Out-coupling grating structures and diffractive optical waveguides, augmented reality devices

Abstract

This invention provides a coupling grating structure, a diffracting waveguide, and an augmented reality device. The coupling grating structure is configured to diffract and couple an image beam transmitted in a waveguide substrate from the waveguide substrate. It includes a two-dimensional coupling grating comprising multiple grating units. The transverse cross-section of each grating unit includes an outer contour and an inner contour. Both the outer and inner contours are closed structures, with the inner contour located inside the outer contour. The refractive index between the inner and outer contours is a first refractive index, and the refractive index inside the inner contour is a second refractive index. The first and second refractive indices are not equal. At least two grating units have inner contours positioned differently relative to their outer contours. This invention specifically improves the diffraction efficiency of the effective utilization order, thereby improving light energy utilization and uniformity.

Description

Technical Field

[0001] This invention relates to the field of AR technology, and more particularly to a coupled-out grating structure, a diffractive waveguide, and an augmented reality device. Background Technology

[0002] Augmented reality (AR) is a technology that blends the real world with virtual information. An AR display system typically includes a micro-projector and an optical display screen. The micro-projector provides virtual content for the AR display system, which is then projected onto the viewer's eyes through the optical display screen. The optical display screen is usually a transparent optical component, allowing the user to see the real world through it at the same time.

[0003] Optical waveguides are one implementation path for optical displays. When the refractive index of the transmission medium is greater than that of the surrounding medium and the angle of incidence in the waveguide is greater than the critical angle for total internal reflection, light can propagate without leakage within the waveguide, resulting in total internal reflection. After the beam of virtual content from the projector is coupled into the waveguide, the beam can continue to propagate without loss within the waveguide to transmit the virtual content until it is coupled out by subsequent optical structures. Currently, optical waveguides on the market are generally divided into geometric array waveguides and diffractive waveguides. Diffractive waveguides are further divided into volume holographic waveguides and surface relief grating waveguides. Surface relief grating waveguides, with their extremely high design freedom and mass production capability brought about by nanoimprint processing, have significant advantages among many solutions.

[0004] Most diffractive waveguides couple the light beam out of the waveguide through grating diffraction. The grating unit of the coupling grating has multiple diffraction orders in multiple directions. Symmetrical diffraction orders among these orders usually have the same diffraction efficiency. However, the number of orders that are effectively utilized may differ at different locations in the coupling region. This results in wasted orders in these regions, leading to poor light energy utilization efficiency. Summary of the Invention

[0005] This invention provides a coupled grating structure, a diffractive waveguide, and an augmented reality device to solve the problem of poor light energy utilization efficiency in the prior art.

[0006] To solve the above-mentioned technical problems, the present invention is achieved through the following technical solution:

[0007] According to a first aspect of the invention, a coupling grating structure is provided, which is configured to diffract and couple an image beam transmitted in a waveguide substrate out of the waveguide substrate;

[0008] The coupled-out grating structure includes: a two-dimensional coupled-out grating, wherein the two-dimensional coupled-out grating includes multiple grating units;

[0009] The transverse section of the grating unit includes an outer contour and an inner contour; both the outer contour and the inner contour are closed structures, and the inner contour is located inside the outer contour.

[0010] The refractive index between the inner contour and the outer contour is a first refractive index, and the refractive index inside the inner contour is a second refractive index. The first refractive index and the second refractive index are not equal.

[0011] At least two of the grating units have different positions of their inner contours relative to their outer contours.

[0012] Preferably, along the first direction, the two-dimensional coupling grating is divided into multiple regions; along the first direction, the inner contour is positioned differently relative to the outer contour in different regions;

[0013] The first direction is a direction that is different from the direction of propagation of the image beam within the waveguide substrate.

[0014] Preferably, the plurality of regions includes a reference region; the reference region is the area where the two-dimensional coupling grating is located, which is pointed to by the direction of light propagation in the central field of view; the diffraction efficiency of the light propagating to both sides within the reference region is equivalent;

[0015] The plurality of regions further includes: a first variation region adjacent to the reference region along the positive direction of the first direction, and / or a second variation region adjacent to the reference region along the negative direction of the first direction; wherein the diffraction efficiency of the first variation region and the second variation region when diffracting towards the reference region is greater than the diffraction efficiency when diffracting away from the reference region.

[0016] Preferably, when the second refractive index is less than the first refractive index: the position of the inner contour of the grating unit in the first variation region relative to the outer contour, relative to the position of the inner contour of the grating unit in the reference region relative to the outer contour, deviates in the positive direction of the first direction; the position of the inner contour of the grating unit in the second variation region relative to the outer contour, relative to the position of the inner contour of the grating unit in the reference region relative to the outer contour, deviates in the negative direction of the first direction.

