Evaluation Method of Metallization Coating Uniformity of Hemispherical Resonator

Abstract

A method for evaluating the uniformity of a hemispherical resonator metallization coating can effectively evaluate the overall uniformity distribution of the resonator film thickness, avoid repeated tests, save costs, and has important applications in the fields of hemispherical resonator processing and debugging.

Description

Technical Field

[0001] The invention relates to a hemispherical resonator gyroscope of an inertial navigation system, in particular to a method for evaluating the uniformity of a metallized coating of a hemispherical resonator. Background Art

[0002] The hemispherical resonant gyroscope is a new type of solid-state gyroscope. It uses the radial vibration standing wave precession effect of the hemispherical shell lip to sense the rotation of the base. It is a Columbia-type vibrating gyroscope with inertial navigation performance. Compared with traditional mechanical gyroscopes, hemispherical resonant gyroscopes are vibration rotation sensors with the advantages of high precision, small size, long life, high stability, low noise, high resolution, high impact resistance, low power consumption, and radiation resistance. Compared with the current laser gyroscopes and fiber optic gyroscopes, the hemispherical resonant gyroscope has a simpler structure and greatly reduced number of parts. In theory, the accuracy does not depend on the size, and the noise performance is not limited by quantum effects. Therefore, the hemispherical resonant gyroscope is the most potential gyroscope to achieve high precision, miniaturization, and low cost.

[0003] The hemispherical resonator is the core component of the hemispherical resonator gyroscope, which consists of a hemispherical shell and a center rod. The fused quartz resonator is made of high-Q quartz glass through ultra-precision processing. Because the hemispherical resonator gyroscope works based on the vibration of the resonator and the acquisition of vibration signals, in order to ensure the efficiency of the electrostatic excitation of the resonator, the surface of the hemispherical resonator must be metallized. The unevenness of the metal film layer will cause the asymmetry of the mass of the resonator along the axial direction, thereby increasing the frequency difference and loss of the resonator. Therefore, the metallization coating process of the resonator should minimize the impact on the performance of the resonator, which requires the metallization film layer to have a high uniformity. The thickness of the metallization film layer of the resonator is about several hundred nanometers. It is very difficult to measure the thickness of the film layer without destroying the resonator. At present, there are two main methods for evaluating the uniformity of the metallization coating of the resonator:

[0004] One is to measure the film thickness by the patch method, where a small-sized accompanying plating sheet is directly attached to the surface of the resonator or the surface of a metal model of the same size as the resonator with tape or mechanical structure, and plated into a step sheet. After the patch surface is metallized and coated, it is removed to measure the film layer steps, and then the uniformity distribution of the film layer thickness is obtained. Since the resonator is a special-shaped part, and the patch is generally a flat sheet of several millimeters in size and has a certain thickness, using a flat coated element instead of a curved element will result in a large difference in the actual uniformity distribution of the resonator, making the uniformity of the patch film layer unable to fully represent the uniformity of the resonator film layer.

[0005] Another method is to destroy the resonator after the metallization coating is completed, perform cross-sectional tests on the coated parts of the resonator, and use a scanning electron microscope to analyze the film thickness to obtain the uniformity distribution of the film thickness of the resonator. This method requires the destruction of the resonator, and as the number of measurement points increases, more measurement points will need to be cross-sectionally analyzed. Although this method can more accurately evaluate the uniformity of the resonator film layer, it is costly and inefficient for evaluating the overall uniformity of the resonator. Summary of the invention

[0006] The present invention aims to provide a method for evaluating the uniformity of a hemispherical resonator metallization coating, which overcomes the limitations of the existing patch method and electron microscope cross-section analysis method and solves the technical difficulty of comprehensively evaluating the uniformity of the resonator metallization film layer.

[0007] To achieve the above-mentioned purpose, the technical solution of the present invention is as follows:

[0008] A method for evaluating the uniformity of a hemispherical resonator metallization coating, characterized in that the method comprises the following steps:

[0009] 1) The supporting rod of the hemispherical resonator before coating is vertically fixed on a turntable equipped with a clamp, the turntable is placed in a vacuum chamber as a whole, a rubber hammer driven by piezoelectric ceramics is installed on the side of the hemispherical resonator, the vacuum chamber is placed on a shock-absorbing air-floating platform as a whole, a laser vibrometer is set up on the air-floating platform, so that the laser spot emitted by the laser vibrometer is horizontally and vertically incident on the lip edge surface of the hemispherical resonator through the window of the vacuum chamber, the other end of the laser vibrometer is connected to the input end of the computer, and the control end of the computer is connected to the rubber hammer via a controller;

[0010] 2) The computer controls the rubber hammer through the controller to strike and vibrate the hemispherical resonator with a certain impact force. At the same time, the laser spot output by the laser vibrometer contacts the lip edge of the hemispherical resonator and changes its frequency due to the Doppler effect. The laser spot is reflected by the hemispherical resonator to form a reflected light signal. The reflected light signal is received by the laser vibrometer and then input into the computer.

