Micromechanical ultrasonic transducers and display

An apparatus may include a one- or two-dimensional array of micromechanical ultrasonic transducer (PMUT) elements positioned below, beside, with, on, or above a backplane of a visual display. The backplane may be a thin-film transistor (TFT) backplane. The array of PMUT elements may be a piezoelectric micromechanical ultrasonic transducer (PMUT) array or a capacitive micromechanical ultrasonic transducer (CMUT) array. The PMUT array may be configurable to operate in modes corresponding to multiple frequency ranges. When operating in the low-frequency mode, the apparatus may be capable of gesture detection. A high-frequency mode may include a fingerprint sensor mode or a stylus detection mode.

TECHNICAL FIELD

This disclosure relates to displays that include sensor elements, and more particularly to a piezoelectric ultrasonic transducer suitable for use in an electronic sensor array or interactive display for biometric sensing, imaging, and touch or gesture recognition.

DESCRIPTION OF THE RELATED TECHNOLOGY

Current display touchscreens, such as liquid crystal display (LCD) and organic light-emitting diode (OLED) touchscreens, generally include pixels with at least three (e.g., RGB) sub-pixel elements and rely on overlying capacitive touch screens for detecting the touch of a finger. The resolution of the capacitive touch screens is generally insufficient for fingerprint imaging or stylus detection, and the range of detection is generally insufficient for gesture detection because capacitive touch detection is typically limited to a few millimeters from the touchscreen surface.

SUMMARY

The systems, methods and devices of the disclosure each have several innovative aspects, no single one of which is solely responsible for the desirable attributes disclosed herein. One innovative aspect of the subject matter described in this disclosure can be implemented in an apparatus which includes an array of piezoelectric micromechanical ultrasonic transducer (PMUT) elements positioned proximate (e.g., below, beside, on, or above) a display. The apparatus may include a control system.

In some implementations, the control system may be capable of making a determination whether to operate at least a portion of the PMUT array in a low-frequency mode and/or a high-frequency mode. The control system may be capable of controlling at least a portion of the PMUT array to operate in the low-frequency mode and/or the high-frequency mode, according to the determination. The display device may include an interface system. In some examples, the determination may be made, at least in part, according to input received from the interface system.

According to some implementations, the low-frequency mode may correspond to a frequency range of approximately 50 kHz to 200 kHz. In some examples, the low-frequency mode may correspond to a gesture detection mode, wherein free-space gestures near the display may be detected. According to some implementations, the high-frequency mode may correspond to a frequency range of approximately 1 MHz to 25 MHz. In some examples, the high-frequency mode may correspond to a fingerprint sensor mode or a stylus detection mode.

In some implementations, the control system may be capable of performing an authentication process based, at least in part, on fingerprint data acquired while the PMUT array operates in the fingerprint sensor mode. In some examples, the apparatus may include a memory system. In some such examples, the authentication process may involve the following: providing a prompt, via the display, to place at least one finger on a surface of the display device; receiving, via at least a portion of the PMUT array, at least one fingerprint image; determining received fingerprint data corresponding to the at least one fingerprint image; and comparing the received fingerprint data with stored fingerprint data in the memory system.

According to some implementations, the control system may be capable of making a determination whether to operate at least a portion of the PMUT array in the high-frequency mode, the low-frequency mode and/or a medium-frequency mode. The control system may be capable of controlling at least a portion of the PMUT array to operate in the high-frequency mode, the low-frequency mode and/or the medium-frequency mode, according to the determination. In some examples, the medium-frequency mode may correspond to a frequency range of approximately 200 kHz to 1 MHz. According to some implementations, the display device may be capable of providing touch sensor functionality when the control system is controlling at least a portion of the PMUT array to operate in the medium-frequency mode.

In some implementations, the control system may be capable of controlling some PMUT elements of the PMUT array to operate in the low-frequency mode and other PMUT elements of the PMUT array to operate in the high-frequency mode. Alternatively, or additionally, the control system may be capable of controlling the same PMUT element of the PMUT array to operate in the low-frequency mode and to operate in the high-frequency mode. In some examples, the PMUT array may be a piezoelectric micromechanical ultrasonic transducer (pMUT) array or a capacitive micromechanical ultrasonic transducer (cMUT) array.

According to some implementations, the control system may be capable of addressing at least a portion of the PMUT array for at least one of wavefront beam forming, beam steering, receive-side beam forming, or selective readout of returned signals. For example, in some implementations the control system may be capable of addressing at least a portion of the PMUT array to produce wavefronts of a substantially planar, spherical or cylindrical shape. In some implementations, the control system may be capable of addressing at least a portion of the PMUT array to produce constructive or destructive interference in at least one location.

In some examples, the control system may be capable of exciting PMUT elements of the PMUT array and detecting responses via the same PMUT elements. Alternatively, or additionally, the control system may be capable of controlling a first PMUT element of the PMUT array as an acoustic transmitter and a second PMUT element of the PMUT array as an acoustic receiver.

According to some implementations, at least a portion of the PMUT array may be an active matrix PMUT array. In some examples, the active matrix PMUT array may include drive circuitry and sense circuitry. In some implementations, the active matrix PMUT array may include row and column addressing circuitry, multiplexer circuitry, demultiplexer circuitry, local amplification circuitry and/or analog-to-digital conversion circuitry.

In some implementations, at least a portion of the PMUT array may be disposed behind substantially all of the display. In some such implementations, a single PMUT element of the PMUT array may correspond with a single pixel of the display. However, in some examples, at least a portion of the PMUT array may be disposed behind only a part of the display.

Alternatively, or additionally, at least a portion of the PMUT array may be disposed in a peripheral area of the display. According to some implementations, the control system may be capable of controlling a portion of the PMUT array that is disposed in the peripheral area of the display for fingerprint sensor functionality, signature pad functionality, stylus detection functionality, gesture detection functionality and/or button functionality.

In some examples, at least a portion of the PMUT array may be disposed on a substrate. According to some implementations, the substrate may be a glass substrate. However, in alternative implementations the substrate may be formed of another suitable material, which may or may not be transparent according to the particular implementation.

According to some implementations, at least one array of thin-film transistors (TFTs) also may be disposed on the substrate. In some such implementations, at least one array of TFTs may include circuitry for controlling the display. In some examples, at least one array of TFTs may include circuitry for controlling at least a portion of the PMUT array. In some such implementations, the circuitry for controlling at least a portion of the PMUT array and the circuitry for controlling the display may be capable of sharing a flex cable. According to some implementations, at least one array of TFTs that includes circuitry for controlling the display may be disposed on a second substrate.

In some implementations, the apparatus may include a cover glass and electrodes disposed on the cover glass. The electrodes may be configured for topside electrical connections to circuitry for controlling at least a portion of the PMUT array. In some such implementations, the electrodes may be configured for connections with circuitry for at least one PMUT element that may be disposed on a periphery of the display.

Other features, aspects, and advantages will become apparent from a review of the disclosure. Note that the relative dimensions of the drawings and other diagrams of this disclosure may not be drawn to scale. The sizes, thicknesses, arrangements, materials, etc., shown and described in this disclosure are made only by way of example and should not be construed as limiting.

