Patent Publication Number: US-2023148255-A1

Title: Biometric sensor device with in-glass fingerprint sensor

Description:
PRIORITY CLAIM AND CROSS-REFERENCE 
     This application claims priority to U.S. provisional application Ser. No. 63/116,704 filed Nov. 20, 2020 and is a continuation-in-part of U.S. non-provisional application Ser. No. 17/336,006 filed Jun. 1, 2021, the disclosures of which are hereby incorporated by reference in their entirety. 
    
    
     TECHNICAL FIELD 
     The present disclosure is generally related to a biometric sensor device and, more particularly, to a sensor device with an in-glass biometric fingerprint sensor. 
     BACKGROUND 
     Nowadays the convenience of mobile appliances like IC cards, smart phones and notebook computers brings us better life but also into privacy threat. The more widespread these mobile appliances are, the more significant the issue on personal security is. As a result, the demand for user authentication is becoming more and more important. Some biometric features, such as fingerprint, palm print, finger vein, iris and voiceprint, have been popularly applied in user authentication. Because of the property of low-cost, easy integration and high reliability, fingerprint sensors have been extensively developed. However, the integration of the existing fingerprint sensor with other device, such as a display module, still may not provide satisfactory performance. It may therefore be desirable to have a fingerprint sensor design that is able to be compatible with the display module while maintaining a compact size. 
     SUMMARY 
     According to embodiments of the present invention, a device includes: a first biometric sensor formed on a substrate and configured to access a first biometric feature of a user; and a second biometric sensor arranged under the first biometric sensor and configured to access second a biometric feature of the user, wherein the second biometric sensor includes a light emitter configured to emit light to reach the user through the substrate and receive a reflection light for deriving the second biometric feature. 
     In some embodiments, the first biometric sensor is a fingerprint sensor. 
     In some embodiments, the first biometric sensor includes a substrate made of silicon oxide. 
     In some embodiments, the substrate is transparent to light emitted by the second biometric sensor. 
     In some embodiments, the device further includes a controller configured to: accessing the first biometric feature of the user during the accessing of the second biometric feature. 
     In some embodiments, the controller is further configured to continue with accessing the second biometric feature in response to determining that the user&#39;s identity is unchanged during the accessing of the second biometric feature. 
     In some embodiments, the determining of the user&#39;s identity as unchanged comprises repeatedly accessing the first biometric feature of the user during a time period of the accessing of the second biometric feature. 
     In some embodiments, the controller is further configured to clear data of the second biometric feature of the user in response to determining that the user&#39;s identity is changed or lost. 
     In some embodiments, the controller is further configured to resume a procedure of accessing the first biometric feature and the second biometric feature in response to determining that the user&#39;s identity is changed or lost. 
     In some embodiments, second biometric feature includes at least one of a blood oxygen level and a blood alcohol concentration. 
     According to embodiments of the present invention, a device includes a biometric sensor; and an oximeter disposed under the biometric sensor and configured to be operated associated with a biometric feature of a user. Light is generated by the self-light emitting device toward the user through the biometric sensor. 
     In some embodiments, the biometric sensor is a fingerprint sensor. 
     According to embodiments of the present invention, a method of operating a biometric sensor device includes: accessing a first biometric feature from a finger of a user by a first biometric sensor; and accessing a second biometric feature from the finger of the user by a second biometric sensor, wherein the first biometric sensor is stacked with the second biometric sensor. 
     In some embodiments, the accessing the first biometric feature comprises repeatedly accessing the first biometric feature during a time period of accessing the second biometric feature. 
     In some embodiments, the method further includes continuing with accessing the second biometric feature in response to determining that the user&#39;s identity is unchanged during the accessing of the second biometric feature. 
     In some embodiments, the determining of the user&#39;s identity as unchanged comprises repeatedly accessing the first biometric feature of the user during a time period of the accessing of the second biometric feature. 
     In some embodiments, the method further includes clearing data of the second biometric feature of the user in response to determining that the user&#39;s identity is changed or lost. 
