Apparatus and method for ultrasonic fingerprinting and force sensing

Abstract

A method can involve estimating a force exerted by a target object on a surface, determining at least one ultrasonic fingerprint sensor parameter modification based at least in part on the force, and updating at least one setting of an ultrasonic fingerprint sensor based at least in part on the ultrasonic fingerprint sensor parameter modification. The method can involve controlling the ultrasonic fingerprint sensor to transmit first and second ultrasonic waves toward a target object, and receiving first and second ultrasonic receiver signals from the ultrasonic fingerprint sensor, the first and second ultrasonic receiver signals including signals corresponding to reflections of the first and second ultrasonic waves from the target object. The method can involve performing an authentication process based at least in part on the first and second ultrasonic receiver signals.

Description

[0001] Cross-references to related applications

[0002] This application claims priority to U.S. Patent Application No. 16 / 940,285, filed July 27, 2020, entitled “APPARATUS AND METHOD FORULTRASONIC FINGERPRINT AND FORCE SENSING”, which is incorporated herein by reference for all purposes. Technical Field

[0003] This invention generally relates to ultrasonic fingerprint sensors and methods for using such systems.

[0004] Related technical descriptions

[0005] Ultrasonic fingerprint sensors have been incorporated into devices such as smartphones, ATMs, and automobiles for user authentication. While some existing ultrasonic fingerprint sensors offer satisfactory performance, improved ultrasonic fingerprint sensors are desirable.

[0006] Overview

[0007] The systems, methods, and apparatus disclosed herein each have several innovative aspects, and no single aspect is solely responsible for the desired properties disclosed herein.

[0008] One innovative aspect of the subject matter described in this disclosure can be implemented in an apparatus. The apparatus may include an ultrasonic fingerprint sensor and a control system configured to communicate with the ultrasonic fingerprint sensor. In some examples, at least a portion of the control system may be coupled to the ultrasonic fingerprint sensor. In some implementations, a mobile device may be or may include the apparatus. For example, a mobile device may include the apparatus disclosed herein. In some examples, the apparatus may include a force sensor.

[0009] According to some examples, the control system may be configured to control an ultrasonic fingerprint sensor to transmit a first ultrasonic wave toward a target object in contact with a surface. The surface may be the surface of the ultrasonic fingerprint sensor or a device surface adjacent to the area where the ultrasonic fingerprint sensor resides. In some examples, the control system may be configured to receive a first ultrasonic receiver signal from the ultrasonic fingerprint sensor. The first ultrasonic receiver signal may include a signal corresponding to the reflection of the first ultrasonic wave from the target object.

[0010] According to some implementations, the control system can be configured to acquire an estimate of the force exerted on a surface by a target object. In some examples, the control system can be configured to determine at least one ultrasonic fingerprint sensor parameter modification based at least partially on the force. According to some examples, the control system can be configured to update at least one setting of the ultrasonic fingerprint sensor based at least partially on the ultrasonic fingerprint sensor parameter modification.

[0011] In some examples, the control system may be configured to control the ultrasonic fingerprint sensor to transmit a second ultrasonic wave toward a target object. In some implementations, the control system may be configured to receive a second ultrasonic receiver signal from the ultrasonic fingerprint sensor. The second ultrasonic receiver signal may include a signal corresponding to the reflection of the second ultrasonic wave from the target object. According to some implementations, the control system may be configured to perform an authentication process based at least in part on the first and second ultrasonic receiver signals. In some instances, the device may be integrated into a mobile device.

[0012] In some instances, the modification of at least one ultrasonic fingerprint sensor parameter may include a change in gain, a change in the frequency of the transmitted ultrasonic wave, a change in range gate delay, a change in the range gate window, and / or a change in bias conditions. According to some implementations, determining the modification of at least one ultrasonic fingerprint sensor parameter may involve obtaining at least one new ultrasonic fingerprint sensor parameter from a portion of a force-corresponding data structure. This data structure may, for example, include a force value and the corresponding ultrasonic fingerprint sensor parameter.

[0013] In some examples, the estimation of this force may be based at least in part on the analysis of the first ultrasonic receiver signal. According to some implementations, the estimation of this force may be based at least in part on the analysis of a first fingerprint image corresponding to the first ultrasonic receiver signal. In some such implementations, the estimation of this force may be based on the contact area, the ridge-to-cavity ratio, and / or the ridge distance of the first fingerprint image.

[0014] According to some implementations, the device may include a force sensor. In some such examples, the estimation of the force may be based at least in part on a force sensor signal received from the force sensor. In some such implementations, the force sensor may be integrated into the circuitry of an ultrasonic fingerprint sensor. However, in other implementations, the force sensor may be separate from the ultrasonic fingerprint sensor. In some examples, the force sensor may include, or may be, a piezoresistive sensor, a capacitive sensor, and / or a polymer-based thin-film sensor. In some such implementations, the piezoresistive sensor may include silicon, metal, polycrystalline silicon, and / or glass.

[0015] In some examples, the control system may be further configured to perform an anti-spoofing process that may be at least partially based on the force. In some such implementations, the anti-spoofing process may also be at least partially based on a first fingerprint image corresponding to a first ultrasonic receiver signal and / or on a second fingerprint image corresponding to a second ultrasonic receiver signal. According to some examples, the anti-spoofing process may involve a process of estimating the material properties of the target object.

[0016] According to some implementations, the control system may be configured to estimate a first force corresponding to a first ultrasonic receiver signal and a second force corresponding to a second ultrasonic receiver signal. In some such implementations, the device may include a display or be configured to communicate with a display. In some such implementations, the control system may be further configured to control the display to provide a prompt for applying different forces after the first force has been estimated.

[0017] In some implementations, the ultrasonic fingerprint sensor may include an electrode layer adjacent to the ultrasonic transmitter layer. In some such implementations, a first ultrasonic receiver signal may be acquired via the electrode layer. The estimation of this force may be based at least in part on the analysis of the first ultrasonic receiver signal.

[0018] Other inventive aspects of the subject matter described in this disclosure can be implemented in methods for controlling an ultrasonic fingerprint sensor. In some examples, the method may involve controlling the ultrasonic fingerprint sensor to transmit a first ultrasonic wave toward a target object in contact with a surface. The surface may be the surface of the ultrasonic fingerprint sensor or a device surface adjacent to the area where the ultrasonic fingerprint sensor resides. In some instances, the method may involve receiving a first ultrasonic receiver signal from the ultrasonic fingerprint sensor, the first ultrasonic receiver signal including a signal corresponding to the reflection of the first ultrasonic wave from the target object.

[0019] In some examples, the method may involve obtaining an estimate of the force exerted on the surface by a target object. In some instances, the method may involve determining at least one ultrasonic fingerprint sensor parameter modification based at least in part on the force. The method may involve updating at least one setting of the ultrasonic fingerprint sensor based at least in part on the ultrasonic fingerprint sensor parameter modification.

[0020] In some instances, the method may involve controlling an ultrasonic fingerprint sensor to transmit a second ultrasonic wave toward a target object. In some examples, the method may involve receiving a second ultrasonic receiver signal from the ultrasonic fingerprint sensor. The second ultrasonic receiver signal may include a signal corresponding to the reflection of the second ultrasonic wave from the target object. In some instances, the method may involve performing an authentication process based at least in part on a first ultrasonic receiver signal and a second ultrasonic receiver signal.

[0021] According to some examples, the modification of at least one ultrasonic fingerprint sensor parameter may include modification of the gain value, modification of the frequency of the transmitted ultrasonic wave, modification of the range gating pulse delay, modification of the range gating pulse window, and / or modification of the bias condition. In some examples, determining the modification of the at least one ultrasonic fingerprint sensor parameter may involve obtaining at least one new ultrasonic fingerprint sensor parameter from a portion of a data structure corresponding to the force. This data structure may, for example, include a force value and the corresponding ultrasonic fingerprint sensor parameter.

[0022] In some examples, the estimation of the force may be based at least in part on the analysis of a first ultrasonic receiver signal. According to some implementations, the estimation of the force may be based at least in part on the analysis of a first fingerprint image corresponding to the first ultrasonic receiver signal. In some such implementations, the estimation of the force may be based on the contact area, ridge-to-cavity ratio, and / or ridge distance of the first fingerprint image. In some implementations, the estimation of the force may be based at least in part on a force sensor signal received from a force sensor.

[0023] In some instances, the method may involve performing an anti-spoofing process that may be at least partially based on the force. In some such examples, the anti-spoofing process may also be at least partially based on a first fingerprint image corresponding to a first ultrasonic receiver signal and / or a second fingerprint image corresponding to a second ultrasonic receiver signal. In some such examples, the anti-spoofing process may involve a process of estimating the material properties of the target object.

[0024] In some instances, the method may involve estimating a first force corresponding to a first ultrasonic receiver signal and estimating a second force corresponding to a second ultrasonic receiver signal. In some such examples, the method may involve controlling a display and / or a speaker to provide a prompt to apply a different force after estimating the first force. In some examples, an ultrasonic fingerprint sensor may be integrated into a mobile device.

[0025] Some or all of the operations, functions, and / or methods described herein may be performed by one or more devices according to instructions (e.g., software) stored on one or more non-transient media. Such non-transient media may include memory devices such as those described herein, including but not limited to random access memory (RAM) devices, read-only memory (ROM) devices, etc. Accordingly, some innovative aspects of the subject matter described herein may be implemented in one or more non-transient media on which software is stored.

[0026] For example, the software may include instructions for controlling one or more devices to perform a method of controlling an ultrasonic fingerprint sensor. In some examples, the method may involve controlling the ultrasonic fingerprint sensor to transmit a first ultrasonic wave toward a target object in contact with a surface. The surface may be the surface of the ultrasonic fingerprint sensor or a device surface adjacent to the area where the ultrasonic fingerprint sensor resides. In some instances, the method may involve receiving a first ultrasonic receiver signal from the ultrasonic fingerprint sensor, the first ultrasonic receiver signal including a signal corresponding to the reflection of the first ultrasonic wave from the target object.

[0027] In some instances, the method may involve obtaining an estimate of the force exerted on the surface by a target object. In some instances, the method may involve determining at least one ultrasonic fingerprint sensor parameter modification based at least in part on the force. In some examples, the method may involve updating at least one setting of the ultrasonic fingerprint sensor based at least in part on the ultrasonic fingerprint sensor parameter modification.

