Patent Publication Number: US-2023141246-A1

Title: Electronic device and method of estimating bio-information using the same

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application claims priority from Korean Patent Application No. 10-2021-0154636, filed on Nov. 11, 2021, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference in its entirety. 
     BACKGROUND 
     1. Field 
     Apparatuses and methods consistent with example relate to estimating bio-information using an electronic device, and more particularly to non-invasively estimating antioxidant levels. 
     2. Description of the Related Art 
     Reactive oxygen species act as an important biological defense factor such as white blood cells protecting the body against infections. However, it has been known that excessive generation of reactive oxygen species in the body may lead to various tissue diseases. Common factors that cause the reactive oxygen species include stress, alcohol, peroxides, medicine, and the like. The reactive oxygen species produced by these factors may cause cranial nerve diseases, circulatory diseases, cancer, digestive tract diseases, liver diseases, arteriosclerosis, renal diseases, diabetes, aging, and the like. Our bodies have a series of antioxidant defense systems to protect against oxygen toxicity. For normal operation of the systems, it is essential to consume sufficient antioxidants such as vitamin E, vitamin C, carotenoid, flavonoid, and the like, and it is important to eat as many foods that are rich in antioxidants as possible for an effective antioxidant action. Accordingly, there is a need for an apparatus for easily identifying the amount of antioxidants in the body. 
     SUMMARY 
     According to an aspect of an example embodiment, there is provided an electronic device including: an optical sensor configured to emit a reference light to a reference object and detect the reference light reflected from the reference object during calibration, and emit a measurement light to a target object and detect the measurement light reflected from the target object during a measurement; a display; and a processor configured to: when the electronic device is placed on a charger and is in a charging state, perform the calibration of the optical sensor based on the reference light reflected from the reference object; control the display to output guide information for estimating bio-information according to progress stages of the measurement after charging of the electronic device; and estimate the bio-information based on a light quantity of the measurement light that is reflected from the target object, and a light quantity of the reference light reflected from the reference object. 
     The optical sensor may include a light source configured to emit the reference light onto the reference object during the charging state, and a detector configured to detect the reference light reflected from the reference object, wherein the processor may be further configured to store calibration information including the light quantity of the reference light, in a memory. 
     When charging of the electronic device is complete or when the electronic device is removed from the charger, the processor may be configured to output, on the display, a text message that guides a user to estimate the bio-information. 
     The processor may be further configured to determine an estimation recommendation time based on a user pattern, and based on a current time corresponding to the estimation recommendation time, output on the display, a text message that guides a user to estimate the bio-information. 
     In response to the target object coming into contact with the optical sensor, the processor may be further configured to determine a contact position and guide a user to change or maintain the contact position based on a determination of the contact position. 
     The processor may be further configured to: control the display to display at least one of a first graphic object indicating the contact position of the target object, a second graphic object indicating a predetermined measurement position, a third graphic object guiding movement from the contact position to the predetermined measurement position, and a fourth graphic object indicating that the contact position coincides with the predetermined measurement position. 
     The optical sensor may include a light source disposed at a center of the optical sensor, and a plurality of detectors arranged to surround the light source, wherein the processor may be further configured to determine the contact position of the target object based on absorbances measured by the plurality of detectors. 
     In response to a first portion of the target object coming into contact with a measurement position of the optical sensor, the processor may be further configured to control the display to output a graphic object indicating a contact pressure between the first portion and the optical sensor. 
     When a second portion of the target object comes into contact with the display and applies pressure to the display while the first portion is in contact with the optical sensor, the processor may be configured to output a pressure gauge in a region other than a contact region of the second portion on the display. 
     The processor may be further configured to change a color of the graphic object that indicates the contact pressure, according to the progress stages of the measurement. 
     The processor may be configured to output a text message, indicating a corresponding measurement stage among the progress stages of the measurement. 
     Upon completing estimation of the bio-information, the processor may be further configured to output an estimation result to the display. 
     The processor may be further configured to calculate absorbances at each wavelength of the measurement light based on the light quantity of the reference light that is measured during the calibration, and the light quantity of the measurement light measured from the target object, obtain a feature value based on the calculated absorbances at each wavelength, and estimate the bio-information based on the obtained feature value. 
     The processor may be further configured to combine the calculated absorbances at each wavelength, obtain an antioxidant peak by correcting a baseline of a waveform, and obtains an antioxidant level based on the obtained antioxidant peak by using a predefined antioxidant level estimation model. 
     According to an aspect of another example embodiment, there is provided a method of estimating bio-information by using an electronic device, the method including: in response to the electronic device being placed on a charger and being in a charging state, performing calibration of an optical sensor by emitting a reference light from the optical sensor to a reference object disposed on the charger, and detecting the reference light reflected from the reference object; guiding estimation of bio-information through a display, according to progress stages of a measurement after charging of the electronic device; measuring a light quantity of a measurement light that is emitted from the optical sensor to a target object and is detected by the optical sensor after being reflected from the target object; and estimating the bio-information based on the light quantity of the measurement light and a light quantity of the reference light. 
     The performing of the calibration may include: emitting the reference light onto the reference object by driving a light source of the optical sensor during the charging; detecting the reference light reflected from the reference object by using a detector of the optical sensor; and storing calibration information, including information of the light quantity of the reference light, in a memory. 
     The method may further include: when the charging is complete or when the electronic device is removed from the charger, outputting a text message that guides a user to estimate the bio-information, to the display. 
     In response to the target object coming into contact with the sensor, the guiding may include determining a contact position and guiding a user to change or maintain the contact position based on a determination of the contact position. 
     In response to a first portion of the target object coming into contact with a measurement position of the optical sensor, the guiding may include outputting a graphic object, guiding a contact pressure to be applied between the first portion and the optical sensor, to the display. 
     The estimating of the bio-information may include: calculating absorbances at each wavelength based on the light quantity of the reference light measured from the reference object during the calibration, and the light quantity of the measurement light that is measured from the target object; obtaining a feature value based on the calculated absorbances at each wavelength; and estimating the bio-information based on the obtained feature value. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and/or other aspects will be more apparent by describing certain example embodiments, with reference to the accompanying drawings, in which: 
         FIG.  1    is a block diagram illustrating an electronic device according to an example embodiment of the present disclosure; 
