阅读说明：本技术 基于同相激励的标量原子磁强计闭环控制系统及方法 (Scalar atomic magnetometer closed-loop control system and method based on in-phase excitation ) 是由 秦杰 郭宇豪 万双爱 薛帅 刘建丰 于 2019-09-18 设计创作，主要内容包括：本发明涉及磁探测技术领域,公开了一种基于同相激励的标量原子磁强计闭环控制系统及方法。该系统包括：检测光源产生检测光；原子气室充有用于敏感角速率的介质；驱动光源产生驱动光；激励线圈方向与检测光通过原子气室方向相同；直接数字式频率合成器输出激励信号驱动线圈产生同相激励磁场；偏振分光棱镜将检测光分为两路不同方向的偏振光；第一探测器和第二探测器对两路不同方向的偏振光进行探测；减法器对两路输出信号进行相减；乘法器对减法器输出信号和激励信号相乘；滤波器对乘法器输出信号滤波；累加器对滤波器输出信号累加平均并将累加平均后得到的信号输出至频率合成器对激励信号进行反馈调节。由此提高了磁强计的灵敏度和稳定性。(The invention relates to the technical field of magnetic detection, and discloses a scalar atomic magnetometer closed-loop control system and method based on in-phase excitation. The system comprises: the detection light source generates detection light; the atomic gas chamber is filled with a medium for sensitive angular rate; driving a light source to generate driving light; the direction of the exciting coil is the same as the direction of the detection light passing through the atomic gas chamber; the direct digital frequency synthesizer outputs an excitation signal to drive a coil to generate an in-phase excitation magnetic field; the polarization beam splitter prism divides the detection light into two paths of polarized light in different directions; the first detector and the second detector detect two paths of polarized light in different directions; the subtracter subtracts the two paths of output signals; the multiplier multiplies the output signal of the subtracter by the excitation signal; the filter filters the output signal of the multiplier; the accumulator accumulates and averages the output signals of the filter and outputs the signals obtained after accumulation and averaging to the frequency synthesizer to perform feedback adjustment on the excitation signals. Thereby improving the sensitivity and stability of the magnetometer.)

1. A scalar atomic magnetometer closed-loop control system based on in-phase excitation, the system comprising:

a detection light source for generating detection light;

an atomic gas cell filled with a medium for sensitive angular rate;

the driving light source is used for generating driving light to enable the atoms in the atom gas chamber to point to the same direction;

the atomic gas cell is arranged between the exciting coils, and the direction of the exciting coils is the same as the direction of the detection light passing through the atomic gas cell;

the direct digital frequency synthesizer is used for outputting an excitation signal to drive the excitation coil to generate an in-phase excitation magnetic field;

the polarization beam splitter prism is used for splitting the detection light passing through the atomic gas chamber into two paths of polarized light in different directions;

the first detector and the second detector are respectively used for detecting two paths of polarized light in different directions;

a subtractor for subtracting an output signal of the first detector and an output signal of the second detector;

a multiplier for multiplying the signal output by the subtracter and the excitation signal output by the direct digital frequency synthesizer;

a filter for filtering the signal output by the multiplier;

and the accumulator is used for accumulating and averaging the signals output by the filter and outputting the signals obtained after accumulating and averaging to the direct digital frequency synthesizer to perform feedback regulation on the excitation signals.

2. The system of claim 1, wherein the filter is a low pass filter.

3. The system of claim 1 or 2, wherein the first detector and the second detector are photodetectors.

4. The system of claim 1 or 2, wherein the detection light source and the driving light source are both laser light sources.

