WO2024093642A1

WO2024093642A1 - In-coupling grating structure, diffraction optical waveguide, and augmented reality device

Info

Publication number: WO2024093642A1
Application number: PCT/CN2023/124353
Authority: WO
Inventors: 张雅琴; 楼歆晔
Original assignee: 上海鲲游科技有限公司
Priority date: 2022-10-31
Filing date: 2023-10-12
Publication date: 2024-05-10

Abstract

An in-coupling grating structure (1), a diffraction optical waveguide (3), and an augmented reality device. The in-coupling grating structure (1) is configured to couple an image light beam into a waveguide substrate (3); grating parameters of different parts of the in-coupling grating structure (1) are different; and the different parts are distributed along the surface of the waveguide substrate or along a grating depth direction. The in-coupling grating structure (1) has good diffraction efficiency, a wide FOV bandwidth, and good FOV uniformity.

Description

In-coupled grating structure and diffractive optical waveguide, augmented reality device

Technical Field

The present invention relates to the field of AR technology, and in particular to an in-coupling grating structure, a diffraction optical waveguide, and an augmented reality device.

Background technique

Augmented reality (AR) is a technology that integrates the real world and virtual information. The AR display system usually includes a micro projector and an optical display screen. The micro projector provides virtual content for the AR display system, and the virtual content is projected into the human eye through the optical display screen. The optical display screen is usually a transparent optical component, so that the user can see the real world through the optical display screen at the same time.

Optical waveguides are a way to realize optical display screens. When the refractive index of the transmission medium is greater than that of the surrounding medium and the incident angle in the waveguide is greater than the critical angle of total reflection, light can be transmitted in the waveguide without leakage, and total reflection occurs. After the light beam of the virtual content from the projector is coupled into the waveguide, the light beam can continue to propagate losslessly in the waveguide to transmit the virtual content until it is coupled out by the subsequent optical structure. Currently, optical waveguides on the market are generally divided into geometric array waveguides and diffraction waveguides, among which diffraction waveguides are further divided into volume holographic waveguides and surface relief grating waveguides. The essence of diffraction waveguides is to couple the incident light beam into the waveguide through grating diffraction. Surface relief grating waveguides have obvious advantages among many solutions due to their extremely high design freedom and mass production brought by nanoimprint processing.

On the one hand, the AR display system couples the light beam of the virtual content from the projector into the waveguide, and the image light beam coupled into the optical waveguide can be used later, so the coupling needs to be as efficient as possible. Taking the diffraction optical waveguide system as an example, the coupling structure is set as a coupling grating, so the diffraction efficiency of the coupling order of the coupling grating is required to be as high as possible.

On the other hand, AR (augmented reality) glasses are a process of expanding the pupil of the image light emitted by the micro-projector and projecting it into the human eye, so that the wearer can see the virtual image projected by the micro-projector while seeing the real world. Taking the diffraction waveguide system as an example, the optical system of AR glasses usually includes a micro-projector and a waveguide lens. The design combination of the two determines the final product form. As a product for display purposes, its most important and basic requirement is a good display effect, including an ideal eyebox uniformity. , FOV uniformity and high efficiency.

Although the diffraction efficiency of the above-mentioned inclined grating is higher than that of a conventional rectangular beam, its FOV bandwidth is not ideal and its FOV uniformity is poor.

In summary, the existing coupling grating cannot take into account the problems of diffraction efficiency, bandwidth and uniformity.

Summary of the invention

The present invention provides a coupled grating structure, a diffraction optical waveguide, and an augmented reality device to solve the problem in the prior art that the diffraction efficiency, bandwidth, and uniformity cannot be taken into account at the same time.

To solve the above technical problems, the present invention is achieved through the following technical solutions:

According to a first aspect of the present invention, there is provided an incoupling grating structure configured to couple an image beam into a waveguide substrate;

The grating parameters of different parts of the coupling grating structure are different;

The different locations are distributed along the surface of the waveguide substrate or along the depth direction of the grating.

Preferably, when the different parts are distributed along the surface of the waveguide substrate, at least one grating parameter among the multiple grating parameters of the different parts of the coupled-in grating structure is different;

The multiple grating parameters include: grating tilt angle, grating depth, and grating duty cycle.

Preferably, one grating parameter of different parts of the coupling-in grating structure is different, and other grating parameters are the same.

Preferably, one grating parameter of different parts of the coupling grating structure is different, and other grating parameters are the same, specifically:

The grating duty ratios of different parts of the coupled grating structure are different, and other grating parameters are the same;

Alternatively, the grating inclination angles of different parts of the coupling-in grating structure are different, and other grating parameters are the same;

Alternatively, the grating depths of different parts of the coupling-in grating structure are different, and other grating parameters are the same.

Preferably, the different parts are distributed along the grating direction of the coupling-in grating structure.

Preferably, the closer to the out-coupling grating structure along the grating direction, the larger the grating duty cycle of the in-coupling grating structure;

Wherein, the outcoupling grating structure is configured to be able to couple the image light beam out of the waveguide substrate.

Preferably, when the different parts are distributed along the grating depth direction, the different coupling into the grating structure The duty cycle of the grating in the same part is different.

Preferably, the deeper the grating depth is, the larger the grating duty cycle of the coupled-in grating structure is.

According to a second aspect of the present invention, there is provided a diffractive optical waveguide, comprising:

A waveguide substrate and a first grating region located on a surface of the waveguide substrate;

The first grating region includes: the coupling-in grating structure described in any one of the first aspects of the present invention.

Preferably, the diffractive optical waveguide further comprises: a second grating region located on the surface of the waveguide substrate;

The grating structure in the second grating region is used to diffract and deflect the image light beam coupled into the waveguide substrate to propagate in different directions, and diffract and couple out of the waveguide substrate when propagating in different directions.

Preferably, the grating structure in the second grating region comprises a two-dimensional outcoupling grating, the two-dimensional outcoupling grating comprises a plurality of grating units, and along the first direction, the two-dimensional outcoupling grating is divided into a plurality of regions, and the grating units in different regions have different orientations;

The first direction is a direction different from a traveling direction of the image light beam in the waveguide substrate.

Preferably, the plurality of regions include a reference region; the reference region is a region where the two-dimensional out-coupling grating is located, where the grating direction of the in-coupling grating structure points; the diffraction efficiency of diffraction propagation to both sides in the reference region is equivalent;

The multiple regions also include: a first change region adjacent to the reference region along the positive direction of the first direction, and/or a second change region adjacent to the reference region along the negative direction of the first direction; wherein the diffraction efficiency of the first change region and the second change region when diffracting and propagating deflected toward the reference region is greater than the diffraction efficiency of the first change region and the second change region when diffracting and propagating deflected away from the reference region.

