Optical waveguide and augmented reality device
By providing a grating on the first substrate of the optical waveguide and a second substrate with a refractive index lower than the first substrate on at least one surface of the first substrate, the brightness caused by the secondary diffraction of light in the optical waveguide is solved. Loss problems achieve more efficient light propagation and lower process complexity.
Patent Information
- Application Number
- CN202310961873.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-08-01
- Publication Date
- 2025-02-14
AI Technical Summary
Existing optical waveguides are prone to secondary diffraction during light propagation, resulting in brightness loss. Especially in monolithic full-color optical waveguide design, blue light is more prone to secondary diffraction brightness loss.
By providing a grating on the first substrate of the optical waveguide and a second substrate on at least one side of the first substrate, the refractive index is lower than the refractive index of the first substrate, thereby avoiding light in the optical waveguide from occurring in the optical waveguide Secondary diffraction.
It effectively reduces the brightness loss of the optical waveguide, increases the propagation distance of light in the plane, and avoids secondary diffraction. At the same time, due to the low-refractive index substrate, the increased weight and process complexity are lower.
Smart Images
Figure CN119439360A_ABST
Abstract
Description
Technical Field
[0001] The disclosed embodiments relate to the field of extended reality technology, and in particular to optical waveguides and extended reality devices. Background Art
[0002] Optical waveguides are important components in XR (Extended Reality) displays, especially the core of AR (Augmented Reality) display systems. The working principle of optical waveguides is to couple the light emitted by the optical machine into transparent parallel plates, transmit the light losslessly in the parallel plates through total internal reflection, and finally output the light through the coupling grating at the human eye and enter the human eye, thereby realizing the fusion of the displayed image and the real world. Summary of the invention
[0003] The embodiments of the present application provide an optical waveguide and an extended reality device.
[0004] In a first aspect, an embodiment of the present application provides an optical waveguide, comprising: a grating, a first substrate, and a second substrate; wherein the grating is arranged on at least one side of the first substrate, and the second substrate is arranged on at least one side of the first substrate; the refractive index of the second substrate is lower than the refractive index of the first substrate.
[0005] In some embodiments, the grating is disposed on a first surface of the first substrate, and the second substrate is disposed on a second surface of the first substrate.
[0006] In some embodiments, the first surface of the first substrate is a surface close to the light source.
[0007] In some embodiments, the second surface of the first substrate is a surface close to the light source.
[0008] In some embodiments, the first substrate and the second substrate are connected to each other by van der Waals forces.
[0009] In some embodiments, the thickness of the second substrate is less than or equal to the thickness of the first substrate.
[0010] In some embodiments, the second substrate is disposed on both sides of the first substrate.
[0011] In some embodiments, the total thickness of the second substrate on both sides of the first substrate is less than or equal to the thickness of the first substrate.
[0012] In some embodiments, the grating is disposed between the first substrate and the second substrate.
[0013] In a second aspect, an embodiment of the present application provides an extended reality device, including: the optical waveguide of the first aspect.
[0014] The optical waveguide and extended reality device provided by the embodiments of the present disclosure include: a grating, a first substrate, and a second substrate, wherein the grating is arranged on at least one side of the first substrate, and the second substrate is arranged on at least one side of the first substrate, and the refractive index of the second substrate is lower than the refractive index of the first substrate, thereby avoiding secondary diffraction of light in the optical waveguide and reducing the brightness loss of the optical waveguide. In addition, since the material density of the low refractive index substrate is generally low, the substrate layer will not increase too much weight, and the low refractive index substrate has no grating structure, and the process only needs to add the step of gluing, so the process complexity is low. BRIEF DESCRIPTION OF THE DRAWINGS
[0015] The above and other features, advantages and aspects of the embodiments of the present disclosure will become more apparent with reference to the following detailed description in conjunction with the accompanying drawings. Throughout the accompanying drawings, the same or similar reference numerals represent the same or similar elements. It should be understood that the drawings are schematic and the originals and elements are not necessarily drawn to scale.
