Fingerprint sensors have become ubiquitous in mobile devices as well as other devices (e.g., locks on cars and buildings) and applications for authenticating a user's identity. They provide a fast and convenient way for the user to unlock a device, provide authentication for payments, etc. It is essential that fingerprint sensors operate at a level of security that, at a minimum, reduces the potential for circumvention of security of fingerprint authentication. For instance, fake fingers having fake or spoofed fingerprints can be used to attempt to circumvent fingerprint authentication at fingerprint sensors.
The accompanying drawings, which are incorporated in and form a part of the Description of Embodiments, illustrate various non-limiting and non-exhaustive embodiments of the subject matter and, together with the Description of Embodiments, serve to explain principles of the subject matter discussed below. Unless specifically noted, the drawings referred to in this Brief Description of Drawings should be understood as not being drawn to scale and like reference numerals refer to like parts throughout the various figures unless otherwise specified.
The following Description of Embodiments is merely provided by way of example and not of limitation. Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding background or in the following Description of Embodiments.
Reference will now be made in detail to various embodiments of the subject matter, examples of which are illustrated in the accompanying drawings. While various embodiments are discussed herein, it will be understood that they are not intended to limit to these embodiments. On the contrary, the presented embodiments are intended to cover alternatives, modifications and equivalents, which may be included within the spirit and scope the various embodiments as defined by the appended claims. Furthermore, in this Description of Embodiments, numerous specific details are set forth in order to provide a thorough understanding of embodiments of the present subject matter. However, embodiments may be practiced without these specific details. In other instances, well known methods, procedures, components, and circuits have not been described in detail as not to unnecessarily obscure aspects of the described embodiments.
Some portions of the detailed descriptions which follow are presented in terms of procedures, logic blocks, processing and other symbolic representations of operations on data within an electrical device. These descriptions and representations are the means used by those skilled in the data processing arts to most effectively convey the substance of their work to others skilled in the art. In the present application, a procedure, logic block, process, or the like, is conceived to be one or more self-consistent procedures or instructions leading to a desired result. The procedures are those requiring physical manipulations of physical quantities. Usually, although not necessarily, these quantities take the form of acoustic (e.g., ultrasonic) signals capable of being transmitted and received by an electronic device and/or electrical or magnetic signals capable of being stored, transferred, combined, compared, and otherwise manipulated in an electrical device.
It should be borne in mind, however, that all of these and similar terms are to be associated with the appropriate physical quantities and are merely convenient labels applied to these quantities. Unless specifically stated otherwise as apparent from the following discussions, it is appreciated that throughout the description of embodiments, discussions utilizing terms such as “capturing,” “extracting,” “applying,” “determining,” “performing,” “providing,” “receiving,” “analyzing,” “confirming,” “displaying,” “presenting,” “using,” “completing,” “instructing,” “comparing,” “executing,” or the like, refer to the actions and processes of an electronic device such as an electrical device.
Embodiments described herein may be discussed in the general context of processor-executable instructions residing on some form of non-transitory processor-readable medium, such as program modules, executed by one or more computers or other devices. Generally, program modules include routines, programs, objects, components, data structures, etc., that perform particular tasks or implement particular abstract data types. The functionality of the program modules may be combined or distributed as desired in various embodiments.
In the figures, a single block may be described as performing a function or functions; however, in actual practice, the function or functions performed by that block may be performed in a single component or across multiple components, and/or may be performed using hardware, using software, or using a combination of hardware and software. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, logic, circuits, and steps have been described generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present disclosure. Also, the example fingerprint sensing system and/or mobile electronic device described herein may include components other than those shown, including well-known components.
Various techniques described herein may be implemented in hardware, software, firmware, or any combination thereof, unless specifically described as being implemented in a specific manner. Any features described as modules or components may also be implemented together in an integrated logic device or separately as discrete but interoperable logic devices. If implemented in software, the techniques may be realized at least in part by a non-transitory processor-readable storage medium comprising instructions that, when executed, perform one or more of the methods described herein. The non-transitory processor-readable data storage medium may form part of a computer program product, which may include packaging materials.
The non-transitory processor-readable storage medium may comprise random access memory (RAM) such as synchronous dynamic random access memory (SDRAM), read only memory (ROM), non-volatile random access memory (NVRAM), electrically erasable programmable read-only memory (EEPROM), FLASH memory, other known storage media, and the like. The techniques additionally, or alternatively, may be realized at least in part by a processor-readable communication medium that carries or communicates code in the form of instructions or data structures and that can be accessed, read, and/or executed by a computer or other processor.
Various embodiments described herein may be executed by one or more processors, such as one or more motion processing units (MPUs), sensor processing units (SPUs), host processor(s) or core(s) thereof, digital signal processors (DSPs), general purpose microprocessors, application specific integrated circuits (ASICs), application specific instruction set processors (ASIPs), field programmable gate arrays (FPGAs), a programmable logic controller (PLC), a complex programmable logic device (CPLD), a discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein, or other equivalent integrated or discrete logic circuitry. The term “processor,” as used herein may refer to any of the foregoing structures or any other structure suitable for implementation of the techniques described herein. As it employed in the subject specification, the term “processor” can refer to substantially any computing processing unit or device comprising, but not limited to comprising, single-core processors; single-processors with software multithread execution capability; multi-core processors; multi-core processors with software multithread execution capability; multi-core processors with hardware multithread technology; parallel platforms; and parallel platforms with distributed shared memory. Moreover, processors can exploit nano-scale architectures such as, but not limited to, molecular and quantum-dot based transistors, switches and gates, in order to optimize space usage or enhance performance of user equipment. A processor may also be implemented as a combination of computing processing units.
In addition, in some aspects, the functionality described herein may be provided within dedicated software modules or hardware modules configured as described herein. Also, the techniques could be fully implemented in one or more circuits or logic elements. A general purpose processor may be a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, e.g., a combination of an SPU/MPU and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with an SPU core, MPU core, or any other such configuration.
Discussion begins with a description of a device including a fingerprint sensor, upon which described embodiments can be implemented. An example fingerprint sensor and system for determining whether a fingerprint image is generated using a real finger or a fake finger is then described, in accordance with various embodiments. Example operations of a fingerprint sensor for determining whether a fingerprint image is generated using a real finger or a fake finger using transient features are then described.
Fingerprint sensors are used in electronic devices for user authentication, such as mobile electronic devices and applications operating on mobile electronic devices, locks for accessing cars or buildings, for protecting against unauthorized access to the devices and/or applications. Authentication of a fingerprint at a fingerprint sensor is performed before providing access to a device and/or application. In order to circumvent fingerprint authentication, attempts can be made to copy or spoof fingerprints of an authorized user using a fake or artificial finger. As such, fingerprint sensors should be capable of distinguishing real fingers from fake, artificial, or even dead fingers, also referred to herein as performing “spoof detection” or “fake finger detection”. A “spoofed” fingerprint is a fake or artificial fingerprint that is used to attempt to circumvent security measures requiring fingerprint authentication. For example, an artificial finger may be used to gain unauthorized access to the electronic device or application, by making an unauthorized copy of the fingerprint of an authorized user, e.g., “spoofing” an actual fingerprint. The spoof detection may be performed by analyzing fingerprint images captured by the fingerprint sensor, e.g., performing biometric analysis of the fingerprint images, or looking at any characteristics that can help distinguish a fake/spoof fingerprint from a real fingerprint. These characteristics may be static features or dynamic features which have a certain time dependency because they change over time.
