Manufacturing method of optical waveguide and optical waveguide

Abstract

The invention discloses a manufacturing method of an optical waveguide and the optical waveguide. The manufacturing method of the optical waveguide comprises the following steps: coating a material on the surface of a relief grating; and performing exposure treatment on the smeared material by using a single light source to cure the material so as to form a second layer of grating on the surface of the embossment grating. Therefore, the material is smeared on the surface of the embossment grating, so that the smeared material enters the nicks on the surface of the embossment grating, then the smeared material is hardened through the single light source to complete manufacturing of the second layer of grating, and interference fringes generated by two beams of coherent light do not need to serve as the nicks of the second layer of grating. The manufacturing difficulty of the second-layer grating is effectively reduced, and the reject ratio of the second-layer grating is reduced.

Description

Technical Field

[0001] The present application relates to the technical field of AR devices, and more specifically, to a method for manufacturing an optical waveguide and an optical waveguide. Background Art

[0002] Gratings have important application value in the field of augmented reality technology, especially in holographic waveguide display technology. As a key component for achieving light field guidance and image display in AR glasses, gratings can guide image beams with high diffraction efficiency, and accurately project image beams in front of the user through a multi-step process of input coupling, expansion, and output coupling, achieving a lightweight and miniaturized display effect.

[0003] The manufacturing accuracy, uniformity and consistency of the grating directly affect the display effect of the AR device, and thus directly affect the final user experience. In related technologies, the manufacturing technology of the grating mainly relies on the interference fringes generated by the interference exposure of two coherent light beams. This process not only requires precise control of the coherent light, but also places stringent requirements on the stability of the coherent light and environmental conditions.

[0004] However, since the process of generating a grating by interferometric exposure of two coherent light beams has a high dependence on the optical path accuracy, phase stability and environmental control of the coherent light, the production of the grating is difficult and the grating defect rate is prone to be high. Summary of the invention

[0005] In view of the above problems, the present application proposes a method for manufacturing an optical waveguide and an optical waveguide, which can effectively reduce the difficulty of manufacturing a grating and reduce the defective rate of the grating.

[0006] In a first aspect, an embodiment of the present application provides a method for manufacturing an optical waveguide, which comprises: applying a material on the surface of a relief grating; exposing the applied material using a single light source to solidify the material to form a second layer of grating on the surface of the relief grating.

[0007] In a second aspect, an embodiment of the present application further provides an optical waveguide, comprising: an optical waveguide body, an entrance pupil area and an exit pupil area, wherein the entrance pupil area and the exit pupil area are arranged on the surface of the optical waveguide body, wherein: the entrance pupil area and / or the exit pupil area include a relief grating and a second layer of grating arranged on the surface of the relief grating.

[0008] The technical solution provided in the present application, the method for manufacturing the optical waveguide includes: applying material on the surface of the relief grating; exposing the applied material with a single light source to solidify the material to form a second layer of grating on the surface of the relief grating. Thus, by applying the material on the surface of the relief grating so that the applied material enters the grooves on the surface of the relief grating, and then hardening the applied material with a single light source to complete the manufacturing of the second layer of grating, there is no need to use interference fringes generated by two coherent light beams as the grooves of the second layer of grating. The difficulty of manufacturing the second layer of grating is effectively reduced, and the defective rate of the second layer of grating is reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present application, not all embodiments. Based on the embodiments of the present application, all other embodiments and drawings obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0010] Figure 1 A schematic structural diagram of an optical waveguide provided in an embodiment of the present application is shown.

[0011] Figure 2 A schematic structural diagram of another optical waveguide provided in an embodiment of the present application is shown.

[0012] Figure 3 A schematic structural diagram of another optical waveguide provided in an embodiment of the present application is shown.

[0013] Figure 4 A schematic structural diagram of another optical waveguide provided in an embodiment of the present application is shown.

[0014] Figure 5 A schematic structural diagram of another optical waveguide provided in an embodiment of the present application is shown.

[0015] Figure 6 A schematic flow chart of a method for manufacturing an optical waveguide provided in an embodiment of the present application is shown. DETAILED DESCRIPTION

[0016] In order to make the purpose, technical solutions and advantages of the present application clearer, the present application will be further described in detail below in conjunction with the accompanying drawings. The described embodiments should not be regarded as limiting the present application. All other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of this application.

