WO2017181635A1

WO2017181635A1 - Terminal and method for measuring blood pressure

Info

Publication number: WO2017181635A1
Application number: PCT/CN2016/102685
Authority: WO
Inventors: 刘登宽; 王帆
Original assignee: 华为技术有限公司
Priority date: 2016-04-21
Filing date: 2016-10-20
Publication date: 2017-10-26
Also published as: CN105748053A

Abstract

A terminal and method for measuring blood pressure, the terminal comprising: a flash light (41), a processor (42) and at least two cameras (43). Every two of the cameras (43) are separated by a predetermined distance (L). The flash light (41) emits, under the control of the processor (42), light of a predetermined frequency. The at least two cameras (43) collect, under the control of the processor (42), a photoplethysmography (PPG) signal, the PPG signal being an optical signal reflected by a body of a user covering the cameras (43) and received by the cameras (43). The processor (42) controls the flash light (41) to emit light of a predetermined frequency, controls each of the cameras (43) to start sequential collection of a PPG signal at a predetermined frequency, receives at least one PPG signal collected by each of the cameras (43), determines a pulse wave velocity on the basis of the PPG signal collected by each of the cameras (43), and acquires a blood pressure measurement of the user on the basis of the pulse wave velocity. The terminal and method for measuring blood pressure of the present invention can improve the precision of blood pressure measurements.

Description

Terminal and blood pressure measurement method

Technical field

The present invention relates to the field of intelligent terminal technologies, and in particular, to a terminal and a blood pressure measuring method.

Background technique

Blood pressure is the side pressure on the blood vessel wall when the blood flows in the blood vessel. The blood pressure directly reflects the key factors of the human body such as blood ejection ability, blood viscosity, blood vessel elasticity, and peripheral blood vessel resistance. High blood pressure may cause arteriosclerosis. Coronary heart disease, heart failure, etc., low blood pressure may cause myocardial infarction or shock, therefore, high blood pressure too low (hypotension, high blood pressure) can have serious consequences. At present, there are as many as 130 million patients with hypertension in China, and nearly half of them do not know that they have high blood pressure. The treatment rate and control rate of hypertension are lower, 28.2% and 2.9% respectively. Therefore, how accurate, fast, and Convenient detection of blood pressure has become an important topic of current concern.

At present, the technique of measuring blood pressure mainly calculates the pulse wave velocity (PWV) by obtaining the pulse wave through the distance between the two points of the artery and the pulse transit time (PPT), according to PWV and The linear relationship of blood pressure measures the blood pressure of the user. Figure 1 is a schematic diagram of current measurement of blood pressure using the PTT measurement method. As shown in Figure 1, two photoplethysmography (PPG) sensors (such as PPG1 and PPG2 in Figure 1) are placed in the user's radial artery (Fig. 1). On the skin of position 1) and the middle finger artery (position 2 in Figure 1), the distance between the two points of the artery can be obtained by measuring the distance between the radial artery and the middle finger artery, by measuring the time of the pulse wave at position 1. At the point T1 and at the time point T2 of the position 2, the transit time of the pulse wave can be obtained, and the blood pressure of the user is measured.

However, with the current PTT measurement method, since the distance between the two sensors is easily changed by the movement of the human body, it directly affects the pulse transit time PTT, so that the measured blood pressure and the actual blood pressure have errors, thereby causing the measured blood pressure. The accuracy is not high.

Summary of the invention

The present invention provides a terminal and blood pressure measuring method which can improve the accuracy of the measured blood pressure.

A terminal provided by the first aspect of the present invention includes: a flash, a processor, and at least two cameras, each of which has a preset distance between the two cameras; the processor is configured to control the flash, and the flash is used to issue a pre-control under the control of the processor. The frequency of the light; the processor is also used to control at least two cameras, at least two cameras are used to collect the PPG signal under the control of the processor, the PPG signal is reflected by the user's limbs covered by the camera and received by the camera The processor is further configured to obtain at least one PPG signal collected by each camera, determine a pulse wave propagation speed according to a preset distance and at least one PPG signal collected by each camera, and acquire a user according to the pulse wave propagation speed. Measurement of blood pressure. It ensures that the PTT is not interfered with the pre-ejection period and human body motion, and the terminal uses at least two cameras to solve the change of the sensor distance caused by the user's arm movement, thus ensuring the stability of the measured pulse wave transmission time PTT. , thereby improving the accuracy of the measured blood pressure.

In combination with the first aspect, in a first implementation manner of the first aspect, the processor is configured to obtain at least one PPG signal collected by each camera, and determine a pulse according to the preset distance and at least one PPG signal collected by each camera. The wave propagation speed is specifically used to: determine, according to at least one PPG signal collected by each camera, a target PPG signal corresponding to each camera; and determine each of the target PPG signals of any two adjacent channels corresponding to the same pulse. The difference between the time points corresponding to the domain feature points; the pulse wave propagation speed is obtained according to the ratio of the preset distance to the pulse wave transit time; and the measured blood pressure of the user is obtained according to the pulse wave propagation speed. The pulse wave propagation speed is obtained according to the time point corresponding to the same time domain feature point in the PPG signal, thereby obtaining the measured blood pressure of the user.

In conjunction with the first aspect and the first implementation of the first aspect, in a second implementation of the first aspect, the camera is specifically configured to: at least two cameras are used for control of the processor at intervals in which the flash emits light Next, the ambient light of the user's limbs covered by the light on the camera is sequentially collected at a preset frequency. When the flash emits light, at least two cameras sequentially collect the light at a preset frequency and pass the limb reflection of the user covering the camera. Correspondingly, when the processor is configured to obtain at least one PPG signal collected by each camera, the processor is specifically configured to: obtain each camera according to the difference signal between the reflected light and the ambient light collected by each camera The acquired at least one PPG signal can achieve at least one PPG signal for each camera. After the light is used as a light source, the returned light is received by the dual camera after being transmitted/reflected by the human finger or other position, thereby completing the portable blood. The pressure detection function enables each camera to obtain at least one PPG signal.