Embodiments described herein provide methods and systems for determining whether a finger interacting with a fingerprint sensor, for purposes of authentication, is a real finger or a fake finger based on dynamic features, also referred to herein as transient features. Transient features may refer to the characteristics of the signals or changes of the signal (e.g., a transient signal feature), or may refer to any dynamic characteristics of the fingerprint itself (e.g., a transient spatial feature). For example, a transient spatial feature may include how the fingerprint, or feature of the fingerprint, deform when pressed on the sensor surface or lifted from the sensor surface. Physiological transient features may also be used, such as the influence of transpiration on the measurements.
Embodiments described herein provide for determining whether a finger is a real finger at an ultrasonic fingerprint sensor. A sequence of images of a fingerprint of a finger are captured at an ultrasonic fingerprint sensor, wherein the sequence of images includes images captured during a change in contact state between the finger and the ultrasonic fingerprint sensor. In one embodiment, the sequence of images includes images of the finger separating or lifting from a contact surface of the ultrasonic fingerprint sensor. In one embodiment, the sequence of images includes images of the finger contacting or pressing on a contact surface of the ultrasonic fingerprint sensor. It should be appreciated that the sequence of images can include images of the finger contacting the contact surface of the ultrasonic fingerprint sensor and separating from the contact surface of the ultrasonic fingerprint sensor.
A plurality of transient features of the finger is extracted from the sequence of images. In some embodiments, extracting the plurality of transient features of the finger from the sequence of images includes extracting the plurality of transient features of the finger from the sequence of images at pixels of the sequence of images that satisfy a certain criteria, e.g., a signal change criteria. In one embodiment, the pixels of the sequence of images exhibiting signal changes relative to other pixels exceeding a change threshold include pixels at ridges of the fingerprint. In other embodiments, extracting the plurality of transient features of the finger from the sequence of images includes extracting the plurality of transient features of the finger from the sequence of images at pixels corresponding to a ridge of the fingerprint.
In some embodiments, the plurality of transient features includes at least one transient signal feature. In some embodiments, the plurality of transient features includes at least one transient spatial feature. In some embodiments, the at least one transient spatial feature includes a transient fingerprint pattern feature. In some embodiments, the at least one transient spatial feature includes a transient contact pattern feature. In some embodiments, at least one transient feature of the plurality of transient features is related to a deformation of the finger, the fingerprint pattern, or the ridge/valley pattern or profile.
A classifier is applied to the plurality of transient features to classify the finger as one of a real finger and a fake finger. In some embodiments, one or more transient features of the plurality of transient features are used as a feature vector of the classifier. In some embodiments, the classifier is constrained to considering the finger for an enrolled user. It is determined whether the finger is a real finger based on an output of the classifier. In some embodiments, the output of the classifier includes a probability whether the finger is a real finger or a fake finger.
Turning now to the figures,
As depicted in
Host processor 110 can be one or more microprocessors, central processing units (CPUs), DSPs, general purpose microprocessors, ASICs, ASIPs, FPGAs or other processors which run software programs or applications, which may be stored in host memory 130, associated with the functions and capabilities of electronic device 100.
Host bus 120 may be any suitable bus or interface to include, without limitation, a peripheral component interconnect express (PCIe) bus, a universal serial bus (USB), a universal asynchronous receiver/transmitter (UART) serial bus, a suitable advanced microcontroller bus architecture (AMBA) interface, an Inter-Integrated Circuit (I2C) bus, a serial digital input output (SDIO) bus, a serial peripheral interface (SPI) or other equivalent. In the embodiment shown, host processor 110, host memory 130, display 140, interface 150, transceiver 160, sensor processing unit (SPU) 170, and other components of electronic device 100 may be coupled communicatively through host bus 120 in order to exchange commands and data. Depending on the architecture, different bus configurations may be employed as desired. For example, additional buses may be used to couple the various components of electronic device 100, such as by using a dedicated bus between host processor 110 and memory 130.
Host memory 130 can be any suitable type of memory, including but not limited to electronic memory (e.g., read only memory (ROM), random access memory, or other electronic memory), hard disk, optical disk, or some combination thereof. Multiple layers of software can be stored in host memory 130 for use with/operation upon host processor 110. For example, an operating system layer can be provided for electronic device 100 to control and manage system resources in real time, enable functions of application software and other layers, and interface application programs with other software and functions of electronic device 100. Similarly, a user experience system layer may operate upon or be facilitated by the operating system. The user experience system may comprise one or more software application programs such as menu navigation software, games, device function control, gesture recognition, image processing or adjusting, voice recognition, navigation software, communications software (such as telephony or wireless local area network (WLAN) software), and/or any of a wide variety of other software and functional interfaces for interaction with the user can be provided. In some embodiments, multiple different applications can be provided on a single electronic device 100, and in some of those embodiments, multiple applications can run simultaneously as part of the user experience system. In some embodiments, the user experience system, operating system, and/or the host processor 110 may operate in a low-power mode (e.g., a sleep mode) where very few instructions are processed. Such a low-power mode may utilize only a small fraction of the processing power of a full-power mode (e.g., an awake mode) of the host processor 110.
Display 140, when included, may be a liquid crystal device, (organic) light emitting diode device, or other display device suitable for creating and visibly depicting graphic images and/or alphanumeric characters recognizable to a user. Display 140 may be configured to output images viewable by the user and may additionally or alternatively function as a viewfinder for camera. It should be appreciated that display 140 is optional, as various electronic devices, such as electronic locks, doorknobs, car start buttons, etc., may not require a display device.
Interface 150, when included, can be any of a variety of different devices providing input and/or output to a user, such as audio speakers, touch screen, real or virtual buttons, joystick, slider, knob, printer, scanner, computer network I/O device, other connected peripherals and the like.
Transceiver 160, when included, may be one or more of a wired or wireless transceiver which facilitates receipt of data at electronic device 100 from an external transmission source and transmission of data from electronic device 100 to an external recipient. By way of example, and not of limitation, in various embodiments, transceiver 160 comprises one or more of: a cellular transceiver, a wireless local area network transceiver (e.g., a transceiver compliant with one or more Institute of Electrical and Electronics Engineers (IEEE) 802.11 specifications for wireless local area network communication), a wireless personal area network transceiver (e.g., a transceiver compliant with one or more IEEE 802.15 specifications for wireless personal area network communication), and a wired a serial transceiver (e.g., a universal serial bus for wired communication).
Electronic device 100 also includes a general purpose sensor assembly in the form of integrated Sensor Processing Unit (SPU) 170 which includes sensor processor 172, memory 176, a fingerprint sensor 178, and a bus 174 for facilitating communication between these and other components of SPU 170. In some embodiments, SPU 170 may include at least one additional sensor 180 (shown as sensor 180-1, 180-2, . . . 180-n) communicatively coupled to bus 174. In some embodiments, at least one additional sensor 180 is a force or pressure sensor (e.g. a touch sensor) configured to determine a force or pressure or a temperature sensor configured to determine a temperature at electronic device 100. The force or pressure sensor may be disposed within, under, or adjacent fingerprint sensor 178. In some embodiments, all of the components illustrated in SPU 170 may be embodied on a single integrated circuit. It should be appreciated that SPU 170 may be manufactured as a stand-alone unit (e.g., an integrated circuit), that may exist separately from a larger electronic device and is coupled to host bus 120 through an interface (not shown). It should be appreciated that, in accordance with some embodiments, that SPU 170 can operate independent of host processor 110 and host memory 130 using sensor processor 172 and memory 176.
