CN113777703A - Optical waveguide structure and near-eye display - Google Patents
Optical waveguide structure and near-eye display Download PDFInfo
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- CN113777703A CN113777703A CN202110984625.6A CN202110984625A CN113777703A CN 113777703 A CN113777703 A CN 113777703A CN 202110984625 A CN202110984625 A CN 202110984625A CN 113777703 A CN113777703 A CN 113777703A
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- 230000001154 acute effect Effects 0.000 claims description 4
- 238000002840 optical waveguide grating Methods 0.000 claims 1
- 230000000694 effects Effects 0.000 abstract description 18
- 238000003384 imaging method Methods 0.000 abstract description 15
- 239000010410 layer Substances 0.000 description 19
- 210000001747 pupil Anatomy 0.000 description 13
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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
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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
- G02B27/017—Head mounted
- G02B27/0172—Head mounted 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
- G02B5/1814—Diffraction gratings structurally combined with one or more further optical elements, e.g. lenses, mirrors, prisms or other diffraction gratings
- G02B5/1819—Plural gratings positioned on the same surface, e.g. array of 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
- G02B27/01—Head-up displays
- G02B27/017—Head mounted
- G02B2027/0178—Eyeglass type
Abstract
The invention provides an optical waveguide structure and a near-eye display. The optical waveguide structure includes an optical waveguide sheet; the coupling-in grating is a two-dimensional grating; the turning gratings at least comprise two turning gratings, the two turning gratings are respectively arranged on the same or different surfaces of the optical waveguide sheet, the projections of the two turning gratings on the optical waveguide sheet are arranged in an angle, and the turning gratings are used for receiving light coupled into the gratings; the light coupling grating is used for receiving light of the light coupling grating and the turning grating and coupling the light out of the optical waveguide sheet, the light coupling grating is multiple, the multiple light coupling gratings at least comprise a first light coupling grating and a second light coupling grating, the first light coupling grating is a one-dimensional grating, the second light coupling grating is a two-dimensional grating, the first light coupling grating and the second light coupling grating are located on different surfaces of the optical waveguide sheet, and the projections of the first light coupling grating and the second light coupling grating on the optical waveguide sheet are overlapped. The invention solves the problem of poor imaging effect of the optical waveguide structure in the prior art.
Description
Technical Field
The invention relates to the technical field of optical imaging equipment, in particular to an optical waveguide structure and a near-eye display.
Background
With the development of society and continuous innovation of technology, Virtual Reality (VR), Augmented Reality (AR), and Mixed Reality (MR) have gradually come into people's lives, wherein in the aspect of AR augmented reality, optical waveguide technology is an indispensable step, and it adopts a flat optical waveguide sheet with a diffraction grating to transmit and expand the pupil of an image emitted from a light source assembly to human eyes, so that a user observes the light source assembly while seeing a real world and projects a virtual image superimposed on the world.
Various design schemes are available on the market, but the display effect is not ideal enough because the light transmission in the optical waveguide sheet causes the loss of light intensity energy and the characteristics of the diffraction grating cause the uneven efficiency of the coupled light. Such non-uniformity may affect image display, resulting in poor imaging observed by human eyes.
That is, the optical waveguide structure in the related art has a problem of poor imaging effect.
Disclosure of Invention
The invention mainly aims to provide an optical waveguide structure and a near-eye display to solve the problem that the optical waveguide structure in the prior art is poor in imaging effect.
In order to achieve the above object, according to one aspect of the present invention, there is provided an optical waveguide structure comprising: an optical waveguide sheet; the coupling grating is arranged on the optical waveguide sheet, is a two-dimensional grating and is used for coupling light emitted by an external light source component into the optical waveguide sheet; the turning gratings are multiple and at least comprise two turning gratings which are respectively arranged on the same or different surfaces of the optical waveguide sheet, the projections of the two turning gratings on the optical waveguide sheet are arranged in an angle, and the turning gratings are used for receiving light coupled into the gratings; the light coupling grating is used for receiving light of the light coupling grating and the turning grating and coupling the light out of the optical waveguide sheet, the light coupling grating is multiple, the multiple light coupling gratings at least comprise a first light coupling grating and a second light coupling grating, the first light coupling grating is a one-dimensional grating, the second light coupling grating is a two-dimensional grating, the first light coupling grating and the second light coupling grating are located on different surfaces of the optical waveguide sheet, and the projections of the first light coupling grating and the second light coupling grating on the optical waveguide sheet are overlapped.
