Three-axis real-time magnetic field measurement method and device based on elliptically polarized light SERF atom magnetometer

Abstract

According to the three-axis real-time magnetic field measurement method and device based on the elliptically polarized light SERF atom magnetometer, three-axis magnetic field information is coded through the asymmetrical coupling characteristic of elliptically polarized light, z-axis magnetic field signal components with different frequencies are synchronously demodulated based on a calculation module of an FPGA, and therefore effective superposition of z-axis magnetic field information is achieved; the method comprises the following steps of: 1, performing sideband demodulation on a differential amplification signal which takes elliptically polarized light as pumping light, acts on an atomic gas chamber, is converted by a polarization differential detection module and is output by utilizing an FPGA (Field Programmable Gate Array)-based calculation module in an elliptically polarized light SERF atom magnetometer system; respectively extracting a sum frequency signal component P + and a difference frequency signal component P-containing different z-axis magnetic field information; step 2, carrying out combined processing on P + and P-to generate a comprehensive data signal containing richer three-axis magnetic field information; and step 3, decoupling the signal into a magnetic field intensity component in an orthogonal direction, and forming a three-axis real-time magnetic field measurement result as a magnetometer signal output.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of based on ellipsometric SERF atomic magnetometer three-axis real-time magnetic field measurement method and device, belong to atomic magnetometer technical field. BACKGROUND

[0002] Atomic magnetometer is a kind of through optical pumping to realize alkali atom spin polarization, and then detect its Larmor precession to realize weak magnetic field precision measurement instrument, wherein, Spin-Exchange Relaxation-Free (SERF) magnetometer is under high temperature and weak magnetic environment, by making atomic spin exchange rate far greater than Larmor precession frequency, sufficiently suppresses atomic spin exchange relaxation, greatly improves the magnetic field measurement sensitivity to fT order, shows great development potential and application value in the field of frontiers of physics research, magnetic anomaly detection, biological extremely weak magnetic measurement etc.

[0003] Ellipsometric SERF atomic magnetometer is based on single-beam configuration, and circularly polarized light component is used to pump atom, linearly polarized light component is used to detect atomic spin, while based on polarization differential detection method, it has the technical advantages of small volume and high sensitivity, and has broad development prospect. However, the existing ellipsometric SERF atomic magnetometer can basically only realize single-axis, double-axis magnetic field measurement, cannot realize three-axis real-time magnetic field measurement, it is difficult to obtain more comprehensive magnetic field information, which restricts the development of ellipsometric SERF atomic magnetometer in the application of, such as heart and brain magnetic imaging. SUMMARY

[0004] The present application aims at the deficiencies of the prior art, and proposes a three-axis real-time magnetic field measurement method and device based on an ellipsometric SERF atomic magnetometer. Different frequency two-axis sinusoidal modulation magnetic fields are applied to the ellipsometric SERF (Spin-Exchange Relaxation-Free, spin-exchange relaxation-free) atomic magnetometer, the in-phase and difference frequency components of the differential amplification signal are extracted based on the sideband demodulation technology, more abundant three-axis magnetic field information is obtained, the dynamic calibration of the phase difference and the effective superposition of the z-axis magnetic field signal are realized based on the windowed interpolation Fast Fourier Transform (FFT) algorithm, finally the magnetometer signal is processed and output by the data processing unit, and a high-sensitivity ellipsometric three-axis SERF atomic magnetometer is obtained. Compared with the conventional SERF atomic magnetometer configuration, the ellipsometric detection configuration is adopted in the present application, the volume of the magnetometer head is significantly reduced, the digital signal processing algorithm is combined for optimization processing, the synchronous improvement of the three-axis magnetic field measurement sensitivity is realized, the functions such as demodulation, phase difference correction and data processing are integrated into the calculation module based on the Field-Programmable Gate Array (FPGA), the real-time processing and output of the magnetic field signal are ensured, and the technical progress of the ellipsometric SERF atomic magnetometer in the field of miniaturization and three-axis real-time magnetic field measurement is effectively promoted.

