A method and apparatus for fabricating a laser gyroscope reflector

Abstract

This invention discloses a processing method and apparatus for laser gyroscope reflectors, belonging to the field of laser gyroscope processing technology. The method presets a reference thickness based on a benchmark deposition rate, fits a reflectivity function based on multiple sets of reference thicknesses and equivalent reflectivity, and rapidly predicts the real-time thickness of the current deposition layer during processing by combining the real-time reflectivity of the reflector. Based on the real-time thickness, the real-time deposition rate is calculated, and the ion beam current is adjusted according to the real-time deposition rate to make the deposition rate of the current deposition layer approach the benchmark deposition rate, ensuring that the reference thickness preset based on the benchmark deposition rate is consistent with the on-site processing conditions. This invention can effectively improve the accuracy of secondary processing of laser gyroscope reflectors, thereby obtaining reflectors with high reflectivity and low loss.

Description

Technical Field

[0001] This invention relates to the field of laser gyroscope processing technology, and in particular to a processing method and apparatus for a laser gyroscope reflector. Background Technology

[0002] When a laser gyroscope is working, two laser beams, one clockwise and one counterclockwise, run internally. These two beams form a circuit within the resonant cavity via a reflector. When the carrier rotates around the sensitive axis of the laser gyroscope, the two laser beams generate a phase difference proportional to the angular velocity of the carrier, thus measuring the angular velocity. The reflector is the core component for laser phase measurement. In particular, the surface reflection effect of the reflector produces significant light scattering and loss, leading to a latch-up effect in the laser gyroscope, increasing random walk, and significantly impacting the linearity and stability of the laser gyroscope's output. Therefore, secondary processing is required after polishing the reflector substrate. Existing technologies have proposed several processing methods, such as those described in Chinese patent applications 201010049535X and 202210475062.2. To reduce the optical loss of the laser gyroscope, existing technologies require the reflector to be sputtered with more deposition layers. Each interface reflects a portion of the light, and when the light reflected from all deposition layers is in phase at the exit surface, they superimpose and enhance each other, resulting in extremely strong reflected light. However, the secondary processing inevitably introduces process errors. The more deposition layers there are, the greater the accumulated error becomes, even exceeding a quarter of the wavelength, which in turn affects reflectivity. Therefore, it is necessary to improve the processing method for multi-deposition-layer mirrors. Summary of the Invention

[0003] To address the shortcomings of existing technologies, this invention proposes a method and apparatus for processing laser gyroscope reflectors. This invention allows for rapid prediction of the deposited layer thickness by using a pre-set reference thickness, improving the accuracy of secondary processing. Furthermore, this invention adjusts the ion beam current through real-time deposition rate feedback to ensure consistency between the pre-set reference thickness and the on-site processing conditions.

[0004] The technical solution of this invention is implemented as follows:

[0005] A method for fabricating a laser gyroscope reflector includes the following steps:

[0006] Step 1: Clean the mirror substrate, then fix the mirror substrate in the deposition chamber, preset the target deposition sequence, the target deposition sequence includes different layers of deposition thickness, initialize the ion beam current and beam current regulation ratio, and initialize the number of layers n=1;

[0007] Step 2: Generate multiple reference thicknesses based on the baseline deposition rate and deposition thickness, calculate the equivalent reflectance corresponding to each reference thickness, and fit the reflectance function with multiple sets of reference thicknesses and equivalent reflectances;

[0008] Step 3: The ion source emits an ion beam into the deposition chamber. After the ion beam bombards the target material, it sputters target atoms, and the target atoms form a deposition layer on the reflector substrate.

[0009] Step 4: The light generator emits incident light into the reflector substrate through the first channel, and the light receiver receives the reflected light through the second channel and measures the intensity of the reflected light to calculate the real-time reflectivity;

[0010] Step 5: Predict the real-time thickness based on the reflectivity function and real-time reflectivity. If the real-time thickness is less than the deposition thickness of layer number n, proceed to step 6; otherwise, proceed to step 7.

[0011] Step 6: Define a sliding window based on the number of samplings, calculate the real-time deposition rate from multiple sets of real-time thicknesses within the sliding window, update the beam current adjustment ratio, adjust the ion beam current of the ion source, and return to Step 3;

[0012] Step 7: If n is less than the maximum number of layers N+1, adjust the target material so that n=n+1 and return to step 2; otherwise, end the task.

