CN114615933A

CN114615933A - PPG sensor, physiological parameter sensor and intelligent wearable equipment

Info

Publication number: CN114615933A
Application number: CN202180005942.7A
Authority: CN
Inventors: 周勇
Original assignee: Shenzhen Maidu Technology Co ltd
Current assignee: Shenzhen Maidu Technology Co ltd
Priority date: 2021-07-12
Filing date: 2021-12-07
Publication date: 2022-06-10

Abstract

A PPG sensor (100,300,500,600), a physiological parameter sensor and a smart wearable device. The PPG sensor (100,300,500,600) comprises: a sensor sequence (400,602), wherein the sensor sequence (400,602) includes at least three emitter/detector sets that are selectively activated to provide at least three PPG signals, the at least three PPG signals corresponding one-to-one to the activated emitter/detector sets; and a processor. The processor is configured to receive the at least three PPG signals and provide an output of the PPG sensor (100,300,500,600), the output of the PPG sensor (100,300,500,600) including at least a pulse wave transit direction. The pulse wave transfer direction is determined from the phase difference between the at least three PPG signals and the layout of the PPG sensor (100,300,500,600), which is determined from the activated emitter/detector set. In this way, the PPG measurement is improved and the measurement accuracy is increased.

Description

PPG sensor, physiological parameter sensor and intelligent wearable equipment

Technical Field

The application relates to the technical field of intelligent terminals, in particular to a PPG sensor, a physiological parameter sensor and intelligent wearable equipment.

Background

With the development of intelligent terminal technology, intelligent wearable equipment has gained huge application in monitoring human relevant physiological parameters. Wearable equipment of intelligence has added the function of measuring various physiological parameters especially blood relevant parameter like intelligent wrist-watch, intelligent bracelet etc.. Among these, non-invasive measurement techniques, in particular techniques for obtaining blood flow characteristics, blood parameters and/or performing blood analyses by means of optical measurements, have gained great use. An optical-based blood measuring device generally includes an emitting end and a detecting end, and is closely attached to a part of a user's body such as a wrist, a finger, an ear, a forehead, a cheek, or an eyeball, light radiation is transmitted into or reflected by the part of the body by the emitting end, and then light attenuated by the part of the body is detected by the detecting end to obtain a measurement signal. These measurement signals can be used to analyze and determine physiological parameters such as blood oxygen saturation, pulse, etc. Optical-based blood measurement techniques rely on the principle that light passing through the part of the body can be absorbed, reflected or refracted to cause attenuation. Wherein the part of the body comprises components of skin, muscle, bone, fat, pigments, etc., the attenuation of light due to which is usually constant or considered to be substantially constant during the measurement, while the flow of blood in the blood vessels, in particular in the arterial blood vessels, causes a change in the attenuation of light. This is shown in that the measurement signal can be divided into a time-invariant Direct Current (DC) signal and a time-variant Alternating Current (AC) signal, and the AC signal in the measurement signal can be extracted to obtain blood flow characteristics, blood parameters and/or perform blood analysis. For example, Photoplethysmography (PPG) measures the attenuation light reflected and absorbed by blood vessels and tissues of a human body to obtain the blood flow change of a volume pulse wave, thereby tracing the pulse state of the blood vessels and measuring the pulse wave velocity. As another example, Pulse Oximetry (Pulse Oximetry) measures the blood oxygen saturation, i.e., the volume of oxygenated hemoglobin bound by oxygen in blood as a percentage of the total bindable hemoglobin volume, by detecting the change in light absorption by blood, using the principle that the amount of light absorbed by arterial blood varies with the pulsation of the Pulse.

The principle of PPG measurement and PPG sensor is that Light emitted by a transmitter, such as a Light Emitting Diode (LED), is reflected by blood and tissue at a specific part of a human body, such as a wrist, and then received by a sensor, such as a Photodiode (PD), and the AC signal can be obtained by detecting the Light reflected by the human body (e.g., analyzing an electrical signal after photoelectric conversion) and further detecting physiological parameters such as blood oxygen or heart rate. The measurement accuracy and the detection effect of the PPG sensor are affected by the ratio of the AC signal to the DC signal (also referred to as modulation depth), and in practice, the ratio of the AC signal to the DC signal is generally less than one in a thousand, and the PPG sensor is also affected by various noises, such as background noise, electronic circuit disturbance and device state offset, which may also cause negative effects. For this reason, it is necessary to increase the Ratio of the AC Signal to the DC Signal and to increase the Signal to Noise Ratio (SNR) of the system.

In the prior art, chinese patent application publication No. CN 105748053a discloses that two cameras are used to obtain two PPG signals of the same Pulse Wave, and then a Pulse Wave transmission Time (PTT) is calculated by using a difference value or an average value of the difference value between Time points corresponding to Time domain feature points on the two PPG signals, and then a Pulse Wave transmission speed (PWV) is calculated based on a preset distance of the two cameras, thereby improving the accuracy of obtaining the PTT and PWV; also disclosed is the use of three PPG signals of different wavelengths, such as Red (Red) Green (Green) and Blue (Blue), from which the two or three signals are selected as the average or the one with the highest SNR is selected as the target PPG signal. International application No. PCT/CN2018/091071 and PCT application publication No. WO 2019/237281a1 disclose requirements for power consumption and a ratio of an AC signal to a DC signal in different application scenarios with different distances between PDs and LEDs, respectively, a layout between PDs and LEDs is designed such that the distance between PDs and LEDs has a long distance and a short distance, for example, three LEDs each of which is RGB triad and two PDs are shown therein, thereby forming a total of 18 light paths including 12 long distance paths and 6 short distance paths, and improving detection accuracy by setting different weights to reflected light intensities on the 18 light paths or by signal differences between the 12 long distance paths. However, the above-mentioned prior art does not sufficiently consider the influence of the pulse wave propagation direction and the influence of the artery direction at the measurement site, and only improves the measurement accuracy by averaging, weighting, or calculating the difference between the reflected light intensities in different light paths. Depending on the pulse wave propagation direction or the relative orientation of the artery orientation to the specific layout between PD and LED, for example the pulse wave propagation direction to each of the two light paths to be compared, poor measurement results may result and such negative effects are difficult to compensate by later algorithms such as averaging or weighting. Moreover, PPG measurement is used for different parts of the human body, each part also has different arterial distribution and trend, each user also has different situations in the same part as an individual, and these factors all affect the final measurement accuracy.

Therefore, a PPG sensor, a physiological parameter sensor and a smart wearable device are needed, which not only can consider the influence of the pulse wave transmission direction or the artery trend on the PPG measurement, but also can flexibly cope with complex and changeable application scenarios, including individual differences applicable to different parts of the human body and different users.

Disclosure of Invention

The embodiment of the application aims at solving the problem that the influence of the pulse wave transmission direction or the artery trend on the PPG measurement can be considered, and the complex and changeable application scene can be flexibly coped with, including the individual difference suitable for different parts of a human body and different users, so that the technical problem is solved by providing the PPG sensor, the physiological parameter sensor and the intelligent wearable equipment, thereby realizing the improvement of the PPG measurement result and the improvement of the measurement precision.

In a first aspect, an embodiment of the present application provides a PPG sensor. The PPG sensor comprises: a sensor sequence, wherein the sensor sequence comprises at least three emitter/detector sets that are selectively activated to provide at least three PPG signals that correspond one-to-one with the activated emitter/detector set; and a processor. Wherein the processor is configured to receive the at least three PPG signals and provide an output of the PPG sensor that includes at least a pulse wave propagation direction. Wherein the pulse wave transfer direction is determined from the phase difference between the at least three PPG signals and the layout of the PPG sensor determined from the activated set of emitters/detectors.