Sensor processor 172 can be one or more microprocessors, CPUs, DSPs, general purpose microprocessors, ASICs, ASIPs, FPGAs or other processors which run software programs, which may be stored in memory 176, associated with the functions of SPU 170. It should also be appreciated that fingerprint sensor 178 and additional sensor 180, when included, may also utilize processing and memory provided by other components of electronic device 100, e.g., host processor 110 and host memory 130.
Bus 174 may be any suitable bus or interface to include, without limitation, a peripheral component interconnect express (PCIe) bus, a universal serial bus (USB), a universal asynchronous receiver/transmitter (UART) serial bus, a suitable advanced microcontroller bus architecture (AMBA) interface, an Inter-Integrated Circuit (I2C) bus, a serial digital input output (SDIO) bus, a serial peripheral interface (SPI) or other equivalent. Depending on the architecture, different bus configurations may be employed as desired. In the embodiment shown, sensor processor 172, memory 176, fingerprint sensor 178, and other components of SPU 170 may be communicatively coupled through bus 174 in order to exchange data.
Memory 176 can be any suitable type of memory, including but not limited to electronic memory (e.g., read only memory (ROM), random access memory, or other electronic memory). Memory 176 may store algorithms or routines or other instructions for processing data received from fingerprint sensor 178 and/or one or more sensor 180, as well as the received data either in its raw form or after some processing. Such algorithms and routines may be implemented by sensor processor 172 and/or by logic or processing capabilities included in fingerprint sensor 178 and/or sensor 180.
A sensor 180 may comprise, without limitation: a temperature sensor, a humidity sensor, an atmospheric pressure sensor, an infrared sensor, a radio frequency sensor, a navigation satellite system sensor (such as a global positioning system receiver), an acoustic sensor (e.g., a microphone), an inertial or motion sensor (e.g., a gyroscope, accelerometer, or magnetometer) for measuring the orientation or motion of the sensor in space, or other type of sensor for measuring other physical or environmental factors. In one example, sensor 180-1 may comprise an acoustic sensor, sensor 180-2 may comprise a temperature sensor, and sensor 180-n may comprise a motion sensor.
In some embodiments, fingerprint sensor 178 and/or one or more sensors 180 may be implemented using a microelectromechanical system (MEMS) that is integrated with sensor processor 172 and one or more other components of SPU 170 in a single chip or package. It should be appreciated that fingerprint sensor 178 may be disposed behind display 140. Although depicted as being included within SPU 170, one, some, or all of fingerprint sensor 178 and/or one or more sensors 180 may be disposed externally to SPU 170 in various embodiments. It should be appreciated that fingerprint sensor 178 can be any type of fingerprint sensor, including without limitation, an ultrasonic sensor, an optical sensor, a camera, etc.
Fingerprint images 215 are captured at fingerprint image capture 210. It should be appreciated that, in accordance with various embodiments, fingerprint image capture 210 is an ultrasonic sensor (e.g., a sensor capable of transmitting and receiving ultrasonic signals). The fingerprint sensor is operable to emit and detect ultrasonic waves (also referred to as ultrasonic signals or ultrasound signals). An array of ultrasonic transducers (e.g., Piezoelectric Micromachined Ultrasonic Transducers (PMUTs)) may be used to transmit and receive the ultrasonic waves. The emitted ultrasonic waves are reflected from any objects in contact with (or in front of) the fingerprint sensor, and these reflected ultrasonic waves, or echoes, are then detected. Where the object is a finger, the waves are reflected from different features of the finger, such as the surface features on the skin, fingerprint, or features present in deeper layers of the finger (e.g., the dermis). Examples of surface features of a finger are ridges and valleys of a fingerprint. For example, the reflection of the sound waves from the ridge/valley pattern enables the fingerprint sensor to produce a fingerprint image that may be used for identification of the user.
Fingerprint image capture 210 is configured to capture a plurality of fingerprint images 215 in a sequence, where the sequence of images includes images captured during a change in contact state between the finger and the ultrasonic fingerprint sensor. A sequence of images is used to capture the transient nature of the signals, features, and characteristics of the fingerprint. In one embodiment, the sequence of images includes images of the finger contacting a contact surface of the ultrasonic fingerprint sensor, or changing a contact state. In one embodiment, the sequence of images includes images of the finger separating from a contact surface of the ultrasonic fingerprint sensor. It should be appreciated that the sequence of images can include images of the finger contacting the contact surface of the ultrasonic fingerprint sensor and separating from the contact surface of the ultrasonic fingerprint sensor. Capturing the sequence of images when the user presses a finger on the contact surface, or lifts a finger from the contact surface, enables the capturing of the sequence of images during a state of change. This change of state is related to the fact that a finger may deform and the contact between the fingerprint sensor and the finger changes. The characteristics of this changes are different for a real finger and a fake finger. The more the fake finger resembles a real finger, the smaller the difference in these characteristics. The transient features discussed in this disclosure enable a characterization of the state of change and are therefore used to differentiate between a real finger and a fake finger. Although, in the example embodiments discussed herein, a sequence of fingerprint images is used to derive the transient feature, it should be appreciated that other transient features may be derived directly from the received ultrasonic signals, without the forming of an image. Moreover, other types of transient features may be utilized in accordance with the described embodiments, such as temperature information (e.g., initial and steady state temperatures) detected by the ultrasonic fingerprint sensor or a temperature sensor of or related to the ultrasonic fingerprint sensor.
The capturing of the image sequence may be initiated whenever a change in signal is detected. For example, to capture the image sequence when the user presses the finger on the sensor, the image capture may be started as soon an object or finger starts interacting with the sensor. For an ultrasonic sensor with an array of ultrasonic transducers, a subset of transducers may be active in a low power mode, and as soon as a finger start interacting with the sensor, the full sensor may be activated to capture the sequence of images. In another example, where the user starts lifting the finger, a change in signal may occur as the pressure of the finger is reduced, and this may initiate the image sequence capture. The change of contact state may this be determined by the fingerprint sensor itself, or it may be detected by a second sensor associated with the fingerprint sensor. For example, a pressure sensor, a force sensor, or a touch sensor may be position near, below, or above the fingerprint sensor and this additional sensor may be used to detect a change in contact state that initiates the capturing of the image sequence.
The sequence of fingerprint images 215 can include any number of fingerprint images. In some embodiments, fingerprint images 215 are captured at periodic intervals (e.g., every 10 milliseconds) over a time period (e.g., 10 seconds). In some embodiments, the sequence of fingerprint images 215 includes at least three fingerprint images. In some embodiments, the fingerprint sensor may have a higher image capture rate when a change of contact state is detected, and a lower image capture rate during a steady state. For example, the sequence of fingerprint images 215 forwarded to transient feature extractor 220 may include two or more images captured during the change of contact state right after a finger is detected on the ultrasonic sensor, and a steady state image captured at a fixed amount of time after the finger is detected. In embodiments where the transient feature are deduced directly from the ultrasonic signals, the data transferred to the transient feature extractor 220 includes of a sequence of ultrasonic signal data.
