Phase difference-based magnetometer magnetic field measurement method, system and equipment and medium

Abstract

The invention belongs to the technical field of magnetic field measurement, discloses a magnetometer magnetic field measurement method, system and equipment based on phase difference and a medium, and aims to solve the problems that an existing multi-probe magnetic gradiometer system is high in complexity and high in cost, and the measurement stability is easily influenced by the performance and synchronization precision of a frequency meter. The method comprises the following steps: acquiring a corresponding relation between phase difference and voltage through a first magnetometer and a signal generation device, and determining a conversion coefficient between magnetic field intensity and voltage; connecting an output signal of the second magnetometer to a radio frequency coil of the first magnetometer, acquiring a phase difference between the output signal of the second magnetometer and the output signal of the first magnetometer, and converting the phase difference into a second voltage; and calculating the magnetic field intensity of the to-be-measured magnetic field according to the second voltage and the conversion coefficient. According to the invention, a multi-channel synchronous acquisition technology and a complex differential circuit are not needed, and the system structure is greatly simplified, the cost is reduced and the measurement stability is improved while the noise suppression level equivalent to that of the traditional magnetic gradient technology is maintained.

Description

Technical Field

[0001] This invention belongs to the field of magnetic field measurement technology, and specifically relates to a method, system, equipment and medium for measuring magnetic fields using a magnetometer based on phase difference. Background Technology

[0002] Optically pumped magnetometers are quantum magnetic sensors based on the Zeeman effect of alkali metal atoms. They feature high precision and sensitivity and are widely used in geological exploration, national defense, and medical examinations. However, single-probe optically pumped magnetometers can only measure scalar information about the magnetic field, making them susceptible to interference from diurnal variations in the geomagnetic field and environmental magnetic noise, thus limiting measurement accuracy. To suppress environmental magnetic field noise interference, two or more optically pumped magnetometer probes are typically used to form a magnetic gradiometer. By measuring the frequencies of the output signals from multiple probes and performing differential processing, common-mode background noise is eliminated, resulting in cleaner magnetic field measurement results.

[0003] Currently, magnetic gradient measurement technology based on optically pumped magnetometers is relatively mature and widely used in the measurement of total magnetic field gradients. For example, the SeaSPY marine magnetometer from Marine Magnetics in Canada uses a combination of four independent magnetometers to achieve gradient detection with an absolute accuracy of 0.2 nT; the CS-3 cesium optically pumped magnetic gradiometer manufactured by Scintrex in Canada has an operating range of 15,000 nT to 105,000 nT, a gradient difference of 40,000 nT / m, and a sensitivity of 0.6 pT / √Hz rms. These technical solutions all employ a multi-probe structure and suppress environmental noise through frequency difference methods.

[0004] However, existing magnetic gradient measurement techniques have significant limitations. The core measurement principle of optically pumped magnetometers is to determine the magnetic field strength by measuring the Larmor frequency of atomic gas under the influence of an external magnetic field. Therefore, in multi-probe gradient measurement systems, it is necessary to simultaneously measure the output frequencies of multiple probes and perform differential calculations. This requires the use of high-precision multi-channel frequency meters and places extremely stringent requirements on the frequency meter's acquisition accuracy, multi-channel time synchronization, and differential algorithms. These factors result in high complexity and cost for multi-probe magnetic gradient meter systems, and the measurement stability is easily affected by the performance of the frequency meter and the synchronization accuracy. Summary of the Invention

[0005] Based on the aforementioned shortcomings and deficiencies in the prior art, one of the objectives of this invention is to at least solve one or more of the aforementioned problems in the prior art. In other words, one of the objectives of this invention is to provide a method, system, device, and medium for measuring magnetic fields based on phase difference that meets one or more of the aforementioned requirements, so as to simplify the structure of the magnetic measurement system, reduce equipment costs, improve measurement stability, and effectively suppress environmental magnetic field noise.

[0006] To achieve the above-mentioned objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a method for measuring magnetic fields using a magnetometer based on phase difference, comprising the following steps: S1. Obtain the relationship between phase difference and voltage through the first magnetometer and signal generator to determine the conversion coefficient between magnetic field strength and voltage; S2. Connect the output signal of the second magnetometer to the radio frequency coil of the first magnetometer, obtain the phase difference between the output signal of the second magnetometer and the output signal of the first magnetometer, and convert the phase difference into a second voltage; S3. Calculate the magnetic field strength of the magnetic field to be measured based on the second voltage and the conversion coefficient.

[0007] As a preferred embodiment, step S1 includes: S11. In a controllable magnetic field environment, the first magnetometer is used to measure the artificially controlled magnetic field, and the frequency of the artificially controlled magnetic field output by the output module of the first magnetometer is measured using a frequency meter. S12. Disconnect the radio frequency coil of the first magnetometer from its output module, connect the signal generating device to the radio frequency coil, and perform frequency sweep output with the human-controlled magnetic field frequency as the center frequency; S13. Use the output signal of the signal generator as the reference signal of the lock-in amplifier, use the signal output by the first magnetometer output module as the input signal of the lock-in amplifier, and use the lock-in amplifier to measure the phase difference between the reference signal and the input signal and convert it into a first voltage. S14. The conversion coefficient is calculated based on the magnetic field strength of the artificially controllable magnetic field and the first voltage.