         FIG.  2    is a block diagram illustrating an electronic device according to another example embodiment of the present disclosure; 
         FIG.  3    is a diagram illustrating a smart watch wearable device according to an example embodiment of the present disclosure; 
         FIG.  4    is a diagram explaining an example of performing calibration of a sensor of an electronic device; 
         FIG.  5    is a diagram explaining an example of guiding estimation of bio-information; 
         FIGS.  6 A to  6 D  are diagrams explaining an example of guiding a measurement position of a bio-signal; 
         FIGS.  7 A to  7 D  are diagrams explaining an example of guiding measurement pressure for measuring a bio-signal; 
         FIGS.  8 A to  8 C  are diagrams explaining an example of outputting a bio-information estimation result; and 
         FIG.  9    is a flowchart illustrating a method of estimating bio-information according to an example embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Example embodiments are described in greater detail below with reference to the accompanying drawings. 
     In the following description, like drawing reference numerals are used for like elements, even in different drawings. The matters defined in the description, such as detailed construction and elements, are provided to assist in a comprehensive understanding of the example embodiments. However, it is apparent that the example embodiments can be practiced without those specifically defined matters. Also, well-known functions or constructions are not described in detail since they would obscure the description with unnecessary detail. 
     It will be understood that, although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. Any references to singular may include plural unless expressly stated otherwise. In addition, unless explicitly described to the contrary, an expression such as “comprising” or “including” will be understood to imply the inclusion of stated elements but not the exclusion of any other elements. Also, the terms, such as ‘unit’ or ‘module’, etc., should be understood as a unit that performs at least one function or operation and that may be embodied as hardware, software, or a combination thereof. Expressions such as “at least one of,” when preceding a list of elements, modify the entire list of elements and do not modify the individual elements of the list. For example, the expression, “at least one of a, b, and c,” should be understood as including only a, only b, only c, both a and b, both a and c, both b and c, all of a, b, and c, or any variations of the aforementioned examples. 
     An electronic device according to various embodiments of the present disclosure which will be described below may include, for example, at least one of a wearable device, a smartphone, a tablet PC, a mobile phone, a video phone, an electronic book reader, a desktop computer, a laptop computer, a netbook computer, a workstation, a server, a PDA, a portable multimedia player (PMP), an MP3 player, a medical device, and a camera. The wearable device may include at least one of an accessory type wearable device (e.g., wristwatch, ring, bracelet, anklet, necklace, glasses, contact lens, or head mounted device (HMD)), a textile/clothing type wearable device (e.g., electronic clothing), a body-mounted type wearable device (e.g., skin pad or tattoo), and a body implantable type wearable device. However, the wearable device is not limited thereto and may include home appliances, such as a television, a digital video disk (DVD) player, a stereo system, a refrigerator, an air conditioner, a vacuum cleaner, an oven, a microwave oven, a washing machine, an air cleaner, a set-top box, a home automation control panel, a security control panel, a media box, a game console, an electronic dictionary, an electronic key, a camcorder, an electronic picture frame, etc., or may include various medical devices, for example, various portable medical measuring devices (blood glucose monitoring device, heart rate monitor, blood pressure measuring device, thermometer, etc.), magnetic resonance angiography (MRA), magnetic resonance imaging (MRI), computed tomography (CT), imaging system, ultrasonic system, etc.). However, the electronic device is not limited to the above devices. 
       FIG.  1    is a block diagram illustrating an electronic device according to an example embodiment of the present disclosure. 
     Referring to  FIG.  1   , the electronic device  100  includes a sensor  110 , an output device  120 , and a processor  130 . 
     The sensor  110  may be disposed on a first surface (e.g., a rear surface) of a main body of the electronic device  110 , and may include a light source  111  and a detector  112 . The sensor  110  may be implemented as any one or any combination of an optical health sensor, an antioxidant sensor, a blood glucose monitoring sensor, a triglyceride monitoring sensor, a blood alcohol detecting sensor, and a photoplethysmography (PPG) sensor. The light source  111  may include a light emitting diode (LED), a laser diode, a phosphor, and the like. There may be one or more light sources, each of which may emit light of different wavelengths (e.g., red wavelength, green wavelength, blue wavelength, infrared wavelength, etc.). For example, the light sources may emit light in a wavelength range of 400 nm to 600 nm. The detector  112  may include a photodiode (PD), a phototransistor (PTr), a Complementary Metal Oxide Semiconductor (CMOS) image sensor, a charge-coupled device (CCD) image sensor, and the like. The detector  112  may be formed as a single detector, a plurality of detectors, or a detector array. The plurality of detectors or the detector array may be formed in a predetermined shape, for example, a concentric circle with the detectors being arranged around the outside of the light source  111 , or in various shapes, such as a square, a triangle, and the like. 
     The output device  120  may visually or non-visually output data generated or processed by the electronic device  100 . The output device  120  may include a display device  121 , as well as a sound output device, an audio module, and/or a haptic module, etc., which are not illustrated herein. 
     The display device  121  may visually provide information to the outside of the electronic device  100 . The display device  121  may include, for example, a display, a hologram device, or a projector and control circuitry to control the devices. The display device  121  may include touch circuitry adapted to detect a touch, and/or sensor circuitry (e.g., force sensor, pressure sensor, etc.) adapted to measure the intensity of force incurred by the touch. In the following disclosure, the force sensor may also refer to the pressure sensor, and force measured by the force sensor may also refer to pressure. By contrast, the pressure sensor may also refer to the force sensor, and pressure measured by the pressure sensor may also refer to force. 
     The sound output device may output sound signals to the outside of the electronic device  100 . The sound output device may include a speaker and/or a receiver. The speaker may be used for general purposes, such as playing multimedia or playing record, and the receiver may be used for incoming calls. The receiver may be implemented separately from, or as part of, the speaker. 
     The audio module may convert a sound into an electrical signal or vice versa. The audio module may obtain the sound via the input device, or may output the sound via the sound output device, and/or a speaker and/or a headphone of another electronic device directly or wirelessly connected to the electronic device. 
     The haptic module may convert an electrical signal into a mechanical stimulus (e.g., vibration, motion, etc.) or electrical stimulus which may be recognized by a user by tactile sensation or kinesthetic sensation. The haptic module may generate and apply forces, vibrations, or motions to a user. The haptic module may include, for example, a motor, a piezoelectric element, and/or an electric stimulator. 
     The processor  130  may be electrically or wirelessly connected to various components of the electronic device  100 , such as the sensor  110 , the output device  120 , etc., so as to control these components and to perform various data processing or computation. 
     For example, by controlling the sensor  110  and using light quantity data of light received by the detector  112  of the sensor  110 , the processor  130  may perform calibration of the sensor  110  and/or may estimate bio-information. In particular, the bio-information may be antioxidant levels, including a concentration of carotenoid accumulated in skin. However, this is merely an example, and the bio-information may include a variety of information including blood glucose, triglyceride, alcohol, lactate, skin pigment, bloodstream amount, and the like. 
     First, the processor  130  may perform calibration of the sensor  110  using a reference object. In particular, the reference object may be a reflector (e.g., 100% reflection mirror, white reflector), or an object coated with a reflective material. The reflective material may be a diffuse reflection material having a reflectivity of 1% to 99%, and may be, for example, Barium sulfate (BaSO4), Teflon (PTFE), etc., but is not limited thereto. 
