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 preset optical functions are arranged on the waveguide substrate; a grating structure formed by grating units which are periodically distributed is arranged in the grating area; a part of or all of the grating units comprise a first grating part and a second grating part, and each of the first grating part and the second grating part comprises at least one grating layer; and the first grating part and the second grating part have different effective refractive indexes.

Description

Technical Field

[0001] The present application relates to the field of display technology, and in particular to an optical waveguide and a near-eye display module. Background Art

[0002] At present, AR glasses are developing in the direction of lightweight and color display. They usually adopt a light engine with three colors (RGB, i.e., red, green, and blue) of light in combination with a single optical waveguide (for a single camera), so that the three colors of RGB light are transmitted in a single optical waveguide.

[0003] However, for this solution, reference Figure 1 Since the wavelengths of the three colors of RGB light are inconsistent, the diffraction angles of the RGB light (such as Figure 1 The three angles α, β, and γ shown in the figure) and the diffraction efficiency are different, which will affect the display effects such as brightness uniformity and color uniformity, thereby seriously affecting the user's viewing experience. Utility Model Content

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

[0005] Based on one aspect of the present application, an embodiment of the present application provides an optical waveguide, the optical waveguide comprising a waveguide substrate, on which two or more grating regions with preset optical functions are arranged;

[0006] The grating region is provided with a grating structure composed of periodically distributed grating units; part or all of the grating units include a first grating portion and a second grating portion, and the first grating portion and the second grating portion each include at least one grating layer;

[0007] The first grating portion and the second grating portion have different equivalent refractive indexes.

[0008] Optionally, when the first grating portion or the second grating portion includes more than one grating layer, the refractive index of each grating layer is different.

[0009] Optionally, a part of the grating layers in the first grating portion and a part of the grating layers in the second grating portion have the same material, refractive index and depth.

[0010] Optionally, the grating layer with the same material, refractive index and depth is located at the same level between the first grating portion and the second grating portion.

[0011] Optionally, the grating layer with the same material, refractive index and depth is one layer, two layers or multiple layers in contact with and / or close to the waveguide matrix.

[0012] Optionally, a depth of the first grating portion in the third direction is greater than or equal to a depth of the second grating portion in the third direction.

[0013] Optionally, the morphology of part or all of the grating layers in the first grating portion is the same as the morphology of part or all of the grating layers in the second grating portion.

[0014] Optionally, a morphology formed by stacking part or all of the grating layers in the first grating portion is the same as a morphology formed by stacking part or all of the grating layers in the second grating portion.

[0015] Optionally, the depths of some or all grating layers in the first grating portion are the same; the depths of some or all grating layers in the second grating portion are the same.

[0016] Based on another aspect of the present application, an embodiment of the present application provides a near-eye display module, including an image projection device and the aforementioned light waveguide, wherein the image projection device is used to generate image light and project it onto a corresponding grating area on the light waveguide, and output through the corresponding grating area after being transmitted through the light waveguide.

[0017] Other features and advantages of the present application will be described in the subsequent description, and partly become apparent from the description, or understood by implementing the technical solution of the present application. The purpose and other advantages of the present application can be realized and obtained through the structures and / or processes specifically pointed out in the description, claims and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Other features, objects and advantages of the present application will become more apparent by reading the detailed description of non-limiting embodiments made with reference to the following drawings:

[0019] Figure 1 It is a schematic diagram of RGB light propagating in the waveguide;

[0020] Figure 2a is a schematic diagram of a waveguide structure provided in an embodiment of the present application;

[0021] Figure 2b A schematic diagram of a grating structure is provided in an embodiment of the present application;

[0022] Figure 2c A schematic diagram of a grating unit structure is provided in an embodiment of the present application;

[0023] Figure 3a is a schematic structural diagram of a grating unit 300 provided in an embodiment of the present application;

[0024] Figure 3b yes Figure 3a A schematic diagram of a data curve related to the diffraction efficiency of the grating unit 300;

[0025] Figure 4a is a structural schematic diagram of a grating unit 400 provided in an embodiment of the present application;

[0026] Figure 4b yes Figure 4a A schematic diagram of a data curve related to the diffraction efficiency of the grating unit 400;

[0027] Figure 5a is a schematic structural diagram of a grating unit 500 provided in an embodiment of the present application;

[0028] Figure 5b yes Figure 5a A schematic diagram of a data curve related to the diffraction efficiency of the grating unit 500;

