Dual-frequency ultrasonic sensor system with frequency divider

Abstract

A device may include an ultrasonic sensor system having a first layer stack and a second layer stack. The first layer stack may include a first ultrasonic transmitter, and the second layer stack may include a second ultrasonic transmitter. The first layer stack and / or the second layer stack may include an ultrasonic receiver. A frequency division layer may be located between the first layer stack and the second layer stack.

Description

[0001] Priority Declaration

[0002] This patent application claims priority to non-provisional application serial number 16 / 453,898, filed on June 26, 2019, entitled “DUAL-FREQUENCY ULTRASONICSENSOR SYSTEM WITH FREQUENCY SPLITTER,” which is assigned to the assignee of the present application and is hereby expressly incorporated by reference into this application. Technical Field

[0003] The present disclosure generally relates to sensor devices and related methods, including but not limited to ultrasonic sensor systems and methods for using such systems. Background Art

[0004] Biometric authentication can be an important feature for controlling access to devices and the like. Many existing products include some type of biometric authentication. Although some existing biometric authentication technologies provide satisfactory performance, improved methods and devices would be desirable. Summary of the Invention

[0005] The systems, methods, and devices of the present disclosure each have several innovative aspects, no single one of which is solely responsible for the desirable attributes disclosed herein.

[0006] One innovative aspect of the subject matter described in this disclosure can be implemented in an apparatus. The apparatus can include an ultrasonic sensor system having a first layer stack and a second layer stack. The first layer stack can include a first ultrasonic transmitter, and the second layer stack can include a second ultrasonic transmitter. The first layer stack and / or the second layer stack can include an ultrasonic receiver. In some implementations, a frequency division layer is located between the first layer stack and the second layer stack. In some cases, a mobile device can be or include the apparatus. For example, a mobile device can include an apparatus as disclosed herein. According to some examples, a display device can include the apparatus.

[0007] In some examples, the apparatus may include a control system that may include one or more general-purpose single-chip 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, discrete hardware components, or combinations thereof.

[0008] According to some examples, the control system may be configured to control the first ultrasonic transmitter to transmit a first ultrasonic wave. The first ultrasonic wave may include a first frequency. In some examples, the control system may be configured to receive a first signal from the first ultrasonic receiver, the first signal corresponding to a reflection of the first ultrasonic wave from a surface of a portion of a target object located on an outer surface of the device.

[0009] According to some implementations, the control system can be configured to perform an authentication process based at least in part on the first signal.In some examples, the control system can be configured to obtain fingerprint data based on portions of the first signal received within a time interval corresponding to the fingerprint.

[0010] In some implementations, the control system can be configured to control the second ultrasonic transmitter to transmit a second ultrasonic wave through the frequency division layer and the first layer stack. The second ultrasonic wave can include a second frequency lower than the first frequency.

[0011] According to some examples, the frequency-splitting layer may have an acoustic impedance relatively lower than the acoustic impedance of the first adjacent layer of the first stack and the second adjacent layer of the second stack, and a thickness corresponding to half the wavelength of the second frequency. In some implementations, the frequency-splitting layer may have an acoustic impedance relatively higher than the acoustic impedance of the first adjacent layer of the first stack and the second adjacent layer of the second stack, and a thickness corresponding to an odd-integer multiple of a quarter wavelength of the second frequency. In some such implementations, the frequency-splitting layer may have a thickness corresponding to a quarter wavelength of the first frequency.

[0012] In some examples, the second layer stack may include a second ultrasonic receiver. In some such examples, the control system may be configured to receive a second signal from the second ultrasonic receiver, the second signal corresponding to a reflection of the second ultrasonic wave from an interior of a portion of the target object and to perform an authentication process based at least in part on the second signal. According to some such examples, the second signal may include dermis layer information corresponding to a reflection of the second ultrasonic wave received from the portion of the target object within a time interval corresponding to the dermis layer. The authentication process may be based at least in part on the dermis layer information. In some examples, the authentication process may be based at least in part on both the first signal and the second signal.

[0013] In some implementations, the first signal may also correspond to a reflection of a harmonic of the second ultrasonic wave from a surface of a portion of the target object. According to some examples, the second signal may also correspond to a reflection of a subharmonic of the first ultrasonic wave from an interior portion of the target object. In some cases, the first frequency may be in the range of 10 MHz to 20 MHz. In some such examples, the second frequency may be in the range of 1 MHz to 10 MHz.

[0014] In some cases, a single piezoelectric layer or multilayer piezoelectric structure of the first layer stack acts as both a first ultrasonic transmitter and a first ultrasonic receiver. According to some examples, the frequency-splitting layer can be proximate to a first side of the second layer stack. Some such examples can include a high-impedance backing layer proximate to a second side of the second layer stack. For example, the backing layer can have a thickness in the range of 10 to 100 microns.

[0015] Another innovative aspect of the subject matter described in this disclosure can be implemented in a device. The device can include an ultrasonic sensor system having a first layer stack and a second layer stack. The first layer stack can include a first ultrasonic transmitter, and the second layer stack can include a second ultrasonic transmitter. The first layer stack and / or the second layer stack can include an ultrasonic receiver. In some implementations, a frequency division layer is located between the first layer stack and the second layer stack.

[0016] In some examples, the apparatus may include a control system that may include one or more general-purpose single-chip 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, discrete hardware components, or combinations thereof.

[0017] According to some examples, the control system can be configured to control a first ultrasonic transmitter to transmit a first ultrasonic wave through a frequency-splitting layer and a second layer stack. The first ultrasonic wave may include a first frequency. In some examples, the control system can be configured to receive a first signal from a first ultrasonic receiver, the first signal corresponding to a reflection of the first ultrasonic wave from a surface of a portion of a target object located on an outer surface of the device. The outer surface can be on a first side of the second layer stack, and the frequency-splitting layer can be on a second, opposite side of the second layer stack. According to some examples, the control system can be configured to perform an authentication process based at least in part on the first signal.

[0018] In some implementations, the control system may be configured to control the second ultrasonic transmitter to transmit a second ultrasonic wave. The second ultrasonic wave may include a second frequency lower than the first frequency. In some such implementations, the control system may be configured to receive a second signal from the first ultrasonic receiver, the second signal corresponding to a reflection of the second ultrasonic wave from a surface of a portion of the target object. In some cases, the second signal may also correspond to a reflection of a harmonic of the second ultrasonic wave.

[0019] In some examples, the second layer stack may include a second ultrasonic wave receiver. The control system may be configured to receive a third signal from the second ultrasonic wave receiver, the third signal corresponding to a reflection of the second ultrasonic wave from an interior portion of the target object. The authentication process may be based at least in part on the third signal.

[0020] Other innovative aspects of the subject matter described in this disclosure can be implemented in a method of controlling an ultrasonic sensor system. In some examples, the method may involve controlling a first ultrasonic transmitter in a first layer stack to transmit a first ultrasonic wave. The first ultrasonic wave may include a first frequency. The method may involve controlling a second ultrasonic transmitter in a second layer stack to transmit a second ultrasonic wave through the first layer stack and through a frequency dividing layer between the first and second layer stacks. The second ultrasonic wave may include a second frequency lower than the first frequency.

[0021] The method may involve performing an authentication process based at least in part on a first signal and / or a second signal. The first signal may correspond to a reflection of a first ultrasonic wave from a surface of a portion of a target object located on an exterior surface of an apparatus comprising the ultrasonic sensor system. The second signal may correspond to a reflection of a second ultrasonic wave from an interior portion of the target object.

