Diffractive optical waveguide and augmented reality display device

Abstract

The application provides a diffractive optical waveguide, comprising: the diffractive optical waveguide comprises a waveguide substrate, a coupling-in region, a turning region and a coupling-out region, a grating structure in the turning region comprises a plurality of first grating units, and the first grating unit comprises a first grating tooth and a first grating groove; wherein the height of the same first grating groove changes along the extension direction of the first grating groove, and the height perpendicular to the extension direction remains consistent, and / or the height of the same first grating tooth changes along the extension direction, and the height perpendicular to the extension direction remains consistent, so that the light rays propagating in different paths in the turning region experience different phase shifts when converging. The scheme provided by the application can improve the display effect of the diffractive optical waveguide.

Description

Technical Field

[0001] This application relates to the field of optical technology, and more particularly to a diffractive waveguide and an augmented reality display device. Background Technology

[0002] Augmented reality is a technology that blends the real world with virtual information. Augmented reality display systems typically include micro-projectors and optical displays. The micro-projectors provide virtual display content for the augmented reality display system, which is then projected onto the viewer's eyes through the optical displays. The optical displays are usually transparent optical components, so that users can also see the real world through the optical displays at the same time.

[0003] Diffractive waveguides are a type of optical display screen. They typically use grating structures to expand the exit pupil. When expanding the exit pupil, there are multiple expansion paths, which in turn generate a large number of light rays with equal optical path differences that propagate in the same direction. When these light rays are coupled out to the human eye, they will undergo constructive or destructive interference, resulting in bright and dark stripes in the display screen, which greatly affects the display effect. Summary of the Invention

[0004] This application provides a diffractive waveguide and an augmented reality display device, which can improve or even eliminate undesirable interference effects, thereby enhancing the display effect of the diffractive waveguide.

[0005] A diffractive optical waveguide includes a waveguide substrate, a coupling region, a transition region, and a coupling out region. The grating structure in the transition region includes a plurality of first grating units, each of which includes a first grating tooth and a first grating groove.

[0006] Wherein, the height of the same first grating groove varies along the extension direction of the first grating groove, and remains consistent along the height perpendicular to the extension direction, and / or, the height of the same first grating tooth varies along the extension direction, and remains consistent along the height perpendicular to the extension direction, so that light rays propagating along different paths in the turning region experience different phase shifts when they converge.

[0007] Implementably, the height of the same first grating tooth varies in a stepped manner along the extension direction, and / or the height of the same first grating groove varies in a stepped manner along the extension direction.

[0008] In practice, the surfaces of each first grating tooth away from the waveguide substrate are on the same horizontal plane, and the height of the same first grating groove varies along the extension direction of the first grating groove, while maintaining a consistent height along the perpendicular direction of the extension direction, so that light rays propagating along different paths in the transition region experience different phase shifts when they converge; or, the groove surfaces of each first grating groove are on the same horizontal plane, and the height of the same first grating tooth varies along the extension direction, while maintaining a consistent height along the perpendicular direction of the extension direction, so that light rays propagating along different paths in the transition region experience different phase shifts when they converge.

[0009] In practice, the phase difference between light rays propagating along different paths in the turning region when they converge is... Q is a non-negative integer.

[0010] In practice, the height of the grating structure within the transition region satisfies the following condition:

[0011] h i *y i =∫z i dy

[0012] h i =h0+r i

[0013] Where h0 is the desired height of the grating structure within the transition region, h i r is the average height of the i-th first grating unit within the transition region. i Let y be the random offset of the height of the i-th first grating unit. i z is the dimension of the i-th first grating tooth along the extension direction. i The dimension of the i-th first grating tooth is in the normal direction of the waveguide substrate and varies along the extension direction, which is the Y-axis direction, and the normal direction of the waveguide substrate surface is the Z-axis direction.

