A system and method for photoelectric pulse wave detection using an incoherent light source that modulates an electrical signal

Abstract

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

Description

Technical Field

[0001] The present invention relates to a visible light sensing system using an incoherent light source, and in particular to an application field in which an incoherent visible light is generated by a light emitting diode that modulates an electrical signal and the light source is used for photoelectric pulse wave detection. Background Art

[0002] Smart healthcare is a major strategy for my country's future and a key application area for information technologies such as communication technology and computer technology. In smart healthcare, the focus is on monitoring and managing mobile health (including heart rate, blood oxygen, blood pressure, blood sugar and temperature) in the form of wearable devices. At present, there are still many problems in the field of wearable mobile health measurement, which makes the research on blood composition and heart rate parameter detection more important.

[0003] Non-invasive detection of blood components is not only of great significance for the diagnosis of various diseases, the management of chronic diseases such as diabetes and anemia, and the monitoring of perioperative or emergency patients, but also can achieve early screening of diseases, save medical resources, and promote environmental protection. At the same time, economic development and the improvement of living standards have prompted ordinary people to pay more attention to health and the effectiveness of obtaining health information. In order to improve people's quality of life, cardiovascular diseases must be effectively prevented, and the threat of cardiovascular diseases determines the necessity of continuous monitoring of physiological parameters including heart rate, blood pressure, blood oxygen and blood viscosity.

[0004] At present, photoplethysmography (PPG) and its related technologies are important technical means for non-invasive detection of blood components and continuous dynamic monitoring of physiological parameters. They have attracted the attention of many researchers at home and abroad and have produced a large number of research results. Photoplethysmography (PPG) was first proposed by Hertzman in 1938. It is a method to evaluate the blood perfusion information of skin tissue by carrying subcutaneous blood information through the reflection or transmission of input light in skin tissue. Due to the pulsation of the heart, part of the blood will flow into the fingertips through the arteries at various levels, causing the arteriolar network of the fingertips to expand. The blood that enters the capillary bed through the precapillary sphincter will return to the heart by flowing into the veins after nutrient exchange. The capillary sphincter has a large resistance to blood flow, and the capillary bed has sufficient volume to attenuate the pulsation of the arterioles. In general, it is believed that only the arterioles pulsate, while the capillaries, veins and other tissues do not pulsate. The change of the detection light power over time obtained by the PPG method is shown in the figure below. Figure 1 shown.

[0005] Reference 1 proposed a non-invasive continuous blood pressure measurement method based on photoplethysmography. The study proposed the idea of ​​normalizing the photoplethysmography, established a method for extracting cardiovascular system parameters and calculating diastolic pressure based on the normalized pulse wave model, and used this method to design a non-invasive continuous blood pressure measurement system that combines software and hardware.

[0006] Reference 2 uses a dynamic spectroscopy method for non-invasive detection of blood components. This method is based on the transmitted photoplethysmogram and uses the changes in spectral absorption caused by arterial filling to directly extract the optical density reflecting arterial blood components at multiple wavelengths. This theoretically reduces the impact of individual differences and measurement conditions, and has significant advantages over other methods. The dynamic spectral values ​​at different hemoglobin concentrations were obtained in the reference, and the correlation coefficient with hemoglobin concentration was calculated, thereby verifying the feasibility of the dynamic spectroscopy method.

[0007] Reference 3 selects a combined spectrum of 523nm green light, 660nm red light, and 810nm infrared light as the detection light source, and introduces a "mesh"-shaped slot structure in the structural design to eliminate ambient light interference and improve the signal-to-noise ratio of the measurement signal. Based on the traditional generalized morphological baseline drift removal algorithm, an improvement is made to achieve a simplified baseline drift removal algorithm.

[0008] These documents are all based on the research of photoplethysmography, but the signal obtained by photoplethysmography is weak, and new solutions are still needed in the detection system and method. It is for the above reasons that arterial signal detection technology based on electro-optical and acousto-optic methods is a key research topic in the development of current medical equipment.

[0009] References:

[0010] 1. Li Dingli, Research on non-invasive continuous blood pressure measurement method based on pulse wave, PhD dissertation, unit: Zhejiang University, completion time: April 2008.

[0011] 2. Zhou Mei, Methods and applications for improving dynamic spectral signal-to-noise ratio, PhD dissertation, unit: Tianjin University, completion time: May 2014.

