Spatial two-dimensional linear displacement measurement method based on planar differential four-quadrant capacitor

Abstract

The invention discloses a spatial two-dimensional linear displacement measurement method based on a planar differential four-quadrant capacitor, and the method comprises the steps: firstly fixing a drive module on a device which needs to measure the two-dimensional linear displacement of a moving part, then connecting a detection capacitor with the moving part, and constructing a differential four-quadrant capacitance sensor; when the detection capacitor carries out planar two-dimensional linear displacement along with a moving part in the equipment, differential output capacitance between a first quadrant and a third quadrant and differential output capacitance between a second quadrant and a fourth quadrant are obtained, and a differential output displacement matrix is constructed; four paths of dual-frequency aliasing excitation signals are constructed to construct a decoupling matrix, driving capacitors in four quadrants are respectively excited through the four paths of excitation signals to realize decoupling, and then current signals output by detection capacitors are acquired; and the current signal is demodulated by using a synchronous demodulation technology to obtain two paths of components of the current signal, and the quadrant of the detection capacitor moving along with the moving part and the corresponding displacement can be determined based on the two paths of components.

Description

Technical Field

[0001] The present invention relates to the field of two-dimensional measurement technology, and in particular to a spatial two-dimensional linear displacement measurement method based on planar differential four-quadrant capacitance. Background Art

[0002] Taking the processing and manufacturing solutions of advanced instrumentation equipment such as lithography machines and ultra-large aperture astronomical telescopes as an example, modern precision instrumentation equipment has an increasingly urgent demand for low-cost, small-volume, ultra-precision two-dimensional linear displacement detection and measurement sensors. The measurement accuracy of planar two-dimensional linear displacement is directly related to the control and positioning accuracy of certain key components in the instrumentation, which in turn determines the overall performance level of such instrumentation equipment. How to improve the measurement accuracy of planar two-dimensional linear displacement is of great practical significance for improving the overall performance level of precision instrumentation equipment.

[0003] Planar two-dimensional linear motion belongs to two-degree-of-freedom motion. The displacement signals in the X and Y directions are coupled with each other, and it is difficult for conventional measuring devices to measure directly. Most traditional methods are based on the scheme of "multiple sets of sensors for single-degree-of-freedom measurement and recombination", that is, single-degree-of-freedom sensors are used to measure the displacement in the X and Y directions respectively, and then the two-dimensional linear displacement of the plane is measured by combined analysis. However, this scheme has defects such as multi-axis error accumulation, introduction of Abbe error, and high cost. Therefore, scholars have proposed an optical measurement method based on the interference and diffraction characteristics of optics. However, the optical measurement method has the disadvantages of complex optical path system, poor environmental adaptability, high cost, etc., and has strict requirements on installation space and working environment in practical applications. Summary of the invention

[0004] The purpose of the present invention is to provide a spatial two-dimensional linear displacement measurement method based on planar differential four-quadrant capacitors to solve the problems existing in the prior art in terms of measurement accuracy, installation conditions, environmental adaptability and cost.

[0005] In order to achieve the above tasks, the present invention adopts the following technical solutions:

[0006] A spatial two-dimensional linear displacement measurement method based on planar differential four-quadrant capacitance, comprising:

[0007] For a device that needs to measure the two-dimensional linear displacement of a moving part, first fix the driving module on the device, then connect the detection capacitor to the moving part, so that the detection capacitor and the driving module are arranged in parallel, with a gap between them; wherein the driving module includes four mutually insulated driving capacitors of the same size, the center of the entire driving module is taken as the origin o of the Cartesian coordinate system, and the length and width directions of the driving module are defined as the x and y axes respectively; the four driving capacitors are respectively located in the four quadrants of the xoy plane, and together with the detection capacitor, form a differential four-quadrant capacitive sensor; initially, the center of the detection capacitor is located directly above the center of the driving module;

[0008] When the moving parts in the detection capacitor follow the device undergo two-dimensional linear displacement, the relative areas between the four measurement capacitors change differentially in pairs, generating corresponding differential output capacitances; obtaining the differential output capacitance C between the first quadrant and the third quadrant 13 And the differential output capacitance C between the second quadrant and the fourth quadrant 24 ;

[0009] According to the differential output capacitance C 13 , differential output capacitance C 24 The relationship between the position of the detection capacitor and the position of the detection capacitor is used to construct the differential output displacement matrix C;

[0010] Two sinusoidal excitation signals with different frequencies are used to construct four dual-frequency mixed excitation signals to construct a decoupling matrix. The driving capacitors in the four quadrants are stimulated by the four excitation signals respectively. The differential output displacement matrix C and the decoupling matrix are used to realize the decoupling of the displacement signal, and then the current signal I output on the detection capacitor is obtained. The current signal I is demodulated using synchronous demodulation technology to obtain two components of the current signal. Based on these two components, the quadrant in which the detection capacitor moves following the moving part and the corresponding displacement can be determined.

