Optical waveguide and augmented reality equipment

Abstract

The invention discloses an optical waveguide and augmented reality equipment, and relates to the technical field of optical display. The optical waveguide comprises at least one layer of waveguide substrate and at least two sub-gratings, the at least two sub-gratings are respectively arranged on the surface of the at least one layer of waveguide substrate, the projections of the at least two sub-gratings in the stacking direction of the optical waveguide are at least partially overlapped, the at least two sub-gratings form a grating structure, and the thickness of the grating structure is a preset height. According to the optical waveguide and the augmented reality device, on the basis that the coupling-out efficiency is not reduced, the difference between the coupling-out grating and the surrounding area in the aspect of transmittance can be reduced, and the user experience is improved.

Description

Technical Field

[0001] This application relates to the field of optical display technology, and more specifically, to an optical waveguide and augmented reality device. Background Technology

[0002] Diffractive waveguides, as core optical components in augmented reality (AR) display devices, have become one of the mainstream solutions for near-eye display technology due to their advantages such as thinness, mass production capability, and good compatibility with microdisplay chips. Their basic working principle involves using micro / nano grating structures set on or inside the waveguide substrate to sequentially couple external image light in, transmit it via total internal reflection, and finally achieve image extraction. A typical diffractive waveguide system usually includes a coupling grating, a deflection grating, and an extraction grating, with the extraction grating directly determining the quality and field-of-view uniformity of the image seen by the user.

[0003] However, in existing technologies, there is a significant difference in optical transmission characteristics between the grating region (especially large-area coupled gratings) and the surrounding unprocessed non-grating region. Specifically, because the grating structure is formed into a periodic relief on the waveguide substrate through nanoscale etching, this structure inevitably introduces additional scattering, Fresnel reflection, and mode loss, resulting in an average transmittance of only about 80% to 85% in the visible light band; while the transmittance of the unetched flat waveguide region can be as high as 95% or more. The difference in transmittance between the two exceeds 10 percentage points. Under ambient light, the grating region exhibits obvious shadows and striped visual effects, which are clearly visible even without an image display.

[0004] This uneven transmittance severely damages the appearance consistency and transparency of AR glasses, affecting not only the aesthetics of industrial design but also potentially causing users to have a negative perception of product quality. Summary of the Invention

[0005] The purpose of this application is to provide an optical waveguide and augmented reality device that can reduce the difference in transmittance between the grating structure and the surrounding area without reducing diffraction efficiency, thereby improving the user experience.

[0006] The embodiments of this application are implemented as follows: A first aspect of this application provides an optical waveguide, including at least one waveguide substrate and at least two sub-gratings. The at least two sub-gratings are respectively disposed on the surface of the at least one waveguide substrate, and the projections of the at least two sub-gratings in the optical waveguide stacking direction at least partially overlap. The at least two sub-gratings form a grating structure, and the thickness of the grating structure is a preset height.

[0007] As one possible implementation, the sub-grating includes two sub-gratings, the waveguide substrate includes one layer, and the two sub-gratings are respectively disposed on the upper surface and the lower surface of the waveguide substrate.

[0008] As one possible implementation, the waveguide substrate includes multiple waveguide substrates, which are arranged sequentially along the thickness direction, and the multiple sub-gratings include a first grating disposed on the upper surface of the waveguide substrate and a second grating disposed on the lower surface of the waveguide substrate.

[0009] As one possible implementation, the multiple sub-gratings include multiple first gratings and a second grating located on the lowest waveguide substrate.

[0010] As one possible implementation, the waveguide substrate includes two layers, and the sub-grating includes a first grating disposed on the upper waveguide substrate and a second grating disposed on the lower waveguide substrate.

[0011] As one possible implementation, the grating structure is disposed in the coupling region as a coupling grating, or the grating structure is disposed in the transition region as a transition grating.

[0012] As one possible implementation, each sub-grating has the same height.

[0013] As one possible implementation, the height of each sub-grating is less than 0.85 times the preset height.

[0014] As one possible implementation, the height of the sub-grating closest to the light wave output side is greater than the height of the other sub-gratings.

