Patent Publication Number: US-2023135449-A1

Title: Electronic device and method for performing face authentication using a plurality of cameras

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application is a continuation application, claiming priority under § 365(c), of an International application No. PCT/KR2022/000058, filed on Jan. 4, 2022, which is based on and claims the benefit of a Korean patent application number 10-2021-0148725, filed on Nov. 2, 2021, in the Korean Intellectual Property Office, the disclosure of which is incorporated by reference herein in its entirety. 
    
    
     TECHNICAL FIELD 
     The disclosure relates to an electronic device and a method for performing face authentication by using multiple cameras. 
     BACKGROUND ART 
     A face authentication technology is a biometric authentication technology used by an electronic device to authenticate a user based on a face image acquired through a camera. The face authentication technology may be used to confirm the identity of an authentication target in a contactless manner. The face authentication technology, due to convenience and efficiency thereof, has recently been widely used in various application fields such as security systems, mobile authentication, and multimedia data search. 
     The above information is presented as background information only to assist with an understanding of the disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with regard to the disclosure. 
     DISCLOSURE OF INVENTION 
     Technical Problem 
     Electronic devices have recently been equipped with multiple cameras, and respective cameras may have different characteristics. For example, the characteristics may include the angle of view, resolution, noise characteristics, or transmittance characteristics of the cameras. An electronic device may pre-register the user&#39;s face information through a first camera, and the electronic device may perform face authentication based on a face image acquired through the first camera after the pre-registration or a face image acquired through a second camera. In this case, face authentication through the first camera may be highly reliable, but face authentication through the second camera having second characteristics different from the first characteristics may have low reliability. This is because characteristics of a face image captured through the second camera are different from characteristics of a face image captured through the first camera. 
     Aspects of the disclosure are to address at least the above-mentioned problems and/or disadvantages and to provide at least the advantages described below. Accordingly, an aspect of the disclosure is to provide an electronic device and a method, wherein in connection with face authentication by an electronic device having multiple cameras, reliability of the face authentication can be improved, and user convenience can be improved. 
     Technical problems to be solved by the disclosure are not limited to the above-mentioned technical problems, and other technical problems not mentioned herein will be clearly understood from the following description by those skilled in the art to which the disclosure pertains. 
     Additional aspects will be set forth in part in the description which follows and, in part, will be apparent from the description, or may be learned by practice of the presented embodiments. 
     Solution to Problem 
     In accordance with an aspect of the disclosure, an electronic device is provided. The electronic device includes a first camera device having a first characteristic, a second camera device having a second characteristic different from the first characteristic, a memory, and a processor operatively connected to the first camera device, the second camera device, and the memory, wherein the memory is configured to store instructions which, when being executed, cause the processor to receive a request for registration of face information through the first camera device, acquire, based on the request, multiple first images through the first camera device, perform filtering for each of the multiple first images to generate multiple second images reflecting the second characteristic of the second camera device, generate multiple first templates, based on the multiple first images, generate multiple second templates, based on the multiple second images, and store the multiple first templates and the multiple second templates in the memory, thereby completing the registration of the face information. 
     In accordance with another aspect of the disclosure, a method of an electronic device including a memory, a first camera device having a first characteristic, and a second camera device having a second characteristic different from the first characteristic is provided. The method includes receiving a request for registration of face information through the first camera device, acquiring, based on the request, multiple first images through the first camera device, performing filtering for each of the multiple first images to generate multiple second images reflecting the second characteristic of the second camera device, generating multiple first templates, based on the multiple first images, generating multiple second templates, based on the multiple second images, and storing the multiple first templates and the multiple second templates in the memory, thereby completing the registration of the face information. 
     Advantageous Effects of Invention 
     An electronic device and a method according to various embodiments of the disclosure may, in connection with face authentication by an electronic device having multiple cameras, improve reliability of the face authentication and may improve user convenience. 
     Other aspects, advantages, and salient features of the disclosure will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses various embodiments of the disclosure. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The above and other aspects, features, and advantages of certain embodiments of the disclosure will be more apparent from the following description taken in conjunction with the accompanying drawings, in which: 
         FIG.  1    is block diagram of an electronic device in a network environment according to an embodiment of the disclosure; 
         FIG.  2    illustrates an unfolded state of an electronic device according to an embodiment of the disclosure; 
         FIG.  3    illustrates a folded state of the electronic device in  FIG.  2    according to an embodiment of the disclosure; 
         FIG.  4    is a block diagram of an electronic device according to an embodiment of the disclosure; 
         FIG.  5    is a flowchart illustrating operations of an electronic device according to an embodiment of the disclosure; 
         FIG.  6    illustrates an operation of generating a conversion filter according to an embodiment of the disclosure; 
         FIG.  7    illustrates an operation of converting an image acquired from a first camera device according to an embodiment of the disclosure; 
         FIG.  8    illustrates an operation of converting an image acquired from a second camera device according to an embodiment of the disclosure; 
         FIG.  9    illustrates an operation in which an electronic device according to an embodiment generates multiple first and second templates by using an image acquired from a second camera device according to an embodiment of the disclosure; 
         FIG.  10    illustrates an operation in which an electronic device according to an embodiment generates multiple first and second templates by using an image acquired from a first camera device according to an embodiment of the disclosure; 
         FIG.  11    is a flowchart illustrating an operation of managing multiple templates by an electronic device according to an embodiment of the disclosure; 
         FIG.  12    illustrates an operation of optimizing multiple templates by an electronic device according to an embodiment of the disclosure; 
         FIG.  13    illustrates an operation of adjusting priorities of multiple templates on the basis of a matching score by an electronic device according to an embodiment of the disclosure; and 
         FIG.  14    is a flowchart illustrating an operation of performing face authentication by an electronic device according to an embodiment of the disclosure. 
     
    
    
     Throughout the drawings, it should be noted that like reference numbers are used to depict the same or similar elements, features, and structures. 
     MODE FOR THE INVENTION 
     The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of various embodiments of the disclosure as defined by the claims and their equivalents. It includes various specific details to assist in that understanding but these are to be regarded as merely exemplary. Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the various embodiments described herein can be made without departing from the scope and spirit of the disclosure. In addition, descriptions of well-known functions and constructions may be omitted for clarity and conciseness. 
     The terms and words used in the following description and claims are not limited to the bibliographical meanings, but, are merely used by the inventor to enable a clear and consistent understanding of the disclosure. Accordingly, it should be apparent to those skilled in the art that the following description of various embodiments of the disclosure is provided for illustration purpose only and not for the purpose of limiting the disclosure as defined by the appended claims and their equivalents. 
     It is to be understood that the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “a component surface” includes reference to one or more of such surfaces. 
       FIG.  1    is a block diagram illustrating an electronic device in a network environment according to an embodiment of the disclosure. 
     Referring to  FIG.  1   , an electronic device  101  in a network environment  100  may communicate with an electronic device  102  via a first network  198  (e.g., a short-range wireless communication network), or at least one of an electronic device  104  or a server  108  via a second network  199  (e.g., a long-range wireless communication network). According to an embodiment, the electronic device  101  may communicate with the electronic device  104  via the server  108 . According to an embodiment, the electronic device  101  may include a processor  120 , memory  130 , an input module  150 , a sound output module  155 , a display module  160 , an audio module  170 , a sensor module  176 , an interface  177 , a connecting terminal  178 , a haptic module  179 , a camera module  180 , a power management module  188 , a battery  189 , a communication module  190 , a subscriber identification module (SIM)  196 , or an antenna module  197 . In some embodiments, at least one of the components (e.g., the connecting terminal  178 ) may be omitted from the electronic device  101 , or one or more other components may be added in the electronic device  101 . In some embodiments, some of the components (e.g., the sensor module  176 , the camera module  180 , or the antenna module  197 ) may be implemented as a single component (e.g., the display module  160 ). 
     The processor  120  may execute, for example, software (e.g., a program  140 ) to control at least one other component (e.g., a hardware or software component) of the electronic device  101  coupled with the processor  120 , and may perform various data processing or computation. According to one embodiment, as at least part of the data processing or computation, the processor  120  may store a command or data received from another component (e.g., the sensor module  176  or the communication module  190 ) in volatile memory  132 , process the command or the data stored in the volatile memory  132 , and store resulting data in non-volatile memory  134 . According to an embodiment, the processor  120  may include a main processor  121  (e.g., a central processing unit (CPU) or an application processor (AP)), or an auxiliary processor  123  (e.g., a graphics processing unit (GPU), a neural processing unit (NPU), an image signal processor (ISP), a sensor hub processor, or a communication processor (CP)) that is operable independently from, or in conjunction with, the main processor  121 . For example, when the electronic device  101  includes the main processor  121  and the auxiliary processor  123 , the auxiliary processor  123  may be adapted to consume less power than the main processor  121 , or to be specific to a specified function. The auxiliary processor  123  may be implemented as separate from, or as part of the main processor  121 . 
     The auxiliary processor  123  may control at least some of functions or states related to at least one component (e.g., the display module  160 , the sensor module  176 , or the communication module  190 ) among the components of the electronic device  101 , instead of the main processor  121  while the main processor  121  is in an inactive (e.g., sleep) state, or together with the main processor  121  while the main processor  121  is in an active state (e.g., executing an application). According to an embodiment, the auxiliary processor  123  (e.g., an image signal processor or a communication processor) may be implemented as part of another component (e.g., the camera module  180  or the communication module  190 ) functionally related to the auxiliary processor  123 . According to an embodiment, the auxiliary processor  123  (e.g., the neural processing unit) may include a hardware structure specified for artificial intelligence model processing. An artificial intelligence model may be generated by machine learning. Such learning may be performed, e.g., by the electronic device  101  where the artificial intelligence is performed or via a separate server (e.g., the server  108 ). Learning algorithms may include, but are not limited to, e.g., supervised learning, unsupervised learning, semi-supervised learning, or reinforcement learning. The artificial intelligence model may include a plurality of artificial neural network layers. The artificial neural network may be a deep neural network (DNN), a convolutional neural network (CNN), a recurrent neural network (RNN), a restricted boltzmann machine (RBM), a deep belief network (DBN), a bidirectional recurrent deep neural network (BRDNN), deep Q-network or a combination of two or more thereof but is not limited thereto. The artificial intelligence model may, additionally or alternatively, include a software structure other than the hardware structure. 
     The memory  130  may store various data used by at least one component (e.g., the processor  120  or the sensor module  176 ) of the electronic device  101 . The various data may include, for example, software (e.g., the program  140 ) and input data or output data for a command related thereto. The memory  130  may include the volatile memory  132  or the non-volatile memory  134 . 
     The program  140  may be stored in the memory  130  as software, and may include, for example, an operating system (OS)  142 , middleware  144 , or an application  146 . 
     The input module  150  may receive a command or data to be used by another component (e.g., the processor  120 ) of the electronic device  101 , from the outside (e.g., a user) of the electronic device  101 . The input module  150  may include, for example, a microphone, a mouse, a keyboard, a key (e.g., a button), or a digital pen (e.g., a stylus pen). 
