Optical physiological signal evaluation system and method and associated wearable device

Abstract

The present application provides an optical physiological signal evaluation system and method and a related wearable device. The method comprises: obtaining a first set of signal data in time domain using PPG; converting the first set of signal data into a second set of signal data in frequency domain using FFT; calculating a signal quality index from the second set of signal data using a first algorithm to represent a quality level of the second set of signal data; performing a filter smoothing process on the second set of signal data using a second algorithm to generate a third set of signal data in frequency domain; calculating a noise ratio index from the second set of signal data and the third set of signal data using a third algorithm to represent a noise level of the second set of signal data; and determining whether the signal quality index is higher than a lower limit value of the signal quality index and whether the noise ratio index is lower than an upper limit value of the noise ratio index. In this way, a user can easily check whether a device for detecting optical physiological signals worn by the user is properly worn.

Description

Technical Field

[0001] This invention relates to evaluation systems and methods, and related wearable devices, particularly to evaluation systems and methods for optical physiological signals, and related wearable devices. Background Technology

[0002] As physiological signal sensing technology matures, wearable products are becoming increasingly common. Physiological signal sensing can be achieved using optical or ultrasonic sensing architectures. Optical sensing is currently one of the most important development directions in physiological signal sensing technology. For example, pulse, blood pressure, and blood oxygen saturation monitoring in wearable products utilizes optical photoplethysmography (PPG) to analyze physiological signals.

[0003] However, abnormal wearing conditions (too tight, too loose, not worn, etc.) can affect the accuracy and reliability of detected physiological signals.

[0004] To ensure the accuracy and reliability of physiological signals, this invention uses algorithms to analyze and evaluate the detected physiological signals. Based on the evaluation results, it determines whether the wearer is wearing the wearable device correctly and whether adjustments are necessary, thus ensuring accurate and reliable physiological signals are detected. Summary of the Invention

[0005] To effectively address the aforementioned problems, one embodiment of the present invention proposes a method for evaluating optical physiological signals, comprising: acquiring a first set of signal data in the time domain using photovolume change mapping (PPG); converting the first set of signal data in the time domain into a second set of signal data in the frequency domain using Fast Fourier Transform (FFT); calculating a signal quality index from the second set of signal data using a first algorithm to represent the quality level of the second set of signal data; filtering and smoothing the second set of signal data using a second algorithm to generate a third set of signal data in the frequency domain; calculating a noise ratio index from the second set of signal data and the third set of signal data using a third algorithm to represent the noise level of the second set of signal data; and confirming whether the signal quality index is higher than a lower limit of the signal quality index and whether the noise ratio index is lower than an upper limit of the noise ratio index.

[0006] According to an embodiment of the present invention, preferably, the signal quality index is represented by SQI, then:

[0007]

[0008] Where A1 is the integral value of the second group of signal data within the first frequency range (f1–α) to (f1+α), and A2 is the integral value of the second group of signal data within the second frequency range ((f2–α) to (f2+α). T I(f) is the integral value of the second group of signal data within the third frequency range (0–10.0 Hz), I(f) is the data value of the second group of signal data corresponding to frequency f and varies with frequency f, α is the standard deviation value, f represents the frequency, f1 is the first frequency value corresponding to the maximum value I1 of the second group of signal data in the frequency range of 0.5–4.0 Hz, and f2 is the second frequency value corresponding to the maximum value I2 of the second group of signal data in the frequency range of f1–3f1.

[0009] The noise ratio index is expressed as NSRI, then:

[0010]

[0011] Where, N T It is the total noise value, which is the sum of the absolute values ​​of the differences between the second group of signal data and the corresponding third group of signal data, P. T It is the sum of path values, which is the sum of the absolute values ​​of the differences between adjacent signal data in the third group of signal data. I(i) is the i-th signal data value in the second group of signal data, I'(i) is the i-th signal data value in the third group of signal data, I'(i+1) is the (i+1)-th signal data value in the third group of signal data, and n is any positive integer.

[0012] According to an embodiment of the present invention, preferably, the lower limit of the signal quality index is 0.18, the upper limit of the noise ratio index is 3.00, and the standard deviation value α is 0.40 Hz.

[0013] One embodiment of the present invention provides an evaluation system for optical physiological signals, comprising: a signal processing unit configured to perform the evaluation method for optical physiological signals as described in the preceding paragraphs.