[0015] A second aspect of this application provides an augmented reality device, including an image source and the aforementioned optical waveguide disposed on the light-emitting side of the image source, wherein the light beam emitted from the image source is imaged through the optical waveguide.

[0016] The beneficial effects of the embodiments of this application include: The optical waveguide of this application embodiment includes at least one waveguide substrate and at least two sub-gratings. The at least two sub-gratings are respectively disposed on the surface of the at least one waveguide substrate, and the projections of the at least two sub-gratings in the waveguide stacking direction at least partially overlap. The at least two sub-gratings form a grating structure, and the thickness of the grating structure is a preset height. With the thickness of multiple sub-gratings being a preset height, the light beam inside the waveguide substrate is diffracted by the multiple sub-gratings. The diffraction efficiencies of the multiple sub-gratings are superimposed to form the diffraction efficiency of the grating structure. The preset height of the grating structure ensures that the diffraction efficiencies of the multiple sub-gratings are equal to the diffraction efficiency of the grating structure. The preset height of the grating structure ensures a preset diffraction efficiency. Therefore, the optical waveguide implemented in this application ensures diffraction efficiency. Because the thickness of each sub-grating is small, the abrupt change in transmittance caused by a single-layer sub-grating is effectively reduced, decreasing grating visibility and significantly improving the appearance consistency and visual appeal of the entire optical waveguide display module, thereby enhancing the user experience. Therefore, the optical waveguide of this application embodiment can reduce the difference in transmittance between the grating structure and the surrounding area without reducing diffraction efficiency, thereby improving the user experience. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is one of the schematic diagrams of an optical waveguide provided in an embodiment of this application; Figure 2 This is a second schematic diagram of an optical waveguide structure provided in an embodiment of this application; Figure 3 This is the third schematic diagram of an optical waveguide structure provided in the embodiments of this application; Figure 4 This is the fourth schematic diagram of an optical waveguide structure provided in the embodiments of this application; Figure 5 This is the fifth schematic diagram of an optical waveguide structure provided in the embodiments of this application; Figure 6 This is the sixth schematic diagram of an optical waveguide provided in the embodiments of this application.

[0019] Icons: 100 - Optical waveguide; 110 - Waveguide substrate; 120 - Coupling grating structure; 121 - Sub-grating; 130 - Coupling grating; 140 - Turning grating structure. Detailed Implementation

[0020] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. The described embodiments are only some embodiments of this application, not all embodiments. Similar reference numerals and letters in the following drawings indicate similar items. Once an item is defined in one drawing, it does not need to be further defined in other drawings.

[0021] The terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product is in use. They are used only for the convenience of describing this application and should not be construed as limiting this application. The terms "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0022] Unless otherwise expressly specified and limited, the terms "set up," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to connections within two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0023] To address the issue of diminished user experience caused by uneven transmittance between the coupling region and the waveguide substrate, some existing technologies attempt to improve the overall transmittance of the grating region and reduce its visual discernibility by optimizing the grating etching depth, adjusting period parameters, using low-refractive-index contrast materials, or filling the grating trenches with matching media. However, these methods are often strongly coupled with key optical properties such as the grating's diffraction efficiency, exit angle, and field of view: excessive pursuit of high transmittance may lead to decreased coupling efficiency, insufficient image brightness, or field distortion; conversely, ensuring optical performance makes it difficult to completely eliminate visible traces of the grating.

[0024] This application provides an optical waveguide 100, such as... Figures 1 to 4 As shown, it includes at least one waveguide substrate 110 and at least two sub-gratings 121. The at least two sub-gratings 121 are respectively disposed on the surface of the at least one waveguide substrate 110, and the projections of each sub-grating 121 in the waveguide stacking direction at least partially overlap. The at least two sub-gratings form a grating structure, and the thickness of the grating structure is a preset height.

[0025] The optical waveguide 100 provided in this application embodiment is used in augmented reality devices to conduct light beams and emit them into the human eye. Specifically, the optical waveguide 100 in this application embodiment includes at least one waveguide substrate 110. The waveguide substrate serves as the medium for light beam transmission and is typically made of highly transparent glass or polymer material. It also includes a grating structure, which is used to couple or deflect the light beam propagating in the waveguide substrate 110.

