Heart sound detection device and method based on bionic diaphragm type optical fiber acoustic sensor

Abstract

The invention discloses a heart sound detection device and method based on a bionic diaphragm type optical fiber acoustic sensor, and belongs to the technical field of heart sound detection and optical fiber sensing. The heart sound detection device is sequentially provided with a laser, a circulator, a single-mode optical fiber, a bionic diaphragm, an optical signal processing unit and a signal processing unit according to the light propagation direction, emergent light of the laser passes through the circulator and then enters the single-mode optical fiber to be transmitted, after the emergent light reaches the end face of the single-mode optical fiber, one part of the emergent light is directly reflected, and the other part of the emergent light is emitted from the end face, is reflected by the bionic diaphragm and then is coupled to enter the single-mode optical fiber to interfere with the directly-reflected part; and the interference light enters the optical signal processing unit through the circulator and is converted into an electric signal, and then a heart sound signal is obtained by the signal processing unit. The invention has the advantages of high detection sensitivity, good low-frequency response characteristic and strong anti-electromagnetic interference capability.

Description

Technical Field

[0001] The invention discloses a heart sound detection device and method based on a bionic diaphragm type optical fiber acoustic sensor, belonging to the technical field of heart sound detection and optical fiber sensing. Background Art

[0002] The incidence of cardiovascular diseases in the population is increasing, seriously endangering people's health. Heart sounds are an important indicator of cardiac physiology and pathology, and auscultation of heart sounds is the main means of diagnosis and treatment of cardiovascular diseases. However, traditional mechanical stethoscopes are overly dependent on human hearing and are limited by the subjective experience of doctors. They have been gradually replaced by electronic stethoscopes.

[0003] In 2016, A. Madhubabu et al. prepared a capacitive microphone heart sound sensor, which uses the vibration of the diaphragm to receive sound pressure and convert it into an electrical signal; the sensor has good stability, but low sensitivity and poor signal-to-noise ratio. In 2017, SAFattah et al. prepared a piezoelectric heart sound sensor using PVDF piezoelectric film. By utilizing the piezoelectric effect of the membrane, the strain generated by the external pressure on the diaphragm is converted into voltage, thereby measuring the strength of the heart sound; the sensor has high sensitivity, but is easily affected by environmental noise, has a poor signal-to-noise ratio, is easy to damage, has poor stability, and is costly. In 2018, R. Martinek et al. prepared an interferometric heart sound sensor using optical fiber. Its interference structure consists of a reference arm and a measuring arm. The measuring arm is encapsulated in PDMS, and the heart sound signal is measured by solving the interference signal; the sensor has high sensitivity and accuracy, but the production cost is high and the environmental requirements are high. In 2019, a new structure of MEMS heart sound sensor with bionic cilia pickup mechanism was proposed. This structure detects the acceleration signal caused by acoustic vibration, uses the swinging bionic cilia to drive the deformation of the cantilever arm, and uses the piezoresistive effect to realize the acoustic-to-electric conversion of heart sound signals. However, the sensitivity of this structure gradually decreases with decreasing frequency.

[0004] The aforementioned structure realizes the measurement of heart sound signals by detecting sound pressure signals or acceleration signals. When measuring through sound pressure signals, the effective sound pressure value felt by the diaphragm is affected by the structural parameters of the sensor, and its fidelity is generally low; and the sound pressure measurement sensitivity and the working frequency band of the sensor are mutually restricted; and when measuring heart sounds through acceleration signals, its measurement sensitivity gradually decreases as the frequency decreases. The frequency band of heart sound signals is in the range of 20Hz-600Hz. How to improve the sensitivity of the sensor while ensuring the working bandwidth and reduce the processing and manufacturing cost of the sensor is the problem solved by the present invention. Summary of the invention

[0005] In view of the above problems, the present invention proposes a heart sound detection device and method based on a bionic membrane type optical fiber acoustic sensor to solve the problems of low detection sensitivity, poor low-frequency response characteristics and poor anti-electromagnetic interference ability of traditional heart sound sensors.