Preferably, the plurality of regions include a reference region, a first change region adjacent to the reference region along a positive direction of the first direction, and/or a second change region adjacent to the reference region along a negative direction of the first direction;

The reference region is a region where the two-dimensional out-coupling grating is located, pointed to by the grating direction of the in-coupling grating structure; and the out-coupling efficiency of the reference region is lower than the out-coupling efficiency of the first changing region and the second changing region.

Preferably, when the coupling-in grating structure is located on the left side of the coupling-out grating structure, the orientation of the grating unit in the first changing region is consistent with the orientation of the grating unit in the reference region after clockwise rotation, and the orientation of the grating unit in the second changing region is consistent with the orientation of the grating unit in the reference region after counterclockwise rotation;

When the coupling-in grating structure is located on the right side of the coupling-out grating structure, the first change region The orientation of the grating unit in the domain is consistent with the orientation of the grating unit in the reference area after counterclockwise rotation, and the orientation of the grating unit in the second change area is consistent with the orientation of the grating unit in the reference area after clockwise rotation;

Wherein, the counterclockwise rotation angle and the clockwise rotation angle are both less than 90 degrees.

Preferably, the first change region is divided into a plurality of first sub-regions along the first direction, and along the positive direction of the first direction, the difference between the diffraction efficiency of the first sub-regions diffracting and propagating toward the reference region and the diffraction efficiency of the first sub-regions diffracting and propagating away from the reference region gradually increases;

The second change region is divided into a plurality of second sub-regions along the first direction. Along the negative direction of the first direction, the difference between the diffraction efficiency of the second sub-regions deflected toward the reference region and the diffraction efficiency of the second sub-regions deflected away from the reference region gradually increases.

Preferably, the first change region is divided into a plurality of first sub-regions along the first direction, and the coupling-out efficiency of the first sub-regions gradually increases along the positive direction of the first direction;

The second change region is divided into a plurality of second sub-regions along the first direction, and the coupling-out efficiency of the second sub-regions gradually increases along the negative direction of the first direction.

Preferably, when the coupling-in grating structure is located on the left side of the coupling-out grating structure, along the positive direction of the first direction, the clockwise rotation angles of the grating units in the plurality of first sub-regions relative to the grating units in the reference region gradually increase; along the negative direction of the first direction, the counterclockwise rotation angles of the grating units in the plurality of second sub-regions relative to the grating units in the reference region gradually increase;

When the coupling-in grating structure is located on the right side of the coupling-out grating structure, along the positive direction of the first direction, the counterclockwise rotation angles of the grating units in the multiple first sub-regions relative to the grating units in the reference region gradually increase; along the negative direction of the first direction, the clockwise rotation angles of the grating units in the multiple second sub-regions relative to the grating units in the reference region gradually increase.

Preferably, the included angle of the two-dimensional outcoupling grating is 60 degrees, and the grating unit is a non-centrosymmetric structure.

Preferably, directions of the two-dimensional grating units in adjacent edge regions between any two adjacent regions in the plurality of regions change continuously to transition from one direction to another.

Preferably, the grating structure in the second grating region further includes a turning grating, and the turning grating is configured to expand the image light beam transmitted in the waveguide substrate toward the first direction.

According to a third aspect of the present invention, there is provided an augmented reality device, comprising: The coupling-in grating structure, or the diffraction optical waveguide described in any one of the above items.

The coupled grating structure, diffraction optical waveguide, and augmented reality device provided by the present invention can not only improve its diffraction efficiency, but also effectively increase its FOV bandwidth and effectively improve FOV uniformity by distributing the coupled grating structure differently along the surface of the waveguide substrate or along the grating depth direction.

In an optional solution of the present invention, when multiple regions are distributed along the light incident surface, at least one of the multiple grating parameters of the coupled gratings in different regions is different, and the multiple grating parameters include: grating tilt angle, grating depth, and grating duty cycle; the diffraction efficiency is higher than that of a conventional rectangular structure, and the FOV bandwidth is wider than that of an oblique tooth structure with parallel side walls, and the FOV uniformity is good. In addition, the grating structure is simple and the manufacturing process is less difficult than that of a grating with non-parallel side walls.

In an optional solution of the present invention, the coupling grating is a tilted grating, and when multiple regions of the coupling grating structure are distributed along the grating depth direction, the grating duty ratios of the coupling gratings in different regions are different, that is, the two side walls of the grating are not parallel, which has higher diffraction efficiency than that of a conventional rectangular structure, and wider FOV bandwidth and better FOV uniformity than that of an oblique tooth structure with parallel two side walls.

In an optional scheme of the present invention, after the grating structure in the first grating region couples the image light beam into the waveguide substrate, the grating structure in the second grating region can diffract and deflect the image light beam coupled into the waveguide substrate to propagate in different directions, and diffract and couple out of the waveguide substrate while propagating in different directions, forming multiple pupil expansion paths, and coupling out while expanding the pupil on the multiple pupil expansion paths, which can effectively reduce the area occupied by the entire grating to achieve personalized morphology and miniaturization.

In an optional solution of the present invention, since the orientation change of the out-coupling grating unit can obtain efficiency distributions of different diffraction orders, the out-coupling grating can be divided into different areas according to the incident direction of the image light beam, and the arrangement of the internal microstructure units of the out-coupling grating structure is optimized according to the functional requirements of different areas, which can improve the uniformity and out-coupling efficiency. For example, for the area used to achieve light beam expansion, the expansion efficiency can be effectively improved by arranging the microstructure units, and for the area used to achieve light beam outcoupling, the out-coupling efficiency can be effectively improved by arranging the microstructure units at different angles.

In an optional solution of the present invention, the out-coupling grating structure also includes a turning grating, which can expand the image light beam transmitted in the waveguide substrate in one dimension, that is, to copy and expand a single entrance pupil into a strip-shaped large-area entrance pupil, and then incident on the out-coupling grating for two-dimensional pupil expansion and out-coupling, thereby improving uniformity.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, The drawings required for use in the examples or descriptions of the prior art are briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

FIG1 is a schematic diagram of an in-coupling grating structure according to an embodiment of the present invention;

FIG2 is a schematic diagram showing a comparison of the diffraction efficiency of an in-coupled grating structure according to an embodiment of the present invention and that of a conventional ideal tilted grating as a function of FOV;

FIG3 is a schematic diagram of an in-coupling grating structure according to another embodiment of the present invention;

FIG4 is a schematic diagram of an in-coupling grating structure according to another embodiment of the present invention;

FIG5 is a schematic diagram of an in-coupling grating structure according to another embodiment of the present invention;

FIG6 is a schematic diagram of the layout of a diffraction optical waveguide in the prior art;

FIG7 is a schematic diagram of a diffractive optical waveguide according to an embodiment of the present invention;

FIG8 is a K-domain diagram of the diffraction optical waveguide coupling and expansion shown in FIG7;

FIG9 is a K-domain diagram of the diffraction optical waveguide coupled out of FIG7 ;

FIG10 is a schematic diagram of a diffractive optical waveguide according to another embodiment of the present invention;

