Diffractive optical waveguide and near-eye display device

Abstract

The application relates to the technical field of optical display, in particular to a diffractive optical waveguide and a near-eye display device, which comprises a waveguide substrate; a coupling-out area and a transition area are arranged on the waveguide substrate; the transition area surrounds the periphery of the coupling-out area; the coupling-out area is provided with a first coupling-out grating; the transition area is provided with a second coupling-out grating; the grating line arrangement direction of the second coupling-out grating is parallel to or is arranged at an angle with the grating line arrangement direction of the first coupling-out grating; and the period of the second coupling-out grating is less than or equal to the period of the first coupling-out grating. The application can effectively reduce the transmittance difference between the coupling-out area and the transition area while maintaining the high-efficiency light coupling-out performance, realize the visual uniformity in appearance, and improve the product appearance and user experience.

Description

Technical Field

[0001] This application relates to the field of optical display technology, and more specifically, to a diffractive waveguide and near-eye display device. Background Technology

[0002] In diffractive waveguides, the coupling grating, as a key optical element, is usually composed of periodic micro-nano structures. Its main function is to efficiently couple the guided mode light propagating in the waveguide in the manner of total internal reflection out of the waveguide and realize the two-dimensional exit pupil expansion, thereby forming a virtual image that can be observed by the human eye.

[0003] However, in existing technologies, there are significant differences in physical structure and optical performance between the coupled grating region and the transparent region without a grating (i.e., the non-grating region). Specifically, due to the periodic etching structure on the surface of the coupled grating region, Fresnel reflection, Rayleigh scattering, and diffraction losses are inevitably introduced, resulting in an average transmittance of only 80–85% in the visible light band; while the adjacent non-grating region, due to its smooth and flat surface, can have an intrinsic transmittance of over 95%. This transmittance difference of more than 10% between the two creates a significant contrast between light and dark under natural light or bright environments, making the coupled grating region appear as a visible "mark" or "window".

[0004] This problem not only severely compromises the industrial design consistency and aesthetics of consumer electronics products such as AR glasses, but also causes visual interference during user wear—for example, uneven brightness in the coupled grating area can distract attention and even cause visual fatigue when observing real-world scenes. Although existing technologies have attempted to mitigate this problem by reducing grating depth, optimizing duty cycle, or using anti-reflective coatings, these methods often come at the cost of sacrificing diffraction efficiency or increasing process complexity, making it difficult to achieve a good balance between high brightness display performance and high visual transparency. Utility Model Content

[0005] The purpose of this application is to provide a diffractive waveguide and a near-eye display device that can effectively reduce the transmittance difference between the coupling area and the transition area while maintaining high-efficiency optical coupling performance, thereby achieving visual uniformity in appearance and improving the aesthetics and user experience of the product.

[0006] This application is implemented as follows: In a first aspect, this application provides a diffractive optical waveguide, including a waveguide substrate; the waveguide substrate has a coupling region and a transition region; the transition region surrounds the outer periphery of the coupling region; the coupling region has a first coupling grating; the transition region has a second coupling grating; the grating line arrangement direction of the second coupling grating is parallel to or at an angle to the grating line arrangement direction of the first coupling grating; the period of the second coupling grating is less than or equal to the period of the first coupling grating.

[0007] As an optional implementation, the period of the second coupling grating is half the period of the first coupling grating. n Where n is greater than or equal to 0, and the period of the second coupled grating is greater than or equal to 5nm.

[0008] As an optional implementation, the transition region includes at least two sets, with the inner and outer edges of adjacent sets of transition regions connected; from the inside to the outside, the period of the second coupling grating in each set of transition regions decreases sequentially.

[0009] As an optional implementation, the waveguide substrate further includes a coupling region and a turning region; the coupling region is used to couple image light into the waveguide substrate; the turning region is used to receive the image light and transmit the image light to the coupling region.

[0010] As an optional implementation, the coupling region, turning region, coupling out region, and transition region are disposed on the surface of the waveguide substrate close to the user's eye.

