Optical waveguide and near-eye display device
By setting a range-extending layer on the surface of the optical waveguide substrate to reflect light, the problem of secondary diffraction in the coupling region of the optical waveguide is solved, improving optical efficiency and reducing cost and weight.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2024-08-28
- Publication Date
- 2026-03-17
AI Technical Summary
Even after increasing the thickness of the coupling region, existing optical waveguides still suffer from secondary diffraction of light, resulting in light energy loss and increased manufacturing costs and weight.
An extension layer is placed on the substrate surface of the optical waveguide. The refractive index of the extension layer is between that of air and the substrate. It reflects light so that it is incident outside the coupling region, thus avoiding secondary diffraction.
This reduces secondary diffraction in the optical waveguide, improves optical efficiency, and lowers manufacturing costs and weight.
Smart Images
Figure CN118962887B_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of optical technology, and in particular to an optical waveguide and near-eye display device. Background Technology
[0002] 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.
[0003] 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
[0004] 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.
[0005] In a first aspect, this application provides an optical waveguide, comprising:
[0006] Waveguide substrate, comprising opposing first and second surfaces;
[0007] 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;
[0008] 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;
[0009] 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.
[0010] 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.
[0011] 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
[0012] 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.
[0013] Figure 1 This is a schematic diagram of the structure of an optical waveguide in the prior art;
[0014] Figure 2 This is a schematic diagram of the structure of an optical waveguide provided in an embodiment of this application;
[0015] Figure 3 A K-vector diagram of an optical waveguide provided in one embodiment of this application;
[0016] Figure 4 This is a schematic diagram of the structure of an optical waveguide provided in another embodiment of this application;
[0017] Figure 5 This is a K-vector diagram corresponding to an optical waveguide provided in another embodiment of this application;
[0018] Figure 6 This is a schematic diagram of the structure of an optical waveguide provided in another embodiment of this application;
[0019] Figure 7 This is a K-vector diagram corresponding to an optical waveguide provided in another embodiment of this application;
[0020] Figure 8 This is a schematic diagram of the structure of an optical waveguide provided in another embodiment of this application;
[0021] Figure 9 This is a K-vector diagram corresponding to an optical waveguide provided in another embodiment of this application;
[0022] Figure 10 This is a schematic diagram of the structure of an optical waveguide provided in another embodiment of this application;
[0023] Figure 11 This is a schematic diagram of the structure of a near-eye display device provided in an embodiment of this application. Detailed Implementation
[0024] 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.
[0025] Please see Figure 1 , Figure 1 This is a schematic diagram of the structure of an optical waveguide in the prior art.
[0026] In a near-eye display device 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 rays corresponding to the image emitted from the optomechanical system into the waveguide substrate 10, and the directional transmission of the light rays is achieved through total internal reflection of the waveguide substrate 10. However, if... Figure 1As shown, after the light is coupled into the waveguide substrate 10 in the coupling region 20, the light propagating in the waveguide substrate 10 may be incident on the coupling region 20 again and 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 waveguide efficiency. 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.
[0027] 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.
[0028] 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.
[0029] Please see Figure 2 , Figure 2 This is a schematic diagram of the structure of an optical waveguide 100 provided in an embodiment of this application.
[0030] 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.
[0031] 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.
[0032] like Figure 2 As shown, after the incident light enters the coupling region 20, the diffraction microstructure in the coupling region 20 diffracts the incident light to obtain coupled light, which couples the incident light into the waveguide substrate 10 and allows the coupled light to propagate in the waveguide substrate 10. During the propagation of the coupled light in the waveguide substrate 10, light rays 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, so that when the reflected light re-enters the first surface, the incident point is located outside the coupling region, avoiding the coupled light from re-entering the coupling region 20 and undergoing secondary diffraction, thus reducing the energy loss of the coupled light.
[0033] 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.
[0034] 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.
[0035] 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.
[0036] 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.
[0037] 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.
[0038] Please see Figure 3 , Figure 3 This is a K-vector diagram corresponding to the optical waveguide 100 provided in one embodiment of this application. Specifically, Figure 3 for Figure 2 The provided K-vector diagram for optical waveguide 100.
[0039] like Figure 3As shown, 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 coupling 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.
