Micro-nano waveguide structure and augmented reality display device

Abstract

The present invention provides a micro-nano waveguide structure and an augmented reality display device, belonging to the technical field of grating waveguides, which includes a waveguide substrate, a first output grating, and a second output grating; the first output grating is located on the surface of the waveguide substrate, and the second output grating is superimposed on the side of the first output grating away from the waveguide substrate; both the first output grating and the second output grating are used to couple and output the total reflection diffracted light conducted in the waveguide substrate towards the human eye direction; the structures of the first output grating and the second output grating are different. The present invention couples and outputs the total reflection diffracted light conducted in the waveguide substrate towards the human eye direction through two output gratings with different structures. The two output gratings with different structures can jointly enhance the light energy coupled towards the human eye direction, and thus jointly weaken the light energy coupled towards the external environment, thereby reducing the intensity of the leaked light, reducing the light leakage of the two-dimensional grating waveguide, and improving the diffraction efficiency of the two-dimensional grating waveguide.

Description

Technical Field

[0001] The present invention relates to the technical field of grating waveguides, and in particular to a micro-nano waveguide structure and an augmented reality display device. Background Art

[0002] Augmented Reality (AR) technology is a technology that integrates virtual information generated by a computer with the real world. An AR display device represented by AR glasses transmits the image of a microdisplay to the human eye through an optical imaging element (such as a metasurface grating waveguide), and its perspective characteristic enables real scenes to be simultaneously projected into the human eye, greatly enhancing the real experience. The unit structure of the metasurface grating waveguide is close to λ / 10. Based on the optical path accumulation effect of the traditional diffraction grating depending on the periodic structure, each unit structure of the metasurface grating adds a sudden phase on the surface based on the resonance effect, and can arbitrarily control the spatial phase distribution of diffracted lights of each order, promising to greatly improve the diffraction efficiency of the grating waveguide.

[0003] A two-dimensional grating waveguide includes a one-dimensional coupling grating and a two-dimensional output grating. The two-dimensional output grating has both the functions of expansion and output. After the diffracted light generated by the diffraction of the one-dimensional coupling grating is conducted to the two-dimensional output grating, it will be diffracted into two parts of diffracted light. One part of the diffracted light is conducted in the direction of the human eye and enters the human eye for imaging, and the other part of the diffracted light is coupled and output to the external environment, forming light leakage.

[0004] The current two-dimensional grating waveguide has the problems of strong light energy coupled out to the external environment and much light leakage, which not only reduces the diffraction efficiency, but also the diffracted light entering the external environment can be seen by others, resulting in the leakage of user privacy. Summary of the Invention

[0005] The present invention provides a micro-nano waveguide structure and an augmented reality display device to solve the technical problem of much light leakage in the two-dimensional grating waveguide in the prior art, reduce the light leakage of the two-dimensional grating waveguide, and improve the diffraction efficiency of the two-dimensional grating waveguide.

[0006] The present invention provides a micro-nano waveguide structure, including a waveguide substrate, and the micro-nano waveguide structure further includes a first output grating and a second output grating;

[0007] The first output grating is located on the surface of the waveguide substrate, and the second output grating is superimposed on the side of the first output grating away from the waveguide substrate;

[0008] Both the first output grating and the second output grating are used to couple and output the total reflection diffracted light conducted in the waveguide substrate in the direction of the human eye;

[0009] The structures of the first output grating and the second output grating are different.

[0010] According to a micro-nano waveguide structure provided by the present invention, the first output grating includes two overlapping first diffractive optical elements, the second output grating includes two overlapping second diffractive optical elements, and the structures of the first diffractive optical element and the second diffractive optical element are different;

[0011] Each of the first diffractive optical elements is configured to couple the total reflection diffracted light to the other first diffractive optical element, and couple the light to the human eye for output;

[0012] Each of the second diffractive optical elements is configured to couple the total reflection diffracted light to the other second diffractive optical element, and couple the light to the human eye for output.

[0013] According to a micro-nano waveguide structure provided by the present invention, the first diffractive optical element is formed by arranging a plurality of I-shaped structures in an array, and the middle parts of the corresponding two I-shaped structures in the two first diffractive optical elements overlap each other.

[0014] According to a micro-nano waveguide structure provided by the present invention, the second diffractive optical element is formed by arranging a plurality of linear structures in an array, and the middle parts of the corresponding two linear structures in the two second diffractive optical elements overlap each other.