The technical scheme described in the first aspect realizes the improvement of the PPG measurement result and the improvement of the measurement precision.

According to a possible implementation manner of the technical solution of the first aspect, the embodiments of the present application further provide that any two emitter/detector groups of the at least three emitter/detector groups have different emitters or different detectors or different emitters and detectors.

According to a possible implementation manner of the technical solution of the first aspect, an embodiment of the present application further provides that the at least three transmitter/detector groups include: three emitter/detector groups consisting of one emitter and three detectors, respectively, or three emitter/detector groups consisting of one detector and three emitters, respectively, or four emitter/detector groups consisting of two emitters and two detectors, respectively.

According to a possible implementation manner of the technical solution of the first aspect, an embodiment of the present application further provides that the emitter is an LED, and the detector is a PD.

According to a possible implementation manner of the technical solution of the first aspect, the embodiment of the present application further provides that the output result of the PPG sensor further includes a pulse wave transfer time PTT or a pulse wave transfer velocity PWV.

According to a possible implementation manner of the technical solution of the first aspect, an embodiment of the present application further provides that the determining of the layout of the PPG sensor according to the activated emitter/detector group includes: determining a plurality of light paths and respective midpoints of the plurality of light paths according to the activated emitter/detector group, wherein the layout of the PPG sensor comprises side lengths and internal angles of a polygon formed by the respective midpoints of the plurality of light paths.

According to a possible implementation manner of the technical solution of the first aspect, an embodiment of the present application further provides that the determining of the layout of the PPG sensor according to the activated emitter/detector group includes: determining a plurality of light ray paths and respective midpoints of the plurality of light ray paths from the activated set of emitters/detectors, the layout of the PPG sensor including distances and relative orientations between the respective midpoints of the plurality of light ray paths.

According to a possible implementation manner of the technical solution of the first aspect, the present application embodiment further provides that the positions of all transmitter/detector groups included in the sensor sequence on the PPG sensor are preset.

According to a possible implementation manner of the technical solution of the first aspect, an embodiment of the present application further provides that the PPG sensor further includes: a light field distribution compensation module communicatively coupled to the sensor sequence, the light field distribution compensation module calculating a light field distribution compensation result for the activated transmitter/detector group based on an overlap between the transmitted and received light fields of the activated transmitter/detector group.

According to a possible implementation manner of the technical solution of the first aspect, the embodiment of the present application further provides that the light field distribution compensation module further calculates a light field distribution compensation result of the activated transmitter/detector group according to at least one of the following: a wavelength of light emitted by the activated emitter/detector set, an emission angle of the activated emitter/detector set, a reception angle of the activated emitter/detector set, a degree of curvature of a measurement area of the PPG sensor.

According to a possible implementation manner of the technical solution of the first aspect, an embodiment of the present application further provides that the determining of the layout of the PPG sensor according to the activated emitter/detector group includes: determining a plurality of light ray paths and respective midpoints of the plurality of light ray paths according to the activated emitter/detector group, calculating respective effective sampling points of the plurality of light ray paths according to a light field distribution compensation result of the activated emitter/detector group and respective midpoints of the plurality of light ray paths by the light field distribution compensation module or the processor, and calculating a spatial relationship between the respective effective sampling points of the plurality of light ray paths by the layout of the PPG sensor.

According to a possible implementation manner of the technical solution of the first aspect, an embodiment of the present application further provides that the spatial relationship between the respective effective sampling locations of the plurality of light paths includes a side length and an inner angle of a polygon formed by the respective effective sampling locations of the plurality of light paths, or a distance and a relative orientation of the respective effective sampling locations of the plurality of light paths.

According to a possible implementation manner of the technical solution of the first aspect, an embodiment of the present application further provides that the PPG sensor further includes: a sampling rate adjustment module communicatively coupled to the sensor sequence, the sampling rate adjustment module configured to adjust a sampling frequency according to the activated set of emitters/detectors.

According to a possible implementation manner of the technical solution of the first aspect, the embodiment of the present application further provides that the processor provides the output result of the PPG sensor based on a depth machine learning model, and the depth machine learning model is trained to calculate the pulse wave transfer direction according to the phase difference between the at least three PPG signals and the layout of the PPG sensors.

According to a possible implementation manner of the technical solution of the first aspect, an embodiment of the present application further provides that the PPG sensor further includes: and presetting a physiological model library, wherein the preset physiological model library provides a model of the trend of the arterial blood vessels of a specific part of the human body to the deep machine learning model.

According to a possible implementation manner of the technical solution of the first aspect, an embodiment of the present application further provides that the PPG sensor further includes: a user model library, wherein the user model library provides a model of arterial vessel trend for a particular user to the deep machine learning model based on historical data of the PPG sensor.

According to a possible implementation manner of the technical solution of the first aspect, an embodiment of the present application further provides that the PPG sensor further includes: and the user model updating module is used for updating the user model library according to the output result of the PPG sensor.

According to a possible implementation manner of the technical solution of the first aspect, the embodiment of the present application further provides that the measurement region of the PPG sensor is located on a wrist, a finger, an ear, a forehead, a cheek, or an eyeball.

In a second aspect, embodiments of the present application provide a physiological parameter sensor. The physiological parameter sensor comprises a PPG sensor according to any of the first aspects, the physiological parameter sensor determining a physiological parameter from the pulse wave transfer direction.

According to a possible implementation manner of the technical solution of the second aspect, embodiments of the present application further provide that the physiological parameter is a blood-related parameter, and the blood-related parameter includes at least one of: blood pressure, hemoglobin concentration, pulse, blood oxygen saturation, respiratory rate, perfusion index, blood flow reactivity, methemoglobin, carboxyhemoglobin, bilirubin, oxygen content, blood lipids, and blood glucose.

According to a possible implementation manner of the technical solution of the second aspect, the physiological parameter is a pigment-related parameter, and the pigment-related parameter includes a pigment distribution map, pigment interference, or pigment-related background noise.

In a third aspect, an embodiment of the present application provides a smart wearable device. The smart wearable device comprising a PPG sensor according to any of the first aspects, the smart wearable device providing a medical monitoring result from an output of the PPG sensor.

According to a possible implementation manner of the technical solution of the third aspect, the embodiment of the present application further provides that the medical monitoring result is based on a blood-related parameter, the blood-related parameter is determined according to the output result of the PPG sensor, and the blood-related parameter includes at least one of the following: blood pressure, hemoglobin concentration, pulse, blood oxygen saturation, respiratory rate, perfusion index, blood flow reactivity, methemoglobin, carboxyhemoglobin, bilirubin, oxygen content, blood lipids, and blood glucose.

According to a possible implementation manner of the technical solution of the third aspect, the embodiment of the present application further provides that the medical monitoring result is based on a pigment-related parameter, the pigment-related parameter is determined according to the output result of the PPG sensor, and the pigment-related parameter includes a pigment distribution map, pigment interference, or pigment-related background noise.

Drawings

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

Fig. 1 shows a schematic diagram of a layout of a PPG sensor provided in an embodiment of the present application.

Fig. 2 shows a schematic diagram of measuring a pulse wave transmission direction by using the PPG sensor shown in fig. 1 according to an embodiment of the present application.

