Waveguide structure and near-eye display device
Patent Information
- Application Number
- CN202510350411.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-24
- Publication Date
- 2026-09-25
Smart Images
Figure CN122815601A_ABST
Abstract
Description
Technical Field
[0001] At least one embodiment of this disclosure relates to a waveguide structure and a near-eye display device. Background Technology
[0002] Augmented Reality (AR) technology creates an interactive experience that blends the virtual and real worlds by overlaying virtual information onto the real world. Near-eye display devices, such as AR glasses, have attracted widespread attention as a new type of wearable device. Summary of the Invention
[0003] At least one embodiment of this disclosure provides a waveguide structure and a near-eye display device.
[0004] At least one embodiment of this disclosure provides a waveguide structure, including a waveguide substrate, a diffraction grating, a cladding layer, and an antireflection layer. The waveguide substrate includes two surfaces disposed opposite to each other; the diffraction grating is located on at least one surface of the waveguide substrate; the cladding layer covers the diffraction grating and the waveguide substrate; the antireflection layer is located on the side of the cladding layer away from the waveguide substrate; wherein the refractive index of the cladding layer is less than the refractive index of the diffraction grating and less than the refractive index of the antireflection layer.
[0005] For example, according to at least one embodiment of this disclosure, the surface of the cover layer away from the waveguide substrate is a flat surface.
[0006] For example, according to at least one embodiment of this disclosure, the covering layer is in direct contact with the diffraction grating.
[0007] For example, according to at least one embodiment of the present disclosure, the difference between the refractive index of the capping layer and the refractive index of the diffraction grating is 1.0 to 2.0.
[0008] For example, according to at least one embodiment of the present disclosure, the refractive index of the covering layer is 1.0 to 1.7.
[0009] For example, according to at least one embodiment of the present disclosure, the diffraction grating includes a plurality of grating structures extending along a first direction and arranged in a second direction, wherein the first direction intersects the second direction;
[0010] The cover layer includes a cover portion that overlaps with at least one of the plurality of grating structures in a direction perpendicular to the waveguide substrate, the thickness of the cover portion being less than the thickness of at least a portion of the cover layer excluding the cover portion.
[0011] For example, according to at least one embodiment of this disclosure, the thickness of the covering portion is 20 nanometers to 200 nanometers.
[0012] For example, according to at least one embodiment of the present disclosure, the diffraction grating includes an insertion grating, a transition grating, and an exit grating, and the covering portion includes a first sub-portion, a second sub-portion, and a third sub-portion. In a direction perpendicular to the waveguide substrate, the insertion grating overlaps with the first sub-portion, the transition grating overlaps with the second sub-portion, and the exit grating overlaps with the third sub-portion; at least two of the first sub-portion, the second sub-portion, and the third sub-portion have different thicknesses.
[0013] For example, according to at least one embodiment of the present disclosure, the covering layer includes a transparent adhesive layer.
[0014] For example, according to at least one embodiment of this disclosure, the cover layer is in direct contact with the antireflective layer.
[0015] For example, according to at least one embodiment of the present disclosure, the antireflection layer includes multiple layers of films stacked together, at least one of the multiple layers including a grating antireflection portion and a substrate antireflection portion, wherein the orthographic projection of the grating antireflection portion on the waveguide substrate overlaps with the orthographic projection of the diffraction grating on the waveguide substrate, and the orthographic projection of the substrate antireflection portion on the waveguide substrate does not overlap with the orthographic projection of the diffraction grating on the waveguide substrate; the refractive index of the grating antireflection portion is different from the refractive index of the substrate antireflection portion.
[0016] For example, according to at least one embodiment of this disclosure, the grating anti-reflection portion includes a first anti-reflection portion, a second anti-reflection portion, and a third anti-reflection portion; the diffraction grating includes a coupling-in grating, a folding grating, and a coupling-out grating; the orthographic projection of the first anti-reflection portion on the waveguide substrate overlaps with the orthographic projection of the coupling-in grating on the waveguide substrate; the orthographic projection of the second anti-reflection portion on the waveguide substrate overlaps with the orthographic projection of the folding grating on the waveguide substrate; and the orthographic projection of the third anti-reflection portion on the waveguide substrate overlaps with the orthographic projection of the coupling-out grating on the waveguide substrate; at least two of the first anti-reflection portion, the second anti-reflection portion, and the third anti-reflection portion have different refractive indices.
[0017] For example, according to at least one embodiment of this disclosure, the multilayer film includes a first film and a second film, each of the first film and the second film including a first antireflective portion, a second antireflective portion, and a third antireflective portion; the first film and the second film are configured to satisfy at least one of the following conditions: the refractive index of the first antireflective portion of the first film is different from the refractive index of the first antireflective portion of the second film; the refractive index of the second antireflective portion of the first film is different from the refractive index of the second antireflective portion of the second film; the refractive index of the third antireflective portion of the first film is different from the refractive index of the third antireflective portion of the second film.
[0018] For example, according to at least one embodiment of the present disclosure, the antireflective layer includes multiple layers stacked together, the multiple layers including a third layer and a fourth layer, the third layer having the same refractive index in different regions, the fourth layer having the same refractive index in different regions; the third layer having a third refractive index, the fourth layer having a fourth refractive index, and the third refractive index being different from the fourth refractive index.
[0019] For example, according to at least one embodiment of the present disclosure, the refractive index of each of the multilayer films is 1.4-2.5.
[0020] For example, according to at least one embodiment of the present disclosure, the thickness of each of the multilayer films is 20 nanometers to 200 nanometers.
[0021] For example, according to at least one embodiment of the present disclosure, the waveguide structure further includes a cover layer located on the side of the antireflection layer away from the diffraction grating.
[0022] For example, according to at least one embodiment of the present disclosure, the waveguide structure includes a first region, and the diffraction grating is located in the first region; the difference between the transmittance of the waveguide structure in the first region and the transmittance of the waveguide structure in a second region other than the first region is less than 0.1.
[0023] At least one embodiment of this disclosure provides a near-eye display device, including the waveguide structure described in any of the above embodiments. Attached Figure Description
[0024] To more clearly illustrate the technical solutions of the embodiments of this disclosure, the accompanying drawings of the embodiments will be briefly described below. Obviously, the drawings described below only relate to some embodiments of this disclosure and are not intended to limit this disclosure.
[0025] Figure 1 This is a schematic diagram of a diffractive optical waveguide.
[0026] Figure 2 This is a cross-sectional schematic diagram of a waveguide structure provided as an example in at least one embodiment of the present disclosure.
[0027] Figure 3A This is a planar schematic diagram of a portion of the waveguide structure provided in one example of at least one embodiment of the present disclosure.
