Method and equipment for measuring refractive index of coated anti-reflection coating

Abstract

The invention relates to the technical field of refractive index measurement, in particular to a method and equipment for measuring the refractive index of an anti-reflection coating, and the method comprises the steps: obtaining a reflection spectrum intensity sequence, a three-dimensional data volume matrix, temperature and humidity at each moment; obtaining the structure mismatch degree at the current moment according to the power spectrum density of the spectrum sequence of the reflection spectrum intensity sequence at the current moment and the gradient characteristics of the three-dimensional data volume matrix; according to the structure mismatch degree, the temperature and the humidity at each moment, obtaining a predicted value of the structure mismatch degree at the current moment, and according to the maximum value and the complexity of the predicted value of the structure mismatch degree, obtaining a refractive index disturbance index at the current moment; and judging the deviation condition of the refractive index measurement value at the current moment, and correcting the refractive index measurement value at the current moment by using the refractive index disturbance index at the current moment. By quantifying the refractive index deviation degree at each moment, the refractive index at each moment is corrected, and the accuracy of refractive index measurement is improved.

Description

Technical Field

[0001] This application relates to the technical field of refractive index measurement, and particularly to a method and device for measuring the refractive index of an anti-reflection coating. Background Art

[0002] Anti-reflection coatings (AR coatings) are widely used in fields such as lenses, solar cells, and display screens by reducing surface reflection light loss. As a core parameter, the refractive index of the coating directly affects its optical performance. Therefore, accurately measuring the refractive index has become the key to optimizing coating design. In the early days, most coatings were single-layer structures, and refractive index measurement relied on traditional ellipsometers or spectrophotometry. With the development of metamaterials, the complexity of the coating structure has increased significantly.

[0003] In the measurement of the refractive index of a multi-layer anti-reflection coating structure, a multi-layer heterogeneous system (such as a graded refractive index coating) often forms a non-abrupt refractive index change due to material interpenetration, interface diffusion, or compositional segregation in the deposition process, resulting in a significant deviation between the refractive index measured by a traditional optical model based on the stepped layering assumption and the actual refractive index. Existing technologies mainly address this technical problem by improving the model adaptability, such as introducing a continuous gradient function or subdividing virtual sub-layers, and combining an inverse optimization algorithm to invert the gradient parameters. However, this method is not easy to select the distribution function and still results in systematic measurement errors in the refractive index. Therefore, there is an urgent need for a method that can improve the measurement accuracy of the refractive index measured by a traditional optical model based on the stepped layering assumption. Summary of the Invention

[0004] In order to solve the above technical problems, the purpose of this application is to provide a method and device for measuring the refractive index of an anti-reflection coating, and the specific technical solutions adopted are as follows: In the first aspect, an embodiment of this application provides a method for measuring the refractive index of an anti-reflection coating, and the method includes the following steps: Obtain the reflection spectrum intensity data, temperature, humidity, and refractive index data in the lateral, longitudinal, and depth directions of the anti-reflection coating at each moment; use the preset time period before each moment as the monitoring period for each moment; obtain the reflection spectrum intensity sequence at each moment according to the reflection spectrum intensity data within the monitoring period of each moment; obtain the three-dimensional data volume matrix at each moment according to the refractive index data in three directions within the monitoring period of each moment; Obtain the structural mismatch degree at the current moment according to the power spectral density of the frequency spectrum sequence of the reflection spectrum intensity sequence at the current moment and the first derivative of each row in the three-dimensional data volume matrix; obtain the predicted value of the structural mismatch degree at each moment within the future preset time length at the current moment according to the structural mismatch degree, temperature, and humidity at each moment within the monitoring period of the current moment; obtain the refractive index perturbation index at the current moment according to the maximum value and complexity of all the predicted values of the structural mismatch degree within the future preset time length at the current moment; Obtain the refractive index measurement values of the antireflection coating in each direction at the current moment, judge the deviation of the refractive index measurement values in each direction at the current moment, and correct the refractive index measurement values in each direction at the current moment by using the refractive index perturbation index at the current moment.

[0005] Preferably, the specific process of obtaining the reflection spectrum intensity sequence at each moment is as follows: Arrange all the reflection spectrum intensity data within the monitoring period at each moment in ascending order of time to obtain the reflection spectrum intensity sequence at each moment.