[0013] In this invention, in step 1, the reflector consists of a reflector substrate, an N / 2+1 layer of Ta2O5 deposition layer, and an N / 2 layer of SiO2 deposition layer, where N is an even number and 12≤N≤18, within a preset target deposition sequence [x1, x2,..., x...]. n-1 , x n ,...,x N-1 , x N In the figure, when n is odd, the deposition thickness x n =λ0 / (4ε1), when n is even, the deposition thickness x n =λ0 / (4ε2), where λ0 is the wavelength of the laser gyroscope, ε1 is the refractive index of the Ta2O5 deposition layer, and ε2 is the refractive index of the SiO2 deposition layer.

[0014] In this invention, step 1, the initialization of the ion beam includes the following steps:

[0015] Step 101: Preset the saturation discharge voltage and power density of the ion source;

[0016] Step 102: Set the thermal accumulation correction coefficient based on the number of layers, and set the ion source power for each deposition layer according to the power density and the thermal accumulation correction coefficient;

[0017] Step 103: Initialize the ion beam current of each deposition layer according to the saturation discharge voltage and ion source power.

[0018] In this invention, in step 2, the interpolation step size is calculated based on the baseline deposition rate and sampling interval, multiple reference thicknesses are determined based on the interpolation step size and deposition thickness, the equivalent reflectance is calculated based on the reference feature matrix of each reference thickness and the cumulative feature matrix of layer number n-1, and then the reflectance function of layer number n is fitted with the reference thickness as the horizontal axis and the equivalent reflectance as the vertical axis.

[0019] In this invention, the corresponding phase thickness is calculated based on the refractive index of the number of layers n and the reference thickness. The reference feature matrix of the reference thickness is generated by combining the optical admittance of the number of layers n. The cumulative feature matrix is ​​updated based on the final thickness of the number of layers n-1. The coefficient matrix is ​​generated according to the reference feature matrix and the cumulative feature matrix. The equivalent admittance is calculated based on the coefficient matrix, and finally the equivalent reflectivity is obtained.

[0020] In this invention, in step 5, the real-time reflectivity is substituted into the reflectivity function, and the corresponding thickness value is the real-time thickness.

[0021] In this invention, in step 6, the beam current regulation ratio is the ratio of deposition rate to ion beam current. The effective deposition area is collected, the target density and deposition density are input, the beam current regulation ratio is initialized, and the beam current regulation ratio is updated in combination with the current ion beam current and the real-time deposition rate.

[0022] In this invention, in step 7, the real-time thickness predicted in step 5 is stored as the final thickness of layer n, the single-layer error of layer n is calculated, the cumulative error and cumulative compensation are calculated by combining the single-layer error of each deposition layer, the cumulative compensation is allocated to the deposition thickness of the remaining deposition layers, the thickness compensation amount of each remaining deposition layer is generated, and the target deposition sequence is updated.

[0023] A processing apparatus for implementing the processing method of the laser gyroscope reflector, comprising:

[0024] The deposition chamber is configured to hold the reflector substrate;

[0025] An ion source is configured to emit an ion beam that bombards a target plate and sputters target atoms.

[0026] The first gas source is configured to provide working gas to the ion source;

[0027] A light generator is configured to emit incident light toward a reflector substrate;

[0028] A light receiver is configured to receive reflected light from a reflector substrate;

[0029] The data processing unit is configured to predict real-time thickness;

[0030] The internal control unit is configured to adjust the ion beam current based on the real-time deposition rate;

[0031] The external control unit is configured to calculate the accumulated error and update the target deposition sequence.

[0032] Before each deposition process begins, the data processing unit fits a reflectivity function based on a baseline deposition rate. After each deposition process begins, the real-time thickness is periodically updated based on the reflectivity function and the real-time reflectivity.

[0033] The processing method and apparatus for a laser gyroscope reflector according to the present invention have the following beneficial effects: Before each deposition process, the present invention presets multiple sets of reference thicknesses based on a reference deposition rate and sampling interval. These reference thicknesses serve as references for thickness changes during subsequent processing. To smooth the data, a reflectivity function is fitted to the reference thickness and the equivalent reflectivity. During processing, the real-time thickness of the current deposition layer can be quickly found from the reflectivity function by combining the current real-time reflectivity, eliminating the process of repetitive data calculation, resulting in fast data processing speed and improved processing accuracy. Furthermore, the present invention adjusts the ion beam current through real-time deposition rate feedback, making the deposition rate at the current processing site approach the reference deposition rate, ensuring that the reference thickness preset based on the reference deposition rate is consistent with the on-site processing conditions. Attached Figure Description

