Electroencephalogram signal sensor, manufacturing method thereof and electroencephalogram signal acquisition system

Abstract

The invention relates to the technical field of optical fiber sensing, in particular to an electroencephalogram signal sensor, a manufacturing method thereof and an electroencephalogram signal acquisition system. The electroencephalogram signal sensor comprises an electrostriction structure; the sensing optical fiber is provided with an active phase shift grating, and the electrostriction structure is attached to the active phase shift grating; wherein the electrostriction structure is configured to stretch after receiving an electroencephalogram signal so as to drive the phase change of the active phase shift grating on the sensing optical fiber. The sensitivity and the anti-interference capability of electroencephalogram signal acquisition are improved, and the measurement accuracy is improved.

Description

Technical Field

[0001] This application relates to the field of fiber optic sensing technology, and particularly to an electroencephalogram signal sensor, a manufacturing method thereof, and an electroencephalogram signal acquisition system. Background Art

[0002] Electroencephalogram (EEG) is a bioelectrical signal generated by the electrical activities of brain neurons and can be detected through skin surface electrodes. EEG is widely used in fields such as neuroscience, clinical medicine, and psychology, and is particularly significant in aspects such as epilepsy, sleep research, and brain-computer interfaces. The EEG reflects the activity states of different regions of the brain and provides an important basis for understanding brain functions and diagnosing nervous system diseases.

[0003] In related technologies, EEG measurement methods mainly rely on electrodes attached to the scalp to receive and amplify the electrical activities from the cerebral cortex. These electrodes are usually connected to an amplifier through cables, and the signals are transmitted to a computer for processing and analysis. With the progress of technology, modern EEG devices already have relatively high acquisition accuracy and can monitor EEG activities in real time, and are widely used in fields such as clinical diagnosis and electroencephalogram monitoring.

[0004] However, EEG measurement methods in related technologies generally face the problem of electromagnetic interference. Since the intensity of EEG signals is weak and the frequency range is wide, they are extremely vulnerable to interference from external electromagnetic fields, especially when there are strong electromagnetic radiation sources in the environment, such as hospital equipment and electrical equipment. These electromagnetic interferences will cause an increase in signal noise and affect the accuracy and reliability of measurements.

[0005] Therefore, there is an urgent need to provide a new means for collecting EEG signals to solve the above technical problems. Summary of the Invention

[0006] Embodiments of this application provide an electroencephalogram signal sensor, a manufacturing method thereof, and an electroencephalogram signal acquisition system, which increase the sensitivity and anti-interference ability of collecting EEG signals and improve the accuracy of measurements.

[0007] In some embodiments, an electroencephalogram signal sensor is provided, including: an electrostrictive structure; a sensing optical fiber provided with an active phase shift grating, and the electrostrictive structure is attached to the active phase shift grating; wherein, the electrostrictive structure is configured to expand and contract after receiving an EEG signal to drive a phase change of the active phase shift grating on the sensing optical fiber.

[0008] By using the electroencephalogram (EEG) signal sensor provided in the embodiments of the present application, an axial strain is generated in the stretching direction after the electrostrictive structure receives the EEG signal. After the active phase-shifted grating is subjected to the axial strain, the central wavelength of the reflected light generated undergoes a corresponding transformation. Therefore, the reflected light generated by the active phase-shifted grating can be collected by a photodetector and a data acquisition card, and the collected signal can be demodulated to recover the EEG information. Since the electrostrictive material can generate a highly sensitive axial strain in response to the EEG signal, the sensitivity of collecting the EEG signal is improved. Moreover, since the acquisition of the EEG signal does not rely on electrical signals, the anti-interference ability of the EEG signal sensor is enhanced.

[0009] Optionally, the electrostrictive structure includes: ferroelectric copolymer or piezoelectric ceramic.

[0010] Optionally, a plurality of active phase-shifted gratings are arranged at intervals on the sensing optical fiber; the number of electrostrictive structures is plural; the electrostrictive structures and the active phase-shifted gratings are arranged in one-to-one correspondence.

[0011] Optionally, when the electrostrictive structure includes piezoelectric ceramics and the number of electrostrictive structures is plural, the piezoelectric ceramics include piezoelectric stack ceramics.

[0012] In some embodiments, a manufacturing method of an EEG signal sensor is provided. The manufacturing method of the EEG signal sensor is used to manufacture the EEG signal sensor provided in any one of the above embodiments. The manufacturing method of the EEG signal sensor includes: stretching the length of the active phase-shifted grating so that the central wavelength of the reflected light generated by the active phase-shifted grating is the target wavelength; using AB glue to bond the sensing optical fiber and the electrostrictive structure on both sides of the active phase-shifted grating.

[0013] Optionally, stretching the length of the active phase-shifted grating includes: using a stretching platform to stretch the active phase-shifted grating.

