Biplanar coil pair design method, coil pair structure and atomic magnetometer array

Abstract

The invention provides a biplane coil pair design method, a coil pair structure and an atomic magnetometer array. The biplane coil pair design method comprises the following steps: S1, providing two to-be-arranged coils and oppositely arranging the two to-be-arranged coils; the opposite surfaces of the two to-be-arranged coils serve as inner sides and are arranged to be uniform areas; the non-opposite surfaces of the two coils to be arranged serve as outer sides and are arranged as stray regions; and S2, current paths corresponding to the two coils to be arranged are solved based on the loss function satisfied by the uniform region and the stray region. The invention provides a new anti-crosstalk arrangement, optimizes radio frequency magnetic field crosstalk between the atomic magnetometers, and improves the spatial resolution of atomic magnetometer imaging.

Description

Technical Field

[0001] The present invention relates to the field of magnetic field detection, and in particular to a double-plane coil pair design method, a coil pair structure and an atomic magnetometer array. Background Art

[0002] Magnetic imaging technology plays an important role in many fields such as healthcare, geophysics, and aerospace. Biomagnetic imaging technology is particularly suitable for medical prediction, where magnetoencephalography and magnetocardiography can capture magnetic field signals generated by electrical activity in the brain and heart. Magnetoencephalography has significant advantages in accurately diagnosing brain diseases such as epilepsy and Alzheimer's disease; while magnetocardiography plays a key role in the screening and diagnosis of cardiovascular diseases such as coronary heart disease, valvular disease, aneurysm, and abnormal heart rate.

[0003] In order to obtain magnetoencephalograms and magnetocardiograms, an atomic magnetometer array is needed to measure the spatial magnetic field distribution of the brain and heart. The quality of the reconstructed current density image will improve with the increase of magnetometer sensor density, so the magnetometer array needs to have a sufficiently high spatial resolution.

[0004] However, the existing atomic magnetometer arrays suitable for magnetoencephalography and magnetocardiography have the problem of radio frequency magnetic field crosstalk between the atomic magnetometers because different frequency radio frequency signals need to be set in each atomic magnetometer in the atomic magnetometer array.

[0005] It should be noted that the above introduction to the technical background is only for the convenience of providing a clear and complete description of the technical solutions of the present application and for the convenience of understanding by those skilled in the art. It cannot be considered that the above technical solutions are well known to those skilled in the art simply because they are described in the background technology section of the present application. Summary of the invention

[0006] In view of the above-mentioned shortcomings of the prior art, an object of the present invention is to provide a dual-plane coil pair design method, a coil pair structure and an atomic magnetometer array, which are used to solve the problem of radio frequency magnetic field crosstalk between atomic magnetometers in the prior art.

[0007] To achieve the above objectives and other related objectives, the present invention provides a dual-plane coil pair design method, comprising:

[0008] S1. Provide two coils to be set and set the two coils to be set opposite to each other; the opposite surfaces of the two coils to be set are used as inner sides and set as uniform areas; the non-opposite surfaces of the two coils to be set are used as outer sides and set as stray areas;

[0009] S2. Based on the loss function satisfied by the uniform area and the stray area, current paths corresponding to the two coils to be set are obtained by solving the loss function.

[0010] Optionally, step S2 includes:

[0011] S21, setting the midpoint of the line connecting the center points of the opposite surfaces of the two coils to be set as the coordinate origin; the distance between the coordinate origin and each coil to be set is less than half the side length of the coil to be set; discretizing the uniform area and the stray area to obtain at least two discrete points respectively, and characterizing the position of each discrete point based on the coordinate origin;

[0012] S22. A set of simultaneous equations is established based on each point and the loss function corresponding to each point, and the simultaneous equations are solved by pseudo-inverse matrix to obtain the current paths corresponding to the two double-plane coils; wherein the field strength value and gradient value of each point satisfy the loss function of the corresponding point.

[0013] Optionally, the weights of the field strength value and the gradient value in the loss function of each point are set to be the same.

[0014] To achieve the above objectives and other related objectives, the present invention provides a dual-plane coil pair structure, including two dual-plane coil structures arranged opposite to each other; the dual-plane coil structure includes: a coil body, a first coil portion, and a magnetic field compensation portion;

[0015] The first coil portion is arranged on the first surface of the coil body, and includes at least two first coils, at least two second coils and at least one first connecting wire; each first coil is arranged concentrically around a first center, and the area of ​​each first coil increases as the distance between each first coil and the first center increases; each second coil is arranged concentrically around a second center, and the area of ​​each second coil increases as the distance between each second coil and the second center increases; the current direction of each first coil is opposite to the current direction of each second coil; each first connecting wire is used to sequentially connect the coils in the first coil portion in series, so as to input the current from the center of the surface away from the first coil portion to the center of the surface of the first coil portion;

[0016] The magnetic field compensation portion is arranged on the second surface of the coil body and includes at least one second connecting wire; the second connecting wire is arranged corresponding to the first connecting wire to output the current from the center of the first coil portion to the direction away from the center of the first coil portion to offset the magnetic field interference introduced by the first connecting wire.

[0017] Optionally, the first center and the second center are set at the same position and are the center of the first coil portion, and each first coil is located inside the smallest second coil.

[0018] Optionally, the dual-plane coil structure also includes four second coil portions arranged on the first surface of the coil body; each second coil portion is outside the first coil portion and is centrally symmetrically arranged along the first center; each second coil portion has at least two third coils; the current direction of each third coil is the same as the current direction of each first coil; and at least two third coils inside the second coil portion are connected in series through a third connecting wire.

[0019] Optionally, the magnetic field compensation unit further includes four fourth connecting wires; each fourth connecting wire is used to offset the magnetic field interference introduced by each second coil unit.

[0020] Optionally, the first center and the second center are arranged at different positions on the same straight line, and each first coil is axially symmetrical with each second coil.

[0021] Optionally, the first coil portion further includes a third coil portion and a fourth coil portion; the third coil portion and the fourth coil portion are respectively arranged on both sides of the first coil portion; the third coil portion and the fourth coil portion are arranged axially symmetrically, and are the same symmetry axis as the symmetry axis of the first coil portion;

[0022] The third coil portion includes at least two fourth coils, each of which is concentrically arranged around the third center and the area of ​​each fourth coil increases as the distance between each fourth coil and the third center increases; each fourth coil is connected in series via a fifth connecting line;

[0023] The fourth coil portion includes at least two fifth coils, each of which is concentrically arranged around a fourth center and the area of ​​each fifth coil increases as the distance between each fifth coil and the fifth center increases; each fifth coil is connected in series via a sixth connecting wire;

[0024] The third center, the fourth center, the first center and the second center are all located on the same straight line;

[0025] The third coil portion is arranged on a side close to the second center and away from the first center, and the current direction of each fourth coil in the third coil portion is the same as that of each first coil;

[0026] The fourth coil unit is arranged on a side close to the first center and away from the second center, and the current direction of each fifth coil in the fourth coil unit is the same as that of each second coil. Optionally, the magnetic field compensation unit further includes a seventh connecting wire and an eighth connecting wire; the seventh connecting wire is used to offset the magnetic field interference introduced by the third coil unit; and the eighth connecting wire is used to offset the magnetic field interference introduced by the fourth coil unit.

[0027] Optionally, the dual-plane coil structure is manufactured based on at least one of PCB, FPC, and thin-film alumina ceramic processes.

[0028] To achieve the above-mentioned object and other related objects, the present invention provides an atomic magnetometer array, comprising: at least two atomic magnetometers arranged in an array; each atomic magnetometer comprises an optical path emission module, an atomic chamber, a detection module and two of the above-mentioned double-plane coil structures;

[0029] The optical path transmission module is used to generate incident light of a specific wavelength and convert the output to obtain corresponding polarized light; the incident light includes pump light and detection light;

[0030] The atomic chamber is arranged on the optical path of the polarized light, and each atomic gas in the atomic chamber interacts with the polarized light to change the polarization direction of the polarized light and obtain an outgoing light; the detection module receives the outgoing light to obtain a magnetic field signal to be measured;

[0031] Two double-plane coil structures are arranged opposite to each other and are respectively arranged on two surfaces of the atomic chamber to prevent crosstalk between the atomic magnetometers;

[0032] The line connecting the surface centers of the two double-plane coil structures perpendicularly bisects the optical path of the polarized light, or the line connecting the surface centers of the two double-plane coil structures is colinear with the optical path of the polarized light.

