIG. 5E illustrates vibration mode shapes of a MUT according to an embodiment of the present disclosure. [Figure 6A] FIG. 6A shows a plot of the acoustic response of a MUT as a function of frequency in accordance with an embodiment of the present disclosure. [Figure 6B] FIG. 6B illustrates a plan view of a MUT according to an embodiment of the present disclosure. [Figure 6C] FIG. 6C illustrates the areal density distribution of the top electrode according to an embodiment of the present disclosure. [Figure 7A] FIG. 7A shows a plot of the acoustic response of a MUT as a function of frequency in accordance with an embodiment of the present disclosure. [Figure 7B] FIG. 7B illustrates a plan view of the MUT according to an embodiment of the present disclosure. [Figure 7C] FIG. 7C illustrates the areal density distribution of the top electrode according to an embodiment of the present disclosure. [Figure 8A] FIG. 8A shows a plot of the acoustic response of a MUT as a function of frequency in accordance with an embodiment of the present disclosure. [Figure 8B] FIG. 8B illustrates a plan view of the MUT according to an embodiment of the present disclosure. [Figure 8C] FIG. 8C illustrates the areal density distribution of the top electrode according to an embodiment of the present disclosure. [Figure 9A] FIG. 9A shows a plot of the acoustic response of a MUT as a function of frequency in accordance with an embodiment of the present disclosure. [Figure 9B] FIG. 9B illustrates a plan view of a MUT according to an embodiment of the present disclosure. [Figure 9C] FIG. 9C illustrates the areal density distribution of the top electrode according to an embodiment of the present disclosure. [Figure 10A] FIG. 10A shows a plot of the acoustic response of a MUT as a function of frequency in accordance with an embodiment of the present disclosure. [Figure 10B] FIG. 10B illustrates a plan view of the MUT according to an embodiment of the present disclosure. [Figure 10C] FIG. 10C illustrates the areal density distribution of the top electrode according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] In the following description, for purposes of explanation, specific details are set forth in order to provide an understanding of the present disclosure. However, it will be apparent to one skilled in the art that these details may be practiced without the need for such details. Furthermore, one skilled in the art will recognize that the embodiments of the present disclosure described below can be implemented in various ways, such as as a process, an apparatus, a system, or a device.

[0010] The elements / components shown in the figures are illustrative of exemplary embodiments of the disclosure and are not intended to obscure the disclosure. Reference herein to "one embodiment," "preferred embodiment," "embodiment," or "embodiments" means that a particular feature, structure, characteristic, or function described in connection with an embodiment is present in at least one embodiment of the disclosure and may be present in more than one embodiment. The appearance of the phrases "in one embodiment," "in an embodiment," or "in embodiments" in various places in this specification do not necessarily all refer to the same embodiment. The terms "include," "including," "comprise," and "comprising" are to be understood as open terms, and any listing preceding them is merely exemplary and is not meant to be limited to the listed items. Any headings used herein are for organizational purposes only and are not to be used to limit the scope of the description or claims. Additionally, the use of certain terms in various places in this specification is merely exemplary and should not be construed as limiting.

[0011] FIG. 1 shows a schematic diagram of an imaging system (100) according to an embodiment of the present disclosure. As depicted, the system (100) may include an imaging device (120) that generates and transmits pressure waves (122) to an internal organ (112), such as the heart, and receives reflected pressure waves from the internal organ, in a transmission mode / process, and a device (102) that transmits and receives signals to the imaging device through a communication path (130). In an embodiment, the internal organ ( The pressure wave (122) can be reflected by the pressure transducer (112) to the imaging device (120), which in a receiving mode / process can capture the reflected pressure wave and generate an electrical signal. The imaging device (120) can communicate the electrical signal to the device (102), which can use the electrical signal to display an image of the organ or target on the display / screen (104).

[0012] In an embodiment, the imaging device 120 may also be used to take images of the animal's internal organs. The imaging device 120 may also be used to determine blood flow direction and velocity in arteries and veins, as done in Doppler mode imaging, and to measure tissue stiffness. In an embodiment, the pressure waves 122 may be acoustic waves that can pass through the human / animal body and be reflected by the internal organs, tissues, or arteries and veins.