[0011] As an optional implementation, the surface of the waveguide substrate near the user's eye is divided into an exposed area and a shielded area; the coupling-in area and the transition area are both located in the shielded area; the sum of the areas of the coupling-out area and the transition area is equal to the area of ​​the exposed area.

[0012] As an optional implementation, the exposed area and the shielded area have a boundary line, and one side of the coupling area coincides with the boundary line.

[0013] As an optional implementation, a turning region is provided on each side of the coupling region; there are two coupling out regions, each corresponding to one of the two turning regions; the image light entering through the coupling region propagates to both sides, turns after passing through the turning regions on both sides, and is coupled out by the two coupling out regions to form outgoing light beams for the user's left and right eyes to observe respectively.

[0014] As an optional implementation, the coupling region has the turning region on at least one side, and the coupling out region receives the image light after it has been turned by the turning region and couples the image light out to the user's right or left eye.

[0015] Secondly, this application provides a near-eye display device, including an image generation unit and the aforementioned diffractive waveguide; the image generation unit is used to emit image light into the coupling region of the diffractive waveguide.

[0016] The beneficial effects of this application include: The diffractive waveguide and near-eye display device of this application effectively alleviate the problem of obvious imprints or light-dark boundaries caused by the difference in transmittance between the coupling grating area and the transparent non-grating area in traditional diffractive waveguides by setting a second coupling grating with a smaller period but parallel grating line direction as a transition area around the coupling area. Since the small-period grating has low diffraction efficiency and weak scattering in the visible light band, it is difficult for the human eye to perceive its existence. Thus, while maintaining the high diffraction efficiency of the central coupling area, it significantly improves the overall appearance uniformity and ambient light transmittance consistency of the waveguide. It avoids visual interference and fatigue, and takes into account both high display performance and industrial aesthetic requirements. The entire diffractive waveguide has a uniform gray or neutral semi-transparent appearance, with a visual effect similar to sunglasses, realizing the synergistic optimization of optical performance and user experience of AR near-eye display devices. 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 structural schematic diagrams of the diffractive waveguide in the embodiments of this application; Figure 2 This is a second schematic diagram of the structure of the diffractive waveguide in an embodiment of this application; Figure 3 This is the third schematic diagram of the diffractive waveguide structure in the embodiments of this application; Figure 4 This is the fourth schematic diagram of the diffractive waveguide structure in the embodiments of this application; Figure 5 This is the fifth schematic diagram of the diffractive waveguide structure in the embodiments of this application.

[0019] Icons: 100-waveguide substrate; 101-coupled region; 102-transition region; 103-first coupled-out grating; 104-second coupled-out grating; 105-coupled-in region; 106-turning region; 107-exposed region; 108-shaded region; 109-boundary line. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, 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, and not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0021] Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0022] It should be noted that similar reference numerals and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. Furthermore, the terms "first," "second," "third," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0023] In the description of this application, it should also be noted that, unless otherwise expressly specified and limited, the terms "set up," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0024] In diffractive waveguides, the coupling grating, as a key optical element, is usually composed of periodic micro-nano structures. Its main function is to efficiently couple the guided mode light propagating in the waveguide in the manner of total internal reflection out of the waveguide and realize the two-dimensional exit pupil expansion, thereby forming a virtual image that can be observed by the human eye.

[0025] However, in existing technologies, there are significant differences in physical structure and optical performance between the coupled grating region and the transparent region without a grating (i.e., the non-grating region). Specifically, due to the periodic etching structure on the surface of the coupled grating region, Fresnel reflection, Rayleigh scattering, and diffraction losses are inevitably introduced, resulting in an average transmittance of only 80–85% in the visible light band; while the adjacent non-grating region, due to its smooth and flat surface, can have an intrinsic transmittance of over 95%. This transmittance difference of more than 10% between the two creates a significant contrast between light and dark under natural light or bright environments, making the coupled grating region appear as a visible "mark" or "window".