     The sound output module  155  may output sound signals to the outside of the electronic device  101 . The sound output module  155  may include, for example, a speaker or a receiver. The speaker may be used for general purposes, such as playing multimedia or playing record. The receiver may be used for receiving incoming calls. According to an embodiment, the receiver may be implemented as separate from, or as part of the speaker. 
     The display module  160  may visually provide information to the outside (e.g., a user) of the electronic device  101 . The display module  160  may include, for example, a display, a hologram device, or a projector and control circuitry to control a corresponding one of the display, hologram device, and projector. According to an embodiment, the display module  160  may include a touch sensor adapted to detect a touch, or a pressure sensor adapted to measure the intensity of force incurred by the touch. 
     The audio module  170  may convert a sound into an electrical signal and vice versa. According to an embodiment, the audio module  170  may obtain the sound via the input module  150 , or output the sound via the sound output module  155  or a headphone of an external electronic device (e.g., an electronic device  102 ) directly (e.g., wiredly) or wirelessly coupled with the electronic device  101 . 
     The sensor module  176  may detect an operational state (e.g., power or temperature) of the electronic device  101  or an environmental state (e.g., a state of a user) external to the electronic device  101 , and then generate an electrical signal or data value corresponding to the detected state. According to an embodiment, the sensor module  176  may include, for example, a gesture sensor, a gyro sensor, an atmospheric pressure sensor, a magnetic sensor, an acceleration sensor, a grip sensor, a proximity sensor, a color sensor, an infrared (IR) sensor, a biometric sensor, a temperature sensor, a humidity sensor, or an illuminance sensor. 
     The interface  177  may support one or more specified protocols to be used for the electronic device  101  to be coupled with the external electronic device (e.g., the electronic device  102 ) directly (e.g., wiredly) or wirelessly. According to an embodiment, the interface  177  may include, for example, a high definition multimedia interface (HDMI), a universal serial bus (USB) interface, a secure digital (SD) card interface, or an audio interface. 
     A connecting terminal  178  may include a connector via which the electronic device  101  may be physically connected with the external electronic device (e.g., the electronic device  102 ). According to an embodiment, the connecting terminal  178  may include, for example, a HDMI connector, a USB connector, an SD card connector, or an audio connector (e.g., a headphone connector). 
     The haptic module  179  may convert an electrical signal into a mechanical stimulus (e.g., a vibration or a movement) or electrical stimulus which may be recognized by a user via his tactile sensation or kinesthetic sensation. According to an embodiment, the haptic module  179  may include, for example, a motor, a piezoelectric element, or an electric stimulator. 
     The camera module  180  may capture a still image or moving images. According to an embodiment, the camera module  180  may include one or more lenses, image sensors, image signal processors, or flashes. 
     The power management module  188  may manage power supplied to the electronic device  101 . According to one embodiment, the power management module  188  may be implemented as at least part of, for example, a power management integrated circuit (PMIC). 
     The battery  189  may supply power to at least one component of the electronic device  101 . According to an embodiment, the battery  189  may include, for example, a primary cell which is not rechargeable, a secondary cell which is rechargeable, or a fuel cell. 
     The communication module  190  may support establishing a direct (e.g., wired) communication channel or a wireless communication channel between the electronic device  101  and the external electronic device (e.g., the electronic device  102 , the electronic device  104 , or the server  108 ) and performing communication via the established communication channel. The communication module  190  may include one or more communication processors that are operable independently from the processor  120  (e.g., the application processor (AP)) and supports a direct (e.g., wired) communication or a wireless communication. According to an embodiment, the communication module  190  may include a wireless communication module  192  (e.g., a cellular communication module, a short-range wireless communication module, or a global navigation satellite system (GNSS) communication module) or a wired communication module  194  (e.g., a local area network (LAN) communication module or a power line communication (PLC) module). A corresponding one of these communication modules may communicate with the external electronic device via the first network  198  (e.g., a short-range communication network, such as Bluetooth™, wireless-fidelity (Wi-Fi) direct, or infrared data association (IrDA)) or the second network  199  (e.g., a long-range communication network, such as a legacy cellular network, a 5 th  generation (5G) network, a next-generation communication network, the Internet, or a computer network (e.g., LAN or wide area network (WAN)). These various types of communication modules may be implemented as a single component (e.g., a single chip), or may be implemented as multi components (e.g., multi chips) separate from each other. The wireless communication module  192  may identify and authenticate the electronic device  101  in a communication network, such as the first network  198  or the second network  199 , using subscriber information (e.g., international mobile subscriber identity (IMSI)) stored in the subscriber identification module  196 . 
     The wireless communication module  192  may support a 5G network, after a 4 th  generation (4G) network, and next-generation communication technology, e.g., new radio (NR) access technology. The NR access technology may support enhanced mobile broadband (eMBB), massive machine type communications (mMTC), or ultra-reliable and low-latency communications (URLLC). The wireless communication module  192  may support a high-frequency band (e.g., the mmWave band) to achieve, e.g., a high data transmission rate. The wireless communication module  192  may support various technologies for securing performance on a high-frequency band, such as, e.g., beamforming, massive multiple-input and multiple-output (massive MIMO), full dimensional MIMO (FD-MIMO), array antenna, analog beam-forming, or large scale antenna. The wireless communication module  192  may support various requirements specified in the electronic device  101 , an external electronic device (e.g., the electronic device  104 ), or a network system (e.g., the second network  199 ). According to an embodiment, the wireless communication module  192  may support a peak data rate (e.g., 20 Gbps or more) for implementing eMBB, loss coverage (e.g., 164 dB or less) for implementing mMTC, or U-plane latency (e.g., 0.5 ms or less for each of downlink (DL) and uplink (UL), or a round trip of 1 ms or less) for implementing URLLC. 
     The antenna module  197  may transmit or receive a signal or power to or from the outside (e.g., the external electronic device) of the electronic device  101 . According to an embodiment, the antenna module  197  may include an antenna including a radiating element composed of a conductive material or a conductive pattern formed in or on a substrate (e.g., a printed circuit board (PCB)). According to an embodiment, the antenna module  197  may include a plurality of antennas (e.g., array antennas). In such a case, at least one antenna appropriate for a communication scheme used in the communication network, such as the first network  198  or the second network  199 , may be selected, for example, by the communication module  190  (e.g., the wireless communication module  192 ) from the plurality of antennas. The signal or the power may then be transmitted or received between the communication module  190  and the external electronic device via the selected at least one antenna. According to an embodiment, another component (e.g., a radio frequency integrated circuit (RFIC)) other than the radiating element may be additionally formed as part of the antenna module  197 . 
     According to various embodiments, the antenna module  197  may form a mmWave antenna module. According to an embodiment, the mmWave antenna module may include a printed circuit board, a RFIC disposed on a first surface (e.g., the bottom surface) of the printed circuit board, or adjacent to the first surface and capable of supporting a designated high-frequency band (e.g., the mmWave band), and a plurality of antennas (e.g., array antennas) disposed on a second surface (e.g., the top or a side surface) of the printed circuit board, or adjacent to the second surface and capable of transmitting or receiving signals of the designated high-frequency band. 
     At least some of the above-described components may be coupled mutually and communicate signals (e.g., commands or data) therebetween via an inter-peripheral communication scheme (e.g., a bus, general purpose input and output (GPIO), serial peripheral interface (SPI), or mobile industry processor interface (MIPI)). 
     According to an embodiment, commands or data may be transmitted or received between the electronic device  101  and the external electronic device  104  via the server  108  coupled with the second network  199 . Each of the electronic devices  102  or  104  may be a device of a same type as, or a different type, from the electronic device  101 . According to an embodiment, all or some of operations to be executed at the electronic device  101  may be executed at one or more of the external electronic devices  102  or  104 , or the server  108 . For example, if the electronic device  101  should perform a function or a service automatically, or in response to a request from a user or another device, the electronic device  101 , instead of, or in addition to, executing the function or the service, may request the one or more external electronic devices to perform at least part of the function or the service. The one or more external electronic devices receiving the request may perform the at least part of the function or the service requested, or an additional function or an additional service related to the request, and transfer an outcome of the performing to the electronic device  101 . The electronic device  101  may provide the outcome, with or without further processing of the outcome, as at least part of a reply to the request. To that end, a cloud computing, distributed computing, mobile edge computing (MEC), or client-server computing technology may be used, for example. The electronic device  101  may provide ultra low-latency services using, e.g., distributed computing or mobile edge computing. In another embodiment, the external electronic device  104  may include an internet-of-things (IoT) device. The server  108  may be an intelligent server using machine learning and/or a neural network. According to an embodiment, the external electronic device  104  or the server  108  may be included in the second network  199 . The electronic device  101  may be applied to intelligent services (e.g., smart home, smart city, smart car, or healthcare) based on 5G communication technology or IoT-related technology. 
     The electronic device according to various embodiments may be one of various types of electronic devices. The electronic devices may include, for example, a portable communication device (e.g., a smartphone), a computer device, a portable multimedia device, a portable medical device, a camera, a wearable device, or a home appliance. According to an embodiment of the disclosure, the electronic devices are not limited to those described above. 
     It should be appreciated that various embodiments of the disclosure and the terms used therein are not intended to limit the technological features set forth herein to particular embodiments and include various changes, equivalents, or replacements for a corresponding embodiment. With regard to the description of the drawings, similar reference numerals may be used to refer to similar or related elements. As used herein, each of such phrases as “A or B,” “at least one of A and B,” “at least one of A or B,” “A, B, or C,” “at least one of A, B, and C,” and “at least one of A, B, or C,” may include any one of, or all possible combinations of the items enumerated together in a corresponding one of the phrases. As used herein, such terms as “1st” and “2nd,” or “first” and “second” may be used to simply distinguish a corresponding component from another, and does not limit the components in other aspect (e.g., importance or order). It is to be understood that if an element (e.g., a first element) is referred to, with or without the term “operatively” or “communicatively”, as “coupled with,” “coupled to,” “connected with,” or “connected to” another element (e.g., a second element), it means that the element may be coupled with the other element directly (e.g., wiredly), wirelessly, or via a third element. 
     As used in connection with various embodiments of the disclosure, the term “module” may include a unit implemented in hardware, software, or firmware, and may interchangeably be used with other terms, for example, “logic,” “logic block,” “part,” or “circuitry”. A module may be a single integral component, or a minimum unit or part thereof, adapted to perform one or more functions. For example, according to an embodiment, the module may be implemented in a form of an application-specific integrated circuit (ASIC). 
     Various embodiments as set forth herein may be implemented as software (e.g., the program  140 ) including one or more instructions that are stored in a storage medium (e.g., internal memory  136  or external memory  138 ) that is readable by a machine (e.g., the electronic device  101 ). For example, a processor (e.g., the processor  120 ) of the machine (e.g., the electronic device  101 ) may invoke at least one of the one or more instructions stored in the storage medium, and execute it, with or without using one or more other components under the control of the processor. This allows the machine to be operated to perform at least one function according to the at least one instruction invoked. The one or more instructions may include a code generated by a complier or a code executable by an interpreter. The machine-readable storage medium may be provided in the form of a non-transitory storage medium. Wherein, the term “non-transitory” simply means that the storage medium is a tangible device, and does not include a signal (e.g., an electromagnetic wave), but this term does not differentiate between where data is semi-permanently stored in the storage medium and where the data is temporarily stored in the storage medium. 