Furthermore, the coupling-in grating is one of a rectangular grating, a parallelogram grating and a rhombus grating; and/or the turning grating is a one-dimensional grating, and the one-dimensional grating is one of a blazed grating, an inclined grating, a rectangular grating, a double-ridge grating and a multilayer grating; and/or the first out-coupling grating is one of a blazed grating, an inclined grating, a rectangular grating, a double-ridge grating and a multi-layer grating; and/or the second outcoupling grating is one of a rectangular grating, a parallelogram grating and a rhomboid grating.
Furthermore, the coupling grating comprises a first grating grid line direction and a second grating grid line direction, and an included angle is formed between the first grating grid line direction and the second grating grid line direction and is an acute angle or an obtuse angle.
Furthermore, the two turning gratings are arranged on the optical waveguide sheet along a straight line, and the coupling grating is positioned between the projections of the two turning gratings on the optical waveguide sheet; or the coupling grating is positioned between the projections of the two turning gratings on the optical waveguide sheet, and the coupling grating and the two turning gratings are arranged in a splayed shape.
Furthermore, the incoupling grating, the turning grating and the outcoupling grating are diffraction gratings.
Further, the duty cycle of the coupled-in grating is greater than or equal to 30% and less than or equal to 80%; and/or the height of the incoupling grating is greater than or equal to 100 nanometers and less than or equal to 500 nanometers; and/or the period of the incoupling grating is equal to or greater than 300 nm and equal to or less than 600 nm.
Furthermore, the duty ratio of the turning grating is more than or equal to 30% and less than or equal to 80%; and/or the height of the turning grating is more than or equal to 30 nanometers and less than or equal to 300 nanometers; and/or when the turning grating is a multilayer grating, the number of layers of the multilayer grating is more than or equal to 1 layer and less than or equal to 10 layers; and/or the period of the turning grating is more than or equal to 300 nanometers and less than or equal to 600 nanometers.
Further, the duty cycle of the out-coupling grating is greater than or equal to 30% and less than or equal to 80%; and/or the height of the out-coupling grating is greater than or equal to 30 nanometers and less than or equal to 300 nanometers; and/or when the first coupling grating is a multilayer grating, the number of layers of the multilayer grating is more than or equal to 1 layer and less than or equal to 10 layers; and/or the period of the out-coupling grating is equal to or greater than 300 nanometers and equal to or less than 600 nanometers.
Further, the thickness of the optical waveguide sheet is 400 μm or more and 1 mm or less.
According to another aspect of the present invention, there is provided a near-eye display including: a light source assembly; in the above optical waveguide structure, the light source assembly emits light to the optical waveguide structure, and the optical waveguide structure couples out light into human eyes.
By applying the technical scheme of the invention, the optical waveguide structure comprises an optical waveguide sheet, an in-coupling grating, a turning grating and an out-coupling grating. By arranging the optical waveguide sheet, the optical waveguide sheet provides installation positions for the coupling-in grating, the turning grating and the coupling-out grating, the use reliability of the coupling-in grating, the turning grating and the coupling-out grating is improved, the transmission uniformity of light in the optical waveguide sheet is ensured, and the uniform imaging of an optical waveguide structure is ensured. The coupling-in grating is arranged on the optical waveguide sheet, so that the coupling-in grating can couple most of light emitted by an external light source component into the optical waveguide sheet, and the coupling-in efficiency of the optical waveguide sheet is ensured. The incoupling grating is a two-dimensional grating, so that the light coupled into the optical waveguide sheet through the incoupling grating can be transmitted along two directions, and the transmission path of the light in the optical waveguide sheet is effectively planned. The turning gratings are at least two turning gratings, the two turning gratings are respectively arranged on the same or different surfaces of the optical waveguide sheet, and the projections of the two turning gratings on the optical waveguide sheet are arranged in an angle, so that the arrangement positions of the turning gratings are planned, the lights in two directions, which are coupled into the optical waveguide sheet by the coupling gratings, can be respectively received by the two turning gratings, most of the lights coupled into the gratings can be coupled into the turning gratings, and the turning gratings can turn, expand and copy the light in the two directions along the specific direction, namely, pupil expanding transmission is carried out.
