Ultrasonic sensor array control to facilitate screen protection films

Abstract

Techniques for operating an ultrasonic sensor array disposed below a platen include determining whether to recalibrate the ultrasonic sensor array based on whether a first screen protection film disposed above the platen has been removed or replaced by a second screen protection film; when it is determined that the ultrasonic sensor array is to be recalibrated, the ultrasonic sensor array is recalibrated. In some cases, the techniques include prompting a user to indicate whether the screen protection film has been replaced or removed, and recalibrating the ultrasonic sensor array only after confirmation from the user.

Description

[0001] This application is a divisional application of a patent application filed on May 13, 2020, entitled “ULTRASONIC SENSOR ARRAY CONTROL TO FACILITATE SCREEN PROTECTIVE FILM” and application number 202080034666.2.

[0002] Claiming priority under 35 U.S.C. §119

[0003] This patent application claims the benefit of non-provisional application No. 16 / 414,164, filed on May 16, 2019, entitled “ULTRASONIC SENSORARRAY CONTROL TO FACILITATE SCREEN PROTECTORS”, which has been assigned to the assignee of this application and is hereby expressly incorporated herein by reference. Technical Field

[0004] In general, the present disclosure relates to ultrasound transducer arrays, and more particularly, the present disclosure relates to techniques for detecting the presence of a screen protector disposed over an ultrasound transducer array. Background Art

[0005] The ultrasonic sensor system can use a transmitter to generate ultrasonic waves and send ultrasonic waves to an object to be detected and / or imaged through a transmission medium. The ultrasonic transmitter can be operably coupled to an ultrasonic sensor array, which is configured to detect a portion of the ultrasonic waves reflected from the object. At each material interface encountered by the ultrasonic pulse, a portion of the ultrasonic pulse can be reflected. In some implementations, the ultrasonic pulse can be generated by starting and stopping the transmitter during a short time interval (e.g., less than 1 microsecond). The ultrasonic sensor system may include a biometric sensor, such as a fingerprint or handprint sensor and / or other ultrasonic imaging applications.

[0006] Piezoelectric ultrasonic transducers are attractive candidates for such applications and may include a piezoelectric micromechanical ultrasonic transducer (PMUT) configured as a multilayer stack including a piezoelectric layer stack. The piezoelectric layer stack may include a piezoelectric material layer, such as, for example, a polyvinylidene fluoride (PVDF) layer or a PVDF copolymer layer. The piezoelectric layer may convert the vibration caused by the reflection of the ultrasonic wave into an electrical output signal. In some implementations, the ultrasonic sensor system also includes a thin film transistor (TFT) layer, which may include an array of sensor pixel circuits, which may, for example, amplify the electrical output signal generated by the piezoelectric layer.

[0007] In some applications, a two-dimensional array of a large number of PMUT elements ("PMUT array") can be integrated with and arranged behind or "under" a platen ("cover plate" or "cover glass") configured as a display screen with which a user interacts. For example, the display screen can provide a user touch interface and / or be incorporated into a personal electronic device such as a mobile phone or tablet computer. Such a display screen can benefit from a removable and / or disposable "screen protector", which is typically a protective sheet of transparent material (such as glass or plastic) that protects the underlying display screen. Summary of the invention

[0008] Each of the systems, methods and devices of the disclosure has several innovative aspects, no single one of which is responsible for the desirable attributes disclosed herein.

[0009] One innovative aspect of the subject matter described in the present disclosure relates to a method for operating an ultrasonic sensor array disposed below a platen, the method comprising: determining whether to recalibrate the ultrasonic sensor array based on whether a first screen protective film disposed above the platen has been removed or replaced with a second screen protective film; and recalibrating the ultrasonic sensor array when the determination is to recalibrate the ultrasonic sensor array.

[0010] In some examples, the determination can be made by performing a background estimation process. In some examples, the background estimation process can include obtaining features of an air image and comparing the obtained features to features of a baseline air image. In some examples, the baseline air image can include an air image obtained by operating the ultrasonic sensor array without any screen protector.

[0011] In some examples, the method may further include prompting a user to indicate whether the first screen protector has been removed or replaced, and recalibrating the ultrasonic sensor array may be performed only after confirmation from the user.

[0012] In some examples, the method may also include mitigating the effects of removing or replacing the first screen protector by adjusting at least one sensor tuning offset. In some examples, the at least one sensor tuning offset may include one or more of: range gate delay, frequency offset, time delay offset, and phase correction offset.

[0013] In some examples, the determination can be made based on any one or more of the following: phase of received ultrasonic waves, platen temperature gradient, changes in signal-to-noise ratio (SNR) or image quality (IQ) versus range gate delay characteristics, changes in SNR or IQ characteristics with background calibration, or changes in touch screen capacitance.

[0014] In some examples, the method may further include operating the ultrasound sensor array with a modified sensor drive scheme, the modification being configured to provide one or both of transmit tone bursts of increased duration and quasi-continuous wave transmit signals.

[0015] In some examples, the method may further include operating the ultrasound sensor array and processing image data using a point spread function (PSF) image reconstruction technique.

[0016] In some examples, at least one of the first screen protector or the second screen protector may include a multi-layer stack having a thickness of approximately 0.75λ or 1.25λ, where λ is a characteristic wavelength of ultrasonic transmissions generated by the ultrasonic sensor array.

[0017] According to some implementations, a device includes a controller and an ultrasonic sensor array, wherein the ultrasonic sensor array is disposed below a pressure plate. The controller is configured to: determine whether to recalibrate the ultrasonic sensor array based on whether a first screen protective film disposed above the pressure plate has been removed or replaced by a second screen protective film; and when the determination is to recalibrate the ultrasonic sensor array, recalibrate the ultrasonic sensor array.

[0018] In some examples, the controller is configured to make the determination by way of a background estimation process. In some examples, the background estimation process may include obtaining features of an air image and comparing the obtained features to features of a baseline air image. In some examples, the baseline air image may relate to an air image obtained by operating the ultrasonic sensor array without any screen protector.

[0019] In some examples, the controller may be further configured to prompt a user to indicate whether the first screen protector has been removed or replaced, and the controller may be configured to recalibrate the ultrasonic sensor array only after confirmation from the user.

[0020] In some examples, the controller can be further configured to mitigate the effects of removing or replacing the first screen protector by adjusting at least one sensor tuning offset. In some examples, the at least one sensor tuning offset can include one or more of: range gate delay, frequency offset, time delay offset, and phase correction offset.

