Optical waveguide and near-eye display device

Abstract

Provided in the present application are an optical waveguide and a near-eye display device. The optical waveguide comprises a waveguide substrate, an in-coupling region, an out-coupling region and a path extension layer, wherein the waveguide substrate comprises a first surface and a second surface that are opposite to each other; the in-coupling region is formed on the first surface of the waveguide substrate and is used for coupling incident rays into the waveguide substrate; the out-coupling region is formed on the first surface or the second surface of the waveguide substrate, and couples out rays that propagate in the waveguide substrate; and the path extension layer is arranged on the second surface of the waveguide substrate, the refractive index of the path extension layer is greater than the refractive index of air and is less than the refractive index of the waveguide substrate, the path extension layer is configured to reflect rays that are incident into the path extension layer from the waveguide substrate, and incident points of the reflected rays on the first surface are located outside the in-coupling region. By means of the present application, rays that are coupled into an optical waveguide can be prevented from being incident into an in-coupling region again, such that the optical efficiency of the optical waveguide is improved, and the manufacturing costs and weight of the optical waveguide are reduced.

Description

Optical waveguides and near-eye display devices

[0001] This application claims priority to Chinese Patent Application No. 2024111954106, filed on August 28, 2024, entitled "Optical Waveguide and Near-Eye Display Device", the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application relates to the field of optical technology, and in particular to an optical waveguide and near-eye display device. Background Technology

[0003] Near-eye display technology is now maturing. Near-eye display devices integrate an optical engine and use optical waveguides to achieve directional transmission of light emitted from the optical engine, thereby enabling the display of images generated by the optical engine to the user.

[0004] Typically, optical waveguides have coupling-in and coupling-out regions to achieve light coupling. However, since the coupling-in region covers part of the waveguide's surface, coupled light rays may propagate within the area covered by the coupling-in region and then re-enter the coupling-in region, undergoing secondary diffraction and being coupled out. This results in energy loss and hinders the improvement of the waveguide's optical efficiency. Increasing the thickness of the coupling-in region can reduce secondary diffraction, but since incident light rays include rays with multiple different incident angles and potentially different incident positions, secondary diffraction will still occur even after increasing the thickness of the coupling-in region, leading to energy loss. Increasing the overall thickness of the waveguide to overcome secondary diffraction would increase the manufacturing cost and weight of the waveguide. Summary of the Invention

[0005] This application provides an optical waveguide and a near-eye display device, which aims to prevent light coupled into the optical waveguide from re-entering the coupling region, thereby improving the optical efficiency of the optical waveguide and reducing the manufacturing cost and weight of the optical waveguide.

[0006] In a first aspect, this application provides an optical waveguide, comprising:

[0007] Waveguide substrate, comprising opposing first and second surfaces;

[0008] A coupling region is formed on the first surface of the waveguide substrate, the coupling region being used to couple incident light rays into the waveguide substrate;

[0009] A coupling region is formed on a first or second surface of the waveguide substrate, the coupling region being used to couple out light propagating in the waveguide substrate;

[0010] An extension layer is disposed on the second surface of the waveguide substrate. The refractive index of the extension layer is greater than that of air and less than that of the waveguide substrate. The extension layer is used to reflect light incident from the waveguide substrate into the extension layer. The incident point of the reflected light on the first surface is located outside the coupling region.

[0011] Secondly, this application also provides a near-eye display device, which includes at least an optical engine and an optical waveguide as provided in the first aspect, wherein the optical engine is used to emit signal light and the optical waveguide is used to directionally transmit the signal light to the human eye.

[0012] This application provides an optical waveguide and a near-eye display device. The optical waveguide provided by this application includes a waveguide substrate, a coupling region, a coupling out region, and a range extender layer. The waveguide substrate includes a first surface and a second surface opposite to each other. A coupling region for coupling incident light into the waveguide substrate is formed on the first surface, and a coupling out region for coupling light propagating in the waveguide substrate is formed on the first surface or the second surface. The range extender layer is disposed on the second surface, wherein the refractive index of the range extender layer is greater than the refractive index of air and less than the refractive index of the waveguide substrate, so that light incident from the waveguide substrate at various angles into the range extender layer can be reflected within the range extender layer, and the incident point of the reflected light on the first surface of the optical waveguide is located outside the coupling region. This solves the problem that some light still couples out from the coupling region even when the thickness of the optical waveguide coupling region is increased, further reducing secondary diffraction occurring in the coupling region, and reducing the manufacturing cost and weight of the optical waveguide. Attached Figure Description

[0013] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0014] Figure 1 is a schematic diagram of the structure of an optical waveguide in the prior art;

[0015] Figure 2 is a schematic diagram of the structure of an optical waveguide provided in an embodiment of this application;

[0016] Figure 3 is a K-vector diagram of an optical waveguide provided in an embodiment of this application;

[0017] Figure 4 is a schematic diagram of the structure of an optical waveguide provided in another embodiment of this application;

[0018] Figure 5 is a K-vector diagram of an optical waveguide provided in another embodiment of this application;

[0019] Figure 6 is a schematic diagram of the structure of an optical waveguide provided in another embodiment of this application;

[0020] Figure 7 is a K-vector diagram of an optical waveguide provided in another embodiment of this application;

[0021] Figure 8 is a schematic diagram of the structure of an optical waveguide provided in another embodiment of this application;

[0022] Figure 9 is a K-vector diagram of an optical waveguide provided in another embodiment of this application;

[0023] Figure 10 is a schematic diagram of the structure of an optical waveguide provided in another embodiment of this application;

[0024] Figure 11 is a schematic diagram of the structure of a near-eye display device provided in an embodiment of this application. Detailed Implementation

[0025] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0026] Please refer to Figure 1, which is a schematic diagram of the structure of an optical waveguide in the prior art.