[0029] Figure 6a is a schematic structural diagram of a grating unit 600 provided in an embodiment of the present application;

[0030] Figure 6b yes Figure 6a A schematic diagram of a data curve related to the diffraction efficiency of the grating unit 600;

[0031] Figure 7a is a schematic structural diagram of a grating unit 700 provided in an embodiment of the present application;

[0032] Figure 7b is a schematic diagram of a modified example of the grating unit 700;

[0033] Figure 8a is a structural schematic diagram of a grating unit 800 provided in an embodiment of the present application;

[0034] Figure 8b is a schematic diagram of a modified example of the grating unit 800;

[0035] Figure 9a is a schematic structural diagram of a grating unit 900 provided in an embodiment of the present application;

[0036] Figure 9b 2 is a schematic diagram of a modified example of the grating unit 900 . DETAILED DESCRIPTION

[0037] The present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the relevant utility model, rather than to limit the utility model. It is also necessary to explain that, for ease of description, only the parts related to the relevant utility model are shown in the accompanying drawings.

[0038] In the embodiment of the present application, the light engine (which may also be referred to as an image projection device in the present application) may be based on at least one display technology or device applicable to the field of AR glasses, such as LCOS, MicroLED, MicroOLED, Micro-Electro-Mechanical Systems (MEMS) scanning mirror, fiber scanner, and may generally emit light of three colors, RGB (i.e., corresponding to three wavelengths). Since the diffraction angles and diffraction efficiencies of the three wavelengths of light are different after passing through the grating, in order to maximize the brightness uniformity and color uniformity of the three wavelengths of light after passing through the grating, the present application provides an optical waveguide with a corresponding grating structure.

[0039] refer to Figure 2a , an optical waveguide 100 provided in an embodiment of the present application, comprises: a waveguide substrate 101 and a grating region with a specific optical function disposed on the waveguide substrate 101. The optical region further comprises an incoupling region 102, a relay region 103 and an outcoupling region 104.

[0040] A grating structure is provided in the coupling-in region 102, the relay region 103 and the coupling-out region 104. The grating structure can be implemented by processes such as imprinting, coating, and etching, which are not limited here. In the subsequent description of this application, the grating structure provided in the coupling-in region 102 may be referred to as a coupling-in grating; the grating structure provided in the relay region 103 may be referred to as a relay grating; and the grating structure provided in the coupling-out region 104 may be referred to as a coupling-out grating.

[0041] The light can be coupled into the waveguide matrix 101 through the coupling-in region 102 and transmitted therein. The relay region 103 receives the light transmitted by the coupling-in region 101 and deflects the light to the decoupling region 104 after expanding the light. The decoupling region 104 receives the light deflected by the relay region 103 and couples the light out of the waveguide matrix 101.

[0042] certainly, Figure 2a The contours and relative positions of the coupling-in region 102, the relay region 103, and the coupling-out region 104 shown in the figure are exemplary and may vary in actual applications. For example, the coupling-in region 102 may not be Figure 2a The square outline shown in the figure may be circular, trapezoidal, etc.; the relay region 102 may be located below the outcoupling region 104. Therefore, Figure 2a The structure of the waveguide 100 shown should not be construed as limiting the present application.

[0043] It should be noted that in the drawings of the present application, an xyz coordinate system is shown. For ease of description, in the embodiments of the present application, the direction parallel to the y-axis may also be referred to as the first direction, the vertical direction, or the longitudinal direction; the direction parallel to the x-axis may also be referred to as the second direction, the horizontal direction, or the transverse direction; the direction perpendicular to the xy plane may be considered as the z-axis direction, and the direction parallel to the z-axis may also be referred to as the third direction or the depth direction. This coordinate system is used in other views or embodiments of the present application, and the description of the corresponding direction names is also applicable throughout the text.

[0044] refer to Figure 2b-2c , a grating structure 20 in the embodiment of the present application, whose cross section in the xz plane is as follows Figure 2b As shown, the grating structure 20 includes a plurality of periodically distributed grating units 200 . Figure 2c , which shows the specific structure of the grating unit 200, including: a first grating portion 201 and a second grating portion 202. The first grating portion 201 further includes a rectangular grating layer 201i (i=1, 2...), wherein i is at least equal to 1, that is, the first grating portion 201 has at least one grating layer; the second grating portion 202 further includes a rectangular grating layer 202j (j=1, 2...), wherein j is at least equal to 1, that is, the second grating portion 202 has at least one grating layer. In some embodiments, the grating layers 201i can be made of different materials and have different refractive indices. The grating layer 202j can also be made of different materials and have different refractive indices. In other embodiments, for the first grating portion 201, part or all of the grating layers 201i are made of the same material; for the second grating portion 202, part or all of the grating layers 202j are made of the same material.

