CN111248889B

CN111248889B - A pulse wave measuring device and method based on LED diode and LED display matrix

Info

Publication number: CN111248889B
Application number: CN202010060676.5A
Authority: CN
Inventors: 林沛颖; 皇甫江涛
Original assignee: Zhejiang University ZJU
Current assignee: Zhejiang University ZJU
Priority date: 2020-01-19
Filing date: 2020-01-19
Publication date: 2021-10-08
Anticipated expiration: 2040-01-19
Also published as: CN111248889A

Abstract

The invention discloses a pulse wave measuring device and method based on an LED diode and an LED display matrix. The measuring method uses a plurality of LED diodes to contact human skin, emit light through a part of the LED, and another part of the LED receives the light signal reflected by the skin and converts it into an electrical signal; the device designed by the present invention includes a plurality of LED diodes in the same plane. Matrix of different shapes, hardware filter acquisition module and data processing and analysis module; LED diodes in LED matrix have both display and detection functions. When working, the matrix contacts the skin of one or more parts such as human fingers, and one or more are The LEDs with the designated detection function and the surrounding LEDs are in the light-emitting mode, the LEDs with the detection function are connected to the amplifier to obtain electrical signals, and the analog-to-digital conversion circuit is used to collect the signals. The invention can be used to measure the multi-point pulse wave on the surface of the human body to obtain information such as pulse, heart rate variability and the like.

Description

Pulse wave measuring device and method based on LED diode and LED display matrix

Technical Field

The invention relates to the technical field of photoelectric and human health monitoring, in particular to a pulse wave measuring device and method based on an LED diode and an LED display matrix.

Background

The non-invasive detection of human health and characteristic data is one of the leading directions in the field of current medical engineering, and the optoelectronic method is a research hotspot in recent years, wherein the relatively representative method is photoplethysmography (PPG), and the method has the advantages of low cost, safety, high efficiency and high data precision, and thus is widely applied and researched. According to the Lamber-Beer law, the absorbance of a substance at a certain wavelength is proportional to its concentration. When light of a constant frequency is incident on a tissue of a human body, absorption of the light by the tissue such as skin, blood, and muscle is not changed, and thus characteristics and change information of the irradiated human body tissue are included by detecting the light absorbed and reflected through the human body tissue. The pulse is mainly generated by the relaxation and contraction of the human heart, and the movement is reflected in the relaxation and contraction of the arteries. Capillary vessels are rich in parts such as fingertips, wrists, elbows and necks of a human body, so that the measurement parts of the traditional photoelectric pulse wave sensor are usually designed at the positions of the fingertips or the wrists, and when the heart contracts, the capillary vessels have large blood flow and strong light absorption; when the heart relaxes, the capillary blood flow is small and the reflected light intensity is high. The pulse wave of a human body is reflected by detecting the intensity of reflected light, most of the existing photoelectric pulse wave sensors are used for detecting fingertips, and phototriodes are used as photosensitive elements and can only be used as independent instruments.

The LED screen used in daily life is essentially a matrix formed by PN junction diodes, and the diodes can emit light when forward voltage is connected to the two ends of the LEDs; on the contrary, according to the photoelectric effect, when light irradiates on the PN junction diode, photons carrying energy enter the PN junction, the energy is transferred to bound electrons on a covalent bond, so that part of electrons break loose from the covalent bond to generate electron-hole pairs, also called photocarriers, and the existence of the electron-hole pairs causes reverse current to be obviously increased, thereby generating an electric signal. The LED screen on the market only utilizes the display function of the LED screen, and the photoelectric characteristic of the LED screen is not fully utilized. This patent introduces the photoplethysmography detection function on the basis that LED is luminous and shows, is the new detection means of the compatible demonstration simultaneously of the present pulse ripples of fungible product and lighting system.

Disclosure of Invention

In order to solve the problems in the background art, the invention provides a pulse wave measuring device and method based on an LED diode and an LED display matrix. The invention mainly aims to utilize the photoelectric effect to enable the LED diode to receive the optical signal reflected by the capillary blood and convert the optical signal into an electric signal, and further obtain the health and characteristic information of a human body through signal processing and data analysis.