[0022] The method may involve obtaining fingerprint data based on a portion of the first signal received within a time interval corresponding to the fingerprint. In some examples, the second signal may include dermis layer information. In some cases, the first signal also corresponds to a reflection of a harmonic of the second ultrasonic wave from a surface of the portion of the target object. In some examples, the second signal may also correspond to a reflection of a subharmonic of the first ultrasonic wave from an interior of the portion of the target object.

[0023] In some cases, the first frequency may be in the range of 10 MHz to 20 MHz. In some examples, the second frequency may be in the range of 1 MHz to 10 MHz. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Details of one or more implementations of the subject matter described in this specification are set forth in the accompanying drawings and the following description. Additional features, aspects, and advantages will become apparent from the description, drawings, and claims. Note that the relative dimensions of the following figures may not be drawn to scale. Like reference numerals and names in the various figures represent like elements.

[0025] Figure 1A Examples of subepidermal features are shown.

[0026] Figure 1B is a block diagram illustrating example components of an apparatus according to some disclosed implementations.

[0027] Figure 2 are flow diagrams providing examples of operations according to some disclosed methods.

[0028] Figure 3A Shown and included Figure 1B An example of a device showing an outer surface of the apparatus contacting a target object.

[0029] Figure 3B Shown and included Figure 1B Another example of a target object being contacted by an outer surface of a device of the apparatus is shown.

[0030] Figure 4 Example components of an apparatus according to some disclosed implementations are shown.

[0031] Figure 5A and Figure 5B is a graph of delta signal strength versus divider thickness according to two examples.

[0032] Figure 6 is a graph illustrating an example of differential signal enhancement that may be achieved by some implementations of the disclosed ultrasonic sensor system.

[0033] Figure 7 are flow diagrams providing examples of operations according to some disclosed methods.

[0034] Figure 8 Representatively depicted are aspects of a 4x4 pixel array of sensor pixels for an ultrasonic sensor system.

[0035] Figure 9A An example of an exploded view of an ultrasonic sensor system is shown.

[0036] Figure 9B An exploded view of an alternative example of an ultrasonic sensor system is shown. DETAILED DESCRIPTION

[0037] For the purpose of describing the innovative aspects of the present disclosure, the following description is directed to certain implementations. However, one of ordinary skill in the art will readily recognize that the teachings herein can be applied in a variety of different ways. The described implementations can be implemented in any device, apparatus, or system including a biometric identification system as disclosed herein. In addition, it is contemplated that the described implementations can be included in or associated with various electronic devices, such as, but not limited to: mobile phones, multimedia internet-enabled cellular phones, mobile television receivers, wireless devices, smart phones, smart cards, wearable devices such as bracelets, armbands, wristbands, rings, headbands, patches, etc., Bluetooth devices, personal data assistants (PDAs), wireless email receivers, handheld or portable computers, netbooks, notebooks, smart books, tablet computers, printers, copiers, scanners, fax machines, global positioning system (GPS) receivers / navigators, cameras, digital media players (such as MP3 players), camcorders, game consoles, watches, clocks, calculators, television monitors, flat panel displays 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 electronics, steering wheels or other automotive components, varactors, liquid crystal devices, electrophoretic devices, drive schemes, manufacturing processes, and electronic test equipment. Thus, the present teachings are not intended to be limited to only the implementations depicted in the accompanying drawings, but rather have broad applicability, as will be apparent to one of ordinary skill in the art.

[0038] Many existing products, including but not limited to mobile phones, are configured for fingerprint-based authentication. However, even top mobile phone manufacturers have successfully hacked the fingerprint-based authentication systems of their devices shortly after product launch. In some cases, spoofing can involve using a finger-like object, such as silicone rubber, polyvinyl acetate (white glue), gelatin, glycerin, etc., with the fingerprint pattern of the legitimate user formed on the outer surface. In some cases, the hacker can form the fingerprint pattern of the legitimate user on a sleeve or part of a sleeve that can be slid over or over the hacker's finger.

[0039] Authentication methods based at least in part on subsurface features may be more reliable than authentication methods based solely on fingerprints, in part because subsurface features are more difficult to spoof. Figure 1A An example of subepidermal features is shown. As used herein, the term "subepidermal features" may refer to any tissue layer below the epidermis, including the dermis, papillary layer, reticular layer, subcutaneous tissue, etc., as well as any blood vessels, lymphatic vessels, sweat glands, hair follicles, hair papillae, fat lobules, etc. that may exist in these tissue layers. Therefore, subepidermal features may also include Figure 1A Features not shown in the figure, such as muscle tissue, bone material, etc.

[0040] Thus, some disclosed implementations may be configured to perform authentication methods based at least in part on subcutaneous features. Some such implementations may include an ultrasonic sensor system capable of obtaining image data (e.g., fingerprint image data) from the epidermis as well as image data corresponding to the subcutaneous features. The data received from the ultrasonic sensor system may be referred to herein as "ultrasonic image data," "image data," or the like, although the data will typically be received from the ultrasonic sensor system in the form of electrical signals. Thus, without additional processing, such image data will not necessarily be perceived by humans as an image.

[0041] Designing an ultrasonic sensor system suitable for imaging both fingerprints and subcutaneous features can be challenging. For example, relatively high frequencies (e.g., 10 MHz or higher) are suitable for fingerprint imaging, while relatively low frequencies (e.g., less than 10 MHz) are suitable for imaging subcutaneous features. If an ultrasonic sensor system is configured to transmit both high-frequency and low-frequency ultrasonic waves simultaneously, "crosstalk" can result.

[0042] Some disclosed devices include an ultrasonic sensor system having a first ultrasonic transmitter in a first layer stack, a second ultrasonic transmitter layer in a second layer stack, and a frequency division layer between the first and second layer stacks. In some examples, the first layer stack can be configured to transmit relatively high frequencies suitable for fingerprint imaging, while the second layer stack can be configured to transmit relatively low frequencies suitable for imaging subcutaneous features. Such a device may or may not include ultrasonic receivers in both the first and second layer stacks, depending on the specific implementation. For example, some implementations may include ultrasonic receivers only in the first layer stack.

[0043] In some examples, the frequency separation layer can be configured to pass relatively low frequencies suitable for imaging subepidermal features. In some such examples, the frequency separation layer can be configured to suppress relatively high frequencies suitable for fingerprint imaging. In some such implementations, the frequency separation layer can have an acoustic impedance that is relatively lower than the acoustic impedance of a first adjacent layer of the first stack and a second adjacent layer of the second stack. According to some such examples, the frequency separation layer can have a thickness corresponding to half the wavelength of a frequency suitable for imaging subepidermal features.

[0044] Certain implementations of the subject matter described in this disclosure can be implemented to achieve one or more of the following potential advantages. In some examples, the frequency separation layer can be configured to suppress crosstalk between the first layer stack and the second layer stack. According to some implementations, the frequency separation layer can be configured to enhance the amplitude of frequencies suitable for imaging subepidermal features.

[0045] Figure 1B is a block diagram illustrating example components of an apparatus according to some disclosed implementations. As with other disclosed implementations, Figure 1B The number, type and arrangement of elements shown in are given as examples only. Figure 1B Not shown, the device 100 may include other components, such as a cover glass, a sensor substrate, etc. Some examples are described below.

[0046] In this implementation, device 100 includes a first layer stack 101, a frequency-splitting layer 103, and a second layer stack 105. Frequency-splitting layer 103 may be located between first layer stack 101 and second layer stack 105. In this example, first layer stack 101 includes a first ultrasonic transmitter, and second layer stack 105 includes a second ultrasonic transmitter. Device 100 may or may not include an ultrasonic receiver in both first layer stack 101 and second layer stack 105, depending on the specific implementation. For example, some implementations may include an ultrasonic receiver only in first layer stack 101. According to some implementations, a single piezoelectric layer or multilayer piezoelectric structure in first layer stack 101 and / or second layer stack 105 may function as both an ultrasonic transmitter and an ultrasonic receiver.