[0017] When the second refractive index is greater than the first refractive index: the position of the inner contour of the grating unit in the first variation region relative to the outer contour, relative to the position of the inner contour of the grating unit in the reference region relative to the outer contour, deviates in the negative direction of the first direction; the position of the inner contour of the grating unit in the second variation region relative to the outer contour, relative to the position of the inner contour of the grating unit in the reference region relative to its corresponding outer contour, deviates in the positive direction of the first direction.

[0018] Preferably, the first variation region is divided into multiple 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-region deflected towards the reference region and the diffraction efficiency deflected away from the reference region gradually increases.

[0019] The second variation region is divided into multiple 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 towards the reference region and the diffraction efficiency deflected away from the reference region gradually increases.

[0020] Preferably, when the second refractive index is less than the first refractive index: along the positive direction of the first direction, the position of the inner contour of the grating unit in the first variation region relative to the outer contour, relative to the position of the inner contour of the grating unit in the reference region relative to the outer contour, gradually deviates in the positive direction of the first direction; along the negative direction of the first direction, the position of the inner contour of the grating unit in the second variation region relative to the outer contour, relative to the position of the inner contour of the grating unit in the reference region relative to the outer contour, gradually deviates in the negative direction of the first direction.

[0021] When the second refractive index is greater than the first refractive index: along the positive direction of the first direction, the position of the inner contour of the grating unit in the first variation region relative to the outer contour, relative to the position of the inner contour of the grating unit in the reference region relative to the outer contour, gradually deviates towards the negative direction of the first direction; along the negative direction of the first direction, the position of the inner contour of the grating unit in the second variation region relative to the outer contour, relative to the position of the inner contour of the grating unit in the reference region relative to the outer contour, gradually deviates towards the positive direction of the first direction.

[0022] Preferably, the inner contour includes multiple straight edges and multiple curved edges, wherein the straight edges and curved edges are connected sequentially at intervals; and / or,

[0023] The outer contour includes: multiple straight edges and multiple curved edges, wherein the straight edges and curved edges are connected sequentially at intervals.

[0024] Preferably, the angle between the extensions of two adjacent straight edges of the outer contour is less than 180°, and the angle between the extensions of two adjacent straight edges of the inner contour is less than 180°.

[0025] Preferably, the inner contour curved edge and the outer contour curved edge are circular arc edges or elliptical arc edges.

[0026] Preferably, the radii of curvature of the inner contour and the outer contour are any values ​​between 30nm and 300nm.

[0027] Preferably, the included angle of the grating period lines of the two-dimensional coupled grating is any value between 20° and 90°.

[0028] According to a second aspect of the present invention, a diffractive optical waveguide is provided, comprising the coupling grating structure described in any of the preceding claims.

[0029] According to a third aspect of the present invention, an augmented reality device is provided, which includes the coupling grating structure described in any of the preceding claims.

[0030] The present invention provides a coupled grating structure, a diffractive waveguide, and an augmented reality device. The grating unit includes an inner contour and an outer contour. The refractive index between the inner contour and the outer contour is different from the refractive index inside the inner contour. In addition, the inner contour of at least two grating units has a different position relative to the outer contour. When the inner contour is at a different position relative to the outer contour, the distribution of diffraction efficiency between different orders is also different. The position of the inner contour relative to the outer contour can be set according to the order that needs to be utilized in the region, so that the diffraction efficiency of the effectively utilized order is improved, thereby improving the light energy utilization efficiency.

[0031] Furthermore, by using at least two grating units with different inner contours relative to outer contours, different settings can be achieved for the diffraction efficiency distribution of multiple diffraction orders in different regions. In regions where pupil expansion is required, the diffraction efficiency for pupil expansion can be increased, and in regions where coupling is required, the diffraction efficiency for coupling can be increased, thereby improving coupling uniformity.

[0032] In one alternative embodiment of the present invention, from one coupling region to another, the position of the inner contour relative to the outer contour gradually deviates and gradually transitions, further improving the coupling uniformity of the grating.

