Thin film fabrication method, thin film grating optical waveguide, and augmented reality device

Abstract

The application relates to a thin film preparation method, a thin film grating optical waveguide and an augmented reality device. The thin film preparation method comprises the following steps: providing a substrate, the substrate being provided with an incident grating area, an emission grating area and a folding grating area; coating the incident grating area, the emission grating area and the folding grating area with conductive particles; controlling the line width distribution of the coating position through an electric field to generate a differentiated refractive index at the coating position through the line width distribution, thereby forming a thin film grating; and performing overall exposure to obtain a thin film optical waveguide. The thin film preparation method can confirm the light efficiency of each independent area by coating the grating of each independent area, and the conductive particles are stacked and distributed to form a grating through charged coating. On the one hand, the method is beneficial to avoiding the problem of large material loss caused by the traditional rotary coating method, and on the other hand, the method is beneficial to accurately controlling the position of a specific area, thereby ensuring the exposure effect.

Description

Technical Field

[0001] This application relates to the field of augmented reality, and in particular to a thin film preparation method, a thin film grating waveguide, and an augmented reality device. Background Technology

[0002] Regarding the technological development of Augmented Reality (AR) products, the current main technological trend is the adoption of optical waveguide technology. Optical waveguide technology can be further divided into two main application technologies: geometric waveguide and diffractive waveguide. Among them, volumetric holographic thin-film waveguides are developing the fastest. Volumetric holographic thin-film waveguides are realized through volumetric holographic gratings, which are composed of periodic microstructures with alternating high and low refractive indices. Assuming the incident light is single-wavelength red light, it will be divided into several diffraction orders by a diffraction grating. Each diffraction order continues to propagate in different directions, including reflective diffraction (R0, R±1, R±2, ...) and transmissive diffraction (T0, T±1, T±2, ...). The diffraction angle (θm, m = ±1, ±2, ...) corresponding to each diffraction order is determined by the incident angle (θ) of the light and the period (Λ) of the grating. By designing other parameters of the grating, such as the refractive index n and thickness of the material, the diffraction efficiency of a certain diffraction order, i.e., a certain direction, can be optimized to the maximum, so that most of the light propagates mainly in this direction after diffraction. However, volume holographic gratings have the problem of dispersion.

[0003] The volumetric holographic thin-film optical waveguide technology for diffraction waveguides mainly utilizes laser light to expose volumetric holographic thin films, generating gratings with different refractive indices to fabricate diffraction waveguides. Therefore, the development of volumetric holographic thin-film optical waveguides is of great importance.

[0004] The traditional method for preparing volumetric holographic films involves first applying a full-surface coating using spin coating, followed by alignment exposure. This inevitably leads to two drawbacks: firstly, spin coating results in the loss of a large amount of material, which is wasteful; secondly, relying on exposure control of specific areas makes it difficult to control the exposure position of specific areas on the entire surface, such as causing poor exposure in specific areas like the light-incident area, transition area, and light-outcrystal area. Summary of the Invention

[0005] Therefore, it is necessary to provide a thin film preparation method, a thin film grating waveguide, and an augmented reality device.

[0006] In one embodiment, a method for preparing a thin film includes the following steps:

[0007] S100, a substrate is provided, the substrate having an incident grating region, an exit grating region and a folded grating region;

[0008] S200: Conductive particles are used to coat the incident grating region, the exit grating region, and the folded grating region. The linewidth distribution at the coating position is controlled by an electric field to generate a differential refractive index at the coating position through the linewidth distribution, thereby forming a thin film grating.

[0009] S300, overall exposure, to obtain thin-film optical waveguide.

[0010] The above-mentioned thin film preparation method confirms the light efficiency of each independent region by coating gratings on their respective independent regions. Furthermore, by using charged coating, conductive particles are distributed and stacked to form gratings. This method helps to avoid the problem of material loss caused by traditional spin coating methods. It also helps to precisely control the position of specific regions, ensuring the exposure effect. Moreover, the prepared thin film waveguide can be used as a volumetric holographic thin film waveguide.