[0006] The object of the present invention is achieved in that:

[0007] A heart sound detection device based on a bionic membrane-type optical fiber acoustic sensor is provided in sequence according to the light propagation direction: a laser, a circulator, a single-mode optical fiber, a bionic membrane, an optical signal processing unit and a signal processing unit;

[0008] The end face of the single-mode optical fiber is cut at a 0-degree angle and polished; the single-mode optical fiber is arranged vertically to the bionic membrane, the end face of the single-mode optical fiber is parallel to the bionic membrane, and the distance between the end face of the single-mode optical fiber and the bionic membrane is 0.1 mm-1 mm;

[0009] After passing through the circulator, the laser's output light enters the single-mode optical fiber for transmission. After reaching the end face of the single-mode optical fiber, a part of it is directly reflected, and the other part is emitted from the end face, reflected by the bionic membrane, and then coupled into the single-mode optical fiber to interfere with the directly reflected part; the interference light then passes through the circulator and enters the optical signal processing unit, and after being converted into an electrical signal, the signal processing unit obtains the heart sound signal.

[0010] The above-mentioned heart sound detection device based on the bionic diaphragm-type optical fiber acoustic sensor, the bionic diaphragm has a diameter of 3mm-20mm, the middle area is a circular complete area with a diameter not exceeding 1mm, the circular complete area is supported by a circle of mesh fiber structure and connected to the surrounding frames or fixed structures, and the nanofiber structures are fixed by transverse fiber structures with gradually changing lengths.

[0011] The diameter of the nanofiber structure does not exceed 10 microns, and the material is gold, silver, chromium, PMMA, PI, PU, ​​PC or PET.

[0012] The circular complete area is deposited with a metal film or a multi-layer dielectric film with a thickness less than 1 micron and a reflectivity greater than 90%, and the working bandwidth of the metal film or the multi-layer dielectric film is 1525nm-1605nm.

[0013] In the above-mentioned heart sound detection device based on the bionic membrane type optical fiber acoustic sensor, the end face of the single-mode optical fiber is deposited with a multilayer dielectric film with a reflectivity of no more than 10%, and the working bandwidth of the multilayer dielectric film is 1525nm-1605nm.

[0014] In the above-mentioned heart sound detection device based on the bionic diaphragm type optical fiber acoustic sensor, the bionic diaphragm and the single-mode optical fiber are fixed on a bracket.

[0015] The bionic diaphragm and the bracket are arranged in the housing.

[0016] The heart sound detection method based on the bionic membrane type optical fiber acoustic sensor has the following steps:

[0017] When the heart sound signal radiates through the human body surface to the surface of the bionic membrane, the fluid vibration caused by the heart sound signal will drive the bionic membrane to produce vibrations with the same frequency and amplitude;

[0018] After the laser's outgoing light is transmitted through the end face of the single-mode optical fiber, it is incident on the surface of the bionic membrane and reflected, interfering with the reflected light from the end face of the single-mode optical fiber.

[0019] When the bionic membrane vibrates under the drive of the heart sound signal, the distance between the bionic membrane and the end face of the single-mode optical fiber changes with the same frequency and amplitude, causing the reflected light signal to change, and then causing the interference light to change;

[0020] The interference light signal carrying the heart sound signal is transmitted to the optical signal processing unit through the single-mode optical fiber, the interference light signal is converted into an electrical signal, and sent to the signal processing unit, and after analysis and processing, the heart sound information is obtained.

[0021] The beneficial effects of the present invention are:

[0022] First, the acoustically sensitive diaphragm is designed as a bionic diaphragm composed of nanoscale fiber structures. The vibration of this structure is driven by the fluid vibration velocity caused by the heart sound signal. Different from the traditional sound pressure drive or acceleration drive method, this method enables the bionic diaphragm to have extremely high sensitivity and a wide working bandwidth, so that weak heart sound signals can be extracted with high fidelity.

[0023] Second, the bionic diaphragm designed by the present invention uses the biological principle that the organism uses the ciliary structure to perceive the external flow field. Since the ciliary structure is in a high damping state in the fluid, the ciliary movement will be mainly dominated by the damping force generated by the surrounding fluid on the ciliary. Therefore, the bionic diaphragm of the present invention can perceive the fluid movement caused by acoustic vibration, obtain the maximum physical coupling efficiency in a wide frequency range, and the speed transfer ratio is close to 1, so it can still maintain good measurement accuracy in the low frequency band;

[0024] Third, the signal extraction method using fiber optic interferometer sensors is not affected by electromagnetic interference. Compared with electronic sensors, it has better anti-interference ability and higher reliability, and can work stably in environments with complex electromagnetic interference such as hospitals and electric field environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a structural schematic diagram of a heart sound detection device based on a bionic membrane type optical fiber acoustic sensor of the present invention.

[0026] Figure 2It is a schematic diagram of the structure of the bionic diaphragm.

[0027] Figure 3 Simulation results of frequency response characteristics of ciliary structures with different diameters.