[0045] In addition, in some embodiments, part of the grating layer 201i in the first grating portion 201 and part of the grating layer 202j in the second grating portion 202 are made of the same material and have the same refractive index, and the depths of these grating layers with the same material and refractive index (i.e., the thickness of the grating layer in the Z-axis direction) are also the same. It should be noted here that the grating layers with the same material, refractive index, and depth in the first grating portion 201 and the second grating portion 202 are located at the same level between the first grating portion 201 and the second grating portion 202, which are usually one, two, or more layers in contact with and / or close to the waveguide matrix 101.

[0046] In some embodiments, the refractive index of the grating layer 201i may be partially the same or completely the same. Similarly, the refractive index of the grating layer 202j may be partially the same or completely the same. It should be noted that, in the embodiment of the present application, regardless of whether the refractive index of the grating layer of the first grating portion 201 and the second grating portion 202 is the same or different, the equivalent refractive index of the first grating portion 201 is different from the equivalent refractive index of the second grating portion 202.

[0047] By configuring the grating layer structure and the corresponding refractive index of the grating layer, the grating structure in the embodiment of the present application can flexibly adjust the modulation characteristics of the grating to incident light of different wavelengths.

[0048] In the embodiment of the present application, the material of part or all of the grating layer 201i in the first grating portion 201 and part or all of the grating layer 202j in the second grating portion 202 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.

[0049] Optionally, the material of part or all of the grating layer 201i and the grating layer 202j 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.

[0050] Optionally, the material of part or all of the grating layer 201i and the grating layer 202j 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.

[0051] Optionally, the material of part or all of the grating layer 201i and the grating layer 202j may also include a composite material obtained based on the aforementioned compound through a process such as doping.

[0052] Optionally, the material of a specific grating layer in the grating layer 201i or 202j may also include an exit space medium, such as air or a material used for the waveguide substrate 101, etc.

[0053] In addition to the above-mentioned differences in materials and refractive index, in the embodiment of the present application, the first grating portion 201 and the second grating portion 202 may also have differences in structure, morphology, etc. Specifically, the depth of the first grating portion 201 in the Z-axis direction is greater than or equal to the depth of the second grating portion 202 in the Z-axis direction.

[0054] Optionally, the morphology of part or all of the grating layers 201i in the first grating portion 201 is the same as the morphology of part or all of the grating layers 201j in the second grating portion 202. Of course, in other embodiments of the present application, the morphology of part of the grating layers in the first grating portion 201 may be different from the morphology of part of the grating layers in the second grating portion 202.

[0055] Optionally, the morphology formed by stacking part or all of the grating layers 201i in the first grating section 201 may be the same as the morphology formed by stacking part or all of the grating layers 201j in the second grating section 202. Of course, in other embodiments of the present application, the morphology formed by stacking part or all of the grating layers 201i in the first grating section 201 may be different from the morphology formed by stacking part or all of the grating layers 201j in the second grating section 202 (for example, see Figure 7a to Figure 9b )

[0056] Based on the material, refractive index, structure and other aspects of the grating layer, the freedom of grating control can be increased, which is more conducive to the modulation of light of different wavelengths.

[0057] Furthermore, the layered structure adopted by the first grating portion 201 and the second grating portion 202 can be used to balance the diffraction efficiency of light of different wavelengths, thereby facilitating the adjustment of the color uniformity of the system.

[0058] refer to Figure 3a , shows a grating unit 300, including: a first grating portion 301 and a second grating portion 302. In this example, the first grating portion 301 includes three grating layers 3011-3013; the second grating portion 302 includes three grating layers 3021-3023.

[0059] The grating layers 3011 to 3013 are made of different materials, and their refractive indices are denoted by n 311 、n 312 and n 313 The depths of the grating layers 3011 to 3013 are denoted as t 311 ,t 312 and t 313 .t 311 ,t 312 and t 313 The range can be 20-400nm.

[0060] The grating layers 3021 to 3023 are also made of different materials, and their refractive indices are denoted by n and 321 、n 322 and n 323 The depths of the grating layers 3021 to 3023 are denoted as t 321 ,t 322 and t 323 .t321 ,t 322 and t 323 The range can be 20-400nm.

