Metasurface grating waveguide and augmented reality display device

Abstract

The present invention relates to the field of optical technology, and provides a metasurface grating waveguide and an augmented reality display device. The metasurface grating waveguide comprises: an in-coupling grating, a waveguide substrate and an out-coupling grating, the out-coupling grating comprises a first diffraction grating and a second diffraction grating, the in-coupling grating is located on the surface of the waveguide substrate, and is used to diffract and couple a light beam to the waveguide substrate, the first diffraction grating is located on the surface of the waveguide substrate, and the second diffraction grating and the first diffraction grating are overlapped; the waveguide substrate is used to conduct the light beam to the first diffraction grating by total reflection, the diffraction efficiency of the first diffraction grating is lower than that of the second diffraction grating, so that the diffracted light of the first diffraction grating is more evenly expanded and conducted in the waveguide, and the light intensity coupled out of the second diffraction grating is more uniform, thereby improving the exit pupil uniformity and field of view uniformity of the entire augmented reality display device.

Description

Technical Field

[0001] The present invention relates to the field of optical technology, and in particular to a supersurface grating waveguide and an augmented reality display device. Background Art

[0002] Augmented reality is a technology that integrates computer-generated virtual information with the real world. Near-eye display devices, such as AR glasses, transmit the images of microdisplays to the human eye through a series of optical imaging elements, greatly enhancing the sense of reality.

[0003] In the prior art, near-eye display devices mostly use two-dimensional diffraction grating waveguides as the main optical elements. The two-dimensional diffraction grating waveguide uses two regions: a one-dimensional coupling-in grating and a two-dimensional coupling-out grating. During the propagation of the light beam in the coupling-out grating region, part of the light is continuously expanded and coupled out. As the light beam continues to propagate and expand in the direction away from the coupling-in grating, the intensity of the light beam emitted from the coupling-out grating continues to decrease, resulting in a larger light intensity emitted from the coupling-out grating on the side close to the coupling-in grating, and a smaller light intensity emitted on the side away from the coupling-in grating, which ultimately leads to the non-uniformity of the exit pupil of the coupling-out grating, making it difficult to ensure the uniformity of the field of view of the near-eye display device, reducing the user experience. Summary of the invention

[0004] The present invention provides a metasurface grating waveguide and an augmented reality display device, which are used to solve the problem of poor exit pupil uniformity and field of view uniformity of the grating waveguide in the prior art.

[0005] In a first aspect, the present invention provides a metasurface grating waveguide, comprising: an in-coupling grating, a waveguide substrate and an out-coupling grating, wherein the out-coupling grating comprises a first diffraction grating and a second diffraction grating, the in-coupling grating is located on the surface of the waveguide substrate, and is used to diffract and couple a light beam to the waveguide substrate, the first diffraction grating is located on the surface of the waveguide substrate, and the second diffraction grating and the first diffraction grating are arranged to overlap; wherein the direction of the engraved lines of the first diffraction grating and the direction of the engraved lines of the second diffraction grating form a certain angle;

[0006] The waveguide substrate is used to conduct the light beam to the first diffraction grating by total reflection, and the diffraction efficiency of the first diffraction grating is lower than that of the second diffraction grating, so that the diffracted light of the first diffraction grating is uniformly expanded and conducted in the waveguide substrate and is uniformly coupled out by the second diffraction grating;

[0007] Wherein, the first diffraction grating has a plurality of first grooves arranged at equal intervals along its periodic direction;

[0008] The second diffraction grating has a plurality of second grooves and third grooves which are alternately arranged in sequence along its periodic direction, the width of the second grooves is different from the width of the third grooves, and the distance between two adjacent first grooves is greater than the distance between two adjacent second grooves and the third grooves.

[0009] According to a metasurface grating waveguide provided by the present invention, the width of the first groove is greater than the width of the second groove, and the width of the second groove is greater than the width of the third groove.

[0010] According to a metasurface grating waveguide provided by the present invention, the first diffraction grating is a rectangular grating;

[0011] A fourth groove is provided between two adjacent second grooves and third grooves. The second groove, the third groove and the fourth groove are all rectangular. The width of the fourth groove is smaller than that of the second groove and larger than that of the third groove.

[0012] According to a metasurface grating waveguide provided by the present invention, the first diffraction grating is an elliptical grating;

[0013] The second diffraction grating has a first elliptical groove and a second elliptical groove;

[0014] A plurality of the first elliptical grooves are sequentially connected along the direction of the lines of the second diffraction grating to form the second grooves;

[0015] A plurality of the second elliptical grooves are sequentially connected along the direction of the engraved lines of the second diffraction grating to form the third engraved grooves.

