Diffractive optical waveguide based on two-dimensional gratings

Abstract

The application provides a two-dimensional grating-based diffractive optical waveguide, characterized by integration of in-coupling, pupil expansion and out-coupling of the diffractive optical waveguide, and the diffractive optical waveguide comprises a waveguide substrate and a grating structure arranged on a surface of the waveguide substrate, the grating structure comprises a plurality of grating units arranged periodically and forms at least a first periodic line and a second periodic line, and the first periodic line and the second periodic line cross each other. The application can realize in-coupling, pupil expansion and out-coupling of a micro projector image by using a two-dimensional grating, effectively reduces optical installation precision of the optical waveguide and the micro projector and expands a visual area of the optical waveguide, and effectively realizes low-cost manufacturing of an augmented reality display device.

Description

[0001] This application is a divisional application. The original patent application was entitled "Diffractive Waveguide Based on Two-Dimensional Grating", patent number: 201980003965.7, and the application date was December 26, 2019. Technical Field

[0002] This application relates to the field of augmented reality technology, and in particular to diffractive waveguides based on two-dimensional gratings. Background Technology

[0003] Augmented reality (AR) technology is a new technology that seamlessly integrates real-world and virtual-world information. It takes virtual information that is difficult to experience within a certain time and space in the real world, simulates it using computers, and then overlays it onto the real world, applying the virtual information to be perceived by human senses, thus achieving a sensory experience that transcends reality. The real environment and virtual objects are superimposed in real time onto the same scene or space, existing simultaneously.

[0004] Augmented reality technology has wide applications not only in fields similar to virtual reality, such as aircraft research and development, data model visualization, virtual training, entertainment and art, but also has significant advantages over virtual reality technology in fields such as medical research and anatomical training, precision instrument manufacturing and maintenance, engineering design and remote robot control due to its ability to enhance the display output of the real environment.

[0005] To achieve an optically perceptual augmented reality display solution, some researchers have designed freeform prism elements. By using a reflective optical path and a compensating prism, they have achieved an optically perceptual augmented reality display. However, due to the curvature requirement of the freeform prism, the thickness of the optical system in this solution cannot be made very thin while achieving a good visual experience, which limits the further thinning of glasses-type augmented reality displays.

[0006] Other designs use planar waveguides, which utilize total internal reflection of light within the planar waveguide element to transmit the projector output beam. Multiple reflective surfaces or gratings are used to intercept the transmitted beam to expand the exit pupil of the optical system, effectively reducing the thickness of the optical element. However, in existing planar waveguide designs, the image coupling, pupil expansion, and coupling-out parts usually need to be designed and fabricated separately, which is difficult and costly to manufacture. Furthermore, the display area of ​​the waveguide is limited, resulting in low flexibility. Summary of the Invention

[0007] To overcome the shortcomings of existing technologies, this application provides a planar optical waveguide based on a two-dimensional grating that integrates coupling in, pupil expansion, and coupling out. The optical waveguide of this application is easy to fabricate and flexible and convenient to use.

[0008] The technical solution of this application is as follows:

[0009] A planar optical waveguide based on a two-dimensional grating includes an optical waveguide transmission mechanism and a grating working mechanism; the optical waveguide transmission mechanism is a transparent parallel waveguide; the grating working mechanism is composed of a two-dimensional grating with a fixed period and an included angle of 60°; the two-dimensional grating protrudes or is recessed on the upper surface of the parallel waveguide.

[0010] The parallel waveguide is a planar structure made of a visible light transparent optical material, and the upper and lower surfaces of the parallel waveguide are parallel.

[0011] In use, the light emitted by the micro-projector, after passing through any area of ​​the grating mechanism, is diffracted by the two-dimensional grating into multiple orders of light directions that enter the optical waveguide. Within the waveguide transmission mechanism, it is transmitted outwards via total internal reflection. Each time light enters the grating mechanism, diffraction occurs again. A portion of the light is diffracted out of the waveguide and enters the human eye, while the remaining light is diffracted into multiple orders of directions and continues to propagate within the waveguide. Ultimately, light is coupled out throughout the entire grating mechanism area, allowing the human eye to observe a complete and continuous image across the entire grating mechanism area.

[0012] As a preferred embodiment, the refractive index of the parallel waveguide is 1.4–2.2, and the thickness is 0.3–2.5 mm. Currently, the refractive index of commercially available optical materials is generally within this range. Theoretically, the higher the refractive index of the parallel waveguide in this application, the better.

[0013] As a preferred embodiment, the period of the two-dimensional grating is 200–700 nm.

[0014] As a preferred embodiment, the two-dimensional grating is cylindrical or prismatic with a rhomboid base. Of course, the two-dimensional grating can also be other feasible shapes.

[0015] As a preferred embodiment, the diameter or side length of the two-dimensional grating is 50-650 nm, and the height or depth is 80-650 nm.

[0016] As a preferred embodiment, a fixed coupling point is set on the grating working mechanism. In order to solve the problem that the light transmission intensity in the optical waveguide weakens after the light rays are coupled out of the two-dimensional grating, which in turn causes the brightness of the final image to gradually weaken in the light transmission direction, the depth of the two-dimensional grating is controlled by dividing it into regions, thereby controlling the uniformity of the light coupling intensity in each region.

[0017] To facilitate control of intensity uniformity, a fixed coupling point is set on the grating working mechanism. Of course, if the uniformity requirement is not high, depth modulation can be omitted, and coupling can be performed at any position, i.e., there is no need to specifically set a coupling point.

[0018] Furthermore, the diameter or side length of the coupling point is 200–650 nm, and the height or depth is 200–650 nm.

[0019] As a preferred embodiment, the diameter or side length of the insertion point is greater than the diameter or side length of each insertion point located around it, and the height or depth is greater than the height or depth of each insertion point located around it.

[0020] Furthermore, the farther the coupling point is from the coupling point, the larger its diameter or side length.

[0021] As a preferred option, the farther the coupling point is from the coupling point, the greater its height or depth.

[0022] The depth and shape of the two-dimensional grating are modulated to ensure good uniformity of light coupling intensity in each region.

[0023] According to another aspect of this application, a two-dimensional grating-based optical waveguide is further provided, comprising:

[0024] Waveguide substrate; and

[0025] A grating structure, wherein the grating structure is disposed on a surface of the waveguide substrate, wherein the grating structure includes a set of grating units and periodic lines having each of the grating units arranged along a periodic direction, wherein the periodic lines include a first periodic line and a second periodic line that intersect each other and have an included angle of 60°.

[0026] In one embodiment, the grating unit is a protruding structure that protrudes from the surface of the waveguide substrate.

[0027] In one embodiment, the surface of the waveguide substrate has a groove, and the grating structure protrudes from the bottom surface of the groove.

[0028] In one embodiment, the grating unit is perpendicular to the surface of the waveguide substrate.

[0029] In one embodiment, the diffraction efficiency of the grating structure is preset based on adjusting the duty cycle of the grating structure or the height of the grating unit.

[0030] In one embodiment, the grating unit has a certain tilt angle with the surface of the waveguide substrate.

[0031] In one embodiment, the diffraction efficiency of the grating structure is preset based on adjusting the duty cycle of the grating structure, the height of the grating unit, or the tilt angle.

[0032] In one embodiment, adjacent grating units have a certain bevel angle.

[0033] In one embodiment, the diffraction efficiency of the grating structure is preset based on adjusting the duty cycle of the grating structure, the height of the grating unit, or the included angle of the inclined plane.

[0034] In one embodiment, the waveguide substrate has a refractive index of 1.4 to 2.2 and a thickness of 0.3 mm to 2.5 mm.

[0035] In one embodiment, the period of the grating structure is 200 nm to 700 nm.