DETAILED DESCRIPTION

It can be challenging to provide a gesture detection system and/or a fingerprint imaging system on a display device, particularly on a mobile display device. Capacitive touch systems (e.g., projected capacitive touch or PCT) are commonly included with a mobile display device. However, the resolution of capacitive touch screens is generally insufficient for fingerprint imaging or stylus detection. Moreover, the range of detection provided by capacitive touch screens is generally insufficient for gesture detection, because capacitive touch detection is typically limited to a few millimeters from the touchscreen surface.

Some implementations disclosed herein include an apparatus having a one- or two-dimensional array of piezoelectric micromechanical ultrasonic transducer (PMUT) elements positioned proximate (e.g., below, beside, on, or above) a backplane of a display. The backplane may, for example, be a thin-film transistor (TFT) backplane. The PMUT array or sub-arrays thereof may be configurable to operate in modes corresponding to multiple frequency ranges. When operating in the low-frequency mode, the apparatus may be capable of gesture detection. A high-frequency mode may, for example, be a fingerprint sensor mode, a stylus detection mode, or a touch detection mode. In some implementations, a portion of the PMUT elements of the PMUT array or sub-array may operate in a low-frequency mode, and a second portion of the PMUT array or sub-array may operate in a high-frequency mode. In some implementations, PMUT elements of the PMUT array may operate in either a low-frequency or high-frequency mode.

Particular aspects of the subject matter described in this disclosure can be implemented to realize one or more of the following potential advantages. Some implementations may provide a PMUT array capable of both gesture detection and fingerprint imaging. In some such implementations, the PMUT array may be capable of transmitting and receiving ultrasonic signals through at least a portion of an array of display pixels. Such implementations may reduce the peripheral area of a display device that is not occupied by the display. In some implementations, the PMUT array also may provide touch sensor functionality. In some such implementations, the touch screen normally provided with a display device may be omitted. However, in other implementations at least of a portion of the PMUT array, which may provide fingerprint sensor, signature pad, stylus detection, gesture detection and/or button functionality, may be located in a peripheral area.

Moreover, PMUT devices have generally been fabricated on a silicon or silicon-on-insulator (SOI) substrate with connections made to circuitry external to the substrate. Such configurations can limit the number of PMUT devices in an array, may require a large number of interconnects to the external circuitry, and can potentially add expense, packaging constraints, and loss in signal integrity. In some implementations provided herein, a PMUT array may be co-fabricated with TFT circuitry on the same substrate, which may reduce the number of interconnects to external circuitry and can potentially reduce expense and enhance signal integrity. Co-fabrication of PMUT elements with TFT circuitry allows large array sizes typical of mobile and stationary displays. Co-fabrication of PMUT elements and TFT circuitry on the same (e.g., common) substrate reduces the number of parts to assemble in a display device, and may reduce the total thickness of the display device. The number of external interconnects may be vastly reduced with large array sizes, as many of the interconnections between PMUT elements and TFT circuity may be done with metal traces on the TFT substrate.

A piezoelectric micromechanical ultrasonic transducer (PMUT) array may include one or more microstructures such as diaphragms, plates, membranes or ribbons that may be actuated piezoelectrically. A deposited thin-film piezoelectric layer and associated electrodes formed on, in or under the microstructure may serve to actuate the microstructure in one or more modes to generate ultrasonic waves. The ultrasonic waves may be used to detect free-space gestures in some implementations. In other implementations, the ultrasonic waves may be used to detect touches on the surface of a display device. Ultrasonic waves at higher frequencies (smaller wavelengths) may be used to detect a stylus or other small or finely featured object placed on the display surface. In some implementations, a high density (e.g., about 500 pixels per inch) of PMUT elements in an array of sufficient size may be used to detect a tip of a stylus and/or image the ridges and valleys of a fingerprint for verification or authentication of a user. The PMUT elements may be used as ultrasonic receivers, configured to detect ultrasonic waves that may be received after being reflected from an object in air or on the surface of the display. Many examples of PMUT arrays are provided in this disclosure and associated applications incorporated by reference into the present application. However, in some implementations a micromechanical ultrasonic transducer (MUT) array may include other types of MUT elements, such as capacitive micromechanical ultrasonic transducer (CMUT) elements. A further description of CMUTs and PMUT elements is described below with respect toFIGS. 1B and 1C.

FIG. 1Ais a block diagram that shows examples of elements of a display device. In this example, the display device40includes a display30, a PMUT array105and a control system110. The PMUT array105may be proximate the display30. In some implementations, the PMUT array105may be coextensive with the active display area and formed substantially in the same plane as the display subpixels (e.g., in-cell configurations). In some implementations, the PMUT array105may be substantially the same size as the display30yet positioned behind the active area of the display. In some implementations, at least a portion of the PMUT array105may be disposed behind substantially the entire display30. In some implementations, the PMUT array105may be disposed behind only a portion of the display30. Alternatively, or additionally, at least a portion of the PMUT array105may be disposed in a peripheral area of the display30, such as an area outside the active display area of a display module. Numerous examples of these and other configurations are provided herein.

Portions of the PMUT array105disposed in a peripheral area of the display30may, for example, be controlled by the control system110to provide fingerprint sensor functionality, touchpad or signature (e.g., stylus) pad functionality, stylus detection functionality, gesture detection functionality and/or button functionality. The button functionality may involve controlling some aspect of the display device40with or without authentication functionality. Accordingly, such buttons may be referred to as “authenticating” buttons or “non-authenticating” buttons.

The PMUT array105may, for example, be a PMUT array or in some implementations a CMUT array. The control system110may include one or more processors, such as one or more general purpose single- or multi-chip processors, digital signal processors (DSPs), application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs) or other programmable logic devices, discrete gate or transistor logic, such as TFTs, discrete hardware components, or combinations thereof. The control system110may be capable of performing the methods described herein, at least in part.

For example, the control system110may be capable of determining whether to operate at least a portion of the PMUT array105in a low-frequency mode or a high-frequency mode and controlling at least a portion of the PMUT array105according to the determination. Some implementations of the display device40may include an interface system. The determining process may be performed, at least in part, according to input received from the interface system. The interface system may, for example, include one or more network interfaces, user interfaces, etc. The interface system may include one or more universal serial bus (USB) interfaces or similar interfaces. The interface system may include wireless or wired interfaces.

FIG. 2is a graph that shows examples of frequency ranges for PMUT excitation. InFIG. 2, the horizontal axis indicates potential excitation frequencies according to a logarithmic scale and the vertical axis corresponds to a typical output voltage (Vout) from one or more PMUT elements in a PMUT array. In this example, a low-frequency mode corresponds to a frequency range between approximately 50 kHz and 400 kHz and a high-frequency mode corresponds to a frequency range between approximately 5 MHz and 50 MHz. However, in alternative implementations, the low-frequency mode and/or the high-frequency mode may correspond to different frequency ranges. In some such implementations, the low-frequency mode may correspond to a frequency range of approximately 50 kHz to 200 kHz and the high-frequency mode may correspond to a frequency range of approximately 1 MHz to 25 MHz. Alternatively, or additionally, in some implementations, the PMUT array may be configurable to operate in a medium-frequency mode corresponding to a frequency range between the low-frequency range and the high-frequency range (e.g., about 200 kHz to about 1 MHz). When operating in the medium-frequency mode, the apparatus may be capable of providing touch sensor functionality and gesture detection capability, although with somewhat less resolution than the high-frequency mode.

