Optical waveguide and near-to-eye display module

Abstract

The embodiment of the utility model discloses an optical waveguide and a near-to-eye display module, the optical waveguide comprises a waveguide substrate, and two or more grating areas with specific optical functions are arranged on the waveguide substrate; a grating is arranged in the grating area, the grating arranged in part or all of the grating area comprises at least two stacked grating layers, each grating layer at least comprises one kind of grating part, and the grating part is rectangular; and the grating layers in the grating have the same periodic size.

Description

Technical Field

[0001] This application relates to the field of display technology, specifically to an optical waveguide and a near-eye display module. Background Technology

[0002] Currently, with the development of Augmented Reality (AR) display technology, AR glasses products are gradually becoming more widespread. Common AR glasses products typically employ a combination of a light engine and a waveguide. That is, the waveguide can be used as a lens for the AR glasses (in this case, it can be called a waveguide lens). The light output from the light engine is transmitted through the waveguide lens and then enters the wearer's eyes, allowing the wearer to view AR content.

[0003] However, this approach can lead to light leakage. Light leakage occurs when light rays from the waveguide lens are coupled through the grating to the viewer's eye, and simultaneously some light rays are coupled out to the external environment. This phenomenon allows the image content within the waveguide lens to be seen from the external environment, which is detrimental to user privacy. Utility Model Content

[0004] Based on the above, this application provides an optical waveguide and a near-eye display module to solve the problems existing in the current optical waveguide.

[0005] Based on one aspect of this application, an embodiment of this application provides an optical waveguide, which includes a waveguide substrate, on which two or more grating regions with specific optical functions are disposed;

[0006] A grating is provided in the grating region, and the grating provided in part or all of the grating region comprises at least two stacked grating layers, each grating layer comprising at least one type of grating portion, the grating portion being rectangular;

[0007] Different grating sections within the same grating layer are made of different materials and have different refractive indices;

[0008] Each of the grating layers in the grating has the same period size.

[0009] Optionally, the same grating layer has the same depth;

[0010] If the same grating layer contains different grating portions, then the different grating portions in the grating layer have the same depth.

[0011] Optionally, different grating layers in the same grating may have different depths.

[0012] Optionally, each grating layer of the same grating includes a grating portion made of the same material.

[0013] Optionally, the grating includes a grating layer made of the same material.

[0014] Optionally, if there are two or more grating layers made of the same material, the two or more layers are not adjacent to each other.

[0015] Optionally, if adjacent grating layers each contain different grating portions, the grating portions of the adjacent grating layers are arranged in a staggered manner.

[0016] Optionally, each of the grating layers in the grating has the same period size in the second direction.

[0017] Based on another aspect of this application, an embodiment of this application provides a near-eye display module, including an image projection device and the aforementioned optical waveguide. The image projection device is used to generate image light rays and project them onto a grating area on the optical waveguide for coupling in the light rays, and after transmission through the optical waveguide, output the light rays through the grating area for coupling out the light rays.

[0018] Other features and advantages of this application will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the technical solutions of this application. The objectives and other advantages of this application may be realized and obtained by means of the structures and / or processes particularly pointed out in the description, claims and drawings. Attached Figure Description

[0019] Other features, objects, and advantages of this application will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0020] Figure 1 This is a schematic diagram of a waveguide structure provided in an embodiment of this application;

[0021] Figure 2a This is a schematic diagram of the structure of a grating 200 provided in an embodiment of this application;

[0022] Figure 2b This is a schematic diagram of the structure of the grating unit 230 in the grating 200;

[0023] Figure 3a This is a schematic diagram of the structure of a grating 300 provided in an embodiment of this application;

[0024] Figure 3b This is a schematic diagram of the structure of the grating unit 330 in the grating 300;

[0025] Figure 4a This is a schematic diagram of the structure of a grating 400 provided in an embodiment of this application;

[0026] Figure 4b This is a schematic diagram of the structure of the grating unit 430 in the grating 400;

[0027] Figure 5a This is a schematic diagram of the structure of a grating unit 530 provided in an embodiment of this application;

[0028] Figure 5b yes Figure 5a A schematic diagram of the light leakage ratio and diffraction efficiency of the grating unit 530 in the diagram;

[0029] Figure 6a This is a schematic diagram of the structure of a grating unit 630 provided in an embodiment of this application;

[0030] Figure 6b yes Figure 6a A schematic diagram of the light leakage ratio and diffraction efficiency of the grating unit 630 in the diagram;

[0031] Figure 7a This is a schematic diagram of the structure of a grating unit 730 provided in an embodiment of this application;

