A control method and system for improving the accuracy of laser gyroscopes

Abstract

This invention proposes a control system for improving the accuracy of a laser gyroscope, comprising: a first phototube (1) that receives a clockwise or counterclockwise beam from the laser gyroscope and converts the optical signal into a first electrical signal, the first electrical signal containing backscattered light intensity information; a second phototube (2) that receives a beat frequency optical signal resulting from the interference of clockwise and counterclockwise light from the laser gyroscope and converts this beat frequency optical signal into a second electrical signal; a computing device that coherently demodulates the AC component in the first electrical signal and one AC component in the second electrical signal to obtain information on the backscattering amplitude; and a PZT driving circuit that drives the displacement of the reflector of the laser gyroscope to minimize the backscattering amplitude. This invention also proposes a corresponding control method for backscattering in a laser gyroscope. This invention can effectively reduce the impact of backscattering on the laser gyroscope, improve the zero-bias stability and repeatability of the laser gyroscope, and reduce hardware overhead.

Description

Technical Field

[0001] This invention relates to error elimination technology for laser gyroscopes, and more specifically, to a control method and system for improving the accuracy of laser gyroscopes. Background Technology

[0002] Laser gyroscopes are sensors used to measure the angular rate of moving bodies and are one of the commonly used sensor types in modern inertial navigation technology. Commonly used laser gyroscope resonant cavities are quadrilateral or triangular in shape, with corresponding resonant cavity mirrors of 4 or 3.

[0003] Laser gyroscopes exhibit a "lock-in region," also known as the "lock-in effect," during operation. Backscattering is the primary cause of this lock-in region, and reducing its impact is crucial for improving the accuracy and lifespan of laser gyroscopes. Backscattering mainly originates from the polishing condition of the mirror surface, scattering by optical components, and scattering and absorption by gas dust.

[0004] The mechanism by which backscattering affects the locking of a laser gyroscope is as follows: the backscattered light from the mirror and the two clockwise and counterclockwise beams that should propagate independently within the ring resonator produce a certain degree of coupling effect, causing these four beams (the two original clockwise and counterclockwise beams in the resonator cavity, and the backscattered light in both directions, totaling four beams) to synchronize their frequencies to a certain extent, thus causing locking.

[0005] In order to reduce the impact of the lock zone on the laser gyroscope, the main methods adopted at home and abroad are: (1) improving the coating level and reducing the loss of the mirror; (2) adopting a small jitter frequency offset working mode for the gyroscope; (3) adopting four-frequency differential technology; (4) optimizing the design and control of the laser gyroscope's control method and signal processing method.

[0006] In fact, after adding jitter frequency offset measures, the laser gyroscope still needs to control the locking region by controlling the backscatter magnitude, so that the locking threshold is stable or extremely small, further reducing the impact of the locking region, and thus improving the performance of the laser gyroscope.

[0007] The signal output from the phototube used to detect the clockwise (CW) and counterclockwise (CCW) beams of a laser gyroscope includes a portion representing the backscattering signal within the gyroscope. This backscattering comprises light scattering from the mirror, the capillary aperture of the resonant cavity, and the aperture. This scattering enters the CW and CCW beams and couples with them, creating a locked region. Through proper cavity tuning, resonant cavity design, and the fabrication of the capillary aperture and aperture, the scattering in the capillary aperture and on the aperture can be reduced. After optimizing these parameters, backscattering is primarily caused by the surface condition of the mirror.

[0008] Since backscattering is the main cause of region locking in laser gyroscopes, the region locking can be controlled by adjusting the amount of backscattering on the reflector, keeping the lock-up threshold stable or minimal. The task of region locking control is to minimize the backscattering signal from the reflector within a specified temperature range. Traditional region locking control systems utilize the AC components of two DC phototubes. The optical signals from the two phototubes are converted into voltage signals by preamplifiers. These two signals are then sent to a coherent demodulator to demodulate the signal carrying backscattering information. After passing through a low-pass filter, the signal is converted into a DC amplitude related to the backscattering signal. This DC amplitude is then sent to an A / D converter via an analog switch. The A / D converter converts the signal into digital form, which is then sent to the computing device. In the computing device, the main control program, based on the amplitude information of the backscattering signal, sends an adjustment signal through the D / A converter. This signal is amplified and drives the actuator PZT of the system. The reflector, fixed to the PZT, moves according to the command, achieving the purpose of region locking control.

