CN113970806A - Waveguide assembly and near-to-eye display device including the same - Google Patents

Waveguide assembly and near-to-eye display device including the same Download PDF

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Publication number
CN113970806A
CN113970806A CN202011398056.9A CN202011398056A CN113970806A CN 113970806 A CN113970806 A CN 113970806A CN 202011398056 A CN202011398056 A CN 202011398056A CN 113970806 A CN113970806 A CN 113970806A
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grating
coupling
reflection
light
waveguide
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CN202011398056.9A
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CN113970806B (en
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马珂奇
徐钦锋
杜佳玮
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Ningbo Sunny Opotech Co Ltd
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Ningbo Sunny Opotech Co Ltd
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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
    • G02B6/0001—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems
    • G02B6/0011—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems the light guides being planar or of plate-like form
    • G02B6/0033—Means for improving the coupling-out of light from the light guide
    • 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
    • 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
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/18—Diffraction gratings
    • 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
    • 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
    • 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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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Engineering & Computer Science (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Diffracting Gratings Or Hologram Optical Elements (AREA)
  • Optical Couplings Of Light Guides (AREA)

Abstract

The invention provides a waveguide assembly and a near-eye display device comprising the waveguide assembly. The waveguide assembly includes: the grating light source comprises a waveguide sheet, an coupling-in area and a coupling-out grating which are arranged on the surface of the waveguide sheet, a primary reflection grating which is arranged oppositely and used for reflecting light which is not coupled out through the coupling-out grating back to the coupling-out grating for coupling out, and a secondary reflection grating which is used for reflecting light which is not coupled out after being reflected by the primary reflection grating back to the coupling-out grating for coupling out. The period of the first-order reflection grating is the same as the period of the coupling-out grating in the vertical direction and the diffraction efficiency of the second-order diffracted light is maximized, or the period is half of the period of the coupling-out grating in the vertical direction and the diffraction efficiency of the first-order diffracted light is maximized. The period of the second-order reflection grating is the same as the period of the coupling grating in the horizontal direction and the diffraction efficiency of the second-order diffracted light is maximized, or the period is half of the period of the coupling grating in the horizontal direction and the diffraction efficiency of the first-order diffracted light is maximized.

Description

Waveguide assembly and near-to-eye display device including the same
The present application is a divisional application of the chinese patent application having an application number of 202010728499.3, an application date of 2020, 7/24/entitled "waveguide assembly and near-eye display device including the waveguide assembly".
Technical Field
The present application relates to the field of optical transmission technology, and in particular, to a waveguide assembly and a near-eye display device including the waveguide assembly.
Background
The near-eye display device is mainly used for displaying pictures or videos to human eyes, and can be widely applied to the fields of virtual reality, augmented reality, mixed reality, military and the like.
The near-eye display equipment comprises components such as a light source component and a waveguide, wherein the waveguide is provided with an incoupling area and an outcoupling area, light emitted by the light source component is coupled into the waveguide through the incoupling area, and the light is transmitted to human eyes through the outcoupling waveguide in the outcoupling area.
However, since the diffraction efficiency of light is low in the coupling-out region, most of the light energy is absorbed by the side of the waveguide or escapes from the side of the waveguide, resulting in low utilization of the overall light energy of the waveguide, and thus low exit pupil density of the near-eye display device. Furthermore, the energy is gradually reduced as the light propagates through the waveguide, resulting in uneven brightness of the outcoupled light.
Disclosure of Invention
It is a primary object of the present application to provide a waveguide assembly and a near-eye display device including the waveguide assembly that has high light energy utilization, high exit pupil density, and uniform brightness.
The present application provides a waveguide assembly comprising:
a waveguide sheet;
the coupling-in region is arranged on the surface of the waveguide sheet and is used for coupling light into the waveguide sheet and enabling the light to be diffused and transmitted in the waveguide sheet;
the coupling-out grating is arranged on the surface of the waveguide sheet and is used for coupling light coupled in from the coupling-in area out of the waveguide sheet; and
a first reflection grating and a second reflection grating which are oppositely arranged, wherein the first reflection grating is arranged for reflecting the light which passes through the light coupling grating and is not coupled out to the light coupling grating for coupling out again, the second reflection grating is arranged for reflecting the light which is not coupled out after being reflected by the first reflection grating to the light coupling grating for coupling out again,
wherein a period of the first-order reflection grating is the same as a period of the outcoupling grating in the vertical direction and a diffraction efficiency of second-order diffracted light in diffraction orders is set to be maximum, or a period of the first-order reflection grating is half of the period of the outcoupling grating in the vertical direction and a diffraction efficiency of first-order diffracted light in diffraction orders is set to be maximum,
wherein the period of the second-order reflection grating is the same as the period of the outcoupling grating in the horizontal direction and the diffraction efficiency of the second-order diffracted light in the diffraction orders is set to be maximum, or the period of the second-order reflection grating is half of the period of the outcoupling grating in the horizontal direction and the diffraction efficiency of the first-order diffracted light in the diffraction orders is set to be maximum.
In one embodiment, the first sub-reflection grating includes a first reflection grating and a second reflection grating that are disposed separately.
In one embodiment, the first-time reflection grating is a sinusoidal grating, a rectangular grating, a blazed grating, or a tilted grating tilted in the direction of the outcoupling grating.
In one embodiment, the waveguide assembly further comprises a second sub-reflection grating disposed on the same surface of the waveguide sheet as the first sub-reflection grating;
the second reflection grating and the first reflection grating are arranged oppositely and are respectively positioned at two sides of the coupling grating;
the groove lines of the second-order reflection grating are parallel to the groove lines of the coupling-out grating, the period of the second-order reflection grating is the same as that of the coupling-out grating, and the diffraction efficiency of second-order diffraction light in diffraction orders is set to be maximum, or the period of the second-order reflection grating is half of that of the coupling-out grating, and the diffraction efficiency of first-order diffraction light in diffraction orders is set to be maximum;
the light which is not coupled out after being reflected by the first reflection grating is transmitted to the second reflection grating and is reflected back to the coupling-out grating by the second reflection grating.
In one embodiment, the first sub-reflection grating includes a first reflection grating and a second reflection grating which are arranged separately, the second sub-reflection grating includes a third reflection grating and a fourth reflection grating which are arranged separately, the first reflection grating and the third reflection grating are arranged oppositely, and the second reflection grating and the fourth reflection grating are arranged oppositely.
In one embodiment, the second-reflection grating is a sinusoidal grating, a rectangular grating, a blazed grating or a tilted grating tilted in the direction of the outcoupling grating.
