Compensation method and device for light intensity matching of radio frequency excitation light source of helium optically pumped magnetometer

Abstract

The invention relates to the technical field of application of helium optically pumped magnetometers for high-precision magnetic field measurement, in particular to a compensation method for light intensity matching of a radio frequency excitation light source of a helium optically pumped magnetometer. Applying high-voltage excitation to the helium lamp and the atomic gas chamber, adjusting the radio-frequency excitation frequency to enable the helium lamp and the atomic gas chamber to be in an impedance matching state, and recording a radio-frequency excitation frequency word at the moment; under the impedance matching frequency, adjusting the gain of the driving circuit, adjusting the light intensity of the helium lamp and the atomic gas chamber to a preset empirical value range, and recording a radio frequency excitation gain value at the moment; in a fixed magnetic field environment, the radio frequency excitation frequency and amplitude are adjusted through iteration, the magnetic field test noise level is monitored and reduced to the minimum, and the optimal radio frequency excitation parameter is recorded. According to the method, redundant and complex radio frequency excitation device parameter debugging work of each helium optically pumped magnetometer caused by the individual difference of the helium lamp and the atomic gas chamber can be avoided, and the adaptability of the helium optically pumped magnetometer to the individual difference of the helium lamp and the atomic gas chamber is improved.

Description

Technical Field

[0001] This invention relates to the field of application technology of helium optical pump magnetometer for high-precision magnetic field measurement, specifically to a compensation method and device for matching the light intensity of the radio frequency excitation light source of a helium optical pump magnetometer. Background Technology

[0002] The helium optically pumped magnetometer is a device that utilizes the interaction between helium atoms and light and magnetic fields to achieve high-precision magnetic field measurement. It boasts advantages such as high sensitivity and a large measurement bandwidth, and is widely used in geophysical exploration, military reconnaissance, and biomedical research. Its core working process includes: a helium lamp excites helium atoms, with the emission peak serving as the detection wavelength; helium atoms in the atomic gas cell transition to a metastable state under high-frequency excitation and undergo Zeeman splitting in an external magnetic field; collimated polarized light illuminates the gas cell, causing the metastable helium atoms to absorb energy and undergo directional transitions, achieving polarization; polarized atoms undergo Larmor precession in the external magnetic field, and magnetic resonance occurs when the radio frequency field frequency matches the precession frequency, leading to changes in the light intensity transmitted through the gas cell. The magnetic field measurement is achieved by detecting these changes in the light signal using a photodetector. The core problem faced by traditional technologies is:

[0003] When helium lamps and atomic gas chambers are operated continuously for a long time or over a wide temperature range (day-night temperature difference, seasonal temperature changes), there is a problem of excitation device parameter drift, which leads to deviation in magnetic field test accuracy and deterioration of noise level.

[0004] Existing methods mitigate the effects of temperature by limiting the operating temperature range or by implementing temperature compensation measures, but they cannot compensate for long-term drift caused by device aging, natural decay of helium chamber parameters, etc.

[0005] Due to limitations in the sintering process, helium lamps and atomic gas chambers exhibit significant individual and batch variations. Under the same excitation energy, the system noise level is inconsistent, requiring targeted adjustment of excitation parameters, which increases the complexity of product design and production.

[0006] Magnetometers using temperature-sensitive light sources cannot adapt to wide temperature environments; temperature compensation technology is costly and can only compensate for parameter changes caused by temperature, but cannot solve the problems of aging and individual differences.

[0007] Traditional methods struggle to adaptively adjust excitation parameters after changes in the capacitive parameters of the helium lamp and the atomic gas chamber, especially since they do not involve intensity matching compensation between the two light sources, making it impossible to dynamically optimize noise performance.

[0008] Currently, helium optically pumped magnetometers lack adaptive adjustment for matching the light intensity of arbitrary helium lamps and atomic gas cells, and lack a dynamic compensation mechanism based on magnetic field noise levels. This results in performance instability in complex environments (such as temperature variations and long-term operation) or mass production scenarios. Therefore, there is an urgent need for a compensation method and device that can balance light intensity stability, optimal noise matching, and environmental adaptability. Summary of the Invention

[0009] This invention provides a compensation method and apparatus for matching the light intensity of the radio frequency excitation light source in a helium optically pumped magnetometer. Its purpose is to achieve stable light intensity of the radio frequency excitation light source and maintain optimal noise levels. The system is simple to implement and highly accurate and efficient, providing strong technical support for the commercialization, mass production, and application in complex environments of helium optically pumped magnetometers.