[0033] In one optional embodiment of the present invention, the two straight edges of the inner contour are connected by curved edges of the inner contour, and / or the two straight edges of the outer contour are connected by curved edges of the outer contour. Compared with using straight edges at the connection, using curved edges is easier to manufacture, simpler to manufacture, and more closely matches the actual finished product. Attached Figure Description

[0034] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0035] Figure 1 This is a top view of a grating unit of a coupling grating structure according to an embodiment of the present invention;

[0036] Figure 2 This is a cross-sectional view of a grating unit of a coupling grating structure according to an embodiment of the present invention;

[0037] Figure 3 This is a partial grating unit arrangement diagram of a coupling grating structure according to an embodiment of the present invention;

[0038] Figure 4 This is a schematic diagram of the diffraction order of a grating unit in a coupling grating structure according to an embodiment of the present invention;

[0039] Figure 5 This is a schematic diagram of the diffraction order of another grating unit in a coupling grating structure according to an embodiment of the present invention;

[0040] Figure 6 This is a schematic diagram of the diffraction order of another grating unit in a coupling grating structure according to an embodiment of the present invention;

[0041] Figure 7 This is a schematic diagram of the coupling grating structure according to an embodiment of the present invention;

[0042] Figure 8 This is a schematic diagram of the coupling grating structure according to another embodiment of the present invention;

[0043] Figure 9 This is a schematic diagram of the coupling grating structure according to another embodiment of the present invention;

[0044] Figure 10 This is a schematic diagram of the coupling grating structure according to another embodiment of the present invention;

[0045] Figure 11 This is a schematic diagram of the outer or inner contour of a grating unit in a coupling grating structure according to another embodiment of the present invention.

[0046] Figure 12 This is a schematic diagram of the outer or inner contour of a grating unit in a coupling grating structure according to another embodiment of the present invention.

[0047] Figure 13 This is a schematic diagram of the outer or inner contour of a grating unit in a coupling grating structure according to another embodiment of the present invention.

[0048] Figure 14 This is a schematic diagram of the outer or inner contour of a grating unit in a coupling grating structure according to another embodiment of the present invention.

[0049] Figure 15 This is a schematic diagram of the outer or inner contour of a grating unit in a coupling grating structure according to another embodiment of the present invention.

[0050] Figure 16 This is a schematic diagram of a grating unit of a coupling grating structure according to an embodiment of the present invention;

[0051] Figure 17 This is a schematic diagram of a grating unit of a coupling grating structure according to another embodiment of the present invention;

[0052] Figure 18 This is a schematic diagram of a grating unit of a coupling grating structure according to another embodiment of the present invention;

[0053] Explanation of reference numerals in the attached figures:

[0054] 1-grating unit,

[0055] 11-Outer contour,

[0056] 12-Inner contour;

[0057] 21-First Upper Region

[0058] 22-First Middle Area,

[0059] 23-First Lower Region;

[0060] 31-Second Upper Region

[0061] 32-Second Middle Area

[0062] 33 - Second Lower Region. Detailed Implementation

[0063] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0064] In the description of this invention, it should be understood that the terms "upper part", "lower part", "upper end", "lower end", "lower surface", "upper surface", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention.

[0065] In the description of this invention, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature.

[0066] In the description of this invention, "a plurality of" means multiple, such as two, three, four, etc., unless otherwise explicitly specified.

[0067] In the description of this invention, unless otherwise explicitly specified and limited, the term "connection" and other such terms should be interpreted broadly. For example, it can refer to a fixed connection, a detachable connection, or an integral connection; it can refer to a mechanical connection, an electrical connection, or a connection that allows communication between the components; it can refer to a direct connection or an indirect connection through an intermediate medium; it can refer to the internal communication between two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0068] The technical solution of the present invention will be described in detail below with reference to specific embodiments. These specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments.

[0069] Because two-dimensional gratings have symmetrical diffraction orders, not all locations within the coupling region utilize all symmetrical orders simultaneously. For example, for ±1 diffraction orders, some locations utilize the +1 order more, resulting in some wasted energy of the -1 order; conversely, some locations utilize the -1 order more, resulting in some wasted energy of the +1 order. For instance, in some examples, the upper region of the coupling region primarily aims to reduce light wastage by reducing upward propagation, thus requiring lower diffraction efficiency for the +1 order and higher diffraction efficiency for the -1 order. In other examples, the lower region of the coupling region primarily aims to reduce light wastage by reducing downward propagation, thus requiring lower diffraction efficiency for the -1 order and higher diffraction efficiency for the +1 order.

[0070] In view of this, embodiments of the present invention provide a coupling grating structure configured to diffract and couple an image beam transmitted in a waveguide substrate out of the waveguide substrate. The coupling grating structure includes a two-dimensional coupling grating, which comprises a plurality of grating elements 1. (See reference...) Figure 3 , Figure 3 This is a diagram of the grating unit in the partially coupled region. The transverse section of grating unit 1 includes: outer contour 11 and inner contour 12. Please refer to [reference needed]. Figure 1 Both the outer contour 11 and the inner contour 12 are closed structures, with the inner contour 12 located inside the outer contour 11.

[0071] The refractive index between the inner contour 12 and the outer contour 11 is the first refractive index n1, and the refractive index inside the inner contour is the second refractive index n2. Please refer to [reference needed]. Figure 1 , Figure 2 The first refractive index is not equal to the second refractive index.