[0009] Traditional methods use no fewer than three phototubes, resulting in significant hardware overhead, complex algorithms, and incompatibility with most existing gyroscope hardware solutions in China. Summary of the Invention

[0010] To address the aforementioned technical problems, this invention proposes a control system for improving the accuracy of a laser gyroscope, comprising: a first phototube, which is a single-quadrant phototube, receiving a clockwise or counterclockwise beam from the laser gyroscope and converting the clockwise or counterclockwise emitted light signal into a first electrical signal, the first electrical signal containing backscattered light intensity information; a second phototube, which is a dual-quadrant phototube, receiving a beat frequency light signal resulting from the interference of clockwise and counterclockwise light from the laser gyroscope and converting this beat frequency light signal into a second electrical signal; a computing device, which receives the first electrical signal and the second signal, and performs coherent demodulation on the AC component in the first electrical signal and one AC component in the second electrical signal to obtain backscattering amplitude information; and a PZT driving circuit, which drives the displacement direction of the laser gyroscope's mirror to minimize the backscattering amplitude.

[0011] Preferably, the computing device determines the coherent demodulation result based on the periodic relationship between the cavity length and light intensity of the laser gyroscope while keeping the cavity length of the laser gyroscope constant. The minimum value of R, where R 10 I is the backscattering coefficient. 10 I 20 β1 represents the light intensity amplitude of clockwise or counterclockwise light, β2 represents the phase of the backscattered light in the light signal received in that direction, and the PZT driving circuit drives the displacement direction and distance of the reflector of the laser gyroscope so that the result of coherent demodulation reaches the minimum value.

[0012] Preferably, the computing device performs low-pass filtering on the first electrical signal to obtain a sinusoidal modulation voltage, which is then applied to the PZT driving circuit of the laser gyroscope, so that the laser gyroscope operates at a stable frequency point.

[0013] Preferably, the computing device includes a high-pass filter and a low-pass filter, wherein the first electrical signal is passed through the high-pass filter to obtain the AC component, the first electrical signal is passed through the low-pass filter to obtain the DC component, and the coherently demodulated signal and the DC component are applied to the PZT driving circuit so that the laser gyroscope operates at a stable frequency point.

[0014] Preferably, the displacement of the reflector includes: reflection angle; simultaneously moving closer to the center of the laser gyroscope; simultaneously moving away from the center of the laser gyroscope; one moving closer to the center of the laser gyroscope and the other moving away from the center of the laser gyroscope.

[0015] Preferably, while keeping the cavity length constant, the PZT control circuit adjusts the position of the reflector according to the backscattering amplitude information, and the computing device detects the light intensity signal and backscattering amplitude until the light intensity signal reaches its maximum value and the backscattering amplitude is at its minimum.

[0016] This invention proposes a control method to improve the accuracy of a laser gyroscope, comprising: receiving clockwise or counterclockwise light from the laser gyroscope through a single-quadrant phototube and converting the optical signal into a first electrical signal; receiving a beat frequency optical signal resulting from the interference of clockwise and counterclockwise light from the laser gyroscope through a dual-quadrant phototube and converting this beat frequency optical signal into a second electrical signal; performing coherent demodulation on the AC signal in the first electrical signal and one AC component in the second electrical signal to obtain backscattering amplitude information; and driving the displacement direction of the reflector of the laser gyroscope to minimize the backscattering amplitude.