[0005] The technical solution of the present application is as follows:

[0006] The three-axis real-time magnetic field measurement method based on the ellipsometric SERF atomic magnetometer comprises the following steps:

[0007] Step 1: in the ellipsometric SERF atomic magnetometer system, the calculation module based on the FPGA is used to perform sideband demodulation on the differential amplification signal output after the polarization difference detection module is converted after the ellipsometric light is used as pumping light to act on the atomic cell, and the in-phase signal component P + and the difference frequency signal component P - are extracted.

[0008] Step 2: P + and P - are jointly processed to generate a comprehensive data signal containing more abundant three-axis magnetic field information.

[0009] Step 3: decouples the signal into magnetic field strength components in the orthogonal direction to form a three-axis real-time magnetic field measurement result as the magnetometer signal output.

[0010] The following expressions are included in step 1:

[0011]

[0012]

[0013] wherein is the optical pumping rate, is the 0th order Bessel function related to the y-axis modulation magnetic field index, is the 1st order Bessel function related to the y-axis modulation magnetic field index, is the 1st order Bessel function related to the x-axis modulation magnetic field index, is the 0th order Bessel function related to the x-axis modulation magnetic field index, Γ is the zero-field resonance linewidth, Ω is the x-axis modulation magnetic field frequency, γ e is the electron gyromagnetic ratio, B z is the z-axis magnetic field to be measured.

[0014] The step 2 comprises the following expression:

[0015]

[0016] The step 2 comprises performing spectrum refinement analysis on P + and P - respectively by windowed interpolation FFT algorithm, accurately extracting the amplitude and phase parameters thereof, and performing phase difference calibration and signal superposition on P + and P - based on the system phase delay, to generate a comprehensive data signal with consistent phase.

[0017] The FPGA-based calculation module is embedded with a segmented phase dynamic tracking architecture, and performs double-channel FFT operation in parallel, accurately extracts the dynamic phase characteristics of the two signals P + and P - to generate correction parameters, so as to realize real-time phase synchronization of the two signals with the same frequency.

[0018] The elliptical polarization light exit side of the atomic cell sequentially passes through a quarter-wave plate and a linear polarizer connected with a fiber collimator, the fiber collimator is connected with a narrow-line-width semiconductor laser in the photoelectric integrated system through a polarization maintaining optical fiber, and the optical axes of the linear polarizer and the quarter-wave plate are arranged at an included angle α, so as to convert the incident linearly polarized laser into elliptical polarized light with an ellipticity of α.

[0019] The elliptical polarization light exit side of the atomic cell sequentially passes through a quarter-wave plate, a lateral displacement polarization beam splitter prism, a photoelectric detector and a differential amplification circuit in the polarization difference detection module, and is connected with the FPGA-based calculation module in the photoelectric integrated system.

[0020] ​​​The atomic gas chamber is located in a boron nitride ceramic oven, the boron nitride ceramic oven is located in a three-axis magnetic field coil, the three-axis magnetic field coil is located in a magnetic shielding system, and the three-axis magnetic field coil is connected to a three-channel high-precision current source in an optoelectronic integrated system, and the three-channel high-precision current source provides a three-axis magnetic field coil control current.

[0021] The three-axis real-time magnetic field measurement device based on the ellipsometric SERF atomic magnetometer has the characteristics of the three-axis real-time magnetic field measurement method based on the ellipsometric SERF atomic magnetometer.

