Patent Description:
Body temperature is a critical vital sign with important clinical significance. A body temperature sensor may be applied to various applications, such as checking infections in patients, monitoring thermal side effects of medications, or identifying the time of ovulation in women.

Body temperature sensors may be classified into contact and non-contact types. Examples of the contact type sensor may include a sensor for detecting a change in electrical resistance, such as a Resistance Temperature Detector (RTD), a thermistor, etc., a thermocouple for detecting electromotive force, and the like. Further, examples of the non-contact type sensor may include a thermopile, a micro-bolometer, etc., which measures body temperature by detecting infrared rays radiating from a body surface.

Core body temperature refers to body temperature of main internal organs, and remains constant unlike the skin temperature that varies greatly with environment factors such as atmospheric temperature. Measuring core body temperature may require multiple sensors to collect various data points. However, compact wearable devices have limited space, making it challenging to include multiple measurement sensors. <CIT> discloses a core body temperature monitoring apparatus that is placed super-dermally over a user's skin, that includes a first temperature sensor, a second temperature sensor, a thermal insulation layer positioned intermediate the first and second temperature sensor and a heater for heating the apparatus and a subdermal tissue region underlying the user's skin. The subdermal tissue region is configured with variable thermal tissue parameters. A controller includes a switch configured for alternating between a calibration mode, wherein the heater is activated for calculating an instantaneous thermal tissue parameter, and a measurement mode, wherein the heater is inactive and the core body temperature is determined, based on the calculated instantaneous thermal tissue parameter. <CIT> discloses an internal body temperature measurement device that includes: a temperature sensor which measures an epidermis temperature of a living body; a heat flux sensor which measures a magnitude of a heat flux discharged from a body surface of the living body; a blood flow sensor which measures a blood flow rate in a vicinity of the heat flux sensor; and a storage unit which stores a relation between the blood flow rate in the vicinity of the heat flux sensor and a core temperature depth. A correction amount of the core temperature depth corresponding to the blood flow rate in the vicinity of the heat flux sensor is obtained on a basis of the relation stored in the storage unit, and a core temperature of the living body is calculated from the epidermis temperature, the magnitude of the heat flux, and the correction amount of the core temperature depth. <CIT> discloses tissue-mounted devices and methods for monitoring a thermal transport property (e.g., thermal conductivity, thermal diffusivity, heat capacity) of tissue, such as skin. The devices conformally mount to the tissue and comprise one or more thermal actuators and a plurality of sensors. The actuator applies heat to the tissue and the sensors detect a spatio temporal distribution of a physiological tissue parameter or physical property resulting from the heating. This spatio temporal information may be correlated with a rate, velocity and/or direction of blood flow, the presence of a vascular occlusion, circulation changes due to inflammation, hydration level and other physiological parameters. <CIT> discloses a core body temperature sensor for measuring the core body temperature of a body in a non-invasive way via applying the core body temperature sensor to a surface of the body. The core body temperature sensor comprises: at least a first thermistor pair of opposing thermistors across a first thermal insulator and a second thermistor pair, adjacent to the first thermistor pair, of opposing thermistors across a second thermal insulator, and a means to measure blood perfusion. The core body temperature sensor is an essential planar sandwich structure formed of the at least first and second thermistor pairs across the respective first and second thermal insulators sandwiched between opposing carriers. The present disclosure further concerns a method for determining a core body temperature and a method for the manufacturing of a core body temperature sensor.

It is the object of the present invention to provide an improved method and electronic device for estimating a core body temperature of a user.

According to an aspect of the present invention, an electronic device comprises: a first temperature sensor configured to measure a first temperature of a skin surface of a user when the user comes into contact with a main body of the electronic device; a first heating element spaced apart from the first temperature sensor by a first predetermined distance; a second temperature sensor spaced apart from the first heating element by a second predetermined distance and configured to measure a second temperature inside the main body; a photoplethysmography, PPG, sensor configured to measure a PPG signal of the user; and a processor configured to: estimate heat flux based on the first temperature and the second temperature; estimate a blood perfusion rate of the user based on a temperature of the first heating element and the first temperature; estimate an amount of heat generation by metabolism based on the PPG signal; and estimate a core body temperature of the user based on the first temperature, the estimated heat flux, the estimated blood perfusion rate, and the estimated amount of heat generation.

