A method and device for measuring the refractive index of a coating with an anti-reflective coating

Abstract

The present application relates to the field of refractive index measurement technology, and specifically to a method and apparatus for measuring the refractive index of an anti-reflective coating. The method comprises: obtaining a reflection spectrum intensity sequence, a three-dimensional data volume matrix, temperature, and humidity at each moment; obtaining a structural mismatch at the current moment based on the power spectral 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; obtaining a predicted value of the structural mismatch at the current moment based on the structural mismatch, temperature, and humidity at each moment, and obtaining a refractive index perturbation index at the current moment based on the maximum value and complexity of the predicted structural mismatch; determining the deviation of the refractive index measurement value at the current moment, and using the refractive index perturbation index at the current moment to correct the refractive index measurement value at the current moment. The present application improves the accuracy of refractive index measurement by quantifying the degree of refractive index deviation at each moment and correcting the refractive index at each moment.

Description

Technical Field

[0001] The present application relates to the technical field of refractive index measurement, and in particular to a method and device for measuring the refractive index of a coating coated with an anti-reflective coating. Background Art

[0002] Anti-reflective coatings (AR coatings) are widely used in lenses, solar cells, displays, and other fields by reducing surface reflected light loss. The refractive index of the coating is a core parameter that directly affects its optical performance, making accurate refractive index measurement crucial for optimizing coating design. Early coatings were mostly single-layer structures, and refractive index measurement relied on traditional ellipsometers or spectrophotometry. However, with the development of metamaterials, the complexity of coating structures has increased significantly.

[0003] In the refractive index measurement of multilayer structures of anti-reflective coatings, multilayer heterogeneous systems (such as gradient refractive index coatings) often form non-abrupt refractive index changes due to material interpenetration, interface diffusion, or composition segregation during the deposition process. This causes the refractive index measured by the traditional optical model based on the step-by-step stratification assumption to deviate significantly from the actual refractive index. Existing technologies mainly address this technical problem by improving the adaptability of the model, such as introducing a continuous gradient function or subdividing virtual sublayers, and combining inverse optimization algorithms to invert the gradient parameters. However, this method is not easy to select the distribution function and still leads to 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 the traditional optical model based on the step-by-step stratification 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 anti-reflective coatings. The technical solutions adopted are as follows:

[0005] In a first aspect, an embodiment of the present application provides a method for measuring the refractive index of an anti-reflective coating, the method comprising the following steps:

[0006] Obtaining 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; using a preset time period before each moment as a monitoring period at each moment; obtaining a reflection spectrum intensity sequence at each moment based on the reflection spectrum intensity data within the monitoring period at each moment; and obtaining a three-dimensional data volume matrix at each moment based on the refractive index data in three directions within the monitoring period at each moment;

[0007] The structural mismatch at the current moment is obtained based on the power spectral density of the spectrum sequence of the reflection spectrum intensity sequence at the current moment and the first-order derivative of the three-dimensional data volume matrix in each row; the predicted value of the structural mismatch at each moment within a preset time length in the future at the current moment is obtained based on the structural mismatch, temperature, and humidity at each moment in the monitoring period at the current moment; the refractive index perturbation index at the current moment is obtained based on the maximum value and complexity of all the predicted structural mismatch values ​​within the preset time length in the future at the current moment;

[0008] Obtain the refractive index measurement values ​​of the anti-reflection 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 use the refractive index perturbation index at the current moment to correct the refractive index measurement values ​​in each direction at the current moment.

[0009] Preferably, the specific process of obtaining the reflection spectrum intensity sequence at each moment is: arranging all reflection spectrum intensity data within the monitoring period at each moment in ascending time order to obtain the reflection spectrum intensity sequence at each moment.

[0010] Preferably, the acquisition process of the three-dimensional data volume matrix at each moment is: all the refractive index data in the horizontal, vertical and depth directions within the monitoring period at each moment are respectively arranged as the first row, second row and third row in ascending order of time to obtain the three-dimensional data volume matrix at each moment.

[0011] Preferably, the calculation formula of the structural mismatch degree at the current moment is: Where, is the structural mismatch degree at the current moment, E is the power spectral density of the 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, second, and third rows respectively.