[0027] In near-eye display devices equipped with an optomechanical system and an optical waveguide, the image emitted from the optomechanical system can be directionally transmitted to the eyes of the user wearing the near-eye display device via the optical waveguide, allowing the user to see the image emitted from the optomechanical system. Specifically, a coupling region 20 is formed on the optical waveguide to couple the light corresponding to the image emitted from the optomechanical system into the waveguide substrate 10, and the directional transmission of the light is achieved through total internal reflection of the waveguide substrate 10. However, as shown in Figure 1, after the light is coupled into the waveguide substrate 10 by the coupling region 20, the light propagating in the waveguide substrate 10 may re-enter the coupling region 20 and be coupled out by the coupling region 20, resulting in secondary diffraction. Secondary diffraction leads to the loss of coupled light energy, which is detrimental to improving the optical efficiency of the optical waveguide. Existing solutions include increasing the thickness of the optical waveguide in the coupling region 20, so that light rays coupled into the coupling region 20 will not re-enter the coupling region 20 after total internal reflection. However, increasing the thickness of the optical waveguide in the coupling region 20 has limitations. For example, after setting the thickness according to a preset incident angle range, light rays incident within the preset incident angle range may not re-enter the coupling region 20 after total internal reflection. However, in practical applications, due to different images to be displayed, light rays with incident angles outside the preset incident angle range may be incident. These light rays still have the risk of re-entering the coupling region 20 after entering the waveguide substrate 10. Furthermore, to prevent light rays with incident angles within a larger range from re-entering the coupling region 20, the thickness of the coupling region 20 needs to be further increased, and even the thickness of the adjacent area of ​​the coupling region 20 needs to be increased to meet the light reflection requirements. It can be seen that this solution still has the risk of secondary diffraction of light rays, and the process of solving the secondary diffraction problem will increase the weight and cost of the optical waveguide.

[0028] This application provides an optical waveguide and a near-eye display device. The optical waveguide incorporates a range extender layer, enabling light incident from the waveguide substrate at various angles to be reflected within the range extender layer. Furthermore, the incident point of the reflected light on the first surface of the optical waveguide is located outside the coupling region. This solves the problem that some light still escapes from the coupling region even when the thickness of the coupling region is increased, further reducing secondary diffraction within the coupling region and lowering the manufacturing cost and weight of the optical waveguide.

[0029] The following detailed description of some embodiments of this application is provided in conjunction with the accompanying drawings. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0030] Please refer to Figure 2, which is a schematic diagram of the structure of an optical waveguide 100 provided in an embodiment of this application.

[0031] The optical waveguide 100 includes a waveguide substrate 10, a coupling region 20, a coupling region (not shown in the figure), and a range extender layer 30. The waveguide substrate 10 includes a first surface and a second surface opposite to each other. The coupling region 20, which couples incident light into the waveguide substrate 10, is formed on the first surface of the optical waveguide 100. The coupling region, which couples light propagating in the waveguide substrate 10 out, is formed on either the first surface or the second surface. The range extender layer 30 is disposed on the second surface of the waveguide substrate 10. The refractive index of the range extender layer 30 is greater than that of air and less than that of the waveguide substrate 10. The range extender layer 30 is used to reflect light incident from the waveguide substrate 10 into the range extender layer 30. The incident point of the reflected light on the first surface is located outside the coupling region 20.

[0032] For example, diffraction microstructures are provided in the coupling-in region 20 and the coupling-out region to diffract light incident on the diffraction microstructures, thereby achieving coupling-in or coupling-out of light. Specifically, the diffraction microstructures are disposed inside the waveguide substrate 10 or outside the waveguide substrate 10.

[0033] As shown in Figure 2, after the incident light beam enters the coupling region 20, the diffraction microstructure in the coupling region 20 diffracts the incident light beam to obtain a coupled light beam, which couples the incident light beam into the waveguide substrate 10 and allows the coupled light beam to propagate in the waveguide substrate 10. During the propagation of the coupled light beam in the waveguide substrate 10, light beams that are incident at certain angles at the interface between the waveguide substrate 10 and the extension layer 30 will enter the extension layer 30. The extension layer 30 performs total internal reflection on the incident light beam, ensuring that when the reflected light beam re-enters the first surface, the incident point is located outside the coupling region, preventing the coupled light beam from re-entering the coupling region 20 and causing secondary diffraction, thus reducing the energy loss of the coupled light.