In addition, the coupling-out grating is used for receiving light of the coupling-in grating and the turning grating and coupling the light out of the optical waveguide sheet, the coupling-out gratings are multiple, the coupling-out gratings at least comprise a first coupling-out grating and a second coupling-out grating, the first coupling-out grating is a one-dimensional grating, the second coupling-out grating is a two-dimensional grating, the first coupling-out grating and the second coupling-out grating are located on different surfaces of the optical waveguide sheet, and projections of the first coupling-out grating and the second coupling-out grating on the optical waveguide sheet are overlapped. The arrangement enables most of the light energy of the turning grating to enter the coupling-out grating, and then the coupling-out grating couples the light out of the optical waveguide sheet and further enters human eyes for imaging. The second coupling grating is arranged to be the two-dimensional grating, so that the second coupling grating plays a role of pupil expanding and light homogenizing, light rays which are homogenized by the pupil expanding of the second coupling grating are coupled out to human eyes by the first coupling grating, light coupled out to the human eyes is more uniform, the uniformity of coupled light is ensured, images observed by a user are clearer, and the imaging quality is improved. By reasonably arranging the coupling-in grating, the turning grating and the coupling-out grating, the wide field angle is favorably obtained, simultaneously, the intensity uniformity of coupled light is increased, and the final imaging effect is ensured.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the invention and, together with the description, serve to explain the invention and not to limit the invention. In the drawings:
FIG. 1 shows a schematic diagram of a prior art optical waveguide structure;
FIG. 2 shows a schematic diagram of another prior art optical waveguide structure;
FIG. 3 is a diagram showing the effect of the light guide structure of FIG. 2;
fig. 4 is a schematic diagram showing an optical waveguide structure according to a first embodiment of the present invention;
FIG. 5 is a diagram showing the effect of the light guide structure of FIG. 4;
FIG. 6 is a schematic diagram showing an optical waveguide structure according to a second embodiment of the present invention;
fig. 7 is a view showing the display effect of the optical waveguide structure of fig. 6.
Wherein the figures include the following reference numerals:
10. coupling in a grating; 11. a first grating direction; 12. a second grating direction; 20. turning the grating; 31. a first out-coupling grating; 32. a second outcoupling grating.
Detailed Description
It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict. The present invention will be described in detail below with reference to the embodiments with reference to the attached drawings.
It is noted that, unless otherwise indicated, 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 application belongs.
In the present invention, unless specified to the contrary, use of the terms of orientation such as "upper, lower, top, bottom" or the like, generally refer to the orientation as shown in the drawings, or to the component itself in a vertical, perpendicular, or gravitational orientation; likewise, for ease of understanding and description, "inner and outer" refer to the inner and outer relative to the profile of the components themselves, but the above directional words are not intended to limit the invention.
The invention provides an optical waveguide structure and a near-eye display, aiming at solving the problem that the imaging effect of the optical waveguide structure in the prior art is poor.
Example one
As shown in fig. 4 to 5, the optical waveguide structure includes an optical waveguide sheet, an incoupling grating 10, a turning grating 20 and an outcoupling grating, the incoupling grating 10 is disposed on the optical waveguide sheet, the incoupling grating 10 is a two-dimensional grating, and the incoupling grating 10 is used for coupling light emitted from an external light source component into the optical waveguide sheet; the plurality of the turning gratings 20 at least include two turning gratings 20, the two turning gratings 20 are respectively disposed on the same or different surfaces of the optical waveguide sheet, and the projections of the two turning gratings 20 on the optical waveguide sheet are disposed in an angle, the turning gratings 20 are used for receiving the light coupled into the grating 10; the coupling-out grating is used for receiving the light coupled into the grating 10 and the turning grating 20 and coupling the light out of the optical waveguide sheet, the coupling-out grating is multiple, the multiple coupling-out gratings at least comprise a first coupling-out grating 31 and a second coupling-out grating 32, the first coupling-out grating 31 is a one-dimensional grating, the second coupling-out grating 32 is a two-dimensional grating, the first coupling-out grating 31 and the second coupling-out grating 32 are located on different surfaces of the optical waveguide sheet, and the projections of the first coupling-out grating 31 and the second coupling-out grating 32 on the optical waveguide sheet are overlapped.
