Diffraction waveguide device, near-eye display equipment and stray light suppression method

Abstract

The embodiment of the invention provides a diffraction waveguide device, near-eye display equipment and a stray light suppression method. The diffraction waveguide device comprises a waveguide substrate, a micro-nano structure region and a light absorption layer, the waveguide substrate is provided with a main body area for transmitting image light and an edge area surrounding the main body area; the micro-nano structure region is arranged in the edge region; the light absorption layer at least covers the micro-nano structure region; wherein the micro-nano structure area is configured to be capable of leading out stray light transmitted to the edge area and enabling the stray light to be absorbed by the light absorption layer by destroying a total reflection condition at an interface between the waveguide substrate and the light absorption layer.

Description

Technical Field

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

[0002] Diffractive waveguide technology is a core display solution in near-eye display devices such as augmented reality (AR) and mixed reality (MR). Its principle is to achieve image transmission and output through diffractive optical elements (such as coupling-in gratings and coupling-out gratings) within the waveguide substrate. However, stray light often exists outside the intended imaging optical path within the waveguide, propagating unexpectedly. This stray light mainly originates from non-ideal diffraction efficiency of the grating, interface scattering, and ambient light incidence. It repeatedly propagates within the waveguide substrate to satisfy total internal reflection conditions. Eventually, some of this stray light enters the exit pupil, causing a decrease in image contrast, image blurring, and the so-called "ghosting" phenomenon, negatively impacting the user experience.

[0003] To suppress stray light, the current industry approach involves coating the sidewalls of waveguides with ink, a light-absorbing material. The initial design intention is to absorb stray light propagating to the edges after it enters the ink layer. However, traditional methods have limitations: to achieve a wider field of view, waveguides typically use high-refractive-index glass or optical plastics as the substrate material. This makes the refractive index difference between the waveguide substrate and the light-absorbing ink on the sidewalls significant. According to the Fresnel reflection principle, when stray light is incident at a large angle (e.g., >25°) at the waveguide-ink interface, total internal reflection or high reflection is likely to occur. Specifically, most of the light cannot effectively couple into the ink layer but is reflected back into the waveguide to continue propagating, unable to be effectively absorbed, thus continuing to interfere with the normal image as stray light. Improved solutions attempt to coat the upper and lower edges of the waveguide with light-absorbing ink as well, aiming to capture stray light reflected back from the sidewalls a second time. However, this approach still fails to overcome the total internal reflection problem caused by the inherent refractive index difference between the waveguide substrate and the light-absorbing material. For stray light at large angles, it also faces the problem of high reflectivity at the ink coating interface at the upper and lower surface edges, resulting in limited improvement in suppression effect.

[0004] Therefore, there is still an urgent need in the field for a new technology that can fundamentally improve the absorption efficiency of stray light at large angles in order to break through the bottleneck of the contrast performance of current diffractive waveguide devices. Summary of the Invention

[0005] The purpose of this application is to provide a new technology solution for a diffractive waveguide device, a near-eye display device, and a stray light suppression method for a diffractive waveguide device, so as to solve the problem that the existing technology has poor stray light suppression effect at large angles due to the difference in refractive index between the waveguide substrate and the light absorption layer.

[0006] In a first aspect, embodiments of this application provide a diffractive waveguide device, the diffractive waveguide device comprising: A waveguide substrate having a main region for transmitting image light and an edge region surrounding the main region; Micro / nanostructure regions are disposed in the edge regions; and, A light-absorbing layer covers at least the micro / nano structure region; The micro / nano structure region is configured to allow stray light transmitted to the edge region to be directed out and absorbed by the light absorption layer by disrupting the total internal reflection condition at the interface between the waveguide substrate and the light absorption layer.

[0007] Optionally, the edge region includes the sidewall of the waveguide substrate and the portion of the upper and lower surfaces of the waveguide substrate adjacent to the sidewall; The micro / nano structure region is formed on at least one of the upper surface, the lower surface, and the sidewall; The light-absorbing layer covers the micro / nano structure region and the sidewalls not covered by the micro / nano structure region.

[0008] Optionally, an input grating and an output grating are provided on the main body area; The orthographic projection of the micro / nano structure region onto the waveguide substrate does not overlap with the orthographic projections of the coupling-in grating and the coupling-out grating.

[0009] Optionally, the micro / nano structure region constitutes a strip-shaped region surrounding the periphery of the main body region, and the width of the strip-shaped region is 0.5mm to 2mm.

