Method, computer program product and electronic device for calculating blood oxygen concentration

Abstract

A method for calculating blood oxygen concentration, comprising: obtaining a red light signal and at least one non-red light signal reflected from the skin; using the time point when the at least one non-red light signal has a peak as the time point when the red light signal has a peak; using the time point when the at least one non-red light signal has a trough as the time point when the red light signal has a trough; and calculating the blood oxygen concentration based on the red light signal at the time of the peak and the time of the trough. The method for calculating blood oxygen concentration of the disclosed embodiment proposes to find the periodic wave of the red light signal in an auxiliary manner by means of other light source signals, so that the calculation result of the red light signal is more accurate. The present invention also relates to a computer program product and an electronic device.

Description

Technical Field

[0001] The present disclosure relates to a signal processing method, and more particularly to a method, a computer program product and an electronic device for calculating blood oxygen concentration. Background Art

[0002] The ear-hook oximeter is installed in the ear and uses the photoplethysmography (PPG) signal reflected by the skin in the ear to measure the physiological information of the human body. Generally speaking, the PPG signal can be received by a light sensor that can receive green light, red light and infrared light. The ear-hook oximeter uses the PPG signal to analyze and calculate data including heart rate, blood oxygen concentration, blood perfusion index, etc.

[0003] However, if the ear structure of the user is not easy to fit the ear-hook oximeter, or the signal light source does not contact the ear blood vessels, the quality of the PPG signal will be poor, resulting in misjudgment of physiological measurement data. Summary of the invention

[0004] The method for calculating blood oxygen concentration according to an embodiment of the present disclosure includes: defining an extreme point of a non-red light signal as an extreme point of a red light signal; and calculating the blood oxygen concentration according to the extreme point of the red light signal.

[0005] The method as described above further includes: filtering the red light signal to exclude outliers of the red light signal.

[0006] The method as described above also includes: obtaining a peak value when the red light signal has a first peak; obtaining a first trough value and a second trough value when the red light signal has two troughs adjacent to the first peak; calculating an average value of the first trough value and the second trough value; calculating a difference between the peak value and the average value to obtain an alternating current (AC) value of the red light signal.

[0007] In the method as described above, filtering the red light signal includes: excluding a peak value, where the peak value is correspondingly smaller than the first trough value or the second trough value.

[0008] In the method as described above, filtering the red light signal includes: excluding an intermediate value, the intermediate value corresponding to the red light signal being between a first wave crest and one of two wave valleys adjacent to the first wave crest, and the intermediate value being greater than the wave crest value.

[0009] As described above, the method of filtering the red light signal includes: excluding AC values, the AC values ​​corresponding to the AC values ​​at the first peak, and the AC values ​​are more than 1.5 times the average value of the first three peaks in the red light signal that are earlier than the first peak.

[0010] As described above, the method of filtering the red light signal includes: excluding AC values, the AC values ​​corresponding to the AC values ​​of the first peak, and the AC values ​​are less than 0.67 times the average AC values ​​of the three peaks before the first peak in the red light signal.

[0011] The method as described above further includes: obtaining a direct current (DC) value of the red light signal according to an average value of the first wave valley value and the second wave valley value; and calculating the blood oxygen concentration according to the alternating current value and the direct current value of the red light signal.

[0012] The method as described above further includes: obtaining a red light signal, a green light signal and an infrared light signal reflected from the skin; using the time point at which the green light signal has a peak as the time point at which the red light signal has a peak; using the time point at which the infrared light signal has a trough as the time point at which the red light signal has a trough. The green light signal has a dicrotic wave, while the red light signal and the infrared light signal do not have a dicrotic wave.

[0013] In the method as described above, the red light signal and the non-red light signal are photoplethysmography (PPG) signals.

[0014] According to an embodiment of the present disclosure, a method for calculating blood oxygen concentration is loaded and executed by an electronic device having a processor, and the computer program product includes: a peak alignment instruction, a trough alignment instruction, and a calculation instruction. The peak and trough alignment instruction enables the processor to define an extreme point of a non-red light signal as an extreme point of a red light signal. The calculation instruction enables the processor to calculate the blood oxygen concentration based on the extreme point of the red light signal.

[0015] The computer program product as described above, when executed by the electronic device, further includes a filtering instruction which enables the processor to filter the red light signal to exclude outliers of the red light signal.

[0016] The computer program product as described above, the electronic device executes a peak alignment instruction, a valley alignment instruction, a valley average instruction, and an AC value calculation instruction. The peak alignment instruction enables the processor to obtain a peak value when a first peak occurs in the red light signal. The valley alignment instruction enables the processor to obtain a first valley value and a second valley value when two valleys adjacent to the first peak occur in the red light signal. The valley average instruction enables the processor to calculate an average value of the first valley value and the second valley value. The AC value calculation instruction enables the processor to calculate a difference between the peak value and the average value to obtain an AC value of the red light signal.

