Optical waveguide, display device and head-up display system
By designing multi-layer structures and grating regions in optical waveguides, the problem of poor image uniformity in two-dimensional grating waveguides is solved, and a more uniform brightness distribution and better display effect is achieved.
Patent Information
- Application Number
- CN202323550898.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2023-12-25
- Publication Date
- 2025-02-18
- Estimated Expiration
- 2033-12-25
AI Technical Summary
The existing two-dimensional grating waveguides have poor image uniformity, which affects the display effect of the augmented reality head-up display system.
An optical waveguide is designed, including a first waveguide layer and a second waveguide layer, and the second waveguide layer is laminated on the first waveguide layer. The coupling area of the first waveguide layer has a plurality of bright strip regions and a non-bright strip regions. A plurality of first grating regions and a second grating regions are provided on the second waveguide layer. The coupling efficiency of the second grating region is higher than that of The first grating area.
By adjusting the propagation path of light in the second waveguide layer, brightness uniformity is improved, the bright band effect is weakened, and the display effect is improved.
Smart Images
Figure CN222506660U_ABST
Abstract
Description
Technical Field
[0001] The present application relates to the field of optical imaging technology, and more specifically, to an optical waveguide, a display device, and a head-up display system. Background Art
[0002] At present, as the optical waveguide solution is applied to the augmented reality head-up display system, the limitation that the optical waveguide coupling / outcoupling areas in the original optical waveguide solution cannot overlap in space is eliminated, and a more compact central coupling waveguide architecture is extended. In the central coupling waveguide architecture, the coupling area is located in the center of the outcoupling area. By setting the coupling area and the outcoupling area of the central coupling waveguide as two-dimensional gratings, pupil expansion in two dimensions can be achieved.
[0003] However, the existing two-dimensional grating waveguide has the problem of poor image uniformity, which affects the display effect of the augmented reality head-up display system. Utility Model Content
[0004] The present application proposes an optical waveguide, a display device and a head-up display system to improve the above-mentioned defects.
[0005] In a first aspect, an embodiment of the present application provides an optical waveguide, a first waveguide layer and a second waveguide layer, wherein the second waveguide layer is stacked on the first waveguide layer;
[0006] The first waveguide layer includes a first coupling-in region and a first coupling-out region, the first coupling-out region has a plurality of bright stripe regions and a plurality of non-bright stripe regions, when light is coupled into the first waveguide layer from the first coupling-in region and then propagates to the first coupling-out region for coupling out, the brightness of the first light emitted from the bright stripe region is greater than the brightness of the second light emitted from the non-bright stripe region; the second waveguide layer includes a grating structure arranged thereon, the grating structure includes a plurality of first grating regions and a plurality of second grating regions, each of the second grating regions corresponds to a bright stripe region of the first coupling-out region, and the coupling-in efficiency of the second grating region is higher than the coupling-in efficiency of the first grating region.
[0007] Optionally, the plurality of first grating regions and the plurality of second grating regions are all one-dimensional gratings, and the transmission efficiency of the first grating regions is higher than the transmission efficiency of the second grating regions.
[0008] Optionally, the grating structure includes multiple sub-grating structures, each of the second grating regions is correspondingly arranged on one of the sub-grating structures, the area other than the second grating region on each of the sub-grating structures is the first grating region, and multiple sub-grating structures are spliced to form the grating structure; wherein, the second grating region is located on the symmetry axis of the sub-grating structure.
[0009] Optionally, a grating period direction of each of the sub-grating structures is perpendicular to a symmetry axis of the sub-grating structure.
[0010] Optionally, the second waveguide layer includes multiple sub-waveguide layers, each of the sub-grating structures is correspondingly arranged on one of the sub-waveguide layer structures, and multiple sub-waveguide layers are spliced to form the second waveguide layer; wherein the side wall of each sub-waveguide layer is coated with a light absorbing material.
