Laser pumping magnetometer and control method thereof

Abstract

The invention provides a laser pumping magnetometer and a control method thereof. The laser pumping magnetometer comprises a pumping light source, a collimation polarization module, an atomic gas chamber, a radio frequency coil, a photoelectric detector, an amplifier and a control module, linearly polarized light emitted by the pump light source passes through the collimation polarization module to obtain parallel circularly polarized light, the circularly polarized light passes through the atomic gas chamber, atoms in the atomic gas chamber are polarized under the action of the circularly polarized light, atomic magnetic moment generates precession in a magnetic field to be measured, and the circularly polarized light is partially absorbed by the atoms in the atomic gas chamber to obtain transmission light. The transmission light enters a photoelectric detector; the radio frequency coil is wound outside the atomic gas chamber, and the winding axial direction of the radio frequency coil is the same as the light path direction; the photoelectric detector is connected with the input end of the amplifier; the output end of the amplifier is connected with the radio frequency coil; the control module comprises a frequency measurement module, and the frequency measurement module is connected with the radio frequency coil. The problem that a traditional optical pump magnetometer is not high in measurement precision is solved.

Description

Technical Field

[0001] The present application relates to the field of precision instrument measurement technology, and in particular to a laser pumped magnetometer and a control method thereof. Background Art

[0002] Magnetometer is a basic instrument for magnetic detection and ground magnetic field observation, and is widely used in geological exploration, medical diagnosis, aerospace and other fields. Among them, the optically pumped magnetometer (OPM) can be installed on a rod outside the satellite body as a satellite-borne absolute scalar magnetometer to detect the magnetic field in space.

[0003] The measurement accuracy of traditional optically pumped magnetometers is not high. Therefore, there is an urgent need for a laser-pumped magnetometer with high measurement accuracy. Summary of the invention

[0004] In view of this, an embodiment of the present application provides a laser pumped magnetometer and a control method thereof to solve the problem of low measurement accuracy of traditional optical pumped magnetometers in the prior art.

[0005] In a first aspect of an embodiment of the present application, a laser pumped magnetometer is provided, comprising a pump light source, a collimation polarization module, an atomic gas chamber, a radio frequency coil, a photodetector, an amplifier, and a control module;

[0006] The pump light source, the collimated polarization module, the atomic gas chamber and the photoelectric detector are arranged in sequence and the entrances and exits are arranged oppositely, wherein the linearly polarized light emitted by the pump light source passes through the collimated polarization module to obtain parallel circularly polarized light, and the circularly polarized light passes through the atomic gas chamber, and the atoms in the atomic gas chamber are polarized under the action of the circularly polarized light, and the atomic magnetic moment precesses in the magnetic field to be measured, and the circularly polarized light is partially absorbed by the atoms in the atomic gas chamber to obtain transmitted light, and the transmitted light enters the photoelectric detector;

[0007] The radio frequency coil is wound outside the atomic gas chamber, and the axial direction of the radio frequency coil is the same as the direction of the optical path, and is used to generate a radio frequency magnetic field through a radio frequency signal;

[0008] The photodetector is connected to the input end of the amplifier, and is used to convert the transmitted light into an electrical signal and send it to the amplifier;

[0009] The output end of the amplifier is connected to the radio frequency coil, and is used to perform phase shift amplification on the electrical signal to obtain a radio frequency adjustment signal, and feed the radio frequency adjustment signal back to the radio frequency coil. The radio frequency adjustment signal is used to adjust the frequency of the radio frequency signal in the radio frequency coil to be the same as the precession frequency of the atomic magnetic moment, so that the radio frequency magnetic field resonates with the magnetic field to be measured, and the frequency of the radio frequency signal is locked at the precession frequency;

[0010] The control module includes a frequency measurement module, which is connected to the radio frequency coil and is used to measure the frequency of the radio frequency signal.

[0011] A second aspect of an embodiment of the present application provides a control method for a laser pumped magnetometer, which is applied to the above-mentioned laser pumped magnetometer, comprising:

[0012] Controlling the operating temperature of the pump light source within a first preset temperature range, and controlling the temperature of the atomic gas chamber within a second preset temperature range;

[0013] Controlling the output power of the pump light source to be a preset power, and controlling the emission wavelength of the pump light source to be a preset wavelength;

[0014] Controlling the radio frequency coil to generate a radio frequency magnetic field;

[0015] Control the pump light source to emit linearly polarized light, and control the linearly polarized light to pass through the collimation polarization module and the atomic gas chamber in sequence to obtain the transmitted light corresponding to the linearly polarized light; wherein the atomic magnetic moment in the atomic gas chamber produces precession in the magnetic field to be measured;

[0016] Control the photodetector to receive the optical signal corresponding to the transmitted light and convert the optical signal into an electrical signal;

[0017] The electrical signal is phase-shifted and amplified by an amplifier to obtain a radio frequency adjustment signal, and the radio frequency adjustment signal is controlled to be fed back to the radio frequency coil, the radio frequency adjustment signal is used to adjust the radio frequency signal in the radio frequency coil to a frequency that is equal to the precession frequency of the atomic magnetic moment, so that the radio frequency magnetic field resonates with the magnetic field to be measured, and the frequency of the radio frequency signal is locked at the precession frequency;

[0018] The frequency measurement module obtains the radio frequency signal in the radio frequency coil, determines the frequency of the radio frequency signal, and sends the frequency of the radio frequency signal to the host computer through the data communication module;

[0019] When the intensity of the light signal received by the photodetector is the largest, the intensity of the magnetic field to be measured is determined by the host computer according to the frequency of the radio frequency signal.

