Optical waveguide and augmented reality display device

Abstract

An optical waveguide and an augmented reality display device. The optical waveguide comprises: an optical waveguide substrate; and a grating layer, wherein the grating layer is disposed on the surface of the optical waveguide substrate, the grating layer comprises a grating region and a blank region, and the height (h) of the blank region is 0.7 to 1.3 times the height (hg) of the grating region. Ghosting phenomena occurring during the usage of the optical waveguide can be mitigated.

Description

Optical waveguides and augmented reality display devices Cross-reference to related applications

[0001] This application claims priority to Chinese patent application filed on February 19, 2025, with application number 202510188297.7 and entitled "Optical Waveguide and Augmented Reality Display Device". Technical Field

[0002] This application relates to the field of display technology, and in particular to an optical waveguide and an augmented reality display device. Background Technology

[0003] Augmented reality display technologies implemented using optical waveguides already exist in this field. However, existing optical waveguides suffer from motion blur (as shown in Figure 1), and this problem becomes more severe between different frames during dynamic imaging. Currently, there is no effective method to mitigate this motion blur issue. Therefore, there is an urgent need in this field for an optical waveguide that can reduce or eliminate motion blur during use, thereby providing a higher quality display effect. Summary of the Invention

[0004] Therefore, this application aims to provide an optical waveguide and augmented reality display device that can reduce the ghosting phenomenon generated during use.

[0005] In one aspect, this application provides an optical waveguide, comprising: an optical waveguide substrate; and a grating layer disposed on the surface of the optical waveguide substrate, the grating layer including a grating region and a blank region, the height of the blank region being between 0.7 and 1.3 times the height of the grating region.

[0006] In one possible implementation of this application, the height of the blank area varies between 0.7 times and 1.3 times the height of the raster area.

[0007] In one possible implementation of this application, the height of the blank area varies continuously.

[0008] In one possible implementation of this application, the height of the blank area varies in a stepped manner. In one possible implementation of this application, the height of the blank area at the first end immediately adjacent to the grating area is between 1 and 1.3 times the height of the grating area, and the height of the blank area at the second end opposite to the first end is between 0.7 and 1 times the height of the grating area, with the height of the blank area gradually increasing from the second end to the first end.

[0009] In one possible implementation of this application, the grating region includes a first grating region and a second grating region. The first grating region has a first height, and the second grating region has a second height. The first height is less than the second height, and the difference between the first height and the second height is less than or equal to 30% of the second height. A blank region is disposed between the first grating region and the second grating region, and the height of the blank region is between 0.7 times the second height and 1.3 times the first height.

[0010] In one possible implementation of this application, the grating region includes a first grating region and a second grating region. The first grating region has a first height, and the second grating region has a second height. The first height is less than the second height. A blank region is disposed between the first grating region and the second grating region. The height of the blank region at the first end adjacent to the first grating region is between 0.7 and 1.3 times the first height, and the height of the blank region at the second end adjacent to the second grating region is between 0.7 and 1.3 times the second height. The height of the blank region varies between the height at the first end and the height at the second end.

[0011] In one possible implementation of this application, the grating region includes a first grating region and a second grating region, the first grating region and the second grating region having varying heights, a blank region disposed between the first grating region and the second grating region, the end of the blank region immediately adjacent to the first grating region being designated as the first end, the end of the blank region immediately adjacent to the second grating region being designated as the second end, the first grating region having a first height at the end immediately adjacent to the first end, the second grating region having a second height at the end immediately adjacent to the second end, the first height being less than the second height and the difference between the first height and the second height being less than or equal to 30% of the second height; wherein, the height of the blank region is between 0.7 times the second height and 1.3 times the first height.

[0012] In one possible implementation of this application, the grating region includes a first grating region and a second grating region, the first grating region and the second grating region having varying heights, a blank region disposed between the first grating region and the second grating region, the end of the blank region immediately adjacent to the first grating region being designated as a first end, the end of the blank region immediately adjacent to the second grating region being designated as a second end, the first grating region having a first height at the end immediately adjacent to the first end, and the second grating region having a second height at the end immediately adjacent to the second end, the first height being less than the second height; wherein, the height of the first end is between 0.7 and 1.3 times the first height, the height of the second end is between 0.7 and 1.3 times the second height, and the height of the blank region varies between the height of the first end and the height of the second end.