With reference to the second implementation manner of the first aspect, in a third implementation manner of the first aspect, the at least one PPG signal collected by each camera includes: a red light R, a green light G, and a blue light B three-way PPG signal; Correspondingly, the processor is configured to: when determining, according to the at least one PPG signal collected by each camera, a target PPG signal corresponding to each camera, specifically: detecting a signal to noise ratio SNR of the three PPG signals collected by each camera, and obtaining The PPG signal with the largest SNR among the three PPG signals collected by each camera is used as the target PPG signal. By obtaining the signal with the largest signal-to-noise ratio as the target PPG signal, the feature signal is selected by using one signal with the largest signal-to-noise ratio, which greatly reduces the influence of motion interference on the algorithm.

In conjunction with the third implementation manner of the first aspect, in a fourth implementation manner of the first aspect, the processor is further configured to: acquire a feature of a PPG signal with the largest SNR among the three PPG signals collected by each camera The parameter sequence, the characteristic parameter sequence is a set of frequency domain feature points of the PPG signal; the processor is configured to acquire the user's measured blood pressure according to the pulse wave propagation speed, and is specifically used to: obtain the user's measured blood pressure according to the pulse wave propagation speed and the characteristic parameter sequence . By combining the time difference PTT of a feature point of the PPG signal with the characteristic parameter sequence to form the final characteristic parameter sequence, as an input parameter for measuring the blood pressure algorithm, more parameters related to the measured blood pressure are provided, which overcomes the current Insufficient critical information on blood pressure-related parameters makes the measured blood pressure less accurate.

In combination with the third implementation manner of the first aspect and the four implementation manners of the first aspect, in a fifth implementation manner of the first aspect, the processor is further configured to: detect three three-way PPG signals collected by each camera After the SNR, the SNR of the three PPG signals collected by each camera is compared with a preset threshold; if the SNR of the three PPG signals is less than the preset threshold, the measurement indication information is sent to the user, and the measurement indication information is used. Instructs the user to re-cover the user's limbs on each camera. By judging the SNR of the three-way PPG signal, the user can be reminded to re-measure when the user measures the blood pressure sway too much, and the accuracy of the measured blood pressure is improved.

With reference to the first implementation manner of the first aspect, in a sixth implementation manner of the first aspect, the at least one PPG signal collected by each camera includes: a red light R, a green light G, and a blue light B three-way PPG signal; Correspondingly, the processor is configured to: when determining, according to at least one PPG signal collected by each camera, a target PPG signal corresponding to each camera, specifically: acquiring three PPG signals collected by each camera, and collecting each of the cameras Three-way PPG signal The average value is taken as the target PPG signal. By using the average value of the three PPG signals collected by each camera as the target PPG signal, the average value of the three PPG signals is used to select the feature points, thereby greatly reducing the influence of the motion interference on the algorithm.

With reference to the fifth aspect, the fifth implementation manner of the first aspect, in the seventh implementation manner of the first aspect, the processor is configured to: when acquiring the pulse wave transit time according to the difference, specifically: according to any pulse corresponding to any pulse The difference between the time points corresponding to the time domain feature points in the target PPG signals of the adjacent two channels or the time point corresponding to the time domain feature points in the target PPG signals of any two adjacent channels corresponding to the at least two pulses The average value of the difference is obtained by the pulse wave transit time, which can improve the accuracy of obtaining the pulse wave transit time, thereby improving the accuracy of the acquired user's measured blood pressure.

With reference to the seventh aspect, the seventh implementation of the first aspect, in the eighth implementation manner of the first aspect, the terminal further includes: a display screen, configured to display the measured blood pressure of the user under the control of the processor, to implement The user's measured blood pressure is displayed, making it easy for the user to know the size of his or her blood pressure.

A blood pressure measuring method according to a second aspect of the present invention includes: a processor controlling a flash to emit a preset frequency of light; and a processor controlling at least two cameras to collect a PPG signal, wherein the PPG signal is a light reflection of a user passing through a camera covering the camera and a signal received by the camera; the processor obtains at least one PPG signal collected by each camera, and determines a pulse wave propagation speed according to a preset distance between the two cameras and at least one PPG signal collected by each camera, according to the pulse rate The wave propagation speed acquires the user's measured blood pressure. It ensures that the PTT is not interfered with in the early stage of ejection and human motion, and the change of the sensor distance caused by the arm movement is solved by using at least two cameras, thereby ensuring the stability of the measured pulse wave transit time PTT. Improve the accuracy of the measured blood pressure. The refinement of each step in the method corresponds to various implementations in the first aspect, and details are not described herein again.

The terminal and the blood pressure measuring method provided by the embodiment of the invention control the flash to emit a preset frequency of the light, control at least two cameras to collect the PPG signal, and obtain at least one PPG signal collected by each camera, according to each camera The collected PPG signal determines the pulse wave propagation speed, obtains the user's measured blood pressure according to the pulse wave propagation speed, ensures that the PTT is not interfered by the pre-ejection period and the human body motion, and solves the arm movement by using at least two cameras. The resulting change in sensor distance thus ensures the transmission of the measured pulse wave The stability of the time PTT is delivered, thereby improving the accuracy of the measured blood pressure.

DRAWINGS

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, a brief description of the drawings used in the embodiments or the prior art description will be briefly described below. Obviously, the drawings in the following description It is a certain embodiment of the present invention, and other drawings can be obtained from those skilled in the art without any inventive labor.

Figure 1 is a schematic diagram of current measurement of blood pressure using the PTT measurement method;

2 is a schematic diagram of a measurement principle of a PPG;

Figure 3 is a waveform diagram of a PPG obtained by PPG tracing;

4 is a schematic structural diagram of a terminal according to Embodiment 1 of the present invention;

FIG. 5 is a schematic structural diagram of a terminal according to Embodiment 2 of the present invention;

FIG. 6 is a schematic diagram of obtaining a difference between time points corresponding to time domain feature points according to an embodiment of the present disclosure;

FIG. 7 is a flowchart of controlling two cameras and a flash according to an embodiment of the present invention; FIG.

