Micro-miniature atom magnetometer device for measuring biomagnetism and measuring method

Abstract

The invention discloses a microminiature atom magnetometer device for measuring biomagnetism. The microminiature atom magnetometer device comprises a laser light source, a control circuit, a probe and the like. The laser light source comprises a pump light laser and a probe light laser, and the control circuit comprises an alternating current heating circuit, a data acquisition circuit and a magnetic compensation circuit. The probe comprises an atomic gas chamber, a heating furnace, a pump light path, a detection light path, a three-axis magnetic compensation coil and a probe shell. According to the invention, the problem of organism body surface detection is solved by arranging heat insulation. The precise adjustable spectacle frame is arranged, so that the problems of daily precise adjustment and the like of the device are solved. In addition, the optical elements are modularized and are convenient to replace and adjust. The method is used for biomagnetic detection and is of great significance to non-contact medical detection.

Description

Technical Field

[0001] The present invention relates to the field of remote sensing, and specifically relates to a micro atomic magnetometer device for measuring biomagnetism, and also relates to a measurement method for measuring biomagnetism, which is applicable to biomagnetic detection such as magnetocardiogram and magnetoencephalogram. Background Technique

[0002] In the field of medical detection, the precise measurement of biomagnetism (such as magnetocardiogram, magnetoencephalogram, myomagnetism, lung magnetism, etc.) has broad application prospects. Biomagnetism can form information complementarity with bioelectricity, which helps to achieve non-invasive monitoring of the physiological state of organisms. However, the intensity of biomagnetism is very weak and decays rapidly with the increase of distance. For example, the magnetocardiogram generated by human heart activity is in the pT magnitude, and the magnetoencephalogram generated by human brain nerve activity is in the fT magnitude. Measuring these weak biomagnetisms requires a high-sensitivity magnetometer device.

[0003] An atomic magnetometer is a high-sensitivity magnetic measurement tool that accurately determines the magnetic field magnitude by measuring the non-linear magneto-optical rotation effect of polarized alkali metal atoms; compared with the traditional SQUID magnetometer used for measuring biomagnetism, it does not require a cryogenic system and has great development potential. The atomic magnetometer mainly includes a laser light source, a heating and temperature control system, a probe system, etc.

[0004] The atomic magnetometer for biomagnetic detection needs to meet the following requirements:

[0005] Precise heating and temperature control system. The detection sensitivity of the atomic magnetometer is closely related to the atomic number density in the atomic gas chamber, and the atomic number density is positively correlated with the temperature of the atomic gas chamber. Therefore, to achieve a high-sensitivity atomic magnetometer, it is usually necessary to heat the atomic gas chamber to 150 - 200 °C and stably control the temperature of the atomic gas chamber at the set temperature. This places high requirements on the heating accuracy, heating time of the heating system, and control accuracy of the temperature control system, etc.;

[0006] The heat insulation performance of the probe heat insulation device must be very high. The atomic gas chamber in the probe usually needs to be stabilized at a certain temperature point between 150 - 200 °C, and to meet the safety requirements, the part of the probe in contact with the human body should not exceed 43 °C (the probe area is less than 10% of the total body area) [Section 11.1 of the standard GB9706.1-2020 "Medical Electrical Equipment - Part 1: General Requirements for Basic Safety and Essential Performance"]. Since the working temperature of the atomic gas chamber in the probe is usually higher than 150 °C, the temperature difference between the inside and outside of the probe is greater than 100 °C, which places very high requirements on the heat insulation performance of the probe heat insulation device.

[0007] The distance from the atomic gas cell inside the probe to the human body should be small enough. For example, magnetoencephalography can be approximated as a magnetic dipole model, and the magnetic field decays with the cube of the distance. For every 1 mm increase in the distance between the atomic gas cell and the head, the magnetoencephalogram signal will drop sharply. Therefore, distance has a crucial impact on the performance of magnetoencephalography measurement;

[0008] Since the magnetoencephalography measurement device requires being non-magnetic and insulated, common metal materials and conductive non-metal materials (such as graphene, etc.) cannot be used for the atomic magnetometer probe.

[0009] Currently, several devices for biomagnetic measurement have been developed. The patent "Biomagnetic Field Automatic Measurement Device and Method for Single-Channel SERF Atomic Magnetometer (CN 116953573 A)" adopts a single-beam scheme. It introduces laser into the magnetometer probe through polarization-maintaining optical fiber. The core is a moving platform for the object to be measured above the atomic gas cell, realizing the measurement of different positions of the object to be measured. However, it does not have a heat insulation device and cannot be attached to the surface of the organism for biomagnetic detection. And since it is a single-light probe, it cannot form a probe array for simultaneous measurement of various parts of the organism. The linear polarization degree of the probe light, on the one hand, will cause the AC Stark frequency shift effect of alkali metal atoms, affecting the magnetic measurement accuracy; on the other hand, it is not conducive to the measurement of the polarization rotation angle of the probe light. Summary of the Invention

[0010] The purpose of the present invention is to provide a micro-miniature atomic magnetometer device for measuring biomagnetism and a measurement method for measuring biomagnetism in view of the above problems existing in the prior art. The present invention first solves the problem of detecting on the surface of the organism, and sets a heat insulation device, which can be used for skin-friendly measurement on the surface of the organism. At the same time, it solves the problem of precise adjustment of the polarization state of the light beam, and sets an adjustable mirror mount. On the one hand, it can be precisely adjusted during the equipment installation stage to achieve the optimal performance; on the other hand, an opening design is added, and users can adjust it by themselves during daily maintenance. In addition, the substrate of the present invention adopts a nickel-free immersion gold process, and each optical element is modular, which is convenient for replacement and adjustment.

