Passive laser gyroscope based on double-pass optical path and detection method

Abstract

The invention discloses a passive laser gyroscope based on a bi-pass optical path and a detection method. In the passive laser gyroscope, a frequency-stabilized laser device is used for generating frequency-locked first resonant laser; the first resonant laser is injected into the annular resonant cavity from the first cavity mirror in the clockwise direction. Transmission laser of the first resonant laser transmitted from the fourth cavity mirror is emitted to the cavity mode reflecting mirror; the cavity mode reflector is used for coupling the transmission laser into second resonant laser in a coherent mode; second resonant laser is injected into the annular resonant cavity from the fourth cavity mirror in the anticlockwise direction; the first resonant laser and the second resonant laser are emitted from the second cavity mirror after being resonated by the annular resonant cavity; the signal detection device is used for detecting beat frequency signals of the two beams of resonant laser emitted from the annular resonant cavity, determining a Sagnac phase difference, realizing a two-way propagation mode with natural coherence and overlapped common-mode paths, enhancing the spatial symmetry of forward and reverse beams, and improving the measurement sensitivity and common-mode rejection ratio capability of the beat frequency signals.

Description

Technical Field

[0001] This invention relates to the field of laser gyroscope technology, and in particular to a passive laser gyroscope and detection method based on a dual-path optical path. Background Technology

[0002] Laser gyroscopes, based on the Sagnac effect, are instruments for measuring rotational angular velocity and are widely used in inertial navigation and other fields. They are characterized by high resolution, good stability, and a wide dynamic range. Most existing gyroscopes are active laser gyroscopes, which are ring laser interferometers composed of four highly reflective cavity mirrors filled with He-Ne gas gain medium; they are themselves active ring lasers. The Sagnac effect states that in a ring resonant cavity, if the system rotates in the plane of light propagation, the actual optical path lengths of light propagating in the clockwise (CW) and counterclockwise (CCW) directions are not equal. If two beams of light propagating in opposite directions simultaneously resonate with the same longitudinal mode resonant peak of the ring resonant cavity, their resonant frequencies will differ due to the rotation; this difference is called the Sagnac frequency, i.e.: .in, Here, is the Sagnac frequency, which is the frequency difference between the resonant lasers in the clockwise and counterclockwise directions; A is the area surrounding the annular cavity. Where λ is the wavelength of the laser, and P is the circumference of the ring cavity. It is the rotational angular velocity of the ring cavity. The design concept of this active laser gyroscope is relatively simple and direct. Currently, the limiting factors mainly come from two aspects: first, it is limited by spontaneous emission noise and disturbances in the cavity medium; second, the jitter frequency shifting and other frequency shifting techniques used to overcome the frequency lock-up phenomenon of laser gyroscopes will reduce the stability of the laser gyroscope.

[0003] In passive laser gyroscopes, the laser source is located outside the ring cavity, effectively avoiding spontaneous emission noise and disturbances in the cavity medium. External modulation also effectively avoids the frequency lock-in phenomenon widely found in laser gyroscopes. Specifically, in the ring resonant cavity, two monochromatic laser beams propagate clockwise and counterclockwise towards each other around a closed-loop optical path, resonating to form a closed optical loop. The passive laser gyroscope is excited and oscillates by external laser injection into the ring resonant cavity. The frequencies of the two laser beams are locked to the resonant frequency of the ring resonant cavity; the difference between them is equal to the Sagnac frequency. The angular velocity can be measured by interferometric beat frequency signals. To achieve a highly stable operating mode, existing technologies typically employ a frequency stabilization method (Pound–Drever–Hall, PDH). This involves adding phase modulation before laser injection, using the phase difference between the non-resonant reflected light and the modulation reference signal to generate an error signal. This error signal is fed back to the laser to achieve high-precision locking between the laser frequency and the ring cavity resonant mode.

[0004] In traditional passive laser gyroscope structures, a beam from the same laser is typically split into two paths by a beam splitter, and injected into a ring resonant cavity in clockwise and counterclockwise directions, respectively. This single-pass incident structure can establish a symmetrical propagation path within the cavity and obtain a difference frequency signal through beam combining interference. However, because the two beams are injected independently, there are problems such as imperfect optical path symmetry and difficulty in canceling common-mode noise, which limits the measurement sensitivity and common-mode rejection ratio. Summary of the Invention

[0005] This invention provides a passive laser gyroscope and detection method based on a dual-path optical path, which solves the technical problems of existing passive laser gyroscopes that typically use two independent optical injection paths, resulting in imperfect optical path symmetry and difficulty in canceling common-mode noise, thus limiting measurement sensitivity and common-mode rejection ratio.