[0012] 3. Li Xiru, Research on dynamic measurement technology of human physiological parameters based on photoplethysmography, PhD dissertation, Unit: University of Science and Technology of China, Completion time: May 2017. Summary of the invention

[0013] In view of the needs in the background technology, the purpose of the present invention is to provide a system and method for photoelectric pulse wave detection using an incoherent light source that modulates an electrical signal. The method is different in principle from the traditional method of using a light-emitting diode to directly emit light and detect the reflected or transmitted signal. The present invention modulates an electrical signal with a frequency f1 onto a light-emitting diode, receives a modulated visible light signal transmitted from blood vessels, blood or human tissue under the skin, and converts it into an electrical signal through a photodetector, and the electrical signal includes two parts: a) a low-frequency signal carrying arterial information, and b) a high-frequency signal carrying arterial information near the center frequency f1. Since the two parts of the signal are subject to different interference during transmission or scattering, the arterial signal can be extracted from the two parts of the signal. This method is somewhat different from the traditional photoplethysmography (PPG) method and provides a new detection dimension, but it can be compatible with the advantages of PPG and can be used to detect heart rate, blood pressure, and other blood-related parameters. At the same time, this method can be integrated with new technologies such as pattern recognition in the computer field to improve the quality of the detection signal.

[0014] The basic structure of the present invention comprises:

[0015] The visible light transmitting module (10) comprises an LED power driving circuit for providing a stable driving voltage suitable for the light emitting requirements of an LED or an LED array, and an LED radio frequency signal transmitter driving circuit for selecting a bias voltage V bias and a single frequency radio frequency signal (20), and modulate the sum of the two signals onto an LED lamp bead or an LED lamp bead array, and finally send the modulated incoherent light onto human skin;

[0016] A single frequency radio frequency signal (20)s(t) is used to load on an LED lamp bead or an LED lamp bead array to provide a modulated visible light waveform. When encountering blood vessels, blood or human tissue under the skin, the visible light containing the single frequency radio frequency signal will be partially incident on the visible light receiving module (30). Assuming that the single frequency is f1 and the signal amplitude is V ac ;

[0017] The visible light receiving module (30) comprises a photodetector and a related amplifying circuit, as well as a signal processing circuit, and is used to receive visible light signals transmitted from blood vessels, blood or human tissue under the skin, and convert them into electrical signals through the photodetector, and the electrical signals comprise two parts: a) a low-frequency signal m carrying arterial information; a (t), b) High-frequency signal m carrying arterial information near the center frequency f1 b (t)V ac cos(2πf1t);

[0018] The signal processing module (40) processes the part a) signal according to the traditional PPG method, that is, processes the low-frequency signal carrying the arterial information; and at the same time, demodulates the part b) high-frequency signal carrying the arterial information near the center frequency f1 to obtain a baseband signal carrying the arterial information, and combines the result of processing the part a) signal with the result of processing the part b) signal to obtain the final arterial signal, thereby obtaining the heart rate, blood pressure, and other blood-related parameters.

[0019] Considering the distance limitation of visible light waves in human organs, the LED lamp beads can be high-power LED lamp beads, which are used to send stronger visible light signals, thereby increasing the intensity of the detected visible light signals.

[0020] Furthermore, the visible light transmitting module (10) and the visible light receiving module (30) can be located on both sides of the finger, and what is received at this time is the transmission signal, such as Figure 3 As shown; or the visible light transmitting module (10) and the visible light receiving module (30) are located on the same side of the finger, and the reflected signal is received at this time, such as Figure 2 shown.

[0021] Furthermore, the LED light source can be a red (R) LED lamp bead, or a green (G) LED lamp bead, or a blue (B) LED lamp bead, or a white LED lamp bead composed of three colors of RGB, which is used to send visible light signals of different wavelengths, thereby improving the visible light communication detection of the visible light signals reflected in the blood vessels, blood or human tissues below, and improving the accuracy of human photoelectric pulse wave detection.

[0022] Furthermore, in the present invention, the final arterial signal can be obtained according to the following method: Among them, m a (t) is the arterial signal extracted from the signal containing low-frequency interference, m b (t) is the arterial signal extracted from the signal containing high-frequency interference.