[0014] Optionally, the stretching platform includes a fixed stage, a fixture, and a knob. The fixture is disposed on the fixed stage, and the fixed stage is configured to place the active phase-shifted grating. The fixture includes a first fixing portion and a second fixing portion, and the first fixing portion and the second fixing portion are respectively configured to clamp the sensing optical fibers at opposite ends of the active phase-shifted grating. The knob is configured to adjust the distance between the first fixing portion and the second fixing portion. Stretching the active phase-shifted grating using the stretching platform includes: placing the active phase-shifted grating on the fixed stage; using the first fixing portion and the second fixing portion to respectively clamp the sensing optical fibers at opposite ends of the active phase-shifted grating; connecting the active phase-shifted grating to the fiber grating demodulator using an optical fiber jumper; the central wavelength of the active phase-shifted grating being the initial wavelength; the fiber grating demodulator being configured to measure the central wavelength of the reflected light generated by the active phase-shifted grating; using the knob to adjust the distance between the first fixing portion and the second fixing portion to stretch the active phase-shifted grating so that the central wavelength of the active phase-shifted grating is the target wavelength, and the initial wavelength being less than the target wavelength.

[0015] Optionally, the electrostrictive structure includes PMN-RT multi-functional ceramics. Bonding the active phase-shifted grating and the electrostrictive structure using AB glue includes: using AB glue to dot and adhesively fix on both sides of the active phase-shifted grating and the PMN-RT multi-functional ceramics for more than 5 hours.

[0016] In some embodiments, an electroencephalogram (EEG) signal acquisition system is provided, including: a pump laser; an EEG signal sensor, including the EEG signal sensor provided in any one of the above embodiments, or an EEG signal sensor manufactured by the manufacturing method of the EEG signal sensor provided in any one of the above embodiments; an isolator; an interferometer; a demodulator; the pump laser is configured to output laser to the EEG signal sensor; the EEG signal collector is configured to receive the influence of the laser and the EEG signal and output an optical signal corresponding to the EEG signal; the isolator is configured to block the reflected light in the subsequent optical path of the isolator; the interferometer is configured to receive the optical signal corresponding to the EEG signal and cause the optical signal corresponding to the EEG signal to interfere and output an interference optical signal; the demodulator is configured to receive the interference optical signal and demodulate to obtain the EEG signal.

[0017] Optionally, receiving the interference optical signal and demodulating to obtain the EEG signal includes: using a single-channel differential division algorithm based on two channels to demodulate the interference optical signal to determine the EEG signal.

[0018] It can be understood that for the beneficial effects that can be achieved by the above-provided manufacturing method of the EEG signal sensor and the technical solution of the EEG signal acquisition system, reference can be made to the beneficial effects in the EEG signal sensor and any one of its optional implementation manners, which will not be elaborated here. Description of the Drawings

[0019] To more clearly illustrate the technical solutions of the present application, the accompanying drawings required for use in the embodiments will be briefly introduced below. Obviously, for those of ordinary skill in the art, other accompanying drawings can also be obtained based on these drawings without creative efforts.

[0020] Figure 1 The first structural schematic diagram of the electroencephalogram signal sensor provided by the embodiment of the present application;

[0021] Figure 2 The cross-sectional view along the optical axis direction of the electroencephalogram signal sensor provided by the embodiment of the present application;

[0022] Figure 3 The force schematic diagram of the active phase-shifting grating provided by the embodiment of the present application;

[0023] Figure 4 The second structural schematic diagram of the electroencephalogram signal sensor provided by the embodiment of the present application;

[0024] Figure 5 The schematic diagram of the relationship between time and amplitude measured by the electroencephalogram signal sensor provided by the embodiment of the present application;

[0025] Figure 6 The schematic diagram of the relationship between frequency and amplitude measured by the electroencephalogram signal sensor provided by the embodiment of the present application;

[0026] Figure 7 The flowchart of the manufacturing method of the electroencephalogram signal sensor provided by the embodiment of the present application;

[0027] Figure 8 The third structural schematic diagram of the electroencephalogram signal sensor provided by the embodiment of the present application;

[0028] Figure 9 The structural block diagram of the first electroencephalogram signal acquisition system provided by the embodiment of the present application;

[0029] Figure 10 The structural block diagram of the second electroencephalogram signal acquisition system provided by the embodiment of the present application.

[0030] Reference numerals:

[0031] 1. Electroencephalogram signal sensor; 11. Electrostrictive structure; 111. Piezoelectric stack ceramics; 12. Active phase-shifting grating; 13. AB glue;

[0032] 2. Electroencephalogram signal acquisition system; 21. Pump laser; 22. Interferometer; 221. Fiber optic resonance modulator; 222. Delay optical fiber; 223. Coupler; 224. PZT; 23. Demodulator; 24. Isolator. Detailed implementation manners

[0033] The technical solutions in the embodiments of the present application will be clearly described below in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all embodiments. Based on the embodiments of the present application, other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present application.

[0034] Hereinafter, terms such as "first" and "second" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first", "second", etc. may explicitly or implicitly include one or more of such features. In the description of the present application, unless otherwise specified, the meaning of "a plurality" is two or more.

[0035] In addition, in the present application, orientation terms such as "upper", "lower", "inner", "outer", etc. are defined relative to the orientation of the components shown in the accompanying drawings. It should be understood that these directional terms are relative concepts, which are used for relative description and clarification, and they may change accordingly with the change of the orientation of the components placed in the accompanying drawings.

[0036] For the convenience of understanding the technical solutions of the application, the related technologies involved in the present application will be described below first.