[0014] According to an embodiment of the present invention, preferably, the optical physiological signal evaluation system further includes: a light-emitting unit configured to emit detection light to illuminate a skin area of ​​a subject, wherein the detection light is partially reflected by the skin area to form reflected light, and / or partially transmitted by the skin area to form transmitted light; and a photosensitive unit configured to receive the reflected light and / or the transmitted light to generate a first set of signal data regarding the reflected light and / or the transmitted light in the time domain.

[0015] According to an embodiment of the present invention, preferably, the light-emitting unit includes at least one of a light-emitting diode, a micro light-emitting diode, and an organic light-emitting diode, and the detection light includes at least one of blue light, green light, red light, and infrared light.

[0016] According to an embodiment of the present invention, preferably, the photosensitive unit is at least one of a photodiode image sensor, a complementary metal-oxide-semiconductor image sensor, and a charge-coupled device image sensor.

[0017] According to an embodiment of the present invention, preferably, the evaluation system for optical physiological signals further includes: a display unit for displaying comparison results of the evaluation methods for optical physiological signals.

[0018] One embodiment of the present invention provides a wearable device for detecting optical physiological signals, comprising an evaluation system for the optical physiological signals as described in the preceding paragraphs.

[0019] According to an embodiment of the present invention, preferably, the display unit is used to display a message indicating whether the wearable device is in normal condition based on the comparison result of the evaluation method of the optical physiological signal.

[0020] Users can easily check whether their wearable device for detecting optical physiological signals is worn properly using this invention.

[0021] To enable those skilled in the art to understand the purpose, features and effects of the present invention, the present invention will now be described in detail through the following specific embodiments and in conjunction with the accompanying drawings. Attached Figure Description

[0022] Figure 1 A graph of intensity signal versus time in the time domain, as illustrated in an embodiment of the present invention.

[0023] Figure 2 A graph of intensity signal versus frequency in the frequency domain, as illustrated in an embodiment of the present invention.

[0024] Figure 3 This is a block diagram of an optical physiological signal evaluation system according to an embodiment of the present invention;

[0025] Figure 4 This is a flowchart of an optical physiological signal evaluation method according to an embodiment of the present invention.

[0026] Explanation of reference numerals in the attached figures:

[0027] 100 - Optical physiological signal evaluation system, 110 - Light emission unit, 120 - Photosensitive unit, 130 - Signal processing unit, S10 - Step, S20 - Step, S30 - Step, S40 - Step, S50 - Step, S60 - Step. Detailed Implementation

[0028] PPG (Photodetector Photogrammetry) is a non-invasive method for detecting changes in blood volume in living tissue using photoelectric techniques. When a light beam of a certain wavelength shines on the skin surface of the fingertip, the contraction and expansion of blood vessels due to the heartbeat affect the transmission (e.g., light passing through the fingertip in transmissive PPG) or the reflection (e.g., light reflected from the wrist or near the finger surface in reflective PPG). When light passes through skin tissue (e.g., the skin tissue of the finger, including subcutaneous tissue, microvessels, etc.) and is then reflected and / or transmitted to the photosensitive component, the light intensity will attenuate and change over time because the blood volume and blood oxygen saturation in the microvessels change with the pulse. By analyzing the changes in the transmitted or reflected light signals using corresponding algorithms, physiological data such as pulse, blood pressure, and / or blood oxygen saturation can be obtained. Details of related prior art techniques will not be elaborated here.

[0029] Optical photoplethysmography can be applied to wearable devices; however, abnormal wearing conditions (too tight, too loose, not worn, etc.) can affect the accuracy and reliability of the detected physiological signals.

[0030] To ensure the accuracy and reliability of physiological signals, this invention uses algorithms to analyze and evaluate the detected physiological signals. Based on the evaluation results, it determines whether the wearer is wearing the wearable device correctly and whether adjustments are needed, thus ensuring accurate and reliable physiological signals are detected.

[0031] The technical content of the present invention will be described below with reference to the accompanying drawings.

[0032] Figure 1 A graph of intensity signal versus time in the time domain, as illustrated in an embodiment of the present invention. Figure 2 A graph of intensity signal versus frequency in the frequency domain, as illustrated in an embodiment of the present invention; and Figure 3 This is a block diagram of an optical physiological signal evaluation system according to an embodiment of the present invention.

[0033] Please refer to Figure 1 According to embodiments of the present invention, the signal of reflected or transmitted light reflected or transmitted through the skin tissue of the subject's hand (e.g., the skin tissue of the fingers, wrist, etc.) using photoplethysmography can be used as follows: Figure 1 As shown, where, Figure 1 The graph shown is a curve of intensity signal versus time in the time domain, which is regarded as the first set of signal data. The horizontal axis is time and the vertical axis is intensity. The unit of intensity can be any unit (relative quantity comparison) or light intensity unit (e.g., light intensity, illuminance, etc.), but the present invention is not limited thereto.