[0036] In one embodiment, the length or linewidth of the grating unit is 50 nm to 650 nm, and the height or depth is 80 nm to 650 nm.

[0037] In one embodiment, the grating unit is a columnar structure, a cylindrical structure, an elliptical columnar structure, a prism structure, a conical structure, a pyramidal structure, a frustum-like structure, or a frustum-like structure.

[0038] In one embodiment, the grating structure is located on the surface of the waveguide substrate, wherein the surface is a plane, and the height of each grating unit is consistent.

[0039] In one embodiment, the grating structure is located on the surface of the waveguide substrate, wherein the surface is a plane, and the grating structure includes adjacent first regions and second regions sequentially divided along the direction of light propagation, wherein the first region has a plurality of first grating units, wherein the second region has a plurality of second grating units, and wherein the height of the first grating unit is not equal to the height of the second grating unit.

[0040] In one embodiment, the grating structure further includes a third region adjacent to the second region, divided along the direction of light propagation, wherein the third region has a plurality of third grating units, and the height of the third grating units is not equal to the height of the second grating units.

[0041] In one embodiment, the first grating unit in the first region, the second grating unit in the second region, and the third grating unit in the third region rise in a stepped manner.

[0042] In one embodiment, the surface includes a first surface and a second surface that are not on the same plane and are divided along the direction of light propagation.

[0043] In one embodiment, the grating structure includes a plurality of first grating units located on the first surface and a plurality of second grating units located on the second surface, wherein the height difference between the second grating units and the first grating units is equal to the height difference between the first surface and the second surface.

[0044] In one embodiment, the first surface is higher than the second surface in the thickness direction of the waveguide substrate.

[0045] In one embodiment, the surface further includes a third surface adjacent to the second surface but not on the same plane, and the grating structure further includes a third grating unit located on the third surface, wherein the height difference between the third grating unit and the second grating unit is equal to the height difference between the third surface and the second surface.

[0046] In one embodiment, the first surface, the second surface, and the third surface descend in a stepped manner.

[0047] According to another aspect of this application, an augmented reality display device is further provided, comprising:

[0048] Equipment body; and

[0049] At least one optical waveguide, wherein the optical waveguide is disposed in the device body, wherein the optical waveguide comprises:

[0050] Waveguide substrate;

[0051] A grating structure, wherein the grating structure is disposed on a surface of the waveguide substrate, wherein the grating structure includes a set of grating units and periodic lines having each of the grating units arranged along a periodic direction, wherein the periodic lines include a first periodic line and a second periodic line that intersect each other and have an included angle of 60°.

[0052] In one embodiment, the device body includes a housing and at least one projection unit, wherein the projection unit and the optical waveguide are mounted on the housing, wherein the projection unit is used to project image light onto the optical waveguide, wherein the light is coupled into the waveguide substrate for total internal reflection, and wherein the light that is totally internally reflected in the waveguide substrate is coupled out through the grating structure.

[0053] In one embodiment, the device body further includes an image sensor, a position sensor, and a processor. The image sensor is used to acquire external image information, the position sensor is used to determine spatial position coordinates and orientation, and the processor is used to generate an image signal that can render a virtual image of the real world based on the spatial position coordinates and orientation and the image information. The projection unit projects corresponding image rays onto the optical waveguide based on the image signal to present the real world rendered by the virtual image in the user's field of view.

[0054] In one embodiment, the image sensor is an RGB camera, a monochrome camera, a depth camera, or a combination thereof.

[0055] In one embodiment, the device body further includes a memory for storing information about the display device.

[0056] In one embodiment, the projection unit includes a display and a lens group, wherein the lens group is disposed in the projection light path of the display, wherein the display is used to project corresponding image light based on the image signal, and wherein the light is collimated and magnified by the lens group and then projected onto the optical waveguide.

[0057] In one embodiment, the device body is a glasses device body that can be worn on the user's head or an immersive device body.

[0058] In one embodiment, the device body further includes a network communication interface, wherein the network communication interface is used to receive signals of virtual images transmitted from the outside.

[0059] In one embodiment, the position sensor includes determining translational degrees of freedom along the X, Y, and Z axes of a three-dimensional spatial coordinate system and rotational degrees of freedom about the X, Y, and Z axes.

[0060] In one embodiment, the device body further includes at least one hand device, wherein the hand device can be worn on a user's hand, and wherein the position sensor is disposed on the hand device to determine the spatial position coordinates and orientation of the user's hand.

[0061] In one embodiment, the device body further includes a connection port for connecting at least two of the display devices to allow interaction between the display devices.

[0062] According to another aspect of this application, a method for manufacturing an optical waveguide based on a two-dimensional grating is further provided, comprising:

[0063] A. Provide the waveguide substrate; and

[0064] B. A grating structure is formed on one surface of the waveguide substrate, wherein the grating structure includes a set of grating units and periodic lines having each of the grating units arranged along a periodic direction, wherein the periodic lines include a first periodic line and a second periodic line that intersect each other and have an included angle of 60°.

[0065] In one embodiment, in step B, the grating structure is formed on the surface of the waveguide substrate by photolithography, etching, growth, molding, or injection molding.

[0066] In one embodiment, step B includes:

[0067] B1. A master template is provided, wherein the master template has a grating structure to be transferred corresponding to the grating structure, wherein the grating structure to be transferred includes grating units to be transferred arranged with a first periodic line and a second periodic line with an included angle of 60°, wherein the grating units to be transferred are consistent with the structural shape, arrangement, height and line width of the grating units.

[0068] B2. A sub-mold is formed by polymerizing the master plate, wherein the sub-mold has a complementary structure that complements the grating structure to be transferred on the master plate, and the complementary structure forms a cavity that matches the structural shape, arrangement, height and line width of the grating unit.

[0069] B3. Apply the uncured grating substrate material of the grating structure to the surface of the waveguide substrate;

[0070] B4. The uncured grating substrate material is imprinted by the sub-mold to fill the cavity of the sub-mold with the uncured grating substrate material, and the grating substrate material is cured to form the grating structure on the surface of the waveguide substrate.

[0071] In one embodiment, the method further includes removing the sub-mode to obtain the optical waveguide.

[0072] In one embodiment, the grating substrate material is a resin material.

[0073] In one embodiment, in step B4, the grating substrate material is cured by ultraviolet light or by heat.

[0074] In one embodiment, in step B4, the sub-mode is pressed against the surface of the waveguide substrate by pressure, so that the uncured grating substrate material fills the cavity of the sub-mode by pressure and vacuum.

[0075] In one embodiment, in step B1, the master template can be prepared by etching methods including electron beam etching, reactive ion beam etching, magnetically enhanced reactive ion etching, high-density plasma etching, inductively coupled plasma etching, voltage-coupled plasma etching, or electron cyclotron resonance etching, vacuum ion evaporation, magnetron sputtering, MBE molecular beam epitaxy, PLD laser sputtering deposition, etc.

[0076] In one embodiment, the height of the grating structure is modulated by controlling the etching time and exposure intensity of the electron beam or ion beam on the master substrate.

[0077] In one embodiment, in step B1, the grating structure to be transferred is a protruding structure that protrudes from the surface of the master plate.

[0078] In one embodiment, in step B1, there is a height difference between the grating units to be transferred in different regions of the grating structure to be transferred.

[0079] In one embodiment, in step B1, the grating units of the grating structure to be transferred are arranged in a stepped manner along the periodic direction.

[0080] According to another aspect of this application, a diffractive waveguide based on a two-dimensional grating is provided, wherein the diffractive waveguide integrates coupling-in, pupil expansion, and coupling-out, and the diffractive waveguide includes:

[0081] Waveguide substrate; and

[0082] A grating structure is disposed on the surface of the waveguide substrate. The grating structure includes a plurality of periodically arranged grating units and forms at least a first periodic line and a second periodic line, the first periodic line and the second periodic line intersecting each other.