Fig. 3 shows a schematic diagram of a layout of a PPG sensor according to another embodiment provided in the examples of the present application.

Fig. 4 shows a schematic diagram of a sensor sequence for a PPG sensor provided in an embodiment of the present application.

Fig. 5 shows a schematic structural diagram of a PPG sensor incorporating light field distribution compensation provided by an embodiment of the present application.

Fig. 6 shows a block diagram of a PPG sensor according to another embodiment provided in this application.

Detailed Description

The embodiment of the application can also flexibly deal with complex and changeable application scenes in order to solve the influence of the pulse wave transmission direction or the artery trend on the PPG measurement, and provides a PPG sensor, a physiological parameter sensor and intelligent wearable equipment including individual differences applicable to different parts of a human body and different users. The PPG sensor comprises: a sensor sequence, wherein the sensor sequence comprises at least three emitter/detector sets that are selectively activated to provide at least three PPG signals that correspond one-to-one with the activated emitter/detector set; and a processor. Wherein the processor is configured to receive the at least three PPG signals and provide an output of the PPG sensor that includes at least a pulse wave propagation direction. Wherein the pulse wave transfer direction is determined from the phase difference between the at least three PPG signals and the layout of the PPG sensor determined from the activated set of emitters/detectors. In this way, improved PPG measurement results and improved measurement accuracy are achieved.

The embodiments of the present application can be used in any application scenarios including, but not limited to, any physiological measurement through the skin, such as measuring blood pressure, hemoglobin concentration, pulse, blood oxygen saturation, respiratory rate, blood perfusion index, blood flow reactivity, methemoglobin, carboxyhemoglobin, bilirubin, oxygen content, etc. through photoplethysmography or pulse waves, or measuring the above physiological parameters or any suitable human body related physiological parameters by measuring pulse wave transit time or measuring pulse wave amplitudes of different wavelengths or measuring pulse wave phases, etc.

The embodiments of the present application may be modified and improved according to specific application environments, and are not limited herein.

In order to make the technical field of the present application better understand, embodiments of the present application will be described below with reference to the accompanying drawings in the embodiments of the present application.

Referring to fig. 1, fig. 1 shows a schematic diagram of a layout of a PPG sensor provided in an embodiment of the present application. As shown in fig. 1, PPG sensor 100 includes one emitter 102 and three detectors, detector 110, detector 112 and detector 114, respectively. Emitter 102 here refers to any light-emitting electronic device, or any suitable light source. Light emitted by emitter 102, referred to herein as either emitted light or incident light, is understood to be electromagnetic radiation in a general sense and includes radiation of frequencies or wavelengths such as visible, infrared, and ultraviolet, or the like, or such as red, green, and blue light, which are commonly used for PPG measurements. Emitter 102 may be any light source suitable for generating one or more wavelengths, such as a Light Emitting Diode (LED), as long as the light source meets the specific functions and features described in the embodiments herein. The emitter 102 may emit light of only one specific wavelength, for example, centered on the specific wavelength and having a small line width. The emitter 102 may also emit multiple wavelengths, for example, a first wavelength and a second wavelength and the second wavelength being different from the first wavelength. The wavelengths that emitter 102 may emit include, for example, 400 nanometers (nm), 2000nm, and even greater than 10000nm, and any wavelength suitable for PPG measurement or Optical Coherence Tomography (OCT) or medical detection based Optical sensing technology, such as visible light (e.g., red, green, and blue light, etc.), infrared, and ultraviolet, etc. The

detectors

110, 112 and 114 are configured to detect light emitted by the emitter 102, and in particular light reflected back from the body via the light emitted by the emitter 102, and the detectors themselves, or in combination with other necessary circuitry or devices, may convert the detected light into corresponding PPG signals. The

detectors

110, 112 and 114 may employ any suitable detection means, such as photodiodes PD, photoresistors, phototransistors, photoconverters, and the like. The detection principle of the PPG signal can refer to the above PPG measurement principle and the prior art, and is not described herein again. It should be understood that any suitable PPG measurement method and PPG signal detection method may be applied to the present application, which is not specifically limited herein, and the present application is intended to cover the PPG measurement method and PPG signal detection method proposed at the filing date of the application, as long as the basic principles thereof belong to the category of photoplethysmography PPG measurements or photoplethysmography (photoplethysmography).

The emitter 102 and the detector 110, the detector 112 and the detector 114 each form three light ray paths, which means that the point of convergence between the light or emitted light field emitted by the emitter 102 and the light or detected light field detected by the respective detector is on the light ray path corresponding to that detector. For example, there is a position M1 in the light path between the emitter 102 and the detector 110, and a position M1 represents a point of convergence between the emitted light field of the emitter 102 and the detected light field of the detector 110, i.e., a valid measurement location or a valid sampling location between the emitter 102 and the detector 110. This means that the PPG signal recorded by the detector 110 is sampled at the position M1, where the sampling frequency is determined by the pulse rate of the emitter 102 and the detection performance of the detector 110. From a light field distribution perspective, position M1 is the region of maximum overlap between the transmitted light field of transmitter 102 and the detected light field of detector 110. The position M1 is affected by a number of factors, including the distance between the emitter 102 and the detector 110, the degree of curvature of the detected body part, the angle of emission of the emitter 102 and the angle of reception of the detector 110, and the wavelength of the emitted light, among others. In general, it can be assumed that there is a maximum light field distribution at the midpoint of the line connecting the emitter 102 and the detector 110, i.e., the position M1. In the embodiment shown in fig. 1, the position M1 should be understood as the midpoint of the line connecting the emitter 102 and the detector 110, and how to further determine where to record the PPG signal in combination with factors such as the light field distribution will be described in detail below. Similarly, position M2 is understood to be the end point of the line connecting emitter 102 and detector 114, at which position M2 the PPG signal recorded by detector 114 is sampled; position M3 is understood to be the end point of the line connecting the emitter 102 and the detector 112, at which position M3 the PPG signal recorded by the detector 112 is sampled.

With reference to fig. 1, a triangle formed by connecting the three positions M1, M2 and M3 has three sides D1, D2 and D3, an inner angle a1 with the position M1 as the vertex, an inner angle a2 with the position M2 as the vertex and an inner angle A3 with the position M3 as the vertex. The triangle defined by position M1, position M2, and position M3, including its three sides and three interior corners, or any equivalent mathematical representation or geometric description, is understood to be a relative spatial relationship between the three of position M1, position M2, and position M3. Also, it is assumed above that position M1, position M2, and position M3 are respective midpoints of lines between the emitter 102 and the

detectors

110, 114, and 112, respectively, and thus the spatial relationship between position M1, position M2, and position M3, that is, the spatial relationship between the emitter 102 and the

detectors

110, 114, and 112. Therefore, information about the layout of the PPG sensor 100, i.e. the distance and orientation between any number of emitters and any number of detectors comprised by the PPG sensor 100, or relative coordinates of each other, etc., can be used to determine the spatial relationship between the position M1, the position M2 and the position M3. Thus, the spatial relationship between position M1, position M2, and position M3 is determined by the layout of the PPG sensor 100.

