Method, apparatus and terminal device for blood oxygen measurement

Abstract

The application discloses a blood oxygen measurement method, device and terminal equipment. The measurement method comprises the following steps: acquiring a PPG direct current signal, and acquiring a corresponding direct current component according to the PPG direct current signal; acquiring a PPG alternating current signal, and acquiring M target wave crests and N target wave troughs according to the PPG alternating current signal, the M target wave crests reaching collinearity, and the N target wave troughs reaching collinearity; calculating a corresponding alternating current component according to the ordinate of the M target wave crests and the N target wave troughs; calculating a perfusion index according to the direct current component and the alternating current component; and calculating a blood oxygen saturation according to the perfusion index. The M target wave crests reach collinearity, the N target wave troughs reach collinearity, the alternating current component corresponding to the PPG alternating current signal is calculated according to the ordinate of the M target wave crests and the N target wave troughs, and then the blood oxygen saturation is calculated, so that the influence of noise interference on the blood oxygen saturation can be effectively avoided, and the accuracy of the blood oxygen saturation is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of blood oxygen measurement, in particular to a blood oxygen measurement method, device and terminal equipment. BACKGROUND

[0002] The blood oxygen saturation (SPO2) is the percentage of the volume of oxygenated hemoglobin (HbO2) combined with oxygen in the blood to the total volume of hemoglobin (Hb) that can be combined, which is an important physiological parameter of the human body. The traditional blood oxygen saturation measurement method needs to take blood from the human body to be measured first, and then perform electrochemical analysis on the collected blood to calculate the blood oxygen saturation. This method is relatively cumbersome, and the user's comfort is poor because the human body to be measured needs to be bled. In order to solve this problem, a method for non-invasive measurement of blood oxygen saturation is proposed in the related art. However, the method for non-invasive measurement of blood oxygen saturation in the related art is easily disturbed by noise and has low accuracy. SUMMARY

[0003] The present application aims to at least solve one of the above technical problems. To this end, one object of the present application is to provide a blood oxygen measurement method, which achieves collinearity of M target wave crests and N target wave troughs, and calculates the alternating component corresponding to the PPG alternating current signal according to the longitudinal coordinates of the M target wave crests and the N target wave troughs, and then calculates the blood oxygen saturation, which can effectively avoid the influence of noise on the blood oxygen saturation and improve the accuracy of the blood oxygen saturation.

[0004] A second object of the present application is to provide a blood oxygen measurement device.

[0005] A third object of the present application is to provide a terminal equipment.

[0006] A fourth object of the present application is to provide an electronic device.

[0007] A fifth object of the present application is to provide a computer readable storage medium.

[0008] To achieve the above object, the first aspect of the present application provides a blood oxygen measurement method, comprising: acquiring a photoplethysmography (PPG) direct current (DC) signal, and acquiring a DC component corresponding to the PPG DC signal according to the PPG DC signal, the DC component being a longitudinal coordinate average value of the PPG DC signal; acquiring a PPG alternating current (AC) signal, and acquiring M target peaks and N target troughs corresponding to the PPG AC signal according to the PPG AC signal, wherein the M target peaks reach collinearity, and the N target troughs reach collinearity; calculating an AC component corresponding to the PPG AC signal according to longitudinal coordinates of the M target peaks and the N target troughs; calculating a perfusion index of a PPG signal according to the DC component and the AC component, the PPG signal comprising the PPG DC signal and the PPG AC signal; and calculating a blood oxygen saturation according to the perfusion index.

[0009] The blood oxygen measurement method according to the embodiments of the present application can effectively avoid the influence of noise interference on the blood oxygen saturation and improve the accuracy of the blood oxygen saturation.

[0010] In addition, the blood oxygen measurement method according to the above embodiments of the present application can have the following additional technical features:

[0011] In an embodiment of the present application, the calculating of the AC component corresponding to the PPG AC signal according to the longitudinal coordinates of the M target peaks and the N target troughs comprises: calculating a target peak longitudinal coordinate average value according to the longitudinal coordinates of the M target peaks; calculating a target trough longitudinal coordinate average value according to the longitudinal coordinates of the N target troughs; and calculating an absolute value of a difference between the target peak longitudinal coordinate average value and the target trough longitudinal coordinate average value to obtain the AC component corresponding to the PPG AC signal.

[0012] In an embodiment of the present application, the method further comprises: obtaining P candidate peaks or Q candidate troughs corresponding to the PPG alternating signal according to the PPG alternating signal; performing normalization processing on the horizontal coordinates and the vertical coordinates of the candidate peaks or the candidate troughs respectively to obtain normalized horizontal coordinates and normalized vertical coordinates of the candidate peaks or the candidate troughs; obtaining a set of straight line intersection points of the P candidate peaks or the Q candidate troughs in a polar coordinate Hough space according to the normalized horizontal coordinates and the normalized vertical coordinates; determining a target intersection point in the set of straight line intersection points according to the local density of each intersection point in the set of straight line intersection points; and determining the M target peaks or the N target troughs from the P candidate peaks or the Q candidate troughs according to the target intersection point.

[0013] In an embodiment of the present application, the method further comprises: obtaining a plurality of peaks or troughs corresponding to the PPG alternating signal by using a first-order differential zero-crossing point detection method; and determining the candidate peaks or the candidate troughs as the peaks or the troughs in the plurality of peaks or troughs whose amplitudes are greater than a set amplitude threshold.

[0014] In an embodiment of the present application, the method further comprises: calculating a first ratio of the horizontal coordinates of the candidate peaks or the candidate troughs to the average value of the corresponding horizontal coordinates; calculating a second ratio of the vertical coordinates of the horizontal coordinates of the candidate peaks or the candidate troughs to the average value of the corresponding vertical coordinates; obtaining the normalized horizontal coordinates by subtracting one from the first ratio; and obtaining the normalized vertical coordinates by subtracting one from the second ratio.

[0015] In an embodiment of the present application, the method further comprises: calculating the intersection points of the straight lines of the P candidate peaks or the Q candidate troughs in the polar coordinate Hough space according to the normalized horizontal coordinates and the normalized vertical coordinates, respectively, to obtain the set of straight line intersection points.

