Ultrafast laser modification tuning method and device for quartz gyroscope

Abstract

The invention discloses an ultrafast laser modification tuning method and device for a quartz gyroscope, and solves the defects of the existing tuning technology in the aspects of efficiency, precision and damage. According to the method, a laser Doppler vibration measurement system is used for accurately completing the frequency test of a harmonic oscillator, then an ultrafast laser processing system is used for carrying out ablation removal or modification treatment on a local area of a gyroscope, finally, the area is subjected to local chemical corrosion through a micromanipulation system, and operation is repeated according to a test result until the target precision is reached. The high efficiency of ultrafast laser ablation and the low damage characteristic of chemical corrosion are combined, the tuning efficiency and quality are remarkably improved, and meanwhile the tuning precision is effectively guaranteed through the vibration measuring system, the machining system and the micromanipulation system. The method and the device have the outstanding characteristics of high removal efficiency, low material damage, high tuning precision and wide applicable objects, and a better scheme is provided for precise tuning of the quartz gyroscope.

Description

Technical Field

[0001] The present invention relates to the technical field of vibration gyro tuning, and specifically relates to an ultrafast laser tuning method for a quartz gyroscope. Background Technique

[0002] The gyroscope is an important component for measuring angular velocity in an inertial navigation system. According to different working principles, common gyroscopes are divided into rotor gyroscopes, optical gyroscopes, vibration gyroscopes, etc. Among them, the vibration gyroscope combined with advanced MEMS technology has significant advantages such as small size, low energy consumption, and high reliability, and has broad development prospects.

[0003] Fused quartz has good thermodynamic properties and small thermoelastic damping, and is an ideal material for manufacturing high-performance vibration gyroscopes. During the manufacturing process of quartz gyroscopes, manufacturing errors and residual stresses will both cause the working mode frequencies of the resonators to mismatch, thereby affecting the performance of the gyroscope such as sensitivity and zero-bias stability. Therefore, carrying out modal tuning work on the manufactured quartz resonator is the key to improving the overall performance of the gyroscope.

[0004] Currently, the precision tuning technologies for quartz resonators mainly include ultrafast laser processing, ion beam processing, and chemical etching methods.

[0005] The ultrafast laser processing method has high tuning efficiency and tuning accuracy. National University of Defense Technology reduced the frequency splitting of a quartz microhemispherical resonator to below 10 mHz by means of femtosecond laser mass removal [Li Bin, Xi Xiang, Lu Kun, et al. High-precision frequency difference adjustment method for microhemispherical resonant gyro based on mass-stiffness decoupling [J]. Science China: Technological Sciences, 2023, 53(08): 1400-1410]. However, the laser ablation process will introduce thermal stress, even generate microcracks and damage the coating layer, directly reducing the quality factor and output performance of the resonator.

[0006] The ion beam etching method has significant advantages of almost no damage and ultra-high precision. Harbin Institute of Technology proved through experiments that this method can increase the quality factor during modal tuning. However, the ion beam processing technology is complex, and when facing the processing task of large mass and small area, the efficiency is extremely low. In response to this problem, the invention patent with the publication number of CN 116372376A realizes cross-scale adjustment by combining femtosecond laser and ion beam etching methods. However, for unbalanced masses above the nanogram level, ultrafast laser removal still needs to be carried out first, and the defects brought by laser processing cannot be effectively avoided.

[0007] Chemical etching processing of quartz results in relatively low damage and also has a positive effect on the quality factor. However, it has poor controllability and no advantage in tuning accuracy compared to other tuning methods. The invention patent with the publication number CN 111504292 A determines the etching time based on the n = 1 harmonic error value and chemical modification parameters, achieving the trimming effect. In actual operation, it is difficult to accurately control the etching time. For the n = 1 mode, this error is acceptable. However, for modes n = 2 and above, they are more sensitive to mass perturbation, and the accuracy of this method is difficult to meet, and over-tuning and other situations are likely to occur. In addition, for the resonator manufactured by the laser cutting method, there is a modified layer on its cutting section, and it is impossible to accurately and microscopically remove the frequency-sensitive part, severely restricting the application effect of the chemical etching method.