     In some embodiments, the method further includes resuming a procedure of accessing the first biometric feature and the second biometric feature in response to determining that the user&#39;s identity is changed or lost. 
     In some embodiments, the first biometric information includes a fingerprint of the user. 
     In some embodiments, the second biometric information includes a blood oxygen level or a blood alcohol concentration of the user. 
     The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter. It should be appreciated by persons having ordinary skill in the art that the conception and specific embodiments disclosed may be readily utilized as a basis for modifying or designing other structures or processes for carrying out the same purposes of the present invention without departing from the spirit and scope of the invention as set forth in the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Details of one or more embodiments of the disclosure are set forth in the accompanying drawings and the description below. Other features and advantages of the disclosure will be apparent from the description, drawings and claims. Throughout the various views and illustrative embodiments, like reference numerals are used to designate like elements. Reference will now be made in detail to exemplary embodiments illustrated in the accompanying drawings. 
         FIG.  1 A  is a cross-sectional view of a biometric sensor device, in accordance with some embodiments of the present invention. 
         FIG.  1 B  is a cross-sectional view of a biometric sensor device, in accordance with some embodiments of the present invention. 
         FIGS.  2 A and  2 B  are top views of a protective layer of the biometric sensor device shown in  FIG.  1 A , in accordance with various embodiments of the present invention. 
         FIGS.  3 A and  3 B  are a schematic top view and a schematic bottom view, respectively, of a biometric sensor device, in accordance with various embodiments of the present invention. 
         FIGS.  3 C and  3 D  are a schematic left side view and a schematic right side view, respectively, of a biometric sensor device shown in  FIG.  3 A , in accordance with various embodiments of the present invention. 
         FIG.  4    is a cross-sectional view of a biometric sensor device, in accordance with an embodiment of the present invention. 
         FIG.  5    is a schematic flowchart of a method of operating a biometric sensor device, in accordance with various embodiments of the present invention. 
     
    
    
     DETAIL DESCRIPTION 
     In order to make the disclosure comprehensible, detailed steps and structures are provided in the following description. Obviously, implementation of the disclosure does not limit special details known by persons skilled in the art. In addition, known structures and steps are not described in detail, so as not to limit the disclosure unnecessarily. Preferred embodiments of the disclosure will be described below in detail. However, in addition to the detailed description, the disclosure may also be widely implemented in other embodiments. The scope of the disclosure is not limited to the detailed description, and is defined by the claims. 
     Further, it will be understood that when an element is referred to as being “connected to” or “coupled to” or “coupled with” another element, it may be directly connected to or coupled to the other element, or intervening elements may be present. 
       FIG.  1 A  is a cross-sectional view of a biometric sensor device  100 , in accordance with some embodiments of the present invention. In some embodiments, the biometric sensor device  100  is configured to sense biometric data and authenticate the user through the biometric data. The biometric sensor device  100  may be adapted to work with an electronic device (not shown), such as a smart phone, a personal computer and a personal digital assistant. Alternatively, the biometric sensor device  100  is adapted to work with a personal item protected by a tangible key or a password, such as a door lock, a combination lock, an identity card, a safe or the like, such that the biometric sensor device  100  can be used to protect personal information of the user in place of the key or password. In the present embodiment, the biometric sensor device  100  includes a fingerprint or palm print sensor and the biometric feature is the user&#39;s fingerprint and/or palm print patterns. The biometric sensor device  100  may be configured as a touch-mode sensor device, in which a stimulus source, e.g., the fingerprint, may be received by the sensing elements during a touch event of the biometric sensor device  100 . 
     Referring to  FIG.  1 A , the biometric sensor device  100  includes a first circuit board  110 , a second circuit board  120 , a third circuit board  130 , a conductive pillar  140  and a frame  150 . The biometric sensor device  100  further includes a biometric sensor  112 , a protective layer  114 , a cover plate  116 , a display  122 , and an adhesive layer  124 . 