In one embodiment, the out-coupling grating is a one-dimensional grating.
In one embodiment, the coupling-out grating is formed by two one-dimensional gratings respectively arranged on two surfaces of the waveguide sheet or formed by two one-dimensional gratings arranged on the same surface of the waveguide sheet in a superposition manner.
In one embodiment the angle between the two one-dimensional gratings of the out-coupling grating is 50-70 degrees.
In one embodiment, the coupling-out grating is a rectangular grating, a blazed grating, an inclined grating, a sinusoidal grating or a holographic grating, and the groove depth is 50-200 nm.
In one embodiment, the first sub-reflection grating borders the outcoupling grating.
In one embodiment, the width of the first order reflection grating is greater than 3 mm.
In one embodiment, the outcoupling grating is a rectangular grating, and the first-time reflection grating and/or the second-time reflection grating is a tilted grating or a blazed grating.
In one embodiment, the incoupling region comprises an incoupling grating for incoupling light into the waveguide.
In one embodiment, the incoupling grating is a rectangular grating, a blazed grating, an inclined grating, a sinusoidal grating or a holographic grating, and has a period of 300-600 nm and a groove depth of 40-500 nm.
In one embodiment, the coupling-in region further includes a turning grating for diffusing and transmitting the light coupled in from the coupling-in grating in the waveguide.
In one embodiment, the turning grating is a rectangular grating, a blazed grating, an inclined grating, a sinusoidal grating or a holographic grating, and has a period of 300-600 nm and a groove depth of 40-500 nm.
In one embodiment, the coupling-in region and the coupling-out grating are located on the same surface of the waveguide sheet or on two surfaces opposite to the waveguide sheet respectively.
In one embodiment, the thickness of the waveguide sheet is 0.3-2.5 mm, the material of the waveguide sheet is an optical material transparent to visible light, and the refractive index of the waveguide sheet is 1.4-2.2.
An embodiment of the present application further provides a near-eye display device, including a projection optical machine and a waveguide assembly, where the waveguide assembly is the waveguide assembly described in any of the above embodiments.
Has the advantages that:
the utility model provides a waveguide assembly, set up the first reflection grating on one side surface of waveguide piece, and make the first reflection grating parallel with the groove line of coupling grating, the first reflection grating is the same and the diffraction efficiency of second order diffraction light is set up to the biggest in the diffraction order with the cycle of coupling grating, or the first reflection grating is half of coupling grating cycle and the diffraction efficiency of first order diffraction light is set up to the biggest in the diffraction order, thereby make through coupling grating and the light of not coupling out return coupling grating by first reflection grating, thereby couple out, thereby the holistic light energy utilization of waveguide assembly has been improved, the holistic exit pupil density of waveguide assembly has been increased. And because the light returned by the first reflection grating and coupled out supplements the original coupled out light, the brightness uniformity of the coupled out light in the whole visible area of the waveguide sheet is improved. In addition, according to the optical design of the invention, only the first-time reflection grating is required to be arranged on one side surface of the waveguide sheet, the manufacturing process is simple, and the production and the manufacturing are convenient. In addition, the waveguide assembly provided by this embodiment allows light that is not coupled out by the coupling-out grating for the first time to return to the coupling-out grating only through one first reflection grating, so that the light energy utilization rate is higher.
Drawings
The advantages of the above and/or additional aspects of the present invention will become apparent and readily appreciated from the following description of the embodiments taken in conjunction with the accompanying drawings of which:
fig. 1 is a schematic structural diagram of a waveguide assembly according to an embodiment of the present application;
FIG. 2 is a side view of the waveguide assembly shown in FIG. 1;
FIG. 3 is a grating vector diagram of the waveguide assembly shown in FIG. 1;
fig. 4 is a graph showing simulation results of light diffraction of a waveguide assembly according to an embodiment of the present application;
FIG. 5 is a schematic illustration of the waveguide assembly of FIG. 1 with grating vectors;
FIG. 6 is a schematic structural diagram of a waveguide assembly according to an embodiment of the present application;
FIG. 7 is a schematic structural diagram of a waveguide assembly according to an embodiment of the present application;
FIG. 8 is a schematic structural diagram of a waveguide assembly according to an embodiment of the present application;
FIG. 9 is a side view of a portion of the waveguide assembly shown in FIG. 8;
FIG. 10 is a grating vector diagram of the waveguide assembly of FIG. 8;
FIG. 11 is a grating vector diagram of the waveguide assembly of FIG. 8;
FIG. 12 is a grating vector diagram of the waveguide assembly of FIG. 8;
FIG. 13 is a grating vector diagram of the waveguide assembly of FIG. 8;
fig. 14 is a schematic structural diagram of a near-eye display device according to an embodiment of the present application;
fig. 15 is a schematic structural diagram of a near-eye display device according to an embodiment of the present application.
Wherein, the correspondence between the reference numbers and the part names in fig. 1 to 15 is:
1. a waveguide sheet; 2. a coupling-in region; 21. coupling in a grating; 22. turning the grating; 3. coupling out the grating; 4. a first-time reflective grating; 41. a first reflective grating; 42. a second reflective grating; 5. a second reflection grating; 51. a third reflective grating; 52. a fourth reflective grating; 6 projection light machine.
Detailed Description
In order that the above objects, features and advantages of the present invention can be more clearly understood, a more particular description of the invention will be rendered by reference to the appended drawings. It should be noted that the embodiments and features of the embodiments of the present application may be combined with each other without conflict.
Example 1
Fig. 1 is a schematic structural diagram of a waveguide assembly according to an embodiment of the present application.
As shown in fig. 1, the present embodiment provides a waveguide assembly, including:
a waveguide sheet 1;
the coupling-in area 2 is arranged on one surface of the waveguide sheet 1, and the coupling-in area 2 is used for coupling light into the waveguide sheet 1 and enabling the light to be diffused and transmitted in the waveguide sheet 1;
the coupling-out grating 3 is arranged on one surface of the waveguide sheet 1, and the coupling-out grating 3 is used for coupling light coupled in from the coupling-in area 2 out of the waveguide sheet 1; and
the first reflection grating 4 and the coupling grating 3 are arranged on the same surface of the waveguide sheet 1 and located at the tail end of the coupling grating 3 in the light transmission direction, the first reflection grating 4 is parallel to the groove line of the coupling grating 3, the period of the first reflection grating 4 is the same as that of the coupling grating 3, the diffraction efficiency of second-order diffraction light in diffraction order is set to be maximum, or the first reflection grating 4 is half of the period of the coupling grating 3, the diffraction efficiency of first-order diffraction light in diffraction order is set to be maximum, and the first reflection grating 4 is used for reflecting light which passes through the coupling grating 3 and is not coupled back to the coupling grating 3 for coupling.
