A light-pumped magnetometer and its frequency-hopping closed-loop control method

Abstract

This invention relates to the field of weak magnetic field detection and navigation positioning technology, and provides an optically pumped magnetometer and its frequency-hopping closed-loop control method. The method includes obtaining the initial operating point of the radio frequency coil and the initial center frequency of the radio frequency magnetic field by frequency sweeping; setting a hopping frequency, constructing a frequency-hopping magnetic field based on the hopping frequency and the initial center frequency of the radio frequency magnetic field; applying the frequency-hopping magnetic field with the initial operating point of the radio frequency coil as the center point, and obtaining the resonant frequency by adjusting the initial center frequency of the radio frequency magnetic field to make the amplitudes of the two frequency-hopping frequencies equal, and converting the resonant frequency into an external magnetic field value. This invention obtains the measurement result of the magnetic field under test using the signal amplitude value without relying on the signal observation phase, avoiding measurement errors caused by phase measurement errors or phase noise fluctuations.

Description

Technical Field

[0001] This invention relates to the field of weak magnetic field detection and navigation positioning technology, and in particular to an optically pumped magnetometer and its frequency hopping closed-loop control method. Background Technology

[0002] The main physical principle of an optically pumped magnetometer is to use optical pumping to concentrate alkali metal atoms from various Zeeman sublevels to a specific Zeeman sublevel. After the optical pumping ends, the atoms are concentrated in one or two sublevels and no longer absorb light. At this point, a radio frequency field is introduced. When the frequency of the radio frequency field equals the Larmor precession frequency, a photomagnetic resonance effect is generated. When the energy of the radio frequency field satisfies the energy difference between the Zeeman sublevels, the atoms originally concentrated in one or two sublevels are redistributed to other Zeeman sublevels. This effect can be used to measure external magnetic fields.

[0003] The optically pumped magnetometer consists of two parts: a magnetic sensing probe and a closed-loop control system. The magnetic sensing probe includes a laser, several polarization optics, an atomic gas cell, a radio frequency coil, and a photodetector. Its function is to acquire the current signal output by the system under magnetic resonance conditions and transmit it to the closed-loop control system. The closed-loop control system calculates the Larmor precession frequency under magnetic resonance conditions from the current signal transmitted from the magnetic sensing probe, thereby obtaining the value of the magnetic field to be measured. Simultaneously, it adjusts the radio frequency magnetic field in real time to achieve closed-loop control of the system.

[0004] The working process of the magnetic sensing probe is as follows: First, the magnetic sensing probe is placed in the magnetic field environment to be measured, with its axis at an angle to the direction of the magnetic field. The laser beam, after passing through a half-wave plate, a polarizing beam splitter, and a quarter-wave plate, becomes parallel left-handed circularly polarized light and enters the atomic gas cell. Due to the external magnetic field, the Zeeman sublevels of the atoms split, resulting in optical pumping under the influence of the left-handed circularly polarized light. At this point, a uniform radio frequency magnetic field is generated by the radio frequency coil. When the frequency of the radio frequency magnetic field equals the Larmor precession frequency of the atoms, a photomagnetic double resonance effect occurs. The intensity of the light beam passing through the gas cell varies with the radio frequency signal frequency and has a 90° phase shift relative to the radio frequency signal; this optical signal is the photodetector magnetic resonance signal. This signal is converted into a current signal output by a photodetector; this current signal is the measured signal output by the magnetic sensing probe. The amplitude, phase, and frequency information of this signal are detected in the closed-loop control system, which then controls the radio frequency coil, thus forming a closed-loop system.

[0005] In traditional control schemes, a lock-in amplifier circuit is used. Based on the characteristic that the phase of the signal differs from that of the radio frequency signal by 90°, the phase of the signal to be measured is used as the controlled variable. By adjusting the frequency of the radio frequency magnetic field, the phase is compensated by 90° and controlled to be near 0°, so as to achieve closed-loop control. Summary of the Invention

[0006] This invention aims to at least solve one of the technical problems existing in related technologies. To this end, this invention provides an optically pumped magnetometer and its frequency-hopping closed-loop control method. The method involves obtaining the initial operating point of the radio frequency coil and the initial center frequency of the radio frequency magnetic field through frequency sweeping; setting a hopping frequency; constructing a frequency-hopping magnetic field based on the hopping frequency and the frequency value of the initial operating point; applying the frequency-hopping magnetic field with the initial operating point of the radio frequency coil as the center point; and obtaining the resonant frequency by adjusting the initial center frequency of the radio frequency magnetic field to make the amplitudes at the two hopping frequencies equal. The resonant frequency is then converted into an external magnetic field value. This invention obtains the measurement result of the magnetic field under test using the signal amplitude value without relying on the signal observation phase, avoiding measurement errors caused by phase measurement errors or phase noise fluctuations.

