Installation error elimination method based on double-beam CPT vector magnetometer

Abstract

Based on the dual-beam CPT vector magnetometer installation error elimination method, a model is established to analyze the angular relationship between two beams of orthogonal linearly polarized light and a standard three-axis magnetic field, thereby correcting the angular output affected by the installation error of the experimental probe device placed on the generating device platform. Two linearly polarized light beams with mutually orthogonal propagation directions are used to configure the CPT magnetometer. Based on the relationship between the three key vectors of the laser wave vector K, the polarization direction e, and the magnetic field direction B and the CPT resonance amplitude, the angular output of the proposed CPT magnetometer magnetic field vector is modeled and analyzed, thereby obtaining an analytical solution for the magnetic field angle. However, the prerequisite of this model is that the two beams need to be configured orthogonally, which is difficult to achieve in actual situations. Based on the dual-beam measurement model, the present invention proposes a solution for correcting installation errors, and theoretically analyzes and discusses how to obtain the installation error angle and correct the magnetometer angle output when the system has installation errors.

Description

Technical Field

[0001] The invention relates to a method for eliminating installation errors based on a double-beam CPT vector magnetometer, and belongs to the field of interaction and automatic control between light and alkali metal atoms. Background Art

[0002] CPT atomic magnetometer can be widely used in geophysics, medicine and basic physics and other disciplines (CPT, coherent population trapping, coherent population trapping), CPT magnetometer has the potential for high sensitivity It can achieve the advantages of miniaturization, vector measurement and geomagnetic environment measurement. In many application scenarios, understanding the vector component of the magnetic field is crucial to fully understand the specific information of the field. Generally speaking, the measurement of the two-dimensional magnetic field direction can be carried out by changing the polarization direction of a single beam of light and observing the 0-level peak amplitude of the CPT resonance signal to determine the plane of the magnetic field. The polarization direction e of the linearly polarized light is orthogonal to the magnetic field direction B, so the linear polarization direction e can be obtained to achieve the vector measurement of the magnetic field. For the measurement of the three-dimensional magnetic field direction, it is only necessary to convert the three-dimensional magnetic field into a two-dimensional magnetic field. The typical magnetic compensation technology can easily achieve the conversion of the magnetic field, but this method inevitably couples the magnetic compensation with the magnetic field to be measured.

[0003] The dual-beam magnetic field vector measurement method avoids the magnetic field coupling issues associated with traditional magnetic compensation methods, enabling more accurate acquisition of magnetic field magnitude and direction. However, the dual-beam magnetic field vector measurement method relies on the polarization rotation angle of the two beams to obtain direction. The vector result is highly dependent on the propagation direction of the two beams, and inevitably suffers from installation errors, resulting in a decrease in the accuracy of the magnetic field direction. Given this, the method of the present invention focuses on reducing the angular error of the dual-beam CPT vector magnetometer and improving the angle measurement accuracy. By rigorously modeling the system, the method implements a method for eliminating installation errors based on the dual-beam CPT vector magnetometer. Summary of the Invention

[0004] In view of the defects or shortcomings of the existing technology, the present invention proposes a method for eliminating installation errors based on a double-beam CPT vector magnetometer, which is beneficial to reducing the angular error of the double-beam CPT vector magnetometer and improving the angle measurement accuracy.

[0005] The technical solutions of the present invention are as follows:

[0006] The method for eliminating installation errors of a double-beam CPT vector magnetometer is characterized by comprising the following steps:

[0007] Step 1, using a dual-beam CPT vector magnetometer measurement system to generate multi-color laser;

[0008] Step 2: Split the multi-color laser into a first beam and a second beam of light of equal intensity, and adjust the linear polarization directions of the two beams of light by controlling half-wave plates through respective stepper motors;

[0009] Step 3: Based on the relationship between the laser wave vector, polarization direction, magnetic field direction and CPT resonance amplitude, the angle output of the magnetic field vector is modeled and analyzed, including establishing a Cartesian coordinate system XYZ, the wave vector K1 of the first beam of light is consistent with the X-axis direction, the wave vector K2 of the second beam of light is consistent with the Y-axis direction, the angle between the linear polarization direction e1 of the first beam of light and the Z axis is θ, and the angle between the linear polarization direction e2 of the second beam of light and the Z axis is For the unknown magnetic field direction B, the polarization rotation angle is achieved by adjusting e1 and e2 respectively and observing the amplitude of the 0-level peak of the CPT signal of both. Determine B by making B perpendicular to e1 and e2 at the same time;

[0010] Step 4, calculating the installation error angle by obtaining the polarization rotation angle when the CPT signal amplitude is maximum;

[0011] Step 5: Establish a magnetometer angle output correction model to eliminate installation errors.