[0020] Compared with the prior art, the embodiments of the present application have the following beneficial effects: linearly polarized light is emitted by a pump light source, and the linearly polarized light passes through a collimated polarization module to obtain parallel circularly polarized light. The circularly polarized light passes through an atomic gas chamber and is partially absorbed by atoms in the atomic gas chamber to obtain transmitted light. The transmitted light enters a photodetector, and an RF coil wound outside the atomic gas chamber generates an RF magnetic field through an RF signal, adjusts the frequency of the RF signal to make the RF magnetic field resonate with the magnetic field to be measured, and locks the frequency of the RF signal at the precession frequency. Since the precession frequency is proportional to the size of the magnetic field to be measured, the frequency of the RF signal is measured by a frequency measurement module, and the size of the magnetic field to be measured can be calculated, thereby achieving high-precision measurement of the magnetic field to be measured. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0022] Figure 1 It is a structural schematic diagram of a laser pumped magnetometer provided in an embodiment of the present application;

[0023] Figure 2 is a schematic structural diagram of a collimating polarization module provided in an embodiment of the present application;

[0024] Figure 3 is a schematic diagram of the local connection relationship of the control module provided in the embodiment of the present application;

[0025] Figure 4A It is a schematic diagram of the connection relationship between the microcontroller and other modules provided in the embodiment of the present application;

[0026] Figure 4B This is a schematic diagram of the connection relationship between the power supply module and other modules provided in an embodiment of the present application;

[0027] Figure 4C It is a schematic diagram of the connection relationship between the data communication module and other modules provided in the embodiment of the present application;

[0028] Figure 5 It is a flow chart of a control method of a laser pumped magnetometer provided in an embodiment of the present application;

[0029] Figure 6 It is a structural diagram of a host computer provided in an embodiment of the present application. DETAILED DESCRIPTION

[0030] In the following description, specific details such as specific system structures, technologies, etc. are provided for the purpose of illustration rather than limitation, so as to provide a thorough understanding of the embodiments of the present application. However, it should be clear to those skilled in the art that the present application may also be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted to prevent unnecessary details from obstructing the description of the present application.

[0031] The terms "first", "second", etc. in the specification and claims of this application are used to distinguish similar objects, and are not used to describe a specific order or sequence. It should be understood that the data used in this way can be interchangeable where appropriate, so that the embodiments of the present application can be implemented in an order other than those illustrated or described here, and the objects distinguished by "first", "second", etc. are generally of the same type, and the number of objects is not limited. For example, the first object can be one or more. In addition, "and / or" in the specification and claims represents at least one of the connected objects, and the character " / " generally indicates that the objects associated with each other are in an "or" relationship.

[0032] In addition, it should be noted that the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "includes..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0033] A laser pumped magnetometer and a control method thereof according to an embodiment of the present application will be described in detail below with reference to the accompanying drawings.

[0034] Figure 1 is a schematic diagram of the structure of a laser pumped magnetometer provided in an embodiment of the present application, Figure 1 Arrows indicate the direction of the light path.

[0035] like Figure 1 As shown, the laser pumped magnetometer includes a pump light source 1, a collimation polarization module 2, an atomic gas chamber 3, a radio frequency coil 4, a photodetector 5, an amplifier 6, and a control module 7;

[0036] The pump light source 1, the collimated polarization module 2, the atomic gas chamber 3 and the photodetector 5 are arranged in sequence and the entrances and exits are arranged opposite to each other, wherein the linearly polarized light emitted by the pump light source 1 passes through the collimated polarization module 2 to obtain parallel circularly polarized light, and the circularly polarized light passes through the atomic gas chamber 3, and the atoms in the atomic gas chamber 3 are polarized under the action of the circularly polarized light, and the atomic magnetic moment precesses in the magnetic field to be measured, and the circularly polarized light is partially absorbed by the atoms in the atomic gas chamber 3 to obtain transmitted light, and the transmitted light enters the photodetector 5;

[0037] The radio frequency coil 4 is wound outside the atomic gas chamber 3, and the axial direction of the radio frequency coil 4 is the same as the direction of the optical path, and is used to generate a radio frequency magnetic field through a radio frequency signal;