[0022] The technical effects of the present application are as follows: the three-axis real-time magnetic field measurement method and device based on the ellipsometric SERF atomic magnetometer provide a scheme for real-time measurement of three-axis magnetic field for the ellipsometric SERF atomic magnetometer, and the z-axis magnetic field sensitivity is optimized and improved. The device and method designed by the present application apply different frequency two-axis sinusoidal modulation magnetic fields to the ellipsometric SERF atomic magnetometer, extract the sum frequency and difference frequency signal components of the differential amplification signal based on the sideband demodulation technology, obtain more abundant three-axis magnetic field information, realize dynamic calibration of phase difference based on windowed interpolation FFT algorithm, realize effective superposition of z-axis magnetic field signal, finally process and output the magnetometer signal through the data processing unit, and obtain the high-sensitivity ellipsometric three-axis SERF atomic magnetometer. Compared with the conventional SERF atomic magnetometer configuration, the present application adopts the ellipsometric detection configuration, significantly reduces the volume of the magnetometer head, optimizes the processing by combining the digital signal processing algorithm, realizes the synchronous improvement of the three-axis magnetic field measurement sensitivity, encapsulates the demodulation, phase difference correction and data processing functions in the calculation module based on FPGA, ensures the real-time processing and output of the magnetic field signal, and effectively promotes the technical progress of the ellipsometric SERF atomic magnetometer in the field of miniaturization and three-axis real-time magnetic field measurement.

[0023] The advantages of the present application compared with the prior art are:

[0024] (1) The traditional ellipsometric SERF atomic magnetometer can usually only realize single-axis or two-axis magnetic field measurement, and it is difficult to completely analyze three-axis magnetic field information, which limits its application in the field of high-precision magnetic field measurement. The present application is based on two-axis sinusoidal modulation technology, and different frequency modulation magnetic fields are applied to the x-axis and y-axis respectively, which directly decouples the three-axis magnetic field information, thereby realizing the synchronous real-time measurement of three-axis magnetic field, and solving the problem of insufficient information dimension of the traditional ellipsometric SERF atomic magnetometer.

[0025] (2) The traditional single-beam ellipsometric SERF atomic magnetometer z-axis (perpendicular to the light propagation direction) magnetic field sensitivity is obviously lower than that of x-axis and y-axis, the application extracts z-axis magnetic field signal components of different frequencies through the FPGA-based calculation module, and the signal is superimposed by combining the phase calibration algorithm, so that the z-axis magnetic field effective information is effectively amplified. Meanwhile, the phase calibration algorithm is solidified into the FPGA-based calculation module, and the windowed interpolation FFT algorithm is used to dynamically calibrate the phase difference according to the z-axis magnetic field signal characteristics, so that the phase offset between the sum frequency signal component and the difference frequency signal component is compensated in real time, the errors caused by temperature drift, circuit delay and other factors are eliminated, and the superposition efficiency of the z-axis signal is enhanced, and the signal-to-noise ratio is improved. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 The SERF atomic magnetometer system structure diagram involved in the application of the three-axis real-time magnetic field measurement method based on the ellipsometric SERF atomic magnetometer.

[0027] The reference signs are explained as follows: 1-photoelectric integrated system; 2-narrow linewidth semiconductor laser; 3-polarization maintaining optical fiber; 4-three-channel high-precision current source; 5-three-axis magnetic field coil control current; 6-FPGA-based calculation module; 7-atomic magnetometer meter head; 8-optical fiber collimator; 9-linear polarizer; 10-quarter wave plate; 11-atomic gas chamber; 12-boron nitride ceramic oven; 13-three-axis magnetic field coil; 14-polarization difference detection module; 15-half wave plate; 16-lateral displacement polarization beam splitter prism; 17-photoelectric detector; 18-differential amplification circuit; 19-differential amplification signal; 20-magnetometer meter head shell; 21-magnetic shielding system. DETAILED DESCRIPTION

[0028] The application will be described below in conjunction with the drawings Figure 1 ) and examples.