[0010] To achieve the above objectives, the technical solution of the present invention is as follows:

[0011] A compensation method for intensity matching of the radio frequency excitation light source in a helium optically pumped magnetometer includes the following steps:

[0012] High voltage excitation is applied to the helium lamp and the atomic gas chamber, and the radio frequency excitation frequency is adjusted to make the two impedance matched. The radio frequency excitation frequency at this time is recorded.

[0013] At the impedance matching frequency, adjust the gain of the drive circuit to adjust the light intensity of the helium lamp and the atomic gas cell to the preset empirical value range, and record the RF excitation gain value at this time.

[0014] In a fixed magnetic field environment, the magnetic field test noise level is monitored and reduced to a minimum by iteratively adjusting the radio frequency excitation frequency and amplitude, and the optimal radio frequency excitation parameters are recorded.

[0015] When temperature changes or device aging cause changes in light intensity, the radio frequency excitation parameters are adjusted based on the light intensity monitoring results to keep the magnetic field test noise within the optimal range.

[0016] Furthermore, the RF excitation frequency adjustment range is 50MHz, with a graduation value of 0.01MHz, and impedance matching is achieved through the adjustable capacitor of the matching network.

[0017] Furthermore, the preset empirical value is a proportional value 'a' to the upper limit of light intensity, and the light intensity adjustment threshold is ±10% of the empirical value, which is adjusted through a variable gain drive circuit.

[0018] Furthermore, the magnetic field test noise level is calculated by averaging M, the absolute value of the difference in magnetic field data per unit time. C Confirmed, the formula is: Where S is the noise monitoring sampling rate; when M C Exceeding the threshold (M) Cmin When the effective noise count N exceeds the threshold n (+0.3nT), the radio frequency parameter adjustment is triggered.

[0019] Furthermore, the frequency of the radio frequency excitation parameter adjustment is staggered from the frequency of the external magnetic field change and the Larmor excitation modulation frequency to avoid interfering with the magnetic field detection results.

[0020] An apparatus for implementing a compensation method for matching the light intensity of a radio frequency excitation source in a helium optically pumped magnetometer, comprising:

[0021] The physical unit, including a helium lamp, an atomic gas chamber, and an optical path adjustment system, is used to generate a light source and enable the interaction between light and atoms.

[0022] The monitoring unit includes a light intensity monitoring circuit containing a photodetector, used to collect light intensity signals from the helium lamp and the atomic gas chamber in real time.

[0023] The driving unit includes a helium lamp and gas chamber impedance matching circuit, an RF power driver, and a variable gain driving circuit, used to adjust the frequency and amplitude of the RF excitation.

[0024] The control unit includes a light intensity feedback and compensation control unit and a computer monitoring and control module, which are used to receive light intensity signals, calculate optimal radio frequency parameters and inject them into the drive unit.

[0025] Furthermore, the helium lamp and gas chamber impedance matching circuit includes a matching network with an adjustable capacitor for frequency adjustment and impedance matching.

[0026] Furthermore, the light intensity feedback and compensation control unit integrates an analog-to-digital conversion module and a digital signal processing module for digital processing of light intensity signals and operation of noise assessment algorithms.

[0027] Furthermore, the computer monitoring and control module is used to set initial excitation parameters, including excitation frequency F0, excitation gain A0, and empirical value of light intensity V0, and to store optimal parameters and noise data.

[0028] Furthermore, the photodetector gain is 10. 4 The light intensity monitoring accuracy reaches 0.1mV, meeting the requirements for high-precision compensation.

[0029] The beneficial effects achieved by this invention are as follows:

[0030] (1) This patent proposes a compensation method and device for matching the light intensity of the radio frequency excitation light source in a helium optical pump magnetometer. This method can maintain stable excitation of the helium lamp and the atomic gas cell by adaptively adjusting the excitation parameters of the helium lamp and the atomic gas cell. It can avoid the redundant and complicated radio frequency excitation device parameter debugging work caused by the individual differences of the helium lamp and the atomic gas cell in each helium optical pump magnetometer, improve the adaptability of the helium optical pump magnetometer to the individual differences of the helium lamp and the atomic gas cell, realize the parameter debugging of the helium lamp and the atomic gas cell without debugging, and simplify the design and implementation of the helium optical pump magnetometer.