[0026] Specifically, the grating structure is set in the coupling region as a coupling grating, or the grating structure is set in the transition region as a transition grating. The following explanation uses the grating structure as a coupling grating as an example.

[0027] In this embodiment, the coupling grating structure 120 includes multiple sub-gratings 121, which are respectively disposed on the surface of the waveguide substrate 110. The projections of each sub-grating 121 in the stacking direction overlap. The sum of the thicknesses of the multiple sub-gratings 121 is a preset height, meaning the thickness of the coupling grating structure is a preset height. This preset height can be the thickness of the grating structure that ensures coupling efficiency when the grating structure is a single-layer grating. In other words, this embodiment divides the coupling grating with a preset height in the prior art into multiple layers of sub-gratings 121, and the sum of the thicknesses of the multiple sub-gratings 121 is the height of a single coupling grating in the prior art. Specifically, the preset height is usually related to the target operating wavelength to satisfy the diffraction phase matching condition and ensure efficient coupling.

[0028] Since the sum of the thicknesses of the multiple sub-gratings 121 is equal to the height of the coupling grating in the prior art, the light beam inside the waveguide substrate 110 is coupled out by the multiple sub-gratings 121 respectively. That is, the coupling efficiency of the multiple sub-gratings 121 is superimposed, so that the sum of the coupling efficiency of the multiple sub-gratings 121, that is, the coupling efficiency of the coupling grating structure 120, is equivalent to the efficiency of a single coupling grating. Therefore, the optical waveguide 100 implemented in this application ensures the coupling efficiency.

[0029] By setting the coupled grating structure 120 as multiple sub-gratings 121, the thickness of each sub-grating 121 is reduced, thereby effectively weakening the abrupt change in transmittance caused by a single-layer sub-grating 121, reducing grating visibility, and thus significantly improving the appearance consistency and visual appeal of the entire optical waveguide 100 display module, and enhancing the user experience.

[0030] In other words, by setting the coupling grating structure 120 as multiple sub-gratings 121, the function of the coupling grating structure is distributed among multiple shallower sub-gratings 121, thus preserving the effective diffraction capability of the beam and optimizing the influence of the overall morphology on ambient light. In summary, the optical waveguide 100 of this embodiment can reduce the difference in transmittance between the coupling grating and the surrounding area without reducing the coupling efficiency, thereby improving the user experience.

[0031] It is understood that the optical waveguide 100 in this application embodiment further includes at least a coupling grating 130. When the waveguide substrate 110 includes one, the coupling grating 130 is disposed on one side of the waveguide substrate 110. When the waveguide substrate 110 includes multiple layers, the multiple waveguide substrates 110 are bonded together to form a waveguide group, and the coupling grating 130 is disposed on one side of the waveguide group.

[0032] In addition, in practical applications, the height of the output grating structure 120 can be set to be the same as the height of the input grating 130.

[0033] The optical waveguide 100 of this application embodiment includes at least one waveguide substrate 110 and at least two sub-gratings 121. The at least two sub-gratings 121 are respectively disposed on the surface of the at least one waveguide substrate 110, and the projections of the at least two sub-gratings overlap in the waveguide stacking direction. The at least two sub-gratings form a grating structure, and the thickness of the grating structure is a preset height. Since the thickness of the multiple sub-gratings is a preset height, the light beam inside the waveguide substrate 110 is diffracted by the multiple sub-gratings. The diffraction efficiencies of the multiple sub-gratings are superimposed to form the diffraction efficiency of the grating structure. The preset height of the grating structure ensures that the diffraction efficiency of the multiple sub-gratings is equal to the diffraction efficiency of the grating structure. The preset height of the grating structure ensures a preset diffraction efficiency. Therefore, the optical waveguide implemented in this application ensures diffraction efficiency. Because the thickness of each sub-grating is small, the abrupt change in transmittance caused by a single-layer sub-grating is effectively reduced, reducing grating visibility and significantly improving the appearance consistency and visual appeal of the entire optical waveguide display module, thereby enhancing the user experience. Therefore, the optical waveguide of this application embodiment can reduce the difference in transmittance between the grating structure and the surrounding area without reducing diffraction efficiency, thereby improving the user experience.

