Patent Publication Number: US-2022211284-A1

Title: Electronic device including multiple optical sensors and method for controlling the same

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a bypass continuation application, claiming priority under § 365(c) to International Application No. PCT/KR2022/000160, filed on Jan. 5, 2022, which is based on and claims priority to Korean Patent Application Serial No. 10-2021-0001595, filed on Jan. 6, 2021 in the Korean Intellectual Property Office, the disclosures of each of which is incorporated herein by reference in its entirety. 
    
    
     BACKGROUND 
     1. Field 
     The disclosure is generally related to an electronic device including multiple optical sensors, and more particularly, to an electronic device including multiple optical sensors which may be worn on a user&#39;s body so as to acquire the user&#39;s biometric information. 
     2. Description of Related Art 
     Electronic devices have evolved to have smaller sizes and to be able to perform various functions in various manners according to user needs. Such electronic devices may include, for example, various types of wearable devices that can be directly attached to a part of the user&#39;s body. 
     Such wearable devices are used to acquire various pieces of information from the user&#39;s body, and various services are provided based thereon. 
     A wearable electronic device, such as, for example, a ring-type wearable electronic device worn on a finger, may be equipped with a photoplethysmography (PPG) sensor so as to acquire information from the user&#39;s body, to calculate information such as heart rate, stress, blood oxygen saturation (SpO2), and blood pressure based thereon, and to provide the same to the user. 
     A wearable electronic device, such as, for example, a ring-type wearable electronic device, may easily spin when worn on the user such that, even if multiple optical sensors are employed, the position of each optical sensor may frequently change, thereby making accurate measurement difficult. 
     SUMMARY 
     Embodiments described herein may provide a method in which, in connection with an electronic device including multiple optical sensors, each optical sensor is controlled based on signal characteristics of each of the multiple optical sensors, and the electronic device. 
     According to an aspect, an electronic device is provided that includes a housing, a motion sensor, and optical sensors disposed on one surface of the housing so as to be brought into contact with an object to be measured when the electronic device is worn. Each of the optical sensors comprises a respective light emitter and a respective light receiver. The electronic device also includes a sensor controller configured to control the optical sensors, and a processor operatively connected to the motion sensor and the sensor controller. The processor is configured to separately drive the optical sensors through the sensor controller to determine a respective signal characteristic of each of the optical sensors, and determine a current state of the object to be measured, based on at least one signal received through the motion sensor or the optical sensors. The processor is also configured to drive a light emitter of at least one of the optical sensors through the sensor controller, based on the respective signal characteristics of the optical sensors according to the current state of the object to be measured, and select and receive, based on the respective signal characteristics of the optical sensors, a light signal sensed through a light receiver of at least one of the optical sensors. 
     According to an aspect, a method is provided for controlling an electronic device including a motion sensor and optical sensors. Each of the optical sensors includes a light emitter and a light receiver. The optical sensors are separately driven to determine a respective signal characteristic of each of the optical sensors. A current state of an object to be measured is determined, based on at least one signal received through the motion sensor or the optical sensors. A light emitter of at least one of the optical sensors is driven, based on the respective signal characteristics of the optical sensors according to the current state of the object to be measured. Based on the respective signal characteristics of the optical sensors, a light signal sensed through a light receiver of at least one of the optical sensors is selected and received. 
     Signal characteristics of multiple optical sensors which may change according to a wearing state of an electronic device are identified, and the multiple optical sensors may be individually controlled based thereon, thereby acquiring more accurate measurement values. 
     Multiple optical sensors may be individually controlled based on signal characteristics of the multiple optical sensors according to a usage state of an electronic device, thereby acquiring more accurate measurement values. 
     Multiple optical sensors may be controlled in view of signal characteristics of the multiple optical sensors based on an event type when a designated event occurs according to a usage state of an electronic device, thereby acquiring more accurate measurement values. 
    
    
     
       BRIEF DESCRIPTION OF THE 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 a block diagram illustrating an electronic device in a network environment; according to an embodiment: 
         FIGS. 2A and 2B  are diagrams illustrating exterior shapes of an electronic device having multiple optical sensors, according to an embodiment; 
         FIG. 3  is a diagram illustrating a principle of an optical sensor, according to an embodiment; 
         FIG. 4  is a block diagram illustrating an electronic device having multiple optical sensors, according to an embodiment; 
         FIG. 5  is a block diagram illustrating an optical sensor module of an electronic device having multiple optical sensors, according to an embodiment; 
         FIG. 6  is a diagram illustrating a state in which an electronic device having multiple optical sensors is worn, according to an embodiment; 
         FIG. 7  is a diagram illustrating signal characteristics of multiple optical sensors of an electronic device, according to an embodiment; 
         FIG. 8  is a flowchart illustrating a method for determining signal characteristics of multiple optical sensors of an electronic device, according to an embodiment; 
         FIG. 9  is a flowchart illustrating a method for controlling multiple optical sensors of an electronic device based on signal characteristics of the multiple optical sensors, according to an embodiment; 
         FIGS. 10A, 10B, and 10C  are diagrams illustrating operations for controlling multiple optical sensors based on signal characteristics of the multiple optical sensors, according to an embodiment; 
         FIG. 11  is a flowchart illustrating operations for controlling multiple optical sensors of an electronic device based on designated event occurrence, according to an embodiment; and 
         FIGS. 12A and 12B  are diagrams illustrating operations for controlling multiple optical sensors based on a designated event occurrence, according to an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments are described in detail with reference to the accompanying drawings. The same or similar components may be designated by the same or similar reference numerals although they are illustrated in different drawings. Detailed descriptions of constructions or processes known in the art may be omitted to avoid obscuring the subject matter of the disclosure. The embodiments and the terms used herein are not intended to limit the technology disclosed herein to specific forms, and should be understood to include various modifications, equivalents, and/or alternatives to the corresponding embodiments. A singular expression may include a plural expression unless they are definitely different in context. 
       FIG. 1  is a block diagram illustrating an electronic device in a network environment, according to an embodiment. 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, a 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 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 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 ,  104 , or  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 present 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. It is to be understood that a singular form of a noun corresponding to an item may include one or more of the things, unless the relevant context clearly indicates otherwise. 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. 
     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 still 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. 
       FIGS. 2A and 2B  are diagrams illustrating exterior shapes of an electronic device, according to an embodiment. 
     As illustrated in  FIGS. 2A and 2B , an electronic device  200  may be a wearable device that can be worn on a finger. However, the electronic device  200  is not limited thereto. Various types of electronic devices, each of which having an optical sensor module (e.g., a PPG sensor) mounted thereto and acquiring biometric information of a user, may correspond to the electronic device  200  described herein. For example, the electronic device  200  may also be implemented as various wearable devices such as body-attachable devices (e.g., health patches or digital tattoos), clothing-type devices (e.g., smart clothing or gloves), or band-type devices (e.g., wrist/arm/finger bands or smart rings). 
     As illustrated in  FIGS. 2A and 2B , the electronic device  200  includes a housing  201 . The housing  201  may be implemented in a ring shape so as to at least partially surround the outer surface of an object to be measured (e.g., a finger of a user) when being worn, thereby preventing the housing  201  from being separated by the movement of the object to be measured. 
     The housing  201  includes a first surface  203 , which is an inner surface brought into contact with the outer surface of a part of the user&#39;s body when the user wears the electronic device. The housing also includes a second surface  205 , which is an outer surface viewable from the outside when the user wears the electronic device. 