[0038] The photodetector 5 is connected to the input end of the amplifier 6, and the photodetector 5 is used to convert the transmitted light into an electrical signal and send it to the amplifier 6;

[0039] The output end of the amplifier 6 is connected to the radio frequency coil 4, and is used to perform phase shift amplification on the electrical signal to obtain a radio frequency adjustment signal, and feed the radio frequency adjustment signal back to the radio frequency coil 4. The radio frequency adjustment signal is used to adjust the frequency of the radio frequency signal in the radio frequency coil 4 to be the same as the precession frequency of the atomic magnetic moment, so that the radio frequency magnetic field resonates with the magnetic field to be measured, and the frequency of the radio frequency signal is locked at the precession frequency;

[0040] The control module 7 includes a frequency measurement module 71 , which is connected to the radio frequency coil 4 and is used to measure the frequency of the radio frequency signal.

[0041] Specifically, when the atomic magnetic moment is in the magnetic field to be measured, if the magnetic moment of the atomic nucleus is in a direction different from that of the magnetic field to be measured, a plane is determined according to the direction of the magnetic moment and the direction of the magnetic field to be measured. Under the action of the magnetic field, the atomic nucleus will be subjected to a torque perpendicular to the plane. Under the action of the torque, the atomic magnetic moment will precess. During the precession process, the quantum state of the atom also changes rapidly. Due to the different absorption and dispersion characteristics of different quantum states to the laser, the light beam passing through the atomic gas produces a light intensity change corresponding to the precession frequency. The corresponding change signal of the precession frequency is neutralized by the transmitted light, and after a series of processing, the radio frequency adjustment signal is sent back to the radio frequency coil surrounding the atomic gas chamber to form positive feedback. When the frequency of the radio frequency signal in the radio frequency coil resonates with the precession frequency of the atom, the transmitted light can generate the strongest detection signal, and the self-excited oscillation formed by the positive feedback will be stabilized at the atomic precession frequency. Since the precession frequency is proportional to the size of the magnetic field to be measured, the high-precision measurement of the magnetic field to be measured can be achieved by measuring the frequency of the self-excited oscillation.

[0042] According to the technical solution provided in the embodiment of the present application, linearly polarized light is emitted by a pump light source, and the linearly polarized light passes through a collimated polarization module to obtain parallel circularly polarized light. The circularly polarized light passes through an atomic gas chamber and is partially absorbed by the atoms in the atomic gas chamber to obtain transmitted light. The transmitted light enters a photodetector, and an RF coil wound outside the atomic gas chamber generates an RF magnetic field through an RF signal. The frequency of the RF signal is adjusted to make the RF magnetic field resonate with the magnetic field to be measured, and the frequency of the RF signal is locked at the precession frequency. Since the precession frequency is proportional to the size of the magnetic field to be measured, the frequency of the RF signal is measured by a frequency measurement module, and the size of the magnetic field to be measured can be calculated, thereby achieving high-precision measurement of the magnetic field to be measured.

[0043] In some embodiments, Figure 2 As shown, the collimating polarization module 2 includes a collimating lens 21, a filter 22 and a quarter wave plate 23, and the collimating lens 21, the filter 22 and the quarter wave plate 23 are arranged in sequence and their centers are aligned;

[0044] The linearly polarized light passes through the collimating lens 21, the filter 22 and the quarter wave plate 23 in sequence;

[0045] The collimating lens 21 is used to convert the linear polarized light into parallel linear polarized light to obtain the first light;

[0046] The filter 22 is used to eliminate the light whose wavelength is not the preset wavelength in the first light to obtain the second light;

[0047] The quarter wave plate 23 is used to increase the phase difference between the ordinary light and the extraordinary light in the second light by π / 2, so as to obtain parallel circularly polarized light.

[0048] Specifically, the divergence angle of the laser is very small and has good directivity, so it can be considered as approximately parallel light. However, approximately parallel does not mean no divergence at all. In order to ensure that the light entering the atomic gas chamber is parallel, a collimating lens is needed to collimate the linearly polarized light emitted by the pump light source to further improve its directivity.

[0049] Lasers also have the characteristics of narrow frequency range and good monochromaticity. However, in actual use, the wavelength of the laser emitted by the pump light source may drift due to temperature changes, mechanical vibrations, etc. In order to ensure the stability of the wavelength of the light entering the atomic gas chamber, it is necessary to use a filter to eliminate the light in the first light whose wavelength is not the preset wavelength. The preset wavelength is equal to the emission wavelength of the pump light source.

[0050] To polarize the alkali metal atoms in the atomic gas chamber, it is necessary to pump the alkali metal atoms from the ground state Zeeman sublevel to the excited state by circularly polarized light, but the laser emitted by the pump light source is linearly polarized light, so it is necessary to pass a quarter wave plate to generate a phase delay of π / 2 in the second light to obtain circularly polarized light. Circularly polarized light can be left-handed light or right-handed light, and the embodiments of the present application do not make specific restrictions.