5. A scalar atomic magnetometer closed-loop control method based on in-phase excitation is characterized by comprising the following steps:

the detection light source generates detection light and the detection light is incident to the polarization beam splitter prism through the atomic gas chamber, wherein a medium for sensitive angular rate is filled in the atomic gas chamber, the atomic gas chamber is arranged between the excitation coils, the direction of the excitation coils is the same as that of the detection light passing through the atomic gas chamber, the driving light source generates driving light to enable atoms in the atomic gas chamber to point to the same direction, and the direct digital frequency synthesizer outputs an excitation signal to drive the excitation coils to generate an in-phase excitation magnetic field;

the polarization beam splitter prism splits the detection light passing through the atomic gas chamber into two paths of polarized light in different directions;

the first detector and the second detector respectively detect two paths of polarized light in different directions;

the subtracter subtracts the output signal of the first detector and the output signal of the second detector;

the multiplier multiplies the signal output by the subtracter and the excitation signal output by the direct digital frequency synthesizer;

the filter filters the signal output by the multiplier;

and the accumulator performs accumulation and average on the signals output by the filter and outputs the signals obtained after accumulation and average to the direct digital frequency synthesizer to perform feedback regulation on the excitation signals.

Technical Field

The invention relates to the technical field of magnetic detection, in particular to a scalar atomic magnetometer closed-loop control system and method based on in-phase excitation.

Background

The magnetic anomaly detection is a technology for detecting and identifying magnetic objects by measuring the disturbance of magnetic lines of force of the earth caused by the magnetic objects and utilizing magnetic anomaly information, has the advantages of high positioning precision, pure passive detection, good environmental adaptability and the like, and is widely applied to the fields of resource exploration of oil and gas minerals, underwater target identification and the like. The scalar atomic magnetometer has the outstanding advantages of high sensitivity, small volume, insensitivity to attitude and the like, and is particularly suitable for the fields of ocean resource exploration, underwater target magnetic anomaly detection and the like. Taking magnetic anomaly latency as an example, an atomic magnetometer is required to have high sensitivity and high stability. Generally, the magnetic resonance state is assumed to be the atomic spin precession phase orthogonal to the excitation magnetic field phase, and this is taken as the basis of the magnetic field measurement. Therefore, the phase error in the detection loop of the atomic magnetometer is directly converted into the magnetic field measurement error, and the accuracy of the atomic magnetometer is influenced.

The traditional scalar atomic magnetometer forms a closed-loop control loop through orthogonal excitation and a phase shifter, and has the characteristics of simple structure, analog output and easy realization. However, this method entails 90 ° phase shifting the magnetometer output using a phase shifter and then closed loop feedback as the excitation input. The phase shifter can only realize accurate phase shifting at specific frequency, so that the precision of the magnetometer in wide-range high-dynamic application is limited; in addition, the phase noise of the phase shifter itself is equivalent to the magnetic field measurement noise of the magnetometer, and the stability of the magnetometer is affected.

Disclosure of Invention

The invention aims to overcome the defects of the prior art, provides a scalar atomic magnetometer closed-loop control system and method based on in-phase excitation, and can solve the problem that the sensitivity and stability of a magnetometer are influenced in the prior art.

The technical solution of the invention is as follows: a scalar atomic magnetometer closed-loop control system based on in-phase excitation, wherein the system comprises:

a detection light source for generating detection light;

an atomic gas cell filled with a medium for sensitive angular rate;

the driving light source is used for generating driving light to enable the atoms in the atom gas chamber to point to the same direction;

the atomic gas cell is arranged between the exciting coils, and the direction of the exciting coils is the same as the direction of the detection light passing through the atomic gas cell;

the direct digital frequency synthesizer is used for outputting an excitation signal to drive the excitation coil to generate an in-phase excitation magnetic field;

the polarization beam splitter prism is used for splitting the detection light passing through the atomic gas chamber into two paths of polarized light in different directions;

the first detector and the second detector are respectively used for detecting two paths of polarized light in different directions;

a subtractor for subtracting an output signal of the first detector and an output signal of the second detector;

a multiplier for multiplying the signal output by the subtracter and the excitation signal output by the direct digital frequency synthesizer;

a filter for filtering the signal output by the multiplier;

and the accumulator is used for accumulating and averaging the signals output by the filter and outputting the signals obtained after accumulating and averaging to the direct digital frequency synthesizer to perform feedback regulation on the excitation signals.

Preferably, the filter is a low pass filter.

Preferably, the first detector and the second detector are photodetectors.

Preferably, the detection light source and the driving light source are both laser light sources.