     In the present embodiment, the display  122  is a self-light emitting display. The display  122  is arranged over and electrically connected to the second circuit board  120 . The display  122  may be formed of an organic light emitting diode (OLED) panel or other suitable self-luminous display. As an exemplary OLED display panel, the display  122  may include, but not limited to, a substrate, an anode layer, a hole transport layer, a light emitting layer, an electron transport layer, and a cathode layer arranged in a stack for emitting light in response to biasing voltages on the anode layer and the cathode layer. The light of the display  122  may transmit toward the user above the cover plate  116  through the adhesive layer  124 , the biometric sensor  112 , the protective layer  114  and the cover plate  116 . 
     The biometric sensor  112  is formed over the display  122 . The biometric sensor  112  may include a fingerprint sensor configured to capture or sense fingerprint or palm print data of a user&#39;s hand. In some embodiments, the biometric sensor  112  includes a first side  112 A facing toward a finger or a palm of the user and a second side  112 B opposite to the first side  112 A. The biometric sensor  112  includes a substrate made of a transparent material to the light emitted by the display  122  such that the image of the display  122  is visible through the biometric sensor  112 . The substrate of the biometric sensor  112  is formed of silicon oxide and may be in the form of glass or quartz, and thus the biometric sensor  112  is referred to herein as “in-glass fingerprint sensor.” 
     The biometric sensor  112  includes one or more sensing electrodes  113  on the top surface of the substrate of the biometric sensor  112 . The sensing electrodes  113  may include a plurality of sensing electrodes. In some embodiments, the sensing electrodes  113  include transparent conductive materials, such as indium tungsten oxide (ITO), fluorine doped tin oxide (FTO) or doped zinc oxide. In some embodiments, the biometric sensor  112  further include a sensing circuitry (not shown) connected to the sensing electrodes  113 . The sensing circuitry may include one or more transistors configured to provide a sensing voltage according to the sensing capacitance or sensing voltage according to the sensing electrodes. In some embodiments, the sensing voltage is transmitted to the third circuit board  130  for further processing. 
     In some embodiments, the adhesive layer  124  is used to adhere the biometric sensor  112  to the display  122 . The adhesive layer  124  may include an optically clear adhesive (OCA), such as LOCA (liquid optically clear adhesive). 
     The cover plate  116  is arranged over the biometric sensor  112 . In some embodiments, the cover plate  116  is transparent to a radiation spectrum of the display  122  such that the image of the display  122  is visible to the user through the cover plate  116 . The cover plate  116  is made of glass or other suitable transparent materials. 
     In some embodiments, the protective layer  114  is formed between the biometric sensor  112  and the cover plate  116  and configured to protect the biometric sensor  112  or other features of the biometric sensor device  100  from damage by an electrostatic discharge (ESD) effect. In some embodiments, the protective layer  114  is arranged over the first side  112 A of the biometric sensor  112 .  FIG.  2 A  shows a top view of the protective layer  114  overlaid with the biometric sensor  112 , in which the cross-sectional view of  FIG.  1 A  is taken from the sectional line AA of  FIG.  2 A . Referring to  FIG.  1 A  and  FIG.  2 A , the biometric sensor  112  includes a plurality of sensing electrodes  113  configured to detect a coupled capacitance with the user&#39;s finger. In some embodiments, the sensing electrodes  113  are arranged in a grid or array. In some embodiments, the sensing electrodes  113  are classified into drive electrodes for providing driving signals and receive electrodes for receiving sensing signals. The drive electrodes may be alternatively arranged with the receive electrodes. 
     In some embodiments, the protective layer  114  includes a conductive layer  114 C and an insulating layer  114 D surrounding the conductive layer  114 C. In some embodiments, the conductive layer  114 C is formed of conductive materials, such as copper, tungsten, aluminum, or other suitable conductive materials. The insulating layer  114 D is used for electrically insulate the conductive layer  114 C from other conductive features of the biometric sensor device  100 . The insulating layer  114 D may be formed of a dielectric material, such as silicon oxide, silicon nitride, resin, epoxy, polymer, or other suitable materials. 
