Phased array ultrasound device for creating a pressure focus point

Abstract

A phased array ultrasound device includes transducer elements arranged in a two dimensional array; first electrodes, each first electrode extending along a first direction; and second electrodes, each second electrode extending along a second direction, where each transducer element is associated with one first electrode and one second electrode, where each transducer element includes a material located between its associated first electrode and second electrode, and is configured to emit an ultrasonic wave induced by a vibration force or an oscillation force of its material when the transducer element is actuated based on control signals applied to its associated first electrode and second electrode, where each transducer element has a unipolar actuation force direction, and where the phased array ultrasound device is configured to create a pressure focus point by actuating a set of transducer elements to form a combined ultrasonic wave.

Claims

1. A phased array ultrasound device comprising: a first plurality of electrodes each extending along a first direction; a second plurality of electrodes each extending along a second direction; a plurality of transducer elements arranged into rows of transducer elements and columns of transducer elements, wherein each of the rows of transducer elements is connected to an electrode of the first plurality of electrodes and each of the columns of transducer elements is connected to an electrode of the plurality of second electrodes; and an actuator configured to provide: a first control signal to a first electrode of the first plurality of electrodes, additional first control signals to second electrodes of the first plurality of electrodes, wherein the first control signal is phase delayed with respect to the additional first control signals, a second control signal to a first electrode of the second plurality of electrodes, and additional second control signals to second electrodes of the second plurality of electrodes, wherein the second control signal is phase delayed with respect to the additional second control signals, thereby generating a combined ultrasonic wave that originates from a transducer element of the plurality of transducer elements that corresponds to the first electrode and the second electrode, wherein the plurality of transducer elements each comprise a ferroelectric material.

2. The phased array ultrasound device according to claim 1, wherein the plurality of transducer elements each have a unipolar actuation force direction.

3. The phased array ultrasound device according to claim 1, wherein the plurality of transducer elements comprises micromachined ultrasonic transducers.

4. The phased array ultrasound device according to claim 1, wherein the plurality of transducer elements comprises piezoelectric transducer elements.

5. The phased array ultrasound device according to claim 1, wherein: the plurality of transducer elements comprises capacitive transducer elements, and the phased array ultrasound device is configured to actuate each transducer element of the plurality of transducer elements by applying an AC voltage without DC bias, as control signals, to the first plurality of electrodes and the second plurality of electrodes.

6. The phased array ultrasound device according to claim 5, wherein the AC voltage is configured to induce an electrostatic force on the transducer element.

7. The phased array ultrasound device according to claim 5, wherein each transducer element of the plurality of transducer elements has an actuation force that is proportional to a square of the AC voltage.

8. The phased array ultrasound device according to claim 1, wherein the phased array ultrasound device is further configured to: obtain position information corresponding to a desired pressure focus point to be created; determine the combined ultrasonic wave based on the position information that corresponds to creating the desired pressure focus point; and determine a set of transducer elements to be actuated according to the combined ultrasonic wave.

9. The phased array ultrasound device according to claim 1, wherein each electrode of the first plurality of electrodes connects a row of transducer elements of the plurality of transducer elements and each electrode of the second plurality of electrodes connects a column of the plurality of transducer elements.

10. The phased array ultrasound device according to claim 1 wherein a total number of electrodes in the phased array ultrasound device is equal to a number of rows plus a number of columns in the phased array ultrasound device.

11. The phased array ultrasound device according to claim 1, wherein each transducer element of the plurality of transducer elements comprises a material located between the first plurality of electrodes and the second plurality of electrodes.

12. The phased array ultrasound device according to claim 1, wherein the phased array ultrasound device is configured to create a pressure focus point above or below the phased array ultrasound device by actuating a set of transducer elements of the plurality of transducer elements to form an ultrasonic wave.

13. The phased array ultrasound device of claim 1, further comprising: a display, wherein the plurality of transducer elements is arranged in or below the display and is configured to create a pressure focus point above the display.

14. A method comprising: determining a combined ultrasonic wave which corresponds to a pressure focus point above or below a phased array ultrasound device that includes a first plurality of electrodes each extending along a first direction and a second plurality of electrodes each extending along a second direction; determining, for a plurality of transducer elements in the phased array ultrasound device, control signals for creating the combined ultrasonic wave with the plurality of transducer elements, wherein the plurality of transducer elements are arranged into rows of transducer elements and columns of transducer elements, wherein each of the rows of transducer elements is connected to an electrode of the first plurality of electrodes and each of the columns of transducer elements is connected to an electrode of the second plurality of electrodes; and creating, via a unipolar actuation force at each transducer element of the plurality, the pressure focus point by actuating the plurality of transducer elements by applying control signals to the first plurality of electrodes and the second plurality of electrodes associated with the plurality of transducer elements, wherein applying the control signals comprises providing: a first control signal to a first electrode of the first plurality of electrodes, additional first control signals to second electrodes of the first plurality of electrodes, wherein the first control signal is phase delayed with respect to the additional first control signals, a second control signal to a first electrode of the second plurality of electrodes, and additional second control signals to second electrodes of the second plurality of electrodes, wherein the second control signal is phase delayed with respect to the additional second control signals, thereby generating the combined ultrasonic wave that originates from a transducer element of the plurality of transducer elements that corresponds to the first electrode and the second electrode.

