Diffraction optical waveguide and near-to-eye display equipment

Abstract

The invention discloses a diffraction optical waveguide and near-to-eye display equipment, the diffraction optical waveguide comprises a waveguide substrate, the surface of the waveguide substrate is provided with a coupling-in grating, a first transfer grating, a second transfer grating and a coupling-out grating, image light is not directly transmitted to the coupling-out grating after being coupled into the waveguide substrate from the coupling-in grating, and the coupling-out grating is not directly transmitted to the coupling-out grating after being coupled into the waveguide substrate from the coupling-in grating. Wherein one part of the image light is transmitted to the first transfer grating and then deflected to the out-coupling grating, the other part of the image light is transmitted to the second transfer grating and then deflected to the out-coupling grating, and the first transfer grating and the second transfer grating are used for deflecting the light transmission direction. And the first transfer grating and the second transfer grating are arranged opposite to the coupling-out grating, so that the color change trends of imaging pictures which are transmitted to the coupling-out grating from the first transfer grating and the second transfer grating respectively and are coupled out are opposite. According to the technical scheme provided by the invention, the color uniformity of the diffraction optical waveguide can be improved.

Description

Technical Field

[0001] The present application relates to the field of augmented reality, and in particular to a diffraction optical waveguide and a near-eye display device. Background Art

[0002] Augmented reality is a technology that integrates the real world and virtual information. The augmented reality display system usually includes a micro projector and an optical display screen. The micro projector provides virtual display content for the augmented reality display system and projects it into the human eye through the optical display screen. The optical display screen is usually a transparent optical component, so that users can also see the real world through the optical display screen.

[0003] Diffraction waveguides are a commonly used method for implementing optical displays. However, light of different wavelengths is diffracted at different angles by the diffraction grating, resulting in different exit pupil densities for light of different colors and fields of view. This causes one side of the image to be bluer and the other side to be redder, affecting color uniformity. Summary of the Invention

[0004] The embodiments of the present application provide a diffraction optical waveguide and a near-eye display device, which can split the light into two transmission paths and enter the outcoupling grating from two opposite directions. The color uniformity of the imaging picture can be improved by superimposing the outputs of the two imaging pictures with opposite color change trends.

[0005] An embodiment of the present application provides a diffractive optical waveguide, comprising:

[0006] A waveguide substrate, wherein a coupling-in grating, a first relay grating, a second relay grating, and an outcoupling grating are provided on the surface of the waveguide substrate. After the image light is coupled into the waveguide substrate from the coupling-in grating, it is not directly transmitted to the outcoupling grating. A portion of the image light is first transmitted to the first relay grating and then deflected to the outcoupling grating, and another portion of the image light is first transmitted to the second relay grating and then deflected to the outcoupling grating. The first relay grating and the second relay grating are used to deflect the transmission direction of the light and are arranged relative to the outcoupling grating so that the color change trends of the imaging images coupled out by being transmitted from the first relay grating and the second relay grating, respectively, are opposite.

[0007] In practice, the first transfer grating and the second transfer grating can receive the full-field light coupled into the waveguide substrate via the coupling-in grating.

[0008] In practice, the regions where the coupling-in grating, the first transfer grating and the second transfer grating are located are all circular.

[0009] In practice, the first transfer grating includes a plurality of first sub-gratings, each of the first sub-gratings is arranged in sequence and the area in which they are located is circular, and the areas where adjacent first sub-gratings are located are tangent to each other; the second transfer grating includes a plurality of second sub-gratings, each of the second sub-gratings is arranged in sequence and the area in which they are located is circular, and the areas where adjacent second sub-gratings are located are tangent to each other.

[0010] In practice, the first sub-gratings that are closer to the in-coupling grating are farther from the out-coupling grating, and the second sub-gratings that are closer to the in-coupling grating are also farther from the out-coupling grating.

[0011] Implementably, the size of the region where the first sub-grating is located is smaller than or equal to the size of the region where the coupling-in grating is located, and the size of the region where the second sub-grating is located is smaller than or equal to the size of the region where the coupling-in grating is located.

[0012] In practice, the center of the wave vector area before the image light is incident on the coupling grating, the center of the wave vector area after the image light passes through the coupling grating and the first relay grating, and the center of the wave vector area after the image light passes through the coupling grating and the second relay grating are located on the same straight line.