[0007] This invention provides a frequency-hopping closed-loop control method for an optically pumped magnetometer, comprising:

[0008] S1: Obtain the initial operating point of the RF coil and the initial center frequency of the RF magnetic field by frequency sweeping;

[0009] S2: Set the switching frequency and construct the frequency-hopping magnetic field based on the switching frequency and the initial center frequency of the radio frequency magnetic field;

[0010] S3: With the initial operating point of the RF coil as the center point, apply a frequency-hopping magnetic field. By adjusting the initial center frequency of the RF magnetic field, make the amplitudes of the two frequency-hopping frequencies equal, and obtain the resonant frequency.

[0011] S4: Convert the resonant frequency into an external magnetic field value.

[0012] Furthermore, step S1 includes:

[0013] Set the operating frequency and sweep step size of the RF coil. Starting from the frequency corresponding to the minimum range value of the RF coil operating frequency according to the sweep step size, sweep the frequency to the frequency corresponding to the maximum range value according to the sweep step size, and record the output signal amplitude.

[0014] Save the operating point with the largest amplitude and the frequency value of the operating point with the largest amplitude;

[0015] The operating point frequency with the largest amplitude is taken as the initial center frequency of the radio frequency magnetic field, and the operating point with the largest amplitude is taken as the initial operating point of the radio frequency coil.

[0016] Furthermore, the switching frequency is half the frequency difference between two frequency points that is 0.5 times the maximum amplitude.

[0017] Furthermore, the frequency-hopping magnetic field is a radio frequency magnetic field with a frequency of the initial center frequency of the radio frequency magnetic field plus the switching frequency applied in the first half of the same cycle, and a radio frequency magnetic field with a frequency of the initial center frequency of the radio frequency magnetic field minus the switching frequency applied in the second half of the cycle.

[0018] Furthermore, step S3 includes:

[0019] Set a first amplitude threshold K, and let the applied radio frequency magnetic field frequency be... The amplitude of the output signal at that time is The applied radio frequency magnetic field frequency is The amplitude of the output signal at that time is ,in, The initial center frequency of the radio frequency magnetic field. For the frequency jump;

[0020] when If necessary, rescan the frequency to determine. ;

[0021] when At that time, the center frequency of the radio frequency magnetic field is adjusted by PID control or conditional judgment method to make To obtain the resonant frequency.

[0022] Furthermore, PID control includes:

[0023] The error quantity is obtained, and the expression for calculating the error quantity is:

[0024]

[0025] in, This is the error amount;

[0026] The resonant frequency is obtained through PID control, and the calculation expression is as follows:

[0027]

[0028] in, for The resonant frequency at a given moment for The resonant frequency at a given moment This is the proportionality coefficient. The integral coefficient is... These are the differential coefficients. for Error term at time, for Error term at time, for Error term for time.

[0029] Furthermore, the conditional judgment method includes:

[0030] Set a second amplitude threshold It is 0.75 times the maximum amplitude, and the calculation expression is:

[0031]

[0032] in, This represents the maximum amplitude.

[0033] like ,but and Located on the same side of the resonant frequency,

[0034] when and When it is located to the right of the resonant frequency, then ;

[0035] when and When it is located to the left of the resonant frequency, then ;

[0036] like ,but and Located on both sides of the resonant frequency,

[0037] when hour, Located to the right of the resonant frequency, it needs to be reduced. The value;

[0038] when hour, Located to the left of the resonant frequency, it needs to be increased. The value;

[0039] when hour, It equals the resonant frequency.

[0040] Furthermore, the expression for calculating the external magnetic field value is as follows:

[0041]

[0042] in, The value of the external magnetic field. The resonant frequency, It is the gyromagnetic ratio.

[0043] This invention also provides an optically pumped magnetometer for implementing the aforementioned frequency-hopping closed-loop control method for an optically pumped magnetometer, comprising a magnetic sensing probe and a closed-loop control system.

