CN114947765A

CN114947765A - Signal detection method and related product

Info

Publication number: CN114947765A
Application number: CN202110221641.XA
Authority: CN
Inventors: 贾峥; 张�杰; 傅小煜; 黄振龙
Original assignee: Huawei Technologies Co Ltd
Current assignee: Huawei Technologies Co Ltd
Priority date: 2021-02-27
Filing date: 2021-02-27
Publication date: 2022-08-30

Abstract

The embodiment of the application discloses a signal detection method and a related product, wherein the method comprises the following steps: when the target condition is met, the wearable device heats a target skin area of the user; the target conditions include: the signal-to-noise ratio of the first photoplethysmography PPG signal is below a signal-to-noise ratio threshold, and the first temperature is below a first temperature threshold; the first PPG signal is obtained by the wearable device measuring the target skin area, and the first temperature is obtained by the wearable device measuring the target skin area; measuring, by the wearable device, a second PPG signal after stopping heating the target skin area; a second PPG signal is obtained by measuring the target skin area for the wearable device, the second PPG signal being used for processing one or more physiological indicators. The signal detection method disclosed by the embodiment of the application can be used for measuring the PPG signal with high signal-to-noise ratio in a low-temperature environment.

Description

Signal detection method and related product

Technical Field

The present application relates to the field of signal detection, and in particular, to a signal detection method and related product.

Background

Photoplethysmography (PPG) is a non-invasive method of detecting changes in blood volume in living tissue by means of photodetection techniques. The basic principle of PPG is: when light emitted from a light-emitting diode (LED) is directed to the skin, the light reflected back through the skin tissue is received by a Photodiode (PD) and converted into an electrical signal, which is then converted into a digital signal via analog-to-digital conversion. The signal obtained in this way is called the PPG signal. The digital signal is filtered, enhanced and the like, and then the physiological signal processing and analysis of the software level are carried out, so that the physiological indexes of blood pressure, blood oxygen and the like can be obtained.

The optical signal received by the PD contains two components, a substantially constant dc component and a pulsating ac component. The alternating current component is superposed on the direct current component, is synchronous with the heart rate and is positively correlated with the arterial blood volume, and reflects the absorption condition of arterial blood. The direct current component in the PPG signal is insensitive to cold and hot stimulation, but the variation degree of the alternating current component is sensitive to the cold and hot stimulation and is easily influenced by the ambient temperature and the skin temperature. Research experiments show that the signal-to-noise ratio of the PPG signal in a warm environment is more than 2 times that in a cold environment. The higher the signal-to-noise ratio of the PPG signal is, the more accurate the physiological indexes such as blood pressure, blood oxygen and the like obtained by measuring the PPG signal are. In a low-temperature environment, the signal-to-noise ratio of the PPG signal is reduced, and the detection of physiological signals such as blood pressure is influenced. Therefore, there is a need to solve the problem of how to measure PPG signals with high signal-to-noise ratio in low temperature environments.

Disclosure of Invention

The embodiment of the application discloses a signal detection method and a related product, which can measure and obtain a PPG signal with high signal-to-noise ratio in a low-temperature environment.

In a first aspect, an embodiment of the present application provides a signal detection method, including: upon satisfaction of a target condition, the wearable device heats a target skin area of the user; the target conditions include: the signal-to-noise ratio of the first photoplethysmography PPG signal is below a signal-to-noise ratio threshold, and the first temperature is below a first temperature threshold; the first PPG signal is obtained by the wearable device measuring the target skin area, and the first temperature is obtained by the wearable device measuring the target skin area; measuring, by the wearable device, a second PPG signal after stopping heating the target skin area; the second PPG signal is obtained by measuring the target skin area with the wearable device, and the second PPG signal is used for processing one or more physiological indicators.

In the embodiment of the application, when the target condition is met, the wearable device heats the target skin area of the user, so that the temperature of the target skin area can be increased; measuring a second PPG signal after stopping heating the target skin area; a PPG signal with a higher signal-to-noise ratio can be obtained.

In one possible implementation, the target condition further includes: the temperature of the wearable device is below a second temperature threshold.

The second temperature threshold may be understood as an upper limit of the safe temperature of the wearable device. If the temperature of the wearable device exceeds the second temperature threshold, adverse consequences may occur. For example, too high a temperature causes a user wearing the wearable device to feel that the temperature is too high. As another example, excessive temperatures can lead to a reduced service life of the wearable device.

In this implementation, the target skin area of the user can only be heated when the temperature of the wearable device is below a second temperature threshold; adverse effects caused by over-temperature of the wearable device can be avoided.

In one possible implementation, before the wearable device heats the target skin area of the user, the method further comprises: the wearable device determines a first temperature difference value to be increased according to the first temperature and the first temperature threshold; the wearable device generates a first heating scheme according to the first temperature difference value; the wearable device heating a target skin area of a user comprises: an optical signal transmitter in the wearable device transmits light waves to the target skin area according to the first heating protocol. The first heating protocol may include the length and frequency of heating the target skin area. It should be appreciated that the optical signal emitter may emit light waves to the targeted skin area at the frequency and for the duration specified by the first heating protocol.

The larger the first temperature difference, the longer the time is required to heat the target skin area of the user. It will be appreciated that the first temperature difference is directly related to the time period required to heat the target skin area of the user. The signal-to-noise threshold may be understood as a lower limit of the signal-to-noise ratio of the valid PPG signal. That is, if the signal-to-noise ratio of a PPG signal exceeds the signal-to-noise ratio threshold, the physiological index can be accurately measured using the PPG signal; otherwise, the physiological index cannot be accurately measured using the PPG signal.

In this implementation, a first heating profile is generated based on the first temperature difference. After the optical signal transmitter transmits the light waves to the target skin area according to the first heating scheme, the temperature of the target skin area can exceed the first temperature threshold value, so that a PPG signal with a higher signal-to-noise ratio is obtained, and the heating time length is reduced.

In one possible implementation, the method further includes: the wearable device determines a second temperature difference value to be increased according to a second temperature and the first temperature threshold; the second temperature is the temperature of the target skin area measured by the wearable device after the first temperature is measured; the wearable device generates a second heating scheme according to the second temperature difference value; the optical signal transmitter in the wearable device transmits light waves to the targeted skin area according to the second heating protocol.

In this implementation, the wearable device generates a second heating protocol based on the second temperature difference, and emits the light waves to the targeted skin area according to the second heating protocol. That is to say, wearable equipment can be according to PPG signal and the temperature that current measurement obtained, dynamic adjustment heating scheme to constantly optimize heating scheme, reduce heating duration.

In one possible implementation, the method further includes: the wearable device monitors a length of time the target skin area is heated; in the event that the length of time to heat the target skin area exceeds a length of time threshold, the wearable device ceases heating the target skin area; or, the wearable device monitors the frequency of heating the target skin area; in the event that the frequency of heating the target skin area exceeds a frequency threshold, the wearable device ceases heating the target skin area; or, the wearable device monitors its own temperature; in an instance in which the temperature of the wearable device exceeds a second temperature threshold, the wearable device ceases heating the target skin area.

Heating the target skin area for a long period of time may cause damage to the skin of the target skin area. When the time length for heating the target skin area exceeds the time length threshold value, the wearable device stops heating the target skin area, and damage to the skin of a user can be avoided. Similarly, heating the target skin area more frequently than the frequency threshold may also cause damage to the user's skin. Under the condition that the frequency of heating the target skin area exceeds the frequency threshold, the wearable device stops heating the target skin area, and damage to the skin of the user can be avoided. When the temperature of the wearable device exceeds the second temperature threshold, injury to the user's skin may result. Under the condition that the temperature of the wearable device exceeds the second temperature threshold, the wearable device stops heating the target skin area, and damage to the skin of the user can be avoided.

In this implementation, the wearable device can avoid causing injury to the skin of the user by stopping heating the target skin region, and the safety is high.

In one possible implementation, the method further includes: the wearable device receiving a threshold setting instruction from the user; and the wearable equipment sets the signal-to-noise ratio threshold and/or the first temperature threshold according to the threshold setting instruction.

In the implementation mode, a user sets a required signal-to-noise ratio threshold and/or a first temperature threshold by himself/herself, so that different user requirements can be met.

In one possible implementation, the method further includes: the wearable device receiving a temperature setting instruction from the user; and the wearable equipment sets the second temperature threshold according to the temperature setting instruction.