[0034] Optional, such as Figure 2 and Figure 6 As shown, there are two sub-gratings 121, and the waveguide substrate 110 includes one layer. The two sub-gratings 121 are respectively disposed on the upper surface or the lower surface of the waveguide substrate 110.

[0035] Figure 2 The sub-grating 121 comprises two sub-gratings with a preset height of h. The height of each sub-grating 121 is h / 2, and the height of the coupling grating 130 is also h. The two sub-gratings 121 are respectively disposed on two sides of the waveguide substrate 110, and the projections of the two sub-gratings 121 completely overlap. This double-sided distributed sub-grating 121 design replaces the traditional single-sided deep-etched grating. While maintaining the overall diffraction function, it disperses the grating morphology to both sides of the waveguide, effectively reducing the structural depth and optical abrupt changes on a single surface.

[0036] Specifically, the light beam propagating in the waveguide substrate 110 interacts sequentially or simultaneously with two sub-gratings 121 on the upper and lower surfaces, achieving efficient coupling through phase matching and coherent superposition. For ambient light, since each surface has only a shallow sub-grating 121, the surface roughness and refractive index step are significantly reduced, thereby greatly suppressing scattering and reflection losses. This makes the average visible light transmittance of the entire coupling grating structure 120 closer to that of the unetched area, significantly reducing visual shadowing or fogging effects.

[0037] It is understandable that when the two sub-gratings 121 are respectively disposed on the two sides of the waveguide substrate 110, in order to make the output light located on the same side, one of the two sub-gratings 121 is a reflective grating and the other is a transmissive grating.

[0038] In this embodiment, the coupling grating 130 has a height of 1 nm, and the coupling grating is divided into two sub-gratings 121, which are respectively disposed on the upper and lower surfaces of the optical waveguide 100. The etching depth of each sub-grating 121 is 0.5 nm. Each sub-grating 121 has the following typical structural parameters: grating period of 400 nm, duty cycle of 0.5, and refractive index modulation value Δn of 0.06. According to estimates, this structure can achieve a diffraction efficiency of approximately 0.3 per layer of sub-gratings 121, while maintaining an overall transmittance of approximately 0.87. Compared with the traditional single-layer deep grating structure (depth of 1 nm, transmittance can be as low as below 0.80), it effectively improves transmittance while maintaining a high coupling efficiency, significantly improving the device's appearance consistency and visual appeal.

[0039] Figure 6 The waveguide substrate 110 comprises two sub-gratings 121, each with a preset height of h and a height of h / 2. The coupling grating 130 also has a height of h. The two sub-gratings 121 are respectively disposed on two sides of the waveguide substrate 110, and their projected portions overlap. The etching depth of both sub-gratings is h / 2. For example, when the original design depth h = 0.4 nm, the depth of each sub-grating is 0.2 nm. The two sub-gratings are arranged to partially overlap horizontally, so that in the overlapping region, the beam in the waveguide substrate is modulated by both the upper and lower gratings simultaneously, while in the misaligned region of the two sub-gratings, the beam is modulated by only one sub-grating.

[0040] Specifically, both sub-gratings use the same grating period of 400 nm, duty cycle of 0.5, and refractive index modulation value Δn of 0.06. In the misaligned region of the two sub-gratings, due to the modulation by only a single-layer sub-grating with a depth of 0.2 nm, the local transmittance can be maintained at approximately 0.92, meaning the visible impact of the sub-gratings on the human eye is significantly reduced. In the overlapping region, although the beam passes through two shallow gratings, increasing its equivalent coupling modulation intensity, the visual transmittance can still be maintained above 0.90 due to the small depth of each sub-grating layer.

[0041] Simulation estimates suggest that each sub-grating layer can generate a diffraction efficiency of approximately 0.15. In the partially overlapping region, the two sub-grating layers work together to increase the overall effective coupling efficiency to approximately 0.30. The misaligned regions of the two sub-gratings primarily enhance transmittance and reduce visible structures, thus optimizing the balance between efficiency and visual effect. Because the overlapping region provides stronger light modulation and forms a wider effective light-emitting band, this embodiment can, to some extent, expand the exit pupil range of the optical waveguide compared to a completely non-overlapping sub-grating layout, thereby increasing the visible area of ​​the displayed image.