[0072] Among them, at least two grating units have different positions of their inner contours relative to their outer contours.

[0073] This invention creatively discovers that when the position of the inner contour relative to the outer contour is different, the efficiency distribution for the symmetry order is also different. The distribution of diffraction efficiency among the symmetry orders changes with the position of the inner contour relative to the outer contour. This characteristic can be used to meet the different requirements of different coupling regions for different diffraction orders.

[0074] The position of the inner contour in the grating unit provided by the present invention can be adjusted, and the position of the inner contour affects the diffraction efficiency of the symmetrical diffraction order of the two-dimensional grating.

[0075] The following section describes in detail the relationship between the position of the inner contour and the diffraction efficiency of the symmetrical diffraction order of the two-dimensional grating.

[0076] Please refer to Figure 4 When the two axes of symmetry of the inner and outer contours of the grating unit coincide, the diffraction efficiency of the +1st order is equal to that of the -1st order.

[0077] Please refer to Figure 5 , 6 When the relative positions of the inner and outer contours of the grating unit change, the diffraction efficiency of different orders also changes accordingly.

[0078] Specifically, such as Figure 5 In this case, the major axis of the inner contour deviates from the major axis of the outer contour, shifting towards the +1 order. In this case, if the second refractive index is less than the first refractive index (e.g., the inner contour is hollow), the diffraction efficiency of the +1 order is less than that of the -1 order; if the second refractive index is greater than the first refractive index (e.g., the inner contour is filled with a high-refractive-index material), the diffraction efficiency of the +1 order is greater than that of the -1 order; and the greater the deviation, the greater the difference in diffraction efficiency.

[0079] like Figure 6 In this case, the major axis of the inner contour deviates from the major axis of the outer contour, shifting towards the -1st order. In this case, if the second refractive index is less than the first refractive index (e.g., the inner contour is hollow), the diffraction efficiency of the +1st order is greater than that of the -1st order; if the second refractive index is greater than the first refractive index (e.g., the inner contour is filled with a high refractive index material), the diffraction efficiency of the +1st order is less than that of the -1st order; and the greater the deviation, the greater the difference in diffraction efficiency.

[0080] Based on the influence of the inner contour position on the diffraction efficiency of different diffraction orders of the two-dimensional grating, when setting the coupling grating unit in the coupling region, the long axis direction of the coupling grating unit is consistent with the light propagation direction of the central field of view, and the inner contour position of the coupling grating unit in different regions is not exactly the same.

[0081] Specifically: for regions in the coupling area where the diffraction efficiency in the +1st order direction and the -1st order direction is required to be equivalent, the major axes of the inner and outer contours of the coupling grating unit are set to coincide.

[0082] For regions in the coupling region that require higher diffraction efficiency in the +1 order direction, the major axis of the inner contour of the coupling grating unit is set to deviate from the major axis of the outer contour. When the second refractive index is less than the first refractive index, it is shifted to the -1 order, and when the second refractive index is greater than the first refractive index, it is shifted to the +1 order.

[0083] For regions in the coupling region that require higher diffraction efficiency in the -1st order direction, the major axis of the inner contour of the coupling grating unit is set to deviate from the major axis of the outer contour. When the second refractive index is less than the first refractive index, it is shifted to the +1st order, and when the second refractive index is greater than the first refractive index, it is shifted to the -1st order.

[0084] In one embodiment, to achieve a second refractive index lower than the first refractive index, the inner contour can be hollowed out without filling material. Alternatively, in other embodiments, the inner contour can be filled with a low-refractive-index material, the refractive index of which is lower than the first refractive index. To achieve a second refractive index greater than the first refractive index, the inner contour can be filled with a high-refractive-index material, the refractive index of which is higher than the first refractive index. High-refractive-index materials can include titanium oxide, silicon carbide, niobium oxide, etc.

[0085] To address the different requirements of different coupling regions for different diffraction orders, one embodiment provides a method for dividing the coupling regions: along a first direction, the two-dimensional coupling grating is divided into multiple regions; along the first direction, the inner contour of each region has a different position relative to the outer contour; the first direction is a direction different from the forward direction of the image beam within the waveguide substrate.

[0086] The direction of image beam propagation within the waveguide substrate is the direction in which the image beam travels within the waveguide substrate to the two-dimensional coupling grating. The first direction is a direction different from this propagation direction; preferably, the first direction is orthogonal to the propagation direction. It should be noted that the beam propagating in the waveguide substrate is not perfectly collimated; therefore, the direction of beam propagation is not an absolute, unique direction. In this application, the direction of image beam propagation is only an approximate orientation and is not limited to precise positioning. When the two-dimensional coupling grating is divided into multiple regions along the first direction, it is not required that the boundary lines between the divided regions be orthogonal to the first direction, nor is it required that the boundary lines between the regions be parallel to each other; it is sufficient that the divided regions are arranged substantially along the first direction.