[0006] The first aspect of the present invention provides a passive laser gyroscope based on a dual-path optical path, comprising: a frequency-stabilized laser device, a ring resonant cavity, a cavity mode mirror, and a signal detection device;

[0007] The frequency-stabilized laser device is used to generate a frequency-locked first resonant laser.

[0008] The ring resonant cavity includes a first cavity mirror, a second cavity mirror, a third cavity mirror, and a fourth cavity mirror arranged in a clockwise direction.

[0009] The first resonant laser is injected into the annular resonant cavity from the first cavity mirror in a clockwise direction; the transmitted laser beam from the first resonant laser beam transmitted from the fourth cavity mirror is directed towards the cavity mode reflector.

[0010] The cavity mode reflector is used to receive the transmitted laser and coherently couple it into a second resonant laser; the second resonant laser is injected from the fourth cavity mirror into the annular resonant cavity in a counterclockwise direction;

[0011] After the first resonant laser and the second resonant laser resonate through the ring resonant cavity, they are emitted from the second cavity mirror;

[0012] The signal detection device is used to detect the laser beat frequency signal of the two resonant laser beams emitted from the ring resonant cavity; and to determine the phase difference between the first resonant laser and the second resonant laser based on the laser beat frequency signal, thereby determining the Sagnac phase difference.

[0013] Optionally, the frequency-stabilized laser device includes a laser, an electro-optic modulator, an optical isolator, and a half-wave plate;

[0014] The laser is used to excite an initial laser beam; the initial laser beam is modulated by an electro-optic modulator, and the modulated initial laser beam is sequentially adjusted by the optical isolator and the half-wave plate before being emitted onto the first cavity mirror of the annular resonant cavity.

[0015] Optionally, the frequency-stabilized laser device further includes: an initial photodetector, a signal generator, a mixer, a loop filter, and a servo amplifier;

[0016] The initial photodetector, the mixer, and the signal generator are connected in sequence; the initial photodetector is used to detect the initial laser reflected by the first cavity mirror; the mixer is used to demodulate the phase of the detected initial laser and the signal generated by the signal generator, generate an error signal, and output it to the loop filter;

[0017] The loop filter, the servo amplifier, and the laser are connected in sequence; the error signal passes through the loop filter and the servo amplifier in sequence and is output to the laser; the laser locks the frequency of the initial laser to the resonant frequency of the ring resonant cavity according to the error signal, thereby generating the frequency-locked first resonant laser.

[0018] Optionally, the signal detection device includes: a first reflector, a second reflector, a beam combiner, a first photodetector, a second photodetector, a differential amplifier, and a lock-in amplifier;

[0019] The first reflector is used to adjust the direction of the first resonant laser emitted from the second cavity mirror so that it is directed toward the beam combiner;

[0020] The second reflector is used to adjust the direction of the second resonant laser emitted from the second cavity mirror so that it is directed toward the beam combiner;

[0021] The beam combiner is used to combine the first resonant laser and the second resonant laser to obtain a first combined beam and a second combined beam, and to direct the first combined beam toward the first photodetector and the second combined beam toward the second photodetector.

[0022] The first photodetector is used to detect the first laser beat frequency signal of the first combined beam;

[0023] The second photodetector is used to detect the second laser beat frequency signal of the second combined beam;

[0024] The differential amplifier is connected to the signals of the first photodetector and the second photodetector respectively, and is used to determine the phase difference between the first resonant laser and the second resonant laser based on the first laser beat frequency signal and the second laser beat frequency signal;

[0025] The lock-in amplifier is connected to the differential amplifier and the first reflector signal respectively, and is used to adjust the position of the first reflector according to the phase difference, so that the phase difference between the first resonant laser and the second resonant laser remains constant, thereby determining the Sagnac phase difference.

[0026] Optionally, the cavity mode reflector is specifically a planar reflector with stability and subwavelength adjustment accuracy. The planar position and angle of the cavity mode reflector are precisely controlled by a fine-tuning mechanism to achieve cavity mode spatial mode matching between the second resonant laser and the annular resonant cavity and to achieve high-efficiency reinjection, thereby eliminating the need for independent frequency locking of the second resonant laser.

[0027] Optionally, the beam combiner may employ a non-polarizing beam combiner prism, a reflective beam splitter structure, or an integrated optical interference module structure.

[0028] Optionally, the photodetector may be a single detector or a quadrant differential detector.

