PATENT DOCUMENT

Publication Number: US-9092653-B2
Application Number: US-201314108410-A
Country: US
Kind Code: B2

Title: Finger biometric sensor including laterally adjacent piezoelectric transducer layer and associated methods

Abstract:
A finger biometric sensor may include a finger biometric sensing layer having an upper major surface and at least one sidewall surface adjacent thereto. The finger biometric layer may be for generating signals related to at least one biometric characteristic of the user&#39;s finger when positioned adjacent the first major surface. The finger biometric sensor may also include a piezoelectric transducer layer coupled to the at least one sidewall surface of the finger biometric sensing layer and a plurality of electrically conductive layers coupled to the piezoelectric transducer layer to define transducer electrodes. At least one of the electrically conductive layers may also cooperate with the finger biometric sensing layer for sensing the at least one biometric characteristic.

Claims:
That which is claimed is: 
     
       1. A finger biometric sensor comprising:
 a finger biometric sensing layer capable of generating signals related to at least one finger biometric characteristic; 
 a piezoelectric transducer layer laterally adjacent said finger biometric sensing layer; and 
 a plurality of electrically conductive layers coupled to said piezoelectric transducer layer to define transducer electrodes, at least one of said electrically conductive layers comprising a drive electrode capable of cooperating with said finger biometric sensing layer and coupling a radio frequency (RF) signal with a finger. 
 
     
     
       2. The finger biometric sensor according to  claim 1  further comprising a drive circuit coupled to said transducer electrodes and capable of driving said piezoelectric transducer layer to impart a force to the finger. 
     
     
       3. The finger biometric sensor according to  claim 1  further comprising a sense circuit coupled to said transducer electrodes and capable of sensing from said piezoelectric transducer layer a force imparted by the finger. 
     
     
       4. The finger biometric sensor according to  claim 3  further comprising:
 a reading circuit coupled to said finger biometric sensing layer and capable of reading signals therefrom; and 
 a power up circuit capable of selectively powering up said reading circuit based upon said sense circuit. 
 
     
     
       5. The finger biometric sensor according to  claim 3  wherein said sense circuit is capable of generating a pressure output signal related to pressure applied by the finger. 
     
     
       6. The finger biometric sensor according to  claim 1  further comprising a matcher coupled to said finger biometric sensing layer and capable of determining a match based upon the at least one finger biometric characteristic. 
     
     
       7. The finger biometric sensor according to  claim 1  further comprising a navigation circuit coupled to said transducer electrodes and capable of performing at least one navigation function. 
     
     
       8. The finger biometric sensor according to  claim 1  further comprising a feedback circuit coupled to said transducer electrodes and capable of performing at least one feedback function. 
     
     
       9. The finger biometric sensor according to  claim 1  wherein said finger biometric sensing layer comprises an integrated circuit finger biometric sensing layer. 
     
     
       10. The finger biometric sensor according to  claim 1  wherein the at least one finger biometric characteristic comprises a fingerprint pattern. 
     
     
       11. A method for making a finger biometric sensor comprising:
 forming a finger biometric sensing layer capable of generating signals related to at least one finger biometric characteristic; 
 forming a piezoelectric transducer layer laterally adjacent the finger biometric sensing layer; and 
 forming a plurality of electrically conductive layers coupled to the piezoelectric transducer layer to define transducer electrodes, at least one of the electrically conductive layers comprising a drive electrode capable of cooperating with the finger biometric sensing layer and coupling a radio frequency (RF) signal with a finger. 
 
     
     
       12. The method according to  claim 11  further comprising forming a drive circuit coupled to the transducer electrodes and capable of driving the piezoelectric transducer layer to impart a force to the finger. 
     
     
       13. The method according to  claim 11  further comprising forming a sense circuit coupled to the transducer electrodes and capable of sensing from the piezoelectric transducer layer a force imparted by the finger. 
     
     
       14. The method according to  claim 11  wherein forming the finger biometric sensing layer comprises forming the finger biometric sensing layer as part of an integrated circuit. 
     
     
       15. The method according to  claim 11  wherein the at least one finger biometric characteristic comprises a fingerprint pattern. 
     
     
       16. A finger biometric sensor comprising:
 a finger biometric sensing layer capable of generating signals related to at least one finger biometric characteristic and comprising a plurality of electric field sensing pixels; 
 a piezoelectric transducer layer laterally adjacent said finger biometric sensing layer; and 
 a plurality of electrically conductive layers coupled to said piezoelectric transducer layer to define transducer electrodes. 
 