[0032] Figure 7b yes Figure 7a A schematic diagram of the light leakage ratio and diffraction efficiency of the grating unit 730 in the diagram;

[0033] Figure 8a This is a schematic diagram of the structure of a grating unit 830 provided in an embodiment of this application;

[0034] Figure 8b yes Figure 8a A schematic diagram of the light leakage ratio and diffraction efficiency of the grating unit 830 in the diagram;

[0035] Figure 9a This is a schematic diagram of the structure of a grating unit 930 provided in an embodiment of this application;

[0036] Figure 9b yes Figure 9a A schematic diagram of the light leakage ratio and diffraction efficiency of the grating unit 930 in the diagram. Detailed Implementation

[0037] The present application will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, only the parts relevant to the invention are shown in the accompanying drawings.

[0038] In the embodiments of this application, the light engine (also referred to as an image source, image projection device or optical engine in this application) can be based on at least one display technology and related devices suitable for the AR glasses field, such as LCOS, MicroLED, MicroOLED, Micro-Electro-Mechanical Systems (MEMS) scanning mirror, fiber scanner, etc., and can emit light of corresponding colors, such as red, green and blue light, that is, RGB light.

[0039] refer to Figure 1 An exemplary optical waveguide 10 provided in this application embodiment includes: a waveguide substrate 101, a coupling region 102, a relay region 103, and a coupling out region 104. The coupling region 102, relay region 103, and coupling out region 104 are all disposed on the waveguide substrate 101. Corresponding grating structures are disposed within the coupling region 102, relay region 103, and coupling out region 104. The grating structures can be implemented using processes such as imprinting, coating, and etching, and are not limited here.

[0040] certainly, Figure 1 The outlines, dimensions, and relative positions of the coupling region 102, relay region 103, and coupling region 104 shown are exemplary and not limited to specific regions. Figure 1 As shown. For example, in practical applications, the contour shape of the coupling region 102 may not be... Figure 1 The circular outline shown can be a rectangle, trapezoid, etc.; similarly, the outline of the relay region 103 can also be a trapezoid or a rounded rectangle; for example, the relative positions of the three may be arranged obliquely; for example, in this embodiment, the coupling region 102, the relay region 103 and the coupling region 104 are disposed on the same side of the waveguide substrate 101, which faces the user's eyes when used as AR glasses, but in other embodiments, the coupling region 102 may also be located on other surfaces of the waveguide substrate 101 (related to the arrangement of the light engine), and not on the same side as the relay region 103 and the coupling region 104.

[0041] In this embodiment, the grating structure provided in the coupling region 102 can be called a coupling grating; the grating structure provided in the relay region 103 can be called a relay grating; and the grating structure provided in the coupling region 104 can be called a coupling grating. The specific grating type can be a one-dimensional grating.

[0042] In this embodiment, when the optical waveguide is used as a lens for AR glasses, it can also be called an optical waveguide lens (for ease of description, it is uniformly referred to as an optical waveguide in this embodiment). Image light output from the image source can be coupled into the optical waveguide and transmitted to the user's eyes via total internal reflection (TIR) ​​within the optical waveguide, thereby allowing the user to view the corresponding AR image. More specifically, light can be coupled into the waveguide substrate 101 via the coupling region 102 and transmitted therein. The relay region 103 receives the light transmitted by the coupling region 102 and deflects the light after expanding it to the coupling region 104. The coupling region 104 receives the light deflected by the relay region 103 and couples the light out from the waveguide substrate 101.

[0043] However, due to the limitations of the existing coupling grating design, while the light transmitted in the optical waveguide is output towards the human eye's observation side (i.e., the direction of the human eye), a considerable amount of light is also output towards the environment side (i.e., the direction opposite to the human eye). This results in people around the AR glasses user being able to see the image content displayed by the AR glasses, which not only leaks the user's privacy but also affects the social atmosphere.

[0044] Therefore, in this application embodiment, a corresponding optical waveguide is provided and a corresponding grating structure is designed to minimize the amount of light output to the environment.

[0045] It should be noted that when optical waveguides are used as lenses for AR glasses, their coupling area typically faces the wearer's eyes. Figure 1 The shown viewpoint is essentially the same as the viewing angle of a user wearing AR glasses. Therefore, in the accompanying drawings of this application, the xyz coordinate system shown refers to the viewing angle of the AR glasses user. For ease of description, in the embodiments of this application, the direction parallel to the y-axis can also be called: the first direction, the vertical direction, or the longitudinal direction; the direction parallel to the x-axis can also be called: the second direction, the horizontal direction, or the transverse direction; the direction perpendicular to the xy plane can be considered as the z-axis direction, and the direction parallel to the z-axis can also be called: the third direction or the depth direction. This coordinate system is used in other views or embodiments of this application, and the descriptions of the corresponding direction names are also applicable throughout.