[0029] A second aspect of the present invention also provides a detection method for a passive laser gyroscope based on a dual-path optical path, applicable to any of the passive laser gyroscopes described above, the method comprising:

[0030] A frequency-locked first resonant laser is generated by a frequency-stabilized laser device and injected into the first cavity mirror of the annular resonant cavity in a clockwise direction;

[0031] When the first resonant laser is transmitted from the fourth cavity mirror of the ring resonant cavity, the transmitted laser is coherently coupled into a second resonant laser through the cavity mode reflector, and the second resonant laser is injected into the fourth cavity mirror of the ring resonant cavity in a counterclockwise direction.

[0032] The laser beat frequency signals of the first and second resonant lasers emitted from the ring resonant cavity are detected by a signal detection device; the phase difference between the first and second resonant lasers is determined based on the laser beat frequency signals, and the Sagnac phase difference is determined.

[0033] A third aspect of the present invention also provides a computer device, including a memory, a processor, and a computer program stored in the memory, wherein the processor executes the computer program to implement the steps of the detection method as described above.

[0034] A fourth aspect of the present invention also provides a computer-readable storage medium having a computer program / instructions stored thereon, which, when executed by a processor, implements the steps of the detection method described above.

[0035] As can be seen from the above technical solutions, the present invention has the following advantages:

[0036] This invention provides a passive laser gyroscope and detection method based on a dual-path optical path. The passive laser gyroscope includes: a frequency-stabilized laser device, a ring resonant cavity, a cavity mode mirror, and a signal detection device. The frequency-stabilized laser device is used to generate a frequency-locked first resonant laser. The ring resonant cavity includes a first cavity mirror, a second cavity mirror, a third cavity mirror, and a fourth cavity mirror arranged in a clockwise direction. The first resonant laser is injected into the ring resonant cavity from the first cavity mirror in a clockwise direction. The transmitted laser from the first resonant laser through the fourth cavity mirror is directed to the cavity mode mirror. The cavity mode mirror is used to receive the transmitted laser and coherently couple it into a second resonant laser. The second resonant laser is injected into the ring resonant cavity from the fourth cavity mirror in a counterclockwise direction. After the first and second resonant lasers resonate in the ring resonant cavity, they are emitted from the second cavity mirror. The signal detection device is used to detect the laser beat frequency signal of the two resonant lasers emitted from the ring resonant cavity. The phase difference between the first and second resonant lasers is determined based on the laser beat frequency signal, and the Sagnac phase difference is determined.

[0037] This invention proposes a dual-path optical structure. By transmitting a first resonant laser from the annular resonant cavity in a clockwise direction to a cavity mode mirror, and then coupling the cavity mode mirror to form a second resonant laser which propagates back into the annular resonant cavity in a counterclockwise direction, the first and second resonant laser sources are the same, achieving a bidirectional propagation mode with natural coherence and overlapping common-mode paths. This enhances the spatial symmetry of the clockwise and counterclockwise beams, simplifies optical alignment, and improves the measurement sensitivity and common-mode rejection ratio of the beat frequency signal. This solves the technical problem that existing passive laser gyroscopes typically use two independent light injections, resulting in incomplete optical path symmetry and difficulty in canceling common-mode noise, which limits the measurement sensitivity and common-mode rejection ratio. Attached Figure Description

[0038] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0039] Figure 1 A schematic diagram of a passive laser gyroscope based on a dual-channel optical path is provided for this application;

[0040] Figure 2 A flowchart illustrating the steps of a detection method based on a dual-path passive laser gyroscope provided in this application;

[0041] The attached figures are labeled as follows:

[0042] The system includes a frequency-stabilized laser device 10, a laser 101, an electro-optic modulator 102, an optical isolator 103, a half-wave plate 104, an initial photodetector 105, a signal generator 106, a mixer 107, a loop filter 108, a servo amplifier 109, a ring resonant cavity 20, a first cavity mirror 201, a second cavity mirror 202, a third cavity mirror 203 and a fourth cavity mirror 204, a cavity mode reflector 30, a signal detection device 40, a first reflector 401, a second reflector 402, a beam combiner 403, a first photodetector 404, a second photodetector 405, a differential amplifier 406 and a lock-in amplifier 407. Detailed Implementation

[0043] This invention provides a passive laser gyroscope and detection method based on a dual-path optical path, which solves the technical problems of existing passive laser gyroscopes that typically use two independent optical injection paths, resulting in inconsistent coupling efficiency due to incomplete optical path asymmetry and difficulty in completely canceling common-mode noise, thus limiting measurement sensitivity and common-mode rejection ratio.

