In-coupling grating, optical waveguide, and near-eye display device

Abstract

The application discloses a coupling-in grating, an optical waveguide and a near-eye display device, relates to the technical field of diffracted light, and discloses a coupling-in grating applied to an entrance pupil area of an optical waveguide. The coupling-in grating comprises N grating blocks arranged continuously, and the N grating blocks comprise a reference grating block. The reference grating block is a grating block with the shortest entrance pupil optical path among the N grating blocks, and the entrance pupil optical path of the remaining grating blocks gradually becomes longer in a direction away from the reference grating block. The duty cycle and / or etching depth of the N grating blocks gradually change in a direction away from the reference grating block, wherein N is greater than 1. The application can improve the coupling-in efficiency of the entrance pupil area in the existing optical waveguide display system.

Description

Technical Field

[0001] This application relates to the field of diffractive light technology, and more particularly to a coupling grating, an optical waveguide, and a near-eye display device. Background Technology

[0002] In augmented reality display devices, optical waveguide technology, as one of the core display pathways, has been widely used to achieve lightweight, high transmittance, and wide field-of-view display effects. An optical waveguide system typically includes an entrance pupil region and an exit pupil region. The light coupling efficiency of the entrance pupil region directly affects the brightness and energy efficiency of the entire system, and is one of the key factors influencing the performance of the waveguide system.

[0003] In existing technologies, surface-embossed gratings are commonly used as grating coupling structures to couple the image light output from the optomechanical engine into the waveguide via diffraction. However, due to certain limitations in the design of existing gratings, these structures cannot fully utilize the light energy emitted by the optomechanical engine, resulting in significant energy loss. Utility Model Content

[0004] This application provides a coupling grating, an optical waveguide, and a near-eye display device, which can improve the coupling efficiency of the entrance pupil region in existing optical waveguide display systems.

[0005] In a first aspect, this application proposes a coupling grating, wherein the coupling grating is applied to the entrance pupil region of an optical waveguide, and the reference grating block is the grating block with the shortest or longest entrance pupil optical path among the N grating blocks. The duty cycle and / or etching depth of the N grating blocks gradually change from the reference grating block away from it, where N is greater than 1.

[0006] In one optional embodiment of the first aspect, the reference grating block is the grating block with the shortest entrance pupil optical path among the N grating blocks, and the duty cycle of the reference grating block is a%. Along the direction away from the reference grating block, the duty cycle of the remaining grating blocks gradually changes to b%, where |a-50|>|b-50|.

[0007] In one alternative embodiment of the first aspect, the reference grating block is the grating block with the shortest entrance pupil optical path among the N grating blocks, and the etching depth of the N grating blocks gradually increases from the reference grating block away from the reference grating block.

[0008] In one optional embodiment of the first aspect, the reference grating block is the grating block with the longest entrance pupil optical path among the N grating blocks, and the duty cycle of the reference grating block is c%. Along the direction away from the reference grating block, the duty cycle of the remaining grating blocks gradually changes to d%, where |c-50|<|d-50|.

[0009] In one alternative embodiment of the first aspect, the reference grating block is the grating block with the longest entrance pupil optical path among the N grating blocks, and the etching depth of the N grating blocks gradually decreases from the reference grating block as a starting point in a direction away from the reference grating block.

[0010] In one optional embodiment of the first aspect, when the optical waveguide is a symmetrical structure, the reference grating block is the grating block located at the center of the N grating blocks, and the N grating blocks are arranged symmetrically with the reference grating block as the center.

[0011] In one alternative embodiment of the first aspect, the optical waveguide is a monocular waveguide or a binocular waveguide.

[0012] In one alternative embodiment of the first aspect, the tilt angle of the coupled grating is 15° to 60°.

[0013] In a second aspect, this application provides an optical waveguide, a waveguide substrate, a coupling grating, and the coupling grating provided in the first aspect above; the coupling grating and the coupling grating are disposed on the surface of the waveguide substrate.

[0014] Thirdly, this application provides a near-eye display device, including an optomechanism and an optical waveguide as provided in the second aspect, wherein the optomechanism is used to emit an image beam toward the entrance pupil region of the optical waveguide.