By arranging the optical waveguide sheet, the optical waveguide sheet provides installation positions for the coupling-in grating 10, the turning grating 20 and the coupling-out grating, so that the use reliability of the coupling-in grating 10, the turning grating 20 and the coupling-out grating is improved, the uniformity of light transmission in the optical waveguide sheet is ensured, and the uniform imaging of an optical waveguide structure is ensured. By arranging the coupling-in grating 10 on the optical waveguide sheet, the coupling-in grating 10 can couple most of the light emitted by the external light source component into the optical waveguide sheet, so as to ensure the coupling-in efficiency of the optical waveguide sheet. The incoupling grating 10 is a two-dimensional grating, and is arranged such that light coupled into the optical waveguide sheet through the incoupling grating 10 can be transmitted in two directions, effectively planning a transmission path of light in the optical waveguide sheet. The plurality of the turning gratings 20 at least include two turning gratings 20, the two turning gratings 20 are respectively disposed on the same or different surfaces of the optical waveguide sheet, and the projections of the two turning gratings 20 on the optical waveguide sheet are disposed in an angle, so that the arrangement positions of the turning gratings 20 are planned, so as to ensure that the light coupled into the optical waveguide sheet from the incoupling grating 10 in two directions can be respectively received by the two turning gratings 20, so that most of the light coupled into the grating 10 can be incident into the turning gratings 20, and the turning gratings 20 can turn, expand and copy the light in two directions along the specific direction, i.e., perform pupil expansion transmission.
In addition, the coupling-out grating is used for receiving the light coupled into the grating 10 and the turning grating 20 and coupling the light out of the optical waveguide sheet, the coupling-out grating is plural, the plural coupling-out gratings at least include a first coupling-out grating 31 and a second coupling-out grating 32, the first coupling-out grating 31 is a one-dimensional grating, the second coupling-out grating 32 is a two-dimensional grating, the first coupling-out grating 31 and the second coupling-out grating 32 are located on different surfaces of the optical waveguide sheet, and the projections of the first coupling-out grating 31 and the second coupling-out grating 32 on the optical waveguide sheet are overlapped. The arrangement is such that most of the light energy of the turning grating 20 is incident into the coupling-out grating, and then the coupling-out grating couples the light out of the optical waveguide sheet, and further enters human eyes for imaging. Through setting the second coupling-out grating 32 into a two-dimensional grating, the second coupling-out grating 32 plays a role of pupil-expanding dodging, and light rays which are dodged by the pupil expanding of the second coupling-out grating 32 are coupled out to human eyes by the first coupling-out grating 31, so that the light coupled out to the human eyes is more uniform, the uniformity of the coupled-out light is ensured, images observed by a user are clearer, and the imaging quality is improved. By reasonably arranging the coupling grating 10, the turning grating 20 and the coupling grating, the wide field angle can be obtained, the coupling light intensity uniformity is increased, and the final imaging effect is ensured.
It should be noted that, in the present application, the two turning gratings 20 are respectively disposed on different surfaces of the optical waveguide sheet, and of course, the two turning gratings 20 may also be disposed on the same side surface of the optical waveguide sheet, and may be disposed according to specific situations.
Specifically, the incoupling grating 10 is one of a rectangular grating, a parallelogram grating, and a rhomboid grating. Thus, the two-dimensional characteristic of the incoupling grating 10 can be ensured, so that light coupled into the optical waveguide sheet by the incoupling grating 10 can be diffracted in two directions, the incoupling light is transmitted in the optical waveguide sheet along two directions, the transmission direction of the light in the optical waveguide sheet is planned, and the working stability of the incoupling grating 10 is ensured.
It should be noted that the incoupling grating 10 can be selected according to the actual situation.
Specifically, the turning grating 20 is a one-dimensional grating, and the one-dimensional grating is one of a blazed grating, an inclined grating, a rectangular grating, a double-ridge grating, and a multi-layer grating. The two turning gratings 20 are one-dimensional gratings, so that the two turning gratings 20 respectively receive the coupled light in the two directions, and the two turning gratings 20 transmit the corresponding coupled light in the one-dimensional direction, and perform pupil expansion transmission on the coupled light in a specific direction, so as to perform pupil expansion transmission on information of an external light source assembly. The turning grating 20 may be chosen according to the actual situation, and the two turning gratings 20 are the same size.