[0008] In summary, the current technical means have different types of shortcomings in terms of efficiency, accuracy, and damage in the quartz gyro tuning method, and a cross-scale tuning method and device with high efficiency, high accuracy, and extremely low damage are needed. Summary of the Invention

[0009] The present invention aims to solve the problem that the tuning efficiency, accuracy, and removal damage cannot be simultaneously satisfied when the main technical means are used for mass removal tuning of quartz resonators. To address this problem, the present invention provides an ultrafast laser modification tuning method and device, which combines the advantages of high efficiency and high accuracy of ultrafast lasers and low damage of chemical etching, realizes cross-scale mass removal of resonators of different sizes and nanoscale processing roughness, and achieves mode matching under the condition of ensuring the quality factor of the resonator.

[0010] To achieve the above object, the present invention provides an ultrafast laser modification tuning method, which mainly includes the following steps:

[0011] S1 Measure the ablation threshold and modification threshold of the material on a sample of the same material as the quartz resonator, determine the sizes of the ablation and modification regions under different laser energies and processing speeds, and the further removal amounts under different concentrations of etching solution and etching times.

[0012] S2 Conduct modal simulation on the resonator in simulation software to analyze the relationship between frequency splitting and mass removal.

[0013] S3 Use a laser Doppler and vacuum test system to measure the modal frequency and the orientation of the rigid axis of the quartz resonator.

[0014] S4 Place the quartz resonator in a laser processing system, and use a precision motion platform and a vision system to align the laser focus to the target processing orientation.

[0015] S5 Adjust the laser energy to ablate or modify the target area of the quartz resonator, and the energy size and the target area range are determined according to the frequency splitting of the quartz resonator.

[0016] S6 removes the harmonic oscillator from the platform, places the cut qualitative filter paper on the target area, and drops a small amount of etching solution on the qualitative filter paper. The concentration and etching time of the etching solution are determined by the frequency splitting of the quartz resonator. During the etching process, a piezoelectric ceramic is used to provide ultrasonic assistance.

[0017] S7 After the etching is completed, wash the harmonic oscillator and test the frequency splitting of the resonator in a vacuum test system. If the target accuracy is not met, repeat steps S5 and S6 until the target accuracy is achieved.

[0018] Preferably, in the vacuum test of the quartz resonator, the vacuum degree is lower than 0.01 Pa.

[0019] Preferably, the laser pulse width is less than 500 fs and the single-pulse energy is less than 3 μJ.

[0020] Preferably, the side length of the filter paper cut during etching is less than the ablation or modification area, the volume of the chemical etching solution in each area does not exceed 0.01 mL, the concentration of the chemical etching solution is higher than 10%, and the ultrasonic frequency during etching is higher than 20 kHz.

[0021] Optionally, the chemical etching time is within 10 minutes.

[0022] Optionally, the laser repetition frequency is less than 100 kHz.

[0023] Furthermore, the ablation threshold of the ultrafast laser and fused quartz is measured by the epitaxial method, and the modification threshold range is determined by the etching removal under the energy lower than the ablation threshold.

[0024] The present invention also provides an apparatus for ultrafast laser modification and tuning.

[0025] It includes: a laser vibration measurement system, an ultrafast laser processing system, and a micro-operation system.

[0026] The described laser vibration measurement system is composed of a laser Doppler vibrometer, an excitation system, a moving platform, a vacuum chamber, a mechanical pump, and a molecular pump: non-contact vibration measurement of different scales and different regions can be achieved through the objective lens conversion of the vibrometer and the movement of the moving platform; the excitation system provides vibration excitation at a specific frequency by a lock-in amplifier and a piezoelectric sheet; the vacuum chamber is provided with a glass window, and the measurement laser can be focused on the surface of the object to be measured in the vacuum chamber through the glass window; the mechanical pump and the molecular pump can provide a vacuum environment lower than 0.01 Pa.

[0027] The described ultrafast laser processing system consists of a laser, necessary optical elements in the optical path, an imaging module, and a motion platform: The laser, in cooperation with optical elements such as an objective lens and a mirror, can achieve laser modification or ablation removal; The imaging module composed of a light source and a CCD camera, in cooperation with a six-axis motion platform, can accurately locate the processing position of the resonant device to ensure the accuracy of the modification and ablation positions.

[0028] The described micromanipulation system includes a microscope, a motion platform, and a micro-injection pump, and can accurately drip a small amount of corrosive liquid onto the filter paper in the modified area.

[0029] The core of the method for tuning the ultrafast laser modification of a quartz resonator provided by the present invention is to use an ultrashort pulse laser to change the local crystal structure of the quartz material, achieve a high corrosion ratio at this part, and then remove the mass at the tuning part through local chemical corrosion to achieve high-efficiency and low-damage tuning.

