CN113116313A

CN113116313A - System and method for detecting photoelectric pulse wave by incoherent light source for modulating electric signal

Info

Publication number: CN113116313A
Application number: CN201911426538.8A
Authority: CN
Inventors: 桂林
Original assignee: Individual
Current assignee: Individual
Priority date: 2019-12-31
Filing date: 2019-12-31
Publication date: 2021-07-16
Anticipated expiration: 2039-12-31
Also published as: CN113116313B

Abstract

The invention provides a system and method for photoelectric pulse wave detection using an incoherent light source modulated with electrical signals. The method is different in principle from the traditional method in which the light-emitting diode is used to emit light directly, and the reflected or transmitted signal is detected. The present invention modulates the electrical signal with frequency f1 on the light emitting diode, and receives the modulated visible light signal transmitted from the blood vessels, blood or human tissue under the skin, and converts it into an electrical signal through a photodetector, and the electrical signal is converted into an electrical signal. The signal contains two parts: a) a low-frequency signal carrying arterial information, and b) a high-frequency signal carrying arterial information near the center frequency f1. The arterial signal can be extracted from the two parts of the signal because the interference of the two parts of the signal is different in the process of transmission or scattering. This method is different from the traditional photoplethysmography, and provides a new detection dimension, which can be used to detect heart rate, blood pressure, and other parameters related to blood.

Description

System and method for detecting photoelectric pulse wave by incoherent light source for modulating electric signal

Technical Field

The invention relates to a visible light sensing system adopting an incoherent light source, in particular to the application field of photoelectric pulse wave detection by utilizing an incoherent visible light generated by a light emitting diode for modulating an electric signal.

Background

The intelligent medical treatment is a future war of China, is also a key application field of information technology development to a certain stage such as communication technology, computer technology and the like, and in the intelligent medical treatment, the gravity center is in wearable mobile health (including heart rate, blood oxygen, blood pressure, blood sugar and temperature) monitoring management in a form of representation. At present, in the field of wearable mobile health measurement, a plurality of problems still exist, which makes the research on the detection of blood components and heart rate parameters more significant.

The noninvasive detection of blood components has important significance for the diagnosis of various diseases, the management of chronic diseases such as diabetes, anemia and the like, and the monitoring of perioperative or emergency patients, and can realize the early screening of diseases, save medical resources and promote environmental protection. Meanwhile, the economic development and the improvement of living standard promote the attention degree of general people to health and the effectiveness of health information acquisition to be continuously improved, in order to improve the living quality of people, cardiovascular diseases must be effectively prevented, and the threat of the cardiovascular diseases determines the necessity of continuously monitoring physiological parameters including heart rate, blood pressure, blood oxygen, blood viscosity and the like.

Currently, in the aspects of noninvasive detection of blood components and continuous dynamic physiological parameter monitoring, photoplethysmography (PPG) and related technologies are important technical means, attract the attention of many researchers at home and abroad, and produce a great deal of research results. Photoplethysmography (PPG), first proposed by Hertzman in 1938, is a method for evaluating information about the perfusion of skin tissue by subcutaneous blood information carried by the reflection or transmission of input light in the skin tissue. Due to the beating of the heart, part of blood flows into the finger tip through the arteries of all stages step by step, so that the small artery network of the finger tip is expanded. Blood entering the capillary bed through the pre-capillary sphincter will return to the heart by flowing into the vein after nutrient exchange has occurred. The capillary sphincter offers a greater resistance to blood flow and the capillary bed has sufficient volume to attenuate the pulsation of the arterioles. It is generally believed that only arterioles pulsate, while capillaries, veins and other tissues do not. The detected optical power change over time obtained according to the PPG method is shown in fig. 1.

Document 1 proposes a noninvasive continuous blood pressure measurement method based on photoplethysmography, and researches and proposes the idea of normalizing the photoplethysmography, establishes a cardiovascular system parameter extraction and diastolic pressure calculation method according to a normalized pulse wave model, and designs a noninvasive continuous blood pressure measurement system combining software and hardware by applying the method.

Document 2 employs a dynamic spectroscopic method for non-invasive detection of blood components, which directly extracts optical densities reflecting arterial blood components at multiple wavelengths based on transmitted photoplethysmography, using changes in spectral absorption by arterial filling degree, theoretically reducing individual differences and the influence of measurement conditions, and has significant advantages over other methods. The feasibility of the dynamic spectrum method is verified by acquiring dynamic spectrum values under different hemoglobin concentrations and calculating a correlation coefficient with the hemoglobin concentration in the literature

In document 3, a combined spectrum of 523nm green light, 660nm red light and 810nm infrared light is selected as a detection light source, and a 'mesh' type groove structure is introduced in the structural design to eliminate the ambient light interference and improve the signal-to-noise ratio of a measurement signal. The baseline wander removing method is improved on the basis of the traditional generalized morphology baseline wander removing algorithm, and a simplified baseline wander removing algorithm is realized.