[0034] Figure 1 A schematic diagram of a preferred laser gyroscope;

[0035] Figure 2 To optimize the optical path diagram of the laser gyroscope;

[0036] Figure 3 This is a flowchart of the processing method for the laser gyroscope reflector of the present invention;

[0037] Figure 4 Reflectance curves of deposited layers with different refractive indices;

[0038] Figure 5 This is a schematic diagram of the ion beam bombardment target of the present invention;

[0039] Figure 6 This is a schematic diagram of the fitted reflectance function of the present invention;

[0040] Figure 7 This is a schematic diagram of the data cyclic update of the present invention;

[0041] Figure 8 The final thickness curves for each layer number under different processing methods;

[0042] Figure 9 This is a flowchart of the initialization process for the ion beam in this invention;

[0043] Figure 10 This is a flowchart illustrating the updated beam control ratio of the present invention;

[0044] Figure 11 This is a block diagram of the processing apparatus for implementing the processing method of the laser gyroscope reflector of the present invention.

[0045] The reference numerals in the attached figures are as follows: laser gyroscope 10, cathode emitter 11, resonant cavity 12, anode emitter 13, first plane mirror 14, second plane mirror 15, spherical mirror 16, light combining prism 17, deposition chamber 21, ion source 22, first gas source 23, light generator 24, light receiver 25, target plate 26, vacuum pump 27, second gas source 28, neutralizer 29, target material 30, and mirror substrate 40. Detailed Implementation

[0046] To better understand the purpose, technical solution, and advantages of this application, the application is described and illustrated below in conjunction with the accompanying drawings and embodiments.

[0047] Laser gyroscopes are commonly used components in modern inertial navigation technology and can be installed in angular rate measurement devices. They typically consist of a ring-shaped helium-neon laser, which operates with two laser beams, one clockwise and one counterclockwise. For example... Figure 1 and Figure 2 As shown, the laser gyroscope 10 includes a cathode emitter 11, a resonant cavity 12, an anode emitter 13, a first plane mirror 14, a second plane mirror 15, a spherical mirror 16, and a beam combiner prism 17. The cathode emitter 11 and the two sets of anode emitters 13 generate a first laser and a second laser, respectively. The first and second lasers are emitted in opposite directions and intersect at the beam combiner prism 17 after passing through the first plane mirror 14, the second plane mirror 15, and the spherical mirror 16. A photodetector receives the imaging signal from the beam combiner prism 17 and measures the angular velocity of the laser gyroscope based on the interference data of the imaging signal.

[0048] A reflector is an indispensable component in a laser gyroscope. Its function is to change the direction of light propagation, causing photons to circulate repeatedly in the resonant cavity and form a stable standing wave. Any tiny energy loss will make it difficult to maintain laser oscillation or cause frequency instability. Existing technology uses secondary deposition coating on the reflector to reduce energy loss. This invention can quickly predict the thickness of each deposition layer on the reflector by using a preset reference thickness before processing, thus improving the accuracy of secondary processing. Example 1

[0049] like Figures 1 to 8 As shown, a method for processing a laser gyroscope reflector according to the present invention includes the following steps. Before each deposition process, the present invention presets a reference thickness based on a baseline deposition rate. During the processing, the real-time thickness of the deposition layer can be quickly predicted by combining the current real-time reflectivity, thereby improving the processing accuracy.

[0050] Step 1: Clean the mirror substrate, then fix the mirror substrate in the deposition chamber, preset the target deposition sequence, the target deposition sequence includes different layers with different deposition thicknesses, initialize the ion beam current and beam current regulation ratio, and initialize the number of layers n=1.

[0051] The reflector substrate is pre-cleaned with a cleaning solution, and then wiped while being cleaned using the spray solution. This prevents the substrate from retaining fine dust, fingerprints, oil, or fibers from packaging materials. The cleaning solution typically consists of the following proportions: 50%–90% deionized water, 10%–30% distilled alcohol, and 0–20% distilled acetone. The pressure of the cleaning solution is usually controlled within a low pressure range of 0.1–0.5 MPa, and the flow rate is generally controlled at 8–20 L / min.