[0044] The magnetic sensing probe includes a laser, which emits laser light. The laser light is converted into parallel left-handed circularly polarized light by passing through a half-wave plate, a polarizing beam splitter, and a quarter-wave plate in sequence. The parallel left-handed circularly polarized light enters the atomic gas cell and is then converted into an electrical signal by a photodetector. The electrical signal generates a radio frequency magnetic field signal through the closed-loop control system. The radio frequency magnetic field signal is sent to the radio frequency coil. The radio frequency coils on both sides of the atomic gas cell generate a radio frequency magnetic field and apply it to the atomic gas cell.

[0045] Furthermore, the alkali metal atoms used in the atomic gas chamber include any one of potassium, rubidium, and cesium.

[0046] The above-described one or more technical solutions in the embodiments of the present invention have at least one of the following technical effects:

[0047] This invention achieves closed-loop control by adjusting the signal amplitude, without relying on the signal's phase information throughout the process. This fundamentally avoids the impact of potential errors and phase noise fluctuations on the measurement results during phase measurement, thereby improving measurement stability.

[0048] By utilizing the symmetry of signal amplitude for closed-loop control, and comparing the output amplitude at different frequencies through frequency hopping and adjusting the center frequency, the resonant frequency can be locked more accurately, thereby obtaining more precise external magnetic field measurement results.

[0049] By continuously monitoring the amplitude relationship at the frequency hopping frequency and dynamically adjusting the center frequency of the radio frequency magnetic field, it is possible to track changes in the external magnetic field in real time, ensuring the real-time performance of magnetic field measurement. This is suitable for scenarios that require dynamic monitoring of the magnetic field.

[0050] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0051] To more clearly illustrate the technical solutions in this 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 some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0052] Figure 1 This is a flowchart illustrating a frequency-hopping closed-loop control method for an optically pumped magnetometer provided by the present invention.

[0053] Figure 2 This is a structural block diagram of an optically pumped magnetometer provided by the present invention.

[0054] Figure 3This is a schematic diagram of the frequency hopping setting of a frequency hopping closed-loop control method for an optically pumped magnetometer provided by the present invention.

[0055] Figure label:

[0056] 1. Laser; 2. Half-wave plate; 3. Polarizing beam splitter; 4. Quarter-wave plate; 5. Radio frequency coil; 6. Atomic gas cell; 7. Photodetector; 8. Closed-loop control system. Detailed Implementation

[0057] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention. The following embodiments are used to illustrate this invention but cannot be used to limit the scope of this invention.

[0058] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0059] The following is combined Figures 1 to 3 This invention describes an optically pumped magnetometer and its frequency-hopping closed-loop control method.

[0060] like Figure 2 As shown, an optically pumped magnetometer includes a magnetic sensing probe and a closed-loop control system 8. The magnetic sensing probe includes a laser 1, which emits laser light. The laser light passes sequentially through a half-wave plate 2, a polarizing beam splitter 3, and a quarter-wave plate 4 to be converted into parallel left-handed circularly polarized light. The parallel left-handed circularly polarized light enters an atomic gas cell 6 and is then converted into an electrical signal by a photodetector 7. The electrical signal generates a radio frequency magnetic field signal through the closed-loop control system 8. The radio frequency magnetic field signal is sent to a radio frequency coil 5. The radio frequency coils on both sides of the atomic gas cell 6 generate a radio frequency magnetic field and apply it to the atomic gas cell 6 to achieve closed-loop control.

[0061] The alkali metal atoms used in atomic gas chamber 6 include any one of potassium, rubidium, and cesium.

[0062] In some specific embodiments of the invention, the laser generates laser light of a specific frequency with a wavelength of 795 nm, and the alkali metal atoms in the atomic gas cell are rubidium atoms. The corresponding laser wavelength can be selected based on the different alkali metal atoms. Due to the influence of the external magnetic field, the Zeeman sublevels of the atoms in the atomic gas cell split, resulting in optical pumping under the influence of left-handed circularly polarized light. At this time, a uniform radio frequency magnetic field is generated by the radio frequency coil. When the frequency of the radio frequency magnetic field equals the Larmor precession frequency of the atoms, a photomagnetic double resonance effect is generated. The intensity of the light beam passing through the gas cell varies with the radio frequency signal frequency. This is converted into a current signal output by a photodetector, and this current signal is the measured signal output by the magnetic sensing probe. The amplitude, phase, and frequency information of this signal are detected in the closed-loop control system, thereby controlling the frequency of the radio frequency coil to form a closed-loop system.