     
     
       17. The finger biometric sensor according to  claim 16  wherein at least one of said plurality of electrically conductive layers is capable of cooperating with said finger biometric sensing layer. 
     
     
       18. The finger biometric sensor according to  claim 16  further comprising a drive circuit coupled to said transducer electrodes and capable of driving said piezoelectric transducer layer to impart a force to the finger. 
     
     
       19. The finger biometric sensor according to  claim 16  further comprising a sense circuit coupled to said transducer electrodes and capable of sensing from said piezoelectric transducer layer a force imparted by the finger. 
     
     
       20. The finger biometric sensor according to  claim 16  further comprising a matcher coupled to said finger biometric sensing layer and capable of determining a match based upon the at least one finger biometric characteristic. 
     
     
       21. The finger biometric sensor according to  claim 16  wherein said finger biometric sensing layer comprises an integrated circuit finger biometric sensing layer. 
     
     
       22. The finger biometric sensor according to  claim 16  wherein the at least one finger biometric characteristic comprises a fingerprint pattern. 
     
     
       23. A method for making a finger biometric sensor comprising:
 forming a finger biometric sensing layer capable of generating signals related to at least one finger biometric characteristic and comprising a plurality of electric field sensing pixels; 
 forming a piezoelectric transducer layer laterally adjacent the finger biometric sensing layer; and 
 forming a plurality of electrically conductive layers coupled to the piezoelectric transducer layer to define transducer electrodes. 
 
     
     
       24. The method according to  claim 23  wherein forming the plurality of electrically conductive layers comprises forming at least one of said electrically conductive layers to be capable of cooperating with said finger biometric sensing layer. 
     
     
       25. The method according to  claim 23  further comprising forming a drive circuit coupled to the transducer electrodes and capable of driving the piezoelectric transducer layer to impart a force to the finger. 
     
     
       26. The method according to  claim 23  further comprising forming a sense circuit coupled to the transducer electrodes and capable of sensing from the piezoelectric transducer layer a force imparted by the finger. 
     
     
       27. The method according to  claim 23  wherein forming the finger biometric sensing layer comprises forming the finger biometric sensing layer as part of an integrated circuit. 
     
     
       28. The method according to  claim 23  wherein the at least one finger biometric characteristic comprises a fingerprint pattern.