[0052] The reflector consists of a reflector substrate, an N / 2+1 layer of Ta2O5 deposition layer, and an N / 2 layer of SiO2 deposition layer, where N is an even number and 12 ≤ N ≤ 18. For example... Figure 4 In the figure, relative thickness refers to the ratio of the deposition thickness to the laser gyroscope wavelength. For example, a relative thickness of 0.25 indicates a deposition thickness of 1 / 4 wavelength. According to the operating requirements of the laser gyroscope, the deposition thickness should be as close as possible to 1 / 4 wavelength of the corresponding deposition layer. In the preset target deposition sequence [x1, x2,..., x...] n-1 , x n ,..., x N-1 , x N In the figure, when n is odd, the deposition thickness x n =λ0 / (4ε1), when n is even, the deposition thickness x n =λ0 / (4ε2), where λ0 is the wavelength of the laser gyroscope, ε1 is the refractive index of the Ta2O5 deposition layer, and ε2 is the refractive index of the SiO2 deposition layer. The method for initializing the ion beam current can be referred to in Example 2. The method for initializing the beam current adjustment ratio can be referred to in Example 4.

[0053] Step 2: Generate multiple reference thicknesses based on the baseline deposition rate and deposition thickness, calculate the equivalent reflectance corresponding to each reference thickness, and fit a reflectance function using multiple sets of reference thicknesses and equivalent reflectances. The deposition thickness is the target thickness of this deposition layer. The interpolation step size is calculated based on the baseline deposition rate and sampling interval, and the deposition thickness is divided into multiple arithmetic progression reference thicknesses based on the interpolation step size. The equivalent reflectance is calculated based on the reference feature matrix of each reference thickness and the cumulative feature matrix of layer number n-1. Then, a reflectance function is fitted with reference thickness as the horizontal axis and equivalent reflectance as the vertical axis, corresponding to layer number n. The reflectance function represents the smoothed reflectance-thickness relationship, and can be used to quickly find the thickness fitted to each reflectance. Combined with the reflectance curve, the preferred reflectance function can be a trigonometric function, such as... Figure 6As shown. The preferred reflectivity function generation process is as described in Example 3.

[0054] Specifically, the phase thickness is calculated based on the refractive index of the nth layer and the reference thickness. A reference characteristic matrix for this reference thickness is generated by combining the optical admittance of the nth layer. The cumulative characteristic matrix is ​​updated based on the final thickness of the n-1th layer. A coefficient matrix is ​​generated based on the reference characteristic matrix and the cumulative characteristic matrix. The equivalent admittance is calculated based on the coefficient matrix, and finally, the equivalent reflectivity is obtained. When n=1, the cumulative characteristic matrix is ​​the identity matrix.

[0055] Step 3: The ion source emits an ion beam into the deposition chamber. The ion beam bombards the target material, sputtering target atoms, which then form a deposition layer on the reflector substrate. For example... Figure 5 As shown, a target material is mounted on the target plate, and target atoms are gradually deposited on the reflector substrate. As bombardment continues, the real-time thickness of the deposited layer gradually increases. The real-time deposition rate is related to the effective deposition area, ion beam current, and saturation discharge voltage.

[0056] Step 4: The light generator emits incident light onto the reflector substrate through the first channel, and the light receiver receives the reflected light through the second channel and measures the intensity of the reflected light to calculate the real-time reflectivity. As the real-time thickness gradually increases, the intensity of the reflected light will change due to the change in the equivalent reflectivity. The real-time reflectivity can be calculated in reverse based on the intensity of the reflected light. Figure 5 The light generator and light receiver are fixed on the opposite side of the sputtering zone to reduce the space required for the deposition chamber. In another embodiment, the light generator and light receiver can be fixed on the same side of the sputtering zone, and the reflected light intensity can be periodically collected by setting a switchable working platform. The present invention can also provide a first and a second light-shielding channel to reduce light intensity interference from the ion beam.

[0057] Step 5: Predict the real-time thickness based on the reflectivity function and real-time reflectivity. If the real-time thickness is less than the deposition thickness of layer number n, proceed to step 6; otherwise, proceed to step 7. Since the sampling interval remains the same, substitute the real-time reflectivity into the reflectivity function; the corresponding thickness value is the real-time thickness. It should be noted that if substituting the reflectivity function yields two sets of thickness values ​​at that reflectivity, the thickness value closest to the previously sampled real-time thickness can be selected. For example... Figure 7 As shown, the processing method of the present invention includes N deposition steps for depositing layers. In each deposition step, a reflectivity function is first generated based on the deposition thickness and a reference deposition rate. In each sampling of the deposition step, the real-time reflectivity is calculated based on the incident and reflected light, and then the reflectivity function is used to predict the real-time thickness. Simultaneously, the ion beam current is updated according to the real-time deposition rate so that the current operating conditions are consistent with the reference thickness initially set by the system.

