Diffraction optical waveguide

Abstract

The embodiment of the utility model provides a diffraction optical waveguide, and relates to the technical field of optics. The diffraction optical waveguide provided by the embodiment of the utility model comprises a coupling-in area and a grating area used for receiving light transmitted in the optical waveguide, and the coupling-in area is used for coupling external light to the optical waveguide; a grating structure is arranged in the grating area, the duty ratio of the grating structure is linearly and gradually increased at a constant shrinkage rate in the diffusion direction of external light in the optical waveguide, and the shrinkage rate is the ratio of the duty ratio value of the end, with the smaller duty ratio, of the grating structure in the unit length to the duty ratio value of the end, with the larger duty ratio, of the grating structure. The shrinkage rate ranges from 85% to 99%. According to the diffraction optical waveguide provided by the embodiment of the utility model, the duty ratio of the grating structure is linearly increased, so that the coupling-out intensity of the diffused light in the diffraction optical waveguide is not influenced by the diffusion distance of the diffused light in the grating structure, and the intensity of the light coupled out of the grating area is more uniform in space.

Description

Technical Field

[0001] The utility model relates to the technical field of optics, in particular to a diffraction optical waveguide. Background Art

[0002] In existing diffraction waveguides, the outcoupling efficiency remains consistent at any position of the outcoupling grating. However, as light from the outcoupling grating is continuously coupled out, its intensity gradually decreases. This results in the intensity of light coupled out earlier being greater than the intensity of light coupled out later. This results in significant brightness variations in the spatial distribution of the outcoupling light and poor brightness uniformity. If the outcoupling grating is a two-dimensional grating, the main ray hitting the outcoupling grating will generate light in three directions, all of which exhibit a decreasing brightness trend. Utility Model Content

[0003] The embodiment of the utility model provides a diffraction optical waveguide, which can make the intensity of light coupled out of the grating area more uniform in space.

[0004] The embodiment of the present invention provides a diffraction optical waveguide, comprising: an incoupling region and a grating region for receiving light transmitted in the optical waveguide, wherein the incoupling region is used to couple external light into the optical waveguide;

[0005] A grating structure is provided in the grating area, and the duty cycle of the grating structure increases linearly and gradually at a constant shrinkage rate along the diffusion direction of the external light in the optical waveguide. The shrinkage rate is the ratio of the duty cycle value at the end with the smaller duty cycle to the duty cycle value at the end with the larger duty cycle within a unit length of the grating structure, and the shrinkage rate ranges from 85% to 99%.

[0006] Optionally, the grating region includes a turning region, in which a turning grating structure is provided, and the turning grating structure is a one-dimensional grating structure, which includes a grating substrate and a plurality of grating strips provided on the grating substrate;

[0007] Each grating strip in the turning grating structure extends along the vector sum direction of the main light direction and the turning light direction formed by the external light in the turning area, and increases linearly and gradually at a constant shrinkage rate; and forms a stepped arrangement in the grating vector direction of the turning grating structure in a manner of gradually moving backward along the extension direction; the main light direction is more inclined to the turning light direction than the duty cycle direction of the turning grating structure, and the duty cycle direction is the direction in which the duty cycles of each grating strip are equal and consistent.

[0008] Optionally, the grating region further includes an outcoupling region, in which an outcoupling grating structure is provided. The outcoupling grating structure is a one-dimensional grating structure, which includes a grating substrate and a plurality of grating strips provided on the grating substrate.

[0009] The duty cycle direction of the out-coupling grating structure is perpendicular to the duty cycle direction of the turning grating structure, the extension direction of each grating strip in the out-coupling grating structure is parallel to the duty cycle direction of the turning grating structure, and the transmission direction of the turning light in the out-coupling area is not parallel to the duty cycle direction of the out-coupling grating structure.

[0010] Optionally, along the extension direction of each grating strip, the duty cycle of the grating strip includes a starting duty cycle and an ending duty cycle. When the duty cycle of the grating strip forms a linear gradient and tends to increase, the starting duty cycle is smaller than the ending duty cycle. The starting duty cycle ranges from 10% to 80%, and the ending duty cycle ranges from 20% to 90%. Optionally, the grating region includes an out-coupling region, in which an out-coupling two-dimensional grating structure is provided. The out-coupling two-dimensional grating structure has a plurality of quadrilateral projections on a plane perpendicular to the grating region. Each quadrilateral projection includes a first set of oppositely disposed edges and a second set of oppositely disposed edges. Each second set of edges is sequentially arranged along the direction in which the first set of edges extends. Each first set of edges is sequentially arranged along the direction in which the second set of edges extends. The direction in which the second set of edges extends intersects with the direction in which the first set of edges extends.

[0011] In the direction in which the first set of sides extends and toward the first direction of light diffusion, the lengths of the second set of sides gradually increase in sequence; in the direction in which the second set of sides extends and toward the second direction of light diffusion, the lengths of the first set of sides gradually increase in sequence.

[0012] Optionally, the first group of sides includes a first side and a second side arranged opposite to each other, and the second group of sides includes a third side and a fourth side arranged opposite to each other. In the direction in which the first group of sides extends and in the first direction of light diffusion, the third side and the fourth side are arranged in sequence. In the direction in which the second group of sides extends and in the second direction of light diffusion, the first side and the second side are arranged in sequence. The length of the first side is smaller than the length of the second side, and the length of the third side is smaller than the length of the fourth side.

[0013] Optionally, the outcoupling region is rectangular, and the direction of the main light formed by the external light in the outcoupling region is parallel to the short side of the rectangle and coincides with the center line of the long side of the rectangle;

[0014] The out-coupling two-dimensional grating structure is an axisymmetric structure, and the projections of each quadrilateral are axisymmetric figures. The angle between the symmetry axis of the out-coupling two-dimensional grating structure and the symmetry axis of each quadrilateral projection is 0°, and coincides with the direction of the main light formed by the external light in the out-coupling area. The symmetry axis of each quadrilateral projection is the angle bisector of each quadrilateral projection.

[0015] Optionally, the outcoupling region is rectangular, and the direction of the main light formed by the external light in the outcoupling region is parallel to the center line of the long side of the outcoupling two-dimensional grating structure and is at a preset distance;

[0016] The center line of the long side of the out-coupling two-dimensional grating structure is parallel to or has an angle with the short side of the rectangle;

[0017] When the diffusion length of the light in the first direction of light diffusion is shorter than the diffusion length in the second direction of light diffusion, the length of the first side is longer than the length of the fourth side.