     The electronic device  200  includes multiple optical sensors  210 . The multiple optical sensors  210  are mounted on the first surface  203  of the housing  201  so as to be brought into contact with the outer surface of a part of the user&#39;s body, and so as to emit at least light in the inward direction of the housing  201 . For example, when the user wears the electronic device  200 , the multiple optical sensors  210  may emit light to the outer surface of a part of the user&#39;s body placed in the inward direction of the housing  201 , and may sense light reflected therefrom. 
     The multiple optical sensors  210  may include at least one PPG sensor. In the PPG sensor, a light receiver  213  (e.g., a photodiode) may at least partially sense reflected light when light output by a light emitter  211  (e.g., a light emitting diode (LED)) is reflected by an external object (e.g., a finger of the user). The electronic device  200  may acquire, biometric information such as heart rate, stress, and blood oxygen saturation of (SpO 2 ) of the user, based on the reflected light sensed by the at least one light receiver  213 . 
     The multiple optical sensors  210  may be viewable from the outside through at least a part of the housing  201 . 
     The multiple optical sensors  210  may be arranged in a ring shape of a one-column array at designated intervals (e.g., identical intervals or different intervals) along the first surface  203  of the housing  201 , for example, along the inner circumference thereof. The number and/or arrangement of the multiple optical sensors  210  is not limited to those illustrated, and various numbers of optical sensors  210  may be arranged in consideration of the size or shape (e.g., the circumferential length and width) of the housing  201  of the electronic device  200 . Furthermore, the multiple optical sensors  210  may be arranged in various forms in consideration of the size and/or sensing efficiency of the optical sensors  210 . 
     Each of the multiple optical sensors  210  may include at least one light emitter  211  and at least one light receiver  213 . As illustrated in  FIGS. 2A and 2B , each optical sensor  210  includes one light emitter  211  and one light receiver  213 , but the number and/or arrangement of light emitters  211  and light receivers  213 , included in each optical sensor  210 , may not be limited thereto. For example, each optical sensor  210  may include multiple light emitters  211  and/or multiple light receivers  213 . 
     The light emitter  211  included in each of the multiple optical sensors  210  may output light of a visible light band (e.g., green, red, blue) and/or an infrared band (e.g., infra-red). For example, the light emitter  211  may output blue light having a wavelength of about 400 nm to about 550 nm, green light having a wavelength of about 450 nm to about 650 nm, red light having a wavelength of about 550 nm to about 700 nm, and/or infra-red (IR) light having a wavelength of about 880 nm to about 940 nm. When green light is used, the green light may be not sensitive to motion, but may have low skin transmissivity. When red light or IR is used, the red light or IR light may have high skin transmissivity, but may have a low signal intensity and may be sensitive to motion. 
     The light emitter  211  included in each of the multiple optical sensors  210  may be implemented so as to be able to output light of various wavelength bands and/or various intensities. For example, the light emitter  211  included in each of the multiple optical sensors  210  may include multiple light-emitting elements (e.g., LEDs) capable of outputting at least one of green light, red light, and/or IR light. For example, the light emitter  211  may include at least one among an LED, an organic LED (OLED), a laser diode (LD), a solid laser, and an infrared (IR) diode. 
     The light receiver  213  included in each of the multiple optical sensors  210  may include various elements capable of sensing a light signal, converting the light signal to an electrical signal, and outputting the electrical signal. For example, the light receiver  213  may include at least one among a photo diode (PD), an avalanche PD (APD), a phototransistor, and an image sensor. 
     An optical sensor module may further include an analog front end (AFE), such as, for example, an amplifier, a band pass filter (BPF), and/or an analog-to-digital converter (ADC), for processing the electrical signal output by the light receiver  213 . 
     The electronic device  200  may filter the electrical signal output by the light receiver  213  through analog control, such as, for example, offset correction and gain adjustment, using the AFE, and then may acquire biometric row data in the form of a digital signal. The electronic device  200  may calculate, based on the biometric raw data, biometric information such as the heart rate, stress, and blood oxygen saturation (SpO 2 ) of the user. 
     The light receiver  213  included in each of the multiple optical sensors  210  may sense reflected light of at least a part of the light output by the light emitter  211  included in the same optical sensor  210  among the multiple optical sensors  210 , may sense reflected light of at least a part of light output by a light emitter  211  included in a different optical sensor  210 , and/or may sense reflected light of at least a part of light output by all light emitters  211  included in the multiple optical sensors  210 . The principle of acquiring biometric information of a user using the optical sensors  210  is described in greater detail below with reference to  FIG. 3 . 
     A display may be disposed on the second surface  205  (e.g., a surface viewable from the outside when the user wears the electronic device) of the housing  201 . For example, the display may display various application screens, such as, for example, time information, a message, or a call. 
     The electronic device  200  may further include a motion sensor. The motion sensor may include various types of sensors capable of sensing motion of the electronic device  200 , such as, for example, a gyro sensor, an acceleration sensor, or a geomagnetic sensor. The motion sensor may acquire at least one sensing signal changing depending on the motion of a user wearing the electronic device  200 . The electronic device  200  may determine, based on the sensing signal of the motion sensor, the degree of motion of the electronic device  200  and/or the user wearing the electronic device  200 . 
       FIG. 3  is a diagram illustrating a principle of an optical sensor, according to an embodiment. 
       FIG. 3  illustrates a principle by which reflected light of at least a part of light, which has been output from light-emitting elements of the light emitter  211 , has hit an external object  310  (e.g., a user&#39;s finger), and then has been reflected, is sensed through the light receiver  213  while a user wears the electronic device  200 .  FIG. 3  illustrates an optical sensor which includes the light emitter  211  having two light-emitting elements, and the light receiver  213 . However, as described above, the electronic device  200  may include multiple optical sensors  210 , and each optical sensor may include multiple light emitters  211  and light receivers  213 . 
     The light emitter  211  may output light of a designated wavelength band (e.g., green, red, blue, IR), based on a control signal of a processor. Light output by the light emitter  211  may be reflected by a perfused tissue  311  and/or a bone  313 , and the properties of a reflected light signal received by the light receiver  213  may vary depending on the user&#39;s body condition. For example, when blood flowing through a blood vessel of the user&#39;s wrist increases, the blood vessel dilates, and thus, the amount of reflected light, which is reflected and sensed by the light receiver  213 , may decrease. Therefore, the electronic device  200  may measure biometric information such as the heart rate, stress, and blood oxygen saturation (SpO 2 ) of the user based on the properties of the reflected light sensed by the light receiver  213 . 
       FIG. 4  is a block diagram illustrating an electronic device, according to an embodiment. 
     As illustrated in  FIG. 4 , an electronic device  400  includes an optical sensor module  410 , a motion sensor  420 , a processor  430 , a memory  440 , a display  450 , and a communication module  460 . The elements illustrated in  FIG. 4  are merely an example, and some elements may be omitted or replaced, or may be integrated as a single module. 
     The electronic device  400  may include the wearable electronic device  200  described above through  FIGS. 2A and 2B , but is not limited thereto. Thus, various types of electronic devices, which include the optical sensor module  410  and can acquire biometric information of a user, may correspond to the electronic device  400 . For example, the electronic device  400  may include wearable devices such as a body-attachable device (e.g., a health patch, or a digital tattoo), a clothing device (e.g., smart clothing or gloves), and a band-type device (e.g., a wrist/arm/finger band, or a smart ring). 