Referring again toFIG. 1A, in some implementations when the control system operates at least a portion of the PMUT array105in the low-frequency mode, the display device40may be capable of emitting sound waves that are capable of relatively greater penetration into air than when the display device40is operating in the high-frequency mode. In some examples, such lower-frequency sound waves may be transmitted through various overlying layers, such as a cover glass, a touchscreen, a display array, a backlight, and/or other layers which may vary according to the implementation. In some implementations, the lower frequency sound waves may be transmitted through one or more holes in the cover glass or cover lens of the display device. Various configurations are disclosed herein.

In some implementations, a port may be opened through one or more of the overlying layers to optimize coupling from the PMUT array105into air. The lower-frequency sound waves may be transmitted through the air above the display surface, reflected from one or more objects near a surface of the display device40, transmitted through the air and back through the overlying layers, and detected by an ultrasonic receiver (e.g., of the PMUT array105). Accordingly, when operating in the low-frequency mode, the display device40may be capable of operating in a gesture detection mode, wherein free-space gestures near the display may be detected.

When operating in the high-frequency mode, the display device40may be capable of imaging at relatively higher resolution. Accordingly, the display device40may be capable of detecting touch, fingerprint, stylus, and/or biometric information from an object such as a finger placed on the surface of the display device40. In some implementations, the high-frequency mode may correspond to a touch detection mode and/or a stylus detection mode. In some implementations, the high-frequency mode may correspond to a fingerprint sensor mode.

In some instances the control system110may be capable of performing an authentication process based, at least in part, on fingerprint data acquired while at least a portion of the PMUT array105operates in the fingerprint sensor mode. The authentication process may involve providing a prompt, via the display, to place at least one finger on a surface of the display device and receiving, via at least a portion of the PMUT array105, at least one fingerprint image. In some implementations, the portion of the PMUT array105that the control system110controls to obtain the fingerprint image(s) may be disposed in a peripheral area of the display device40, such as on an edge, side or corner of the display30.

The control system110may be capable of determining received fingerprint data corresponding to the received fingerprint image(s). The term “fingerprint data” as used herein includes data that may be used to characterize fingerprint minutiae, such as data corresponding to the types, locations, orientations and/or spacing of fingerprint minutiae. Fingerprint data may also include pattern or image information of surface fingerprints and other biometric data associated with sub-surface features.

The control system110may be capable of comparing the received fingerprint data with stored fingerprint data as part of the authentication process. In some implementations, the stored fingerprint data may be stored in a memory system of the display device40. The memory system may include one or more non-transitory media, such as random access memory (RAM) and/or read-only memory (ROM). The memory system may include one or more other suitable types of non-transitory storage media, such as flash memory, one or more hard drives, etc. In some implementations, an interface system may include at least one interface between the control system110and the memory system. However, in some implementations the authentication process may involve retrieving stored fingerprint data from another device via the interface system. For example, the stored fingerprint data may reside on a server accessible via the Internet.

In some implementations, the control system110may be capable of controlling the PMUT array105to operate in a medium-frequency mode. In some implementations, the medium-frequency mode may correspond to operation in a frequency range of approximately 200 kHz to 1 MHz. The display device40may be capable of providing touch sensor functionality when the control system110is controlling at least a portion of the PMUT array105to operate in the medium-frequency mode. According to some implementations, the control system110may be capable of determining whether to operate at least a portion of the PMUT array105in the high-frequency mode, the low-frequency mode or the medium-frequency mode and controlling at least a portion of the PMUT array105to operate in the high-frequency mode, the low-frequency mode or the medium-frequency mode, according to the determination.

In some implementations, the control system110may be capable of addressing at least a portion of the PMUT array105for wavefront beam forming, beam steering, receive-side beam forming, and/or selective readout of returned signals. In some implementations, the control system110may control an array of transmitters of the PMUT array105to produce wavefronts of a particular shape, such as planar, circular (spherical) or cylindrical wave fronts. The control system110may control the magnitude and/or phase of the array of transmitters of the PMUT array105to produce constructive or destructive interference in desired locations. For example, the control system110may control the magnitude and/or phase of the array of transmitters to produce constructive interference in one or more locations of the display device40in which a touch or gesture has been detected.

The generation and emission of planar ultrasonic waves (e.g., plane waves) may be achieved by exciting and actuating a large number of PMUT elements in the PMUT array105in a simultaneous manner, which may generate an ultrasonic wave with a substantially planar wavefront. Actuation of single PMUT elements in the PMUT array105may generate substantially spherical waves in a forward direction, with the PMUT element serving as the source of the spherical waves. Alternatively, the spherical waves may be generated by selecting and exciting an individual PMUT element (the center element), determining a first ring of PMUT elements around the center PMUT element and actuating the first ring in a delayed manner, determining a second ring of PMUT elements around the first ring and actuating the second ring in a further delayed manner, and so forth as needed. The timing of the excitations may be selected to form a substantially spherical wavefront. Similarly, a cylindrical wave may be generated by selecting and exciting a group of PMUT elements in a row, with the row of PMUT elements serving as the source of the cylindrical waves. Alternatively, the cylindrical waves may be generated by selecting and exciting a row of PMUT elements (the center row), determining and exciting adjacent rows of PMUT elements equidistant from the center row with a controlled time delay, and so forth. The timing of the excitations may be selected to form a substantially cylindrical wavefront.

While exciting an array of PMUT elements simultaneously may produce an ultrasonic plane wave traveling perpendicular to the PMUT array, phase control of PMUT excitation may allow redirection of the plane wave in various directions, depending on the amount of phase delay. For example, if a phase delay of 10 degrees is applied to adjacent rows of PMUT elements that are positioned a distance of one-tenth of a wavelength apart, then the wavefront will transmit a plane wave at an angle of about 15.5 degrees from the normal. Scanning a plane wave at different angles while detecting echoes (reflected portions) from an object positioned in front of the PMUT array may allow detection of the approximate shape, distance and position of the object. Consecutive determinations of object distance and position may allow determination of air gestures.

Other forms of transmit-side beam forming may be utilized. For example, a set of PMUT elements in the PMUT array105may be fired in a manner to focus the wavefront of an ultrasonic wave at a particular location in front of the array. For example, the focused wavefront may be cylindrical or spherical by adjusting the timing (e.g., phase) of selected PMUT elements so that the generated wave from each selected PMUT element arrives at a predetermined location in the region in front of the PMUT array at a predetermined time. Focused wavefronts may generate appreciably higher acoustic pressure at a point of interest, and the reflected signal from an object at the point of interest may be detected by operating the PMUT array in a receive mode. The wavefronts emitted from various PMUT elements may interfere constructively in the focal region. The wavefronts from various PMUT elements may interfere destructively in regions near the focal region, providing further isolation of the focused beam energy (amplitude) and increasing the signal-to-noise ratio of the return signal. Similarly, control of the phase at which detection occurs for various PMUT elements in the PMUT array105allows receive-side beam forming, in which the return signals may be correlated with distance from a region in space and combined accordingly to generate an image of an object in the detection region. Controlling the frequency, amplitude and phase of the transmitted waves from PMUT elements in the PMUT array105may also allow beam shaping and beam forming. In some implementations, not all of the PMUT elements in the PMUT array need be read out for each mode of operation or for each frame. To save processing time and reduce drain on battery life, return signals detected by a select group of PMUT elements may be read out during acquisition. The control system110may be configured to address a portion of the PMUT array for wavefront beam forming, beam steering, receive-side beam forming, or selective readout of returned signals.