[0083] In one embodiment, after light is coupled into any region of the grating structure, it is diffracted by the grating unit of the grating structure to generate multiple orders of light rays that enter the waveguide substrate in different directions, and light rays are coupled out of the entire grating structure, so that the coupling, pupil expansion and coupling out of light can be achieved through a single grating structure.

[0084] In one embodiment, the diameter or side length of the grating unit in the light coupling region of the grating structure is greater than the diameter or side length of the grating unit located around the coupling region; or the height or depth of the grating unit in the light coupling region of the grating structure is greater than the height or depth of the grating unit located around the coupling region.

[0085] In one embodiment, the first periodic line and the second periodic line intersect each other at an angle of 60°.

[0086] In one embodiment, the first surface of the waveguide substrate is planar, and the grating structure is disposed on the first surface. The grating structure is divided into multiple regions, and multiple grating units are disposed in each region. The coupling output efficiency of the grating units in adjacent regions is different.

[0087] In one embodiment, the coupling output efficiency of the grating structure is optimized as follows:

[0088]

[0089] Where, η N The output diffraction efficiency is the Nth region coupled, where N is the output order of the region modulation. T η is the total number of modulation regions. T The proportion of light energy coupled out of the effective area of ​​the grating structure to the total light energy of total internal reflection.

[0090] In one embodiment, the first surface of the waveguide substrate is a stepped surface with different heights for adjacent steps. The grating structure is disposed on the first surface, and the grating units of the grating structure are located on the same plane on the side away from the waveguide substrate.

[0091] In one embodiment, the height of the stepped surfaces arranged along the direction of light propagation gradually decreases.

[0092] The beneficial effects of this application are as follows:

[0093] 1. The optical waveguide transmission mechanism is a transparent parallel waveguide, and the grating working mechanism is a two-dimensional grating with a fixed period and an included angle of 60°. The image of the micro-projector can be incident on the optical waveguide in any area of ​​the grating working mechanism, and the human eye can view the emitted image in any area of ​​the grating working mechanism.

[0094] 2. This application can achieve the coupling, pupil expansion and coupling out of the micro-projector image using a single two-dimensional grating, effectively reducing the optical installation accuracy between the optical waveguide and the micro-projector and expanding the visible area of ​​the optical waveguide, thus effectively realizing the low-cost manufacturing of augmented reality display devices.

[0095] 3. The depth and shape of the light output intensity in each region can be modulated by a grating on the surface of the parallel waveguide, thereby improving the uniformity of the light output intensity in each region.

[0096] 4. This application has a simple structure, is easy to mass-produce and process, and has flexible usage, making it highly valuable for industrial applications.

[0097] 5. Ensure that the image brightness seen by the user is uniform (the brightness presented at each viewing angle is equivalent), and that the image brightness remains stable when there is relative displacement between the human eye and the display device such as AR glasses (i.e., uniform brightness within the viewing window).

[0098] The further objectives and advantages of this application will become fully apparent from the following description and accompanying drawings.

[0099] These and other objects, features and advantages of this application are fully apparent from the following detailed description, the accompanying drawings and the claims. Attached Figure Description

[0100] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art 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.

[0101] Figure 1A A schematic diagram of a diffractive waveguide based on a two-dimensional grating provided in an embodiment of this application;

[0102] Figure 1B A schematic diagram of a diffractive waveguide based on a two-dimensional grating provided in another embodiment of this application;

[0103] Figure 2 This is a schematic diagram showing that the grating unit of the grating structure in one embodiment of this application is cylindrical;

[0104] Figure 3 A schematic diagram of the internal transmission principle of a diffractive waveguide provided in one embodiment of this application;

[0105] Figure 4 This is a schematic diagram of the grating structure divided into regions in one embodiment of this application;

[0106] Figure 5 This is a schematic diagram showing that the grating unit of the grating structure in one embodiment of this application is prismatic (with a rhomboid cross-section);

[0107] Figure 6 This is a schematic diagram showing that the grating unit of the grating structure in one embodiment of this application is elliptical cylindrical;

[0108] Figure 7 This is a schematic diagram showing that the grating unit of the grating structure in one embodiment of this application is prismatic (with a double rhombus cross-section);

[0109] Figure 8 This is a schematic diagram showing that the grating unit of the grating structure in one embodiment of this application is triangular prism-shaped;

[0110] Figure 9A This is a partial cross-sectional schematic diagram of the grating structure perpendicular to the surface of the waveguide substrate in one embodiment of this application;

[0111] Figure 9B This is a partial cross-sectional schematic diagram of a grating structure and a waveguide substrate having a certain tilt angle in one embodiment of this application;

[0112] Figure 9C This is a partial cross-sectional schematic diagram showing that adjacent grating units of a grating structure have a certain angle between their inclined surfaces in one embodiment of this application;

[0113] Figure 10A This is a partial cross-sectional schematic diagram of the grating structure perpendicular to the surface of the waveguide substrate in another embodiment of this application;

[0114] Figure 10B This is a partial cross-sectional schematic diagram showing the grating structure and waveguide substrate having a certain tilt angle in another embodiment of this application;

[0115] Figure 10C This is a partial cross-sectional schematic diagram showing the grating structure and waveguide substrate having a certain tilt angle in another embodiment of this application;

[0116] Figure 11A This is a partial three-dimensional schematic diagram of a diffractive waveguide in one embodiment of this application;

[0117] Figure 11B This is a partial three-dimensional schematic diagram of a diffractive waveguide in another embodiment of this application. Detailed Implementation

[0118] The following description is intended to disclose this application and enable those skilled in the art to implement it. The preferred embodiments described below are merely examples, and other obvious variations will occur to those skilled in the art. The basic principles of this application defined in the following description can be applied to other embodiments, modifications, improvements, equivalents, and other technical solutions that do not depart from the spirit and scope of this application.

[0119] Those skilled in the art should understand that, in the disclosure of this application, the terms "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the above terms should not be construed as limitations on this application.

[0120] It is understood that the term "a" should be understood as "at least one" or "one or more", that is, in one embodiment, the number of an element can be one, while in another embodiment, the number of the element can be multiple, and the term "a" should not be understood as a limitation on the number.

[0121] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0122] To make the technical means, creative features, objectives and effects of this application easier to understand, this application will be further explained below with specific illustrations and examples.

[0123] like Figure 1A , Figure 1B As shown, the planar optical waveguide based on a two-dimensional grating in this application includes an optical waveguide transmission mechanism 1 and a grating working mechanism 2.

[0124] The optical waveguide transmission mechanism 1 is a transparent parallel waveguide. The parallel waveguide is a planar structure made of a visible-light-transparent optical material. The upper and lower surfaces of the parallel waveguide are parallel, and its thickness is 0.3–2.5 mm. The refractive index of the waveguide material is 1.4–2.2. (Refer to...) Figure 2 The grating working mechanism 2 consists of a two-dimensional grating with a fixed period and an included angle of 60°. The grating period T ranges from 200 to 700 nm. The grating can be modulated in depth and shape on the waveguide surface according to the region. Figure 2 The shape of a two-dimensional grating is cylindrical, but two-dimensional gratings can also be other shapes, such as... Figure 5 , Figure 6 , Figure 7 , Figure 8 As shown.