[0034] Please refer to Figure 2 According to embodiments of the present invention, Figure 1 The plotted intensity signal versus time curve in the time domain can be transformed using a Fast Fourier Transform (FFT) as shown below. Figure 2 The plotted intensity signal versus frequency curve in the frequency domain is considered as the second set of signal data, where the horizontal axis represents frequency and the vertical axis represents intensity. The unit of intensity can be any unit (relative quantity comparison) or number of times (counting), but the present invention is not limited thereto.

[0035] like Figure 2 As shown, under normal circumstances, the second set of signal data in the frequency domain can have a maximum peak value in the range of 0.5 to 4.0 Hz, corresponding to the percussion wave frequency of the heart rhythm; and after the maximum peak value, there will be a high peak value, corresponding to the dicrotic wave frequency of the heart rhythm. The main focus of this invention is to analyze the quality and noise level of the signal data from these two peaks in order to evaluate and determine whether the detected data is reliable, and thus determine whether the wearable device associated with it is worn properly.

[0036] Please refer to Figure 3 According to an embodiment of the present invention, the optical physiological signal evaluation system 100 may include a light-emitting unit 110, a photosensitive unit 120, and a signal processing unit 130, wherein the light-emitting unit 110 and the photosensitive unit 120 may be electrically connected to the signal processing unit 130. The optical physiological signal evaluation system 100 of the present invention may also be an optical physiological signal detection system; that is, the evaluation function is integrated into the optical physiological signal detection system and executed by the signal processing unit 130.

[0037] The light-emitting unit 110 of the present invention may include one or more light-emitting components for emitting detection light to illuminate a subject's skin area (such as the skin area of ​​the fingers, wrist, arm, etc.), such that the detection light is reflected and / or transmitted to form reflected light and / or transmitted light. The light-emitting component may be at least one of a light-emitting diode, a micro light-emitting diode, and an organic light-emitting diode, but the present invention is not limited thereto, and the user may choose any type of light-emitting component according to requirements. The detection light may be at least one of blue light, green light, red light, and infrared light, but the present invention is not limited thereto, and the user may choose any wavelength range of the detection light according to requirements.

[0038] The photosensitive unit 120 of the present invention may include one or more photosensitive components for performing the step of acquiring data: receiving reflected and / or transmitted light reflected and / or transmitted by a skin site to generate intensity signals of the reflected and / or transmitted light in the time domain, i.e., a first set of signal data. For example, the photosensitive unit 120 may include one photosensitive component for receiving reflected or transmitted light reflected or transmitted by a skin site. For example, the photosensitive unit 120 may include multiple photosensitive components disposed at different locations to simultaneously receive reflected and transmitted light reflected and transmitted by a skin site. The photosensitive component may be at least one of a photodiode image sensor, a complementary metal-oxide-semiconductor image sensor, and a charge-coupled device image sensor, but the present invention is not limited thereto, and the user may choose any type of photosensitive component according to requirements.

[0039] The signal processing unit 130 of the present invention may include a processor and memory. After receiving a signal generated by the photosensitive unit 120, it processes and analyzes a first set of signal data in the time domain. The signal processing unit 130 of the present invention can generate, process, and analyze a first set of signal data in the time domain after receiving a signal generated by the photosensitive unit 120. The memory may store algorithms for performing calculations related to photovolume change mapping and for analyzing and judging signal evaluation. The signal processing unit 130 may perform the step of converting data: converting the first set of signal data in the time domain generated by the photosensitive unit 120 into an intensity signal in the frequency domain, i.e., a second set of signal data, using a fast Fourier transform.

[0040] According to an embodiment of the present invention, the signal processing unit 130 can perform the step of calculating a signal quality index: using a first algorithm, calculating a signal quality index from a second set of signal data to represent the quality level of the second set of signal data. The signal quality index can be represented by SQI, then:

[0041]

[0042] Where A1 is the integral value of the second set of signal data within the first frequency range (f1–α) to (f1+α), and A2 is the integral value of the second set of signal data within the second frequency range (f2–α) to (f2+α). T I(f) is the integral value of the second set of signal data within the third frequency range (0-10.0Hz). I(f) is the data value of the second set of signal data corresponding to frequency f and varies with frequency f. α is the standard deviation value, f represents the frequency, f1 is the first frequency value corresponding to the maximum value I1 of the second set of signal data in the frequency range of 0.5-4.0Hz, corresponding to the main wave frequency of the heart rhythm, and f2 is the second frequency value corresponding to the maximum value I2 of the second set of signal data in the frequency range of f1-3f1, corresponding to the dicrotic wave frequency of the heart rhythm.

