Micro-nano waveguide structure and augmented reality display device

Abstract

The invention provides a micro-nano waveguide structure and an augmented reality display device, and belongs to the technical field of grating waveguides, and the micro-nano waveguide structure comprises a waveguide substrate, a first out-coupling grating and a second out-coupling grating. The first coupling-out grating is located on the surface of the waveguide substrate, and the second coupling-out grating is stacked on the side, away from the waveguide substrate, of the first coupling-out grating; the first coupling-out grating and the second coupling-out grating are both used for coupling and outputting total reflection diffraction light conducted in the waveguide substrate towards the direction of human eyes; the first coupling-out grating and the second coupling-out grating are different in structure. Total reflection diffraction light conducted in the waveguide substrate is coupled and output towards the human eye direction through the two layers of coupling-out gratings with different structures, the two layers of coupling-out gratings with different structures can jointly enhance light energy coupled out towards the human eye direction, and then light energy coupled out towards the external environment is jointly weakened. Therefore, the intensity of leaked light is reduced, the light leakage of the two-dimensional grating waveguide is reduced, and the diffraction efficiency of the two-dimensional grating waveguide is improved.

Description

Technical Field

[0001] The present invention relates to the field of grating waveguide technology, 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 computer-generated virtual information with the real world. AR display devices represented by AR glasses transmit the images of micro displays to the human eye through optical imaging elements (such as metasurface grating waveguides), and their perspective characteristics allow real scenes to be reflected in the human eye at the same time, greatly enhancing the sense of reality. The unit structure of the metasurface grating waveguide is close to λ / 10. On the basis of the optical path accumulation effect of the traditional diffraction grating that relies on the periodic structure, each unit structure of the metasurface grating adds a sudden phase on the surface based on the resonance effect, which can arbitrarily control the spatial phase distribution of each level of diffracted light, and is expected to greatly improve the diffraction efficiency of the grating waveguide.

[0003] The two-dimensional grating waveguide includes a one-dimensional coupling-in grating and a two-dimensional coupling-out grating. The two-dimensional coupling-out grating has both expansion and coupling-out functions. The diffraction light generated by the one-dimensional coupling-in grating is transmitted to the two-dimensional coupling-out grating and then diffracted to generate two parts of diffraction light. One part of the diffraction light is transmitted toward the human eye and enters the human eye for imaging, and the other part of the diffraction light is coupled out to the external environment to form light leakage.

[0004] The current two-dimensional grating waveguide has the problem of strong light energy coupled to the external environment and causing a lot of light leakage. Not only does it reduce the diffraction efficiency, but the diffracted light that enters the external environment can also be seen by others, causing the user's privacy to be leaked. Summary of the invention

[0005] The present invention provides a micro-nano waveguide structure and an augmented reality display device, which are used to solve the technical problem of excessive light leakage of a 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, comprising a waveguide substrate, wherein the micro-nano waveguide structure further comprises a first outcoupling grating and a second outcoupling grating; The first out-coupling grating is located on the surface of the waveguide substrate, and the second out-coupling grating is superimposed on a side of the first out-coupling grating away from the waveguide substrate; The first out-coupling grating and the second out-coupling grating are both used to couple out the total reflection diffraction light transmitted in the waveguide substrate toward the direction of the human eye; The first outcoupling grating and the second outcoupling grating have different structures.

[0007] According to a micro-nano waveguide structure provided by the present invention, the first outcoupling grating includes two mutually overlapping first diffractive optical elements, the second outcoupling grating includes two mutually overlapping second diffractive optical elements, and the first diffractive optical element and the second diffractive optical element have different structures; Each of the first diffractive optical elements is used to couple the total reflected diffraction light to another first diffractive optical element, and couple the light out in the direction of the human eye; Each of the second diffractive optical elements is used to couple the total reflected diffraction light to another second diffractive optical element, and couple the light out in the direction of the human eye.

[0008] According to a micro-nano waveguide structure provided by the present invention, the first diffractive optical element is formed by an array of multiple I-shaped structures, and the middle parts of the corresponding two I-shaped structures in two of the first diffractive optical elements overlap with each other.