     For example, the reference object may be formed on one surface of a charger, i.e., a surface opposite to or coming into contact with a first surface of a main body when the main body of the electronic device  110  is placed on the charger. For example, when a user places the main body on the charger for charging the electronic device  100 , the processor  130  may sense a charging state and may automatically start to perform calibration during charging. However, even in the charging state, the processor  130  may not perform calibration if calibration conditions are not satisfied, including a case where a predetermined calibration cycle is not started, or a case where a residual battery capacity until charging is complete is less than or equal to a threshold (20%), and the like. 
     The processor  130  may drive the light source  111  of the sensor  110  to emit light onto the reference object of the charger, and may store a quantity of light, reflected from the reference object and detected by the detector  112 , as a reference light quantity. The processor  130  may repeat or iterate this process a number of times, and may obtain a statistical value (e.g., an arithmetic mean value, a weighted mean value, a median value, a mode, a valley value, a peak value, etc.) of quantities of the reflected light, detected each number of times, as the reference light quantity of the light source. In addition, when the plurality of detectors  112  detect light quantities for each light source  111 , the processor  130  may obtain a statistical value (e.g., an arithmetic mean value, a weighted mean value, a median value, a mode, a valley value, a peak value, etc.) of the light quantities detected by the respective detectors  112  as the reference light quantity of the corresponding light source. 
     In another example, the reference object may be a reflector, such as paper, a holder with no charging function, etc., which may be easily used by a user, and in response to a user’s request, the processor  130  perform calibration by using a user’s reflector. In this case, reflectivity may vary depending on a type of the user’s reflector, such that in order to correct the reflectivity, the processor  130  may perform primary calibration at the initial time of use of the user’s reflector, at predetermined calibration intervals, or in response to a user’s request, by using the reference object formed on the charger, and then may perform secondary calibration by using the user’s reflector and may correct the secondary calibration based on a result of the primary calibration. 
     Then, the processor  130  may determine a measurement state of the electronic device  100 , and while providing a user with appropriate guide information for each stage through the output device  120  disposed on a second surface of the main body, the processor  130  may estimate bio-information by using the measured light quantity detected from a first portion (e.g., index finger) of the object and the calibration result. 
     For example, if the electronic device  100  is in a state before estimating bio-information, the processor  130  may output visual information for guiding a user to estimate bio-information at a predetermined time of recommendation for estimation. For example, when the electronic device  100  is placed on the charger and calibration is performed during charging, the processor  130  may output a text message, indicating estimation recommendation, at a time when the charging is complete or when the user removes the electronic device  100  from the charger to use the electronic device  100 . In this case, the processor  130  may further output an estimation recommendation alarm by a sound signal, vibrations, tactile sensation, etc., using a sound output device, a haptic device, and the like of the output device  120 . 
     Alternatively, by analyzing user patterns, such as a predetermined user preferred measurement time, a significant change in bio-information before a measurement time, or a change in life patterns, such as drinking, exercise, etc., the processor  130  may determine an estimation recommendation time, and upon determining that the estimation recommendation time has come, the processor  130  may output a text message, guiding a user to estimate bio-information, to the display device  121 . 
     Subsequently, when a user places a first portion on the sensor  110  for estimating bio-information, the processor  130  may display appropriate guide information on the display device  121  for each stage of estimation. 
     First, the processor  130  may determine a contact position of the first portion of the object being in contact with the sensor  110 , and may guide the user on a measurement position of the sensor  110  through the display device  121 . In the case where the light source  111  of the sensor  110  is disposed at the center thereof, and the plurality of detectors  112  are arranged around the outside of the light source  111 , the processor  130  may calculate absorbance of each detector  112  based on quantities of light received by the respective detectors  112 , and may determine a contact position of the object based on the absorbance. 
     For example, if the contact position of the first portion does not coincide with the measurement position, the processor  130  may output a graphic object indicating the contact position, a graphic object indicating the measurement position, and/or a graphic object guiding movement from the contact position to the measurement position, and the like on the display device  121 . The processor  130  may repeat the process, and if the contact position finally coincides with the measurement position or falls within a predetermined threshold range (e.g., a distance between the center of a touched fingerprint of the index finger and a center point of the measurement position being less than or equal to a threshold value), the processor  130  may output a graphic object, indicating that the contact position coincides with the measurement position, to the display device  121 . 
     In another example, based on characteristics of the first portion, for example, if the first portion does not cover the entire surface of the sensor  110 , the processor  130  may determine the detector  112 , which is in contact with the first portion, based on the absorbance measured by the detector  112  rather than repeatedly guiding the measurement position as described above, and may proceed to a next process to measure a bio-signal by using the detector  112  being in contact with the first portion. In this case, if a contact region of the first portion does not satisfy a predetermined number of detectors  112 , or if the sensor  110  fails to come into contact with a predetermined range (e.g., 70%) of the contact region, the processor  130  may guide the measurement position as described above. 
     Next, once the first portion comes into contact with the predetermined measurement position according to the guide, the processor  130  may guide measurement pressure through the display device  121 . For example, if the user places a second portion (e.g., thumb) on the display device  121  and applies pressure thereto while placing the first portion on the measurement position of the sensor  110 , the processor  130  may display a graphic object (e.g., pressure gauge), indicating the applied pressure and/or reference pressure, on an outer region of the display device  121  which is not in contact with the second portion. 
     In this case, the processor  130  may output the graphic object in different colors or shapes according to progress stages (e.g., before measurement, during measurement, or after measurement) or based on a pressurization state. In addition, during measurement, i.e., while the light source  111  of the sensor  110  emits light onto the first portion, and the detector  112  detects light scattered or reflected from the first portion, the processor  130  may output, on the graphic object guiding the measurement pressure or at another position, a text message indicating that the measurement is in progress, and/or an alarm message indicating that the measurement is in progress as a sound signal using the sound output device. In addition, if the measurement is in progress or if the applied pressure falls outside a threshold range of the reference pressure, the processor  130  may cause the graphic object or the text message to flicker. 
     Then, when the sensor  110  completes the measurement, the processor  130  may calculate absorbance at each wavelength based on the measured light quantity and the reference light quantity, and may extract a feature value by using the absorbance at each wavelength. For example, the processor  130  may calculate a feature value by combining the calculated absorbances and correcting a baseline of a waveform. The processor  130  may obtain bio-information by applying the obtained feature value to a predefined estimation model. The following Equations 1 to 3 represent an example of calculating absorbance at each wavelength and determining antioxidant levels based on the calculation.  
     