[0015] According to a micro-nano waveguide structure provided by the present invention, the first output grating is formed by arranging a herringbone structure array formed by connecting the tails of three T-shaped structures, wherein one of the first diffractive optical elements includes the T-shaped structures at the lower left of each herringbone structure, and the other first diffractive optical element includes the T-shaped structures at the lower right of each herringbone structure, and the two first diffractive optical elements simultaneously include the T-shaped structures above each herringbone structure.

[0016] According to a micro-nano waveguide structure provided by the present invention, the second output grating is formed by arranging a herringbone structure array formed by connecting the ends of three linear structures, wherein one of the second diffractive optical elements includes the linear structures at the lower left of each herringbone structure, and the other second diffractive optical element includes the linear structures at the lower right of each herringbone structure, and the two second diffractive optical elements simultaneously include the linear structures above each herringbone structure.

[0017] According to a micro-nano waveguide structure provided by the present invention, the first diffractive optical element is formed by arranging a plurality of first structural units with a T-shaped head and a linear tail in an array, and the middle parts of the corresponding two first structural units in the two first diffractive optical elements overlap each other.

[0018] A micro-nano waveguide structure provided by the present invention, wherein the second diffractive optical element is formed by arranging a plurality of second structural units with both the head and the tail being in a straight shape in an array, and the middle parts of the two corresponding second structural units in the two second diffractive optical elements overlap with each other.

[0019] A micro-nano waveguide structure provided by the present invention further includes an input grating, which is located on the surface of the waveguide substrate and is used for diffracting incident light to generate the total reflection diffracted light.

[0020] The present invention also provides an augmented reality display device, including any one of the above micro-nano waveguide structures.

[0021] The micro-nano waveguide structure and the augmented reality display device provided by the present invention couple and output the total reflection diffracted light conducted in the waveguide substrate towards the human eye through two output gratings with different structures. The two output gratings with different structures can jointly enhance the light energy coupled towards the human eye, and thus jointly weaken the light energy coupled towards the external environment, thereby reducing the intensity of the leaked light, reducing the light leakage of the two-dimensional grating waveguide, and improving the diffraction efficiency of the two-dimensional grating waveguide. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0023] Figure 1 is a side view of a two-dimensional grating waveguide in the prior art.

[0024] Figure 2 is a top view of a two-dimensional grating waveguide in the prior art.

[0025] Figure 3 is one of the structural schematic diagrams of the micro-nano waveguide structure provided by the present invention.

[0026] Figure 4 is one of the structural schematic diagrams of the first output grating provided by the present invention.

[0027] Figure 5 is one of the structural schematic diagrams of the second output grating provided by the present invention.

[0028] Figure 6 is one of the schematic diagrams showing the change of the diffraction efficiency with the incident angle provided by the present invention. [[ID=..]]

[0029] Figure 7It is a schematic diagram showing the effect of suppressing light leakage by the micro-nano waveguide structure provided by the present invention.

[0030] Figure 8 It is the second schematic diagram of the structure of the first output grating provided by the present invention.

[0031] Figure 9 It is the second schematic diagram of the structure of the second output grating provided by the present invention.

[0032] Figure 10 It is the second schematic diagram showing the variation of the diffraction efficiency with the incident angle provided by the present invention.

[0033] Figure 11 It is the third schematic diagram of the structure of the first output grating provided by the present invention.

[0034] Figure 12 It is the third schematic diagram of the structure of the second output grating provided by the present invention.

[0035] Figure 13 It is the third schematic diagram showing the variation of the diffraction efficiency with the incident angle provided by the present invention. Detailed implementation manners

[0036] To make the objectives, technical solutions and advantages of the present invention clearer, the technical solutions in the present invention will be clearly and completely described below with reference to the accompanying drawings in the present invention. Obviously, the described embodiments are some but not all of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present invention without making creative efforts shall fall within the protection scope of the present invention.

[0037] It should be noted that in the description of the present invention, the terms "include", "comprise" or any other variant thereof are intended to cover non-exclusive inclusion, such that a process, method, article or device comprising a series of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "comprising a..." does not exclude the presence of additional identical elements in the process, method, article or device comprising the element. The terms "upper", "lower", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation of the present invention. Unless otherwise expressly specified and limited, the terms "mount", "connect", "couple" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and can be the communication inside two elements. 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.