     According to an embodiment, a method according to various embodiments of the disclosure may be included and provided in a computer program product. The computer program product may be traded as a product between a seller and a buyer. The computer program product may be distributed in the form of a machine-readable storage medium (e.g., compact disc read only memory (CD-ROM)), or be distributed (e.g., downloaded or uploaded) online via an application store (e.g., PlayStore™), or between two user devices (e.g., smart phones) directly. If distributed online, at least part of the computer program product may be temporarily generated or at least temporarily stored in the machine-readable storage medium, such as memory of the manufacturer&#39;s server, a server of the application store, or a relay server. 
     According to various embodiments, each component (e.g., a module or a program) of the above-described components may include a single entity or multiple entities, and some of the multiple entities may be separately disposed in different components. According to various embodiments, one or more of the above-described components may be omitted, or one or more other components may be added. Alternatively or additionally, a plurality of components (e.g., modules or programs) may be integrated into a single component. In such a case, according to various embodiments, the integrated component may perform one or more functions of each of the plurality of components in the same or similar manner as they are performed by a corresponding one of the plurality of components before the integration. According to various embodiments, operations performed by the module, the program, or another component may be carried out sequentially, in parallel, repeatedly, or heuristically, or one or more of the operations may be executed in a different order or omitted, or one or more other operations may be added.  FIG.  2    illustrates the unfolded state of an electronic device according to an embodiment of the disclosure. 
       FIG.  3    illustrates the folded state of the electronic device  200  in  FIG.  2    according to an embodiment of the disclosure. 
     Referring to  FIGS.  2  and  3   , the electronic device  200  may include a pair of housings  210  and  220  (e.g., foldable housings) coupled to each other to be rotatable about a folding axis A 1  through a hinge module (not shown) so as to be folded toward each other, and a first display  230  (e.g., a flexible display, a foldable display, or a main display) and a second display  251  (e.g., a sub-display) disposed through the pair of housings  210  and  220 . According to an embodiment, the hinge module may be disposed so as not to be viewed from outside through a first housing  210  and a second housing  220  while being folded, and may be disposed so as to protect the hinge module, while being unfolded, and not to be viewed from outside through a hinge cover  265  configured to cover a foldable part. In various embodiments of the disclosure, a surface on which the first display  230  is disposed may be defined as the front surface of the electronic device  200 , and the opposite surface to the front surface may be defined as the rear surface of the electronic device  200 . Furthermore, a surface surrounding the space between the front surface and the rear surface may be defined as the side surface of the electronic device  200 . 
     According to various embodiments, the pair of housings  210  and  220  may include the first housing  210  and the second housing  220 , which are disposed to be foldable toward each other through the hinge module. According to an embodiment, the pair of housings  210  and  220  are not limited to the type or coupling illustrated in  FIGS.  2  and  3   , and may also be implemented by other shapes or a combination and/or coupling of components. According to an embodiment, the first housing  210  and the second housing  220  may be disposed at opposite sides about a folding axis A 1 , and may have shapes which are overall symmetric with respect to the folding axis A 1 . According to an embodiment, the first housing  210  and the second housing  220  may be asymmetrically folded with reference to the folding axis A 1 . According to an embodiment, the angle or distance formed by the first housing  210  and the second housing  220  may vary depending on whether the electronic device  200  is in an unfolded state (e.g., a first state), is in a folded state (e.g., a second state), or is in an intermediate state (e.g., a third state). 
     According to various embodiments, the first housing  210  may be connected to the hinge module while the electronic device  200  is in the unfolded state, and may include a first surface  211  disposed to face the front surface of the electronic device  200 , a second surface  212  facing a direction opposite to the direction faced by the first surface  211 , and a first side member  213  at least partially surrounding a first space between the first surface  211  and the second surface  212 . According to an embodiment, in the unfolded state of the electronic device  200 , the second housing  220  may be connected to the hinge module, and may include a third surface  221  disposed to face the front surface of the electronic device  200 , a fourth surface  222  facing a direction opposite to the direction faced by the third surface  221 , and a second side member  223  at least partially surrounding a second space between the third surface  221  and the fourth surface  222 . According to an embodiment, the first surface  211  may face the same direction as the third surface  221  in the unfolded state, and may face the third surface  221  in the folded state. According to an embodiment, the electronic device  200  may include a recess  201  formed to receive the first display  230  through a structural coupling of the first housing  210  and the second housing  220 . According to an embodiment, the recess  201  may have substantially the same size as the first display  230 . 
     According to various embodiments, the hinge cover  265  may be disposed between the first housing  210  and the second housing  220  so as to cover the hinge module. According to an embodiment, depending on the unfolded state, folded state, or intermediate state of the electronic device  200 , the hinge cover  265  may be covered by a part of the first housing  210  and the second housing  220  or may be exposed outside. For example, when the electronic device  200  is in the unfolded state, the hinge cover  265  may be covered by the first housing  210  and the second housing  220 , and thus may not be exposed. According to an embodiment, when the electronic device  200  is in the folded state, the hinge cover  265  may be exposed outside between the first housing  210  and the second housing  220 . According to an embodiment, in the intermediate state in which the first housing  210  and the second housing  220  form a predetermined angle (are folded with a certain angle), the hinge cover  265  may be at least partially exposed outside the electronic device  200  between the first housing  210  and the second housing  220 . For example, an area of the hinge cover  265 , which is exposed outside, may be smaller than that in a completely folded state. According to an embodiment, the hinge cover  265  may include a curved surface. 
     According to various embodiments, when the electronic device  200  is in the unfolded state (e.g., the state in  FIG.  2   ), the first housing  210  and the second housing  220  form an angle of about 180 degree, and a first area  230   a , a folding area  230   c , and a second area  230   b  of the first display  230  form an identical plane, and may be placed to face the same direction. In another embodiment, when the electronic device  200  is in the unfolded state, the first housing  210  may rotate by an angle of 360 degrees with respect to the second housing  220  to be reversely folded such that the second surface  212  faces the fourth surface  222  (out folding method). 
     According to various embodiments, when the electronic device  200  is in the folded state (e.g., the state in  FIG.  3   ), the first surface  211  of the first housing  210  and the third surface  221  of the second housing  220  may be placed to face each other. In this case, the first area  230   a  and the second area  230   b  of the first display  230  may form a narrow angle (e.g., a range of 0 degrees-about 10 degrees) therebetween through the folding area  230   c , and may be placed to face each other. According to an embodiment, the folding area  230   c  may be at least partially formed as a curved surface having a predetermined curvature radius. According to an embodiment, when the electronic device  200  is in the intermediate state, the first housing  210  and the second housing  220  may be placed with a predetermined angle (a certain angle). In this case, the first area  230   a  and the second area  230   b  of the first display  230  may form an angle which is larger than that in the folded state and smaller than that in the unfolded state, and the curvature radius of the folding area  230   c  may be larger than that in the folded state. In an embodiment, the first housing  210  and the second housing  220  may form, through the hinge module, an angle at which the same can stop at a folding angle between the folded state and the unfolded state (a free stop function). In an embodiment, the first housing  210  and the second housing  220  may operate while receiving pressure applied in a direction of being unfolded or in a direction of being folded, through the hinge module, with reference to a designated inflection angle. 
     According to various embodiments, the electronic device  200  may include at least one among at least one display  230  or  251 , an input device  215 , sound output devices  227  and  228 , sensor modules  217   a ,  217   b , and  226 , camera modules  216   a ,  216   b , and  225 , key input devices  219 , an indicator (not shown), or a connector port  229 , which are disposed in the first housing  210  and/or the second housing  220 . In an embodiment, the electronic device  200  may omit at least one of the elements, or may additionally include at least one other element. 
     According to various embodiments, the at least one display  230  or  251  may include a first display  230  (e.g., a flexible display) disposed to receive support of the third surface  221  of the second housing  220  through the hinge module from the first surface  211  of the first housing  210 , and a second display  251  disposed to be viewable from outside through the fourth surface  222  in the inner space of the second housing  220 . According to an embodiment, the first display  230  may be mainly used in the unfolded state of the electronic device  200 , and the second display  251  may be mainly used in the folded state of the electronic device  200 . According to an embodiment, in the case of the intermediate state, the electronic device  200  may use the first display  230  or the second display  251 , based on the folding angle of the first housing  210  and the second housing  220 . 
     According to various embodiments, the first display  230  may be disposed in a space formed by the pair of housings  210  and  220 . For example, the first display  230  may be seated in the recess  201  formed by the pair of housings  210  and  220 , and may be disposed to occupy substantially most of the front surface of the electronic device  200 . According to an embodiment, the first display  230  may include a flexible display having at least a partial area deformable as a flat surface or a curved surface. According to an embodiment, the first display  230  may include the first area  230   a  facing the first housing  210 , the second area  230   b  facing the second housing  220 , and the folding area  230   c  which connects the first area  230   a  to the second area  230   b  and faces the hinge module. 
     According to an embodiment, the first area  230   a  of the first display  230  may form, substantially, the first surface  211  of the first housing  210 . According to an embodiment, the second area  230   b  of the first display  230  may form, substantially, the third surface  221  of the second housing  220 . 
     According to an embodiment, the division of area of the first display  230  is merely a physical division by the pair of housings  210  and  220  and the hinge module, and, substantially, the first display  230  may be displayed as a seamless single full screen through the pair of housings  210  and  220  and the hinge module. According to an embodiment, the first area  230   a  and the second area  230   b  may have overall symmetric shapes with reference to the folding area  230   c , or may have partially asymmetric shapes. 
     Although not illustrated, according to various embodiments, the electronic device  200  may include multiple hinge modules and/or multiple folding areas  230   c . For example, the electronic device  200  may include two hinge modules and two folding areas (not shown) corresponding to the two hinge modules (not shown), respectively. In this case, the electronic device  200  may be folded in an alphabet Z shape. For example, the electronic device  200  may include three hinge modules (not shown) and three folding areas (not shown) corresponding to the three hinge modules (not shown), respectively. In this case, the electronic device  200  may be folded in an alphabet W shape. 
     According to various embodiments, the electronic device  200  may include a first rear cover  240 , disposed on the second surface  212  of the first housing  210 , and a second rear cover  250 , disposed on the fourth surface  222  of the second housing  220 . In an embodiment, at least a part of the first rear cover  240  may be formed integrally with the first side member  213 . In an embodiment, at least a part of the second rear cover  250  may be formed integrally with the second side member  223 . According to an embodiment, at least one of the first rear cover  240  and the second rear cover  250  may be formed of substantially transparent plates (e.g., a polymer plate or a glass plate including various coating layers) or an opaque plate. According to an embodiment, the first rear cover  240  may be formed of an opaque plate made of, for example, coated or colored glass, ceramic, polymer, metal (e.g., aluminum, stainless steel (STS), or magnesium), or a combination of at least two of the materials. According to an embodiment, the second rear cover  250  may be formed of a substantially transparent plate made of, for example, glass or polymer. Therefore, the second display  251  may be disposed to be viewable from outside through the second rear cover  250  in the inner space of the second housing  220 . 