[0013] In an embodiment, the imaging apparatus (120) may be a portable device and may communicate signals to the device (102) over a communication channel (130) wirelessly (using a protocol such as 802.11) or via a cable (such as USB2, USB3, USB 3.1, USB-C, and USB Thunderbolt). In an embodiment, the device (102) may be a mobile device such as a cell phone or iPad, or a fixed computing device capable of displaying images to a user.

[0014] In embodiments, more than one imaging device may be used to develop an image of a target organ, for example, a first imaging device may transmit pressure waves to the target organ while a second imaging device may receive reflected pressure waves from the target organ and generate an electric charge in response to the received waves.

[0015] FIG. 2 shows a schematic diagram of an imaging device (120) according to an embodiment of the present disclosure. In an embodiment, the imaging device (120) may be an ultrasound imaging device. As depicted in FIG. 2, the imaging device (120) includes a transceiver tile (210) for transmitting and receiving pressure waves, a coating layer (212) that acts as a lens for directing and / or focusing the pressure waves or acts as an acoustic impedance interface between the transceiver tile and the human body (110), a controller (202) such as an ASIC chip (or ASIC for short) coupled to the transducer tile (210) by protrusions for controlling the transceiver tile (210), and a field programmable logic (PLC) for controlling the components of the imaging device (120). The imaging device may include a field programmable gate array (FPGA) (214), circuitry such as an analog front end (AFE) (215) for signal processing / conditioning, an acoustic absorbing layer (203) for absorbing waves generated by the transducer tile (210) and propagating towards the circuitry (215), a communication unit (208) for communicating data with an external device such as the device (102) through one or more ports (216), a memory (218) for storing data, a battery (206) for powering the components of the imaging device, and optionally a display (217) for displaying an image of the target organ.

[0016] In an embodiment, the device (102) may include a display / screen. In such cases, a display may not be present in the imaging device (120). In an embodiment, the imaging device (120) may receive power from the device (102) through one of the ports (216). In such cases, the imaging device (120) may not include a battery (206). It should be noted that one or more of the components of the imaging device (120) may be combined into one integral electrical component. Similarly, the components of the imaging device (120) may each be implemented in one or more electrical components.

[0017] In an embodiment, a user may apply gel to the skin of the human body (110) before the human body (110) comes into direct contact with the coating layer (212), which improves impedance matching at the interface between the coating layer (212) and the human body (110), i.e., reduces losses of the pressure wave (122) at the interface, and also reduces losses of the reflected wave traveling towards the imaging device (120) at the interface. In an embodiment, the transceiver tile (210) is mounted on a substrate and includes an acoustic absorbing layer (212). The acoustically absorbing layer absorbs any ultrasound signals that are reflected back, which would otherwise be reflected and interfere with the quality of the image.

[0018] As discussed below, the coating layer (212) may be only a horizontal matching layer that maximizes the transmission of the acoustic signal from the transducer to the body and vice versa. Beam focusing is not necessary in this case since it can be implemented electronically in the control device (202). The imaging device (120) can use the reflected signal to create an image of the organ (112), the results of which may be displayed on a screen in various formats as graphs, plots, and statistical data with or without an image of the organ (112).

[0019] In an embodiment, the controller (202), such as an ASIC, may be assembled with the transceiver tile as a single unit. In other embodiments, the controller (202) may be located external to the imaging device (120) and electrically connected to the transceiver tile (210) by a cable. In an embodiment, the imaging device (120) may include a housing that encloses the components (202)-(215) and a heat dissipation mechanism for dissipating thermal energy generated by the components.

[0020] FIG. 3A illustrates a side view of a transceiver array (200) according to an embodiment of the present disclosure. FIG. 3B illustrates a top view of a transceiver tile (210) according to an embodiment of the present disclosure. In an embodiment, the array (200) may comprise one or more transceiver tiles (210). As depicted, the transceiver array (200) may comprise one or more transceiver tiles (210) arranged in a predetermined manner. For example, as depicted in FIG. 3A, the transceiver tiles (or, for short, tiles) (210) may be physically bent and placed on the imaging device (120) to further form a curved transceiver array. It will be apparent to one of ordinary skill in the art that the imaging device (120) may comprise any suitable number of tiles, the tiles may be arranged in any suitable manner, and each tile (210) may have any suitable number of piezoelectric elements (302) disposed on the transceiver substrate (304). One or more temperature sensors (320) may be located in the substrate (304) to monitor the temperature of the transceiver tiles (210) during operation. In an embodiment, the transceiver array (200) may be a micromachined array fabricated from the substrate.