[0038] The terms "first", "second", etc. in the present invention are used to distinguish similar objects and are not used to describe a specific order or sequence. It should be understood that such data can be interchanged under appropriate circumstances so that the embodiments of the present invention can be implemented in an order other than those illustrated or described herein, and the objects distinguished by "first", "second", etc. are generally of the same category and do not limit the number of objects. For example, the first object can be one or multiple. In addition, "and / or" means at least one of the connected objects, and the character " / " generally indicates an "or" relationship between the associated objects before and after.

[0039] The following Figures 1-10 describes the micro-nano waveguide structure and augmented reality display device provided by the present invention, aiming to couple the total reflection diffracted light conducted in the waveguide substrate to the human eye direction through two output gratings with different structures, reduce the light leakage of the two-dimensional grating waveguide, and improve the diffraction efficiency of the two-dimensional grating waveguide.

[0040] Such as Figure 1 and Figure 2As shown, a two-dimensional grating waveguide generally includes an input grating 10, a waveguide substrate 11, and a two-dimensional output grating 12. Both the input grating 10 and the two-dimensional output grating 12 are located on the surface of the waveguide substrate 11. The input grating 10 is used to diffract incident light to generate total reflection diffracted light, and the total reflection diffracted light is conducted in the waveguide substrate 11 in a total reflection manner towards the two-dimensional output grating 12. When it reaches the two-dimensional output grating 12, diffraction occurs to generate two parts of diffracted light. One part of the diffracted light is conducted towards the human eye 13 and enters the human eye for imaging, and the other part of the diffracted light is coupled and output to the external environment, causing light leakage.

[0041] In some embodiments, the material of the waveguide substrate 11 can be glass, polymer, or other materials transparent to visible light, and its form is a flat plate with two smooth surfaces; the input grating 10 and the two-dimensional output grating 12 can be located on the same surface or different surfaces of the waveguide substrate 11, and the input grating 10 and the two-dimensional output grating 12 can be prepared by photolithography or nanoimprinting technology; the incident light can be light with image information output by a microdisplay.

[0042] Generally, in order to reduce light leakage, a single-layer two-dimensional output grating with the function of reducing light leakage can be used, but the effect of reducing light leakage of the single-layer two-dimensional output grating is poor.

[0043] Figure 3 is a schematic structural diagram of the micro-nano waveguide structure provided by the present invention. As Figure 3 shown, it includes a waveguide substrate 11, a first output grating 14, and a second output grating 15;

[0044] The first output grating 14 is located on the surface of the waveguide substrate 11, and the second output grating 15 is superimposed on the side of the first output grating 14 away from the waveguide substrate 11;

[0045] Both the first output grating 14 and the second output grating 15 are used to couple and output the total reflection diffracted light conducted in the waveguide substrate 11 towards the human eye 13;

[0046] The structures of the first output grating 14 and the second output grating 15 are different.

[0047] Among them, both the first output grating 14 and the second output grating 15 can be two-dimensional gratings.

[0048] Considering that if the structures of the first output grating 14 and the second output grating 15 are the same, then the superposition of the first output grating 14 and the second output grating 15 is equivalent to a single-layer output grating with a higher height, and the effect of reducing light leakage is still very poor. Therefore, the structures of the first output grating 14 and the second output grating 15 need to be different.

[0049] It can be understood that since both the first output grating 14 and the second output grating 15 are used to couple and output the total reflection diffracted light conducted in the waveguide substrate 11 in the direction of the human eye, the first output grating 14 and the second output grating 15 can jointly enhance the light energy coupled in the direction of the human eye, and thus jointly weaken the light energy coupled to the external environment, thereby reducing the intensity of the leakage light, reducing the light leakage of the two-dimensional grating waveguide, and improving the diffraction efficiency of the two-dimensional grating waveguide.

[0050] That is to say, in the present invention, the total reflection diffracted light conducted in the waveguide substrate 11 is coupled and output in the direction of the human eye through two output gratings with different structures, which can reduce the light leakage of the two-dimensional grating waveguide and improve the diffraction efficiency of the two-dimensional grating waveguide.

[0051] In some embodiments, the first output grating 14 of the present invention may include two overlapping first diffractive optical elements, and the second output grating 15 may include two overlapping second diffractive optical elements, and the structures of the first diffractive optical element and the second diffractive optical element are different;

[0052] Each first diffractive optical element is used to couple the total reflection diffracted light to another first diffractive optical element, and to couple and output the light in the direction of the human eye;

[0053] Each second diffractive optical element is used to couple the total reflection diffracted light to another second diffractive optical element, and to couple and output the light in the direction of the human eye.