[0010] Optionally, the micro / nano structure region includes a plurality of periodically arranged micro / nano structure units, and the period of the micro / nano structure region is greater than 1 / 2 of the period of the coupling grating.

[0011] Optionally, the period of the micro / nano structure region is greater than or equal to the period of the coupled grating.

[0012] Optionally, for stray light transmitted to the edge region within the waveguide substrate at an incident angle greater than 25°, the micro / nano structure region reduces the light reflectivity at the interface between the waveguide substrate and the light absorption layer by at least 50% compared to the same waveguide substrate without the micro / nano structure region.

[0013] Optionally, the light-absorbing layer is an ink layer; The thickness of the light-absorbing layer on the waveguide substrate is greater than 2 μm; and / or, The light-absorbing layer has an overflow portion formed on the outside of the micro / nano structure region, and the thickness of the overflow portion is greater than 2 μm.

[0014] Optionally, the light-absorbing layer has an overflow portion formed on the outside of the micro / nano structure region; The light-absorbing layer has an overflow portion formed on the outside of the micro / nano structure region; The width of the overflow portion is w, the thickness of the waveguide substrate is d, the reflection angle of the imaging ray propagating in the waveguide substrate is a, and d = w × tan(a) satisfies w < 2 mm.

[0015] Optionally, the sum of the angles between the normals of the upper surface and the sidewall of the waveguide substrate is 90°, and the sum of the angles between the normals of the lower surface and the sidewall is 90°.

[0016] Secondly, embodiments of this application provide a near-eye display device, the near-eye display device comprising: An image source, used to generate an imaging beam carrying image information; and, The diffraction waveguide device as described in the first aspect is configured to receive and conduct the imaging beam.

[0017] Thirdly, embodiments of this application provide a stray light suppression method for diffractive waveguide devices, the stray light suppression method comprising: Micro- and nanostructure regions are set in the edge region of the waveguide substrate; A light-absorbing layer is coated on the micro / nano structure region; The micro / nano structure region disrupts the total internal reflection condition of stray light propagating to the edge region within the waveguide substrate at the interface between the waveguide substrate and the light absorption layer, thereby directing the stray light outside the waveguide substrate and allowing it to be absorbed by the light absorption layer.

[0018] The beneficial effects of this application are as follows: Compared to the problem in existing technologies where large-angle stray light is difficult to effectively absorb due to total internal reflection at the waveguide substrate-light absorption layer interface caused by refractive index differences, this application addresses the issue by setting micro / nano structures in the edge region of the waveguide substrate and covering them with a light absorption layer. By actively disrupting the total internal reflection condition using these micro / nano structures, stray light that would otherwise be reflected back into the waveguide substrate can be efficiently extracted and captured by the light absorption layer, thereby significantly improving the suppression capability of stray light, especially large-angle stray light.

[0019] Other features and advantages of this specification will become clear from the following detailed description of exemplary embodiments with reference to the accompanying drawings. Attached Figure Description

[0020] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments of this specification and, together with their description, serve to explain the principles of this specification.

[0021] Figure 1 Optical path diagram of a traditional diffraction waveguide scheme; Figure 2 Optical path diagram of an improved diffraction waveguide scheme; Figure 3 for Figure 2 The reflectivity curves of stray light at different incident angles are shown in the improved diffraction waveguide scheme. Figure 4 This is one of the magnified schematic diagrams showing the interaction between the micro / nano structure region and the light absorption layer in the diffraction waveguide device provided in the embodiments of this application.

[0022] Figure 5 Reflectivity curves of stray light at different incident angles in the diffractive waveguide device provided in the embodiments of this application; Figure 6 This is a second enlarged schematic diagram of the interaction between the micro / nano structure region and the light absorption layer in the diffraction waveguide device provided in the embodiments of this application. Figure 7 This is a schematic diagram of a diffractive waveguide device provided in an embodiment of this application.

[0023] Explanation of reference numerals in the attached figures: 1. Waveguide substrate; 101. Edge region; 11. Upper surface; 12. Lower surface; 2. Micro / nano structure region; 3. Light absorption layer; a. Coupled-in grating; b. Coupled-out grating; c. Turning grating. Detailed Implementation

[0024] Various exemplary embodiments of the present application will now be described in detail with reference to the accompanying drawings. It should be noted that, unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of the present application.

[0025] The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the scope of this application and its application or use.

[0026] Technologies and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, such technologies and equipment should be considered part of the specification.

[0027] In all the examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values.

[0028] It should be noted that similar labels and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be discussed further in subsequent figures.