[0021] FIG 4A shows a plan view of a MUT (400) according to an embodiment of the present disclosure. FIG 4B shows a cross-sectional view of a MUT according to an embodiment of the present disclosure taken along line 4-4 in FIG 4A. As depicted, the MUT may include a membrane layer (406) suspended from a substrate (402), a bottom electrode (O) (408) disposed on the membrane layer (or membrane for short) (406), a piezoelectric layer (410) disposed on the bottom electrode (O) (408), and a top electrode (X) (412) disposed on the piezoelectric layer (410).

[0022] In an embodiment, the substrate (402) and the membrane (406) may be integrally formed, and a cavity (404) may be formed to define the membrane (406). In an embodiment, the cavity (404) may be filled with a gas at a predetermined pressure or an acoustic damping material to control vibration of the membrane (406). In an embodiment, the geometry of the projected area of ​​the upper electrode (412) may be configured to control the dynamic performance and capacitance magnitude of the pMUT (400).

[0023] In an embodiment, each of the MUTs (400) may be a pMUT, and may be selected from PZT, KNN, PZT-N, PMN-Pt, AlN, Sc-AlN, ZnO, PVDF, and LiNiO 3 In an alternative embodiment, each of the MUTs (400) may be a cMUT. In FIG. 4A, each of the MUTs (400) is shown as a rectangle. In an embodiment, each of the MUTs (400) may comprise an upper electrode that is elliptical when viewed from the top of the MUT (400). Hereinafter, the term shape of the upper electrode (412) refers to the two-dimensional shape of the upper electrode taken by projecting the upper electrode onto the xy plane. Furthermore, the shape of the upper electrode is called symmetrical when it is symmetrical with respect to two lines (450) and (452). In that case, the lines (450) and (452) are symmetrical with respect to the x-axis and x-axis, respectively. y-axis and passes through the midpoint of the top electrode on the x-axis. Further, hereinafter, the x-axis extends along the longest dimension of the top electrode. It will be apparent to one skilled in the art that the top electrode may have other suitable symmetrical shapes, such as square, circular, rectangular, and elliptical.

[0024] 5A-5E show five vibration modes (500), (510), (520), (530), and (540) according to embodiments of the present disclosure. In FIG. 5A-5E, each of the MUTs (502), (512), (522), (532), and (542) is shown as a single line for illustrative purposes, where each single line represents the curvature of the stack within the MUT. During actuation, the stack including the membrane (406), the bottom electrode (408), the piezoelectric layer (410), and the top electrode (412) can move as a unit in the vertical direction and may be deformed to have a single-line curvature in the xz plane. Furthermore, the lines (502), (512), (522), (532), and (542) corresponding to different vibration modes represent the curvature of the stack in the different vibration modes.

[0025] In an embodiment, five vibration modes (500), (510), (520), (530), and (540) may be associated with five vibrational resonant frequencies, f1, f2, f3, f4, and f5, respectively. In Figures 5A-5E, only five vibrational modes are shown. However, it will be apparent to one skilled in the art that the MUT can operate with more than five vibrational resonant modes (or, for short, vibrational modes).

[0026] In Figure 5A, the MUT (502) can be operated in a first vibration mode (500), where the arrow (504) indicates that the MUT (502) (specifically the stack) moves vertically in the first vibration mode (500). In an embodiment, the first vibration mode (500) can be symmetric, i.e., the shape of the mode is symmetric about the centerline (506) of the MUT. In an embodiment, the shape of the top electrode of the MUT (502) can be symmetric and similar to the shape of the top electrode (412).

[0027] In FIG. 5C, the MUT (522) can operate in a third vibration mode (520). In an embodiment, the third vibration mode (520) can be symmetric, i.e., the mode shape is symmetric with respect to the centerline (506). Hereinafter, the term symmetric vibration mode refers to a vibration mode in which the positions of antinodes, such as (525), (526), ​​and (527) (i.e., peak amplitude), are arranged symmetrically with respect to the centerline (506), and the centerline (506) represents a line that passes through the midpoint of the MUT on the x-axis and is parallel to the z-axis. Similarly, the term asymmetric vibration mode refers to a vibration mode in which the positions of antinodes, such as (516) and (517) in FIG. 5B, are arranged asymmetrically with respect to the centerline (506).

