Optical structures and optical devices

Abstract

This application provides an optical structure and optical device. The optical structure includes: a waveguide; a first coupling grating disposed on the waveguide; a second coupling grating disposed on the waveguide; a third coupling grating disposed on the waveguide, located between the first and second coupling gratings; and an insertion grating disposed on the same side of the first, second, and third coupling gratings, with the insertion grating and the third coupling grating arranged side-by-side. The third coupling grating includes at least two sub-coupling gratings, the boundary between two adjacent sub-coupling gratings being located within the eyebox of the optical structure, and the diffraction efficiency of the sub-coupling gratings farther from the insertion grating is greater than that of the sub-coupling gratings closer to the insertion grating. Based on this, the solution of this application both improves the light-extracting efficiency of the third coupling grating and minimizes the intensity difference of the light extracted by the third coupling grating.

Description

[0001] This application is a divisional application of Chinese Patent Application No. 202110871693.1, filed with the Chinese Patent Office on July 30, 2021, entitled "Optical Structure and Optical Device", the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application relates to the field of optical technology, and in particular to an optical structure and optical device. Background Technology

[0003] Optical devices such as Augmented Reality (AR) devices and Virtual Reality (VR) devices can display images using their respective display devices. AR and / or VR technologies are increasingly being applied in various fields, such as military, medical, construction, education, engineering, film and television, and entertainment.

[0004] AR glasses are one of the main ways to implement AR devices. Their near-eye display system uses pixels on the display device to form a distant virtual image through a series of optical imaging elements and projects it into the viewer's eye. AR glasses products need to meet the "see-through" requirement, meaning they need to see both the real external world and virtual information; therefore, the imaging system cannot obstruct the view. This can be achieved by adding one or more optical combiners, layering them to integrate virtual information with the real scene.

[0005] Among related technologies, AR glasses have many optical implementation schemes such as catadioptric waveguides, reflective waveguides, one-dimensional diffractive waveguides, two-dimensional diffractive waveguides, and holographic waveguides. Among them, the two-dimensional diffractive waveguide (TDDW) is considered the most promising optical solution for consumer-grade AR glasses due to its thinness, high light transmittance, good color reproduction, and large field of view.

[0006] In related technologies, the coupling grating in a typical TDDW architecture couples light from the projector into a waveguide. The coupled light then undergoes total internal reflection and propagates towards the output grating. Upon reaching the output grating, it is diffracted and split into left-propagating and right-propagating pupil-expanding rays. Each time the light interacts with the output grating, a portion of its energy is coupled out into the user's eye, allowing the user to see the image projected from the projector. Currently, AR glasses exhibit significant brightness differences in the light coupled into different areas of the eye, severely impacting the user experience. Summary of the Invention

[0007] This application provides an optical structure and optical device that can minimize the intensity difference of the light emitted by the third coupling grating, thereby making it less likely for users to perceive brightness differences and improving the user experience.

[0008] This application also provides an optical structure comprising:

[0009] Wave conductor;

[0010] A first coupling grating is disposed on the waveguide;

[0011] A second coupling grating is disposed on the waveguide;

[0012] A third coupling grating is disposed on the waveguide, the third coupling grating being located between the first coupling grating and the second coupling grating; and

[0013] A coupling grating is disposed on the same side of the first coupling grating, the second coupling grating, and the third coupling grating, and the coupling grating and the third coupling grating are arranged side by side;

[0014] The third coupling grating includes at least two sub-coupling gratings, the junction of two adjacent sub-coupling gratings is located within the eyebox of the optical structure, and the diffraction efficiency of the sub-coupling gratings farther from the coupling grating is greater than that of the sub-coupling gratings closer to the coupling grating.

[0015] This application also provides an optical device, which includes:

[0016] A projector light source configured to provide augmented reality or virtual reality images; and

[0017] Optical structure as described in any of the preceding items.

[0018] In this embodiment, the diffraction efficiency of the sub-outgoing grating farther from the incoming grating is greater than that of the sub-outgoing grating closer to the incoming grating. This ensures that the overall energy of the light rays coupled out by the third outgoing grating is approximately the same, without affecting the intensity of the light rays coupled out by the third outgoing grating. Consequently, the intensity difference of the light rays coupled out by the third outgoing grating is small, and users are less likely to perceive a difference in brightness, thus improving the user experience. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] To gain a more complete understanding of this application and its beneficial effects, the following description will be provided in conjunction with the accompanying drawings, wherein the same reference numerals in the following description denote the same parts.

[0021] Figure 1 This is a schematic diagram of the optical structure provided in an embodiment of this application.

[0022] Figure 2 A perspective view of the optical structure provided in the embodiments of this application.

[0023] Figure 3 This is a schematic diagram of the transmission of the central field of view ray in the optical structure, provided for an embodiment of this application.

[0024] Figure 4 This is a schematic diagram of the transmission of edge field rays in an optical structure, provided for an embodiment of this application.

[0025] Figure 5 This is a schematic diagram of the optical structure light transmission process in k-space provided in the embodiments of this application.

[0026] Figure 6 This is a schematic diagram of the transmission of the central field of view ray along a plane in an optical structure, as provided in an embodiment of this application.

[0027] Figure 7 This is a schematic diagram of the transmission of edge field rays along a plane in an optical structure, as provided in an embodiment of this application.

[0028] Figure 8 This is a schematic diagram illustrating the application scenario of the optical structure in the embodiments of this application.

[0029] Figure 9 This is a schematic diagram of the grating vector of the first coupled-out grating in an embodiment of this application.

[0030] Figure 10 This is a schematic diagram of the optical structure provided in the embodiments of this application, and a partial structure of the first coupling grating in the optical structure.

[0031] Figure 11 This is a partial structural diagram of the first coupling grating in the optical structure provided in the embodiments of this application.

[0032] Figure 12 This is a partial structural diagram of the first coupling grating in the optical structure provided in the embodiments of this application.

[0033] Figure 13 This is a partial structural diagram of the first coupling grating in the optical structure provided in the embodiments of this application.

[0034] Figure 14 This is a partial structural diagram of the first coupling grating in the optical structure provided in the embodiments of this application.

[0035] Figure 15 This is a partial structural diagram of the first coupling grating in the optical structure provided in the embodiments of this application.

[0036] Figure 16 A schematic diagram of the optical structure provided in the embodiments of this application.

[0037] Figure 17 A schematic diagram of the optical structure provided in the embodiments of this application.

[0038] Figure 18 A schematic diagram of the optical structure provided in the embodiments of this application.