[0051] According to the technical solution provided in the embodiment of the present application, the linearly polarized light emitted by the pump light source is collimated by a collimating lens, the filter eliminates stray light, and the quarter-wave plate realizes phase delay, thereby obtaining the parallel circularly polarized light required for polarizing alkali metal atoms.

[0052] In some embodiments, the pump light source 1 is a vertical-cavity surface-emitting laser (VCSEL) with single-mode output, and the parameters of the VCSEL satisfy that the output power is less than a preset power threshold, the spot diameter is a first preset diameter, and the emission wavelength is the wavelength corresponding to the cesium atom D1 line.

[0053] Specifically, compared with the traditional edge-emitting laser (EEL), VCSEL has the characteristics of small beam divergence angle and low power consumption. Its single-mode characteristics are stable for a long time, polarization is stable, and there will be no mode hopping and power fluctuation. It can achieve stable output of single-mode narrow-linewidth laser under high temperature conditions.

[0054] The preset power threshold can be 2W, 3W, 4W, etc., and the first preset diameter can be 2mm, 3mm, 4mm, etc. The specific value can be set according to the device parameters in actual use.

[0055] The D1 line of cesium atom is the 6S1 / 2→6P1 / 2 transition absorption line, which is about 894nm.

[0056] According to the technical solution provided in the embodiment of the present application, by utilizing VCSEL to emit linearly polarized light, stable output of single-mode narrow-linewidth laser is achieved.

[0057] In some embodiments, the atomic gas chamber 3 is a cylindrical cesium absorption chamber, and the bottom diameter of the cylindrical cesium absorption chamber is a second preset diameter, and the longitudinal height is a preset height.

[0058] Specifically, the spin exchange collision cross sections of commonly used alkali metal atoms are similar, and the physical limits of magnetometer sensitivity are basically the same. However, cesium atoms have the highest vapor pressure at the same temperature and can operate at lower temperatures, which is beneficial to reducing the power consumption of the magnetometer. Therefore, cesium atoms are selected as the working atoms of the magnetometer.

[0059] The second preset diameter may be 7 mm, 8 mm, 9 mm, etc., and the preset height may be 7 mm, 8 mm, 9 mm, etc.

[0060] According to the technical solution provided in the embodiment of the present application, by adopting a cylindrical cesium absorption chamber with a small diameter and height as an atomic gas chamber, the volume and weight of the laser pumped magnetometer are reduced, which is conducive to miniaturization of the laser pumped magnetometer while reducing power consumption.

[0061] In some embodiments, the pressure in the atomic gas chamber 3 is a first preset pressure, and is filled with nitrogen gas at a second preset pressure.

[0062] Specifically, the first preset pressure may be 101 kPa, and the second preset pressure may be 760 torr.

[0063] Once the angular momentum of alkali metal atoms collides with the glass wall of the atomic gas cell, the polarization direction will change. To obtain a longer spin coherence time, the relaxation caused by the collision of the atomic gas cell wall must be prevented. Therefore, high-pressure inert gas nitrogen is added to the atomic gas cell to prevent the diffusion of alkali metal atoms and reduce the effect of collisions between atoms and the gas cell on the reduction of the polarization lifetime of cesium atoms.

[0064] According to the technical solution provided in the embodiment of the present application, nitrogen is filled into the atomic gas chamber, thereby reducing the effect of collisions between atoms and the gas chamber on the polarization lifetime of cesium atoms.

[0065] In some embodiments, the atomic gas chamber 3 is made of high borosilicate glass, and the outer side is evenly wrapped with thermal insulation asbestos, which is wrapped by high-temperature tape.

[0066] Specifically, asbestos has good thermal insulation properties, so asbestos is used to insulate the atomic gas chamber; but since asbestos fibers are harmful to the human body, high-temperature tape is used to wrap the insulating asbestos to prevent the flocs from flying out and contacting the skin or being inhaled into the lungs to cause harm to the human body.

[0067] According to the technical solution provided in the embodiment of the present application, the atomic gas chamber is wrapped with thermal insulation asbestos to achieve thermal insulation of the atomic gas chamber, and the thermal insulation asbestos is wrapped with high-temperature tape to improve safety.

