Method and device for dynamic dispersion balance of four-frequency differential laser gyroscope

Abstract

The application discloses a four-frequency-difference dynamic dispersion balance method and device of a laser gyroscope, which comprises the following steps: inputting a constant current into a dispersion coil through a gain medium coil current control module, and applying a constant axial magnetic field to a gas gain medium by the dispersion coil; inputting a controllable current into a Faraday coil by a Faraday coil current control module, controlling an axial bias magnetic field of a Faraday cell, changing a frequency offset generated by a light beam when passing through the Faraday cell, and making the frequency offset of the Faraday cell equal to a Zeeman effect frequency offset, so as to realize dynamic dispersion balance of the four-frequency-difference laser gyroscope. In the dynamic dispersion balance process, unlike the fact that the change of the axial magnetic field of the gain medium directly affects the frequency offset of the gyroscope, the change caused by the change of the axial bias magnetic field of the Faraday cell is removed by difference during the operation of the gyroscope, so that the influence on the final output of the gyroscope is very small, and the modulation of the cavity length during the operation of the gyroscope is avoided.

Description

TECHNICAL FIELD

[0001] The present application mainly relates to the technical field of four-frequency differential laser gyroscopes, and particularly relates to a four-frequency differential laser gyroscope dynamic dispersion balancing method and device. BACKGROUND

[0002] As an optical inertial device, a laser gyroscope has a series of advantages such as a large dynamic range, instantaneous start, excellent scale factor, strong impact and vibration resistance, high reliability, direct digital output, small size and low cost compared with traditional mechanical gyroscopes, and is called an ideal component of a strapdown inertial navigation / guidance system.

[0003] A laser gyroscope is an optical gyroscope based on the Sagnac effect, and its essence is a ring laser. At least a pair of counter-propagating light waves operate in the optical resonant cavity of the laser. When rotating around the sensitive axis relative to the inertial space, the frequency of the counter-propagating waves is split to form a beat frequency proportional to the rotation rate, and the rotation information relative to the inertial space can be obtained by measuring the beat frequency. Due to the energy coupling between the counter-propagating waves in the resonant cavity, the laser gyroscope has a lock-in effect, which leads to its inability to measure low rotation rates. The most common method to overcome the lock-in is mechanical dithering of the frequency, but mechanical dithering can easily interfere with other instruments in the inertial system, and in addition, it also increases the random walk and reduces the signal bandwidth.

[0004] A four-frequency differential laser gyroscope uses an optical frequency offset method to overcome the lock-in and does not produce mechanical interference, and has superiority in principle. Four wave modes operate in the resonant cavity of the four-frequency differential laser gyroscope. A quartz rotator or a non-planar cavity is used to split the frequencies of left-handed and right-handed polarized counter-propagating waves. A Faraday frequency offset device or a longitudinal magnetic field applied to the gain medium is used to establish a non-reciprocal frequency offset between counter-propagating waves of the same polarization state to overcome the lock-in. A pair of left-handed polarized counter-propagating waves and a pair of right-handed polarized counter-propagating waves form left-handed and right-handed single gyroscopes, respectively, and the four laser modes operate simultaneously. Through the difference between the beat frequencies of the two single gyroscopes, the non-reciprocal frequency offset is eliminated in the output signal, so it is not affected by the instability of the non-reciprocal frequency offset, and the sensitivity to rotation is doubled. Since the gyroscope is far from the lock-in region during normal operation and has no mechanical moving parts, the four-frequency differential laser gyroscope is a truly full solid-state gyroscope, and has a series of advantages such as high angular resolution, good real-time performance, etc. in addition to the advantages of mechanical dithering gyroscopes.

[0005] However, four laser modes in the four-frequency differential laser gyro operate simultaneously, and the four modes all have dispersion effect. Due to the asymmetry of the gain curve and the influence of temperature, the dispersion amount of the four modes is different and is influenced by temperature, and finally zero drift is generated. At present, some people have proposed a method of dynamic dispersion balance, the core idea of which is to dynamically eliminate the zero bias caused by the dispersion effect of the gain medium by adjusting the cavity length to obtain the dispersion balance control amount through the phase-sensitive detection method. Although this method can achieve dynamic dispersion balance of the four-frequency differential laser gyro, it needs to modulate the gyro cavity length, which will directly cause periodic modulation of the gyro output signal. The four-frequency differential laser gyro using this scheme must be integrated for a long time to eliminate the influence of periodic modulation, which reduces the real-time performance of the four-frequency differential laser gyro and limits its use in occasions with large measurement bandwidth. SUMMARY

[0006] In view of the defects and deficiencies of the prior art, the present application provides a four-frequency differential laser gyro dynamic dispersion balance method and device.