Specifically, the first outcoupling grating 31 is one of a blazed grating, an inclined grating, a rectangular grating, a double-ridge grating and a multi-layer grating, so that the one-dimensional characteristic of the first outcoupling grating 31 is ensured, the effect of light in the outcoupling waveguide of the first outcoupling grating 31 is ensured, and the improvement of the light intensity of the outcoupling light is facilitated. The second coupling-out grating 32 is one of a rectangular grating, a parallelogram grating and a rhombus grating, and the arrangement ensures the light-uniformizing effect of the second coupling-out grating 32, so that the second coupling-out grating 32 performs two-dimensional pupil expansion on the light of the turning grating 20, thereby uniformly dividing and re-coupling the light efficiency, and achieving the purpose of light uniformizing.
It should be noted that the projections of the first outcoupling grating 31 and the second outcoupling grating 32 on the optical waveguide sheet are completely overlapped and have the same area. Of course, the projections of the first outcoupling grating 31 and the second outcoupling grating 32 on the optical waveguide sheet may not be completely coincident, and may be selected according to actual situations.
The blazed grating is a grating having a blazed characteristic, in which the groove surface is not parallel to the normal of the grating, that is, a small included angle exists between the groove surface and the normal of the grating. The sawtooth type grating is an ideal blazed grating, and the cross section of the sawtooth type grating is in a sawtooth structure for diffraction. The tilted grating is a grating in which the plane of the grating and the tangential direction of the grating form a certain inclination angle. The rectangular grating is a grating which diffracts light with a rectangular cross section.
As shown in fig. 4, the incoupling grating 10 includes a first grating line direction 11 and a second grating line direction 12, and an included angle is formed between the first grating line direction 11 and the second grating line direction 12, and the included angle is an acute angle or an obtuse angle. As shown in the figure, an included angle between the first grating line direction 11 and the second grating line direction 12 towards the side of the light coupling grating is an acute angle. The arrangement of the first grating grid line direction 11 and the second grating grid line direction 12 in the coupling grating 10 is planned, so that the use reliability of the coupling grating 10 is improved, and the arrangement of the two turning gratings 20 is facilitated. Certainly, the included angle between the first grating grid line direction 11 and the second grating grid line direction 12 facing to the coupling grating side can also be an obtuse angle, and at this time, the positions of the turning gratings 20 at both sides need to be adjusted to ensure that the two turning gratings 20 can smoothly receive the light coupled into the grating 10.
Specifically, the coupling grating 10 is located between the projections of the two turning gratings 20 on the optical waveguide sheet, and the coupling grating 10 and the two turning gratings 20 are arranged in a splay shape, and the projections of the two turning gratings 20 on the optical waveguide sheet are symmetrically arranged on both sides of the coupling grating 10. The arrangement is such that one turning grating 20 can mostly receive the light transmitted in the first grating raster line direction 11 of the coupling-in grating 10, and the other turning grating 20 can mostly receive the light transmitted in the second grating raster line direction 12 of the coupling-in grating 10, and the use efficiency and the use reliability of the turning grating 20 are ensured by reasonably arranging the positions of the two turning gratings 20.
Specifically, the duty ratio of the incoupling grating 10 is greater than or equal to 30% and less than or equal to 80%; the height of the incoupling grating 10 is equal to or greater than 100 nm and equal to or less than 500 nm; the period of the coupling grating 10 is equal to or greater than 300 nm and equal to or less than 600 nm. The duty cycle, height and period of the coupling grating 10 are controlled within a reasonable range to ensure the coupling efficiency of the coupling grating 10, and the specific parameters can be adjusted according to the actual situation to make the uniformity of the coupled light intensity meet the specific requirements.
Specifically, the duty cycle of the turning grating 20 is greater than or equal to 30% and less than or equal to 80%; the height of the turning grating 20 is more than or equal to 30 nanometers and less than or equal to 300 nanometers; when the turning grating 20 is a multi-layer grating, the number of layers of the multi-layer grating is greater than or equal to 1 and less than or equal to 10, and for the multi-layer grating, the height refers to the height of a single-layer grating, that is, the height of each layer of grating is greater than or equal to 30 nm and less than or equal to 300 nm.