[0028] Figure 4 The simulation results of the frequency response characteristics of the bionic diaphragm under specific parameters.

[0029] In the figure: 1 laser, 2 circulator, 3 single-mode optical fiber, 4 bionic membrane, 5 optical signal processing unit, 6 signal processing unit, 7 membrane support structure, 8 housing. DETAILED DESCRIPTION

[0030] The specific implementation modes of the present invention will be further described in detail below with reference to the accompanying drawings. Specific implementation method 1

[0032] The following is a specific implementation of the heart sound detection device based on the bionic membrane type optical fiber acoustic sensor of the present invention.

[0033] The heart sound detection device based on the bionic membrane type optical fiber acoustic sensor in this specific embodiment is as follows: Figure 1 As shown, according to the light propagation direction, the following are arranged in sequence: a laser 1, a circulator 2, a single-mode optical fiber 3, a bionic membrane 4, an optical signal processing unit 5 and a signal processing unit 6;

[0034] The end face of the single-mode optical fiber 2 is cut at a 0-degree angle and polished; the single-mode optical fiber 3 is arranged vertically to the bionic membrane 4, the end face of the single-mode optical fiber 3 is parallel to the bionic membrane 4, and the distance between the end face of the single-mode optical fiber 3 and the bionic membrane 4 is 0.1 mm-1 mm;

[0035] The output light of the laser 3 passes through the circulator 6 and enters the single-mode optical fiber 2 for transmission. After reaching the end face of the single-mode optical fiber 2, a part of it is directly reflected, and the other part is emitted from the end face, reflected by the bionic membrane 4, and then coupled into the single-mode optical fiber 2 to interfere with the directly reflected part; the interference light then passes through the circulator 2 and enters the optical signal processing unit 5, and after being converted into an electrical signal, the signal processing unit 6 obtains the heart sound signal. Specific implementation method 2

[0037] The following is a specific implementation of the heart sound detection device based on the bionic membrane type optical fiber acoustic sensor of the present invention.

[0038] The heart sound detection device based on the bionic diaphragm-type optical fiber acoustic sensor under this specific implementation is further defined on the basis of the specific implementation method one: the diameter of the bionic diaphragm 4 is 3mm-20mm, the middle area is a circular complete area with a diameter not exceeding 1mm, the circular complete area is supported by a circle of mesh fiber structure and connected to the surrounding frame or fixed structure, and the nanofiber structures are fixed by transverse fiber structures with gradually changing lengths, such as Figure 2 shown.

[0039] Due to the introduction of the mesh support structure, the bionic diaphragm has good acoustic compliance and acoustic impedance, and can be well coupled with air vibration, thereby eliminating the acoustic coupling agent required for traditional acoustic signal detection and improving the coupling efficiency of acoustic signals. Specific implementation method three

[0041] The following is a specific implementation of the heart sound detection device based on the bionic membrane type optical fiber acoustic sensor of the present invention.

[0042] The heart sound detection device based on the bionic membrane type optical fiber acoustic sensor under this specific implementation is further defined on the basis of the second specific implementation method: the diameter of the nanofiber structure does not exceed 10 microns, and the material is gold, silver, chromium, PMMA, PI, PU, ​​PC or PET. Specific implementation method four

[0044] The following is a specific implementation of the heart sound detection device based on the bionic membrane type optical fiber acoustic sensor of the present invention.

[0045] The heart sound detection device based on the bionic diaphragm-type optical fiber acoustic sensor under this specific implementation is further defined on the basis of the second specific implementation to improve the optical reflectivity of the diaphragm: the metal film or multilayer dielectric film with a thickness of less than 1 micron and a reflectivity greater than 90% is deposited in the circular complete area, and the working bandwidth of the metal film or multilayer dielectric film is 1525nm~1605nm. Specific implementation method five

[0047] The following is a specific implementation of the heart sound detection device based on the bionic membrane type optical fiber acoustic sensor of the present invention.

[0048] The heart sound detection device based on the bionic membrane type optical fiber acoustic sensor under this specific implementation is further defined on the basis of specific implementation method one in order to improve the optical detection sensitivity: a multilayer dielectric film with a reflectivity not exceeding 10% is deposited on the end face of the single-mode optical fiber 2, and the working bandwidth of the multilayer dielectric film is 1525nm~1605nm. Specific implementation method 6

[0050] The following is a specific implementation of the heart sound detection device based on the bionic membrane type optical fiber acoustic sensor of the present invention.