[0016] According to a metasurface grating waveguide provided by the present invention, the first diffraction grating is a diamond grating;

[0017] The second diffraction grating has rhombus grooves; a plurality of the rhombus grooves are sequentially connected along the direction of the engraved lines of the second diffraction grating to form the second engraved grooves;

[0018] The third groove is rectangular;

[0019] The groove width of the diamond grating is the same as the groove width of the diamond groove, and the groove width of the third groove is smaller than the groove width of the diamond groove.

[0020] According to a metasurface grating waveguide provided by the present invention, the angle between the direction of the engraved lines of the first diffraction grating and the direction of the engraved lines of the second diffraction grating is 45° to 120°.

[0021] According to a metasurface grating waveguide provided by the present invention, the metasurface grating waveguide has a first out-coupling region and a second out-coupling region, the first out-coupling region and the second out-coupling region are respectively provided with the first diffraction grating and the second diffraction grating, the first diffraction grating of the first out-coupling region and the first diffraction grating of the second out-coupling region are symmetrically arranged, and the second diffraction grating of the first out-coupling region and the second diffraction grating of the second out-coupling region are symmetrically arranged.

[0022] According to a metasurface grating waveguide provided by the present invention, the metasurface grating waveguide also has a third outcoupling region, the third outcoupling region is provided with a two-dimensional grating, the third outcoupling region is located between the first outcoupling region and the second outcoupling region, and the two-dimensional grating is used to receive the diffracted light transmitted by total reflection of the waveguide substrate and expand and transmit the diffracted light to the first diffraction grating and the second diffraction grating of the first outcoupling region and the second outcoupling region respectively.

[0023] According to a metasurface grating waveguide provided by the present invention, the coupling-in grating is any one of a rectangular grating, a tilted grating, a blazed grating or a metasurface grating.

[0024] In a second aspect, the present invention further provides an augmented reality display device, comprising a microdisplay and a metasurface grating waveguide as described in any one of the above items, wherein the microdisplay is used to output image light to the coupling-in grating.

[0025] The present invention provides a metasurface grating waveguide and an augmented reality display device, wherein a coupling-in grating is located on the surface of a waveguide substrate and is used to diffract and couple a light beam to the waveguide substrate, a first diffraction grating is located on the surface of the waveguide substrate, a second diffraction grating and the first diffraction grating are overlapped, the waveguide substrate totally reflects and transmits the diffracted light generated by the coupling-in grating to the first diffraction grating in a total reflection manner, the first diffraction grating is used to receive the total reflected light transmitted by the waveguide substrate and diffract the total reflected light to generate diffracted light, so that the diffracted light is expanded and transmitted in the waveguide, the second diffraction grating serves as a final coupling-out grating and couples the light beam from the metasurface grating waveguide to a human eye, since the diffraction efficiency of the first diffraction grating is lower than that of the second diffraction grating, the diffracted light of the first diffraction grating is more evenly expanded and transmitted in the waveguide, and the light intensity coupled out by the second diffraction grating is more uniform, thereby improving the exit pupil uniformity of the metasurface grating waveguide and the field of view uniformity of the entire augmented reality display device. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] 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.

[0027] Figure 1 It is a schematic diagram of light transmission of a grating waveguide in the prior art.

[0028] Figure 2 It is a schematic diagram of light transmission of the supersurface grating waveguide provided by the present invention.

[0029] Figure 3 It is a schematic diagram of the structure of the supersurface grating waveguide provided by the present invention.

[0030] Figure 4 It is an enlarged view of the first diffraction grating and the second diffraction grating of an embodiment provided by the present invention.

[0031] Figure 5 The present invention provides Figure 4 One of the comparison diagrams of diffraction efficiency of the corresponding embodiment at different diffraction orders.

[0032] Figure 6 The present invention provides Figure 4 The second comparison diagram of diffraction efficiency of the corresponding embodiment at different diffraction orders.

[0033] Figure 7 is the exit pupil uniformity diagram of the grating waveguide of the prior art.

[0034] Figure 8 This is an exit pupil uniformity diagram of the supersurface grating waveguide provided by the present invention.

[0035] Fig. 9 It is an enlarged view of the first diffraction grating and the second diffraction grating of another embodiment provided by the present invention.

[0036] Fig.10 The present invention provides Fig. 9 A comparison chart of diffraction efficiency of the corresponding embodiments at different diffraction orders.

[0037] Fig.11 It is an enlarged view of the first diffraction grating and the second diffraction grating of another embodiment provided by the present invention.

[0038] Fig.12 The present invention provides Fig.11 A comparison chart of diffraction efficiency of the corresponding embodiments at different diffraction orders.

[0039] Fig.13 It is an enlarged view of the first diffraction grating and the second diffraction grating of another embodiment provided by the present invention.