[0012] Preferably, the process of obtaining the predicted value of the structural mismatch degree for a preset time length in the future at the current moment is: recording the sequences composed of the structural mismatch degree, temperature, and humidity data of all moments within the monitoring period at the current moment in ascending time order as the structural mismatch degree sequence, temperature sequence, and humidity sequence at the current moment; using the structural mismatch degree sequence, temperature sequence, and humidity sequence at the current moment as inputs of the random forest algorithm, and outputting the predicted value of the structural mismatch degree for a preset time length in the future at the current moment.

[0013] Preferably, the calculation formula of the refractive index disturbance index at the current moment is: Where, is the refractive index perturbation index at the current moment, It is the maximum value of all predicted values ​​of structural mismatch within the preset time length in the future at the current moment. The approximate entropy of all predicted values ​​of structural mismatch within a preset time length in the future from the current moment.

[0014] Preferably, the specific process of obtaining the refractive index measurement values ​​of the anti-reflection coating in each direction at the current moment is: using the reflection spectrum intensity data at the current moment, adopting a traditional optical model based on the step-by-step layering assumption to obtain the refractive index measurement values ​​of the anti-reflection coating in each direction at the current moment.

[0015] Preferably, the specific process of determining the deviation of the refractive index measurement values ​​in each direction at the current moment is as follows: obtaining a calibration database that stores the reference refractive indices under various process scenarios; respectively calculating the difference between the refractive index measurement value in each direction at the current moment and the reference refractive index corresponding to the same process scenario in the calibration database; if the difference is equal to 0, determining that the refractive index measurement value in the corresponding direction at the current moment has no deviation; otherwise, the refractive index measurement value in the corresponding direction at the current moment has a deviation.

[0016] Preferably, the specific process of correcting the refractive index measurement values ​​in each direction at the current moment is:

[0017] 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 of 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 in the historical moment, is the preset compensation coefficient;

[0018] 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: ;

[0019] When the difference is equal to 0, there is no need to correct the refractive index measurement value of a single direction at the current moment.

[0020] In a second aspect, an embodiment of the present application further provides a refractive index measuring device for an anti-reflective coating, comprising a memory, a processor, and a computer program stored in the memory and running on the processor, wherein when the processor executes the computer program, the steps of any one of the above-mentioned methods for measuring the refractive index of an anti-reflective coating are implemented.

[0021] This application has at least the following beneficial effects:

[0022] 1. This application addresses the problem that traditional step-layered models cannot describe nonlinear refractive index gradients, resulting in low refractive index measurement accuracy. First, an adaptive Fourier decomposition algorithm is used to extract the frequency domain energy distribution feature vector. Combined with local weighted regression fitting of the spatial gradient, this method quantifies the nonlinear intensity and spatial gradient intensity of the coating refractive index change. This helps quantify the deviation of the refractive index measured by subsequent traditional optical models based on the step-layered assumption.

[0023] 2. To address the unpredictable measurement errors caused by material interpenetration, environmental disturbances, and process fluctuations, a random forest algorithm is used to predict the structural mismatch within the future timeframe, taking the structural mismatch sequence and environmental parameters as input. This algorithm constructs a refractive index disturbance index, eliminates the one-sided influence of a single environmental factor or process fluctuation, and comprehensively quantifies the measurement errors caused by the coupling of multiple factors in anti-reflection coatings.

[0024] 3. The refractive index measurement value at each moment is dynamically corrected based on the refractive index perturbation index, achieving high precision and strong robustness in the refractive index measurement of the anti-reflection coating. This solves the problem of systematic error accumulation in the traditional optical model based on the step-by-step stratification assumption in nonlinear gradient scenarios, and improves the accuracy of the refractive index measurement of the anti-reflection coating. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions and advantages of the embodiments of the present application or the prior art, the following is a brief introduction to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0026] Figure 1 A flowchart of a method for measuring the refractive index of an anti-reflective coating provided in one embodiment of the present application;

[0027] Figure 2 A flowchart for correcting the refractive index measurement values ​​in various directions at the current moment is provided in accordance with one embodiment of the present application. DETAILED DESCRIPTION

[0028] To further illustrate the technical means and effectiveness of this application to achieve its intended purpose, the following, in conjunction with the accompanying drawings and preferred embodiments, details the specific implementation, structure, features, and effectiveness of a method and apparatus for measuring the refractive index of an anti-reflective coating applied according to this application. In the following description, references to different "one embodiment" or "another embodiment" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics of one or more embodiments may be combined in any suitable manner.