It should be understood that the PPG sensor 100 shown in fig. 1 includes one emitter and three detectors, or the layout shown in fig. 1 includes three detection groups formed by one emitter and three detectors, each detection group corresponds to a combination of one emitter and one detector and measures one path of PPG signals, and there are at least different emitters or different detectors between different detection groups. In a possible embodiment, combining the above PPG measurement principle, a similar effect, i.e. measuring three PPG signals, can also be achieved by three detection groups of three emitters and one detector. Specifically, the emitter 102 shown in fig. 1 may be replaced with a detector, and the detector 110, the detector 114, and the detector 112 may be replaced with three emitters, respectively. This combination of three emitters and one detector is required to avoid confusion of PPG signals of different paths by time-division or frequency-division or other suitable means. In another possible embodiment, three pairs of emitters and detectors may be used, each pair of emitters and detectors is a detection group and measures one PPG signal, and aliasing of the PPG signals measured by different detection groups may be avoided by using different wavelengths. Thus, there are many possible variations and combinations of the layout of the PPG sensor 100, and what is shown in fig. 1 is just one example, and other possible combinations are understood to fall within the scope disclosed for the PPG sensor 100 shown in fig. 1, as long as three PPG signals are provided, whose respective measurement locations correspond to the three positions M1, M2, and M3 shown in fig. 1. In one possible implementation, the PPG sensor 100 shown in fig. 1 may include multiple emitters/detectors including three detection groups, with different emitters or detectors between any two detection groups, each providing three separate PPG signals. In another possible embodiment, the PPG sensor 100 shown in fig. 1 may comprise a multiple emitter/detector arrangement and provide three separate PPG signals. The three separate PPG signals correspond to the three positions M1, M2, and M3 shown in fig. 1, respectively, each of which identifies the measurement location of the PPG signal corresponding to that position or the midpoint of the line of emitters/detectors of the PPG signal corresponding to that position. How to further determine the measurement location of the PPG signal after taking into account the light field distribution etc. will be explained in detail below.

For the sake of brevity, the following embodiments and the accompanying drawings only schematically show three positions M1, M2 and M3 or other positions, but in connection with the above description, these positions each correspond to a detection group or an emitter/detector combination and to any suitable layout of the PPG sensor 100, for example a PPG sensor comprising at least 3 LED light sources and at least 1 detector. How to measure the pulse wave propagation direction using the layout of the PPG sensor 100 of fig. 1 is explained below.

Referring to fig. 2, fig. 2 is a schematic diagram illustrating a method for measuring a pulse wave propagation direction by using the PPG sensor shown in fig. 1 according to an embodiment of the present application. For the sake of clarity, fig. 2 shows only three positions M1, M2, and M3, corresponding respectively to the three-way PPG signal measured by the PPG sensor of fig. 1. Fig. 2 also shows the spatial relationship between position M1, position M2, and position M3, including three sides D1, D2, and D3, and an interior angle a1 with position M1 as the vertex, an interior angle a2 with position M2 as the vertex, and an interior angle A3 with position M3 as the vertex. Fig. 2 also shows the blood flow directions L1 and L2. The blood flow directions L1 and L2 may also represent the arterial distribution and trend of the measured site. As described above, the three positions M1, M2, and M3 correspond to respective sampling locations of the three PPG signals, i.e., the three PPG signals are sampled at the three positions M1, M2, and M3, respectively. In combination with the general knowledge about the distribution of arteries in the human body, it is known that when the measurement site is small or the area for PPG measurement is sufficiently small, in this area there is an arterial vessel or arterial vessel branch, or in this area the pulse wave transmitted in a single arterial vessel has a major influence on the measurement result. The measurement effect of the PPG sensor in this area, including the ratio of the AC signal to the DC signal and the system SNR, is mainly determined by the measurement effect of the pulse wave propagating along the single arterial wall, and therefore the relation between the course of the single arterial vessel and the layout of the PPG sensor, in particular the distribution of the sampling locations therein, needs to be taken into account.

As shown in fig. 2, when the arterial vascularity is along the direction L1, this means that the pulse wave transmission direction is also substantially along the direction L1. Thus, the signals sampled at the three positions M1, M2 and M3 with respect to the pulse wave passing along the direction L1 are phase-shifted with respect to each other, as determined by the spatial relationship of the direction L1 with respect to the positions M1, M2 and M3. Specifically, the pulse wave transmitted along the direction L1 first reaches the position M3, which is reflected by first recording a time-domain feature point, such as a peak value or a zero value of the PPG signal, on the PPG signal corresponding to the position M3; the same pulse wave arrives at the position M1 after the first transfer time and arrives at the position M2 after the second transfer time, which is reflected in that the corresponding PPG signal at the position M1 and the corresponding PPG signal at the position M2 have a first phase difference and a second phase difference respectively relative to the corresponding PPG signal at the position M3. As can be seen from the comparison of the waveform analysis, a time domain feature point, such as a peak or a zero value, recorded on the PPG signal corresponding to the position M3 appears on the PPG signal corresponding to the position M1 after a first phase difference, and appears on the PPG signal corresponding to the position M2 after a second phase difference. Therefore, by means of waveform analysis comparison and phase difference analysis among three total PPG signals respectively sampled at the position M1, the position M2 and the position M3, and by combining the spatial relationship among the position M1, the position M2 and the position M3, the transfer direction L1 of the pulse wave can be calculated, and further the PPG measurement result can be improved according to the calculated transfer direction L1 of the pulse wave, and the measurement accuracy is improved.

In addition, when the direction of transmission of the pulse wave slightly changes, for example, slightly rotates or angularly changes in the direction L1 shown in fig. 2, these slight changes are also reflected in the changes in the phase difference between the three paths of PPG signals corresponding to the position M1, the position M2, and the position M3, respectively. Specifically, as long as the position where the same pulse wave arrives first is determined, for example, the pulse wave with the direction of L1 arrives at the position M3 first, the PPG signal corresponding to the position M3 that arrives first is taken as the reference PPG signal, the two paths of PPG signals corresponding to the other two positions M1 and M2 are taken as the first target PPG signal and the second target PPG signal, respectively, and the transfer direction L1 of the pulse wave can be estimated and the slight change occurring in the direction L1 can be captured by comparing the phase difference between the reference PPG signal and the first target PPG signal and the phase difference between the reference PPG signal and the second target PPG signal, thereby facilitating the estimation of the transfer direction of the pulse wave. In some exemplary embodiments, the transmission direction of the pulse wave can be estimated by other suitable mathematical tools or geometric theories and the slight change of the transmission direction of the pulse wave can be captured, which also belong to the content of the present disclosure.

As shown in fig. 2, when the arterial vascularity is along the direction L2, this means that the pulse wave transmission direction is also substantially along the direction L2. The pulse wave transmitted along the direction L2 first reaches the position M1, the PPG signal corresponding to the position M1 is used as the reference PPG signal, and the two PPG signals corresponding to the positions M2 and M3 are used as the first target PPG signal and the second target PPG signal, and by comparing the phase difference between the reference PPG signal and the first target PPG signal and the phase difference between the reference PPG signal and the second target PPG signal, the transmission direction L2 of the pulse wave can be estimated and the slight change in the direction L2 can be captured, so that the transmission direction of the pulse wave can be estimated, the PPG measurement result can be improved, and the measurement accuracy can be improved. Therefore, when the measurement area of the PPG sensor changes, the arterial blood vessel distribution within the measurement area also changes, for example when the measurement location of the PPG sensor changes from the left wrist to the right wrist of the human body, which results in a change of the direction of transmission of the pulse wave from L1 to L2. In the face of the changed measurement area, one of the three paths of PPG signals can be selected as a reference PPG signal, and the other two paths of PPG signals are used as a first target PPG signal and a second target PPG signal, so as to compare the phase difference between the reference PPG signal and the first target PPG signal and the phase difference between the reference PPG signal and the second target PPG signal. For example, when the pulse wave transmission direction changes from L1 to L2, the path of PPG signal corresponding to position M3 is changed to the path of PPG signal corresponding to position M1. In addition, the criterion for selecting the reference PPG signal may be, in addition to the PPG signal corresponding to the sampling location where the pulse wave first arrives, the PPG signal corresponding to the sampling location where the pulse wave finally arrives, because it is necessary to calculate the propagation direction of the pulse wave to determine the phase difference between each of the other two PPG signals and the reference PPG signal serving as the reference. In some exemplary embodiments, the three PPG signals may be averaged, weighted, summed, or otherwise mathematically processed to obtain a reference PPG signal, and these specific implementations are based on the basic principle described above, that is, the pulse wave propagation direction is calculated by waveform analysis comparison and phase difference analysis between the three PPG signals sampled at position M1, position M2, and position M3, respectively, and then by combining the spatial relationship between position M1, position M2, and position M3.