[0028] Figure 3B for Figure 3A A planar schematic diagram of the diffraction grating structure in the waveguide structure shown.
[0029] Figure 4 For along Figure 3A A schematic diagram of the local cross-section structure intercepted by line AA'.
[0030] Figure 5 For along Figure 3A A schematic diagram of the local cross-section structure intercepted by line BB'.
[0031] Figure 6 This is a cross-sectional schematic diagram of a waveguide structure provided as an example in at least one embodiment of the present disclosure. Detailed Implementation
[0032] To make the objectives, technical solutions, and advantages of the embodiments of this disclosure clearer, the technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this disclosure. Based on the described embodiments of this disclosure, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this disclosure.
[0033] Unless otherwise defined, the technical or scientific terms used in this disclosure shall have the ordinary meaning understood by one of ordinary skill in the art to which this disclosure pertains. The terms “first,” “second,” and similar terms used in this disclosure do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as “comprising” or “including” mean that an element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects.
[0034] As used in this disclosure, the characteristics such as "parallel," "perpendicular," and "identical" include the strict meanings of "parallel," "perpendicular," and "identical," as well as cases where "approximately parallel," "approximately perpendicular," and "approximately identical" include a certain degree of error, taking into account the measurement and the error associated with the measurement of a specific quantity (i.e., the limitations of the measurement system), and represent the acceptable deviation range for a specific value as determined by a person skilled in the art. For example, "approximately" can mean within one or more standard deviations, or within 10% or 5% of said value.
[0035] A diffractive waveguide is an optical element used in near-eye display devices such as AR glasses. It utilizes the diffraction phenomenon of light to guide its propagation path, thereby transmitting image light to the user's eyes.
[0036] Figure 1 This is a schematic diagram of a diffractive optical waveguide.
[0037] refer to Figure 1The diffractive waveguide includes a waveguide substrate 1 and a diffraction grating 2 disposed on the waveguide substrate 1. For example, the diffractive waveguide includes a coupling region, a turning region, and a coupling region, and the diffraction grating can be disposed in the coupling region, the turning region, and the coupling region in a relief form.
[0038] In their research, the inventors of this application discovered that, due to the diffraction effect of the diffraction grating, the transmittance of the area with the diffraction grating is lower than that of the area without the diffraction grating. This results in differences in transmittance in different areas of the diffraction waveguide, affecting the user's viewing experience.
[0039] At least one embodiment of this disclosure provides a waveguide structure including a waveguide substrate, a diffraction grating, a cladding layer, and an antireflection layer. The waveguide substrate includes two opposing surfaces, with the diffraction grating located on at least one surface of the waveguide substrate. The cladding layer covers both the diffraction grating and the waveguide substrate. The antireflection layer is located on the side of the cladding layer away from the waveguide substrate. The refractive index of the cladding layer is less than the refractive index of the diffraction grating and less than the refractive index of the antireflection layer.
[0040] At least one embodiment of this disclosure provides a near-eye display device, including the waveguide structure described in the above embodiments.
[0041] The waveguide structure and near-eye display device provided in at least one embodiment of this disclosure, by setting a capping layer between a diffraction grating and an anti-reflection layer, and setting the refractive index of the capping layer to be less than the refractive index of the diffraction grating and less than the refractive index of the anti-reflection layer, can protect the diffraction grating while ensuring its coupling efficiency. Furthermore, the capping layer covering the diffraction grating provides a relatively flat coating surface for the anti-reflection layer. This results in a more uniform and higher-quality anti-reflection coating, which is beneficial for improving the overall transmittance of the waveguide structure. Moreover, by designing the difference between the refractive index of the capping layer and the refractive index of the anti-reflection layer, the transmittance uniformity of the waveguide structure can be improved. Therefore, users can obtain a better visual experience through the waveguide structure, and the uniform transmittance makes the waveguide structure more aesthetically pleasing, thus making the near-eye display device including this waveguide structure more attractive.
[0042] The waveguide structure and near-eye display device are described below with reference to the accompanying drawings and through some embodiments.
[0043] Figure 2 This is a cross-sectional schematic diagram of a waveguide structure provided as an example in at least one embodiment of the present disclosure.
[0044] refer to Figure 2 In at least one embodiment of this disclosure, a waveguide structure is provided. The waveguide structure includes a waveguide substrate 100, a diffraction grating 200, a cladding layer 300, and an anti-reflection layer 400.
[0045] refer to Figure 2 The waveguide substrate 100 includes two surfaces disposed opposite to each other (e.g., Figure 2 Surfaces S1 and S2 are shown. The diffraction grating 200 is located on at least one side surface of the waveguide substrate 100. For example, Figure 2 The diagram schematically shows a diffraction grating 200 located on one side of surface S1 of the waveguide substrate 100. However, this disclosure is not limited to this; for example, diffraction gratings may be provided on both sides of the waveguide substrate.
[0046] refer to Figure 2 The cladding layer 300 covers the diffraction grating 200 and the waveguide substrate 100. For example, a portion of the cladding layer 300 covers the diffraction grating 200, and another portion covers the waveguide substrate 100. The antireflection layer 400 is located on the side of the cladding layer 300 away from the waveguide substrate 100. The refractive index of the cladding layer 300 is less than the refractive index of the diffraction grating 200 and less than the refractive index of the antireflection layer 400.
[0047] The waveguide structure provided in this disclosure, by setting a capping layer between the diffraction grating and the antireflection layer, and setting the refractive index of the capping layer to be less than the refractive index of both the diffraction grating and the antireflection layer, can protect the diffraction grating while ensuring its coupling efficiency. Furthermore, the capping layer covering the diffraction grating provides a relatively flat coating surface for the antireflection layer. This results in a more uniform and higher-quality antireflection coating, which is beneficial for improving the overall transmittance of the waveguide structure. Moreover, by designing the difference between the refractive index of the capping layer and the antireflection layer, the transmittance uniformity of the waveguide structure can be improved. Therefore, users can obtain a better visual experience through the waveguide structure, and the uniform transmittance makes the waveguide structure more aesthetically pleasing, thus making near-eye display devices including this waveguide structure more attractive.
[0048] Specifically, improving the overall transmittance of the waveguide structure allows sufficient light to pass through and reach the human eye, which is beneficial for enhancing the brightness and clarity of virtual images, increasing color saturation, and providing users with a more vivid visual experience. Furthermore, increased transmittance improves optical coupling efficiency, reduces power consumption, and optimizes the performance of near-eye display devices that include the waveguide structure. For example, improving the overall transmittance of the waveguide structure includes both increasing the transmittance for zero-order light and increasing the transmittance for non-zero-order light. Zero-order light refers to light that does not diffract after passing through a diffraction grating, or whose diffraction angle is 0 degrees. This improves the coupling efficiency of the diffraction grating in the waveguide structure. For example, by adding a capping layer and an anti-reflection layer, the transmittance for zero-order light of the waveguide structure can be increased by 5% to 10%.