FIG11 is a K-domain diagram of the diffraction optical waveguide coupling and expansion shown in FIG10;

FIG12 is a K-domain diagram of the diffraction optical waveguide coupled out of FIG10 ;

FIG13 is a schematic diagram of the orientation of a two-dimensional grating unit according to an embodiment of the present invention;

FIG14 is a schematic diagram of the orientation of a two-dimensional grating unit according to another embodiment of the present invention;

FIG15 is a schematic diagram of the orientation of a two-dimensional grating unit according to another embodiment of the present invention;

FIG16 is a schematic diagram of the area division and grating unit arrangement of the outcoupling grating of the diffraction optical waveguide according to an embodiment of the present invention;

FIG17 is a schematic diagram of the area division and grating unit arrangement of the outcoupling grating of the diffraction optical waveguide according to another embodiment of the present invention;

FIG18 is a schematic diagram of the area division and grating unit arrangement of the outcoupling grating of the diffraction optical waveguide according to another embodiment of the present invention;

Description of reference numerals:

1-in-coupled grating structure, 111-first part, 112-second part, 113-third part; 121-first part, 122-second part, 123-third part; 131-first part, 132-second part, 133-third part; 2-out-coupled grating structure, 21-first upper region, 22-first lower region, 23-second upper region, 24-middle region, 25-second lower region; 3-waveguide substrate, 4-turning grating, 110-first grating region Domain, 120 - second grating region.

Detailed ways

The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

In the description of the specification of the present invention, it is necessary to understand that the orientations or positional relationships indicated by the terms "upper part", "lower part", "upper end", "lower end", "lower surface", "upper surface", etc. are based on the orientations or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

In the description of the present specification, the terms "first" and "second" are used for descriptive purposes only and are not to be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features.

In the description of the present invention, "plurality" means a plurality, such as two, three, four, etc., unless otherwise clearly and specifically defined.

In the description of the present invention, unless otherwise clearly specified and limited, the term "connection" and other terms should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection, or mutual communication; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

The technical solution of the present invention is described in detail with specific embodiments below. The following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described in detail in some embodiments.

It can be understood that the image beam of the virtual content from the projector in the augmented reality display system can only be used after being coupled into the optical waveguide, so the coupling structure used to couple the image beam into the optical waveguide needs to have as high a coupling efficiency as possible. Taking the diffraction optical waveguide system as an example, the coupling structure is set to The coupling grating requires the diffraction efficiency of the coupling order of the coupling grating to be as high as possible. The current mainstream grating structure that can achieve efficient coupling is the helical tooth structure, which has higher coupling efficiency than the conventional rectangular grating structure, but its FOV bandwidth is not ideal and the FOV uniformity is not good.

In view of this, an embodiment of the present invention proposes a novel coupling grating structure, in which different parts of the coupling grating structure have different grating parameters, and the different parts are distributed along the grating depth direction.

Specifically, when different parts of the grating parameters coupled into the grating structure are distributed along the grating depth direction, the grating duty ratios of different parts of the grating coupled into the grating structure are different.

Practically, FIG1 shows a grating structure in which the grating duty cycle varies with the grating depth. The grating period of the grating structure is d, the width of the upper surface of the grating is f _top , the width of the lower surface is f _bottom , the duty cycle of the upper surface is f _top /d, the duty cycle of the lower surface is f _bottom /d, the left tilt angle is θ _left , and the right tilt angle is θ _right . In the figure, the deeper the grating depth, the greater the grating duty cycle coupled into the grating structure, that is, the two side walls of the grating structure are not parallel, and it is a tilted grating that is narrow at the top and wide at the bottom.

FIG2 shows a comparison chart of the diffraction efficiency of the narrow-at-top-and-wide-at-bottom tilted grating (solid line) of this embodiment and the existing ideal tilted grating (dashed line) as the FOV changes. It can be seen from FIG2 that the average diffraction efficiency of the narrow-at-top-and-wide-at-bottom tilted grating is comparable to that of the ideal tilted grating, but the narrow-at-top-and-wide-at-bottom tilted grating has better FOV uniformity, which can improve the FOV uniformity (min./max.) from 38% to 69%.

The change of the grating duty ratio with the grating depth may also be that the deeper the grating depth, the smaller the grating duty ratio, or it may first increase and then decrease, or it may first decrease and then increase, etc. The change of the grating duty ratio may also be discontinuous, such as a step-type change, etc. As long as the diffraction efficiency can meet the performance requirements of the optical waveguide and the grating structure can optimize the FOV bandwidth and uniformity, it is included in the scope defined by the present invention.

In the embodiment of the present invention, when different parameter settings of the coupling grating structure are distributed along the grating depth direction, the grating duty ratio or refractive index of the coupling grating at different positions is different. The grating arranged in this optional manner has a higher diffraction efficiency of the coupled diffraction order than the conventional straight tooth grating; compared with the conventional tilted grating, the diffraction efficiency of the coupled diffraction order is equivalent, but the grating arranged in this manner has a wider FOV bandwidth and better FOV uniformity.

It can be understood that the tilted grating with a grating duty ratio that varies along the grating depth direction can be realized in the process preparation, but it is difficult. In view of this, another novel coupling grating structure is proposed in the embodiment of the present invention, in which the grating parameters of different parts of the coupling grating structure are different, and the different parts are distributed along the surface of the waveguide substrate.

Specifically, when the grating parameters of the coupled grating structure are distributed at different locations along the surface of the waveguide substrate, That is, at least one of the multiple grating parameters of the grating structure in different areas on the waveguide surface is different; the multiple grating parameters include: grating tilt angle, grating depth, grating duty cycle, refractive index, etc.

In one embodiment, a grating parameter of different parts of the coupled-in grating structure is different, and other grating parameters are the same. Optionally, the grating duty ratio of different parts of the coupled-in grating structure is different, and other grating parameters are the same; or, the grating tilt angle of different parts of the coupled-in grating structure is different, and other grating parameters are the same; or, the grating depth of different parts of the coupled-in grating structure is different, and other grating parameters are the same; or, the refractive index of different parts of the coupled-in grating structure is different, and other grating parameters are the same.

In practice, one grating parameter of different parts of the coupling grating structure 1 is different, and other grating parameters are the same, specifically: the grating tilt angle, grating depth, and refractive index of the grating structure in different parts are the same, and the grating duty cycle is different. Referring to FIG3, the coupling grating structure 1 is divided into three parts: a first part 111, a second part 112, and a third part 113, and the grating duty cycles of the three parts are different.

Preferably, the grating duty cycle can vary from the upper surface duty cycle (f _top /d) to the lower surface duty cycle (f _bottom /d) of the upper narrow and lower wide tilted grating in the embodiment of FIG1. In this case, the performance of the grating structure with the grating duty cycle distributed along the surface of the waveguide substrate is equivalent to the performance of the upper narrow and lower wide tilted grating (upper surface duty cycle: f _top /d, lower surface duty cycle: f _bottom /d).