[0037] Electroencephalogram (EEG) is a bioelectrical signal generated by the electrical activities of brain neurons and can be detected through skin surface electrodes. EEG is widely used in fields such as neuroscience, clinical medicine, and psychology, and is particularly significant in aspects such as epilepsy, sleep research, and brain-computer interfaces. EEG reflects the activity states of different regions of the brain and provides an important basis for understanding the functions of the brain and diagnosing nervous system diseases.

[0038] The measurement principle of EEG is based on the potential difference generated by the electrical activities of neurons. Specifically, when brain neurons transmit signals, charge changes will occur, and these changes will form an electric field on the surface of the cerebral cortex. These electric fields will be conducted through the scalp and can be detected by surface electrodes.

[0039] The detection of electroencephalogram (EEG) signals relies on electrodes. The electrodes contact the scalp through conductive substances (such as saline, gel, etc.) to form an electric circuit. The electrodes can detect the potential difference between the skin surface and the cerebral cortex. The electric field changes in the brain generate voltage signals between the electrodes and the skin. These electrodes are usually connected to an amplifier through cables, and the signals are transmitted to a computer for processing and analysis. With the advancement of technology, modern EEG devices already have high acquisition accuracy and can monitor EEG activities in real time, being widely used in fields such as clinical diagnosis and electroencephalogram monitoring.

[0040] However, in related technologies, the methods for measuring EEG signals generally face the problem of electromagnetic interference. Since the intensity of EEG signals is weak and the frequency range is wide, they are extremely vulnerable to external electromagnetic field interference, especially when there are strong electromagnetic radiation sources in the environment, such as hospital equipment, electrical equipment, etc. These electromagnetic interferences will increase the signal noise, affecting the accuracy and reliability of the measurement. In addition, traditional electrode systems often require long cable connections, and the cables themselves may also become interference sources, further increasing the signal noise.

[0041] To solve the problems in related technologies such as large electromagnetic interference, high crosstalk, and low integration in the measurement of EEG signals, the embodiments of this application provide an EEG signal sensor 1, its manufacturing method, and an EEG signal acquisition system 2. By applying an EEG signal to an electrostrictive structure 11, an active phase-shifted grating 12 generates an axial strain, causing a change in the reflected light wavelength of the active phase-shifted grating 12. Thus, by demodulating and analyzing the wavelength signal, the EEG information is restored, realizing the detection of highly sensitive, anti-interference, and highly integrated EEG signals.

[0042] Figure 1 This is the first structural schematic diagram of the EEG signal sensor provided by the embodiments of this application.

[0043] Figure 2 This is the cross-sectional view along the optical axis direction of the EEG signal sensor provided by the embodiments of this application.

[0044] Combined Figure 1 and Figure 2 As shown, the embodiments of this application provide an EEG signal sensor 1, including: an electrostrictive structure 11 and a sensing optical fiber. The sensing optical fiber is provided with an active phase-shifted grating 12. The electrostrictive structure 11 is attached to the active phase-shifted grating 12. Among them, the electrostrictive structure 11 is configured to expand and contract after receiving an EEG signal to drive the phase change of the active phase-shifted grating 12 on the sensing optical fiber.

[0045] By using the electroencephalogram (EEG) signal sensor 1 provided in the embodiment of the present application, when the electrostrictive structure 11 receives an EEG signal, an axial strain is generated in the stretching direction. After the active phase-shifted grating 12 is subjected to the axial strain, the central wavelength of the reflected light generated changes accordingly. Therefore, the reflected light generated by the active phase-shifted grating 12 can be collected by a photodetector and a data acquisition card, and the collected signal can be demodulated to recover the EEG information. Since the electrostrictive material can generate a highly sensitive axial strain in response to the EEG signal, the sensitivity of collecting the EEG signal is improved. Moreover, since the acquisition of the EEG signal does not rely on an electrical signal, the anti-interference ability of the EEG signal sensor 1 is improved.

[0046] Specifically, the sensor with the active phase-shifted grating 12 belongs to a type of fiber optic sensor. The active phase-shifted grating 12 can directly measure physical quantities such as temperature and strain, and has the advantages of high sensitivity, anti-electromagnetic interference, good electrical insulation performance, corrosion resistance, small volume, light weight, plastic geometric shape, small transmission loss, large transmission capacity, and the ability to achieve multi-point distributed measurement. In the embodiment of the present application, by attaching an excitation material (i.e., the electrostrictive structure 11) to the active phase-shifted grating 12, the EEG signal causes the excitation material to significantly stretch, resulting in a change in the central wavelength of the reflected light generated by the active phase-shifted grating 12. Furthermore, through a multi-position phase independent demodulation method, signal isolation can be achieved, crosstalk can be reduced, and the sensitivity and anti-interference ability of collecting the EEG signal can be improved.

[0047] Figure 3 It is a schematic diagram of the force on the active phase-shifted grating provided in the embodiment of the present application.

[0048] Specifically, the active phase-shifted grating 12 refers to introducing a sudden change in refractive index modulation at a certain position in the middle of a Fiber Bragg Grating (FBG) to generate refractive index modulation. The active phase-shifted grating 12 in the pre-tensioned sensing optical fiber is fixed to the electrostrictive structure 11 through AB glue 13. Due to the electrostrictive effect, the EEG signal causes the electrostrictive structure 11 to generate an axial strain in the optical axis direction, and the central wavelength of the reflected light generated by the active phase-shifted grating 12 changes accordingly under the influence of the axial strain. Among them, the schematic diagram of the force F (along the optical axis direction of the sensing optical fiber) on the active phase-shifted grating 12 is as Figure 3 shown.