[0058] Step 6: Define a sliding window based on the number of samplings. Calculate the real-time deposition rate from multiple sets of real-time thicknesses within the sliding window, update the beam current regulation ratio, adjust the ion beam current of the ion source, and return to Step 3. For the sampling period, a sliding window can be set, with each sliding window containing 4 samplings. Record the real-time thickness of 4 consecutive sampling sets, and then calculate the real-time deposition rate. The beam current regulation ratio is the ratio of the deposition rate to the ion beam current. Combining the current ion beam current and the real-time deposition rate, the ratio of the current deposition rate to the ion beam current can be predicted, and the beam current regulation ratio can be updated. Then, based on the difference between the current real-time deposition rate and the reference deposition rate, and the beam current regulation ratio, adjust the ion beam current of the ion source. This invention adjusts the ion beam current through real-time deposition rate feedback, making the current on-site deposition rate approach the reference deposition rate, ensuring that the reference thickness preset based on the reference deposition rate is consistent with the on-site processing conditions, as described in Example 4.

[0059] Step 7: If n is less than the maximum number of layers N+1, adjust the target material, n=n+1, and return to step 2; otherwise, end the task. Typically, high-reflectivity Ta2O5 and low-reflectivity SiO2 deposition layers are deposited alternately, so the target material also switches between them, and both n=1 and n=N+1 use Ta2O5 targets. Due to the periodicity of optical detection, real-time thickness inevitably deviates. This invention calculates the cumulative error and updates the target deposition sequence, reducing the impact of error accumulation on the overall optical performance of the mirror. This invention stores the real-time thickness predicted in step 5 as the final thickness of layer number n, and calculates the single-layer error of layer number n based on the final thickness and the deposition thickness. In one embodiment, the cumulative error and cumulative compensation are calculated by combining the single-layer error of each deposition layer, and the cumulative compensation is allocated to the deposition thickness of the remaining deposition layers to generate the thickness compensation amount for each remaining deposition layer, updating the target deposition sequence. Figure 8 The solid and dashed curves represent the final thickness curves of each layer in the processing methods proposed in this invention and the prior art, respectively. Compared with the prior art, the fluctuation range of the final thickness curve of this invention is significantly smaller. Example 2

[0060] like Figure 9 As shown, this embodiment further discloses preferred steps for initializing the ion beam. In a simpler embodiment, a fixed ion beam of 100-500 mA can be initialized and gradually adjusted during subsequent deposition. This embodiment sets a more precise ion beam based on sputtering principles to improve the iterative convergence speed.

[0061] Step 101: Preset the saturation discharge voltage and power density of the ion source. The effect of discharge voltage on sputtering yield has a saturation region. To obtain higher efficiency and better deposition quality, the discharge voltage U is usually within this saturation region, typically U = 1000V. The power density of the Ta₂O₅ deposition layer is typically around 2W / cm². 2 The power density of SiO2 deposits is typically around 1.6 W / cm². 2 about.

[0062] Step 102: Set the heat accumulation correction factor based on the number of layers. Set the ion source power for each deposition layer according to the power density and the heat accumulation correction factor. As the number of layers increases, heat gradually accumulates in the deposition chamber. It is necessary to compensate for the impact of heat accumulation on the power. The measured value of the heat accumulation correction factor T is typically -0.1. Ion source power P n =ρ n S f [1+T(n-1) / (N-1)], N≥2, where S f For effective deposition area, it is typically 300 mm. 2 Up to 1200mm 2 Between. ρ n Let n be the power density of sediment layer n. The total number of sediment layers is N+1, where n = 1, 2, ..., N+1.

[0063] Step 103: Initialize the ion beam current for each deposition layer based on the saturation discharge voltage and ion source power. Ion beam current I n =P n / U. Considering the thermal accumulation effect, the ion beam current of the same target material gradually decreases with the increase of the number of deposition layers. Typically, the ion beam current of Ta2O5 deposition layers is greater than that of SiO2 deposition layers. Example 3

[0064] This embodiment further discloses a preferred method for generating a reflectivity function. The present invention generates a reference thickness based on a baseline deposition rate and deposition thickness, and generates a reflectivity function based on multiple sets of reference thicknesses and equivalent reflectivities. During processing, it can combine the current real-time reflectivity to quickly predict the real-time thickness of the deposition layer, thereby improving processing accuracy.

