Sleep monitoring device and method based on optical fiber Michelson interferometer

Abstract

The invention relates to the field of optical fiber sensing technology and sleep monitoring, in particular to a sleep monitoring device and method based on an optical fiber Michelson interferometer. On one hand, the sleep monitoring sensitivity is remarkably improved through phase demodulation, and heartbeat, breath and other weak signals generated in the sleep process can be accurately monitored; on the other hand, through simultaneous monitoring and data fusion analysis of multiple sensor signals, the accuracy of breathing and heartbeat signals needed by sleep evaluation can be improved, and human body movement information in the sleep process can be monitored; according to the invention, the sleep monitoring sensitivity can be effectively improved, the problem that the Mach-Zehnder interferometer is susceptible to polarization interference can be avoided, and body movement monitoring can be realized through a plurality of sensors.

Description

Technical Field

[0001] The present invention relates to the field of optical fiber sensing technology and sleep monitoring, and in particular to a sleep monitoring device and method based on an optical fiber Michelson interferometer. Background Art

[0002] Sleep is an important physiological process that is indispensable for maintaining human physiological functions, promoting cognitive function recovery, and ensuring physical and mental health. Its monitoring technology has received widespread attention in recent years. Traditional polysomnography (PSG) systems have inherent defects such as complex equipment to wear, limited detection environment, high cost, and great impact on sleep. It is difficult to meet the needs of long-term continuous monitoring in home scenarios. In recent years, sleep monitoring sensor systems with less impact on sleep have received a lot of attention.

[0003] Existing sleep monitoring sensor systems are mainly divided into two categories: contact and non-contact. The contact solution mostly uses wearable devices. The national invention patent application "A wristband sleep monitoring device" (publication number: CN102499656A, publication date: 2012-06-20) discloses a wristband sleep monitoring device that obtains physiological signals through a pulse sensor and a temperature sensor. However, such devices have problems such as discomfort when worn and signals are easily interfered by motion artifacts, and long-term use compliance is poor. In the non-contact solution, millimeter wave radar (such as "A sleep monitoring method and system based on millimeter wave radar and pressure sensor" (publication number: CN118965265A, publication date: 2024-11-15)) and video image analysis system (such as a non-contact sleep monitoring method and system, ZL201510166500.7) can achieve non-sensing monitoring, but the former is susceptible to electromagnetic interference and cannot distinguish signals from multiple beds, and the latter has privacy leakage risks and occlusion failure defects.

[0004] In recent years, mattress-type monitoring devices in non-contact sensing systems have gradually become a research hotspot due to their characteristics of no need to wear and non-sensitive detection. The technical implementation paths are mainly divided into two categories: piezoelectric film sensing and optical fiber sensing: Mattress-type sleep monitoring system based on piezoelectric film sensor (publication number CN116649890A, publication date: 2023-08-29) is based on the piezoelectric effect of polyvinylidene fluoride (PVDF), and generates charge signals by detecting micro-strain on the surface of the mattress. Although this type of solution has the advantages of low cost and easy integration, it is limited by the stiffness and sensitivity threshold of piezoelectric materials, and has insufficient response capabilities to low-frequency weak signals (such as breathing signals <0.5Hz). In addition, the temperature and humidity sensitivity of piezoelectric film causes significant signal baseline drift, requiring temperature calibration.

[0005] Compared with electrical sensors, optical fiber sensors have the advantages of high sensitivity, compact structure, light weight, anti-electromagnetic interference, and easy multiplexing. In addition, solutions based on optical fiber sensors have no electrical devices at the sensor end and are safer. At present, most non-contact sleep monitoring systems based on optical fiber sensors use optical fiber grating or optical fiber micro-bend pressure sensing structures. The national invention patent application "Human sleep health monitoring method based on optical fiber grating sensor" (publication number: CN114469004A, publication date: 2022-05-13) discloses a human sleep health monitoring device and method based on optical fiber grating sensor. The national invention patent "Sleep quality monitoring device and method based on optical fiber micro-bend pressure sensing" (ZL201910728687.3) discloses a sleep quality monitoring device and method based on optical fiber micro-bend pressure sensing. The above two schemes realize signal sensing based on wavelength demodulation and light intensity demodulation, respectively, and the sensing sensitivity is low. The paper (Sleep condition detection and assessment with optical fiber interferometer based on machine learning. iScience. 2023 Jun 30;26(7):107244) presents a sleep monitoring method based on Mach-Zehnder interferometer. However, this method has two disadvantages: first, the Mach-Zehnder interferometer is susceptible to polarization disturbances, which may distort the measurement signal and generate false signals; second, there is only one interferometer on the entire mattress, which cannot sense and distinguish the signals from different parts of the body. Summary of the invention

