Coated optical element and method for producing and using the same

Abstract

This invention relates to the field of optical manufacturing technology, and provides a coated optical element, its preparation method, and its application. The coated optical element includes: a substrate, and a composite reflective film system disposed on at least one surface of the substrate; wherein, along a direction away from the substrate, the composite reflective film system comprises a substrate layer, a silver film layer, an aluminum oxide layer, and a first protective layer sequentially stacked. This invention can significantly improve light utilization and reduce imaging brightness loss.

Description

Technical Field

[0001] This invention relates to the field of optical manufacturing technology, specifically to coated optical elements, their preparation methods, and applications. Background Technology

[0002] The equivalent negative refractive plate lens is a key optical component for achieving aerial imaging. Its core structure is usually composed of a micron-sized lattice array. By depositing a reflective film on the lattice reflective surface, it can achieve multiple reflections and transmissions of light, ultimately forming a real image in the air.

[0003] Currently, aluminum films are commonly used for the reflective coatings in related technologies. However, as the requirements for image brightness and contrast in aerial imaging applications continue to increase, the inherent defects of aluminum film reflective systems have become increasingly prominent: First, the reflectivity of aluminum films exhibits significant wavelength dependence across the entire visible light spectrum, especially in the short-wavelength blue-violet region (approximately 400nm), where the reflectivity is significantly lower than in the long-wavelength band, leading to loss of image brightness and color distortion; second, the light path needs to undergo two reflections within the crystal lattice, and the low reflectivity of aluminum films amplifies the loss of light efficiency, making it difficult to meet the needs of high-brightness scenarios. Summary of the Invention

[0004] This invention aims to at least partially address one of the technical problems in related technologies. To this end, this invention provides a coated optical element, its fabrication method, and its application, which can significantly improve light utilization and reduce imaging brightness loss.

[0005] A first aspect of the present invention provides a coated optical element, comprising: A substrate, and a composite reflective film system disposed on at least one surface of the substrate; The composite reflective film system comprises, along the direction away from the substrate, a substrate layer, a silver (Ag) film layer, an aluminum oxide (Al2O3) layer and a first protective layer, which are stacked sequentially.

[0006] Therefore, using a silver film instead of the traditional aluminum film as the core reflective layer can significantly improve light utilization and reduce image brightness loss by leveraging silver's higher reflectivity in the visible light band compared to aluminum. Applying a base coat enhances the adhesion between the silver film and the substrate, preventing the silver film from peeling off during processes such as stacking, cutting, and polishing; it also prevents substances from the substrate from migrating to the silver film, thus improving the long-term stability of the silver film. The aluminum oxide layer, as an intermediate transition layer, possesses high density and good bonding ability with both silver and the first protective layer. Therefore, it not only enhances the adhesion of the silver film but also forms a dense physical barrier. Combined with the first protective layer, it effectively isolates water and oxygen, achieving comprehensive protection for the silver film.

[0007] According to embodiments of the present invention, the above-mentioned coated optical element may further include at least one of the following additional technical features: In some embodiments, the coated optical element satisfies at least one of the following conditions: The underlayer comprises at least one of silicon dioxide (SiO2) and niobium pentoxide, preferably silicon dioxide; The first protective layer comprises at least one of silicon dioxide and niobium pentoxide, preferably silicon dioxide; The substrate includes one or more of glass, sapphire, and optical plastics.

[0008] In some embodiments, the coated optical element satisfies at least one of the following conditions: The thickness of the substrate is 0.2mm to 1.0mm; The thickness of the substrate layer is 8nm~12nm; The thickness of the silver film layer is 70nm~90nm; The thickness of the aluminum oxide layer is 20nm~30nm; The thickness of the first protective layer is 8nm~12nm.

[0009] A second aspect of the present invention provides a method for preparing the aforementioned coated optical element, comprising: An underlayer, a silver film layer, an aluminum oxide layer, and a first protective layer are sequentially formed on at least one side of the substrate to form a composite reflective film system, thereby forming the coated optical element.