[0026] This problem not only severely compromises the industrial design consistency and aesthetics of consumer electronics products such as AR glasses, but also causes visual interference during user wear—for example, uneven brightness in the coupled grating area can distract attention and even cause visual fatigue when observing real-world scenes. Although existing technologies have attempted to mitigate this problem by reducing grating depth, optimizing duty cycle, or using anti-reflective coatings, these methods often come at the cost of sacrificing diffraction efficiency or increasing process complexity, making it difficult to achieve a good balance between high brightness display performance and high visual transparency.

[0027] To address the aforementioned technical problems, embodiments of this application provide a diffractive waveguide and a near-eye display device.

[0028] Reference Figure 1 , Figure 2 As shown, the diffractive waveguide provided in this embodiment includes a waveguide substrate 100; the waveguide substrate 100 is provided with a coupling region 101 and a transition region 102; the transition region 102 surrounds the outer periphery of the coupling region 101; the coupling region 101 is provided with a first coupling grating 103; the transition region 102 is provided with a second coupling grating 104; the grating line arrangement direction of the second coupling grating 104 is parallel to the grating line arrangement direction of the first coupling grating 103; the period of the second coupling grating 104 is less than the period of the first coupling grating 103.

[0029] It should be noted that, in this embodiment of the application, a coupling region 101 and a transition region 102 surrounding the outer periphery are provided on the waveguide substrate 100, and a first coupling grating 103 and a second coupling grating 104 with different periods but parallel grating line directions are arranged in the two regions respectively. The smaller period of the second coupling grating 104 makes it exhibit lower diffraction efficiency and higher average transmittance in the visible light band, thereby visually bridging the transmittance difference between the coupling region 101 and the surrounding non-grating transparent region.

[0030] The above configuration ensures that the transmittance of both the first coupling grating 103 and the second coupling grating 104 is within the range of 80%-85%, with a transmittance difference of less than 5%. The entire diffractive waveguide has a uniform gray or neutral semi-transparent appearance, with a visual effect similar to sunglasses.

[0031] Since the human eye is not sensitive to the scattering and diffraction effects of high-frequency (small-period) gratings, the transition region 102 effectively weakens the imprinting effect while maintaining a certain optical continuity. This maintains the high-efficiency optical coupling performance of the central coupling region 101 and significantly improves the uniformity of the entire waveguide and the realistic scene perception when worn, achieving synergistic optimization of high display performance and high transparency aesthetics.

[0032] It should be noted that the first coupling grating 103 and the second coupling grating 104 are integrally formed without any physical gap between them. High-precision nanoimprinting or electron beam lithography can be used to ensure the consistency of the grating structure and reduce scattering caused by manufacturing defects.

[0033] The waveguide substrate 100 can be made of glass or optical plastic, and those skilled in the art can choose the appropriate material as needed.

[0034] This embodiment of the application effectively alleviates the problem of obvious imprints or light-dark boundaries caused by the difference in transmittance between the coupling grating region and the transparent non-grating region in traditional diffractive waveguides by setting a second coupling grating 104 with a smaller period but parallel grating line direction as a transition region 102 around the coupling region 101. Since the small period grating has low diffraction efficiency and weak scattering in the visible light band, it is difficult for the human eye to perceive its existence. Thus, while maintaining the high diffraction efficiency of the central coupling region 101, it significantly improves the overall appearance uniformity and ambient light transmittance consistency of the waveguide. It avoids visual interference and fatigue, and takes into account the requirements of high display performance and industrial aesthetics. The entire diffractive waveguide has a uniform gray or neutral semi-transparent appearance, with a visual effect similar to sunglasses, realizing the synergistic optimization of optical performance and user experience of AR near-eye display devices.

[0035] As an optional implementation method, refer to Figure 5 As shown, in this embodiment, the grating line arrangement direction of the second coupling grating 104 can also be set at an angle to the grating line arrangement direction of the first coupling grating 103, with the angle ranging from 1 to 90°. No particular limitation is made in this regard, and those skilled in the art can choose according to their needs. When the grating line arrangement direction of the second coupling grating 104 is at an angle to the grating line arrangement direction of the first coupling grating 103, the period of the second coupling grating 104 can be equal to the period of the first coupling grating 103.