[0023] Furthermore, the system may also include a filtering algorithm (50) based on the photoelectric pulse wave, which is used to filter the low-frequency signal m a (t) and the high-frequency signal m carrying arterial information near the center frequency f1 b (t)V ac cos(2πf1t) are processed separately, thus forming the m of the arterial signal a (t) part and m b The photoelectric pulse wave filtering algorithm (50) may include artificial neural network, machine learning, deep learning or other artificial intelligence algorithms.

[0024] Furthermore, the bias voltage V applied to the LED can be adjusted. bias , thereby enhancing the arterial signal to be extracted, thereby improving the accuracy of photoelectric pulse wave detection.

[0025] Furthermore, the RF signal amplitude V loaded on the LED can be adjusted ac , thereby enhancing the arterial signal to be extracted, thereby improving the accuracy of photoelectric pulse wave detection.

[0026] Furthermore, in the experiment, the modulation frequency f1 with the smallest radio frequency 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.

[0027] Furthermore, in order to solve the problem of human body differences in this method, the information of each user's measurement each time can be recorded in a computer database as a basis for updating the photoelectric pulse wave filtering algorithm (50), and the electrical pulse wave filtering algorithm (50) is adaptively adjusted according to the historical data recorded in the database. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The above and other objects, features and advantages of the present invention will become apparent from the following detailed description of exemplary embodiments with reference to the accompanying drawings, in which:

[0029] Figure 1 Graph containing arterial signals obtained using photoplethysmography (PPG). A typical PPG signal contains both AC and DC components.

[0030] Figure 2 It is a schematic diagram of the system structure of the present invention, detecting the reflected signal.

[0031] Figure 3 It is a schematic diagram of the system structure of the present invention, detecting the transmission signal. DETAILED DESCRIPTION

[0032] 1. Embodiments of photoelectric pulse wave detection using the system and method of the present invention:

[0033] The basic structure of the system is as follows: a visible light transmitting module (10), including an LED power drive circuit, used to provide a stable drive voltage suitable for the light emission requirements of the LED or LED array, and an LED radio frequency signal transmitter drive circuit, used to select a bias voltage V bias and a single frequency radio frequency signal (20), and modulate the sum of the two signals onto an LED lamp bead or an LED lamp bead array, and finally send the modulated incoherent light onto human skin;

[0034] A single frequency radio frequency signal (20)s(t) is used to load on an LED lamp bead or an LED lamp bead array to provide a modulated visible light waveform. When encountering blood vessels, blood or human tissue under the skin, the visible light containing the single frequency radio frequency signal will be partially incident on the visible light receiving module (30). Assuming that the single frequency is f1 and the signal amplitude is V ac ; Here, f1 = 10kHz, V ac =5Vpp.

[0035] The visible light receiving module (30) comprises a photodetector and a related amplifying circuit, as well as a signal processing circuit, and is used to receive visible light signals transmitted from blood vessels, blood or human tissue under the skin, and convert them into electrical signals through the photodetector, and the electrical signals comprise two parts: a) a low-frequency signal m carrying arterial information; a (t), b) High-frequency signal m carrying arterial information near the center frequency f1 b (t)V ac cos(2πf1t);

[0036] Here we select to detect the reflected signal, that is, select Figure 2 The structure diagram is shown. At this time, the light power of the LED is selected to be 5W.

[0037] The signal processing module (40) processes the part a) signal according to the traditional PPG method, that is, processes the low-frequency signal carrying the arterial information; and at the same time, demodulates the part b) high-frequency signal carrying the arterial information near the center frequency f1 to obtain a baseband signal carrying the arterial information, and combines the result of processing the part a) signal with the result of processing the part b) signal to obtain the final arterial signal, thereby obtaining the heart rate, blood pressure, and other blood-related parameters.

[0038] Of course, the present invention may have many other embodiments. Without departing from the spirit and essence of the present invention, technicians familiar with the field may make various corresponding changes and modifications based on the present invention, but these corresponding changes and modifications should all fall within the scope of protection of the claims attached to the present invention.