[0015] The coupling grating, optical waveguide, and near-eye display device provided in this application have the following beneficial effects: By gradually setting the duty cycle and / or etching depth of the coupling grating, the change in its duty cycle and / or etching depth can be set according to the optical path distance from the exit pupil to the entrance pupil. This achieves dynamic spatial matching of the coupling capability of the coupling grating, significantly improving the waveguide system's light energy utilization efficiency and display brightness uniformity. Attached Figure Description

[0016] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0017] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 A schematic diagram of the structure of the coupling grating with a simultaneous gradient design of duty cycle and etching depth provided in an embodiment of this application; Figure 2 A schematic diagram of the structure of the coupling grating with a duty cycle gradient design provided in the embodiments of this application; Figure 3 Image display comparison diagrams of conventional design and duty cycle gradient design provided for embodiments of this application; Figure 4 A schematic diagram of the structure of the coupling grating with a gradient etching depth design provided in the embodiments of this application; Figure 5 Image display comparison diagrams of conventional design and etching depth gradient design provided for embodiments of this application; Figure 6 This is a schematic diagram of the structure of an optical waveguide provided in an embodiment of this application. Detailed Implementation

[0019] It should be understood that the specific embodiments described herein are merely illustrative of the technical solutions of this application and are not intended to limit this application.

[0020] In existing technologies, surface-embossed gratings are commonly used as grating coupling structures to couple the image light output from the optomechanical system into the waveguide via diffraction. However, because existing grating designs typically employ fixed tilt angles, duty cycles, and etching depths, their diffraction efficiency is significantly limited in practical applications. This is especially true in single-optical-mechanical binocular waveguide structures, where the light energy needs to be distributed to two eyepieces, making the coupling efficiency requirements even more stringent. Existing grating structures cannot fully utilize the energy emitted by the optomechanical system, resulting in a large amount of light energy being reflected or scattered in the entrance pupil region, causing significant energy loss.

[0021] To address these issues, some studies have attempted to improve diffraction efficiency by optimizing grating materials, adjusting the incident angle, or employing multi-level structures. However, the following problems still exist: First, existing designs lack differentiated structural control for the spatial distribution of the entrance pupil region, and cannot dynamically adjust coupling parameters according to the region's location. Second, the grating diffraction efficiency remains low under different incident angles and spectral conditions, making it difficult to meet the requirements of high-brightness displays. Third, it is difficult to achieve a good balance between efficiency, brightness, and process technology using a single structural parameter.

[0022] The root cause of the above technical problems is that existing coupling gratings usually use fixed structural parameters (such as fixed duty cycle and etching depth), and fail to make differentiated designs for the coupling characteristics at different positions in the entrance pupil region. This results in insufficient grating diffraction efficiency in some areas, especially under high incident angle or specific wavelength conditions, which makes the brightness distribution of the screen display uneven.

[0023] To address the aforementioned issues, this application proposes a coupling grating that can be applied to the entrance pupil region of optical waveguides, particularly the entrance pupil region of single-optical-mechanical dual-optical waveguides. This application achieves dynamic spatial matching of the coupling capability of the coupling grating by designing a gradient of its duty cycle and / or etching depth, allowing the direction of change of the duty cycle and / or etching depth to be set according to the optical path distance from the entrance pupil in the exit pupil. This significantly improves the waveguide system's light energy utilization efficiency and display brightness uniformity.

[0024] The technical solution of this application will be described in detail below with reference to the accompanying drawings.

[0025] like Figure 1 As shown, the coupled grating 1 provided in this embodiment includes N consecutively arranged grating blocks 10 ( Figure 1 (A block separated by two adjacent black dashed lines represents a grating block). N grating blocks include a reference grating block 10a, which is the grating block with the shortest entrance pupil optical path among the N grating blocks. The entrance pupil optical path of the remaining grating blocks gradually increases in the direction away from the reference grating block 10a. Alternatively, the reference grating block 10a is the grating block with the longest entrance pupil optical path among the N grating blocks. The entrance pupil optical path of the remaining grating blocks gradually decreases in the direction away from the reference grating block 10a.

[0026] The duty cycle and / or etching depth of the N grating blocks gradually change from the reference grating block 10a away from the reference grating block 10a, where N is greater than 1.