[0029] Figure 1 The SERF atomic magnetometer system structure diagram involved in the application of the three-axis real-time magnetic field measurement method based on the ellipsometric SERF atomic magnetometer. Referring to Figure 1 , the three-axis real-time magnetic field measurement method based on the ellipsometric SERF atomic magnetometer includes the following steps: step 1, in the ellipsometric SERF atomic magnetometer system, using the FPGA-based calculation module, the differential amplification signal output after the polarization difference detection module is converted after the ellipsometric light as pumping light acts on the atomic gas chamber is sideband demodulated, and the sum frequency signal component P + and the difference frequency signal component P - containing different z-axis magnetic field information are extracted; step 2, P + and P -The combined processing generates a comprehensive data signal containing richer tri-axial magnetic field information ; step 3, decoupling the signal into orthogonal directional magnetic field strength components to form tri-axial real-time magnetic field measurement results as the magnetometer signal output.

[0030] The following expression is included in step 1:

[0031] ,

[0032] ,

[0033] wherein is the optical pumping rate, is a 0th order Bessel function related to the y-axis modulation magnetic field index, is a 1st order Bessel function related to the y-axis modulation magnetic field index, is a 1st order Bessel function related to the x-axis modulation magnetic field index, is a 0th order Bessel function related to the x-axis modulation magnetic field index, Γ is the zero-field resonance linewidth, Ω is the x-axis modulation magnetic field frequency, γ e is the electron gyromagnetic ratio, B z is the z-axis magnetic field to be measured.

[0034] The following expression is included in step 2:

[0035] .

[0036] Step 2 includes performing spectral refinement analysis on P + and P - respectively through windowed interpolation FFT algorithm, accurately extracting the amplitude and phase parameters thereof, and performing phase difference calibration and signal superposition on P + and P - based on the system phase delay, to generate a comprehensive data signal with consistent phase.

[0037] The FPGA-based calculation module is embedded with a segmented phase dynamic tracking architecture, and performs double-channel FFT operation in parallel, accurately extracts the dynamic phase characteristics of the two signals P + and P - to generate correction parameters, so as to realize real-time phase synchronization of the two signals with the same frequency.

[0038] ​The ellipsoidal incident side of the atomic gas cell 11 is connected to the fiber collimator 8 via a quarter-wave plate 10 and a linear polarizer 9. The fiber collimator 8 is connected to the narrow-linewidth semiconductor laser 2 in the optoelectronic integrated system 1 via a polarization-maintaining fiber 3. The optical axes of the linear polarizer 9 and the quarter-wave plate 10 are arranged at an angle α (α≠0) to convert the incident linearly polarized laser into ellipsoidally polarized light with an ellipticity of α. The ellipsoidal exit side of the atomic gas cell 11 is connected to the FPGA-based computing module 6 in the optoelectronic integrated system 1 via a half-wave plate 15, a lateral displacement polarization beam splitter prism 16, a photodetector 17, and a differential amplifier circuit 18 in the polarization difference detection module 14. The atomic gas chamber 11 is located inside the boron nitride ceramic oven 12, which is located inside the triaxial magnetic field coil 13. The triaxial magnetic field coil 13 is located inside the magnetic shielding system 21. The triaxial magnetic field coil 13 is connected to the three-channel high-precision current source 4 in the optoelectronic integrated system 1. The three-channel high-precision current source 4 provides the control current 5 for the triaxial magnetic field coil.

[0039] A triaxial real-time magnetic field measurement device based on an ellipsometric SERF atomic magnetometer is used to implement the above-mentioned triaxial real-time magnetic field measurement method based on an ellipsometric SERF atomic magnetometer.

[0040] A triaxial real-time magnetic field measurement device and method based on an ellipsometric SERF atomic magnetometer includes an optoelectronic integrated system (1), a narrow linewidth semiconductor laser (2), a polarization-maintaining fiber (3), a three-channel high-precision current source (4), a triaxial magnetic field coil control current (5), an FPGA-based computing module (6), an atomic magnetometer head (7), an optical fiber collimator (8), a linear polarizer (9), a quarter-wave plate (10), an atomic gas cell (11), a boron nitride ceramic oven (12), a triaxial magnetic field coil (13), a polarization differential detection module (14), a half-wave plate (15), a lateral displacement polarization beam splitter (16), a photodetector (17), a differential amplifier circuit (18), a differential amplified signal (19), a magnetometer head housing (20), and a magnetic shielding system (21).

