Photoelectric signal conversion system of magnetometer

Abstract

The invention relates to the technical field of magnetometers, and provides a photoelectric signal conversion system of a magnetometer. The photoelectric signal conversion system of the magnetometer comprises an optical lens group, a photoelectric signal conversion module and a photoelectric signal conversion module, which are sequentially arranged along a light propagation direction, wherein the optical lens group is used for carrying out light path adjustment on laser; the quarter-wave plate is used for converting the laser subjected to light path adjustment into circular polarized light from linear polarized light; the coil and the atomic gas chamber are used for receiving the circular polarized light, and the circular polarized light and alkali metal atoms in the atomic gas chamber interact in the superimposed magnetic field to form transmission light containing magnetic resonance information; the variable-focus lens group is used for performing variable-focus focusing on the transmission light; and the photoelectric detector is used for converting the focused transmission light into a voltage signal and outputting the voltage signal so as to determine the current environment magnetic field according to the voltage signal.

Description

Technical Field

[0001] The present disclosure relates to the technical field of magnetometers, and in particular to a photoelectric signal conversion system of a magnetometer. Background Art

[0002] Magnetometers are basic instruments for magnetic detection and ground magnetic field observation, and their performance directly determines the accuracy of magnetic field measurement. OPM (Optical-Pumping Magnetometer) refers to a type of magnetometer that uses the optical pumping effect to polarize atoms and destroys the polarization state by applying an external radio frequency field to achieve magnetic field measurement.

[0003] In the laser pump magnetometer, alkali metal atoms and the pump laser entering the atomic gas chamber realize laser pumping in the atomic gas chamber. The light intensity after passing through the atomic gas chamber will change with the strength of the magnetic field to be measured. A modulated magnetic field with known magnetic field strength and frequency is added in the same direction as the magnetic field to be measured. The modulated magnetic field makes the transmitted light intensity contain modulation information. After the transmitted light is converted into a voltage signal by the photodetector, the magnetic field value to be measured can be obtained according to the voltage signal.

[0004] In the related art, when the optical signal containing magnetic resonance information transmitted from the atomic gas chamber is incident on the photodetector, the beam size of the optical signal may not match the photosensitive surface of the photodetector, which will cause the voltage signal output by the photodetector to be inaccurate, thereby resulting in low accuracy of the magnetic field strength measurement results of the magnetometer. Summary of the invention

[0005] In view of this, an embodiment of the present disclosure provides a photoelectric signal conversion system of a magnetometer to solve the technical problem of low accuracy of magnetic field intensity measurement results of a magnetometer in the prior art.

[0006] To achieve the above objectives, the technical solution adopted by the present disclosure is:

[0007] The disclosed embodiment provides a photoelectric signal conversion system of a magnetometer, and the photoelectric signal conversion system of the magnetometer includes: the photoelectric signal conversion system includes: an optical lens group arranged in sequence along the light propagation direction, used for adjusting the optical path of the laser; a quarter-wave plate, used for converting the laser after the optical path adjustment from linear polarization to circular polarization; a coil and an atomic gas chamber, used for receiving the circularly polarized light, the circularly polarized light interacts with the alkali metal atoms in the atomic gas chamber in a superimposed magnetic field to form a transmitted light containing magnetic resonance information, and the superimposed magnetic field is formed by superimposing the radio frequency magnetic field generated by the coil and the current environmental magnetic field; a variable focus lens group, used for performing variable focus on the transmitted light; a photodetector, used for converting the focused transmitted light into a voltage signal and outputting it, so as to determine the current environmental magnetic field according to the voltage signal.

[0008] In one embodiment, the optical lens assembly includes: a collimating lens for collimating the laser; and a folding prism for changing the optical path of the collimated laser.

[0009] In one embodiment, a folding prism is used to change the optical path of the laser by 90°.

[0010] In one embodiment, the optical-electrical signal conversion system further includes a polarization-maintaining optical fiber for transmitting the laser light generated by the laser to the optical mirror assembly.

[0011] In one embodiment, the alkali metal atoms in the atomic gas cell are cesium atoms.

[0012] In one embodiment, the atomic gas cell comprises a cylindrical atomic gas cell.

[0013] In one embodiment, the photodetector is a photodiode.

[0014] In one embodiment, the optical-to-electrical signal conversion system further includes a vertical cavity surface emitting laser, which is used to generate laser light.

[0015] In one embodiment, the variable focus lens group includes a convex lens and a concave lens. The magnification of the optical system can be adjusted by changing the position of the convex lens, and the outgoing light can be adjusted to be parallel light by adjusting the concave lens.