[0011] Furthermore, the differential output capacitance C 13 , differential output capacitance C 24 The relationship between the detection capacitor and the position of the detection capacitor is used to construct the differential output displacement matrix C using the plane coordinates of the detection capacitor position, including:

[0012] When the center of the detection capacitor moves to different positions in the xoy plane, the differential output capacitance C 13 , C 24 The expression is:

[0013]

[0014] Then the differential output displacement matrix C is expressed as follows:

[0015]

[0016] Where ε is the dielectric constant of air, d0 is the gap between the driving capacitor and the detection capacitor, a is half the side length of the square driving capacitor, and x and y are the displacement signal components of the detection capacitor center on the x-axis and y-axis in the xoy plane, respectively.

[0017] Furthermore, the excitation signals and decoupling matrix of the four-way dual-frequency aliasing are expressed as follows:

[0018]

[0019] Wherein, A represents the amplitude of the signal, ω1 and ω2 are two signal angular frequencies with different values, t is the time parameter, δ1, δ2, δ3, and δ4 represent four-way dual-frequency mixed excitation signals, which are used to excite the driving capacitors in the first to fourth quadrants respectively.

[0020] Furthermore, decoupling is achieved by respectively exciting the driving capacitors in the four quadrants through four excitation signals, which is expressed as:

[0021]

[0022] The amplitude modulated signal in the first row in the above formula represents the decoupling output when the center of the detection capacitor moves to the first quadrant; the amplitude modulated signal in the second row represents the decoupling output when the center of the detection capacitor moves to the second quadrant; the amplitude modulated signal in the third row represents the decoupling output when the center of the detection capacitor moves to the third quadrant; the amplitude modulated signal in the fourth row represents the decoupling output when the center of the detection capacitor moves to the fourth quadrant.

[0023] Furthermore, after the decoupling operation, the response signal of the capacitor, that is, the two components I1 and I2 of the current signal, can be solved by synchronous demodulation technology:

[0024]

[0025] By using synchronous demodulation, I1 and I2 can be obtained, and then the analytical expressions I1=4jω1x, I2=4jω2y can be used to solve the displacement signals x and y. The displacement quadrant can be determined by its positive and negative values, thereby obtaining the displacement quadrant of the moving part and the specific displacement amount, realizing two-dimensional linear displacement measurement.

[0026] Furthermore, the signal processing circuit for linear displacement measurement includes a driving circuit, a detection circuit and an FPGA, wherein:

[0027] First, the FPGA controls the timing of the two digital-to-analog converters DAC in the driving circuit, so that the two DACs output two sinusoidal excitation signals Asin(ω1t) and Asin(ω2t) with different frequencies. After being amplified by the first-stage amplifier circuit, the two sinusoidal excitation signals enter the operational amplifier network in the driving circuit, and the operational amplifier network is used to perform operation processing on the two sinusoidal signals to output four dual-frequency mixed excitation signals δ1, δ2, δ3, and δ4. These four signals respectively excite the driving capacitors in the four quadrants.

[0028] The detection circuit detects, amplifies and decouples the current signal output by the detection capacitor, and synchronously demodulates the decoupled signal, and determines the position of the detection electrode according to the demodulation result.

[0029] Furthermore, the structure of the driving circuit includes a digital-to-analog converter DAC, a first-stage amplification circuit consisting of six operational amplifiers and their input resistors and feedback resistors, and an operational amplifier network consisting of four operational amplifiers and their input resistors and feedback resistors.

