Diffraction optical waveguide and near-to-eye display equipment

Abstract

The invention discloses a diffraction optical waveguide and a near-to-eye display device. The diffraction optical waveguide comprises a substrate and a plurality of grating structure units which are formed on the surface of the substrate and are arranged in an array. The section pattern of each grating structure unit is formed by overlapping two first patterns and at least one second pattern; the centers of the two first patterns are spaced by a preset distance and are located on the same straight line, and the two first patterns are at least partially overlapped; the center of the second graph coincides with the center of the graph formed by the two first graphs, the second graph is a symmetrical graph, and a preset included angle is formed between the symmetry axis and the straight line; at least one of the size of the first pattern, the size of the second pattern, the relative position between the second pattern and the first pattern and the relative position between the two first patterns gradually changes along the propagation direction of image light when the image light is transmitted in the area where the plurality of grating structure units arranged in the array are located; therefore, the diffraction efficiency along the propagation direction is gradually increased. Through the structure, the energy utilization rate and exit pupil uniformity are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of diffractive optical waveguides, and particularly to a diffractive optical waveguide and a near-eye display device. Background Art

[0002] Augmented reality is a technology that combines the real world and virtual information. An augmented reality display system generally includes a micro-projector and an optical display screen. The micro-projector provides virtual display content for the augmented reality display system, which is projected into the human eye through the optical display screen. The optical display screen is usually a transparent optical component, so that the user can also see the real world through the optical display screen at the same time.

[0003] A diffractive optical waveguide is a way to implement an optical display screen. Figure 1 FIG. is a schematic structural diagram of a diffractive optical waveguide provided in the related art. Figure 2 FIG. is a schematic structural diagram of the basic diffraction orders of a two-dimensional grating provided in the related art. Refer to Figure 1 and Figure 2 As shown, 101 is an input grating, 102 is an output grating, 103 is the image light ray that is coupled into the waveguide by the input grating, and 104 is the observation area of the human eye, that is, the eyebox, which can also be called the eyebox. Specifically, the input grating 101 couples the image light ray into the diffractive optical waveguide, and after total internal reflection, it is transmitted to the output grating 102. After being turned, pupil-expanded and coupled out by the output grating 102, it is incident into the eyebox, so that the human eye can see the display screen. It can be seen from Figure 2 that the output grating 102 has 6 basic diffraction orders. Since the output grating 102 has different diffraction orders, light can be diffracted, so that the image light ray can be transmitted in different directions and finally coupled out from the output grating 102. However, the existing two-dimensional gratings still have problems that need to be solved urgently, such as improving the pupil uniformity and energy utilization rate. Summary of the Invention

[0004] The present invention provides a diffractive optical waveguide and a near-eye display device to solve the defects existing in the prior art, improve the energy utilization rate of the diffractive optical waveguide, enhance the display effect of the diffractive optical waveguide, and further enhance the user experience.

[0005] In a first aspect, the present invention provides a diffractive optical waveguide, including a substrate and a plurality of grating structure units formed on the surface of the substrate and arranged in an array;

[0006] The cross-sectional pattern of the grating structure unit is formed by the overlap of two first patterns and at least one second pattern, and the cross-sectional pattern is intercepted by a plane parallel to the surface of the substrate where the two-dimensional output grating is located;

[0007] The centers of two first figures are separated by a preset distance and located on the same straight line, and the two first figures at least partially overlap;

[0008] The center of the second figure coincides with the center of the figure formed by the two first figures. The second figure is a symmetric figure and its axis of symmetry forms a preset angle with the straight line;

[0009] At least one of the size of the first figure, the size of the second figure, the relative position between the second figure and the first figure, and the relative position between the two first figures in the grating structure unit gradually changes along the propagation direction when the image light travels in the region where multiple grating structure units are arranged in an array, so that the diffraction efficiency along the propagation direction gradually increases.

[0010] Optionally, the first figure is a first ellipse, the second figure is a second ellipse, the two first ellipses are the same and their major axes are on the same straight line, and the included angle between the extension direction of the major axis of the second ellipse and the extension direction of the major axis of the first ellipse is a preset angle;

[0011] At least one of the height or depth of the grating structure unit in the direction perpendicular to the plane of the substrate, the major axis size of the first ellipse, the minor axis size of the first ellipse, the preset distance, the major axis size of the second ellipse, and the minor axis size of the second ellipse gradually changes along the propagation direction when the image light travels in the region where multiple grating structure units are arranged in an array.