[0016] Figure 1 is a schematic structural diagram of an embodiment of an optical waveguide according to the present application;
[0017] Figure 2 is a schematic diagram of the structure of an existing optical waveguide;
[0018] Figure 3 is a schematic structural diagram of another embodiment of an optical waveguide according to the present application;
[0019] Figure 4 is a schematic structural diagram of another embodiment of an optical waveguide according to the present application;
[0020] Figure 5 is a schematic structural diagram of another embodiment of an optical waveguide according to the present application;
[0021] Figure 6 is a schematic diagram of an embodiment of an extended reality device according to the present application. DETAILED DESCRIPTION
[0022] The present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the relevant invention, rather than to limit the invention. It is also necessary to explain that, for ease of description, only the parts related to the relevant invention are shown in the accompanying drawings.
[0023] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.
[0024] Figure 1FIG. 2 shows a schematic structural diagram of an embodiment of an optical waveguide according to the present application. Figure 1 As shown, the optical waveguide 100 may include a grating 101, a first substrate 102 and a second substrate 103. The refractive index of the second substrate 103 is generally lower than that of the first substrate 102 and higher than that of air. An optical waveguide is a medium device that guides light waves to propagate therein.
[0025] The optical properties of the grating (e.g., refractive index) vary periodically in one or more directions, and this period is close to or even smaller than the wavelength of visible light, between 200-500nm (nanometers). When the propagation direction of the diffracted light in the direction perpendicular to the substrate is consistent with the original incident light, the grating is a transmission grating. When the propagation direction of the diffracted light in the direction perpendicular to the substrate is opposite to the original incident light, the grating is a reflection grating.
[0026] A refined grating has thousands or even tens of thousands of grooves within a 1 cm width. This kind of grating that uses the diffraction of transmitted light is called a transmission grating. There is also a grating that uses the diffraction of reflected light between two grooves. For example, if many parallel grooves are engraved on a metal-plated surface, the smooth metal surface between the two grooves can reflect light. This kind of grating is called a reflection grating.
[0027] Here, the grating 101 can be set on at least one side of the first substrate 102. For example, the grating 101 can be a plurality of periodic structures engraved on the first substrate 102, such as a plurality of parallel grooves, or a plurality of periodic structures added to the first substrate 102, such as a plurality of parallel protrusions.
[0028] The second substrate 103 can be arranged on at least one side of the first substrate 102. For example, the grating 101 and the second substrate 103 can be arranged on the same side of the first substrate 102. The second substrate 103 can be connected to the first substrate 102 by gluing. For example, the first substrate and the second substrate can be bonded by using OCA (Optically Clear Adhesive). OCA is a special adhesive used for gluing transparent optical elements (such as lenses, etc.). It is required to be colorless and transparent, have a light transmittance of more than 95%, good bonding strength, can be cured at room temperature or medium temperature, and have small curing shrinkage.
[0029] It should be noted that in Figure 1 In the embodiment, the grating and the second substrate are arranged on the same surface of the first substrate. This is just a schematic diagram of the optical waveguide. In a specific implementation, the positional relationship between the grating, the second substrate and the first substrate can be limited according to actual conditions.
[0030] It should also be noted that Figure 1The grating size in the figure is just a schematic diagram, the actual grating thickness is usually smaller.
[0031] The diffraction efficiency of existing optical waveguides is usually low, which limits the brightness provided by the XR optical system. One important reason for the low diffraction efficiency of optical waveguides is that the secondary diffraction of light with the coupled-in grating causes the coupled-in light to be decoupled, resulting in brightness loss.
[0032] Please refer to Figure 2 , Figure 2 The figure shows a schematic diagram of the structure of an existing optical waveguide. Figure 2 In the process, the incident light is diffracted after encountering the grating, and is reflected when entering the optical waveguide substrate. The reflected light is diffracted again after encountering the grating, and is coupled out of the waveguide, so it cannot continue to propagate and enter the human eye.
[0033] This phenomenon is more serious in the design of a monolithic full-color optical waveguide. Since the diffraction angles of the three colors of light, red, green and blue, are different, blue light propagates at a smaller total internal reflection angle and is more susceptible to secondary diffraction and brightness loss.
[0034] In order to solve this problem, two optical waveguides are generally used for full-color display, one of which transmits red and green light, and the other transmits green and blue light. Through the two optical waveguides, the blue light is also transmitted at a larger angle, thereby avoiding the loss caused by secondary diffraction. However, the design of two optical waveguides increases weight, cost and process complexity. Therefore, a single full-color optical waveguide is still a more ideal solution.