[0017] In the following description, reference is made to "some embodiments", which describes a subset of all possible embodiments, but it is understood that "some embodiments" may be the same subset or different subsets of all possible embodiments, and may be combined with each other without conflict. In the following description, reference is made to the term "multiple" to mean at least two.

[0018] In the following description, the terms "first\second" involved are merely used to distinguish similar objects and do not represent a specific ordering of the objects. It can be understood that "first\second" can be interchanged with a specific order or sequence where permitted, so that the embodiments of the present application described herein can be implemented in an order other than that illustrated or described herein.

[0019] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein are only for the purpose of describing the embodiments of this application and are not intended to limit this application.

[0020] Augmented Reality (AR) is widely used in various fields such as games, education, and medical treatment. AR devices provide users with an immersive experience by combining virtual information with the real world. As one of the key hardware of AR technology, AR glasses need to have characteristics such as lightweight, high resolution, large field of view (FOV), high brightness, and low power consumption to meet users' wearing comfort and experience requirements.

[0021] Among them, gratings have important application value in the field of augmented reality technology, especially in holographic waveguide display technology. As a key component for achieving light field guidance and image display in AR glasses, gratings can guide image beams with high diffraction efficiency, and accurately project image beams in front of the user through a multi-step process of input coupling, expansion, and output coupling, achieving a lightweight and miniaturized display effect.

[0022] The manufacturing accuracy, uniformity and consistency of the grating directly affect the display effect of the AR device, and thus directly affect the final user experience. In related technologies, the manufacturing technology of the grating mainly relies on the interference fringes generated by the interference exposure of two coherent light beams. This process not only requires precise control of the coherent light, but also places stringent requirements on the stability of the coherent light and environmental conditions.

[0023] For example, if slight errors occur during the process of generating interference fringes by interferometric exposure of two coherent light beams (for example, the phases of the two light beams are inconsistent, or the interference fringes are uneven), the performance of the grating will be reduced, thus affecting the display effect of the AR device.

[0024] However, since the process of generating a grating by interferometric exposure of two coherent light beams has a high dependence on the optical path accuracy, phase stability and environmental control of the coherent light, the production of the grating is difficult and the grating defect rate is prone to be high.

[0025] In order to improve the above-mentioned problems, the present application provides a method for manufacturing an optical waveguide and an optical waveguide, wherein the optical waveguide includes a relief grating, and the method for manufacturing the optical waveguide includes: applying a material on the surface of the relief grating; exposing the applied material using a single light source to solidify the material to form a second layer of grating on the surface of the relief grating.

[0026] Therefore, by applying material on the surface of the relief grating so that the applied material enters the grooves on the surface of the relief grating, and then hardening the applied material by a single light source to complete the production of the second layer of grating, it is not necessary to use interference fringes generated by two coherent light beams as the grooves of the second layer of grating. The production difficulty of the second layer of grating is effectively reduced, and the defective rate of the second layer of grating is reduced.

[0027] In order to enable those skilled in the art to better understand the solution of the present application, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application.

[0028] See also Figure 1 , Figure 1 FIG. 1 shows a schematic diagram of the structure of an optical waveguide provided in an embodiment of the present application. Figure 1 As shown, the optical waveguide 100 includes an optical waveguide body 110 , an entrance pupil region 120 and an exit pupil region 130 .

[0029] The entrance pupil region 120 is used to couple the image light beam sent by the optical machine into the optical waveguide body 110. The optical machine may be a micro projector, for example, a DLP projector, an LCOS projector, and a micro light emitting diode (MicroLED).

[0030] The optical waveguide body 110 is used to propagate at least part of the image light beam coupled into the entrance pupil region 120 to the exit pupil region 130. In a specific embodiment, the optical waveguide body 110 may be a holographic optical waveguide.

[0031] The exit pupil region 130 is used to couple at least part of the image light beam propagated by the light guide body 110 out of the light guide body 110 , so that a user can obtain an image formed by the image light beam in the area where the image light beam is coupled out of the exit pupil region 130 .