[0012] Optionally, the diffractive optical waveguide includes an input region and an output region. Multiple grating structure units arranged in an array are located in the output region. In the plane of the substrate, taking the arrangement direction of the input region and the output region as the X direction and the direction perpendicular to the X direction as the Y direction, a two-dimensional coordinate system is established; the coordinates of the center of the cross-sectional image of any one grating structure unit in the two-dimensional coordinate system are (x, y);

[0013] The height gratingdepth of the grating structure unit in the direction perpendicular to the plane of the substrate satisfies the following relationship:

[0014]

[0015] where x1 = x * cos(θ) - y * sin(θ), y1 = |y * cos(θ) + x * sin(θ)|, A0, B0, C0, D0, E0, F0 are a set of height adjustment parameters, gratingdepth0 is the height value at the starting point of the gradient; θ is the included angle between the gradient direction and the X direction; the gradient direction is the propagation direction;

[0016] And / or, the major axis a1 of the first ellipse satisfies the following relationship:

[0017] Among them, \(x1 = x*\cos(\theta)-y*\sin(\theta)\), \(y1 = |y*\cos(\theta)+x*\sin(\theta)|\), \(A1\), \(B1\), \(C1\), \(D1\), \(E1\), \(F1\) are the first major axis regulation parameter group, and \(a10\) is the major axis value of the first ellipse at the starting point of the gradient; \(\theta\) is the angle between the gradient direction and the X direction; the gradient direction is the propagation direction;

[0018] And / or, the minor axis \(b1\) of the first ellipse satisfies the following relational expression:

[0019] Among them, \(x1 = x*\cos(\theta)-y*\sin(\theta)\), \(y1 = |y*\cos(\theta)+x*\sin(\theta)|\), \(A2\), \(B2\), \(C2\), \(D2\), \(E2\), \(F2\) are the first minor axis regulation parameter group, and \(b10\) is the minor axis value of the first ellipse at the starting point of the gradient; \(\theta\) is the angle between the gradient direction and the X direction; the gradient direction is the propagation direction;

[0020] And / or, the distance \(S\) between the centers of the two first ellipses satisfies the following relational expression:

[0021] Among them, \(x1 = x*\cos(\theta)-y*\sin(\theta)\), \(y1 = |y*\cos(\theta)+x*\sin(\theta)|\), \(A3\), \(B3\), \(C3\), \(D3\), \(E3\), \(F3\) are the spacing regulation parameter group, and \(S0\) is the spacing between the centers of the two first ellipses at the starting point of the gradient; \(\theta\) is the angle between the gradient direction and the X direction; the gradient direction is the propagation direction;

[0022] And / or, the major axis \(a2\) of the second ellipse satisfies the following relational expression:

[0023] Among them, \(x1 = x*\cos(\theta)-y*\sin(\theta)\), \(y1 = |y*\cos(\theta)+x*\sin(\theta)|\), \(A4\), \(B4\), \(C4\), \(D4\), \(E4\), \(F4\) are the second major axis regulation parameter group, \(a20\) is the major axis value of the second ellipse at the starting point of the gradient, and \(\theta\) is the angle between the gradient direction and the X direction; the gradient direction is the propagation direction;

[0024] And / or, the minor axis \(b2\) of the second ellipse satisfies the following relational expression:

[0025] Where x1 = x * cos(θ) - y * sin(θ), y1 = |y * cos(θ) + x * sin(θ)|, A5, B5, C5, D5, E5, F5 are the second minor axis regulation parameters, b20 is the minor axis value of the second ellipse at the gradient starting point, and θ is the angle between the gradient direction and the X direction; the gradient direction is the propagation direction.

[0026] Optionally, the number of propagation directions is one or more. The edge of the output grating close to the input grating is the first edge. The angles between the lines connecting the center of the input grating to the two boundaries of the first edge and the X-axis are α and β respectively, where α > 0 and β < 0, and the value range of θ is [β, α].

[0027] Optionally, A i , C i , D i and F i all have a value range of [-5, 5], and B i and E i all have a value range of [-3, 3]; where i takes values 1, 2, 3, 4, 5.

[0028] Optionally, the value range of gratingdepth0 is 0 to 70 nm.

[0029] Optionally, the value range of a10 is 50 to 800 nm, and / or the value range of b10 is 50 to 460 nm.

[0030] Optionally, the value range of S0 is 0 to 400 nm.

[0031] Optionally, the value range of a20 is 50 to 1000 nm, and / or the value range of b20 is 50 to 400 nm.

[0032] In a second aspect, the present invention also provides a near-eye display device, including a projection optical machine and the above-mentioned diffractive optical waveguide, and the projection optical machine is used to emit the image light.