[0125] Reference Figure 3When the light from the micro-projector 3 illuminates any area a of the grating working area, the light is diffracted by the grating to produce four diffraction orders b, c, d, and e, which are transmitted in four directions within the optical waveguide. The angle between these four beams and the waveguide interface is greater than the Brewster angle required for total internal reflection, ensuring lossless transmission of light within the waveguide transmission section. When the b, c, d, and e beams illuminate the grating working area again, some of them will be diffracted and coupled out of the waveguide. The remaining beams will be diffracted again by the two-dimensional grating into three orders and continue to be transmitted by total internal reflection within the optical waveguide. For example, the b beam will be diffracted into f, g, and h beams and continue to be transmitted within the optical waveguide. This cycle continues until light is coupled out throughout the entire grating working area, so that the human eye 4 can see a complete and continuous image at any position. Figure 4 This is a schematic diagram of the grating working mechanism of an optical waveguide divided into regions.

[0126] Figure 1A The two-dimensional grating protrudes from the upper surface of the parallel waveguide. (Refer to...) Figure 1B Furthermore, the planar optical waveguide based on the two-dimensional grating in this application can also be recessed on the upper surface of the parallel waveguide.

[0127] In other words, such as Figure 1A As shown, the upper surface of the waveguide substrate of the optical waveguide is a flat surface, i.e., a single plane, in which the grating structure of the grating working mechanism 1 is located on the surface of the waveguide substrate. Figure 1B As shown, the upper surface of the waveguide substrate has a groove 101, wherein the grating structure is located on the bottom surface of the groove 101, and the bottom surface of the groove 101 is lower than the upper surface of the waveguide substrate, that is, they are not on the same plane.

[0128] Example 1

[0129] like Figure 1A , Figure 2 As shown, the planar optical waveguide based on a two-dimensional grating in this application includes an optical waveguide transmission mechanism 1 and a grating working mechanism 2.

[0130] In this embodiment, the optical waveguide transmission mechanism 1 is a parallel flat glass with a thickness of 0.5 mm and a refractive index of 1.5.

[0131] A cylindrical two-dimensional grating with an included angle of 60°, a period T of 360nm, a diameter R of 100nm, and a depth of 150nm is fabricated on the surface of a parallel flat glass (optical waveguide) to form the grating working mechanism 2.

[0132] The optical waveguide was divided into 30 regions, namely, longitudinal region A to E and transverse region 1 to 6. The image from the micro-projector was projected into the optical waveguide from region C5. The image intensity was measured in the remaining regions and normalized. The measurement results are shown in Table 1.

[0133] Table 1 is a table showing the image intensity test results of the optical waveguide in Embodiment 1 of this application.

[0134] A 0.5 0.6 0.7 0.8 0.7 0.8 B 0.6 0.65 0.75 1 0.8 1 C 0.65 0.7 0.8 0.9 Coupled in 0.9 D 0.6 0.65 0.75 1 0.8 1 E 0.5 0.6 0.7 0.8 0.7 0.8

[0135] Example 2

[0136] like Figure 1A , Figure 1B As shown, the planar optical waveguide based on a two-dimensional grating in this application includes an optical waveguide transmission mechanism 1 and a grating working mechanism 2.

[0137] In this embodiment, the optical waveguide transmission mechanism 1 is a parallel flat glass with a thickness of 1.9 mm and a refractive index of 1.8.

[0138] A two-dimensional prism grating with a 60° included angle, a period T of 450nm, a side length of 200nm, and a depth of 250nm is fabricated on the surface of a parallel flat glass (optical waveguide) to form a rhomboid bottom surface, thus constituting the grating working mechanism 2.

[0139] The optical waveguide was divided into 30 regions, namely, longitudinal region A to E and transverse region 1 to 6. The image of the micro-projector was projected into the optical waveguide from region C4. The image intensity was measured in the remaining regions and normalized. The measurement results are shown in Table 2.

[0140] Table 2 is a table showing the image intensity test results of the optical waveguide in Embodiment 2 of this application.

[0141]

[0142]

[0143] Example 3

[0144] like Figure 1A , Figure 1B As shown, the planar optical waveguide based on a two-dimensional grating in this application includes an optical waveguide transmission mechanism 1 and a grating working mechanism 2.

[0145] In this embodiment, the optical waveguide transmission mechanism 1 is a parallel flat glass with a thickness of 0.5 mm and a refractive index of 1.5.

[0146] A cylindrical two-dimensional grating with an included angle of 60°, a period T of 360nm, and a diameter of 100nm is fabricated on the surface of a parallel flat glass (optical waveguide) to form the grating working mechanism 2.

[0147] To address the issue that the light transmission intensity within the optical waveguide weakens after light rays are coupled out of the two-dimensional grating, leading to a gradual decrease in brightness in the final image along the light transmission direction, the depth of the two-dimensional grating is controlled by dividing it into regions. This controls the uniformity of light coupling intensity within each region. The optical waveguide is divided into 30 regions: longitudinal region A to E and transverse region 1 to 6. The depth division of the two-dimensional grating cylinder is shown in Table 3.

[0148] Table 3 is a table showing the depth or height of the grating units in the divided regions of the grating structure of the optical waveguide in Embodiment 3 of this application.

[0149] A 250nm 200nm 170nm 140nm 120nm 140nm B 200nm 170nm 140nm 120nm 100nm 120nm C 200nm 170nm 140nm 120nm 250nm 120nm D 200nm 170nm 140nm 120nm 100nm 120nm E 250nm 200nm 170nm 140nm 120nm 140nm

[0150] The microprojector image was projected from region C5 into the optical waveguide, and the image intensity was measured in the remaining regions and normalized. The measurement results are shown in Table 4.

[0151] Table 4 is a table showing the image intensity test results of the optical waveguide in Embodiment 3 of this application.

[0152] A 0.85 0.88 0.95 0.96 0.7 0.96 B 0.9 0.92 0.95 1 0.8 1 C 0.9 0.92 0.95 0.97 Coupled in 0.97 D 0.9 0.92 0.95 1 0.8 1 E 0.85 0.88 0.95 0.97 0.7 0.97

[0153] Example 4

[0154] like Figure 1A , Figure 1B As shown, the planar optical waveguide based on a two-dimensional grating in this application includes an optical waveguide transmission mechanism 1 and a grating working mechanism 2.

[0155] In this embodiment, the optical waveguide transmission mechanism 1 is a parallel flat glass with a thickness of 0.5 mm and a refractive index of 1.5.

[0156] A cylindrical two-dimensional grating with an included angle of 60°, a period T of 360nm, and a depth of 150nm is fabricated on the surface of a parallel flat glass (optical waveguide) to form the grating working mechanism 2.

[0157] To address the issue that the light transmission intensity within the optical waveguide weakens after light rays are coupled out of the two-dimensional grating, leading to a gradual decrease in the brightness of the final image along the light transmission direction, the diameter, length, or width of the two-dimensional grating is controlled by dividing it into regions. This controls the uniformity of the light coupling intensity within each region. The optical waveguide is divided into 30 regions: longitudinal region A to E and transverse region 1 to 6. The diameter R of the two-dimensional grating cylinder is shown in Table 5.

[0158] Table 5 is a table showing the diameter, length, or width of the grating units in the divided regions of the grating structure of the optical waveguide in Embodiment 4 of this application, such as the diameter of a cylindrical grating unit.

[0159] A 260nm 240nm 210nm 170nm 130nm 170nm B 240nm 210nm 170nm 130nm 110nm 130nm C 240nm 210nm 170nm 130nm 220nm 130nm D 240nm 210nm 170nm 130nm 100nm 130nm E 260nm 240nm 210nm 170nm 130nm 170nm

[0160] The microprojector image was projected from region C5 into the optical waveguide, and the image intensity was measured in the remaining regions and normalized. The measurement results are shown in Table 6.

[0161] Table 6 is a table showing the image intensity test results of the optical waveguide in Embodiment 4 of this application.