In the implementation mode, the user sets the required second temperature threshold value by himself, so that different user requirements can be met.

In one possible implementation, the method further includes: the wearable device receives a duration setting instruction from the user; and the wearable equipment sets the duration threshold according to the duration setting instruction.

In the implementation mode, the user sets the time length threshold value by himself, and different user requirements can be met.

In one possible implementation, the method further includes: the wearable device receives a frequency setting instruction from the user; and the wearable equipment sets the frequency threshold according to the frequency setting instruction.

In the implementation mode, the user sets the frequency threshold value by himself, and different user requirements can be met.

In one possible implementation, the method further includes: the wearable device receiving a cease-heating instruction from the user; in response to the cease heating instruction, the wearable device discontinues heating the target skin region.

In the implementation mode, the user manually stops heating the target skin area, heating of the target skin area can be stopped in time, and energy is saved.

In one possible implementation, the method further includes: the wearable device receives an activation heating instruction from the user; in response to the initiate heating instruction, the wearable device heats the target skin area.

In this implementation, the user manually initiates heating of the target skin area, which may be initiated in time.

In one possible implementation, the method further includes: the wearable device receiving a skin type selection instruction from the user; the wearable device sets the first temperature threshold or the second temperature threshold according to the skin type selection instruction.

In the implementation mode, the wearable device sets the first temperature threshold or the second temperature threshold according to the skin type selection instruction, the user operation is simple, and the requirements of different users can be met.

In a second aspect, an embodiment of the present application provides a wearable device, including: the device comprises a processor, an optical signal transmitter, a photoelectric receiver and a temperature sensor; the optical signal transmitter, the photoelectric receiver and the temperature sensor are respectively coupled with the processor; the processor is used for controlling the optical signal transmitter to transmit a first optical signal to a target skin area of a user; the photoelectric receiver is used for converting the received second optical signal from the target skin area into a first electric signal and transmitting the first electric signal to the processor; the processor is further used for obtaining a first photoplethysmography (PPG) signal according to the first electric signal; the temperature sensor is used for measuring the temperature of the target skin area and transmitting the obtained first temperature to the processor; the processor is further used for controlling the optical signal transmitter to heat the target skin area when a target condition is met; the target conditions include: a signal-to-noise ratio of the first PPG signal is below a signal-to-noise ratio threshold, and the first temperature is below a first temperature threshold; the processor is further configured to control the optical signal emitter to emit a third optical signal to the target skin area after the heating of the target skin area is stopped; the photoelectric receiver is used for converting the received fourth optical signal from the target skin area into a second electric signal and transmitting the second electric signal to the processor; and the processor is also used for processing the second electrical signal to obtain a second PPG signal.

In the embodiment of the application, when the target condition is met, the processor controls the optical signal emitter to heat the target skin area, so that the temperature of the target skin area can be increased; measuring a second PPG signal after stopping heating the target skin area; the PPG signal with higher signal-to-noise ratio can be obtained.

In one possible implementation manner, the temperature sensor is further configured to measure a temperature of the wearable device, and transmit the measured temperature of the wearable device to the processor; the target conditions further include: the temperature of the wearable device is below a second temperature threshold.

In one possible implementation manner, the processor is further configured to determine a first temperature difference value to be increased according to the first temperature and the first temperature threshold; generating a first heating scheme according to the first temperature difference value; the processor is further configured to control the optical signal emitter to emit light waves toward the target skin region according to the first heating protocol.

In one possible implementation manner, the processor is further configured to determine a second temperature difference to be increased according to a second temperature and the first temperature threshold; the second temperature is the temperature of the target skin area measured by the wearable device after the first temperature is measured; the processor is further configured to generate a second heating scheme according to the second temperature difference; the processor is further configured to control the optical signal emitter to emit light waves toward the target skin area according to the second heating protocol.

In one possible implementation, the processor is further configured to monitor a duration of heating the target skin region; controlling the optical signal transmitter to stop heating the target skin area under the condition that the time length for heating the target skin area exceeds a time length threshold value; or, the processor is further configured to monitor a frequency of heating the target skin region; controlling the optical signal transmitter to stop heating the target skin area if the frequency of heating the target skin area exceeds a frequency threshold; or, the processor is further configured to monitor a temperature of the wearable device; controlling the light signal emitter to stop heating the target skin area if the temperature of the wearable device exceeds a second temperature threshold.

In one possible implementation, the processor is further configured to receive a threshold setting instruction from the user; and setting the signal-to-noise ratio threshold value and/or the first temperature threshold value according to the threshold value setting instruction.

In one possible implementation, the processor is further configured to receive a temperature setting instruction from the user; and setting the second temperature threshold according to the temperature setting instruction.

In a possible implementation manner, the processor is further configured to receive a duration setting instruction from the user; and setting the time length threshold according to the time length setting instruction.

In one possible implementation, the processor is further configured to receive a frequency setting instruction from the user; and setting the frequency threshold according to the frequency setting instruction.

In one possible implementation, the processor is further configured to receive a heating discontinuation instruction from the user; and in response to the heating stopping instruction, stopping controlling the optical signal transmitter to heat the target skin area.

In one possible implementation, the processor is further configured to receive a start heating instruction from the user; and controlling the optical signal transmitter to heat the target skin area in response to the starting heating instruction.

In one possible implementation, the processor is further configured to receive a skin type selection instruction from the user; and setting the first temperature threshold or the second temperature threshold according to the skin type selection instruction.

With regard to the technical effects brought about by the second aspect or various possible implementations, reference may be made to the introduction of the technical effects of the first aspect or the corresponding implementations.

In a third aspect, the present application provides a computer-readable storage medium for storing a computer program which, when run on a computer, causes the method illustrated in the first aspect or any possible implementation manner of the first aspect described above to be performed.

In a fourth aspect, the present application provides a computer program product comprising a computer program or computer code which, when run on a computer, causes the method illustrated by the first aspect or any possible implementation form of the first aspect described above to be performed.

In a fifth aspect, the present application provides a computer program which, when run on a computer, performs the method of the first aspect described above or shown in any possible implementation form of the first aspect.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments or the background art of the present application, the drawings required to be used in the embodiments or the background art of the present application will be described below.

Fig. 1 is a schematic structural diagram of an example of a PPG instrument provided in an embodiment of the present application;

fig. 2 is a schematic diagram of light absorption of a PPG signal provided herein;

FIG. 3 is a graph showing a comparison of the PPG signal measured in a cold environment and the PPG signal measured in a warm environment;

FIG. 4 is a schematic comparison of blood vessels in a cold environment and blood vessels in a warm environment;

FIG. 5 is a schematic diagram of a comparison of vasoconstriction and vasodilation;

fig. 6A is a schematic hardware structure diagram of a wearable device according to an embodiment of the present disclosure;

fig. 6B is a system architecture of a wearable device according to an embodiment of the present disclosure;

fig. 7 is a flowchart of a signal detection method according to an embodiment of the present application;

FIG. 8 is a schematic comparison of a light source illuminating the skin to dilate blood vessels;

FIG. 9 is a graph showing the reflectance of light waves striking the skin;

fig. 10 is a flowchart of another signal detection method provided in the embodiments of the present application;

fig. 11 is a flowchart of another signal detection method according to an embodiment of the present disclosure.

Detailed Description

In order to make the objects, technical solutions and advantages of the present application more clear, the present application will be further described with reference to the accompanying drawings.

The terms "first" and "second," and the like in the description, claims, and drawings of the present application are used solely to distinguish between different objects and not to describe a particular order. Furthermore, the terms "comprising" and "having," as well as any variations thereof, are intended to cover non-exclusive inclusions. Such as a process, method, system, article, or apparatus that comprises a list of steps or elements is not limited to only those steps or elements listed, but may alternatively include other steps or elements not listed, or inherent to such process, method, article, or apparatus.

Reference herein to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the application. The appearances of the phrase in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. Those skilled in the art will explicitly and implicitly appreciate that the embodiments described herein may be combined with other embodiments.

In this application, "at least one" means one or more, "a plurality" means two or more, "at least two" means two or three and more, "and/or" for describing the association relationship of the associated objects, indicating that there may be three relationships, for example, "a and/or B" may indicate: only A, only B and both A and B are present, wherein A and B may be singular or plural. The character "/" generally indicates that the former and latter associated objects are in an "or" relationship. "at least one item(s) below" or similar expressions refer to any combination of these items. For example, at least one (one) of a, b, or c, may represent: a, b, c, "a and b," a and c, "" b and c, "or" a and b and c.

