A signal demodulation system for an FP electrostatic sensor

Abstract

The utility model discloses a signal demodulation system of FP electrostatic sensor, include: excitation device for emitting excitation light signal to the FP electrostatic sensor to drive the FP electrostatic sensor to produce simple harmonic vibration, detection device for emitting detection light signal to the FP electrostatic sensor to make the FP electrostatic sensor output interference light signal, demodulation device for receiving and demodulating the interference light signal of FP electrostatic sensor output to obtain the frequency response curve of FP electrostatic sensor, coupling device for connecting excitation device, detection device and demodulation device together to the input output end of FP electrostatic sensor. This signal demodulation system can make with smaller minimum detection value and higher detection sensitivity.

Description

Technical Field

[0001] This utility model relates to the field of electrostatic sensing, and in particular to a signal demodulation system for an FP electrostatic sensor. Background Technology

[0002] The FP electrostatic sensor is an electrostatic detection device designed based on the principle of Fabry-Perot Interferometer (FPI). It is mainly used to accurately measure parameters such as electrostatic field strength and charge density on the surface of the environment or target object. Unlike traditional capacitive and electric field type electrostatic sensors, its core advantages are high detection sensitivity, wide dynamic range and anti-electromagnetic interference capability.

[0003] For example, Chinese Patent Application No. CN202110470636.2 discloses a chip-packaged electrostatic measurement sensor based on the FP interferometry principle, including a capacitive scanning probe, an optical fiber electric field sensor, an optical fiber sensor demodulator, and a computer. The two outputs of the capacitive scanning probe are connected to the two poles of the sensitive material of the optical fiber electric field sensor. The optical fiber interface of the optical fiber electric field sensor is connected to the channel on the optical fiber sensor demodulator. The communication interface of the optical fiber sensor demodulator is connected to the input of the computer. The optical fiber electric field sensor also includes an acrylic tube and a piezoelectric ceramic sheet. A plastic plate is set inside the acrylic tube, and a piezoelectric ceramic sheet is set at one end of the acrylic tube. A ceramic pin is fixed on the plastic plate along the axial direction of the acrylic tube. The piezoelectric ceramic sheet is perpendicular to the ceramic pin. The end of the ceramic pin is connected to the optical fiber interface. Electrodes are plated on both sides of the piezoelectric ceramic sheet. The two electrodes are connected to the capacitive scanning probe through transmission wires. This electrostatic measurement sensor uses a capacitive scanning probe to sense and collect electrostatic charges on charged objects, and converts them into electric fields at both ends of a piezoelectric ceramic sheet. This drives the piezoelectric ceramic sheet to deform in the thickness direction, thereby causing a change in the length of the Fabry-Perot cavity between the piezoelectric ceramic sheet and the ceramic pin. By demodulating the change in the length of the Fabry-Perot cavity, the magnitude of the electrostatic charge on the charged object can be calculated.

[0004] However, when the electrostatic charge on a charged object is small or the electrostatic change is small, the electric field formed by the electrostatic charge through the capacitive scanning probe may not be able to drive the piezoelectric ceramic sheet to deform. This causes the electrostatic measurement sensor to be unable to measure some small electrostatic charges and small changes in electrostatic charge. In other words, the minimum detection value of the electrostatic measurement sensor is large and the detection sensitivity is low. Utility Model Content

[0005] To address the shortcomings of the prior art, this invention provides a signal demodulation system that enables the FP electrostatic sensor to have a smaller minimum detection value and higher detection sensitivity.

[0006] The technical problem to be solved by this utility model is achieved through the following technical solution: A signal demodulation system for an FP electrostatic sensor, comprising: An excitation device is used to emit an excitation light signal to the FP electrostatic sensor to drive the FP electrostatic sensor to generate simple harmonic vibration; The detection device is used to emit a detection light signal to the FP electrostatic sensor so that the FP electrostatic sensor outputs an interference light signal; A demodulation device is used to receive and demodulate the interference light signal output by the FP electrostatic sensor to obtain the frequency response curve of the FP electrostatic sensor. A coupling device is used to connect the excitation device, the detection device, and the demodulation device together to the input and output terminals of the FP electrostatic sensor.

[0007] Furthermore, the coupling device includes a coupler and a circulator. The coupler has a first input terminal, a second input terminal, and an output terminal. The circulator has a first end, a second end, and a third end. The output terminal of the excitation device is connected to the first input terminal of the coupler, and the output terminal of the detection device is connected to the second input terminal of the coupler. The first end of the circulator is connected to the output terminal of the coupler, the second end of the circulator is connected to the input and output terminals of the FP electrostatic sensor, and the third end of the circulator is connected to the input terminal of the demodulation device.