[0021] In some examples, at least one of the first screen protector or the second screen protector may include a multi-layer stack having a thickness of approximately 0.75λ or 1.25λ, where λ is a characteristic wavelength of ultrasonic transmissions generated by the ultrasonic sensor array.

[0022] According to some implementations, for a non-transitory computer-readable medium storing program code to be executed by a controller of an ultrasonic sensor array, the ultrasonic sensor array is disposed below a pressure plate, the program code including instructions configured to cause the controller to perform the following operations: determine whether to recalibrate the ultrasonic sensor array based on whether a first screen protective film disposed above the pressure plate has been removed or replaced with a second screen protective film; and recalibrate the ultrasonic sensor array when the determination is to recalibrate the ultrasonic sensor array.

[0023] In some examples, the determination may be made by performing a background estimation process. In some examples, the background estimation process may include obtaining features of an air image and comparing the obtained features to features of a baseline air image. In some examples, the baseline air image may relate to an air image obtained by operating the ultrasonic sensor array without any screen protector.

[0024] In some examples, the program code may also include instructions configured to cause the controller to prompt a user to indicate whether the first screen protector has been removed or replaced, and to cause the controller to recalibrate the ultrasonic sensor array only after confirmation from the user.

[0025] In some examples, the program code may also include instructions configured to cause the controller to perform the following operations: mitigate the effects of removing or replacing the first screen protector by adjusting at least one sensor tuning offset. In some examples, the at least one sensor tuning offset may include one or more of the following: adjusting a range gate delay, a frequency offset, a time delay offset, and a phase correction offset.

[0026] In some examples, the determination can be made by evaluating one or more of: the phase of the received ultrasonic wave, the temperature gradient of the platen, the change in the signal-to-noise ratio (SNR) or image quality (IQ) versus the range gate delay characteristics, the change in the SNR or IQ characteristics with background calibration, and the change in the touch screen capacitance.

[0027] In some examples, the program code may also include instructions configured to cause the controller to operate the ultrasonic sensor array with a modified sensor drive scheme, the modification being configured to provide one or both of transmit tone bursts of increased duration and quasi-continuous wave transmit signals.

[0028] In some examples, the program code may also include instructions configured to cause the controller to operate the ultrasound sensor array and process image data using a point spread function (PSF) image reconstruction technique.

[0029] In some examples, at least one of the first screen protector or the second screen protector may include a multi-layer stack having a thickness of approximately 0.75λ or 1.25λ, where λ is a characteristic wavelength of ultrasonic transmissions generated by the ultrasonic sensor array.

[0030] According to some implementations, a device includes: an ultrasonic sensor array disposed below a pressure plate; a first unit for determining whether to recalibrate the ultrasonic sensor array based on whether a screen protector disposed above the pressure plate undergoes a change; and a second unit for recalibrating the ultrasonic sensor array when the determination is to recalibrate the ultrasonic sensor array.

[0031] In some examples, the determination is performed by performing a background estimation process. In some examples, the background estimation process may include obtaining features of an air image and comparing the obtained features to features of a baseline air image. In some examples, the baseline air image may relate to an air image obtained by operating the ultrasonic sensor array without any screen protector.

[0032] In some examples, the determination can be made by evaluating one or more of: the phase of the received ultrasonic wave, the temperature gradient of the platen, the change in the signal-to-noise ratio (SNR) or image quality (IQ) versus the range gate delay characteristics, the change in the SNR or IQ characteristics with background calibration, and the change in the touch screen capacitance.

[0033] In some examples, at least one of the first screen protector or the second screen protector may include a multi-layer stack having a thickness of approximately 0.75λ or 1.25λ, where λ is a characteristic wavelength of ultrasonic transmission generated by the ultrasonic sensor array. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In the present disclosure and the accompanying drawings, the details of one or more implementations of the subject matter described in this specification are set forth. Other features, aspects and advantages will become apparent through a review of the present disclosure. It should be noted that the relative dimensions in the accompanying drawings and other figures of the present disclosure are not depicted to scale. The dimensions, thicknesses, arrangements, materials, etc. shown and described in the present disclosure are only examples and should not be construed as limiting. The same reference numerals and names in the various drawings represent the same elements.

[0035] Figure 1 According to some implementations, a front view of a diagrammatic representation of an example of an electronic device including an ultrasound sensing system is shown.

[0036] Figure 2A According to some implementations, a block diagram representation of components of an example of an ultrasound sensing system is shown.

[0037] Figure 2B According to some implementations, block diagram representations of components of an example of an electronic device are shown.

[0038] Figure 3A-3C According to some implementations, a cross-sectional view of an example of an ultrasound sensing system is shown.

[0039] Figure 4 A process flow chart for detecting the effect of screen protectors on image quality is shown.

[0040] Figure 5 An example of a range gate delay is shown.

[0041] Figure 6 According to some implementations, a graph of signal-to-noise ratio as a function of range gate delay (RGD) is shown.

[0042] Figure 7 According to some implementations, examples of adjusting RGD and performing background calibration are shown.

[0043] Figure 8 Example graphs showing thermal gradients for a glass platen without a screen protector and with a plastic screen protector.

[0044] Fig. 9 According to some implementations, an example of a screen protector stack disposed on a platen is shown.

[0045] Fig.10 According to some implementations, an example of a process flow for a method of operating an ultrasound sensor array is shown. DETAILED DESCRIPTION