[0006] In order to overcome the problems existing in the existing mattress-type sleep monitoring method, the present invention provides a sleep monitoring device and method based on a fiber Michelson interferometer, and implants a fiber Michelson interferometer sensor array into a mattress to achieve contactless monitoring of sleep status; on the one hand, the present invention significantly improves the sensitivity of sleep monitoring through phase demodulation, and can accurately monitor the heartbeat, breathing and other weak signals generated during the sleep process; on the other hand, through the simultaneous monitoring and data fusion analysis of multiple sensor signals, the accuracy of the breathing and heartbeat signals required for sleep assessment can be improved, and the human body movement information during sleep can be monitored. The present invention can effectively improve the sensitivity of sleep monitoring, avoid the problem that the Mach-Zehnder interferometer is susceptible to polarization interference, and can also achieve body movement monitoring through multiple sensors.

[0007] In order to achieve the above technical objectives, the present invention provides a sleep monitoring device based on a fiber Michelson interferometer. The device includes: a single-frequency laser, a fiber beam splitter, a sensor array, a multi-channel photodetector, and a signal acquisition and processing module; the output end of the single-frequency laser is connected to the input end of the fiber beam splitter for emitting laser light; the N output ends of the fiber beam splitter are respectively connected to the N input ends of the sensor array for splitting a beam of light into N beams of light; the N output ends of the sensor array are respectively connected to the N input ends of the multi-channel photodetector, and the multi-channel photodetector is used to convert the optical signal into an electrical signal; the output end of the multi-channel photodetector is connected to the signal acquisition and processing module, and the signal acquisition and processing module is used to realize the acquisition and phase demodulation of the sensor array signal, and extract the breathing, heartbeat signals and body movement information at different positions of the human body; the sensor array is composed of N fiber Michelson interferometers, and the N fiber Michelson interferometers are implanted in different positions of the mattress to sense the signals generated by the sleep process at different positions of the human body, and N is an integer greater than 1.

[0008] Further, the single-frequency laser may be a single-frequency tunable laser or a non-tunable laser; Furthermore, the ends of the two arms of the optical fiber Michelson interferometer are respectively connected to Faraday rotators to overcome the interference of polarization fading; The present invention also provides a sleep monitoring method based on the above device, which is divided into the following steps: S1. The output light of the single-frequency laser is divided into N beams by a fiber beam splitter; S2. The N beams of light output by the fiber beam splitter enter N fiber Michelson interferometers through N input ports in the sensor array respectively; S3. N fiber Michelson interferometers are implanted in different positions of the mattress. When a person lies on the mattress, the signals generated during sleep cause the optical fibers of the N fiber Michelson interferometers to deform, resulting in changes in the phase of the output light of the N fiber Michelson interferometers. S4. The output optical signal of the fiber Michelson interferometer enters the multi-channel photodetector through the N output ends of the sensor array, and the optical signal is converted into an electrical signal by the multi-channel photodetector; S5. The electrical signal output by the multi-channel photoelectric detector enters the signal acquisition and processing module for processing, and the phase signals of N fiber Michelson interferometers are demodulated. The specific demodulation process refers to the national invention patent "A fiber optic sensing and demodulation method and device based on electro-optic phase modulator" (ZL 202210853498.0).