[0018] Optionally, the outcoupling region is rectangular, and the direction of the main light formed by the external light in the outcoupling region is parallel to the long side of the rectangle and coincides with the center line of the short side of the rectangle; or, the direction of the main light formed by the external light in the outcoupling region forms an angle with the long side of the rectangle;

[0019] The out-coupling two-dimensional grating structure is an axisymmetric structure, and the symmetry axis of the out-coupling two-dimensional grating structure coincides with the direction of the main light formed by the external light in the out-coupling region;

[0020] Among them, on one side of the symmetry axis of the outcoupling two-dimensional grating structure, the length of the third side is greater than the length of the second side, and on the other side of the symmetry axis of the outcoupling two-dimensional grating structure, the length of the first side is greater than the length of the fourth side.

[0021] Optionally, the two-dimensional grating structure includes a first one-dimensional grating structure and a second one-dimensional grating structure, the first one-dimensional grating structure and the second one-dimensional grating structure are located in different planes, the grating bars of the first one-dimensional grating structure extend in a first direction, and the grating bars of the second one-dimensional grating structure extend in a second direction, and on the plane of the two-dimensional grating structure, the projections of the first one-dimensional grating structure and the second one-dimensional grating structure overlap with each other to form a quadrilateral projection.

[0022] Optionally, the two-dimensional grating structure includes overlapping portions of a plurality of quadrilateral projection patterns.

[0023] The diffraction optical waveguide provided by the embodiment of the present invention sets the duty cycle of the grating structure to increase linearly in the diffusion direction of the diffused light, so that the coupling efficiency of the grating structure gradually increases in the diffusion direction of the diffused light, thereby compensating for the decrease in the light intensity of the diffused light after diffraction in the diffraction optical waveguide along the diffusion direction, so that the coupling intensity of the diffused light in the diffraction optical waveguide is not affected by the diffusion distance of the diffused light in the diffraction optical waveguide, and thus the intensity of the light coupled out of the diffraction optical waveguide is more uniform in space.

[0024] It should be understood that the content described in this section is not intended to identify the key or important features of the embodiments of the present invention, nor is it intended to limit the scope of the present invention. Other features of the present invention will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, 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 invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0026] Figure 1 This is a principle diagram of the optical path of light coupled out of a diffraction optical waveguide in the prior art;

[0027] Figure 2 It is the intensity spatial distribution diagram of the light coupled out of the diffraction optical waveguide in the prior art;

[0028] Figure 3 A schematic structural diagram of a diffraction optical waveguide provided in an embodiment of the present utility model;

[0029] Figure 4 This is a schematic structural diagram of another diffraction optical waveguide provided by an embodiment of the present utility model;

[0030] Figure 5 This is a schematic structural diagram of another diffraction optical waveguide provided by an embodiment of the present utility model;

[0031] Figure 6 This is a schematic diagram of a transition grating structure provided by an embodiment of the present utility model;

[0032] Figure 7 This is a schematic structural diagram of another diffraction optical waveguide provided by an embodiment of the present utility model;

[0033] Figure 8 This is a schematic diagram of an outcoupling grating structure provided by an embodiment of the present utility model;

[0034] Figure 9 This is a schematic structural diagram of a grating strip provided by an embodiment of the present utility model;

[0035] Figure 10 This is a schematic structural diagram of another diffraction optical waveguide provided by an embodiment of the present utility model;

[0036] Figure 11 Schematic diagram of an out-coupling two-dimensional grating structure provided by an embodiment of the present utility model;

[0037] Figure 12 It is a structural diagram of the outcoupling area provided by an embodiment of the present utility model;

[0038] Figure 13 yes Figure 12 A comparison diagram of the spatial distribution of the intensity of the light coupled out of the diffraction waveguide and the spatial distribution of the intensity of the light coupled out of the grating with a constant duty cycle in the prior art;

[0039] Figure 14 This is a schematic structural diagram of another outcoupling region provided by an embodiment of the present utility model;

[0040] Figure 15 This is a structural diagram of another outcoupling region provided by an embodiment of the present utility model;

[0041] Figure 16 yes Figure 14 A comparison diagram of the spatial distribution of the intensity of the light coupled out of the diffraction waveguide and the spatial distribution of the intensity of the light coupled out of the grating with a constant duty cycle in the prior art;

[0042] Figure 17 This is a structural diagram of another outcoupling region provided by an embodiment of the present utility model;

[0043] Figure 18 This is a structural diagram of another outcoupling region provided by an embodiment of the present utility model;

[0044] Figure 19 yes Figure 17 A comparison diagram of the spatial distribution of the intensity of the light coupled out of the diffraction waveguide and the spatial distribution of the intensity of the light coupled out of the grating with a constant duty cycle in the prior art;

[0045] Figure 20 1 is a graph showing the relationship between the quadrilateral projection size and the outcoupling efficiency, pupil expansion efficiency, and pupil expansion light outcoupling efficiency provided by an embodiment of the present invention;

[0046] Figure 21 is a schematic diagram of a first one-dimensional grating structure and a second one-dimensional grating structure provided by an embodiment of the present utility model;

[0047] Figure 22 is a schematic diagram of a two-dimensional grating structure provided by an embodiment of the present utility model;

[0048] Figure 23 is a schematic diagram of another first one-dimensional grating structure and a second one-dimensional grating structure provided by an embodiment of the present utility model;

[0049] Figure 24 is a schematic diagram of another two-dimensional grating structure provided by an embodiment of the present utility model;

[0050] Figure 25 is a schematic diagram of another first one-dimensional grating structure and a second one-dimensional grating structure provided by an embodiment of the present utility model;

[0051] Figure 26 This is a schematic diagram of another two-dimensional grating structure provided by an embodiment of the present utility model;

[0052] Figure 27is a schematic diagram of another first one-dimensional grating structure and a second one-dimensional grating structure provided by an embodiment of the present utility model;

[0053] Figure 28 This is a schematic diagram of another two-dimensional grating structure provided by an embodiment of the present utility model;

[0054] Figure 29 is a schematic diagram of another first one-dimensional grating structure and a second one-dimensional grating structure provided by an embodiment of the present utility model;

[0055] Figure 30 This is a schematic diagram of another two-dimensional grating structure provided by an embodiment of the present utility model;

[0056] Figure 31 This is a principle diagram of the optical path of the diffraction optical waveguide outcoupling light proposed in an embodiment of the utility model. DETAILED DESCRIPTION