[0017] According to an embodiment of the present disclosure, the electronic device includes: a light emitting unit, a light sensor, and a processor. The light emitting unit is used to emit a red light signal and a non-red light signal to the skin. The light sensor is used to receive the red light signal and the non-red light signal reflected from the skin. The processor is used to execute the following steps: defining the extreme point of the non-red light signal as the extreme point of the red light signal; and calculating the blood oxygen concentration according to the extreme point of the red light signal.

[0018] In the electronic device as described above, the processor execution further includes: filtering the red light signal to exclude outliers of the red light signal.

[0019] In the electronic device as described above, the processor execution also includes: obtaining a peak value when a red light signal has a first peak; obtaining a first valley value and a second valley value when the red light signal has two valleys adjacent to the first peak; calculating an average value of the first valley value and the second valley value; and calculating a difference between the peak value and the average value to obtain an AC value of the red light signal. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Schematic diagram of oxygenated hemoglobin in the blood and the absorption rate of hemoglobin to light of different wavelengths.

[0021] Figure 2 The present invention is a flowchart of a method for calculating blood oxygen concentration according to an embodiment of the present invention.

[0022] Figure 3 3 is a waveform diagram of a green light signal 300 , a red light signal 302 , and an infrared light signal 304 according to an embodiment of the present disclosure.

[0023] Figure 4 FIG. 4 is a schematic diagram of calculating the alternating current (AC) value and the direct current (DC) value of the PPG signal 400 according to an embodiment of the present disclosure.

[0024] Figure 5A FIG. 5 is a schematic diagram of scenario 1 of filtering a PPG signal 500 according to an embodiment of the present disclosure.

[0025] Figure 5B FIG. 5 is a schematic diagram of scenario 2 of filtering a PPG signal 510 according to an embodiment of the present disclosure.

[0026] Figure 5C Schematic diagram of scenario 3 of filtering the PPG signal 520 according to an embodiment of the present disclosure.

[0027] Figure 6 is a block diagram of an electronic device according to an embodiment of the present disclosure.

[0028] Description of reference numerals:

[0029] 100,102: Curve

[0030] S200, S202: Steps

[0031] 300: Green light signal

[0032] 302: Red light signal

[0033] 304: Infrared light signal

[0034] 310,312: Heavy Stroke Wave

[0035] t1, t2, t3, t4, t5, t6, t7, t8: time points

[0036] t5',t6',t7',t8': time points

[0037] 400:PPG signal

[0038] (X P1 ,Y P1 ): Peak value

[0039] (X V1 ,Y V1 ),(X V2 ,Y V2 ): trough value

[0040] (X',Y'): Mean value

[0041] M: Slope

[0042] AC: alternating current value

[0043] DC: Direct current value

[0044] ①: Peak

[0045] ②,③:Trough

[0046] X,Y: Coordinate axis

[0047] 500,510,520:PPG signal

[0048] 502,504,506,508: Peak

[0049] 512,514,516,518: Peak

[0050] AC1,AC2,AC3,AC: AC value

[0051] 524,526: Trough

[0052] 522: Crest

[0053] 528,530: points

[0054] 600: Electronic devices

[0055] 602: Processor

[0056] 604: Light emitting unit

[0057] 606: Light sensor

[0058] 610: Red light signal

[0059] 612: At least one non-red light signal

[0060] 610': Reflected red light signal

[0061] 612': At least one non-red light signal is reflected DETAILED DESCRIPTION

[0062] The present disclosure is described with reference to the accompanying drawings, in which the same reference numerals throughout the drawings indicate similar or identical elements. The above drawings are not depicted according to the actual scale, and they only provide an explanation of the present disclosure. Some forms of the invention are described below as references for illustrated exemplary applications. This means that many special details, relationships and methods are described to provide a complete understanding of this invention. In any case, a person with general knowledge of the relevant field will recognize that this invention can still be implemented without one or more special details or with other methods. For other examples, well-known structures or operations are not listed in detail to avoid confusion about this invention. The present disclosure is not limited to the order of the actions or events described, such as some actions may occur in different orders or simultaneously with other actions or events. In addition, not all described actions or events need to be performed in the same method as the existing invention.

[0063] The principle of photoplethysmography (PPG) is to transmit light through human tissue and receive continuous light signals reflected from human tissue through sensors. When light passes through human tissue, it will be absorbed and attenuated by different human tissues, so the PPG signal is divided into two parts: direct current (DC) and alternating current (AC). Assuming that the composition of the human body is fixed and the attenuation of light is also fixed, the DC value of the PPG signal is the fixed absorbed part. The AC value of the PPG signal is the signal that changes with the volume of the blood vessels.

