All-solid-state active laser gyroscope and measuring method

Abstract

According to the technical scheme, a millimeter-level single non-planar annular cavity is used as a resonant cavity, and the all-solid-state active laser gyroscope has the advantages of being compact in structure, stable in structure, small in influence of external air pressure, temperature and other environmental factors and the like. Compared with the disadvantage that an existing helium-neon gas laser gyroscope is large in size and not easy to integrate, the gyroscope has the advantages that the laser crystal used by the gyroscope is only in the millimeter order, small-sized integrated assembly can be achieved, the lockout effect can be avoided without using complex technical schemes such as mechanical shaking or four-frequency differential motion, and measurement of the low rotating speed can be achieved.

Description

Technical Field

[0001] The present application relates to the technical field of laser gyroscopes, and in particular to a fully solid-state active laser gyroscope and a measurement method thereof. Background Art

[0002] Ring laser gyroscope (RLG) is the main representative of optical gyroscope. It is divided into two categories based on the working mode: active RLG and passive RLG. The core difference between the two lies in the position of the light source. The active RLG itself is a laser, usually a helium-neon gas laser. It is filled with helium-neon gas, and realizes dual-mode (or multi-mode) laser resonance output under high voltage or radio frequency excitation conditions, and finally obtains the rotation signal through the beat frequency between different modes; the light source of the passive RLG is located outside the ring resonance. After injecting laser into the high-quality ring resonator, the rotation signal is obtained by detecting the phase difference of the laser in different transmission directions.

[0003] Traditional active He-Ne RLGs have achieved great success in inertial navigation, inertial measurement, attitude and heading reference, etc. However, the gas gain medium, vacuum tube, high-voltage discharge circuit and bulky optical components they use hinder their further reduction in size, weight, power and cost. At the same time, the special structure of the resonant cavity makes the gyroscope bulky as a whole, and there are technical problems of high material and processing costs. Summary of the invention

[0004] The present application provides a fully solid-state active laser gyroscope and a measurement method, which are used to solve the technical problems that the existing laser gyroscopes are bulky as a whole due to the special structure of the resonant cavity, and have high material and processing costs.

[0005] In order to solve the above technical problems, the first aspect of the present application provides a fully solid-state active laser gyroscope, comprising: a pump laser module, a spectrometer, a signal processing module, a single non-planar annular cavity crystal, a magnet unit and a reflector, wherein the magnet unit is used to apply a directional magnetic field to the single non-planar annular cavity crystal;

[0006] The pump laser module is connected to the optical splitter through an optical path, the first branch port of the optical splitter is optically connected to the single non-planar ring cavity crystal, and the second branch port is optically connected to the signal processing module;

[0007] The laser output from the first branch port is emitted from the first plane of the single non-planar annular cavity crystal, and after being reflected inside the single non-planar annular cavity crystal, is emitted from the first plane to the reflector, so as to reflect the original path of the light output from the single non-planar annular cavity crystal through the reflector.

[0008] Preferably, the pump laser module comprises: a pump laser diode, an optical fiber and a coupling lens.

[0009] Preferably, the pump laser diode is optically connected to the coupling lens via an optical fiber, and the coupling lens is used for optical path connection to an optical path input port of the optical splitter.

[0010] Preferably, the signal processing module comprises: a photodetector and a measuring device;

[0011] The photodetector is used to receive the laser signal output from the second branch port of the optical splitter to convert the laser signal into an analog circuit signal and send the analog circuit signal to the measuring device.

[0012] Preferably, the measuring device comprises: a spectrum analyzer and a frequency counter.

[0013] Preferably, the first plane of the single non-planar annular cavity crystal serves as the incident and exit planes;

[0014] The second plane to the fourth plane are total reflection planes, which are used for forming an intra-cavity optical path and emitting from the first plane again when the laser is incident from the first plane of the single non-planar annular cavity crystal and is reflected by the three reflection planes inside the single non-planar annular cavity crystal, wherein the intra-cavity optical path is not in the same plane.