     The optical sensor module  410  includes multiple optical sensors  411 - 1 ,  411 - 2 , . . . ,  411 -N. The multiple optical sensors  411 - 1 ,  411 - 2 , . . . ,  411 -N included in the optical sensor module  410  include respective light emitters  413 - 1 ,  413 - 2 , . . . ,  413 -N and respective light receivers  415 - 1 ,  415 - 2 , . . . ,  415 -N. 
     As described with reference to  FIGS. 2A and 2B , the multiple optical sensors  411 - 1 ,  411 - 2 , . . . ,  411 -N of the optical sensor module  410  may be arranged in a line at a predetermined interval along the circumference of the inner surface of a housing of the electronic device  400 , and may be brought into contact with (or may approach) the surface of a part of the user&#39;s body when the user wears the electronic device  400 . 
     Each of the light emitters  413 - 1 ,  413 - 2 , . . . ,  413 -N included in the respective optical sensors  411 - 1 ,  411 - 2 , . . . ,  411 -N may include multiple light-emitting elements in order to output light having a designated wavelength band and/or different light intensities and including green light, red light, blue light and/or IR light. Each optical sensor is shown to include one light emitter  413 - 1 ,  413 - 2 , . . . ,  413 -N, but there may be more than one light emitter included in each optical sensor. Each of the light receivers  415 - 1 ,  415 - 2 , . . . ,  415 -N included in the multiple optical sensors  411 - 1 ,  411 - 2 , . . . ,  411 -N may include at least one light-receiving element (e.g., a PD, an APD, a phototransistor, or an image sensor) capable of sensing a light signal, converting the light signal to an electrical signal, and outputting the electrical signal. Each optical sensor is shown to include one light receiver  415 - 1 ,  415 - 2 , . . . ,  415 -N, but there may be more than one light receiver included in each optical sensor. 
     The optical sensor module  410  may be electrically connected to the processor  430 , and each of the multiple optical sensors  411 - 1 ,  411 - 2 , . . . ,  411 -N may independently operate based on a control signal of the processor  430 . 
     The multiple optical sensors  411 - 1 ,  411 - 2 , . . . ,  411 -N may be controlled to operate at different timings, based on a control signal of the processor  430 , or the multiple optical sensors may be controlled to operate at a substantially identical timing. For example, the respective light emitters  413 - 1 ,  413 - 2 , . . . ,  413 -N of the multiple optical sensors  411 - 1 ,  411 - 2 , . . . ,  411 -N may be controlled to sequentially emit light at different timings, respectively, or all of the light emitters  413 - 1 ,  413 - 2 , . . .  413 -N may be controlled to emit light at a substantially identical timing. 
     Operations of the respective light emitters  413 - 1 ,  413 - 2 , . . . ,  413 -N and the respective light receivers  415 - 1 ,  415 - 2 , . . . ,  415 -N of the multiple optical sensors  411 - 1 ,  411 - 2 , . . . ,  411 -N may be independently controlled based on the control signal of a processor  430 . 
     Each of the light receivers  415 - 1 ,  415 - 2 , . . . ,  415 -N of the multiple optical sensors  411 - 1 ,  411 - 2 , . . . ,  411 -N may receive, when light is emitted from a light emitter of an identical optical sensor among the respective light emitters  413 - 1 ,  413 - 2 , . . . ,  413 -N of the multiple optical sensors  411 - 1 ,  411 - 2 , . . . ,  411 -N, a light signal received by reflection of the emitted light. For example, a light receiver  415 - n  of an optical sensor (e.g.,  411 - n,  1≤n≤N) may receive a light signal when light emitted by a light emitter  413 - n  of the optical sensor  411 - n  is reflected and received. 
     Each of the light receivers  415 - 1 ,  415 - 2 , . . . ,  415 -N of the multiple optical sensors  411 - 1 ,  411 - 2 , . . . ,  411 -N may receive, even when light is emitted from light emitters of other optical sensors among the respective light emitters  413 - 1 ,  413 - 2 , . . . ,  413 -N of the multiple optical sensors  411 - 1 ,  411 - 2 , . . . ,  411 -N, light signals received by reflection of the emitted light. For example, a light receiver ( 415 - n ) of an optical sensor (e.g.,  411 - n,  1≤n≤N) may receive a light signal received by reflection of light emitted by a light emitter ( 413 - m ) of another optical sensor (e.g.,  411 - m,  1≤m≤N, m≠n) different from the optical sensor ( 411 - n ). 
     When light is emitted from all the light emitters  413 - 1 ,  413 - 2 , . . . ,  413 -N of the multiple optical sensors  411 - 1 ,  411 - 2 , . . . ,  411 -N, the respective light receivers  415 - 1 ,  415 - 2 , . . . ,  415 -N of the multiple optical sensors  411 - 1 ,  411 - 2 , . . . ,  411 -N may receive light signals received by reflection of the emitted light. For example, when the respective light emitters  413 - 1 ,  413 - 2 , . . . ,  413 -N of the multiple optical sensors  411 - 1 ,  411 - 2 , . . . ,  411 -N emit light while being controlled to substantially simultaneously emit light, reflected light signals may be received by the respective light receivers  415 - 1 ,  415 - 2 , . . . ,  415 -N. 
     The optical sensor module  410  further includes a sensor controller  417  electrically connected to the multiple optical sensors  411 - 1 ,  411 - 2 , . . . ,  411 -N and capable of independently controlling an operation of each of the optical sensors. 
     The sensor controller  417  may operate as an analog front end for processing a light signal received from the multiple optical sensors  411 - 1 ,  411 - 2 , . . . ,  411 -N and transmitting the light signal to the processor  430 . For example, the sensor controller  417  may perform a signal pre-processing process through filtering such as gain control and/or offset correction with respect to an electrical signal converted from the light signal received from the multiple optical sensors  411 - 1 ,  411 - 2 , . . . ,  411 -N, and may convert the electrical signal to a digital signal. 
     The sensor controller  417  may be operatively connected to the processor  430  and the multiple optical sensors  411 - 1 ,  411 - 2 , . . . ,  411 -N, and may function as an interface for controlling signal transmission/reception between the processor  430  and the multiple optical sensors  411 - 1 ,  411 - 2 , . . . ,  411 -N. For example, the sensor controller  417  may receive a control signal of the processor  430  to drive a light emitter ( 413 - n ) of at least one optical sensor (e.g.,  411 - n,  1≤n≤N) among the multiple optical sensors  411 - 1 ,  411 - 2 , . . . ,  411 -N, such that the light emitter emits light having a designated intensity in a designated wavelength band. For example, the sensor controller  417  may receive a control signal of the processor  430  to process a light signal sensed by a light receiver ( 415 - m ) of at least one optical sensor (e.g.,  411 - m,  1≤m≤N) among the multiple optical sensors  411 - 1 ,  411 - 2 , . . . ,  411 -N, and may provide the processed light signal to the processor  430 . 
     The motion sensor  420  may include various types of sensors capable of sensing the motion of the electronic device  400 , such as gyro sensor and an acceleration sensor. The motion sensor  420  may be electrically connected to the processor  430 , and may provide, to the processor  430 , a motion signal generated based on sensing of the motion of the electronic device  400 . 
     The memory  440  may include a volatile memory and/or a nonvolatile memory  440 , may be electrically connected to the processor  430 , and may store various instructions executed by the processor  430 . The instructions may include a control command, such as arithmetic and logic calculation, data movement, or an input/output, which can be recognized by a control circuit, and may be defined on a framework stored in the memory  440 . Furthermore, the memory  440  may store at least a part of the program  140  in  FIG. 1 . 