[0049] Furthermore, the more uniform transmittance of the waveguide structure improves the consistency of brightness areas between the virtual image and the real scene seen by the user through the near-eye display device, reducing eye strain. Simultaneously, the uniform transmittance helps improve the clarity and contrast of the virtual image, enhancing its overall quality. In addition, uniform transmittance prevents imperfections such as localized reflections or shadows from forming in the waveguide structure, resulting in a clearer, more transparent appearance and improving the overall aesthetics of the near-eye display device incorporating this structure.
[0050] For example, the diffraction grating can be a two-dimensional (2D) grating. For example, the material of the diffraction grating can include at least one of titanium dioxide and silicon dioxide. For example, the diffraction grating can be attached to a waveguide substrate. For example, after forming a grating substrate layer on the waveguide substrate, multiple grating structures and grooves between adjacent grating structures can be formed on the grating substrate layer to form a diffraction grating.
[0051] For example, the refractive index of the diffraction grating can be the same as that of the antireflection layer. Alternatively, the refractive index of the diffraction grating can be greater than that of the antireflection layer. Or, the refractive index of the diffraction grating can be less than that of the antireflection layer. This disclosure does not impose any limitations in this regard.
[0052] For example, in conjunction with the examples described later, when the antireflection layer comprises multiple layers, the refractive index of the antireflection layer is less than the refractive index of any one of the multiple layers, and the refractive index of the antireflection layer is less than the overall refractive index of the antireflection layer formed by the multiple layers.
[0053] refer to Figure 2 In some examples, the surface of the capping layer 300 away from the waveguide substrate 100 is a flat surface. This provides a flat coating surface for the antireflection layer 400, improving its coating quality. For example, this flat surface can be a near-planar surface. For instance, the capping layer 300 can fill the grooves of the diffraction grating 200 to flatten it, forming a flat surface.
[0054] refer to Figure 2 In some examples, the capping layer 300 is in direct contact with the antireflection layer 400. For instance, there are no other structures or films between the capping layer 300 and the antireflection layer 400. This allows the antireflection layer to be directly deposited onto the capping layer, which improves the flatness of the antireflection layer. Furthermore, the absence of other media between the antireflection layer and the capping layer not only reduces interfacial reflection losses but also simplifies the design of the refractive index parameters of both the antireflection layer and the capping layer.
[0055] refer to Figure 2In some examples, the capping layer 300 includes a transparent adhesive layer. For example, the transparent adhesive can be applied to the grooves of the diffraction grating using a spin-coating or inkjet process, and then dried to form an antireflective layer covering the diffraction grating and the waveguide substrate. For example, if the material of the diffraction grating is not silicon dioxide, the material of the capping layer may include silicon dioxide. However, this disclosure is not limited thereto, and the capping layer may also be a transparent layer formed of other materials.
[0056] refer to Figure 2 In some examples, the capping layer 300 is in direct contact with the diffraction grating 200. For instance, there are no other structures or films between the capping layer 300 and the diffraction grating 200. This prevents other media from filling the grooves of the diffraction grating, and the uniform refractive index of the capping layer prevents excessive scattering or reflection of light due to abrupt changes in refractive index during propagation, thus improving light transmission efficiency and reducing light coupling loss.
[0057] refer to Figure 2 In some examples, the difference between the refractive index of the cladding layer 300 and the refractive index of the diffraction grating 200 is 0.5-1.8. By setting the difference in refractive index between the cladding layer and the diffraction grating, light rays incident on the waveguide substrate 100 at a certain incident angle can undergo total internal reflection within the waveguide substrate 100.
[0058] For example, the difference between the refractive index of the cladding layer and the refractive index of the diffraction grating can be from 0.51 to 1.79. For example, the difference between the refractive index of the cladding layer and the refractive index of the diffraction grating can be from 0.6 to 1.7. For example, the difference between the refractive index of the cladding layer and the refractive index of the diffraction grating can be from 0.7 to 1.6. For example, the difference between the refractive index of the cladding layer and the refractive index of the diffraction grating can be from 0.8 to 1.5. For example, the difference between the refractive index of the cladding layer and the refractive index of the diffraction grating can be from 0.9 to 1.4. For example, the difference between the refractive index of the cladding layer and the refractive index of the diffraction grating can be from 1.0 to 1.3. For example, the difference between the refractive index of the cladding layer and the refractive index of the diffraction grating can be from 1.1 to 1.2. Of course, the difference between the refractive index of the cladding layer and the refractive index of the diffraction grating can also be other values, which will not be elaborated here.
[0059] refer to Figure 2 In some examples, the refractive index of the capping layer 300 is between 1.0 and 1.7. For example, the refractive index of the capping layer 300 can approach the refractive index of air. For example, the capping layer can include a material with a low refractive index. For example, the capping layer can replace the air between other film layers (e.g., cover plates) and the grating structure to satisfy total internal reflection propagation of light.
[0060] For example, the refractive index of the coating layer can be from 1.01 to 1.69. For example, the refractive index of the coating layer can be from 1.1 to 1.6. For example, the refractive index of the coating layer can be from 1.2 to 1.5. For example, the refractive index of the coating layer can be from 1.3 to 1.4. For example, the refractive index of the coating layer can be 1.35. Of course, the refractive index of the coating layer can also be other values, which will not be elaborated here.
[0061] Figure 3A This is a planar schematic diagram of a portion of the waveguide structure provided in one example of at least one embodiment of the present disclosure. Figure 3B for Figure 3A A planar schematic diagram of the diffraction grating structure in the waveguide structure shown.
[0062] refer to Figure 2 , Figure 3A and Figure 3B In some examples, the diffraction grating 200 includes a plurality of grating structures 210 extending along a first direction V and arranged in a second direction X, the first direction V intersecting the second direction X. For example, both the first direction V and the second direction X are parallel to the waveguide substrate 100.
[0063] For example, Figure 3B The illustration schematically shows a first direction V perpendicular to a second direction X, but the disclosure is not limited thereto. For example, the first direction may also have an angle other than 90 degrees with the second direction. For example, the first direction may be the extension direction of the central axis of the grating structure.
[0064] For example, the second direction refers to the arrangement direction of the grating structures in each diffraction grating. It is understood that the second direction can be different for different diffraction gratings, and this disclosure does not limit this.
[0065] For example, refer to Figure 3A and Figure 3B The diffraction grating 200 also includes a grating substrate 220 connected between two adjacent grating structures 210. For example, in conjunction with the foregoing example, the two adjacent grating structures 210 and the grating substrate 220 together form a groove, in which the cover layer 300 can fill the groove.