[0057] In order to help those skilled in the art better understand the present invention, the following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0058] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that the numbers used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0059] Figure 1 This is a principle diagram of the optical path of the light coupled out of the diffraction waveguide in the prior art, such as Figure 1 As shown, during the process of light being coupled out of the diffractive optical waveguide, the intensity of the light in the diffractive optical waveguide decreases with the order in which the light is output from the diffractive optical waveguide, i.e., the intensity of the light coupled out first is greater than the intensity of the light coupled out later. The diffractive optical waveguide includes a waveguide substrate 00 and a grating region 200 located on the waveguide substrate 00. Figure 2This is the intensity spatial distribution diagram of the light coupled out of the diffraction waveguide in the prior art, refer to Figure 2 This intensity spatial distribution diagram corresponds to the outcoupling grating in the diffraction waveguide with a constant duty cycle. The light outcoupling efficiency is the same at all locations of the outcoupling grating. Therefore, along the propagation direction of the light in the outcoupling grating, the intensity of the light in the outcoupling grating gradually decreases, and the intensity of the outcoupled light also gradually decreases, resulting in a large difference in the intensity distribution of the outcoupled light in the propagation direction of the light in the diffraction waveguide.

[0060] Based on the above technical problems, an embodiment of the present invention provides a diffraction optical waveguide, which gradually changes the duty cycle of the grating structure in the diffusion direction of the diffused light, so that the intensity of the light in the optical waveguide gradually decreases while the coupling efficiency of the grating is improved, thereby making the intensity distribution of the light coupled out of the diffraction optical waveguide more uniform.

[0061] The embodiment of the utility model provides a diffraction optical waveguide, Figure 3 A structural diagram of a diffraction optical waveguide provided by an embodiment of the present utility model, referring to Figure 3 The diffraction waveguide includes an incoupling region 100 and a grating region 200 for receiving light transmitted through the waveguide. The incoupling region 100 is used to couple external light into the waveguide. The grating region 200 includes a grating structure whose duty cycle increases linearly and gradually along the diffusion direction of external light in the waveguide at a constant shrinkage rate. The shrinkage rate is the ratio of the duty cycle at the lower end of the grating structure to the duty cycle at the higher end within a unit length. The shrinkage rate ranges from 85% to 99%. It should be noted that the unit length used to calculate the shrinkage rate of the duty cycle of this product is 1 mm.

[0062] When the diffraction waveguide is a one-dimensional diffraction waveguide, the diffraction waveguide includes an incoupling region 100, a turning region 200a, and an outcoupling region 200b. The turning region 200a and / or the outcoupling region 200b may be provided with a grating structure similar to the grating region 200 described above. When the diffraction waveguide is a two-dimensional diffraction waveguide, the outcoupling region 200b may be provided with a grating structure similar to the grating region 200 described above. It should be noted that, along the light transmission direction, the duty cycle of the grating structure in the grating region 200 gradually increases to increase the outcoupling efficiency at the far end of the light transmission.

[0063] Taking the turning region 200a of the one-dimensional diffraction waveguide as an example, Figure 3As shown, external light is coupled into the optical waveguide through the coupling region 100 and diffuses within the optical waveguide. The diffused light S1 within the optical waveguide is incident on the grating region 200, i.e., the turning region 200a. Its propagation direction is changed by the grating structure and it is then output from the grating region 200. Along the diffusion direction of the diffused light S1 within the optical waveguide, the duty cycle of the grating structure increases linearly at a constant contraction rate. As the diffused light S1 diffuses within the grating structure, it diffracts, and some of the light within the diffused light S1 is redirected by the grating structure to become turning light. In the direction in which the turning light diffuses, the duty cycle of the grating structure also increases linearly at a constant contraction rate. The greater the duty cycle of the grating structure, the more efficient the grating structure is in coupling out light. Furthermore, although the intensities of the diffused light S1 and the turned light decrease as the diffused light S1 diffuses in the grating structure and the turned light is transmitted in the grating structure, the outcoupling efficiency of the grating structure increases, so that the difference between the intensities of the various lights output from the grating area 200 is reduced.

[0064] Since the intensity of the diffused light S1 output by the grating structure at any point is the product of the input intensity of the diffused light S1 at that point and the outcoupling efficiency of the grating structure at that point, there exists a specific shrinkage factor that allows the intensity of the diffused light S1 outcoupled from the grating structure to remain virtually constant along the diffusion direction of the diffused light S1. In other words, the outcoupling intensity of the diffused light S1 from the grating structure does not significantly decrease as the diffusion distance of the diffused light S1 within the grating structure increases. Experimental results show that when the shrinkage factor is between 85% and 99%, the intensity of the diffused light S1 outcoupled from the grating structure remains virtually constant along the diffusion direction of the diffused light S1.

[0065] Similarly, in Figure 3 The grating structure is also configured as above in the light diffusion direction of the outcoupling region 200b. Figure 4 The grating structure is also configured as above in the three light diffusion directions in the outcoupling region 200b. Figure 3 and Figure 4 A specific grating structure can be set in the dotted box shown in FIG.

[0066] The diffraction optical waveguide provided by the embodiment of the present invention increases the duty cycle of the grating structure linearly in the diffusion direction of the diffused light, so that the coupling efficiency of the grating structure gradually increases in the diffusion direction of the diffused light, thereby compensating for the decrease in the intensity of the diffused light after diffraction in the diffraction optical waveguide. As a result, the coupling intensity of the diffused light in the diffraction optical waveguide is not affected by the diffusion distance of the diffused light in the diffraction optical waveguide, and the intensity of the light coupled out of the diffraction optical waveguide is more uniform in space.

[0067] Figure 5This is a schematic structural diagram of another diffraction optical waveguide provided by an embodiment of the present utility model. Figure 6 This is a schematic diagram of a transition grating structure provided by an embodiment of the present invention, combined with Figure 5 and Figure 6 As shown, the grating region 200 includes a turning region 200a, in which a turning grating structure is provided. The turning grating structure is a one-dimensional grating structure, which includes a grating substrate and a plurality of grating strips 221 provided on the grating substrate. Each grating strip 221 in the turning grating structure extends along the vector sum direction of the main light ray S2 and the turning light ray S3 formed by external light in the turning region 200a, and increases linearly and gradually at a constant shrinkage rate. A stepped arrangement is formed in the grating vector direction 2211 of the turning grating structure in a manner of gradually shifting backward along the extension direction. The main light ray S2 direction is more inclined to the turning light ray S3 direction than the duty cycle direction 2212 of the turning grating structure. The duty cycle direction 2212 is a direction in which the duty cycles of each grating strip are equal and consistent.