[0010] Therefore, this method possesses all the features and advantages of the aforementioned coated optical elements, which will not be elaborated upon here.

[0011] In some embodiments, the formation of the underlayer, silver film layer, aluminum oxide layer and first protective layer includes at least one of vapor deposition or magnetron sputtering.

[0012] A third aspect of the present invention provides an equivalent negative refractive plate lens, comprising: Two waveguide arrays that fit together, and the waveguide extension directions of the two waveguide arrays are orthogonal to each other; The waveguide array is composed of multiple waveguide units arranged side by side, and each waveguide unit is formed by stacking and bonding multiple of the aforementioned coated optical elements or coated optical elements prepared by the aforementioned method.

[0013] Therefore, it can effectively improve the output light flux, reduce blue light loss, achieve a brighter and more realistic aerial image, meet the requirements of high-definition display, and the equivalent negative refractive plate lens has all the features and advantages of the aforementioned coated optical elements, which will not be repeated here.

[0014] In some embodiments, at least one end face of the waveguide unit is covered with a second protective layer; Preferably, the waveguide unit has a second protective layer covering both opposite end faces.

[0015] In some embodiments, the equivalent negative refractive plate lens satisfies at least one of the following conditions: The second protective layer comprises at least one of silicon dioxide and niobium pentoxide, preferably silicon dioxide; The thickness of the second protective layer is 10nm~20nm.

[0016] A fourth aspect of the present invention provides a method for preparing the aforementioned equivalent negative refractive plate lens, comprising: The coated optical elements are stacked and then divided to obtain waveguide units, wherein the coated optical elements include the aforementioned coated optical elements or coated optical elements prepared by the aforementioned method. Multiple waveguide units are arranged side by side to form two waveguide arrays, and the two waveguide arrays are orthogonally attached along the waveguide extension direction.

[0017] Therefore, this method possesses all the features and advantages of the aforementioned coated optical elements or equivalent negative refractive plate lenses, which will not be elaborated upon here.

[0018] In some embodiments, after obtaining the waveguide unit, the method further includes: forming a second protective layer on at least one end face of the waveguide unit; preferably, forming the second protective layer on opposite end faces of the waveguide unit.

[0019] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0020] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which: Figure 1 This is a schematic diagram of the composite reflective film layer described in Embodiment 1 of the present invention; Figure 2 This is a schematic diagram of the protective coating on the end face of the waveguide unit in Embodiment 1 of the present invention; Figure 3 This is a cross-sectional schematic diagram of the protective coating on the end face of the waveguide unit in Embodiment 1 of the present invention; Figure 4 The reflectance curves of the coated optical elements described in Embodiment 1 and Comparative Example 1 of the present invention in the visible light band are shown. Figure 5This is a photograph of the coated optical element described in Embodiment 1 of the present invention after it has been exposed to air; Figure 6 This is a photograph of the coated optical element described in Comparative Example 2 of the present invention after it has been exposed to air.

[0021] Figure reference numerals: 1-substrate; 2-underlay layer; 3-silver film layer; 4-alumina layer; 5-first protective layer; 6-second protective layer; 7-waveguide unit. Detailed Implementation

[0022] The embodiments of the present invention are described in detail below. The embodiments described below are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0023] It should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. Furthermore, in the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0024] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0025] In this document, the terms “comprising” or “including” are open-ended expressions, meaning that they include the contents specified in this invention, but do not exclude other aspects.

[0026] In this document, the terms “optionally,” “optionally,” or “optionally” generally refer to an event or condition that may, but may not, occur, and the description includes both cases in which the event or condition occurs and cases in which the event or condition does not occur.

[0027] The low overall reflectivity of aluminum films across the entire visible light spectrum results in low image brightness, making it difficult to meet the requirements of high-brightness scenarios. Considering that silver films have higher reflectivity than aluminum films, they are theoretically a better metal film material. However, the interfacial adhesion between the silver film and the substrate is extremely weak, leading to poor film adhesion and easy peeling during subsequent stacking, cutting, and polishing processes. Furthermore, silver films are easily oxidized, significantly reducing the long-term stability and optical performance of the lens. Therefore, related technologies have consistently failed to successfully apply silver films to the field of equivalent negative refractive flat lens technology.