The technical scheme adopted by the invention is as follows:

pulse wave measuring device based on LED diode and LED display matrix

The hardware filtering acquisition module mainly comprises a filtering amplification circuit and an analog-to-digital conversion circuit;

the detection module is a plurality of LED diodes or an LED display matrix formed by a plurality of LED diodes in array arrangement, each LED diode comprises an emitting LED and a receiving LED, and each receiving LED is surrounded by the adjacent emitting LED; the detection module is provided with a detection area contacted with the skin of a human body;

the driving circuit is connected with the detection module, and the hardware filtering acquisition module is connected with the receiving LED and is not connected with the emitting LED; the detection module, the hardware filtering acquisition module and the drive circuit are powered by a power supply.

The detection module has the functions of display and detection at the same time; when the detection module is in a display function, the emitting LED diode is in a common light-emitting state, the brightness and the color of the LED diode are controlled by the driving circuit, the receiving diode is switched between the driving circuit and the hardware filtering acquisition module at a high speed at a frequency of more than 30Hz, when the hardware filtering acquisition module receives a change of an electric signal, the object to be detected is close to a detection area, and at the moment, the LED display matrix is switched to the detection function; when the detection module is in a detection function, the receiving LED in the detection area is not controlled by the driving circuit, the receiving LED converts a received optical signal into an electric signal through a photoelectric effect and then inputs the electric signal into the hardware filtering acquisition module, and the emitting LED in the detection area emits light with a frequency higher than that of the receiving LED.

The pulse rate monitoring and analyzing device is characterized by further comprising a data processing and analyzing module, the data processing and analyzing module is connected with the hardware filtering and collecting module, after the hardware filtering and collecting module transmits pulse signals to the data processing and analyzing module, the data processing and analyzing module processes the data and then can obtain data such as pulse, heart rate variability and the like of a human body.

The LED diode is a single-color LED or a three-color LED, and the frequency of the emitting LED is higher than that of the receiving LED.

The detection area is designed into various shapes which are matched with the shape of human skin, such as the shape of a fingertip or a palm.

The human skin includes all surfaces of the skin rich in capillaries, such as fingertips, wrists, elbows or necks.

Pulse wave measuring method based on LED diode and LED display matrix

When a detection area on the detection module is contacted with the skin of a human body, the detection module is in a detection state, the driving circuit controls the emitting LED to emit incident light to irradiate the surface of the skin of the human body, the incident light irradiates the receiving LED through reflected light reflected by the capillary vessel 4, the receiving LED converts received optical signals into electric signals and transmits the electric signals to the filtering and amplifying circuit, the filtering and amplifying circuit carries out filtering and amplifying processing on the electric signals, and the signals passing through the filtering and amplifying circuit are converted into pulse wave signals through the analog-to-digital conversion circuit.

The change of the electric signal reflects the change of the blood oxygen concentration, so that the pulse, heart rate variability and other information of the human body can be reflected.

The invention has the beneficial effects that:

(1) the pulse wave measuring method and device based on the LED diode and the LED display matrix, which are designed by the invention, utilize the LED to receive the optical signals reflected by the capillary vessels and convert the optical signals into electric signals, clear pulse wave signals with obvious characteristics can be obtained through signal processing of hardware, and the device is compatible with the existing LED screen on the market, so that the device has double functions of display and real-time detection.

(2) The pulse wave measuring device based on the LED diode and the LED display matrix can be used for measuring the pulse waves of multiple points on the surface of a human body to obtain information such as pulse, heart rate variability and the like.

(3) The device used by the invention has simple structure, compact circuit and low cost; the pulse wave detection device is a new detection means which can replace the existing pulse wave detection product and is compatible with a display and illumination system.

Drawings

Fig. 1 is a schematic diagram of a pulse wave measuring method based on an LED diode according to the present invention.

Fig. 2 is a structural diagram of a pulse wave measuring device based on an LED diode according to the present invention.

FIG. 3 is a schematic diagram of a pulse wave measuring device based on an LED display matrix according to the present invention.

FIG. 4 is a flow diagram of a hardware filter acquisition module of the present invention.

FIG. 5 is a flow diagram of a data processing analysis module of the present invention.

In the figure: the LED detection device comprises an LED diode, 11 an emitting LED, 12 a receiving LED,21 incident light, 22 reflected light, 3 human skin, 4 capillary vessels, 5 a driving circuit, 6 a hardware filtering and collecting module, 7 a data processing and analyzing module, 8 a filtering and amplifying circuit, 9 an analog-to-digital conversion circuit, 10 a power supply, 13 a detection area and 14 an LED display matrix.

