Wide-angle-domain optical anti-reflection method based on equivalent gradient refractive index matching and phase angle constraint

Abstract

The invention discloses a wide-angle-domain optical anti-reflection method based on equivalent gradient refractive index matching and phase angle constraint, and the method comprises the steps: selecting two dielectric materials with different refractive indexes, respectively controlling the thicknesses of dielectric layers, and converting the dielectric layers into equivalent dielectric layers with different equivalent refractive indexes and equivalent thicknesses according to a transmission matrix; the problem that dielectric materials corresponding to some refractive indexes do not exist at present is solved, and the requirement for follow-up gradient refractive index matching is met. Besides, the change of the propagation phase is constrained by limiting the propagation angle of the incident light in the dielectric layer, so that the insensitivity of the propagation phase to the angle change meets the requirement of wide-angle-domain transmission enhancement, and the dielectric material with the corresponding refractive index can be determined according to the propagation angle constraint range. According to the method, the dielectric material capable of realizing wide-angle-domain optical anti-reflection can be quickly selected, and the time cost required for selecting the dielectric material is greatly reduced.

Description

Technical Field

[0001] The present invention belongs to the field of optical transparent devices, and in particular, relates to a wide-angle optical transmittance enhancement method based on equivalent gradient refractive index matching and phase angle constraint. Background Art

[0002] Optical substrates play a vital role in imaging and detection systems. On the one hand, they can isolate the external environment from the imaging and detection systems and protect the systems. On the other hand, their transparency can ensure that optical signals are smoothly transmitted to the sensor elements, and they are key components for the system to achieve imaging and detection. With the development of imaging and detection technology, the requirements for optical substrates are getting higher and higher. Optical substrates are not only required to have good stability to withstand the test of harsh environments, but also to have good optical transparency to ensure that the incident light can achieve high transmission in a wide band and wide angle range, meeting the needs of the imaging detection system to fully utilize the incident energy.

[0003] The transparency requirements of the imaging system are mainly concentrated in the visible 0.4-0.7μm band, and the transparency requirements of the detection system are mainly concentrated in 3-5μm and 8-12μm, so the optical substrate needs to have a wide transmission band. Sulfur-based glass, zinc sulfide, zinc selenide or germanium and other materials are usually selected as optical substrates to meet the optical performance requirements of the imaging system and the detection system. However, the transmittance that can be achieved by these optical substrates is relatively low. For example, the transmittance of zinc sulfide in the range of 1-12μm is 86%, which is difficult to meet the need to fully utilize the incident energy. In addition, due to the lack of a protective layer on the outside of the optical substrate, it is exposed to the air environment and is easily affected by harsh environmental factors.

[0004] With the development of thin film anti-reflection theory, by depositing a dielectric layer on an optical substrate, it can not only act as an anti-reflection film to reduce reflection and enhance the transmission of the optical substrate, but also act as a protective film to isolate the optical substrate from the external environment to ensure the stability of the optical substrate performance. Therefore, designing a multi-layer dielectric composite structure on an optical substrate is one of the effective ways to ensure the stability of the optical substrate performance and enhance the transmission of the optical substrate.

[0005] 1. Patent 201810009762.6 "A 3-12μm ZnS substrate optical infrared anti-reflection film and its preparation method" describes a preparation method of sequentially coating three layers of infrared anti-reflection film on an optical substrate ZnS, which increases the transmittance of the optical substrate at 3-12μm to 89% or more.

[0006] 2. Patent 201210426609.6 "A gradient refractive index anti-reflection film for crystalline silicon solar cells and its preparation method" describes a preparation method of sequentially coating three layers of gradient refractive index anti-reflection films on a silicon-based substrate of a crystalline silicon solar cell, which can reduce the reflectivity of the silicon-based substrate at 400-1200nm to less than 5%.

[0007] 3. Wang Daxing et al. from Changchun University of Science and Technology reported a method for preparing an infrared anti-reflection protective film on a magnesium fluoride substrate. By depositing a H4-MgF2 periodic structure on a magnesium fluoride substrate multiple times and finally depositing a SiO2 dielectric layer on the outermost side of the film layer, the transmittance of the magnesium fluoride substrate at 3-5μm can be increased to more than 95%, and the composite structure can be isolated from the external environment to protect it. (Wang Daxing et al., "Research and Preparation of 3-5μm Infrared Anti-reflection Protective Film on Magnesium Fluoride Substrate").