The invention also provides a scalar atomic magnetometer closed-loop control method based on in-phase excitation, wherein the method comprises the following steps:

the detection light source generates detection light and the detection light is incident to the polarization beam splitter prism through the atomic gas chamber, wherein a medium for sensitive angular rate is filled in the atomic gas chamber, the atomic gas chamber is arranged between the excitation coils, the direction of the excitation coils is the same as that of the detection light passing through the atomic gas chamber, the driving light source generates driving light to enable atoms in the atomic gas chamber to point to the same direction, and the direct digital frequency synthesizer outputs an excitation signal to drive the excitation coils to generate an in-phase excitation magnetic field;

the polarization beam splitter prism splits the detection light passing through the atomic gas chamber into two paths of polarized light in different directions;

the first detector and the second detector respectively detect two paths of polarized light in different directions;

the subtracter subtracts the output signal of the first detector and the output signal of the second detector;

the multiplier multiplies the signal output by the subtracter and the excitation signal output by the direct digital frequency synthesizer;

the filter filters the signal output by the multiplier;

and the accumulator performs accumulation and average on the signals output by the filter and outputs the signals obtained after accumulation and average to the direct digital frequency synthesizer to perform feedback regulation on the excitation signals.

Through the technical scheme, the direction of the exciting coil is parallel to the direction of the detection light on the basis of a driving-detection form, the exciting coil is driven by an output exciting signal generated by a direct digital frequency synthesizer, so that the exciting magnetic field and the detection light are in the same direction, and the exciting signal and the output signal of the detector are subjected to data acquisition, multiplication, filtering and accumulation and then fed back to adjust the exciting signal, so that the magnetic field measurement is realized. Therefore, a phase shift link required by the traditional magnetometer is not needed, various noises caused by phase errors are fundamentally avoided, and the sensitivity and the stability of the magnetometer are further improved.

Drawings

The accompanying drawings, which are included to provide a further understanding of the embodiments of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention. It is obvious that the drawings in the following description are only some embodiments of the invention, and that for a person skilled in the art, other drawings can be derived from them without inventive effort.

FIG. 1 is a schematic diagram of a scalar atomic magnetometer closed-loop control system based on in-phase excitation according to an embodiment of the present invention;

FIG. 2 is a schematic Lorentzian line according to an embodiment of the present invention;

FIG. 3 is a schematic diagram of a noise spectrum of a magnetometer in an embodiment of the invention.

Detailed Description

Specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. In the following description, for purposes of explanation and not limitation, specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be apparent to one skilled in the art that the present invention may be practiced in other embodiments that depart from these specific details.

It should be noted that, in order to avoid obscuring the present invention with unnecessary details, only the device structures and/or processing steps that are closely related to the scheme according to the present invention are shown in the drawings, and other details that are not so relevant to the present invention are omitted.

Fig. 1 is a schematic diagram of a scalar atomic magnetometer closed-loop control system based on in-phase excitation according to an embodiment of the present invention.

As shown in fig. 1, an embodiment of the present invention provides a scalar atomic magnetometer closed-loop control system based on in-phase excitation, wherein the system includes:

a detection light source 10 for generating detection light;

an atomic gas cell 12, wherein the atomic gas cell 12 is filled with a medium for sensitive angular velocity;

a driving light source 14 for generating driving light to make the atoms in the atom gas cell 12 point to the same direction;

that is, kinetic energy is imparted to the atoms of the medium in the atomic gas chamber so that the atoms point in the same direction.

Excitation coils 16, the atomic gas cell is arranged between the excitation coils 16, and the direction of the excitation coils 16 is the same as the direction of the detection light passing through the atomic gas cell 12;

a direct digital frequency synthesizer 18 for outputting an excitation signal (excitation frequency) to drive the excitation coil to generate an in-phase excitation magnetic field;

for example, the exciting coil may be connected in series with a resistor with a suitable resistance value to be connected to the voltage output terminal of the direct digital frequency synthesizer; the direct digital frequency synthesizer outputs an excitation signal (i.e., a frequency signal) to drive the excitation coil to generate an in-phase excitation magnetic field. The amplitude of the excitation magnetic field can be in the range of 10 nT-100 nT by adjusting the resistance value of the series resistor and the output amplitude of the direct digital frequency synthesizer.