[0036] For example, the angle between the grating line arrangement direction of the second coupling grating 104 and the grating line arrangement direction of the first coupling grating 103 is 30°, and the period of the second coupling grating 104 is half the period of the first coupling grating 103.

[0037] For example, the angle between the grating line arrangement direction of the second coupling grating 104 and the grating line arrangement direction of the first coupling grating 103 is 45°, and the period of the second coupling grating 104 is one-third of the period of the first coupling grating 103.

[0038] It should be noted that although non-parallel arrangements are slightly inferior to completely parallel structures in terms of diffraction phase matching and optical field continuity, from a macroscopic visual perspective, as long as the period of the second coupling grating 104 is small, it still exhibits "quasi-transparent" characteristics with low scattering and low diffraction to visible light. This can still alleviate the abrupt change in transmittance between the coupling region and the surrounding transparent region to a certain extent and weaken the imprinting phenomenon. This design provides greater process flexibility and optical control freedom for grating layout, and is especially suitable for AR optical systems that need to take into account multi-directional optical field expansion or space constraints.

[0039] As an optional implementation, the period of the second coupling grating 104 is half the period of the first coupling grating 103. n Where n is greater than or equal to 0, and the period of the second coupling grating 104 is greater than or equal to 5 nm.

[0040] For example, when n equals 1, the period of the second output grating 104 is half that of the first output grating 103.

[0041] It should be noted that, in this embodiment, the period of the second coupling grating 104 is set to be half the period of the first coupling grating 103. n Where n is greater than 0 and its period is greater than 5 nm, it is ensured that it is at the subwavelength scale but still manufacturable. The design of this application embodiment utilizes the physical property that small-period gratings are difficult to excite effective diffraction orders in the visible light band. When the period of the second coupling grating 104 is much smaller than the working wavelength, only zero-order transmission exists, and almost no visible diffraction or scattering effect is generated, thus making it visually close to transparent. At the same time, since the grating line directions of the second coupling grating 104 and the first coupling grating 103 are parallel, the transmittance gradient between the transition region 102 and the coupling region 101 can be smoothed while maintaining optical phase continuity. This structure avoids the window effect caused by the traditional abrupt boundary and does not significantly interfere with the coupling efficiency of the main optical path, thereby effectively improving the appearance consistency and wearing comfort of the diffracted waveguide without sacrificing display performance.

[0042] In this embodiment, the period of the second coupling grating 104 is set to 1 / 2 of the period of the first coupling grating 103.n Furthermore, the wavelength is greater than 5nm, placing it within the subwavelength range of the visible light band. This significantly suppresses the diffraction and scattering effects of the transition region 102 while maintaining the consistent orientation of the grating lines, making it nearly transparent to the human eye. This design effectively bridges the abrupt change in transmittance between the coupling region 101 and the surrounding non-grating regions, greatly reducing or even eliminating the imprints or light-dark boundaries caused by the grating structure in traditional optical waveguides. This not only improves the aesthetic appearance and ambient light consistency of near-eye display devices such as AR glasses, but also avoids visual interference and fatigue for users when observing real-world scenes. At the same time, it does not sacrifice the high-efficiency light extraction performance of the central coupling region, achieving high display quality.

[0043] As an optional implementation, the transition region 102 includes at least two sets, with the inner and outer edges of adjacent sets of transition regions 102 connected; from the inside to the outside, the period of the second coupling grating 104 of each set of transition regions 102 decreases sequentially.