[0011] Optionally, the first waveguide layer and the second waveguide layer are cylindrical in shape of the same size, the sub-grating structures are fan-shaped, and each of the sub-grating structures has a central angle of 60°.
[0012] Optionally, the first in-coupling region is arranged in the first out-coupling region along a projection direction of the first out-coupling region, and the first in-coupling region and the first out-coupling region are two-dimensional grating structures.
[0013] In a second aspect, an embodiment of the present application further provides a display device, comprising a light source and the optical waveguide as described above, wherein the light source is used to emit light, and the first waveguide layer is disposed between the second waveguide layer and the light source.
[0014] Optionally, the light is coupled into the first waveguide layer from the first coupling-in region and then propagates to the first coupling-out region for outcoupling to form the first light and the second light, at least a portion of the first light is transmitted from the second grating region through the second waveguide layer to form a third light, at least a portion of the first light is coupled into the second waveguide layer from the second grating region and then propagates to the first grating region for outcoupling, and combines with at least a portion of the second light transmitted from the first grating region through the second waveguide layer to form a fourth light.
[0015] In a third aspect, an embodiment of the present application further provides a head-up display system, comprising a display glass and a display device as described above, wherein light emitted by the display device reaches the display glass and is reflected to a target observation position, wherein the second waveguide layer is disposed between the display glass and the first waveguide layer.
[0016] Therefore, the present application provides an optical waveguide, a display device and a head-up display system, wherein the optical waveguide comprises: a first waveguide layer and a second waveguide layer, wherein the second waveguide layer is stacked on the first waveguide layer; the first waveguide layer comprises a first coupling-in region and a first coupling-out region, wherein the first coupling-out region has a plurality of bright stripe regions and a plurality of non-bright stripe regions, and when light is coupled into the first waveguide layer from the first coupling-in region and then propagates to the first coupling-out region for coupling out, the brightness of the first light emitted from the bright stripe region is greater than the brightness of the second light emitted from the non-bright stripe region; the second waveguide layer comprises a grating structure arranged thereon, wherein the grating structure comprises a plurality of first grating regions and a plurality of second grating regions, wherein each of the second grating regions corresponds to a bright stripe region of the first coupling-out region, and the coupling-in efficiency of the second grating region is higher than the coupling-in efficiency of the first grating region. Therefore, part of the first light emitted from the bright stripe area is directly transmitted through the first grating area and emitted from the second waveguide layer, and part of the first light is coupled into the second waveguide layer from the second grating area and propagated to the rear coupling-out. That is to say, the light emitted from the second grating area of the second waveguide layer has part of the light energy transferred through the coupling-in process of the second grating area, so that the brightness of the original bright stripe area is weakened, thereby improving the brightness uniformity. Furthermore, part of the light coupled into the second waveguide layer from the second grating area is propagated to the first grating area for coupling-out. Therefore, the light emitted from the first grating area of the second waveguide layer includes the light emitted from the original non-bright stripe area and part of the light emitted from the bright stripe area, so that the brightness of the original non-bright stripe area is improved, and the bright stripe effect is further weakened.
[0017] Other features and advantages of the embodiments of the present application will be described in the subsequent description, and partly become apparent from the description, or can be understood by practicing the embodiments of the present application. The purposes and other advantages of the embodiments of the present application can be realized and obtained by the structures specifically pointed out in the written description, claims, and drawings. BRIEF DESCRIPTION OF THE DRAWINGS
[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.
[0019] Figure 1 A schematic structural diagram of a two-dimensional top-input waveguide and its output image in the prior art is shown.
[0020] Figure 2 A schematic structural diagram of an optical waveguide shown in an embodiment of the present application is shown.
[0021] Figure 3a A top view of the structure of a first waveguide layer shown in an embodiment of the present application is shown.
[0022] Figure 3b A schematic diagram showing the distribution of the bright stripe region of the first waveguide layer in an embodiment of the present application is shown.
[0023] Figure 4 A top view of a grating structure of a second waveguide layer shown in an embodiment of the present application is shown.