[0046] refer to Figures 2a-4b The gratings 200, 300, and 400 and their corresponding grating units 230, 330, and 430 provided in the embodiments of this application are provided. Among them, gratings 200, 300, and 400 are all output gratings. In some embodiments, gratings 200, 300, and 400 may also be input gratings and / or relay gratings. This should not be construed as a limitation of this application. Figure 2a , 3aFigures 4a and 4a show the cross-sections of gratings 200, 300, and 400 in the xz plane, respectively. In this embodiment, the gratings are designed to have two or more grating layers, such as grating layers 22 and 24 in grating 200, and grating layers 42, 44, and 46 in grating 400. Each grating layer has a rectangular shape, but the distribution of the rectangular shapes in different grating layers is different. In this embodiment, the shape structure in the grating layer is formed by "grating portions," such as grating portions 221 and 222 in grating layer 22, both of which have a rectangular shape and are periodically distributed; similarly, grating portions 461 and 462 in grating layer 46 also have a rectangular shape and are periodically distributed. Different grating portions are made of different materials.

[0047] refer to Figure 2a The grating 200 includes a grating layer 22 and a grating layer 24. The grating layer 22 further includes grating portions 221 and 222, both of which are rectangular in shape. Grating portion 221 has a longer length in the second direction, while grating portion 222 has a shorter length in the second direction. The two grating portions are made of two different materials. Figure 2a and Figure 2b (Using different colors to represent); the grating layer 24 further includes grating portions 241 and grating portions 242, both of which are rectangular in shape. Grating portion 241 has a longer length in the second direction, while grating portion 242 has a shorter length in the second direction. The two grating portions are also made of two different materials. The grating portions of grating layers 22 and 24 are staggered, and the materials used in the grating portions of grating layers 22 and 24 include a common material. Specifically, the material used in grating portion 222 of grating layer 22 is the same as the material used in grating portion 242 of grating layer 24. In this embodiment, this material can be a filler material when fabricating the grating 200.

[0048] It should be noted that, generally, if the material used for the grating portion is a filler material, then it can be considered that, during the grating fabrication process, the fabrication process sequence corresponding to this grating portion is after the fabrication sequence of grating portions made of other materials in the same grating layer. Taking the fabrication of grating layer 22 as an example, grating portion 221 is fabricated first, and then grating portion 222 is fabricated using the filler material. Of course, this also applies to the subsequent embodiments of this application, so it will not be described separately in the following content.

[0049] refer to Figure 3aThe grating 300 includes a grating layer 32 and a grating layer 34. The grating layer 32 further includes a grating portion 321 and a grating portion 322. Both grating portions are rectangular in shape. The grating portion 321 has a longer length in the second direction, while the grating portion 322 has a shorter length in the second direction. The two grating portions are made of two different materials. The grating layer 34 further includes a grating portion 341 and a grating portion 342. Both grating portions are rectangular in shape. The grating portion 341 has a longer length in the second direction, while the grating portion 342 has a shorter length in the second direction. The two grating portions are made of two different materials. The grating portions of grating layer 32 and grating layer 34 are staggered with each other, and the materials used for the grating portions of grating layer 32 and grating layer 34 include the same material. Specifically, the grating portion 322 in grating layer 32 and the grating portion 342 in grating layer 34 are made of the same material. In this embodiment, this material can be a filler material when fabricating grating 300.

[0050] refer to Figure 4a The grating 400 comprises three grating layers: grating layer 42, grating layer 44, and grating layer 46. The grating portions in each grating layer are rectangular. Grating layer 42 further comprises grating portions 421 and 422, with grating portion 421 having a longer length in the second direction and grating portion 422 having a shorter length in the second direction. These two types of grating portions are made of two different materials. Grating layer 44 is composed of grating portions 441 made of the same material; in this embodiment, such a grating layer can also be referred to as a material layer. Grating layer 46 further comprises grating portions 461 and 462, with grating portion 461 having a longer length in the second direction and grating portion 462 having a shorter length in the second direction. These two types of grating portions are made of two different materials. The grating portions of grating layers 42 and 46 are arranged in a staggered manner. In this embodiment, the grating portions in each grating layer of the grating 400 contain the same material; that is, the grating portion 422 in grating layer 42, the grating portion 441 in grating layer 44, and the grating portion 462 in grating layer 46 use the same material. This material is used as a filler material during the fabrication of the grating 400.