[0013] In practice, the coupling-in grating includes a first coupling-in grating and a second coupling-in grating, wherein the first coupling-in grating and the second coupling-in grating are both one-dimensional gratings, and the dividing line between the first coupling-in grating and the second coupling-in grating is modulated left and right on the dividing line of the two directions in which the image light is transmitted respectively to the first relay grating and the second relay grating, so as to modulate the efficiency ratio between the image light transmitted respectively in the two directions.

[0014] In practice, the waveguide substrate includes a first waveguide substrate and a second waveguide substrate, the coupling-in grating, the first transfer grating and the second transfer grating are provided on the first waveguide substrate, and the first transfer grating, the second transfer grating and the coupling-out grating are provided on the second waveguide substrate, wherein, after the image light is coupled into the first waveguide substrate from the coupling-in grating, it is transmitted to the first transfer grating and the second transfer grating respectively, and is coupled out of the first waveguide substrate by the first transfer grating and the second transfer grating, and then is incident on the corresponding first transfer grating and the second transfer grating on the second waveguide substrate, and then is transmitted to the coupling-out grating and coupled-out to form an image; and a focusing optical element is provided between the first transfer grating of the first waveguide substrate and the first transfer grating of the second waveguide substrate, and between the second transfer grating of the first waveguide substrate and the second transfer grating of the second waveguide substrate.

[0015] An embodiment of the present application further provides a near-eye display device, which includes the diffraction light waveguide and the projection optical engine as described in any of the above items.

[0016] The present application provides a diffraction optical waveguide and near-eye display device. An input grating, a first relay grating, a second relay grating, and an output grating are disposed on the surface of a waveguide substrate. After being coupled into the waveguide substrate via the input grating, image light is not directly transmitted to the output grating. Instead, a portion is first transmitted to the first relay grating and then deflected to the output grating, while another portion is first transmitted to the second relay grating and then deflected to the output grating. The first and second relay gratings are used to deflect the direction of light transmission and are positioned relative to the output grating. This splits the light into two paths, which are transmitted and enter the output grating from two opposite directions. This ensures that the color change trends of the imaged images coupled out from the first and second relay gratings are opposite, thereby optimizing the color uniformity of the imaged images by superimposing the outputs with opposite color change trends. Furthermore, both the first and second relay gratings receive the full field of view light coupled into the waveguide substrate via the input grating, thereby improving color uniformity across the entire field of view.

[0017] Furthermore, the center of the wave vector area before the image light is incident on the coupling grating, the center of the wave vector area after the image light is acted upon by the coupling grating and the first relay grating, and the center of the wave vector area after the image light is acted upon by the coupling grating and the second relay grating are located on the same straight line. This ensures that light entering the coupling grating from two directions can be coupled out from the coupling grating at the same angle, thereby avoiding ghosting. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0019] Figure 1 A schematic structural diagram of a diffraction optical waveguide provided in an embodiment of the present application;

[0020] Figure 2 A schematic structural diagram of another diffraction optical waveguide provided in an embodiment of the present application;

[0021] Figure 3 K domain of image light propagation in the diffraction light waveguide provided in the embodiment of the present application Figure 1 ;

[0022] Figure 4 K domain of image light propagation in the diffraction light waveguide provided in the embodiment of the present application Figure 2 ;

[0023] Figure 5A schematic structural diagram of another diffraction optical waveguide provided in an embodiment of the present application;

[0024] Figure ID:

[0025] 110: waveguide substrate; 111: first waveguide substrate; 112: second waveguide substrate;

[0026] 120: coupling grating; 121: first coupling grating; 122: second coupling grating;

[0027] 130: first transfer grating; 131: first sub-grating;

[0028] 140: second transfer grating; 141: second sub-grating;

[0029] 150: outcoupling grating. DETAILED DESCRIPTION

[0030] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0031] The following specific embodiments are used to describe the technical solution of the present application in detail. The following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described in detail in some embodiments.