[0028] In the third vibration mode (520), the MUT (522) may have two nodes and three antinodes (equally or similarly three peak amplitude points) (525), (526), ​​and (527). In an embodiment, the shape of the upper electrode of the MUT (522) may be symmetrical and similar to the shape of the upper electrode (412).

[0029] In FIG. 5E, the MUT (542) can operate in a fifth vibration mode (540). In an embodiment, the fifth vibration mode (540) can be symmetric, i.e., the shape of the mode is symmetric about the centerline (506). In the fifth vibration mode, the MUT (542) can have four nodes and five antinodes (i.e., five peak amplitude points) (544), (545), (546), (547), and (548). In an embodiment, the shape of the upper electrode of the MUT (542) can be symmetric and similar to the shape of the upper electrode (412).

[0030] In an embodiment, if the geometry of the upper electrode is symmetric, the MUT can operate in symmetric vibration modes (500), (520), and (540). In an embodiment, the geometry of the upper electrode may be altered so that the MUT can vibrate in one or more symmetric or asymmetric vibration modes. In FIG. 5B, the MUT (512) can operate in an asymmetric second vibration mode (510). In the asymmetric second vibration mode, the MUT (512) may have one node and two antinodes (or equivalently two peak amplitude points) (516) and (517). The geometry of the upper electrode corresponding to the MUT (512) is also described in FIGS. 7A-7C.

[0031] In FIG. 5D , the MUT (532) can operate in an asymmetric third vibration mode (530). As depicted, the vibration mode (530) can be asymmetric with respect to the centerline (506). In the asymmetric third vibration mode, the MUT (532) can have two nodes and three antinodes (or equivalently three peak amplitude points) (534), (535), and (537). In an embodiment, the peak amplitude (539) of the asymmetric third vibration mode (530) can be higher than the peak amplitude (529) of the symmetric third vibration mode (520). Overall, the asymmetric vibration mode (e.g., (530)) can have a higher peak amplitude than the symmetric vibration mode (e.g., (520)) of the same order.

[0032] Overall, the acoustic pressure performance refers to the energy of the acoustic pressure wave generated by each MUT at a certain frequency. The acoustic pressure performance can increase as the peak amplitude of the MUT increases at that frequency. As depicted in FIGS. 5C and 5D, the asymmetric vibration mode may have a higher peak amplitude than the symmetric vibration mode of the same order. Therefore, a MUT operating in an asymmetric vibration mode may produce a higher acoustic pressure performance than a MUT operating in a symmetric vibration mode of the same order. Furthermore, the frequency of the symmetric vibration mode may be different from the frequency of the asymmetric vibration mode of the same order. Therefore, in an embodiment, the vibration resonant frequency of each MUT can be adjusted by switching from a symmetric mode to an asymmetric mode of the same order (or vice versa).

[0033] FIG. 6A shows a plot (600) of the acoustic response of a MUT (620) comprising a top electrode (622) according to an embodiment of the present disclosure. FIG. 6B shows a top view of the MUT (620) according to an embodiment of the present disclosure. In FIG. 6B, height H (641) represents the vertical dimension of the top electrode, and FIG. 6C shows a distribution (660) of height H (641) (i.e., areal density distribution) along the x-axis (642) according to an embodiment of the present disclosure. For illustrative purposes, the vibration mode (500) of FIG. 5A is shown above the plot (660). As depicted, the projected area of ​​the top electrode (622) is in the shape of an ellipse, and the ellipse is symmetrical about both the centerline (630) and the x-axis (642), i.e., the shape of the top electrode is symmetrical. As such, the MUT (620) may have strong acoustic responses at symmetric vibration modes f1, f3, and f5. Additionally, the MUT (620) may have very weak acoustic responses in the asymmetric vibration modes (510) (f2) and (530) (f4), as indicated by circles (612) and (614).

[0034] In an embodiment, the location (625) of maximum height H (641) is the same as the location (503) where the antinode (i.e., peak amplitude) of vibration mode (500) occurs. As a result, as shown by circle (602), the acoustic response of the MUT (620) is strongest at frequency f1, where f1 corresponds to the first symmetric vibration mode (500).