[0066] refer to Figure 2In some examples, the cladding layer 300 includes an overburden portion 310 that overlaps with at least one of the plurality of grating structures 210 in a direction perpendicular to the waveguide substrate. The thickness D1 of the overburden portion 310 is less than the thickness D2 of at least a portion of the cladding layer 300 excluding the overburden portion 310. This thinner overburden portion 310 covering the grating structure 210 is advantageous for reducing optical loss and for forming a flat surface on the side of the cladding layer 300 away from the waveguide substrate 100. Furthermore, varying thicknesses of the cladding layer 300 can improve the uniformity of transmittance in different regions of the waveguide structure.
[0067] refer to Figure 2 For example, the cover portion 310 refers to the portion of the cover layer 300 located between the two surfaces of the grating structure 210 and the antireflective layer 400 facing each other, that is... Figure 2 The part between the two dashed lines.
[0068] For example, the thickness of the cover portion refers to the dimension of the cover portion in the direction perpendicular to the waveguide substrate. For example, this dimension can be the average value of the dimensions of the cover portion in the direction perpendicular to the waveguide substrate, or it can be the maximum value of the dimensions of the cover portion in the direction perpendicular to the waveguide substrate, and this disclosure does not limit it in this way.
[0069] For example, the thickness of at least a portion of the cover layer other than the covered portion refers to the dimension of that portion in the direction perpendicular to the waveguide substrate. For example, this dimension can be the average value of the dimension of that portion in the direction perpendicular to the waveguide substrate, or it can be the maximum value of the dimension of that portion in the direction perpendicular to the waveguide substrate, and this disclosure does not limit it in this way.
[0070] refer to Figure 2 For example, during the formation of the capping layer 300, the filling amount can be controlled by partitioning, resulting in different thicknesses of the capping layer 300 in different regions. This helps to overcome the limitations of spin coating processes, making the surface of the capping layer 300 away from the waveguide substrate 100 flatter.
[0071] For example, the thickness of the covering portion may be less than the thickness of the entire covering layer excluding the covering portion. However, this disclosure is not limited thereto; for example, the thickness of the covering portion may be less than the thickness of a portion of the covering layer excluding the covering portion, and the thickness of the covering portion may be greater than or equal to the thickness of another portion of the covering portion excluding the covering portion.
[0072] refer to Figure 2For example, the capping layer 300 can be in direct contact with the waveguide substrate 100. For example, at least a portion of the capping layer other than the capping portion can be in direct contact with the waveguide substrate. For example, during the filling process, no additional protection may be provided for the non-grating areas, so that at least a portion of the capping layer other than the capping portion is formed directly on the waveguide substrate, thereby making direct contact with the waveguide substrate.
[0073] For example, the capping layer may not be in direct contact with the waveguide substrate. Referring to the examples described later, when the diffraction grating includes a coupling-in grating, a bend grating, and a coupling-out grating, the waveguide structure may include a substrate layer disposed on the waveguide substrate and located in a non-grating region. The substrate layer may be connected between any two of the coupling-in grating, bend grating, and coupling-out grating. For example, the substrate layer and the grating substrates of different gratings (e.g., coupling-in grating, bend grating, coupling-out grating) may be formed on the waveguide substrate in the same process. The capping layer formed in the non-grating region may be in direct contact with the substrate layer.
[0074] refer to Figure 2 For example, during the filling process, no additional protection may be provided for the non-grating areas, thereby allowing the portion of the cover layer other than the covered portion to be formed in the non-grating areas. For instance, a groove may be provided between two adjacent grating structures in the second direction, and at least a portion of the cover layer other than the covered portion may be filled within the groove.
[0075] For example, Figure 2 The schematic diagram shows a grating structure including a side perpendicular to the waveguide substrate. However, this disclosure is not limited thereto; for example, the grating structure may also include a side having an angle other than 90 degrees with the waveguide substrate. It will be understood that when the side of the grating structure has an angle other than 90 degrees with the waveguide substrate, the grating structure is tilted relative to the waveguide substrate.
[0076] In some examples, the thickness of the cover 310 ranges from 20 nanometers to 200 nanometers. By designing the thickness range of the cover, the coupling loss of light can be reduced while providing good protection for the grating structure.
[0077] For example, the thickness of the cover portion can be from 21 nanometers to 199 nanometers. For example, the thickness of the cover portion can be from 25 nanometers to 190 nanometers. For example, the thickness of the cover portion can be from 30 nanometers to 180 nanometers. For example, the thickness of the cover portion can be from 40 nanometers to 170 nanometers. For example, the thickness of the cover portion can be from 50 nanometers to 160 nanometers. For example, the thickness of the cover portion can be from 60 nanometers to 150 nanometers. For example, the thickness of the cover portion can be from 70 nanometers to 140 nanometers. For example, the thickness of the cover portion can be from 80 nanometers to 130 nanometers. For example, the thickness of the cover portion can be from 90 nanometers to 120 nanometers. For example, the thickness of the cover portion can be from 100 nanometers to 110 nanometers.
[0078] Figure 4 For along Figure 3A A schematic diagram of the local cross-section structure intercepted by line AA'. Figure 5 For along Figure 3A A schematic diagram of the local cross-section structure intercepted by line BB'.
[0079] Figure 2 The waveguide structure shown is Figure 3A , Figure 4 and Figure 5 The difference in the waveguide structures shown is that... Figure 2 The schematic diagram illustrates that the antireflection layer in the waveguide structure comprises three film layers. Figure 3A , Figure 4 and Figure 5 The antireflection layer of the waveguide structure shown comprises two layers. However, this disclosure does not limit the number of layers in the antireflection layer; this will be explained in detail in the examples described later. Of course, Figure 3A , Figure 4 and Figure 5 The waveguide structure shown can also be combined with Figure 2 The waveguide structures shown have many differences, but this disclosure does not limit them.
[0080] For example, Figure 3A The relative positions of the coupling grating, the bend grating, and the coupling output grating are only schematically shown. However, this disclosure is not limited to this; the relative positions of the coupling grating, the bend grating, and the coupling output grating can be adaptively adjusted according to actual needs. For example, Figure 3A The area containing the coupling grating is schematically shown in a circular frame, and the areas containing the turning grating and the coupling grating are schematically shown in a rectangular frame, but this disclosure does not limit the outer contour shape of the coupling grating, the turning grating, and the coupling grating.
[0081] For example, Figure 3A The illustration shows that the cladding layer, anti-reflection layer, and waveguide substrate can have the same outer contour, that is, the cladding layer and anti-reflection layer can completely cover the waveguide substrate. However, this disclosure is not limited thereto, and the cladding layer, anti-reflection layer, and waveguide substrate can also have different outer contours.