[0033] Optionally, the optical path transmission module includes a laser and a polarization conversion unit; the laser is used to generate incident light and output it after conversion by the polarization conversion unit; the polarization conversion unit is used to convert the incident light into polarized light and output it.

[0034] Optionally, the atomic chamber includes a shell; a cavity is formed inside the shell; the inside of the cavity is used to accommodate alkaline metal atoms; the shell is also provided with an incident port for the polarized light to pass through and an exit port for the reflected light to exit.

[0035] Optionally, the detection module includes a photoelectric detector; the photoelectric detector is used to perform photoelectric conversion on the emitted light to obtain a detection electrical signal.

[0036] Optionally, when a line connecting the surface centers of the two double-plane coil structures is collinear with the optical path of the polarized light, through holes are further provided at the surface centers of the two double-plane coil structures.

[0037] Optionally, the area of ​​the dual-plane coil structure is greater than or equal to 4 times the surface area of ​​the atomic chamber.

[0038] As described above, the dual-plane coil pair design method, coil pair structure and atomic magnetometer array of the present invention have the following features:

[0039] Beneficial effects:

[0040] 1. The dual-plane coil pair design method of the present invention can constrain the external radio frequency magnetic field, has a good anti-magnetic crosstalk effect, and can be applied to the field of magnetic field detection to at least shield the internal radio frequency magnetic field signal emitted outward.

[0041] 2. The dual-plane coil pair structure of the present invention can constrain the inner RF magnetic field under the premise of the current path set by the dual-plane coil pair design method, and at the same time, a magnetic field compensation part is provided to avoid the additional magnetic field generated by the RF magnetic field being injected into the magnetic field coil itself, resulting in inaccurate measurement.

[0042] 3. The anti-crosstalk effect between the atomic magnetometers in the atomic magnetometer array of the present invention is good, which can effectively improve the spatial resolution of atomic magnetometer imaging, thereby improving the accuracy of detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 It is a schematic diagram showing the steps of the dual-plane coil pair design method of the present invention.

[0044] Figure 2 Display as Figure 1 Schematic diagram of step S2 in the dual-planar coil pair design method.

[0045] Figure 3 It is a schematic plan view of a dual-plane Z-coil structure of the present invention.

[0046] Figure 4 Display as Figure 3 Side view of the dual-planar coil structure.

[0047] Figure 5 Shown is a schematic diagram illustrating the principle of a first connecting line.

[0048] Figure 6 Display as Figure 5 Schematic diagram illustrating the compensation principle of the corresponding second connecting line.

[0049] Figure 7 FIG. 4 is a plan view schematically showing another dual-plane X-coil structure of the present invention.

[0050] Figure 8 Shown is a schematic structural diagram of an atomic magnetometer of the present invention.

[0051] Fig. 9 Shown is a schematic structural diagram of another atomic magnetometer of the present invention.

[0052] Fig.10A simulation model and evaluation diagram suitable for exploring different coils and attenuation effects of the present invention are shown.

[0053] Fig.11 Shown is a schematic diagram of the structure of a Helmholtz coil.

[0054] Fig.12 Shown are the normalized magnetic field distributions along the Y-axis for the three types of coils.

[0055] Fig.13 Display as Fig.11 A partial enlarged schematic diagram of .

[0056] Fig.14 The diagram shows a comparison of the magnetic field distribution of the two dual-plane coils of the present invention attenuated along the X-axis and the Y-axis.

[0057] Fig.15 Shown is a schematic diagram of the attenuation of the Helmholtz coil in the first attenuation region.

[0058] Fig.16 Shown is a schematic diagram of the attenuation of the Helmholtz coil in the second attenuation region.

[0059] Fig.17 Shown is a schematic diagram of the attenuation of the Helmholtz coil in the third attenuation region.

[0060] Fig.18 It is a schematic diagram showing the attenuation of the dual-plane X-coil of the present invention in the first attenuation region.

[0061] Fig.19 It is a schematic diagram showing the attenuation of the dual-plane X-coil of the present invention in the second attenuation region.

[0062] Fig. 20 It is a schematic diagram showing the attenuation of the dual-plane X-coil of the present invention in the third attenuation region.

[0063] Fig.21 It is a schematic diagram showing the attenuation of the dual-plane Z-coil of the present invention in the first attenuation region.

[0064] Fig. 22 It is a schematic diagram showing the attenuation of the dual-plane Z-coil of the present invention in the second attenuation region.

[0065] Fig.23 It is a schematic diagram showing the attenuation of the dual-plane Z coil of the present invention in the third attenuation region.

[0066] Component number description

[0067] 1 Atomic magnetometer

[0068] 11 Dual Planar Coil Structure

[0069] 111 First coil part

[0070] 1111 First Coil

[0071] 1112 Second coil

[0072] 1113 First Connection Line

[0073] 1114 Through hole

[0074] 112 Magnetic Field Compensation Unit

[0075] 1121 Second connection line

[0076] 113 Second coil part

[0077] 1131 Third Coil

[0078] 12 Dual Planar Coil Structure

[0079] 121 Third coil unit

[0080] 1211 Fourth Coil

[0081] 122 fourth coil part

[0082] 1221 Fifth Coil

[0083] 13 Optical path transmission module

[0084] 131 Laser

[0085] 132 Polarization conversion unit

[0086] 1321 Lens

[0087] 1322 Polarization beam splitter

[0088] 1323 Wave Plate

[0089] 14 Atomic Chamber

[0090] 15 Photodetector

[0091] 2 Helmholtz coil DETAILED DESCRIPTION

[0092] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention.

[0093] See also Figure 1 to Figure 23It should be noted that the illustrations provided in this embodiment are only used to illustrate the basic concept of the present invention in a schematic manner, and the drawings only show components related to the present invention rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout may also be more complicated.

[0094] Optically pumped atomic magnetometers achieve precise magnetic field detection by using spin-polarized magnetically sensitive atomic vapor. Depending on whether a magnetic shielding environment is required, atomic magnetometers can be divided into zero-field atomic magnetometers (magnetic shielding devices are required) and full-field atomic magnetometers (magnetic shielding devices are not required).

[0095] Although the zero-field atomic magnetometer has no spin relaxation exchange, its sensitivity can reach ~ However, its dynamic range is small and it cannot work in the geomagnetic field environment. In contrast, the full-field atomic magnetometer can work in the geomagnetic field environment and does not require a complex magnetic shielding structure, which can greatly simplify the size of the magnetometer. For example, the common Mz / Mx scalar atomic magnetometer is usually used to measure larger magnetic fields. However, it itself needs to use the radio frequency magnetic field to drive the atoms, and the magnetic field gradient in each atomic magnetometer in the Mz / Mx atomic magnetometer array will cause the magnetic field frequency of each sensor in the array to be inconsistent. Therefore, there is inevitably a problem of radio frequency magnetic field crosstalk between the atomic magnetometers. This will directly lead to the spatial resolution of the Mz / Mx atomic magnetometer array being not high enough, which will affect the image quality and accuracy of biomagnetic imaging.

[0096] Embodiment 1

[0097] In order to solve the above problems and similar magnetic field crosstalk problems, this embodiment provides a dual-plane coil pair design method, the designed dual-plane coil pair can better constrain the external magnetic field signal, and the dual-plane coil pair has a better anti-magnetic crosstalk effect when used together.

[0098] like Figure 1-2 As shown, this embodiment provides a dual-plane coil pair design method, including:

[0099] S1. Provide two coils to be set, and set the two coils to be set opposite to each other. The opposite surfaces of the two coils to be set are used as inner sides and set as uniform areas; the non-opposite surfaces of the two coils to be set are used as outer sides and set as stray areas.