Detailed Description

The invention will be further described and illustrated with reference to the accompanying drawings and examples.

As shown in fig. 1 and fig. 2, the embodiment of the present invention includes at least one pulse wave measuring device based on LED diodes 1 or LED display matrix, and each complete device includes a plurality of LED diodes 1 or LED display matrix 14, a driving circuit 5, a hardware filtering acquisition module 6, a data processing and analyzing module 7, and a power supply 10. When the device works, the power supply 10 supplies power to the drive circuit 5 and the hardware filtering acquisition module 6. The LED display matrix 14 contacts human skin 3 of one or more parts, one or more receiving LEDs 12 are surrounded by adjacent emitting LEDs 11, and the electrical signals converted by the receiving LEDs 12 are input to the hardware filtering acquisition module 6.

As shown in fig. 3 and 4, the LED display matrix 14 possesses both display and detection functions. When the display state is displayed, all the LED diodes 1 are in a common light-emitting state, and the brightness and the color of the LED diodes 1 are controlled by the driving circuit 5; the receiving diode 12 is switched between the driving circuit 5 and the hardware filtering acquisition module 6 at a high speed with a frequency greater than 30Hz, when an object to be detected approaches the detection area 13, an electric signal received by the hardware filtering acquisition module 6 changes, and the LED display matrix 14 is switched to a detection function. When the LED display matrix 14 is in the detection state, the receiving LED12 in the detection region 13 is not controlled by the driving circuit 5, the receiving LED12 converts the received optical signal into an electrical signal and inputs the electrical signal to the hardware filtering and collecting module 6, and the emitting LED11 in the detection region 13 emits light with a frequency higher than that of the receiving LED 12. The emitting LEDs 11 and the receiving LEDs 12 are alternately arranged in the inspection region 13 such that each receiving LED12 is surrounded by the emitting LED11, and the inspection region 13 may be designed in various shapes such as a fingertip shape or a palm shape according to inspection needs.

In specific implementation, the hardware filtering acquisition module 6 is composed of a filtering amplification circuit 8 and an analog-to-digital conversion circuit 9, and is powered by a power supply 10 during operation. The filtering and amplifying circuit 8 filters the original signal to reduce the interference of noise such as power frequency and the like, improves the signal-to-noise ratio, amplifies the pulse wave signal through the operational amplifier circuit, and finally collects the optimized signal through the analog-to-digital conversion circuit 9.

The LED diode 1 may be a single-color LED or a three-color LED, and needs to be a relatively high-frequency LED11 as an emitting LED and a relatively low-frequency LED12 as a receiving LED.

The skin 3 of the human body contacted with the method comprises all skin surfaces rich in the capillary vessels 4, such as fingertips, wrists, elbows, necks and the like, and the measurement method is applicable.

In the specific implementation, the data processing and analyzing module 7 is further included, the data processing and analyzing module 7 comprises two parts of filtering processing and peak value detection, band-pass filtering is firstly carried out in the filtering processing process, a proper filtering function is selected to be convoluted with an original signal to obtain a high-pass decomposition signal and a low-pass decomposition signal, a high-pass component coefficient is used as a judgment condition to select a low-pass component, and the interference caused by power frequency, respiration, baseline offset and the like can be removed by subtracting the low-pass component from the original signal. A moving window is established in the peak detection part to continuously slide, and all peak data can be obtained by carrying out average filtering and solving the maximum value of the second derivative in the window. The data such as pulse and heart rate variability of the human body can be obtained according to the processed data analysis, and the information can reflect the health characteristics of the human body or be used for assisting means such as fingerprint identification and palm print identification to carry out identity authentication.

Suitable filter functions include Daubechies series functions, symlets series functions, Haar functions, Mexican Hat functions, Morlet functions, Meyer functions, Biorthogonal functions, Coiffet series functions, and the like.