[0027] In this context, the etching depth of the grating refers to the vertical height of the groove (or protrusion) formed by etching on the surface of the waveguide substrate, i.e., the vertical distance from the surface of the waveguide substrate to the bottom of the groove (or the top of the protrusion). The duty cycle of the grating refers to the ratio of the width of the area containing grating material to the length of the entire grating period within a single grating cycle. The entrance pupil optical path length refers to the optical transmission path length from when the image beam emitted by the optomechanical system enters the entrance pupil region of the optical waveguide, is coupled into the waveguide substrate via the coupling grating, and then propagates within the waveguide substrate via total internal reflection until it reaches the exit pupil region (the effective optical region observed by the human eye). Its core is the equivalent optical path length of the entire link from the entrance pupil coupling into the waveguide to the exit pupil coupling out.

[0028] The duty cycle and / or etching depth of the coupling grating in this embodiment are designed according to the distance of the optical path from the entrance pupil to the exit pupil, so as to adaptively adjust the optical coupling capability of different grating regions. By designing a gradual change in the duty cycle, the coupling efficiency of the grating region with a longer optical path from the entrance pupil can be enhanced, and over-coupling of the grating region with a shorter optical path from the entrance pupil can be prevented. By designing a gradual change in the etching depth, regional control of the grating diffraction efficiency can be achieved, effectively compensating for the energy loss caused by the attenuation of light energy outside the center.

[0029] In some embodiments, the optical waveguide has a symmetrical structure, specifically a symmetrical single-optical-mechanism binocular waveguide with the entrance pupil at the center. The reference grating block is the central grating block among N grating blocks, and the N grating blocks are arranged symmetrically around the reference grating block. The overall structure of the coupling grating in this application has a centrally symmetrical layout, ensuring that the light output from the optomechanism has a symmetrical energy distribution and coupling effect in the left and right eyepiece channels. This symmetrical design helps to improve the consistency of binocular display and reduce the brightness difference between the left and right eyes. In addition, although the coupling grating in this application maintains structural symmetry, the gratings on both sides have a clear directional arrangement, that is, designed according to the incident direction of the optomechanism and the light guiding path of the waveguide, so that the light has directional selectivity during coupling, thereby improving coupling efficiency and suppressing crosstalk.

[0030] In other embodiments, the optical waveguide may also be a monocular waveguide.

[0031] Understandably, in traditional waveguide structures, the grating in the entrance pupil region uses a uniform structural design without differentiated adaptation to the entrance pupil optical path distribution. This leads to two typical brightness unevenness problems in the displayed image: one is that the central area is too bright and the side areas are dark, and the other is that the central area is dark and the side areas are too bright. The core of these problems is the difference in the entrance pupil optical path distribution: the longer the optical path, the greater the transmission loss of the beam in the waveguide (such as material absorption loss and interface scattering loss); the shorter the optical path, the smaller the transmission loss. At the same time, this phenomenon is also affected by the superposition of factors such as waveguide manufacturing process deviations and waveguide structural layout design.

[0032] Based on this core principle, the design principle for achieving brightness uniformity in this application is as follows: for regions with longer optical path lengths, transmission loss needs to be compensated by "improving grating diffraction efficiency," while for regions with shorter optical path lengths, excess energy needs to be balanced by "reducing grating diffraction efficiency." The specific structural design of the optical waveguide will be detailed below, taking into account the two types of brightness unevenness scenarios mentioned above.

[0033] Scenario 1: Structural design for "bright center, dark sides" In this case, the reference grating block is the grating block with the shortest entrance pupil optical path (i.e., the lowest light energy loss) among the N grating blocks, and the entrance pupil optical path of the other grating blocks gradually increases in the direction away from the reference grating block. At this time, the structure of the coupled grating can be set as follows: The duty cycle of the reference grating block is a%, and the duty cycle of the remaining grating blocks gradually changes to b% along the direction away from the reference grating block, where |a-50|>|b-50|, and / or, the etching depth of the N grating blocks gradually increases from the reference grating block away from the reference grating block.

[0034] For example, the value range of a can be [15, 35] or [65, 85], and the value range of b can be [45, 55].

[0035] Scenario 2: Structural design for a "dark middle and bright sides" layout In this case, the reference grating block is the grating block with the longest entrance pupil optical path (i.e., the greatest light energy loss) among the N grating blocks, and the entrance pupil optical path of the other grating blocks gradually shortens along the direction away from the reference grating block. At this time, the structure of the coupled grating can be set as follows: The duty cycle of the reference grating block is c%, and the duty cycle of the remaining grating blocks gradually changes to d% along the direction away from the reference grating block, where |c-50|<|d-50|, and / or, the etching depth of the N grating blocks starts from the reference grating block and gradually becomes shallower along the direction away from the reference grating block.