       
         
           
             A 
             
               λ 
             
             = 
             − 
             
               
                 log 
               
               
                 10 
               
             
             
               
                 
                   I 
                   m 
                 
               
               
                 
                   I 
                   0 
                 
               
             
           
         
       
     
     Herein, A(λ) denotes the absorbance at each wavelength, I m  denotes the measured light quantity, which is measured from the first portion of the object at a specific wavelength, and I 0  denotes the reference light quantity obtained by calibration at the specific wavelength.  
     
       
         
           
             A 
             O 
             = 
             
               A 
               
                 
                   λ 
                   2 
                 
               
             
             − 
             
               
                 
                   
                     
                       λ 
                       3 
                     
                     − 
                     
                       λ 
                       2 
                     
                   
                   
                     
                       λ 
                       3 
                     
                     − 
                     
                       λ 
                       1 
                     
                   
                 
               
             
             × 
             
               A 
               
                 
                   λ 
                   1 
                 
               
             
             − 
             
               
                 
                   
                     
                       λ 
                       2 
                     
                     − 
                     
                       λ 
                       1 
                     
                   
                   
                     
                       λ 
                       3 
                     
                     − 
                     
                       λ 
                       1 
                     
                   
                 
               
             
             × 
             
               A 
               
                 
                   λ 
                   3 
                 
               
             
           
         
       
     
     Herein, AO denotes, as an example of the feature value, an antioxidant peak obtained by combining the absorbances at each wavelength and correcting the baseline of the waveform; λ 1 , λ 2 , and λ 3  denote wavelengths; and A λ1 , A λ2 , and A λ3  denote the absorbances at each wavelength which are obtained using Equation 1, in which the wavelengths are relatively long in the order of λ1, λ 2 , and Aλ 3 .  
     