[0013] On the other hand, this application provides an augmented reality display device, including the aforementioned optical waveguide. Attached Figure Description

[0014] The specific embodiments of this application are described in detail below with reference to the accompanying drawings, wherein:

[0015] Figure 1 shows the ghosting phenomenon in the displayed image of a display device using an optical waveguide;

[0016] Figure 2 shows a top view of an optical waveguide according to an embodiment of this application;

[0017] Figure 3 shows a side cross-sectional view of the optical waveguide according to the embodiment of Figure 2;

[0018] Figure 4A shows a top view of an optical waveguide according to an embodiment of this application;

[0019] Figure 4B shows a top view of another optical waveguide according to the embodiment of Figure 4A;

[0020] Figure 4C shows a top view of another optical waveguide according to the embodiment of Figure 4A;

[0021] Figure 5 shows a side cross-sectional view of an optical waveguide according to an embodiment of the present application;

[0022] Figure 6A shows a schematic diagram of an optical waveguide according to an embodiment of this application;

[0023] Figure 6B shows a schematic diagram of the scattering and diffraction of the optical waveguide according to the embodiment of Figure 6A;

[0024] Figure 7A shows a schematic diagram of an optical waveguide according to an embodiment of this application;

[0025] Figure 7B shows a schematic diagram of the scattering and diffraction of the optical waveguide according to the embodiment of Figure 7A;

[0026] Figure 8 shows the R0 order scattering diffraction spectrum of an optical waveguide according to an embodiment of this application;

[0027] Figure 9A shows a schematic diagram of an optical waveguide according to an embodiment of this application;

[0028] Figure 9B shows a schematic diagram of another optical waveguide structure according to the embodiment of Figure 9A;

[0029] Figure 9C shows a schematic diagram of another optical waveguide structure according to the embodiment of Figure 9A;

[0030] Figure 10A shows a schematic diagram of an optical waveguide according to an embodiment of this application;

[0031] Figure 10B shows a schematic diagram of another optical waveguide structure according to the embodiment of Figure 10A;

[0032] Figure 10C shows a schematic diagram of another optical waveguide structure according to the embodiment of Figure 10A;

[0033] Figure 11A shows a schematic diagram of an optical waveguide according to an embodiment of this application;

[0034] Figure 11B shows a schematic diagram of another optical waveguide structure according to the embodiment of Figure 11A;

[0035] Figure 12 shows a schematic diagram of an optical waveguide according to an embodiment of this application;

[0036] Figure 13 shows a schematic diagram of an optical waveguide according to an embodiment of this application. Detailed Implementation

[0037] To enable those skilled in the art to more clearly understand the concepts and ideas of this application, the application is described in detail below with reference to specific embodiments. It should be understood that the embodiments given herein are only a part of all possible embodiments of this application. After reading the specification of this application, those skilled in the art are capable of making improvements, modifications, or substitutions to parts or the entirety of the following embodiments, and such improvements, modifications, or substitutions are also included within the scope of protection claimed in this application.

[0038] In this document, the terms "one," "an," and other similar words are not intended to indicate that only one of the described things exists, but rather that the description refers only to one of the described things, which may have one or more. In this document, the terms "comprising," "including," and other similar words are intended to indicate a logical relationship, not a spatial relationship. For example, "A includes B" means that logically B belongs to A, not that spatially B is located inside A. Furthermore, the meanings of the terms "comprising," "including," and other similar words should be considered open-ended, not closed-ended. For example, "A includes B" means that B belongs to A, but B does not necessarily constitute all of A; A may also include other elements such as C, D, and E.

[0039] In this document, the terms "first," "second," and other similar terms are not intended to imply any order, quantity, or importance, but are merely used to distinguish different elements. In this document, the terms "embodiment," "this embodiment," "an embodiment," or "an example" do not indicate that the description applies only to one specific embodiment, but rather that such description may also be applicable to one or more other embodiments. Those skilled in the art will understand that any description made herein with respect to one embodiment can be substituted, combined, or otherwise combined with the descriptions in one or more other embodiments, and the new embodiments resulting from such substitutions, combinations, or other combinations are readily conceived by those skilled in the art and fall within the scope of protection of this application.

[0040] In the various embodiments of this application, an optical waveguide can refer to a structure capable of confining light within itself and guiding light to propagate along a specific path. The working principle of an optical waveguide is based on the phenomenon of total internal reflection. When light enters the optical waveguide at a certain angle, due to the difference in refractive index between the optical waveguide and the surrounding medium, total internal reflection occurs at the boundary of the optical waveguide, thereby confining the light within the optical waveguide for propagation.

[0041] In the embodiments of this application, an augmented reality display device can refer to a device that combines virtual digital information with a real scene and presents the fused content to the user. It senses the environment through sensors such as cameras and gyroscopes, and displays the information using optical or video perspective methods. During operation, it matches virtual and real information based on sensor data. This type of device has wide applications, allowing users to see virtual elements in real-world scenes and enhancing their perception of the world.