[0028] Based on the above research, this application proposes a coated optical element. Applying this coated optical element to an equivalent negative refractive flat lens can effectively improve the problems of insufficient adhesion between the silver film and the substrate, easy oxidation of the silver film surface and the split end face, and improve imaging brightness and long-term stability.

[0029] In view of this, please refer to Figure 1 The first aspect of the present invention provides a coated optical element, comprising: Substrate 1, and a composite reflective film system disposed on at least one side surface of the substrate 1; In the direction away from the substrate 1, the composite reflective film system includes a substrate 2, a silver film layer 3, an aluminum oxide layer 4, and a first protective layer 5 stacked sequentially.

[0030] Therefore, using a silver film instead of the traditional aluminum film as the core reflective layer can take advantage of silver's higher reflectivity in the visible light band (especially in the short-wavelength blue-violet band, where silver's reflectivity attenuation is much less than aluminum's), significantly improving light utilization and reducing image brightness loss. It also improves color distortion caused by fluctuations in aluminum film reflectivity, resulting in brighter, clearer images with a better visual experience. Applying a base coat enhances the adhesion between the silver film and the substrate, forming interfacial chemical bonds to prevent the silver film from peeling off during stacking, cutting, and polishing processes. Furthermore, it blocks the migration of alkali metal ions from the glass substrate to the silver film, preventing corrosion or oxide spots and improving the long-term stability of the silver film. The aluminum oxide layer, serving as an intermediate transition layer, possesses high density and excellent adhesion to both silver and the first protective layer. Furthermore, during the coating process, the aluminum oxide layer typically exhibits compressive stress. This characteristic allows it to achieve stress matching with layers exhibiting tensile stress (such as silicon dioxide), thereby optimizing the stress distribution of the entire film system and enhancing its overall mechanical stability. Therefore, the aluminum oxide layer both strengthens the adhesion of the silver film and forms a dense physical barrier. The first protective layer physically isolates water, oxygen, and sulfides, preventing the silver film from oxidizing and turning black. It also possesses scratch resistance and corrosion resistance; additionally, it enhances the reflectivity of the silver film through interference effects, improving the long-term optical stability of the lens.

[0031] Therefore, the combination of the base layer, silver film layer, aluminum oxide layer and first protective layer can provide comprehensive protection for the silver film by enhancing adhesion, dense protection and effectively isolating water and oxygen, thus achieving efficient and stable reflection of the silver film.

[0032] In some embodiments, the underlayer 2 comprises at least one of silicon dioxide and niobium pentoxide, preferably silicon dioxide. This allows for the formation of a stable interface between the substrate and the silver film, blocking the migration of alkali ions and significantly improving the adhesion and long-term stability of the silver film. Furthermore, the refractive index of silicon dioxide matches well with air, and through interference effects, the reflectivity of the silver film in the visible light band can be further enhanced.

[0033] In some embodiments, the first protective layer 5 comprises at least one of silicon dioxide and niobium pentoxide, preferably silicon dioxide. This effectively isolates water and oxygen, reduces silver film oxidation, and provides mechanical protection, which is beneficial for improving the long-term stability of the coated optical element; furthermore, the refractive index of silicon dioxide matches well with air, and through interference effects, it can further enhance the reflectivity of the silver film in the visible light band.

[0034] In some embodiments, the substrate 1 comprises one or more of glass, sapphire, and optical plastic.

[0035] In some embodiments, the thickness of the substrate 1 is 0.2mm to 1.0mm, specifically 0.2mm, 0.3mm, 0.4mm, 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm, 1.0mm, etc. Within this range, sufficient mechanical strength of the substrate can be ensured while also achieving a thinner lens and improved processing efficiency. If the substrate is too thin, its mechanical strength may be insufficient, making it prone to warping, cracking, or fragmentation during stacking, cutting, and polishing processes, leading to a decrease in finished product quality. If the substrate is too thick, the overall thickness and weight of the lens will increase, hindering the thinner design and prolonging the cutting and polishing processing time, reducing production efficiency, and potentially lowering imaging accuracy.