[0047] For example, in some implementations, the first layer stack 101 and / or the second layer stack 105 can include a piezoelectric layer, such as a PVDF polymer layer or a PVDF-TrFE copolymer layer. In some implementations, a single piezoelectric layer can act as an ultrasonic transmitter. In some implementations, a single piezoelectric layer can act as both a transmitter and a receiver. In some implementations, other piezoelectric materials can be used in the piezoelectric layer, such as aluminum nitride (AlN) or lead zirconate titanate (PZT).

[0048] In some examples, the first layer stack 101 and / or the second layer stack 105 may include an array of ultrasonic transducer elements, such as a piezoelectric micromachined ultrasonic transducer (PMUT) array, a capacitive micromachined ultrasonic transducer (CMUT) array, etc. In some such examples, a piezoelectric receiver layer, a PMUT element in a single-layer PMUT array, or a CMUT element in a single-layer CMUT array may act as both an ultrasonic transmitter and an ultrasonic receiver. According to some alternative examples, the first layer stack 101 and / or the second layer stack 105 may include an ultrasonic plane wave generator, such as those described below.

[0049] In some examples, the frequency division layer 103 may include polyethylene terephthalate (PET). In other examples, the frequency division layer 103 may include a pressure-sensitive adhesive, a plastic spacer, and / or a metal tape, such as a copper tape. In some implementations, the frequency division layer 103 may be configured to suppress relatively high frequency ultrasonic waves suitable for fingerprint imaging. According to some such implementations, relatively high frequency ultrasonic waves may be transmitted by the first layer stack 101 and may include a frequency referred to herein as a "first frequency." The first frequency may be, for example, in the range of 10 MHz to 20 MHz.

[0050] In some examples, the frequency-splitting layer 103 can be configured to pass relatively low-frequency ultrasound waves suitable for imaging sub-epidermal features. According to some such implementations, the relatively low-frequency ultrasound waves can be transmitted by the second layer stack 105 and can include a frequency referred to herein as a "second frequency." The second frequency can be, for example, in the range of 1 MHz to 10 MHz.

[0051] In some implementations, the frequency-splitting layer 103 can have an acoustic impedance that is relatively lower than the acoustic impedance of a first adjacent layer of the first stack and a second adjacent layer of the second stack. According to some such examples, the frequency-splitting layer 103 can have a thickness corresponding to half a wavelength of the second frequency. In some cases, the frequency-splitting layer 103 can have a thickness corresponding to an odd-integer multiple of a quarter wavelength of the first frequency.

[0052] However, in some examples, the frequency splitting layer 103 may have an acoustic impedance relatively higher than the acoustic impedances of the first adjacent layer of the first layer stack and the second adjacent layer of the second layer stack. According to some such examples, the frequency splitting layer 103 may have a thickness corresponding to an odd multiple of a quarter wavelength of the second frequency.

[0053] In some examples, apparatus 100 may include an interface system 107, a control system 109, and / or a display system 111. In some implementations, first layer stack 101 may be located near, for example, below, display system 111. In some implementations, optional display system 111 may be or may include a light emitting diode (LED) display, such as an organic light emitting diode (OLED) display.

[0054] The control system 109 may include one or more general purpose single-chip 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, discrete hardware components, or a combination thereof. The control system 109 may also include one or more storage devices (and / or be configured to communicate with one or more storage devices), such as one or more random access memory (RAM) devices, read-only memory (ROM) devices, etc. Thus, the apparatus 100 may have a storage system including one or more storage devices, even though the storage system is not in the Figure 1B The control system 109 may be capable of receiving and processing data from the first layer stack 101 and / or the second layer stack 105, for example, as described below. In some implementations, the functionality of the control system 109 may be split between one or more controllers or processors (e.g., a dedicated sensor controller and an application processor of a mobile device).

[0055] Some implementations of the apparatus 100 can include an interface system 107. In some examples, the interface system can include a wireless interface system. In some implementations, the interface system can include a user interface system, one or more network interfaces, one or more interfaces between the control system 109 and a memory system, and / or one or more interfaces between the control system 109 and one or more external device interfaces (e.g., a port or application processor).

[0056] The interface system 107 can be configured to provide communication (which can include wired or wireless communication, such as electrical communication, radio communication, etc.) between components of the device 100. In some such examples, the interface system 107 can be configured to provide communication between the control system 109 and the first layer stack 101 and / or the second layer stack 105. According to some such examples, a portion of the interface system 107 can couple at least a portion of the control system 109 to the first layer stack 101 and / or the second layer stack 105, for example, via a conductive material.

[0057] According to some examples, the interface system 107 can be configured to provide communication between the apparatus 100 and other devices and / or humans. In some such examples, the interface system 107 can include one or more user interfaces. In some examples, the interface system 107 can include one or more network interfaces and / or one or more external device interfaces (e.g., one or more universal serial bus (USB) interfaces). In some implementations, the apparatus 100 can include a storage system. In some examples, the interface system 107 can include at least one interface between the control system 109 and the storage system.

[0058] The apparatus 100 can be used in a variety of different contexts, many examples of which are disclosed herein. For example, in some implementations, a mobile device such as a cell phone, a smartphone, a tablet computer, a laptop computer (e.g., a laptop touchpad), etc. may include at least a portion of the apparatus 100. In some implementations, a wearable device may include at least a portion of the apparatus 100. The wearable device may be, for example, a watch, a bracelet, an armband, a wristband, a ring, a headband, and a patch. In some implementations, the control system 109 may be located in more than one device. For example, a portion of the control system 109 may be located in a wearable device, and another portion of the control system 109 may be located in another device, such as a mobile device (e.g., a smartphone or tablet computer) and / or a server. In some such examples, the interface system 107 may also be located in more than one device.

[0059] Figure 2 is a flowchart providing an example of operation according to some disclosed methods. For example, Figure 2 The block can be composed of Figure 1B The device 100 or similar device is executed. As with other methods disclosed herein, Figure 2 The methods outlined in the may include more or fewer blocks than indicated. Additionally, the blocks of the methods disclosed herein are not necessarily executed in the order indicated.

[0060] In this example, block 203 involves controlling a first ultrasonic transmitter of the ultrasonic sensor system to transmit a first ultrasonic wave. In this example, a first layer is stacked, e.g. Figure 1B The first layer stack 101 includes a first ultrasonic transmitter. Here, the first ultrasonic wave comprises a first frequency. For example, the first frequency may be within a frequency range suitable for fingerprint imaging. In some examples, the first frequency may be within a range of 10 MHz to 20 MHz. However, in other examples, the first frequency may include frequencies above 20 MHz and / or below 10 MHz.

[0061] Depending on the implementation, block 205 involves receiving a first signal from a first ultrasonic receiver, the first signal corresponding to a reflection of the first ultrasonic wave from a surface of a portion of a target object located on an exterior surface of a device including the ultrasonic sensor system. If the target object is a finger, the first signal may correspond to a reflection of the first ultrasonic wave from the surface of the finger. (As used herein, the term "finger" may refer to any digit, including a thumb. Thus, a thumbprint would be considered a type of "fingerprint.") In some examples, method 200 may involve performing an authentication process based at least in part on the first signal.

[0062] According to some implementations, method 200 may involve obtaining fingerprint data based on a portion of the first signal received within a time interval corresponding to the fingerprint. The time interval may be measured, for example, relative to the time at which the first ultrasonic wave is transmitted. Obtaining the fingerprint data may, for example, involve extracting a first target object feature from the first signal via a control system. The first target object feature may, for example, include a fingerprint feature. According to some examples, the fingerprint feature may include fingerprint minutiae, key points, and / or sweat pores. In some examples, the fingerprint feature may include ridge end information, ridge bifurcation information, short ridge information, ridge flow information, island information, spur information, delta information, core information, and the like.

