阅读说明：本技术 一种核磁共振陀螺探测系统及方法 (Nuclear magnetic resonance gyro detection system and method ) 是由 雷兴 蒋樱子 胡强 李俊 李攀 郭卫华 于 2019-08-16 设计创作，主要内容包括：本发明属于惯性导航领域,具体涉及一种原子核磁共振陀螺的探测系统及方法。本发明核磁共振陀螺探测系统包括磁屏蔽系统,原子气室、无磁加热系统、一路圆偏振抽运光路、两路线偏振探测光路。所述无磁加热系统设置在原子气室表面,且二者设置在磁屏蔽系统内,其中,所述两路线偏振探测光路正交穿过原子气室后分别被探测器接收,并由差分探测系统进行信号处理得到陀螺信号。本发明提出通过利用正交探测的方案进行核磁共振陀螺提取,能有效提升对惰性气体横向磁矩信号的提取,抑制不同轴信号之间的耦合,可以实现对核磁共振陀螺信号的精确测量。另外,本发明无需要求陀螺信号的正弦分量幅值为零,易于实现,简单可行。(The invention belongs to the field of inertial navigation, and particularly relates to a detection system and a detection method of an atomic nuclear magnetic resonance gyroscope. The nuclear magnetic resonance gyro detection system comprises a magnetic shielding system, an atomic gas chamber, a non-magnetic heating system, a circular polarization pumping light path and two linear polarization detection light paths. The non-magnetic heating system is arranged on the surface of the atomic gas chamber, and the non-magnetic heating system and the magnetic shielding system are arranged in the magnetic shielding system, wherein the two lines of polarized detection light paths are respectively received by the detector after orthogonally passing through the atomic gas chamber, and the difference detection system is used for carrying out signal processing to obtain a gyro signal. The invention provides a method for extracting the nuclear magnetic resonance gyroscope by using an orthogonal detection scheme, which can effectively improve the extraction of the transverse magnetic moment signal of the inert gas, inhibit the coupling between different axial signals and realize the accurate measurement of the nuclear magnetic resonance gyroscope signal. In addition, the invention does not need to require the amplitude of the sinusoidal component of the gyro signal to be zero, is easy to realize and is simple and feasible.)

1. The utility model provides a nuclear magnetic resonance gyro detection system, its characterized in that includes magnetic shield system (17), atomic air chamber (18), no magnetism heating system (19), circular polarization pumping light path, two linear polarization detection light paths of the same kind, wherein, no magnetism heating system (19) set up on atomic air chamber (18) surface, and the two sets up in magnetic shield system (17), wherein, two routes polarization detection light path orthogonality is received by the detector respectively after passing atomic air chamber to carry out signal processing by differential detection system and obtain the gyro signal, the perpendicular above-mentioned quadrature light beam of circular polarization pumping light path of the same kind passes atomic air chamber perpendicularly simultaneously.

2. The gyromagnetic resonance gyro detection system as claimed in claim 1, wherein the two paths of polarized detection light are formed by two orthogonal light beams split by the same light source via the beam splitter or by orthogonal light beams emitted by two independent light sources.

3. The system according to claim 2, wherein one path of the linear polarization detection light path comprises a detection light source (1), a collimating lens (2), a beam splitter (3) and a differential detection system which are sequentially arranged along the light path, wherein the beam splitter (4) and the differential detection system are respectively located at two sides of the magnetic shielding system (17), and the other path of the linear polarization detection light path comprises the components, and further comprises two reflectors which are matched with the beam splitter to realize the orthogonality of the two paths of linear polarization detection light.

4. The system according to claim 1, wherein the differential detection system comprises a polarization beam splitter prism, two optical filters and two detectors, wherein the polarization beam splitter prism receives the light beam emitted from the atomic gas chamber, splits the light beam into two paths with equal light intensity, and receives the two paths of light beam from the detectors through the optical filters respectively.

5. The gyromagnetic resonance detection system of claim 4, wherein the filter is disposed at an angle with respect to the optical path.

6. The system according to claim 1, wherein the detector is connected to a signal processing module, the signal processing module includes two signal input terminals, two reference signal terminals, two multipliers, two filters, an adder, a subtractor, and two signal output terminals, wherein the two signal input terminals are respectively connected to the two reference signal terminals and the respective multipliers, the multipliers are connected to the filters, and the two filter outputs are respectively connected to and output from the adder and the subtractor, and wherein the two signal input terminals are respectively differential detection signals output by the differential detection system of the two linear polarization detection optical paths.