The processor may be further configured to estimate the heat flux based on a difference between the first temperature and the second temperature.

By operating the first heating element, the processor may be further configured to estimate the blood perfusion rate based on a phase difference between the temperature of the first heating element and the first temperature.

The processor may be further configured to control an on state and an off state of the first heating element so that a temperature phase of the first heating element has a sine wave pattern over time.

The processor may be further configured to: estimate thermal contact resistance between the main body and the skin surface that is generated when the main body comes into contact with the skin surface; and correct the estimated blood perfusion rate based on the estimated thermal contact resistance.

The electronic device may further include a second heating element disposed between the first heating element and the second temperature sensor, wherein by operating the second heating element, the processor may be further configured to estimate, as the heat flux, power of the second heating element at a time when the first temperature and the second temperature become equal to each other.

Each of the first heating element and the second heating element may be formed in a multi-layer structure.

The processor may be further configured to operate the first heating element and the second heating element independently of each other.

At least one of the first temperature sensor and the second temperature sensor may be a contact type temperature sensor.

The first temperature sensor may be disposed at a center of a first end of the main body, and the second temperature sensor may be disposed at a center of a second end of the main body.

The electronic device may further include an output interface configured to provide the user with the estimated core body temperature of the user by a visual or non-visual method.

According to another aspect of the present invention, a method of estimating core body temperature by an electronic device comprising a main body, a strap connected to the main body, a first temperature sensor, a second temperature sensor, a first heating element disposed between the first temperature sensor and the second temperature sensor, a photoplethysmography, PPG, sensor, and a processor, includes the steps of: measuring, by the first temperature sensor, a first temperature of a skin surface of a user when the user comes into contact with the main body of the wearable device; measuring, by the second temperature sensor, a second temperature inside the main body; and estimating, by the processor, heat flux based on the first temperature and the second temperature; estimating a blood perfusion rate of the user based on a temperature of the first heating element and the first temperature; measuring, by the PPG sensor, a PPG signal of the user; estimating, by the processor, an amount of heat generation by metabolism based on the PPG signal; and estimating, by the processor, a core body temperature of the user based on the first temperature, the estimated heat flux, the estimated blood perfusion rate, and the estimated amount of heat generation.

The estimating of the heat flux may include estimating the heat flux based on a difference between the first temperature and the second temperature.

The estimating of the blood perfusion rate may include estimating the blood perfusion rate based on a phase difference between the temperature of the first heating element and the first temperature.

The estimating of the blood perfusion rate may include: estimating thermal contact resistance between the main body and the skin surface that is generated when the main body comes into contact with the skin surface; and correcting the estimated blood perfusion rate based the estimated thermal contact resistance.

The method may further include, by an output interface, providing the user with the estimated core body temperature of the user by a visual or non-visual method.

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. 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.

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, for example, various portable medical measuring devices (antioxidant measuring device, blood glucose monitor, 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.), and the like. However, the electronic device is not limited to the above devices.

<FIG> is a block diagram illustrating an electronic device according to an embodiment of the present disclosure. <FIG> is a diagram illustrating an example of a structure of an electronic device.

Referring to <FIG>, an electronic device <NUM> includes a sensor <NUM>, a heating element <NUM>, and a processor <NUM> in a main body <NUM>. The sensor <NUM> includes a plurality of temperature sensors, and the processor <NUM> estimates a user's core body temperature by using data obtained by the sensor <NUM> and the heating element <NUM>.

The sensor <NUM> includes a first temperature sensor <NUM> configured to measure a first temperature of a skin surface when an object comes into contact with the main body, and a second temperature sensor <NUM> spaced apart from the heating element <NUM> by a predetermined distance (e.g., within <NUM>) and configured to measure a second temperature inside the main body. The object may be a body part where the core body temperature may be easily measured, such as an area adjacent to the radial artery on the wrist, an upper part of the wrist where capillary blood or venous blood passes, or a peripheral part of the body, such as toes and the like, and may also be the ears, forehead, chest, and other areas.