[0017] Preferably, while keeping the cavity length of the laser gyroscope constant, the result of coherent demodulation is determined based on the periodic relationship between the cavity length and the light intensity of the laser gyroscope. The minimum value of R, where R 10 I is the backscattering coefficient. 10 I 20 β1 represents the light intensity amplitude of clockwise or counterclockwise light, and β2 represents the phase of the backscattered light in the light signal received in that direction; the displacement direction and distance of the multiple mirrors of the laser gyroscope are driven by the minimum value.

[0018] Preferably, a sinusoidal modulation voltage is obtained by low-pass filtering the first electrical signal and applied to the PZT driving circuit of the laser gyroscope, so that the laser gyroscope operates at a stable frequency point; and the light intensity signal and backscatter amplitude are detected until the light intensity signal reaches its maximum value and the backscatter amplitude is at its minimum.

[0019] Preferably, the displacement of the reflector includes: the reflection angle of the reflector; simultaneously moving closer to the center of the laser gyroscope; simultaneously moving away from the center of the laser gyroscope; one moving closer to the center of the laser gyroscope and the other moving away from the center of the laser gyroscope.

[0020] The beneficial effects of this invention include: using only one single-quadrant phototube and one dual-quadrant phototube to output signals during the control process, and using coherent demodulation to calculate backscatter, eliminating the previous hardware requirement of needing two single-quadrant phototubes to simultaneously detect both CW and CCW beams for backscatter calculation. This results in good hardware compatibility, reduced hardware overhead, and effectively reduced impact of backscatter on the laser gyroscope, significantly improving the zero-bias stability and repeatability of the laser gyroscope. Attached Figure Description

[0021] To facilitate understanding of the invention, it will be described in more detail with reference to the specific embodiments shown in the accompanying drawings. These drawings depict only typical embodiments of the invention and should not be considered as limiting the scope of protection of the invention.

[0022] Figure 1 This is a schematic diagram of the laser gyroscope structure and the positions of some components of the present invention.

[0023] Figure 2 This is a schematic diagram of the system of the present invention.

[0024] Figure 3 This diagram illustrates the photoelectric signal conversion process of the single-quadrant phototube of the present invention.

[0025] Figure 4 This is a partially enlarged view of the dual-quadrant phototube of the present invention.

[0026] Figure 5 This diagram illustrates the photoelectric signal conversion process of the dual-quadrant phototube of the present invention.

[0027] Figure 6 This is a schematic diagram illustrating the processing principle of the computing device of the present invention.

[0028] Figure 7 This is the curve showing the relationship between light intensity and the length of the laser gyroscope resonant cavity.

[0029] Figure 8 This is the scanning curve of the laser gyroscope.

[0030] Figure 9 and Figure 10 The backscattering and frequency-stabilized voltage relationship curves obtained for two gyroscopes using the method of this invention.

[0031] Figure 11 This is a schematic diagram illustrating the motion direction of the PZT under frequency stabilization control and backscattering control.

[0032] Figure 12This is a flowchart of one embodiment of the method of the present invention.

[0033] Figure Labels

[0034] 1-First phototube; 2-Second phototube; 3-First piezoelectric ceramic; 4-Second piezoelectric ceramic; 5-Reflector; 5-1 Right reflector; 5-2 Left reflector; 6-Light; 7-Optical signal converted into electrical signal. Detailed Implementation

[0035] Embodiments of the present invention are described below with reference to the accompanying drawings, wherein like parts are indicated by like reference numerals. Unless otherwise specified, the following embodiments and technical features described herein can be combined with each other.

[0036] like Figure 1-2 As shown, the system of the present invention includes: a first phototube 1 and a second phototube 2, a computing device, and a PZT driving circuit.