Description:
FIELD OF THE INVENTION 
     The present invention relates to the field of electronics, and, more particularly, to the field of finger biometric sensors, and associated manufacturing methods. 
     BACKGROUND OF THE INVENTION 
     Fingerprint sensing and matching is a reliable and widely used technique for personal identification or verification. In particular, a common approach to fingerprint identification involves scanning a sample fingerprint or an image thereof and storing the image and/or unique characteristics of the fingerprint image. The characteristics of a sample fingerprint may be compared to information for reference fingerprints already in a database to determine proper identification of a person, such as for verification purposes. 
     A particularly advantageous approach to fingerprint sensing is disclosed in U.S. Pat. No. 5,953,441 to Setlak and assigned to the assignee of the present invention. The fingerprint sensor is an integrated circuit sensor that drives the user&#39;s finger with an electric field signal and senses the electric field with an array of electric field sensing pixels on the integrated circuit substrate. 
     U.S. Pat. No. 6,289,114 to Mainguet discloses a fingerprint sensor that includes a finger sensing integrated circuit (IC). The finger sensing IC includes a layer of piezoelectric or pyroelectric material placed between upper and lower electrodes to provide electric signals representative of an image of the ridges and valleys of the fingerprint. 
     A particularly advantageous approach to multi-biometric fingerprint sensing is disclosed in U.S. Pat. No. 7,361,919 to Setlak, which is assigned to the assignee of the present invention and is incorporated in its entirety by reference. The Setlak patent discloses a multi-biometric finger sensor sensing different biometric characteristics of a user&#39;s finger that have different matching selectivities. 
     It may also be desirable to have a finger biometric sensor powered down or in a low power consumption mode until a finger is placed in a position to be sensed. The finger biometric sensor may desirably detect when the finger is in a sensing position and then activate itself and any other devices, such as processors, needed to perform the functions desired by the user. 
     Several approaches for detecting the presence of a finger in a desired position are known. Typically, in some approaches, a small part of a finger imaging system may be activated on a periodic basis to determine if a finger is present. A negative aspect of these approaches is that they dissipate power in the finger biometric sensor, and/or its supporting circuitry, during a time when the finger imaging system is waiting for the finger to appear. Quiescent power consumption while in a finger detect (waiting) mode drains a battery in a portable electronic device. 
     In an attempt to reduce the quiescent power consumption, some finger presence detection approaches have been proposed where the fingerprint sensor is mounted on a mechanically actuated electrical switching element. Finger pressure on the fingerprint sensor moves the switching element, causing the switch to close and activating sensor electronics or the supporting circuitry. While this approach may consume no quiescent current, it may be difficult to reliably implement because it requires the finger biometric sensor itself to be a moving part. 
     Several approaches to finger biometric sensors including a switch are disclosed in U.S. Pat. No. 4,120,585 to DePalma et al.; U.S. Pat. No. 6,522,773 to Houdeau; U.S. Pat. No. 6,912,299 to Hoshino et al.; and U.S. Pat. No. 7,266,226 to Hwang. U.S. Published Application No. 2004/0155752 to Radke also discloses a switch associated with a finger biometric sensor. U.S. Patent Application No. 2007/0076923 to Chiu, for example, discloses a finger sensing device that has a power control switch at the tip of the sensor panel, and a second switch underneath the finger sensor to initiate the finger sensing operation. 
     Other finger biometric sensors may include power controls integrated within the finger print imaging system, or adjacent the fingerprint sensor, such as disclosed in U.S. Published Application No. 2006/0239517 to Creasy et al. Still, other finger biometric sensors, such as disclosed in U.S. Pat. No. 5,940,526 to Setlak et al., include power control to only active portions of the finger sensor, thus resulting in a standby mode. 
     Still further, it may be desirable to provide the user with tactile feedback when a finger is placed on the biometric finger sensor. U.S. Published Application No. 2001/0017934 to Paloniemi et al. discloses a fingerprint sensor mounted on a switch. When the fingerprint sensor is tapped, the switch is operated and provides an audible and/or tactile feedback to a user, for example, by movement of a domed membrane. U.S. Published Application No. 2005/0111707 to Bohn et al. discloses a fingerprint scanner that provides a tactile and/or audible indication from an end of scan switch located on a housing frame. 
     U.S. Published Application No. 2006/0239517 to Creasey et al., as briefly described above, further discloses a finger sensor mounted on a housing of a device and providing feedback to a user in the form of physical feeling. A platen receives a user&#39;s finger and is coupled to a base of the housing. An activation sensor, which may be a piezoelectric sensor, is coupled to the platen and detects force on the platen in response to a user&#39;s finger pressed on the sensor. 
     SUMMARY OF THE INVENTION 
     In view of the foregoing background, it is therefore an object of the present invention to provide a finger biometric sensor with power control and/or feedback features. 