[0009] S6. The signal acquisition and processing module processes the demodulated phase signals of the N fiber Michelson interferometers, extracts the breathing and heartbeat signals at different positions of the human body, and infers the sleep body movement state according to the energy and frequency characteristics of the signals collected by the fiber Michelson interferometers at different positions, as follows: S6.1 performs filtering processing on the demodulated phase signals of the N optical fiber Michelson interferometers to extract the breathing and heartbeat signals of different parts of the human body. The filtering processing method is the Butterworth bandpass filtering method. The specific filtering frequency band range refers to the current standard "Sleep Monitoring Signal Machine Analysis and Interpretation Specification" (T / CPAM 002-2020).

[0010] S6.2 calculates the frequency band energy of the breathing and heartbeat signals of different parts of the human body. The energy size reflects the distance between the sensor and the heart. The position of the human heart is determined based on the frequency band energy and the distribution of the sensor array on the mattress. The breathing and heartbeat signals collected by the sensor at this position have the highest accuracy.

[0011] S6.3 collects the frequency band energy of sleep signals based on N sensors and the distribution of the sensor array on the mattress. It can obtain the distribution of the total energy generated by human sleep on the mattress. The movement of different parts of the human body will cause changes in the energy distribution. By comparing the energy distribution at adjacent moments, it can be determined whether different parts of the human body move on the mattress. The position changes of different parts of the human body can be combined to obtain the nighttime sleep body movement information.

[0012] The present invention has the following beneficial effects: On the one hand, the fiber optic Michelson interferometer overcomes the interference of polarization disturbance on the monitoring process, improves the sensitivity of sleep signal monitoring, and can accurately monitor the heartbeat, breathing and other weak signals generated during the sleep process; on the other hand, by implanting multiple fiber optic Michelson interferometers in different positions of the mattress, accurate monitoring of sleep signals at different positions of the human body can be achieved, which can effectively improve the accuracy of the breathing and heartbeat signals required for sleep evaluation, and at the same time realize the monitoring of human activities during sleep. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The present invention is further described in detail below with reference to the accompanying drawings Figure 1 It is a structural schematic diagram of a specific embodiment of the present invention; In the figure: 2 is a single-frequency laser, 3 is a fiber beam splitter, 4 is a multi-channel photoelectric detector, 5 is a signal acquisition and processing module, and 6-N is a fiber Michelson interferometer in the sensor array.

[0014] The output end 21 of the single-frequency laser 2 is connected to the input end 31 of the optical fiber beam splitter 3, the output ends 32-3N of the optical fiber beam splitter 3 are respectively connected to the input ends 61, 71...N1 of the optical fiber Michelson interferometer 6-N in the sensor array, the output ends 62, 72...N2 of the interferometer 6-N are respectively connected to the input ends 42-4N of the multi-channel photodetector 4, and the output end 41 of the photodetector 4 is connected to the input end 51 of the signal acquisition and processing module 5.

[0015] Figure 2 is a structural schematic diagram of the mattress device provided with a fiber optic Michelson interferometer sensor array; In the figure: 1 is a mattress, and the black dots are fiber optic Michelson interferometers in the sensor array.

[0016] The interferometers are arranged within the areas 11, 12, 13, 14 of the mattress 1 to sense signals generated by different parts of the human body during sleep.

[0017] Figure 3 is the breathing signal waveform with the highest accuracy in one embodiment; Figure 4 is the heartbeat signal waveform with the highest accuracy in one embodiment; Figure 5 is an energy distribution diagram of N sensors on a mattress at a certain moment in one embodiment; In the figure: 6-N on the horizontal axis represents the sensor number, and the vertical axis value represents the energy size of the breathing and heartbeat signal frequency band collected by the sensor. DETAILED DESCRIPTION

[0018] Various exemplary embodiments of the present application will now be described in detail with reference to the accompanying drawings. It should be noted that unless otherwise specifically stated, the relative arrangement of components and steps, numerical expressions and numerical values ​​set forth in these embodiments do not limit the scope of the present application.

[0019] The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the present application, its application, or uses.

[0020] Technologies, methods, and equipment known to ordinary technicians in the relevant art may not be discussed in detail, but where appropriate, the technologies, methods, and equipment should be considered as part of the specification.