In practice, one grating parameter of different parts of the coupling grating structure 1 is different, and other grating parameters are the same, specifically: the grating depth, grating duty cycle and refractive index of the grating structure of different parts are the same, and the grating tilt angles are different. Referring to FIG4 , the coupling grating structure 1 is divided into three parts: a first part 121, a second part 122, and a third part 123, and the grating tilt angles of the three parts are different.

Preferably, the range of variation of the grating tilt angle can be from the right side tilt angle (θ _right ) to the left side tilt angle (θ _left ) of the grating that is narrow at the top and wide at the bottom in the embodiment of Figure 1 , and the performance of the grating structure with this grating tilt angle distributed along the surface of the waveguide substrate is equivalent to the performance of the tilted grating that is narrow at the top and wide at the bottom (right side tilt angle: θ _right , to left side tilt angle: θ _left ).

Practically, different parts of the coupled grating structure 1 have different grating parameters, and other grating parameters are the same, specifically: the grating tilt angle, grating duty cycle and refractive index of the grating structure in different parts are the same, and the grating depths are different; referring to Figure 5, the coupled grating structure 1 is divided into three parts: a first part 131, a second part 132, and a third part 133, and the grating depths of the three parts are different.

Practically, one grating parameter of different parts of the coupled grating structure 1 is different, and other grating parameters are the same, specifically: the grating tilt angle, grating duty cycle and grating depth of the grating structure at different parts are the same, and the refractive index is different.

It should be noted that, Figures 3-5 are used as an example for explanation of the three parts, but this is not limited to this. Different embodiments may have more or fewer parts; and the changing trend of the grating parameters is only for illustration, but this is not limited to this. In different embodiments, the grating parameters may have other changing trends.

The novel coupling grating structure distributed along the surface of the waveguide substrate at different locations proposed by the present invention can be a grating structure with parallel two side walls, which reduces the difficulty of manufacturing process compared with the inclined grating structure with the grating duty ratio changing in the grating depth direction. Moreover, the novel coupling grating structure distributed along the surface of the waveguide substrate at different locations can achieve the same level of performance as the inclined grating structure with the grating duty ratio changing in the grating depth direction through parameter modulation, including diffraction efficiency, FOV bandwidth and FOV uniformity.

It should be noted that the changing trend of the parameters of the grating structure in different parts can be a single change (i.e. gradually increasing or decreasing) or multiple changes (for example, first increasing and then decreasing, first decreasing and then increasing, first decreasing and then increasing and then decreasing, etc.), and different settings can be made according to actual needs.

In one embodiment, the parts of the coupling-in grating structure with different grating parameters are distributed along the grating direction of the coupling-in grating structure. Optionally, the closer to the coupling-out grating structure along the grating direction, the larger the grating duty cycle of the coupling-in grating structure; or, the deeper the grating depth of the coupling-in grating structure; or, the larger the grating tilt angle of the coupling-in grating structure; or, the larger the refractive index of the coupling-in grating structure.

The out-coupling grating structure is configured to couple the image light beam out of the waveguide substrate. The grating direction of the in-coupling grating structure is perpendicular to the grating line direction of the in-coupling grating structure.

As shown in Figures 3-4, the grating direction of the coupling-in grating structure 1 is the direction from the coupling-in grating structure 1 to the coupling-out grating structure 2, which is the arrangement direction of different parts of the grating parameters of the coupling-in grating structure. In addition, the arrangement direction can also be other directions or include more directions, such as a chessboard-like arrangement.

In addition, when the parts with different grating parameters proposed in the embodiment of the present invention are distributed along the surface of the waveguide substrate, the sizes of the parts along the distribution direction may be the same or different.

In the embodiment of the present invention, when different parameter settings of the coupled grating structure are distributed along the light incident surface, the grating parameters that can be set with high freedom include: grating tilt angle, grating depth, grating duty cycle, refractive index, etc. The grating set in this optional manner has a higher diffraction efficiency of the coupled diffraction order than the conventional straight tooth grating; compared with the conventional tilted grating, the diffraction efficiency of the coupled diffraction order is equivalent, but the grating set in this manner has a wider FOV bandwidth and better FOV uniformity.

In one embodiment, a diffraction optical waveguide is further provided, which includes: a waveguide substrate 3 and a first grating region located on the surface of the waveguide substrate; the first grating region includes: a coupling-in grating structure 1, please refer to Figures 3-5; the coupling-in grating structure is a coupling-in grating structure as described in any of the above embodiments.

Specifically, the diffraction optical waveguide further includes: a second grating region, and the second grating region includes: an out-coupling grating structure. The in-coupling grating structure 1 and the out-coupling grating structure 2 are respectively arranged at different positions of the waveguide substrate 3, the in-coupling grating structure 1 is configured to couple the image light beam into the waveguide substrate, and the out-coupling grating structure 2 is configured to couple the image light beam transmitted in the waveguide substrate out.

It can be understood that, as shown in the prior art "one-dimensional grating architecture" of FIG6, the image light beam S emitted by the optical machine is coupled into the optical waveguide substrate 102 through the coupling grating 101, and then expanded in one dimension through the pupil expansion grating 103 and turned to the coupling grating 104, and then expanded again in another dimension by the coupling grating 104 and coupled out into the human eye. In this grating layout mode, the turning grating will occupy an additional large morphological area, which is not conducive to the morphological personalized miniaturization design.

In view of this, preferably, in the diffraction optical waveguide of an embodiment of the present invention, the outcoupling grating structure 2 is configured to be able to diffract and deflect the image light beam coupled into the waveguide substrate to propagate in different directions and couple out, forming multiple pupil expansion paths while expanding the pupil and coupling out, which can effectively reduce the area occupied by the entire grating to achieve personalized morphology and miniaturization, please refer to Figures 7 and 10.

Specifically, the outcoupling grating structure includes: a two-dimensional outcoupling grating, wherein the angle of the two-dimensional outcoupling grating is diverse. Preferably, the angle between the grating periodic lines of the two-dimensional outcoupling grating can be any value between 20° and 90°. For example, the two-dimensional outcoupling grating can be a two-dimensional grating with an angle of 60°, or it can be an orthogonal two-dimensional grating.

For example, referring to Figures 7 and 9, the two-dimensional outcoupling grating may be a two-dimensional grating with an angle of 60°, and the two-dimensional outcoupling grating may deflect the image light beam in two directions that deviate from the positive direction of the X-axis by 60°. Referring to Figures 10 and 12, the two-dimensional outcoupling grating may also be an orthogonal two-dimensional grating, and the two-dimensional outcoupling grating may deflect the image light beam in four directions that deviate from the positive direction of the X-axis by 45° and 90°.

