Diffractive optical waveguide, display device, and diffractive optical waveguide design method

Abstract

The present application discloses a diffractive optical waveguide for optical pupil expansion, a display device including the diffractive optical waveguide, and a diffractive optical waveguide design method. The diffractive optical waveguide includes a waveguide substrate and an input grating and an output grating disposed above or within the substrate. The output grating is at least partially formed on a random partition region, the random partition region includes a plurality of partitions, the output grating includes a plurality of sub-gratings formed in the plurality of partitions, and the sub-gratings in at least some of the partitions have different optical structures. In the diffractive optical waveguide and its design method according to the embodiments of the present invention, the partitions of the output grating are randomly formed within a certain region, and different grating optical structures are adopted in different partitions, and the optimization design is carried out with the final waveguide effect as the evaluation. Compared with the regular partitions and / or fixed grating structures in other diffractive optical waveguides and their design methods, it has a higher design freedom, and its optimization result can also be closer to the optimal solution.

Description

Technical Field

[0001] The present invention relates to diffraction-based display technologies, particularly diffraction optical waveguides applicable to augmented reality displays, display devices including such diffraction optical waveguides, and diffraction optical waveguide design methods. Background Art

[0002] With the highly developed semiconductor process, the interaction mode between humans and computers is developing rapidly. Among them, augmented reality (AR) display can provide humans with information in more dimensions and has received extensive attention. AR glasses are one of the important media in the field of augmented reality display. Existing AR glasses based on geometric optics use a free-form surface solution, which has size limitations; the design principle of AR glasses based on arrayed optical waveguides is relatively simple, but the process is difficult and not suitable for mass production. Moreover, since arrayed optical waveguides need to be paired with specific optical engines, it also restricts their large-scale promotion.

[0003] Diffraction optical waveguides have advantages such as strong mass producibility, thinness, etc., and are gradually recognized in the field of AR display, and are expected to become the mainstream technology development direction in the future AR field. For diffraction optical waveguides used in AR displays, especially two-dimensional grating waveguides, due to their gratings having multi-order diffraction and being sensitive to polarization, the entire waveguide coupling system has high irregularity. If the grating region is not partitioned and optimized, within the final eyebox range, the light intensity received by the human eye at different positions is different, making it difficult for the human senses to accept using a diffraction optical waveguide as the display module of AR glasses. Summary of the Invention

[0004] The purpose of the present invention is to provide a diffraction optical waveguide for optical pupil expansion, a display device including such diffraction optical waveguide, and a diffraction optical waveguide design method, which can improve the uniformity of the light energy distribution of the outgoing light field of the diffraction optical waveguide and at least partially overcome the deficiencies in the prior art.

[0005] According to one aspect of the present invention, there is provided a diffraction optical waveguide for optical pupil expansion, which includes a waveguide substrate and an input grating and an output grating disposed on or within the waveguide substrate. The input grating is configured to couple an input light beam into the waveguide substrate so that it is coupled to the output grating by total internal reflection. Wherein, at least part of the output grating is formed on a random partition region, the random partition region includes a plurality of partitions with randomly formed shapes, sizes, and / or positions, the output grating includes a plurality of sub-gratings formed in the plurality of partitions, and the sub-gratings in at least part of the partitions have different optical structures.

[0006] According to an embodiment of the present invention, the plurality of sub-gratings are configured such that the light energy distribution of the light output field of the diffractive optical waveguide is substantially uniform.

[0007] Preferably, the plurality of sub-gratings include two-dimensional gratings, and the two-dimensional gratings have a first grating vector, a second grating vector, and a third grating vector.

[0008] Preferably, the two-dimensional gratings among the plurality of sub-gratings have the same grating vectors as each other.

[0009] In some embodiments, the output grating may be symmetric about an axis.

[0010] Preferably, the plurality of partitions are Voronoi partitions divided according to a Voronoi diagram.

[0011] More preferably, the plurality of partitions are Voronoi partitions divided according to a Voronoi diagram formed based on random point scattering.

[0012] Preferably, the plurality of partitions include non-diffractive partitions where the sub-gratings are not formed, and the area of the non-diffractive partitions is less than a predetermined threshold, and the predetermined threshold is less than or equal to the average pupil area of the human eye, preferably less than or equal to one half of the average pupil area of the human eye. More preferably, the plurality of partitions include at least one partition whose area is less than or equal to at least one of the non-diffractive partitions and in which the sub-gratings are formed.

[0013] Preferably, the optical structure of the sub-gratings in at least one partition has a cross-sectional shape and / or size different from that of the sub-gratings in another partition.

[0014] Preferably, the optical structure of the sub-gratings in at least one partition has an irregular cross-sectional shape.

[0015] Preferably, the optical structure of the sub-gratings in at least one partition has a height or depth different from that of the sub-gratings in another partition.

[0016] According to another aspect of the present invention, there is provided a display device, which includes the diffractive optical waveguide as described above.

[0017] Preferably, the display device is a near-eye display device, and includes a lens and a frame for holding the lens close to the eye, and the lens includes the diffractive optical waveguide.

[0018] Preferably, the display device is an augmented reality display device.