[0035] FIG. 7A shows an acoustic response plot (700) of a MUT (720) with a top electrode (722) according to an embodiment of the present disclosure. FIG. 7B shows a top view of the MUT (720) according to an embodiment of the present disclosure. In FIG. 7B, height H (741) represents the vertical dimension of the top electrode. FIG. 7C shows a distribution (760) of height H (741) (or equivalently an areal density distribution) along the x-axis (742) according to an embodiment of the present disclosure. For illustrative purposes, the vibration mode (510) of FIG. 5B is shown above the areal density distribution plot (760). As discussed above, the terms height and areal density are used interchangeably, as the height distribution (760) may represent the distribution of areal density of the top electrode (722) along the x-axis (742).

[0036] As depicted in FIG. 7B, the shape of the top electrode (722) may be asymmetric since the top electrode (722) is not symmetric about a centerline (730) passing through the midpoint of the top electrode on the x-axis. As a result, the MUT (720) may operate in both symmetric vibration modes (f1, f3, and f5) and asymmetric vibration modes (f2 and f4). In an embodiment, the locations (726) and (728) of the local maxima H1 (735) and H2 (737) of the areal density distribution (760) coincide with the antinodes (516) and (517), respectively, of the vibration mode (510). As a result, the MUT (720) may have the strongest acoustic response at frequency f2, as indicated by circle (702).

[0037] In an embodiment, the ratio of L1 (731) to L2 (733) may be adjusted to adjust the positions (726) and (728) of the local maxima of the areal density distribution. For example, the ratio of L1 (731) to L2 (733) may be greater than 1.05. In an embodiment, the ratio of H1 (735) to H2 (737) may be adjusted to adjust the acoustic response at frequency f2. For example, the ratio of height H1 (735) to H2 (737) may be greater than 1.05.

[0038] In an embodiment, the areal density distribution (760) of the upper electrode (722) may affect the acoustic response of the MUT (720). As described in connection with Figures 9A-9C, the areal density distribution of the upper electrode (722) may be modified such that the acoustic response has a maximum value at frequency f4.

[0039] FIG. 8A shows a plot (800) of the acoustic response of a MUT (820) with a top electrode (822) according to an embodiment of the present disclosure. FIG. 8B shows a top view of the MUT (820) according to an embodiment of the present disclosure. FIG. 8C shows a distribution (860) of the height H (841) of the top electrode (822) along the x-axis (843) (or equivalently an areal density distribution). For illustrative purposes, the symmetric vibration mode (520) of FIG. 5C is also shown on the plot (860). As depicted, the top electrode (822) may be symmetric, since it is symmetric about both the x-axis (843) and the centerline (830). As a result, the MUT (820) may have a strong acoustic response in the symmetric vibration modes (f1, f3, and f5) and a very weak acoustic response in the asymmetric vibration modes (f2 and f4), as shown by the circles (804) and (806).

[0040] As depicted, areal density distribution (860) may have local maxima at three locations (824), (825), and (826). Moreover, these three locations (824), (825), and (826) coincide with locations (525), (526), ​​and (527), respectively, where antinodes of the third symmetric vibration mode (520) exist. As a result, the MUT (820) may have its strongest acoustic response at frequency f3, as indicated by circle (802).

[0041] In an embodiment, the ratio of L3 (844) to L4 (846) may be adjusted to adjust the location of the maximum (824) of the areal density distribution. For example, the ratio of L3 (844) to L4 (846) may be 10 or greater. In an embodiment, the ratio of H3 (850) to H4 (852) may be adjusted to adjust the acoustic response at frequency f2. For example, the ratio of H3 (850) to H4 (852) may be 1.05 or greater.

[0042] FIG. 9A illustrates an acoustic response plot (900) of a MUT (920) with a top electrode (922) according to an embodiment of the present disclosure. FIG. 9B illustrates a top view of a MUT (920) according to an embodiment of the present disclosure. FIG. 9C illustrates a distribution (960) of height H (941) along the x-axis (943). For illustrative purposes, the asymmetric vibration modes (530) of FIG. 5D are also shown on the height (or areal density) distribution plot (960). As depicted, the top electrode (922) may be asymmetric with respect to the centerline (930). As a result, the MUT (920) may have both symmetric vibration modes (f1, f3, and f5) and asymmetric vibration modes (f2 and f4). Furthermore, in an embodiment, the acoustic response may be strongest at the asymmetric vibration frequency f4 (530), as indicated by the circle (902).