[0024] Figure 5 A schematic structural diagram of a display device shown in an embodiment of the present application is shown.
[0025] Figure 6 A schematic structural diagram of a head-up display system shown in an embodiment of the present application is shown. DETAILED DESCRIPTION
[0026] In order to make those skilled in the art better understand the present application scheme, the technical scheme in the present application embodiment will be clearly and completely described below in conjunction with the drawings in the present application embodiment. Obviously, the described embodiment is only a part of the present application embodiment, rather than all the embodiments. The components of the present application embodiment usually described and shown in the drawings here can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the present application for protection, but merely represents the selected embodiment of the present application. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without making creative work belong to the scope of protection of the present application.
[0027] It should be noted that similar reference numerals and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings. At the same time, in the description of this application, the terms "first", "second", etc. are only used to distinguish the description and cannot be understood as indicating or implying relative importance.
[0028] For the two-dimensional grating waveguide in the prior art, there is a problem of local bright stripe display defects in the entire field of view. Figure 1 , Figure 1The schematic diagram of the structure of the two-dimensional top-input waveguide and its output image in the prior art is shown, wherein the light coupled into the optical waveguide 101 from the coupling-in region propagates to the coupling-out region and is coupled out of the optical waveguide 101 to form an output image as shown in 102, and the coupling-out region is a two-dimensional grating structure. After many experiments, the inventors found that for the two-dimensional grating coupled optical waveguide, a bright strip 103 distributed in a diffuse shape along the coupling-in direction of the light will be formed on the output image, that is, the two-dimensional grating waveguide has a problem of local bright strip display defects in the entire field of view, resulting in poor image uniformity and deterioration of its display effect.
[0029] See also Figure 2 , Figure 2 A schematic structural diagram of an optical waveguide shown in an embodiment of the present application is shown, which includes a first waveguide layer 210 and a second waveguide layer 220 , wherein the second waveguide layer 220 is stacked on the first waveguide layer 210 .
[0030] In this embodiment, the first waveguide layer 210 includes a first coupling-in region 211 and a first coupling-out region 212. When light is coupled into the first waveguide layer 210 from the first coupling-in region 211, total reflection occurs in the first waveguide layer 210 and propagates to the first coupling-out region 212 and couples out of the first waveguide layer 210, forming a first light emitted from the bright stripe region and a second light emitted from the non-bright stripe region, and the brightness of the first light is higher than that of the second light.
[0031] It should be noted that, in this embodiment, the bright stripe area refers to an area where the brightness of the light emitted from the area is greater than that of other areas, that is, the non-bright stripe area. Correspondingly, the non-bright stripe area refers to an area where the brightness of the light emitted from the area is less than that of other areas, that is, the bright stripe area.
[0032] Further, in this embodiment, the second waveguide layer 220 includes a plurality of first grating regions and a plurality of second grating regions, and each second grating region corresponds to a bright stripe region of the first outcoupling region 212, the first grating region is arranged around the second grating region, and the coupling efficiency of the second grating region is higher than the coupling efficiency of the first grating region, and further, the transmission efficiency of the first grating region is higher than the transmission efficiency of the second grating region. Thus, at least part of the first light emitted from the bright stripe region of the first outcoupling region 212 will be coupled into the second waveguide layer 220 from the second grating region corresponding to the bright stripe region, and then be coupled out from the first grating region to form a third light, and part of the first light will directly exit the second waveguide layer 220 from the second grating region; at the same time, at least part of the second light emitted from the non-bright stripe region of the first outcoupling region 212 will directly pass through the first grating region corresponding to the non-bright stripe region and exit the second waveguide layer 220 to form a fourth light. It can be understood that, since only a portion of the first light emitted from the bright stripe region of the first waveguide layer 210 is directly transmitted through the second waveguide layer 220 from the second grating region to form the emitted light from the bright stripe region, and another portion of the light is coupled into the second waveguide layer 220 from the second grating region and then emitted from the second waveguide layer 220 from the first grating region after propagating in the second waveguide layer 220 along other propagation directions, then this portion of the emitted third light is combined with the fourth light formed by the second light being transmitted from the first grating region through the second waveguide layer 220 to form the emitted light from the non-bright stripe region.