[0029] The following description, in conjunction with the accompanying drawings, details the diffractive waveguide device, near-eye display device, and stray light suppression method for the diffractive waveguide device provided in the embodiments of this application.

[0030] According to one embodiment of this application, a diffractive waveguide device is provided, see [link to relevant documentation]. Figure 4 The diffraction waveguide device includes: a waveguide substrate 1, a micro / nano structure region 2, and a light absorption layer 3; the waveguide substrate 1 has a main region for transmitting image light and an edge region 101 surrounding the main region; the micro / nano structure region 2 is disposed on the edge region 101; the light absorption layer 3 covers at least the micro / nano structure region 2; wherein the micro / nano structure region 2 is configured to be able to guide stray light transmitted to the edge region 101 and absorb it by the light absorption layer 3 by disrupting the total internal reflection condition at the interface between the waveguide substrate 1 and the light absorption layer 3.

[0031] The diffractive waveguide device provided in this application is suitable for waveguide-type near-eye display devices with strict requirements for image quality. Specifically, this diffractive waveguide device aims to solve problems such as image haze, ghosting, and reduced signal-to-noise ratio caused by stray light inherent in diffractive waveguide devices in near-eye display devices such as augmented reality (AR) and mixed reality (MR). Through innovative edge region micro-nano structure design, it provides an effective technical path for stray light management in high-refractive-index waveguide substrates, and is suitable for next-generation consumer electronics and professional display products that pursue thin and compact structures and high-quality image experiences.

[0032] It should be noted that, to suppress stray light, the commonly used optical solution in the industry is to coat the sidewall of the waveguide substrate 1 with a high-absorption ink material as the light absorption layer 3, see [reference]. Figure 1 The initial design intent of this optical scheme was to prevent stray light transmitted to the edge of waveguide substrate 1 (the formation of which can be found in [reference]). Figure 1 Light ray B (which ultimately produces stray light) can enter the light absorption layer 3, i.e., the ink layer, and be absorbed and consumed. However, this traditional optical solution has obvious technical limitations: as display technology continues to demand higher viewing angles, diffractive waveguide devices generally use high-refractive-index glass or optical plastics as substrate materials. This material choice leads to a further widening of the refractive index difference between the waveguide substrate and the light absorption layer 3 (i.e., the ink layer) on the sidewall.

[0033] According to the Fresnel reflection principle, when stray light is incident at a large angle (e.g., an incident angle greater than 25°) at the interface between the waveguide substrate and the ink layer on the sidewall, total internal reflection or high reflection is likely to occur. Specifically, most of the stray light will be unable to effectively couple into the ink layer. Figure 1 The light-absorbing layer 3 shown is the ink layer, which is reflected back into the waveguide substrate 1 to form a light absorption layer 3. Figure 1 The undesired optical path shown by ray B continues to propagate within waveguide substrate 1 and cannot be effectively absorbed. These reflected stray lights undergo multiple reflections within waveguide substrate 1, and some still eventually enter the exit pupil region, forming background noise and interfering with the display quality of the normal image. This technical bottleneck makes... Figure 1 The traditional sidewall coating scheme shown is difficult to effectively suppress stray light, especially large-angle stray light, when dealing with high-refractive-index waveguides.

[0034] An existing improved optical solution, see [link to solution]. Figure 2 A light-absorbing ink material is coated onto the upper and lower surface edges of the waveguide substrate 1 to form a light-absorbing layer 3. This design aims to absorb stray light reflected from the sidewalls of the waveguide substrate 1 (see [link to relevant documentation]). Figure 2 The light rays (B) are captured a second time. However, this scheme still fails to overcome the total internal reflection problem caused by the inherent refractive index difference between the waveguide substrate 1 and the light-absorbing layer 3 (i.e., the ink layer). For stray light at large angles, it also faces the dilemma of high reflectivity at the ink coating interface at the edges of the upper and lower surfaces, resulting in limited improvement in suppression effect. See Figure 3 When the incident angle of light is greater than 25°, its reflectivity at the interface between the waveguide substrate 1 and the ink layer on the sidewall still increases sharply, resulting in the improved optical scheme still not achieving ideal absorption of stray light at large angles. It should be noted that... Figure 2 The light ray A shown is a beam used for imaging that is transmitted normally by total internal reflection within the waveguide substrate 1.

[0035] To address numerous problems in existing technologies, this application provides a novel diffractive waveguide device design that achieves efficient suppression of stray light through a specific optical structure design. The technical solution of the diffractive waveguide device provided in this application is described in detail below with reference to the accompanying drawings.