It should be understood that fig. 2 only shows three positions M1, M2, and M3, which may be achieved by any PPG sensor, as long as the PPG sensor comprises a multiple emitter/detector arrangement and provides three separate PPG signals. The three mutually independent PPG signals correspond to three positions M1, M2 and M3, respectively, each of which identifies the measurement location of the PPG signal corresponding to that position or the region of maximum overlap between the emitted light field of the emitter and the detected light field of the detector of the PPG signal corresponding to that position. Generally, the measurement or sampling location of the PPG signal, i.e. the location corresponding to the PPG signal, is the midpoint of the line between the emitter and the detector or the midpoint of the light path formed by the emitter and the detector. How to further determine the measurement location of the PPG signal after taking into account factors such as the light field distribution will be described in detail below.

Referring to fig. 3, fig. 3 is a schematic diagram illustrating a layout of a PPG sensor according to another embodiment provided in the embodiments of the present application. As shown in fig. 3, PPG sensor 300 includes one emitter 302 and four detectors, detector 310, detector 312, detector 314, and detector 316, respectively. The emitter 302 and the detector 310, the detector 312, the detector 314, and the detector 316 form four light paths, respectively, and correspond to four positions M1, M2, M3, and M4, respectively. Unlike the three positions M1, M2, and M3 shown in fig. 2, there is one more position M4 in fig. 3, and there is one more PPG signal, i.e., the PPG signal measured by the detection group consisting of the emitter 302 and the detector 316. The embodiments in fig. 1 and fig. 2 describe how to deduce the transfer direction of the pulse wave by waveform analysis comparison and phase difference analysis between three total PPG signals sampled at position M1, position M2 and position M3, respectively, and combining the spatial relationship between position M1, position M2 and position M3. Similarly, in fig. 3, the direction of transmission of the pulse wave is estimated by waveform analysis comparison and phase difference analysis between the four total PPG signals sampled at position M1, position M2, position M3 and position M4, respectively, in combination with the spatial relationship between position M1, position M2, position M3 and position M4. Here, the spatial relationship among the position M1, the position M2, the position M3, and the position M4 includes four sides D1, D2, D3, and D4, and an interior angle a1 with the position M1 as a vertex, an interior angle a2 with the position M2 as a vertex, an interior angle A3 with the position M3 as a vertex, and an interior angle a4 with the position M4 as a vertex. Thus, by adding a new position M4 and a corresponding fourth PPG signal, the spatial relationship of the triangles shown in fig. 1 and 2 becomes the spatial relationship of the quadrilaterals shown in fig. 3. Accordingly, after selecting the reference PPG signal, the PPG sensor 300 shown in fig. 3 uses three additional PPG signals as the first target PPG signal, the second target PPG signal, and the third target PPG signal, respectively, and then, according to the phase difference between the reference PPG signal and the first target PPG signal, the phase difference between the reference PPG signal and the second target PPG signal, and the phase difference between the reference PPG signal and the third target PPG signal, the pulse wave transfer direction in the measurement area of the PPG sensor 300 can be calculated, so that the PPG measurement result is improved, and the measurement accuracy is improved. It should be understood that, the criterion for selecting the reference PPG signal may be, besides the above-mentioned PPG signal corresponding to the sampling location where the pulse wave first arrives, also the PPG signal corresponding to the sampling location where the pulse wave finally arrives, because it is necessary to calculate the phase difference between each of the other two PPG signals and the reference PPG signal as the reference to calculate the transfer direction of the pulse wave. In some exemplary embodiments, the result of averaging, weighted summing, or other mathematical processing of the four PPG signals may also be used as the reference PPG signal.

With reference to fig. 1, 2 and 3, the layout of the PPG sensor may include at least three detection groups, each detection group corresponding to a combination of one emitter and one detector and measuring one PPG signal, and there are at least different emitters or different detectors between different detection groups. Alternatively, the layout of the PPG sensor may comprise an emitter/detector combination that is capable of measuring at least three PPG signals. More PPG signals means that there are more sampling or measurement locations of the corresponding PPG signals. The spatial relationship between the respective corresponding sampling locations of all PPG signals, including the distances and relative orientations between these sampling locations, e.g. expressed as the side lengths and interior angles of a triangle as shown in fig. 2 and the side lengths and interior angles of a quadrilateral as shown in fig. 3, may be determined according to the layout of the PPG sensor, and the sampling locations of the PPG signals may generally be considered as the midpoints of the light paths formed by the emitter and the detector corresponding to the PPG signals. Therefore, the PPG sensor provided in the embodiments of the present application may have three detection sets and three PPG signals as shown in fig. 1 and 2, four detection sets and four PPG signals as shown in fig. 3, and in other embodiments, more detection sets and more PPG signals, which may be determined according to the layout of the PPG sensor. In general, more detection groups and more paths of PPG signals are helpful to provide more accurate estimation results of pulse wave propagation direction, which is beneficial to improve measurement accuracy. With the addition of more detection groups, more paths of PPG signals and corresponding sampling locations, the transfer direction of the pulse wave can be calculated and the slight change of the transfer direction of the pulse wave can be captured by using a suitable mathematical tool or a geometric theory, such as a geometric theory for polygons, and the like, and by using techniques such as frequency domain analysis and multi-signal processing analysis.

Referring to fig. 4, fig. 4 shows a schematic diagram of a sensor sequence for a PPG sensor provided in an embodiment of the present application. The sensor sequence 400 shown in fig. 4 includes a total of 16 emitters/detectors of 4x 4. The sensor sequence 400 also includes emitters/

detectors

402, 404, 406, and 410 labeled with black fill color. Depending on the actual requirements, the sensor sequence 400 may selectively activate several emitters/detectors to form different emitter/detector combinations, and thus different layouts of the PPG sensors. In one possible implementation, assuming that the same emitter (not shown) is present and that all included in sensor sequence 400 are detectors, sensor sequence 400 may activate

detectors

402, 404, and 406 to form a first layout and may also activate

detectors

402, 404, and 410 to form a second layout. Wherein the first and second layouts correspond to the same emitter but to different combinations of detectors. As such, by activating different detectors, the sensor sequence 400 can change the layout of the PPG sensors, and thus change the spatial relationship between the sampling locations corresponding to the layout of the PPG sensors. Sensor sequence 400 may also activate a greater number of detectors, such as

detectors

402, 404, 406, and 410 simultaneously. Therefore, by presetting the sensor sequence 400 including the number of emitters/detectors included therein, the preset position and the preset orientation, and then activating several of the emitters/detectors therein to form different emitter/detector combinations, different layouts of the PPG sensors are formed, which is beneficial to flexibly adjusting the spatial relationship between the sampling locations corresponding to the layouts of the PPG sensors, such as the side length and the inner angle of a polygon formed by the sampling locations.