[0033] Therefore, according to the above analysis, it can be known that the brightness of the first light originally emitted from the bright stripe area is different from that of the second light emitted from the non-bright stripe area. However, by setting the second waveguide layer, part of the first light directly passes through the second waveguide layer to be emitted to form a third light, and part of it propagates in the second waveguide layer to be emitted from the non-bright stripe position. In addition, there is also a second light originally incident on it and transmitted out at the non-bright stripe position. These parts of light combine to form a fourth light. Thus, the brightness of the final emitted light is regulated by the second waveguide layer, and the brightness of the emitted light is made more uniform without causing additional light energy loss, thereby improving the display effect of the optical waveguide. Exemplarily, the brightness difference between the third light emitted from the original bright stripe area and the fourth light emitted from the original non-bright stripe area is less than the brightness threshold, where the brightness threshold is a preset value. Further, by adjusting the coupling parameters and transmission parameters of the second grating area to the light, the brightness difference of the final emitted light can meet the threshold condition.
[0034] Optionally, the first coupling region is a two-dimensional grating, and the first coupling region is also a two-dimensional grating. It should be understood that the pupil expansion characteristic of the two-dimensional grating enables the light incident therein to propagate in the waveguide in a variety of different propagation directions. Therefore, when the first coupling region is a two-dimensional grating, its coupled light will have a variety of coupling directions. According to the above analysis, after the light propagates in the optical waveguide, it couples out of the optical waveguide from the first coupling region and forms an output image. There will also be a plurality of bright stripes corresponding to different coupling directions on the output image. Therefore, the plurality of bright stripes on the output image can be corresponded to the first coupling region, that is, the first coupling region 212 has a plurality of bright stripe regions and a plurality of non-bright stripe regions. Thus, the light is coupled into the first waveguide layer 210 from the first coupling region 211 and propagates to the first coupling region 212 to couple out, and the brightness of the first light formed by coupling out of the bright stripe region on the first coupling region 212 will be significantly higher than the brightness of the second light formed by coupling out of the non-bright stripe region on the first coupling region 212.
[0035] Optionally, the first grating region and the second grating region are both one-dimensional gratings.
[0036] As an implementation manner, the first waveguide layer 210 is cylindrical. Specifically, reference may be made to Figure 3a and Figure 3b , Figure 3a A top view of the structure of a first waveguide layer shown in an embodiment of the present application is shown, wherein the first coupling-in region 211 is located in the central region of the first waveguide layer 210, and the first coupling-out region 212 is arranged around the first coupling-in region 211; Figure 3b The distribution diagram of the bright stripe region of the first waveguide layer in the embodiment of the present application is shown, wherein the angle between two adjacent bright stripe regions 213 is 60°, and the areas outside the bright stripe regions 213 are all non-bright stripe regions 214. It can be understood that the distribution characteristics of the bright stripe regions 213 are affected by the coupling direction of the light in the first coupling region. Figure 3b What is shown in the figure is only a possible implementation and is not a limitation, and will not be described in detail here.