[0043] In an embodiment, areal density distribution (960) may have local maxima at three locations (924), (925), and (926). Furthermore, these three locations (924), (925), and (926) may coincide with locations (534), (535), and (537) where antinodes of vibration mode (530) exist. As a result, MUT (920) may have its strongest acoustic response at frequency f4, as shown by circle (902).

[0044] FIG. 10A shows a plot (1000) of the acoustic response of a MUT (1020) having a top electrode (1022) according to an embodiment of the present disclosure. FIG. 10B shows a top view of the MUT (1020) according to an embodiment of the present disclosure. FIG. 10C shows a plot (1000) of the acoustic response along the x-axis (1043). 5E. The distribution (1060) of height H (1041) is shown. For illustrative purposes, the symmetric vibration modes (540) of FIG. 5E are also shown on the plot (1060). As depicted, the upper electrode (1022) may be symmetric, since it is symmetric about both the x-axis (1043) and the centerline (1030). As a result, the MUT (1020) may have a strong acoustic response at the symmetric vibration modes (f1, f3, and f5) and a very weak acoustic response at the asymmetric vibration modes (f2 and f4). Furthermore, the acoustic response is strongest at the fifth symmetric vibration mode f5, as indicated by the circle (1002).

[0045] In an embodiment, the areal density distribution (1060) may have local maxima at five locations (1024), (1025), (1026), (1027), and (1028). Furthermore, these five locations (1024), (1025), (1026), (1027), and (1028) may coincide with locations (544), (545), (546), (547), and (548) where the peak amplitude of vibration mode (540) is present. As a result, the MUT (1020) may have its strongest acoustic response at frequency f5.

[0046] In an embodiment, a symmetric upper electrode may have a strong acoustic response in a symmetric vibration mode and a very weak acoustic response in an asymmetric vibration mode, as described in connection with Figures 6A-10C. Furthermore, in an embodiment, an asymmetric upper electrode may have a strong acoustic response in both the symmetric and asymmetric vibration modes. In an embodiment, to increase the acoustic response in a vibration mode, the areal density distribution of the upper electrode may be adjusted such that a local maximum (or maximum) of the areal density distribution is located at a location where an antinode of the vibration mode is located.

[0047] For illustrative purposes, only five vibration modes f1-f5 are shown in Figures 6A-10C. However, it will be apparent to one skilled in the art that the MUT may have more than five vibration modes. Furthermore, it will be apparent to one skilled in the art that the areal density distribution may be adjusted to adjust the magnitude of the acoustic response at the higher vibration modes, as described in Figures 6A-10C.

[0048] It should be noted that each of the MUTs (302) in FIG. 3B may be a piezoelectric micromachined ultrasonic transducer (pMUT). However, it will be apparent to one skilled in the art that the transceiver tile (210) may comprise an array of capacitive micromachined ultrasonic transducers (cMUTs), i.e., the piezoelectric elements (302) may be replaced with cMUTs. In such a case, the top electrode of the CMUT may be shaped similar to one of the top electrode shapes (622), (722), (822), (922), and (1022). As a result, the acoustic response of the cMUT is tailored at various vibration resonant frequencies based on the principles described in connection with FIGS. 6A-10C.

[0049] While the invention is susceptible to various modifications and alternative forms, specific examples thereof have been shown in the drawings and are described in detail herein, it is to be understood, however, that the invention is not limited to the specific forms disclosed, but on the contrary, the invention covers all modifications, equivalents, and alternatives falling within the scope of the appended claims.

Claims

1. a first electrode having at least a first symmetric vibration mode and a first asymmetric vibration mode, the first electrode having a first axis extending along a direction in which a dimension of the first electrode is longest, and a second axis perpendicular to the first axis and passing through a midpoint between both ends of the first electrode on the first axis; the first symmetric vibration mode corresponds to a first vibration frequency and the first asymmetric vibration mode corresponds to a second vibration frequency; an acoustic response of the first electrode in the first asymmetric vibration mode is greater than an acoustic response of the first electrode in the first symmetric vibration mode; A micromachined ultrasonic transducer (MUT) comprising:

2. The micromachined ultrasonic transducer (MUT) of claim 1 , wherein the micromachined ultrasonic transducer (MUT) is a capacitive micromachined ultrasonic transducer (cMUT).