[0047] In order to describe the innovative aspects of the present disclosure, the following description is directed to certain implementations. However, those skilled in the art will readily recognize that the teachings of this document may be applied in a variety of different ways. The described implementations may be implemented in any device, apparatus, or system that includes a sensor system. In addition, it is contemplated that the described implementations may be included in or associated with a variety of electronic devices, such as, but not limited to: mobile phones, cellular phones with multimedia Internet capabilities, mobile television receivers, wireless devices, smart phones, smart cards, wearable devices (such as bracelets, armbands, wristbands, rings, headbands, and patches, etc.), devices, personal data assistants (PDAs), wireless email receivers, handheld or portable computers, netbooks, notebooks, smartbooks, tablet devices, printers, copiers, scanners, fax devices, global positioning system (GPS) receivers / navigators, cameras, digital media players (such as MP3 players), camcorders, game consoles, watches, clocks, calculators, television displays, flat panel displays, electronic reading devices (e.g., e-readers), mobile health devices, computer monitors, automotive displays (including odometer and speedometer displays, etc.), cockpit controls and / or displays, Steering wheels, camera view displays (such as, for example, displays for rear-view cameras in vehicles), electronic photographs, electronic billboards or signs, projectors, architectural structures, microwave ovens, refrigerators, stereo systems, cassette recorders or players, DVD players, CD players, VCRs, radios, portable memory chips, washing machines, dryers, washer / dryers, automated teller machines (ATMs), parking meters, packaging (such as, in electromechanical systems (EMS) applications, which include microelectromechanical systems (MEMS) applications as well as non-EMS applications), aesthetic structures (such as, displaying an image on a piece of jewelry or clothing), and various EMS devices. In addition, the teachings herein may also be used in applications such as, but not limited to, electronic switching devices, radio frequency filters, sensors, accelerometers, gyroscopes, motion sensing devices, magnetometers, inertial components for consumer electronics, components for consumer electronic products, varactor diodes, liquid crystal devices, electrophoretic devices, drive schemes, manufacturing processes, and electronic test equipment. Therefore, the teachings herein are not limited to the implementations described only in the accompanying drawings, but have a wide range of applicability, as will be readily appreciated by those skilled in the art.

[0048] In some implementations, an ultrasound sensor system includes a piezoelectric material for transmitting and receiving ultrasound waves.

[0049] For example, a voltage applied across a piezoelectric material corresponding to a transmitter can cause the piezoelectric material to stretch or contract (e.g., deform), causing the material to strain in response to the applied voltage, thereby obtaining the generation of ultrasonic waves, as previously discussed. A reflected signal (e.g., a reflected portion of the ultrasonic wave, as previously discussed) can cause the piezoelectric material corresponding to a receiver to stretch or contract. This results in the generation of a surface charge, and thus a voltage across the piezoelectric material, which can be used as an electrical output signal representing a portion of the original image data representing the fingerprint image data.

[0050] Some implementations of the subject matter described in this disclosure may be practiced to realize one or more of the following potential advantages: The disclosed technology relates to detecting installation, removal, or replacement of a screen protector, and / or recalibrating an ultrasonic sensor array (sensing system) to account for the installation, removal, or replacement.

[0051] Figure 1 According to some implementations, a front view of a diagrammatic representation of an example of an electronic device 100 including an ultrasonic sensing system is shown. The electronic device 100 can represent, for example, various portable computing devices, such as cellular phones, smart phones, multimedia devices, personal gaming devices, tablet computers and laptop computers, and other types of portable computing devices. However, the various implementations described herein are not limited to applications for portable computing devices. In fact, the various techniques and principles disclosed herein can be applied to traditional non-portable devices and systems, such as, for computer displays, television displays, kiosks, vehicle navigation devices and audio systems, and other applications.

[0052] In the illustrated implementation, the electronic device 100 includes a housing (or "housing") 102 within which various circuits, sensors, and other electrical components may be arranged. In the illustrated implementation, the electronic device 100 also includes a display (which may be referred to herein as a "touch screen display" or "touch-sensitive display") 104. The display 104 may generally represent any of a variety of suitable display types employing any of a variety of suitable display technologies. For example, the display 104 may be a digital microshutter (DMS)-based display, a light emitting diode (LED) display, an organic LED (OLED) display, a liquid crystal display (LCD), an LCD display using LEDs as a backlight, a plasma display, an interferometric modulator (IMOD)-based display, or other types of displays suitable for use in conjunction with a touch-sensitive user interface (UI) system.

[0053] The electronic device 100 may include various other devices or components for interacting with a user or otherwise transmitting information to or receiving information from a user. For example, the electronic device 100 may include one or more microphones 106, one or more speakers 108, and in some cases one or more at least partially mechanical buttons 110. The electronic device 100 may include various other components that enable additional features, such as, for example, one or more video or still image cameras 112, one or more wireless network interfaces 114 (e.g., Bluetooth, WiFi, or cellular), and one or more non-wireless interfaces 116 (e.g., a universal serial bus (USB) interface or an HDMI interface).

[0054] The electronic device 100 may include an ultrasonic sensing system 118 capable of imaging an object signature such as a fingerprint, palm print, or hand print. In some implementations, the ultrasonic sensing system 118 may be used as a touch-sensitive control button. In some implementations, it may be implemented by a mechanical or voltage-sensitive system located below the ultrasonic sensing system 118 or otherwise integrated with the ultrasonic sensing system 118. In other words, in some implementations, the area occupied by the ultrasonic sensing system 118 may be used as both a user input button for controlling the electronic device 100 and a sensor for enabling security features (such as user authentication) based on, for example, a fingerprint, palm print, or hand print.

[0055] Figure 2A According to some implementations, a block diagram representation of components of an example of an ultrasound sensing system is shown. In the implementation shown, the ultrasound sensing system 200 includes a sensor system 202 and a control system 204 electrically coupled to the sensor system 202. The sensor system 202 is capable of scanning a target object and providing raw measurement image data that can be used to obtain an object signature of, for example, a human appendage (such as, one or more fingers or toes, a palm, a hand, or a foot). The control system 204 is capable of controlling the sensor system 202 and processing the raw measurement image data received from the sensor system 202. In some implementations, the ultrasound sensing system 200 may include an interface system 206 that is capable of sending or receiving data (such as raw or processed measurement image data) to or from various components within or integrated with the ultrasound sensing system 200, or in some implementations, data to or from various components, devices, or other systems external to the ultrasound sensing system 200.

[0056] Figure 2B According to some implementations, a block diagram representation of components of an example of an electronic device is shown. In the example shown, the electronic device 210 includes Figure 2A For example, the electronic device 210 may be the ultrasonic sensing system 200 described above. Figure 1A block diagram representation of the electronic device 100 shown and described. The sensor system 202 of the ultrasound sensing system 200 of the electronic device 210 can be implemented using an ultrasound sensor array 212. The control system 204 of the ultrasound sensing system 200 can be implemented using a controller 214 electrically coupled to the ultrasound sensor array 212. Although the controller 214 is shown and described as a single component, in some implementations, the controller 214 can be collectively referred to as two or more different control units or processing units that are in electrical communication with each other. In some implementations, the controller 214 may include one or more of the following: a general-purpose single-chip or multi-chip processor designed to perform the functions and operations described herein, a central processing unit (CPU), a digital signal processor (DSP), an application processor, an application-specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device (PLD), a discrete gate or transistor logic unit, a discrete hardware component, or any combination thereof.