[0061] The period P of the grating unit 300 is in the range of 200-500 nm. The range of the refractive index boundary coefficient r n is 0-1.

[0062] In this example, the grating layer 3013 in the first grating portion 301 and the grating layer 3023 in the second grating portion 302 are made of the same material and have the same refractive index (ie, n 313 =n 323 ), are located at the bottom layer of the grating part and have the same depth (i.e., t 313 =t 323 ). This structure can balance the diffraction efficiency at different propagation angles.

[0063] According to the above parameters, the objective function f m Perform parameter optimization, objective function f m Including multiple targets such as grating out-coupling diffraction efficiency and RGB three-color ratio, the local optimal solution of the parameters corresponding to each target of the grating structure can be obtained.

[0064] Further, referring to Table 1 and Figure 3b ,Compared with the basic rectangular grating, Table 1 shows the setting values ​​of various parameters of the grating graphics.

[0065]

[0066]

[0067] Table 1

[0068] Figure 3b The RGB outcoupling diffraction efficiency of two optimized grating structures under multiple fields of view is given respectively. And the corresponding B / R ratio and B / G ratio based on Figure 3b It can be seen that the grating design of this scheme reduces the B / R ratio and the B / G ratio, thereby effectively improving the color uniformity.

[0069] refer to Figure 4a , shows a grating unit 400, including: a first grating portion 401 and a second grating portion 402. In this example, the first grating portion 401 includes two grating layers 4011 and 4012; the second grating portion 402 includes two grating layers 4021 and 4022.

[0070] The grating layers 4011 and 4012 are made of different materials, and their refractive indices are denoted by n and411 and n 412 The depth of the grating layers 4011 and 4012 is denoted as t 411 and t 412 .

[0071] The grating layers 4021 and 4022 are also made of different materials, and their refractive indices are denoted by n and 421 and n 422 The depth of the grating layer 4022 is t 421 and t 422 It should be noted that, in this example, the material of the grating layer 4021 is the exit space medium (such as air). Figure 4a This representation is also applicable to the subsequent embodiments, and will not be described in detail.

[0072] In this example, the depths t of the grating layers 4011, 4012, and 4022 are 411 ,t 412 and t 422 The refractive index boundary coefficient r between the first grating portion 401 and the second grating portion 402 may be in the range of 20-400 nm. n The range of can be 0-1. The period P of the grating unit 400 is in the range of 200-500 nm.

[0073] According to the above parameters, the objective function f m Perform parameter optimization, objective function f m Including multiple targets such as grating out-coupling diffraction efficiency and RGB three-color ratio, the local optimal solution of the parameters corresponding to each target of the grating structure can be obtained.

[0074] Further, referring to Table 2 and Figure 4b ,Compared with the basic rectangular grating, Table 2 shows the setting values ​​of various parameters of the grating graphics.

[0075]

[0076]

[0077] Table 2

[0078] Figure 4b The RGB outcoupling diffraction efficiency of two optimized grating structures under multiple fields of view is given respectively. And the corresponding B / R ratio and B / G ratio based on Figure 4b It can be seen that the grating design of this scheme reduces the B / R ratio and improves color uniformity by improving the red light efficiency.

[0079] refer to Figure 5a, shows a grating unit 500, including: a first grating portion 501 and a second grating portion 502. In this example, the first grating portion 501 includes two grating layers 5011 and 5012; the second grating portion 502 includes three grating layers 5021-5023.

[0080] The grating layers 5011 and 5012 are made of different materials, and their refractive indices are denoted by n and 511 and n 512 The depths of the grating layers 5011 and 5012 are denoted as t 511 and t 512 .t 511 and t 512 The range can be 20-400nm.

[0081] The grating layers 5021 to 5023 are made of different materials, and their refractive indices are denoted by n 521 、n 522 and n 523 The depths of the grating layers 5011 to 5013 are denoted as t 511 ,t 522 and t 523 .t 511 ,t 522 and t 523 The range can be 20-400nm.

[0082] The period P of the grating unit 500 is in the range of 200-500 nm. The range of the refractive index boundary coefficient r n is 0-1.

[0083] In this example, the grating layer 5012 in the first grating portion 501 and the grating layer 5023 in the second grating portion 502 are made of the same material and have the same refractive index (ie, n 512 =n 523 ), are located at the bottom layer of the grating part and have the same depth (i.e., t 512 =t 523 ). In addition, the material of the grating layer 5021 is the exit space medium (such as air).