     This and other objects, features, and advantages in accordance with the present invention are provided by a finger biometric sensor that may include a finger biometric sensing layer having an upper major surface at least one sidewall surface and for generating signals related to at least one biometric characteristic of the user&#39;s finger when positioned adjacent the upper major surface. A piezoelectric transducer layer may be adjacent the at least one sidewall surface of the finger biometric sensing layer. A plurality of electrically conductive layers may also be coupled to the piezoelectric transducer layer to define transducer electrodes. At least one of the electrically conductive layers may also cooperate with the finger biometric sensing layer for sensing the at least one biometric characteristic. Accordingly, a finger biometric sensor is provided that may include power control and/or feedback features. 
     More particularly, the at least one electrically conductive layer may include a drive electrode for the finger biometric sensing layer. The finger biometric sensor may further include a drive circuit coupled to the transducer electrodes to drive the piezoelectric transducer layer to impart a force to the user&#39;s finger, for example. The finger biometric sensor may further include a sense circuit coupled to the transducer electrodes to sense from the piezoelectric transducer layer a force imparted by the user&#39;s finger. Advantageously, the finger biometric sensor may provide tactile feedback to the user&#39;s finger, it may provide finger presence detection for power control, or it may provide both. 
     Additionally, the finger biometric sensor may further include a reading circuit coupled to the finger biometric sensing layer for reading signals therefrom, for example. The finger biometric sensor may also include a power up circuit for selectively powering up the reading circuit based upon the sense circuit. The sense circuit may generate a pressure output signal related to an amount of pressure applied by the user&#39;s finger, for example, for other functions besides power control. 
     The finger biometric sensor may further include a matcher coupled to the finger biometric sensing layer for determining a match based upon the at least one biometric characteristic of the user&#39;s finger. The finger biometric sensor may also include a navigation circuit coupled to the transducer electrodes for performing at least one navigation function, for example. Additionally, the finger biometric sensor may also include a feedback circuit coupled to the transducer electrodes for performing at least one feedback function. The feedback circuit and/or the navigation circuit may be embodied in a processor, which may be included within or external to the finger biometric sensor or shared between the sensor and external circuitry. 
     The finger biometric sensing layer may include or be part of an integrated circuit. Additionally, the finger biometric sensor may include a flexible mounting substrate overlaying the piezoelectric transducer layer and the finger biometric sensing layer. 
     Another aspect is directed to a method for making a finger biometric sensor. The method may include providing a finger biometric sensing layer having an upper major surface and at least one sidewall surface adjacent thereto and for generating signals related to at least one biometric characteristic of the user&#39;s finger when positioned adjacent the first major surface. The method may further include positioning a piezoelectric transducer layer adjacent the at least one sidewall major surface of the finger biometric sensing layer. The method may still further include coupling a plurality of electrically conductive layers to the piezoelectric transducer layer to define transducer electrodes. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic plan view of a cellular telephone including a finger biometric sensor in accordance with the present invention. 
         FIG. 2  is a schematic cross-sectional view of the finger biometric sensor shown in  FIG. 1 . 
         FIG. 3  is a schematic block diagram of the finger biometric sensor and related circuitry shown in  FIG. 1 . 
         FIG. 4  is a more detailed schematic block diagram of the finger biometric sensor and related circuitry shown in  FIG. 3 . 
         FIG. 5  is a schematic block diagram of another embodiment of a finger biometric sensor and related circuitry in accordance with the present invention. 
         FIG. 6  is a more detailed schematic block diagram of the finger biometric sensor and related circuitry of  FIG. 5 . 
         FIG. 7  is a schematic block diagram of yet another embodiment of a finger biometric sensor and related circuitry in accordance with the present invention. 
         FIG. 8  is a more detailed schematic block diagram of the finger biometric sensor and related circuitry of  FIG. 7 . 
         FIG. 9  is a schematic block diagram of another embodiment of the finger biometric sensor and related circuitry in accordance with the present invention. 
         FIG. 10  is a schematic cross-sectional view of another embodiment of the finger biometric sensor. 
         FIG. 11  is a perspective view of another embodiment of the finger biometric sensor. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout, and prime and multiple prime notations are used to indicate similar elements in different embodiments. 
     Referring initially to  FIGS. 1-4 , an embodiment of a finger sensor  10  in accordance with the present invention are now described. The finger sensor  10  is illustratively mounted on an exposed surface of a cellular telephone  50 . Of course, the finger sensor  10  can also be used other portable and stationary electronic devices as well. 