As mentioned in the background, there is a need to solve the problem of how to measure PPG signals with high signal-to-noise ratio in low temperature environments. Since the signal detection scheme provided by the present application relates to the related knowledge of PPG, the related knowledge of PPG to which the present application relates is first introduced below.

The following description will first be made of a process of measuring a PPG signal and generating a physiological indicator, with reference to a schematic structural diagram of an example of a PPG apparatus. The PPG instrument can be used for pulse oxyhemoglobin saturation measurement, heart rate variation monitoring, maximum oxygen uptake measurement, photoelectric heart rate monitoring, blood pressure measurement and the like. Fig. 1 is a schematic structural diagram of an example of a PPG instrument provided in an embodiment of the present application. As shown in fig. 1, the PPG instrument comprises: LED, PD, Analog Front End (AFE). PPG instruments also relate to optical structures, LED/PD layouts, and gap models. Referring to fig. 1, the LED emits a light beam with a certain wavelength, the light beam irradiates the skin surface, and the transmitted or reflected light signal is transmitted to the PD; the PD converts the optical signal into an electric signal, the AFE converts the analog signal into a digital signal, and the processing such as filtering, enhancing and the like is carried out; then, the physiological signal processing and analysis of the software level are carried out to obtain the required physiological index.

The optical signal received by the PD contains two components: the first is a substantially stable Direct Current (DC) component, and the second is an Alternating Current (AC) component that varies in a pulsating manner. The alternating current component is superposed on the direct current component, is synchronous with the heart rate and is positively correlated with the arterial blood volume, and reflects the absorption condition of arterial blood. Fig. 2 is a schematic diagram of light absorption of a PPG signal provided herein. In fig. 2, the pulsation component absorption indicates the light absorption amount of the pulsation component, the non-pulsation artery absorption indicates the light absorption amount of the non-pulsation artery absorption, the vein component absorption indicates the light absorption amount of the vein component absorption, and the other tissue absorption indicates the light absorption amount of the other tissue. As shown in fig. 2, the pulsatile component absorption varies with pulsatile, non-pulsatile arterial absorption, venous component absorption, and other tissue absorption are stable. It is understood that in arteries, arterioles, and capillaries connecting arterioles, the amount of light absorbed by blood varies with the pulsation of the arterial blood vessel, while the amount of light absorbed by tissues such as bone, muscle, venous blood, etc. is stable.

The light source in PPG instruments is typically an LED, which emits light waves that are actually electromagnetic waves with a wavelength in the range of 500-1500 nm. About 30% to 60% of the light waves that strike the skin are absorbed by the body. Of these, only about 10% to 15% of the light energy can reflect the change in the absorption of the pulsatile component. If the variation amplitude of the pulse component is large, the variation amplitude of the light energy is large, and the variation amplitude of the light signal received by the PD is large. Compared with the noise with stable intensity, the signal-to-noise ratio of the PPG signal is higher, and the method is favorable for accurately measuring physiological indexes such as blood pressure, blood oxygen and the like.

The signal-to-noise ratio of the PPG signal is estimated, which can be measured indirectly using the Perfusion Index (PI).

Perfusion Index (PI) ═ AC value ÷ DC value; wherein the AC value represents a value corresponding to the AC component, i.e., an amount of absorption of light by the pulsation component; the DC value indicates a value corresponding to the DC component, i.e., an amount of absorption of light by the non-pulsating component.

The PI value (i.e. PI) reflects the limb blood perfusion condition of the detected person, and can be used for evaluating the quality and reliability of the PPG signal.

The DC value can be regarded as a constant value, and as the ambient temperature decreases, the vessel volume decreases and the amplitude of the pulsation decreases. The amplitude of the change in the AC value decreases, and the PI value decreases. When the ambient temperature increases, the blood vessel volume increases, the amplitude of pulsation increases, the amplitude of change in the AC value increases, and the PI value increases. For example, if the light source emits red light to measure the PPG signal, the quality of the PPG signal is acceptable when the PI > 0.03% (corresponding to the signal-to-noise threshold); when PI is less than 0.03%, the reliability of the PPG signal is low, and the quality is poor. As another example, if the light source emits infrared light to measure the PPG signal, the signal quality is acceptable when PI > 0.05% (corresponding to the signal-to-noise threshold); when PI is less than 0.05%, signal reliability is low and quality is poor. If the light source emits a green light measurement PPG signal, the signal quality is acceptable when PI > 0.1% (corresponding to the signal-to-noise threshold); when PI is less than 0.1%, signal reliability is low and quality is poor. Studies have shown that the signal-to-noise ratio of the PPG signal measured in warm environments is more than 2 times the signal-to-noise ratio of the PPG signal measured in cold environments. A cold environment refers to an environment having a relatively low temperature, for example, an environment having a temperature of less than 12 ℃. The temperature in a warm environment is higher than the temperature in a cold environment, e.g. an environment with a temperature above 20 ℃. The direct current component in the PPG signal is insensitive to cold and hot stimulation, but the variation degree of the alternating current component is sensitive to the cold and hot stimulation and is easily influenced by the ambient temperature and the skin temperature. Figure 3 is a schematic comparison of the PPG signal measured in a cold environment and the PPG signal measured in a warm environment. As can be seen from fig. 3, the signal-to-noise ratio of the PPG signal measured in a warm environment is higher than the signal-to-noise ratio of the PPG signal measured in a cold environment. It was found that the reason why the signal-to-noise ratio of the PPG signal measured in a warm environment is higher than that of the PPG signal measured in a cold environment is: vasoconstriction in cold environments and vasodilation in warm environments. Fig. 4 is a schematic diagram comparing blood vessels in a cold environment with blood vessels in a warm environment. In fig. 4, the blood vessel on the left represents a blood vessel in a cold environment, and the blood vessel on the right represents a blood vessel in a warm environment. As shown in fig. 4, blood vessels shrink in cold environments, retaining heat in the body; in warm environments, the blood vessels relax, dissipating heat by radiation and air convection. FIG. 5 is a schematic diagram of a comparison of vasoconstriction and vasodilation. For example, if the PPG instrument detects a location at the finger tip, the optimal ambient temperature is about 23 deg.c and the optimal finger tip temperature is about 32 deg.c. At the moment, the vasodilatation degree is moderate, the blood volume change intensity is moderate, and the signal-to-noise ratio of the PPG signal is good.

From a physiological point of view, the reason why this phenomenon occurs is further explained. When the environmental temperature is lower, the skin temperature is reduced, the epinephrine level is increased, the sympathetic nerve is excited, the peripheral blood vessel is contracted, the volume of the peripheral blood vessel is reduced, the Total Peripheral Resistance (TPR) is increased, the peripheral blood flow is reduced, the variation amplitude of the blood volume on the surface layer of the skin along with the pulsation is reduced, and the signal-to-noise ratio of a PPG signal is reduced. When the environmental temperature is higher, the skin temperature rises, the epinephrine level is reduced, the sympathetic nerve excitation is inhibited, the peripheral blood vessel is dilated, the volume of the peripheral blood vessel is increased, the TPR is reduced, the peripheral blood flow is increased, the variation amplitude of the blood volume on the surface layer of the skin along with the pulsation is increased, and the signal-to-noise ratio of the PPG signal is increased.

As described above, in a low-temperature environment (also referred to as a cold environment), the signal-to-noise ratio of the measured PPG signal is low, and detection of physiological signals such as blood pressure is affected.

In order to solve the problem of how to obtain a PPG signal with a high signal-to-noise ratio in a low-temperature environment, the application provides a signal detection method capable of obtaining a PPG signal with a high signal-to-noise ratio in a low-temperature environment. The signal detection method provided by the application is suitable for wearable equipment which adopts a PPG device (also called a PPG instrument) to detect physiological indexes, such as watches, bracelets, rings, earphones, finger clamps, ear clamps and the like. The PPG apparatus is part of a wearable device. The physiological index includes parameters such as blood flow, blood pressure, blood oxygen, blood sugar, pulse rate, microcirculation, vascular resistance and the like. The LED light source in the PPG device can be used for heating the skin and collecting physiological signals. The following first introduces a hardware structure of a wearable device that implements the signal detection method provided by the present application with reference to the drawings.