     According to various embodiments, the input device  215  may include a microphone  215 . In an embodiment, the input device  215  may include multiple microphones  215  disposed to sense the direction of sound. According to an embodiment, the sound output devices  227  and  228  may include speakers  227  and  228 . According to an embodiment, the speakers  227  and  228  may include a call receiver (i.e., speaker  227 ) disposed through the fourth surface  222  of the second housing  220 , and an outer speaker  228  disposed through the side member of the second housing  220 . In an embodiment, the microphone  215 , the speakers  227  and  228 , and the connector port  229  may be disposed in spaces of the first housing  210  and/or the second housing  220 , and may be exposed to an external environment through at least one hole formed in the first housing  210  and/or the second housing  220 . In an embodiment, the holes formed in the first housing  210  and/or the second housing  220  may be commonly used for the microphone  215  and the speakers  227  and  228 . In an embodiment, the sound output devices  227  and  228  may include a speaker (e.g., a piezo speaker) operated without any hole formed in the first housing  210  and/or the second housing  220 . 
     According to various embodiments, the camera modules  216   a ,  216   b , and  225  may include a first camera device  216   a  disposed on the first surface  211  of the first housing  210 , a third camera device  216   b  disposed on the second surface  212  of the first housing  210 , and/or a second camera device  225  disposed in the fourth surface  222  of the second housing  220 . According to an embodiment, the electronic device  200  may include a flash  218  disposed near the third camera device  216   b . According to an embodiment, the flash  218  may include, for example, a light-emitting diode or a xenon lamp. According to an embodiment, the camera devices  216   a ,  216   b , and  225  may include one lens or multiple lenses, an image sensor, and/or an image signal processor. In an embodiment, at least one camera device among the camera devices  216   a ,  216   b , and  225  may include at least two lenses (wide-angle and telephoto lenses) and image sensors, and may be disposed together on one surface of the first housing  210  and/or the second housing  220 . 
     According to various embodiments, at least one camera device (e.g., the first camera device  216   a ) among the camera devices  216   a ,  216   b , and  225  may be disposed under the display area of a display (e.g., the first display  230 ), and thus may not be visually viewable from outside. In this case, the at least one camera device (e.g., the first camera device  216   a ) may acquire an image an external subject, based on reception of light having passed through the display area of the display (e.g., the first display  230 ), and may be called an under-display camera (UDC) or an under-panel camera (UPC). 
     According to various embodiments, at least one camera device (e.g., the second camera device  225 ) among the camera devices  216   a ,  216   b , and  225  may be disposed to be visually viewable from outside through an opening (e.g., a punch hole) formed by punching a part of a display (e.g., the second display  251 ). 
     According to various embodiments, the sensor modules  217   a ,  217   b , and  226  may generate an electrical signal or data value, which corresponds to an operation state inside the electronic device  200  or an environmental state outside the electronic device  200 . According to an embodiment, the sensor modules  217   a ,  217   b , and  226  may include a first sensor module  217   a  disposed in the first surface  211  of the first housing  210 , a second sensor module  217   b  disposed on the second surface  212  of the first housing  210 , and/or a third sensor module  226  disposed in the fourth surface  222  of the second housing  220 . In an embodiment, the sensor modules  217   a ,  217   b , and  226  may include at least one of a gesture sensor, a grip sensor, a color sensor, an infrared (IR) sensor, an illuminance sensor, an ultrasonic sensor, an iris recognition sensor, or a distance detection sensor (a time of flight (TOF) sensor or a light detection and ranging (LiDAR) scanner). 
     According to various embodiments, the electronic device  200  may further include at least one of unillustrated sensor modules, for example, a barometric pressure sensor, a magnetic sensor, a biosensor, a temperature sensor, a humidity sensor, or a fingerprint recognition sensor. In an embodiment, the fingerprint recognition sensor may be disposed through at least one side member among the first side member  213  of the first housing  210  and/or the second side member  223  of the second housing  220 . 
     According to various embodiments, the key input devices  219  may be disposed to be exposed outside through the first side member  213  of the first housing  210 . In an embodiment, the key input devices  219  may also be disposed to be exposed outside through the second side member  223  of the second housing  220 . In an embodiment, the electronic device  200  may not include some or all of the above-described key input devices  219 , and the key input device  219 , which is not included therein, may be implemented in another form, such as a soft key, on the at least one display  230  or  251 . In another embodiment, the key input device  219  may be implemented using a pressure sensor included in the at least one display  230  or  251 . 
     According to various embodiments, the connector port  229  may receive a connector (for example, a USB connector or an interface connector port module (IF module)) for transmitting or receiving power and/or data to or from the external electronic device  101 . In an embodiment, the connector port  229  may also perform a function of transmitting or receiving an audio signal to or from the external electronic device  101 , or a separate connector port (e.g., an ear jack hole) for performing an audio signal transmission/reception function may be further included. 
     An electronic device (e.g., the electronic device  101  in  FIG.  1   ) according to various embodiments may include a first camera device (e.g., the first camera device  216   a  in  FIG.  2   ) having a first characteristic, a second camera device (e.g., the second camera device  225  in  FIG.  2   ) having a second characteristic different from the first characteristic, a memory (e.g., the memory  130  in  FIG.  1   ), and a processor (e.g., the processor  120  in  FIG.  1   ) operatively connected to the first camera device  216   a , the second camera device  225 , and the memory  130 , wherein the memory  130  stores instructions which, when being executed, cause the processor  120  to receive a request for registration of face information through the first camera device  216   a , acquire, based on the request, multiple first images (e.g., multiple first images  920  in  FIG.  9   ) through the first camera device  216   a , perform filtering for each of the multiple first images  920  to generate multiple second images (e.g., multiple second images  910  in  FIG.  9   ) reflecting the second characteristic of the second camera device  225 , generate multiple first templates (e.g., multiple first templates  930  in  FIG.  9   ) based on the multiple first images  920 , generate multiple second templates (e.g., multiple second templates  940  in  FIG.  9   ) based on the multiple second images  910 , and store the multiple first templates  930  and the multiple second templates  940  in the memory  130 , thereby completing the registration of the face information. 
     According to an embodiment, the memory  130  may include a first template repository (e.g., the first template repository  413  in  FIG.  4   ) configured to correspond to the first camera device  216   a , and a second template repository (e.g., the second template repository  414  in  FIG.  4   ) configured to correspond to the second camera device  225 , and the first template repository  413  and the second template repository  414  may be separate from each other in terms of hardware or software. 
     According to an embodiment, the first template repository  413  may store the multiple first templates  930  and the multiple second templates  940 , wherein the multiple first templates  930  has priority applied thereto and are thus arranged to precede the multiple second templates  940  in the sort order. The second template repository  414  may store the multiple first templates  930  and the multiple second templates  940 , wherein the multiple second templates  940  has priority applied thereto, and are thus arranged to precede the multiple first templates  930  in the sort order. 
     According to an embodiment, the first camera device  216   a  may be a UDC disposed under the display area of a first display of the electronic device  101 , and the second camera device  225  may be a camera device disposed at a part of a second display of the electronic device  101  or around the second display. 
     According to an embodiment, the processor  120  may receive a face authentication request through the second camera device  225  after completing the registration of the face information, may compare, based on the face authentication request, the multiple first templates  930  and the multiple second templates  940 , stored in the second template repository  414 , with an image acquired through the second camera device  225 , and may determine, based on the comparison result, whether to perform face authentication. 
     According to an embodiment, the processor  120  may perform an operation of optimizing each of the multiple first templates  930  and each of the multiple second templates  940  after completing the registration of the face information, and, as the optimization operation, may display a screen requesting a user to capture a face image again through a user interface, may calculate the degree of similarity of the face image of the user, captured through the first camera device  216   a , and a first template designated among the multiple first templates  930 , and when the degree of similarity of the designated first template has a value smaller than a designated reference value, may delete the designated first template and a second template which is designated among the multiple second templates  940  and forms a pair with the designated first template. 
     According to an embodiment, the electronic device may further include a first housing, a second housing, and a hinge module disposed between the first housing and the second housing, wherein the first display is disposed to extend from a part of the first housing to the second housing, and the second display is disposed to face a direction opposite to a direction faced by the first display in an unfolded state in which the first housing and the second housing are placed parallel to each other. 
     According to an embodiment, the first camera device  216   a  may capture an image by receiving light having passed through at least a part of the first display, and the second camera device  225  may be disposed to face a direction identical to the direction faced by the second display. 
     According to an embodiment, the processor  120  may receive a face authentication request after completing the registration of the face information, may determine, based on the face authentication request, whether the electronic device  101  is in the unfolded state or is in a folded state in which the first housing and the second housing face each other, may perform face authentication based on acquiring a face image through the first camera device  216   a  when the electronic device  101  is in the unfolded state, and may perform authentication based on acquiring a face image through the second camera device  225  when the electronic device  101  is in the folded state. 
     According to an embodiment, the processor  120  may receive a request for registration of face information through the second camera device  225 , may acquire, based on the request, multiple second images  910  through the second camera device  225 , may perform filtering for each of the multiple second images  910  to generate multiple first images  920  reflecting the first characteristic of the first camera device  216   a , may generate multiple first templates  930 , based on the multiple first images  920 , may generate multiple second templates  940 , based on the multiple second images  910 , and may store the multiple first templates  930  and the multiple second templates  940  in the memory  130 , thereby completing the registration of the face information. 
     According to various embodiments, a method of an electronic device  101  including a memory  130 , a first camera device  216   a  having a first characteristic, and a second camera device  225  having a second characteristic different from the first characteristic may include an operation of receiving a request for registration of face information through the first camera device  216   a , an operation of acquiring, based on the request, multiple first images  920  through the first camera device  216   a , an operation of performing filtering for each of the multiple first images  920  to generate multiple second images  910  reflecting the second characteristic of the second camera device  225 , an operation of generating multiple first templates  930  based on the multiple first images  920 , an operation of generating multiple second templates  940  based on the multiple second images  910 , and an operation of storing the multiple first templates  930  and the multiple second templates  940  in the memory  130 , thereby completing the registration of the face information. 
     According to an embodiment, the memory  130  may include a first template repository  413  configured to correspond to the first camera device  216   a , and a second template repository  414  configured to correspond to the second camera device  225 , and the first template repository  413  and the second template repository  414  may be separate from each other in terms of hardware or software. 
     According to an embodiment, the method may further include an operation of storing the multiple first templates  930  and the multiple second templates  940  in the first template repository  413 , wherein the multiple first templates  930  has priority applied thereto and are thus arranged to precede the multiple second templates  940  in the sort order, and an operation of storing the multiple first templates  930  and the multiple second templates  940  in the second template repository  414 , wherein the multiple second templates  940  have priority applied thereto, and are thus arranged to precede the multiple first templates  930  in the sort order. 
     According to an embodiment, the first camera device  216   a  may be a UDC disposed under the display area of a first display of the electronic device  101 , and the second camera device  225  may be a camera device disposed at a part of a second display of the electronic device  101  or around the second display. 
     According to an embodiment, the method may further include an operation of receiving a face authentication request through the second camera device  225  after completing the registration of the face information, an operation of comparing, based on the face authentication request, the multiple first templates  930  and the multiple second templates  940 , stored in the second template repository  414 , with an image acquired through the second camera device  225 , and an operation of determining, based on the comparison result, whether to perform face authentication. 