[0014] In practice, the transition region includes multiple transition partitions, and the desired height of the grating structure within each transition partition gradually increases in a direction away from the coupling region. The height of the grating structure within each transition partition satisfies the following condition:

[0015] h i，j *y i，j =∫z i，j dy

[0016] max(z i，j )-min(z i，j ) < C j

[0017] h i，j=h j +r i，j

[0018] Among them, h j h is the desired height of the grating structure within the j-th transition zone. i，j r is the average height of the i-th first grating unit within the j-th transition zone. i，j y is the random height offset of the first raster unit within the j-th transition partition. i，j z is the dimension of the i-th first grating tooth within the j-th turning section along the extending direction. i，j Let C be the dimension of the i-th first grating tooth within the j-th transition zone in the direction normal to the waveguide substrate, and vary along the extension direction. j It is a constant.

[0019] In practice, the grating structure within the transition region is sampled from the sample grating region through a sampling window; the sample grating within the sample grating region includes a plurality of sample grating units, each sample grating unit having the same parameters and having its ends aligned; the sample grating region includes a first side and a second side arranged relatively parallel to each other, as well as a third side and a fourth side arranged relatively parallel to each other, the third side and the fourth side being parallel to the extension direction of the grating groove of the sample grating unit; the sampling window includes a first side and a second side arranged relatively parallel to each other, the angle between the first side and the first side being an acute angle, and the angle between the second side and the first side being an acute angle.

[0020] Implementably, the height of the same first grating groove along the extension direction gradually decreases in the direction away from the coupling region, or the height of the same first grating tooth along the extension direction gradually increases in the direction away from the coupling region.

[0021] In practice, the grating structure within the coupling region includes a plurality of second grating units, each second grating unit including a second grating tooth and a second grating groove; wherein the height of the same second grating groove varies along the extension direction of the second grating groove, and remains consistent along the height perpendicular to the extension direction, and / or the height of the same second grating tooth varies along the extension direction, and remains consistent along the height perpendicular to the extension direction, so that light rays propagating along different paths in the coupling region experience different phase shifts when they converge.

[0022] An augmented reality display device, the augmented reality display device comprising: a projection optical engine and a diffractive waveguide as described in any of the preceding claims.

[0023] The diffractive waveguide provided in this application, based on the existing architecture, features a special design for the grating structure units in the transition region. The height of the same first grating groove varies along the extension direction of the first grating groove, while maintaining a consistent height perpendicular to the extension direction. And / or, the height of the same first grating tooth varies along the extension direction, while maintaining a consistent height perpendicular to the extension direction. The phase change at different positions is obtained by adjusting the sag of the grating structure, so that light rays propagating along different paths in the transition region experience different phase shifts when they converge. This modulates the phase difference between different interfering light rays without introducing an additional optical path. When the phase difference changes, the interference effect between different light rays is averaged or even eliminated, thereby improving the display effect of the diffractive waveguide.

[0024] The augmented reality display device provided in this application includes the aforementioned diffractive waveguide, and thus possesses the advantages of the aforementioned diffractive waveguide. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 A schematic diagram of a diffractive optical waveguide provided for existing technology;

[0027] Figure 2 A schematic diagram of a diffractive waveguide provided in one embodiment of this application;

[0028] Figure 3 This is a schematic diagram of a grating structure provided in one embodiment of this application;

[0029] Figure 4 A schematic diagram of a grating structure provided in another embodiment of this application;

[0030] Figure 5 A schematic diagram of the inner grating structure for obtaining the transition region provided in one embodiment of this application;

[0031] Attached image labels:

[0032] 100: Waveguide substrate; 110: Coupled-in region; 120: Turning region; 130: Coupled-out region; 200: Grating unit; 210: Grating tooth; 220: Grating groove; 510: Sample grating region; 520: Window. Detailed Implementation

[0033] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of protection of the present application.

[0034] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0035] Existing technologies typically employ grating structures in the transition and / or coupling regions of diffractive waveguides to deflect light propagating in the waveguide substrate, thereby achieving pupil expansion. However, the propagation path of the light is often not unique during pupil expansion. (Refer to...) Figure 1 For example, in the transition region 120, light rays can reach point C from either ABC or ADC. The optical path length of light rays reaching point C via different paths is the same, therefore the phase difference is zero. Furthermore, the light rays transmitted through these two paths have the same frequency and polarization components in the same direction. Therefore, the light rays transmitted through these two paths will interfere at point C. This results in bright and dark fringes of light energy visible to the human eye in the coupling region, significantly affecting the display effect.