[0044] To make the objectives, features, and advantages of this invention more apparent and understandable, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described below are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0045] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0046] Unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0047] Please see Figure 1 (Appendix) Figure 1 In the diagram, solid lines represent optical paths and dashed lines represent circuits. The first aspect of this invention provides an embodiment of a passive laser gyroscope based on a dual-path optical path, comprising: a frequency-stabilized laser device 10, a ring resonant cavity 20, a cavity mode reflector 30, and a signal detection device 40.

[0048] Frequency-stabilized laser device 10 is used to generate a frequency-locked first resonant laser;

[0049] The ring resonant cavity 20 includes a first cavity mirror 201, a second cavity mirror 202, a third cavity mirror 203 and a fourth cavity mirror 204 arranged in a clockwise direction.

[0050] The first resonant laser is injected into the annular resonant cavity 20 from the first cavity mirror 201 in a clockwise direction; the transmitted laser transmitted from the first resonant laser through the fourth cavity mirror 204 is directed toward the cavity mode reflector 30.

[0051] The cavity mode reflector 30 is used to receive the transmitted laser and coherently couple it into a second resonant laser; the second resonant laser is injected from the fourth cavity mirror 204 into the annular resonant cavity 20 in a counterclockwise direction.

[0052] After the first and second resonant lasers resonate through the annular resonant cavity 20, they are emitted from the second cavity mirror 202.

[0053] The signal detection device 40 is used to detect the beat frequency signal of the two resonant lasers emitted from the ring resonant cavity 20; and to determine the phase difference between the first resonant laser and the second resonant laser based on the laser beat frequency signal, thereby determining the Sagnac phase difference.

[0054] It should be noted that the frequency-stabilized laser device 10 is mainly used for frequency-stabilized laser beams, wherein the frequency of the laser beam needs to be locked to the resonant frequency of the ring resonant cavity 20, so that the laser can enter the ring resonant cavity 20 and achieve transmission. The ring resonant cavity 20 includes four highly reflective cavity mirrors, namely the first cavity mirror 201, the second cavity mirror 202, the third cavity mirror 203, and the fourth cavity mirror 204; wherein the first cavity mirror 201 and the third cavity mirror 203 serve as input cavity mirrors, while the second cavity mirror 202 and the fourth cavity mirror 204 serve as output cavity mirrors, used to inject or output lasers propagating in different directions respectively.

[0055] In the laser propagation direction, the first resonant laser propagates cyclically along the first cavity mirror 201, the second cavity mirror 202, the third cavity mirror 203, the fourth cavity mirror 204, and the first cavity mirror 201 in a clockwise direction. The laser transmitted from the first resonant laser through the second cavity mirror 202 is used for subsequent beat frequency modulation, while the transmitted laser from the first resonant laser through the fourth cavity mirror 204 is coupled through the cavity mode reflector 30 to form the second resonant laser, which then enters the fourth cavity mirror 204. The second resonant laser propagates cyclically along the fourth cavity mirror 204, the third cavity mirror 203, the second cavity mirror 202, the first cavity mirror 201, and the fourth cavity mirror 204 in a counterclockwise direction. The laser transmitted from the second cavity mirror 202 is used for subsequent beat frequency modulation. Thus, the two resonant laser beams propagate in clockwise and counterclockwise directions respectively within the annular resonant cavity 20, forming a pair of common-source dual-pass laser paths. Due to the Sagnac effect, the resonant frequency matching the cavity mode shifts, resulting in a phase difference between the two resonant laser beams. The phase change that occurs when two resonant laser beams interact with a ring cavity can be detected by a signal detection device, thereby determining the Sagnac phase difference, which is used to characterize the change in angular velocity.

[0056] In this embodiment, the second resonant laser is formed by the frequency-locked first resonant laser output from the ring resonant cavity 20, and the frequency of the second resonant laser is naturally matched with that of the ring resonant cavity 20. Since the two resonant lasers originate from the same source, common-mode suppression is achieved by eliminating common-mode noise and other influencing factors. The second resonant laser is reinjected into the ring resonant cavity 20 through a high-precision cavity mode reflector 30, forming a dual-path optical path. Independent frequency locking is not required; only optical mode coupling needs to be ensured. This allows the passive laser gyroscope to operate stably and enhance common-mode suppression capabilities.

[0057] The dual-path optical design of this invention enhances the common-mode consistency and spatial symmetry of the forward and reverse beams, thereby improving the contrast and common-mode rejection capability of the beat frequency signal. The passive laser gyroscope has a compact design and simplified optical alignment, making it suitable for high-sensitivity, high-stability angular velocity measurement scenarios.