[0040] by Figure 2 For example, let D characterize 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 re-entering the first surface is located outside the coupling region 20, then d ≥ D must be satisfied. Here, d indicates the propagation period of the coupled light after being amplified by the range extender layer 30, and d is determined by the distance between the incident point of the coupled light on the first surface and the incident point re-entering the first surface. In specific implementation, after the incident light enters the diffraction microstructure of the coupling region 20, it is coupled into the waveguide substrate 10 and propagates under the diffraction effect of the diffraction microstructure. Figure 2 In the scenario indicated by the K vector diagram, all coupled light rays to the waveguide substrate 10 can penetrate the waveguide substrate 10 and be incident on the extension layer 30 and reflected within the extension layer 30. When the light rays pass through the extension layer 30 and are incident on the first surface of the waveguide substrate 10 again, 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 on the extension layer 30 as indicated by region a2 and the maximum distance D of the diffraction microstructure.
[0041] 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 rays will be refracted after entering the extension layer 30 from the waveguide substrate 10, and the refracted light rays will deflect to the right (e.g., Figure 2 As shown, the reflection angle of the light increases, so the light will be reflected further. Therefore, by fabricating a thinner range extender layer 30, the lateral propagation period of the coupled light can be increased significantly, thereby reducing the weight of the optical waveguide 100.
[0042] Please see Figure 4 , Figure 4 This is a schematic diagram of the structure of an optical waveguide 100 provided in another embodiment of this application.
[0043] 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.
[0044] 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.
[0045] exist Figure 4 In the diagram, 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. For example... Figure 4 As shown, incident light rays with an incident angle greater than the first preset angle, after being coupled into the waveguide substrate 10, satisfy the total internal reflection condition at the interface between the waveguide substrate 10 and the extension layer 30, thus achieving total internal reflection at the interface between the waveguide substrate 10 and the extension layer 30, and the incident point of the reflected light on the first surface is located outside the coupling region 20. Meanwhile, incident light rays with an incident angle less than or equal to the first preset angle will be incident into the extension layer 30 and reflected within the extension layer 30.
[0046] Please see Figure 5 , Figure 5 This is a K-vector diagram corresponding to the optical waveguide 100 provided in another embodiment of this application. Specifically, Figure 5 for Figure 4 The provided K-vector diagram for optical waveguide 100.
[0047] like Figure 5As shown, 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. This ensures that 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.
[0048] 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.
[0049] 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.
[0050] In some embodiments, the refractive index is the same at any two locations within the range extender layer 30.
[0051] 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.
[0052] Please see Figure 6 , Figure 6 This is a schematic diagram of the structure of an optical waveguide 100 provided in another embodiment of this application.
[0053] 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.
[0054] 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.
[0055] 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.
[0056] 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.
[0057] 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.
[0058] 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.
[0059] Please see Figure 7 , Figure 7 This is a K-vector diagram corresponding to the optical waveguide 100 provided in another embodiment of this application. Specifically, Figure 7 for Figure 6 The provided K-vector diagram of optical waveguide 100.
[0060] The following text combines Figure 7 The working principle of the optical waveguide 100 is explained. 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. Figure 7 In this process, circles with the refractive index of the first sublayer 31 and the refractive index of the second sublayer 32 both intersect region a2, allowing coupled rays with different propagation angles in region a2 to 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.
[0061] 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.
[0062] 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.
[0063] 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.
[0064] Please see Figure 8 , Figure 8 This is a schematic diagram of the structure of an optical waveguide 100 provided in another embodiment of this application.
[0065] 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.
[0066] like Figure 8 As shown, because the refractive index within the range extender layer 30 increases or decreases in the direction perpendicular to the first surface, light 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 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.
[0067] In some embodiments, the refractive index within the range extender layer 30 gradually decreases in the direction away from the waveguide substrate 10.
[0068] 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.
[0069] Please see Figure 9 , Figure 9 This is a K-vector diagram corresponding to the optical waveguide 100 provided in another embodiment of this application. Specifically, Figure 9 for Figure 8 The provided K-vector diagram for optical waveguide 100.
[0070] The following text combines Figure 9The operation of the optical waveguide 100 is explained. Region a1 indicates incident rays at all incident angles, region a2 indicates the coupled rays corresponding to the incident rays, Kg is the grating vector of the grating set in the coupling region 20, na indicates the refractive index of the space where the incident rays are located, ng indicates the refractive index of the waveguide substrate 10, ne1 is the refractive index of the extension layer 30 near the waveguide substrate 10, and nen is the refractive index of the extension layer 30 away from the waveguide substrate 10; Figure 9 In the process, the refractive index of the extension layer 30 is represented by a ring, and the ring intersects with region a2. At different intersection points between region a2 and the ring, the light rays with the corresponding incident angle in region a2 undergo total internal reflection at different positions of the extension layer 30.
[0071] Please see Figure 10 , Figure 10 This is a schematic diagram of the structure of an optical waveguide 100 provided in another embodiment of this application.