[0036] According to one aspect of this application, a diffractive waveguide is provided, including a waveguide substrate, a coupling region, a transition region, and a coupling out region. The grating structure in the transition region includes a plurality of first grating units, each first grating unit including a first grating tooth and a first grating groove. The height of the same first grating groove varies along the extension direction of the first grating groove, and remains consistent along the height perpendicular to the extension direction. And / or, the height of the same first grating tooth varies along the extension direction, and remains consistent along the height perpendicular to the extension direction, so that light rays propagating along different paths in the transition region experience different phase shifts when they converge.

[0037] Specifically, within the transition region, the height of the same first grating groove in some or all grating units varies along the extension direction of the first grating groove, while maintaining a consistent height perpendicular to the extension direction. Alternatively, the height of the same first grating tooth in some or all grating units within the transition region varies along the extension direction, while maintaining a consistent height perpendicular to the extension direction. Alternatively, the height of the same first grating groove in some grating units within the transition region varies along the extension direction of the first grating groove, while maintaining a consistent height perpendicular to the extension direction, and the height of the same first grating tooth in some grating units varies along the extension direction, while maintaining a consistent height perpendicular to the extension direction. Alternatively, the height of the same first grating groove in some or all grating units within the transition region varies along the extension direction of the first grating groove, while maintaining a consistent height perpendicular to the extension direction, and the height of the same first grating tooth varies along the extension direction, while maintaining a consistent height perpendicular to the extension direction.

[0038] It should be noted that the varying heights of the grating teeth and / or grating grooves in the grating structure disrupt the conventional situation where the optical path lengths of multi-path light rays are the same, preventing light rays from converging with identical phases. This results in different optical path differences and thus different phases when light rays are incident on grating structures with different sagittal heights and exit. The phase differences at different positions can be obtained by varying the sagittal heights of the grating structure, preventing light rays from reaching the same position with the same phase after traveling different paths. This ensures that light rays propagating on different paths in the transition region experience different phase shifts when converging, thereby modulating the phase difference between different interfering light rays without introducing an additional optical path. When the phase difference changes, the interference effect between different light rays is averaged or even eliminated, thus improving the display effect of the diffractive waveguide.

[0039] For example, refer to Figure 2 The diffractive waveguide includes a waveguide substrate 100, a coupling region 110, a transition region 120, and a coupling out region 130; Reference Figure 3 The grating structure includes several grating units 200. Each grating unit 200 includes grating teeth 210 and grating grooves 220. The height of the same grating tooth 210 varies along the extension direction of the grating groove 220, and the height remains consistent along the direction perpendicular to the extension direction. Figure 2 The grating structure within the mid-transition region 120 can be selected to use Figure 3 The grating structure shown is designed with different grating tooth heights at different positions to achieve phase changes at different positions, so that light rays propagating along different paths in the transition region experience different phase shifts when they converge, thereby improving the display effect of the diffractive waveguide.

[0040] It should be noted that the "first grating unit" here and the "second grating unit" later in the text are both grating units. The terms "first" and "second" are only used to distinguish similar objects and do not impose any other limitations. The parameters of the "first grating unit" and the "second grating unit" can be the same or different.

[0041] Implementably, the height of the same first grating tooth varies in a stepped manner along the extension direction, and / or the height of the same first grating groove varies in a stepped manner along the extension direction. The step height and the dimensions of the step surface can be randomly selected, and the step height and dimensions of the step surface at different locations can be the same or different. However, the step height should not be too large to avoid abrupt changes in the height of the grating structure affecting the performance of the diffractive waveguide. For example, the step height can be no greater than 1%, 2%, 5%, or 10% of the grating tooth height; the dimensions of the step surface should also not be too large to avoid the light converging before the phase difference between different interfering rays has been modulated. Moreover, each step surface is parallel to the surface of the waveguide substrate, which effectively ensures the total internal reflection propagation process of light in the diffractive waveguide and prevents the total internal reflection transmission of light from being broken.