[0087] In an implementable manner, the two-dimensional coupling grating structure includes multiple regions, including a reference region, a first variation region adjacent to the reference region along a positive direction of a first direction, and / or a second variation region adjacent to the reference region along a negative direction of the first direction. The reference region is the area where the two-dimensional coupling grating is located, as indicated by the direction of light propagation from the central field of view. The diffraction efficiencies of the reference region propagating in both directions are comparable. The diffraction efficiencies of the first and second variation regions, when deflected towards the reference region, are both greater than their diffraction efficiencies when deflected away from the reference region.

[0088] Specifically, when the second refractive index is less than the first refractive index: the position of the inner contour of the grating unit in the first variation region relative to the outer contour, relative to the position of the inner contour of the grating unit in the reference region relative to the outer contour, deviates in the positive direction of the first direction. The position of the inner contour of the grating unit in the second variation region relative to the outer contour, relative to the position of the inner contour of the grating unit in the reference region relative to the outer contour, deviates in the negative direction of the first direction.

[0089] When the second refractive index is greater than the first refractive index: the position of the inner contour of the grating unit in the first variation region relative to the outer contour, relative to the position of the inner contour of the grating unit in the reference region relative to the outer contour, deviates in the negative direction of the first direction; the position of the inner contour of the grating unit in the second variation region relative to the outer contour, relative to the position of the inner contour of the grating unit in the reference region relative to its corresponding outer contour, deviates in the positive direction of the first direction.

[0090] Furthermore, in an implementable manner, the first variation region is divided into multiple first sub-regions along the first direction. Along the positive direction of the first direction, the difference between the diffraction efficiency of the first sub-regions diffracting towards the reference region and diffracting away from the reference region gradually increases. The second variation region is divided into multiple 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 diffracting towards the reference region and diffracting away from the reference region gradually increases.

[0091] Specifically, when the second refractive index is less than the first refractive index: along the positive direction of the first direction, the position of the inner contour of the grating unit in the first variation region relative to the outer contour, and the position of the inner contour of the grating unit in the reference region relative to the outer contour, gradually deviates towards the positive direction of the first direction; along the negative direction of the first direction, the position of the inner contour of the grating unit in the second variation region relative to the outer contour, and the position of the inner contour of the grating unit in the reference region relative to the outer contour, gradually deviates towards the negative direction of the first direction.

[0092] When the second refractive index is greater than the first refractive index: along the positive direction of the first direction, the position of the inner contour of the grating unit in the first variation region relative to the outer contour, and the position of the inner contour of the grating unit in the reference region relative to the outer contour, gradually deviate towards the negative direction of the first direction; along the negative direction of the first direction, the position of the inner contour of the grating unit in the second variation region relative to the outer contour, and the position of the inner contour of the grating unit in the reference region relative to the outer contour, gradually deviate towards the positive direction of the first direction.

[0093] In practice, the two-dimensional coupling grating structure can be undivided, with the position of the portion of the two-dimensional coupling grating pointed to by the direction of light propagation in the central field of view serving as the reference position. The diffraction efficiency of the grating unit diffracting towards both sides at the reference position is equivalent. Along both the positive and negative directions of the first direction, the diffraction efficiency of the grating unit deflected towards the reference position is greater than that of the grating unit deflected away from the reference region, and the difference increases with each direction.

[0094] Specifically, when the second refractive index is less than the first refractive index: along the positive direction of the first direction, the position of the inner contour of the grating unit relative to the outer contour, and the position of the inner contour of the grating unit at the reference position relative to its corresponding outer contour, gradually deviate towards the positive direction of the first direction; along the negative direction of the first direction, the position of the inner contour of the grating unit relative to the outer contour, and the position of the inner contour of the grating unit at the reference position relative to its corresponding outer contour, gradually deviate towards the negative direction of the first direction.

[0095] When the second refractive index is greater than the first refractive index: along the positive direction of the first direction, the position of the inner contour of the grating unit relative to the outer contour, and the position of the inner contour of the grating unit at the reference position relative to its corresponding outer contour, gradually deviates towards the negative direction of the first direction; along the negative direction of the first direction, the position of the inner contour of the grating unit relative to the outer contour, and the position of the inner contour of the grating unit at the reference position relative to its corresponding outer contour, gradually deviates towards the positive direction of the first direction. The following explanation uses two grating layout architectures as examples.