[0068] Combine Figure 5 and Figure 6 As shown, the turning region 200a is used to change the propagation direction of the principal ray S2 formed by external light in the turning region, transforming the principal ray S2 into the turning ray S3. The grating vector direction 2211 is perpendicular to the extension direction 2213, and the duty cycle of the one-dimensional grating structure remains constant along the duty cycle direction 2212. The size of the grating strips 221 increases linearly along the extension direction 2213. The diffusion direction of the principal ray S2 in the one-dimensional grating structure is at an angle to the duty cycle direction 2212, and the diffusion direction of the principal ray S2 is biased toward the extension direction 2213 of the grating strips 221. As a result, the duty cycle of the one-dimensional grating structure gradually increases in the diffusion direction of the principal ray S2, which means that the output efficiency of the principal ray S2 in the one-dimensional grating structure gradually increases. Although the intensity of the principal light ray S2 in the one-dimensional grating structure gradually decreases as the principal light ray S2 is transmitted, when the angle formed by the diffusion direction of the principal light ray S2 and the duty cycle direction 2212 is within a certain specific range, the output intensity of the principal light ray S2 in the diffusion direction of the principal light ray S2 can be kept constant, thereby making the intensity of the light output from the turning area 200a more uniform in space (that is, the intensity of each turning light ray S3 formed by diffraction of the principal light ray S2 with the grating is more uniform).

[0069] In this embodiment, the corresponding outcoupling region 200 b may be configured as a grating structure with a uniform duty cycle.

[0070] Figure 7 This is a structural diagram of another diffraction optical waveguide provided by an embodiment of the present utility model. Figure 8 This is a schematic diagram of an outcoupling grating structure provided by an embodiment of the present invention, combined with Figure 7 and Figure 8 As shown, the grating region 200 also includes a coupling-out region 200b, in which a coupling-out grating structure is provided. The coupling-out grating structure is a one-dimensional grating structure, which includes a grating substrate and a plurality of grating strips 231 provided on the grating substrate. The duty cycle direction 2312 of the coupling-out grating structure is perpendicular to the duty cycle direction 2212 of the turning grating structure. The extension direction 2313 of each grating strip 231 in the coupling-out grating structure is parallel to the duty cycle direction 2212 of the turning grating structure. The transmission direction of the turning light S3 in the coupling-out region 200b is not parallel to the duty cycle direction 2312 of the coupling-out grating structure.

[0071] Along the duty cycle direction 2312 of the outcoupling grating structure, the duty cycle of the outcoupling grating structure remains unchanged. The diffusion direction of the deflected light S3 forms a certain angle with the duty cycle direction 2312 of the outcoupling grating structure, and the size of the grating bars 231 of the outcoupling grating structure gradually increases along the extension direction 2313 of the grating bars 231 of the outcoupling grating structure. Furthermore, along the diffusion direction of the deflected light S3, the duty cycle of the outcoupling grating structure gradually increases, and the outcoupling efficiency of the deflected light S3 in the outcoupling grating structure gradually increases. Thus, when the angle between the diffusion direction of the deflected light S3 and the duty cycle direction 2312 of the outcoupling grating structure is within a specific range, and the reduction rate of the duty cycle of the outcoupling grating structure in the diffusion direction of the deflected light S3 is within a reasonable range, the outcoupling intensity of the deflected light S3 in its diffusion direction remains constant, thereby making the light intensity coupled out of the outcoupling region 200b more spatially uniform.

[0072] In this embodiment, both the turning region 200a and the outcoupling region 200b of the optical waveguide are provided with a gradient grating structure, so that the transmission brightness in the optical waveguide is more uniform.

[0073] It is understandable that Figure 7 and Figure 8 This is only an example of the diffraction waveguide. In other embodiments, the positions of the turning region 200a and the outcoupling region 200b can be swapped, and the gradient direction of the specific grating structure inside the region can be arranged according to the specific transmission direction of the light, so as to ensure that the duty cycle of the grating structure gradually increases in the light diffusion direction.

[0074] Figure 9 This is a schematic diagram of the structure of a grating strip provided by an embodiment of the present invention, with reference to Figure 9For the grating bars 221 of the turning grating structure and the grating bars 231 of the coupling grating structure, along the extension direction of each grating bar, the duty cycle of the grating bar includes a duty cycle of 240 at the starting end and a duty cycle of 250 at the end. When the duty cycle of the grating bar forms a linear gradient and tends to increase, the duty cycle of 240 at the starting end is greater than the duty cycle of 250 at the end. The range of the duty cycle of 240 at the starting end is 10% to 80%, and the range of the duty cycle of 250 at the end is 20% to 90%.

[0075] Figure 10 This is a structural diagram of another diffraction optical waveguide provided by an embodiment of the present utility model. Figure 11 is a schematic diagram of a two-dimensional out-coupling grating structure provided by an embodiment of the present utility model, Figure 12 It is a structural diagram of the outcoupling area provided by an embodiment of the present utility model; Figure 14 This is a schematic diagram of the structure of another outcoupling region provided by an embodiment of the present utility model. Figure 15 This is a structural diagram of another outcoupling region provided by an embodiment of the present utility model. Figure 17 This is a structural diagram of another outcoupling region provided by an embodiment of the present utility model. Figure 18 2 is a schematic structural diagram of another outcoupling region provided by an embodiment of the present invention. As shown in the above figures, the grating region 200 includes an outcoupling region 200 b, in which an outcoupling two-dimensional grating structure is disposed. The outcoupling two-dimensional grating structure has a plurality of quadrilateral projections 300 on a plane perpendicular to the grating region 200. Each quadrilateral projection 300 includes a first set of oppositely disposed sides 310 and a second set of oppositely disposed sides 320. The second set of sides 320 are sequentially arranged along the direction in which the first set of sides 310 extend, and the first set of sides 310 are sequentially arranged along the direction in which the second set of sides 320 extend. The direction in which the second set of sides 320 extend intersects the direction in which the first set of sides 310 extend. The length of each second set of sides 320 gradually increases in the direction in which the first set of sides 310 extend and in the first direction in which light diffuses. The length of each first set of sides 310 gradually increases in the direction in which the second set of sides 320 extend and in the second direction in which light diffuses.