[0008] As a preferred option: The coil is placed inside a magnetic shielding cylinder, which isolates the external magnetic field. Connect a current source to the coil, and drive the coil to generate the artificially controllable magnetic field.

[0009] As a preferred option: The coil is a torque-free coil or a Helmholtz coil.

[0010] As a preferred embodiment, step S2 includes: S21. Disconnect the radio frequency coil of the first magnetometer from its output module, and connect the output terminal of the second magnetometer to the radio frequency coil of the first magnetometer. S22. Use the output signal of the second magnetometer as the reference signal of the lock-in amplifier, and use the output signal of the first magnetometer output module as the input signal of the lock-in amplifier. Measure the phase difference between the reference signal and the input signal using the lock-in amplifier and convert it into a second voltage. S23. Calculate the magnetic field strength of the magnetic field to be measured based on the second voltage and the conversion coefficient.

[0011] As a preferred option: Both the first magnetometer and the second magnetometer are self-excited optically pumped magnetometers.

[0012] As a preferred embodiment, the first magnetometer may be placed in any of the following orientations: Along the direction of the magnetic field lines, perpendicular to the direction of the magnetic field lines, or intersecting the direction of the magnetic field lines.

[0013] In a second aspect, the present invention provides a magnetometer system for measuring magnetic fields based on phase difference, for implementing the magnetometer method for measuring magnetic fields as described in the first aspect.

[0014] Thirdly, the present invention provides an electronic device, the computer device including a memory, a processor and a computer program, wherein when the computer program is executed by the processor, it implements the method for measuring magnetic fields by a magnetometer as described in the first aspect.

[0015] Fourthly, the present invention provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the method for measuring magnetic fields using a magnetometer as described in the first aspect.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The magnetic field measurement method of this invention only requires the use of a single-channel high-precision frequency meter when determining the voltage-magnetic field conversion coefficient. Subsequent actual measurement steps can effectively suppress external magnetic field noise using a mature and reliable lock-in amplifier. This avoids the drawbacks of existing gradient measurement techniques that rely on high-precision multi-channel frequency meters, eliminating the need for multi-channel synchronous acquisition technology and high-precision frequency differential calculation circuits. While maintaining the noise suppression level of traditional magnetic gradient measurement techniques, it greatly simplifies the magnetic measurement system and improves measurement stability.

[0017] Further or more detailed beneficial effects will be described in conjunction with specific embodiments in the detailed implementation. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic flowchart of the magnetic field measurement method using a magnetometer as described in Embodiment 1 of the present invention.

[0020] Figure 2 This is a structural diagram of the electronic device described in Embodiment 3 of the present invention.

[0021] Figure 3 This is the magnetic field noise spectrum of the experimental group described in Embodiment 5 of the present invention.

[0022] Figure 4 This is the magnetic field noise spectrum of the control group described in Embodiment 5 of the present invention.

[0023] Icon labels: 200. Electronic devices; 201. Processor; 202. Communication bus; 203. User interface; 204. Network interface; 205. Memory. Detailed Implementation

[0024] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0025] In the following description, several embodiments of the present invention are provided. Different embodiments can be substituted or combined. Therefore, the present invention can also be considered to include all possible combinations of the same and / or different embodiments described. Thus, if one embodiment includes features A, B, and C, and another embodiment includes features B and D, then the present invention should also be considered to include embodiments containing one or more other possible combinations of A, B, C, and D, even if such embodiments are not explicitly described in the following text.

[0026] The following description provides examples and does not limit the scope, applicability, or examples set forth in the claims. Changes may be made to the function and arrangement of the described elements without departing from the scope of the invention. Various processes or components may be appropriately omitted, substituted, or added to the various examples. For example, the described methods may be performed in a different order than described, and various steps may be added, omitted, or combined. Furthermore, features described with respect to some examples may be combined into other examples.

[0027] To facilitate a better understanding of the embodiments of the present invention, its application scenarios will be explained before providing a detailed explanation of the specific implementation methods.

[0028] The magnetic field measurement method using a magnetometer described in this specification is applicable to high-precision magnetic field measurement scenarios requiring effective suppression of environmental magnetic field noise, such as geological exploration, national defense and security, medical examination, scientific research, and industrial inspection. In these scenarios, the application of this magnetic field measurement method aims to replace the complex process of measuring frequency difference and performing differential calculations in traditional methods by measuring the phase difference of the output signals from two magnetometers. This simplifies the system structure, reduces equipment costs, and improves measurement stability while ensuring effective noise suppression.