[0034] In the specific implementation process, the range extender layer 30 is a film layer made of transparent plastic material or a film layer made of glass. During the fabrication process, the range extender layer 30 is integrally formed with the waveguide substrate 10, or after the range extender layer 30 and the waveguide substrate 10 are fabricated respectively, the range extender layer 30 is bonded to the second surface of the waveguide substrate 10.

[0035] It should be noted that, in some specific embodiments, a transmission-type diffraction microstructure is provided in the coupling region 20. Incident light is incident on the diffraction microstructure in the coupling region 20 and coupled into the waveguide substrate 10 under the action of the diffraction microstructure, and then incident from the waveguide substrate 10 into the range extender layer 30. In other specific embodiments, a reflection-type diffraction microstructure is provided in the coupling region 20. After the incident light penetrates the range extender layer 30 and the waveguide substrate 10, it is incident on the reflection-type diffraction microstructure and coupled into the waveguide substrate 10 under the action of the diffraction microstructure. The diffraction microstructure on the waveguide substrate 10 includes, but is not limited to, surface relief gratings, volume holographic gratings, and meta-gratings. Specifically, the diffraction microstructure in the coupling region 20 may be the same as or different from the diffraction microstructure in the coupling region. For example, the diffraction microstructure in the coupling region 20 may be a surface relief grating, while the diffraction microstructure in the coupling region may be a meta-grating. This application does not limit the specific diffraction microstructure.

[0036] For example, after total internal reflection by the range extender layer 30, the reflected light re-enters the first surface at an incident point adjacent to the coupling region 20, but does not enter the coupling region 20. Specifically, by adjusting the thickness and refractive index of the range extender layer 30, the incident point of the reflected light on the first surface is made adjacent to the coupling region 20. It should be understood that the required thickness of the range extender layer 30 is minimized when the incident light undergoes total internal reflection at the interface between the range extender layer 30 and the outer region of the optical waveguide 100, and when the incident point of the reflected light on the first surface is adjacent to the coupling region 20, thereby reducing the thickness and weight of the optical waveguide 100.

[0037] In some embodiments, the projection of the coupling region 20 onto the waveguide substrate 10 covers the range extender layer 30, or the area of ​​the coupling region 20 is greater than or equal to that of the range extender layer 30.

[0038] In specific implementations, the projection of the coupling region 20 onto the waveguide substrate 10 completely covers the range extender layer 30. In this case, the range extender layer 30 can meet the reflection requirements while also allowing for a smaller size design, thereby reducing the weight of the optical waveguide 100. In other embodiments, the projection of the coupling region 20 onto the waveguide substrate 10 partially covers the range extender layer 30; that is, the coupling region 20 and the range extender layer 30 can be staggered. In some embodiments, the area of ​​the coupling region 20 is greater than or equal to the area of ​​the range extender layer 30.

[0039] Please refer to Figure 3, which is a K-vector diagram of the optical waveguide 100 provided in one embodiment of this application. Specifically, Figure 3 is the K-vector diagram of the optical waveguide 100 provided in Figure 2.

[0040] As shown in Figure 3, region a1 is used to indicate the incident ray, region a2 is used to indicate the coupled ray corresponding to the incident ray, and Kg is the grating vector of the grating set in the coupled region 20, with a length of λ is the wavelength of the incident light, Λ is the period of the grating set in the coupling region 20, na indicates the refractive index of the space where the incident light is located, ng indicates the refractive index of the waveguide substrate 10, and ne indicates the refractive index of the extension layer 30. This ensures that region a2 is entirely located within the annulus between the circle with radius na and the circle with radius ne. Therefore, the light indicated by region a2 can be entirely incident within the extension layer 30 for reflection, thereby increasing the lateral propagation period. This ensures that when the reflected light re-incidentally reaches the first surface, the incident point is outside the coupling region 20.

[0041] Taking Figure 2 as an example, D represents the maximum distance between any two opposite boundaries of the diffraction microstructure in the coupling region 20. If the incident point of the reflected light that is incident on the first surface is to be located outside the coupling region 20, then d≥D must be satisfied. Here, d is used to indicate the propagation period of the coupled light after being expanded by the extension layer 30. d is determined by the distance between the incident point of the coupled light on the first surface and the incident point of the light that is incident on the first surface again. In the specific implementation process, after the incident light rays are incident on the diffraction microstructure of the coupling region 20, they are coupled into the waveguide substrate 10 and propagate under the diffraction effect of the diffraction microstructure. In the scenario indicated by the K vector diagram in Figure 2, all the coupled light rays that are coupled into the waveguide substrate 10 can penetrate the waveguide substrate 10 and be incident into the extension layer 30 and reflected in the extension layer 30. When the light rays pass through the total internal reflection of the extension layer 30 and are incident again on the first surface of the waveguide substrate 10, the incident point is outside the coupling region 20. Based on this geometric relationship, the thickness and refractive index of the extension layer 30 can be determined according to the minimum incident angle when the coupled light rays are incident into the extension layer 30 indicated by region a2 and the maximum distance D of the diffraction microstructure.

[0042] It should be understood that since the refractive index of the extension layer 30 is less than that of the waveguide substrate 10, the coupled light will be refracted after it is incident from the waveguide substrate 10 to the extension layer 30, and the refracted light will deflect to the right (as shown in Figure 2). The reflection angle of the light increases, so the light will be reflected further. Therefore, by fabricating a thinner extension layer 30, the lateral propagation period of the coupled light can be increased significantly, thereby reducing the weight of the optical waveguide 100.