Fig. 6A is a schematic hardware structure diagram of a wearable device provided in an embodiment of the present application. As shown in fig. 6A, the wearable device may include the following hardware: a microprocessor (which may be another processor), an optical signal transmitter, an optical receiver, and a temperature sensor. The PPG apparatus is included in the wearable device, and a processor (e.g., a microprocessor), a light signal transmitter, and a light receiver in the wearable device may be considered as hardware included in the PPG apparatus. In some embodiments, the optical signal emitter may include an LED that emits a light wave and a mirror that changes the direction of propagation of the light wave. And the photoelectric receiver is used for converting the received optical signal into an electric signal. A temperature sensor for monitoring the temperature of the PPG device (i.e. the wearable device) and the temperature of the skin.

Fig. 6A shows a hardware structure of the wearable device. One possible system architecture (including a hardware level and a software level) of the wearable device provided by the present application is described below with reference to the drawings. Fig. 6B is a system architecture of a wearable device according to an embodiment of the present disclosure. As shown in fig. 6B, the hardware level includes: the system comprises a microprocessor, an optical signal transmitter, a photoelectric receiver and a temperature sensor; the software layer comprises: the device comprises a signal-to-noise ratio monitoring module, a temperature monitoring module, a safety control module and a light intensity control module. The main function of the microprocessor is computation. The functions of the signal-to-noise ratio monitoring module, the temperature monitoring module, the safety control module and the light intensity control module are all realized by a microprocessor. It should be understood that the division of the blocks in the microprocessor is only a division of logical functions, and the functions of the blocks may be implemented by the microprocessor in practice. Referring to fig. 6B, the temperature sensor transmits the measured temperature data to the temperature detection module, and the photoelectric receiver transmits the measured signal to the signal-to-noise ratio monitoring module.

The optical signal emitter comprises an LED and a mirror, wherein the LED emits light waves (also called light rays) with specific wavelengths according to the instruction of the microprocessor, and the light waves are refracted or reflected by the mirror to propagate at a proper angle. And the photoelectric receiver can be used for monitoring the pulsatile change of the optical signal along with the volume of the blood vessel in real time, converting the monitored optical signal into an electric signal and transmitting the electric signal to the microprocessor. A temperature sensor, which can be used to monitor the temperature of the PPG device, as well as the temperature of the skin (corresponding to the target skin area) in the vicinity of the PPG device, in real time, transmitting the temperature data to the microprocessor. The temperature data includes a temperature of the PPG device and a temperature of skin in a vicinity of the PPG device.

And the signal-to-noise ratio monitoring module is used for judging the quality of the PPG signal obtained by current measurement. In one possible implementation, when the noise is more, the output of the snr monitoring module is "snr is lower than the threshold". In another possible implementation, when the noise is more, the output of the snr monitoring module is "snr is lower than the threshold, requiring an increased snr difference". When the noise is less, the output of the signal-to-noise ratio monitoring module is that the signal-to-noise ratio is not lower than the threshold value or the signal-to-noise ratio monitoring module does not output. And the temperature monitoring module is used for calculating the temperature difference value needing to be compensated. When the temperature of the local skin (corresponding to the target skin area) is below a threshold (corresponding to a first temperature threshold), the output of the module is "temperature below threshold, requiring an increased temperature difference". When the temperature of the local skin (corresponding to the target skin area) is not below the threshold (corresponding to the first temperature threshold), the output of the module is "temperature not below threshold" or the module does not output. The local skin may be skin near the PPG apparatus, e.g. skin that the wearable device contacts or covers.

And the safety control module is used for monitoring the temperature, the heating frequency and the heating duration of the PPG device. And if the temperature of the PPG device is too high, the heating frequency is too high or the cumulative time of heating is too long, the light heating function is forbidden to be started. The illumination heating function refers to a function that the LED emits light waves with specific wavelengths to heat local skin according to instructions of the microprocessor. In some possible embodiments, the safety control module supports user-defined skin types (normal, sensitive), manual turning on/off of the light heating function, and the like. And the light intensity control module is used for judging whether to start or stop the illumination heating function according to the output of the signal-to-noise ratio monitoring module and the output of the temperature monitoring module. For example, when the output of the snr monitoring module is "snr is lower than the threshold" and the output of the temperature monitoring module is "temperature is lower than the threshold", the light intensity control module determines to turn on the illumination heating function. For another example, when the output of the signal-to-noise ratio monitoring module is that the signal-to-noise ratio is not lower than the threshold or the output of the temperature monitoring module is that the temperature is not lower than the threshold, the light intensity control module determines to terminate the illumination heating function. In one possible implementation, the light intensity control module is further configured to generate a heating scheme according to the temperature difference value to be increased (i.e., the output of the temperature monitoring module); and dynamically adjusting the heating scheme according to real-time signals fed back by the photoelectric receiver and the temperature sensor. In another possible implementation manner, the light intensity control module is further configured to generate a heating scheme according to the signal-to-noise ratio difference value to be increased (i.e., the output of the signal-to-noise ratio monitoring module) and the temperature difference value to be increased (i.e., the output of the temperature monitoring module); and dynamically adjusting the heating scheme according to the real-time signals fed back by the photoelectric receiver and the temperature sensor. Illustratively, the heating regimen may include the length of time the local skin is heated and/or the wavelength of the light emitted by the LEDs.

The hardware structure of the wearable device and possible system architecture are introduced above. The signal detection method provided by the embodiment of the application is described below with reference to the accompanying drawings.

Fig. 7 is a flowchart of a signal detection method according to an embodiment of the present application. As shown in fig. 7, the method includes:

701. upon satisfaction of the target condition, the wearable device heats the target skin area of the user.

The target conditions include: the signal-to-noise ratio of the first photoplethysmography PPG signal is below a signal-to-noise ratio threshold, and the first temperature is below a first temperature threshold. The first temperature threshold may be 28 ℃, 29 ℃, 30 ℃ or the like. The first temperature is a temperature obtained by the wearable device measuring the target skin area. The target skin area may be a skin area of the user that the optical signal emitter in the wearable device is able to illuminate. For example, the target skin area is included in the skin area where the wearable device is in contact with the user. In one possible implementation, the target condition further includes: the temperature of the wearable device is below a second temperature threshold. The temperature of the wearable device may be a temperature of a PPG apparatus in the wearable device. A temperature sensor in the wearable device may measure both the temperature of the target skin area of the user and the temperature of the PPG apparatus. The second temperature threshold may be understood as an upper limit of the safe temperature of the wearable device. If the temperature of the wearable device exceeds the second temperature threshold, adverse consequences may occur.

In this application, the signal-to-noise ratio of the PPG signal may be the PI value of the PPG signal. The signal-to-noise threshold may be 0.03%, 0.05%, 0.1%, etc., and the application is not limited thereto. In some embodiments, the signal-to-noise ratio threshold may be set according to the light signal used by the wearable device to measure the PPG signal. For example, if the wearable device emits red light (i.e., light signal) to measure the PPG signal, the signal-to-noise threshold is 0.03%. For another example, if the wearable device emits infrared light (i.e., light signal) to measure the PPG signal, the signal-to-noise threshold is 0.05%. For example, if the wearable device emits a green light (i.e., light signal) to measure the PPG signal, the signal-to-noise threshold is 0.1%.

Studies have shown that the signal-to-noise ratio of the PPG signal measured by a wearable device is related to the posture of the user (i.e. the user wearing the wearable device). In some embodiments, the wearable device may detect the user's gesture itself and set the signal-to-noise threshold accordingly. In some embodiments, the wearable device is a device worn on the arm of the user, such as a watch, bracelet, or the like; the wearable device may detect a gesture of an arm of a user; when the flat end of the arm of the user is detected, setting a signal-to-noise ratio threshold value as a first value; when the arm drop of the user is detected, setting the signal-to-noise ratio threshold value as a second value; the signal-to-noise threshold is set to a third value when the user's arm is detected in another pose. Any two of the first value, the second value, and the third value are different. Other postures refer to postures other than the flat end of the arm and the arm drooping. In practical applications, the wearable device may detect the posture of the user's arm through a sensor such as a gyroscope. The first PPG signal is obtained by measuring the target skin area with the wearable device.

In one possible implementation, the method further includes: the wearable device receives a threshold setting instruction from the user; and the wearable equipment sets the signal-to-noise ratio threshold and/or the first temperature threshold according to the threshold setting instruction. That is, the user can set or adjust the signal-to-noise ratio threshold and/or the first temperature threshold by himself/herself according to actual needs.

