Variable channel two-dimensional weak magnetic imaging device with high sensitivity and high temporal-spatial resolution

Abstract

The invention discloses a high-sensitivity high-temporal-spatial-resolution variable-channel two-dimensional weak magnetic imaging device, and relates to the technical field of magnetic detection, and the device comprises a pump light path, a detection light path and an imaging unit. The pump light path is used for converting the linear polarization pump laser into circular polarization pump laser; the detection light path is used for converting detection laser into linear polarization multi-channel detection laser beams, forming coaxial laser by the linear polarization multi-channel detection laser beams and the circular polarization pump laser, and performing conversion, modulation and power distribution on the coaxial laser to obtain two groups of multi-channel differential detection laser beams; and the imaging unit is used for obtaining a 2D dynamic magnetic field image based on the two groups of multi-channel differential detection laser beams. According to the optical pumping magnetometer based on the free induction damped oscillation measurement method, on the basis of ensuring the high spatial resolution of 2D magnetic field imaging, imaging with high time resolution, high dynamic range and fast switching of channel attributes is achieved.

Description

Technical Field

[0001] This application relates to the field of magnetic detection technology, and particularly to a variable-channel two-dimensional weak magnetic imaging device with high sensitivity and high spatio-temporal resolution. Background Art

[0002] Magnetic field imaging is a non-invasive and reliable means for magnetic source localization and characterization. Due to its theoretically ultra-high sensitivity at the sub-fT / √Hz level and mature signal processing technology, the atomic optical pumping magnetometer based on an alkali metal gas cell has been widely used in the fields of industry, national defense, and life science. However, for research fields that require obtaining magnetic field imaging signals, the imaging spatial resolution of a general single-beam atomic magnetometer is insufficient to meet the research needs. Therefore, currently, the integrated atomic magnetometers that are maturely applied generally adopt a structure of a gas cell array or a magnetometer array to improve the spatial resolution of 2D imaging. However, this structure is limited by the volume of the alkali metal gas cell itself and the magnetometer packaging, and it is impossible to obtain a high spatial resolution. Therefore, more and more technical inventions aim to improve the spatial resolution of magnetic field 2D imaging, such as using a displacement stage and a small-diameter detection beam to traverse and scan the polarization space in the gas cell; or using MEMS technology to reduce the volume of the gas cell and improve the integration degree of the atomic magnetometer array, etc., but still cannot reach the spatial resolution at the micron level. Using a CCD camera as an optoelectronic detector (PD) array is an option, but the CCD camera is inferior to the CMOS sensor in imaging speed due to its inherent properties, and it has an over-saturated trailing effect.

[0003] However, for many actual signals to be measured, such as magnetoencephalogram and magnetocardiogram signals, etc. None of the above methods can take into account high spatial resolution, time resolution, and dynamic range. For the solutions that can achieve high spatial resolution, they cannot effectively follow the changes of higher-frequency signals, resulting in the inability to achieve high spatial resolution ability in actual applications, and the operation is complex, and it is impossible to accurately achieve the rapid scanning of a certain part of the space in a single-beam atomic magnetometer. Moreover, currently, most atomic magnetometers use optoelectronic detectors or differential optoelectronic detectors to detect the detection light of the last outgoing gas cell. Finally, if a complete 2D image is to be obtained, it is necessary to import the data output multiple times in subsequent data processing and perform complex fitting, and it is also difficult to ensure temporal synchronization. Currently, although the magnetic field 2D imaging technology using atomic magnetometers has high sensitivity and the test property of being able to detect samples at close range, it cannot take into account ultra-high spatial resolution and time resolution, resulting in the inability of the system with high spatial resolution in the experiment to follow the changes of actual signals due to the lack of high time resolution in actual applications, and it is impossible to achieve high spatial resolution imaging. Finally, the general PD array, gas cell array, and magnetometer array arrangements all have a constant number of channels and a constant spatial resolution, and cannot adapt to all scenarios. Summary of the Invention

[0004] The object of the present application is to provide a variable-channel two-dimensional weak magnetic imaging device with high sensitivity and high spatio-temporal resolution. Based on the optically pumped magnetometer using the free induction decay (FID) oscillation measurement method, it achieves high-time-resolution, high-dynamic-range imaging with a fast-switchable channel property while ensuring high spatial resolution of 2D magnetic field imaging, so as to solve the problems existing in the above-mentioned prior art.

[0005] To achieve the above object, the present application provides the following solutions:

[0006] The present application provides a variable-channel two-dimensional weak magnetic imaging device with high sensitivity and high spatio-temporal resolution. The variable-channel two-dimensional weak magnetic imaging device with high sensitivity and high spatio-temporal resolution includes: a pumping optical path, a detection optical path, and an imaging unit.

[0007] The pumping optical path is used to convert linearly polarized pumping laser into circularly polarized pumping laser.

[0008] The detection optical path is used to convert detection laser into linearly polarized multi-path detection laser beams, and form coaxial laser with the circularly polarized pumping laser. By transforming, modulating, and power-distributing the coaxial laser, two groups of multi-channel differential detection laser beams are obtained.

[0009] The imaging unit is used to obtain a 2D dynamic magnetic field image based on the two groups of multi-channel differential detection laser beams.

[0010] Optionally, the pumping optical path includes:

[0011] A pumping laser (1), which is used to emit partially linearly polarized pumping laser.

[0012] An optical isolator (2), which is used to prevent the linearly polarized pumping laser from being reflected back to the pumping laser (1) again.

[0013] A first polarizer (3), which is used to convert the partially linearly polarized pumping laser into completely polarized laser.

[0014] An acousto-optic modulator (AOM) (4), which is used to perform acousto-optic modulation on the completely polarized laser to obtain several diffracted light beams.

[0015] A diaphragm (5), which is used to block the several diffracted light beams and only allow the first-order diffracted light to pass through.

[0016] A second polarizer (6), which is used to adjust and optimize the power of the first-order diffracted light to obtain optimized linearly polarized pumping laser.

[0017] A first reflector (7), which is used to reflect the optimized linearly polarized pumping laser to obtain reflected linearly polarized pumping laser.

[0018] A beam expander (8) is used to expand the reflected linearly polarized pump laser to obtain an expanded linearly polarized pump laser.

[0019] A first filter (9) is used to combine the expanded linearly polarized pump laser and the linearly polarized multi-path probe laser beam to obtain a combined beam.

[0020] A dual-wavelength wave plate (10) is used to convert the linearly polarized pump laser in the combined beam into a circularly polarized laser.

[0021] Optionally, the detection optical path includes:

[0022] A detection laser (34) is used to emit a detection laser.

[0023] A power optimizer is used to optimize the power of the detection laser to obtain a detection laser with optimized power.

[0024] A window plate (31) is used to divide the detection laser with optimized power into two laser beams; among them, the laser above the preset power is used as a new detection laser and enters the subsequent optical path; the laser below the preset power is used as a feedback laser.

[0025] A photodetector (30) is used to receive the feedback laser and feed it back to the controller of the detection laser (34) through a PID loop.