[0058] In one specific embodiment, the frequency-stabilized laser device 10 includes a laser 101, an electro-optic modulator 102, an optical isolator 103, and a half-wave plate 104.

[0059] Laser 101 is used to excite an initial laser beam; the initial laser beam is modulated by electro-optic modulator 102, and the modulated initial laser beam is successively adjusted by optical isolator 103 and half-wave plate 104 and then emitted onto the first cavity mirror 201 of the ring resonant cavity 20.

[0060] Understandably, the half-wave plate 104 is used to adjust the polarization state of the laser to ensure that the modulated laser is injected into the ring resonator 20 with the optimal polarization state, thereby achieving efficient and stable cavity mode excitation.

[0061] In one specific embodiment, the frequency-stabilized laser device 10 further includes: an initial photodetector 105, a signal generator 106, a mixer 107, a loop filter 108, and a servo amplifier 109.

[0062] An initial photodetector 105, a mixer 107, and a signal generator 106 are connected in sequence. The initial photodetector 105 is used to detect the initial laser reflected by the first cavity mirror 201. The mixer 107 is used to demodulate the phase of the detected initial laser and the signal generated by the signal generator 106, generate an error signal, and output it to the loop filter 108.

[0063] The loop filter 108, servo amplifier 109 and laser 101 are connected in sequence; the error signal passes through the loop filter 108 and servo amplifier 109 in sequence and is output to the laser 101; the laser locks the frequency of the initial laser signal to the resonant frequency of the ring resonant cavity 20 according to the error signal, thereby generating the frequency-locked first resonant laser.

[0064] Understandably, the initial laser is detected by the initial photodetector 105 and reflected by the first cavity mirror 201 to obtain the reflected light signal. The reflected light signal carries the radio frequency sideband introduced by the electro-optic phase modulator (EOM). Based on the frequency stabilization technology (Pound-Drever-Hall, PDH), the frequency detuning information in the reflected light signal is obtained by phase demodulating the reflected light signal, and an error signal is generated. Then, after being processed by the loop filter 108 and the servo amplifier 109, it is fed back to the piezoelectric ceramic of the laser 101 or other response devices such as the electro-optic modulator 102 for frequency compensation. Finally, the ordinary initial laser is locked on the ultra-stable optical cavity, thereby generating the first resonant laser that conforms to the resonant frequency of the ring resonant cavity 20.

[0065] In one specific embodiment, the signal detection device 40 includes: a first reflector 401, a second reflector 402, a beam combiner 403, a first photodetector 404, a second photodetector 405, a differential amplifier 406, and a lock-in amplifier 407.

[0066] The first reflector 401 is used to adjust the direction of the first resonant laser emitted from the second cavity mirror 202 so that it is directed toward the beam combiner 403.

[0067] The second reflector 402 is used to adjust the direction of the second resonant laser emitted from the second cavity mirror 202 so that it is directed toward the beam combiner 403.

[0068] The beam combiner 403 is used to combine the first resonant laser and the second resonant laser to obtain a first combined beam and a second combined beam, and directs the first combined beam toward the first photodetector 404 and the second combined beam toward the second photodetector 405.

[0069] The first photodetector 404 is used to detect the first laser beat frequency signal of the first combined beam;

[0070] The second photodetector 405 is used to detect the second laser beat frequency signal of the second combined beam;

[0071] The differential amplifier 406 is connected to the first photodetector 404 and the second photodetector 405 respectively, and is used to determine the phase difference between the first resonant laser and the second resonant laser based on the first laser beat frequency signal and the second laser beat frequency signal.

[0072] The lock-in amplifier 407 is signal-connected to the differential amplifier 406 and the first reflector 401 respectively, and is used to adjust the position of the first reflector 401 according to the phase difference, so that the phase difference between the first resonant laser and the second resonant laser remains constant, thereby determining the Sagnac phase difference.

[0073] It should be noted that although the first and second resonant lasers originate from the same laser frequency, due to their propagation in opposite directions within the ring resonant cavity 20, their cavity mode resonant frequencies will exhibit a slight shift due to the Sagnac effect. The two resonant lasers have a phase difference and simultaneously form a phase difference at the output end. This difference manifests as a beat frequency signal during the interference process.