[0028] In some examples, the method may involve controlling an ultrasonic fingerprint sensor to transmit a second ultrasonic wave toward a target object. The method may also involve receiving a second ultrasonic receiver signal from the ultrasonic fingerprint sensor. The second ultrasonic receiver signal may include a signal corresponding to the reflection of the second ultrasonic wave from the target object. In some instances, the method may involve performing an authentication process based at least in part on a first ultrasonic receiver signal and a second ultrasonic receiver signal.

[0029] According to some examples, the modification of at least one ultrasonic fingerprint sensor parameter may include modification of the gain value, modification of the frequency of the transmitted ultrasonic wave, modification of the range gating pulse delay, modification of the range gating pulse window, and / or modification of the bias condition. In some examples, determining the modification of the at least one ultrasonic fingerprint sensor parameter may involve obtaining at least one new ultrasonic fingerprint sensor parameter from a portion of a data structure corresponding to the force. This data structure may, for example, include a force value and the corresponding ultrasonic fingerprint sensor parameter.

[0030] In some examples, the estimation of the force may be based at least in part on the analysis of a first ultrasonic receiver signal. According to some implementations, the estimation of the force may be based at least in part on the analysis of a first fingerprint image corresponding to the first ultrasonic receiver signal. In some such implementations, the estimation of the force may be based on the contact area, ridge-to-cavity ratio, and / or ridge distance of the first fingerprint image. In some implementations, the estimation of the force may be based at least in part on a force sensor signal received from a force sensor.

[0031] In some instances, the method may involve performing an anti-spoofing process that may be at least partially based on the force. In some such examples, the anti-spoofing process may also be at least partially based on a first fingerprint image corresponding to a first ultrasonic receiver signal and / or a second fingerprint image corresponding to a second ultrasonic receiver signal. In some such examples, the anti-spoofing process may involve a process of estimating the material properties of the target object.

[0032] In some instances, the method may involve estimating a first force corresponding to a first ultrasonic receiver signal and estimating a second force corresponding to a second ultrasonic receiver signal. In some such examples, the method may involve controlling a display and / or a speaker to provide a prompt that a different force has been applied after the first force has been estimated. In some examples, an ultrasonic fingerprint sensor may be integrated into a mobile device. Brief description of the attached diagram

[0034] 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. Other features, aspects, and advantages will become apparent from this description, the drawings, and the claims. It should be noted that the relative dimensions of the following drawings may not be drawn to scale. Similar reference numerals and designations in the various drawings indicate similar elements.

[0035] Figure 1A An example of a fingerprint image acquired from a dry finger by an ultrasonic fingerprint sensor is shown.

[0036] Figure 1B This is a block diagram illustrating example components of a device based on some publicly available implementations.

[0037] Figure 2A This is a flowchart providing example frames for some of the methods disclosed in this article.

[0038] Figure 2B An example of a cross-sectional view of an apparatus capable of performing at least some of the methods described herein is shown.

[0039] Figure 3 Fingerprint images and examples of stress are shown.

[0040] Figure 4A , 4B Figures 4C and 4C show examples of graphs that indicate changes in a fingerprint image based on variations in the applied finger pressure.

[0041] Figure 5A , 5B Figures 5C and 5D illustrate examples of force sensors integrated into a circuit system of an ultrasonic fingerprint sensor.

[0042] Figure 6 Examples of capture time delay and capture time window are shown based on some implementations.

[0043] Figure 7 An example of capture time delay and capture time window implemented with some substitutions is shown.

[0044] Figure 8 Examples of capture time delay and capture time window based on some implementations of inter-peak sampling are shown.

[0045] Figure 9 and 10A An example of image quality changes after modifying the parameters of an ultrasonic fingerprint sensor is shown.

[0046] Figure 10B The graphs illustrate, based on some examples, the changes in received signal strength as a result of variations in the force applied to the ultrasonic sensor by a finger.

[0047] Figure 11 A representative description of various aspects of the 4×4 pixel array of sensor pixels used in an ultrasonic fingerprint sensor is presented.

[0048] Figure 12A and 12B An example arrangement of the ultrasonic transmitter and receiver in an ultrasonic fingerprint sensor is shown, while other arrangements are also possible.

[0049] Figure 12C An example of an ultrasonic transceiver array in an ultrasonic fingerprint sensor is shown.

[0050] Detailed description

[0051] The following description is directed to certain implementations in order to illustrate the inventive aspects of this disclosure. However, those skilled in the art will readily recognize that the teachings herein can be applied in many different ways. The described implementations can be implemented in any device, apparatus, or system, including biometric systems as disclosed herein. Furthermore, it is contemplated that the described implementations can be included in or associated with a variety of electronic devices, such as, but not limited to: mobile phones, Internet-enabled multimedia cellular phones, mobile television receivers, wireless devices, smartphones, smart cards, wearable devices (such as wristbands, armbands, wrist straps, rings, headbands, patches, etc.). Devices, Personal Data Assistants (PDAs), Wireless Email Receivers, Handheld or Portable Computers, Netbooks, Notebooks, Smartbooks, Tablets, Printers, Copiers, Scanners, Fax Equipment, Global Positioning System (GPS) Receivers / Navigators, Cameras, Digital Multimedia Players (such as MP3 Players), Camcorders, Game Consoles, Wristwatches, Clocks, Calculators, Television Monitors, Flat Panel Displays, Electronic Reading Devices (e.g., E-readers), Mobile Health Devices, Computer Monitors, Automatic Displays (including odometer and speedometer displays), Cockpit Controls and / or Displays, Cameras This includes machine-view displays (such as displays for rearview cameras in vehicles), electronic photographs, electronic billboards or signs, projectors, building structures, microwave ovens, refrigerators, stereo systems, cassette recorders or players, DVD players, CD players, VCRs, radios, portable storage chips, washing machines, dryers, washer / dryer systems, ATMs, parking timers, packages (such as in electromechanical systems (EMS) applications, including microelectromechanical systems (MEMS) applications, along with non-EMS applications), aesthetic structures (such as image displays on a piece of jewelry or clothing), and various EMS devices. The teachings herein can also be applied to 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 of consumer electronics products, car doors, steering wheels or other automotive parts, varactor tubes, liquid crystal devices, electrophoresis equipment, drive schemes, manufacturing processes, and electronic test equipment. Therefore, these teachings are not intended to be limited to the implementations depicted in the figures, but have broad applicability, as will be apparent to those skilled in the art.

[0052] Poor coupling between the finger and the pressure plate of the ultrasonic fingerprint sensor is a common problem. (As used herein, the term "finger" can refer to any finger, including the thumb. Accordingly, the term "fingerprint" as used herein can refer to a fingerprint from any finger, including the thumb.) Poor coupling can occur when the finger is dry and / or when low finger pressure is applied.

[0053] In some implementations, an apparatus may include an ultrasonic fingerprint sensor and a control system. According to some examples, the apparatus may be configured to measure and / or acquire an estimate of a force exerted on a surface by a target object. The control system may be configured to determine at least one modification to an ultrasonic fingerprint sensor parameter based at least in part on the force, and to update at least one setting of the ultrasonic fingerprint sensor based at least in part on the modification to the ultrasonic fingerprint sensor parameter.

[0054] In some such examples, the force estimation may be based at least in part on the analysis of ultrasonic receiver signals reflected from the target object. Alternatively, or additionally, the device may include a force sensor. In some examples, the force sensor may be integrated into the circuitry of the ultrasonic fingerprint sensor. In other examples, the force sensor may be separate from the ultrasonic fingerprint sensor.

[0055] Specific implementations of the subject matter described in this disclosure can be achieved to attain one or more of the following potential advantages. According to some examples, updating one or more settings of an ultrasonic fingerprint sensor can compensate for a loss of image quality that would otherwise typically occur when a target object is lightly touching the surface. For example, modifying the gain value, the frequency of the transmitted ultrasonic waves, the distance gating pulse delay, the distance gating pulse window, and / or the bias conditions can compensate for this light touch.

[0056] According to experiments conducted by the inventors, the image quality of fingerprint images acquired via an ultrasonic fingerprint sensor generally increases with the force applied to the outer surface of the ultrasonic fingerprint sensor or the outer surface of a device including the ultrasonic fingerprint sensor. However, a dry finger generally requires a relatively large force to be pressed against the surface to obtain the same fingerprint image quality as that obtained from a normal finger. In some examples, a dry finger will require approximately three times the force to be pressed against the surface in order to obtain the same fingerprint image quality as that obtained from a normal finger.

[0057] Figure 1A Examples of fingerprint images acquired from a dry finger by an ultrasonic fingerprint sensor are shown. In these examples, images 1 and 5 are from the same part of the finger. Images 3 and 7 both correspond to another part of the finger. Images 1 and 3 were acquired when the finger lightly touched the surface of the ultrasonic fingerprint sensor, while images 5 and 7 were acquired when the finger pressed against the surface of the ultrasonic fingerprint sensor with relatively greater force. In these examples, a light touch corresponds to approximately 30 grams of force, while a heavier touch corresponds to 100 grams of force or greater.

[0058] Figure 1B This is a block diagram illustrating example components of a device according to some disclosed implementations. In this example, device 101 includes an ultrasonic fingerprint sensor 102 and a control system 106. Some implementations of device 101 may include an interface system 104 and / or a force sensor 110.

[0059] In some examples, as suggested by the dashed lines within the ultrasonic fingerprint sensor 102, the ultrasonic fingerprint sensor 102 may include an ultrasonic receiver 103 and a separate ultrasonic transmitter 105. In some such examples, the ultrasonic transmitter 105 may include an ultrasonic plane wave generator, such as those described below.

[0060] However, this document discloses various examples of ultrasonic fingerprint sensors 102, some of which may include a separate ultrasonic transmitter 105, while others may not. Although... Figure 1B While shown as separate elements, in some implementations, the ultrasonic receiver 103 and ultrasonic transmitter 105 may be combined in an ultrasonic transceiver system. For example, in some implementations, the ultrasonic fingerprint sensor 102 may include a piezoelectric receiver layer, such as a polyvinylidene fluoride (PVDF) polymer layer or a polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE) copolymer layer. In some implementations, a single piezoelectric layer may be used as an ultrasonic transmitter. In some implementations, a single piezoelectric layer may be used as both a transmitter and a receiver. In some implementations including a piezoelectric layer, other piezoelectric materials, such as aluminum nitride (AlN) or lead zirconate titanate (PZT), may be used in the piezoelectric layer. In some examples, the ultrasonic fingerprint sensor 102 may include an array of ultrasonic transducer elements, such as a piezoelectric micromechanical ultrasonic transducer (PMUT) array, a capacitive micromechanical ultrasonic transducer (CMUT) array, etc. In some such examples, PMUT elements in a single-layer PMUT array or CMUT elements in a single-layer CMUT array may be used as an ultrasonic transmitter along with an ultrasonic receiver.