[0026] A spatial light pinhole filter is used to filter the new detection laser to obtain a filtered detection laser.

[0027] A third linear polarizer (25) is used to modulate the filtered detection laser into a standard linearly polarized detection laser with a uniform power spatial distribution within the beam cross-section.

[0028] An ultra-high-speed digital micromirror array (DMD) (24) is used to modulate the standard linearly polarized detection laser into a linearly polarized multi-path probe laser beam with a laser diameter smaller than a preset value.

[0029] A first filter (9) is used to combine the expanded linearly polarized pump laser and the linearly polarized multi-path probe laser beam to obtain a combined beam.

[0030] A dual-wavelength wave plate (10) is used to convert the linearly polarized pump laser in the combined beam into a circularly polarized laser; it is also used to transmit the linearly polarized multi-path probe laser beam in the combined beam to obtain a first transmitted linearly polarized multi-path probe laser beam.

[0031] An imaging lens group is used to modulate the overall contour diameter of the circularly polarized laser and the linearly polarized multi-path detection laser beam after the first transmission, so as to obtain a modulated circularly polarized laser and a modulated linearly polarized multi-path detection laser beam.

[0032] A second filter (19) is used to remove the modulated circularly polarized laser and transmit the modulated linearly polarized multi-path detection laser beam, so as to obtain a linearly polarized multi-path detection laser beam after the second transmission.

[0033] An arbitrary power divider is used to divide the power of the linearly polarized multi-path detection laser beam after the second transmission, so as to obtain two groups of multi-channel differential detection laser beams.

[0034] Optionally, the high-sensitivity, high spatio-temporal resolution variable-channel two-dimensional weak magnetic imaging device further includes:

[0035] A magnetic shielding and magnetic field generation system is used to suppress the interference of the geomagnetic field and external stray magnetic fields on the test results.

[0036] The magnetic shielding and magnetic field generation system includes:

[0037] A multi-layer permalloy magnetic shielding cylinder (17) is used to achieve magnetic shielding.

[0038] A solenoid (12) is used to provide a background bias magnetic field.

[0039] Optionally, the arbitrary power divider is a divider composed of a first half-wave plate (20) and a polarization beam splitter (21).

[0040] Optionally, the imaging lens group includes: a first lens (11) and a second lens (18).

[0041] The first lens (11) and the second lens (18) are respectively arranged at both ends of the multi-layer permalloy magnetic shielding cylinder (17), or arranged between the second filter (19) and the first half-wave plate (20).

[0042] Optionally, the spatial light pinhole filter is a filter composed of a second mirror (29), a fourth lens (28), a pinhole (27) and a third lens (26).

[0043] Optionally, the power optimizer is an optimizer composed of a second half-wave plate (33) and a Glan-Thompson prism (GT) (32).

[0044] Optionally, the high-sensitivity, high spatio-temporal resolution variable-channel two-dimensional weak magnetic imaging device further includes:

[0045] A grayscale binary image generation device (23) for outputting a grayscale binary image composed of a number of black and white alternating squares.

[0046] The grayscale binary image generation device (23) and the ultra - high - speed digital micromirror array (24) form a spatial light modulation system; the spatial light modulation system is used to control a number of micromirrors at positions corresponding to the black - colored areas in the grayscale binary image to deflect ±12° around their respective hinge axes, thereby dividing and marking all detection channels.

[0047] Optionally, the highly sensitive high - spatio - temporal resolution variable - channel two - dimensional weak magnetic imaging device further includes: a gas chamber and its heating system.

[0048] The gas chamber and its heating system include:

[0049] A gas chamber (15) containing alkali metal vapor, quenching gas, and inert gas.

[0050] A heating unit (16) arranged symmetrically in space or in a twisted pair around the gas chamber (15) to provide a heating function for the gas chamber (15).

[0051] Heat - insulating and heat - preserving material (13) arranged around the heating unit (16) for heat insulation and heat preservation.

[0052] According to the specific embodiments provided in this application, the following technical effects are disclosed in this application:

[0053] This application provides a highly sensitive high - spatio - temporal resolution variable - channel two - dimensional weak magnetic imaging device, which includes: a pump - light path, a detection light path, and an imaging unit; the pump - light path is used to convert linearly polarized pump laser into circularly polarized pump laser; the detection light path is used to convert detection laser into linearly polarized multi - path detection laser beams, and form a co - axial laser with the circularly polarized pump laser, and through transformation, modulation, and power distribution of the co - axial laser, two groups of multi - channel differential detection laser beams are obtained; the imaging unit is used to obtain a 2D dynamic magnetic - field image based on the two groups of multi - channel differential detection laser beams. Through the design of multi - channel differential detection laser beams in this application, noise can be effectively suppressed, the contrast of signals can be enhanced, thereby significantly improving the sensitivity of magnetic - field detection, being able to detect weaker magnetic - field changes, and broadening the application range of the device in weak - magnetic - field - intensity environments; moreover, the multi - channel design enables the device to image the magnetic - field distribution with finer resolution in space, being able to clearly distinguish the subtle changes and distribution differences of the magnetic field on a two - dimensional plane. At the same time, the dynamic imaging ability ensures a high resolution in the time dimension and can track the change process of the magnetic field in real time. Compared with the traditional single - channel detection method, multi - channel detection can obtain more magnetic - field information simultaneously, greatly improving the imaging efficiency. Description of the Drawings

[0054] To more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the accompanying drawings required for use in the embodiments. Obviously, the accompanying drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can also be obtained based on these drawings.

[0055] Figure 1 It is a schematic structural diagram of a variable-channel two-dimensional weak magnetic imaging device with high sensitivity and high spatio-temporal resolution provided by an embodiment of the present application.

[0056] Figure 2 It is a schematic diagram of the average pixel value change (free induction decay signal) of several adjacent pixel groups detected by a CMOS camera provided by an embodiment of the present application.

[0057] Figure 3 It is a schematic timing diagram of an acousto-optic modulator turning on and off a pump laser provided by an embodiment of the present application.

[0058] Reference numerals:

[0059] 1 - Pump laser, 2 - Optical isolator, 3 - First linear polarizer, 4 - Acousto-optic modulator, 5 - Diaphragm, 6 - Second linear polarizer, 7 - First reflector, 8 - Beam expander, 9 - First filter, 10 - Dual-wavelength wave plate, 11 - First lens, 12 - Solenoid, 13 - Heat insulation material, 14 - Magnetic sample, 15 - Alkali atom gas cell, 16 - Heating unit, 17 - Multilayer permalloy magnetic shielding cylinder, 18 - Second lens, 19 - Second filter, 20 - First half-wave plate, 21 - Polarizing beam splitter, 22 - High-speed CMOS sensor, 23 - Grayscale binary map generation device, 24 - Ultra-high-speed digital micromirror array, 25 - Third linear polarizer, 26 - Third lens, 27 - Pinhole, 28 - Fourth lens, 29 - Second reflector, 30 - Photoelectric detector, 31 - Window plate, 32 - Glan-Thompson prism, 33 - Second half-wave plate, 34 - Detection laser. Specific embodiments

[0060] The following will clearly and completely describe the technical solutions in the embodiments of the present application in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only some embodiments of the present application, rather than all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present application.