[0012] The dual-beam CPT vector magnetometer measurement system in step 1 includes an ECDL laser connected to the incident side of the optical splitter through an optical isolator, a first half-wave plate, a polarization beam splitting prism, a fiber coupler, a first polarization-maintaining fiber, an electro-optical modulator, a second polarization-maintaining fiber and a laser collimator in sequence, the electro-optical modulator is connected to a triangular wave generator through a radio frequency signal generator, the transmission side of the optical splitter forms a first beam of light which passes through a second half-wave plate, an atomic gas chamber and a first photodetector in sequence to connect to a data acquisition system, the reflection side of the optical splitter forms a second beam of light which passes through a third half-wave plate, a first reflector, a second reflector, an atomic gas chamber and a second photodetector in sequence to connect to the data acquisition system, the second half-wave plate is connected to the first stepper motor, the third half-wave plate is connected to the second stepper motor, the atomic gas chamber is located in an oven, the oven is located in a coil, and the coil is located in a shielding layer.

[0013] The output light beam of the electro-optic modulator is converted from monochromatic light to polychromatic light due to modulation, and the frequency difference of the first-order sideband light field generated is equal to 87 Rb hyperfine structure ground state energy level |5 2 S 1 / 2 ,F g =1> and |5 2 S 1 / 2 ,F g =2> frequency difference Δv hfs .

[0014] Step 3 includes the following expression:

[0015]

[0016] Where n is the normal vector of the plane formed by e1 and e2, and B is in the same direction as n. When θ=0, B is in the same direction as the X-axis, and when θ=0, B is in the same direction as the Y-axis.

[0017] Step 4 includes the following expression:

[0018]

[0019] where γ max is the polarization rotation angle when the CPT signal amplitude is maximum, δ x is the angle between the projection of K2 on the XOY plane and the coordinate axis Y, δz is the angle between the projection of K2 on the YOZ plane and the coordinate axis Y, is the magnitude of the magnetic field on the X axis, is the magnitude of the magnetic field along the Y axis.

[0020] Step 5 includes the following expression:

[0021] B=(b·tanθ-c,-tanθ·a,a),

[0022]

[0023] Among them, a, b, and c are all intermediate quantities.

[0024] The technical effects of the present invention are as follows: Based on a method for eliminating installation errors of a dual-beam CPT vector magnetometer, the present invention establishes a model to analyze the angular relationship between two beams of orthogonal linearly polarized light and a standard three-axis magnetic field, thereby correcting the angular output affected by the installation error of the experimental probe device placed on the generating device platform. The dual-beam coherent population trapping (CPT) vector magnetometer magnetic field vector method uses two linearly polarized light beams with mutually orthogonal propagation directions to configure a CPT magnetometer, and based on the relationship between the three key vectors of the laser wave vector K, polarization direction e, and magnetic field direction B and the CPT resonance amplitude, the angular output of the proposed CPT magnetometer magnetic field vector is modeled and analyzed, thereby obtaining an analytical solution for the magnetic field angle. However, the prerequisite of this model is that the two beams need to be configured orthogonally, which is difficult to achieve in actual situations. Based on the dual-beam measurement model, the present invention proposes a correction scheme for installation errors, and theoretically analyzes and discusses how to obtain the installation error angle and correct the magnetometer angle output when the system has installation errors. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1The present invention is a flowchart of a method for eliminating installation errors of a dual-beam CPT vector magnetometer. Figure 1 The method includes step 1, generating multi-color laser; step 2, using BS to split the laser into two beams of equal intensity, and then adjusting the polarization direction through HWP (half-wave plate); step 3, modeling and analyzing the angular output of the magnetic field vector based on the relationship between the laser wave vector, polarization direction, magnetic field direction and CPT resonance amplitude (CPT, Coherent Population Trapping); step 4, calculating the installation error angle by obtaining the polarization rotation angle when the CPT signal amplitude is maximum; step 5, establishing a magnetometer angle output correction model to eliminate the installation error.