[0035] In this solution, a grating is fabricated on a first substrate (high refractive index substrate), and a second substrate (low refractive index substrate) is arranged on the first substrate on the same surface as the grating or on a different surface. Since the refractive index of the second substrate is higher than that of air and lower than that of the first substrate, light is first diffracted by the grating, enters the high refractive index substrate and is reflected. Then, light enters the low refractive index substrate. Since the propagation angle of light in the low refractive index substrate becomes larger, even if the low refractive index substrate is very thin, the propagation distance of light in the plane can be effectively increased, thereby avoiding secondary diffraction as much as possible.
[0036] On the other hand, since the material density of the low refractive index substrate is generally low, this layer of substrate will not add too much weight, and the low refractive index substrate has no grating structure, and the process only needs to add a gluing step, so the process complexity is low.
[0037] In some optional implementations, the grating 101 may be disposed on a first surface of the first substrate 102 , and the second substrate 103 may be disposed on a second surface of the first substrate 102 , that is, the grating 101 and the second substrate 103 are located on two sides of the first substrate 102 , respectively.
[0038] In some optional implementations, the first surface of the first substrate 102 may be a surface close to the light source, that is, the grating 101 is arranged on the surface close to the light source, and the second substrate 103 is arranged on the surface far from the light source.
[0039] Please refer to Figure 3 , Figure 3 FIG. 1 is a schematic diagram of the structure of another embodiment of the optical waveguide according to the present application. Figure 3 In the embodiment, the grating 101 is arranged on the side of the first substrate 102 close to the light source, and the second substrate 103 is arranged on the side of the first substrate 102 far from the light source. In this case, the optical waveguide is a transmission optical waveguide.
[0040] Since the refractive index of the second substrate 103 is higher than that of air and lower than that of the first substrate 102, the light is first diffracted by the grating 101 and enters the first substrate 102. However, due to the presence of the second substrate 103, the total internal reflection condition is destroyed on the side where the first substrate 102 and the second substrate 103 are in contact, and the light enters the second substrate 103. Due to the refraction effect, the propagation angle of the light in the second substrate 103 becomes larger, so that even if the second substrate 103 is very thin, the propagation distance in the plane can be effectively increased, thereby avoiding secondary diffraction as much as possible.
[0041] In some optional implementations, the second surface of the first substrate 102 may be a surface close to the light source, that is, the second substrate 103 is disposed on the surface close to the light source, and the grating 101 is disposed on the surface far from the light source.
[0042] Continue to refer Figure 4 , Figure 4 FIG. 1 is a schematic diagram of the structure of another embodiment of the optical waveguide according to the present application. Figure 4 In the embodiment, the grating 101 is arranged on the side of the first substrate 102 away from the light source, and the second substrate 103 is arranged on the side of the first substrate 102 close to the light source. In this case, the optical waveguide is a reflective optical waveguide.
[0043] The light enters the second substrate 103 and the first substrate 102 in sequence, and is reflected in the first substrate 102. At the side where the first substrate 102 and the second substrate 103 are in contact, the total internal reflection condition is destroyed, and the light enters the second substrate 103. Due to the refraction effect, the propagation angle of the light in the second substrate 103 becomes larger, so that even if the second substrate 103 is very thin, the propagation distance in the plane can be effectively increased, thereby minimizing the occurrence of secondary diffraction.
[0044] In some optional implementations, the first substrate 102 and the second substrate 103 can be interconnected by van der Waals forces. Van der Waals forces can also be called intermolecular forces or van der Waals forces. There are three sources of intermolecular forces: the interaction between the permanent dipole moments of polar molecules; one polar molecule polarizes another molecule, generating an induced dipole moment and attracting each other; the movement of electrons in molecules generates an instantaneous dipole moment, which instantaneously polarizes neighboring molecules, which in turn enhances the instantaneous dipole moment of the original molecule. This mutual coupling generates an electrostatic attraction. The contributions of these three forces are different, and the third effect usually contributes the most. Here, the two substrates are connected to each other by van der Waals forces, further reducing the process complexity of the optical waveguide.
[0045] In some optional implementations, the thickness of the second substrate 103 is usually less than or equal to the thickness of the first substrate 102. Since the propagation angle of light in a low refractive index substrate becomes larger, even if the low refractive index substrate is very thin, the propagation distance of light in the plane can be effectively increased. By limiting the thickness of the low refractive index substrate, the weight of the optical waveguide can be reduced as much as possible.