The first temperature sensor <NUM> and the second temperature sensor <NUM> may be disposed at different positions in the main body <NUM>. For example, the first temperature sensor <NUM> may be disposed at the center of a first end of the main body <NUM> (e.g., lower surface or a position within a predetermined distance above the lower surface), and the second temperature sensor <NUM> be disposed at the center of a second end of the main body <NUM> (e.g., upper surface or a position within a predetermined distance below the upper surface). In this case, the first temperature sensor <NUM> and the second temperature sensor <NUM> may face each other. In addition, the first temperature sensor <NUM> and/or the second temperature sensor <NUM> may be a contact type temperature sensor, such as a thermistor, and may also include a temperature sensor such as a digital temperature sensor, thermopile, and the like. The type of temperature sensor is not limited thereto sensor.

The heating element <NUM> may generate heat in the electronic device <NUM>, and may take the form of a heater or a similar structure. In addition, a heating structure (e.g., battery) already included in the electronic device <NUM> may be used a heater, and an LED capable of light-to-heat-conversion may also be used. The type of the heating element <NUM> is not limited thereto. Further, the heating element <NUM> may be spaced apart by a predetermined distance (e.g., within <NUM>) from the first temperature sensor <NUM> toward the top of the main body, and may also be disposed in contact with the top of the first temperature sensor <NUM>. The position of the heating element <NUM> is not limited thereto.

<FIG> is a diagram illustrating a structure of the heating element <NUM>.

Referring to <FIG>, the heating element <NUM> may be formed of multiple layers. The heating element <NUM> may be implemented as a multiple-layered serpentine heater with a meandering pattern. For example, the heating element <NUM> may be formed with two layers that are alternately arranged (<NUM>) to produce heat uniformly, and these layers may be connected together in series. The two layers may be stacked in a thickness direction of the heating element <NUM> (or the thickness direction of the main body <NUM>). The heating element <NUM> may have an alternate arrangement (<NUM>) for uniform heat generation and may be integrally connected to each other. In addition, the heating element <NUM> may have a width and a length of <NUM> or less.

Referring back to <FIG>, the electronic device <NUM> may further include a thermally low conductive material <NUM> between the heating element <NUM> and the second temperature sensor <NUM>. For example, the first temperature sensor <NUM>, the heating element <NUM>, the thermally low conductive material <NUM>, and the second temperature sensor <NUM> may be formed in a stacked structure from bottom to top. The thermally low conductive material <NUM> may be a dielectric material that has a high electrical and thermal resistance and provides electrical and thermal insulation. The thermally low conductive material <NUM> may be an insulator having a size of, for example, <NUM> to <NUM> and may be a material (e.g., polyurethane foam) having a thermal conductivity of <NUM> W/mK or less. However, the size and thermal conductivity of the thermally low conductive material <NUM> are not limited thereto. In addition, an air-filled structure may also be implemented without incorporating a separate material between the heating element <NUM> and the second temperature sensor <NUM>.

The main body <NUM> may be, for example, of a wearable type which may be worn on a user's body part (e.g., wrist), and may be a smartphone type device which may be carried by a user.

The processor <NUM> may be electrically connected to the sensor <NUM> and the heating element <NUM> and may control the sensor <NUM> and the heating element <NUM> during estimation of a user's core body temperature. The processor <NUM> estimates the user's core body temperature based on data obtained by the sensor <NUM>. The processor <NUM> estimates heat flux based on the first temperature and the second temperature, estimates a blood perfusion amount or a blood perfusion rate by operating the heating element <NUM>, and estimates the user's core body temperature based on the first temperature, the estimated heat flux, and the estimated blood perfusion amount or the estimated blood perfusion rate.

First, the processor <NUM> may estimate the heat flux based on a first temperature of a skin surface which is measured by the first temperature sensor <NUM>, and a second temperature inside the main body which is measured by the second temperature sensor <NUM>. The processor <NUM> may estimate the heat flux based on a difference between the first temperature and the second temperature, and also based on the thickness and thermal conductivity of the thermally conductive material, which may be represented by the following Equation <NUM>.

Herein, q" denotes the heat flux, k denotes the thermal conductivity of the thermally conductive material, and l denotes the thickness of the thermally conductive material. In this case, the thermally conductive material may be air, and the thermal conductivity k of air and a distance between the heating element <NUM> and the second temperature sensor <NUM> may be used as the value of <NUM>.