[0036] In some embodiments, the thickness of the substrate layer 2 is 8nm to 12nm, specifically 8nm, 9nm, 10nm, 11nm, 12nm, etc. Within this range, a continuous and stable transition layer can be formed between the substrate and the silver film, effectively enhancing the adhesion of the silver film and blocking the migration of alkali ions, while avoiding adverse effects on the optical properties of the film system. If the thickness of the substrate layer is too thin, alkali ions may penetrate the interlayer and cause corrosion of the silver film, and the substrate layer itself may affect the growth quality of the subsequent silver film due to discontinuity; if the thickness of the substrate layer is too thick, it will increase the overall thickness of the film system and the deposition time, and a thicker low-refractive-index layer may change the optical properties of the film system, causing a decrease in the reflectivity of the silver film in the target wavelength band.

[0037] In some embodiments, the thickness of the silver film layer 3 is 70nm~90nm, specifically 70nm, 72nm, 75nm, 78nm, 80nm, 82nm, 85nm, 88nm, 90nm, etc. Within the above range, the silver film can achieve a reflectivity close to its theoretical maximum value, and the film layer is continuous and dense, possessing good mechanical strength and adhesion, which is beneficial for meeting the requirements of equivalent negative refractive flat lens for high light efficiency and process stability. If the thickness of the silver film layer is too thin, it may result in a large number of island structures or pinholes, reducing reflectivity and having poor water and oxygen blocking ability, making it prone to penetrating oxidation, leading to rapid attenuation of lens brightness; if the thickness of the silver film layer is too thick, it will increase the accumulation of internal stress in the silver film, thereby increasing the risk of peeling or cracking between it and the underlayer and protective layer, and an excessively thick silver film will also reduce visible light transmittance, which may actually reduce reflectivity.

[0038] In some embodiments, the thickness of the aluminum oxide layer 4 is 20nm~30nm, specifically 20nm, 22nm, 25nm, 28nm, 30nm, etc. Within the above range, the aluminum oxide layer can form a dense anti-oxidation barrier, effectively preventing water and oxygen from penetrating from the outside to the surface of the silver film. At the same time, as an intermediate transition layer between the silver film and the first protective layer, it can improve the interlayer stress matching and adhesion, and enhance the mechanical stability of the entire film system. If the thickness of the aluminum oxide layer is too thin, it is difficult to form a complete and dense barrier layer. Water and oxygen may still penetrate through film defects, causing local oxidation of the silver film. Moreover, the buffering stress and adhesion enhancement effects are insufficient, and the composite reflective film system is prone to failure under thermal cycling or mechanical stress. If the thickness of the aluminum oxide layer is too thick, the internal stress (compressive stress) of the film layer increases significantly, which may lead to an imbalance with the tensile stress of other layers, resulting in substrate warping or even film cracking. Furthermore, an excessively thick aluminum oxide layer may also change the optical interference characteristics of the composite reflective film system, narrowing the high reflectivity bandwidth of the silver film.

[0039] In some embodiments, the thickness of the first protective layer 5 is 8nm to 12nm, specifically 8nm, 9nm, 10nm, 11nm, 12nm, etc. Within the above range, the first protective layer can effectively isolate water, oxygen, and sulfides as a physical barrier, protecting the underlying aluminum oxide layer and silver film. If the thickness of the first protective layer is too thin, it is difficult to form a continuous protective layer, and the silver film at pinholes or defects may be directly exposed to the environment, leading to its oxidation and corrosion. If the thickness of the first protective layer is too thick, it is easy to cause an imbalance in the compressive stress between it and the aluminum oxide layer, resulting in film warping or peeling, and may also reduce the reflectivity of specific wavelengths, introducing additional scattering loss.

[0040] A second aspect of the present invention provides a method for preparing the aforementioned coated optical element, comprising: A base layer 2, a silver film layer 3, an aluminum oxide layer 4, and a first protective layer 5 are sequentially formed on at least one side of the substrate 1 to form a composite reflective film system to form the coated optical element.