In one possible implementation, the method further includes: the wearable device receives a heating stopping instruction from the user; in response to the cease heating instruction, the wearable device discontinues heating the target skin area. In practical applications, the user may suspend the wearable device from heating the target skin area at any time. For example, the wearable device may include an abort heating option in the operation interface, and the wearable device receiving the abort heating instruction from the user may be: the wearable device detects an operation of the user selecting the discontinue heating option. In the implementation mode, the user manually stops heating the target skin area, heating of the target skin area can be stopped in time, and energy is saved.

In one possible implementation, the method further includes: the wearable device receives a heating starting instruction from the user; and responding to the starting heating instruction, and heating the target skin area by the wearable device. For example, the wearable device may include an initiate heating option in the operation interface, and the wearable device may receive an initiate heating instruction from the user by: the wearable device detects the user's selection of the initiate heating option. In this implementation, the user manually initiates heating of the target skin area, which may be initiated in time.

In one possible implementation, the method further includes: the wearable device receives a skin type selection instruction from the user; the wearable device sets the first temperature threshold or the second temperature threshold according to the skin type selection instruction. In some embodiments, the wearable device may include a normal skin option and a sensitive skin option in an operation interface, and the wearable device may receive the skin type selection instruction from the user by: the wearable device detects an operation of the user selecting the normal flesh option or an operation of the user selecting the sensitive flesh option. Illustratively, if the user selects the operation of the general skin option, the second temperature threshold is set to 36 ℃; if the user selects the sensitive skin option, the second temperature threshold is set to 33 ℃. In the implementation mode, the wearable device sets the first temperature threshold or the second temperature threshold according to the skin type selection instruction, the user operation is simple, and the requirements of different users can be met.

In one possible implementation, before performing step 701, the wearable device may perform the following operations: a wearable device; the wearable device determines a first temperature difference value to be increased according to the first temperature and the first temperature threshold; and the wearable device generates a first heating scheme according to the first temperature difference value. As another example, the first temperature is 20 deg.C, the first temperature threshold is 30 deg.C, and the first temperature difference is-10 deg.C. The wearable device heating the target skin area of the user may be: an optical signal transmitter in the wearable device transmits light waves to the targeted skin area according to the first heating protocol. In one possible implementation, the wearable device may dynamically adjust the heating regime according to the measured signal-to-noise ratio of the PPG signal and the temperature of the target skin area. For example, the wearable device may perform the following operations after generating the first heating protocol: the wearable equipment determines a second temperature difference value to be increased according to a second temperature and the first temperature threshold; the wearable device generates a second heating scheme according to the second temperature difference value. After the wearable device generates the second heating scheme, the wearable device emits light waves to the target skin area according to the second heating scheme, that is, the heating scheme adopted by the wearable device is switched from the first heating scheme to the second heating scheme. The second temperature difference is less than the first temperature difference, and the second heating protocol is preferred over the first heating protocol. The second temperature is a temperature of the target skin area measured by the wearable device after the first temperature is measured. That is, the wearable device may dynamically adjust the heating regimen based on the real-time signal (temperature of the target skin region) fed back by the temperature sensor.

702. The wearable device measures a second PPG signal after stopping heating the target skin area.

The second PPG signal is obtained by the wearable device measuring the target skin area. The second PPG signal is used for processing to obtain one or more physiological indexes. In some embodiments, the wearable device utilizes the second PPG signal processing to derive one or more physiological indicators, such as blood pressure, etc.

In a cold environment, the skin temperature of the user is low, the blood vessels contract, the variation amplitude of the local blood volume along with the pulsation is small, and the signal-to-noise ratio of the PPG signal is reduced. By heating the local skin (corresponding to the target skin area), the local skin temperature is raised, the local blood vessels are dilated, the change amplitude of the local blood volume along with the pulsation is increased, and the signal-to-noise ratio of the PPG signal is increased. Illuminating the local skin with a light source (e.g., an LED) is one way to heat the local skin. FIG. 8 is a schematic comparison of a light source illuminating the skin to dilate blood vessels. In fig. 8, the left half shows a local blood vessel when the light source is not irradiating the skin, and the right half shows a local blood vessel after the light source has irradiated the skin for a certain period of time. As can be seen in fig. 8, the light source illuminating the skin causes vasodilatation. After the wearable device heats the target skin area of the user, it is theoretically possible to improve the signal-to-noise ratio of the measured PPG signal. It is feasible to heat the skin using a light source to improve the PPG signal-to-noise ratio, as demonstrated below in connection with the data.

Studies have shown that local heating of the skin can improve the correlation of blood pressure with the harmonic components of the PPG waveform. Referring to medical equipment, infrared physiotherapy equipment, when infrared light waves are irradiated on the body, the infrared light waves are absorbed by the skin, and the human body feels warm.

Heating performance estimation

The hardware performance of the LED light source, i.e. the required illumination time for a local skin elevation of 5 ℃, is estimated below.

There are three common LED light sources used for monitoring physiological signals: infrared, red, green, wavelength range and skin absorption, skin reflectance are shown in table 1 and fig. 9. FIG. 9 is a graph showing the reflectance of light waves striking the skin.

TABLE 1

Taking the example of an LED using 1 green light of 525nm wavelength to raise the temperature of the local skin by 5℃, the calculation of the required illumination duration is as follows:

1) the luminous energy power is voltage multiplied by current multiplied by the luminous energy conversion rate is 1V multiplied by 50mA multiplied by 30 percent which is 0.015W;

2) power of infrared light absorbed by skin (optical energy power × irradiation rate × absorption rate) (0.015W × 0.5 × 0.67) (5.0 × 10) ^-3 )W；

3) Local skin mass (area x depth x density) (3 x 10) ^-4 )m ² ×3×10 ^-3 m×1.1kg/m ³ ＝5.5×10-2g；

4) The required energy (specific heat capacity of skin x weight of skin x temperature increase) is 3.4J/g ℃x5.5 × (10 ^-2 )g×5℃＝(8.4×10 ^-2 )J；

5) The required time is the required energy ÷ the power of the light absorbed by the skin (8.4 × 10) ^-2 )J÷(5.0×10 ^-3 )W≈17s。

Similarly, the time required for the LED to use red light and the LED to use infrared light can be calculated. Using 1 LED light source, the heating area is 3cm ² The skin, 3mm in depth, was heated to 5 ℃ and the estimated results of the time required for raising the temperature are shown in Table 2.

TABLE 2

As can be seen from Table 2, the LED raised the temperature of the local skin by 5 ℃ by light wave irradiation, and the required irradiation time was short. It will be appreciated that irradiating the local skin with light waves can quickly raise the temperature of the local skin to the desired temperature, taking less time. Therefore, it is feasible that the light source heats the skin to improve the PPG signal-to-noise ratio.

Security performance estimation

When the temperature is too high, skin injury may result. To evaluate the high temperature tolerance of human skin, using a wristwatch as an example, a female experiencer with normal skin feel was tested for skin feel at different temperatures. The test results were as follows:

1. the temperature of the chassis (namely the chassis of the watch) contacting the skin reaches 38 ℃ for more than or equal to 45min, the wrist has a hot and itchy feeling, and the skin turns red slightly;

2. the temperature of the chassis contacting the skin reaches 39 ℃, is not less than 15min, and the wrist skin becomes slightly red;

3. when the temperature of the base plate contacting the skin reaches 41 ℃, the wrist starts to feel painful and the skin starts to become red for 7min, and the recovery can be realized for a long time.

Therefore, from a safety point of view, the skin temperature may be limited to below 36 ℃, the temperature of the PPG device may be limited to below 36 ℃ (corresponding to the second temperature threshold), and the heating frequency may be limited to a maximum of 1 heating every 10 minutes. It will be appreciated that by limiting the temperature of the PPG device to 36 ℃ and limiting the heating frequency, damage to the skin of the user can be avoided and safety can be ensured.

In one possible implementation, the wearable device may further perform the following operations:

monitoring, by the wearable device, a duration of heating the target skin area; when the time length for heating the target skin area exceeds a time length threshold value, the wearable device stops heating the target skin area;

monitoring, by the wearable device, a frequency of heating the target skin area; when the frequency of heating the target skin area exceeds a frequency threshold, the wearable device stops heating the target skin area;

the wearable device monitors the temperature of the wearable device; and when the temperature of the wearable device exceeds a second temperature threshold, the wearable device stops heating the target skin area.