[0006] Preferably, the process of obtaining the three-dimensional data volume matrix at each moment is as follows: Take the refractive index data in the horizontal, vertical, and depth directions within the monitoring period at each moment as the first row, the second row, and the third row respectively, and arrange them in ascending order of time to obtain the three-dimensional data volume matrix at each moment.

[0007] Preferably, the calculation formula for the structural mismatch degree at the current moment is: ; where is the structural mismatch degree at the current moment, and E is the power spectral density of the frequency spectrum sequence of the reflection spectrum intensity sequence at the current moment; , and are the first-order derivatives of the three-dimensional data volume matrix at the current moment in the first row, the second row, and the third row respectively.

[0008] Preferably, the process of obtaining the predicted value of the structural mismatch degree for the future preset time length at the current moment is as follows: Denote the sequences formed by arranging the structural mismatch degree, temperature, and humidity data at all moments within the monitoring period at the current moment in ascending order of time as the structural mismatch degree sequence, temperature sequence, and humidity sequence at the current moment; Take the structural mismatch degree sequence, temperature sequence, and humidity sequence at the current moment as the input of the random forest algorithm, and output the predicted value of the structural mismatch degree for the future preset time length at the current moment.

[0009] Preferably, the calculation formula for the refractive index perturbation index at the current moment is: ; where is the refractive index perturbation index at the current moment, is the maximum value among all the predicted values of the structural mismatch degree within the future preset time length at the current moment, is the approximate entropy of all the predicted values of the structural mismatch degree within the future preset time length at the current moment.

[0010] Preferably, the specific process of obtaining the refractive index measurement values of the antireflection coating in each direction at the current moment is as follows: using the reflection spectrum intensity data at the current moment, the refractive index measurement values of the antireflection coating in each direction at the current moment are obtained by adopting a traditional optical model based on the stepped layer hypothesis.

[0011] Preferably, the specific process of judging the deviation of the refractive index measurement values in each direction at the current moment is as follows: obtaining a calibration database storing the reference refractive indices in various process scenarios; respectively calculating the differences between the refractive index measurement values in each direction at the current moment and the reference refractive indices in the corresponding same process scenario in the calibration database; if the difference is equal to 0, it is determined that there is no deviation in the refractive index measurement value in the corresponding direction at the current moment; otherwise, there is a deviation in the refractive index measurement value in the corresponding direction at the current moment.

[0012] Preferably, the specific process of correcting the refractive index measurement values in each direction at the current moment is as follows: When the difference is greater than 0, the expression for correcting the refractive index measurement value in a single direction at the current moment is: ; where is the corrected refractive index in a single direction at the current moment, is the refractive index measurement value in a single direction at the current moment, is the refractive index perturbation index at the current moment, is the maximum value of the refractive index perturbation index within the historical moment, is the preset compensation coefficient; When the difference is less than 0, the expression for correcting the refractive index measurement value in a single direction at the current moment is: ; When the difference is equal to 0, there is no need to correct the refractive index measurement value in a single direction at the current moment.

[0013] In a second aspect, an embodiment of the present application further provides a refractive index measurement device for coating an antireflection coating, including a memory, a processor, and a computer program stored in the memory and running on the processor. When the processor executes the computer program, the steps of the refractive index measurement method for coating an antireflection coating described in any one of the above are implemented.

[0014] The present application has at least the following beneficial effects: 1. In view of the problem that the traditional stepped layer model cannot describe the non - linear refractive index gradient, resulting in low refractive index measurement accuracy, the present application first adopts the adaptive Fourier decomposition algorithm to extract the frequency - domain energy distribution eigenvector, combines local weighted regression to fit the spatial gradient, quantifies the non - linear intensity and spatial gradient intensity of the coating refractive index change, which helps to quantify the deviation of the refractive index measured by the subsequent traditional optical model based on the stepped layer hypothesis. 2. Aiming at the problem that the measurement errors caused by material interpenetration, environmental disturbance and process fluctuation are unpredictable, using the structure mismatch degree sequence and environmental parameters as inputs, the random forest algorithm is adopted to predict the structure mismatch degree within a future time length, construct a refractive index perturbation index, exclude the one-sided influence of a single environmental factor or process fluctuation, and comprehensively quantify the measurement errors caused by the coupling of multiple factors in the antireflection coating.