[0100] Specifically, a magnetic field is set in the uniform area (in the present embodiment, the magnetic field is set to be a radio frequency magnetic field). Since it is necessary to prevent the magnetic field signal from diverging into the space without restriction, it is necessary to constrain the set magnetic field signal as much as possible within the two coils to be set. Therefore, the space is divided into three parts by the two coils to be measured, including stray areas at both ends and the uniform area inside.

[0101] S2. Based on the loss function satisfied by the uniform area and the stray area, the current paths corresponding to the two coils to be set are obtained.

[0102] Specifically, by constraining the uniform area and the stray area based on the same loss function, the current paths in the two coils to be designed under the optimal solution of the loss function are obtained, and the two coils to be designed are used as a double-plane coil pair. Under the action of the double-plane coil pair, the magnetic field existing in the uniform area inside the two double-plane coils is constrained within a certain spatial range as much as possible.

[0103] As an example, Figure 2 As shown, step S2 includes:

[0104] S21. The midpoint of the line connecting the center points of the opposite faces of the two coils to be set is set as the coordinate origin; the distance between the coordinate origin and each coil to be set is less than half the side length of the coil to be set; the uniform area and the stray area are discretized to obtain at least two discrete points respectively, and the position of each discrete point is characterized based on the coordinate origin.

[0105] In this embodiment, the center of the magnetic field is pre-set as the coordinate origin. Preferably, the midpoint of the connecting line of the center points of the two opposing faces of the coils to be set is set as the magnetic field center. The positional relationship of the entire space is established with the coordinate origin, and the spatial region is discretized to obtain each discrete point, and the corresponding equation is established through the point positions, magnetic fields and other characteristics of multiple discrete points.

[0106] In this embodiment, the coil to be set is considered as a square as a whole, and the side length of the coil to be set is the side length of the square. In another embodiment, the coil to be set is considered as a rectangle as a whole, and the side length of the coil to be set is the side length of the shortest side of the rectangle. In fact, as long as the shortest side of the coil to be set is greater than or equal to the distance from the coordinate origin, it is within the protection scope of this embodiment.

[0107] S22. A set of simultaneous equations is established based on each point and the corresponding loss function of each point, and the simultaneous equations are solved by pseudo-inverse matrix to obtain the current paths corresponding to the two double-plane coils; wherein the field strength value and gradient value of each point satisfy the loss function of the corresponding point.

[0108] In this embodiment, the loss function is expressed as the difference between the target magnetic field characteristics and the actual measured magnetic field characteristics. Specifically, in this embodiment, the magnetic field characteristics are characterized by at least field strength values ​​and gradient values. Therefore, as long as the field strength value of the target magnetic field and the gradient value of the target magnetic field, as well as the corresponding difference relationship between the field strength value of the actual measured magnetic field and the gradient value of the actual measured magnetic field are established, the loss function can be obtained. At the same time, the established loss function needs to seek the optimal solution. By deriving the loss function of a point or solving a set of pseudo-inverse matrices of loss functions composed of each point, the optimal solution of the loss function and the corresponding current path under the optimal solution can be obtained.

[0109] It should be noted that, in this embodiment, the method for solving the loss function is not limited to this embodiment, and any method that can solve the optimal solution to the loss function is within the protection scope of this embodiment.

[0110] It should be further explained that the evaluation of whether the RF magnetic field will cause crosstalk to the adjacent atomic magnetometer mainly depends on the attenuation trend of the magnetic field generated by the coil at its periphery. Ideally, the RF magnetic field generated by the dual-plane coil pair is confined within the inner range of the dual-plane coil pair, but the magnetic field generated by the dual-plane coil pair will inevitably extend to the outer stray area of ​​the dual-plane coil pair. Therefore, when selecting the optimal solution, it is necessary to reasonably limit the constraint range of the loss function. Therefore, the dual-plane coil pair based on this embodiment can better further constrain the magnetic field signal on the outer side.

[0111] In this embodiment, the weights of the field strength value and the gradient value in the loss function of each point are set to be the same, that is, the contributions of the field strength value and the gradient value in each loss function are considered to be the same, and it is necessary to find a current path with optimal field strength value and gradient value.

[0112] It should be noted that the specific weight setting can be set to other weights based on needs and is not limited to this embodiment.

[0113] It should be further explained that the process of establishing the loss function is not limited to the present embodiment, and the parameters characterized by it are not limited to the field strength value and gradient value of the present embodiment. In fact, as long as the loss function can be established to solve the set magnetic field signal as much as possible within the space, the setting is protected by the present embodiment.

[0114] The following is a detailed description of the above steps:

[0115] First define the region: define the uniform region r i And the stray area G x , and define the coordinate origin in the uniform region; the uniformity of the magnetic field in the uniform region represents B x , the gradient field in the stray area is expressed as G xIn this embodiment, the two coils to be set are both considered as square planar coils with a side length of L, the length of the line between the center points of the two planar coils is d, and the distance between the origin of the coordinate system and the coil to be set is a / 2 (a<L). The target magnetic field characteristics are set, assuming that the uniformity error of the uniform area and the stray area does not exceed 1%.

[0116] Then define the loss function F:

[0117]

[0118] Where I means discretizing the target area into I points; B t (r i ) is the point r i The magnetic field value of the target magnetic field; b x (r i ) is the actual measured magnetic field value of point ri, which satisfies the Bier-Savart law, that is, b x (r i )=∑jλ j b xj (r i ), λ is the coefficient of the minimization loss function, which is a one-dimensional coefficient vector; j represents the serial number of the λ coefficient vector; α represents the uniform field strength value B x and the gradient field G x In this embodiment, α is 1, which is characterized by a uniform field strength value B x and the gradient field G x The weights between them are the same; g t z i is the position z i The gradient value of the target magnetic field at g x (ri) is in r i The actual measured magnetic field gradient at the position satisfies g x (r i )=∑jλj g xj (r i ).

[0119] The above terms represent the difference between the target magnetic field characteristics and the actual measured magnetic field characteristics at each point in the uniform area and the stray area. To solve it, by selecting the weight λj, dF / dλ is solved. j = 0. The loss function F is converted into a set of linear simultaneous equations, and the solution is obtained by identifying the pseudo-inverse matrix to obtain the current path of the double-plane coil.

[0120] It should be noted that the dual-plane coil obtained based on the above design method constrains the external RF magnetic field, has a good anti-magnetic crosstalk effect, and can be applied to the field of magnetic field detection to at least shield the RF magnetic field signal emitted outward.

[0121] Embodiment 2

[0122] like Figure 3-4 As shown, this embodiment provides a dual-plane coil pair structure, including two dual-plane coil structures 11 arranged opposite to each other; the dual-plane coil structure 11 includes: a coil body, a first coil portion 111 , and a magnetic field compensation portion 112 .

[0123] like Figure 3-4 As shown, the first coil portion 111 is disposed on the first surface of the coil body, and includes at least two first coils 1111, at least two second coils 1112, and at least one first connecting wire 1113 ( Figure 5 Each first coil 1111 is concentrically arranged around the first center, and the area of ​​each first coil 1111 increases as the distance between each first coil 1111 and the first center increases. Each second coil 1112 is concentrically arranged around the second center, and the area of ​​each second coil 1112 increases as the distance between each second coil 1112 and the second center increases. The current direction of each first coil 1111 is opposite to the current direction of each second coil 1112; each first connecting line 1113 is used to connect each coil in the first coil portion 111 in series in sequence ( Figure 3 In order to more intuitively show the coil shape, the first connecting line 1113 is not shown, so as to input the current from the center away from the first coil portion 111 to the center of the first coil portion 111, that is, the current direction points to the center O.

[0124] Specifically, the first center and the second center are set at the same position and are the center point O of the first coil portion 111. Each first coil 1111 is located inside the second coil 1112 with the smallest area, that is, the area of ​​the largest first coil 1111 is also smaller than the area of ​​the second coil 1112 with the smallest area.