[0065] Multiple reference thicknesses are generated. The interpolation step size Δx is calculated based on the baseline deposition rate v0 and the sampling interval Δt, where Δx = v0·Δt. The interpolation step size Δx is then used to calculate the deposition thickness x. n Generate K reference thicknesses w k w k =k·Δx,k=1,2,…,K. K=floor(x n / Δx), floor() is the floor function. The baseline deposition rate can be 3.3 × 10-11 m / s. The sampling interval of this invention is, for example, 10 s.

[0066] Calculate the phase thickness corresponding to each reference thickness. Phase thickness δ k =2πε n w k cosθ n / λ1. Where ε n Let θ be the refractive index of the number of layers n, and λ1 be the wavelength of the incident light. n The refraction angle for the number of layers n can be calculated using the incident angle between the incident light and the reflecting mirror, combined with Snell's law.

[0067] Calculate the reference feature matrix for each reference thickness. Reference Feature Matrix Where i is the imaginary unit, and η n is the optical admittance of the number of layers n, and its value depends on the material of the deposited layer.

[0068] Update the cumulative feature matrix of layer n-1. The cumulative feature matrix of layer n-1 is the product of the feature matrices of the sedimentary layers from layer 1 to layer n-1, i.e., the cumulative feature matrix. The characteristic matrix M of the sedimentary layer of layer j j The final thickness is calculated using the same method as the reference feature matrix. j=1,2,...,n-1.

[0069] Calculate the equivalent reflectivity for each reference thickness. Define the coefficient matrix. The equivalent admittance R of the mirror at the k-th reference thickness k =(R 21 +R 22 ·η') / (R 11 +R 12 ·η'). η' is the optical admittance of the mirror substrate. The mirror substrate is usually glass, η' = 1.52. The equivalent reflectivity Z of the mirror at this time is... k =|(η0-R k ) / (η0+R k )| 2 η0 is the optical admittance of the incident medium. The deposition chamber is a protective gas, and the incident medium is usually air. η0 can be taken as 1.0.

[0070] Generate the reflectance function. For example... Figure 4 As shown, under ideal conditions, since the reference thickness is ≤ one-quarter wavelength, the equivalent reflectance increases monotonically with the monotonic increase of the reference thickness. A reflectance function is obtained by smoothly fitting multiple sets of equivalent reflectance and reference thickness curves. This reflectance function reflects the functional relationship between the reflectance of film layer n and its thickness. Based on the reflectance curve, the preferred reflectance function can be a trigonometric function, such as... Figure 6 As shown. The laser gyroscope is designed with a wavelength of 632.8 nm, a refractive index of 2.15 for Ta2O5, and a refractive index of 1.54 for SiO2. The equivalent reflectivity typically reaches its maximum at one-quarter wavelength. Example 4

[0071] This embodiment further discloses preferred steps for initializing and updating the beam current regulation ratio. The beam current regulation ratio β is the ratio of deposition rate v to ion beam current I. Unlike discharge voltage, which has a saturation range, ion beam current and deposition rate have a strong linear relationship. This invention can acquire the effective deposition area, input the target density and deposition density, and initialize the beam current regulation ratio for each layer.

[0072] Specifically, the beam modulation ratio β for initializing layer number n n =μ·(Ym t ρ f ) / (eS f ρ t μ is the transmission efficiency, typically taken as 0.4-0.7. Y is the sputtering yield, a dimensionless quantity. The sputtering yield varies depending on the target material; typically, Ta₂O₅ has a sputtering yield of 0.6-0.8, and SiO₂ has a sputtering yield of 0.5-0.7. e is the electron charge, typically 1.6 × 10⁻⁶. -19 C. m t S is the atomic mass of the target material. f For the effective deposition area, ρ f ρ is the sediment density. t Let n be the density of the target material. n = 1, 2, ..., N+1.

[0073] The above algorithm is a theoretical formula. In actual operation, due to factors such as temperature, target purity, and equipment power, the beam current adjustment ratio does not strictly satisfy the above relationship. Figure 10 The present invention preferably combines real-time deposition rate update beam adjustment ratio.

[0074] Step 601: Define a sliding window based on the number of samples. For example, the sliding window has M sampling times, where the sampling time of sampling time m is t. nm The real-time thickness is d nm For a sampling period of 10 seconds, a sliding window of 100 seconds can be set, with each sliding window containing 10 samples.