[0076] Combine Figure 10 、 Figure 11 、 Figure 12 、 Figure 14 、 Figure 15 、 Figure 17 and Figure 18As shown, after light is incident on the outcoupling two-dimensional grating structure in the outcoupling region 200b, it will diffract. Then, part of the light will change its diffusion direction and diffuse along the first direction and the second direction, respectively, forming the first pupil-expanding light S5 and the second pupil-expanding light S6. In the first and second directions, the area of ​​the quadrilateral projection 300 gradually increases, that is, the duty cycle of the outcoupling two-dimensional grating structure gradually increases. The outcoupling efficiency of the outcoupling two-dimensional grating structure also increases as the duty cycle of the outcoupling two-dimensional grating structure increases. As the light diffuses along the first and second directions, the intensity of the light gradually decreases due to the continuous outcoupling. However, the gradually increasing outcoupling efficiency of the outcoupling two-dimensional grating structure along the first and second directions compensates for the decrease in light intensity, thereby making the intensity of the outcoupling optical fiber of the outcoupling two-dimensional grating structure more uniform in space.

[0077] Optionally, combined Figure 10 、 Figure 11 、 Figure 12 、 Figure 14 、 Figure 15 、 Figure 17 and Figure 18 As shown, the first set of edges 310 includes a first edge 301 and a second edge 302 disposed opposite each other, and the second set of edges 320 includes a third edge 303 and a fourth edge 304 disposed opposite each other. In the direction in which the first set of edges 310 extend and in the first direction of light diffusion, the third edge 303 and the fourth edge 304 are arranged in sequence, while in the direction in which the second set of edges 320 extend and in the second direction of light diffusion, the first edge 301 and the second edge 302 are arranged in sequence. The length of the first edge 301 is shorter than that of the second edge 302, and the length of the third edge 303 is shorter than that of the fourth edge 304. As a result, the duty cycle of the grating structure increases continuously in the direction of light transmission.

[0078] Figure 12 This is a schematic diagram of the structure of the outcoupling area provided by the embodiment of the present utility model, with reference to Figures 10 to 12 Optionally, the outcoupling region 200b is a rectangle, and the direction of the principal ray S4 formed by the external light in the outcoupling region 200b is parallel to the short side 232 of the rectangle and coincides with the center line of the long side 233 of the rectangle; the outcoupling two-dimensional grating structure is an axisymmetric structure, and each quadrilateral projection 300 is an axisymmetric figure. The angle between the symmetry axis of the outcoupling two-dimensional grating structure and the symmetry axis 234 of each quadrilateral projection 300 is 0°, and coincides with the direction of the principal ray S4 formed by the external light in the outcoupling region 200b. The symmetry axis 234 of each quadrilateral projection 300 is the angle bisector of each quadrilateral projection 300. Since the diffusion direction of the principal ray S4 is parallel to the short side 232 of the rectangle and coincides with the center line of the long side 233 of the rectangle, the principal ray S4 is the symmetry axis of the outcoupling region 200b, that is, the principal ray S4 is the symmetry axis of the outcoupling two-dimensional grating structure. Figure 13 yes Figure 12 The comparison of the spatial distribution of the out-coupling light intensity of the diffraction waveguide and the spatial distribution of the out-coupling light intensity of the grating with constant duty cycle in the prior art is shown in FIG. Figure 13 , A is the spatial distribution of the intensity of the out-coupled light from the grating with constant duty cycle in the prior art, and B is Figure 12 The spatial distribution of the outcoupling light intensity of the diffraction waveguide in the Figure 13 The spatial distribution of the outcoupled light intensity of the diffraction waveguide is more uniform.

[0079] Figure 14 This is a schematic diagram of the structure of another outcoupling region provided by an embodiment of the present utility model. Figure 15 This is a schematic diagram of another structure of the outcoupling region provided by the embodiment of the present utility model, combined with Figure 14 and Figure 15 As shown, optionally, the outcoupling region 200b is a rectangle, and the direction of the main light S4 formed by the external light in the outcoupling region 200b is parallel to the long side center line 235 of the outcoupling two-dimensional grating structure and is at a preset distance; the long side center line 235 of the outcoupling two-dimensional grating structure is parallel to or has an angle with the short side 232 of the rectangle; wherein, when the diffusion length of the light in the first direction of light diffusion is less than the diffusion length in the second direction of light diffusion, the length of the first side 301 is greater than the length of the fourth side 304.

[0080] Combine Figure 14 and Figure 15 As shown, Figure 14 The long side center line 235 of the outcoupling two-dimensional grating structure is parallel to the short side 232 of the rectangle. Figure 15 The long side centerline 235 of the out-coupling two-dimensional grating structure forms an angle with the short side 232 of the rectangle. The unequal lengths of the first side 301 and the fourth side 304 can enhance the out-coupling efficiency of the out-coupling two-dimensional grating structure. Furthermore, the gradually increasing lengths of the quadrilateral projection 300 along the first and second directions of light diffusion increase the out-coupling efficiency of the out-coupling two-dimensional grating structure, thereby ensuring that the intensity of light coupled out of the out-coupling two-dimensional grating structure in the second direction, where the diffusion length is longer, remains constant. Figure 16 yes Figure 14 The comparison of the spatial distribution of the out-coupling light intensity of the diffraction waveguide and the spatial distribution of the out-coupling light intensity of the grating with constant duty cycle in the prior art is shown in FIG. Figure 16 , C is the spatial distribution of the intensity of the out-coupled light from the grating with constant duty cycle in the prior art, and D is Figure 14 The spatial distribution of the outcoupling light intensity of the diffraction waveguide in the Figure 14 The spatial distribution of the outcoupled light intensity of the diffraction waveguide is more uniform.

[0081] Figure 17This is a structural diagram of another outcoupling region provided by an embodiment of the present utility model. Figure 18 This is a schematic diagram of another structure of the outcoupling region provided by the embodiment of the present utility model, combined with Figure 17 and Figure 18 As shown, optionally, the outcoupling region 200b is a rectangle, and the direction of the main light S4 formed by the external light in the outcoupling region 200b is parallel to the long side 233 of the rectangle and coincides with the center line of the short side 232 of the rectangle; or, the direction of the main light S4 formed by the external light in the outcoupling region 200b has an angle with the long side 233 of the rectangle; the outcoupling two-dimensional grating structure is an axisymmetric structure, and the symmetry axis of the outcoupling two-dimensional grating structure coincides with the direction of the main light S4 formed by the external light in the outcoupling region; wherein, on one side of the symmetry axis of the outcoupling two-dimensional grating structure, the length of the third side 303 is greater than the length of the second side 302, and on the other side of the symmetry axis of the outcoupling two-dimensional grating structure, the length of the first side 301 is greater than the length of the fourth side 304.