[0036] For example, the value range of c can be [45, 55], and the value range of d can be [15, 35] or [65, 85].

[0037] In other words, the coupling grating of this application has the following implementation methods in terms of structural design (the following descriptions all use the example of N grating blocks arranged symmetrically with the reference grating block as the center): In the first embodiment, the etching depth of the N grating blocks coupled into the grating is uniform, and the duty cycle of the coupled grating gradually changes from the center to both sides. For example... Figure 2 As shown, Figure 2 The region X, defined by the dashed line in the first grating block 10, represents the area containing grating material. Figure 2 The representation of the regions containing grating material in the remaining grating blocks is similar. Starting from the reference grating block 10a, the duty cycle of the grating blocks 10 on both sides gradually decreases along the direction away from the reference grating block 10a. The specific design logic is as follows: The entrance pupil optical path is shorter in the central region, so its duty cycle is set slightly off from 50% (ideally, the first-order diffraction efficiency reaches its maximum when the duty cycle is around 50%) to reduce coupling strength. The entrance pupil optical path is longer in the edge region, so its duty cycle is set closer to 50% to improve coupling efficiency. The gradual change in duty cycle is continuous to avoid abrupt changes that could cause light interference, and the overall structure meets the principle of central symmetry design, improving the brightness uniformity of the binoculars.

[0038] like Figure 3 As shown in the left image, traditional fixed duty cycle gratings result in an overly bright central area and a darker edge, causing uneven brightness and a poor visual experience. The first implementation method, using a gradual duty cycle, reduces the coupling ability of the central grating area and enhances the coupling ability of the edge grating areas, thus achieving a more uniform brightness distribution and a final display effect as shown... Figure 3 As shown in the right figure.

[0039] In the second embodiment, the duty cycles of the N grating blocks in the coupled grating are all the same, and the etching depth of the coupled grating is gradually distributed from the center to both sides, such as... Figure 4 As shown, Figure 4 The gray arrow in the first raster block 10 indicates the etching depth (d). Figure 4 The etching depth of the remaining grating blocks is represented in a similar way. Starting from the reference grating block 10a, the etching depth of the grating blocks 10 on both sides gradually becomes shallower along the direction away from the reference grating block 10a. The specific design logic is as follows: When the entrance pupil optical path is shorter in the central region and longer in the edge region, the etching depth of the coupling grating gradually and continuously changes from shallow to deep along the center to both sides, i.e., "shallow in the center and deep on both sides". Because the light energy is higher in the central region, a higher coupling efficiency can be achieved even if the etching depth is shallow. The light energy is lower on both sides, so the diffraction efficiency is improved by increasing the etching depth to make up for the insufficient energy and improve the overall brightness uniformity. This method is beneficial for edge compensation and is often used in Gaussian distribution light sources.

[0040] When the entrance pupil optical path is longer in the central region and shorter in the edge region, the etching depth of the coupling grating gradually and continuously changes from deep to shallow along the center to both sides, i.e., "deep in the center and shallow on both sides". When the energy in the central region is lower, stronger coupling capability is required. By increasing the depth, the light energy in the central region is improved, while the energy on both sides is sufficient. Appropriate shallow etching can avoid energy concentration or bright spot phenomenon caused by excessive coupling. This method is beneficial for center enhancement and is often used in edge enhancement light sources or special imaging scenarios.

[0041] As an example, when the image center is dark and the surrounding area is bright, the etching depth of the coupled grating gradually changes from the central region of the entrance pupil to both sides, adopting a "deep in the center, shallow on both sides" structural design. For example, the etching depth in the central region is 150nm, gradually transitioning to 50nm in the edge region, with the gradient direction symmetrically distributed to ensure consistency in binocular display. The depth gradient design can adjust the local diffraction efficiency of the grating, achieving energy balance in spatial distribution.

[0042] In traditional designs, the grating depth of the entrance pupil area is a uniform value, which may result in the central area being darker and the edges being brighter. Figure 5 The left image shows the final image effect using a conventionally designed coupling grating, exhibiting significant brightness unevenness. By employing the "deeper in the center, shallower on both sides" depth-gradient coupling grating structure of this embodiment, the light energy in the edge region is appropriately weakened due to the deeper etching depth, preventing excessive brightness; while the central region, through increased etching depth, effectively improves diffraction efficiency and enhances coupling capability for weak light, resulting in the final image display effect as shown... Figure 5 As shown in the right figure, the entire entrance pupil area achieves a more uniform light energy distribution, the transition of image brightness from the center to the edge is more natural, the problem of dimness in the center is significantly improved, and the comfort and visual consistency of the display effect are enhanced.