Fingerprint images 215 are received at transient feature extractor 220, which is configured to extract transient features from the sequence of fingerprint images 215. Transient features may refer to the characteristics of the signals itself (e.g., a transient signal feature), or of any dynamic characteristics of the fingerprint itself (e.g., a transient spatial feature). For example, a transient spatial feature may include how the fingerprint, fingerprint pattern, or ridge profile deforms when the finger is pressed on the contact surface or lifted away from the contact surface. Physiological transient features may also be used, such as the influence of transpiration on the measurements.
In some embodiment, region selector 310 identifies regions 315 of fingerprint images 215 that satisfy a signal change criteria. For example, a signal change criteria may be a signal change threshold value that, when exceeded, is satisfied. In some embodiments, pixels of the sequence of fingerprint images 215 exhibiting signal changes, e.g., relative to other pixels, exceeding a change threshold include pixels at ridges of the fingerprint. In other embodiments, region selector 310 identifies pixels corresponding to a ridge of the fingerprint.
Regions 315 (local pixel selection or global pixel selection) are received at extractor 320, which is operable to extract a plurality of transient features 225 from pixels of regions 315. In some embodiments, the plurality of transient features 225 includes at least one transient signal feature (e.g., a signal value). In some embodiments, the plurality of transient features 225 includes at least one transient spatial feature (e.g., a width of a fingerprint ridge). In some embodiments, the at least one transient spatial feature includes a transient fingerprint pattern feature, e.g., a flattening of ridges as the pressure of the contact is increased. Another example of transient spatial feature is ridge continuity referring to how broken up a ridge line is or how long the ridge segments are (more or less continuous, or broken up in many parts). In some embodiments, the at least one transient spatial feature includes a transient contact pattern feature, such as the part of the contact surface/image covered by a fingerprint pattern (e.g., starting at the first point of contact and then spreading over the image as the pressure increases, or vice-versa). In some embodiments, at least one transient feature of the plurality of transient features is related to a deformation of the finger due to the change in contact state. The deformation may be limited to the outer surface of the fingerprint, and may involve the deeper layers of the finger (or fingerprint), depending on the penetration depth of the ultrasound. In some embodiments, the transient feature used to determine if the finger is real is a combination of two or more of the above features. For example, comparison of the transient signal feature compare to the transient spatial features may be used as an indication if a finger is a real finger. In other words, does the change in the observed ultrasound signal correspond to the observed change of state based on the spatial feature such as the contact surface area and/or changes in ridges.
As illustrated, graph 415 illustrates that transient features of a real finger illustrate a gradual change in the slope of the ridge signal strength over time relative to the transient features of a fake finger, as shown in graph 425. This is particularly apparent while the finger is making contact with the ultrasonic fingerprint sensor, but is also apparent while the finger is separating from the ultrasonic sensor. By analyzing the transient features extracted from fingerprint images captured during a change in contact state between the finger and the ultrasonic fingerprint sensor. The transient signal features can be extracted from the signal intensities, contrasts etc., as discussed in more detail below. The fingerprint images 412a through 412i of graph 415 also show the change in spatial features that can be used to derive transient spatial features (e.g., area of image showing fingerprint pattern, continuity of ridges, width of ridges). In some embodiments, the transient features are extracted and classification is applied to classify the finger as a real finger or a fake finger.
In one embodiment, the transient features are used as feature vectors in a classifier to determine if the finger is a real finger of a fake finger, but alternative methods to use the transient features to determine if the finger is a real finger may also be used. For example, the transient features (values) may be compared to reference (values), and if the transient features are within a threshold range of the reference, the finger is likely to be a real finger. Thereby, classifying the finger as a real finger or a fake finger based on the comparison. The probability of the finger being a real finger may be deduced from the difference between the transient feature (value) and the reference (value). Using a plurality of transient features may increase the confidence in the determination. The reference values may be predetermined, for example from measurement based on a plurality of users and or a plurality of (different types of) fake fingers. For increased performance, the reference values may be determined for authenticated user, for example during enrollment, and may also be context dependent. The contact dependent can help correct for external influences, such as e.g. temperature because at cold temperature the contact between the finger and sensor is less optimal, often due to dryness of the finger.
With reference again to
As illustrated in graph 800, line 805 bisects graph 800 such that measured fingerprints plotted on the lower right of graph 800 are indicative of a real finger and measured fingerprints plotted on the upper left of graph 800 are indicative of a fake finger. Similarly, as illustrated in graph 810, line 815 bisects graph 800 such that measured fingerprints plotted on the lower right of graph 810 are indicative of a real finger and measured fingerprints plotted on the upper left of graph 810 are indicative of a fake finger. Lines 805 and 815 indicate a class boundary, and thus fingerprint measurements to the bottom right of the boundary are classified as a real finger and fingerprint measurements to the top left of the boundary are classified as a fake finger. The distance between the fingerprint measurements and the boundary can be used as a measure of the confidence in the classification, and this distance can be converted into a probability using any type of transfer function or activation function.
It is determined whether the finger is a real finger based on output 235 of the classifier at faker finger determiner 240. In some embodiments, the output 235 of the classifier includes a probability whether the finger is a real finger or a fake finger. In some embodiments, fake finger determiner 240 receives input from other types of spoof detection or fake finger detection, and makes the determination as to whether the finger is a fake finger based on multiple inputs, including output 235.
At procedure 910 of flow diagram 900, a sequence of images of a fingerprint of a finger are captured at an ultrasonic fingerprint sensor, wherein the sequence of images includes images captured during a change in contact state between the finger and the ultrasonic fingerprint sensor. In one embodiment, the sequence of images includes images of the finger separating from a contact surface of the ultrasonic fingerprint sensor. In one embodiment, the sequence of images includes images of the finger contacting a contact surface of the ultrasonic fingerprint sensor. It should be appreciated that the sequence of images can include images of the finger contacting the contact surface of the ultrasonic fingerprint sensor and separating from the contact surface of the ultrasonic fingerprint sensor.
At procedure 920, a plurality of transient features of the finger is extracted from the sequence of images. In some embodiments, as shown at procedure 922, extracting the plurality of transient features of the finger from the sequence of includes extracting the plurality of transient features of the finger from the sequence of images at pixels of the sequence of images that satisfy a signal change criteria. In one embodiment, as shown at procedure 924, the pixels of the sequence of images exhibiting signal changes relative to other pixels exceeding a change threshold include pixels at ridges of the fingerprint. In other embodiments, extracting the plurality of transient features of the finger from the sequence of includes extracting the plurality of transient features of the finger from the sequence of images at pixels corresponding to a ridge of the fingerprint.
In some embodiments, the plurality of transient features includes at least one transient signal feature. In some embodiments, the plurality of transient features includes at least one transient spatial feature. In some embodiments, the at least one transient spatial feature includes a transient fingerprint pattern feature. In some embodiments, the at least one transient spatial feature includes a transient contact pattern feature. In some embodiments, at least one transient feature of the plurality of transient features is related to a deformation of the finger.
At procedure 930, a classifier is applied to the plurality of transient features to classify the finger as one of a real finger and a fake finger. In some embodiments, each transient feature of the plurality of transient features is a feature vector of the classifier. In some embodiments, the classifier is constrained to considering the finger for an enrolled user. At procedure 940, it is determined whether the finger is a real finger based at least in part on output of the classifier. In some embodiments, the output of the classifier includes a probability whether the finger is a real finger or a fake finger.