FIG. 8 is a flowchart of a blood pressure measuring method according to Embodiment 1 of the present invention.

detailed description

The technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings in the embodiments of the present invention. It is a partial embodiment of the invention, and not all of the embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative efforts are within the scope of the present invention.

At present, the blood volume parameters of blood flowing in blood vessels are mainly obtained by photoelectric volume pulse wave analysis. The photoelectric volume pulse wave method is based on the pulsation change of the blood volume of peripheral microvessels with the heart beat, and then passes through the photoplethysmography (Photoplethysmography). PPG, abbreviated as PPG, is a simple, low-cost optical measurement technique that can be used to detect changes in blood volume in tissue blood vessels. 2 is a schematic diagram of the measurement principle of the PPG. As shown in FIG. 2, the PPG technique is often used in non-invasive measurement of the skin surface to receive an optical signal through a phototransistor, wherein the phototransistor may include a light emitting diode of an infrared wavelength (Light Emitting Diode, LED for short) and red (red) wavelength will be connected The received optical signal is converted into an electrical signal, and after being processed by filtering, amplification, analog-to-digital (A/D) conversion, etc., a blood flow change of the volume pulse wave, that is, a photoelectric volume pulse wave is obtained. Figure 3 is a waveform diagram of PPG obtained by PPG tracing. As shown in Figure 3, the waveform of PPG generally includes alternating current (AC) and direct current (DC): the AC part usually comes from the heart. The change in blood volume caused by beating is generally synchronized with the pulse; while the DC part is the average blood volume in the tissue, which exhibits low frequency fluctuations under the influence of respiration, sympathetic nerve activity and thermoregulation.

4 is a schematic structural diagram of a terminal according to Embodiment 1 of the present invention, and FIG. 5 is a schematic structural diagram of a terminal according to Embodiment 2 of the present invention. As shown in FIG. 4 and FIG. 5, the terminal provided by the embodiment of the present invention includes a flash 41, a processor 42, and at least two cameras 43 having a preset distance between each two cameras 43.

It should be noted that the terminal in the embodiment of the present invention may be a mobile phone, a tablet computer, a notebook computer, or the like. The embodiment of the present invention mainly uses a mobile phone as an example, but is not limited thereto. The embodiment of the present invention mainly uses two cameras as an example, but is not limited thereto.

The processor 42 is used to control the flash 41 for emitting a predetermined frequency of light under the control of the processor 42.

Among them, the preset frequency refers to the fixed number of times the flash switches per second. Those skilled in the art will appreciate that in order to perform sampling better and more timely, the frequency of the flash of the flash and the frequency of signal acquisition by the camera are much greater than the frequency of the pulse.

The processor 42 is further configured to control at least two cameras 43 for collecting PPG signals under the control of the processor 42. The PPG signals are reflected by the limbs of the user covered by the camera and received by the camera 43. signal of.

Specifically, a mobile phone is equipped with two cameras, which are next to the flash, two cameras and a flash to form a hardware acquisition module (blood pressure data acquisition module), that is, by the flash as a light source, through the transmission of human fingers or other positions / After the reflection, the returned light is received by the dual cameras, thereby completing the portable blood pressure detecting function. There is a preset distance between the two cameras (the distance between the centers of the two cameras), and preferably, the preset distance may be from several tens of millimeters to several centimeters.

The processor 42 obtains at least one PPG signal collected by each camera 43, and determines a pulse wave propagation speed according to the preset distance and at least one PPG signal collected by each camera 43. Degree, the user's measured blood pressure is obtained according to the pulse wave propagation speed.

The at least one PPG signal collected by each camera refers to at least one PPG signal collected by each camera. For example, there are two cameras, which are respectively a first camera and a second camera, and the first camera collects at least one road. The PPG signal, the second camera also collects at least one PPG signal. Generally, the camera may include three-way PPG signals of red light R, green light G, and blue light B. In other embodiments, it is not limited to include only one, two, or three paths.

Since the pulse wave propagation speed has a linear relationship with the blood pressure, the measured blood pressure of the user can be obtained according to the pulse wave propagation speed, wherein, in the embodiment of the invention, the measured blood pressure of the user is obtained according to the pulse wave propagation speed and is the same according to the current pulse wave. The linear relationship between the propagation speed and the blood pressure is the same as that of the user's blood pressure, and the embodiment of the present invention is not limited and described herein. The optical signal collected by each camera 43 is collected by the signal amplification, hardware filtering, A/D conversion, and is the collected at least one PPG signal, and at least one PPG signal is processed in the processor of the mobile phone to calculate Blood pressure value.

It should be noted that the processor 42 in the embodiment of the present invention may be a central processing unit (CPU).

In practical applications, the mobile phone generally needs to have two cameras (recorded as PD1, PD2), the preset distance between PD1 and PD2 is L, and the built-in controller of the mobile phone controls the flash (recorded as LED) to open, first collect the PD1 and the PD1. Current data, and then open the current data collected on PD2, the two channels of data depict the waveform, respectively recorded as PPG1 and PPG2. Looking from PPG1 least one feature point in time, denoted by _1, the time to find the corresponding feature point from PPG2 to t, denoted t _2, the _{_{PTT = t 2 -t 1, PWV}} = L / PTT. By using the time difference of the characteristic points between the two signals as the PTT, it is ensured that the PTT is not interfered by the pre-ejection period and the human body motion, and the method of the dual camera of the mobile phone solves the change of the sensor distance caused by the arm movement, thereby ensuring the detection. The stability of the pulse wave transit time PTT.