[0036] See Figure 4 , Figure 6 and Figure 7 The waveguide substrate 1 provided in this application is optically divided into a main region and an edge region 101. This division is based on the analysis of different light transmission characteristics within the waveguide substrate 1: the main region serves as the imaging beam (e.g., Figure 4The main transmission channel (as shown in beam A) has optical elements such as coupling gratings, deflection gratings, and output gratings disposed inside or on its surface to ensure efficient transmission of the imaging beam within the waveguide substrate 1 via total internal reflection. The edge region 101 surrounding the main body region is considered to contain stray light (such as...). Figure 4 (As shown in B) Areas where light tends to gather and propagate continuously.

[0037] The key to the optical design of this application lies in the fact that a micro / nano structure region 2 is set in the edge region 101, see [link to relevant documentation]. Figure 4 and Figure 6 The characteristic dimensions of this micro / nanostructure region 2 are designed on the wavelength or subwavelength order, and it can be a periodic or aperiodic micro / nanostructure. See also Figure 2 The existing improved scheme shown has a significant difference in refractive index between the high-refractive-index waveguide substrate 1 and the light-absorbing layer 3, which causes stray light (especially light with an incident angle greater than 25°) to undergo total internal reflection at the interface between the waveguide substrate 1 and the ink layer on the sidewall and cannot be effectively absorbed.

[0038] This application solves this technical challenge by introducing a micro / nano structure region 2 at a specific location on the waveguide substrate 1. The working principle of this application is: by modulating the propagation characteristics of light waves through the micro / nano-scale micro / nano structure region 2, the phase-matching condition required for total internal reflection at a smooth interface is disrupted. See also... Figure 4 and Figure 6 As indicated by the white arrow, this design prevents stray light that would otherwise be reflected from being reflected. (See...) Figure 4 and Figure 6 As shown by rays B and B2, the propagation direction can be changed, and ray B2 will eventually be extracted from the waveguide substrate 1. Only a small amount of ray B1 will be reflected back into the waveguide substrate 1, but this will not cause significant stray light.

[0039] Furthermore, a light-absorbing layer 3 is designed and designed to cover the micro / nano structure region 2, which together with the micro / nano structure region 2 constitutes a complete optical processing system. The micro / nano structure region 2 is responsible for extracting stray light from the waveguide substrate 1, while the light-absorbing layer 3 absorbs the extracted light. The synergistic effect of both forms a highly efficient stray light suppression mechanism that combines structural extraction and material absorption.

[0040] See Figure 5 The test results shown demonstrate that, by adopting the optical design provided in this application, the light reflectivity of the diffractive waveguide device is significantly reduced across all angular ranges. This directly verifies the superior effect of the optical structure design in suppressing stray light. In particular, this application exhibits a clear technical advantage for handling large-angle stray light, which is difficult to handle with existing technologies.

[0041] This optical structure design effectively solves the technical problem of stray light being difficult to absorb efficiently in high-refractive-index waveguide substrates while ensuring that the performance of the main imaging optical path is not affected, thus providing a reliable technical guarantee for improving the imaging quality of diffractive waveguide devices.

[0042] Therefore, compared with the problem in the prior art that large-angle stray light is difficult to be effectively absorbed due to total internal reflection at the waveguide substrate-light absorption layer interface caused by the difference in refractive index, this application sets a micro-nano structure region 2 on the edge region 101 of the waveguide substrate 1 and covers it with a light absorption layer 3. By actively destroying the total internal reflection condition using the micro-nano structure, the stray light that would originally be reflected back into the waveguide substrate 1 can be efficiently exported and captured by the light absorption layer, thereby significantly improving the ability to suppress stray light, especially large-angle stray light.

[0043] See some examples in this application. Figure 4 , Figure 6 and Figure 7 The edge region 101 includes the sidewall of the waveguide substrate 1 and the portion of the upper surface 11 and lower surface 12 of the waveguide substrate 1 adjacent to the sidewall; the micro / nano structure region 2 is formed on at least one of the upper surface 11, the lower surface 12 and the sidewall; the light absorption layer 3 covers the micro / nano structure region 2 and the sidewall not covered by the micro / nano structure region.

[0044] In this example of the application, the edge region structure of the diffractive waveguide device is further clarified and optimized. See [link to relevant documentation]. Figure 4 , Figure 6 and Figure 7 As shown, the waveguide substrate 1 includes an optically smooth upper surface 11, a lower surface 12, and a sidewall connecting the two, which together constitute the interface for total internal reflection propagation of light within the waveguide.