[0075] Step 602: Calculate the real-time deposition rate. Record multiple sets of real-time thicknesses within the sliding window and calculate the real-time deposition rate. (Refer to...) Figure 7 For M sets of real-time thickness data within the sliding window: {(t n1 ,d n1 ),(t n2 ,dn2 ),…,(t nm ,d nm ),…,(t nM ,d nM Real-time deposition rate .

[0076] Step 603: Update the beam regulation ratio. In one embodiment, the updated beam regulation ratio β n '=v n / I n I n For the current ion beam current. In a more preferred embodiment, the beam current modulation ratio is updated more smoothly by taking historical weights into account. β n '=v n / I n +αβ n α represents the historical weight. In a more robust equipment calibration process, α ≤ 0.3.

[0077] Step 604: Adjust the ion beam current of the ion source. Adjust the ion beam current of the ion source based on the updated beam current control ratio. Adjusted ion beam current I n '=I n +(v0-v n )β n v0 is the baseline deposition rate, which can be between 0.1 nm / s and 5.0 nm / s. Example 5

[0078] like Figure 5 and Figure 11 As shown, a processing apparatus for implementing the processing method of the laser gyroscope reflector according to the present invention includes: a deposition chamber 21, an ion source 22, a first gas source 23, a light generator 24, a light receiver 25, a data processing unit, an internal control unit, and an external control unit.

[0079] The deposition chamber 21 is configured to fix the reflector substrate 40. The ion source 22 is configured to emit an ion beam that bombards a target 30, sputtering target atoms. Similar to the deposition layer material, the target 30 is typically a Ta₂O₅ / SiO₂ sheet. A first gas source 23 is configured to supply a working gas to the ion source. The working gas is, for example, helium.

[0080] Light generator 24 is configured to emit incident light toward the mirror substrate. Light receiver 25 is configured to receive reflected light from the mirror substrate. The incident light is typically monochromatic light at 405 nm, 532 nm, or 633 nm. Light receiver 25 may be equipped with a filter to reduce light intensity interference from the ion beam.

[0081] The data processing unit is configured to predict real-time thickness. Before each deposition step, the data processing unit fits a reflectance function based on a baseline deposition rate. After each deposition step begins, the real-time thickness is periodically updated based on the reflectance function and the real-time reflectance. The internal control unit is configured to adjust the ion beam current based on the real-time deposition rate. The external control unit is configured to calculate the cumulative error and update the target deposition sequence.

[0082] Since there is a strong linear relationship between ion beam current and deposition rate, this invention mainly adjusts the deposition process by regulating the ion beam current of the ion source. Besides the ion beam current, other operating parameters of the processing apparatus of this invention can be determined in conjunction with requirements such as mirror size and processing accuracy, as shown in the table below.

[0083]

[0084] The processing apparatus of the present invention may further include a target plate 26, a target plate control unit, a vacuum pump 27, a second gas source 28, an equipment controller, a storage unit, and a neutralizer 29. The target plate 26 is used to fix the target material 30, and the target plate control unit is used to switch the target plate 26 that fixes different target materials 30. The vacuum pump 27 is used to extract impurity gases from the deposition chamber. The second gas source 28 is used to fill the deposition chamber 21 with a protective gas, such as argon, oxygen, or nitrogen trifluoride. The equipment controller is used to control the operation of the second gas source and the target plate control unit after the real-time thickness of the current deposition layer reaches the target. The storage unit is used to store the updated target deposition sequence to determine the operating time of the equipment controller. The neutralizer 29 is used to provide neutralized ions. The neutralizer 29 emits a low-energy electron stream towards the positively charged ion beam. These negatively charged electron streams combine with the positively charged ion beam, thereby maintaining electroneutrality.