[0029] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

[0030] The following describes in detail a method and device for measuring the refractive index of an anti-reflective coating provided by the present application with reference to the accompanying drawings.

[0031] See also Figure 1 , which shows a flowchart of a method for measuring the refractive index of an anti-reflective coating provided by one embodiment of the present application, the method comprising the following steps:

[0032] Step 1: 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 at each moment; obtain the reflection spectrum intensity sequence at each moment based on the reflection spectrum intensity data within the monitoring period at each moment; obtain the three-dimensional data volume matrix at each moment based on the refractive index data in three directions within the monitoring period at each moment.

[0033] Because the refractive index of an anti-reflection 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 exhibits nonlinear or random gradients in time and space. For example, changes in temperature and humidity can cause subtle changes in the optical properties of the coating material, while dynamic fluctuations in the deposition process exacerbate the inhomogeneity of the refractive index in the depth direction (z-axis), lateral direction (x-axis), and longitudinal direction (y-axis) of the anti-reflection coating, resulting in different refractive indices at different times. Therefore, the refractive index at different times needs to be corrected according to the environmental disturbances and process influences at different times to improve the measurement accuracy of the refractive index.

[0034] In the antireflection coating measurement equipment, a polarization modulation unit is installed at the exit of the broadband light source module to control the polarization state of the incident light in real time. A multi-angle detection system (a high-precision photodetector array) is integrated on the sample stage surface to collect reflection spectral intensity data within the incident angle range of 0° to 80°, which is used to analyze the dynamic optical response of the coating. A high-speed optical coherence tomography (OCT) system, equipped with a high-speed transverse scanning galvanometer, completes a full xy-plane scan at each acquisition moment. The OCT interferometer signal is used to analyze the refractive index distribution in the coating depth direction (z-axis), generating a three-dimensional data volume (x, y, z) of the refractive index distribution in three dimensions. The measurement and acquisition of the reflection spectrum and the three-dimensional spatial distribution of the refractive index described above are well-known techniques in the art and will not be elaborated here. Temperature and humidity sensors monitor the temperature and humidity of the antireflection coating in real time.

[0035] To achieve multi-source data synchronization, the scanning system, spectrometer, and temperature and humidity sensor share the same clock source and adopt a unified acquisition frequency. In this embodiment, the acquisition frequency is set to 100 Hz. The first a seconds of each moment is used as the monitoring period of each moment, and all the reflection spectrum intensity data and three-dimensional data volumes in the monitoring period of each moment are arranged in ascending time order to obtain the reflection spectrum intensity sequence and three-dimensional data volume matrix of 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 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 of that moment.

[0036] Step 2: Obtain the structural mismatch at the current moment based on the power spectral density of the spectrum sequence of the reflection spectrum intensity sequence at the current moment and the first-order derivative of the three-dimensional data volume matrix in each row; obtain the predicted value of the structural mismatch at each moment within the future preset time length based on the structural mismatch, 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 structural mismatch prediction values ​​within the future preset time length at the current moment.

[0037] Since multilayer anti-reflection coatings are prone to forming nonlinear or random refractive index gradients due to material interpenetration, interface diffusion or composition segregation during the deposition process, traditional optical models based on the step-by-step layering assumption are difficult to accurately describe their true physical structure, resulting in model inversion results deviating from reality and causing systematic measurement errors in refractive index and thickness.