[0041] The narrow-linewidth semiconductor laser (2) emits linearly polarized light at a specific frequency that is detuned to the D1 line resonance frequency of the alkali metal atom as the incident laser, which is coupled to the fiber collimator (8) through the polarization-maintaining fiber (3); the fiber collimator (8) is used to collimate the incident laser, outputting a spatial beam of a specific spot diameter and aligning it with the center of the linear polarizer (9); the optical axes of the linear polarizer (9) and the quarter-wave plate (10) are arranged at an angle α, converting the incident linearly polarized laser into elliptically polarized light with an ellipticity of α, which is then introduced into the atomic gas cell (11) and used as the pump laser for the elliptically polarized SERF atomic magnetometer; the polarization difference detection module (14) is composed of the following components. The system consists of a half-wave plate (15), a lateral displacement polarization beam splitter (16), a photodetector (17), and a differential amplifier circuit (18). The pumped laser passes through the half-wave plate (15) and exits, then enters the lateral displacement polarization beam splitter (16), whose optical axis is at an angle of 45° to the optical axis of the half-wave plate (15). The lateral displacement polarization beam splitter (16) decomposes the laser emitted from the half-wave plate (15) into two linearly polarized beams with orthogonal polarization states and parallel propagation directions. The beams are then collimated and incident on the photosensitive surface of the photodetector (17). The differential amplifier circuit (18) differentially amplifies the photoelectric signal output by the photodetector (17) and finally outputs a differential amplified signal (19).

[0042] The atomic gas chamber (11) is filled with alkali metal atoms and placed in a weak magnetic environment, and then heated to a high temperature of 10. 13 ~10 14 pcs / cm 3 The atomic number density is such that the gas chamber is placed in a boron nitride ceramic oven (12), and the two are placed at the geometric center of a triaxial magnetic field coil (13), and a uniform magnetic field of x, y, z axes is applied to it through the triaxial magnetic field coil (13).

[0043] The three-channel high-precision current source (4) applies sinusoidal modulated magnetic fields with frequencies of ω and Ω in the x and y directions of the atomic gas chamber (11), respectively. The magneto-optical modulation effect is converted into a differential amplified signal (18) by the polarization differential detection module (14). The differential amplified signal (18) is subjected to sideband demodulation processing by the FPGA-based computing module (6) to separate the sum-frequency signal component P containing magnetic field information features. + With difference frequency signal component P -The two components have a random phase difference in the time domain. Then, the two components are subjected to spectrum refinement analysis by windowed interpolation FFT algorithm to accurately extract their amplitude and phase parameters. Based on the system phase delay, the phase difference is calibrated and the signals are superimposed to generate a comprehensive data signal with consistent phase. Finally, the data processing unit converts the comprehensive data signal into magnetic field strength components in orthogonal directions according to the three-axis magnetic field decoupling algorithm. After noise suppression, it is output as a magnetometer signal.

[0044] The optoelectronic integrated system (1) consists of a narrow linewidth semiconductor laser (2), a three-channel high-precision current source (4), and an FPGA-based computing module (6). The atomic magnetometer head (7) consists of an optical fiber collimator (8), a linear polarizer (9), a quarter-wave plate (10), an atomic gas chamber (11), a boron nitride ceramic oven (12), a triaxial magnetic field coil (13), and a polarization difference detection module (14), and is encapsulated in the magnetometer head shell (20). Together with the optoelectronic integrated system (1), it forms an atomic magnetometer, which is placed in a magnetic shielding system (21) to fully shield the interference of the geomagnetic field.