[0015] 3. Based on the refractive index perturbation index, the refractive index measurement values at each moment are dynamically corrected, realizing high-precision and strong robustness in the refractive index measurement of the antireflection coating, solving the problem of systematic error accumulation of the traditional optical model based on the stepped layer hypothesis in the non-linear gradient scenario, and improving the accuracy of the refractive index measurement of the antireflection coating. Brief Description of the Drawings

[0016] In order to more clearly illustrate the technical solutions and advantages in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0017] Figure 1 It is a flowchart of the steps of a refractive index measurement method for a coated antireflection coating provided by an embodiment of the present application; Figure 2 It is a flowchart for correcting the refractive index measurement values in each direction at the current moment provided by an embodiment of the present application. Detailed Embodiments

[0018] In order to further elaborate on the technical means and effects adopted by the present application to achieve the intended invention purpose, the following, in combination with the drawings and preferred embodiments, details the specific implementation manners, structures, features and effects of a refractive index measurement method and device for a coated antireflection coating proposed according to the present application. In the following description, different "one embodiment" or "another embodiment" do not necessarily refer to the same embodiment. In addition, the specific features, structures or characteristics in one or more embodiments can be combined in any suitable form.

[0019] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which this application belongs.

[0020] The following specifically describes the specific solutions of a refractive index measurement method and device for a coated antireflection coating provided by the present application in combination with the drawings.

[0021] Please refer to Figure 1, which shows a step flowchart of a refractive index measurement method for a coated antireflection coating provided by an embodiment of the present application. The method includes the following steps: Step 1: Obtain the reflection spectrum intensity data, temperature, humidity, and refractive index data in the lateral, longitudinal, and depth directions of the antireflection coating at each moment; use the preset time period before each moment as the monitoring period for each moment; obtain the reflection spectrum intensity sequence at each moment according to the reflection spectrum intensity data within the monitoring period of each moment; obtain the three-dimensional data volume matrix at each moment according to the refractive index data in the three directions within the monitoring period of each moment.

[0022] Since the refractive index of the antireflection coating is affected by environmental disturbances (such as temperature and humidity fluctuations) and process factors (such as material interpenetration, interface diffusion, or composition segregation), its physical structure shows non-linear or random gradients in time and space. For example, changes in temperature and humidity will cause slight changes in the optical properties of the coating material, while the dynamic fluctuations of the deposition process exacerbate the non-uniformity of the refractive index in the depth direction (z-axis), lateral direction (x-axis), and longitudinal direction (y-axis) of the antireflection coating, resulting in different refractive indices of the antireflection coating at different moments. Therefore, it is necessary to correct the refractive index at different moments according to the environmental disturbances and process effects at different moments to improve the measurement accuracy of the refractive index.

[0023] In the antireflection coating measurement device, a polarization modulation unit is installed at the outlet of the broadband light source module to real-time regulate the polarization state of the incident light; a multi-angle detection system (high-precision photodetector array) is integrated on the surface of the sample stage to collect the reflection spectrum intensity data within the incident angle range of 0° to 80°, for analyzing the dynamic optical response of the coating; at the same time, a high-speed optical coherence tomography (OCT) system is deployed, equipped with a high-speed lateral scanning galvanometer, to complete a full coverage scan of the x-y plane at each acquisition moment, and the refractive index distribution in the depth direction (z-axis) of the coating is analyzed through the interference signal of OCT to generate a three-dimensional data volume (x, y, z) of the refractive index distribution in three-dimensional space. The measurement and acquisition of the reflection spectrum and the three-dimensional space distribution data of the refractive index described above are all well-known techniques to those skilled in the art and will not be elaborated here. The temperature and humidity on the antireflection coating are monitored in real time through a temperature and humidity sensor.