[0049] Optionally, the electrostrictive structure 11 includes: ferroelectric copolymer or piezoelectric ceramic. In this way, when an EEG signal is applied to the electrostrictive structure 11, the electrostrictive effect can be generated, thereby causing a change in the central wavelength of the active phase-shifted grating 12.

[0050] Optionally, in combination with Figure 2As shown, a plurality of active phase shift gratings 12 are arranged at intervals on the sensing optical fiber; the number of electrostrictive structures 11 is multiple, and the electrostrictive structures 11 are arranged in one-to-one correspondence with the active phase shift gratings 12.

[0051] In this embodiment, through the multiple active phase shift gratings 12 spaced on the sensing optical fiber and the electrostrictive structures 11 corresponding to them one by one, the phase information at different positions is demodulated and determined according to the reflected light generated by the active phase shift gratings 12 at multiple positions on the sensing optical fiber, so as to determine the electroencephalogram signal.

[0052] Specifically, based on the characteristics of fiber distributed measurement, the embodiment of the present application proposes a single-fiber multi-point detection technology, that is, etching multiple active phase shift grating 12 sensors on one sensing optical fiber, and combining multiple electrostrictive structures 11 to construct multiple fiber grating sensors to improve the system integration.

[0053] Optionally, when the electrostrictive structure 11 includes piezoelectric ceramics and the number of electrostrictive structures 11 is multiple, the piezoelectric ceramics include piezoelectric stack ceramics 111.

[0054] In this embodiment, by setting the piezoelectric stack ceramics 111, the axial strain generated by the electroencephalogram signal is amplified, so as to increase the change amount of the central wavelength of the reflected light generated by the active phase shift grating 12 and improve the sensitivity of the electroencephalogram signal sensor 1.

[0055] Specifically, the piezoelectric stack ceramics 111 is a multi-layer ceramic device that uses the piezoelectric effect to convert electrical signals into mechanical displacements, and is widely used in fields such as precision displacement control, ultrasonic transducers, and vibration drivers. Its design realizes efficient electro-mechanical conversion by alternately stacking multiple layers of piezoelectric ceramics and electrodes, and can generate large mechanical displacements at low driving voltages.

[0056] Generally speaking, the main components of the piezoelectric stack ceramics 111 include: piezoelectric ceramic layers, electrode layers, insulating layers, and encapsulation layers. Materials with excellent piezoelectric properties (such as PZT ceramics) are used, and each layer is responsible for converting the applied electric field into a small mechanical strain. The electrode layers are alternately distributed between the ceramic layers to apply a uniform electric field, and the materials are mostly highly conductive metals such as silver and nickel. The insulating layer is used to isolate the electrode layers to prevent short circuits and ensure the electrical stability of the structure. The encapsulation layer is usually encapsulated with polymer or metal materials to protect the internal structure from the erosion of the external environment.

[0057] Figure 4 This is the second structural schematic diagram of the electroencephalogram signal sensor provided by the embodiment of the present application.

[0058] In a specific implementation method, combined with Figure 4As shown, the diameter of the sensing optical fiber is 250μm, the length of a single active phase-shifted grating 12 etched on the sensing optical fiber is 31mm, and the electrostrictive structure 11 has a length of 40mm, a width of 2mm, and a height of 10mm.

[0059] Figure 5 It is a schematic diagram of the relationship between time and amplitude measured by the electroencephalogram signal sensor provided by the embodiment of the present application. Among them, Figure 5 (a) is a schematic diagram of the relationship between time and amplitude when the simulated applied voltage is 0.05mv, Figure 5 (b) is a schematic diagram of the relationship between time and amplitude when the simulated applied voltage is 0.1mv, Figure 5 (c) is a schematic diagram of the relationship between time and amplitude when the simulated applied voltage is 0.5mv, Figure 5 (d) is a schematic diagram of the relationship between time and amplitude when the simulated applied voltage is 1mv.

[0060] Figure 6 It is a schematic diagram of the relationship between frequency and amplitude measured by the electroencephalogram signal sensor provided by the embodiment of the present application. Among them, Figure 6 (a) is a schematic diagram of the relationship between frequency and amplitude when the simulated applied voltage is 0.05mv, Figure 6 (b) is a schematic diagram of the relationship between frequency and amplitude when the simulated applied voltage is 0.1mv, Figure 6 (c) is a schematic diagram of the relationship between frequency and amplitude when the simulated applied voltage is 0.5mv, Figure 6 (d) is a schematic diagram of the relationship between frequency and amplitude when the simulated applied voltage is 1mv.

[0061] The electroencephalogram signal sensor 1 provided by the embodiment of the present application is tested. A microvolt signal generator is used to generate signals with different amplitudes at 40Hz to simulate electroencephalogram signals, and they are loaded on the electrostrictive material. The measurement results are as Figure 5 and Figure 6 shown. Moreover, the amplitude of a normal electroencephalogram signal is between 0.01mV and 5mV, and the spectral energy is mainly concentrated between 0.05Hz and 40Hz. It can be seen that the electroencephalogram signal sensor 1 provided by the embodiment of the present application can achieve the measurement of electroencephalogram signals.