[0042] For example, refer to Figure 4 The figure shows that the height of the grating teeth in the grating unit varies in a stepped manner along the extension direction. The extension direction of the grating teeth in the figure is the Y-axis direction, the normal direction of the waveguide substrate surface is the Z-axis direction, h0 is the desired height of the grating structure in the transition region, z(y) is the coordinate dimension of the grating teeth in the Z-axis direction, and when z(y) = 0, it is the plane on the side surface of the waveguide substrate where the grating structure is set, that is, z(y) is the actual height of the grating teeth.

[0043] In an implementable manner, the surfaces of each first grating tooth furthest from the waveguide substrate are on the same horizontal plane, and the height of the same first grating groove varies along its extension direction while remaining consistent along the direction perpendicular to the extension direction. This ensures that light rays propagating along different paths in the transition region experience different phase shifts when they converge. Alternatively, the groove surfaces of each first grating groove are on the same horizontal plane, and the height of the same first grating tooth varies along its extension direction while remaining consistent along the direction perpendicular to the extension direction. This also ensures that light rays propagating along different paths in the transition region experience different phase shifts when they converge. In this way, the surface of each grating tooth furthest from the waveguide substrate is planar and has a consistent height, which reduces the difficulty and complexity of the manufacturing process and improves production efficiency.

[0044] Continue to refer to Figure 3 In the grating structure shown in the figure, the groove surfaces of each grating groove 220 are on the same horizontal plane, the height of the same grating tooth 210 varies along the extension direction of the grating groove 220, and the height remains consistent along the direction perpendicular to the extension direction.

[0045] In practice, the phase difference between light rays propagating along different paths in the turning region when they converge... Q is a non-negative integer. When light rays propagating along different paths converge, they interfere. When the phase difference between interfering rays is a non-negative integer multiple of π, constructive or destructive interference occurs, resulting in bright or dark bars. This application addresses this by scrambling the phase difference between two beams propagating along arbitrary paths, making it no longer equal to Qπ. This averages out or even eliminates the interference effect between different rays, thereby improving the display effect of the diffractive waveguide. Specifically, in the phase difference... The time interference effect is eliminated.

[0046] For example, see reference. Figure 1 Assume points ABCD are points of total internal reflection. Light rays can reach point C from either ABC or ADC. The optical path length of the light ray at point B is r1, and the optical path length at point D is r2. Then the optical path difference between points B and D is Δr = r1 - r2. Finally, the phase difference when the light rays converge at point C is... Therefore, the optical path difference Δr ≠ Qλ / 2. For example, the range of the optical path difference can be: (n-1)·λ / 2<Δr<n·λ / 2, where n is a positive integer.

[0047] In practice, the height of the grating structure within the transition region satisfies the following condition:

[0048] h i *y i =∫z i dy

[0049] h i =h0+r i

[0050] Where h0 is the desired height of the grating structure within the transition region, h i r is the average height of the i-th first grating unit within the transition region. i Let y be the random offset of the height of the i-th first grating unit. i z is the dimension of the i-th first grating tooth along the extension direction. i Let be the dimension of the i-th first grating tooth in the normal direction of the waveguide substrate, and vary along the extension direction, which is the Y-axis direction, and the normal direction of the waveguide substrate surface is the Z-axis direction.

[0051] In practice, the r of the adjacent first grating unit i The difference in the value of r should not be too large to avoid the abrupt change in the height of the grating structure affecting the performance of the diffractive waveguide. i The difference in value can be no greater than 1%, 2%, 5%, or 10% of the grating tooth height, for example: r i+1 -r i <5%·h0.

[0052] The height of the grating structure or grating unit is the dimension of the grating tooth or grating groove in the direction normal to the waveguide substrate. The dimension of the grating tooth in the direction normal to the waveguide substrate is the distance between the surface of the grating tooth away from the waveguide substrate and the surface of the waveguide substrate on which the grating structure is located. The dimension of the grating groove in the direction normal to the waveguide substrate is the distance between the groove surface and the surface of the waveguide substrate on which the grating structure is located.