[0051] It should be noted that in the embodiments of this application, the depth of the grating portions contained in any grating layer within any grating is consistent. Therefore, in some embodiments of this application, the grating includes a material layer. In this case, the division of the grating layers still follows the aforementioned rule. That is, by confirming the depth of different grating portions, the corresponding grating layer can be identified. For example, if the grating 400 contains a material layer 44, the grating layer 42 can be identified by the depth of the grating portion 421, and the grating layer 46 can be identified by the depth of the grating portion 461. Furthermore, the material layer 44 located between the grating layer 42 and the grating layer 46 can be identified.

[0052] Figure 2b , 3b Figures 2 and 4b respectively show multiple periodically distributed grating units 230, 330, and 430 contained in gratings 200, 300, and 400. A grating unit can be considered as the smallest recurring periodic unit for any grating. Based on grating units 230, 330, 430, and grating units in subsequent embodiments, it can be seen that in this embodiment, different grating layers in the grating have the same period, and the size of this period (in the x-axis direction) is the size of the grating unit in the x-axis direction. Of course, the grating units shown in this embodiment and subsequent embodiments are only schematic diagrams of one way of dividing the smallest periodic unit of the grating, and the division of grating units may result in the same type of grating portion in the grating layer being divided into incomplete parts, for example... Figure 2b , 3b As shown in 4b, grating portions 221, 321, and 421 in the three grating units each contain incomplete parts, which will not be described separately in subsequent embodiments. The division of grating units should not be construed as a limitation of this application. Furthermore, the description of "whole" in the overall minimum periodic unit of the grating in this application refers to any grating as a whole, not a specific grating layer.

[0053] For the gratings in the embodiments of this application, each grating layer adopts a grating portion with a rectangular cross-section (xz section). This structural arrangement helps to reduce the processing difficulty and cost. Furthermore, by adding grating layers to the grating, staggering the grating portions between each grating layer, and adding material layers, the adjustable degrees of freedom of the grating can be effectively increased. By adjusting these adjustable degrees of freedom, the diffraction efficiency ratio of the reflection coupling order and the transmission coupling order of the light incident into the optical waveguide and transmitted within a certain angle range can be controlled, thereby effectively reducing the light leakage ratio and causing a significant difference in the brightness of the image finally coupled to the human eye side and coupled to the environment side, thus suppressing the occurrence of light leakage.

[0054] In the embodiments of this application, the material used for part or all of the grating portion in the grating layer may include one or more fluorides with a refractive index in the range of 1.4-1.6, such as: cerium fluoride (CeF3), ytterbium fluoride (YbF3), yttrium fluoride (YF3), aluminum fluoride (AlF3), barium fluoride (BaF2), calcium fluoride (CaF2), magnesium fluoride (MgF2), etc.

[0055] Optionally, the material used for part or all of the grating portion in the grating layer may also include one or more oxides with a refractive index in the range of 1.5-2.5, such as: niobium oxide (Nb2O5), titanium oxides (titanium monoxide TiO, titanium dioxide TiO2, titanium trioxide Ti2O3, titanium pentoxide Ti3O5), zirconium oxide (ZrO2), tantalum pentoxide (Ta2O5), cerium oxide (CeO2), yttrium oxide (Y2O3), hafnium oxide (HfO2), magnesium oxide (MgO), aluminum oxide (Al2O3), indium tin oxide (ITO), silicon dioxide (SiO2), zinc oxide (ZnO), etc.

[0056] Optionally, the material used for part or all of the grating portion in the grating layer may also include one or more compounds with a refractive index greater than 2, such as silicon carbide (SiC), strontium titanate (STO), zinc sulfide (ZnS), silicon nitride (Si3N4), lithium niobate (LiNbO3), etc.

[0057] Optionally, the material used for some or all of the grating portions in the grating layer may also include composite materials obtained from the aforementioned compounds through processes such as doping.

[0058] Optionally, the material of a portion of the grating in the grating layer may also include the outgoing space medium, such as air or the material used in the waveguide substrate 101.

[0059] Apart from the differences in materials and refractive indices mentioned above, in the embodiments of this application, the dimensions (depths) of different grating layers in the Z-axis direction may be different, while the dimensions of different grating portions in the same grating layer in the Z-axis direction are the same.

[0060] By combining the selection of materials and refractive index of the grating layer, the degree of freedom in grating control can be further increased, making it easier to control the light output from the coupled grating toward the ambient side.