[0019] According to still another aspect of the present invention, there is provided a design method for a diffractive optical waveguide for optical pupil expansion, and the design method includes the following processes:

[0020] (1) Randomly partition a target area where an output grating is to be formed to form a plurality of partitions, and the plurality of partitions have randomly formed shapes, sizes, and / or positions;

[0021] (2) Initialize sub-gratings in the plurality of partitions, where each sub-grating includes a plurality of optical structures; and

[0022] (3) Use at least one parameter of the optical structures of each sub-grating as an optimization variable to perform optimization processing to obtain an optimization result, where the optimization objective of the optimization processing includes the uniformity of the optical energy distribution of the output light field of the diffractive optical waveguide.

[0023] Preferably, in process (3), the optimization variables include the cross-sectional shape and / or size of the optical structure and / or the height or depth of the optical structure, and the optimization processing enables the sub-gratings in at least some partitions to have different optical structures.

[0024] Preferably, in process (2), the initialization makes the optical structure of each sub-grating a columnar structure; and in process (3), the optimization processing includes dilation and erosion processing of the cross-section of the columnar structure.

[0025] Preferably, in process (3), the optimization objective of the optimization processing further includes the optical energy coupling efficiency of the diffractive optical waveguide.

[0026] Preferably, process (1) may include: randomly scattering points in the target area, generating a Voronoi diagram based on the randomly scattered points, and partitioning according to the Voronoi diagram.

[0027] Preferably, process (2) may include:

[0028] (2a) Selectively set at least some of the partitions with an area smaller than a predetermined threshold as non-diffractive partitions, and no sub-gratings are formed in the non-diffractive partitions, where the predetermined threshold is less than or equal to the average pupil area of the human eye, preferably less than or equal to half of the average pupil area of the human eye; and

[0029] (2b) Initialize the sub-gratings in the partitions other than the non-diffractive partitions.

[0030] Preferably, the design method may further include the following process:

[0031] (4) Change the random partition of the target area to form a new plurality of partitions, and based on the new plurality of partitions, repeat processes (2) to (3) to obtain multiple optimization results; and

[0032] (5) Compare the multiple optimization results, and determine the partition of the diffractive optical waveguide and the optimized optical structure of the corresponding sub-gratings according to the optimization result that best meets the optimization objective.

[0033] Preferably, process (1) may include: obtaining the number of scattered points M, randomly scattering M points in the target area, generating a Voronoi diagram based on the M points, and partitioning according to the Voronoi diagram; and process (4) includes: changing the number of scattered points M, randomly re-scattering points in the target area based on the changed number of scattered points M, generating a new Voronoi diagram, and partitioning according to the new Voronoi diagram.

[0034] Preferably, the design method may further include the following processes:

[0035] (3a) Change the setting of the non-diffractive partition to form a new non-diffractive partition, and based on the new non-diffractive partition, repeat processes (2b) and (3) to obtain the optimization results corresponding to the same random partition.

[0036] Preferably, the design method may further include the following processes:

[0037] (4’) Change the random partition of the target area to form a new plurality of partitions, and based on the new plurality of partitions, repeat processes (2), (3) and (3a) to obtain multiple optimization results corresponding to multiple random partitions; and

[0038] (5’) Compare the multiple optimization results, and determine the partition of the diffractive optical waveguide and the optimized optical structure of the corresponding sub-gratings according to the optimization result that best meets the optimization objective.

[0039] In the diffractive optical waveguide and its design method according to the embodiments of the present invention, the partition of the out-coupling grating is randomly formed within a certain area, and different grating optical structures are adopted in different partitions, and the optimization design is carried out with the final waveguide effect as the evaluation. Compared with the regular partitions and / or fixed grating structures in other diffractive optical waveguides and their design methods, it has a higher design freedom, and its optimization results can also be closer to the optimal solution. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Other features, objects and advantages of the present invention will become more apparent by reading the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0041] Figure 1 A schematic diagram of an example of a diffractive optical waveguide for optical pupil expansion according to an embodiment of the present invention, wherein the entire out-coupling grating of the diffractive optical waveguide is formed on a randomly partitioned area;

[0042] Figure 2Schematically shows the light coupling-in, propagation, and coupling-out of a diffractive optical waveguide according to an embodiment of the present invention;

[0043] Figure 3 Schematically shows an example of the grating vectors of the coupling-in grating and the coupling-out grating of a diffractive optical waveguide according to an embodiment of the present invention;

[0044] Figure 4 Schematically shows different examples of the optical structure of the sub-gratings of the coupling-out grating;

[0045] Figure 5 Is a schematic diagram of another example of a diffractive optical waveguide for optical pupil expansion according to an embodiment of the present invention, wherein a part of the coupling-out grating of the diffractive optical waveguide is formed on a random partition area;

[0046] Figure 6 Is a schematic diagram of yet another example of a diffractive optical waveguide for optical pupil expansion according to an embodiment of the present invention, wherein the coupling-out grating of the diffractive optical waveguide is of an asymmetric structure;

[0047] Figure 7 Is a flowchart of a design method of a diffractive optical waveguide for optical pupil expansion according to an embodiment of the present invention;

[0048] Figure 8 Is applicable to Figure 7 Is a flowchart of an example of a random partition method for the diffractive optical waveguide design method shown;

[0049] Figure 9 Schematically shows according to Figure 8 An example of random partitioning performed according to the method shown;

[0050] Figure 10 Schematically shows according to Figure 8 And Figure 9 An example of the partition of a diffractive optical waveguide obtained according to the method and example shown;

[0051] Figure 11 Is for Figure 7 Is a flowchart of an extended example of the diffractive optical waveguide design method shown;