[0015] Preferably, the incident surface of the first plane is coated with a pump anti-reflection film, and the output surface is coated with a stimulated radiation high-reflection film.

[0016] The second aspect of the present application provides a laser gyro signal measurement method, which is applied to a fully solid-state active laser gyro as provided in the first aspect of the present application, comprising:

[0017] Through the signal processing module, the laser signal is collected and the corresponding analog circuit signal is obtained through photoelectric conversion;

[0018] Sending the analog circuit signal to the measuring equipment includes: a spectrum analyzer and a frequency counter;

[0019] The spectrum analyzer records the spectrum information of the analog circuit signal, and the frequency counter records the frequency information of the analog circuit signal;

[0020] Determine that the analog circuit signal contains information about the beat frequency signal through a beat frequency signal relationship model;

[0021] The gyroscope rotation data is determined according to the beat frequency signal characteristics and in combination with the relationship between the frequency change and the rotation angular velocity.

[0022] Preferably, the beat frequency signal relationship model is specifically:

[0023]

[0024] In the formula, are the light intensity in CW and CCW directions after feedback, is the light intensity in the CW and CCW directions before feedback, r is the stimulated emission ratio of the laser mode, is the intracavity loss of the modes in two directions and, is the loss introduced by self-feedback, is the CW direction frequency, is the photon flight time from the single non-planar ring cavity crystal to the reflector and then to the single non-planar ring cavity crystal, is the beat frequency signal carried on the optical path.

[0025] Preferably, the relationship between the frequency change and the rotation angular velocity is specifically:

[0026]

[0027] In the formula, represents the frequency change, is the projected area of ​​the intracavity optical loop of the single non-planar annular cavity crystal, is the circumference of the intracavity optical loop of the single non-planar annular cavity crystal, is the wavelength of light, is the rotation speed.

[0028] It can be seen from the above technical solutions that this application has the following advantages:

[0029] The technical solution provided in the present application uses a millimeter-scale single-piece non-planar annular cavity as a resonant cavity, which has the advantages of compact structure, stable structure, and little influence by external air pressure, temperature and other factors. Compared with the disadvantages of existing helium-neon gas laser gyroscopes that are large in size and difficult to integrate, the laser crystal used in this gyroscope is only on the millimeter scale, which can achieve miniaturized integrated assembly and avoid the locking effect without the use of complex technical solutions such as machine dithering or four-frequency differential, thereby achieving measurement of low rotation speeds. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0031] Figure 1 A schematic diagram of the device structure of an all-solid-state active laser gyroscope provided in this application.

[0032] Figure 2 A schematic diagram of the structure of a single non-planar annular cavity crystal in an all-solid-state active laser gyroscope provided in the present application.

[0033] Figure 3 A spectrum diagram of a bidirectional light beat signal obtained based on an all-solid-state active laser gyroscope provided in the present application.

[0034] Figure 4 The figure is a relationship diagram between gyroscope rotation speed and frequency shift obtained based on an all-solid-state active laser gyroscope provided in the present application.

[0035] Figure 5 A frequency noise diagram of a beat signal obtained based on an all-solid-state active laser gyroscope provided in the present application.

[0036] Figure 6 The Allan deviation diagram of the beat signal frequency noise obtained based on an all-solid-state active laser gyroscope provided in the present application.

[0037] Reference numerals in the figures include:

[0038] 1. Pump laser diode, 2. Optical fiber, 3. Coupling lens, 4. Spectroscope, 5. Photodetector, 6. Single non-planar ring cavity crystal, 7. Magnet unit, 8. Semiconductor refrigerator, 9. Reflector, 10. Spectrometer, 11. Frequency counter. DETAILED DESCRIPTION

[0039] The present application provides a fully solid-state active laser gyroscope and a measurement method, which are used to solve the technical problems that the existing laser gyroscopes are bulky as a whole due to the special structure of the resonant cavity, and have high material and processing costs.