[0026] Figure 2 Schematic diagram of the dual-beam magnetic field vector measurement principle. Figure 2 Where O is the origin, XYZ are the three axes of the Cartesian coordinate system (i.e., x-axis, y-axis, and z-axis), K1-x-axis direction light beam (x(K1)) is the first light beam, K2-y-axis direction light beam (y(K2)) is the second light beam, e1-linear polarization direction of the first light beam, e2-linear polarization direction of the second light beam, (e1, e2) is the plane formed by the polarization directions of the two beams, θ-is the angle between e1 and the z-axis (linear polarization angle of the first light beam), φ is the angle between e2 and the z-axis (linear polarization angle of the second light beam), n(B) is the normal vector of (e1, e2), n(B) = [e1×e2], n is the normal vector, n = [e1×e2], and B is the direction of the magnetic field.

[0027] Figure 3 This is a schematic diagram of installation error. Figure 3 Where δx is the angle between the projection of K2 on the XOY plane and the coordinate axis Y, and δz is the angle between the projection of K2 on the YOZ plane and the coordinate axis Y.

[0028] Figure 4 This is the structural principle diagram of the dual-beam CPT vector magnetometer measurement system. Figure 4The invention comprises an ECDL laser (ECDL, external-cavity diode laser, external cavity semiconductor laser) connected to the incident side of the optical splitter through an optical isolator, a first half-wave plate, a polarization beam splitting prism, a fiber coupler, a first polarization-maintaining fiber, an electro-optical modulator, a second polarization-maintaining fiber and a laser collimator, the electro-optical modulator is connected to a triangular wave generator through a radio frequency signal generator, the transmission side (first beam of light) of the optical splitter is connected to a data acquisition system in sequence through a second half-wave plate, an atomic gas chamber and a first photodetector (detecting the first beam of light), the reflection side (second beam of light) of the optical splitter is connected to the data acquisition system in sequence through a third half-wave plate, a first reflector, a second reflector, an atomic gas chamber and a second photodetector (PD, detecting the second beam of light), the second half-wave plate is connected to the first stepper motor, the third half-wave plate is connected to the second stepper motor, the atomic gas chamber is located in an oven, the oven is located in a coil (Helmholtz coil), and the coil is located in a shielding layer. DETAILED DESCRIPTION

[0029] Below is the attached figure ( Figures 1-4 ) and Examples illustrate the present invention.

[0030] Figure 1 The present invention is a flowchart of a method for eliminating installation errors of a dual-beam CPT vector magnetometer. Figure 2 Schematic diagram of the dual-beam magnetic field vector measurement principle. Figure 3 This is a schematic diagram of installation error. Figure 4 This is the structural principle diagram of the dual-beam CPT vector magnetometer measurement system. Figures 1 to 4 As shown, a method for eliminating installation errors of a dual-beam CPT vector magnetometer includes the following steps: step 1, generating a multi-color laser using a dual-beam CPT vector magnetometer measurement system; step 2, dividing the multi-color laser into a first beam and a second beam of light with equal light intensities, and adjusting the linear polarization directions of the two beams of light by controlling a half-wave plate via respective stepper motors; step 3, modeling and analyzing the angular output of the magnetic field vector based on the relationship between the laser wave vector, polarization direction, magnetic field direction and CPT resonance amplitude, including establishing a Cartesian coordinate system XYZ, wherein the wave vector K1 of the first beam of light is consistent with the X-axis direction, the wave vector K2 of the second beam of light is consistent with the Y-axis direction, the angle between the linear polarization direction e1 of the first beam of light and the Z-axis is θ, and the angle between the linear polarization direction e2 of the second beam of light and the Z-axis is For the unknown magnetic field direction B, the polarization rotation angle is achieved by adjusting e1 and e2 respectively and observing the amplitude of the 0-level peak of the CPT signal of both. Determine B by making B perpendicular to e1 and e2 at the same time; Step 4, calculate the installation error angle by obtaining the polarization rotation angle when the CPT signal amplitude is maximum; Step 5, establish a magnetometer angle output correction model to eliminate the installation error.