[0029] The following is a brief explanation of the magnetometer, first magnetometer / second magnetometer, self-excited optically pumped magnetometer, radio frequency coil, output module, artificially controllable magnetic field, controllable magnetic field environment, magnetic shielding cylinder, coil, torque-free coil / Helmholtz coil, signal generating device, frequency meter, lock-in amplifier, conversion coefficient K, phase difference, and gyrometry involved in the various embodiments of this specification: A magnetometer is an instrument used to measure the strength or gradient of a magnetic field. The magnetometer described in this invention specifically refers to an optically pumped magnetometer, which is a quantum magnetic sensor based on the Zeeman effect of alkali metal atoms.

[0030] First Magnetometer / Second Magnetometer: This naming convention is used to distinguish the two magnetometer probes used in this invention. Both the first and second magnetometers are self-excited optically pumped magnetometers, and they are identical in structure and performance. During the calibration phase, only the first magnetometer is used for calibration; during the actual measurement phase, the two magnetometers are connected in a specific manner to form a differential measurement system to suppress common-mode environmental noise.

[0031] Self-excited optically pumped magnetometer: This is one operating mode of the optically pumped magnetometer. In self-excited mode, the magnetometer's radio frequency coil and output module form a positive feedback loop, causing the system to oscillate continuously. The oscillation frequency automatically locks onto the resonant frequency of the atomic system, thus directly outputting a frequency signal proportional to the magnetic field. This operating mode has advantages such as simple structure, fast response speed, and easy acquisition of the output signal.

[0032] Radio frequency (RF) coil: One of the core components of an optically pumped magnetometer, used to apply a radio frequency magnetic field to the atomic gas cell. In a self-excited optically pumped magnetometer, the RF coil is connected to the output module to form a feedback loop; in the method of this invention, the RF coil can be connected to different signal sources (its own output module, signal generator, or the output of a second magnetometer) as needed to achieve different functions.

[0033] Output module: The circuit part of an optically pumped magnetometer used to output the measurement signal. In a self-excited optically pumped magnetometer, the output module typically includes a photodetector, an amplifier circuit, a shaping circuit, etc., and ultimately outputs a frequency signal whose frequency is proportional to the external magnetic field strength.

[0034] Artificially controlled magnetic field: A magnetic field generated artificially during the calibration phase, with known strength and precise controllability. The artificially controlled magnetic field is used to calibrate the conversion factor K and establish a quantitative relationship between the output voltage of the lock-in amplifier and the magnetic field strength. Typically, a precise magnetic field is generated by connecting a current source to a coil (such as a torque-free coil or a Helmholtz coil) and controlling the magnitude of the current.

[0035] A controllable magnetic field environment refers to a pure magnetic space constructed during the calibration phase that can eliminate interference from external environmental magnetic fields. It typically consists of a magnetic shielding cylinder and coils placed inside. The magnetic shielding cylinder isolates the external environmental magnetic field, while the coils generate a known, artificially controlled magnetic field.

[0036] Magnetic shielding cylinder: A cylindrical structure made of high magnetic permeability material (such as permalloy) used to shield external environmental magnetic fields (such as the Earth's magnetic field, laboratory electromagnetic interference, etc.), providing a pure magnetic space free from external interference for calibration experiments. Its geometry should ensure that the magnetic shielding area can completely cover the coils and magnetometer probes placed inside.

[0037] Coil: A device used to generate a magnetic field. Driven by a current source, a uniform magnetic field is generated inside the coil. In this invention, the coil is used to generate an artificially controllable magnetic field during the calibration phase.

[0038] Rectangular coils / Helmholtz coils: two common coil structures capable of generating uniform magnetic fields. A rectangular coil is a specially designed coil with high internal magnetic field uniformity and minimal interference from external magnetic fields; a Helmholtz coil consists of a pair of parallel circular coils, which, when the distance between the two coils equals the coil radius, can generate a highly uniform magnetic field in its central region. This invention preferably uses these two types of coils to ensure the uniformity and accuracy of a controllable magnetic field.

[0039] Signal generating device: An electronic device used to generate precise frequency signals, such as a high-precision signal generator. During the calibration phase of this invention, the signal generating device is connected to the radio frequency coil of the first magnetometer and performs frequency sweep output with the output frequency of the first magnetometer in self-excited mode as the center frequency to simulate drive signals of different frequencies.

[0040] Frequency meter: An electronic device used to accurately measure the frequency of a signal. In this invention, the frequency meter is used only once during the calibration phase to measure the frequency f1 of the artificially controllable magnetic field output by the first magnetometer in self-excited mode, providing a reference frequency for subsequent frequency sweeping and calibration.

[0041] Lock-in amplifier: A precision measuring instrument capable of accurately measuring the phase difference between two signals of the same frequency and linearly converting the phase difference into a voltage output. The lock-in amplifier is the core measuring device of this invention, replacing the expensive and complex high-precision multi-channel frequency meter used in traditional magnetic gradient measurement technology. In this invention, during the calibration phase, the lock-in amplifier measures the phase difference between the signal generator and the output signal of the first magnetometer and outputs a first voltage V1; during the actual measurement phase, it measures the phase difference between the output signal of the second magnetometer and the first magnetometer and outputs a second voltage V2.