[0011] The above object of the present invention is achieved by the following technical means:

[0012] A micro-miniature atomic magnetometer device for measuring biomagnetism, including a probe. The probe includes a substrate, a second atomic gas cell is arranged on the substrate. A pump light path reference groove and a probe light path reference groove are arranged on the substrate. The pump light optical fiber is pressed on the light inlet of the pump light path reference groove by a first pressing plate. After the pump light output from the output end of the pump light optical fiber passes through a first cylindrical mirror and a second cylindrical mirror in sequence, the light spot is shaped into an ellipse. The light emitted from the second cylindrical mirror passes through a first polarizer and a quarter-wave plate in sequence to generate circularly polarized light. The generated circularly polarized light is injected into the second atomic gas cell through a third 45° reflecting mirror.

[0013] The detection light optical fiber is pressed against the light incident port of the corresponding detection optical path reference groove by the second pressing plate. After the detection light output from the output end of the detection light optical fiber passes through the third cylindrical mirror and the fourth cylindrical mirror in sequence, the light spot is shaped into an ellipse. The detection light emitted from the fourth cylindrical mirror passes through the second polarizer and the light of the third half-wave plate, and then passes through the fourth 45° reflector and is injected into the second atomic gas cell. After the detection light exits the second atomic gas cell, it is reflected by the fifth 45° reflector and enters the fourth half-wave plate. The detection light passing through the fourth half-wave plate is incident on the Wollaston prism for polarization beam splitting. The two parts of the detection light transmitted in parallel after polarization beam splitting are received by the second photodetector.

[0014] As described above, the axial meridians of the first cylindrical mirror and the second cylindrical mirror are perpendicular to each other, and the fast axis of the quarter-wave plate and the polarization axis of the first polarizer are adjusted to 45°; the axial meridians of the third cylindrical mirror and the fourth cylindrical mirror are perpendicular to each other.

[0015] As described above, the first polarizer and the quarter-wave plate are bonded to form a combined lens. The combined lens, the second polarizer, and the fourth half-wave plate are respectively arranged in the corresponding adjustable lens frames as adjustable lenses. The adjustable lens frame includes an inner ring, an outer ring, and a bracket. The adjustable lens is fixed in the inner ring, the inner ring is fixed in the outer ring, the outer ring is movably embedded in the circular placement hole of the bracket, the inner end of the rotating rod is fixed to the outer ring, the outer end of the rotating rod passes through the rotating rod through hole communicated with the circular placement hole on the bracket and extends to the outside of the bracket. A threaded hole seat is arranged on the bracket, the threaded end of the fine adjustment screw is screwed into the threaded hole seat and abuts against the outer end of the rotating rod, and a non-magnetic elastic band is connected between the threaded hole seat and the outer end of the rotating rod.

[0016] As described above, the substrate is fixed in the probe housing. The probe housing includes a probe upper cover and a probe lower cover. The rotating rod and the fine adjustment screw of the adjustable lens frame corresponding to the combined lens are located in the lower cover through hole of the probe lower cover; the rotating rod and the fine adjustment screw of the adjustable lens frame corresponding to the second polarizer are located in the corresponding upper cover through hole of the probe upper cover; the rotating rod and the fine adjustment screw of the adjustable lens frame corresponding to the fourth half-wave plate are located in the corresponding upper cover through hole of the probe upper cover.

[0017] As described above, the second atomic gas cell is internally sealed with an alkali metal and a buffer gas. The second atomic gas cell is closely attached to the heating inner furnace outside. A non-magnetic heating sheet is pasted on the outer wall of the heating inner furnace, and a temperature-measuring platinum resistor is pasted on the bottom of the heating inner furnace. The non-magnetic heating sheet includes a flexible printed circuit board and heating wires symmetrically arranged on both sides of the flexible printed circuit board. The current directions of the heating wires on both sides of the flexible printed circuit board are opposite. The temperature-measuring platinum resistor, the non-magnetic heating sheet, and the heating inner furnace as a whole are wrapped by a heat-insulating material. A heating outer furnace is arranged outside the heat-insulating material. The heating inner furnace and the heating outer furnace are both provided with light passing holes, and no heat-insulating material is provided at the light passing holes. A three-axis magnetic compensation coil is wound around the outside of the heating outer furnace.

[0018] A micro-miniature atomic magnetometer device for measuring biomagnetism further includes a laser light source. The laser light source includes a pump laser and a probe laser. The pump light emitted by the pump laser sequentially passes through an optical isolator, a first half-wave plate, and a polarization beam splitting crystal and is divided into two paths. One path enters a saturated absorption frequency locking module, and the other path enters an optical fiber coupler connected to the pump optical fiber. The probe light emitted by the probe laser sequentially passes through an optical isolator and a first half-wave plate and is input into an optical fiber coupler connected to the probe optical fiber.

[0019] As described above, the saturated absorption frequency locking module includes a four-mirror ring cavity, a first atomic cell, and a first photodetector. The incident light enters the four-mirror ring cavity and passes through a coupling mirror. The incident light enters the four-mirror ring cavity and is reflected by the front surface of the coupling mirror to form a first weak reflected light. The remaining incident light transmits through the front surface of the coupling mirror and is reflected again by the rear surface of the coupling mirror to form a second weak reflected light. The light transmitting through the rear surface of the coupling mirror sequentially passes through a second half-wave plate, a second 45° highly reflective mirror, and a beam splitter. The reflected light split by the beam splitter enters the first atomic cell. The first weak reflected light and the second weak reflected light both pass through a first 45° reflector and enter the first atomic cell. The first weak reflected light or the second weak reflected light is collinear in the opposite direction with the light entering the first atomic cell after being reflected by the beam splitter. The first weak reflected light and the second weak reflected light pass through the first atomic cell and then transmit through the beam splitter and enter the first photodetector, forming an atomic spectrum signal through differential amplification. The atomic spectrum signal is fed back to the laser controller, and a frequency discrimination signal is formed through the frequency locking system inside the laser controller. The laser controller adjusts the parameters of the pump laser through the frequency discrimination signal for frequency locking.