[0031] The dual-beam CPT vector magnetometer measurement system in step 1 includes an ECDL laser connected to the incident side of the optical splitter through an optical isolator, a first half-wave plate, a polarization beam splitting prism, a fiber coupler, a first polarization-maintaining fiber, an electro-optical modulator, a second polarization-maintaining fiber and a laser collimator in sequence, the electro-optical modulator is connected to a triangular wave generator through a radio frequency signal generator, the transmission side of the optical splitter forms a first beam of light which passes through a second half-wave plate, an atomic gas chamber and a first photodetector in sequence to connect to a data acquisition system, the reflection side of the optical splitter forms a second beam of light which passes through a third half-wave plate, a first reflector, a second reflector, an atomic gas chamber and a second photodetector in sequence to connect to the data acquisition system, the second half-wave plate is connected to the first stepper motor, the third half-wave plate is connected to the second stepper motor, the atomic gas chamber is located in an oven, the oven is located in a coil, and the coil is located in a shielding layer.

[0032] The output light beam of the electro-optic modulator is converted from monochromatic light to polychromatic light due to modulation, and the frequency difference of the first-order sideband light field generated is equal to 87 Rb hyperfine structure ground state energy level |5 2 S 1 / 2 ,F g =1> and |5 2 S 1 / 2 ,F g =2> frequency difference Δv hfs .

[0033] Step 3 includes the following expression:

[0034]

[0035] Where n is the normal vector of the plane formed by e1 and e2, and B is in the same direction as n. When θ=0, B is in the same direction as the X-axis, and when θ=0, B is in the same direction as the Y-axis.

[0036] Step 4 includes the following expression:

[0037]

[0038] where γ max is the polarization rotation angle when the CPT signal amplitude is maximum, δ x is the angle between the projection of K2 on the XOY plane and the coordinate axis Y, δz is the angle between the projection of K2 on the YOZ plane and the coordinate axis Y, is the magnitude of the magnetic field on the X axis, is the magnitude of the magnetic field along the Y axis.

[0039] Step 5 includes the following expression:

[0040] B=(b·tanθ-c,-tanθ·a,a),

[0041]

[0042] Among them, a, b, and c are all intermediate quantities.

[0043] The present invention addresses the following problem: a method for eliminating installation errors in a dual-beam CPT vector magnetometer. Spatial light is converted into fiber light via a fiber coupling head and then injected into an electro-optical phase modulator to modulate the laser. A radio frequency signal then half-wave modulates the laser frequency to produce a multi-color laser. A beam splitter (BS) is used to produce two beams K1 and K2 of equal intensity. The linear polarization direction of the dual beams is subsequently adjusted using a high-precision stepper motor (HWP) controlled by a high-precision stepper motor. The dual-beam magnetic field measurement is modeled and analyzed based on the magnetic field direction B, light propagation direction K, and linear polarization direction e to obtain an analytical solution for the magnetic field direction. The linearly polarized beam K2 is rotated, and the maximum CPT signal amplitude is observed to determine the theoretical installation error angle. The installation error angle is then combined with the dual-beam measurement model to obtain a correction model for the magnetometer's angle output.

[0044] Principle and coordinate system reference of magnetic field vector measurement system of CPT vector magnetometer Figure 4 .

[0045] According to the experimental design, two lasers are needed to meet the frequency difference between the two hyperfine energy levels of the D1 line of the Rb87 atom. In this experiment, the laser beam passes through an optical isolator, a half-wave plate and a polarization beam splitter in turn to achieve optical power adjustment. The spatial light is then converted into fiber light through a fiber coupling head and injected into the electro-optic phase modulator to achieve laser modulation. A triangular wave signal generator is used to generate a scanning signal to modulate the radio frequency signal with a frequency of 3.417 GHz generated by the radio frequency signal generator. The radio frequency output signal is connected to the electro-optical modulator to achieve half-wave modulation of the laser frequency. At this time, the output beam of the electro-optical modulator is transformed from monochromatic light to polychromatic light due to modulation, and the frequency difference of the first-order sideband light field generated by it is exactly equal to 87 Rb hyperfine structure ground state energy level |5 2 S 1 / 2 ,F g =1> and |5 2 S 1 / 2 ,F g =2. Frequency difference Δν hfs , meeting the conditions.

[0046] This protocol requires two beams of equal intensity to achieve dual-beam measurement of magnetic field direction. After generating the multicolor laser, it is transmitted via polarization-maintaining fiber to a laser collimator, where the laser spot diameter is adjusted to 5 mm. Using a beam splitter (BS), the laser is split into two beams of equal intensity, each regulated to 50 μW. Both beams pass through a half-wave plate (HWP) controlled by a high-precision stepper motor to adjust the linear polarization direction during the experiment.