[0042] Conversion coefficient K: A key parameter in the method of this invention, defined as the proportionality coefficient between the output voltage of the lock-in amplifier and the frequency difference, with units of V / Hz. The conversion coefficient K is obtained during the calibration stage. In the actual measurement stage, the conversion coefficient K is used to convert the second voltage V2 output by the lock-in amplifier into a frequency difference, thereby calculating the magnetic field strength B of the magnetic field to be measured.

[0043] Phase difference refers to the difference in phase between two signals of the same frequency, usually expressed in degrees or radians. In this invention, phase difference is the core measurement object. Based on the derivation of the atomic Bloch equation, near the resonance point, there is a definite correspondence between the phase of the output signal of the optically pumped magnetometer and the detuning of the external magnetic field relative to the atomic resonance frequency (i.e., the frequency difference). Therefore, by measuring the phase difference, frequency difference information can be indirectly obtained, thereby realizing magnetic field measurement. Simultaneously, since the two magnetometer probes are in the same ambient noise environment, measuring their phase difference can automatically cancel out the influence of common-mode noise.

[0044] Gyromagnetic ratio: An important parameter in atomic physics, denoted by γ and measured in Hz / T. It is an inherent property of atoms, characterizing the ratio of their magnetic moment to angular momentum. For a specific atom (such as cesium-133), the gyromagnetic ratio is constant.

[0045] Example 1: This embodiment provides a method for measuring magnetic fields using a magnetometer based on phase difference. This method establishes a conversion relationship between phase difference voltage and magnetic field strength during the calibration stage, and then uses this conversion relationship during the actual measurement stage to suppress ambient magnetic field noise by measuring the phase difference of the output signals of the two magnetometers, thereby obtaining an accurate value of the magnetic field to be measured.

[0046] like Figure 1 As shown, the method for measuring magnetic fields using a magnetometer includes the following steps: Step S1: Obtain the correspondence between phase difference and voltage using a first magnetometer and a signal generator to determine the conversion coefficient between magnetic field strength and voltage. This step is the calibration stage, aiming to establish a quantitative relationship between the output voltage of the lock-in amplifier and the actual magnetic field strength. By constructing a controllable, noise-free calibration environment, the conversion coefficient used for subsequent actual measurements is obtained using the first magnetometer and the signal generator.

[0047] Specifically, step S1 further includes sub-steps S11 to S14: S11. In a controllable magnetic field environment, the first magnetometer is used to measure the artificially controlled magnetic field, and the frequency of the artificially controlled magnetic field output by the output module of the first magnetometer is measured using a frequency meter.

[0048] First, a controllable magnetic field environment is constructed. Specifically, the coil is placed inside a magnetically shielded cylinder, which isolates the external magnetic field, providing a pure magnetic space free from external interference for the calibration experiment. The magnetically shielded cylinder is made of a high-permeability material, and its geometry ensures that the magnetic shielding area completely covers the coil. A current source is connected to the coil, driving it to generate the artificially controlled magnetic field. The proportionality coefficient between the magnetic field generated by the coil and the driving current should be clearly calibrated to ensure the accuracy of the artificially controlled magnetic field. As a preferred embodiment, the coil is a torque-free coil or a Helmholtz coil; in this embodiment, a torque-free coil is used, and the magnetic field strength at its center is calibrated to 100 nT / mA.

[0049] A first magnetometer is placed at the center of the torque-free coil, and its working posture is adjusted to ensure that it can output a stable magnetic field frequency signal. The first magnetometer is a self-excited optically pumped magnetometer. To avoid the "dead zone" effect of the optically pumped magnetometer (i.e., when the pump light is parallel or perpendicular to the direction of the static magnetic field, the signal output will drop significantly), the placement orientation of the first magnetometer needs to be adjusted so that it maintains a certain angle with the direction of the magnetic field inside the torque-free coil. The placement orientation of the first magnetometer includes, but is not limited to, along the direction of the magnetic field lines, perpendicular to the direction of the magnetic field lines, or intersecting the direction of the magnetic field lines. In this embodiment, it is adjusted to form a 45-degree angle with the direction of the magnetic field to ensure the strongest and most stable signal.

[0050] A current source is activated, generating a stable, artificially controlled magnetic field, denoted as magnetic field strength B1, through a torque-free coil. At this time, the output module of the first magnetometer outputs a frequency signal, the frequency f1 of which is determined by the atomic Larmor frequency, satisfying the relationship f1 = γ1·B1, where γ1 is the gyrometry of the atomic gas used in the first magnetometer. A frequency meter is connected to the output module of the first magnetometer to accurately measure and record the frequency f1 of this output signal.

[0051] S12. Disconnect the radio frequency coil of the first magnetometer from its output module, connect the signal generating device to the radio frequency coil, and perform frequency sweep output with the human-controlled magnetic field frequency as the center frequency.

[0052] Keeping the artificially controllable magnetic field B1 unchanged in step S11, disconnect the connection between the radio frequency coil of the first magnetometer and its own output module, so that it no longer operates in the self-excited oscillation mode. Connect the output terminal of the signal generator (a high-precision signal generator is used in this embodiment) to the radio frequency coil of the first magnetometer.