[0016] In one embodiment, the material of the quarter wave plate is optical glass or fused silica.

[0017] Compared with the prior art, the beneficial effect of the disclosed embodiment is as follows: by setting a variable focus lens group in the photoelectric signal conversion system of the magnetometer, the transmitted light emitted by the atomic gas chamber can be variable focused using different optical magnifications, thereby ensuring that the light signal incident on the photodetector is adapted to the photosensitive surface of the photodetector, thereby improving the accuracy of the magnetic field intensity measurement results of the magnetometer.

[0018] Specifically, by providing a variable focus lens group that can perform variable focus on the transmitted light, the beam size of the transmitted light of the atomic gas chamber can be adjusted so that the beam size is equal to the photosensitive surface of the photodetector, so that the photodetector can generate a more accurate voltage signal, thereby obtaining a more accurate magnetic field strength measurement value of the magnetometer. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present disclosure, 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 disclosure. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0020] Figure 1 is a structural schematic diagram of a photoelectric signal conversion system of a magnetometer provided in an embodiment of the present disclosure;

[0021] Figure 2 is a structural schematic diagram of another photoelectric signal conversion system of a magnetometer provided in an embodiment of the present disclosure;

[0022] Figure 3 It is a schematic diagram of the structure of a variable focus lens group provided in an embodiment of the present disclosure. DETAILED DESCRIPTION

[0023] The disclosed embodiments will now be described more fully with reference to the accompanying drawings in which the embodiments are shown. However, the disclosed embodiments may be implemented in many different forms and should not be construed as being limited to the embodiments specifically set forth herein; rather, the purpose of providing these embodiments is to make the disclosure exhaustive and complete and to fully convey the concepts of the embodiments to those skilled in the art so that they can implement the invention. The same reference numerals in the drawings represent the same elements, and therefore their descriptions will be omitted.

[0024] It should be understood that when an element is referred to as being connected to another element or being connected with another element, the element can be directly connected to another element, or there may be intervening elements between them. On the contrary, when an element is referred to as being directly connected to another element, there are no intervening elements.

[0025] Unless otherwise defined, all terms (including technical terms and scientific terms) used herein have the same meaning as those commonly understood by those skilled in the art to which the disclosed embodiments belong. It should also be understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning consistent with their meaning in the context of the relevant field, and unless explicitly defined as such in this article, will not be interpreted in an idealized or overly rigid sense.

[0026] The term "device" used in the embodiments may be a software component or a hardware component configured to perform a specific function. The hardware component may include a field programmable gate array (FPGA) or an application specific integrated circuit (ASIC). A software component may refer to data used by an executable code and / or data stored in an addressable storage medium and used by the executable code. Therefore, a software component may be, for example, an object-oriented software component, a class component, and a working component, and may include a process, a function, a property, a procedure, a subroutine, a program code segment, a driver, firmware, microcode, a circuit, data, a database, a data structure, a table, an array, or a variable.

[0027] The words used herein are for the purpose of describing specific embodiments and are not intended to be limiting of the present disclosure. It should be understood that the terms "include", "comprises", "comprising", "having", etc., when used in this specification, indicate the presence and characteristics, quantities, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other characteristics, quantities, steps, operations, elements, components and / or groups thereof.

[0028] The photoelectric signal conversion system of the magnetometer according to the embodiment of the present disclosure will be described in detail below with reference to the accompanying drawings.

[0029] Figure 1 is a structural schematic diagram of a photoelectric signal conversion system of a magnetometer provided in an embodiment of the present disclosure; Figure 2 is a structural schematic diagram of another photoelectric signal conversion system of a magnetometer provided in an embodiment of the present disclosure; Figure 3 Schematic diagram of the structure of the variable focus lens group provided by the embodiment of the present disclosure. Figures 1 to 3 The photoelectric signal conversion system of the magnetometer provided by the embodiment of the present disclosure is described together.

[0030] like Figure 1 As shown, the embodiment of the present disclosure provides a photoelectric signal conversion system of a magnetometer, and the photoelectric signal conversion system of the magnetometer includes: an optical lens group 101 arranged in sequence along the light propagation direction, used for adjusting the optical path of the laser; a quarter wave plate 102, used for converting the laser after the optical path adjustment from linear polarization to circular polarization; a coil and an atomic gas chamber 103, used for receiving the circularly polarized light, the circularly polarized light interacts with the alkali metal atoms in the atomic gas chamber in a superimposed magnetic field to form a transmitted light containing magnetic resonance information, and the superimposed magnetic field is formed by superimposing the radio frequency magnetic field generated by the coil and the current environmental magnetic field; a variable focus lens group 104, used for performing variable focus on the transmitted light; a photodetector 105, used for converting the focused transmitted light into a voltage signal and outputting it, so as to determine the current environmental magnetic field according to the voltage signal.