These documents are based on the development of photoplethysmography, but the signals obtained by photoplethysmography are weak, and new solutions are still needed in the detection systems and methods. For the above reasons, the artery signal detection technology based on the electro-optical and acoustic-optical methods is a key research subject of the development of the current medical devices.

Reference documents:

1. lie, study of noninvasive continuous blood pressure measurement method based on pulse wave, doctor's academic thesis, unit: zhejiang university, completion time: month 4 in 2008.

2. Zhoumei, a method for improving dynamic spectral signal-to-noise ratio and application thereof, a doctor academic thesis, unit: tianjin university, completion time: year 2014 5 months.

3. Li Xiu, study of dynamic measurement technology of physiological parameters of human body based on photoplethysmography, doctor's academic thesis, unit: china university of science and technology, completion time: year 2017, month 5.

The invention content is as follows:

in view of the above-mentioned needs in the art, it is an object of the present invention to provide a system and method for photoelectric pulse wave detection using incoherent light sources for modulating electrical signals. The method is different from the traditional method in principle in that the light emitting diode is used for directly emitting light and detecting reflected or transmitted signals. The invention modulates an electric signal with frequency f1 to a light-emitting diode, receives a modulated visible light signal transmitted from blood vessels, blood or human tissues under the skin, converts the modulated visible light signal into an electric signal by a photoelectric detector, and the electric signal comprises two parts: a) a low frequency signal carrying arterial information, b) a high frequency signal carrying arterial information around a center frequency f 1. Because the two parts of signals are subjected to different interferences in the transmission or scattering process, the artery signals can be extracted from the two parts of signals. This method differs from conventional photoplethysmography (PPG) in that it provides a new detection dimension, but is compatible with the advantages of PPG, and can be used to detect heart rate, blood pressure, and other blood-related parameters. Meanwhile, the method can be fused with new technologies such as pattern recognition in the field of computers, and the quality of detection signals is improved.

The basic structure of the present invention includes:

visible light emitting module (10) comprising an LED power supply driving circuit for providing a stable driving voltage suitable for the lighting requirements of the LED or LED array, an LED radio frequency signal transmitter driving circuit for selecting a bias voltage V_biasAnd radio frequency signal (20) of the single frequency, and modulate the sum of these two kinds of signals to LED lamp pearl or LED lamp pearl array, send the incoherent light after modulating to the human skin finally;

a single frequency RF signal (20) s (t) for loading on the LED lamp bead or LED lamp bead array to provide a modulated visible light waveform, wherein when encountering blood vessels, blood or human tissue beneath the skin, the visible light containing the single frequency RF signal will be partially incident on the visible light receiving module (30), assuming that the single frequency is f₁Signal amplitude of V_ac；

Visible light receiving module (30) comprising a photodetector and an associated amplification circuit, and a telecommunications systemThe signal processing circuit is used for receiving visible light signals transmitted from blood vessels, blood or human tissues under the skin and converting the visible light signals into electric signals through the photoelectric detector, and the electric signals comprise two parts: a) low-frequency signal m carrying artery information_a(t), b) center frequency f₁Nearby high-frequency signal m carrying arterial information_b(t)V_accos(2πf₁t)；

The signal processing module (40) is used for processing the part a) of signals according to a traditional PPG method, namely processing low-frequency signals carrying artery information; simultaneously to the center frequency f of part b)₁And demodulating nearby high-frequency signals carrying artery information to obtain baseband signals carrying artery information, and combining a) partial signal processing results and b) partial signal processing results to obtain final artery signals, so as to obtain the heart rate, the blood pressure and other blood related parameters.

In consideration of the distance limit of visible light wave transmission in human organs, the LED lamp beads can be high-power LED lamp beads and are used for sending stronger visible light signals, and therefore the intensity of the detected visible light signals is improved.

Further, the visible light emitting module (10) and the visible light receiving module (30) may be located on both sides of the finger, and receive the transmitted signal, as shown in fig. 3; or the visible light emitting module (10) and the visible light receiving module (30) are positioned on the same side of the finger, and the reflected signal is received at the moment, as shown in figure 2.

Further, the LED light source can be a red light (R) LED lamp bead, a green light (G) LED lamp bead, a blue light (B) LED lamp bead or a white light LED lamp bead formed by RGB three colors, and is used for sending visible light signals with different wavelengths, so that visible light signals reflected by blood vessels, blood or human tissues below visible light communication detection are improved, and the accuracy of human photoelectric pulse wave detection is improved.