[0008] 4. Huang Hongyu et al. from Changchun University of Science and Technology reported a preparation method for coating infrared anti-reflection protective film on chalcogenide glass substrate. By depositing Ge, ZnS and YbF3 thin films with matching refractive index on chalcogenide glass substrate as three high, medium and low refractive index materials of anti-reflection film, the transmittance of chalcogenide glass substrate at 8-12μm can be increased to 91.1% and has good moisture resistance, high hardness, and strong film reliability, which meets the expected performance requirements. (Huang Hongyu et al., "Preparation of high-strength moisture-proof infrared anti-reflection and protective film on chalcogenide glass substrate").

[0009] In summary, the main defects of the prior art are:

[0010] 1. The need for wide-angle incident anti-reflection is not considered: The above optical substrate only considers achieving high transmittance in a specific wide band, and the designed optical substrate anti-reflection composite structure only considers the improvement of wide-band transmittance. The transmission results are not tested in a wide-angle range, which cannot meet the need for full utilization of incident energy. Therefore, it is urgent to find a design method for an optical substrate anti-reflection composite structure that can improve wide-angle transmittance.

[0011] 2. It is difficult to achieve the need for broadband transmission enhancement: Imaging and detection systems require optically transparent devices to have high transparency in the visible band, 3-5μm and 8-12μm. However, the above-mentioned optical substrate and the designed optical substrate anti-reflection composite structure can only achieve transmission enhancement in a specific band, which is difficult to meet the need for broadband transmission enhancement. Therefore, it is urgent to find a design method for an optical substrate anti-reflection composite structure that can improve broadband transmittance.

[0012] 3. Lack of design principles and methods for optical substrate anti-reflection composite structures: The existing methods for achieving optical substrate transmission enhancement are mainly focused on the preparation process. By plating a dielectric layer structure with given parameters on the optical substrate, only the transmission enhancement of a specific optical substrate can be achieved. In addition, the above preparation process only gives the relevant parameters of the dielectric layer without specific implementation principles and design methods. It is difficult to design an optical substrate anti-reflection composite structure corresponding to any optical substrate. Therefore, it is urgent to find a design method that can obtain a corresponding optical substrate anti-reflection composite structure based on a given optical substrate.

[0013] 4. Lack of corresponding refractive index materials to meet the needs of gradient refractive index matching: The design of optical substrate anti-reflection composite structures usually adopts gradient refractive index to meet the matching conditions, but in the design and preparation process, due to the limitations of actual conditions, it is often difficult to find dielectric materials with corresponding refractive indexes, which cannot meet the needs of gradient refractive index matching, making it difficult to achieve optical substrate wide-band and wide-angle transmission enhancement. Therefore, it is urgent to find an equivalent refractive index design method that can solve the problem that the corresponding material of the actual refractive index does not exist.

[0014] In view of this, the present invention is proposed. Summary of the invention

[0015] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a wide-angle optical transmittance enhancement method based on equivalent gradient refractive index matching and phase angle constraint, thereby solving the problems raised in the above-mentioned background technology.

[0016] In order to solve the above technical problems, the basic concept of the technical solution adopted by the present invention is:

[0017] A wide-angle optical anti-reflection method based on equivalent gradient refractive index matching and phase angle constraint, in order to achieve wide-angle optical anti-reflection in the range of -45° to 45° for visible 0.4-0.7μm and infrared 1-12μm, the corresponding dielectric layer material is selected by limiting the propagation angle and thus constraining the change of the propagation phase, so as to meet the phase angle constraint condition for achieving wide-angle optical anti-reflection. Then, by sequentially depositing dielectric layers with refractive indexes from large to small on the optical substrate, the total equivalent admittance is close to 1, and the gradient refractive index matching condition for achieving wide-angle optical anti-reflection is met. For the non-existent refractive index, an equivalent refractive index is used to replace it, and a series of equivalent dielectric layers with a decreasing equivalent refractive index gradient are constructed to meet the equivalent gradient refractive index matching condition for achieving wide-angle optical anti-reflection. The specific method is described as follows, and the steps are:

[0018] Ⅰ. Select two dielectric materials with different refractive indices as dielectric layer A and dielectric layer B. The refractive indices of dielectric layer A and dielectric layer B are n1 and n2 respectively, and the thicknesses are d1 and d2 respectively;

[0019] II. Based on the refractive index of dielectric layer A and dielectric layer B, and Calculate the reflection coefficient and transmission coefficient of each interface, and construct the interface action matrix I from the reflection coefficient and transmission coefficient k-1，k , whose expression is: Where n k-1 and n k are the refractive indices of two adjacent layers;

[0020] III. Based on the thickness determined in step Ⅰ, Calculate the propagation phase in each dielectric layer and construct the propagation matrix of the dielectric layer Among them, n k is the refractive index of the dielectric layer, d k is the thickness of the dielectric layer, λ is the wavelength for which anti-reflection is designed;

[0021] IV. Multiply the interface action matrix and the propagation matrix in order to obtain the total transfer matrix S of the entire multilayer dielectric structure, which is expressed as: S = I 01 L1I 12 L2I 23 ;

[0022] V. Based on the total transfer matrix calculated in step IV, let the total transfer matrix of dielectric layer A and dielectric layer B be equal to the transfer matrix of the single-layer medium S = I' 01 L'1I′ 12 , determine the equivalent refractive index n of the equivalent dielectric layer i and equivalent thickness d i ;

[0023] VI. By adjusting the thicknesses d1 and d2 of the two initial media, a series of dielectric layers with decreasing equivalent refractive index are generated to form an equivalent dielectric gradient layer that meets the gradient refractive index matching condition;

[0024] VII. The equivalent refractive index gradient layers generated in step VI are deposited on the optical substrate in descending order of refractive index, and finally an optical anti-reflection composite structure with decreasing gradient refractive index is formed.

[0025] Optionally, the optical substrate includes, but is not limited to, magnesium fluoride, zinc sulfide, zinc selenide, silicon and germanium.

[0026] Optionally, the optical anti-reflection composite structure is composed of a dielectric layer A and a dielectric layer B, and the design of an equivalent dielectric layer is achieved by controlling the thickness of the dielectric layer A and the dielectric layer B.

[0027] Optionally, the material of dielectric layer A and dielectric layer B includes but is not limited to one of TiO2 and YbF3

[0028] Optionally, the equivalent refractive index n obtained in step V i Greater than or equal to 1.7 to achieve wide-angle transmission enhancement, and the equivalent refractive index n i ≥1.7 can limit the propagation angle to within 25° to constrain the propagation phase, thereby achieving transmission enhancement of the optical substrate anti-reflection composite structure in a wide angle range.

[0029] Optionally, to reduce the equivalent admittance, the admittance of the optical basis is set to α+iβ, where α is the real part of the optical basis admittance and β is the imaginary part of the optical basis admittance;

[0030] Combining the optical base admittance α+iβ and the dielectric layer admittance m i , calculate the total equivalent admittance x+iy of the optical substrate antireflection composite structure, which satisfies the following relationship in δ i is the propagation phase in the medium, x and y are the real and imaginary parts of the equivalent admittance respectively; m i is the admittance of the dielectric material;

[0031] By selecting dielectric materials with decreasing refractive index and adjusting the thickness of each layer, the total equivalent admittance x+iy is close to 1, satisfying the following condition x+iy≈1, where the total admittance matches the admittance of air to minimize reflection and enhance transmission;

[0032] When the above conditions are met, the optical substrate anti-reflection composite structure can achieve an optical anti-reflection effect in a wide angle range.

[0033] Optionally, a multilayer film system for achieving equivalent gradient refractive index matching has a total number of layers between 2 and 20 and a period within 1 to 10.