[0032] In a specific embodiment, the entrance pupil region 120 and the exit pupil region 130 are disposed on the same surface of the light guide body 110. For example, the entrance pupil region 120 and the exit pupil region 130 are disposed on the upper surface of the light guide body 110. For another example, the entrance pupil region 120 and the exit pupil region 130 are disposed on the lower surface of the light guide body 110.

[0033] In a specific embodiment, the entrance pupil region 120 and the exit pupil region 130 are disposed on different surfaces of the light guide body 110. For example, the entrance pupil region 120 is disposed on the upper surface of the light guide body 110, and the exit pupil region 130 is disposed on the lower surface of the light guide body 110. For another example, the entrance pupil region 120 is disposed on the lower surface of the light guide body 110, and the exit pupil region 130 is disposed on the upper surface of the light guide body 110.

[0034] It is understandable that the entrance pupil region 120 and the exit pupil region 130 are disposed on any surface of the optical waveguide body 110 , and the present application does not limit the specific location of the entrance pupil region 120 and the exit pupil region 130 .

[0035] Further, in one embodiment, please refer to Figure 2 , Figure 2 FIG. 2 shows a schematic diagram of the structure of another optical waveguide provided in an embodiment of the present application. Figure 2 As shown, the entrance pupil region 120 includes a relief grating 121 and a second layer grating 122 disposed on the surface of the relief grating 121. One side of the relief grating 121 is attached to the optical waveguide body 110, and the other side of the relief grating 121 faces the second layer grating 122. The grooves of the relief grating 121 and the grooves of the second layer grating 122 are distributed in a staggered manner.

[0036] In some embodiments, please continue to refer to Figure 1 The exit pupil region 130 includes a relief grating 131 and a second layer grating 132 disposed on the surface of the relief grating 131. One side of the relief grating 131 is attached to the optical waveguide body 110, and the other side of the relief grating 131 faces the second layer grating 132. The notches of the relief grating 131 and the notches of the second layer grating 132 are distributed in an alternating manner.

[0037] The material of the relief grating (including the relief grating 121 and the relief grating 131) is photoresist, and the material of the second layer grating (including the second layer grating 122 and the second layer grating 132) is a holographic material. The material may be a functional material (for example, a holographic material). Further, the second layer grating may include one or more of a photosensitive material, an optical recording material, a volume holographic material, a liquid crystal material, a nanocomposite material or glue.

[0038] In a specific embodiment, the photosensitive material may be a silver salt emulsion and a photosensitive polymer. The optical recording material may be a photorefractive crystal and a photochromic material. The volume holographic material may be a polymer dispersed liquid crystal and an optical glass. The novel holographic material may be a nanocomposite material, a quantum dot material and a two-dimensional material.

[0039] It can be seen from the above description that the entrance pupil region 120 and / or the exit pupil region 130 may be provided with a two-layer grating structure (one layer is a relief grating, and the other layer is a second-layer grating).

[0040] By adjusting the period of the second grating layer, the transmittance and reflectivity of the second grating layer can be adjusted. When the entrance pupil region 120 is set to a two-layer grating structure, the period of the second grating layer 122 can be adjusted to enhance the transmittance of the second grating layer 122, so that more image beams can be coupled into the optical waveguide body 110. Alternatively, when the entrance pupil region 120 is set to a two-layer grating structure, the period of the second grating layer 122 can be adjusted to enhance the reflectivity of the second grating layer 122, so that the image beam coupled into the entrance pupil region 120 can be better propagated to the exit pupil region 130, so as to increase the number or intensity of the image beam coupled out of the exit pupil region 130.

[0041] When the exit pupil region 130 is configured as a two-layer grating structure, the period of the second grating layer 132 can be adjusted to enhance the transmittance of the second grating layer 132, so that more image light beams can be coupled out of the optical waveguide body 110. Alternatively, when the exit pupil region 130 is configured as a two-layer grating structure, the period of the second grating layer 132 can be adjusted to enhance the reflectivity of the second grating layer 132, so that more image light beams can be coupled out of the optical waveguide body 110.

[0042] That is to say, by adjusting the period of the second layer grating 132 so that the energy proportion of the second layer grating 132 toward the user side is high and the energy proportion toward the outside is low, the brightness of the image seen by the user can be improved and the intensity of light leakage to the outside can be reduced, thereby protecting the user's privacy.