Fig. 2 is a side view of the waveguide assembly shown in fig. 1.
As shown in fig. 2, the operation principle process of the waveguide assembly provided by the present embodiment is as follows:
the light is coupled into the waveguide plate 1 from the coupling-in region 2 and is transmitted in the waveguide plate 1 to the coupling-out grating 3 by diffusion. The light-coupling grating 3 couples the light A out of the waveguide sheet 1, so that the light A is observed by human eyes, i.e. a visible region is formed. The light B that is not coupled out will continue to propagate to the first reflection grating 4, the first reflection grating 4 reflects the light B back to the coupling-out grating 3, and then is coupled out by the coupling-out grating 3, i.e. the light C, and the light C is parallel to the light a.
Figure 3 is a grating vector diagram of the waveguide assembly shown in figure 1.
As shown in fig. 3, the incoupling area 2 has a grating vector G0, the outcoupling grating 3 has a grating vector G1, and the first-order reflection grating 4 has a grating vector G2. Because the first-time reflection grating 4 is parallel to the groove line of the coupling-out grating 3, the grating vectors of the first-time reflection grating 4 and the coupling-out grating 3 are parallel to each other, and the light B which is not coupled out is reflected back to the coupling-out grating 3 by the first-time reflection grating 4. And the period of the first reflection grating 4 determines its vector magnitude. And when the period of the first reflection grating 4 is the same as that of the coupled-out grating 3, the diffraction efficiency of the second-order diffracted light in the diffraction order is set to be the maximum, so that the grating vector size corresponding to the second-order diffracted light is twice as large as that of the coupled-out grating 3 vector when the light B is diffracted at the first reflection grating 4, and further the grating vector G0+ G1+ G2 is 0, and finally the light C is coupled out, so that the light energy utilization rate is improved, and the exit pupil density is improved due to the existence of the light C. And because the energy of the light is gradually weakened when the light is transmitted in the waveguide sheet, the un-coupled light is reflected back to the coupled-out grating 3 and is partially diffracted and coupled out, the energy of the part of the light is also gradually weakened when the light is transmitted, the propagation direction of the part of the light is just opposite to the propagation direction of the light A in the waveguide sheet 1, the energy weakening when the light A is transmitted in the waveguide sheet 1 is just compensated, and the brightness uniformity of the coupled-out light in the whole visible area of the waveguide sheet is improved.
When the period of the first-order reflection grating 4 is half of the period of the coupling grating 3, the diffraction efficiency of the first-order diffracted light in the diffraction order is set to be the maximum, so the vector size is twice of the vector size of the coupling grating 3, the grating vector G0+ G1+ G2 is also made to be 0, the light ray C can be coupled out, the light energy utilization rate is improved, and the exit pupil density is improved due to the existence of the light ray C. And because the un-coupled light is reflected back to the coupled-out grating 3 and is partially diffracted and coupled out, the energy weakening of the light A during transmission in the waveguide sheet 1 is just compensated by the part of the light, and the brightness uniformity of the coupled-out light in the whole visible area of the waveguide sheet is improved.
In this embodiment, since the light that is not coupled out is transmitted by total reflection in the waveguide sheet 1, the first reflection grating 4 needs to be disposed at the end of the coupling-out grating 3 along the light transmission direction.
In the waveguide assembly provided by this embodiment, the first-order reflection grating 4 is disposed on the surface of one side of the waveguide sheet 1, and the first-order reflection grating 4 is parallel to the groove line of the coupling-out grating 3, the period of the first-order reflection grating 4 is the same as that of the coupling-out grating 3, and the diffraction efficiency of the second-order diffracted light in the diffraction order is set to be the maximum, or the first-order reflection grating 4 is half of the period of the coupling-out grating 3 and the diffraction efficiency of the first-order diffracted light in the diffraction order is set to be the maximum, so that the light passing through the coupling-out grating 3 and not coupled out is returned to the coupling-out grating 3 by the first-order reflection grating 4, thereby coupling out is performed, thereby improving the overall optical energy utilization rate of the waveguide assembly and increasing the overall exit pupil density of the waveguide assembly. And because the light returned by the first reflection grating 4 and coupled out again supplements the original coupled out light, the brightness uniformity of the coupled out light in the whole visible area of the waveguide sheet 1 is improved. Moreover, according to the optical design of the invention, only the first-time reflection grating 4 needs to be arranged on one side surface of the waveguide sheet 1, the manufacturing process is simple, and the production and the manufacturing are convenient. In addition, in the waveguide assembly provided in this embodiment, the light that is not coupled out by the coupling-out grating 3 for the first time can return to the coupling-out grating 3 only by passing through the first reflection grating 4, so that the light energy utilization rate is higher.
Furthermore, the first reflection grating 4 is adjacent to the light coupling grating 3, and the first reflection grating 4 and the light coupling grating 3 are arranged on the same side of the waveguide sheet 1, so that the waveguide assembly is simple and convenient to manufacture. In other embodiments, there is a gap between the first sub-reflection grating 4 and the light coupling grating 3, which is not limited herein.
In this embodiment, the width of the first-time reflection grating 4 is greater than 3mm, and the reflection efficiency is high.
In this embodiment, the first-time reflective grating 4 is a sinusoidal grating, a rectangular grating, a blazed grating, or an inclined grating inclined toward the direction of the outcoupled grating 3, and the groove depth is 400-600 nm. In some preferred embodiments, the first reflection grating 4 may be an inclined grating or a blazed grating, and compared to a conventional rectangular grating, the inclined grating or the blazed grating may be configured to concentrate diffraction energy on a certain order, so as to improve the reflection efficiency of the first reflection grating 4, thereby improving the light energy utilization rate of the waveguide sheet 1.
Fig. 4 is a diagram illustrating simulation results of light diffraction of a waveguide assembly according to an embodiment of the present application.
As shown in fig. 4, as an example, the period of the first reflection grating 4 is 340nm, the height is 500nm, the duty ratio is 0.74, the inclination angle of the first reflection grating 4 with respect to the horizontal direction is 66.7 °, the refractive indexes of the first reflection grating 4 and the waveguide sheet are both set to 1.7, the wavelength of light is 460nm, the maximum diffraction efficiency thereof can reach 95% or more, and the average thereof reaches about 75%, and the energy utilization rate of the waveguide sheet 1 can be significantly improved.