[0064] PPG signals mainly have three light sources: green light, red light and infrared light. Different light sources have different penetration depths into human tissue. For example, green light has the shallowest penetration depth, red light has the second deepest penetration depth, and infrared light has the deepest penetration depth. Figure 1 It is a schematic diagram of oxygenated hemoglobin in the blood and the absorption rate of hemoglobin to light of different wavelengths. Figure 1As shown, curve 100 represents the absorption rate of hemoglobin (Hb) in the blood to light of different wavelengths. Curve 102 represents the absorption rate of oxygenated hemoglobin (HbO2) in the blood to light of different wavelengths. Most of the green light with a wavelength of 530 nanometers will be absorbed by red blood cells, so it can cause more attenuation of light intensity, which is suitable for calculating heart rate. Since hemoglobin and oxygenated hemoglobin have the largest difference in absorption rate to red light with a wavelength of 660 nanometers and infrared light with a wavelength of 940 nanometers, for example, the absorption rate of hemoglobin to red light is higher than the absorption rate of oxygenated hemoglobin to red light, but the absorption rate of hemoglobin to infrared light is lower than the absorption rate of oxygenated hemoglobin to infrared light, so red light and infrared light are suitable for calculating blood oxygen concentration.

[0065] Figure 2 FIG. 1 is a flow chart of a method for calculating blood oxygen concentration according to an embodiment of the present disclosure. Figure 2 As shown, the method for calculating the blood oxygen concentration of the embodiment of the present disclosure first obtains a red light signal and a non-red light signal reflected from the skin. In the embodiment of the present disclosure, the obtained red light signal and non-red light signal are reflected from the skin inside the ear, but are not limited to this. In step S200, the method for calculating the blood oxygen concentration of the embodiment of the present disclosure defines the extreme point (for example, a peak or a trough) of the non-red light signal as the extreme point of the red light signal. Next, in step S202, the method for calculating the blood oxygen concentration of the embodiment of the present disclosure calculates the blood oxygen concentration based on the extreme point of the red light signal.

[0066] In some embodiments, the non-red light signal is a green light signal and / or an infrared light signal. In some embodiments, the red light signal and the non-red light signal are emitted by a light emitting unit of an ear-hook type electronic device. For example, the light emitting unit of the ear-hook type electronic device includes a green light LED, a red light LED, and an infrared light LED, which are used to emit corresponding green light signals, red light signals, and infrared light signals, respectively. Figure 3 300, red light signal 302 and infrared light signal 304 of the embodiment of the present disclosure. In some embodiments, Figure 3 The horizontal axis is the number of samples, and the vertical axis is the amplitude (μV), wherein the number of samples may correspond to time. In some embodiments, Figure 3 The waveform diagram is read from a light sensor of the ear-hook electronic device. The light sensor is used to receive a green light signal 300, a red light signal 302, and an infrared light signal 304 reflected from the skin.

[0067] like Figure 3As shown, at time point t1, time point t2, time point t3, and time point t4, the green light signal 300, the red light signal 302, and the infrared light signal 304 all have peaks. In other words, since at time point t1, time point t2, time point t3, and time point t4, the peaks of the green light signal 300, the red light signal 302, and the infrared light signal 304 are aligned with each other, the method for calculating the blood oxygen concentration of the embodiment of the present disclosure can use the time point when the green light signal 300 or the infrared light signal 304 has a peak as the time point when the red light signal 302 has a peak. Then, at time point t5, time point t6, time point t7, and time point t8, the red light signal 302 and the infrared light signal 304 have troughs, but the green light signal 300 does not have a trough until time point t5', time point t6', time point t7', and time point t8'. In other words, at time point t5 , time point t6 , time point t7 , and time point t8 , the trough of the red light signal 302 is aligned with the trough of the infrared light signal 304 , but is not aligned with the trough of the green light signal 300 .

[0068] In some embodiments, since the red light signal 302 and the infrared light signal 304 detect the physiological characteristic "dicrotic wave" from the human body from time point t5 to time point t5', time point t6 to time point t6', time point t7 to time point t7', and time point t8 to time point t8' (for example, dicrotic wave 310 and dicrotic wave 312 from time point t8 to time point t8'), the trough of the red light signal 302 and the trough of the infrared light signal 304 cannot be aligned with the trough of the green light signal 300. In some embodiments, the dicrotic wave comes from the reflected shock wave formed by the blood hitting the aortic valve caused by the aortic blood pressure. Therefore, the method for calculating the blood oxygen concentration in the embodiment of the present disclosure uses the time point (for example, time point t1-t4) when the non-red light signal (for example, the green light signal 300 or the infrared light signal 304) has a peak as the time point when the red light signal 302 has a peak. Furthermore, the method for calculating blood oxygen concentration in the embodiment of the present disclosure uses the time point (eg, time point t5-t8) when the non-red light signal (eg, infrared light signal 304) has a trough as the time point when the red light signal 302 has a trough.