[0016] In one embodiment of the present application, the method further comprises: defining the local density of each intersection point in the set of straight line intersection points by using a Gaussian kernel function; determining candidate intersection points by taking intersection points whose local density is greater than the local density of neighbor intersection points within a set distance range as the candidate intersection points; and determining the target intersection points by taking candidate intersection points whose distance to other candidate intersection points is greater than a set distance threshold as the target intersection points.

[0017] In one embodiment of the present application, the method further comprises: calculating a longitudinal coordinate reference value according to the polar coordinates of the target intersection point; calculating the absolute value of the difference between the longitudinal coordinate of the candidate wave peak or candidate wave valley and the longitudinal coordinate reference value; and determining the target wave peak or target wave valley by taking the candidate wave peak or candidate wave valley whose absolute value is equal to or less than a set difference threshold as the target wave peak or target wave valley.

[0018] To achieve the above object, the second aspect of the present application provides a blood oxygen measurement device, comprising: a first obtaining module, configured to obtain a photoplethysmography (PPG) direct current (DC) signal, and obtain a DC component corresponding to the PPG DC signal according to the PPG DC signal, wherein the DC component is the average value of the longitudinal coordinates of the PPG DC signal; a second obtaining module, configured to obtain a PPG alternating current (AC) signal, and obtain M target wave peaks and N target wave valleys corresponding to the PPG AC signal according to the PPG AC signal, wherein the M target wave peaks reach collinearity, and the N target wave valleys reach collinearity; a first calculating module, configured to calculate an AC component corresponding to the PPG AC signal according to the longitudinal coordinates of the M target wave peaks and the N target wave valleys; a second calculating module, configured to calculate a perfusion index of a PPG signal according to the DC component and the AC component, wherein the PPG signal comprises the PPG DC signal and the PPG AC signal; and a third calculating module, configured to calculate a blood oxygen saturation according to the perfusion index.

[0019] The blood oxygen measurement device provided by the embodiments of the present application can effectively avoid the influence of noise interference on the blood oxygen saturation, and improve the accuracy of the blood oxygen saturation.

[0020] In addition, the blood oxygen measurement device provided by the above embodiments of the present application can further have the following additional technical features:

[0021] In one embodiment of the present application, the first calculation module is specifically configured to: calculate a target peak longitudinal coordinate average value according to the longitudinal coordinates of the M target peaks; calculate a target valley longitudinal coordinate average value according to the longitudinal coordinates of the N target valleys; and calculate an absolute value of a difference between the target peak longitudinal coordinate average value and the target valley longitudinal coordinate average value to obtain the alternating component corresponding to the PPG alternating signal.

[0022] In one embodiment of the present application, the second acquisition module is specifically configured to: acquire P candidate peaks or Q candidate valleys corresponding to the PPG alternating signal according to the PPG alternating signal; perform normalization processing on the horizontal coordinates and the longitudinal coordinates of the candidate peaks or the candidate valleys respectively to obtain normalized horizontal coordinates and normalized longitudinal coordinates of the candidate peaks or the candidate valleys; acquire a straight line intersection point set of the P candidate peaks or the Q candidate valleys in a polar coordinate Hough space according to the normalized horizontal coordinates and the normalized longitudinal coordinates; determine a target intersection point in the straight line intersection point set according to a local density of each intersection point in the straight line intersection point set; and determine the M target peaks or the N target valleys according to the target intersection point in the P candidate peaks or the Q candidate valleys.

[0023] In one embodiment of the present application, the second acquisition module is specifically configured to: acquire a plurality of peaks or valleys corresponding to the PPG alternating signal by using a first-order differential zero-crossing point detection manner; and determine the candidate peaks or the candidate valleys as peaks or valleys in the plurality of peaks or valleys whose amplitudes are greater than a set amplitude threshold value.

[0024] In one embodiment of the present application, the second acquisition module is specifically configured to: calculate a first ratio of the horizontal coordinates of the candidate peaks or the candidate valleys to a corresponding horizontal coordinate average value; calculate a second ratio of the longitudinal coordinates of the horizontal coordinates of the candidate peaks or the candidate valleys to a corresponding longitudinal coordinate average value; obtain the normalized horizontal coordinates by subtracting one from the first ratio; and obtain the normalized longitudinal coordinates by subtracting one from the second ratio.

[0025] In one embodiment of the present application, the second acquisition module is specifically configured to: calculate, according to the normalized horizontal coordinates and the normalized longitudinal coordinates, intersection points of straight lines of two-by-two combinations of the P candidate peaks or two-by-two combinations of the Q candidate valleys in the polar coordinate Hough space to obtain the straight line intersection point set.

[0026] In an embodiment of the present application, the second obtaining module is specifically configured to: define local densities of each intersection point in the set of straight line intersection points by using a Gaussian kernel function; determine an intersection point as a candidate intersection point if the local density of the intersection point is greater than local densities of neighbor intersection points within a set distance range around the intersection point; and determine a candidate intersection point as the target intersection point if the distance between the candidate intersection point and other candidate intersection points is greater than a set distance threshold.

[0027] In an embodiment of the present application, the second obtaining module is specifically configured to: calculate a longitudinal coordinate reference value according to the polar coordinates of the target intersection point; calculate absolute values of differences between longitudinal coordinates of the candidate wave crests or candidate wave troughs and the longitudinal coordinate reference value; and determine the candidate wave crest or candidate wave trough with an absolute value equal to or less than a set difference threshold as the target wave crest or target wave trough.

[0028] To achieve the above object, the third aspect of the present application provides a terminal device, comprising the blood oxygen measurement device of the second aspect of the present application.

[0029] The terminal device of the embodiment of the present application can effectively avoid the influence of noise interference on the blood oxygen saturation and improve the accuracy of the blood oxygen saturation.

[0030] In addition, the terminal device according to the above embodiments of the present application can have the following additional technical features:

[0031] In an embodiment of the present application, the terminal device is a wearable terminal device.

[0032] To achieve the above object, the fourth aspect of the present application provides an electronic device, comprising a memory and a processor; wherein the processor runs a program corresponding to an executable program code stored in the memory by reading the executable program code, to implement the blood oxygen measurement method of the first aspect of the present application.

[0033] The electronic device of the embodiment of the present application can effectively avoid the influence of noise interference on the blood oxygen saturation and improve the accuracy of the blood oxygen saturation.