[0044] It should be noted that, in this embodiment, the transition region 102 is designed to include at least two sets of concentrically distributed sub-transition regions 102, with seamless connection between the inner and outer edges of adjacent sets, and the period of the second coupling grating 104 set in each set decreasing sequentially from the inner to the outer. This multi-level gradient structure achieves a smooth transition of transmittance from the high diffraction efficiency of the central coupling region 101 to the highly transparent non-grating region on the periphery by gradually reducing the grating period: the inner transition region 102 retains a certain diffraction capability to assist in the expansion of the exit pupil, while the outer transition region 102 tends to be optically "invisible" because the period enters the subwavelength range. This stepped period reduction design effectively suppresses the visual discontinuity caused by a single abrupt boundary, significantly weakens the imprinting effect and improves the uniformity of appearance, while taking into account the light field modulation performance and the consistency of ambient light transmittance, further optimizing the visual comfort and product aesthetics of the AR near-eye display device.

[0045] Reference Figure 1 As shown, as an optional implementation, the waveguide substrate 100 further includes a coupling region 105 and a turning region 106; the coupling region 105 is used to couple image light into the waveguide substrate 100; the turning region 106 is used to receive image light and transmit image light to the coupling region 101.

[0046] It should be noted that, in this embodiment of the application, the waveguide substrate 100 further integrates the coupling region 105, the turning region 106 and the coupling region 101 to form a complete optical path transmission link: the coupling region 105 is responsible for efficiently coupling the image light from the display light source into the waveguide and exciting the guided mode; the turning region 106 deflects the propagation direction through a specially arranged grating structure, guiding the light to be transmitted horizontally to the coupling region 101; and finally, the coupling region 101 and its surrounding transition region 102 uniformly expand and couple the image light to the human eye.

[0047] The integrated design of this application embodiment not only realizes the light field control function required for two-dimensional exit pupil expansion, but also effectively alleviates the visual imprinting problem caused by abrupt changes in optical performance in traditional structures by introducing a periodically gradually changing transition grating around the coupling region 101. While ensuring high brightness and large field of view display performance, it significantly improves the appearance transparency and wearing experience of the entire waveguide, and is suitable for AR near-eye display devices with high integration and high aesthetic requirements.

[0048] Reference Figure 1 As shown, as an optional implementation, the coupling region 105, the turning region 106, the coupling out region 101, and the transition region 102 are disposed on the surface of the waveguide substrate 100 near the user's eye.

[0049] It should be noted that the coupling region 105, the turning region 106, the coupling region 101, and the transition region 102 are all integrated on the surface of the waveguide substrate 100 closest to the user's eye, so that the entire optical path control structure is concentrated on the inner surface facing the human eye. This layout avoids the ambient light reflection interference and appearance defects that may be caused by setting a complex grating structure on the outer surface far from the human eye. On the other hand, it facilitates the alignment and manufacturing of multi-region gratings through single-sided processes, improving processing consistency. At the same time, since the transition region 102 is adjacent to the coupling region 101 and located on the critical path of the field of view, its periodic gradient design can more directly compensate for the uneven transmittance under the human eye's perspective, effectively suppressing the window effect. While ensuring efficient light coupling, transmission, and coupling, it significantly enhances the visual naturalness of AR glasses when superimposed on real scenes.

[0050] Reference Figure 1 , Figure 3 As shown, in one optional implementation, the surface of the waveguide substrate 100 near the user's eye is divided into an exposed area 107 and a shielded area 108; the coupling region 105 and the transition region 106 are both located in the shielded area 108; the sum of the areas of the coupling region 101 and the transition region 102 is equal to the area of ​​the exposed area 107.

[0051] It should be noted that, in this embodiment, the surface of the waveguide substrate 100 near the user's eye is divided into an exposed area 107 and an obstructed area 108. The coupling region 105 and the transition region 106 are located within the obstructed area 108, specifically in areas within the lens that are typically covered by the frame or opaque structures and are not visible. This prevents these functional gratings from affecting the user's observation of the real world due to diffraction or scattering. The coupling region 101 and the transition region 102 completely occupy the exposed area 107, with a total area consistent with the exposed area 107, ensuring that only optimized coupling and transition gratings exist within the visible range of the human eye. This design cleverly utilizes the product's structural layout to separate optical performance requirements from visual transparency—ensuring efficient light transmission and uniform exit pupil expansion, while effectively eliminating abrupt changes in transmittance within the exposed area 107 through the periodic gradient of the transition region 102. This significantly improves the visual consistency and aesthetic performance of AR glasses in bright environments, while simplifying the optical performance requirements for non-critical areas, thus reducing costs and improving yield.