[0042] Augmented Reality (AR) near-eye display systems, as a technology that merges virtual information with the real world, typically include micro-projectors and optical displays, with optical waveguides being one implementation path for these displays. Currently, optical waveguide solutions are mainly divided into geometric waveguides and diffractive waveguides. The essence of a diffractive waveguide is to utilize the diffraction properties of a grating to couple an incident light beam into the waveguide. When light propagates in the waveguide, it passes sequentially through the grating region and the blank region. The boundary between these two regions, due to the height difference, forms a step, causing abnormal scattering and diffraction, resulting in motion blur. During dynamic imaging, the motion blur problem becomes even more pronounced between different frames.

[0043] In some embodiments of this application, various designs are provided for different situations. The height of the blank area is set to the range of 0.7hg to 1.3hg (hg represents the height of the grating area) or a gradual height is set within this range. The size of the blank area is determined by the two adjacent grating areas, which can effectively reduce the generation of ghosting and improve the imaging quality of the diffractive waveguide.

[0044] In some embodiments of this application, the height at the boundary between the grating region and the blank region without a grating is set to a range of 0.7hg to 1.3hg, or a gradually varying height is set within this range. This effectively reduces or eliminates the trailing effect of the diffracted waveguide, improving imaging quality.

[0045] In some embodiments of this application, the size of the blank area at the boundary is determined by the size of the adjacent grating area, thereby avoiding the introduction of additional steps that would cause diffraction and scattering.

[0046] In some embodiments of this application, various applicable designs are provided, making the design results universal. This design method can be implemented under various partition designs and various grating structures, making the design method versatile.

[0047] Figure 2 shows a top view of an optical waveguide according to an embodiment of this application.

[0048] As shown in Figure 2, the optical waveguide includes an optical waveguide substrate 210 and a grating layer disposed on the surface of the optical waveguide substrate 210. The grating layer includes a grating region and a blank region 224. A grating is disposed in the grating region, and no grating is disposed in the blank region. In Figure 2, the grating region includes a coupling-in region 221, a turning region 222, and a coupling-out region 223. The coupling-in region 221 is used to couple image light emitted from an external optomechanism into the waveguide substrate, serving as the entry point for image information into the optical waveguide. The turning region 222 is used to expand and redirect the image light emitted from the coupling-in region, guiding the light to propagate along a predetermined path within the waveguide substrate to the coupling-out region. The coupling-out region 223 is used to couple the image light propagating within the waveguide substrate out, allowing the light to enter the human eye and thus be observed as a virtual image.

[0049] Specifically, when designing a surface relief grating diffractive waveguide, a three-section or two-section design is usually adopted to achieve two-dimensional pupil expansion. Figure 2 shows one layout design of a three-section diffractive waveguide.

[0050] Figure 3 shows a side cross-sectional view of the optical waveguide according to the embodiment of Figure 2.

[0051] As shown in Figure 3, the optical waveguide includes an optical waveguide substrate 310 and a grating layer 320. The grating in the grating layer 320 includes an input grating 321, a bend grating 322, and an output grating 323. The input grating 321 couples light rays into the optical waveguide. The bend grating 322 bends the coupled light rays. The output grating 323 couples the bend grating out of the optical waveguide.

[0052] It should be noted that, for ease of representation and simplification, Figure 3 shows the coupling grating 321, the turning grating 322, and the coupling grating 323 as being arranged equidistantly in a horizontal manner. However, as can be seen from Figure 2, these three grating regions are arranged at right angles in the top view, and their side cross-sectional view may not be arranged equidistantly in the horizontal manner as shown in Figure 3.

[0053] Specifically, during design and optimization, the optical waveguide substrate and the grating structure on it are typically considered. The tooth profile of the grating is not unique. In this embodiment, the gratings in the coupling region, transition region, and coupling region are all rectangular gratings of equal height. Those skilled in the art will understand that other tooth profiles and combinations of different heights can also be selected for the design.

[0054] Figures 4A to 4C show top views of three optical waveguides according to an embodiment of this application.

[0055] As shown in Figures 4A to 4C, the optical waveguide includes an optical waveguide substrate 410 and a grating layer. The grating layer includes a grating region and a blank region 420. The grating region includes a coupling-in region 421, a transition region 422, and a coupling-out region 423.

[0056] Figure 4A shows a three-part design, in which there is a blank area 431 between the coupling in region 421 and the transition region 422, and there is also a blank area 432 between the transition region 422 and the coupling out region 423.

[0057] Figure 4B shows a three-part design in which there is no blank area between the coupling in region 421 and the transition region 422, but there is a blank area 432 between the transition region 422 and the coupling out region 423.