[0034] Optionally, for a non-existent medium refractive index, an equivalent refractive index can be used to replace the non-existent medium refractive index, which specifically includes the following steps:

[0035] A medium layer with a refractive index of n1 and a medium layer with a refractive index of n2 are selected, wherein the refractive indices of n1 and n2 are both within the range of the refractive index of air and the refractive index of the optical substrate.

[0036] By adjusting the thicknesses d1 and d2 of the two dielectric layers within a range of 300 nm, the propagation phase of light in the two dielectric layers is adjusted to achieve a combination of different equivalent refractive indices and construct an equivalent dielectric layer that meets the design requirements.

[0037] By adjusting the refractive index and thickness combination of the two dielectric layers, a series of equivalent dielectric layers with gradually decreasing equivalent refractive index are generated, thereby satisfying the gradient refractive index matching condition and achieving admittance matching between the optical substrate and the air.

[0038] To be more specific: the present invention selects a dielectric layer with a refractive index of n1 and a dielectric layer with a refractive index of n2, calculates the reflection coefficient and transmission coefficient of the corresponding interface, and obtains an action matrix; calculates the propagation phase according to the thickness of dielectric layers A and B, and obtains a propagation matrix; multiplies the action matrix and the propagation matrix to obtain a total transfer matrix; sets the total transfer matrix equal to the transfer matrix of a single-layer medium to obtain the equivalent refractive index and equivalent thickness of the equivalent dielectric layer; obtains a series of equivalent dielectric layers by changing the thickness of dielectric layers A and B; limits the range of the equivalent refractive index to limit the change of the propagation phase, thereby satisfying the phase angle constraint condition for realizing wide-angle domain anti-reflection; superimposes the equivalent dielectric layers on the optical substrate in the order of decreasing gradient of the equivalent refractive index from large to small, and satisfies the equivalent gradient refractive index matching condition for realizing wide-angle domain anti-reflection. The wide-angle domain optical anti-reflection method can design a corresponding optical substrate anti-reflection composite structure according to a given optical substrate to realize wide-angle domain optical anti-reflection in the range of -45 to 45° for visible 0.4-0.7μm and infrared 1-12μm. Furthermore, by using an equivalent refractive index to replace a non-existent refractive index, the refractive index gradient change can be made smoother, thereby further improving the wide-angle transmittance of the optical substrate.

[0039] After adopting the above technical solution, the present invention has the following beneficial effects compared with the prior art. Of course, any product implementing the present invention does not necessarily need to achieve all the advantages described below at the same time:

[0040] 1. The present invention proposes a method for selecting dielectric layer materials for wide-angle optical enhancement based on phase angle constraint. By limiting the propagation angle of incident light in the dielectric layer to constrain the change of propagation phase, the insensitivity of propagation phase to angle change is achieved to meet the needs of wide-angle transmission enhancement, and the dielectric material with the corresponding refractive index can be determined according to the range of propagation angle constraint. According to the above method, dielectric materials that can achieve wide-angle optical enhancement can be quickly selected, greatly shortening the time cost required for selecting dielectric materials.

[0041] 2. The present invention proposes a method for designing the equivalent refractive index and equivalent thickness of an equivalent dielectric layer. By selecting two dielectric materials with different refractive indices and controlling the thickness of the dielectric layers respectively, they can be converted into equivalent dielectric layers with different equivalent refractive indices and equivalent thicknesses according to the transmission matrix, solving the problem that some dielectric materials corresponding to the refractive index do not exist at present, so as to meet the needs of subsequent gradient refractive index matching.

[0042] 3. The present invention proposes a design method for an optical substrate anti-reflection composite structure based on equivalent gradient refractive index matching. By depositing a series of equivalent dielectric layers that meet the equivalent gradient refractive index matching on the optical substrate, the equivalent admittance of the optical substrate anti-reflection composite structure is reduced to 1, satisfying the condition of matching the admittance of air, thereby achieving transmission enhancement in a wide band and wide angle domain. According to the above method, the relevant parameters of the required equivalent dielectric layer can be obtained, thereby obtaining the corresponding optical substrate anti-reflection composite structure to achieve optical anti-reflection in a wide angle domain.