[0043] Please refer to Figure 4, which is a schematic diagram of the structure of an optical waveguide 100 provided in another embodiment of this application.

[0044] In some embodiments, the incident light includes incident light with an incident angle less than or equal to a first preset angle and incident light with an incident angle greater than the first preset angle; the incident light with an incident angle less than or equal to the first preset angle can penetrate the waveguide substrate 10 and be incident into the range extender layer 30, and the incident point of the light reflected by the range extender layer 30 on the first surface is located outside the coupling region 20; the incident light with an incident angle greater than the first preset angle is reflected at the interface between the waveguide substrate 10 and the range extender layer 30, and the incident point of the reflected light on the first surface is located outside the coupling region 20.

[0045] For example, since the light incident on the coupling region 20 is not just a single beam incident at a fixed angle, or the incident angle of the light is adjusted when it is incident on the coupling region 20, in practical applications, the coupling region 20 needs to diffract the light incident at multiple angles. Specifically, after the incident light with an incident angle less than or equal to a first preset angle is coupled into the waveguide substrate 10, the corresponding coupled light fails to meet the total internal reflection condition at the interface between the waveguide substrate 10 and the extension layer 30. Therefore, the coupled light will be incident into the extension layer 30 and reflected by the extension layer 30. In specific implementation, the light incident into the extension layer 30 is reflected within the extension layer 30, or is totally internally reflected at the interface between the extension layer 30 and the outside of the optical waveguide 100. It should be understood that adopting a scheme in which the light incident into the extension layer 30 undergoes total internal reflection can reduce the thickness of the extension layer 30 or reduce the refractive index of the extension layer 30, thereby reducing the cost of fabricating the extension layer 30.

[0046] In Figure 4, dashed lines represent incident rays with an incident angle greater than the first preset angle, and solid lines represent incident rays with an incident angle less than or equal to the first preset angle. As shown in Figure 4, after incident rays with an incident angle greater than the first preset angle are coupled into the waveguide substrate 10, the corresponding coupled rays satisfy the total internal reflection condition at the interface between the waveguide substrate 10 and the extension layer 30, resulting in total internal reflection at the interface between the waveguide substrate 10 and the extension layer 30, and the incident point of the reflected rays on the first surface is located outside the coupling region 20. Coupled rays with an incident angle less than or equal to the first preset angle are incident into the extension layer 30 and reflected within the extension layer 30.

[0047] Please refer to Figure 5, which is a K-vector diagram of the optical waveguide 100 provided in another embodiment of this application. Specifically, Figure 5 is the K-vector diagram of the optical waveguide 100 provided in Figure 4.

[0048] As shown in Figure 5, region a1 is used to indicate the incident light, region a2 is used to indicate the coupled light corresponding to the incident light, Kg is the grating vector of the grating set in the coupled region 20, na is used to indicate the refractive index of the space where the incident light is located, ng is used to indicate the refractive index of the waveguide substrate 10, and ne is used to indicate the refractive index of the extension layer 30. This makes region a2 partially located in the annulus between the circle with radius na and the circle with radius ne, and another part of region a2 located in the annulus between the circle with radius ne and the circle with radius ng. As a result, only a portion of the coupled light corresponding to region a2 can be incident into the extension layer 30, while the rest undergoes total internal reflection at the interface between the waveguide substrate 10 and the extension layer 30 and cannot enter the extension layer 30.

[0049] For example, the first preset angle is determined by at least one of the optical parameters of the diffraction microstructure in the coupling region 20, the refractive index of the waveguide substrate 10, or the refractive index of the extension layer 30, or after the first preset angle is preset, at least one of the optical parameters of the diffraction microstructure, the refractive index of the waveguide substrate 10, or the refractive index of the extension layer 30 is adjusted accordingly.

[0050] It should be understood that after the incident light is coupled into the waveguide substrate 10, the reflection angle of some of the coupled light is large enough that the incident point of the reflected light when it is re-incident on the first surface is outside the coupling region 20. By adjusting the refractive index, size and / or thickness of the extension layer 30, this part of the coupled light does not need to be incident into the extension layer 30, and the coupled light that does not meet the above conditions can be incident into the extension layer 30 for reflection. Based on the above light reflection requirements and reflection conditions, the size and thickness of the extension layer 30 can be designed in a targeted manner, and excessive stray light can be avoided.

[0051] In some embodiments, the refractive index is the same at any two locations within the range extender layer 30.

[0052] It should be noted that in the above embodiments, the refractive index within the range extender layer 30 is isotropic, so that light will not be refracted or scattered within the range extender layer 30, simplifying the design of the optical path in the optical waveguide 100.

[0053] Please refer to Figure 6, which is a schematic diagram of the structure of an optical waveguide 100 provided in another embodiment of this application.