[0053] Thus, through the design of the grating structure height in the aforementioned embodiments, the heights of at least one total internal reflection point on one path and at least one total internal reflection point on another path are different when the light rays propagating on different paths converge in the transition region. That is, the heights of the grating teeth or grating grooves are different, so that the light rays propagating on different paths in the transition region experience different phase shifts when they converge. The phase difference is not always a non-negative integer multiple of π, thereby modulating the phase difference between different interfering light rays without introducing an additional optical path. When the phase difference changes, the interference effect between different light rays is averaged or even eliminated, thereby improving the display effect of the diffractive waveguide.

[0054] It should be noted that grating structures with different sag heights not only affect the phase of the light rays but also the diffraction efficiency. In the design of diffractive waveguides, in order to obtain better uniformity, the transition region and / or coupling interval are generally divided into sections, and different grating heights are set for different sections.

[0055] In one embodiment, the transition region includes multiple transition partitions, and the desired height of the grating structure within each transition partition gradually increases in the direction away from the coupling region. The height of the grating structure within each transition partition satisfies the following condition:

[0056] h i，j *y i，j =∫z i，j dy

[0057] max(z i，j )-min(z i，j ) < C j

[0058] h i，j =h j +r i，j

[0059] Among them, h j Let h be the desired height of the grating structure within the j-th transition zone. The transition zone number j gradually increases in the direction away from the coupling region. j <h j+1 h i，j r is the average height of the i-th first grating unit within the j-th transition zone. i，jLet h be the random height offset of the first grating unit within the j-th transition partition, and be related to h. j-1 h j h j+1 Related. y i，j z is the dimension of the i-th first grating tooth within the j-th turning section along the extending direction. i，j Let max(z) be the dimension of the i-th first grating tooth within the j-th turning section in the direction normal to the waveguide substrate, and vary along the extension direction. i，j )≤min(z i，j+1 C j C is a constant, and C varies with different values ​​of j. j The values ​​of can be the same or different, and are related to h. j-1 h j h j+1 Relevant. Both i and j are positive integers.

[0060] For example, the transition region is divided into four transition partitions, sequentially along the direction away from the coupling region: transition partition 1, transition partition 2, transition partition 3, and transition partition 4. The expected heights of the corresponding grating structures are h1, h2, h3, and h4, respectively. For the second transition partition, the height of the i-th grating unit is randomly offset by r. i，2 Then the average height h of the i-th grating unit i，2 =h2+r i，2 Optionally, r i，2 The range of values ​​can be The height of the i-th grating unit satisfies: max(z) i，2 )≤min(z i，3 ), max(z i，1 )≤min(z i，2 ).

[0061] In the above embodiments, after setting the desired height for each transition zone, the height of the grating unit in each transition zone changes, so that the phase difference of light rays propagating along different paths in the transition zone can be modulated to optimize the interference effect; moreover, the range of the grating unit height in each transition zone also meets certain constraints, so that the diffraction efficiency in the transition zone is modulated and the uniformity is optimized.

[0062] In another embodiment, the grating structure within the transition region is sampled from the sample grating region through a sampling window; the sample grating within the sample grating region includes a plurality of sample grating units, each sample grating unit having the same parameters and having its ends aligned; the sample grating region includes a first side and a second side arranged relatively parallel to each other, as well as a third side and a fourth side arranged relatively parallel to each other, the third side and the fourth side being parallel to the extension direction of the grating groove of the sample grating unit; the sampling window includes a first side and a second side arranged relatively parallel to each other, the angle between the first side and the first side being an acute angle, and the angle between the second side and the first side being an acute angle.

[0063] Among them, the height of the same first grating groove along the extension direction gradually decreases in the direction away from the coupling region, or the height of the same first grating tooth along the extension direction gradually increases in the direction away from the coupling region.

[0064] Specifically, in this embodiment, when optimizing uniformity, it is no longer necessary to divide the transition region into sections. Instead, a grating structure is extracted from the sample grating region using a sampling window, and the extracted grating structure is then filled into the transition region. The contour and size of the sampling window are consistent with the contour and size of the transition region. When filling the transition region with the extracted grating structure, the placement orientation of the grating structure on the waveguide substrate needs to be determined based on the grating direction and grating period design of the grating structures in the coupling-in and coupling-out regions, ensuring that the light emitted from the optomechanical system meets the coupling-in and coupling-out conditions.