[0008] Furthermore, the excitation device includes an excitation light source, an electro-optic modulator, and a signal generator. The electro-optic modulator has an input terminal, an output terminal, and a control terminal. The output terminal of the excitation light source is connected to the input terminal of the electro-optic modulator, and the output terminal of the signal generator is connected to the control terminal of the electro-optic modulator. The output terminal of the electro-optic modulator serves as the output terminal of the excitation device.

[0009] Furthermore, the detection device includes a detection light source, and the output end of the detection light source serves as the output end of the detection device.

[0010] Furthermore, the demodulation device includes a bandpass filter, a photodetector, a spectrum analyzer, and a host computer. The output of the bandpass filter is connected to the input of the photodetector, the output of the photodetector is connected to the input of the spectrum analyzer, and the output of the spectrum analyzer is connected to the input of the host computer. The input of the bandpass filter serves as the input of the demodulation device.

[0011] Furthermore, the FP electrostatic sensor includes a single-mode optical fiber, a first glass tube, a second glass tube, an inner sensing film, and an outer sensing film. The first glass tube is connected to one end of the single-mode optical fiber. The inner sensing film is disposed on the end of the first glass tube away from the single-mode optical fiber. The second glass tube is connected to the end of the first glass tube away from the single-mode optical fiber. The outer sensing film is disposed on the end of the second glass tube away from the inner sensing film. The end face of the single-mode optical fiber near the first glass tube is parallel to the inner sensing film, and the inner sensing film is parallel to the outer sensing film. The other end of the single-mode optical fiber serves as the input / output terminal of the FP electrostatic sensor.

[0012] Furthermore, both ends of the first glass tube are port structures.

[0013] Furthermore, the end of the second glass tube closest to the first glass tube has a port structure, and the end furthest from the inner sensing film has a flat-bottom structure. The outer sensing film is disposed on the flat bottom of the end of the second glass tube furthest from the inner sensing film.

[0014] Furthermore, the outer diameter of the first glass tube is equal to the diameter of the single-mode optical fiber, and the port of the first glass tube is connected to the end face of the single-mode optical fiber; the inner diameter of the second glass tube is larger than the outer diameter of the first glass tube, and one end of the first glass tube with the inner sensing film is inserted and fixed into the second glass tube.

[0015] Furthermore, both the inner and outer sensing films are metal films.

[0016] This invention has the following advantages: The signal demodulation system of this invention demodulates the FP electrostatic sensor based on the cavity optomechanical effect of the Fabry-Perot interferometer. Under the drive of the excitation light signal, the FP electrostatic sensor can generate simple harmonic vibration and modulate the detection light signal, thereby outputting an interference light signal with its vibration information. The demodulation device can obtain the frequency response curve of the FP electrostatic sensor by acquiring and demodulating the interference light signal. The frequency response curve has a resonant peak, which corresponds to the resonant frequency of the FP electrostatic sensor. The magnitude of the electrostatic charge can be calculated by the frequency change of the resonant peak of the FP electrostatic sensor before and after the electrostatic charge is applied. Compared with demodulating the change of FP cavity length, the resonant frequency of the FP electrostatic sensor can change under a small electrostatic force, thus having a smaller minimum detection value and higher detection sensitivity, and can measure some small electrostatic charges and small changes in electrostatic charge. Attached Figure Description

[0017] Figure 1This is a schematic diagram of the signal demodulation system provided by this utility model.

[0018] Figure 2 This utility model provides a schematic diagram of another signal demodulation system.

[0019] Figure 3 This is a schematic diagram of the structure of the FP electrostatic sensor in the signal demodulation system provided by this utility model. Detailed Implementation

[0020] The present invention will now be described in detail with reference to the accompanying drawings and embodiments, examples of which are shown in the drawings. Throughout the drawings, the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0021] In the description of this utility model, it should be understood that the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0022] Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first," "second," or "third" may explicitly or implicitly include one or more of that feature. In the description of this utility model, "multiple" means two or more, unless otherwise explicitly specified.

[0023] In this utility model, unless otherwise explicitly specified and limited, the terms "installation," "connection," "joining," "fixing," and "setting," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.

[0024] Example 1 like Figure 1 and 2As shown, a signal demodulation system for an FP electrostatic sensor 7 includes: An excitation device is used to emit an excitation light signal to the FP electrostatic sensor 7 to drive the FP electrostatic sensor 7 to generate simple harmonic vibration; The detection device is used to emit a detection light signal to the FP electrostatic sensor 7 so that the FP electrostatic sensor 7 outputs an interference light signal; A demodulation device is used to receive and demodulate the interference light signal output by the FP electrostatic sensor 7 to obtain the frequency response curve of the FP electrostatic sensor 7. A coupling device is used to connect the excitation device, the detection device, and the demodulation device together to the input and output terminals of the FP electrostatic sensor 7.