[0007] To achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows:

[0008] On the one hand, the present application provides a four-frequency differential laser gyro dynamic dispersion balance device, which comprises a gyro cavity, wherein the gyro cavity is provided with a ring resonator, and the ring resonator is an annular light path enclosed by a first mirror, a second mirror, a third mirror and a fourth mirror in sequence.

[0009] The gyro cavity is filled with a gas gain medium, and the gyro cavity is provided with an excitation electrode structure for exciting the gas gain medium, and the gas gain medium generates laser oscillation under the excitation of the excitation electrode structure.

[0010] A dispersion coil is wound around the light path between the second mirror and the third mirror of the annular light path, and the dispersion coil is connected with a gain medium coil current control module to control the current size in the dispersion coil.

[0011] A Faraday cell is arranged on the light path between the fourth mirror and the first mirror of the annular light path, the Faraday cell contains a Faraday optical rotator inside, and a Faraday cell permanent magnet is arranged outside the Faraday cell for providing an axial bias magnetic field, and a Faraday coil is wound around the Faraday cell permanent magnet, the Faraday coil is connected with a Faraday coil current control module, and the current size in the Faraday coil is controlled by the Faraday coil current control module to realize that the frequency deviation of the Faraday cell is equal to the frequency deviation of the Zeeman effect, and the dispersion balance of the four-frequency differential laser gyro is realized.

[0012] Further, the outer side of the fourth reflecting mirror is provided with a light combining prism for receiving the outgoing light from the fourth reflecting mirror and generating interference, and a photoelectric detector receives the output light beam of the light combining prism to detect the interference signal; a gyro output signal demodulation module is connected to the photoelectric detector for calculating the rotation information and generating a Faraday coil current control signal; a Faraday coil current control module is connected to the gyro output signal demodulation module, and under the control of the Faraday coil current control module, the Faraday coil current is dynamically adjusted to make the frequency offset of the Faraday cell equal to the frequency offset of the Zeeman effect, so that the dispersion balance of the four-frequency differential laser gyroscope is realized.

[0013] Further, at least one reflecting mirror in the ring resonant cavity is connected with a cavity length controller, the cavity length controller is connected with a cavity length control module, the cavity length control module outputs a voltage for controlling the displacement of the cavity length controller, and the displacement of the cavity length controller drives the corresponding reflecting mirror synchronously to adjust the cavity length of the ring resonant cavity.

[0014] Further, the application provides a dynamic dispersion balance method of the four-frequency differential laser gyroscope, which is realized based on the four-frequency differential laser gyroscope dynamic dispersion balance device and includes the following steps.

[0015] The gain medium coil current control module inputs a constant current to the dispersion coil, and the dispersion coil applies a constant axial magnetic field to the gas gain medium.

[0016] The Faraday coil current control process: the Faraday coil current control module inputs a controllable current with variable current size to the Faraday coil to control the axial bias magnetic field of the Faraday cell, changes the frequency offset generated by the light beam when passing through the Faraday cell, and makes the frequency offset of the Faraday cell equal to the frequency offset of the Zeeman effect, so that the dynamic dispersion balance of the four-frequency differential laser gyroscope is realized.

[0017] Compared with the prior art, the application has the following beneficial effects:

[0018] The application aims to eliminate the gyro zero drift caused by the dispersion effect of the gain medium, inputs a controllable current with variable current size to the Faraday coil through the Faraday coil current control module, controls the axial bias magnetic field of the Faraday cell, changes the frequency offset generated by the light beam when passing through the Faraday cell, and makes the frequency offset of the Faraday cell equal to the frequency offset of the Zeeman effect, so that the dynamic dispersion balance of the four-frequency differential laser gyroscope is realized.