[0061] Force sensor 110 (if present in device 101) may be a piezoresistive sensor, a capacitive sensor, a thin-film sensor (e.g., a polymer-based thin-film sensor), or another suitable type of force sensor. If force sensor 110 includes a piezoresistive sensor, the piezoresistive sensor may comprise silicon, metal, polycrystalline silicon, and / or glass. In some instances, fingerprint sensor 102 and force sensor 110 may be mechanically coupled. In some such examples, force sensor 110 may be integrated into the circuitry of ultrasonic fingerprint sensor 102. However, in other implementations, force sensor 110 may be separate from ultrasonic fingerprint sensor 102. In some examples, ultrasonic fingerprint sensor 102 and force sensor 110 may be indirectly coupled. For example, ultrasonic fingerprint sensor 102 and force sensor 110 may each be coupled to a portion of device 101. In some such examples, ultrasonic fingerprint sensor 102 and force sensor 110 may each be coupled to a portion of a control system.

[0062] Control system 106 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. According to some examples, control system 106 may include dedicated components for controlling ultrasonic fingerprint sensor 102 and / or force sensor 110. Control system 106 may also include one or more memory devices (and / or be configured to communicate with one or more memory devices), such as one or more random access memory (RAM) devices, read-only memory (ROM) devices, etc. Accordingly, device 101 may have a memory system including one or more storage devices, although such memory system is not... Figure 1B As shown below, the control system 106 can be configured to receive and process data from the ultrasonic fingerprint sensor 102 (e.g., from the ultrasonic receiver 103). If the device 101 includes a separate ultrasonic transmitter 105, the control system 106 can be configured to control the ultrasonic transmitter 105, for example, as disclosed elsewhere herein. In some implementations, the functionality of the control system 106 can be partitioned among one or more controllers or processors, such as between a dedicated sensor controller and an application processor of the mobile device. Some examples are described below.

[0063] Some implementations of device 101 may include interface system 104. In some examples, interface system 104 may include a wireless interface system. In some implementations, interface system 104 may include a user interface system, one or more network interfaces, one or more interfaces between control system 106 and memory system, and / or one or more interfaces between control system 106 and one or more external device interfaces (e.g., ports or application processors).

[0064] Interface system 104 may be configured to provide communication between components of device 101 (which may include wired or wireless communication, such as electrical communication, radio communication, etc.). In some such examples, interface system 104 may be configured to provide communication between control system 106 and ultrasonic fingerprint sensor 102, and between control system 106 and force sensor 110. According to some such examples, interface system 104 may couple at least a portion of control system 106 to ultrasonic fingerprint sensor 102 and force sensor 110, for example, via a conductive material (e.g., via conductive metal wires or traces). If device 101 includes ultrasonic transmitter 105 separate from ultrasonic receiver 103, interface system 104 may be configured to provide communication between at least a portion of control system 106 and ultrasonic transmitter 105. According to some examples, interface system 104 may be configured to provide communication between device 101 and other devices and / or humans. In some such examples, interface system 104 may include one or more user interfaces. In some examples, interface system 104 may include one or more network interfaces and / or one or more external device interfaces (such as one or more Universal Serial Bus (USB) interfaces or Serial Peripheral Interface (SPI)). In some implementations, device 101 may include a memory system. In some examples, interface system 104 may include at least one interface between control system 106 and memory system.

[0065] Device 101 can be used in a variety of different contexts, some of which are disclosed herein. For example, in some implementations, a mobile device may include at least a portion of device 101. In some implementations, a wearable device may include at least a portion of device 101. For example, a wearable device may be a bracelet, armband, wristband, ring, headband, or patch. In some implementations, control system 106 may reside in more than one device. For example, a portion of control system 106 may reside in a wearable device, while another portion of control system 106 may reside in another device (such as a mobile device (e.g., a smartphone)). In some such examples, interface system 104 may also reside in more than one device.

[0066] Figure 2A This is a flowchart providing example frames for some of the methods disclosed in this article. For example, Figure 2A The frame can be made of Figure 1B The apparatus 101 or a similar apparatus is used to perform this. As with other methods disclosed herein, Figure 2A The methods 200 outlined herein may include more or fewer boxes than those indicated. Furthermore, the boxes of the methods disclosed herein are not necessarily executed in the indicated order. In some examples, some of the method boxes disclosed herein may be executed concurrently.

[0067] According to this example, method 200 is a method of controlling a device including an ultrasonic fingerprint sensor. According to this implementation, block 203 relates to control (e.g., a control system via the device, such as...) Figure 1B The control system 106 of the device 101 shown is an ultrasonic fingerprint sensor for transmitting a first ultrasonic wave toward a target object in contact with a surface. The surface may be the surface of the ultrasonic fingerprint sensor or the surface of a device adjacent to the area where the ultrasonic fingerprint sensor resides.

[0068] In some examples, block 203 may relate to controlling the ultrasonic fingerprint sensor to transmit ultrasonic waves in the range of 1 MHz to 30 MHz. For example, the ultrasonic transmitter of the ultrasonic fingerprint sensor may be controlled to transmit a first ultrasonic wave.

[0069] According to some examples, the device may include a touch sensor system. In some such examples, the preceding process of method 200 may have involved a control system determining the position of a target object based on one or more signals received from the touch sensor system. In some such examples, block 203 may involve controlling an ultrasonic fingerprint sensor based on the finger position. However, in some alternative examples, the control system may be configured to determine the finger position based on one or more signals received from the ultrasonic fingerprint sensor and / or from a force sensor.

[0070] In this implementation, block 205 relates to receiving a first ultrasonic receiver signal from an ultrasonic fingerprint sensor. The first ultrasonic receiver signal includes a signal corresponding to the reflection of a first ultrasonic wave from a target object.

[0071] According to this implementation, block 207 relates to obtaining an estimate of a force exerted by a target object on the surface of the device or on the surface of a device including the device. In this example, the control system of the device is configured to obtain the force estimate. The device may or may not include a force sensor, depending on the specific implementation. If the device includes a force sensor, the force estimate may be based on a force sensor signal received from the force sensor.

[0072] In some examples (e.g., examples where the device does not include a force sensor), the force estimation may be based at least in part on the analysis of a first ultrasonic receiver signal. In some instances, the force estimation may be based at least in part on the analysis of a first fingerprint image corresponding to the first ultrasonic receiver signal. The force estimation may be based, for example, on the contact area of ​​the target object (e.g., the contact area of ​​a finger), the ridge-to-cavity ratio of the first fingerprint image, and / or the ridge distance. Some examples are disclosed herein and described below.

[0073] In this example, box 209 relates to determining at least one ultrasonic fingerprint sensor parameter modification based at least partially on the force. According to some examples, box 209 may relate to determining the ultrasonic fingerprint sensor parameter modification based at least partially on one or more other factors. Such factors may include, but are not limited to, image quality corresponding to the first ultrasonic receiver signal. In some examples, box 209 may relate to determining an image quality score based on one or more image quality metrics. In some examples, the image quality metric may be based at least partially on contrast. According to some examples, the image quality metric may be based at least partially on signal-to-noise ratio. In some implementations, the image quality metric may be based at least partially on the mean and / or standard deviation of the signal amplitude. In some examples, the image quality metric may be based at least partially on the skewness and / or kurtosis of the signal. In some implementations, the image quality metric may be based on all of the foregoing parameters. According to some such examples, box 209 may relate to determining the ultrasonic fingerprint sensor parameter modification based at least partially on whether the image quality score is less than a threshold and / or on the difference between the threshold and the image quality score. Here, box 211 relates to updating at least one setting of the ultrasonic fingerprint sensor based at least partially on the ultrasonic fingerprint sensor parameter modification.

[0074] Modifications to the ultrasonic fingerprint sensor parameters (such as) may include modifications to the gain value, the frequency of the transmitted ultrasonic waves, the range gating pulse delay, the range gating pulse window, and / or the bias conditions. Examples of these parameters are described below with reference to the accompanying drawings. According to some examples, determining the modification of the ultrasonic fingerprint sensor parameters (such as) may involve obtaining one or more new ultrasonic fingerprint sensor parameters from a data structure. For example, determining the modification of the ultrasonic fingerprint sensor parameters (such as) may involve obtaining one or more new ultrasonic fingerprint sensor parameters from a portion of a data structure corresponding to a force. This data structure may include a force value and the corresponding ultrasonic fingerprint sensor parameter.

[0075]

[0076] Table 1

[0077] Table 1 provides a simple example of a portion of such a data structure. Table 1 shows examples of parameters for an ultrasonic fingerprint sensor corresponding to a 1 Newton force, including a 25-volt voltage boost (VBOOST), a 6.5-volt bias voltage (DBIAS), a 1.5-µs integration time, a 1.25-µs distance gating pulse delay (RGD), and a 0.02-µs distance gating pulse window (RGW). See below for reference. Figure 6The discussion covers the meanings of the terms DBIAS, RGD, and RGW, along with illustrative examples. "Integration time" corresponds to the time interval during which a pixel is able to sense each frequency modulation burst. It is a good indicator of system latency. Voltage boost (VBOOST) refers to the boost voltage applied to the transmitter.

[0078] In this example, block 213 relates to controlling the ultrasonic fingerprint sensor to transmit a second ultrasonic wave toward a target object. According to this implementation, block 215 relates to receiving a second ultrasonic receiver signal from the ultrasonic fingerprint sensor. Here, the second ultrasonic receiver signal includes a signal corresponding to the reflection of the second ultrasonic wave from the target object.

[0079] According to this example, box 217 relates to performing an authentication process based at least in part on a first ultrasonic receiver signal received at box 205 and a second ultrasonic receiver signal received at box 215. In some instances, box 217 may relate to acquiring fingerprint image data corresponding to these signals. As used herein, the term "fingerprint image data" generally refers to data obtained from an ultrasonic receiver or data based on signals obtained from an ultrasonic receiver. In some instances, the fingerprint image data may at least in part correspond to a target object such as a finger that may include a fingerprint. The fingerprint image data may or may not be presented in a form that is human-recognizable as an image. For example, the fingerprint image data may be or may include a data structure in which values ​​are arranged and / or stored. In some examples, the values ​​may correspond to signals received from an ultrasonic fingerprint sensor, an optical sensor system, a capacitive sensor system, etc. In some examples, the fingerprint image data may correspond to signals received from a sensor system during a time window. In some instances, the fingerprint image data may correspond to signals received from a specific area, such as a fingerprint contact area.