[0011] In one embodiment, step S100 includes: S110, forming mutually spaced grooves on the same or different surfaces of the substrate as the incident grating region, the exit grating region and the folded grating region.

[0012] In one embodiment, the groove depth is 15 μm to 500 μm; and / or, a reflective layer is sputtered on the side of the groove, the reflective layer thickness being 10 nm to 300 nm.

[0013] In one embodiment, after step S110, step S100 further includes: S120, providing a transparent conductive layer in the groove.

[0014] In one embodiment, after step S120, step S100 further includes: S130, forming patterned transparent conductive lines on the transparent conductive layer by etching.

[0015] In one embodiment, in step S200, the incident grating region, the exit grating region, and the folded grating region are coated with adhesive by dispensing or slit coating.

[0016] In one embodiment, the grating width of the thin-film grating ranges from 0.2 μm to 3 μm, and the period ranges from 0.3 μm to 5 μm; and / or, the difference in grating brightness and darkness of the thin-film grating ranges from 0.05 to 0.08.

[0017] In one embodiment, in step S200, the substrate is brought into contact with conductive particles in the coating that have the opposite charge, and then charged coating is performed.

[0018] In one embodiment, a thin-film grating waveguide is fabricated using the thin-film fabrication method described in any embodiment.

[0019] In one embodiment, an augmented reality device includes a curved optical structure having a thin-film grating waveguide as described in any embodiment. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of this application or the conventional technology, the drawings used in the description of the embodiments or the conventional technology will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a schematic flowchart of an embodiment of the thin film preparation method described in this application.

[0022] Figure 2 This is a schematic flowchart of another embodiment of the thin film preparation method described in this application.

[0023] Figure 3 for Figure 1 A schematic diagram of the substrate layout in the embodiment shown.

[0024] Figure 4 for Figure 3 A cross-sectional schematic diagram of one aspect of the embodiment shown.

[0025] Figure 5 for Figure 3 Another cross-sectional view of the embodiment shown.

[0026] Figure 6 This is a schematic diagram of electric field controlled coating, representing another embodiment of the thin film preparation method described in this application.

[0027] Figure 7 This is a photographic illustration of an embodiment of the thin-film grating waveguide described in this application.

[0028] Figure 8 This is a photographic illustration of another embodiment of the thin-film grating waveguide described in this application.

[0029] Reference numerals: substrate 100, top surface 110, incident grating region 111, exit grating region 112, folded grating region 113, conductive particle carrier 200, conductive particle 210, electric field 300. Detailed Implementation

[0030] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, the specific embodiments of this application are described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of this application. However, this application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0031] It should be noted that when a component is referred to as being "fixed to" or "set on" another component, it can be directly on the other component or there may be an intermediate component. When a component is considered to be "connected to" another component, it can be directly connected to the other component or there may be an intermediate component present. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used in this application's specification are for illustrative purposes only and do not represent the only possible implementation.

[0032] Furthermore, 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 technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0033] In this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature and the second feature are in indirect contact through an intermediate medium. Furthermore, "above," "over," and "on top" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0034] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used in this application includes any and all combinations of one or more of the associated listed items.

[0035] On the one hand, to overcome the problem of material waste caused by the traditional rotation method of coating conductive particles onto the entire surface of a volumetric holographic thin film, and on the other hand, to overcome the problem of insufficient exposure position caused by the traditional alignment exposure method, this application discloses a thin film preparation method, which includes some or all of the steps of the following embodiments; that is, the thin film preparation method includes some or all of the following technical features. In one embodiment of this application, a thin film preparation method is as follows: Figure 1 As shown, the method includes the following steps: S100, providing a substrate, the substrate having an incident grating region, an exit grating region, and a folded grating region; S200, coating the incident grating region, the exit grating region, and the folded grating region with conductive particles, controlling the linewidth distribution of the coating position by an electric field, so as to generate differentiated refractive indices at the coating position through the linewidth distribution, forming a thin film grating; S300, overall exposure to obtain a thin film optical waveguide. The above thin film preparation method, by confirming the coating grating in each independent region, allows for separate confirmation of the light efficiency of each independent region. Furthermore, by using charged coating to distribute and stack conductive particles to form a grating, it avoids the problem of significant material loss caused by traditional spin coating methods, and allows for precise control of the position of specific regions, ensuring the exposure effect. Moreover, the resulting thin film optical waveguide can serve as a volumetric holographic thin film optical waveguide.