     The processor  430  may perform calculation or data processing regarding communication and/or control of each of the elements of the electronic device  400 , and may include at least a part of the configuration and/or function of the processor  120  in  FIG. 1 . For example, the processor  430  may be electrically connected to the optical sensor module  410 , the motion sensor  420 , the memory  440 , the display  450 , and the communication module  460  to control these elements and/or process calculation and/or data related to operations of these elements. 
     The processor  430  may load the instructions stored in the memory  440 , and may control the elements of the electronic device  400  to perform operations of implementing various embodiments based on the loaded instructions and/or may process calculation and/or data related to operations of these elements. 
     The processor  430  may use the optical sensor module  410  to acquire a bio-signal from a part of a user&#39;s body (e.g., a user&#39;s finger), and may calculate, based on the bio-signal, biometric information such as the heart rate, stress, and blood oxygen saturation (SpO 2 ) of the user. 
     In order to acquire desired biometric information, the processor  430  may determine, based on signals sensed by the optical sensor module  410  and/or the motion sensor  420 , the current state (e.g., a normal state, a sleep state, an exercise state, or an event occurrence state) of the user wearing the electronic device  400 . 
     The processor  430  may control, based on the determined current state of the user, the sensor controller  417  of the optical sensor module  410  such that, based on signal characteristics of the multiple optical sensors  411 - 1 ,  411 - 2 , . . . ,  411 -N, the light emitter ( 413 - n ) of the at least one optical sensor (e.g.,  411 - n,  1≤n≤N) emits light and such that a reflected and received light signal is received through the light receiver ( 415 - m ) of the at least one optical sensor (e.g.,  411 - m,  1≤m≤N). 
     The display  450  may include at least a part of the configuration and/or function of the display module in  FIG. 1 . For example, the display  450  may include a liquid crystal display (LCD), an LED display, or an OLED display. 
     The display  450  may provide various types of visual information related to biometric information acquired by the processor  430 . For example, the display  450  may display various types of visual information generated based on biometric information or a necessary visual notification in relation to biometric information acquisition. 
     The communication module  460  may include at least a part of the configuration and/or function of the communication module  190  in  FIG. 1 . For example, the communication module  460  may provide, under control of the processor  430 , communication with various external electronic devices (e.g., the electronic devices  102  and  104  or the server  108  in  FIG. 1 ). For example, the electronic device  400  may perform short-range wireless communication by using the communication module  460 . The electronic device  400  may communicate with at least one external electronic device  102 ,  104 , or  108 , based on near field communication (NFC), Bluetooth, Bluetooth low energy (BLE), Wi-Fi Direct, and/or ultra-wideband (UWB) communication. In another example, the electronic device  400  may perform long-range wireless communication by using the communication module  460 . The electronic device  400  may be connected to an external network (e.g., a cellular network) by using the communication module  460 . 
       FIG. 5  is a block diagram illustrating an optical sensor module of an electronic device, according to an embodiment. 
       FIG. 5  illustrates the circuit structure of an optical sensor unit  510  and a sensor controller  520  for controlling the optical sensor unit of an optical sensor module of an electronic device  500 . 
     For example, the optical sensor unit  510  includes multiple optical sensors (e.g., a first optical sensor  511 , a second optical sensor  512 , a third optical sensor  513 , and a fourth optical sensor  514 ). Four optical sensors are illustrated as an example, however, the number of multiple optical sensors is not limited, and various numbers of optical sensors may be adopted. 
     As illustrated in  FIG. 5 , each of the optical sensors  511 ,  512 ,  513 , and  514  of the multiple optical sensors may include one light emitter (e.g., a first light emitter  511   a , a second light emitter  512   a , a third light emitter  513   a , and a fourth light emitter  514   a ) and one light receiver (e.g., a first light receiver  511   b , a second light receiver  512   b , a third light receiver  513   b , and a fourth light receiver  514   b ), respectively. Each of the optical sensors has been illustrated as including one light emitter and one light receiver, but embodiments are not limited thereto. Each of the optical sensors may be implemented so as to have at least two light emitters and/or at least two light receivers. 
     The sensor controller  520  is electrically provided between a processor  530  and the optical sensor unit  510 , and may control the multiple optical sensors  511 ,  512 ,  513 , and  514  based on a control signal of the processor  530  to drive the respective light emitters  511   a ,  512   a    513   a , and  514   a . The sensor controller  520  may provide, to the processor  530 , signals received from the respective light receivers  511   b ,  512   b ,  513   b , and  514   b . For example, the sensor controller  520  may include the sensor controller  417  described with reference to  FIG. 4 . Under control of the processor  530 , the sensor controller  520  may emit light through at least one light emitter  511   a ,  512   a ,  513   a , or  514   a  of the multiple optical sensors  511 ,  512 ,  513 , and  514 , and may perform a signal pre-processing process through filtering, such as, for example, gain control and/or offset correction, with respect to a light signal received through at least one light receiver  511   b ,  512   b ,  513   b , or  514   b , to convert the light signal to a digital signal. 
     The sensor controller  520  includes a light emitter driving circuit  521 , a multiplexer (MUX)  523 , and an analog-to-digital converter (ADC)  525 . 
     The light emitter driving circuit  521  may drive, based on a control signal of the processor  530 , at least one light emitter, for example, the first light emitter  511   a , the second light emitter  512   a , the third light emitter  513   a , and/or the fourth light emitter  514   a , of the multiple optical sensors, for example, the first optical sensor  511 , the second optical sensor  512 , the third optical sensor  513 , and/or the fourth optical sensor  514 . 
     The first light emitter  511   a , the second light emitter  512   a , the third light emitter  513   a , and/or the fourth light emitter  514   a  may have various output intensities and output wavelengths. For example, the first light emitter  511   a , the second light emitter  512   a , the third light emitter  513   a , and/or the fourth light emitter  514   a  may have multiple light-emitting elements having different attributes in output intensity and/or output wavelength. The control signal, which the sensor controller  520  (or, the light emitter driving circuit  521 ) receives from the processor  530 , may include information about a light emitter to be driven and information about the output intensity and/or output wavelength of light that is to be output by the light emitter to be driven. 
     The first light receiver  511   b , the second light receiver  512   b , the third light receiver  513   b , and/or the fourth light receiver  514   b  of the multiple optical sensors may sense the amount of light and may output an analog electrical signal (hereinafter, referred to as “light signal”) corresponding to the sensed amount of light. For example, each of the first light receiver  511   b , the second light receiver  512   b , the third light receiver  513   b , and/or the fourth light receiver  514   b  may include at least one light-receiving element (e.g., a PD, an APD, a phototransistor, and/or an image sensor) capable of sensing the amount of light and outputting an analog electrical signal corresponding to the sensed amount of light. 
     A light signal that is output from each of the first light receiver  511   b , the second light receiver  512   b , the third light receiver  513   b , and/or the fourth light receiver  514   b  of the multiple optical sensors may be input into the MUX  523 , and the MUX  523  may transfer, under control the processor  530 , the light signal to the processor  530  through the ADC  525 . For example, the MUX  523  may output signals transferred from the light receivers  511   b ,  512   b ,  513   b , and  514   b  to the ADC  525  through separate respective channels. The MUX  523  may output some signals selected from among signals transmitted from the respective light receivers  511   b ,  512   b ,  513   b , and  514   b  to the ADC  525  through corresponding channels. The MUX  523  may output all of the signals transmitted from the respective light receivers  511   b ,  512   b ,  513   b , and  514   b  to the ADC  525  through corresponding channels. All of the signals transmitted from the respective light receivers  511   b ,  512   b ,  513   b , and  514   b  may be outputted to the ADC  525  through one channel. 