[0040] Fig.14 The present invention provides Fig.13 A comparison chart of diffraction efficiency of the corresponding embodiments at different diffraction orders.

[0041] Fig.15 It is an enlarged view of the first diffraction grating and the second diffraction grating of the second outcoupling region provided by the present invention.

[0042] Fig.16 It is a schematic diagram of light transmission of the metasurface grating waveguide provided by the present invention when the incident angle of the light beam is (θ, φ) = (10°, 20°).

[0043] Fig.17 It is a schematic diagram of light transmission of the supersurface grating waveguide provided by the present invention when the incident angle of the light beam is (θ, φ) = (10°, -20°).

[0044] Fig.18 is a graph of the exit pupil uniformity of the prior art grating waveguide when the incident angle of the light beam is (θ, φ) = (10°, 20°).

[0045] Fig.19 This is an exit pupil uniformity diagram of the metasurface grating waveguide provided by the present invention when the incident angle of the light beam is (θ, φ) = (10°, 20°).

[0046] Fig. 20 is a graph of the exit pupil uniformity of the prior art grating waveguide when the incident angle of the light beam is (θ, φ) = (10°, -20°).

[0047] Fig.21 This is an exit pupil uniformity diagram of the metasurface grating waveguide provided by the present invention when the incident angle of the light beam is (θ, φ) = (10°, -20°).

[0048] Fig. 22 It is a schematic structural diagram of a supersurface grating waveguide according to another embodiment of the present invention.

[0049] Reference numerals:

[0050] 1. In-coupled grating; 2. Waveguide substrate; 100. Human eye;

[0051] 3, outcoupling grating; 31, first diffraction grating; 32, second diffraction grating; 301, outcoupling region; 3011, first outcoupling region; 3012, second outcoupling region; 3013, third outcoupling region;

[0052] 311, first groove; 321, second groove; 322, third groove; 323, fourth groove; 324, first elliptical groove; 325, second elliptical groove; 326, diamond groove;

[0053] 200. Traditional coupling-in grating; 300. Waveguide substrate; 400. Traditional coupling-out grating; 500. Micro display. DETAILED DESCRIPTION

[0054] 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.

[0055] The features of the terms "first" and "second" in the specification and claims of the present invention may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "plurality" means two or more. In addition, "and / or" in the specification and claims means at least one of the connected objects, and the character " / " generally means that the objects connected before and after are in an "or" relationship.

[0056] In the description of the present invention, it is to be understood that the terms “center”, “longitudinal”, “lateral”, “length”, “width”, “thickness”, “up”, “down”, “front”, “back”, “left”, “right”, “vertical”, “horizontal”, “top”, “bottom”, “inside”, “outside”, “clockwise”, “counterclockwise”, “axial”, “radial”, “circumferential”, etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0057] In the description of the present invention, it should be noted that, 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 indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0058] Combine the following Figure 1-Figure 22, through specific embodiments and their application scenarios, a metasurface grating waveguide and an augmented reality display device provided by an embodiment of the present invention are described in detail.

[0059] Figure 1 It is a schematic diagram of light transmission of the grating waveguide of the prior art. The grating waveguide includes a conventional coupling-in grating 200, a waveguide substrate 300 and a conventional coupling-out grating 400. The conventional coupling-in grating 200 and the conventional coupling-out grating 400 are located on the same surface or different surfaces of the waveguide substrate 300. A light beam carrying image information is emitted by the microdisplay and incident on the conventional coupling-in grating 200. The light beam diffracts in the region of the conventional coupling-in grating 200 to generate diffracted light, and the diffracted light is totally reflected in the waveguide substrate 300 and transmitted to the conventional coupling-out grating 400. When the light beam is transmitted to the region of the conventional coupling-out grating, it continues to diffract to generate diffracted light and couples out of the grating waveguide and enters the human eye 100 to form an image. As shown in FIG. Figure 1 As shown, the direction of the arrow indicates the propagation direction of the light beam. The intensity of the light coupled out from the side area of ​​the traditional coupling-out grating 400 close to the traditional coupling-in grating 200 is relatively large, while the intensity of the light coupled out from the side area of ​​the traditional coupling-out grating 400 far from the traditional coupling-in grating 200 is relatively small. In the prior art, since the diffraction efficiency of the traditional coupling-out grating 400 is constant, after the diffracted light is expanded and coupled out multiple times, the energy carried by the diffracted light in the grating waveguide gradually decreases, resulting in uneven pupil of the grating waveguide. Lights of different intensities are simultaneously transmitted toward the direction of the human eye and enter the human eye 100 for imaging. When the human eye 100 is located in different coupling-out areas for observation, the brightness of the image seen will be different. The human eye 100 receives light of different intensities at the same time, which is prone to eye fatigue and eye damage, and can easily cause a very bad user experience for the user.