[0058] Figure 4C shows a two-part design in which the grating region does not include the transition region and there is only a blank region 433 between the coupling-in region 421 and the coupling-out region 423.

[0059] Specifically, to reduce or eliminate the trailing phenomenon of diffracted waveguides, the boundary between the grating region and the blank region needs to be considered during the design process. Since only the propagation process of light is considered, only the blank regions between each grating section need to be analyzed. A three-section design or a two-section design as shown in Figures 4A to 4C can be adopted. The blank region 420 includes: a blank region 431 between the coupling-in region 421 and the transition region 422 in the three-section section, the size of which is determined by the size of the coupling-in region 421 and the transition region 422; a blank region 432 between the transition region 422 and the coupling-out region 423 in the three-section section, the length of which is consistent with the length of the corresponding grating section; and a blank region 433 between the coupling-in region 421 and the coupling-out region 423 in the two-section section, the size of which is determined by the size of the coupling-in region 421 and the coupling-out region 423. In some cases, since the grating tooth shape and height of the three sections are consistent, it is sufficient to discuss the scattering and diffraction of a certain edge region.

[0060] Figure 5 shows a side cross-sectional view of an optical waveguide according to an embodiment of this application.

[0061] As shown in Figure 5, the optical waveguide includes an optical waveguide substrate 510 and a grating layer 520. The grating layer 520 includes a grating region and a blank region. The grating region includes an input grating 521, a transition grating 522, and an output grating 523. The blank region includes a blank region 524 between the input grating 521 and the transition grating 522, and a blank region 525 between the transition grating 522 and the output grating 523.

[0062] Specifically, for diffractive waveguide samples prepared by nanoimprint technology, the waveguide substrate 510 not only contains the designed grating structure but also residual adhesive. This is because during the nanoimprint sample preparation process, a layer of adhesive is first spin-coated onto the waveguide substrate 510, and then the grating structure on the sub-plate is imprinted onto the waveguide substrate 510, forming the designed grating tooth shape in the adhesive layer. For blank areas, the adhesive does not disappear but remains on the waveguide substrate 510. At the junction of the blank area formed by the residual adhesive and the grating area, a step with a certain height difference is formed (shown by the dashed box in Figure 5). The presence of this step will cause additional scattering and diffraction of light during propagation, resulting in ghosting in the diffractive waveguide imaging display, thus affecting the imaging quality.

[0063] Figures 6A and 6B show schematic diagrams of scattering and diffraction of an optical waveguide according to an embodiment of this application.

[0064] As shown in Figure 6A, the optical waveguide includes an optical waveguide substrate and a grating layer. The grating layer includes a grating region and a blank region, where the height of the blank region is h and the height of the grating region is hg, where h is less than hg.

[0065] Specifically, Figure 6A shows a schematic diagram where the height of the blank area is lower than the height of the grating area. When the incident light ray I propagates inside the waveguide, it undergoes diffraction, producing R0 and R-1 orders, with the R-1 order to the left of the R0 order. To ensure that the light ray can undergo total internal reflection inside the waveguide, the incident angle is set to be greater than the total internal reflection angle; for example, the incident angle here is set to 40°.

[0066] Figure 6B shows the analysis of scattering and diffraction results at the boundary between the blank area and the grating area. The horizontal axis "angle" represents the scattering and diffraction angle (which corresponds to the diffraction angle), and the vertical axis log(|E|^2) represents the scattering and diffraction intensity. At this time, the scattering and diffraction intensity of the R0 order is higher than that of the R-1 order. The scattering and diffraction patterns of the R0 and R-1 orders are the same, and the bandwidth of their scattering and diffraction peaks is wider on the right than on the left. This will cause a trailing shadow on the right side in actual optical waveguide imaging. The arrow in Figure 1 points to the direction in which the trailing shadow appears.

[0067] Figures 7A and 7B show schematic diagrams of scattering and diffraction of an optical waveguide according to an embodiment of this application.

[0068] As shown in Figure 7A, the optical waveguide includes an optical waveguide substrate and a grating layer. The grating layer includes a grating region and a blank region, where the height of the blank region is h and the height of the grating region is hg, where h is greater than hg.

[0069] Specifically, Figure 7A shows a schematic diagram where the height of the blank area is higher than the height of the grating area. As shown in Figure 7B, the scattering and diffraction patterns of the R0 and R-1 orders are the same, with the bandwidth of their scattering and diffraction peaks being wider on the right than on the left. This leads to a trailing effect on the right side during actual optical waveguide imaging. Since the scattering and diffraction intensity of the R0 order in this embodiment is significantly higher than that of the R-1 order, the trailing effect is mainly contributed by the R0 order. Therefore, we mainly focus on the scattering and diffraction of the R0 order.