[0051] The heart sound detection device based on the bionic membrane type optical fiber acoustic sensor in this specific implementation is further defined on the basis of the above specific implementation: the bionic membrane 1 and the single-mode optical fiber 2 are fixed on the bracket 7. Specific implementation method seven

[0053] The following is a specific implementation of the heart sound detection device based on the bionic membrane type optical fiber acoustic sensor of the present invention.

[0054] The heart sound detection device based on the bionic diaphragm type optical fiber acoustic sensor in this specific embodiment is further defined on the basis of specific embodiment 6 in order to improve the detection effect: the bionic diaphragm 1 and the bracket 7 are arranged in the housing 8. Specific implementation method eight

[0056] The following is a specific implementation of the heart sound detection method based on the bionic membrane type optical fiber acoustic sensor of the present invention.

[0057] The heart sound detection method based on the bionic membrane type optical fiber acoustic sensor in this specific implementation is implemented on the heart sound detection device based on the bionic membrane type optical fiber acoustic sensor in any of the above specific implementations, and the steps are as follows:

[0058] When the heart sound signal is radiated to the surface of the bionic membrane 4 through the human body surface, the fluid vibration caused by the heart sound signal will drive the bionic membrane 4 to generate vibrations with the same frequency and amplitude;

[0059] After being transmitted from the end face of the single-mode optical fiber 3, the emitted light of the laser 1 is incident on the surface of the bionic membrane 4 and reflected, thereby interfering with the reflected light from the end face of the single-mode optical fiber 3;

[0060] When the bionic membrane 4 vibrates under the drive of the heart sound signal, the distance between the bionic membrane 4 and the end face of the single-mode optical fiber 3 changes with the same frequency and amplitude, thereby causing the reflected light signal to change, and then causing the interference light to change;

[0061] The interference light signal carrying the heart sound signal is transmitted to the optical signal processing unit 5 through the single-mode optical fiber 3, the interference light signal is converted into an electrical signal, and sent to the signal processing unit 6, and the heart sound information is obtained after analysis and processing. Specific implementation method nine

[0063] The following is a simulation of the heart sound detection device and method based on the bionic membrane type optical fiber acoustic sensor of the present invention.

[0064] Biological bodies use ciliary structures to perceive external flow fields. Ciliary structures are in a high damping state in the fluid. At this time, ciliary motion will be mainly dominated by the damping force generated by the surrounding fluid on the cilia. Based on the above biological principles, the bionic diaphragm 4 of the present invention can perceive the fluid motion caused by acoustic vibration. If the maximum physical coupling efficiency can be obtained in a wider frequency range, the present invention can not only have extremely high sensitivity and a wider working bandwidth, thereby extracting weak heart sound signals with high fidelity, but also maintain good perception accuracy in the low frequency band.

[0065] To this end, the following simulation is performed. The spider web presented by the bionic membrane 4 of the present invention is simplified and analyzed, decomposed into a series of cilia combinations, and firstly the force equation of the cilia in the flow field is established, assuming that the radius of the cilia is r and the length is L. The cilia are subjected to the effects of Euler-Bernoulli bending, axial tension and fluid forces of the surrounding medium, and the force equation is expressed as follows:

[0066]

[0067] When r is relatively small, the main force acting on the ciliary motion is proportional to v(t), that is, the relative motion of the cilia with the surrounding medium; So we get:

[0068]

[0069] The above formula shows that when the cilia are thin enough, they will flow synchronously with the fluid. Therefore, the movement of cilia can represent the movement of the surrounding medium.

[0070] The one-dimensional ciliary motion equation was used for simulation analysis to obtain the transmission efficiency of ciliary structures with different diameters. The results are as follows: Figure 3 As shown, the diameter of the cilia in (a) is 0.5 μm, and the diameter of the cilia in (b) is 1 μm. The simulation results show that when the diameter of the cilia is small enough, high-fidelity extraction of the vibration of the surrounding fluid medium can be achieved, thereby achieving high sensitivity perception of the bionic diaphragm 4 to acoustic signals, especially low-frequency acoustic signals.

[0071] In the present invention, PMMA is selected as the material of the bionic membrane 4, the overall diameter of the bionic membrane 4 is 10 mm, and the line width of the cilia is 2 μm. Under the above parameters, the bionic membrane 4 is simulated in the frequency range of 1 Hz-10000 Hz, and the frequency response when a plane acoustic wave with an intensity of 1 Pa is applied to the bionic membrane 4 is analyzed. Figure 4 As shown in FIG. 1 , (a) is a schematic diagram of the structure of the bionic diaphragm 4, and (b) is a simulation result. The simulation results show that the speed transfer ratio of the bionic diaphragm 4 in the low frequency band can still be close to 1, that is, V silk / Vair≈1, that is, good measurement accuracy can still be maintained in the low frequency band.