[0043] The specific implementation modes of the present invention are further described in detail below in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The drawings described below are only some embodiments. For those skilled in the art, other drawings can be obtained based on these drawings without creative work. In the drawings:

[0045] Figure 1 It is a schematic diagram of realizing wide-angle transmittance enhancement by controlling the equivalent refractive index to constrain the propagation angle as described in the present invention.

[0046] Figure 2 It is a schematic diagram of reducing the optical substrate admittance by adopting gradient refractive index matching as described in the present invention.

[0047] Figure 3 This is one of the schematic diagrams of realizing equivalent dielectric layer design by controlling the thickness of dielectric layer A and dielectric layer B as described in the present invention.

[0048] Figure 4 It is a schematic diagram of the optical substrate anti-reflection composite structure designed in the visible 0.4-0.7μm and infrared 1-12μm bands of the present invention.

[0049] Figure 5 It is a schematic diagram of the admittance of the optical substrate anti-reflection composite structure designed in the visible 0.4-0.7μm and infrared 1-12μm bands described in the present invention.

[0050] Figure 6 It is a schematic diagram of the transmittance of the optical substrate anti-reflection composite structure designed in the visible 0.4-0.7μm and infrared 1-12μm bands described in the present invention.

[0051] Figure 7 This is the second schematic diagram of realizing wide-angle transmittance enhancement by controlling the equivalent refractive index to constrain the propagation angle as described in the present invention.

[0052] In the accompanying drawings, the components represented by the reference numerals are listed as follows:

[0053] 1. Dielectric layer A; 2. Dielectric layer B; 3. Equivalent dielectric layer; 4. TiO2 dielectric layer; 5. YbF3 dielectric layer; 6. ZnS optical substrate.

[0054] It should be noted that these drawings and textual descriptions are not intended to limit the conceptual scope of the present invention in any way, but are intended to illustrate the concept of the present invention for those skilled in the art by referring to specific embodiments. DETAILED DESCRIPTION

[0055] The present invention will now be described in further detail with reference to the accompanying drawings.

[0056] See also Figure 1-7 As shown, in this embodiment, a wide-angle optical anti-reflection method based on equivalent gradient refractive index matching and phase angle constraint is provided, in order to achieve wide-angle optical anti-reflection in the range of -45° to 45° in the visible light band 0.4-0.7μm and the infrared band 1-12μm, which includes the following steps:

[0057] Ⅰ. Select two dielectric materials with different refractive indices as dielectric layer A1 and dielectric layer B2. The refractive indices of dielectric layer A1 and dielectric layer B2 are n1 and n2 respectively, and the thicknesses are d1 and d2 respectively;

[0058] II. Based on the refractive index of dielectric layer A1 and dielectric layer B2, and Calculate the reflection coefficient and transmission coefficient of each interface, and construct the interface action matrix I from the reflection coefficient and transmission coefficient k-1，k , whose expression is: Where n k-1 and n k are the refractive indices of two adjacent layers;

[0059] III. Based on the thickness determined in step Ⅰ, Calculate the propagation phase in each dielectric layer and construct the propagation matrix of the dielectric layer Among them, n k is the refractive index of the dielectric layer, d k is the thickness of the dielectric layer, λ is the wavelength for which anti-reflection is designed;

[0060] IV. Multiply the interface action matrix and the propagation matrix in order to obtain the total transfer matrix S of the entire multilayer dielectric structure, which is expressed as: S = I 01 L1I 12 L2I 23 ;

[0061] V. Based on the total transfer matrix calculated in step IV, let the total transfer matrix of dielectric layer A1 and dielectric layer B2 be equal to the transfer matrix S=I' of the single-layer dielectric 01 L'1I′12 , determine the equivalent refractive index n of the equivalent dielectric layer 3 i and equivalent thickness d i ;

[0062] VI. By adjusting the thicknesses d1 and d2 of the two initial media, a series of dielectric layers with decreasing equivalent refractive index are generated to form an equivalent dielectric gradient layer that meets the gradient refractive index matching condition;

[0063] VII. The equivalent refractive index gradient layers generated in step VI are deposited on the optical substrate in descending order of refractive index, and finally an optical anti-reflection composite structure with decreasing gradient refractive index is formed.