[0031] The photoelectric signal conversion system of the magnetometer of the embodiment of the present disclosure can adjust the beam size of the transmitted light of the atomic gas chamber by providing a variable focus lens group that can perform variable focus on the transmitted light, so that the beam size is equal to the photosensitive surface of the photodetector, so that the photodetector can generate a more accurate voltage signal, and then obtain a more accurate magnetic field intensity measurement value of the magnetometer.

[0032] When the optical lens assembly 101 adjusts the optical path of the laser, the laser can be collimated and the optical path can be changed. Light collimation means making the light parallel, and optical path change means changing the propagation direction of the light. Specifically, the optical lens assembly 101 may include a collimating lens and a folding lens. The collimating lens is used to collimate the laser; the folding prism is used to change the optical path of the collimated laser. The collimating lens refers to an instrument that can convert the light from each point in the aperture column into a parallel collimated light beam. The laser forms parallel light after passing through the collimating lens.

[0033] In the disclosed embodiment, the folding prism can change the optical path of the laser by 90°. The folding prism is a polyhedron made of transparent materials such as glass and crystal, which can be an isosceles right triangle prism, but is not limited to this. The prism surface of the isosceles right triangle prism consists of an inclined plane and a first right-angled plane and a second right-angled plane respectively connected to the two sides of the inclined plane and perpendicular to each other. The first right-angled plane is the light incident plane, the inclined plane is the total reflection plane, and the second right-angled plane is the light exit plane. The right triangle prism can change the optical path by 90°.

[0034] In the disclosed embodiment, the optoelectronic signal conversion system further includes a polarization-maintaining fiber for transmitting the laser light generated by the laser to the optical mirror assembly. The polarization-maintaining fiber can maintain the polarization state of the incident light by artificially introducing birefringence so that the birefringence at each axial position in the optical fiber remains unchanged. According to the size of the birefringence, the polarization-maintaining fiber can be divided into a high-birefringence fiber and a low-birefringence fiber.

[0035] In the technical solution of the embodiment of the present disclosure, the laser can be introduced through a polarization-maintaining optical fiber and then collimated by a collimating lens. The direction of the optical path is changed by 90° through a returning prism and then converted into circularly polarized light through a 1 / 4 wave plate. After the circularly polarized light is incident on an atomic gas chamber for detecting magnetic fields, the laser interacts with the alkali metal atoms in the atomic gas chamber in the presence of a magnetic field, and the transmitted light is converted into a voltage signal by a photodetector and then output.

[0036] The magnetometer in the disclosed embodiment can be an alkali metal atomic magnetometer. The alkali metal atomic magnetometer is based on alkali metal vapor as the atomic gas. The alkali metal vapor can be the vapor of potassium, rubidium and cesium atoms, but is not limited thereto. Once the angular momentum of the alkali metal atom collides with the glass wall of the atomic gas chamber, the polarization direction will change. To obtain a longer spin coherence time, the relaxation caused by the atomic gas chamber wall collision must be prevented. Therefore, high-pressure inert gas nitrogen can be added to the atomic gas chamber to prevent the diffusion of alkali metal atoms and reduce the effect of the collision between atoms and the gas chamber on the polarization lifetime of cesium atoms. Prolonging the wall collision relaxation time by filling a buffer gas or coating an anti-relaxation film on the inner surface of the wall is beneficial to improving the sensitivity and reducing the size of the atomic gas chamber.

[0037] The spin exchange collision cross sections of commonly used alkali metal atoms are similar, and the physical limit of the sensitivity of the magnetometer, namely the standard quantum limit, is basically the same. Cesium atoms have the highest vapor pressure, namely the atomic density, at the same temperature, and can work at a lower temperature, which is beneficial to reduce the power consumption of the magnetometer. Therefore, in the embodiment of the present disclosure, cesium atoms are used as the working atoms of the magnetometer, and the alkali metal atoms in the atomic gas chamber are cesium atoms, and the atomic gas chamber can be a cylindrical atomic gas chamber. The material of the container of the atomic gas chamber is generally made of an inert material that does not react with alkali metal vapor, which can be glass or metal, but is not limited to this.