[0020] A micro-miniature atomic magnetometer device for measuring biomagnetism further includes an AC heating circuit. The AC heating circuit includes a temperature-measuring platinum resistor, a temperature acquisition module, a sine signal generator, a multiplier, a power amplifier, and a non-magnetic heating sheet. The temperature acquisition module is connected to the temperature-measuring platinum resistor and the upper computer through wires. The upper computer calculates and outputs power according to the difference between the set temperature and the acquired temperature. The output power is converted into a control voltage through a digital-to-analog converter. The multiplier multiplies the high-frequency sine signal emitted by the sine signal generator and the control voltage for modulation and outputs a modulation signal. The modulation signal is output to the non-magnetic heating sheet in the probe through the power amplifier.

[0021] A micro-miniature atomic magnetometer device for measuring biomagnetism further includes a data acquisition circuit. The data acquisition circuit includes a transimpedance amplifier circuit, a differential amplifier circuit, a filter, and a data acquisition card. The transimpedance amplifier circuit performs transimpedance amplification on the current signal of the second photodetector output by the probe, and then performs differential amplification through the differential amplifier circuit. Subsequently, the differentially amplified signal is transmitted to the data acquisition card. The data acquisition card processes the analog signal into a digital signal and transmits it to the upper computer, and the upper computer processes it and displays and records the magnetic field signal.

[0022] It further includes a magnetic compensation circuit. The magnetic compensation circuit includes three current sources connected to the three-axis magnetic compensation coils. By controlling the magnitudes of the currents of the three current sources, the background magnetic field in the three-axis directions is compensated.

[0023] A method for measuring biomagnetism includes the following steps: Turn on the AC heating circuit. Wait until the second atomic gas chamber is heated to the set temperature. Turn on the pump laser and the probe laser. Wait until the temperature of the second atomic gas chamber is stable and the pump laser and the probe laser are stable for a set time. Adjust the wavelengths and powers of the pump light and the probe light. Then inject the pump light and the probe light into the pump light optical fiber and the probe light optical fiber of the probe respectively. Turn on the magnetic compensation circuit and the data acquisition module. After the subject lies in the magnetic shielding barrel, measure the biomagnetism through the probe.

[0024] The present invention has the following beneficial effects compared with the prior art:

[0025] 1. The present invention has the advantages of flexibility and portability.

[0026] 2. Compared with the existing electrocardiogram and other devices, the present invention has the advantage of non-contact measurement, which is convenient for detecting the cardiac magnetism and brain magnetism of patients with skin diseases, burns, etc. At the same time, the problem of precise adjustment of the beam polarization state is solved.

[0027] 3. The present invention is provided with a double-beam setup. In the prior art for the probe array required for biomagnetism measurement, a single-beam probe needs a modulation coil, and crosstalk will occur between the probes due to the modulation magnetic field. While the double-beam probe has no modulation coil and will not cause crosstalk due to the modulation magnetic field. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a system block diagram of the present invention.

[0029] Figure 2 It is a schematic diagram of the laser light source of the present invention.

[0030] Figure 3 It is a schematic diagram of the AC heating circuit.

[0031] Figure 4 It is a schematic diagram of the data acquisition circuit.

[0032] Figure 5 It is a schematic diagram of the internal structure of the probe of the present invention.

[0033] Figure 6 It is a cross-sectional view of the probe system.

[0034] Figure 7 It is a schematic diagram of the structure of the pump optical path of the probe.

[0035] Figure 8It is a schematic structural diagram of the detection optical path of the probe.

[0036] Figure 9 It is a schematic structural diagram of the adjustable mirror frame.

[0037] Figure 10 It is a schematic diagram of the probe appearance.

[0038] In the figure: 1 - external cavity semiconductor laser, 2 - optical isolator, 3 - first half-wave plate, 4 - polarization beam splitting crystal, 5 - fiber optic coupler, 6 - first atomic gas cell, 7 - first photodetector, 8 - laser controller, 9 - coupling mirror, 10 - first 45° reflecting mirror, 11 - second half-wave plate, 12 - second 45° highly reflective mirror, 13 - beam splitter, 14 - oscilloscope, 15 - upper computer, 16 - platinum resistance thermometer, 17 - sine signal generator, 18 - multiplier, 19 - power amplifier, 20 - non-magnetic heating sheet, 21 - transimpedance amplifier circuit, 22 - differential amplifier circuit, 23 - filter, 24 - data acquisition card, 25 - second photodetector, 26 - second atomic gas cell, 27 - inner heating furnace, 28 - aerogel, 29 - outer heating furnace, 30 - substrate, 31 - pump light optical fiber, 32 - first pressing plate, 33 - first cylindrical lens, 34 - second cylindrical lens, 35 - first polarizer, 36 - quarter-wave plate, 37 - inner ring, 38 - outer ring, 39 - bracket, 40 - locking screw, 41 - rotating rod, 42 - non-magnetic elastic band, 43 - fine adjustment screw, 44 - third 45° reflecting mirror, 45 - detection light optical fiber, 46 - second pressing plate, 47 - third cylindrical lens, 48 - fourth cylindrical lens, 49 - second polarizer, 50 - third half-wave plate, 51 - fourth 45° reflecting mirror, 52 - fourth half-wave plate, 53 - fifth 45° reflecting mirror, 54 - Wollaston prism, 55 - three-axis magnetic compensation coil, 56 - probe upper cover, 57 - lower cover through hole, 58 - probe lower cover, 59 - upper cover through hole, 60 - outlet, 61 - temperature acquisition module, 62 - circular placement hole, 63 - rotating rod through hole, 64 - threaded hole seat, 65 - locking through hole. Detailed implementation mode

[0039] In order to facilitate the understanding and implementation of the present invention by those of ordinary skill in the art, the present invention will be further described in detail below in conjunction with the implementation examples. The implementation examples described herein are only used to illustrate and explain the present invention, and are not intended to limit the present invention.