[0060] In order to improve the exit pupil uniformity and field of view uniformity of the grating waveguide, such as Figure 2 and Figure 3 As shown, the present invention provides a supersurface grating waveguide, comprising: an in-coupling grating 1, a waveguide substrate 2 and an out-coupling grating 3. Figure 4 As shown, the out-coupling grating 3 includes a first diffraction grating 31 and a second diffraction grating 32. The in-coupling grating 1 is located on the surface of the waveguide substrate 2, and is used to diffract and couple the light beam to the waveguide substrate 2. The first diffraction grating 31 is also located on the surface of the waveguide substrate 2, and the second diffraction grating 32 and the first diffraction grating 31 are overlapped. The engraved line direction of the first diffraction grating 31 and the engraved line direction of the second diffraction grating 32 form a certain angle.

[0061] The waveguide substrate 2 is used to conduct the light beam to the first diffraction grating 31 by total reflection. The diffraction efficiency of the first diffraction grating 31 is lower than that of the second diffraction grating 32. The diffracted light generated by the diffraction of the first diffraction grating 31 expands and conducts in two directions in the waveguide. The second diffraction grating 32 couples the diffracted light out of the waveguide and enters the human eye for imaging.

[0062] It is understandable that if Figure 3 As shown, the coupling grating 1 is located on the surface of the waveguide substrate 2 and on one side of the waveguide substrate 2. The micro display 500 of the near-eye display device incidents the light beam with image information into the coupling grating 1. The coupling grating 1 can be any one of a rectangular grating, a tilted grating, a blazed grating or a metasurface grating.

[0063] Optionally, the waveguide substrate 2 may be glass, transparent polymer or other visible light transparent materials. The waveguide substrate 2 is in a flat plate shape and has a smooth surface, which is conducive to the waveguide substrate 2 transmitting the diffracted light to the first diffraction grating 31 by total reflection.

[0064] like Figure 4 As shown, the first diffraction grating 31 and the second diffraction grating 32 are located on the surface of the waveguide substrate 2 and on the +x direction side of the coupling grating 1 on the waveguide substrate 2. The first diffraction grating 31 and the second diffraction grating 32 are overlapped. The engraved line direction of the first diffraction grating 31 and the engraved line direction of the second diffraction grating 32 form a certain angle.

[0065] Optionally, the angle between the direction of the lines of the first diffraction grating 31 and the direction of the lines of the second diffraction grating 32 may be 45° to 120°. Figure 4 As shown, the angle between the engraved line direction of the first diffraction grating 31 and the engraved line direction of the second diffraction grating 32 is 60°.

[0066] The first diffraction grating 31 and the second diffraction grating 32 may be located on the same surface or different surfaces of the waveguide substrate 2 as the coupling-in grating 1 .

[0067] Figure 2 The direction of the arrow indicates the propagation direction of the light beam. Figure 2 As shown, the light beam with image information is diffracted and coupled to the waveguide substrate 2 through the coupling-in grating 1. The waveguide substrate 2 transmits the light beam to the first diffraction grating 31 in a total reflection manner. The first diffraction grating 31 can receive the diffracted light transmitted by the waveguide substrate 2, and expand and transmit the diffracted light in the waveguide. The second diffraction grating 32 serves as the final coupling-out grating, receives the diffracted light generated by the diffraction of the first diffraction grating 31, and couples the diffracted light out of the metasurface grating waveguide and enters the human eye 100 for imaging. Since the diffraction efficiency of the first diffraction grating 31 is lower than that of the second diffraction grating 32, the first diffraction grating 31 enables the diffracted light to be more evenly expanded and transmitted in the metasurface grating waveguide, thereby making the light intensity coupled out of the second diffraction grating 32 more uniform, thereby improving the exit pupil uniformity and field of view uniformity of the metasurface grating waveguide.

[0068] Specifically, Figure 4As shown, the first diffraction grating 31 has a plurality of first grooves 311 arranged at equal intervals along its periodic direction. Figure 4 As shown, the second diffraction grating 32 has a plurality of second grooves 321 and third grooves 322 arranged alternately in sequence along its periodic direction. The width of the second groove 321 is different from the width of the third groove 322, and the distance between two adjacent first grooves 311 is greater than the distance between two adjacent second grooves 321 and third grooves 322.

[0069] It is understandable that the first diffraction grating 31 may be a rectangular grating. The first diffraction grating 31 has a plurality of first grooves 311 of the same width along its periodic direction. The plurality of first grooves 311 are arranged in parallel.