       
         
           
             Y 
             = 
             a 
             × 
             A 
             O 
             + 
             b 
           
         
       
     
     Herein, Y denotes the antioxidant level, AO denotes the antioxidant peak, and a and b denote predetermined values. While Equation 3 denotes an antioxidant level estimation model which is defined as a linear function equation, the equation is not limited thereto and may be defined as a nonlinear function equation, such as a logarithmic function equation, an exponential function equation, and the like. 
     Then, the processor  130  may provide a bio-information estimation result to a user through the output device  120 . For example, the processor  130  may display information, such as an estimated bio-information value, an estimation history graph, recommendations based on the estimated bio-information value, etc., and along with the information, the processor  130  may output alarm information by using a sound output device, a haptic device, and the like. 
       FIG.  2    is a block diagram illustrating an electronic device according to another example embodiment of the present disclosure. 
     Referring to  FIG.  2   , an electronic device  200  includes the sensor  110 , the output device  120 , the processor  130 , a communication module  210 , and a memory  220 . The sensor  110 , the output device  120 , and the processor  130  are described above, such that a detailed description thereof will be omitted. 
     The communication module  210  may support establishment of a direct (e.g., wired) communication channel and/or a wireless communication channel between the electronic device and other electronic device, a server, or the sensor device within a network environment, and performing of communication via the established communication channel. The communication module  210  may include one or more communication processors that are operable independently from the processor  130  and support a direct communication and/or a wireless communication. The communication module  210  may include a wireless communication module, e.g., a cellular communication module, a short-range wireless communication module, or a global navigation satellite system (GNSS) communication module, etc., and/or a wired communication module, e.g., a local area network (LAN) communication module, a power line communication (PLC) module, and the like. These various types of communication modules may be integrated into a single chip, or may be separately implemented as multiple chips. The wireless communication module may identify and authenticate the electronic device  200  in a communication network by using subscriber information (e.g., international mobile subscriber identity (IMSI), etc.) stored in a subscriber identification module. 
     For example, the communication module  210  may transmit necessary data so that an external device (e.g., smartphone, desktop PC) may output guide information for estimating bio-information at the same time when the output device  120  outputs guide information for estimating bio-information, and when the processor  120  completes estimation of bio-information, the communication module  210  may transmit a bio-information estimation result to the external device so that the estimation result may be output in various manners. Further, the communication module  210  may receive various data related to operation (e.g., estimation of bio-information) of the electronic device  200  from the external device. 
     The memory  220  may store operating conditions for operating the sensor device, and various data required for other components of the electronic device. The various data may include, for example, software and input data and/or output data for a command related thereto. For example, the memory may store, as calibration results (e.g., the reference light quantity I 0  obtained through calibration to be used in Equation 1), various data including the reference light quantity, the estimated bio-information value, the bio-information estimation model, and/or user characteristic information, such as a user’s age, gender, health condition, and the like. 
     The memory  220  may include at least one storage medium of a flash memory type memory, a hard disk type memory, a multimedia card micro type memory, a card type memory (e.g., an SD memory, an XD memory, etc.), a Random Access Memory (RAM), a Static Random Access Memory (SRAM), a Read Only Memory (ROM), an Electrically Erasable Programmable Read Only Memory (EEPROM), a Programmable Read Only Memory (PROM), a magnetic memory, a magnetic disk, and an optical disk, and the like, but is not limited thereto. 
     Hereinafter, various examples of visual guiding by the electronic devices  100  and  200  will be described with reference to  FIG.  3  to  8 C . 
       FIG.  3    illustrates a smart watch wearable device as an example of the above electronic devices  100  and  200 . 
     Referring to  FIG.  3   , the wearable device  300  includes a main body  310  and a strap  320 . The main body  310  forms the exterior of the wearable device  300 , and may have the display device  121  formed on a front surface thereof as illustrated herein, such that a variety of information including time information, received message information, bio-information estimation guide information, bio-information estimation results, and the like may be displayed thereon. Further, the sensor  110  may be disposed on a rear surface of the main body  310 . Although not illustrated herein, a force sensor may be further disposed at a lower end of the sensor  110 . The force sensor may measure a force applied when a user presses the sensor with a finger. If a force measured by the force sensor is equal to or greater than a threshold value, the processor  130  mounted in the main body  310  may calculate antioxidant levels based on an optical signal measured by the detector  112 . In another example, the force sensor may be disposed at a lower end of the display device  121 . In this case, the force sensor may measure a force applied when the user presses the display device  121 . 
       FIG.  4    is a diagram explaining an example of performing calibration of a sensor of an electronic device. 
     Referring to  FIGS.  3  and  4   , the smartwatch wearable device  300  may be placed on a charger  400  for wired or wireless charging. A reference object  400  may be disposed on the charger  400 . As illustrated herein, the reference object  410  may be disposed at a position coming into contact with or opposite to the sensor  110 , disposed on a rear surface of the main body  310 , when the main body  310  of the wearable device  300  is placed on the charger  400 . The reference object may be a reflector (e.g., 100% reflection mirror, white reflector), or an object coated with a reflective material, for example, a diffuse reflection material having a reflectivity of 1% to 99%, and may be, for example, Barium sulfate (BaSO4), Teflon (PTFE), and the like. 