7. A nuclear magnetic resonance gyro detection method is characterized in that two beams of orthogonal linear polarization detection light are transversely injected from the vertical direction of pumping light, and the magnetic moment of inert gas is differentially extracted by adopting an orthogonal demodulation mode.

8. The method of claim 7, wherein the following steps are performed: two beams of orthogonal linear polarization detection light respectively enter the atom air chamber and interact with alkali metal in the atom air chamber, so that the polarization directions of the two beams of orthogonal linear polarization detection light are changed, and after the two beams of orthogonal linear polarization detection light are respectively received by the differential detection system, the two paths of differential detection signals are output by the signal processing module to be subjected to orthogonal demodulation processing, the extraction of the magnetic moment of the inert gas is realized, and the detection of a gyro signal is realized.

Technical Field

The invention belongs to the field of inertial navigation, and particularly relates to a detection system and a detection method of an atomic Magnetic Resonance gyro (or NMRG).

Background

The concept of the nuclear magnetic resonance gyroscope originated in the 60's of the 20 th century, and mainly includes an atomic gas chamber system, an optical system, a magnetic field system and a detection system because of the advantages of miniaturization and high precision, which are more emphasized by the academic world in recent years. Wherein the gas chamber system is a nuclear magnetic resonance gyro core component.

The atomic gas chamber system comprises alkali metal atoms, inert gas, buffer gas atom steam and a plurality of quenching gases. The main working process is that the polarization state of alkali metal atoms is transferred to inert gas atoms through the spin collision exchange effect by optically pumping polarized alkali metal atoms, so that the macroscopic magnetic moment of the inert gas atoms appears. And placing the gas chamber in a static magnetic field, carrying out Larmor precession on the inert gas macroscopic magnetic moment around the static magnetic field, and obtaining the carrier rotating speed information by measuring the change of Larmor precession frequency. Therefore, the key technology of the nuclear magnetic resonance gyroscope can be divided into 1) inert gas atom polarization; 2) and (4) measuring macroscopic precession magnetic moment of inert gas atoms.

The current general scheme for measuring the macroscopic precession magnetic moment of the inert gas atoms is to measure by utilizing the natural magnetic measurement capability of polarized alkali metal atoms in a gas chamber, the measurement precision of the scheme is high and generally can reach pT magnitude, and the magnetic field generated by the precession magnetic moment of the inert gas in the gas chamber exceeds nT magnitude.

Linear polarization detection light is applied in the direction perpendicular to the pumping light and the static magnetic field, the polarization direction of the detection light is modulated by the macroscopic magnetic moment of the inert gas after the detection light passes through the atomic gas chamber, and the modulation frequency is Larmor precession frequency. In order to improve the signal-to-noise ratio of the gyroscope, a high-frequency carrier magnetic field is usually applied in the direction of a static magnetic field, and the extraction of a gyroscope signal is realized by utilizing phase-sensitive demodulation. The x-axis magnetic field and the y-axis magnetic field correspond to x and y components of macroscopic magnetic moment of the inert gas, and the rotation speed of the carrier is measured by detecting the change period of the components.

However, this measurement method has the following disadvantages: in the practical operation, due to the phase delay, the strict alignment of the phase-sensitive demodulation phase is difficult to realize, so that the decoupling of the magnetic field of the x axis and the y axis is not thorough, the signal-to-noise ratio of the gyroscope is difficult to improve, and the precision improvement is limited.

Disclosure of Invention

The purpose of the invention is:

aiming at the current situation that the magnetic moment measurement of the inert gas has errors in the current nuclear magnetic resonance gyroscope measurement scheme, a system and a method for extracting the magnetic moment of the inert gas by introducing another beam of probe light in the direction orthogonal to the pumping light and the original probe light and adopting an orthogonal demodulation mode are provided.

The technical scheme of the invention is as follows:

the utility model provides a nuclear magnetic resonance gyro detection system, its includes magnetic shield system 17, atomic air chamber 18, no magnetism heating system 19, circular polarization pump light path all the way, two linear polarization detection light paths, wherein, no magnetism heating system 19 sets up on atomic air chamber 18 surface, and the two sets up in magnetic shield system 17, wherein, two routes polarization detection light path orthogonality is received by the detector respectively after passing atomic air chamber to carry out signal processing by differential detection system and obtain the gyro signal, circular polarization pump light path perpendicular above-mentioned quadrature light beam all the way passes atomic air chamber perpendicularly simultaneously.

The two paths of polarized detection light are formed by two paths of orthogonal light beams which are divided by the same light source through the spectroscope or orthogonal light beams emitted by two independent light sources.