[0052] Figure 12 Schematically shows according to Figure 11 Another example of the partition of a diffractive optical waveguide obtained according to the extended example shown;

[0053] Figure 13 Is for Figure 7 Is a flowchart of another extended example of the diffractive optical waveguide design method shown;

[0054] Figure 14 Schematically shows according to Figure 13An example of a diffractive optical waveguide partition obtained from the extended example shown, in which a non-diffractive partition is provided;

[0055] Figure 15 is Figure 14 a partial enlarged schematic view of the part marked by the dashed circle in

[0056] Figure 16 Schematically shows Figure 13 another example of a diffractive optical waveguide partition obtained from the extended example shown, in which a non-diffractive partition different from Figure 14 the one shown is provided. Detailed implementation manners

[0057] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It can be understood that the specific embodiments described herein are only used to explain the related invention, rather than limiting the invention. For the sake of description, only the parts related to the invention are shown in the drawings.

[0058] It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the drawings and embodiments.

[0059] First, a diffractive optical waveguide for optical pupil expansion according to an embodiment of the present invention will be introduced with reference to the accompanying drawings.

[0060] Figure 1 FIG. is a schematic diagram of a diffractive optical waveguide 10, which is an example of a diffractive optical waveguide for optical pupil expansion according to an embodiment of the present invention. Figure 2 Schematically shows the coupling-in, propagation, and coupling-out of light by the diffractive optical waveguide according to an embodiment of the present invention. As Figure 1 shown, the diffractive optical waveguide 10 for optical pupil expansion includes a waveguide substrate 10a and an input grating 11 and an output grating 12 provided on or in the waveguide substrate 10a. As Figure 2 more clearly shown in, the input grating 11 is configured to couple an input light beam b1 into the waveguide substrate 10a so that it is coupled to the output grating 12 by total internal reflection. To achieve optical pupil expansion, as Figure 2 shown, after receiving the thinner incident light beam from the input grating 11, the output grating 12 diffracts and expands the light beam continuously in two directions in the plane and at the same time partially couples the light out of the waveguide substrate 10a, realizing the function of expanding the pupil in the plane, so that an observer can observe the display information carried by the incident light beam within a larger viewing window EB (see Figure 2 ).

[0061] Returning to refer to Figure 1, according to an embodiment of the present invention, the output grating 12 is formed on a random partition region 12a, and the random partition region 12a includes a plurality of partitions (such as Figure 1 the partitions d1, d2, d3 shown) having randomly formed shapes, sizes, and / or positions. According to an embodiment of the present invention, the output grating 12 of the diffractive optical waveguide 10 includes a plurality of sub-gratings formed in the plurality of partitions (such as the sub-gratings g1, g2, g3 formed in the partitions d1, d2, d3), and the sub-gratings in at least some of the partitions have different optical structures.

[0062] The diffractive optical waveguide according to an embodiment of the present invention adopts randomly formed partitions within a certain region of the output grating and different grating optical structures in different partitions, enabling the optimization of the sub-gratings in different partitions with the goal of the uniformity of the light energy distribution of the output light field. Moreover, compared with the diffractive optical waveguide having regular partitions and / or fixed grating structures, it has a higher design freedom, and its optimization result is also closer to the optimal solution.

[0063] Preferably, the plurality of sub-gratings of the output grating are configured such that the light energy distribution of the output light field of the diffractive optical waveguide is substantially uniform.

[0064] According to an embodiment of the present invention, preferably, the plurality of partitions in the random partition region 12a of the output grating 12 are Voronoi partitions divided according to a Voronoi diagram. More preferably, the plurality of partitions are Voronoi partitions divided according to a Voronoi diagram formed based on random point scattering. The Voronoi diagram is used to describe the spatial proximity relationship, and it approximates the irregular units in nature with irregular small facets. In the present invention, by using the Voronoi diagram, especially the Voronoi diagram formed based on random point scattering, random partitioning is effectively realized, avoiding and eliminating the fixed rules regarding shape, position, and size in the partitioning process, providing as high a degree of freedom as possible for the optimal design of the diffractive optical waveguide, so that it can approach the optimal solution as much as possible through optimal design.

[0065] In Figure 1 the shown example, the input grating 11 is centered relative to the output grating 12 in the up-down direction shown in the figure, and the central axis cc of the output grating 12 passes through the input grating 11 in a plane ( Figure 1 the drawing plane perpendicular to the waveguide substrate 10a). In this case, in order to obtain a uniform light energy distribution in the output light field of the output grating 12, preferably, the output grating 12 can be symmetrically structured relative to the central axis cc in the up-down direction, as Figure 1 shown.

[0066] Although Figure 2The input grating 11 and the output grating 12 are shown as being formed on the same surface of the waveguide substrate 10a. However, in some other cases, the input grating 11 and the output grating 12 can be formed on two opposite surfaces of the waveguide substrate 10a respectively. In still other cases, either the input grating 11 or the output grating 12 can also be formed inside the waveguide substrate 10a. It should be understood that the diffractive optical waveguide according to the present invention is not limited to any specific positions of the input grating and the output grating in the waveguide substrate.

