Single-beam optical pumping atomic magnetometer three-axis magnetic field zeroing method and system, terminal and medium

Abstract

The application provides a single-beam optical pumping atomic magnetometer three-axis magnetic field zeroing method, system, terminal and medium, the method comprises the following steps: adding scanning magnetic fields and modulation magnetic fields with different frequencies along the x-axis and the y-axis perpendicular to the optical path direction respectively; adding a direct current compensation magnetic field in the optical path direction to make the x-axis response signal and the y-axis response signal both single-frequency sine waves; adding a direct current compensation magnetic field along the x-axis to make the direct current bias of the x-axis response signal be 0, and adding a direct current compensation magnetic field along the y-axis to make the direct current bias of the y-axis response signal be 0. The application compensates the in-situ three-axis residual magnetic field of the single-beam OPM sensor; the three-axis magnetic field compensation time is fast, the magnetic field setting in the sensitive axis direction has no influence on the reaction effect in other directions, no circulation iteration is needed, and the magnetic field offset time is saved; the resolution of the magnetic field offset in the non-sensitive axis direction of the OPM is evaluated, and finally the resolutions of the residual magnetic field offsets of the x-axis, the y-axis and the z-axis are better than 0.6 pT, 0.6 pT and 5 pT.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of precise magnetic field measurement, in particular to a single-beam optical pumping atomic magnetometer three-axis magnetic field zeroing method and system, a terminal and a medium. BACKGROUND

[0002] In recent years, biological weak magnetic signal detection has been widely used in disease diagnosis and neuroscience research. The most sensitive weak magnetic detection sensors currently available are optical pumping atomic magnetometers (OPMs) and superconducting quantum interference devices (SQUIDs). Compared with OPMs, SQUIDs are still the most commonly used biomedical magnetic measurement devices, but their large size and high operating costs hinder their widespread application. With the continuous development of laser technology and microfabrication technology, OPMs are more miniaturized and portable, making them have a wider development prospect in magnetic field detection. The most sensitive OPM sensors currently available need to work in a spin-exchange relaxation-free (SERF) mechanism, and SERF-OPMs have been successfully used to measure magnetocardiograms, magnetoencephalograms, and myomagnetograms. In the late 20th century and early 21st century, it was found that a near-zero magnetic field working environment is crucial for SERF-OPMs to achieve the highest sensitivity, because the relaxation caused by atomic spin-exchange collisions can be eliminated by working in a near-zero magnetic field environment, and a larger background magnetic field will reduce the sensitivity of the sensor and even prevent it from working normally.

[0003] To achieve a near-zero magnetic field working environment, the background magnetic field should be shielded or eliminated. The ubiquitous geomagnetic field and electromagnetic interference represented by power frequency 50Hz can affect the normal operation of the sensor. Generally, SERF-OPMs should be operated in a high magnetic permeability magnetic shielding device, such as a magnetic shielding chamber or a magnetic shielding barrel, i.e. passive shielding (passive shielding). However, it is worth noting that passive magnetic shielding devices can usually only reduce the residual magnetic field to the level of several nT. Further reducing the magnetic field will make the shielding device very bulky and expensive. Another method to reduce the magnetic field at the location of the OPM is to use active magnetic shielding (active shielding), in which coils carrying specific currents are used to generate magnetic fields to compensate for the residual magnetic field, which usually requires the use of additional magnetometers for three-axis magnetic field compensation. Since the additional magnetometers cannot accurately measure the in-situ magnetic field of each OPM, this will result in inaccurate compensation results and will make the structure complex.

[0004] In order to make SERF-OPM work in a changing magnetic field environment, the integrated SERF-OPM sensor usually contains a magnetic field compensation coil inside the sensor, and uses the inherent characteristics of the sensor itself to compensate for the three-axis magnetic field, which can reduce the position error of the magnetic field compensation. In recent years, many in-situ three-axis residual magnetic field compensation methods for SERF optical pumping magnetometers have been proposed. S.J. Seltzera et al. proposed a method for simultaneously measuring three-axis residual magnetic field by small modulation field, which can compensate the residual magnetic field to near zero based on the three-axis feedback system. By maximizing the first derivative of the zero-field resonance signal, Zhao Junpeng et al. realized the synchronous compensation of the magnetic field along the pump direction and the probe direction, and the magnetic field compensation resolution of x, z and y axes is 9pT, 7pT and 0.05pT. Zou Sheng et al. showed a cross-modulation method based on electron paramagnetic resonance to detect the three components of the residual magnetic field. This method can reduce the residual magnetic field in the shield from about 10nT to dozens of pT, meeting the requirements of OPM working in SERF mechanism for the background magnetic field. Although most of the above systems can compensate the residual magnetic field to almost zero, they use a dual-laser setup, which makes the sensor complex and cannot be minimized for portable applications. In order to meet the demand of small size and simple structure of the sensor, in recent years, the OPM with single laser beam instead of dual laser setup has been studied. Fang et al. proposed a method based on the dynamic characteristics of the atomic spin polarization of the atomic magnetometer itself to compensate the magnetic field. Zhang Shaowen et al. showed a three-axis magnetic field compensation method for zero-field OPM based on single-beam structure, which first compensates the magnetic field to several nT through pre-compensation, and then further compensates the residual magnetic field through single-axis high-frequency magnetic field modulation.

[0005] However, there are certain limitations to these methods. The magnetic field setting in one direction has a significant impact on the shift of the magnetic field to other directions, so it needs to be iterated in a loop, which is very time-consuming. In addition, the magnetic field compensation resolution of the light path direction cannot be accurately evaluated.