[0070] like Figure 4 As shown, the second diffraction grating 32 has a second groove 321 and a third groove 322 of different widths. There are a plurality of second grooves 321 and a plurality of third grooves 322. The second grooves 321 and the third grooves 322 are alternately arranged in parallel. The distance between two adjacent first grooves 311 is greater than the distance between two adjacent second grooves 321 and the third grooves 322, so that the diffraction efficiency of the first diffraction grating 31 is lower than the diffraction efficiency of the second diffraction grating 32.

[0071] Optionally, the width of the second groove 321 can be greater than the width of the third groove 322, or less than the width of the third groove 322, as long as it can ensure that the distance between two adjacent first grooves 311 is greater than the distance between two adjacent second grooves 321 and the third groove 322, so that the diffraction efficiency of the first diffraction grating 31 can be lower than the diffraction efficiency of the second diffraction grating 32.

[0072] The present invention provides a metasurface grating waveguide, wherein a coupling-in grating 1 is located on the surface of a waveguide substrate 2 and is used for diffraction coupling a light beam to the waveguide substrate 2, a first diffraction grating 31 is located on the surface of the waveguide substrate 2, a second diffraction grating 32 and the first diffraction grating 31 are overlapped, the waveguide substrate 2 reflects and transmits the diffracted light generated by the coupling-in grating 1 to the first diffraction grating 31 in a total reflection manner, the first diffraction grating 31 receives the diffracted light transmitted by the waveguide substrate 2 and diffracts to generate diffracted light that is expanded and transmitted in the waveguide, the second diffraction grating 32 serves as a final coupling-out grating and couples the light beam from the metasurface grating waveguide to a human eye, and since the diffraction efficiency of the first diffraction grating 31 is lower than that of the second diffraction grating 32, the first diffraction grating 31 enables the diffracted light to be expanded and transmitted more uniformly in the metasurface grating waveguide, thereby making the light intensity coupled out by the second diffraction grating 32 more uniform, thereby improving the exit pupil uniformity and field of view uniformity of the entire metasurface grating waveguide.

[0073] Some embodiments in which the diffraction efficiency of the first diffraction grating 31 is lower than the diffraction efficiency of the second diffraction grating 32 when the width of the second groove 321 is greater than the width of the third groove 322 are described in detail below.

[0074] Further, in a specific embodiment, if Figure 4 As shown, the distance between two adjacent first grooves 311 is greater than the distance between two adjacent second grooves 321 and the third groove 322, and the width of the first groove 311 is greater than the width of the second groove 321, and the width of the second groove 321 is greater than the width of the third groove 322, so that the diffraction efficiency of the first diffraction grating 31 is lower than the diffraction efficiency of the second diffraction grating 32.

[0075] The outcoupling region of the metasurface grating waveguide is Figure 4 When the grating structure is shown, the efficiencies of the (0,0)R, (1,1)R and (1,-1)R diffraction orders are calculated as follows: Figure 5 As shown. Due to the asymmetry of the grating structure, the efficiency of the (1,1)R-order diffraction light is significantly greater than the efficiency of the (1,-1)R-order diffraction light, which can improve the exit pupil uniformity of the metasurface grating waveguide. In addition, as Figure 6 As shown, the efficiency of the (2,0)R-order diffraction light of the outcoupling waveguide is significantly greater than the efficiency of the (2,0)T-order diffraction light, so that the outcoupling light of the metasurface grating waveguide is more concentrated on the side observed by the human eye, thereby reducing the leakage light of the waveguide and improving energy utilization.

[0076] Figure 7 This is the exit pupil uniformity diagram of the traditional grating waveguide when the light beam is coupled into the grating at vertical incidence. Figure 8 This is a diagram of the uniformity of the exit pupil of the metasurface grating waveguide provided by the present invention when light is vertically incident and coupled into the grating 1. Figure 7 and Figure 8 It can be seen that Figure 8 The light intensity in each area is obviously more uniform, and the brightness of the light is brighter, indicating that the metasurface grating waveguide provided by the present invention not only improves the exit pupil uniformity and field of view uniformity of the waveguide, but also improves the utilization rate of the waveguide light energy to a certain extent.

[0077] Further, in a specific embodiment, if Fig. 9 As shown, the first diffraction grating 31 is a rectangular grating. A fourth groove 323 is provided between two adjacent second grooves 321 and third grooves 322. The second grooves 321, the third grooves 322 and the fourth grooves 323 are all rectangular, and the width of the fourth groove 323 is smaller than the width of the second grooves 321 and larger than the width of the third grooves 322.

[0078] In this embodiment, if Fig. 9As shown, the grating pitch of the first diffraction grating 31 is greater than the distance between two adjacent grooves of the second diffraction grating 32, and the width of the first groove 311 is greater than the width of the second groove 321, so that the diffraction efficiency of the first diffraction grating 31 is lower than the diffraction efficiency of the second diffraction grating 32.