[0125] In this embodiment, the current direction of the first coil 1111 is clockwise, and the current direction of the second coil 1112 is counterclockwise. At the same time, in this embodiment, since the first coils 1111 in the first coil portion 111 are sequentially connected in series, and the second coils 1112 are sequentially connected in series, and the first coils 1111 and the second coils 1112 are also in a series relationship, the first coils 1111, the second coils, and the second coil 1112 with the smallest area and the first coil 1111 with the largest area are all connected through the first connecting wire 1113. At this time, the current direction of the first connecting wire 1113 is set to be from outside to inside (from the direction away from the center of the face O to the direction facing O).

[0126] For ease of understanding, Figure 5 Taking the coil structure of 1111 as an example, the connection method of the first connecting wire 1113 is described as follows: Figure 5 The coil structure includes three coils with current in the clockwise direction and one coil with current in the counterclockwise direction, and the above four coils are all wound around a common center Q. The coils are connected in series through the first connecting wire 1113, and the current direction of the first connecting wire 1113 is from outside to inside, that is, the direction pointing to Q is the current direction of the first connecting wire 1113.

[0127] It should be noted that, in the actual design of each first coil 1111 and each second coil 1112, the magnetic field introduced by the current has been avoided by setting the current directions of the two coils to be opposite. However, due to the existence of the first connecting line 1113, it cannot be directly offset by the first coil 1111 and each second coil 1112. Therefore, in the actual design, it is also necessary to consider the excess magnetic field caused by the current introduced by the first connecting line 1113.

[0128] It needs to be further explained that Figure 5 The coil structure is only a simple example of the first connecting line 1113 and does not relate to Figure 3 The structure of the first coil portion 111 is the same as that of the first coil portion 111. Figure 5 The principle will Figure 3 The coils in the first coil unit 111 are connected in series.

[0129] like Figure 4 As shown, the magnetic field compensation part 112 is arranged on the second surface of the coil body. The magnetic field compensation part 112 includes at least one second connecting wire; the second connecting wire 1121 is arranged corresponding to the first connecting wire 1113 to output the current from the center of the first coil part 111 to the direction away from the center of the first coil part 111 to offset the magnetic field interference introduced by the first coil part 111.

[0130] For ease of understanding, refer to Figure 5 The magnetic field compensation unit 112 is set with a coil structure as shown below: Figure 6 The second connecting line 1121 shown in FIG. Figure 5 The first connecting lines 1113 in the figure are set correspondingly (the positions of the second connecting lines 1121 are set correspondingly to the positions of the first connecting lines 1113, such as Figure 5 As shown, each first connecting line 1113 is arranged on the upper side of the center Q, then Figure 6The second connecting wire 1121 is arranged on the upper side of the center Q) and in order to ensure that the redundant magnetic field introduced by each first connecting wire 1113 can be completely offset, the length of the second connecting wire 1121 is equal to the sum of the lengths of each first connecting wire 1113. In addition, in order to ensure that the current directions of the first connecting wire 1113 and the second connecting wire 1121 are opposite and the current magnitudes are the same, the first connecting wire 1113 is arranged to introduce the current into the second connecting wire 1121 through the through hole 1114. At this time Figure 5 and Figure 6 It forms a complete current loop.

[0131] It should be noted that Figure 6 The second connection line 1121 is only used as Figure 5 A simple explanation of the compensation principle of the coil structure is given in Figure 3 When the first coil portion 111 is used, it is necessary to Figure 3 The specific setting of the first connecting line 1113 is referred to.

[0132] As an example, in this embodiment, if Figure 3 As shown, the double-plane coil structure 11 also includes four second coil parts 113 arranged on the first surface of the coil body; each second coil part 113 is arranged outside the first coil part 111 and is centrally symmetrically arranged along the first center (the surface center O in this embodiment); each second coil part 113 has at least two third coils 1131; the current direction of each third coil 1131 is the same as the current direction of each first coil 1111. The at least two third coils 1131 inside the second coil part 113 are connected in series through a third connecting line (not shown in the figure).

[0133] In this embodiment, since the number of coils of the second coil in the first coil portion 111 is equal to the number of coils of the first coil, the sum of the magnetic fields of the first coils 1111 is smaller than the sum of the magnetic fields of the second coils 1112. Therefore, four second coil portions 113 are arranged on the outside of the second coil 1112 (on the side away from the center of mass O) to offset the magnetic field that has not been completely offset by the first coil portion 111.

[0134] In this embodiment, at least two third coils 1131 inside different second coil parts 113 are wound along different third centers P, and each third center P is centrally symmetrical about the surface center O. In fact, the specific structure is not limited to this embodiment.

[0135] In this embodiment, when the dual-plane coil structure 11 includes four second coil portions 113 , the magnetic field compensation portion 112 also includes four fourth connecting wires (not shown in the figure); each fourth connecting wire is used to offset the magnetic field interference introduced by each second coil portion 113 .

[0136] It should be noted that, since four second coil parts 113 are introduced, each second coil part 113 is connected in series through the third coil 1131, and the multiple third connecting wires introduced in series will still introduce additional magnetic field interference, so it is necessary to add a fourth connecting wire in the magnetic field compensation part 112, and the fourth connecting wire is used to ensure that the magnetic field interference introduced by the second coil part 113 is offset. At this time, a fourth connecting wire corresponds to offsetting the magnetic field interference of a second coil part 113. Specifically, a fourth connecting wire has opposite current directions and the same current magnitude as the multiple third connecting wires connected in series in the corresponding second coil part 113 to ensure the offset effect. Its specific working distance can be understood by referring to the previous text, and will not be repeated here one by one.

[0137] It should be further explained that the dual-plane coil structure 11 obtained based on this embodiment cancels the magnetic field by setting coils with different counterclockwise and clockwise directions on the first surface of the coil body, and compensates the series connection lines on the first surface by setting a magnetic field compensation part 112 on the second surface of the coil body, thereby ensuring that the dual-plane coil structure 11 is difficult to generate an additional magnetic field, thereby ensuring that in the subsequent use process, especially when applied to magnetic field detection, the dual-plane coil structure 11 of this embodiment can still avoid generating additional magnetic fields on the coil body after inputting radio frequency signals, thereby ensuring the accuracy of magnetic field detection. In addition, the specific structures of the first coil part 111 and the second coil part 113 in this embodiment can be obtained based on the dual-plane coil pair design method of Example 1.

[0138] Specifically, the dual-planar coil structure 11 is manufactured based on at least one of the following processes: PCB process (printed circuit board process, i.e., copper layer etching technology forms a conductive path on an insulating substrate), FPC process (flexible printed circuit, i.e., using polyimide or other flexible materials as a substrate and forming a conductive layer by etching), and thin-film alumina ceramic process (i.e., depositing a conductive film on a ceramic substrate).

[0139] Preferably, a thin film alumina ceramic process is set to process and manufacture the dual-plane coil structure 11. Compared with the traditional Helmholtz coil, since the number of coils in the dual-plane coil structure is large and the size required for application is relatively small, strict requirements are placed on the processing accuracy. At the same time, considering that if the dual-plane coil structure 11 is used for an atomic magnetometer, the coil may be damaged by heating in a high temperature environment (160°C), it is necessary to ensure that the temperature in the manufacturing process will not cause a large error caused by the dual-plane coil structure 11. Therefore, the dual-plane coil structure is manufactured by using an alumina ceramic circuit process, which ensures higher processing accuracy, and the position error of each coil does not exceed 4μm, while avoiding the coil from generating a gradient magnetic field or an inaccurate field current ratio. In addition, it can also avoid the situation where the coil is damaged by heating when used in a high temperature environment, thereby improving the stability of the dual-plane coil structure.

[0140] It should be noted that the specific process is not limited to this embodiment. Any manufacturing process that can ensure the coil processing accuracy, and at the same time, can set a current path for compensation while setting the series connection line of each coil current loop to avoid unnecessary magnetic field interference, are all within the protection scope of this embodiment.