[0006] Specifically, in the background of in-situ three-axis residual magnetic field compensation technology of single-beam-based zero-field optical pumping atomic magnetometer, the technical problems are as follows:

[0007] (1) The magnetic shielding problem of SERF-OPM working in a larger residual magnetic field. The working environment of SERF-OPM is near zero field. SERF-OPM used for biomagnetic measurement needs to detect weak magnetic signals of biology, which is about nT or even less than pT level. The ubiquitous geomagnetic field (about 50-60uT) and electromagnetic interference represented by power frequency 50Hz will affect the normal work of the sensor. SERF-OPM should work in a high magnetic permeability magnetic shielding device, such as a magnetic shielding chamber or a magnetic shielding barrel. Here we place the sensor in a magnetic shielding barrel to offset the residual magnetic field to within 5nT.

[0008] (2) The three-axis residual magnetic field cancellation system and method in situ of OPM. Passive shielding can only shield the residual magnetic field within several nT, and the sensitivity of SERF-OPM is related to the size of the residual magnetic field. In practical applications, it is necessary to reduce the residual magnetic field at the position of the sensor as much as possible to optimize the sensitivity of SERF-OPM. This requires a three-axis residual magnetic field cancellation system to be strictly centered on the cell inside the sensor, and the three-axis magnetic field cancellation at the sensor is performed using the inherent characteristics of the sensor itself, without the need for other sensors, thereby simplifying the sensor structure design and enabling in-situ residual field cancellation of the sensor.

[0009] (3) Fast three-axis magnetic field cancellation method. In practical applications, it is necessary to respond quickly to changes in the external magnetic field, which requires the steps of three-axis residual magnetic field cancellation to be simplified, and the method used should not cause the magnetic field to deviate to other directions in one direction, in order to reduce the time consumed by repeated iterations.

[0010] (4) Evaluation of the magnetic field resolution in the non-sensitive axis direction of the single-beam OPM. In practical applications, it is necessary to approximately evaluate the magnetic field cancellation results of each axis. This requires not only the ability to evaluate the magnetic field compensation resolution in the sensitive axis direction (i.e., the non-optical path direction), but also the ability to evaluate the magnetic field compensation resolution in the non-sensitive axis direction (i.e., the optical path direction). SUMMARY

[0011] In view of the above-mentioned disadvantages of the prior art, the purpose of the present application is to provide a single-beam optical pumping atomic magnetometer three-axis magnetic field zero adjustment method, system, terminal and medium, which is used to solve the technical problems of SERF-OPM working in a larger residual magnetic field, being unable to effectively cancel the three-axis residual magnetic field in situ of the OPM, being unable to quickly cancel the three-axis magnetic field, and being unable to evaluate the magnetic field resolution in the non-sensitive axis direction of the single-beam OPM.

[0012] To achieve the above-mentioned purposes and other related purposes, the first aspect of the present application provides a single-beam optical pumping atomic magnetometer three-axis magnetic field zero adjustment method, comprising: adding different frequency scanning magnetic fields and modulation magnetic fields along the x-axis and y-axis perpendicular to the optical path direction, respectively; adding a direct current compensation magnetic field in the optical path direction to make the x-axis response signal and the y-axis response signal both single-frequency sinusoidal waves; adding a direct current compensation magnetic field along the x-axis to make the direct current bias of the x-axis response signal 0; and adding a direct current compensation magnetic field along the y-axis to make the direct current bias of the y-axis response signal 0.

[0013] In some embodiments of the first aspect of the present application, the different frequency scanning magnetic fields and modulation magnetic fields added along the x-axis and y-axis are represented as:

[0014] in, The modulated magnetic field added to the x-axis. The scanning magnetic field added to the x-axis;

[0015] in, The modulated magnetic field added to the y-axis. The scanning magnetic field added to the y-axis.

[0016] In some embodiments of the first aspect of the present invention, adding a DC compensation magnetic field in the optical path direction to make both the x-axis response signal and the y-axis response signal a single-frequency sine wave includes: adding a DC compensation magnetic field along the optical path direction. Until the x-axis response signal β is satisfied x For containing only a single frequency A sine wave without frequency And satisfying the y-axis response signal β y For containing only a single frequency A sine wave without frequency

[0017] In some embodiments of the first aspect of the invention, the method is carried out in a magnetically shielded space capable of counteracting a portion of the magnetic field in the Earth's magnetic field.

[0018] In some embodiments of the first aspect of the present invention, the magnetic shielding space comprises five layers of magnetic shielding barrels.

[0019] To achieve the above and other related objectives, a second aspect of the present invention provides a three-axis magnetic field zeroing system for a single-beam optically pumped atomic magnetometer, comprising: an OPM sensor, a three-axis Helmholtz coil, a signal generator, and a lock-in amplifier; the OPM sensor and the three-axis Helmholtz coil are located in a magnetically shielded container, and the three-axis Helmholtz coil is fixed to the outer shell of the OPM sensor; the OPM sensor emits a laser beam, and the modulation signals f(x) and f(y) of the three-axis Helmholtz coil are generated by the signal generator and used as reference signals; the reference signal and the sensor response signal are processed by the lock-in amplifier; the resulting signals are output after passing through a low-pass filter to obtain demodulated x-axis and y-axis response signals; wherein, the three-axis Helmholtz coil adds a modulation magnetic field, a scanning magnetic field, and a three-axis compensation magnetic field according to the three-axis magnetic field zeroing method of the single-beam optically pumped atomic magnetometer.