[0040] Example 1:

[0041] A micro-miniature atomic magnetometer device for measuring biomagnetism mainly includes a laser light source, a control circuit, a probe, etc.

[0042] The laser light source includes a pump laser and a probe laser, both of which are external cavity semiconductor lasers. Among them, the pump laser needs to be frequency locked, so a saturated absorption frequency locking module is set up, such as Figure 2 shown.

[0043] The control circuit includes an AC heating circuit, a data acquisition circuit, and a magnetic compensation circuit.

[0044] The probe includes an atomic gas cell, a heating furnace, a pump optical path, a probe optical path, a three-axis magnetic compensation coil, and a probe housing.

[0045] As Figure 2 shown, for the laser light source: the pump light emitted by the pump laser sequentially passes through an optical isolator 2, a first half-wave plate 3, and a polarization beam splitting crystal 4 and then is divided into two paths. One path enters the saturated absorption frequency locking module, and the other path enters a fiber optic coupler 5 connected to a pump optical fiber 31. The function of the optical isolator 2 is to prevent the reflected light from the subsequent optical path from damaging the laser tube of the external cavity semiconductor laser 1. The probe laser does not need to be provided with a saturated absorption module, and the probe light emitted by the probe laser sequentially passes through the optical isolator 2 and the first half-wave plate 3 and then is input into the fiber optic coupler 5 connected to a probe optical fiber 45.

[0046] In some embodiments, the saturated absorption frequency locking module includes a four-mirror ring cavity, a first atomic gas cell 6, and a first photodetector 7. The coupling mirror 9 in the four-mirror ring cavity (the four-mirror ring cavity is a prior art, and the coupling mirror is a part of the four-mirror ring cavity, and the coupling mirror works in cooperation with other components) is a thick glass with a thickness of about 1 cm. When the incident light enters the four-mirror ring cavity and passes through the coupling mirror 9, about 96% of the optical power is transmitted. A first weak reflected light with a power of about 2% is reflected by the front surface of the coupling mirror 9 when the incident light enters the four-mirror ring cavity. The remaining incident light is transmitted through the front surface of the coupling mirror 9, and then a second weak reflected light with a power of about 2% is reflected again by the back surface of the coupling mirror 9. The light transmitted through the back surface of the coupling mirror 9 passes through the second half-wave plate 11, the second 45° highly reflective mirror 12, and the beam splitter 13 in sequence. The beam splitter 13 splits the light into two beams of light with perpendicular propagation directions. Among them, the transmitted light with an unchanged propagation direction is useless, and the reflected light with a changed propagation direction enters the first atomic gas cell 6. The first weak reflected light and the second weak reflected light reflected by the front and back surfaces of the coupling mirror 9 both enter the first atomic gas cell 6 after being reflected by the first 45° reflecting mirror 10. Among them, the first weak reflected light or the second weak reflected light is collinear and in the opposite direction to the light (strong light) that enters the first atomic gas cell 6 after being reflected by the beam splitter 13. The first weak reflected light and the second weak reflected light pass through the first atomic gas cell 6 and then the transmitted light enters the first photodetector 7 after passing through the beam splitter 13, and an atomic spectrum signal is formed through differential amplification. The atomic spectrum signal is transmitted to the oscilloscope 14 for display in one path, and is fed back to the laser controller 8 in another path. A frequency discrimination signal is formed through the frequency locking system inside the laser controller 8. The frequency discrimination signal is also transmitted to the oscilloscope 14. The laser controller 8 adjusts the parameters of the pump light laser through the frequency discrimination signal to achieve frequency locking.

[0047] In some embodiments, the alternating current heating circuit includes a platinum resistance thermometer 16, a temperature acquisition module 61, a sine signal generator 17, a multiplier 18, a power amplifier 19, and a non-magnetic heating sheet 20. The temperature acquisition module 61 is connected to the platinum resistance thermometer 16 arranged inside the probe through a wire, acquires the temperature and converts it into a digital signal, and the digital signal is transmitted to the host computer 15. The host computer 15 calculates and outputs the power according to the difference between the set temperature and the acquired temperature, and the output power is converted into a control voltage through a digital-to-analog converter. The multiplier 18 multiplies the high-frequency sine signal emitted by the sine signal generator 17 and the control voltage to achieve modulation, and outputs a modulation signal. Subsequently, the modulation signal is output to the non-magnetic heating sheet 20 inside the probe through the power amplifier 19. Thus, the heating-thermostat closed loop is completed. The modulation frequency of the high-frequency sine signal is 50 kHz, the length of the non-magnetic heating sheet 20 is 60 mm, and the resistance is 14 Ω; the temperature measurement accuracy of the platinum resistance thermometer 16 is 0.001 °C.

[0048] In some embodiments, the data acquisition circuit includes a transimpedance amplifier circuit 21, a differential amplifier circuit 22, a filter 23, and a data acquisition card 24. The transimpedance amplifier circuit 21 performs transimpedance amplification on the current signal of the second photodetector 25 output by the probe, and then performs differential amplification through the differential amplifier circuit 22. Subsequently, the differentially amplified signal is transmitted to the data acquisition card 24. The data acquisition card 24 processes the analog signal into a digital signal and then transmits it to the host computer 15, and the host computer 15 processes and displays and records the magnetic field signal.