[0096] In one embodiment, taking a left-side center-projection grating layout architecture as an example, the two-dimensional coupled grating is divided into three regions along the first direction: a first upper region 21, a first middle region 22, and a first lower region 23. Please refer to [reference needed]. Figure 7 , Figure 8 ,like Figure 7 The example shown is based on the premise that the second refractive index is less than the first refractive index. Figure 8 The example shown uses a second refractive index greater than the first refractive index. Specifically, region 22 in the first region is a reference region, mainly used to achieve uniform pupil expansion towards the upper and lower regions. This region requires comparable diffraction efficiencies in the +1st and -1st order directions. Therefore, this region uses grating units with comparable diffraction efficiencies in both the +1st and -1st order directions. For example, [the following text is incomplete and requires further context]. Figure 4 The grating unit is shown. The first upper region 21 aims to diffract downwards to keep light within the coupling region and utilize it, avoiding wasting light as it leaves the coupling region due to upward diffracting. Therefore, this region needs a diffraction efficiency greater than the diffraction efficiency in the -1st order direction. Figure 7 The diagram shows the need for grating units arranged with their inner contours offset towards the +1 order direction. If this can be achieved... Figure 5 The grating unit shown; and Figure 8 The diagram shows the need for grating units arranged with their inner contours offset towards the -1 order direction. If this can be achieved... Figure 6 The grating unit is shown. In the first lower region 23, it is desirable to expand the pupil upwards to keep the light within the coupling region and utilize it, avoiding the waste of light as it expands the pupil downwards and leaves the coupling region. Therefore, this region needs a diffraction efficiency in the +1st order direction greater than in the -1st order direction. Figure 7 The diagram shows the need for grating units arranged with their inner contours offset to the -1 order. For example, a layout like this could be used... Figure 6 The grating unit shown; and Figure 8 The diagram shows the need for grating units arranged with the inner contour offset to the +1 order. For example, a layout like this could be used... Figure 5 The grating unit shown.

[0097] In one embodiment, taking the left-side upward projection grating layout architecture as an example, the two-dimensional coupled grating is also divided into three regions along the first direction: the second upper region 31, the second middle region 32, and the second lower region 33, but with... Figure 7 , Figure 8 The specific boundaries vary; please refer to [the relevant documentation]. Figure 9 , Figure 10 ,like Figure 9 The example shown is based on the premise that the second refractive index is less than the first refractive index. Figure 10The example shown uses a second refractive index greater than the first refractive index. Specifically, the second region 32 is a reference region, mainly used to achieve uniform pupil expansion towards the upper and lower regions. This region requires comparable diffraction efficiencies in the +1st and -1st order directions. Therefore, this region uses grating units with comparable +1st and -1st order diffraction efficiencies. Since the light propagation direction of the central field of view is oblique in this embodiment, the grating units in this region can be... Figure 4 The grating unit shown is obtained by rotating it by a certain angle. The second upper region 31 aims to expand the pupil downwards to keep the light within the coupling region and utilize it, avoiding the upward expansion of the pupil that leaves the coupling region and is wasted. Therefore, this region needs a diffraction efficiency greater than that in the +1st order direction. Figure 9 The diagram shows the need for a grating unit arrangement with its inner contour offset towards the +1 order direction; while Figure 10 The diagram shows the need for a grating unit arrangement with its inner contour offset towards the -1 order direction. In the second lower region 33, it is desirable to expand the pupil upwards to retain light within the coupling region for utilization, avoiding wasted light as it leaves the coupling region due to downward pupil expansion. Therefore, this region requires a diffraction efficiency in the +1 order direction greater than that in the -1 order direction. Figure 9 The diagram shows the need for grating units arranged with their inner contours offset to the -1 order; while Figure 10 The diagram shows that the grating units need to be arranged with the inner contour offset by +1 order.

[0098] In another embodiment, for the side-projection grating layout architecture, along the first direction, the two-dimensional coupling grating can also be divided into upper and lower regions. The upper region is the part of the two-dimensional coupling grating that the light propagation direction of the central field of view points to, which is a reference region. The grating unit used in this region is a grating unit that makes the diffraction efficiency of the +1st order and the -1st order in this region equivalent. The grating unit in the lower region is a grating unit that makes the diffraction efficiency of the +1st order in this region greater than the diffraction efficiency of the -1st order.

[0099] In the above example, the number of partitions, partition boundaries, and partitioning methods are for illustrative purposes only. In different embodiments, the two-dimensional coupled gratings may be divided in other ways, but regardless of the division method, the grating units in different regions can be arranged according to the above principles.