[0061] General PD arrays, gas cell arrays, and magnetometer arrays have a constant number of channels and a constant spatial resolution, and cannot adapt to all scenarios. This device can quickly switch such properties through spatial light modulation. The principle of this device is based on a free induction decay atomic magnetometer: after the pump light polarizes the alkali atoms, the projection of the polarization state on the plane perpendicular to the pump beam will decay continuously at the Larmor precession frequency after the pump light is turned off. This frequency is proportional to the magnetic field at the location. The decay change will cause the refractive index of the alkali atoms for left and right circularly polarized light to change. At this time, if a linearly polarized light passes through the gas cell, its polarization plane will deflect at the Larmor precession frequency following the polarization state. By detecting this deflection, the magnetic field can be calculated by fitting.

[0062] To make the above objects, features, and advantages of the present application more obvious and understandable, the present application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0063] In an exemplary embodiment, as Figure 1 shown, a variable-channel two-dimensional weak magnetic imaging device with high sensitivity and high spatio-temporal resolution is provided. The variable-channel two-dimensional weak magnetic imaging device with high sensitivity and high spatio-temporal resolution includes: a pump optical path, a detection optical path, and an imaging unit.

[0064] The pump optical path is used to convert linearly polarized pump laser into circularly polarized pump laser.

[0065] The detection optical path is used to convert the detection laser into a linearly polarized multi-path detection laser beam, and form a coaxial laser with the circularly polarized pump laser. By transforming, modulating, and power distributing the coaxial laser, two groups of multi-channel differential detection laser beams are obtained.

[0066] The imaging unit is used to obtain a 2D dynamic magnetic field image based on the two groups of multi-channel differential detection laser beams.

[0067] Specifically, the pump optical path includes:

[0068] A pump laser (1) for emitting partially linearly polarized pump laser.

[0069] An optical isolator (2) for preventing the linearly polarized pump laser from being reflected back to the pump laser (1) again.

[0070] A first linear polarizer (3) for converting the partially linearly polarized pump laser into fully polarized laser.

[0071] An acousto-optic modulator (4) for performing acousto-optic modulation on the fully polarized laser to obtain a plurality of diffracted lights.

[0072] A diaphragm (5) for blocking the plurality of diffracted lights and allowing only the first-order diffracted light to pass through.

[0073] A second linear polarizer (6) for adjusting and optimizing the power of the first-order diffracted light to obtain an optimized linearly polarized pump laser.

[0074] A first reflector (7) for reflecting the optimized linearly polarized pump laser to obtain a reflected linearly polarized pump laser.

[0075] A beam expander (8) for expanding the reflected linearly polarized pump laser to obtain an expanded linearly polarized pump laser.

[0076] A first filter (9) for combining the expanded linearly polarized pump laser and the linearly polarized multi-path detection laser beam to obtain a combined beam.

[0077] A dual-wavelength wave plate (10) for converting the linearly polarized pump laser in the combined beam into a circularly polarized laser.

[0078] In the pump optical path, the laser wavelength emitted by the pump laser (1) is frequency-stabilized to the D1 line of the alkali metal species contained in the gas cell (15), and is converted into a circularly polarized pump laser by the second linear polarizer (6) and the dual-wavelength wave plate (10) for pumping the alkali atoms in the polarization gas cell (15). The first filter (9) is regarded as a combiner, which can only reflect the laser with a wavelength near the D1 line and can only transmit the laser with a wavelength near the D2 line.

[0079] For the pump optical path, it is necessary to first perform time-domain modulation on the laser emitted by the pump laser (1) with a square wave having a certain duty cycle and a certain frequency through an acousto-optic modulator (4) or other fast-response optical path switches. The frequency needs to be approximately close to the magnetic field to be measured, so that the alkali atoms in the gas cell (15) undergo polarization transitions; then, the pump laser is completely turned off through the acousto-optic modulator (AOM) or other fast-response optical path switches (4), so that the alkali atoms in the gas cell (15) generate spin-polarized free induction decay oscillations (FID). The first filter (9) with a laser transmittance greater than 99.8% near the D2 line wavelength and a laser reflectance greater than 99.8% near the D1 line wavelength is considered a combiner, enabling the probe light and the pump light to propagate coaxially.

[0080] Specifically, the detection optical path includes:

[0081] A detection laser (34) for emitting detection laser.

[0082] A power optimizer for optimizing the power of the detection laser to obtain an optimized detection laser.

[0083] A window slice (31) for splitting the detection laser with optimized power into two laser beams. Among them, the laser above the preset power is used as the new detection laser and enters the subsequent optical path, while the laser below the preset power is used as the feedback laser.

[0084] A photodetector (30) for receiving the feedback laser and feeding it back to the controller of the detection laser (34) through a PID loop.

[0085] A spatial light pinhole filter for filtering the new detection laser to obtain the filtered detection laser.

[0086] A third linear polarizer (25) for modulating the filtered detection laser into a standard linearly polarized detection laser with a uniform power spatial distribution within the beam cross-section.

[0087] An ultra-high-speed digital micromirror array (24) for modulating the standard linearly polarized detection laser into a linearly polarized multi-path detection laser beam with a laser diameter smaller than the preset value.

[0088] A first filter (9) for combining the expanded linearly polarized pump laser and the linearly polarized multi-path detection laser beam to obtain a combined beam.

[0089] A dual-wavelength wave plate (10) for converting the linearly polarized pump laser in the combined beam into a circularly polarized laser, and also for transmitting the linearly polarized multi-path detection laser beam in the combined beam to obtain a first transmitted linearly polarized multi-path detection laser beam.

[0090] An imaging lens group for modulating the overall contour diameter of the circularly polarized laser and the first transmitted linearly polarized multi-path detection laser beam to obtain a modulated circularly polarized laser and a modulated linearly polarized multi-path detection laser beam.

[0091] A second filter (19) for removing the modulated circularly polarized laser and transmitting the modulated linearly polarized multi-path detection laser beam to obtain a second transmitted linearly polarized multi-path detection laser beam.

[0092] An arbitrary power distributor for distributing the power of the second transmitted linearly polarized multi-path detection laser beam to obtain two groups of multi-channel differential detection laser beams.

[0093] As an optional implementation, the highly sensitive and high spatio-temporal resolution variable-channel two-dimensional weak magnetic imaging device further includes:

[0094] A magnetic shielding and magnetic field generation system for suppressing the interference of the geomagnetic field and external stray magnetic fields on the test results.

[0095] The magnetic shielding and magnetic field generation system includes:

[0096] A multi-layer permalloy magnetic shielding cylinder (17) for achieving magnetic shielding.

[0097] A solenoid (12) for providing a background bias magnetic field.

[0098] In the magnetic shielding and magnetic field generation system, a magnetic sample to be measured (14) (with the motion direction sensitive to magnetic measurement already marked) is placed. The multi-layer permalloy magnetic shielding cylinder (17) has a light passing hole for the detection light and the pump light to pass through, and a wire groove for the power supply wire of the solenoid (12) and the power signal wire of the heating unit (16) to pass through. The solenoid (12) provides a background bias magnetic field for this device.