[0049] In some embodiments, the magnetic compensation circuit is mainly implemented by a current source and an automatic magnetic compensation algorithm. The three-axis magnetic compensation coils 55 of the probe are respectively connected to three current sources, and the automatic magnetic compensation algorithm controls the current magnitudes of the three current sources to compensate the background magnetic field in the three-axis directions, so that the background magnetic field in the three-axis directions is as close as possible to 0 nT.

[0050] In some embodiments, the probe part: The probe includes a second atomic gas cell 26, which is made of borosilicate glass and manufactured by an anodic oxidation process bonding technique. It is internally sealed with 87 Rb alkali metal and filled with buffer gases such as N2 and He. The specification of the second atomic gas cell 26 is 0.8 cm × 0.8 cm × 1.6 cm in length × width × height. The second atomic gas cell 26 is heated to 160 °C to meet the required atomic density. The heating inner furnace 27 is closely attached to the outside of the second atomic gas cell 26, and the heating inner furnace 27 tightly wraps the second atomic gas cell 26. The heating inner furnace 27 is made of boron nitride ceramic material to make the second atomic gas cell 26 uniformly heated. Non-magnetic heating sheets 20 are pasted on the two pairs of side outer walls, the top outer wall, and the bottom outer wall of the heating inner furnace 27. A temperature-measuring platinum resistor 16 is pasted on the bottom of the heating inner furnace 27 to sense the temperature of the probe. The non-magnetic heating sheet 20 includes a flexible printed circuit board and heating wires symmetrically arranged on both sides of the flexible printed circuit board. The current directions of the heating wires on both sides of the flexible printed circuit board are opposite. The non-magnetic heating sheet 20 uses a flexible printed circuit board with double-sided current reverse wiring (that is, the current path positions on both sides correspond and the current directions are opposite), and its material is a high-temperature resistant and low-thermal conductivity material. The temperature-measuring platinum resistor 16, the non-magnetic heating sheet 20, and the heating inner furnace 27 are integrally wrapped by a heat-insulating material, and the heat-insulating material is aerogel 28. The thickness of the aerogel 28 at the bottom of the heating inner furnace 27 is about 3 mm, and the thickness of the aerogel 28 around and at the top of the heating inner furnace 27 is about 10 mm. The purpose is to create a temperature difference inside and outside the atomic gas cell 26. A heating outer furnace 29 is arranged outside the heat-insulating material. The heating outer furnace 29 is made of PEEK material and is not heated, mainly used to protect the heating inner furnace 27 and the aerogel 28. The heating inner furnace 27 and the heating outer furnace 29 are both provided with rectangular light-transmitting holes with a side length of 5 mm, and no heat-insulating material is provided at the light-transmitting holes. The three-axis magnetic compensation coil 55 is wound around the outside of the heating outer furnace 29.

[0051] Optical path part of the probe: To achieve a non-magnetic probe, all materials are made of non-magnetic materials. To ensure efficient interaction between light and atoms, polarization-maintaining fibers are used for all optical fibers. To achieve the accuracy of the optical path, the probe is located in a magnetic shielding barrel. The probe includes a probe housing and a substrate 30 fixed inside the probe housing. The second atomic gas chamber 26 is arranged on the substrate 30. A pump optical path reference groove and a detection optical path reference groove are provided on the substrate 30. The probe housing includes an upper probe cover 56 and a lower probe cover 58.

[0052] The pump optical fiber 31 is pressed against the light inlet of the corresponding pump optical path reference groove by a first pressing plate 32. A first cylindrical mirror 33 and a second cylindrical mirror 34 with mutually perpendicular axial meridians are arranged behind the output end of the pump optical fiber 31. For the first cylindrical mirror 33 and the second cylindrical mirror 34, the light beam enters from the plane of the cylindrical mirror and exits from the convex surface. The first cylindrical mirror 33 and the second cylindrical mirror 34 are used to shape the light spot output from the output end of the pump optical fiber 31 into an ellipse. That is, the pump light output from the output end of the pump optical fiber 31 passes through the first cylindrical mirror 33 and the second cylindrical mirror 34 in sequence, and the light spot is shaped into an ellipse. A first polarizer 35 and a quarter-wave plate 36 are arranged behind the second cylindrical mirror 34. The fast axis of the quarter-wave plate 36 and the polarization axis of the first polarizer 35 are adjusted to 45°. Then, the first polarizer 35 and the quarter-wave plate 36 are bonded together to form a combined lens to generate circularly polarized light. That is, the light beam exiting from the second cylindrical mirror 34 passes through the first polarizer 35 and the quarter-wave plate 36 in sequence to generate circularly polarized light. The generated circularly polarized light is injected into the second atomic gas chamber 26 through a third 45° reflecting mirror 44. The third 45° reflecting mirror 44 is installed at the intersection position of the optical path where the second atomic gas chamber 26 is located directly below and the pump optical fiber 31. The combined lens is arranged on an adjustable mirror mount.