In some embodiments of the present invention, as shown in Figures 7 and 10, the grating structure in the second grating region also includes a turning grating 4, which is configured to expand the image light beam transmitted in the waveguide substrate in the first direction, so that the turning grating can replicate and expand the initial entrance pupil into a strip-shaped large-area entrance pupil, and then be incident on the coupling-out grating for two-dimensional pupil expansion and coupling-out, which can improve uniformity.

In some embodiments of the present invention, there is an angle between the grating direction of the turning grating and the grating direction of the coupling grating structure. Preferably, the angle between the grating direction of the turning grating and the grating direction of the coupling grating structure is in the range of: 90°≤θ≤135°. The grating direction is a direction perpendicular to the grating lines.

For example, referring to FIG7 and FIG8 , the grating direction of the coupled grating structure is the positive direction of the X axis. The angle between the grating direction of the turning grating and the grating direction of the coupled grating structure can be 120°, and the image light beam is deflected to propagate in a direction that deviates from the negative direction of the Y-axis by a certain angle; referring to Figures 10 and 11, the grating direction of the coupled grating structure is the positive direction of the X-axis, and the angle between the grating direction of the turning grating and the grating direction of the coupled grating structure can be 135°, and the image light beam is deflected to propagate in the negative direction of the Y-axis.

In some embodiments of the present invention, the turning grating 4 and the two-dimensional outcoupling grating 2 may be continuous. In this case, the grating direction of the turning grating 4 should be the same as one of the grating directions (direction 1) of the two-dimensional outcoupling grating 2, and the grating period of the turning grating 4 is consistent with the grating period of the grating direction (direction 1).

In some embodiments of the present invention, the turning grating 4 is discontinuous with the two-dimensional outcoupling grating 2. After the image light beam coupled into the waveguide substrate is acted upon by the expansion grating, a portion of it will propagate in the deflected direction, and a portion of it will continue to propagate in the original direction. The light beam deflected by an even number of diffractions will reach the outcoupling region, and the light beam deflected by an odd number of diffractions will propagate in the deflected direction. The discontinuity between the turning grating and the outcoupling grating can prevent the light beam propagating in the deflected direction (the light beam propagating in the dotted line direction in FIGS. 7 and 10 ) from directly touching the outcoupling region and causing crosstalk.

In practice, the smaller the angle between the grating direction of the turning grating and the grating direction of the coupling-in grating structure (positive direction of the X-axis), the larger the spacing between the turning grating and the two-dimensional coupling-out grating. When the spacing between the turning grating 4 and the two-dimensional coupling-out grating is far, the selection of the grating direction and period of the turning grating is more flexible.

It can be understood that in the augmented reality display system, the image light beam of the virtual content from the projector is coupled into the optical waveguide and then coupled out by the coupling structure into the human eye. Based on the requirement of image uniformity, the coupling structure used to couple the image light beam out of the optical waveguide needs to have the best possible coupling uniformity.

In view of this, an embodiment of the present invention proposes a novel two-dimensional grating structure, which is used as a two-dimensional outcoupling grating in the second grating region. The two-dimensional outcoupling grating includes a plurality of grating units. Along a first direction, the second grating region is divided into a plurality of regions, and the grating units in different regions have different orientations; wherein the first direction is a direction different from the advancing direction of the image light beam in the waveguide substrate.

The forward direction of the image light beam in the waveguide substrate is the forward direction of the image light beam from the first grating region to the two-dimensional out-coupling grating in the waveguide substrate after being coupled into the waveguide substrate, or when a turning grating is present, the forward direction of the image light beam from the waveguide substrate to the two-dimensional out-coupling grating after being turned by the turning grating. The first direction is a direction different from the forward direction, and preferably, the first direction is a direction orthogonal to the forward direction. It should be noted that the light beam transmitted in the waveguide substrate is not a completely collimated light beam, so the forward direction of the light beam is not an absolute unique direction. When the second grating region is divided into multiple regions along the first direction, it is not limited to the boundary line between the divided regions being orthogonal to the first direction, nor is it limited to The boundary lines between the regions are parallel to each other, and the divided regions only need to be arranged substantially along the first direction.

It should be noted that the two-dimensional grating has diffraction orders in multiple directions, and the diffraction efficiencies of different diffraction orders are different. The diffraction efficiency distribution is related to the grating unit of the two-dimensional grating. For example, the change of the orientation of the grating unit will cause the diffraction efficiency distribution of the multiple diffraction orders to change. For another example, the change of the shape of the grating unit will also cause the diffraction efficiency distribution of the multiple diffraction orders to change.

In practice, the shape of the grating unit may be a non-centrosymmetrical shape such as a rhombus or an ellipse.

Optionally, the shape of the grating units in the first changing region and/or the second changing region may be the same as or different from the shape of the grating units in the reference region. For example, the shape of the grating units in the reference region is diamond-shaped, and the shapes of the grating units in the first changing region and the second changing region are elliptical.

Specifically, the following takes the case where the coupling-in is located on the left side of the coupling-out, the angle of the two-dimensional grating is 60°, and the shape of the grating unit is a rhombus as an example to explain the change in the diffraction efficiency distribution caused by the change in the orientation of the grating unit. Referring to FIG13 , the diagonal major axis of the grating unit of the two-dimensional grating shown in the figure is along the X direction, and the two-dimensional grating can be equivalent to the overlap of two groups of one-dimensional gratings K1 and K2. The diffraction efficiency of the R1 diffraction order of the light beam incident along direction 1 under the action of the K1/K2 grating (i.e., the expansion efficiency along the X-axis deflection of plus or minus 60°) is about 5.5%, and the efficiency of the out-coupling diffraction order under the action of the K0 grating is about 0.2%.

The two-dimensional grating in FIG13 is rotated counterclockwise, and the diffraction efficiency of the R1 diffraction order under the action of the K1/K2 grating changes. The diffraction efficiency of the R1 diffraction order under the action of the K1 grating is greater than the diffraction efficiency of the R1 diffraction order under the action of the K2 grating, and the greater the rotation angle, the greater the difference between the two. For example, after the two-dimensional grating in FIG13 is rotated counterclockwise by 60°, as shown in FIG14, the two-dimensional grating can be equivalent to the overlap of two groups of one-dimensional gratings K0 and K2. The expansion efficiency of the light beam incident along direction 1 is higher when it is deflected 60° counterclockwise along the X axis than when it is deflected 60° clockwise along the X axis; and the efficiency of the light beam incident along directions 1 and 2 coupled out through the grating can be increased to about 2%.

The two-dimensional grating in FIG13 is rotated clockwise, and the diffraction efficiency of the R1 diffraction order under the action of the K1/K2 grating changes. The diffraction efficiency of the R1 diffraction order under the action of the K2 grating is greater than the diffraction efficiency of the R1 diffraction order under the action of the K1 grating, and the greater the rotation angle, the greater the difference between the two. For example, after the two-dimensional grating in FIG13 is rotated clockwise by 60°, as shown in FIG15, the two-dimensional grating can be equivalent to the overlap of two groups of one-dimensional gratings K0 and K1. The expansion efficiency of the light beam incident along direction 1 is lower than the expansion efficiency of the light beam incident along direction 1 and direction 3. The efficiency of the light beam coupled out through the grating can be increased to about 2%.