[0043] In the third embodiment, both the duty cycle and etching depth of the grating gradually change synchronously from the center to both sides. For example... Figure 1 As shown, Figure 1 In the first grating block 10, the gray arrow indicates the etching depth (d), and X represents the area containing grating material. Figure 1 It can be seen that its duty cycle and etching depth are both designed with gradients, forming a two-dimensional gradient structure.

[0044] The specific design approach is as follows: the entrance pupil optical path is shorter in the central region, so its duty cycle deviates slightly from 50% and the etching depth is shallower; the entrance pupil optical path is longer in the edge region, so its duty cycle is close to 50% and the etching depth is deeper; the duty cycle and etching depth gradually change symmetrically in the horizontal direction to adapt to the entrance pupil region in the single-optical-mechanical binocular waveguide structure. The change process of the two parameters is smooth and continuous to ensure the uniformity of optical effects and reduce interface reflection or interference.

[0045] The reason for adopting the above design is that the light intensity at the center of the optical engine is high and the entrance pupil optical path in the central region is short. If a grating structure with a duty cycle of 50% and a deep depth is used directly, it may lead to over-coupling, resulting in "overexposure" or "bright spots" in the center of the image. By appropriately deviating the duty cycle of the central region from 50% (such as slightly smaller or larger), the diffraction efficiency can be controlled at a slightly lower level, which can reduce the coupling strength. At the same time, a shallower etching depth is used to further reduce the amount of local light energy coupled in. This design is structurally equivalent to "limiting the central light energy input", which is used to suppress the phenomenon of excessive brightness in the center and balance the overall brightness output.

[0046] Waveguide edge regions often suffer from insufficient brightness due to weak optomechanical output and long pupil optical path lengths, and their viewing angles are also more off, leading to greater energy attenuation. To improve coupling efficiency in this region, the duty cycle should be as close to 50% as possible to achieve maximum first-order diffraction efficiency. Simultaneously, deeper etching depth can enhance diffraction capabilities and increase the amount of light coupled per unit area. This design aims to enhance coupling efficiency in low-light regions, effectively compensating for insufficient edge brightness and achieving edge compensation for image brightness.

[0047] In traditional waveguide structures, the uniform grating structure in the entrance pupil region fails to consider differences in energy distribution, leading to the following problems in the displayed image: the central area is too bright, resulting in an overexposed image; the edge area lacks brightness, causing vignetting or a grayish appearance; and the overall image brightness decreases sharply from the center to the edge, resulting in a discontinuous viewing experience. By implementing the combined duty cycle and etching depth gradient design of this invention, the structural coupling capability dynamically matches spatial changes. The coupling strength in the central region is reduced to avoid excessive energy concentration; the coupling capability in the edge region is enhanced to compensate for energy attenuation; ultimately, the image brightness distribution is more uniform, the transition from the center to the edge is natural, and the brightness consistency perceived by the user is significantly improved. This structure is particularly suitable for high field-of-view, low-power display systems, effectively improving image quality and visual experience without increasing optomechanical power.

[0048] In some implementations, the coupling grating is designed with a certain tilt angle, which is in the range of 15° to 60°, to adapt to the incident angle of the optomechanical system, optimize the diffraction direction, and improve the coupling efficiency.

[0049] By integrating the above structural features, the solution of this application can effectively improve the entrance pupil coupling capability of the waveguide system without increasing the system complexity, and has good optical efficiency, manufacturing adaptability and application versatility.

[0050] like Figure 6As shown, this application embodiment also provides an optical waveguide 100, including a waveguide substrate 10, a coupling grating 2, and a coupling grating 1 provided in the above embodiment; wherein the coupling grating 2 and the coupling grating 1 are disposed on the surface of the waveguide substrate 10. The optical waveguide 100 may also include a pupil-expanding grating 3.

[0051] This application also provides a near-eye display device, including an optomechanism and the optical waveguide provided in the above embodiments, wherein the optomechanism is used to emit an image beam into the entrance pupil region of the optical waveguide.