[0062] Figure 7 It is a flowchart of the manufacturing method of the electroencephalogram signal sensor provided by the embodiment of the present application.

[0063] Figure 8 It is the third structural schematic diagram of the electroencephalogram signal sensor provided by the embodiment of the present application.

[0064] Corresponding to the embodiment of the foregoing electroencephalogram signal sensor 1, an embodiment of the present application further provides a manufacturing method of the electroencephalogram signal sensor 1. The manufacturing method of the electroencephalogram signal sensor 1 is used to manufacture the electroencephalogram signal sensor 1 provided in any one of the foregoing embodiments (such as Figure 8 shown), as Figure 7 shown, the manufacturing method of the electroencephalogram signal sensor 1 includes step S1 and step S2, specifically as follows:

[0065] Step S1, stretching the length of the active phase-shifted grating 12 so that the central wavelength of the reflected light generated by the active phase-shifted grating 12 is the target wavelength.

[0066] Step S2, using AB glue 13 to bond the sensing optical fibers and the electrostrictive structure 11 on both sides of the active phase-shifted grating 12.

[0067] Adopting the manufacturing method of the electroencephalogram signal sensor 1 provided by the embodiment of the present application, first manufacture the active phase-shifted grating 12 with the target wavelength, and then bond the sensing optical fibers at both ends of the active phase-shifted grating 12 with the target wavelength to the electrostrictive structure 11, so that when the electrostrictive structure 11 generates axial strain, it can drive the active phase-shifted grating 12 to expand and contract, thereby completing the manufacture of the electroencephalogram signal sensor 1. The manufactured electroencephalogram signal sensor 1 has the characteristics of high sensitivity, high anti-interference ability and high integration.

[0068] Optionally, step S1 includes step S11, specifically as follows:

[0069] Step S11, using a stretching platform to stretch the active phase-shifted grating 12.

[0070] In this embodiment, the active phase-shifted grating 12 is stretched by a stretching platform, so that the active phase-shifted grating 12 is stretched evenly and accurately to improve the manufacturing accuracy.

[0071] Optionally, the stretching platform includes a fixed platform, a fixture and a knob. The fixture is arranged on the fixed platform. The fixed platform is configured to place the active phase-shifted grating 12. The fixture includes a first fixing part and a second fixing part. The first fixing part and the second fixing part are respectively configured to clamp the sensing optical fibers at opposite ends of the active phase-shifted grating 12; the knob is configured to adjust the distance between the first fixing part and the second fixing part.

[0072] Optionally, step S11 includes steps S111 to S114, specifically as follows:

[0073] Step S111, placing the active phase-shifted grating 12 on the fixed platform.

[0074] Step S112, using the first fixing part and the second fixing part to clamp the sensing optical fibers at opposite ends of the active phase-shifted grating 12 respectively.

[0075] Step S113: Connect the active phase-shifted grating 12 to the fiber grating demodulator 23 using an optical fiber jumper; the central wavelength of the active phase-shifted grating 12 is the initial wavelength, and the fiber grating demodulator 23 is configured to measure the central wavelength of the reflected light generated by the active phase-shifted grating 12.

[0076] Step S114: Use a knob to adjust the distance between the first fixing part and the second fixing part to stretch the active phase-shifted grating 12 so that the central wavelength of the active phase-shifted grating 12 is the target wavelength, and the initial wavelength is less than the target wavelength.

[0077] In this embodiment, by setting the active phase-shifted grating 12 on the stretching platform, the knob of the stretching platform is used to adjust the distance between the first fixing part and the second fixing part, thereby stretching the length of the active phase-shifted grating 12, and further changing the central wavelength of the active phase-shifted grating 12 so that the central wavelength of the active phase-shifted grating 12 is the target wavelength.

[0078] Optionally, the electrostrictive structure 11 includes PMN-RT multi-functional ceramics, and step S2 includes step S21, which is specifically as follows:

[0079] Step S21: Use AB glue 13 to adhere and fix the two sides of the active phase-shifted grating 12 to the PMN-RT multi-functional ceramics for more than 5 hours.

[0080] In this embodiment, by using AB glue 13 to bond the active phase-shifted grating 12 and the PMN-RT multi-functional ceramics, the fixed connection of the electroencephalogram signal sensor 1 is realized, and by setting the fixed connection time, the problem that the stretching fails due to excessive retraction of the active phase-shifted grating 12 is ensured.

[0081] Exemplarily, the bonding position of the AB glue 13 is as Figure 8 shown.

[0082] Exemplarily, the model of the active phase-shifted grating 12 is 2024072401, and the electrostrictive structure 11 is PMN-RT multi-functional ceramics.