[0067] Figure 3 The grating vectors of the input grating 11 and the output grating 12 of the diffractive optical waveguide 10 are schematically shown. Advantageously, the input grating 11 can employ a one-dimensional grating having a grating vector G0. The plurality of sub-gratings of the output grating 12 preferably includes two-dimensional gratings, and preferably, as Figure 3 shown, such two-dimensional sub-gratings have a first grating vector G1, a second grating vector G2, and a third grating vector G3. In the Figure 3 illustrations, for clarity, the grating vectors G1, G2, and G3 are drawn separately, but it should be understood that for the sub-gratings that are two-dimensional gratings, the above three grating vectors can exist / form simultaneously anywhere. For example, see Figure 4 , the two-dimensional grating can include a plurality of optical structures s1 / s2 arranged periodically in three directions, thereby forming grating vectors in three directions respectively. In the present application, the "direction of the grating vector" is the direction along which the structure of the grating changes / arranges periodically (e.g., the direction perpendicular to the grating lines / grooves), and the "magnitude of the grating vector" is 2π / t, where t is the period / pitch of the grating structure in the "direction of the grating vector".

[0068] To improve the optical coupling efficiency of the diffractive optical waveguide, preferably, the two-dimensional sub-gratings in the plurality of partitions of the output grating 12 have the same grating vectors as each other.

[0069] It should be understood that the output grating in the diffractive optical waveguide according to the embodiments of the present invention can also include two one-dimensional gratings respectively having, for example, Figure 3 the first grating vector G1 and the second grating vector G2 shown. Although not shown, these two one-dimensional gratings can be formed on two opposite surfaces of the waveguide substrate 10a respectively, for example. In this case, the random partitioning in the random partitioning region 12a of the output grating 12 as Figure 1 shown can be similarly applied to these two one-dimensional gratings, thereby achieving the same or similar technical effects. For the sake of clear and concise discussion, the following will discuss by taking the sub-gratings of the output grating as two-dimensional gratings as an example.

[0070] For ease of understanding, Figure 4Exemplary optical structures with different cross-sections that can be used to couple out sub-gratings of a grating are schematically shown. Figure 4 In FIG. (a) of Figure 4 , the optical structure s1 in the sub-grating of the grating for coupling out, which is a two-dimensional grating, is a columnar structure with a square cross-section; FIG. (b) shows the optical structure s2 in the sub-grating of the grating for coupling out, which is a two-dimensional grating, and the optical structure s2 is a columnar structure with an irregular cross-section. It should be understood that Figure 4 the illustrations are only exemplary and not restrictive. The sub-grating optical structures employed in the grating for coupling out in the diffractive optical waveguide according to the present invention may have other different cross-sectional shapes, such as basic geometric shapes like circular, triangular, parallelogram, elliptical, or shapes formed by simple combinations (including "addition" or "subtraction") of these basic geometric shapes, which are herein referred to as "regular shapes". It should be noted that the "irregular shape" as used in this application refers to shapes other than the above-mentioned basic geometric shapes and "regular shapes". As a supplement or alternative, the optical structures of the sub-gratings in different partitions may also have different cross-sectional dimensions.

[0071] In addition, according to an embodiment of the present invention, the optical structures of the sub-gratings of the grating for coupling out in the diffractive optical waveguide may also have different heights or depths (in the direction perpendicular to Figure 4 the plane of the drawing).

[0072] In addition, although not shown, the multiple partitions of the random partition region 12a of the grating for coupling out 12 may include non-diffractive partitions where no sub-gratings are formed. The area of such non-diffractive partitions is less than a predetermined threshold, and the predetermined threshold is preferably less than or equal to the average pupil area of the human eye, preferably less than or equal to one-half of the average pupil area of the human eye. In the non-diffractive partitions, since no grating structure is formed, light continues to propagate in the waveguide substrate by total internal reflection in this region without being coupled out, so the intensity of the coupled-out light in the non-diffractive partitions is theoretically zero; however, since the area of the non-diffractive partitions is less than the average pupil area of the human eye, the situation where the intensity of the coupled-out light is zero is not directly perceived by the human eye. By setting such non-diffractive partitions, on the one hand, it can be used as a means to adjust or suppress the light coupling efficiency in a specific region, increasing the degree of freedom for optimal design, and on the other hand, it can eliminate the workload of optimizing the sub-grating optical structure in such a small region, improving the optimization efficiency.

[0073] Preferably, for partitions with an area smaller than the above-mentioned predetermined threshold, only a part of them can be selected to be set as non-diffractive partitions, so that at least one partition is included in multiple partitions of the random partition region of the output grating, the area of which is smaller than or equal to at least one non-diffractive partition and in which a sub-grating is formed. In this way, it can be avoided that when several partitions with an area smaller than the above-mentioned predetermined threshold are adjacent to each other and are all set as non-diffractive partitions, the area of the actually continuous non-diffractive partitions exceeds the average pupil area of the human eye, causing a "dark area" visible to the human eye in the display based on the diffractive optical waveguide. In addition, since the setting of the non-diffractive partitions is selective rather than set according to a fixed rule based on the area of the partitions, greater freedom can be provided for the optimized design, thereby allowing a better effect to be achieved. The setting of the non-diffractive partitions will be described in more detail with reference to the accompanying drawings when introducing the diffractive optical waveguide design method according to the present invention hereinafter, and will not be elaborated herein.

[0074] Figure 1 In the example shown, the entire output grating 12 of the diffractive optical waveguide 10 is formed on the random partition region 12a, and the output grating 12 has a symmetric structure with respect to the central axis cc. However, the diffractive optical waveguide according to the embodiment of the present invention is not limited to Figure 1 the above-mentioned structure shown.