[0074] Specifically, the two resonant laser beams are reflected by the first reflector 401 and the second reflector 402, respectively, and guided to the beam combiner 403 for spatial overlap and interference, resulting in a first combined beam and a second combined beam. The first combined beam is obtained by combining the transmitted light of the first resonant laser and the reflected light of the second resonant laser, and the second combined beam is obtained by combining the transmitted light of the second resonant laser and the reflected light of the first resonant laser. Since the phase changes of the two resonant laser beams, which are clockwise and counterclockwise, are different when interacting with the ring cavity, this embodiment uses one direction of the laser as a phase reference to perform phase discrimination on the other direction of the laser.

[0075] The first photodetector 404 and the second photodetector 405 respectively detect the laser beat frequency signals of the first and second resonant lasers to determine the Sagnac frequency of the passive laser gyroscope, which is used to quantitatively characterize the change in angular velocity. Since the two laser beams propagate in opposite directions, a relative optical path difference will occur when the ring cavity rotates, leading to a shift in their resonant frequency. This shift is ultimately manifested as a frequency difference in the interference signal, i.e.:

[0076]

[0077] In the formula: Let be the Sagnac frequency, representing the frequency difference between the resonant lasers in the clockwise and counterclockwise directions; A is the surrounding area of ​​the ring resonant cavity. Where λ is the wavelength of the laser, and P is the perimeter of the ring resonator. This is the rotational angular velocity of the ring resonant cavity. Therefore, after determining the Sagnac frequency, the angular velocity change of the passive laser gyroscope can be calculated based on the above formula.

[0078] The phase difference between resonant lasers in clockwise and counterclockwise directions can be expressed as:

[0079]

[0080] In the formula: The phase difference between the resonant laser beams in clockwise and counterclockwise directions; It is the speed of light.

[0081] The differential amplifier 406 determines the phase difference between the two resonant lasers based on their laser beat frequency signals. Specifically, the differential amplifier 406 determines the phase difference between the two resonant lasers based on the Sagnac frequency of their laser beat frequency signals. In this embodiment, the second resonant laser is used as a phase reference to perform phase detection on the first resonant laser. The lock-in amplifier 407 locks the phase difference between the two resonant lasers and feeds it back to the first reflector 401 in real time to adjust the position of the first reflector 401, so that the phase difference between the two resonant lasers remains constant. At this time, the phase difference signal output by the lock-in amplifier 407 is represented as the Sagnac phase difference, which is used to characterize the change in angular velocity.

[0082] In this specific embodiment, the two resonant laser beams share a common source and are formed through a dual-path optical system, exhibiting natural common-mode consistency. This significantly improves the common-mode rejection ratio (CMRR) of the passive laser gyroscope. Furthermore, due to the automatic symmetry of the optical path, it further reduces systematic errors such as temperature drift and mechanical interference, thereby contributing to improved stability and sensitivity of the beat frequency signal.

[0083] In one specific embodiment, the cavity mode reflector 30 is a planar reflector with high stability and subwavelength adjustment accuracy. The planar position and angle of the cavity mode reflector 30 are precisely controlled by a fine-tuning mechanism to achieve cavity mode spatial mode matching between the second resonant laser and the ring resonant cavity 20 and to achieve high-efficiency reinjection, thereby eliminating the need for independent frequency locking of the second resonant laser.

[0084] In one specific embodiment, the beam combiner 403 adopts a non-polarizing beam combining prism or a reflective beam splitting film structure or an integrated optical interference module structure, which can improve the stability of the passive laser gyroscope. Furthermore, adopting an integrated optical interference module structure and integrating it onto the first photodetector 404 and the second photodetector 405 can also simplify the optical path layout.

[0085] In one specific embodiment, the first photodetector 404 and the second photodetector 405 employ a single detector or a quadrant-type differential detector to further suppress interference signals introduced by the asymmetric mode. Furthermore, the signal detection device 40 can be constructed using discrete optical components or integrated using an integrated optical module or prism structure to achieve functional integration.

[0086] This invention simplifies the optical system architecture of a passive laser gyroscope based on a dual-path optical design. By re-injecting a laser beam back into the ring cavity via a mirror for reverse propagation, a bidirectional propagation mode with natural coherence and overlapping common-mode paths is achieved. This enhances the common-mode consistency and spatial symmetry of the forward and reverse beams, effectively improving common-mode suppression capability and signal sensitivity. It avoids the alignment and synchronization problems required for independent injection of two lasers. The dual-path optical design simultaneously utilizes the common-mode optical path overlap characteristic to effectively improve the beat frequency signal quality. It is suitable for high-precision measurement scenarios of weak rotational signals such as Earth's rotational angular velocity, crustal movement, and platform attitude.

