CN114660692B - Two-dimensional grating, forming method thereof, optical waveguide and near-to-eye display device - Google Patents
Two-dimensional grating, forming method thereof, optical waveguide and near-to-eye display device Download PDFInfo
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Classifications
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B5/00—Optical elements other than lenses
- G02B5/18—Diffraction gratings
- G02B5/1814—Diffraction gratings structurally combined with one or more further optical elements, e.g. lenses, mirrors, prisms or other diffraction gratings
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
- G02B27/0081—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00 with means for altering, e.g. enlarging, the entrance or exit pupil
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
- G02B27/01—Head-up displays
- G02B27/0101—Head-up displays characterised by optical features
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B5/00—Optical elements other than lenses
- G02B5/18—Diffraction gratings
- G02B5/1847—Manufacturing methods
- G02B5/1857—Manufacturing methods using exposure or etching means, e.g. holography, photolithography, exposure to electron or ion beams
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B5/00—Optical elements other than lenses
- G02B5/18—Diffraction gratings
- G02B5/1866—Transmission gratings characterised by their structure, e.g. step profile, contours of substrate or grooves, pitch variations, materials
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
- G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
- G02B6/122—Basic optical elements, e.g. light-guiding paths
- G02B6/124—Geodesic lenses or integrated gratings
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/24—Coupling light guides
- G02B6/26—Optical coupling means
- G02B6/34—Optical coupling means utilising prism or grating
Abstract
The embodiment of the invention relates to the field of optical devices and discloses a two-dimensional grating and a forming method thereof, an optical waveguide and near-to-eye display equipment.
Description
Technical Field
The embodiment of the invention relates to the technical field of optical devices, in particular to a two-dimensional grating, a forming method thereof, an optical waveguide and near-eye display equipment.
Background
Augmented reality (Augmented Reality, AR) technology is a technology of fusing virtual information and the real world with each other, and an augmented reality technology represented by augmented reality glasses is currently coming up in various industries, especially in the fields of security and industry, and greatly improves an information interaction mode. The optical display scheme in the current mature augmented reality technology is mainly divided into a prism scheme, a birdbath scheme, a free-form surface scheme and a light guide (Lightguide) scheme, and the former three schemes have larger volumes, so that the application of the optical display scheme in the aspect of intelligent wearing, namely the aspect of augmented reality glasses is limited, and the light guide scheme is the optimal optical display scheme in the current augmented reality glasses.
The optical waveguide scheme is divided into a geometric waveguide scheme, a relief grating waveguide scheme and a volume holographic waveguide scheme, wherein the geometric waveguide scheme uses a coated semi-transparent half mirror of an array to achieve virtual information display, but the view field and the eye movement range of the scheme are limited, and an array lens brings a stripe effect to a picture, so that the geometric waveguide scheme cannot present an optimal display effect to human eyes. Volume holographic waveguide solutions are currently limited in mass production. The relief grating waveguide scheme is the most studied technical scheme at present due to the convenience of nano imprinting, and has the advantages of large field of view and large eye movement range.
The scheme path of the existing relief grating waveguide mainly comprises a one-dimensional grating-based optical waveguide scheme and a two-dimensional grating-based optical waveguide scheme, wherein the two-dimensional grating waveguide is divided into a coupling-in area and a coupling-out area, and the coupling-out area adopts a two-dimensional grating structure to achieve the functions of extension and coupling-out.
In the process of implementing the embodiments of the present invention, the inventors found that at least the following problems exist in the above related art: in the current optical waveguide scheme based on the two-dimensional grating structure, the two-dimensional grating structure used in the coupling-out area is generally in a cylindrical structure and a diamond structure, and the two structures have fewer adjustable parameters, so that the coupling-out efficiency is not easy to adjust.
Disclosure of Invention
The embodiment of the application provides a two-dimensional grating, a forming method thereof, an optical waveguide and near-eye display equipment.
