A method for calculating and analyzing the transmittance of a glass surface film system using a finite element method

Abstract

The application discloses a method for calculating and analyzing glass surface film system transmittance by using a finite element method, and relates to the technical field of glass surface film system transmittance calculation. An optical model containing an air domain, a substrate domain and a dielectric film layer is constructed by using a finite element software. The film system composition in the dielectric film layer is determined, and the air domain refractive index, the substrate domain refractive index, the refractive index of each component film layer material in the dielectric film layer and the reference wavelength of incident light of the material are determined. The application can realize the following effects: the transmittance of the whole optical device can be predicted by only inputting the refractive index of each film structure in the film system, and the original film system composition and film thickness can be changed to provide more film design schemes for optical film research and development workers to meet specific requirements.

Description

Technical Field

[0001] This invention belongs to the field of thin film transmittance calculation technology, specifically a method for calculating and analyzing the transmittance of a glass surface film system using the finite element method. Background Technology

[0002] Glass transmittance is a crucial indicator of glass quality, referring to the proportion of light that passes through the glass. High transmittance directly impacts indoor lighting, occupant comfort, and building energy efficiency. High transmittance glass allows more natural light to enter the room, reducing reliance on artificial lighting, thus saving energy and creating a more comfortable lighting environment. Appropriate transmittance prevents glare and improves visual comfort, which is especially important for people who spend long hours working or studying indoors.

[0003] Currently, many high-transmittance glasses are available on the market, but the requirements for glass vary depending on the application scenario. For example, cover glass in the field of solar cells requires higher transmittance to meet better battery performance; Low-e glass needs to ensure transmittance while reducing infrared light transmission to lower heat radiation. Therefore, glass thin-film researchers need to conduct extensive experiments to find suitable materials and better processes, which not only wastes a lot of materials but also reduces research efficiency. Thus, simulation methods are needed to assist in the early exploration of materials and processes during the experimental phase. Summary of the Invention

[0004] This invention aims to solve at least one of the technical problems existing in the prior art;

[0005] Therefore, this invention proposes a method for calculating and analyzing the transmittance of a glass surface film system using the finite element method, which specifically includes the following steps:

[0006] An optical model including the air domain, substrate domain, and dielectric thin film layer was constructed using finite element software.

[0007] Determine the composition of the film system in the dielectric thin film layer, and then determine the air domain refractive index, substrate domain refractive index, and refractive index of each component film material in the dielectric thin film layer and the reference wavelength of the incident light.

[0008] Set the thickness of each component layer material in the dielectric thin film layer;

[0009] A suitable meshing method was selected for the two-dimensional model to perform mesh generation and light transmittance calculation. The initial transmittance curve was obtained. When the spectral performance transmittance of the initial thin film structure was found to be low and fluctuating significantly, optimization was performed to determine the optimized thin film thickness parameters.

[0010] Furthermore, the specific optimization methods are as follows:

[0011] Before optimization, the objective function T_Objective and the required range of film thickness were determined. The Nelder-Mead gradient-free method was adopted for optimization, with an optimization tolerance of 0.01 and the optimization type being "minimization". Optimization calculations were performed to obtain the final optimized film thickness parameters.

[0012] The latest film thickness was re-examined.

[0013] Furthermore, the governing equations for the optical model are as follows:

[0014] Furthermore, the parameters of the incident light include the incident direction, the position and intensity of the incident light, and the wavelength range of the incident light.

[0015] Furthermore, the refractive index of each component film material is the refractive index within the wavelength range of the incident light.

[0016] Compared with the prior art, the beneficial effects of the present invention are:

[0017] The present application provides a method for calculating and analyzing the transmittance of a glass surface film system using the finite element method. Its advantages are that the transmittance of the entire optical device can be predicted simply by inputting the refractive index of each thin film layer in the film system. Furthermore, it can change the original film system composition and thickness to provide optical thin film researchers with more thin film design options to meet specific needs. The present invention is simple, effective, and easy to use. Attached Figure Description

[0018] Figure 1 This is a flowchart of the present invention;

[0019] Figure 2 This is a model diagram of a glass coating constructed based on the finite element method in this invention;

[0020] Figure 3 This is a mesh division diagram of the present invention;

[0021] Figure 4 This is a transmittance curve before and after optimization in this invention. Detailed Implementation

[0022] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] Please see Figures 1-4This application provides a method for calculating and analyzing the transmittance of a glass surface film system using the finite element method;

[0024] In the wavelength range of 400-1200nm, a broadband antireflection film is designed using soda-lime glass as a substrate. The final design goal is to achieve an average transmittance of greater than 96% in the selected wavelength range.

[0025] Our membrane system design follows these principles: minimizing the number of membrane layers to achieve the highest possible permeability, fully integrating with actual preparation processes and methods, and paying particular attention to the following key considerations:

[0026] 1) The refractive index of the thin film layer should be matched with the refractive index of the adjacent material to minimize reflection loss;

[0027] 2) The thickness of the film should be precisely controlled according to the required optical path length to achieve phase tuning at a specific wavelength, and the thickness of each layer in the film system should be kept uniform. Excessive film thickness can induce significant stress, potentially affecting the stability of the film system. Conversely, excessively thin films are difficult to monitor and may lead to large thickness errors, thus negatively impacting the overall spectral profile.

[0028] 3) In order to reduce the accumulation of errors during the film preparation process, too many film layers may lead to complex control problems, making the entire film system more susceptible to the influence of preparation errors. Therefore, the total number of layers should be reduced as much as possible to maintain the uniformity and stability of the film.

[0029] Therefore, Al2O3, TiO2, and SiO2 were chosen as the three membrane materials for the membrane system design.