[0036] In step S100, a substrate is provided, the substrate having the incident grating region, the exit grating region, and the folded grating region; in one embodiment, the substrate material includes optical glass and optical plastic. In one embodiment, the optical plastic includes, but is not limited to, polymethyl methacrylate (PMMA), polystyrene (PS), polycarbonate (PC), copolymers of cycloolefin (COC), and cyclo olefin polymer (COP). It is understood that the embodiments of this application do not have specific limitations on the material of the substrate. Furthermore, in one embodiment, the substrate is provided with mutually spaced incident grating regions, exiting grating regions, and folded grating regions; further, in one embodiment, the spacing between the incident grating regions, exiting grating regions, and folded grating regions satisfies the requirement that the width of the coating position is controlled by an external electric field, in order to meet the technical requirement of controlling the linewidth distribution of the coating position by an electric field when coating the incident grating regions, exiting grating regions, and folded grating regions with conductive particles in subsequent steps. This design, by partitioning the thin-film gratings and allowing for separate verification of light efficiency in each independent region, helps improve the overall process yield and accuracy.

[0037] In one embodiment, step S100 includes: S110, forming mutually spaced grooves on the same or different surfaces of the substrate as the incident grating region, the exit grating region and the folded grating region. In one embodiment, the substrate typically has a flat plate shape, such as a rectangular or other shaped plate, with two opposing surfaces and multiple side surfaces between them. For example, a rectangular plate has two surfaces and four side surfaces. The surfaces can be divided into a bottom surface and a top surface according to their relative positions. That is, in step S110, mutually spaced grooves are formed on the top surface and / or bottom surface of the substrate as the incident grating region, the exit grating region, and the folded grating region; that is, mutually spaced grooves are formed on the top surface of the substrate as the incident grating region, the exit grating region, and the folded grating region; or, mutually spaced grooves are formed on the bottom surface of the substrate as the incident grating region, the exit grating region, and the folded grating region; or, one or two of the incident grating region, the exit grating region, and the folded grating region are formed on the top surface of the substrate, and the remaining two or one are formed on the bottom surface of the substrate. Typically, the surface of the substrate and the distribution of its grooves can be designed according to the design requirements of the thin-film grating waveguide or its volumetric holographic film.

[0038] In one embodiment, the groove depth is 15 μm to 500 μm; in another embodiment, a reflective layer is sputtered onto the side of the groove, the reflective layer having a thickness of 10 nm to 300 nm. Further, in one embodiment, the resistivity of the reflective layer is 1 × 10⁻⁶. 5 Ω / cm to 5×10 5 Ω / cm. In one embodiment, the groove depth is 15μm to 500μm; and a reflective layer is sputtered on the side of the groove, the thickness of which is 10nm to 300nm. Other embodiments follow the same principle and will not be elaborated further. In one embodiment, after step S110, step S100 further includes: S120, setting a transparent conductive layer in the groove. The material of the transparent conductive layer includes indium tin oxide, zinc oxide, cadmium tin oxide, indium oxide, and silver nanowires, etc. In one embodiment, after step S120, step S100 further includes: S130, forming patterned transparent conductive lines on the transparent conductive layer by etching. This design allows for the obtaining of the incident grating region, the exit grating region, and the folded grating region to be coated in subsequent steps, along with their corresponding grating distribution positions. Since these are the coating targets, the grating distribution positions can also be referred to as target positions.