     According to an embodiment, the method may further include an operation of optimizing each of the multiple first templates  930  and each of the multiple second templates  940  after completing the registration of the face information. The optimization operation may include an operation of displaying a screen requesting a user to capture a face image again through a user interface, an operation of calculating the degree of similarity of the face image of the user, captured through the first camera device  216   a , and a first template designated among the multiple first templates  930 , and an operation of deleting the designated first template and a second template, which is designated among the multiple second templates  940  and forms a pair with the designated first template, when the degree of similarity of the designated first template has a value smaller than a designated reference value. 
     According to an embodiment, the electronic device  101  may further include a first housing, a second housing, and a hinge module disposed between the first housing and the second housing, wherein the first display is disposed to extend from a part of the first housing to the second housing, and the second display is disposed to face a direction opposite to a direction faced by the first display in an unfolded state in which the first housing and the second housing are placed parallel to each other. 
     According to an embodiment, the method may further include an operation of capturing an image by the first camera device  216   a  through reception of light having passed through at least a part of the first display, wherein the second camera device  225  is disposed to face a direction identical to the direction faced by the second display. 
     According to an embodiment, the method may further include an operation of receiving a face authentication request after completing the registration of the face information, an operation of determining, based on the face authentication request, whether the electronic device  101  is in the unfolded state or is in a folded state in which the first housing and the second housing face each other, an operation of performing face authentication based on acquiring a face image through the first camera device  216   a  when the electronic device  101  is in the unfolded state, and an operation of performing authentication based on acquiring a face image through the second camera device  225  when the electronic device  101  is in the folded state. 
     According to an embodiment, the method may further include an operation of receiving a request for registration of face information through the second camera device  225 , an operation of acquiring, based on the request, multiple second images  910  through the second camera device  225 , an operation of performing filtering for each of the multiple second images  910  to generate multiple first images  920  reflecting the first characteristic of the first camera device  216   a , an operation of generating multiple first templates  930 , based on the multiple first images  920 , an operation of generating multiple second templates  940 , based on the multiple second images  910 , and an operation storing the multiple first templates  930  and the multiple second templates  940  in the memory  130 , thereby completing the registration of the face information. 
       FIG.  4    is a block diagram of an electronic device according to an embodiment of the disclosure. 
     The electronic device  101  illustrated in  FIG.  4    may be at least partially similar to the electronic device  101  illustrated in  FIG.  1   , or may include another embodiment. 
     The electronic device  101  illustrated in  FIG.  4    may be at least partially similar to the electronic device  200  illustrated in  FIGS.  2  and  3   , or may include another embodiment. 
     Referring to  FIG.  4   , the electronic device  101  according to an embodiment may include a processor  120 , a first camera device  216   a , a second camera device  225 , and a memory (e.g., the memory  130  in  FIG.  1   ). 
     The embodiment of the disclosure discloses that the first camera device  216   a  may be an under-display camera (UDC) or an under panel camera (UPC) and that the second camera device  225  may be a hole-in display (HID) camera. However, this is only one example, and may not be limited. For example, the types of the first camera device  216   a  and the second camera device  225  do not matter if the same are cameras having different characteristics. 
     According to an embodiment, the first camera device  216   a  may be the first camera device  216   a  described with reference to  FIGS.  2  and  3   . For example, the first camera device  216   a  may be a camera device disposed on at least a part of a first display (e.g., the first display  230  in  FIG.  2   ) or around the first display  230  such that a user can perform selfie image capturing while looking at the first display  230 . According to an embodiment, the first camera device  216   a  may be an under-display camera (UDC) or an under panel camera (UPC) disposed under the display area of a display (e.g., the first display  230 ). 
     According to an embodiment, the second camera device  225  may be the second camera device  225  described with reference to  FIGS.  2  and  3   . For example, the second camera device  225  may be a camera device disposed on at least a part of a second display (e.g., the second display  251  in  FIG.  2   ) or around the second display  251  such that the user can perform selfie image capturing while looking at the second display  251 . According to an embodiment, the second camera device  225  may be disposed to be visually viewable from outside through an opening (e.g., a punch hole) formed by punching a part of the second display  251 . 
     According to an embodiment, the processor  120  may acquire image data through the first camera device  216   a  and/or the second camera device  225 . 
     According to an embodiment, the processor  120  may generate multiple first templates (e.g., the multiple first templates  930  in  FIG.  10   ) and multiple second templates (e.g., the multiple second templates  940  in  FIG.  10   ) for face authentication, based on a first image (e.g., the first image  920  in  FIG.  10   ) acquired from the first camera device  216   a . According to an embodiment, the processor  120  may generate multiple first templates  930  and multiple second templates  940  for face authentication, based on a second image (e.g., the second image  910  in  FIG.  9   )) acquired from the second camera device  225 . 
     According to an embodiment, the processor  120  may receive a face authentication request after performing an operation of generating the multiple first and second templates  930  and  940 . According to an embodiment, the processor  120  may acquire a face image of a user by using the first camera device  216   a  or the second camera device  225  in response to the face authentication request, and may perform face authentication based on comparing the acquired face image with the multiple first and second templates  930  and  940 . 
     According to an embodiment, in performing the face authentication, the processor  120  may compare the face image with the multiple first and second templates  930  and  940 , based on a priority corresponding to the type of a camera device which has captured the face image. For example, when the camera device, which has captured the face image, is the first camera device  216   a , the processor  120  may configure priorities with respect to the multiple first templates  930  corresponding to the first camera device  216   a  among the multiple first and second templates  930  and  940 . For example, when the camera device, which has captured the face image, is the second camera device  225 , the processor  120  may configure priorities with respect to the multiple second templates  940  corresponding to the second camera device  225  among the multiple first and second templates  930  and  940 . The priorities may imply the order of templates compared with the face image. For example, the processor  120  may first compare the face image with a template having a relatively high priority, and subsequently compare the face image with a template having a relatively low priority. 
     According to an embodiment, the processor  120  may update, based on the result of the face authentication, a matching score (e.g., a matching score  1301  in  FIG.  13   ) for each of the multiple first and second templates  930  and  940  used for the face authentication. For example, the processor  120  may reduce the matching score  1301  with respect to a template which has failed in the face authentication among the multiple first and second templates  930  and  940 . For example, the processor  120  may increase the matching score  1301  with respect to a template which has succeeded in the face authentication among the multiple first and second templates  930  and  940 . 
     According to an embodiment, the processor  120  may change, based on the result of the face authentication, priorities of templates configured to correspond to the first camera device  216   a . For example, when the camera device that has captured the face image is the first camera device  216   a , the multiple first templates  930 , corresponding to the first camera device  216   a  among the multiple first and second templates  930  and  940 , may be configured to have priority, but a second template designated based on the result of performing the face authentication may be configured to have priority over the multiple first templates  930 . For example, when the camera device that has captured the face image is the second camera device  225 , the multiple second templates  940 , corresponding to the second camera device  225  among the multiple first and second templates  930  and  940 , may be configured to have priority, but a first template designated based on the result of performing the face authentication may be configured to have priority over the multiple second templates  940 . 
     According to an embodiment, the processor  120  may provide a secure execution environment having a relatively high level of security through the memory  130 . For example, the electronic device  101  may operate a normal execution environment and a secure execution environment. According to an embodiment, the normal execution environment may be called a rich execution environment (REE), and may have a relative low level of security. According to an embodiment, the secure execution environment may be called a trusted execution environment (TEE), and may have a relatively high level of security compared with the normal execution environment. The secure execution environment may include, for example, TrustZone. 
     According to an embodiment, in the secure execution environment, the electronic device  101  may store data requiring a relatively high security level in a secure environment, and may perform a pertinent operation. The secure execution environment is operated by the processor  120  of the electronic device  101 , and may be operated based on a trustable hardware structure determined in the process of manufacturing the electronic device  101 . The secure execution environment may partition the processor  120  or the memory  130  into a normal area and a secure area, and may operate the same in the secure area. The electronic device  101  may operate the secure execution environment through a physical change in hardware or a logical change in software. For example, the secure execution environment and the normal execution environment are logically separate memory areas, and may be included in the same memory in terms of hardware. 
     According to an embodiment, the secure execution environment may operate while being separate from the normal execution environment in terms of hardware or in terms of software in the same hardware. 
     According to an embodiment, the processor  120  may provide the secure execution environment through the memory  130 , and may manage data necessary for face authentication through the secure execution environment. For example, the secure execution environment implemented in the memory  130  by the processor  120  may include an image conversion data  411 , a multi-face image generator  412 , a first template repository  413 , a second template repository  414 , a matching module  415 , and/or a template control module  416 . 
     According to an embodiment, the image conversion data  411  may include a filter data set calculated based on a difference value corresponding to a characteristic difference of each of multiple camera devices (e.g., the first camera device  216   a  and the second camera device  225 ) included in the electronic device  101 . According to an embodiment, the image conversion data  411  may include at least one piece of conversion filter data. According to an embodiment, the conversion filter data may include at least one first conversion filter for converting a first image captured through the first camera device  216   a  to an image which is substantially identical or similar to a second image captured through the second camera device  225 . For example, the processor  120  may apply the first conversion filter to the first image captured through the first camera device  216   a , thereby generating an image which is substantially identical or similar to the second image captured through the second camera device  225 . According to an embodiment, the conversion filter data may include a second conversion filter for converting the second image captured through the second camera device  225  to an image which is substantially identical or similar to the first image captured through the first camera device  216   a . For example, the processor  120  may apply the second conversion filter to the second image captured through the second camera device  225 , thereby generating an image which is substantially identical or similar to the first image captured through the first camera device  216   a . 
     According to an embodiment, the multi-face image generator  412  may generate, using the image conversion data  411 , multiple images from an image acquired through a designated camera device. The generated multiple images may be images reflecting characteristics of other cameras excluding the designated camera device. According to an embodiment, when the first image captured through the first camera device  216   a  is input by the processor  120 , the multi-face image generator  412  may use the image conversion data  411  (e.g., the first conversion filter) to generate, from the input first image, an image which is substantially identical or similar to the second image captured through the second camera device  225 . According to an embodiment, when the second image captured through the second camera device  225  is input by the processor  120 , the multi-face image generator  412  may use the image conversion data  411  (e.g., the second conversion filter) to generate, from the input second image, an image which is substantially identical or similar to the first image captured through the first camera device  216   a.    
     According to an embodiment, the first template repository  413  may store multiple templates for performing face authentication through the first camera device  216   a . According to an embodiment, the multiple templates stored in the first template repository  413  may include not only the multiple first templates  930  generated based on a characteristic of the first camera device  216   a  but also at least one second template generated based on a characteristic of the second camera device  225 . According to an embodiment, the electronic device  101  may configure first storing and sorting, in the first template repository  413 , the multiple first templates  930  generated based on a characteristic of the first camera device  216   a . After the above configuration, the electronic device  101  may receive a face authentication request through the first camera device  216   a , and, when the face authentication is successfully performed using a designated second template generated based on the characteristic of the second camera device  225  in a face authentication operation, may increase priority and sort order of the designated second template in the first template repository  413 . 