[0030] Furthermore, the detection circuit includes a T-type transimpedance amplifier, two multipliers, two low-pass filter circuits, and an analog-to-digital converter ADC; first, the T-type transimpedance amplifier collects and amplifies the current signal I output by the differential four-quadrant capacitance sensor; secondly, the two multipliers mix the reference signal with the amplified current signal respectively; then, the two low-pass filter circuits integrate the mixing results of the multipliers to obtain the results after synchronous demodulation, and pass them to the FPGA through the ADC; the FPGA solves the displacement signal and transmits the solved results to the host computer for display.

[0031] Compared with the prior art, the present invention has the following technical features:

[0032] 1. The present invention measures the two-dimensional linear displacement of a plane based on a plane differential four-quadrant capacitance sensor, thus avoiding the problem of multi-axis error accumulation and the introduction of Abbe error;

[0033] 2. The present invention only needs one detection capacitor and one four-quadrant driving capacitor to detect the two-dimensional linear displacement of the plane, with a small number of capacitors, simple structure, low cost and high reliability;

[0034] 3. The present invention uses a driving circuit that outputs "four-way dual-frequency superposition excitation signals" to decouple the coupled displacement signals, and is suitable for any differential four-quadrant structure (planar type, spherical type), with strong versatility. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 A left view and a top view of the planar differential four-quadrant capacitive sensor provided by the present invention;

[0036] Figure 2 A schematic diagram of a signal processing circuit according to an embodiment of the present invention;

[0037] Figure 3 A schematic diagram of a driving circuit provided by an embodiment of the present invention;

[0038] Figure 4 A schematic diagram of a detection circuit provided for one embodiment of the present invention. DETAILED DESCRIPTION

[0039] Capacitive sensors have the advantages of high dynamics, low cost, and strong environmental adaptability, which can effectively make up for the technical deficiencies of optical measurement solutions. If the technical advantages of capacitive sensors can be used to design a linear displacement measurement method, it will be of great significance to improve the measurement accuracy and control accuracy of the two-dimensional linear displacement of the mask stage in industrial assembly lines and instrumentation equipment, and thus improve the performance level of the overall system.

[0040] Based on the above idea, the present invention proposes a planar two-dimensional linear displacement measurement method based on planar differential four-quadrant capacitors, which uses the capacitance changes between differential four-quadrant capacitors to achieve the measurement of planar two-dimensional linear displacement.

[0041] Referring to the accompanying drawings, the measuring method provided by the present invention comprises the following steps:

[0042] Step 1, for the equipment that needs to measure the two-dimensional linear displacement of the moving part, first fix the driving module on the equipment, and then connect the detection capacitor to the moving part, so that the detection capacitor and the driving module are arranged in parallel, and there is a gap between the two; wherein, the driving module includes four mutually insulated and identical driving capacitors, and in this embodiment, the driving capacitor is a square structure; the center of the entire driving module is taken as the origin o of the Cartesian coordinate system, the length and width directions of the driving module are defined as the x and y axes respectively, and the thickness direction is the z axis; initially, the center of the detection capacitor is located directly above the center of the driving module, and in this embodiment, the initial position of the center of the detection capacitor is (0mm, 0mm, 1mm), that is, 1mm above the driving module; the four driving capacitors are respectively located in the four quadrants of the xoy plane, and together with the detection capacitor constitute a differential four-quadrant capacitive sensor.

[0043] Step 2: When the moving part in the detection capacitor follower device undergoes a two-dimensional linear displacement, the relative areas between the four measurement capacitors change differentially in pairs, generating corresponding differential output capacitances; the driving capacitances from the first quadrant to the fourth quadrant are C1 to C4 respectively, and the differential output capacitance C between the first quadrant and the third quadrant is obtained. 13 And the differential output capacitance C between the second quadrant and the fourth quadrant 24 .

[0044] By detecting the driving capacitors C1 and C3, the differential output capacitance C of the first and third quadrants can be obtained. 13 Similarly, by detecting the driving capacitors C2 and C4, the differential output capacitors C of the second and fourth quadrants can be obtained. 24 ; Initially, the detection capacitor and the four drive capacitors of the drive module are in a balanced state. At this time, the differential output capacitor C 13 and C 24 are all zero; when the detection capacitor moves along the 45° direction (or 135° direction) on the xoy plane, the electrical detection capacitor and the four drive capacitors are unbalanced. At this time, the differential output capacitor C 13 (or C 24 ) is proportional to the displacement in the 45° direction (or 135° direction), while the other differential output capacitance is zero; when the detection capacitor moves in any direction on the xoy plane, the electrical detection capacitor and the four driving capacitors are unbalanced, and the differential output capacitance C 13 , C 24 Both will change with the x-direction displacement and the y-direction displacement.