[0045] The micro / nano structure region 2 is formed in the edge region near the sidewall of the upper surface 11 and the lower surface 12, and may also extend to the sidewall. See [link / reference needed]. Figure 6 This location is where stray light energy is concentrated when propagating at the edge of the waveguide. Setting up micro-nano structures here can effectively disturb the light propagation interface, disrupt the total internal reflection condition, and cause stray light to be extracted from the waveguide substrate 1.

[0046] The light-absorbing layer 3 not only covers the micro / nano structure region 2, but also further covers the sidewalls. This design forms a synergistic absorption mechanism: the micro / nano structure region 2 is mainly responsible for guiding stray light from the waveguide substrate 1 to the outside of the substrate; while the light-absorbing layer covering the sidewalls directly absorbs stray light propagating laterally or extracted from the micro / nano structure region, preventing it from being reflected back into the waveguide substrate 1.

[0047] This example demonstrates how to achieve three-dimensional control of stray light in the edge region 101 by rationally arranging the micro-nano structure area and expanding the coverage of the light absorption layer 3. This significantly improves the overall stray light suppression effect while ensuring that the imaging optical path performance is not affected.

[0048] See some examples in this application. Figure 7 The main body region is provided with an input grating and an output grating; the orthographic projection of the micro / nano structure region 2 on the waveguide substrate 1 does not overlap with the orthographic projections of the input grating and the output grating.

[0049] In this example of the application, the functional partitioning and spatial layout of the diffractive waveguide device have been optimized. See [link to example]. Figure 7 The main body of the waveguide substrate 1 is provided with optical elements that realize the core imaging function—coupled-in grating a and coupled-out grating b. The coupled-in grating a is responsible for coupling the light emitted from an external image source (such as an optomechanical system) into the waveguide substrate 1, while the coupled-out grating b is responsible for coupling the transmitted image light out of the waveguide substrate 1 and guiding it to the human eye.

[0050] Meanwhile, the orthographic projection of the micro / nano structure region 2 onto the waveguide substrate 1 maintains a non-overlapping spatial relationship with the orthographic projections of both the coupling-in grating and the coupling-out grating. This design ensures the following technical effects: Functional isolation: Through a projection-free design, the micro / nano structure region 2, responsible for stray light management, is completely spatially separated from the grating region responsible for normal imaging. This physical isolation effectively avoids interference from the micro / nano structure region 2 on the normal imaging optical path, ensuring that the energy efficiency and imaging quality of the coupling, conduction, and coupling processes are not affected.

[0051] Zoning Optimization: This design embodies the concept of functional zoning. The main region focuses on high-quality image transmission while maintaining the integrity of its optical surface; while the edge region 101 focuses on stray light processing, achieving efficient light absorption through the micro / nano structure region 2. The two regions are spatially adjacent but optically independent, achieving optimization of the overall performance of the waveguide device.

[0052] In addition, the clear spatial relationships provide clear process guidance for the manufacturing of diffractive waveguide devices, making it easy to precisely control the position and size of each functional area through micro-nano processing technologies such as photolithography and nanoimprinting, thus ensuring product consistency and reliability.

[0053] This spatial layout design in the example enables the diffraction waveguide device of this application to achieve efficient suppression of stray light while maintaining excellent imaging performance, solving the technical problem of difficulty in balancing imaging quality and stray light control in traditional solutions.

[0054] It should be noted that the micro / nano structure region 2 can be disposed on the inner sidewalls of the upper surface 11 and the lower surface 12 of the waveguide substrate 1, or it can be disposed on the surface of the waveguide substrate 1 in the same way as the coupling grating and the coupling grating.

[0055] In addition, the diffractive waveguide device provided in this application may also have a bend grating c disposed on its waveguide substrate 1, see [reference]. Figure 7 As shown. Under this structural design, the orthographic projection of the micro / nano structure region 2 on the waveguide substrate 1 does not overlap with the orthographic projections of the coupling grating a, the turning grating c, and the output grating b.

[0056] In some examples of this application, the micro / nano structure region 2 constitutes a strip-shaped region surrounding the periphery of the main body region, and the width of the strip-shaped region is 0.5 mm to 2 mm.

[0057] In this example of the application, the spatial morphology and size of the micro / nano structure region 2 have been specifically optimized. The micro / nano structure region 2 is constructed as a continuous strip-shaped region surrounding the periphery of the main body region of the waveguide substrate 1. This design is based on consideration of the stray light propagation characteristics: stray light may arrive at the edge region of the waveguide substrate 1 from various directions, and the annular strip structure can ensure that stray light can be effectively captured and processed regardless of the angle at which it is incident on the edge region.