[0061] To further clarify the scheme of this application, several specific examples will be described below.

[0062] Specific Example 1

[0063] refer to Figure 5a This illustrates a grating unit 530 corresponding to a grating, from Figure 5aAs can be seen, the grating unit 530 includes two grating layers: grating layer 52 and grating layer 54, both of which are rectangular in shape. Grating layer 52 further includes grating portions 521 and 522. Grating portion 521 is rectangular, with a longer length in the second direction, and is made of a material with a refractive index of n1. Grating portion 522 is also rectangular, with a shorter length in the second direction, and is made of a filling material with a refractive index of n2. Grating layer 54 further includes grating portions 541 and 542. Both types of grating portions are rectangular in shape but differ significantly in length in the second direction; grating portion 541 is longer in the second direction than grating portion 542. The two types of grating portions are made of different materials: grating portion 541 is made of a material with a refractive index of n3, and grating portion 542 is made of a filling material with a refractive index of n2.

[0064] In this embodiment, the grating period corresponding to the grating unit 530 is 359.7nm, the refractive index n1 is specifically 2.5, the refractive index n2 is specifically 1, and the refractive index n3 is specifically 2.1. That is, in this embodiment, the filling material is the outgoing space medium (e.g., air); the depth of the grating layer 52 is 31nm, and the duty cycle of the filling material is 0.18; the depth of the grating layer 54 is 35nm, and the duty cycle of the filling material is 0.19.

[0065] By setting the above grating parameters, the light leakage ratio and diffraction efficiency data of the grating corresponding to grating unit 530 under different fields of view can be obtained. (Reference) Figure 5b The diagram shows the diffraction efficiency of the grating corresponding to the grating unit 530 for RGB light in multiple fields of view. And the corresponding light leakage ratio. Among them, T represents the diffraction efficiency of light rays coupled out of the optical waveguide at the +1st order at the corresponding wavelengths. avg R represents the diffraction efficiency of light rays propagating in an optical waveguide, which is coupled out of the ambient side at the +1st order. avg T represents the diffraction efficiency of light rays propagating in an optical waveguide, which are coupled out of the human eye's observation side at the +1st order. avg / R avg This represents the light leakage ratio, and a lower value is better. Commonly used gratings, such as rectangular gratings and tilted gratings, typically have a light leakage ratio above 0.5. Figure 5b As shown in the left figure, the horizontal axis represents the field of view of the optical waveguide, and the vertical axis represents the optical leakage ratio. It can be seen that the optical leakage ratio in this embodiment does not exceed 0.3, the optical leakage ratio of each field of view of red light is less than 0.2, and the optical leakage ratio of each field of view of green light is around 0.1. In terms of diffraction efficiency, the overall optical leakage is reduced by about 2-5 times compared with commonly used gratings.

[0066] Furthermore, when RGB light propagates within an optical waveguide, its diffraction angle increases sequentially, with blue light exhibiting the smallest diffraction angle and red light the largest. This results in blue light being coupled out more frequently and red light less frequently within the same coupling region, making it difficult to adjust the color uniformity of the optical waveguide. And as... Figure 5b As shown in the right figure, the horizontal axis represents the field of view of the optical waveguide, and the vertical axis represents the diffraction efficiency of the RGB light coupled out under the corresponding field of view. It can be seen that the diffraction efficiency distribution of the RGB light in this embodiment is more uniform. Compared with the commonly used grating, the ratio of its blue light diffraction efficiency to red light diffraction efficiency is smaller. As the ratio of blue light diffraction efficiency to red light diffraction efficiency decreases, red light can increase the coupled brightness by increasing the coupled efficiency with fewer coupled out times, thereby making the color uniformity of the corresponding optical waveguide better.

[0067] Specific Example 2

[0068] refer to Figure 6a This illustrates a grating unit 630 corresponding to a grating, from Figure 6a As can be seen, the grating unit 630 includes two grating layers: grating layer 62 and grating layer 64, both of which are rectangular in shape. Grating layer 62 further includes grating portions 621 and 622. Grating portion 621 is rectangular, with a shorter length in the second direction, and is made of a material with a refractive index of n1. Grating portion 622 is also rectangular, with a longer length in the second direction, and is made of a filling material with a refractive index of n2. Grating layer 64 further includes grating portions 641 and 642. Both types of grating portions are rectangular in shape but differ significantly in length in the second direction; grating portion 641 is longer in the second direction than grating portion 642. The two types of grating portions are made of different materials: grating portion 641 is made of a material with a refractive index of n3, and grating portion 642 is made of a filling material with a refractive index of n2.