[0038] In one embodiment of the present disclosure, the atomic gas chamber is a glass cavity filled with cesium (Cs-133) atoms.

[0039] In one embodiment of the present disclosure, a cylindrical cesium absorption chamber can be selected, with dimensions of 8 mm in bottom diameter and 8 mm in vertical height, made of high borosilicate glass, with an internal pressure of 101 kPa and filled with 760 torr of nitrogen (N2).

[0040] The temperature range of the atomic gas chamber is 80℃~150℃, which is conducive to the generation of cesium atomic vapor. However, the higher the temperature of the cesium atomic gas chamber, the better. Because the spin relaxation of the cesium atoms in the gas chamber and the collision with the wall will increase with the increase of the gas chamber temperature, and excessive relaxation will cause the polarized cesium atoms to depolarize, reducing the sensitivity of the magnetometer system. Therefore, the cesium atomic gas chamber needs to be maintained at a constant optimal temperature. In order to further reduce the influence of residual magnetism on the magnetic field signal, a high-temperature resistant and insulating asbestos can be selected. The asbestos is wrapped with high-temperature tape to prevent flocs from flying out, and it is evenly wrapped on the side of the cylindrical atomic gas chamber. In addition, the atomic gas chamber is packaged with a thermistor with a resistance of 10kΩ and a B value of 3950K+ / -1%@25 degrees Celsius.

[0041] The coil in the embodiment of the present disclosure is a radio frequency coil, which is arranged outside the atomic gas chamber and is used to generate a radio frequency magnetic field for magnetic resonance to modulate the magnetic field around the atomic gas chamber. The material of the coil can be oxygen-free copper, the diameter of the coil can be 70 mm, the number of turns can be 10, and it is not limited thereto.

[0042] The fixing bracket of the atomic gas chamber can be made of plastic material and placed inside the coil. The structural materials of the coil and the atomic gas chamber need to exclude magnetic materials. For example, polycarbonate, thermoplastic polymer structural materials and other materials can be selected for packaging structure processing to ensure that the overall structure has no magnetic properties and ensure the precise alignment of each miniaturized structural component.

[0043] The performance of the photodetector directly affects the magnetometer noise. In the disclosed embodiment, the photodetector can use a photodiode with high quantum efficiency and low dark current. In addition, since the dark current of the photodiode is closely related to the area of ​​the photodiode, it is necessary to reasonably select the size of the photodiode and adjust the variable focus lens group according to the size of the light beam so that the light signal incident on the photodetector is adapted to the photosensitive surface of the photodetector, thereby improving the accuracy of the magnetometer's magnetic field intensity measurement results. In addition, the operating temperature of the photodiode will also affect the size of the dark current, and a reasonable probe thermal design will also have an impact on reducing the noise of the photodiode.

[0044] The technical solution of the disclosed embodiment adopts a single-beam magnetic field modulation method, which only requires one beam of pump light, and the system structure is compact, which can significantly reduce the volume and system complexity. In the disclosed embodiment, the photoelectric signal conversion system can be a VCSEL (Vertical-Cavity Surface-Emitting Laser).

[0045] The light source of the pump light of the single-beam magnetic field modulation method of the technical solution of the embodiment of the present disclosure is a vertical cavity surface emitting laser, which is used to generate laser. Specifically, the light source can be a VCSEL semiconductor laser with a wavelength of 894nm.

[0046] like Figure 2 As shown, the pump light enters the atomic gas chamber along the x direction, and the alkali metal atoms and the laser realize laser pumping in the gas chamber. Through the laser pumping action, a large number of alkali metal atoms form a macroscopic polarization P. The macroscopic polarization P forms Larmor precession under the action of the external magnetic field to be measured, and the light intensity after passing through the atomic gas chamber will change with the magnitude of the magnetic field strength to be measured. At this time, a modulation magnetic field with a known magnetic field strength and frequency is added in the same direction of the magnetic field to be measured through the coil 204. The modulation magnetic field makes the transmitted light intensity contain modulation information. After being converted into a voltage signal by the photodetector, it is demodulated by a phase-locked amplifier. The voltage signal output after demodulation is approximately considered to be linearly related to the magnetic field strength to be measured, and the magnetic field value to be measured can be obtained according to the voltage signal. Specifically, when the optical magnetic resonance effect occurs in the optical system of the above-mentioned self-excited cesium atomic optical pump magnetometer, and there is a stable oscillation signal in the positive feedback loop composed of the electrical system, the external magnetic field strength to be measured can be obtained by measuring the frequency of the signal in the loop.

