Design methods of diffractive optical waveguides and diffractive optical waveguides
By partitioning the turning region of the diffractive waveguide and introducing a grating structure design with phase differences along different paths, the interference problem caused by the non-unique propagation path of light is solved, thus improving the display effect.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SHANGHAI NORTH OCEAN TECH CO LTD
- Filing Date
- 2023-09-19
- Publication Date
- 2026-06-30
Smart Images
Figure CN119667844B_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of optical technology, and in particular to a design method for a diffractive optical waveguide and a diffractive optical waveguide. Background Technology
[0002] Augmented reality is a technology that blends the real world with virtual information. Augmented reality display systems typically include micro-projectors and optical displays. The micro-projectors provide virtual display content for the augmented reality display system, which is then projected onto the viewer's eyes through the optical displays. The optical displays are usually transparent optical components, so that users can also see the real world through the optical displays at the same time.
[0003] Diffractive waveguides are a type of optical display screen. They typically use grating structures to expand the exit pupil. When expanding the exit pupil, there are multiple expansion paths, which in turn generate a large number of light rays with equal optical path differences that propagate in the same direction. When these light rays are coupled out to the human eye, they will undergo constructive or destructive interference, resulting in bright and dark stripes in the display screen, which greatly affects the display effect. Summary of the Invention
[0004] This application provides a design method and a diffractive waveguide, which can improve or even eliminate undesirable interference effects, thereby enhancing the display effect of the diffractive waveguide.
[0005] A design method for a diffractive optical waveguide, the diffractive optical waveguide comprising a waveguide substrate, a coupling region, a transition region, and a coupling out region, the design method comprising:
[0006] The transition region is divided into several transition partitions, and the shape and size of the sampling window are determined according to the shape and size of the transition partitions.
[0007] Determine the grating parameters of the grating structure within the sample grating region, and select the initial sampling position for sampling the grating structure from the sample grating region using the sampling window, wherein the grating period, grating direction, and grating duty cycle of the grating structure within the sample grating region remain consistent;
[0008] The process involves traversing each of the transition partitions where a grating structure is desired, assigning the sampling result of the grating structure sampling performed from the sample grating region at the initial sampling position to the first transition region being traversed, and determining the target sampling position of the sampling window based on the positional relationship between the traversed transition partition and the first traversed transition partition, so as to perform grating structure sampling from the sample grating region at the target sampling position and assign the sampling result to the traversed transition region, until each of the transition partitions where a grating structure is desired has been assigned a sampling structure.
[0009] In practice, when light rays propagating along different paths in the transition region converge, the grating teeth between at least one transition partition on one path and at least one transition partition on another path are staggered, so that light rays propagating along different paths in the transition region experience different phase shifts when they converge.
[0010] In practice, determining the target sampling position of the sampling window based on the positional relationship between the traversed transition partition and the first traversed transition partition includes:
[0011] Determine the sliding direction of the sampling window and the sliding step size along the sliding direction;
[0012] Each of the transition zones for which a grating structure is to be set is assigned a multidimensional number, wherein the dimensions of the multidimensional number are consistent with and correspond one-to-one with the number of sliding directions;
[0013] Based on the number of each dimension in the multidimensional numbering and the corresponding sliding step size of the sliding direction, calculate the offset of the target sampling position from the initial sampling position along each sliding direction.
[0014] Implementably, the offset of the target sampling position from the initial sampling position along each of the sliding directions is calculated using the following formula:
[0015] Δd i =(k i -1)·d si
[0016] Where, Δd i It is the offset of the target sampling position from the initial sampling position along the i-th sliding direction, k i d is the dimension number corresponding to the i-th sliding direction. si It is the sliding step size along the i-th sliding direction, 1≤i≤N, where N is the number of sliding directions, 1≤k. i ≤M i M i It is the number of transition partitions of the grating structure that are expected to be set in the dimension corresponding to the i-th sliding direction.
[0017] In practice, the phase difference between light rays propagating along different paths in the turning region when they converge is... Satisfy the following formula:
[0018]
[0019] Where, d s1 It is the sliding step size along the first sliding direction, m is the number of turning sections with grating structures that the light passes through in the first sliding direction, and d is the sliding step size along the first sliding direction.s2 θ is the sliding step size along the second sliding direction, n is the number of turning sections with grating structures that the light passes through in the second sliding direction, the first sliding direction and the second sliding direction are parallel to and orthogonal to the waveguide substrate surface, θ is the angle between the grating direction of the grating structure and the second sliding direction, and Q is a non-negative integer.