[0037] The first phototube 1 is installed downstream of the first reflecting mirror of the laser gyroscope, receiving clockwise or counterclockwise light 6 (CW light or CCW light, see...). Figure 3-4 The second phototube 2 is installed downstream of the second reflector of the laser gyroscope. It receives the beat frequency stripe signals generated by the clockwise and counterclockwise light beams and converts the beat frequency light signals into electrical signals (the first electrical signal). Figure 5 Preferably, the first phototube 1 is a single-quadrant phototube, and the second phototube 2 is a dual-quadrant phototube, or vice versa. Then, the two electrical signals are input to the computing device. The computing device includes a coherent demodulator that receives the first electrical signal and the second electrical signal, and performs coherent demodulation on the first electrical signal and the second electrical signal to obtain backscattering amplitude information.

[0038] The intensity I1 (CW or CCW) of the backscattered light received by the first phototube 1 can be expressed as:

[0039]

[0040] Among them, I 10 I 20 The amplitudes of CW and CCW light, respectively, R 10 is the backscattering coefficient, which is proportional to the intensity of the backscattered light to be obtained, and f1 and f2 are the frequencies of the clockwise and counterclockwise light, respectively. and β1 represents the phase of the clockwise and counterclockwise light, respectively, and β2 represents the phase of the backscattered light in the optical signal received in this direction.

[0041] The formula for the normal beat frequency of a laser gyroscope:

[0042]

[0043]

[0044] I Asin and I Bsin These are the beat frequency light signals received in each quadrant of the dual-quadrant phototube in the second phototube 2.

[0045] The AC component in this signal is:

[0046]

[0047]

[0048] After high-pass filtering the optical signal from formula (1), the AC component is obtained, and the AC signal in the first phototube 1 is:

[0049]

[0050] Among them, I 10 I 20 The amplitudes of CW and CCW light, respectively, R 10 Let f1 and f2 be the backscattering coefficients, and f1 and f2 be the frequencies of the clockwise and counterclockwise light, respectively. and β1 represents the phase of the clockwise and counterclockwise light, respectively, and β2 represents the phase of the backscattered light in the optical signal received in this direction.

[0051] Coherent demodulation of the signals from formulas (6) and (4 / 5) yields the backscattering coefficient. During demodulation, only one AC component from the second phototube 2 is used in coherent demodulation with the AC signal from the first phototube 1 to obtain R. 10 The value of R. This AC signal carries backscattered light information. 10 The backscattered signal is extremely small, making it difficult to extract the effective backscattered signal from the noise using conventional detection methods. Therefore, coherent demodulation with one AC signal from the second phototube 2 is performed. Only the coherent portion will have an output, which can significantly improve the signal-to-noise ratio. The output of the coherent demodulation is:

[0052]

[0053] The result of coherent demodulation shown in formula (7) is proportional to the magnitude of the backscattering of the laser gyroscope.

[0054] Figure 6The diagram illustrates the principle of coherent demodulation performed by the computing device. After acquiring (through a signal acquisition device) the first and second electrical signals, the computing device passes the first electrical signal through a high-pass filter (HPF) and a low-pass filter (LPF) to extract the AC and DC components of the first electrical signal, respectively. Multiplying the AC component of the first electrical signal by the second electrical signal and calculating its effective value yields the backscattering coefficient R. 10 .

[0055] Specifically, the computing device includes: a first signal acquisition unit connected to the first phototube 1 to obtain the first electrical signal; a second signal acquisition unit connected to the second phototube 2 to obtain the second electrical signal; a high-pass filter connected to the first signal acquisition unit to obtain the AC component of the first electrical signal; a low-pass filter connected to the first signal acquisition unit to obtain the DC component of the first electrical signal; a calculator connected to the high-pass filter and the second signal acquisition unit for correlation demodulation, the output of the calculator being connected to the PID controller; and a PID controller receiving the output of the calculator, the output of the PID controller being connected to the PZT drive circuit.