The duration threshold may be 5 minutes, 6 minutes, etc. The heating frequency may be the number of times the wearable device heats the target skin area every 10 minutes. The frequency threshold may be every 10 minutes. That is, the wearable device heats the user's skin up to 1 time every 10 minutes. In this implementation, wearable device heats above-mentioned target skin region through stopping, can avoid causing the injury to user's skin, and the security is high.

In the embodiment of the application, when the target condition is met, the wearable device heats the target skin area of the user, so that the temperature of the target skin area can be increased; measuring a second PPG signal after stopping heating the target skin area; the PPG signal with higher signal-to-noise ratio can be obtained.

Fig. 10 is a flowchart of another signal detection method according to an embodiment of the present application. The method flow in fig. 10 is a refinement and refinement of the method flow in fig. 7. As shown in fig. 10, the method includes:

1001. the wearable device detects that the first temperature is below a first temperature threshold and that a signal-to-noise ratio of the first PPG signal is below a signal-to-noise ratio threshold.

The first temperature threshold may be 30 ℃, 32 ℃, 33 ℃ and the like, and can be set according to actual needs. The first temperature is a temperature measured by the wearable device at a target skin area of the user. The first PPG signal is obtained by measuring a target skin area for the wearable device. In one possible implementation, a temperature sensor in the wearable device detects a temperature of the skin of the user (corresponding to a first temperature), and a PPG apparatus in the wearable device measures a PPG signal (corresponding to a first PPG signal). In practical applications, the wearable device may detect the temperature of a target skin area of the user and measure the target skin area in real time or periodically to obtain the PPG signal.

1002. The wearable device heats the user's skin by illumination.

In one possible implementation, the wearable device may perform the following operations before performing step 1002: the wearable device determines a first temperature difference value to be increased according to the first temperature and the first temperature threshold; and the wearable device generates a first heating scheme according to the first temperature difference value. The implementation of step 1002 may be: the wearable device heats the skin of the user, i.e. the skin of the target skin area, according to the first heating protocol. The wearable device heating the user's skin by illumination may be: a microcontroller in the wearable device sends control instructions to the LEDs, and the LEDs in the wearable device emit light waves to the skin of the user according to the control instructions according to a first heating protocol.

Some scenarios may lead to inaccurate measurements if the user's blood vessels are over-dilated. For example, a miniature camera in a biological cavity needs to carry a light source to irradiate tissues, and blood vessels with excessive diastole may interfere with normal observation. Then in this scenario the optics should select a cold light source that generates less heat. That is, in certain scenarios, the wearable device may heat the user's skin by light waves emitted by the cold light source.

1003. The wearable device stops heating the user's skin by the illumination.

In one possible implementation, the wearable device stops heating the user's skin by the illumination upon detecting that the temperature of the user's skin is equal to or above the first temperature threshold. In another possible implementation, the wearable device stops heating the user's skin by illumination when the measured signal-to-noise ratio of the PPG signal is equal to or above the signal-to-noise ratio threshold.

In some embodiments, the wearable device stops heating the user's skin by illumination when any of the following conditions are met: 1. the signal-to-noise ratio of the PPG signal obtained by measurement is higher than a signal-to-noise ratio threshold value; 2. the temperature of the user's skin (corresponding to the target skin area) is above a first temperature threshold; 3. the light safety control condition is not satisfied. The quality of the PPG signal is acceptable when the signal-to-noise ratio of the measured PPG signal is above a signal-to-noise ratio threshold or the temperature of the skin of the user (corresponding to the target skin area) is above a first temperature threshold, with which the desired physiological indicator can be generated more accurately. When not satisfying light safety control condition, wearable equipment stops to heat user's skin through illumination, can in time avoid the user to receive the injury, and the security is high. The non-satisfaction of the light safety control condition may be any one of: the length of time that the skin of the user is heated by the illumination exceeds a length of time threshold, the frequency that the skin of the user is heated by the illumination exceeds a frequency threshold, and the temperature of the wearable device exceeds a second temperature threshold.

1004. The wearable device measures a second PPG signal.

The signal-to-noise ratio of the second PPG signal is equal to or above the signal-to-noise ratio threshold.

1005. The wearable device utilizes the second PPG signal to process, and at least one physiological index is obtained.

Since it is a common technical means in the art to obtain physiological indexes such as blood pressure by processing the PPG signal, the implementation of step 1005 will not be described in detail.

The signal detection method provided by the embodiment of the application utilizes the light source to irradiate the local skin of the user to heat the local skin, and the signal to noise ratio of PPG is improved. The method does not need to greatly change the hardware structure of the wearable device, solves the problem of reduction of the signal-to-noise ratio of the PPG signal caused by vasoconstriction in a cold environment, improves the temperature, the vasodilation degree and the blood volume change amplitude of local skin, and further improves the signal-to-noise ratio of the PPG.

The following describes a detailed example of the wearable device implementing the signal detection procedure provided in the present application with reference to the drawings.

Fig. 11 is a flowchart of another signal detection method according to an embodiment of the present disclosure. The method flow in fig. 11 is a refinement and refinement of the method flow in fig. 7. As shown in fig. 11, the method includes:

1101. a microprocessor in the wearable device acquires the first temperature, a temperature of the PPG apparatus, and a first PPG signal.

The wearable device may be the wearable device in fig. 6B. The first temperature may be a temperature of the skin of the user, e.g. a temperature of a target skin area of the user. The temperature of the PPG apparatus may be considered the temperature of the wearable device. In one possible implementation, a temperature sensor in the wearable device may detect a temperature of skin of the user and a temperature of the PPG apparatus, and the microprocessor may acquire the first temperature and the temperature of the PPG apparatus from the temperature sensor; a photo receiver in the wearable device may obtain a PPG signal, and a microprocessor may acquire a first PPG signal from the photo receiver. In some embodiments, a temperature sensor in the wearable device may detect the temperature of the user's skin and the temperature of the PPG apparatus in real-time or periodically, and a photo-receiver in the wearable device may measure the PPG signal in real-time or periodically. Referring to fig. 11, in the safety control module, a second temperature threshold, that is, an upper limit of the safety temperature of the PPG device, is set; the temperature detection module is provided with a first temperature threshold value, namely a lower limit of the skin proper temperature; in the signal-to-noise ratio monitoring module, a signal-to-noise ratio threshold value, namely, a lower limit of an effective signal-to-noise ratio threshold value, is set. Because the entities corresponding to the safety control module, the temperature detection module and the signal-to-noise ratio monitoring module are all microprocessors, the microprocessors are provided with a first temperature threshold, a second temperature threshold and a signal-to-noise ratio threshold.

1102. The microprocessor compares the first temperature with a first temperature threshold, the temperature of the PPG device with a second temperature threshold, the first PPG signal, and a signal-to-noise threshold, respectively.

1103. The microprocessor judges whether a first condition is satisfied.

The first condition may be that the temperature of the PPG device is less than the second temperature threshold.

If yes, go to step 1104, otherwise, not start the light heating function (i.e. not perform any operation).

1104. The microprocessor judges whether a second condition is satisfied.

The second condition may be that the first PPG signal is less than a signal-to-noise threshold. If yes, go to step 1105, otherwise, not start the light heating function (i.e. not perform any operation).

1105. The microprocessor judges whether a third condition is satisfied.

The third condition may be that the first temperature is less than a first temperature threshold. If yes, go to step 1106, otherwise, not start the light heating function (i.e., not perform any operation). The purpose of steps 1103 to 1105 is to determine whether a trigger condition for starting the light heating function is satisfied. The starting of the illumination heating function refers to heating the skin of the user through illumination, and the specific expression is that the microprocessor controls the optical signal emitter to emit light waves to heat the skin of the user. The trigger condition for starting the illumination heating function needs to satisfy the first condition, the second condition, and the third condition at the same time. In the method flow of fig. 11, the order in which step 1103, step 1104 and step 1105 are executed is not limited. That is, the microprocessor may sequentially determine whether the first condition, the second condition, and the third condition are satisfied according to any sequence; whether the first condition, the second condition, and the third condition are satisfied may also be determined at the same time. For example, the microprocessor first determines whether a third condition is satisfied; if the third condition is met, judging whether the second condition is met; and if the second condition is met, judging whether the first condition is met. For another example, the microprocessor first determines whether a second condition is satisfied; if the second condition is met, judging whether the first condition is met; and if the first condition is met, judging whether a third condition is met. This is not illustrated here.