[0020] In some embodiments of the second aspect of the present invention, the magnetic shielding barrel is a 5-layer magnetic shielding barrel.

[0021] In some embodiments of the second aspect of the invention, the lock-in amplifier includes a low-pass filter for filtering out high-frequency components.

[0022] To achieve the above object and other related objects, the third aspect of the present application provides a computer readable storage medium, which stores a computer program, and the computer program is executed by a processor to implement the three-axis magnetic field zero adjustment method of single-beam optical pumping atomic magnetometer.

[0023] To achieve the above object and other related objects, the fourth aspect of the present application provides an electronic terminal, which comprises a processor and a memory; the memory is used to store a computer program, and the processor is used to execute the computer program stored in the memory to make the terminal execute the three-axis magnetic field zero adjustment method of single-beam optical pumping atomic magnetometer.

[0024] As described above, the three-axis magnetic field zero adjustment method, system, terminal and medium of single-beam optical pumping atomic magnetometer have the following beneficial effects:

[0025] (1) The present application can compensate the three-axis residual magnetic field of the OPM sensor with single-beam structure in situ.

[0026] (2) The present application has a relatively fast three-axis magnetic field compensation time, and the magnetic field setting in the sensitive axis direction such as the x-axis direction has basically no influence on the reaction effect in other directions (such as the y direction), so there is no need for cyclic iteration, and the time for magnetic field offset is saved.

[0027] (3) The present application can evaluate the resolution of the magnetic field offset in the non-sensitive axis direction (i.e. the light path direction) of the OPM with single-beam structure, and the resolutions of the residual magnetic fields of the x-axis, y-axis and z-axis finally reached are better than 0.6 pT, 0.6 pT and 5 pT. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 A schematic diagram showing the addition of modulation magnetic fields with different frequencies in two directions perpendicular to the laser beam in an embodiment of the present application.

[0029] Figure 2 A schematic diagram showing the process of demodulating the output signal of the OPM at different frequencies in an embodiment of the present application.

[0030] Figure 3 A schematic diagram showing the flow of the three-axis magnetic field zero adjustment method of single-beam optical pumping atomic magnetometer in an embodiment of the present application.

[0031] Figure 4 A schematic diagram showing the structure of the three-axis magnetic field zero adjustment system of single-beam optical pumping atomic magnetometer in an embodiment of the present application.

[0032] Figure 5A A time-domain graph showing the response signal β of the three-axis magnetic field before compensation in an embodiment of the present application. x ​

[0033] Figure 5B Time domain plot of response signal β before three-axis magnetic field compensation in an embodiment of the present application. x

[0034] Figure 5C Time domain plot of response signal β before three-axis magnetic field compensation in an embodiment of the present application. y

[0035] Figure 5D Frequency domain plot of response signal β before three-axis magnetic field compensation in an embodiment of the present application. y

[0036] Figure 6A Time domain plot of response signal β after three-axis magnetic field compensation in an embodiment of the present application. x

[0037] Figure 6B Frequency domain plot of response signal β after three-axis magnetic field compensation in an embodiment of the present application. x

[0038] Figure 6C Time domain plot of response signal β after three-axis magnetic field compensation in an embodiment of the present application. y

[0039] Figure 6D Frequency domain plot of response signal β after three-axis magnetic field compensation in an embodiment of the present application. y

[0040] Figure 7 Schematic diagram of x-axis magnetic field compensation resolution evaluation in an embodiment of the present application.

[0041] Figure 8 Schematic diagram of three-axis magnetic field zeroing device of single-beam optical pumping atomic magnetometer in an embodiment of the present application.

[0042] Figure 9 Schematic diagram of electronic terminal in an embodiment of the present application.

[0043] Figure 10 Schematic diagram of z-axis magnetic field compensation resolution evaluation in an embodiment of the present application. DETAILED DESCRIPTION

[0044] ​​​​​​​The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that, unless otherwise specified, the following embodiments and features described therein can be combined with each other.

[0045] It should be noted that in the following description, reference is made to the accompanying drawings, which illustrate several embodiments of the present invention. It should be understood that other embodiments may also be used, and changes in mechanical composition, structure, electrical system, and operation may be made without departing from the spirit and scope of the invention. The following detailed description should not be considered limiting, and the scope of the embodiments of the invention is defined only by the claims of the published patents. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention. Spatially related terms, such as “upper,” “lower,” “left,” “right,” “below,” “below,” “lower part,” “above,” “upper part,” etc., may be used herein to illustrate the relationship between one element or feature shown in the figures and another element or feature.

[0046] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," "fixing," and "holding" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0047] Furthermore, as used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context indicates otherwise. It should be further understood that the terms “comprising,” “including,” indicate the presence of the stated feature, operation, element, component, item, kind, and / or group, but do not preclude the presence, occurrence, or addition of one or more other features, operations, elements, components, items, kinds, and / or groups. The terms “or” and “and / or” as used herein are interpreted as inclusive, or mean any one or any combination thereof. Thus, “A, B, or C” or “A, B, and / or C” means “any one of: A; B; C; A and B; A and C; B and C; A, B, and C.” Exceptions to this definition arise only when combinations of elements, functions, or operations are inherently mutually exclusive in some manner.

[0048] To solve the problems in the background art, the application provides a single-beam optical pumping atomic magnetometer three-axis magnetic field zeroing method, system, terminal and medium, aiming to compensate the in-situ three-axis residual magnetic field of the OPM sensor with a single-beam structure; the three-axis magnetic field compensation time is fast, the magnetic field setting of the sensitive axis direction has no influence on the reaction effect of other directions, no need for cyclic iteration, and the magnetic field offset time is saved; the resolution of the magnetic field offset of the OPM non-sensitive axis direction is evaluated, and finally the resolutions of the residual magnetic field offsets of the x-axis, y-axis and z-axis are better than 0.6 pT, 0.6 pT and 5 pT.