     When the main body  310  of the wearable device  300  is placed on the charger  400 , the processor  130  may automatically start to sense a charging state, and may output a status bar  421 , indicating a charging level, to the display device  121 . Further, while the wearable device  300  is in a charging state, the processor  130  may perform calibration of the sensor, and at the same time may display a text message  422 , indicating that calibration is in progress, on the display device  422 . For example, the processor  130  may control the sensor  110  to emit light onto the reference object and to detect light reflected from the reference object  410  and may store the detected light quantity as the reference light quantity I 0  in the memory  220 . 
       FIG.  5    is a diagram explaining an example of guiding estimation of bio-information. 
     The processor  130  may determine a bio-information measurement state, and if the electronic device is in a state before measuring bio-information, the processor  130  may display information for recommending estimation of bio-information on the display device  121 . For example, as illustrated herein, when charging is complete while the main body  310  is placed on the charger  400 , the processor  130  may display a text message  511 , such as “would you like to measure your antioxidant level?”, on the display device  121 . Alternatively, the processor  130  may output a message  511  for recommending estimation of bio-information at a time when a user removes the main body  310  from the charger  400  to use the wearable device  300  or at predetermined intervals. Alternatively, when a user does intense exercise while wearing the wearable device  300  on the wrist, if a user pattern changes, such as in the case where health-related data including an antioxidant level, an alcohol level, blood pressure, blood glucose, triglyceride, and the like during a predetermined period, fall outside a predetermined range, the processor  130  may output a text message for recommending estimation of bio-information. 
       FIGS.  6 A to  6 D  are diagrams explaining an example of guiding a measurement position of a bio-signal. 
     As illustrated in  FIG.  6 A , when a user places, for example, an index finger  611  on the sensor  110  disposed on the rear surface of the main body  310  to estimate bio-information, the processor  130  may determine whether the index finger  611  accurately comes into contact with a measurement position of the sensor  110  through the display device  121 , and may visually guide the measurement position. In this manner, when placing the index finger on the rear side of the main body  310 , the user may easily check a contact state through the display device  121  formed on the front side, without need to flip over the watch. 
     Referring to (1) of  FIG.  6 B , when a contact position does not coincide with a measurement position, the processor  130  may display, on the display device  121 , a graphic object  612  indicating an actual contact position, e.g., the index finger pointing to the contact position. Along with the graphic object  612 , the processor  130  may display a graphic object  613  of various shapes, for example, circular shape, crisscross shape, square shape, etc., which indicates the measurement position, and/or a graphic object  614 , e.g., an arrow, for guiding movement of the contact position to the measurement position on the display device  121 . The process may be repeated until the center of the contact position coincides with the measurement position. In this case, if a distance between the center of the contact position and the center of the measurement position is less than or equal to a predetermined threshold value, the processor  130  may determine that the two positions coincide with each other. In addition, as illustrated in (2) of  FIG.  6 B , if the contact position coincides with the measurement position, the processor  130  may display a graphic object  615  indicating that the positions coincide with each other. 
     The processor  130  may determine whether the contact position of the finger is in proper contact with the measurement position, based on light quantities measured by a plurality of detectors (a plurality of PDs in the embodiment of  FIG.  6 C ) included in the sensor  110 . Referring to  FIG.  6 C  as one embodiment, the sensor  110  may include the light source LED disposed at the center thereof, and the plurality of detectors PD arranged in a concentric circle around the outside of the light source LED. When the index finger is placed on the sensor  110 , the processor  130  may calculate absorbances for the respective detectors PD by using the light quantities detected by the respective PDs as shown in the above Equation 1, and may determine the contact position based on the calculated absorbances. For example,  FIG.  6 D  illustrates the absorbances measured by the respective PDs at each contact position. It can be seen from A1 that the finger mainly comes into contact with the upper portion of the sensor  110  of  FIG.  6 C , such that relatively small light quantities are detected by the detectors PD2 and PD3 at the lower portion which is not in contact with the finger, and thus the measured absorbances at the lower portion are relatively greater than the other detectors. Likewise, it can be seen from A2 that the finger mainly comes into contact with the lower portion of the sensor  110 , such that absorbances measured by the detectors PD6 and PD7 at the upper portion are relatively greater than the other detectors. It can be seen from A3 that when the finger relatively accurately comes into contact with the sensor  110 , all the detectors may measure relatively uniform absorbance. 
     When the respective detectors PD calculate absorbances to determine whether the contact position of the finger coincides with the measurement position, the processor  130  may control the light source  111  to emit light in only one specific wavelength range. In another example, when the respective detectors PD calculate absorbances to determine whether the contact position of the finger coincides with the measurement position, the processor  130  may control the light source  111  to sequentially emit light in different wavelength ranges, in which case the respective detectors PD may calculate absorbances for each wavelength range. 
     For example, if all the absorbances calculated by the respective PDs are less than a threshold value, the processor  130  may determine that the contact position of the user’s finger is in proper contact with the measurement position. In this case, the threshold value may be a predetermined value smaller than zero. If the light source  111  emits light in different wavelength ranges, different threshold values to be compared with the absorbances may be used for each wavelength range. Obviously, the processor  130  may also determine whether the contact position of the user’s finger coincides with the measurement position by using the same threshold value regardless of wavelength ranges of light emitted by the light source  111 . 