[0037] As an implementation method, the second waveguide layer 220 is also cylindrical. Figure 4 , Figure 4 1 shows a top view of a grating structure of a second waveguide layer shown in an embodiment of the present application, wherein the grating structure of the second waveguide layer 220 includes a plurality of sub-grating structures 221, and each second grating region 222 is correspondingly arranged on a sub-grating structure 221, and the area other than the second grating region 222 on each sub-grating structure 221 is the first grating region ( Figure 4), a plurality of sub-grating structures 221 are spliced to form the grating structure of the second waveguide layer 220. Moreover, each sub-grating structure 221 has a grating period direction K, and the direction of the grating period direction is perpendicular to the symmetry axis of the sub-grating structure 221. Further, the grating period direction is used to change the wave vector of the first light incident on the second grating region, so that the propagation direction of the first light incident thereon in the second waveguide layer changes to a direction perpendicular to the symmetry axis of the sub-grating structure 221. Specifically, the grating period direction changes the direction of the image light wave vector to be the same as the direction it has, that is, when the grating period direction of the grating has a direction perpendicular to the symmetry axis of the sub-grating structure 221, the grating has the ability to change the propagation direction of the image light incident thereon to be perpendicular to the symmetry axis of the sub-grating structure 221. Furthermore, the second grating region 222 is a grating, and its ability to couple light is limited by its coupling efficiency, that is, when light is incident on the second grating region 222, only part of the incident light is guaranteed to be coupled into the second waveguide layer 220 and propagates to other positions of the second waveguide layer 220 along the changed propagation direction, while the remaining incident light will directly penetrate the second waveguide layer 220 and be emitted. Exemplarily, the energy ratio of the coupled light incident on the second grating region 222 and the transmitted light can be changed by adjusting the structural parameters such as the depth and duty cycle of the one-dimensional grating of the second grating region 222.
[0038] Optionally, the second waveguide layer 220 includes a plurality of sub-waveguide layers, each sub-grating structure 221 is disposed on a corresponding sub-waveguide layer, the sub-grating structure 221 is fan-shaped, each of the sub-grating structures has a central angle of 60°, and each sub-waveguide layer is also fan-shaped with a central angle of 60°. Figure 3a and Figure 3b As can be seen from the above analysis, the angle between each bright stripe region 213 of the first coupling region 211 on the first waveguide layer 210 is also 60°. Therefore, the second grating region 222 at the symmetry axis position of each sub-grating structure 221 on the second waveguide layer 220 can just correspond to a bright stripe region 213 of the first waveguide layer 210, thereby ensuring that the first light emitted from the bright stripe region 213 of the first waveguide layer 210 can just enter the second waveguide layer 210 from the second grating region 221 of the second waveguide layer 210. It can be understood that the first grating region on the second waveguide layer 220 also corresponds to the non-bright stripe region 214 on the first waveguide layer 210, so that the second light emitted from the non-bright stripe region 214 of the first waveguide layer 210 can just transmit through the second waveguide layer 210 from the first grating region 222 of the second waveguide layer 210.
[0039] Therefore, after the first light emitted from the bright stripe area of the first outcoupling area reaches the second grating area of the second waveguide layer, part of the first light directly transmits through the second waveguide layer from the second grating area to form the third light emitted from the second grating area; part of the first light is coupled into the second waveguide layer from the second grating area, and under the action of the grating period direction, changes the propagation direction to propagate toward the first grating area, thereby propagating in the second waveguide layer to the position of the first grating area, thereby emitting from the second waveguide layer, and the second light emitted from the non-bright stripe area of the first outcoupling area will also reach the first grating area of the second waveguide layer and emit from the second waveguide layer, and the two together constitute the fourth light emitted from the first grating area. Therefore, the third light emitted from the second grating area of the second waveguide layer has part of its light energy transferred through the coupling process of the second grating area, so that the brightness on the original bright stripe area is weakened, thereby improving the brightness uniformity. Furthermore, since the fourth light emitted from the first grating area of the second waveguide layer includes the light emitted from the original non-bright stripe area and the light emitted from part of the bright stripe area, the brightness of the third image light is increased, the brightness of the original non-bright stripe area is improved, and the bright stripe effect is further weakened.
[0040] Optionally, the transmittance of the first grating region is higher than the transmittance of the second grating region. The high transmittance of the first grating region ensures that the light can be efficiently transmitted through the second waveguide layer after entering the first grating region, that is, the bright stripe effect is weakened by enhancing the brightness of the light on the original non-bright stripe area.