       FIG. 6  is a diagram illustrating a state in which an electronic device including multiple optical sensors is worn, according to an embodiment. 
     The structure and operation of an electronic device  600  illustrated in  FIG. 6  is similar or identical to the structure of the electronic device  200  illustrated in  FIGS. 2A and 2B  and the operation of the electronic device  400  or  500  illustrated in  FIG. 4 or 5 , and a description of technical features described above are omitted below. For example, the electronic device  600  in  FIG. 6  will be described with, for example, four optical sensors among multiple optical sensors as in the electronic device  500  of  FIG. 5  for convenience of description. 
     A first surface  603  of a housing  601  of the electronic device  600  may be brought into contact with a part (e.g., a finger) of a user&#39;s body when the electronic device  600  is worn by the user, and a second surface  605  may be visually viewable from the outside. A first optical sensor  611 , a second optical sensor  612 , a third optical sensor  613 , and a fourth optical sensor  614  of the electronic device  600  respectively include a first light emitter  611   a , a second light emitter  612   a , a third light emitter  613   a , and a fourth light emitter  614   a , each of which emits light in a designated intensity and/or a designated wavelength band. For example, each of the first light emitter  611   a , the second light emitter  612   a , the third light emitter  613   a , and the fourth light emitter  614   a  may include multiple light-emitting elements (e.g., LEDs) that can output blue light having a wavelength of about 400 nm to about 550 nm, green light having a wavelength of about 450 nm to about 650 nm, red light having a wavelength of about 550 nm to about 700 nm, and/or infra-red (IR) light having a wavelength of about 880 nm to about 940 nm, respectively. 
     The first optical sensor  611 , the second optical sensor  612 , the third optical sensor  613 , and the fourth optical sensor  614  of the electronic device  600  respectively include at least one first light receiver  611   b , at least one second light receiver  612   b , at least one third light receiver  613   b , and at least one fourth light receiver  614   b . For example, the at least one first light receiver  611   b , the at least one second light receiver  612   b , the at least one third light receiver  613   b , and the at least one fourth light receiver  614   b  may output light signals corresponding to the amount of light which is emitted by at least one of the first light emitter  611   a , the second light emitter  612   a , the third light emitter  613   a , and the fourth light emitter  614   a , is reflected by a part of the user&#39;s body, and is received. For example, each of the first light receiver  611   b , the second light receiver  612   b , the third light receiver  613   b , and the fourth light receiver  614   b  may include at least one light-receiving element (e.g., a PD, an APD, a phototransistor, or an image sensor). 
     The first optical sensor  611 , the second optical sensor  612 , the third optical sensor  613 , and the fourth optical sensor  614  of the electronic device  600  are disposed on the first surface  603  of the housing  601  along the inner circumference at a designated interval. 
     The electronic device  600  includes a display  620  that is mounted on the second surface  605  of the housing  601  and is viewed from the outside when the user wears the electronic device  600 . For example, the electronic device  600  may display various application screens, such as, for example, time information, a message notification, and a call through the display  620 . In another example, the electronic device  600  may provide, through the display  620 , various types of visual information related to biometric information acquired by the processor  430  or  530  of  FIG. 4 or 5 . For example, the display  620  may display various types of visual information generated based on biometric information or a necessary visual notification related to biometric information acquisition. 
     When the electronic device  600  is worn, each of the first optical sensor  611 , the second optical sensor  612 , the third optical sensor  613 , and the fourth optical sensor  614  may be brought into contact with a part (e.g., a finger) of the user&#39;s body at a designated position or in a designated direction along the circumference of the user&#39;s finger. 
     For example, in the case of the ring-type wearable electronic device  600 , the electronic device  600  may often rotate without being fixed to the finger of the user while being worn. The position or direction in which each optical sensor of the electronic device  600  is brought into contact with the finger may be changed over time. 
       FIG. 6  illustrates an example in which, while the electronic device  600  is worn on an object  790  (e.g., the user&#39;s finger) to be measured, the first optical sensor  611  among the multiple optical sensors along the circumference of the finger is positioned in the palmar-side direction  791 , the second optical sensor  612  is positioned at about 90 degrees in the clockwise direction from the first optical sensor  611 , the third optical sensor  613  is positioned in the dorsal-side direction  793 , and the fourth optical sensor  614  is positioned at about 270 degrees in the clockwise direction from the first optical sensor  611 . 
     A processor may separately operate each of the first optical sensor  611 , the second optical sensor  612 , the third optical sensor  613 , and the fourth optical sensor  614 . For example, the processor  430  or  530  may drive and control at least one among the first light emitter  611   a , the second light emitter  612   a , the third light emitter  613   a , and the fourth light emitter  614   a  of the first optical sensor  611 , the second optical sensor  612 , the third optical sensor  613 , and the fourth optical sensor  614 , to output light. The processor  430  or  530  may receive a light signal from at least one among the first light receiver  611   b , the second light receiver  612   b , the third light receiver  613   b , and the fourth light receiver  614   b  of the first optical sensor  611 , the second optical sensor  612 , the third optical sensor  613 , and the fourth optical sensor  614 . 
     The processor  430  or  530  may separately operate each of the first optical sensor  611 , the second optical sensor  612 , the third optical sensor  613 , and the fourth optical sensor  614  at a different timing to receive a light signal. 
     The processor  430  or  530  may sequentially operate the first optical sensor  611 , the second optical sensor  612 , the third optical sensor  613 , and the fourth optical sensor  614 , to receive light signals. For example, the processor  430  or  530  may drive the first light emitter  611   a  to receive a light signal through the first light receiver  611   b , may subsequently operate the second light emitter  612   a  to receive a light signal through the second light receiver  612   b , may subsequently operate the third light emitter  613   a  to receive a light signal through the third light receiver  613   b , and may subsequently operate the fourth light emitter  614   a  to receive a light signal through the fourth light receiver  614   b . The processor  430  or  530  may sequentially drive the first light emitter  611   a , the second light emitter  612   a , the third light emitter  613   a , and the fourth light emitter  614   a  at a designated interval (e.g., an interval of 0.025 sec) to receive light signals through the respective light receivers. 
     An electronic device is provided that includes a housing, a motion sensor, and optical sensors disposed on one surface of the housing so as to be brought into contact with an object to be measured when the electronic device is worn. Each of the optical sensors comprises a respective light emitter and a respective light receiver. The electronic device also includes a sensor controller configured to control the optical sensors, and a processor operatively connected to the motion sensor and the sensor controller. The processor is configured to separately drive the optical sensors through the sensor controller to determine a respective signal characteristic of each of the optical sensors, and determine a current state of the object to be measured, based on at least one signal received through the motion sensor or the optical sensors. The processor is also configured to drive a light emitter of at least one of the optical sensors through the sensor controller, based on the respective signal characteristics of the optical sensors according to the current state of the object to be measured, and select and receive, based on the respective signal characteristics of the optical sensors, a light signal sensed through a light receiver of at least one of the optical sensors. 
     The housing may include a ring type housing, and the optical sensors may be disposed at a designated interval on the inner surface of the housing. 
     The processor may be configured to separately receive light signals, reflected from light output by driving, through the sensor controller, respective light emitters included in at least two of the optical sensors, and sensed by the light receivers of the at least two optical sensors. When intensities of at least two of the separately received light signals are larger than a designated value, the processor may be configured to drive the optical sensors to determine the respective signal characteristic of each of the optical sensors. 