[0075] For example, Figure 5 FIG. is a schematic diagram of another example of a diffractive optical waveguide for optical pupil expansion according to an embodiment of the present invention, in which a part of the output grating 12' of the diffractive optical waveguide 10' is formed on the random partition region 12a, and another part is formed on other regions 12b, where the "other regions" can be regular partition regions or regions that are not further partitioned. As Figure 5 shown, preferably, the random partition region 12a of the output grating 12' is arranged closer to the input grating 11 than the other regions 12b, because the optical energy density of the light propagating in the region closer to the input grating 11 is higher, and the influence on the pupil expansion ability of the output grating 12' (including, for example, the uniformity of the optical energy distribution of the output light field and the optical coupling efficiency) is greater, and it is more necessary to improve its pupil expansion ability through an optimized design based on random partitioning.

[0076] In addition, Figure 6 FIG. is a schematic diagram of yet another example of a diffractive optical waveguide for optical pupil expansion according to an embodiment of the present invention, in which the input grating 11" of the diffractive optical waveguide 10" is offset in the Figure 6 vertical direction shown with respect to the output grating 12", and accordingly, the output grating 12" and the partitions in its random partition region 12a" are formed in an asymmetric structure to achieve good optical pupil expansion under the offset optical coupling condition. Of course, it should be understood that Figure 6The illustrated example is for illustrative purposes only and not restrictive. The diffractive optical waveguide according to an embodiment of the present invention may also adopt an asymmetric structure under other different circumstances.

[0077] Although not shown, the present invention also provides a display device, which includes the diffractive optical waveguide as described above according to an embodiment of the present invention. Preferably, the display device is a near-eye display device and includes a lens and a frame for holding the lens close to the eye, wherein the lens includes the diffractive optical waveguide according to an embodiment of the present invention. Preferably, the display device is an augmented reality display device.

[0078] Next, a design method of a diffractive optical waveguide for optical pupil expansion according to an embodiment will be introduced with reference to the accompanying drawings.

[0079] Figure 7 It is a flowchart of a design method 1 of a diffractive optical waveguide for optical pupil expansion according to an embodiment of the present invention. As Figure 7 shown, the diffractive optical waveguide design method 1 includes the following processes:

[0080] S1: Randomly partition a target area where an output grating is to be formed to form a plurality of partitions, and the plurality of partitions have randomly formed shapes, sizes, and / or positions;

[0081] S2: Initialize the sub-gratings in the plurality of partitions, where each sub-grating includes a plurality of optical structures; and

[0082] S3: Use at least one parameter of the optical structures of each sub-grating as an optimization variable, perform an optimization process, and obtain an optimization result.

[0083] The "target area" in the diffractive optical waveguide design method 1 according to an embodiment of the present invention corresponds to the randomly partitioned area of the output grating in the diffractive optical waveguide according to an embodiment of the present invention. For example, Figure 1 the randomly partitioned area 12a as shown and Figure 5 the randomly partitioned area 12a' as shown, that is, the area where the output grating is intended to be optimized and designed based on random partitioning; this target area can be formed as the entire area of the output grating or a part of the area occupied by the output grating.

[0084] The optimization objective of the optimization process in the diffractive optical waveguide design method 1 according to an embodiment of the present invention includes the uniformity of the light energy distribution of the output light field of the diffractive optical waveguide. In some implementation manners, the non-uniformity of the light energy distribution within the range of the view window EB (see Figure 3 ) (the range of human eye movement where an image can be seen) can be used to characterize the uniformity of the light energy distribution of the output light field of the diffractive optical waveguide. In other implementation manners, the viewing angle range e (see Figure 3) The uniformity of the optical energy within is used to characterize the uniformity of the optical energy distribution of the output optical field of the diffractive optical waveguide. Alternatively, in other implementations, the above two methods for characterizing the optical energy distribution uniformity may also be combined, for example, by weighted calculation.

[0085] Preferably, the optimization objective of the optimization process may further include the optical energy coupling efficiency. If the incident optical energy of the incident light entering the coupling grating of the diffractive optical waveguide is I in , and the total optical energy within the window EB exiting from the output grating is I E , then the optical energy coupling efficiency of the diffractive optical waveguide is r = I E / I in . As an example, the diffractive optical waveguide design method 1 according to an embodiment of the present invention may use the optical energy coupling efficiency r being greater than or equal to a predetermined value as one of the optimization objectives.

[0086] "Optimization process" herein refers to a process in which, by changing the assignment of optimization variables (such as at least one parameter of the sub-grating optical structure), multiple results corresponding to the optimization objective (such as quantities representing the optical energy distribution uniformity and / or the optical energy coupling efficiency) are obtained, and based on whether they meet the optimization objective, one of the results is selected, and the assignment of the optimization variable corresponding to this result and other parameters (such as the settings of the non-diffractive grating partitions and / or the random partitions introduced below with reference to Figure 11 and Figure 13 ) are used as the optimization result.

[0087] Figure 8 FIG. is a flowchart of an example of a random partitioning method, which can be used in the process S1 of the diffractive optical waveguide design method 1. As shown in the figure, the random partitioning method / process S1 may include the following steps:

[0088] S1a: Randomly scatter points in the target area;

[0089] S1b: Generate a Voronoi diagram based on the randomly scattered points; and

[0090] S1c: Perform partitioning according to the Voronoi diagram.