[0041] Optionally, a light absorbing material is coated on the side wall of each sub-waveguide layer of the second waveguide layer, so that the first light that is coupled into and propagates in the second waveguide layer and ultimately fails to be coupled out of the second waveguide layer can be absorbed by the light absorbing material on the side wall after being incident on the side wall of each sub-waveguide layer.
[0042] In this embodiment, different sub-grating structures 221 on the second waveguide layer have grating period directions in different directions. Therefore, as an implementation method, the method for preparing the grating structure of the second waveguide layer may be to use an interference exposure method, and use a sector mask to expose different positions of the circular template in batches, and adjust the direction after each exposure, so that the preparation of a one-dimensional grating can be achieved. This preparation method only needs to use one template to manufacture a complete grating structure, thereby saving resources. As an implementation method, the method for preparing the grating structure of the second waveguide layer may be to make the second waveguide layer spliced by a plurality of sub-waveguide layers with the same grating structure, in each sector sub-waveguide layer, the grating region near the sector symmetry axis is the second grating region, and the remaining grating region is the first grating region, and the grating period direction of the second grating region is perpendicular to the sector symmetry axis. Since the second waveguide layer adopts the combination of six waveguides, there is no need to process gratings in different grating period directions in this embodiment. Instead, the waveguides in a single period direction can be mass-produced through processes such as nanoimprinting, and then cut into fan-shaped shapes and spliced to obtain the second waveguide layer, thereby reducing the processing difficulty.
[0043] Therefore, the present application provides an optical waveguide, comprising: a first waveguide layer and a second waveguide layer, wherein the second waveguide layer is stacked on the first waveguide layer; the first waveguide layer comprises a first coupling-in region and a first coupling-out region, wherein the first coupling-out region has a plurality of bright stripe regions and a plurality of non-bright stripe regions, and when light is coupled into the first waveguide layer from the first coupling-in region and then propagates to the first coupling-out region for coupling out, the brightness of the first light emitted from the bright stripe region is greater than the brightness of the second light emitted from the non-bright stripe region; the second waveguide layer comprises a grating structure arranged thereon, wherein the grating structure comprises a plurality of first grating regions and a plurality of second grating regions, wherein each of the second grating regions corresponds to a bright stripe region of the first coupling-out region, the first grating region is arranged around the second grating region, and the coupling-in efficiency of the second grating region is higher than the coupling-in efficiency of the first grating region. Therefore, part of the first light emitted from the bright stripe area is directly emitted from the second waveguide layer from the second grating area, and part of the first light is coupled into the second waveguide layer from the second grating area and coupled out of the second waveguide layer from the first coupling area after propagation, and the second light emitted from the non-bright stripe area is also transmitted through the first coupling area to emit out of the second waveguide layer, that is, the light emitted from the second grating area of the second waveguide layer is partially transferred through the coupling process of the second grating area, so that the brightness of the original bright stripe area is weakened, thereby improving the brightness uniformity. Furthermore, since the light emitted from the first grating area of the second waveguide layer includes the light emitted from the original non-bright stripe area and the light emitted from part of the bright stripe area, the brightness of the original non-bright stripe area is improved, thereby further weakening the bright stripe effect.
[0044] See also Figure 5 , Figure 5 A display device shown in an embodiment of the present application is shown, comprising a light source 301 and an optical waveguide 302 as described in the above embodiment, wherein the light source 301 is used to emit light, and the first waveguide layer in the optical waveguide 302 is arranged between the second waveguide layer and the light source. Furthermore, after the light is coupled into the first waveguide layer from the first coupling-in region, it is propagated to the first coupling-out region for coupling out, forming the first light and the second light, at least part of the first light is transmitted through the second waveguide layer from the second grating region, forming the third light, at least part of the first light is coupled into the second waveguide layer from the second grating region, it is propagated to the first grating region for coupling out, and combined with at least part of the second light transmitted through the second waveguide layer from the first grating region, a fourth light is formed. The specific implementation method can refer to the above embodiment, which will not be repeated here.