In addition, the processor <NUM> may estimate the heat flux by directly using the difference between the first temperature and the second temperature. For example, the processor <NUM> may determine the heat flux, corresponding to the difference between the first temperature and the second temperature, by using a prestored model that defines a relationship between the heat flux and the difference between the first temperature and the second temperature.

The electronic device <NUM> further includes a heating element in the main body, and the processor estimates the heat flux by using the included heating element.

<FIG> is a block diagram illustrating an electronic device according to another embodiment of the present disclosure, and <FIG> is a diagram illustrating another example of a structure of an electronic device.

Referring to <FIG> and <FIG>, the electronic device <NUM> may further include a second heating element <NUM> between the heating element <NUM> and the second temperature sensor <NUM>. The second heating element <NUM> may be disposed, for example, on a lower contact surface of the second temperature sensor <NUM>. By operating the second heating element <NUM>, the processor <NUM> may estimate, as the heat flux, power (W/m<NUM>) of the second heating element <NUM> at a time when the first temperature and the second temperature become equal to each other. For example, when the processor <NUM> operates the second heating element <NUM>, and the first temperature and the second temperature become equal to each other, thermal equilibrium is reached between heat flux from the core to the skin surface and heat flux from the second heating element <NUM> to the skin surface, resulting in zero heat flux, and may estimate the heat flux at the time based on power of the second heating element <NUM>. In order to accurately estimate the heat flux, the first temperature sensor <NUM>, the second heating element <NUM>, and the second temperature sensor <NUM> may be arranged in series on the same line.

Then, by operating the first heating element <NUM>, the processor <NUM> may estimate a blood perfusion rate based on a phase difference between temperature of the first heating element <NUM> and the first temperature. The temperature of the first heating element <NUM> may be determined using a temperature sensor that measures the temperature of the first heating element <NUM>, or without a temperature sensor by using a temperature control module of the processor <NUM>. For example, the temperature control module may adjust an on/off time of the first heating element <NUM> and/or an amount of power supply to the first heating element <NUM> according to a target temperature that is set for the first heating element <NUM>. In such a case, the target temperature may be used as the temperature of the first heating element <NUM>. The blood perfusion rate may be computed based on the following Equation <NUM>. Generally, the perfusion amount refers to an amount of blood flow per minute in blood vessels.

Herein, ωb denotes the blood perfusion rate, ρ denotes the subcutaneous tissue, e.g., the density of adipose tissue, ρb denotes the density of blood, cp denotes specific heat at constant pressure of the subcutaneous tissue, cpb denotes specific heat at constant pressure of blood, ω denotes a predetermined frequency of a heater, and φ denotes the phase difference between the temperature of the first heating element <NUM> and the first temperature, in which ρ, ρb, cp, and cpb may be predetermined common values.

The processor <NUM> may control an on/off state of the first heating element <NUM> so that the temperature phase of the first heating element <NUM> may exhibit a sine wave pattern over time. For example, when the processor <NUM> operates the first heating element <NUM> so that the temperature phase over time has a sine wave pattern, the first temperature, which is the temperature of the skin surface, also has the sine wave pattern and follows the phase of the first heating element <NUM>, thereby causing a phase difference between the temperature of the first heating element <NUM> and the temperature of the first temperature. The blood perfusion rate may be obtained by substituting the generated phase difference φ into the above Equation <NUM>.

The processor <NUM> may adjust a frequency of the first heating element <NUM> based on a user's selection, thereby selecting a body part, from which the blood perfusion rate is to be obtained, among body parts (e.g., dermis layer, subcutaneous adipose layer, and muscle layer).

<FIG> is a graph showing a relationship between a frequency of a heating element and thermal penetration depth.

Referring to <FIG>, it can be seen that in order to obtain a blood perfusion rate of a body part located relatively deep inside the body, such as the adipose layer or the muscle layer, it is required to reduce a driving frequency of the heating element to, for example, <NUM> or less; and in order to obtain a blood perfusion rate of a body part located at a relatively shallow depth, such as the dermis layer, it is required to increase a driving frequency of the heating element to, for example, <NUM> or more.