[0020] Implementably, assigning the sampling result to the traversed transition region includes:
[0021] When the shape and size of the sampling window are consistent with those of the traversed transition region, the sampling result of the sampling window is completely copied to the traversed transition region so that the grating structure in the traversed transition region is completely consistent with the grating structure of the sampling window.
[0022] When the shape and / or size of the sampling window are inconsistent with the shape and / or size of the transition region to which it is traversed, the geometric center of the sampling window and the transition region to which it is traversed are determined respectively. After aligning the two geometric centers, the sampling result of the sampling window is copied to the transition region to which it is traversed.
[0023] In practice, the transition region may be regularly partitioned or randomly partitioned, and the outline of the transition region may include straight lines and / or curves.
[0024] In practice, the turning partition has a dimension greater than the entrance pupil size but less than twice the entrance pupil size in at least one direction parallel to the surface of the waveguide substrate.
[0025] Alternatively, the transition region may also include a transition zone without a grating structure.
[0026] A diffractive optical waveguide is designed according to any of the above design methods.
[0027] The design method for diffractive waveguides provided in this application, based on the existing architecture, divides the transition region into partitions. When setting grating structures in each transition partition where a grating structure is desired, a method of local sampling and refilling from the sample grating region is cleverly adopted. This introduces phase differences between the grating structures set in different transition partitions, but the grating period, grating direction, and grating duty cycle remain consistent. In this way, when light is incident on these transition partitions and diffracts, the original optical path is not changed, but there is an additional phase change. Thus, the phase difference between different interfering rays is modulated without introducing an additional optical path. When the phase difference changes, the interference effect between different rays is averaged or even eliminated, thereby improving the display effect of the diffractive waveguide.
[0028] The diffractive waveguide provided in this application is designed using the aforementioned design method, and thus possesses the advantages of the aforementioned design method. Attached Figure Description
[0029] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0030] Figure 1 A schematic diagram of a diffractive optical waveguide provided for existing technology;
[0031] Figure 2 This is a flowchart illustrating a design method for a diffractive waveguide according to an embodiment of this application.
[0032] Figure 3 A schematic diagram of the partitioning of the turning region of a diffractive waveguide provided in one embodiment of this application;
[0033] Figure 4 This is a schematic diagram of a sampling grating structure from a sample grating region provided in one embodiment of this application;
[0034] Figure 5 A schematic diagram of the partitioning of the turning region of a diffractive waveguide provided in another embodiment of this application;
[0035] Figure 6 This is a schematic diagram of a grating structure filling a transition zone according to an embodiment of this application;
[0036] Attached image labels:
[0037] 110, 310, 510: Turning point;
[0038] 311, 511, 611: Transitional zones;
[0039] 400: Sample grating area;
[0040] 410: Initial sampling position;
[0041] 420: Target sampling location;
[0042] 430, 630: Sampling window. Detailed Implementation
[0043] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of protection of the present application.
[0044] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.
[0045] Existing technologies typically employ grating structures in the transition and / or coupling regions of diffractive waveguides to deflect light propagating in the waveguide substrate, thereby achieving pupil expansion. However, the propagation path of the light is often not unique during pupil expansion. (Refer to...) Figure 1 For example, in the transition region 110, light rays can reach point C from either ABC or ADC. The optical path length of light rays reaching point C via different paths is the same, therefore the phase difference is zero. Furthermore, the light rays transmitted through these two paths have the same frequency and polarization components in the same direction. Therefore, the light rays transmitted through these two paths will interfere at point C. This results in bright and dark fringes of light energy visible to the human eye in the coupling region, significantly affecting the display effect.
[0046] According to one aspect of this application, reference is made to Figure 2 This application provides a design method for a diffractive optical waveguide, which includes a waveguide substrate, a coupling region, a transition region, and a coupling out region. The design method includes:
[0047] S210, the transition region is divided into several transition partitions, and the shape and size of the sampling window are determined according to the shape and size of the transition partitions.