[0039] In one embodiment, the thin film preparation method is as follows: Figure 2As shown, the process includes the following steps: S110, providing a substrate, and forming mutually spaced grooves on the same or different surfaces of the substrate as an incident grating region, an exit grating region, and a folded grating region; S120, distributing a transparent conductive layer in the grooves; S130, forming patterned transparent conductive lines on the transparent conductive layer by etching; S200, coating the incident grating region, the exit grating region, and the folded grating region with conductive particles, controlling the linewidth distribution at the coating location by an electric field to generate differentiated refractive indices at the coating location through the linewidth distribution, thereby forming a thin-film grating; S300, exposing the entire structure to obtain a thin-film optical waveguide. Further, in each embodiment, a coating material containing conductive particles is used to coat the incident grating region, the exit grating region, and the folded grating region.

[0040] like Figure 3 As shown, the top surface 110 of the substrate 100 is provided with mutually spaced grooves, including the incident grating region 111, the exit grating region 112, and the folded grating region 113, combined with... Figure 4 and Figure 5 The incident grating region 111, the exit grating region 112, and the folded grating region 113 are spaced apart from each other. For example, according to the design scheme, a substrate groove is etched, which can be located on the same side or opposite sides. Then, a transparent conductive material is sputtered to form a transparent conductive layer, which is then patterned, and then transparent conductive lines are etched. This completes the optical waveguide substrate structure with a groove design. The groove can be on the same side or opposite sides, with a groove depth of 15μm to 500μm. A reflective layer with a thickness of about 100nm to 300nm can be sputtered on the side of the groove. The above-mentioned grooved substrate has a patterned transparent conductive layer, which can be ITO or nano silver wires, with a thickness of about 100nm to 300nm and a resistivity of 1×10⁵Ω / cm to 5×10⁵Ω / cm. 5 Ω / cm. The grating width ranges from 0.2μm to 3μm, the period ranges from 0.3μm to 5μm, and the difference in refractive index between light and dark areas of the grating ranges from 0.05 to 0.08.

[0041] In step S200, conductive particles are used to coat the incident grating region, the exit grating region, and the folded grating region. The linewidth distribution at the coating location is controlled by an electric field to generate differentiated refractive indices at the coating location through the linewidth distribution, thus forming a thin-film grating. That is, differentiated refractive indices are generated through different widths, so that each region, including the incident grating region, the exit grating region, and the folded grating region, has a differentiated refractive index at the coating location of the region, thereby forming a thin-film grating. Further, in one embodiment, a coating material containing conductive particles is used to coat the incident grating region, the exit grating region, and the folded grating region; the coating material includes microcapsule material and liquid optical adhesive, and the weight percentage of microcapsule material relative to liquid optical adhesive is 10% to 40%. The microcapsule material includes iron manganese black and carbon black, etc., and the shell material of the microcapsules is a UV-degradable material, with a microcapsule particle size of 0.2 μm to 3 μm. Furthermore, in one embodiment, the driving voltage of the electric field is 10V to 100V.

[0042] In one embodiment, in step S200, the incident grating region, the exit grating region, and the folded grating region are coated using dispensing or slot die coating. That is, by using dispensing or slot die coating, conductive particles are accurately guided and positioned under electric field control, precisely placed at target locations in the incident grating region, the exit grating region, and the folded grating region. In other words, this application proposes a substrate structure design that uses conductive particles for coating, for example, by dispensing or slot die coating for area coating. During coating, the substrate is electrically controlled to achieve the desired linewidth distribution and simultaneously create a difference in refractive index, thereby forming a thin-film grating. Finally, overall exposure completes the thin-film optical waveguide.

[0043] In one embodiment, the grating width of the thin-film grating ranges from 0.2 μm to 3 μm, and the period ranges from 0.3 μm to 5 μm; in another embodiment, the grating width ranges from 0.5 μm to 1.5 μm, and the period ranges from 1 μm to 3 μm. In one embodiment, the difference in grating brightness and refractive index ranges from 0.05 to 0.08; in another embodiment, the difference in grating brightness and refractive index ranges from 0.06 to 0.07. The difference in grating brightness and refractive index is the range of the difference in the grating's refractive index. Both height difference and refractive index difference affect the phase difference of light in different regions. In the embodiments of this application, conductive particles are used for coating, so the impact of height difference is not significant; the focus can be on the difference in grating brightness and refractive index. In one embodiment, the grating width of the thin-film grating ranges from 1 μm, the period ranges from 1 μm, and the difference in grating brightness and refractive index ranges from 0.06. It is understandable that the above range values ​​are only examples, and the requirements can be flexibly set in actual applications.