[0034] To achieve the above object, the fifth aspect of the present application provides a computer readable storage medium, which stores a computer program, and the program is executed by a processor to realize the blood oxygen measurement method in the first aspect of the present application.

[0035] The computer readable storage medium of the embodiment of the present application stores a computer program and is executed by a processor, M target wave crests reaching collinearity and N target wave troughs reaching collinearity are obtained, and the AC component corresponding to the PPG AC signal is calculated according to the longitudinal coordinates of the M target wave crests and the N target wave troughs, and then the blood oxygen saturation is calculated, which can effectively avoid the influence of noise interference on the blood oxygen saturation and improve the accuracy of the blood oxygen saturation.

[0036] Additional aspects and advantages of the present application will be made apparent by the following description and the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0037] The above and / or additional aspects and advantages of the present application will become apparent and be readily understood from the following description, taken in conjunction with the accompanying drawings, in which:

[0038] Figure 1 Flow chart of the blood oxygen measurement method according to one embodiment of the present application;

[0039] Figure 2 Schematic diagram of the PPG DC signal in the blood oxygen measurement method according to one embodiment of the present application;

[0040] Figure 3 Schematic diagram of the PPG AC signal in the blood oxygen measurement method according to one embodiment of the present application;

[0041] Figure 4 Flow chart of obtaining M target wave crests or Q target wave troughs corresponding to the PPG AC signal according to the PPG AC signal in the blood oxygen measurement method according to one embodiment of the present application;

[0042] Figure 5 Schematic diagram of the PPG AC signal and the candidate wave crests corresponding thereto in the blood oxygen measurement method according to one embodiment of the present application;

[0043] Figure 6 For Figure 5 Schematic diagram of the straight line intersection set of the plurality of candidate wave crests corresponding to the PPG AC signal in the polar coordinate Hough space;

[0044] Figure 7 Block schematic diagram of the blood oxygen measurement device according to one embodiment of the present application;

[0045] Figure 8a block schematic diagram of a terminal device according to an embodiment of the present application; and

[0046] Figure 9 a block schematic diagram of an electronic device according to an embodiment of the present application. DETAILED DESCRIPTION

[0047] Embodiments of the present application are described below in detail with reference to the accompanying drawings, wherein the same or similar notations used throughout the drawings and the detailed description denote the same or similar elements or elements having the same or similar functions. The embodiments described below by reference to the accompanying drawings are exemplary and are intended to explain the present application, and are not to be understood as limiting the present application.

[0048] The blood oxygen measurement method, device, terminal device, electronic device and computer readable storage medium according to the embodiments of the present application are described below in conjunction with the accompanying drawings.

[0049] Figure 1 a flow chart of a blood oxygen measurement method according to an embodiment of the present application.

[0050] As shown in Figure 1 the blood oxygen measurement method according to the embodiments of the present application comprises:

[0051] S101, acquiring a photo-plethysmography (PPG) direct current signal, and acquiring a direct current component corresponding to the PPG direct current signal according to the PPG direct current signal, the direct current component being a vertical coordinate average value of the PPG direct current signal.

[0052] In the embodiments of the present disclosure, photo-plethysmography (PPG) can be used to measure blood oxygen saturation.

[0053] The blood oxygen saturation (SPO2) is the percentage of the volume of oxygenated hemoglobin (HbO2) combined in the blood to the total volume of hemoglobin (Hb) that can be combined, which is an important physiological parameter of the human body. The oxygenated hemoglobin (HbO2) and hemoglobin (Hb) in the blood have different spectral absorption characteristics for different wavelengths. According to the principle that the spectral absorption rates of the oxygenated hemoglobin (HbO2) and hemoglobin (Hb) are different, the photo-plethysmography can be used to measure the absorption amount of light by the blood, and then the blood oxygen saturation can be obtained. Alternatively, the photo-plethysmography can be used to measure the absorption amount of light by the blood at 660nm (nanometer) and 904nm wavelengths, and then the blood oxygen saturation can be obtained.

[0054] In a specific implementation, the PPG detection can be performed on a human body to be measured first to acquire a PPG signal, then the PPG signal can be filtered to obtain a PPG direct current signal, and then a direct current component corresponding to the PPG direct current signal can be acquired according to the PPG direct current signal.

[0055] Optionally, the PPG signal can be filtered by a low-pass filter to obtain a PPG direct current signal. For example, a RAW PPG signal, a DC PPG signal obtained by using a low-pass filter with a cutoff frequency of 0.67 Hz (Hertz) is as shown in FIG. 2. Figure 2

[0056] In an embodiment of the present application, the direct current component corresponding to the PPG direct current signal is the average value of the ordinate of the PPG direct current signal. Optionally, obtaining the direct current component corresponding to the PPG direct current signal according to the PPG direct current signal can include periodically obtaining a plurality of ordinate of the PPG direct current signal, and taking the average value of the plurality of ordinate of the PPG direct current signal as the direct current component corresponding to the PPG direct current signal.

[0057] S102, obtaining a PPG alternating current signal, and obtaining M target peaks and N target troughs corresponding to the PPG alternating current signal according to the PPG alternating current signal, wherein the M target peaks reach collinearity, and the N target troughs reach collinearity.

[0058] In a specific implementation, the PPG signal can be filtered to obtain a PPG alternating current signal.

[0059] Optionally, the PPG signal can be filtered by a band-pass filter to obtain a PPG alternating current signal. For example, an AC PPG signal obtained by using a band-pass filter with a band-pass frequency range of (0.67~5) Hz, a top envelope of the PPG alternating current signal, and a bottom envelope of the PPG alternating current signal are as shown in FIG. 3. Figure 3

[0060] Further, after obtaining the PPG alternating current signal, the M target peaks and the N target troughs corresponding to the PPG alternating current signal can be obtained according to the PPG alternating current signal. Wherein, M and N are both integers greater than 1.

[0061] In an embodiment of the present application, the M target peaks reach collinearity, and the N target troughs reach collinearity. Wherein, collinearity refers to that the M target peaks corresponding to the PPG alternating current signal are approximately on a straight line, i.e., the M target peaks can fit a straight line, and the N target troughs corresponding to the PPG alternating current signal are approximately on a straight line, i.e., the N target troughs can fit a straight line.