[0038] Therefore, the current reflectance spectral intensity sequence is used as input to the adaptive Fourier decomposition (AFD) algorithm. To balance high-frequency noise suppression and gradient feature preservation, the Daubechies4 wavelet basis function and a five-level decomposition depth are set. The resulting spectrum sequence is a spectral sequence of the current reflectance spectral intensity sequence. This spectral sequence quantifies the nonlinear characteristics of the coating's refractive index variation through frequency-domain energy focusing. Its high-frequency components correspond to sudden interface changes, while its low-frequency components reflect gradual changes. Furthermore, the power spectral density of the current spectrum sequence is calculated. The calculation of the power spectral density of frequency-domain energy is well known, and the specific process is not repeated here.

[0039] Each row of the current 3D data volume matrix is ​​then used as input for a locally weighted regression (LOESS) algorithm. 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 characterizes the refractive index gradient of the antireflection coating in the x, y, and z directions at the current moment. LOESS's weighted neighborhood strategy maintains the spatial continuity of the gradient field, avoiding gradient jumps caused by discrete sampling.

[0040] As a preferred embodiment, the structural mismatch at the current moment is obtained based on the power spectral density of the spectral sequence of the reflection spectrum intensity sequence at the current moment and the first-order derivative of the three-dimensional data volume matrix in each row, which is used to characterize the overall abnormality of the coating refractive index during the monitoring period at the current moment.

[0041] In this embodiment, the structural mismatch degree at the current moment is recorded as , and its specific calculation formula is: Where, is the structural mismatch degree at the current moment, E is the power spectral density of the 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, second, and third rows respectively.

[0042] The power spectral density characterizes the significance of the nonlinear characteristics of the refractive index change. The larger the value, the more significant the nonlinear characteristics of the refractive index change of the coating, and the higher the risk of failure of the traditional optical model based on the step-by-step stratification assumption. 、 and It is used to quantify the refractive index gradient of the antireflection coating in various directions. It squares and sums the gradients in each direction, eliminating directional effects and amplifying the contribution of high-intensity gradient regions. A larger value indicates a greater absolute intensity of the refractive index change, and a more abnormal refractive index gradient is observed. The structural mismatch, A, comprehensively quantifies the overall degree of anomaly in the coating's refractive index during the current monitoring period. A larger value indicates a greater deviation between the actual refractive index of the antireflection coating and the refractive index measured by the traditional model.

[0043] The structural mismatch degrees A at all moments within the monitoring period at the current moment are sorted in ascending time order as the structural mismatch degree sequence at the current moment.

[0044] Furthermore, due to the influence of material interpenetration, interface diffusion and environmental temperature and humidity fluctuations in the multi-layer heterogeneous system of anti-reflection coatings, there are systematic errors in the refractive index inversion of traditional optical models, and the dynamic fluctuations of the coating preparation process further aggravate the deviation between the measurement results and the actual physical structure.

[0045] Therefore, the temperature and humidity data for all moments within the current monitoring period, in ascending chronological order, are recorded as the current temperature and humidity sequences. The structural mismatch sequence, temperature sequence, and humidity sequence at the current moment are used as inputs to the random forest algorithm. The number of trees is set to 200 to avoid overfitting and improve generalization, and the maximum depth is set to 8 to limit complexity to accommodate small sample data. The predicted structural mismatch values ​​for each moment in the future h seconds from the current moment are output to represent the predicted refractive index measurement error, where h is a preset time length; in this embodiment, h is 10. The predicted structural mismatch value quantifies the nonlinear correlation between the inversion error of the traditional optical model and the gradient characteristics and environmental disturbances, reflecting the cumulative impact of material interpenetration in complex gradient coatings on measurement accuracy.

[0046] As a preferred embodiment, the refractive index perturbation index at the current moment is obtained based on the maximum value and complexity of all structural mismatch prediction values ​​within a preset time length in the future at the current moment, which is used to characterize the comprehensive deviation degree of the refractive index measurement of the anti-reflection coating at the current moment.

[0047] In this embodiment, the refractive index disturbance index at the current moment is recorded as , and its calculation relationship is: Where, is the refractive index perturbation index at the current moment, It is the maximum value of all predicted values ​​of structural mismatch within the preset time length in the future at the current moment. The approximate entropy of all predicted values ​​of structural mismatch within a preset time length in the future from the current moment.