[0045] This invention provides a triaxial real-time magnetic field measurement method based on an ellipsometric SERF atomic magnetometer. It encodes triaxial magnetic field information using the asymmetric coupling characteristics of ellipsometric light, combines this with biaxial sinusoidal modulation technology to obtain the triaxial magnetic field information, and uses an FPGA-based computing module to synchronously demodulate the z-axis magnetic field signal components of different frequencies. Furthermore, it employs a windowed interpolation FFT algorithm for dynamic phase calibration, thereby achieving effective superposition of the z-axis magnetic field information. Ultimately, this results in synchronous, high-sensitivity triaxial magnetic field measurement and system miniaturization. (Reference) Figure 1 The specific implementation steps of this invention are as follows:

[0046] (1) Adjust the output frequency of the narrow linewidth semiconductor laser 2 so that it outputs linearly polarized light that is 100 GHz detuned to the resonant frequency of the D1 line of alkali metal atom rubidium (Rb) atom. The linearly polarized light is transmitted to the fiber collimator 8 through the polarization-maintaining fiber 3 to form a collimated beam with a beam diameter of 3.5 mm. After passing through the linear polarizer 9 and the quarter-wave plate 10, it is converted into elliptically polarized light with an ellipticity of π / 8. The elliptically polarized light is used as a pump laser and is perpendicularly incident on the atomic gas cell 11 filled with Rb atoms with an outer surface size of 4 mm to excite the pumping process of alkali metal atoms.

[0047] (2) After completing step (1), the atomic gas chamber 11 in the boron nitride ceramic oven 14 is heated at high temperature to achieve the required atomic number density. At the same time, the environmental magnetic field sensed by the atomic gas chamber 8 is compensated to zero using in-situ three-dimensional magnetic compensation technology. The three-channel high-precision current source 4 is controlled to apply sinusoidal modulated magnetic fields with frequencies of Ω / 2π=1kHz and ω / 2π=5kHz in the x and y directions, respectively. The differential amplified signal (18) contains the z-axis alkali metal atom polarizability P containing z-axis magnetic field information. z Its expression is:

[0048]

[0049] In the formula, P z R represents the polarizability of alkali metal atoms along the z-axis. op Let Γ be the optical pump rate, J0 = J0(u1) and J1 = J1(u1) be the 0th and 1st Bessel functions related to the y-axis modulation magnetic field index u1, respectively; ξ0 = ξ0(J0(u1)u2) and ξ1 = ξ1(J0(u1)u2) be the 0th and 1st Bessel functions related to the x-axis modulation magnetic field index u2, respectively; Γ be the zero-field resonance linewidth; Ω be the x-axis modulation magnetic field frequency; and ω be the frequency of the modulation magnetic field. x ω y and ω z , respectively, are the precession frequencies of the x-axis, y-axis and z-axis under the action of the magnetic field, and ω is the frequency of the modulated magnetic field on the y-axis;

[0050] (3) After completing step (2), the FPGA-based computing module (6) uses lock-in amplification technology to demodulate the differential amplified signal (18) with sidebands, and extracts the sum-frequency signal component P containing the z-axis magnetic field information at frequencies of ω+Ω and ω-Ω respectively. + Sum and difference frequency signal components P - The two can be approximated as:

[0051]

[0052] In the formula, γ e For electron gyromagnetic ratio, B z It is the magnetic field to be measured along the z-axis;

[0053] (4) After completing step (3), the FPGA-based computing module (6) processes the demodulated sum-frequency signal component P. + Sum and difference frequency signal components P - For joint processing, the difference frequency component P is first processed using a windowed interpolation FFT algorithm. - Spectral refinement analysis was performed to suppress spectral leakage and accurately extract its phase parameters. Then, combined with a pre-calibrated system phase delay model, the P... -Dynamic compensation and frequency domain interpolation correction are performed to compensate for phase shifts introduced by timing differences and environmental interference in the components. Component and frequency component P + Synchronous superposition is achieved to generate a comprehensive data signal containing richer triaxial magnetic field information. Its expression is:

[0054]

[0055] Finally, after being processed by the data processing unit, it is output as a magnetometer signal.