[0009] According to a micro-nano waveguide structure provided by the present invention, the second diffractive optical element is formed by a plurality of in-line structures arranged in an array, and the middle portions of the corresponding two in-line structures in two of the second diffractive optical elements overlap with each other.

[0010] According to a micro-nano waveguide structure provided by the present invention, the first outcoupling grating is formed by an array of herringbone structures formed by connecting the tails of three T-shaped structures to each other, one of the first diffractive optical elements includes a T-shaped structure at the lower left of each of the herringbone structures, another first diffractive optical element includes a T-shaped structure at the lower right of each of the herringbone structures, and two of the first diffractive optical elements simultaneously include a T-shaped structure above each of the herringbone structures.

[0011] According to a micro-nano waveguide structure provided by the present invention, the second outcoupling grating is formed by a herringbone structure array arrangement formed by connecting the ends of three in-line structures to each other, wherein one of the second diffractive optical elements includes a in-line structure at the lower left of each of the herringbone structures, another of the second diffractive optical elements includes a in-line structure at the lower right of each of the herringbone structures, and two of the second diffractive optical elements simultaneously include a in-line structure above each of the herringbone structures.

[0012] According to a micro-nano waveguide structure provided by the present invention, the first diffractive optical element is formed by an array of multiple first structural units with a T-shaped head and a straight-line tail, and the middle parts of the corresponding two first structural units in two first diffractive optical elements overlap with each other.

[0013] According to a micro-nano waveguide structure provided by the present invention, the second diffractive optical element is formed by an array of multiple second structural units with head and tail portions arranged in a straight line, and the middle portions of two corresponding second structural units in two second diffractive optical elements overlap each other.

[0014] A micro-nano waveguide structure provided according to the present invention further includes a coupling-in grating, wherein the coupling-in grating is located on the surface of the waveguide substrate, and the coupling-in grating is used to diffract the incident light to generate the total reflection diffraction light.

[0015] The present invention also provides an augmented reality display device, comprising any one of the above-mentioned micro-nano waveguide structures.

[0016] The micro-nano waveguide structure and augmented reality display device provided by the present invention couple the total reflected diffraction light transmitted in the waveguide substrate toward the direction of the human eye through two layers of outcoupling gratings with different structures. The two layers of outcoupling gratings with different structures can jointly enhance the light energy coupled toward the direction of the human eye, and then jointly weaken the light energy coupled toward 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. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0018] Figure 1 is a side view of a two-dimensional grating waveguide in the prior art.

[0019] Figure 2 It is a top view of a two-dimensional grating waveguide in the prior art.

[0020] Figure 3 This is one of the structural schematic diagrams of the micro-nano waveguide structure provided by the present invention.

[0021] Figure 4 This is one of the structural schematic diagrams of the first outcoupling grating provided by the present invention.

[0022] Figure 5 This is one of the structural schematic diagrams of the second outcoupling grating provided by the present invention.

[0023] Figure 6 This is one of the schematic diagrams of the diffraction efficiency varying with the incident angle provided by the present invention.

[0024] Figure 7It is a schematic diagram of the effect of suppressing light leakage of the micro-nano waveguide structure provided by the present invention.

[0025] Figure 8 This is the second structural schematic diagram of the first outcoupling grating provided by the present invention.

[0026] Fig. 9 This is the second structural schematic diagram of the second outcoupling grating provided by the present invention.

[0027] Fig.10 This is the second schematic diagram of the diffraction efficiency varying with the incident angle provided by the present invention.

[0028] Fig.11 This is the third structural schematic diagram of the first outcoupling grating provided by the present invention.

[0029] Fig.12 This is the third structural schematic diagram of the second outcoupling grating provided by the present invention.

[0030] Fig.13 This is the third schematic diagram of the diffraction efficiency varying with the incident angle provided by the present invention. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] 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, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "include one..." do not exclude the existence of other identical elements in the process, method, article or device including the elements. The orientation or position relationship indicated by the terms "upper", "lower" and the like is based on the orientation or position relationship shown in the drawings, which is 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 therefore cannot be understood as a limitation of the present invention. Unless otherwise clearly specified and limited, the terms "installed", "connected" and "connected" 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 a direct connection, or it can be an indirect connection through an intermediate medium, or it can be a connection between the two elements. For those skilled in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0033] 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 the data used in this way 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 type, and the number of objects is not limited. For example, the first object can be one or more. In addition, "and / or" means at least one of the connected objects, and the character " / " generally indicates that the objects associated with each other are in an "or" relationship.