[0054] In some embodiments, the incident light also includes incident light with an incident angle less than or equal to a second preset angle, wherein the second preset angle is less than a first preset angle; the range extender layer 30 includes at least a first sub-layer 31 and a second sub-layer 32, wherein the first sub-layer 31 and the second sub-layer 32 are stacked; the coupled light corresponding to the incident light with an incident angle less than or equal to the first preset angle and greater than the second preset angle is incident on the first sub-layer 31 and reflected within the first sub-layer 31; the coupled light corresponding to the incident light with an incident angle less than or equal to the second preset angle penetrates the first sub-layer 31 and is incident on the second sub-layer 32, and reflected within the second sub-layer 32; wherein the incident points of the light reflected in the first sub-layer 31 and the light reflected in the second sub-layer 32 on the first surface are both located outside the coupled region 20.

[0055] For example, the range extender layer 30 includes at least a first sublayer 31 and a second sublayer 32. The first sublayer 31 and the second sublayer 32 can meet the reflection requirements of different light rays, so that incident light rays that can be incident on the optical waveguide 100 at any angle and / or position will not undergo secondary diffraction in the coupling region 20, thereby reducing the energy loss of the coupled light and improving the optical efficiency of the optical waveguide 100.

[0056] In the specific implementation process, the incident light rays with an incident angle less than or equal to the first preset angle and greater than the second preset angle can be incident on the first sub-layer 31 during the propagation of the waveguide substrate 10, and undergo total internal reflection within the first sub-layer 31 or at the interface between the first sub-layer 31 and the second sub-layer 32. The incident light rays with an incident angle less than or equal to the second preset angle will also be incident on the first sub-layer 31 during the propagation of the waveguide substrate 10. If the incident angle of these incident light rays does not meet the total internal reflection condition corresponding to the first sub-layer 31, they will continue to be incident on the second sub-layer 32, and undergo total internal reflection within the second sub-layer 32 or at the interface between the second sub-layer 32 and the outer region of the optical waveguide 100. It should be understood that the incident points of the light rays reflected from the first sub-layer 31 and the second sub-layer 32 when they re-incidentally strike the first surface are all located outside the coupling region 20, in order to avoid secondary diffraction in the coupling region 20.

[0057] Based on the propagation angle of the coupled light in different ranges, corresponding sub-layers are set in the range extender layer 30, which can optimize the size and thickness of each sub-layer in a targeted manner and reduce light crosstalk and stray light.

[0058] In one embodiment, the refractive index is the same at any two locations within the first sublayer 31, and the refractive index is the same at any two locations within the second sublayer 32, and the refractive index of the first sublayer 31 is greater than the refractive index of the second sublayer 32.

[0059] It should be noted that the refractive indexes in the first sublayer 31 and the second sublayer 32 are isotropic, so as to avoid reducing the refraction or scattering of light during the propagation of light in the first sublayer 31 and / or the second sublayer 32, and to avoid the loss of light energy.

[0060] Please refer to Figure 7, which is a K-vector diagram of the optical waveguide 100 provided in another embodiment of this application. Specifically, Figure 7 is the K-vector diagram of the optical waveguide 100 provided in Figure 6.

[0061] The working principle of the optical waveguide 100 is explained below with reference to Figure 7. Region a1 is used to indicate incident rays at all incident angles, region a2 is used to indicate the coupled rays corresponding to the incident rays, Kg is the grating vector of the grating set in the coupling region 20, na is used to indicate the refractive index of the space where the incident rays are located, ng is used to indicate the refractive index of the waveguide substrate 10, ne1 is used to indicate the refractive index of the first sublayer 31, and ne2 is used to indicate the refractive index of the second sublayer 32. In Figure 7, the circles with the refractive index of the first sublayer 31 and the circles with the refractive index of the second sublayer 32 both intersect region a2, so that coupled rays with different propagation angles in region a2 can selectively enter different sublayers for reflection. Specifically, the coupled light rays corresponding to the portion of region a2 within the annulus formed by the circles with radii ne2 and na can propagate from the waveguide substrate 10 through the first sublayer 31 to the second sublayer 32, and undergo total internal reflection within the second sublayer 32 or at the interface between the second sublayer 32 and the outer region of the optical waveguide 100. The coupled light rays corresponding to the portion of region a2 within the annulus formed by the circles with radii ne2 and n1 can propagate from the waveguide substrate 10 to the first sublayer 31, and undergo total internal reflection within the first sublayer 31 or at the interface between the first sublayer 31 and the second sublayer 32. The coupled light rays corresponding to the portion of region a2 within the annulus formed by the circles with radii ne1 and ng only propagate within the waveguide substrate 10 and do not propagate to the first sublayer 31 or the second sublayer 32. In practical implementation, the K-vector diagram corresponding to the optical waveguide 100 provides a theoretical basis for the design of the waveguide substrate 10, the first sublayer 31, and the second sublayer 32.

[0062] In some embodiments, the number of sublayers in the range extender layer 30 is positively correlated with the number of incident angles corresponding to the incident light rays.

[0063] By setting multiple sub-layers in the range extender layer 30, the reflection requirements of incident light at different incident angles can be met. Specifically, the larger the range of incident angles corresponding to the incident light, the more sub-layers are set.

[0064] It should be noted that this application does not limit the number of sublayers corresponding to a specific incident angle range. The number of sublayers can be set according to the actual use of the optical waveguide 100 to meet the different usage requirements of different optical waveguides 100.