It is understandable that different outcoupling areas have different beam sources, pupil expansion requirements, and outcoupling requirements. The out-coupling partition can be performed according to the beam source, pupil expansion requirements, and out-coupling requirements at each position of the out-coupling area. In practice, the multiple areas of the second grating area include a reference area, and a first change area adjacent to the reference area along the positive direction of the first direction, and/or a second change area adjacent to the reference area along the negative direction of the first direction; wherein the reference area is a portion of the second grating area pointed to by the grating direction of the grating structure in the first grating area; the diffraction efficiency of diffraction propagation to both sides in the reference area is equivalent, the diffraction efficiency of the first change area and the second change area deflected toward the reference area is greater than the diffraction efficiency of the diffraction propagation deflected away from the reference area, and/or the out-coupling efficiency of the reference area is lower than the out-coupling efficiency of the first change area and the second change area.

Specifically, when the first grating region is located on the left side of the second grating region, the orientation of the grating unit in the first changing region is consistent with the orientation of the grating unit in the reference region after clockwise rotation, so that the diffraction efficiency of the diffraction propagation deflected toward the reference region in the first changing region is greater than the diffraction efficiency of the diffraction propagation deflected away from the reference region; the orientation of the grating unit in the second changing region is consistent with the orientation of the grating unit in the reference region after counterclockwise rotation, so that the diffraction efficiency of the diffraction propagation deflected toward the reference region in the second changing region is greater than the diffraction efficiency of the diffraction propagation deflected away from the reference region; and the coupling efficiency of the reference region is relatively lower than the coupling efficiency of the first changing region and the second changing region. When the first grating region is located on the right side of the second grating region, the orientation of the grating unit in the first changing region is consistent with the orientation of the grating unit in the reference region after counterclockwise rotation, so that the diffraction efficiency of the diffraction propagation deflected toward the reference region in the first changing region is greater than the diffraction efficiency of the diffraction propagation deflected away from the reference region; the orientation of the grating unit in the second changing region is consistent with the orientation of the grating unit in the reference region after clockwise rotation, so that the diffraction efficiency of the diffraction propagation deflected toward the reference region in the second changing region is greater than the diffraction efficiency of the diffraction propagation deflected away from the reference region; and the out-coupling efficiency of the reference region is relatively lower than the out-coupling efficiency of the first changing region and the second changing region. Wherein, the counterclockwise rotation angle and the clockwise rotation angle are both less than 90 degrees.

It should be noted that the main source light beam of the part of the second grating area pointed by the grating direction of the coupling-in grating structure has undergone fewer pupil expansion times and higher light energy. The pupil expansion demand of this part of the area is higher than the coupling-out demand, and the pupil expansion efficiency requirements on both sides are not much different; the main source light beam of the remaining part of the second grating area has undergone more pupil expansion times and more light energy attenuation. The coupling-out demand of this part of the area is higher than the pupil expansion demand, and there is a difference in the pupil expansion efficiency requirements on both sides. Therefore, the part of the second grating area pointed by the grating direction of the coupling-in grating structure is usually used as the reference area, and the two-dimensional grating units are arranged in a direction with uniform pupil expansion efficiency on both sides. The grating unit orientation arrangement of the area on one or both sides of the reference area is adjusted according to actual functional requirements.

For example, assuming that the light beam is transmitted from left to right, if there is a remaining second out-coupling area above the reference area, the orientation of the two-dimensional grating unit in this area is the result of rotating the two-dimensional grating unit orientation of the reference area clockwise; if there is a remaining second out-coupling area below the reference area, the orientation of the two-dimensional grating unit in this area is the result of rotating the two-dimensional grating unit orientation of the reference area counterclockwise.

Optionally, the orientation of the two-dimensional grating units in the edge area adjacent to any two adjacent areas in the plurality of areas of the second grating area changes continuously to transition from one direction to another. For example, area 1 and area 2 of the second grating area are adjacent, the orientation of the two-dimensional grating in area 1 is direction 1, and the orientation of the grating in area 2 is direction 2, that is, the orientation of the two-dimensional grating units at the main body position of area 1 is direction 1, and the orientation of the two-dimensional grating units at the main body position of area 2 is direction 2; in the edge area adjacent to area 1 and area 2, along the direction from area 1 to area 2, the orientation of the two-dimensional grating units changes continuously to transition from direction 1 to direction 2.

Further, it can be implemented that the first change region is divided into a plurality of sub-regions along the first direction, and when the light beam is transmitted from left to right, along the positive direction of the first direction, the clockwise rotation angle of the grating units in the plurality of sub-regions relative to the grating units in the reference region gradually increases. In this way, in the sub-regions of the first change region along the positive direction of the first direction, the difference between the diffraction efficiency of the diffraction propagation deflected to the reference region and the diffraction efficiency of the diffraction propagation deflected away from the reference region gradually increases, and the coupling efficiency gradually increases, thereby meeting the functional requirements of the first change region. The second change region is divided into a plurality of sub-regions along the first direction, and when the light beam is transmitted from left to right, along the negative direction of the first direction, the counterclockwise rotation angle of the grating units in the plurality of sub-regions relative to the grating units in the reference region gradually increases. In this way, in the sub-regions of the second change region along the negative direction of the first direction, the difference between the diffraction efficiency of the diffraction propagation deflected to the reference region and the diffraction efficiency of the diffraction propagation deflected away from the reference region gradually increases, and the coupling efficiency gradually increases, thereby meeting the functional requirements of the first change region. It can be understood that when the light beam is transmitted from right to left, the rotation direction is opposite.

The following uses two grating layout architectures as examples for explanation.

In one embodiment, taking the left-side upward projection grating layout architecture as an example, as shown in FIGS. 16 and 17 , the positive direction of the X-axis is approximately regarded as the advancing direction of the image beam, the first direction is the Y direction, and along the first direction, the second grating area is divided into two areas: a first upper area 21 and a first lower area 22. Specifically, the first upper area is the part of the second grating area pointed to by the grating direction of the grating structure in the first grating area, which is a reference area, and a grating unit arrangement with uniform pupil expansion efficiency on both sides and relatively low outcoupling efficiency is selected, and the orientation of the two-dimensional grating unit in the first lower area is the direction of the two-dimensional grating unit in the first upper area after being rotated counterclockwise by a certain angle, so that the upward pupil expansion efficiency in this area is higher than the downward pupil expansion efficiency. The pupil efficiency is improved, and the coupling-out efficiency is improved. For example, as shown in FIG16, the first upper region 21 uses the grating unit arrangement shown in FIG13, and the first lower region 22 uses the grating unit arrangement shown in FIG14. For another example, as shown in FIG17, the first upper region 21 uses the grating unit arrangement shown in FIG13, and the first lower region 22 uses the grating unit orientation arrangement shown in FIG14, but the shape is elliptical. Wherein, practicably, the first upper region 21 and the first lower region 22 respectively use the grating unit arrangement shown in FIG14 and FIG13, which means that the main region (middle region) uses the grating arrangement, and the orientation of the two-dimensional grating unit in the adjacent edge region between the first upper region 21 and the first lower region 22 continuously changes to transition from the direction shown in FIG14 to the direction shown in FIG13.

