CN114660692A - Two-dimensional grating and forming method thereof, optical waveguide and near-to-eye display device - Google Patents
Two-dimensional grating and forming method thereof, optical waveguide and near-to-eye display device Download PDFInfo
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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
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- 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
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- 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, wherein the two-dimensional grating comprises repeating units which are periodically and flatly arranged on the surface of a waveguide substrate along the horizontal direction and the vertical direction, each repeating unit comprises a first concave/convex part and a second concave/convex part which are arranged along a first horizontal line, and a third concave/convex part which is arranged along a second horizontal line, the first concave/convex part and the second concave/convex part are arranged in an axial symmetry manner, a combined structure formed by the first concave/convex part and the second concave/convex part which are adjacent in two adjacent repeating units in the horizontal direction is in a water drop shape, the third concave/convex part is in a water drop shape in an inverted manner, and the third concave/convex part is in an axial symmetry pattern, the optical waveguide can be formed by etching on the optical waveguide according to the requirement on the light coupling-out efficiency, has higher adjustment freedom degree, is easy to process, and realizes better exit pupil/field uniformity.
Description
Technical Field
The embodiment of the invention relates to the technical field of optical devices, in particular to a two-dimensional grating and a forming method thereof, an optical waveguide and near-to-eye display equipment.
Background
Augmented Reality (AR) technology is a technology that integrates virtual information with the real world, and the Augmented Reality technology represented by Augmented Reality glasses is beginning to rise in various industries at present, and particularly in the fields of security and industry, the information interaction mode is greatly improved. Currently, optical display schemes in a relatively mature augmented reality technology are mainly divided into a prism scheme, a birdbath scheme, a free-form surface scheme and an optical waveguide (Lightguide) scheme, the first three schemes have large volumes, and limit the application of the schemes in the aspect of intelligent wearing, namely the aspect of augmented reality glasses, and the optical waveguide scheme is the best optical display scheme in the current augmented reality glasses.
The optical waveguide scheme is divided into a geometric waveguide scheme, an embossed grating waveguide scheme and a volume holographic waveguide scheme, wherein the geometric waveguide scheme is to use an array of coated semi-transparent and semi-reflective mirrors to display virtual information, but the field of view and the eye movement range of the scheme are limited, and the array lenses can bring stripe effects to pictures, so the geometric waveguide scheme cannot present the optimal display effect to human eyes. Volume holographic waveguide solutions are currently limited to large scale mass production. The embossed 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 existing scheme paths of the embossed grating waveguide mainly include a one-dimensional grating-based optical waveguide scheme and a two-dimensional grating-based optical waveguide scheme, 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 and has the functions of expansion and coupling-out.
In implementing the embodiments of the present invention, the inventors found that at least the following problems exist in the above related art: in the existing optical waveguide scheme based on the two-dimensional grating structure, the two-dimensional grating structure used in the coupling-out area is usually a cylindrical structure and a rhombic structure, and the two structures have fewer adjustable parameters, so that the adjustment of the coupling-out efficiency is not facilitated.
Disclosure of Invention
The embodiment of the application provides a two-dimensional grating, a forming method of the two-dimensional grating, an optical waveguide and a near-eye display device.
The purpose of the embodiment of the invention is realized by the following technical scheme:
in order to solve the above technical problem, in a first aspect, an embodiment of the present invention provides a two-dimensional grating, including repeating units arranged on a surface of a waveguide substrate in a horizontal direction and a vertical direction, the repeating units include first and second recesses arranged along a first horizontal line, and a third recess arranged along a second horizontal line, the first and second horizontal lines are two virtual lines parallel to the horizontal direction, the first and second recesses are arranged in axial symmetry 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 and second horizontal lines, a combined structure of adjacent first and second recesses in two horizontally adjacent repeating units is in a droplet shape, the third sunken part is in an inverted water-drop shape, and the third sunken part is in an axisymmetric pattern with the central shaft as a symmetry axis.
In some embodiments, the first and second recesses are the same size, the first and second recesses have a vertical characteristic dimension that is less than a vertical characteristic dimension of the third recess, and the third recess has a horizontal characteristic dimension that is less than a vertical characteristic dimension of the third recess.
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 to 1 μm.
In some embodiments, the surface of the repeating unit is plated with a metal oxide film having a thickness of 10nm to 200 nm.