[0043] The standard deviation value α of this invention can be arbitrarily adjusted according to the requirements of accuracy or convenience in signal evaluation. For example, the standard deviation value α can be 0.2, 0.3, 0.4, 0.5 or 0.6 Hz, but this invention is not limited thereto.

[0044] According to an embodiment of the present invention, the signal processing unit 130 may perform the step of filtering and smoothing data: using a second algorithm to perform filtering and smoothing processing on the second set of signal data to generate a third set of signal data in the frequency domain.

[0045] For example, the filtering and smoothing process of the present invention can be processed using algorithms such as the least squares method of linear regression and convolution smoothing method, but the present invention is not limited to these.

[0046] According to an embodiment of the present invention, the signal processing unit 130 can perform the step of calculating the noise ratio index: using a third algorithm, calculating the noise ratio index from the second set of signal data and the third set of signal data to represent the noise level of the second set of signal data in the frequency domain. The noise ratio index can be represented by NSRI, then:

[0047]

[0048] Where, N T It is the total noise value, which is the sum of the absolute values ​​of the differences between the second group of signal data and the corresponding third group of signal data, P. TThe path value summation is the sum of the absolute values ​​of the differences between adjacent signal data in the third group of signal data. I(i) is the i-th signal data value in the second group of signal data, I'(i) is the i-th signal data value in the third group of signal data, I'(i+1) is the (i+1)-th signal data value in the third group of signal data, and n is any positive integer. For example, the step of calculating the noise ratio exponent is performed for signal data in the third frequency range (0–10.0 Hz), but the invention is not limited thereto.

[0049] According to an embodiment of the present invention, the signal processing unit 130 can perform the following steps to analyze data: confirming whether the signal quality index is higher than the lower limit of the signal quality index, and confirming whether the noise ratio index is lower than the upper limit of the noise ratio index.

[0050] The lower limit of the signal quality index and the upper limit of the noise ratio index of this invention can be arbitrarily adjusted according to the needs of accuracy or convenience in signal evaluation. For example, the lower limit of the signal quality index can be 0.10, 0.14, 0.18, 0.22, or 0.24, and the upper limit of the noise ratio index can be 2.00, 2.50, 3.00, 3.50, or 4.00, but this invention is not limited to these. For example, the lower limit of the signal quality index can be set to 0.18, and the upper limit of the noise ratio index can be set to 3.00. If the signal quality index is lower than 0.18 and / or the noise ratio index is higher than 3.00, the wearing condition can be judged as abnormal; otherwise, the wearing condition can be judged as normal.

[0051] According to an embodiment of the present invention, the optical physiological signal evaluation system 100 of the present invention may further include a display unit for displaying the comparison results of the evaluation methods of optical physiological signals.

[0052] Next, we will describe the method of using the optical physiological signal evaluation system of the present invention.

[0053] Please refer to Figure 4According to an embodiment of the present invention, the method for evaluating optical physiological signals includes the following steps. First, step S10: using photovolume change mapping (PPG), a first set of signal data in the time domain is acquired. Step S20: using Fast Fourier Transform (FFT), the first set of signal data in the time domain is converted into a second set of signal data in the frequency domain. Step S30: using a first algorithm, a signal quality index is calculated from the second set of signal data to represent the quality level of the second set of signal data. Step S40: using a second algorithm, the second set of signal data is filtered and smoothed to generate a third set of signal data in the frequency domain. Step S50: using a third algorithm, a noise ratio index is calculated from the second set of signal data and the third set of signal data to represent the noise level of the second set of signal data. Finally, step S60: confirming whether the signal quality index is higher than the lower limit of the signal quality index and confirming whether the noise ratio index is lower than the upper limit of the noise ratio index. The relevant details are the same as those previously described in the description of the optical physiological signal evaluation system 100 of the present invention, and will not be repeated here.

[0054] The optical physiological signal evaluation system and method of the present invention can be implemented by a wearable device. For example, the optical physiological signal evaluation system of the present invention can be included in a smart ring, smart bracelet, smart earring, etc., but the present invention is not limited thereto. Any part of the subject's skin can be the detection site of the corresponding wearable device containing the optical physiological signal evaluation system of the present invention.