The aim of the embodiment of the invention is realized by the following technical scheme:
in order to solve the above-mentioned technical problems, in a first aspect, the present invention provides a two-dimensional grating, which includes a repeating unit periodically tiled on a surface of a waveguide substrate along a horizontal direction and a vertical direction, where the repeating unit includes a first recess portion and a second recess portion disposed along a first horizontal line, and a third recess portion disposed along a second horizontal line, where the first horizontal line and the second horizontal line are two virtual lines parallel to the horizontal direction, the first recess portion and the second recess portion are disposed in axisymmetric along a central axis of the repeating unit, the central axis is a virtual axis capable of bisecting the repeating unit and perpendicular to the first horizontal line and the second horizontal line, a combined structure formed by the adjacent first recess portion and second recess portion in the horizontal direction is in a water drop shape, the third recess portion is in an inverted water drop shape, and the third recess portion is in axisymmetric about the central axis as a symmetric axis.
In some embodiments, the first recess and the second recess are the same size, a feature size of the first recess and the second recess in a vertical direction is smaller than a feature size of the third recess in a vertical direction, and a feature size of the third recess in a horizontal direction is smaller than a feature size of the third recess in a vertical direction.
In some embodiments, the period of the repeating units in the horizontal direction is 200nm-2 μm.
In some embodiments, the period of the repeating unit in the vertical direction is 10nm-1 μm.
In some embodiments, the surface of the repeating unit is plated with a metal oxide film having a thickness of 10nm to 200nm.
In order to solve the above-mentioned technical problem, in a second aspect, the present invention provides a two-dimensional grating, which includes a repeating unit periodically tiled on a surface of a waveguide substrate along a horizontal direction and a vertical direction, where the repeating unit includes a first protruding portion and a second protruding portion that are disposed along a first horizontal line, and a third protruding portion that is disposed along a second horizontal line, where the first horizontal line and the second horizontal line are two virtual lines parallel to the horizontal direction, the first protruding portion and the second protruding portion are disposed in axisymmetric along a central axis of the repeating unit, the central axis is a virtual axis that can bisect the repeating unit and is perpendicular to the first horizontal line and the second horizontal line, a combined structure formed by the first protruding portion and the second protruding portion that are adjacent to each other in the horizontal direction is in a water drop shape, the third protruding portion is in an inverted shape, and the third protruding portion is in an axisymmetric pattern with the central axis as a symmetric axis.
In some embodiments, the first and second lobes are the same size, a feature size of the first and second lobes in a vertical direction is less than a feature size of the third lobe in a vertical direction, and a feature size of the third lobe in a horizontal direction is less than a feature size of the third lobe in a vertical direction.
In some embodiments, the period of the repeating units in the horizontal direction is 200nm-2 μm.
In some embodiments, the period of the repeating unit in the vertical direction is 10nm-1 μm.
In some embodiments, the surface of the repeating unit is plated with a metal oxide film having a thickness of 10nm to 200nm.
In order to solve the above technical problem, in a third aspect, an embodiment of the present invention provides a method for forming a two-dimensional grating, including: according to the requirement on the light coupling-out efficiency, determining an optimization variable of the two-dimensional grating according to the first aspect, wherein the optimization variable comprises: a feature size of the first recess and the second recess in a horizontal direction, a feature size of the first recess and the second recess in a vertical direction, a feature size of the third recess in a horizontal direction, a feature size of the third recess in a vertical direction, a distance between the first recess or the second recess and the third recess in a vertical direction, and/or a height of each recess with respect to the waveguide substrate surface recess; and carrying out etching operation on the optical waveguide at the positions of the first concave part, the second concave part and the third concave part according to the optimized variable so as to form the two-dimensional grating.
In order to solve the above technical problem, in a fourth aspect, an embodiment of the present invention provides a method for forming a two-dimensional grating, including: determining an optimization variable of the two-dimensional grating according to the second aspect according to the requirement on the light coupling-out efficiency, wherein the optimization variable comprises: a feature size of the first and second protrusions in a horizontal direction, a feature size of the first and second protrusions in a vertical direction, a feature size of the third protrusion in a horizontal direction, a feature size of the third protrusion in a vertical direction, a distance of the first or second protrusion from the third protrusion in a vertical direction, and/or a height of each protrusion relative to the waveguide substrate surface; and on the optical waveguide, etching operation is carried out on positions avoiding the first protruding part, the second protruding part and the third protruding part according to the optimized variable so as to form the two-dimensional grating.