[0019] Further, when the Zeeman splitting caused by the axial magnetic field is equal to the non-reciprocal splitting caused by the Faraday cell, the dispersion amount of the clockwise pair of modes and the counterclockwise pair of modes is equal. By using this principle, the best Faraday frequency can be found by finding the Faraday frequency point at which the output signal of the gyroscope is least sensitive to the change of the cavity length of the ring resonator, and the size of the current supplied to the Faraday cell coil is controlled in real time during the operation of the four-frequency differential laser gyroscope to control the magnetic field strength of the axial bias magnetic field of the Faraday cell so as to stabilize the Faraday frequency at the best Faraday frequency, thereby achieving dynamic dispersion balance of the four-frequency differential laser gyroscope.

[0020] In particular, the present application proposes to apply a constant axial magnetic field to the gas gain medium by the dispersion coil, to control the axial bias magnetic field of the Faraday cell by supplying a controllable current with varying size to the Faraday coil, to find the best Faraday frequency, and to adjust the axial bias magnetic field of the Faraday cell in real time so as to equalize the Zeeman splitting and the non-reciprocal splitting, thereby achieving dynamic dispersion balance of the four-frequency differential laser gyroscope.

[0021] The present application dynamically adjusts the non-reciprocal splitting caused by the Faraday cell by adjusting the magnetic field strength of the axial bias magnetic field of the Faraday cell to eliminate the dispersion zero bias based on the non-reciprocal splitting of the Faraday cell. During the dynamic dispersion balance process, the amount of change caused by the variation of the axial bias magnetic field of the Faraday cell is all removed by the differential during the operation of the gyroscope, so the impact on the final output of the gyroscope is very small, and the modulation of the cavity length during the operation of the gyroscope is avoided. BRIEF DESCRIPTION OF DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor based on the drawings shown.

[0023] Figure 1 Fig. 1 is a structural schematic diagram of a dynamic dispersion balance device of a four-frequency differential laser gyroscope in an embodiment;

[0024] Figure 2 Fig. 2 is a cross-sectional schematic diagram of a Faraday cell without a Faraday coil;

[0025] Figure 3 Fig. 3 is a cross-sectional schematic diagram of a Faraday cell with a Faraday coil;

[0026] Markings in the drawings:

[0027] 1, gyro cavity, 2a, first mirror, 2b, second mirror, 2c, third mirror, 2d, fourth mirror, 3, Faraday chamber, 4, cavity length controller, 5, photodetector, 6, light combiner prism, 7, anode, 8, cathode, 9, dispersion coil, 10, Faraday chamber permanent magnet, 11, Faraday optical rotator, 12, Faraday coil, 13, gyro output signal demodulation module, 14, Faraday coil current control module, 15, cavity length control module, 16, gain medium coil current control module. DETAILED DESCRIPTION

[0028] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0029] Referring to Figure 1 , Figure 2 and Figure 3 , one embodiment provides a four-frequency differential laser gyro dynamic dispersion balancing device, comprising a gyro cavity 1, wherein a ring resonator is arranged in the gyro cavity 1, and the ring resonator is a ring-shaped light path enclosed by a first mirror 2a, a second mirror 2b, a third mirror 2c and a fourth mirror 2d in sequence.

[0030] The gyro cavity 1 is filled with a gas gain medium, and the gyro cavity 1 is provided with an excitation electrode structure for exciting the gas gain medium, and the gas gain medium generates laser oscillation under the excitation of the excitation electrode structure. As shown in Figure 1 , the excitation electrode structure comprises two anodes 7 and one cathode 8 arranged on the gyro cavity 1, the gyro cavity 1 is symmetrically provided with two anodes 7 on the left and right sides, and the gyro cavity 1 between the two anodes 7 is provided with a cathode 8, and the gas gain medium between the cathode 8 and the anode 7 will constitute a gain region for generating laser oscillation.

[0031] A dispersion coil 9 is wound around the light path between the second mirror 2b and the third mirror 2c of the ring-shaped light path, and the dispersion coil 9 is connected with the gain medium coil current control module 16 to control the current size in the dispersion coil 9;

[0032] A Faraday cell 3 is arranged on the optical path between the fourth mirror 2d and the first mirror 2a of the ring optical path, the Faraday cell 3 internally contains a Faraday rotator 11, and a Faraday cell permanent magnet 10 is arranged outside the Faraday cell 3 for providing an axial bias magnetic field, the Faraday cell permanent magnet 10 is wound with a Faraday coil 12, the Faraday coil 12 is connected with a Faraday coil current control module 14, the Faraday coil current control module 14 controls the current size in the Faraday coil 12 to realize that the Faraday cell frequency offset is equal to the Zeeman effect frequency offset, and the dispersion balance of the four-frequency differential laser gyroscope is realized.