[0021] In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not limiting. Therefore, other examples of the exemplary embodiments may have different values.

[0022] like Figure 1As shown, the sleep monitoring device based on the fiber Michelson interferometer of this embodiment includes a single-frequency laser 2, a fiber beam splitter 3, a multi-channel photodetector 4, a signal acquisition and processing module 5, and a fiber Michelson interferometer 6-N in the sensor array. The output end 21 of the single-frequency laser 2 is connected to the input end 31 of the fiber beam splitter 3, the output ends 32-3N of the fiber beam splitter 3 are respectively connected to the input ends 61, 71...N1 of the fiber Michelson interferometer 6-N in the sensor array, the output ends 62, 72...N2 of the interferometer 6-N are respectively connected to the input ends 42-4N of the multi-channel photodetector 4, and the output end 41 of the photodetector 4 is connected to the input end 51 of the signal acquisition and processing module 5.

[0023] like Figure 2 As shown, the mattress device with a fiber Michelson interferometer sensor array in this embodiment includes a mattress 1 and a fiber Michelson interferometer in the sensor array. The interferometer is represented by a black dot and is arranged in areas 11, 12, 13, and 14 in the mattress 1 to sense signals generated during sleep at different positions of the human body.

[0024] The specific implementation of the present invention is: S1. The output light of the single-frequency laser 2 is divided into N beams of light by the optical fiber beam splitter 3; S2. The N beams of light outputted from the output end 32-3N of the optical fiber beam splitter 3 enter the optical fiber Michelson interferometer 6-N through the input ends 61, 71, ... N1 of the sensor array respectively; S3. The fiber Michelson interferometer 6-N is implanted in regions 11, 12, 13, and 14 on the mattress 1. When a person lies on the mattress, signals generated by different parts of the human body during sleep cause the optical fiber of the fiber Michelson interferometer 6-N to deform, resulting in a change in the phase of the output light of the fiber Michelson interferometer 6-N. S4. The output optical signal of the fiber Michelson interferometer 6-N is output through the output terminals 62, 72 ... N2 of the sensor array, and enters the multi-channel photodetector 4 through the input terminals 42-4N of the multi-channel photodetector, respectively, and the optical signal is converted into an electrical signal by the multi-channel photodetector 4; S5. The electrical signal output from the output terminal 41 of the multi-channel photodetector 4 enters the signal acquisition and processing module 5 for processing, and demodulates the phase signal of the optical fiber Michelson interferometer 6-N; S6. The signal acquisition and processing module 5 processes the demodulated phase signals of the N fiber Michelson interferometers, extracts the breathing and heartbeat signals at different positions of the human body, and infers the sleep body movement state according to the energy and frequency characteristics of the fiber Michelson interferometer signals collected at different positions, as follows: S6.1 performs filtering processing on the demodulated phase signals of the N optical fiber Michelson interferometers to extract the breathing and heartbeat signals of different parts of the human body. The filtering processing method is the Butterworth bandpass filtering method. The specific filtering frequency band range refers to the current standard "Sleep Monitoring Signal Machine Analysis and Interpretation Specification" (T / CPAM 002-2020).

[0025] S6.2 calculates the frequency band energy of the breathing and heartbeat signals of different parts of the human body. The energy size reflects the distance between the sensor and the heart. The position of the human heart is determined based on the frequency band energy and the distribution of the sensor array on the mattress. The breathing and heartbeat signals collected by the sensor at this position have the highest accuracy.

[0026] S6.3 collects the frequency band energy of sleep signals based on N sensors and the distribution of the sensor array on the mattress. It can obtain the distribution of the total energy generated by human sleep on the mattress. The movement of different parts of the human body will cause changes in the energy distribution. By comparing the energy distribution at adjacent moments, it can be determined whether different parts of the human body move on the mattress. The position changes of different parts of the human body can be combined to obtain the body movement information during sleep at night.