[0068] In some embodiments, Figure 3 As shown, the control module 7 also includes a light source constant current control module 72, a light source frequency stabilization module 73, a temperature acquisition module 74 and a temperature control module 75;

[0069] The light source constant current control module 72 is connected to the pump light source 1, and is used to supply power to the pump light source 1 and control the output power of the pump light source 1 to remain unchanged;

[0070] The light source frequency stabilization module 73 is connected to the pump light source 1 and is used to adjust the parameters of the pump light source 1 so that the emission wavelength of the pump light source 1 is maintained at the wavelength corresponding to the cesium atom D1 line;

[0071] The temperature acquisition module 74 is connected to the pump light source 1 and the atomic gas chamber 3, and is used to acquire the working temperature of the pump light source 1 and the temperature of the atomic gas chamber 3;

[0072] The temperature control module 75 includes a light source constant temperature control module 751 and an air chamber constant temperature control module 752; wherein the light source constant temperature control module 751 is connected to the pump light source 1, and is used to perform closed-loop control on the operating temperature of the pump light source 1 according to the operating temperature of the pump light source 1 using a proportional-integral-differential (PID) algorithm, so that the operating temperature of the pump light source 1 is maintained within a first preset temperature range; the air chamber constant temperature control module 752 is connected to the atomic gas chamber 3, and is used to perform closed-loop control on the temperature of the atomic gas chamber 3 according to the temperature of the atomic gas chamber 3 using a PID algorithm, so that the temperature of the atomic gas chamber 3 is maintained within a second preset temperature range.

[0073] Specifically, the first preset temperature range may be -35 to 135 degrees Celsius, and the second preset temperature range may be 80 to 150 degrees Celsius.

[0074] For the pump light source, since the accuracy and reliability of the pump light source directly determine the performance indicators of the magnetometer, it is necessary to keep the output power and emission wavelength of the pump light source accurate and reliable. In addition, in order to avoid temperature effects such as temperature drift, it is necessary to ensure that the operating temperature of the pump light source does not change with the external environment and its own heat.

[0075] For the atomic gas cell, the collision between the spin relaxation of cesium atoms in the atomic gas cell and the device wall will increase with the increase of the gas cell temperature. Excessive relaxation will cause the polarized cesium atoms to depolarize and reduce the sensitivity of the system. Therefore, the atomic gas cell needs to be maintained at a constant optimal temperature.

[0076] According to the technical solution provided in the embodiment of the present application, the output power of the pump light source is controlled by the light source constant current control module, the light source frequency stabilization module controls the emission wavelength of the pump light source, and the temperature acquisition module and the temperature control module monitor and control the temperature of the pump light source and the atomic gas chamber to ensure the accuracy and sensitivity of the laser pumped magnetometer.

[0077] In some embodiments, Figure 4A , Figure 4B , Figure 4C As shown, the control module 7 also includes a microcontroller 76, a power supply module 77 and a data communication module 78;

[0078] The microcontroller 76 is connected to the remaining modules in the control module 7 and is used to control the modules other than the microcontroller 76;

[0079] The power supply module 77 is connected to the external power supply and to the remaining modules in the control module 7, and is used to convert the voltage of the external power supply into the voltage required by the modules other than the power supply module 77, and to supply power to the modules other than the power supply module 77;

[0080] The data communication module 78 is connected to the host computer and the microcontroller 76, and is used to send the frequency of the radio frequency signal obtained by the frequency measurement module 71 to the host computer, so that the host computer determines the strength of the magnetic field to be measured according to the frequency of the radio frequency signal.

[0081] Specifically, the step of calculating the strength of the magnetic field to be measured according to the frequency of the radio frequency signal is handed over to the host computer for execution, thereby reducing the number of components on the laser pumped magnetometer and minimizing the volume and weight of the laser pumped magnetometer.

[0082] According to the technical solution provided in the embodiment of the present application, the other modules are controlled by a microcontroller, the power supply module provides the voltage required for the operation of the other modules, and the data communication module sends the frequency of the radio frequency signal to the host computer so that the host computer can calculate the strength of the magnetic field to be measured, thereby ensuring the normal operation of the entire laser pumped magnetometer and reducing the volume and weight of the laser pumped magnetometer, which is conducive to the miniaturization of the laser pumped magnetometer.

[0083] In some embodiments, the microcontroller 76 is STM32F373CCT6 and the time-to-digital converter is TDC7200;

[0084] The voltage required by the modules in the control module 7 except the microcontroller 76 and the frequency measurement module 71 is 5V;

[0085] The voltage required by the microcontroller 76 and the frequency measurement module 71 is 3.3V.

[0086] Specifically, the STM32F373CCT6 has high performance, real-time functions, digital signal processing, low power consumption and low voltage operation characteristics, while maintaining high integration and easy development.

[0087] The TDC7200 has a built-in self-calibrated time base that compensates for time and temperature deviations, allowing the time-to-digital converter to achieve picosecond accuracy.

[0088] The power supply module 77 obtains a 5V voltage through an external power supply, and can directly supply the 5V voltage to modules other than the microcontroller 76 and the frequency measurement module 71; in addition, since the operating voltage of the STM32F373CCT6 and the time-to-digital converter is 3.3V, the 5V voltage cannot be used directly, so the power supply module 77 adjusts the 5V voltage to 3.3V through a step-down circuit, and then supplies the 3.3V voltage to the microcontroller 76 and the frequency measurement module 71.