The linear polarization detection light path comprises a detection light source 1, a collimating lens 2, a beam splitter 3 and a differential detection system which are sequentially arranged along the light path, wherein the beam splitter 4 and the differential detection system are respectively positioned on two sides of a magnetic shielding system 17, the other line of the linear polarization detection light path simultaneously comprises the components, and the linear polarization detection light path further comprises two reflectors matched with the beam splitter, so that the orthogonality of the two lines of linear polarization detection light is realized.

The differential detection system comprises a polarization beam splitter prism, two optical filters and two detectors, wherein the polarization beam splitter prism receives light beams emitted from the atomic gas chamber, divides the light beams into two paths with equal light intensity, and receives the light beams by the detectors through the optical filters respectively.

The filter is arranged obliquely relative to the optical path.

The detector is connected with the signal processing module, the signal processing module comprises two signal input ends, two reference signal ends, two multipliers, two filters, an adder, a subtracter and two signal output ends, wherein the two signal input ends are respectively connected with the two reference signal ends to the respective multipliers, the multipliers are connected with the filters, the outputs of the two filters are respectively connected with the adder and the subtracter and output, and the two signal input ends are respectively differential detection signals output by a differential detection system of two linear polarization detection light paths.

A nuclear magnetic resonance gyro detection method is characterized in that two beams of orthogonal linear polarization detection light are transversely injected from the vertical direction of pumping light, and the magnetic moment of inert gas is differentially extracted in an orthogonal demodulation mode.

The nuclear magnetic resonance gyro detection method comprises the following steps: two beams of orthogonal linear polarization detection light respectively enter the atom air chamber and interact with alkali metal in the atom air chamber, so that the polarization directions of the two beams of orthogonal linear polarization detection light are changed, and after the two beams of orthogonal linear polarization detection light are respectively received by the differential detection system, the two paths of differential detection signals are output by the signal processing module to be subjected to orthogonal demodulation processing, the extraction of the magnetic moment of the inert gas is realized, and the detection of a gyro signal is realized.

The invention has the beneficial effects that:

compared with the prior art, the invention has the beneficial effects that:

the invention provides a method for extracting the nuclear magnetic resonance gyroscope by using an orthogonal detection scheme, which can effectively improve the extraction of the transverse magnetic moment signal of the inert gas, inhibit the coupling between different axial signals and realize the accurate measurement of the nuclear magnetic resonance gyroscope signal.

The invention provides a data processing scheme related to an orthogonal detection scheme, and has important significance for realizing the performance of a nuclear magnetic resonance gyroscope.

Drawings

FIG. 1 shows a schematic diagram of a magnetic resonance gyroscope according to the present invention;

FIG. 2 is a data specific process flow;

the elements in the figures being indicated by numerals

1-a detection light source, 2-a collimating lens, 3-a transflective lens, 4-a first reflector, 5-a second reflector, 6-a transverse oscillating magnetic field group, 7-a first polarizing beam splitter prism, 8-a first optical filter, 9-a first detector, 10, a second optical filter, 11-a second detector, 12-a second polarizing beam splitter prism, 13-a third optical filter, 14-a third detector, 15-a fourth optical filter, 16-a fourth detector, 17-a magnetic shielding system, 18-an atomic gas chamber system and 19-a non-magnetic heating system;

20-x axis measurement input signal, 21-Y axis measurement input signal, 22-first modulation and demodulation signal, 23-second modulation and demodulation signal, 24-first multiplier, 25-second multiplier, 26-first filter, 27-second filter, 28-first adder, 29-first subtracter, 30-first gain factor, 31-second gain factor, 32-second adder, 33-second subtracter, 34-Y axis magnetic field signal output port and 31-x axis magnetic field signal output port.

Detailed Description

The invention is further illustrated by the following examples in conjunction with the accompanying drawings