[0062] ​​It can be understood that the PPG alternating signal can have multiple peaks and multiple troughs, and the PPG alternating signal in a short time (for example, 5 seconds) should be relatively stable, at which time most of the peaks of the PPG alternating signal can be fitted into a straight line, and most of the troughs of the PPG alternating signal can also be fitted into a straight line. If there is noise interference, the stability of the PPG alternating signal in a short time is poor, at which time most of the peaks of the PPG alternating signal cannot be fitted into a straight line, and most of the troughs of the PPG alternating signal cannot be fitted into a straight line.

[0063] It can be understood that the M target peaks and the N target troughs obtained in the method reach collinearity, and the peaks and the troughs disturbed by noise can be removed from all the peaks and all the troughs of the PPG alternating signal, respectively, so that the M target peaks and the N target troughs obtained are not disturbed by noise, and can reflect the real PPG alternating signal.

[0064] S103, calculating an alternating component corresponding to the PPG alternating signal according to the longitudinal coordinates of the M target peaks and the N target troughs.

[0065] Optionally, calculating the alternating component corresponding to the PPG alternating signal according to the longitudinal coordinates of the M target peaks and the N target troughs can include calculating a target peak longitudinal coordinate average value according to the longitudinal coordinates of the M target peaks, and calculating a target trough longitudinal coordinate average value according to the longitudinal coordinates of the N target troughs, and then calculating an absolute value of a difference between the target peak longitudinal coordinate average value and the target trough longitudinal coordinate average value to obtain the alternating component corresponding to the PPG alternating signal.

[0066] For example, assuming that the longitudinal coordinates of the M target peaks are , and the longitudinal coordinates of the N target troughs are , then the alternating component PPG AC corresponding to the PPG alternating signal is as follows:

[0067]

[0068] S104, calculating a perfusion index of a PPG signal according to the direct current component and the alternating component, the PPG signal including a PPG direct current signal and a PPG alternating signal.

[0069] Optionally, a formula for calculating the perfusion index (Perfusion Index) of the PPG signal according to the direct current component and the alternating component is as follows:

[0070] PI=PPG AC / PPG DC

[0071] Wherein, PI is the perfusion index of the PPG signal, PPG ACPPG AC component corresponding to the PPG AC signal, PPG DC DC component corresponding to the PPG DC signal.

[0072] S105, calculate the blood oxygen saturation according to the perfusion index.

[0073] In a specific implementation, the perfusion index PI1 when the light of 660 nm wavelength is acquired, and the perfusion index PI2 when the light of 904 nm wavelength is acquired, then the formula for calculating the blood oxygen saturation SPO2 according to the two perfusion indexes PI1 and PI2 acquired above is as follows:

[0074] SPO2 ∝ PI1 / PI2

[0075] In summary, according to the blood oxygen measurement method of the embodiment of the present application, the M target peaks acquired reach collinearity, the N target troughs reach collinearity, and the AC component corresponding to the PPG AC signal is calculated according to the ordinate of the M target peaks and the N target troughs, and then the blood oxygen saturation is calculated, which can effectively avoid the influence of noise interference on the blood oxygen saturation, and improve the accuracy of the blood oxygen saturation.

[0076] On the basis of any of the above embodiments, the photoplethysmogram is reflective.

[0077] At present, the photoplethysmogram has two types of transmission and reflection, and the transmission photoplethysmogram needs to measure a specific part of the human body, for example, to measure the fingers, toes, earlobes, and nose of the human body, which will limit the user's daily activities, and the user's comfort is still not high.

[0078] The reflective photoplethysmogram can be applied to most parts of the human body, and has less restriction on the user's daily activities, but the physiological signal acquired by the reflective photoplethysmogram is weaker than that of the transmission photoplethysmogram, and is more susceptible to noise interference, so the accuracy of the blood oxygen saturation measurement is not high.

[0079] The blood oxygen measurement method of the embodiment of the present application can be applied to the reflective photoplethysmogram, which can effectively remove the influence of noise interference on the measurement accuracy of the reflective photoplethysmogram, improve the measurement accuracy of the reflective photoplethysmogram for blood oxygen saturation, and also has the advantage of high user comfort.

[0080] On the basis of any of the above embodiments, after the M target peaks and the N target troughs corresponding to the PPG AC signal are acquired in step S102, if M is less than a preset peak number threshold and / or N is less than a preset trough number threshold, the PPG signal is re-acquired, and the subsequent steps of acquiring the PPG DC signal are returned to be executed.

[0081] It can be understood that if M is less than the preset peak number threshold and / or N is less than the preset trough number threshold, it indicates that most of the peaks in the PPG alternating current signal cannot be fitted into a straight line and / or most of the troughs cannot be fitted into a straight line, the stability of the obtained PPG alternating current signal is poor, the influence of noise interference is large, and the accuracy of the obtained PPG alternating current signal is also low. If the ordinate of the M target peaks and the N target troughs obtained at this time is used to calculate the PPG alternating current component, the accuracy of the obtained PPG alternating current component is also low, and the accuracy of the blood oxygen saturation is also low.

[0082] The preset peak number threshold and the preset trough number threshold can be calibrated according to actual conditions. For example, assuming that the length of the obtained PPG signal is 10 seconds, the preset peak number threshold and the preset trough number threshold can be calibrated to 5.

[0083] Therefore, when the number of target peaks obtained is less than the preset peak number threshold and / or the number of target troughs obtained is less than the preset trough number threshold, the method can reacquire the PPG signal and return to execute the subsequent steps of acquiring the PPG direct current signal, which can effectively avoid the influence of noise interference on the blood oxygen saturation and improve the accuracy of the blood oxygen saturation.

[0084] On the basis of any of the above embodiments, as shown in Figure 4 The step S102 of acquiring M target peaks or Q target troughs corresponding to the PPG alternating current signal from the PPG alternating current signal can include:

[0085] S201, acquiring P candidate peaks or Q candidate troughs corresponding to the PPG alternating current signal from the PPG alternating current signal.

[0086] Optionally, the first-order differential zero-crossing detection method can be used to acquire the plurality of peaks or troughs corresponding to the PPG alternating current signal, and then the peaks or troughs with an amplitude greater than a set amplitude threshold in the plurality of peaks or troughs are determined as the candidate peaks or candidate troughs.