The period of the turning grating 20 is equal to or more than 300 nanometers and equal to or less than 600 nanometers. The duty ratio, height and period of the turning grating 20 are controlled within a reasonable range, which is beneficial to ensuring the stable operation of the turning grating 20, and the specific parameters can be adjusted according to the actual situation, so that the uniformity of the coupled light intensity can meet the specific requirements.
Specifically, the duty cycle of the coupled-out grating is greater than or equal to 30% and less than or equal to 80%; the height of the coupled-out grating is more than or equal to 30 nanometers and less than or equal to 300 nanometers; when the first outcoupling grating 31 is a multi-layer grating, the number of layers of the multi-layer grating is greater than or equal to 1 and less than or equal to 10, and for the multi-layer grating, the height refers to the height of a single-layer grating, that is, the height of each layer of grating is greater than or equal to 30 nm and less than or equal to 300 nm. The period of the coupled-out grating is greater than or equal to 300 nanometers and less than or equal to 600 nanometers. The duty ratio, the height and the period of the coupling-out grating are controlled within a reasonable range, so that the coupling-out efficiency of the coupling-out grating is favorably ensured, and specific parameters can be adjusted according to actual conditions, so that the uniformity of coupled-out light intensity meets specific requirements.
Specifically, the thickness of the optical waveguide sheet is 400 μm or more and 1 mm or less. If the thickness of the optical waveguide sheet is less than 400 microns, the optical waveguide sheet is not easy to manufacture, the processing difficulty of the optical waveguide sheet is enhanced, and meanwhile, the optical waveguide sheet is easy to break in the using process, and the structural strength of the optical waveguide sheet is reduced. If the thickness of the optical waveguide sheet is larger than 1 mm, the thickness of the optical waveguide sheet becomes too large, which is disadvantageous to miniaturization of the optical waveguide sheet. The thickness of the optical waveguide sheet is limited within the range of 400 micrometers to 1 millimeter, so that the structural strength of the optical waveguide sheet is ensured while the optical waveguide sheet is ensured to be light and thin.
It should be noted that the material of the optical waveguide sheet is high-refractive-index glass, and the refractive index is greater than or equal to 1.7 and less than or equal to 2.3, so that the high-refractive-index characteristic of the optical waveguide sheet is ensured, and the high refractive index can improve the size of the field angle, so as to realize the optical waveguide sheet with an ultra-large field angle. Of course, different materials can be selected according to actual requirements.
Specifically, the incoupling grating 10, the turning grating 20 and the outcoupling grating are diffraction gratings. Due to the characteristics of the diffraction grating, there exists non-uniformity in the out-coupled light intensity, which appears as spatial non-uniformity that causes differences in the brightness of the observed image when the eye is in different positions within the eye box, and angular non-uniformity that causes differences in the brightness of different angles of view. The optical waveguide structure of the invention compensates the problem of uneven light output of the coupled grating while providing a field angle through a specific arrangement mode, and solves the problem of uneven light intensity emitted by the optical waveguide structure in the prior art.
As shown in fig. 1, in the conventional optical waveguide structure, the optical waveguide sheet has a grating on one surface, and the grating is capable of expanding pupil and transmitting light emitted from an external light source assembly, but the display effect is not good because the diffraction efficiency is low under a large viewing angle, and the effective viewing angle is small due to unclear observed images, and it is necessary to increase the total diffraction efficiency to increase the effective viewing angle.