[0057] Figure 2B The ultrasound sensing system 200 may include an image processing module 218. In some implementations, the raw measurement image data provided by the ultrasound sensor array 212 may be sent, transmitted, communicated, or otherwise provided to the image processing module 218. The image processing module 218 may include any appropriate combination of hardware, firmware, and software that is configured, adapted, or otherwise operable to process the image data provided by the ultrasound sensor array 212. In some implementations, the image processing module 218 may include a signal or image processing circuit or circuit component, which includes, for example, an amplifier (such as an instrumentation amplifier or a buffer amplifier), an analog or digital mixer or multiplier, a switch, an analog-to-digital converter (ADC), a passive or active analog filter, and the like. In some implementations, one or more of such circuits or circuit components may be integrated within the controller 214, for example, where the controller 214 is implemented as a system on chip (SoC) or a system in package (SIP). In some implementations, one or more of such circuits or circuit components may be integrated within a DSP included in or coupled to the controller 214. In some implementations, the image processing module 218 may be implemented at least in part via software. For example, one or more functions of, or operations performed by, one or more of the circuits or circuit components just described may alternatively be performed by, for example, one or more software modules executed in a processing unit of the controller 214 (e.g., in a general purpose processor or DSP).

[0058] In some implementations, in addition to the ultrasound sensing system 200, the electronic device 210 may include a separate processor 220, a memory 222, an interface 216, and a power supply 224. In some implementations, the controller 214 of the ultrasound sensing system 200 may control the ultrasound sensor array 212 and the image processing module 218, and the processor 220 of the electronic device 210 may control other components of the electronic device 210. In some implementations, the processor 220 transmits data including, for example, instructions or commands to the controller 214. In some such implementations, the controller 214 may transmit data (e.g., including raw or processed image data) to the processor 220. It should also be understood that in some other implementations, the functions of the controller 214 may be fully or at least partially implemented by the processor 220. In some such implementations, because the functions of the controller 214 may be performed by the processor 220 of the electronic device 210, the ultrasound sensing system 200 may not require a separate controller 214.

[0059] Depending on the implementation, one or both of the controller 214 and the processor 220 may store data in the memory 222. For example, the data stored in the memory 222 may include raw measured image data, filtered or otherwise processed image data, estimated PSF or estimated image data, and final refined PSF or final refined image data. The memory 222 may store processor executable code or other executable computer readable instructions that can be executed by one or both of the controller 214 and the processor 220 to perform various operations (or cause other components such as the ultrasound sensor array 212, the image processing module 218, or other modules to perform operations), which include any of the calculations, operations, estimates, or other determinations described herein (including those presented in any of the following equations). It should also be understood that the memory 222 may be collectively referred to as one or more storage devices (or "components"). For example, depending on the implementation, the controller 214 may access data in a storage device different from the processor 220 and store data therein. In some implementations, one or more of the memory components may be implemented as a NOR or NAND-based flash array. In some other implementations, one or more of these memory components may be implemented as different types of non-volatile memory. In addition, in some implementations, one or more of these memory components may include a volatile memory array (such as, for example, a type of RAM).

[0060] In some implementations, the controller 214 or the processor 220 may transmit data stored in the memory 222 or data received directly from the image processing module 218 via the interface 216. For example, such transmitted data may include image data or data derived from the image data or otherwise determined based on the image data. The interface 216 may be collectively referred to as one or more interfaces of one or more different types. In some implementations, the interface 216 may include: a memory interface for receiving data from an external memory such as a removable storage device or storing data to an external memory such as a removable storage device. Additionally or alternatively, the interface 216 may include one or more wireless network interfaces or one or more wired network interfaces, enabling the transmission of raw or processed data to an external computing device, system, or server, and the receipt of data from an external computing device, system, or server.

[0061] The power supply 224 can provide power to some or all components in the electronic device 210. The power supply 224 may include one or more of a variety of energy storage devices. For example, the power supply 224 may include a rechargeable battery (such as a nickel-cadmium battery or a lithium-ion battery). Additionally or alternatively, the power supply 224 may include one or more supercapacitors. In some implementations, the power supply 224 may be charged (or "rechargeable") using power accessed from, for example, a wall outlet (or "outlet") or a photovoltaic device (or "solar cell" or "solar cell array") integrated with the electronic device 210. Additionally or alternatively, the power supply 224 may be wirelessly rechargeable.

[0062] As used hereinafter, the term "processing unit" refers to any combination of one or more of the following: a controller of the ultrasound system (e.g., the controller 214), an image processing module (e.g., the image processing module 218), or a separate processor of a device including the ultrasound system (e.g., the processor 220). In other words, the operations described below as being performed by or using the processing unit may be performed by one or more of the following: a controller of the ultrasound system, an image processing module, or a separate processor of a device including the ultrasound sensing system.

[0063] Figure 3A According to some implementations, a cross-section of an example of an ultrasound sensing system is shown. Figure 3B According to some implementations, it is shown Figure 3A In the example shown, the ultrasound sensing system 300 can be implemented with reference to Figure 1 The ultrasonic sensing system 118 described herein or with reference to Figure 2A and Figure 2BThe ultrasonic sensing system 200 is shown and described. The ultrasonic sensing system 300 may include an ultrasonic transducer 302 located above a substrate 304 and below a platen ("cover plate" or "cover glass") 306. The ultrasonic transducer 302 may include both an ultrasonic transmitter 308 and an ultrasonic receiver 310.

[0064] The ultrasonic transmitter 308 can be configured to generate ultrasonic waves toward the platen 306 and the target object 312 located on the upper surface of the platen 306. In the illustrated implementation, the object 312 is depicted as a finger, but the present technology contemplates any appendage or body part, as well as any other natural or man-made object. In some implementations, the ultrasonic transmitter 308 can be more specifically configured to generate an ultrasonic plane wave toward the platen 306. In some implementations, the ultrasonic transmitter 308 includes a layer of piezoelectric material, such as, for example, polyvinylidene fluoride (PVDF) or a PVDF copolymer (such as, PVDF-TrFE). For example, the piezoelectric material of the ultrasonic transmitter 308 can be configured to convert an electrical signal provided by a controller of the ultrasonic sensing system into a continuous or pulsed sequence of ultrasonic plane waves at a scanning frequency. In some implementations, the ultrasonic transmitter 308 can additionally or alternatively include a capacitive ultrasonic device.