[0049] In order to make the objectives, technical solutions and advantages of the present application clearer, the technical solutions of the embodiments of the present application are further described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only used to explain the present application and not used to limit the present application.

[0050] Before the present application is further described, the terms and phrases involved in the embodiments of the present application are explained, and the terms and phrases involved in the embodiments of the present application are applicable to the following explanations:

[0051] (1) Helmholtz coil: a pair of coaxial circular (square) coils in parallel and connected to each other, the current directions in the two coils are consistent and the sizes are the same. When the distance d between the coils is exactly equal to the radius R of the circular coil, such a circular current-carrying coil is called a Helmholtz coil. The characteristic of such a coil is that a relatively wide uniform magnetic field can be generated near the midpoint of the common axis. A three-axis Helmholtz coil can generate a three-direction magnetic field, and the magnetic field can realize X, Y and Z axial magnetic fields, and can be used for generating a standard magnetic field, offsetting and compensating the earth's magnetic field, simulating the geomagnetic environment, determining the magnetic shielding effect, simulating electromagnetic interference experiments, calibrating Hall probes and various magnetometers, researching biological magnetic fields and the magnetic properties of matter, etc.

[0052] (2) Lock-in amplifier: an amplifier for phase-sensitive detection of alternating signals. It uses a reference signal with the same frequency and phase relationship as the measured signal as a comparison reference, and only responds to noise components with the same frequency (or multiple frequency) and phase as the measured signal itself, so it can greatly suppress unwanted noise and improve the detection signal-to-noise ratio.

[0053] (3) OPM (Optical-pumping managetometer): optical pumping magnetometer is based on the Zeeman splitting of helium, mercury, nitrogen and alkali metals such as rubidium and cesium, and is developed by using optical pumping and magnetic resonance technology.

[0054] The embodiment of the present application provides a single-beam optical pumping atomic magnetometer three-axis magnetic field zero adjustment method, a single-beam optical pumping atomic magnetometer three-axis magnetic field zero adjustment method system, and a storage medium storing an executable program for implementing the single-beam optical pumping atomic magnetometer three-axis magnetic field zero adjustment method. In terms of the implementation of the single-beam optical pumping atomic magnetometer three-axis magnetic field zero adjustment method, the embodiment of the present application will illustrate an exemplary implementation scenario of the single-beam optical pumping atomic magnetometer three-axis magnetic field zero adjustment.

[0055] In the embodiment of the present application, in order to enable the normal operation of the three-axis cancellation method, it needs to be performed in a magnetic shielding space (such as a magnetic shielding chamber or a magnetic shielding barrel) to cancel most of the magnetic field in the geomagnetic field and shield the external geomagnetic field within 5nT. In order to perform in-situ magnetic field cancellation, a small and non-magnetic three-axis Helmholtz coil system is designed and fixed on the sensor shell as part of the OPM sensor. The uniform region of the magnetic field generated by the three-axis Helmholtz coil covers the position of the coil cell with 10mm*10mm*10mm.

[0056] In order to cancel the residual magnetic field in three directions, frequency-different modulation magnetic fields are added in two directions perpendicular to the laser beam, and the frequencies are f x and f y , as shown in Figure 1 . In order to study the response characteristics of the OPM to the three-axis magnetic field, frequency-different low-frequency scanning magnetic fields are added in two directions perpendicular to the laser beam, and the output signals of the OPM are demodulated at different frequencies, and then the high-frequency components are filtered out through a low-pass filter.

[0057] The demodulation process is shown in Figure 2 : the reference signal is input in the x-axis; after the phase change of +90° of the reference signal, it enters the phase-locked amplifier; the original signal P z also enters the phase-locked amplifier and is processed with the phase-changed reference signal; the obtained signal enters the low-pass filter and the output demodulated response signal β x is obtained. The reference signal is input in the y-axis; after the phase change of +90° of the reference signal, it enters the phase-locked amplifier; the original signal P z also enters the phase-locked amplifier and is processed with the phase-changed reference signal; the obtained signal enters the low-pass filter and the output demodulated response signal β y is obtained.

[0058] Through the above demodulation principle and experimental verification, it can be concluded that when there is no residual magnetic field in the z-axis direction, the response signals β x and β yThe time-domain graphs of β and β are both single-frequency (corresponding to the frequency of the scanning magnetic field along the axis) sinusoidal waves; when the z-axis direction contains a residual magnetic field, the residual magnetic field along the z-axis will rotate the scanning magnetic field along an axis perpendicular to the optical path direction to another direction, at which time the response signals β x and β y become irregular and are not single-frequency sinusoidal waves, but are mixtures of two frequencies. When the x-axis contains a residual magnetic field, the time-domain curve of the response signal β x will contain a direct-current bias magnetic field, which will be offset to 0 by offsetting the residual magnetic field along the x-axis, and the same conclusion can be drawn for the y-axis direction. Meanwhile, when a magnetic field exists along an axis perpendicular to the optical path direction (i.e., the x-axis or the y-axis), the residual magnetic field along the optical path direction (the z-axis) will affect the time-domain direct-current bias of the response signals β x and β y .