[0082] For example, Figure 17 In the embodiment, the direction of the main light S4 formed by the external light in the outcoupling region 200b is parallel to the long side 233 of the rectangle and coincides with the center line of the short side 232 of the rectangle. Figure 18 In the example, the direction of the principal ray S4 formed by the external light in the outcoupling region 200b forms an angle with the long side 233 of the rectangle. By setting the length of the third side 303 greater than the length of the second side 302 on one side of the symmetry axis of the outcoupling two-dimensional grating structure, and the length of the first side 301 greater than the length of the fourth side 304 on the other side of the symmetry axis of the outcoupling two-dimensional grating structure, the sides of the quadrilateral projection 300 become increasingly longer in the direction of the diffused light transmission, i.e., the duty cycle becomes increasingly larger. However, in other directions, the sides of the quadrilateral projection 300 are shorter, which can save costs. Figure 19 yes Figure 17 The comparison of the spatial distribution of the out-coupling light intensity of the diffraction waveguide and the spatial distribution of the out-coupling light intensity of the grating with constant duty cycle in the prior art is shown in FIG. Figure 19 , E is the spatial distribution of the intensity of the out-coupled light from the grating with constant duty cycle in the prior art, and F is Figure 17 The spatial distribution of the outcoupling light intensity of the diffraction waveguide in the Figure 17 The spatial distribution of the outcoupled light intensity of the diffraction waveguide is more uniform.

[0083] Figure 20 This is a diagram showing the relationship between the quadrilateral projection size and the outcoupling efficiency, pupil expansion efficiency, and pupil expansion light outcoupling efficiency provided by the embodiment of the present invention. Figure 20 , as the size of the quadrilateral projection 300 increases, the outcoupling efficiency, pupil expansion efficiency, and outcoupling efficiency of pupil expansion light all increase. Figure 20The outcoupling efficiency graph in the upper left corner shows the changing trend of the outcoupling efficiency of the principal ray in the diffractive waveguide as the size of the quadrilateral projection 300 increases. The pupil expansion efficiency graph in the lower left corner shows the changing trend of the pupil expansion efficiency of the principal ray in the diffractive waveguide as the size of the quadrilateral projection 300 increases. The outcoupling efficiency graph in the lower right corner shows the changing trend of the outcoupling efficiency of the pupil expansion ray in the diffractive waveguide as the size of the quadrilateral projection 300 increases.

[0084] It should be noted that the above-mentioned two-dimensional grating structure can be formed by overlapping two one-dimensional grating axes. The overlapping method can be to overlap on the same plane and leave only the overlapping area structure, or to maintain the morphology of each one-dimensional grating on different planes. Figures 21 to 30 .

[0085] Figure 21 is a schematic diagram of a first one-dimensional grating structure and a second one-dimensional grating structure provided by an embodiment of the present utility model, Figure 22 This is a schematic diagram of a two-dimensional grating structure provided by an embodiment of the present invention, combined with Figure 21 and Figure 22 As shown, the two-dimensional grating structure includes a first one-dimensional grating structure 400 and a second one-dimensional grating structure 500. The first one-dimensional grating structure 400 and the second one-dimensional grating structure 500 are located in different planes. The grating strips of the first one-dimensional grating structure 400 extend in a first direction, and the grating strips of the second one-dimensional grating structure 500 extend in a second direction. The first one-dimensional grating structure 400 and the second one-dimensional grating structure 500 are symmetrical about a symmetry axis 600. On the plane of the two-dimensional grating structure, the projections of the first one-dimensional grating structure 410 and the second one-dimensional grating structure 510 overlap to form a quadrilateral projection 300. It can form a projection as shown in FIG. Figure 10 and Figure 12 The outcoupling grating structure in .

[0086] In other words, the two one-dimensional gratings are symmetrical along a direction perpendicular to the duty cycle direction, so that the duty cycle directions of the two one-dimensional gratings overlap, are parallel, and are in opposite directions. This makes the duty cycles of the two one-dimensional gratings on the line parallel to the duty cycle direction equal. The overlapping two-dimensional grating morphology is axisymmetric, and the duty cycle gradually changes in a single direction. The projection of a single structure is close to a parallelogram with four equal sides. Figure 10 and Figure 12As shown, the grating vector of the coupled-in 1D grating is the symmetry axis and principal ray direction of the coupled-out grating region. The length of the coupled-out 2D region along the grating vector is shorter than the length perpendicular to the grating vector. The structure of the coupled-out 2D grating region is the aforementioned 2D grating structure. The symmetry axis of this structure is parallel to the grating vector. Since the duty cycle of the structure increases gradually along both the principal ray direction and the pupil expansion ray direction, both the coupling efficiency and the pupil expansion efficiency increase gradually. This allows the brightness of the principal ray to be transferred to both sides more quickly, making the brightness of each part of the pupil expansion ray closer together and improving uniformity.

[0087] Figure 23 is a schematic diagram of another first one-dimensional grating structure and a second one-dimensional grating structure provided by an embodiment of the present invention, Figure 24 This is a schematic diagram of another two-dimensional grating structure provided by an embodiment of the present invention, combined with Figure 23 and Figure 24 As shown, the duty cycle direction 420 of the first one-dimensional grating structure 400 is parallel to the duty cycle direction 520 of the second one-dimensional grating structure 500, and the first one-dimensional grating structure 400 and the second one-dimensional grating structure 500 are symmetrical about a symmetry axis 600 parallel to the duty cycle direction 420 of the first one-dimensional grating structure 400. Figure 23 The first one-dimensional grating structure 400 and the second one-dimensional grating structure 500 overlap to form Figure 24 The two-dimensional grating structure shown in FIG. Figure 17 The outcoupling grating structure in .