[0080] In some examples, box 217 may involve extracting features from an ultrasonic receiver signal. The authentication process may be based at least in part on these features. According to some examples, these features may be fingerprint features, such as the location, orientation, and / or type of fingerprint minutiae. In some such examples, fingerprint image data may include indications of one or more fingerprint features detected in at least a portion of the signal from a sensor system (such as an ultrasonic fingerprint sensor). These fingerprint features may include one or more fingerprint ridge features and one or more fingerprint valley features. For example, these fingerprint features may be generated by a control system (such as...) Figure 1B The control system 106 is used for detection.

[0081] Signals indicating fingerprint ridge features are typically obtained from sensor pixels of an ultrasonic sensor, which respond to ultrasonic waves reflected from the platen / fingerprint ridge interface. Signals indicating fingerprint valley features are also typically obtained from sensor pixels, which respond to ultrasonic waves reflected from the platen / fingerprint valley interface. Reflections from the platen / fingerprint valley interface are generally from the platen / air interface, while reflections corresponding to the area where the fingerprint ridge contacts the platen are generally from the platen / skin interface. Because the platen / fingerprint valley interface generally has a much higher acoustic impedance contrast than the platen / fingerprint ridge interface, it will generally produce relatively higher amplitude reflections.

[0082] Figure 2B An example cross-sectional view of an apparatus capable of performing at least some of the methods described herein is shown. For example, apparatus 101 may be capable of performing the methods described herein. Figure 2A The method described. Here, device 101 is the one referred to above. Figure 1B An example of the described device 101. Similar to other implementations shown and described herein, Figure 2B The types of components, their arrangement, and their dimensions described herein are merely examples.

[0083] Figure 2B An example of ultrasonic waves reflected from a target object is shown. In this example, the target object is a finger 206 that is penetrated by the transmitted ultrasonic wave 214. In this example, the transmitted ultrasonic wave 214 is the one described above. Figure 2A Examples of the first and second ultrasonic waves described in 203 and 213. Here, the reflected ultrasonic wave 216 received by at least a portion of the ultrasonic receiver 103 is as described above. Figure 2A Examples of the reflection of the first and second ultrasonic waves from the target object, as described in 205 and 217.

[0084] In this example, the ultrasound waves are transmitted by an ultrasound transmitter 105, which is separate from the ultrasound receiver 103. Figure 2B In the example shown, at least a portion of device 101 includes an ultrasonic transmitter 105 that can be used as a plane wave ultrasonic transmitter. In some implementations, the ultrasonic transmitter 105 may include a piezoelectric transmitter layer, wherein transmitter excitation electrodes are arranged on each side of the piezoelectric transmitter layer. In some examples, the ultrasonic transmitter 105 may be or may include a piezoelectric layer, such as a PVDF polymer layer or a PVDF-TrFE copolymer layer. In this example, electrode layer 222 resides between the ultrasonic transmitter 105 and passivation layer 224. According to some examples, the control system ( Figure 2B (not shown in the image) (such as...) Figure 1BThe control system 106 can control the ultrasonic transmitter 105 based on the electrical signal provided via the electrode layer 222.

[0085] In this example, the ultrasonic receiver 103 serves as an ultrasonic receiver array. In some such examples, the ultrasonic receiver 103 may include an array of pixel input electrodes and sensor pixels partially formed by a TFT circuit system, a piezoelectric receiver layer 220 overlaid with a piezoelectric material (such as PVDF or PVDF-TrFE), and an upper electrode layer (which will sometimes be referred to herein as a receiver bias electrode) located on the piezoelectric receiver layer. Examples of suitable ultrasonic transmitters and ultrasonic receiver arrays are described below.

[0086] However, in alternative implementations, the ultrasonic receiver 103 and the ultrasonic transmitter 105 may be combined in an ultrasonic transceiver array. For example, in some implementations, the ultrasonic sensor 102 may include a piezoelectric receiver layer, such as a PVDF polymer layer or a PVDF-TrFE copolymer layer. In some implementations, a single piezoelectric layer may be used as an ultrasonic transmitter. In some examples, a single piezoelectric layer may be used as both a transmitter and a receiver. In some implementations, other piezoelectric materials, such as aluminum nitride (AlN) or lead zirconate titanate (PZT), may be used in the piezoelectric layer. In some examples, the ultrasonic sensor 102 may include an array of ultrasonic transducer elements, such as a piezoelectric micromechanical ultrasonic transducer (PMUT) array, a capacitive micromechanical ultrasonic transducer (CMUT) array, etc. In some such examples, a piezoelectric receiver layer, PMUT elements in a single-layer PMUT array, or CMUT elements in a single-layer CMUT array may be used as both an ultrasonic transmitter and an ultrasonic receiver.

[0087] In this example, the transmitted ultrasonic waves 214 are transmitted from the ultrasonic transmitter 105 through the sensor stack 218 into the overlying finger 206. In some examples, the individual layers of the sensor stack 218 may include one or more substrates of glass or other materials substantially transparent to visible light, such as plastic or sapphire. In this example, the sensor stack 218 includes a substrate 210 coupled to a light source system (not shown), which, according to some implementations, may be a backlight for a display. In alternative implementations, the light source system may be coupled to a front light. Accordingly, in some implementations, the light source system may be configured to illuminate the display and the target object. Other implementations may not include substrate 210.

[0088] In this implementation, substrate 210 is coupled to thin-film transistor (TFT) substrate 212 for ultrasonic receiver 103. According to this example, piezoelectric receiver layer 220 covers sensor pixels 202a of ultrasonic receiver 103, and pressure plate 225 covers piezoelectric receiver layer 220. Accordingly, in this example, device 101 is capable of transmitting ultrasonic waves 214 via one or more substrates of sensor stack 218, which includes ultrasonic receiver 103 having TFT substrate 212 and pressure plate 225, which can also be considered as substrates. In an alternative example, sensor pixels 202a and 202b of ultrasonic receiver 103 may reside between substrate 212 and ultrasonic transmitter 105.

[0089] According to this example, a force sensor is integrated into the circuitry of an ultrasonic fingerprint sensor. In this implementation, sensor pixel 202b is the force sensor pixel of the force sensor.

[0090] In some implementations, sensor pixels 202a and 202b may be transparent, partially transparent, or substantially transparent, so that device 101 may be able to transmit light from the light source system through the elements of ultrasonic receiver 103. In some implementations, ultrasonic receiver 103 and associated circuitry may be formed on or within a glass, plastic, or silicon substrate.

[0091] Refer again Figure 2A In some implementations, method 200 may involve performing an anti-spoofing process. According to some implementations, method 200 may involve additional processes depending on the outcome of the authentication and / or anti-spoofing processes (if any) at box 217. For example, if the authentication and / or anti-spoofing processes (if any) successfully terminate, the control system may allow access to the device and / or secure area. In some such instances, the control system may unlock a mobile device, laptop computer, door, car, or another device.

[0092] In some instances, the anti-spoofing process may also be based at least in part on a first fingerprint image corresponding to a first ultrasonic receiver signal and / or a second fingerprint image corresponding to a second ultrasonic receiver signal. Some implementations may involve an anti-spoofing process based at least in part on at least one measured or estimated force.

[0093] Figure 3 A fingerprint image and an example of stress are shown. The indicated forces are in grams per force (gF). Although a gram is actually a unit of mass, not force, for convenience and to save language, the unit of force or pressure may be referred to as "gram" in the discussion of this invention. Figure 3 In Chinese, "RT" means right thumb, while "LT" means left thumb.

[0094] exist Figure 3 In these images, the relatively darker areas correspond to regions with relatively high amplitude reflection. As mentioned above, relatively high amplitude reflection generally corresponds to the air / plate interface, or more generally to the air / outer surface interface, which occurs when fingerprint ridges are adjacent to the outer surface. The relatively high amplitude reflection occurs because the air / outer surface interface has a higher acoustic impedance contrast than the skin / outer surface interface that occurs when fingerprint ridges are in contact with the outer surface.

[0095] As can be seen, image 301 has a much higher percentage of dark areas than image 305. This is because image 301 was acquired when a normal right thumb pressed the outer surface with a force of 10 grams, while image 305 was acquired when a normal right thumb pressed the outer surface with a force of 300 grams. In the latter case, the fingerprint ridges respond to the applied force by exhibiting a laterally expanded appearance, partly because portions of the fingerprint ridges that were not in contact with the surface when a lower force was applied are now pressed against the surface. As a result, image 305 was acquired when a relatively high percentage of the image corresponds to the fingerprint ridge / outer surface interface (which corresponds to the lighter areas of image 305).

[0096] For oily fingers, the above effects may be less noticeable. For example, refer to... Figure 3 In the example of the "oily finger" of the right thumb, it can be observed that although image 309 has a slightly higher percentage of dark areas compared to image 311, the difference is almost as large as the difference between images 301 and 305.

[0097] like Figure 3 As shown, some fingerprint image features may become clearer when greater force is applied. For example, terminal 303 is shown more clearly in image 305 compared to image 301.

[0098] However, other fingerprint features may become clearer when less force is applied. For example, wrinkle 307a is prominent in image 301 but not in image 305. Similarly, wrinkle 307b is easily observed in image 313 but not in image 315.

[0099] According to some publicly available implementations, the anti-spoofing process can be based on one or more features or other aspects of the fingerprint image that change with pressure. In some such implementations, the fingerprint registration process may involve acquiring ultrasonic fingerprint image data of the same portion of the finger under multiple different forces. For example, after acquiring a first set of ultrasonic fingerprint image data from a portion of the user's finger with a first measured (or estimated) force, the user may be prompted (e.g., via text and / or images provided on a display and / or audio prompts provided via a speaker) to press the same portion of the finger more firmly against the outer surface of the ultrasonic fingerprint sensor surface (or the device surface adjacent to the area where the ultrasonic fingerprint sensor resides). A second force may be measured (or estimated), and a second set of ultrasonic fingerprint image data may be acquired from the same portion of the user's finger. In some instances, the process may be repeated to acquire third, fourth, and / or fifth sets of ultrasonic fingerprint image data when the finger is pressed against the outer surface with a third, fourth, and / or fifth measured or estimated force. According to some implementations, the process may be repeated for multiple fingers of the user during the registration process.