[0031] (2) This patent uses the noise level measured by the magnetic field as the basis for judging whether the helium lamp excitation and the gas cell excitation are optimally matched, thus avoiding misjudgment of the noise factors of the helium optical pump magnetometer in the intermediate process. This patent can directly reduce the impact of radio frequency excitation noise, helium lamp and atomic gas cell impurity noise, and light intensity matching noise between the helium lamp and the atomic gas cell on the performance of the magnetometer.

[0032] (3) This patent uses a method of independently adjusting the light intensity of the helium lamp and the atomic gas chamber to compensate for the light intensity changes caused by variations in the parameters of a single light source, thus maintaining both light sources within their optimal operating range. This method avoids the problem of mismatch between the light intensities of the two light sources when adjusting the light intensity of a single light source.

[0033] (4) This patent compensates for the impact of light intensity variations caused by temperature changes and device aging on the performance of the helium optical pump magnetometer by adaptively adjusting the radio frequency excitation parameters of the helium lamp and atomic gas cell. This method avoids the system complexity issues caused by conventional temperature compensation measures. The proposed compensation method for the attenuation of parameters at the end of the helium lamp and atomic gas cell's lifespan can improve the equipment's service life and long-term operational reliability. Attached Figure Description

[0034] 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 the structures shown in these drawings without creative effort.

[0035] Figure 1 This is a schematic diagram of a compensation device for matching the intensity of the radio frequency excitation light source in a helium optical pump magnetometer.

[0036] Figure 2 A schematic diagram of a compensation method for matching the intensity of the radio frequency excitation light source in a helium optical pump magnetometer.

[0037] Figure 3 This refers to the impedance matching process of the radio frequency excitation circuit.

[0038] Figure 4 The compensation method for matching the light intensity of the radio frequency excitation light source of the helium optical pump magnetometer is adapted to different light sources to achieve the optimal state of magnetic field test noise.

[0039] Figure 5 A compensation method and device for matching the light intensity of the radio frequency excitation source of a helium optical pump magnetometer is proposed to compensate for the increased magnetic field test noise caused by changes in radio frequency excitation parameters.

[0040] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0041] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0042] It should be noted that if the embodiments of the present invention involve directional indicators (such as up, down, left, right, front, back, etc.), the directional indicators are only used to explain the relative positional relationship and movement of the components in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicators will also change accordingly.

[0043] Furthermore, if the embodiments of this invention involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, if the word "and / or" appears throughout the text, it means including three parallel solutions; for example, "A and / or B" includes solution A, solution B, or a solution that simultaneously satisfies A and B. Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0044] like Figure 1 As shown, the RF excitation adjustment process using a helium lamp as an example is explained below. First, the host computer control program sets the excitation frequency F0, excitation gain A0, and empirical light intensity V0 for a specific type of helium lamp and atomic gas cell. These parameters are written to the register, and the device is run to bring the helium lamp and gas cell into a stable excitation state. The frequency is adjusted until the helium lamp and gas cell reach their maximum light intensity Vmax. The excitation frequency F1 at this point is recorded. This frequency is considered to be in a matched state for the helium lamp RF excitation. The frequency adjustment range is 50MHz, with a frequency division value of 0.01MHz, which can cover the RF excitation range requirements in helium optical pump magnetometer applications. The matching process is as follows: Figure 3 As shown, the matching network has a reserved adjustable capacitor for adjusting the impedance matching position.

[0045] To ensure that any helium lamp and atomic gas chamber are in an excited luminescent state, the host computer sets a relatively high initial gain to output sufficient power to meet the excitation power requirements. When the frequency is adjusted to the matching state, the light intensity monitored by photodetector 1 is greater than the initial value V0. The gain of the amplifier circuit is adjusted so that the light intensity V1 detected by the photodetector is within the range of V0 ± 10% (different thresholds can be set according to different application scenarios). At this point, the light intensity is considered to be within the empirical value range.