[0011] 3) The computer performs data analysis on the reflected light signal to obtain a decay curve of the vibration speed of the hemispherical resonator over time, and based on the result, calculates the vibration frequency f0 and decay time τ of the hemispherical resonator, thereby obtaining the quality factor Q1 of the hemispherical resonator;

[0012] 4) The position of the hemispherical resonator is adjusted by the turntable, and the quality factors Q2, Q3, ..., Q at other positions along the lip of the hemispherical resonator are measured in turn. N , where N is the number of measurement points of the hemispherical resonator lip along the circumferential direction, and the Q value curves of N hemispherical resonator lips with equal angular position changes along the circumferential direction can be obtained;

[0013] 5) performing ultrasonic cleaning on the hemispherical resonator and then performing metallization coating;

[0014] 6) The support rod of the metallized coated hemispherical resonator is fixed vertically on the turntable, the position of the metallized coated hemispherical resonator is adjusted according to step 1), and the lip of the metallized coated hemispherical resonator is measured at N positions along the circumferential direction according to steps 2), 3), and 4), and the values ​​Q are obtained respectively. ′ 1. Q ′ 2. Q ′ 3……Q ′ N The computer performs differential calculation on the Q value change ΔQ of each measuring point before and after coating, ΔQ i =Q i -Q i ′ , respectively obtain the Q value changes ΔQ1, ΔQ2, ΔQ3...ΔQ N , Q value variation curve of the hemispherical resonator before and after coating along the circumferential direction of the lip;

[0015] 7) Perform statistical analysis on the Q value change curve before and after coating in the circumferential direction, analyze the measurement results exceeding 1 standard deviation σ, and focus on the data points in the range of -3σ~-2σ and 2σ~3σ. The former reflects that the film layer at the corresponding measurement position is thicker than the average film thickness, while the latter reflects that the film thickness at the corresponding measurement position is thinner than the average film thickness.

[0016] Beneficial effects of the present invention:

[0017] 1) Based on the laser vibration measurement system, the uniformity of the metallized coating is evaluated by the change of the Q value of the hemispherical resonator lip along the circumferential direction before and after coating.

[0018] 2) This method can avoid complex and delicate measurement processes such as resonator cross-section sample preparation and scanning electron microscope analysis without destroying the hemispherical resonator.

[0019] 3) By refining the measurement points, the uniformity of the metallized film layer along the lip of the hemispherical resonator can be comprehensively evaluated. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1This is a schematic diagram of a Q value test platform for a hemispherical resonator of the present invention;

[0021] Figure 2 The test results of the hemispherical resonator vibration of the present invention;

[0022] Figure 3 The Q value distribution curve of the hemispherical resonator lip along the circumferential direction before the hemispherical resonator is metallized and plated according to the present invention;

[0023] Figure 4 The Q value distribution curve of the hemispherical resonator lip along the circumferential direction after the hemispherical resonator is metallized and plated according to the present invention;

[0024] Figure 5 It is a schematic diagram of the Q value variation curve of the metallized coating of the present invention on the lip of the hemispherical resonator along the circumferential direction and the analysis of the uniformity abnormal points; DETAILED DESCRIPTION

[0025] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the technical solutions in the embodiments of the present invention are clearly and completely described below in conjunction with the accompanying drawings. The described embodiments are only some embodiments of the present invention, rather than all embodiments.

[0026] The laser Doppler vibrometer uses the Doppler effect of light to measure the displacement and velocity of an object's surface. Its working principle is that the laser beam emitted by the laser source is decomposed by a spectroscope into a measuring beam and a reference beam of the same frequency and phase; the measuring beam is focused on the vibrating surface of the object being measured through a lens, the frequency of the light wave changes, and is reflected from the vibrating surface to the photosensitive element; by calculating the frequency difference between the measuring beam and the reference beam, the vibration velocity of the object being measured can be obtained:

[0027]

[0028] Where Δf is the frequency difference between the measurement beam and the reference beam, v is the vibration velocity of the structure being measured, and λ is the wavelength of the measurement laser.