[0091] Preferably, in step S1a, the number of points M for randomly scattering points may first be determined based on, for example, the area of the target area.

[0092] For ease of understanding, Figure 9 schematically shows an example of random partitioning according to the method shown in Figure 8 . Figure 9Randomly scattered dot pattern A obtained through step S1a, Voronoi diagram B obtained based on the randomly scattered dot pattern A through step S1b, and random partition diagram C obtained based on the Voronoi diagram B through step S1c are shown in sequence from left to right.

[0093] Figure 10 Further shown is an example of the partition of a diffractive optical waveguide obtained according to the Figure 8 and Figure 9 shown method and example, where the diffractive optical waveguide 100 includes a waveguide substrate 100a and an input grating 110 and an output grating 120 formed on or in the waveguide substrate 100a, and the output grating 120 forms partitions as shown in the random partition diagram C in Figure 9 in the target area 120a.

[0094] Returning to refer to Figure 7 , in process S2 of the diffractive optical waveguide design method 1, the sub-gratings in multiple partitions are initialized. Each sub-grating obtained by initialization includes multiple optical structures. Preferably, in process S2, the two-dimensional sub-gratings in different partitions have the same grating vector. In some implementations, this initialization can make the optical structure of each sub-grating a columnar structure, for example, a columnar optical structure with a square cross-section as shown in figure (a) in Figure 4 . In the optimization process of process S3, it can include obtaining columnar structures with optimized cross-sections through dilation and erosion processing of the cross-sections of these columnar structures, for example, columnar structures with irregular cross-sections as shown in figure (b) in Figure 4 . Only as an example, algorithms such as genetic algorithm (GA), particle swarm optimization (PSO), and simulated annealing algorithm (SA) can be used to optimize the shape and / or size of the cross-section of the optical structure of the sub-grating starting from the columnar structure. The above-introduced optimization of the cross-section of the optical structure of the sub-grating through dilation and erosion processing provides a higher degree of freedom for the design of the optical structure of the sub-grating, so that the optimization result can be closer to the optimal solution.

[0095] In addition, in process S3 of the diffractive optical waveguide design method 1, the height or depth of the optical structure of the sub-grating can also be used as an optimization variable for optimization processing. In summary, after the optimization process, at least some of the sub-gratings in the random partitions have different optical structures.

[0096] The optimization results obtained in process S3 can include but are not limited to, for example, the partition of the diffractive optical waveguide, the optimized optical structure of the sub-grating, and the corresponding uniformity of light energy distribution.

[0097] The diffraction optical waveguide design method according to an embodiment of the present invention adopts randomly formed partitions in a certain area of the output grating, and optimizes the optical structures of the sub-gratings in different partitions, so as to avoid / eliminate the limitations brought by fixed partition rules and / or fixed grating structures to the diffraction optical waveguide design, improve the design freedom, and thus make the optimization result closer to the optimal solution.

[0098] Figure 11 For Figure 7 FIG. is a flowchart of an extended example of the diffraction optical waveguide design method shown (i.e., diffraction optical waveguide design method 2). As Figure 11 shown, the diffraction optical waveguide design method 2 includes the following processes:

[0099] S1: Perform random partitioning in a target area where an output grating is to be formed to form a plurality of partitions, and the plurality of partitions have randomly formed shapes, sizes, and / or positions;

[0100] S2: Initialize the sub-gratings in the plurality of partitions, where each sub-grating includes a plurality of optical structures;

[0101] S3: Use at least one parameter of the optical structure of the sub-grating as an optimization variable, perform optimization processing, and obtain an optimization result;

[0102] S4: Change the random partitioning of the target area to form a new plurality of partitions, and based on the new plurality of partitions, return to execute process S2, thereby repeatedly executing processes S2 to S3 to obtain a plurality of optimization results; and

[0103] S5: Compare the plurality of optimization results, and determine the partitioning of the diffraction optical waveguide and the optimized optical structure of the corresponding sub-grating according to an optimization result that best meets the optimization goal.

[0104] The above processes S1, S2, and S3 of the diffraction optical waveguide design method 2 are the same as Figure 7 the processes S1, S2, and S3 in the diffraction optical waveguide design method 1 shown, and will not be elaborated here.

[0105] The optimization goal in process S5 of the diffraction optical waveguide design method 2 can be the same as the goal of the optimization processing in process S3. For specific details, reference can be made to the discussion of the optimization goal of the optimization processing of the design method 1 shown above, and will not be elaborated here. Figure 7

[0106] In a preferred implementation, process S4 of the diffraction optical waveguide design method 2 may include: Based on Figure 9 ​The random partitioning method shown changes the number of scattering points M, re - randomly scatters points in the target area based on the changed number of scattering points M, generates a new Voronoi diagram, and partitions according to the new Voronoi diagram. In this case, the number of scattering points M is also used as a type of optimization variable for the diffractive optical waveguide design method 2.

[0107] In some other implementation manners, in process S4, for example, points can be re - scattered without changing the number of scattering points, a new Voronoi diagram is generated, and partitioning is performed according to the new Voronoi diagram.

[0108] It should be understood that the diffractive optical waveguide design method according to the embodiments of the present invention may not be limited to a specific random partitioning method. In the case of not performing random partitioning based on the Voronoi diagram, in process S4, a corresponding method of re - random partitioning can be adopted.