In some implementations, the PMUT array105may include one or more active matrix PMUT arrays. In such implementations, the active matrix PMUT arrays can eliminate the large number of external interconnects that may be required for passive PMUT arrays by including active components (e.g., TFTs) on the same substrate. Such active components may be part of the control system110. Some such active matrix PMUT arrays may include both drive circuitry and sense circuitry. In some such implementations, the TFTs may be capable of driving the PMUT elements of the PMUT array105in a synchronous manner. Alternatively, or additionally, in some implementations the TFTs may be capable of driving the PMUT elements of the PMUT array105in a phased manner. The active matrix also may include sense circuitry to detect return signals from the PMUT elements of the PMUT array105.

In some examples, the control system110may include row and column addressing circuitry. In some implementations, the control system110may include multiplexer and/or demultiplexer circuitry, local amplification circuitry, analog to digital (A/D) conversion circuitry and/or other control circuitry.

FIG. 1Bshows an example of a PMUT element. The PMUT element100amay have one or more layers of piezoelectric material such as aluminum nitride (AlN) or lead zirconium titanate (PZT) in a piezoelectric layer that may be used to actuate the PMUT element to generate ultrasonic waves or to detect received ultrasonic waves. The piezoelectric layer stack may include a lower electrode layer112, a piezoelectric layer115, and an upper electrode layer114, with the piezoelectric layer115sandwiched between at least a portion of the lower and upper electrodes112and114. One or more dielectric layers116may provide electrical isolation for a metal interconnect layer118, while allowing connections to lower and upper electrodes112and114, respectively. The piezoelectric layer stack may be disposed on, below or above a mechanical layer130. An anchor structure170may support the PMUT membrane or diaphragm that is suspended over a cavity120and a substrate160. The substrate160may have TFT circuitry for driving and sensing the PMUT100aand for generating a visual display. The piezoelectric layer stack and mechanical layer130may flex, bend or vibrate in response to drive voltages Va and Vb applied across the electrode layers114and112, respectively. Vibrations of the PMUT element100amay generate ultrasonic waves190at a frequency determined by the excitation frequency of the drive voltages. Ultrasonic waves striking the PMUT diaphragm may result in generation of sense voltages Va and Vb with flexing of the diaphragm. An underlying cavity120allows for deflections of the PMUT element100awithout contacting the underlying substrate160. The operating frequencies of the PMUT elements100amay be tailored for high-frequency operation, low-frequency operation, medium-frequency operation, or a combination of frequencies.

FIG. 1Cshows an example of a CMUT element. The CMUT element100bmay have a mechanical layer130supported above a cavity120and a substrate160by an anchor structure170. Lower electrode112on the substrate below the cavity and upper electrode114above the cavity120may be driven with an excitation voltage applied to terminals Va and Vb to generate ultrasonic waves190. A potential difference between electrodes112and114causes an electrostatic force to be generated that attracts the flexible diaphragm of CMUT element100bdownwards towards the substrate. As electrostatic forces are attractive in this configuration whether Va is larger than Vb or Vb is larger than Va, one of the electrodes may need to be biased at a relatively high DC voltage to allow small applied AC voltages to drive the diaphragm up and down. Biasing is also required for sensing deflections of the CMUT diaphragm above the cavity120.

PMUT element100a, while somewhat more complex to fabricate than CMUT element100b, generally requires smaller operating voltages than the CMUT element100bto generate similar acoustic power. The PMUT element100adoes not suffer from consequential pull-in voltages for electrostatic devices such as CMUT element100b, allowing a fuller range of travel. Furthermore, CMUT elements100bmay require significantly higher bias voltages to allow detection of incoming ultrasonic waves.

FIG. 3Ashows an example of a PMUT array. In this example, the PMUT array105has been co-fabricated with TFT circuitry on the same substrate305, which may be a glass or plastic substrate in some implementations. The TFT circuitry may be part of the control system110ofFIG. 1A.

The TFT circuitry may include row and column addressing electronics, multiplexers, local amplification stages and control circuitry. In some examples, at least one array of TFTs includes circuitry for controlling the display. According to some implementations, at least one array of TFTs that includes circuitry for controlling the display may be disposed on a second substrate. In some implementations, at least one array of TFTs includes circuitry for controlling at least a portion of the PMUT array105. According to some such implementations, the circuitry for controlling at least a portion of the PMUT array and the circuitry for controlling the display may be capable of sharing a flex cable.

FIGS. 3B-3Fshow various examples of TFT circuitry elements and PMUT elements.FIG. 3Bshows a single PMUT element310, which is a pMUT element in this instance. A PMUT array, such as the PMUT array105ofFIG. 3A, may include multiple instances of the PMUT element310and/or of other types of PMUT elements disclosed herein. In some examples, as described in more detail elsewhere herein, at least some of the PMUT elements310of a PMUT array105may correspond with individual pixels of a display30.

In the example shown inFIG. 3B, the PMUT element310may be configured as both a transmitting element (Tx) and a receiving element (Rx). In this implementation, the TFT circuitry element315may include a driver stage and a sense stage. Accordingly, in this example the TFT circuitry element315is capable of causing the PMUT element310to emit ultrasonic waves. Moreover, in this example the TFT circuitry element315is capable of detecting responses from the same PMUT element310, corresponding to ultrasonic waves sensed by the PMUT element310.

In the implementation shown inFIG. 3C, the PMUT element310ais capable of functioning as an acoustic transmitter and a second PMUT element310bis capable of functioning as an acoustic receiver. In this example, the TFT circuitry element315ais capable of controlling the PMUT element310aand the TFT circuitry element315bis capable of providing signals corresponding to ultrasonic waves sensed by the PMUT element310b.

In some configurations, different PMUT elements310of the PMUT array105may be capable of low- and high-frequency operation (e.g. for gestures and for fingerprint/stylus detection). In the example shown inFIG. 3D, the PMUT element310cis capable of functioning as a high-frequency (Hi-F) acoustic transmitter and receiver, and the PMUT element310dis capable of functioning as a low-frequency (Lo-F) acoustic transmitter and receiver. Although inFIG. 3Dthe PMUT element310cand the PMUT element310dare shown to be approximately the same size, in some examples the PMUT element310cmay be smaller than the PMUT element310d. In this implementation, the TFT circuitry element315cis capable of controlling the PMUT element310cfor high-frequency operation and TFT circuitry element315dis capable of controlling the PMUT element310dfor low-frequency operation.