[0100] As mentioned above Figure 3 The described registration process, involving the acquisition of fingerprint image data when two or more different forces are applied, can reveal finger features that are difficult to fake. For example, if a hacker possesses an image like image 305, the hacker will not be able to successfully represent the crease 307a shown in image 301. Similarly, if a hacker possesses image 315, the hacker will not be able to successfully represent the crease 307b shown in image 313.

[0101] During the "runtime" operation following successful registration, the anti-spoofing process may be based at least in part on data acquired during the registration process. In some instances, the anti-spoofing process may also be based at least in part on a first fingerprint image of the target object corresponding to a first ultrasonic receiver signal (such as the first ultrasonic receiver signal received in box 205 of FIG. 2) and / or a second fingerprint image of the target object corresponding to a second ultrasonic receiver signal (such as the second ultrasonic receiver signal received in box 215 of FIG. 2). Some anti-spoofing processes may involve acquiring a third fingerprint image of the target object corresponding to a third ultrasonic receiver signal. In some instances, the target object may be a finger. In some implementations, the anti-spoofing process may be based at least in part on a measured or estimated force of the finger pressed against an outer surface at the time the ultrasonic receiver signal is acquired.

[0102] For example, some examples of method 200 may involve measuring and / or estimating a first force corresponding to a first ultrasound receiver signal and measuring and / or estimating a second force corresponding to a second ultrasound receiver signal. In some such examples, method 200 may involve controlling a display and / or a speaker to provide a prompt to apply a different force after the first force has been measured and / or estimated.

[0103] Figure 4A , 4B Figures 4C and 4C show examples of graphs that indicate changes in a fingerprint image based on variations in the applied finger pressure. Figure 4A An example is shown showing how the contact area of ​​different fingers changes with increasing pressure. Figure 4A The curves in the figure correspond to the left and right thumbs (LT and RT) of three different individuals (J, M, and H). In these examples, J_RT and J_LT correspond to normal fingers, M_RT and M_LT correspond to worn fingers, and H_RT and H_LT correspond to dry fingers. Figure 4A As can be seen from the above description, the contact area generally increases with increasing pressure. However, each finger responds to increasing pressure in a different way. For example, it can... Figure 4A As can be seen, the contact areas of these fingers differ substantially at the same pressure level. For example, the H_RT curve indicates slightly more than 50% contact area at an applied pressure of 100 grams, while the curves M_RT, M_LT, and H_LT indicate slightly less than 30% contact area at an applied pressure of 100 grams.

[0104] exist Figure 4A It can also be seen that the slopes of the H_RT and H_LT curves increase as the pressure increases from 200 g to 300 g. Both curves are concave upwards. In contrast, the slope of the J_LT curve is generally constant in the pressure range of 10 to 300 g. In this pressure range, the slope of the J_RT curve changes significantly, resulting in a concave downwards curve. Figure 4B The curve shown illustrates the variation of the aforementioned contact area with pressure. For example... Figure 4A and 4B As shown, these variations are characteristics of a specific finger and can vary significantly between individuals and between fingers of the same individual.

[0105] Figure 4C An example is shown of how the ridge ratio of a fingerprint image varies with the applied pressure. Fingerprint “gaps” are also referred to as fingerprint valleys in this paper. Figure 4C The curves in the figure correspond to the left and right thumbs (L and R) of individuals J, M, and H. Figure 4C The values ​​and slope variations shown are characteristics of a specific finger. Both values ​​and slopes can vary significantly between individuals and between fingers of the same individual.

[0106] Based on some examples, the anti-spoofing process may involve estimating the material properties of the target object. In some such examples, the material properties of the target object may be based on... Figure 4A , 4B And the slope of one or more curves shown in 4C. For example, Figure 4A The slope in the graph indicates the degree of finger deformation as the applied force increases. The stiffer the finger, the less deformation occurs. Generally, there is a positive correlation between finger stiffness and dryness. By tracking this information, material properties such as Young's modulus and Poisson's ratio can be further derived. Under the same nominal force, the change in the contact area indicates the strain on the skin. The strain-stress ratio can be calculated to indicate the relative value of Young's modulus. The ratio of lateral strain (which can be estimated from the change in the contact area) to axial strain (which can be estimated from depth information extracted from a subcutaneous scan) is used to obtain Poisson's ratio.

[0107] Figure 5A , 5B Figures 5C and 5D illustrate examples of force sensors integrated into a circuit system of an ultrasonic fingerprint sensor. Figure 5A A cross-section of an example metal-oxide-semiconductor field-effect transistor (MOSFET) is shown, in this example, the MOSFET is a complementary metal-oxide-semiconductor (CMOS). Figure 5A The image shows only a single n-type thin-film transistor (NTFT) and a single p-type TFT (PTFT). However, in actual ultrasonic fingerprint sensors with this type of structure, there are typically tens of thousands of NTFT / PTFT pairs.

[0108] Depending on the specific implementation, Figure 5A The portions of the stacked conductive layers shown can be used as pressure sensors. In some examples, a portion of the pixel electrode layer can be used as a pressure sensor. In other examples, a portion of the source / drain (S / D) electrode layer can be used as a pressure sensor. According to some implementations, a portion of the gate electrode layer can be used as a pressure sensor. In some examples, a portion of the polysilicon (poly-Si) layer can be used as a pressure sensor. In some implementations, the polysilicon layer may include low-temperature polysilicon (LTPS).

[0109] Figure 5B An example top view of an ultrasonic fingerprint sensor is shown. In this example, the sensor pixel array and sensor peripheral driver each include, for example, Figure 5A The diagram illustrates several examples of CMOS. In one example, a portion of the pixel electrode layer is configured as a conductive portion for a pressure sensor. According to this implementation, pins 1, 2, and the connection portion 503 of the pixel electrode layer are configured as pressure sensor electrodes. In this example, other pins (which are located in...) Figure 5A The pin labeled "Sensor Operation Pin to ASIC" can be used to connect the ultrasonic fingerprint sensor to the corresponding part of the control system. The control system may or may not include an ASIC, depending on the specific implementation. According to some examples, the pressure sensor may also include a portion of one or more layers of piezoelectric material included in the ultrasonic fingerprint sensor.

[0110] Figure 5C It shows Figure 5B The image shows a perspective view of an ultrasonic fingerprint sensor. Figure 5C It also shows with Figure 5D The cross-section line A / A' corresponding to the cross-section shown in the figure.

[0111] Figure 5D Through Figure 5C The image shows a simplified cross-section of an ultrasonic fingerprint sensor. (Compared to...) Figure 5A similar, Figure 5D The example shows only a single NTFT / PTFT pair, while actual ultrasonic fingerprint sensors with this type of structure typically have many NTFT / PTFT pairs. In this example, the cross-sectional line A / A' is shown passing through the pixel electrode layer and includes both the pixel electrode and the pressure sensor electrode. An alternative example, in which a portion of a deeper layer (such as a portion of a source / drain (S / D) electrode layer, a portion of a gate electrode layer, or a portion of a polysilicon layer) is used to form the pressure sensor electrode, could include vias connecting the deeper layer to chip pins or other corresponding portions of the control system.

[0112] As mentioned elsewhere in this document, in some examples, at least one ultrasonic fingerprint sensor parameter modification may be based at least in part on a measured or estimated force exerted by a target object on the surface of the ultrasonic fingerprint sensor or on a device surface adjacent to the area where the ultrasonic fingerprint sensor resides. In some examples, the modified parameters may include a gain value, the frequency of the transmitted ultrasonic wave, a distance gating pulse delay, a distance gating pulse window, or a bias condition. Examples of these parameters will now be referred to. Figure 6 Describe it, etc.

[0113] Figure 6 Examples of capture time delay and capture time window are shown based on some implementations. Figure 6 An example, referred to herein as "DBIAS sampling," is provided, in which the receiver bias voltage level changes as the signal is sampled. In this example, the receiver bias voltage level also changes as the signal is transmitted. Figure 6In this context, the capture time delay is denoted as "RGD," an abbreviation for "range strobe pulse delay," and the capture time window is denoted as "RGW," an abbreviation for "range strobe pulse window." Figure 602a shows the transmitted signal 604 initiated at time t0. The transmitted signal 604 can be, for example, an ultrasonic pulse. For instance, an ultrasonic pulse could correspond to the above reference... Figure 2A The “first ultrasound” or “second ultrasound” described in boxes 203 and 213.

[0114] Graph 602b illustrates an example of a first acquisition time delay RGD1 and a first acquisition time window RGW1. The received wave 606a represents the reflected ultrasound waves received by the ultrasonic sensor array and sampled after the first acquisition time delay RGD1 and during the first acquisition time window RGW1. In some examples, the acquisition time delay can range from about 10 nanoseconds to about 20,000 nanoseconds or greater. In some implementations, the first acquisition time window can be in the range of 5 to 50 nanoseconds, or approximately 5 to 50 nanoseconds. In some examples, "approximately" or "about" may mean within ±5%, while in other examples, "approximately" or "about" may mean within ±10%, ±15%, or ±20%. However, in some implementations, the first acquisition time window may exceed 50 nanoseconds.

[0115] According to some examples, device 101 may include a pressure plate. The pressure plate may be positioned relative to ultrasonic sensor system 102. For example, the pressure plate may be positioned adjacent to and / or attached to ultrasonic sensor system 102. In some such examples, a first capture time delay may correspond to the expected amount of time for ultrasonic waves reflected from the surface of the pressure plate to be received by at least a portion of ultrasonic sensor system 102. Accordingly, the first capture time delay and a first capture time window may be selected to capture one or more fingerprint features of a target object placed on the surface of the pressure plate. For example, in some implementations of a pressure plate with a thickness of about 400 micrometers, the capture time delay (RGD) may be set to about 1000 nanoseconds, and the capture time window (RGW) may be set to about 50 nanoseconds.

[0116] Figure 7 Examples of capture time delay and capture time window are shown based on some alternative implementations. Figure 7 An example, referred to herein as "interpeak sampling," is provided. Unlike DBIAS sampling, in the case of interpeak sampling, the receiver bias voltage level (in...) Figure 7 The symbol marked as Rbias remains unchanged when the signal is sampled.

[0117] Figure 7 The specific values ​​mentioned, including time and voltage values, are provided as examples only and are not intended to be limiting. Figure 7 As mentioned above, this peak-to-peak example involves sampling based on the time interval between the received negative signal peak 705 and the received positive signal peak 710. According to this example, RGW corresponds to the time interval between the received negative signal peak 705 and the received positive signal peak 710. In this example, RGW corresponds to half a cycle of the drive frequency; in some examples, the drive frequency can be in the range of 10 to 200 ns.