     The processor may be configured to receive light signals, reflected from light output by driving, through the sensor controller, light emitters included in the optical sensors at different timings and sensed by the light receivers of the optical sensors. The processor may be further configured to determine, based on the light signals, the respective signal characteristics of the optical sensors. 
     The processor may be further configured to analyze characteristics of the light signals to determine an optical sensor having an optimal signal characteristic from among the optical sensors. 
     The processor may be further configured to drive, based on the current state, a light emitter of the optical sensor having the optimal signal characteristic to emit light. 
     The processor may be further configured to select and receive, based on the current state, a light signal sensed through a light receiver of the optical sensor having the optimal signal characteristic, through the sensor controller. 
     The processor may be further configured to select and receive, based on the current state, a light signal sensed through a light receiver of an optical sensor positioned, in the housing, opposite to the optical sensor having the optimal signal characteristic, through the sensor controller. 
     The processor may be further configured to cause, through the sensor controller, the light emitters included in the optical sensors to emit, based on the current state, light at an identical timing. The processor may be further configured to select and receive light signals sensed by the light receivers included in the optical sensors. 
     The processor may be further configured to determine, based on the at least one signal received through the motion sensor or the multiple optical sensors, that the current state of the object is at least one among a normal state, a sleep state, an exercise state, and an event occurrence state. 
     The processor may be further configured to adjust, based on the current state, at least one of an intensity and a wavelength of at least one light emitter included in the optical sensors so as to emit light. 
     The processor may be further configured to, when the current state is determined to be the exercise state, separately receive light signals, which are reflected from light output by driving, through the sensor controller, the light emitters included in the optical sensors at different timings and, which are sensed by light receivers of the optical sensors. 
     The processor may be further configured to separately drive the optical sensors through the sensor controller for each designated period to determine the respective signal characteristic of each of the optical sensors. The processor may be further configured to determine the current state of the object, based on the at least one signal received through the motion sensor or the optical sensors. 
     The processor may be further configured to, when a designated event occurs according to the determination of the current state of the object, control, based on the type of the designated event, driving of the light emitter of at least one of the optical sensors through the sensor controller to emit light, and select and receive a light signal sensed through the light receiver of the at least one of the optical sensors. 
       FIG. 7  is a diagram illustrating signal characteristics of multiple optical sensors of an electronic device, according to an embodiment. In  FIG. 7 , the horizontal axis indicates the number of samples. Samples may be acquired in units of about 5 ms, and 200 samples may imply one second. In  FIG. 7 , the vertical axis indicates a magnitude value of a light signal. 
     Referring to  FIG. 7 , a first signal  711  indicates a light signal that has been received through the first light receiver  611   b  of the first optical sensor  611  positioned in the palmar-side direction by driving the first light emitter  611   a  of the first optical sensor  611  positioned in the palmar-side direction. A third signal  713  indicates a light signal that has been received through the third light receiver  613   b  of the third optical sensor  613  positioned in the dorsal-side direction by driving the third light emitter  613   a  of the third optical sensor  613  positioned in the dorsal-side direction. A second signal  712  indicates a light signal that has been received through the second light receiver  612   b  of the second optical sensor  612  by driving the second light emitter  612   a  of the second optical sensor  612 . A fourth signal  714  indicates a light signal that has been received through the fourth light receiver  614   b  of the fourth optical sensor  614  by driving the fourth light emitter  614   a  of the fourth optical sensor  614 . 
     A processor may analyze and compare signal characteristics of the first signal  711 , the second signal  712 , the third signal  713 , and the fourth signal  714 , which are light signals sensed through the first optical sensor  611 , the second optical sensor  612 , the third optical sensor  613 , and the fourth optical sensor  614 , respectively. The processor may determine a signal, which is the most suitable for biometric information acquisition, based on the result of comparison between the signal characteristics. For example, the signal characteristics may include the magnitude of noise (e.g., a signal-to-noise ratio (SNR) or an AC component (e.g., a peak-to-peak value). 
     Referring to  FIG. 7  again, for example, it can be found that an AC component  711   a  (e.g., a peak-to-peak value) of the first signal  711 , which is a light signal sensed by the first optical sensor  611  positioned in the palmar-side direction, has a largest value when compared with other signals (e.g., the second signal  712 , the third signal  713 , and the fourth signal  714 ). 
     The processor  430  or  530  may determine, based on the signal characteristics of light signals sensed by the first optical sensor  611 , the second optical sensor  612 , the third optical sensor  613 , and the fourth optical sensor  614 , an optical sensor that is to be used as a main sensor among the first optical sensor  611 , the second optical sensor  612 , the third optical sensor  613 , and the fourth optical sensor  614  in order to sense a bio-signal. For example, the processor may determine that the AC component of the first signal  711 , which is a light signal sensed by the first optical sensor  611 , has the largest value when compared with AC components of other signals (e.g., the second signal  712 , the third signal  713 , and the fourth signal  714 ), and may determine, based on the signal characteristics, that the first optical sensor  611  is a main sensor to be used to sense a bio-signal. 
     When time passes, the positions of contact of multiple optical sensors with a part (e.g., a finger) of a user&#39;s body may vary depending on the motion of the electronic device, and thus, for example, the processor may drive each of the first optical sensor  611 , the second optical sensor  612 , the third optical sensor  613 , and the fourth optical sensor  614  at a different timing at a designated time interval (e.g., every 10 minutes) or at the time of occurrence of a biometric information measurement event to determine, as described above, a signal characteristic of a light signal sensed by each optical sensor, and may determine, based thereon, a sensor to be used as a main sensor. 
       FIG. 8  is a flowchart illustrating a method for determining signal characteristics of multiple optical sensors of an electronic device, according to an embodiment. 
     Operations of an electronic device including multiple optical sensors, illustrated in  FIG. 8 , may be performed by a processor, and, hereinafter, will be described with main reference to the structure of the electronic device  600  in  FIG. 6 . A description of technical features that are described in detail above, are omitted below. 
     At  801 , the processor determines whether the electronic device is worn on a user&#39;s body. 
     For example, the processor may control multiple optical sensors to be separately driven. When at least two, or most, of the magnitudes of respectively received light signals have a value greater than a designated value, the processor may determine that the electronic device is in a worn state. Optical sensors that are driven in order to determine whether the electronic device is in a worn state may be all of the multiple optical sensors, or may be limited to at least two optical sensors that are designated based on each direction (e.g., four optical sensors at a 90-degree interval, or three optical sensors at a 120-degree interval) among the multiple optical sensors. 
     For example, the processor may control, through a sensor controller, the first optical sensor  611 , the second optical sensor  612 , the third optical sensor  613 , and the fourth optical sensor  614  of  FIG. 6  to respectively drive the first light emitter  611   a , the second light emitter  612   a , the third light emitter  613   a , and the fourth light emitter  614   a  of  FIG. 6 , so as to emit light (e.g., IR light) having a designated intensity and/or wavelength. The processor may determine that the electronic device is in the worn state, when the magnitude of a IR light signal received through each of the first light receiver  611   b , the second light receiver  612   b , the third light receiver  613   b , and the fourth light receiver  614   b  is greater than or equal to a designated value. 
     At  803 , the processor drives the multiple optical sensors at different timings in order to determine a signal characteristic of each of the multiple optical sensors. For example, with respect to  FIG. 6 , the processor may sequentially drive the first light emitter  611   a , the second light emitter  612   a , the third light emitter  613   a , and the fourth light emitter  614   a  of the first optical sensor  611 , the second optical sensor  612 , the third optical sensor  613 , and the fourth optical sensor  614 . 