[0072] 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.
[0073] like Figure 10 As shown, 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.
[0074] 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.
[0075] 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.
[0076] 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.
[0077] 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.
[0078] 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.
[0079] Please see Figure 11 , Figure 11 This is a schematic diagram of the structure of a near-eye display device provided in an embodiment of this application.
[0080] like Figure 11 As shown, 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.
[0081] 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.
[0082] 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.
[0083] 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, characterized by, The optical waveguide comprises: a waveguide substrate comprising opposite first and second surfaces; a coupling-in region formed on the first surface of the waveguide substrate, the coupling-in region being configured to couple an incident light ray into the waveguide substrate; a coupling-out region formed on the first or second surface of the waveguide substrate, the coupling-out region being configured to couple a light ray propagating in the waveguide substrate out of the waveguide substrate; a range-extending layer disposed on the second surface of the waveguide substrate, the range-extending layer having a refractive index greater than that of air and less than that of the waveguide substrate, the range-extending layer being configured to reflect a light ray incident from the waveguide substrate into the range-extending layer, the reflected light ray being incident on the first surface at a point outside the coupling-in region; the incident light rays comprise incident light rays having an incident angle less than or equal to a first preset angle and incident light rays having an incident angle greater than the first preset angle; the coupling-in light ray corresponding to the incident light ray having an incident angle less than or equal to the first preset angle is capable of penetrating the waveguide substrate and being incident into the range-extending layer, and the light ray reflected by the range-extending layer is incident on the first surface at a point outside the coupling-in region; the coupling-in light ray corresponding to the incident light ray having an incident angle greater than the first preset angle is reflected at the interface between the waveguide substrate and the range-extending layer, and the reflected light ray is incident on the first surface at a point outside the coupling-in region.
2. The optical waveguide of claim 1, wherein, The incident light rays further comprise incident light rays having an incident angle less than or equal to a second preset angle, wherein the second preset angle is less than the first preset angle; the range-extending layer comprises at least a first sub-layer and a second sub-layer, the first sub-layer and the second sub-layer being disposed in a stack; the coupling-in light ray corresponding to the incident light ray having an incident angle less than or equal to the first preset angle and greater than the second preset angle is incident into the first sub-layer and is reflected in the first sub-layer; the coupling-in light ray corresponding to the incident light ray having an incident angle less than or equal to the second preset angle penetrates the first sub-layer and is incident into the second sub-layer and is reflected in the second sub-layer; wherein the incident points on the first surface of the light rays reflected in the first sub-layer and the light rays reflected in the second sub-layer are both outside the coupling-in region.
3. The optical waveguide of claim 2, wherein, The number of sub-layers in the range-extending layer is positively correlated with the number of incident angles of the incident light rays.
4. The optical waveguide of claim 2, wherein, In the first sub-layer, the refractive index at any two positions is the same, and in the second sub-layer, the refractive index at any two positions is the same, and the refractive index of the first sub-layer is greater than that of the second sub-layer.
5. The optical waveguide of claim 1, wherein, In the range-extending layer, the refractive index at any two positions is the same.
6. The optical waveguide of claim 1, wherein, The refractive index in the range-extending layer increases or decreases in a direction perpendicular to the first surface, so that light rays incident into the range-extending layer at different incident angles in the waveguide substrate are reflected at different reflection points in the range-extending layer, wherein the distances between each reflection point and the waveguide substrate are not equal.
7. The optical waveguide of claim 6, wherein, The refractive index in the range-extending layer gradually decreases in a direction away from the waveguide substrate.
8. The optical waveguide of claim 6, wherein, The range-extended layer comprises at least a first sub-layer and a second sub-layer, and the light incident to the range-extended layer comprises 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 incident at the first angle and the light incident at the second angle in the first sub-layer are both located in the first sub-layer, and the distances from the two reflection points to the waveguide substrate are different, and the light incident at the third angle penetrates the first sub-layer to be incident to the second sub-layer and is reflected in the second sub-layer; or the reflection point of the light incident at the first angle in the first sub-layer is located in 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 to be incident to the second sub-layer and is reflected in the second sub-layer.
9. The optical waveguide of claim 1, wherein, The projection of the in-coupling region on the waveguide substrate covers the range-extended layer, or the area of the in-coupling region is greater than or equal to the area of the range-extended layer.
10. A near-eye display device, comprising: The near-eye display device comprises at least an optical machine and the optical waveguide according to any one of claims 1-9, wherein the optical machine is configured to emit signal light, and the optical waveguide is configured to direct the signal light to the human eye.
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