[0065] The ultrasonic receiver 310 can be configured to detect ultrasonic reflections 314 generated by the interaction of ultrasonic waves emitted by the ultrasonic transmitter 308 with ridges 316 and valleys 318 defining the surface texture of the target object 312 being scanned. In some implementations, the ultrasonic transmitter 308 covers the ultrasonic receiver 310, for example, Figure 3A and Figure 3BAs shown in . In some other implementations, the ultrasonic receiver 310 may cover the ultrasonic transmitter 308. The ultrasonic receiver 310 may be configured to generate and output an electrical output signal corresponding to the detected ultrasonic reflection. In some implementations, the ultrasonic receiver 310 may include a second piezoelectric layer different from the piezoelectric layer of the ultrasonic transmitter 308. For example, the piezoelectric material of the ultrasonic receiver 310 may be any suitable piezoelectric material (such as, for example, a PVDF layer or a PVDF copolymer layer). The piezoelectric layer of the ultrasonic receiver 310 may convert the vibration caused by the ultrasonic reflection into an electrical output signal. In some implementations, the ultrasonic receiver 310 also includes a thin film transistor (TFT) layer. In some such implementations, the TFT layer may include a sensor pixel circuit array, which is configured to amplify the electrical output signal generated by the piezoelectric layer of the ultrasonic receiver 310. Then, the amplified electrical signal provided by the sensor pixel circuit array can be provided as raw measurement image data to a processing unit for processing the image data, identifying a fingerprint associated with the image data, and in some applications, authenticating a user associated with the fingerprint. In some implementations, a single piezoelectric layer can be used as an ultrasound transmitter 308 and an ultrasound receiver 310. In some implementations, the substrate 304 can be a glass, plastic, or silicon substrate on which electronic circuits can be fabricated. In some implementations, the sensor pixel circuit array and associated interface circuits of the ultrasound receiver 310 can be configured by CMOS circuits formed in or on the substrate 304. In some implementations, the substrate 304 can be located between the pressure plate 306 and the ultrasound transmitter 308 and / or the ultrasound receiver 310. In some implementations, the substrate 304 can be used as the pressure plate 306. One or more protective layers, acoustic matching layers, anti-fouling layers, adhesive layers, decorative layers, conductive layers, or other coatings (not shown) can be included on one or more sides of the substrate 304 and the pressure plate 306.

[0066] The platen 306 may be formed of any suitable material capable of acoustically coupling with the ultrasonic transmitter 308. For example, the platen 306 may be formed of one or more of glass, plastic, ceramic, sapphire, metal, or a metal alloy. In some implementations, the platen 306 may be a cover plate, such as, for example, a cover glass or lens glass of an underlying display. In some implementations, the platen 306 may include one or more polymers (such as, one or more types of polyparaxylene) and may be significantly thinner. In some implementations, the platen 306 may have a thickness in the range of about 10 micrometers (μm) to about 1000 μm or more.

[0067] like Figure 3A and Figure 3BAs shown in FIG, target object 312 is in direct contact with platen 306. However, as indicated above, a screen protector may be disposed over platen 306. Figure 3C An implementation is shown in which a screen protector 3000 is disposed over the platen 306. Such a screen protector may be installed (or removed) by a user or a third party after factory calibration of the ultrasound sensing system 300. Furthermore, in the absence of the presently disclosed techniques, installing or removing a screen protector may adversely affect the imaging capabilities of the ultrasound sensing system.

[0068] Figure 4 A process flow chart for detecting the effect of a screen protector on image quality is shown. In general, in the absence of a target object to be detected, a well-calibrated ultrasonic sensor is expected to present a mostly amorphous blank "air" image, such as shown in detail A. During the factory calibration process, a background estimation process can be performed to achieve such an amorphous air image regardless of whether the ultrasonic sensor is provided with a screen protector. The inventors have recognized that subsequent installation or removal of a screen protector may result in a more structured, frame-like air image, as shown in detail B. In one implementation, method 400 includes: at box 401, obtaining an air image. At box 403, analysis of the obtained air image can be performed to detect whether a screen protector has been installed or removed. Box 403 can include: comparing the air image obtained in box 401 with a baseline air image (e.g., detail A) obtained during the factory calibration process or otherwise associated with the factory calibration process.

[0069] When analysis of the air image obtained at block 401 with the baseline air image indicates that a screen protector has been installed or removed (e.g., because the obtained air image has a structured frame-like element, such as shown in detail B), the method can initiate a prompt at block 404, requesting the user to confirm whether the user has installed or removed the screen protector. In the absence of user confirmation, the process can return to block 401, and the steps can be repeated at some regular or irregular time intervals. In some implementations, execution of method 400 (e.g., starting at block 401) can occur at intervals of tens of seconds or minutes.

[0070] If the user confirms that screen protector installation or removal has occurred, the process can continue at block 405 to recalibrate the ultrasound sensor array by applying, for example, sensor tuning shifts (such as frequency shifts, time delay shifts, and phase correction shifts, etc.), and perform a new background estimation process (block 407) to obtain the desired amorphous air image (detail C). After completing the new background estimation at block 407, the method can return to block 401.

[0071] Optionally, box 404 for checking for user confirmation can be omitted, and the method can consider going directly from box 403 to box 405. Therefore, in this optional case, a new background estimation and recalibration of the ultrasonic sensor array can be performed without prompting the user to confirm the installation or removal of the screen protector as occurs. For example, in such an implementation, the control system 204 can be configured to perform an analysis of the obtained air image at box 403 and determine whether a screen protector has been installed or removed. In some implementations, the control system 204 can make such a determination after, for example, a machine learning process.