[0047] In the experiment, the propagation directions of the two linearly polarized light beams are arranged orthogonally. The wave vectors K1 and K2 of the two light beams correspond to the coordinate axes X and Y respectively, and the direction of the coordinate axis Z is determined by the right-hand rule. The angles between the polarization directions e1 and e2 of the two light beams and the Z axis are For the unknown magnetic field direction B, the polarization rotation angle is achieved by adjusting the polarization directions of the two beams of light respectively and observing the amplitude of the 0-level peak of the CPT signal of both. According to the previous conclusion, the magnetic field direction B should be perpendicular to both the linear polarization directions e1 and e2. As shown in the figure, a Cartesian coordinate system is established. According to the constraints, the linear direction of the magnetic field can be easily determined. In the figure, X, Y, and Z satisfy the right-hand coordinate system. K1 and K2 are the propagation directions of the two beams, and their linear polarization directions are represented by e1 and e2 respectively. Figure 2 .

[0048] pass Figure 2 The Cartesian coordinate system shown in the figure is used to analyze the magnetic field vector measurement method in general: First, when When , the polarization direction vectors of the two beams can be expressed as e1=(0,y1,y1·cotθ), In order to simplify the calculation of the direction vector, let x1=y1=1, that is, e1=(0,1,cotθ), in For the plane (e1, e2) formed by the polarization directions of the two beams, it is assumed that its normal vector is n = (n x , n y , n z ), and the normal vector satisfies n=[e1×e2], we can further get the equation:

[0049]

[0050] This equation is an underdetermined equation, so let n z =1, and the normal vector is further obtained as:

[0051]

[0052] The direction of the magnetic field B is perpendicular to both the linear polarization directions e1 and e2, that is, the direction vector of the magnetic field is consistent with the normal vector n of the plane (e1, e2). For θ=0, cotθ→∞, the direction of the magnetic field B can be expressed as That is, it can be considered that the direction of the magnetic field B coincides with the coordinate axis Y. When , the direction of the magnetic field B coincides with the coordinate axis X.

[0053] The above-mentioned prerequisite for the magnetic field normal vector is that the two beams need to be arranged orthogonally, which is difficult to achieve in actual situations. The present invention theoretically analyzes and discusses the method of obtaining the installation error angle and correcting the magnetometer angle output when there is an installation error.

[0054] The double beam installation errors involved in the experiment are as follows: Figure 3 As shown, where δ x ,δ z Respectively represent the angles between the linearly polarized light beam K2 and the coordinate axis Y when projected onto the YOZ plane and the XOY plane. The experimental probe device is placed on the platform of a standard three-axis magnetic field generator, and the polarization direction e1 of the linearly polarized light beam K1 is continuously rotated. After aligning the light beam K1 with the X-axis of the magnetic field coordinate, only the Y-axis magnetic field is applied. Due to installation errors, the polarization direction e2 of the linearly polarized light beam K2 is rotated, and the CPT signal amplitude does not remain unchanged. At this time, the polarization rotation angle γ when the CPT signal amplitude is maximum is recorded. max , which can be parsed as:

[0055]

[0056] The polarization direction e2 is further restored to its initial position and remains unchanged, a fixed magnetic field is applied along the Y axis, and the X axis magnetic field is changed at the same time. When the CPT signal amplitude reaches the maximum, the magnitude of the X and Y axis magnetic fields is recorded. Based on this δ x It can be expressed as:

[0057]

[0058] Substituting into the above formula, we can get δ z Finally, the installation error angle δ between the beam K2 and the Y axis is obtained. x , δ z .

[0059] After obtaining the installation error angle of the light beam K2 and the Y axis, assume that B = (X0, Y0, Z0), and combine it with the polarization angles output by the two light beams K1 and K2 respectively. You can get:

[0060] B=(b·tanθ-c,-tanθ·a,a) (5)

[0061] in

[0062]

[0063] Each term in the equation is a known term, and when the installation error angle δ x ,δ z = 0, the magnetic field B is consistent with its normal vector n, which further verifies the generality of the modified model.