[0041] Therefore, this method possesses all the features and advantages of the aforementioned coated optical elements, which will not be elaborated upon here.

[0042] In some embodiments, a base layer 2, a silver film layer 3, an aluminum oxide layer 4, and a first protective layer 5 are sequentially formed on both sides of the substrate 1 to form a composite reflective film system, thereby forming the coated optical element. This enables the waveguide array to achieve complete high reflectivity of the silver film, improving the overall light efficiency and imaging brightness of the equivalent negative refractive plate lens; simultaneously, the bilaterally symmetrical film system can balance the stress on both sides of the substrate, reducing substrate warping caused by unilateral stress, and improving process yield and long-term stability.

[0043] In some embodiments, the formation of the underlayer 2, silver film layer 3, aluminum oxide layer 4 and first protective layer 5 includes at least one of vapor deposition or magnetron sputtering.

[0044] In some embodiments, the coating linear speed for forming the underlayer 2 is 1 m / min, and the power supply is 5 kW ± 0.1 kW.

[0045] In some embodiments, the deposition linear speed for forming the silver film layer 3 is 1 m / min, and the power supply is 8 kW ± 0.1 kW.

[0046] In some embodiments, the coating linear speed for forming the aluminum oxide layer 4 is 1 m / min, and the power supply is 6.5 kW ± 0.1 kW.

[0047] In some embodiments, the coating linear speed for forming the first protective layer 5 is 1 m / min, and the power supply is 5 kW ± 0.1 kW.

[0048] A third aspect of the present invention provides an equivalent negative refractive plate lens, comprising: Two waveguide arrays that fit together, and the waveguide extension directions of the two waveguide arrays are orthogonal to each other; The waveguide array is composed of multiple waveguide units arranged side by side, and each waveguide unit is formed by stacking and bonding multiple of the aforementioned coated optical elements or coated optical elements prepared by the aforementioned method.

[0049] Therefore, it can effectively improve the output light flux, reduce blue light loss, achieve a brighter and more realistic aerial image, meet the requirements of high-definition display, and the equivalent negative refractive plate lens has all the features and advantages of the aforementioned coated optical elements, which will not be repeated here.

[0050] In some embodiments, please refer to Figures 2-3 At least one end face of the waveguide unit 7 is covered with a second protective layer 6; preferably, both opposite end faces of the waveguide unit 7 are covered with the second protective layer 6. This provides end-face edge sealing protection for the exposed silver film cross-section, reducing lateral penetration of oxygen and water vapor along the silver film cross-section, solving the problem of silver film edge oxidation, and helping the silver film maintain high reflectivity throughout the lens's lifespan, thus improving the lens's yield and reliability. Furthermore, by providing comprehensive protection for the silver film through both the planar surface (composite reflective film system) and the cut cross-section (second protective layer), a synergistic effect is achieved, successfully integrating the high reflectivity advantage of the silver film into an equivalent negative refractive flat lens, significantly improving the light efficiency and image quality of aerial imaging.

[0051] It should be noted that the "end face" mentioned in this invention refers to the segmented surface formed after the waveguide unit is divided, on which the exposed silver film layer has a cross-section. Before this invention, although the field of equivalent negative refractive flat lens recognized that silver film was significantly superior to aluminum film in terms of reflectivity, it had never been successfully applied. The fundamental reason is that the industry had not recognized the unique failure mode of the silver film end face being exposed over a large area and undergoing lateral continuous oxidation after the lattice array is divided. All protection schemes for metal films in related technologies only focus on the large-area surface protection of coated optical elements, completely ignoring the defects of the oxidation path caused by the segmented end face, let alone specifically solving this defect. This invention reveals for the first time the existence of the above-mentioned end face oxidation problem and its decisive influence on the long-term stability of the silver film, and creatively proposes to cover the end face of the segmented waveguide unit with a second protective layer for sealing, thereby solving the long-standing problem restricting the application of silver film in this field.