[0024] To achieve multi-source data synchronization, the scanning system, spectrometer, and temperature and humidity sensors share the same clock source and adopt a unified acquisition frequency, which is set to 100 Hz in this embodiment. The first a seconds of each moment are used as the monitoring period for each moment. All the reflected spectral intensity data and three-dimensional data volumes within the monitoring periods of each moment are sorted in ascending order of time, obtaining the reflected spectral intensity sequences and three-dimensional data volume matrices for each moment. Among them, the first row, second row, and third row of the three-dimensional data volume matrix are the refractive indices of the anti-reflection coating in the x direction, y direction, and z direction respectively. In this embodiment, a is taken as 10. It should be noted that when the monitoring time before a moment is less than a seconds, the actual existing monitoring time period is used as the monitoring period for that moment.

[0025] Step 2: Obtain the structural mismatch degree at the current moment based on the power spectral density of the frequency spectrum sequence of the reflected spectral intensity sequence at the current moment and the first-order derivative of each row of the three-dimensional data volume matrix; obtain the predicted values of the structural mismatch degrees at each moment within the future preset time length at the current moment based on the structural mismatch degrees, temperature, and humidity at each moment within the monitoring period at the current moment; obtain the refractive index perturbation index at the current moment based on the maximum value and complexity of all the predicted values of the structural mismatch degrees within the future preset time length at the current moment.

[0026] Since it is easy to form non-linear or random refractive index gradients due to material interpenetration, interface diffusion, or compositional segregation during the deposition of multi-layer anti-reflection coatings, traditional optical models based on the stepped-layer hypothesis are difficult to accurately describe their true physical structures, resulting in the deviation of the model inversion results from the actual situation and causing systematic measurement errors in refractive index and thickness.

[0027] Therefore, taking the reflected spectral intensity sequence at the current moment as the input of the Adaptive Fourier Decomposition (AFD) algorithm, in order to balance high-frequency noise suppression and gradient feature retention, the Daubechies4 wavelet basis function and a decomposition depth of 5 layers are set, and the frequency spectrum sequence of the reflected spectral intensity sequence at the current moment is output. This frequency spectrum sequence quantifies the non-linear characteristics of the refractive index change of the coating through frequency-domain energy focusing, where its high-frequency components correspond to interface mutations and the low-frequency components reflect the gradual change trend. Further, calculate the power spectral density of the frequency spectrum sequence at the current moment; the calculation of the power spectral density of frequency-domain energy is a well-known technology, and the specific process will not be elaborated here.

[0028] Subsequently, each row of the three-dimensional data volume matrix at the current moment is taken as the input of the Locally Weighted Scatterplot Smoothing (LOESS) respectively, and the window width is set to 15% of the local sample size, and the first-order derivative of each row is output. The first-order derivative of each row is used to characterize the refractive index gradients of the anti-reflection coating in the x, y, and z directions at the current moment. The weighted neighborhood strategy of LOESS can maintain the spatial continuity of the gradient field and avoid gradient jumps caused by discrete sampling.

[0029] As a preferred embodiment, according to the power spectral density of the spectral sequence of the reflection spectral intensity sequence at the current moment, and the first derivative of each row of the three-dimensional data volume matrix, the structural mismatch degree at the current moment is obtained, which is used to characterize the overall abnormal degree of the coating refractive index during the monitoring period at the current moment.

[0030] In this embodiment, the structural mismatch degree at the current moment is denoted as , and its specific calculation formula is: ; in the formula, is the structural mismatch degree at the current moment, and E is the power spectral density of the spectral sequence of the reflection spectral intensity sequence at the current moment; , and are the first derivatives of the three-dimensional data volume matrix at the first row, the second row, and the third row at the current moment, respectively.

[0031] The power spectral density characterizes the significance degree of the non-linear characteristics of the refractive index change. When its value is larger, it indicates that the non-linear characteristics of the refractive index change of the coating are more significant, and the higher the risk of failure of the hypothesis of the traditional optical model based on the stepped layer hypothesis; , and are used to quantify the refractive index change gradient in each direction of the anti-reflection coating. The squares of the gradients in each direction are summed to eliminate the directional influence and amplify the contribution of the high-intensity gradient region. When its value is larger, it indicates that the absolute intensity of the refractive index change is larger, and then the refractive index gradient of the coating is more abnormal. The structural mismatch degree A comprehensively quantifies the overall abnormal degree of the coating refractive index during the monitoring period at the current moment. The larger the value of A, the more serious the deviation between the actual refractive index of the anti-reflection coating at the current moment and the refractive index measurement value of the traditional model.