Further, in the present invention, the final arterial signal can be obtained as follows

Wherein m is_a(t) is an arterial signal extracted from a signal containing low-frequency interference, m_b(t) is an arterial signal extracted from a signal containing high frequency interference.

Further, the system may also include a filtering algorithm (50) based on the photoplethysmographic wave, which is applied to the signal m from the low frequency_a(t) and center frequency f₁Nearby high-frequency signal m carrying arterial information_b(t)V_accos(2πf₁t) are processed separately, thereby forming m of the arterial signal_a(t) moieties and m_bAnd (t) section. The filtering algorithm (50) of the photoelectric pulse wave can comprise artificial intelligence algorithms such as artificial neural networks, machine learning or deep learning.

Further, the bias voltage V loaded on the LED can be adjusted_biasTherefore, the arterial signal to be extracted is enhanced, and the accuracy of photoelectric pulse wave detection is improved.

Further, the amplitude V of the radio frequency signal loaded on the LED can be adjusted_acTherefore, the arterial signal to be extracted is enhanced, and the accuracy of photoelectric pulse wave detection is improved.

Furthermore, the modulation frequency f with the minimum radio frequency loss in visible light transmission can be obtained in experiments₁Therefore, the arterial signal to be extracted is enhanced, and the accuracy of photoelectric pulse wave detection is improved.

Further, in order to solve the problem of human body difference in the method, information measured by each user each time can be recorded in a database of a computer to serve as a basis for updating the filtering algorithm (50) of the photoelectric pulse wave, and the filtering algorithm (50) of the photoelectric pulse wave is adaptively adjusted according to historical data recorded in the database.

Drawings

The above and other objects, features and advantages of the present invention will become apparent from the following detailed description of exemplary embodiments thereof, which is to be read in connection with the accompanying drawings, wherein:

fig. 1 is a graph containing an arterial signal obtained from photoplethysmography (PPG), a typical PPG signal containing ac and dc components.

Fig. 2 is a schematic diagram of the system of the present invention, detecting the reflected signal.

Fig. 3 is a schematic diagram of the system of the present invention for detecting the transmission signal.

Detailed Description

The embodiment of photoelectric pulse wave detection by using the system and the method of the invention comprises the following steps:

the basic structure of the system is as follows: visible light emitting module (10) comprising an LED power supply driving circuit for providing a stable driving voltage suitable for the lighting requirements of the LED or LED array, an LED radio frequency signal transmitter driving circuit for selecting a bias voltage V_biasAnd radio frequency signal (20) of the single frequency, and modulate the sum of these two kinds of signals to LED lamp pearl or LED lamp pearl array, send the incoherent light after modulating to the human skin finally;

a single frequency RF signal (20) s (t) for loading on the LED lamp bead or LED lamp bead array to provide a modulated visible light waveform, wherein when encountering blood vessels, blood or human tissue beneath the skin, the visible light containing the single frequency RF signal will be partially incident on the visible light receiving module (30), assuming that the single frequency is f₁Signal amplitude of V_ac(ii) a Here, f₁＝10kHz，V_ac＝5Vpp。

The visible light receiving module (30) comprises a photoelectric detector and a related amplifying circuit, and a signal processing circuit, and is used for receiving a visible light signal transmitted from blood vessels, blood or human tissues under the skin, converting the visible light signal into an electric signal through the photoelectric detector, wherein the electric signal comprises two parts: a) low-frequency signal m carrying artery information_a(t), b) center frequency f₁Nearby high-frequency signal m carrying arterial information_b(t)V_accos(2πf₁t)；

Here, the reflected signal is selected to be detected, i.e., the block diagram shown in fig. 2 is selected. The optical power of the LED is then chosen to be 5W.

A signal processing module (40) for the part a) according to the traditional PPG methodProcessing the sub-signals, namely processing the low-frequency signals carrying artery information; simultaneously to the center frequency f of part b)₁And demodulating nearby high-frequency signals carrying artery information to obtain baseband signals carrying artery information, and combining a) partial signal processing results and b) partial signal processing results to obtain final artery signals, so as to obtain the heart rate, the blood pressure and other blood related parameters.

The present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof, and it is therefore intended that all such changes and modifications as fall within the true spirit and scope of the invention be considered as within the following claims.