[0063] like Figure 1 As shown, a frequency-hopping closed-loop control method for an optically pumped magnetometer, implemented using the aforementioned optically pumped magnetometer, includes:

[0064] S1: Obtain the initial operating point of the RF coil and the initial center frequency of the RF magnetic field by frequency sweeping;

[0065] After powering on and waiting for the atomic gas chamber to heat up to the designated temperature, turn on the laser.

[0066] Set the operating frequency and sweep step size of the RF coil. Starting from the frequency corresponding to the minimum range value of the RF coil operating frequency according to the sweep step size, sweep the frequency to the frequency corresponding to the maximum range value according to the sweep step size, and record the output signal amplitude.

[0067] Save the operating point with the largest amplitude and the frequency value of the operating point with the largest amplitude;

[0068] The operating point frequency with the largest amplitude is taken as the initial center frequency of the radio frequency magnetic field, and the operating point with the largest amplitude is taken as the initial operating point of the radio frequency coil.

[0069] In some specific embodiments of the present invention, the frequency corresponding to the minimum range is 70kHz, and the frequency corresponding to the maximum range is 700kHz.

[0070] S2: Set the switching frequency and construct the frequency-hopping magnetic field based on the switching frequency and the initial center frequency of the radio frequency magnetic field;

[0071] like Figure 3 As shown, the switching frequency is set to half the frequency difference between two frequency points, which is 0.5 times the maximum amplitude.

[0072] In some specific embodiments of the invention, the switching frequency is set to 830Hz.

[0073] A frequency-hopping magnetic field is a radio frequency magnetic field with a frequency of the initial center frequency plus the hopping frequency applied in the first half of the same cycle, and a frequency of the initial center frequency minus the hopping frequency applied in the second half of the cycle. This is continuously applied in a cyclical manner, so that the frequency of the radio frequency magnetic field always switches between the initial center frequency plus the hopping frequency and the initial center frequency minus the hopping frequency.

[0074] S3: With the initial operating point of the RF coil as the center point, apply a frequency-hopping magnetic field. By adjusting the initial center frequency of the RF magnetic field, make the amplitudes of the two frequency-hopping frequencies equal, and obtain the resonant frequency.

[0075] When the frequency of the radio frequency magnetic field is far from the resonance point, the output signal amplitude is very small. Only when the frequency of the radio frequency magnetic field is near the resonance point is the output signal amplitude large. When the frequency of the radio frequency magnetic field is exactly at the resonance point, the signal amplitude reaches its maximum value.

[0076] Set a first amplitude threshold K, and let the applied radio frequency magnetic field frequency be... The amplitude of the output signal at that time is The applied radio frequency magnetic field frequency is The amplitude of the output signal at that time is ,in, The initial center frequency of the radio frequency magnetic field. For the frequency jump;

[0077] when If necessary, rescan the frequency to determine. ;

[0078] when At that time, the center frequency of the radio frequency magnetic field is adjusted by PID control or conditional judgment method to make To obtain the resonant frequency.

[0079] In some specific embodiments of the invention, K is set as the signal amplitude at a frequency of 5000Hz.

[0080] PID control includes:

[0081] The error quantity is obtained, and the expression for calculating the error quantity is:

[0082]

[0083] in, This is the error amount;

[0084] The resonant frequency is obtained through PID control, and the calculation expression is as follows:

[0085]

[0086] in, for The resonant frequency at a given moment for The resonant frequency at a given moment This is the proportionality coefficient. The integral coefficient is... These are the differential coefficients. for Error term at time, for Error term at time, for Error term for time.

[0087] By adjusting , , The value of can be used to achieve frequency control.

[0088] Conditional judgment methods include:

[0089] Set a second amplitude threshold The initial center frequency of the radio frequency magnetic field is determined by the amplitude summation and comparison method. Is it far from the resonant frequency? If Being slightly further away from the resonant frequency makes and These two frequency points are located on the same side of the resonant frequency but on the outer side. Significant adjustment is required at this point. The value of makes To approach the resonant frequency point more quickly. Judgment and There are many ways to determine whether these two frequency points are on opposite sides or on the same side of the resonant frequency. This invention adopts the amplitude summation comparison method.