[0029] By testing and analyzing the vibration frequency f0 and decay time τ of the hemispherical resonator, the Q value of the hemispherical resonator is obtained:

[0030] Q = π·f0·τ.

[0031] Figure 1 Schematic diagram of a Q-value test platform for a hemispherical resonator according to an embodiment of the present invention.

[0032] The method for evaluating the uniformity of the metallization coating of a hemispherical resonator of the present invention comprises the following steps:

[0033] 1) The supporting rod of the hemispherical resonator 1 before coating is vertically fixed on a turntable 2 equipped with a clamp, and the turntable is placed in a vacuum chamber 3 as a whole. A piezoelectric ceramic driven rubber hammer 4 is installed on the side of the hemispherical resonator 1. The vacuum chamber 3 is placed on a shock-absorbing air floating platform as a whole. A laser vibrometer 6 is set up on the air floating platform, so that the laser spot emitted by the laser vibrometer 6 is horizontally and vertically incident on the lip edge surface of the hemispherical resonator 1 through the window 7 of the vacuum chamber 3. The other end of the laser vibrometer 6 is connected to the input end of a computer 8, and the control end of the computer 8 is connected to the rubber hammer 4 via a controller 5;

[0034] 2) The computer 8 controls the rubber hammer 4 through the controller 5 to strike and vibrate the hemispherical resonator 1 with a certain impact force. At the same time, the laser spot output by the laser vibrometer 6 contacts the lip edge of the hemispherical resonator 1 and changes its frequency due to the Doppler effect. The laser spot is reflected by the hemispherical resonator 1 to form a reflected light signal. The reflected light signal is received by the laser vibrometer 6 and then input into the computer 8.

[0035] 3) The computer 8 performs data analysis on the reflected light signal to obtain a decay curve of the vibration speed of the hemispherical resonator 1 over time, and based on the result, calculates the vibration frequency f0 and decay time τ of the hemispherical resonator 1, thereby obtaining the quality factor Q1 of the hemispherical resonator 1;

[0036] 4) The position of the hemispherical resonator 1 is adjusted by the turntable 2, and the quality factors Q2, Q3, ..., Q at other positions along the lip of the hemispherical resonator 1 are measured in turn. N , where N is the number of measurement points of the lip of the hemispherical resonator 1 along the circumferential direction, and N Q value curves of the lip of the hemispherical resonator 1 along the circumferential direction with equal angular position changes can be obtained;

[0037] 5) performing ultrasonic cleaning on the hemispherical resonator 1 and then performing metallization coating;

[0038] 6) The support rod of the metallized hemispherical resonator 1 is fixed vertically on the turntable 2, the position of the metallized hemispherical resonator 1 is adjusted according to step 1), and the lip of the metallized hemispherical resonator 1 is measured along the circumferential direction at N positions according to steps 2), 3), and 4), and the values ​​Q′1, Q′2, Q′3, ..., Q′ are obtained respectively. N The computer (8) performs differential calculation on the Q value change ΔQ of each measuring point before and after coating, ΔQ i =Q i -Q′ i, respectively obtain the Q value changes ΔQ1, ΔQ2, ΔQ3...ΔQ N , Q value variation curve of the hemispherical resonator before and after coating along the circumferential direction of the lip;

[0039] 7) Perform statistical analysis on the Q value change curve before and after coating in the circumferential direction, analyze the measurement results exceeding 1 standard deviation σ, and focus on the data points in the range of -3σ~-2σ and 2σ~3σ. The former reflects that the film layer at the corresponding measurement position is thicker than the average film thickness, while the latter reflects that the film thickness at the corresponding measurement position is thinner than the average film thickness.

[0040] The vibration frequency f0 of the hemispherical resonator 1 in this embodiment is 5041 Hz and the decay time τ is 257.8, and the quality factor Q1 of the hemispherical resonator at this point is obtained as Q1=4082719. Figure 2 As shown;

[0041] The position of the hemispherical resonator 1 is adjusted by the turntable 2, and the quality factors Q1, Q2, Q3, ... Q at other positions along the lip of the hemispherical resonator 1 are measured in turn. N , obtain the Q value curve of the hemispherical resonator 1 lip along the circumferential direction, such as Figure 3 As shown;

[0042] The Q values ​​Q′1, Q′2, Q′3, ... Q′ of the lip of the hemispherical resonator 1 after metallization coating along the circumferential direction are N Measure again, such as Figure 4 As shown;