[0040] In order to make the purpose, features, and advantages of the invention of this application more obvious and easy to understand, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the drawings in the embodiments of this application. Obviously, the embodiments described below are only part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0041] First, a detailed description of an embodiment of a fully solid-state active laser gyro device provided by the present application is as follows:

[0042] See also Figure 1In a first aspect, the present application provides a fully solid-state active laser gyroscope, comprising: a pump laser module, a spectrometer 4, a signal processing module, a single non-planar annular cavity crystal 6, a magnet unit 7 and a reflector, wherein the magnet unit 7 is used to apply a directional magnetic field to the single non-planar annular cavity crystal;

[0043] The pump laser module is connected to the optical splitter through an optical path, the first branch port of the optical splitter is optically connected to the single non-planar ring cavity crystal, and the second branch port is optically connected to the signal processing module, wherein the optical splitter can be a beam splitter 4;

[0044] The laser output from the first branch port is emitted from the first plane of the single non-planar annular cavity crystal, and after being reflected inside the single non-planar annular cavity crystal, is emitted from the first plane to the reflector, so as to reflect the original path of the light output from the single non-planar annular cavity crystal through the reflector.

[0045] Furthermore, the pump laser module comprises: a pump laser diode 1, an optical fiber 2 and a coupling lens 3;

[0046] The pump laser emitted by the pump laser diode 1 is optically connected to the coupling lens 3 through the optical fiber 2, and the coupling lens 3 is used for optical path connection to the optical path input port of the optical splitter.

[0047] Further, the signal processing module includes: a photoelectric detector 5 and a measuring device;

[0048] The photodetector 5 is used to receive the laser signal output from the second branch port of the optical splitter to convert the laser signal into an analog circuit signal, and send the analog circuit signal to the measuring device.

[0049] Furthermore, the measuring device includes: a spectrum analyzer 10 and a frequency counter 11 .

[0050] Further, the first plane of the single non-planar annular cavity crystal 6 serves as the incident and exit planes;

[0051] The second plane to the fourth plane are total reflection planes, which are used for forming an intra-cavity optical path and emitting from the first plane again when the laser is incident from the first plane of the single non-planar annular cavity crystal 6 and is reflected by the three reflection planes inside the single non-planar annular cavity crystal, wherein the intra-cavity optical path is not in the same plane.

[0052] Furthermore, the incident surface of the first plane is coated with a pump anti-reflection film, and the output surface is coated with a stimulated radiation light high-reflection film.

[0053] It should be noted that the specific structure of the all-solid-state active laser gyroscope provided in this embodiment is as follows: Figure 1 As shown, it includes: a pump laser diode 1, an optical fiber 2, a coupling lens 3, a beam splitter 4, a photodetector 5, a single non-planar ring cavity crystal 6, a magnet unit 7, a semiconductor refrigeration plate 8, a reflector 9, a spectrometer 10, and a frequency counter 11. The magnet unit 7 can be a permanent magnet, or it can be replaced by an electromagnetic solenoid, or by a combination of a permanent magnet and an electromagnetic solenoid. When the electromagnetic solenoid is used, a driving power supply is required to power the electromagnetic solenoid. The pump laser diode can be selected in the form of spatial light. In this case, no optical fiber is required, and the pump light can be directly injected into the single non-planar ring cavity crystal 6 through the coupling lens 3 and the beam splitter 4. The main material of the single non-planar ring cavity crystal 6 can be crystal, glass or other composite (bonded) materials. The measuring equipment includes but is not limited to the spectrometer 10 and the frequency counter 11, and other forms of devices or equipment capable of measuring the beat frequency or phase can be selected.