It is further preferred that the first order reflection grating 4 is an inclined grating inclined toward the direction of the outcoupled grating 3, and the second order diffracted light has a higher diffraction efficiency, and in some embodiments, the second order diffraction efficiency is greater than 80%.
In the present embodiment, the coupling-out grating 3 is a diffraction grating or a holographic grating. When the coupling-out grating 3 is a diffraction grating, the grating may be a rectangular grating, a blazed grating, an inclined grating, a sinusoidal grating, or a holographic grating, and the groove depth is 50 to 200 nm.
In a preferred embodiment, the coupling-out grating 3 is set as a common rectangular grating, the first reflection grating 4 is set as an inclined grating or a blazed grating, and the light energy utilization rate of the waveguide sheet 1 is greatly improved due to the presence of the first reflection grating 4, so the coupling-out grating 3 does not need to be set as an inclined grating with higher diffraction efficiency (in a conventional scheme, because the common rectangular grating has low diffraction efficiency, the inclined grating can be selected as the coupling-out grating, but the inclined grating has higher energy coupling out due to higher diffraction efficiency, and the field of view far from the coupling-in area 2 has lower energy coupling out, so that the energy distribution in the whole visible area is uneven).
In the present embodiment, the thickness of the waveguide sheet 1 is 0.3 to 2.5mm, the material of the waveguide sheet 1 is an optical material transparent to visible light, and the refractive index of the waveguide sheet 1 is 1.4 to 2.2.
In the present embodiment, the outcoupling grating 3 is a one-dimensional grating. As will be readily appreciated by those skilled in the art, in other embodiments, the outcoupling grating 3 is a two-dimensional grating, which should also be within the scope of the present application, and is not specifically limited herein. When the coupling-out grating 3 is a two-dimensional grating, it may be formed by two one-dimensional gratings respectively disposed on both sides of the waveguide sheet 1 or by two one-dimensional gratings disposed on one side of the waveguide sheet 1 being superimposed.
Example 2
In the present embodiment, as shown in fig. 1, the incoupling region 2 includes an incoupling grating 21, and the incoupling grating 21 is used for incoupling light into the waveguide sheet 1. The coupling-in grating 21 is a rectangular grating, a blazed grating, an inclined grating, a sinusoidal grating or a holographic grating, and has a period of 300-600 nm and a groove depth of 40-500 nm.
Furthermore, the coupling-in region 2 further includes a turning grating 22, the turning grating 22 is used for diffusing and transmitting the light coupled in from the coupling-in grating 21 in the waveguide sheet 1, and the addition of the turning grating 22 can further increase the light energy utilization rate. Furthermore, the turning grating 22 is a rectangular grating, a blazed grating, an inclined grating, a sinusoidal grating or a holographic grating, and has a period of 300-600 nm and a groove depth of 40-500 nm.
Fig. 5 is a schematic view of the waveguide assembly of fig. 1 with grating vectors.
In the present embodiment, as shown in fig. 5, the incoupling grating 21 has a grating vector G0a, the turning grating 22 has a grating vector G0b, and the sum of the vectors of the incoupling grating 21 and the turning grating 22 is equal to the grating vector G0 of the incoupling area 2, i.e., G0a + G0b is G0. While keeping the first-time reflection grating 4 parallel to the groove lines of the outcoupling grating 3, so that the non-coupled light B is reflected back to the outcoupling grating 3 by the first-time reflection grating 4. And the period of the first reflection grating 4 is the same as that of the coupling grating 3, and the diffraction efficiency of the second order diffraction light in the diffraction orders is set to be maximum; or when the period of the first-time reflection grating 4 is half of the period of the coupling grating 3, the diffraction efficiency of the first-order diffracted light in the diffraction order is set to be the maximum, so that the grating vector size corresponding to the second-order diffracted light is twice as large as the vector of the coupling grating 3 when the light B is diffracted at the first-time reflection grating 4, and further the grating vector G0+ G1+ G2 is 0, and finally the light C is coupled out, so that the light energy utilization rate is improved, and the exit pupil density is improved due to the existence of the light C. And because the energy of the light is gradually weakened when the light is transmitted in the waveguide sheet, the un-coupled light is reflected back to the coupled-out grating 3 and is partially diffracted and coupled out, the energy of the part of the light is also gradually weakened when the light is transmitted, the propagation direction of the part of the light is just opposite to the propagation direction of the light A in the waveguide sheet 1, the energy weakening when the light A is transmitted in the waveguide sheet 1 is just compensated, and the brightness uniformity of the coupled-out light in the whole visible area of the waveguide sheet is improved.
In the present embodiment, the coupling-in region 2 and the coupling-out grating 3 are located on the same surface of the waveguide sheet 1. In other embodiments, the coupling-in region 2 and the coupling-out grating 3 are respectively located on two surfaces of the waveguide sheet 1 opposite to each other, and are not limited herein.
In the present embodiment, the outcoupling grating 3 is a one-dimensional grating. As will be readily appreciated by those skilled in the art, in other embodiments, the outcoupling grating 3 is a two-dimensional grating, which should also be within the scope of the present application, and is not specifically limited herein. When the coupling-out grating 3 is a two-dimensional grating, it may be formed by two one-dimensional gratings respectively disposed on both sides of the waveguide sheet 1 or by two one-dimensional gratings disposed on one side of the waveguide sheet 1 being superimposed.
In the present embodiment, the coupling grating 3 is a rectangular grating, a blazed grating, an inclined grating, a sinusoidal grating or a holographic grating, and has a groove depth of 50 to 200 nm.
Example 3
Fig. 6 is a schematic structural diagram of a waveguide assembly according to an embodiment of the present application.
As shown in fig. 6, in the present embodiment, the first sub-reflection grating 4 includes a first reflection grating 41 and a second reflection grating 42 that are arranged separately, and the grating vector sum of the first reflection grating 41 and the second reflection grating 42 is G2.
In the present embodiment, the coupling-in region 2 includes a coupling-in grating 21 and a turning grating 22.
The incoupling grating 21 has a grating vector G0a, the turning grating 22 has a grating vector G0b, and G0a + G0b is made G0.
The grating vector of the outcoupled grating 3 is G1.