[0032] An embodiment of the present application provides a diffraction optical waveguide, comprising: a waveguide substrate, wherein a coupling-in grating, a first relay grating, a second relay grating, and an outcoupling grating are arranged on the surface of the waveguide substrate. After the image light is coupled into the waveguide substrate from the coupling-in grating, it is not directly transmitted to the outcoupling grating. A portion of the light is first transmitted to the first relay grating and then deflected to the outcoupling grating, and another portion of the light is first transmitted to the second relay grating and then deflected to the outcoupling grating. The first relay grating and the second relay grating are used to deflect the transmission direction of the light and are arranged relative to the outcoupling grating so that the color change trends of the imaging images coupled out by being transmitted from the first relay grating and the second relay grating, respectively, are opposite.

[0033] For example, refer to Figure 1The diffraction optical waveguide includes a waveguide substrate 110, on the surface of which an in-coupling grating 120, a first relay grating 130, a second relay grating 140, and an out-coupling grating 150 are arranged. The first relay grating 130 and the second relay grating 140 are arranged relative to the out-coupling grating 150. After the image light is coupled into the waveguide substrate 110 by the in-coupling grating 120, it is not directly transmitted to the out-coupling grating 150. A portion of the image light is first transmitted to the first relay grating 130 and then deflected to the out-coupling grating 150, while another portion of the image light is first transmitted to the second relay grating 140 and then deflected to the out-coupling grating 150.

[0034] In this way, the imaging image of the light entering the outcoupling grating 150 from the first transfer grating 130 is bluer on the side close to the first transfer grating 130 and redder on the side close to the second transfer grating 140; while the imaging image of the light entering the outcoupling grating 150 from the second transfer grating 140 is redder on the side close to the first transfer grating 130 and bluer on the side close to the second transfer grating 140. Since the first transfer grating 130 and the second transfer grating 140 are arranged relative to each other with respect to the outcoupling grating 150, after the two imaging images are superimposed, the reddish portion of one overlaps with the bluish portion of the other, thereby improving the color uniformity of the output image of the diffraction light waveguide.

[0035] It should be noted that in the prior art, in a diffraction light waveguide with a one-dimensional structure, for example, it includes a coupling-in grating, a pupil expansion grating and a coupling-out grating, wherein the pupil expansion grating plays the role of deflecting the transmission direction of the light on the one hand, and on the other hand, which is more important, it is used to realize pupil expansion in one direction, thereby realizing two-dimensional pupil expansion together with the coupling-out grating. However, the first transfer grating and the second transfer grating in the present application are not used as pupil expansion structures, but are used to deflect the transmission direction of the image light. In order to improve the color uniformity of the diffraction light waveguide by using image superposition, the image light is not directly transmitted into the coupling-out grating after being coupled into the waveguide base from the coupling-in grating, but is transmitted in two ways to both sides of the coupling-out grating, and then deflected by the first transfer grating and the second transfer grating respectively in the transmission direction and then enters the coupling-out grating for coupling-out superposition. However, it is not ruled out that the first transfer grating and the second transfer grating passively bring about the pupil expansion effect due to their certain area.

[0036] In practice, the first and second relay gratings can receive the entire field of view of light coupled into the waveguide substrate via the coupling grating. The first relay grating can receive the entire field of view of light coupled into the waveguide substrate via the coupling grating, and the second relay grating can also receive the entire field of view of light coupled into the waveguide substrate via the coupling grating. This can improve color uniformity across the entire field of view.

[0037] In practice, the regions containing the coupling grating, the first transfer grating, and the second transfer grating are all circular. Specifically, the optical machine exit pupil is circular, and the region containing the coupling grating is also configured to be circular. Since image light has a certain field of view, the regions containing the first and second transfer gratings for deflecting the light transmission direction are also circular, and their dimensions are larger than those of the region containing the coupling grating.

[0038] Wherein, when the area where the first transfer grating and the second transfer grating are located is selected to be circular, the size of the circle is the minimum size that can meet the requirement of receiving the full-field light coupled into the waveguide substrate through the coupling grating.

[0039] For example, refer to Figure 1 The areas where the coupling-in grating 120, the first transfer grating 130 and the second transfer grating 140 are located are all circular. The size of the area where the first transfer grating 130 and the second transfer grating 140 are located is larger than the size of the area where the coupling-in grating 120 is located.

[0040] It can be understood that, as mentioned in the above embodiments, the first transfer grating and the second transfer grating are not used as pupil expansion structures, but since the first transfer grating and the second transfer grating have a certain area, they will inevitably bring about a certain pupil expansion effect. When the pupil expansion effect exists, it will bring about light loss and light interference problems.