[0042] By partially overlapping two sub-gratings, the coupling efficiency is improved without significantly reducing transmittance, and the overall appearance consistency is enhanced. At the same time, a larger exit pupil range is achieved, making it suitable for waveguide display devices that have high requirements for both appearance and display effect.

[0043] By arranging sub-gratings 121 on two sides of a waveguide substrate 110, the number of waveguide layers can be increased without increasing the number of waveguide layers, thus balancing performance improvement and the size of the optical waveguide 100.

[0044] As an feasible approach, such as Figure 1 , Figure 3 and Figure 4 As shown, the waveguide substrate 110 includes multiple waveguide substrates 110, and the multiple waveguide substrates 110 are sequentially attached along the thickness direction. The multiple sub-gratings include a first grating disposed on the upper surface of the waveguide substrate and a second grating disposed on the lower surface of the waveguide substrate.

[0045] The optical waveguide 100 in this embodiment is a multilayer stacked optical waveguide structure, formed by tightly bonding multiple transparent waveguide substrates 110 along the thickness direction. Sub-gratings 121 are fabricated on the surfaces of these waveguide substrates 110, and all sub-gratings 121 completely overlap in their projection regions along the stacking direction, forming a spatially layered but functionally coordinated coupling grating structure 120. The sum of the physical thicknesses of all sub-gratings 121 is controlled to a preset height, which is typically related to the target operating wavelength to satisfy the diffraction phase matching condition and ensure efficient coupling.

[0046] Specifically, the position of the sub-grating 121 is not limited in this embodiment, nor is the specific number of the first and second gratings or their correspondence with the waveguide substrate, as long as the projection of each sub-grating 121 overlaps in the stacking direction. It is understood that the sub-grating disposed between two adjacent waveguide substrates can serve as either the first or the second grating.

[0047] When the light beam enters the waveguide substrate 110 through the coupling grating 130, it propagates horizontally within the stack of multiple waveguide substrates 110 to the coupling region. At this point, the beam sequentially passes through multiple bonded waveguide substrates 110 and interacts with sub-gratings 121 distributed on different layer surfaces. Since the sub-gratings 121 are aligned laterally, their diffraction wavefronts coherently superimpose in the emission direction, jointly completing the beam coupling task. Simultaneously, for external ambient light, each grating encountered during its penetration through the entire multilayer structure is a shallowly etched structure, avoiding the strong scattering and high reflection caused by deep etching in traditional single-layer structures. Furthermore, the multilayer interface can be further optimized for light transmission through anti-reflection design, making the overall transmittance closer to that of flat glass.

[0048] It is understood that when the waveguide substrate 110 includes multiple layers, the refractive index of the multiple waveguide substrates 110 is the same, so that the light beam can propagate by total internal reflection within the stack. Specifically, the coupling grating 130 is disposed on one side of the stack, so that the light beam is coupled into the stack and propagates by total internal reflection between the two sides of the stack.

[0049] Optional, such as Figure 4 As shown, the multiple sub-gratings 121 include multiple first gratings and a second grating located on the lowest waveguide substrate. In other words, the waveguide substrate 110 includes N, and the sub-gratings 121 include N+1. The sub-gratings 121 are respectively disposed between two adjacent waveguide substrates 110 and on the outer surfaces of the upper and lower waveguide substrates 110.

[0050] The optical waveguide 100 of this embodiment includes N layers of transparent waveguide substrates 110, which are sequentially bonded together along the thickness direction to form a waveguide assembly. On the N+1 optical interfaces formed by these waveguide substrates 110, including the top surface of the top layer, N… One internal adjacent interface and the bottom surface are provided with one sub-grating 121 on each of the N+1 optical interfaces, for a total of N+1. The projection areas of all sub-gratings 121 in the direction perpendicular to the waveguide plane completely overlap, together forming a coupling grating structure.