[0039] Figure 19 A schematic diagram of the optical structure provided in the embodiments of this application.

[0040] Figure 20 A schematic diagram of the optical structure provided in the embodiments of this application. Detailed Implementation

[0041] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the protection scope of this application.

[0042] Please see Figure 1 , Figure 1 This is a schematic diagram of the optical structure provided in an embodiment of this application, showing a reference frame (x, y, z). The optical structure 200 includes a waveguide 250, a coupling grating 240 disposed on the waveguide, and a plurality of coupling gratings (coupling gratings 210, 220, and 230). The waveguide 260, coupling grating 240, and the plurality of coupling gratings (coupling gratings 210, 220, and 230) of the optical structure 200 are all arranged in the xy plane.

[0043] In this design, the waveguide 250 serves as the carrier of the optical structure 200. The waveguide 250 is capable of transmitting optical signals, such as through total internal reflection. The waveguide 250 may have two oppositely arranged surfaces, such as a first surface 252 and a second surface arranged opposite to each other. The second surface is arranged opposite to the first surface 252. Figure 1 It is obscured in the view and not displayed.

[0044] The coupling grating 240 is disposed on one of the surfaces of the waveguide 250, such as the first surface 252. The coupling grating 240 can receive optical signals (also referred to as light rays) emitted from a projection optical engine (not shown in the figure) and couple the optical signals into the waveguide 250. After receiving the optical signals coupled in from the coupling grating 240, the waveguide 250 can conduct the optical signals.

[0045] The coupling grating 240 can be any of a blazed grating, a rectangular grating, or a tilted grating. The coupling grating 240 can be a one-dimensional grating.

[0046] The plurality of coupling gratings may include a first coupling grating 210, a second coupling grating 220, and a third coupling grating 230. The first coupling grating 210, the second coupling grating 220, and the third coupling grating 230 are all disposed on the waveguide 250, with the third coupling grating 230 located between the first coupling grating 210 and the second coupling grating 220. In some embodiments, the first coupling grating 210, the second coupling grating 220, and the third coupling grating 230 are disposed on the same surface of the waveguide 250, such as the first surface 252. It should be noted that the first coupling grating 210, the second coupling grating 220, and the third coupling grating 230 may also all be disposed on the other side of the waveguide 250, i.e., the second surface opposite to the first surface.

[0047] In other embodiments, one of the first coupling grating 210, the second coupling grating 220, and the third coupling grating 230 may be disposed on one side of the waveguide 250, such as the first surface 252, while the other two of the first coupling grating 210, the second coupling grating 220, and the third coupling grating 230 may be disposed on the other side and the second surface of the waveguide 250. It is understood that any combination of the coupling grating 240, the first coupling grating 210, the second coupling grating 220, and the third coupling grating 230 disposed on any side of the waveguide 250 is within the protection scope of the embodiments of this application.

[0048] In this embodiment, the coupling grating 240 can be disposed on the same side of the first coupling grating 210, the second coupling grating 220, and the third coupling grating 230, with the coupling grating 240 and the third coupling grating 230 arranged side by side. In this embodiment, the first coupling grating 210 and the second coupling grating 220 have the same shape and are symmetrically arranged with respect to the third coupling grating 230. Alternatively, they can be understood as mirror images of each other. It should be noted that the shapes of the first coupling grating 210 and the second coupling grating 220 may also be different, or they may not be symmetrically arranged with respect to the third coupling grating 230.

[0049] The waveguide 250 directs the optical signal coupled into the input grating 240 through total internal reflection towards the first output grating 210, the second output grating 220, and the third output grating 230. After reaching these gratings, the signal is diffracted and split into several parts, propagating in multiple directions. A portion of the optical signal is coupled out and reaches the user's eye, allowing the user to see the image projected from the optical engine.

[0050] Please see Figure 2 , Figure 2 A perspective view of the optical structure provided in the embodiments of this application, and Figure 2 The diagram illustrates the optical signal transmission after diffraction following the incident central field-of-view ray, and shows the reference frame (x, y, z). After the central field-of-view ray is incident on the coupling grating 240, it propagates ray 201 towards the third coupling grating 230 via the waveguide 250. Ray 201, after interacting with the third coupling grating 230, is diffracted and split into four rays: ray 2011, ray 2012, ray 2013, and ray 2014.

[0051] Ray 2011 travels along the original path of ray 201. It can be understood that ray 201, after interacting with the third coupling grating 230 and undergoing diffraction, is split into four rays. As ray 2011 travels along its original path, it interacts with the third coupling grating 230 multiple times, each interaction resulting in diffraction and splitting into four rays. That is, as ray 2011 travels along its original path, it interacts with the third coupling grating 230 multiple times, resulting in diffraction and splitting into multiple rays 2013, multiple rays 2014, multiple rays 2014, and multiple rays 2011. Since these multiple rays 2011 all travel along the original path of ray 201, they appear as a single ray. Each time ray 2011 interacts with the third coupling grating 230, the energy of the ray traveling along its original path decreases.

[0052] Ray 2012 is directly coupled out from the third coupling grating 230, which can be understood as ray 2012 being coupled out in the positive z-direction based on the xy plane. In this embodiment, all rays directly coupled out from the third coupling grating 230 are defined as ray 2012. It is understood that the energy of different rays directly coupled out from different positions of the third coupling grating 230 is different.

[0053] After interacting with the first coupling grating 210, ray 2013 is diffracted and split into two rays, ray 2013A and ray 2013B. Ray 2013A is directly coupled out from the first coupling grating 210, which can be understood as ray 2013A being coupled out in the positive z-direction based on the xy plane. Ray 2013B travels along the original path of ray 2013. In this embodiment, the ray propagating from the third coupling grating 230 towards the first coupling grating 210 is defined as ray 2013. There are multiple rays 2013, and each ray 2013 is diffracted after interacting with the first coupling grating 210 and split into multiple rays 2013A and multiple rays 2013B. It is understood that different rays 2013 have different energies, different rays 2013A have different energies, and different rays 2013B have different energies.

[0054] After interacting with the second coupling grating 220, ray 2014 is diffracted and split into two rays, ray 2014A and ray 2014B. Ray 2014A is directly coupled out from the second coupling grating 210, which can be understood as ray 2014A being coupled out in the positive z-direction based on the xy-plane. Ray 2014B travels along the original path of ray 2014. In this embodiment, the ray propagating from the third coupling grating 230 towards the second coupling grating 220 is defined as ray 2014. There are multiple rays 2014, and each ray 2014 is diffracted after interacting with the second coupling grating 220 and split into multiple rays 2014A and multiple rays 2014B. It is understood that different rays 2014 have different energies, different rays 2014A have different energies, and different rays 2014B have different energies.