[0032] Sort the structural mismatch degrees A at all moments during the monitoring period at the current moment in ascending order of time as the structural mismatch degree sequence at the current moment.

[0033] Furthermore, due to the influence of material interpenetration, interface diffusion, and environmental temperature and humidity fluctuations in the multi-layer heterogeneous system of the anti-reflection coating, there is a systematic error when the traditional optical model inverses the refractive index, and the dynamic fluctuations of the coating preparation process further exacerbate the deviation between the measurement result and the true physical structure.

[0034] Therefore, the sequences composed of temperature and humidity data at all times within the monitoring period at the current time in ascending order of time are denoted as the temperature sequence and humidity sequence at the current time. The structure mismatch degree sequence, temperature sequence, and humidity sequence at the current time are used as the input of the random forest algorithm. The number of trees is set to 200 to avoid overfitting and improve the generalization ability. The maximum depth is set to 8 to limit the complexity to adapt to small sample data. The predicted values of the structure mismatch degree at each time within the next h seconds at the current time are output, which are used to characterize the prediction result of the refractive index measurement error. h is the preset time length, and h takes 10 in this embodiment. The predicted value of the structure mismatch degree quantifies the non-linear correlation between the inversion error of the traditional optical model, gradient characteristics, and environmental perturbations, and reflects the cumulative impact of material interpenetration on the measurement accuracy in complex gradient coatings.

[0035] As a preferred implementation manner, according to the maximum value and complexity of all structure mismatch degree predicted values within the preset time length in the future at the current time, the refractive index perturbation index at the current time is obtained, which is used to characterize the comprehensive deviation degree of the anti-reflection coating refractive index measurement at the current time.

[0036] In this embodiment, the refractive index perturbation index at the current time is denoted as , and its calculation formula is: ; In the formula, is the refractive index perturbation index at the current time, is the maximum value of all structure mismatch degree predicted values within the preset time length in the future at the current time, is the approximate entropy of all structure mismatch degree predicted values within the preset time length in the future at the current time.

[0037] quantifies the most serious measurement deviation of the anti-reflection coating at the current time due to material interpenetration, interface diffusion, or environmental perturbations. The larger its value, the more significant the deviation between the actual refractive index and the model-assumed refractive index of the anti-reflection coating at the current time, resulting in a greater possible systematic error in the measurement system; characterizes the complexity of the influence of environmental temperature and humidity fluctuations and coating dynamic process fluctuations on the measurement error. The larger its value, the more multi-factor coupling effects exist in the anti-reflection coating at the current time, and the more difficult it is to accurately predict its refractive index error through a single model; comprehensively quantifies the comprehensive deviation degree of the anti-reflection coating refractive index measurement at the current time, and reflects the severity of measurement inaccuracy caused by non-linear refractive index distribution and environmental perturbations in complex gradient coatings. The larger its value, the greater the deviation between the refractive index measured by the traditional optical model and the actual refractive index of the anti-reflection coating at the current time.

[0038] Step 3: Obtain the refractive index measurement values of the antireflection coating in each direction at the current moment, determine the deviation of the refractive index measurement values in each direction at the current moment, and correct the refractive index measurement values in each direction at the current moment using the refractive index perturbation index at the current moment.

[0039] The traditional optical model based on the stepped layer assumption establishes a reflectivity calculation model based on the Fresnel equation and thin film interference theory by assuming that the antireflection coating is an ideal stepped layer structure. The transfer matrix method is used to calculate the reflection and transmission behaviors of light waves at each interface layer by layer, and the theoretical reflection spectrum is generated after superimposing the interference effect. Subsequently, a nonlinear least squares fitting algorithm (such as Levenberg-Marquardt) is used to iteratively adjust the initial value of the refractive index to minimize the mean square error between the theoretical refractive index curve and the experimental measurement spectrum, and the refractive index measurement value in a single direction at the current moment is finally output through the Fresnel formula. The single direction refers to any one of the x direction, y direction, and z direction of the antireflection coating. The traditional optical model based on the stepped layer assumption is a well-known technology in the field and will not be elaborated here.