[0065] Please refer to Figure 8, which is a schematic diagram of the structure of an optical waveguide 100 provided in another embodiment of this application.

[0066] In some embodiments, the refractive index within the range extender layer 30 increases or decreases in a direction perpendicular to the first surface, so that light incident on the waveguide substrate 10 at different incident angles into the range extender layer 30 is reflected at different reflection points within the range extender layer 30, wherein the distance between each reflection point and the waveguide substrate 10 is not equal.

[0067] As shown in Figure 8, because the refractive index within the range extender layer 30 increases or decreases in the direction perpendicular to the first surface, light rays incident at different incident angles into the range extender layer 30 can undergo total internal reflection at different positions within the range extender layer 30, and the distance between the reflection position corresponding to each incident angle and the waveguide substrate 10 is different. By setting the range extender layer 30 with a changing refractive index within a single layer, total internal reflection of light rays at different incident angles can also be achieved, thereby reducing the number of sublayers in the range extender layer 30 and / or simplifying the fabrication process of the range extender layer 30.

[0068] In some embodiments, the refractive index within the range extender layer 30 gradually decreases in the direction away from the waveguide substrate 10.

[0069] For example, by setting the refractive index in the range extender layer 30 to gradually decrease in the direction away from the waveguide substrate 10, the coupled light corresponding to the incident light at a smaller incident angle can be totally internally reflected at a position in the range extender layer 30 that is further away from the waveguide substrate 10 when it is incident on the range extender layer 30 through the waveguide substrate 10. This results in a greater increase in the propagation period of the light, so that when the coupled light incident at each angle is reflected by the range extender layer 30 and then incident on the first surface again, the incident point is located outside the coupling region 20.

[0070] Please refer to Figure 9, which is a K-vector diagram of the optical waveguide 100 provided in another embodiment of this application. Specifically, Figure 9 is the K-vector diagram of the optical waveguide 100 provided in Figure 8.

[0071] The operation of the optical waveguide 100 is explained below with reference to Figure 9. Region a1 is used to indicate incident rays at all incident angles, region a2 is used to indicate the coupled rays corresponding to the incident rays, Kg is the grating vector of the grating set in the coupling region 20, na is used to indicate the refractive index of the space where the incident rays are located, ng is used to indicate the refractive index of the waveguide substrate 10, ne1 is the refractive index of the extension layer 30 on the side close to the waveguide substrate 10, and nen is the refractive index of the extension layer 30 on the side away from the waveguide substrate 10. In Figure 9, the refractive index of the extension layer 30 is represented by a ring, and the ring intersects with region a2. Different intersection points between region a2 and the ring indicate that the rays at the incident angles corresponding to region a2 undergo total internal reflection at different positions of the extension layer 30.

[0072] Please refer to Figure 10, which is a schematic diagram of the structure of an optical waveguide 100 provided in another embodiment of this application.

[0073] In some embodiments, the range extender layer 30 includes at least a first sublayer 31 and a second sublayer 32. Light incident on the range extender layer 30 includes light incident at a first angle, light incident at a second angle, and light incident at a third angle, all of which are different. The reflection points of the light incident at the first angle and the light incident at the second angle in the first sublayer 31 are both located within the first sublayer 31, and both reflection points are located within the waveguide substrate 1. The distance is different. The light rays incident at the third angle penetrate the first sub-layer 31 and enter the second sub-layer 32, and are reflected in the second sub-layer 32; or the reflection point of the light rays incident at the first angle in the first sub-layer 31 is located in the first sub-layer 31, and the reflection point of the light rays incident at the second angle in the first sub-layer 31 is located at the interface between the first sub-layer 31 and the second sub-layer 32, and the light rays incident at the third angle penetrate the first sub-layer 31 and enter the second sub-layer 32, and are reflected in the second sub-layer 32.

[0074] As shown in Figure 10, the range extender layer 30 includes at least a first sublayer 31 and a second sublayer 32 stacked together. The first sublayer 31 is located between the second sublayer 32 and the waveguide substrate 10, and the refractive index in the first sublayer 31 and the second sublayer 32 increases or decreases in the direction perpendicular to the first surface. Specifically, it gradually decreases in the direction away from the waveguide substrate 10.

[0075] The first sub-layer 31 can reflect incident rays with incident angles less than or equal to a first preset angle and greater than a second preset angle. Both the first and second angles are within the angle range between the first and second preset angles. Therefore, incident rays at the first and second angles that reach the range extender layer 30 can all enter the first sub-layer 31 and undergo total internal reflection within it. However, due to different incident angles, the reflection points within the first sub-layer 31 are also different. Rays with larger incident angles have a greater distance between their reflection points and the reflection points within the first sub-layer 31. The closer to the waveguide substrate 10, the more likely light rays incident at the second angle to the first sub-layer 31 will undergo total internal reflection at the interface between the first sub-layer 31 and the second sub-layer 32 in some cases. The second sub-layer 32 can reflect the coupled light rays corresponding to incident light rays with an incident angle less than or equal to the second preset angle, and the third angle is less than or equal to the second preset angle. Therefore, light rays incident at the third angle to the first sub-layer 31 can penetrate the first sub-layer 31 and enter the second sub-layer 32, so as to undergo total internal reflection in the second sub-layer 32 or at the interface between the second sub-layer 32 and the air.