[0030] The above technical solutions of the present invention have the following advantages:

[0031] (1) The present invention adopts the methods of ultrafast laser modification and chemical corrosion, and realizes the frequency tuning of the quartz gyro through local mass removal. The bottom surface roughness of the removed area is much lower than that of laser ablation removal.

[0032] (2) The present invention uses filter paper to prevent the diffusion of the corrosive liquid, absorbs the corrosive liquid within a specific range, and most of the corrosive liquid is used for local corrosion of the modified area, effectively improving the accuracy and controllability of chemical corrosion.

[0033] (3) The present invention can, according to the frequency splitting size of the resonator, achieve cross-scale, high-precision, and high-efficiency tuning by regulating the ultrafast laser modification area (area and volume), as well as the chemical corrosion time and the concentration of the corrosive liquid. Description of the Drawings

[0034] The drawings are used to provide a further understanding of the embodiments of the present invention, and constitute a part of the specification. Together with the following specific embodiments, they are used to explain the embodiments of the present invention, but do not constitute a limitation to the embodiments of the present invention. In the drawings:

[0035] Figure 1 is a schematic flow diagram of the present invention;

[0036] Figure 2 and Figure 3 respectively show the simulation of the modal frequency and frequency splitting of the resonator with the removed mass in the embodiments of the present invention;

[0037] Figure 4 is a schematic structural diagram of the ultrafast laser processing system and the laser vibration measurement system in the embodiments of the present invention;

[0038] Figure 5This is a schematic diagram of the local corrosion device for the resonator in the embodiments of the present invention. Detailed implementation manners

[0039] The following will describe in detail the specific implementation manners of the embodiments of the present invention, and clearly and completely describe the technical solutions in the embodiments of the present invention. The described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0040] It should be noted that the frequency splitting of the resonator wine glass mode (n = 2) is mainly caused by the fourth harmonic errors of mass and stiffness. Therefore, 4 symmetric removal points separated by 90 degrees are used for tuning.

[0041] A femtosecond laser modification tuning method and implementation process for a quartz microhemispherical resonator are as shown in the attached Figure 1 figures, and mainly include the modal test of the resonator, femtosecond laser local modification, and local chemical corrosion. The specific steps are as follows:

[0042] S1. Measure the ablation threshold and modification threshold of quartz through experiments, and determine the relationship between the removal depth and frequency splitting on the low-frequency rigid axis through simulation. As shown in Figure 2 Figure 3, the two have a linear relationship.

[0043] S2. As shown in the attached Figure 4 figures, place the resonator in a vacuum chamber and use a vacuum pump and a molecular pump to pump the air pressure in the vacuum chamber to below 0.01 Pa. Use a laser Doppler vibrometer system to measure the natural frequencies and rigid axis orientations of the gyro driving mode and the detection mode.

[0044] S3. Use the femtosecond laser processing system shown in the attached Figure 4 figures. Through CCD-assisted observation and a six-axis motion system, ensure that the laser processes in the low-frequency axis orientation of the resonator.

[0045] S4. Adjust the attenuation sheet to adjust the single-pulse energy of the laser to 2 μJ; the moving platform moves at a speed of 20 mm / s, and modifications are carried out in 4 low-frequency axis orientations respectively, and the modification area is 150 μm × 300 μm (the modification area is determined by frequency splitting).

[0046] S5. Place the locally modified resonator together with the piezoelectric sheet on the micromanipulator, place the cut filter paper (150 μm × 300 μm) on the 4 modified areas, and operate a micro-injection pump to drop 0.01 mL of 40% hydrofluoric acid solution above each filter paper. During the corrosion process, use 40 kHz vibration to assist the corrosion process. As shown in Figure 5 Figure.

[0047] S6. Clean the resonator with distilled water and absolute ethanol, blow all impurities on the resonator clean with high-purity nitrogen, place the clean resonator in the vacuum chamber, and retest its frequency splitting and the orientation of the rigid axis.

[0048] S7. Repeat steps S4 - S6 until the frequency splitting of the gyroscope drops to the target value.