     When the multiple optical sensors are sequentially driven in at  803 , the processor receives, at  805 , light signals sequentially sensed by the multiple optical sensors. For example, the processor may receive light signals sequentially sensed through the first light receiver  611   b , the second light receiver  612   b , the third light receiver  613   b , and the fourth light receiver  614   b  of  FIG. 6 , respectively, when light emitted by sequentially driving the first light emitter  611   a , the second light emitter  612   a , the third light emitter  613   a , and the fourth light emitter  614   a  is reflected by a part of the user&#39;s body. 
     At  807 , the processor analyzes a signal characteristic of each of the sensed light signals. For example, the processor may analyze an AC component of each of the light signals sensed through the first light receiver  611   b , the second light receiver  612   b , the third light receiver  613   b , and the fourth light receiver  614   b  of  FIG. 6  to determine signal characteristics of the first optical sensor  611 , the second optical sensor  612 , the third optical sensor  613 , and the fourth optical sensor  614 . 
       FIG. 9  is a flowchart illustrating a method for controlling multiple optical sensors of an electronic device based on signal characteristics of the multiple optical sensors, according to an embodiment. 
     Operations of an electronic device including multiple optical sensors according to various embodiments, illustrated in  FIG. 9 , may be performed by a processor, and, hereinafter, will be described with main reference to the structure of the electronic device  600  of  FIG. 6 . A description of technical features described in detail above are omitted below. 
     At  901 , the processor determines signal characteristics of multiple optical sensors. For example, the processor may analyze signal characteristics of the first optical sensor  611 , the second optical sensor  612 , the third optical sensor  613 , and the fourth optical sensor  614  of  FIG. 6 , according to operations  801  to  807  of  FIG. 8 , and may determine, based on the analysis result, an optical sensor (e.g., the first optical sensor  611 ) to be used as a main sensor. 
     At  903 , the processor determines the current state (e.g., a normal state, a sleep state, an exercise state, or a designated event occurrence state) of a user wearing the electronic device. 
     For example, the processor may determine, based on a sensing signal of a motion sensor, the current state (e.g., a normal state, a sleep state, an exercise state, or a designated event state) of a user wearing the electronic device. For example, the processor may determine the current state of the user to be an exercise state when it is determined, based on the sensing signal of the motion sensor, that the motion of the electronic device has a value greater than or equal to a designated first threshold value, may determine the current state of the user to be a sleep state when it is determined that the motion of the electronic device has a value less than or equal to a designated second threshold value, and may determine the current state of the user to be a normal state in the other cases. To this end, the processor may determine sensing signals of the motion sensor periodically (e.g., every 10 minutes). 
     For example, the processor may acquire biometric information (e.g., heart rate information) from a light signal received through at least one of the multiple optical sensors, and may determine, based thereon, the current state (e.g., a normal state, a sleep state, an exercise state, or a designated event state) of the user. To this end, the processor may periodically drive at least one optical sensor (e.g., the optical sensor determined as a main sensor) among the multiple optical sensors to receive a light signal, and may determine the current state of the user. 
     For example, the processor may also determine the current state (e.g., a normal state, a sleep state, an exercise state, or a designated event state) of the user wearing the electronic device, based on a sensing signal of a motion sensor and biometric information (e.g., heart rate information) acquired from a light signal received through at least one of the multiple optical sensors. 
     At  905 , in order to acquire biometric information according to the determined current state of the user, the processor may control driving of a light emitter of at least one optical sensor selected from among the multiple optical sensors, based on the signal characteristics of the multiple optical sensors. 
     At  907 , in order to acquire biometric information according to the determined current state of the user, the processor may receive a light signal sensed by a light receiver of at least one optical sensor selected from among the multiple optical sensors, based on the signal characteristics of the multiple optical sensors. The processor may be configured to acquire a bio-signal, based thereon. The at least one light receiver, which receives a light signal, is controlled to be identical to a light receiver of an optical sensor, which includes the at least one selected light emitter driven at  905  (e.g., the first light receiver  611   b  receives a light signal from light emitted by the first light emitter  611   a ), but may be controlled to be different from the optical sensor (e.g., the third light receiver  613   b  receives a light signal from light emitted by the first light emitter  611   a ), and the number thereof may be different (e.g., each light receiver simultaneously receives light signals from light emitted by multiple light emitters  611   a ,  612   a ,  613   a , and  614   a ). 
       FIGS. 10A, 10B, and 10C  are diagrams illustrating operations of controlling multiple optical sensors based on signal characteristics of the multiple optical sensors, according to an embodiment. In order to acquire biometric information according to the current state of a user, the processor may determine, based on signal characteristics of multiple optical sensors, the position and/or the number of light emitters of optical sensors to be driven among the multiple optical sensors. The processor may determine the driving timing, light intensity, and/or light wavelength of a light emitter to be driven. 
     Referring to  FIG. 10A , for example, when it is determined that the current state of the user is a normal state, the processor may drive, based on the signal characteristics of the multiple optical sensors determined at  901  of  FIG. 9 , the first light emitter  611   a  of the first optical sensor  611  determined as a main sensor to emit light. For example, the processor may receive, through the first light receiver  611   b , reflected light of light emitted by the first light emitter  611   a  of the first optical sensor  611 . 
     Referring to  FIG. 10B , for example, when it is determined that the current state of the user is an exercise state, the processor may drive the first light emitter  611   a , the second light emitter  612   a , the third light emitter  613   a , and the fourth light emitter  614   a  of the multiple optical sensors, may receive light signals through the first light receiver  611   b , the second light receiver  612   b , the third light receiver  613   b , the fourth light receiver  614   b  of the multiple optical sensors, and may acquire biometric information in consideration of all of the received light signals. For example, the first light emitter  611   a , the second light emitter  612   a , the third light emitter  613   a , and the fourth light emitter  614   a  of the multiple optical sensors may be separately driven at different timings, and light signals may be separately received through the first light receiver  611   b , the second light receiver  612   b , the third light receiver  613   b , and the fourth light receiver  614   b  of the multiple optical sensors. In the exercise state, the motion of the electronic device becomes more frequent, and thus, the position of contact of the multiple optical sensors with a part of the user&#39;s body may be frequently changed and signal characteristics may also be frequently changed. Therefore, it may be required to acquire as much light signal information as possible from each optical sensor. For example, the processor may control all light-emitting elements, included in each light emitter, to be driven at the time of driving of the each light emitter such that the each light emitter can emit light in as large amount as possible. 
     Referring to  FIG. 10C , for example, when it is determined that the current state of the user is a sleep state, the processor may drive the first light emitter  611   a  of the first optical sensor  611  determined as a main sensor based on the signal characteristics of the multiple optical sensors, where a wavelength band of light to be emitted may be designated, thereby controlling the light emitter to be driven therein. For example, in order to prevent the wavelength band of light emitted in the sleep state from disturbing sleep, the processor may drive only a light-emitting element of the remaining designated wavelength band excluding a green wavelength, or may drive a red light-emitting element or an IR light-emitting element to emit only light having a red wavelength or IR wavelength. 
     In order to acquire biometric information, the processor may drive multiple optical sensors when a request is made or when a designated event occurs. 
     For example, in order to acquire biometric information at the time point of determining the current state of the user or at the time point of determining a change in the current state of the user, the processor may determine the signal characteristics of the multiple optical sensors, and may control, based on the determination, driving of a light emitter of at least one of the multiple optical sensors. 