[0087] Please see Figure 2 The second aspect of the present invention also provides a detection method for a passive laser gyroscope based on a dual-path optical path, applied to the aforementioned passive laser gyroscope, the method comprising:

[0088] Step 101: Generate a frequency-locked first resonant laser using a frequency-stabilized laser device and inject the first resonant laser into the first cavity mirror of the ring resonant cavity in a clockwise direction.

[0089] It should be noted that the frequency-stabilized laser device can lock the frequency of the first resonant laser injected into the ring resonant cavity to the resonant frequency of the ring resonant cavity, so that the first resonant laser can enter the ring resonant cavity and achieve transmission. In the ring resonant cavity, the first resonant laser propagates in a clockwise direction along the first cavity mirror, the second cavity mirror, the third cavity mirror, the fourth cavity mirror, and the first cavity mirror.

[0090] Step 102: When the first resonant laser is transmitted from the fourth cavity mirror of the ring resonant cavity, the transmitted laser is coherently coupled into the second resonant laser through the cavity mode reflector, and the second resonant laser is injected into the fourth cavity mirror of the ring resonant cavity in a counterclockwise direction.

[0091] It should be noted that the cavity mode mirror is used to reflect the clockwise propagating first resonant laser mode of the ring resonant cavity. After precise alignment, the cavity mode mirror couples the reflected laser back into the ring resonant cavity in a correlated manner to form the second resonant laser. In the ring resonant cavity, the second resonant laser propagates in a counterclockwise direction along the fourth cavity mirror, the third cavity mirror, the second cavity mirror, the first cavity mirror, and the fourth cavity mirror.

[0092] It is understandable that the second resonant laser is formed by the output of the first resonant laser after frequency locking from the ring resonant cavity. The frequency of the second resonant laser is naturally matched with the ring resonant cavity, and the second resonant laser does not need to be independently frequency locked, which makes the forward and reverse propagating light have higher common mode consistency and coherence.

[0093] Step 103: Detect the laser beat frequency signals of the first and second resonant lasers emitted from the ring resonant cavity using a signal detection device; determine the phase difference between the first and second resonant lasers based on the laser beat frequency signals, and determine the Sagnac phase difference.

[0094] It should be noted that although the first and second resonant lasers originate from the same laser frequency, due to the fact that the two resonant lasers propagate in opposite directions in the ring resonant cavity, their cavity mode resonant frequencies will be slightly shifted due to the Sagnac effect. The phase changes that occur when the two resonant lasers interact with the ring cavity are different, resulting in a phase difference between the two resonant lasers, which in turn forms a phase difference signal at the interference output end.

[0095] To detect this phase difference, when the first and second resonant lasers are transmitted through the second cavity mirror, the laser beat frequency signals of the first and second resonant lasers emitted from the ring resonant cavity are detected by a signal detection device. Based on the phase information extracted from the laser beat frequency signals of the two resonant lasers, and using the second resonant laser as a phase reference, the first resonant laser is phase-discriminated to form a phase difference signal. The phase difference is exactly the Sagnac phase difference. The angular velocity difference of the passive laser gyroscope is calculated, realizing high common-mode rejection ratio, high stability, and high sensitivity angular velocity measurement.

[0096] A third aspect of the present invention also provides a computer device, including a memory, a processor, and a computer program stored in the memory, wherein the processor executes the computer program to implement the steps of the detection method described above.

[0097] A fourth aspect of the present invention also provides a computer-readable storage medium having a computer program / instructions stored thereon, which, when executed by a processor, implements the steps of the detection method described above.

[0098] The above-described embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A passive laser gyroscope based on a two-pass optical path, characterized in that, The application relates to a frequency-stabilized laser device, a ring resonator, a cavity mode mirror and a signal detection device. The frequency-stabilized laser device is used for generating a first resonant laser with frequency locked. The ring resonator comprises a first cavity mirror, a second cavity mirror, a third cavity mirror and a fourth cavity mirror arranged in sequence in a clockwise direction. The first resonant laser is injected into the ring resonator from the first cavity mirror in the clockwise direction; and the transmitted laser, which is transmitted from the fourth cavity mirror, is shot to the cavity mode mirror. The cavity mode mirror is used for receiving the transmitted laser to be coupled into a second resonant laser in a coherent manner; and the second resonant laser is injected into the ring resonator from the fourth cavity mirror in an anticlockwise direction. The first resonant laser and the second resonant laser are emitted from the second cavity mirror after resonating in the ring resonator. The signal detection device is used for detecting laser beat signals of the two resonant lasers emitted from the ring resonator; and the phase difference between the first resonant laser and the second resonant laser is determined according to the laser beat signals, so as to determine a Sagnac phase difference. The frequency-stabilized laser device comprises a laser, an electro-optical modulator, an optical isolator and a half-wave plate.