[0056] Based on the obtained backscattered light amplitude information and frequency stabilization control information, the computing device performs PID calculations and adjusts the corresponding D / A output. The D / A output, after amplification, drives the control voltage of the corresponding PZT drive circuit on the periphery of the laser gyroscope. While maintaining a constant cavity length, the positions of the right reflector 5-1 and the left reflector 5-2 in reflector 5 are adjusted (the reflector positions of the laser gyroscope are moved according to the obtained backscattered amplitude information) to ensure that the CW and CCW light intensity signals reach their maximum values ​​while the backscattered light amplitude is minimized (e.g., ...). Figure 7 As shown, the laser gyroscope is operated near point D to achieve backscatter control. Specifically, when the first piezoelectric ceramic 3 and the second piezoelectric ceramic 4 of the laser gyroscope are pushed or pulled, the R of the backscattered light... 10 The wavelength changes periodically, with a period equal to twice the wavelength. Control is achieved by pushing and pulling the right reflector 5-1 at the first piezoelectric ceramic 3 and the left reflector 5-2 at the second piezoelectric ceramic 4 to detect when the above formula (Equation 7) reaches its minimum value, thereby achieving the purpose of zone locking control. Preferably, a preamplifier is installed downstream of the first phototube 1 and the second phototube 2 in the optical path, and the electrical signal is amplified before being input to the computing device.

[0057] The PZT driving circuit precisely controls the control voltage applied to the first piezoelectric ceramic 3 and the second piezoelectric ceramic 4 of the laser gyroscope based on the results of coherent demodulation. This effectively reduces the impact of backscattering on the laser gyroscope and improves its zero-bias stability. The backscattering control principle is as follows: The PZT driving circuit has two inputs and two outputs. The two inputs are the PZT control voltage output from the computing device. The PZT driving circuit outputs two proportionally amplified PZT control driving voltages, which are applied to the first piezoelectric ceramic 3 and the second piezoelectric ceramic 4 of the laser gyroscope, respectively, controlling the piezoelectric ceramics to drive the reflector to produce displacement. The control voltage changes according to the magnitude of backscattering from the laser gyroscope. Therefore, after coherent demodulation, the PZT driving circuit can achieve both region locking control and frequency stabilization based on the output of the coherent demodulation and photoelectric signals.

[0058] The lock-in control of a laser gyroscope minimizes the backscattering signal from the mirror within a specified temperature range. In lock-in control, a two-stage differential amplification suppresses the DC light intensity signal, extracting only the AC component reflecting the magnitude of the backscattering signal and amplifying it to the required level. This level is multiplied by a second electrical signal to obtain the backscattering coefficient. Simultaneously, the obtained first electrical signal is passed through a low-pass filter to obtain an accurate light intensity signal. After processing by a frequency stabilization program and a lock-in control program, the light intensity signal is converted from a D / A converter to an analog voltage signal and amplified to drive the actuator PZT of the system. The mirror, fixed to the PZT, moves according to commands, achieving optimal frequency stabilization and lock-in control.

[0059] The frequency stabilization control of a laser gyroscope involves taking the highest operating point at the center of the sweep curve within a specified temperature range and keeping the operating point near the center of the curve to ensure that the cavity length of the laser gyroscope remains stable.

[0060] Therefore, the backscattering control system must simultaneously meet two basic requirements: (1) the total optical path of the loop remains stable; (2) the total energy coupling caused by the backscattering wave from the mirror is minimized, that is, the backscattering amplitude is minimized.

[0061] In frequency stabilization control, the backscattering AC component and noise in the optical signal are suppressed after the signal passes through a low-pass filter, and the filtered DC component is calculated. In the frequency stabilization (cavity length control) system of the laser gyroscope, the classic small jitter control method is used. The small jitter control process involves superimposing a small sinusoidal modulation voltage onto the PZT driving voltage. The modulated voltage causes a periodic change in the cavity length of the resonant cavity, and simultaneously causes a corresponding change in the longitudinal mode frequency of the resonant cavity, thereby modulating the output light intensity signal.