[0052] Reference Figure 1 , Figure 3 As shown, in one optional implementation, the exposed area 107 and the shielded area 108 have a boundary line 109, and one side of the coupling area 101 coincides with the boundary line 109.

[0053] It should be noted that in this embodiment, a clear dividing line 109 is provided between the exposed area 107 and the occluded area 108, and one edge of the coupling region 101 precisely coincides with the dividing line 109. This design ensures that the coupling region 101 is completely located within the user-visible exposed area 107, ensuring that the display light is efficiently coupled out only within the range of human eye observation. The adjacent occluded area 108 is used to accommodate non-display-related gratings such as the coupling region 105 and the transition region 106, preventing them from interfering with the visual experience of the real scene. At the same time, the transition region 102 can extend along the dividing line 109 into the exposed area 107, using a periodically gradually changing second coupling grating 104 to smooth the optical abrupt changes at the boundary of the coupling region 101, effectively suppressing the light and dark imprints caused by area switching. By aligning the functional partitions with the product structure boundaries, this solution further improves the integration, appearance consistency, and wearing immersion of the diffractive waveguide in AR glasses while ensuring optical performance.

[0054] Reference Figure 1 As shown, as an optional implementation, a turning region 106 is provided on each side of the coupling region 105; there are two coupling out regions 101, which correspond to the two turning regions 106 respectively; the image light entering through the coupling region 105 propagates to both sides, turns after passing through the turning regions 106 on both sides, and is coupled out by the two coupling out regions 101 to form outgoing beams for the user's left and right eyes to observe respectively.

[0055] It should be noted that two transition regions 106 are symmetrically arranged on both sides of the coupling region 105, corresponding to two coupling out regions 101, forming a binocular independent optical path structure. Image light from the microdisplay first enters the waveguide substrate 100 through the central coupling region 105 and propagates along the left and right sides of the waveguide; subsequently, the transition regions 106 on both sides deflect the corresponding mode beams by 90°, guiding them towards the user's left and right eyes; finally, the two beams are uniformly coupled out by the corresponding coupling out regions 101 and their surrounding transition regions 102, forming independent output beams for the left and right eyes, realizing stereoscopic vision display. This design not only supports binocular parallax and large field of view requirements, but also effectively eliminates transmittance unevenness and window effect within the binocular visible area by integrating periodically gradient transition gratings around each coupling out region 101, ensuring high brightness and high uniformity binocular display performance.

[0056] As an optional implementation, the coupling region 105 has a turning region 106 on at least one side, and the coupling region 101 receives the image light after it has been turned by the turning region 106 and couples the image light out to the user's right eye or left eye.

[0057] It should be noted that, referring to Figure 4 As shown, if necessary, only one coupling region 105 and one coupling region 101 can be provided on the waveguide substrate 100.

[0058] It should be noted that the coupling region 105 has a turning region 106 on at least one side. After the image light enters the waveguide substrate 100 through the coupling region 105, it propagates along the waveguide to the turning region 106 on that side, where the light path is deflected and guided to the corresponding output region 101. Subsequently, the output region 101 efficiently couples out the deflected image light, forming an output beam for the user's left or right eye to observe individually. This single-sided optical path design is suitable for monocular AR display scenarios or as a channel in a binocular system, with a compact structure and concentrated light effect. At the same time, the output region 101, together with its surrounding transition region 102, can effectively mitigate abrupt changes in transmittance within the visible area, avoid vignetting, and improve appearance transparency and visual comfort while ensuring monocular display performance.

[0059] The near-eye display device provided in this application embodiment includes an image generation unit and the aforementioned diffractive waveguide; the image generation unit is used to emit image light rays into the coupling region 105 of the diffractive waveguide. The near-eye display device includes a blocking member that covers the blocking area 108.