Claims

1. An ultrafast laser modification and tuning method for a quartz gyroscope, characterized in that, The method uses an ultrafast laser to ablate and modify the target position of the resonator, and then assists chemical etching to achieve high-efficiency and low-damage removal of local mass, reduce the frequency splitting of the resonator, and improve the overall performance of the resonator. The method includes the following steps: S1 Measure the ablation threshold and modification threshold of the material on a sample of the same material as the quartz resonator, determine the sizes of the ablation and modification areas under different laser energies and processing speeds, and the further removal amounts under different concentrations of etching solution and etching times. S2 Perform modal simulation analysis on the resonator in simulation software, simulate the tuning process of the resonator under different mass imbalances, and determine the tuning position and the relationship between frequency splitting and removed mass. S3 Use a laser Doppler and vacuum test system to measure the modal frequency and the orientation of the rigid axis of the quartz resonator. S4 Place the quartz resonator in a laser processing system, and use a precision motion platform and a vision system to align the laser focus with the target processing orientation. S5 Adjust the laser energy to ablate or modify the target area of the quartz resonator. The energy size and the target area range are determined according to the frequency splitting of the quartz resonator. S6 Remove the resonator from the platform, place a cut qualitative filter paper on the target area, and drop a small amount of etching solution on the qualitative filter paper. The concentration of the etching solution and the etching time are determined by the frequency splitting of the quartz resonator. During the etching process, a piezoelectric ceramic is used to provide ultrasonic assistance. S7 After the etching is completed, wash the resonator, and test the frequency splitting of the resonator in a vacuum test system. If the target accuracy is not met, repeat steps S5 and S6 until the target accuracy is achieved.

2. The tuning method according to claim 1, wherein The described resonator is made of quartz material and is one of a hemispherical shape, a micro-hemispherical shape, a cylindrical shape, a spider-web shape, and a disk shape.

3. The tuning method according to claim 1, characterized in that, The described frequency test device is a laser Doppler vibrometer, which can meet the vibration measurement and tuning requirements of both coated and uncoated resonators.

4. The tuning method according to claim 1, wherein For mass imbalances above the nanogram level, after processing with energy higher than the laser ablation threshold, chemically etch the peripheral modified layer of the ablation area; for mass imbalances below the nanogram level, perform modification with energy lower than the ablation threshold and chemically etch the modified area.

5. The tuning method according to claim 1, wherein The described method precisely controls the removed mass through the laser modification position, laser energy, chemical etching time, and etching solution concentration.

6. The tuning method according to claim 1, characterized in that, During the chemical etching process, use a qualitative filter paper to absorb the etching solution near the processed area, and provide ultrasonic excitation through a piezoelectric ceramic and a signal generator to improve the etching accuracy and efficiency.

7. The tuning method according to claim 1, wherein This tuning method can be applied to the adjustment of harmonic errors of each order of the resonator. The adjustment of the fourth harmonic error of the wine glass mode (n = 2) is only one example of this resonator.

8. The tuning method according to claim 1, characterized in that After the femtosecond laser is focused by a focusing lens, ablation or modification of the target area is achieved. The focusing lens is selected from a convex lens and an objective lens according to the size of the frequency splitting, and further select the focal length of the convex lens or the magnification of the objective lens. The laser beam is selected from a Gaussian beam, a Bessel beam, and a flat-top beam according to the size of the frequency splitting and the shape of the removed area.

9. An ultrafast laser modification and tuning device, characterized in that: Comprising: Laser vibration measurement system, ultrafast laser processing system, and microscopic operation system. The described laser vibration measurement system consists of a laser Doppler vibrometer, an excitation system, a moving platform, a vacuum chamber, a mechanical pump, and a molecular pump: non-contact vibration testing of different scales and regions is achieved through the objective lens conversion of the vibrometer and the movement of the moving platform; the excitation system provides vibration excitation at a specific frequency by a lock-in amplifier and a piezoelectric sheet; the vacuum chamber is provided with a glass window, and the vibration measurement laser is focused on the surface of the object to be measured in the vacuum chamber through the glass window; the mechanical pump and the molecular pump can provide a vacuum environment that meets the requirements for the resonator test. The described ultrafast laser processing system consists of a laser, optical elements necessary in the optical path, an imaging module, and a moving platform: the optical path realizes beam switching and energy regulation through a flip mirror frame and a filter; the laser cooperates with the optical path and the moving platform to achieve laser modification or ablation removal of different areas; the imaging module composed of a light source and a CCD camera cooperates with the six-axis moving platform to accurately position the processing location of the resonator device, ensuring the accuracy of the modification and ablation locations. The described microscopic operation system includes a microscope, a moving platform, and a micro-injection pump, and can accurately drip a small amount of corrosive liquid onto the filter paper in the modified area.

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