15. The method according to claim 14, further comprising: obtaining position information corresponding to the pressure focus point to be created; and determining the combined ultrasonic wave based on the position information.

16. The phased array ultrasound device of claim 1, wherein the ferroelectric material comprises lead zirconate titanate (PZT).

17. The method of claim 14, wherein the control signals include an AC signal with no DC bias.

18. The method of claim 14, wherein the plurality of transducer elements each include a ferroelectric material.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) The above, as well as additional, features will be better understood through the following illustrative and non-limiting detailed description of example embodiments, with reference to the appended drawings.

(2) The above described aspects and implementations are explained in the following description of embodiments with respect to the enclosed drawings:

(3) FIG. 1 is a schematic view of a phased array ultrasound device, according to an embodiment.

(4) FIG. 2 is a schematic view of an electronic device, according to an embodiment.

(5) FIG. 3 is a diagram illustrating the butterfly unipolar deflection-actuation curve of a PZT, according to an embodiment.

(6) FIG. 4A is a diagram illustrating a force across CMUTs of transducer elements in an array for forming a desired combined ultrasound wave, according to an embodiment.

(7) FIG. 4B is a diagram illustrating differences between phase delays, according to an embodiment.

(8) FIG. 5 shows a simulation result performed on the pressure focusing of a large array of PMUTs with and without unipolar actuation, according to an embodiment.

(9) FIG. 6 is a flowchart of a method for operating a phased array ultrasound device, according to an embodiment.

(10) FIG. 7 is a schematic view of a conventional PMUT, according to an embodiment.

(11) FIG. 8 is an image of a fabricated 64×64 array of PMUTs, according to an embodiment.

(12) FIG. 9 is a diagram illustrating the creation of a focusing point using the MUTs, according to an embodiment.

(13) FIG. 10 is a diagram illustrating the delay that is applied to every individual MUT of a 32×32 MUT array for obtaining the highest pressure at the focus point, according to an embodiment.

(14) FIG. 11A is a diagram illustrating a force across PMUTs of transducer elements in an array for forming a desired combined ultrasound wave, according to an embodiment.

(15) FIG. 11B is a diagram illustrating differences between phase delays, according to an embodiment.

(16) FIG. 12A is a schematic view of an arrangement of electrodes of the phased array ultrasound device, according to an embodiment.

(17) FIG. 12B is a schematic view of an arrangement of electrodes of the phased array ultrasound device, according to an embodiment.

(18) All the figures are schematic, not necessarily to scale, and generally only show parts which are necessary to elucidate example embodiments, wherein other parts may be omitted or merely suggested.

DETAILED DESCRIPTION

(19) Example embodiments will now be described more fully hereinafter with reference to the accompanying drawings. That which is encompassed by the claims may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided by way of example. Furthermore, like numbers refer to the same or similar elements or components throughout.

(20) FIG. 1 shows a phased array ultrasound device 10, according to an embodiment of the disclosure.

(21) The phased array ultrasound device 10 comprises a plurality of transducer elements 11 arranged in a two dimensional (2D) array 4. Further, it comprises a plurality of first electrodes 1, each first electrode 1 extending along a first direction, and, for example, below the 2D array 4. Further, it comprises a plurality of second electrodes 2, each second electrode 2 extending along a second direction, and, for example, above the 2D array 4.

(22) Each transducer element 11 (of the phased array ultrasound device 10) is associated with one first electrode 1 and one second electrode 2. Furthermore, each transducer element 11 comprises a material 3, which is located between its associated first electrode 1 and second electrode 2. Each transducer element 11 is configured to emit an ultrasonic wave induced by a vibration force or an oscillation force of its material 3, when the transducer element 11 is actuated based on control signals applied to its associated first electrode 1 and second electrode 2. Furthermore, each transducer element 11 has a unipolar actuation force direction.

(23) Moreover, the phased array ultrasound device 10 is configured to create a pressure focus point above or below the 2D array 4, by actuating a set of transducer elements 11 to form a combined ultrasonic wave.