3. The micromachined ultrasonic transducer (MUT) of claim 1 , wherein the micromachined ultrasonic transducer (MUT) is a piezoelectric micromachined ultrasonic transducer (pMUT).

4. The shape of the first electrode is asymmetric with respect to the second axis. The micromachined ultrasonic transducer (MUT) of claim 1.

5. 5. The micromachined ultrasonic transducer (MUT) of claim 1, wherein the first electrode has a plurality of symmetric vibration modes including the first symmetric vibration mode and a plurality of asymmetric vibration modes including the first asymmetric vibration mode.

6. 6. The micromachined ultrasonic transducer (MUT) of claim 1, wherein an acoustic response of the first electrode in the first asymmetric vibration mode and an acoustic response of the first electrode in the first symmetric vibration mode are greater than an acoustic response of a symmetric electrode in an asymmetric vibration mode.

7. A substrate on which the first electrode is provided; a second electrode disposed on the substrate, the second electrode not being in the same plane as the first electrode; The micromachined ultrasonic transducer (MUT) of any one of claims 1 to 6, comprising:

8. A substrate; a film on the substrate; A second electrode provided on the substrate; a piezoelectric layer provided on the second electrode; having The first electrode is provided on the piezoelectric layer. A micromachined ultrasonic transducer (MUT) according to any one of claims 1 to 7.

9. The piezoelectric layer is selected from the group consisting of PZT, KNN, PZT-N, PMN-Pt, AlN, Sc-AlN, ZnO, PVDF and LiNiO ３ 9. The micromachined ultrasonic transducer (MUT) of claim 8, made from at least one of:

10. a transducer array including a plurality of micromachined ultrasonic transducers (MUTs); Each micromachined ultrasonic transducer (MUT) a first electrode having at least a first symmetric vibration mode and a first asymmetric vibration mode, the first electrode having a first axis extending along a direction in which a dimension of the first electrode is longest, and a second axis perpendicular to the first axis and passing through a midpoint between both ends of the first electrode on the first axis; the first symmetric vibration mode corresponds to a first vibration frequency and the first asymmetric vibration mode corresponds to a second vibration frequency; an acoustic response of the first electrode in the first asymmetric vibration mode is greater than an acoustic response of the first electrode in the first symmetric vibration mode; 1. An image processing device comprising:

11. The image processing device of claim 10, wherein the micromachined ultrasonic transducer (MUT) is a capacitive micromachined ultrasonic transducer (cMUT).

12. The image processing apparatus of claim 10 , wherein the micromachined ultrasonic transducer (MUT) is a piezoelectric micromachined ultrasonic transducer (pMUT).

13. The shape of the first electrode is asymmetric with respect to the second axis. The image processing device according to claim 10.

14. The image processing device according to any one of claims 10 to 13, wherein the first electrode has a plurality of symmetric vibration modes including the first symmetric vibration mode and a plurality of asymmetric vibration modes including the first asymmetric vibration mode.

15. The image processing device according to any one of claims 10 to 14, characterized in that the acoustic response of the first electrode in the first asymmetric vibration mode and the acoustic response of the first electrode in the first symmetric vibration mode are greater than the acoustic response of a symmetric electrode in an asymmetric vibration mode.

16. A substrate on which the first electrode is provided; a second electrode disposed on the substrate, the second electrode not being in the same plane as the first electrode; The image processing device according to any one of claims 10 to 15, further comprising:

17. A substrate; a film on the substrate; A second electrode provided on the substrate; a piezoelectric layer provided on the second electrode; having The first electrode is provided on the piezoelectric layer.