[0052] In some embodiments, the second protective layer 6 comprises at least one of silicon dioxide and niobium pentoxide, preferably silicon dioxide. This allows for the formation of a dense, stable sealing layer that effectively isolates water and oxygen and prevents oxidation of the silver film end face.

[0053] In some embodiments, the thickness of the second protective layer 6 is 10nm to 20nm, specifically 10nm, 12nm, 15nm, 18nm, 20nm, etc. Within the above range, the second protective layer can completely cover and seal the exposed silver film cross-section of the waveguide unit end face, forming a continuous and dense physical barrier, effectively blocking the lateral penetration of oxygen and water vapor. If the thickness of the second protective layer is too thin, it is difficult to form a continuous and complete covering layer, and pinholes or defects may expose the silver film, leading to local oxidation and continuous inward erosion along the cross-section, resulting in insufficient sealing effect; if the thickness of the second protective layer is too thick, the internal stress of the film layer increases, which may cause the waveguide unit to warp or the second protective layer itself to crack, or even reduce the adhesion between the silver film and adjacent layers due to stress transmission.

[0054] A fourth aspect of the present invention provides a method for preparing the aforementioned equivalent negative refractive plate lens, comprising: The coated optical elements are stacked and then divided to obtain waveguide units, wherein the coated optical elements include the aforementioned coated optical elements or coated optical elements prepared by the aforementioned method. Multiple waveguide units are arranged side by side to form two waveguide arrays, and the two waveguide arrays are orthogonally attached along the waveguide extension direction.

[0055] Therefore, this method possesses all the features and advantages of the aforementioned coated optical elements or equivalent negative refractive plate lenses, which will not be elaborated upon here.

[0056] In some embodiments, after obtaining the waveguide unit, the method further includes polishing the waveguide unit. This achieves optical-grade smoothness on the reflecting and transmitting surfaces of the lattice unit. Specifically, the waveguide unit can be fixed on a coating fixture (such as a planetary gear) and subjected to double-sided grinding and chemical mechanical polishing.

[0057] In some embodiments, after the waveguide unit is polished, the surface finish of its optical surface reaches a grade of 40 / 20 (according to US military standard MIL-PRF-13830B, scratches are no higher than number 40 and pits are no higher than number 20).

[0058] In some embodiments, please refer to Figures 2-3 After obtaining the waveguide unit 7, the method further includes: forming a second protective layer 6 on at least one end face of the waveguide unit 7; preferably, forming the second protective layer 6 on opposite end faces of the waveguide unit 7. This forms a dense and stable sealing layer, effectively isolating water and oxygen and preventing oxidation of the silver film end face.

[0059] It should be noted that if the method includes a polishing step of the waveguide unit, the step of forming the second protective layer occurs after polishing. If the second protective layer is formed before polishing, the subsequent grinding and polishing process will remove the protective layer along with surface contaminants and defect layers, causing the silver film end face to be re-exposed to the air, thus failing to achieve a sealing effect. Therefore, a smooth and flat optical surface must be obtained in the polishing step before depositing the second protective layer to ensure that the protective layer directly covers and seals the silver film end face, thereby effectively blocking the lateral penetration of water and oxygen along the cross-section.

[0060] In some embodiments, the second protective layer 6 is formed by at least one of vapor deposition or magnetron sputtering.

[0061] In some embodiments, the coating linear speed for forming the second protective layer 6 is 1 m / min, and the power supply is 7.5 kW ± 0.1 kW.

[0062] In some embodiments, after orthogonally bonding the two waveguide arrays along the waveguide extension direction, the method further includes bonding a protective glass sheet to the outermost layer.

[0063] In some embodiments, the thickness of the protective glass sheet is 0.5mm to 2mm, specifically 0.5mm, 0.8mm, 1.0mm, 1.5mm, 2.0mm, etc. This provides sufficient mechanical support and dust and moisture protection for the lens, while maintaining an overall thin and light-transmitting profile.