In other configurations, the same PMUT element310may be used for low- and high-frequency operation. In the example shown inFIG. 3E, the PMUT element310eis capable of functioning as a high-frequency acoustic transmitter and receiver, and as a low-frequency acoustic transmitter and receiver. In this implementation, the TFT circuitry element315eis capable of controlling the PMUT element310efor high-frequency operation and for low-frequency operation. In one mode of operation, the TFT circuitry element315emay control the PMUT element310eto operate in either a high-frequency mode (e.g., for touch, stylus or fingerprint detection) or a low-frequency mode (e.g., for gesture or low-resolution touch detection). In another mode of operation, the TFT circuitry element315emay control the PMUT element310eto operate in an alternating mode, flipping at a relatively high rate (e.g. at a frame rate between about 5 and about 240 frames per second) between high-frequency and low-frequency modes. In another mode of operation, the PMUT element310emay be excited with a drive signal having a high-frequency component and a low-frequency component, so that low-resolution gestures and high-resolution fingerprint imaging may be performed at the same time. Electronic filtering may be used to distinguish the return signals at the various frequencies.

FIG. 3Fshows an example of a PMUT array105. The PMUT array105shown inFIG. 3Fmay, for example, be a PMUT sub-array that is a portion of a larger PMUT array105. In this example, the PMUT array105includes the PMUT elements310f-310i. Here, the TFT circuitry element315fincludes row and column addressing electronics for controlling the PMUT elements310f-310i. In this example, the TFT circuitry element315gincludes multiplexer circuitry and local amplification circuitry.

FIG. 4shows another example of active components and a PMUT array on the same substrate. In this example, the PMUT array105and TFT circuitry are both provided on the common substrate305, which may be glass or plastic in some implementations. Here, the TFT circuitry includes row drivers405aand405b, as well as data multiplexer and control circuitry410. Here, the row drivers405aand405bare capable of addressing individual rows of the PMUT array105. In some examples, the TFT circuitry may be capable of addressing individual columns, rows, PMUT elements310and/or groups of PMUT elements310of the PMUT array105.

In this example, an array of flex pads415may provide connectivity with other components of a device. According to some implementations, the components shown inFIG. 4are part of a display device, such as the display device40ofFIG. 1A. Accordingly, the TFT circuitry shown inFIG. 4may be part of the control system110ofFIG. 1A. In some implementations, the control signals and/or data being input via the flex pads415may be sent from the control system110, and the data being output via the flex pads415may be sent to the control system110, e.g., via a flex cable. In some examples, the TFT circuitry and the circuitry for controlling the display may be capable of sharing a flex cable connected to the flex pads415. In some implementations, the TFT circuitry (and/or other components of the control system110) may be capable of addressing at least a portion of the PMUT array105for wavefront beam forming, beam steering, receive-side beam forming, and/or selective readout of returned signals.

FIG. 5Ashows an example of a display device that includes a PMUT array. In this example, a single display pixel505of the display device40corresponds to a single PMUT element310of the PMUT array105. Such implementations may be referred to herein as “in-cell” implementations. In some implementations, a PMUT element310may correspond with each display pixel505in the display30. In some implementations, PMUT elements310may be positioned in a portion of the display pixels505or in select areas of the display30such as near a corner or edge of the active display area.

In this example, the display pixel505includes a red subpixel505a, a green subpixel505band a blue subpixel505c. Other in-cell implementations may include display pixels505with different numbers and/or colors of subpixels. Still other in-cell implementations may have display pixels505that do not include subpixels, such as multi-state IMOD pixels, each of which can provide a range of colors.

In some high-resolution implementations of the display device40, the display30may include pixels500having a spacing or pitch of 50 microns, which is approximately 500 dots or pixels per inch. In order to have a sufficiently high resolution for fingerprint detection, fingerprint sensor arrays also may need to have a spacing on the order of 500 dots or pixels per inch. Accordingly, some in-cell implementations of a display device40, such as that shown inFIG. 5A, may provide a high-resolution display30and a PMUT array105having a sufficiently high resolution for fingerprint sensor functionality.

In the in-cell implementation shown inFIG. 5A, the PMUT elements310of the PMUT array105are positioned in substantially the same plane as the display subpixels, such that a portion of the display area is utilized by the PMUT elements. In such implementations, it is desirable for the PMUT elements310to be non-transparent or substantially non-transparent. In other in-cell implementations, a portion or all of each PMUT element310of the PMUT array105may be positioned over or under one or more display subpixels of the display pixels505. In such implementations, it is desirable for the PMUT elements310to be transparent, or substantially transparent.

According to some implementations, at least a portion of the PMUT array105may be disposed behind substantially all of the display30.FIG. 5Bshows an example of a display device having a PMUT array that is co-extensive with an array of display pixels. In this example, the PMUT array105is positioned behind the display30: the display pixels505are between the PMUT elements310and a viewer510. In this example, the PMUT array105is disposed on the substrate305, which may be formed of any suitable material. For implementations in which light will be transmitted through the substrate305(e.g., if the substrate305is positioned between the display30and a backlight panel), the substrate305may be a glass, plastic or another transparent or substantially transparent material. However, if it is not necessary for light to be transmitted through the substrate305(e.g., if the substrate305is positioned below a backlight panel or if the display30is an emissive display, such as an organic light-emitting diode (OLED) display), the substrate305need not be formed of a transparent or substantially transparent material. Here, the display30includes an array of display pixels505on a substrate515, which may be a glass or plastic substrate in some implementations.

The PMUT array105may include various types of PMUT elements310, depending on the particular implementation. In some implementations, the PMUT array105may include PMUT elements310configurable as low-frequency emitters and/or receivers for ultrasonic gesture detection. In some implementations, the PMUT array105may include PMUT elements310configurable as high-frequency emitters and/or receivers, e.g., for ultrasonic fingerprint, stylus and/or other biometric detection. In some implementations, the PMUT array105may include PMUT elements310configurable as both low-frequency and high-frequency emitters and/or receivers, e.g., for gesture detection and biometric sensing. In some configurations, the PMUT array105may include PMUT elements310that are capable of button functionality, which may be authenticating button functionality and/or non-authenticating button functionality. In some implementations, the PMUT array105may include PMUT elements310configurable to operate in a medium-frequency mode. When operating in a medium-frequency mode, the display device40may be capable of providing gesture detection capability and/or touch sensor functionality, although with somewhat less resolution than operation in low-frequency or high-frequency modes.

In the example shown inFIG. 5B, the substrate305and the substrate515may be joined via a coupling agent520. Here, the substrate515and the cover glass525are joined via an adhesive530. The coupling agent520may include silicone, an adhesive such as epoxy, a pressure-sensitive adhesive (PSA), or other material with suitable acoustic and optical properties. For example, the coupling agent520may have a small or substantially zero acoustic impedance mismatch with the substrate305and the substrate515. Similarly, the adhesive530may have a small acoustic impedance mismatch with the substrate515and the cover glass525. Preferably, there are substantially no air gaps between the PMUT array105and the cover glass525.