[0090] Specifically, a second amplitude threshold is set. It is 0.75 times the maximum amplitude, and the calculation expression is:

[0091]

[0092] in, This represents the maximum amplitude.

[0093] like ,but and Located on the same side of the resonant frequency, at this time and The size relationship remains constant, and all require significant adjustment. The value of makes Approaching the resonant frequency point more quickly

[0094] when and When it is located to the right of the resonant frequency, then ;

[0095] when and When it is located to the left of the resonant frequency, then ;

[0096] like ,but and Located on either side of the resonant frequency, due to the symmetry of the signal amplitude, their amplitudes are nearly equal. Therefore, it is necessary to slowly adjust the center frequency. The value of makes and The values ​​satisfy the equality condition;

[0097] when hour, Located to the right of the resonant frequency, it needs to be reduced. The value;

[0098] when hour, Located to the left of the resonant frequency, it needs to be increased. The value;

[0099] when hour, It equals the resonant frequency.

[0100] The second amplitude threshold Setting it to 0.75 times the maximum amplitude will make To rapidly approach the resonant frequency while maintaining stability at the resonant frequency, the jump frequency is set to half the frequency difference between the two frequency points (0.5 times the maximum amplitude). This allows for accurate judgment. and When considering the size relationship, and The steepest slope of the change is beneficial for stable control of the center frequency point.

[0101] S4: Convert the resonant frequency into an external magnetic field value;

[0102] The expression for calculating the value of the external magnetic field is as follows:

[0103]

[0104] in, The value of the external magnetic field. The resonant frequency, It is the gyromagnetic ratio.

[0105] In some specific embodiments of the present invention .

[0106] This invention, after powering on and waiting for the atomic gas chamber to heat to the specified temperature, turns on the laser, sets the operating frequency and sweep step size of the RF coil, and gradually increases the frequency from the minimum range to the maximum range, recording the output signal amplitude during this process and saving the frequency value of the point with the maximum amplitude. After the sweep is complete, this frequency value is set as the initial operating point frequency value. Next, a frequency-hopping magnetic field is applied to the RF coil to... Centered on point , apply a frequency value that repeats over time. and That is, within the same cycle, the frequency applied in the first half of the cycle is The radio frequency magnetic field is applied at a frequency of [frequency value missing] during the second half-cycle. A radio frequency magnetic field is continuously applied in a cyclical manner, and the frequency of the radio frequency magnetic field remains constant at... Switching between them. Utilizing the symmetry of the output signal amplitude, the amplitude relationship is determined and continuously adjusted. The value, ultimately when the frequency is and When the signal output amplitudes are equal, at this time This is the resonant frequency, and the magnitude of the magnetic field to be measured can be obtained by conversion.

[0107] This invention achieves closed-loop control by adjusting the signal amplitude, without relying on the signal's phase information throughout the process. This fundamentally avoids the impact of potential errors and phase noise fluctuations on the measurement results during phase measurement, thereby improving measurement stability.

[0108] By utilizing the symmetry of signal amplitude for closed-loop control, and comparing the output amplitude at different frequencies through frequency hopping and adjusting the center frequency, the resonant frequency can be locked more accurately, thereby obtaining more precise external magnetic field measurement results.

[0109] By setting the first amplitude threshold To determine whether the system needs to be rescanned, the center frequency gain is dynamically adjusted by using the amplitude summation comparison method. This ensures that the system can respond quickly and operate stably when the magnetic field changes, thereby improving the system's anti-interference capability and reliability.

[0110] By continuously monitoring the amplitude relationship at the frequency hopping frequency and dynamically adjusting the center frequency of the radio frequency magnetic field, it is possible to track changes in the external magnetic field in real time, ensuring the real-time performance of magnetic field measurement. This is suitable for scenarios that require dynamic monitoring of the magnetic field.

[0111] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A frequency-hopping closed-loop control method for an optically pumped magnetometer, characterized in that, include: S1: Obtain the initial operating point of the RF coil and the initial center frequency of the RF magnetic field by frequency sweeping; S2: Set the switching frequency and construct the frequency-hopping magnetic field based on the switching frequency and the initial center frequency of the radio frequency magnetic field; S3: With the initial operating point of the RF coil as the center point, apply a frequency-hopping magnetic field. By adjusting the initial center frequency of the RF magnetic field, make the amplitudes of the two frequency-hopping frequencies equal, and obtain the resonant frequency. S4: Convert the resonant frequency into an external magnetic field value.