[0084] According to the above parameters, the objective function f m Perform parameter optimization, objective function f m Including multiple targets such as grating out-coupling diffraction efficiency and RGB three-color ratio, the local optimal solution of the parameters corresponding to each target of the grating structure can be obtained.

[0085] Further, refer to Table 3 and Figure 5b ,Compared with the basic rectangular grating, Table 3 shows the setting values ​​of various parameters of the grating graphics.

[0086]

[0087]

[0088] Table 3

[0089] Figure 5b The RGB outcoupling diffraction efficiency of two optimized grating structures under multiple fields of view is given respectively. And the corresponding B / R ratio and B / G ratio based on Figure 5b It can be seen that the grating design of this scheme reduces the B / R ratio and B / G ratio by improving the efficiency of green light and red light, thereby greatly improving color uniformity.

[0090] refer to Figure 6a , shows a grating unit 600, including: a first grating portion 601 and a second grating portion 602. In this example, the first grating portion 601 includes three grating layers 6011-6013; the second grating portion 602 includes three grating layers 6021-6023.

[0091] The grating layers 6011 to 6013 are made of different materials, and their refractive indices are denoted by n 611 、n 612 and n 613 The depths of the grating layers 6011 to 6013 are denoted as t 611 ,t 612 and t 613 .t 611 ~t 613 The range can be 20-400nm.

[0092] The grating layers 6021 to 6023 are made of different materials, and their refractive indices are denoted by n 621 、n 622 and n 623 The depths of the grating layers 6021 to 6023 are denoted as t 621 ,t 622 and t 623 .t 621 ,t 622 and t 623 The range can be 20-400nm.

[0093] In this example, the grating layer 6013 in the first grating portion 601 and the grating layer 6023 in the second grating portion 602 are made of the same material and have the same refractive index (ie, n 613 =n 623 ), are located at the bottom layer of the grating part and have the same depth (i.e., t 613 =t 623). In addition, the material of the grating layer 6021 is the exit space medium (eg, air).

[0094] According to the above parameters, the objective function f m Perform parameter optimization, objective function f m Including multiple targets such as grating out-coupling diffraction efficiency and RGB three-color ratio, the local optimal solution of the parameters corresponding to each target of the grating structure can be obtained.

[0095] Further, referring to Table 4 and Figure 6b , compared with the basic rectangular grating, Table 4 shows the setting values ​​of various parameters of the grating graphics.

[0096]

[0097] Table 4

[0098] Figure 6b The RGB outcoupling diffraction efficiency of two optimized grating structures under multiple fields of view is given respectively. And the corresponding B / R ratio and B / G ratio based on Figure 5b It can be seen that the grating design of this scheme reduces the B / R ratio and B / G ratio by improving the efficiency of green light and red light, thereby greatly improving color uniformity.

[0099] Furthermore, in other embodiments of the present application, the grating layer in the grating unit may have different forms.

[0100] refer to Figure 7a , shows a grating unit 700, which includes a first grating portion 701 and a second grating portion 702. The first grating portion 701 includes four grating layers 7011-7014. The sizes of the grating layers 7011-7013 gradually increase in the first direction, forming a "triangular" stacking morphology. The grating layer 7014 is rectangular in shape.

[0101] The second grating portion 702 includes three grating layers 7021-7023, which are divided into two parts, so that the grating layers 7021-7023 are distributed on both sides of the "triangular" stacking morphology formed by the grating layers 7011-7013, that is, the grating layers 7021-7023 form two "inverted triangles" on both sides of the "triangular" grating layers 7011-7013, so that the grating unit 700 is rectangular as a whole.

[0102] Figure 7b 2 shows other deformation structures of the grating unit 700, which will not be described in detail here.

[0103] refer to Figure 8a, shows a grating unit 800, which includes a first grating portion 801 and a second grating portion 802. The first grating portion 801 includes four grating layers 8011-8014. The sizes of the grating layers 8011-8013 gradually increase in the first direction, forming a "trapezoidal" stacking morphology. The grating layer 8014 is rectangular in shape.

[0104] The second grating portion 802 includes three grating layers 8021-8023, which are also divided into two parts, so that the grating layers 8021-8023 are distributed on both sides of the "trapezoidal" stacking morphology formed by the grating layers 8011-8013, that is, the grating layers 8021-8023 form two "inverted triangles" on both sides of the "trapezoidal" grating layers 8011-8013, so that the grating unit 800 is rectangular as a whole.