[0033] In the technical solution of the present invention, the cross-sectional pattern of the grating structure unit of the diffractive optical waveguide is an asymmetric pattern formed by the overlapping of two first patterns and at least one second pattern. By changing the dimensions of each item in the first pattern and the second pattern, and / or the relative positional relationship between the second pattern and the first pattern, and the relative positional relationship between the two first patterns, the diffraction efficiency ratio of each diffraction order of the grating structure unit can be adjusted, and the diffraction efficiency of the required order at different positions when the grating structure unit is applied to the structural area of the diffractive optical waveguide can be improved. Moreover, each parameter gradually changes along the propagation direction of the image light, and the change in diffraction efficiency brought about by this gradual change of the parameter better meets the requirements of uniformity optimization and can achieve a better uniformity optimization effect. Description of the Drawings

[0034] Figure 1 FIG. 1 is a schematic structural diagram of a diffractive optical waveguide provided in the related art;

[0035] Figure 2 FIG. 2 is a schematic structural diagram of the basic diffraction order of a two-dimensional grating provided in the related art;

[0036] Figure 3 FIG. 3 is a schematic structural diagram of a two-dimensional output grating provided in an embodiment of the present invention;

[0037] Figure 4 FIG. 4 is a schematic structural diagram of a specific two-dimensional output grating provided in an embodiment of the present invention;

[0038] Figure 5 FIG. 5 is a schematic structural diagram of a two-dimensional coordinate system provided in an embodiment of the present invention;

[0039] Figure 6 FIG. 6 is a schematic structural diagram of a structure in which an output grating has multiple symmetric regions provided in an embodiment of the present invention;

[0040] Figure 7 FIG. 7 is a schematic structural diagram of a propagation direction, and the included angle between the line connecting the center of the input grating to the two boundaries of the first edge and the X-axis provided in an embodiment of the present invention;

[0041] Figure 8 FIG. 8 is a brightness distribution diagram of the output grating before modulation provided in an embodiment of the present invention;

[0042] Figure 9 FIG. 9 is a brightness distribution diagram of the output grating after modulation provided in an embodiment of the present invention. Detailed Embodiments

[0043] The present invention will be further described in detail below with reference to the drawings and embodiments. It can be understood that the specific embodiments described herein are only used to explain the present invention, rather than limiting the present invention. Additionally, it should be noted that for the sake of description, only parts related to the present invention are shown in the drawings, rather than all the structures.

[0044] The terms used in the embodiments of the present invention are for the purpose of describing specific embodiments only and are not intended to limit the present invention. It should be noted that the orientation terms such as "upper", "lower", "left", and "right" described in the embodiments of the present invention are described from the angles shown in the drawings and should not be construed as limiting the embodiments of the present invention. In addition, in the context, it should also be understood that when it is mentioned that an element is formed "on" or "under" another element, it can not only be directly formed "on" or "under" another element, but also be indirectly formed "on" or "under" another element through an intermediate element. The terms "first", "second", etc. are only used for descriptive purposes and do not indicate any order, quantity, or importance, but are only used to distinguish different components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0045] The term "comprising" and its variations used in the present invention are open-ended, that is, "including but not limited to". The term "based on" is "at least partially based on". The term "an embodiment" means "at least one embodiment".

[0046] It should be noted that the concepts such as "first" and "second" mentioned in the present invention are only used to distinguish the corresponding contents and are not used to limit the order or the interdependent relationship.

[0047] It should be noted that the modification of "one" and "a plurality" mentioned in the present invention is illustrative rather than restrictive. Those skilled in the art should understand that unless otherwise clearly specified in the context, it should be understood as "one or more".

[0048] Figure 3 The figure is a schematic structural diagram of a two-dimensional output grating provided for the embodiments of the present invention. Refer to Figure 3 As shown, the two-dimensional output grating 5 includes a plurality of grating structure units 2 arranged in an array; the cross-sectional pattern of the grating structure unit 2 is formed by the overlap of two first patterns and at least one second pattern, and the cross-sectional pattern is intercepted by a plane parallel to the surface of the substrate 1 where the two-dimensional output grating 5 is located; the centers of the two first patterns are separated by a preset distance and are located on the same straight line, and the two first patterns at least partially overlap; the center of the second pattern coincides with the center of the pattern formed by the two first patterns, the second pattern is a symmetric pattern and the axis of symmetry forms a preset angle with the straight line; at least one of the size of the first pattern, the size of the second pattern, the relative position between the second pattern and the first pattern, and the relative position between the two first patterns in the grating structure unit 2 gradually changes along the propagation direction when the image light propagates in the region where the plurality of grating structure units 2 arranged in an array are located, so that the diffraction efficiency along the propagation direction gradually increases.

[0049] Exemplarily, the cross-sectional pattern of the grating structure unit 2 can be formed by the overlap of two first patterns and one second pattern; the cross-sectional pattern of the grating structure unit 2 can also be formed by the overlap of two first patterns and two second patterns. Among them, the shape of the first pattern can be a rhombus shape, an elliptical shape, etc., and the shape of the second pattern can be a symmetric shape such as an elliptical shape. In addition, the positional relationship between the two first patterns can be arranged in the horizontal direction or the vertical direction. Thus, the size of the first pattern, the size of the second pattern, the relative position between the second pattern and the first pattern, and the relative position between the two first patterns can all be modulated to modulate the diffraction efficiency of different diffraction orders of the two-dimensional output grating 5, and then the diffraction efficiency of the required order in different regions of the two-dimensional output grating 5 can be specifically increased, so that more light energy is expanded in the waveguide exit pupil, making the waveguide exit pupil more uniform and improving the energy utilization rate at the same time.