[0045] See also Figure 6 , Figure 6A head-up display system shown in an embodiment of the present application is shown, comprising a display glass 401 and a display device 402 as described in the above embodiment, the light emitted by the display device 402 reaches the display glass 401 and is reflected to the target observation position, and the second waveguide layer in the display device is arranged between the display glass and the first waveguide layer. Generally speaking, the target observation position can refer to the human eye. The specific implementation method can refer to the above embodiment, and will not be repeated here.
[0046] 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. An optical waveguide, characterized in that: include: a first waveguide layer and a second waveguide layer, wherein the second waveguide layer is stacked on the first waveguide layer; The first waveguide layer comprises a first coupling-in region and a first coupling-out region, wherein the first coupling-out region has a plurality of bright stripe regions and a plurality of non-bright stripe regions, and when light is coupled into the first waveguide layer from the first coupling-in region and then propagates to the first coupling-out region for coupling out, the brightness of the first light emitted from the bright stripe region is greater than the brightness of the second light emitted from the non-bright stripe region; The second waveguide layer includes a grating structure arranged thereon, wherein the grating structure includes a plurality of first grating regions and a plurality of second grating regions, each of the second grating regions corresponds to a bright strip region of the first out-coupling region, and the coupling efficiency of the second grating region is higher than the coupling efficiency of the first grating region.
2. The optical waveguide according to claim 1, characterized in that The plurality of first grating regions and the plurality of second grating regions are all one-dimensional gratings, and the transmission efficiency of the first grating regions is higher than the transmission efficiency of the second grating regions.
3. The optical waveguide according to claim 1, characterized in that The grating structure comprises a plurality of sub-grating structures, each of the second grating regions is correspondingly arranged on one of the sub-grating structures, the region other than the second grating region on each of the sub-grating structures is the first grating region, and a plurality of the sub-grating structures are spliced to form the grating structure; Wherein, the second grating region is located on the symmetry axis of the sub-grating structure.
4. The optical waveguide according to claim 3, characterized in that The grating period direction of each of the sub-grating structures is perpendicular to the symmetry axis of the sub-grating structure.
5. The optical waveguide according to claim 3, characterized in that The second waveguide layer includes a plurality of sub-waveguide layers, each of the sub-grating structures is correspondingly arranged on one of the sub-waveguide layers, and a plurality of the sub-waveguide layers are spliced to form the second waveguide layer; Wherein, the side wall of each sub-waveguide layer is coated with light absorbing material.
6. The optical waveguide according to claim 3, characterized in that The first waveguide layer and the second waveguide layer are cylindrical in shape and have the same size. The sub-grating structures are fan-shaped, and each sub-grating structure has a central angle of 60°.
7. The optical waveguide according to claim 1, characterized in that The first coupling-in region is arranged in the first outcoupling region along a projection direction of the first outcoupling region, and the first coupling-in region and the first outcoupling region are two-dimensional grating structures.
8. A display device, characterized in that: The optical waveguide comprises a light source and the optical waveguide according to any one of claims 1 to 7, wherein the light source is used to emit light, and the first waveguide layer is arranged between the second waveguide layer and the light source.
9. The display device according to claim 8, characterized in that: The light is coupled into the first waveguide layer from the first coupling-in region and then propagates to the first coupling-out region for coupling out, thereby forming the first light and the second light. At least a portion of the first light is transmitted through the second waveguide layer from the second grating region to form a third light. At least a portion of the first light is coupled into the second waveguide layer from the second grating region and then propagates to the first grating region for coupling out, thereby forming a fourth light in combination with at least a portion of the second light transmitted through the second waveguide layer from the first grating region to form a fourth light.
10. A head-up display system, characterized in that: The invention comprises a display glass and the display device as claimed in claim 9, wherein the light emitted by the display device reaches the display glass and is reflected to a target observation position, wherein the second waveguide layer is arranged between the display glass and the first waveguide layer.