Method and apparatus for optical signal detection and processing

Abstract

The present application provides a kind of optical signal detection and processing method and device, and the physiological signal of optical detection is obtained by detecting blood volume change in human tissue blood vessel through photoelectric sensor in the working process of optical equipment, it is characterized in that, the method includes the following steps in the computing module of the optical equipment: set a data buffer zone, the data buffer zone can store the physiological signal of optical detection of at least 3 predetermined time units;Acquisition and calculation step, the each DC component of the physiological signal of optical detection collected is stored in the data buffer zone, the variance of the value of the DC component is calculated, and the first waveform reference index value is obtained;Comparison step;The first waveform reference index value is compared with the pre-stored reference index value range;Determination step, if the first waveform reference index value is greater than the maximum value of the reference index value, then the signal of the output device is off;If the first waveform reference index value is not greater than the maximum value of the reference index value, continue to collect new physiological signal of optical detection, then the acquisition and calculation step is executed.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of human health monitoring devices, and more particularly, to an optical signal detection and processing method and device. BACKGROUND

[0002] Oxygen saturation (SpO2) and heart rate (HR) are two very important human parameters, and real-time detection of them can help people understand their own physical condition at any time. To some extent, it can avoid the occurrence of accidents caused by cardiovascular diseases and insufficient cardiopulmonary function and other factors. In particular, real-time monitoring of oxygen saturation has become an important indicator for judging the oxygen supply condition of the human body and whether the respiratory system and circulatory system of the human body are normal. By using optical detection of physiological signals such as PPG signals, photoplethysmographic (PPG) signals can be used to monitor SpO2. The optical detection of physiological signals contains a lot of human physiological information such as heart rate and blood oxygen, and the use of photoplethysmographic signals to extract heart rate and blood oxygen has been widely applied. For the sake of convenience, the popularity of small and portable physiological signal optical devices with built-in batteries or dry batteries is becoming more and more widespread. For example, a finger sleeve type photoelectric sensor can be used to measure oxygen saturation. When measuring, the sensor only needs to be worn on the finger, and the finger is used as a transparent container containing hemoglobin. Red light with a wavelength of 660 nm and near-infrared light with a wavelength of 940 nm are used as incident light sources, the light transmission intensity through the tissue bed is determined, and the hemoglobin concentration and oxygen saturation are calculated. The instrument can display the oxygen saturation of the human body, providing a continuous non-invasive blood oxygen measurement instrument for clinical use.

[0003] The portable optical device generally uses a battery, in order to ensure the endurance time, the device will enter the sleep or low power consumption state when the device is detached from the finger. At present, the basic scheme for judging the detachment of human tissue for the optical device such as SpO2 mainly includes the physiological signal feature judgment scheme and the scheme for monitoring the light intensity to judge the detachment state. However, in the two schemes, either the low-power operation unit of the device needs to perform complex calculation with high energy consumption, occupying the valuable operation resources of the portable device; or the light emitting device needs to be kept emitting light to make the judgment, which still consumes a large amount of power. For the scheme of monitoring the light intensity, the optical device still emits light normally in the detachment state, and only the light intensity is reduced. The LED of the scheme needs to be in the light emitting state all the time, which is not suitable for low-power products such as battery-powered products. For the scheme of using physiological signal analysis, it is also not suitable for low-power products, because a large amount of data calculation is involved in the physiological analysis process, and the low-power MCU is not suitable for a large amount of data calculation, which not only wastes operation time, but also consumes a certain amount of power. In addition, for the scheme of monitoring the light intensity, if the receiver is intentionally shielded, the device may incorrectly identify that the finger is inserted and start monitoring work, thereby affecting the accuracy of the monitoring result. SUMMARY

[0004] In order to solve the deficiencies and defects in the prior art, the present disclosure proposes a detachment detection method for SpO2 optical device.

[0005] In an aspect according to the present disclosure, the optical detection physiological signal is obtained by detecting the blood volume change in the human tissue blood vessel through the photoelectric sensor during the operation of the optical device, and the method comprises the following steps performed in the calculation module of the optical device:

[0006] A data buffer is set, which can store the optical detection physiological signal of at least 3 predetermined time units;

[0007] In the collecting and calculating step, each DC component of the collected optical detection physiological signal is stored in the data buffer, and the variance of the value of the DC component is calculated to obtain a first waveform reference index value;

[0008] In the comparison step, the first waveform reference index value is compared with the pre-stored reference index value range;

[0009] In the determination step, if the first waveform reference index value is greater than the maximum value of the reference index value, a signal of device detachment is output; if the first waveform reference index value is not greater than the maximum value of the reference index value, new optical detection physiological signal is collected, and then the collecting and calculating step is performed.