[0062] In fact, the laser gyroscope achieves its strongest light intensity when it is at a certain longitudinal mode frequency, satisfying the standing wave condition. Figure 7As shown, each maximum light intensity point (longitudinal mode) corresponds to a cavity length (frequency). Therefore, in practical applications, by detecting the output light intensity signal of the laser gyroscope as a feedback control signal and stabilizing the cavity length at the required value, the laser frequency can be stabilized at a certain longitudinal mode. By scanning the modes, the PZT driving voltage value when the DC component of the light intensity modulation signal is at its maximum value can be obtained. Figure 8 This is the pattern sweep curve of a certain type of laser gyroscope, with a sweep drive voltage range of 50–250V. From... Figure 8 As can be seen, there are a total of 6 longitudinal modes within the driving voltage range of 50 to 250V; the light intensity curves have good symmetry and consistent repeatability, and can be used as a reference for cavity length control.

[0063] After determining the stable operating point (6 longitudinal modes) of the laser gyroscope, it is necessary to further determine the optimal operating point for the lock-in control. This is because in the cavity length control of the laser gyroscope, using only the DC component of the CW / CCW intensity modulation signal as the feedback signal for the control system will reduce the accuracy of the control system. That is, when only considering stable frequency control, to ensure the cavity length of the laser gyroscope remains constant, mirrors 5-1 and 5-2 can be controlled to move forward or backward by the same distance simultaneously, or they can be controlled to move in opposite phases, one forward and one backward; therefore, the control method is not unique.

[0064] Therefore, preferably, the laser gyroscope needs to simultaneously optimize frequency stabilization control and zone locking control during operation. Backscattering amplitude is incorporated as an optimization parameter, such as... Figure 9 and Figure 10 As shown, the backscattering amplitude of the two laser gyroscopes varies periodically with the frequency stabilization voltage of the PZT driving circuit, and the period is twice that of the mode sweeping program. To ensure that the cavity length of the laser gyroscope remains constant and the backscattering amplitude is minimized, the frequency stabilization voltage of the PZT driving circuit can be uniquely determined. Figure 7 Point D can uniquely determine the direction and distance of the mirror's movement by controlling the cavity length.

[0065] The clockwise and counterclockwise light beams CW and CCW running within the resonant cavity are amplified into I1 and I2 by reflectors 1 and 2 connected at phototubes 1 and 2. Simultaneously, CW and CCW are converted into beat frequency signals by the reflectors, beam combining prisms, and phototubes mounted on them, and then converted into electrical signals. The first and second electrical signals are coherently demodulated to obtain backscattering amplitude information. The result of the coherent demodulation algorithm is proportional to the magnitude of the backscattering of the laser gyroscope. This result is input to the computing device via A / D sampling. The computing device adjusts the corresponding D / A output according to the obtained backscattering light magnitude, and then outputs the D / A output again. After amplification, the output drives the corresponding PZT driving voltage around the laser gyroscope. The voltage signal obtained after modulation and demodulation is applied as a feedback control signal to the cavity length control reflector. The driving voltages of the two reflectors are 180° out of phase and their displacement directions are opposite, so as to perform area locking control without affecting the cavity length control loop and maintain a constant cavity length. While keeping the cavity length constant, adjust the positions of the two mirrors, right mirror 5-1 and left mirror 5-2, in mirror 5 (controlling the mirror position of the laser gyroscope to move according to the obtained backscatter amplitude information) until the amplitude of the obtained backscattered light is minimized, and make the laser gyroscope work near this minimum value.

[0066] Reference Figure 1 , Figure 7 and Figure 8 The purpose of frequency stabilization is to maintain a constant total cavity length during the operation of the laser gyroscope, meaning the gyroscope always operates on the same longitudinal mode. In laser gyroscope circuits without backscattering control, the PZT device only performs frequency stabilization. During actual operation, the relationship between the DC component of the optical signal received by the first phototube and the cavity length is as follows: Figure 7 As shown in curve a, the first phototube in the frequency stabilization loop controls the PZT voltage by collecting DC light intensity information, ensuring that the DC light intensity collected by the first phototube is always near a certain maximum value (points A, B, C, and D) in curve a. This corresponds to the gyroscope cavity length always being a certain integer multiple of the wavelength. For a quadrilateral gyroscope with two adjustable PZT devices, when only the frequency stabilization control closed loop is used, the two PZT piezoelectric ceramics can share the same control terminal, that is, simultaneously move towards or away from the center of the gyroscope to adjust the cavity length.