[0059] To realize in-situ three-axis magnetic field offsetting of a single-beam OPM sensor, the flow of the three-axis magnetic field zeroing method of the single-beam optical pumping atomic magnetometer according to the embodiment of the present application is shown in Figure 3 , and mainly includes the following steps.

[0060] Step S31: Different-frequency scanning magnetic fields and modulation magnetic fields are added along the x-axis and the y-axis perpendicular to the optical path direction, respectively.

[0061] In the embodiment of the present application, the different-frequency scanning magnetic fields and modulation magnetic fields added along the x-axis are denoted as:

[0062]

[0063] wherein, is the modulation magnetic field added along the x-axis, is the scanning magnetic field added along the x-axis. It should be understood that the scanning magnetic field refers to a magnetic field that changes with time, and its effect is equivalent to unfolding the resonance phenomenon on the time axis of an oscilloscope for observation. The modulation magnetic field refers to a magnetic field generated when an electric current passes through a magnetic material, and the strength and direction of the magnetic field are modulated by changing the direction and size of the electric current.

[0064] Similarly to the different-frequency scanning magnetic fields and modulation magnetic fields added along the x-axis, the different-frequency scanning magnetic fields and modulation magnetic fields added along the y-axis are denoted as:

[0065]

[0066] wherein, is the modulation magnetic field added along the y-axis, is the scanning magnetic field added along the y-axis.

[0067] Step S32: a direct current compensation magnetic field is added in the light path direction to make the x-axis response signal and the y-axis response signal both single frequency sine waves.

[0068] Specifically, a direct current compensation magnetic field is added in the light path direction (z-axis) until the x-axis response signal β x is a single frequency sine wave without containing frequency and the y-axis response signal β y is a single frequency sine wave without containing frequency

[0069] Step S33: a direct current compensation magnetic field is added along the x-axis to make the direct current bias of the x-axis response signal 0; and a direct current compensation magnetic field is added along the y-axis to make the direct current bias of the y-axis response signal 0.

[0070] Specifically, a direct current compensation magnetic field is added along the x-axis until the direct current bias of the x-axis response signal a direct current compensation magnetic field is added along the y-axis until the direct current bias of the y-axis response signal It should be noted that the magnetic field compensation sequence of the x-axis and the y-axis can be performed simultaneously or in any order (first the x-axis performs magnetic field compensation and then the y-axis performs magnetic field compensation or vice versa).

[0071] By using the above-provided single-beam optical pumping atomic magnetometer three-axis magnetic field zero adjustment method, in-situ three-axis residual magnetic field compensation can be performed on the OPM sensor with a single-beam structure; this method is fast in three-axis magnetic field compensation time, and the magnetic field setting in the sensitive axis direction such as the x-axis direction has basically no effect on the reaction effect in other directions (such as the y direction), so there is no need for circulation and iteration, saving the time for magnetic field offset; the resolution of the magnetic field offset in the non-sensitive axis direction (i.e. the light path direction) of the OPM with a single-beam structure can be evaluated, and the finally achieved residual magnetic field offset resolutions of the x-axis, the y-axis and the z-axis are better than 0.6 pT, 0.6 pT and 5 pT.

[0072] As shown in Figure 4 , a structure schematic diagram of a single-beam optical pumping atomic magnetometer three-axis magnetic field zero adjustment system in an embodiment of the present application is shown.

[0073] The single-beam optical pumping atomic magnetometer three-axis magnetic field zero adjustment system in the embodiment of the present application comprises an OPM sensor, a three-axis Helmholtz coil, a signal generator and a lock-in amplifier; the OPM sensor and the three-axis Helmholtz coil are located in a magnetic shielding barrel, and the three-axis Helmholtz coil is fixed to the shell of the OPM sensor.

[0074] The OPM sensor emits a laser beam, and the modulation signals f(x) and f(y) of the three-axis Helmholtz coil generate a reference signal after being processed by a signal generator; the reference signal and the original signal enter a phase-locked amplifier for signal superposition; the superimposed signal enters a low-pass filter to output the demodulated x-axis response signal and y-axis response signal. The three-axis Helmholtz coil is used to add a modulation magnetic field, a scanning magnetic field and a three-axis compensation magnetic field, specifically including: adding scanning magnetic fields and modulation magnetic fields with different frequencies in the x-axis and y-axis perpendicular to the light path direction; adding a direct current compensation magnetic field in the light path direction to make the x-axis response signal and the y-axis response signal both be single-frequency sine waves; adding a direct current compensation magnetic field along the x-axis to make the direct current bias of the x-axis response signal be 0; and adding a direct current compensation magnetic field along the y-axis to make the direct current bias of the y-axis response signal be 0.

[0075] In some examples, the scanning magnetic fields and the modulation magnetic fields with different frequencies added along the x-axis are represented as:

[0076]

[0077] wherein, is the modulation magnetic field added to the x-axis, is the scanning magnetic field added to the x-axis. It should be understood that the scanning magnetic field refers to a magnetic field that changes over time, and its effect is equivalent to unfolding the resonance phenomenon on the time axis of the oscilloscope for observation. The modulation magnetic field refers to a magnetic field generated when an electric current passes through a magnetic material, and the strength and direction of the magnetic field are modulated by changing the direction and size of the electric current.

[0078] In some examples, similar to the scanning magnetic fields and the modulation magnetic fields with different frequencies added to the x-axis, the scanning magnetic fields and the modulation magnetic fields with different frequencies added to the y-axis are represented as:

[0079]

[0080] wherein, is the modulation magnetic field added to the y-axis, is the scanning magnetic field added to the y-axis.