[0027] The breathing signal waveform with the highest accuracy in this embodiment is as follows Figure 3 As shown in the figure, it has obvious regular large fluctuations and a large frequency; the most accurate heartbeat signal waveform is as follows Figure 4 As shown, the fluctuation is relatively small and the frequency is relatively small; the energy distribution of N sensors on the mattress at a certain moment is as follows Figure 5 As shown, the energy of the signals collected by N sensors is different. By comparing the energy distribution on the mattress at adjacent moments, the sleep movement state of the human body can be analyzed.

Claims

1. A sleep monitoring device based on an optical fiber Michelson interferometer, characterized in that: The device comprises a single-frequency laser, an optical fiber beam splitter, a sensor array, a multi-channel photoelectric detector, and a signal acquisition and processing module; the output end of the single-frequency laser is connected to the input end of the optical fiber beam splitter for emitting laser light; the N output ends of the optical fiber beam splitter are respectively connected to the N input ends of the sensor array for splitting a beam of light into N beams of light; the N output ends of the sensor array are respectively connected to the N input ends of the multi-channel photoelectric detector, and the multi-channel photoelectric detector is used to convert the optical signal into an electrical signal; the output end of the multi-channel photoelectric detector is connected to the signal acquisition and processing module, and the signal acquisition and processing module is used to realize the acquisition and phase demodulation of the sensor array signal, and extract the breathing, heartbeat signals and body movement information at different positions of the human body; the sensor array is composed of N optical fiber Michelson interferometers, and the N optical fiber Michelson interferometers are implanted at different positions of the mattress, and are used to sense the signals generated by the sleep process at different positions of the human body, and N is an integer greater than 1.

2. The sleep monitoring device based on the optical fiber Michelson interferometer according to claim 1, characterized in that: The single-frequency laser is a single-frequency tunable laser or a non-tunable laser.

3. The sleep monitoring device based on the optical fiber Michelson interferometer according to claim 1, characterized in that: The ends of the two arms of the optical fiber Michelson interferometer are respectively connected with Faraday rotating mirrors to overcome the interference of polarization fading.

4. The sleep monitoring method according to any one of claims 1 to 3, characterized in that: The method is divided into the following steps: S1. The output light of the single-frequency laser is divided into N beams by a fiber beam splitter; S2. The N beams of light output by the fiber beam splitter enter N fiber Michelson interferometers through N input ports in the sensor array respectively; S3. N fiber Michelson interferometers are implanted in different positions of the mattress. When a person lies on the mattress, the signals generated during sleep cause the optical fibers of the N fiber Michelson interferometers to deform, resulting in changes in the phase of the output light of the N fiber Michelson interferometers. S4. The output optical signal of the fiber Michelson interferometer enters the multi-channel photodetector through the N output ends of the sensor array, and the optical signal is converted into an electrical signal by the multi-channel photodetector; S5. The electrical signal output by the multi-channel photoelectric detector enters the signal acquisition and processing module for processing, and demodulates the phase signal of N fiber Michelson interferometers; S6. The signal acquisition and processing module processes the demodulated phase signals of the N fiber Michelson interferometers, extracts the breathing and heartbeat signals at different positions of the human body, and infers the sleep body movement state according to the energy and frequency characteristics of the signals collected by the fiber Michelson interferometers at different positions, as follows: S6.1 performs filtering processing on the demodulated phase signals of the N optical fiber Michelson interferometers to extract the breathing and heartbeat signals of different parts of the human body; S6.2 calculates the frequency band energy of the breathing and heartbeat signals of different parts of the human body. The energy reflects the distance between the sensor and the heart. The position of the human heart is determined based on the frequency band energy and the distribution of the sensor array on the mattress. The breathing and heartbeat signals collected by the sensor at this position have the highest accuracy. S6.3 collects the frequency band energy of sleep signals based on N sensors and the distribution of the sensor array on the mattress. It can obtain the distribution of the total energy generated by human sleep on the mattress. The movement of different parts of the human body will cause changes in the energy distribution. By comparing the energy distribution at adjacent moments, it can be determined whether different parts of the human body move on the mattress. The position changes of different parts of the human body can be combined to obtain the body movement information during sleep at night.

5. The sleep monitoring method according to claim 4, characterized in that: In S6.1, the filtering processing method is a Butterworth bandpass filtering method.

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