[0010] Preferably, in the falling-off detection method according to the present disclosure, the method can further comprise the following steps performed in the computing module of the optical device: setting a ring buffer; filtering the optical detected physiological signal, calculating the peak-to-peak value of the waveform of the AC component in the optical detected physiological signal in a predetermined time unit; then caching the obtained peak-to-peak value in the ring buffer; calculating the variance of the data in the ring buffer, taking the variance as a second reference index value; comparing the second reference index value with the bias reference value, if the second reference index value is greater than the bias reference value; then outputting a signal of device falling-off.

[0011] In one specific mode of the falling-off detection method according to the present disclosure, the reference index value ranges from 100 to 3000; and the second reference index value is 3000.

[0012] Preferably, in the falling-off detection method according to the present disclosure, each predetermined time unit can be the same and greater than 1.5 seconds.

[0013] According to another aspect of the present disclosure, an optical signal detection and processing device is provided, wherein the computing module of the device runs the aforementioned optical signal detection and processing method.

[0014] An energy-saving method for a Spo2 optical device is also provided, wherein the aforementioned falling-off detection method is applied in the computing module of the optical device; and the optical device is set to run in a power-saving mode, in which the transmitter and receiver of the optical device are all powered off, and the receiver and transmitter are activated once at a predetermined time interval to read the DC value of the current optical detected physiological signal; when the DC value is within a predetermined range, the power-saving mode is ended and a normal mode is entered: the power of the transmitter and receiver is turned on, and normal data collection and processing are started; if not within the normal range, the power-saving mode is continued.

[0015] Preferably, in the energy-saving method according to the present disclosure, the receiver and transmitter are activated once every 1 second.

[0016] Additional advantages, objects, and features of the application will be set forth in part by the description that follows, and will become apparent to those skilled in the art upon examination of the following or can be learned from practice of the application. The advantages and objects of the application can be derived from the written description, claims, and appended drawings.

[0017] Those skilled in the art will understand that the objects and advantages of the application can be realized and attained by means of the subject-matter as described in the following detailed description and as illustrated in the accompanying drawings. The subject-matter of the present application will become more readily apparent from the detailed description given herein below and the appended claims, taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0018] The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this application, illustrate embodiments of the application and together with the description serve to explain the principles of the application. In the drawings:

[0019] Figure 1 physiological signal waveforms of optical detection in different states of the SpO2 optical device are shown; wherein Figure 1 (a) physiological signal waveforms of optical detection in normal working state are shown, Figure 1 (b) and Figure 1 (c) physiological signal waveforms of optical detection when the device is off are shown, respectively;

[0020] Figure 2 a schematic diagram of steps of one specific mode of the off detection method for the SpO2 optical device according to the present disclosure is shown;

[0021] Figure 3 a schematic diagram of steps of one preferred specific mode of the off detection method for the SpO2 optical device according to the present disclosure is shown;

[0022] Figure 4 a schematic diagram of switching between power saving mode and normal mode for one embodiment of the SpO2 optical device according to the present disclosure is shown. DETAILED DESCRIPTION

[0023] In order to make the objects, technical solutions and advantages of the present application clearer, the present application will be further described in detail below in conjunction with the embodiments and drawings. Herein, the illustrative embodiments of the present application and their descriptions are used to explain the present application, but are not as limitations to the present application.

[0024] Herein, it is also to be noted that, in order to avoid the present application being obscured by unnecessary details, only the corrections and methods closely related to the solutions according to the present application are shown in the drawings, the technical contents related to SpO2 monitoring known in the art, and the technical contents of the physiological signals of optical detection (such as the processing of PhotoPlethysmoGraph (PPG) signals) known to those skilled in the art are not shown, unless otherwise specified.

[0025] It is known in the art that the SpO2 value based on the optical detection of physiological signals can be calculated as long as a specific algorithm formula is followed. However, it is also necessary to identify whether the human tissue is in contact with the device. If there is no such disengagement identification measure, it is possible to calculate a seemingly reasonable SpO2 value even in a disengaged state, thereby interfering with the normal monitoring value and accuracy. Therefore, it is crucial to perform disengagement detection on the SpO2 device.

[0026] In the known SpO2 optical device, the solutions for judging the disengagement of human tissue mainly include physiological signal feature judgment and monitoring light intensity judgment.

[0027] The disengagement state is judged by physiological signal feature judgment. In SpO2 monitoring, the optical detection of physiological signals includes alternating current (AC) components and direct current (DC) components. The AC components are analyzed by data analysis to determine whether the waveform of the optical detection of physiological signals is normal, thereby judging the disengagement state of human tissue. As shown in the accompanying drawings Figure 1 (a) shows the AC component waveform of good optical detection of physiological signals.

[0028] In the solution of judging the disengagement state by monitoring the light intensity, for example, in the blood oxygen function monitoring module of the plug-in physiological instrument, the blood oxygen part of the physiological instrument is in the state of disengagement. The finger clip is still in normal light. The physiological instrument does not turn off the light but weakens the light intensity. Then, the light intensity detected by the photodiode is used to judge the disengagement state.