In order to solve the above technical problem, in a fifth aspect, an embodiment of the present invention provides an optical waveguide, including: a waveguide substrate; the coupling-in area is arranged on the light incident side of the waveguide substrate; a coupling-out region of the two-dimensional grating according to the first or second aspect is provided, said coupling-out region being provided at the light-exit side of the waveguide substrate.
In some embodiments, the waveguide substrate is a curved waveguide substrate.
In order to solve the above technical problem, a sixth aspect of the present invention further provides a near-eye display device, including: the optical waveguide of the fifth aspect.
Compared with the prior art, the invention has the beneficial effects that: in contrast to the prior art, the embodiment of the invention provides a two-dimensional grating, a forming method thereof, an optical waveguide and a near-eye display device, wherein the two-dimensional grating comprises a repeating unit which is periodically tiled on the surface of a waveguide substrate along a horizontal direction and a vertical direction, the repeating unit comprises a first concave part (or a first convex part) and a second concave part (or a second convex part) which are arranged along a first horizontal line, and a third concave part (or a third convex part) which is arranged along a second horizontal line, the first horizontal line and the second horizontal line are two virtual lines parallel to the horizontal direction, the first concave part (or the first convex part) and the second concave part (or the second convex part) are axially symmetrically arranged along the central axis of the repeating unit, the central axis is a virtual axis which can bisect the repeating units and is perpendicular to the first horizontal line and the second horizontal line, a combined structure formed by a first concave part (or a first protruding part) and a second concave part (or a second protruding part) which are adjacent to each other in the horizontal direction in the repeating units is in a water drop shape, the third concave part (or the third protruding part) is in a water drop shape, and the third concave part (or the third protruding part) is in an axisymmetric graph taking the central axis as a symmetry axis.
Drawings
One or more embodiments are illustrated by way of example and not limitation in the figures of the accompanying drawings, in which like references indicate similar elements/modules and steps, and in which the figures do not include the true to scale unless expressly indicated by the contrary reference numerals.
FIG. 1 is a top view of a two-dimensional grating according to a first embodiment of the present invention;
FIG. 2 is a top view of a single repeating unit of the two-dimensional grating shown in FIG. 1;
FIG. 3 (a) is a K-vector diagram of the two-dimensional grating shown in FIG. 1;
FIG. 3 (b) is a diffraction efficiency profile of the two-dimensional grating shown in FIG. 1;
FIG. 4 is a top view of a two-dimensional grating according to a second embodiment of the present invention;
FIG. 5 is a top view of a single repeating unit of the two-dimensional grating of FIG. 4;
FIG. 6 is a K-vector diagram of the two-dimensional grating of FIG. 4;
fig. 7 is a flow chart of a method for forming a two-dimensional grating according to a third embodiment of the present invention;
fig. 8 is a flow chart of a method for forming a two-dimensional grating according to a fourth embodiment of the present invention;
fig. 9 is a schematic structural view of an optical waveguide according to a fifth embodiment of the present invention;
fig. 10 is a schematic structural diagram of a near-eye display device according to a sixth embodiment of the present invention.
Detailed Description
The present invention will be described in detail with reference to specific examples. The following examples will assist those skilled in the art in further understanding the present invention, but are not intended to limit the invention in any way. It should be noted that variations and modifications could be made by those skilled in the art without departing from the inventive concept. These are all within the scope of the present invention.
In order to make the objects, technical solutions and advantages of the present application more apparent, the present application will be further described in detail with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the present application.
It should be noted that, if not conflicting, the various features of the embodiments of the present invention may be combined with each other, which are all within the protection scope of the present application. In addition, while functional block division is performed in a device diagram and logical order is shown in a flowchart, in some cases, the steps shown or described may be performed in a different order than the block division in the device, or in the flowchart. Moreover, the words "first," "second," "third," and the like as used herein do not limit the data and order of execution, but merely distinguish between identical or similar items that have substantially the same function and effect.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and/or" as used in this specification includes any and all combinations of one or more of the associated listed items.