     In another example, if all the light quantities, measured by the respective detectors PD, are greater than a threshold value, the processor  130  may determine that the contact position of the user’s finger is in proper contact with the measurement position. In this case, the threshold value may be a predetermined value greater than zero. 
       FIGS.  7 A to  7 D  are diagrams explaining an example of guiding measurement pressure for measuring a bio-signal. 
     When a user places the thumb and the index finger on a front surface (portion of the display device  121 ) and a rear surface (portion of the sensor  110 ) of the main body  310  of the watch-type wearable device as illustrated in the embodiment of  FIG.  7 A , the processor  130  may measure force or pressure, applied by the user, by using a force sensor or a pressure sensor disposed at a lower end of the display device  121  or the sensor  110 . 
     When the user places the index finger on the measurement position of the sensor  110  according to guide information, the processor  130  may guide the user on a contact pressure through the display device  121 . As illustrated in  FIG.  7 A , if the user places a thumb  712  on the display device  121  for applying pressure to the index finger  711  being in contact with the sensor  110 , the processor  130  may display a graphic object  713  in the form of a pressure gauge outside a region of the display device  121  being in contact with the index finger  712 . The pressure gauge displays markings or a bar indicative of reference pressure to be applied over time, and/or marking or a bar indicative of an actual contact pressure according to pressure applied by the thumb  712 , and the markings or the bar may be distinguished by different colors. 
       FIGS.  7 B to  7 D  are diagrams illustrating an example of guiding a user to gradually increase pressing pressure over time. 
     Referring to  FIG.  7 B , when the thumb comes into contact with a first portion  121   a  of the display device  121 , the processor  130  may display pressure gauges  713   a ,  713   b , and  713   c  in an outer region  121   b , so that the user may adjust a pressing force according to the reference pressure over time, and may display an increased/decreased bar/markings on the pressure gauges according to an increase/decrease of the reference pressure. In this case, the color/shape of the gauges may be displayed in the same color (e.g., blue)/shape regardless of the increase/decrease of the reference pressure. Alternatively, as the reference pressure gradually increases/decreases, the processor  130  may display the markings which gradually change from a light/dark color to a dark/light color or to another color. 
     In addition, as in the second view of  FIG.  7 C , if the actual contact pressure (30%) falls outside a normal range (e.g., ±5%) of the reference pressure (50%), the processor  130  may provide alarm information for a user by changing the pressure gauge  713  be to another color (e.g., red)/shape or by causing the pressure gauge  713  be to flicker for a predetermined period of time. In this case, as a difference between the actual contact pressure and the reference pressure increases, the processor  130  may display the gauge in a darker color or may cause the gauge to flicker faster. In this case, the processor  130  may also provide an alarm as sound to a user through the sound output device. 
     Referring to  FIG.  7 D , if pressure applied by the thumb reaches a target measurement pressure according to the guide, the processor  130  may change the color (e.g. blue)/shape of the pressure gauge  713  to another color (e.g., yellow)/shape, and may operate the sensor  110  to measure an optical signal from the index finger placed on the sensor  110 . In this case, as illustrated herein, the processor  130  may output a text message  721 , indicating that measurement is in progress, on the pressure gauge  713 , and at the same time may display the text message  721  as sound through the sound output device. 
     In one embodiment, the processor  130  may guide whether a user applies an appropriate level of force through a UI displayed on  FIG.  7 D . In this case, the processor  130  may guide a user to further apply a force using the text message  721 , or may notify a user that an appropriate level of force is applied. Alternatively, by changing the color of the graphic object  713  displayed in the outer region of the display device  121 , the processor  130  may also guide the user as to whether the user currently applies an appropriate level of force or whether the user needs to apply a greater force. 
     Further, the processor  130  may provide a user with bio-information measurement progress through the UI illustrated in  FIG.  7 B . For example, when starting to measure the antioxidant level, the processor  130  may display a circular progress bar which may gradually increase in length over time along the outer region of the display device  121 , as shown in the graphic objects  713   a ,  713   b , and  713   c  of  FIG.  7 B . The longer progress bar may indicate that the outer region of the display device  121  is gradually filled with a predetermined color. When the measurement of bio-information is complete, the progress bar may stop changing. In the embodiment of  FIG.  7 B , the graphic object  713  showing a progress bar starts in the 9 o’clock direction and ends in the 3 o’clock direction in the outer region of the display device  121 , but the start portion and the end portion are not limited thereto. For example, the graphic object  713  may start in the 9 o’clock direction, may turn full circle of the outer region of the display device  121 , and then may end in the 9 o’clock direction again. The change in this embodiment may also be applied to the embodiment of  FIG.  7 B  illustrating the graphic object  713  that displays an applied pressure level. Further, the display device  121  may have a circular shape as illustrated in each embodiment, or although not illustrated herein, the display device  121  may have a square shape with rounded edges. In the case where the display device  121  has a square shape with rounded edges, the graphic object  713  provided along the outer region of the display device  121  may also be displayed in a square shape with rounded edges. 
       FIGS.  8 A to  8 C  are diagrams explaining an example of outputting a bio-information estimation result. 
     Once an optical signal is measured from the index finger, the processor  130  may obtain, for example, the antioxidant level, by using the reference light quantity which is obtained based on the measured light quantity and by calibration, and may display the antioxidant level on the display device  121  by using various visual methods, such as a circular chart  811  and/or a text  812  indicating the antioxidant level as illustrated in  FIG.  8 A , so that a user may easily recognize an estimation result. The processor  130  may estimate the antioxidant level of an object in real time, or at the same time while the sensor  110  is collecting an optical signal from the object. 