[0162] A 0.82 0.88 0.91 0.94 0.94 0.94 B 0.88 0.91 0.95 1 0.96 1 C 0.88 0.91 0.93 0.96 Coupled in 0.96 D 0.88 0.91 0.93 1 0.96 1 E 0.82 0.88 0.91 0.94 0.94 0.94

[0163] This application utilizes a fixed-period two-dimensional grating waveguide to achieve image coupling, pupil expansion, and coupling-out. Light emitted from the micro-projector, after passing through any region of the grating's working mechanism, is diffracted by the two-dimensional grating, resulting in multiple orders of light rays entering the waveguide. Within the waveguide, light is transmitted through total internal reflection and then coupled out, ultimately allowing the image to be seen in any region of the grating's working section. This application features a simple structure, is easy to mass-produce, and offers flexible usage, making it highly valuable for industrial applications.

[0164] like Figures 9A to 11B As shown, in this embodiment, the optical waveguide transmission mechanism 1 includes a waveguide substrate 11, wherein a grating working mechanism 2 is formed on the surface 12 of the waveguide substrate 11, wherein the surface 12 may be a part or all of the surface of one side of the waveguide substrate 11, such as the upper surface. Preferably, the grating working mechanism 2 is formed on the surface 12 of the waveguide substrate 11.

[0165] Optionally, surface 12 can be a concave or recessed surface of the waveguide substrate 11, or surface 12 can be the bottom surface of a groove on the surface of the waveguide substrate 11, that is, the grating structure of the grating working mechanism 2 can be located on the concave or recessed surface of the waveguide substrate 11, i.e., the grating structure is recessed into the surface of the waveguide substrate 11. Figure 1B As shown, the upper surface of the waveguide substrate 11 has a groove 101, wherein the grating structure 20 is located on the bottom surface of the groove 101, and the bottom surface of the groove 101 is lower than the upper surface of the waveguide substrate 11, i.e., they are not on the same plane.

[0166] The waveguide substrate 11 can be a flat plate structure made of an optical material that is transparent to visible light, such as flat glass or resin, wherein the grating working mechanism 2 can be integrally formed on the surface 12 of the waveguide substrate 11, such as by surface processing. Alternatively, the grating working mechanism 2 can be tightly attached to the surface 12 of the waveguide substrate 11, or the grating working mechanism 2 can be embedded inside the waveguide substrate 11.

[0167] Furthermore, the grating working mechanism 2 includes a grating structure 20 composed of a set of grating units 201 arranged periodically. The grating structure 20 has periodic lines 202 where each grating unit is arranged along a periodic direction. The periodic lines 202 are defined as the lines connecting grating units 201 arranged in the same periodic direction. The period T of the grating structure 20 is preferably 360 nm, and the angle between intersecting periodic lines 202 is preferably 60°. In practical applications, the light rays totally reflected within the waveguide substrate 11 can be coupled out to the human eye from all positions of the grating structure 20 of the grating working mechanism 2, resulting in uniform image brightness (equivalent brightness at each viewing angle). Furthermore, the image brightness remains stable even when there is relative displacement between the human eye and the display device, such as AR glasses (i.e., uniform brightness within the viewing window).

[0168] like Figure 9A and Figure 11A As shown, in the first specific example of this preferred embodiment, the grating structure 20 is disposed on the surface 12 of the waveguide substrate 11. The grating structure 20 is a tooth-like protruding structure, and each grating unit 20 is a protruding structure protruding from the surface 12, such as a cylindrical structure, an elliptical cylindrical structure, or a prismatic structure such as a triangular prism, a square prism, or an octagonal prism, a conical structure, a pyramidal structure such as a triangular pyramid or a square pyramid, or a frustum-like or frustum-shaped structure, etc. Furthermore, each grating unit 20 has a certain spacing between it, so as to be arranged in a tooth-like pattern. In other words, in the direction of the periodic line 202 of the grating structure 20, each grating unit 201 of the grating structure 20 is arranged periodically with a certain spacing. Viewed from the cross-section in the direction of the periodic line 202, each grating unit 201 of the grating structure 20 is arranged in a tooth-like pattern. In other words, from the top view of the grating structure 20, the grating units 201 of the grating structure 20 are arranged in a mesh-like pattern.

[0169] Furthermore, the grating unit 201 is a quasi-cylindrical structure perpendicular to surface 12, meaning the angle between the grating unit 20 and the surface of the waveguide substrate 11 is approximately 90°. Even further, the grating unit 201 is a quasi-cylindrical structure, wherein the linewidth w (diameter of the quasi-cylindrical structure) and height h of the grating unit 201, as well as the period T of the grating structure 20, can be preset to adjust the diffraction efficiency of the grating structure 20. Specifically, the diffraction efficiency of the grating structure 20 can be changed by preset adjustment of the duty cycle ff = w / T or the height h of the grating unit 201.

[0170] In this embodiment, the periodic line 202 includes a set of parallel first periodic lines 2021 and a set of parallel second periodic lines 2022, wherein the first periodic lines 2021 and the second periodic lines 2022 intersect each other and have a preset included angle θ, preferably 60°. In other words, the periodic line 202 includes intersecting first periodic lines 2021 and second periodic lines 2022, and the included angle θ between the first periodic lines 2021 and the second periodic lines 2022 is preferably 60°. The period of each grating unit 201 on the first periodic line 2021 is equal to the period of each grating unit 201 on the second periodic line 2022. That is, each grating unit 201 of the grating structure 20 is periodically arranged in a first direction to form the first periodic line 2021, and in a second direction deviating from the first direction by 60° to form the second periodic line 2022.

[0171] Furthermore, the grating unit 201 is preferably a regularly protruding structure, wherein the periodic line 202 is a line connecting the centers 2011 of each grating unit 201 in the periodic direction. It can be understood that the periodic line 202 may also include a third periodic line formed by the periodic arrangement of each grating unit 201 along a third direction.

[0172] like Figure 9B As shown, optionally, the grating unit 201 is a cylindrical protrusion structure with a certain tilt angle α between the grating unit 201 and the surface 12, wherein the tilt angle α is not equal to 90°. That is, the grating unit 201 is a protrusion structure tilted to the surface of the waveguide substrate 11. The diffraction efficiency of the grating structure 20 can be changed by preset adjustment of the duty cycle ff = w / T, the height h of the grating unit 201, or the tilt angle α.

[0173] like Figure 9C As shown, optionally, the grating unit 201 is a pyramidal protrusion structure, such as a pyramidal structure with a triangular vertical cross-section, wherein the triangle is preferably a right triangle, and the bases of each grating unit 201 are adjacent. Further, there is a certain angle b between the two faces of two adjacent grating units 201, wherein the angle b is preferably not equal to 90°. The diffraction efficiency of the grating structure 20 can be changed by preset adjustment of the duty cycle ff = w / T, the height h of the grating unit 201, or the angle b.

[0174] In the first specific example, the height h of each grating unit 201 of the grating structure 20 is consistent, that is, the grating structure 20 is a raised structure with equal height.

[0175] like Figure 10A and 11BAs shown, in a second specific example of this preferred embodiment, the grating structure 20 further includes adjacent first regions 203 and second regions 204 sequentially divided according to the direction of light propagation. The first region 203 has a plurality of first grating units 201A, and the second region 204 has a plurality of second grating units 201B. Preferably, the height h1 of the first grating unit 201A is lower than the height h2 of the second grating unit 201B. Optionally, the width w of the first grating unit 201A and the second grating unit 201B are equal, and the period T of each first grating unit 201A in the first region 203 is also equal to the period T of each second grating unit 201B in the second region 204. Optionally, both the first grating unit 201A and the second grating unit 201B are perpendicular to the surface 12. Optionally, as... Figure 10B As shown, both the first grating unit 201A and the second grating unit 201B are inclined on surface 12 and have a certain inclination angle α. Optionally, the first grating unit 201A and the second grating unit 201B have a certain inclined plane angle b, and the inclined plane angle b is not equal to 90°. It can be understood that the shape and structure of the first grating unit 201A and the second grating unit 201B can be a columnar, pyramidal, conical, pyramidal, frustum, or truncated cone structure, etc.