[0034] Combine the following Figure 1-Figure 10 The present invention describes a micro-nano waveguide structure and an augmented reality display device, which are intended to couple the total reflected diffraction light transmitted in the waveguide substrate toward the human eye through two layers of outcoupling gratings with different structures, thereby reducing the light leakage of the two-dimensional grating waveguide and improving the diffraction efficiency of the two-dimensional grating waveguide.

[0035] like Figure 1 and Figure 2As shown, the two-dimensional grating waveguide generally includes an in-coupling grating 10, a waveguide substrate 11 and a two-dimensional out-coupling grating 12, and both the in-coupling grating 10 and the two-dimensional out-coupling grating 12 are located on the surface of the waveguide substrate 11. The in-coupling grating 10 is used to diffract the incident light to generate total reflection diffraction light, and the total reflection diffraction light is transmitted in the waveguide substrate 11 in a total reflection manner toward the two-dimensional out-coupling grating 12, and diffracts when it is transmitted to the two-dimensional out-coupling grating 12 to generate two parts of diffraction light, one part of the diffraction light is transmitted toward the human eye 13 and enters the human eye to form an image, and the other part of the diffraction light is coupled out to the external environment, causing light leakage.

[0036] In some embodiments, the waveguide substrate 11 may be made of glass, polymer or other materials transparent to visible light, and may be in the form of a flat plate with two smooth surfaces; the coupling-in grating 10 and the two-dimensional coupling-out grating 12 may be located on the same surface or different surfaces of the waveguide substrate 11, and the coupling-in grating 10 and the two-dimensional coupling-out grating 12 may be prepared by photolithography or nanoimprinting technology; the incident light may be light with image information output by the microdisplay.

[0037] Generally, in order to reduce light leakage, a single-layer two-dimensional outcoupling grating with the function of reducing light leakage can be used, but the effect of reducing light leakage by the single-layer two-dimensional outcoupling grating is poor.

[0038] Figure 3 Schematic diagram of the structure of the micro-nano waveguide structure provided by the present invention. Figure 3 As shown, it includes a waveguide substrate 11, a first outcoupling grating 14 and a second outcoupling grating 15; The first outcoupling grating 14 is located on the surface of the waveguide substrate 11, and the second outcoupling grating 15 is superimposed on a side of the first outcoupling grating 14 away from the waveguide substrate 11; The first outcoupling grating 14 and the second outcoupling grating 15 are both used to couple the total reflection diffraction light conducted in the waveguide substrate 11 to the direction of the human eye 13; The first outcoupling grating 14 and the second outcoupling grating 15 have different structures.

[0039] The first outcoupling grating 14 and the second outcoupling grating 15 may both be two-dimensional gratings.

[0040] Considering that if the first outcoupling grating 14 and the second outcoupling grating 15 have the same structure, then the superposition of the first outcoupling grating 14 and the second outcoupling grating 15 is equivalent to a outcoupling grating with a higher single-layer height, and the effect of reducing light leakage is still very poor, therefore, the first outcoupling grating 14 and the second outcoupling grating 15 need to have different structures.

[0041] It can be understood that since the first out-coupling grating 14 and the second out-coupling grating 15 are both used to couple the total reflected diffraction light transmitted in the waveguide substrate 11 to the direction of the human eye, the first out-coupling grating 14 and the second out-coupling grating 15 can jointly enhance the light energy coupled to the direction of the human eye, and then 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.

[0042] That is to say, the present invention couples the total reflected diffraction light conducted in the waveguide substrate 11 toward the human eye through two layers of outcoupling gratings with different structures, thereby reducing the light leakage of the two-dimensional grating waveguide and improving the diffraction efficiency of the two-dimensional grating waveguide.

[0043] In some embodiments, the first outcoupling grating 14 of the present invention may include two first diffractive optical elements overlapping each other, and the second outcoupling grating 15 may include two second diffractive optical elements overlapping each other, and the first diffractive optical element and the second diffractive optical element have different structures; Each first diffractive optical element is used to couple the total reflected diffraction light to another first diffractive optical element, and couple the light out in the direction of the human eye; Each second diffractive optical element is used for coupling the total reflected diffraction light to another second diffractive optical element, and coupling the light out in the direction of the human eye.