[0064] The present invention will be explained below with reference to embodiments. Those skilled in the art will understand that the following embodiments are for illustrative purposes only and should not be considered as limiting the scope of the invention. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in the field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0065] Example 1 S1, Ultra-thin glass substrate coating like Figure 1 As shown, an ultrathin glass with a thickness of 0.4 mm was selected as the substrate. Vacuum magnetron sputtering was performed on both sides of the substrate to form a composite reflective film layer with a total thickness of 125 nm. The vacuum level and temperature of the cavity were controlled during the coating process to ensure that the film layer was dense and uniform. The details are as follows: The substrate is SiO2, the target material is a Si target with a length of 1850mm, the coating line speed is 1m / min; the power supply uses two medium frequency power supplies, each with a power of 5kw; the single layer film thickness is 10nm; oxygen is introduced at 50sccm to ensure that Si is completely oxidized to form SiO2. The target material for the silver film layer is an Ag target with a length of 1850mm, and the coating linear speed is 1m / min; two DC power supplies are used, each with a power of 8kw; the thickness of a single layer is 40nm, and the total thickness of Ag on both sides is 80nm. The aluminum oxide layer target material is an Al target with a length of 1850 mm, and the coating linear speed is 1 m / min; the power supply uses two medium frequency power supplies, each with a power of 6.5 kW; the single layer film thickness is 25 nm; oxygen is introduced at 50 sccm to ensure that Al is completely oxidized to form Al2O3; The first protective layer is SiO2. The target material is a Si target with a length of 1850mm. The coating linear speed is 1m / min. Two medium-frequency power supplies are used, each with a power of 5kW. The single-layer film thickness is 10nm. 50sccm of oxygen gas is introduced to ensure that Si is completely oxidized to form SiO2.

[0066] S2, Stacking and Slicing The coated glass sheets are stacked into square bricks at the designed angle, and then cut along the lattice arrangement direction using a high-precision slicer to obtain waveguide units with characteristic lattice thickness ratios.

[0067] S3, Grinding and Polishing The waveguide unit is fixed on the planetary wheel of the coating fixture and subjected to double-sided grinding and chemical mechanical polishing to achieve optical-grade smoothness on the reflective and transmissive surfaces of the lattice unit, i.e., a surface smoothness of 40-20 (US military standard).

[0068] S4, End Face Protective Coating After cleaning the polished waveguide unit, place it into a magnetron sputtering coating device, such as... Figures 2-3 As shown, a 15nm thick layer of silicon dioxide (second protective layer) is deposited on both the upper and lower end faces to ensure that the cross-section of the silver film is completely covered. A Si target with a length of 1850mm is selected as the target material, and the coating linear speed is 1m / min; a medium-frequency power supply is used with a single power of 7.5kW; the single-layer film thickness is 15nm; and 50sccm of oxygen gas is introduced to ensure that Si is completely oxidized to form SiO2.

[0069] S5, Orthogonal bonding and encapsulation The waveguide unit with the second protective layer is precisely bonded together, with the upper and lower layers orthogonally bonded, using optical adhesive. Finally, protective glass sheets with a thickness of 0.5 mm are bonded to the outermost layers on both sides to fabricate a complete equivalent negative refractive flat lens.

[0070] Comparative Example 1 This comparative example is based on Example 1, and the only difference from Example 1 is that the silver film in Example 1 is replaced with an aluminum film.

[0071] Comparative Example 2 This comparative example is based on Example 1, and the only difference from Example 1 is that the base layer and the first protective layer in Example 1 are not used.

[0072] Performance Analysis 1. The reflectance of the coated optical elements described in Example 1 and Comparative Example 1 in the visible light band was tested using a spectrophotometer, and the results are as follows: Figure 4 As shown.

[0073] like Figure 4As shown, the reflectivity of a silver film in the visible light band (such as 550nm green light) can reach over 97%, while the reflectivity of an aluminum film in the same band is only around 90%. Therefore, according to optical theory, the single-reflection light loss of the mirror can theoretically be reduced by about 7 percentage points after using a silver film. In an equivalent negative refractive plate lens, light needs to undergo multiple reflections, and the light utilization rate is increased exponentially. Therefore, the brightness of the final aerial image can be increased by more than 25% by using a silver film.