[0043] For details, please refer to Figure 2 When the image beam is coupled out from the exit pupil area 130 to the area A, and the user is located in the area A to obtain the image beam, so as to obtain the image information corresponding to the image beam, the transmittance of the second layer grating 132 can be enhanced so that the image beam can better pass through the second layer grating 132. When the image beam is coupled out from the exit pupil area 130 to the area B, and the user is located in the area B to obtain the image beam, so as to obtain the image information corresponding to the image beam, the reflectivity of the second layer grating 132 can be enhanced so that the image beam can be better reflected to the area B.

[0044] In some embodiments, see Figure 3 , Figure 3 FIG. 2 shows a schematic diagram of the structure of another optical waveguide provided in an embodiment of the present application. Figure 3 As shown, the entrance pupil region 120 includes a relief grating 121, and the exit pupil region 130 includes a relief grating 131 and a second layer of grating 132 disposed on the surface of the relief grating 131. In other words, the entrance pupil region 120 may also adopt a structure of only one layer of grating, that is, the entrance pupil region 120 is composed of only one layer of relief grating 121.

[0045] In some embodiments, see Figure 4 , Figure 4 FIG. 2 shows a schematic diagram of the structure of another optical waveguide provided in an embodiment of the present application. Figure 4 As shown, the optical waveguide 100 includes two exit pupil regions 130. In a specific embodiment, the two exit pupil regions 130 are located on both sides of the entrance pupil region 120, respectively.

[0046] In order to further improve the efficiency of coupling out the image light beam from the exit pupil region 130, in some embodiments, please refer to Figure 5 , Figure 5 FIG. 2 shows a schematic diagram of the structure of another optical waveguide provided in an embodiment of the present application. Figure 5 As shown, the optical waveguide 100 further includes a turning region 140 , and the turning region 140 is used to transmit at least part of the image light beam coupled out of the entrance pupil region 120 to the exit pupil region 130 .

[0047] In a specific embodiment, the turning region 140 may consist of only one layer of grating structure, that is, the turning region 140 consists of only one layer of relief grating. In another specific embodiment, the turning region 140 may consist of two layers of grating structure, that is, the turning region 140 consists of one layer of relief grating and one layer of second grating.

[0048] The entrance pupil region 120, the exit pupil region 130 and the turning region 140 may be arranged on the same surface of the optical waveguide body 110; the entrance pupil region 120, the exit pupil region 130 and the turning region 140 may be arranged on different surfaces of the optical waveguide body 110. In other words, the turning region 140 may be arranged on any surface of the optical waveguide body 110.

[0049] In some embodiments, the optical waveguide 100 includes two turning regions 140, which are respectively located on both sides of the entrance pupil region 120. One of the turning regions 140 is used to propagate the image light beam coupled into the entrance pupil region 120 to one of the exit pupil regions 130, and the other turning region 140 is used to propagate the image light beam coupled into the entrance pupil region 120 to the other exit pupil region 130.

[0050] As can be seen from the above description, by setting a second layer of grating in the corresponding area to enhance the transmittance or reflectivity of the corresponding area, the brightness of the image formed by the coupled image light beam can be enhanced, and the image light beam can be effectively prevented from leaking to the outside, thereby leaking the privacy of the user. The transmittance or reflectivity of the corresponding area is enhanced by adjusting the period of the second layer of grating. In the prior art, the period of the second layer of grating is determined by exposing the material for making the second layer of grating by coherently exposing two beams of light to the material, and then determining it according to the stripes generated by the exposure. In other words, in order to enhance the transmittance or reflectivity of the corresponding area, the second layer of grating can only be exposed by coherently exposing two beams of light to meet the actual needs. However, in this process, not only the coherent light needs to be precisely controlled, but also the stability of the coherent light and the environmental conditions need to be strictly required, which makes the production of the second layer of grating difficult and prone to a high defect rate of the second layer of grating.