[0069] In some embodiments, the wavelength of the green light signal 300 is shorter and its penetration depth is shallow, so it will be directly absorbed by the blood vessels. In other words, since the human body tissue has a good absorption rate for the green light signal 300, the green light signal 300 can reflect more obvious changes in blood flow, so the waveform vibration of the green light signal 300 is larger (for example, Figure 3The amplitude of the green light signal 300 is greater than that of the red light signal 302 and the infrared light signal 304), the interference will be less (that is, the signal-to-noise ratio (SNR) is higher). The wavelengths of the red light signal 302 and the infrared light signal 304 are longer, and their penetrating power is stronger than that of the green light signal 300, and it is easier for them to hit the bones and other human tissues. Therefore, the red light signal 302 and the infrared light signal 304 will be more sensitive and more susceptible to interference. Therefore, the method for calculating the blood oxygen concentration in the embodiment of the present disclosure uses the time point when the peak of the green light signal 300 occurs as the time point when the peak of the red light signal 302 occurs.

[0070] In some embodiments, the light emitting unit of the ear-hook electronic device does not emit three light sources (e.g., green light signal 300, red light signal 302, and infrared light signal 304) at the same time, but emits the three light sources one by one according to the design of the firmware. However, since the switching time of the light emitting unit of the ear-hook electronic device to emit the three light sources separately is very short (i.e., the light source switching speed is very fast), the method for calculating blood oxygen concentration in the embodiment of the present disclosure can implement the waveform alignment method of step S200. In some embodiments, the method for calculating blood oxygen concentration in the embodiment of the present disclosure must first intercept the extreme value of the PPG signal (e.g., green light signal 300, red light signal 302, and infrared light signal 304) to calculate physiological measurements. For example, the peak of the green light signal 300 is used to calculate the heart rate, the peak and trough of the infrared light signal 304 are used to calculate the blood perfusion index, and the peak and trough of the red light signal 302 and the infrared light signal 304 are used to calculate the blood oxygen concentration.

[0071] Table 1 shows the method for calculating blood oxygen concentration according to the embodiment of the present disclosure with auxiliary signals (e.g. Figure 1 The time point at which the green light signal 300 and the infrared light signal 304) have a peak or a trough is taken as Figure 1 An example statistical table of time points at which the red light signal 302 has a peak or a trough.

[0072]

[0073]

[0074] Table 1

[0075] The reference standard of blood oxygen concentration in Table 1 is the medical product finger-clip oximeter (Fingertip Pulse Oximeter). As shown in Table 1, in Example 1, the method for calculating blood oxygen concentration in the embodiment of the present disclosure uses the time point when the green light signal 300 has a peak as the time point when the red light signal 302 has a peak in step S200, and uses the time point when the green light signal 300 has a trough as the time point when the red light signal 302 has a trough in step S200. Figure 3, since the trough of the green light signal 300 is not aligned with the trough of the red light signal 302, the accuracy of the blood oxygen concentration calculated by the method for calculating the blood oxygen concentration of the embodiment of the present disclosure in step S202 is only 91%. In Example 2, the method for calculating the blood oxygen concentration of the embodiment of the present disclosure uses the time point when the green light signal 300 has a peak as the time point when the red light signal 302 has a peak in step S200, but does not use any auxiliary signal as the time point when the red light signal 302 has a trough, that is, directly using the time point when the red light signal 302 has a trough, so the accuracy of the blood oxygen concentration calculated by the method for calculating the blood oxygen concentration of the embodiment of the present disclosure is 95%.

[0076] In Example 3, the method for calculating blood oxygen concentration in the embodiment of the present disclosure uses the time point when the green light signal 300 reaches a peak as the time point when the red light signal 302 reaches a peak in step S200, and uses the time point when the infrared light signal 304 reaches a trough as the time point when the red light signal 302 reaches a trough in step S200. Therefore, the accuracy of the blood oxygen concentration calculated by the method for calculating blood oxygen concentration in step S202 of the embodiment of the present disclosure reaches 98%. In Example 4, the method for calculating blood oxygen concentration in the embodiment of the present disclosure does not use any auxiliary signal as the time point when the red light signal 302 reaches a peak, but uses the green light signal 300 as the time point when the red light signal 302 reaches a trough. Based on Figure 3 Since the trough of the green light signal 300 is not aligned with the trough of the red light signal 302 , the accuracy of the blood oxygen concentration calculated in step S202 of the method for calculating the blood oxygen concentration of the embodiment of the present disclosure is only 88%.