[0087] In a specific implementation, the first-order differential zero-crossing detection method can be used to acquire the plurality of peaks corresponding to the PPG alternating current signal, which can include acquiring a first-order differential of adjacent two PPG alternating current signals. If the first-order differential is positive at a certain alternating current signal and before the alternating current signal, and the first-order differential is negative after the alternating current signal, the alternating current signal can be taken as a peak corresponding to the PPG alternating current signal.

[0088] In specific implementation, the method for obtaining the plurality of wave troughs corresponding to the PPG alternating current signal by using the first-order differential zero-crossing detection can include the following steps: obtaining the first-order differential of two adjacent PPG alternating current signals, if the first-order differential is negative before and after a certain alternating current signal, and the first-order differential is positive after the alternating current signal, the alternating current signal can be taken as the wave trough corresponding to the PPG alternating current signal.

[0089] It can be understood that noise interference can bring fluctuations to the PPG alternating current signal, and can form a wave peak or wave trough with a small height.

[0090] Further, the wave peak or wave trough with an amplitude greater than the set amplitude threshold value can be determined as the candidate wave peak or candidate wave trough. The method can screen the wave peak or wave trough with a larger amplitude from the plurality of wave peaks or wave troughs, and take it as the candidate wave peak or candidate wave trough, so as to effectively remove the influence of noise interference on the PPG alternating current signal.

[0091] The set amplitude threshold value can be calibrated according to actual conditions, for example, can be calibrated as 1 / 5 of the average amplitude of the PPG alternating current signal.

[0092] S202, the abscissa and ordinate of the candidate wave peak or candidate wave trough are normalized respectively to obtain the normalized abscissa and normalized ordinate of the candidate wave peak or candidate wave trough.

[0093] It can be understood that the normalization of the abscissa and ordinate of the candidate wave peak or candidate wave trough is helpful to simplify the calculation and reduce the calculation difficulty.

[0094] Optionally, the ratio of the abscissa and ordinate of the candidate wave peak or candidate wave trough to the corresponding average abscissa and average ordinate can be calculated respectively, and then the ratio is reduced by one to obtain the normalized abscissa and normalized ordinate.

[0095] S203, obtaining the straight line intersection set of the P candidate wave peaks or Q candidate wave troughs in the polar coordinate Hough space according to the normalized abscissa and normalized ordinate.

[0096] In specific implementation, assuming that the normalized abscissa and normalized ordinate of a certain candidate wave peak A are x A and y A , that is, the normalized coordinates of the candidate wave peak A are (x A , y A ), the straight line equation corresponding to the candidate wave peak A in the polar coordinate Hough space (ρ, θ) is as follows:

[0097] ρ=x A cosθ+y A sinθ

[0098] Similarly, assuming the normalized abscissa and ordinate of a candidate peak B are x B , y B , i.e., the normalized coordinates of the candidate peak B are (x B , y B ), then the straight line equation corresponding to the candidate peak B in the polar coordinate Hough space (p, q) is as follows:

[0099] p = x B cos q + y B sin q

[0100] Then, according to the straight line equations corresponding to the candidate peaks A and B in the polar coordinate Hough space, the straight line intersection point C (p C , q C ) of the candidate peaks A and B in the polar coordinate Hough space can be obtained, and the formulas of the polar coordinates p C , q C of the straight line intersection point C are as follows:

[0101]

[0102] It can be understood that the normalized abscissa and ordinate of the P candidate peaks or the Q candidate valleys can be used to calculate the intersection points of the straight lines formed by the two-to-two combination of the P candidate peaks or the Q candidate valleys in the polar coordinate Hough space, so as to obtain a set of straight line intersection points. For example, the number of straight line intersection points formed by the two-to-two combination of the P candidate peaks in the polar coordinate Hough space is P(P-1) / 2.

[0103] For example, Figure 5 is a PPG alternating signal with a time length of 10 seconds, and 11 candidate peaks are obtained by using a first-order differential zero-crossing point detection method on the PPG alternating signal in Figure 5 . The set of straight line intersection points of the 11 candidate peaks in the polar coordinate Hough space is shown in Figure 6 .

[0104] In S204, a target intersection point in the set of straight line intersection points is determined according to the local density of each intersection point in the set of straight line intersection points.

[0105] It can be understood that each straight line intersection point in the polar coordinate Hough space corresponds to a local density. If there are more straight line intersection points in the region around a certain straight line intersection point, the local density of the straight line intersection point is larger, which indicates that the straight line corresponding to the straight line intersection point in the rectangular coordinate system can contain more target peaks or target valleys, and the straight line intersection point can be used as a target intersection point. This method can obtain M target peaks or N target valleys that meet the collinearity by determining the target intersection point in the set of straight line intersection points of the candidate peaks or candidate valleys.

[0106] Optionally, determining the target intersection point in the set of straight line intersection points according to the local density of each intersection point in the set of straight line intersection points can include defining the local density of each intersection point in the set of straight line intersection points using a Gaussian kernel function, determining the intersection point whose local density is greater than the local density of the neighbor intersection points within a set distance range as a candidate intersection point, and determining the candidate intersection point whose distance to other candidate intersection points is greater than a set distance threshold as the target intersection point. The set distance range and the set distance threshold can be calibrated according to actual conditions. Thus, the method can screen the target intersection point whose local density is greater than the local density of the neighbor intersection points within a set distance range and whose distance to other candidate intersection points is greater from the set of straight line intersection points.

[0107] S205, determining M target wave crests or N target wave troughs according to the target intersection point in the P candidate wave crests or the Q candidate wave troughs.

[0108] It should be noted that, assuming that the coordinates of the target intersection point D in the polar coordinate Hough space are (ρ i , θ i ), the straight line equation corresponding to the target intersection point D in the rectangular coordinate system is as follows:

[0109]

[0110] It can be understood that the target wave crest or the target wave trough is on the straight line corresponding to the target intersection point in the rectangular coordinate system, and thus M target wave crests or Q target wave troughs that substantially conform to the straight line equation can be determined from the candidate wave crests or the candidate wave troughs according to the normalized horizontal coordinates and the normalized vertical coordinates of the candidate wave crests or the candidate wave troughs and the straight line equation corresponding to the target intersection point in the rectangular coordinate system.