The examples set forth herein were presented in order to best explain, to describe particular applications, and to thereby enable those skilled in the art to make and use embodiments of the described examples. However, those skilled in the art will recognize that the foregoing description and examples have been presented for the purposes of illustration and example only. Many aspects of the different example embodiments that are described above can be combined into new embodiments. The description as set forth is not intended to be exhaustive or to limit the embodiments to the precise form disclosed. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims.
Reference throughout this document to “one embodiment,” “certain embodiments,” “an embodiment,” “various embodiments,” “some embodiments,” or similar term means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, the appearances of such phrases in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics of any embodiment may be combined in any suitable manner with one or more other features, structures, or characteristics of one or more other embodiments without limitation.
This application claims priority to and the benefit of U.S. Patent Provisional Patent Application 62/866,510, filed on Jun. 25, 2019, entitled “FAKE FINGER INVESTIGATION USING TRANSIENT FEATURES,” by Akhbari et al., and assigned to the assignee of the present application, which is incorporated herein by reference in its entirety.
Number | Name | Date | Kind |
---|---|---|---|
5575286 | Weng et al. | Nov 1996 | A |
5684243 | Gururaja et al. | Nov 1997 | A |
5808967 | Yu et al. | Sep 1998 | A |
5867302 | Fleming | Feb 1999 | A |
5911692 | Hussain et al. | Jun 1999 | A |
6071239 | Cribbs et al. | Jun 2000 | A |
6104673 | Cole et al. | Aug 2000 | A |
6289112 | Jain et al. | Sep 2001 | B1 |
6292576 | Brownlee | Sep 2001 | B1 |
6350652 | Libera et al. | Feb 2002 | B1 |
6428477 | Mason | Aug 2002 | B1 |
6483932 | Martinez | Nov 2002 | B1 |
6500120 | Anthony | Dec 2002 | B1 |
6676602 | Barnes et al. | Jan 2004 | B1 |
6736779 | Sano et al. | May 2004 | B1 |
7067962 | Scott | Jun 2006 | B2 |
7109642 | Scott | Sep 2006 | B2 |
7243547 | Cobianu et al. | Jul 2007 | B2 |
7257241 | Lo | Aug 2007 | B2 |
7400750 | Nam | Jul 2008 | B2 |
7433034 | Huang | Oct 2008 | B1 |
7459836 | Scott | Dec 2008 | B2 |
7471034 | Schlote-Holubek et al. | Dec 2008 | B2 |
7489066 | Scott et al. | Feb 2009 | B2 |
7634117 | Cho | Dec 2009 | B2 |
7739912 | Schneider et al. | Jun 2010 | B2 |
8018010 | Tigli et al. | Sep 2011 | B2 |
8139827 | Schneider et al. | Mar 2012 | B2 |
8255698 | Li et al. | Aug 2012 | B2 |
8311514 | Bandyopadhyay et al. | Nov 2012 | B2 |
8335356 | Schmitt | Dec 2012 | B2 |
8433110 | Kropp et al. | Apr 2013 | B2 |
8508103 | Schmitt et al. | Aug 2013 | B2 |
8515135 | Clarke et al. | Aug 2013 | B2 |
8666126 | Lee et al. | Mar 2014 | B2 |
8703040 | Liufu et al. | Apr 2014 | B2 |
8723399 | Sammoura et al. | May 2014 | B2 |
8805031 | Schmitt | Aug 2014 | B2 |
9056082 | Liautaud et al. | Jun 2015 | B2 |
9070861 | Bibl et al. | Jun 2015 | B2 |
9224030 | Du et al. | Dec 2015 | B2 |
9245165 | Slaby et al. | Jan 2016 | B2 |
9424456 | Kamath Koteshwara et al. | Aug 2016 | B1 |
9572549 | Belevich et al. | Feb 2017 | B2 |
9582102 | Setlak | Feb 2017 | B2 |
9582705 | Du et al. | Feb 2017 | B2 |
9607203 | Yazdandoost et al. | Mar 2017 | B1 |
9607206 | Schmitt et al. | Mar 2017 | B2 |
9613246 | Gozzini et al. | Apr 2017 | B1 |
9665763 | Du et al. | May 2017 | B2 |
9747488 | Yazdandoost et al. | Aug 2017 | B2 |
9785819 | Oreifej | Oct 2017 | B1 |
9815087 | Ganti et al. | Nov 2017 | B2 |
9817108 | Kuo et al. | Nov 2017 | B2 |
9818020 | Schuckers et al. | Nov 2017 | B2 |
9881195 | Lee et al. | Jan 2018 | B2 |
9881198 | Lee et al. | Jan 2018 | B2 |
9898640 | Ghavanini | Feb 2018 | B2 |
9904836 | Yeke Yazdandoost et al. | Feb 2018 | B2 |
9909225 | Lee et al. | Mar 2018 | B2 |
9922235 | Cho et al. | Mar 2018 | B2 |
9934371 | Hong et al. | Apr 2018 | B2 |
9939972 | Shepelev et al. | Apr 2018 | B2 |
9953205 | Rasmussen et al. | Apr 2018 | B1 |
9959444 | Young et al. | May 2018 | B2 |
9967100 | Hong et al. | May 2018 | B2 |
9983656 | Merrell et al. | May 2018 | B2 |
9984271 | King et al. | May 2018 | B1 |
10275638 | Yousefpor et al. | Apr 2019 | B1 |
10315222 | Salvia et al. | Jun 2019 | B2 |
10387704 | Dagan et al. | Aug 2019 | B2 |
10461124 | Berger et al. | Oct 2019 | B2 |
10478858 | Lasiter et al. | Nov 2019 | B2 |
10515255 | Strohmann et al. | Dec 2019 | B2 |
10539539 | Garlepp et al. | Jan 2020 | B2 |
10600403 | Garlepp et al. | Mar 2020 | B2 |
10656255 | Ng et al. | May 2020 | B2 |
10670716 | Apte et al. | Jun 2020 | B2 |
10706835 | Garlepp et al. | Jul 2020 | B2 |
10755067 | De Foras et al. | Aug 2020 | B2 |
20020135273 | Mauchamp et al. | Sep 2002 | A1 |
20030013955 | Poland | Jan 2003 | A1 |
20040085858 | Khuri-Yakub et al. | May 2004 | A1 |
20040122316 | Satoh et al. | Jun 2004 | A1 |
20040174773 | Thomenius et al. | Sep 2004 | A1 |
20050023937 | Sashida et al. | Feb 2005 | A1 |
20050057284 | Wodnicki | Mar 2005 | A1 |
20050100200 | Abiko et al. | May 2005 | A1 |
20050110071 | Ema et al. | May 2005 | A1 |
20050146240 | Smith et al. | Jul 2005 | A1 |
20050148132 | Wodnicki et al. | Jul 2005 | A1 |
20050162040 | Robert | Jul 2005 | A1 |
20060052697 | Hossack et al. | Mar 2006 | A1 |
20060079777 | Karasawa | Apr 2006 | A1 |
20060280346 | Machida | Dec 2006 | A1 |
20070046396 | Huang | Mar 2007 | A1 |
20070047785 | Jang et al. | Mar 2007 | A1 |
20070073135 | Lee et al. | Mar 2007 | A1 |
20070202252 | Sasaki | Aug 2007 | A1 |