[0044] Specifically, any one of the first diffractive optical elements can couple the total reflected diffraction light to another first diffractive optical element, and can also couple the light coupled from another first diffractive optical element to the direction of the human eye.

[0045] Specifically, any one of the second diffractive optical elements can couple the total reflected diffraction light to another second diffractive optical element, and can also couple the light coupled from another second diffractive optical element to the direction of the human eye.

[0046] By coupling and coupling out light through two overlapping first diffraction optical elements, the function of the first coupling-out grating 14 coupling out the total reflected diffraction light toward the human eye can be realized. By coupling and coupling out light through two overlapping second diffraction optical elements, the function of the second coupling-out grating 15 coupling out the total reflected diffraction light toward the human eye can be realized.

[0047] In some embodiments, Figure 4 , Figure 8 and Fig.11 As 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 angle formed by the two first diffractive optical elements 141 is , It can be 30-100 degrees, for example 60 degrees.

[0048] In some embodiments, Figure 5 , Fig. 9 and Fig.12 As 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 angle formed by the two second diffractive optical elements 151 is , It may also be 30-100 degrees, for example 60 degrees.

[0049] In some embodiments, Figure 4 As shown, the first diffractive optical element 141 of the present invention may be formed by an array of multiple I-shaped structures, and the middle portions of the corresponding two I-shaped structures in the two first diffractive optical elements 141 overlap each other.

[0050] The I-shaped structure can realize the function that any first diffractive optical element 141 couples the total reflected diffraction light to another first diffractive optical element 141 , and another first diffractive optical element 141 couples the light out toward the direction of the human eye.

[0051] In some embodiments, Figure 5 As shown, the second diffractive optical element 151 of the present invention may be formed by a plurality of in-line structures arranged in an array, and the middle portions of the corresponding two in-line structures in the two second diffractive optical elements 151 overlap each other.

[0052] The inline structure can realize the function that any second diffractive optical element 151 couples the total reflected diffraction light to another second diffractive optical element 151 and another second diffractive optical element 151 couples the light out toward the direction of the human eye.

[0053] 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, the structural units of the first diffractive optical element 141 and the second diffractive optical element 151 correspond to each other and are aligned one by one.

[0054] The first outcoupling grating 14 and the second outcoupling grating 15 can make the total reflection diffraction light evenly expand and couple out in the outcoupling grating area, and produce 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 diffraction light, and the direction does not change; (1,-1)R and (1,1)R are expansion conduction orders, which make the diffraction light expand along the x and y directions in the waveguide substrate 11; (2,0)R and (2,0)T are reflection and transmission outcoupling orders, which are respectively reflected and transmitted perpendicular to the plane where the outcoupling grating is located to the outside of the waveguide substrate 11, (2,0)R is coupled out in the direction of the human eye and enters the human eye for imaging, while (2,0)T is coupled out to the external environment to cause light leakage. The purpose of the present invention is to enhance (2,0)R and weaken (2,0)T.

[0055] During the experiment, a 80nm high Figure 4 The first outcoupling grating 14 shown is used as an outcoupling grating alone, and (2,0)R and (2,0)T are calculated as a function of the incident angle. The diffraction efficiency of the change (the angle between the incident light and the total reflection diffracted light generated by the coupling grating 10 and the waveguide normal) is as follows Figure 6 As shown in Figure 1, the ratio of (2,0)R to (2,0)T is 1.49, 1.47, and 1.33 when the incident angle is 40°, 60°, and 80°, respectively. In other words, when the incident angle changes, the diffraction efficiency of (2,0)R and (2,0)T is close, and the light energy coupled out to the external environment is strong, indicating that the single-layer outcoupling grating has a poor effect in reducing light leakage.