In addition, the processor <NUM> may estimate thermal contact resistance generated when the main body <NUM> comes into contact with the skin surface, and may correct the blood perfusion rate based on an estimation result.

Thermal contact resistance is a phenomenon in which thermal resistance significantly increases at the interface of two contacting materials in physical contact when heat flows through the materials. The thermal contact resistance may be obtained by dividing a temperature difference between two objects by heat flux. For example, thermal contact resistance may occur when the main body <NUM> of the electronic device <NUM> comes into contact with a skin surface (e.g., wrist), and the thermal contact resistance may affect the accuracy of the estimated blood perfusion rate. Accordingly, the processor <NUM> may correct the estimated blood perfusion rate by estimating thermal contact resistance between the main body <NUM> and the skin surface. For example, the processor may calculate, for example, a mean value or standard deviation of thermal contact resistance for a plurality of periods by changing the frequency of the heating element, and may correct the estimated blood perfusion rate by using the calculated mean value or standard deviation as a correction value.

In one embodiment, the processor <NUM> may operate the first heating element <NUM> and the second heating element <NUM> independently of each other to reduce interference between the heat generated by the first heating element <NUM> and the second heating element <NUM>. For example, when estimating the blood perfusion rate, the processor <NUM> may operate only the first heating element <NUM> without operating the second heating element <NUM>, and when estimating the heat flux, the processor <NUM> may operate only the second heating element <NUM> without operating the first heating element <NUM>. The operation of the heating elements by the processor <NUM> is not limited thereto.

Then, the processor <NUM> estimates a user's core body temperature based on the first temperature, the estimated heat flux, and the estimated blood perfusion rate. The electronic device <NUM> further includes photoplethysmography (PPG) sensor for measuring a pulse wave signal of an object. The processor <NUM> further estimates an amount of heat generation by metabolism based on a PPG signal obtained by the PPG sensor, and estimates a user's core body temperature based on the first temperature, the estimated heat flux, the estimated blood perfusion rate, and the estimated amount of heat generation.

First, the processor <NUM> may estimate the amount of heat generation by metabolism in a user's body based on the user's heart rate, age, height, weight, and the like.

For example, the processor <NUM> may estimate the amount of heat generation by the user's metabolism based further on the heart rate in addition to age, height, and weight. In this case, the heart rate may be input by the user, may be received from an external device, or may be estimated by extracting the heart rate from the PPG signal measured by the PPG sensor <NUM>.

The processor <NUM> may estimate the amount of heat generation by the user's metabolism by using a known relational expression with variables, such as the equivalent metabolic rate, Maximum Work Capacity (MWC), resting metabolism, average heart rate (HR), a user's gender, age, height, weight, and the like.

In another example, the processor <NUM> may also estimate a basal metabolic rate by using a known relational expression for estimating a basal metabolic rate based on age, height, and weight. The processor <NUM> may estimate an amount of heat generation by the user's metabolism based on a value obtained by multiplying the estimated basal metabolic rate by a predetermined constant depending on the user's amount of activity, e.g., the number of times of exercise, moving distance, and the like.

However, without estimating the amount of heat generation by the user's metabolism, the processor <NUM> may receive an amount of heat generation by the user's metabolism, which is estimated by an external device, through a communication interface and the like that communicate with the external device, or may receive an amount of heat generation which is previously input by a user.

Then, the processor <NUM> may estimate the user's core body temperature by applying the first temperature T<NUM>, the estimated heat flux q", the estimated blood perfusion rate ωb, and the estimated amount of heat generation to a human heat model, which may be represented by the following Equations <NUM> and <NUM>. <MAT><MAT>.

Herein, Tcore denotes the core body temperature, and k denotes thermal conductivity of, for example, a user's wrist tissue and may be a predetermined common value or may be defined differently for each user's characteristics. In this case, the user's wrist tissue may include muscle, fat, bone, skin, and the like. In addition, q‴ denotes the amount of heat generation, R denotes a radius of the user's wrist, and I<NUM> and I<NUM> denote the Bessel function which is a solution of heat transfer differential equation.