In addition, the technical features of the embodiments of the present invention described below may be combined with each other as long as they do not collide with each other.
Specifically, embodiments of the present invention will be further described below with reference to the accompanying drawings; it should be understood that in the schematic structure of the two-dimensional grating and its repeating units, the shaded portions in the figure are grating structures.
Example 1
The present embodiment provides a two-dimensional grating, please refer to fig. 1 and 2, wherein fig. 1 shows a top view structure of the two-dimensional grating provided by the present embodiment, fig. 2 is a structure of a single repeating unit in the two-dimensional grating provided by the present embodiment, the two-dimensional grating includes repeating units periodically tiled on a surface of a waveguide substrate along a horizontal direction and a vertical direction, the repeating units include a first recess S1 and a second recess S2 disposed along a first horizontal line l1, and a third recess S3 disposed along a second horizontal line l2, the first horizontal line l1 and the second horizontal line l2 are two virtual lines parallel to the horizontal direction, the first recess S1 and the second recess S2 are axisymmetrically disposed along a central axis l3 of the repeating unit, the central axis l3 is a virtual axis capable of bisecting the repeating unit and perpendicular to the first horizontal line l1 and the second horizontal line l2, two adjacent repeating units in the horizontal direction are adjacent to each other, the first recess S1 and the second recess S3 are in an inverted axial shape, and the second recess S3 is in an inverted axial shape, and the water drop shape is formed in a combination of the two recesses S3. Wherein white portions in the figure represent protrusions and black portions represent depressions.
In some embodiments, a feature size D of the first recess S1 and the second recess S2 in the vertical direction is smaller than a feature size D of the third recess S3 in the vertical direction, and a feature size L of the third recess S3 in the horizontal direction is smaller than the feature size D of the third recess S3 in the vertical direction.
In some embodiments, the period of the repeating unit in the horizontal direction is 200nm-2 μm; in some embodiments, the period of the repeating unit in the vertical direction is 10nm-1 μm; in some embodiments, the surface of the repeating unit is coated with a metal oxide film having a thickness of 10nm to 200nm, and the material for coating may be selected from, for example, titanium dioxide (TiO 2 ) And aluminum oxide (Al) 2 O 3 ) At least one of the metal oxides.
In this embodiment, by adjusting the feature size G of the combined structure formed by the first recess S1 and the second recess S2, the feature size D of the first recess S1 and the second recess S2, the feature size L of the third recess S3, the feature size D of the third recess S3, the distance J between the first recess S1 or the second recess S2 and the third recess S3, and the like, the two-dimensional grating formed can adjust the K vectors of one or more diffraction orders for the incident light, so as to achieve relatively uniform coupling efficiency when the light beam propagates in the coupling-out region. Specifically, when the period is 800nmx nm, the two-dimensional grating shown in fig. 1 can realize the adjustment of the K vector of partial diffraction orders shown in fig. 3 (a); when the beam propagates in the coupling-out region, the distribution of diffraction efficiencies in the vector directions of the partial diffraction orders is as shown in fig. 3 (b), and R0, R1, R2, R3, R4, and R5 in fig. 3 (b) correspond to the forward order 0, the extended order 1, the extended order 2, the extended order 3, the extended order 4, and the return order 5 in fig. 3 (a), respectively.
In this embodiment, the rounded end of the drop-shaped structure formed by the first recess S1 and the second recess S2 is disposed near one side of the rounded end of the inverted drop-shaped structure formed by the third recess S3 in the vertical direction, and the first recess S1 and the second recess S2 are not on the same vertical line as the third recess S3. In other embodiments, the arrangement of the first recess S1, the second recess S2, and the third recess S3 may be other arrangements, which are not limited to the present embodiment.