The terminal provided by the embodiment of the present invention comprises a flash, a processor and at least two cameras, wherein each of the two cameras has a preset distance, and at least two cameras and a flash constitute a blood pressure data acquisition module, that is, a flash light is used as a light source. After being transmitted/reflected by a human finger or other position, the returned light is received by at least the camera, thereby enabling a portable blood pressure detecting function. At the same time, the processor controls the flash to emit a preset frequency of light, and controls at least two cameras to collect the PPG signal to obtain at least the collected by each camera. A PPG signal determines the pulse wave propagation speed according to at least one PPG signal collected by each camera, and obtains the user's measured blood pressure according to the pulse wave propagation speed, thereby ensuring that the PTT is not interfered by the pre-ejection period and the human body motion, and the terminal adopts The manner of at least two cameras solves the change of the sensor distance caused by the arm movement, thereby ensuring the stability of the measured pulse wave transit time PTT, thereby improving the accuracy of the measured blood pressure.

Further, in the example shown in FIG. 4, the processor 42 is configured to obtain at least one PPG signal collected by each camera 43, and determine pulse wave propagation according to a preset distance and at least one PPG signal collected by each camera 43. The speed is specifically used to: determine, according to at least one PPG signal collected by each camera 43, a target PPG signal corresponding to each camera 43; and determine each of the target PPG signals of any two adjacent channels corresponding to the same pulse. The difference between the time points corresponding to the domain feature points; the pulse wave transit time is obtained according to the difference; the pulse wave propagation speed is obtained according to the ratio of the preset distance to the pulse wave transit time; and the measured blood pressure of the user is obtained according to the pulse wave propagation speed.

Specifically, the camera 43 may include a red light R, a green light G, and a blue light B three-way PPG signal, and the processor 42 determines, according to at least one PPG signal collected by each camera 43 , a target PPG signal corresponding to each camera 43. However, the method is not limited to the following: the processor 43 may use any one of the at least one PPG signals collected by each camera 43 as the target PPG signal, or may select at least one of the PPG signals collected by each camera 43. The average value of any two signals is used as the target PPG signal; the average of the three signals in at least one PPG signal collected by each camera 43 may be used as the target PPG signal, or at least one PPG collected by each camera 43 may be used. The one of the three signals in the signal has the largest SNR as the target PPG signal, which is not limited in this embodiment. The processor 42 determines a difference between time points corresponding to respective time domain feature points in any two adjacent target PPG signals corresponding to the same pulse. The time domain feature point refers to a point in the signal waveform of the time domain that can reflect the characteristics of the pulse wave signal. Preferably, the time domain feature point may be a peak in the PPG signal. Correspondingly, the time difference is the time difference between two time points corresponding to the two peaks respectively.

FIG. 6 is a schematic diagram of obtaining a difference between time points corresponding to time domain feature points according to an embodiment of the present invention. As shown in FIG. 6 , the target PPG signals acquired by the processor through two cameras are respectively marked as PPG1 and PPG2. Assuming that the largest peak in the waveform is a time domain feature point, there are multiple time domain feature points in both PPG1 and PPG2 shown in FIG. 6, for example, there are three time domain feature points in PPG1, PPG2 There are 4 time domain feature points in it. According to different acquisition times of the two PPG signals, the difference between the time points corresponding to the respective time domain points in the target two PPG signals corresponding to the same pulse is different, specifically:

(1) Assuming that the camera corresponding to PPG1 first collects the pulse wave, the PPG1 signal will first appear a peak (time domain feature point), and then a peak appears on the PPG2 signal. At this time, the formula T1=t ₃ can be used. t ₁ calculates the difference;

(2) Assuming that the camera corresponding to PPG2 first collects the pulse wave, the PPG2 signal will first appear a peak, and then a peak appears on the PPG1 signal. At this time, the difference can be calculated by the formula T2=t ₅ -t ₃ value.

Further, in the example shown in FIG. 4, when the processor 42 is configured to acquire the pulse wave transit time according to the difference, the processor 42 is specifically configured to: time domain features in the target PPG signals of any two adjacent channels corresponding to any pulse. The pulse wave transit time is obtained by the difference between the time points corresponding to the points or the average of the differences between the time points corresponding to the time domain feature points in the target PPG signals of any two adjacent channels corresponding to at least two pulses.

Specifically, as shown in FIG. 6, a plurality of pulse waves exist in both PPG1 and PPG2 shown in FIG. 6, and one pulse wave may have multiple time domain feature points. For example, there are three pulse waves in PPG1, and each has three pulse waves. pulse wave can select two time domain feature points a and b, PPG2 there are four pulse wave, each pulse wave may select two time domain feature point a ₁ and Example b _1, specifically, the present invention Obtaining the pulse wave transit time based on the difference may include the following cases:

In the first case, the pulse wave transit time is obtained according to the difference between the time points corresponding to the time domain feature points in the target PPG signals of any two adjacent channels corresponding to any pulse wave, specifically:

(1) Select a feature point from a pulse wave. Assuming that the camera corresponding to PPG1 first collects the pulse wave, the PPG1 signal will first appear a time domain feature point a, and then a time domain feature point a ₁ appears on the PPG2 signal. At this time, the formula T1=t ₃ can be used. t ₁ is calculated the difference T1, embodiments of the present invention may transmit the time difference T1 as the pulse wave.

(2) Selecting a plurality of feature points from one pulse wave. Assuming that the camera corresponding to PPG1 first collects the pulse wave, the PPG1 signal will first appear in the time domain feature points a and b, and then the time domain feature points a ₁ and b ₁ appear on the PPG2 signal. At this time, the formula T1= can be used. t _{3 -} t ₁ calculates a first difference T1, and calculates a second difference T3 by using the formula T3 = t _{4 -} t ₂ . In the embodiment of the invention, the first difference T1 and the second difference T3 can be calculated. Any one of the differences is used as the pulse wave transit time, and the average of the first difference T1 and the second difference T3 may be used as the pulse wave transit time.