Referring to fig. 5, fig. 5 shows a schematic structural diagram of a PPG sensor incorporating light field distribution compensation provided in an embodiment of the present application. As mentioned above, the sampling location of the PPG signal can be regarded as the midpoint of the light path formed by the emitter and the detector corresponding to the PPG signal, and in order to achieve better measurement, the maximum overlap region between the emitted light field of the emitter and the detected light field of the detector needs to be selected in combination with the light field distribution compensation. The positions M1, M2, and M3 shown in fig. 5 coincide with the positions M1, M2, and M3 shown in fig. 1, and each represent a measurement location of the PPG signal corresponding to the position or a midpoint of a line connecting the emitters/detectors of the PPG signal corresponding to the position. The positions N1, N2 and N3 shown in fig. 5 then represent the sample locations re-determined in combination with the compensation of the light field distribution. In particular, the PPG sensor 500 shown in fig. 5 comprises an emitter 502 and a detector 510, a detector 512 and a detector 514. The emitter 502 and the detector 510, the detector 512 and the detector 514 form three light paths, respectively. Where the midpoint of the light path between the emitter 502 and the detector 510 is position M1, and position N1 represents the point of convergence between the emitted light field of the emitter 502 and the detected light field of the detector 510, i.e., the sampling point between the emitter 502 and the detector 510. This means that the PPG signal recorded by the detector 510 is sampled at position N1, where the sampling frequency is determined by the pulse rate of the emitter 502 and the detection performance of the detector 510. From a light field distribution perspective, position N1 is the region of maximum overlap between the transmitted light field of transmitter 502 and the detected light field of detector 510. The distance between the position N1 as the sampling point and the position M1 as the midpoint of the light path is mainly affected by the light field distribution, which is affected by various factors including the degree of curvature of the detected human body part, the emission angle of the emitter 502 and the reception angle of the detector 510, the wavelength of the emitted light, and the like. Similarly, the midpoint in the path of light rays between the emitter 502 and the detector 514 is position M2, while position N2 represents the point of convergence between the emitted light field of the emitter 502 and the detected light field of the detector 514, i.e. the sampling point between the emitter 502 and the detector 514, which means that the PPG signal recorded by the detector 514 was sampled at position N2; the midpoint in the light path between the emitter 502 and the detector 512 is position M3, and position N3 represents the point of convergence between the emitted light field of the emitter 502 and the detected light field of the detector 512, i.e. the sampling point between the emitter 502 and the detector 512, which means that the PPG signal recorded by the detector 512 was sampled at position N3. Thus, in conjunction with the light field distribution compensation, the PPG signal sampling points shown in fig. 1, 2 and 3, which are default to the light ray path middle point, are improved, the junction or maximum overlapping area of the transmitted light field and the detected light field is used as an effective sampling point, and the spatial relationship between the effective sampling points, such as positions N1, N2 and N3 shown in fig. 5, is used as a basis to estimate the pulse wave transmission direction, thereby improving the measurement accuracy.

Specifically, the valid sampling location may be determined by: the default sampling location, i.e. the midpoint of the light path of the emitter/detector, is first determined from the layout of the PPG sensor, as shown in fig. 1 for three positions M1, M2 and M3; calculating the light field distribution compensation by various factors influencing the light field distribution compensation, including the layout of the PPG sensor, the position and the direction of a default sampling place, the bending degree of a measuring area (different bending degrees of different parts of a human body), the emission angle of an emitter, the receiving angle of a detector, the parameters of a light source providing incident light, the wavelength of the incident light and the like; and adjusting the default sampling location according to the calculated light field distribution compensation so as to obtain an adjusted effective sampling location. The calculation of the light field distribution compensation based on the various factors described above can be predicted by any suitable scientific tool, such as an optical analysis tool, and also by deep machine learning techniques in conjunction with a pre-set model. The light field distribution compensation may be performed separately for each default sampling location, e.g. by changing its position along the path of the light rays, or by shifting it by a distance, in conjunction with the layout of the particular PPG sensor. It should be understood that the method for predicting the pulse wave transit direction using the spatial relationship between the default sampling locations, such as the position M1, the position M2, and the position M3 in fig. 2, as shown in fig. 2, is also applicable to the method for predicting the pulse wave transit direction using the spatial relationship between the effective sampling locations, such as the position N1, the position N2, and the position N3 in fig. 5, and it is only necessary to replace the default sampling locations with the effective sampling locations in the correlation calculation and formula. That is to say, in combination with the PPG sensor with light field distribution compensation, the layout of the multiple emitters/detectors included therein and providing multiple paths of PPG signals independent of each other may determine the effective sampling location of each path of PPG signals according to the layout of the multiple emitters/detectors and other factors affecting the light field distribution, and calculate the transfer direction of the pulse wave according to the spatial relationship between the multiple effective sampling locations and the analysis of the phase difference and waveform of the multiple paths of PPG signals, thereby improving the PPG measurement result and improving the measurement accuracy.

Referring to fig. 6, fig. 6 shows a block diagram of a PPG sensor according to another implementation manner provided in the embodiments of the present application. As shown in fig. 6, the PPG sensor 600 includes a sensor sequence 602, a light field distribution compensation module 604, a sampling speed adjustment module 606, a machine learning model 610, a user model library 620, a user model update module 622, and a preset physiological model library 630. Wherein the sensor sequence 602 includes a plurality of emitters/detectors distributed according to preset distances and orientations, the sensor sequence 602 may form different emitter/detector combinations by selectively activating the emitters/detectors therein, thereby forming different layouts of the PPG sensors. Therefore, the PPG sensor 600 has an adjustable layout by the sensor sequence 602, in particular the multi-path PPG signals provided by the PPG sensor 600 correspond one-to-one to a plurality of sampling locations, and the spatial relationship between these sampling locations is adjustable. The light field distribution compensation module 604 is communicatively connected to the sensor sequence 602, and obtains the currently activated emitter/detector, or the layout of the current PPG sensor 600 from the sensor sequence 602, so as to calculate a plurality of effective sampling points corresponding to the multi-path PPG signals with reference to the PPG sensor 500 combined with light field distribution compensation shown in fig. 5, and send information of the effective sampling points to the machine learning model 610. The sensor sequence 602 also sends the acquired multi-path PPG signals to the machine learning model 610. The sampling rate adjustment module 606 is used to adjust the sampling frequency, and specifically, by increasing the sampling frequency, the distance between the sampling locations can be shortened to reduce the measurement error, but at the same time, the resource consumption can also be increased. The sampling rate adjustment module 606 is communicatively connected to the sensor sequence 602, obtains the currently activated emitter/detector, or the current layout of the PPG sensor 600, from the sensor sequence 602, and adjusts the sampling frequency according to the current layout of the PPG sensor 600 to reduce the measurement error.