[0079] The outcoupling region of the metasurface grating waveguide is Fig. 9 When the grating structure is shown, the efficiencies of the (0,0)R, (1,1)R and (1,-1)R diffraction orders are calculated as follows: Fig.10 As shown. Due to the asymmetry of the grating structure, the efficiency of the (1,1) R-order diffraction light is significantly greater than the efficiency of the (1,-1) R-order diffraction light, thereby improving the exit pupil uniformity of the metasurface grating waveguide.

[0080] Further, in a specific embodiment, if Fig.11 As shown, the first diffraction grating 31 is a one-dimensional grating arranged in an elliptical structure array. The second diffraction grating 32 has a first elliptical groove 324 and a second elliptical groove 325. A plurality of first elliptical grooves 324 are sequentially connected along the direction of the engraved lines of the second diffraction grating 32 to form a second engraved groove 321. A plurality of second elliptical grooves 325 are sequentially connected along the direction of the engraved lines of the second diffraction grating 32 to form a third engraved groove 322.

[0081] In this embodiment, if Fig.11 As shown, the grating pitch of the first diffraction grating 31 is greater than the spacing between two adjacent second grooves 321 and third grooves 322, and the groove width of the first elliptical groove 324 is greater than the groove width of the second elliptical groove 325, so that the diffraction efficiency of the first diffraction grating 31 is lower than the diffraction efficiency of the second diffraction grating 32.

[0082] The outcoupling region of the metasurface grating waveguide is Fig.11 When the grating structure is shown, the efficiencies of the (0,0)R, (1,1)R and (1,-1)R diffraction orders are calculated as follows: Fig.12 As shown. Due to the asymmetry of the grating structure, the efficiency of the (1,1) R-order diffraction light is significantly greater than the efficiency of the (1,-1) R-order diffraction light, thereby improving the exit pupil uniformity of the metasurface grating waveguide.

[0083] Further, in a specific embodiment, if Fig.13 As shown, the first diffraction grating 31 is a one-dimensional grating arranged in a rhombus structure array. The second diffraction grating 32 has a rhombus groove 326. A plurality of rhombus grooves 326 are sequentially connected along the direction of the engraved lines of the second diffraction grating 32 to form a second engraved groove 321. The third engraved groove 322 is rectangular. The engraved groove width of the rhombus structure of the first diffraction grating 31 is the same as the groove width of the rhombus groove 326, and the engraved groove width of the third engraved groove 322 is smaller than the groove width of the rhombus groove 326.

[0084] In this embodiment, if Fig.13 As shown, the grating pitch of the first diffraction grating 31 is greater than the spacing between two adjacent second grooves 321 and the third groove 322, the width of the first groove 311 of the diamond structure is the same as the groove width of the diamond groove 326, and the groove width of the diamond groove 326 is greater than the groove width of the third groove 322, so that the diffraction efficiency of the first diffraction grating 31 is lower than the diffraction efficiency of the second diffraction grating 32.

[0085] The outcoupling region of the metasurface grating waveguide is Fig.13 When the grating structure is shown, the efficiencies of the (0,0)R, (1,1)R and (1,-1)R diffraction orders are calculated as follows: Fig.14 As shown. Due to the asymmetry of the grating structure, the efficiency of the (1,1) R-order diffraction light is significantly greater than the efficiency of the (1,-1) R-order diffraction light, thereby improving the exit pupil uniformity of the metasurface grating waveguide.

[0086] Furthermore, in order to improve the overall optical efficiency of the metasurface grating waveguide and increase the energy utilization, e.g. Figure 3 As shown, the outcoupling region 301 of the metasurface grating waveguide provided by the present invention comprises a first outcoupling region 3011 and a second outcoupling region 3012. The grating structures of the first outcoupling region 3011 and the second outcoupling region 3012 are symmetrical about the x-axis, and the grating structure in each region comprises a first diffraction grating 31 and a second diffraction grating 32.

[0087] Combination Figure 3 , Figure 4 and Fig.15 As shown, the first outcoupling region 3011 adopts Figure 4 The grating structure shown in the figure, the second outcoupling region 3012 adopts Fig.15 The grating structure shown in the figure: The first diffraction grating 31 of the first outcoupling region 3011 and the first diffraction grating 31 of the second outcoupling region 3012 are symmetrical about the X direction, and the angles between the two and the X direction are ±30° respectively.

[0088] The second diffraction grating 32 of the first outcoupling region 3011 and the second diffraction grating 32 of the second outcoupling region 3012 are also symmetrical about the X direction, and the angles between the two and the X direction are also ±30°.

[0089] In this embodiment, since the first outcoupling region 3011 and the second outcoupling region 3012 are symmetrical about the X direction, the waveguide substrate 2 can evenly distribute the total reflected light to the first outcoupling region 3011 and the second outcoupling region 3012 .