[0030] As an embodiment of this application, its specific method includes the following steps:

[0031] Step S1: Establish a two-dimensional geometric optical model using finite element method software (ANSYS or similar software). The model includes an air domain, a substrate domain, and a dielectric thin film layer, with the dielectric thin film layer located at the boundary between the air and substrate domains. Establish a simulation region with a side length of 1m, dividing this region into upper and lower parts: the upper part is air, the lower part is soda-lime glass, and the middle part is the dielectric film layer region. Figure 2 As shown;

[0032] The governing equations for the optical model mentioned here are:

[0033] Step S2: Determine the film system composition in the dielectric thin film layer; the dielectric thin film is set as Al2O3, TiO2 and SiO2;

[0034] Step S3: Determine the material parameters, including the air domain refractive index, the substrate domain refractive index, the refractive indices of each component layer material in the dielectric thin film layer, and the reference wavelength of the incident light; the reference wavelength is set to 630 nm; the refractive index of air is 1, the refractive index of soda-lime glass is 1.5, the refractive index of SiO2 is 1.45, the refractive index of Al2O3 is 1.62, and the refractive index of TiO2 is 2.34; the incident light parameters here include the incident direction, the incident light position and intensity, and the incident light wavelength range; and the refractive index of each component layer material here should be the refractive index within the wavelength range of the incident light.

[0035] Step S4: Set process parameters; the process parameters include the thickness of each component layer material in the dielectric thin film layer; the table below shows the composition and thickness of the initial film system. The thin film in direct contact with the glass is Al₂O₃;

[0036] material thickness air / <![CDATA[SiO2]]> 106.75 <![CDATA[TiO2]]> 20.18 <![CDATA[SiO2]]> 32.03 <![CDATA[TiO2]]> 134.51 <![CDATA[SiO2]]> 32.03 <![CDATA[TiO2]]> 20.18 <![CDATA[Al2O3]]> 97.22 glass 1000

[0037] Step S5: Select a suitable meshing method to divide the two-dimensional model into a mesh and calculate the light transmittance; the meshing method adopts a free triangle meshing method, and the specific calculation method uses a ray tracing algorithm; the initial transmittance curve is obtained, as shown below. Figure 4 As shown by the black line, we can observe that while a maximum transmittance of 99.82% is achieved at 1040 nm within the desired wavelength range of 400-1100 nm, transmittance is lower and fluctuates significantly at shorter wavelengths. Particularly at 641 nm, the transmittance is only 95.80%. This result indicates that the initial thin film structure's spectral performance does not meet the broad requirements for broadband anti-reflection in terms of bandwidth and transmittance, thus necessitating further performance optimization.

[0038] Step S6: Add an optimization module to the physical field. Before optimization, determine the objective function T_Objective and the required range of film thickness. The optimization method adopts the Nelder-Mead gradient-free method with an optimization tolerance of 0.01 and the optimization type is "minimization". This optimization method is existing technology, but it lacks specific implementation for this film thickness design problem. This method requires an objective function and is implemented through constraints, that is, the upper and lower limits of the optimization parameters are the range of film thickness in this application. The final result obtained through optimization is the film thickness that meets the target. Setting upper and lower limits here can reduce the iteration time of optimization and improve computational efficiency.

[0039] Step S7: Perform optimization calculations to obtain the final optimized thin film thickness parameters.

[0040] The table below shows the optimized membrane composition and thickness:

[0041] material thickness air / <![CDATA[SiO2]]> 97.18 <![CDATA[TiO2]]> 22.06 <![CDATA[SiO2]]> 27.85 <![CDATA[TiO2]]> 148.24 <![CDATA[SiO2]]> 24.13 <![CDATA[TiO2]]> 20.59 <![CDATA[Al2O3]]> 95.53 glass 1000

[0042] The light transmittance curve obtained by recalculating the latest film thickness is as follows: Figure 4 As shown by the red line, the average transmittance of the optimized film is 97.8%, with a minimum transmittance of 97.2%. Furthermore, the thickness of the optimized film is mostly smaller than that before optimization, but no extreme thicknesses were observed, thus saving experimental costs.

[0043] The above embodiments are only used to illustrate the technical methods of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical methods of the present invention without departing from the spirit and scope of the technical methods of the present invention.

Claims

1. A method for calculating and analyzing the transmittance of a glass surface film system using the finite element method, characterized in that, The method specifically includes the following steps: An optical model including the air domain, substrate domain, and dielectric thin film layer was constructed using finite element software. Determine the composition of the film system in the dielectric thin film layer, and then determine the air domain refractive index, substrate domain refractive index, and refractive indices of each component film material in the dielectric thin film layer and the parameters of the incident light. Set the thickness of each component layer material in the dielectric thin film layer; The two-dimensional model was meshed using a free triangular meshing method, and the light transmittance was calculated. The initial transmittance curve was obtained. When the spectral transmittance of the initial thin film structure was found to be lower than the initial transmittance set by the administrator, optimization was performed to determine the optimized thin film thickness parameters. The specific optimization method is as follows: Before optimization, the objective function T_Objective and the required range of film thickness are determined. The Nelder-Mead gradient-free method is adopted for optimization, with an optimization tolerance of 0.01 and the optimization type is "minimization". Optimization calculations are performed to obtain the final optimized film thickness parameters. The latest film thickness was re-inspected; The governing equation for the study of the optical model is .

2. The method for calculating and analyzing the transmittance of a glass surface film system using the finite element method according to claim 1, characterized in that, The parameters of the incident light include the incident direction, the position and intensity of the incident light, and the wavelength range of the incident light.

3. The method for calculating and analyzing the transmittance of a glass surface film system using the finite element method according to claim 1, characterized in that, The refractive index of each component film material is the refractive index within the wavelength range of the incident light.

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