[0065] Furthermore, by setting the sample grating within the sample grating region to include several sample grating units, with each sample grating unit having identical parameters and aligned ends, the height of the grating structure when truncated using a sampling window is inconsistent along the direction of the first side S1. Even further, when the height of the same first grating groove along the extension direction gradually decreases away from the coupling region, or the height of the same first grating tooth along the extension direction gradually increases away from the coupling region, the height of the truncated grating structure gradually increases along the direction of the first side S1, and also gradually increases along the extension direction of the grating groove, thus optimizing both interference effects and uniformity.

[0066] For example, refer to Figure 5 The sample grating region 510 includes a first side L1 and a second side L2 arranged relatively parallel to each other, and a third side L3 and a fourth side L4 arranged relatively parallel to each other. The third side L3 and the fourth side L4 are parallel to the extension direction P1 of the grating groove of the sample grating unit. The sampling window 520 includes a first side S1 and a second side S2 arranged relatively parallel to each other. The angle θ1 between the first side S1 and the first side L1 is an acute angle, and the angle θ2 between the second side S2 and the first side L1 is an acute angle. Assume that the grating structure intercepted by the sampling window 520 is filled to... Figure 2When the grating structure is filled within the transition region 120 shown, it needs to be rotated, that is, rotated so that the first side S1 coincides with the side of the transition region 120 away from the coupling region 130.

[0067] In this embodiment of the application, the grating structure in the coupling region may also include a plurality of second grating units, the second grating unit including a second grating tooth and a second grating groove; wherein, the height of the same second grating groove varies along the extension direction of the second grating groove, and the height remains consistent along the perpendicular extension direction, and / or, the height of the same second grating tooth varies along the extension direction, and the height remains consistent along the perpendicular extension direction, so that the light rays propagating along different paths in the coupling region experience different phase shifts when they converge.

[0068] It should be noted that the "second grating unit" may have the structural features of the "first grating unit" in the aforementioned embodiments, such as height variation relationship and height constraint conditions; however, the "second grating unit" is a grating unit with a grating structure in the coupling region, while the "first grating unit" is a grating unit with a grating structure in the transition region. Therefore, in terms of the specific parameter settings, the "second grating unit" is adapted to the requirements of the coupling region, while the "first grating unit" is adapted to the requirements of the transition region.

[0069] According to one aspect of this application, an augmented reality display device is also provided, comprising: a projection optical engine and a diffractive waveguide as described in any of the preceding claims. The projection optical engine is used to emit image light. The augmented reality display device can be specifically implemented as augmented reality glasses or an augmented reality helmet, etc. The augmented reality display device provided by this application includes the aforementioned diffractive waveguide, and therefore possesses the advantages of the aforementioned diffractive waveguide.

[0070] The specific embodiments described above do not constitute a limitation on the scope of protection of this application. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A diffractive optical waveguide, characterized in that, The diffractive waveguide includes a waveguide substrate, a coupling region, a transition region, and a coupling out region. The grating structure within the transition region includes a plurality of first grating units. Each first grating unit includes a first grating tooth and a first grating groove. The height of the first grating unit is the height of either the first grating tooth or the first grating groove. The heights of both the first grating tooth and the first grating groove are dimensions in the normal direction of the waveguide substrate. The dimension of the first grating tooth in the normal direction of the waveguide substrate is the distance between the surface of the grating tooth away from the waveguide substrate and the surface of the waveguide substrate on which the grating structure is located. The dimension of the first grating groove in the normal direction of the waveguide substrate is the distance between the groove surface and the surface of the waveguide substrate on which the grating structure is located. Wherein, the height of the same first grating groove varies along the extension direction of the first grating groove, and remains consistent along the height perpendicular to the extension direction, and / or, the height of the same first grating tooth varies along the extension direction, and remains consistent along the height perpendicular to the extension direction, so that light rays propagating along different paths in the turning region experience different phase shifts when they converge.