[0081] In some examples, a direct current compensation magnetic field is added along the x-axis until the direct current bias of the x-axis response signal is a direct current compensation magnetic field is added along the y-axis until the direct current bias of the y-axis response signal is It should be noted that the magnetic field compensation sequence of the x-axis and the y-axis can be performed simultaneously or in any order (first performing magnetic field compensation on the x-axis and then performing magnetic field compensation on the y-axis, or reversing the order).

[0082] The above describes the single-beam optical pumping atomic magnetometer three-axis magnetic field zeroing method and system provided by the embodiment of the application in detail. The following will show the technical effects produced by using the method and system provided by the embodiment of the application through experiments.

[0083] As shown in Figures 5A-5D , the time-domain graph and the frequency-domain graph of the response signal before three-axis magnetic field compensation in the embodiment of the application are shown. Figure 5A The time-domain graph of the response signal β x before three-axis magnetic field compensation, Figure 5B the frequency-domain graph of the response signal β x before three-axis magnetic field compensation, Figure 5C the time-domain graph of the response signal β y before three-axis magnetic field compensation, Figure 5D the frequency-domain graph of the response signal β y before three-axis magnetic field compensation. At this time, the residual magnetic fields of the x-axis, the y-axis and the z-axis are respectively As can be seen from the graphs, the response signals β x and β y of the x-axis and the y-axis are both irregular and are signals mixed with two different frequencies.

[0084] As shown in Figures 6A-6D , the time-domain graph and the frequency-domain graph of the response signal after three-axis magnetic field compensation in the embodiment of the application are shown. Figure 6A The time-domain graph of the response signal β x after three-axis magnetic field compensation, Figure 6B the frequency-domain graph of the response signal β x after three-axis magnetic field compensation, Figure 6C the time-domain graph of the response signal β y after three-axis magnetic field compensation, Figure 6D the frequency-domain graph of the response signal β y after three-axis magnetic field compensation. As can be seen from the graphs: when the z-axis residual magnetic field is compensated to 0, β x and β y both become single-frequency sine waves. As shown by the dashed curve in Figure 6A , when the x-axis residual magnetic field is compensated from 1.9 nT to 0 nT, the direct current bias of β x also becomes 0; as shown by the dashed curve in Figure 6C , when the y-axis residual magnetic field is finally compensated from 1.4 nT to 0 nT, the direct current bias of β y also becomes 0. The experimental results show that the three-axis magnetic field compensation scheme is feasible.

[0085] As shown in Figure 7As shown in FIG. 8, a schematic diagram of x-axis magnetic field compensation resolution evaluation is shown. A sinusoidal excitation magnetic field with an amplitude of 5 pT and a frequency of 1 Hz is added along the x-axis, as shown by the dashed curve, and the response of β x is shown by the solid curve. As can be seen from the curve, when the magnetic field strength along the x-axis is 5 pT, the signal fluctuates significantly, so the x-axis magnetic field compensation resolution is better than 5 pT. According to Fourier transform calculation, the signal-to-noise ratio of the signal is 18 dB, which means that the final resolution of the method is about 0.6 pT. The evaluation of the y-axis magnetic field compensation resolution is similar to that of the x-axis. As shown in FIG. 9, a schematic diagram of y-axis magnetic field compensation resolution evaluation is shown. A sinusoidal excitation magnetic field with an amplitude of 5 pT and a frequency of 1 Hz is added along the y-axis, as shown by the dashed curve, and the response of β Figure 10 is shown by the solid curve. As can be seen from the curve, when the magnetic field strength along the y-axis is 5 pT, the signal fluctuates significantly, so the y-axis magnetic field compensation resolution is better than 5 pT. According to Fourier transform calculation, the signal-to-noise ratio of the signal is 18 dB, which means that the final resolution of the method is about 0.6 pT. y As shown in FIG. 10, a schematic diagram of z-axis magnetic field compensation resolution evaluation is shown. After three-axis magnetic field compensation, a sinusoidal excitation magnetic field with an amplitude of 50 pT and a frequency of 1 Hz is added along the z-axis, and the response of β is shown by the solid curve. As can be seen from the curve, the compensation method can identify a 50 pT magnetic field change along the z-axis direction, which means that the resolution of the method along the z-axis is better than 50 pT, and the signal-to-noise ratio of the signal is about 20 dB. Therefore, it is deduced that the estimated resolution of the method along the z-axis is about 5 pT.

[0086] The above experiments verify the feasibility of the three-axis magnetic field zeroing scheme of the single-beam optical pumping atomic magnetometer proposed in the present application, and the resolution of the z-axis magnetic field compensation is evaluated to be 5 pT. The magnetic field compensation resolutions of the x-axis and y-axis are both better than 0.6 pT.

[0087] As shown in FIG. 11, a schematic diagram of a three-axis magnetic field zeroing device of a single-beam optical pumping atomic magnetometer in an embodiment of the present application is shown. The three-axis magnetic field zeroing device 800 of the single-beam optical pumping atomic magnetometer in the embodiment of the present application includes a magnetic field adding module 801, a z-axis compensation magnetic field module 802, and an xy-axis compensation magnetic field module 803.

[0088] The magnetic field adding module 801 is used to add scanning magnetic fields and modulation magnetic fields with different frequencies along the x-axis and y-axis perpendicular to the optical path direction, respectively. The z-axis compensation magnetic field module 802 is used to add a direct current compensation magnetic field along the optical path direction to make the x-axis response signal and the y-axis response signal both single-frequency sinusoidal waves. The xy-axis compensation magnetic field module 803 is used to add a direct current compensation magnetic field along the x-axis to make the direct current bias of the x-axis response signal be 0; and add a direct current compensation magnetic field along the y-axis to make the direct current bias of the y-axis response signal be 0.