[0055] Light rays coupled from the xy plane in the positive z-direction will enter the human eye, allowing the user to see the image projected from the optical engine. Please continue reading. Figure 2 ,like Figure 2 In the example shown, light ray 2012, which is coupled out from the third coupling grating 230 in the positive z direction, enters the human eye; light ray 2013A, which is coupled out from the first coupling grating 210 in the positive z direction, enters the human eye; and light ray 2014A, which is coupled out from the second coupling grating 220 in the positive z direction, enters the human eye.

[0056] It should be noted that, Figure 2 The rays 2011, 2012, 2013, and 2014 shown are exemplary and do not limit the number of rays coupled out of the optical structure 200. Alternatively, it can be understood as... Figure 2 A portion of the light rays emitted by the optical structure 200 of this embodiment are shown; the remaining light rays are not shown.

[0057] Please see Figure 3 and Figure 4 , Figure 3 This is a schematic diagram illustrating the transmission of the central field-of-view ray in the optical structure, as provided in an embodiment of this application. Figure 4 This is a schematic diagram illustrating the transmission of edge field-of-view rays in an optical structure according to an embodiment of this application. The coupling grating 240 transmits the coupled rays 201 through the waveguide 250 to the third coupling grating 230, where they interact and split into multiple rays such as rays 2011, 2012, 2013, and 2014. The transmission directions of rays 2011, 2012, 2013, and 2014 can be found in [reference needed]. Figure 2 Related details will not be elaborated here. It should be noted that ray 2012 is represented by a dot in the xy-plane. Ray 2013 interacts with the first coupling grating 210, splitting into multiple rays such as ray 2013A and ray 2013B. Rays 2013A and ray 2013B can be found in [reference needed]. Figure 2 Related details will not be elaborated here. It should be noted that ray 2013A is represented by a dot in the xy-plane. Ray 2014 interacts with the second coupling grating 220, splitting into multiple rays such as ray 2014A and ray 2014B. Rays 2014A and ray 2014B can be found in [reference needed]. Figure 2 And related content, will not be repeated here. It should be noted that ray 2014A in the xy-plane is represented by a dot. From Figure 3 and Figure 4 As can be seen from the diagram, each dot represents a ray of light that interacts with a coupling grating, and the ray represented by the dot can enter the human eye.

[0058] Figure 3 and Figure 4 It is shown that each output grating can couple out multiple rays along the positive z-axis.

[0059] It should be noted that, Figure 3 and Figure 4 Only a portion of the light rays represented by the center dot will enter the human eye.

[0060] Please see Figure 5 , Figure 5 This is a schematic diagram of the optical structure light transmission process in k-space provided in the embodiments of this application, and a reference frame (kx, ky, kz) is shown. Figure 5The radii of the two circles shown are the ambient refractive index and the waveguide refractive index, respectively. The smaller circle, located within the inner circle, represents the ambient refractive index, while the larger circle, located outside the outer circle, represents the waveguide refractive index. Rectangles represent the field of view (FOV). Each rectangle represents a FOV, and rectangles in different positions indicate different states of light rays within the FOV. For example, the rectangle at the center of the ring represents light rays (rays 2012, 2013A, and 2014A) incident or coupled from the projector into the waveguide 250. Rectangles within the ring (between the two circles) represent light rays propagating within the waveguide 240 after coupling through gratings (first coupling grating 210, second coupling grating 220, and input grating 240). If the FOV is within the smaller circle, it means the light rays can couple out of the waveguide 250; if the FOV is within the ring, it means the light rays propagate within the waveguide 250; and if the FOV is outside the larger circle, it means the light rays do not actually exist. At the origin, the light ray 201 is diffracted by the coupling grating 240 (k1) and coupled into the waveguide 250. Then, the ray 201 is transformed by the six diffraction components (k22) of the third coupling grating 230 to six different positions around its k-space. Rays 2013 and 2014 remain within the ring, indicating they will propagate along the kx-axis with total internal reflection to the left and right respectively, becoming pupil-expanding rays. Some rays will be diffracted upwards, coinciding with the original incident image, indicating they (such as ray 2012) will directly couple out. The remaining three positions are outside the ring, meaning these three diffraction components do not exist. Not all the energy of ray 201 is diffracted; instead, it retains most of its energy, meaning a significant portion continues to propagate along its propagation direction through total internal reflection.

[0061] In this embodiment, the area where the optical structure 200 is coupled out and enters the human eye is defined as the eyebox 260. That is, light rays located within the eyebox 260 and coupled out along the positive z-axis will enter the human eye.

[0062] The following is an explanation of the eye box.

[0063] Please see Figures 6 to 8 , Figure 6 This is a schematic diagram illustrating the transmission of the central field-of-view ray along a plane in an optical structure, as provided in an embodiment of this application. Figure 7 This is a schematic diagram illustrating the transmission of edge field-of-view rays along a plane in an optical structure, as provided in an embodiment of this application. Figure 8This is a schematic diagram illustrating the application scenario of the optical structure in this application embodiment. Assume the incident field of view has an angle between its angle and the z-axis in the yz plane ranging from -a° to a°, meaning the maximum incident field of view F2 has an angle between its angle and the z-axis in the yz plane ranging from a°, and the minimum incident field of view F1 has an angle between its angle and the z-axis in the yz plane ranging from -a°. The distance from the human eye to the waveguide 250 (eye relief) is b, meaning the distance from the Eyebox plane, or the human eye's observation plane, to the waveguide 250 is b. Then the length of the eyebox 260 in the y-axis direction is B, where B = A - 2b * tan(a).

[0064] Where A is the minimum length of the first coupling grating 210 in the y-axis direction, and A can also be the minimum length of the second coupling grating 210 in the y-axis direction. It should be noted that in the embodiments of this application, the minimum length of the first coupling grating 210 in the y-axis direction and the minimum length of the second coupling grating 220 in the y-axis direction are the same.

[0065] In one optional embodiment of this application, the center of the eye box 260 may coincide with the center of the third coupling grating 230.

[0066] Please continue reading. Figure 2 , Figure 3 and Figure 6 When the central field of view light is incident on the optical structure 200, a portion of the light rays coupled out by the first coupling grating 210, the second coupling grating 220 and the third coupling grating 230, such as light ray 2012, light ray 2013A and light ray 2014A, will be inside the eye box 260, that is, they will enter the human eye.