In order to solve the above technical problem, in a second aspect, an embodiment of the present invention provides a two-dimensional grating, including a repeating unit periodically tiled on a surface of a waveguide substrate in horizontal and vertical directions, where the repeating unit includes a first protruding portion and a second protruding portion arranged along a first horizontal line, and a third protruding portion 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 portion and the second protruding portion are axially symmetrically arranged 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 of the first protruding portion and the second protruding portion adjacent to each other in the horizontal direction is in a water droplet shape, the third bulge is in an inverted water drop shape, and the third bulge is in an axisymmetric pattern taking the central shaft as a symmetry axis.
In some embodiments, the first and second bosses are the same size, a characteristic dimension of the first and second bosses in the vertical direction is smaller than a characteristic dimension of the third boss in the vertical direction, and a characteristic dimension of the third boss in the horizontal direction is smaller than a characteristic dimension of the third boss 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 to 1 μm.
In some embodiments, the surface of the repeating unit is plated with a metal oxide film having a thickness of 10nm to 200 nm.
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: determining an optimization variable of the two-dimensional grating according to the first aspect, wherein the optimization variable comprises: the characteristic size of the first and second recesses in the horizontal direction, the characteristic size of the first and second recesses in the vertical direction, the characteristic size of the third recess in the horizontal direction, the characteristic size of the third recess in the vertical direction, the distance between the first or second recess and the third recess in the vertical direction, and/or the height of each recess recessed relative to the surface of the waveguide substrate; and etching the positions of the first depressed part, the second depressed part and the third depressed part on the optical waveguide according to the optimized variable to form the two-dimensional grating.
In order to solve the foregoing 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, wherein the optimization variable comprises: the characteristic size of the first protruding part and the second protruding part in the horizontal direction, the characteristic size of the first protruding part and the second protruding part in the vertical direction, the characteristic size of the third protruding part in the horizontal direction, the characteristic size of the third protruding part in the vertical direction, the distance between the first protruding part or the second protruding part and the third protruding part in the vertical direction, and/or the height of each protruding part protruding relative to the surface of the waveguide substrate; and etching the optical waveguide at positions avoiding the first protruding part, the second protruding part and the third protruding part according to the optimized variable 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 provided with a two-dimensional grating as described in the first or second aspect, the coupling-out region being arranged at the light-exit side of the waveguide substrate.
In some embodiments, the waveguide substrate is a curved waveguide substrate.
To solve the above technical problem, according to a sixth aspect, an embodiment of the present invention further provides a near-eye display device, including: an optical waveguide as claimed in the fifth aspect.
Compared with the prior art, the invention has the beneficial effects that: in contrast to the state of the art, embodiments of the present invention provide a two-dimensional grating and a method of forming the same, an optical waveguide, and a near-eye display device, where the two-dimensional grating includes a repeating unit periodically tiled on a surface of a waveguide substrate in a horizontal direction and a vertical direction, the repeating unit includes a first concave portion (or a first convex portion) and a second concave portion (or a second convex portion) arranged along a first horizontal line, and a third concave portion (or a third convex portion) 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 portion (or the first convex portion) and the second concave portion (or the second convex portion) are axisymmetrically arranged 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, the two-dimensional grating provided by the embodiment of the invention can improve the adjustment freedom 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, and realizes better exit pupil uniformity and field uniformity.
Drawings
The embodiments are illustrated by the figures of the accompanying drawings which correspond and are not meant to limit the embodiments, in which elements/modules and steps having the same reference number designation may be referred to by similar elements/modules and steps, unless otherwise indicated, and in which the drawings are not to scale.
Fig. 1 is a top view of a two-dimensional grating according to an embodiment of the present invention;
FIG. 2 is a top view of a single repeating unit of the two-dimensional grating of FIG. 1;
FIG. 3(a) is a K vector diagram of the two-dimensional grating shown in FIG. 1;
FIG. 3(b) is a graph showing the diffraction efficiency distribution 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 shown in FIG. 4;
FIG. 6 is a K vector diagram of the two-dimensional grating shown in FIG. 4;
fig. 7 is a schematic flowchart of a method for forming a two-dimensional grating according to a third embodiment of the present invention;
fig. 8 is a schematic flowchart of a method for forming a two-dimensional grating according to a fourth embodiment of the present invention;
fig. 9 is a schematic structural diagram 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 invention, but are not intended to limit the invention in any way. It should be noted that variations and modifications can be made by persons skilled in the art without departing from the spirit of the invention. All falling 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 is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present application and are not intended to limit the present application.