[0099] Specifically, the arbitrary power divider is a divider composed of a first half-wave plate (20) and a polarization beam splitter (21).

[0100] Specifically, the imaging lens group includes: a first lens (11) and a second lens (18).

[0101] The first lens (11) and the second lens (18) are respectively arranged at both ends of the multi-layer permalloy magnetic shielding cylinder (17), or are arranged between the second filter (19) and the first half-wave plate (20).

[0102] Specifically, the spatial light pinhole filter is a filter composed of a second mirror (29), a fourth lens (28), a pinhole (27), and a third lens (26).

[0103] Specifically, the power optimizer is an optimizer composed of a second half-wave plate (33) and a Glan-Thompson prism (32).

[0104] In the detection optical path, the detection laser (34) emits laser light with a wavelength detuned near the D2 line of the alkali metal species contained in the gas chamber (15), and is converted into standard linearly polarized light by the third linear polarizer (25) to detect the amount of beam polarization rotation caused by the polarization of atoms by the pump light under the condition of minimizing atomic interaction. The dual-wavelength wave plate (10) has a phase delay of 1 / 4 for the laser with the D1 line wavelength and a phase delay of 1 / 2 for the laser with a wavelength near the D2 line. Therefore, the linearly polarized pump laser can be converted into circularly polarized laser after passing through the dual-wavelength wave plate (10), and the linearly polarized detection laser remains linearly polarized after passing through the dual-wavelength wave plate (10).

[0105] The optical components of the complete PID feedback loop for optical power stabilization and noise attenuation include a power optimizer composed of a second half-wave plate (33) and a Glan-Thompson prism (32), a window (31) and a photodetector (30). The window (31) reflects a small portion of the detection light to the sensing unit of the photodetector (30) as the input of the PID loop.

[0106] In the detection optical path, the first lens (11) and the second lens (18) serve as an imaging lens group to suppress or eliminate the effect of light diffraction in the high-speed CMOS sensor (22). The dual-wavelength wave plate (10) delays the phase of the laser light with the wavelength of the D1 line by 1 / 4 and delays the phase of the laser light with the wavelength near the D2 line by 1 / 2. Therefore, the linearly polarized pump laser can be converted into circularly polarized laser light after passing through the dual-wavelength wave plate (10), and the linearly polarized detection laser can still be linearly polarized laser light after passing through the dual-wavelength wave plate (10), thereby achieving selective polarization modulation of the pump laser and the detection laser in the same beam path. The second filter (19) can transmit most of the detection light (~D2 line wavelength) and block most of the pump light (D1 line wavelength), so that the high-speed CMOS sensor (22) can only obtain the detection light carrying the light polarization rotation signal. The combination of the first half-wave plate (20) and the polarization beam splitter (21) is an arbitrary power distribution beam splitter that can distribute different output power ratios according to different polarization directions of the incident laser. It converts polarization rotation information into power differential information and can suppress common mode noise. The photosensitive unit of the high-speed CMOS sensor (22) is evenly divided into two parts, which respectively receive two differential beams from the polarization beam splitter (21). Several independent adjacent pixel groups in the sensing unit of the high-speed CMOS sensor (22) are regarded as a 2D photodetector array with extremely high filling density, which can achieve high spatial resolution. The average size of the pixel value of each pixel group is considered to be the beam polarization direction deflection response of the corresponding channel. Figure 2 shown.

[0107] As an optional embodiment, the highly sensitive and high temporal and spatial resolution variable channel two-dimensional weak magnetic imaging device further includes:

[0108] A grayscale binary image generating device (23) is used for outputting a grayscale binary image consisting of a plurality of black and white squares.

[0109] The grayscale binary image generating device (23) and the ultra-high-speed digital micromirror array (24) form a spatial light modulation system; the spatial light modulation system is used to control a plurality of micromirrors at positions corresponding to the black areas shown in the grayscale binary image to deflect ±12° around their respective hinge axes, thereby dividing and marking all detection channels. That is, the spatial light modulation system includes an ultra-high-speed digital micromirror array (24) and a grayscale binary image generating device (23); after the grayscale binary image is loaded into the memory of the ultra-high-speed digital micromirror array (24), a plurality of micromirrors at positions corresponding to the black areas shown in the grayscale binary image can be controlled to deflect ±12° around their respective hinge axes, thereby dividing and marking all detection channels.

[0110] In the spatial light modulation system, the ultra-high-speed digital micromirror array (24) can arbitrarily change the channel side length, interval, spatial position and quantity. The characteristics of the magnetic measurement channels can be arbitrarily switched according to the grayscale value of the loaded picture and the corresponding position, and the degree of electrical crosstalk between pixels can be quickly evaluated according to the different spatial resolution data obtained by the high-speed CMOS sensor (22), without customizing a new PD array. The ultra-high-speed digital micromirror array (24) can also quickly traverse and search for channel data, and associate and pair the contour positions of all differential beam pairs to prevent misselection of differential beam pairs during subsequent data fitting.

[0111] As an optional implementation manner, the high-sensitivity, high-spatiotemporal resolution variable-channel two-dimensional weak magnetic imaging device further includes: a gas chamber and its heating system.

[0112] The gas chamber and its heating system include:

[0113] A gas chamber (15) containing a certain amount of alkali metal vapor, quenching gas and inert gas.

[0114] A heating unit (16) symmetrically arranged in space or arranged in a twisted manner around the gas chamber (15) to provide a heating function for the gas chamber (15). The heating unit (16) can be a twisted heating wire or an S-shaped double-layer symmetrically arranged heating film, with a high-frequency intermittent heating method.

[0115] Thermal insulation material (13) is arranged around the heating unit (16) for thermal insulation.

[0116] The heating system can increase the density of alkali metal vapor and improve the signal response. Among them, the heating unit (16) is arranged symmetrically in space or twisted pair, which minimizes the stray magnetic field generated during heating. In addition, the heating method is high-frequency intermittent heating. The power supply input frequency of the heating unit is much higher than the frequency of the polarization change information carried by the probe light, eliminating the stray magnetic field information brought by the heating unit (16) in the frequency domain. The heating interruption period is the data acquisition period of the probe light during the off stage of the pump light, eliminating the stray magnetic field information brought by the heating unit (16) in the time domain. Therefore, the magnetic field information obtained by the high-speed CMOS sensor (22) does not contain the stray magnetic field information brought by the heating unit. The gas chamber is filled with inert gas and quenching gas, and has an anti-relaxation coating, which can increase the polarization uniformity of alkali metal atoms.