[0046] The process of radio frequency excitation and adjustment of the gas chamber is similar to that of the helium lamp. By adjusting the gas chamber excitation frequency F2 and light intensity V2 through the above process, they are also within the empirically determined range of matching values. The empirically determined ratio of the radio frequency excitation power to the upper limit of the gas chamber light intensity is denoted as 'a', and can be adjusted via parameters set on the host computer.

[0047] The helium lamp intensity monitoring outputs as result (V1) from photodetector 1, while the atomic gas chamber intensity monitoring outputs as result (V2) from photodetector 2. When the helium lamp and atomic gas chamber intensities are weak, the number of helium atoms resonating with the external magnetic field within the atomic gas chamber is insufficient, resulting in a weak magnetic field test signal. The signal-to-noise ratio increases with increasing light intensity. Conversely, when the helium lamp and atomic gas chamber intensities are strong, optical noise is generated, leading to significant noise in the magnetic field test, broadening of the magnetic field signal, and reduced sensitivity. Therefore, the intensities of the helium lamp and atomic gas chamber need to be optimally matched.

[0048] The device is placed in a magnetic field for magnetic field measurement. By adaptively adjusting the light intensity of the helium lamp and the atomic gas chamber, the noise level of the magnetic measurement results per unit time can be minimized. The difference between the current magnetic field test and the previous magnetic field data is recorded as ΔM. The absolute value of ΔM is recorded as the first magnetic field noise. The average magnetic field noise M per unit time (1 second) is calculated based on the noise monitoring sampling rate S. C The light intensity of the helium lamp and the atomic gas cell was adjusted by modifying their radio frequency excitation parameters, and the radio frequency parameters and M were recorded each time. C When M C When the value is at its minimum (M) Cmin The helium lamp and atomic gas chamber operate at optimal noise levels.

[0049]

[0050] Based on the target magnetic field characteristics, set the noise monitoring sampling rate S (generally the sampling rate of the helium optical pump magnetometer) and the noise threshold b (M). Cmin+0.3nT, parameters can be set according to different application scenarios) and noise over-limit threshold n. When the absolute value of ΔM is greater than the preset noise threshold b, it is recorded as one effective noise. The number of effective magnetic field noise N times per unit time (1s) is recorded. The system sets two effective noise counters with a counting time difference of 0.5s, which reduces the amount of computation and maintains a sufficient sampling frequency. When N>n, the noise of the helium optical pump magnetometer exceeds the set noise tolerance, and the noise of the helium optical pump magnetometer increases. The noise is maintained within the optimal noise range (M) by adjusting the radio frequency excitation parameters. Cmin Within +0.1nT). By adjusting the sampling rate and the over-limit threshold n, misjudgments caused by changes in the magnetic field are eliminated.

[0051] Figure 4 and Figure 5 The compensation method and device for matching the light intensity of the radio frequency excitation source of the helium optical pump magnetometer as described in this patent were tested to assess the adaptive excitation of the helium lamp and the atomic gas cell, noise level adjustment, and parameter offset compensation effects. The center frequency of the helium lamp radio frequency excitation was set to 50MHz, the gain to 2, and the initial light intensity value to 4.5V (the photodetector gain was 10). 4 The center frequency of the atomic gas cell radio frequency excitation was set to 21MHz, the gain to 2, and the initial light intensity to 0.15V (the photodetector gain was 10). 4 The magnetic field sampling rate is set to 20, and the effective noise over-limit threshold is set to M. Cmin +0.3nT, the threshold for the number of times noise exceeds the limit is set to 15.

[0052] Figure 4 A compensation method for matching the intensity of the RF excitation source in a helium-pumped magnetometer is presented. The device adaptively matches different light sources to achieve the optimal noise level for magnetic field testing. The first part of the data shows the adaptive adjustment process of the RF excitation parameters by the compensation device. The results indicate that the optimal noise level achieved through adaptive compensation can ensure that the magnetic field testing noise level is below 0.1 nT (magnetic field sampling rate of 20 Hz).