[0070] Figure 8 shows the R0 order scattering diffraction spectrum of an optical waveguide according to an embodiment of this application.

[0071] Figure 8 shows the R0 diffraction order scattering diffraction spectrum as a function of the blank area height, specifically the R0 order scattering diffraction spectrum as the step height of the blank area changes. The grating height is set to 140 nm (this height is not fixed and can be adjusted according to the actual design). The vertical axis "thickness" represents the height of the blank area, varying from 0 nm to 200 nm. The dashed line corresponds to the height of the blank area where the scattering diffraction bandwidth is narrowest, i.e., the trailing effect is weakest, and hg represents the grating height. Within this height range of h to hg, the corresponding scattering diffraction bandwidths are all relatively small, and the trailing effect is weaker than at other heights. Therefore, when the grating height is set to hg, the blank area height can be set to within the range of 0.7hg to hg, at which point the trailing effect of the diffracted waveguide is weakest. To meet the design requirements of all structures, this height range can be extended to ±30% of hg, i.e., 0.7hg to 1.3hg.

[0072] Figures 9A to 9C show schematic diagrams of the structure of an optical waveguide according to an embodiment of this application.

[0073] Figure 9A shows a schematic diagram of the structure when the height of the step in the blank area corresponds to h in Figure 8. As shown in Figure 9A, the optical waveguide includes an optical waveguide substrate and a grating layer. The grating layer is disposed on the surface of the optical waveguide substrate and includes a grating region and a blank region. The height h of the blank region is between 0.7 and 1.3 times the height hg of the grating region. Through extensive research and practice, the inventors of this application have discovered that the motion blur problem of the optical waveguide is caused by the height difference at the boundary between the grating region and the blank region. To address this issue, this application limits the height difference between the grating region and the blank region to a certain range. Specifically, this application specifies that the height of the blank region is 0.7-1.3 times that of the grating region. In this way, the motion blur problem caused by the height difference at the boundary between the grating region and the blank region will be greatly alleviated, thereby providing a better display effect and user experience.

[0074] Specifically, Figure 9A is a structural schematic diagram when the height h of the blank area is set to the range of 0.7hg to 1.3hg. The height h of the blank area remains constant, meaning the top surface of the blank area is horizontal.

[0075] In this embodiment, the preparation (or height adjustment) of the blank area can be carried out in the following ways. When the grating is manufactured using nanoimprinting, a material with a refractive index similar to that of the grating is filled on the residual adhesive layer in the blank area; or, when imprinting the master / daughter plate, the shape of the blank area is taken into account and designed to the corresponding master / daughter plate size. When the grating is manufactured using an etching process, the grating area is covered, and a material with a refractive index similar to that of the blank area is deposited only for filling.

[0076] Figure 9B shows a schematic diagram of a structure where the blank area is set with a gradually varying height. As shown in Figure 9B, the height h of the blank area varies between 0.7 times and 1.3 times the height hg of the raster area. By varying the height of the blank area within a specified range, the height difference at the boundary between the blank area and other areas (such as the raster area) can be reduced, and the abrupt change in height at the boundary can be decreased. This allows the blank area to connect with other areas more smoothly, which helps to further reduce the ghosting phenomenon caused by the height difference.

[0077] For example, the height h of the blank area can be varied in a stepped manner. By adopting a stepped variation, the ghosting phenomenon can be reduced while improving the ease of processing and reducing manufacturing costs.

[0078] Specifically, as shown in Figure 9B, since the height of the blank area at the edge can vary within a range, the height of this area can also be set as a stepped gradient, with the lowest gradient height being 0.7hg and the highest being hg or 1.3hg.

[0079] Figure 9C shows a schematic diagram of a structure where the steps in the blank area are set to a smoothly gradual height. As shown in Figure 9C, the height h of the blank area changes continuously. By adopting a continuous change, the height change of the blank area can be made smoother, which helps to further reduce the ghosting phenomenon caused by the height difference.

[0080] At this point, the height of the blank area at the first end (right end in the diagram) adjacent to the raster area is between 1 and 1.3 times the height hg of the raster area, and the height of the blank area at the second end (left end in the diagram) opposite to the first end is between 0.7 and 1 times the height hg of the raster area. The height h of the blank area gradually increases from the second end to the first end. By making the blank area gradually increase from the end furthest from the raster area to the end adjacent to the raster area, and making the height of the end adjacent to the raster area 1-1.3 times the height of the raster area, the blank area can have a smoother height change pattern, and at the boundary with the raster area, it has a height range that can better reduce ghosting, thereby improving the display effect.