     According to an embodiment, the second template repository  414  may store multiple templates for performing face authentication through the second camera device  225 . According to an embodiment, the multiple templates stored in the second template repository  414  may include not only the multiple second templates  940  generated based on the characteristic of the second camera device  225  but also at least one first template generated based on the characteristic of the first camera device  216   a . According to an embodiment, the electronic device  101  may configure first storing and sorting, in the second template repository  414 , the multiple second templates  940  generated based on a characteristic of the second camera device  225 . After the above configuration, the electronic device  101  may receive a face authentication request through the second camera device  225 , and, when the face authentication is successfully performed using a designated first template generated based on the characteristic of the first camera device  216   a  in a face authentication operation, may increase the priority or sort order of the designated first template in the second template repository  414 . 
     According to an embodiment, the templates generated in the face information registration operation may be stored according to identification information of each camera device. For example, templates may be stored in the first template repository  413  so as to correspond to face authentication by the first camera device  216   a , and the first templates generated based on the characteristic of the first camera device  216   a  may be first arranged. For example, templates may be stored in the second template repository  414  so as to correspond to face authentication by the second camera device  225 , and the second templates generated based on the characteristic of the second camera device  225  may be first arranged. 
     According to various embodiments, in storing templates, each of the first template repository  413  and the second template repository  414  may include image source information indicating which one among multiple camera devices has generated an image on the basis of which a corresponding template is generated. 
     According to an embodiment, when a face authentication request is received by the processor  120 , the matching module  415  may compare the face image acquired through the designated camera device with multiple templates with reference to the first template repository  413  or the second template repository  414 , and may determine, based on the comparison result, whether to perform face authentication. For example, when a face authentication request through the first camera device  216   a  is received, the matching module  415  may compare, based on the request, multiple templates stored in the first template repository  413  with a face image acquired through the first camera device  216   a , and may determine, based on the comparison result, whether to perform the face authentication. For example, when a face authentication request is received through the second camera device  225 , the matching module  415  may compare, based on the request, multiple templates stored in the second template repository  414  with a face image acquired through the second camera device  225 , and may determine, based on the comparison result, whether to perform the face authentication. 
     According to an embodiment, the template control module  416  may control, under control of the processor  120 , operations related to face authentication. For example, the template control module  416  may control the matching module  415 , and may change, based on the result of face authentication by the matching module  415 , the priority and sort order of multiple templates stored in the first template repository  413  and/or multiple templates stored in the second template repository  414 . 
     The electronic device  101  according to various embodiments may improve security by performing and managing operations and data related to face authentication in the secure execution environment. 
       FIG.  5    is a flowchart illustrating operations of an electronic device  101  according to an embodiment of the disclosure. 
     At least some of the operations illustrated in  FIG.  5    may be omitted. At least some operations described with reference to other drawings according to various embodiments of the disclosure may be added before or after at least some operations illustrated in  FIG.  5   . 
     Referring to  FIG.  5   , the operations illustrated in  FIG.  5    may be performed by a processor  120  (e.g., the processor  120  in  FIG.  1  or  4   ). For example, a memory  130  (e.g., the memory  130  in  FIG.  1  or  4   ) of the electronic device  101  may store instructions which, when being executed by the processor  120 , cause the electronic device  101  to perform at least some operations illustrated in  FIG.  5   . 
     The operations of the electronic device  101  according to various embodiments may include operation  510  for registering face information in the electronic device  101 , and operation  520  for performing face authentication by the electronic device  101 , based on preregistered face information. 
     According to an embodiment, operation  510  of the electronic device  101  for registering face information may include the following operations. 
     In operation  511 , the electronic device  101  according to an embodiment may receive a request for registration of face information through the first camera device  216   a . For example, as described with reference to  FIG.  2   , the electronic device  101  may receive a request of registration of face information through the first camera device  216   a  in an unfolded state of the electronic device  101 . In another embodiment, although not illustrated, the electronic device  101  may receive a request for registration of face information through the second camera device  225 . For example, as described with reference to  FIG.  3   , the electronic device  101  may receive a request for registration of face information through the second camera device  225  in a folded state of the electronic device  101 . Hereinafter, in various embodiments of the disclosure, an embodiment described with reference to  FIG.  5    describes only receiving a face information registration request through the first camera device  216   a , but can also be changed into or substituted with receiving a face information registration request through the second camera device  225 . 
     In operation  512 , the electronic device  101  according to an embodiment may acquire multiple first images (e.g., the first image  920  in  FIG.  10   ) through the first camera device  216   a . For example, in the unfolded state, the electronic device  101  may capture multiple first images  920  including a user&#39;s face through the first camera device  216   a.    
     In operation  513 , the electronic device  101  according to an embodiment may perform filtering (e.g., the filtering  701  in  FIG.  7   ) for each of the multiple first images  920  to generate multiple second images (e.g., the second images  910  in  FIG.  10   ). According to an embodiment, the electronic device  101  may control the multi-face image generator  412  to generate, using the image conversion data  411 , multiple images from an image acquired through a designated camera device. The generated multiple images may be images reflecting characteristics of other camera devices excluding the designated camera device. According to an embodiment, when a first image  920  captured through the first camera device  216   a  is input by the processor  120 , the multi-face image generator  412  may use the image conversion data  411  (e.g., the first conversion filter) to generate, from the input first image  920 , a second image  910  substantially identical or similar to an image captured through the second camera device  225 . Although not illustrated, according to an embodiment, when a second image (e.g., the second image  910  in  FIG.  9   ) captured through the second camera device  225  is input by the processor  120 , the multi-face image generator  412  may use the image conversion data  411  (e.g., the second conversion filter) to generate, from the input second image  910 , a first image (e.g., the first image  920  in  FIG.  9   ) substantially identical or similar to an image captured through the first camera device  216   a.    
     In operation  514 , the electronic device  101  according to an embodiment may generate multiple first templates  930 , based on respective face areas (e.g., the face areas  921  in  FIG.  10   ) of multiple first images (e.g., the first image  920  in  FIG.  10   ). For example, the electronic device  101  may determine a face area from each of the multiple first images, and may generate the multiple first templates  930 , based on the determined face area  921 . According to an embodiment, the electronic device  101  may store the generated multiple first templates  930  in the first template repository  413  of a secure execution environment. 
     In operation  515 , the electronic device  101  according to an embodiment may generate multiple second templates  940 , based on a face area (e.g., the face area  911  in  FIG.  9   ) of each of multiple second images (e.g., the second image  910  in  FIG.  9   ). For example, the electronic device  101  may determine a face area from each of multiple second images  910 , and may generate the multiple second templates  940 , based on the determined face area  911 . According to an embodiment, the electronic device  101  may store the generated multiple second templates  940  in a second template repository (e.g., the second template repository  414  in  FIG.  4   ) of secure execution environment. According to an embodiment, the second template repository  414  may be a repository which is physically separate from the first template repository (e.g., the first template repository  413  in  FIG.  4   ) or separate therefrom in terms of software. 
     According to an embodiment, operation  520  of the electronic device  101  for performing face authentication may include the following operations. For example, the electronic device  101  according to an embodiment may receive a face authentication request after performing a registration operation such as operation  510 , and may perform the following operations in response to the face authentication request. 
     In operation  521 , the electronic device  101  according to an embodiment may receive a face authentication request through the second camera device  225 . For example, the electronic device  101  may receive the face authentication request through the second camera device  225  in a folded state of the electronic device  101  as described with reference to  FIG.  3   . In another embodiment, although not illustrated, the electronic device  101  may receive a face authentication request through the first camera device  216   a . For example, the electronic device  101  may receive a face authentication request through the first camera device  216   a  in an unfolded state of the electronic device  101 , as described with reference to  FIG.  2   . Hereinafter, in various embodiments of the disclosure, an embodiment described with reference with  FIG.  5    describes only receiving a face authentication request through the second camera device  225 , but may be changed into or substituted with receiving a face authentication request through the first camera device  216   a.    
     In operation  522 , the electronic device  101  according to an embodiment may perform face authentication based on at least one of an image acquired through the second camera device  225  and the multiple second templates  940  and the multiple first templates  930 . For example, when receiving a face authentication request through the second camera device  225 , the electronic device  101  may compare, by controlling the matching module  415 , multiple templates stored in the second template repository  414  with a face image acquired through the second camera device  225 , and may determine, based on the comparison result, whether to perform face authentication. In the multiple templates stored in the second template repository  414 , priority and sort order may be configured with respect to multiple second templates  940  generated based on a characteristic of the second camera device  225 , but at least one first template generated based on a characteristic of the first camera device  216   a  may also be included. This may be, as described above, because the template control module  416  has changed, based on the face authentication result, the priority and sort order of the multiple templates stored in the second template repository  414 . 
     Although not illustrated, when receiving a face authentication request through the first camera device  216   a , the electronic device  101  may compare, by controlling the matching module  415 , multiple templates stored in the first template repository  413  with a face image acquired through the first camera device  216   a , and may determine, based on the comparison result, whether to perform face authentication. In the multiple templets stored in the first template repository  413 , priority and sort order may be configured with respect to multiple first templates  930  generated based on the characteristic of the first camera device  216   a , but at least one second template generated based on a characteristic of the second camera device  225  may also be included. This may be, as described above, because the template control module  416  has changed, based on the face authentication result, the priority and sort order of the multiple templates stored in the first template repository  413 . 
       FIG.  6    illustrates an operation of generating a conversion filter according to an embodiment of the disclosure. 
       FIG.  7    illustrates an operation of converting an image acquired from a first camera device according to an embodiment of the disclosure. 
       FIG.  8    illustrates an operation of converting an image acquired from a second camera device  225  according to an embodiment of the disclosure. 
     According to an embodiment, the electronic device  101  may previously perform an operation of generating and storing a conversion filter before performing operation  510  of the electronic device  101  for registering face information, described with reference to  FIG.  5   . 
     Referring to  FIG.  6   , the electronic device  101  according to an embodiment may acquire multiple first images  601  through the first camera device  216   a . For example, a first image  601  may include a face image acquired by imaging a user&#39;s face using the first camera device  216   a.    
     According to an embodiment, the electronic device  101  may acquire multiple second images  602  through the second camera device  225 . For example, a second image  602  may include a face image acquired by imaging the user&#39;s face through the second camera device  225 . 
     According to an embodiment, as in  611  of  FIG.  6   , the electronic device  101  may compare the multiple first images  601  with the multiple second images  602  to calculate differences between the first images  601  and the second images  602 . According to an embodiment, the electronic device  101  may use a deep learning method as a method for calculating differences between the first images  601  and the second images  602 . For example, the electronic device  101  may calculate a difference value by comparing a first image  601  and a second image  602 , captured in a resolution, an illuminance, and/or a designated light source. 