[0082] refer to Figure 3A , Figure 4 and Figure 5In some examples, the diffraction grating 200 includes an insertion grating 201, a transition grating 202, and an exit grating 203. The cover portion 310 includes a first sub-portion 311, a second sub-portion 312, and a third sub-portion 313. In the direction Z perpendicular to the waveguide substrate 100, the insertion grating 201 overlaps with the first sub-portion 311, the transition grating 202 overlaps with the second sub-portion 312, and the exit grating 203 overlaps with the third sub-portion 313. At least two of the first sub-portion 311, the second sub-portion 312, and the third sub-portion 313 have different thicknesses, which is beneficial for matching with different gratings (e.g., insertion grating 201, transition grating 202, and exit grating 203) and improving the uniformity of the transmittance of the waveguide structure in different regions.
[0083] refer to Figure 3A , Figure 4 and Figure 5 For example, the thicknesses of the first sub-section 311, the second sub-section 312, and the third sub-section 313 can be set according to the different diffraction capabilities of different gratings, so that the overall transmittance of the waveguide structure tends to be consistent.
[0084] For example, the thickness of the first sub-part can be different from the thickness of the second sub-part. For example, the thickness of the second sub-part can be different from the thickness of the third sub-part. For example, the thickness of the first sub-part can be different from the thickness of the third sub-part. For example, two of the thicknesses of the first, second, and third sub-parts can be different. For example, the thicknesses of the first, second, and third sub-parts can all be different.
[0085] For example, during the fabrication of the capping layer, the filling amount can be controlled in sections to form first, second, and third sub-sections with different thicknesses. For instance, different diffraction gratings (e.g., coupling-in gratings, folding gratings, and coupling-out gratings) have different duty cycles, resulting in different dimensions between the surface of the grating structure furthest from the waveguide substrate and the waveguide substrate in different diffraction gratings, i.e., different grating structure heights. Setting the thicknesses of the first, second, and third sub-sections helps compensate for the height differences of the grating structures in different diffraction gratings, improving the flatness of the surface of the capping layer furthest from the waveguide substrate.
[0086] refer to Figure 3A , Figure 4 and Figure 5The antireflection layer 400 includes multiple layers (e.g., layer 401, layer 402) stacked together. At least one of the multiple layers includes a grating antireflection portion 4A and a substrate antireflection portion 4B. The orthographic projection of the grating antireflection portion 4A onto the waveguide substrate 100 overlaps with the orthographic projection of the diffraction grating 200 onto the waveguide substrate 100, while the orthographic projection of the substrate antireflection portion 4B onto the waveguide substrate 100 does not overlap with the orthographic projection of the diffraction grating 200 onto the waveguide substrate 100. The refractive index of the grating antireflection portion 4A is different from that of the substrate antireflection portion 4B, which balances the diffraction effect of the diffraction grating, making the transmittance of the waveguide structure in the region without the diffraction grating tend to be consistent with the transmittance of the region with the diffraction grating.
[0087] For example, the shape of the orthographic projection of a diffraction grating onto a substrate can be the shape of the outer contour of the orthographic projection of all the grating structures arranged along the second direction in a diffraction grating onto the substrate.
[0088] refer to Figure 3A , Figure 4 and Figure 5 In some examples, the grating anti-reflection section 4A may include a first anti-reflection section 411, a second anti-reflection section 413, and a third anti-reflection section 413. The diffraction grating 200 includes a coupling-in grating 201, a folding grating 202, and a coupling-out grating 203. The orthographic projection of the first anti-reflection section 411 on the waveguide substrate 100 overlaps with the orthographic projection of the coupling-in grating 201 on the waveguide substrate 100. The orthographic projection of the second anti-reflection section 412 on the waveguide substrate 100 overlaps with the orthographic projection of the folding grating 202 on the waveguide substrate 100. The orthographic projection of the third anti-reflection section 413 on the waveguide substrate 100 overlaps with the orthographic projection of the coupling-out grating 203 on the waveguide substrate 100. At least two of the first anti-reflection section 411, the second anti-reflection section 412, and the third anti-reflection section 413 have different refractive indices, which is beneficial for matching with different gratings (e.g., coupling grating 201, folding grating 202, and coupling out grating 203) and improving the uniformity of the transmittance of the waveguide structure in different regions.
[0089] refer to Figure 3A , Figure 4 and Figure 5 For example, the refractive indices of the first anti-reflection section 411, the second anti-reflection section 413, and the third anti-reflection section 413 can be set according to the different diffraction capabilities of different gratings, so that the overall transmittance of the waveguide structure tends to be consistent.
[0090] For example, the refractive index of each layer can be adjusted by setting the thickness of each layer in a multilayer film. For example, two antireflective coatings can be made to have different thicknesses, thus giving them different refractive indices.
[0091] For example, the thickness of each layer in a multilayer film refers to the dimension of that layer in the direction perpendicular to the waveguide substrate. For example, this dimension can be the average value of the dimensions of the layer in the direction perpendicular to the waveguide substrate, or it can be the maximum value of the dimensions of the layer in the direction perpendicular to the waveguide substrate; this disclosure does not limit it in this way.
[0092] For example, the coating process can be controlled in sections, allowing the film layer to have different thicknesses in different areas. Similarly, through section control, the same film layer can have different parameters (e.g., different thicknesses, different refractive indices) in different regions. This allows for separate optimization of waveguide structure parameters for different regions, simplifying the optimization process and improving efficiency.
[0093] Understandably, by using a zoned control approach, when optimizing the region containing the diffraction grating, the relevant parameters of the diffraction grating can be substituted for optimization. However, when optimizing regions other than the region containing the diffraction grating, the relevant parameters of non-diffraction grating structures can be substituted for the diffraction grating parameters. For example, the relevant parameters of the waveguide substrate or the substrate layer in the aforementioned example can be substituted for optimization.
[0094] For example, the refractive index of the first antireflective coating may be different from that of the second antireflective coating. For example, the refractive index of the second antireflective coating may be different from that of the third antireflective coating. For example, the refractive index of the first antireflective coating may be different from that of the third antireflective coating. For example, two of the refractive indices of the first, second, and third antireflective coatings may be different. For example, the refractive indices of the first, second, and third antireflective coatings may all be different.
[0095] For example, at least two of the refractive indices of the first, second, and third antireflection layers can be different, while the thicknesses of the first, second, and third sub-layers can be the same. Thus, at least one of the multilayer antireflection layers has a different refractive index in different regions, allowing it to be matched with different gratings, thereby improving the transmittance uniformity of the waveguide structure. Simultaneously, it also simplifies the fabrication process of the waveguide structure.