[0043] The Q value changes ΔQ of each measuring point before and after coating are calculated by computer 8 (such as ΔQ1=Q1-Q′1), and the Q value changes ΔQ1, ΔQ2, ΔQ3, ... ΔQ are obtained respectively. N The curve of the change of the hemispherical resonator along the circumferential direction of the lip is as follows: Figure 5 As shown;

[0044] The Q value change curves before and after coating in the circumferential direction are statistically analyzed, and the measurement results exceeding 1 standard deviation σ are analyzed (such as Figure 5 The data points in the range of -3σ to -2σ and 2σ to 3σ are analyzed in detail (e.g. Figure 5 The former shows that the film thickness at the corresponding measurement position is thicker than the average film thickness, while the latter shows that the film thickness at the corresponding measurement position is thinner than the average film thickness. Based on the above method, the uniformity of the metallization coating on the surface of the resonator can be quickly and completely evaluated.

[0045] Experiments show that the present invention overcomes the limitations of the existing patch method and electron microscope cross-section analysis method, and solves the technical problem of comprehensive evaluation of the uniformity of the metallized film layer of the resonator. The present invention can effectively evaluate the overall uniformity distribution of the resonator film thickness, avoid repeated experiments, save costs, and has important applications in the field of hemispherical resonator processing and debugging.

Claims

1. A method for evaluating the uniformity of metallization coating of a hemispherical resonator, characterized in that: The method comprises the following steps: 1) The support rod of the hemispherical resonator (1) before coating is vertically fixed on a turntable (2) equipped with a clamp, the turntable is placed in a vacuum chamber (3), a piezoelectric ceramic driven rubber hammer (4) is installed on the side of the hemispherical resonator (1), the vacuum chamber (3) is placed on a shock-absorbing air-floating platform, a laser vibrometer (6) is set up on the air-floating platform, so that the laser spot emitted by the laser vibrometer (6) is horizontally and vertically incident on the lip edge surface of the hemispherical resonator (1) through a window (7) of the vacuum chamber (3), the other end of the laser vibrometer (6) is connected to the input end of a computer (8), and the control end of the computer (8) is connected to the rubber hammer (4) via a controller (5); 2) the computer (8) controls the rubber hammer (4) through the controller (5) to strike the hemispherical resonator (1) with a certain impact force to excite the hemispherical resonator (1). At the same time, the laser spot output by the laser vibrometer (6) contacts the lip edge of the hemispherical resonator (1) and changes its frequency due to the Doppler effect. The laser spot is reflected by the hemispherical resonator (1) to form a reflected light signal. The reflected light signal is received by the laser vibrometer (6) and then input into the computer (8); 3) the computer (8) performs data analysis on the reflected light signal to obtain a decay curve of the vibration speed of the hemispherical resonator (1) over time, and based on the result, calculates the vibration frequency f0 and decay time τ of the hemispherical resonator (1), thereby obtaining the quality factor Q1 of the hemispherical resonator (1); 4) The position of the hemispherical resonator (1) is adjusted by the turntable (2), and the quality factors Q2, Q3, ..., Q at other positions of the lip of the hemispherical resonator (1) are measured in sequence. N , where N is the number of measurement points along the circumferential direction of the lip of the hemispherical resonator (1), and N Q value curves of the lip of the hemispherical resonator (1) with equal angular position changes along the circumferential direction can be obtained; 5) performing ultrasonic cleaning on the hemispherical resonator (1) and then performing metallization coating; 6) The support rod of the metallized coated hemispherical resonator (1) is fixed vertically on the turntable (2), the position of the metallized coated hemispherical resonator (1) is adjusted according to step 1), and the lip of the metallized coated hemispherical resonator (1) is measured at N positions along the circumferential direction according to steps 2), 3), and 4), and the values ​​Q are obtained respectively. ′ 1. Q ′ 2. Q ′ 3……Q ′ N The computer (8) performs differential calculation on the Q value change ΔQ of each measuring point before and after coating, ΔQ i =Q i -Q i ′ , respectively obtain the Q value changes ΔQ1, ΔQ2, ΔQ3...ΔQ N , Q value variation curve of the hemispherical resonator before and after coating along the circumferential direction of the lip; 7) Perform statistical analysis on the Q value change curve before and after coating in the circumferential direction, analyze the measurement results exceeding 1 standard deviation σ, and focus on the data points in the range of -3σ~-2σ and 2σ~3σ. The former reflects that the film layer at the corresponding measurement position is thicker than the average film thickness, while the latter reflects that the film thickness at the corresponding measurement position is thinner than the average film thickness.

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