Example 1

Fingertip pulse wave health monitoring device based on multiple LED diodes

As shown in fig. 1 and fig. 2, the device is mainly used for collecting waveform changes of pulse waves of capillary vessels of fingertips so as to analyze health data such as pulse and heart rate variation rate of a human body. The whole system consists of three parts, namely signal acquisition, signal amplification optimization and data analysis. In the signal acquisition part, 5 LED diodes 1 are included, the 5 LED diodes 1 can be controlled by the driving circuit 5 to perform display function, the central LED is set as the receiving LED12 and is not controlled by the driving circuit 5, and the rest surrounding the central LED is the emitting LED11 which is controlled by the driving circuit 5 to emit light normally. The emitting LED11 is used as a light source to emit incident light 21 to irradiate the surface of the human skin 3, reflected light carrying blood oxygen information is irradiated on the receiving LED12 after being reflected by the capillary 4, and the receiving LED12 converts the received optical information into electrical information due to photoelectric effect.

In the hardware filtering acquisition module 6, firstly, the input original signal is subjected to RC filtering through the filtering amplification circuit 8 to reduce the influence of power frequency, then the original signal is amplified by 70 times by using the operational amplification circuit and acquired into the data processing analysis module 7 through the analog-to-digital conversion circuit 9, the signal-to-noise ratio of the signal passing through the hardware filtering acquisition module 6 is improved, useful information is amplified, the fluctuation of pulse waves can be observed obviously, but the interference of power frequency, baseline drift, respiration and the like still exists, and therefore the following data processing analysis module 7 is needed.

As shown in fig. 5, the data processing and analyzing module 7 in the present embodiment includes two parts, namely, a filtering process and a peak detection.

And (3) filtering treatment: in the filtering process, firstly, band-pass filtering is carried out, and the pass band is set to be 0.4-4Hz to filter noise interference of power frequency and respiration; for the problem of baseline shift, a suitable filter function is selected, for example, Daubechies fourth-order basis function is selected to be convolved with the original signal X:

c0＝(1+sqrt(3))/(4*sqrt(2))

c1＝(3+sqrt(3))/(4*sqrt(2))

c2＝(3-sqrt(3))/(4*sqrt(2))

c3＝(1-sqrt(3))/(4*sqrt(2))

lp＝[c0,c1,c2,c3]

hp＝[c3,-c2,c1,-c0]

the original signal X is continuously decomposed into high-pass components

And a low-pass component

Stopping the decomposition when a specified order is reached to obtain a corresponding low-pass component for peak detection

Order size by calculating the high-pass component

The energy coefficient clac is judged, and when the energy coefficient clac is minimum, the energy coefficient clac is taken as a specified order:

peak detection: subtracting the low-pass component from the original signal

The signals after power frequency, respiration and baseline shift elimination can be obtained. The peak value detection is carried out by using the signal, a moving window is established in the peak value detection part to continuously slide, and average filtering is carried out in the window and the maximum value of the second derivative is obtained, thus obtaining all peak value data. To liftHigh accuracy, carrying out window sliding again after the detected peak value, verifying whether the T wave is false detected or not, obtaining the peak value times N in the detection time T, and calculating the HEART RATE HEART _ RATE formula as follows;

HEART_RATE＝N/t*60

besides, the heart rate variability and the human health characteristic information such as blood pressure related to the heart rate variability can be obtained through calculation, and the real-time information can be obtained by connecting the signal acquisition end with the terminal, so that the health monitoring effect is achieved.

Example 2

Palm multi-point blood oxygen change detection device based on LED display matrix

As shown in fig. 3, the LED display matrix 14 is formed by arranging 28 × 14 LED diodes 1, and the detection region 13 is designed in the shape of a palm according to the actual functional requirements. The LED display matrix 14 has dual functions of detection and display, when the matrix 14 is in the display function, 28 × 14 LED diodes 1 are controlled by the driving circuit 5 to normally emit light, the receiving diode 12 is switched between the driving circuit 5 and the hardware filtering acquisition module 6 at a high speed at a frequency greater than 30Hz, when an electric signal is received and changed, the LED display matrix 14 is switched to the detection function when the palm is close to the detection area 13, and the LED diodes 1 in and at the edge of the detection area 13 are used for detection. The emitting LEDs 11 and the receiving LEDs 12 are evenly distributed in the LED diodes 1, and each receiving LED12 can be surrounded by the LED11 by adopting a staggered arrangement mode, when the receiving LED12 works, light emitted by the emitting LED11 adjacent to the receiving LED12 enters the skin 3 of a human body as shown in fig. 1, and is reflected to the receiving LED12 by blood in the capillary 4, because the photoelectric effect LED2 converts received optical information into electrical information, the electrical information is input into the hardware filtering acquisition module 4 and the data processing analysis module 7, and the specific optimization modes of signal filtering amplification and the like are the same as those in the embodiment 1.