Example two
The present embodiment provides a two-dimensional grating, please refer to fig. 4 and 5, wherein fig. 4 shows a top view structure of the two-dimensional grating provided by the present embodiment, fig. 5 is a structure of a single repeating unit in the two-dimensional grating provided by the present embodiment, the two-dimensional grating includes repeating units periodically tiled on a surface of a waveguide substrate along a horizontal direction and a vertical direction, the repeating units include a first protruding portion S4 and a second protruding portion S5 disposed along a first horizontal line, and a third protruding portion S6 disposed along a second horizontal line, the first horizontal line l1 'and the second horizontal line l2' are two virtual lines parallel to the horizontal direction, the first protruding portion S4 and the second protruding portion S5 are axisymmetrically disposed along a central axis l3 'of the repeating unit, the central axis l3' is a virtual axis capable of bisecting the repeating unit and perpendicular to the first horizontal line l1 'and the second horizontal line l2', and the two adjacent protruding portions S4 in the horizontal direction are in an inverted shape, and the second protruding portion S6 is formed as an inverted shape, and the two protruding portions S6 are formed as an inverted shape. Wherein white portions in the figure represent protrusions and black portions represent depressions.
In some embodiments, the first and second protrusions S4 and S5 are the same size, the feature size D of the first and second protrusions S4 and S5 in the vertical direction is smaller than the feature size D of the third protrusion S6 in the vertical direction, and the feature size L of the third protrusion S6 in the horizontal direction is smaller than the feature size D of the third protrusion S6 in the vertical direction.
In some embodiments, the period of the repeating unit in the horizontal direction is 200nm-2 μm; in some embodiments, the period of the repeating unit in the vertical direction is 10nm-1 μm; in some embodiments, the surface of the repeating unit is coated with a metal oxide film having a thickness of 10nmThe material used for the coating can be selected from, for example, titanium dioxide (TiO 2 ) And aluminum oxide (Al) 2 O 3 ) At least one of the metal oxides.
In the embodiment of the present invention, by adjusting the feature sizes G of the first and second adjacent protrusions S4 and S5 in the horizontal direction, the feature sizes D of the first and second protrusions S4 and S5 in the vertical direction, the feature sizes L of the third protrusions S6 in the horizontal direction, the feature sizes D of the third protrusions S6 in the vertical direction, the distances J between the first or second protrusions S4 and S5 and the third protrusions S6 in the vertical direction, etc., the formed two-dimensional grating may perform adjustment of K vectors of one or more diffraction orders on the incident light beam, so as to achieve relatively uniform coupling-out efficiency when the light beam propagates in the coupling-out region. Specifically, the two-dimensional grating shown in fig. 4 has an inverse concave-convex structure to the two-dimensional grating shown in fig. 1, and the two-dimensional grating shown in fig. 4 can realize the adjustment of the K vector of the partial diffraction order as shown in fig. 6. The two-dimensional grating shown in fig. 4 is used to achieve an expanded propagation of the light beam in the coupling-out region, and the distribution of diffraction efficiency in the vector direction of the partial diffraction orders is slightly different from that of the two-dimensional grating shown in fig. 1.
In the embodiment of the present invention, the rounded ends of the droplet-shaped structures formed by the first protruding portion S4 and the second protruding portion S5 are disposed near one side of the rounded end of the inverted droplet-shaped structure formed by the third protruding portion S6 in the vertical direction, and the first protruding portion S4 and the second protruding portion S5 are not on the same vertical line with the third protruding portion S6. In other embodiments, the arrangement of the first boss S4, the second boss S5, and the third boss S6 may be other arrangements, which are not limited to the present embodiment.
Example III
An embodiment of the present invention provides a method for forming a two-dimensional grating, please refer to fig. 7, which shows a flow of the method for forming a two-dimensional grating provided by the embodiment of the present invention, the method includes:
step S11: according to the requirement for light outcoupling efficiency, the optimization variables of the two-dimensional grating according to embodiment one are determined,
wherein the optimization variables include: a feature size of the first recess and the second recess in a horizontal direction, a feature size of the first recess and the second recess in a vertical direction, a feature size of the third recess in a horizontal direction, a feature size of the third recess in a vertical direction, a distance between the first recess or the second recess and the third recess in a vertical direction, and/or a height of each recess with respect to the waveguide substrate surface recess;
step S12: and carrying out etching operation on the optical waveguide at the positions of the first concave part, the second concave part and the third concave part according to the optimized variable so as to form the two-dimensional grating.