[0117] In summary, the present application provides a variable-channel two-dimensional weak magnetic imaging device with high sensitivity and high spatio-temporal resolution, including a pump optical path, a detection optical path, a spatial light modulation system, a gas chamber, a heating system, and a magnetic shielding and magnetic field generation system; the pump optical path modulates the on-off of the circularly polarized pump light to quickly polarize and depolarize the alkali metal atoms in the gas chamber; in the detection optical path, the linearly polarized detection light is modulated by the spatial light modulation system to modulate its spatial distribution, and multiple channels are segmented and encoded. Each channel detects the depolarization process at the corresponding position of the hot gas chamber. The polarization state oscillation attenuation frequency during the depolarization process is proportional to the magnetic field value at the position; the heating system expands the response of the oscillation attenuation signal without introducing additional stray magnetic fields; the CMOS sensor synchronously detects the oscillation attenuation signals on all channels, and the two-dimensional magnetic field at the position of the gas chamber cross-section is obtained through subsequent data processing and a non-linear fitting algorithm based on the damping oscillation attenuation model a*exp(-b*x)*sin(c*x+d)+e paradigm, where a = R p / (R p +R rel ), b = R rel , c = ω0; R p is the pumping (pump) rate, R rel is the relaxation rate, ω0 = γB0 is the oscillation frequency of Larmor precession (γ is the electron gyromagnetic ratio, B0 is the magnitude of the static magnetic field), d represents the phase at the initial simple harmonic vibration, and e represents the small deviation between the experimental setting zero point and the actual zero point. The magnetic shielding and magnetic field generation system suppresses the interference of the geomagnetic field and external stray magnetic fields on the test results. For this imaging device, the channel characteristics can be quickly switched, providing a basis for high-precision rapid positioning of sub-millimeter to micron-scale objects and characterization of the spin polarization uniformity of the atomic gas chamber.

[0118] The specific optical path process is as follows: The pump laser (1) emits pump laser, and the wavelength of the pump laser is frequency-stabilized to the D1 line wavelength corresponding to the alkali metal atoms contained in the gas cell (15) by the wavelength meter feedback loop or the saturated absorption spectrum feedback loop (not marked in the figure); The optical isolator (2) prevents accidental high-power pump laser from being reflected back into the laser diode in the pump laser (1) and plays a protective role; The first linear polarizer (3) converts part of the linearly polarized pump laser into completely polarized light and stabilizes its polarization direction to the modulation direction sensitive to the acousto-optic crystal in the acousto-optic modulator (4) in free space; The aperture (5) blocks multiple diffracted lights emitted by the acousto-optic modulator (4) and only allows the first-order diffracted light to pass through; The combination of the first linear polarizer (3), the acousto-optic modulator (4) and the aperture (5) can be replaced by other fast optical switch devices, such as electro-optic modulators, etc.; Then, the pump laser passes through the second linear polarizer (6), and the power of the pump laser can be adjusted and optimized by rotating the second linear polarizer (6); The linearly polarized pump laser that has undergone time modulation and power optimization is reflected by the first mirror (7), expanded by the beam expander (8), reflected by the first filter (9) again, and combined with all the subsequent multi-channel detection lasers to become coaxial laser, and the cross-section of the pump laser beam needs to completely cover or exceed the cross-section of all channel detection laser beams to ensure that all detection laser beams carry magnetic field information; Here, the first filter (9) plays a beam combination role due to its different transmittance / reflection rates for the lasers with D1 and D2 line wavelengths; The combined linearly polarized pump laser is converted into circularly polarized laser after passing through the dual-wavelength wave plate (10). Here, the dual-wavelength wave plate (10) has a phase delay of 1 / 4 for the laser at the D1 line wavelength; The already circularly polarized pump laser passes through the first lens (11), the left reserved light hole of the multi-layer permalloy magnetic shielding cylinder (17), the left reserved light hole of the heat insulation material (13), the left reserved light hole of the heating unit (16), the gas cell (15), the right reserved light hole of the heating unit (16), the right reserved light hole of the heat insulation material (13), the right reserved light hole of the multi-layer permalloy magnetic shielding cylinder (17), and the second lens (18), and terminates at the second filter (19). The first lens (11) and the second lens (18) jointly modulate the overall profile diameter of the pump beam and the detection beam, jointly determine the size of the total magnetic field sensitive area with the ultra-high-speed digital micromirror array (24). Secondly, the first lens (11) and the second lens (18) are imaging lenses for the high-speed CMOS sensor (22). If not sensitive to the size of the total magnetic field measurement area or only the ultra-high-speed digital micromirror array (24) is required to determine, the first lens (11) and the second lens (18) can be placed adjacent to each other and arranged between the second filter (19) and the first half-wave plate (20); The second filter (19) has a very low transmittance for the laser with a wavelength near the D1 line and can block the pump laser.

[0119] The detection laser (34) emits detection laser, and the wavelength of the detection laser is detuned from the D2 line of the alkali metal atoms contained in the gas chamber (15); then, the detection laser passes through a power optimizer composed of a second half-wave plate (33) and a Glan-Thompson prism (32), and this combination can be replaced by other optical devices with optimized power ratios; the detection laser after power optimization passes through the window plate (31) and is split into two laser beams with one strong and one weak. The laser beam with strong power is used as the detection laser and enters the subsequent optical path. The laser beam with weak power is received by the photodetector (30) and fed back to the controller of the detection laser (34) through the PID loop, which plays a role in stabilizing the power and reducing the power noise; here, the window plate (31) can be replaced by other non-polarizing beam splitters; the detection laser with stable power and after beam splitting passes through the second mirror (29), a spatial light pinhole filter composed of a fourth lens (28), a pinhole (27), and a third lens (26), and a third linear polarizer (25) in sequence, and is modulated into a linearly polarized detection laser with a uniform power spatial distribution within the beam cross-section. This single large-diameter linearly polarized detection laser passes through the ultra-high-speed digital micromirror array (24) and is spatially modulated into multiple small-diameter linearly polarized detection lasers. The relative spatial positions of the small-diameter detection laser group are controlled by the grayscale binary image loaded by the ultra-high-speed digital micromirror array (24); the multi-path detection laser beams are then combined with the pump laser through the first filter (9) into a coaxial optical path; after that, the linearly polarized multi-path detection laser beam passes through the dual-wavelength wave plate (10), the first lens (11), the left reserved optical hole of the multi-layer permalloy magnetic shielding cylinder (17), the left reserved optical hole of the heat insulation material (13), the left reserved optical hole of the heating unit (16), the gas chamber (15), the right reserved optical hole of the heating unit (16), the right reserved optical hole of the heat insulation material (13), the right reserved optical hole of the multi-layer permalloy magnetic shielding cylinder (17), the second lens (18), and the second filter (19) in sequence. Here, the dual-wavelength wave plate (10) introduces a phase delay of 1 / 2 for the laser with a wavelength near the D2 line, so the linear polarization state of the multi-path detection laser only deflects the polarization direction, and it remains a linearly polarized laser; the first lens (11) and the second lens (18) are imaging lenses for the high-speed CMOS sensor (22) and can be placed adjacent to each other between the second filter (19) and the first half-wave plate (20); the second filter (19) has a high transmittance for the laser with a wavelength near the D2 line and has almost no influence on the power of the detection laser. Finally, the detection laser passes through an arbitrary power splitter composed of the first half-wave plate (20) and the polarization beam splitter (21) and becomes two groups of multi-channel differential detection lasers, which are incident on the sensing unit of the high-speed CMOS sensor (22). The sensing unit of the high-speed CMOS sensor (22) is considered an array of photodetectors with a very high spatial arrangement density, and the pixel value magnitudes on all pixels are considered the power response values of the detection laser. The oscillation attenuation frequency of the detected power response value is proportional to the magnetic field value near the gas chamber (15).