The machine learning model 610 is a trained artificial intelligence model for calculating a transfer direction of a pulse wave from various input information and determining a pulse wave transfer time PTT and a pulse wave transfer speed PWV from a plurality of PPG signals and the calculated transfer direction of the pulse wave, and further calculating various physiological parameters including, but not limited to, blood pressure, hemoglobin concentration, pulse, blood oxygen saturation, respiratory rate, blood perfusion index, blood flow reactivity, methemoglobin, carboxyhemoglobin, bilirubin, oxygen content, blood lipid, and blood glucose. It should be understood that in one possible embodiment, the machine learning model 610 is only used to calculate the pulse wave transfer direction from the various information input and determine the pulse wave transfer time PTT and the pulse wave transfer velocity PWV from the multiple PPG signals and the calculated pulse wave transfer direction. The PPG sensor 600 also includes other modules (not shown) that obtain the PTT and PWV from the machine learning model 610 and then perform the calculation of the physiological parameters by other modules, such as application specific integrated circuits or chips based on programmable logic technology. In another possible embodiment, the machine learning model 610 is only used to calculate the transfer direction of the pulse wave according to the various input information, and transmit the calculated transfer direction of the pulse wave to other modules (not shown) of the PPG sensor 600, which calculate the PTT and PWV and the physiological parameters. In summary, the machine learning model 610 is at least configured to calculate the direction of propagation of the pulse wave of the measurement area, or in other words the arterial vascularity of the measurement area.

As described above, the machine learning model 610 obtains multiple paths of PPG signals from the sensor sequence 602, obtains multiple effective sampling locations compensated by combining the light field distribution from the light field distribution compensation module 604, obtains a sampling frequency corresponding to the current layout of the PPG sensor 600 from the sampling speed adjustment module, and then the machine learning model 610 calculates the transfer direction of the pulse wave according to the input signal and the trained artificial intelligence model. The artificial intelligence model of the machine learning model 610 may be based on any suitable artificial intelligence technique, such as a Deep machine learning technique, and on any suitable machine learning framework and model, such as a Deep convolutional Neural Network (DNN) model, which may be adjusted or modified according to actual needs, and is not limited herein. Machine learning model 610 may refer to a processor, chip, integrated circuit, or any suitable electronic device for executing a machine learning algorithm or artificial intelligence model. In addition, for the purpose of speeding up calculation, the machine learning model 610 may also obtain, instead of obtaining multiple effective sampling locations from the light field distribution compensation module 604 after compensation of the light field distribution, the current layout of the PPG sensor 600 from the sensor sequence 602 and replace the effective sampling locations with default sampling locations, that is, replace the maximum overlapping regions of the transmitting square and the receiving light field with the middle points of the light paths described above. Although this may lose some measurement accuracy, the step of calculating the light field distribution compensation may be saved, which may be suitable in some cases to accelerate the calculation, for example, when the human body is in a state of intense motion and the measurement area changes drastically.

Different parts of a human body usually have different arterial blood vessel distributions, namely different pulse wave transmission directions, and the transmission direction of the pulse wave can be calculated by utilizing a multi-path PPG signal, a plurality of effective sampling places and sampling frequency which are input data through the multitask processing function of the machine learning model 610, and other output data such as PTT, PWV and the like can also be provided. Considering certain regularity and repeatability of the distribution of artery blood vessels at the same part of a human body, for example, the anatomical maps of the segmented arteries at the wrists of different people can be known to have approximate trend trends according to relevant knowledge of human anatomy. In addition, the same user usually wears the PPG sensor on several fixed parts, such as the left and right wrists or the ears and the forehead, and the PPG sensor located at these parts usually also measures in several specific measurement areas, and the artery trend of the same user in these specific measurement areas also keeps a certain consistency and regularity. Therefore, the user model library 620 is used to provide the historical data and the calculation model of the same user to the machine learning model 610, so that the calculation speed and the measurement accuracy can be improved when the PPG sensor 600 is repeatedly used by the same user, and the user model updating module 622 is used to update the user model library 620 according to the result calculated by the machine learning model 610, so that the data and the model recorded by the user model library 620 better conform to the individual characteristics of the current user. The user model update module 622 may implement adaptive update data and models through algorithms such as supervised learning. The preset physiological model library 630 stores preset physiological models of artery directions and pulse wave transmission directions of different parts of the human body, such as a physiological model of the left wrist of the human body, and provides the preset physiological models to the machine learning model 610, so as to further improve the efficiency of calculating the pulse wave transmission direction according to the preset physiological models.

With reference to fig. 1 to 6, in the PPG sensor provided in the embodiments of the present application, in consideration of the influence of the pulse wave transmission direction or the artery trend on the PPG measurement, sampling locations corresponding to multiple paths of PPG signals are obtained while measuring the multiple paths of PPG signals, and the transmission direction of the pulse wave is calculated according to the spatial relationship between the sampling locations and the waveform analysis and the phase difference analysis of the multiple paths of PPG signals, so that the PPG measurement result can be improved and the measurement accuracy can be improved. In addition, the PPG sensor provided in the embodiment of the present application further considers light field distribution compensation, and a plurality of effective sampling locations after the light field distribution compensation are obtained through, for example, the light field distribution compensation module 604 shown in fig. 6, so as to improve the measurement effect. Moreover, the PPG sensor provided in the embodiments of the present application also provides an easily adjustable layout (such as the sensor sequence 400 shown in fig. 4) by providing a sensor sequence in which emitters/detectors can be selectively activated, so that the PPG sensor can obtain different layouts by selectively activating different combinations of emitters/detectors in an application, which is beneficial to improve the measurement effect. In addition, the PPG sensor provided by the embodiment of the present application further provides a sampling speed adjustment module in consideration of the influence of the sampling frequency, so that the sampling frequency is adjusted according to the layout of the current PPG sensor, thereby reducing the measurement error. In addition, the PPG sensor provided by the embodiment of the application also considers certain regularity and repeatability of arterial blood vessel distribution at the same part on a human body and human body characteristics of the same user, provides a user model library and a preset physiological model, and further improves the efficiency of calculating the pulse wave transmission direction.

The embodiments provided herein may be implemented in any one or combination of hardware, software, firmware, or solid state logic circuitry, and may be implemented in connection with signal processing, control, and/or application specific circuitry. Particular embodiments of the present application provide an apparatus or device that may include one or more processors (e.g., microprocessors, controllers, Digital Signal Processors (DSPs), Application Specific Integrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs), etc.) that process various computer-executable instructions to control the operation of the apparatus or device. Particular embodiments of the present application provide an apparatus or device that can include a system bus or data transfer system that couples the various components together. A system bus can include any of a variety of different bus structures or combination of different bus structures, such as a memory bus or memory controller, a peripheral bus, a universal serial bus, and/or a processor or local bus that utilizes any of a variety of bus architectures. The devices or apparatuses provided in the embodiments of the present application may be provided separately, or may be part of a system, or may be part of other devices or apparatuses.

Particular embodiments provided herein may include or be combined with computer-readable storage media, such as one or more storage devices capable of providing non-transitory data storage. The computer-readable storage medium/storage device may be configured to store data, programmers and/or instructions that, when executed by a processor of an apparatus or device provided by embodiments of the present application, cause the apparatus or device to perform operations associated therewith. The computer-readable storage medium/storage device may include one or more of the following features: volatile, non-volatile, dynamic, static, read/write, read-only, random access, sequential access, location addressability, file addressability, and content addressability. In one or more exemplary embodiments, the computer-readable storage medium/storage device may be integrated into a device or apparatus provided in the embodiments of the present application or belong to a common system. The computer-readable storage medium/memory device may include optical, semiconductor, and/or magnetic memory devices, etc., and may also include Random Access Memory (RAM), flash memory, read-only memory (ROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), registers, a hard disk, a removable disk, a recordable and/or rewriteable Compact Disc (CD), a Digital Versatile Disc (DVD), a mass storage media device, or any other form of suitable storage media.