[0088] That is to say, the two one-dimensional gratings overlap symmetrically along the duty cycle direction, so that the duty cycle directions of the two one-dimensional gratings are parallel and in the same direction, and the two-dimensional grating formed by the overlap presents a multi-directional duty cycle gradient. The single structural morphology gradually changes from a rhombus to a parallelogram with four sides of equal length. The grating vector of the coupled one-dimensional grating is the symmetry axis and the main light direction of the coupled out grating area. The length of the coupled out two-dimensional area along the grating vector direction is longer than the length perpendicular to the grating vector direction. The structure of the coupled out two-dimensional grating area is the above-mentioned two-dimensional grating structure. Figure 17 As shown, the symmetry axis of the above structure is parallel to the grating vector. Since the structure is relatively stable along the direction of the main light, the duty cycle of the structure along the direction of the pupil expansion light gradually increases toward a parallelogram, that is, the coupling efficiency and the pupil expansion efficiency both gradually increase, so that the brightness of the main light is transmitted more to the far end of the main light, and the brightness of each part of the pupil expansion light is coupled out faster, thereby improving uniformity.

[0089] Figure 25 is a schematic diagram of another first one-dimensional grating structure and a second one-dimensional grating structure provided by an embodiment of the present utility model, Figure 26 This is a schematic diagram of another two-dimensional grating structure provided by an embodiment of the present invention, combined with Figure 25 and Figure 26As shown, in a duty cycle direction 420 perpendicular to the first one-dimensional grating structure 400, the starting end 240 of the first one-dimensional grating structure 400 and the starting end 240 of the grating bar in the second one-dimensional grating structure 500 are at a certain distance, and the duty cycle direction 420 of the first one-dimensional grating structure 400 is parallel to the duty cycle direction 520 of the second one-dimensional grating structure 500. Figure 25 The first one-dimensional grating structure 400 and the second one-dimensional grating structure 500 overlap to form Figure 26 The two-dimensional grating structure shown in FIG. Figure 14 The outcoupling grating structure in .

[0090] In other words, the two one-dimensional gratings are symmetrically offset along a direction perpendicular to the duty cycle direction, so that the duty cycle directions of the two one-dimensional gratings are non-overlapping, parallel, and opposite, making the duty cycles of the two one-dimensional gratings equal on lines parallel to the duty cycle direction. The overlapping two-dimensional grating morphology is axially symmetrical, and the duty cycle gradually changes in multiple directions. The projection of a single structure approximates a parallelogram with four sides of equal length. The grating vector of the coupled-in one-dimensional grating is in the direction of the principal light ray and is parallel to the symmetry axis of the coupled-out grating region. The length of the coupled-out two-dimensional region along the grating vector direction is shorter than the length perpendicular to the grating vector direction. The structure of the coupled-out two-dimensional grating region is the above-mentioned two-dimensional grating structure. In this architecture, the distances between the left and right sides of the principal light ray are unequal. The light to the right of the principal light ray needs to travel a longer distance, requiring a higher coupling efficiency at the far right end. The symmetry axis of the above structure is parallel to the grating vector. Since the structure is asymmetric on the left and right sides, the left and right sides of the structure on the same horizontal line in the figure are close to parallelograms, with the long sides in opposite directions. Compared with the diamond structure, the parallelogram has a greater outcoupling efficiency for pupil expansion light, which can make the brightness of the far end on the right side higher and improve uniformity.

[0091] Figure 27 is a schematic diagram of another first one-dimensional grating structure and a second one-dimensional grating structure provided by an embodiment of the present utility model, Figure 28 This is a schematic diagram of another two-dimensional grating structure provided by an embodiment of the present invention, combined with Figure 27 and Figure 28 As shown, the angle formed by the extension direction 410 of the first one-dimensional grating structure 400 and the extension direction 510 of the grating strips in the second one-dimensional grating structure 500 is not 0° or 180°. Figure 27 The first one-dimensional grating structure 400 and the second one-dimensional grating structure 500 overlap to form Figure 28 The two-dimensional grating structure shown in FIG. Figure 15 The outcoupling grating structure in .

[0092] Figure 29 is a schematic diagram of another first one-dimensional grating structure and a second one-dimensional grating structure provided by an embodiment of the present utility model, Figure 30This is a schematic diagram of another two-dimensional grating structure provided by an embodiment of the present invention, combined with Figure 29 and Figure 30 As shown, the angle formed by the extension direction 410 of the first one-dimensional grating structure 400 and the radiation direction 510 of the grating strips in the second one-dimensional grating structure 500 is not 0° or 180°. Figure 29 The first one-dimensional grating structure 400 and the second one-dimensional grating structure 500 overlap to form Figure 30 The two-dimensional grating structure shown in FIG. Figure 18 The outcoupling grating structure in .

[0093] That is to say, the two one-dimensional gratings are at a certain angle, which is the angle between the two grating vector directions, and the angle is not 0° or 180°. This makes the two-dimensional grating formed by the overlap of the two one-dimensional gratings present a multi-directional duty cycle gradient. The single structure morphology gradually changes from a rhombus to a parallelogram with four sides of equal length. The grating vector coupled into the one-dimensional grating passes through the coupling-out grating area, and there is no symmetry between the left and right sides of the main light. The structure of the coupling-out two-dimensional grating area is the above-mentioned two-dimensional grating structure. Due to the different duty cycle gradients on the left and right sides of the structure, the coupling-out efficiency is related to the distance from the main light. The coupling-out efficiency of the structure at the far end of the main light is greater than that at the near end, which makes the brightness of each part closer and improves uniformity.

[0094] In the above embodiment, the two-dimensional grating structure can be formed by overlapping the first one-dimensional grating structure 400 and the second one-dimensional grating structure 500. Therefore, to form such a two-dimensional grating structure, only two one-dimensional grating structures need to be manufactured, and the manufacturing difficulty and cost are relatively low.

[0095] Optionally, the two-dimensional grating structure includes overlapping portions of a plurality of quadrilateral projection patterns. The two-dimensional grating structure can also be obtained by directly manufacturing quadrilateral projection patterns. This two-dimensional grating structure does not require the overlapping of multiple gratings, and thus has a smaller thickness.

[0096] In summary, Figure 31 This is the optical path principle diagram of the diffraction optical waveguide outcoupling light proposed in the embodiment of the utility model. Compared with Figure 1 As shown in the schematic diagram in FIG, the intensity distribution of the light coupled out of the diffraction light waveguide in the embodiment of the present invention remains substantially uniform along the order of coupling out.

[0097] The above specific embodiments do not limit the scope of protection of this utility model. Those skilled in the art will appreciate that various modifications, combinations, sub-combinations, and substitutions may be made based on design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this utility model shall be included within the scope of protection of this utility model.