It should be noted that, if not conflicted, the various features of the embodiments of the invention may be combined with each other within the scope of protection of the present application. Additionally, while functional block divisions are performed in device schematics, with logical sequences shown in flowcharts, in some cases, steps shown or described may be performed in a different order than the block divisions in devices, or in flowcharts. Further, the terms "first," "second," "third," and the like, as used herein, do not limit the data and the execution order, but merely distinguish the same items or similar items having substantially the same functions and actions.
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. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.
In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
Specifically, the embodiments of the present invention will be further explained with reference to the drawings; it should be understood that in the structural schematic diagram of the two-dimensional grating and its repeating units, the hatched portion in the figure is the grating structure.
Example one
In the present embodiment, a two-dimensional grating is provided, please refer to fig. 1 and fig. 2, wherein fig. 1 illustrates a top view structure of the two-dimensional grating provided in the present embodiment, fig. 2 is a structure of a single repeating unit in the two-dimensional grating provided in the present embodiment, the two-dimensional grating includes repeating units periodically tiled on a surface of a waveguide substrate in a horizontal direction and a vertical direction, the repeating unit includes a first recessed portion S1 and a second recessed portion S2 arranged along a first horizontal line l1, and a third recessed portion S3 arranged 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 recessed portion S1 and the second recessed portion S2 are axially symmetric along a central axis l3 of the repeating unit, the central axis l3 is a virtual axis capable of bisecting and perpendicular to the first horizontal line l1 and the second horizontal line l2, adjacent two in the horizontal direction the integrated configuration that first depressed part S1 and second depressed part S2 constitute in the repeating unit, next is the drop shape, third depressed part S3 is the inversion drop shape, just third depressed part S3 is for use center pin l3 is the axisymmetric figure of symmetry axle. In the figure, white portions represent projections, 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 a 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 to 2 μm; in some embodiments, the period of the repeating unit in the vertical direction is 10nm to 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 coating material may be selected from, for example, titanium dioxide (TiO)2) And aluminum oxide (Al)2O3) And the like.
In this embodiment, by adjusting the feature size G in the horizontal direction of the combined structure formed by the adjacent first and second recesses S1 and S2, the feature size D in the vertical direction of the first and second recesses S1 and S2, the feature size L in the horizontal direction of the third recess S3, the feature size D in the vertical direction of the third recess S3, the distance J in the vertical direction between the first or second recess S1 or S2 and the third recess S3, etc., the formed two-dimensional grating can adjust the K vectors of one or more diffraction orders of the incident light beam, so as to achieve uniform coupling efficiency when the light beam propagates in the expanded coupling-out region. Specifically, the two-dimensional grating shown in fig. 1 can realize the adjustment of the K vector of the partial diffraction order as shown in fig. 3(a) when the period is 800nmx462 nm; when the light beam propagates in the extended direction in the coupling-out region, the diffraction efficiency distribution in the vector direction of the partial diffraction order is as shown in fig. 3(b), and R0, R1, R2, R3, R4, and R5 in fig. 3(b) correspond to the previous pass order 0, the extended pass order 1, the extended pass order 2, the extended pass order 3, the extended pass order 4, and the return pass order 5 in fig. 3(a), respectively.
It should be noted that, in this embodiment, the rounded end of the drop-shaped structure formed by the first recessed portion S1 and the second recessed portion S2 is disposed close to one side of the rounded end of the inverted drop-shaped structure formed by the third recessed portion S3 in the vertical direction, and both the first recessed portion S1 and the second recessed portion S2 are not on the same vertical line as the third recessed portion S3. In other embodiments, the arrangement of the first recess S1, the second recess S2, and the third recess S3 may be other arrangements, and is not limited to this embodiment.
Example two
This embodiment provides a two-dimensional grating, please refer to fig. 4 and 5, wherein fig. 4 illustrates a top view structure of the two-dimensional grating provided by this embodiment, fig. 5 illustrates a structure of a single repeating unit in the two-dimensional grating provided by this 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 unit includes a first protrusion S4 and a second protrusion S5 arranged along a first horizontal line, and a third protrusion S6 arranged along a second horizontal line, the first horizontal line l1 'and the second horizontal line l 2' are two virtual lines parallel to the horizontal direction, the first protrusion S4 and the second protrusion S5 are axially symmetric along a central axis l3 'of the repeating unit, the central axis l 3' is an axis that can bisect and is perpendicular to the first horizontal line l1 'and the second horizontal line l 2', adjacent two on the horizontal direction the integrated configuration that among the repeating unit, adjacent first bellying S4 and second bellying S5 constitute is the drop shape, third bellying S6 is the inversion drop shape, just third bellying S6 is for use center pin l 3' is the axisymmetric figure of symmetry axis. In the figure, white portions represent projections, and black portions represent depressions.