[0033] In actual application, the arrangement of the excitation electrode structure is not limited to Figure 1 the form shown, and the excitation electrode structure can also include two cathodes and one anode arranged on the gyroscope cavity, the gyroscope cavity is symmetrically arranged with two cathodes on the left and right sides, and the anode is arranged on the gyroscope cavity between the two cathodes, the gas gain medium between the cathode and the anode will constitute a gain region for generating laser oscillation. In addition, those skilled in the art can also design the excitation electrode structure to include multiple cathodes and multiple anodes according to actual application requirements, as long as the gas gain medium can generate laser oscillation under the excitation of the excitation electrode structure.

[0034] Further, in Figure 1 the embodiment shown, the outside of the fourth mirror 2d is arranged with a light combining prism 6 for receiving the outgoing light from the fourth mirror 2d and generating interference, a photodetector 5 receives the output light beam of the light combining prism 6, a gyro output signal demodulation module 13 is connected with the photodetector 5 for calculating rotation information and generating a Faraday coil current control signal; the Faraday coil current control module 14 is connected with the gyro output signal demodulation module 13, and under the control of the Faraday coil current control module 14, the Faraday coil current is dynamically adjusted to realize that the Faraday cell frequency offset is equal to the Zeeman effect frequency offset, and the dispersion balance of the four-frequency differential laser gyroscope is realized.

[0035] The first mirror 2a is connected with a cavity length controller 4, which can be piezoelectric ceramic. The cavity length controller 4 is connected with a cavity length control module 15, which outputs a voltage for controlling the displacement of the cavity length controller, and the displacement of the cavity length controller 4 synchronously drives the first mirror 2a, so as to adjust the cavity length of the ring resonator. It can be understood that in actual application, the cavity length controller 4 is not limited to being connected with the first mirror 2a, but can also be connected with other mirrors in the ring resonator, or multiple mirrors (such as two mirrors connected with corresponding cavity length controllers) in the environment resonator. The cavity length controller 4 is connected with the cavity length control module 15, which outputs a voltage for controlling the displacement of the cavity length controller, and the displacement of the cavity length controller 4 synchronously drives the corresponding mirror, so as to adjust the cavity length of the ring resonator. In summary, at least one mirror in the ring resonator is connected with a cavity length controller, the cavity length controller is connected with a cavity length control module, which outputs a voltage for controlling the displacement of the cavity length controller, and the displacement of the cavity length controller synchronously drives the corresponding mirror, so as to adjust the cavity length of the ring resonator.

[0036] The physical root of the problem of gyro dispersion balance lies in that the four-frequency differential laser gyro splits two pairs of frequencies from left and right gyro through various non-reciprocal elements (such as Faraday optical rotator, magnetic mirror, etc.). In an ideal case, the gain curve should be strictly symmetrical, but in actual application, the gain curve has asymmetry, and the four-frequency differential laser gyro introduces an additional zero bias when working through the dispersion effect of the gain medium. The approximate expression of the zero bias of the four-frequency differential laser gyro is as follows:

[0037] ;

[0038] Wherein, c is the speed of light, L op is the cavity length of the ring resonator, v z is the Zeeman effect frequency shift amount, v F is the Faraday cell frequency shift amount, k3 is a constant with an order of 1, is the cavity loss, v d is the average frequency of the four modes of the gyro relative to v d0 , that is, the detuning frequency, which is used to determine the relative position of the four modes and the gain curve of the gyro.

[0039] Therefore, when the Zeeman effect frequency shift amount v z is equal to the Faraday cell frequency shift amount v F , the zero bias is zero, at this time, the output signal of the gyro is least sensitive to the change of the cavity length L op of the ring resonator, and the dispersion balance is achieved.

[0040] When axial magnetic field is applied in the gyroscopic gain region, it will cause the splitting of atomic energy level of the gas gain medium, thus generating two split gain curves, which will make the left-handed circularly polarized light and the right-handed circularly polarized light interact with different gain curves respectively, thus realizing frequency shift.