2. The frequency-hopping closed-loop control method for an optically pumped magnetometer according to claim 1, characterized in that, Step S1 includes: Set the operating frequency and sweep step size of the RF coil. Starting from the frequency corresponding to the minimum range value of the RF coil operating frequency according to the sweep step size, sweep the frequency to the frequency corresponding to the maximum range value according to the sweep step size, and record the output signal amplitude. Save the operating point with the largest amplitude and the frequency value of the operating point with the largest amplitude; The operating point frequency with the largest amplitude is taken as the initial center frequency of the radio frequency magnetic field, and the operating point with the largest amplitude is taken as the initial operating point of the radio frequency coil.

3. The frequency-hopping closed-loop control method for an optically pumped magnetometer according to claim 1, characterized in that, The switching frequency is half the frequency difference between two frequency points that are 0.5 times the maximum amplitude.

4. The frequency-hopping closed-loop control method for an optically pumped magnetometer according to claim 1, characterized in that, The frequency-hopping magnetic field is a radio frequency magnetic field with a frequency of the initial center frequency of the radio frequency magnetic field plus the jumping frequency applied in the first half of the same cycle, and a frequency of the initial center frequency of the radio frequency magnetic field minus the jumping frequency applied in the second half of the cycle.

5. The frequency-hopping closed-loop control method for an optically pumped magnetometer according to claim 1, characterized in that, Step S3 includes: Set a first amplitude threshold K, and let the applied radio frequency magnetic field frequency be... The amplitude of the output signal at that time is The applied radio frequency magnetic field frequency is The amplitude of the output signal at that time is ,in, The initial center frequency of the radio frequency magnetic field. For the frequency jump; when If necessary, rescan the frequency to determine. ; when At that time, the center frequency of the radio frequency magnetic field is adjusted by PID control or conditional judgment method to make To obtain the resonant frequency.

6. The frequency-hopping closed-loop control method for an optically pumped magnetometer according to claim 5, characterized in that, PID control includes: The error quantity is obtained, and the expression for calculating the error quantity is: in, This is the error amount; The resonant frequency is obtained through PID control, and the calculation expression is as follows: in, for The resonant frequency at a given moment for The resonant frequency at a given moment This is the proportionality coefficient. The integral coefficient is... These are the differential coefficients. for Error term at time, for Error term at time, for Error term for time.

7. The frequency-hopping closed-loop control method for an optically pumped magnetometer according to claim 5, characterized in that, Conditional judgment methods include: Set a second amplitude threshold It is 0.75 times the maximum amplitude, and the calculation expression is: in, This represents the maximum amplitude. like ,but and Located on the same side of the resonant frequency, when and When it is located to the right of the resonant frequency, then ; when and When it is located to the left of the resonant frequency, then ; like ,but and Located on both sides of the resonant frequency, when hour, Located to the right of the resonant frequency, it needs to be reduced. The value; when hour, Located to the left of the resonant frequency, it needs to be increased. The value; when hour, It equals the resonant frequency.

8. The frequency-hopping closed-loop control method for an optically pumped magnetometer according to claim 1, characterized in that, The expression for calculating the value of the external magnetic field is as follows: in, The value of the external magnetic field. The resonant frequency, It is the gyromagnetic ratio.

9. A light-pumped magnetometer, used to implement the frequency-hopping closed-loop control method for a light-pumped magnetometer as described in any one of claims 1 to 8, characterized in that, Including magnetic sensing probes and closed-loop control systems, The magnetic sensing probe includes a laser, which emits laser light. The laser light is converted into parallel left-handed circularly polarized light by passing through a half-wave plate, a polarizing beam splitter, and a quarter-wave plate in sequence. The parallel left-handed circularly polarized light enters the atomic gas cell and is then converted into an electrical signal by a photodetector. The electrical signal generates a radio frequency magnetic field signal through the closed-loop control system. The radio frequency magnetic field signal is sent to the radio frequency coil. The radio frequency coils on both sides of the atomic gas cell generate a radio frequency magnetic field and apply it to the atomic gas cell.

10. A light-pumped magnetometer according to claim 9, characterized in that, The alkali metal atoms used in the atomic gas chamber include any one of potassium, rubidium, and cesium.

Images