[0100] Furthermore, the concept of partitioning can be weakened, with no clear partition boundaries, and the inner contour gradually shifts away from the outer contour. For example, in the above application... Figures 7-10In the architecture, the inner and outer contours of the grating unit in the middle region coincide. The higher the grating unit deviates from the middle region, the more the hollow inner contour deviates from the long axis of the outer contour in the +1 order direction. The lower the grating unit deviates from the middle region, the more the hollow inner contour deviates from the long axis of the outer contour in the -1 order direction. Alternatively, the higher the grating unit deviates from the middle region, the more the inner contour filled with high folds deviates from the long axis of the outer contour in the -1 order direction. The lower the grating unit deviates from the middle region, the more the inner contour filled with high folds deviates from the long axis of the outer contour in the +1 order direction.

[0101] In one embodiment, the offset Δt of the inner contour is 1nm-10nm.

[0102] In one embodiment, when the inner contour shape is the same as the outer contour shape, the ratio of the inner contour size to the outer contour size can be: the modulation duty cycle φ is 20%-40%.

[0103] In one embodiment, the included angle of the grating period lines of the two-dimensional coupled grating is any value between 20° and 90°.

[0104] In one embodiment, the inner contour includes multiple inner contour straight edges and multiple inner contour curved edges, with the inner contour straight edges and inner contour curved edges connected sequentially at intervals; and / or, the outer contour includes multiple outer contour straight edges and multiple outer contour curved edges, with the outer contour straight edges and outer contour curved edges connected sequentially at intervals. Please refer to [reference needed]. Figure 11-15 In the diagram, L represents a straight edge and S represents a curved edge. Connecting two straight edges with a curved edge is easier to manufacture and better reflects the actual processing effect compared to directly connecting two straight edges. In actual processing, it is very difficult to manufacture the angle formed by directly connecting two straight edges.

[0105] The number of straight edges on the inner contour and the outer contour must be at least three, and can be any number of three. Please refer to [reference needed]. Figure 11 It can also be four; please refer to the following: Figure 12 13; or five, please refer to the following: Figure 14 It can also be six; please refer to the following: Figure 15 Of course, in different embodiments, the number of straight edges can also be other, which will not be listed here.

[0106] The shape formed by the straight edges of the inner and outer contours can be varied. For example, when there are four straight edges, it can also be a square-like shape. Please refer to [reference needed]. Figure 12 It can also be a rhombus-like shape; please refer to the reference. Figure 13 Of course, in different embodiments, other shapes are also possible. For example, when there are four, it can be a rectangle-like shape, which will not be listed here. When the number of straight sides is other values, there can also be various shapes.

[0107] The outer and inner contours of the same grating unit can have the same shape, such as... Figure 1 , Figure 16 They can also be different, such as Figure 17 , 18 The above four examples are just examples; in practical applications, different combinations can be made as needed, which will not be elaborated here.

[0108] In one embodiment, the angle between the extensions of two adjacent outer contour straight edges is less than 180°, and the angle between the extensions of two adjacent inner contour straight edges is less than 180°. Please refer to [reference needed]. Figure 11-15 .

[0109] In one embodiment, the inner contour curved edge and the outer contour curved edge are circular arc edges or elliptical arc edges, please refer to [reference needed]. Figures 11-15 .

[0110] In one embodiment, the radii of curvature of the inner contour curve and the outer contour curve are any values ​​between 30nm and 300nm.

[0111] In one embodiment, a diffractive waveguide is also provided, which includes the coupling grating structure described in any of the above embodiments.

[0112] In one embodiment, an augmented reality device is also provided, which includes the coupling grating structure described in any of the above embodiments, or a diffractive waveguide including the coupling grating structure described in any of the above embodiments.

[0113] In one embodiment, the augmented reality device may further include: a device body and an optical engine. The device body is used to carry the diffractive waveguide and the optical engine; the optical engine is used to project the image beam.

[0114] In one embodiment, the main body of the device can be implemented as an eyeglass frame, wherein the eyeglass frame includes a beam and temples, and the temples extend rearward from at least one of the left and right sides of the beam, wherein a diffractive waveguide is correspondingly disposed on the beam.

[0115] In one embodiment, the main body of the device can also be implemented as a windshield, and a diffractive waveguide is correspondingly disposed on the inner side of the windshield, so that the image beam projected by the optomechanical system is projected onto the windshield after being transmitted through the diffractive waveguide to form a virtual image.

[0116] In the description of this specification, the references to terms such as "an embodiment," "an example," "a specific implementation process," and "an example" indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0117] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions 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

1. A coupling grating structure, characterized in that, It is configured to diffract and couple an image beam transmitted in a waveguide substrate out of the waveguide substrate; The coupled-out grating structure includes: a two-dimensional coupled-out grating, wherein the two-dimensional coupled-out grating includes multiple grating units; The transverse section of the grating unit includes an outer contour and an inner contour; both the outer contour and the inner contour are closed structures, and the inner contour is located inside the outer contour. The refractive index between the inner contour and the outer contour is a first refractive index, and the refractive index inside the inner contour is a second refractive index. The first refractive index and the second refractive index are not equal. At least two of the grating units have different positions of their inner contours relative to their outer contours.