[0054] Specifically, any one of the first diffractive optical elements can couple the total reflection diffracted light to another first diffractive optical element, and can also couple the light coupled by another first diffractive optical element in the direction of the human eye.

[0055] Specifically, any one of the second diffractive optical elements can couple the total reflection diffracted light to another second diffractive optical element, and can also couple the light coupled by another second diffractive optical element in the direction of the human eye.

[0056] The function of the first output grating 14 to couple and output the total reflection diffracted light in the direction of the human eye can be realized by the coupling and output of light by two overlapping first diffractive optical elements, and the function of the second output grating 15 to couple and output the total reflection diffracted light in the direction of the human eye can also be realized by the coupling and output of light by two overlapping second diffractive optical elements.

[0057] In some embodiments, such as Figure 4 、 Figure 8 and Figure 11As shown, one of the first diffractive optical elements 141 rotates clockwise along the z-axis, and the other first diffractive optical element 141 rotates counterclockwise along the z-axis. The included angle formed by the two first diffractive optical elements 141 is , which can be 30 - 100 degrees, for example, 60 degrees.

[0058] In some embodiments, such as Figure 5 , Figure 9 and Figure 12 shown, one of the second diffractive optical elements 151 rotates clockwise along the z-axis, and the other second diffractive optical element 151 rotates counterclockwise along the z-axis. The included angle formed by the two second diffractive optical elements 151 is , which can also be 30 - 100 degrees, for example, 60 degrees.

[0059] In some embodiments, such as Figure 4 shown, the first diffractive optical element 141 of the present invention can be formed by arranging a plurality of I-shaped structures in an array, and the middle parts of the corresponding two I-shaped structures in the two first diffractive optical elements 141 overlap each other.

[0060] Through the I-shaped structure, any one of the first diffractive optical elements 141 can couple the total reflection diffracted light to the other first diffractive optical element 141, and the other first diffractive optical element 141 can couple the light out towards the human eye.

[0061] In some embodiments, such as Figure 5 shown, the second diffractive optical element 151 of the present invention can be formed by arranging a plurality of linear structures in an array, and the middle parts of the corresponding two linear structures in the two second diffractive optical elements 151 overlap each other.

[0062] Through the linear structure, any one of the second diffractive optical elements 151 can couple the total reflection diffracted light to the other second diffractive optical element 151, and the other second diffractive optical element 151 can couple the light out towards the human eye.

[0063] It should be noted that since the first diffractive optical element 141 and the second diffractive optical element 151 of the present invention are both arrays, each structural unit of the first diffractive optical element 141 corresponds to and aligns with each structural unit of the second diffractive optical element 151.

[0064] The first output grating 14 and the second output grating 15 can evenly expand the conduction and output of the total reflection diffracted light in the output grating region, generating diffraction orders such as (0,0)R, (1,-1)R, (1,1)R, (2,0)R, and (2,0)T. Among them, (0,0)R is the continuation of the total reflection diffracted light with no change in direction; (1,-1)R and (1,1)R are the expansion conduction orders, causing the diffracted light to expand along the x and y directions within the waveguide substrate 11; (2,0)R and (2,0)T are the reflection and transmission output orders, respectively reflecting and transmitting perpendicularly to the plane where the output grating is located outside the waveguide substrate 11. (2,0)R is output towards the human eye direction and enters the human eye for imaging, while (2,0)T is output to the external environment, causing light leakage. The objective of the present invention is to enhance (2,0)R and weaken (2,0)T.

[0065] During the experiment, first, the first output grating 14 with a height of 80 nm Figure 4 shown was used alone as the output grating, and the diffraction efficiencies of (2,0)R and (2,0)T with respect to the incident angle (the angle between the incident light and the total reflection diffracted light generated by the input grating 10 and the waveguide normal) were calculated as Figure 6 shown in single-layer R and single-layer T. When the incident angles were 40°, 60°, and 80°, the ratios of (2,0)R to (2,0)T were 1.49, 1.47, and 1.33, respectively. That is to say, when the incident angle changes, the diffraction efficiencies of (2,0)R and (2,0)T are close, and the light energy output to the external environment is relatively strong, indicating that the effect of reducing light leakage by the single-layer output grating is poor.