[0051] Based on the above situation, the present application provides a method for manufacturing an optical waveguide, so as to manufacture the above-described relief grating and the second layer grating. Specifically, please refer to Figure 6 , Figure 6 FIG. 1 is a flow chart of a method for manufacturing an optical waveguide provided in an embodiment of the present application. Figure 6 As shown, the method for manufacturing the optical waveguide includes steps 210 to 220, wherein:

[0052] In step 210, a material is applied to the surface of the relief grating.

[0053] In one embodiment, by applying a material on the surface of the relief grating, the applied material will enter the grooves on the relief grating, so that in the subsequent step, the applied material is exposed to light so that after the material is solidified, the grooves of the material are composed of the parts that enter the grooves on the relief grating. Unlike the prior art, the material for making the second layer of grating is exposed by coherent two beams of light, so that the grooves of the second layer of grating are determined according to the stripes generated by the exposure. This effectively reduces the difficulty of making the second layer of grating and reduces the defective rate of the second layer of grating.

[0054] In a preferred embodiment, by applying material on the surface of the relief grating with grooves, the material will enter the grooves on the relief grating, so that in the subsequent step, the applied material is exposed to light so that after the material is solidified, the grooves of the material are composed of the parts that enter the grooves on the relief grating. Instead of exposing the material for making the second layer of grating by coherently exposing two beams of light as in the prior art, the grooves of the second layer of grating are determined according to the stripes generated by the exposure. This effectively reduces the difficulty of making the second layer of grating and reduces the defect rate of the second layer of grating.

[0055] The material may be a functional material (eg, a holographic material). Further, the second grating layer may include one or more of a photosensitive material, an optical recording material, a volume holographic material, a liquid crystal material, a nanocomposite material or glue.

[0056] In a specific embodiment, the photosensitive material may be a silver salt emulsion and a photosensitive polymer. The optical recording material may be a photorefractive crystal and a photochromic material. The volume holographic material may be a polymer dispersed liquid crystal and an optical glass. The novel holographic material may be a nanocomposite material, a quantum dot material and a two-dimensional material.

[0057] And since the period of the second layer grating is determined by the grooves of the second layer grating, it can be seen from the above description that during the production process of the second layer grating, the material is smeared on the surface of the relief grating, and the smeared material will enter the grooves on the surface of the relief grating. The material entering the grooves of the relief grating forms the grooves of the second layer grating. In other words, the grooves of the second layer grating are determined by the grooves of the relief grating.

[0058] Therefore, when the period of the second grating layer needs to be adjusted, it is only necessary to adjust the period of the relief grating to adjust the light transmittance and reflectivity of the second grating layer by adjusting the period of the second grating layer. The period refers to the distance between adjacent grooves in the relief grating, or the distance between adjacent grooves in the second grating layer.

[0059] That is to say, to adjust the period of the second grating layer, it is necessary to set the relief grating to the required period, and then set a second grating layer on one side of the relief grating by applying material on the surface of the relief grating.

[0060] In a specific embodiment, the period of the relief grating is the same as the period of the second layer grating.

[0061] It can be seen from the above description that the second grating layer is formed by arranging the relief grating on the optical waveguide and applying material on the surface of the relief grating. Specifically, in one embodiment, the method for manufacturing the optical waveguide further includes the following steps:

[0062] (1) Applying photoresist to the target area on the optical waveguide;

[0063] (2) Imprinting a preset mold on the photoresist and performing a curing process to form a relief grating in a target area, wherein the surface of the relief grating away from the optical waveguide has a notch.

[0064] The target region may be a region corresponding to the coupling-in region, the turning region or the coupling-out region.

[0065] The preset mold has a grating shape with a preset period. That is, when a second layer of grating with a specific period is required, the preset mold can be pre-made according to the required period.

[0066] The curing process may be ultraviolet curing or heat curing.

[0067] By applying photoresist to the areas corresponding to the coupling-in area, the turning area or the coupling-out area on the optical waveguide, and then pressing a preset mold on the photoresist on these areas, and then curing these areas to harden the applied photoresist, the grating shape on the preset mold is printed on the applied photoresist.

[0068] In some implementations, it is also necessary to scrape off excess photoresist from the relief grating, and a microscope may be used to check whether there is any imprint missing from the relief grating to ensure that the relief grating can transmit light normally.