[0067] Please continue reading. Figure 4 and Figure 7 When edge field-of-view rays are incident on optical structure 200, only a portion of the rays 2012 and 2014A coupled from the second coupling grating 220 and the third coupling grating 230 will be within eyebox 260, while rays coupled from the first coupling grating 210, such as ray 2013A, will almost entirely be outside eyebox 260. In other words, the energy of the rays coupled from the second coupling grating 220 and the third coupling grating 230 is utilized, while the energy of the rays coupled from the first coupling grating 210 is wasted, often resulting in poor exit pupil uniformity at the edge field of view.

[0068] Furthermore, under the waveguide architecture in related technologies, the uniformity of the exit pupil in the edge field of view is significantly worse than that in the center field of view. This means that when viewing the projected optical engine image at certain Eyebox positions, the difference in brightness between the center field of view and the edge field of view will be relatively large, causing discomfort for the user.

[0069] Based on this, the first coupling grating 210 defined in this embodiment adopts a two-dimensional grating structure and has multiple first gratings, each of which is asymmetrical in shape. This makes the light propagation efficiency of the first coupling grating 210 in the first direction higher than that in the second direction. This results in less wasted energy in the coupled light from the first coupling grating 210 compared to other light rays, thereby improving the exit pupil brightness and uniformity of each field of view and reducing the energy difference between fields of view. For example, it can improve the exit pupil brightness and uniformity of the edge fields of view and reduce the energy difference between the edge and center fields of view. Especially when this optical structure 200 is applied to head-mounted display products such as AR, it can improve the suppression of the rainbow effect of sunlight and enhance the image quality of the product.

[0070] The first direction is the direction from the first coupling grating 210 toward the second coupling grating 220, such as... Figure 1 The negative direction of the x-axis is shown. The second direction is the direction from the second coupling grating 220 toward the first coupling grating 210, such as... Figure 1 The positive direction of the x-axis is shown. In the embodiments of this application, the first and second directions are opposite.

[0071] Please see Figure 9 , Figure 9 This is a schematic diagram of the grating vectors of the first coupling grating according to an embodiment of this application. The first coupling grating 210 has multiple levels of diffraction vectors, including (1,1), (1,0), (0,1), (0,-1), (-1,0), and (-1,-1). The diffraction efficiency of the (1,0) and (-1,0) orders in the diffraction order of the first coupling grating 210 is significantly higher than that of the (0,1) and (0,-1) orders. When light 201 is incident on the first coupling grating 210, light 2014B is generated by the (-1,0) order diffraction of the first coupling grating 210, and light 2013B is generated by the (0,1) order diffraction of the first coupling grating 210. Therefore, the efficiency of light 2014B propagating to the left (first direction) in the figure is much higher than that of light 2013B propagating to the right (second direction) in the figure.

[0072] To illustrate in detail how the asymmetrical shape of the first grid 212 in this embodiment enables the light propagation efficiency of the first coupling grating 210 in the first direction to be higher than that in the second direction, the following description is provided with reference to a schematic diagram of the first coupling grating 210.

[0073] Please see Figures 10 to 13 , Figure 10 This is a schematic diagram of the optical structure provided in the embodiments of this application, and a partial structure of the first coupling grating in the optical structure. Figure 11This is a partial structural diagram of the first coupling grating in the optical structure provided in the embodiments of this application. Figure 12 This is a partial structural diagram of the first coupling grating in the optical structure provided in the embodiments of this application. Figure 13 This is a partial structural diagram of the first coupling grating in the optical structure provided in an embodiment of this application. Figure 10 The partial structure M of the first coupling grating 210 shown is defined as the first part M. That is, the plurality of first grids 212 in the first part M are part of the first coupling grating 210.

[0074] All the first grids 212 of the first coupling grating 210 can have approximately the same shape. For example, each first grid 212 has four vertices such as vertex c, vertex d, vertex e, and vertex f, which can form a first diagonal ce and a second diagonal df. The length of the first diagonal ce is greater than the length of the second diagonal df, and the angle θacx between the first diagonal ac and the third coupling grating 230 in a third direction is an acute angle, while the angle θacy between the second diagonal bd and the third coupling grating in a third direction is an obtuse angle.

[0075] The third direction is the direction from the third output grating 230 to the input grating 240.

[0076] In one optional embodiment of this application, first grids 212 of the same shape are arranged periodically in a hexagonal lattice on the xy plane, having two periodic directions, namely periodic direction a and periodic direction b, which form a 30° angle with each other. Periodic direction a is parallel to the y-axis, and the distance between two first grids 212 along periodic direction a is Pa. Periodic direction b forms a 30° angle with the y-axis, and the distance between two first grids 212 along periodic direction b is Pb. Pa can be from 0.4 μm to 3 μm, and Pb can be from 0.2 μm to 2 μm. Pa and Pb must satisfy the relationship: Pa = Pb / 2cos(30°).

[0077] The asymmetrical shape of the first grid 212 in this embodiment can also be understood as the first grid 212 being asymmetrical about both the x-axis and y-axis. The first diagonal ce of the first grid 212 is always longer than the second diagonal df, and the angle θacy between the first diagonal ce and the positive y-axis is obtuse, while the angle θacx between the first diagonal ce and the positive x-axis is acute.

[0078] The first coupling grating 210 has multiple sets of grating groups 211, each set of grating groups 211 including multiple first gratings 212, and each first grating 212 in each set of grating groups 211 intersects with its adjacent first grating 212, and the sets of grating groups 211 are spaced apart from each other. In an optional embodiment of this application, the sets of grating groups 211 are parallel to each other. The first gratings in each set of grating groups 211 are arranged along the sixth direction. It can also be understood that the upper right and lower left corners of each first grating 212 intersect with the next adjacent first grating 212 in the diagonal direction.

[0079] The sixth direction is the direction of the seventh direction rotated 30 degrees clockwise, where the seventh direction is the direction from the third output grating 230 towards the input grating 240. It should be noted that the seventh direction can also be understood as the positive direction of Pa, that is, the sixth direction is the direction of Pb1.

[0080] It should be noted that the number of vertices in the first grid 211 is not limited to four. For example, the first grid may include at least five vertices, that is, the first grid 211 may have five or more vertices. This application embodiment uses five vertices as an example for illustration.