[0069] In this embodiment, the grating period corresponding to the grating unit 630 is 359.7nm, the refractive index n1 is specifically 2, the refractive index n2 is specifically 2.6, and the refractive index n3 is specifically 1.5; the depth of the grating layer 62 is 41nm, and the duty cycle of the filling material is 0.66; the depth of the grating layer 64 is 29nm, and the duty cycle of the filling material is 0.19.

[0070] By setting the above grating parameters, the light leakage ratio and diffraction efficiency data of the grating corresponding to grating unit 630 for RGB light can be obtained under different viewing fields. (Reference) Figure 6b The diagram shows the diffraction efficiency of the grating corresponding to the grating unit 630 for RGB light under multiple fields of view. And the corresponding light leakage ratio. Unlike the specific example one above, after using the filling material in this embodiment, the light leakage ratio of each field of view is further reduced, and the overall light leakage ratio is less than 0.2. The light leakage ratio of red light decreases less, while the light leakage ratio of blue and green light decreases more. Regarding diffraction efficiency, similar to the specific example one above, the diffraction efficiency distribution of RGB light still maintains good uniformity. However, unlike the specific example one above, the diffraction efficiency ratio of blue light to red light is generally less than 1. Since the propagation angle of blue light is usually smaller than that of red light when propagating light inside the optical waveguide, the number of times blue light is coupled out is much greater than that of red light. The grating structure in this embodiment allows the coupling efficiency of blue light with more coupling out times to be low, and the coupling efficiency of red light with fewer coupling out times to be high. This makes it easier to adjust the color uniformity and brightness uniformity of the coupled image. Therefore, the diffraction efficiency distribution of RGB light in this embodiment is more conducive to designing waveguides with better monocular color uniformity.

[0071] Specific Example 3

[0072] refer to Figure 7a This illustrates a grating unit 730 corresponding to a grating, from Figure 7a As can be seen, the grating unit 730 includes three grating layers: grating layer 72, grating layer 74, and grating layer 76. All three grating layers are rectangular in shape (for clarity, in...). Figure 7a (The dashed lines used to identify each grating layer are not intended to limit this application.) Grating layer 72 further includes grating portions 721 and 722. Grating portion 721 is rectangular, with a longer length in the second direction, and is made of a material with a refractive index of n1. Grating portion 722 is also rectangular, with a shorter length in the second direction, and is made of a filling material with a refractive index of n2. Grating layer 74 is a material layer composed of grating portions 741 using the same filling material with a refractive index of n2. Grating layer 76 further includes grating portions 761 and 762, both of which are rectangular in shape. Grating portion 761 uses a material with a refractive index of n3, and grating portion 762 uses a filling material with a refractive index of n2. The depth of grating layer 72 is significantly greater than the depths of grating layers 74 and 76.

[0073] In this example, the fabrication process of the grating unit 730 can be considered as follows: first, a grating portion 721 (using a material with a refractive index of n1) is first fabricated on a substrate material (such as waveguide substrate 101). Then, a filling material with a refractive index of n2 is stacked by means of coating or the like to form a grating portion 722, a grating layer 74, and a grating layer 76, respectively. After that, the grating layer 76 can be planarized. Then, a grating portion 761 is made of a material with a refractive index of n3 by means of etching or the like, forming a grating layer 76 containing the grating portion 761 and the grating portion 762.

[0074] In this embodiment, the grating period corresponding to the grating unit 730 is 359.7nm, the refractive index n1 is specifically 2, the refractive index n2 is specifically 2.55, and the refractive index n3 is specifically 1.5; the depth of the grating layer 72 is 133nm, and the duty cycle of the filling material is 0.18; the depth of the grating layer 74 is 37nm; the depth of the grating layer 76 is 27nm, and the duty cycle of the filling material is 0.71.

[0075] By setting the above grating parameters, the light leakage ratio and diffraction efficiency data of the grating corresponding to grating unit 730 for RGB light can be obtained under different viewing fields. (Reference) Figure 7b The diagram illustrates the diffraction efficiency and corresponding light leakage ratio of the grating corresponding to the grating unit 730 for RGB light under multiple viewing fields. Compared with the two examples above, after adding a material layer to the grating unit 730, the light leakage ratio of blue light did not continue to decrease compared to specific example two, but returned to the same level as specific example one; while the reduction in the light leakage ratio of red light became larger, with the overall light leakage ratio of red light decreasing to about 0.1; the overall light leakage ratio of green light remained below 0.1. Regarding diffraction efficiency, in this embodiment, the diffraction efficiency of red light is greater than that of blue light under all viewing fields, which means that with the number of couplings remaining unchanged, the coupling brightness can be greatly increased by increasing the coupling efficiency, thereby maximizing the uniformity of the color of the waveguide coupling. However, due to the excessively high diffraction efficiency of some red light viewing fields, the overall field uniformity of red light is lower than that of the aforementioned examples.