[0141] Specifically, during use, two relatively arranged dual-plane coil structures are respectively injected with RF signals. In the embodiment, the direction of the uniform magnetic field generated by the dual-plane coil structure is perpendicular to the coil plane, so the dual-plane coil structure of this embodiment is called a dual-plane Z coil. At this time, the dual-plane coil is stimulated and regulated by the RF signal to control the space inside the structure. At this time, the relatively arranged dual-plane coil structure can further constrain the external RF magnetic field based on the previously designed current path, and has a good anti-magnetic crosstalk effect; on the other hand, it can avoid the additional magnetic field generated by the RF magnetic field injected into the magnetic field coil itself, resulting in inaccurate measurement.

[0142] Embodiment 3

[0143] like Figure 7 As shown, this embodiment provides another dual-plane coil pair structure, which is basically the same as the second embodiment, except that the positions of the first center and the second center of the dual-plane coil structure 12 in the dual-plane coil pair structure do not overlap.

[0144] like Figure 7 As shown, in this embodiment, the first center O1 and the second center O2 of the double-plane coil structure 12 are located at different positions on the same straight line, and accordingly, each first coil 1111 is axially symmetrical with each second coil 1112 (the axis of symmetry is the perpendicular bisector of the line between the first center O1 and the second center O2).

[0145] Specifically, the number of first coils 1111 is the same as the number of second coils 1112, the corresponding coils have the same area, and the shape is axially symmetrical. At this time, each first coil 1111 is axially symmetrical with each second coil 1112. Since the current direction of the first coil 1111 is opposite to that of the second coil 1112 (in this embodiment, the current direction of the first coil 1111 is clockwise, and the current direction of the second coil 1112 is counterclockwise), no additional magnetic field interference is introduced on the first surface of the coil body. At this time, at least there are at least two groups of first connecting wires 1113, the first group is connected in series with each first coil 1111, and the second group is connected in series with each second coil 1112. Correspondingly, the magnetic field compensation part 112 includes two second connecting wires 1121, the first one is set corresponding to each first coil 1111, and the second one is set corresponding to each second coil 1112. The principle and position of the specific setting can be referred to the previous text, and will not be repeated here.

[0146] Specifically, in this embodiment, the dual-plane coil structure 12 further includes a third coil portion 121 and a fourth coil portion 122 .

[0147] Furthermore, the third coil portion 121 and the fourth coil portion 122 are respectively disposed on both sides of the first coil portion 111 ; the third coil portion 121 and the fourth coil portion 122 are axially symmetrically disposed, and are the same symmetry axis as the symmetry axis of the first coil portion 111 .

[0148] As an example, the third coil portion 121 includes at least two fourth coils 1211, each of the fourth coils 1211 is concentrically arranged around the third center P1 and the area of ​​each fourth coil 1211 increases as the distance between each fourth coil 1211 and the third center P1 increases; each fourth coil 1211 is connected in series via a fifth connecting line (not shown in the figure).

[0149] As an example, the fourth coil portion 122 includes at least two fifth coils 1221, each of which is concentrically arranged around the fourth center P2 and the area of ​​each fifth coil 1221 increases as the distance between each fifth coil 1221 and the fifth center P2 increases; each fifth coil 1221 is connected in series via a sixth connecting line (not shown in the figure).

[0150] It should be noted that, in this embodiment, the third coil portion 121 and the fourth coil portion 122 are axially symmetrical, that is, the number of fourth coils 1211 in the third coil portion 121 is the same as the number of fifth coils 1121 in the fourth coil portion 122, the areas of the corresponding coils are the same, and the shapes are axially symmetrical.

[0151] In this embodiment, the third center P3, the fourth center P4, the first center O1 and the second center O2 are all located on the same straight line. The third coil portion 121 is disposed on a side close to the second center O2 and away from the first center O1, and the current direction of each fourth coil 1211 in the third coil portion 121 is the same as that of each first coil 1111. The fourth coil portion 122 is disposed on a side close to the first center O1 and away from the second center O2, and the current direction of each fifth coil 1221 in the fourth coil portion 122 is the same as that of each second coil 1112. By setting the third coil portion 121 and the fourth coil portion 122 to have opposite current directions, and the current direction between the third coil portion 121 and each adjacent second coil 1112 is opposite, and the current direction between the fourth coil portion 122 and each adjacent first coil 1111 is opposite. Therefore, as Figure 7 As shown, the current directions at this time are clockwise, counterclockwise, clockwise, and counterclockwise, respectively. This arrangement ensures that the magnetic field introduced on the first surface of the coil body is offset as much as possible. However, similarly, due to the existence of the first connecting wire, the fifth connecting wire, and the sixth connecting wire, an additional offset method needs to be set to further offset them.

[0152] Specifically, the magnetic field compensation part (not shown in the figure) also includes a seventh connecting line (not shown in the figure) and an eighth connecting line (not shown in the figure); the seventh connecting line is used to offset the magnetic field interference introduced by the third coil part 121 (corresponding to the magnetic field interference introduced by the fifth connecting line in this embodiment); the eighth connecting line is used to offset the magnetic field interference introduced by the fourth coil part 122 (corresponding to the magnetic field interference introduced by the sixth connecting line in this embodiment). The specific offset principle can be set with reference to the foregoing, and is not limited to this embodiment.

[0153] It should be noted that the specific structures of the third coil portion 121 and the fourth coil portion 122 in this embodiment are not limited to this embodiment, and any coil structure pair that can achieve mutual cancellation is within the protection scope of this embodiment.

[0154] Therefore, in this embodiment, the dual-plane coil structure 12 still performs preliminary magnetic field compensation on the first surface of the coil body by arranging coils with different counterclockwise and clockwise directions, and compensates for the series connection lines on the first surface by arranging a magnetic field compensation part 112 on the second surface of the coil body, thereby ensuring that the dual-plane coil structure 11 is difficult to produce additional magnetic fields.

[0155] In this embodiment, the direction of the uniform magnetic field generated by the dual-plane coil structure is parallel to the coil plane, so the dual-plane coil structure of this embodiment is called a dual-plane X-coil. For the dual-plane X-coil, a hole needs to be drilled in the center of the dual-plane coil during the manufacturing process, so the dual-plane X-coil does not have a circuit path set in the center to ensure smooth subsequent drilling.

[0156] Embodiment 4

[0157] like Figure 8 As shown, this embodiment provides an atomic magnetometer array, including: at least two atomic magnetometers 1 arranged in an array; each atomic magnetometer 1 includes an optical path emission module 13, an atomic chamber 14, a detection module 15 and the above-mentioned dual-plane coil pair structure (Example 2 or Example 3). In this embodiment, in order to facilitate intuitive understanding, the dual-plane coil structure in this embodiment is set to the dual-plane coil structure 11 of Example 2.

[0158] like Figure 8 As shown, in this embodiment, the atomic magnetometers in the atomic magnetometer array are set to M Z Full-field atomic magnetometer and M X At least one type of atomic magnetometer in full-field atomic magnetometer measurement. Z The full-field atomic magnetometer is a magnetometer that measures the magnetic field component perpendicular to the ground or horizontal plane; the Mx full-field atomic magnetometer is a magnetometer that measures the magnetic field component parallel to the ground or horizontal plane.

[0159] like Figure 8 As shown, the optical path transmitting module 13 is used to generate incident light of a specific wavelength and convert the output to obtain corresponding polarized light; the incident light includes pump light and detection light.

[0160] Specifically, the optical path transmitting module 13 includes a laser 131 and a polarization conversion unit 132 ; the laser 131 is used to generate incident light and convert it into output through the polarization conversion unit 132 ; the polarization conversion unit 133 is used to convert the incident light into polarized light and output it.