[0063] In some examples, method 200 may involve performing an authentication process based at least in part on a fingerprint feature. In some examples, block 209 may involve comparing the fingerprint feature with a fingerprint feature of an authorized user. For example, the fingerprint feature of the authorized user may have been received during a previous registration process.

[0064] In some examples, the control system can be configured to control access to the apparatus or another device based at least in part on an authentication process. For example, in some implementations, a mobile device (e.g., a cell phone) can include the apparatus. In some such examples, the control system can be configured to control access to the mobile device based at least in part on an authentication process.

[0065] In some implementations, an Internet of Things (IoT) device may include apparatus 100. For example, in some such implementations, a device intended for use in a home, such as a remote control (e.g., a remote control for a smart TV), a stove, an oven, a refrigerator, a furnace, a coffee maker, an alarm system, a door lock, a mail / package box lock, a thermostat, etc., may include apparatus 100. In some such examples, a control system may be configured to control access to the IoT device based at least in part on a first authentication process.

[0066] In alternative implementations, an automobile (including but not limited to a partially or fully autonomous automobile), a partially or fully autonomous delivery vehicle, a drone, or another device typically used outside of the home may include apparatus 100. In some such examples, the control system may be configured to control access to the vehicle, drone, etc. based at least in part on the first authentication process.

[0067] In some examples, including but not limited to many IoT implementations, there may be a metal, plastic, ceramic, or polymer layer between the outer surface of the device 100 or the outer surface of a device including the device 100 and the first layer stack 101 and / or the second layer stack 105. In such an implementation, sound waves from a finger or other target may need to pass through the metal layer before reaching the first layer stack 101 and / or the second layer stack 105. Ultrasonic waves and other sound waves can be successfully sent through metal layers, while some other types of waves (such as light waves) cannot. Similarly, ultrasonic waves and other sound waves can be successfully sent through optically opaque plastic, ceramic, or polymer layers, while some other types of waves, such as light waves, cannot. This feature is another potential advantage of some disclosed implementations compared to devices that rely on optical or capacitive fingerprint sensors.

[0068] Figure 3A Shown and included Figure 1B 3. An example of a target object contacting an outer surface of a device of the apparatus shown. In this example, target object 307 is a finger, which is in contact with outer surface 309 of display stack 311. Display stack 311 may be Figure 1B In an alternative example, the target object 307 may be in contact with an outer surface of a platen, which may be transparent or opaque to visible light.

[0069] here, Figure 3A The device 100 includes a high-frequency ultrasonic sensor stack 301, a frequency division layer 103, and a low-frequency ultrasonic sensor stack 305. According to this implementation, the high-frequency ultrasonic sensor stack 301 is Figure 1B The example of the first layer stack 101 shown, and the low frequency ultrasonic sensor stack 305 is Figure 1B An example of the second layer stack 105 is shown. As with other disclosed implementations, the type, number, and arrangement of components, as well as the dimensions of the components, are merely examples. In some implementations, for example, the high-frequency ultrasonic sensor stack 301 can occupy a different (e.g., smaller) area than the low-frequency ultrasonic sensor stack 305.

[0070] In this example, apparatus 100 is configured to perform the operations of method 200 . Figure 3A The arrow 313 shown in FIG corresponds to the first ultrasonic wave comprising the first frequency, as described above with reference to FIG. Figure 2 This is described in block 203 of FIG. Arrow 314 corresponds to reflection of the first ultrasonic wave from the surface of a portion of the target object located on the outer surface of the device.

[0071] According to this example, the method 200 further involves controlling the ultrasonic transmitter of the low-frequency ultrasonic sensor stack 305 via a control system (not shown) to transmit a second ultrasonic wave (at Figure 3A The second ultrasound wave may include a second frequency lower than the first frequency mentioned above in the discussion of block 203. The second frequency may be within an ultrasound frequency range suitable for imaging subepidermal features. For example, the second frequency may be within a range of 1 MHz to 10 MHz. In some implementations, the second frequency may be within a range of 2 MHz to 7 MHz.

[0072] In some examples, the low frequency ultrasonic sensor stack 305 may include a second ultrasonic receiver. The control system may be configured to receive a second signal from the second ultrasonic receiver, the second signal being in phase with the second ultrasonic wave (at Figure 3A In some such examples, the control system may be configured to perform an authentication process based at least in part on the second signal. The second signal may, for example, include dermis layer information corresponding to the reflection of the second ultrasonic wave received from the portion of the target object 307. The dermis layer information may be obtained within a time interval corresponding to the dermis layer. The authentication process may be based at least in part on the dermis layer information. According to some implementations, the authentication process may be based at least in part on both the first signal and the second signal.

[0073] Alternatively or additionally, the second signal may include information about other subepidermal layers (e.g., papillary layer, reticular layer, subcutaneous tissue, etc.), as well as any blood vessels, lymphatic vessels, sweat glands, hair follicles, hair papillae, fat lobules, etc. that may be present in these tissue layers. Figure 1A Some examples are described. However, the second signal may include information about Figure 1A Information about subcutaneous features not shown in the image (e.g., muscle tissue, bone material, etc.).

[0074] According to some examples, the first signal may also be combined with the harmonics of the second ultrasonic wave (in Figure 3A The second signal may correspond to a reflection of the first ultrasonic wave (indicated by arrow 318 in FIG) from the surface of the target object 307. Alternatively or additionally, the second signal may also correspond to a reflection of a subharmonic of the first ultrasonic wave from an interior of a portion of the target object 307.

[0075] Figure 3B Shown and included Figure 1B 307 is an example of a target object in contact with an outer surface of another device of the apparatus shown. As with other disclosed implementations, the type, number, and arrangement of elements, as well as the dimensions of the elements, are merely examples. In some implementations, for example, the high-frequency ultrasonic sensor stack 301 may occupy a different (e.g., smaller) area than the low-frequency ultrasonic sensor stack 305. In this example, the target object 307 is a finger in contact with the outer surface 309 of the display stack 311. The display stack 311 may be Figure 1B In an alternative example, the target object 307 may be in contact with an outer surface of a platen, which may be transparent or opaque to visible light.

[0076] Similar to Figure 3A The device 100, Figure 3B The device 100 further includes a high frequency ultrasonic sensor stack 301, a frequency division layer 103 and a low frequency ultrasonic sensor stack 305. However, according to this implementation, when Figure 3B As shown, low-frequency ultrasonic sensor stack 305 is "above" high-frequency ultrasonic sensor stack 301. In other words, exterior surface 309 is on a first side of low-frequency ultrasonic sensor stack 305, and frequency separation layer 103 is on a second, opposite side of low-frequency ultrasonic sensor stack 305. Alternatively, display stack 311 is on a first side of low-frequency ultrasonic sensor stack 305, and frequency separation layer 103 is on a second, opposite side of low-frequency ultrasonic sensor stack 305.

[0077] In this example, apparatus 100 is configured to perform additional examples of method 200 . Figure 3A The arrow 313 shown in FIG corresponds to an example of a first ultrasonic wave comprising a first frequency, as described above with reference to FIG. Figure 2This is described in block 203 of FIG. In this example, the first ultrasonic wave propagates through the frequency separation layer 103 and the low-frequency ultrasonic sensor stack 305 before reaching the target object. Arrow 314 corresponds to an example of the first ultrasonic wave being reflected from the surface of a portion of the target object 307 located on the outer surface 309 of the device.