[0096] For example, at least two of the thicknesses of the first sub-section, the second sub-section, and the third sub-section can be set to be different, and the refractive indices of the first anti-reflection section, the second anti-reflection section, and the third anti-reflection section can be set to be the same. Thus, the capping layer has different thicknesses in different regions, allowing it to be matched with different gratings, thereby improving the transmittance uniformity of the waveguide structure. Simultaneously, it also simplifies the fabrication process of the waveguide structure.
[0097] For example, at least two of the refractive indices of the first antireflection layer, the second antireflection layer, and the third antireflection layer can be set, and at least two of the thicknesses of the first sub-part, the second sub-part, and the third sub-part can be set to be different, thereby jointly optimizing the antireflection layer and the cover layer. The cover layer and the antireflection layer work together to improve the uniformity of the overall transmittance of the waveguide structure.
[0098] refer to Figure 3A , Figure 4 and Figure 5 In some examples, the multilayer film includes a first film layer 401 and a second film layer 402, each including a first antireflective portion 411, a second antireflective portion 412, and a third antireflective portion 413. The first film layer 401 and the second film layer 402 are configured to satisfy at least one of the following conditions: the refractive index of the first antireflective portion of the first film layer 401 is different from the refractive index of the first antireflective portion of the second film layer 402; the refractive index of the second antireflective portion of the first film layer 401 is different from the refractive index of the second antireflective portion of the second film layer 402; and the refractive index of the third antireflective portion of the first film layer 401 is different from the refractive index of the third antireflective portion of the second film layer 402. This increases the design freedom of each film layer, provides more possibilities for joint optimization, and allows for a wider adjustable range of transmittance in different regions of the waveguide structure. Thus, while improving the transmittance of the waveguide structure, the overall transmittance of the waveguide structure can be made more uniform.
[0099] refer to Figure 3A , Figure 4 and Figure 5 For example, the first anti-reflection portion of the first film layer 401 and the first anti-reflection portion of the second film layer 402 can work together to improve the transmittance of the region where the coupling grating is located. For example, the second anti-reflection portion of the first film layer 401 and the second anti-reflection portion of the second film layer 402 can work together to improve the transmittance of the region where the deflection grating is located. For example, the third anti-reflection portion of the first film layer 401 and the third anti-reflection portion of the second film layer 402 can work together to improve the transmittance of the region where the coupling grating is located.
[0100] For example, the first membrane layer and the second membrane layer can be configured to satisfy one of the above conditions. For example, the first membrane layer and the second membrane layer can be configured to satisfy two of the above conditions. For example, the first membrane layer and the second membrane layer can be configured to satisfy all three of the above conditions. This disclosure does not impose any limitations in this regard.
[0101] For example, multilayer films can be like Figure 4 and Figure 5 As shown, it includes a first film layer and a second film layer. For example, a multilayer film layer may include, for example, Figure 2The three layers shown may include a first layer 401, a second layer 402, and a layer 403. Layer 403 may be identical to the first layer 401, thus the multilayer film includes two first layers and one second layer. For example, the refractive index of the first layer 401, the refractive index of the second layer 402, and the refractive index of the layer 403 may have a gradual trend, such as gradually increasing or gradually decreasing.
[0102] However, this disclosure is not limited thereto. For example, the multilayer film may include multiple first films and multiple second films, which may be stacked alternately. For example, the multiple first films and multiple second films may also form a stacked structure in other ways, as long as different regions of different films can be utilized to improve the transmittance of the waveguide structure while improving the uniformity of the transmittance of the waveguide structure. This disclosure does not impose any limitations in this regard.
[0103] Figure 6 This is a cross-sectional schematic diagram of a waveguide structure provided as an example in at least one embodiment of the present disclosure.
[0104] Figure 6 The waveguide structure shown is Figure 2 The difference in the waveguide structure shown is that, Figure 6 The antireflection layer of the waveguide structure shown is different from that of the waveguide structure shown. Figure 2 The antireflection layer of the waveguide structure shown. Of course, Figure 6 The waveguide structure shown can also be combined with Figure 2 The waveguide structures shown have many differences, such as Figure 6 The waveguide structure shown has a cover layer, but this disclosure does not limit its application. It is understood that, as... Figure 6 The cover plate layer shown can also be set as follows: Figures 2 to 5 In any of the waveguide structures shown.
[0105] refer to Figure 6 In some examples, the antireflective layer 400 comprises a multilayer film stacked together, including a third film layer 400A and a fourth film layer 400B. The third film layer 400A has the same refractive index in different regions, and the fourth film layer 400B has the same refractive index in different regions. For example, the refractive index of the entire third film layer 400A is the same everywhere. For example, the refractive index of the entire fourth film layer 400B is the same everywhere.
[0106] refer to Figure 6The third layer 400A has a third refractive index, and the fourth layer 400B has a fourth refractive index; the third and fourth refractive indices are different. Therefore, the difference in refractive indices between the third layer 400A and the fourth layer 400B can be used to improve the overall transmittance of the waveguide structure. This improves the joint optimization efficiency of the waveguide structure and simplifies its fabrication process, reducing manufacturing costs.
[0107] For example, when fabricating the third and fourth film layers, zonal control can be omitted. This allows for consistent parameters throughout the same film layer when depositing the film on a flat surface of the capping layer.
[0108] For example, the refractive indices of the third and fourth layers can be set to be different, while the thicknesses of the first, second, and third sub-sections can be set to be the same. Thus, the antireflection layer improves the transmittance of the waveguide structure, and the antireflection layer and the capping layer together enhance the uniformity of the overall transmittance of the waveguide structure.
[0109] For example, the refractive indices of the third and fourth layers can be set to be different, and at least two of the thicknesses of the first, second, and third sub-parts can be set to be different, thereby jointly optimizing the anti-reflection layer and the cover layer. The cover layer and the anti-reflection layer work together to improve the uniformity of the overall transmittance of the waveguide structure.
[0110] For example, in conjunction with the foregoing examples, the multilayer antireflection layer may include two or more of a first layer, a second layer, a third layer, and a fourth layer. It is understood that the multilayer layer may include layers with non-uniform refractive indexes (e.g., layers with non-uniform thicknesses), such as the first layer, or layers with uniform refractive indexes (e.g., layers with uniform thicknesses), such as the third layer. Furthermore, different antireflection layers can be matched with different capping layers; for example, the thicknesses of multiple capping portions in a capping layer may be the same or different. It is understood that this disclosure does not impose any limitations on improving the transmittance of the waveguide structure while simultaneously enhancing its transmittance uniformity, provided that the materials and parameters of the diffraction grating, capping layer, and antireflection layer are jointly optimized.