     In contrast, for example, when a biometric information measurement request is made through an input module, the processor  430  or  530  may control, based on the signal characteristics of the multiple optical sensors, driving of a light emitter of at least one of the multiple optical sensors. 
     Furthermore, for example, the processor may periodically (e.g., every 10 minutes) measure the signal characteristics of the multiple optical sensors, and may control, based thereon, driving of a light emitter of at least one of the multiple optical sensors to acquire a bio-signal. 
     For example, the processor may periodically determine the current state of the user. When it is determined, based on the determined current state of the user, that a designated event has occurred, the processor may control driving of a light emitter of at least one of the multiple optical sensors based on the signal characteristics of the multiple optical sensors according to the type of the designated event to emit light. The processor may select a light signal received through a light receiver of at least one of the multiple optical sensors to acquire a bio-signal. 
     For example, the designated event may include the case in which the current state of the user of the electronic device is rapidly changed or is maintained as a designated state for a designated time or longer. A detailed description thereof is provided below with reference to  FIG. 11 . 
       FIG. 11  is a flowchart illustrating operations of controlling multiple optical sensors of an electronic device based on designated event occurrence, according to an embodiment. 
     Operations of an electronic device including multiple optical sensors, illustrated in  FIG. 11 , may be performed by a processor, and, hereinafter, will be described with main reference to the structure of the electronic device  600  in  FIG. 6 . Detailed descriptions of the technical features illustrated above are omitted below. 
     At  1101 , the processor determines whether a designated event has occurred. 
     For example, the processor may determine whether a designated event has occurred, based on sensor signals received through a motion sensor and/or multiple optical sensors. 
     For example, the occurrence of the designated event and the type of the designated event may be determined in overall consideration of change or maintenance of a sensor signal value by the motion sensor and/or the multiple optical sensors, the degree of change, time required for change, or time for which the sensor signal value remains constant. The designated event may include the case in which the motion of the electronic device rapidly increases, the case in which is a lot of the motion of the electronic device is maintained and then the motion of electronic device decreases, the case in which the motion of the electronic device, which is almost motionless, increases and then the time for which there is no motion is maintained, the case in which the time for which the motion of the electronic device is scarcely made is maintained, the case in which a heart rate is maintained in a designated interval, the case in which a heart rate is rapidly increased, or the case in which a heart rate is high but gradually decreases. 
     For example, considering a situation in which the user has a cough, the motion of the electronic device or the heart rate may rapidly increase. When it is determined that this type of designated event has occurred, the processor may control driving of the multiple optical sensors in order to measure, for example, SpO 2 . 
     For example, considering a situation in which the user intensely exercises and then enters a recovery time, a state in which there is a lot of motion is maintained or the heart rate is maintained at a predetermined level or higher, and then the motion rapidly decreases or the heart rate gradually decreases. When it is determined that this type of designated event has occurred, the processor may control driving of the multiple optical sensors in order to measure, for example, SpO 2 . 
     For example, considering a situation in which the user maintains the same posture without any motion, a state in which there is no motion of the electronic device may be maintained according to a sensor signal of the motion sensor. When it is determined that this type of designated event has occurred, the processor may control driving of the multiple optical sensors in order to measure, for example, blood pressure. 
     For example, considering a situation in which the user switches from a wakened state to a sleep state or from a sleep state to a wakened state, the processor may determine this event type, based on a sensor signals of the motion sensor and/or the optical sensor, and may change and control a method for driving the multiple optical sensors. 
     For example, considering a situation in which the user switches from a normal state to an exercise state or from an exercise state to a normal state, the processor may determine this event type, based on a sensor signal of the motion sensor and/or the optical sensor, and may change and control a method for driving the multiple optical sensors. 
     Referring back to  FIG. 11 , when it is determined that the event occurs at  1101 , the processor controls driving of a light emitter of at least one of multiple optical sensors, based on the signal characteristics of the multiple optical sensors according to an event type, in order to emit light, at  1103 . 
     At  1105 , the processor acquires a bio-signal based on a signal that is received by a light receiver of at least one of the multiple optical sensors, based on the signal characteristics of the multiple optical sensors according to the event type. 
       FIGS. 12A and 12B  are diagrams illustrating operations of controlling multiple optical sensors based on a designated event occurrence, according to an embodiment. 
     Referring to  FIG. 12A , in order to measure SpO 2  according to the event type, the processor may drive the first light emitter  611   a  of the first optical sensor  611  (determined as a main sensor according to the signal characteristics) to emit light, may selectively receive a light signal received by the third light receiver  613   b  of the third optical sensor  613  positioned in the opposite direction among the multiple optical sensors and measure SpO 2 , based on the light signal. For example, in order to measure SpO 2 , the processor may drive the first light emitter  611   a ) of the first optical sensor  611  (determined as a main sensor according to the signal characteristics) of the multiple optical sensors to sequentially emit light of a red wavelength band and light of a IR wavelength band, and may substantially simultaneously receive a light signal by the third light receiver  613   b  of the third optical sensor  613  positioned in the opposite direction among the multiple optical sensors and measure SpO 2 , based on the light signal. 
     The received light signal may be considered emitted light that has passed through the user&#39;s body (e.g., a finger) and then received. 
     For example, in order to measure SpO 2  according to the event type, in the case of an event type in which measurement is made in an exercise state, the processor may drive, at different timings, the second light emitter  612   a , the third light emitter  613   a , and the fourth light emitter  614   a  of the second optical sensor  612 , the third optical sensor  613 , and the fourth optical sensor  614 , in addition to the first optical sensor  611  determined as a main sensor. In response thereto, the processor may select light signals received by the fourth light receiver  614   b , the first light receiver  611   b , and the second light receiver  612   b  of the fourth optical sensor  614 , the first optical sensor  611 , and the second optical sensor  612 , positioned in the opposite direction, and to process the selected light signals such that SpO 2  is obtained. 
     Referring to  FIG. 12B , for example, in order to measure blood pressure according to an event type, the processor may substantially simultaneously drive the first light emitter  611   a , the second light emitter  612   a , the third light emitter  613   a , and the fourth light emitter  614   a  of the first optical sensor  611 , the second optical sensor  612 , the third optical sensor  613 , and the fourth optical sensor  614  to emit light in as large amount as possible, may receive all of light signals received by the first light receiver  611   b , the second light receiver  612   b , the third light receiver  613   b , and the fourth light receiver  614   b  of the multiple optical sensors, respectively, and may acquire blood pressure information based on the light signals. 
     For example, light, which has been substantially simultaneously emitted from all light emitters (e.g., the first light emitter  611   a , the second light emitter  612   a , the third light emitter  613   a , and the fourth light emitter  614   a ), and has been reflected or has passed through a part (e.g., a finger) of the user&#39;s body, may be sensed by light receivers (e.g., the third light receiver  613   b , the fourth light receiver  614   b , the first light receiver  611   b , and the second light receiver  612   b  in order) disposed at opposite positions, respectively, and blood pressure may be measured in overall consideration of the sensed signal values. Therefore, the amount of light can be maximally ensured and multiple light signals can be simultaneously acquired, thereby minimizing noise and reducing time necessary for blood pressure measurement. 
     While the disclosure has been shown and described with reference to certain embodiments therefor, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the scope of the disclosure. 
     Therefore, the scope of the disclosure should not be defined as being limited to the embodiments, but should be defined by the appended claims and equivalents thereof.