[0050] Specifically, since there are usually multiple grating structure units 2 provided on the substrate 1, and each grating structure unit 2 includes at least two first patterns and at least one second pattern, in order to ensure the diffraction efficiency of the diffractive optical waveguide and improve the energy utilization rate of the diffractive optical waveguide, the shapes and structures of the multiple grating structure units 2 provided on the substrate 1 will not be exactly the same, but the grating structure units 2 will be arranged on the substrate 1 in a certain pattern according to the characteristics of the image light transmission on the diffractive optical waveguide to optimize the diffraction efficiency distribution in the entire grating region. Usually, when setting the grating structure unit 2 for the image light, at least one of the size of the first pattern, the size of the second pattern, the relative position between the second pattern and the first pattern, and the relative position between the two first patterns in the corresponding grating structure unit 2 gradually changes along the propagation direction of the image light when it propagates in the region where the multiple grating structure units are arranged in an array, so that the diffraction efficiency along the propagation direction of the image light gradually increases.

[0051] In the technical solution of the present invention, the cross-sectional pattern of the grating structure unit of the diffractive optical waveguide is an asymmetric pattern formed by the overlap of two first patterns and at least one second pattern. By changing the dimensions of the first pattern and the second pattern, and / or, the relative positional relationship between the second pattern and the first pattern, and the relative positional relationship between the two first patterns, the diffraction efficiency ratio of each diffraction order of the grating structure unit can be adjusted, and the diffraction efficiency of the required order at different positions when the grating structure unit is applied to the structural region of the diffractive optical waveguide can be increased. Moreover, each parameter gradually changes along the propagation direction of the image light, and the change in diffraction efficiency brought about by this gradual change in parameters better meets the requirements of uniformity optimization and can achieve a better uniformity optimization effect.

[0052] As an alternative embodiment, Figure 4This is a schematic structural diagram of a specific two-dimensional output grating provided by an embodiment of the present invention. Refer to Figure 4 As shown, the first figure is the first ellipse 21, and the second figure is the second ellipse 22. The two first ellipses 21 are the same and their major axes are located on a straight line. The extension direction of the major axis of the second ellipse 22 forms a preset angle with the extension direction of the major axis of the first ellipse 21; at least one of the height or depth gratingdepth of the grating structure unit 2 in the direction perpendicular to the plane of the substrate 1, the major axis dimension a1 of the first ellipse 21, the minor axis dimension b1 of the first ellipse 21, the preset distance S, the major axis dimension a2 of the second ellipse 22, and the minor axis dimension b2 of the second ellipse 22 gradually changes along the propagation direction when the image light travels in the area where the plurality of grating structure units 2 arranged in an array are located.

[0053] Specifically, the extension direction of the major axis of the second ellipse 22 forms a preset angle with the extension direction of the major axis of the first ellipse 21. Different sizes of the preset angle indicate different positional relationships between the two first ellipses 21 and at least one second ellipse 22 provided on the grating structure unit 2.

[0054] In addition, at least one of the height or depth gratingdepth of the grating structure unit 2 in the direction perpendicular to the plane of the substrate 1, the major axis dimension a1 of the first ellipse 21, the minor axis dimension b1 of the first ellipse 21, the preset distance S, the major axis dimension a2 of the second ellipse 22, and the minor axis dimension b2 of the second ellipse 22 gradually changes along the propagation direction when the image light travels in the area where the plurality of grating structure units 2 arranged in an array are located, so that the diffraction efficiency of the image light gradually increases along the propagation direction, which can improve the pupil uniformity of the diffractive optical waveguide and also improve the energy utilization rate of the diffractive optical waveguide.

[0055] Optionally, Figure 5 This is a schematic structural diagram of a two-dimensional coordinate system provided by an embodiment of the present invention. Refer to Figure 5 As shown, the diffractive optical waveguide includes an input grating 3 and an output grating 4. A plurality of grating structure units 2 arranged in an array are located in the area of the output grating 4. On the plane of the substrate 1, a two-dimensional coordinate system is established with the arrangement direction of the areas of the input grating 3 and the output grating 4 as the X direction and the direction perpendicular to the X direction as the Y direction; the coordinates of the center of the cross-sectional image of any one grating structure unit 2 in the two-dimensional coordinate system are (x, y).