In some embodiments, the first and second bosses S4 and S5 are the same size, a vertical characteristic dimension D of the first and second bosses S4 and S5 is less than a vertical characteristic dimension D of the third boss S6, and a horizontal characteristic dimension L of the third boss S6 is less than the vertical characteristic dimension D of the third boss S6.
In some embodiments, the period of the repeating unit in the horizontal direction is 200nm to 2 μm; in some embodiments, the period of the repeating unit in the vertical direction is 10nm to 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 coating material may be selected from, for example, titanium dioxide (TiO)2) And aluminum oxide (Al)2O3) And the like.
In the embodiment of the present invention, by adjusting the feature size G of the adjacent first protrusion S4 and second protrusion S5 in the horizontal direction, the feature size D of the first protrusion S4 and second protrusion S5 in the vertical direction, the feature size L of the third protrusion S6 in the horizontal direction, the feature size D of the third protrusion S6 in the vertical direction, the distance J between the first protrusion S4 or second protrusion S5 and the third protrusion S6 in the vertical direction, etc., the formed two-dimensional grating can adjust the K vectors of one or more diffraction orders of the incident light, so as to achieve uniform coupling-out efficiency when the light beam spreads in the coupling-out region. Specifically, the two-dimensional grating shown in fig. 4 has an opposite concave-convex structure to the two-dimensional grating shown in fig. 1, and the two-dimensional grating shown in fig. 4 can realize adjustment of the K vector of a partial diffraction order as shown in fig. 6. The two-dimensional grating shown in fig. 4 is used to realize the expanded propagation of the light beam in the coupling-out region, and the distribution of the 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 end of the droplet-shaped structure formed by the first protruding portion S4 and the second protruding portion S5 is disposed close to one side of the rounded end of the inverted droplet-shaped structure formed by the third protruding portion S6 in the vertical direction, and both the first protruding portion S4 and the second protruding portion S5 are not on the same vertical line as the third protruding portion S6. In some other embodiments, the arrangement of the first protrusion S4, the second protrusion S5, and the third protrusion S6 may be other arrangements, and is not limited to this embodiment.
EXAMPLE III
An embodiment of the present invention provides a method for forming a two-dimensional grating, please refer to fig. 7, which illustrates a flow of the method for forming a two-dimensional grating according to the embodiment of the present invention, where the method includes:
step S11: according to the requirement of the light outcoupling efficiency, the optimization variables of the two-dimensional grating according to the first embodiment are determined,
wherein the optimization variables include: the characteristic size of the first and second recesses in the horizontal direction, the characteristic size of the first and second recesses in the vertical direction, the characteristic size of the third recess in the horizontal direction, the characteristic size of the third recess in the vertical direction, the distance between the first or second recess and the third recess in the vertical direction, and/or the height of each recess recessed relative to the surface of the waveguide substrate;
step S12: and etching the positions of the first depressed part, the second depressed part and the third depressed part on the optical waveguide according to the optimized variable to form the two-dimensional grating.
According to the method for forming the two-dimensional grating provided by the embodiment of the present invention, according to the requirement of the optical waveguide required by the user for the diffraction efficiency as shown in fig. 3(a) and 3(b), the dimensional parameters in the structure of the two-dimensional grating in the example shown in the first embodiment are optimized, so as to obtain the actual manufacturing parameters of the two-dimensional grating, that is, the optimized variables of the two-dimensional grating, and the first concave portion, the second concave portion, and the third concave portion, that is, the black portions in fig. 1 and 2, are etched on the optical waveguide substrate according to the obtained optimized variables, so as to form the two-dimensional grating as shown in the first embodiment.