Generally, various measured values are required in order to measure the core body temperature. However, due to the limited structure of the wearable device, it may be challenging to mount all sensors for obtaining the required measured values in the main body. The embodiment of the present disclosure has effects in that the device may be manufactured in a compact size by reducing the number of sensors, and the core body temperature may be estimated using a human heat model, thereby increasing the accuracy of estimation.

<FIG> is a block diagram illustrating an electronic device according to another embodiment of the present disclosure.

Referring to <FIG>, an electronic device <NUM> includes, in the main body <NUM>, the sensor <NUM> including the first temperature sensor <NUM>, the second temperature sensor <NUM>, and the PPG sensor <NUM>, the first heating element <NUM>, the second heating element <NUM>, the processor <NUM>, a storage <NUM>, an output interface <NUM>, and a communication interface <NUM>. In this case, the sensor <NUM>, the first heating element <NUM>, the second heating element <NUM>, and the processor <NUM> are the same as those in the embodiments of <FIG> and <FIG>, such that a detailed description thereof will be omitted.

The storage <NUM> may store information related to estimating core body temperature. For example, the storage <NUM> may store temperature data obtained by the sensor <NUM>, thickness and thermal conductivity of a thermally conductive material, a selected frequency of the heating element, and processing results of the processor <NUM> such as heat flux, blood perfusion rate, amount of heat generation, and the like.

The storage <NUM> may include a storage medium having at least one type of a flash memory type, a hard disk type, a multimedia card micro type, a card type (e.g., a SD memory, a 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 disc, or an optical disc, etc., but is not limited thereto.

The output interface <NUM> may provide the processing results of the processor <NUM> to a user. For example, the processor <NUM> may provide the estimated core body temperature of the user by a visual or non-visual method.

The output interface <NUM> may include a display to show a core body temperature value that is estimated by the processor <NUM>,. If the estimated core body temperature value falls outside a (predetermined) normal range, the output interface <NUM> may provide a user with a warning message, by changing color or line thickness, or by displaying the abnormal value along with the normal range, so that the user may easily recognize and response to the abnormal core body temperature value.

Further, along with or without the information visually displayed on the display, the output interface <NUM> may provide the user with the estimated core body temperature value in a non-visual manner by voice, vibrations, tactile sensation, and the like using an audio output module such as a speaker and the like, or a haptic module.

The display may include touch circuitry adapted to detect a touch, and/or sensor circuitry (e.g., pressure sensor, etc.) adapted to measure the intensity of force incurred by the touch. An 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. A 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 include components such as a motor, a piezoelectric element, and/or an electric stimulator.

<FIG> and <FIG> are diagrams illustrating an example of displaying core body temperature information on a display of the electronic device <NUM>.

Referring to <FIG> and <FIG>, a display 840a may be disposed on a front surface of a wearable device and may display an estimated core body temperature value. A display 840b may be disposed on a front surface of a smart device and may display an estimated core body temperature value, a change of core body temperature during a day, sleep quality related to the estimated core body temperature, and the like. In this case, the smart device may interwork with another external electronic device, e.g., wristwatch wearable device, ear-wearable device, etc., to estimate core body temperature based on data measured by a sensor part of the external electronic device, and may display the estimated core body temperature value on the display 840b. However, the output of the core body temperature value on the displays 840a and 840b is not limited thereto and may vary.

Referring back to <FIG>, the communication interface <NUM> may communicate with an external device to transmit and receive various data related to estimating core body temperature. The external device may include an information processing device, such as a smartphone, a tablet PC, a desktop computer, a laptop computer, and the like. For example, the communication interface <NUM> may transmit a core body temperature estimation result to the external device, such as a smartphone and the like, and a user may monitor the estimated core body temperature over time by using the smartphone.

The communication interface <NUM> may communicate with the external device by using various wired and wireless communication techniques including Bluetooth communication, Bluetooth Low Energy (BLE) communication, Near Field Communication (NFC), WLAN communication, Zigbee communication, Infrared Data Association (IrDA) communication, Wi-Fi Direct (WFD) communication, Ultra-Wideband (UWB) communication, Ant+ communication, WIFI communication, Radio Frequency Identification (RFID) communication, third generation (<NUM>), fourth generation (<NUM>), fifth generation (<NUM>), and sixth generation (<NUM>) communications, and the like. However, the communication techniques are not limited thereto.