[0072] In some implementations, the adverse effects of installing or removing a screen protector can be mitigated by adjusting the "range gate delay" of the ultrasonic sensor. Figure 5 An example of range gate delay as the term is used herein is shown. Specifically, Figure 5 An example of a transmitter excitation signal and a receiver bias voltage level varying over time is illustrated. The transmitter excitation signal (upper graph) may be provided to an ultrasound transmitter, while a receiver bias voltage (lower graph) may be applied to the RBias electrode of an ultrasound sensor element. One or more cycles of an ultrasound transmitter excitation signal may be applied to the ultrasound transmitter, such as Figure 5 As shown in the above figure. In some implementations, a single transmitter excitation cycle can be used. In some implementations, as shown in the figure, multiple excitation cycles can be used, such as two cycles, three cycles, four cycles, five cycles or more. In some implementations, the transmitter excitation signal can be a square wave, a rectangular wave, a divided wave, a pulse wave, a multi-frequency wave, a chirped wave, a low or high duty cycle wave, a variable amplitude wave, a variable frequency wave, or other appropriate waveform for driving an ultrasonic transmitter. During the first portion of time ("Tx Block") when outgoing ultrasonic transmission occurs, the bias voltage applied to the RBias electrode can correspond to a "block value" so that the receiver bias electrode prevents signals reflected from the outgoing transmission wave from being captured by the sensor pixel circuit.

[0073] During the subsequent time portion ("Rx sampling"), the bias level of the control signal applied to the RBias electrode is set to the "sampling value", and the reflected ultrasonic signal can be the captured sensor pixel. The Rx sampling period can start when the range gate delay ("RGD") period is completed. The RGD period can typically be in the range of 0.5-2 microseconds. The duration of the Rx sampling period can be called the range gate window ("RGW") period. The RGW period can typically be less than one microsecond. In some implementations, the RGW period can be in the range of approximately 200 to 1000 nanoseconds. In order to prevent the detection of unwanted internal reflections, the bias level applied to the receiver bias electrode can be restored to the block value at the end of the RGW period. In the implementation shown, the RGW period can correspond to a time interval roughly similar to the period of the transmitter excitation period ("tone burst"). In other implementations, the RGW period can be shorter or longer than the period of the tone burst. During the RGW period, it can be said that the sensor pixel is in the "reading mode" of operation. During or near the RGW period, the receiver may output a signal that originates from or corresponds to the localized charge generated by the piezoelectric receiver layer and collected by the pixel input electrode.

[0074] The present inventors have discovered that the adverse effect on image quality (IQ) caused by the reduced signal-to-noise ratio (SNR) caused by the screen protector can be significantly mitigated by adjusting the RGD taking into account the thickness and material properties of the screen protector. Figure 6 Graphs of SNR as a function of RGD are shown. Referring first to detail D, an example graph of SNR as a function of RGD is shown for an example ultrasonic sensor without a screen protector. It can be observed that the peak SNR (approximately 4.5-6) ​​is obtained at an RGD 601 of approximately 1.075 μsec. Referring next to details EH, four example graphs of SNR as a function of RGD are shown for example ultrasonic sensors including a screen protector. Each of the four examples is for a respective screen protector having respective characteristics, for example, the characteristics include material properties and thickness. It can be observed that the peak SNR (approximately 3.5-5.5) occurs at RGD values ​​in the range of 1.23 to 1.28 μsec.

[0075] It will be appreciated that by properly adjusting the RGD, the adverse effect of the screen protector on the SNR can be significantly reduced. The SNR vs. RGD data shown in detail E for the first screen protector type shows that the adjusted RGD 602 ​​(1) is in the range of 4 to 5.5. Without adjusting the RGD, the SNR at RGD 601 would be in the range of 2.5-4. The SNR vs. RGD data shown in detail F for the second screen protector type shows that the adjusted RGD 602 ​​(2) is in the range of 3.9 to 5.2. Without adjusting the RGD, the SNR at RGD 601 would be in the range of 2.4-3.3. The SNR vs. RGD data shown in detail G for the third screen protector type shows that the adjusted RGD 602 ​​(3) is in the range of 4.5 to 5.6. Without adjustment for RGD, the SNR at RGD 601 would be in the range of 3-4.0. The SNR vs. RGD data shown in Detail H for the fourth screen protector type shows a peak SNR in the range of 3.6 to 5.4 at the adjusted RGD 602 ​​(4) of 1.23 μsec. Without adjustment for RGD, the SNR at RGD 601 would be in the range of 2.8-3.8.

[0076] In some implementations, adjusting RGD can be combined with performing a background calibration. Figure 7 An example of adjusting RGD and performing background calibration is shown. In detail J, a plot of SNR versus RGD is presented for an example ultrasonic sensor without a screen protector (curve 710(1)), and a plot of SNR versus RGD is presented for an example ultrasonic sensor with a screen protector (curve 710(2)). By adjusting RGD from about 1.02 μsec (RGD 701) to about 1.15 μsec (RGD 702), it can be observed that the SNR has increased from about 2 to 2.5. By additionally performing background calibration, curve 720(2) (detail K) shows that the peak SNR has been further improved to about 4.2.

[0077] Alternatively or in addition to the techniques disclosed above, one or more of the following indicators can be used to detect the installation or removal of the screen protector: the phase of the received ultrasonic wave, the pressure plate temperature gradient, the change in SNR relative to the RGD characteristic and / or the change with the background calibration, and the change in the touch screen capacitance. More specifically, in some implementations, the change in the phase characteristic of the received ultrasonic wave reflected from the target object can be detected by the ultrasonic sensor, and the change is related to the change in the effective thickness of the material of the pressure plate plus the screen protector (if present) (through which the ultrasonic wave is received). In some implementations, the installation or removal of the screen protector can be indicated by the change in the thermal characteristics of the pressure plate plus the screen protector (if present), in particular the change in thermal conductivity, which can result in a detectable change in the temperature gradient pattern. The inventors have found that when the screen protector is plastic, the change in the temperature gradient pattern may be particularly obvious because the thermal conductivity of glass is much higher than that of plastic. Figure 8 Example graphs of thermal gradients for a glass press plate without a screen protector and with a plastic screen protector are shown. Comparing detail L (glass press plate) to detail M (plastic screen protector), it can be observed that when a heat source (or cold source) is applied, the glass press plate exhibits a smaller maximum ΔT, and generally a smaller affected area, than the plastic screen protector.