[0081] Specifically, as shown in Figure 9C, the height of the blank area at the boundary can be set to a smooth gradient. The designs in Figures 9A to 9C can effectively improve the motion blur of the optical waveguide and enhance imaging quality.

[0082] Figures 10A to 10C show schematic diagrams of the structure of an optical waveguide according to an embodiment of this application.

[0083] When the grating heights of different zones are inconsistent, there are two scenarios to consider. One scenario is that the height difference between the first height hg1 of the first grating region and the second height hg2 of the second grating region is less than or equal to 30% of the larger of the first and second heights, i.e., the height difference dh ≤ 30% * max(hg1, hg2). Figures 10A to 10C illustrate the analysis of the case where the grating height difference dh ≤ 30% * max(hg1, hg2).

[0084] As shown in Figure 10A, the grating region includes a first grating region and a second grating region. The first grating region has a first height hg1, and the second grating region has a second height hg2. The first height hg1 is less than the second height hg2, and the difference between the first height hg1 and the second height hg2 is less than or equal to 30% of the first height hg2. A blank area is positioned between the first grating region and the second grating region. In this case, the height of the blank area can remain constant (the top is horizontal), and its height is between 0.7 times the second height hg2 and 1.3 times the first height hg1. When the blank area is positioned between two grating regions with different heights, if the height difference between the two grating regions is less than 30% of the higher height, then the blank area can be between 1.3 times the lower height and 0.7 times the higher height. In this way, the height difference of the blank area at the boundary with the first grating region will not exceed 30% of the first height, and the height difference at the boundary with the second grating region will not exceed 30% of the second height, thus ensuring that no severe ghosting occurs at either end of the blank area.

[0085] Specifically, Figure 10A shows a schematic diagram of the structure when the blank area is set to the same height as the lower grating area (i.e., the first grating area) (h = hg1). As shown in Figure 10A, the height of the blank area can be based on the height of the lower of the first and second grating areas, and the height of the blank area can be kept consistent with the height hg1 of the first grating area.

[0086] As shown in Figure 10B, the grating region includes a first grating region and a second grating region. The first grating region has a first height hg1, and the second grating region has a second height hg2. The first height hg1 is less than the second height hg2. A blank region is disposed between the first grating region and the second grating region. The height of the blank region at the first end adjacent to the first grating region is between 0.7 and 1.3 times the first height hg1, and the height of the blank region at the second end adjacent to the second grating region is between 0.7 and 1.3 times the second height hg2. The height of the blank region varies between the height at the first end and the height at the second end.

[0087] Specifically, Figure 10B shows a schematic diagram of a blank area with a stepped, gradually changing height. As shown in Figure 10B, the blank area can be set with a stepped, gradually changing height. The number of steps is not specifically required.

[0088] Figure 10C shows a schematic diagram of a blank area with a smooth gradient height. In Figure 10C, the blank area can be set with a smooth gradient height, with the gradient range being 130% of the larger of the first and second heights to 70% of the smaller of the first and second heights, that is, from 130%*max(hg1,hg2) to 70%*min(hg1,hg2).

[0089] Figures 11A and 11B show schematic diagrams of an optical waveguide according to an embodiment of this application.

[0090] When the grating heights of the different zones are inconsistent, there are two scenarios to consider. Besides the scenario shown in Figures 10A to 10C, another scenario is where the height difference between the first height hg1 of the first grating region and the second height hg2 of the second grating region is greater than or equal to 30% of the larger of the first and second heights, i.e., the height difference dh ≥ 30% * max(hg1, hg2). Figures 11A and 11B illustrate the analysis of the scenario where the grating height difference dh ≥ 30% * max(hg1, hg2).

[0091] As shown in Figure 11A, the grating region includes a first grating region and a second grating region. The first grating region has a first height hg1, and the second grating region has a second height hg2. The first height hg1 is less than the second height hg2. A blank region is disposed between the first grating region and the second grating region. The height of the blank region at the first end adjacent to the first grating region is between 0.7 and 1.3 times the first height hg1, and the height of the blank region at the second end adjacent to the second grating region is between 0.7 and 1.3 times the second height hg2. The height of the blank region varies between the height at the first end and the height at the second end. When a blank area is placed between two grating areas at different heights, if the height difference between the two grating areas is greater than 30% of the higher height, the height of the blank area can be varied. It can be stipulated that the height difference between each end of the blank area and the first and second grating areas does not exceed 30%, that is, the height of the first end is 0.7-1.3 times the first height, and the height of the second end is 0.7-1.3 times the second height. This ensures that even if the height difference between the two grating areas is large, there will be no severe ghosting at the junction of the blank area and the two grating areas.