[0109] For ease of understanding, Figure 12 Another example of the new random partitioning of the diffractive optical waveguide obtained according to the diffractive optical waveguide design method 2 is schematically shown. The diffractive optical waveguide 200 includes a waveguide substrate 200a and an input grating 210 and an output grating 220 formed above or within the waveguide substrate 200a, and the output grating 220 has a partition formed in the target area 220a that is different from Figure 9 the partition shown in the random partitioning diagram C.

[0110] According to the diffractive optical waveguide design method 2, after process S4, based on the new random partitioning, process S2 is returned to for execution, so as to repeatedly execute processes S2 to S3 to obtain multiple optimization results. The process of this repeated execution will not be elaborated here.

[0111] In summary, in the diffractive optical waveguide design method 2, on the basis of the optimization process of the design method 1 shown in Figure 7 the random partitioning itself is further used as an optimization variable, further improving the design freedom and facilitating obtaining an optimization structure closer to the optimal one.

[0112] Figure 13 For Figure 7 the flowchart of another extended example (i.e., the diffractive optical waveguide design method 3) of the diffractive optical waveguide design method shown. As shown in Figure 13 the diffractive optical waveguide design method 3 includes the following processes:

[0113] S1: Perform random partitioning in a target area where an output grating is to be formed to form multiple partitions, and the multiple partitions have randomly formed shapes, sizes, and / or positions;

[0114] S2a: Selectively set at least a part of the partitions with an area smaller than a predetermined threshold as non - diffractive partitions;

[0115] S2b: Initialize the sub-gratings in the partitions other than the non-diffraction partition

[0116] S3: Under the condition of keeping the grating vectors of the sub-gratings unchanged, use at least one parameter of the optical structure of the sub-gratings as the optimization variable to perform optimization processing to obtain an optimization result;

[0117] S3a: Change the setting of the non-diffraction partition to form a new non-diffraction partition, and based on the new non-diffraction partition, return to execute process S2b, so as to repeatedly execute process S2b to process S3 to obtain multiple optimization results corresponding to the same random partition;

[0118] S4’: Change the random partition of the target area to form a new plurality of partitions, and based on the new plurality of partitions, return to execute process S2a, so as to repeatedly execute process S2a to process S3 to obtain multiple optimization results corresponding to various random partitions; and

[0119] S5’: Compare multiple optimization results, and determine the partition of the diffractive optical waveguide and the optimized optical structure of the corresponding sub-gratings according to the optimization result that best meets the optimization goal.

[0120] The above processes S1, S3 and S5’ of the diffractive optical waveguide design method 3 are the same as Figure 11 processes S1, S3 and S5 in the shown diffractive optical waveguide design method 2, and will not be elaborated here.

[0121] In process S4’ of the diffractive optical waveguide design method 3, changing the random partition of the target area can be achieved in the same way as Figure 11 process S4 in the shown diffractive optical waveguide design method 2, and will not be elaborated here.

[0122] The main difference between the diffractive optical waveguide design method 3 and the diffractive optical waveguide design method 2 is that in the diffractive optical waveguide design method 3, a non-diffraction partition is further set on the basis of the random partition, and the non-diffraction partition is the partition where no sub-gratings are formed. In this way, the process of initializing the sub-gratings in the random partition in design method 3 is divided into two parts, namely Figure 13 the shown processes S2a and S2b. In a preferred implementation, in process S2a, select the partitions with an area smaller than a predetermined threshold as the non-diffraction partitions, where the predetermined threshold is less than or equal to the average pupil area of the human eye, preferably less than or equal to half of the average pupil area of the human eye.

[0123] As discussed above when introducing the diffractive optical waveguide according to an embodiment of the present invention, in the non-diffractive region, since no grating structure is formed, light continues to propagate in the waveguide substrate by total internal reflection in this region without being coupled out. Therefore, the theoretically coupled-out light intensity in the non-diffractive region is zero. However, since the area of the non-diffractive region is smaller than the average pupil area of the human eye, the situation where the above-mentioned coupled-out light intensity is zero is not directly perceived by the human eye. The diffractive optical waveguide design method 3 can, on the one hand, adjust or suppress the light coupling efficiency in a specific region by setting such a non-diffractive region, increasing the degree of freedom of optimal design. On the other hand, it can eliminate the workload of optimizing the sub-grating optical structure in such a small region, improving the optimization efficiency.

[0124] Preferably, in process S2a, for a partition with an area smaller than the above-mentioned predetermined threshold, only a part of it can be selected to be set as the non-diffractive region. In this way, it can be avoided that when several partitions with areas smaller than the above-mentioned predetermined threshold are adjacent to each other and are all set as non-diffractive regions, the area of the actually continuous non-diffractive region exceeds the average pupil area of the human eye, causing a "dark area" visible to the human eye in the display based on this diffractive optical waveguide. For ease of understanding, Figure 14 An example of the partition of the diffractive optical waveguide is schematically shown, in which a non-diffractive region is provided; Figure 15 is shown Figure 14 a partial enlarged schematic view of the part marked by the dashed circle in Figure 14 The shown diffractive optical waveguide 200A has basically the same structure and partition as Figure 12 the shown diffractive optical waveguide 200. The difference mainly lies in that a non-diffractive region 221 is further provided in the random partition region 220a of the output grating 220 of the diffractive optical waveguide 200A. As Figure 15 more clearly shown, if several partitions with areas smaller than the predetermined threshold but adjacent to each other are all set as non-diffractive regions (see Figure 5 the shown non-diffractive regions 221a, 221b, and 221c), then these non-diffractive regions may form a continuous non-diffractive region with an area larger than the predetermined threshold. Therefore, in process S2a, it is beneficial to selectively set only a part of the partitions with areas smaller than the above-mentioned predetermined threshold as non-diffractive regions.