[0161] As an example, the laser 131 includes, for example, a diode laser or a solid-state laser. In the present embodiment, the laser 131 generates a 795nm pump light and a probe light that propagate along the Z axis. Among them, the pump light is used to excite atoms to a specific energy level, making them more sensitive to changes in the magnetic field. The pump light is usually one or more laser beams that interact with the atoms so that the magnetic moment of the atoms is aligned with the external magnetic field. The probe light is used to detect changes in the atomic state. When the magnetic moment of the atom is aligned with the external magnetic field (after the atom is aligned by the pump light), the probe light can be used to measure the magnetic resonance frequency of the atom, which is proportional to the intensity of the external magnetic field. Therefore, in actual use, the laser 131 first emits pump light for magnetic moment adjustment, and then sends probe light for magnetic field detection.

[0162] As an example, the polarization conversion unit 132 includes a lens 1321, a polarization beam splitter prism 1322, and a wave plate 1323, which are sequentially arranged along the optical path of the incident light. The lens 1321 receives the incident light and performs at least one of focusing and shaping operations on it to adjust the intensity and shape of the light beam. The polarization beam splitter prism 1322 receives the light beam emitted by the lens 1321, and polarizes and separates the light beam according to different polarization directions of the light to obtain polarized light. The wave plate 1323 receives the polarized light emitted by the polarization beam splitter prism 1322, and is used to adjust the polarization form of the polarized light incident on the atomic sample. In this embodiment, the adjusted polarized light is set to circularly polarized light.

[0163] like Figure 8 As shown, the atomic chamber 14 is arranged on the optical path of the polarized light, and each atomic gas in the atomic chamber 14 interacts with the polarized light to change the polarization direction of the polarized light and obtain the output light.

[0164] Specifically, the atomic chamber 14 includes a shell; a cavity is formed inside the shell; the inside of the cavity is used to accommodate alkali metal atoms; the shell is also provided with an incident port for polarized light to pass through and an exit port for reflected light to exit.

[0165] As an example, to ensure uniform heating, the outer side of the shell of the atomic chamber 14 is provided with boron nitride ceramic.

[0166] As an example, the atomic chamber 14 contains alkaline metal atoms, such as cesium or rubidium, which exhibit a specific magnetic resonance frequency in a magnetic field. By measuring this frequency, the strength of the magnetic field can be determined very accurately. Specifically, when polarized light is irradiated on the atomic gas, the atoms absorb photons and transition to an excited state. The transitioned atoms may return to the ground state through spontaneous radiation or radiationless transition, with or without emitting photons. The reflected or transmitted light signal is detected by a photodetector. By measuring the changes in light, the interaction between atoms and light can be inferred, and the strength of the external magnetic field can be calculated.

[0167] In this embodiment, the polarized light output by the optical path transmitting module 13 is set to resonate with the D1 line transition of the 87Rb atom.

[0168] In this embodiment, a non-magnetic heater is also provided inside the atomic chamber 14 for heating the atomic gas; the non-magnetic heater is provided on the non-light-transmitting surface of the atomic chamber 14 (i.e., the surface where the inlet and outlet are not provided); the non-magnetic heater is provided with a flexible material to ensure that it can be applied to different material surfaces. In addition, thermal conductive silicone grease is provided tightly between the non-magnetic heater and the atomic chamber 14 for better heat conduction. Among them, the non-magnetic heater is driven by an alternating current with a frequency of 40kHz, and a PT1000 temperature sensor is used to measure the temperature of the vapor chamber. The measurement result is input into a PID temperature controller (Proportional-Integral-Derivative controller PID) for closed-loop control of the vapor chamber temperature to ensure that the temperature fluctuation of the vapor chamber is kept within 0.1°C.

[0169] like Figure 8 As shown, the two dual-plane coil structures 11 are arranged opposite to each other and are respectively arranged on the two surfaces of the atomic chamber 14 to prevent mutual crosstalk between the atomic magnetometers 1. Specifically, the radio frequency magnetic field is generated by the two dual-plane coil structures 11 driven by the voltage-controlled oscillator, and the radio frequency magnetic field frequency is continuously locked at the atomic Larmor precession frequency through the PID frequency locking program (proportional-integral-differential controller PID). Since the direction of the radio frequency magnetic field needs to be parallel to the optical path direction of the polarized light, the two dual-plane coil structures 11 are set to the following two example locations:

[0170] Specifically, as a first example ( Figure 7 and Figure 8 The surface center connection line between the two double-plane coil structures 12 (two double-plane X coils shown in the figure) is collinear with the optical path of the polarized light. At this time, the two double-plane coil structures 12 are placed on the surfaces on the left and right of the atomic chamber 14. In this embodiment, through holes are also provided at the surface centers of the two double-plane coil structures 12. Since when the double-plane X coils are used to generate a radio frequency magnetic field, the scattered light needs to pass through the double-plane X coils to reach the atomic chamber 14 and be emitted through another double-plane X coil, a through hole (not shown in the figure) needs to be left at the geometric center of the coil to ensure that the optical path is unobstructed.

[0171] Specifically, as the second example ( Figure 3 and Fig. 9 The two double-plane Z coils shown in the figure are arranged such that the line connecting the face centers of the two double-plane coil structures 11 perpendicularly bisects the optical path of the polarized light. At this time, the two double-plane coil structures 11 are placed on the upper and lower surfaces of the atomic chamber 14. During use, the optical path does not pass through the double-plane Z coils, so there is no need to set a through hole.

[0172] It should be noted that, considering the magnetic field gradient existing within the atomic magnetometer array, this will cause the radio frequency magnetic field frequency of each atomic magnetometer 1 within the atomic magnetometer array to be different, so there will be crosstalk between the radio frequency magnetic fields of each atomic magnetometer 1. The two dual-plane coil structures 11 of this embodiment can effectively prevent magnetic field crosstalk between the atomic magnetometers 1.

[0173] In addition, since the positional relationship between the atomic magnetometers is not completely consistent, the setting positions of the two dual-plane coil structures 11 are adjusted based on needs in actual use. For example, in the first atomic magnetometer, the two dual-plane coil structures 11 are placed on the left and right surfaces of the atomic chamber 14, then in the atomic magnetometer adjacent to the first atomic magnetometer, the two dual-plane coil structures 11 can be placed on the left and right surfaces of the atomic chamber 14, or on the upper and lower surfaces of the atomic chamber 14.

[0174] It should be further explained that, in order to provide a sufficiently uniform radio frequency magnetic field through the dual-plane coil, the area of ​​the dual-plane coil structure is greater than or equal to 4 times the surface area of ​​the atomic chamber 14 .

[0175] like Figure 8 As shown, the detection module receives the emitted light to obtain the magnetic field signal to be measured.

[0176] It should be noted that, in this embodiment, two sets of coils placed in parallel generate a relatively uniform magnetic field, eliminate the interaction between the coils, and generate a high-precision magnetic field in a specific area. Based on the geometric design of the double-plane coil in the first embodiment, the use of the double-plane coil pair structure in this embodiment can effectively reduce the interference of the stray magnetic field and improve the uniformity of the magnetic field.

[0177] Specifically, the detection module includes a photodetector 15; the photodetector 15 is used to perform photoelectric conversion on the emitted light to obtain a detection electrical signal.

[0178] As an example, the detection module also includes a phase-locked amplifier (not shown in the figure) and a data acquisition system (not shown in the figure). The first input end of the phase-locked amplifier is connected to the output end of the photodetector 15, and the second input end of the phase-locked amplifier is connected to the reference signal. The magnetic field signal to be measured is demodulated based on the reference signal to obtain a dispersion signal. The data acquisition system collects the magnetic field signal to be measured and the dispersion signal and performs subsequent calculation operations.

[0179] The working process of the atomic magnetometer array of this embodiment is described below:

[0180] First, each atomic magnetometer 1 in the atomic magnetometer array is turned on to enter a working state.

[0181] Among them, the opening of each atomic magnetometer 1 at least includes debugging the positional relationship between the optical path transmitting module 13, the atomic chamber 14, the detection module and the two above-mentioned double-plane coil structures 11 to ensure the smoothness of each optical path. At the same time, the opening of each atomic magnetometer 1 also includes the optical path transmitting module 13 emitting incident light until the detection module 15 outputs a detection electrical signal. Among them, the atomic chamber 14 is maintained in a high-temperature heating environment, and the double-plane coil structure 11 is internally injected with a signal to generate a radio frequency magnetic field.