[0090] like Figure 3As shown, the first diffraction grating 31 of the first out-coupling region 3011 and the second out-coupling region 3012 expands and conducts the diffracted light along the X and Y directions, and the second diffraction grating 32 couples the diffracted light out of the waveguide. Since the diffraction efficiencies of the first diffraction grating 31 and the second diffraction grating 32 are different, the light coupled out of the metasurface grating waveguide is more concentrated on the side observed by the human eye, and the energy carried by the light is greater, thereby improving the brightness of the light, reducing the leakage light of the metasurface grating waveguide, and improving the light energy utilization rate.

[0091] like Fig.16 As shown, the light from the microdisplay 500 is incident on the coupling grating 1 at an angle of (θ, φ) = (10°, 20°). Wherein, θ represents the angle between the light beam emitted by the microdisplay 500 and the normal of the waveguide substrate 2; φ represents the angle between the projection of the light beam in the XY plane and the X direction; the coupled light in the waveguide coupling-out region is conducted toward the human eye at (θ, φ) = (10°, -20°) and enters the human eye for imaging. Since the light coupled out from the left side of the coupling-out region 301 is within the human eye's field of vision, more light can enter the human eye for imaging, while the light coupled out from the right side of the coupling-out region 301 is not within the human eye's field of vision and cannot enter the human eye for imaging, the left side of the coupling-out region 301 can emit more light into the human eye, thereby improving the light energy utilization rate of the metasurface grating waveguide provided by the present invention. However, the intensity of the emitted light on the left and right sides of the coupling-out region of the conventional grating waveguide is the same, resulting in the inability of the emitted light to be effectively coupled out to the human eye for imaging, resulting in energy waste.

[0092] like Fig.17 As shown, the light from the micro display 500 is incident on the coupling grating 1 at an angle of (θ, φ) = (10°, -20°), and the coupled light in the waveguide coupling region is conducted toward the human eye at (θ, φ) = (10°, 20°) and enters the human eye for imaging. Since the light coupled out from the right side of the coupling region 301 is within the human eye's field of vision, more light can enter the human eye for imaging, while the light coupled out from the left side of the coupling region 301 is not within the human eye's field of vision and cannot enter the human eye for imaging, more light can be emitted from the right side of the coupling region 301 to enter the human eye, thereby improving the light energy utilization rate of the metasurface grating waveguide provided by the present invention. However, the outgoing light intensities on the left and right sides of the coupling region of the conventional grating waveguide are the same, resulting in the inability of the outgoing light to be effectively coupled out to the human eye for imaging, resulting in energy waste.

[0093] Fig.18 and Fig.19 The exit pupil uniformity diagrams of the conventional grating waveguide and the metasurface grating waveguide provided by the present invention when the light is incident at an angle of incidence (θ, φ) = (10°, 20°) and is coupled into the grating. Fig.18 and Fig.19 It can be seen that Fig.19The light intensity in the left area is obviously brighter, and more outcoupled light on the left side enters the human eye for imaging, indicating that the metasurface grating waveguide provided in this embodiment improves the utilization rate of light energy.

[0094] Fig. 20 and Fig.21 The exit pupil uniformity diagrams of the conventional grating waveguide and the metasurface grating waveguide provided by the present invention when the light is incident at an angle of incidence (θ, φ) = (10°, -20°) and is coupled into the grating. Fig. 20 and Fig.21 It can be seen that Fig.21 The light intensity in the right area is obviously brighter, and more outcoupled light on the right side enters the human eye for imaging, indicating that the metasurface grating waveguide provided in this embodiment improves the utilization rate of light energy.

[0095] In other embodiments, Fig. 22 As shown, the outcoupling region 301 also has a third outcoupling region 3013. The third outcoupling region 3013 is located between the first outcoupling region 3011 and the second outcoupling region 3012. The diffracted light from the coupling-in grating 1 is transmitted in the waveguide in a total reflection manner toward the third outcoupling region 3013. When it is transmitted to the third outcoupling region 3013, diffraction occurs to generate diffracted light, which is coupled out of the waveguide and enters the human eye. At the same time, the generated diffracted light is transmitted to the first outcoupling region 3011 and the second outcoupling region 3012. The third outcoupling region 3013 can be provided with a traditional symmetrical two-dimensional grating structure, such as a diamond grating, an elliptical grating, a cross grating, etc., so that the diffracted light is uniformly transmitted to the first outcoupling region 3011 and the second outcoupling region 3012. The first outcoupling region 3011 and the second outcoupling region 3012 then allow the diffracted light to be more uniformly and effectively coupled out of the waveguide and enter the human eye for imaging.