[0053] The detection light optical fiber 45 is pressed against the light incident port of the corresponding detection optical path reference groove by the second pressing plate 46. Behind the output end of the detection light optical fiber 45, a third cylindrical mirror 47 and a fourth cylindrical mirror 48 with perpendicular axial meridians are arranged. For the third cylindrical mirror 47 and the fourth cylindrical mirror 48, the light beam enters from the plane of the cylindrical mirror and exits from the convex surface. The two cylindrical mirrors are used to shape the light spot into an ellipse, that is, after the detection light output from the output end of the detection light optical fiber 45 passes through the third cylindrical mirror 47 and the fourth cylindrical mirror 48 in sequence, the light spot is shaped into an ellipse. Behind the fourth cylindrical mirror 48, a second polarizer 49 and a third half-wave plate 50 are arranged. The second polarizer 49 generates linearly polarized light and converts the polarization noise of the detection light into intensity noise; the third half-wave plate 50 can change the polarization axis of the linearly polarized light and rotate the polarization direction of the linearly polarized light by 90°. The detection light exiting from the fourth cylindrical mirror 48 passes through the second polarizer 49 and the light of the third half-wave plate 50 and then is injected into the second atomic gas cell 26 through the fourth 45° reflecting mirror 51. The fourth 45° reflecting mirror 51 is installed at the intersection position of the geometric central axis of the second atomic gas cell 26 and the optical path where the detection light optical fiber 45 is located. After the detection light exits the second atomic gas cell 26, it is reflected by the fifth 45° reflecting mirror 53 and enters the fourth half-wave plate 52. The fifth 45° reflecting mirror 53 and the fourth 45° reflecting mirror 51 are symmetrically distributed with respect to the second atomic gas cell 26. The second polarizer 49 and the fourth half-wave plate 52 are respectively arranged in the corresponding adjustable mirror mounts.

[0054] The combined lens, the second polarizer 49 and the fourth half-wave plate 52 are respectively arranged in the corresponding adjustable mirror mounts as adjustable lenses. The adjustable mirror mount includes an inner ring 37, an outer ring 38, and a bracket 39. The inner ring 37 tightly presses the adjustable lens (combined lens or second polarizer 49 or fourth half-wave plate 52), and the inner ring 37 is embedded in the outer ring 38. A locking screw 40 is arranged on the outer ring 38. The threaded end of the locking screw 40 is screwed into the threaded hole on the outer ring 38 and abuts against the inner ring 37 for locking the relative position between the inner ring 37 and the outer ring 38. The outer ring 38 is movably embedded in the circular placement hole 62 of the bracket 39. The outer ring 38 can rotate in the circular placement hole 62. The inner end of the rotating rod 41 is fixed to the outer ring 38. The outer end of the rotating rod 41 passes through the rotating rod through hole 63 communicated with the circular placement hole 62 on the bracket 39 and extends to the outside of the bracket 39. The aperture of the rotating rod through hole 63 is larger than the outer diameter of the rotating rod 41. The rotating rod 41 has a certain flipping stroke in the rotating rod through hole 63. When the rotating rod 41 flips, it drives the outer ring 38, the inner ring 37 and the adjustable lens (combined lens or second polarizer 49 or fourth half-wave plate 52) to rotate integrally in the circular placement hole 62. A threaded hole seat 64 is arranged on the bracket 39. The threaded end of the fine adjustment screw 43 is screwed into the threaded hole seat 64 and abuts against the outer end of the rotating rod 41. A non-magnetic elastic band 42 is connected between the threaded hole seat 64 and the outer end of the rotating rod 41. As Figure 9As shown, the non-magnetic elastic band 42 provides resistance to the counterclockwise rotation of the rotating rod 41, while the fine adjustment screw 43 provides power for the clockwise rotation of the rotating rod 41 by adjusting the threaded end. By adjusting the fine adjustment screw 43, the rotating rod 41 is rotated to different positions, thereby realizing the overall rotation angle of the outer ring 38, the inner ring 37, and the adjustable lens (compound lens or second polarizer 49 or fourth half-wave plate 52).

[0055] In some embodiments, the threaded end of the locking screw 40 passes through the locking through hole 65 on the bracket 39 and is screwed into the threaded hole on the outer ring 38 and abuts against the inner ring 37. When the outer ring 38, the inner ring 37, and the adjustable lens (compound lens or second polarizer 49 or fourth half-wave plate 52) rotate as a whole, the locking screw 40 can swing in the locking through hole 65 without being blocked.

[0056] The fine adjustment screw 43 of the adjustable frame corresponding to the compound lens is located in the lower cover through hole 57 of the probe lower cover 58. The outside world can adjust the flipping angle of the rotating rod 41 by adjusting the fine adjustment screw 43 exposed from the lower cover through hole 57. Then, the rotating rod 41 drives the inner ring, the outer ring, and the compound lens to rotate. Thus, the polarization axis of the first polarizer 35 of the compound lens is changed, and the polarization axis of the first polarizer 35 is adjusted to the polarization axis of the incident light of the first polarizer 35, so that the light is transmitted to the maximum extent. Since the first polarizer 35 is relatively stationary with the quarter-wave plate 36, the circular polarization characteristic will not be changed, only the light power and the transmittance of the incident light will be increased.

[0057] The fine adjustment screw 43 of the adjustable frame corresponding to the second polarizer 49 is located in the corresponding upper cover through hole 59 of the probe upper cover 56. The outside world can adjust the flipping angle of the rotating rod 41 by adjusting the fine adjustment screw 43 exposed from the upper cover through hole 59. The rotating rod 41 drives the inner ring, the outer ring, and the second polarizer 49 to rotate. Rotating the rotating rod 41 changes the polarization direction of the detection light and converts the polarization noise of the detection light into intensity noise.

[0058] The fine adjustment screw 43 of the adjustable mount corresponding to the fourth half-wave plate 52 is located within the corresponding upper cover through-hole 59 of the probe upper cover 58. The outside world can adjust the flipping angle of the rotating rod 41 by adjusting the fine adjustment screw 43 exposed from the upper cover through-hole 59, and the rotating rod 41 drives the inner ring, the outer ring, and the fourth half-wave plate 52 to rotate. Rotating the rotating rod 41 also changes the polarization direction of the detection light, and ultimately changes the optical power of the detection light passing through the fourth half-wave plate 52 projected on the two polarization axes of the Wollaston prism 54. The detection light passing through the fourth half-wave plate 52 is polarization split by the Wollaston prism 54, and the two parts of the parallel-transmitted detection light are received by the second photodetector 25. The two parallel detection lights are incident on the response region of the second photodetector 25. The second photodetector 25 is connected to a flexible wire, transmits data from within the outlet 60, and inputs the signal into the data acquisition module, and then the biomagnetic signal can be measured.