As shown in fig. 2 and fig. 3, in order to solve the problem of small angle of view, a light waveguide structure is proposed in the prior art, two turning gratings 20 of the light waveguide structure respectively correspond to two grating grid lines directions of the coupling grating 10, and when light enters at different angles of view, the turning gratings 20 respectively take charge of performing pupil expansion transmission corresponding to light within the range of the angle of view, for example, when the light incident angle in the vertical direction is-15 ° to 15 °, the first turning grating 20 takes charge of transmitting-15 ° to 0 °, and the second turning grating 20 takes charge of transmitting 0 ° to 15 °. By using the two turning gratings 20 in a targeted design, the diffraction efficiency at the viewing angle can be greatly improved, and the size of the display viewing angle can be effectively improved. However, the display surface of the structure has the situation that the central light intensity is greater than the edge light intensity, and the display effect in the eye box is poor. The display uniformity of the field angle under the optical waveguide structure in fig. 2 is greatly improved compared with that in fig. 1, but the uniformity in some eye boxes still has a certain problem, as shown in fig. 2 and fig. 3, when the normal incidence condition is shown, the transmission condition of light in the waveguide and the display condition in the eye box can be shown, the obvious display difference can be found when the eye box is observed at some angles, and the difference between the display effect at the strongest point of efficiency and the effect at the lowest point is too large.
Therefore, the optical waveguide structure of the present invention is proposed, the coupling grating 10 and the turning grating 20 are fixed, and the adjustment is performed at the coupling grating, and an additional coupling grating is added, both sides are designed to be coupled out, the first coupling grating 31 is designed as a one-dimensional grating for coupling out energy compensation, and the light transmitted to the coupling grating is coupled out to human eyes as much as possible; the second coupling grating 32 is designed as a two-dimensional grating for pupil-expanding dodging, so that the second coupling grating 32 can perform two-dimensional pupil expansion to uniformly and re-couple out the light efficiency.
As shown in fig. 4 and 5, the light is transmitted in the optical waveguide sheet, and the uniform light re-coupling is performed again in the coupling grating relative to the structure of fig. 2, so that the uniformity of the light can be increased, and the corresponding data is calculated by the following normalized variance formula, wherein the normalized variance in the eye box in fig. 2 is 187.1%, and the normalized variance in the eye box in fig. 4 is 39.9%.
The near-eye display includes a light source assembly that emits light into an optical waveguide structure that couples light out into a human eye, and the optical waveguide structure described above. As light propagates within the optical waveguide sheet, the optical waveguide sheet expands the received light in at least one dimension so that the light propagates in at least one direction. The coupling-in grating 10 is designed to couple light emitted from an external light source assembly into the optical waveguide sheet, and the turning grating 20 is designed to receive the light coupled into the grating 10 and expand the pupil, so that the expanded light is coupled out of the optical waveguide sheet by the coupling-out grating and output to the human eye for imaging. The near-eye display with the optical waveguide structure has the advantages of large visual angle and uniform light emission, and the imaging quality of the near-eye display is greatly improved.
It should be noted that the near-eye display may be an AR head-mounted device.
Example two
The difference from the first embodiment is that the coupling grating 10 is different, and the turning grating 20 is arranged differently.
As shown in fig. 6 and 7, the two turning gratings 20 are arranged along a straight line on the optical waveguide sheet, and the incoupling grating 10 is located between the projections of the two turning gratings 20 on the optical waveguide sheet. At this time, an included angle between the first grating line direction 11 and the second grating line direction 12 of the incoupling grating 10 is a right angle. The normalized variance in the box in fig. 6 is 62.7%.
Compared with the first embodiment, the present embodiment reduces the occupied areas of the coupling-in grating 10, the turning grating 20 and the coupling-out grating on the optical waveguide sheet, and ensures miniaturization, and meanwhile, the optical waveguide structure of the second embodiment has a better light intensity effect in some directions than that of the first embodiment, and the optical waveguide structure of the second embodiment has a lower light intensity effect in some directions than that of the first embodiment.
It is to be understood that the above-described embodiments are only a few, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments according to the present application. As used herein, the singular is intended to include the plural unless the context clearly dictates otherwise, and it should be further understood that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of features, steps, operations, devices, components, and/or combinations thereof.