[0076] Specific Example 4

[0077] refer to Figure 8a This illustrates a grating unit 830 corresponding to a grating, from Figure 8a As can be seen, the grating unit 830 includes three grating layers: grating layer 82, grating layer 84, and grating layer 86, all of which are rectangular in shape. Grating layer 82 further includes grating portions 821 and 822. Grating portion 821 is rectangular, with a longer length in the second direction, and is made of a material with a refractive index of n1. Grating portion 822 is also rectangular, with a shorter length in the second direction, and is made of a filling material with a refractive index of n2. Grating layer 84 further includes grating portions 841 and 842, both of which are rectangular. Grating portion 841 is made of a material with a refractive index of n3, and grating portion 842 is made of a filling material with a refractive index of n2. The grating layer 86 further includes a grating portion 861 and a grating portion 862. Both grating portions are rectangular in shape, and the length of the grating portion 861 in the second direction is significantly longer than that of the grating portion 862. The grating portion 861 is made of a material with a refractive index of n4, and the grating portion 862 is made of a filling material with a refractive index of n2.

[0078] In this embodiment, the grating period corresponding to the grating unit 830 is 359.7 nm, the refractive index n1 is specifically 2.5, the refractive index n2 is specifically 1, the refractive index n3 is specifically 1.8, and the refractive index n4 is specifically 2.35. That is, in this embodiment, the filling material is the outgoing space medium (e.g., air); the depth of the grating layer 82 is 22 nm, and the duty cycle of the filling material is 0.32; the depth of the grating layer 84 is 20 nm, and the duty cycle of the filling material is 0.53; the depth of the grating layer 86 is 31 nm, and the duty cycle of the filling material is 0.18.

[0079] By setting the above grating parameters, the light leakage ratio and diffraction efficiency data of the grating corresponding to grating unit 830 for RGB light can be obtained under different viewing fields. (Reference) Figure 8b The diagram illustrates the diffraction efficiency and corresponding light leakage ratio of the grating corresponding to grating unit 830 for RGB light under multiple fields of view. It can be seen that while adding grating layers generally reduces the light leakage ratio (e.g., the overall green and red light leakage ratios are below 0.3), the blue light leakage ratio in the central field of view increases significantly, essentially reaching the same level as that of commonly used basic gratings. Regarding diffraction efficiency, the ratio of blue to red light diffraction efficiency in this embodiment is not as low as in the embodiments described above. For a three-layer grating structure with air as the duty cycle filler, its light leakage ratio and diffraction efficiency uniformity are significantly inferior to a two-layer grating structure, but still superior to commonly used basic gratings.

[0080] Specific Example 5

[0081] refer to Figure 9a This illustrates a grating unit 930 corresponding to a grating, from Figure 9a As can be seen, the grating unit 930 includes five grating layers: grating layer 90, grating layer 92, grating layer 94, grating layer 96, and grating layer 98. All five grating layers are rectangular in shape (for clarity, in...). Figure 9a(The dashed lines used to identify each grating layer are not intended to limit this application.) Grating layer 90 further includes grating portions 901 and 902, both rectangular in shape. Grating portion 901 is shorter in the second direction than grating portion 902. Grating portion 901 uses a material with a refractive index of n1, while grating portion 902 uses a filling material with a refractive index of n2. Grating layer 92 is a material layer, composed of grating portions 921 using the same filling material with a refractive index of n2. Grating layer 94 further includes grating portions 941 and 942, both rectangular in shape. Grating portion 941 uses a material with a refractive index of n3, while grating portion 942 uses a filling material with a refractive index of n2. Grating layer 96 is also a material layer, composed of grating portions 961 using the same filling material with a refractive index of n2. The grating layer 98 further includes a grating portion 981 and a grating portion 982, both of which are rectangular in shape. The length of the grating portion 981 in the second direction is shorter than the length of the grating portion 982 in the second direction. The grating portion 981 is made of a material with a refractive index of n4, and the grating portion 982 is made of a filling material with a refractive index of n2.