     The cellular phone  50  includes a housing  51 , a display  52  carried by the housing, and processor/operating circuitry  53  also carried by the housing and connected to the display and to the finger sensor  10 . An array of input keys  54  are also provided and used for conventional cellphone dialing and other applications as will be appreciated by those skilled in the art. 
     The finger sensor  10  may be of the slide type where the user&#39;s finger  21  slides over the sensing area to generate a sequence of finger images. Alternatively, the finger sensor  10  could be of the static placement type, where the user simply places his finger  21  onto the sensing surface to generate a finger image. Of course, the finger sensor  10  may also include circuitry embedded therein and/or in cooperation with the processor/circuitry  53  to provide menu navigation and selection functions, tactile feedback, and/or power up functions as will be appreciated by those skilled in the art and as described in further detail below. 
     Referring more particularly to  FIG. 2 , the finger biometric sensor  10  includes a finger biometric sensing layer  11  having opposing first and second major surfaces  12 ,  13  and for generating signals related to at least one biometric characteristic of the user&#39;s finger when positioned adjacent the first major surface. The finger biometric sensor  10  may include electric field sensing pixels, for example, as described in U.S. Pat. No. 7,358,515, and assigned to the assignee of the present application, the entire contents of which are herein incorporated by reference. Other finger biometric sensing technologies may be used, as will be appreciated by those skilled in the art. 
     A piezoelectric transducer layer  14  is illustratively coupled to the second major surface  13  of the finger biometric sensing layer  11 . The piezoelectric transducer layer  14  may be a polyvinylidene fluoride material, or more specifically Kynar®, which is available from Arkuna, Inc., of Philadelphia, Pa. A polyvinylidene fluoride material can advantageously be fabricated down to a thickness to about 25 microns, for example, thus reducing the overall size impact to the finger biometric sensor  10 . Other piezoelectric materials may be used, such as piezo-ceramic materials or piezo-plastic materials, for example. 
     Moreover, the piezoelectric transducer layer  14  may be applied to the finger biometric sensor  10  as a pre-formed film, for example. Alternatively, the piezoelectric transducer layer  14  can be printed or spun. However, if the piezoelectric transducer layer  14  is not pre-formed, it may be polarized as part of its manufacturing process. Polarization of the piezoelectric transducer layer  14  typically involves using controlled high-voltage corona discharges across the piezoelectric transducer layer. The piezoelectric transducer layer  14  may be applied using other methods, or in other forms, as will be appreciated by those skilled in the art. 
     Electrically conductive layers  16 ,  17  are coupled to the piezoelectric transducer layer  14  to define transducer electrodes. More particularly, the upper conductive layer  16  may be considered as a voltage reference plane and is illustratively coupled between the finger sensing layer  11  and the piezoelectric transducer layer  14 . Additionally, the lower conductive layer  17  may be considered as a voltage collection layer coupled to a bottom of the piezoelectric transducer layer  14 . As will be appreciated by those skilled in the art, a piezoelectric voltage is generated between the upper conductive layer  16  and the lower conductive layer  17  when a force is imparted by a user&#39;s finger to the piezoelectric transducer layer  14  via the intervening electrically conductive layer  16 . In other embodiments there may be no intervening layer or more than one intervening layer. 
     The finger biometric sensing layer  11  is advantageously packaged as an integrated circuit, for example, in a ball grid array package illustratively including the mounting substrate  27  below the electrically conductive layer  17 , and the array of electrically conductive balls  37  carried by the substrate. Other packaging arrangements will be appreciated by those skilled in the art. 
     A finger drive electrode  18  is illustratively positioned on the mounting substrate  27  and is separated from the biometric sensing layer  11  and the piezoelectric transducer layer  14  by a molded plastic ring  19 . This finger drive electrode  18  is advantageously used with electric field sensing pixels as will be appreciated by those skilled in the art, but may not be needed for other sensing technologies. 
     Referring more particularly to  FIGS. 3-4 , the finger biometric sensor  10  includes a drive circuit  22  that is illustratively coupled to the transducer electrodes, that is, the electrically conductive layers  16 ,  17  to impart a force to the user&#39;s finger  21 . More particularly, the drive circuit  22  advantageously generates a drive voltage waveform that is applied to the piezoelectric transducer layer  14 , which, in turn, generates a mechanical force on a user&#39;s finger  21  when positioned adjacent the first major surface of the finger biometric sensing layer  11 . One possible implementation of a drive circuit  22  includes a zener diode  35  coupled in parallel with the electrically conductive layers  16 ,  17  to operate as a shunt regulator, and a drive amplifier  36  coupled to the zener diode, as illustrated in  FIG. 4 . As will be appreciated by those skilled in the art, the piezoelectric transducer layer  14  will vibrate when the drive circuit  22  provides an AC voltage to the piezoelectric transducer layer. The drive circuit  22  may drive the piezoelectric transducer layer  14  at voltage levels similar to an audio amplifier driving a piezoelectric headphone, for example. 