[0176] It is understandable that the height h1 of the first grating unit 201A and the height h2 of the second grating unit 201B can be adjusted and preset to change the diffraction efficiency of the grating structure 20 so as to make the brightness of the coupled image uniform.

[0177] In other words, because the heights of the first grating units 201A in the first region 201 of the grating structure 20 are inconsistent with the heights of the second grating units 202B in the second region 202, the coupling output diffraction efficiencies of the grating structure 20 differ in the two regions. Therefore, based on the characteristic of the grating structure 20 to achieve exit pupil expansion through stepwise energy output, when the coupling output diffraction efficiency of the grating structure 20 is optimized to the result given by equation (1), the luminous flux output per unit area in the effective region remains constant, thus presenting a uniform image brightness to the user, and maximizing the display efficiency of the display device, i.e., maximizing the image brightness under a certain system power consumption or minimizing the system power consumption under a certain image brightness.

[0178] Equation (1):

[0179]

[0180] Where N is the output order of the region modulation, N T η is the total number of modulation regions. N The output diffraction efficiency is the coupling efficiency of the Nth region.

[0181] Due to limitations in the structure or fabrication precision of diffractive optical elements, when the optimized coupling output efficiency of the grating structure 20 cannot equal the result given by equation (1), the light energy coupled out within its effective region is a portion of the light energy reflected by total internal reflection within the waveguide substrate 11. Assume that this portion of light energy accounts for η of the total light energy reflected by total internal reflection. T In order to make the image brightness uniform within the exit pupil range, the coupling output efficiency of the grating structure 20 is optimized as follows (2).

[0182] Equation (2):

[0183]

[0184] Optionally, the diffraction efficiency of the grating structure 20 can be changed by presetting the duty cycle ff = w / T of the grating structure 20, or the height h of the grating unit 201 (the height h1 of the first grating unit 201A and the height h2 of the second grating unit 201B), or the tilt angle a (if any), or the angle between the inclined planes b (if any).

[0185] In the manufacturing process of the grating structure 20, the etching methods available for preparing the master substrate include electron beam etching, reactive ion beam etching, magnetically enhanced reactive ion etching, high-density plasma etching, inductively coupled plasma etching, voltage-coupled plasma etching, electron cyclotron resonance etching, vacuum ion evaporation, magnetron sputtering, MBE molecular beam epitaxy, PLD laser sputtering deposition, etc. The height h of the modulated grating unit 20 can be achieved by controlling the etching time and exposure intensity of the electron beam or ion beam on the master substrate. To meet the needs of large-scale mass production, the grating structure on the master substrate can be replicated to the surface 12 of the waveguide substrate 11 through photolithography, etching, growth, nanoimprinting, casting, molding, injection molding, etc., to form the grating structure 20.

[0186] Furthermore, each of the first grating units 201A in the first region 203 and each of the second grating units 201B in the second region 204 has a first periodic line 2021 and a second periodic line 2022 that intersect each other, and the included angle is 60°.

[0187] In the second specific example, surface 12 is a coplanar plane, wherein the bottom surfaces of each first grating unit 201A in the first region 203 and each second grating unit 201B in the second region 204 are all kept on the same plane, i.e., surface 12. Accordingly, the top surface of the second grating unit 201B is higher than the top surface of the first grating unit 201A, and the height difference is h2-h1. In other words, the upper surface of each second grating unit 201B in the second region 204 rises in a stepped manner relative to the upper surface of each first grating unit 201A in the first region 203.

[0188] Furthermore, the grating structure 20 further includes a third region 205 adjacent to the second region 204, sequentially divided according to the direction of light propagation. The third region 205 has multiple third grating units 201C, wherein the height h3 of each third grating unit 201C is higher than the height h1 of the second grating unit 201B, i.e., h3 is greater than h2. Optionally, the width w and period T of each third grating unit 201C within the third region 205 are consistent with the width and period T of the first grating unit 201A and the second grating unit 201B. Each third grating unit 201C within the third region 205 has intersecting first periodic lines 2021 and second periodic lines 2022, with an included angle of 60°.

[0189] Accordingly, the bottom surfaces of each grating unit 201 in the first region 203, the second region 204, and the third region 205 are all kept on the same plane, that is, the surface 12 of the waveguide substrate 11 is on the same plane. The upper surfaces of each first grating unit 201A in the first region 203, the upper surfaces of each second grating unit 201B in the second region 204, and the upper surfaces of each third grating unit 201C in the third region 205 rise in a stepped manner.

[0190] Understandably, the grating structure 20 may further include multiple grating units in the fourth, fifth, or even more regions, without limitation.

[0191] like Figure 10C As shown in the third specific example of this application, the top surfaces of each grating unit 201 in each region (first region 203, second region 204, and third region 205) of the grating structure 20 remain on the same plane, while the bottom surfaces of each grating unit 201 descend in a stepped manner. That is, the surfaces 12 are not on the same plane, or the surfaces 12 are stepped surfaces.

[0192] Specifically, surface 12 includes a first surface 121 and a second surface 122 that are not on the same plane and are divided along the direction of light propagation. In the thickness direction of waveguide substrate 11, the first surface 121 is higher than the second surface 122. Each first grating unit 201A in the first region 203 is located on the first surface 121, and each second grating unit 201B in the second region 204 is located on the second surface 122. That is, the height difference between the first surface 121 and the second surface 122 is approximately equal to the height difference h2-h1 between the second grating unit 201B and the first grating unit 201A.

[0193] Furthermore, surface 12 further has a third surface 123 that is not in the same plane. In the thickness direction of waveguide substrate 11, the third surface 123 is lower than the second surface 122, wherein each third grating unit 201C in the third region 205 is located on the third surface 123. That is, the height difference between the second surface 122 and the third surface 123 is approximately equal to the height difference h3-h2 between the second grating unit 201B and the third grating unit 201C. In other words, the upper surfaces of the first grating unit 201A, the second grating unit 201B, and the third grating unit 201C are in the same plane. Preferably, the first surface 121, the second surface 122, and the third surface 123 gradually descend in a stepped manner.

[0194] Furthermore, the first surface 121 and the second surface 122 are connected by a first transition surface 124, wherein the first transition surface 124 is a transition surface between the first surface 121 and the second surface 122, such as an arc surface. Furthermore, the second surface 122 and the third surface 123 can also be connected by a second transition surface 125, which is also an arc surface.

[0195] Optionally, surface 12 has multiple surfaces 121, 122, and 123 that descend in a stepped manner. Simultaneously, the upper surfaces of the first grating unit 201A, the second grating unit 201B, and the third grating unit 201C can also rise in a stepped manner. That is, the height difference between the first grating unit 201A and the second grating unit 201B can be greater than the height difference between the first surface 121 and the second surface 122, and the height difference between the second grating unit 201B and the third grating unit 201C can be greater than the height difference between the second surface 122 and the third surface 123.

[0196] Optionally, the grating units 201 of the grating structure 20 are linearly obliquely intersected, and the intersection angle is the angle θ between the first periodic line 2021 and the second periodic line 2022. Optionally, the refractive index n of the grating units 201 of the grating structure 20 can be 1.7.