Since the groove lines of the first reflection grating 41 and the second reflection grating 42 are both parallel to the groove lines of the outcoupling grating 3, and the periods of the first reflection grating 41 and the second reflection grating 42 are the same as the period of the outcoupling grating 3, the diffraction efficiency of the second-order diffracted light is set to be the largest in the diffraction orders thereof; or the period of the first reflection grating 41 and the second reflection grating 42 is half of the period of the coupling grating 3, and the diffraction efficiency of the first-order diffracted light in the diffraction order is set to be the maximum, so that G0+ G1+ G2 is 0, and finally the light C is coupled out, thereby improving the light energy utilization rate, the exit pupil density and the brightness uniformity.
The waveguide assembly provided by the embodiment sets the first-time reflection grating 4 as the reflection grating of two separation structures, so that light can be reflected from multiple directions, omission is avoided, the light energy utilization rate is further improved, the exit pupil density is increased, and the brightness uniformity is increased.
In the present embodiment, the outcoupling grating 3 is a one-dimensional grating. As will be readily appreciated by those skilled in the art, in other embodiments, the outcoupling grating 3 is a two-dimensional grating, which should also be within the scope of the present application, and is not specifically limited herein. When the coupling-out grating 3 is a two-dimensional grating, it may be formed by two one-dimensional gratings respectively disposed on both sides of the waveguide sheet 1 or by two one-dimensional gratings disposed on one side of the waveguide sheet 1 being superimposed.
In the present embodiment, the coupling grating 3 is a rectangular grating, a blazed grating, an inclined grating, a sinusoidal grating or a holographic grating, and has a groove depth of 50 to 200 nm.
In the present embodiment, the thickness of the waveguide sheet 1 is 0.3 to 2.5mm, the material of the waveguide sheet 1 is an optical material transparent to visible light, and the refractive index of the waveguide sheet 1 is 1.4 to 2.2.
In other embodiments, the coupling-in region 2 may have only the coupling-in grating 21 and no turning grating 22.
Example 4
Fig. 7 is a schematic structural diagram of a waveguide assembly according to an embodiment of the present application.
As shown in fig. 7, the waveguide assembly provided in this embodiment further includes a second sub-reflection grating 5, and the second sub-reflection grating 5 and the first sub-reflection grating 4 are disposed on the same surface of the waveguide sheet 1.
The second-time reflection grating 5 is arranged opposite to the first-time reflection grating 4 and is respectively positioned at two sides of the coupling-out grating 3.
The groove lines of the second-reflection grating 5 are parallel to the groove lines of the outcoupling grating 3, the period of the second-reflection grating 5 is the same as the period of the outcoupling grating 3 and the diffraction efficiency of the second-order diffracted light in the diffraction order is set to be maximum, or the period of the second-reflection grating 5 is half of the period of the outcoupling grating 3 and the diffraction efficiency of the first-order diffracted light in the diffraction order is set to be maximum.
The light which is not coupled out after being reflected by the first reflection grating 4 is transmitted to the second reflection grating 5, and is reflected back to the coupling-out grating 3 by the second reflection grating 5 and then is coupled out.
In the present embodiment, the coupling-in region 2 includes a coupling-in grating 21 and a turning grating 22.
The sum of the grating vectors coupled into the grating 21 and the turning grating 22 is equal to G0 described in the previous embodiment, the first sub-reflection grating 4 has a grating vector G1, and the sum of the grating vectors of the coupled-out grating 3 and the second sub-reflection grating 5 is G2. Because the first reflection grating 4 and the second reflection grating 5 are arranged in the groove lines, the period and the diffraction order, G0+ G1+ G2 is 0, and finally the light is coupled out after being reflected by the first reflection grating 4 or the light is coupled out after being reflected by the second reflection grating 5, so that the light energy utilization rate, the exit pupil density and the brightness uniformity are improved.
In the waveguide assembly provided in this embodiment, the second-order reflection grating 5 is disposed on the waveguide sheet 1, the second-order reflection grating 5 and the first-order reflection grating 4 are disposed on the same side of the waveguide sheet 1, and the groove lines of the second-order reflection grating 5 are parallel to the groove lines of the coupling grating 3, the period of the second-order reflection grating 5 is the same as the period of the coupling grating 3, and the diffraction efficiency of the second-order diffraction light in the diffraction order is set to be the maximum, or the period of the second-order reflection grating 5 is half of the period of the coupling grating 3, and the diffraction efficiency of the first-order diffraction light in the diffraction order is set to be the maximum, so that after the light not coupled out by the coupling grating 3 is reflected back to the coupling grating 3 by the first reflection grating 41, the light not coupled out is reflected back to the coupling grating 3 by the second-order reflection grating 5, thereby further improving the light energy utilization rate, and increasing the exit pupil density, The brightness uniformity is improved.
In the present embodiment, the second-reflection grating 5 is a sinusoidal grating, a rectangular grating, a blazed grating, or an inclined grating inclined toward the direction of the outcoupled grating 3. Preferably, the second-order reflection grating 5 is a tilted grating, where the diffraction efficiency is high (may exceed 80%). Furthermore, the second-order reflection grating 5 is inclined towards the outcoupling grating 3, further improving the reflection efficiency of the second-order reflection grating 5.
In the present embodiment, the outcoupling grating 3 is a one-dimensional grating. As will be readily appreciated by those skilled in the art, in other embodiments, the outcoupling grating 3 is a two-dimensional grating, which should also be within the scope of the present application, and is not specifically limited herein. When the coupling-out grating 3 is a two-dimensional grating, it may be formed by two one-dimensional gratings respectively disposed on both sides of the waveguide sheet 1 or by two one-dimensional gratings disposed on one side of the waveguide sheet 1 being superimposed.
In the present embodiment, the coupling grating 3 is a rectangular grating, a blazed grating, an inclined grating, a sinusoidal grating or a holographic grating, and has a groove depth of 50 to 200 nm.
In the present embodiment, the thickness of the waveguide sheet 1 is 0.3 to 2.5mm, the material of the waveguide sheet 1 is an optical material transparent to visible light, and the refractive index of the waveguide sheet 1 is 1.4 to 2.2.
In other embodiments, the coupling-in region 2 may have only the coupling-in grating 21 and no turning grating 22.
Example 5
Fig. 8 is a schematic structural diagram of a waveguide assembly according to an embodiment of the present application.
In this embodiment, as shown in fig. 8, the first sub-reflection grating 4 includes a first reflection grating 41 and a second reflection grating 42 that are separately disposed, the second sub-reflection grating 5 includes a third reflection grating 51 and a fourth reflection grating 52 that are separately disposed, the first reflection grating 41 and the third reflection grating 51 are disposed oppositely, and the second reflection grating 42 and the fourth reflection grating 52 are disposed oppositely, that is, the first reflection grating 41, the second reflection grating 42, the third reflection grating 51, and the fourth reflection grating 52 are disposed around the coupling-in region 2 and the coupling-out grating 3 in sequence.