Since the blood flow and blood oxygen content of the capillary 4 affect the intensity of the reflected light 22, the light information received by the receiving LED12 carries the characteristic information of the human body, and after being converted into the electrical information, the electrical information shows the pulse wave with individual differences in period, shape, and the like. And a plurality of receiving LEDs 12 in the detection area 13 can measure a plurality of points simultaneously, so that multi-point blood oxygen change characteristic information with densely distributed palms can be obtained, and the information can be used for living body identification and identity identification by means of other fingerprint and palm print identification.

The above description is only an example of the system of the present invention for performing fingertip pulse wave detection and palm print characteristic analysis by using a plurality of LED diodes and LED display matrixes, and is not intended to limit the method and system of the present invention in any way, and persons skilled in the art may modify or modify the above embodiments to be equivalent examples of equivalent variations by using the technical content disclosed above, but any simple modification, equivalent variations and modifications made by the technical essence of the present invention are still within the protection scope of the present invention without departing from the technical solution content of the present invention.

Claims

1. A pulse wave measuring device based on an LED diode and an LED display matrix, characterized in that: comprising a detection module, a drive circuit (5), a hardware filtering acquisition module (6) and a power supply (10), a hardware filtering acquisition module ( 6) It is mainly composed of a filter amplifying circuit (8) and an analog-to-digital conversion circuit (9);

The detection module is a plurality of LED diodes (1) or an LED display matrix (14) composed of a plurality of LED diodes (1) arranged in an array, and the LED diodes (1) include a transmitting LED (11) and a receiving LED (12), Each receiving LED (12) is surrounded by adjacent transmitting LEDs (11); the detection module is provided with a detection area (13) in contact with the human skin (3);

The drive circuit (5) is connected to the detection module, and the hardware filtering and acquisition module (6) is connected to the receiving LED and not to the transmitting LED (11); the detection module, the hardware filtering and acquisition module (6), and the driving circuit (5) are powered by a power supply (10) Power supply;

The detection module has both display and detection functions; when the detection module is in the display function, the LED diode (1) is in a normal light-emitting state, the brightness and color of the LED diode (1) are controlled by the driving circuit (5), and the receiving diode (12) The frequency greater than 30Hz is switched at high speed between the drive circuit (5) and the hardware filter acquisition module (6). When the hardware filter acquisition module (6) receives a change in the electrical signal, it indicates that the object to be detected is close to the detection area (13). At this time, the LED display matrix (14) is switched to the detection function; when the detection module is in the detection function, the receiving LED (12) in the detection area (13) is not controlled by the driving circuit (5), and the receiving LED (12) passes through the photoelectric effect. The received optical signal is converted into an electrical signal and then input to the hardware filtering acquisition module (6), and the transmitting LED (11) in the detection area (13) emits light with a frequency higher than that of the receiving LED (12).

2. A pulse wave measuring device based on an LED diode and an LED display matrix according to claim 1, characterized in that: the LED diode (1) is a single-color LED or a tri-color LED, and the emitting LED (11) The frequency is higher than the receive LED (12).

3 . The pulse wave measuring device based on LED diodes and LED display matrix according to claim 1 , wherein the detection area ( 13 ) is designed in a variety of shapes suitable for the shape of human skin ( 3 ). 4 . .

4. A pulse wave measuring device based on LED diode and LED display matrix according to claim 1, characterized in that: the human skin (3) includes all skin surfaces rich in capillaries (4), such as finger Point, wrist, elbow or neck.

5. A pulse wave measurement method based on an LED diode and an LED display matrix using any one of the devices of claims 1-4, characterized in that: when the detection area (13) on the detection module is in contact with the human skin (3) , the detection module is in the detection state, the drive circuit (5) controls the emission LED (11) to emit incident light (21) to irradiate the surface of the human skin (3), and the incident light (21) reflected by the capillaries 4 is irradiated on the receiving surface. On the LED (12), the receiving LED (12) converts the received optical signal into an electrical signal and transmits it to the filter amplifying circuit (8), and the filter amplifying circuit (8) filters and amplifies the electrical signal. 8) The signal is converted into a pulse wave signal through the analog-to-digital conversion circuit (9).