[0067] For a circuit that needs to achieve both frequency stabilization and backscattering, in addition to referring to the relationship between the light intensity received by the first phototube and the cavity length in curve a, it is also necessary to refer to the relationship between the backscattering magnitude and the cavity length obtained after coherent demodulation of the AC signals from the first and second phototubes in curve b. As can be seen from curve b, backscattering is also a periodic signal related to the cavity length, with a period twice that of the DC light intensity signal. Therefore, there are several cavity length values ​​that satisfy both the maximum DC light intensity in curve a and the minimum backscattering value in curve b. That is, at these positions (point D), the laser gyroscope can achieve both frequency stabilization and backscattering control. In this case, the two PZT piezoelectric ceramics usually have independent control terminals. During actual operation, one of the two PZTs may move towards the center of the gyroscope, while the other moves away from the center (e.g., ...). Figure 11 In this way, the total cavity length remains unchanged (frequency stabilization function is normal), while the magnitude of backscattering is determined by the relative positions of the two PZTs. It is always possible to find a position with minimal backscattering while keeping the total cavity length constant. Figure 7 (Point D), thereby achieving backscatter control.

[0068] In summary, this invention uses one single-quadrant phototube and one double-quadrant phototube to output voltage signals to achieve the pushing and pulling of two reflectors (left and right reflectors); thus, by changing the control voltage of the first piezoelectric ceramic 3 and the second piezoelectric ceramic 4, the position of the reflectors in the frequency-stabilized resonant cavity can be adjusted to change the shape of the resonant cavity.

[0069] The system of this invention uses one single-quadrant phototube and one dual-quadrant phototube, along with a coherent demodulation algorithm. This eliminates the hardware requirement of simultaneously detecting two light signals, CW and CCW, in the prior art for calculating backscattered light and obtaining gyroscope rotation speed information. This requires two single-quadrant phototubes and one dual-quadrant phototube, resulting in better hardware compatibility, reduced hardware overhead, and significantly improved zero-bias stability and repeatability of the laser gyroscope.

[0070] According to another aspect of the invention, such as Figure 12 As shown, a control method for a laser gyroscope is proposed, including:

[0071] S1 receives the clockwise or counterclockwise beam of the laser gyroscope through the first phototube and converts the optical signal into a first electrical signal. It also receives the beat frequency signals of the clockwise and counterclockwise light from the laser gyroscope through the second phototube and converts the optical signals into a second electrical signal.

[0072] S2, coherent demodulation is performed on the first and second electrical signals. Specifically, the AC component of the first electrical signal of the laser gyroscope is extracted and coherently demodulated with the AC component of the second electrical signal to obtain the backscattering amplitude information of the laser gyroscope.

[0073] S3, adjust the voltage applied to the piezoelectric ceramic of the laser gyroscope according to the amplitude of the backscattering, control the movement of the reflector, and achieve minimum backscattering.

[0074] The embodiments described above are merely preferred embodiments of the present invention. Ordinary variations and substitutions made by those skilled in the art within the scope of the technical solutions of the present invention should be included within the protection scope of the present invention.