[0077] In Example 5, the method for calculating the blood oxygen concentration in the embodiment of the present disclosure does not use any auxiliary signal as the time point when the red light signal 302 reaches a peak, nor does it use any auxiliary signal as the time point when the red light signal 302 reaches a trough. In other words, the method for calculating the blood oxygen concentration in the embodiment of the present disclosure directly calculates the blood oxygen concentration based on the peaks and troughs of the red light signal 302, and the accuracy of the calculated blood oxygen concentration is 95%. In Example 6, the method for calculating the blood oxygen concentration in the embodiment of the present disclosure does not use any auxiliary signal as the time point when the red light signal 302 reaches a peak, but in step S200, uses the time point when the infrared light signal 304 reaches a trough as the time point when the red light signal 302 reaches a trough. Based on Figure 3 Since the trough of the infrared light signal 304 is aligned with the trough of the red light signal 302 , the accuracy of the blood oxygen concentration calculated in step S202 of the method for calculating the blood oxygen concentration of the embodiment of the present disclosure is 95%.

[0078] In Example 7, the method for calculating the blood oxygen concentration of the disclosed embodiment uses the time point when the infrared light signal 304 has a peak as the time point when the red light signal 302 has a peak in step S200, and uses the time point when the green light signal 300 has a trough as the time point when the red light signal 302 has a trough in step S200. Figure 3 , since the trough of the green light signal 300 is not aligned with the trough of the red light signal 302, the accuracy of the blood oxygen concentration calculated by the method for calculating the blood oxygen concentration of the embodiment of the present disclosure in step S202 is only 89%. In Example 8, the method for calculating the blood oxygen concentration of the embodiment of the present disclosure uses the time point when the infrared light signal 304 has a peak as the time point when the red light signal 302 has a peak in step S200, but does not use any auxiliary signal as the time point when the red light signal 302 has a trough, that is, directly using the time point when the red light signal 302 has a trough, so the accuracy of the blood oxygen concentration calculated by the method for calculating the blood oxygen concentration of the embodiment of the present disclosure is 93%.

[0079] In Example 9, the method for calculating blood oxygen concentration in the embodiment of the present disclosure uses the time point when the infrared light signal 304 has a peak as the time point when the red light signal 302 has a peak in step S200, and uses the time point when the infrared light signal 304 has a trough as the time point when the red light signal 302 has a trough in step S200. Figure 3 Since the peaks and troughs of the infrared light signal 304 are aligned with the peaks and troughs of the red light signal 302, the accuracy of the blood oxygen concentration calculated by the method for calculating the blood oxygen concentration of the embodiment of the present disclosure reaches 99%. According to Embodiments 1-9, the method for calculating the blood oxygen concentration of the embodiment of the present disclosure can use a light source with a better absorption rate (such as the green light signal 300 or the infrared light signal 304) to assist a light source with a poorer absorption rate (such as the red light signal 302).

[0080] Figure 4 FIG. 4 is a schematic diagram of calculating the alternating current (AC) value and the direct current (DC) value of the PPG signal 400 according to an embodiment of the present disclosure. Figure 4 As shown, in order to obtain a PPG signal (e.g. Figure 1 The method for calculating the blood oxygen concentration of the embodiment of the present disclosure first obtains the peak value (X) of the PPG signal 400 at the peak ①. P1 ,Y P1 ). Then, the method for calculating the blood oxygen concentration of the embodiment of the present disclosure obtains the trough value (X V1 ,Y V1 ), and the trough value (X V2 ,Y V2). Furthermore, the method for calculating blood oxygen concentration in the embodiment of the present disclosure calculates the trough value (X V1 ,Y V1 ) and the trough value (X V2 ,Y V2 In some embodiments, the method for calculating the blood oxygen concentration of the disclosed embodiment calculates the trough value (X V1 ,Y V1 ) to the trough value (X V2 ,Y V2 ) has a slope M.

[0081]

[0082] Reference Figure 4 As shown, since X'=X P1 , so Y' can be obtained by the slope M. Finally, the method for calculating the blood oxygen concentration in the embodiment of the present disclosure calculates the peak value (X P1 ,Y P1 ) and the average value (X', Y'), and obtain the AC value of the PPG signal 400, for example, AC value = Y P1 Next, the method for calculating the blood oxygen concentration of the embodiment of the present disclosure calculates a difference between the average value (X', Y') and the X-axis (ie, Y=0) to obtain a DC value of the PPG signal 400, for example, DC value=Y'.

[0083] In some embodiments, the method for calculating blood oxygen concentration in the disclosed embodiment calculates blood oxygen concentration (SpO2) in step S202 using Formula 2.

[0084]

[0085] In equation 2, R ac is the AC value of the red light signal 302, R dc is the DC value of the red light signal 302, IR ac is the alternating current (AC) value of the infrared light signal 304, IR dc is the direct current (DC) value of the infrared light signal 302 .