According to the method for forming the two-dimensional grating provided by the embodiment of the invention, the dimensional parameters in the structure of the two-dimensional grating in the example shown in the first embodiment can be optimized according to the diffraction efficiency requirement of the optical waveguide required by a user as shown in fig. 3 (a) and 3 (b), so as to obtain the actual manufacturing parameters of the two-dimensional grating, namely the optimized variables of the two-dimensional grating, and the first concave part, the second concave part and the third concave part are etched on the optical waveguide substrate according to the obtained optimized variables, namely the black parts in fig. 1 and 2 are etched to form the two-dimensional grating shown in the first embodiment.
Example IV
An embodiment of the present invention provides a method for forming a two-dimensional grating, please refer to fig. 8, which shows a flow of the method for forming a two-dimensional grating provided by the embodiment of the present invention, the method includes:
step S21: according to the requirement for the light coupling-out efficiency, the optimization variables of the two-dimensional grating are determined as described in the second embodiment,
wherein the optimization variables include: a feature size of the first and second protrusions in a horizontal direction, a feature size of the first and second protrusions in a vertical direction, a feature size of the third protrusion in a horizontal direction, a feature size of the third protrusion in a vertical direction, a distance of the first or second protrusion from the third protrusion in a vertical direction, and/or a height of each protrusion relative to the waveguide substrate surface;
step S22: and on the optical waveguide, etching operation is carried out on positions avoiding the first protruding part, the second protruding part and the third protruding part according to the optimized variable so as to form the two-dimensional grating.
According to the method for forming the two-dimensional grating, provided by the embodiment of the invention, the dimension parameters in the structure of the two-dimensional grating in the example shown in the second example can be optimized according to the requirement of the diffraction efficiency of the optical waveguide required by a user, so that the actual manufacturing parameters of the two-dimensional grating, namely the optimized variables of the two-dimensional grating, are obtained, and other parts except the protruding parts are etched on the optical waveguide substrate according to the obtained optimized variables, so that the first protruding part, the second protruding part and the third protruding part are formed in the final unetched part of the optical waveguide. Illustratively, the black portions are etched in fig. 4 and 5, resulting in a two-dimensional grating as shown in embodiment two.
Example five
Referring to fig. 9, a structure of an optical waveguide according to an embodiment of the present invention is shown, where the optical waveguide 10 includes: a waveguide substrate 11; a coupling-in region 12 composed of a one-dimensional grating, disposed on the light-incident side of the waveguide substrate 11; a coupling-out region 13 of the two-dimensional grating according to the first or second embodiment is provided, and the coupling-out region 13 is disposed on the light-emitting side of the waveguide substrate 11.
The coupling-in region 12 may be provided with a one-dimensional grating structure such as a rectangular grating, an oblique grating, a trapezoidal grating, an echelle grating, a holographic grating, etc., and specifically, the coupling-in region 12 may diffractively couple the projection light of the optical machine into the waveguide substrate 11 to perform total reflection propagation in a direction toward the coupling-out region 13, and may be set according to actual needs.
The coupling-out region 13 is provided with a two-dimensional grating as described in the first embodiment or the second embodiment, which is easy to process and is beneficial to adjusting the coupling-out efficiency, specifically, please refer to the first embodiment or the second embodiment and the drawings thereof, which will not be described in detail herein, the coupling-out region 13 can diffuse and propagate light, and couple part of the light out of the waveguide substrate 11 into human eyes, thereby realizing pupil expansion display.
Further, referring to fig. 9, in an embodiment of the present invention, the waveguide substrate 11 is a curved waveguide substrate. In other embodiments, the shape and size of the waveguide substrate 11 may be designed according to practical needs, which is not limited by the embodiments of the present invention; in addition, the bending dimension of the waveguide substrate can be designed according to actual requirements and process requirements.