[0089] According to the technical solution provided in the embodiment of the present application, by using STM32F373CCT6 as a microcontroller and TDC7200 as a time-to-digital converter, low power consumption and high precision of the control module are ensured; and the required voltage is provided to each module to ensure the normal operation of the control module.

[0090] Figure 5 It is a flow chart of a control method of a laser pumped magnetometer provided in an embodiment of the present application. Figure 5 The control method of the laser pumped magnetometer can be performed by the above-mentioned laser pumped magnetometer. Figure 5 As shown, the control method of the laser pumped magnetometer includes:

[0091] S501, controlling the radio frequency coil to generate a radio frequency magnetic field.

[0092] Specifically, a frequency generator may be used to input an initial radio frequency signal into the radio frequency coil, thereby generating an initial radio frequency magnetic field.

[0093] S502, controlling the pump light source to emit linearly polarized light, and controlling the linearly polarized light to pass through the collimating polarization module and the atomic gas chamber in sequence, to obtain transmitted light corresponding to the linearly polarized light.

[0094] The atomic magnetic moments in the atomic gas chamber precess in the magnetic field to be measured.

[0095] Specifically, the specific linear polarized light emitted by the pump light source resonates with the atomic energy level transition, and becomes parallel circular polarized light after passing through the collimated polarization module. Under the action of the circular polarized light, the spins of the atoms in the atomic gas chamber obtain the angular momentum corresponding to the polarization of the light, and the disordered arrangement in the thermal equilibrium state is changed into a neat and consistent arrangement. Since the atomic magnetic moment and the atomic angular momentum have a corresponding relationship, the atomic magnetic moment also achieves the same direction, thus generating a macroscopic magnetic moment.

[0096] The atoms in the atomic gas cell precess in the magnetic field to be measured, the circularly polarized light is partially absorbed by the atoms in the atomic gas cell, and the optical signal intensity of the transmitted light changes with the precession frequency.

[0097] S503, controlling the photodetector to receive the optical signal corresponding to the transmitted light, and converting the optical signal into an electrical signal.

[0098] Specifically, the optical signal of the transmitted light is converted into an electrical signal through a photodetector to facilitate subsequent analysis and processing.

[0099] S504, phase-shifting and amplifying the electrical signal through the amplifier to obtain a radio frequency adjustment signal, and controlling the radio frequency adjustment signal to be fed back to the radio frequency coil. The radio frequency adjustment signal is used to adjust the radio frequency signal in the radio frequency coil to a frequency that is equal to the precession frequency of the atomic magnetic moment, so that the radio frequency magnetic field resonates with the magnetic field to be measured, and the frequency of the radio frequency signal is locked at the precession frequency.

[0100] Specifically, the electrical signal is phase matched and amplified, and the obtained radio frequency adjustment signal is fed back to the radio frequency coil to form positive feedback, so that the system generates self-excited oscillation.

[0101] S505, obtaining the radio frequency signal in the radio frequency coil through the frequency measurement module, determining the frequency of the radio frequency signal, and sending the frequency of the radio frequency signal to the host computer through the data communication module.

[0102] Specifically, the frequency measurement module obtains the RF signal, converts the RF signal through TDC7200, obtains the time difference between the rising edges of the START signal and several STOP signals, and further calculates the single cycle time and the frequency of the RF signal.

[0103] S506, when the intensity of the light signal received by the photodetector is the largest, the intensity of the magnetic field to be measured is determined by the host computer according to the frequency of the radio frequency signal.

[0104] Specifically, when the intensity of the optical signal is maximum, it indicates that the system has generated self-oscillation and the frequency of the radio frequency signal has been locked at the precession frequency. At this time, the intensity of the magnetic field to be measured can be calculated based on the frequency of the radio frequency signal.

[0105] According to the technical solution provided in the embodiment of the present application, linearly polarized light is generated by a pump light source, and the linearly polarized light becomes parallel circularly polarized light after passing through a collimated polarization module. Under the action of the circularly polarized light, the atoms in the atomic gas chamber are polarized; the radio frequency signal in the radio frequency coil is positively feedback regulated until the system self-oscillates, and the radio frequency signal is locked at the precession frequency. The strength of the magnetic field to be measured is determined according to the frequency of the radio frequency signal, thereby achieving high-precision magnetic field measurement.

[0106] In some embodiments, before controlling the pump light source to emit linearly polarized light, the method further includes:

[0107] Controlling the operating temperature of the pump light source within a first preset temperature range, and controlling the temperature of the atomic gas chamber within a second preset temperature range;

[0108] The output power of the pump light source is controlled to be a preset power, and the emission wavelength of the pump light source is controlled to be a preset wavelength.

[0109] Specifically, the preset power may be controlled to be 1W, 2W, 3W, etc., and the preset power is less than a preset power threshold.

[0110] According to the technical solution provided in the embodiment of the present application, by controlling the operating temperature and output power of the pump light source and the temperature of the atomic gas chamber, the pump light source and the atomic gas chamber are ensured to operate stably, thereby ensuring the accuracy of the magnetic field measurement.