[0120] Optionally, the dual-wavelength wave plate (10) can be placed at any position between the first filter (9) and the heat insulation material (13) in the beam combining optical path.

[0121] Optionally, the second mirror (29) and the first mirror (7) can be not used in the scenario where the overall space volume requirement of the magnetic field imaging device is not high.

[0122] Optionally, the frequency stabilization system of the pump laser (1) can be not used.

[0123] Optionally, the first linear polarizer (3), the acousto-optic modulator (4) and the aperture (5) can be replaced by other fast optical switch devices.

[0124] Optionally, the second half-wave plate (33) and the Glan-Thompson prism (32) can be replaced by other polarization beam splitting optical devices with arbitrary power ratios.

[0125] Optionally, the window plate (31) can be replaced by other non-polarization beam splitters.

[0126] Optionally, the spatial light pinhole filter and the third linear polarizer (25) can be placed at any position between the window plate (31) and the ultra-high speed digital micromirror array (24) on the optical path.

[0127] Optionally, the multi-layer permalloy magnetic shielding cylinder (17) can be not used under the intervention of the active magnetic shielding coil, or replaced by other magnetic shielding measures.

[0128] Optionally, the electric heating method of the heating unit (16) can be replaced by other non-magnetic / low-magnetic heating methods such as hot air flow heating and laser heating.

[0129] Optionally, the position of the gas chamber (15) in the optical path direction can be controlled by a single-axis precision low-magnetic displacement stage to achieve three-dimensional magnetic field imaging.

[0130] Optionally, the gas chamber (15) can be fabricated into a thin-film gas chamber by MEMS technology, or fabricated by glass anodic bonding, and an anti-relaxation film can be optionally plated or not plated.

[0131] Conventional magnetic field imaging devices are difficult to balance sensitivity and dynamic range while meeting the spatial resolution requirement. This application is based on the fact that the spin-polarized free precession decay frequency during the interaction between a pump-probe beam and alkali metal atoms reflects the magnetic field magnitude at the location. It uses an ultra-high-speed digital micromirror array to perform detection beam (channel) segmentation, channel coding and marking, and contour position correlation of all differential beam pairs. A two-quadrant high-speed CMOS image sensor is used to synchronously receive multi-path detection optical differential signals carrying frequency information. This device balances sensitivity and dynamic range without reducing spatial resolution. Adding a DMD allows for freely setting the interval, side length, number, and spatial position of the detection channels, and enables free trade-off between the magnetic field measurement spatial resolution and the pixel crosstalk of the CMOS image sensor. Several independent adjacent pixel groups of the two-quadrant high-speed CMOS sensor are regarded as a 2D photodetector array with extremely high filling density.

[0132] The advantages of this application compared with the prior art are as follows:

[0133] This application uses a coaxial optical path design, which is easy to integrate.

[0134] This application uses a high-speed CMOS sensor (22) to detect differential optical rotation signals, replacing conventional photodetectors, photodetector arrays, and CCD cameras, which can greatly improve the imaging speed, imaging resolution, eliminate overexposure and trailing phenomena, and suppress common-mode noise.

[0135] This application uses an ultra-high-speed digital micromirror array to freely segment, encode, and pair differential detection beams, and can change the magnetic field imaging spatial resolution and the size of the magnetic field measurement area at any time without having to customize a new PD array.

[0136] This application uses an ultra-high-speed digital micromirror array to control the side length, number, and position of the channels. In addition to realizing the magnetic field measurement function, it can also measure the degree of electrical crosstalk between the pixels of the CMOS camera at one time.

[0137] This application uses the combination of DMD and CMOS sensor to reduce the participation of mechanical moving parts and reduce mechanical noise.

[0138] The optical path layout of this application is reasonable, the structure is compact, the installation and adjustment are convenient, and many unnecessary optical and mechanical components are reduced or replaced.

[0139] One of the purposes of this application is to provide a variable-channel two-dimensional weak magnetic imaging device with high sensitivity and high spatio-temporal resolution. Based on an atomic magnetometer using the method of measuring the free induction decay oscillation frequency with the optical rotation angle, it uses an ultra-high-speed digital micromirror array and a high-speed CMOS sensor (22) to perform spatial modulation coding and receive multi-path differential signals respectively to solve the problems existing in the above prior art.

[0140] In specific applications, such asFigures 1 - 3 As shown in Figures 1 - 3 , a variable-channel two-dimensional weak magnetic imaging device with high sensitivity and high spatio-temporal resolution includes a pump optical path, a detection optical path, a spatial light modulation system, a gas chamber, a heating system, a magnetic shielding and a magnetic field generation system.

[0141] The pump optical path emits circularly polarized pump laser synchronously amplitude-modulated by an acousto-optic modulator to cyclically polarize and depolarize alkali atoms; the detection optical path emits multi-pass linearly polarized detection laser spatially modulated by a digital micromirror array to cyclically detect the change in spin projection during the depolarization process of alkali atoms at different positions. The spatial light modulation system controls and optimizes various characteristics of the channels (side length, number, interval, position) to balance sensitivity, spatial resolution, and electrical crosstalk between pixels; the gas chamber and heating system provide a high-density alkali metal vapor to improve signal response; the magnetic shielding and magnetic field generation system shields the interference of the geomagnetic field and external stray magnetic fields on the signals collected by the CMOS sensor.

[0142] The specific principle is as follows: Polarized atoms along the direction of the pump laser will experience polarization decay due to various relaxation effects during the precession around the magnetic field to be measured. The decay frequency is the Larmor precession frequency, which is in a fixed ratio to the magnetic field value at the location, and this ratio is the known gyromagnetic ratio. Detecting this frequency allows the magnetic field magnitude to be fitted. At this time, if a linearly polarized detection light beam is incident into the alkali metal vapor and intersects the cross-section of the gas chamber and the pump extraction laser, its polarization plane will rotate by an angle, which is proportional to the spin component of the polarized atoms in this direction. Demodulating the deflection angle of the outgoing detection light beam can obtain the atomic spin decay information.