Claims

1. A diffraction optical waveguide, characterized in that: include: a coupling-in region and a grating region for receiving light guided in the optical waveguide, wherein the coupling-in region is used to couple external light into the optical waveguide; A grating structure is provided in the grating area, and the duty cycle of the grating structure increases linearly and gradually at a constant shrinkage rate along the diffusion direction of the external light in the optical waveguide. The shrinkage rate is the ratio of the duty cycle value at the end with a smaller duty cycle to the duty cycle value at the end with a larger duty cycle within a unit length of the grating structure, and the shrinkage rate ranges from 85% to 99%.

2. The diffractive optical waveguide according to claim 1, wherein The grating region includes a turning region, wherein a turning grating structure is provided in the turning region, and the turning grating structure is a one-dimensional grating structure, and the one-dimensional grating structure includes a grating substrate and a plurality of grating strips provided on the grating substrate; Each of the grating strips in the turning grating structure extends along the vector sum direction of the main light direction and the turning light direction formed by the external light in the turning area, and is linearly and gradually increased at the constant shrinkage rate; and forms a stepped arrangement in the grating vector direction of the turning grating structure in a manner of gradually moving backward along the extension direction; the main light direction is more biased towards the turning light direction than the duty cycle direction of the turning grating structure, and the duty cycle direction is the direction in which the duty cycles of each of the grating strips are equal and consistent.

3. The diffractive optical waveguide according to claim 2, wherein: The grating region further includes an outcoupling region, wherein an outcoupling grating structure is provided in the outcoupling region, and the outcoupling grating structure is a one-dimensional grating structure, and the one-dimensional grating structure includes a grating substrate and a plurality of grating strips provided on the grating substrate; The duty cycle direction of the outcoupling grating structure is perpendicular to the duty cycle direction of the turning grating structure, the extension direction of each grating strip in the outcoupling grating structure is parallel to the duty cycle direction of the turning grating structure, and the transmission direction of the turning light in the outcoupling area is not parallel to the duty cycle direction of the outcoupling grating structure.

4. The diffractive optical waveguide according to claim 2 or 3, characterized in that: Along the extension direction of each grating bar, the duty cycle of the grating bar includes a starting duty cycle and an ending duty cycle. When the duty cycle of the grating bar forms a linear gradient and tends to increase, the starting duty cycle is smaller than the ending duty cycle. The starting duty cycle ranges from 10% to 80%, and the ending duty cycle ranges from 20% to 90%.

5. The diffractive optical waveguide according to claim 1, wherein The grating region includes an outcoupling region, wherein an outcoupling two-dimensional grating structure is disposed in the outcoupling region; the outcoupling two-dimensional grating structure has a plurality of quadrilateral projections on a plane perpendicular to the grating region, each of the quadrilateral projections includes a first set of oppositely disposed sides and a second set of oppositely disposed sides, each of the second set of sides is sequentially arranged along a direction in which the first set of sides extends, and each of the first set of sides is sequentially arranged along a direction in which the second set of sides extends; and the direction in which the second set of sides extends intersects with the direction in which the first set of sides extends. In the direction in which the first set of sides extends and toward the first direction of light diffusion, the length of each of the second set of sides gradually increases; in the direction in which the second set of sides extends and toward the second direction of light diffusion, the length of each of the first set of sides gradually increases.

6. The diffractive optical waveguide according to claim 5, characterized in that The first group of sides includes a first side and a second side that are arranged opposite to each other, and the second group of sides includes a third side and a fourth side that are arranged opposite to each other. In the direction in which the first group of sides extends and in the first direction in which light diffuses, the third side and the fourth side are arranged in sequence, and in the direction in which the second group of sides extends and in the second direction in which light diffuses, the first side and the second side are arranged in sequence; the length of the first side is smaller than the length of the second side, and the length of the third side is smaller than the length of the fourth side.

7. The diffractive optical waveguide according to claim 5, characterized in that The outcoupling area is rectangular, and the direction of the main light formed by the external light in the outcoupling area is parallel to the short side of the rectangle and coincides with the center line of the long side of the rectangle; The out-coupling two-dimensional grating structure is an axisymmetric structure, and each of the quadrilateral projections is an axisymmetric figure. The angle between the symmetry axis of the out-coupling two-dimensional grating structure and the symmetry axis of each of the quadrilateral projections is 0°, and coincides with the direction of the main light formed by the external light in the out-coupling area. The symmetry axis of each of the quadrilateral projections is the angle bisector of each of the quadrilateral projections.

8. The diffractive optical waveguide according to claim 6, wherein: The outcoupling region is rectangular, and the main light direction formed by the external light in the outcoupling region is parallel to the long side center line of the outcoupling two-dimensional grating structure and is at a preset distance; The center line of the long side of the out-coupling two-dimensional grating structure is parallel to or has an angle with the short side of the rectangle; When the diffusion length of the light in the first direction of light diffusion is shorter than the diffusion length in the second direction of light diffusion, the length of the first side is longer than the length of the fourth side.

9. The diffractive optical waveguide according to claim 6, characterized in that The outcoupling region is rectangular, and the direction of the main light formed by the external light in the outcoupling region is parallel to the long side of the rectangle and coincides with the center line of the short side of the rectangle; or, the direction of the main light formed by the external light in the outcoupling region forms an angle with the long side of the rectangle; The out-coupling two-dimensional grating structure is an axisymmetric structure, and the symmetry axis of the out-coupling two-dimensional grating structure coincides with the direction of the main light formed by the external light in the out-coupling region; Wherein, on one side of the symmetry axis of the outcoupling two-dimensional grating structure, the length of the third side is greater than the length of the second side, and on the other side of the symmetry axis of the outcoupling two-dimensional grating structure, the length of the first side is greater than the length of the fourth side.

10. The diffractive optical waveguide according to claim 5, wherein: The two-dimensional grating structure includes a first one-dimensional grating structure and a second one-dimensional grating structure, the first one-dimensional grating structure and the second one-dimensional grating structure are located in different planes, the grating bars of the first one-dimensional grating structure extend in the first direction, and the grating bars of the second one-dimensional grating structure extend in the second direction, and on the plane of the two-dimensional grating structure, the projections of the first one-dimensional grating structure and the second one-dimensional grating structure overlap with each other to form the quadrilateral projection.

11. The diffractive optical waveguide according to claim 5, wherein The two-dimensional grating structure includes overlapping portions of a plurality of quadrilateral projection patterns.

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