(24) The phased array ultrasound device 10 may use an array of MUTs as the transducer elements 11, in which each MUT has a unipolar force direction. The phased array ultrasound device 10 can improve the phase delay map of the array, without adding any extra switch transistors in the array.

(25) The material may be based on a vibrating material, for example, a piezoelectric material, which may be used for providing a piezoelectric actuation, or it may be a capacitive material (for example, it may be just a vacuum) and an electrostatic force may create an oscillating force in the phased array ultrasound device.

(26) The phased array ultrasound device 10 can help address the problem of 180 degree phase jumps, which occur in the conventional devices. The phased array ultrasound device 10 may thus provide an improved (higher) pressure at the pressure focus point.

(27) Reference is now made to FIG. 2, which shows an electronic device 20, according to an embodiment of the disclosure.

(28) The electronic device 20 comprises a display 21 and a phased array ultrasound device 10. The electronic device 20 may be, for example, a smartphone. The phased array ultrasound device 10 of the electronic device 20 is arranged in or below the display 21, and is configured to create a pressure focus point above the display 21.

(29) For example, the phased array ultrasound device 10 may comprise a plurality of transducer elements 11, which are arranged in a 2D array 4; a plurality of first electrodes 1, each first electrode 1 extending along a first direction, and, for example, above the 2D array 4; and a plurality of second electrodes 2, each second electrode 2 extending along a second direction, and, for example, below the 2D array 4.

(30) Furthermore, each transducer element 11 of the phased array ultrasound device 10 of the electronic device 20 may be associated with one first electrode 1 and one second electrode 2. Each transducer element 11 comprises a material 3 located between its associated first electrode 1 and second electrode 2, and is configured to emit an ultrasonic wave induced by a vibration force or an oscillation force of its material, when the transducer element 11 is actuated based on control signals applied to its associated first electrode 1 and second electrode 2. Each transducer element 11 has a unipolar actuation force direction.

(31) Moreover, the phased array ultrasound device 10 of the electronic device 20 may be configured to create a pressure focus point above or below the 2D array 4, by actuating a set of transducer elements 11 to form a combined ultrasonic wave.

(32) The electronic device 20 may be configured to provide haptic feedback (e.g., by using the phased array ultrasound device 10).

(33) In some embodiments, the above mentioned driving scheme may be used (e.g., for the phased array ultrasound device 10) in combination with arrays of transducer elements 11, in which each transducer element 11 has the unipolar force direction (as opposed to the bipolar force direction of the PMUT array described above, where the force on the PMUT membrane could be pointing upwards AND downwards).

(34) Moreover, it may be possible to improve the phase delay map of the array, without adding any extra switch transistors to the array.

(35) Examples of MUTs having a unipolar force direction are PMUTs with, e.g., a PZT ferroelectric piezo material and capacitive micromachined ultrasonic transducers (CMUTs).

(36) For example, in some embodiments, the transducer elements 11 of the phased array ultrasound device 10 may comprise piezoelectric transducer elements, in particular piezoelectric MUTs (PMUTs); and the material 3 may comprise a PZT ferroelectric piezo material, which generally shows a butterfly unipolar deflection-actuation curve.

(37) FIG. 3 is a diagram illustrating the butterfly unipolar deflection-actuation curve of a PZT. The PZT may be used by the phased array ultrasound device 10.

(38) Moreover, in some embodiments, the transducer elements 11 of the phased array ultrasound device 10 may comprise capacitive transducer elements, in particular, capacitive (CMUTs).

(39) For example, the material 3 may comprise a capacitive material, and the phased array ultrasound device 10 may be configured to actuate each transducer element 11 by applying an AC voltage without DC bias, as the control signals, to its associated first electrode 1 and second electrode 2.

(40) The actuation of the CMUTs may arise from an electrostatic force between two electrically actuated electrodes. While the CMUT driving force is typically made artificially “bipolar” by adding a constant DC bias voltage, the electrostatic force is intrinsically nonlinear since it is proportional to the square of the applied voltage. However, when only an AC voltage V is applied to the CMUT (of the phased array ultrasound device 10) the force is proportional to V.sup.2. It is therefore generally in the same direction no matter the sign of V.

(41) For instance, the actuation force and driving phase in the 36×36 array example is affected by the square term of the CMUT electrostatic force. This test case is selected for ease of mathematical computation since the absolute value operator otherwise required for the PZT PMUT is not as simple to evaluate in a few equations.