[0086] In some embodiments, the method for calculating blood oxygen concentration in the disclosed embodiment calculates the blood perfusion index using Formula 3. The blood perfusion index is an indicator used to observe blood flow.

[0087]

[0088] In equation 3, IR acis the alternating current (AC) value of the infrared light signal 304, IR dc is the direct current (DC) value of the infrared light signal 302 .

[0089] After completing step S200 and before executing step S202 , the method for calculating blood oxygen concentration in the embodiment of the present disclosure further filters the red light signal 302 to exclude outliers of the red light signal 302 . Figure 5A FIG. 5 is a schematic diagram of a first scenario of filtering a PPG signal 500 according to an embodiment of the present disclosure. Figure 5A As shown, the PPG signal 500 (e.g., the red light signal 302) of the embodiment of the present disclosure has a peak 502, a peak 504, a peak 506, and a peak 508. At the peak 502, the PPG signal 500 has an AC value AC1. At the peak 504, the PPG signal 500 has an AC value AC2. At the peak 506, the PPG signal 500 has an AC value AC3. At the peak 508, the PPG signal 500 has an AC value AC. When the AC value AC of the PPG signal 500 at the peak 508 is 1.5 times the average value (e.g., average value = (AC1 + AC2 + AC3) / 3) of the AC value AC1 at the peak 502, the AC value AC2 at the peak 504, and the AC value AC3 at the peak 506, the method for calculating the blood oxygen concentration of the embodiment of the present disclosure excludes the AC value AC at the peak 508. In other words, the method for calculating the blood oxygen concentration in the embodiment of the present disclosure does not use the alternating current value AC at the peak 508 as the basis for calculating the blood oxygen concentration in step S202 .

[0090] Figure 5B FIG. 5 is a schematic diagram of a second scenario of filtering a PPG signal 510 according to an embodiment of the present disclosure. Figure 5B As shown, the PPG signal 510 (e.g., the red light signal 302) of the embodiment of the present disclosure has peaks 512, 514, 516, and 518. At the peak 512, the PPG signal 510 has an AC value AC1. At the peak 514, the PPG signal 510 has an AC value AC2. At the peak 516, the PPG signal 510 has an AC value AC3. At the peak 518, the PPG signal 510 has an AC value AC. When the AC value AC of the PPG signal 510 at the peak 518 is 0.67 times the average value (e.g., average value = (AC1 + AC2 + AC3) / 3) of the AC value AC1 at the peak 512, the AC value AC2 at the peak 514, and the AC value AC3 at the peak 516, the method for calculating the blood oxygen concentration of the embodiment of the present disclosure excludes the AC value AC at the peak 518. In other words, the method for calculating the blood oxygen concentration in the embodiment of the present disclosure does not use the alternating current value AC at the peak 518 as the basis for calculating the blood oxygen concentration in step S202 .

[0091] Figure 5C FIG. 5 is a schematic diagram of scenario 3 of filtering the PPG signal 520 according to an embodiment of the present disclosure. Figure 5C As shown, the PPG signal 520 (e.g., the red light signal 302) of the embodiment of the present disclosure has a peak 522, a trough 524, and a trough 526. When the AC value of the PPG signal 520 at a point 528 between the peak 522 and the trough 524 is greater than the AC value (i.e., the peak value) of the PPG signal 520 at the peak 522, or the AC value of the PPG signal 520 at a point 530 between the peak 522 and the trough 526 is greater than the AC value of the PPG signal 520 at the peak 522, the method for calculating the blood oxygen concentration of the embodiment of the present disclosure excludes the AC value at point 528 or point 530 in the PPG signal 520. In other words, the method for calculating the blood oxygen concentration of the embodiment of the present disclosure does not use the AC value at point 528 or point 530 as the basis for calculating the blood oxygen concentration in step S202.

[0092] In some embodiments, Figure 5C As shown, when the AC value at the peak 522 (i.e., the peak value) is less than or equal to the AC value at the trough 524 or trough 526 (i.e., the trough value), the AC value at the peak 522 is excluded. In other words, the method for calculating the blood oxygen concentration in the embodiment of the present disclosure does not use the AC value at the peak 522 as the basis for calculating the blood oxygen concentration in step S202.

[0093] The present disclosure also discloses a computer program product for an electronic device having a processor. In some embodiments, the electronic device executes a peak-to-valley alignment instruction and a calculation instruction. The peak-to-valley alignment instruction enables the processor to execute Figure 2 The computing instruction enables the processor to execute Figure 2 After executing the peak-to-valley alignment instruction and before executing the calculation instruction, the electronic device of the present embodiment further executes a filtering instruction. The filtering instruction causes the processor to process the red light signal 302 in the form of Figure 5A Scene 1: Figure 5B Scene 2, and Figure 5C The outlier of the red light signal 302 is eliminated by filtering in the manner of scenario 3.