[0085] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for fabricating a laser gyroscope reflector, characterized in that, Includes the following steps: Step 1: Clean the mirror substrate, then fix the mirror substrate in the deposition chamber, preset the target deposition sequence, the target deposition sequence includes different layers of deposition thickness, initialize the ion beam current and beam current regulation ratio, and initialize the number of layers n=1; Step 2: Generate multiple reference thicknesses based on the baseline deposition rate and deposition thickness, calculate the equivalent reflectance corresponding to each reference thickness, and fit the reflectance function with multiple sets of reference thicknesses and equivalent reflectances; Step 3: The ion source emits an ion beam into the deposition chamber. After the ion beam bombards the target material, it sputters target atoms, and the target atoms form a deposition layer on the reflector substrate. Step 4: The light generator emits incident light into the reflector substrate through the first channel, and the light receiver receives the reflected light through the second channel and measures the intensity of the reflected light to calculate the real-time reflectivity; Step 5: Predict the real-time thickness based on the reflectivity function and real-time reflectivity. If the real-time thickness is less than the deposition thickness of layer number n, proceed to step 6; otherwise, proceed to step 7. Step 6: Define a sliding window based on the number of samplings, calculate the real-time deposition rate from multiple sets of real-time thicknesses within the sliding window, update the beam current adjustment ratio, adjust the ion beam current of the ion source, and return to Step 3; Step 7: If n is less than the maximum number of layers N+1, adjust the target material so that n=n+1, and return to step 2; otherwise, end the task. In step 2, the interpolation step size is calculated based on the baseline deposition rate and sampling interval. Multiple reference thicknesses are determined based on the interpolation step size and deposition thickness. The equivalent reflectance is calculated based on the reference feature matrix of each reference thickness and the cumulative feature matrix of layer number n-1. Then, a reflectance function of layer number n is fitted with the reference thickness as the horizontal axis and the equivalent reflectance as the vertical axis. The phase thickness is calculated based on the refractive index of layer number n and the reference thickness. A reference characteristic matrix is ​​generated for this reference thickness using the optical admittance of layer number n. The cumulative characteristic matrix is ​​updated based on the final thickness of layer number n-1. A coefficient matrix is ​​generated based on the reference characteristic matrix and the cumulative characteristic matrix. The equivalent admittance is calculated based on the coefficient matrix, and finally, the equivalent reflectance is obtained. In step 6, the beam current regulation ratio is the ratio of deposition rate to ion beam current. The effective deposition area is collected, the target density and deposition density are input, the beam current regulation ratio is initialized, and the beam current regulation ratio is updated in combination with the current ion beam current and real-time deposition rate.

2. The method for processing the laser gyroscope reflector according to claim 1, characterized in that, In step 1, the reflector consists of a reflector substrate, an N / 2+1 layer of Ta2O5 deposition layer, and an N / 2 layer of SiO2 deposition layer, where N is an even number and 12≤N≤18. The reflector is positioned within a preset target deposition sequence [x1, x2,..., x...]. n-1 , x n ,..., x N-1 , x N In the figure, when n is odd, the deposition thickness x n =λ0 / (4ε1), when n is even, the deposition thickness x n =λ0 / (4ε2), where λ0 is the wavelength of the laser gyroscope, ε1 is the refractive index of the Ta2O5 deposition layer, and ε2 is the refractive index of the SiO2 deposition layer.

3. The processing method of the laser gyroscope reflector according to claim 1, characterized in that, In step 1, the initialization of the ion beam includes the following steps: Step 101: Preset the saturation discharge voltage and power density of the ion source; Step 102: Set the thermal accumulation correction coefficient based on the number of layers, and set the ion source power for each deposition layer according to the power density and the thermal accumulation correction coefficient; Step 103: Initialize the ion beam current of each deposition layer according to the saturation discharge voltage and ion source power.

4. The processing method of the laser gyroscope reflector according to claim 1, characterized in that, In step 5, the real-time reflectivity is substituted into the reflectivity function, and the corresponding thickness value is the real-time thickness.

5. The method for processing the laser gyroscope reflector according to claim 1, characterized in that, In step 7, the real-time thickness predicted in step 5 is stored as the final thickness of layer n, the single-layer error of layer n is calculated, the cumulative error and cumulative compensation are calculated by combining the single-layer error of each deposition layer, the cumulative compensation is allocated to the deposition thickness of the remaining deposition layers, the thickness compensation amount of each remaining deposition layer is generated, and the target deposition sequence is updated.

6. A processing apparatus for implementing the processing method of the laser gyroscope reflector according to any one of claims 1 to 5, characterized in that, include: The deposition chamber is configured to hold the reflector substrate; An ion source is configured to emit an ion beam that bombards a target plate and sputters target atoms. The first gas source is configured to provide working gas to the ion source; A light generator is configured to emit incident light toward a reflector substrate; A light receiver is configured to receive reflected light from a reflector substrate; The data processing unit is configured to predict real-time thickness; The internal control unit is configured to adjust the ion beam current based on the real-time deposition rate; The external control unit is configured to calculate the accumulated error and update the target deposition sequence. Before each deposition process begins, the data processing unit fits a reflectivity function based on a baseline deposition rate. After each deposition process begins, the real-time thickness is periodically updated based on the reflectivity function and the real-time reflectivity.

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