[0078] In some implementations, the change characteristics of IQ vs. RGD can be related to the installation or removal of a screen protector. Figure 6 and Figure 7 As described, the installation or removal of a screen protector can result in a detectable change in the characteristic that the SNR changes with RGD (which can be related to IQ). For example, it is often observed that the RGD may be preferred when a screen protector is installed, which is longer than the optimal RGD when there is no screen protector. This phenomenon can be used to determine whether a screen protector has been installed or removed. For example, the SNR or IQ can be determined for multiple RGD values, and the obtained characteristic signature can be compared with one or more baseline signatures. Similarly, because it has been found that when a screen protector is installed, the effect of recalibration based on background estimation on IQ is more significant than when the screen protector is not installed, such recalibration can also be used to determine whether a screen protector is installed or removed. Finally, the installation or removal of a screen protector can be indicated by a detected change in the capacitance and / or capacitance behavior of a touch screen device associated with an ultrasonic sensor.

[0079] In some implementations, the impact of the installation or removal of a screen protector on the performance of the ultrasound sensor array is further mitigated by innovative sensor drive schemes and image processing. For example, in some implementations, the sensor drive scheme can advantageously be configured to provide a wider RGD range within which an acceptably high SNR value can be expected. For example, this can be achieved by increasing the duration of the transmit tone burst and / or using a quasi-continuous wave transmit signal instead of a pulse signal. As a result, near-optimal sensor performance can be obtained regardless of the presence or absence of a screen protector. In some implementations, image processing techniques can increase the range of optimal operating settings. For example, point spread function (PSF) image reconstruction techniques can be considered. Alternatively or additionally, receiver beamforming can be implemented.

[0080] In some implementations, the impact of installing or removing a screen protector can be minimized by judiciously choosing the screen protector design guidelines. Fig. 9 An example of a screen protector stack disposed on a press plate is shown. In the example shown, the press plate 906 is covered with a screen protector stack 9000. The screen protector stack 9000 includes a first transparent plastic layer 9010(1) and a second transparent plastic layer 9010(2). In the example shown, the transparent plastic layers can be composed of polyethylene terephthalate (PET) and are bonded together by an optically clear adhesive (OCA) layer 9020(1). The second OCA layer 9020(2) can bond the second PET layer 9010(2) to the press plate 906. The inventors have discovered that by configuring the stack 9000 to have a total stack thickness selected based on a characteristic wavelength λ of ultrasonic transmission, the impact of installation or removal of the screen protector stack 9000 can be reduced. For example, the stack thickness can be advantageously selected to be approximately about 0.75λ or 1.25λ. Advantageously, the OCA layer can be configured as a high modulus adhesive with good acoustic transmission properties.

[0081] Fig.10 An example of a process flow for a method of operating an ultrasonic sensor array is shown. As described above, the ultrasonic array can be disposed below a platen. Above the platen, there may or may not be a removable screen protector. Method 1000 may begin at box 1010, where a determination is made as to whether to recalibrate the ultrasonic sensor array based on whether the screen protector has undergone a change. The change may be related to installing a screen protector, removing a screen protector, or replacing a first screen protector with a second screen protector. At box 1020, the method may continue to recalibrate the ultrasonic sensor array when it is determined at box 1010 that the ultrasonic sensor array is to be recalibrated.

[0082] Thus, techniques have been disclosed for detecting the installation or removal or replacement of a screen protector disposed over an ultrasound sensor array, and calibrating the ultrasound sensor array for such changes. It should be understood that a variety of alternative configurations and operating techniques are contemplated.

[0083] As used herein, a phrase referring to "at least one of" a list of items refers to any combination of those items, including single members. For example, "at least one of a, b, or c" is intended to cover: a, b, c, ab, ac, bc, and abc.

[0084] The various exemplary logics, logic blocks, modules, circuits, and algorithmic processes described in conjunction with the implementations disclosed herein may be implemented as electronic hardware, computer software, or a combination of the two. In order to generally represent the interchangeability between hardware and software, the various exemplary components, blocks, modules, circuits, and processes are generally described above in terms of their functions. Whether such functions are implemented as hardware or software depends on the specific application and the design constraints imposed on the overall system.

[0085] A general purpose single-chip or multi-chip processor, digital signal processor (DSP), application specific integrated circuit (ASIC), field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic device, discrete hardware components, or any combination thereof for performing the functions described herein may be used to implement or execute the various exemplary logics, logic blocks, modules, and circuits described in conjunction with the aspects disclosed herein. A general purpose processor may be a microprocessor, or the processor may be any conventional processor, controller, microcontroller, or state machine. The processor may also be implemented as a combination of computing devices, such as a combination of a DSP and a microprocessor, a plurality of microprocessors, a combination of one or more microprocessors and a DSP core, or any other such structure. In some implementations, specific processes and methods may be performed by circuits specific to a given function.

[0086] In one or more aspects, the functions described may be implemented in hardware, digital electronic circuitry, computer software, firmware (including the structures disclosed in this specification and their structural equivalents), or any combination thereof. Implementations of the subject matter described in this specification may also be implemented as one or more computer programs, i.e., one or more modules of computer program instructions encoded on a computer storage medium, to be executed by a data processing device or to control the operation of the data processing device.

[0087] When implemented in software, these functions can be stored on a computer-readable medium (e.g., a non-temporary medium) or transmitted as one or more instructions or codes on a computer-readable medium. The processing of the method or algorithm disclosed herein can be implemented in a processor-executable software module located on a computer-readable medium. Computer-readable media include computer storage media and communication media, wherein the communication media include any medium that facilitates the transmission of a computer program from one place to another. The storage medium can be any available medium that a computer can access. For example, but not limiting, non-temporary media may include RAM, ROM, EEPROM, CD-ROM or other optical disk storage, disk storage or other magnetic storage device, or any other medium that can be used to store the desired program code in the form of an instruction or data structure and can be accessed by a computer. In addition, any connection can be appropriately referred to as a computer-readable medium. As used herein, disks and discs include compact discs (CDs), laser discs, optical discs, digital versatile discs (DVDs), floppy disks, and blue-ray discs, wherein disks usually copy data magnetically, while optical discs use lasers to optically copy data. The above combination should also be included in the scope of protection of computer-readable media. In addition, the operations of a method or algorithm may be embodied as a code and instruction set, or any combination of code and instruction sets, on a machine-readable medium or computer-readable medium, which may be incorporated into a computer program product.

[0088] It will be apparent to those skilled in the art that various modifications may be made to the implementations described in the present disclosure, and the general principles defined herein may also be applied to other implementations without departing from the spirit or scope of the present disclosure. Therefore, the present disclosure is not limited to the implementations shown herein, but is consistent with the widest scope of the claims, principles, and novel features disclosed herein. The word "exemplary" is used herein, if any, to mean "serving as an example, illustration, or illustration." Any implementation described herein as "exemplary" should not be construed as being more preferred or advantageous over other implementations.