[0048] In practice, the partitioning of the transition region can be regular partitioning or irregular partitioning (random partitioning). Specifically, regular partitioning involves dividing the region along at least one direction into multiple partitions of the same shape (excluding partitions located at the boundaries), for example... Figure 3The transition region 310 is divided into multiple regular partitions along two different directions. Of course, in other embodiments, it can also be divided along more directions (such as three directions, four directions, etc.). Random partitioning refers to randomly dividing the region into multiple partitions of random shape and size, for example... Figure 5 The mid-transition region 510 is randomly divided into multiple partitions of random shape and size.
[0049] Implementably, the outline of the transition zone includes straight lines and / or curves. The shape of the transition zone can be circular, elliptical, polygonal, or a shape enclosed by straight lines and curves.
[0050] In practice, the size of the transition partition is greater than the entrance pupil size but less than twice the entrance pupil size in at least one direction parallel to the waveguide substrate surface. This allows the pupil to be acted upon by the grating structure within the same transition partition, ensuring that the transition partition is neither too small nor too large, thus preventing interference cancellation. Typically, the entrance pupil size is 2mm-4mm, and the maximum size of the transition partition and the coupling partition in at least one direction should be greater than this size but less than twice this size.
[0051] Preferably, the sampling window is designed to be a regular shape, such as a rectangle. The size of the sampling window is greater than or equal to the size of the transition partition, meaning the sampling window can completely cover the transition partition.
[0052] S220, determine the grating parameters of the grating structure within the sample grating region, and select the initial sampling position for sampling the grating structure from the sample grating region using the sampling window, wherein the grating period, grating direction, and grating duty cycle of the grating structure within the sample grating region remain consistent.
[0053] It should be noted that the grating period, grating direction, and grating duty cycle of the grating structure within the sample grating area remain consistent. This ensures that after the grating structure is sampled from the sample grating area and filled into the transition region, the grating period, grating direction, and grating duty cycle of the grating structure within the transition region remain consistent. Consequently, when light is incident on these transition partitions and undergoes diffraction, no new optical path is introduced, thus avoiding additional interference.
[0054] S230, traverse each transition zone where the grating structure is to be set, assign the sampling result of the grating structure sampling from the sample grating region at the initial sampling position to the first transition zone traversed, and determine the target sampling position of the sampling window based on the positional relationship between the transition zone traversed and the first transition zone traversed, so as to perform grating structure sampling from the sample grating region at the target sampling position, and assign the sampling result to the transition zone traversed, until each transition zone where the grating structure is to be set is assigned a sampling structure.
[0055] In practice, the target sampling position of the sampling window is determined based on the positional relationship between the traversed transition partition and the first traversed transition partition. This includes: determining the sliding direction of the sampling window and the sliding step size along the sliding direction; assigning multi-dimensional numbers to each transition partition for which a grating structure is to be set, wherein the number of dimensions of the multi-dimensional numbers is consistent with and corresponds one-to-one with the number of sliding directions; and calculating the offset of the target sampling position from the initial sampling position along each sliding direction based on the number of each dimension in the multi-dimensional numbers and the corresponding sliding step size of the sliding direction.
[0056] In practice, the offset of the target sampling position from the initial sampling position along each sliding direction is calculated using the following formula:
[0057] Δd i =(k i -1)·d si
[0058] Where, Δd i It is the offset of the target sampling position from the initial sampling position along the i-th sliding direction, k i d is the dimension number corresponding to the i-th sliding direction. si It is the sliding step size along the i-th sliding direction, 1≤i≤N, where N is the number of sliding directions, 1≤k. i ≤M i M i This refers to the number of transition zones of the grating structure that are expected to be set in the dimension corresponding to the i-th sliding direction. The sliding step size can be the same or different in different sliding directions, and the value of the sliding step size can range from, for example, 0.1nm to 50nm.