[0092] Specifically, Figure 11A shows a schematic diagram of a blank area with a stepped, gradually changing height. The blank area can be set with a gradually changing height, ranging from 1.3hg2 to 0.7hg1, with a number of changes ≥ 1, as shown in the stepped, gradually changing height diagram in Figure 11A.

[0093] Figure 11B shows a schematic diagram of a blank area with a smooth gradient height. The blank area can be set to a gradient height, with a gradient range of 1.3hg2 to 0.7hg1, as shown in the smooth gradient height in Figure 11B.

[0094] It should be understood that the difference between Figures 11A-B and Figures 10A-C is that, in the case of Figure 11A-B, the height difference between the first and second grating regions on both sides of the blank area is relatively large, exceeding 30% of the height of the higher grating region. In this case, if the height of the blank area is set to be constant, i.e., the top of the blank area is set to be horizontal as in Figure 10A, it is possible that the height difference between the blank area and the first or second grating region at the left or right end will exceed 30% of the height of the corresponding grating region. Therefore, in the case of Figures 11A-B, it is best to set the height of the blank area to be variable, such as a stepped or smooth gradient, and the height at both ends of the blank area should be specified to be between 0.7 and 1.3 times the height of the adjacent grating region. This ensures that the height difference of the blank area at either end will not exceed 30% of the height of the corresponding grating region.

[0095] Figure 12 shows a schematic diagram of an optical waveguide according to an embodiment of this application.

[0096] Figure 12 illustrates the case where height modulation exists in each grating section. The optical waveguide includes an optical waveguide substrate 1210 and a grating layer 1220. The grating layer 1220 includes a first grating region 1221, a second grating region 1222, and a blank region 1223. When the grating heights of the different sections are inconsistent, the height of the blank region 1223 is determined by the first grating region 1221 and the second grating region 1222 closest to the boundary.

[0097] As shown in Figure 12, the grating region includes a first grating region 1221 and a second grating region 1222. The first grating region 1221 and the second grating region 1222 have varying heights. A blank region 1223 is disposed between the first grating region 1221 and the second grating region 1222. The end of the blank region 1223 adjacent to the first grating region 1221 is the first end, and the end of the blank region 1223 adjacent to the second grating region 1222 is the second end. The first grating region 1221 has a first height hg1 at the end adjacent to the first end, and the second grating region 1222 has a second height hg2 at the end adjacent to the second end. The first height hg1 is less than the second height hg2.

[0098] At this point, if the difference between the first height hg1 and the second height hg2 is less than or equal to 30% of the second height hg2, and the height of the blank area 1223 remains unchanged, then the height of the blank area 1223 is between 0.7 times the second height hg2 and 1.3 times the first height hg1. If the heights of the first and second grating areas are variable, then the height design of the blank area only needs to consider the heights of the grating areas immediately adjacent to the ends of the blank area. If the height difference between the ends of the first and second grating areas immediately adjacent to the blank area does not exceed 30%, then the height of the blank area can be specified to be between 0.7 times the second height and 1.3 times the first height, thereby ensuring that the height difference between the blank area and the boundary of the first or second grating area does not exceed 30%, thus reducing the ghosting phenomenon caused by the height difference. Alternatively, if the height of the blank area varies between the height of the first end and the height of the second end, then regardless of whether the difference between the first height hg1 and the second height hg2 is greater than or less than 30% of the second height hg2, the height of the first end should be between 0.7 and 1.3 times the first height hg1, and the height of the second end should be between 0.7 and 1.3 times the second height hg2. If the heights of the first and second grating regions vary, only the heights of their ends immediately adjacent to the blank area need to be considered. If the height of the blank area varies in this case, then it is only necessary to ensure that the height difference between the first and second ends of the blank area and the height of the end of the grating region immediately adjacent to the blank area does not exceed 30%, that is, the height of the first end should be 0.7-1.3 times the first height, and the height of the second end should be 0.7-1.3 times the second height. This ensures that no severe ghosting occurs at the boundary between the blank area and the two grating regions.

[0099] Figure 13 shows a schematic diagram of an optical waveguide according to an embodiment of this application.

[0100] Figure 13 illustrates the filling between the partitioned gratings. Specifically, Figure 13 shows a schematic diagram of the filling structure of the diffractive waveguide. The waveguide includes a waveguide substrate 1310, a grating layer 1320, and a cover plate 1330 (or a second waveguide layer), with a dielectric 1340 filling the space between the grating layer 1320 and the cover plate 1330. The grating layer 1320 includes a first grating region 1321, a second grating region 1322, and a blank region 1323.