[0025] The signal demodulation system of this invention demodulates the FP electrostatic sensor 7 based on the cavity optomechanical effect of the Fabry-Perot interferometer. Driven by the excitation light signal, the FP electrostatic sensor 7 generates simple harmonic vibrations and modulates the probe light signal, thereby outputting an interference light signal carrying its vibration information. The demodulation device acquires and demodulates the interference light signal to obtain the frequency response curve of the FP electrostatic sensor 7. The frequency response curve contains a resonant peak, which corresponds to the resonant frequency of the FP electrostatic sensor 7. The magnitude of the electrostatic charge can be calculated by the frequency change of the resonant peak before and after the application of electrostatic charge. Compared to demodulating changes in the FP cavity length, the resonant frequency of the FP electrostatic sensor 7 can change under relatively small electrostatic forces, thus exhibiting a smaller minimum detection value and higher detection sensitivity, enabling the measurement of minute electrostatic charges and minute changes in electrostatic charge.

[0026] like Figure 2 As shown, the coupling device includes a coupler 5 and a circulator 6. The coupler 5 has a first input terminal, a second input terminal, and an output terminal. The circulator 6 has a first end, a second end, and a third end. The output terminal of the excitation device is connected to the first input terminal of the coupler 5, and the output terminal of the detection device is connected to the second input terminal of the coupler 5. The first end of the circulator 6 is connected to the output terminal of the coupler 5, the second end of the circulator 6 is connected to the input and output terminals of the FP electrostatic sensor 7, and the third end of the circulator 6 is connected to the input terminal of the demodulation device.

[0027] During measurement, the excitation light signal emitted by the excitation device and the detection light signal emitted by the detection device are mixed in the coupler 5, with the excitation light signal accounting for 90% and the detection light signal accounting for 10%. The mixed excitation light signal and detection light signal enter the FP electrostatic sensor 7 through the circulator 6. The excitation light signal in the mixed light drives the FP electrostatic sensor 7 to generate simple harmonic vibration, and the detection light signal in the mixed light is modulated by the FP electrostatic sensor 7 to form the interference light signal. The interference light signal is output to the demodulation device through the circulator 6. After the demodulation device collects the interference light signal, it performs light intensity demodulation on the interference light signal to obtain the frequency response curve of the FP electrostatic sensor 7.

[0028] The excitation device includes an excitation light source 2, an electro-optic modulator 3, and a signal generator 4. The electro-optic modulator 3 has an input terminal, an output terminal, and a control terminal. The output terminal of the excitation light source 2 is connected to the input terminal of the electro-optic modulator 3, and the output terminal of the signal generator 4 is connected to the control terminal of the electro-optic modulator 3. The output terminal of the electro-optic modulator 3 serves as the output terminal of the excitation device.

[0029] During measurement, the electro-optic modulator 3, under the control of the signal generator 4, generates a frequency comb or sweep signal to modulate the excitation light signal emitted by the excitation light source 2, so that the frequency range of the excitation light signal covers the inherent frequency of the FP electrostatic sensor 7.

[0030] The detection device includes a detection light source 1, and the output end of the detection light source 1 serves as the output end of the detection device.

[0031] During measurement, the wavelengths of the detection light signal emitted by the detection light source 1 and the excitation light signal emitted by the excitation light source 2 are different, and the wavelength of the detection light signal is consistent with the operating wavelength of the FP electrostatic sensor 7.

[0032] The demodulation device includes a bandpass filter 8, a photodetector 9, a spectrum analyzer 10, and a host computer 11. The output of the bandpass filter 8 is connected to the input of the photodetector 9, the output of the photodetector 9 is connected to the input of the spectrum analyzer 10, and the output of the spectrum analyzer 10 is connected to the input of the host computer 11. The input of the bandpass filter 8 serves as the input of the demodulation device.

[0033] During measurement, the interference light signal output by the FP electrostatic sensor 7 is collected by the photodetector 9 after passing through the bandpass filter 8. The bandpass filter 8 is used to filter out the excitation light signal doped in the interference light signal. The photodetector 9 performs photoelectric conversion on the collected interference light signal and outputs it to the spectrum analyzer 10 for light intensity demodulation, thereby obtaining the frequency response curve. Finally, the host computer 11 calculates the magnitude of the electrostatic charge based on the frequency change of the resonant peak in the frequency response curve.