[0143] The specific steps are as follows:

[0144] In the embodiment, under the action of an external current controller, a temperature stabilizer, a wavelength meter, and a frequency stabilization system (not marked in the figure), the pump laser (1) emits partially linearly polarized pump pumping light corresponding to the D1 line wavelength of the alkali metal atoms contained in the gas chamber (15); a double-stage optical isolator (2) is used to prevent possible pump laser from being reflected back into the pump laser (1) to protect the laser; then, the first linear polarizer (3) is rotated to convert the partially linearly polarized pump laser into completely polarized laser, and its polarization direction is adjusted to be in the modulation direction sensitive to the acousto-optic crystal in the free-space acousto-optic modulator (4); a function generator (not marked in the figure) and a DC power supply (not marked in the figure) are connected to the RF driver of the AOM (not marked in the figure), and the AOM RF driver is connected to the acousto-optic modulator (4); the function generator is loaded with Figure 3The square-wave TTL timing sequence shown, where the square-wave frequency in the synchronous modulation stage is close to the magnetic field value to be measured, and the duty cycle is preferably selected between 35% and 75%. In this stage, the pump polarizes the alkali atoms. In the detection stage, a low-level signal is loaded to make the acousto-optic modulator (4) almost completely close the pump optical path. Then, finely adjust the light-passing diameter and the position of the light-passing hole of the aperture (5) so that it only allows the first-order diffracted light emitted by the acousto-optic modulator (4) to pass through. Then, the pump laser passes through the second linear polarizer (6), and the power of the pump laser is adjusted and optimized by rotating the second linear polarizer (6). The linearly polarized pump laser after time modulation and power optimization is reflected by the first mirror (7) and enters the beam expander (8) for beam expansion, and is reflected by the first filter (9) again, and is combined with the multi-channel detection laser described later to become a coaxial laser. Here, the cross-section of the pump laser beam needs to completely cover or exceed the cross-section of all channel detection laser beams to ensure that all detection laser beams carry atomic spin change information. Then, rotate the dual-wavelength wave plate (10) to convert the combined linearly polarized pump laser into a completely circularly polarized light. The already circularly polarized pump laser passes through the first lens (11), the left reserved light hole of the magnetic shielding cylinder (17), the left reserved light hole of the heat insulation material (13), the left reserved light hole of the heating unit (16), the gas cell (15), the right reserved light hole of the heating unit (16), the right reserved light hole of the heat insulation material (13), the right reserved light hole of the magnetic shielding cylinder (17), and the second lens (18), and terminates at the second filter (19). Adjust the distance between the first lens (11) and the second lens (18) in the optical path to make the gas cell contour image clear on the high-speed CMOS sensor (22). Then, connect the DC power supply (not shown in the figure) outside the multi-layer permalloy magnetic shielding cylinder (17) to the solenoid (12) to generate a vertical diametric bias magnetic field. Connect the temperature controller and the power supply (not shown in the figure) outside the multi-layer permalloy magnetic shielding cylinder (17) to the heating unit (16) and its non-magnetic thermistor (not shown in the figure) to make it heated in a high-frequency intermittent manner, and the high-frequency frequency is much higher than the Larmor precession frequency, and the heating intermittent period is the detection signal acquisition period in the pump light off stage. Heating will increase the density of alkali metal vapor in the atomic gas cell and improve the spin response and signal quality. In the presence of the bias field and the magnetic sample to be measured, what is obtained by fitting the data of the high-speed CMOS sensor (22) is the overall comprehensive distribution of the bias magnetic field, the system remanence and the magnetic field of the magnetic sample to be measured. In the presence of the bias field and the absence of the magnetic sample to be measured, what is obtained by fitting is the overall comprehensive distribution of the system remanence and the bias magnetic field. Subtracting the magnetic field data fitted in the two cases can obtain the true magnetic field distribution of the magnetic sample to be measured.Under the action of an external current controller, a temperature controller, and a wavelength meter (not shown in the figure), the detection laser (34) emits partially linearly polarized detection laser light. The wavelength of the detection laser is detuned from the D2 line of the alkali metal atoms contained in the gas cell (15) to ensure that as little interaction with the alkali atoms occurs as possible. Then, the detection laser passes through a power ratio adjuster composed of a second half-wave plate (33) and a Glan-Thompson prism (32) to optimize the power. The detection laser with optimized power is split into two laser beams of different intensities after passing through the window plate (31). The laser beam with higher power is used as the detection laser to enter the subsequent optical path, and the laser beam with lower power is received by the photodetector (30) and fed back to the external current controller of the detection laser (34) through a PID loop, which plays a role in stabilizing the power and reducing the power noise. The detection laser with stable power and after beam splitting passes through the second mirror (29), a spatial light pinhole filter composed of a fourth lens (28), a pinhole (27), and a third lens (26), and a third linear polarizer (25) in sequence, and is modulated into linearly polarized detection laser light with a uniform power spatial distribution within the beam cross-section. The fourth lens (28) and the third lens (26) on both sides of the spatial light pinhole filter also act as beam expanders at the same time, and the third linear polarizer (25) also acts as a power regulator at the same time. Then, a grayscale binary image with alternating black edges is designed according to the number of channels, side lengths, intervals, and positions suitable for the sample to be measured, and is loaded into the memory of the ultra-high-speed digital micromirror array (24). If the channel attributes need to be switched, just switch the corresponding grayscale binary image. After being spatially modulated by the ultra-high-speed digital micromirror array (24), the single large-diameter linearly polarized detection laser becomes multiple small-diameter linearly polarized detection laser beams. The relative spatial positions of the small-diameter detection laser beams are controlled by the grayscale binary image loaded into the ultra-high-speed digital micromirror array (24). Taking the 0 / 255 binary range as an example, the micromirrors corresponding to the pixel positions with a pixel value of 255 in the grayscale binary image are deflected by +12°, and the micromirrors corresponding to the pixel positions with a pixel value of 0 in the grayscale binary image are deflected by -12°. The light deflected by +12° (or -12°) enters the subsequent detection optical path, while the light deflected by -12° (or +12°) is discarded. By arranging positions with different pixel values on the personal PC host computer, the number of channels, side lengths, intervals, and positions of the detection laser split can be selected and controlled. The multi-channel detection light beams are then combined with the pump light into a coaxial optical path after passing through the first filter (9). After that, the linearly polarized multi-channel detection laser beam passes through a dual-wavelength wave plate (10), a lens 11, the left reserved optical hole of the multi-layer permalloy magnetic shielding cylinder (17), the left reserved optical hole of the heat insulation material (13), the left reserved optical hole of the heating unit (16), the gas cell (15), the right reserved optical hole of the heating unit (16), the right reserved optical hole of the heat insulation material (13), the right reserved optical hole of the multi-layer permalloy magnetic shielding cylinder (17), a second lens (18), and a second filter (19) in sequence. Here, the second filter (19) has a relatively high transmittance for laser light with a wavelength near the D2 line and has almost no effect on the power of the detection laser.Finally, all the detection laser beams are transformed into two groups of multi-channel differential detection laser beams after passing through an arbitrary power divider composed of a first half-wave plate (20) and a polarization beam splitter (21), and are incident on the sensing unit of a high-speed CMOS sensor (22). Here, it is necessary to rotate the first half-wave plate (20) to an appropriate position to ensure that the total intensity of the two groups of detection light is equal when there is no atomic polarization. After exporting the sensor data, the average signal of each pixel group is fitted with a nonlinear curve using the Levenberg-Marquardt algorithm and the damped oscillation attenuation model a*exp(-b*x)*sin(c*x+d)+e to obtain the c value, which is then divided by the gyromagnetic ratio to obtain the magnetic field information of the channel. The magnetic field data of each channel is interpolated and smoothed, and the above operation is repeated to present a 2D dynamic magnetic field image.