[0111] In a specific implementation, the vertical coordinate reference value can be calculated according to the polar coordinates of the target intersection point, the absolute value of the difference between the vertical coordinate of the candidate wave crest or the candidate wave trough and the vertical coordinate reference value can be calculated, and then the candidate wave crest or the candidate wave trough whose absolute value is equal to or less than a set difference threshold value is determined as the target wave crest or the target wave trough.

[0112] The vertical coordinate reference value can be calculated according to the polar coordinates of the target intersection point, which can include obtaining the horizontal coordinates of the candidate wave crest or the candidate wave trough, and then bringing the horizontal coordinates of the candidate wave crest or the candidate wave trough into the straight line equation corresponding to the target intersection point in the rectangular coordinate system to obtain the vertical coordinate reference value corresponding to the candidate wave crest or the candidate wave trough. The set difference threshold value can be calibrated according to actual conditions.

[0113] Thus, the method can screen the target wave crest or the target wave trough that substantially conforms to the straight line equation corresponding to the target intersection point in the rectangular coordinate system from the P candidate wave crests or the Q candidate wave troughs, and the M target wave crests reach collinearity and the N target wave troughs reach collinearity.

[0114] Thus, the method can screen the target wave crest or the target wave trough that substantially conforms to the straight line equation corresponding to the target intersection point in the rectangular coordinate system from the P candidate wave crests or the Q candidate wave troughs, and the M target wave crests reach collinearity and the N target wave troughs reach collinearity.Figure 7 A block diagram of a blood oxygen measurement device according to an embodiment of the present application.

[0115] As shown in Figure 7 The blood oxygen measurement device 100 according to the embodiment of the present application includes a first obtaining module 11, a second obtaining module 12, a first calculating module 13, a second calculating module 14, and a third calculating module 15.

[0116] The first obtaining module 11 is configured to obtain a photoplethysmography (PPG) direct current (DC) signal, and obtain a DC component corresponding to the PPG DC signal according to the PPG DC signal, wherein the DC component is a vertical coordinate average value of the PPG DC signal.

[0117] The second obtaining module 12 is configured to obtain a PPG alternating current (AC) signal, and obtain M target wave crests and N target wave troughs corresponding to the PPG AC signal according to the PPG AC signal, wherein the M target wave crests reach collinearity, and the N target wave troughs reach collinearity.

[0118] The first calculating module 13 is configured to calculate an AC component corresponding to the PPG AC signal according to vertical coordinates of the M target wave crests and the N target wave troughs.

[0119] The second calculating module 14 is configured to calculate a perfusion index of a PPG signal according to the DC component and the AC component, wherein the PPG signal includes the PPG DC signal and the PPG AC signal.

[0120] The third calculating module 15 is configured to calculate a blood oxygen saturation according to the perfusion index.

[0121] In an embodiment of the present application, the first calculating module 13 is specifically configured to: calculate a target wave crest vertical coordinate average value according to vertical coordinates of the M target wave crests; calculate a target wave trough vertical coordinate average value according to vertical coordinates of the N target wave troughs; and calculate an absolute value of a difference between the target wave crest vertical coordinate average value and the target wave trough vertical coordinate average value to obtain the AC component corresponding to the PPG AC signal.

[0122] In an embodiment of the present application, the second obtaining module 12 is specifically configured to: obtain P candidate wave crests or Q candidate wave troughs corresponding to the PPG alternating current signal according to the PPG alternating current signal; normalize the abscissa and ordinate of the candidate wave crests or candidate wave troughs respectively to obtain normalized abscissa and normalized ordinate of the candidate wave crests or candidate wave troughs; obtain a straight line intersection set of the P candidate wave crests or the Q candidate wave troughs in a polar coordinate Hough space according to the normalized abscissa and the normalized ordinate; determine a target intersection point in the straight line intersection set according to the local density of each intersection point in the straight line intersection set; and determine the M target wave crests or the N target wave troughs according to the target intersection point in the P candidate wave crests or the Q candidate wave troughs.

[0123] In an embodiment of the present application, the second obtaining module 12 is specifically configured to: obtain a plurality of wave crests or wave troughs corresponding to the PPG alternating current signal by using a first-order differential zero-crossing point detection method; and determine the wave crest or wave trough with an amplitude greater than a set amplitude threshold value in the plurality of wave crests or wave troughs as the candidate wave crest or candidate wave trough.

[0124] In an embodiment of the present application, the second obtaining module 12 is specifically configured to: calculate a first ratio of the abscissa of the candidate wave crest or candidate wave trough to the corresponding average abscissa; calculate a second ratio of the ordinate of the abscissa of the candidate wave crest or candidate wave trough to the corresponding average ordinate; obtain the normalized abscissa by subtracting one from the first ratio; and obtain the normalized ordinate by subtracting one from the second ratio.

[0125] In an embodiment of the present application, the second obtaining module 12 is specifically configured to: calculate the intersection of the straight lines of the P candidate wave crests or the Q candidate wave troughs in the polar coordinate Hough space according to the normalized abscissa and the normalized ordinate, respectively, to obtain the straight line intersection set.

[0126] In an embodiment of the present application, the second obtaining module 12 is specifically configured to: define the local density of each intersection point in the straight line intersection set by using a Gaussian kernel function; determine a candidate intersection point by using an intersection point with a local density greater than the local density of a neighbor intersection point within a set distance range; and determine a target intersection point by using a candidate intersection point with a distance greater than a set distance threshold value from other candidate intersection points.

[0127] In an embodiment of the present application, the second obtaining module 12 is specifically configured to: calculate a longitudinal coordinate reference value according to the polar coordinates of the target intersection; calculate absolute values of differences between longitudinal coordinates of the candidate wave peaks or candidate wave troughs and the longitudinal coordinate reference value; and determine the candidate wave peak or candidate wave trough with the absolute value equal to or smaller than a set difference threshold value as the target wave peak or target wave trough.

[0128] It should be noted that details of the blood oxygen measurement device not disclosed in the embodiments of the present application are referred to the details disclosed in the blood oxygen measurement method in the above embodiments of the present application, which will not be described herein.

[0129] In summary, the blood oxygen measurement device in the embodiments of the present application, the M target wave peaks reach collinearity, the N target wave troughs reach collinearity, and the AC component corresponding to the PPG AC signal is calculated according to the longitudinal coordinates of the M target wave peaks and the N target wave troughs, and then the blood oxygen saturation is calculated, which can effectively avoid the influence of noise interference on the blood oxygen saturation, and improve the accuracy of the blood oxygen saturation.