It should be noted that the terms "first," "second," and the like in the description and claims of this application and in the drawings described above are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used is interchangeable under appropriate circumstances such that the embodiments of the application described herein are capable of operation in sequences other than those illustrated or described herein.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. An optical waveguide structure, comprising:
an optical waveguide sheet;
the incoupling grating (10), the incoupling grating (10) is arranged on the optical waveguide sheet, the incoupling grating (10) is a two-dimensional grating, and the incoupling grating (10) is used for coupling light emitted by an external light source component into the optical waveguide sheet;
the optical waveguide grating comprises a plurality of turning gratings (20), the turning gratings (20) are multiple, the turning gratings (20) at least comprise two turning gratings (20), the two turning gratings (20) are respectively arranged on the same or different surfaces of the optical waveguide sheet, the projections of the two turning gratings (20) on the optical waveguide sheet are arranged in an angle, and the turning gratings (20) are used for receiving the light coupled into the gratings (10);
an outcoupling grating (30), outcoupling grating (30) are used for receiving incoupling grating (10) with the light of turning grating (20) and will the light outcoupling the optical waveguide piece, outcoupling grating (30) are a plurality of, a plurality of outcoupling grating (30) includes at least first outcoupling grating (31) and second outcoupling grating (32), first outcoupling grating (31) is the one-dimensional grating, second outcoupling grating (32) is the two-dimensional grating, first outcoupling grating (31) with second outcoupling grating (32) is located on the different surfaces of optical waveguide piece, just first outcoupling grating (31) with second outcoupling grating (32) is in the projection coincidence on the optical waveguide piece.
2. The optical waveguide structure of claim 1,
the incoupling grating (10) is one of a rectangular grating, a parallelogram grating and a rhombus grating; and/or
The turning grating (20) is a one-dimensional grating, and the one-dimensional grating is one of a blazed grating, an inclined grating, a rectangular grating, a double-ridge grating and a multi-layer grating; and/or
The first coupling grating (31) is one of a blazed grating, an inclined grating, a rectangular grating, a double-ridge grating and a multilayer grating; and/or
The second outcoupling grating (32) is one of a rectangular grating, a parallelogram grating and a rhomboid grating.
3. Optical waveguide structure according to claim 1, characterized in that the incoupling grating (10) comprises a first grating gridline direction (11) and a second grating gridline direction (12), the first grating gridline direction (11) and the second grating gridline direction (12) having an angle therebetween, the angle being an acute angle or an obtuse angle.
4. The optical waveguide structure of claim 1,
the two turning gratings (20) are arranged on the optical waveguide sheet along a straight line, and the coupling grating (10) is positioned between the projections of the two turning gratings (20) on the optical waveguide sheet; or
The incoupling grating (10) is positioned between the projections of the two turning gratings (20) on the optical waveguide sheet, and the incoupling grating (10) and the two turning gratings (20) are arranged in a splayed shape.
5. Optical waveguide structure according to claim 1, characterized in that the incoupling grating (10), the turning grating (20) and the outcoupling grating (30) are diffraction gratings.
6. The optical waveguide structure of claim 1,
the duty cycle of the incoupling grating (10) is greater than or equal to 30% and less than or equal to 80%; and/or
The height of the incoupling grating (10) is greater than or equal to 100 nanometers and less than or equal to 500 nanometers; and/or
The period of the incoupling grating (10) is greater than or equal to 300 nm and less than or equal to 600 nm.
7. The optical waveguide structure of claim 1,
the duty ratio of the turning grating (20) is more than or equal to 30% and less than or equal to 80%; and/or
The height of the turning grating (20) is more than or equal to 30 nanometers and less than or equal to 300 nanometers; and/or
When the turning grating (20) is a multilayer grating, the number of layers of the multilayer grating is more than or equal to 1 layer and less than or equal to 10 layers; and/or
The period of the turning grating (20) is more than or equal to 300 nanometers and less than or equal to 600 nanometers.
8. The optical waveguide structure of claim 1,
the duty cycle of the outcoupling grating (30) is greater than or equal to 30% and less than or equal to 80%; and/or
The height of the coupling-out grating (30) is greater than or equal to 30 nanometers and less than or equal to 300 nanometers; and/or
When the first coupling grating (31) is a multilayer grating, the number of layers of the multilayer grating is more than or equal to 1 layer and less than or equal to 10 layers; and/or
The period of the outcoupling grating (30) is equal to or greater than 300 nm and equal to or less than 600 nm.
9. The optical waveguide structure according to any one of claims 1 to 8, wherein the thickness of the optical waveguide sheet is 400 μm or more and 1 mm or less.
10. A near-eye display, comprising:
a light source assembly;
the optical waveguide structure of any one of claims 1 to 9, the light source assembly emitting light into the optical waveguide structure, the optical waveguide structure coupling the light out into the human eye.
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