[0074] 2. After exposing the coated optical elements described in Example 1 and Comparative Example 2 to air for 24 hours, their condition was observed, and the results were as follows: Figures 5-6 As shown.

[0075] like Figures 5-6 As shown, in Comparative Example 2, the silver film exhibited significant peeling after exposure to air, while in Example 1, the silver film did not peel off. This demonstrates that the sequential layering of the underlayer, silver film layer, aluminum oxide layer, and first protective layer in this invention enhances the adhesion of the silver film and effectively isolates it from water and oxygen, achieving comprehensive protection for the silver film. Simultaneously, the composite protection of aluminum oxide and silicon dioxide, along with the end-face sealing process, avoids problems such as blackening and decreased reflectivity caused by oxidation, allowing the high reflectivity of the silver film to be maintained for a long time and improving the long-term stability of the lens.

[0076] In the description of this specification, the references to terms such as "an embodiment," "some embodiments," "a method of implementation," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0077] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A coated optical element, characterized in that, include: A substrate, and a composite reflective film system disposed on at least one surface of the substrate; In the direction away from the substrate, the composite reflective film system comprises a substrate layer, a silver film layer, an aluminum oxide layer and a first protective layer stacked sequentially.

2. The coated optical element according to claim 1, characterized in that, At least one of the following conditions must be met: The underlayer comprises at least one of silicon dioxide and niobium pentoxide, preferably silicon dioxide; The first protective layer comprises at least one of silicon dioxide and niobium pentoxide, preferably silicon dioxide; The substrate includes one or more of glass, sapphire, and optical plastics.

3. The coated optical element according to claim 1, characterized in that, At least one of the following conditions must be met: The thickness of the substrate is 0.2mm to 1.0mm; The thickness of the substrate layer is 8nm~12nm; The thickness of the silver film layer is 70nm~90nm; The thickness of the aluminum oxide layer is 20nm~30nm; The thickness of the first protective layer is 8nm~12nm.

4. A method for preparing a coated optical element as described in any one of claims 1 to 3, characterized in that, include: An underlayer, a silver film layer, an aluminum oxide layer, and a first protective layer are sequentially formed on at least one side of the substrate to form a composite reflective film system, thereby forming the coated optical element.

5. The method according to claim 4, characterized in that, The formation of the underlayer, silver film layer, aluminum oxide layer and first protective layer includes at least one of vapor deposition or magnetron sputtering.

6. An equivalent negative refractive plate lens, characterized in that, include: Two waveguide arrays that fit together, and the waveguide extension directions of the two waveguide arrays are orthogonal to each other; The waveguide array is composed of multiple waveguide units arranged side by side, and each waveguide unit is formed by stacking and bonding multiple coated optical elements as described in any one of claims 1 to 3, or coated optical elements prepared by the method described in claim 4 or 5.

7. The equivalent negative refractive plate lens according to claim 6, characterized in that, At least one end face of the waveguide unit is covered with a second protective layer; preferably, both opposite end faces of the waveguide unit are covered with a second protective layer.

8. The equivalent negative refractive plate lens according to claim 7, characterized in that, At least one of the following conditions must be met: The second protective layer comprises at least one of silicon dioxide and niobium pentoxide, preferably silicon dioxide; The thickness of the second protective layer is 10nm~20nm.

9. A method for preparing an equivalent negative refractive plate lens as described in any one of claims 6 to 8, characterized in that, include: The coated optical elements are stacked and then divided to obtain waveguide units, wherein the coated optical elements include the coated optical elements according to any one of claims 1 to 3, or the coated optical elements prepared by the method according to claim 4 or 5. Multiple waveguide units are arranged side by side to form two waveguide arrays, and the two waveguide arrays are orthogonally attached along the waveguide extension direction.

10. The method according to claim 9, characterized in that, After obtaining the waveguide unit, the method further includes: forming a second protective layer on at least one end face of the waveguide unit; preferably, forming the second protective layer on opposite end faces of the waveguide unit.

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