The periods of the first reflection grating 41 and the second reflection grating 42 are equal to the period in the vertical direction of the coupling grating 3, and the diffraction efficiency of the second-order diffracted light is set to be the maximum, which can be optimized to be more than 80%. The periods of the third reflection grating 51 and the fourth reflection grating 52 are equal to the period of the coupling grating 3 in the horizontal direction, the diffraction efficiency of the second-order diffraction light is set to be maximum, and can reach more than 80% through optimization, so that the non-coupled light can be transmitted back and forth in the opposite reflection gratings (41, 51 or 42, 52), and the light energy utilization rate, the exit pupil density and the brightness uniformity of the waveguide sheet 1 are improved. It is understood that the periods of the first reflection grating 41, the second reflection grating 42, the third reflection grating 51 and the fourth reflection grating 52 may also be set to be half of the period of the outcoupled grating 3, and the diffraction efficiency of the first order diffracted light among the corresponding diffraction orders thereof is set to be the maximum.
The waveguide assembly provided by the embodiment has the advantages that the first-time reflection grating 4 is arranged into two separated reflection gratings (41, 42), the second-time reflection grating 5 is arranged into two separated reflection gratings (51, 52), so that light can be reflected back from multiple directions, and the light can be transmitted back and forth between the reflection gratings (between 41 and 51 or between 42 and 52), so that the light energy utilization rate, the exit pupil density and the brightness uniformity are improved.
In the present embodiment, the outcoupling grating 3 is a two-dimensional grating. Specifically, the coupling-out grating 3 may be formed by two one-dimensional gratings respectively disposed on two sides of the waveguide sheet 1 or by two one-dimensional gratings disposed on one side of the waveguide sheet 1 in a superimposed manner. In other embodiments, the outcoupling grating 3 may also be a one-dimensional grating, which is not limited herein.
In the present embodiment, the incoupling region 2 comprises only the incoupling grating 21. In other embodiments, the coupling-in region may further include a coupling-in grating 21 and a turning grating 22.
In the present embodiment, the coupling grating 3 is a rectangular grating, a blazed grating, an inclined grating, a sinusoidal grating or a holographic grating, and has a groove depth of 50 to 200 nm.
Example 6
Fig. 9 is a side view of a portion of the waveguide assembly shown in fig. 8.
In the present embodiment, as shown in fig. 9, the coupling-out grating 3 is a two-dimensional grating and is composed of two one-dimensional gratings (31, 32) respectively provided on both surfaces of the waveguide sheet 1.
Light is coupled into the waveguide sheet 1 through the coupling-in region 2, and light which is not coupled out by the two-dimensional coupling-out grating 3(31, 32) is reflected by the first reflection grating 4 (or 41) and then coupled out by the two-dimensional coupling-out grating 3(31, 32).
Fig. 10 is a grating vector diagram of the waveguide assembly shown in fig. 8.
The coupling-in area 2 has a grating vector G0, the one-dimensional coupling-out grating 31 has a grating vector G1, the one-dimensional coupling-out grating 32 has a grating vector G2, the first-time reflection grating 4(42) has a grating vector G3, and because the groove lines are parallel and the period and diffraction order are set, G0+ G1+ G2+ G3 is 0, so that the light which is not coupled out is coupled out by the two-dimensional coupling-out grating 3(31, 32) after being reflected by the first-time reflection grating 4(42), the light energy utilization rate is improved, the exit pupil density is increased, and the brightness uniformity is increased.
Fig. 11 is a grating vector diagram of the waveguide assembly shown in fig. 8.
As shown in fig. 11, the coupling-in region 2 has a grating vector G0, the one-dimensional coupling-out grating 31 has a grating vector G1, the one-dimensional coupling-out grating 32 has a grating vector G2, the first-time reflection grating 4(42) has a grating vector G3, and the second-time reflection grating 5(52) has a grating vector G4, and since the groove lines are parallel and the period and diffraction order are set, G0+ G1+ G2+ G3+ G4 are 0, so that the light that is not coupled out after being reflected by the first-time reflection grating 4(42) is transmitted to the second-time reflection grating 5(52) and reflected back to the coupling-out grating 3(31, 32) by the second-time reflection grating 5(52) to be coupled out, thereby improving the light energy utilization rate, increasing the pupil density and increasing the brightness uniformity.
Fig. 12 is a grating vector diagram of the waveguide assembly shown in fig. 8.
As shown in fig. 12, the coupling-in region 2 has a grating vector G0, the one-dimensional coupling-out grating 31 has a grating vector G1, the first-time reflection grating 4(41) has a grating vector G2, and the one-dimensional coupling-out grating 32 has a grating vector G3, and since the groove lines are parallel and the period and diffraction order are set, G0+ G1+ G2+ G3 is 0, so that the light diffracted by the one-dimensional coupling-out grating 31 and not coupled out by the one-dimensional coupling-out grating 32 is reflected by the first-time reflection grating 4(41) and then coupled out by the coupling-out grating 31, thereby improving the light energy utilization rate, increasing the exit pupil density, and increasing the brightness uniformity.
Fig. 13 is a grating vector diagram of the waveguide assembly shown in fig. 8.
As shown in fig. 13, the coupling-in region 2 has a grating vector G0, the one-dimensional coupling-out grating 32 has a grating vector G1, the second-time reflection grating 5(51) has a grating vector G2, and the one-dimensional coupling-out grating 32 has a grating vector G3, and since the groove lines are parallel and the period and diffraction order are set, G0+ G1+ G2+ G3 is 0, so that the light diffracted by the one-dimensional coupling-out grating 32 and not coupled out by the one-dimensional coupling-out grating 31 is reflected by the second-time reflection grating 5(51) and then coupled out by the coupling-out grating 32, thereby improving the light energy utilization rate, increasing the exit pupil density, and increasing the brightness uniformity.
Further, the angle between the two one-dimensional gratings of the outcoupling grating 3 is 50-70 degrees.
In the present embodiment, the coupling grating 3 is a rectangular grating, a blazed grating, an inclined grating, a sinusoidal grating or a holographic grating, and has a groove depth of 50 to 200 nm.
In other embodiments, the coupling grating 3 is formed by two one-dimensional gratings disposed on the same surface of the waveguide sheet 1.