20070215964 | Khuri-Yakub et al. | Sep 2007 | A1 |
20070223791 | Shinzaki | Sep 2007 | A1 |
20070230754 | Jain et al. | Oct 2007 | A1 |
20080125660 | Yao et al. | May 2008 | A1 |
20080150032 | Tanaka | Jun 2008 | A1 |
20080194053 | Huang | Aug 2008 | A1 |
20080240523 | Benkley et al. | Oct 2008 | A1 |
20090005684 | Kristoffersen et al. | Jan 2009 | A1 |
20090182237 | Angelsen et al. | Jul 2009 | A1 |
20090274343 | Clarke | Nov 2009 | A1 |
20090303838 | Svet | Dec 2009 | A1 |
20100030076 | Vortman et al. | Feb 2010 | A1 |
20100046810 | Yamada | Feb 2010 | A1 |
20100113952 | Raguin et al. | May 2010 | A1 |
20100168583 | Dausch et al. | Jul 2010 | A1 |
20100195851 | Buccafusca | Aug 2010 | A1 |
20100201222 | Adachi et al. | Aug 2010 | A1 |
20100202254 | Roest et al. | Aug 2010 | A1 |
20100239751 | Regniere | Sep 2010 | A1 |
20100251824 | Schneider et al. | Oct 2010 | A1 |
20100256498 | Tanaka | Oct 2010 | A1 |
20100278008 | Ammar | Nov 2010 | A1 |
20110285244 | Lewis et al. | Nov 2011 | A1 |
20110291207 | Martin et al. | Dec 2011 | A1 |
20120016604 | Irving et al. | Jan 2012 | A1 |
20120092026 | Liautaud et al. | Apr 2012 | A1 |
20120095335 | Sverdlik et al. | Apr 2012 | A1 |
20120095347 | Adam et al. | Apr 2012 | A1 |
20120147698 | Wong et al. | Jun 2012 | A1 |
20120224041 | Monden | Sep 2012 | A1 |
20120232396 | Tanabe | Sep 2012 | A1 |
20120238876 | Tanabe et al. | Sep 2012 | A1 |
20120263355 | Monden | Oct 2012 | A1 |
20120279865 | Regniere et al. | Nov 2012 | A1 |
20120288641 | Diatezua et al. | Nov 2012 | A1 |
20120300988 | Ivanov et al. | Nov 2012 | A1 |
20130051179 | Hong | Feb 2013 | A1 |
20130064043 | Degertekin et al. | Mar 2013 | A1 |
20130127297 | Bautista et al. | May 2013 | A1 |
20130127592 | Fyke et al. | May 2013 | A1 |
20130133428 | Lee et al. | May 2013 | A1 |
20130201134 | Schneider et al. | Aug 2013 | A1 |
20130271628 | Ku et al. | Oct 2013 | A1 |
20130294202 | Hajati | Nov 2013 | A1 |
20140060196 | Falter et al. | Mar 2014 | A1 |
20140117812 | Hajati | May 2014 | A1 |
20140176332 | Alameh et al. | Jun 2014 | A1 |
20140208853 | Onishi et al. | Jul 2014 | A1 |
20140219521 | Schmitt et al. | Aug 2014 | A1 |
20140232241 | Hajati | Aug 2014 | A1 |
20140265721 | Robinson et al. | Sep 2014 | A1 |
20140294262 | Schuckers | Oct 2014 | A1 |
20140313007 | Harding | Oct 2014 | A1 |
20140355387 | Kitchens et al. | Dec 2014 | A1 |
20150036065 | Yousefpor et al. | Feb 2015 | A1 |
20150049590 | Rowe et al. | Feb 2015 | A1 |
20150087991 | Chen et al. | Mar 2015 | A1 |
20150097468 | Hajati et al. | Apr 2015 | A1 |
20150145374 | Xu et al. | May 2015 | A1 |
20150164473 | Kim et al. | Jun 2015 | A1 |
20150165479 | Lasiter et al. | Jun 2015 | A1 |
20150169136 | Ganti et al. | Jun 2015 | A1 |
20150189136 | Chung et al. | Jul 2015 | A1 |
20150198699 | Kuo et al. | Jul 2015 | A1 |
20150206738 | Rastegar | Jul 2015 | A1 |
20150213180 | Herberholz | Jul 2015 | A1 |
20150220767 | Yoon et al. | Aug 2015 | A1 |
20150241393 | Ganti et al. | Aug 2015 | A1 |
20150261261 | Bhagavatula et al. | Sep 2015 | A1 |
20150286312 | Kang et al. | Oct 2015 | A1 |
20150301653 | Urushi | Oct 2015 | A1 |
20150345987 | Hajati | Dec 2015 | A1 |
20150371398 | Qiao et al. | Dec 2015 | A1 |
20160051225 | Kim et al. | Feb 2016 | A1 |
20160063294 | Du et al. | Mar 2016 | A1 |
20160063300 | Du et al. | Mar 2016 | A1 |
20160070967 | Du | Mar 2016 | A1 |
20160070968 | Gu et al. | Mar 2016 | A1 |
20160086010 | Merrell et al. | Mar 2016 | A1 |
20160092715 | Yazdandoost et al. | Mar 2016 | A1 |
20160092716 | Yazdandoost et al. | Mar 2016 | A1 |
20160100822 | Kim et al. | Apr 2016 | A1 |
20160107194 | Panchawagh et al. | Apr 2016 | A1 |
20160117541 | Lu et al. | Apr 2016 | A1 |
20160180142 | Riddle et al. | Jun 2016 | A1 |
20160326477 | Fernandez-Alcon et al. | Nov 2016 | A1 |
20160350573 | Kitchens et al. | Dec 2016 | A1 |
20160358003 | Shen et al. | Dec 2016 | A1 |
20170004352 | Jonsson | Jan 2017 | A1 |
20170330552 | Garlepp et al. | Jan 2017 | A1 |
20170032485 | Vemury | Feb 2017 | A1 |
20170075700 | Abudi et al. | Mar 2017 | A1 |
20170100091 | Eigil et al. | Apr 2017 | A1 |
20170110504 | Panchawagh et al. | Apr 2017 | A1 |
20170119343 | Pintoffl | May 2017 | A1 |
20170124374 | Rowe et al. | May 2017 | A1 |
20170168543 | Dai et al. | Jun 2017 | A1 |
20170185821 | Chen et al. | Jun 2017 | A1 |
20170194934 | Shelton et al. | Jul 2017 | A1 |
20170200054 | Du | Jul 2017 | A1 |
20170219536 | Koch et al. | Aug 2017 | A1 |
20170231534 | Agassy et al. | Aug 2017 | A1 |
20170255338 | Medina et al. | Sep 2017 | A1 |
20170293791 | Mainguet et al. | Oct 2017 | A1 |
20170316243 | Ghavanini | Nov 2017 | A1 |
20170316248 | He et al. | Nov 2017 | A1 |
20170322290 | Ng | Nov 2017 | A1 |
20170322291 | Salvia et al. | Nov 2017 | A1 |
20170322292 | Salvia et al. | Nov 2017 | A1 |
20170322305 | Apte et al. | Nov 2017 | A1 |
20170323133 | Tsai | Nov 2017 | A1 |
20170326590 | Daneman | Nov 2017 | A1 |
20170326591 | Apte et al. | Nov 2017 | A1 |
20170326593 | Garlepp et al. | Nov 2017 | A1 |
20170326594 | Berger et al. | Nov 2017 | A1 |
20170328866 | Apte et al. | Nov 2017 | A1 |
20170328870 | Garlepp et al. | Nov 2017 | A1 |
20170330012 | Salvia et al. | Nov 2017 | A1 |
20170330553 | Garlepp et al. | Nov 2017 | A1 |
20170357839 | Yazdandoost et al. | Dec 2017 | A1 |
20180025202 | Ryshtun | Jan 2018 | A1 |
20180032788 | Krenzer | Feb 2018 | A1 |
20180101711 | D'Souza et al. | Apr 2018 | A1 |
20180107852 | Fenrich | Apr 2018 | A1 |
20180129849 | Strohmann et al. | May 2018 | A1 |
20180129857 | Bonev | May 2018 | A1 |
20180206820 | Anand et al. | Jul 2018 | A1 |
20180225495 | Jonsson et al. | Aug 2018 | A1 |