[0089] Certain features described in this specification in the context of different implementations may also be implemented in combination in a single implementation. Conversely, various features described in the context of a single implementation may also be implemented in multiple implementations individually or in any suitable subcombination. In addition, although some features are described above as operating in certain combinations (even if initially claimed to be so), in some cases, one or more features in a claimed combination may be cut out of the combination, and the claimed combination may be directed to a certain subcombination or a variation of a subcombination.

[0090] Similarly, although the operations are described in a specific order in the accompanying drawings, it should not be understood that in order to obtain the desired result, it is necessary to perform these operations in the specific order or serial order shown, or all the operations shown must be performed. In addition, the accompanying drawings can schematically depict one or more example processes in the form of a flow chart. However, other operations not depicted can be incorporated into the example processes schematically illustrated. For example, one or more other operations can be performed before, after, at the same time, or between any of the operations shown. In some environments, multitasking and parallel processing are advantageous. In addition, the division of each system component in the implementation described above should not be understood as requiring such division in all implementations, but it should be understood that the described program components and systems can generally be integrated together into a single software product, or encapsulated into multiple software products. In addition, other implementations also fall within the scope of protection of the attached claims. In some cases, the actions stated in the claims can be performed in different orders and still obtain the desired results.

[0091] It should be understood that unless the features in any of the specifically described implementations are explicitly identified as being incompatible with each other, or the surrounding context implies that they are mutually exclusive and not easily combined in a complementary and / or supporting sense, the entire content of the present disclosure contemplates and contemplates that the specific features of these complementary implementations may be selectively combined to provide one or more comprehensive but slightly different technical solutions. Therefore, it should also be understood that the above description is given by way of example only, and modifications of detail may be made within the scope of the present disclosure.

Claims

1. A method for operating an ultrasonic sensor array, the ultrasonic sensor array being disposed below a platen, the method comprising: determining whether one or more characteristics indicate that a first screen protective film disposed over the platen has been removed or replaced with a second screen protective film, the one or more characteristics comprising one or more of: a phase of received ultrasonic waves, a platen temperature gradient, a change in signal-to-noise ratio (SNR) or image quality (IQ) versus one or more range gate delay characteristics, a change in SNR or IQ characteristics with background calibration, or a change in touch screen capacitance; as well as When the determination is that the one or more features indicate that the first screen protective film disposed over the platen has been removed or replaced with the second screen protective film, the ultrasonic sensor array is recalibrated.

2. The method according to claim 1, wherein: The method involves performing a background estimation process, and wherein the determining is based at least in part on one or more results of the background estimation process.

3. The method according to claim 2, wherein: The background estimation process includes obtaining features of an air image and comparing the obtained features with features of a baseline air image.

4. The method according to claim 3, wherein: The baseline air image comprises an air image obtained by operating the ultrasound sensor array without any screen protector.

5. The method according to claim 1, further comprising: A user is prompted to indicate whether the screen protector has been removed or replaced, and wherein the recalibration is performed only after confirmation from the user.

6. The method according to claim 1, further comprising: The effects of removing or replacing the first screen protector are mitigated by adjusting at least one sensor tuning offset.

7. The method according to claim 6, wherein: The at least one sensor tuning offset comprises one or more of: a range gate delay, a frequency offset, a time delay offset, or a phase correction offset.

8. An apparatus comprising: Ultrasonic sensor array; Press plate; as well as A controller, wherein the controller is configured to: determining whether one or more characteristics of the received ultrasonic waves indicate that a first screen protective film disposed over the platen has been removed or replaced with a second screen protective film; and In response to determining that the one or more characteristics of the received ultrasonic waves indicate that the first screen protective film disposed over the platen has been removed or replaced with the second screen protective film, the ultrasonic sensor array is recalibrated.

9. The device according to claim 8, wherein: The pressing plate is a cover plate or a cover glass.

10. The device according to claim 8, wherein: The controller is configured to perform a background estimation process, and wherein the determination is based at least in part on one or more results of the background estimation process.

11. The device according to claim 10, wherein: The background estimation process involves obtaining features of an air image and comparing the obtained features with features of a baseline air image.

12. The device according to claim 11, wherein The baseline air image corresponds to an air image obtained by operating the ultrasound sensor array without any screen protector.

13. The device according to claim 8, wherein: The controller is further configured to: A user is prompted to indicate whether the first screen protective film has been removed or replaced, and wherein the controller is configured to recalibrate the ultrasonic sensor only after receiving confirmation from the user that the first screen protective film has been removed or replaced.

14. The device according to claim 8, wherein: The controller is further configured to mitigate the effects of removing or replacing the first screen protector by adjusting at least one sensor tuning offset.

15. The device according to claim 14, wherein: The at least one sensor tuning offset comprises one or more of: a range gate delay, a frequency offset, a time delay offset, or a phase correction offset.

16. A non-transitory computer readable medium storing program code to be executed by a controller of an apparatus including an ultrasonic sensor array disposed below a platen, the program code comprising instructions configured to cause the controller to: determining whether one or more characteristics indicate that a first screen protective film disposed over the pressure plate has been removed or replaced with a second screen protective film, the one or more characteristics comprising one or more of: a change in a pressure plate temperature gradient or a touch screen capacitance; and In response to determining that the one or more features indicate that the first screen protective film disposed over the platen has been removed or replaced with the second screen protective film, the ultrasonic sensor array is recalibrated.

17. The computer-readable medium of claim 16, wherein: The instructions are configured to cause the controller to perform a context estimation process, and wherein the one or more features include one or more results of the context estimation process.

18. The computer-readable medium of claim 17, wherein: The background estimation process includes obtaining features of an air image and comparing the obtained features with features of a baseline air image.

19. The computer-readable medium of claim 18, wherein: The baseline air image corresponds to an air image obtained by operating the ultrasound sensor array without any screen protector.

20. The computer readable medium of claim 16, wherein the program code further comprises instructions configured to cause the controller to: Prompting a user to indicate whether the first screen protective film has been removed or replaced, and causing the controller to recalibrate the ultrasonic sensor only after receiving confirmation from the user that the first screen protective film has been removed or replaced.

Images