[0069] It can be seen that the period of the second grating layer is determined by first making a relief grating corresponding to the required period on the optical waveguide, and then applying material on the surface of the relief grating so that part of the applied material enters the grooves of the relief grating. More specifically:

[0070] In step 220, the applied material is exposed using a single light source to solidify the material, thereby forming a second layer of gratings on the surface of the relief gratings.

[0071] In some embodiments, the single light source includes one of ultraviolet light, infrared light, visible light, and laser.

[0072] That is to say, a relief grating corresponding to the required period is first made on the optical waveguide, and then material is applied on the surface of the relief grating so that part of the applied material enters the grooves of the relief grating. The applied material is then exposed to light with a single light source to solidify the applied material, thereby completing the second layer of grating on the relief grating.

[0073] Compared with the prior art, in which two beams of light are coherently used to expose the material for making the second layer of grating, and the grooves of the second layer of grating are determined according to the stripes generated by the exposure, the present application only needs to use a single light source to expose the applied material to solidify the applied material, without the need to accurately control the light source, nor to impose strict requirements on the stability of the light source and environmental conditions. This effectively reduces the difficulty of making the second layer of grating, and further reduces the defective rate of the second layer of grating.

[0074] The present application also provides an AR device, which includes an optical machine and the optical waveguide described above. The optical machine is used to emit an image light beam to the coupling-in area on the optical waveguide. The optical machine can be a micro projector. For example, a DLP projector, an LCOS projector, and a micro light emitting diode (MicroLED).

[0075] The embodiments of the present application provide a method for manufacturing an optical waveguide and an optical waveguide, the method for manufacturing the optical waveguide comprising: applying a material on the surface of a relief grating; exposing the applied material with a single light source to solidify the material to form a second layer of grating on the surface of the relief grating. Thus, by applying the material on the surface of the relief grating so that the applied material enters the grooves on the surface of the relief grating, and then hardening the applied material with a single light source to complete the production of the second layer of grating, there is no need to use interference fringes generated by two coherent light beams as the grooves of the second layer of grating. The difficulty of manufacturing the second layer of grating is effectively reduced, and the defective rate of the second layer of grating is reduced.

[0076] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for manufacturing an optical waveguide, characterized in that: The optical waveguide comprises a relief grating, and the method comprises: Applying material on the surface of the relief grating; The applied material is exposed using a single light source to solidify the material, thereby forming a second layer of grating on the surface of the relief grating.

2. The method for manufacturing an optical waveguide according to claim 1, characterized in that: The period of the relief grating is the same as the period of the second layer grating.

3. The method for manufacturing an optical waveguide according to claim 1, characterized in that: Before applying material on the surface of the relief grating, the method further comprises: Applying photoresist to a target area on the optical waveguide; A preset mold is imprinted on the photoresist and cured to form the relief grating in the target area. The surface of the relief grating away from the optical waveguide has grooves.

4. The method for manufacturing an optical waveguide according to claim 1, characterized in that: The material comprises one or more of a photosensitive material, an optical recording material, a volume holographic material, a liquid crystal material, a nanocomposite material or glue.

5. The method for manufacturing an optical waveguide according to claim 1, characterized in that: The single light source includes one of ultraviolet light, infrared light, visible light and laser.

6. An optical waveguide, characterized in that: The optical waveguide comprises an optical waveguide body, an entrance pupil area and an exit pupil area, wherein the entrance pupil area and the exit pupil area are arranged on the surface of the optical waveguide body, wherein: The entrance pupil area and / or the exit pupil area comprises a relief grating and a second layer of grating arranged on the surface of the relief grating.

7. The optical waveguide according to claim 6, characterized in that The entrance pupil area includes the relief grating, and the exit pupil area includes the relief grating and the second layer of grating arranged on the surface of the relief grating.

8. The optical waveguide according to claim 6, characterized in that The optical waveguide further includes a turning region, and the turning region is used to propagate at least part of the image light beam coupled out of the entrance pupil region to the exit pupil region.

9. The optical waveguide according to claim 6, characterized in that The optical waveguide includes two exit pupil regions.

10. The optical waveguide according to claim 9, characterized in that The two exit pupil areas are respectively located on both sides of the entrance pupil area.

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