[0054] The implementation process of this embodiment is as follows: the pump laser diode 1 emits pump light, the wavelength parameter of the pump light is preferably 808nm, and is converged into the interior of a single non-planar annular cavity crystal 6 through a coupling lens 3. The single non-planar annular cavity crystal 6 used in this embodiment is a Nd:YAG crystal, which can also be replaced by neodymium-doped glass, erbium-doped crystal or glass, thulium-doped crystal or glass or other composite crystals or glass materials, etc. The temperature of the single non-planar annular cavity crystal 6 is controlled by a semiconductor refrigeration plate 8. The non-planar annular cavity crystal generates unstable bidirectional stimulated radiation light (clockwise CW and counterclockwise CCW directions) under the magnetic field of the magnet unit 7. At this time, the counterclockwise (CCW) stimulated radiation light is reflected back into the cavity through a reflector 9, so that the bidirectional light output can be stable. According to the intrinsic polarization theory of the non-planar annular cavity, the modes of the two beams of light are not degenerate, and the frequency difference is related to the strength of the external magnetic field, usually hundreds of KHz to several MHz, which is reflected in the photodetector 5 as a beat frequency signal of hundreds of KHz to several MHz. Since the annular optical path inside the crystal is closed, the stimulated radiation light inside the crystal follows the Sagnac effect. When the device rotates, the beat frequency signal will move accordingly, and the frequency shift is linearly related to the angular velocity of rotation. Based on this property, it can be used as a laser gyroscope.

[0055] The working principle of a single non-planar ring cavity crystal is as follows: the non-planar ring cavity is a single-piece structure integrating a laser crystal and a non-planar ring cavity, such as Figure 2As shown, the first plane A is the incident and exit plane, coated with a pump light anti-reflection film and a stimulated radiation light high-reflection film, the second plane B, the third plane C and the fourth plane D are all total reflection planes, and ABCD is the optical path in the cavity. A non-planar ring cavity specifically refers to the ABCD optical paths not being in the same plane. According to the intrinsic polarization theory of a non-planar ring cavity, when the pump light passes through a coupling lens and enters the crystal, it is absorbed by the cavity and converted into the gain of stimulated radiation light, and four resonant mode light beams are generated; and light beams in different resonant modes have different losses and different frequency splittings (compared to the four times degenerate frequency). Under a certain magnetic field environment, the two clockwise (CW) and counterclockwise (CCW) light beams with the smallest loss difference resonate, and the two resonant light beams have a specific frequency splitting amount under the corresponding magnetic field. Then through Figure 1 The self-feedback interference phenomenon introduced by the middle reflector 9 causes the CW photons and CCW photons to couple, and a beat signal relationship model as shown below is obtained. Since the laser gyro of this embodiment uses the principle of self-feedback interference measurement, clockwise and counterclockwise photons are coupled in the cavity and carry each other's information, so only single-channel measurement is required without beam combining to achieve the extraction of the beat signal.

[0056] The beat frequency signal relationship model is specifically:

[0057]

[0058] In the formula, are the light intensity in CW and CCW directions after feedback, is the light intensity in the CW and CCW directions before feedback, r is the stimulated emission ratio of the laser mode, is the intracavity loss of the modes in two directions and, is the loss introduced by self-feedback, is the CW direction frequency, is the photon flight time from the single non-planar ring cavity crystal to the reflector and then to the single non-planar ring cavity crystal, is the beat frequency signal carried on the optical path.

[0059] From the beat frequency signal relationship model formula, it can be seen that the two optical paths each carry beat frequency information, thus having the characteristics of extracting beat frequency signals by single-path measurement (measuring a single CW or CCW without combining the two beams). At this time, the typical morphology of the beat frequency signal is as follows: Figure 3 shown.

[0060] Since the optical path of the non-planar ring cavity is as follows Figure 2 For the closed circular optical path shown, the formula for frequency change and angular velocity derived from the Sagnac effect is:

[0061]

[0062] In the formula, represents the frequency change, is the projected area of ​​the intracavity optical loop of the single non-planar annular cavity crystal, is the circumference of the intracavity optical loop of the single non-planar annular cavity crystal, is the wavelength of light, is the rotation speed. According to the Sagnac principle, the relationship between the frequency shift and the rotation speed of the gyroscope is measured as shown in the figure below: Figure 4 As shown in the figure, the scattered points are the speed measurement values, and the solid line is the fitted straight line. It can be seen that the measurement values ​​have a strong linear relationship. To further demonstrate the gyro performance, the frequency noise of the gyro beat signal is shown as follows Figure 5 As shown, Figure 5 The corresponding Allan deviation is Figure 6 As shown, from Figure 6 It can be seen from the Allan deviation in the figure that the bias instability (BI) of the laser gyro provided in this embodiment is , the angular random walk (ARW) is .