[0064] In this embodiment, the optical substrate includes but is not limited to magnesium fluoride, zinc sulfide, zinc selenide, silicon and germanium.

[0065] In this embodiment, the optical anti-reflection composite structure is composed of a dielectric layer A1 and a dielectric layer B2, and the design of the equivalent dielectric layer 3 is achieved by controlling the thickness of the dielectric layer A1 and the dielectric layer B2.

[0066] In this embodiment, the material of dielectric layer A1 and dielectric layer B2 is not limited to one of TiO2 and YbF3.

[0067] In this embodiment, the equivalent refractive index n obtained in step V i Greater than or equal to 1.7 to achieve wide-angle transmission enhancement, and the equivalent refractive index n i ≥1.7 can limit the propagation angle to within 25° to constrain the propagation phase, thereby achieving transmission enhancement of the optical substrate anti-reflection composite structure in a wide angle range.

[0068] In this embodiment, in order to reduce the equivalent admittance, the admittance of the optical base is set to α+iβ, where α is the real part of the optical base admittance and β is the imaginary part of the optical base admittance;

[0069] Combining the optical base admittance α+iβ and the dielectric layer admittance m i , calculate the total equivalent admittance x+iy of the optical substrate antireflection composite structure, which satisfies the following relationship in δ i is the propagation phase in the medium, x and y are the real and imaginary parts of the equivalent admittance respectively; m i is the admittance of the dielectric material; according to the above formula, by adopting a series of dielectric materials whose refractive index decreases gradually within the range of the optical substrate and the refractive index of air, the equivalent admittance of the optical substrate anti-reflection composite structure can be reduced to 1 to meet the condition of matching with the air admittance, thereby achieving optical anti-reflection in a wide angle range.

[0070] By selecting dielectric materials with decreasing refractive index and adjusting the thickness of each layer, the total equivalent admittance x+iy is close to 1, satisfying the following condition x+iy≈1, where the total admittance matches the air admittance to minimize reflection and enhance transmission; air admittance is a quantitative property of electromagnetic wave transmission in free space or air, usually normalized to 1, and used as a benchmark for admittance matching in optical systems. In anti-reflection design, light transmission can be enhanced by adjusting the admittance of the material to gradually approach the air admittance.

[0071] When the above conditions are met, the optical substrate anti-reflection composite structure can achieve an optical anti-reflection effect in a wide angle range.

[0072] In the present embodiment, the multilayer film system for achieving equivalent gradient refractive index matching has a total number of layers between 2 and 20 and a period within 1 to 10.

[0073] In this embodiment, for a non-existent medium refractive index, an equivalent refractive index can be used to replace the non-existent medium refractive index, which specifically includes the following steps:

[0074] A medium layer with a refractive index of n1 and a medium layer with a refractive index of n2 are selected, wherein the refractive indices of n1 and n2 are both within the range of the refractive index of air and the refractive index of the optical substrate.

[0075] By adjusting the thicknesses d1 and d2 of the two dielectric layers within a range of 300 nm, the propagation phase of light in the two dielectric layers is adjusted to achieve a combination of different equivalent refractive indices, thereby constructing an equivalent dielectric layer 3 that meets the design requirements;

[0076] By adjusting the refractive index and thickness combination of the two dielectric layers, a series of equivalent dielectric layers 3 with gradually decreasing equivalent refractive index are generated, thereby satisfying the gradient refractive index matching condition and achieving admittance matching between the optical substrate and the air.

[0077] Depend on Figure 1 As shown, by controlling the equivalent refractive index to be greater than or equal to 1.7, the propagation angle of the incident light in the equivalent medium layer 3 can be constrained within a range of 25°, thereby limiting the change of the propagation phase with the incident angle, so as to meet the phase angle constraint conditions of wide-angle optical anti-reflection and achieve wide-angle transmission enhancement.

[0078] Depend on Figure 2 As shown, by depositing dielectric layers with decreasing refractive indices on the optical substrate and controlling the thickness of the dielectric layers, the equivalent admittance of the optical substrate can be reduced to near 1, thereby satisfying the condition of matching the admittance of air and achieving anti-reflection and anti-transmission of the optical substrate.