[0055] According to embodiments of the present invention, steps S30 to S60 of the optical physiological signal method of the present invention described above can be performed by an evaluation unit of an external device other than the wearable device or the optical physiological signal detection system of the present invention, for example, by an external computer. Such a configuration can be applied to optimize custom wearable devices, selecting or customizing non-adjustable wearable devices that match the wearing area of ​​the subject or user, such as non-adjustable rings, bracelets, watches, etc.

[0056] The above describes the implementation of the present invention through specific embodiments. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification.

[0057] The above description is only a preferred embodiment of the present invention and is not intended to limit the scope of the present invention; any equivalent changes or modifications made without departing from the spirit disclosed in the present invention should be included within the scope of patent protection of this application.

Claims

1. A method for evaluating optical physiological signals, characterized in that, include: The first set of signal data in the time domain was acquired using photovolume change plethysmography (PPG). The first set of signal data in the time domain is converted into the second set of signal data in the frequency domain using the Fast Fourier Transform (FFT) method. Using the first algorithm, a signal quality index is calculated from the second set of signal data to represent the quality level of the second set of signal data; The second algorithm is used to filter and smooth the second set of signal data to generate a third set of signal data in the frequency domain. Using a third algorithm, a noise ratio index is calculated from the second set of signal data and the third set of signal data to represent the noise level of the second set of signal data; as well as Confirm whether the signal quality index is higher than the lower limit of the signal quality index, and confirm whether the noise ratio index is lower than the upper limit of the noise ratio index.

2. The method for evaluating optical physiological signals as described in claim 1, characterized in that: The signal quality index is represented by SQI, then: Where A1 is the integral value of the second group of signal data within the first frequency range (f1–α) to (f1+α), and A2 is the integral value of the second group of signal data within the second frequency range (f2–α) to (f2+α). T I(f) is the integral value of the second group of signal data within the third frequency range (0–10.0 Hz), I(f) is the data value of the second group of signal data corresponding to frequency f and varies with frequency f, α is the standard deviation value, f represents the frequency, f1 is the first frequency value corresponding to the maximum value I1 of the second group of signal data in the frequency range of 0.5–4.0 Hz, and f2 is the second frequency value corresponding to the maximum value I2 of the second group of signal data in the frequency range of f1–3f1. The noise ratio index is expressed as NSRI, then: Where, N T It is the total noise value, which is the sum of the absolute values ​​of the differences between the second group of signal data and the corresponding third group of signal data, P. T It is the sum of path values, which is the sum of the absolute values ​​of the differences between adjacent signal data in the third group of signal data. I(i) is the i-th signal data value in the second group of signal data, I'(i) is the i-th signal data value in the third group of signal data, I'(i+1) is the (i+1)-th signal data value in the third group of signal data, and n is any positive integer.

3. The method for evaluating optical physiological signals as described in claim 2, characterized in that, The lower limit of the signal quality index is 0.18, the upper limit of the noise ratio index is 3.00, and the standard deviation α is 0.40 Hz.

4. An optical physiological signal evaluation system, characterized in that, include: The signal processing unit is configured to perform the evaluation method for optical physiological signals as described in any one of claims 1 to 3.

5. The optical physiological signal evaluation system as described in claim 4, characterized in that, The optical physiological signal evaluation system also includes: A light-emitting unit is configured to emit detection light to illuminate a skin area of ​​a subject, wherein the detection light is partially reflected by the skin area to form reflected light, and / or partially transmitted by the skin area to form transmitted light; and A photosensitive unit is configured to receive the reflected light and / or the transmitted light to generate the first set of signal data regarding the reflected light and / or the transmitted light in the time domain.

6. The evaluation system for optical physiological signals as described in claim 5, characterized in that: The light-emitting unit includes at least one of light-emitting diodes, micro light-emitting diodes, and organic light-emitting diodes, and The detection light includes at least one of blue light, green light, red light, and infrared light.

7. The optical physiological signal evaluation system as described in claim 5, characterized in that, The photosensitive unit includes at least one of a photodiode image sensor, a complementary metal-oxide-semiconductor image sensor, and a charge-coupled device image sensor.

8. The optical physiological signal evaluation system as described in claim 5, characterized in that, The optical physiological signal evaluation system also includes: The display unit is used to display the comparison results of the evaluation methods for the optical physiological signals.

9. A wearable device for detecting optical physiological signals, characterized in that, An evaluation system for optical physiological signals as described in any one of claims 4 to 8.

10. The wearable device for detecting optical physiological signals as described in claim 9, characterized in that, The display unit of the optical physiological signal evaluation system is used to display a message indicating whether the wearable device is in normal condition based on the comparison results of the optical physiological signal evaluation method.

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