[0051] The sub-grating 121 located between adjacent waveguide substrates 110 can be fabricated on the lower surface of one layer or the upper surface of another layer, or embedded into the interface through nanoimprinting / bonding process to ensure optical continuity and structural stability.

[0052] By utilizing N+1 interface-distributed sub-gratings 121, the depth, period, or duty cycle of each sub-grating 121 can be finely controlled while maintaining the total grating height, achieving a more flexible phase distribution, which is beneficial for improving coupling efficiency, suppressing stray light, or expanding the field of view.

[0053] Specifically, such as Figure 4 As shown, the optical waveguide 100 includes two bonded waveguide substrates 110, each with three sub-gratings 121. The etching depth of each sub-grating 121 is one-third of the original total depth h, approximately 0.33 nm. The three sub-gratings 121 are located between the two waveguide substrates 110 and on the outer surfaces of the two waveguide substrates 110, respectively, and their projections overlap in the stacking direction. The three sub-gratings 121 work together to complete the beam emission function. The period of each grating structure is set to 400 nm, the duty cycle is 0.5, and the refractive index modulation value Δn is 0.06. Through simulation calculations, this three-layer structure can achieve a total diffraction efficiency of approximately 0.27, while maintaining a relatively shallow etching depth for each grating layer, which helps to improve the transmittance of each waveguide layer, with an overall transmittance of over 0.91. That is, this embodiment of the application effectively improves the visibility problem of the coupling area while ensuring light emission efficiency, enhancing the overall visual consistency and appearance quality of the device.

[0054] As an feasible approach, such as Figure 3 As shown, the waveguide substrate 110 includes two layers. The sub-grating includes a first grating disposed on the upper waveguide substrate and a second grating disposed on the lower waveguide substrate. It can be understood that there are two sub-gratings 121. The waveguide substrate 110 includes two layers, and the two sub-gratings 121 are respectively disposed on the sides of the two waveguide substrates 110 that are far apart from each other.

[0055] The optical waveguide 100 of this embodiment is formed by stacking two transparent waveguide substrates 110 along the thickness direction. A sub-grating 121 is disposed on each of the two outermost surfaces of the stack, namely the upper surface of the upper waveguide substrate 110 and the lower surface of the lower waveguide substrate 110, for a total of two sub-gratings 121. The projected areas of these two sub-gratings 121 completely overlap in the direction perpendicular to the waveguide plane, together forming a coupling grating structure 120.

[0056] In this embodiment, the coupling grating structure 120 is configured with two sub-gratings 121, respectively disposed in the upper and lower waveguide layers, with each sub-grating 121 having an etching depth of 0.2 nm. The grating period is 400 nm, the duty cycle is 0.5, and the refractive index modulation Δn is set to 0.06. According to simulation calculations, this dual-layer sub-grating 121 structure can achieve a total diffraction efficiency of approximately 0.24, while maintaining an overall transmittance of approximately 0.91, significantly higher than the approximately 80% of traditional deep grating structures. This structure, while ensuring a usable light extraction efficiency, significantly improves the visual consistency of the waveguide appearance, making it suitable for augmented reality display devices with high aesthetic requirements.

[0057] To reduce the size of the optical waveguide, the thickness of the waveguide substrate should be kept as small as possible while ensuring total internal reflection propagation. Specifically, the thickness of the waveguide substrate should be less than 0.4 mm.

[0058] As one possible approach, the grating structure is positioned in the coupling region as a coupling grating, or the grating structure is positioned in the transition region as a transition grating.

[0059] When the grating structure is a folding grating, such as Figure 5 As shown, after the light beam enters the waveguide through the coupling grating 130, it encounters the deflection grating structure 140 in a certain region. Multiple deflection gratings work together to expand the light in one or two dimensions within the waveguide through diffraction. Since the total height of the deflection gratings is the second preset height and they are distributed across multiple interfaces, both the deflection grating and the output grating adopt a multi-layer distributed structure. Each grating precisely controls the phase through a preset height and a second preset height, achieving high-efficiency pupil expansion and high-brightness coupling, thus improving the overall optical performance. In addition, the deflection grating structure 140 and the output grating structure 120 significantly reduce interference with ambient light due to shallow etching and multi-interface distribution, allowing the AR glasses to present a uniform and transparent appearance from any viewing angle, improving the user experience.