FIG. 5Cshows an example stack for a display device that includes an LCD display and a PMUT array. For the sake of simplicity, the adhesive layers of the stack are not shown. Here, the display device40may include a PMUT array105, a backlight panel532, an LCD display module535, a touch panel540and a cover glass525.

In this example, the PMUT array105may include a pMUT array and TFT circuitry on a substrate305. Here, the backlight panel532includes a backlight substrate, a reflector film, a diffuser film and a brightness enhancement film (BEF). In this implementation, the LCD display module535includes polarizing layers, a TFT substrate, TFT circuitry, liquid crystal material, color filters and a color filter glass. In this example, the touch panel540includes a touch panel substrate, which is formed of glass in this instance, as well as transparent electrode layers, which are indium tin oxide (ITO) layers in this implementation. In some implementations, the TFT circuitry for controlling the PMUT array105and the TFT circuitry for controlling the LCD display module535may be capable of sharing a flex cable.

FIG. 5Dshows an example stack for a display device that includes an OLED display and a PMUT array. In this example, the stack is substantially simpler than that shown inFIG. 5C. The OLED display module545, which includes a TFT substrate, TFT circuitry and OLED material, is substantially simpler than the LCD display module535shown inFIG. 5C. Moreover, because the OLED display module545is an emissive display module, no backlight panel is required. In some implementations, the TFT circuitry for controlling the PMUT array105and the TFT circuitry for controlling the OLED display module545may be capable of sharing a flex cable.

As noted above, having a “full-size” PMUT array105that is co-extensive with an array of display pixels can provide various potential advantages. However, a full-size PMUT array105attached to the back of a display30can add substantially to expense and increase the display device thickness.

According to some implementations, at least a portion of the PMUT array105may be disposed behind only a part of the display30.FIG. 6Ashows an example of a display device that includes a PMUT array behind only a portion of a display. The elements shown inFIG. 6Aare substantially similar to those shown inFIG. 5B. However, in the example ofFIG. 6A, the area605occupied by the PMUT array105is substantially smaller than the area610occupied by the display30.

In some implementations, the PMUT array105may include PMUT elements310configurable as high-frequency emitters and/or receivers, e.g., for ultrasonic fingerprint, stylus and/or other biometric detection. In some such implementations, the PMUT array105may correspond to a fingerprint sensor area or ultrasonic touchpad area of the display device40. In some implementations, the PMUT array105may include PMUT elements310configurable as low-frequency emitters and/or receivers for ultrasonic gesture detection. In some such implementations, the display device40may include multiple areas605, each of which corresponds to a PMUT array105. In some implementations, the PMUT array105may include PMUT elements310configurable as both low-frequency and high-frequency emitters and/or receivers, e.g., for gesture detection and biometric sensing. In some implementations, the PMUT array105may include PMUT elements310configurable to operate in a medium-frequency mode, e.g., for lower resolution gesture detection and/or touch sensor functionality.

According to some implementations, at least a portion of the PMUT array105may be disposed in a peripheral area of the display30. A control system, such as the control system110ofFIG. 1A, may be capable of controlling a portion of the PMUT array105that is disposed in the peripheral area of the display30for biometric sensor functionality (such as fingerprint sensor functionality), touchpad or signature (e.g., stylus) pad functionality, gesture detection functionality and/or button functionality.

FIGS. 6B-Dshow examples of a display device that includes a PMUT array near a periphery of a display. As shown inFIG. 6B, a display device40(a portion of which is shown) may include a visual display30formed on a substrate660along with a PMUT array105. The display30may be optically and mechanically coupled to a cover lens or cover glass630. One or more holes180may be formed in the cover glass630to allow for the transmission and reception of acoustic and ultrasonic waves190. The holes180may include, for example, one or more circular holes, rectangular or square holes, elongated holes, tapered holes or slots.FIG. 6Cshows a portion of a display device40with a display30and a PMUT array105formed on a substrate660, with the assembly optically and mechanically coupled to a cover glass630having one or more holes180formed therein. The holes180may be filled with an acoustic coupling material186such as a silicone gel to provide some environmental protection for the PMUT array105while allowing for the transmission and reception of ultrasonic waves190.FIG. 6Dshows a thin cover or coating188disposed over a coupling material186positioned inside a hole180formed in a cover glass630. An adhesive layer184may connect a protective membrane182to the cover glass630, while the protective membrane may be attached to the PMUT array105that may be formed on the substrate660along with the visual display30. The coating188may be a hard coating such as diamond-like carbon (DLC), an acrylic, or other suitable coating material that is sufficiently compliant for the transmission of ultrasonic waves190while providing additional environmental protection for the PMUT array105, associated circuitry, and display30of display device40.

FIGS. 7A-7Fshow examples of PMUT arrays disposed in peripheral areas of a display. In these examples, TFT circuitry for the display and TFT circuitry for the PMUT arrays105are disposed on the same (e.g., common) substrate.

InFIG. 7A, for example, TFT circuitry705for the PMUT array105is disposed on the same substrate (the substrate305) as TFT circuitry730for a display. The display may, for example, be an LCD or an OLED display. Here, the data multiplexer and control circuitry410may be connected to the flex pads415via the fanout region710. In this example, the PMUT array105is a single pMUT array configurable as a fingerprint sensor or ultrasonic touchpad. However, in alternative implementations at least a portion of the PMUT array105may be configurable for other functionality, such as gesture detection functionality and/or button functionality. In this implementation, the PMUT array105is disposed in a corner of the display device40, outside of an active display area. The display area may be approximately coextensive with the area of the TFT circuitry730shown inFIG. 7A. In some implementations, one or more flex pads on substrate305may provide for electrical connection between TFT circuitry705and external circuitry. One or more flex cables may be attached and electrically connected to at least a portion of the flex pads415on substrate305. For example, a flex cable may be shared between circuitry for controlling at least a portion of the PMUT array105and TFT circuitry730for controlling the display.

InFIG. 7B, the TFT circuitry705for the PMUT array105is disposed on the same substrate305as the TFT circuitry730for a display. In this example, the PMUT array105includes PMUT sub-arrays105aand105b. In this implementation, the PMUT sub-arrays105a-bare disposed outside of the active display area. In this implementation, the PMUT sub-arrays105aand105bextend along at least a portion of the sides715aand715b, respectively, of the display device40. For example, a one-dimensional string of low-frequency PMUT elements may be positioned along a first side715aof the display device40, and another string of low-frequency PMUT elements may be positioned along a second side715bof the display device40. In another example, a first PMUT element may be positioned along the first side715anear one corner of the display device40, and a second PMUT element may be positioned along the first side715anear a second corner of the display device40. A third and fourth PMUT element may be positioned along the second side715bnear a third and fourth corner of the display device40. The PMUT elements configured near each of the four corners of the display device40may allow for gesture detection via triangulation of a finger, hand or other object positioned above the display device40. More than one PMUT element in a sub-array may be configured in each corner or along one or more sides of the display device40. In some examples, the PMUT sub-arrays105aand105bmay be configurable for gesture detection. In this implementation, the PMUT sub-arrays105aand105bmay be driven by TFT circuitry705, which may be disposed in two corners of the display device40. In alternative implementations, the TFT circuitry705and PMUT arrays105may be configurable for other functionality, such as fingerprint sensor functionality or button functionality.