[0081] Please see Figure 14 , Figure 14 This is a partial structural diagram of the first coupling grating in the optical structure provided in the embodiments of this application. The vertices of the first grating 212 include two vertices (vertices c and d) close to the third coupling grating 230 and two vertices (vertices e and f) far from the third coupling grating 230. The two vertices close to the third coupling grating 230 (vertices c and d) and the two vertices far from the third coupling grating 230 (vertices e and f) can form a third diagonal ce and a fourth diagonal df. The length of the third diagonal ce is greater than the length of the fourth diagonal df, and the angle between the third diagonal ce and the third coupling grating 230 in the fourth direction is an acute angle, while the angle between the fourth diagonal df and the third coupling grating 230 in the fourth direction is an obtuse angle.

[0082] The fourth direction refers to the direction from the third output grating 230 to the input grating 240. That is, the fourth direction can be understood as the third diagonal. The third diagonal ce and the fourth diagonal df can be found in [reference needed]. Figures 11 to 13 The third diagonal ce and the fourth diagonal df shown are not described in detail here. The first grid 212 and grid group 211 can be referred to in [reference needed]. Figures 11 to 13 The first grid 212 and grid group 211 shown will not be described in detail here.

[0083] It should be noted that the number of vertices in the first grid 211 is not limited to four, five, or more than five. For example, the first grid may include three vertices, that is, the first grid 211 may have three vertices.

[0084] Please see Figure 15 , Figure 15 This is a partial structural diagram of the first coupling grating in the optical structure provided in this application embodiment. The vertices of the first grating 212 include vertices c, d, and e. Vertices c, d, and e are interconnected to form a first vertex connecting edge cd, a second vertex connecting edge de, and a third vertex connecting edge ce. The first vertex connecting edge cd is closer to the third coupling grating 230, and the second vertex connecting edge de is farther from the third coupling grating 230. The length of the first vertex connecting edge cd is greater than the length of the second vertex connecting edge de, and the angle between the first vertex connecting edge cd and the third coupling grating 230 in the fifth direction is an acute angle, while the angle between the second vertex connecting edge de and the third coupling grating 230 in the fifth direction is an obtuse angle.

[0085] The fifth direction is the direction from the third output grating 230 to the input grating 240. That is, the fifth direction can be understood as the third direction. For details on the first vertex connection edge cd and the second vertex connection edge de, please refer to [reference needed]. Figures 11 to 13 The third diagonal ce and the fourth diagonal df shown are not described in detail here. The first grid 212 and grid group 211 can be referred to in [reference needed]. Figures 11 to 13 The first grid 212 and grid group 211 shown will not be described in detail here.

[0086] In this embodiment, the first coupling grating 210 and the second coupling grating 220 have the same shape, and are symmetrically arranged with respect to the third coupling grating 230. This can also be understood as the first coupling grating 210 and the second coupling grating 220 being mirror images of the third coupling grating 230. That is, each of the multiple gratings in the second coupling grating 220 is a two-dimensional grating, and the shape and arrangement of the grating structure of each two-dimensional grating are the same as those of the first grating 212. For example, the second coupling grating 220 may be a two-dimensional grating with multiple second gratings, where all the second gratings in the second coupling grating 220 have the same shape and arrangement as all the first gratings in the first coupling grating 210. For specific shapes and arrangements, please refer to [reference needed]. Figures 11 to 15 This will not be elaborated upon here.

[0087] The third coupling grating 230 is a two-dimensional grating with multiple third gratings. These third gratings are symmetrical, such as bilaterally symmetrical, so that the efficiency of light propagating to the left is relative to that propagating to the right, which is beneficial for increasing the size of the eyebox 260 at the edge field of view. The third gratings can be arranged in a hexagonal lattice. The grating vector can be found in [reference needed]. Figure 9Its (1,1)th order diffraction vector is parallel to the y-axis. The third grating can be any shape symmetrical along the y-axis, such as a circle, a positive direction, a rhombus, a hexagon, an octagon, etc. The region of the third coupling grating 230 can be rectangular, for example, the horizontal width in the x-axis direction can be 1mm to 15mm, and the vertical width in the y-axis direction can be 20mm to 35mm.

[0088] In one optional embodiment of this application, the grating periods of the first coupling grating 210, the second coupling grating 220, and the third coupling grating 230 are equal, and the refractive index of any one of the first coupling grating 210, the second coupling grating 220, and the third coupling grating 230 is 1.5-3 with respect to the waveguide 250. The grating period of the coupling grating 240 is half the grating period of any one of the first coupling grating 210, the second coupling grating 220, and the third coupling grating 230 in a direction perpendicular to the first direction. Alternatively, the grating period of the coupling grating 240 is half the grating period of any one of the first coupling grating 210, the second coupling grating 220, and the third coupling grating 230 in the y-axis direction.

[0089] The materials of the coupling grating 240, the first coupling grating 210, the second coupling grating 220 and the third coupling grating 230 can all be silicon, plastic, glass, polymer or some combination of the above materials.

[0090] Please continue reading. Figure 2 The display brightness at each location within the Eyebox260 is determined by the intensity of the emitted light at that location. Therefore, the intensity of rays 2012, 2013A, and 2014A directly determines the display quality of the Eyebox260. However, in practical applications, the intensity of ray 2012 is significantly weaker than that of rays 2013A and 2014A, resulting in a noticeable dark area at the location corresponding to ray 2012 within the Eyebox260. This significantly impacts the user experience. The reason ray 2012 is weaker than rays 2013A and 2014A is that the coupling efficiency of the third coupling grating 230 cannot be set too high. Otherwise, the main ray 201 will attenuate too quickly during propagation. This rapid attenuation of ray 201 leads to differences in light intensity between rays 2012, ultimately causing more severe uneven brightness in the Eyebox260.

[0091] Based on this, this application proposes an optical structure to improve the efficiency of the third coupling grating 230 without causing intensity differences between the rays 2012. For example, the optical structure 200 of this application divides the third coupling grating 230 into multiple regions along the y-axis, with the efficiency of different regions gradually increasing along the y-axis. Although the main ray 201 will attenuate during propagation, the efficiency of the corresponding coupling gratings of the rays 2012 and even later coupled rays can be gradually improved. Although the main ray 201 attenuates faster due to the increased efficiency of the third coupling grating 230, the energy difference between the rays 2012 and even later coupled rays can be reduced. This makes the energy of the rays 2012 closer to that of rays 2013A and 2014A, while reducing the intensity difference between the rays 2012. Ultimately, the brightness and brightness uniformity of the Eyebox 260 are improved simultaneously, and the energy and brightness uniformity of the Eyebox 260 are significantly improved. In summary, the present application embodiment introduces a technique of dividing the third coupling grating 230 into multiple gratings, which solves the above-mentioned problems and greatly improves the energy and brightness uniformity of Eyebox 260. Thus, the present application embodiment has great practical significance and is a high-performance diffraction waveguide architecture.