[0064] This method requires five steps to implement the installation error elimination method based on the dual-beam CPT vector magnetometer.

[0065] Step 1: Multicolor laser generation

[0066] According to the experimental design, two lasers are required to meet the frequency difference between the two hyperfine energy levels of the D1 line of the Rb87 atom. In this experiment, the laser beam passes through an optical isolator, a half-wave plate, and a polarization beam splitter in sequence to achieve optical power adjustment. The spatial light is then converted into fiber light through a fiber coupling head and injected into the electro-optic phase modulator to achieve laser modulation. A triangular wave signal generator is used to generate a scanning signal to modulate the radio frequency signal with a frequency of 3.417 GHz generated by the radio frequency signal generator. The radio frequency output signal is connected to the electro-optic modulator to achieve half-wave modulation of the laser frequency. At this time, the output beam of the electro-optic modulator is transformed from monochromatic light to polychromatic light due to modulation, and the frequency difference of the first-order sideband light field generated by it is exactly equal to the ground state energy level of the 87Rb hyperfine structure|5 2 S 1 / 2 ,F g =1> and |5 2 S 1 / 2 ,F g =2> frequency difference Δv hfs , meeting the conditions.

[0067] Step 2: Obtain dual laser beams

[0068] This protocol requires two beams of equal intensity to achieve dual-beam measurement of magnetic field direction. After generating the multicolor laser, it is transmitted via polarization-maintaining fiber to a laser collimator, where the laser spot diameter is adjusted to 5 mm. Using a beam splitter (BS), the laser is split into two beams of equal intensity, each regulated to 50 μW. Both beams pass through a half-wave plate (HWP) controlled by a high-precision stepper motor to adjust the linear polarization direction during the experiment.

[0069] Step 3: Dual-beam magnetic field measurement modeling and analysis

[0070] In the experiment, the propagation directions of the two linearly polarized light beams are arranged orthogonally. The wave vectors K1 and K2 of the two light beams correspond to the coordinate axes X and Y respectively, and the direction of the coordinate axis Z is determined by the right-hand rule. The angles between the polarization directions e1 and e2 of the two light beams and the Z axis are For the unknown magnetic field direction B, the polarization rotation angle is achieved by adjusting the polarization directions of the two beams of light respectively and observing the amplitude of the 0-level peak of the CPT signal of both. According to the previous conclusion, the magnetic field direction B should be perpendicular to both the linear polarization directions e1 and e2. As shown in the figure, a Cartesian coordinate system is established. According to the constraints, the linear direction of the magnetic field can be easily determined. In the figure, X, Y, and Z satisfy the right-hand coordinate system. K1 and K2 are the propagation directions of the two beams, and their linear polarization directions are represented by e1 and e2 respectively. Figure 2 .

[0071] pass Figure 2 The Cartesian coordinate system shown in FIG2 can be used to perform a general analysis of the magnetic field vector measurement method to obtain the normal vector expression, see the above formula (2).

[0072] Step 4: Obtain the installation error angle

[0073] The prerequisite for the analytical expression of the magnetic field normal vector is that the two beams need to be arranged orthogonally, which is difficult to achieve in actual situations. This paper discusses the method of obtaining the installation error angle and correcting the magnetometer angle output when there is an installation error from a theoretical perspective. Figure 3 .

[0074] The double beam installation errors involved in the experiment are as follows: Figure 3 As shown, where δ x ,δ z Respectively represent the angles between the linearly polarized light beam K2 and the coordinate axis Y when projected onto the YOZ plane and the XOY plane. The experimental probe device is placed on the platform of a standard three-axis magnetic field generator, and the polarization direction e1 of the linearly polarized light beam K1 is continuously rotated. After aligning the light beam K1 with the X-axis of the magnetic field coordinate, only the Y-axis magnetic field is applied. Due to installation errors, the polarization direction e2 of the linearly polarized light beam K2 is rotated, and the CPT signal amplitude does not remain unchanged. At this time, the polarization rotation angle γ when the CPT signal amplitude is maximum is recorded. max , we can get the analytical expression, see the above formulas (3) and (4).

[0075] Step 5: Correction of magnetometer installation error angle

[0076] After obtaining the installation error angle of the light beam K2 and the Y axis, assume that B = (X0, Y0, Z0), and combine it with the polarization angles output by the two light beams K1 and K2 respectively. The above formulas (5), (6), (7), and (8) can be obtained.