[0053] The output frequency of the signal generator is set to the center frequency f1 measured in step S11, and a certain sweep frequency range is set (for example, the starting frequency is f1-1kHz and the ending frequency is f1+1kHz), and continuous sweep frequency output is performed. At this time, the radio frequency signal output by the signal generator acts on the atomic gas cell of the first magnetometer through the coil, driving the atomic system to resonate.

[0054] S13. Use the output signal of the signal generator as the reference signal of the lock-in amplifier, use the signal output by the first magnetometer output module as the input signal of the lock-in amplifier, and use the lock-in amplifier to measure the phase difference between the reference signal and the input signal and convert it into a first voltage.

[0055] The output signal of the signal generator (whose frequency varies around f1) is connected to the reference signal input of the lock-in amplifier. The signal output by the first magnetometer output module (which reflects the response of the atomic system under the drive of an external radio frequency field) is connected to the input signal input of the lock-in amplifier.

[0056] A lock-in amplifier (LIA) is an instrument capable of accurately measuring the phase difference between two signals of the same frequency. When the output frequency of the signal generator is precisely equal to the resonant frequency f1 of the atomic system, a specific phase relationship will exist between the response of the atomic system and the driving signal. When the driving frequency deviates from the resonant frequency, this phase difference will change accordingly. The LIA measures the phase difference φ between the reference signal and the input signal in real time, and linearly converts the phase difference φ into a voltage value, denoted as the first voltage V1, according to its internal settings. The LIA continuously outputs V1 during frequency sweep, thus obtaining the phase difference-voltage curve as a function of frequency.

[0057] S14. The conversion coefficient K is calculated based on the magnetic field strength of the artificially controllable magnetic field and the first voltage.

[0058] According to the measurement principle of the optically pumped magnetometer, the Larmor frequency of the atomic system and the strength of the external magnetic field satisfy a certain relationship. Derived from the atomic Bloch equation, it is known that near the resonance point, the phase difference and frequency detuning are linearly related. Therefore, a conversion coefficient K can be defined to link the voltage output of the lock-in amplifier to the frequency. When the output frequency of the signal generator is equal to the frequency f1 measured in step S11, the relationship between the first voltage V1 output by the lock-in amplifier and the magnetic field strength B1 of the artificially controllable magnetic field can be expressed as: γ1·B1= , in, 1 represents the gyromagnetic ratio of the atomic gas in the first magnetometer. From this, the formula for calculating the conversion coefficient K can be obtained as follows: K= , Since f1 = γ1·B1 (i.e., the output frequency of the first magnetometer measured by the frequency meter), the above formula can also be written as: K= , Where V1 is the first voltage output by the lock-in amplifier at frequency f1, and f1 is the first magnetometer output frequency measured by the frequency meter. The conversion factor K is the voltage value corresponding to a unit frequency difference, with units of V / Hz. This conversion factor will be used in the subsequent actual measurement stage to convert the voltage value back into the frequency difference, and then obtain the magnetic field value.

[0059] At this point, the calibration phase is complete, and the key parameter for subsequent measurements—the conversion coefficient K—is obtained.

[0060] Step S2: Connect the output signal of the second magnetometer to the radio frequency coil of the first magnetometer, obtain the phase difference between the output signal of the second magnetometer and the output signal of the first magnetometer, and convert the phase difference into a second voltage.

[0061] This step is the actual measurement stage of this method, aiming to perform measurements in a real magnetic field environment using a calibrated system. By constructing a differential system with two magnetometers and directly measuring their phase difference using a lock-in amplifier, common-mode environmental noise is suppressed.

[0062] Specifically, such as Figure 1 As shown, step S2 further includes sub-steps S21 to S22: S21. Disconnect the RF coil of the first magnetometer from its output module, and connect the output terminal of the second magnetometer to the RF coil of the first magnetometer.

[0063] In the actual magnetic field environment to be measured, first ensure that both the first and second magnetometers are placed in the area to be measured, and that their positions are sufficiently close to ensure that the ambient magnetic field noise is common-mode. The second magnetometer is the same type as the first magnetometer, both being self-excited optically pumped magnetometers.

[0064] Disconnect the RF coil of the first magnetometer from its own output module. Connect the output of the second magnetometer directly to the RF coil of the first magnetometer. At this point, the output signal of the second magnetometer (whose frequency f2 is determined by the magnetic field B2 at the location of the second magnetometer) will act as a driving signal, directly affecting the RF coil of the first magnetometer and driving its atomic system. The output module of the first magnetometer will then output a signal, which is its response to the driving signal from the second magnetometer.

[0065] S22. Use the output signal of the second magnetometer as the reference signal of the lock-in amplifier, and use the output signal of the first magnetometer output module as the input signal of the lock-in amplifier. Measure the phase difference between the reference signal and the input signal using the lock-in amplifier and convert it into a second voltage V2.

[0066] Connect the output signal of the second magnetometer to the reference signal input terminal of the lock-in amplifier. Connect the output signal of the first magnetometer output module to the input signal input terminal of the lock-in amplifier.