[0056] The height gratingdepth of the grating structure unit 2 in the direction perpendicular to the plane of the substrate 1 satisfies the following relationship:

[0057]

[0058] where x1 = x * cos(θ) - y * sin(θ), y1 = |y * cos(θ) + x * sin(θ)|, A0, B0, C0, D0, E0, F0 are the height adjustment parameter groups, gratingdepth0 is the height value at the starting point of the gradient; θ is the angle between the gradient direction and the X direction; the gradient direction is the propagation direction;

[0059] and / or, the major axis a1 of the first ellipse 21 satisfies the following relational expression:

[0060] where x1 = x * cos(θ) - y * sin(θ), y1 = |y * cos(θ) + x * sin(θ)|, A1, B1, C1, D1, E1, F1 are the first major axis adjustment parameter groups, a10 is the major axis value of the first ellipse 21 at the starting point of the gradient; θ is the angle between the gradient direction and the X direction; the gradient direction is the propagation direction;

[0061] and / or, the minor axis b1 of the first ellipse 21 satisfies the following relational expression:

[0062] where x1 = x * cos(θ) - y * sin(θ), y1 = |y * cos(θ) + x * sin(θ)|, A2, B2, C2, D2, E2, F2 are the first minor axis adjustment parameter groups, b10 is the minor axis value of the first ellipse 21 at the starting point of the gradient; θ is the angle between the gradient direction and the X direction; the gradient direction is the propagation direction;

[0063] and / or, the distance S between the centers of the two first ellipses 21 satisfies the following relational expression:

[0064] where x1 = x * cos(θ) - y * sin(θ), y1 = |y * cos(θ) + x * sin(θ)|, A3, B3, C3, D3, E3, F3 are the spacing adjustment parameter groups, S0 is the spacing between the centers of the two first ellipses 21 at the starting point of the gradient; θ is the angle between the gradient direction and the X direction; the gradient direction is the propagation direction;

[0065] and / or, the major axis a2 of the second ellipse 22 satisfies the following relational expression:

[0066] where x1 = x * cos(θ) - y * sin(θ), y1 = |y * cos(θ) + x * sin(θ)|, A4, B4, C4, D4, E4, F4 are the second major axis adjustment parameter groups, a20 is the major axis value of the second ellipse 22 at the starting point of the gradient, θ is the angle between the gradient direction and the X direction; the gradient direction is the propagation direction;

[0067] And / or, the minor axis b2 of the second ellipse 22 satisfies the following relational expression:

[0068] where x1 = x * cos(θ) - y * sin(θ), y1 = |y * cos(θ) + x * sin(θ)|, A5, B5, C5, D5, E5, F5 are the second minor axis regulation parameters, b20 is the minor axis value of the second ellipse 22 at the starting point of the gradual change, and θ is the angle between the gradual change direction and the X direction; the gradual change direction is the propagation direction;

[0069] Specifically, after the grating structure unit 2 is arranged on the substrate 1, according to the grating structure unit 2, in each output grating 4, it can be known that the height gratingdepth of each grating structure unit 2 in the direction perpendicular to the plane where the substrate 1 is located, the major axis a1 of the first ellipse 21, the minor axis b1 of the first ellipse 21, the distance S between the centers of the two first ellipses 21, the major axis a2 of the second ellipse 22, and the minor axis b2 of the second ellipse 22 will gradually change along the propagation direction when the image light is transmitted in the area where the plurality of grating structure units 2 arranged in an array are located.

[0070] Reference Figure 5 As shown, in the two-dimensional coordinate system, if the magnitude of the central coordinate value (x, y) of a certain grating structure unit 2 is known, then according to x1 = x * cos(θ) - y * sin(θ) and y1 = |y * cos(θ) + x * sin(θ)|, the coordinates (x1, y1) can be calculated. Substitute the calculated (x1, y1) coordinate values into the above corresponding calculation formulas for gratingdepth, a1, b1, S, a2, and b2, and then combine with the regulation parameter group of the corresponding parameters and the initial parameter values corresponding to the grating structure unit 2 closest to the input grating 3, and finally the specific values of the height gratingdepth of the grating structure unit 2 in the direction perpendicular to the plane where the substrate 1 is located, the major axis a1 of the first ellipse 21, the minor axis b1 of the first ellipse 21, the distance S between the centers of the two first ellipses 21, the major axis a2 of the second ellipse 22, and the minor axis b2 of the second ellipse 22 can be calculated. When y1 < 0, θ > 0; when y1 > 0, θ < 0, and the initial point parameter values and the gradual change direction of each of the above parameters can be set independently.

[0071] In the variation formula of the aforementioned parameter gradient, it includes a first-order term and an indefinite-order term of the spatial distance. It itself has a certain degree of flexibility. Through the combination of the first-order term and the indefinite-order term, it can balance and avoid the unnecessary computational amount caused by too many function terms and too large a power exponent of the independent variable, and also has good flexibility, making the change in diffraction efficiency brought about by the change in parameters more in line with expectations and obtaining a better uniformity optimization effect. Moreover, compared with the variation relationships of other possible complex functions, the variation formula of the parameter gradient adopted in this application can well and flexibly balance the improvement degree of the diffraction optical waveguide performance optimization and the optimization computational amount.

[0072] Moreover, the gradual change of the parameters in this application means that the parameters change continuously and smoothly. The continuous and smooth change is not limited to the absolute continuity in the mathematical sense, and also includes the situation where the change rate of the parameters is within a certain allowable range that does not cause sudden changes. The change rate of the parameters is, for example, 1%, 2%, 5%, and 10%.