[0111] In the multilayer antireflection layer, the refractive index of each layer can vary, the thickness of each layer can be unequal, and there can even be two identical layers. Therefore, by setting up a multilayer antireflection layer, the amplitudes of light can be superimposed, achieving coherent and constructive transmission of transmitted light, thereby increasing the transmittance of light from the waveguide substrate.
[0112] refer to Figures 2 to 6The refractive index of each of the multilayer films is 1.4-2.5. By setting the refractive index of the films, it is possible to meet the requirements of light coupling efficiency while satisfying total internal reflection propagation, and to prevent the diffraction effect of the diffraction grating from being affected.
[0113] For example, the refractive index of each of the multilayer films can be 1.41-2.49. For example, the refractive index of each of the multilayer films can be 1.5-2.4. For example, the refractive index of each of the multilayer films can be 1.6-2.3. For example, the refractive index of each of the multilayer films can be 1.7-2.2. For example, the refractive index of each of the multilayer films can be 1.8-2.1. For example, the refractive index of each of the multilayer films can be 1.9-2.0.
[0114] refer to Figures 2 to 6 Each of the multilayer films has a thickness ranging from 20 nanometers to 200 nanometers. By adjusting the thickness of the films, the waveguide structure can be made thinner and lighter while still meeting coupling efficiency requirements. This makes it possible to create smaller and lighter near-eye display devices that incorporate this waveguide structure.
[0115] For example, in a multilayer film, the thickness of any two films can be the same or different, and this disclosure does not impose any restrictions on this.
[0116] For example, the material of the multilayer film may include at least one of titanium dioxide, aluminum dioxide, and silicon dioxide. However, this disclosure is not limited to this, and other materials may also be used to achieve the anti-reflection effect.
[0117] refer to Figure 6 The waveguide structure may also include a cover layer 500, located on the side of the antireflection layer 400 away from the diffraction grating 200. The cover layer 500, together with the antireflection layer 400 and the cladding layer 300, can protect the diffraction grating 200. Moreover, since the cladding layer 300 can protect the diffraction grating 200, the cover layer 500 can be made thinner, which is beneficial for reducing the weight of the waveguide structure.
[0118] For example, an adhesive layer may be provided between the cover plate layer and the anti-reflective layer to attach and fix the cover plate layer. For example, an air gap may be provided between the cover plate layer and the anti-reflective layer, and the cover plate layer may be supported and fixed between the cover plate layer and the anti-reflective layer by a support structure such as a support column. This disclosure does not limit these possibilities.
[0119] For example, refer to Figure 2The waveguide structure includes a first region M, where a diffraction grating 200 is located. The difference between the transmittance of the waveguide structure in the first region M and the transmittance of the waveguide structure in a second region N (excluding the first region M) is less than 0.1. After setting the capping layer 300 and the antireflection layer 400, the refractive index of the waveguide structure in the first region M and the refractive index of the waveguide structure in the second region N can tend to be consistent, thereby improving the transmittance uniformity of the waveguide structure. Therefore, users can obtain a better visual experience through the waveguide structure, and the uniform transmittance makes the waveguide structure more aesthetically pleasing, thus making the near-eye display device including this waveguide structure more attractive.
[0120] For example, the difference between the transmittance of the waveguide structure in the first region and the transmittance of the waveguide structure in the second region (excluding the first region) can be 0 to 0.1. For example, the difference between the transmittance of the waveguide structure in the first region and the transmittance of the waveguide structure in the second region (excluding the first region) can be 0.01 to 0.09. For example, the difference between the transmittance of the waveguide structure in the first region and the transmittance of the waveguide structure in the second region (excluding the first region) can be 0.02 to 0.08. For example, the difference between the transmittance of the waveguide structure in the first region and the transmittance of the waveguide structure in the second region (excluding the first region) can be 0.03 to 0.07. For example, the difference between the transmittance of the waveguide structure in the first region and the transmittance of the waveguide structure in the second region (excluding the first region) can be 0.04 to 0.06. For example, the difference between the transmittance of the waveguide structure in the first region and the transmittance of the waveguide structure in the second region (excluding the first region) can be 0.05.
[0121] Based on the above example, by optimizing the waveguide structure and jointly optimizing the parameters and materials of elements such as the cladding layer and antireflection layer, the overall transmittance of the waveguide structure can be improved, while reducing the transmittance differences in different regions, thus enhancing the transmittance uniformity of the waveguide structure. Taking a two-dimensional diffraction grating as an example, before adding the cladding layer and antireflection layer, the transmittance of the waveguide structure is 78.3%. After adding the cladding layer and antireflection layer and jointly optimizing the parameters, the transmittance of the waveguide structure can be increased to 85.9%.
[0122] The waveguide structure of this disclosure will now be illustrated by an example.
[0123] For example, in a waveguide structure, the diffraction grating is a two-dimensional (2D) grating made of titanium dioxide, while the waveguide substrate is made of lithium niobate. The diffraction grating is attached to the waveguide substrate. The period of the grating structure is 265.78 nanometers, and the lattice vectors of the grating structure have a certain angle. The planar shape of the grating structure is rectangular, with a long side of 320 nanometers and a short side of 125 nanometers. The central axis of the rectangle has an angle with the alignment direction of the grating structure, meaning the grating structure has a certain rotation angle.
[0124] Without a cladding layer on the diffraction grating, the waveguide structure exhibits an average transmittance of 78.3% in the region containing the diffraction grating and an average transmittance of 82.1% in the region excluding the diffraction grating. This indicates that without the cladding layer, the waveguide structure consists only of a lithium niobate substrate and a titanium dioxide diffraction grating in the region excluding the diffraction grating.
[0125] A capping layer is formed on the diffraction grating. The capping layer has a refractive index of 1.4 to 1.55 and a thickness of 150 to 160 nanometers. Due to process variations, the thickness of the capping layer differs slightly in different regions (e.g., the region containing the diffraction grating and regions other than the region containing the diffraction grating). The antireflection layer comprises a titanium dioxide layer and a silicon dioxide layer. The titanium dioxide layer has a thickness of 60 to 80 nanometers, and the silicon dioxide layer has a thickness of 70 to 85 nanometers. Both the titanium dioxide and silicon dioxide layers have the same thickness.
[0126] When a cladding layer and an anti-reflection layer are provided on the diffraction grating, the average transmittance of the waveguide structure in the region where the diffraction grating is located can reach 85.9%, and the average transmittance of the waveguide structure in the region other than the region where the diffraction grating is located can reach 95%.