[0067] Since the two magnetometer probes are in the same noisy environment, changes in the ambient magnetic field (such as geomagnetic diurnal variations and interference from surrounding electrical appliances) will simultaneously affect the output signals of both probes; this noise is common-mode. When the signal from the second magnetometer drives the first magnetometer, the phase effects of the common-mode noise contained in the output signals of the two probes will cancel each other out. The lock-in amplifier measures the phase difference between the two signals; therefore, its output voltage V2 directly corresponds to the frequency difference caused by the difference in the magnetic fields (B1 - B2) at the locations of the two probes, and the common-mode noise has been effectively suppressed.

[0068] Step S3: Calculate the magnetic field strength of the magnetic field to be measured based on the second voltage and the conversion coefficient.

[0069] After obtaining the second voltage V2 output by the lock-in amplifier, the relevant information of the magnetic field to be measured can be calculated by combining it with the conversion coefficient K obtained in step S1.

[0070] First, the frequency difference between the output signals of the two magnetometers is calculated using the voltage V2 and the conversion factor K. : = V2 / K, Based on the measurement principle of the optically pumped magnetometer, the magnetic field strength B of the magnetic field to be measured can be calculated using the following formula: γ·B= , Wherein, γ is the atomic gas gyrometry ratio of the magnetometer (the first and second magnetometers use the same atoms, so γ is the same), and K is the conversion coefficient obtained in step S14.

[0071] If a specific magnetic field value is required, it can be expressed as: B= , Therefore, the magnetic field measurement method described in this embodiment only requires a single-channel frequency meter for calibration. In actual measurement, it relies entirely on a lock-in amplifier to measure the phase difference voltage, which can effectively suppress ambient magnetic field noise and achieve the measurement of magnetic field strength.

[0072] The magnetic field measurement method described in this embodiment cleverly transforms the traditional measurement of frequency difference into the measurement of phase difference. It uses a lock-in amplifier to replace the expensive and complex multi-channel high-precision frequency meter. While achieving the same or even better noise suppression effect, it greatly simplifies the system structure, reduces costs, and improves the measurement stability of the system.

[0073] Example 2: This embodiment provides a phase difference-based magnetometer system for measuring magnetic fields, used to implement the magnetometer method for measuring magnetic fields as described in Embodiment 1.

[0074] Example 3: like Figure 2 As shown, this embodiment provides an electronic device, which may include: at least one processor, at least one network interface, a user interface, a memory, and at least one communication bus.

[0075] The communication bus can be used to enable communication between the various components mentioned above.

[0076] The user interface may include buttons, and optional user interfaces may also include standard wired interfaces and wireless interfaces.

[0077] The network interface may include, but is not limited to, Bluetooth modules, NFC modules, Wi-Fi modules, etc.

[0078] The processor may include one or more processing cores. It connects various parts of the electronic device via various interfaces and lines, executing instructions, programs, code sets, or instruction sets stored in memory, and accessing data stored in memory to perform various functions and process data. Optionally, the processor can be implemented using at least one hardware form of DSP, FPGA, or PLA. The processor may integrate one or more of the following: CPU, GPU, and modem. The CPU primarily handles the operating system, user interface, and applications; the GPU is responsible for rendering and drawing the content required for display; and the modem handles wireless communication. It is understood that the modem may also be implemented as a separate chip without being integrated into the processor.

[0079] The memory may include RAM or ROM. Optionally, the memory may include a non-transitory computer-readable medium. The memory can be used to store instructions, programs, code, code sets, or instruction sets. The memory may include a program storage area and a data storage area, wherein the program storage area may store instructions for implementing an operating system, instructions for at least one function (such as touch function, sound playback function, image playback function, etc.), instructions for implementing the above-described method embodiments, etc.; the data storage area may store data involved in the above-described method embodiments, etc. Optionally, the memory may also be at least one storage device located remotely from the aforementioned processor. The memory, as a computer storage medium, may include an operating system, a network communication module, a user interface module, and a measurement application program. The processor can be used to call the measurement application program stored in the memory and execute the steps of the magnetometer measurement magnetic field method mentioned in the foregoing embodiments.

[0080] Example 4: This embodiment provides a computer-readable storage medium storing instructions that, when executed on a computer or processor, cause the computer or processor to perform the above-described instructions. Figure 1 One or more steps in the illustrated embodiment. If the constituent modules of the above-described electronic device are implemented as software functional units and sold or used as independent products, they can be stored in the computer-readable storage medium.

[0081] In the above embodiments, implementation can be achieved, in whole or in part, through software, hardware, firmware, or any combination thereof. When implemented in software, it can be implemented, in whole or in part, as a computer program product. The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, all or part of the processes or functions described in the embodiments of this specification are generated. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in or transmitted through a computer-readable storage medium. The computer instructions can be transmitted from one website, computer, server, or data center to another website, computer, server, or data center via wired (e.g., coaxial cable, fiber optic, Digital Subscriber Line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) means. The computer-readable storage medium can be any available medium accessible to a computer or a data storage device such as a server or data center that integrates one or more available media. The available media may be magnetic media (e.g., floppy disks, hard disks, magnetic tapes), optical media (e.g., Digital Versatile Discs (DVDs)), or semiconductor media (e.g., Solid State Disks (SSDs)).