[0045] Step 3: According to the differential output capacitance C 13 , differential output capacitance C 24 The relationship between the detection capacitor and the position of the detection capacitor is used to construct the differential output displacement matrix C using the plane coordinates of the detection capacitor.

[0046] According to the capacitance measurement principle, when the center of the detection capacitor moves to the first quadrant of the xoy plane, the differential output capacitance C between the first and third quadrants 13 And the differential output capacitance C between the second quadrant and the fourth quadrant 24 for:

[0047]

[0048] Where ε is the dielectric constant of air, d0 is the gap between the driving capacitor and the detection capacitor, a is half the side length of the square driving capacitor, and x and y are the displacement signal components of the center of the detection capacitor on the x-axis and y-axis in the xoy plane, that is, the position coordinates in the plane.

[0049] Similarly, when the center of the detection capacitor moves to different positions in the xoy plane, the differential output capacitance C 13 , C 24 The expression is:

[0050]

[0051] Formula 3 and Formula 4 are expressed as follows using a differential output displacement matrix C:

[0052]

[0053] Step 4, using two sinusoidal excitation signals with different frequencies to construct four dual-frequency aliased excitation signals to construct a decoupling matrix, respectively excite the driving capacitors in the four quadrants through the four excitation signals, use the differential output displacement matrix C and the decoupling matrix to achieve decoupling of the displacement signal, and then obtain the current signal I output on the detection capacitor; use the synchronous demodulation technology to demodulate the current signal I to obtain two components of the current signal, and based on these two components, the quadrant and the corresponding displacement in which the detection capacitor moves following the moving part can be determined; the specific description is as follows:

[0054] According to Equation 5, the displacements in the x-direction and y-direction are coupled to each other, and it is impossible to directly detect C 13 , C 24 Thus, the values ​​of x and y are known; for this purpose, the signal processing circuit is used in this scheme to realize the generation of the excitation signal and the demodulation of the current signal.

[0055] See also Figure 2 The signal processing circuit of the present invention includes a driving circuit, a detection circuit and an FPGA, wherein:

[0056] First, the FPGA controls the timing of the two digital-to-analog converters DAC in the driving circuit, so that the two DACs output two sinusoidal excitation signals with different frequencies, Asin(ω1t) and Asin(ω2t); wherein A represents the amplitude of the signal, ω1 and ω2 represent the angular frequencies of the two signals with different values, and t represents the time parameter; A can be selected according to the maximum operating voltage limit of the circuit device, for example, A is 1V; the two sinusoidal excitation signals are amplified by a first-stage amplifier circuit and then enter the operational amplifier network in the driving circuit, and the operational amplifier network is used to perform operation processing on the two sinusoidal signals, and output four dual-frequency mixed excitation signals δ1, δ2, δ3, and δ4, which respectively excite the driving capacitors in the four quadrants;

[0057] The detection circuit detects, amplifies and decouples the current signal output by the detection capacitor, and synchronously demodulates the decoupled signal, and determines the position of the detection electrode according to the demodulation result.

[0058] By configuring the input resistors and feedback resistors in the operational amplifier network to construct a subtraction circuit, the driving circuit finally outputs four dual-frequency aliased excitation signals δ1, δ2, δ3, and δ4 to realize the construction of the decoupling matrix:

[0059]

[0060]

[0061] The decoupling matrix is ​​as follows:

[0062]

[0063] After performing matrix operation C·V on the differential output displacement matrix C, the coupled x-direction displacement and y-direction displacement are decoupled:

[0064]

[0065] The amplitude modulated signal in the first row in the above formula represents the decoupling output when the center of the detection capacitor moves to the first quadrant; the amplitude modulated signal in the second row represents the decoupling output when the center of the detection capacitor moves to the second quadrant; the amplitude modulated signal in the third row represents the decoupling output when the center of the detection capacitor moves to the third quadrant; the amplitude modulated signal in the fourth row represents the decoupling output when the center of the detection capacitor moves to the fourth quadrant.

[0066] After the decoupling operation of Formula 11, the displacement signals x and y coupled in Formula 5 are modulated into the amplitude modulated signals in Formula 11. The elements in Formula 11 are amplitude demodulated to obtain the displacement signals x and y.