[0078] According to this example, the method 200 further involves controlling the ultrasonic transmitter of the low frequency ultrasonic sensor stack 305 to transmit a second ultrasonic wave (at Figure 3B The second ultrasound wave may include a second frequency lower than the first frequency mentioned above in the discussion of block 203. The second frequency may be in an ultrasound frequency range suitable for imaging subepidermal features. For example, the second frequency may be in a range of 1 MHz to 10 MHz. In some implementations, the second frequency may be in a range of 2 MHz to 7 MHz.

[0079] At least a portion of the second ultrasonic wave (e.g., Figure 3B The reflected waves (as shown by arrows 316a in FIG. 3 ) may be reflected from a surface of a portion of the target object 307. At least a portion of these reflected waves may propagate through the frequency-splitting layer 103 and may be received by a receiver of the high-frequency ultrasonic sensor stack 301. According to some examples, at least a portion of these reflected waves may include harmonics of the second ultrasonic wave.

[0080] In some examples, the low frequency ultrasonic sensor stack 305 may include a second ultrasonic receiver. The control system may be configured to receive a third signal from the second ultrasonic receiver, the third signal being in phase with the second ultrasonic wave (at Figure 3A In some examples, the control system may be configured to perform an authentication process based at least in part on the third signal. The third signal may, for example, include dermis layer information corresponding to the reflection of the second ultrasonic wave received from the portion of the target object 307. The dermis layer information may be obtained within a time interval corresponding to the dermis layer. The authentication process may be based at least in part on the dermis layer information. According to some implementations, the authentication process may be based at least in part on the first signal, the second signal, and the third signal.

[0081] Alternatively or additionally, the third signal may include information about other subepidermal layers (e.g., papillary layer, reticular layer, subcutaneous tissue, etc.), as well as any blood vessels, lymphatic vessels, sweat glands, hair follicles, hair papillae, fat lobules, etc. that may be present in these tissue layers. Figure 1A Some examples are described. However, the third signal may include information about Figure 1A Information about subcutaneous features not shown in the image (e.g., muscle tissue, bone material, etc.).

[0082] Figure 4 Example components of an apparatus according to some disclosed implementations are shown. As with other disclosed implementations, the types, quantities, and arrangements of components, as well as the dimensions of the components, are merely examples. According to this example, apparatus 100 is configured to perform at least some of the methods disclosed herein. In this example, display stack 311 includes an OLED display and is attached to high-frequency ultrasonic sensor stack 301 via adhesive layer 401.

[0083] According to this implementation, the high-frequency ultrasonic sensor stack 301 includes a thin film transistor (TFT) layer 403 that is coupled to at least a portion of the control system 109 and an upper portion of a piezoelectric layer 405 via a portion of an interface system 107 that includes a conductive material. In this implementation, the piezoelectric layer 405 includes one or more piezoelectric polymers. In this example, the interface system 107 also includes a silver ink layer 407 that provides electrical conductivity between the portion of the control system 109 and the lower portion of the piezoelectric layer 405. Although Figure 4 Not shown, a portion of the interface system 107 also provides electrical conductivity between portions of the control system 109 and the low frequency ultrasonic sensor stack 305 .

[0084] In this example, the epoxy film 409 couples the high-frequency ultrasonic sensor stack 301 to the frequency separation layer 103, and the adhesive layer 411 couples the low-frequency ultrasonic sensor stack 305 to the frequency separation layer 103. In some implementations, the frequency separation layer 103 can have an acoustic impedance that is relatively lower than the acoustic impedances of the epoxy film 409 and the adhesive layer 411. In some such implementations, the frequency separation layer 103 can have a thickness corresponding to half the wavelength of the frequency of the ultrasonic wave transmitted by the ultrasonic transceiver 413 (referred to as the "second frequency" elsewhere herein).

[0085] However, in some examples, the frequency dividing layer 103 may have an acoustic impedance relatively higher than the acoustic impedances of the epoxy film 409 and the adhesive layer 411. In some such implementations, the frequency dividing layer 103 may have a thickness corresponding to an odd-integer multiple of a quarter wavelength of the second frequency of the ultrasonic wave transmitted by the ultrasonic transceiver 413.

[0086] exist Figure 4In the illustrated example, device 100 includes a backing layer 415. In this example, backing layer 415 is configured to absorb energy to mitigate or prevent signal interference. According to this example, frequency separation layer 103 is located adjacent to a first side of low-frequency ultrasonic sensor stack 305, and backing layer 415 is located adjacent to a second side of low-frequency ultrasonic sensor stack 305. In this example, backing layer 415 has an acoustic impedance higher than the acoustic impedance of the second side of low-frequency ultrasonic sensor stack 305. In some implementations, backing layer 415 can have a thickness in the range of 10 to 100 microns. In this case, backing layer 415 comprises tungsten.

[0087] Figure 5A and 5B is a graph of differential signal strength versus divider thickness for two examples. In each example, the divider is composed of a two-part epoxy. Figure 5A and 5B In the example shown, the differential signal strength indication corresponds to the fingerprint ridge (at Figure 5A and 5B The signal corresponding to the fingerprint valley (shown as "R" in Figure 5A and 5B The difference between the signals (shown as "V") in Figure 5A In the example of FIG, ultrasonic waves are transmitted at 5 MHz (an example of the second frequency), while Figure 5B In the example of , ultrasound is transmitted at 12 MHz (an example of the first frequency). By comparison Figure 5A and 5B , it can be observed that the same divider thickness (10 -4 meters) also greatly suppresses the 12MHz signal.

[0088] Figure 6 is a graph illustrating examples of differential signal enhancement that can be achieved by some implementations of the disclosed ultrasonic sensor system. Each example corresponds to an implementation having an upper ultrasonic sensor stack, a lower ultrasonic sensor stack, and a frequency division layer between the two ultrasonic sensor stacks, for example, as described above with reference to Figure 1B As described. In this example, the frequency division layer is composed of epoxy resin. In various implementations studied, the epoxy resin layer varies from 5 microns to 150 microns. According to this example, signal 601 corresponds to the reflection received after transmitting 5.5 MHz ultrasonic waves only from the upper ultrasonic sensor stack, and signal 603 corresponds to the reflection received after transmitting 12 MHz ultrasonic waves only from the upper ultrasonic sensor stack. For example, 12 MHz ultrasonic waves can be used for fingerprint imaging, and 5.5 MHz ultrasonic waves can be used for subcutaneous imaging, such as dermis imaging. Here, signal 601 and signal 603 correspond to baseline (BL) signals.

[0089] In this example, signal 605 corresponds to the reflections received after transmitting 5.5 MHz ultrasonic waves from the upper and lower ultrasonic sensor stacks, and signal 607 corresponds to the reflections received after transmitting 12 MHz ultrasonic waves from the upper and lower ultrasonic sensor stacks. Comparing signal 603 and signal 607, it can be seen that the differential signal amplitude for fingerprint imaging (@12 MHz) is approximately doubled compared to the differential signal amplitude of the baseline signal. Comparing signal 601 and signal 605, it can be seen that the differential signal amplitude for subcutaneous imaging (@5.5 MHz) is as much as 20 times that of the baseline signal.

[0090] Figure 7 is a flowchart that provides examples of operations according to some disclosed methods. For example, Figure 7 The block can be composed of Figure 1B , 3 or 4 or similar devices. As with other methods disclosed herein, Figure 7 The methods outlined in the may include more or fewer blocks than indicated. Additionally, the blocks of the methods disclosed herein are not necessarily executed in the order indicated.

[0091] In this example, block 703 involves controlling a first ultrasonic transmitter of the ultrasonic sensor system to transmit a first ultrasonic wave. In this example, a first stack, e.g. Figure 1B The first stack 101 includes a first ultrasonic transmitter. Here, the first ultrasonic wave comprises a first frequency. For example, the first frequency may be within a frequency range suitable for fingerprint imaging. In some examples, the first frequency may be within a range of 10 MHz to 20 MHz. However, in other examples, the first frequency may include frequencies above 20 MHz and / or below 10 MHz.