[0041] In the example given in the present application, the axial magnetic field of the gas gain medium is provided by the dispersion coil surrounding the gain region, and the generated frequency shift amount can be calculated by the following formula:

[0042] ;

[0043] wherein g is the Lande g factor, β is the Bohr magneton, is the axial magnetic field strength of the gas gain medium, and h is the Planck constant. Meanwhile, in practical application, in order to avoid the interference of external magnetic field, adding magnetic shielding to the gyroscopic gain region can make the frequency shift amount generated by the Zeeman effect more stable.

[0044] The Faraday cell is composed of a Faraday rotator made of magneto-optical medium and a Faraday cell permanent magnet surrounding it, and the Faraday cell permanent magnet provides a longitudinal magnetic field for the Faraday rotator to generate Faraday rotation effect. The Faraday cell of the four-frequency differential laser gyroscope is based on magneto-optical effect, and a magnetic field is applied in the direction of light beam propagation, and the polarization state of the light beam will be deflected, and the deflection angle satisfies the following formula:

[0045] ;

[0046] wherein V is the magnetic rotation coefficient, L is the length of the Faraday rotator along the direction of light beam propagation, B is the magnetic induction intensity.

[0047] In the four-frequency differential laser gyroscope, the circularly polarized light of the same polarization state will generate a certain frequency shift amount when passing through the Faraday rotator made of magneto-optical medium, and the formula of the frequency shift amount is as follows:

[0048] ;

[0049] wherein V is the magnetic rotation coefficient, c is the speed of light, is the magnetic field strength of the Faraday cell, μ is the medium permeability.

[0050] The application adds a Faraday coil to the permanent magnet around the Faraday chamber, adjusts the current flowing into the Faraday coil, thereby adjusts the magnetic induction intensity around the Faraday optical rotator, changes the frequency deviation generated by the light beam when passing through the Faraday chamber, makes the frequency deviation of the Zeeman splitting (i.e. the frequency deviation of the Zeeman effect) equal to the frequency deviation of the non-reciprocal frequency of the Faraday chamber (i.e. the frequency deviation of the Faraday chamber), and realizes the dynamic dispersion balance of the four-frequency differential laser gyroscope.

[0051] Figure 1 The whole of the middle gyro cavity 1 is made of microcrystalline glass with low expansion coefficient, and four mirrors are connected together with the gyro cavity by optical cementing.

[0052] In an embodiment, a four-frequency differential laser gyroscope dynamic dispersion balance method is provided, which is based on the four-frequency differential laser gyroscope dynamic dispersion balance device provided in the above embodiment to realize the dynamic dispersion balance of the four-frequency differential laser gyroscope, and includes the following steps:

[0053] The gain medium coil current control module inputs a constant current to the dispersion coil, and the dispersion coil applies a constant axial magnetic field to the gas gain medium;

[0054] The Faraday coil current control module inputs a controllable current with variable current size to the Faraday coil, controls the axial bias magnetic field of the Faraday chamber, changes the frequency deviation generated by the light beam when passing through the Faraday chamber, and makes the frequency deviation of the Faraday chamber equal to the frequency deviation of the Zeeman effect, so as to realize the dynamic dispersion balance of the four-frequency differential laser gyroscope.

[0055] In a preferred embodiment, a four-frequency differential laser gyroscope dynamic dispersion balance method is provided, which includes the following steps:

[0056] The gain medium coil current control module inputs a constant current to the dispersion coil, and the dispersion coil applies a constant axial magnetic field to the gas gain medium;

[0057] The Faraday coil current control process includes:

[0058] Determination of the optimal Faraday frequency deviation: the magnetic field intensity of the Faraday chamber is adjusted by changing the current flowing into the Faraday chamber coil to adjust the Faraday frequency deviation, the cavity length control module outputs a periodically changing voltage to make the connected cavity length controller periodically displace, thereby making the ring resonant cavity length periodically change, the relationship between the ring resonant cavity length and the gyroscope output signal under different Faraday frequency deviations is obtained by using the sweep mode, and the working point of the Faraday frequency deviation with the minimum change of the frequency of the gyroscope output signal with the change of the ring resonant cavity length is found, that is, the optimal Faraday frequency deviation is obtained;

[0059] Stop scanning mode, adjust the length of the ring resonator cavity until the left-handed light and right-handed light intensity of the gyro output is equal, in the process of four-frequency differential laser gyro, the Faraday coil current control module controls the current of the Faraday room coil in real time, controls the magnetic field intensity of the Faraday room axial bias magnetic field to stabilize the Faraday frequency at the optimal Faraday frequency, makes the Faraday frequency equal to the Zeeman effect frequency, so as to realize the dynamic dispersion balance of the four-frequency differential laser gyro.