[0094] In some embodiments, the electronic device of the disclosed embodiment further executes a peak alignment instruction, a valley alignment instruction, a valley average instruction, and an AC value calculation instruction. The peak alignment instruction enables the processor of the electronic device to obtain a peak value (for example, Figure 4 The peak value (X) of the PPG signal 400 at the peak ① P1 ,Y P1)). The valley alignment instruction enables the processor to obtain a first valley value and a second valley value when the red light signal has two valleys adjacent to the first peak (for example, Figure 4 The trough value (X V1 ,Y V1 ), and the trough value (X V2 ,Y V2 )). The valley average instruction causes the processor to calculate an average of the first valley value and the second valley value (for example, Figure 4 The trough value (X) of the PPG signal 400 of trough ② is calculated V1 ,Y V1 ) and the trough value (X V2 ,Y V2 The AC value calculation instruction enables the processor to calculate a difference between the peak value and the average value to obtain an AC value of the red light signal (for example, Figure 4 Calculate the peak value (X P1 ,Y P1 ) and the average value (X', Y') to obtain the alternating current (AC) value of the PPG signal 400).

[0095] The present disclosure also discloses an electronic device. Figure 6 6 is a block diagram of an electronic device 600 according to an embodiment of the present disclosure. In some embodiments, the electronic device 600 is an ear-hook type electronic device. The electronic device 600 includes a light emitting unit 604, a light sensor 606, and a processor 602. The light emitting unit 604 is used to emit a red light signal 610 and at least one non-red light signal 612 to the skin 620. In some embodiments, the light emitting unit 604 includes a green light LED, a red light LED, and an infrared light LED (not shown), but the embodiments of the present disclosure are not limited thereto. The light sensor 606 is used to receive a red light signal 610' (e.g., a red light signal 302) and at least one non-red light signal 612' (e.g., a green light signal 300 and / or an infrared light signal 304) reflected from the skin 620. In some embodiments, the light sensor 606 transmits the received light signal to the processor 602 in digital form. The processor 602 then executes Figure 2 In some embodiments, after the processor 602 completes step S200 and before executing step S202, the processor 602 further processes the reflected red light signal 610′ with Figure 5A Scene 1: Figure 5B Scene 2, and Figure 5C The method of scene 3 is used to filter out outliers of the reflected red light signal 610'.

[0096] In some embodiments, the processor 602 further includes: obtaining a peak value (eg, Figure 4 The peak value (X) of the PPG signal 400 at the peak ① P1 ,Y P1 )); obtain a first trough value and a second trough value when the red light signal 610' occurs at two troughs adjacent to the first peak (for example, Figure 4 The trough value (X V1 ,Y V1 ), and the trough value (X V2 ,Y V2 )); calculate an average value of the first valley value and the second valley value (for example, Figure 4 The trough value (X) of the PPG signal 400 of trough ② is calculated V1 ,Y V1 ) and the trough value (X V2 ,Y V2 ) an average value (X', Y'); and calculate a difference between the peak value and the average value to obtain an AC value of the red light signal (for example, Figure 4 Calculate the peak value (X P1 ,Y P1 ) and the average value (X', Y') to obtain the alternating current (AC) value of the PPG signal 400).

[0097] In some embodiments, the processor 602 of the electronic device 600 of the disclosed embodiment further performs a wearing stability judgment before executing step S200 to detect whether the user is in a stationary state. If the user is not in a stationary state (for example, the user's movement is too large), the processor 602 will not execute step S200. In some embodiments, the processor 602 of the electronic device 600 of the disclosed embodiment performs a dynamic timing warping (DTW). Simply put, the processor 602 first receives a template waveform of a PPG signal and uses the template waveform as a reference. Afterwards, when the processor 602 receives subsequent PPG signals from the light sensor 606, the processor 602 will match the waveform of each subsequent PPG signal with the template waveform to determine whether each PPG signal is a good signal.

[0098] Although the embodiments of the present invention are described above, it should be understood that what is presented above is only an example, not a limitation. Many changes to the above exemplary embodiments can be implemented without violating the concept and scope of the invention according to this embodiment. Therefore, the breadth and scope of the present invention should not be limited by the embodiments described above. More specifically, the scope of the present invention should be defined by the following claims and their equivalents.

[0099] Although the invention has been illustrated and described above with reference to one or more implementations, equivalent changes and modifications will occur to others familiar with the art based on the above specification and drawings. In addition, although a particular feature of an embodiment of the invention has been demonstrated with reference to one of the multiple implementations, the feature may be combined with one or more other features as may be desirable and useful for any known or particular application.