[0089] It should be noted that the single-beam optical pumping atomic magnetometer three-axis magnetic field zero adjustment device provided in the above embodiment is used for adjusting the three-axis magnetic field of the single-beam optical pumping atomic magnetometer, and the above-mentioned division of the program modules is used for example, and in actual application, the above-mentioned processing can be completed by different program modules according to the needs, that is, the internal structure of the device is divided into different program modules to complete all or part of the above-mentioned processing. In addition, the single-beam optical pumping atomic magnetometer three-axis magnetic field zero adjustment device and the single-beam optical pumping atomic magnetometer three-axis magnetic field zero adjustment method provided in the above embodiment belong to the same concept, and the specific implementation process is described in the method embodiment, which will not be repeated here.

[0090] The single-beam optical pumping atomic magnetometer three-axis magnetic field zero adjustment method provided in the embodiment of the application can be implemented on the terminal side or the server side. As for the hardware structure of the single-beam optical pumping atomic magnetometer three-axis magnetic field zero adjustment terminal, please refer to Figure 9 An optional hardware structure schematic diagram of the terminal 900 provided in the embodiment of the application is shown in FIG. 9. The terminal 900 can be a mobile phone, a computer device, a tablet device, a personal digital processing device, a factory background processing device, etc. The terminal 900 includes at least one processor 901, a memory 902, at least one network interface 904 and a user interface 906. Various components in the device are coupled together through a bus system 905. It can be understood that the bus system 905 is used to realize the connection and communication between the components. In addition to the data bus, the bus system 905 also includes a power bus, a control bus and a status signal bus. However, in order to clearly illustrate, all kinds of buses are marked as the bus system in Figure 9 .

[0091] The user interface 906 can include a display, a keyboard, a mouse, a trackball, a click gun, a key, a button, a touchpad or a touch screen, etc.

[0092] It can be understood that the memory 902 can be a volatile memory or a non-volatile memory, and can also include both volatile and non-volatile memories. The non-volatile memory can be a read-only memory (ROM, Read Only Memory), a programmable read-only memory (PROM, Programmable Read-Only Memory), which is used as an external cache. By way of example but not limitation, many forms of RAM can be used, such as static random access memory (SRAM, Static Random Access Memory), synchronous static random access memory (SSRAM, Synchronous Static Random Access Memory). The memory described in the embodiment of the application is intended to include but not limited to these and any other suitable category of memory.

[0093] The memory 902 in the embodiments of the present application is configured to store various types of data to support the operation of the terminal 900. Examples of the data include any executable programs for operating the single-beam optical pumping atomic magnetometer three-axis magnetic field zeroing terminal 900, such as an operating system 9021 and an application program 9022. The operating system 9021 includes various system programs, such as a framework layer, a core library layer, a driver layer, and the like, for implementing various basic services and processing hardware-based tasks. The application program 9022 can include various application programs, such as a media player (MediaPlayer), a browser (Browser), and the like, for implementing various application services. The single-beam optical pumping atomic magnetometer three-axis magnetic field zeroing method provided by the embodiments of the present application can be included in the application program 9022.

[0094] The method disclosed in the embodiments of the present application can be applied to the processor 901 or implemented by the processor 901. The processor 901 can be an integrated circuit chip having a processing capability of signals. In the implementation process, each step of the above method can be completed by integrated logic circuits or instructions in the form of software in the processor 901. The processor 901 described above can be a general-purpose processor, a digital signal processor (DSP), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, and the like. The processor 901 can implement or execute the disclosed methods, steps, and logic block diagrams in the embodiments of the present application. The general-purpose processor 901 can be a microprocessor or any conventional processor, and the like. In combination with the steps of the accessory optimization method provided by the embodiments of the present application, the hardware decoding processor can be directly embodied to complete the execution, or a combination of hardware and software modules in the decoding processor can be used to complete the execution. The software module can be located in a storage medium, which is located in the memory. The processor reads the information in the memory and combines the hardware to complete the steps of the above method.

[0095] In the exemplary embodiments, the terminal 900 can be implemented by one or more application-specific integrated circuits (ASICs), DSPs, programmable logic devices (PLDs), complex programmable logic devices (CPLDs), and the like for executing the above method.

[0096] Those skilled in the art can understand that all or part of the steps of the above-mentioned method embodiments can be completed by computer program related hardware. The aforementioned computer program can be stored in a computer readable storage medium. The program executes the steps of the above-mentioned method embodiments when executed; and the aforementioned storage medium includes ROM, RAM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage device, flash memory, U disk, mobile hard disk, or any other medium capable of storing desired program code in the form of instructions or data structures and capable of being accessed by a computer. In addition, any connection can be appropriately referred to as a computer readable medium. For example, if instructions are sent from a website, server or other remote source using a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL) or wireless technology such as infrared, radio and microwave, the coaxial cable, fiber optic cable, twisted pair, DSL or wireless technology such as infrared, radio and microwave is included in the definition of the medium. However, it should be understood that the computer readable storage medium and the data storage medium do not include connections, carriers, signals or other transitory media, but are intended to be directed to non-transitory, tangible storage media. As used in the application, magnetic disks and optical disks include compact disks (CD), laser disks, optical disks, digital versatile disks (DVD), floppy disks and Blu-ray disks, wherein magnetic disks typically magnetically copy data, and optical disks optically copy data with a laser.