[0060] The cavity length control module 15 outputs a periodically changing voltage, so that the connected cavity length controller 4 (i.e. piezoelectric ceramic) is periodically displaced, so that the length of the ring resonator cavity is periodically changed. The gyro output signal demodulation module 13 integrates and analyzes the gyro output signal in a change cycle of the ring resonator cavity length under different Faraday frequencies, to obtain the relationship between the ring resonator cavity length under different Faraday frequencies and the gyro output signal, until the Faraday frequency working point at which the frequency of the gyro output signal changes the least or the change amplitude is less than a set threshold is found, that is, the optimal Faraday frequency is obtained (i.e. under the optimal Faraday frequency, the change amplitude of the frequency of the gyro output signal in a change cycle of the ring resonator cavity length is the least or less than a set threshold).

[0061] The remaining matters of the present application are known technologies.

[0062] The technical features of the above embodiments can be combined arbitrarily, and in order to make the description concise, not all possible combinations of the technical features in the above embodiments are described, however, as long as the combinations of the technical features do not exist contradictory, they should be considered as the scope of the present application.

[0063] The above-described embodiments only express several implementation manners of the present application, and the description is more specific and detailed, but it should not be understood as a limitation on the scope of the application. It should be pointed out that for ordinary skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are within the protection scope of the present application.

[0064] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A dynamic dispersion balance device for a four-frequency differential laser gyroscope, comprising a gyroscope cavity, characterized in that: a ring resonator is arranged in the gyroscope cavity, and the ring resonator is a ring-shaped light path enclosed by a first mirror, a second mirror, a third mirror and a fourth mirror in sequence; a gas gain medium is filled in the gyroscope cavity, and an excitation electrode structure for exciting the gas gain medium is arranged on the gyroscope cavity, and the gas gain medium generates laser oscillation under the excitation of the excitation electrode structure; a dispersion coil is wound around the light path between the second mirror and the third mirror of the ring-shaped light path, and the dispersion coil is connected with a gain medium coil current control module to control the current size in the dispersion coil; a Faraday cell is arranged on the light path between the fourth mirror and the first mirror of the ring-shaped light path, the Faraday cell contains a Faraday optical rotator inside, a Faraday cell permanent magnet is arranged outside the Faraday cell to provide an axial bias magnetic field, a Faraday coil is wound around the Faraday cell permanent magnet, and the Faraday coil is connected with a Faraday coil current control module to control the current size in the Faraday coil, so as to realize that the frequency offset of the Faraday cell is equal to the Zeeman effect frequency offset, and the dispersion balance of the four-frequency differential laser gyroscope is realized. The outside of the fourth mirror is provided with a light combiner prism for receiving the outgoing light from the fourth mirror and generating interference, and a photoelectric detector receives the output light beam of the light combiner prism to detect the interference signal; a gyroscope output signal demodulation module is connected with the photoelectric detector to calculate the rotation information and generate a Faraday coil current control signal; and the Faraday coil current control module is connected with the gyroscope output signal demodulation module to dynamically adjust the Faraday coil current under the control of the Faraday coil current control module, so as to realize that the frequency offset of the Faraday cell is equal to the Zeeman effect frequency offset, and the dispersion balance of the four-frequency differential laser gyroscope is realized. The excitation electrode structure comprises two anodes and one cathode arranged on the gyroscope cavity, the two anodes are symmetrically arranged on the left and right sides of the gyroscope cavity, the cathode is arranged on the gyroscope cavity between the two anodes, and the gas gain medium between the cathode and the anode will form a gain region for generating laser oscillation. Alternatively, the excitation electrode structure comprises two cathodes and one anode arranged on the gyroscope cavity, the two cathodes are symmetrically arranged on the left and right sides of the gyroscope cavity, the anode is arranged on the gyroscope cavity between the two cathodes, and the gas gain medium between the cathode and the anode will form a gain region for generating laser oscillation. The gyroscope cavity is made of microcrystalline glass.