[0082] Those skilled in the art will understand that all or part of the processes in the method of Embodiment 1 described above can be implemented by a computer program instructing related hardware. This program can be stored in a computer-readable storage medium, and when executed, it can include the processes of the embodiments of the methods described above. The aforementioned storage medium includes various media capable of storing program code, such as ROM, RAM, magnetic disks, or optical disks. Unless otherwise specified, the technical features of this embodiment and the implementation scheme can be combined arbitrarily.

[0083] Example 5: To verify the effectiveness of the phase difference-based magnetometer method for measuring magnetic fields described in this specification, this embodiment compares the magnetic field measurement results of a single optically pumped magnetometer (control group) with a dual magnetometer system using the method of this invention (experimental group) under the same environment, in order to verify the suppression effect of the method of this invention on environmental magnetic field noise.

[0084] The experimental testing platform mainly consists of the following equipment: two self-excited optically pumped magnetometers, serving as the first and second magnetometers; a high-precision frequency meter; a lock-in amplifier (model: SR865A); a signal generator (model: DG4062); a high-precision current source (model: Keysight B2962A 6.5-bit low-noise high-precision current source); a magnetic shielding cylinder; and a torque-free coil.

[0085] During the experiment, the torque-free coil was placed inside a magnetically shielded cylinder to isolate it from external magnetic field interference. A current source was connected to the torque-free coil, driving it to generate a stable, artificially controllable magnetic field. The magnetic field strength at the center of the torque-free coil was calibrated to be 100 nT / mA.

[0086] Two self-excited optically pumped magnetometer probes are placed near the center of the torque-free coil, and their placement direction is adjusted so that they are at a certain angle to the direction of the magnetic field (45 degrees in this embodiment) to avoid the "dead zone" effect of the optically pumped magnetometer and ensure stable output signal.

[0087] The calibration phase is performed according to step S1 as described in Example 1, specifically: First, a stable, artificially controlled magnetic field, denoted as magnetic field strength B1, is generated by driving a torque-free coil with a current source. This magnetic field is measured using a first magnetometer, and the frequency signal output by its output module is precisely measured by a frequency meter and denoted as f1. In this experiment, the average frequency output by the first magnetometer is 100.142 kHz.

[0088] Subsequently, disconnect the RF coil of the first magnetometer from its output module, and connect the output terminal of the signal generator to the RF coil of the first magnetometer. Set the output frequency of the signal generator to f1 (100.142kHz) as the center frequency, the starting frequency to 99.142kHz, and the ending frequency to 101.142kHz, and perform frequency sweep output.

[0089] The output signal of the signal generator is used as the reference signal of the lock-in amplifier, and the signal output by the first magnetometer output module is used as the input signal of the lock-in amplifier. The lock-in amplifier measures the phase difference between the reference signal and the input signal and converts it into a first voltage V1 output. During the frequency sweep process, when the output frequency of the signal generator is equal to f1, the first voltage V1 output by the lock-in amplifier is recorded, and the conversion coefficient K is calculated. In this experiment, the calculated conversion coefficient K = 0.106V / Hz.

[0090] The measurement phase involves performing actual magnetic field measurements according to steps S2 to S3 as described in Example 1, specifically: Disconnect the RF coil of the first magnetometer from its output module, and directly connect the output of the second magnetometer to the RF coil of the first magnetometer. At this point, the output signal of the second magnetometer acts as a drive signal on the RF coil of the first magnetometer.

[0091] The output signal of the second magnetometer is used as the reference signal of the lock-in amplifier, and the output signal of the first magnetometer output module is used as the input signal of the lock-in amplifier. The lock-in amplifier measures the phase difference between the two signals and converts it into a second voltage V2 output. The voltage data output by the lock-in amplifier is continuously acquired using a data acquisition card, and the acquired voltage data V2 is converted into magnetic field data to obtain the time series of the magnetic field strength B of the magnetic field to be measured.

[0092] To verify the noise suppression effect of the method of the present invention, a control group experiment was set up. Under the same experimental environment, only a single optically pumped magnetometer (first magnetometer) was used to directly measure the magnetic field in self-excited mode. The output signal of the first magnetometer was connected to a frequency meter, and its output frequency was directly recorded and converted into magnetic field data.

[0093] The magnetic field data measured in the experimental group (using the method of this invention) and the control group (using a single magnetometer) were processed by Fast Fourier Transform (FFT) to obtain magnetic field noise spectra, as shown below. Figure 3 and Figure 4 As shown.

[0094] contrast Figure 3 and Figure 4 It can be seen that: The control group had an ambient common-mode noise intensity of 8 nT at 33 Hz, while the experimental group's noise intensity at the same frequency was reduced to 0.018 nT. Calculations show that the method of this invention attenuates ambient common-mode noise by approximately 40 times.