[0118] This example of interpeak sampling involves two additional control signals, which in Figure 7 The peaks are labeled S1 and S2. In this example of inter-peak sampling, RGW and RGD are used to control when sampling occurs. However, the definition of RGD in this example differs from... Figure 6 The definition of the DBIAS sampling example differs from that in this example of inter-peak sampling. In this example, RGD changes as RGW changes. In other words, RGD is related to the timing of the received positive signal peak 710. One advantage of inter-peak sampling is that it can reduce frequency modulation burst voltage, which in turn leads to lower costs on electronic components, better reliability, and so on.

[0119] Figure 8 Examples of acquisition time delays and acquisition time windows based on some implementations of inter-peak sampling are shown. Curve 850a shows the transmitted signal 860 initiated at time t0. The transmitted signal 860 can be, for example, an ultrasonic pulse. For example, an ultrasonic pulse can correspond to the above reference. Figure 2A The “first ultrasound” or “second ultrasound” described in boxes 203 and 213. In an alternative example, multiple ultrasound pulses may be transmitted.

[0120] Curve 850b shows the first capture time delay RGD C and the first capture time window RGW C Example. The received wave 870a represents the wave received by the ultrasonic sensor array and delayed by RGD in the first acquisition time. C Then, during the first capture time window, RGW C The captured reflected ultrasound waves are sampled during the period. In some examples, the capture time delay can range from about 10 nanoseconds to about 20,000 nanoseconds or greater. In some implementations, the first capture time window can be in the range of 5 to 50 nanoseconds, or approximately 5 to 50 nanoseconds. In some examples, "approximately" or "about" may mean within ±5%, while in other examples, "approximately" or "about" may mean within ±10%, ±15%, or ±20%. However, in some implementations, the first capture time window may exceed 50 nanoseconds.

[0121] Figure 9Figures 1 and 10 illustrate examples of image quality changes after modifications to the ultrasonic fingerprint sensor parameters. In these examples, the ultrasonic fingerprint sensor parameter modifications are based, at least in part, on indications that the measured or estimated force exerted by the target object on the surface of the ultrasonic fingerprint sensor or on the device surface adjacent to the area where the ultrasonic fingerprint sensor resides is below a threshold. In these examples, the ultrasonic fingerprint sensor parameter modifications are also based on a fingerprint image quality metric. In this example, the fingerprint image quality metric is the signal-to-noise ratio (SNR).

[0122] Reference Figure 9 In this example, target images 907a and 907b are acquired via an ultrasonic fingerprint sensor using the same input fingerprint sensor parameters except for DBIAS. In this example, a 3.5-volt DBIAS setting produces target image 907a with an SNR of 3.7, while a 5-volt DBIAS setting produces target image 907b with an SNR of 5.5. In these examples, increasing the DBIAS setting results in fingerprint image 907b having higher image quality than fingerprint image 907a.

[0123] Reference Figure 10A Based on the same input fingerprint sensor parameters except VBOOST, target images 1007a and 1007b are acquired via an ultrasonic fingerprint sensor. A lower VBOOST results in a smaller excitation voltage, and therefore a weaker backhaul signal. If the signal is below a threshold, VBOOST can be adjusted to boost the signal. Figure 10A In the example shown, VBOOST is increased from 23 volts to 30 volts while keeping all other ultrasonic fingerprint sensor parameters unchanged, and SNR is increased from 4.8 to 6.0.

[0124] Figure 10B This is a graph illustrating the change in received signal strength based on variations in the force applied to the ultrasonic sensor by a finger, using several examples. Figure 10B In the depicted example, the ultrasonic sensor system used for scanning is Figure 2B The illustration shows a typical type of ultrasonic sensor system. In this example, the ultrasonic sensor system 102 includes a piezoelectric layer (e.g., an ultrasonic transmitter 105) and an electrode layer 222 adjacent to one side of the piezoelectric layer. In these examples, the ultrasonic signal corresponding to the ultrasonic scan is acquired via "direct sampling": instead of reading the signal from each individual sensor pixel of the ultrasonic receiver 103, the reflected ultrasonic wave is received via the electrode layer 222. Figure 10B Each data point shown corresponds to the average of six independent trials. Figure 10B The signal strength shown indicates the signal reflection from the finger / plate interface. The greater the contact force, the larger the contact area corresponding to the fingerprint ridge, and therefore the smaller the returned signal from the finger / plate interface.

[0125] Figure 11 A 4×4 pixel array for an ultrasonic fingerprint sensor is representatively depicted. Each sensor pixel 1134 may be associated, for example, with a local region of piezoelectric sensor material (PSM), a pixel input electrode 1137, a peak detection diode (D1), and a readout transistor circuitry (M3); many or all of these elements may be formed on or in a substrate to form pixel circuitry 1136. In practice, the local region of the piezoelectric sensor material of each sensor pixel 1134 can convert the received ultrasonic energy into electrical charge. The peak detection diode D1 can record the maximum amount of charge detected by the local region of the piezoelectric sensor material PSM. Each row of the pixel array 1135 can then be scanned, for example, via a row selection mechanism, a gate driver, or a shift register, and the readout transistor circuitry M3 of each column can be triggered to allow the amplitude of the peak charge of each sensor pixel 1134 to be read by additional circuitry (e.g., a multiplexer and an A / D converter). Pixel circuitry 1136 may include one or more TFTs to allow gating, addressing, and resetting of the sensor pixels 1134.

[0126] Each pixel circuit 1136 provides a small amount of information about the object detected by the ultrasonic fingerprint sensor. Although for ease of explanation... Figure 11 The example shown has a relatively coarse resolution, but ultrasonic sensors with resolutions on the order of 500 pixels per inch or higher can be configured with appropriately scaled structures. The detection area of ​​an ultrasonic fingerprint sensor can be selected depending on the intended target. For example, the detection area can range from approximately 8mm x 3mm, 5mm x 5mm, or 9mm x 4mm 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 appropriately used for the target object.

[0127] Figure 12A An example exploded view of an ultrasonic fingerprint sensor is shown. In this example, the ultrasonic fingerprint sensor 1200a includes an ultrasonic transmitter 20 and an ultrasonic receiver 30 located below a pressure plate 40. According to some implementations, the ultrasonic receiver 30 may be… Figure 1B The example shown is the ultrasonic receiver 103 as described above. In some implementations, the ultrasonic transmitter 20 may be... Figure 1BAn example of the ultrasonic transmitter 105 shown and described above. The ultrasonic transmitter 20 may include a substantially planar piezoelectric transmitter layer 22 and may be configured to function as a plane wave generator. Ultrasonic waves can be generated by applying a voltage to the piezoelectric layer, depending on the applied signal, to cause the layer to expand or contract, thereby generating a plane wave. In this example, the control system 106 may be configured to cause a voltage that can be applied to the planar piezoelectric transmitter layer 22 via a first transmitter electrode 24 and a second transmitter electrode 26. In this way, ultrasonic waves can be generated by changing the thickness of the layer via the piezoelectric effect. The generated ultrasonic waves can travel toward a finger (or other object to be detected), thus passing through the pressure plate 40. A portion of the wave that is not absorbed or transmitted by the object to be detected can be reflected so that it is returned through the pressure plate 40 and received by the ultrasonic receiver 30. The first and second transmitter electrodes 24 and 26 may be metallized electrodes, for example, metal layers covering opposite sides of the piezoelectric transmitter layer 22.

[0128] The ultrasonic receiver 30 may include an array of sensor pixel circuits 32 disposed on a substrate 34 (which may also be referred to as a backplane) and a piezoelectric receiver layer 36. In some implementations, each sensor pixel circuit 32 may include one or more TFT-based or silicon-based elements, electrical interconnect traces, and in some implementations, one or more additional circuit elements (such as diodes, capacitors, etc.). Each sensor pixel circuit 32 may be configured to convert surface charges generated by the piezoelectric receiver layer 36 adjacent to the pixel circuit into electrical signals. Each sensor pixel circuit 32 may include a pixel input electrode 38 electrically coupling the piezoelectric receiver layer 36 to the sensor pixel circuit 32.

[0129] In the described implementation, the receiver bias electrode 39 is arranged on the side of the piezoelectric receiver layer 36 adjacent to the pressure plate 40. The receiver bias electrode 39 may be a metallized electrode and may be grounded or biased to control which signals can be transmitted to the array of sensor pixel circuits 32. Ultrasonic energy reflected from the exposed (top) surface of the pressure plate 40 can be converted into surface charge by the piezoelectric receiver layer 36. The generated surface charge can be coupled to the pixel input electrode 38 and the underlying sensor pixel circuit 32. The charge signal can be amplified or buffered by the sensor pixel circuit 32 and provided to the control system 106.

[0130] The control system 106 may 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 106 may operate substantially as described above. For example, the control system 106 may be configured to process amplified signals received from the sensor pixel circuit 32.

[0131] The control system 106 may be configured to control the ultrasonic transmitter 20 and / or the ultrasonic receiver 30 to acquire ultrasonic data, which may include fingerprint data. According to some implementations, the control system 106 may be configured to provide functionality as described herein.

[0132] Regardless of whether the ultrasonic fingerprint sensor 1200a includes a separate ultrasonic transmitter 20, in some implementations, the control system 106 may be configured to acquire attribute information from ultrasonic data. In some examples, the control system 106 may be configured to control access to one or more devices based at least in part on the attribute information. The ultrasonic fingerprint sensor 1200a (or associated devices) may include a memory system containing one or more memory devices. In some implementations, the control system 106 may include at least a portion of the memory system. The control system 106 may be configured to acquire attribute information from ultrasonic data and store that attribute information in the memory system. In some implementations, the control system 106 may be configured to capture a fingerprint image, acquire attribute information from the fingerprint image, and store the attribute information acquired from the fingerprint image (which may be referred to herein as fingerprint image information) in the memory system. According to some examples, the control system 106 may be configured to capture a fingerprint image, acquire attribute information from the fingerprint image, and store the attribute information acquired from the fingerprint image, even when the ultrasonic transmitter 20 is kept in an "off" state.

[0133] In some implementations, the control system 106 may be configured to operate the ultrasonic fingerprint sensor 1200a in either ultrasonic imaging mode or force sensing mode. In some implementations, the control system may be configured to keep the ultrasonic transmitter 20 in an "off" state when operating the ultrasonic fingerprint sensor in force sensing mode. The ultrasonic receiver 30 may be configured to function as a force sensor when the ultrasonic fingerprint sensor 1200a is operating in force sensing mode. In some implementations, the control system 106 may be configured to control other devices, such as display systems, communication systems, etc. In some implementations, the control system 106 may be configured to operate the ultrasonic fingerprint sensor 1200a in capacitive imaging mode.