     The conductive layer  114 C is formed over the array of the sensing electrodes  113  and configured to protect the sensing electrodes  113  from the ESD damage. In the present embodiment, the mesh pattern of the conductive layer  114 C partitions the electrodes of the sensing electrodes  113  into electrode groups each including four electrodes from a top-view perspective. However, the present disclosure is not limited thereto. The mesh pattern of the conductive layer  114 C may be configured otherwise to partition the sensing electrodes  113  into electrode groups of various electrode numbers. In some embodiments, the protective layer  114  has a thickness in the z-direction in a range between about 1 μm and about 3 μm, such as 2 μm. In some embodiments, the first circuit board  110  has a thickness substantially equal to a thickness sum of the biometric sensor  112 , the protective layer  114  and the cover plate  116 . In some embodiments, the first circuit board  110  has a thickness substantially equal to a thickness sum of the biometric sensor  112 , the protective layer  114 , the cover plate  116  and the adhesive layer  124 . 
       FIG.  2 B  is a top view of the protective layer  114  overlaid with the biometric sensor  112 , in accordance with another embodiment. In the embodiment shown in  FIG.  2 B , the protective layer  114  includes a conductive layer  114 E and an insulating layer  114 D. The conductive layer  114 E is similar to the conductive layer  114 C in many aspects, except that the conductive layer  114 E forms a mesh pattern which partitions the array of sensing electrodes  113  into individual electrodes. In some embodiments, each of the sensing electrodes  113  is laterally surrounded by the mesh pattern of the conductive layer  114 E from a top-view perspective. 
     Referring to  FIG.  1 A , the first circuit board  110 , the second circuit board  120  and the third circuit board  130  are arranged in parallel along the xy-plane over one another. A stack formed of the cover plate  116 , the protective layer  114 , the biometric sensor  112 , the adhesive layer  124  and the display  122  is formed over the second circuit board  120  and extends through the first circuit board  110 . The first circuit board  110 , the second circuit board  120  and the third circuit board  130  are connected by the conductive pillar  140 . The conductive pillar  140  may be formed of a screw, a bolt, a nail, or other conductive members, and may run in the z-direction perpendicular to the xy-plane through the first circuit board  110 , the second circuit board  120  and the third circuit board  130 . In some embodiments, the circuit board  110 ,  120  or  130  has a thickness in the z-direction in a range between about 600 μm and about 1000 μm, such as 700 μm. In some embodiments, each of the circuit boards  110 ,  120  and  130  include insulating materials, e.g., a solder mask, configured to electrically insulate the conductive pillar  140  from the conductive features of the circuit boards  110 ,  120  and  130 . The conductive pillar  140  may serve the function of securing the circuit boards  110 ,  120  and  130 . Further, the conductive pillar  140  is configured to provide electric signals, e.g., a sensing clock signal, between the circuit boards  110  and  130 . The electric signals may be transmitted to the user&#39;s finger and aid in establishing an electric field between the user&#39;s finger and the sensing electrodes  113  to thereby generate a coupled capacitance in the presence of the user&#39;s finger. 
     The frame  150  is arranged over the first circuit board  110  and adjacent to the cover plate  116 . In some embodiments, the frame  150  include a cover portion exposing the cover plate  116 . The frame  150  may be formed of a rigid material for providing mechanical support of the first circuit board  110 . A molding material  118  is provided between the cover plate  116  and the frame  150  to encapsulate the cover plate  116 . The molding material  118  may be formed of resin, epoxy, and the like. In some embodiments, the frame  150  is formed of conductive materials and configured to receive electric signals, in response to a touch event, to the circuit boards  110 ,  120  or  130 . Although not separately shown, the frame  150  may include a bevel portion surrounding sidewalls of the cover plate  116 , the protective layer  114  and the biometric sensor  112 . 