[0056] Then, a 40nm high Figure 4 The first outcoupling grating 14 is shown with a height of 40 nm. Figure 5 The second outcoupling grating 15 shown is superimposed and used together as an outcoupling grating, and the diffraction efficiency of (2,0)R and (2,0)T as the incident angle changes is calculated as follows: Figure 6 Double-layer 1-R and double-layer 1-T are shown. When the incident angles are 40°, 60°, and 80°, the ratios of (2,0)R and (2,0)T are 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, and compared with the single-layer outcoupling grating, the diffraction efficiency of (2,0)R increases and the diffraction efficiency of (2,0)T decreases, so that the ratio of (2,0)R and (2,0)T increases, indicating that the light energy coupled to the human eye is enhanced and the light energy coupled to the external environment is weakened, thereby reducing the leakage light intensity.

[0057] Then, a 40nm high Figure 4 The first outcoupling grating 14 is shown with a height of 60 nm. Figure 5The second outcoupling grating 15 shown is superimposed and used together as an outcoupling grating, and the diffraction efficiency of (2,0)R and (2,0)T as the incident angle changes is calculated as follows: Figure 6 Double-layer 2-R and double-layer 2-T are shown. When the incident angles are 40°, 60° and 80°, the ratios of (2,0)R and (2,0)T are 6.58, 3.7 and 3.09 respectively. After the height of the second outcoupling grating 15 is increased, the diffraction efficiency of (2,0)R is much greater than that of (2,0)T, and compared with the single-layer outcoupling grating, the diffraction efficiency of (2,0)R increases more, while the diffraction efficiency of (2,0)T is almost unchanged, thereby reducing the leakage light intensity.

[0058] It can be understood that when the outcoupling grating is a double-layer structure consisting of the first outcoupling grating 14 and the second outcoupling grating 15, the light energy of the diffracted light transmitted toward the human eye and entering the human eye for imaging is increased, while the light energy of the diffracted light coupled out to the external environment is reduced, thereby achieving the effect of reducing light leakage. Figure 7 shown.

[0059] In some embodiments, Figure 8 As shown, the first out-coupling grating 14 of the present invention can also be formed by an array of herringbone structures formed by connecting the tails of three T-shaped structures to each other, wherein one first diffraction optical element 141 includes a T-shaped structure at the lower left of each herringbone structure, another first diffraction optical element 141 includes a T-shaped structure at the lower right of each herringbone structure, and the two first diffraction optical elements 141 simultaneously include a T-shaped structure above each herringbone structure.

[0060] It can be understood that the T-shaped structure is composed of a transverse structure and a vertical structure, and the tail of the T-shaped structure is the free end of the vertical structure.

[0061] The herringbone structure can realize the function that any first diffractive optical element 141 couples the total reflected diffraction light to another first diffractive optical element 141 , and another first diffractive optical element 141 couples the light out toward the direction of the human eye.

[0062] In some embodiments, Fig. 9 As shown, the second out-coupling grating 15 of the present invention can also be formed by an array of herringbone structures formed by connecting the ends of three in-line structures to each other, wherein one second diffractive optical element 151 includes an in-line structure at the lower left of each herringbone structure, another second diffractive optical element 151 includes an in-line structure at the lower right of each herringbone structure, and both second diffractive optical elements 151 include an in-line structure above each herringbone structure.

[0063] The herringbone structure can realize the function that any second diffractive optical element 151 couples the total reflected diffraction light to another second diffractive optical element 151 , and another second diffractive optical element 151 couples the light out toward the direction of the human eye.

[0064] During the experiment, a 80nm high Figure 8 The first out-coupling grating 14 shown is used as an out-coupling grating alone, and the diffraction efficiencies of (2,0)R and (2,0)T as the incident angles vary are calculated as follows: Fig.10 As shown in Figure 1, the ratio of (2,0)R to (2,0)T is 1.72, 2.07, and 2.99 when the incident angle is 40°, 60°, and 80°, respectively. In other words, when the incident angle changes, the diffraction efficiency of (2,0)R and (2,0)T is close, and the light energy coupled out to the external environment is strong, indicating that the single-layer outcoupling grating has a poor effect in reducing light leakage.