[0073] It should be noted that when the image light travels in the region where multiple grating structure units are arranged in an array, the propagation direction is not uniquely constant. The propagation directions of the image light in different fields of view are different, and the propagation directions of different diffraction orders after each diffraction are also different. In this application, the gradient direction of the parameters can be the microscopic propagation direction of the image light or the macroscopic propagation direction of the image light; the gradient direction of the parameters can be one or more, and the starting position of the parameter gradient can be one or more. Optionally, there can be multiple parameter gradients in one gradient direction, or different parameters can be changed respectively in multiple gradient directions, or the same parameters can be changed in multiple gradient directions, etc. There can be different starting points of the gradient in multiple gradient directions, or the same starting points of the gradient in multiple gradient directions.

[0074] Figure 6 It is a schematic structural diagram of an out-coupling grating provided by an embodiment of the present invention with multiple symmetric regions. Figure 7 It is a schematic structural diagram of the propagation direction, the included angle between the line connecting the center of the in-coupling grating to the two boundaries of the first edge and the X-axis provided by an embodiment of the present invention. Refer to Figure 6 and Figure 7 As shown, exemplarily, the range of the gradient direction can be defined in the following manner. Refer to Figure 6Define the edge of the output grating 4 close to the input grating 3 as the first edge 411. The angles between the lines connecting the center of the input grating 3 to the two boundaries of the first edge 411 and the X-axis are α and β respectively, where α > 0 and β < 0. The value range of the angle θ between the gradient direction and the X-axis is [β, α]. It can be understood that the above definition method is defined based on the transmission direction when the image light travels from the input grating to the output grating. However, after the image light diffracts in the output grating 4, the transmission direction of the image light also changes. At this time, more possible gradient directions can also be defined based on the new transmission direction.

[0075] Optionally, continue to refer to Figure 6 、 Figure 7 As shown, the propagation direction of the central field-of-view image light transmitted from the input grating 3 to the output grating 4 is perpendicular to the side boundary of the output grating 4 close to the input grating 3. In particular, when the symmetry axes of the input grating 3 and the output grating 4 are coaxial, there is a region in the output grating 4 where the grating structure units 2 are symmetric.

[0076] Refer to Figure 6 As shown, the output grating 4 includes multiple symmetric regions, and the mutually symmetric regions are symmetric about the symmetry axis 11. Exemplarily, when the symmetry axis 11 is perpendicular to the first edge 411, within the output grating 4 including the symmetry axis 11, since the grating structure units 2 are symmetrically distributed on both sides of the symmetry axis 11, when the image light propagates in this output grating 4, diffraction will occur after it propagates to the grating structure units 2 on both sides, and the diffraction efficiencies after diffraction are equal. Moreover, in this embodiment, the gradient direction includes the direction where the symmetry axis is located, and the parameters of the grating structure units 2 can also gradually change along the direction of the symmetry axis. For example, the minor axis and / or major axis dimensions of the first pattern gradually increase, so that the brightness of the image light finally emitted to the human eye is more uniform and higher, thereby improving the diffraction efficiency of the diffractive optical waveguide and enhancing the display effect. In addition, the grating structure units 2 on both sides of the symmetry axis 11 are also used to expand and transmit the image light to both sides. Therefore, the parameters of the grating structure units 2 can also gradually change along the new propagation direction. For example, the major axis dimension of the second pattern gradually increases, further enhancing the brightness and uniformity of the image light emitted to the human eye.

[0077] Since there may be a situation where the region shape of the output grating 4 is irregular, which may cause the symmetry axis 11 therein to be not perpendicular to the first edge 411, and the multiple grating structure units 2 therein are not symmetric in pairs with the symmetry axis 11 as the symmetry axis. Due to the limitation of the region shape, there may be some grating structures 2 that do not have symmetric grating structure units 2 on the opposite side of the symmetry axis 11.

[0078] It should be noted that Figure 6Only multiple grating structure units 2 on both sides of the symmetry axis 11 are exemplarily shown in the figure. In actual production, the setting of the grating structure units 2 can be adjusted according to the actual situation.

[0079] Reference Figure 7 , it can be understood that the value range of θ is [β, α], that is, β ≤ θ ≤ α, where α > 0 and β < 0. In this way, it can be ensured that when the image light is incident, it can all be incident into the diffraction region of the output grating 4 for diffraction, improving the diffraction efficiency of the diffraction optical waveguide.

[0080] Figure 8 This is the brightness distribution diagram before modulation of the output grating provided by the embodiment of the present invention. Figure 9 This is the brightness distribution diagram after modulation of the output grating provided by the embodiment of the present invention. Reference Figure 4 、 Figure 8 and Figure 9 As shown, where Fovx is the brightness value in the x direction, Fovy is the brightness value in the y direction, and the right legend represents the distribution value of the brightness and the color distribution of different brightnesses. It can be seen from the figure that by setting the output grating 4 as the Figure 4 shown grating structure unit 2, the brightness and brightness uniformity are greatly increased.