     In some embodiments, the frame  150  includes a conductive material, e.g., formed of a metallic material, and electrically coupled to the conductive pillar  140 . The frame  150  faces the user&#39;s finger and conducts electric current through the conductive pillar  140 . During operation, when the user&#39;s finger touches the cover plate  116 , the user&#39;s finger will also touches the conductive frame  150 . In this way, the finger will conduct current by help of the frame  150  to facilitate the sensing process of the fingerprint. In some embodiments, the first circuit board  110  includes a conductive layer exposed from the upper surface of the first circuit board  110 . The conductive layer of the first circuit board  110  may face the frame  150  and the finger of the user, in which the conductive layer is configured to convey electric signals to the user&#39;s finger from the conductive pillar  140  during a touch event. In some other embodiments, the frame  150  is formed of non-conductive materials, such as glass, plastics, ceramic, or the like. 
     The first circuit board  110  is configured to support the frame  150 . In some embodiments, the first circuit board  110  is configured to secure and electrically connect to the biometric sensor  112 . The first circuit board  110  may be a printed circuit board (PCB), a metal core PCB (MCPCB) or a flexible PCB (FPCB). The first circuit board  110  may include an opening defined by a peripheral region, in which the biometric sensor  112  is embedded in the opening and laterally surrounded by the peripheral region of the first circuit board  110 . In some embodiments, although not explicitly shown, the first circuit board  110  includes a bus, e.g., formed of conductive wirings or vias, electrically connected to the biometric sensor  112 . 
     In some embodiments, the first circuit board  110  includes a conductive layer  117  formed on the upper surface of the first circuit board  110  and laterally surrounding the cover plate  116 . The conductive layer  117  may be electrically coupled to the frame  150  and configured to transmit electric signals, in response to a touch event, to the second circuit board  120  or the third circuit board  130  through the frame  150 . 
     The second circuit board  120  includes an upper surface on which the display  122  is disposed. In some embodiments, the second circuit board  120  is configured to electrically connect the display  122  with external devices. The second circuit board  120  may be a PCB, a MCPCB or a FPCB. In some embodiments, the second circuit board  120  includes an electronic device  126  disposed on a lower surface thereof opposite to the upper surface of the second circuit board  120 . The electronic device  126  may be a display driver device configured to control display functions of the display  122 . In some embodiments, the second circuit board  120  includes a bus  128  to electrically connect the display  122  with the electronic device  126 . The bus  128  may a bus formed as a flexible printed circuit (FPC), or including bonding wires or conductive vias extending through the second circuit board  120 . 
     The third circuit board  130  is configured to electrically connect the first circuit board  110  and the second circuit board  120  to external devices. The third circuit board  130  may be a PCB, a MCPCB or a FPCB. The third circuit board  130  includes an electronic device  132 , a connector  134  and a connection port  136  disposed on a lower surface. The third circuit board  130  also includes and an electronic device  138  and a connector  142  disposed on an upper surface opposite to the lower surface of the third circuit board  130 . 
     The electronic device  132  may be a processor, a microcontroller, a signal processing unit, or the like configured to control the sensing functions of the biometric sensor  112  and the display functions of the display  122 . The third circuit board  130  is electrically connected to the biometric sensor  112  through a bus  135 , e.g., an FPC, a bonding wire, or the connector  134  on the third circuit board  130 . The connector  134  may be a socket or solder pads to be electrically coupled to the bus  135 . The connector  134  may be a serial connector or a parallel connector. In some embodiments, the connection port  136  is a universal serial bus (USB) port for electrically connect the third circuit board  130  with devices external to the biometric sensor device  100 . 
     In some embodiments, the electronic device  138  is a sensor driver device configured to enable the sensing functions of the biometric sensor  112 . In some embodiments, the electronic device  132  is configured to control the biometric sensor  112  and the display  122  through the electronic devices  138  and  126 , respectively. The electronic device  138  may be electrically connected to the biometric sensor  112  through the bus  135  and the connector  134 , and optionally through conductive vias of the third circuit board  130 . In some embodiments, the electronic device  138  is configured to generate the sensing clock signals and transmit the sensing clock signals to the user&#39;s finger through the first circuit board  110  or the frame  150 . 