In the present embodiment, the thickness of the waveguide sheet 1 is 0.3 to 2.5mm, the material of the waveguide sheet 1 is an optical material transparent to visible light, and the refractive index of the waveguide sheet 1 is 1.4 to 2.2.
Example 7
Fig. 14 is a schematic structural diagram of a near-eye display device according to an embodiment of the present application.
As shown in fig. 14, an embodiment of the present application further provides a near-eye display device including a projection light machine 6 and a waveguide assembly, where the waveguide assembly is the waveguide assembly described in any of the embodiments above. In this embodiment, a waveguide assembly includes:
a waveguide sheet 1;
the coupling-in area 2 is arranged on one surface of the waveguide sheet 1, and the coupling-in area 2 is used for coupling light into the waveguide sheet 1 and enabling the light to be diffused and transmitted in the waveguide sheet 1;
the coupling-out grating 3 is arranged on one surface of the waveguide sheet 1, and the coupling-out grating 3 is used for coupling light coupled in from the coupling-in area 2 out of the waveguide sheet 1; and
the first reflection grating 4 and the coupling grating 3 are arranged on the same surface of the waveguide sheet 1 and located at the tail end of the coupling grating 3 in the light transmission direction, the first reflection grating 4 is parallel to the groove line of the coupling grating 3, the period of the first reflection grating 4 is the same as that of the coupling grating 3, the diffraction efficiency of second-order diffraction light in diffraction order is set to be maximum, or the first reflection grating 4 is half of the period of the coupling grating 3, the diffraction efficiency of first-order diffraction light in diffraction order is set to be maximum, and the first reflection grating 4 is used for reflecting light which passes through the coupling grating 3 and is not coupled back to the coupling grating 3 for coupling.
The working principle and process of the waveguide assembly provided by the embodiment are as follows:
the light emitted by the projection light engine 6 is coupled into the waveguide plate 1 by the coupling-in region 2, and is diffused and transmitted to the coupling-out grating 3 in the waveguide plate 1. The light-coupling grating 3 couples out the light ray a to the outside of the waveguide chip 1, and is observed by human eyes, thereby forming a visible region. The light B that is not coupled out will continue to propagate to the first reflection grating 4, the first reflection grating 4 reflects the light B back to the coupling-out grating 3, and then is coupled out by the coupling-out grating 3, i.e. the light C, and the light C is parallel to the light a.
The near-to-eye display device comprises a projection light machine 6 and a waveguide assembly, wherein the waveguide assembly is provided with a first-time reflection grating 4 on one side surface of a waveguide sheet 1, the first-time reflection grating 4 is parallel to a groove line of an outcoupling grating 3, the period of the first-time reflection grating 4 is the same as that of the outcoupling grating 3, and the diffraction efficiency of second-order diffraction light in diffraction orders is set to be the maximum, or the first-time reflection grating 4 is half of the period of the outcoupling grating 3, and the diffraction efficiency of first-order diffraction light in diffraction orders is set to be the maximum, so that light which is not coupled out through the outcoupling grating 3 is returned to the outcoupling grating 3 by the first-time reflection grating 4, thereby coupling out is performed, the whole light energy utilization rate of the waveguide assembly is improved, and the whole exit pupil density of the waveguide assembly is increased. And because the light returned by the first reflection grating 4 and coupled out again supplements the original coupled out light, the brightness uniformity of the coupled out light in the whole visible area of the waveguide sheet 1 is improved. Moreover, according to the optical design of the invention, only the first-time reflection grating 4 needs to be arranged on one side surface of the waveguide sheet 1, the manufacturing process is simple, and the production and the manufacturing are convenient. In addition, in the waveguide assembly provided in this embodiment, the light that is not coupled out by the coupling-out grating 3 for the first time can return to the coupling-out grating 3 only by passing through the first reflection grating 4, so that the light energy utilization rate is higher.
Example 8
Fig. 15 is a schematic structural diagram of a near-eye display device according to an embodiment of the present application.
In this embodiment, the waveguide assembly further includes a second sub-reflection grating 5, and the second sub-reflection grating 5 and the first sub-reflection grating 4 are disposed on the same surface of the waveguide sheet 1.
The second-time reflection grating 5 is arranged opposite to the first-time reflection grating 4 and is respectively positioned at two sides of the coupling-out grating 3.
The groove lines of the second-reflection grating 5 are parallel to the groove lines of the outcoupling grating 3, the period of the second-reflection grating 5 is the same as the period of the outcoupling grating 3 and the diffraction efficiency of the second-order diffracted light in the diffraction order is set to be maximum, or the period of the second-reflection grating 5 is half of the period of the outcoupling grating 3 and the diffraction efficiency of the first-order diffracted light in the diffraction order is set to be maximum.
The light which is not coupled out after being reflected by the first reflection grating 4 is transmitted to the second reflection grating 5, and is reflected back to the coupling-out grating 3 by the second reflection grating 5 and then is coupled out.
The working principle and process of the waveguide assembly provided by the embodiment are as follows:
the light emitted by the projection light engine 6 is coupled into the waveguide plate 1 by the coupling-in region 2, and is diffused and transmitted to the coupling-out grating 3 in the waveguide plate 1. The light-coupling grating 3 couples the light A out of the waveguide sheet 1, thereby forming a visible region. The light B that is not coupled out will continue to propagate to the first reflection grating 4, the first reflection grating 4 reflects the light B back to the coupling-out grating 3, and then is coupled out by the coupling-out grating 3, i.e. the light C, and the light C is parallel to the light a. Still, a part of the light D is not coupled out and continuously transmitted to the second reflection grating 5, and is reflected back to the coupling grating 3 by the second reflection grating 5, and the coupling grating 3 couples out the light E.
In the near-eye display device provided in this embodiment, the second-time reflection grating 5 is disposed on the waveguide sheet 1 of the waveguide assembly, the second-time reflection grating 5 and the first-time reflection grating 4 are disposed on the same side of the waveguide sheet 1, the groove lines of the second-time reflection grating 5 are parallel to the groove lines of the coupling-out grating 3, the period of the second-time reflection grating 5 is the same as the period of the coupling-out grating 3, and the diffraction efficiency of the second-order diffracted light in the diffraction order is set to be the maximum, or the period of the second-time reflection grating 5 is half of the period of the coupling-out grating 3, and the diffraction efficiency of the first-order diffracted light in the diffraction order is set to be the maximum, so that after the light not coupled out by the coupling-out grating 3 is reflected back to the coupling-out grating 3 by the first-time reflection grating 41, the light not coupled out is reflected back to the coupling-out grating 3 by the second-time reflection grating 5, thereby further improving the light energy utilization rate, The exit pupil density is increased and the brightness uniformity is improved.