[0065] Then, a 40nm high Figure 8 The first outcoupling grating 14 is shown with a height of 40 nm. Fig. 9 The second outcoupling grating 15 shown is superimposed and used together as an outcoupling grating, and the diffraction efficiency of (2,0)R and (2,0)T as the incident angle changes is calculated as follows: Fig.10 Double-layer 1-R and double-layer 1-T are shown. When the incident angles are 40°, 60°, and 80°, the ratios of (2,0)R and (2,0)T are 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 outcoupling grating, the diffraction efficiency of (2,0)R increases, while the diffraction efficiency of (2,0)T remains basically unchanged, so that the ratio of (2,0)R and (2,0)T increases, indicating that the light energy coupled to the human eye is enhanced, and the light energy coupled to the external environment is weakened, thereby reducing the leakage light intensity.

[0066] Then, a 40nm high Figure 8 The first outcoupling grating 14 is shown with a height of 60 nm. Fig. 9 The second outcoupling grating 15 shown is superimposed and used together as an outcoupling grating, and the diffraction efficiency of (2,0)R and (2,0)T as the incident angle changes is calculated as follows: Fig.10 Double-layer 2-R and double-layer 2-T are shown. When the incident angles are 40°, 60° and 80°, the ratios of (2,0)R and (2,0)T are 2.35, 2.98 and 2.14, respectively. After the height of the second outcoupling grating 15 is increased, the diffraction efficiency of (2,0)R is much greater than that of (2,0)T, and compared with the single-layer outcoupling grating, the diffraction efficiency of (2,0)R increases more, thereby reducing the leakage light intensity.

[0067] In some embodiments, Fig.11As shown, the first diffractive optical element 141 of the present invention can also be formed by an array of multiple first structural units 1411 with a T-shaped head and a straight-line tail, and the middle parts of the corresponding two first structural units 1411 in the two first diffractive optical elements 141 overlap each other.

[0068] The first structural units 1411 that overlap each other in the middle can realize the function that any first diffractive optical element 141 couples the total reflected diffraction light to another first diffractive optical element 141 and another first diffractive optical element 141 couples the light out toward the direction of the human eye.

[0069] In some embodiments, Fig.12 As shown, the second diffractive optical element 151 of the present invention can also be formed by an array of multiple second structural units 1511 with their heads and tails in a straight line, and the middle parts of the corresponding two second structural units 1511 in the two second diffractive optical elements 151 overlap each other.

[0070] The second structural units 1511 that overlap each other in the middle can realize the function that any second diffractive optical element 151 couples the total reflected diffraction light to another second diffractive optical element 151 and another second diffractive optical element 151 couples the light out toward the direction of the human eye.

[0071] During the experiment, a 80nm high Fig.11 The first out-coupling grating 14 shown is used as an out-coupling grating alone, and the diffraction efficiencies of (2,0)R and (2,0)T as the incident angles vary are calculated as follows: Fig.13 As shown in Figure 1, the ratio of (2,0)R to (2,0)T is 1.29, 1.29, and 1.25 when the incident angle is 40°, 60°, and 80°, respectively. In other words, when the incident angle changes, the diffraction efficiency of (2,0)R and (2,0)T is close, and the light energy coupled out to the external environment is strong, indicating that the single-layer outcoupling grating has a poor effect in reducing light leakage.

[0072] Then, a 40nm high Fig.11 The first outcoupling grating 14 is shown with a height of 40 nm. Fig.12 The second outcoupling grating 15 shown is superimposed and used together as an outcoupling grating, and the diffraction efficiency of (2,0)R and (2,0)T as the incident angle changes is calculated as follows: Fig.13Double-layer 1-R and double-layer 1-T are shown. When the incident angles are 40°, 60°, and 80°, the ratios of (2,0)R and (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, and compared with the single-layer outcoupling grating, the diffraction efficiency of (2,0)T is greatly reduced, so that the ratio of (2,0)R and (2,0)T increases, indicating that the light energy coupled to the human eye is enhanced and the light energy coupled to the external environment is weakened, thereby reducing the leakage light intensity.