[0034] When the signal demodulation system is set up, the detection light source 1, excitation light source 2, electro-optic modulator 3, coupler 5, circulator 6, FP electrostatic sensor 7, bandpass filter 8, and photodetector 9 are connected by optical fibers to form the optical path required for optical signal transmission; the electro-optic modulator 3 is connected to the signal generator 4, the photodetector 9 is connected to the spectrum analyzer 10, and the spectrum analyzer 10 is connected to the host computer 11 by communication cables to form the circuit required for electrical signal transmission.

[0035] like Figure 3 As shown, the FP electrostatic sensor 7 includes a single-mode optical fiber 71, a first glass tube 72, a second glass tube 73, an inner sensing film 74, and an outer sensing film 75. The first glass tube 72 is connected to one end of the single-mode optical fiber 71. The inner sensing film 74 is disposed on the end of the first glass tube 72 away from the single-mode optical fiber 71. The second glass tube 73 is connected to the end of the first glass tube 72 away from the single-mode optical fiber 71. The outer sensing film 75 is disposed on the end of the second glass tube 73 away from the inner sensing film 74. The end face of the single-mode optical fiber 71 near the first glass tube 72 is parallel to the inner sensing film 74, and the inner sensing film 74 is parallel to the outer sensing film 75. The other end of the single-mode optical fiber 71 serves as the input / output terminal of the FP electrostatic sensor 7.

[0036] In the FP electrostatic sensor 7, the end face of the single-mode fiber 71, the cavity of the first glass tube 72, and the inner sensing film 74 together constitute a Fabry-Perot interferometer. The Fabry-Perot interferometer has an operating wavelength, which is related to the cavity length of the first glass tube 72 and coincides with the wavelength of the detection light signal. When the excitation light signal passes sequentially through the single-mode fiber 71 and the first glass tube 72 and finally reaches the inner sensing film 74, it acts on the inner layer through photomechanical or photothermal effects. On the sensing film 74, thereby driving the inner sensing film 74 to generate forced vibration; the probe light signal undergoes a first reflection when passing through the end face of the single-mode fiber 71, and a second reflection when reaching the inner sensing film 74. The two reflected lights interfere with each other to generate the interference light signal. Since the second reflected light is modulated by the vibration of the inner sensing film 74, the interference light signal carries the vibration information of the inner sensing film 74, specifically, the resonant peak of its frequency response curve corresponds to the resonant frequency of the inner sensing film 74. When the outer sensing film 75 comes into contact with a charged object, the electrostatic charge on the charged object is transferred to the outer sensing film 75. After absorbing the electrostatic charge, the outer sensing film 75 generates an electrostatic field. Under the action of the electrostatic field, the free electrons inside the inner sensing film 74 undergo directional movement, causing its two surfaces to also carry charges (the surface closer to the outer sensing film 75 carries the opposite charge, and the surface farther away from the outer sensing film 75 carries the same charge). Finally, an internal induced electric field is generated between the inner sensing film 74 and the outer sensing film 75. The internal induced electric field causes stress changes or deformation in the inner sensing film 74, ultimately leading to a change in the resonant frequency of the inner sensing film 74.

[0037] When the static electricity on the charged object is large, the internal induced electric field between the inner sensing film 74 and the outer sensing film 75 is also large. Under this internal electric field force, the inner sensing film 74 can deform, thereby causing a change in the resonant frequency. When the static electricity on the charged object is small, the internal induced electric field between the inner sensing film 74 and the outer sensing film 75 is also small. Even if the inner sensing film 74 cannot deform under this internal electric field force, stress changes will occur (the vibration resistance of the inner sensing film 74 increases), which also causes a change in the resonant frequency.

[0038] Preferably, both the inner sensing film 74 and the outer sensing film 75 are metal films to better induce electric field, such as aluminum thin film, copper thin film, gold thin film, silver thin film, or palladium thin film, with a thickness between 50-100 nm. A gap is left between the inner sensing film 74 and the outer sensing film 75, but this gap should be as small as possible to facilitate electric field induction; this gap is between 10-30 μm.

[0039] In this embodiment, both ends of the first glass tube 72 are port structures. The inner sensing film 74 is disposed on the port of the first glass tube 72 away from the single-mode optical fiber 71, so as to be suspended in front of the first microcavity. The end of the second glass tube 73 near the first glass tube 72 is a port structure, and the end away from the inner sensing film 74 is a flat-bottom structure. The outer sensing film 75 is disposed on the flat bottom of the end of the second glass tube 73 away from the inner sensing film 74.