[0048] Quantifies the most serious measurement deviation of the anti-reflection coating at the current moment due to material interpenetration, interface diffusion or environmental disturbance. The larger the value, the more significant the deviation between the actual refractive index of the anti-reflection coating at the current moment and the refractive index assumed by the model, which may lead to greater systematic errors in the measurement system. This characterizes the complexity of the effects of environmental temperature and humidity fluctuations and coating dynamic process fluctuations on measurement errors. The larger the value, the more likely it is that the anti-reflection coating is experiencing multi-factor coupling, making it more difficult to accurately predict its refractive index error using a single model. The comprehensive deviation degree of the refractive index measurement of the anti-reflection coating at the current moment is comprehensively quantified, reflecting the severity of the measurement inaccuracy caused by the nonlinear refractive index distribution and environmental disturbances in the complex gradient coating. The larger the value, the greater the deviation between the refractive index measured by the traditional optical model at the current moment and the actual refractive index of the anti-reflection coating.

[0049] Step 3: Obtain the refractive index measurement values ​​of the anti-reflection 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 use the refractive index perturbation index at the current moment to correct the refractive index measurement values ​​in each direction at the current moment.

[0050] The traditional optical model based on the step-by-step layering assumption assumes that the anti-reflection coating has an ideal step-by-step layered structure. A reflectivity calculation model is established based on the Fresnel equation and thin-film interference theory. The reflection and transmission behavior of light waves at each interface is calculated layer by layer using the transfer matrix method. The theoretical reflection spectrum is generated by superimposing the interference effects. A nonlinear least-squares fitting algorithm (such as Levenberg-Marquardt) is then 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 experimentally measured spectrum. The Fresnel formula is then used to ultimately output the refractive index measurement value in a single direction at the current moment. The single direction refers to any one of the x, y, and z directions of the anti-reflection coating. This traditional optical model based on the step-by-step layering assumption is well known to those skilled in the art and will not be elaborated upon here.

[0051] To address the problem of large measurement deviations in traditional models when the refractive index perturbation index is high, this application dynamically corrects the refractive index measurement values ​​in all directions at all times. The specific correction method is as follows:

[0052] By introducing a calibration database, the benchmark refractive index under various process scenarios (such as material interpenetration, temperature and humidity mutations) is pre-stored; the difference between the refractive index measurement value in a single direction at the current moment obtained by inversion using the traditional optical model and the benchmark refractive index corresponding to the same process scenario in the calibration database is calculated.

[0053] 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 perturbation index at the current moment is used to correct the refractive index measurement value in a single direction 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 of 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 in the historical moment, is a preset compensation coefficient, which is 0.2 in this embodiment and can be determined by the implementer according to actual conditions.

[0054] 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 disturbance index at the current moment is: .

[0055] 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.

[0056] 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 When the correction amount reaches the upper limit , which can effectively reduce the refractive index deviation caused by nonlinear gradient or process fluctuations; and 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 applying normalization constraints, the correction amount is always proportional to the mismatch degree of the current refractive index measurement value, which can not only actively correct the deviation in high disturbances but also maintain measurement stability in low risk conditions. This makes the refractive index measurement results obtained after correction more accurate.

[0057] 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 follows: Figure 2 shown.

[0058] Based on the same inventive concept as the above method, an embodiment of the present application further provides a refractive index measuring device for an anti-reflective coating, comprising 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 any one of the above-mentioned methods for measuring the refractive index of an anti-reflective coating are implemented.

[0059] It should be noted that the order in which the embodiments of the present application are presented is for illustrative purposes only and does not necessarily represent the superiority or inferiority of the embodiments. Furthermore, the foregoing descriptions of specific embodiments of this specification are provided. Furthermore, the processes depicted in the accompanying drawings do not necessarily require the specific order or sequential sequence shown to achieve the desired results. In certain embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0060] The various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on the differences from other embodiments.

[0061] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent replacements, improvements, etc. made within the principles of the present application shall be included in the scope of protection of the present application.