1106. The microprocessor generates a heating schedule.

The implementation of step 1106 may be: a light intensity control module in the microprocessor generates a heating profile. In some embodiments, the light intensity control module generates the heating scheme according to a difference between the first temperature and a first temperature threshold (i.e., a first temperature difference), and a difference between a signal-to-noise ratio of the first PPG signal and a signal-to-noise ratio threshold.

1107. The microprocessor stops monitoring the physiological indicator using the PPG signal.

The microprocessor ceasing to monitor the physiological indicator using the PPG signal may be interpreted as the wearable device ceasing to monitor the physiological indicator. The sequence of step 1107 and step 1106 is not limited. Because the second condition is satisfied, the currently measured PPG signal cannot accurately monitor the physiological indicator. The microprocessor stops monitoring the physiological index by the PPG signal, and the processing amount can be reduced.

1108. The microprocessor controls the optical signal emitter to heat the skin of the user according to a heating scheme.

In some embodiments, the microprocessor controls the optical signal emitter to heat the targeted skin area of the user according to a heating protocol. The target skin area may be a skin area of the user that the optical signal emitter in the wearable device is able to illuminate.

1109. The microprocessor determines whether a fourth condition is satisfied.

If yes, go to step 1110; if not, go to step 1112.

The fourth condition is that the heating time length exceeds the time length threshold or the heating frequency exceeds the frequency threshold. Satisfying the fourth condition means that the heating time period exceeds the time period threshold or the heating frequency exceeds the frequency threshold. Not meeting the fourth condition means that the heating duration does not exceed the duration threshold and the heating frequency does not exceed the frequency threshold.

1110. The microprocessor judges whether a first condition is satisfied.

If yes, go to step 1111; if not, go to step 1112.

1111. The microprocessor judges whether a fifth condition is satisfied.

The fifth condition may be that the heating protocol is performed. If yes, go to step 1112; if not, go to step 1108. In one possible implementation, the heating protocol is heating the user's skin by light waves for a target duration (e.g., 1 minute); determining whether the fifth condition is satisfied may be: judging whether the time length for heating the skin of the user reaches a target time length or not; if not, the fifth condition is met, otherwise, the fifth condition is not met. In another possible implementation manner, the determining whether the fifth condition is satisfied may further be: it is determined whether the signal-to-noise ratio of the measured PPG signal is above a signal-to-noise ratio threshold or whether the temperature of the skin of the user (corresponding to the target skin area) is above a first temperature threshold. In practical applications, after the microprocessor starts to control the optical signal transmitter to heat the skin of the user according to the heating scheme, it may determine whether the signal-to-noise ratio of the measured PPG signal is higher than a signal-to-noise ratio threshold and/or determine whether the temperature of the skin (corresponding to the target skin region) of the user is higher than a first temperature threshold. For example, the heating protocol is heating the user's skin with infrared light for 50 seconds; the wearable device periodically determines, after starting heating of the user's skin by infrared light, whether a signal-to-noise ratio of the measured PPG signal is above a signal-to-noise ratio threshold and/or whether a temperature of the user's skin (corresponding to the target skin area) is above a first temperature threshold. If the wearable device judges that the signal-to-noise ratio of the measured PPG signal is higher than the signal-to-noise ratio threshold or that the temperature of the skin (corresponding to the target skin area) of the user is higher than the first temperature threshold before the duration of heating the skin of the user does not reach 50 seconds, it is judged that the fifth condition is satisfied, that is, it is judged that the heating scheme is completed.

The purpose of steps 1109 to 1111 is to determine whether a trigger condition for stopping the light heating function is satisfied. The function of stopping heating by illumination is to stop heating the skin of the user by illumination, and is characterized in that the microprocessor controls the optical signal emitter to stop emitting light waves for heating the skin of the user. In the method flow of fig. 11, the order in which step 1109, step 1110 and step 1111 are executed is not limited. That is, the microprocessor may sequentially determine whether the fourth condition, the first condition, and the fifth condition are satisfied according to any sequence; whether the fourth condition, the first condition, and the fifth condition are satisfied may also be determined at the same time. For example, the microprocessor first determines whether a first condition is satisfied; if the first condition is met, judging whether a fourth condition is met; and if the fourth condition is met, judging whether the fifth condition is met. For another example, the microprocessor first determines whether a fifth condition is satisfied; if the fifth condition is met, judging whether the first condition is met; and if the first condition is met, judging whether a fourth condition is met. This is not illustrated here.

1112. The microprocessor controls the optical signal emitter to stop heating the skin of the user.

The signal detection method provided by the embodiment of the application utilizes the light source to irradiate the local skin of the user to heat the local skin, so that the signal-to-noise ratio of PPG is improved. The method does not need to greatly change the hardware structure of the wearable device, solves the problem of reduction of the signal-to-noise ratio of the PPG signal caused by vasoconstriction in a cold environment, improves the temperature, the vasodilation degree and the blood volume change amplitude of local skin, and further improves the signal-to-noise ratio of the PPG. In addition, the signal detection method provided by the embodiment of the application also solves the decision problem of judging whether the light source needs to be started to heat the skin or not and the light safety problem caused by overhigh illumination intensity, and avoids the skin of a user from being damaged.

The foregoing describes a signal detection method provided by the present application. The functions realized by the components of the wearable device in the process of realizing signal detection are described below.

Referring to fig. 6A, a wearable device provided in an embodiment of the present application includes: microprocessor, light signal transmitter, photoelectric receiver and temperature sensor. The optical signal transmitter, the photoelectric receiver and the temperature sensor are respectively coupled with the microprocessor. The microprocessor may be replaced with other microprocessors.

The microprocessor is used for controlling the optical signal transmitter to transmit a first optical signal to a target skin area of a user;

the photoelectric receiver is used for converting the received second optical signal from the target skin area into a first electric signal and transmitting the first electric signal to the microprocessor;

the microprocessor is also used for processing the first electric signal to obtain a first photoplethysmography (PPG) signal;

the temperature sensor is used for measuring the temperature of the target skin area and transmitting the obtained first temperature to the microprocessor;

the microprocessor is also used for controlling the optical signal emitter to heat the target skin area when target conditions are met; the above target conditions include: the signal-to-noise ratio of the first PPG signal is below a signal-to-noise ratio threshold, and the first temperature is below a first temperature threshold;

the microprocessor is further configured to control the optical signal transmitter to transmit a third optical signal to the target skin area after the heating of the target skin area is stopped;

the photoelectric receiver is used for converting a received fourth optical signal from the target skin area into a second electric signal and transmitting the second electric signal to the microprocessor;

and the microprocessor is also used for processing the second electric signal to obtain a second PPG signal.

In a possible implementation manner, the temperature sensor is further configured to measure a temperature of the wearable device, and transmit the measured temperature of the wearable device to the microprocessor; the above target conditions further include: the temperature of the wearable device is below a second temperature threshold.

In a possible implementation manner, the microprocessor is further configured to determine a first temperature difference to be increased according to the first temperature and the first temperature threshold; generating a first heating scheme according to the first temperature difference; the microprocessor is further configured to control the optical signal emitter to emit light waves to the target skin area according to the first heating profile. For example, the light intensity control module in the microprocessor generates a first heating scheme according to the first temperature difference. In the implementation mode, a signal-to-noise ratio monitoring module in the microprocessor can judge whether the signal-to-noise ratio of the first PPG signal is lower than a signal-to-noise ratio threshold value or not and transmit the signal-to-noise ratio of the first PPG signal to the microprocessor; a temperature monitoring module in the microprocessor calculates a temperature difference value needing to be compensated, namely a first temperature difference value, and transmits the temperature difference value to the microprocessor.

In a possible implementation manner, the microprocessor is further configured to determine a second temperature difference to be increased according to a second temperature and the first temperature threshold; the second temperature is a temperature of the target skin area measured by the wearable device after the first temperature is measured; the microprocessor is further configured to generate a second heating scheme according to the second temperature difference; the microprocessor is further configured to control the optical signal emitter to emit light waves to the target skin area according to the second heating protocol. For example, the light intensity control module in the microprocessor generates a second heating schedule according to the second temperature difference. In this implementation, a temperature monitoring module in the microprocessor calculates a temperature difference value to be supplemented, i.e., a second temperature difference value, and transmits the second temperature difference value to the microprocessor. That is, the signal-to-noise ratio monitoring module in the microprocessor can monitor the signal-to-noise ratio of the PPG signal and feed back the monitored signal-to-noise ratio of the PPG signal to the light intensity control module in the microprocessor in real time; the temperature monitoring module in the microprocessor can monitor the temperature of the target skin area and feed back the temperature difference value to be increased to the light intensity control module in the microprocessor in real time; the light intensity control module in the microprocessor can dynamically adjust the heating scheme according to the temperature difference fed back by the temperature monitoring module.