     The connector  142  may electrically connect the third circuit board  130  to the second circuit board  120 . In some embodiments, the connector  142  includes a bus, e.g., an FPC or a bonding wire, and a socket for electrically coupling the second circuit board  120  to the third circuit board  130  to thereby provide power or signals between the circuit boards  120  and  130 . The connector  142  may be a serial connector or a parallel connector. 
     During a touch event, the biometric sensor  112  is configured to sense the presence of the user&#39;s finger. The biometric sensor  112  and the electronic device  132  are configured to authenticate the user through recognizing the fingerprint pattern of the user. In some embodiments, the display  122  is configured to generate an image which contains instructions or recognition results that can be shown to the user through the in-glass biometric sensor  112 . In some embodiments, the display  122  is configured to show the image to the user in response to a sensing result, associated with a biometric feature of the user, of the biometric sensor  112 . In some embodiments, the display  122  is configured to display the image associated with the sensing result provided by the biometric sensor  112  before, during, or after the fingerprint recognition process is performed. Since the substrate and the sensing electrodes  113  of the biometric sensor  112  are made of transparent materials, the image of the display  122  can be readily visible to the user during the touch event. No extra areas are required for the individual biometric sensor  112  and the display  122 . Therefore, the biometric sensor device  100  is capable of providing both the display and fingerprint recognition functions with a minimized device size. 
       FIG.  1 B  is a cross-sectional view of a biometric sensor device  200 , in accordance with some embodiments of the present invention. In some embodiments, the biometric sensor device  200  is similar to the biometric sensor device  100  in many aspects, and thus descriptions of these similar features are not repeated for brevity. The biometric sensor device  200  is different from the biometric sensor device  100  in that the conductive layer  114 C, which laterally surrounds the sensing electrodes  113 , is arranged in the same level of the sensing electrodes  113 . In such arrangement, the conductive layer  114 C is arranged on the first side  112 A of the biometric sensor  112 . In some embodiments, the sensing electrodes  113  are insulated from the conductive layer  114 C by an insulating material. The insulating material may include a material similar to the tha of the insulating layer  114 D. The insulating layer is arranged over the sensing electrodes  113  and the conductive layer  114 C. 
       FIGS.  3 A and  3 B  are a schematic top view and a schematic bottom view, respectively, of a biometric sensor device  300 , in accordance with various embodiments of the present invention.  FIGS.  3 C and  3 D  are a schematic left side view and a schematic right side view, respectively, of the biometric sensor device  300  shown in  FIG.  3 A , in accordance with various embodiments of the present invention. The biometric sensor device  300  is similar to the biometric sensor device  100  in many features, and thus descriptions of these features are omitted for brevity. Referring to  FIG.  3 A , the top view of the biometric sensor device  300  includes the cover plate  116 , the biometric sensor  112  and the display  122  stacked in the z-direction, in which the screen of the display  122  is visible through the biometric sensor  112  and the cover plate  116 . The biometric sensor  112  includes a sensing circuit  304  and the sensing electrodes  113 . In some embodiments, the sensing circuit  304  may be non-transparent to the light emitted by the display  122 . In some embodiments, the sensing circuit  304  is formed of semiconductor materials, such as silicon, germanium, or the like. In some embodiments, the biometric sensor  112  fully overlaps the display  122  from a top-view perspective. In some embodiments, the sensing electrodes  113  of the biometric sensor  112  occupy an area substantially equal to the area of the display  122 . In some embodiments, the biometric sensor  112  has an area greater than the area of the display  122  due to the sensing circuit  304 . 