2. The coupling grating structure according to claim 1, characterized in that, Along the first direction, the two-dimensional coupling grating is divided into multiple regions; along the first direction, the inner contour is positioned differently relative to the outer contour in different regions; The first direction is a direction that is different from the direction of propagation of the image beam within the waveguide substrate.

3. The coupling grating structure according to claim 2, characterized in that, The plurality of regions includes a reference region; the reference region is the area where the two-dimensional coupling grating is located, which is pointed to by the direction of light propagation in the central field of view; The diffraction efficiency is equivalent when diffracting in both directions within the reference region; The plurality of regions further includes: a first variation region adjacent to the reference region along the positive direction of the first direction, and / or a second variation region adjacent to the reference region along the negative direction of the first direction; wherein the diffraction efficiency of the first variation region and the second variation region when diffracting towards the reference region is greater than the diffraction efficiency when diffracting away from the reference region.

4. The coupling grating structure according to claim 3, characterized in that, When the second refractive index is less than the first refractive index: the position of the inner contour of the grating unit in the first variation region relative to the outer contour, relative to the position of the inner contour of the grating unit in the reference region relative to the outer contour, deviates in the positive direction of the first direction; the position of the inner contour of the grating unit in the second variation region relative to the outer contour, relative to the position of the inner contour of the grating unit in the reference region relative to the outer contour, deviates in the negative direction of the first direction. When the second refractive index is greater than the first refractive index: the position of the inner contour of the grating unit in the first variation region relative to the outer contour, relative to the position of the inner contour of the grating unit in the reference region relative to the outer contour, deviates in the negative direction of the first direction; the position of the inner contour of the grating unit in the second variation region relative to the outer contour, relative to the position of the inner contour of the grating unit in the reference region relative to its corresponding outer contour, deviates in the positive direction of the first direction.

5. The coupling grating structure according to claim 3, characterized in that, The first variation region is divided into multiple first sub-regions along the first direction. Along the positive direction of the first direction, the difference between the diffraction efficiency of the first sub-region deflected towards the reference region and the diffraction efficiency deflected away from the reference region gradually increases. The second variation region is divided into multiple 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 towards the reference region and the diffraction efficiency deflected away from the reference region gradually increases.

6. The coupling grating structure according to claim 5, characterized in that, When the second refractive index is less than the first refractive index: along the positive direction of the first direction, the position of the inner contour of the grating unit in the first variation region relative to the outer contour, relative to the position of the inner contour of the grating unit in the reference region relative to the outer contour, gradually deviates towards the positive direction of the first direction; along the negative direction of the first direction, the position of the inner contour of the grating unit in the second variation region relative to the outer contour, relative to the position of the inner contour of the grating unit in the reference region relative to the outer contour, gradually deviates towards the negative direction of the first direction. When the second refractive index is greater than the first refractive index: along the positive direction of the first direction, the position of the inner contour of the grating unit in the first variation region relative to the outer contour, relative to the position of the inner contour of the grating unit in the reference region relative to the outer contour, gradually deviates towards the negative direction of the first direction; along the negative direction of the first direction, the position of the inner contour of the grating unit in the second variation region relative to the outer contour, relative to the position of the inner contour of the grating unit in the reference region relative to the outer contour, gradually deviates towards the positive direction of the first direction.

7. The coupling grating structure according to any one of claims 1 to 6, characterized in that, The inner contour includes multiple straight edges and multiple curved edges, wherein the straight edges and curved edges are connected sequentially at intervals; and / or The outer contour includes: multiple straight edges and multiple curved edges, wherein the straight edges and curved edges are connected sequentially at intervals.

8. The coupling grating structure according to claim 7, characterized in that, The angle between the extensions of two adjacent straight edges of the outer contour is less than 180°, and the angle between the extensions of two adjacent straight edges of the inner contour is less than 180°.

9. The coupling grating structure according to claim 7, characterized in that, The inner contour curved edge and the outer contour curved edge are either circular arc edges or elliptical arc edges.

10. The coupling grating structure according to claim 9, characterized in that, The radius of curvature of the inner contour and the outer contour is any value between 30nm and 300nm.

11. The coupling grating structure according to any one of claims 1 to 6, characterized in that, The included angle of the grating period lines of the two-dimensional coupled grating is any value between 20° and 90°.

12. A diffractive optical waveguide, characterized in that, include: The coupling grating structure as described in any one of claims 1-11.

13. An augmented reality device, characterized in that, include: The coupling grating structure as described in any one of claims 1-11, or the diffractive waveguide as described in claim 12.

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