[0073] Then, a 40nm high Fig.11 The first outcoupling grating 14 is shown with a height of 60 nm. Fig.12 The second outcoupling grating 15 shown is superimposed and used together as an outcoupling grating, and the diffraction efficiency of (2,0)R and (2,0)T as the incident angle changes is calculated as follows: Fig.13 Double-layer 2-R and double-layer 2-T are shown. When the incident angles are 40°, 60° and 80°, the ratios of (2,0)R and (2,0)T are 2.84, 2.68 and 2.58, respectively. After the height of the second outcoupling grating 15 is increased, the diffraction efficiency of (2,0)R is much greater than that of (2,0)T, and compared with the single-layer outcoupling grating, the diffraction efficiency of (2,0)R is slightly increased and the diffraction efficiency of (2,0)T is greatly reduced, thereby reducing the leakage light intensity.

[0074] The present invention also provides an augmented reality display device, comprising any one of the micro-nano waveguide structures described above, wherein the micro-nano waveguide structure comprises a waveguide substrate 11, a first outcoupling grating 14 and a second outcoupling grating 15; the first outcoupling grating 14 is located on the surface of the waveguide substrate 11, and the second outcoupling grating 15 is superimposed on the side of the first outcoupling grating 14 away from the waveguide substrate 11; the first outcoupling grating 14 and the second outcoupling grating 15 are both used to couple out the total reflection diffraction light transmitted in the waveguide substrate 11 in the direction of the human eye; the structures of the first outcoupling grating 14 and the second outcoupling grating 15 are different.

[0075] 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 it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions 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 outcoupling grating and a second outcoupling grating; The first out-coupling grating is located on the surface of the waveguide substrate, and the second out-coupling grating is superimposed on a side of the first out-coupling grating away from the waveguide substrate; The first out-coupling grating and the second out-coupling grating are both used to couple out the total reflection diffraction light transmitted in the waveguide substrate toward the direction of the human eye; The first outcoupling grating and the second outcoupling grating have different structures.

2. The micro-nano waveguide structure according to claim 1, characterized in that: The first outcoupling grating includes two mutually overlapping first diffractive optical elements, the second outcoupling grating includes two mutually overlapping second diffractive optical elements, and the first diffractive optical element and the second diffractive optical element have different structures; Each of the first diffractive optical elements is used to couple the total reflected diffraction light to another first diffractive optical element, and couple the light out in the direction of the human eye; Each of the second diffractive optical elements is used to couple the total reflected diffraction light to another second diffractive optical element, and couple the light out in the direction of the human eye.

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

4. The micro-nano waveguide structure according to claim 2 or 3, characterized in that: The second diffractive optical element is formed by a plurality of in-line structures arranged in an array, and middle portions of two in-line structures corresponding to two of the second diffractive optical elements overlap with each other.

5. The micro-nano waveguide structure according to claim 2, characterized in that: The first out-coupling grating is formed by an array of herringbone structures formed by connecting the tails of three T-shaped structures to each other, wherein one of the first diffractive optical elements includes a T-shaped structure at the lower left of each of the herringbone structures, another of the first diffractive optical elements includes a T-shaped structure at the lower right of each of the herringbone structures, and two of the first diffractive optical elements simultaneously include a T-shaped structure above each of the herringbone structures.

6. The micro-nano waveguide structure according to claim 2 or 5, characterized in that: The second out-coupling grating is formed by an array of herringbone structures formed by connecting the ends of three in-line structures to each other, wherein one of the second diffractive optical elements includes an in-line structure at the lower left of each of the herringbone structures, another of the second diffractive optical elements includes an in-line structure at the lower right of each of the herringbone structures, and two of the second diffractive optical elements simultaneously include an in-line structure above each of the herringbone structures.

7. The micro-nano waveguide structure according to claim 2, characterized in that: The first diffractive optical element is formed by an array of a plurality of first structural units with a T-shaped head and a straight-line tail, and the middle portions of the corresponding two first structural units in two first diffractive optical elements overlap each other.

8. The micro-nano waveguide structure according to claim 2 or 7, characterized in that: The second diffractive optical element is formed by an array of a plurality of second structural units with head portions and tail portions both being in a straight line, and the middle portions of the corresponding two second structural units in two second diffractive optical elements overlap each other.

9. The micro-nano waveguide structure according to claim 1, characterized in that: The invention also includes a coupling-in grating, which is located on the surface of the waveguide substrate and is used for diffracting the incident light to generate the total reflection diffraction light.

10. An augmented reality display device, characterized in that: The invention comprises the micro-nano waveguide structure as described in any one of claims 1 to 9.

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