[0077] Any content not described in detail in this specification is prior art known to those skilled in the art. It should be noted that the above description is intended to help those skilled in the art understand the present invention, but does not limit the scope of protection of the present invention. Any equivalent substitution, modification, improvement, and / or simplification of the above description that does not depart from the essence of the present invention shall fall within the scope of protection of the present invention.

Claims

1. A method for eliminating installation errors based on a dual-beam CPT vector magnetometer, characterized in that: The following steps are involved: Step 1, using a dual-beam CPT vector magnetometer measurement system to generate multi-color laser; Step 2: Split the multi-color laser into a first beam and a second beam of light of equal intensity, and adjust the linear polarization directions of the two beams of light by controlling half-wave plates through respective stepper motors; Step 3: Based on the relationship between the laser wave vector, polarization direction, magnetic field direction and CPT resonance amplitude, the angle output of the magnetic field vector is modeled and analyzed, including establishing a Cartesian coordinate system XYZ, the wave vector K1 of the first beam of light is consistent with the X-axis direction, the wave vector K2 of the second beam of light is consistent with the Y-axis direction, the angle between the linear polarization direction e1 of the first beam of light and the Z axis is θ, and the angle between the linear polarization direction e2 of the second beam of light and the Z axis is For the unknown magnetic field direction B, the polarization rotation angle θ is achieved by adjusting e1 and e2 respectively and observing the amplitude of the 0-level peak of the CPT signal of both. Determine B by making B perpendicular to e1 and e2 at the same time; Step 4, calculating the installation error angle by obtaining the polarization rotation angle when the CPT signal amplitude is maximum; Step 5: Establish a magnetometer angle output correction model to eliminate installation errors.

2. The method for eliminating installation errors based on a dual-beam CPT vector magnetometer according to claim 1, characterized in that: The dual-beam CPT vector magnetometer measurement system in step 1 includes an ECDL laser connected to the incident side of the optical splitter through an optical isolator, a first half-wave plate, a polarization beam splitting prism, a fiber coupler, a first polarization-maintaining fiber, an electro-optical modulator, a second polarization-maintaining fiber and a laser collimator in sequence, the electro-optical modulator is connected to a triangular wave generator through a radio frequency signal generator, the transmission side of the optical splitter forms a first beam of light which passes through a second half-wave plate, an atomic gas chamber and a first photodetector in sequence to connect to a data acquisition system, the reflection side of the optical splitter forms a second beam of light which passes through a third half-wave plate, a first reflector, a second reflector, an atomic gas chamber and a second photodetector in sequence to connect to the data acquisition system, the second half-wave plate is connected to the first stepper motor, the third half-wave plate is connected to the second stepper motor, the atomic gas chamber is located in an oven, the oven is located in a coil, and the coil is located in a shielding layer.

3. The method for eliminating installation errors based on a dual-beam CPT vector magnetometer according to claim 2, characterized in that: The output light beam of the electro-optic modulator is converted from monochromatic light to polychromatic light due to modulation, and the frequency difference of the first-order sideband light field generated is equal to 87 Rb hyperfine structure ground state energy level |5 2 S 1 / 2 ,F g =1> and |5 2 S 1 / 2 ,F g =2> frequency difference Δv hfs .

4. The method for eliminating installation errors based on a dual-beam CPT vector magnetometer according to claim 1, characterized in that: Step 3 includes the following expression: Where n is the normal vector of the plane formed by e1 and e2, and B is in the same direction as n. When θ=0, B is in the same direction as the X-axis, and when θ=0, B is in the same direction as the Y-axis.

5. The method for eliminating installation errors based on a dual-beam CPT vector magnetometer according to claim 1, characterized in that: Step 4 includes the following expression: where γ max is the polarization rotation angle when the CPT signal amplitude is maximum, δ x is the angle between the projection of K2 on the XOY plane and the coordinate axis Y, δz is the angle between the projection of K2 on the YOZ plane and the coordinate axis Y, is the magnitude of the magnetic field on the X axis, is the magnitude of the magnetic field along the Y axis.

6. The method for eliminating installation errors based on a dual-beam CPT vector magnetometer according to claim 1, characterized in that: Step 5 includes the following expression: B=(b·tanθ-c,-tanθ·a,a), Among them, a, b, and c are all intermediate quantities.

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