[0067] The transfer function Z of the known capacitor C c Expressed as: Z c =1 / jωC, ω represents the signal angular frequency, j is an imaginary unit, which represents the phase here; when AC excitation V=sin(ωt) is applied to the capacitor, V / Z can be achieved c =I, the output response I of the capacitor is: I=jωCsin(ωt); based on this principle, the drive circuit is designed to output the waveform curve of formula 10.

[0068] When the four-way dual-frequency mixed excitation signals excite the driving capacitors in the four quadrants respectively, the C·V decoupling operation is realized; after the decoupling operation, the response signal of the capacitor, that is, the analytical expression of the two components of the current signal is: I1=4jω1x,I2=4jω2y; I1 and I2 can be solved by synchronous demodulation technology:

[0069]

[0070] Therefore, after obtaining the current signal I output by the detection electrode, the information it represents is as shown in Formula 11; using synchronous demodulation, I1 and I2 can be obtained, and then using the analytical formula I1=4jω1x, I2=4jω2y, the displacement signals x and y can be calculated; the displacement quadrant can be determined by its positive and negative values, thereby obtaining the displacement quadrant of the moving part and the specific displacement amount, realizing two-dimensional linear displacement measurement.

[0071] In one embodiment of the present invention, see Figure 3 and Figure 4 :

[0072] See also Figure 3An embodiment of the present invention provides a structure of a driving circuit, including a digital-to-analog converter DAC, a first-stage amplification circuit consisting of six operational amplifiers and their input resistors and feedback resistors, and an operational amplifier network consisting of four operational amplifiers and their input resistors and feedback resistors.

[0073] See also Figure 4 An embodiment of the present invention provides a structure of a detection circuit, including a T-type transimpedance amplifier, two multipliers, two low-pass filter circuits, and an analog-to-digital converter ADC; first, the T-type transimpedance amplifier collects and amplifies the current signal I output by the differential four-quadrant capacitance sensor; secondly, the two multipliers respectively mix the reference signal with the amplified current signal; then, the two low-pass filter circuits integrate the mixing results of the multipliers to obtain the results after synchronous demodulation, and pass them to the FPGA through the ADC; the FPGA solves the displacement signal and transmits the solved results to the host computer for display.

[0074] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application, and should all be included in the protection scope of the present application.

Claims

1. A spatial two-dimensional linear displacement measurement method based on planar differential four-quadrant capacitance, characterized in that: include: For a device that needs to measure the two-dimensional linear displacement of a moving part, first fix the driving module on the device, then connect the detection capacitor to the moving part, so that the detection capacitor and the driving module are arranged in parallel, with a gap between them; wherein the driving module includes four mutually insulated driving capacitors of the same size, the center of the entire driving module is taken as the origin o of the Cartesian coordinate system, and the length and width directions of the driving module are defined as the x and y axes respectively; the four driving capacitors are respectively located in the four quadrants of the xoy plane, and together with the detection capacitor, form a differential four-quadrant capacitive sensor; initially, the center of the detection capacitor is located directly above the center of the driving module; When the moving parts in the detection capacitor follow the device undergo two-dimensional linear displacement, the relative areas between the four measurement capacitors change differentially in pairs, generating corresponding differential output capacitances; obtaining the differential output capacitance C between the first quadrant and the third quadrant 13 And the differential output capacitance C between the second quadrant and the fourth quadrant 24 ; According to the differential output capacitance C 13 , differential output capacitance C 24 The relationship between the position of the detection capacitor and the position of the detection capacitor is used to construct the differential output displacement matrix C; Two sinusoidal excitation signals with different frequencies are used to construct four dual-frequency mixed excitation signals to construct a decoupling matrix. The driving capacitors in the four quadrants are stimulated by the four excitation signals respectively. The differential output displacement matrix C and the decoupling matrix are used to realize the decoupling of the displacement signal, and then the current signal I output on the detection capacitor is obtained. The current signal I is demodulated using synchronous demodulation technology to obtain two components of the current signal. Based on these two components, the quadrant in which the detection capacitor moves following the moving part and the corresponding displacement can be determined.