[0092] According to this example, block 705 involves controlling a second ultrasonic transmitter of the ultrasonic sensor system to transmit ultrasonic waves through the first layer stack and through the frequency division layer between the first layer stack and the second layer stack. In this example, the second layer stack, e.g. Figure 1B The second layer stack 105 includes a second ultrasonic transmitter. Here, the second ultrasonic wave comprises a second frequency lower than the first frequency. The second frequency can, for example, be within a frequency range suitable for subepidermal imaging (e.g., dermal imaging). In some examples, the second frequency can be in the range of 1 MHz to 10 MHz. However, in other examples, the first frequency can include frequencies higher than 10 MHz and / or lower than 1 MHz.

[0093] In this example, block 707 involves performing an authentication process based at least in part on at least one of the first signal or the second signal. In this example, the first signal corresponds to a reflection of a first ultrasonic wave from a surface of a portion of a target object located on an exterior surface of the device comprising the ultrasonic sensor system. Here, the second signal corresponds to a reflection of a second ultrasonic wave from an interior portion of the target object. The second signal may, for example, include dermal layer information.

[0094] In some examples, method 700 may involve obtaining fingerprint data based on a portion of the first signal received within a time interval corresponding to the fingerprint. According to some examples, the first signal may also correspond to a reflection of a harmonic of the second ultrasonic wave from a surface of the portion of the target object. In some cases, the second signal may also correspond to a reflection of a subharmonic of the first ultrasonic wave from an interior of the portion of the target object.

[0095] Figure 8 Aspects of a 4×4 pixel array of sensor pixels for an ultrasonic sensor system are representatively depicted. Each pixel 834 can be associated with, for example, a localized area of ​​piezoelectric sensor material (PSM), a peak detection diode (D1), and a readout transistor (M3); many or all of these components can be formed on or in a substrate to form pixel circuitry 836. In practice, the localized area of ​​piezoelectric sensor material in each pixel 834 can convert received ultrasonic energy into an electrical charge. The peak detection diode D1 can record the maximum amount of charge detected by the localized area of ​​piezoelectric sensor material PSM. Each row of the pixel array 835 can then be scanned, for example, by a row selection mechanism, a gate driver, or a shift register, and the readout transistor M3 of each column can be triggered to allow the magnitude of the peak charge of each pixel 834 to be read by additional circuitry (e.g., a multiplexer and an A / D converter). The pixel circuitry 836 can include one or more TFTs to allow the pixels 834 to be gated, addressed, and reset.

[0096] Each pixel circuit 836 can provide information about a small portion of the object detected by the ultrasonic sensor system. Although for ease of illustration, Figure 8 The example shown has a relatively coarse resolution, but ultrasonic sensors with a resolution of approximately 500 pixels per inch or higher can be configured with appropriately sized structures. The detection area of ​​the ultrasonic sensor system can be selected based on the intended detection object. For example, the detection area can range from approximately 5 mm x 5 mm for a single finger to approximately 3 inches x 3 inches for four fingers. Smaller and larger areas, including square, rectangular, and non-rectangular geometries, can be used appropriately for target objects.

[0097] Figure 9AAn example of an exploded view of an ultrasonic sensor system is shown. In this example, the ultrasonic sensor system 900a includes an ultrasonic transmitter 20 and an ultrasonic receiver 30 below the pressure plate 40. According to some implementations, the ultrasonic receiver 30 can be an example of the acoustic receiver system 102 shown in FIG. 1 and described above. In some implementations, the ultrasonic transmitter 20 can be an example of the optional ultrasonic transmitter 108 shown in FIG. 1 and described above. However, some implementations of the ultrasonic sensor system 900a (and those described below with reference to FIG. 1 ) may be examples of the ultrasonic transmitter 20 and the ultrasonic receiver 30. Figure 9B Some implementations of the described ultrasonic sensor system 900b) do not include the ultrasonic transmitter 20. In some such implementations, the ultrasonic receiver 30 can be configured as an ultrasonic transceiver.

[0098] However, in Figure 9A In the example shown, the ultrasonic transmitter 20 includes a substantially planar piezoelectric transmitter layer 22 and is capable of functioning as a plane wave generator. Ultrasonic waves can be generated by applying a voltage to the piezoelectric layer to stretch or contract the layer (depending on the applied signal), thereby generating a plane wave. In this example, the control system 109 can be capable of inducing a voltage to be applied to the planar piezoelectric transmitter layer 22 via the first transmitter electrode 24 and the second transmitter electrode 26. In this manner, ultrasonic waves can be generated by varying the thickness of the layer via the piezoelectric effect. The ultrasonic waves can travel through the platen 40 toward the finger (or other object to be detected). A portion of the wave not absorbed or transmitted by the object to be detected can be reflected, thereby traveling back through the platen 40 and being received by at least a portion of the ultrasonic receiver 30. The first and second transmitter electrodes 24 and 26 can be metallized electrodes, for example, metal layers coating opposing sides of the piezoelectric transmitter layer 22.

[0099] The ultrasound receiver 30 can include an array of sensor pixel circuits 32 and a piezoelectric receiver layer 36 disposed on a substrate 34, which can also be referred to as a backplate. In some implementations, each sensor pixel circuit 32 can include one or more TFT elements, electrical interconnect traces, and, in some implementations, one or more additional circuit elements such as diodes, capacitors, and the like. Each sensor pixel circuit 32 can be configured to convert charge generated in the piezoelectric receiver layer 36 proximate to the pixel circuit into an electrical signal. Each sensor pixel circuit 32 can include a pixel input electrode 38 that electrically couples the piezoelectric receiver layer 36 to the sensor pixel circuit 32.

[0100] In the illustrated implementation, a receiver bias electrode 39 is disposed on a side of the piezoelectric receiver layer 36 proximal to the platen 40. The receiver bias electrode 39 can be a metallized electrode and can be grounded or biased to control which signals are passed to the array of sensor pixel circuits 32. Ultrasonic energy reflected from the exposed (top) surface of the platen 40 can be converted by the piezoelectric receiver layer 36 into localized charges. These localized charges can be collected by the pixel input electrodes 38 and passed to the underlying sensor pixel circuits 32. The charges can be amplified or buffered by the sensor pixel circuits 32 and provided to the control system 109.

[0101] The control system 109 can be electrically connected (directly or indirectly) to the first transmitter electrode 24 and the second transmitter electrode 26, as well as to the receiver bias electrode 39 and the sensor pixel circuit 32 on the substrate 34. In some implementations, the control system 109 can operate substantially as described above. For example, the control system 109 can be capable of processing the amplified signal received from the sensor pixel circuit 32.

[0102] The control system 109 may be capable of controlling the ultrasonic transmitter 20 and / or the ultrasonic receiver 30, for example, by obtaining a fingerprint image to obtain ultrasonic image data. Regardless of whether the ultrasonic sensor system 900a includes the ultrasonic transmitter 20, the control system 109 may be capable of obtaining attribute information from the ultrasonic image data. In some examples, the control system 109 may be capable of controlling access to one or more devices based, at least in part, on the attribute information. The ultrasonic sensor system 900a (or a related device) may include a storage system comprising one or more storage devices. In some implementations, the control system 109 may include at least a portion of the storage system. The control system 109 may be capable of obtaining attribute information from the ultrasonic image data and storing the attribute information in the storage system. In some implementations, the control system 109 may be capable of capturing a fingerprint image, obtaining attribute information from the fingerprint image, and storing the attribute information obtained from the fingerprint image (hereinafter referred to as fingerprint image information) in the storage system. According to some examples, the control system 109 may be capable of capturing a fingerprint image, obtaining attribute information from the fingerprint image, and storing the attribute information obtained from the fingerprint image even when the ultrasonic transmitter 20 is maintained in an "off" state.