[0047] A quarter wave plate is an optical element used to change the polarization state of light. Its main principle is to adjust the polarization state of light by changing the phase difference of the light wave. When a certain wavelength of light is vertically incident through a quarter wave plate, a phase difference of 1 / 4 wavelength will be generated between the outgoing ordinary light (o light) and the extraordinary light (e light). This wave plate is usually made of a birefringent material cut in a direction parallel to the optical axis to form a parallel plane plate, and its thickness should be precisely an odd multiple of the product of the refractive index difference of the two principal axes of the birefringent material and 1 / 4 of the given wavelength. Quarter wave plates are often used in optical paths to convert linearly polarized light into circularly polarized light or elliptically polarized light. In the embodiments disclosed herein, the material of the quarter wave plate can be optical glass or fused quartz, but is not limited thereto.

[0048] like Figure 3 As shown, the variable focus lens group includes a convex lens 1041 and a concave lens 1042. The magnification of the optical system can be adjusted by changing the position of the convex lens, and the emitted light can be adjusted to be parallel light by adjusting the concave lens. By adjusting the position of the convex lens 1041 and / or the concave lens 1042, the optical magnification of the variable focus lens group can be changed, so that the transmitted light of the atomic gas chamber can be better focused on the photosensitive surface of the photodetector, so that the photodetector outputs a more accurate voltage signal, thereby improving the measurement accuracy of the magnetometer.

[0049] In one embodiment of the present disclosure, the optical lens assembly only includes a collimating lens. Figure 2 As shown, the semiconductor laser emitted by the laser 201 is first collimated by a collimating lens, and then converted into circularly polarized light by a quarter wave plate 102. The circularly polarized light then enters the atomic gas chamber and interacts with the cesium atoms in the atomic gas chamber. The circularly polarized light is incident on the atomic gas chamber 205 to form an optical signal containing magnetic resonance information and is emitted. The optical signal containing magnetic resonance information transmitted from the atomic gas chamber is focused onto the photosensitive surface of the photodetector 105 by the variable focus lens group 104, and the photodetector 105 converts the collected optical signal into an electrical signal.

[0050] In another embodiment of the present disclosure, the optical lens group includes a collimating lens and a folding prism. The semiconductor laser emitted by the laser is first collimated by the collimating lens, then the optical path is changed by the folding prism, and then converted into circularly polarized light by the quarter wave plate. After that, the circularly polarized light enters the atomic gas chamber and interacts with the cesium atoms in the atomic gas chamber. After the circularly polarized light is incident on the atomic gas chamber, a light signal containing magnetic resonance information is formed and emitted. The light signal containing magnetic resonance information transmitted from the atomic gas chamber is focused onto the photosensitive surface of the photodetector through the variable focus lens group, and the photodetector converts the collected light signal into an electrical signal.

[0051] In the disclosed embodiment, the photoelectric signal conversion system of the magnetometer includes a positive feedback loop composed of a filter, an intensity modulator, a photodetector and a coil, and the voltage signal output by the photodetector is a stable oscillation signal of the positive feedback loop. After the transmitted light formed by the laser passing through the coil and the atomic gas chamber is received by the photodetector, it is filtered by the filter and input into the intensity modulator, which changes the magnetic field intensity and frequency generated by the coil to form a new transmitted light. This cycle is repeated several times to form a stable oscillation. When the optical magnetic resonance effect occurs in the optical system of the self-excited cesium atomic optical pump magnetometer, and there is a stable oscillation signal in the positive feedback loop composed of the electrical system, the frequency of the signal in the positive feedback loop is measured and substituted into the formula to obtain the external magnetic field intensity to be measured.

[0052] The light beam emitted by the VCSEL laser tube is collimated by a converging lens to obtain parallel optical pump light, which is converted into circularly polarized light through a 1 / 4 wave plate. Under the action of polarized light, the atoms in the micro atomic gas chamber are polarized, and the RF coil generates an RF magnetic field. When the frequency of the RF field resonates with the external field to be measured, the polarization component of the atom causes the photodiode to receive a signal with the same frequency as the driving field, which is fed back to the coil through the amplifier. When the feedback loop meets certain loop gain and phase conditions, the system self-oscillates, and measuring the self-oscillation frequency can achieve the measurement of the size of the external magnetic field.