[0029] The above solutions have the problem of high power consumption in portable devices using batteries. For the solution of analyzing physiological signals, it is not suitable for low-power products because a large amount of data calculation is involved in the physiological analysis process. Generally, a low-power MCU (Microcontroller Unit; MCU) is not suitable for large amounts of data calculation. This not only occupies the computing power of the chip unit and wastes operation time, but also consumes a certain amount of power. For example, in a low-power MCU with model NRF52832, the memory is still small (512 kB of flash memory in total). Optimizing the disengagement detection calculation method is more conducive to improving the overall performance and endurance time of the device.

[0030] The present disclosure proposes a disengagement detection method for an SpO2 optical device, which includes evaluating the stability of the waveform of the optical detection of physiological signals and evaluating the DC bias.

[0031] In one aspect of the present application, the physiological signal is optically detected by detecting blood volume changes in a blood vessel of a human body tissue by means of a photosensor during operation of the optical device, and the method comprises the following steps performed in a computing module of the optical device:

[0032] a data buffer is set up, which is capable of storing the optically detected physiological signal for at least 3 predetermined time units;

[0033] a collecting and calculating step, in which each DC component of the optically detected physiological signal collected is stored in the data buffer, and a variance of the value of the DC component is calculated to obtain a first waveform reference index value;

[0034] a comparing step, in which the first waveform reference index value is compared with a pre-stored reference index value range;

[0035] a determining step, in which if the first waveform reference index value is greater than the maximum value of the reference index value, a signal of device detachment is output; and if the first waveform reference index value is not greater than the maximum value of the reference index value, new optically detected physiological signal is collected, and then the collecting and calculating step is performed.

[0036] Preferably, in the detachment detection method according to the present disclosure, the method further comprises the following steps performed in the computing module of the optical device: a ring buffer is set up; the optically detected physiological signal is filtered to calculate a peak-to-peak value of a waveform of an AC component of the optically detected physiological signal in a predetermined time unit; then the obtained peak-to-peak value is cached in the ring buffer; a variance of the data in the ring buffer is calculated, and the variance is taken as a second reference index value; the second reference index value is compared with a bias reference value, and if the second reference index value is greater than the bias reference value, a signal of device detachment is output.

[0037] In one specific mode of the detachment detection method according to the present application, the reference index value range is 100 to 3000; and the second reference index value is 3000.

[0038] It can be understood that the second reference index value, which is a variance value, is not necessarily a fixed value or a fixed range. For example, if the length of the ring buffer is doubled, the change of one data will not produce a large ripple, the variance will not change greatly, and the range will naturally become smaller, which is determined according to the situation. For example, if the length of the ring buffer is set to 5, the normal range of the variance is between 0 and 3000.

[0039] Preferably, in the detachment detection method according to the present application, each predetermined time unit can be the same and greater than 1.5 seconds.

[0040] According to another aspect of the present disclosure, an energy saving method for a SpO2 optical device is also provided, in which the aforementioned method for detecting the falling-off is applied in the calculation module of the optical device; the optical device is set to run in a power saving mode, in which the transmitter and receiver of the optical device are all powered off, and the receiver and transmitter are started once at a predetermined time interval to read the DC value of the current optical detection physiological signal; when the DC value is within a predetermined range, the power saving mode is ended and the normal mode is entered: the transmitter and receiver are powered on, and normal data acquisition and processing are started; if it is not within the normal range, the power saving mode is continued.

[0041] Preferably, in the energy saving method according to the present disclosure, the receiver and transmitter are started once every 1 second.

[0042] For example, in one embodiment according to the present disclosure, although there are many ways to evaluate the quality of the waveform of the optical detection physiological signal, in the embodiment of the present disclosure, only evaluating the stability of the waveform of the optical detection physiological signal and the size of the DC value of the waveform can effectively detect the falling-off.

[0043] In one embodiment, for example, in a finger clip SpO2 optical device, the AC component value (representing complexity) of the optical detection physiological signal can be cached in a buf (buffer) with a length of 3-5 time units in the code running in the calculation module, and then each time a new AC component value is obtained, it is stored in the buf. Then the variance of the data in the buf is calculated. Thus, the stability of the waveform can be evaluated by the value of the variance. In the technical solution of the present application, the standard deviation is not calculated, thereby reducing the calculation of the square root and saving the operation resources of the MCU.

[0044] The waveform of the optical detection physiological signal in the normal working state is shown in Figure 1 (a), and the variance value calculated based on the waveform is between 100 and 3000 for the red light signal.

[0045] The waveform when the device is falling off, for example, when the finger clip is removed, is shown in Figure 1 (b), and the variance value calculated at this time is far more than 3000 for both the red light and the infrared.