Example six
An embodiment of the present invention provides a near-eye display device, please refer to fig. 10, which illustrates a structure of the near-eye display device provided by the embodiment of the present invention, where the near-eye display device 100 includes: the optical waveguide 10 as described in embodiment five.
In the near-eye display device 100 provided by the embodiment of the invention, the optical waveguide 10 adopts the two-dimensional grating as the coupling-out structure, which is shown in the first embodiment or the second embodiment of the invention, and the two-dimensional grating has more optimized variables, so that multi-parameter regulation and control can be performed to realize the adjustment of diffraction efficiency.
The embodiment of the invention provides a two-dimensional grating and a forming method thereof, an optical waveguide and near-eye display equipment, wherein the two-dimensional grating comprises a repeating unit which is periodically tiled on the surface of a waveguide substrate along the horizontal direction and the vertical direction, the repeating unit comprises a first concave part (or a first protruding part) and a second concave part (or a second protruding part) which are arranged along a first horizontal line, and a third concave part (or a third protruding part) which is arranged along a second horizontal line, the first horizontal line and the second horizontal line are two virtual lines parallel to the horizontal direction, the first concave part (or the first protruding part) and the second concave part (or the second protruding part) are arranged along the central axis of the repeating unit in an axisymmetric way, the central axis is a virtual axis which can bisect the repeating units and is perpendicular to the first horizontal line and the second horizontal line, a combined structure formed by a first concave part (or a first convex part) and a second concave part (or a second convex part) which are adjacent to each other in the horizontal direction in the two repeating units is in a water drop shape, the third concave part (or the third convex part) is in an axisymmetric graph taking the central axis as a symmetry axis, the two-dimensional grating can be etched and formed on the optical waveguide according to the requirement on the light coupling efficiency, the two-dimensional grating provided by the embodiment of the invention can improve the adjustment freedom degree of the two-dimensional grating in the diffraction optical waveguide on the premise of not increasing the processing difficulty, can better control the coupling efficiency distribution, better exit pupil uniformity and field of view uniformity are achieved.
It should be noted that the above-described apparatus embodiments are merely illustrative, and the units described as separate units may or may not be physically separate, and units shown as units may or may not be physical units, may be located in one place, or may be distributed over a plurality of network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of this embodiment.
From the above description of embodiments, it will be apparent to those skilled in the art that the embodiments may be implemented by means of software plus a general purpose hardware platform, or may be implemented by hardware. Those skilled in the art will appreciate that all or part of the processes implementing the methods of the above embodiments may be implemented by a computer program for instructing relevant hardware, where the program may be stored in a computer readable storage medium, and the program may include processes of the embodiments of the methods described above when executed. The storage medium may be a magnetic disk, an optical disk, a Read-Only Memory (ROM), a random access Memory (Random Access Memory, RAM), or the like.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention, and are not limiting; the technical features of the above embodiments or in the different embodiments may also be combined within the idea of the invention, the steps may be implemented in any order, and there are many other variations of the different aspects of the invention as described above, which are not provided in detail for the sake of brevity; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit of the invention.
Claims (15)
1. A two-dimensional grating is characterized by comprising a repeating unit which is periodically tiled on the surface of a waveguide substrate along the horizontal direction and the vertical direction, wherein the repeating unit comprises a first concave part and a second concave part which are arranged along a first horizontal line and a third concave part which is arranged along a second horizontal line, the first horizontal line and the second horizontal line are two virtual lines parallel to the horizontal direction,
the first concave part and the second concave part are axisymmetrically arranged along the central axis of the repeating unit, the central axis is a virtual axis which can bisect the repeating unit and is perpendicular to the first horizontal line and the second horizontal line, the combined structure formed by the first concave part and the second concave part which are adjacent to each other in the horizontal direction in the two repeating units is in a water drop shape,
the third concave part is in an inverted water drop shape, and is in an axisymmetric graph taking the central axis as a symmetric axis.
2. The two-dimensional grating according to claim 1, wherein,
the feature size of the first concave part and the second concave part in the vertical direction is smaller than the feature size of the third concave part in the vertical direction,
the feature size of the third concave part in the horizontal direction is smaller than the feature size of the third concave part in the vertical direction.