Claims

1. A method for measuring the refractive index of an anti-reflective coating, characterized in that: The method comprises the following steps: Obtaining 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; using a preset time period before each moment as a monitoring period at each moment; obtaining a reflection spectrum intensity sequence at each moment based on the reflection spectrum intensity data within the monitoring period at each moment; and obtaining a three-dimensional data volume matrix at each moment based on the refractive index data in three directions within the monitoring period at each moment; The structural mismatch at the current moment is obtained based on the power spectral density of the spectrum sequence of the reflection spectrum intensity sequence at the current moment and the first-order derivative of the three-dimensional data volume matrix in each row; the predicted value of the structural mismatch at each moment within a preset time length in the future at the current moment is obtained based on the structural mismatch, temperature, and humidity at each moment in the monitoring period at the current moment; the refractive index perturbation index at the current moment is obtained based on the maximum value and complexity of all the predicted structural mismatch values ​​within the preset time length in the future at the current moment; Obtain the refractive index measurement values ​​of the anti-reflection 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 use the refractive index perturbation index at the current moment to correct the refractive index measurement values ​​in each direction at the current moment.

2. The method for measuring the refractive index of an anti-reflection coating according to claim 1, wherein: The specific process of obtaining the reflection spectrum intensity sequence at each moment is: arranging all reflection spectrum intensity data within the monitoring period at each moment in ascending time order to obtain the reflection spectrum intensity sequence at each moment.

3. The method for measuring the refractive index of an anti-reflection coating according to claim 1, wherein: The acquisition process of the three-dimensional data volume matrix at each moment is as follows: all the refractive index data in the horizontal, vertical and depth directions within the monitoring period at each moment are respectively arranged as the first row, second row and third row in ascending time order to obtain the three-dimensional data volume matrix at each moment.

4. The method for measuring the refractive index of an anti-reflection coating according to claim 1, wherein: The calculation formula of the structural mismatch degree at the current moment is: Where, is the structural mismatch degree at the current moment, E is the power spectral density of the 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, second, and third rows respectively.

5. The method for measuring the refractive index of an anti-reflection coating according to claim 1, wherein: The process of obtaining the predicted value of the structural mismatch degree for a preset time length in the future at the current moment is as follows: the sequences of the structural mismatch degree, temperature, and humidity data of all moments within the monitoring period at the current moment, in ascending time order, are recorded as the structural mismatch degree sequence, temperature sequence, and humidity sequence at the current moment; the structural mismatch degree sequence, temperature sequence, and humidity sequence at the current moment are used as inputs of the random forest algorithm, and the predicted value of the structural mismatch degree for a preset time length in the future at the current moment is output.

6. The method for measuring the refractive index of an anti-reflection coating according to claim 1, wherein: The calculation formula of the refractive index disturbance index at the current moment is: Where, is the refractive index perturbation index at the current moment, It is the maximum value of all predicted values ​​of structural mismatch within the preset time length in the future at the current moment. The approximate entropy of all predicted values ​​of structural mismatch within a preset time length in the future from the current moment.

7. The method for measuring the refractive index of an anti-reflection coating according to claim 1, wherein: The specific process of obtaining the refractive index measurement values ​​of the anti-reflection coating in various directions at the current moment is: using the reflection spectrum intensity data at the current moment and adopting a traditional optical model based on the step-by-step layering assumption to obtain the refractive index measurement values ​​of the anti-reflection coating in various directions at the current moment.

8. The method for measuring the refractive index of an anti-reflection coating according to claim 1, wherein: The specific process of determining the deviation of the refractive index measurement value in each direction at the current moment is as follows: obtaining a calibration database storing reference refractive indices under various process scenarios; calculating the difference between the refractive index measurement value in each direction at the current moment and the reference refractive index corresponding to the same process scenario in the calibration database; If the difference is equal to 0, it is determined that the refractive index measurement value of the corresponding direction at the current moment has no deviation; otherwise, the refractive index measurement value of the corresponding direction at the current moment has a deviation.

9. The method for measuring the refractive index of an anti-reflection coating according to claim 8, wherein: 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 of 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 in 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 of a single direction at the current moment.

10. A refractive index measuring device for an anti-reflective coating, comprising a memory, a processor, and a computer program stored in the memory and running on the processor, wherein: When the processor executes the computer program, the steps of the method for measuring the refractive index of an anti-reflection coating as claimed in any one of claims 1 to 9 are implemented.

Images