[0100] Unless otherwise defined, all terms (including technical or scientific terms) used herein are generally understood by those having ordinary skill in the art to which the above invention belongs. We should further understand that the above terms, as defined in commonly used dictionaries, should be interpreted as having the same meaning in the context of the relevant art. Unless otherwise explicitly defined herein, the above terms are not to be interpreted as having an idealized or overly formal meaning.

Claims

1. A method for calculating blood oxygen concentration, comprising: An extreme value point of a non-red light signal is defined as an extreme value point of a red light signal, so as to align the non-red light signal with the red light signal; as well as Calculate the blood oxygen concentration based on the extreme value point of the red light signal; The time point at which the non-red light signal has a peak is the time point at which the green light signal has a peak, and the time point at which the non-red light signal has a trough is the time point at which the infrared light signal has a trough.

2. The method of claim 1, further comprising: The red light signal is filtered to exclude outliers of the red light signal.

3. The method of claim 2, further comprising: Obtaining a peak value when the red light signal has a first peak; Obtaining a first trough value and a second trough value when the red light signal has two troughs adjacent to the first peak; Calculating an average value of the first valley value and the second valley value; and A difference between the peak value and the average value is calculated to obtain an AC value of the red light signal.

4. The method of claim 3, wherein: The red light signal is filtered, including: Excluding the peak value, the peak value is correspondingly smaller than the first trough value or the second trough value.

5. The method of claim 3, wherein: The red light signal is filtered, including: excluding an intermediate value, the intermediate value corresponding to the red light signal being between the first wave peak and one of the two wave valleys adjacent to the first wave peak, and the intermediate value being greater than the wave peak value.

6. The method of claim 3, wherein: The red light signal is filtered, including: Excluding the AC value, the AC value corresponds to the AC value at the first peak, and the AC value is more than 1.5 times an average AC value of three peaks before the first peak in the red light signal.

7. The method of claim 3, wherein: The red light signal is filtered, including: excluding the AC value, which corresponds to the AC value at the first peak, and the AC value is less than 0.67 times an average AC value of three peaks before the first peak in the red light signal.

8. The method of claim 3, further comprising: Obtaining a DC value of the red light signal according to the average value of the first wave valley value and the second wave valley value; as well as The blood oxygen concentration is calculated according to the AC value and the DC value of the red light signal.

9. The method of claim 1, wherein: The green light signal has a dicrotic wave, while the red light signal and the infrared light signal do not have a dicrotic wave.

10. The method of claim 2, wherein: The red light signal and the non-red light signal are photoplethysmography signals.

11. A computer program product, adapted to be loaded into an electronic device having a processor and to execute a method for calculating blood oxygen concentration, the computer program product comprising: a peak-to-valley alignment instruction, causing the processor to define an extreme point of a non-red light signal as an extreme point of a red light signal, so as to align the non-red light signal with the red light signal; a calculation instruction, causing the processor to calculate the blood oxygen concentration according to the extreme value point of the red light signal; The time point at which the non-red light signal has a peak is the time point at which the green light signal has a peak, and the time point at which the non-red light signal has a trough is the time point at which the infrared light signal has a trough.

12. The computer program product of claim 11, wherein the computer program product further comprises: A filtering instruction causes the processor to filter the red light signal to exclude outliers of the red light signal.

13. The computer program product of claim 11, wherein the computer program product further comprises: A peak alignment instruction enables the processor to obtain a peak value when the red light signal has a first peak; A valley alignment instruction enables the processor to obtain a first valley value and a second valley value when the red light signal has two valleys adjacent to the first peak; a valley average instruction, causing the processor to calculate an average value of the first valley value and the second valley value; and An AC value calculation instruction enables the processor to calculate a difference between the peak value and the average value to obtain an AC value of the red light signal.

14. An electronic device comprising: a light emitting unit for emitting a red light signal and a non-red light signal to the skin; a light sensor for receiving the red light signal and the non-red light signal reflected from the skin; A processor for executing: The extreme value point of the non-red light signal is defined as the extreme value point of the red light signal, so as to align the non-red light signal with the red light signal; Calculate the blood oxygen concentration based on the extreme value point of the red light signal; The time point at which the non-red light signal has a peak is the time point at which the green light signal has a peak, and the time point at which the non-red light signal has a trough is the time point at which the infrared light signal has a trough.

15. The electronic device as claimed in claim 14, wherein: The processor also performs: The red light signal is filtered to exclude outliers of the red light signal.

16. The electronic device according to claim 14, wherein: The processor also performs: Obtaining a peak value when the red light signal has a first peak; Obtaining a first trough value and a second trough value when the red light signal has two troughs adjacent to the first peak; Calculating an average value of the first valley value and the second valley value; and A difference between the peak value and the average value is calculated to obtain an AC value of the red light signal.

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