[0182] Secondly, at least one of the temperature signal of the atomic chamber 14 of the atomic magnetometer 1 and the power signal of the incident light is regulated to optimize the sensitivity of the corresponding atomic magnetometer.

[0183] The temperature of the atomic chamber 14 in the atomic magnetometer 1 is optimized, because the temperature of the atomic chamber 14 will directly affect the atomic density and thus affect the total number of atoms interacting with the laser and the collision relaxation time between atoms, and ultimately affect the sensitivity of the atomic magnetometer 1. Therefore, the change curve between the sensitivity of the atomic magnetometer 1 and the temperature of the atomic chamber 14 is recorded by the control variable method, and the optimal temperature of the atomic chamber 14 is determined based on the change curve. Among them, the sensitivity is characterized by the ratio between the line width and the signal-to-noise ratio by measuring the signal-to-noise ratio and the line width of the atomic spectrum signal. In this embodiment, according to 87 The gyromagnetic ratio of Rb atoms is calculated. The magnetic resonance point occurs at 70kHz. The atomic magnetic resonance signal can be obtained by scanning the RF magnetic field frequency in the range of 50-90kHz. The sensitivity of the atomic magnetometer can be calculated by recording the atomic magnetic resonance signal output by the detection module, fitting the full width at half maximum (FWHM) of the signal and calculating the signal-to-noise ratio of the magnetic resonance signal.

[0184] It should be noted that when the atomic chamber 14 is heated, the temperature of the atomic chamber 14 needs to be controlled to be stable within 0.1° C., otherwise the measurement of the sensitivity of the atomic magnetometer 1 will be affected due to the change in atomic density.

[0185] The laser power output by the optical path transmitting module 13 is optimized. When the laser power changes, the intensity of the interaction between the atomic gas and the laser will also change accordingly. The change curve between the sensitivity of the atomic magnetometer 1 and the laser power is recorded by the control variable method to determine the optimal laser power.

[0186] Preferably, the above two methods are set simultaneously to optimize the performance of a single atomic magnetometer 1 , thereby ensuring that the sensitivity of the atomic magnetometer 1 is maintained at a relatively high sensitivity.

[0187] Again, the output frequency and amplitude of the RF magnetic field are controlled so that the RF magnetic field oscillates at the Larmor precession frequency. At the same time, due to the dual-plane coil structure provided in this embodiment, the amplitude of the RF magnetic field can be further adjusted so that the RF magnetic field strength can be reduced as much as possible under the premise of high sensitivity, thereby effectively reducing the crosstalk between the RF magnetic fields of adjacent atomic magnetometers 1.

[0188] Finally, based on the above settings, the magnetic field to be measured is detected to obtain an atomic magnetometer array with high spatial resolution, and output biomagnetic imaging with high image quality and high accuracy. Fig. 9 The simulation model and evaluation diagram are shown. The two coils are set relative to each other along the Z direction, and three attenuation regions are set along the three axis directions (X axis, Y axis, and Z axis). The crosstalk effect is characterized by exploring the distribution of the RF magnetic field and the attenuation in the attenuation region. In this embodiment, the two coils are set as Helmholtz coils, dual-plane Z coils, and dual-plane X coils, respectively. The anti-crosstalk effect is determined by characterizing the second attenuation region. Fig.10 and Fig.11 As shown:

[0189] In a pair of ratios, such as Fig.10 The two Helmholtz coils 2 are respectively arranged at Fig. 9 The square Helmholtz coil 2 generates a 10μT uniform magnetic field along the Z axis. The magnetic field distribution of the Helmholtz coil along the Y axis is simulated (the second attenuation region). The attenuation of the Helmholtz coil 2 is very slow both inside and outside the Helmholtz coil. The positions where the stray field attenuates to 5%, 1%, 0.5%, and 0.1% of the magnetic field at the center of the Helmholtz coil 2 are -13.213cm, -23.033cm, -23.684cm, and -23.684cm, respectively.

[0190] In the first example, if Figure 3 The two dual-plane Z coils are arranged in Fig. 9 The double-plane Z coils are located in the plane position and are arranged relatively, and the double-plane Z coils generate a radio frequency magnetic field with the atomic Larmor precession frequency. The magnetic field distribution of the double-plane Z coil along the Y-axis direction is simulated (the second attenuation region). At this time, it is found that the stray field of the double-plane Z coil in the Y direction decays faster, and the positions where the stray field decays to 5%, 1%, 0.5%, and 0.1% of the central magnetic field are -4.668cm, -8.453cm, -9.073cm, and -10.104cm respectively.

[0191] In the second example, if Figure 7 The two dual-plane X-coils are arranged in Fig. 9The plane positions of the coils are relatively arranged, and the dual-plane X coil generates a radio frequency magnetic field with the atomic Larmor precession frequency. The magnetic field distribution of the dual-plane X coil along the Y-axis direction is simulated (the second attenuation region). The positions where the stray field of the dual-plane X coil in the Y direction attenuates to 5%, 1%, 0.5%, and 0.1% of the central magnetic field are -11.11cm, -15.425cm, -17.733cm, and -23.527cm, respectively.

[0192] Based on the above Fig.11 and Fig.12 It can be seen that the stray field of the dual-plane Z coil decays the fastest and has the least interference with the RF magnetic field of the adjacent atomic magnetometer. If the crosstalk of the RF magnetic field of the atomic magnetometer to the adjacent atomic magnetometer is guaranteed to be less than 0.1%, it is considered that the crosstalk is small and can be accurately detected; when the Helmholtz coil is used to generate the RF magnetic field, the spacing between adjacent atomic magnetometers needs to be 23.84cm, while when the dual-plane Z coil is used to generate the RF magnetic field, the spacing between adjacent atomic magnetometers only needs to be 10.10cm, which greatly improves the spatial resolution of the atomic magnetometer array. Therefore, using a dual-plane Z coil to generate an RF magnetic field can reduce the crosstalk of the atomic magnetometer array by 57.6%, and the spatial resolution of the array can be improved by 57.6%.

[0193] under Fig.13 The measured magnetic field distribution along the Y axis (second attenuation region) using the dual-plane Z coil and the magnetic field distribution along the X axis (third attenuation region) and Y axis (second attenuation region) using the dual-plane X coil are shown. It can be clearly found that the dual-plane coil has the fastest attenuation along the Y axis and the best anti-crosstalk effect.

[0194] Combination Figures 15 to 23As shown, the two coils are respectively set as Helmholtz coils, dual-plane Z coils, and dual-plane X coils, wherein the magnetic field attenuation ratio in each figure is expressed as the ratio of the magnetic field value at that position to the central magnetic field of the atomic chamber 14, which is used to measure the attenuation of the magnetic field in the stray area. That is, the smaller the magnetic field attenuation ratio is, the smaller the magnetic field value at that position is, which is characterized by more magnetic field attenuation. Based on this, the stray field is characterized by marking the isovalue lines in the first attenuation area, the second attenuation area, and the third attenuation area to attenuate to 10%, 3%, 1%, 0.3%, and 0.1% of the central magnetic field of the coil. The black arrow represents the farthest path vector, and the magnetic field radiates from the center to the specific isovalue line, showing a ripple pattern. At this time, compared with the Helmholtz coil, the magnetic field attenuation of the normal phase dual-plane coil (dual-plane Z coil and dual-plane X coil) in the first attenuation area, the second attenuation area, and the third attenuation area is attenuated faster, and the magnetic field attenuation of the dual-plane Z coil is the fastest among the three coils, and the magnetic field attenuation is 0.1% at -10.27cm. Therefore, among the above three coils, the dual-plane Z coil and the dual-plane X coil provided by the present invention both effectively reduce the crosstalk between the atomic magnetometers relative to the Helmholtz coil, further improving the spatial resolution of atomic magnetometer imaging. At the same time, the dual-plane Z coil has the best effect and can ensure the minimum crosstalk between the atomic magnetometers as much as possible.