In the second case, the pulse wave transit time is obtained according to the average value of the difference between the time points corresponding to the time domain feature points in the target PPG signals of any two adjacent channels corresponding to the at least two pulse waves, specifically:

(1) One of a plurality of pulse waves selects one feature point. Assuming that the camera corresponding to PPG1 first collects the pulse wave, the PPG1 signal will first have a first peak a (time domain feature point), and then a peak a ₁ appears on the PPG2 signal. At this time, the formula T1=t can be used. _{3 -} t ₁ calculates a first difference T1 corresponding to the first peak a; after that, the PPG1 signal first appears a second peak c, and then a peak c ₁ appears on the PPG2 signal, at which time, a formula can be used T4=t ₇ -t ₅ calculates a third difference T4 corresponding to the second peak c. In this embodiment, any one of the first difference T1 and the third difference T4 can be used as the pulse wave transmission time. The average of the first difference value T1 and the third difference value T4 may also be used as the pulse wave transit time.

(2) A plurality of feature points are selected for each of the plurality of pulse waves. Assuming that the camera corresponding to PPG1 first collects the pulse wave, the PPG1 signal will first appear in the time domain feature points a and b, and then the time domain feature points a ₁ and b ₁ appear on the PPG2 signal. At this time, the formula T1= can be used. t ₃ -t ₁ calculates the time domain feature point corresponding to a first difference T1, using the formula T3 = t ₄ -t ₂ calculates the second difference time domain feature point b corresponding to T3; then, PPG1 signal will first The time domain feature points c and d appear, and then the time domain feature points c ₁ and d ₁ appear on the PPG2 signal. At this time, the third corresponding to the time domain feature point c can be calculated by the formula T4=t ₇ -t ₅ For the difference T4, the fourth difference T5 corresponding to the time domain feature point d is calculated by using the formula T5=t ₈ -t ₆ . In this embodiment, the first difference T1 can be calculated by using the formula D1=(T1+T3)/2. And the average value D1 of the second difference T3, the average value D1 is taken as the pulse wave transit time, and the average value of the third difference T4 and the fourth difference T5 can also be calculated by the formula D2=(T4+T5)/2 D2, the average value D2 is used as the pulse wave transit time, and the average value of the average value D1 and the average value D2 may be used as the pulse wave transit time.

It should be noted that, in the embodiment of the present invention, the pulse wave is acquired by taking the pulse wave corresponding to the camera corresponding to the PPG1 as an example, and the camera corresponding to the PPG2 first collects the pulse wave and the camera corresponding to the PPG1 to acquire the pulse wave first. The principle of the pulse transit time is the same, and the present embodiment will not be described again here.

The terminal provided by the embodiment of the present invention, according to the difference between the time points corresponding to any one of the target PPG signals of any two adjacent channels corresponding to the same pulse or the time points corresponding to all the time domain feature points The average value of the difference is obtained by the pulse wave transit time, and the accuracy of the pulse wave transit time can be obtained by increasing the value, thereby improving the accuracy of the measured blood pressure of the acquired user.

Further, in the embodiment shown in FIG. 4, the camera 43 is specifically configured to: at intervals of the light emitted by the flash 41, at least two cameras 43 are used to sequentially collect the light illumination at a preset frequency under the control of the processor. Ambient light of the user's limb on the camera; when the flash 41 emits light, at least two cameras 43 sequentially collect the reflected light of the light reflected by the user's limb covering the camera at a preset frequency.

Correspondingly, when the processor 42 is configured to obtain the at least one PPG signal collected by each camera 43 , specifically, the camera 42 is obtained according to the difference signal between the reflected light and the ambient light collected by each camera 43 . At least one PPG signal acquired.

Specifically, in the embodiment of the present invention, FIG. 7 is a control flowchart of two cameras and a flash provided by an embodiment of the present invention. As shown in FIG. 7, the flash flashes at a certain preset frequency, that is, the flash is A fixed frequency alternately illuminates. In the interval where the flash is lit twice, the ambient light measured by the two cameras is measured separately; when the flash is turned on twice, the reflected light detected by the two cameras is measured separately, and each camera is collected every time. The difference signal between the reflected light and the ambient light is used as at least one PPG signal collected by each camera.

Further, in the embodiment shown in FIG. 4, at least one PPG signal collected by each camera includes: red light R, green light G, and blue light B three-way PPG signals.

Specifically, the mobile phone camera can obtain PPG signals of R, G, and B. The PPG signals of different wavelengths can reflect the information of different depths of the blood vessels. Through the analysis of the three signals, the wavelength combination may result in more types of PPG. Waveforms provide more information for feature extraction.

Using the mobile phone flash as a light emitter, the dual camera of the mobile phone acts as a light receiver, and by selectively selecting three colors of RGB, three kinds of PPG waveforms of RGB can be obtained.

Correspondingly, the processor 42 is configured to: when determining, according to the at least one PPG signal collected by each camera 43, the target PPG signal corresponding to each camera 43, specifically for detecting the three-way PPG signal collected by each camera 43 A signal-to-noise ratio (SNR) is obtained, and a PPG signal with the largest SNR among the three PPG signals collected by each camera 43 is obtained. Target the PPG signal.

Where SNR is the ratio of the effective signal amplitude to the noise amplitude of the PPG signal.

Specifically, the PPG signal read from the mobile phone is generally divided into three paths, namely R, G, and B, which are determined by the arrangement principle of the camera sensor. In general, for human skin, the penetration depth of light of different wavelengths and the absorption rate of skin are different. The longer the wavelength, the deeper the penetration depth, and the static signal-to-noise ratio of Green PPG is optimal, but Also the most susceptible to interference. When the nine-axis inertial sensor detects that the person is moving (such as shaking with a mobile phone), it can report it to the processor, and the processor sends a command to detect the signal-to-noise ratio of the three-way PPG signal, and the three-way letter of R, G, and B The noise ratio is compared, the signal with the largest signal-to-noise ratio is read, and the feature signal is selected and judged by using the signal with the largest signal-to-noise ratio. For example, when the signal-to-noise ratio of the green PPG is judged to be large When it is affected, the red (PP) PPG can be read and used to select and judge the feature points, thereby greatly reducing the influence of motion interference on the algorithm.

It should be noted that the nine-axis inertial sensor is a three-axis accelerometer, a three-axis gyroscope, and a three-axis magnetic field sensor. The acceleration sensor is used for measuring a straight line, the gyroscope is mainly for measuring rotation, and the magnetic field sensor is a reference correction for a gyroscope. The nine-axis inertial sensor has the same principle as the nine-axis inertial sensor in the prior art, and the embodiments of the present invention are not described herein.