Claims

1. A control system for improving the accuracy of a laser gyroscope, characterized in that, include: The first phototube (1) is a single-quadrant phototube. The first phototube (1) receives the clockwise or counterclockwise beam of the laser gyroscope and converts the clockwise or counterclockwise emitted light signal into a first electrical signal. The first electrical signal contains the light intensity information of the backscattered signal. The second phototube (2) is a dual-quadrant phototube. The second phototube (2) receives the beat frequency light signal after the clockwise and counterclockwise light of the laser gyroscope interferes, and converts this beat frequency light signal into a second electrical signal. A computing device that coherently demodulates the AC component in the first electrical signal and one AC component in the second electrical signal to obtain information on the backscattering amplitude. The PZT driving circuit drives the displacement direction of the reflector of the laser gyroscope to minimize the backscattering amplitude. The computing device includes a high-pass filter and a low-pass filter. The first electrical signal passes through the high-pass filter to obtain the AC component, and the first electrical signal passes through the low-pass filter to obtain the DC component. The coherently demodulated signal and the DC component are applied to the PZT driving circuit so that the laser gyroscope operates at a stable frequency point.

2. The control system according to claim 1, characterized in that, While keeping the cavity length of the laser gyroscope constant, the computing device determines the result of the coherent demodulation based on the periodic relationship between the cavity length and the light intensity of the laser gyroscope. The minimum value of , where, R 10 The backscattering coefficient is... I 10 , I 20 These represent the light intensity amplitudes for clockwise and counterclockwise light, respectively. β 1 The phase of the backscattered light in the optical signal received in this direction. The PZT driving circuit drives the displacement direction and distance of the laser gyroscope's reflector, so that the result of the coherent demodulation reaches the minimum value.

3. The control system according to claim 1, characterized in that, The displacement of the reflector includes: reflection angle; simultaneously moving closer to the center of the laser gyroscope; simultaneously moving away from the center of the laser gyroscope; one moving closer to the center of the laser gyroscope and the other moving away from the center of the laser gyroscope.

4. The control system according to claim 1, characterized in that, Keeping the cavity length constant, the PZT control circuit adjusts the position of the reflector according to the backscattering amplitude information, and the computing device detects the light intensity signal and backscattering amplitude until the light intensity signal reaches its maximum value and the backscattering amplitude is at its minimum.

5. A control method for improving the accuracy of a laser gyroscope, characterized in that, include: The single-quadrant phototube receives clockwise or counterclockwise light from the laser gyroscope and converts the light signal into a first electrical signal, which contains the light intensity information of the backscattered signal. The beat frequency light signal obtained by the interference of clockwise and counterclockwise light from the laser gyroscope is received by a dual-quadrant phototube, and this beat frequency light signal is converted into a second electrical signal. The first electrical signal is filtered using a high-pass filter to obtain the AC component of the first electrical signal, and the first electrical signal is filtered using a low-pass filter to obtain the DC component. Coherent demodulation is performed on the AC signal in the first electrical signal and one AC component in the second electrical signal to obtain backscatter amplitude information; The coherently demodulated signal and the DC component are applied to the PZT driving circuit to make the laser gyroscope operate at a stable frequency point, wherein the PZT driving circuit drives the displacement direction of the laser gyroscope's mirror to minimize the backscattering amplitude.

6. The control method according to claim 5, characterized in that, Also includes: While keeping the cavity length of the laser gyroscope constant, the result of coherent demodulation is determined based on the periodic relationship between the cavity length and the light intensity. The minimum value of , where, R 10 The backscattering coefficient is... I 10 , I 20 These represent the light intensity amplitudes for clockwise and counterclockwise light, respectively. β 1 The phase of the backscattered light in the optical signal received in this direction; The displacement direction and distance of the reflector driving the laser gyroscope are adjusted so that the result of the coherent demodulation is minimized.

7. The control method according to claim 6, characterized in that, The light intensity signal and backscatter amplitude are detected until the light intensity signal reaches its maximum value and the backscatter amplitude reaches its minimum value.

8. The control method according to claim 6, characterized in that, The displacement of the reflector includes: the reflection angle of the reflector; simultaneously moving closer to the center of the laser gyroscope; simultaneously moving away from the center of the laser gyroscope; one moving closer to the center of the laser gyroscope and the other moving away from the center of the laser gyroscope.

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