[0059] For example, refer to Figure 3 The transition region 310 is divided into several transition partitions along two mutually orthogonal directions (P1, P2) parallel to the waveguide substrate surface. Each transition partition where a grating structure is desired is assigned a multidimensional number (k1, k2), where 1 ≤ k1 ≤ M1, M1 is the number of transition partitions where a grating structure is desired in the first partition direction P1, and 1 ≤ k2 ≤ M2, M2 is the number of transition partitions where a grating structure is desired in the second partition direction P2. (Reference) Figure 4 The dimensions of the multidimensional numbering correspond one-to-one with the number of sliding directions. The first sliding direction S1 corresponds to the first partitioning direction P1, and the sliding step size of the sampling window in this direction is d. s1 The second sliding direction S2 corresponds to the second partitioning direction P2, and the sliding step size of the sampling window in this direction is d. s2 .
[0060] For example, taking the transition partition numbered (1, 1) as the first transition partition to be traversed, and taking the lower left corner of the sample grating region 400 as the initial sampling position 410, the sampling result of the grating structure sampling from the sample grating region 400 at the initial sampling position 410 is assigned to the transition partition (1, 1), and the traversal continues. When traversing to the transition partition numbered (2, 1), the sampling window is shifted from the initial sampling position 410 along the first sliding direction S1 by Δd1 = (2-1)·d s1 =d s1 The offset along the second sliding direction S2 is Δd2=(1-1)·d s2 =0, reaching the target sampling position 420, sampling the grating structure from the sample grating region 400 at the target sampling position 420, and assigning the sampling result to the transition region (2,1), continuing the traversal. When traversing to the transition partition numbered (3,2), the sampling window is shifted from the initial sampling position 410 along the first sliding direction S1 by Δd1 = (3-1)·d s1 =2d s1 The offset along the second sliding direction S2 is Δd2=(2-1)·d s2 =d s2 Once the target sampling position 420 is reached, grating structure sampling is performed from the sample grating region 400 at the target sampling position 420, and the sampling result is assigned to the transition region (3, 2). This process is repeated until each transition region for which the grating structure is to be set has been assigned a sampling structure.
[0061] In an implementable manner, the grating teeth between at least one turning partition on one path and at least one turning partition on another path are staggered in the turning partitions that the light rays propagating on different paths in the turning region experience when they converge, so that the light rays propagating on different paths in the turning region experience different phase shifts when they converge.
[0062] It should be noted that the size of the sample grating region along the i-th sliding direction is greater than or equal to (M i -1)·d si +D i D i Let be the size of the acquisition window along the i-th sliding direction, so that any transition partition within the transition region can sample the grating structure from the sample grating region, and there are no N d values for N sliding directions. si Simultaneously satisfying d si =QD iQ is a non-negative integer, used to disrupt the conventional case where all grating teeth in the transition zone are aligned, thus preventing the grating structure from having the same phase in each sampling. This results in different phases when light rays exit after being incident on the grating structure at the initial sampling position and the grating structure at the target sampling position, respectively. The phase difference between the two is: (k1-1)·d s1 cosθ+(k2-1)·d s2 sinθ, where θ is the angle between the grating direction of the grating structure and the second sliding direction. This allows for the use of phase differences between the grating structures set within different transition zones to prevent light rays from arriving at the same position via different paths and having the same phase.
[0063] In this way, when setting grating structures in each transition zone where a grating structure is desired, the method of locally sampling and then filling from the sample grating area can bring about phase differences between the grating structures set in different transition zones. However, the grating period, grating direction, and grating duty cycle of the grating structures set in different transition zones remain consistent. In this way, when light is incident on these transition zones and diffracts, it does not change the original light path but brings about new phase changes. Thus, the phase difference between different interfering rays is modulated without introducing an additional light path. When the phase difference changes, the interference effect between different rays is averaged or even eliminated, thereby improving the display effect of the diffracted waveguide.
[0064] Furthermore, practically, the phase difference between light rays propagating along different paths in the turning region when they converge... Satisfy the following formula:
[0065]
[0066] Where, d s1 It is the sliding step size along the first sliding direction, m is the number of turning sections with grating structures that the light ray passes through in the first sliding direction, and d is the sliding step size along the first sliding direction. s2 θ is the sliding step size along the second sliding direction, n is the number of turning sections with grating structures that the light passes through in the second sliding direction, the first sliding direction and the second sliding direction are parallel to and orthogonal to the waveguide substrate surface, θ is the angle between the grating direction of the grating structure and the second sliding direction, j is a positive integer, and Q is a non-negative integer.