[0076] It should be noted that the first angle and the second angle are two angles within the incident angle range (less than or equal to the first preset angle and greater than the second preset angle) corresponding to the coupled light rays that can be incident on the first sub-layer 31 and reflected within the first sub-layer 31. Incident at other angles within this incident angle range can also achieve the same effect as incident at the first angle and the second angle. Similarly, the third angle is an angle within the incident angle range (less than or equal to the second preset angle) corresponding to the coupled light rays that can be incident on the second sub-layer 32 and reflected within the second sub-layer 32. Incident at other angles within this incident angle range can also achieve the same effect as incident at the third angle. This application does not limit the specific angle.

[0077] It should be understood that by setting multiple sub-layers and setting increasing or decreasing refractive indices within each sub-layer, the reflection requirements of light with a wider range of incident angles can be met, and the thickness and size of the extension layer 30 can be reduced, thereby reducing the weight of the optical waveguide 100.

[0078] The optical waveguide 100 provided in the above embodiments solves the problem of secondary diffraction of coupled light in the coupling region 20 of the optical waveguide 100 by setting an extension layer 30. It should be understood that when it is necessary to meet the reflection of light with a wider range of incident angles, this application sets multiple sub-layers with different refractive indices in the extension layer 30 or sets the extension layer 30 to increase or decrease the refractive index to meet the total internal reflection of light with more different incident angles. This achieves the reflection of light with various incident angles to avoid secondary diffraction of light with different incident angles in the coupling region 20, reduces the loss of coupled light energy, improves the optical efficiency of the optical waveguide 100, and the extension layer 30 can also reduce the thickness and manufacturing cost of the optical waveguide 100 that solves the secondary diffraction problem.

[0079] It should be noted that the optical paths in the structural diagrams corresponding to the optical waveguide 100 provided in the above embodiments are all illustrative drawings. The actual optical paths are determined based on the actual optical parameters of the optical waveguide 100 and are not limited here.

[0080] Please refer to Figure 11, which is a schematic diagram of the structure of a near-eye display device provided in an embodiment of this application.

[0081] As shown in Figure 11, the near-eye display device includes at least an optical engine and an optical waveguide as provided in the above embodiments. The optical engine transmits signal light to a coupling region on the optical waveguide. The coupling region couples the signal light to the waveguide substrate to obtain a corresponding coupled ray. The coupled ray does not undergo secondary diffraction in the coupling region during its propagation on the waveguide substrate, thus ensuring the coupled light energy and improving the optical efficiency of the optical waveguide. The coupled ray propagates on the waveguide substrate to the coupling region and is coupled out in the coupling region, so that the user wearing the near-eye display device can view the image corresponding to the signal light emitted from the optical engine, thereby realizing the directional transmission of light.

[0082] It should be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the scope of the application. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0083] It should also be understood that the term "and / or" as used in this specification and the appended claims refers to any combination and all possible combinations of one or more of the associated listed items, and includes such combinations. It should be noted that, herein, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or system that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or system. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or system that includes that element.

[0084] The sequence numbers of the embodiments in this application are for descriptive purposes only and do not represent the superiority or inferiority of the embodiments. The above descriptions are merely specific implementations of this application, but the scope of protection of this application is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in this application, and these modifications or substitutions should all be covered within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. An optical waveguide, wherein, The optical waveguide includes: Waveguide substrate, comprising opposing first and second surfaces; A coupling region is formed on the first surface of the waveguide substrate, the coupling region being used to couple incident light rays into the waveguide substrate; A coupling region is formed on a first or second surface of the waveguide substrate, the coupling region being used to couple out light propagating in the waveguide substrate; An extension layer is disposed on the second surface of the waveguide substrate. The refractive index of the extension layer is greater than that of air and less than that of the waveguide substrate. The extension layer is used to reflect light incident from the waveguide substrate into the extension layer. The incident point of the reflected light on the first surface is located outside the coupling region.

2. The optical waveguide as described in claim 1, wherein, The incident light includes incident light with an incident angle less than or equal to a first preset angle and incident light with an incident angle greater than the first preset angle; The incident light rays with an incident angle less than or equal to the first preset angle can penetrate the waveguide substrate and be incident into the range extender layer, and the incident point of the light rays reflected by the range extender layer on the first surface is located outside the coupling region. The incident light rays with an incident angle greater than the first preset angle are reflected at the interface between the waveguide substrate and the range extender layer, and the incident point of the reflected light rays on the first surface is located outside the coupling region.

3. The optical waveguide as described in claim 1 or 2, wherein, The incident light also includes incident light with an incident angle less than or equal to a second preset angle, wherein the second preset angle is less than a first preset angle; The range extender layer includes at least a first sub-layer and a second sub-layer, wherein the first sub-layer and the second sub-layer are stacked together; The incident light rays with an incident angle less than or equal to the first preset angle and greater than the second preset angle are incident on the first sub-layer and reflected within the first sub-layer. The incident light rays with an incident angle less than or equal to the second preset angle penetrate the first sub-layer and are incident into the second sub-layer, and are reflected within the second sub-layer; wherein, the incident points of the light rays reflected in the first sub-layer and the light rays reflected in the second sub-layer on the first surface are both located outside the coupling region.