[0056] (5) The FPGA-based computing module (6) in step (4) embeds a segmented phase dynamic tracking architecture and performs dual-channel FFT operations in parallel to accurately extract the dynamic phase features of the two signals and generate correction parameters so as to achieve real-time phase synchronization of the two signals with the same frequency. The core objective of the algorithm is to convert the sum-frequency signal component P + Sum and difference frequency signal components P - Let φ1(t) be defined as P, serving as the reference signal and the signal to be corrected, respectively. + The real-time phase, φ2(t) is P - The real-time phase, where t is the total signal duration, t∈[0,T], and T is the signal duration, P + and P - Divide the window into N segments according to the preset window length L, where N = T·f s / L represents the total number of segments, f s For each sampling frequency, windowing, FFT, and phase difference calculation are performed independently. A dynamic search window is set, defined as W(n)=[C(n)-ΔR(n),C(n)+ΔR(n)] as the phase search window for the nth segment, where n∈{0,1,2,...,N-1}, C(n) is the phase reference point for the nth segment, C(0)=φ1(0) is the initial phase, and ΔR(n) is the preset phase fluctuation tolerance threshold. The phase difference is dynamically shrunk according to the following rule: ΔR(n+1)=γΔR(n), where γ∈(0,1) is the convergence acceleration factor, and ΔR(0)=R0 is the initial tolerance. After segmenting and initializing the signal, a Hanning window is applied to the nth segment signal to suppress spectral leakage. P is obtained by dual-channel FFT calculation. + and P -The spectrums Y1(n) and Y2(n) are obtained. By extracting the main frequency phases φ1(n) = arg(Y1(n)) and φ2(n) = arg(Y2(n)), the phase deviation Δφ(n) = |φ1(n) - φ2(n)| of the nth segment is obtained. When Δφ(n) < ξ in real time, where ξ is the preset phase synchronization tolerance threshold, it indicates that the phase difference between the two data signals can be ignored. The current phase reference is maintained: C(n+1) = C(n), and the window is shrunk: ΔR(n+1) = γΔR(n). If Δφ(n) ≥ ξ, it indicates that there is a large phase difference between the two data signals. The phase compensation algorithm will be automatically activated to calculate the current phase deviation. : K p For proportional gain, k is the segment number before the current segment number n. It is the phase deviation of the k-th segment, K i The integral gain is used to update the reference phase: C(n+1) = C(n) + Δφ correct (n), and reset the window tolerance: ΔR(n+1)=γΔR(n); then correct the phase Applied to the current segment P - The phase difference calibration of the two signals is completed; after the phase compensation algorithm is completed, the requirement Δφ(t) < ξ is satisfied, and the corrected difference frequency signal is obtained. and the original sum-frequency signal P + Maintaining phase consistency, the two data signals are superimposed to obtain... Finally, it is output as a magnetometer signal.

[0057] In summary, a triaxial real-time magnetic field measurement method based on an ellipsometric SERF atomic magnetometer is proposed. This method combines biaxial sinusoidal modulation to encode triaxial magnetic field information through the asymmetric coupling characteristics of ellipsometric light. An FPGA-based computing module is used to synchronously demodulate and extract the sum and difference frequency magnetic field signal components. A dynamic phase calibration system is constructed, and the phase deviation is corrected in real time through a windowed interpolation FFT algorithm to effectively enhance anti-interference performance. Hardware integration effectively improves the dynamic response speed and significantly enhances the decoupling capability of multi-axis information. The method also has the advantages of miniaturization and high stability.

[0058] Contents not described in detail in this specification are prior art known to those skilled in the art. It is hereby indicated that the above description is intended to help those skilled in the art understand this invention, but does not limit the scope of protection of this invention. Any equivalent substitutions, modifications, improvements, and / or simplifications of the above descriptions that do not depart from the essential content of this invention fall within the scope of protection of this invention.