[0130] In order to realize the above-mentioned embodiments, the present application further provides a terminal device 200, as shown in the following Figure 8 which comprises the above-mentioned blood oxygen measurement device 100.

[0131] In an embodiment of the present application, the terminal device is a wearable terminal device.

[0132] The terminal device in the embodiments of the present application, the M target wave peaks reach collinearity, the N target wave troughs reach collinearity, and the AC component corresponding to the PPG AC signal is calculated according to the longitudinal coordinates of the M target wave peaks and the N target wave troughs, and then the blood oxygen saturation is calculated, which can effectively avoid the influence of noise interference on the blood oxygen saturation, and improve the accuracy of the blood oxygen saturation.

[0133] In order to realize the above-mentioned embodiments, the present application further provides an electronic device 300, as shown in the following Figure 9 which comprises a memory 31 and a processor 32. The processor 32 runs a program corresponding to an executable program code stored in the memory 31 by reading the executable program code, so as to realize the above-mentioned blood oxygen measurement method.

[0134] The electronic device in the embodiments of the present application, by the processor executing the computer program stored on the memory, the M target wave peaks reach collinearity, the N target wave troughs reach collinearity, and the AC component corresponding to the PPG AC signal is calculated according to the longitudinal coordinates of the M target wave peaks and the N target wave troughs, and then the blood oxygen saturation is calculated, which can effectively avoid the influence of noise interference on the blood oxygen saturation, and improve the accuracy of the blood oxygen saturation.

[0135] In order to realize the above-mentioned embodiments, the application further provides a computer readable storage medium, which stores a computer program, and the program is executed by a processor to realize the blood oxygen measurement method.

[0136] The computer readable storage medium of the embodiments of the application can effectively avoid the influence of noise interference on the blood oxygen saturation and improve the accuracy of the blood oxygen saturation by storing a computer program and being executed by a processor, obtaining M target wave crests reaching collinearity and N target wave troughs reaching collinearity, and calculating an alternating component corresponding to a PPG alternating signal according to the longitudinal coordinates of the M target wave crests and the N target wave troughs.

[0137] In the description of the application, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the application and simplifying the description, and does not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation of the application.

[0138] In addition, the terms "first", "second" are only for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features defined with "first", "second" can explicitly or implicitly include one or more of the features. In the description of the application, the meaning of "multiple" is two or more, unless otherwise specifically limited.

[0139] In the application, unless otherwise specifically defined and limited, the terms "mounting", "connection", "connection", "fixing" and the like should be understood in a broad sense, for example, it can be fixed connection, or detachable connection, or integral; it can be mechanical connection, or electrical connection; it can be directly connected, or indirectly connected through an intermediate medium; it can be the internal communication of two elements or the interaction relationship between two elements. For those skilled in the art, the specific meaning of the above terms in the application can be understood according to the specific circumstances.

[0140] In the present application, unless otherwise explicitly specified and limited, a first feature is "on" or "under" a second feature can mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, the first feature "over", "above" and "on top of" the second feature can mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is horizontally higher than the second feature. The first feature "under", "below" and "underneath" the second feature can mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is horizontally lower than the second feature.

[0141] In the description of the present application, the description of the terms "one embodiment", "some embodiments", "an example", "a specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the present application, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any appropriate manner in one or more embodiments or examples. In addition, the person skilled in the art can combine and combine the different embodiments or examples described in the present application and the features of the different embodiments or examples without contradiction.

[0142] Although the embodiments of the present application have been shown and described above, it is understood that the above-described embodiments are exemplary and are not to be construed as limiting the present application, and the person skilled in the art can make changes, modifications, replacements and variations to the above-described embodiments within the scope of the present application.

Claims

1. A method for measuring blood oxygen saturation, characterized in that, include: Acquire the photoplethysmography (PPG) DC signal, and obtain the DC component corresponding to the PPG DC signal based on the PPG DC signal. The DC component is the average value of the vertical axis of the PPG DC signal. Acquire PPG AC signals, and obtain M target peaks and N target troughs corresponding to the PPG AC signals, wherein the M target peaks achieve collinearity and the N target troughs achieve collinearity. The AC component corresponding to the PPG AC signal is calculated based on the ordinates of the M target peaks and the N target troughs. The perfusion index of the PPG signal is calculated based on the DC component and the AC component, wherein the PPG signal includes the PPG DC signal and the PPG AC signal; Blood oxygen saturation is calculated based on the perfusion index.

2. The blood oxygen measurement method according to claim 1, characterized in that, The step of calculating the AC component corresponding to the PPG AC signal based on the ordinates of the M target peaks and N target troughs includes: Calculate the average value of the ordinate of the target peaks based on the ordinate of the M target peaks; Calculate the average value of the vertical coordinates of the target valleys based on the vertical coordinates of the N target valleys; The absolute value of the difference between the average value of the target peak ordinate and the average value of the target trough ordinate is calculated to obtain the AC component corresponding to the PPG AC signal.

3. The blood oxygen measurement method according to claim 1, characterized in that, Based on the PPG AC signal, the M target peaks or N target troughs corresponding to the PPG AC signal are obtained using a collinearity rule, including: Based on the PPG AC signal, obtain P candidate peaks or Q candidate troughs corresponding to the PPG AC signal; The x-coordinate and y-coordinate of the candidate peak or candidate trough are normalized respectively to obtain the normalized x-coordinate and normalized y-coordinate of the candidate peak or candidate trough. The set of line intersections of the P candidate peaks or the Q candidate troughs in polar coordinate Hough space is obtained based on the normalized abscissa and the normalized ordinate. Based on the local density of each intersection point in the set of line intersection points, determine the target intersection point in the set of line intersection points; Based on the target intersection point, determine the M target peaks or N target valleys from the P candidate peaks or Q candidate valleys.

4. The blood oxygen measurement method according to claim 3, characterized in that, The step of obtaining P candidate peaks or Q candidate troughs corresponding to the PPG AC signal based on the PPG AC signal includes: Multiple peaks or troughs corresponding to the PPG AC signal are obtained by first-order differential zero-crossing detection. The peaks or troughs with amplitudes greater than a set amplitude threshold among the multiple peaks or troughs are identified as candidate peaks or candidate troughs.