Referring to FIG. 1, the z-axis is directed vertically outward, and in this direction there is a circularly polarized pump light at the frequency of the line of the alkali metal D1 involved and a static magnetic field coil, which can be either a Helmholtz coil pair or a coaxial solenoid. The detection light source 1 emits linearly polarized light after passing through the collimating lens 2, and the frequency of the linearly polarized light is the frequency of the related alkali metal D2. The detection light is divided into two beams of polarized light with equal light intensity by the beam splitter 3, wherein one beam of polarized light sequentially passes through the magnetic shielding system 17 and the atom air chamber 18 and is received by the first detector 9 and the second detector 11, the detectors 9 and 11, the first polarization splitting prism 7 and the light filters 8 and 10 form a differential detection system for inhibiting measurement interference generated by light intensity jitter of the detection light. The other path of detection light reflected by the beam splitter 3 enters the magnetic shielding system 17 after passing through the first reflector 4 and the second reflector 5, sequentially passes through the transverse oscillating magnetic field 8, the non-magnetic heating system 19 and the magnetic shielding system 17 after passing through the atom air chamber 18, and is received by the third detector 14 and the fourth detector 16, and the detectors 14 and 16, the second polarization beam splitter prism 12 and the optical filters 13 and 16 form a differential detection system for inhibiting the measurement interference generated by the light intensity jitter of the detection light. The optical filters involved are all obliquely arranged so as to eliminate the problem that scattered light enters the air chamber again and limit the improvement of the gyro precision.

In fig. 2, the x, y-axis signals measured after differencing are fed into the data processing system via input ports 20, 21. The first reference signal 22 and the second reference signal 23 respectively demodulate two paths of signals, the two paths of reference signals have the same frequency and strictly orthogonal phases, the demodulated signals are filtered by low-pass filters 26 and 27, then the demodulated signals are added in a 28-first adder and a 29-second subtracter, the demodulated signals are subjected to subtraction processing, the processed signals are subjected to specific gain factor processing, then the processed signals are added and subtracted again in a 30-second adder and a 31-second subtracter, and then the signals are output, so that decoupling between x-axis magnetic fields and y-axis magnetic fields is realized, and the signal-to-noise ratio of gyro signals is improved.

The method is based on the following principle: in an atomic gas chamber, a macroscopic magnetic field generated by the inert gas precession magnetic moment can influence the change of the polarization direction of alkali metal to probe light (the linear frequency and the linear polarization of the alkali metal D2), two beams of orthogonal probe light are transversely injected from the vertical direction of the pump light, so that the crosstalk between the magnetic moments in the orthogonal axis direction of the inert gas of a measurement result can be eliminated, and the signal to noise ratio of signal detection is improved.

The signal processing procedure of the nuclear magnetic resonance gyro detection method of the present invention is given below:

the signals extracted from the X, Y directions, respectively, based on the interaction between atoms and light are:

denoting Bessel functions of order n, hereinafter J for the sake of brevity_nInstead of the former

Sig in the above equation_x，Sig_yRespectively representing the directly measured x-axis, y-axis signals, B_x，B_yThen respectively represent the magnetic fields of x and y axes of the gyroscope, and when a resonant magnetic field is applied to the x axis, B_xIs the x-axis component of the magnetic moment of the resonant magnetic field and inert gas, B_yIs the y-axis component of the magnetic moment of the inert gas, gamma_AlkaliIs alkali metal magnetic rotation ratio, B_cIs the carrier magnetic field amplitude, omega_cIs the carrier magnetic field frequency. The measurement signals between the formulas 1) and 2) contain crosstalk of x and y signals, so that the inert gas magnetic moment cannot be directly obtained, and further processing is needed to demodulate x and y axis magnetic field signals.

Using co-frequency signals cos (omega)_ct+θ)，sin(ω_ct + θ) demodulates the first harmonic in its equations (1), (2), where θ is the phase mismatch between the modulated signals of the demodulated signal caused by the system delay. Equation (1) uses cos (ω)_ct + θ) demodulation is output after low pass as:

Sig'_x＝KJ₁(-B_y(J₂+J₀)cosθ+B_x(J₂-J₀)sinθ) (3)

equation (2) uses sin (ω)_ct + θ) demodulation is output after low pass as:

Sig'_y＝KJ₁(B_x(J₂+J₀)sinθ-B_y(J₂-J₀)cosθ) (4)

differencing the result after demodulation by:

A＝(4)+(5)＝2KJ₁(-B_yJ₂cosθ+B_xJ₂sinθ) (5)

the result after demodulation is summed with:

B＝(4)-(5)＝2KJ₁(-B_yJ₀cosθ-B_xJ₀sinθ) (6)

the gains of A and B are adjusted as follows:

through the processing from the formula 1) to the formula 7), the pair B is realized_x，B_yAnd (4) separating signals, wherein when an oscillating magnetic field is applied to an x axis, a gyro signal selects a y axis signal, and the influence of the oscillating magnetic field on the gyro signal is the lowest. In the whole process, the phase of the reference signal does not need to be adjusted to be strictly aligned, and decoupling of the x-axis magnetic field and the y-axis magnetic field can be realized only through quadrature demodulation, so that the method is simple and easy to realize and has a large practical application value.