     In some embodiments, referring to  FIGS.  3 A,  3 C and  3 D , the first circuit board  110  laterally surrounds the cover plate  116  and the biometric sensor  112 . In some embodiments, the first circuit board  110  includes the conductive layer  117  formed on the upper surface of the first circuit board  110  and laterally surrounding the cover plate  116 . The conductive layer  117  may be in a circular shape or a ring shape, and is substantially level with the cover plate  116  or arranged facing the finger of the user. In some embodiments, the bus  135  is electrically coupled to the first circuit board  110  or the sensing circuit  304  of the biometric sensor  112 . 
       FIG.  4    is a cross-sectional view of a biometric sensor device  400 , in accordance with an embodiment of the present invention. The biometric sensor device  400  is similar to the biometric sensor device  100  in many features, and thus descriptions of these features are omitted for brevity. The biometric sensor device  400  differs from the biometric sensor device  100  in that the biometric sensor device  400  alternatively or additionally includes another biometric sensor  402 , which is configured as a health condition detector e.g., a pulse oximeter, or simply an oximeter, a blood alcohol concentration detector, or the like. In some embodiments, the biometric sensor  402  serving as a self-light emitting device and arranged on the second circuit board  120 . As shown in  FIG.  4   , the biometric sensor  112  fully overlaps or aligns the biometric sensor  402  in a vertical direction. In some embodiments, biometric sensor  402  is configured as a pulse oximeter to measure the oxygen level in the user&#39;s blood stream as a health condition of the user in a non-invasive manner through transmission of sensing light to the user&#39;s finger through the biometric sensor  112  and the cover plate  116 . In some embodiments, the sensing light of the pulse oximeter  402  is in a range of red light and infrared light. In a touch event, the biometric sensor device  400  is capable of performing user authentication and blood oxygen level (BOL) at the same time. In addition, due to the transparent substrate and the transparent sensing electrode  113  of the biometric sensor  112 , the sensing light of the pulse oximeter  402  can be readily transmitted to the user and reflected to the pulse oximeter  402  during the touch event. No extra areas are required for disposing individual biometric sensor  112  and the pulse oximeter  402 . Therefore, the biometric sensor device  400  is capable of providing both the BOL measurement and fingerprint recognition functions with a minimized device size. 
     In some embodiments, the biometric sensor  402  is configured as a blood alcohol concentration (BAC) detector, or simply an alcohol detector, to detect the alcohol concentration in the blood stream of the user. The alcohol detector  402  may be useful in accessing the state of consciousness of the user by determining the BAC in the blood stream of the user. In some embodiments, the alcohol detector  402  is configured to emit a sensing light to a finger artery or a finger vein of the user and receive a reflection light reflected from the blood stream in the artery or vein of the user. In a touch event, the biometric sensor device  400  is capable of performing user authentication and BAC at the same time. Due to the transparent property of the substrate and the transparent sensing electrode  113  of the biometric sensor  112 , the sensing light of the alcohol detector  402  can be readily transmitted to the user and reflected to the alcohol detector  402  during the touch event. No extra circuit areas are required for the alcohol detector  402 . Therefore, the biometric sensor device  400  is capable of providing both the BAC measurement and fingerprint recognition functions with a minimized device size. 
     Since the biometric sensor  112  and the biometric sensor  402  are integrated in the single biometric sensor device  400 , and the biometric sensor  402  is configured to perform BOL or BAC detection through the same user finger(s) during user authentication by the biometric sensor  112 , the biometric sensor  112  can help authenticate the identity of the user who is subjected to the BOL or BAC test. The chances of fraud of counterfeit of the BOL or BAC test by the user can be effectively reduced. 
     In some embodiments, the alcohol detector  402  includes an optical device for performing BAC detection. The optical device may include a self-light emitter and a light receiver (e.g., a photodiode) configured to emit the light and receive the reflection light, respectively, wherein the light is incident on the user&#39;s artery or vein in the finger in contact with the biometric sensor device  400 . The light used in the alcohol detector  402  may be in a range of red light and invisible light, e.g., infrared light. In some embodiments, at least one of the light&#39;s properties, e.g., light strength, the wavelength, propagation time, or the like, is changed according to the alcohol concentration in the blood stream. The BAC of the user can be derived based on the changed light property in a non-invasive manner. 