     According to an embodiment, as in  612  of  FIG.  6   , the electronic device  101  may acquire a first conversion filter and a second conversion filter, based on a difference value resulting from performing the deep learning. According to an embodiment, the first conversion filter and the second conversion filter may be used when the electronic device  101  generates templates for each of the first camera device  216   a  and the second camera device  225 . For example, in operation  513  in  FIG.  5   , the electronic device  101  may use the first conversion filter to generate multiple second images (e.g., the second images  910  in  FIG.  10   ). For example, when performing an operation of registering face information, the electronic device  101  may use the first conversion filter and/or the second conversion filter to not only generate templates corresponding to a characteristic of a camera device which has captured an image but also generate templates corresponding to characteristics of the remaining camera devices excluding the camera device which has captured the image. 
     According to an embodiment, at the time of performing image capturing through the first camera device  216   a  and/or the second camera device  225 , the electronic device  101  may perform deep learning for images captured in an environment in which various light sources such as a red light source and/or a purple light source emit light, images captured in respective levels of external illuminance environments, and/or images captured in respective resolutions, thereby generating a most appropriate conversion filter. 
     According to an embodiment, an image captured by a normal camera such as the second camera device  225 , may have relatively low noise compared with an image captured by a UDC such as the first camera device  216   a . Therefore, the electronic device  101  may generate the first conversion filter capable of reducing noise with respect an image captured by the second camera device  225  and reducing light blurring caused by the dispersion of light according to a characteristic of a display. 
     Referring to  FIG.  7   , the electronic device  101  may perform filtering  701  of applying the first conversion filter to a first image  711  captured through the first camera device  216   a  to acquire a converted image  712  that is substantially identical or similar to an image captured through the second camera device  225 . Unlike the first image  711  which is an original image captured through the first camera device  216   a , the acquired converted image  712  is an image having less noise and reduced light blurring, and may be substantially identical or similar to the image captured through the second camera device  225 . 
     According to an embodiment, when the electronic device  101  generates, from an original image captured through the first camera device  216   a , a converted image substantially identical or similar to an image captured through the second camera device  225 , the converted image may be generated by applying a sharpness filter to a part in which a blur phenomenon has been caused by a characteristic of a UDC. According to various embodiments, in generating the first conversion filter, the electronic device  101  may calculate a radius value or a color noise value of a camera device and/or a threshold value through deep learning, and may consider a characteristic of a UDC and/or attributes of a display (e.g., the first display  230 ) overlapping the UDC. 
     According to an embodiment, in the case of an image captured by a UDC such as the first camera device  216   a , spot blur may be caused. The electronic device  101  may generate a conversion filter, having an effect similar to a bokeh effect, by deep learning considering the characteristic of the UDC. According to an embodiment, the electronic device  101  may generate a conversion filter to which various characteristics are applied based on attributes of a display disposed to overlap the UDC, for example, the first display  230 . According to an embodiment, in the case of a UDC such as the first camera device  216   a , a designated noise may be caused in an image by a physical condition in which received light is needed to pass through a display area of a display. According to an embodiment, the electronic device  101  may generate the second conversion filter by deep learning for the designated noise. 
     Referring to  FIG.  8   , the electronic device  101  may perform filtering  801  of applying the second conversion filter to a second image  811  captured through the second camera device  225 , thereby acquiring a converted image  812  substantially identical or similar to an image captured through the first camera device  216   a . Unlike the second image  811  which is an original image captured through the second camera device  225 , the acquired converted image  812  is an image having more noise and a light blurring phenomenon intentionally applied thereto, and may be substantially identical or similar to the image captured through the first camera device  216   a.    
       FIG.  9    illustrates an operation in which an electronic device according to an embodiment generates multiple first and second templates by using an image acquired from a second camera device according to an embodiment of the disclosure. 
     Referring to  FIG.  9   , a request for registration of face information may be received in a folded state of the electronic device  200 , as described with reference to  FIG.  3   . According to an embodiment, the electronic device  200  may activate the second camera device  225  in response to the request, and may acquire at least one second image  910  through the second camera device  225 . For example, the second image  910  may include a user&#39;s face image self-captured through the second camera device  225  in the folded state of the electronic device  200 . 
     According to an embodiment, the electronic device  200  may determine a face area  911  from the second image  910 , and may generate a second template  940 , based on the determined face area  911 . For example, the electronic device  200  may extract a face image corresponding to the face area  911  of the second image  910 , and may generate the second template  940 , based on the extracted face image. According to an embodiment, the electronic device  200  may determine a face area  911  from each of multiple second images  910 , and may generate multiple second templates  940 , based on the determined face area  911 . 
     According to an embodiment, the electronic device  200  may acquire multiple first images  920  by performing filtering (e.g., the filtering  801  in  FIG.  8   ) of applying a second conversion filter to each of the multiple second images  910  in the secure execution environment of the memory  130 . The multiple first images  920  are not images directly captured through the first camera device  216   a . However, the filtering (e.g., the filtering  801  in  FIG.  8   ) may be performed with respect to the multiple second images  910 , and thus the multiple first images  920  may be substantially identical or similar to images captured through the first camera device  216   a.    
     According to an embodiment, the electronic device  200  may determine face areas from the multiple first images  920 , and may generate multiple first templates  930 , based on the determined face areas. 
     According to an embodiment, the electronic device  200  may store the multiple first templates  930  in a first template repository (e.g., the first template repository  413  in  FIG.  4   ), and may store the multiple second templates  940  in a second template repository (e.g., the second template repository  414  in  FIG.  4   ) which is physically separate from the first template repository  413  or separate therefrom in terms of software. 
       FIG.  10    illustrates an operation in which an electronic device  200  according to an embodiment generates multiple first and second templates  930  and  940  by using an image acquired from a first camera device  216   a  according to an embodiment of the disclosure. 
     Referring to  FIG.  10   , a request for registration of face information may be received in an unfolded state of the electronic device  200 , as described with reference to  FIG.  2   . According to an embodiment, the electronic device  200  may activate the first camera device  216   a  in response to the request, and may acquire multiple first images  920  or at least one first image  920  through the first camera device  216   a . For example, the first image  920  may include a user&#39;s face image self-captured through the first camera device  216   a  in the unfolded state of the electronic device  200 . 
     According to an embodiment, the electronic device  200  may determine a face area  921  from the first image  920 , and may generate a first template  930 , based on the determined face area  921 . For example, the electronic device  200  may extract a face image corresponding to the face area  921  of the first image  920 , and may generate a first template  930 , based on the extracted face image. According to an embodiment, the electronic device  200  may determine a face area  921  of each of the multiple first images  920 , and may generate multiple first templates  930 , based on the determined face area  921 . 
     According to an embodiment, the electronic device  200  may acquire multiple second images  910  by performing filtering (e.g., the filtering  701  in  FIG.  7   ) of applying a first conversion filter to each of the multiple first images  920  in the secure execution environment of the memory  130 . The multiple second images  910  are not images directly captured through the second camera device  225 . However, the filtering (e.g., the filtering  701  in  FIG.  7   ) is performed with respect to the multiple first images  920 , and thus the multiple second images  910  may be substantially identical or similar to images captured through the second camera device  225 . 
     According to an embodiment, the electronic device  200  may determine face areas from the multiple second images  910 , and may generate multiple second templates  940 , based on the determined face areas. 
     According to an embodiment, the electronic device  200  may store the multiple first templates  930  in the first template repository  413 , and may store the multiple second templates  940  in the second template repository  414  which is physically separate from the first template repository  413  or separate therefrom in terms of software. 
       FIG.  11    is a flowchart illustrating an operation of managing multiple templates by an electronic device according to an embodiment of the disclosure. 
       FIG.  12    illustrates an operation of optimizing multiple templates by an electronic device  200  according to an embodiment of the disclosure. 
       FIG.  13    illustrates an operation of adjusting priorities of multiple templates on the basis of a matching score by an electronic device according to an embodiment of the disclosure. 
     At least some of operations illustrated in  FIG.  11    may be omitted. At least some operations described with reference to other drawings in various embodiments of the disclosure may be added before or after at least some operations illustrated in  FIG.  11   . 
     The operations illustrated in  FIG.  11    may be performed by a processor  120  (e.g., the processor  120  in  FIG.  1   ). For example, a memory  130  (e.g., the memory  130  in  FIG.  1   ) of the electronic device  200  may store instructions which, when being executed by the processor  120 , cause the electronic device  200  to perform at least some operations illustrated in  FIG.  11   . 
     Herein, an operation of managing multiple templates by the electronic device  200  according to an embodiment will be described in conjunction with  FIGS.  11  to  13   . 
     According to various embodiments, the electronic device  200  may perform an operation of managing multiple templates stored in the memory  130 , for example, multiple first templates  930  and multiple second templates  940 . For example, operation  510  of the electronic device  200 , described with reference to  FIG.  5   , may further include operation  516  of optimizing multiple templates in a face information registration operation. Alternatively, after face authentication is completed, the electronic device  200  may further perform operation  1100  of adjusting matching scores and/or priorities of predetermined multiple templates, based on the result of the face authentication. 
     According to various embodiments, operation  516  and operation  1100  may be performed independently of each other. 
     Referring to  FIG.  11   , when the multiple first templates  930  and the multiple second templates  940  in the face information registration operation, the electronic device  200  according to an embodiment may perform, in operation  516 , an operation of optimizing the generated templates. 
     Referring to  FIG.  12   , after the multiple first templates  930  and the multiple second templates  940  are generated, the electronic device  200  may provide a user interface  1201  for optimizing the generated templates. The electronic device  200  may request, through the user interface  1201 , a user to capture a face image once again. The electronic device  200  may acquire an image (e.g.,  1210  in  FIG.  12   ) through the first camera device  216   a  and/or the second camera device  225 , and may determine a face area (e.g.,  1211  in  FIG.  12   ) in the acquired image (e.g.,  1210  in  FIG.  12   ). The electronic device  200  may compare a face image corresponding to the determined face area (e.g.,  1211  in  FIG.  12   ) with the multiple first templates  930  and the multiple second templates  940 , which are generated in advance. 
     According to an embodiment, the electronic device  200  may evaluate the degree of similarity of each of the multiple first templates  930  and the multiple second templates  940  to a face image (e.g., a face image corresponding to the face area  1211  in  FIG.  12   ). According to an embodiment, the electronic device  200  may configure a designated reference value (e.g.,  1220  in  FIG.  12   ) with respect to the degree of similarity to the face image, may store only some templates having the degree of similarity that have values equal to or greater than designated reference value (e.g.,  1220  in  FIG.  12   ) among the multiple first templates  930  and the multiple second templates  940 , and may delete the remaining templates having the degree of similarity that has a value smaller than the designated reference value (e.g.,  1220  in  FIG.  12   ). 
     For example, in  FIG.  12   , a template  931 , a template  932 , a template  933 , and the template  934  are illustrated as multiple first templates  930  before performing the optimization operation. In addition, a template  941 , a template  942 , a template  943 , and a template  944  are illustrated as multiple second templates  940  before performing the optimization operation. According to an embodiment, the multiple first templates  930  and the multiple second templates  940  may be configured such that templates generated based on one face image form a pair. For example, the electronic device  200  may acquire multiple face images by capturing images multiple times in the face information registration operation, and may generate a first template  930  and a second template  940 , which are a pair of templates, from each of the face images. 
     According to the illustrated example, the template  931  and the template  941  may be configured to form a pair, and may be templates generated based on one face image. 
     According to the illustrated example, the template  932  and the template  942  may be configured to form a pair, and may be templates generated based on one face image. 