[0058] The width of the aforementioned strip region is optimized to be within the range of 0.5mm to 2mm. This size range was determined based on consideration of multiple factors: A width of not less than 0.5 mm ensures that the micro / nano structure region 2 has sufficient area to effectively handle stray light. An excessively narrow width would cause some stray light to escape and not be promptly extracted and absorbed.

[0059] A width of no more than 2 mm fully considers the space utilization of the diffraction waveguide device. This size ensures stray light suppression while maximizing the usable area of ​​the main body of the waveguide substrate 1, ensuring that the imaging optical path is not affected.

[0060] For example, the micro / nano structure region 2 constitutes a strip-shaped region surrounding the periphery of the waveguide substrate 1, and the width of the strip-shaped region is 0.5 mm, 1 mm, 1.5 mm, or 2 mm.

[0061] This annular strip design and precise width control enable the micro / nano structure region 2 to achieve maximum stray light management efficiency within a limited edge space, reflecting the comprehensive consideration of this application in terms of optical structure design and optical performance optimization.

[0062] In some examples of this application, the micro / nano structure region 2 includes a plurality of periodically arranged micro / nano structure units, and the period of the micro / nano structure region 2 is greater than 1 / 2 of the period of the coupling grating b.

[0063] In this example of the application, a lower limit is set for the periodic design of the micro / nano structure region 2: its period must be greater than half, i.e., 1 / 2, of the period of the coupling grating b. This design aims to achieve at least two core objectives: (1) Avoid optical crosstalk: Ensure that the diffraction characteristics of the micro / nano structure region 2 are effectively separated from the working wavelength and angle of the coupling grating b. If the period of the micro / nano structure region 2 is too small (e.g., close to or less than half the period of the coupling grating), its diffraction may interfere with the effective light rays at a specific angle in the imaging optical path, thereby affecting the uniformity and quality of the normal image.

[0064] (2) Functional orientation design: This lower limit of the period ensures that the optical response of the micro / nano structure region 2 (such as its diffraction or scattering characteristics) can be optimized specifically for stray light, especially those large-angle, undesirable light rays, rather than acting on the imaging beam together with the coupling grating.

[0065] This design rule ensures in principle that the micro / nano structure region 2 can efficiently perform stray light suppression without negatively affecting the performance of the main imaging optical path, which is the basic guarantee for suppressing stray light without compromising image quality.

[0066] In some examples of this application, the period of the micro / nano structure region 2 is greater than or equal to the period of the coupling grating b.

[0067] In this preferred example of the application, a further optimization is proposed for the period of the micro / nano structure region 2: its period is designed to be greater than or equal to the period of the coupling grating b. This is a further optimization of the stray light suppression performance based on meeting the above basic requirements.

[0068] In diffractive optics, structures with larger periods distribute their optical energy more widely across lower diffraction orders (such as the 0th and ±1st orders). This means more concentrated light energy, higher diffraction efficiency, and easier control of the optical path. For stray light suppression, this translates to higher extraction efficiency—meaning that the micro / nano structure region 2 can more effectively transfer stray light energy out of the waveguide.

[0069] According to the grating equation, a larger period, for a given wavelength, can couple (i.e. diffract) light rays with larger angles. This is precisely the core problem that this application aims to solve—suppressing stray light that propagates at large angles (near the total reflection angle) within the waveguide substrate and is inaccessible to conventional light-absorbing layers (i.e., ink layers). Therefore, by designing the period of the micro / nano structure region 2 to be equal to or greater than the period of the coupling grating b, its ability to extract the most difficult-to-handle large-angle stray light is optimized.

[0070] More preferably, the period of the micro / nano structure region 2 is greater than the period of the coupled grating b.

[0071] In some examples of this application, for stray light transmitted to the edge region 101 at an incident angle greater than 25° within the waveguide substrate 1, the micro / nano structure region 2 reduces the light reflectivity at the interface between the waveguide substrate 1 and the light absorption layer 3 by at least 50% compared to the same waveguide substrate without the micro / nano structure region. See [reference needed]. Figure 3 and Figure 5 .

[0072] This example from the present application demonstrates, through quantified performance metrics, that the present application has achieved a significant improvement in the suppression performance of stray light at large angles.

[0073] Directional optimization was achieved for the critical angle range where stray light is difficult to absorb due to total internal reflection in existing schemes, where the incident angle is greater than 25°. (See also...) Figure 5 This demonstrates the superior performance of the micro / nano structure region 2 in disrupting total internal reflection and promoting light extraction, enabling most stray light energy to be effectively extracted and captured by the light absorption layer 3, rather than reflected back to the waveguide substrate 1.