[0103] In some implementations, the control system 109 may be capable of operating the ultrasonic sensor system 900a in either an ultrasonic imaging mode or a force sensing mode. In some implementations, when operating the ultrasonic sensor system in the force sensing mode, the control system may be capable of maintaining the ultrasonic transmitter 20 in an "off" state. When the ultrasonic sensor system 900a is operating in the force sensing mode, the ultrasonic receiver 30 may be capable of functioning as a force sensor. In some implementations, the control system 109 may be capable of controlling other devices, such as a display system, a communication system, etc. In some implementations, the control system 109 may be capable of operating the ultrasonic sensor system 900a in a capacitive imaging mode.

[0104] The pressure plate 40 can be any suitable material capable of acoustically coupling to the receiver, including, for example, plastic, ceramic, sapphire, metal, and glass. In some implementations, the pressure plate 40 can be a cover plate, such as cover glass or lens glass for a display. In particular, when using the ultrasonic transmitter 20, fingerprint detection and imaging can be performed with a relatively thick pressure plate (e.g., 3 mm and above), if necessary. However, for implementations in which the ultrasonic receiver 30 is capable of imaging fingerprints in a force detection mode or a capacitive detection mode, a thinner and relatively more flexible pressure plate 40 may be required. According to some such implementations, the pressure plate 40 can include one or more polymers, such as one or more types of parylene, and can be significantly thinner. In some such implementations, the pressure plate 40 can be tens of microns thick or even less than 10 microns thick.

[0105] Examples of piezoelectric materials that can be used to form the piezoelectric receiver layer 36 include piezoelectric polymers having suitable acoustic properties, for example, an acoustic impedance between approximately 2.5 MRayls and 5 MRayls. Specific examples of piezoelectric materials that can be used include ferroelectric polymers, such as polyvinylidene fluoride (PVDF) and polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE) copolymers. Examples of PVDF copolymers include 60:40 (mole percent) PVDF-TrFE, 70:30 PVDF-TrFE, 80:20 PVDF-TrFE, and 90:10 PVDF-TrFE. Other examples of piezoelectric materials that can be used include polyvinylidene chloride (PVDC) homopolymers and copolymers, polytetrafluoroethylene (PTFE) homopolymers and copolymers, and diisopropylammonium bromide (DIPAB).

[0106] The thickness of each of the piezoelectric transmitter layer 22 and the piezoelectric receiver layer 36 can be selected to be suitable for generating and receiving ultrasonic waves. In one example, the PVDF planar piezoelectric transmitter layer 22 is approximately 28 microns thick, and the PVDF-TrFE receiver layer 36 is approximately 12 microns thick. Example frequencies of ultrasonic waves can be in the range of 5 MHz to 30 MHz, with wavelengths on the order of millimeters or less.

[0107] Figure 9B An exploded view of an alternative example of an ultrasonic sensor system is shown. In this example, the piezoelectric receiver layer 36 has been formed into discrete components 37. Figure 9B In the illustrated implementation, each discrete component 37 corresponds to a single pixel input electrode 38 and a single sensor pixel circuit 32. However, in alternative implementations of the ultrasonic sensor system 900b, there need not be a one-to-one correspondence between each discrete component 37, a single pixel input electrode 38, and a single sensor pixel circuit 32. For example, in some implementations, there may be multiple pixel input electrodes 38 and sensor pixel circuits 32 for a single discrete component 37.

[0108] Figure 9A and 9B An example arrangement of ultrasonic transmitters and receivers in an ultrasonic sensor system is shown, although other arrangements are possible. For example, in some implementations, the ultrasonic transmitter 20 may be above the ultrasonic receiver 30 and, therefore, closer to the object to be detected. In some implementations, the ultrasonic transmitter may be included in an ultrasonic sensor array (e.g., a single layer of transmitters and receivers). In some implementations, the ultrasonic sensor system may include an acoustic delay layer. For example, the acoustic delay layer may be incorporated into the ultrasonic sensor system between the ultrasonic transmitter 20 and the ultrasonic receiver 30. The acoustic delay layer can be used to adjust the timing of ultrasonic pulses while electrically insulating the ultrasonic receiver 30 from the ultrasonic transmitter 20. The acoustic delay layer can have a substantially uniform thickness, with the material used for the delay layer and / or the thickness of the delay layer selected to provide a desired delay in the time it takes for reflected ultrasonic energy to reach the ultrasonic receiver 30. In doing so, energy pulses carrying information about the object, due to reflection from the object, can be made to reach the ultrasonic receiver 30 during a time range when energy reflected from other parts of the ultrasonic sensor system is less likely to reach the ultrasonic receiver 30. In some implementations, the substrate 34 and / or the press plate 40 can act as an acoustic delay layer.

[0109] As used herein, a phrase referring to "at least one" of a list of items refers to any combination of those items, including individual members. As an example, "at least one of a, b, or c" is intended to encompass: a, b, c, ab, ac, bc, and abc.

[0110] The various illustrative logics, logic blocks, modules, circuits, and algorithmic processes described in conjunction with the implementations disclosed herein can be implemented as electronic hardware, computer software, or a combination of both. The interchangeability of hardware and software has been generally described in terms of functionality and illustrated in the various illustrative components, blocks, modules, circuits, and processes described above. Whether such functionality is implemented in hardware or software depends on the specific application and the design constraints imposed on the overall system.

[0111] The hardware and data processing apparatus for implementing the various illustrative logics, logic blocks, modules, and circuits described in conjunction with the aspects disclosed herein may be implemented or performed using a general-purpose single-chip or multi-chip processor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general-purpose processor may be a microprocessor or any conventional processor, controller, microcontroller, or state machine. A 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 configuration. In some implementations, specific processes and methods may be performed by circuits specific to a given function.

[0112] 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 computer storage media for execution by, or to control the operation of, data processing apparatus.

[0113] If implemented in software, the function can be stored as one or more instructions or codes in a computer-readable medium (e.g., a non-transitory medium) or transmitted via a computer-readable medium. The process of the method or algorithm disclosed herein can be implemented in a software module executable by a processor, which can reside on a computer-readable medium. Computer-readable media include both computer storage media and communication media, and the communication media include any medium capable of transmitting a computer program from one place to another. The storage medium can be any available medium that can be accessed by a computer. As an example and not limitation, non-transitory media can include RAM, ROM, EEPROM, CD-ROM or other optical disk storage, disk storage or other magnetic storage devices, or any other medium that can be used to store the required program code in the form of instructions or data structures and can be accessed by a computer. In addition, any connection can be appropriately referred to as a computer-readable medium. The disk and disc used herein include compact discs (CDs), laser discs, optical discs, digital versatile discs (DVDs), floppy disks and Blu-ray discs, wherein disks usually reproduce data magnetically, while discs reproduce data optically with lasers. The above combination should also be included in the scope of computer-readable media. Additionally, the operations of a method or algorithm may reside as one or any combination or set of codes and instructions on a machine-readable medium or computer-readable medium, which may be incorporated into a computer program product.

[0114] Various modifications to the implementations described in this disclosure will be apparent to those skilled in the art, and the general principles defined herein may be applied to other implementations without departing from the spirit or scope of this disclosure. Therefore, this disclosure is not intended to be limited to the implementations shown herein, but to be accorded the widest scope consistent with the claims, principles, and novel features disclosed herein. The word "exemplary" is used herein, if at all, specifically to mean "serving as an example, instance, or illustration." Any implementation described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other implementations.