     According to the illustrated example, the template  933  and the template  943  may be configured to form a pair, and may be templates generated based on one face image. 
     According to the illustrated example, the template  934  and the template  944  may be configured to form a pair, and may be templates generated based on one face image. 
     According to an embodiment, the electronic device  200  may perform an operation of optimizing the multiple first templates  930  or the multiple second templates  940 , and when one of a first template  930  and a second template  940 , which are configured to form a pair, has a value smaller than a predesignated reference value (e.g.,  1220  in  FIG.  12   ), may delete all of the first template  930  and the second template  940 , which are configured to form a pair. For example, the electronic device  200  may acquire a face image through the first camera device  216   a , and may calculate the degree of similarity between the acquired face image and the template  931 . When the degree of similarity of the template  931  has a value equal to or greater than the designated reference value (e.g.,  1220  in  FIG.  12   ), the electronic device  200  may store the template  931  and the template  941  forming a pair with the template  931 , thereby completing optimization of the template  931  and the template  941 . For example, the electronic device  200  may acquire a face image through the first camera device  216   a , and may calculate the degree of similarity between the acquired face image and the template  933 . When the degree of similarity of the template  933  has a value smaller than the designated reference value (e.g.,  1220  in  FIG.  12   ), the electronic device  200  may delete the template  933  and the template  943  forming a pair with the template  933 , thereby completing optimization of the template  933  and the template  943 . For example, the electronic device  200  according to an embodiment may acquire a face image through the second camera device  225 , and may calculate the degree of similarity between the acquired face image and the template  941 . When the degree of similarity of the template  941  has a value equal to or greater than the designated reference value (e.g.,  1220  in  FIG.  12   ), the electronic device  200  may store the template  941  and the template  931  forming a pair with the template  941 , thereby completing optimization of the template  931  and the template  941 . Although not illustrated, for example, the electronic device  200  may acquire a face image through the second camera device  225 , and may calculate the degree of similarity between the acquired face image and the template  943 . When the degree of similarity of the template  943  has a value smaller than the designated reference value (e.g.,  1220  in  FIG.  12   ), the electronic device  200  may delete the template  943  and the template  933  forming a pair with the template  943 , thereby completing optimization of the template  933  and the template  943 . 
     The electronic device  200  according to various embodiments may perform the optimization operation, thereby preventing unnecessary use of the memory  130  and increasing a processing speed. 
     In performing the optimization operation, the electronic device  200  according to various embodiments may perform the optimization operation in a background in the final operation of the face information registration operation without any additional input of a user. For example, the electronic device  200  may perform the optimization operation in a background while a progress rate of a designated value, for example, a registration progress rate of 80% is displayed through a user interface for registering face information. 
     Operation  520  illustrated in  FIG.  11    may be at least partially similar or substantially identical to operation  520  illustrated in  FIG.  5   . 
     When face authentication is completed in operation  520  (e.g., the result of operation  520  is “Yes”), the electronic device  200  according to an embodiment may perform operation  1110 . Operation  1110  may include the following operations. 
     In operation  1110 , the electronic device  200  according to an embodiment may determine a matching score of each of multiple templates, based on the face authentication result. For example, the electronic device  200  may configure a matching score of each of the multiple first templates  930  and the multiple second templates  940 , and the matching score may be adjusted based on the face authentication result. According to an embodiment, when a specific template among multiple templates succeeds in face authentication, the electronic device  200  may increase a matching score of the corresponding template. According to an embodiment, when a specific template among multiple templates fails in face authentication, the electronic device  200  may reduce a matching score of the corresponding template. The electronic device  200  may update, through the above-described method, optimal templates corresponding to a corresponding camera device whenever a user performs face authentication. 
     In operation  1120 , the electronic device  200  according to an embodiment may determine, based on the matching score (e.g.,  1301  in  FIG.  13   ) of each of the multiple templates, priority on the basis of which each of the multiple templates is stored in the memory  130 . The priority may be a factor which determines the sort order of the templates compared with a face image acquired through a camera device when the face authentication operation is performed. For example, when face authentication is performed through the first camera device  216   a , the electronic device  200  may sequentially compare the templates, starting from templates having higher priority among the multiple first templates  930  and the multiple second templates  940  stored in the first template repository  413  corresponding to the first camera device  216   a , with a face image acquired through the first camera device  216   a . To this end, when being sorted in the first template repository  413 , multiple templates may be sorted in the order from templates having higher priority to templates having lower priority. 
     In operation  1130 , the electronic device  200  according to an embodiment may update, based on the priority, the sort order of the multiple templates stored in the memory  130 . 
     Referring to  FIG.  13   , the electronic device  200  according to an embodiment may configure first storing and sorting, in the first template repository  413 , multiple first templates  930  generated based on a characteristic of the first camera device  216   a . After the above configuration, the electronic device  200  may receive a face authentication request through the first camera device  216   a , and, when face authentication is successfully performed, in a face authentication operation, by using a designated second template generated based on a characteristic of the second camera device  225 , may increase the priority and sort order of the designated second template in the first template repository  413 . 
     Referring to  FIG.  13   , the electronic device  200  according to an embodiment may configure first storing and sorting, in the second template repository  414 , multiple second templates  940  generated based on a characteristic of the second camera device  225 . After the above configuration, the electronic device  200  may receive a face authentication request through the second camera device  225 , and, when face authentication is successfully performed, in a face authentication operation, by using a designated first template generated based on a characteristic of the first camera device  216   a , may increase the priority and sort order of the designated first template in the second template repository  414 . 
     According to an embodiment, at the time of face authentication, the order of templates to be first matched may be determined based on the type of a camera device currently attempting authentication. For example, when a camera device attempting authentication is a UDC, templates generated in consideration of a characteristic of the UDC may be first used for a matching work, and subsequently, templates generated in consideration of characteristics of other camera device excluding the UDC may be used for the matching work. 
     For example, when a camera device attempting authentication is a UDC and when authentication is not completed although templates generated in consideration of a characteristic of the UDC has been used for a matching work, the electronic device may use, for the matching work, templates generated in consideration of characteristics of other camera device excluding the UDC. In a state in which the camera device attempting authentication is a UDC, when authentication is completed by the templates generated in consideration of the characteristics of other camera device excluding the UDC, the electronic device  200  may increase a matching score of the designated template (e.g., the matching score is increased by +1). 
     According to an embodiment, in a state in which the camera device attempting authentication is a UDC, when all templates of a template repository (e.g., the first template repository  413 ) configured to correspond to the UDC are not matched, an electronic device may use, for a matching work, templates included in a template repository (e.g., the second template repository  414 ) corresponding to another camera device. When authentication is completed through a designated template among the templates included in the template repository (e.g., the second template repository  414 ) corresponding to the other camera device, an electronic device may copy the designated template to the template repository (e.g., the first template repository  413 ) configured to correspond to the UDC, and may delete a template having the lowest matching score in the template repository (e.g., the first template repository  413 ) configured to correspond to the UDC. 
       FIG.  14    is a flowchart illustrating an operation of performing face authentication by an electronic device  200  according to an embodiment of the disclosure. 
     At least some of operations illustrated in  FIG.  14    may be omitted. At least some operations described with reference to other drawings in various embodiments of the disclosure may be added before or after at least some operations illustrated in  FIG.  14   . 
     The operations illustrated in  FIG.  14    may be performed by a processor  120  (e.g., the processor  120  in  FIG.  1   ). For example, a memory  130  (e.g., the memory  130  in  FIG.  1   ) of the electronic device  200  may store instructions which, when being executed by the processor  120 , cause the electronic device  200  to perform at least some operations illustrated in  FIG.  14   . 
     The flowchart illustrated in  FIG.  14    may include an embodiment which is at least partially similar to or different from operation  520  described with reference to  FIG.  5   . 
     Referring to  FIG.  14   , in operation  1410 , the electronic device  200  according to an embodiment may receive a face authentication request. For example, the electronic device  200  may sense, based on an executed application, face authentication request event occurrence for identifying a person to be authenticated. For example, the electronic device  200  may perform, through face authentication, secure authentication required through a designated application, or may release the locked state of the electronic device  200 . 
     In operation  1420 , the electronic device  200  according to an embodiment may determine a camera device for performing face authentication, based on the state of the electronic device  200 . According to an embodiment, the electronic device  200  may determine the state of electronic device  200 , based on the reception of the face authentication request. For example, the electronic device  200  may determine whether the electronic device  200  is in a folded state or is in an unfolded state. According to an embodiment, when the electronic device  200  is in the unfolded state, the electronic device  200  may determine to perform face authentication through the first camera device  216   a . According to an embodiment, when the electronic device  200  is in the folded state, the electronic device  200  may determine to perform face authentication through the second camera device  225 . 
     In operation  1430 , the electronic device  200  according to an embodiment may determine whether the camera device for performing face authentication is the first camera device  216   a . According to an embodiment, when the camera device for performing face authentication is the first camera device  216   a  (e.g., the result of operation  1430  is “Yes”), the electronic device  200  may perform operation  1441 . According to an embodiment, when the camera device for performing face authentication is not the first camera device  216   a  (e.g., the result of operation  1430  is “No”, that is, when the camera device for performing face authentication is the second camera device  225 , the electronic device  200  may perform operation  1451 . 
     In operation  1441 , the electronic device  200  according to an embodiment may acquire a first face image through the first camera device  216   a . For example, the electronic device  200  may acquire a first image including a user&#39;s face and self-captured through the first camera device  216   a , and may acquire the first face image corresponding to a face area from the first image. 
     In operation  1442 , the electronic device  200  according to an embodiment may compare the first face image with multiple first templates and second templates, based on priority corresponding to the first camera device  216   a . According to an embodiment, the electronic device  200  may refer to the first template repository  413  in order to perform face authentication through the first camera device  216   a . In the first template repository  413 , the multiple first templates  930  generated based on a characteristic of the first camera device  216   a  are first stored and sorted, and at least one second template generated based on a characteristic of the second camera device  225  may also be stored. According to an embodiment, the electronic device  200  may complete the face authentication, based on the result of comparing the first face image with the multiple first templates and second templates stored in the first template repository  413 . 
     In operation  1451 , the electronic device  200  according to an embodiment may acquire a second face image through the second camera device  225 . For example, the electronic device  200  may acquire a second image including the user&#39;s face and self-captured through the second camera device  225 , and may acquire the second face image corresponding to a face area from the second image. 
     In operation  1452 , the electronic device  200  according to an embodiment may compare the second face image with multiple first templates  930  and second templates  940 , based on priority corresponding to the second camera device  225 . According to an embodiment, the electronic device  200  may refer to the second template repository  414  in order to perform face authentication through the second camera device  225 . In the second template repository  414 , the multiple second templates  940  generated based on a characteristic of the second camera device  225  are first stored and sorted, and at least one first template generated based on a characteristic of the first camera device  216   a  may also be stored. According to an embodiment, the electronic device  200  may complete the face authentication, based on the result of comparing the second image with the multiple first templates  930  and second templates  940  stored in the second template repository  414 . 
     While the disclosure has been shown and described with reference to various embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the disclosure as defined by the appended claims and their equivalents.