[0066] Next, the first output grating 14 with a height of 40 nm Figure 4 shown was superimposed with the second output grating 15 with a height of 40 nm Figure 5 shown and used together as the output grating, and the diffraction efficiencies of (2,0)R and (2,0)T with respect to the incident angle were calculated as Figure 6 shown in double-layer 1-R and double-layer 1-T. When the incident angles were 40°, 60°, and 80°, the ratios of (2,0)R to (2,0)T were 6.47, 3.77, and 3.11, respectively. When the incident angle changes, the diffraction efficiency of (2,0)R is always greater than that of (2,0)T. Compared with the single-layer output grating, the diffraction efficiency of (2,0)R increases and the diffraction efficiency of (2,0)T decreases. As a result, the ratio of (2,0)R to (2,0)T increases, indicating that the light energy output towards the human eye direction increases and the light energy output to the external environment decreases, thereby reducing the leakage light intensity.

[0067] Next, the first output grating 14 with a height of 40 nm Figure 4 shown was superimposed with the second output grating 15 with a height of 60 nm Figure 5The second output grating 15 shown is superimposed and used as the output grating together. The diffraction efficiencies of (2,0)R and (2,0)T varying with the incident angle are calculated as Figure 6 shown in double-layer 2-R and double-layer 2-T. When the incident angles are 40°, 60°, and 80°, the ratios of (2,0)R to (2,0)T are 6.58, 3.7, and 3.09 respectively. After the height of the second output grating 15 increases, the diffraction efficiency of (2,0)R is much greater than that of (2,0)T, and compared with the single-layer output grating, the diffraction efficiency of (2,0)R increases more, while the diffraction efficiency of (2,0)T remains nearly unchanged, thereby reducing the intensity of the leakage light.

[0068] It can be understood that when the output grating is a double-layer structure composed of the first output grating 14 and the second output grating 15, the light energy of the diffracted light conducted towards the human eye and entering the human eye for imaging is increased, while the light energy of the diffracted light coupled and output to the external environment is reduced, thereby achieving the effect of reducing light leakage, as Figure 7 shown.

[0069] In some embodiments, as Figure 8 shown, the first output grating 14 of the present invention can also be formed by arranging an array of herringbone structures formed by connecting the tails of three T-shaped structures to each other. One first diffractive optical element 141 includes the T-shaped structure at the lower left of each herringbone structure, and another first diffractive optical element 141 includes the T-shaped structure at the lower right of each herringbone structure. The two first diffractive optical elements 141 simultaneously include the T-shaped structure above each herringbone structure.

[0070] It can be understood that the T-shaped structure is composed of a horizontal structure and a vertical structure, and the tail of the T-shaped structure is the free end of the vertical structure.

[0071] Through the herringbone structure, any one of the first diffractive optical elements 141 can couple the total reflection diffracted light to another first diffractive optical element 141, and the other first diffractive optical element 141 can couple the light towards the human eye.

[0072] In some embodiments, as Figure 9 shown, the second output grating 15 of the present invention can also be formed by arranging an array of herringbone structures formed by connecting the ends of three linear structures to each other. One second diffractive optical element 151 includes the linear structure at the lower left of each herringbone structure, and another second diffractive optical element 151 includes the linear structure at the lower right of each herringbone structure. The two second diffractive optical elements 151 simultaneously include the linear structure above each herringbone structure.

[0073] Through the herringbone structure, any one of the second diffractive optical elements 151 can couple the total reflection diffracted light to another second diffractive optical element 151, and the other second diffractive optical element 151 can couple the light out towards the human eye.

[0074] During the experiment, first, the first output grating 14 with a height of 80 nm Figure 8 shown in the figure was used alone as the output grating, and the diffraction efficiencies of (2,0)R and (2,0)T varying with the incident angle were calculated as Figure 10 shown in single-layer R and single-layer T. When the incident angles were 40°, 60°, and 80°, the ratios of (2,0)R to (2,0)T were 1.72, 2.07, and 2.99 respectively. That is to say, when the incident angle changes, the diffraction efficiencies of (2,0)R and (2,0)T are close, and the light energy coupled out to the external environment is strong, indicating that the effect of reducing light leakage by the single-layer output grating is poor.