[0115] Certain features described in this specification in the context of separate 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. Furthermore, although features may be described above as functioning in certain combinations and even initially claimed as such, in some cases one or more features from a claimed combination may be deleted from that combination, and a claimed combination may be directed to a subcombination or variation of a subcombination.

[0116] Similarly, while operations are depicted in a particular order in the accompanying drawings, this should not be understood as requiring that the operations be performed in the particular order shown, or in the order shown, or that all illustrated operations be performed, to achieve the desired results. In some cases, multitasking and parallel processing may be advantageous. Furthermore, the separation of various system components in the above-described implementations should not be understood as requiring such separation in all implementations, and it should be understood that the described program components and systems can generally be integrated into a single software product or packaged into multiple software products. Furthermore, other implementations are also within the scope of the following claims. In some cases, the actions recited in the claims can be performed in a different order and still achieve the desired results.

[0117] It should be understood that unless the features in any particular described implementation are explicitly identified as incompatible with each other, or the surrounding context suggests that they are mutually exclusive and not easily combined in a complementary and / or supportable sense, the overall anticipation of the present disclosure and the specific features of the implementations that contemplate these complements can be selectively combined to provide one or more comprehensive, but slightly different technical solutions. Therefore, it will be further understood that the above description is given only as an example and that modifications in detail may be made within the scope of the present disclosure.

Claims

1. A biometric authentication device, comprising: Ultrasonic sensor system, comprising: The first ultrasonic transmitter in the first layer stack of the ultrasonic sensor system The first stack includes a first ultrasonic receiver; A second ultrasonic transmitter in a second layer stack of the ultrasonic sensor system layer, the second layer stack comprising a second ultrasonic receiver; and a frequency division layer between the first layer stack and the second layer stack; and A control system configured to: controlling the first ultrasonic transmitter to transmit a first ultrasonic wave, wherein the first ultrasonic wave comprises a first frequency; A first signal is received from the first ultrasonic receiver, the first signal being a corresponding reflection of the ultrasonic wave from a surface of a portion of the target object located on an outer surface of the device; Control the second ultrasonic transmitter to transmit a second ultrasonic wave through the frequency division layer and the first stack, wherein the second ultrasonic wave includes a second frequency lower than the first frequency. Rate; A second signal is received from the second ultrasonic receiver, the second signal being two corresponding reflections of the ultrasonic wave from the interior of the portion of the target object; and An authentication process based at least in part on the second signal is performed. 2 . The apparatus of claim 1 , wherein the control system is configured to perform an authentication process based at least in part on the first signal. 3 . The apparatus of claim 1 , wherein the control system is configured to obtain fingerprint data based on a portion of the first signal received within a time interval corresponding to a fingerprint. 4 . The device of claim 1 , wherein the frequency dividing layer has an acoustic impedance relatively lower than acoustic impedances of a first adjacent layer of the first layer stack and a second adjacent layer of the second layer stack, and a thickness corresponding to half a wavelength of the second frequency.

5. The device of claim 1, wherein the frequency dividing layer has an acoustic impedance relatively higher than that of a first adjacent layer of the first layer stack and a second adjacent layer of the second layer stack, and a thickness corresponding to an odd multiple of a quarter wavelength of the second frequency. The device according to claim 5 , wherein the frequency-splitting layer has a thickness corresponding to a quarter wavelength of the first frequency. 7 . The apparatus according to claim 1 , wherein the second signal comprises dermis layer information corresponding to reflections of the second ultrasonic wave received from the portion of the target object within a time interval corresponding to a dermis layer.

8. The apparatus of claim 7, wherein the authentication process is based at least in part on the dermis layer information.

9. The apparatus of claim 1, wherein the authentication process is based at least in part on both the first signal and the second signal.

10. The apparatus of claim 1, wherein the first signal further corresponds to reflection of a harmonic of the second ultrasonic wave from the surface of the portion of the target object.

11. The apparatus of claim 1, wherein the second signal further corresponds to reflection of a subharmonic of the first ultrasonic wave from an interior of the portion of the target object.

12. The apparatus of claim 1, wherein the first frequency is in the range of 10 MHz to 20 MHz, and wherein the second frequency is in the range of 1 MHz to 10 MHz.

13. The device according to claim 1, wherein the single piezoelectric layer or multi-layer piezoelectric structure of the first stack serves as the first ultrasonic transmitter and the first ultrasonic receiver.

14. The device of claim 1, wherein the frequency dividing layer is proximate a first side of the second layer stack, the device further comprising a high impedance backing layer proximate a second side of the second layer stack.

15. The device of claim 14, wherein the backing layer has a thickness in the range of 10 to 100 microns.

16. A biometric authentication device comprising: Ultrasonic sensor system, comprising: a first ultrasonic transmitter in a first layer stack of the ultrasonic sensor system, The first layer stack includes a first ultrasonic receiver; A second ultrasonic transmitter in a second layer stack of the ultrasonic sensor system Layer; and A frequency division layer is located between the first stack and the second stack. time; and A control system configured to: Controlling the first ultrasonic transmitter to transmit a first ultrasonic wave through the frequency division layer and the second stack, wherein the first ultrasonic wave comprises a first frequency; receiving a first signal from the first ultrasonic receiver, the first signal corresponding to a reflection of the first ultrasonic wave from a surface of a portion of a target object located on an outer surface of the device, the outer surface being on a first side of the second layer stack, and the crossover layer being on a second and opposite side of the second layer stack; and An authentication process based at least in part on the first signal is performed.

17. The device according to claim 16, wherein The control system is configured to control the second ultrasonic transmitter to transmit a second ultrasonic wave including a second frequency lower than the first frequency.

18. The device according to claim 17, wherein The control system is configured to receive a second signal from the first ultrasonic receiver, the second signal corresponding to a reflection of the second ultrasonic wave from the surface of the portion of the target object.

19. The apparatus of claim 18, wherein the second signal further corresponds to a reflection of a harmonic of the second ultrasonic wave.

20. The apparatus of claim 17 , wherein the second layer stack includes a second ultrasonic receiver, and wherein the control system is configured to receive a third signal from the second ultrasonic receiver, the third signal corresponding to a reflection of the second ultrasonic wave from an interior of the portion of the target object, wherein the authentication process is based at least in part on the third signal.

21. A method of controlling an ultrasonic sensor system, the method comprising: controlling a first ultrasonic transmitter of the first stack to transmit a first ultrasonic wave, wherein the first ultrasonic wave comprises a first frequency; controlling a second ultrasonic transmitter of a second layer stack to transmit a second ultrasonic wave through the first layer stack and through a frequency dividing layer between the first layer stack and the second layer stack, the second ultrasonic wave including a second frequency lower than the first frequency; and An authentication process is performed that is based at least in part on at least one of a first signal or a second signal, wherein the first signal corresponds to a reflection of the first ultrasonic wave from a surface of a portion of a target object located on an exterior surface of an apparatus comprising the ultrasonic sensor system, and wherein the second signal corresponds to a reflection of the second ultrasonic wave from an interior of the portion of the target object.

22. The method of claim 21, further comprising obtaining fingerprint data based on a portion of the first signal received within a time interval corresponding to a fingerprint. The method according to claim 21 , wherein the second signal comprises dermis layer information.

24. The method of claim 21, wherein the first signal further corresponds to reflection of a harmonic of the second ultrasonic wave from the surface of the portion of the target object.

25. The method of claim 21, wherein the second signal further corresponds to reflection of a subharmonic of the first ultrasonic wave from the interior of the portion of the target object.

26. The method of claim 21, wherein the first frequency is in the range of 10 MHz to 20 MHz, and wherein the second frequency is in the range of 1 MHz to 10 MHz.

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