[0083] Place the active phase-shifting grating 12 with the model number 2024072401 on the stretching platform, fix both ends of the active phase-shifting grating 12 to the fixtures on the fixed platform respectively, place the PMN-RT multi-functional ceramic below the grating, and connect it to the fiber grating demodulator 23 through an optical fiber jumper. Before stretching, the central wavelength (i.e., the initial wavelength) of the active phase-shifting grating 12 is 1549.982 nm. Adjust the knob to stretch the optical fiber wavelength by 1 nm, and the central wavelength of the active phase-shifting grating 12 reaches 1551.0305 nm. Then use AB glue 13 to dot and fix it to the PMN-RT multi-functional ceramic on the outer sides of both ends of the active phase-shifting grating 12 for more than 5 hours. After loosening the fixture, the central wavelength of the active phase-shifting grating 12 is 1550.27 nm, and the actual stretch is 0.3 nm.

[0084] Specifically, after stretching is completed, remove the sensing optical fiber. Place the active phase-shifting grating 12 above the PMN-RT multi-functional ceramic, and the PMN-RT multi-functional ceramic leads out two electrodes (positive and negative). The electroencephalogram signal (U) of the PMN-RT multi-functional ceramic will cause the PMN-RT multi-functional ceramic to generate the inverse piezoelectric effect (∈), resulting in a displacement difference (ΔL), which in turn causes a slight change in the wavelength (λ B ) of the active phase-shifting grating 12 (i.e., Δλ B ), and finally obtain the corresponding phase change.

[0085] The conduction formula is shown as the following formulas (1) to (4):

[0086] ΔL = d 33 nU (1);

[0087]

[0088]

[0089] Among them, d 33 is the strain coefficient (m / v) of the PMN-RT multi-functional ceramic, P e is the photoelastic constant of the sensing optical fiber, L is the propagation distance of the light wave, n is the number of piezoelectric ceramic sheets in the PMN-RT multi-functional ceramic, U is the driving voltage (V), ΔL is the deformation amount of the piezoelectric material (i.e., the PMN-RT multi-functional ceramic), and ∈1 is the strain amount of the active phase-shifting grating. Exemplarily, d 33 = +635 pm / V.

[0090] The electroencephalogram signal is transmitted to the PMN-RT multi-functional ceramic through a wire. The PMN-RT multi-functional ceramic has the inverse piezoelectric effect. After applying a voltage to the PMN-RT multi-functional ceramic, the PMN-RT multi-functional ceramic will be in the polarization direction (generally the length direction, such as Figure 4In the direction of the telescopic shaft shown in the figure, an elongation deformation occurs, and the elongation is about 1.5‰. For example, the displacement generated by a piezoelectric ceramic with a length of 18 mm is about 28 μm. The optical fiber can be pasted on the surface of the ceramic. When the PMN-RT multi-functional ceramic generates displacement, the optical fiber will be uniformly stretched. Moreover, the surface of the PMN-RT multi-functional ceramic is smooth and easy for optical fiber bonding, which is very suitable for optical fiber stretching and the like. The strain coefficient of the PMN-RT multi-functional ceramic is equal to the elongation deformation divided by the original length of the ceramic, and the strain coefficient of the PMN-RT multi-functional ceramic is approximately the same as that of the active phase-shifted grating 12. For every 1 με change in the active phase-shifted grating 12, the phase of the reflected light changes by 1.21 pm.

[0091] Figure 9 It is a structural block diagram of the first electroencephalogram signal acquisition system provided by an embodiment of the present application.

[0092] Corresponding to the embodiment of the electroencephalogram signal sensor 1 described above, the present application also provides an embodiment of the electroencephalogram signal acquisition system 2. Combining Figure 9 As shown, the electroencephalogram signal acquisition system 2 includes: a pump laser 21, an electroencephalogram signal sensor 1, an isolator 24, an interferometer 22, and a demodulator 23. The electroencephalogram signal sensor 1 includes the electroencephalogram signal sensor 1 provided in any one of the above embodiments, or the electroencephalogram signal sensor 1 manufactured by the manufacturing method of the electroencephalogram signal sensor 1 provided in any one of the above embodiments. The pump laser 21 is configured to output laser light to the electroencephalogram signal sensor 1. The isolator 24 is configured to block the reflected light in the subsequent optical path of the isolator 24. The electroencephalogram signal collector is configured to receive the influence of the laser and the electroencephalogram signal and output an optical signal corresponding to the electroencephalogram signal. The interferometer 22 is configured to receive the optical signal corresponding to the electroencephalogram signal, cause the optical signal corresponding to the electroencephalogram signal to interfere, and output an interference optical signal. The demodulator 23 is configured to receive the interference optical signal and demodulate to obtain the electroencephalogram signal.

[0093] By using the electroencephalogram signal acquisition system 2 provided by the embodiment of the present application, after the laser output by the pump laser 21 is transmitted into the electroencephalogram signal sensor 1, different reflected lights are generated at each active phase-shifted grating 12. After transmitting the reflected light to the interferometer 22, based on the interferometer 22, a first laser and a second laser with a phase difference are formed for the reflected light. Then, the demodulator 23 is used to collect the signals of the first laser and the second laser, and the center wavelength of the reflected light is determined by demodulating the first laser and the second laser, so as to demodulate and restore the electroencephalogram signal.