3. A two-dimensional grating according to claim 1 or 2, characterized in that,
the period of the repeating unit in the horizontal direction is 200nm to 2 μm.
4. A two-dimensional grating according to claim 3,
the period of the repeating unit in the vertical direction is 10nm-1 μm.
5. The two-dimensional grating according to claim 4, wherein,
the surface of the repeating unit is plated with a metal oxide film, and the thickness of the metal oxide film is 10nm-200nm.
6. A two-dimensional grating is characterized by comprising a repeating unit which is periodically tiled on the surface of a waveguide substrate along the horizontal direction and the vertical direction, wherein the repeating unit comprises a first protruding part and a second protruding part which are arranged along a first horizontal line and a third protruding part which is arranged along a second horizontal line, the first horizontal line and the second horizontal line are two virtual lines parallel to the horizontal direction,
the first protruding part and the second protruding part are axisymmetrically arranged along the central axis of the repeating unit, the central axis is a virtual axis which can bisect the repeating unit and is perpendicular to the first horizontal line and the second horizontal line, the combined structure formed by the first protruding part and the second protruding part which are adjacent to each other in the horizontal direction is in a water drop shape,
the third protruding portion is in an inverted water drop shape, and is in an axisymmetric graph taking the central axis as a symmetric axis.
7. The two-dimensional grating according to claim 6, wherein,
the feature sizes of the first protruding portion and the second protruding portion in the vertical direction are smaller than the feature size of the third protruding portion in the vertical direction, and the feature size of the third protruding portion in the horizontal direction is smaller than the feature size of the third protruding portion in the vertical direction.
8. A two-dimensional grating according to claim 6 or 7, characterized in that,
the period of the repeating unit in the horizontal direction is 200nm to 2 μm.
9. The two-dimensional grating of claim 8, wherein,
the period of the repeating unit in the vertical direction is 10nm-1 μm.
10. The two-dimensional grating according to claim 9, wherein,
the surface of the repeating unit is plated with a metal oxide film, and the thickness of the metal oxide film is 10nm-200nm.
11. A method of forming a two-dimensional grating, comprising:
according to the requirements for light outcoupling efficiency, an optimization variable of the two-dimensional grating according to any of the claims 1-5 is determined,
wherein the optimization variables include: a feature size of the first recess and the second recess in a horizontal direction, a feature size of the first recess and the second recess in a vertical direction, a feature size of the third recess in a horizontal direction, a feature size of the third recess in a vertical direction, a distance between the first recess or the second recess and the third recess in a vertical direction, and/or a height of each recess with respect to the waveguide substrate surface recess;
and carrying out etching operation on the optical waveguide at the positions of the first concave part, the second concave part and the third concave part according to the optimized variable so as to form the two-dimensional grating.
12. A method of forming a two-dimensional grating, comprising:
determining the optimization variables of the two-dimensional grating according to any of claims 6-10 based on the requirements for light outcoupling efficiency,
wherein the optimization variables include: a feature size of the first and second protrusions in a horizontal direction, a feature size of the first and second protrusions in a vertical direction, a feature size of the third protrusion in a horizontal direction, a feature size of the third protrusion in a vertical direction, a distance of the first or second protrusion from the third protrusion in a vertical direction, and/or a height of each protrusion relative to the waveguide substrate surface;
and on the optical waveguide, etching operation is carried out on positions avoiding the first protruding part, the second protruding part and the third protruding part according to the optimized variable so as to form the two-dimensional grating.
13. An optical waveguide, comprising:
a waveguide substrate;
the coupling-in area is arranged on the light incident side of the waveguide substrate;
coupling-out regions provided with a two-dimensional grating as claimed in any of the claims 1-10, said coupling-out regions being arranged on the light-exit side of the waveguide substrate.
14. The optical waveguide of claim 13 wherein,
the waveguide substrate is a curved waveguide substrate.
15. A near-eye display device, comprising: an optical waveguide as claimed in claim 13 or 14.
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