[0197] It is worth mentioning that the height of the grating units 201 in each region of the grating structure 20 may not be completely consistent. The height of the grating units 201 in some regions may be consistent, while the height of the grating units 201 in other regions may be inconsistent. That is to say, along the direction of light propagation, the height of the grating units 201 in each region is not necessarily gradually decreasing or gradually increasing. In some optional embodiments, the height of the grating units 201 in the middle region may be lower or higher than the height of the grating units 201 in the two side regions, which is not limited here.

[0198] In Example 1, the waveguide substrate 11 is made of glass material with a thickness of 0.5 mm and a refractive index of 1.5. The period T of the grating structure 20 is 360 nm. Each grating unit 201 in each region is a cylindrical structure with a diameter (width w) of 100 nm and a height of 150 nm. The angle between the first period line 2021 and the second period line 2022 is 60°.

[0199] In Example 2, the waveguide substrate 11 is made of glass material with a thickness of 1.9 mm and a refractive index of 1.8. The period T of the grating structure 20 is 450 nm. The grating unit 201 in each region is a rhombic prism structure with a side length of 200 nm and a height of 250 nm. The angle between the first period line 2021 and the second period line 2022 is 60°.

[0200] In embodiment 3, the waveguide substrate 11 is made of glass material with a thickness of 0.5 mm and a refractive index of 1.5. The period T of the grating structure 20 is 450 nm, and the grating unit 201 is a cylindrical structure with a diameter of 100 nm. However, the height h of the grating unit 201 in different regions of the grating structure 20 is not completely consistent. That is, the height of the grating unit 201 in some regions is consistent, while the height of the grating unit 201 in other regions is inconsistent. The angle between the first periodic line 2021 and the second periodic line 2022 is 60°. In other words, the height of the second grating unit 201B in the second region 204 can be higher or lower than the height of the first grating unit 201A in the first region 203 and the third grating unit 201C in the third region 205, respectively.

[0201] It is understood that the diameter, width, or length of each grating unit 201 in the grating structure 20 can be from 50 nm to 650 nm, and the height or depth can be from 80 nm to 650 nm. The period of the grating structure 20 can be from 200 nm to 700 nm. The refractive index of the waveguide substrate 11 can be from 1.4 to 2.2, and the thickness can be from 0.3 mm to 2.5 mm.

[0202] Furthermore, this application also provides a method for manufacturing an optical waveguide based on a two-dimensional grating, the method comprising:

[0203] S10, providing waveguide substrate 11; and

[0204] S20. Each grating unit 201 forming the grating structure 20 is located on the surface (i.e., surface 12) of the waveguide substrate 11, wherein the grating structure 20 has periodic lines in which each grating unit 201 is arranged along the periodic direction.

[0205] 202, wherein the periodic line 202 includes a first periodic line 2021 and a second periodic line 2022 with an included angle of 60°.

[0206] In step S20, a grating structure 20 can be formed on the surface of the waveguide substrate 11 by photolithography, etching, growth, nanoimprinting, casting, molding, or injection molding to achieve mass production.

[0207] For example, in step S20, a grating structure 20 is formed on the surface of the waveguide substrate 11 by nanoimprint lithography, including:

[0208] S21. A master plate is provided, wherein the master plate has a grating structure to be transferred corresponding to the grating structure 20, wherein the grating structure to be transferred includes grating units to be transferred arranged with a first periodic line 2021 and a second periodic line 2022 at an angle of 60°, wherein the grating units to be transferred are consistent with the structural shape, arrangement, height and width of the grating unit 201.

[0209] S22. A sub-mold is formed by polymerizing the master plate, wherein the sub-mold has a complementary structure that complements the grating structure to be transferred on the master plate, and the complementary structure forms a cavity that matches the structural shape, arrangement, height and width of the grating unit 201.

[0210] S23. Coat the grating substrate material of the uncured grating structure 20 onto the surface of the waveguide substrate 11;

[0211] S24. The uncured grating substrate material is imprinted by the sub-mold to fill the cavity of the sub-mold with the uncured grating substrate material, and the grating substrate material is cured to form the grating structure 20 on the surface of the waveguide substrate 11.

[0212] Furthermore, in the method, after removing the sub-mode, an optical waveguide based on a two-dimensional grating is obtained.

[0213] The grating substrate material can be a resin material, such as a UV-curable resin material or a thermosetting resin material. In step S24, the grating substrate material can be cured by UV light or by heat to form the grating structure 20.

[0214] That is, in step S23, the grating substrate material is not cured, and the grating substrate material is coated on the surface 12 of the waveguide substrate 11 in a non-solid state. In step S24, the sub-mode is pressed onto the surface 12 of the waveguide substrate 11 by pressure, so that the uncured grating substrate material fills the cavity of the sub-mode by pressure and vacuum.

[0215] In step S21, etching methods can be used to prepare the master substrate, including electron beam etching, reactive ion beam etching, magnetically enhanced reactive ion etching, high-density plasma etching, inductively coupled plasma etching, voltage-coupled plasma etching, electron cyclotron resonance etching, vacuum ion evaporation, magnetron sputtering, MBE molecular beam epitaxy, PLD laser sputtering deposition, etc. The height h of the modulation grating unit 20 can be achieved by controlling the etching time and exposure intensity of the electron beam or ion beam on the master substrate.

[0216] Furthermore, the grating structure to be transferred is a protruding structure that protrudes from the surface of the master plate.

[0217] Furthermore, there is a height difference between the grating units to be transferred in different regions of the grating structure to be transferred. Similar to the structure of the grating structure 20 described above, the heights of the grating units to be transferred in the first region, the second region, and the third region are different. Even further, the grating units to be transferred in the grating structure to be transferred are arranged in a stepped manner along the periodic direction.

[0218] On the other hand, this embodiment further provides an augmented reality display device, which includes a device body and at least one optical waveguide. The optical waveguide is disposed on the device body and includes a waveguide substrate 11 and a grating structure 20. The grating structure 20 is disposed on the surface (i.e., surface 12) of the waveguide substrate 11. The grating structure 20 includes a set of grating units 201 and periodic lines 202 having each grating unit 201 arranged along a periodic direction. The periodic lines 202 include a first periodic line 2021 and a second periodic line 2022 that intersect each other at an angle of 60°. Optionally, the structure of the optical waveguide is consistent with or similar to that of the optical waveguides in the specific examples described above, and will not be described in detail here.

[0219] In this embodiment, the main body of the device includes a housing and at least one projection unit, wherein the projection unit and the optical waveguide are mounted in the housing. The projection unit projects image light onto the optical waveguide, wherein the light is coupled into the waveguide substrate 11 and totally internally reflected, and the light totally internally reflected in the waveguide substrate 11 is coupled out through the grating structure 20. In other words, the projection unit projects image light toward the optical waveguide so that the light is coupled into the waveguide substrate 11 and totally internally reflected. That is, the optical waveguide is disposed in the optical path that receives the image light projected by the projection unit, wherein the light is coupled into the waveguide substrate 11 and totally internally reflected through the input diffraction optical element of the grating structure 20.

[0220] Preferably, the projection unit includes a display and a lens group, wherein the lens group is disposed in the projection light path of the display, and the display projects corresponding image light based on an image signal. The light is collimated and magnified by the lens group before being projected onto the optical waveguide. In other words, the lens group includes, but is not limited to, one or more optical lenses such as collimating lenses and magnifying lenses, for optical processing such as collimation or magnification of the image light emitted by the display. Optionally, the display can be a microdisplay, which may include a transmissive liquid crystal display (LCD) that forms an image by modulating the projection of backlight by liquid crystal molecules, or a reflective modulation method, commonly including digital light processors (DLP) and liquid crystal on silicon (LCoS). The display may also include self-emissive organic light-emitting diodes (OLEDs) and micro light-emitting diodes (Micro LEDs). The display may also include a microelectromechanical scanning mirror (MEMS scanning mirror).