<FIG> is a flowchart illustrating a method of estimating core body temperature according to an embodiment of the present disclosure.

The method of <FIG> is an example of a method of estimating core body temperature by the electronic device <NUM> according to the embodiments of <FIG> and <FIG>, which are described above, and thus the method will be briefly described below in order to avoid redundancy.

Referring to <FIG>, the electronic device first measures a first temperature of a skin surface in operation <NUM> by using the first temperature sensor when an object comes into contact with the main body, and measures a second temperature inside the main body in operation <NUM> by using the second temperature sensor disposed further away from the first temperature sensor than the first heating element spaced apart from the first temperature sensor by a predetermined distance.

Then, the electronic device estimates heat flux based on the first temperature and the second temperature in operation <NUM>. In this case, in the estimating of the heat flux, the electronic device may estimate the heat flux based on a difference between the first temperature and the second temperature and the thickness and thermal conductivity of a thermally conductive material. In addition, the electronic device may also estimate the heat flux by directly using the difference between the first temperature and the second temperature, and may further include another thermally conductive material to estimate the heat flux by using the included thermally conductive material.

Subsequently, the electronic device estimates a blood perfusion rate by operating the first heating element in operation <NUM>. In this case, the electronic device may estimate the blood perfusion rate based on a phase difference between the temperature of the first heating element and the first temperature, may estimate thermal contact resistance generated when the main body comes into contact with the skin surface, and may correct the estimated blood perfusion rate based on a result of the thermal contact resistance estimation.

Next, the electronic device estimates an amount of heat generation by metabolism based on a PPG signal obtained by a PPG sensor in operation <NUM>, and estimates a user's core body temperature based on the first temperature, the estimated heat flux, the estimated blood perfusion rate, and the estimated amount of heat generation in operation <NUM>. In this case, the electronic device may estimate the user's core body temperature by applying the first temperature, the estimated heat flux, the estimated blood perfusion rate, and the estimated amount of heat generation to a human heat model.

Then, the electronic device may provide a result of the estimated core body temperature to the user by a visual or non-visual method in operation <NUM>. For example, the electronic device may display the estimated core body temperature value on the display. In this case, if the estimated core body temperature value falls outside a normal range, the electronic device may provide a user with information, such as warning, by changing color, line thickness, etc., or by displaying the abnormal value along with the normal range, so that the user may easily recognize the estimated value.

<FIG> are diagrams illustrating examples of structures of an electronic device for estimating core body temperature. Examples of the electronic device may include not only a smartwatch, but also a smartphone, a smart band, smart glasses, a smart necklace, and an ear-wearable device, but the electronic device is not limited thereto.

Referring to <FIG>, the electronic device may be implemented as a smart watch-type wearable device <NUM> which includes a main body MB and a wrist strap ST.

The main body MB may be formed in various shapes. A battery may be embedded in the main body MB and/or the strap ST to supply power to various components of the wearable device. The strap ST may be connected to both ends of the main body to allow the main body to be worn on a user's wrist, and may be flexible so as to be wrapped around the user's wrist. The strap ST may be composed of a first strap and a second strap which are separated from each other. One ends of the first strap and the second strap are connected to both sides of the main body MB, and the other ends thereof may be connected to each other via a fastening means. In this case, the connecting means may be formed as magnetic fastening, Velcro fastening, pin fastening, and the like, but is not limited thereto. Further, the strap ST is not limited thereto, and may be integrally formed as a non-detachable band.

The main body MB may include a sensor <NUM>, a processor, a heating element, an output interface, a storage, a communication interface, and the like. However, depending on the size and shape of a form factor and the like, some of the display, the storage, and the communication interface may be omitted.

A manipulator <NUM> may be formed on a side surface of the main body MB, as illustrated herein. The manipulator <NUM> may receive a user command and may transmit the received command to the processor. In addition, the manipulator <NUM> may have a power button to turn on/off the wearable device <NUM>.

The sensor <NUM> may include temperature sensors disposed at different positions and attached to a structure in the main body. For example, a smartwatch may include a first temperature sensor for measuring a first temperature of a skin surface when an object comes into contact with the main body, and a second temperature sensor for measuring a second temperature inside the main body. In addition, a plurality of heating elements may be disposed between the first temperature sensor and the second temperature sensor in the main body.