[0063] In the description of the present application, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present application. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0064] Unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0065] As described above, the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A fully solid-state active laser gyroscope, characterized in that: include: A pump laser module, a spectrometer, a signal processing module, a single non-planar annular cavity crystal, a magnet unit and a reflector, wherein the magnet unit is used to apply a directional magnetic field to the single non-planar annular cavity crystal; The pump laser module is connected to the optical splitter through an optical path, the first branch port of the optical splitter is optically connected to the single non-planar ring cavity crystal, and the second branch port is optically connected to the signal processing module; The laser output from the first branch port is emitted from the first plane of the single non-planar annular cavity crystal, and after being reflected inside the single non-planar annular cavity crystal, is emitted from the first plane to the reflector, so as to reflect the original path of the light output from the single non-planar annular cavity crystal through the reflector.

2. The all-solid-state active laser gyroscope according to claim 1, characterized in that: The pump laser module comprises: a pump laser diode, an optical fiber and a coupling lens.

3. The all-solid-state active laser gyroscope according to claim 2, characterized in that: The pump laser diode is optically connected to the coupling lens via an optical fiber, and the coupling lens is used for optical path connection to the optical path input port of the optical splitter.

4. The all-solid-state active laser gyroscope according to claim 1, characterized in that: The signal processing module includes: a photoelectric detector and a measuring device; The photodetector is used to receive the laser signal output from the second branch port of the optical splitter to convert the laser signal into an analog circuit signal and send the analog circuit signal to the measuring device.

5. The all-solid-state active laser gyroscope according to claim 4, characterized in that: The measuring device comprises: a spectrum analyzer and a frequency counter.

6. The all-solid-state active laser gyroscope according to claim 1, characterized in that: The first plane of the single non-planar annular cavity crystal serves as the incident and exit planes; The second plane to the fourth plane are total reflection planes, which are used for forming an intra-cavity optical path and emitting from the first plane again when the laser is incident from the first plane of the single non-planar annular cavity crystal and is reflected by the three reflection planes inside the single non-planar annular cavity crystal, wherein the intra-cavity optical path is not in the same plane.

7. The all-solid-state active laser gyroscope according to claim 6, characterized in that: The incident surface of the first plane is coated with a pump anti-reflection film, and the output surface is coated with a stimulated radiation light high reflection film.

8. A laser gyro signal measurement method, applied to a fully solid-state active laser gyro as claimed in any one of claims 1 to 7, characterized in that: include: Through the signal processing module, the laser signal is collected and the corresponding analog circuit signal is obtained through photoelectric conversion; Sending the analog circuit signal to the measuring equipment includes: a spectrum analyzer and a frequency counter; The spectrum analyzer records the spectrum information of the analog circuit signal, and the frequency counter records the frequency information of the analog circuit signal; Determine that the analog circuit signal contains information about the beat frequency signal through a beat frequency signal relationship model; The gyroscope rotation data is determined according to the beat frequency signal characteristics and in combination with the relationship between the frequency change and the rotation angular velocity.

9. A laser gyro signal measurement method according to claim 8, characterized in that: The beat frequency signal relationship model is specifically: In the formula, are the light intensity in CW and CCW directions after feedback, is the light intensity in the CW and CCW directions before feedback, r is the stimulated emission ratio of the laser mode, is the intracavity loss of the modes in two directions and, is the loss introduced by self-feedback, is the CW direction frequency, is the photon flight time from the single non-planar ring cavity crystal to the reflector and then to the single non-planar ring cavity crystal, is the beat frequency signal carried on the optical path.

10. The laser gyro signal measurement method according to claim 8, characterized in that: The relationship between the frequency change and the rotation angular velocity is specifically: In the formula, represents the frequency change, is the projected area of ​​the intracavity optical loop of the single non-planar annular cavity crystal, is the circumference of the intracavity optical loop of the single non-planar annular cavity crystal, is the wavelength of light, is the rotation speed.

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