2. The passive ring laser gyroscope of claim 1, wherein, The laser is used for exciting an initial laser; the initial laser is modulated by the electro-optical modulator, and the modulated initial laser is adjusted to be emitted onto the first cavity mirror of the ring resonator by the optical isolator and the half-wave plate in sequence. The frequency-stabilized laser device further comprises an initial photoelectric detector, a signal generator, a frequency mixer, a loop filter and a servo amplifier.

3. The passive ring laser gyroscope of claim 2, wherein, The initial photoelectric detector, the frequency mixer and the signal generator are connected in sequence; the initial photoelectric detector is used for detecting the initial laser reflected by the first cavity mirror; the frequency mixer is used for phase demodulating the detected initial laser and the generated signal of the signal generator, generating an error signal and outputting the error signal to the loop filter; The loop filter, the servo amplifier and the laser are connected in sequence; the error signal is output to the laser by the loop filter and the servo amplifier in sequence; and the frequency of the initial laser is locked to the resonant frequency of the ring resonator according to the error signal, so as to generate the first resonant laser with frequency locked. The signal detection device comprises a first reflector, a second reflector, a beam combiner, a first photoelectric detector, a second photoelectric detector, a differential amplifier and a phase-locked amplifier.

4. The passive ring laser gyroscope of claim 1, wherein, The first reflector is used for adjusting the direction of the first resonant laser emitted from the second cavity mirror to be shot to the beam combiner. The second reflector is used for adjusting the direction of the second resonant laser emitted from the second cavity mirror to be shot to the beam combiner. The beam combiner is used for combining the first resonant laser and the second resonant laser to obtain first combined light and second combined light, and shooting the first combined light to the first photoelectric detector and shooting the second combined light to the second photoelectric detector. The first photoelectric detector is used for detecting a first laser beat signal of the first combined light. The second photoelectric detector is used for detecting a second laser beat signal of the second combined light. ​ The differential amplifier is connected with the first photodetector and the second photodetector respectively, and is used for determining the phase difference of the first resonant laser and the second resonant laser according to the first laser beat signal and the second laser beat signal. The phase-locked amplifier is connected with the differential amplifier and the first mirror signal respectively, and is used for adjusting the position of the first mirror according to the phase difference, so that the phase difference of the first resonant laser and the second resonant laser remains constant, thereby determining the Sagnac phase difference.

5. The passive ring laser gyroscope of claim 1, wherein, The cavity mode mirror is specifically a plane mirror with stability and subwavelength adjustment precision, and the plane position and angle of the cavity mode mirror are accurately controlled by a fine adjustment mechanism, which is used for realizing the spatial mode matching of the second resonant laser and the cavity mode of the ring resonant cavity and realizing high-efficiency back injection, thereby eliminating the need for independent frequency locking of the second resonant laser.

6. The passive ring laser gyroscope of claim 4, wherein, The beam combiner adopts a non-polarization beam combiner prism or a reflective beam splitter film structure or an integrated optical interference module integrated structure.

7. The passive ring laser gyroscope of claim 4, wherein, The photodetector adopts a single detector or a quadrant differential detector.

8. A detection method of a passive laser gyroscope based on a double-pass optical path, characterized in that, The method is applied to the passive laser gyroscope as claimed in any one of claims 1-7, and the method comprises: generating a frequency-locked first resonant laser by a frequency stabilization laser device and injecting the first resonant laser into a first cavity mirror of a ring resonant cavity in a clockwise direction; when the first resonant laser is transmitted from a fourth cavity mirror of the ring resonant cavity, coupling the transmitted transmitted laser into a second resonant laser in a coherent manner by a cavity mode mirror, and injecting the second resonant laser into the fourth cavity mirror of the ring resonant cavity in a counterclockwise direction; detecting laser beat signals of the first resonant laser and the second resonant laser emitted by the ring resonant cavity by a signal detection device; determining the phase difference of the first resonant laser and the second resonant laser according to the laser beat signals, and determining the Sagnac phase difference.

9. A computer apparatus comprising a memory, a processor, and a computer program stored on the memory, wherein the computer program, when executed by the processor, causes the processor to perform the method of any one of claims 1 to 8. The processor executes the computer program to realize the steps of the detection method as claimed in claim 8.

10. A computer readable storage medium having stored thereon computer programs / instructions, characterized in that, The computer program / instruction is executed by the processor to realize the steps of the detection method as claimed in claim 8.

Images