[0094] Specifically, the electroencephalogram (EEG) signal is transmitted to the electrostrictive structure 11 of the EEG signal sensor 1, causing the electrostrictive structure 11 to expand and contract to generate axial strain, thereby driving the active phase-shifted grating 12 on the sensing optical fiber in the EEG signal sensor 1 to generate axial strain, so as to change the central wavelength of the reflected light generated by the active phase-shifted grating 12. Furthermore, the reflected light generated by different active phase-shifted gratings 12 on the same optical fiber is collected, and the phase information can be demodulated based on the collected signal to restore the EEG information.

[0095] Exemplarily, when the EEG signal acts on the active phase-shifted grating 12, the output optical wavelength of the EEG signal sensor 1 changes, and the output phase difference of the interferometer 22 also changes. Furthermore, this causes the output optical intensity of the interferometer 22 to change. The photodetector converts the output optical intensity signal of the interferometer 22 into a photocurrent. At this time, the photocurrent already contains the characteristics of the EEG signal change. Therefore, the photocurrent can be processed after differential amplification and band-pass filtering to restore the change characteristics of the EEG signal.

[0096] Figure 10 It is a structural block diagram of the second EEG signal acquisition system provided by the embodiment of the present application.

[0097] Exemplarily, in combination with Figure 10 As shown, based on the WDM (Wavelength Division Multiplexing) technology, multiple reflected light signals with different wavelengths (i.e., the reflected light generated by the active phase-shifted grating 12 in the embodiment of the present application) are simultaneously transmitted in the same sensing optical fiber, thereby facilitating the demodulation and restoration of the EEG signal. Specifically, WDM is an optical fiber communication technology that improves the transmission capacity by simultaneously transmitting signals with multiple different wavelengths (i.e., different optical frequencies) in the same optical fiber. The WDM technology is usually used in optical fiber sensing systems to expand the bandwidth of the system, enabling multiple sensing signals to be transmitted on the same optical fiber.

[0098] Specifically, in combination with Figure 10As shown in the figure, the interferometer 22 includes an unbalanced Michelson interferometer 22, and the unbalanced Michelson interferometer 22 includes two fiber optic resonance modulators 221, a delay fiber 222, a coupler 223, and a PZT 224. The first optical path is composed of a fiber optic resonance modulator 221 and a delay fiber 222, and the second optical path is composed of a fiber optic resonance modulator 221 and a PZT 224. Among them, after the reflected light output by the electroencephalogram signal sensor 1 enters the interferometer 22, it enters the first optical path and the second optical path respectively through the coupler 223. Under the action of the fiber optic resonance modulator 221, the delay fiber 222, and the PZT 224, the reflected light entering the first optical path and the second optical path respectively forms a first laser and a second laser with a phase difference. The first laser and the second laser pass through the coupler 223 again to output the interferometer 22, and thus are collected and demodulated by the demodulator 23 to restore the electroencephalogram information.

[0099] Optionally, the demodulator 23 is specifically configured to: demodulate the interference optical signal using a single-channel differential division algorithm based on two channels to determine the electroencephalogram signal, that is, restore the electroencephalogram information.

[0100] In this embodiment, the interference optical signal output by the interferometer 22 is demodulated by an algorithm to restore the electroencephalogram signal received by the electrostrictive material, that is, restore the electroencephalogram information.

[0101] Specifically, the signal of the first laser collected by the digital acquisition card is the first signal, and the signal of the second laser is the second signal. The process of the single-channel differential division algorithm based on two channels includes: obtaining the first signal and the second signal; performing differential processing on the first signal and the second signal; dividing the differential first signal and the differential second signal to determine a third signal; and determining the electroencephalogram signal based on the third signal.

[0102] Exemplarily, assuming that the interferometer arm length difference d and the fiber core refractive index n do not change with the electroencephalogram signal, the change amount of the interferometer phase difference caused by the electroencephalogram signal can be obtained as shown in the following formula (5):

[0103]

[0104] According to the optical waveguide theory, the signal output from the interferometer can be shown by the following formula (6):

[0105]

[0106] In the formula, A is the direct current component, B is the interference signal amplitude, C is the modulation depth, and ω0 is the modulation frequency. is the electroencephalogram signal to be measured.

[0107] After removing the direct current and normalizing the output signal of the interferometer, it can be expanded by Bessel functions, and the following formula (7) can be obtained:

[0108]

[0109] Among them, J n (C) is the nth-order Bessel function of C. Multiply the above formula by the carrier signal Gcosω0t and the second harmonic of the carrier signal Hcos2ω0t respectively to obtain two outputs. After the two outputs pass through a low-pass filter to remove the high-frequency terms and are normalized, the output signals S1 and S2 can be obtained as shown in the following formula (8) and formula (9):

[0110]

[0111] Differentiating S1 gives S ′ 1 (as shown in the following formula (10)), and differentiating S2 gives S ′ 2 (as shown in the following formula (11)).

[0112]

[0113]

[0114] Cross-multiplying and then taking the difference gives S3 as shown in the following formula (12):

[0115]

[0116] Performing an integration operation on the above formula gives the demodulated EEG signal S d as shown in the following formula (13):

[0117]

[0118] It should be noted that those skilled in the art will readily think of other implementation schemes of this application after considering the specification and practicing the application disclosed here. This application is intended to cover any variations, uses, or adaptations of this application, and these variations, uses, or adaptations follow the general principles of this application and include common general knowledge or conventional technical means in this technical field that are not disclosed in this application. The specification and examples are only regarded as exemplary, and the true scope of this application is pointed out by the claims.