Optionally, the processor 42 is configured to: when determining, according to the at least one PPG signal collected by each camera 43, the target PPG signal corresponding to each camera 43, specifically: acquiring the three paths collected by each camera 43 The PPG signal uses the average value of the three PPG signals collected by each camera 43 as the target PPG signal.

Specifically, by using the average value of the three PPG signals collected by each camera as the target PPG signal, the average value of the three-way PPG signals is used to select the feature points, thereby greatly reducing the influence of the motion interference on the algorithm.

Further, in the embodiment shown in FIG. 4, the processor 42 is further configured to: acquire a characteristic parameter sequence of a PPG signal with the largest SNR among the three PPG signals collected by each camera 43, and the characteristic parameter sequence is a PPG signal. A collection of frequency domain feature points.

The processor 42 is configured to acquire the measured blood pressure of the user according to the pulse wave propagation speed and the characteristic parameter sequence when acquiring the measured blood pressure of the user according to the pulse wave propagation speed.

Wherein, a sequence of characteristic parameters of the signal is obtained from each of the collected signals, and the sequence of characteristic parameters includes, but is not limited to, time coordinates of feature points (bottom point, vertex, inflection point, first-order differential zero-crossing point), The height difference of the feature points, the total area of the waveform, the rising area, the falling area, the width of each specific point of the waveform, and the like.

Specifically, in the embodiment of the present invention, the terminal performs a Fourier transform on the obtained PPT waveform, converts the PPT waveform in the time domain into a frequency domain waveform, and performs spectrum analysis on the frequency domain waveform after the Fourier transform. A sequence of feature parameters is obtained. The time difference PTT of a certain feature point of the PPG signal is combined with the characteristic parameter sequence to form the final characteristic parameter sequence, which is used as an input parameter for measuring the blood pressure algorithm, and provides more parameters related to the measured blood pressure, overcoming the current and blood pressure. The key information of the relevant parameters is insufficient, making the measured blood pressure less accurate.

It should be noted that, in the embodiment of the present invention, one is to extract the high-order frequency domain features of the PPG signal, and through the big data analysis, it is found that extracting the high-order frequency domain features has a high correlation with blood pressure, and can be regarded as an important feature. Adding to the prediction of blood pressure; the second is to fuse the current multivariate linear fitting algorithm with the machine learning algorithm, first perform feature categorization and clustering on the database, and then perform multiple linear fitting on the data in each class, the precision ratio A single algorithm is 20% higher.

The terminal provided by the embodiment of the present invention performs the feature extraction of the PPG signal in the high-order frequency domain on the basis of the foregoing embodiment, and combines the feature clustering and the machine learning algorithm to solve the shortcomings of the current method. Get more accurate blood pressure calculation results.

Further, in the embodiment shown in FIG. 4, the processor 42 is further configured to: after detecting the signal to noise ratio SNR of the three PPG signals collected by each camera 43, respectively, respectively, the three PPG signals collected by each camera The SNR is compared with the preset threshold. If the SNR of the three-way PPG signal is less than the preset threshold, the measurement indication information is sent to the user, and the measurement indication information is used to instruct the user to re-cover the user's limb on each camera.

Specifically, after separately detecting the signal-to-noise ratio SNR of the three PPG signals in each group of PPG signals, the terminal separately calculates the SNR of each PPG signal in each group of PPG signals, and separately sets each group of PPG signals into three channels. The SNR of the PPG signal is compared with a preset threshold. If the SNR of the three PPG signals is less than a preset threshold, the user is reminded to re-measure.

According to the terminal of the embodiment of the present invention, since the PPG signal is collected by using the dual camera, PPG waveforms of three colors of RGB can be obtained, because R, G, and B represent light reflected from different skin thicknesses of the skin, when there is motion interference. The green light (Green) on the surface of the skin is more susceptible to interference. At this time, red light with low signal-to-noise but less susceptible to interference can be detected, so that interference caused by human motion can be greatly reduced.

Further, in the embodiment shown in FIG. 4, the terminal further includes: a display screen 44. A display screen 44 is used to display the measured blood pressure of the user.

Specifically, the terminal displays the obtained measured blood pressure of the user on the mobile phone screen or other display module.

FIG. 8 is a flowchart of a blood pressure measuring method according to Embodiment 1 of the present invention. As shown in FIG. 8, the blood pressure measurement method provided by the embodiment of the present invention includes:

S801: The processor controls the flash to emit a preset frequency of light.

S802: The processor controls at least two cameras to collect the PPG signal, and the processor obtains at least one PPG signal collected by each camera, and determines a pulse wave propagation speed according to at least one PPG signal collected by each camera, according to the pulse wave propagation speed. Get the user's measured blood pressure.

The PPG signal is a signal that the light is reflected by the user's limb covered by the camera and received by the camera.

According to the blood pressure measuring method provided by the embodiment of the present invention, the processor controls the flash to emit the light of the preset frequency, and the processor controls the at least two cameras to collect the PPG signal, and obtain at least one PPG signal collected by each camera, according to each camera. The collected at least one PPG signal determines the pulse wave propagation speed, obtains the user's measured blood pressure according to the pulse wave propagation speed, ensures that the PTT is not interfered by the pre-ejection period and the human body motion, and solves the arm movement by using at least two cameras. The resulting change in sensor distance thus ensures the stability of the measured pulse wave transit time PTT, thereby improving the accuracy of the measured blood pressure.

Further, in the embodiment shown in FIG. 8, the processor obtains at least one PPG signal collected by each camera, and determines a pulse wave propagation speed according to at least one PPG signal collected by each camera, including:

A target PPG signal corresponding to each camera is determined according to at least one PPG signal collected by each camera.

Determining a difference between time points corresponding to respective time domain feature points in any two adjacent target PPG signals corresponding to the same pulse.