Claims

1. A system for photoelectric pulse wave detection using an incoherent light source modulating an electrical signal, comprising:

A visible light emitting module (10) includes an LED power drive circuit for providing a stable drive voltage suitable for the lighting requirements of the LED or LED array, and an LED radio frequency signal transmitter drive circuit for selecting a bias voltage V _bias and a single frequency radio frequency signal (20), and modulate the sum of these two signals to the LED lamp bead or LED lamp bead array, and finally send the modulated incoherent light to the human skin;

A single frequency radio frequency signal (20)s(t) is used to load the LED lamp bead or LED lamp bead array to provide a modulated visible light waveform, including the blood vessel, blood or human tissue under the skin. The visible light of the single frequency radio frequency signal will be partially incident on the visible light receiving module (30), assuming that the single frequency is f ₁ and the signal amplitude is V _ac ;

The visible light receiving module (30) includes a photodetector, a related amplifying circuit, and a signal processing circuit, and is used for receiving the visible light signal transmitted from the blood vessels, blood or human tissue under the skin, and converting it into electricity through the photodetector. signal, and the electrical signal includes two parts: a) a low-frequency signal m _a (t) carrying arterial information, b) a high-frequency signal m _b (t) V _ac cos (2πf ₁ ) near the center frequency f ₁ carrying arterial information t);

The signal processing module (40) processes a) part of the signal according to the traditional PPG method, that is, processes the low-frequency signal carrying the arterial information; at the same time, decomposes the high-frequency signal carrying the arterial information near the center frequency f1 _of the part b) The baseband signal carrying the arterial information is obtained, and the final arterial signal is obtained by combining the results of a) partial signal processing and b) partial signal processing results, thereby obtaining heart rate, blood pressure, and other parameters related to blood.

2. the system that adopts the incoherent light source of modulated electrical signal to carry out photoelectric pulse wave detection as claimed in claim 1, it is characterized in that:

The visible light emitting module (10) and the visible light receiving module (30) are located on both sides of the finger, and the transmission signal is received at this time; is the reflected signal.

3. The system for photoelectric pulse wave detection using an incoherent light source of modulated electrical signals as claimed in claim 1, wherein:

The LED light source can be red (R) LED lamp beads, or green light (G) LED lamp beads, or blue light (B) LED lamp beads, or white light LED lamp beads composed of three colors of RGB, which are used to transmit different The visible light signal of the wavelength can improve the detection of the visible light signal reflected in the underlying blood vessels, blood or human tissue by visible light communication, and improve the accuracy of the detection of the photoelectric pulse wave of the human body.

4. The system for photoelectric pulse wave detection using an incoherent light source of modulated electrical signals as claimed in claim 1, wherein:

The final arterial signal can be obtained as follows

Among them, m _a (t) is the arterial signal extracted from the signal containing low frequency interference, and m _b (t) is the arterial signal extracted from the signal containing high frequency interference.

5. The system for photoelectric pulse wave detection using an incoherent light source of modulated electrical signals as claimed in claim 1, wherein:

The system may also include a photopulse wave-based filtering algorithm (50) that filters the arterial information _- carrying high-frequency signal m _b ₍ t) V _ac cos ( 2πf ₁ t) are processed separately, thereby forming the ma (t) and m _b ₍ t) parts of the arterial signal.

6. The system for photoelectric pulse wave detection using an incoherent light source of modulated electrical signals as claimed in claim 1, wherein:

The filtering algorithm (50) of the photoelectric pulse wave may include artificial neural network, machine learning or deep learning and other artificial intelligence algorithms.

7. The system for photoelectric pulse wave detection using an incoherent light source of modulated electrical signals as claimed in claim 1, wherein:

The bias voltage V _bias loaded on the LED can be adjusted to enhance the arterial signal to be extracted, thereby improving the detection accuracy of the photoelectric pulse wave.

8. The system for photoelectric pulse wave detection using an incoherent light source of modulated electrical signals as claimed in claim 1, wherein:

The amplitude V _ac of the radio frequency signal loaded on the LED can be adjusted to enhance the arterial signal to be extracted, thereby improving the accuracy of photoelectric pulse wave detection.

9. The system for photoelectric pulse wave detection using an incoherent light source of modulated electrical signals as claimed in claim 1, wherein:

In the experiment, the modulation frequency f ₁ with the smallest RF loss during visible light transmission can be obtained, thereby enhancing the arterial signal to be extracted, thereby improving the accuracy of photoelectric pulse wave detection.

10. The system for photoelectric pulse wave detection using an incoherent light source that modulates electrical signals as claimed in claim 5, wherein:

In order to solve the problem of human body difference in this method, the information measured each time by each user can be recorded in the database of the computer as the basis for updating the filtering algorithm (50) of the photoelectric pulse wave. The adaptive adjustment is made according to the historical data recorded in the database.