The polarization beam splitter prism 20 is used for splitting the detection light passing through the atomic gas cell 12 into two paths of polarized light in different directions;

the first detector 22 and the second detector 24 are respectively used for detecting two paths of polarized light in different directions;

a subtractor 26 for subtracting an output signal of the first detector 22 and an output signal of the second detector 24;

a multiplier 28 for multiplying the signal output from the subtractor 26 by the excitation signal output from the direct digital frequency synthesizer;

a filter 30 for filtering the signal output from the multiplier 28;

and an accumulator 32, configured to perform accumulated averaging on the signal output by the filter 30 and output a signal obtained by the accumulated averaging to the direct digital frequency synthesizer 18 to perform feedback adjustment on the excitation signal.

Wherein the signal obtained by accumulating and averaging the signal output from the filter 30 is the in-phase component M of the excitation signal_j。

For example, a kinetic model of an atomic magnetometer can be constructed from the Bloch equation:

wherein the coordinate system related to the dynamic model is rotationCoordinate system, M_i、M_jRespectively the transverse polarization intensity, M, of different coordinate axis directions under a rotating coordinate system_z、M₀Respectively longitudinal polarization and steady state polarization, gamma is gyromagnetic ratio, B₁For exciting the magnetic field amplitude, T₁And T₂The longitudinal relaxation time and the transverse relaxation time are represented, respectively, and Δ ω represents the shift of the excitation frequency from the resonance frequency. It can be seen that the excitation signal is generated by combining the in-phase component M of the excitation signal_jThe closed loop is locked to zero, namely the direct digital frequency synthesizer outputs the frequency to calculate the magnetic field to be measured (the in-phase component M of the excitation signal)_jWhen the frequency is zero, the atom is in a magnetic resonance state, and the frequency output by the direct digital frequency synthesizer is the resonance frequency):

ω＝γB，

where B is the magnetic field and ω is the excitation frequency. The magnetic field measurement is realized by performing data acquisition, multiplication, filtering, accumulation and averaging on the excitation signal and the output signals of the first detector and the second detector, and then performing feedback adjustment on the excitation frequency output by the direct digital frequency synthesizer.

Through the technical scheme, the direction of the exciting coil is parallel to the direction of the detection light on the basis of a driving-detection form, the exciting coil is driven by an output exciting signal generated by a direct digital frequency synthesizer, so that the exciting magnetic field and the detection light are in the same direction, and the exciting signal and the output signal of the detector are subjected to data acquisition, multiplication, filtering and accumulation and then fed back to adjust the exciting signal, so that the magnetic field measurement is realized. Therefore, a phase shift link required by the traditional magnetometer is not needed, various noises caused by phase errors are fundamentally avoided, and the sensitivity and the stability of the magnetometer are further improved.

For example, the circular polarization driving light frequency can be set at the atomic D1 energy level, and the intensity is 10-100 w/m²Irradiating the atomic gas chamber; the linear polarization detection light frequency can be set to be 0.05-0.2 nm of detuned relative to the D1 energy level and the intensity is 10-100 w/m²The atom-carrying precession signal is transmitted into the polarization beam splitter prism through the atom air chamber, and two paths of polarized light in different directions output by the polarization beam splitter prism are detected through the detector. Heating atomic gas chamberThe density of atoms in the gas chamber reaches 10¹²～10¹⁴/cm³。

It is to be understood by persons skilled in the art that the foregoing description is by way of example only, and not intended as a limitation upon the invention.

According to one embodiment of the invention, the filter is a low pass filter.

That is, the signal output from the multiplier 28 is low-pass filtered by a low-pass filter.

According to an embodiment of the invention, the first detector and the second detector are photodetectors.

Wherein, the photoelectric detector can convert the detected light into an electric signal to be output.

According to an embodiment of the invention, the detection light source and the driving light source are both laser light sources.

FIG. 2 is a schematic Lorentzian line diagram according to an embodiment of the present invention.