[0075] Then, the first output grating 14 with a height of 40 nm Figure 8 shown in the figure was superimposed with the second output grating 15 with a height of 40 nm Figure 9 shown in the figure and used together as the output grating, and the diffraction efficiencies of (2,0)R and (2,0)T varying with the incident angle were calculated as Figure 10 shown in double-layer 1-R and double-layer 1-T. When the incident angles were 40°, 60°, and 80°, the ratios of (2,0)R to (2,0)T were 2.29, 3.34, and 2.4 respectively. When the incident angle changes, the diffraction efficiency of (2,0)R is always greater than that of (2,0)T, and compared with the single-layer output grating, the diffraction efficiency of (2,0)R increases and the diffraction efficiency of (2,0)T basically remains unchanged. Therefore, the ratio of (2,0)R to (2,0)T increases, indicating that the light energy coupled out towards the human eye increases and the light energy coupled out to the external environment decreases, thereby reducing the leakage light intensity.

[0076] Then, the first output grating 14 with a height of 40 nm Figure 8 shown in the figure was superimposed with the second output grating 15 with a height of 60 nm Figure 9 shown in the figure and used together as the output grating, and the diffraction efficiencies of (2,0)R and (2,0)T varying with the incident angle were calculated as Figure 10 shown in double-layer 2-R and double-layer 2-T. When the incident angles were 40°, 60°, and 80°, the ratios of (2,0)R to (2,0)T were 2.35, 2.98, and 2.14 respectively. After the height of the second output grating 15 increases, the diffraction efficiency of (2,0)R is much greater than that of (2,0)T, and compared with the single-layer output grating, the diffraction efficiency of (2,0)R increases more, thereby reducing the leakage light intensity.

[0077] In some embodiments, as Figure 11As shown, the first diffractive optical element 141 of the present invention can also be formed by arranging a plurality of first structural units 1411 with a T-shaped head and a linear tail in an array, and the middle parts of the corresponding two first structural units 1411 in the two first diffractive optical elements 141 overlap each other.

[0078] Through the first structural units 1411 with overlapping middle parts, any one of the first diffractive optical elements 141 can couple the total reflection diffracted light to another first diffractive optical element 141, and the other first diffractive optical element 141 can couple the light out towards the human eye.

[0079] In some embodiments, as Figure 12 shown, the second diffractive optical element 151 of the present invention can also be formed by arranging a plurality of second structural units 1511 with linear heads and tails in an array, and the middle parts of the corresponding two second structural units 1511 in the two second diffractive optical elements 151 overlap each other.

[0080] Through the second structural units 1511 with overlapping middle parts, any one of the second diffractive optical elements 151 can couple the total reflection diffracted light to another second diffractive optical element 151, and the other second diffractive optical element 151 can couple the light out towards the human eye.

[0081] During the experiment, first, the first output grating 14 with a height of 80 nm Figure 11 shown was used alone as the output grating, and the diffraction efficiencies of (2,0)R and (2,0)T varying with the incident angle were calculated as Figure 13 shown in single-layer R and single-layer T. When the incident angles were 40°, 60°, and 80°, the ratios of (2,0)R to (2,0)T were 1.29, 1.29, and 1.25 respectively. That is to say, when the incident angle changes, the diffraction efficiencies of (2,0)R and (2,0)T are close, and the light energy coupled out to the external environment is strong, indicating that the effect of reducing light leakage of the single-layer output grating is poor.

[0082] Then, the first output grating 14 with a height of 40 nm Figure 11 shown was superimposed with the second output grating 15 with a height of 40 nm Figure 12 shown and used together as the output grating, and the diffraction efficiencies of (2,0)R and (2,0)T varying with the incident angle were calculated as Figure 13As shown by the double-layer 1-R and double-layer 1-T. When the incident angles are 40°, 60°, and 80°, the ratios of (2,0)R to (2,0)T are 2.62, 2.4, and 2.3 respectively. When the incident angle changes, the diffraction efficiency of (2,0)R is always greater than that of (2,0)T. Moreover, compared with the single-layer output grating, the diffraction efficiency of (2,0)T drops significantly, so that the ratio of (2,0)R to (2,0)T increases, indicating that the light energy coupled out towards the human eye direction increases while the light energy coupled out towards the external environment decreases, thereby reducing the leakage light intensity.