[0079] Depend on Figure 3As shown, a dielectric layer A1 with a refractive index of n1 and a dielectric layer B2 with a refractive index of n2 are selected, and the thicknesses d1 and d2 of the two dielectric layers are controlled. They can be converted into a new equivalent dielectric layer 3 by calculating the transfer matrix, thereby obtaining a new equivalent refractive index ni and an equivalent thickness di.

[0080] Test example: The composite structure for realizing optical substrate anti-reflection in the visible 0.4-0.7μm and infrared 1-12μm bands is a five-period TiO2 / YbF3 composite structure, wherein 4 is the medium TiO2, 5 is the medium YbF3, and 6 is the optical substrate, which is ZnS. The thickness of the coating layers from top to bottom are as follows: the thickness of the first TiO2 layer is within 15-25nm; the thickness of the second YbF3 layer is within 175-185nm; the thickness of the third TiO2 layer is within 90-100nm; the thickness of the fourth YbF3 layer is within 165-175nm; the thickness of the fifth TiO2 layer is within 75-85nm; the thickness of the sixth YbF3 layer is within 140-150nm; the thickness of the seventh TiO2 layer is within 85-95nm; the thickness of the eighth YbF3 layer is within 140-150nm; the thickness of the ninth TiO2 layer is within 80-90nm; the thickness of the tenth YbF3 layer is within 145-155nm ( Figure 4 ).

[0081] The simulation experiment of the five-period TiO2 / YbF3 composite structure was carried out by Figure 5 As shown in the simulation results, the optical substrate anti-reflection composite structure can reduce the admittance of the optical substrate from about 2.4 to about 1.49, greatly reducing the equivalent admittance of the optical substrate, thereby meeting the condition of matching the admittance of air to achieve anti-reflection and anti-reflection of the optical substrate. In addition. From the simulation results ( Figure 6 ), in the 0.4-0.7μm band, the optical substrate anti-reflection composite structure can increase the original average transmittance of the optical substrate from 83% to 84.5%; in the 1-12μm band, the optical substrate anti-reflection composite structure can increase the original average transmittance of the optical substrate from 86% to 93.5%. And in the wide-angle range, a stable and high transmittance is maintained, which can achieve wide-angle transmission enhancement of the optical substrate.

[0082] The present invention is not limited to the above-mentioned embodiments. Anyone should be aware that any structural changes made under the enlightenment of the present invention, and any technical solutions that are the same or similar to the present invention, fall within the protection scope of the present invention. The technology, shape, and structural parts not described in detail in the present invention are all well-known technologies.

Claims

1. A wide-angle optical anti-reflection method based on equivalent gradient refractive index matching and phase angle constraint is used to achieve wide-angle optical anti-reflection in the range of -45° to 45° in the visible light band of 0.4-0.7μm and the infrared band of 1-12μm, characterized in that: It includes the following steps: Ⅰ. Select two dielectric materials with different refractive indices as dielectric layer A(1) and dielectric layer B(2). The refractive indices of dielectric layer A(1) and dielectric layer B(2) are n1 and n2 respectively, and the thicknesses are d1 and d2 respectively. II. Based on the refractive index of dielectric layer A (1) and dielectric layer B (2), and Calculate the reflection coefficient and transmission coefficient of each interface, and construct the interface action matrix I from the reflection coefficient and transmission coefficient k-1，k , whose expression is: where n k-1 and n k are the refractive indices of two adjacent layers; III. Based on the thickness determined in step Ⅰ, Calculate the propagation phase in each dielectric layer and construct the propagation matrix of the dielectric layer Among them, n k is the refractive index of the dielectric layer, d k is the thickness of the dielectric layer, λ is the wavelength for which anti-reflection is designed; IV. Multiply the interface action matrix and the propagation matrix in order to obtain the total transfer matrix S of the entire multilayer dielectric structure, which is expressed as: S = I 01 L1I 12 L2I 23 ; V. Based on the total transfer matrix calculated in step IV, let the total transfer matrix of dielectric layer A (1) and dielectric layer B (2) be equal to the transfer matrix S = I' of the single-layer dielectric. 01 L'1I' 12 , determine the equivalent refractive index n of the equivalent dielectric layer (3) i and equivalent thickness d i ; VI. By adjusting the thicknesses d1 and d2 of the dielectric layer A (1) and the dielectric layer B (2), a series of dielectric layers with decreasing equivalent refractive index are generated to form an equivalent dielectric gradient layer that meets the gradient refractive index matching condition; VII. The equivalent refractive index gradient layers generated in step VI are deposited on the optical substrate in descending order of refractive index, and finally an optical anti-reflection composite structure with decreasing gradient refractive index is formed.