(42) If the 36×36 array described above comprises CMUTs with only an AC actuation (no DC bias), then each CMUT would generally be subject to an electrostatic driving force proportional to V.sup.2, that is (the proportionality constant is disregarded as it only depends on geometrical/material parameters), according to Eq. (2):

(43) $\begin{array}{cc}F={\left(2V_0\cos \left(2\pi f_{0}t+\frac{1}{2}\left({\varphi }_R+{\varphi }_C\right)\right).Math.\sin \left(\frac{1}{2}\left({\varphi }_R-{\varphi }_C\right)\right)\right)}^2& \mathrm{Eq}.\left(2\right)\end{array}$

(44) which can be mathematically developed according to Eq. (3):

(45) $\begin{array}{cc}F=4V_0^2{\cos }^2\left(2\pi f_{0}t+\frac{1}{2}\left({\varphi }_R+{\varphi }_C\right)\right).Math.{\sin }^2\left(\frac{1}{2}\left({\varphi }_R-{\varphi }_C\right)\right)& \mathrm{Eq}.\left(3\right)\end{array}$

(46) Thus, using a simple trigonometry technique, the Eq. (4) can be derived:

(47) $\begin{array}{cc}F=4V_0^2(\frac{1}{2}+\frac{1}{2}\cos \left(4\pi f_{0}t+\frac{2}{2}\left({\varphi }_R+{\varphi }_C\right)\right).Math.{\sin }^2\left(\frac{1}{2}\left({\varphi }_R-{\varphi }_C\right)\right)& \mathrm{Eq}.\left(4\right)\end{array}$

(48) A constant (static) force term is provided plus a harmonic electric force at double the electric actuation frequency and with a now doubled phase delay. Moreover, in order to still obtain the CMUT membrane resonance frequency, the driving method mentioned above can be (slightly) adapted, i.e., the electric actuation frequency may be halved. Also, the phase delays may be halved as well in order to guarantee the improved or optimal phase delays on the central row and column.

(49) By using the above configuration of the phased array ultrasound device 10, the problem of the 180 degree phase jumps in the above equation can be overcome, since the cause of it (i.e., the sine term that was inverting its sign) is now squared and thus is always positive. With the described driving technique on the 36×36 CMUT array the phase delay map is updated, as it is illustrated in FIG. 4A and FIG. 4B.

(50) Reference is now made to FIG. 4A and FIG. 4B, which show a diagram illustrating force across CMUTs of transducer elements 11 in an array for forming a desired combined ultrasound wave (FIG. 4A), and a diagram illustrating differences between phase delays (FIG. 4B).

(51) It can be derived from FIG. 4A and FIG. 4B that the phased array ultrasound device 10 can (e.g., dramatically) improve and smooth the phase (delay) map, which may potentially lead to an easier driving for creating haptic pressure patterns. Since the phase is closer to optimal, one can also expect higher output pressures. The force applied to each CMUT is shown in FIG. 4A.

(52) Furthermore, in the case of the unipolar PZT (PMUT) array being used in the phased array ultrasound device 10, the phase map would be according to FIG. 4B but the force on each PMUT would still have the same magnitude as the one shown before (FIG. 12B).

(53) Furthermore, simulations performed on the pressure focusing of a large array of PMUTs with and without unipolar actuation are shown in FIG. 5.

(54) As it can be derived from FIG. 5, when the proposed driving scheme is applied to bipolar driven PMUTs, the pressure drops to less than 25% at the focus point (and the focusing does not work correctly anymore). When the technique is used with a unipolar driven PMUT array (e.g., peak voltage across PMUTs is kept below 1× the driving voltage and the factor 2 voltage increase is scaled down) to be comparable to the optimally-driven PMUT array then the pressure at the focus point is 67% of the pressure created by an optimally driven PMUT array.

(55) FIG. 6 shows a method 100 according to an embodiment for operating a phased array ultrasound device 10.

(56) The method 100 may be carried out by the phased array ultrasound device 10 and/or the electronic device 20, as described above.

(57) The method 100 comprises a step S101 of determining a combined ultrasonic wave, which can create a certain pressure focus point above or below the 2D array.

(58) The method 100 further comprises a step S102 of determining, for a set of transducer elements in the 2D array, control signals for creating the determined combined ultrasonic wave with the set of transducer elements.

(59) The method 100 further comprises a step S103 of creating the certain pressure focus point by actuating the set of transducer elements by applying the determined control signals to the first electrodes and second electrodes associated with the set of transducer elements.

(60) While some embodiments have been illustrated and described in detail in the appended drawings and the foregoing description, such illustration and description are to be considered illustrative and not restrictive. Other variations to the disclosed embodiments can be understood and effected in practicing the claims, from a study of the drawings, the disclosure, and the appended claims. The mere fact that certain measures or features are recited in mutually different dependent claims does not indicate that a combination of these measures or features cannot be used. Any reference signs in the claims should not be construed as limiting the scope.