[0083] Then, the first output grating 14 with a height of 40 nm Figure 11 shown in the figure and the second output grating 15 with a height of 60 nm Figure 12 shown in the figure are superimposed and used together as the output grating, and the diffraction efficiencies of (2,0)R and (2,0)T changing with the incident angle are calculated as Figure 13 shown by the double-layer 2-R and double-layer 2-T. When the incident angles are 40°, 60°, and 80°, the ratios of (2,0)R to (2,0)T are 2.84, 2.68, and 2.58 respectively. After the height of the second output grating 15 increases, the diffraction efficiency of (2,0)R is much greater than that of (2,0)T. Moreover, compared with the single-layer output grating, the diffraction efficiency of (2,0)R increases slightly while the diffraction efficiency of (2,0)T drops significantly, thereby reducing the leakage light intensity.

[0084] The present invention also provides an augmented reality display device, including any one of the above-mentioned micro-nano waveguide structures. The micro-nano waveguide structure includes a waveguide substrate 11, a first output grating 14, and a second output grating 15; the first output grating 14 is located on the surface of the waveguide substrate 11, and the second output grating 15 is superimposed on the side of the first output grating 14 away from the waveguide substrate 11; both the first output grating 14 and the second output grating 15 are used to couple and output the total reflection diffracted light conducted in the waveguide substrate 11 towards the human eye direction; the structures of the first output grating 14 and the second output grating 15 are different.

[0085] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A micro-nano waveguide structure, comprising a waveguide substrate, characterized in that, The micro-nano waveguide structure further includes a first output grating and a second output grating; The first output grating is located on the surface of the waveguide substrate, and the second output grating is superimposed on a side of the first output grating away from the waveguide substrate; Both the first output grating and the second output grating are used to couple and output the total reflection diffracted light conducted in the waveguide substrate in the direction of the human eye; The structures of the first output grating and the second output grating are different; The first output grating includes two overlapping first diffractive optical elements, and the second output grating includes two overlapping second diffractive optical elements. The structures of the first diffractive optical element and the second diffractive optical element are different; Each of the first diffractive optical elements is used to couple the total reflection diffracted light to the other first diffractive optical element and to couple and output the light in the direction of the human eye; Each of the second diffractive optical elements is used to couple the total reflection diffracted light to the other second diffractive optical element and to couple and output the light in the direction of the human eye; The respective structural units of the first diffractive optical element and the second diffractive optical element are in one-to-one correspondence and alignment.

2. The micro-nano waveguide structure according to claim 1, characterized in that The first diffractive optical element is formed by an array arrangement of a plurality of I-shaped structures, and the middles of the corresponding two I-shaped structures in the two first diffractive optical elements overlap each other.

3. The micro-nano waveguide structure according to claim 1 or 2, characterized in that, The second diffractive optical element is formed by an array arrangement of a plurality of linear structures, and the middles of the corresponding two linear structures in the two second diffractive optical elements overlap each other.

4. The micro-nano waveguide structure according to claim 1, characterized in that, The first output grating is formed by an array arrangement of a herringbone structure formed by connecting the tails of three T-shaped structures. One of the first diffractive optical elements includes the T-shaped structures at the lower left of each herringbone structure, and the other first diffractive optical element includes the T-shaped structures at the lower right of each herringbone structure. The two first diffractive optical elements simultaneously include the T-shaped structures above each herringbone structure.

5. The micro-nano waveguide structure according to claim 1 or 4, characterized in that, The second output grating is formed by an array arrangement of a herringbone structure formed by connecting the ends of three linear structures. One of the second diffractive optical elements includes the linear structures at the lower left of each herringbone structure, and the other second diffractive optical element includes the linear structures at the lower right of each herringbone structure. The two second diffractive optical elements simultaneously include the linear structures above each herringbone structure.

6. The micro-nano waveguide structure according to claim 1, characterized in that, The first diffractive optical element is formed by an array arrangement of a plurality of first structural units with a T-shaped head and a linear tail, and the middles of the corresponding two first structural units in the two first diffractive optical elements overlap each other.

7. The micro-nano waveguide structure according to claim 1 or 6, characterized in that The second diffractive optical element is formed by an array arrangement of a plurality of second structural units with both a head and a tail being linear, and the middles of the corresponding two second structural units in the two second diffractive optical elements overlap each other.

8. The micro-nano waveguide structure according to claim 1, characterized in that, It further includes an input grating. The input grating is located on the surface of the waveguide substrate, and the input grating is used to diffract incident light to generate the total reflection diffracted light.

9. An augmented reality display device, characterized in that, It includes the micro-nano waveguide structure according to any one of claims 1-8.

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