[0145] The technical features of the above embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0146] This document uses specific examples to illustrate the principles and implementation methods of this application. The description of the above examples is only intended to help understand the method and core concept of this application. At the same time, for those skilled in the art, based on the concept of this application, there may be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting this application.

Claims

1. A variable-channel two-dimensional weak magnetic imaging device with high sensitivity and high spatio-temporal resolution, characterized in that The high-sensitivity, high spatio-temporal resolution variable-channel two-dimensional weak magnetic imaging device includes: a pump optical path, a detection optical path, and an imaging unit; The pump optical path is used to convert linearly polarized pump laser into circularly polarized pump laser; The detection optical path is used to convert the detection laser into linearly polarized multi-path detection laser beams, and form a coaxial laser with the circularly polarized pump laser. By transforming, modulating, and power-distributing the coaxial laser, two sets of multi-channel differential detection laser beams are obtained; The imaging unit is used to obtain a 2D dynamic magnetic field image based on the two sets of multi-channel differential detection laser beams.

2. The highly sensitive and high spatio-temporal resolution variable-channel two-dimensional weak magnetic imaging device according to claim 1, wherein The pump optical path includes: A pump laser (1) for emitting partially linearly polarized pump laser; An optical isolator (2) for preventing the linearly polarized pump laser from being reflected back to the pump laser (1) again; A first polarizer (3) for converting the partially linearly polarized pump laser into fully polarized laser; An acousto-optic modulator (4) for performing acousto-optic modulation on the fully polarized laser to obtain several diffracted light beams; A diaphragm (5) for blocking the several diffracted light beams and only allowing the first-order diffracted light to pass through; A second polarizer (6) for adjusting and optimizing the power of the first-order diffracted light to obtain optimized linearly polarized pump laser; A first reflector (7) for reflecting the optimized linearly polarized pump laser to obtain reflected linearly polarized pump laser; A beam expander (8) for expanding the reflected linearly polarized pump laser to obtain expanded linearly polarized pump laser; A first filter (9) for combining the expanded linearly polarized pump laser and the linearly polarized multi-path detection laser beams to obtain a combined light beam; A dual-wavelength wave plate (10) for converting the linearly polarized pump laser in the combined light beam into circularly polarized laser.

3. The highly sensitive, high spatio-temporal resolution variable-channel two-dimensional weak magnetic imaging device according to claim 2, wherein, The detection optical path includes: A detection laser (34) for emitting detection laser; A power optimizer for optimizing the power of the detection laser to obtain power-optimized detection laser; A window plate (31) for dividing the power-optimized detection laser into two laser beams; among them, the laser above the preset power is used as new detection laser and enters the subsequent optical path; the laser below the preset power is used as feedback laser; A photodetector (30) for receiving the feedback laser and feeding it back to the controller of the detection laser (34) through a PID loop; A spatial light pinhole filter for filtering the new detection laser to obtain filtered detection laser; A third polarizer (25) for modulating the filtered detection laser into a standard linearly polarized detection laser with a uniform power spatial distribution within the light beam cross-section; An ultra-high-speed digital micromirror array (24) for modulating the standard linearly polarized detection laser into a linearly polarized multi-path detection laser beam with a laser diameter smaller than the preset value; A first filter (9) for combining the expanded linearly polarized pump laser and the linearly polarized multi-path detection laser beams to obtain a combined light beam; A dual-wavelength wave plate (10) is used to convert the linearly polarized pump laser in the combined light beam into a circularly polarized laser; and is also used to transmit the linearly polarized multi-path detection laser beam in the combined light beam to obtain a first transmitted linearly polarized multi-path detection laser beam; An imaging lens group is used to modulate the overall profile diameter of the circularly polarized laser light and the first transmitted linearly polarized multi-path detection laser beam to obtain a modulated circularly polarized laser light and a modulated linearly polarized multi-path detection laser beam; A second filter (19) is used to remove the modulated circularly polarized laser light and transmit the modulated linearly polarized multi-path detection laser beam to obtain a second transmitted linearly polarized multi-path detection laser beam; The arbitrary power divider is used to distribute the power of the second transmitted linearly polarized multi-channel detection laser beam to obtain two groups of multi-channel differential detection laser beams.

4. The highly sensitive, high spatio-temporal resolution variable-channel two-dimensional weak magnetic imaging device according to claim 3, characterized in that, The highly sensitive and high temporal and spatial resolution variable channel two-dimensional weak magnetic imaging device further comprises: Magnetic shielding and magnetic field generation system, used to suppress the interference of geomagnetic field and external stray magnetic field on test results; The magnetic shielding and magnetic field generating system comprises: A multi-layer Permalloy magnetic shielding tube (17) for achieving magnetic shielding; The solenoid (12) is used to provide a background bias magnetic field.

5. The highly sensitive and high spatio-temporal resolution variable-channel two-dimensional weak magnetic imaging device according to claim 4, wherein The arbitrary power distributor is a distributor composed of a first half-wave plate (20) and a polarization beam splitter (21).

6. The highly sensitive, high spatio-temporal resolution variable-channel two-dimensional weak magnetic imaging device according to claim 5, wherein The imaging lens group comprises: a first lens (11) and a second lens (18); The first lens (11) and the second lens (18) are respectively arranged at two ends of the multi-layer Permalloy magnetic shielding cylinder (17), or are arranged between the second filter (19) and the first half-wave plate (20).

7. The highly sensitive high spatio-temporal resolution variable-channel two-dimensional weak magnetic imaging device according to claim 6, characterized in that The spatial light pinhole filter is a filter composed of a second reflecting mirror (29), a fourth lens (28), a pinhole (27) and a third lens (26).

8. The highly sensitive, high spatio-temporal resolution variable-channel two-dimensional weak magnetic imaging device according to claim 7, wherein The power optimizer is an optimizer composed of a second half-wave plate (33) and a Glan-Thompson prism (32).

9. The highly sensitive, high spatio-temporal resolution variable-channel two-dimensional weak magnetic imaging device according to claim 8, characterized in that, The highly sensitive and high temporal and spatial resolution variable channel two-dimensional weak magnetic imaging device further comprises: A grayscale binary image generating device (23) is used to output a grayscale binary image consisting of a plurality of black and white squares; The grayscale binary image generating device (23) and the ultra-high-speed digital micromirror array (24) form a spatial light modulation system; the spatial light modulation system is used to control a number of micromirrors at positions corresponding to the black areas displayed in the grayscale binary image to deflect around their respective hinge axes by ±12°, thereby segmenting and marking all detection channels.

10. The highly sensitive and high spatio-temporal resolution variable-channel two-dimensional weak magnetic imaging device according to claim 9, wherein The highly sensitive and high temporal and spatial resolution variable channel two-dimensional weak magnetic imaging device further comprises: an air chamber and a heating system thereof; The air chamber and its heating system include: a gas chamber (15) containing alkali metal vapor, quenching gas and inert gas; A heating unit (16) is spatially symmetrically arranged or twisted around the air chamber (15) to provide a heating function for the air chamber (15); The heat insulation material (13) is arranged around the heating unit (16) to achieve heat insulation.

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