     The vibration of the piezoelectric transducer layer  14  advantageously provides tactile or haptic feedback to the user. Additionally, proper envelope shaping of the waveform along with fine-tuning of the frequency of short AC signal bursts from the drive circuit  22  to the piezoelectric transducer layer  14  can give the user the tactile impression of a click. This feedback may be particularly helpful to a user performing a navigation function on an electronic device, such as the cellphone  50 , for example, where a user is scrolling down a menu and the sensor generates a click each time the cursor crosses from one menu item to the next. Other types of tactile feedback different than a click, such as a longer duration vibration, may be used, and may be used for other applications than menu scrolling, as will be appreciated by those skilled in the art. 
     Referring now additionally to  FIGS. 5-8 , the finger biometric sensor  10 ′ includes a sense circuit  23 ′ that is coupled to the electrically conductive layers  16 ′,  17 ′ to sense a voltage generated by the piezoelectric transducer layer  14 ′ based upon a force imparted by the user&#39;s finger  21 ′. The sense circuit  23 ′ may be used as a standalone circuit or in conjunction with other circuitry. 
     When a user&#39;s finger  21 ′ imparts a force on the piezoelectric transducer layer  14 ′ via the intervening electrically conductive layer  16 ′, an electrical charge displacement signal or voltage signal is generated between the electrically conductive layers  16 ′,  17 ′. The voltage signal will vary depending on the amount of force received by the piezoelectric transducer layer  14 ′. 
     One possible implementation of a sense circuit  23 ′ includes a zener diode  35 ′ coupled in parallel with the electrically conductive layers  16 ′,  17 ′ to operate a shunt regulator with outputs that may be coupled to a level sensitive wake-up input or analog measurement input, for example, as shown in  FIG. 6 . This implementation may be particularly advantageous for power control applications. 
     The sense circuit  23 ′ may also generate a pressure output signal related to an amount of pressure applied by the user&#39;s finger  21 ′. The amount of applied pressure can advantageously be used to enhance a user interface or enhance menu navigation, for example. For example, the pressure information may be advantageously used as a second measurement dimension to assist both fingerprint verification and cursor or control navigation. In a cursor or control navigation mode, a measured increase in pressure, as indicated by an increase in the voltage of the signal, could be interpreted as a command from the user to accelerate the directed cursor movement. Alternatively, a relaxation of pressure, as indicated by a reduction in voltage of the signal, can be interpreted as a command to slow down the cursor movement. It should be understood that other conventions for navigation or control may be used based upon the pressure applied by the user&#39;s finger  21 ′. 
     When used in analog finger pressure measurements, the piezoelectric transducer layer  14 ′ may be coupled to an analog input port, or the signal may be conditioned using adjustable attenuators, or adjustable gain amplifiers. Where readout of the finger pressure is desired, a charge amplifier, or an electrical integrating circuit, including appropriate reset circuitry, may be used to convert the charge displacement generated by the piezoelectric transducer layer  14 ′ into a voltage proportional to the actual pressure. This circuitry may be included on the finger biometric sensor  10 ′ or a boot device external to the finger biometric sensor. Other arrangements may be implemented, as will be appreciated by those skilled in the art. 
     Referring now to  FIG. 7 , in addition to the sense circuit  23 ″ as described above, in other embodiments, the finger biometric sensor  10 ″ also illustratively includes a reading circuit  24 ″ coupled to the finger biometric sensing layer  11 ″ for reading signals therefrom. A power up circuit  25 ″ selectively powers up the reading circuit  24 ″ based upon the sense circuit  23 ″. More particularly, the sense circuit  23 ″ senses the signal or the presence of the force on the piezoelectric transducer layer  14 ″ via the intervening electrically conductive layer  16 ″ and cooperates with the power up circuit  25 ″ to selectively power up the reading circuit  24 ″ based upon the signal or force. 
     The reading circuit  24 ″ reads signals from the finger biometric layer  11 ″. The signals may be fingerprint image signals, or signals representing other finger biometrics. Advantageously, by selectively powering up the reading circuit  24 ″ based upon the charge displacement or pressure signal from an applied force, the finger biometric sensor  10 ″ provides a zero power consumption finger detection capability while in a standby mode, or finger-waiting mode. Thus, overall system power consumption is reduced and battery life in the portable device is increased. 
     The finger biometric sensor  10 ″ also illustratively includes a matcher  26 ″ coupled to the finger biometric sensing layer  11 ″ for determining a match based upon the at least one biometric characteristic of the user&#39;s finger  21 ″. The matcher  26 ″ may include or cooperate with a memory  27 ″ to store biometric characteristics. Each circuit described above may be used alone or in combination with the other circuits described herein or other circuitry that may be included in the finger biometric sensor  10 ″ or part of a host device, or be included in both the finger biometric sensor or the host device, for example. 