[0095] The background noise level of the control group at 1Hz was The background noise level of the experimental group at 1Hz decreased to It is evident that the method of the present invention improves the suppression of background noise by at least one order of magnitude.

[0096] The above experimental data fully demonstrate that the phase difference-based magnetometer method for measuring magnetic fields described in this invention has significant advantages in noise suppression. By converting the traditional measurement of frequency difference into the measurement of phase difference, and using a lock-in amplifier to replace a high-precision multi-channel frequency meter, this invention effectively suppresses environmental magnetic field noise while simplifying the system structure, reducing equipment costs, and improving measurement stability.

[0097] It should be noted that, for the sake of simplicity, the foregoing method embodiments are all described as a series of actions. However, those skilled in the art should understand that the present invention is not limited to the described order of actions, because according to the present invention, some steps can be performed in other orders or simultaneously. Furthermore, those skilled in the art should also understand that the embodiments described in the specification are preferred embodiments, and the actions and modules involved are not necessarily essential to the present invention.

[0098] In the above embodiments, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0099] The above description is merely an exemplary embodiment of the present invention and should not be construed as limiting the scope of the invention. Any equivalent changes and modifications made in accordance with the teachings of this invention are still within the scope of this invention. Those skilled in the art will readily conceive of embodiments of the invention upon considering the specification and practicing the disclosure herein. This invention is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not described herein. The specification and embodiments are to be considered exemplary only, and the scope and spirit of the invention are defined by the claims.

Claims

1. A method for measuring magnetic fields using a magnetometer based on phase difference, characterized in that, Including the following steps: S1. Obtain the relationship between phase difference and voltage through the first magnetometer and signal generator to determine the conversion coefficient between magnetic field strength and voltage; S2. Connect the output signal of the second magnetometer to the radio frequency coil of the first magnetometer, obtain the phase difference between the output signal of the second magnetometer and the output signal of the first magnetometer, and convert the phase difference into a second voltage; S3. Calculate the magnetic field strength of the magnetic field to be measured based on the second voltage and the conversion coefficient.

2. The method for measuring magnetic fields using a magnetometer based on phase difference according to claim 1, characterized in that, Step S1 includes: S11. In a controllable magnetic field environment, the first magnetometer is used to measure the artificially controlled magnetic field, and the frequency of the artificially controlled magnetic field output by the output module of the first magnetometer is measured using a frequency meter. S12. Disconnect the radio frequency coil of the first magnetometer from its output module, connect the signal generating device to the radio frequency coil, and perform frequency sweep output with the human-controlled magnetic field frequency as the center frequency; S13. Use the output signal of the signal generator as the reference signal of the lock-in amplifier, use the signal output by the first magnetometer output module as the input signal of the lock-in amplifier, and use the lock-in amplifier to measure the phase difference between the reference signal and the input signal and convert it into a first voltage. S14. The conversion coefficient is calculated based on the magnetic field strength of the artificially controllable magnetic field and the first voltage.

3. The method for measuring magnetic fields using a magnetometer based on phase difference according to claim 2, characterized in that: The coil is placed inside a magnetic shielding cylinder, which isolates the external magnetic field. Connect a current source to the coil, and drive the coil to generate the artificially controllable magnetic field.

4. The method for measuring magnetic fields using a magnetometer based on phase difference according to claim 3, characterized in that: The coil is a torque-free coil or a Helmholtz coil.

5. The method for measuring magnetic fields using a magnetometer based on phase difference according to claim 1, characterized in that, Step S2 includes: S21. Disconnect the radio frequency coil of the first magnetometer from its output module, and connect the output terminal of the second magnetometer to the radio frequency coil of the first magnetometer. S22. Use the output signal of the second magnetometer as the reference signal of the lock-in amplifier, and use the output signal of the first magnetometer output module as the input signal of the lock-in amplifier. Measure the phase difference between the reference signal and the input signal using the lock-in amplifier and convert it into a second voltage. S23. Calculate the magnetic field strength of the magnetic field to be measured based on the second voltage and the conversion coefficient.

6. The method for measuring magnetic fields using a magnetometer based on phase difference according to claim 1, characterized in that: Both the first magnetometer and the second magnetometer are self-excited optically pumped magnetometers.

7. The method for measuring magnetic fields using a magnetometer based on phase difference according to claim 6, characterized in that, The placement orientation of the first magnetometer includes any of the following: Along the direction of the magnetic field lines, perpendicular to the direction of the magnetic field lines, or intersecting the direction of the magnetic field lines.

8. A magnetic field measurement system based on a phase difference magnetometer, characterized in that, Used to implement the method for measuring magnetic fields with a magnetometer as described in any one of claims 1 to 7.

9. A computer device, the computer device comprising a memory, a processor, and a computer program, characterized in that, When the computer program is executed by the processor, it implements the method for measuring magnetic fields using a magnetometer as described in any one of claims 1 to 7.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the method for measuring magnetic fields using a magnetometer as described in any one of claims 1 to 7.

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