Claims

1. A heart sound detection device based on a bionic membrane type optical fiber acoustic sensor, characterized in that: According to the propagation direction of light, the following are arranged in sequence: a laser (1), a circulator (2), a single-mode optical fiber (3), a bionic membrane (4), an optical signal processing unit (5), and a signal processing unit (6); The end face of the single-mode optical fiber (2) is cut at a 0-degree angle and polished; the single-mode optical fiber (3) and the bionic membrane (4) are arranged vertically, the end face of the single-mode optical fiber (3) is parallel to the bionic membrane (4), and the distance between the end face of the single-mode optical fiber (3) and the bionic membrane (4) is 0.1 mm to 1 mm; The output light of the laser (3) passes through the circulator (6) and enters the single-mode optical fiber (2) for transmission. After reaching the end face of the single-mode optical fiber (2), a part of the light is directly reflected, and the other part is emitted from the end face, reflected by the bionic membrane (4), and then coupled into the single-mode optical fiber (2), where it interferes with the directly reflected part. The interference light then passes through the circulator (2) and enters the optical signal processing unit (5), where it is converted into an electrical signal and then a heart sound signal is obtained by the signal processing unit (6).

2. The heart sound detection device based on the bionic membrane type optical fiber acoustic sensor according to claim 1 is characterized in that: The bionic diaphragm (4) has a diameter of 3 mm to 20 mm, and the middle area is a circular complete area with a diameter not exceeding 1 mm. The circular complete area is supported by a circle of mesh fiber structure and connected to surrounding frames or fixed structures. The nanofiber structures are fixed by transverse fiber structures with gradually varying lengths. Due to the introduction of the mesh support structure, the bionic diaphragm (4) has good acoustic compliance and acoustic impedance, and can be well coupled with air vibration, thereby eliminating the acoustic coupling agent required for traditional acoustic signal detection, thereby improving the coupling efficiency of the acoustic signal.

3. The heart sound detection device based on the bionic membrane type optical fiber acoustic sensor according to claim 2 is characterized in that: The diameter of the nanofiber structure does not exceed 10 microns, and the material is gold, silver, chromium, PMMA, PI, PU, ​​PC or PET.

4. The heart sound detection device based on the bionic membrane type optical fiber acoustic sensor according to claim 2 is characterized in that: The circular complete area is deposited with a metal film or a multi-layer dielectric film with a thickness of less than 1 micron and a reflectivity greater than 90%, and the working bandwidth of the metal film or the multi-layer dielectric film is 1525nm~1605nm.

5. The heart sound detection device based on the bionic membrane type optical fiber acoustic sensor according to claim 1 is characterized in that: The end face of the single-mode optical fiber (2) is deposited with a multilayer dielectric film having a reflectivity of no more than 10%, and the working bandwidth of the multilayer dielectric film is 1525nm~1605nm.

6. The heart sound detection device based on the bionic membrane type optical fiber acoustic sensor according to claim 1 or 2, characterized in that: The bionic membrane (1) and the single-mode optical fiber (2) are fixed on a bracket (7).

7. The heart sound detection device based on the bionic membrane type optical fiber acoustic sensor according to claim 6 is characterized in that: In order to improve the detection effect, the bionic membrane (1) and the bracket (7) are arranged in the housing (8).

8. A heart sound detection method based on a bionic membrane type optical fiber acoustic sensor, characterized in that: Here are the steps: When the heart sound signal is radiated through the human body surface to the surface of the bionic diaphragm (4), the fluid vibration caused by the heart sound signal will drive the bionic diaphragm (4) to generate vibrations with the same frequency and amplitude; After being transmitted through the end face of the single-mode optical fiber (3), the output light of the laser (1) is incident on the surface of the bionic membrane (4) and is reflected, thereby interfering with the reflected light from the end face of the single-mode optical fiber (3); When the bionic diaphragm (4) vibrates under the drive of the heart sound signal, the distance between the bionic diaphragm (4) and the end face of the single-mode optical fiber (3) changes at the same frequency and amplitude, thereby causing the reflected light signal to change, and further causing the interference light to change; The interference light signal carrying the heart sound signal is transmitted to the optical signal processing unit (5) through the single-mode optical fiber (3), the interference light signal is converted into an electrical signal, and sent to the signal processing unit (6), and after analysis and processing, the heart sound information is obtained.

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