2. The four-frequency differential laser gyroscope dynamic dispersion balancing device according to claim 1, characterized in that, At least one mirror in the ring resonator is connected with a cavity length controller, the cavity length controller is connected with a cavity length control module, the cavity length control module outputs a voltage for controlling the displacement of the cavity length controller, and the displacement of the cavity length controller drives the corresponding mirror synchronously to adjust the cavity length of the ring resonator.

3. The four-frequency differential laser gyroscope dynamic dispersion balancing apparatus according to claim 1, characterized in that: The cavity length controller is a piezoelectric ceramic. The method comprises the following steps:

4. The four-frequency differential laser gyroscope dynamic dispersion balancing device according to claim 1 or 2 or 3, characterized in that: The gain medium coil current control module inputs a constant current to the dispersion coil, and the dispersion coil applies a constant axial magnetic field to the gas gain medium.

5. The four-frequency differential laser gyroscope dynamic dispersion balancing device according to claim 4, characterized in that: ​ 6. The four-frequency differential laser gyroscope dynamic dispersion balancing device according to claim 5, characterized in that: ​ 7. A method for dynamic dispersion balancing of a four-frequency differential laser gyroscope, implemented on the basis of the dynamic dispersion balancing device of a four-frequency differential laser gyroscope according to claim 1, characterized in that, ​ ​ The Faraday coil current control process: the Faraday coil current control module supplies controllable current with varying current size to the Faraday coil, controls the axial bias magnetic field of the Faraday chamber, changes the frequency deviation amount generated by the light beam when passing through the Faraday chamber, and makes the frequency deviation amount of the Faraday chamber equal to the Zeeman effect frequency deviation amount, so as to realize dynamic dispersion balance of the four-frequency differential laser gyroscope.

8. The four-frequency differential laser gyroscope dynamic dispersion balancing method according to claim 7, characterized in that: The fourth mirror in the four-frequency differential laser gyroscope dynamic dispersion balance device is provided with a light combining prism outside, which is used for receiving outgoing light from the fourth mirror and generating interference, and a photoelectric detector receives the output light beam of the light combining prism to detect the interference signal; a gyroscope output signal demodulation module is connected to the photoelectric detector, which is used for calculating rotation information and generating a Faraday coil current control signal; and a Faraday coil current control module is connected to the gyroscope output signal demodulation module, which dynamically adjusts the Faraday coil current under the control of the Faraday coil current control module, so as to make the frequency deviation amount of the Faraday chamber equal to the Zeeman effect frequency deviation amount, and realize dispersion balance of the four-frequency differential laser gyroscope.

9. The four-frequency differential laser gyroscope dynamic dispersion balancing method according to claim 8, characterized in that: The first mirror is connected with a cavity length controller, and the cavity length controller is connected with a cavity length control module, which outputs a voltage for controlling the displacement of the cavity length controller, and the displacement of the cavity length controller drives the first mirror synchronously, so as to adjust the cavity length of the ring resonator.

10. The four-frequency differential laser gyroscope dynamic dispersion balancing method according to claim 9, characterized in that, The Faraday coil current control process includes: Determining the optimal Faraday frequency deviation: the magnetic field strength of the Faraday chamber is adjusted by changing the current supplied to the Faraday chamber coil, and the cavity length control module outputs a periodically changing voltage to make the connected cavity length controller periodically displace, so that the cavity length of the ring resonator changes periodically. By using the sweep mode method, the relationship between the cavity length of the ring resonator and the gyroscope output signal under different Faraday frequency deviations is obtained, and the Faraday frequency deviation working point at which the frequency of the gyroscope output signal changes the least with the cavity length of the ring resonator is found, that is, the optimal Faraday frequency deviation is obtained; Stop the sweep mode, adjust the cavity length of the ring resonator until the left-handed light and right-handed light intensities of the gyroscope output are equal. During the operation of the four-frequency differential laser gyroscope, the Faraday coil current control module controls the current size supplied to the Faraday chamber coil in real time, controls the magnetic field strength of the axial bias magnetic field of the Faraday chamber, and stabilizes the Faraday frequency deviation at the optimal Faraday frequency deviation, so that the frequency deviation amount of the Faraday chamber is equal to the Zeeman effect frequency deviation amount, and dynamic dispersion balance of the four-frequency differential laser gyroscope is realized.

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