[0134] The pressure plate 40 can be any suitable material that can be acoustically coupled to the receiver, examples of which include plastics, ceramics, sapphire, metals, and glass. In some implementations, the pressure plate 40 can be a cover plate, such as a cover glass or lens glass for a display. Particularly when using the ultrasonic transmitter 20, fingerprint detection and imaging can be performed with a relatively thick pressure plate (e.g., 3 mm or more) if needed. However, for implementations where the ultrasonic receiver 30 is configured to image fingerprints in force detection mode or capacitance detection mode, a thinner and relatively more compatible pressure plate 40 may be desired. According to some such implementations, the pressure plate 40 can comprise 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 micrometers thick or even less than 10 micrometers thick.

[0135] Examples of piezoelectric materials that can be used to form the piezoelectric receiver layer 36 include piezoelectric polymers with suitable acoustic properties (e.g., acoustic impedance between about 2.5 MNayl and 5 MNayl). 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 (molar percentage) PVDF-TrFE, 70:30 PVDF-TrFE, 80:20 PVDF-TrFE, and 90:10 PVDR-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).

[0136] The thickness of each of the piezoelectric transmitter layer 22 and the piezoelectric receiver layer 36 can be selected to suit the generation and reception of ultrasonic waves. In one example, the PVDF planar piezoelectric transmitter layer 22 is approximately 28 μm thick, and the PVDF-TrFE receiver layer 36 is approximately 12 μm thick. Example frequencies of the ultrasonic waves can range from 5 MHz to 30 MHz, where the wavelength is on the order of millimeters or smaller.

[0137] Figure 12B An exploded view of an alternative example of an ultrasonic fingerprint sensor is shown. In this example, the piezoelectric receiver layer 36 has been formed as a discrete element 37. Figure 12BIn the illustrated implementation, each of the discrete elements 37 corresponds to a single pixel input electrode 38 and a single sensor pixel circuit 32. However, in an alternative implementation of the ultrasonic fingerprint sensor 1200b, there is not necessarily a one-to-one correspondence between each discrete element 37, single pixel input electrode 38, and single sensor pixel circuit 32. For example, in some implementations, multiple pixel input electrodes 38 and sensor pixel circuits 32 may exist for a single discrete element 37.

[0138] Figure 12A and 12B An example arrangement of the ultrasonic transmitter and receiver in an ultrasonic fingerprint sensor is shown, although other arrangements are possible. For example, in some implementations, the ultrasonic transmitter 20 may be above the ultrasonic receiver 30 and thus closer to the object(s) to be detected. In some implementations, the ultrasonic transmitter may be included in an ultrasonic sensor array (e.g., a single-layer transmitter and receiver). In some implementations, the ultrasonic fingerprint sensor may include an acoustic delay layer. For example, an acoustic delay layer may be incorporated into the ultrasonic fingerprint sensor between the ultrasonic transmitter 20 and the ultrasonic receiver 30. The acoustic delay layer may be used to adjust the timing of the ultrasonic pulses and simultaneously electrically insulate the ultrasonic receiver 30 from the ultrasonic transmitter 20. The acoustic delay layer may have a substantially uniform thickness, wherein the material used for the delay layer and / or the thickness of the delay layer are selected to provide a desired delay in terms of the time it takes for reflected ultrasonic energy to reach the ultrasonic receiver 30. Doing so allows the time range of energy pulses carrying information about the object by means of reflection from the object to reach the ultrasonic receiver 30 during the time range during which energy reflected from other parts of the ultrasonic fingerprint sensor is unlikely to be arriving at the ultrasonic receiver 30. In some implementations, substrate 34 and / or pressure plate 40 can be used as an acoustic delay layer.

[0139] Figure 12C An exploded view of an example ultrasonic fingerprint sensor is shown. In this example, the ultrasonic fingerprint sensor 1200c includes an ultrasonic transceiver array 50 below a pressure plate 40. Depending on some implementations, the ultrasonic transceiver array 50 can be used as... Figure 1BBoth the ultrasonic receiver 103 and the ultrasonic transmitter 105 shown and described above. The ultrasonic transceiver array 50 may include a substantially planar piezoelectric transceiver layer 56, which is configured to function as a plane wave generator. Ultrasonic waves can be generated by applying a voltage across the transceiver layer 56. The control system 106 may be configured to generate a transceiver excitation voltage, which may be applied to the piezoelectric transceiver layer 56 via one or more of the lower pixel input electrodes 38 or one or more of the upper transceiver bias electrodes 59. The generated ultrasonic waves can travel toward a finger or other object to be detected, thus passing through the pressure plate 40. The portion of the wave that is not absorbed or transmitted by the object may be reflected so that it is returned through the pressure plate 40 and received by the ultrasonic transceiver 50.

[0140] The ultrasonic transceiver array 50 may include an array of sensor pixel circuits 32 disposed on a substrate 34. In some implementations, each sensor pixel circuit 32 may include one or more TFT-based or silicon-based elements, electrical interconnect traces, and in some implementations, one or more additional circuit elements (such as diodes, capacitors, etc.). Each sensor pixel circuit 32 may include a pixel input electrode 38 electrically coupling the piezoelectric transceiver layer 56 to the sensor pixel circuit 32.

[0141] In the described implementation, the transceiver bias electrode 59 is arranged on the side of the piezoelectric transceiver layer 56 adjacent to the pressure plate 40. The transceiver bias electrode 59 may be a metallized electrode and may be grounded or biased to control which signals are generated and which reflected signals are transmitted to the array of sensor pixel circuits 32. Ultrasonic energy reflected from the exposed (top) surface of the pressure plate 40 can be converted into surface charge by the piezoelectric transceiver layer 56. The generated surface charge can be coupled to the pixel input electrode 38 and the underlying sensor pixel circuit 32. The charge signal can be amplified or buffered by the sensor pixel circuit 32 and provided to the control system 106.

[0142] The control system 106 may be electrically connected (directly or indirectly) to the transceiver bias electrode 59 and the sensor pixel circuitry 32 on the sensor substrate 34. In some implementations, the control system 106 may operate substantially as described above. For example, the control system 106 may be configured to process amplified signals received from the sensor pixel circuitry 32.

[0143] The control system 106 may be configured to control the ultrasonic transceiver array 50 to acquire ultrasonic data, which may include fingerprint data. According to some implementations, the control system 106 may be configured to provide functionality such as that described herein (e.g., functionality as described herein).

[0144] In other examples of ultrasonic fingerprint sensors with an ultrasonic transceiver array, the back side of the sensor substrate 34 may be directly or indirectly attached to the pressure plate 40 above it. In operation, ultrasonic waves generated by the piezoelectric transceiver layer 56 can pass through the sensor substrate 34 and the pressure plate 40, be reflected by the surface of the pressure plate 40, and return through the pressure plate 40 and the sensor substrate 34 before being detected by the sensor pixel circuit 32 on or within the substrate sensor 34.

[0145] As used in this article, the phrase “at least one” in a list of items refers to any combination of those items, including a single member. As an example, “at least one of a, b, or c” is intended to cover: a, b, c, ab, ac, bc, and abc.

[0146] The various descriptive 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. This interchangeability between hardware and software has been generally described in its functional form and is explained in the various descriptive 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.

[0147] Hardware and data processing means for implementing the various descriptive logics, logic blocks, modules, and circuits described in conjunction with the aspects disclosed herein may be implemented or executed using 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, discrete hardware components, or any combination thereof. 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, multiple microprocessors, one or more microprocessors cooperating with a DSP core, or any other such configuration. In some implementations, specific processes and methods may be executed by a circuit system dedicated to a given function.

[0148] In one or more aspects, the described functionality may be implemented in hardware, digital electronic circuit systems, computer software, firmware (including the structures disclosed herein and their structural equivalents), or any combination thereof. Implementation of the subject matter described herein 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 for execution by a data processing apparatus or for controlling the operation of a data processing apparatus.

[0149] If implemented in software, the functions can be stored or transmitted as one or more instructions or codes on or through a computer-readable medium (such as a non-transient medium). The processes of the methods or algorithms disclosed herein can be implemented in a processor-executable software module that can reside on a computer-readable medium. Computer-readable media include both computer storage media and communication media, including any medium that can be implemented to transfer a computer program from one location to another. Storage media can be any available medium accessible to a computer. By way of example, but not limitation, non-transient media can include RAM, ROM, EEPROM, CD-ROM or other optical disc storage, disk storage or other magnetic storage devices, or any other medium that can be used to store desired program code in the form of instructions or data structures and is accessible to a computer. Furthermore, any connection can also be aptly referred to as a computer-readable medium. As used herein, disk and disc include compact discs (CDs), laser discs, optical discs, digital multi-purpose discs (DVDs), floppy disks, and Blu-ray discs, where disks typically reproduce data magnetically and discs optically using lasers. The above combinations should also be included within the scope of computer-readable media. Furthermore, the operation of a method or algorithm may reside as one of code and instructions, or any combination or set of code and instructions, on machine-readable and computer-readable media that can be incorporated into a computer program product.

[0150] Various modifications to the implementations described in this disclosure may be apparent to those skilled in the art, and the general principles defined herein may be applied to other implementations without departing from the scope of this disclosure. Therefore, this disclosure is not intended to be limited to the implementations shown herein, but should be granted the broadest scope consistent with the claims, the principles disclosed herein, and the novel features. The term “exemplary” is used exclusively herein to mean “serving as an example, instance, or illustration.” Any implementation described herein as “exemplary” is not necessarily to be construed as superior to or better than other implementations.

[0151] Some 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 separately or in any suitable sub-combination in multiple implementations. Furthermore, although features may be described above as operating in certain combinations and even originally claimed in this way, one or more features from the claimed combination may be removed from that combination in some cases, and the claimed combination may be for sub-combinations or variations thereof.

[0152] Similarly, although the operations are depicted in a specific order in the accompanying drawings, this should not be construed as requiring such operations to be performed in the specific order shown or in sequential order, or requiring the execution of all described operations to achieve the desired result. In some environments, multitasking and parallel processing may be advantageous. Furthermore, the separation of the various system components in the implementations described above should not be construed as requiring such separation in all implementations, and it should be understood that the described program components and systems can generally be integrated together in a single software product or packaged into multiple software products. Additionally, other implementations also fall within the scope of the appended claims. In some cases, the actions recited in the claims can be performed in a different order and still achieve the desired result.