[0081] Optionally, the value ranges of A i 、C i 、D i and F i are all [-5, 5], and the value ranges of B i and E i are all [-3, 3]; where i takes values 1, 2, 3, 4, 5.

[0082] Among them, the values of A i 、C i 、D i and F i are between -5 and 5. For example, A i 、C i 、D i and F i can be -5, 0, 5, etc. The embodiment of the present invention does not limit the specific numerical relationship. The values of B i and E i are between -3 and 3. For example, B i and E i can be -3, 0, 3, etc. The embodiment of the present invention does not limit the specific numerical relationship. It should be noted that in the foregoing embodiments, the values of the parameters corresponding to the same physical meaning in the relational expressions can be the same or different, but they are independent of each other and determined according to the actual optimization situation. For example, the parameter A iWhen i takes values of 1, 2, 3, 4, and 5, the values are independent of each other and can be the same or different.

[0083] Optionally, the value range of gratingdepth0 is 0 to 70 nm.

[0084] Among them, the value of gratingdepth0 is between 0 and 70 nm. For example, gratingdepth0 can be 0, 20 nm, 30 nm, 50 nm, 70 nm, etc. The embodiments of the present invention do not limit the specific numerical relationship.

[0085] Optionally, the value range of a10 is 50 to 800 nm, and / or the value range of b10 is 50 to 460 nm.

[0086] Among them, the value of a10 is between 50 nm and 800 nm. For example, a10 can be 50 nm, 100 nm, 300 nm, 500 nm, 800 nm, etc. The embodiments of the present invention do not limit the specific numerical relationship. In addition, the value of b10 is between 50 nm and 460 nm. For example, b10 can be 50 nm, 150 nm, 200 nm, 400 nm, 460 nm, etc. The embodiments of the present invention do not limit the specific numerical relationship.

[0087] It can be understood that a10 > b10.

[0088] Optionally, the value range of S0 is 0 to 400 nm.

[0089] Among them, the value of S0 is between 0 and 400 nm. For example, S0 can be 0, 100 nm, 150 nm, 300 nm, 400 nm, etc. The embodiments of the present invention do not limit the specific numerical relationship.

[0090] Optionally, the value range of a20 is 50 to 1000 nm, and / or the value range of b20 is 50 to 400 nm.

[0091] Among them, the value of a20 is between 50 nm and 1000 nm. For example, a20 can be 50 nm, 200 nm, 500 nm, 800 nm, 1000 nm, etc. The embodiments of the present invention do not limit the specific numerical relationship. In addition, the value of b20 is between 50 nm and 400 nm. For example, b20 can be 50 nm, 150 nm, 200 nm, 300 nm, 400 nm, etc. The embodiments of the present invention do not limit the specific numerical relationship.

[0092] It should be noted that a20 > b20.

[0093] Based on the same inventive concept, an embodiment of the present invention further provides a near-eye display device, including a projection optical engine and the above-mentioned diffractive optical waveguide, and the projection optical engine is configured to emit image light. Since this near-eye display device has the technical features of the diffractive optical waveguide provided by the embodiment of the present invention, it can achieve the same beneficial effects as the diffractive optical waveguide provided by the embodiment of the present invention. The same parts are referred to the above description and will not be repeated here.

[0094] Exemplarily, the near-eye display device may include AR glasses and XR glasses.

[0095] Note that the above is only a preferred embodiment of the present invention and the applied technical principles. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein. Various obvious changes, re-adjustments, combinations with each other, and substitutions can be made by those skilled in the art without departing from the protection scope of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments. Without departing from the inventive concept of the present invention, it may further include more other equivalent embodiments, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. A diffractive optical waveguide, characterized in that, It includes a substrate and a plurality of grating structure units formed on the surface of the substrate and arranged in an array; The cross-sectional pattern of the grating structure unit is formed by the overlap of two first patterns and at least one second pattern, and the cross-sectional pattern is intercepted by a plane parallel to the surface of the substrate where the two-dimensional output grating is located; The centers of the two first patterns are separated by a preset distance and are located on the same straight line, and the two first patterns overlap at least partially; The center of the second pattern coincides with the center of the pattern formed by the two first patterns. The second pattern is a symmetric pattern and the axis of symmetry forms a preset angle with the straight line; At least one of the size of the first pattern, the size of the second pattern, the relative position between the second pattern and the first pattern, and the relative position between the two first patterns in the grating structure unit gradually changes along the propagation direction when the image light travels in the region where the plurality of grating structure units arranged in an array are located, so that the diffraction efficiency along the propagation direction gradually increases.