InFIG. 7C, the PMUT array105includes PMUT sub-arrays105a,105band105f, all of which are disposed outside of the active display area. As in the implementation shown inFIG. 7B, the PMUT sub-arrays105aand105bmay extend along a portion or all of sides715aand715b, respectively, of the display device40. In some examples, the PMUT sub-arrays105aand105bmay be configurable for gesture detection. In this implementation, the PMUT sub-array105fmay be configurable for fingerprint sensor or ultrasonic touchpad functionality. Accordingly, in this example the TFT circuitry705for the PMUT array105may include TFT circuitry for fingerprint sensor and gesture detection functionality.

InFIG. 7D, the PMUT array105includes PMUT sub-arrays105g-105i, all of which are disposed outside of the active display area. Here, the fanout region710and the flex pads415are offset to allow space for the PMUT sub-arrays105g-105i. In this implementation, the PMUT sub-arrays105g-105imay be configurable for button functionality. Accordingly, in this example the TFT circuitry705for the PMUT array105may include TFT circuitry for button functionality. The button functionality may involve controlling some aspect of the display device40with or without authentication functionality. Accordingly, such buttons may be referred to as “authenticating” buttons or “non-authenticating” buttons. PMUT sub-arrays for authenticating buttons may include substantially more PMUT elements310than PMUT sub-arrays for non-authenticating buttons, to allow for higher resolution imaging of fingerprints. In some examples, a non-authenticating button may correspond with a single PMUT element310, a small (e.g. two-by-two) array of PMUT elements310, or a larger array of PMUT elements310.

In some implementations, at least one of the PMUT sub-arrays105g-105imay be configurable for authenticating button functionality and at least one of the PMUT sub-arrays105g-105imay be configurable for non-authenticating button functionality. In such implementations, the TFT circuitry705for the PMUT array105may include TFT circuitry for authenticating button functionality (e.g., fingerprint sensor functionality) and non-authenticating button functionality. In some implementations, an authenticating button may also serve as a non-authenticating button.

FIG. 7Eincludes PMUT sub-arrays105jand105k, each of which may be located in a corner of the display device40. In this example, the PMUT sub-array105jis capable of fingerprint sensor functionality and the PMUT sub-array105kis capable of button functionality. Accordingly, in this example the TFT circuitry705afor the PMUT array105includes TFT circuitry for fingerprint sensor functionality and the TFT circuitry705bincludes TFT circuitry for button functionality, which may be authenticating button functionality or non-authenticating button functionality.

FIG. 7Fincludes PMUT sub-arrays105a,105band105l-105n. As in the implementation shown inFIG. 7B, the PMUT sub-arrays105aand105bextend along a portion or all of sides715aand715b, respectively, of the display device40. In this example, the PMUT sub-arrays105aand105bare configurable for gesture detection.

In this implementation, the PMUT sub-array105lis capable of providing both fingerprint sensor functionality and gesture detection functionality. Here, the PMUT sub-array105mis capable of button functionality. In this example, the PMUT sub-array105nis capable of providing both gesture detection functionality and button functionality. Accordingly, in this example the TFT circuitry705cfor the PMUT array105includes TFT circuitry for fingerprint sensor functionality and gesture detection functionality. Here, the TFT circuitry705dincludes TFT circuitry for button functionality, which may be authenticating button functionality or non-authenticating button functionality, as well as TFT circuitry for gesture detection functionality.

In view of the foregoing, it will be apparent to those of ordinary skill in the art that various other configurations are within the scope of the present disclosure. For example, some alternative implementations may include PMUT sub-arrays disposed in each corner of the display periphery that are capable of providing gesture detection functionality. The PMUT sub-arrays may provide full capability to send and receive ultrasonic signals for gesture detection. In some implementations, one or more microphones on a mobile device may be used for receiving ultrasonic waves generated by the PMUT elements to further aid in gesture detection. Typical microphones have limited audio range (e.g. 100 to 10,000 Hz response), whereas higher performing audio microphones may be responsive to ultrasonic frequencies up to 180 kHz or 200 kHz. The microphones may be positioned at various locations in the mobile device, such as near the bottom of the device face. High-performance phones may have multiple microphones on the front and/or back of the phone enclosure for enhanced audio clarity and noise cancellation. Microphones with a high frequency response may aid in gesture detection along with PMUT elements operating in a receive mode. Therefore, in some alternative implementations, at least some receivers used for gesture detection may be microphones of a display device.

In some implementations, a touch panel and at least portions of the PMUT array105may share a common flex cable. According to some implementations, a touch panel substrate or a cover glass may have additional electrodes for topside electrical connections to at least a portion of the PMUT array105located in the periphery of a display area. In some such implementations, these additional electrodes may provide electrical connectivity with at least a portion of a control system.

Some such implementations may have a control system that includes separate TFT circuitry disposed on separate substrates for the display and for at least a portion of the PMUT array105, which may be disposed on a periphery of the display. In some such implementations, these additional electrodes may be configured for electrical connectivity with circuitry, such as TFT circuitry, with a portion of the PMUT array105configured for fingerprint sensor functionality and/or gesture detection functionality. In some such implementations, these additional electrodes may be configured for electrical connectivity with circuitry, such as TFT circuitry, with a portion of the PMUT array105configured for button functionality (e.g., authenticating or non-authenticating button functionality).

FIGS. 8A and 8Bshow examples of system block diagrams illustrating a display device that includes at least one PMUT array as described herein. The display device40can be, for example, a cellular or mobile telephone. However, the same components of the display device40or slight variations thereof are also illustrative of various types of display devices such as televisions, computers, tablets, e-readers, hand-held devices and portable media devices.

The display device40includes a housing41, a display30, an antenna43, a speaker45, an input device48and one or more microphones46. The housing41can be formed from any of a variety of manufacturing processes, including injection molding and vacuum forming. In addition, the housing41may be made from any of a variety of materials, including, but not limited to: plastic, metal, glass, rubber and ceramic, or a combination thereof. The housing41can include removable portions (not shown) that may be interchanged with other removable portions of different color, or containing different logos, pictures, or symbols.

The display30may be any of a variety of displays, including a bi-stable or analog display, as described herein. The display30also can include a flat-panel display, such as plasma, EL, OLED, STN LCD, or TFT LCD, or a non-flat-panel display, such as a CRT or other tube device. In addition, the display30can include an interferometric modulator (IMOD) based display.

The components of the display device40are schematically illustrated inFIG. 8B. The display device40includes a housing41and can include additional components at least partially enclosed therein. For example, the display device40includes a network interface27that includes an antenna43which can be coupled to a transceiver47. The network interface27may be a source for image data that could be displayed on the display device40. Accordingly, the network interface27is one example of an image source module, but the processor21and the input device48also may serve as an image source module. The transceiver47is connected to a processor21, which is connected to conditioning hardware52. The conditioning hardware52may be capable of conditioning a signal (such as filter or otherwise manipulate a signal). The conditioning hardware52can be connected to a speaker45and a microphone46. The processor21also can be connected to an input device48and a driver controller29. The driver controller29can be coupled to a frame buffer28, and to an array driver22, which in turn can be coupled to a display array30. One or more elements in the display device40, including elements not specifically depicted inFIG. 8B, can be capable of functioning as a memory device and be capable of communicating with the processor21. In some implementations, a power supply50can provide power to substantially all components in the particular display device40design.