[0040] Aiming at the problem of large measurement deviation of the traditional model when the refractive index perturbation index is high, the present application dynamically corrects the refractive index measurement values in each direction at each moment. The specific correction method is as follows: By introducing a calibration database, the reference refractive indices under various process scenarios (such as material interpenetration, sudden change in temperature and humidity) are pre-stored; calculate the difference between the refractive index measurement value in a single direction at the current moment obtained by inverting the traditional optical model and the reference refractive index in the corresponding same process scenario in the calibration database.

[0041] If the difference is greater than 0, it is determined that the refractive index measurement value in a single direction at the current moment is too large. Then, the refractive index measurement value in a single direction at the current moment is corrected using the refractive index perturbation index at the current moment. The specific correction formula is: ; where, is the corrected refractive index in a single direction at the current moment, is the refractive index measurement value in a single direction at the current moment, is the refractive index perturbation index at the current moment, is the maximum value of the refractive index perturbation index within the historical moment, is a preset compensation coefficient, which is taken as 0.2 in this embodiment, and the implementer can determine it according to the actual situation.

[0042] If the difference is less than 0, it is determined that the refractive index measurement value at the current moment is too small. Then, the correction formula for correcting the refractive index measurement value using the refractive index perturbation index at the current moment is: .

[0043] If the difference is equal to 0, it is determined that the refractive index measurement value at the current moment has no deviation, and there is no need to correct the refractive index at the current moment.

[0044] According to the above correction method, when the B value increases, it indicates that the model inversion error increases. When B approaches the historical maximum value , the correction amount reaches the upper limit , which can effectively reduce the refractive index deviation caused by non-linear gradient or process fluctuations. When the B value is lower, it indicates that the refractive index of the anti-reflection coating at the current moment is closer to the refractive index measured by the traditional model. At this time, the correction amount approaches 0, avoiding misadjustment of reliable results and maintaining the accuracy advantage of the original model. By performing normalization constraints, the correction amount is always proportional to the mismatch degree of the current refractive index measurement value, which can actively correct deviations at high perturbations and maintain measurement stability at low risks, making the refractive index measurement result obtained after correction more accurate.

[0045] Similarly, the refractive index measurement values in each direction at the current moment can be corrected. The flowchart for correcting the refractive index measurement values in each direction at the current moment is as Figure 2 shown.

[0046] Based on the same inventive concept as the above method, an embodiment of the present application further provides a refractive index measurement device for coating an anti-reflection coating, including a memory, a processor, and a computer program stored in the memory and running on the processor. When the processor executes the computer program, it implements the steps of any one of the above methods for measuring the refractive index of a coated anti-reflection coating.

[0047] It should be noted that the above sequence of embodiments of the present application is only for description and does not represent the superiority or inferiority of the embodiments. In addition, the above specific embodiments of this specification have been described. Additionally, the processes depicted in the drawings do not necessarily require the specific order or continuous order shown to achieve the desired results. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0048] Each embodiment in this specification is described in a progressive manner. The same or similar parts among the embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments.

[0049] The above are only the preferred embodiments of the present application and are not intended to limit the present application. Any modifications, equivalent replacements, improvements, etc. made within the principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for measuring the refractive index of an anti-reflection coating, characterized in that, The method includes the following steps: Obtain the reflection spectral intensity data, temperature, humidity, and refractive index data in the lateral, longitudinal, and depth directions of the antireflection coating at each moment; take the preset time period before each moment as the monitoring period of each moment; obtain the reflection spectral intensity sequence of each moment according to the reflection spectral intensity data within the monitoring period of each moment; obtain the three-dimensional data volume matrix of each moment according to the refractive index data in three directions within the monitoring period of each moment; Obtain the structural mismatch degree of the current moment according to the power spectral density of the frequency spectrum sequence of the reflection spectral intensity sequence of the current moment and the first derivative of each row in the three-dimensional data volume matrix; obtain the predicted value of the structural mismatch degree of each moment within the future preset time length of the current moment according to the structural mismatch degree, temperature, and humidity of each moment within the monitoring period of the current moment; obtain the refractive index perturbation index of the current moment according to the maximum value and complexity of all the predicted values of the structural mismatch degree within the future preset time length of the current moment. Obtain the refractive index measurement values of the antireflection coating in each direction at the current moment, judge the deviation situation of the refractive index measurement values in each direction at the current moment, and correct the refractive index measurement values in each direction at the current moment by using the refractive index perturbation index of the current moment.