[0074] contrast Figure 3 and Figure 5 This significant reduction in reflectivity directly translates into a substantial decrease in stray light intensity, resulting in higher image contrast and lower background noise for the diffractive waveguide device, ultimately improving the overall display quality.

[0075] In some examples of this application, the light-absorbing layer 3 is an ink layer; the thickness of the light-absorbing layer 3 on the waveguide substrate 1 is greater than 2 μm; and / or, the light-absorbing layer 3 has an overflow portion formed on the outside of the micro / nano structure region 2, and the thickness of the overflow portion is greater than 2 μm.

[0076] In this example of the application, the light-absorbing layer 3 is an ink layer with high light absorption performance. To ensure that stray light is fully absorbed, the coating thickness of the light-absorbing layer 3 on the surface of the waveguide substrate 1 is set to be greater than 2 μm. This thickness design is based on the consideration of matching optical absorption depth with refractive index, which can effectively reduce Fresnel reflection of light at the ink-substrate interface and increase the proportion of light entering the ink layer and being absorbed.

[0077] The light-absorbing layer 3 has an overflow portion formed on the outside of the micro / nano structure region 2, and its thickness is also greater than 2 μm. This overflow portion not only expands the physical range of the light-absorbing area, but also covers the tilted outgoing light rays emanating from the micro / nano structure region 2, preventing secondary reflection at the substrate edge.

[0078] In some examples of this application, the light absorption layer 3 has an overflow portion formed on the outside of the micro / nano structure region 2; the width of the overflow portion is w, the thickness of the waveguide substrate 1 is d, the reflection angle of the imaging light propagating in the waveguide substrate 1 is a, and w=d×tan(a).

[0079] In this example of the application, the light-absorbing layer 3 extends outward from the micro / nano structure region 2 to form an overflow portion with a specific width. The width of the overflow portion is designed according to optical geometry: its width w satisfies the formula w=d×tan(a) with the thickness d of the waveguide substrate 1 and the reflection angle α of the imaging light propagating in the waveguide substrate.

[0080] This relationship is established based on the path analysis of light propagation within waveguide substrate 1. For example... Figure 4 As shown, light rays emitted from inside the waveguide substrate 1 after being disturbed by the micro / nano structure region 2 will be emitted at a certain angle to the normal (related to the internal reflection angle α). The overflow portion must have a sufficient lateral width w to effectively intercept and absorb these tilted emitted rays, preventing them from crossing the region where the light absorption layer 3 is located and re-entering free space or causing unnecessary reflection.

[0081] Furthermore, based on the optimized design of this application, the light-absorbing layer 3 on a single sidewall has an angular limitation on the absorption of light. For example, if the ink is only coated on the vertical sidewall, it can typically only effectively absorb light with an incident angle in the range of 0° to 45°. For light with an internal reflection angle greater than 45°, its incident angle at the sidewall will be less than 45°, easily meeting the condition of total internal reflection and thus failing to enter the ink layer on the sidewall, thereby forming unabsorbed stray light.

[0082] Therefore, in this example, large-angle light is extracted through the micro / nano structures at the edges of the upper surface 11 and the lower surface 12, and captured by the overflow portion with a calculated width w, precisely to solve the angular limitation problem of sidewall absorption. This design enables stray light with a reflection angle α greater than 45° to be efficiently absorbed by the ink layer in the overflow portion above or below, even if the total internal reflection is disrupted by the micro / nano structure region, thus achieving comprehensive suppression of stray light over a wider angle range.

[0083] In summary, this example guides the structural design through optical path analysis, ensuring that the width of the overflow section matches the waveguide thickness and the angle of the light rays, thereby guaranteeing the integrity and reliability of stray light absorption in the structure.

[0084] In some examples of this application, the light absorption layer 3 has an overflow portion formed on the outside of the micro / nano structure region 2; the width of the overflow portion is w, the thickness of the waveguide substrate 1 is d, the reflection angle of the imaging light propagating in the waveguide substrate 1 is a, and satisfies d=w×tan(a), where w<2mm.

[0085] If the reflection angle α is taken as 45°, this reflection angle α corresponds to the symmetrical supplementary angle relationship of the reflected light path between the upper and lower surfaces and the sidewalls of the waveguide substrate 1. Based on this, in order to effectively absorb most of the light propagating to the edge region 101, the width w of the overflow portion should satisfy w≥d (d is the thickness of the waveguide substrate 1), thereby ensuring that the light rays emitted from the inside of the waveguide substrate 1 at a large angle can be fully intercepted and absorbed.