In this example, the display device40may also include one or more linear or two-dimensional PMUT arrays77. In some implementations, at least a portion of the PMUT array77may be disposed behind the display30. In some such implementations, a PMUT array77may be disposed behind only part of the display30, whereas in other implementations a PMUT array77may be disposed behind substantially all of the area of the display30. In some implementations, at least a portion of PMUT array77may be included within one or more display pixels of display array30. The processor21may be a portion of a control system that is capable of controlling the PMUT array77(at least in part), as described herein. Accordingly, a control system110as described elsewhere herein may include the processor21and/or other elements of the display device40, such as TFTs.

In some implementations, the processor21(and/or another element of the control system110) may be capable of providing input for controlling the display device40according to one or more gestures detected when the PMUT array77is operating in a low-frequency mode. In some implementations, the processor21(and/or another element of the control system110) may be capable of providing input for controlling the display device40according to one or more touch locations and/or movements determined when the PMUT array77is operating in a medium-frequency mode. In some implementations, the processor21(and/or another element of the control system110) may be capable of providing input for controlling the display device40according to fingerprint data or stylus input data determined when the PMUT array77is operating in a high-frequency mode.

The network interface27includes the antenna43and the transceiver47so that the display device40can communicate with one or more devices over a network. The network interface27also may have some processing capabilities to relieve, for example, data processing requirements of the processor21. The antenna43can transmit and receive signals. In some implementations, the antenna43transmits and receives RF signals according to the IEEE 16.11 standard, including IEEE 16.11(a), (b), or (g), or the IEEE 802.11 standard, including IEEE 802.11a, b, g, n, and further implementations thereof. In some other implementations, the antenna43transmits and receives RF signals according to the Bluetooth® standard. In the case of a cellular telephone, the antenna43can be designed to receive code division multiple access (CDMA), frequency division multiple access (FDMA), time division multiple access (TDMA), Global System for Mobile communications (GSM), GSM/General Packet Radio Service (GPRS), Enhanced Data GSM Environment (EDGE), Terrestrial Trunked Radio (TETRA), Wideband-CDMA (W-CDMA), Evolution Data Optimized (EV-DO), 1xEV-DO, EV-DO Rev A, EV-DO Rev B, High Speed Packet Access (HSPA), High Speed Downlink Packet Access (HSDPA), High Speed Uplink Packet Access (HSUPA), Evolved High Speed Packet Access (HSPA+), Long Term Evolution (LTE), AMPS, or other known signals that are used to communicate within a wireless network, such as a system utilizing 3G, 4G or 5G technology. The transceiver47can pre-process the signals received from the antenna43so that they may be received by and further manipulated by the processor21. The transceiver47also can process signals received from the processor21so that they may be transmitted from the display device40via the antenna43.

In some implementations, the transceiver47can be replaced by a receiver. In addition, in some implementations, the network interface27can be replaced by an image source, which can store or generate image data to be sent to the processor21. The processor21can control the overall operation of the display device40. The processor21receives data, such as compressed image data from the network interface27or an image source, and processes the data into raw image data or into a format that can be readily processed into raw image data. The processor21can send the processed data to the driver controller29or to the frame buffer28for storage. Raw data typically refers to the information that identifies the image characteristics at each location within an image. For example, such image characteristics can include color, saturation and gray-scale level.

The processor21can include a microcontroller, CPU, or logic unit to control operation of the display device40. The conditioning hardware52may include amplifiers and filters for transmitting signals to the speaker45, and for receiving signals from the microphone46. The conditioning hardware52may be discrete components within the display device40, or may be incorporated within the processor21or other components.

The driver controller29can take the raw image data generated by the processor21either directly from the processor21or from the frame buffer28and can re-format the raw image data appropriately for high speed transmission to the array driver22. In some implementations, the driver controller29can re-format the raw image data into a data flow having a raster-like format, such that it has a time order suitable for scanning across the display array30. Then the driver controller29sends the formatted information to the array driver22. Although a driver controller29, such as an LCD controller, is often associated with the system processor21as a stand-alone Integrated Circuit (IC), such controllers may be implemented in many ways. For example, controllers may be embedded in the processor21as hardware, embedded in the processor21as software, or fully integrated in hardware with the array driver22.

The array driver22can receive the formatted information from the driver controller29and can re-format the video data into a parallel set of waveforms that are applied many times per second to the hundreds, and sometimes thousands (or more), of leads coming from the display's x-y matrix of display elements.

In some implementations, the driver controller29, the array driver22, and the display30are appropriate for any of the types of displays described herein. For example, the driver controller29can be a conventional display controller or an IMOD display element controller, such as a multi-state IMOD (MS-IMOD) display element controller). Additionally, the array driver22can be a conventional driver or a bi-stable display driver (such as an MS-IMOD display element driver). Moreover, the display30can be a conventional display array or a bi-stable display array (such as a display including an array of IMOD display elements). In some implementations, the driver controller29can be integrated with the array driver22. Such an implementation can be useful in highly integrated systems, for example, mobile phones, portable-electronic devices, watches or small-area displays.

In some implementations, the input device48can be capable of allowing, for example, a user to control the operation of the display device40. The input device48can include a keypad, such as a QWERTY keyboard or a telephone keypad, a button, a switch, a rocker, a touch-sensitive screen, a touch-sensitive screen integrated with the display array30, or a pressure- or heat-sensitive membrane. The microphone46can be capable of functioning as an input device for the display device40. In some implementations, voice commands through the microphone46can be used for controlling operations of the display device40.

The power supply50can include a variety of energy storage devices. For example, the power supply50can be a rechargeable battery, such as a nickel-cadmium battery or a lithium-ion battery. In implementations using a rechargeable battery, the rechargeable battery may be chargeable using power coming from, for example, a wall socket or a photovoltaic device or array. Alternatively, the rechargeable battery can be wirelessly chargeable. The power supply50also can be a renewable energy source, a capacitor, or a solar cell, including a plastic solar cell or solar-cell paint. The power supply50also can be capable of receiving power from a wall outlet.

In some implementations, control programmability resides in the driver controller29which can be located in several places in the electronic display system. In some other implementations, control programmability resides in the array driver22. The above-described optimization may be implemented in any number of hardware and/or software components and in various configurations.

Various modifications to the implementations described in this disclosure may be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other implementations without departing from the spirit or scope of this disclosure. Thus, the claims are not intended to be limited to the implementations shown herein, but are to be accorded the widest scope consistent with this disclosure, the principles and the novel features disclosed herein. Additionally, a person having ordinary skill in the art will readily appreciate, the terms “upper” and “lower”, “over” and “under”, and “overlying” and “underlying” are sometimes used for ease of describing the figures, and indicate relative positions corresponding to the orientation of the figure on a properly oriented page, and may not reflect the proper orientation of the device as implemented.