It can be understood that for the left-side upward projection grating layout architecture, the upper area of the second grating area, namely the first upper area 21, is mainly used to achieve two-dimensional expansion, and the incident light (the expanded light beam from the left turning grating area) mainly includes one direction, so the arrangement of the microstructure units in this area adopts the method shown in Figure 13 to effectively improve the expansion efficiency. The lower area of the second grating area, namely the first lower area 22, is mainly used to achieve light beam outcoupling. Since the incident light (the expanded light beam from the middle outcoupling area and the expanded light beam from the left turning grating area) mainly includes two directions, the arrangement of the grating units in this area adopts the method shown in Figure 14 to effectively improve the outcoupling efficiency and effectively expand the pupil.

In one embodiment, taking the left-side center-projection grating layout architecture as an example, as shown in FIG18, the second grating area can be divided into three areas in sequence along the first direction: the second upper area 23, the middle area 24, and the second lower area 25, please refer to FIG18. Specifically, the middle area is a reference area, and a grating unit arrangement with uniform pupil expansion efficiency on both sides is selected. The orientation of the two-dimensional grating unit in the second upper area is obtained by rotating the orientation of the two-dimensional grating unit in the middle area clockwise by a certain angle, and the orientation of the two-dimensional grating unit in the second lower area is obtained by rotating the orientation of the two-dimensional grating unit in the middle area counterclockwise by a certain angle. For example, the middle area 24 uses the grating unit arrangement shown in FIG13, so that the pupil expansion efficiency on both sides in this area is uniform, and the coupling-out efficiency is relatively low. The second upper area 23 uses the grating unit arrangement shown in FIG15, so that the downward pupil expansion efficiency in this area is higher than the upward pupil expansion efficiency, and the coupling-out efficiency is improved. The second lower area 25 uses the grating unit arrangement shown in FIG14, so that the upward pupil expansion efficiency in this area is higher than the downward pupil expansion efficiency, and the coupling-out efficiency is improved. Wherein, it can be implemented that the second upper region 23, the middle region 24, and the second lower region 25 respectively select the grating unit arrangement shown in Figures 15, 13, and 14, which means that the main region (middle region) selects the grating arrangement, and the direction of the two-dimensional grating unit in the adjacent edge region between the second upper region 23 and the middle region 24 changes continuously to transition from the direction shown in Figure 15 to the direction shown in Figure 13, and the direction of the two-dimensional grating unit in the adjacent edge region between the middle region 24 and the second lower region 25 changes continuously. Continuously change to transition from the direction shown in FIG. 13 to the direction shown in FIG. 14 .

It can be understood that for the left-side center-projection grating layout architecture, the middle area of the second grating area, namely the middle area 24, is mainly used to achieve two-dimensional expansion. The incident light (the expanded light beam from the left turning grating area) mainly includes one direction, and the arrangement of the microstructure units in this area adopts the method shown in Figure 13 to effectively improve the expansion efficiency. The upper area of the second grating area, namely the second upper area 23, is mainly used to achieve beam outcoupling. Since the incident light (the expanded light beam from the middle outcoupling area and the expanded light beam from the left turning grating area) mainly includes two directions, the arrangement of the microstructure units in this area adopts the method shown in Figure 15 to effectively improve the outcoupling efficiency and effective pupil expansion. The lower area of the second grating area, namely the second lower area 25, is mainly used to achieve beam outcoupling. Since the incident light (the expanded light beam from the middle outcoupling area and the expanded light beam from the left turning grating area) mainly includes two directions, the arrangement of the grating units in this area adopts the method shown in Figure 14 to effectively improve the outcoupling efficiency and effective pupil expansion.

In another embodiment, for the side-up projection grating layout architecture, along the first direction, the second grating area can also be divided into three areas: upper, middle and lower. However, the upper and lower areas are asymmetrically distributed, and their rotation angles are also asymmetrical. The deflection angle value of the upper part is smaller than the deflection angle value of the lower part.

In the above-mentioned examples of the partition of the second grating area of the side-up projection grating layout architecture and the side-center projection grating layout architecture, the angle rotation step is 60 degrees, which is a large value. In different embodiments, the rotation angle can also be continuously changed with a smaller step size, in which case the first change area is divided into a plurality of sub-areas, such as rotating counterclockwise by 1 degree, 2 degrees, 3 degrees until 60 degrees, or the second change area is divided into a plurality of sub-areas, such as rotating clockwise by 1 degree, 2 degrees, 3 degrees until 60 degrees.

In different embodiments, the second grating area may be divided in other ways. However, no matter how the second grating area is divided, the grating units in different areas may be arranged according to the above principles.

In addition, the grating depth and grating duty cycle in the second grating region can be gradually modulated so that the diffraction efficiency of the two-dimensional grating in the two-dimensional grating region gradually increases as it gradually moves away from the first grating region. For example, the depth of the two-dimensional grating in the two-dimensional grating region gradually increases as it gradually moves away from the first grating region.

In one embodiment, an augmented reality device is further provided, comprising: the coupling-in grating structure described in any of the above embodiments, or a diffraction optical waveguide comprising the coupling-in grating structure described in any of the above embodiments.

In one embodiment, the augmented reality device may further include: a device body and an optical machine, wherein the device body is used to carry the diffraction optical waveguide and the optical machine; and the optical machine is used to project the image light beam.

In one embodiment, the device body can be implemented as a glasses frame, wherein the glasses frame includes a beam portion and a temple portion, and the temple portion extends backward from at least one of the left and right sides of the beam portion, wherein the diffraction optical waveguide is correspondingly arranged on the beam portion.

In one embodiment, the device body can also be implemented as a windshield, and the diffraction light waveguide is correspondingly arranged on the inner side of the windshield, so that the image light beam projected by the optical machine is projected onto the windshield to form a virtual image after being transmitted through the diffraction light waveguide.