[0221] Furthermore, the main body of the device includes an image sensor, a position sensor, and a processor. The image sensor is used to acquire external image information, the position sensor is used to determine spatial position coordinates and orientation, and the processor is used to generate an image signal that can render a virtual image of the real world based on the spatial position coordinates, orientation, and image information. The projection unit projects corresponding image rays onto an optical waveguide based on the image signal to present the real world rendered by the virtual image in the user's field of view, so as to enable the user to experience a three-dimensional stereoscopic visual effect.

[0222] In other words, the main body of the device can include various types of sensors, such as image sensors and position sensors, to collect various types of information for augmented reality. Each sensor is communicatively or electrically connected to a processor, which generates corresponding image signals for augmented reality based on the information collected by these sensors. The processor is communicatively or electrically connected to the display of the projection unit so that the projection unit projects corresponding image light.

[0223] Image sensors include, but are not limited to, RGB cameras, monochrome cameras, depth cameras, or combinations thereof. RGB cameras or monochrome cameras are used to acquire color image information of real-world scenes, while depth cameras are used to acquire depth information and depth point clouds of the scene. When the optical axes of the depth camera and the RGB camera or monochrome camera are parallel and synchronized in time, the image sensor can obtain a color stereoscopic image of the real-world scene.

[0224] The position sensor includes sensors that determine the translational degrees of freedom along the X, Y, and Z axes of a three-dimensional coordinate system and the rotational degrees of freedom about the X, Y, and Z axes. Optionally, the position sensor includes, but is not limited to, accelerometers, gyroscopes, magnetometers, GPS receivers, or combinations thereof. Using the positioning provided by the position sensor, the virtual image generated by the processor can accurately render the target location in the real world.

[0225] The main body of the device further includes at least one hand device, which can be worn on a user's hand. Position sensors are disposed on the hand device to determine the spatial coordinates and orientation of the user's hand. The hand device can be a glove, wristband, or a handheld object, etc. The position sensors are used to collect the spatial coordinates and orientation of the hand device, determine the translational degrees of freedom of the hand device along the X, Y, and Z axes of a three-dimensional coordinate system, and the rotational degrees of freedom about the X, Y, and Z axes, thereby identifying the user's hand movements and spatial position.

[0226] The main body of the device is either a pair of glasses or an immersive device that can be worn on the user's head. In other words, the shell of the main body can be a frame-like device or a helmet-like device, wherein the main body can be worn on the user's head, and the optical waveguide is located precisely in front of the user's eyes so that the light coupled out of the grating structure 20 of the optical waveguide enters the user's eyes. Furthermore, there are two optical waveguides, corresponding to the user's left and right eyes respectively.

[0227] The main body of the device further includes a memory for storing information about the display device, such as information about virtual images or a database of programs that can be called. Optionally, the memory can store preset virtual image information, which is then read by the processor to generate corresponding image signals. Alternatively, the display can directly read the virtual image information stored in the memory to project corresponding image rays.

[0228] The main body of the device further includes a network communication interface, which is used to receive signals of virtual images transmitted from the outside. Network communication interfaces include, for example, internet ports, Wi-Fi ports, Bluetooth ports, RJ45 connectors, or USB interfaces. The display projects corresponding image light onto the virtual image signals transmitted from the outside.

[0229] The main body of the device further includes a connection port, which is used to connect at least two display devices for interaction between them. In other words, multiple display devices can interconnect, and the connection port can be a wired connection port or a wireless connection port such as an Internet, wide area network, or local area network connection port.

[0230] Of course, for simplicity, only some of the components in the display device relevant to this application are shown in the figure, omitting components such as buses, input / output interfaces, etc. In addition, the display device may include any other suitable components depending on the specific application.

[0231] The block diagrams of devices, apparatuses, devices, and systems involved in this application are merely illustrative examples and are not intended to require or imply that they must be connected, arranged, or configured in the manner shown in the block diagrams. As those skilled in the art will recognize, these devices, apparatuses, devices, and systems can be connected, arranged, and configured in any manner. Words such as “comprising,” “including,” “having,” etc., are open-ended terms meaning “including but not limited to,” and are used interchangeably with them. The terms “or” and “and” as used herein refer to the terms “and / or,” and are used interchangeably with them unless the context clearly indicates otherwise. The term “such as” as used herein refers to the phrase “such as but not limited to,” and is used interchangeably with it.

[0232] It should also be noted that in the apparatus, equipment, and methods of this application, the components or steps can be disassembled and / or recombined. These disassemblies and / or recombinations should be considered as equivalent solutions of this application.

[0233] The foregoing has shown and described the basic principles, main features, and advantages of this application. Those skilled in the art should understand that this application is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of this application. Various changes and modifications can be made to this application without departing from the spirit and scope thereof, and all such changes and modifications fall within the scope of this application as claimed. The scope of protection of this application is defined by the appended claims and their equivalents.

[0234] Those skilled in the art should understand that the embodiments of this application described above and shown in the accompanying drawings are merely examples and do not limit the scope of this application. The purpose of this application has been fully and effectively achieved. The functions and structural principles of this application have been demonstrated and explained in the embodiments, and any variations or modifications can be made to the implementation of this application without departing from the stated principles.

Claims

1. A diffractive optical waveguide based on a two-dimensional grating, characterized in that, The diffractive waveguide integrates coupling-in, pupil expansion, and coupling-out functions, and the diffractive waveguide includes: Waveguide substrate; and A grating structure is disposed on the surface of the waveguide substrate. The grating structure includes a plurality of periodically arranged grating units and forms at least a first periodic line and a second periodic line, wherein the first periodic line and the second periodic line intersect each other. In this process, after light enters any region of the grating structure, it is diffracted by the grating unit of the grating structure to generate multiple orders of light rays that enter the waveguide substrate in different directions, and light rays are coupled out of the entire grating structure, so that the coupling, pupil expansion and coupling out of light rays can be achieved through a single grating structure.

2. The diffractive waveguide according to claim 1, characterized in that, The diameter or side length of the grating unit in the light coupling region of the grating structure is greater than the diameter or side length of the grating unit located around the coupling region; or the height or depth of the grating unit in the light coupling region of the grating structure is greater than the height or depth of the grating unit located around the coupling region.

3. The diffractive waveguide according to claim 1, characterized in that, The first periodic line and the second periodic line intersect each other at an angle of 60°.

4. The diffractive waveguide according to claim 1, characterized in that, The first surface of the waveguide substrate is planar, and the grating structure is disposed on the first surface. The grating structure is divided into multiple regions, and multiple grating units are disposed in each region. The coupling output efficiency of the grating units in adjacent regions is different.

5. The diffractive waveguide according to claim 4, characterized in that, The coupling output efficiency of the grating structure is optimized as follows: in, Let N be the output diffraction efficiency of the Nth region coupling, where N is the output order of the region modulation. This represents the total number of modulation regions. The proportion of light energy coupled out of the effective area of ​​the grating structure to the total light energy of total internal reflection.

6. The diffractive waveguide according to claim 1, characterized in that, The first surface of the waveguide substrate is a stepped surface with different heights for adjacent steps. The grating structure is disposed on the first surface, and the grating units of the grating structure are located on the same plane on the side away from the waveguide substrate.

7. The diffractive waveguide according to claim 6, characterized in that, The height of the steps arranged along the direction of light propagation gradually decreases.

8. The diffractive waveguide according to claim 1, characterized in that, The waveguide substrate has a refractive index of 1.4 to 2.2 and a thickness of 0.3 mm to 2.5 mm.

9. The diffractive waveguide according to claim 1, characterized in that, The period of the grating structure is 200nm to 700nm.

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