[0041] In this application, the areas of the first and second transfer gratings are reduced without causing other negative effects. Specifically, the first transfer grating includes multiple first sub-gratings, each arranged sequentially and located in a circular area, with adjacent first sub-gratings located in tangent areas. The second transfer grating includes multiple second sub-gratings, each arranged sequentially and located in a circular area, with adjacent second sub-gratings located in tangent areas. This reduces the areas of the first and second transfer gratings, thereby reducing light loss and multipath light interference caused by pupil expansion.

[0042] For example, refer to Figure 2 The diffraction optical waveguide includes a waveguide substrate 110, and an in-coupling grating 120, a first transfer grating 130, a second transfer grating 140, and an out-coupling grating 150 are arranged on the surface of the waveguide substrate 110. The first transfer grating 130 and the second transfer grating 140 are arranged relative to the out-coupling grating 150. The first transfer grating 130 includes a plurality of first sub-gratings 131, each of which is arranged in sequence and located in a circular area, and the areas where adjacent first sub-gratings 131 are located are tangent to each other; the second transfer grating 140 includes a plurality of second sub-gratings 141, each of which is arranged in sequence and located in a circular area, and the areas where adjacent second sub-gratings 141 are located are tangent to each other.

[0043] In one embodiment, the region where the plurality of first sub-gratings 131 are located can be obtained by ray tracing from the region where the first transfer grating 130 is located in the previous embodiment, and the region where the plurality of second sub-gratings 141 are located can be obtained by ray tracing from the region where the second transfer grating 140 is located in the previous embodiment.

[0044] Practically, the size of the region where the first sub-grating is located is smaller than or equal to the size of the region where the coupling-in grating is located, and the size of the region where the second sub-grating is located is smaller than or equal to the size of the region where the coupling-in grating is located.

[0045] Specifically, the number of first sub-gratings is related to the size of the area where the first sub-grating is located and the field of view of the image light emitted by the optical machine. In the present application, the area where the first sub-grating is located is selected to be circular, with a size smaller than or equal to the size of the area where the coupling-in grating is located, and is arranged tangentially in sequence along a certain direction, and all first sub-gratings cooperate to cover the image light in the entire field of view. Similarly, the number of second sub-gratings is related to the size of the area where the second sub-grating is located and the field of view of the image light emitted by the optical machine. In the present application, the area where the second sub-grating is located is selected to be circular, with a size smaller than or equal to the size of the area where the coupling-in grating is located, and is arranged tangentially in sequence along a certain direction, and all second sub-gratings cooperate to cover the image light in the entire field of view.

[0046] Practically, the first sub-gratings that are closer to the in-coupling grating are farther from the out-coupling grating, and the second sub-gratings that are closer to the in-coupling grating are also farther from the out-coupling grating.

[0047] In this embodiment, since the first relay grating has multiple first sub-gratings, each first sub-grating is used to deflect light in a different field of view. By collaboratively modulating the distance between each first sub-grating and the coupling-in grating and the coupling-out grating, the propagation path length of the light in each field of view can be balanced, which is more conducive to optimizing color uniformity.

[0048] On the other hand, in the present application, after the image light is coupled into the waveguide substrate from the coupling-in grating, it is not directly transmitted into the coupling-out grating, but is transmitted in two ways to both sides of the coupling-out grating, and then deflected by the first transfer grating and the second transfer grating respectively, and then enters the coupling-out grating and is coupled out and superimposed. If the light entering the coupling-out grating from two directions has inconsistent emission directions when coupled out, ghosting will occur, thereby affecting the imaging effect of the diffraction waveguide. In practice, the center of the wave vector area before the image light is incident on the coupling-in grating, the center of the wave vector area after the image light is acted upon by the coupling-in grating and the first transfer grating, and the center of the wave vector area after the image light is acted upon by the coupling-in grating and the first transfer grating are located on the same straight line. This ensures that the light entering the coupling-out grating from two directions can be coupled out from the coupling-out grating at the same angle, thus avoiding ghosting.