     In some embodiments, it takes a first period of time T 1  for obtaining a result of BOL or BAC measurement and derivation, and it takes a second period of time T 2  to obtaining a result of a user fingerprint authentication. In some embodiments, the period of time T 1  is greater than the period of time T 2 , and a ratio of T 1 /T 2  may be in a range between about 1.5 and about 10.0, such as 3.0. In that situation, when a user is subjected to a BOL or BAC test using the biometric sensor device  400 , the biometric sensor  112  may be configured to repeat the steps of user authentication to ensure the user identity is kept unchanged during the period of the BOL or BAC test. This synchronous authentication function provided by the biometric sensor  112  may be useful in some usage scenarios for driving a car or operating a machine where high driver/operator concentration is required. The biometric sensor  112  can help confirm the authenticity of the BOL or BAC testing result performed by the biometric sensor  402  when no any other person is present to make sure the testing result is trustable. 
       FIG.  5    is a schematic flowchart of a method  500  of operating a biometric sensor device, in accordance with various embodiments of the present invention. The biometric sensor device may at least include a first biometric sensor, e.g., biometric sensor  112 , and a second biometric sensor, e.g., a health condition detector such as a pulse oximeter or an alcohol detector, integrated in the same biometric sensor device. It should be appreciated that more steps can be added to the method  500  in other embodiments, or some of the steps in the method  500  can be removed or modified. The order of the steps in the method  500  can be interchanged, and some of the steps in the method  500  can be performed independently or at the same time. In some embodiments, the biometric sensor device further includes a controller, e.g., implemented by the electronic device  132 , configured to control operations of the elements of the biometric sensor device and handle the procedures in each step of the method  500 . 
     At step  502 , a first biometric feature associated with an identity of a user is accessed from the first biometric sensor device during a first period of time. In some embodiments, the first biometric feature associated with the user&#39;s identity includes at least one of a user&#39;s fingerprint pattern and palm print pattern. 
     At step  504 , a second biometric feature associated with a health condition of the user is accessed from the second biometric sensor during a second period of time. In some embodiments, the second biometric feature associated with the user&#39;s health condition includes at least one of a BOL and a BAC of the user. 
     At step  506 , the health condition of the user is determined based on the second biometric feature. At step  508 , it is determined whether the identity of the user is changed during the accessing or derivation of the second biometric feature. 
     At step  510 , if it is determined that the user identity is unchanged during the accessing or derivation of the second biometric feature, the biometric sensor device is configured to re-access the first biometric feature to authenticate the user repeatedly until the accessing or derivation of the second biometric feature is completed. In some embodiments, the repeated accessing operations of the first biometric feature may be performed with a time spacing, e.g., every 0.5 seconds, every 1 second, every 3 second, or other suitable time spacing values. In some embodiments, the repeatedly acquired first biometric feature data are accessed in a continuous mode without any time gap. In some embodiments, the first biometric feature is accessed at least twice, e.g., at the starting time and at the completion time of the accessing of the second biometric features. 
     At step  512 , if it is determined that the user identity is changed or lost during the period of accessing or deriving the second biometric feature, it is determined that the accessed second biometric feature is not reliable or trustworthy. The biometric sensor device may be configured to clear all data of the second biometric feature that have been accessed. In some embodiments, the method  500  further loops back to step  502  to resume the accessing procedure of accessing the first and second biometric features. 
     At step  514 , it is determined whether a result of the health condition based on the second biometric feature has been generated. If affirmative, the method  500  proceeds to step  516  to output the result of the health condition. If the result of the health condition is not available yet, the method  500  loops back to step  504  to continue with the accessing of the second biometric feature, to step  506  of determination of the health condition based on the second biometric feature. 
     Although the disclosure has been shown and described with respect to one or more implementations, equivalent alterations and modifications will occur to others skilled in the art based upon a reading and understanding of this specification and the annexed drawings. The disclosure includes all such modifications and alterations and is limited only by the scope of the following claims.