[0067] It should be noted that light rays propagating along different paths will interfere when they converge. When the phase difference between the interfering rays is a non-negative integer multiple of π, constructive or destructive interference will occur, resulting in bright or dark bars. This application improves the display effect of the diffractive waveguide by scrambling the phase difference between two beams propagating along arbitrary different paths so that it is no longer equal to Qπ. The time interference effect is eliminated.
[0068] Implementably, the sampling result is assigned to the traversed transition partition, including: when the shape, outline, and size of the sampling window and the traversed transition partition are consistent, the sampling result of the sampling window is completely copied to the traversed transition partition so that the grating structure in the traversed transition partition is completely consistent with the grating structure of the sampling window; when the shape, outline, and / or size of the sampling window and the traversed transition partition are inconsistent, the geometric centers of the sampling window and the traversed transition partition are determined respectively, and after aligning the two geometric centers, the sampling result of the sampling window is copied to the traversed transition partition.
[0069] It should be noted that when randomly partitioning the transition region, the transition region is numbered in multiple dimensions according to the arrangement of its geometric center, and then the sample grating structure is sampled and filled from the sample grating region according to the multiple dimensions.
[0070] For example, refer to Figure 6 , Figure 6 The sampling window 630 and the transition partition 611 shown in the figure above have the same shape and size. Therefore, the sampling results of the sampling window 630 are directly copied to the transition partition 611. Figure 6 The sampling window 630 and the transition partition 611 shown in the figure below have different shapes, outlines and sizes. Therefore, the geometric centers of the sampling window 630 and the transition partition 611 are determined respectively. After aligning the two geometric centers, the sampling result of the sampling window 630 is copied to the transition partition 611.
[0071] It should be noted that although the foregoing embodiments are illustrated using the division of the transition region and the grating filling design as examples, the design method provided in the foregoing embodiments also applies to the coupling region of the diffractive waveguide. Furthermore, it is also applicable to diffractive waveguide architectures that include both coupling-in and coupling-out regions but do not include the transition region. In addition, the transition partitions and coupling-out partitions are independent of each other, and the shape and size of the partitions do not affect each other.
[0072] In an implementable embodiment, the transition region provided in this application may further include transition zones without a grating structure. The transition zone with the grating structure is a typical waveguide region, where light incident on the grating structure undergoes only total internal reflection without diffraction. This allows for modulation of the light energy distribution, improving pupil dilation uniformity. Furthermore, the coupling region provided in this application may also include coupling zones without a grating structure to modulate coupling uniformity by modulating the energy distribution.
[0073] Furthermore, in the embodiments provided in this application, the pupil dilation efficiency and coupling efficiency can be modulated by adjusting the position and number of the transition partitions including the grating structure and the coupling partitions including the grating structure, thereby improving the uniformity of the diffracted waveguide.
[0074] In practice, the number of transition zones without grating structures gradually decreases along the direction away from the coupling region, and / or the number of output zones without grating structures gradually decreases along the direction away from the coupling region. It is understood that the energy of light decreases continuously with expansion and output. To adjust the uniformity of the emitted light, the number of transition and output zones with grating structures near the front of the expansion direction is less than that near the rear of the expansion direction, and the number of transition and output zones without grating structures near the front of the expansion direction is greater than that near the rear of the expansion direction.
[0075] It should be noted that the partitioning method of the transition region shown in the accompanying drawings, including the position, number, size, and shape of the transition partitions of the grating structure, and excluding the position, number, size, and shape of the transition partitions of the grating structure, are all illustrative and do not limit the scope of protection claimed in this application. Moreover, the various features of the transition partitions in the above embodiments are also applicable to the coupling partitions.
[0076] According to one aspect of this application, a diffractive optical waveguide is also provided, which is designed according to the design method described in any of the preceding embodiments.
[0077] According to one aspect of this application, an augmented reality display device is also provided, comprising: a projection optical engine and a diffractive waveguide as described in any of the preceding claims. The projection optical engine is used to emit light. The augmented reality display device can specifically be implemented as augmented reality glasses or an augmented reality helmet, etc. The augmented reality display device provided by this application includes the aforementioned diffractive waveguide, and therefore possesses the advantages of the aforementioned diffractive waveguide.
[0078] The specific embodiments described above do not constitute a limitation on the scope of protection of this application. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the scope of protection of this application.