4. The optical waveguide as described in claim 3, wherein, The number of sublayers in the range extender layer is positively correlated with the number of incident angles corresponding to the incident light rays.

5. The optical waveguide as described in claim 3, wherein, Within the first sublayer, the refractive index is the same at any two locations, and within the second sublayer, the refractive index is the same at any two locations, and the refractive index of the first sublayer is greater than that of the second sublayer.

6. The optical waveguide as described in claim 3, wherein, The incident light rays with an incident angle less than or equal to the first preset angle and greater than the second preset angle are incident on the first sub-layer and are totally reflected in the first sub-layer or totally reflected at the interface between the first sub-layer and the second sub-layer. The incident light rays with an incident angle less than or equal to the second preset angle penetrate the first sub-layer and are incident into the second sub-layer, and are totally reflected in the second sub-layer or at the interface between the second sub-layer and the outer region of the optical waveguide.

7. The optical waveguide as described in claim 1 or 2, wherein, Within the range extender layer, the refractive index is the same at any two locations.

8. The optical waveguide as described in claim 1, wherein, The refractive index within the range extender increases or decreases in a direction perpendicular to the first surface, so that light incident at different incident angles into the range extender in the waveguide substrate is reflected at different reflection points within the range extender, wherein the distances between each reflection point and the waveguide substrate are not equal.

9. The optical waveguide as described in claim 8, wherein, The refractive index within the range extender layer gradually decreases in the direction away from the waveguide substrate.

10. The optical waveguide as claimed in claim 8, wherein, The range extender layer includes at least a first sublayer and a second sublayer, and the light incident on the range extender layer includes at least light incident at a first angle, light incident at a second angle, and light incident at a third angle, wherein the first angle, the second angle, and the third angle are all different. Wherein, the reflection points of the light rays incident at the first angle and the light rays incident at the second angle in the first sub-layer are both located within the first sub-layer, and the two reflection points are at different distances from the waveguide substrate. The light rays incident at the third angle penetrate the first sub-layer and enter the second sub-layer, where they are reflected; or The reflection point of the light incident at the first angle in the first sub-layer is located within the first sub-layer, the reflection point of the light incident at the second angle in the first sub-layer is located at the interface between the first sub-layer and the second sub-layer, and the light incident at the third angle penetrates the first sub-layer and enters the second sub-layer, and is reflected within the second sub-layer.

11. The optical waveguide as claimed in claim 10, wherein, The first angle and the second angle are two angles within the incident angle range corresponding to the coupled light rays that can be incident on the first sub-layer and reflected within the first sub-layer; The third angle is an angle within the incident angle range corresponding to the coupled light rays that can be incident on the second sub-layer and reflected within the second sub-layer.

12. The optical waveguide as claimed in claim 11, wherein, Both the first angle and the second angle are within the angle range between the first preset angle and the second preset angle, and the third angle is less than or equal to the second preset angle.

13. The optical waveguide as described in claim 1 or 2, wherein, The projection of the coupling region onto the waveguide substrate covers the range extender layer, or the area of ​​the coupling region is greater than or equal to the area of ​​the range extender layer.

14. The optical waveguide as claimed in claim 13, wherein, The projection of the coupling region in the direction of the waveguide substrate completely covers the range extender layer, or the projection of the coupling region in the direction of the waveguide substrate covers part of the range extender layer.

15. The optical waveguide as described in claim 1 or 2, wherein, The thickness and refractive index of the range extender layer are determined based on the minimum incident angle of the incident ray when the coupled ray is incident on the range extender layer and the maximum distance of the diffraction microstructure in the coupled region.

16. The optical waveguide as claimed in claim 2, wherein, The first preset angle is determined by at least one of the optical parameters of the diffraction microstructure in the coupling region, the refractive index of the waveguide substrate, and the refractive index of the range extender layer.

17. The optical waveguide as claimed in claim 2, wherein, After setting the first preset angle, at least one of the optical parameters of the diffraction microstructure in the coupling region, the refractive index of the waveguide substrate, and the refractive index of the range extender layer is adjusted accordingly.

18. The optical waveguide as described in claim 1 or 2, wherein, The coupling region is provided with a diffraction microstructure to diffract the light incident on the diffraction microstructure, thereby achieving the coupling of the light. The coupling region is provided with a diffraction microstructure to diffract the light incident on the diffraction microstructure, thereby achieving the coupling out of the light. The diffraction microstructure is disposed inside the waveguide substrate or outside the waveguide substrate.

19. The optical waveguide as claimed in claim 18, wherein, The diffraction microstructure in the coupling region may be the same as or different from the diffraction microstructure in the coupling region.

20. A near-eye display device, wherein, The near-eye display device includes at least an optical engine and an optical waveguide as described in any one of claims 1-19, wherein the optical engine is used to emit signal light and the optical waveguide is used to directionally transmit the signal light to the human eye.

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