[0092] The third coupling grating 230 in this embodiment includes at least two sub-coupling gratings. The boundary between two adjacent sub-coupling gratings is located within the eyebox 260 of the optical structure 200. The diffraction efficiency of the sub-coupling gratings farther from the input grating 240 is greater than that of the sub-coupling gratings closer to the input grating 240. This ensures that the overall energy of the light rays coupled out of the third coupling grating 230 is approximately the same, or that the energy of the light rays coupled out of each sub-coupling grating of the third coupling grating 230 is approximately the same. Furthermore, it does not affect the intensity of the light rays coupled out of the third coupling grating 230. A detailed description is provided below with reference to the figures.

[0093] In one optional embodiment of this application, the grating depth of the sub-exit grating farther from the coupling grating 240 is greater than the grating depth of the sub-exit grating closer to the coupling grating 240. This allows the diffraction efficiency of the sub-exit grating farther from the coupling grating 240 to be greater than that of the sub-exit grating closer to the coupling grating 240. In other words, the deeper the grating of the optical structure 200 defined in this optional embodiment of the application, the higher its diffraction efficiency.

[0094] Please see Figure 16 and Figure 17 , Figure 16 This is a schematic diagram of the optical structure provided in an embodiment of this application. Figure 17This is a schematic diagram of the optical structure provided in an embodiment of this application. The third coupling grating 230 of the optical structure 200 may include three sub-coupling gratings, at least a portion of each sub-coupling grating being located within the eye box 260. For example, the third coupling grating 230 includes a first sub-coupling grating 231 partially located on one side of the eye box 260, a second sub-coupling grating 232 partially located on the other side of the eye box 260, and a third sub-coupling grating 233 completely located within the eye box 260.

[0095] The length of the first sub-coupled grating 231 along the direction of arrangement of all sub-coupled gratings is greater than the length of the third sub-coupled grating 233 located within the eyebox 260 along the direction of arrangement of all sub-coupled gratings. Alternatively, it can be understood that the length of the first sub-coupled grating 231 along the y-axis is greater than the length of the third sub-coupled grating 233 located within the eyebox 260 along the y-axis.

[0096] The length of the second sub-coupled grating 232 along the direction of arrangement of all sub-coupled gratings is greater than the length of the third sub-coupled grating 233 located within the eyebox 260 along the direction of arrangement of all sub-coupled gratings. Alternatively, it can be understood that the length of the second sub-coupled grating 232 along the y-axis is greater than the length of the third sub-coupled grating 233 located within the eyebox 260 along the y-axis.

[0097] In one optional embodiment of this application, the length of the second sub-coupled grating 232 along the arrangement direction of all sub-coupled gratings can be the same as the length of the first sub-coupled grating 231 along the same direction. The first sub-coupled grating 231 and the second sub-coupled grating 232 can be symmetrically arranged relative to the third sub-coupled grating 233. It should be noted that the lengths of the first sub-coupled grating 231 and the second sub-coupled grating 232 along the arrangement direction of all sub-coupled gratings can also be unequal.

[0098] In this embodiment, the lengths of the first sub-coupled grating 231 along the arrangement direction of all sub-coupled gratings and the second sub-coupled grating 232 along the arrangement direction of all sub-coupled gratings are both greater than the length of the third sub-coupled grating 233 along the arrangement direction of all sub-coupled gratings. In an optional embodiment, the ratio of the length of the first sub-coupled grating 231 along the arrangement direction of all sub-coupled gratings to the total length of all sub-coupled gratings is P1, that is, the ratio of the length of the first sub-coupled grating 231 along the y-axis to the length of the third sub-coupled grating 230 along the y-axis is P1. The ratio of the length of the third sub-coupled grating 233 along the arrangement direction of all sub-coupled gratings to the total length of all sub-coupled gratings is P2, that is, the ratio of the length of the third sub-coupled grating 233 along the y-axis to the length of the third sub-coupled grating 230 along the y-axis is P2. P1 is greater than or equal to 30% and less than or equal to 45%, and P2 is greater than or equal to 10% and less than 30%.

[0099] In one optional embodiment of this application, the portion of the first sub-coupled grating 231 located within the eyebox 260 has the same size as the portion of the second sub-coupled grating 232 located within the eyebox 260. (Combined with...) Figure 5 and Figure 6 The boundary of the sub-coupled gratings of the third coupled grating 230 is located within the range of B / 2 above and below the center of the third coupled grating 230.

[0100] In one optional embodiment of this application, the diffraction efficiency of all sub-exit gratings increases proportionally from the sub-exit grating closest to the coupling grating 240, such as the first sub-exit grating 231, to the sub-exit grating furthest from the coupling grating 240, such as the second sub-exit grating 232. This can also be understood as the diffraction efficiency of all sub-exit gratings increasing proportionally along the positive y-axis. For example, the diffraction efficiency of the third sub-exit grating 233 is n times that of the first sub-exit grating 231, where n is greater than 1. The diffraction efficiency of the second sub-exit grating 232 is n times that of the third sub-exit grating 233. This ensures that the energy of the light rays coupled out by each sub-diffraction grating is not significantly different.

[0101] It should be noted that, Figure 16 and Figure 17 The three-region structure of the third coupling grating 230 shown is merely illustrative and does not constitute a limitation on the number of regions of the third coupling grating 230. For example, the third coupling grating 230 may include two sub-coupling gratings, four sub-coupling gratings, five sub-coupling gratings, etc. Further examples of multiple sub-coupling gratings will not be described here.

[0102] It should also be noted that when the number of sub-exit gratings of the third coupling grating 230 is greater than three, such as four or five, the following condition still holds true: the boundary between any two adjacent sub-exit gratings of the third coupling grating 230 is located within the eyebox 260 of the optical structure 200, and the diffraction efficiency of the sub-exit gratings farther from the input grating 240 is greater than that of the sub-exit gratings closer to the input grating 240. This also ensures that the overall energy of the light rays coupled out of the third coupling grating 230 is approximately the same, or in other words, that the energy of the light rays coupled out of each sub-exit grating of the third coupling grating 230 is approximately the same. Furthermore, this does not affect the intensity of the light rays coupled out of the third coupling grating 230.