By rapidly scanning the excitation signal output by the direct digital frequency synthesizer, the in-phase component M of the excitation signal can be solved in real time_jThe in-phase component M around the atomic resonance frequency can be obtained_jThe Lorentzian dispersion curve is shown in FIG. 2.

Based on the zero point of the dispersion curve shown in FIG. 2, M in each solution cycle_jThe relative zero offset is proportional to Δ ω, so M is proportional to_jThe M is amplified and accumulated to the output frequency increment of the direct digital frequency synthesizer in proportion_jAnd when the locking is zero, the output frequency of the direct digital frequency synthesizer tracks the magnetic field to be detected in real time, so that the closed-loop control of the atomic magnetometer is realized.

The invention also provides a scalar atomic magnetometer closed-loop control method based on in-phase excitation, wherein the method comprises the following steps:

the detection light source generates detection light and the detection light is incident to the polarization beam splitter prism through the atomic gas chamber, wherein a medium for sensitive angular rate is filled in the atomic gas chamber, the atomic gas chamber is arranged between the excitation coils, the direction of the excitation coils is the same as that of the detection light passing through the atomic gas chamber, the driving light source generates driving light to enable atoms in the atomic gas chamber to point to the same direction, and the direct digital frequency synthesizer outputs an excitation signal to drive the excitation coils to generate an in-phase excitation magnetic field;

the polarization beam splitter prism splits the detection light passing through the atomic gas chamber into two paths of polarized light in different directions;

the first detector and the second detector respectively detect two paths of polarized light in different directions;

the subtracter subtracts the output signal of the first detector and the output signal of the second detector;

the multiplier multiplies the signal output by the subtracter and the excitation signal output by the direct digital frequency synthesizer;

the filter filters the signal output by the multiplier;

and the accumulator performs accumulation and average on the signals output by the filter and outputs the signals obtained after accumulation and average to the direct digital frequency synthesizer to perform feedback regulation on the excitation signals.

Through the technical scheme, the direction of the exciting coil is parallel to the direction of the detection light on the basis of a driving-detection form, the exciting coil is driven by an output exciting signal generated by a direct digital frequency synthesizer, so that the exciting magnetic field and the detection light are in the same direction, and the exciting signal and the output signal of the detector are subjected to data acquisition, multiplication, filtering and accumulation and then fed back to adjust the exciting signal, so that the magnetic field measurement is realized. Therefore, a phase shift link required by the traditional magnetometer is not needed, various noises caused by phase errors are fundamentally avoided, and the sensitivity and the stability of the magnetometer are further improved.

The method described above corresponds to the system described in fig. 1, and for specific example description, reference may be made to the description of the system described in fig. 1, which is not described herein again.

FIG. 3 is a schematic diagram of a noise spectrum of a magnetometer in an embodiment of the invention.

FIG. 3 is a graph of the noise spectrum of a scalar atomic magnetometer implemented in accordance with the present invention, where the upper curve is for closed loop operation of the magnetometerThe noise curve and the sensitivity of the magnetometer reach 0.1pT/Hz^1/2And has good low-frequency performance. The lower curve in fig. 3 is the magnetometer quantum noise level.

It can be seen from the above embodiments that the system and method of the present invention do not require a phase shift step required by the conventional magnetometer, thereby fundamentally avoiding various noises caused by phase errors, and further improving the stability of the atomic magnetometer.

Features that are described and/or illustrated above with respect to one embodiment may be used in the same way or in a similar way in one or more other embodiments and/or in combination with or instead of the features of the other embodiments.

It should be emphasized that the term "comprises/comprising" when used herein, is taken to specify the presence of stated features, integers, steps or components but does not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof.

The many features and advantages of these embodiments are apparent from the detailed specification, and thus, it is intended by the appended claims to cover all such features and advantages of these embodiments which fall within the true spirit and scope thereof. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the embodiments of the invention to the exact construction and operation illustrated and described, and accordingly, all suitable modifications and equivalents may be resorted to, falling within the scope thereof.

The invention has not been described in detail and is in part known to those of skill in the art.