[0111] It should be understood that the size of the serial numbers of the steps in the above embodiments does not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0112] Figure 6 Schematic diagram of the host computer 8 provided in the embodiment of the present application. Figure 6 As shown, the host computer 8 of this embodiment includes: a processor 801, a memory 802, and a computer program 803 stored in the memory 802 and executable on the processor 801. When the processor 801 executes the computer program 803, the steps in the above-mentioned method embodiments are implemented. Alternatively, when the processor 801 executes the computer program 803, the functions of the modules / units in the above-mentioned device embodiments are implemented.

[0113] The host computer 8 may be an electronic device such as a desktop computer, a notebook, a PDA, or a cloud server. The host computer 8 may include but is not limited to a processor 801 and a memory 802. Those skilled in the art will appreciate that Figure 6 The above is only an example of the host computer 8 and does not constitute a limitation on the host computer 8 , which may include more or less components than those shown in the figure, or different components.

[0114] The processor 801 may be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc.

[0115] The memory 802 may be an internal storage unit of the host computer 8, for example, a hard disk or memory of the host computer 8. The memory 802 may also be an external storage device of the host computer 8, for example, a plug-in hard disk, a smart media card (SMC), a secure digital (SD) card, a flash card, etc. equipped on the host computer 8. The memory 802 may also include both an internal storage unit of the host computer 8 and an external storage device. The memory 802 is used to store computer programs and other programs and data required by the electronic device.

[0116] Those skilled in the art can clearly understand that for the convenience and simplicity of description, only the division of the above-mentioned functional units and modules is used as an example. In actual applications, the above-mentioned functions can be assigned to different functional units and modules as needed, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above. The functional units and modules in the embodiments can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The above-mentioned integrated unit can be implemented in the form of hardware or in the form of software functional units.

[0117] If the integrated module / unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a readable storage medium (e.g., a computer-readable storage medium). Based on this understanding, the present application implements all or part of the processes in the above-mentioned embodiment method, and can also be completed by instructing the relevant hardware through a computer program. The computer program can be stored in a computer-readable storage medium, and the computer program can implement the steps of the above-mentioned various method embodiments when executed by the processor. The computer program may include computer program code, which may be in source code form, object code form, executable file or some intermediate form. Computer-readable storage media may include: any entity or device capable of carrying computer program code, recording medium, U disk, mobile hard disk, disk, optical disk, computer memory, read-only memory (ROM), random access memory (RAM), electric carrier signal, telecommunication signal and software distribution medium, etc.

[0118] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application, and should all be included in the protection scope of the present application.

Claims

1. A laser pumped magnetometer, It is characterized in that It includes pump light source, collimation polarization module, atomic gas chamber, radio frequency coil, photodetector, amplifier and control module; The pump light source, the collimated polarization module, the atomic gas chamber and the photoelectric detector are arranged in sequence and the entrances and exits are arranged opposite to each other, wherein the linearly polarized light emitted by the pump light source passes through the collimated polarization module to obtain parallel circularly polarized light, the circularly polarized light passes through the atomic gas chamber, the atoms in the atomic gas chamber are polarized under the action of the circularly polarized light, the atomic magnetic moment precesses in the magnetic field to be measured, the circularly polarized light is partially absorbed by the atoms in the atomic gas chamber to obtain transmitted light, and the transmitted light enters the photoelectric detector; The radio frequency coil is wound outside the atomic gas chamber, and the axial direction of the radio frequency coil is the same as the direction of the optical path, and is used to generate a radio frequency magnetic field through a radio frequency signal; The photodetector is connected to the input end of the amplifier, and is used to convert the transmitted light into an electrical signal and send it to the amplifier; The output end of the amplifier is connected to the radio frequency coil, and is used to perform phase shift amplification on the electrical signal to obtain a radio frequency adjustment signal, and feed the radio frequency adjustment signal back to the radio frequency coil, wherein the radio frequency adjustment signal is used to adjust the frequency of the radio frequency signal in the radio frequency coil to be the same as the precession frequency of the atomic magnetic moment, so that the radio frequency magnetic field resonates with the magnetic field to be measured, and the frequency of the radio frequency signal is locked at the precession frequency; The control module includes a frequency measurement module, which is connected to the radio frequency coil and is used to measure the frequency of the radio frequency signal.

2. The laser pumped magnetometer according to claim 1, It is characterized in that The collimating polarization module comprises a collimating lens, a filter and a quarter wave plate, and the collimating lens, the filter and the quarter wave plate are arranged in sequence and their centers are aligned; The linearly polarized light passes through the collimating lens, the filter and the quarter wave plate in sequence; The collimating lens is used to convert the linear polarized light into parallel linear polarized light to obtain a first light; The filter is used to eliminate the light whose wavelength is not the preset wavelength in the first light to obtain the second light; The quarter wave plate is used to increase the phase difference between the ordinary light and the extraordinary light in the second light by π / 2 to obtain the parallel circularly polarized light.