[0044] Based on the attraction between opposite charges, in one embodiment, in step S200, the substrate is charged with a charge opposite to that of the conductive particles in the coating, and then charged coating is performed. Further, in one embodiment, a positively charged electric field is introduced into a target location on the substrate; the target location is the grating distribution position of the incident grating region, the exit grating region, and the folded grating region. The conductive particles in the coating are charged with a negative charge, and the negatively charged conductive particles are used to coat the incident grating region, the exit grating region, and the folded grating region on the substrate, which are then subjected to a positively charged electric field. The linewidth distribution at the coating location is controlled by the positively charged electric field on the substrate. Further, in one embodiment, for the incident grating region, the exit grating region, and the folded grating region of the substrate, an electric field carrying a first charge is sequentially applied to the predetermined coating positions according to the coating sequence. The width distribution of the first charge is controlled by the electric field. Then, a second charge with the opposite charge is applied to control the linewidth distribution of the second charge at the coating positions, so that the second charge is precisely distributed at the coating positions. This allows the second charge to have positions with different refractive indices, i.e., positions with differentiated refractive indices, through the linewidth distribution of the second charge in the incident grating region, the exit grating region, and the folded grating region, thereby forming a thin-film grating. For example, the first charge is positive and the second charge is negative; combined with... Figure 6Under the guidance and control of a positively charged electric field 300, the conductive particle carrier 200 accurately coats negatively charged conductive particles 210 onto the target location. Subsequent exposure steps then form the incident grating region 111, the exit grating region 112, and the folded grating region 113 of the substrate 100, respectively, creating the incident grating, exit grating, and folded grating, thus forming a grating at the target location and obtaining a thin-film optical waveguide. This design, on the one hand, achieves precise control of the zoned coating through precise charged coating, thereby saving the amount of coating material; on the other hand, because the electric field can be precisely controlled, the coating position of the conductive particles can be precisely controlled through the attraction effect of opposite charges, thus ensuring the accuracy of the thin-film grating.

[0045] In step S300, the entire substrate is exposed to obtain a thin-film optical waveguide. Further, in one embodiment, in step S300, the entire surface of the substrate is exposed to obtain the thin-film optical waveguide. Further, in one embodiment, in step S100, mutually spaced grooves are formed on the same side of the substrate as the incident grating region, the exit grating region, and the folded grating region. This allows exposure of only one side of the substrate in step S300, improving processing efficiency. In other embodiments, in step S100, mutually spaced grooves are formed on opposite sides of the substrate as the incident grating region, the exit grating region, and the folded grating region, creating a more significant positional difference. When the incident grating region, the exit grating region, and the folded grating region are located on the same surface, only one exposure is required. When these regions are located on different surfaces of the substrate, two exposures are required, or both surfaces of the substrate must be exposed to an exposeable environment. This design addresses the difficulty in controlling the alignment of specific areas on the entire surface during traditional exposure. Firstly, it ensures the exposure effect of the incident grating region, the exit grating region, and the folded grating region through a pre-processing step. Secondly, the overall exposure process is simpler and improves production efficiency.

[0046] In step S300, the thin-film optical waveguide obtained after overall exposure has a volumetric holographic grating, and therefore can also be called a volumetric holographic thin-film optical waveguide. In practical applications, one embodiment of the obtained thin-film optical waveguide is as follows: Figure 7 As shown, the length of the bright line to bright line is 5.406 μm, the length of the dark line to dark line is 5.140 μm, the width of the bright fringe is 2.715 μm, and the width of the dark fringe is 2.397 μm. Another embodiment of the obtained thin-film optical waveguide is as follows: Figure 8As shown, the length of the bright line to bright line is 0.477 μm, the length of the dark line to dark line is 0.436 μm, the width of the bright fringe is 0.248 μm, and the width of the dark fringe is 0.221 μm. It can be seen that the obtained thin-film optical waveguide meets the requirements for grating design and also has a certain width range.