[0082] In this embodiment, the grating period corresponding to the grating unit 830 is 359.7 nm, the refractive index n1 is specifically 2.1, the refractive index n2 is specifically 2.5, the refractive index n3 is specifically 2.4, and the refractive index n4 is specifically 2; the depth of the grating layer 90 is 109 nm, and the duty cycle of the filling material is 0.64; the depth of the grating layer 92 is 10 nm; the depth of the grating layer 94 is 25 nm, and the duty cycle of the filling material is 0.46; the depth of the grating layer 96 is 42 nm; and the depth of the grating layer 98 is 59 nm, and the duty cycle of the filling material is 0.71.

[0083] By setting the above grating parameters, the light leakage ratio and diffraction efficiency data of the grating corresponding to grating unit 930 for RGB light can be obtained under different viewing fields. (Reference) Figure 9b The diagram illustrates the diffraction efficiency and corresponding light leakage ratio of the grating corresponding to grating unit 930 for RGB light under multi-field viewing conditions. It can be seen that by replacing the filling material and adding a dielectric layer, the overall light leakage ratio of this embodiment is below 0.3, and compared to previous embodiments, the overall red light leakage ratio of this embodiment is the lowest, reaching below 0.05. Simultaneously, this embodiment maintains the diffraction efficiency ratio of blue light to red light at approximately below 1.

[0084] It should be noted that, for the grating structure in the embodiments of this application, the rectangular morphology of each grating portion can be prepared by methods such as imprinting, etching, or deposition. On the prepared grating structure, the desired overall morphology of the grating is finally prepared by using methods such as resist application, directional coating, directional etching, overlay, or controlled substrate tilt deposition. Of course, the preparation process and methods should not be construed as limiting this application.

[0085] In the aforementioned embodiments, the grating structure is disposed on the surface of the grating region of the waveguide; in another embodiment, the grating region is located inside the optical waveguide, rather than on the surface, and correspondingly, the aforementioned grating structure is also disposed inside the optical waveguide.

[0086] Of course, the specific structure adopted will depend on the needs of the actual application, and this does not constitute a limitation on this application.

[0087] Based on the optical waveguide described above, this application embodiment also provides a near-eye display module, which can be applied to AR glasses. The near-eye display module includes: an image projection device and the aforementioned optical waveguide. The image projection device is used to generate image light and project it onto the corresponding grating area (e.g., coupling area) on the optical waveguide, so that the image light can be transmitted in the waveguide and coupled out through the corresponding grating area (e.g., coupling area).

[0088] The terms "first," "second," "first," or "second" as used in the various embodiments of this disclosure may modify various components regardless of their order and / or importance, but these terms do not limit the corresponding components. The above terms are configured only for the purpose of distinguishing one component from another.

[0089] The above description is merely a preferred embodiment of this application and an explanation of the technical principles employed. Those skilled in the art should understand that the scope of the invention involved in this application is not limited to technical solutions formed by specific combinations of the above-described technical features, but should also cover other technical solutions formed by arbitrary combinations of the above-described technical features or their equivalents without departing from the above-described inventive concept. For example, technical solutions formed by substituting the above features with (but not limited to) technical features with similar functions disclosed in this application.

Claims

1. An optical waveguide, characterized in that, The optical waveguide includes a waveguide substrate, on which two or more grating regions with specific optical functions are disposed; A grating is provided in the grating region, and the grating provided in part or all of the grating region comprises at least two stacked grating layers, each grating layer comprising at least one type of grating portion, the grating portion being rectangular; Each of the grating layers in the grating has the same period size.

2. The optical waveguide as described in claim 1, characterized in that, The same grating layer has the same depth; If the same grating layer contains different grating portions, then the different grating portions in the grating layer have the same depth.

3. The optical waveguide as described in claim 1, characterized in that, The depths of different grating layers in the same grating are different.

4. The optical waveguide as described in claim 1, characterized in that, Each of the grating layers of the same grating contains grating portions made of the same material.

5. The optical waveguide as described in claim 4, characterized in that, The grating includes a grating layer made of the same material.

6. The optical waveguide as described in claim 5, characterized in that, If there are two or more grating layers made of the same material, then the two or more layers are not adjacent to each other.

7. The optical waveguide as described in claim 1, characterized in that, If adjacent grating layers each contain different grating portions, then the grating portions of the adjacent grating layers are arranged in a staggered manner.

8. The optical waveguide as described in claim 1, characterized in that, Each of the grating layers in the grating has the same period size in the second direction.

9. A near-eye display module, characterized in that, The device includes an image projection apparatus and an optical waveguide as described in any one of claims 1-8. The image projection apparatus is used to generate image light rays and project them onto a grating region on the optical waveguide for coupling light rays, and after transmission through the optical waveguide, output the light rays through a grating region for coupling light rays.

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