[0053] The voltage signal output by the photodetector of the magnetometer can be digitized using an analog-to-digital converter after further amplification in the later stage. In the process of analog-to-digital conversion, quantization noise will inevitably be introduced, which will reduce the signal-to-noise ratio of the signal. In order to minimize the introduction of quantization noise, a high-precision and high-bit analog-to-digital converter can be used to digitize the voltage signal output by the photodetector. At the same time, in order to demodulate the modulation signal contained in the signal, the sampling rate of the analog-to-digital converter must be at least twice the frequency of the modulation signal, and at least 8 times the frequency in engineering, in order to demodulate and extract the corresponding modulation signal.

[0054] The technical solution of the disclosed embodiment can use LTC2500-32 as the analog-to-digital converter of the magnetometer. The chip ensures 32 bits without missing codes, the typical value of the dynamic range is 148dB at 61sps, the maximum sampling rate can reach 1MHz, and the typical power consumption is 24mW. Therefore, it can well meet the requirements for digitization of high signal-to-noise ratio voltage signals.

[0055] The technical solution of the disclosed embodiment can use the LTC6655LN ultra-low noise voltage reference chip to provide a reference voltage for the analog-to-digital converter. It contains a reference voltage buffer with fast stability and high input impedance, which helps to solve the problem of poor load adjustment and can greatly reduce the reference voltage noise while maintaining DC accuracy. In addition, the LTC6655LN has an internal integrated filter, which can save PCB area and reduce power consumption.

[0056] According to the photoelectric signal conversion system of the magnetometer provided by the embodiment of the present disclosure, a variable focus lens group is arranged in the photoelectric signal conversion system of the magnetometer so that the transmitted light emitted by the atomic gas chamber can be variable-focused using different optical magnifications, thereby ensuring that the light signal incident on the photodetector is adapted to the photosensitive surface of the photodetector, thereby improving the accuracy of the magnetic field intensity measurement results of the magnetometer.

[0057] The above description is only a preferred embodiment of the present disclosure and is not intended to limit the present disclosure. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present disclosure should be included in the protection scope of the present disclosure.

Claims

1. A photoelectric signal conversion system for a magnetometer, characterized in that: The photoelectric signal conversion system includes: An optical lens assembly, used for adjusting the optical path of the laser; A quarter wave plate is used to convert the laser light after the optical path is adjusted from linear polarization to circular polarization; The coil and the atomic gas chamber are used to receive the circularly polarized light, wherein the circularly polarized light interacts with the alkali metal atoms in the atomic gas chamber in a superimposed magnetic field to form a transmitted light containing magnetic resonance information, wherein the superimposed magnetic field is formed by superimposing the radio frequency magnetic field generated by the coil and the current environmental magnetic field; A variable focus lens group, used for performing variable focus on the transmitted light; The photoelectric detector is used to convert the focused transmitted light into a voltage signal and output it, so as to determine the current environmental magnetic field according to the voltage signal.

2. The photoelectric signal conversion system of a magnetometer according to claim 1, characterized in that: The optical lens assembly comprises: A collimating lens, used to collimate the laser; The folding prism is used to change the optical path of the collimated laser.

3. The photoelectric signal conversion system of a magnetometer according to claim 1, characterized in that: The folding prism is used to change the optical path of the laser by 90°.

4. The photoelectric signal conversion system of a magnetometer according to claim 1, characterized in that: The photoelectric signal conversion system further comprises a polarization-maintaining optical fiber for transmitting the laser light generated by the laser to the optical lens assembly.

5. The photoelectric signal conversion system of a magnetometer according to claim 1, characterized in that: The alkali metal atoms in the atomic gas chamber are cesium atoms.

6. The photoelectric signal conversion system of a magnetometer according to claim 1, characterized in that: The atomic gas chamber comprises a cylindrical atomic gas chamber.

7. The photoelectric signal conversion system of a magnetometer according to claim 1, characterized in that: The photodetector is a photodiode.

8. The photoelectric signal conversion system of a magnetometer according to claim 1, characterized in that: The optical-electrical signal conversion system further includes a vertical cavity surface emitting laser, which is used to generate the laser.

9. The photoelectric signal conversion system of a magnetometer according to claim 1, characterized in that: The variable focus lens group includes a convex lens and a concave lens. The magnification of the optical system can be adjusted by changing the position of the convex lens, and the outgoing light can be adjusted to be parallel light by adjusting the concave lens.

10. The photoelectric signal conversion system of a magnetometer according to claim 1, characterized in that: The material of the quarter wave plate is optical glass or fused quartz.

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