3. The laser pumped magnetometer according to claim 1, It is characterized in that The pump light source is a vertical cavity surface emitting laser (VCSEL) with single-mode output, and the parameters of the VCSEL satisfy that the output power is less than a preset power threshold, the spot diameter is a first preset diameter, and the emission wavelength is a wavelength corresponding to the cesium atom D1 line.

4. The laser pumped magnetometer according to claim 1, It is characterized in that The atomic gas chamber is a cylindrical cesium absorption chamber, and the bottom diameter of the cylindrical cesium absorption chamber is a second preset diameter, and the longitudinal height of the cylindrical cesium absorption chamber is a preset height.

5. The laser pumped magnetometer according to claim 1, It is characterized in that The pressure in the atomic gas chamber is a first preset pressure, and the atomic gas chamber is filled with nitrogen gas at a second preset pressure.

6. The laser pumped magnetometer according to claim 1, It is characterized in that The atomic gas chamber is made of high borosilicate glass, and the outer side is evenly wrapped with heat-insulating asbestos, which is wrapped by high-temperature tape.

7. The laser pumped magnetometer according to claim 1, It is characterized in that The control module also includes a light source constant current control module, a light source frequency stabilization module, a temperature acquisition module and a temperature control module; The light source constant current control module is connected to the pump light source, and is used to supply power to the pump light source and control the output power of the pump light source to remain unchanged; The light source frequency stabilization module is connected to the pump light source and is used to adjust the parameters of the pump light source so that the emission wavelength of the pump light source is maintained at the wavelength corresponding to the D1 line of the cesium atom; The temperature acquisition module is connected to the pump light source and the atomic gas chamber, and is used to acquire the working temperature of the pump light source and the temperature of the atomic gas chamber; The temperature control module includes a light source constant temperature control module and an air chamber constant temperature control module; wherein the light source constant temperature control module is connected to the pump light source, and is used to perform closed-loop control on the working temperature of the pump light source using a proportional-integral-differential PID algorithm according to the working temperature of the pump light source, so that the working temperature of the pump light source is maintained within a first preset temperature range; the air chamber constant temperature control module is connected to the atomic gas chamber, and is used to perform closed-loop control on the temperature of the atomic gas chamber using a PID algorithm according to the temperature of the atomic gas chamber, so that the temperature of the atomic gas chamber is maintained within a second preset temperature range.

8. The laser pumped magnetometer according to claim 7, It is characterized in that The control module also includes a microcontroller, a power supply module and a data communication module; The microcontroller is connected to the remaining modules in the control module and is used to control the modules other than the microcontroller; The power supply module is connected to an external power supply and to the remaining modules in the control module, and is used to convert the voltage of the external power supply into the voltage required by the modules other than the power supply module, and to supply power to the modules other than the power supply module; The data communication module is connected to the host computer and the microcontroller, and is used to send the frequency of the radio frequency signal obtained by the frequency measurement module to the host computer, so that the host computer determines the intensity of the magnetic field to be measured according to the frequency of the radio frequency signal.

9. The laser pumped magnetometer according to claim 8, It is characterized in that The microcontroller is STM32F373CCT6, and the time-to-digital converter is TDC7200; The voltage required by the modules in the control module except the microcontroller and the frequency measurement module is 5V; The voltage required by the microcontroller and the frequency measurement module is 3.3V.

10. A control method for a laser pumped magnetometer, applied to the laser pumped magnetometer according to any one of claims 1 to 9, It is characterized in that include: Controlling the radio frequency coil to generate a radio frequency magnetic field; Controlling the pump light source to emit linearly polarized light, and controlling the linearly polarized light to pass through the collimation polarization module and the atomic gas chamber in sequence, to obtain the transmitted light corresponding to the linearly polarized light; wherein the atomic magnetic moment in the atomic gas chamber produces precession in the magnetic field to be measured; Controlling the photodetector to receive a light signal corresponding to the transmitted light and converting the light signal into an electrical signal; Performing phase shift amplification on the electrical signal through an amplifier to obtain a radio frequency adjustment signal, and controlling the radio frequency adjustment signal to be fed back to the radio frequency coil, wherein the radio frequency adjustment signal is used to adjust the radio frequency signal in the radio frequency coil to a frequency that is equal to the precession frequency of the atomic magnetic moment, so that the radio frequency magnetic field resonates with the magnetic field to be measured, and the frequency of the radio frequency signal is locked at the precession frequency; Acquire the radio frequency signal in the radio frequency coil through the frequency measurement module, determine the frequency of the radio frequency signal, and send the frequency of the radio frequency signal to the host computer through the data communication module; When the intensity of the optical signal received by the photoelectric detector is the largest, the intensity of the magnetic field to be measured is determined by the host computer according to the frequency of the radio frequency signal.

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