Claims

1. A system for photoelectric pulse wave detection using an incoherent light source that modulates an electrical signal, comprising: The visible light transmitting module (10) comprises an LED power driving circuit for providing a stable driving voltage suitable for the light emitting requirements of an LED or an LED array, and an LED radio frequency signal transmitter driving circuit for selecting a bias voltage V bias and a single frequency radio frequency signal (20), and modulate the sum of the two signals onto an LED lamp bead or an LED lamp bead array, and finally send the modulated incoherent light onto human skin; A single frequency radio frequency signal (20)s(t) is used to load on an LED lamp bead or an LED lamp bead array to provide a modulated visible light waveform. When encountering blood vessels, blood or human tissue under the skin, the visible light containing the single frequency radio frequency signal will be partially incident on the visible light receiving module (30). Assuming that the single frequency is f1 and the signal amplitude is V ac ; The visible light receiving module (30) comprises a photodetector and a related amplifying circuit, as well as a signal processing circuit, and is used to receive visible light signals transmitted from blood vessels, blood or human tissue under the skin, and convert them into electrical signals through the photodetector, and the electrical signals comprise two parts: a) a low-frequency signal m carrying arterial information; a (t), b) High-frequency signal m carrying arterial information near the center frequency f1 b (t)V ac cos(2πf1t); The signal processing module (40) processes the part a) signal according to the traditional PPG method, that is, processes the low-frequency signal carrying the arterial information; at the same time, demodulates the high-frequency signal carrying the arterial information near the center frequency f1 of the part b) to obtain a baseband signal carrying the arterial information, and combines the result of processing the part a) signal with the result of processing the part b) signal to obtain the final arterial signal. The final arterial signal is obtained according to the following method Among them, m a (t) is the arterial signal extracted from the signal containing low-frequency interference, m b (t) is the arterial signal extracted from the signal containing high-frequency interference, thereby obtaining heart rate, blood pressure, and other blood-related parameters.

2. The system for photoelectric pulse wave detection using an incoherent light source that modulates an electrical signal as claimed in claim 1, characterized in that: The visible light transmitting module (10) and the visible light receiving module (30) are located on both sides of the finger, and what is received is the transmission signal; or the visible light transmitting module (10) and the visible light receiving module (30) are located on the same side of the finger, and what is received is the reflection signal.

3. The system for photoelectric pulse wave detection using an incoherent light source that modulates an electrical signal as claimed in claim 1, characterized in that: The LED light source is a red (R) LED lamp bead, or a green (G) LED lamp bead, or a blue (B) LED lamp bead, or a white LED lamp bead composed of three colors of RGB, which is used to send visible light signals of different wavelengths, thereby improving the visible light communication detection of the visible light signals reflected in the blood vessels, blood or human tissues below, and improving the accuracy of human photoelectric pulse wave detection.

4. The system for photoelectric pulse wave detection using an incoherent light source that modulates an electrical signal as claimed in claim 1, characterized in that: The system also includes a photoelectric pulse wave based filtering algorithm (50) which filters the low frequency signal m a (t) and the high-frequency signal m carrying arterial information near the center frequency f1 b (t)V ac cos(2πf1t) are processed separately, thus forming the m of the arterial signal a (t) part and m b Section (t).

5. The system for photoelectric pulse wave detection using an incoherent light source that modulates an electrical signal as claimed in claim 4, characterized in that: The photoelectric pulse wave filtering algorithm (50) includes an artificial neural network, machine learning or deep learning artificial intelligence algorithm.

6. The system for photoelectric pulse wave detection using an incoherent light source that modulates an electrical signal as claimed in claim 1, characterized in that: Adjust the bias voltage V applied to the LED bias , thereby enhancing the arterial signal to be extracted, thereby improving the accuracy of photoelectric pulse wave detection.

7. The system for photoelectric pulse wave detection using an incoherent light source that modulates an electrical signal as claimed in claim 1, characterized in that: Adjust the RF signal amplitude V loaded on the LED ac , thereby enhancing the arterial signal to be extracted, thereby improving the accuracy of photoelectric pulse wave detection.

8. The system for photoelectric pulse wave detection using an incoherent light source that modulates an electrical signal as claimed in claim 1, characterized in that: In the experiment, the modulation frequency f1 with the smallest radio frequency loss during visible light transmission is obtained, so as 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 that modulates an electrical signal as claimed in claim 5, characterized in that: The information of each user's measurement each time is recorded in the computer database as the basis for updating the photoelectric pulse wave filtering algorithm (50). The electric pulse wave filtering algorithm (50) is adaptively adjusted according to the historical data recorded in the database.

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