The above is an implementation manner of the embodiments of the present application, and it should be noted that the steps in the method described in the embodiments of the present application may be sequentially adjusted, combined, and deleted according to actual needs. In the above embodiments, the descriptions of the respective embodiments have respective emphasis, and for parts that are not described in detail in a certain embodiment, reference may be made to related descriptions of other embodiments. It is to be understood that the embodiments of the present application and the structures shown in the drawings are not to be construed as particularly limiting the devices or systems concerned. In other embodiments of the present application, an apparatus or system may include more or fewer components than the specific embodiments and figures, or may combine certain components, or may separate certain components, or may have a different arrangement of components. Those skilled in the art will understand that various modifications and changes may be made in the arrangement, operation, and details of the methods and apparatus described in the specific embodiments without departing from the spirit and scope of the embodiments herein; without departing from the principles of embodiments of the present application, several improvements and modifications may be made, and such improvements and modifications are also considered to be within the scope of the present application.

Claims

1. A PPG sensor, characterized in that the PPG sensor comprises:

a sensor sequence, wherein the sensor sequence comprises at least three emitter/detector sets that are selectively activated to provide at least three PPG signals that correspond one-to-one with the activated emitter/detector set; and

a processor, wherein the processor is configured to receive the at least three PPG signals and provide an output of the PPG sensor, the output of the PPG sensor including at least a pulse wave propagation direction,

wherein the pulse wave transfer direction is determined from the phase difference between the at least three PPG signals and the layout of the PPG sensor determined from the activated set of emitters/detectors.

2. The PPG sensor of claim 1 wherein any two of the at least three emitter/detector groups have different emitters or different detectors or both emitters and detectors.

3. The PPG sensor of claim 2, wherein the at least three emitter/detector groups comprise: three emitter/detector groups consisting of one emitter and three detectors, respectively, or three emitter/detector groups consisting of one detector and three emitters, respectively, or four emitter/detector groups consisting of one emitter and four detectors, respectively.

4. The PPG sensor of claim 1 wherein the emitter is an LED and the detector is a PD.

5. The PPG sensor of claim 1, wherein the output of the PPG sensor further comprises a pulse wave transit time PTT or a pulse wave transit velocity PWV.

6. The PPG sensor of claim 1, wherein the layout of the PPG sensor is determined from the activated set of emitters/detectors, including: determining a plurality of light paths and respective midpoints of the plurality of light paths according to the activated emitter/detector group, wherein the layout of the PPG sensor comprises side lengths and internal angles of a polygon formed by the respective midpoints of the plurality of light paths.

7. The PPG sensor of claim 1, wherein the layout of the PPG sensor is determined from the activated set of emitters/detectors, including: determining a plurality of light ray paths and respective midpoints of the plurality of light ray paths from the activated set of emitters/detectors, the layout of the PPG sensor including distances and relative orientations between the respective midpoints of the plurality of light ray paths.

8. The PPG sensor of claim 1, wherein the positions of all transmitter/detector groups comprised by the sensor sequence on the PPG sensor are predetermined.

9. The PPG sensor of claim 1, wherein the PPG sensor further comprises:

a light field distribution compensation module communicatively coupled to the sensor sequence, the light field distribution compensation module calculating a light field distribution compensation result for the activated transmitter/detector group based on an overlap between the transmitted and received light fields of the activated transmitter/detector group.

10. The PPG sensor of claim 9 wherein the light field distribution compensation module further calculates a light field distribution compensation result for the activated emitter/detector group based on at least one of: a wavelength of light emitted by the activated emitter/detector set, an emission angle of the activated emitter/detector set, a reception angle of the activated emitter/detector set, a degree of curvature of a measurement area of the PPG sensor.

11. The PPG sensor according to claim 9 or 10, wherein the layout of the PPG sensor is determined from the activated set of emitters/detectors, including: determining a plurality of light ray paths and respective midpoints of the plurality of light ray paths according to the activated emitter/detector group, calculating respective effective sampling points of the plurality of light ray paths according to a light field distribution compensation result of the activated emitter/detector group and respective midpoints of the plurality of light ray paths by the light field distribution compensation module or the processor, and calculating a spatial relationship between the respective effective sampling points of the plurality of light ray paths by the layout of the PPG sensor.

12. The PPG sensor of claim 11 wherein the spatial relationship between the effective sampling locations of each of the plurality of ray paths comprises a side length and an interior angle of a polygon formed by the effective sampling locations of each of the plurality of ray paths, or a distance and a relative orientation of the effective sampling locations of each of the plurality of ray paths.

13. The PPG sensor of claim 1, wherein the PPG sensor further comprises:

a sampling rate adjustment module communicatively coupled to the sensor sequence, the sampling rate adjustment module configured to adjust a sampling frequency according to the activated set of emitters/detectors.

14. The PPG sensor according to claim 1, wherein the processor provides an output result of the PPG sensor based on a depth machine learning model trained to compute the pulse wave transfer direction from phase differences between the at least three PPG signals and a layout of the PPG sensor.

15. The PPG sensor of claim 14, wherein the PPG sensor further comprises:

and presetting a physiological model library, wherein the preset physiological model library provides a model of the trend of the arterial blood vessels of a specific part of the human body to the deep machine learning model.

16. The PPG sensor of claim 14, wherein the PPG sensor further comprises:

a user model library, wherein the user model library provides a model of arterial vessel trend for a particular user to the deep machine learning model based on historical data of the PPG sensor.

17. The PPG sensor of claim 16, wherein the PPG sensor further comprises:

and the user model updating module is used for updating the user model library according to the output result of the PPG sensor.

18. The PPG sensor according to any one of claims 1 to 17, wherein a measurement region of the PPG sensor is located at a wrist, a finger, an ear, a forehead, a cheek, or an eye ball.

19. A physiological parameter sensor characterized in that it comprises a PPG sensor according to any of claims 1 to 18, which determines a physiological parameter depending on the pulse wave propagation direction.

20. A physiological parameter sensor according to claim 19, wherein said physiological parameter is a blood-related parameter comprising at least one of: blood pressure, hemoglobin concentration, pulse, blood oxygen saturation, respiratory rate, perfusion index, blood flow reactivity, methemoglobin, carboxyhemoglobin, bilirubin, oxygen content, blood lipids, and blood glucose.

21. The physiological parameter sensor of claim 19, wherein said physiological parameter is a pigment-related parameter comprising a pigment distribution map, pigment interference, or pigment-related background noise.

22. A smart wearable device comprising a PPG sensor according to any of claims 1-18, the smart wearable device providing a medical monitoring result from an output of the PPG sensor.

23. The smart wearable device of claim 22, wherein the medical monitoring result is based on a blood-related parameter determined from an output of the PPG sensor, the blood-related parameter comprising at least one of: blood pressure, hemoglobin concentration, pulse, blood oxygen saturation, respiratory rate, perfusion index, blood flow reactivity, methemoglobin, carboxyhemoglobin, bilirubin, oxygen content, blood lipids, and blood glucose.

24. The smart wearable device of claim 22, wherein the medical monitoring result is based on a pigment-related parameter determined from an output of the PPG sensor, the pigment-related parameter comprising a pigment distribution map, pigment interference, or pigment-related background noise.