[0049] refer to Figure 3 and Figure 4 The two figures show the K-domain diagrams of image light transmission in a diffraction waveguide. The green rectangular box represents the wave vector region before the image light enters the coupling grating and after the image light is coupled out from the coupling grating. The red rectangular box represents the wave vector region after the image light passes through the coupling grating and the first relay grating, and the blue rectangular box represents the wave vector region after the image light passes through the coupling grating and the second relay grating. It can be seen that the center of the wave vector region before the image light enters the coupling grating, the center of the wave vector region after the image light passes through the coupling grating and the first relay grating, and the center of the wave vector region after the image light passes through the coupling grating and the second relay grating are all located on the same straight line. This ensures that light entering the coupling grating from two directions can be coupled out from the coupling grating at the same angle, thus avoiding ghosting.

[0050] Furthermore, the outcoupling grating is a two-dimensional grating, and the center of the wave vector area of the image light entering the outcoupling grating from the first transfer grating after the pupil expansion effect of the outcoupling grating and the center of the wave vector area of the image light entering the outcoupling grating from the second transfer grating after the pupil expansion effect of the outcoupling grating are also located on the same straight line as the center of the wave vector area of the image light before it enters the incoupling grating. Figure 4 It can be seen that the centers of the wave vector areas relative to each other and the centers of the wave vector areas after the image light is self-coupled from the grating are located on the same straight line.

[0051] In practice, the coupling grating includes a first coupling grating and a second coupling grating, both of which are one-dimensional gratings, and the dividing line between the first coupling grating and the second coupling grating is modulated left and right on the dividing line of the two directions in which the image light is transmitted to the first relay grating and the second relay grating, so as to modulate the efficiency ratio between the image light transmitted in the two directions.

[0052] In the present application, due to the arrangement position of the first transfer grating and the second transfer grating, the image light is coupled from the coupling grating to the waveguide substrate and is transmitted in two directions to the two sides of the out-coupling grating, and the path lengths are different. The coupling grating includes a first coupling grating and a second coupling grating. The image light is transmitted to the first transfer grating under the action of the first coupling grating, and is transmitted to the second transfer grating under the action of the second coupling grating. By modulating the dividing line between the first coupling grating and the second coupling grating left and right on the midline of the two directions in which the image light is transmitted to the first transfer grating and the second transfer grating, respectively, the efficiency ratio between the image light transmitted in the two directions is modulated, thereby further improving the uniformity.

[0053] In the aforementioned embodiment, the diffractive optical waveguide includes a waveguide plate, and the incoupling grating and the outcoupling grating are distributed on the same waveguide plate. In another embodiment, the diffractive optical waveguide may also include more than one waveguide plate, and the incoupling grating and the outcoupling grating are distributed on different waveguide plates.

[0054] In practice, the waveguide substrate includes a first waveguide substrate and a second waveguide substrate, wherein a coupling-in grating, a first transfer grating, and a second transfer grating are provided on the first waveguide substrate, and a first transfer grating, a second transfer grating, and a coupling-out grating are provided on the second waveguide substrate, wherein the image light is coupled into the first waveguide substrate from the coupling-in grating, and then transmitted to the first transfer grating and the second transfer grating respectively, and is coupled out of the first waveguide substrate by the first transfer grating and the second transfer grating, and then is incident on the corresponding first transfer grating and the second transfer grating on the second waveguide substrate, and then is transmitted to the coupling-out grating and coupled-out to form an image; and a focusing optical element is provided between the first transfer grating of the first waveguide substrate and the first transfer grating of the second waveguide substrate, and between the second transfer grating of the first waveguide substrate and the second transfer grating of the second waveguide substrate.

[0055] For example, refer to Figure 5 The waveguide substrate 110 includes a first waveguide substrate 111 and a second waveguide substrate 112. The first waveguide substrate 111 is provided with an incoupling grating 120, a first relay grating 130, and a second relay grating 140. The second waveguide substrate 112 is provided with a first relay grating 130, a second relay grating 140, and an outcoupling grating 150. The first relay grating 130 on the first waveguide substrate 111 corresponds to the first relay grating 130 on the second waveguide substrate 112, and the second relay grating 140 on the first waveguide substrate 112 corresponds to the second relay grating 140 on the second waveguide substrate 112.

[0056] In this embodiment, the presence of focusing optical elements between the first transfer grating of the first waveguide substrate and the first transfer grating of the second waveguide substrate, and between the second transfer grating of the first waveguide substrate and the second waveguide substrate, reduces the spot size and the spacing between the spots, enabling compatibility with optical engines with smaller exit pupils without causing pupil expansion discontinuities. Furthermore, the coupling grating on the first waveguide substrate achieves higher coupling efficiency.