[0052] In this system, the image beam output from a single optomechanical unit is guided to the entrance pupil region of the waveguide substrate via a freeform surface or fiber optic guide. The light is then coupled into the waveguide by a coupling grating and transmitted through the waveguide. Finally, the image light is output to the user's eyes via a coupling grating, achieving simultaneous imaging of the left and right eyes.

[0053] In traditional single-optical-mechanical binocular waveguide systems, the grating structure in the entrance pupil region is usually designed uniformly, which cannot adapt to the uneven spatial distribution of light energy emitted from the optical engine. This results in excessively high brightness in the central region and dimness in the edge region, affecting imaging consistency and visual comfort.

[0054] This application achieves dynamic spatial matching of grating coupling capability by introducing a gradient design of structural parameters (gradual duty cycle, gradual depth, or a combination of both) in the entrance pupil region. This significantly improves the light energy utilization efficiency and display brightness uniformity of the waveguide system, making it particularly suitable for the following typical scenarios: 1. Lightweight AR glasses system: Sensitive to power consumption and brightness requirements, it needs to achieve high brightness display with low power consumption through efficient coupling; 2. Large field-of-view waveguide design: The edge imaging area is large, which is prone to brightness attenuation. It is necessary to enhance edge compensation through local coupling. 3. Multi-user or industrial-grade AR terminals: These must ensure display consistency and long-term viewing comfort, and have strict requirements for optical quality; 4. Mass-producible optical waveguide modules: While ensuring performance, they must have clear structural design rules to facilitate standardized manufacturing.

[0055] In summary, the technical solution of this application has good integrability and versatility in actual system architecture, and can effectively improve the performance of AR waveguide display system without increasing system complexity.

[0056] The above description is only a part of the embodiments of this application and does not limit the patent scope of this application. All equivalent structural transformations made under the technical concept of this application and using the contents of the specification and drawings of this application, or direct / indirect applications in other related technical fields, are included in the patent protection scope of this application.

Claims

1. A coupling grating, characterized in that, The coupling grating is applied to the entrance pupil region of the optical waveguide. The coupling grating includes N consecutively arranged grating blocks, and the N grating blocks include a reference grating block. The reference grating block is the grating block with the shortest or longest entrance pupil optical path among the N grating blocks. The duty cycle and / or etching depth of the N grating blocks gradually change from the reference grating block away from it, where N is greater than 1.

2. The coupling grating as described in claim 1, characterized in that, The reference grating block is the grating block with the shortest entrance pupil optical path among the N grating blocks. The duty cycle of the reference grating block is a%. Along the direction away from the reference grating block, the duty cycle of the remaining grating blocks gradually changes to b%, where |a-50|>|b-50|.

3. The coupling grating as described in claim 1 or 2, characterized in that, The reference grating block is the grating block with the shortest entrance pupil optical path among the N grating blocks, and the etching depth of the N grating blocks gradually increases from the reference grating block away from it.

4. The coupling grating as described in claim 1, characterized in that, The reference grating block is the grating block with the longest entrance pupil optical path among the N grating blocks. The duty cycle of the reference grating block is c%. Along the direction away from the reference grating block, the duty cycle of the remaining grating blocks gradually changes to d%, where |c-50|<|d-50|.

5. The coupling grating as described in claim 1 or 4, characterized in that, The reference grating block is the grating block with the longest entrance pupil optical path among the N grating blocks, and the etching depth of the N grating blocks gradually decreases from the reference grating block away from it.

6. The coupling grating as described in claim 1, characterized in that, When the optical waveguide has a symmetrical structure, the reference grating block is the grating block located at the center of the N grating blocks, and the N grating blocks are arranged symmetrically with the reference grating block as the center.

7. The coupling grating as described in claim 1, characterized in that, The optical waveguide is either a monocular waveguide or a binocular waveguide.

8. The coupling grating as described in claim 1, characterized in that, The tilt angle of the coupled grating is 15° to 60°.

9. An optical waveguide, characterized in that, include: A waveguide substrate, a coupling grating, and an input grating as described in any one of claims 1-8; the coupling grating and the input grating are disposed on the surface of the waveguide substrate.

10. A near-eye display device, characterized in that, It includes an optomechanism and an optical waveguide as described in claim 9, wherein the optomechanism is used to emit an image beam into the entrance pupil region of the optical waveguide.

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