5. The blood oxygen measurement method according to claim 3, characterized in that, The normalization process for the abscissa and ordinate of the candidate peaks or troughs to obtain the normalized abscissa and ordinate of the candidate peaks or troughs includes: Calculate the first ratio of the abscissa of the candidate peak or candidate trough to the average abscissa of the corresponding peak or trough; Calculate the second ratio of the x-coordinate of the candidate peak or trough to the average value of the corresponding y-coordinate; Subtract one from the first ratio to obtain the normalized abscissa; Subtract one from the second ratio to obtain the normalized ordinate.

6. The blood oxygen measurement method according to claim 3, characterized in that, The step of obtaining the set of line intersection points of the P candidate peaks or Q candidate troughs in polar coordinate Hough space based on the normalized abscissa and the normalized ordinate includes: Based on the normalized abscissa and the normalized ordinate, the intersection points of the straight lines in the polar coordinate Hough space are calculated for each pair of the P candidate peaks or the Q candidate troughs, respectively, to obtain the set of straight line intersection points.

7. The blood oxygen measurement method according to claim 3, characterized in that, The step of determining the target intersection point in the set of line intersection points based on the local density of each intersection point in the set of line intersection points includes: The local density of each intersection point in the set of intersection points of the lines is defined using a Gaussian kernel function; Intersections whose local density is greater than the local density of neighboring intersections within a set distance range are identified as candidate intersections; Based on the distance between the candidate intersection points, the candidate intersection points that are more than a set distance threshold from other candidate intersection points are determined as the target intersection points.

8. The blood oxygen measurement method according to claim 3, characterized in that, The step of determining the M target peaks or N target valleys from the P candidate peaks or Q candidate valleys based on the target intersection points includes: Calculate the reference value of the ordinate based on the polar coordinates of the target intersection point; Calculate the absolute value of the difference between the ordinate of the candidate peak or candidate trough and the reference value of the ordinate; The candidate peaks or troughs whose absolute values ​​are equal to or less than a set difference threshold are determined as the target peaks or target troughs.

9. A blood oxygen measuring device, characterized in that, include: The first acquisition module is used to acquire the photoplethysmography (PPG) DC signal and acquire the DC component corresponding to the PPG DC signal based on the PPG DC signal, wherein the DC component is the average value of the vertical axis of the PPG DC signal. The second acquisition module is used to acquire the PPG AC signal and acquire M target peaks and N target troughs corresponding to the PPG AC signal, wherein the M target peaks achieve collinearity and the N target troughs achieve collinearity. The first calculation module is used to calculate the AC component corresponding to the PPG AC signal based on the ordinates of the M target peaks and the N target troughs. The second calculation module is used to calculate the perfusion index of the PPG signal based on the DC component and the AC component, wherein the PPG signal includes the PPG DC signal and the PPG AC signal; The third calculation module is used to calculate blood oxygen saturation based on the perfusion index.

10. The blood oxygen measuring device according to claim 9, characterized in that, The first calculation module is specifically used for: Calculate the average value of the ordinate of the target peaks based on the ordinate of the M target peaks; Calculate the average value of the vertical coordinates of the target valleys based on the vertical coordinates of the N target valleys; The absolute value of the difference between the average value of the target peak ordinate and the average value of the target trough ordinate is calculated to obtain the AC component corresponding to the PPG AC signal.

11. The blood oxygen measuring device according to claim 9, characterized in that, The second acquisition module is specifically used for: Based on the PPG AC signal, obtain P candidate peaks or Q candidate troughs corresponding to the PPG AC signal; The x-coordinate and y-coordinate of the candidate peak or candidate trough are normalized respectively to obtain the normalized x-coordinate and normalized y-coordinate of the candidate peak or candidate trough. The set of line intersections of the P candidate peaks or the Q candidate troughs in polar coordinate Hough space is obtained based on the normalized abscissa and the normalized ordinate. Based on the local density of each intersection point in the set of line intersection points, determine the target intersection point in the set of line intersection points; Based on the target intersection point, determine the M target peaks or N target valleys from the P candidate peaks or Q candidate valleys.

12. The blood oxygen measuring device according to claim 11, characterized in that, The second acquisition module is specifically used for: Multiple peaks or troughs corresponding to the PPG AC signal are obtained by first-order differential zero-crossing detection. The peaks or troughs with amplitudes greater than a set amplitude threshold among the multiple peaks or troughs are identified as candidate peaks or candidate troughs.

13. The blood oxygen measuring device according to claim 11, characterized in that, The second acquisition module is specifically used for: Calculate the first ratio of the abscissa of the candidate peak or candidate trough to the average abscissa of the corresponding peak or trough; Calculate the second ratio of the x-coordinate of the candidate peak or trough to the average value of the corresponding y-coordinate; Subtract one from the first ratio to obtain the normalized abscissa; Subtract one from the second ratio to obtain the normalized ordinate.

14. The blood oxygen measuring device according to claim 11, characterized in that, The second acquisition module is specifically used for: Based on the normalized abscissa and the normalized ordinate, the intersection points of the straight lines in the polar coordinate Hough space are calculated for each pair of the P candidate peaks or the Q candidate troughs, respectively, to obtain the set of straight line intersection points.

15. The blood oxygen measuring device according to claim 11, characterized in that, The second acquisition module is specifically used for: The local density of each intersection point in the set of intersection points of the lines is defined using a Gaussian kernel function; Intersections whose local density is greater than the local density of neighboring intersections within a set distance range are identified as candidate intersections; Based on the distance between the candidate intersection points, the candidate intersection points that are more than a set distance threshold from other candidate intersection points are determined as the target intersection points.

16. The blood oxygen measuring device according to claim 11, characterized in that, The second acquisition module is specifically used for: Calculate the reference value of the ordinate based on the polar coordinates of the target intersection point; Calculate the absolute value of the difference between the ordinate of the candidate peak or candidate trough and the reference value of the ordinate; The candidate peaks or troughs whose absolute values ​​are equal to or less than a set difference threshold are determined as the target peaks or target troughs.

17. A terminal device, characterized in that, include: The blood oxygen measuring device as described in any one of claims 9-16.

18. The terminal device according to claim 17, characterized in that, The terminal device is a wearable terminal device.

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