[0040] Preferably, the outer diameter of the first glass tube 72 is equal to the diameter of the single-mode optical fiber 71, and the port of the first glass tube 72 is connected to the end face of the single-mode optical fiber 71 by means of bonding or fusion, so that the outer periphery of the first glass tube 72 and the single-mode optical fiber 71 are smoothly transitioned; the inner diameter of the second glass tube 73 is larger than the outer diameter of the first glass tube 72, and one end of the first glass tube 72 with the inner sensing film 74 is inserted and fixed into the second glass tube 73 (it can be connected and fixed by means of bonding or fusion), so that the gap between the inner sensing film 74 and the outer sensing film 75 can be adjusted by the insertion depth of the first glass tube 72 during preparation.

[0041] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present utility model and not to limit them. Although the present utility model has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present utility model, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the scope of the technical solutions of the present utility model.

Claims

1. A signal demodulation system for an FP electrostatic sensor, characterized in that, include: An excitation device is used to emit an excitation light signal to the FP electrostatic sensor to drive the FP electrostatic sensor to generate simple harmonic vibration; The detection device is used to emit a detection light signal to the FP electrostatic sensor so that the FP electrostatic sensor outputs an interference light signal; A demodulation device is used to receive and demodulate the interference light signal output by the FP electrostatic sensor to obtain the frequency response curve of the FP electrostatic sensor. A coupling device is used to connect the excitation device, the detection device, and the demodulation device together to the input and output terminals of the FP electrostatic sensor.

2. The signal demodulation system according to claim 1, characterized in that, The coupling device includes a coupler and a circulator. The coupler has a first input terminal, a second input terminal, and an output terminal. The circulator has a first end, a second end, and a third end. The output terminal of the excitation device is connected to the first input terminal of the coupler, and the output terminal of the detection device is connected to the second input terminal of the coupler. The first end of the circulator is connected to the output terminal of the coupler, the second end of the circulator is connected to the input and output terminals of the FP electrostatic sensor, and the third end of the circulator is connected to the input terminal of the demodulation device.

3. The signal demodulation system according to claim 1 or 2, characterized in that, The excitation device includes an excitation light source, an electro-optic modulator, and a signal generator. The electro-optic modulator has an input terminal, an output terminal, and a control terminal. The output terminal of the excitation light source is connected to the input terminal of the electro-optic modulator, and the output terminal of the signal generator is connected to the control terminal of the electro-optic modulator. The output terminal of the electro-optic modulator serves as the output terminal of the excitation device.

4. The signal demodulation system according to claim 1 or 2, characterized in that, The detection device includes a detection light source, and the output end of the detection light source serves as the output end of the detection device.

5. The signal demodulation system according to claim 1 or 2, characterized in that, The demodulation device includes a bandpass filter, a photodetector, a spectrum analyzer, and a host computer. The output of the bandpass filter is connected to the input of the photodetector, the output of the photodetector is connected to the input of the spectrum analyzer, and the output of the spectrum analyzer is connected to the input of the host computer. The input of the bandpass filter serves as the input of the demodulation device.

6. The signal demodulation system according to claim 1 or 2, characterized in that, The FP electrostatic sensor includes a single-mode optical fiber, a first glass tube, a second glass tube, an inner sensing film, and an outer sensing film. The first glass tube is connected to one end of the single-mode optical fiber. The inner sensing film is disposed on the end of the first glass tube away from the single-mode optical fiber. The second glass tube is connected to the end of the first glass tube away from the single-mode optical fiber. The outer sensing film is disposed on the end of the second glass tube away from the inner sensing film. The end face of the single-mode optical fiber near the first glass tube is parallel to the inner sensing film, and the inner sensing film is parallel to the outer sensing film. The other end of the single-mode optical fiber serves as the input / output terminal of the FP electrostatic sensor.

7. The signal demodulation system according to claim 6, characterized in that, Both ends of the first glass tube are port structures.

8. The signal demodulation system according to claim 6, characterized in that, The second glass tube has a port structure at one end near the first glass tube and a flat-bottom structure at the other end away from the inner sensing film. The outer sensing film is disposed on the flat bottom of the second glass tube at the end away from the inner sensing film.

9. The signal demodulation system according to claim 6, characterized in that, The outer diameter of the first glass tube is equal to the diameter of the single-mode optical fiber, and the port of the first glass tube is connected to the end face of the single-mode optical fiber; the inner diameter of the second glass tube is greater than the outer diameter of the first glass tube, and one end of the first glass tube with the inner sensing film is inserted and fixed into the second glass tube.

10. The signal demodulation system according to claim 6, characterized in that, Both the inner and outer sensing films are metal films.

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