[0125] In addition, since the setting of the non-diffractive region is selective rather than set according to a fixed rule based on the area of the partition, it can provide a greater degree of freedom for optimal design, thus allowing a better effect to be achieved.

[0126] For the purpose of illustration only, Figure 16Schematically shows another example of the diffraction optical waveguide partition obtained according to the diffraction optical waveguide design method 3, where for partitions with an area smaller than a predetermined threshold, only a part of the partitions are set as non-diffracting partitions. Specifically, Figure 16 The shown diffraction optical waveguide 200B has a structure and partition that are substantially the same as those of Figure 15 the shown diffraction optical waveguide 200A, with the only difference being that in the diffraction optical waveguide 200B, among the partitions in the randomly partitioned region 220a with an area smaller than the predetermined threshold, only a part of the partitions are set as non-diffracting partitions.

[0127] The diffraction optical waveguide design method 3 optionally and preferably includes process S3a. By changing the setting of the non-diffracting partitions in process S3a and then returning to execute process S2b and process S3, the design method 3 can use the setting of the non-diffracting partitions as an optimization variable, enabling the finding of the optimized non-diffracting partitions under the same random partition and the optimized optical structure of the corresponding sub-gratings, improving the design freedom and facilitating the obtaining of a more optimized design scheme.

[0128] In addition, it should be understood that process S2a and process S2b in the diffraction optical waveguide design method 3 can also be combined into, for example, Figure 7 the shown design method 1 to replace process S2.

[0129] The above description is only a preferred embodiment of the present application and an explanation of the applied technical principles. Those skilled in the art should understand that the scope of the invention involved in the present application is not limited to the technical solutions formed by the specific combination of the above technical features, but should also cover other technical solutions formed by any combination of the above technical features or their equivalent features without departing from the inventive concept. For example, the technical solutions formed by mutually replacing the above features with the (but not limited to) technical features with similar functions disclosed in the present application.

Claims

1. A design method for a diffractive optical waveguide for optical pupil expansion, comprising the following processes: (1) Randomly partition a target area where an output grating is to be formed to form a plurality of partitions, and the plurality of partitions have randomly formed shapes, sizes, and / or positions; (2) Initialize the sub-gratings in the plurality of partitions, where each of the sub-gratings includes a plurality of optical structures; (3) Use at least one parameter of the optical structures of each of the sub-gratings as an optimization variable to perform an optimization process to obtain an optimization result, where the optimization objective of the optimization process includes the uniformity of the light energy distribution of the output light field of the diffractive optical waveguide; (4) Change the random partition of the target area to form a new plurality of partitions, and based on the new plurality of partitions, repeatedly execute processes (2) to (3) to obtain a plurality of optimization results; and (5) Compare the plurality of optimization results, and determine the partition of the diffractive optical waveguide and the optimized optical structures of the corresponding sub-gratings according to an optimization result that best meets the optimization objective, wherein, process (1) includes: obtaining the number of scattered points M, randomly scattering M points in the target area, generating a Voronoi diagram based on the M points, and performing partitioning according to the Voronoi diagram; and process (4) includes: changing the number of scattered points M, re-randomly scattering points in the target area based on the changed number of scattered points M, generating a new Voronoi diagram, and performing partitioning according to the new Voronoi diagram.

2. The design method of the diffractive optical waveguide according to claim 1, wherein, in process (3), the optimization variables include the cross-sectional shape and / or size of the optical structure and / or the height or depth of the optical structure, and the optimization process enables the sub-gratings in at least some partitions to have different optical structures.

3. The design method of the diffractive optical waveguide according to claim 2, wherein, in process (2), the initialization enables the optical structure of each of the sub-gratings to be a columnar structure; and in process (3), the optimization process includes dilation and erosion processing of the cross-section of the columnar structure.

4. The design method of the diffractive optical waveguide according to claim 1, wherein, in process (3), the optimization objective of the optimization process further includes the light energy coupling efficiency of the diffractive optical waveguide.

5. The design method of the diffractive optical waveguide according to claim 1, wherein, process (1) includes: randomly scattering points in the target area, generating a Voronoi diagram based on the random scattering of points, and performing partitioning according to the Voronoi diagram.

6. The design method of the diffractive optical waveguide according to claim 1, wherein, process (2) includes: (2a) Selectively set at least some of the partitions with an area smaller than a predetermined threshold as non-diffractive partitions, and no sub-gratings are formed in the non-diffractive partitions, and the predetermined threshold is less than or equal to the average pupil area of the human eye; and (2b) Initialize the sub-gratings in the partitions other than the non-diffractive partitions.

7. The design method of the diffractive optical waveguide according to claim 6 further includes the following process: (3a) Change the setting of the non-diffractive partition to form a new non-diffractive partition, and based on the new non-diffractive partition, repeatedly execute process (2b) and process (3) to obtain an optimization result corresponding to the same random partition.

8. The design method of a diffractive optical waveguide according to claim 6, wherein, the predetermined threshold is less than or equal to one half of the average pupil area of the human eye.

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