2. The wide-angle optical anti-reflection method based on equivalent gradient refractive index matching and phase angle constraint according to claim 1, characterized in that: Optical substrates include, but are not limited to, magnesium fluoride, zinc sulfide, zinc selenide, silicon, and germanium.

3. The wide-angle optical anti-reflection method based on equivalent gradient refractive index matching and phase angle constraint according to claim 1, characterized in that: The optical anti-reflection composite structure is composed of a dielectric layer A (1) and a dielectric layer B (2), and the design of an equivalent dielectric layer (3) is achieved by controlling the thickness of the dielectric layer A (1) and the dielectric layer B (2).

4. The wide-angle optical anti-reflection method based on equivalent gradient refractive index matching and phase angle constraint according to claim 1, characterized in that: The material of dielectric layer A (1) and dielectric layer B (2) includes but is not limited to one of TiO2 and YbF3.

5. The wide-angle optical anti-reflection method based on equivalent gradient refractive index matching and phase angle constraint according to claim 1, characterized in that: The equivalent refractive index n obtained in step V i Greater than or equal to 1.7 to achieve wide-angle transmission enhancement, and the equivalent refractive index n i ≥1.7 can limit the propagation angle to within 25° to constrain the propagation phase, thereby achieving transmission enhancement of the optical substrate anti-reflection composite structure in a wide angle range.

6. The wide-angle optical anti-reflection method based on equivalent gradient refractive index matching and phase angle constraint according to claim 1, characterized in that: To reduce the equivalent admittance, the admittance of the optical basis is set to α+iβ, where α is the real part of the optical basis admittance and β is the imaginary part of the optical basis admittance; Combining the optical base admittance α+iβ and the dielectric layer admittance m i , calculate the total equivalent admittance x+iy of the optical substrate antireflection composite structure, which satisfies the following relationship in δ i is the propagation phase in the medium, x and y are the real and imaginary parts of the equivalent admittance respectively; m i is the admittance of the dielectric material; By selecting dielectric materials with decreasing refractive index and adjusting the thickness of each layer, the total equivalent admittance x+iy is close to 1, satisfying the following condition x+iy≈1, where the total admittance matches the admittance of air to minimize reflection and enhance transmission; When the above conditions are met, the optical substrate anti-reflection composite structure can achieve an optical anti-reflection effect in a wide angle range.

7. The wide-angle optical anti-reflection method based on equivalent gradient refractive index matching and phase angle constraint according to claim 1, characterized in that: The multilayer film system used to achieve equivalent gradient refractive index matching has a total number of layers between 2 and 20 and a period within 1 to 10.

8. The wide-angle optical anti-reflection method based on equivalent gradient refractive index matching and phase angle constraint according to claim 1, characterized in that: For a non-existent medium refractive index, an equivalent refractive index can be used to replace the non-existent medium refractive index, which specifically includes the following steps: A medium layer with a refractive index of n1 and a medium layer with a refractive index of n2 are selected, wherein the refractive indices of n1 and n2 are both within the range of the refractive index of air and the refractive index of the optical substrate. By adjusting the thicknesses d1 and d2 of the two dielectric layers within a range of 300 nm, the propagation phase of light in the two dielectric layers is adjusted to achieve a combination of different equivalent refractive indices, thereby constructing an equivalent dielectric layer (3) that meets the design requirements; By adjusting the refractive index and thickness combination of the two medium layers, a series of equivalent medium layers (3) with gradually decreasing equivalent refractive index are generated, thereby satisfying the gradient refractive index matching condition and achieving admittance matching between the optical substrate and the air.

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