[0053] Figure 5 A compensation method and device for matching the light intensity of the RF excitation source in a helium optical pump magnetometer are presented to compensate for the increased magnetic field measurement noise caused by changes in RF excitation parameters. The noise increase range in the figure represents the area where, after changing the RF excitation inductance parameters, the compensation device automatically compensates for the parameter changes, maintaining the magnetic field measurement noise within an optimal range. The noise level after compensation for the RF excitation parameter changes has an error of less than 1% compared to the level before the parameter changes.

[0054] The above description is merely an optional embodiment of the present invention and does not limit the patent scope of the present invention. All equivalent structural transformations made using the contents of the present invention's specification and drawings under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A compensation method for intensity matching of the radio frequency excitation light source in a helium optically pumped magnetometer, characterized in that, Includes the following steps: High voltage excitation is applied to the helium lamp and the atomic gas chamber, and the radio frequency excitation frequency is adjusted to make the two impedance matched. The radio frequency excitation frequency at this time is recorded. At the impedance matching frequency, adjust the gain of the drive circuit to adjust the light intensity of the helium lamp and the atomic gas cell to the preset empirical value range, and record the RF excitation gain value at this time. In a fixed magnetic field environment, the magnetic field test noise level is monitored and reduced to a minimum by iteratively adjusting the radio frequency excitation frequency and amplitude, and the optimal radio frequency excitation parameters are recorded. When temperature changes or device aging cause changes in light intensity, the radio frequency excitation parameters are adjusted based on the light intensity monitoring results to keep the magnetic field test noise within the optimal range.

2. The compensation method for intensity matching of the radio frequency excitation light source of a helium optically pumped magnetometer according to claim 1, characterized in that: The radio frequency excitation frequency adjustment range is 50MHz, with a graduation value of 0.01MHz, and impedance matching is achieved through the adjustable capacitor of the matching network.

3. The compensation method for intensity matching of the radio frequency excitation light source of a helium optically pumped magnetometer according to claim 1, characterized in that: The preset empirical value is a proportional value 'a' to the upper limit of light intensity, and the light intensity adjustment threshold is ±10% of the empirical value, which is adjusted by a variable gain drive circuit.

4. The compensation method for intensity matching of the radio frequency excitation light source of a helium optically pumped magnetometer according to claim 1, characterized in that: The magnetic field test noise level is calculated by averaging M, the absolute value of the difference in magnetic field data per unit time. C Confirmed, the formula is: Where S is the noise monitoring sampling rate; when M C Exceeding the threshold (M) Cmin When the effective noise count N exceeds the threshold n (+0.3nT), the radio frequency parameter adjustment is triggered.

5. The compensation method for intensity matching of the radio frequency excitation light source of a helium optically pumped magnetometer according to claim 1, characterized in that: The frequency of the radio frequency excitation parameter adjustment is staggered from the frequency of the external magnetic field change and the Larmor excitation modulation frequency to avoid interference with the magnetic field detection results.

6. An apparatus for implementing the compensation method according to any one of claims 1-5, characterized in that, include: The physical unit, including a helium lamp, an atomic gas chamber, and an optical path adjustment system, is used to generate a light source and enable the interaction between light and atoms. The monitoring unit includes a light intensity monitoring circuit containing a photodetector, used to collect light intensity signals from the helium lamp and the atomic gas chamber in real time. The driving unit includes a helium lamp and gas chamber impedance matching circuit, an RF power driver, and a variable gain driving circuit, used to adjust the frequency and amplitude of the RF excitation. The control unit includes a light intensity feedback and compensation control unit and a computer monitoring and control module, which are used to receive light intensity signals, calculate optimal radio frequency parameters and inject them into the drive unit.

7. The apparatus according to claim 6, characterized in that: The helium lamp and gas chamber impedance matching circuit includes a matching network with an adjustable capacitor for frequency adjustment and impedance matching.

8. The apparatus according to claim 6, characterized in that: The light intensity feedback and compensation control unit integrates an analog-to-digital conversion module and a digital signal processing module for digital processing of light intensity signals and operation of noise assessment algorithms.

9. The apparatus according to claim 6, characterized in that: The computer monitoring and control module is used to set initial excitation parameters, including excitation frequency F0, excitation gain A0, and empirical value of light intensity V0, and to store parameter and noise data.

10. The apparatus according to claim 6, characterized in that: The photodetector has a gain of 10. 4 The light intensity monitoring accuracy reaches 0.1mV level.

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