[0105] Figure 8b 2 shows other deformation structures of the grating unit 800, which will not be described in detail here.

[0106] refer to Figure 9a , shows a grating unit 900, which includes a first grating portion 901 and a second grating portion 902. The first grating portion 901 includes four grating layers 9011-9014. The sizes of the grating layers 9011-9013 gradually increase in the first direction, forming a "parallelogram" stacking morphology. The grating layer 9014 is rectangular in shape.

[0107] The second grating portion 902 includes three grating layers 9021-9023, which are also divided into two parts, so that the grating layers 9021-9023 are distributed on both sides of the "parallelogram" stacking morphology formed by the grating layers 9011-9013, that is, the grating layers 9021-9023 form an "inverted triangle" and a "trapezoide" on both sides of the "parallelogram" grating layers 9011-9013, respectively, so that the grating unit 900 is rectangular as a whole.

[0108] Figure 9b 2 shows other deformation structures of the grating unit 900, which will not be described in detail here.

[0109] In some embodiments, part of the grating structure may be located on different planes, for example, from left to right in the grating region, the convexity of the grating structure along the positive direction of the X-axis gradually increases, so that the grating structure is located on different planes. Of course, this should not be understood as a limitation to the present application.

[0110] For the optical waveguide in the aforementioned embodiment, the grating structure is arranged on the surface of the grating region of the waveguide; in another embodiment, the grating region is located inside the optical waveguide instead of on the surface, and accordingly, the aforementioned grating structure is also arranged inside the optical waveguide.

[0111] Of course, the specific structure to be adopted will depend on the needs of the actual application, and this does not constitute a limitation to the present application.

[0112] Based on the optical waveguide described in the above content, a near-eye display module is also provided in an embodiment of the present application. The near-eye display module 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 to the corresponding grating area (e.g., coupling-in 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-out area).

[0113] The expressions "first", "second", "the first" or "the second" used in various embodiments of the present disclosure may modify various components regardless of order and / or importance, but these expressions do not limit the corresponding components. The above expressions are only configured for the purpose of distinguishing an element from other elements.

[0114] The above description is only a preferred embodiment of the present application and an explanation of the technical principles used. Those skilled in the art should understand that the scope of the utility model involved in the present application is not limited to the technical solution formed by a specific combination of the above technical features, but should also cover other technical solutions formed by any combination of the above technical features or their equivalent features without departing from the above utility model concept. For example, the above features are replaced with the technical features with similar functions disclosed in this application (but not limited to) by each other.

Claims

1. An optical waveguide, characterized in that: The optical waveguide comprises a waveguide substrate, on which two or more grating regions with preset optical functions are arranged; The grating region is provided with a grating structure composed of periodically distributed grating units; part or all of the grating units include a first grating portion and a second grating portion, and the first grating portion and the second grating portion each include at least one grating layer; The first grating portion and the second grating portion have different equivalent refractive indexes.

2. The optical waveguide according to claim 1, wherein When the first grating section or the second grating section includes more than one grating layer, the refractive indexes of the grating layers are different.

3. The optical waveguide according to claim 1, wherein The material, refractive index and depth of a part of the grating layer in the first grating portion and a part of the grating layer in the second grating portion are the same.

4. The optical waveguide according to claim 3, wherein The grating layer having the same material, refractive index and depth is located at the same level between the first grating portion and the second grating portion.

5. The optical waveguide according to claim 3, wherein: The grating layer having the same material, refractive index and depth is one layer, two layers or multiple layers in contact with and / or close to the waveguide substrate.

6. The optical waveguide according to claim 1, wherein A depth of the first grating portion in the third direction is greater than or equal to a depth of the second grating portion in the third direction.

7. The optical waveguide according to claim 1, wherein The morphology of part or all of the grating layers in the first grating portion is the same as the morphology of part or all of the grating layers in the second grating portion.

8. The optical waveguide according to claim 7, wherein The morphology formed by stacking part or all of the grating layers in the first grating portion is the same as the morphology formed by stacking part or all of the grating layers in the second grating portion.

9. The optical waveguide according to claim 1, wherein The depths of some or all grating layers in the first grating portion are the same; The depths of some or all grating layers in the second grating portion are the same.

10. A near-eye display module, characterized in that: It comprises an image projection device and the optical waveguide as claimed in any one of claims 1 to 9, wherein the image projection device is used to generate image light and project it onto the corresponding grating area on the optical waveguide, and then output through the corresponding grating area after being transmitted through the optical waveguide.

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