2. The diffractive optical waveguide according to claim 1, wherein, The first pattern is a first ellipse, the second pattern is a second ellipse, the two first ellipses are the same and the major axes are on the same straight line, and the included angle between the extension direction of the major axis of the second ellipse and the extension direction of the major axis of the first ellipse is the preset angle; At least one of the height or depth of the grating structure unit in the direction perpendicular to the plane of the substrate, the major axis dimension of the first ellipse, the minor axis dimension of the first ellipse, the distance between the preset distances, the major axis dimension of the second ellipse, and the minor axis dimension of the second ellipse gradually changes along the propagation direction when the image light travels in the region where the plurality of grating structure units arranged in an array are located.

3. The diffractive optical waveguide according to claim 2, characterized in that, The diffractive optical waveguide includes an input region and an output region. The plurality of grating structure units arranged in an array are located in the output region. In the plane of the substrate, taking the arrangement direction of the input region and the output region as the X direction and the direction perpendicular to the X direction as the Y direction, a two-dimensional coordinate system is established; the center of the cross-sectional image of any one of the grating structure units has coordinates (x, y) in the two-dimensional coordinate system; The height gratingdepth of the grating structure unit in the direction perpendicular to the plane of the substrate satisfies the following relationship: Wherein, x1 = x*cos(θ) - y*sin(θ), y1 = |y*cos(θ) + x*sin(θ)|, A0, B0, C0, D0, E0, F0 are a set of height adjustment parameters, gratingdepth0 is the height value at the starting point of the gradient; θ is the included angle between the gradient direction and the X direction; the gradient direction is the propagation direction; And / or, the major axis a1 of the first ellipse satisfies the following relational expression: Wherein, x1 = x*cos(θ) - y*sin(θ), y1 = |y*cos(θ) + x*sin(θ)|, A1, B1, C1, D1, E1, F1 are a set of major axis adjustment parameters for the first ellipse, a10 is the major axis value of the first ellipse at the starting point of the gradient; θ is the included angle between the gradient direction and the X direction; the gradient direction is the propagation direction; And / or, the minor axis b1 of the first ellipse satisfies the following relational expression: where x1 = x * cos(θ) - y * sin(θ), y1 = |y * cos(θ) + x * sin(θ)|, A2, B2, C2, D2, E2, F2 are the first minor axis adjustment parameter group, and b10 is the minor axis value of the first ellipse at the starting point of the gradient; θ is the angle between the gradient direction and the X direction; the gradient direction is the propagation direction; And / or, the distance S between the centers of the two first ellipses satisfies the following relational expression: where x1 = x * cos(θ) - y * sin(θ), y1 = |y * cos(θ) + x * sin(θ)|, A3, B3, C3, D3, E3, F3 are the spacing adjustment parameter group, and S0 is the spacing between the centers of the two first ellipses at the starting point of the gradient; θ is the angle between the gradient direction and the X direction; the gradient direction is the propagation direction; And / or, the major axis a2 of the second ellipse satisfies the following relational expression: where x1 = x * cos(θ) - y * sin(θ), y1 = |y * cos(θ) + x * sin(θ)|, A4, B4, C4, D4, E4, F4 are the second major axis adjustment parameter group, and a20 is the major axis value of the second ellipse at the starting point of the gradient, and θ is the angle between the gradient direction and the X direction; the gradient direction is the propagation direction; And / or, the minor axis b2 of the second ellipse satisfies the following relational expression: where x1 = x * cos(θ) - y * sin(θ), y1 = |y * cos(θ) + x * sin(θ)|, A5, B5, C5, D5, E5, F5 are the second minor axis adjustment parameters, and b20 is the minor axis value of the second ellipse at the starting point of the gradient, and θ is the angle between the gradient direction and the X direction; the gradient direction is the propagation direction.

4. The diffractive optical waveguide according to claim 3, wherein The number of the propagation directions is one or more. The edge of the output grating close to the input grating is the first edge. The angles between the lines connecting the center of the input grating to the two boundaries of the first edge and the X-axis are α and β respectively, where α > 0 and β < 0. The value range of θ is [β, α].

5. The diffractive optical waveguide according to claim 3, wherein A i , C i , D i and F i The value range of B is [-5, 5]. i and E i The value range of is [-3, 3]; among them, i takes values ​​of 1, 2, 3, 4, and 5.

6. The diffractive optical waveguide according to claim 3, wherein The value range of gratingdepth0 is 0 - 70 nm.

7. The diffractive optical waveguide according to claim 3, wherein, The value range of a10 is 50 - 800 nm, and / or the value range of b10 is 50 - 460 nm.

8. The diffractive optical waveguide according to claim 3, wherein The value range of S0 is 0 - 400 nm.

9. The diffractive optical waveguide according to claim 3, wherein The value range of a20 is 50 - 1000 nm, and / or the value range of b20 is 50 - 400 nm.

10. A near-eye display device, characterized in that, It includes a projection light machine and the diffractive optical waveguide according to any one of claims 1 - 9, and the projection light machine is used to emit the image light.

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