In one possible implementation, the microprocessor is further configured to monitor a duration of heating the target skin region; controlling the optical signal transmitter to stop heating the target skin area under the condition that the time length for heating the target skin area exceeds a time length threshold value;

or, the microprocessor is further configured to monitor a frequency of heating the target skin area; controlling the optical signal transmitter to stop heating the target skin area when the frequency of heating the target skin area exceeds a frequency threshold;

or, the microprocessor is further configured to monitor a temperature of the wearable device; and controlling the optical signal transmitter to stop heating the target skin area when the temperature of the wearable device exceeds a second temperature threshold.

In this possible implementation, a safety control module in the microprocessor may monitor the temperature, frequency and duration of heating of the PPG device; if the temperature of the PPG device is too high, the heating frequency is too high or the cumulative time of heating is too long (namely, the duration), the light heating function is turned off, namely, the heating of the target skin area is stopped.

In a possible implementation manner, the microprocessor is further configured to receive a threshold setting instruction from the user; and setting the signal-to-noise ratio threshold value and/or the first temperature threshold value according to the threshold value setting instruction.

In a possible implementation manner, the microprocessor is further configured to receive a temperature setting instruction from the user; and setting the second temperature threshold according to the temperature setting instruction.

In a possible implementation manner, the microprocessor is further configured to receive a duration setting instruction from the user; and setting the time length threshold according to the time length setting instruction.

In a possible implementation manner, the microprocessor is further configured to receive a frequency setting instruction from the user; and setting the frequency threshold according to the frequency setting instruction.

In one possible implementation, the microprocessor is further configured to receive a heating stop instruction from the user; and in response to the heating stopping instruction, stopping controlling the optical signal emitter to heat the target skin area.

In a possible implementation manner, the microprocessor is further configured to receive a heating starting instruction from the user; and responding to the starting heating instruction, and controlling the optical signal emitter to heat the target skin area.

In a possible implementation manner, the microprocessor is further configured to receive a skin type selection instruction from the user; and setting the first temperature threshold value or the second temperature threshold value according to the skin type selection instruction.

The present application also provides a computer readable storage medium having stored therein computer code which, when run on a computer, causes the computer to perform the method of the above embodiment.

The present application also provides a computer program product comprising computer code or a computer program which, when run on a computer, causes the signal detection method in the above embodiments to be performed.

The above description is only for the specific embodiments of the present application, but the scope of the present application is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present application, and shall be covered by the scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the above claims.

Claims

1. A method of signal detection, comprising:

upon satisfaction of a target condition, the wearable device heats a target skin area of the user; the target conditions include: the signal-to-noise ratio of the first photoplethysmography PPG signal is below a signal-to-noise ratio threshold, and the first temperature is below a first temperature threshold; the first PPG signal is obtained by the wearable device measuring the target skin area, and the first temperature is obtained by the wearable device measuring the target skin area;

measuring, by the wearable device, a second PPG signal after stopping heating the target skin area; the second PPG signal is obtained by measuring the target skin area with the wearable device, and the second PPG signal is used for processing one or more physiological indicators.

2. The method of claim 1, wherein the target condition further comprises: the temperature of the wearable device is below a second temperature threshold.

3. The method of claim 1 or 2, wherein prior to the wearable device heating the target skin area of the user, the method further comprises:

the wearable device determines a first temperature difference value to be increased according to the first temperature and the first temperature threshold;

the wearable device generates a first heating scheme according to the first temperature difference value;

the wearable device heating a target skin area of a user comprises:

an optical signal transmitter in the wearable device transmits light waves to the target skin area according to the first heating protocol.

4. The method of claim 3, further comprising:

the wearable device determines a second temperature difference value to be increased according to a second temperature and the first temperature threshold; the second temperature is the temperature of the target skin area measured by the wearable device after the first temperature is measured;

the wearable device generates a second heating scheme according to the second temperature difference value;

the optical signal transmitter in the wearable device transmits light waves to the targeted skin area according to the second heating protocol.

5. The method according to any one of claims 1 to 4, further comprising:

the wearable device monitors a length of time the target skin area is heated;

in the event that the length of time to heat the target skin area exceeds a length of time threshold, the wearable device ceases heating the target skin area;

alternatively, the first and second electrodes may be,

the wearable device monitoring a frequency of heating the target skin area;

in the event that the frequency of heating the target skin area exceeds a frequency threshold, the wearable device ceases heating the target skin area;

alternatively, the first and second electrodes may be,

the wearable device monitors the temperature of the wearable device;

in an instance in which the temperature of the wearable device exceeds a second temperature threshold, the wearable device ceases heating the target skin area.

6. The method according to any one of claims 1 to 5, further comprising:

the wearable device receiving a threshold setting instruction from the user;

and the wearable equipment sets the signal-to-noise ratio threshold and/or the first temperature threshold according to the threshold setting instruction.

7. A wearable device, comprising: the device comprises a processor, an optical signal transmitter, a photoelectric receiver and a temperature sensor; the optical signal transmitter, the photoelectric receiver and the temperature sensor are respectively coupled with the processor;

the processor is used for controlling the optical signal transmitter to transmit a first optical signal to a target skin area of a user;

the photoelectric receiver is used for converting the received second optical signal from the target skin area into a first electric signal and transmitting the first electric signal to the processor;

the processor is further used for obtaining a first photoplethysmography (PPG) signal according to the first electric signal;

the temperature sensor is used for measuring the temperature of the target skin area and transmitting the obtained first temperature to the processor;

the processor is further used for controlling the optical signal transmitter to heat the target skin area when a target condition is met; the target conditions include: a signal-to-noise ratio of the first PPG signal is below a signal-to-noise ratio threshold, and the first temperature is below a first temperature threshold;

the processor is further configured to control the optical signal emitter to emit a third optical signal to the target skin area after the heating of the target skin area is stopped;

the photoelectric receiver is used for converting the received fourth optical signal from the target skin area into a second electric signal and transmitting the second electric signal to the processor;

and the processor is also used for processing the second electric signal to obtain a second PPG signal.

8. The wearable device of claim 7,

the temperature sensor is further used for measuring the temperature of the wearable device and transmitting the measured temperature of the wearable device to the processor; the target conditions further include: the temperature of the wearable device is below a second temperature threshold.

9. Wearable device according to claim 7 or 8,

the processor is further configured to determine a first temperature difference value to be increased according to the first temperature and the first temperature threshold; generating a first heating scheme according to the first temperature difference;

the processor is further configured to control the optical signal emitter to emit light waves toward the target skin area according to the first heating protocol.

10. The wearable device of claim 9,

the processor is further configured to determine a second temperature difference to be increased according to a second temperature and the first temperature threshold; the second temperature is the temperature of the target skin area measured by the wearable device after the first temperature is measured;

the processor is further configured to generate a second heating scheme according to the second temperature difference;

the processor is further configured to control the optical signal emitter to emit light waves toward the target skin area according to the second heating protocol.

11. Wearable device according to any of claims 7 to 10,

the processor is further configured to monitor a duration of heating the target skin region; controlling the optical signal transmitter to stop heating the target skin area under the condition that the time length for heating the target skin area exceeds a time length threshold value;

alternatively, the first and second electrodes may be,

the processor further configured to monitor a frequency of heating the target skin region; controlling the optical signal transmitter to stop heating the target skin area if the frequency of heating the target skin area exceeds a frequency threshold;

alternatively, the first and second electrodes may be,

the processor is further configured to monitor a temperature of the wearable device; controlling the light signal emitter to stop heating the target skin area if the temperature of the wearable device exceeds a second temperature threshold.

12. Wearable device according to any of claims 7 to 11,

the processor is further configured to receive a threshold setting instruction from the user; and setting the signal-to-noise ratio threshold value and/or the first temperature threshold value according to the threshold value setting instruction.

13. A computer-readable storage medium, characterized in that a computer program is stored in the computer-readable storage medium, which computer program comprises program instructions that, when executed by a processor, cause the processor to carry out the method of any one of claims 1 to 6.