20180229267 | Ono et al. | Aug 2018 | A1 |
20180276443 | Strohmann et al. | Sep 2018 | A1 |
20180349663 | Garlepp et al. | Dec 2018 | A1 |
20180357457 | Rasmussen et al. | Dec 2018 | A1 |
20180369866 | Sammoura et al. | Dec 2018 | A1 |
20180373913 | Panchawagh et al. | Dec 2018 | A1 |
20190005300 | Garlepp et al. | Jan 2019 | A1 |
20190018123 | Narasimha-Iyer et al. | Jan 2019 | A1 |
20190057267 | Kitchens et al. | Feb 2019 | A1 |
20190073507 | D'Souza et al. | Mar 2019 | A1 |
20190095015 | Han et al. | Mar 2019 | A1 |
20190102046 | Miranto et al. | Apr 2019 | A1 |
20190130083 | Agassy | May 2019 | A1 |
20190171858 | Ataya et al. | Jun 2019 | A1 |
20190188441 | Hall et al. | Jun 2019 | A1 |
20190188442 | Flament et al. | Jun 2019 | A1 |
20190325185 | Tang | Oct 2019 | A1 |
20200030850 | Apte et al. | Jan 2020 | A1 |
20200050816 | Tsai | Feb 2020 | A1 |
20200050817 | Salvia et al. | Feb 2020 | A1 |
20200050828 | Li et al. | Feb 2020 | A1 |
20200074135 | Garlepp et al. | Mar 2020 | A1 |
20200158694 | Garlepp et al. | May 2020 | A1 |
20200210666 | Flament | Jul 2020 | A1 |
20200302140 | Lu et al. | Sep 2020 | A1 |
Number | Date | Country |
---|---|---|
1826631 | Aug 2006 | CN |
102159334 | Aug 2011 | CN |
105264542 | Jan 2016 | CN |
1214909 | Jun 2002 | EP |
2884301 | Jun 2015 | EP |
3086261 | Oct 2016 | EP |
2011040467 | Feb 2011 | JP |
2009096576 | Aug 2009 | WO |
2009137106 | Nov 2009 | WO |
2014035564 | Mar 2014 | WO |
2015009635 | Jan 2015 | WO |
2015112453 | Jul 2015 | WO |
2015120132 | Aug 2015 | WO |
2015131083 | Sep 2015 | WO |
2015134816 | Sep 2015 | WO |
2015183945 | Dec 2015 | WO |
2016007250 | Jan 2016 | WO |
2016011172 | Jan 2016 | WO |
2016040333 | Mar 2016 | WO |
2016061406 | Apr 2016 | WO |
2016061410 | Apr 2016 | WO |
2017003848 | Jan 2017 | WO |
2017053877 | Mar 2017 | WO |
2017192895 | Nov 2017 | WO |
2017196678 | Nov 2017 | WO |
2017196682 | Nov 2017 | WO |
2017192903 | Dec 2017 | WO |
Entry |
---|
Tang, et al., “Pulse-Echo Ultrasonic Fingerprint Sensor on a Chip”, IEEE Transducers, Anchorage, Alaska, USA, Jun. 21-25, 2015, pp. 674-677. |
ISA/EP, Partial International Search Report for International Application No. PCT/US2019/034032, 8 pages, dated Sep. 12, 2019, 8. |
ISA/EP, International Search Report and Written Opinion for International Application # PCT/US2018/063431, pp. 1-15, dated Feb. 5, 2019. |
ISA/EP, International Search Report and Written Opinion for International Application # PCT/US2019/015020, pp. 1-23, dated Jul. 1, 2019. |
ISA/EP, International Search Report and Written Opinion for International Application # PCT/US2019/023440, pp. 1-10, dated Jun. 4, 2019. |
ISA/EP, International Search Report and Written Opinion for International Application No. PCT/US2017/031120, 12 pages, dated Aug. 29, 2017. |
ISA/EP, International Search Report and Written Opinion for International Application No. PCT/US2017/031127, 13 pages, dated Sep. 1, 2017. |
ISA/EP, International Search Report and Written Opinion for International Application No. PCT/US2017/031134, 12 pages, dated Aug. 30, 2017. |
ISA/EP, International Search Report and Written Opinion for International Application No. PCT/US2017/031140, 18 pages, dated Nov. 2, 2017. |
ISA/EP, International Search Report and Written Opinion for International Application No. PCT/US2017/031421 13 pages, dated Jun. 21, 2017. |
ISA/EP, International Search Report and Written Opinion for International Application No. PCT/US2017/031426 13 pages, dated Jun. 22, 2017. |
ISA/EP, International Search Report and Written Opinion for International Application No. PCT/US2017/031431, 14 pages, dated Aug. 1, 2017. |
ISA/EP, International Search Report and Written Opinion for International Application No. PCT/US2017/031434, 13 pages, dated Jun. 26, 2017. |
ISA/EP, International Search Report and Written Opinion for International Application No. PCT/US2017/031439, 10 pages, dated Jun. 20, 2017. |
ISA/EP, International Search Report and Written Opinion for International Application No. PCT/US2017/031824, 18 pages, dated Sep. 22, 2017. |
ISA/EP, International Search Report and Written Opinion for International Application No. PCT/US2017/031827, 16 pages, dated Aug. 1, 2017. |
ISA/EP, International Search Report and Written Opinion for International Application No. PCT/US2017/031831, 12 pages, dated Jul. 21, 2017. |
ISA/EP, International Search Report and Written Opinion for International Application No. PCT/US2018/037364, 10 pages, dated Sep. 3, 2018. |
ISA/EP, International Search Report for International Application No. PCT/US2017/031826, 16 pages, dated Feb. 27, 2018. |
ISA/EP, Partial International Search Report for International Application No. PCT/US2017/031140, 13 pages, dated Aug. 29, 2017. |
ISA/EP, Partial International Search Report for International Application No. PCT/US2017/031826, 12 pages, dated Nov. 30, 2017. |
“Moving Average Filters”, Waybackmachine XP05547422, Retrieved from the Internet: URL:https://web.archive.org/web/20170809081353/https//www.analog.com/media/en/technical-documentation/dsp-book/dsp_book_Ch15.pdf [retrieved on Jan. 24, 2019], Aug. 9, 2017, 1-8. |
Office Action for CN App No. 201780029016.7 dated Mar. 24, 2020, 7 pages. |
“Receiver Thermal Noise Threshold”, Fisher Telecommunication Services, Satellite Communications. Retrieved from the Internet URL:https://web.archive.org/web/20171027075705/http//www.fishercom.xyz:80/satellite-communications/receiver-thermal-noise-threshold.html, Oct. 27, 2017, 3. |
“Sleep Mode”, Wikipedia, Retrieved from the Internet: URL:https://web.archive.org/web/20170908153323/https://en.wikipedia.org/wiki/Sleep_mode [retrieved on Jan. 25, 2019], Sep. 8, 2017, 1-3. |