[0127] It is understood that the waveguide structure provided in this disclosure can significantly improve the average transmittance of the waveguide structure in different regions, and the average transmittance of the waveguide structure in regions other than the region where the diffraction grating is located is higher than the average transmittance of the waveguide structure in the region where the diffraction grating is located. To improve the uniformity of the transmittance of the waveguide structure in different regions, the average transmittance of the waveguide structure in regions other than the region where the diffraction grating is located can be easily controlled to decrease, for example, to achieve an average transmittance of 85.9% in regions other than the region where the diffraction grating is located, thereby making the transmittance of the waveguide structure in different regions tend to be consistent.
[0128] As can be seen from the above description, by adding a cladding layer and an anti-reflection layer to the diffraction grating, the transmittance of the waveguide structure in different regions can be significantly increased, and the uniformity of the transmittance of the waveguide structure in different regions can also be improved.
[0129] At least one embodiment of this disclosure provides a near-eye display device, which includes a waveguide structure of any example in the above embodiments.
[0130] Since the near-eye display device according to the embodiments of this disclosure uses the above-described waveguide structure, it also has corresponding beneficial technical effects, which will not be elaborated here.
[0131] For example, a near-eye display device can be an AR near-eye display device.
[0132] For example, the near-eye display device can be a wearable AR helmet, AR glasses, etc., but the embodiments disclosed herein are not limited to these.
[0133] The following points need to be explained:
[0134] (1) The accompanying drawings of the embodiments of this disclosure only involve the structures involved in the embodiments of this disclosure, and other structures can be referred to the general design.
[0135] (2) Where there is no conflict, features of the same embodiment and different embodiments of this disclosure may be combined with each other.
[0136] The above description is merely an exemplary embodiment of this disclosure and is not intended to limit the scope of protection of this disclosure, which is determined by the appended claims.
Claims
1. A waveguide structure, comprising: A waveguide substrate comprising two surfaces arranged opposite to each other; A diffraction grating is located on at least one side surface of the waveguide substrate; A capping layer covering the diffraction grating and the waveguide substrate; An antireflection layer is located on the side of the capping layer away from the waveguide substrate; The refractive index of the capping layer is less than that of the diffraction grating and less than that of the antireflection layer.
2. The waveguide structure according to claim 1, wherein, The surface of the cover layer away from the waveguide substrate is a flat surface.
3. The waveguide structure according to claim 2, wherein, The covering layer is in direct contact with the diffraction grating.
4. The waveguide structure according to claim 2, wherein, The difference between the refractive index of the capping layer and the refractive index of the diffraction grating is 1.0 to 2.
0.
5. The waveguide structure according to claim 4, wherein, The refractive index of the coating layer is 1.0 to 1.
7.
6. The waveguide structure according to claim 2, wherein, The diffraction grating includes a plurality of grating structures extending along a first direction and arranged in a second direction, wherein the first direction intersects the second direction; The cover layer includes a cover portion that overlaps with at least one of the plurality of grating structures in a direction perpendicular to the waveguide substrate, the thickness of the cover portion being less than the thickness of at least a portion of the cover layer excluding the cover portion.
7. The waveguide structure according to claim 6, wherein, The thickness of the cover is 20 nanometers to 200 nanometers.
8. The waveguide structure according to claim 6, wherein, The diffraction grating includes an insertion grating, a transition grating, and an exit grating. The covering portion includes a first sub-portion, a second sub-portion, and a third sub-portion. In a direction perpendicular to the waveguide substrate, the insertion grating overlaps with the first sub-portion, the transition grating overlaps with the second sub-portion, and the exit grating overlaps with the third sub-portion. At least two of the first sub-part, the second sub-part, and the third sub-part have different thicknesses.
9. The waveguide structure according to any one of claims 1-8, wherein, The covering layer includes a transparent adhesive layer.
10. The waveguide structure according to any one of claims 1-8, wherein, The cover layer is in direct contact with the antireflective layer.
11. The waveguide structure according to claim 1, wherein, The antireflection layer includes multiple layers of film stacked together. At least one of the multiple layers of film includes a grating antireflection portion and a substrate antireflection portion. The orthographic projection of the grating antireflection portion on the waveguide substrate overlaps with the orthographic projection of the diffraction grating on the waveguide substrate, and the orthographic projection of the substrate antireflection portion on the waveguide substrate does not overlap with the orthographic projection of the diffraction grating on the waveguide substrate. The refractive index of the grating anti-reflection section is different from the refractive index of the substrate anti-reflection section.
12. The waveguide structure according to claim 11, wherein, The grating anti-reflection section includes a first anti-reflection section, a second anti-reflection section, and a third anti-reflection section; The diffraction grating includes an insertion grating, a transition grating, and an exit grating. The orthographic projection of the first antireflection portion on the waveguide substrate overlaps with the orthographic projection of the insertion grating on the waveguide substrate. The orthographic projection of the second antireflection portion on the waveguide substrate overlaps with the orthographic projection of the transition grating on the waveguide substrate. The orthographic projection of the third antireflection portion on the waveguide substrate overlaps with the orthographic projection of the exit grating on the waveguide substrate. At least two of the first antireflective coating, the second antireflective coating, and the third antireflective coating have different refractive indices.
13. The waveguide structure according to claim 12, wherein, The multilayer film includes a first film layer and a second film layer, and the first film layer and the second film layer each include a first anti-reflection portion, a second anti-reflection portion and a third anti-reflection portion; The first film layer and the second film layer are configured to satisfy at least one of the following conditions: The refractive index of the first antireflection portion of the first film layer is different from the refractive index of the first antireflection portion of the second film layer; The refractive index of the second antireflection portion of the first film layer is different from the refractive index of the second antireflection portion of the second film layer; The refractive index of the third antireflection portion of the first film layer is different from the refractive index of the third antireflection portion of the second film layer.
14. The waveguide structure according to claim 1, wherein, The antireflective layer comprises multiple layers stacked together, including a third layer and a fourth layer. The third layer has the same refractive index in different regions, and the fourth layer has the same refractive index in different regions. The third film layer has a third refractive index, and the fourth film layer has a fourth refractive index. The third refractive index and the fourth refractive index are different.
15. The waveguide structure according to any one of claims 11-14, wherein, The refractive index of each of the multilayer films is 1.4-2.
5.
16. The waveguide structure according to any one of claims 11-14, wherein, The thickness of each of the multilayer films is 20 nanometers to 200 nanometers.
17. The waveguide structure according to any one of claims 1-8, further comprising: The cover plate layer is located on the side of the antireflection layer away from the diffraction grating.
18. The waveguide structure according to any one of claims 1-8, wherein, The waveguide structure includes a first region, and the diffraction grating is located in the first region; The difference between the transmittance of the waveguide structure in the first region and the transmittance of the waveguide structure in the second region other than the first region is less than 0.
1.
19. A near-eye display device comprising the waveguide structure according to any one of claims 1-18.