[0195] In summary, the present invention provides a dual-plane coil pair design method, a coil pair structure and an atomic magnetometer array, wherein the dual-plane coil pair design method includes: S1, providing two coils to be set and setting the two coils to be set relative to each other; the opposite surfaces of the two coils to be set are used as the inner side and set as the uniform area; the non-opposite surfaces of the two coils to be set are used as the outer side and set as the stray area; S2, solving the loss function satisfied by the uniform area and the stray area to obtain the current path corresponding to the two coils to be set. The present invention provides a new anti-crosstalk setting, optimizes the radio frequency magnetic field crosstalk between the atomic magnetometers, and improves the spatial resolution of atomic magnetometer imaging. Therefore, the present invention effectively overcomes the various shortcomings of the prior art and has a high industrial utilization value.

[0196] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A dual-plane coil pair design method, characterized in that: The dual-plane coil pair design method comprises: S1. Provide two coils to be set and set the two coils to be set opposite to each other; the opposite surfaces of the two coils to be set are used as inner sides and set as uniform areas; the non-opposite surfaces of the two coils to be set are used as outer sides and set as stray areas; S2. Based on the loss function satisfied by the uniform area and the stray area, current paths corresponding to the two coils to be set are obtained by solving the loss function.

2. The dual-plane coil pair design method according to claim 1, characterized in that: The step S2 comprises: S21, setting the midpoint of the line connecting the center points of the opposite surfaces of the two coils to be set as the coordinate origin; the distance between the coordinate origin and each coil to be set is less than half the side length of the coil to be set; discretizing the uniform area and the stray area to obtain at least two discrete points respectively, and characterizing the position of each discrete point based on the coordinate origin; S22. A set of simultaneous equations is established based on each point and the loss function corresponding to each point, and the simultaneous equations are solved by pseudo-inverse matrix to obtain the current paths corresponding to the two double-plane coils; wherein the field strength value and gradient value of each point satisfy the loss function of the corresponding point.

3. The dual-plane coil pair design method according to claim 2, characterized in that: Set the field strength value in the loss function of each point to have the same weight as the gradient value.

4. A dual-plane coil pair structure, characterized in that: The dual-plane coil structure pair comprises two dual-plane coil structures arranged opposite to each other; the dual-plane coil structure comprises: a coil body, a first coil portion, and a magnetic field compensation portion; The first coil portion is arranged on the first surface of the coil body, and includes at least two first coils, at least two second coils and at least one first connecting wire; each first coil is arranged concentrically around a first center, and the area of ​​each first coil increases as the distance between each first coil and the first center increases; each second coil is arranged concentrically around a second center, and the area of ​​each second coil increases as the distance between each second coil and the second center increases; the current direction of each first coil is opposite to the current direction of each second coil; each first connecting wire is used to sequentially connect the coils in the first coil portion in series, so as to input the current from the center of the surface away from the first coil portion to the center of the surface of the first coil portion; The magnetic field compensation portion is arranged on the second surface of the coil body and includes at least one second connecting wire; the second connecting wire is arranged corresponding to the first connecting wire to output the current from the center of the first coil portion to the direction away from the center of the first coil portion to offset the magnetic field interference introduced by the first connecting wire.

5. The dual-plane coil structure according to claim 4, characterized in that: The first center and the second center are arranged at the same position and are the center of the surface of the first coil portion, and each of the first coils is located inside the smallest second coil.

6. The dual-plane coil pair structure according to claim 5, characterized in that: The double-plane coil structure also includes four second coil parts arranged on the first surface of the coil body; each second coil part is outside the first coil part and is centrally symmetrically arranged along the first center; each second coil part has at least two third coils; the current direction of each third coil is the same as the current direction of each first coil; at least two third coils inside the second coil part are connected in series through a third connecting wire.

7. The dual-plane coil pair structure according to claim 6, characterized in that: The magnetic field compensation part further includes four fourth connecting wires; each fourth connecting wire is used to offset the magnetic field interference introduced by each second coil part.

8. The dual-plane coil pair structure according to claim 4, characterized in that: The first center and the second center are arranged at different positions on the same straight line, and each first coil is axially symmetrical with each second coil.

9. The dual-plane coil pair structure according to claim 8, characterized in that: The first coil portion further includes a third coil portion and a fourth coil portion; the third coil portion and the fourth coil portion are respectively arranged on both sides of the first coil portion; the third coil portion and the fourth coil portion are arranged axially symmetrically, and are the same symmetry axis as the symmetry axis of the first coil portion; The third coil portion includes at least two fourth coils, each of which is concentrically arranged around the third center and the area of ​​each fourth coil increases as the distance between each fourth coil and the third center increases; each fourth coil is connected in series via a fifth connecting line; The fourth coil portion includes at least two fifth coils, each of which is concentrically arranged around a fourth center and the area of ​​each fifth coil increases as the distance between each fifth coil and the fifth center increases; each fifth coil is connected in series via a sixth connecting wire; The third center, the fourth center, the first center and the second center are all located on the same straight line; The third coil portion is arranged at a side close to the second center and away from the first center, and the current direction of each fourth coil in the third coil portion is the same as that of each first coil; The fourth coil portion is disposed on a side close to the first center and away from the second center, and the current directions of each fifth coil and each second coil in the fourth coil portion are the same.

10. The dual-plane coil pair structure according to claim 9, characterized in that: The magnetic field compensation unit further includes a seventh connecting line and an eighth connecting line; the seventh connecting line is used to offset the magnetic field interference introduced by the third coil unit; the eighth connecting line is used to offset the magnetic field interference introduced by the fourth coil unit.

11. The dual-plane coil pair structure according to any one of claims 4 to 10, characterized in that: The dual-plane coil structure is manufactured based on at least one of PCB, FPC and thin-film alumina ceramic processes.

12. An atomic magnetometer array, characterized in that: The atomic magnetometer array comprises at least: at least two atomic magnetometers arranged in an array; each atomic magnetometer comprises an optical path emission module, an atomic chamber, a detection module and a double-plane coil pair structure as claimed in any one of claims 4 to 11; The optical path transmission module is used to generate incident light of a specific wavelength and convert the output to obtain corresponding polarized light; the incident light includes pump light and detection light; The atomic chamber is arranged on the optical path of the polarized light, and each atomic gas in the atomic chamber interacts with the polarized light to change the polarization direction of the polarized light and obtain an outgoing light; the detection module receives the outgoing light to obtain a magnetic field signal to be measured; Two double-plane coil structures are arranged opposite to each other and are respectively arranged on two surfaces of the atomic chamber to prevent crosstalk between the atomic magnetometers; The line connecting the surface centers of the two double-plane coil structures perpendicularly bisects the optical path of the polarized light, or the line connecting the surface centers of the two double-plane coil structures is colinear with the optical path of the polarized light.

13. The atomic magnetometer array according to claim 12, characterized in that: The optical path transmission module includes a laser and a polarization conversion unit; the laser is used to generate incident light and convert the incident light into output light through the polarization conversion unit; the polarization conversion unit is used to convert the incident light into polarized light and output the polarized light.

14. The atomic magnetometer array according to claim 12, characterized in that: The atomic chamber includes a shell; a cavity is formed inside the shell; the inside of the cavity is used to accommodate alkali metal atoms; the shell is also provided with an incident port for the polarized light to pass through and an exit port for the reflected light to exit.

15. The atomic magnetometer array according to claim 12, characterized in that: The detection module includes a photoelectric detector; The photoelectric detector is used to perform photoelectric conversion on the emitted light to obtain a detection electrical signal.

16. The atomic magnetometer array according to claim 12, characterized in that: When the line connecting the surface centers of the two double-plane coil structures is collinear with the optical path of the polarized light, through holes are further provided at the surface centers of the two double-plane coil structures.

17. The atomic magnetometer array according to claim 12, characterized in that: The area of ​​the dual-plane coil structure is greater than or equal to 4 times the surface area of ​​the atomic chamber.

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