2. The refractive index measurement method for a coated anti-reflection coating according to claim 1, characterized in that, The specific process of obtaining the reflection spectral intensity sequence of each moment is as follows: arrange all the reflection spectral intensity data within the monitoring period of each moment in ascending order of time to obtain the reflection spectral intensity sequence of each moment.

3. The refractive index measurement method for a coated antireflection coating according to claim 1, characterized in that, The process of obtaining the three-dimensional data volume matrix of each moment is as follows: take all the refractive index data in the lateral, longitudinal, and depth directions within the monitoring period of each moment as the first row, the second row, and the third row respectively, and arrange them in ascending order of time to obtain the three-dimensional data volume matrix of each moment.

4. A refractive index measurement method for a coated anti-reflection coating according to claim 1, characterized in that, The calculation formula for the structural mismatch degree at the current moment is as follows: ; in the formula, is the structural mismatch degree at the current moment, and E is the power spectral density of the spectral sequence of the reflection spectral intensity sequence at the current moment; , and are the first-order derivatives of the three-dimensional data volume matrix at the first row, the second row, and the third row at the current moment, respectively.

5. A refractive index measurement method for a coated anti-reflection coating according to claim 1, characterized in that, The process of obtaining the predicted value of the structural mismatch degree of the future preset time length of the current moment is as follows: record the sequences composed of the structural mismatch degree, temperature, and humidity data of all moments within the monitoring period of the current moment in ascending order of time as the structural mismatch degree sequence, temperature sequence, and humidity sequence of the current moment; take the structural mismatch degree sequence, temperature sequence, and humidity sequence of the current moment as the input of the random forest algorithm, and output the predicted value of the structural mismatch degree of the future preset time length of the current moment.

6. A refractive index measurement method for a coated antireflection coating according to claim 1, characterized in that, The calculation formula for the refractive index perturbation index at the current moment is as follows: ; In the formula, is the refractive index perturbation index at the current moment, is the maximum value among all the predicted values of the structural mismatch degree within the preset future time length at the current moment, is the approximate entropy of all the predicted values of the structural mismatch degree within the preset future time length at the current moment.

7. A refractive index measurement method for a coated anti-reflection coating according to claim 1, characterized in that, The specific process of obtaining the refractive index measurement values of the antireflection coating in each direction at the current moment is as follows: use the reflection spectral intensity data of the current moment and adopt the traditional optical model based on the stepped layer hypothesis to obtain the refractive index measurement values of the antireflection coating in each direction at the current moment.

8. The refractive index measurement method for a coated anti-reflection coating according to claim 1, characterized in that, The specific process of judging the deviation situation of the refractive index measurement values in each direction at the current moment is as follows: obtain the calibration database storing the reference refractive indices under various process scenarios; calculate the differences between the refractive index measurement values in each direction at the current moment and the reference refractive indices corresponding to the same process scenario in the calibration database respectively; If the difference is equal to 0, it is determined that there is no deviation in the refractive index measurement value in the corresponding direction at the current moment; otherwise, there is a deviation in the refractive index measurement value in the corresponding direction at the current moment.

9. The refractive index measurement method for a coated anti-reflection coating according to claim 8, characterized in that, The specific process of correcting the refractive index measurement values in each direction at the current moment is as follows: When the difference is greater than 0, the expression for correcting the refractive index measurement value in a single direction at the current moment is: ; In the formula, is the corrected refractive index in a single direction at the current moment, is the refractive index measurement value in a single direction at the current moment, is the refractive index perturbation index at the current moment, is the maximum value of the refractive index perturbation index within the historical moment, is the preset compensation coefficient; When the difference is less than 0, the expression for correcting the refractive index measurement value in a single direction at the current moment is: ; When the difference value is equal to 0, there is no need to correct the refractive index measurement value in a single direction at the current moment.

10. A refractive index measuring device coated with an antireflection coating, comprising a memory, a processor, and a computer program stored in the memory and running on the processor, characterized in that, When the processor executes the computer program, it implements the steps of the method for measuring the refractive index of a coated anti-reflection coating according to any one of claims 1-9.

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