[0060] Optional, such as Figure 1 and Figure 2 As shown, each sub-grating 121 has the same height.

[0061] Each sub-grating 121 has the same height, which ensures that each sub-grating 121 provides the same diffraction response, ensuring a uniform distribution of diffraction efficiency, which is beneficial for achieving high brightness uniformity and low field distortion.

[0062] As an feasible approach, the height of each sub-grating 121 is less than 0.85 times the preset height.

[0063] By limiting the height of each sub-grating 121 to less than 0.85h, the grating function must be shared by multiple sub-gratings 121, which fundamentally avoids the high scattering problem caused by traditional single deep etching and is a structural guarantee for achieving high transparency.

[0064] Optional, such as Figure 3 As shown, the height of the sub-grating 121 near the light-emitting side of the optical waveguide 100 is greater than the height of the other sub-gratings 121.

[0065] When the light beam propagates within the waveguide substrate 110 to the coupling region, it interacts sequentially with multiple sub-gratings 121. Because the sub-gratings 121 closer to the light-emitting side have a greater height, their diffraction modulation effect on the light beam is stronger, enabling them to more effectively couple light energy to the target emission angle. The sub-gratings 121 farther from the light-emitting side mainly function as phase pre-modulation, wavefront shaping, or suppression of back diffraction. In other words, more diffraction weight is allocated to the sub-gratings 121 closer to the human eye, making the coupled light more concentrated in the effective viewing area, improving brightness utilization, and reducing energy waste.

[0066] This application also provides an augmented reality device, including an image source and the aforementioned optical waveguide 100 disposed on the light-emitting side of the image source, wherein the light beam emitted from the image source is imaged through the optical waveguide 100. Since the structure and beneficial effects of the optical waveguide 100 have been described in detail in the foregoing embodiments, they will not be repeated here.

[0067] The above are merely optional embodiments of this application and are not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

[0068] It should also be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, this application will not describe the various possible combinations separately.

Claims

1. An optical waveguide, characterized by, The light waveguide comprises at least one waveguide substrate and at least two sub-gratings, the at least two sub-gratings are arranged on the surface of the at least one waveguide substrate respectively, and the projections of the at least two sub-gratings on the stacking direction of the light waveguide at least partially overlap, wherein the at least two sub-gratings form a grating structure, and the thickness of the grating structure is a preset height.

2. The optical waveguide of claim 1, wherein, The sub-gratings comprise two, and the waveguide substrate comprises one layer, the two sub-gratings are arranged on the upper surface and the lower surface of the waveguide substrate respectively.

3. The optical waveguide of claim 1, wherein, The waveguide substrate comprises a plurality of waveguide substrates, and the plurality of waveguide substrates are arranged in sequence along the thickness direction, and the plurality of sub-gratings comprise a first grating arranged on the upper surface of the waveguide substrate and a second grating arranged on the lower surface of the waveguide substrate.

4. The optical waveguide of claim 3, wherein, The plurality of sub-gratings comprise a plurality of first gratings and a second grating arranged on the lowermost waveguide substrate.

5. The optical waveguide of claim 3, wherein, The waveguide substrate comprises two layers, and the sub-gratings comprise a first grating arranged on the upper waveguide substrate and a second grating arranged on the lower waveguide substrate.

6. The optical waveguide of claim 1, wherein, The grating structure is arranged in the out-coupling region as an out-coupling grating, or the grating structure is arranged in the turning region as a turning grating.

7. The optical waveguide of claim 1, wherein, The height of each sub-grating is equal.

8. The optical waveguide of claim 1, wherein, The height of each sub-grating is less than 0.85 times of the preset height.

9. The optical waveguide of claim 1, wherein, The height of the sub-grating close to the light exit side of the light waveguide is greater than the height of the other sub-gratings.

10. An augmented reality device, characterized by The light waveguide comprises an image source and a light waveguide as claimed in any one of claims 1-9 arranged on the light exit side of the image source, and the light beam emitted by the image source is imaged through the light waveguide.

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