In the description of the present invention, it should be noted that the terms "upper", "lower", and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, which are only for convenience in describing the present invention and simplifying the description, but do not indicate or imply that the referred device or element must have a specific orientation, be constructed in a specific orientation, and operate, and thus, should not be construed as limiting the present invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.
In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; the communication may be direct, indirect via an intermediate medium, or internal to both elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art. In addition, in the description of the present invention, "a plurality" means two or more unless otherwise specified.
The present invention is not limited to the above preferred embodiments, and any modifications, equivalent replacements, improvements, etc. within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (20)

1. A waveguide assembly, comprising:
a waveguide sheet (1);
the coupling-in area (2) is arranged on the surface of the waveguide sheet (1), and the coupling-in area (2) is used for coupling light into the waveguide sheet (1) and enabling the light to be diffused and transmitted in the waveguide sheet (1);
a coupling-out grating (3) arranged on the surface of the waveguide sheet (1), the coupling-out grating (3) being used for coupling light coupled in from the coupling-in region (2) out of the waveguide sheet (1); and
a first reflection grating (4) and a second reflection grating (5) which are oppositely arranged, wherein the first reflection grating (4) is arranged for reflecting the light which passes through the coupling-out grating (3) and is not coupled out back to the coupling-out grating (3) and then coupling out, the second reflection grating (5) is arranged for reflecting the light which is not coupled out after being reflected by the first reflection grating (4) back to the coupling-out grating (3) and then coupling out,
wherein the period of the first-order reflection grating (4) is the same as the period of the outcoupling grating (3) in the vertical direction and the diffraction efficiency of the second-order diffracted light in the diffraction orders is set to be maximum, or the period of the first-order reflection grating (4) is half of the period of the outcoupling grating (3) in the vertical direction and the diffraction efficiency of the first-order diffracted light in the diffraction orders is set to be maximum,
wherein the period of the second-order reflection grating (5) is the same as the period of the outcoupling grating (3) in the horizontal direction and the diffraction efficiency of the second-order diffracted light in the diffraction order is set to be maximum, or the period of the second-order reflection grating (5) is half of the period of the outcoupling grating (3) in the horizontal direction and the diffraction efficiency of the first-order diffracted light in the diffraction order is set to be maximum.
2. The waveguide assembly according to claim 1, wherein the first sub-reflection grating (4) comprises a first reflection grating (41) and a second reflection grating (42) arranged separately.
3. Waveguide assembly according to claim 1 or 2, wherein the first sub-reflection grating (4) is a sinusoidal grating, a rectangular grating, a blazed grating or a tilted grating tilted in the direction of the outcoupled grating (3).
4. The waveguide assembly according to claim 1, wherein the second sub-reflection grating (5) and the first sub-reflection grating (4) are provided on the same surface of the waveguide sheet (1);
the second reflection grating (5) and the first reflection grating (4) are respectively positioned at two sides of the coupling-out grating (3).
5. The waveguide assembly of claim 4, wherein the first sub-reflection grating (4) comprises a first reflection grating (41) and a second reflection grating (42) which are separately arranged, and the second sub-reflection grating (5) comprises a third reflection grating (51) and a fourth reflection grating (52) which are separately arranged, wherein the first reflection grating (41) and the third reflection grating (51) are oppositely arranged, and the second reflection grating (42) and the fourth reflection grating (52) are oppositely arranged.
6. A waveguide assembly according to claim 4 or 5, characterized in that the second sub-reflection grating (5) is a sinusoidal grating, a rectangular grating, a blazed grating or a tilted grating inclined to the direction of the outcoupling grating (3).
7. A waveguide assembly according to any one of claims 1-5, characterized in that the outcoupling grating (3) is a two-dimensional grating.
8. Waveguide assembly according to any one of claims 1 to 5, wherein the outcoupling grating (3) is formed by two one-dimensional gratings respectively provided on both surfaces of the waveguide sheet (1) or by a superposition of two one-dimensional gratings provided on the same surface of the waveguide sheet (1).
9. Waveguide assembly according to claim 8, characterized in that the angle between the two one-dimensional gratings of the out-coupling grating (3) is 50-70 degrees.
10. A waveguide assembly according to any one of claims 1-5, wherein the outcoupling grating (3) is a rectangular grating, a blazed grating, an inclined grating, a sinusoidal grating or a holographic grating and has a groove depth of 50-200 nm.
11. A waveguide assembly according to claim 1 or 2, wherein the first sub-reflection grating (4) borders the outcoupling grating (3).
12. Waveguide assembly according to claim 1, wherein the width of the first sub-reflection grating (4) is larger than 3 mm.
13. A waveguide assembly according to claim 4 or 5, characterized in that the outcoupling grating (3) is a rectangular grating and the first (4) and/or second (5) reflection grating is a tilted or blazed grating.
14. Waveguide assembly according to any one of claims 1 to 5, characterized in that the incoupling region (2) comprises an incoupling grating (21), which incoupling grating (21) is intended for incoupling light into the waveguide plate (1).
15. Waveguide assembly according to claim 14, wherein the incoupling grating (21) is in a rectangular grating, a blazed grating, an inclined grating, a sinusoidal grating or a holographic grating and has a period of 300-600 nm and a groove depth of 40-500 nm.
16. The waveguide assembly according to claim 14, wherein the coupling-in region (2) further comprises a turning grating (22), the turning grating (22) being configured to allow light coupled in from the coupling-in grating (21) to diffuse and propagate within the waveguide sheet (1).
17. The waveguide assembly according to claim 16, wherein the turning grating (22) is in a rectangular grating, a blazed grating, an inclined grating, a sinusoidal grating or a holographic grating and has a period of 300-600 nm and a groove depth of 40-500 nm.
18. Waveguide assembly according to claim 14 or 16, wherein the coupling-in region (2) and the coupling-out grating (3) are located on the same surface of the waveguide sheet (1) or on two surfaces opposite the waveguide sheet (1), respectively.
19. The waveguide assembly according to any one of claims 1 to 5, wherein the thickness of the waveguide sheet (1) is 0.3 to 2.5mm, the material of the waveguide sheet (1) is an optical material transparent to visible light, and the refractive index of the waveguide sheet (1) is 1.4 to 2.2.
20. A near-eye display device comprising a projection light (6) and a waveguide assembly, the waveguide assembly being as claimed in any one of claims 1-19.
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