[0103] When the number of sub-coupled gratings of the third coupling grating 230 is greater than three, such as four or five, at least a portion of all sub-gratings of the third coupling grating 230 can be located within the eye box 260. That is, the third coupling grating 230 includes one coupling grating partially located on one side of the eye box 260, one sub-coupled grating partially located on the other side of the eye box 260, and two or more sub-coupled gratings completely located within the eye box 260. The sum of the lengths of all sub-coupled gratings completely located within the eye box 260 along the arrangement direction of all sub-coupled gratings of the third coupling grating 230 is less than the length of any sub-coupled grating partially located outside the eye box 260 along the arrangement direction of all sub-coupled gratings of the third coupling grating 230. This can also be understood as the sum of the lengths of all sub-coupled gratings completely located within the eye box 260 along the y-axis being less than the length of any sub-coupled grating partially located outside the eye box 260 along the y-axis.

[0104] and Figure 16 and Figure 17 In contrast, the sum of the lengths along the y-axis of the at least two sub-coupled gratings, which are completely located within the eyebox 260, is P2 compared to the length of the third coupled grating 230 along the y-axis. Further features can be found in [reference needed]. Figure 16 and Figure 17 This will not be elaborated upon here.

[0105] Please see Figure 18 , Figure 18 A schematic diagram of the optical structure provided in the embodiments of this application. Figure 18 The diagram illustrates that the third coupling grating 230 includes four sub-coupling gratings: a first sub-coupling grating 231, a second sub-coupling grating 232, a third sub-coupling grating 233, and a fourth sub-coupling grating 234. The first and second sub-coupling gratings 231 and 232 are described above and will not be repeated here. The third and fourth sub-coupling gratings 233 and 234 are both located within the eye box 260.

[0106] Please see Figure 19 , Figure 19 A schematic diagram of the optical structure provided in the embodiments of this application. Figure 19 The diagram illustrates that the third coupling grating 230 includes five sub-coupling gratings: a first sub-coupling grating 231, a second sub-coupling grating 232, a third sub-coupling grating 233, a fourth sub-coupling grating 234, and a fifth sub-coupling grating 235. The first and second sub-coupling gratings 231 and 232 are described above and will not be repeated here. The third, fourth, and fifth sub-coupling gratings are all located within the eye box 260.

[0107] Considering that the intensity of rays 2012, 2013A, and 2014A directly determines the display quality of Eyebox260, and in practical applications, the intensity of ray 2012 is significantly weaker than that of rays 2013A and 2014A, in some embodiments of this application, the third coupling grating 230 that can couple out ray 2012 is arranged in separate regions. This allows the energy of ray 2012 to be closer to that of rays 2013A and 2014A, while reducing the intensity difference between rays 2012. Ultimately, this improves both the brightness and brightness uniformity of Eyebox260, resulting in a significant improvement in both energy and brightness uniformity. In practical applications, the energy of rays 2013A and 2014A is also lost as they propagate. To further improve both the brightness and brightness uniformity of Eyebox260, in some optional embodiments of this application, the first coupling grating 210 and the second coupling grating 220 are also arranged in separate regions. A detailed description is provided below with reference to the figures.

[0108] Please see Figure 20 , Figure 20 A schematic diagram of the optical structure provided in the embodiments of this application. Figure 20 The first coupling grating 210, the second coupling grating 220, and the third coupling grating 230 in the optical structure 200 shown are evenly distributed into regions. The regional arrangement of the third coupling grating 230 can be found in [reference needed]. Figures 16 to 19 This will not be elaborated upon here.

[0109] The first coupling grating 210 includes at least two sub-coupling gratings, and the number of sub-coupling gratings in the first coupling grating 210 is the same as the number of sub-coupling gratings in the third coupling grating 230, such as three. The boundary between two adjacent sub-coupling gratings in the first coupling grating 210 is located within the eyebox 260 of the optical structure 200. The diffraction efficiency of the sub-coupling gratings in the first coupling grating 210 that are farther from the input grating 240 is greater than that of the sub-coupling gratings that are closer to the input grating 240. This ensures that the overall energy of the light rays coupled out of the first coupling grating 210 is approximately the same, or that the energy of the light rays coupled out of each sub-coupling grating of the first coupling grating 210 is approximately the same, without affecting the intensity of the light rays coupled out of the first coupling grating 210.

[0110] Figure 20The first coupling grating 210 shown here comprises three sub-coupling gratings. The first coupling grating 210 includes a first sub-coupling grating 211, a second sub-coupling grating 212, and a third sub-coupling grating 213. It should be noted that the first sub-coupling grating 211 can be referred to as the first sub-coupling grating 231, the second sub-coupling grating 212 can be referred to as the third sub-coupling grating 233, and the third sub-coupling grating 213 can be referred to as the second sub-coupling grating 232; these will not be repeated here. It should also be noted that when the number of sub-regions in the first coupling grating 210 and the third coupling grating 230 are both greater than three, refer to... Figure 18 and Figure 19 Two, three, or more sub-coupled gratings are arranged between the first sub-coupled grating 211 and the third sub-coupled grating 213, and their arrangement is the same as that of the sub-coupled gratings of the third sub-coupled grating 230, which will not be described in detail here.

[0111] The second coupling grating 220 includes at least two sub-coupling gratings, the number of which is the same as the number of sub-coupling gratings in the third coupling grating 230, such as three. The boundary between two adjacent sub-coupling gratings in the second coupling grating 220 is located within the eyebox 260 of the optical structure 200. The diffraction efficiency of the sub-coupling gratings in the second coupling grating 220 that are farther from the input grating 240 is greater than that of the sub-coupling gratings that are closer to the input grating 240. This ensures that the overall energy of the light rays coupled out of the second coupling grating 220 is approximately the same, or that the energy of the light rays coupled out of each sub-coupling grating of the second coupling grating 220 is approximately the same, without affecting the intensity of the light rays coupled out of the second coupling grating 220.

[0112] Figure 20 The second coupling grating 220 shown is illustrated using three sub-coupling gratings as an example. The second coupling grating 210 includes a first sub-coupling grating 221, a second sub-coupling grating 222, and a third sub-coupling grating 223. It should be noted that the first sub-coupling grating 221 can be referred to as the first sub-coupling grating 231, the second sub-coupling grating 222 can be referred to as the third sub-coupling grating 233, and the third sub-coupling grating 223 can be referred to as the second sub-coupling grating 232; these will not be repeated here. It should also be noted that when the number of sub-regions in both the second coupling grating 220 and the third coupling grating 230 is greater than three, references can be made to... Figure 18 and Figure 19 Two, three, or more sub-coupled gratings are arranged between the first sub-coupled grating 221 and the third sub-coupled grating 223, and their arrangement is the same as that of the sub-coupled gratings of the third sub-coupled grating 230, which will not be described in detail here.