2. The spatial two-dimensional linear displacement measurement method based on planar differential four-quadrant capacitance according to claim 1 is characterized in that: The differential output capacitance C 13 , differential output capacitance C 24 The relationship between the detection capacitor and the position of the detection capacitor is used to construct the differential output displacement matrix C using the plane coordinates of the detection capacitor position, including: When the center of the detection capacitor moves to different positions in the xoy plane, the differential output capacitance C 13 , C 24 The expression is: Then the differential output displacement matrix C is expressed as follows: Where ε is the dielectric constant of air, d0 is the gap between the driving capacitor and the detection capacitor, a is half the side length of the square driving capacitor, and x and y are the displacement signal components of the detection capacitor center on the x-axis and y-axis in the xoy plane, respectively.

3. The spatial two-dimensional linear displacement measurement method based on planar differential four-quadrant capacitance according to claim 1 is characterized in that: The excitation signal and decoupling matrix of the four-way dual-frequency aliasing are expressed as follows: Wherein, A represents the amplitude of the signal, ω1 and ω2 are two signal angular frequencies with different values, t is the time parameter, δ1, δ2, δ3, and δ4 represent four-way dual-frequency mixed excitation signals, which are used to excite the driving capacitors in the first to fourth quadrants respectively.

4. The spatial two-dimensional linear displacement measurement method based on planar differential four-quadrant capacitance according to claim 1 is characterized in that: Decoupling is achieved by respectively exciting the driving capacitors in the four quadrants through four excitation signals, which can be expressed as: The amplitude modulated signal in the first row in the above formula represents the decoupling output when the center of the detection capacitor moves to the first quadrant; the amplitude modulated signal in the second row represents the decoupling output when the center of the detection capacitor moves to the second quadrant; the amplitude modulated signal in the third row represents the decoupling output when the center of the detection capacitor moves to the third quadrant; the amplitude modulated signal in the fourth row represents the decoupling output when the center of the detection capacitor moves to the fourth quadrant.

5. The spatial two-dimensional linear displacement measurement method based on planar differential four-quadrant capacitance according to claim 1 is characterized in that: After decoupling operation, the response signal of the capacitor, that is, the two components I1 and I2 of the current signal, can be solved by synchronous demodulation technology: By using synchronous demodulation, I1 and I2 can be obtained, and then the analytical expressions I1=4jω1x, I2=4jω2y can be used to solve the displacement signals x and y. The displacement quadrant can be determined by its positive and negative values, thereby obtaining the displacement quadrant of the moving part and the specific displacement amount, realizing two-dimensional linear displacement measurement.

6. The spatial two-dimensional linear displacement measurement method based on planar differential four-quadrant capacitance according to claim 1 is characterized in that: The signal processing circuit for linear displacement measurement includes a driving circuit, a detection circuit and an FPGA, wherein: First, the FPGA controls the timing of the two digital-to-analog converters DAC in the driving circuit, so that the two DACs output two sinusoidal excitation signals Asin(ω1t) and Asin(ω2t) with different frequencies. After being amplified by the first-stage amplifier circuit, the two sinusoidal excitation signals enter the operational amplifier network in the driving circuit, and the operational amplifier network is used to perform operation processing on the two sinusoidal signals to output four dual-frequency mixed excitation signals δ1, δ2, δ3, and δ4. These four signals respectively excite the driving capacitors in the four quadrants. The detection circuit detects, amplifies and decouples the current signal output by the detection capacitor, and synchronously demodulates the decoupled signal, and determines the position of the detection electrode according to the demodulation result.

7. The spatial two-dimensional linear displacement measurement method based on planar differential four-quadrant capacitance according to claim 6 is characterized in that: The structure of the driving circuit includes a digital-to-analog converter DAC, a first-stage amplification circuit consisting of six operational amplifiers and their input resistors and feedback resistors, and an operational amplifier network consisting of four operational amplifiers and their input resistors and feedback resistors.

8. The spatial two-dimensional linear displacement measurement method based on planar differential four-quadrant capacitance according to claim 6 is characterized in that: The detection circuit includes a T-type transimpedance amplifier, two multipliers, two low-pass filter circuits, and an analog-to-digital converter ADC; first, the T-type transimpedance amplifier collects and amplifies the current signal I output by the differential four-quadrant capacitance sensor; secondly, the two multipliers respectively mix the reference signal with the amplified current signal; Then, two low-pass filter circuits integrate the mixing results of the multiplier to obtain the synchronous demodulated results, and pass them to the FPGA through the ADC; FPGA solves the displacement signal and transmits the result to the host computer for display.

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