[0057] The present application also provides a near-eye display device, comprising a diffractive optical waveguide as described in any of the preceding embodiments and a projection optical engine. The projection optical engine is configured to project light carrying image information within a predetermined field of view. The projection optical engine in the present application can employ various types of optical engines, such as uLED, LCOS, DLP, LBS, and OLED.

[0058] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A diffraction optical waveguide, characterized in that: The diffractive optical waveguide comprises: A waveguide substrate, wherein a coupling-in grating, a first relay grating, a second relay grating, and an outcoupling grating are provided on the surface of the waveguide substrate. After the image light is coupled into the waveguide substrate from the coupling-in grating, it is not directly transmitted to the outcoupling grating. A portion of the image light is first transmitted to the first relay grating and then deflected to the outcoupling grating, and another portion of the image light is first transmitted to the second relay grating and then deflected to the outcoupling grating. The first relay grating and the second relay grating are used to deflect the transmission direction of the light and are arranged relative to the outcoupling grating so that the color change trends of the imaging images coupled out by being transmitted from the first relay grating and the second relay grating, respectively, are opposite.

2. The diffractive optical waveguide according to claim 1, wherein The first transfer grating and the second transfer grating can receive the full-field light coupled into the waveguide substrate via the coupling grating.

3. The diffractive optical waveguide according to claim 2, wherein: The regions where the coupling-in grating, the first transfer grating and the second transfer grating are located are all circular.

4. The diffractive optical waveguide according to claim 2, wherein: The first transfer grating includes a plurality of first sub-gratings, each of which is arranged in sequence and located in a circular area, and the areas where adjacent first sub-gratings are located are tangent to each other; the second transfer grating includes a plurality of second sub-gratings, each of which is arranged in sequence and located in a circular area, and the areas where adjacent second sub-gratings are located are tangent to each other.

5. The diffractive optical waveguide according to claim 4, characterized in that The first sub-gratings that are closer to the in-coupling grating are farther from the out-coupling grating, and the second sub-gratings that are closer to the in-coupling grating are also farther from the out-coupling grating.

6. The diffractive optical waveguide according to claim 4, characterized in that The size of the region where the first sub-grating is located is smaller than or equal to the size of the region where the coupling-in grating is located, and the size of the region where the second sub-grating is located is smaller than or equal to the size of the region where the coupling-in grating is located.

7. The diffractive optical waveguide according to claim 2, wherein: The center of the wave vector area before the image light is incident on the coupling grating, the center of the wave vector area after the image light passes through the coupling grating and the first relay grating, and the center of the wave vector area after the image light passes through the coupling grating and the second relay grating are located on the same straight line.

8. The diffractive optical waveguide according to claim 1, wherein: The coupling-in grating includes a first coupling-in grating and a second coupling-in grating, both of which are one-dimensional gratings. The dividing line between the first coupling-in grating and the second coupling-in grating is modulated left and right on the dividing line of the two directions in which the image light is transmitted toward the first relay grating and the second relay grating, so as to modulate the efficiency ratio between the image light transmitted toward the two directions.

9. The diffractive optical waveguide according to claim 1, wherein: The waveguide substrate includes a first waveguide substrate and a second waveguide substrate. The coupling-in grating, the first transfer grating, and the second transfer grating are provided on the first waveguide substrate, and the first transfer grating, the second transfer grating, and the coupling-out grating are provided on the second waveguide substrate. The image light is coupled into the first waveguide substrate from the coupling-in grating and then transmitted to the first transfer grating and the second transfer grating respectively. After being coupled out of the first waveguide substrate by the first transfer grating and the second transfer grating, the image light is incident on the corresponding first transfer grating and the second transfer grating on the second waveguide substrate, and then transmitted to the coupling-out grating to be coupled out to form an image. Focusing optical elements are provided between the first transfer grating of the first waveguide substrate and the first transfer grating of the second waveguide substrate, and between the second transfer grating of the first waveguide substrate and the second transfer grating of the second waveguide substrate.

10. A near-eye display device, characterized in that: The near-eye display device includes a diffraction optical waveguide according to any one of claims 1 to 9 and a projection optical engine.

Images