Example four
An embodiment of the present invention provides a method for forming a two-dimensional grating, please refer to fig. 8, which illustrates a flow of the method for forming a two-dimensional grating according to the embodiment of the present invention, where the method includes:
step S21: according to the requirement of the light outcoupling efficiency, the optimization variables of the two-dimensional grating according to the second embodiment are determined,
wherein the optimization variables include: the characteristic size of the first protruding part and the second protruding part in the horizontal direction, the characteristic size of the first protruding part and the second protruding part in the vertical direction, the characteristic size of the third protruding part in the horizontal direction, the characteristic size of the third protruding part in the vertical direction, the distance between the first protruding part or the second protruding part and the third protruding part in the vertical direction, and/or the height of each protruding part protruding relative to the surface of the waveguide substrate;
step S22: and etching the optical waveguide at positions avoiding the first protruding part, the second protruding part and the third protruding part according to the optimized variable to form the two-dimensional grating.
According to the forming method of the two-dimensional grating provided by the embodiment of the invention, according to the requirement of the diffraction efficiency of the optical waveguide required by a user, the size parameters in the structure of the two-dimensional grating in the example shown in the second embodiment are optimized, 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 convex part are etched on the optical waveguide substrate according to the obtained optimized variables, so that the final un-etched parts of the optical waveguide form the first convex part, the second convex part and the third convex part. Illustratively, the black portions in fig. 4 and 5 are etched to obtain the two-dimensional grating as shown in embodiment two.
EXAMPLE five
An optical waveguide is provided in an embodiment of the present invention, please refer to fig. 9, which shows a structure of an optical waveguide provided in an embodiment of the present invention, where the optical waveguide 10 includes: a waveguide substrate 11; a coupling-in region 12 formed by a one-dimensional grating, disposed on the light-incident side of the waveguide substrate 11; a coupling-out region 13 provided with a two-dimensional grating as described in 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 have a one-dimensional grating structure such as a rectangular grating, an inclined grating, a trapezoidal grating, a echelle grating, or a holographic grating, and specifically, the coupling-in region 12 may couple the projection light of the optical machine into the waveguide substrate 11 by diffraction and propagate in a total reflection manner in the direction of the coupling-out region 13, and may be set according to actual needs.
The coupling-out region 13 is provided with the 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, referring to the first embodiment or the second embodiment and the drawings thereof, which are not 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 the extended pupil display.
Further, with continued reference to fig. 9, in the 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 can also be designed according to actual needs, and need not be limited by the embodiments of the present invention; in addition, the bending dimension of the waveguide substrate can be designed according to the actual requirement and the process requirement.
EXAMPLE six
Referring to fig. 10, which shows a structure of a near-eye display device provided in an embodiment of the present invention, the near-eye display device 100 includes: the optical waveguide 10 of embodiment five.
In the near-eye display device 100 provided in the embodiment of the present invention, the optical waveguide 10 adopts the two-dimensional grating shown in the first embodiment or the second embodiment of the present invention as the coupling-out structure, and the two-dimensional grating has more optimized variables, and can perform multi-parameter control to adjust the diffraction efficiency.
The embodiment of the invention provides a two-dimensional grating and a forming method thereof, an optical waveguide and a near-eye display device, wherein the two-dimensional grating comprises repeating units which are periodically and flatly arranged on the surface of a waveguide substrate along a horizontal direction and a vertical direction, each 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 a central axis of the repeating unit, the central axis is a virtual axis which can bisect the repeating unit and is vertical to the first horizontal line and the second horizontal line, the two-dimensional grating provided by the embodiment of the invention can improve the adjustment freedom of the two-dimensional grating in the diffraction optical waveguide on the premise of not increasing the processing difficulty, can better control the distribution of coupling efficiency, and realizes better exit pupil uniformity and field uniformity.
It should be noted that the above-described device embodiments are merely illustrative, where the units described as separate parts may or may not be physically separate, and the parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on multiple network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of the present embodiment.
Through the above description of the embodiments, those skilled in the art will clearly understand that each embodiment can be implemented by software plus a general hardware platform, and certainly can also be implemented by hardware. It will be understood by those skilled in the art that all or part of the processes of the methods of the embodiments described above can be implemented by hardware related to instructions of a computer program, which can be stored in a computer-readable storage medium, and when executed, can include the processes of the embodiments of the methods described above. The storage medium may be a magnetic disk, an optical disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), or the like.
Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; within the idea of the invention, also technical features in the above embodiments or in different embodiments may be combined, 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 present invention has been described in detail with reference to the foregoing embodiments, it should be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.