2. The diffractive waveguide according to claim 1, characterized in that, The height of the same first grating tooth varies in a stepped manner along the extension direction, and / or the height of the same first grating groove varies in a stepped manner along the extension direction.

3. The diffractive waveguide according to claim 1, characterized in that, The surfaces of each first grating tooth away from the waveguide substrate are on the same horizontal plane, and the height of the same first grating groove varies along the extension direction, while the height perpendicular to the extension direction remains consistent, so that light rays propagating along different paths in the turning region experience different phase shifts when they converge. Alternatively, the surface of each of the first grating slots is on the same horizontal plane, and the height of the same first grating tooth varies along the extension direction, while maintaining a consistent height along the direction perpendicular to the extension direction, so that light rays propagating along different paths in the turning region experience different phase shifts when they converge.

4. The diffractive waveguide according to claim 1, characterized in that, The phase difference of light rays propagating along different paths in the turning region when they converge. , It is a non-negative integer.

5. The diffractive waveguide according to claim 1, characterized in that, The height of the grating structure within the transition region satisfies the following condition: in, The desired height of the grating structure within the transition region. The first one within the turning region The average height of the first grating unit For the first Random height offset of the first grating unit For the first The dimension of the first grating tooth along the extending direction For the first The dimensions of the first grating teeth in the normal direction of the waveguide substrate vary along the extension direction, which is the Y-axis direction, and the normal direction of the waveguide substrate surface is the Z-axis direction.

6. The diffractive waveguide according to claim 5, characterized in that, The transition region includes multiple transition partitions, and the desired height of the grating structure within each transition partition gradually increases in the direction away from the coupling region. The height of the grating structure within each transition partition satisfies the following condition: in, For the first The desired height of the grating structure within each transition zone. For the first Within the first turning zone The average height of the first grating unit For the first Within the first turning zone Random height offset of the first grating unit For the first Within the first turning zone The dimension of the first grating tooth along the extending direction Within the first turning zone The dimensions of the first grating teeth in the direction normal to the waveguide substrate vary along the extension direction. It is a constant.

7. The diffractive waveguide according to claim 1, characterized in that, The grating structure within the transition area is sampled from the sample grating area through a sampling window; the sample grating within the sample grating area includes several sample grating units, each sample grating unit having the same parameters and having its ends aligned; the sample grating area includes a first side and a second side arranged relatively parallel to each other, as well as a third side and a fourth side arranged relatively parallel to each other, the third side and the fourth side being parallel to the extension direction of the grating groove of the sample grating unit; the sampling window includes a first side and a second side arranged relatively parallel to each other, the angle between the first side and the first side being an acute angle, and the angle between the second side and the first side being an acute angle.

8. The diffractive waveguide according to claim 7, characterized in that, The height of the same first grating groove along the extension direction gradually decreases in the direction away from the coupling region, or the height of the same first grating tooth along the extension direction gradually increases in the direction away from the coupling region.

9. The diffractive waveguide according to any one of claims 1-8, characterized in that, The grating structure within the coupling region includes a plurality of second grating units, each second grating unit comprising a second grating tooth and a second grating groove. The height of the second grating unit is the height of either the second grating tooth or the second grating groove. Both the heights of the second grating tooth and the second grating groove are dimensions in the normal direction of the waveguide substrate. The dimension of the second grating tooth in the normal direction of the waveguide substrate is the distance between the surface of the grating tooth away from the waveguide substrate and the surface of the waveguide substrate on which the grating structure is disposed. The dimension of the second grating groove in the normal direction of the waveguide substrate is the distance between the groove surface and the surface of the waveguide substrate on which the grating structure is disposed. The height of the same second grating groove varies along its extension direction, but remains consistent along a height perpendicular to the extension direction. Similarly, the height of the same second grating tooth varies along its extension direction, but remains consistent along a height perpendicular to the extension direction, so that light rays propagating along different paths in the coupling region experience different phase shifts when they converge.

10. An augmented reality display device, characterized in that, The augmented reality display device includes: a projection optical engine and a diffractive waveguide as described in any one of claims 1-9.

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