     Moreover, the power up circuit  25 ″ can also be used to wake up the finger biometric sensor  10 ″ when a finger  21 ″ is first applied by connecting the pressure signal to an interrupt line or other wake-up pin in the system. The interrupt line or other wake-up pin may be, for example, on or off the finger biometric sensor  10 ″. In other words, the wake-up pin may be part of a host processor in a host device. 
     Referring now additionally to  FIG. 8 , a possible implementation of the sense circuit  23 ″ and the power up circuit  25 ″ includes a zener diode  35 ″ that is coupled in parallel with the electrically conductive layers  16 ″,  17 ″ to operate as a shunt regulator with out puts that may be coupled to an asynchronous latch  38 ″. The asynchronous latch  38 ″ is illustrated as an SR type, but other types may be used. The outputs of the asynchronous latch  38 ″ may feed the power up circuit  25 ″, which illustratively includes a power switching device  39 ″. The power switching device  39 ″ and the asynchronous latch  38 ″ may be part of the finger biometric sensor  10 ″ or part of a host processor or host integrated circuit, or part of both, for example. Using the voltage limiting components advantageously reduces the amount of quiescent power consumption, as will be appreciated by those skilled in the art. Other components and configurations, such as a Schmidt trigger or a voltage reduction network, may be used. 
     Referring now additionally to  FIG. 9 , a processor  28 ′″, which includes a navigation module or circuit  29 ′″ and a feedback module or circuit  33 ′″, is illustratively included in the finger biometric sensor  10 ′″ and may be coupled to the electrically conductive layers  16 ′″,  17 ′″. While the processor  28 ′″ is illustratively included in the finger biometric sensor  10 ′″, it may be external to the finger biometric sensor, for example, on a host device, or may be included on both the finger biometric sensor or host device. Still further, while the processor  28 ′″ illustratively includes both the navigation circuit  29 ′″, to perform the navigation functions as discussed above, and the feedback circuit  33 ′″, to provide user feedback as discussed above, either circuit may be used independently of the other. Moreover, other modules or circuits may be included in the processor  28 ′″ to perform other functions or cooperate with other circuits to perform those functions. 
     In an alternate embodiment, as illustrated in  FIG. 10 , a finger biometric sensor  40  includes a finger biometric sensing layer  41  having an upper major surface  42  and sidewall surfaces  43   a - 43   b  adjacent thereto. The biometric sensing layer  41  is for generating signals related to at least one biometric characteristic of the user&#39;s finger when positioned adjacent the upper major surface. A piezoelectric transducer layer  45  is adjacent the sidewall surfaces  43   a - 43   b  of the finger biometric sensing layer  41 . The piezoelectric transducer layer  45  is similar in material and form to the piezoelectric transducer layer  14  described above. 
     Ring-shaped, upper and lower, electrically conductive layers  46 ,  47  are coupled to the piezoelectric transducer layer  45  to define transducer electrodes. More particularly the upper conductive layer  46  may also serve as a finger drive electrode and is coupled between the finger sensing layer  41  and the piezoelectric transducer layer  45 . The upper conductive layer  46  advantageously has a shared function as both a drive electrode for the finger sensing layer  41  and one of the transducer electrodes for the piezoelectric transducer layer  45 . A shared function electrode advantageously reduces the number of electrodes, and thus may reduce the overall package size of the finger biometric sensor  40 . However, in some embodiments, the electrode(s) may not be shared, and additional electrode(s) may be included. 
     A second transducer electrode provided by the lower conductive layer  47  may be considered as the piezoelectric voltage electrode and is illustratively coupled to the bottom of the piezoelectric transducer layer  45 . As will be appreciated by those skilled in the art, a piezoelectric voltage is generated between the conductive layers  46 ,  47  when a force is imparted by a user&#39;s finger to the piezoelectric transducer layer  45  via the intervening electrically conductive layer  46 . In other embodiments there may be no intervening layer or more than one intervening layer. 
     The finger biometric sensing layer  41  is advantageously packaged as an integrated circuit, for example. Other packaging arrangements will be appreciated by those skilled in the art. Additionally, a flexible mounting substrate  51  overlays the piezoelectric transducer layer  45  and the finger biometric sensing layer  41 , and is a Kapton® material, available from E. I. du Pont de Nemours and Company. Other substrate materials may be used. An underfill  52  provides separation between the flexible mounting substrate  51  and the finger biometric sensing layer  41 . Additionally the piezoelectric transducer layer  45  and the finger biometric sensing layer  41  are joined by an adhesive  53 . The adhesive  53  may also be used to join other components and layers, as will be appreciated by those skilled in the art. An optional sealing ring  54  is provided overlapping a portion of the flexible mounting substrate  51 . 