[0059] A method for measuring biomagnetism, using the above-mentioned micro-miniature atomic magnetometer device. Specifically, when in use, first turn on the AC heating circuit of the second atomic gas chamber 26. Wait until the second atomic gas chamber 26 is heated to the set temperature (preferred value 160 °C) and turn on the pump light laser and the detection light laser. Wait until the temperature of the second atomic gas chamber 26 is stable and the pump light laser and the detection light laser are stable for a set time, adjust the wavelengths and powers of the pump light and the detection light, and then inject the pump light and the detection light into the pump light optical fiber 31 and the detection light optical fiber 45 of the probe respectively. Subsequently, turn on the magnetic compensation circuit and the data acquisition module, and then turn on the upper computer software, and the atomic magnetometer device can be put into the working state. After the subject lies in the magnetic shielding barrel, the biomagnetic measurement can be started through the probe.

[0060] The specific embodiments described in this document are only examples to illustrate the spirit of the present invention. Those skilled in the art of the present invention can make various modifications or supplements to the described specific embodiments or use similar methods for substitution, but will not deviate from the spirit of the present invention or exceed the scope defined by the appended claims.

Claims

1. A micro-miniature atomic magnetometer device for measuring biomagnetism, comprising a probe, characterized in that, The probe includes a substrate (30), and a second atomic gas cell (26) is disposed on the substrate (30). A pump optical path reference groove and a detection optical path reference groove are provided on the substrate (30). The pump optical fiber (31) is pressed against the light incident port of the pump optical path reference groove by a first pressing plate (32). After the pump light output from the output end of the pump optical fiber (31) passes through a first cylindrical mirror (33) and a second cylindrical mirror (34) in sequence, the light spot is shaped into an ellipse. After the light emitted from the second cylindrical mirror (34) passes through a first polarizer (35) and a quarter-wave plate (36) in sequence, circularly polarized light is generated. The generated circularly polarized light is injected into the second atomic gas cell (26) through a third 45° mirror (44). The detection optical fiber (45) is pressed against the light incident port of the corresponding detection optical path reference groove by a second pressing plate (46). After the detection light output from the output end of the detection optical fiber (45) passes through a third cylindrical mirror (47) and a fourth cylindrical mirror (48) in sequence, the light spot is shaped into an ellipse. The detection light emitted from the fourth cylindrical mirror (48) passes through the second polarizer (49) and the light of the third half-wave plate (50), and then is injected into the second atomic gas cell (26) through a fourth 45° mirror (51). After the detection light exits the second atomic gas cell (26), it is reflected by a fifth 45° mirror (53) and enters a fourth half-wave plate (52). The detection light passing through the fourth half-wave plate (52) is incident on a Wollaston prism (54) for polarization splitting. The two parts of the detection light that are parallelly transmitted after polarization splitting are received by a second photodetector (25).

2. The micro-miniature atomic magnetometer device for measuring biomagnetism according to claim 1, characterized in that, The axial meridians of the first cylindrical mirror (33) and the second cylindrical mirror (34) are perpendicular to each other, and the fast axis of the quarter-wave plate (36) and the polarization axis of the first polarizer (35) are adjusted to 45°; the axial meridians of the third cylindrical mirror (47) and the fourth cylindrical mirror (48) are perpendicular to each other.

3. The micro-miniature atomic magnetometer device for measuring biomagnetism according to claim 1, wherein The first polarizer (35) and the quarter-wave plate (36) are bonded to form a combined lens. The combined lens, the second polarizer (49), and the fourth half-wave plate (52) are respectively disposed in corresponding adjustable lens holders as adjustable lenses. The adjustable lens holder includes an inner ring (37), an outer ring (38), and a bracket (39). The adjustable lens is fixed in the inner ring (37), the inner ring (37) is fixed in the outer ring (38), and the outer ring (38) is movably embedded in a circular placement hole (62) of the bracket (39). The inner end of a rotating rod (41) is fixed to the outer ring (38), and the outer end of the rotating rod (41) passes through a rotating rod through hole (63) communicating with the circular placement hole (62) on the bracket (39) and extends to the outside of the bracket (39). A threaded hole seat (64) is provided on the bracket (39). The threaded end of a fine adjustment screw (43) is screwed into the threaded hole seat (64) and abuts against the outer end of the rotating rod (41). A non-magnetic elastic band (42) is connected between the threaded hole seat (64) and the outer end of the rotating rod (41).

4. The micro-miniature atomic magnetometer device for measuring biomagnetism according to claim 3, wherein The substrate (30) is fixed in the probe housing, which includes an upper probe cover (56) and a lower probe cover (58). The rotating rod (41) and the fine adjustment screw (43) of the adjustable lens holder corresponding to the combined lens are located in the lower cover through hole (57) of the lower probe cover (58); the rotating rod (41) and the fine adjustment screw (43) of the adjustable lens holder corresponding to the second polarizer (49) are located in the corresponding upper cover through hole (59) of the upper probe cover (58); the rotating rod (41) and the fine adjustment screw (43) of the adjustable lens holder corresponding to the fourth half-wave plate (52) are located in the corresponding upper cover through hole (59) of the upper probe cover (58).