“TMS320C5515 Fingerprint Development Kit (FDK) Hardware Guide”, Texas Instruments, Literature No. SPRUFX3, XP055547651, Apr. 2010, 1-26. |
“ZTE V7 Max. 5,5” smartphone on MediaTeck Helio P10 cpu; Published on Apr. 20, 2016; https://www.youtube.com/watch?v=ncNCbpkGQzU (Year: 2016). |
Cappelli, et al., “Fingerprint Image Reconstruction from Standard Templates”, IEEE Transactions on Pattern Analysis and Machine Intelligence, IEEE Computer Society, vol. 29, No. 9, Sep. 2007, 1489-1503. |
Dausch, et al., “Theory and Operation of 2-D Array Piezoelectric Micromachined Ultrasound Transducers”, IEEE Transactions on Ultrasonics, and Frequency Control, vol. 55, No. 11;, Nov. 2008, 2484-2492. |
Feng, et al., “Fingerprint Reconstruction: From Minutiae to Phase”, IEEE Transactions on Pattern Analysis and Machine Intelligence, IEEE Computer Society, vol. 33, No. 2, Feb. 2011, 209-223. |
Hopcroft, et al., “Temperature Compensation of a MEMS Resonator Using Quality Factor as a Thermometer”, Retrieved from Internet: http://micromachine.stanford.edu/˜amanu/linked/MAH_MEMS2006.pdf, 2006, 222-225. |
Hopcroft, et al., “Using the temperature dependence of resonator quality factor as a thermometer”, Applied Physics Letters 91. Retrieved from Internet: http://micromachine.stanford.edu/˜hopcroft/Publications/Hopcroft_QT_ApplPhysLett_91_013505.pdf, 2007, 013505-1-031505-3. |
Jiang, et al., “Ultrasonic Fingerprint Sensor with Transmit Beamforming Based on a PMUT Array Bonded to CMOS Circuitry”, IEEE Transactions on Ultrasonics Ferroelectrics and Frequency Control, Jan. 1, 2017, 1-9. |
Kumar, et al., “Towards Contactless, Low-Cost and Accurate 3D Fingerprint Identification”, IEEE Transactions on Pattern Analysis and Machine Intelligence, IEEE Computer Society, vol. 37, No. 3, Mar. 2015, 681-696. |
Lee, et al., “Low jitter and temperature stable MEMS oscillators”, Frequency Conlrol Symposium (FCS), 2012 IEEE International, May 2012, 1-5. |
Li, et al., “Capacitive micromachined ultrasonic transducer for ultra-low pressure measurement: Theoretical study”, AIP Advances 5.12. Retrieved from Internet: http://scitation.aip.org/content/aip/journal/adva/5/12/10.1063/1.4939217, 2015, 127231. |
Pang, et al., “Extracting Valley-Ridge Lines from Point-Cloud-Based 3D Fingerprint Models”, IEEE Computer Graphics and Applications, IEEE Service Center, New York, vol. 33, No. 4, Jul./Aug. 2013, 73-81. |
Papageorgiou, et al., “Self-Calibration of Ultrasonic Transducers in an Intelligent Data Acquisition System”, International Scientific Journal of Computing, 2003, vol. 2, Issue 2 Retrieved Online: URL: https://scholar.google.com/scholar?q=self-calibration+of+ultrasonic+transducers+in+an+intelligent+data+acquisition+system&hl=en&as_sdt=0&as_vis=1&oi=scholart, 2003, 9-15. |
Qiu, et al., “Piezoelectric Micromachined Ultrasound Transducer (PMUT) Arrays for Integrated Sensing, Actuation and Imaging”, Sensors 15, doi:10.3390/s150408020, Apr. 3, 2015, 8020-8041. |
Ross, et al., “From Template to Image: Reconstructing Fingerprints from Minutiae Points”, IEEE Transactions on Pattern Analysis and Machine Intelligence, IEEE Computer Society, vol. 29, No. 4, Apr. 2007, 544-560. |
Rozen, et al., “Air-Coupled Aluminum Nitride Piezoelectric Micromachined Ultrasonic Transducers at 0.3 MHZ to 0.9 MHZ”, 2015 28th IEEE International Conference on Micro Electro Mechanical Systems (MEMS), IEEE, Jan. 18, 2015, 921-924. |
Savoia, et al., “Design and Fabrication of a cMUT Probe for Ultrasound Imaging of Fingerprints”, 2010 IEEE International Ultrasonics Symposium Proceedings, Oct. 2010, 1877-1880. |
Shen, et al., “Anisotropic Complementary Acoustic Metamaterial for Canceling out Aberrating Layers”, American Physical Society, Physical Review X 4.4: 041033., Nov. 19, 2014, 041033-1-041033-7. |
Thakar, et al., “Multi-resonator approach to eliminating the temperature dependence of silicon-based timing references”, Hilton Head'14. Retrieved from the Internet: http://blog.narotama.ac.id/wp-content/uploads/2014/12/Multi-resonator-approach-to-eliminating-the-temperature-dependance-of-silicon-based-timing-references.pdf, 2014, 415-418. |
Zhou, et al., “Partial Fingerprint Reconstruction with Improved Smooth Extension”, Network and System Security, Springer Berlin Heidelberg, Jun. 3, 2013, 756-762. |
ISA/EP, International Search Report and Written Opinion for International Application No. PCT/US2020/033854, 16 pages, dated Nov. 3, 2020. |
ISA/EP, International Search Report and Written Opinion for International Application No. PCT/US2020/039208, 10 pages, dated Oct. 9, 2020. |
ISA/EP, International Search Report and Written Opinion for International Application No. PCT/US2020/039452, 11 pages, dated Sep. 9, 2020. |
ISA/EP, Partial Search Report for International Application No. PCT/US2020/033854, 10 pages, dated Sep. 8, 2020. |
Office Action for CN App No. 201780029016.7 dated Sep. 25, 2020, 7 pages. |
Tang, et al., “11.2 3D Ultrasonic Fingerprint Sensor-on-a-Chip”, 2016 IEEE International Solid-State Circuits Conference, IEEE, Jan. 31, 2016, 202-203. |
EP Office Action, for Application 17724184.1, dated Oct. 12, 2021, 6 pages. |
EP Office Action, dated Oct. 9, 2021, 6 pages. |
European Patent Office, Office Action, App 17725018, pp. 5, dated Oct. 25, 2021. |
Tang, et al., “Pulse-echo ultrasonic fingerprint sensor on a chip”, 2015 Transducers, 2015 18th International Conference on Solid-State Sensors, Actuators and Microsystems, Apr. 1, 2015, 674-677. |
Number | Date | Country | |
---|---|---|---|
20200410268 A1 | Dec 2020 | US |
Number | Date | Country | |
---|---|---|---|
62866510 | Jun 2019 | US |