Claims

1. A method for triaxial real-time magnetic field measurement based on an ellipsometric SERF atomic magnetometer, characterized in that, Includes the following steps: Step 1: In the ellipsometric SERF atomic magnetometer system, using an FPGA-based computing module, sideband demodulation is performed on the differential amplified signal output after conversion by the polarization difference detection module using ellipsometric light as the pump light. The sum-frequency signal components P containing different z-axis magnetic field information are then extracted. + Sum and difference frequency signal components P - ; Step 2, for P + and P - Joint processing is performed to generate a comprehensive data signal containing richer triaxial magnetic field information. ; Step 3, The signal is decoupled into magnetic field intensity components in orthogonal directions, forming a triaxial real-time magnetic field measurement result as the magnetometer signal output.

2. The triaxial real-time magnetic field measurement method based on an ellipsometric SERF atomic magnetometer according to claim 1, characterized in that, Step 1 includes the following expression: ， ， in It is the light pumping rate. It is a 0th-order Bessel function related to the y-axis modulation magnetic field index. It is a first-order Bessel function related to the y-axis modulation magnetic field index. It is a first-order Bessel function related to the x-axis modulation magnetic field index. It is a 0th-order Bessel function related to the x-axis modulation magnetic field exponent, where Γ is the zero-field resonance linewidth, Ω is the x-axis modulation magnetic field frequency, and γ is the x-axis modulation magnetic field frequency. e For electron gyromagnetic ratio, B z It is the magnetic field to be measured along the z-axis.

3. The triaxial real-time magnetic field measurement method based on an ellipsometric SERF atomic magnetometer according to claim 2, characterized in that, Step 2 includes the following expression: 。 4. The triaxial real-time magnetic field measurement method based on an ellipsometric SERF atomic magnetometer according to claim 1, characterized in that, Step 2 includes applying a windowed interpolation FFT algorithm to P respectively. + and P - Perform a detailed spectral analysis to accurately extract its amplitude and phase parameters, and then analyze P based on the system phase delay. + and P - Phase difference calibration and signal superposition are performed to generate a composite data signal with consistent phase.

5. The triaxial real-time magnetic field measurement method based on an ellipsometric SERF atomic magnetometer according to claim 1, characterized in that, The FPGA-based computing module embeds a segmented phase dynamic tracking architecture, performs dual-channel FFT operations in parallel, and accurately extracts the two signals P. + and P - The dynamic phase characteristics are used to generate correction parameters in order to achieve real-time phase synchronization of two signals with the same frequency.

6. The triaxial real-time magnetic field measurement method based on an ellipsometric SERF atomic magnetometer according to claim 1, characterized in that, The ellipsoidal incident side of the atomic gas cell is connected to an optical fiber collimator via a quarter-wave plate and a linear polarizer in sequence. The optical fiber collimator is connected to a narrow-linewidth semiconductor laser in the optoelectronic integrated system via a polarization-maintaining fiber. The optical axes of the linear polarizer and the quarter-wave plate are arranged at an angle α to convert the incident linearly polarized laser into ellipsoidally polarized light with an ellipticity of α.

7. The triaxial real-time magnetic field measurement method based on an ellipsometric SERF atomic magnetometer according to claim 1, characterized in that, The ellipsoidal polarization emission side of the atomic gas chamber is connected in sequence to the FPGA-based computing module in the optoelectronic integrated system via a half-wave plate, a lateral displacement polarization beam splitter, a photodetector, and a differential amplifier circuit in the polarization difference detection module.

8. The triaxial real-time magnetic field measurement method based on an ellipsometric SERF atomic magnetometer according to claim 1, characterized in that, The atomic gas chamber is located inside a boron nitride ceramic oven, which is located inside a triaxial magnetic field coil. The triaxial magnetic field coil is located inside a magnetic shielding system. The triaxial magnetic field coil is connected to a three-channel high-precision current source in the optoelectronic integrated system. The three-channel high-precision current source provides control current to the triaxial magnetic field coil.

9. A triaxial real-time magnetic field measurement device based on an ellipsometric SERF atomic magnetometer, characterized in that, This method is used to implement the triaxial real-time magnetic field measurement method based on an ellipsometric SERF atomic magnetometer as described in any one of claims 1-8.

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