[0101] In Figure 13, the height of the blank area follows the same pattern as the height variation of the blank area in the embodiments shown in Figures 9A to 12.

[0102] The concepts, principles, and ideas of this application have been described in detail above with reference to specific embodiments (including examples and instances). Those skilled in the art should understand that the embodiments of this application are not limited to those given above. After reading this application, those skilled in the art can make any possible improvements, substitutions, and equivalents to the steps, methods, apparatus, and components in the above embodiments, and such improvements, substitutions, and equivalents should be considered to fall within the scope of this application. The scope of protection of this application is limited to the claims.

Claims

1. An optical waveguide, characterized in that, include: Optical waveguide substrate (310); A grating layer (320) is disposed on the surface of the optical waveguide substrate (310). The grating layer (320) includes a grating region and a blank region (224). The height of the blank region (224) is between 0.7 and 1.3 times the height of the grating region.

2. The optical waveguide according to claim 1, characterized in that, The height of the blank area (224) varies between 0.7 times and 1.3 times the height of the grating area.

3. The optical waveguide according to claim 2, characterized in that, The height of the blank area (224) varies continuously.

4. The optical waveguide according to claim 2, characterized in that, The height of the blank area (224) may vary in a stepped manner.

5. The optical waveguide according to claim 1, characterized in that, The height of the blank area (224) at the first end adjacent to the grating area is between 1 and 1.3 times the height of the grating area, and the height of the blank area (224) at the second end opposite to the first end is between 0.7 and 1 times the height of the grating area. The height of the blank area (224) gradually increases from the second end to the first end.

6. The optical waveguide according to claim 1, characterized in that, The grating region includes a first grating region (1221) and a second grating region (1222). The first grating region (1221) has a first height (hg1), and the second grating region (1222) has a second height (hg2). The first height (hg1) is less than the second height (hg2), and the difference between the first height (hg1) and the second height (hg2) is less than or equal to 30% of the second height (hg2). The blank area (224) is disposed between the first grating region (1221) and the second grating region (1222). The height of the blank area (224) is between 0.7 times the second height (hg2) and 1.3 times the first height (hg1).

7. The optical waveguide according to claim 1, characterized in that, The grating region includes a first grating region (1221) and a second grating region (1222). The first grating region (1221) has a first height (hg1), and the second grating region (1222) has a second height (hg2). The first height (hg1) is less than the second height (hg2). The blank region (224) is disposed between the first grating region (1221) and the second grating region (1222). The height of the blank region (224) at the first end adjacent to the first grating region (1221) is between 0.7 and 1.3 times the first height (hg1). The height of the blank region (224) at the second end adjacent to the second grating region (1222) is between 0.7 and 1.3 times the second height (hg2). The height of the blank region (224) varies between the height at the first end and the height at the second end.

8. The optical waveguide according to claim 1, characterized in that, The grating region includes a first grating region (1221) and a second grating region (1222). The first grating region (1221) and the second grating region (1222) have varying heights. A blank region (224) is disposed between the first grating region (1221) and the second grating region (1222). The end of the blank region (224) adjacent to the first grating region (1221) is the first end, and the end of the blank region (224) adjacent to the second grating region (1222) is the second end. The first grating region (1221) has a first height (hg1) at the end adjacent to the first end, and the second grating region (1222) has a second height (hg2) at the end adjacent to the second end. The first height (hg1) is less than the second height (hg2), and the difference between the first height (hg1) and the second height (hg2) is less than or equal to 30% of the second height (hg2). The height of the blank area (224) is between 0.7 times the second height (hg2) and 1.3 times the first height (hg1).

9. The optical waveguide according to claim 1, characterized in that, The grating region includes a first grating region (1221) and a second grating region (1222). The first grating region (1221) and the second grating region (1222) have varying heights. The blank region (224) is disposed between the first grating region (1221) and the second grating region (1222). The end of the blank region (224) adjacent to the first grating region (1221) is the first end, and the end of the blank region (224) adjacent to the second grating region (1222) is the second end. The first grating region (1221) has a first height (hg1) at the end adjacent to the first end, and the second grating region (1222) has a second height (hg2) at the end adjacent to the second end. The first height (hg1) is smaller than the second height (hg2). The height of the first end is between 0.7 and 1.3 times the first height (hg1), the height of the second end is between 0.7 and 1.3 times the second height (hg2), and the height of the blank area (224) varies between the height of the first end and the height of the second end.

10. An augmented reality display device, characterized in that, The optical waveguide includes any one of claims 1 to 9.

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