[0153] It will be understood that, unless 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 supporting sense, this disclosure generally contemplates and envisions that specific features of those complementary implementations may be selectively combined to provide one or more comprehensive but slightly different technical solutions. Therefore, it will be further appreciated that the above description is given by way of example only and may be modified in detail within the scope of this disclosure.

Claims

1. An apparatus comprising: Ultrasonic fingerprint sensor; as well as The control system is configured to: The ultrasonic fingerprint sensor is controlled to transmit a first ultrasonic wave toward a target object in contact with a surface, wherein the surface is the surface of the ultrasonic fingerprint sensor or the surface of a device adjacent to the area where the ultrasonic fingerprint sensor resides. The ultrasonic fingerprint sensor receives a first ultrasonic receiver signal, the first ultrasonic receiver signal including a signal corresponding to the reflection of the first ultrasonic wave from the target object; Obtain an estimate of the force exerted on the surface by the target object; At least one ultrasonic fingerprint sensor parameter modification is determined based, at least in part, on the force. At least one setting of the ultrasonic fingerprint sensor is updated based at least in part on the modification of the ultrasonic fingerprint sensor parameters; Control the ultrasonic fingerprint sensor to transmit a second ultrasonic wave toward the target object; Receives a second ultrasonic receiver signal from the ultrasonic fingerprint sensor, the second ultrasonic receiver signal including a signal corresponding to the reflection of the second ultrasonic wave from the target object; and The authentication process is performed at least in part based on the first ultrasonic receiver signal and the second ultrasonic receiver signal.

2. The apparatus of claim 1, wherein the modification of the at least one ultrasonic fingerprint sensor parameter includes at least one of the following: modification of gain value, modification of frequency of transmitted ultrasonic wave, modification of distance gating pulse delay, modification of distance gating pulse window, or modification of bias condition.

3. The apparatus of claim 1, wherein determining the at least one ultrasonic fingerprint sensor parameter modification involves obtaining at least one new ultrasonic fingerprint sensor parameter from a portion of a data structure corresponding to the force, the data structure including the force value and the corresponding ultrasonic fingerprint sensor parameter.

4. The apparatus of claim 1, wherein the estimation of the force is based at least in part on the analysis of the signal from the first ultrasonic receiver.

5. The apparatus of claim 1, wherein the estimation of the force is based at least in part on the analysis of a first fingerprint image corresponding to the first ultrasonic receiver signal.

6. The apparatus of claim 5, wherein the estimation of the force is based on one or more of the contact area, the ridge ratio, or the ridge distance of the first fingerprint image.

7. The apparatus of claim 1, further comprising a force sensor, wherein the estimation of the force is based at least in part on a force sensor signal received from the force sensor.

8. The apparatus of claim 7, wherein the force sensor is integrated into the circuitry of the ultrasonic fingerprint sensor.

9. The apparatus of claim 7, wherein the force sensor is separate from the ultrasonic fingerprint sensor.

10. The apparatus of claim 7, wherein the force sensor comprises one or more of a piezoresistive sensor, a capacitive sensor, or a polymer-based thin-film sensor.

11. The apparatus of claim 10, wherein the force sensor comprises the piezoresistive sensor, and wherein the piezoresistive sensor comprises one or more of silicon, metal, polycrystalline silicon, or glass.

12. The apparatus of claim 1, wherein the control system is further configured to perform an anti-spoofing process at least in part based on the force.

13. The apparatus of claim 12, wherein the anti-spoofing process is further based at least in part on a first fingerprint image corresponding to the first ultrasonic receiver signal or a second fingerprint image corresponding to the second ultrasonic receiver signal.

14. The apparatus of claim 12, wherein the anti-spoofing process involves estimating the material properties of a target object.

15. The apparatus of claim 1, wherein the control system is further configured to estimate a first force corresponding to the first ultrasonic receiver signal and to estimate a second force corresponding to the second ultrasonic receiver signal.

16. The apparatus of claim 15, further comprising a display, wherein the control system is further configured to control the display to provide a prompt to apply a different force after estimating the first force.

17. The apparatus of claim 1, wherein the ultrasonic fingerprint sensor includes an electrode layer adjacent to the ultrasonic transmitter layer, wherein the first ultrasonic receiver signal is acquired via the electrode layer, and wherein the estimation of the force is based at least in part on the analysis of the first ultrasonic receiver signal.

18. The apparatus of claim 1, wherein the apparatus is integrated into a mobile device.

19. A method for controlling an ultrasonic fingerprint sensor, the method comprising: The ultrasonic fingerprint sensor is controlled to transmit a first ultrasonic wave toward a target object in contact with a surface, wherein the surface is the surface of the ultrasonic fingerprint sensor or the surface of a device adjacent to the area where the ultrasonic fingerprint sensor resides. The ultrasonic fingerprint sensor receives a first ultrasonic receiver signal, the first ultrasonic receiver signal including a signal corresponding to the reflection of the first ultrasonic wave from the target object; Obtain an estimate of the force exerted on the surface by the target object; At least one ultrasonic fingerprint sensor parameter modification is determined based, at least in part, on the force. At least one setting of the ultrasonic fingerprint sensor is updated based at least in part on the modification of the ultrasonic fingerprint sensor parameters; Control the ultrasonic fingerprint sensor to transmit a second ultrasonic wave toward the target object; Receives a second ultrasonic receiver signal from the ultrasonic fingerprint sensor, the second ultrasonic receiver signal including a signal corresponding to the reflection of the second ultrasonic wave from the target object; and The authentication process is performed at least in part based on the first ultrasonic receiver signal and the second ultrasonic receiver signal.

20. The method of claim 19, wherein the modification of the at least one ultrasonic fingerprint sensor parameter includes at least one of the following: gain modification, frequency modification of the transmitted ultrasonic wave, distance gating pulse delay modification, distance gating pulse window modification, or bias condition modification.

21. The method of claim 19, wherein determining the at least one ultrasonic fingerprint sensor parameter modification involves obtaining at least one new ultrasonic fingerprint sensor parameter from a portion of a data structure corresponding to the force, the data structure including the force value and the corresponding ultrasonic fingerprint sensor parameter.

22. The method of claim 19, wherein the estimation of the force is based at least in part on the analysis of the signal from the first ultrasonic receiver.

23. The method of claim 19, wherein the estimation of the force is based at least in part on the analysis of a first fingerprint image corresponding to the first ultrasonic receiver signal.

24. The method of claim 23, wherein the estimation of the force is based on one or more of the contact area, the ridge-to-cavity ratio, or the ridge distance of the first fingerprint image.

25. The method of claim 19, wherein the estimation of the force is based at least in part on a force sensor signal received from the force sensor.

26. The method of claim 19, further comprising performing an anti-spoofing process at least in part based on the force.

27. The method of claim 26, wherein the anti-spoofing process is further based at least in part on a first fingerprint image corresponding to the first ultrasonic receiver signal or a second fingerprint image corresponding to the second ultrasonic receiver signal.

28. The method of claim 26, wherein the anti-spoofing process involves estimating the material properties of the target object.

29. The method of claim 19, further comprising estimating a first force corresponding to the first ultrasonic receiver signal and estimating a second force corresponding to the second ultrasonic receiver signal.

30. The method of claim 29, further comprising controlling at least one of a display or a speaker to provide a prompt to apply a different force after the first force is estimated.

31. The method of claim 19, wherein the ultrasonic fingerprint sensor is integrated into a mobile device.

32. An equipment comprising: Ultrasonic fingerprint sensor; as well as Control device, which is used for: The ultrasonic fingerprint sensor is controlled to transmit a first ultrasonic wave toward a target object in contact with a surface, the surface being the surface of the ultrasonic fingerprint sensor or the surface of a device adjacent to the area where the ultrasonic fingerprint sensor resides. The ultrasonic fingerprint sensor receives a first ultrasonic receiver signal, the first ultrasonic receiver signal including a signal corresponding to the reflection of the first ultrasonic wave from the target object; Obtain an estimate of the force exerted on the surface by the target object; At least one ultrasonic fingerprint sensor parameter modification is determined based, at least in part, on the force. At least one setting of the ultrasonic fingerprint sensor is updated based at least in part on the modification of the ultrasonic fingerprint sensor parameters; Control the ultrasonic fingerprint sensor to transmit a second ultrasonic wave toward the target object; Receives a second ultrasonic receiver signal from the ultrasonic fingerprint sensor, the second ultrasonic receiver signal including a signal corresponding to the reflection of the second ultrasonic wave from the target object; and The authentication process is performed at least in part based on the first ultrasonic receiver signal and the second ultrasonic receiver signal.

33. The apparatus of claim 32, wherein the modification of the at least one ultrasonic fingerprint sensor parameter includes at least one of the following: gain modification, frequency modification of the transmitted ultrasonic wave, range gating pulse delay modification, range gating pulse window modification, or bias condition modification.

34. The equipment of claim 32, wherein the equipment is integrated into a mobile device.

35. One or more non-transient media having software stored thereon, the software including instructions for performing a method of controlling an ultrasonic fingerprint sensor, the method comprising: The ultrasonic fingerprint sensor is controlled to transmit a first ultrasonic wave toward a target object in contact with a surface, the surface being the surface of the ultrasonic fingerprint sensor or the surface of a device adjacent to the area where the ultrasonic fingerprint sensor resides. The ultrasonic fingerprint sensor receives a first ultrasonic receiver signal, the first ultrasonic receiver signal including a signal corresponding to the reflection of the first ultrasonic wave from the target object; Obtain an estimate of the force exerted on the surface by the target object; At least one ultrasonic fingerprint sensor parameter modification is determined based, at least in part, on the force. At least one setting of the ultrasonic fingerprint sensor is updated based at least in part on the modification of the ultrasonic fingerprint sensor parameters; Control the ultrasonic fingerprint sensor to transmit a second ultrasonic wave toward the target object; Receives a second ultrasonic receiver signal from the ultrasonic fingerprint sensor, the second ultrasonic receiver signal including a signal corresponding to the reflection of the second ultrasonic wave from the target object; and The authentication process is performed at least in part based on the first ultrasonic receiver signal and the second ultrasonic receiver signal.

36. The one or more non-transient media as described in claim 35, wherein the modification of the at least one ultrasonic fingerprint sensor parameter includes at least one of the following: gain value modification, frequency modification of the transmitted ultrasonic wave, distance gating pulse delay modification, distance gating pulse window modification, or bias condition modification.

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