     Further, referring to  FIG.  8 B , while estimating the antioxidant level and/or when completing estimation of bio-information, the processor  130  may transmit data regarding progress and/or estimation result to the external device  800  through the communication module, and the external device  800  may display a graphic object  821  indicating progress and/or a graphic object  822  indicating an estimation result on the display device  820 . In addition, referring to  FIG.  8 C , the external device  800  may manage results received from the wearable device, and in response to a user’ request, the external device  800  may visually display an antioxidant level estimation history in a graph  823 . 
       FIG.  9    is a flowchart illustrating a method of estimating bio-information according to an example embodiment of the present disclosure. 
     The method of  FIG.  9    is an example of a method of estimating bio-information performed by the electronic apparatuses  100  and  200  of  FIGS.  1  and  2   , which will be briefly described below in order to avoid redundancy. 
     First, the electronic device may determine whether the electronic device is in a charging state in operation  911 . 
     Then, when the electronic device is placed on, for example, the charger and charging is started, the electronic device may perform calibration of the sensor by emitting light to a reference object disposed on the charger and then collecting the light reflected from the reference object, in operation  912 . During the calibration, the electronic device may measure a reference light quantity of each light source based on the light reflected from the reference object, may store the reference light quantity in the memory to be used in operation  919 . 
     Subsequently, the electronic device may determine whether the electronic device is in a bio-information measuring state in operation  913 , and if the electronic device is not in the measuring state, the electronic device may guide a user to measure bio-information in operation  914 . For example, when charging is complete after the electronic device is placed on the charger and calibration is performed, or when a user removes the electronic device from the charger to use the electronic device, the electronic device may output a text message, indicating recommendation for estimation, on the display device of the electronic device. Alternatively, by analyzing a predetermined user preferred measurement time or a change in user pattern, the electronic device may determine an estimation recommendation time and may guide the user on the estimation. 
     Next, upon determination in operation  913  that the electronic device is the measuring state, for example, when the user places a first portion of an object on the sensor for estimating bio-information, the electronic device may guide the user on a measurement position in operation  915 . For example, the electronic device may determine a contact position of the first portion of the object being in contact with the sensor, and may guide the user on the measurement position of the sensor through the display device. In this case, based on a difference in quantities of light received by the plurality of detectors, the electronic device may determine the contact position, and may repeat the process until the contact position coincides with the measurement position. For example, the electronic device may determine that the contact position coincides with the measurement position when a distance between the center of a thumb placed on a contact surface of the sensor  110 , and the center of the contact surface of the sensor  110 , is less than or equal to a threshold value. 
     Then, once the contact position coincides with the measurement position according to the guide in operation  916 , the electronic device may guide the user on the measurement pressure in operation  917 . For example, when a second portion of the object presses the display device to apply pressure thereto while the first portion of the object is in contact with the measurement position, the electronic device may display a pressure gauge indicating the applied pressure and/or the reference pressure in an outer region of the display device. In this case, based on a progress stage (e.g., before measurement, during measurement, or after measurement) or a pressurization state, the electronic device may output the graphic object in different colors or shapes. 
     Subsequently, once the contact pressure reaches a target reference pressure according to the guide, the electronic device may operate the sensor to measure an optical signal from the first portion of the object in operation  918 . 
     Next, the electronic device may estimate bio-information in operation  919  by using the light quantity measured in operation  918  and the reference light quantity obtained in operation  912 . For example, the electronic device may calculate absorbance at each wavelength based on a ratio between the measured light quantity and the reference light quantity, may extract a feature value by using the absorbance at each wavelength, and may obtain bio-information by applying the obtained feature value to a predefined estimation model. 
     Then, the electronic device may provide the user with a bio-information estimation result through the output device in  920 . For example, the electronic device may display information, such as an estimated bio-information value, an estimation history graph, recommendations based on the estimated bio-information value, and the like, on the display device and along with the information, the electronic device may provide alarm information by using a sound output device, a haptic device, etc., and may transmit result data and the like to an external device so that the external device may output the data. 
     While not restricted thereto, an example embodiment can be embodied as computer-readable code on a computer-readable recording medium. The computer-readable recording medium is any data storage device that can store data that can be thereafter read by a computer system. Examples of the computer-readable recording medium include read-only memory (ROM), random-access memory (RAM), CD-ROMs, magnetic tapes, floppy disks, and optical data storage devices. The computer-readable recording medium can also be distributed over network-coupled computer systems so that the computer-readable code is stored and executed in a distributed fashion. Also, an example embodiment may be written as a computer program transmitted over a computer-readable transmission medium, such as a carrier wave, and received and implemented in general-use or special-purpose digital computers that execute the programs. Moreover, it is understood that in example embodiments, one or more units of the above-described apparatuses and devices can include circuitry, a processor, a microprocessor, etc., and may execute a computer program stored in a computer-readable medium. 
     The foregoing exemplary embodiments are merely exemplary and are not to be construed as limiting. The present teaching can be readily applied to other types of apparatuses. Also, the description of the exemplary embodiments is intended to be illustrative, and not to limit the scope of the claims, and many alternatives, modifications, and variations will be apparent to those skilled in the art.