[0096] In a second aspect, the present invention further provides an augmented reality display device, comprising a micro display and the metasurface grating waveguide as described above. The micro display is used to output image light to the coupling grating 1 .

[0097] Since the augmented reality display device includes a metasurface grating waveguide, and the specific structure of the metasurface grating waveguide refers to the above embodiment, the augmented reality display device of this embodiment includes all the technical solutions of the above embodiment, and therefore at least has all the beneficial effects achieved by all the technical solutions of the above embodiment, which will not be described one by one here. 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 is described in detail with reference to the above embodiments, ordinary technicians in this field should understand that they can still modify the technical solutions recorded in the above embodiments, or replace some of the technical features therein by equivalent; 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 metasurface grating waveguide, characterized in that: include: A coupling-in grating, a waveguide substrate and a coupling-out grating, wherein the coupling-out grating comprises a first diffraction grating and a second diffraction grating, the coupling-in grating is located on the surface of the waveguide substrate and is used to diffract and couple a light beam to the waveguide substrate, the first diffraction grating is located on the surface of the waveguide substrate, and the second diffraction grating and the first diffraction grating are arranged to overlap; wherein the direction of the engraved lines of the first diffraction grating and the direction of the engraved lines of the second diffraction grating form a certain angle; The waveguide substrate is used to conduct the light beam to the first diffraction grating by total reflection, and the diffraction efficiency of the first diffraction grating is lower than that of the second diffraction grating, so that the diffracted light of the first diffraction grating is uniformly expanded and conducted in the waveguide substrate and is uniformly coupled out by the second diffraction grating; Among them, the first diffraction grating has a plurality of first grooves arranged at equal intervals along its periodic direction; the second diffraction grating has a plurality of second grooves and third grooves arranged alternately in sequence along its periodic direction, the width of the second grooves is different from the width of the third grooves, and the distance between two adjacent first grooves is greater than the distance between two adjacent second grooves and the third grooves.

2. The metasurface grating waveguide according to claim 1, characterized in that: The width of the first groove is greater than the width of the second groove, and the width of the second groove is greater than the width of the third groove.

3. The metasurface grating waveguide according to claim 2, characterized in that: The first diffraction grating is a rectangular grating; A fourth groove is provided between two adjacent second grooves and third grooves. The second groove, the third groove and the fourth groove are all rectangular. The width of the fourth groove is smaller than that of the second groove and larger than that of the third groove.

4. The metasurface grating waveguide according to claim 2, characterized in that: The first diffraction grating is an elliptical grating; The second diffraction grating has a first elliptical groove and a second elliptical groove; A plurality of the first elliptical grooves are sequentially connected along the direction of the lines of the second diffraction grating to form the second grooves; A plurality of the second elliptical grooves are sequentially connected along the direction of the engraved lines of the second diffraction grating to form the third engraved grooves.

5. The metasurface grating waveguide according to claim 1, characterized in that: The first diffraction grating is a diamond grating; The second diffraction grating has rhombus grooves; a plurality of the rhombus grooves are sequentially connected along the direction of the engraved lines of the second diffraction grating to form the second engraved grooves; The third groove is rectangular; The groove width of the diamond grating is the same as the groove width of the diamond groove, and the groove width of the third groove is smaller than the groove width of the diamond groove.

6. The metasurface grating waveguide according to claim 1, characterized in that: The angle between the engraved line direction of the first diffraction grating and the engraved line direction of the second diffraction grating is 45° to 120°.

7. The metasurface grating waveguide according to any one of claims 1 to 6, characterized in that: The metasurface grating waveguide has a first outcoupling region and a second outcoupling region, the first outcoupling region and the second outcoupling region are respectively provided with the first diffraction grating and the second diffraction grating, the first diffraction grating of the first outcoupling region and the first diffraction grating of the second outcoupling region are symmetrically arranged, and the second diffraction grating of the first outcoupling region and the second diffraction grating of the second outcoupling region are symmetrically arranged.

8. The metasurface grating waveguide according to claim 7, characterized in that: The metasurface grating waveguide also has a third outcoupling region, the third outcoupling region is provided with a two-dimensional grating, the third outcoupling region is located between the first outcoupling region and the second outcoupling region, the two-dimensional grating is used to receive the diffracted light transmitted by total reflection of the waveguide substrate and expand and transmit the diffracted light to the first diffraction grating and the second diffraction grating of the first outcoupling region and the second outcoupling region respectively.

9. The metasurface grating waveguide according to claim 1, characterized in that: The coupling-in grating is any one of a rectangular grating, a tilted grating, a blazed grating or a metasurface grating.

10. An augmented reality display device, characterized in that: It comprises a microdisplay and the supersurface grating waveguide according to any one of claims 1 to 9, wherein the microdisplay is used to output image light to the coupling-in grating.

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