[0119] It should be understood that this application is not limited to the exact structure described above and shown in the drawings, and various modifications and changes can be made without departing from its scope. The scope of this application is only limited by the appended claims.

Claims

1. An electroencephalogram signal sensor, characterized in that: include: Electrostrictive structure (11); The sensing optical fiber is provided with an active phase-shift grating (12), and the electrostrictive structure (11) is attached to the active phase-shift grating (12); The electrostrictive structure (11) is configured to expand and contract after receiving an electroencephalogram signal, thereby driving a phase change of the active phase-shift grating (12) on the sensing optical fiber.

2. The electroencephalogram signal sensor according to claim 1, characterized in that: The electrostrictive structure (11) comprises: Ferroelectric copolymers or piezoelectric ceramics.

3. The electroencephalogram signal sensor according to claim 1, characterized in that: A plurality of active phase-shift gratings (12) are arranged at intervals on the sensing optical fiber; The number of the electrostrictive structures (11) is multiple; The electrostrictive structure (11) and the active phase-shift grating (12) are arranged in a one-to-one correspondence.

4. The electroencephalogram signal sensor according to claim 1, characterized in that: When the electrostrictive structure (11) includes piezoelectric ceramics, and the number of the electrostrictive structures (11) is plural, the piezoelectric ceramics include piezoelectric stacked ceramics (111).

5. A method for manufacturing an electroencephalogram signal sensor, characterized in that: The method for manufacturing the electroencephalogram signal sensor is used to manufacture the electroencephalogram signal sensor (1) as claimed in any one of claims 1 to 4, and the method for manufacturing the electroencephalogram signal sensor comprises: stretching the length of the active phase-shift grating (12) so that the central wavelength of the reflected light generated by the active phase-shift grating (12) is the target wavelength; The sensing optical fiber and the electrostrictive structure (11) on both sides of the active phase-shift grating (12) are bonded using AB glue (13).

6. The method for manufacturing the electroencephalogram signal sensor according to claim 5, characterized in that: The length of the stretched active phase-shift grating (12) comprises: The active phase-shift grating (12) is stretched using a stretching platform.

7. The method for manufacturing the electroencephalogram signal sensor according to claim 5, characterized in that: The stretching platform comprises a fixed platform, a clamp and a knob, wherein the clamp is arranged on the fixed platform, the fixed platform is configured to place the active phase shift grating (12), the clamp comprises a first fixing part and a second fixing part, the first fixing part and the second fixing part are respectively configured to clamp the sensing optical fiber at opposite ends of the active phase shift grating (12); the knob is configured to adjust the distance between the first fixing part and the second fixing part; The method of using a stretching platform to stretch the active phase-shift grating (12) comprises: placing the active phase-shift grating (12) on the fixing platform; Using the first fixing part and the second fixing part to clamp the sensing optical fiber at two opposite ends of the active phase shift grating (12); The active phase-shift grating (12) is connected to a fiber grating demodulator (23) using an optical fiber jumper; the central wavelength of the active phase-shift grating (12) is an initial wavelength; the fiber grating demodulator (23) is configured to measure the central wavelength of the reflected light generated by the active phase-shift grating (12); The knob is used to adjust the distance between the first fixing part and the second fixing part to stretch the active phase shift grating (12) so that the central wavelength of the active phase shift grating (12) is a target wavelength, and the initial wavelength is smaller than the target wavelength.

8. The method for manufacturing the electroencephalogram signal sensor according to claim 5, characterized in that: The electrostrictive structure (11) comprises PMN-RT multifunctional ceramics, and the active phase-shift grating (12) and the electrostrictive structure (11) are bonded using AB glue (13), comprising: The AB glue (13) is used to adhere and fix the PMN-RT multifunctional ceramic on both sides of the active phase shift grating (12) for more than 5 hours.

9. An electroencephalogram signal acquisition system, characterized in that: include: Pump laser (21); An electroencephalogram signal sensor (1), comprising the electroencephalogram signal sensor (1) according to any one of claims 1 to 4, or the electroencephalogram signal sensor (1) manufactured by the manufacturing method of the electroencephalogram signal sensor (1) according to any one of claims 5 to 8; Isolator (24); Interferometer (22); Demodulator (23); The pump laser (21) is configured to output laser light to the electroencephalogram signal sensor (1); The electroencephalogram signal sensor (1) is configured to receive the influence of the laser and the electroencephalogram signal, and output a light signal corresponding to the electroencephalogram signal; The isolator (24) is configured to block reflected light in a subsequent optical path of the isolator (24); The interferometer (22) is configured to receive the optical signal corresponding to the EEG signal, and to cause the optical signal corresponding to the EEG signal to interfere, and output an interference optical signal; The demodulator (23) is configured to receive the interference light signal and demodulate it to obtain an electroencephalogram signal.

10. The electroencephalogram signal acquisition system (2) according to claim 9, characterized in that: The receiving the interference light signal and demodulating to obtain the EEG signal comprises: The interference light signal is demodulated using a dual-channel single-path differential phase division algorithm to determine the EEG signal.

Images