[0046] In some optional implementations, the second substrate 103 may be disposed on both sides of the first substrate 102. Figure 5 As shown, Figure 5 FIG. 1 is a schematic diagram of the structure of another embodiment of the optical waveguide according to the present application. Figure 5 In the embodiment, the light is first diffracted by the grating 101 and enters the first substrate 102. However, due to the existence of the second substrate 103, the total internal reflection condition is destroyed at the side where the first substrate 102 and the second substrate 103 are in contact, and the light enters the second substrate 103. Due to the refraction effect, the propagation angle of the light in the second substrate 103 becomes larger. After the total internal reflection of the second substrate 103, the light enters the first substrate 102 and then enters the second substrate 103 again. The propagation angle of the light in the second substrate 103 becomes larger again, thereby further avoiding the occurrence of secondary diffraction.
[0047] It should be noted that Figure 5 The optical waveguide in the figure is only a schematic structural diagram, and the position of the grating can be set according to actual conditions. For example, the grating can be set between the first substrate and the second substrate on the side of the first substrate away from the light source, or the grating can be set on both sides of the first substrate.
[0048] In some optional implementations, the total thickness of the second substrate 103 on both sides of the first substrate 102 is usually less than or equal to the thickness of the first substrate 102. Since the propagation angle of light in the low-refractive index substrate becomes larger, even if the low-refractive index substrate is very thin, the propagation distance of light in the plane can be effectively increased. By limiting the total thickness of the two low-refractive index substrates, the weight of the optical waveguide can be reduced as much as possible.
[0049] In some optional implementations, the grating 101 may be disposed between the first substrate 102 and the second substrate 103. If the second substrate is disposed on both sides of the first substrate, a grating may be disposed between each first substrate and the second substrate.
[0050] Figure 6 FIG. 1 is a schematic diagram showing an embodiment of an extended reality device according to the present application. Figure 6 As shown, the extended reality device may include the optical waveguide described in the embodiment of the present application. The optical waveguide described in the embodiment of the present application includes a first substrate and a second substrate with a lower refractive index than the first substrate. Since the propagation angle of the light in the low refractive index substrate becomes larger, the propagation distance of the light in the plane is effectively increased, and the secondary diffraction of the light in the optical waveguide is avoided. When the user uses the extended reality device including the optical waveguide, more light enters the human eye, reducing the brightness loss. In addition, since the material density of the low refractive index substrate is generally low, this layer of substrate will not add too much weight, and the low refractive index substrate does not have a grating structure, so the process only needs to add a gluing step, so the process complexity is low.
[0051] The above description is only a preferred embodiment of the present disclosure and an explanation of the technical principles used. Those skilled in the art should understand that the scope of the invention involved in the embodiments of the present disclosure is not limited to the technical solutions formed by a specific combination of the above-mentioned technical features, but should also cover other technical solutions formed by any combination of the above-mentioned technical features or their equivalent features without departing from the above-mentioned inventive concept. For example, the above-mentioned features are replaced with the technical features with similar functions disclosed in the embodiments of the present disclosure (but not limited to) to form a technical solution.
Claims
1. An optical waveguide, characterized in that: include: A grating, a first substrate and a second substrate; in The grating is arranged on at least one side of the first substrate, and the second substrate is arranged on at least one side of the first substrate; The refractive index of the second substrate is lower than the refractive index of the first substrate.
2. The optical waveguide according to claim 1, characterized in that The grating is disposed on a first surface of the first substrate, and the second substrate is disposed on a second surface of the first substrate.
3. The optical waveguide according to claim 2, characterized in that The first surface of the first substrate is a surface close to the light source.
4. The optical waveguide according to claim 2, characterized in that The second surface of the first substrate is a surface close to the light source.
5. The optical waveguide according to claim 2, characterized in that The first substrate and the second substrate are connected to each other by van der Waals force.
6. The optical waveguide according to claim 2, characterized in that The thickness of the second substrate is less than or equal to the thickness of the first substrate.
7. The optical waveguide according to claim 1, characterized in that The second substrate is disposed on both sides of the first substrate.
8. The optical waveguide according to claim 7, characterized in that The total thickness of the second substrates on both sides of the first substrate is less than or equal to the thickness of the first substrate.
9. The optical waveguide according to claim 1, characterized in that The grating is disposed between the first substrate and the second substrate.
10. An extended reality device, characterized in that: include: An optical waveguide as claimed in any one of claims 1 to 9.