[0113] It is understood that in other embodiments of this application, the arrangement of only one of the first coupling grating 210, the second coupling grating 220, and the third coupling grating 230 in a regional manner is also within the scope defined by the embodiments of this application. Furthermore, the arrangement of only two of the first coupling grating 210, the second coupling grating 220, and the third coupling grating 230 in a regional manner is also within the scope defined by the embodiments of this application.

[0114] When the third output grating 230 includes multiple sub-output gratings, the first output grating 210, the second output grating 220, and the third output grating 230 can all be two-dimensional gratings, such as... Figures 1 to 15 The details shown will not be repeated here. It should be noted that when the third output grating 230 includes multiple sub-output gratings, the first output grating 210 and the second output grating 220 can also employ other grating structures, such as one-dimensional gratings. When the first output grating 210 and the second output grating 220 are one-dimensional gratings, the third output grating 230 is a two-dimensional grating, and the input grating 240 is a one-dimensional grating. The grating periods of the first output grating 210, the second output grating 220, and the input grating 240 are equal, and the grating period of the third output grating 230 along the arrangement direction of all its sub-output gratings is twice the grating period of any one of the three: the first output grating 210, the second output grating 220, and the input grating 240.

[0115] The optical structures 200 defined in the above embodiments of this application can all be applied to optical devices, which may include a projector and any of the above optical structures 200. The optical device can be an augmented reality device or a virtual reality device.

[0116] The optical structures and optical devices provided in the embodiments of this application have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the embodiments above are only for the purpose of helping to understand the methods and core ideas of this application. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. An optical structure, characterized in that, include: Wave conductor; A first coupling grating is disposed on the waveguide. The first coupling grating has a plurality of first grids, and each first grid is asymmetrical in shape, such that the light propagation efficiency of the first coupling grating in the first direction is higher than the light propagation efficiency of the first coupling grating in the second direction. A second coupling grating is disposed on the waveguide; wherein, the first direction is the direction from the first coupling grating to the second coupling grating, and the second direction is the direction from the second coupling grating to the first coupling grating, and the first direction and the second direction are opposite; A third coupling grating is disposed on the waveguide, the third coupling grating being located between the first coupling grating and the second coupling grating; and A coupling grating is disposed on the same side of the first coupling grating, the second coupling grating, and the third coupling grating, and the coupling grating and the third coupling grating are arranged side by side; The third coupling grating includes at least two sub-coupling gratings, the junction of two adjacent sub-coupling gratings is located within the eyebox of the optical structure, and the diffraction efficiency of the sub-coupling gratings farther from the coupling grating is greater than that of the sub-coupling gratings closer to the coupling grating.

2. The optical structure according to claim 1, characterized in that, The grating depth of the sub-outgoing grating farther from the coupled-in grating is greater than the grating depth of the sub-outgoing grating closer to the coupled-in grating.

3. The optical structure according to claim 1, characterized in that, At least a portion of all sub-coupled gratings are located within the eyebox.

4. The optical structure according to claim 3, characterized in that, The third coupling grating includes at least three sub-coupling gratings, the at least three sub-coupling gratings including a first sub-coupling grating partially located on one side of the eye box, a second sub-coupling grating partially located on the other side of the eye box, and at least one sub-coupling grating completely located within the eye box; The length of the first sub-coupled grating along the arrangement direction of all sub-coupled gratings is greater than the sum of the lengths of at least one sub-coupled grating located within the eye box along the arrangement direction of all sub-coupled gratings; The length of the second sub-coupled grating along the arrangement direction of all sub-coupled gratings is greater than the sum of the lengths of at least one sub-coupled grating located within the eye box along the arrangement direction of all sub-coupled gratings.

5. The optical structure according to claim 4, characterized in that, The sub-outgoing gratings located entirely within the eye box can be one, two, or three, and the diffraction efficiency of all sub-outgoing gratings increases proportionally from the sub-outgoing grating closest to the input grating to the sub-outgoing grating furthest from the input grating.

6. The optical structure according to claim 4, characterized in that, The first sub-coupling grating and the second sub-coupling grating are symmetrically arranged relative to the sub-coupling gratings that are completely located within the eye box.

7. The optical structure according to claim 4, characterized in that, The ratio of the length of the first sub-coupled grating or the second sub-coupled grating along the arrangement direction of all sub-coupled gratings to the length of all sub-coupled gratings is P1, and the ratio of the length of all sub-coupled gratings located entirely within the eye box along the arrangement direction of all sub-coupled gratings to the length of all sub-coupled gratings is P2. Among them, P1 is greater than or equal to 30% and P2 is less than or equal to 45%, and P2 is greater than or equal to 10% and P2 is less than 30%.

8. The optical structure according to any one of claims 1 to 7, characterized in that, The first coupling grating includes at least two sub-coupling gratings. The number of sub-coupling gratings in the first coupling grating is the same as the number of sub-coupling gratings in the third coupling grating. The junction of two adjacent sub-coupling gratings in the first coupling grating is located within the eyebox of the optical structure. The diffraction efficiency of the sub-coupling gratings in the first coupling grating that are far from the coupling grating is greater than the diffraction efficiency of the sub-coupling gratings that are close to the coupling grating. The second coupling grating includes at least two sub-coupling gratings. The number of sub-coupling gratings in the second coupling grating is the same as the number of sub-coupling gratings in the third coupling grating. The junction of two adjacent sub-coupling gratings in the second coupling grating is located within the eyebox of the optical structure. The diffraction efficiency of the sub-coupling gratings in the second coupling grating that are farther from the coupling grating is greater than the diffraction efficiency of the sub-coupling gratings that are closer to the coupling grating is greater.

9. The optical structure according to any one of claims 1 to 7, characterized in that, The third output grating is a two-dimensional grating, the input grating is a one-dimensional grating, the grating period of the third output grating along the arrangement direction of all sub-output gratings of the third output grating is twice the grating period of the input grating, the first output grating and the second output grating are both one-dimensional gratings, or the first output grating and the second output grating are both two-dimensional gratings; The refractive index of any one of the first output grating, the second output grating, the third output grating, and the input grating is 1.5-3 with respect to the waveguide; When the first output grating and the second output grating are one-dimensional gratings, the periods of the first output grating, the second output grating, and the input grating are equal; When the first and second coupled gratings are two-dimensional gratings, the periods of the first coupled grating, the second coupled grating, and the third coupled grating are equal.

10. An optical device, characterized in that, It includes: A projector configured to provide augmented reality or virtual reality images; and The optical structure as described in any one of claims 1 to 9.

Images