5. The micro-miniature atomic magnetometer device for measuring biomagnetism according to claim 1, characterized in that, The second atomic gas chamber (26) is internally sealed with an alkali metal and a buffer gas. The second atomic gas chamber (26) is closely attached to the inner heating furnace (27) on the outside. A non-magnetic heating sheet (20) is pasted on the outer wall of the inner heating furnace (27), and a temperature-measuring platinum resistor (16) is pasted on the bottom of the inner heating furnace (27). The non-magnetic heating sheet (20) includes a flexible printed circuit board and heating wires symmetrically arranged on both sides of the flexible printed circuit board. The current directions of the heating wires on both sides of the flexible printed circuit board are opposite. The temperature-measuring platinum resistor (16), the non-magnetic heating sheet (20) and the inner heating furnace (27) as a whole are wrapped by a heat-insulating material. An outer heating furnace (29) is arranged outside the heat-insulating material. The inner heating furnace (27) and the outer heating furnace (29) are both provided with light passing holes, and no heat-insulating material is provided at the light passing holes. A three-axis magnetic compensation coil (55) is wound around the outside of the outer heating furnace (29).

6. The micro-miniature atomic magnetometer device for measuring biomagnetism according to claim 1, characterized in that, It further includes a laser light source, which includes a pump light laser and a probe light laser. The pump light emitted by the pump light laser passes through an optical isolator (2), a first half-wave plate (3), and a polarization beam splitting crystal (4) in sequence and is divided into two paths. One path enters the saturated absorption frequency locking module, and the other path enters the fiber optic coupler (5) connected to the pump light optical fiber (31). The probe light emitted by the probe light laser passes through the optical isolator (2) and the first half-wave plate (3) in sequence and is input into the fiber optic coupler (5) connected to the probe light optical fiber (45).

7. The micro-miniature atomic magnetometer device for measuring biomagnetism according to claim 6, characterized in that, The saturated absorption frequency locking module includes a four-mirror ring cavity, a first atomic gas cell (6), and a first photodetector (7). The incident light enters the four-mirror ring cavity and passes through the coupling mirror (9). The incident light enters the four-mirror ring cavity and is reflected by the front surface of the coupling mirror (9) to form a first weak reflected light. The remaining incident light transmits through the front surface of the coupling mirror (9), and then is reflected again by the back surface of the coupling mirror (9) to form a second weak reflected light. The light transmitting through the back surface of the coupling mirror (9) sequentially passes through a second half-wave plate (11), a second 45° highly reflective mirror (12), and a beam splitter (13). The reflected light split by the beam splitter (13) enters the first atomic gas cell (6). The first weak reflected light and the second weak reflected light both pass through the first 45° reflecting mirror (10) and are reflected into the first atomic gas cell (6). The first weak reflected light or the second weak reflected light is collinear in the opposite direction with the light entering the first atomic gas cell (6) after being reflected by the beam splitter (13). The first weak reflected light and the second weak reflected light pass through the first atomic gas cell (6), then transmit through the beam splitter (13) and enter the first photodetector (7), and form an atomic spectrum signal through differential amplification. The atomic spectrum signal is fed back to the laser controller (8), and a frequency discrimination signal is formed through the frequency locking system inside the laser controller (8). The laser controller (8) adjusts the parameters of the pump light laser through the frequency discrimination signal for frequency locking.

8. The micro-miniature atomic magnetometer device for measuring biomagnetism according to claim 6, wherein It further includes an AC heating circuit. The AC heating circuit includes a platinum resistance thermometer (16), a temperature acquisition module (61), a sine signal generator (17), a multiplier (18), a power amplifier (19), and a non-magnetic heating sheet (20). The temperature acquisition module (61) is connected to the platinum resistance thermometer (16) and the host computer (15) through wires. The host computer (15) calculates and outputs the power according to the difference between the set temperature and the acquired temperature. The output power is converted into a control voltage through a digital-to-analog converter. The multiplier (18) multiplies and modulates the high-frequency sine signal emitted by the sine signal generator (17) and the control voltage, and outputs a modulated signal. The modulated signal is output to the non-magnetic heating sheet (20) inside the probe through the power amplifier (19).

9. The micro-miniature atomic magnetometer device for measuring biomagnetism according to claim 8, characterized in that, It further includes a data acquisition circuit. The data acquisition circuit includes a transimpedance amplifier circuit (21), a differential amplifier circuit (22), a filter (23), and a data acquisition card (24). The transimpedance amplifier circuit (21) performs transimpedance amplification on the current signal of the second photodetector (25) output by the probe, and then performs differential amplification through the differential amplifier circuit (22). Subsequently, the differentially amplified signal is transmitted to the data acquisition card (24). The data acquisition card (24) processes the analog signal into a digital signal and transmits it to the host computer (15). The host computer (15) processes and displays and records the magnetic field signal. It further includes a magnetic compensation circuit. The magnetic compensation circuit includes three current sources connected to the three-axis magnetic compensation coil (55), and controls the current magnitudes of the three current sources to compensate the background magnetic field in the three-axis direction.

10. A method for measuring biomagnetism, using the micro-miniature atomic magnetometer device described in claim 9, characterized in that, It includes the following steps: Turn on the AC heating circuit. After the second atomic gas cell (26) is heated to the set temperature, turn on the pump laser and the probe laser. After the temperature of the second atomic gas cell (26) is stable and the pump laser and the probe laser are stable for a set time, adjust the wavelengths and powers of the pump light and the probe light, and then inject the pump light and the probe light into the pump light optical fiber (31) and the probe light optical fiber (45) of the probe respectively. Turn on the magnetic compensation circuit and the data acquisition module. After the subject lies in the magnetic shielding barrel, perform biomagnetic measurement through the probe.

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