17. The image processing device according to claim 10, wherein the image processing device is a computer.

18. The piezoelectric layer is selected from the group consisting of PZT, KNN, PZT-N, PMN-Pt, AlN, Sc-AlN, ZnO, PVDF and LiNiO ３ The image processing device according to claim 17, which is made from at least one of the following:

19. a first electrode having at least a first symmetric vibration mode and a first asymmetric vibration mode, the first electrode having a first axis extending along a direction in which a dimension of the first electrode is longest, and a second axis perpendicular to the first axis and passing through a midpoint between both ends of the first electrode on the first axis; the first symmetric vibration mode corresponds to a first vibration frequency and the first asymmetric vibration mode corresponds to a second vibration frequency; an acoustic response of the first electrode in the first asymmetric vibration mode and an acoustic response of the first electrode in the first symmetric vibration mode are greater than an acoustic response of a symmetric electrode in the asymmetric vibration mode; A micromachined ultrasonic transducer (MUT) comprising:

20. 20. The micromachined ultrasonic transducer (MUT) of claim 19, wherein the micromachined ultrasonic transducer (MUT) is a capacitive micromachined ultrasonic transducer (cMUT).

21. 20. The micromachined ultrasonic transducer (MUT) of claim 19, wherein the micromachined ultrasonic transducer (MUT) is a piezoelectric micromachined ultrasonic transducer (pMUT).

22. The shape of the first electrode is asymmetric with respect to the second axis.

20. The micromachined ultrasonic transducer (MUT) of claim 19.

23. 23. The micromachined ultrasonic transducer (MUT) of claim 19, wherein the first electrode has a plurality of symmetric vibration modes including the first symmetric vibration mode and a plurality of asymmetric vibration modes including the first asymmetric vibration mode.

24. A substrate on which the first electrode is provided; a second electrode disposed on the substrate, the second electrode not being in the same plane as the first electrode; The micromachined ultrasonic transducer (MUT) of any one of claims 19 to 23, comprising:

25. A substrate; a film on the substrate; A second electrode provided on the substrate; a piezoelectric layer provided on the second electrode; having The first electrode is provided on the piezoelectric layer. A micromachined ultrasonic transducer (MUT) according to any one of claims 19 to 24.

26. The piezoelectric layer is selected from the group consisting of PZT, KNN, PZT-N, PMN-Pt, AlN, Sc-AlN, ZnO, PVDF and LiNiO ３ 26. The micromachined ultrasonic transducer (MUT) of claim 25, made from at least one of:

27. a transducer array including a plurality of micromachined ultrasonic transducers (MUTs); Each micromachined ultrasonic transducer (MUT) a first electrode having at least a first symmetric vibration mode and a first asymmetric vibration mode, the first electrode having a first axis extending along a direction in which a dimension of the first electrode is longest, and a second axis perpendicular to the first axis and passing through a midpoint between both ends of the first electrode on the first axis; the first symmetric vibration mode corresponds to a first vibration frequency and the first asymmetric vibration mode corresponds to a second vibration frequency; an acoustic response of the first electrode in the first asymmetric vibration mode and an acoustic response of the first electrode in the first symmetric vibration mode are greater than an acoustic response of a symmetric electrode in the asymmetric vibration mode; 1. An image processing device comprising:

28. 28. The image processing device of claim 27, wherein the micromachined ultrasonic transducer (MUT) is a capacitive micromachined ultrasonic transducer (cMUT).

29. 28. The image processing apparatus of claim 27, wherein the micromachined ultrasonic transducer (MUT) is a piezoelectric micromachined ultrasonic transducer (pMUT).

30. The shape of the first electrode is asymmetric with respect to the second axis. The image processing device according to claim 27.

31. The image processing device according to any one of claims 27 to 30, wherein the first electrode has a plurality of symmetric vibration modes including the first symmetric vibration mode and a plurality of asymmetric vibration modes including the first asymmetric vibration mode.

32. A substrate on which the first electrode is provided; a second electrode disposed on the substrate, the second electrode not being in the same plane as the first electrode; The image processing device according to any one of claims 27 to 31, comprising:

33. A substrate; a film on the substrate; A second electrode provided on the substrate; a piezoelectric layer provided on the second electrode; having The first electrode is provided on the piezoelectric layer.

33. The image processing device according to claim 27, wherein the image processing device is a computer.

34. The piezoelectric layer is selected from the group consisting of PZT, KNN, PZT-N, PMN-Pt, AlN, Sc-AlN, ZnO, PVDF and LiNiO ３ 34. The image processing apparatus of claim 33, wherein the image processing apparatus is made from at least one of the following:

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