In the description of this specification, the description with reference to the terms "an implementation", "an example", "a specific implementation process", "an example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

An incoupling grating structure, characterized in that it is configured to couple an image beam into a waveguide substrate;

The grating parameters of different parts of the coupling grating structure are different;

The different locations are distributed along the surface of the waveguide substrate or along the depth direction of the grating.
The coupling-in grating structure according to claim 1, characterized in that when the different parts are distributed along the surface of the waveguide substrate, at least one grating parameter among the multiple grating parameters of the different parts of the coupling-in grating structure is different;

The multiple grating parameters include: grating tilt angle, grating depth, grating duty cycle, and refractive index.
The coupling-in grating structure according to claim 2 is characterized in that one grating parameter of different parts of the coupling-in grating structure is different, and other grating parameters are the same.
The coupling grating structure according to claim 3 is characterized in that one grating parameter of different parts of the coupling grating structure is different, and other grating parameters are the same, specifically:

The grating duty ratios of different parts of the coupled grating structure are different, and other grating parameters are the same;

Alternatively, the grating inclination angles of different parts of the coupling-in grating structure are different, and other grating parameters are the same;

Alternatively, the grating depths of different parts of the coupling grating structure are different, and other grating parameters are the same;

Alternatively, the refractive indices of different parts of the coupling-in grating structure are different, and other grating parameters are the same.
The coupling-in grating structure according to claim 1 is characterized in that the different parts are distributed along the grating direction of the coupling-in grating structure.
The coupling-in grating structure according to claim 5, characterized in that the closer to the coupling-out grating structure along the grating direction, the larger the grating duty cycle of the coupling-in grating structure;

Wherein, the outcoupling grating structure is configured to be able to couple the image light beam out of the waveguide substrate.
The coupling-in grating structure according to claim 1 is characterized in that when the different parts are distributed along the grating depth direction, the grating duty ratios of different parts of the coupling-in grating structure are different.
The coupling-in grating structure according to claim 7 is characterized in that the deeper the grating depth is, the larger the grating duty cycle of the coupling-in grating structure is.
A diffraction optical waveguide, characterized in that it comprises: a waveguide substrate and a first grating region located on the surface of the waveguide substrate;

The first grating region includes: the coupling-in grating structure according to any one of claims 1 to 8.
The diffractive optical waveguide according to claim 9, further comprising: a second grating region located on the surface of the waveguide substrate;

The grating structure in the second grating region is used to diffract and deflect the image light beam coupled into the waveguide substrate to propagate in different directions, and diffract and couple out of the waveguide substrate when propagating in different directions.
The diffraction optical waveguide according to claim 10, characterized in that the grating structure in the second grating region comprises a two-dimensional outcoupling grating, the two-dimensional outcoupling grating comprises a plurality of grating units, and along the first direction, the two-dimensional outcoupling grating is divided into a plurality of regions, and the grating units in different regions have different orientations;

The first direction is a direction different from a traveling direction of the image light beam in the waveguide substrate.
The diffraction optical waveguide according to claim 11, characterized in that the multiple regions include a reference region; the reference region is a region where the two-dimensional out-coupling grating is located, where the grating direction of the in-coupling grating structure points; the diffraction efficiency of diffraction propagation to both sides in the reference region is equivalent;

The multiple regions also include: a first change region adjacent to the reference region along the positive direction of the first direction, and/or a second change region adjacent to the reference region along the negative direction of the first direction; wherein the diffraction efficiency of the first change region and the second change region when diffracting and propagating deflected toward the reference region is greater than the diffraction efficiency of the first change region and the second change region when diffracting and propagating deflected away from the reference region.
The diffractive optical waveguide according to claim 11, characterized in that the plurality of regions include a reference region, a first change region adjacent to the reference region along a positive direction of the first direction, and/or a second change region adjacent to the reference region along a negative direction of the first direction;

The reference region is a region where the two-dimensional out-coupling grating is located, pointed to by the grating direction of the in-coupling grating structure; and the out-coupling efficiency of the reference region is lower than the out-coupling efficiency of the first changing region and the second changing region.
The diffractive optical waveguide according to claim 12 or 13, characterized in that, when the coupling-in grating structure is located on the left side of the coupling-out grating structure, the orientation of the grating unit in the first changing region is consistent with the orientation of the grating unit in the reference region after being rotated clockwise, and the orientation of the grating unit in the second changing region is consistent with the orientation of the grating unit in the reference region after being rotated counterclockwise;

When the coupling-in grating structure is located on the right side of the coupling-out grating structure, the orientation of the grating unit in the first changing region is consistent with the orientation of the grating unit in the reference region after being rotated counterclockwise, and the orientation of the grating unit in the second changing region is consistent with the orientation of the grating unit in the reference region after being rotated clockwise. The direction of the rear is consistent;

Wherein, the counterclockwise rotation angle and the clockwise rotation angle are both less than 90 degrees.
The diffraction optical waveguide according to claim 12, characterized in that the first change region is divided into a plurality of first sub-regions along the first direction, and along the positive direction of the first direction, the difference between the diffraction efficiency of the first sub-regions diffracting and propagating toward the reference region and the diffraction efficiency of the first sub-regions diffracting and propagating away from the reference region gradually increases;

The second change region is divided into a plurality of second sub-regions along the first direction. Along the negative direction of the first direction, the difference between the diffraction efficiency of the second sub-regions deflected toward the reference region and the diffraction efficiency of the second sub-regions deflected away from the reference region gradually increases.
The diffractive optical waveguide according to claim 12, characterized in that the first changing region is divided into a plurality of first sub-regions along the first direction, and the outcoupling efficiency of the first sub-regions gradually increases along the positive direction of the first direction;

The second change region is divided into a plurality of second sub-regions along the first direction, and the coupling-out efficiency of the second sub-regions gradually increases along the negative direction of the first direction.
The diffractive optical waveguide according to claim 15 or 16, characterized in that, when the coupling-in grating structure is located on the left side of the coupling-out grating structure, along the positive direction of the first direction, the clockwise rotation angles of the grating units in the multiple first sub-regions relative to the grating units in the reference region gradually increase; along the negative direction of the first direction, the counterclockwise rotation angles of the grating units in the multiple second sub-regions relative to the grating units in the reference region gradually increase;

When the coupling-in grating structure is located on the right side of the coupling-out grating structure, along the positive direction of the first direction, the counterclockwise rotation angles of the grating units in the multiple first sub-regions relative to the grating units in the reference region gradually increase; along the negative direction of the first direction, the clockwise rotation angles of the grating units in the multiple second sub-regions relative to the grating units in the reference region gradually increase.
The diffraction optical waveguide according to claim 11, characterized in that the angle of the two-dimensional outcoupling grating is 60 degrees, and the grating unit is a non-centrosymmetric structure.
The diffractive optical waveguide according to claim 11, characterized in that the orientation of the two-dimensional grating units in the adjacent edge regions between any two adjacent regions among the plurality of regions changes continuously to transition from one direction to another.
The diffraction optical waveguide according to claim 10, characterized in that the grating structure in the second grating region further comprises a turning grating, and the turning grating is configured to be able to The image light beam transmitted in the substrate expands toward the first direction.
An augmented reality device, characterized in that it comprises: the coupling grating structure as described in any one of claims 1 to 8, or the diffraction optical waveguide as described in any one of claims 9 to 20.