The processor mounted in the main body MB may be electrically connected to various components as well as the sensor <NUM>. For example, when the strap is wrapped around a user's wrist and the main body is worn on the wrist, the processor may estimate heat flux and a blood perfusion rate by operating the plurality of heating elements, and may estimate the user's core body temperature based on the first temperature, the estimated heat flux, and the estimated blood perfusion rate. The sensor <NUM> further includes a PPG sensor for measuring a PPG signal of the object, and the processor estimates an amount of heat generation by metabolism based on the PPG signal obtained by the PPG sensor, and estimates the user's core body temperature based on the first temperature, the estimated heat flux, the estimated blood perfusion rate, and the estimated amount of heat generation.

Referring to <FIG>, the electronic device may be implemented as a mobile device <NUM> such as a smartphone.

The mobile device <NUM> may include a housing and a display panel. The housing may form the exterior of the mobile device <NUM>. The housing has a first surface, on which a display panel and a cover glass may be disposed sequentially, and the display panel may be exposed to the outside through the cover glass. A sensor <NUM>, heating elements, a camera module and/or an infrared sensor, and the like may be disposed on a second surface of the housing.

For example, a plurality of sensors for obtaining data from a user may be disposed on a rear surface of the mobile device <NUM>, and a fingerprint sensor disposed on the front surface thereof, a power button or a volume button disposed on a side surface thereof, sensors disposed on other positions of the front and rear surfaces thereof, and the like may be provided to estimate a user's core body temperature.

In addition, when a user transmits a request for measuring the core body temperature by executing an application and the like installed in the mobile device <NUM>, the mobile device <NUM> may obtain data by using the sensor <NUM> and heating elements, may measure the core body temperature by using the processor in the mobile device <NUM>, and may provide the user with the measured value and guidance information related to the core body temperature through a display.

Referring to <FIG>, the electronic device may also be implemented as an ear-wearable device <NUM>.

The ear-wearable device <NUM> may include a main body and an ear strap. A user may wear the ear-wearable device <NUM> by hanging the ear strap on the user's auricle. The ear strap may be omitted depending on the shape of ear-wearable device <NUM>. The main body may be inserted into the external auditory meatus. A sensor <NUM> and a heating element may be mounted in the main body. The ear-wearable device <NUM> may provide a user with a core body temperature measurement result and/or core body temperature guidance information as sound, or may transmit the information to an external device, e.g., a mobile device, a tablet PC, a personal computer, etc., through a communication module provided in the main body.

Referring to <FIG>, an electronic device <NUM> may be implemented as a patch-type device.

For example, the electronic device <NUM> may be fixed to a body measurement location (e.g., upper arm) by a strap, to measure a user's core body temperature. In this case, the electronic device <NUM> may provide the user with an estimated body temperature as sound or through a display, or may transmit the estimated body temperature to an external device, e.g., a mobile device, a tablet PC, a personal computer, another medical device, etc., through a communication module provided in the electronic device <NUM>.

While not restricted thereto, an example embodiment can be embodied as computer-readable code on a computer-readable recording/storage medium. The computer-readable recording/storage 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/storage 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/storage 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.

Claim 1:
An electronic device (<NUM>) comprising:
a first temperature sensor (<NUM>) configured to measure a first temperature of a skin surface of a user when the user comes into contact with a main body (<NUM>) of the electronic device;
a first heating element (<NUM>) spaced apart from the first temperature sensor by a first predetermined distance;
a second temperature sensor (<NUM>) spaced apart from the first heating element by a second predetermined distance and configured to measure a second temperature inside the main body;
a photoplethysmography, PPG, sensor (<NUM>) configured to measure a PPG signal of the user; and
a processor (<NUM>) configured to:
estimate heat flux based on the first temperature and the second temperature;
estimate a blood perfusion rate of the user based on a temperature of the first heating element and the first temperature;
estimate an amount of heat generation by metabolism based on the PPG signal; and
estimate a core body temperature of the user based on the first temperature, the estimated heat flux, the estimated blood perfusion rate, and the estimated amount of heat generation.