[0060] The near-eye display device provided in this application injects image light emitted from the image generation unit into the coupling region 105 of the diffractive waveguide, and utilizes the turning region 106 and the coupling region 101 within the waveguide to complete beam transmission and exit pupil expansion, achieving high-quality virtual image presentation. Simultaneously, a shielding component is structurally provided to cover the shielding region 108 on the waveguide substrate 100, making it invisible and preventing scattering, reflection, or uneven transmittance caused by the grating structure in these areas from interfering with the user's observation of the real environment. The exposed region 107 only includes the optically optimized coupling region 101 and its transition region 102, the latter effectively bridging the visual difference with the surrounding transparent region through a periodic gradient design, significantly reducing the imprinting effect. This solution combines optical functional zoning and physical shielding strategies, ensuring high-efficiency and high-uniformity display performance while significantly improving the appearance consistency, environmental integration, and wearing immersion of AR devices, balancing industrial aesthetics and user experience.

[0061] The above description is merely a preferred embodiment of this application and is 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.

Claims

1. A diffractive optical waveguide, characterized in that, The system includes a waveguide substrate (100); the waveguide substrate (100) has a coupling region (101) and a transition region (102); the transition region (102) surrounds the outer periphery of the coupling region (101); the coupling region (101) has a first coupling grating (103); the transition region (102) has a second coupling grating (104); the grating line arrangement direction of the second coupling grating (104) is parallel to or at an angle to the grating line arrangement direction of the first coupling grating (103); the period of the second coupling grating (104) is less than or equal to the period of the first coupling grating (103).

2. The diffractive waveguide according to claim 1, characterized in that, The period of the second coupling grating (104) is half the period of the first coupling grating (103). n ; where n is greater than or equal to 0, and the period of the second coupled grating (104) is greater than or equal to 5nm.

3. The diffractive waveguide according to claim 1, characterized in that, The transition region (102) includes at least two sets, with the inner and outer edges of adjacent transition regions (102) connected; from the inside to the outside, the period of the second coupling grating (104) of each set of transition regions (102) decreases sequentially.

4. The diffractive waveguide according to any one of claims 1-3, characterized in that, The waveguide substrate (100) further includes a coupling region (105) and a turning region (106); the coupling region (105) is used to couple image light into the waveguide substrate (100); the turning region (106) is used to receive the image light and transmit the image light to the coupling region (101).

5. The diffractive waveguide according to claim 4, characterized in that, The coupling region (105), the turning region (106), the coupling out region (101), and the transition region (102) are disposed on the surface of the waveguide substrate (100) near the user's eye.

6. The diffractive waveguide according to claim 5, characterized in that, The surface of the waveguide substrate (100) near the user's eye is divided into an exposed area (107) and a shielded area (108); the coupling area (105) and the turning area (106) are both located in the shielded area (108); the sum of the areas of the coupling area (101) and the transition area (102) is equal to the area of ​​the exposed area (107).

7. The diffractive waveguide according to claim 6, characterized in that, The exposed area (107) and the shielded area (108) have a boundary line (109), and one side of the coupling area (101) coincides with the boundary line (109).

8. The diffractive waveguide according to any one of claims 5-7, characterized in that, The coupling-in region (105) has a turning region (106) on each side; there are two coupling-out regions (101), which correspond to the two turning regions (106) respectively; the image light entering through the coupling-in region (105) propagates to both sides, turns after passing through the turning regions (106) on both sides, and is coupled out by the two coupling-out regions (101) to form outgoing light beams for the user's left and right eyes to observe respectively.

9. The diffractive waveguide according to any one of claims 5-7, characterized in that, The coupling-in region (105) has the turning region (106) on at least one side, and the coupling-out region (101) receives the image light after it has been turned by the turning region (106) and couples the image light out to the user's right eye or left eye.

10. A near-eye display device, characterized in that, It includes an image generation unit and a diffractive waveguide as described in any one of claims 1-9; the image generation unit is used to emit image light into the coupling region (105) of the diffractive waveguide.

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