Claims
1. A design method for a diffractive optical waveguide, the diffractive optical waveguide comprising a waveguide substrate, a coupling region, a transition region, and a coupling out region, characterized in that, The design method includes: The transition region is divided into several transition partitions, and the shape and size of the sampling window are determined according to the shape and size of the transition partitions. Determine the grating parameters of the grating structure within the sample grating region, and select the initial sampling position for sampling the grating structure from the sample grating region using the sampling window, wherein the grating period, grating direction, and grating duty cycle of the grating structure within the sample grating region remain consistent; The process iterates through each of the transition zones where a grating structure is desired. The sampling result of the grating structure sampling performed from the sample grating region at the initial sampling position is assigned to the first transition zone being traversed. Based on the positional relationship between the traversed transition zone and the first traversed transition zone, the target sampling position of the sampling window is determined. At the target sampling position, the grating structure is sampled from the sample grating region, and the sampling result is assigned to the traversed transition zone. This process continues until each of the transition zones where a grating structure is desired is assigned a sampling structure, thereby introducing a phase difference between the grating structures set in different transition zones.
2. The design method according to claim 1, characterized in that, In the turning region, the light rays propagating along different paths experience different phase shifts when they converge. In the turning partitions that the light rays propagating along different paths in the turning region experience, the grating teeth between at least one turning partition on one path and at least one turning partition on another path are staggered, so that the light rays propagating along different paths in the turning region experience different phase shifts when they converge.
3. The design method according to claim 1, characterized in that, Determining the target sampling position of the sampling window based on the positional relationship between the traversed transition partition and the first traversed transition partition includes: Determine the sliding direction of the sampling window and the sliding step size along the sliding direction; Each of the transition zones for which a grating structure is to be set is assigned a multidimensional number, wherein the dimensions of the multidimensional number are consistent with and correspond one-to-one with the number of sliding directions; Based on the number of each dimension in the multidimensional numbering and the corresponding sliding step size of the sliding direction, calculate the offset of the target sampling position from the initial sampling position along each sliding direction.
4. The design method according to claim 3, characterized in that, The offset of the target sampling position from the initial sampling position along each of the sliding directions is calculated using the following formula: in, It is along the first The offset of the target sampling position from the initial sampling position in each sliding direction. Is with the first The dimension number corresponding to each sliding direction. It is along the first The sliding step size in each sliding direction, , It is the number of sliding directions. , In the context of the first The number of desired transition zones of the grating structure in the dimension corresponding to each sliding direction.
5. The design method according to claim 4, characterized in that, The phase difference of light rays propagating along different paths in the turning region when they converge. Satisfy the following formula: in, It is the sliding step size along the first sliding direction. It is the number of transition zones, each equipped with a grating structure, that the light passes through in the first sliding direction. It is the sliding step size along the second sliding direction. It is the number of bend sections with grating structures that the light passes through in the second sliding direction, wherein the first sliding direction is parallel to and orthogonal to the waveguide substrate surface. It is the angle between the grating direction of the grating structure and the second sliding direction. It is a non-negative integer.
6. The design method according to claim 1, characterized in that, Assigning the sampling results to the traversed transition region includes: When the shape and size of the sampling window are consistent with those of the traversed transition region, the sampling result of the sampling window is completely copied to the traversed transition region so that the grating structure in the traversed transition region is completely consistent with the grating structure of the sampling window. When the shape and / or size of the sampling window are inconsistent with the shape and / or size of the transition region to which it is traversed, the geometric center of the sampling window and the transition region to which it is traversed are determined respectively. After aligning the two geometric centers, the sampling result of the sampling window is copied to the transition region to which it is traversed.
7. The design method according to claim 1, characterized in that, The dimension of the turning section is greater than the entrance pupil size but less than twice the entrance pupil size in at least one direction parallel to the surface of the waveguide substrate.
8. The design method according to claim 1, characterized in that, The transition region is divided into regular or random partitions, and the outline of the transition partition includes straight lines and / or curves.
9. The design method according to claim 1, characterized in that, The transition area also includes transition zones without a grating structure.
10. A diffractive optical waveguide, characterized in that, The diffractive waveguide is designed according to the design method described in any one of claims 1-9.