[0097] In the embodiments provided by the present application, the computer readable storage medium can include a read-only memory, a random access memory, an EEPROM, a CD-ROM or other optical disk storage, a magnetic disk storage or other magnetic storage device, a flash memory, a U disk, a mobile hard disk, or any other medium capable of storing desired program code in the form of instructions or data structures and capable of being accessed by a computer. In addition, any connection can be appropriately referred to as a computer readable medium. For example, if instructions are sent from a website, server or other remote source using a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL) or wireless technology such as infrared, radio and microwave, the coaxial cable, fiber optic cable, twisted pair, DSL or wireless technology such as infrared, radio and microwave is included in the definition of the medium. However, it should be understood that the computer readable storage medium and the data storage medium do not include connections, carriers, signals or other transitory media, but are intended to be directed to non-transitory, tangible storage media. As used in the application, magnetic disks and optical disks include compact disks (CD), laser disks, optical disks, digital versatile disks (DVD), floppy disks and Blu-ray disks, wherein magnetic disks typically magnetically copy data, and optical disks optically copy data with a laser.

[0098] In summary, the present application provides a single-beam optical pumping atomic magnetometer three-axis magnetic field zeroing method, system, terminal and medium, which can compensate the in-situ three-axis residual magnetic field of the OPM sensor with a single-beam structure. This method has a relatively fast three-axis magnetic field compensation time, and has basically no influence on the reaction effect of the magnetic field setting in the sensitive axis direction such as the x-axis direction on other directions such as the y direction, so it does not need to be iterated, thereby saving the time for magnetic field offset. The resolution of the magnetic field offset in the non-sensitive axis direction (i.e. the light path direction) of the OPM with a single-beam structure can be evaluated, and the resolutions of the residual magnetic fields of the x-axis, y-axis and z-axis finally reached are better than 0.6 pT, 0.6 pT and 5 pT. Therefore, the present application effectively overcomes the various shortcomings in the prior art and has a high industrial utilization value.

[0099] The above embodiments are only illustrative of the principles of the present application and its efficacy, and are not intended to limit the present application. Any modification or change made by any person skilled in the art without departing from the spirit and scope of the present application shall be covered by the claims of the present application.

Claims

1. A single-beam optically pumped atomic magnetometer three-axis magnetic field nulling method, characterized by, The method is performed in a magnetic shielding space capable of offsetting part of the geomagnetic field. Different frequency scanning magnetic fields and modulation magnetic fields are added along the axis and axis perpendicular to the light path direction, respectively Add a DC compensation magnetic field in the direction of the optical path to make Shaft response signal and The shaft response signals are all single-frequency sine waves; along the axis to make the DC bias of the axis response signal 0; and, along the axis to make the DC bias of the axis response signal 0; wherein the different frequencies of the added scanning magnetic field and the modulation magnetic field along the axis, axis are represented as: ; wherein, is a modulation magnetic field added by the axis, is a scanning magnetic field added by the axis; ; wherein, is a modulation magnetic field added by the axis, is a scanning magnetic field added by the axis.

2. The single beam optical pumping atomic magnetometer three-axis magnetic field nulling method of claim 1, wherein, The DC compensation magnetic field is added in the light path direction to make The axial response signal and The axial response signal is a single frequency sine wave, including: adding a DC compensation magnetic field in the light path direction Until the condition is met The axial response signal Is only a single frequency Sine wave without frequency , and the condition is met The axial response signal Is only a single frequency Sine wave without frequency .

3. The single beam optical pumping atomic magnetometer three-axis magnetic field nulling method of claim 1, wherein, The magnetic shielding space comprises a 5-layer magnetic shielding barrel.

4. The single beam optical pumping atomic magnetometer three-axis magnetic field zeroing method of claim 3, wherein, The method comprises the following steps:

5. A single-beam optically pumped atomic magnetometer three-axis magnetic field nulling system, characterized by, An OPM sensor, a three-axis Helmholtz coil, a signal generator and a lock-in amplifier; the OPM sensor and the three-axis Helmholtz coil are located in a magnetic shielding barrel, and the three-axis Helmholtz coil is fixed to the shell of the OPM sensor. The magnetic shielding barrel is a 5-layer magnetic shielding barrel. The OPM sensor emits a laser beam, and the modulation signal of the three-axis Helmholtz coil and The signal generator generates a reference signal at the same time; the reference signal and the response signal of the sensor are input into a lock-in amplifier for signal processing; the obtained signal is input into a low-pass filter and output to obtain a demodulated axial response signal and axial response signal; wherein the three-axis Helmholtz coil is modulated according to the single-beam optical pumping atomic magnetometer three-axis magnetic field zeroing method of any one of claims 1-4 to add a modulation magnetic field, a scanning magnetic field and a three-axis compensation magnetic field.

6. The single-beam optically pumped atomic magnetometer three-axis magnetic field nulling system of claim 5, wherein, The lock-in amplifier is provided with a low-pass filter for filtering high-frequency components.

7. The single beam optical pumping atomic magnetometer three-axis magnetic field nulling system of claim 5, wherein, The computer program is executed by a processor to realize the single-beam optical pumping atomic magnetometer three-axis magnetic field zero adjustment method in any one of claims 1-4.

8. A computer-readable storage medium having stored thereon a computer program, characterized in that, The method comprises the following steps:

9. An electronic terminal, characterized in that A processor and a memory; The memory is used for storing a computer program; The processor is used for executing the computer program stored in the memory, so that the terminal executes the single-beam optical pumping atomic magnetometer three-axis magnetic field zero adjustment method in any one of claims 1-4. ​

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