     Similar to the finger biometric sensor  10  embodiments described above in  FIGS. 1-3 , the finger biometric sensor  40  may be included in a cellular telephone  50 , or other portable electronics device, and also may include a drive circuit  22 . The drive circuit  22  is coupled to the transducer electrodes, or more particularly, to the upper conductive layer  46  and the lower conductive layer  47  to drive the piezoelectric transducer layer  45  to impart a force to the user&#39;s finger. Additionally, the finger biometric sensor  40  may include a sense circuit  23  coupled to the upper conductive layer  46  and the lower conductive layer  47  to sense from the piezoelectric transducer layer  45  a force imparted by the user&#39;s finger. 
     Still further, the finger biometric sensor  40  may include a reading circuit  24  coupled to the finger biometric sensing layer  41  for reading signals therefrom. A power up circuit  25  may also be included for selectively powering up the reading circuit based upon the sense circuit  23 . The sense circuit  23  may generate a pressure output signal related to the amount of pressure applied by the user&#39;s finger. The finger biometric sensor  40  may include a matcher  26  coupled to the finger biometric sensing layer  41  for determining a match based upon the at least one biometric characteristic of the user&#39;s finger, as is similar in structure and implementation to the matcher  26  described above. These circuits  22 ,  23 ,  24 ,  25 ,  26  as they are coupled to the finger biometric sensor  40 , are similar in structure and function to the circuits described above for the finger biometric sensor embodiments illustrated in  FIGS. 1-8 . 
     Similarly, a processor  28 , which includes a navigation circuit  29  and a feedback circuit  33 , is included in the finger biometric sensor  40  and may be coupled to the upper conductive layer  46  and the lower conductive layer  47 . While the processor  28  may be included in the finger biometric sensor  40 , it may be external to the finger biometric sensor, for example, a host processor. Still further, while the processor  28  illustratively includes both the navigation circuit  29  and the feedback circuit  33 , either circuit may be used independently of the other. 
     Referring now to  FIG. 11 , the finger biometric sensor  70  illustratively includes a flex tape or a tab interconnect  73  cooperating with the biometric sensing layer  72 . The biometric sensing layer  72  includes a sensing surface  71  and a sensor back cover  78  enclosing the biometric sensing layer. The upper conductive layer  76  is illustratively coupled to the bottom of the sensor back cover  78  of the biometric sensing layer  72 . The piezoelectric transducer layer  74  is illustratively coupled to the upper conductive layer  76 . The lower conductive layer  77  is coupled to the bottom of the piezoelectric transducer layer  74 . The flex tape, or tab interconnect  73 , advantageously attaches to a circuit (not shown) so that the sensing surface  71  is exposed through an opening in a host device housing for surface access by the user&#39;s finger, for example. 
     Returning again to  FIGS. 1-3 , another aspect is directed to a method of making a finger sensor  10 . The method includes providing a finger biometric sensing layer  11  having opposing first and second major surfaces  12 ,  13 . The finger biometric sensing layer  11  is for generating signals related to at least one biometric characteristic of the user&#39;s finger  21  when positioned adjacent the first major surface  12 . The method further includes coupling a piezoelectric transducer layer  14  to the second major surface  13  of the finger biometric sensing layer  11 . The method further includes coupling two electrically conductive layers, the upper conductive layer  16 , and the lower conductive layer  17 , to the piezoelectric transducer layer  14  to define transducer electrodes. 
     Returning again to  FIG. 10 , another aspect is directed to another method of making the finger sensor  40 . The method includes providing a finger biometric sensing layer  41  having an upper major surface  42  and sidewall surfaces  43   a - 43   b  adjacent thereto. The finger biometric sensing layer  41  is for generating signals related to the user&#39;s finger when positioned adjacent the upper major surface  42 . The method further includes coupling a piezoelectric transducer layer  45  to the sidewall surfaces  43   a - 43   b  of the finger biometric finger sensing layer  41 . The method further includes coupling electrically conductive layers, or more particularly, the upper conductive layer  46  and the lower conductive layer  47 , to the piezoelectric transducer layer  45  to define transducer electrodes. 
     Many modifications and other embodiments of the invention will come to the mind of one skilled in the art having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is understood that the invention is not to be limited to the specific embodiments disclosed, and that modifications and embodiments are intended to be included within the scope of the appended claims.

Metadata:
Filing Date: 20131217
Publication Date: 20150728
Grant Date: 20150728
Priority Date: 20090807
Inventors: SETLAK DALE R.
NEIL JAMES WARREN
WILLIAMS DARYL D.
JONES RICHARD J.
VAN VONNO NICOLAAS W.
Assignee: APPLE INC
CPC Classifications: [{"code": "G06V40/1306", "inventive": true, "first": true, "tree": "[]"}, {"code": "Y10T29/42", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06K9/00013", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06K9/0002", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06V40/1306", "inventive": true, "first": true, "tree": "[]"}, {"code": "Y10T29/42", "inventive": false, "first": false, "tree": "[]"}, {"code": "Y10T29/42", "inventive": false, "first": false, "tree": "[]"}]
Family ID: 43534399