Claims (12)
1. A two-dimensional grating comprising a repeating unit laid out periodically in a horizontal direction and a vertical direction on a surface of a waveguide substrate, the repeating unit comprising a first recess and a second recess arranged along a first horizontal line, and a third recess arranged along a second horizontal line, the first horizontal line and the second horizontal line being two virtual lines parallel to the horizontal direction,
the first concave part and the second concave part are arranged in axial symmetry along the central axis of the repeating unit, the central axis is a virtual axis which can divide the repeating unit into halves 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 in the horizontal direction in two adjacent repeating units is in a drop shape,
the third sunken part is in an inverted water-drop shape, and the third sunken part is in an axisymmetric pattern with the central shaft as a symmetry axis.
2. A two-dimensional grating according to claim 1,
the first and second recesses have a characteristic dimension in the vertical direction smaller than a characteristic dimension in the vertical direction of the third recess,
the characteristic dimension of the third recess in the horizontal direction is smaller than the characteristic dimension of the third recess in the vertical direction.
3. A two-dimensional grating comprising a repeating unit laid out periodically in a horizontal direction and a vertical direction on a surface of a waveguide substrate, the repeating unit comprising first and second convex portions arranged along a first horizontal line, and third convex portions arranged along a second horizontal line, the first and second horizontal lines being two virtual lines parallel to the horizontal direction,
the first lug boss and the second lug boss are arranged in axial symmetry along a central axis of the repeating unit, the central axis is a virtual axis which can divide the repeating unit into halves and is perpendicular to the first horizontal line and the second horizontal line, a combined structure formed by the first lug boss and the second lug boss which are adjacent in the horizontal direction in two adjacent repeating units is in a water drop shape,
the third bulge is in an inverted water-drop shape, and the third bulge is an axisymmetric figure taking the central shaft as a symmetry axis.
4. A two-dimensional grating according to claim 3,
the first boss and the second boss have a characteristic dimension in the vertical direction smaller than a characteristic dimension of the third boss in the vertical direction, and the third boss has a characteristic dimension in the horizontal direction smaller than a characteristic dimension of the third boss in the vertical direction.
5. A two-dimensional grating according to any of claims 1 to 4,
the period of the repeating unit along the horizontal direction is 200nm-2 μm.
6. A two-dimensional grating according to claim 5,
the period of the repeating unit in the vertical direction is 10nm-1 μm.
7. A two-dimensional grating according to claim 6,
and a metal oxide film is plated on the surface of the repeating unit, and the thickness of the metal oxide film is 10nm-200 nm.
8. A method of forming a two-dimensional grating, comprising:
determining an optimized variable of the two-dimensional grating according to any one of claims 1-2 and 5-7 according to the requirement of light outcoupling efficiency,
wherein the optimization variables include: the characteristic size of the first and second recesses in the horizontal direction, the characteristic size of the first and second recesses in the vertical direction, the characteristic size of the third recess in the horizontal direction, the characteristic size of the third recess in the vertical direction, the distance between the first or second recess and the third recess in the vertical direction, and/or the height of each recess recessed relative to the surface of the waveguide substrate;
and etching the positions of the first depressed part, the second depressed part and the third depressed part on the optical waveguide according to the optimized variable to form the two-dimensional grating.
9. A method of forming a two-dimensional grating, comprising:
determining an optimized variable of the two-dimensional grating according to any one of claims 3-7 according to the requirement for light outcoupling efficiency,
wherein the optimization variables include: the characteristic size of the first protruding part and the second protruding part in the horizontal direction, the characteristic size of the first protruding part and the second protruding part in the vertical direction, the characteristic size of the third protruding part in the horizontal direction, the characteristic size of the third protruding part in the vertical direction, the distance between the first protruding part or the second protruding part and the third protruding part in the vertical direction, and/or the height of each protruding part protruding relative to the surface of the waveguide substrate;
and etching the optical waveguide at positions avoiding the first protruding part, the second protruding part and the third protruding part according to the optimized variable to form the two-dimensional grating.
10. An optical waveguide, comprising:
a waveguide substrate;
the coupling-in area is arranged on the light incident side of the waveguide substrate;
outcoupling region provided with a two-dimensional grating according to any of claims 1 to 7, said outcoupling region being arranged at the light exit side of said waveguide substrate.
11. The optical waveguide of claim 10,
the waveguide substrate is a curved waveguide substrate.
12. A near-eye display device, comprising: an optical waveguide according to claim 10 or 11.
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