[0046] Further, the judgment process can follow the following principles:

[0047] Through the above tests, various situations of finger clip operation can be judged. For example, Figure 1(C) shows the physiological signal of optical detection filtering, and then the peak-to-peak value of the waveform is obtained. Then the peak-to-peak value can be cached in a ring buffer, and then the variance of the elements in the ring buffer is calculated. When the finger is not clamped, the emitted light is directly incident on the receiver. At this time, the actual collected data has a large DC value, and the variance can be used as a basis for lead-off detection.

[0048] It can be understood that the calculation of the peak-to-peak value has a time window, for example, the heart rate of a person is about 30-120 times per minute, so the calculation window of the peak-to-peak value can be set to 2 seconds, that is, the optical physiological signal will definitely appear a complete waveform feature (both maximum and minimum values will appear) within 2 seconds.

[0049] As shown in Figure 4 , the SpO2 optical device can work in a power saving mode. In the normal mode, normal ADC (analog-to-digital converter) data acquisition and SpO2 value calculation operations can be performed, and at this time, the transmitter LED beads and the receiver PD tube (photodiode) are in a normal working state, and of course power consumption is inevitable in this mode.

[0050] In the power saving mode, the transmitter LED beads and the receiver PD tube are all in a power-off state, and the PD tube and the infrared LED beads can be started once every second to judge the state of the current DC value. If the dc value is in the normal range, it is considered that the finger is inserted into the finger clip, at this time the red light and the infrared light beads can be continuously turned on, and the power of the receiver PD tube is turned on, and the normal data acquisition and processing is started; if it is not in the normal range, it is considered that the device is still in the lead-off state.

[0051] In the energy-saving low-power management scheme according to the present disclosure, detection is performed every second. Each time the lead-off state is detected, the first step is to detect the DC value, and if the DC value is in the predetermined normal working range, the AC value (peak-to-peak value detection in a period of time) stability is detected. If the first step is incorrect, the second step detection is not performed.

[0052] In the case of device lead-off, the device is still set to start the transmitter light detection every 1 second, and if it passes, it will leave the low-power mode and enter the data acquisition mode, and then further detect the AC value stability. If both pass, the lead-off state is completely left and the lead-on state is entered. Here, lead-off is the lead-off state, and the blood oxygen clip is not clamped with the finger. Lead on is the state of the blood oxygen clip with the finger.

[0053] The technical solution of the present disclosure can accurately determine the falling of the device in a very simple manner, with low power consumption, without occupying too much operation resource of the portable device, and without continuing to light the light-emitting element, so that the optical device has a longer endurance.

[0054] In the present application, the features described and / or illustrated in relation to one embodiment can be used in the same way or in a similar way in one or more other embodiments, and / or in combination with or instead of features of other embodiments.

[0055] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. For those skilled in the art, the embodiments of the present application can be variously changed and modified. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for optical signal detection and processing, wherein physiological signals are obtained by detecting changes in blood volume in human tissue blood vessels using a photoelectric sensor during the operation of an optical device, characterized in that, The optical signal detection and processing method includes performing the following steps within the computing module of the optical device: Set up a data buffer that stores physiological signals from optical detection for at least 3 predetermined time units; Acquisition and calculation steps: Store each DC component of the acquired optically detected physiological signal into the data buffer, calculate the variance of the DC component values, and obtain the first waveform reference index value; Comparison steps: Compare the first waveform reference index value with the pre-stored benchmark index value range; Determination steps: If the first waveform reference index value is greater than the maximum value of the benchmark index value, then output a signal indicating device detachment; if the first waveform reference index value is not greater than the maximum value of the benchmark index value, then perform the following steps: Set up a circular buffer; The physiological signal from optical detection is filtered, and the peak-to-peak value of the AC component in the physiological signal from optical detection within a predetermined time unit is calculated. The resulting peak-to-peak values ​​are then cached in the circular buffer. Calculate the variance of the data within the circular buffer, and use the variance of the data within the circular buffer as the second reference index value; The second reference index value is compared with the bias reference value. If the second reference index value is greater than the bias reference value, a signal indicating that the device has detached is output. After the signal of the output device detachment is received, the optical device is set to operate in power-saving mode. In power-saving mode, the transmitter and receiver of the optical device are both powered off, and the receiver and transmitter are activated once every second to read the value of the DC component of the physiological signal of the current optical detection. If the value of the DC component is within the normal range, the power-saving mode ends and the system switches to normal mode. In normal mode, the transmitter is kept on and the receiver is powered on, and normal physiological signal acquisition and processing begins. If the DC component value is outside the normal range, set the optical device to operate in power-saving mode.

2. An optical device, characterized in that, The optical signal detection and processing method of claim 1 is executed within the computing module of the optical device.

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