The pulse wave transit time is obtained according to the difference between two time points adjacent to the same time domain feature point, and the pulse wave propagation speed is obtained according to the ratio of the preset distance to the pulse wave transit time.

Further, in the embodiment shown in FIG. 8, the pulse wave transit time is obtained according to the difference, and the packet include:

The difference between the time points corresponding to the time domain feature points in the target PPG signals of any two adjacent channels corresponding to any pulse or the phase time in the target PPG signals of any two adjacent channels corresponding to the at least two pulses The average value of the difference between the time points corresponding to the domain feature points acquires the pulse wave transit time.

Further, in the embodiment shown in FIG. 8, the processor controls the at least two cameras to collect the photoplethysmographic PPG signal, including:

The processor controls each camera to sequentially collect ambient light of the limbs of the user covering the camera at a preset frequency at a preset frequency; the processor controls each camera to a preset frequency when the flash emits light. The reflected light after the light reflected by the user covering the camera is sequentially collected.

The processor obtains at least one PPG signal collected by each camera, and comprises: obtaining at least one PPG signal collected by each camera according to a difference signal between the reflected light and the ambient light collected by each camera.

Further, in the embodiment shown in FIG. 8, at least one PPG signal collected by each camera includes: red light R, green light G, and blue light B three-way PPG signals.

Determining, according to at least one PPG signal collected by each camera, a target PPG signal corresponding to each camera, including:

The processor detects the signal-to-noise ratio SNR of the three PPG signals acquired by each camera.

The processor acquires one PPG signal with the largest SNR among the three PPG signals collected by each camera as the target PPG signal.

Optionally, determining, according to at least one PPG signal collected by each camera, a target PPG signal corresponding to each camera, including: the processor acquires three PPG signals collected by each camera, and collects three PPGs collected by each camera. The average value of the signal is used as the target PPG signal.

Further, in the embodiment shown in FIG. 8, the method provided by the embodiment of the present invention further includes:

The processor acquires a characteristic parameter sequence of a PPG signal with the largest SNR among the three PPG signals collected by each camera, and the characteristic parameter sequence is a set of frequency domain feature points of the PPG signal.

Obtain the user's measured blood pressure based on the pulse wave propagation speed, including:

The user's measured blood pressure is obtained based on the pulse wave propagation speed and the characteristic parameter sequence.

Further, in the embodiment shown in FIG. 8, after the processor detects the signal-to-noise ratio SNR of the three-way PPG signals collected by each camera, the method further includes:

Comparing the SNR of the three PPG signals collected by each camera with a preset threshold;

If the SNR of the three-way PPG signal is less than the preset threshold, the measurement indication information is sent to the user, and the measurement indication information is used to instruct the user to re-cover the user's limb on the camera.

The processor control display shows the user's measured blood pressure.

According to the blood pressure measuring method provided by the embodiment of the present invention, the processor controls the flash to emit the light of the preset frequency, and the processor controls the at least two cameras to sequentially start collecting the PPG signals at the preset frequency to obtain at least one PPG signal collected by each camera. According to at least one PPG signal collected by each camera, the pulse wave propagation speed is determined, and the user's measured blood pressure is obtained according to the pulse wave propagation speed, thereby ensuring that the PTT is not interfered by the pre-ejection period and the human body motion, and at least two cameras are used. The method solves the change of the sensor distance caused by the arm movement, thereby ensuring the stability of the measured pulse wave transit time PTT, thereby improving the accuracy of the measured blood pressure. At the same time, by reading the signal with the largest signal to noise ratio and using the signal with the largest signal to noise ratio to select the feature points, the influence of user motion interference on the algorithm is greatly reduced. In addition, the time difference PTT of a certain feature point of the PPG signal and the characteristic parameter sequence together form the final characteristic parameter sequence, as an input parameter for measuring the blood pressure algorithm, providing more parameters related to the measured blood pressure, overcoming the current Insufficient critical information about blood pressure-related parameters makes the measured blood pressure less accurate.

Finally, it should be noted that the above embodiments are merely illustrative of the technical solutions of the present invention, and are not intended to be limiting; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art will understand that The technical solutions described in the foregoing embodiments may be modified, or some or all of the technical features may be equivalently replaced; and the modifications or substitutions do not deviate from the technical solutions of the embodiments of the present invention. range.

Claims

A terminal, comprising: a flash, a processor and at least two cameras, each having a preset distance between the two cameras;

The processor is configured to control the flash, and the flash is used to emit a preset frequency of light under the control of the processor;

The processor is further configured to control the at least two cameras, wherein the at least two cameras are configured to collect a photoplethysmographic PPG signal under the control of the processor, the PPG signal being overlaid on the light a signal reflected by the user on the camera and received by the camera;

The processor is further configured to obtain at least one PPG signal collected by each camera, and determine a pulse wave propagation speed according to the preset distance and at least one PPG signal collected by each camera, according to the pulse wave propagation speed Obtaining the measured blood pressure of the user.
The terminal according to claim 1, wherein the processor is configured to obtain at least one PPG signal collected by each camera, and determine a pulse according to the preset distance and at least one PPG signal collected by each camera. When the wave propagation speed is used, it is specifically used to:

Determining, according to at least one PPG signal collected by each camera, a target PPG signal corresponding to each camera;

Determining a difference between time points corresponding to each time domain feature point in the target PPG signals of any two adjacent channels corresponding to the same pulse;

Obtaining a pulse wave transit time according to the difference;

The pulse wave propagation speed is obtained according to a ratio of the preset distance to the pulse wave transit time.
The terminal according to claim 1 or 2, wherein the camera is specifically configured to:

The at least two cameras are configured to sequentially capture, at the preset frequency, the illumination of the light on the camera over the camera, under the control of the processor. Ambient light of the limb; when the flash emits the light, the at least two cameras sequentially collect the reflected light of the light reflected by the limb of the user covered on the camera at the preset frequency;

Correspondingly, the processor is configured to obtain at least one PPG letter collected by each camera When used, it is specifically used to:

At least one PPG signal collected by each camera is obtained according to a difference signal between the reflected light and the ambient light collected by each camera.
The terminal according to claim 2, wherein the at least one PPG signal collected by each camera comprises: a red light R, a green light G, and a blue light B three-way PPG signal;

Correspondingly, the processor is configured to: when determining, according to the at least one PPG signal collected by each camera, a target PPG signal corresponding to each camera, specifically:

The signal-to-noise ratio SNR of the three-way PPG signals collected by each camera is detected, and one of the three PPG signals collected by each camera is obtained as the target PPG signal.
The terminal according to claim 4, wherein the processor is further configured to:

Acquiring a characteristic parameter sequence of a PPG signal with the largest SNR among the three PPG signals collected by each camera, wherein the characteristic parameter sequence is a set of frequency domain feature points of the PPG signal;

The processor is configured to: when acquiring the measured blood pressure of the user according to the pulse wave propagation speed, specifically for:

The measured blood pressure of the user is obtained according to the pulse wave propagation speed and the characteristic parameter sequence.
The terminal according to claim 4 or 5, wherein the processor is further configured to:

After detecting the signal-to-noise ratio SNR of the three PPG signals collected by each camera, respectively comparing the SNR of the three PPG signals collected by each camera with a preset threshold;

And if the SNR of the three-way PPG signal is less than the preset threshold, sending measurement indication information to the user, where the measurement indication information is used to instruct the user to re-cover the user's limbs in each camera. on.
The terminal according to claim 2, wherein the at least one PPG signal collected by each camera comprises: a red light R, a green light G, and a blue light B three-way PPG signal;

Correspondingly, the processor is configured to: when determining, according to the at least one PPG signal collected by each camera, a target PPG signal corresponding to each camera, specifically:

Obtain three PPG signals collected by each camera, and collect three channels for each camera. The average value of the PPG signal is taken as the target PPG signal.
The terminal according to any one of claims 2 or 4 or 5, wherein the processor is configured to: when acquiring the pulse wave transit time according to the difference, specifically:

The time difference between the time points corresponding to the time domain feature points in the target PPG signals of any two adjacent channels corresponding to any pulse or the time domain in the target PPG signals of any two adjacent channels corresponding to the at least two pulses The average value of the difference between the time points corresponding to the feature points acquires the pulse wave transit time.
A blood pressure measuring method, comprising:

The processor controls the flash to emit a preset frequency of light;

The processor controls at least two cameras to acquire a photoplethysmographic pulse PPG signal, the PPG signal being a signal that the light is reflected by a limb of the user overlying the camera and received by the camera; the processor obtains each At least one PPG signal collected by the camera, determining a pulse wave propagation speed according to a preset distance between the two cameras and at least one PPG signal collected by each camera, and acquiring the user according to the pulse wave propagation speed Measurement of blood pressure.
The method according to claim 9, wherein the processor obtains at least one PPG signal collected by each camera, according to a preset distance between the two cameras and at least one PPG collected by each camera. The signal determines the pulse wave propagation speed, including:

Determining, according to at least one PPG signal collected by each camera, a target PPG signal corresponding to each camera;

Determining a time point corresponding to the same time domain feature point in the target PPG signal corresponding to each camera, and respectively obtaining a difference between two time points adjacent to the same time domain feature point;

Obtaining a pulse wave transit time according to the difference, and acquiring a pulse wave propagation speed according to a ratio of the preset distance to the pulse wave transit time.
The method according to claim 9 or 10, wherein the processor controls the at least two cameras to collect the photoplethysmographic pulse PPG signal, including:

The processor sends an interval of the lights at the flash, and controls each camera to sequentially collect, at the preset frequency, ambient light that is illuminated by the light on a limb of the user covered on the camera; the processor When the flash emits the light, controlling each camera to sequentially collect the light at the preset frequency through the user covered by the camera Reflected light after limb reflex;

The processor obtains at least one PPG signal collected by each camera, including:

At least one PPG signal collected by each camera is obtained according to a difference signal between the reflected light and the ambient light collected by each camera.
The method according to claim 10, wherein the at least one PPG signal collected by each camera comprises: a red light R, a green light G, and a blue light B three-way PPG signal;

Determining, according to at least one PPG signal collected by each camera, a target PPG signal corresponding to each camera, including:

The processor detects a signal to noise ratio SNR of three PPG signals collected by each camera;

The processor acquires one PPG signal with the largest SNR among the three PPG signals collected by each camera as the target PPG signal.
The method of claim 12, wherein the method further comprises:

Obtaining, by the processor, a feature parameter sequence of a PPG signal with the largest SNR among the three PPG signals collected by each camera, where the feature parameter sequence is a set of frequency domain feature points of the PPG signal;

Obtaining the measured blood pressure of the user according to the pulse wave propagation speed, including:

The measured blood pressure of the user is obtained according to the pulse wave propagation speed and the characteristic parameter sequence.
The method according to claim 12 or 13, wherein after the processor detects the signal-to-noise ratio SNR of the three-way PPG signals collected by each camera, the method further includes:

Comparing the SNR of the three PPG signals collected by each camera with a preset threshold;

And if the SNR of the three-way PPG signal is less than the preset threshold, sending measurement indication information to the user, where the measurement indication information is used to instruct the user to re-cover the user's limbs in each camera. on.
The method according to claim 10, wherein the at least one PPG signal collected by each camera comprises: a red light R, a green light G, and a blue light B three-way PPG signal;

Determining, according to at least one PPG signal collected by each camera, a target PPG signal corresponding to each camera, including:

The processor acquires three PPG signals collected by each camera, and uses an average value of three PPG signals collected by each camera as the target PPG signal.
The method according to any one of claims 10 or 12 or 13, wherein the obtaining the pulse wave transit time according to the difference comprises:

The time difference between the time points corresponding to the time domain feature points in the target PPG signals of any two adjacent channels corresponding to any pulse or the time domain in the target PPG signals of any two adjacent channels corresponding to the at least two pulses The average value of the difference between the time points corresponding to the feature points acquires the pulse wave transit time.