[0047] In one embodiment, a thin-film grating waveguide is fabricated using the thin-film fabrication method described in any embodiment. In one embodiment, the thin-film grating waveguide is fabricated using the following steps: S100, a substrate is provided, the substrate having an incident grating region, an exit grating region, and a folded grating region; S200, conductive particles are used to coat the incident grating region, the exit grating region, and the folded grating region, and the linewidth distribution at the coating location is controlled by an electric field to generate differentiated refractive indices at the coating location through the linewidth distribution, thus forming a thin-film grating; S300, the entire structure is exposed to obtain the thin-film waveguide, i.e., the thin-film grating waveguide, also known as a volumetric holographic thin-film waveguide. Other embodiments follow the same principle and will not be described in detail. This design allows for separate verification of light efficiency in each independent region by coating gratings. Furthermore, by using charged coating to distribute and stack conductive particles to form gratings, it avoids the problem of material loss caused by traditional spin coating methods and allows for precise control of the position of specific areas, thus ensuring the exposure effect.

[0048] In one embodiment, an augmented reality device includes a curved optical structure having a thin-film grating waveguide as described in any embodiment. In one embodiment, the augmented reality device includes a wearable device, such as glasses or a helmet. In one embodiment, the augmented reality device or its curved optical structure is a near-eye display optical element, or the augmented reality device or its curved optical structure includes a near-eye display optical element. The structure and process of the near-eye display optical element described in this application allow for grating confirmation for each region, and the light efficiency of each region can be independently confirmed. Furthermore, by using charged coating, conductive particles are distributed and stacked to form a grating. This design overcomes the problem of wasted coating material caused by the traditional rotation method of coating conductive particles on the entire surface of a volumetric holographic film, and also overcomes the problem of insufficient exposure position caused by the traditional alignment exposure method.

[0049] It should be noted that other embodiments of this application also include a thin film preparation method, a thin film grating waveguide, and an augmented reality device formed by combining the technical features of the above embodiments.

[0050] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0051] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the scope of protection of this application. Therefore, the patent protection scope of this application should be determined by the appended claims.

Claims

1. A method for preparing a thin film, characterized in that, Including the following steps: S100, a substrate is provided, the substrate having an incident grating region, an exit grating region, and a folded grating region; wherein, step S100 includes: S110, forming mutually spaced grooves on the same surface or different surfaces of the substrate as the incident grating region, the exit grating region, and the folded grating region; the groove depth is 15μm to 500μm, and a reflective layer is sputtered on the side of the groove, the reflective layer thickness being 10nm to 300nm; S200 involves using conductive particles to apply adhesive or slit-type coating to the incident grating region, the exit grating region, and the folded grating region. The linewidth distribution at the coating location is controlled by an electric field, thereby generating differentiated refractive indices at the coating location through the linewidth distribution, thus forming a thin-film grating. The grating width of the thin-film grating ranges from 0.2 μm to 3 μm, the period ranges from 0.3 μm to 5 μm, and the difference in refractive index between light and dark areas of the thin-film grating ranges from 0.05 to 0.

08. S300, overall exposure, to obtain thin-film optical waveguide.

2. The thin film preparation method according to claim 1, characterized in that, After step S110, step S100 further includes: S120, providing a transparent conductive layer in the groove.

3. The thin film preparation method according to claim 2, characterized in that, After step S120, step S100 further includes: S130, forming patterned transparent conductive lines on the transparent conductive layer by etching.

4. The thin film preparation method according to any one of claims 1 to 3, characterized in that, In step S200, the substrate is brought into contact with conductive particles in the coating that have the opposite charge, and then charged coating is performed.

5. A thin-film grating waveguide, characterized in that, The thin film is prepared by any one of the thin film preparation methods described in claims 1 to 4.

6. An augmented reality device, characterized in that, It includes a curved optical structure having the thin-film grating waveguide of claim 5.

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