[0086] Meanwhile, considering the overall appearance, structural compactness, and fabrication feasibility of the diffractive waveguide device, the width w of the overflow portion is controlled to be less than 2 mm. This design, while ensuring efficient absorption of stray light, also takes into account the overall aesthetics and integration of the diffractive waveguide device, demonstrating a balance between optical performance and practical design.

[0087] In some examples of this application, the sum of the angles between the upper surface 11 of the waveguide substrate 1 and the normals of the sidewall is 90°, and the sum of the angles between the lower surface 12 of the waveguide substrate and the normals of the sidewall is 90°.

[0088] like Figure 4 and Figure 6 As shown, when light propagates within the waveguide substrate 1 via total internal reflection, its continuous reflection paths between the upper and lower surfaces and the sidewalls form a specific combination of angles. The 90° angle between the normals means that the reflection angles of the light between the upper and lower surfaces and the sidewalls exhibit complementary characteristics, which helps to guide stray light propagating to the edge region 101 to the pre-defined micro / nano structure region 2 and the area covered by the light absorption layer 3.

[0089] Specifically, this geometric symmetry allows light rays incident at large angles from the inside of the waveguide to the edge to be more effectively captured and extracted by the micro- and nanostructures on the sidewalls and the edges of the upper and lower surfaces. Combining the overflow width formula d=w×tan(a) mentioned earlier, when the reflection angle a is 45° (i.e., half of 90°), the matching relationship between the width w and the waveguide thickness d can be naturally derived, thus structurally ensuring that the light is fully intercepted and absorbed.

[0090] According to another embodiment of this application, a near-eye display device is provided, the near-eye display device including an image source and a diffraction waveguide as described above; wherein, the image source is configured to generate an imaging beam carrying image information; and the diffraction waveguide is configured to receive and conduct the imaging beam.

[0091] The near-eye display device provided in this application embodiment, by integrating the above-mentioned diffractive waveguide device, is mainly used in augmented reality (AR) and mixed reality (MR) devices that have strict requirements for size, weight and image quality.

[0092] The image source, serving as the optical engine of the near-eye display device, plays a crucial role in generating the original imaging beam carrying image information. It can be a core light-emitting element such as a miniature OLED display, a Micro-LED display, or a laser beam scanner.

[0093] As described above, the diffractive waveguide device serves as the transmission and output element of the near-eye display device, undertaking two key functions: First, it receives the imaging beam from the image source through the coupling grating on it; then, it transmits the beam using the total internal reflection effect within the waveguide substrate, and finally expands and outputs the image information to the human eye through the output grating.

[0094] The advantage of the near-eye display device provided in this application embodiment lies in the fact that its diffractive waveguide device integrates an edge micro / nano structure with a light absorption layer. This design enables the near-eye display device to effectively suppress optical display problems such as ghosting and contrast degradation caused by stray light while maintaining a thin and compact form. Ultimately, it provides users with clearer, purer, and higher-contrast visual information in immersive scenarios.

[0095] According to another embodiment of this application, a stray light suppression method for a diffractive waveguide device is provided, comprising the following steps: Step S100: Set up micro / nano structure region 2 in the edge region of waveguide substrate 1; Step S200: Cover the micro / nano structure region 2 with a light-absorbing layer 3; Step S300: By disrupting the total internal reflection condition at the interface between the waveguide substrate 1 and the light absorption layer 3 by the stray light transmitted to the edge region 101 within the waveguide substrate 1 through the micro-nano structure region 2, the stray light is directed out of the waveguide substrate 1 and absorbed by the light absorption layer 3.

[0096] The stray light suppression method provided in this application achieves efficient management of stray light within diffractive waveguide devices through the following three key steps: First, a micro / nano structure region 2 is formed in the edge region of a waveguide substrate 1. This step is fundamental to constructing the entire stray light suppression system. By fabricating the micro / nano structure region 2 with specific morphology and size in the edge region 101 of the waveguide substrate 1, a key location for stray light convergence, a physical basis is established for subsequent optical manipulation. This step can be achieved through micro / nano fabrication processes such as nanoimprinting, photolithography, and etching, ensuring structural precision and consistency.

[0097] Secondly, a light-absorbing layer 3 is coated onto the micro / nano structure region 2. This step enhances the functional structure. A high-absorption-rate light-absorbing layer 3 (such as a high-absorption-rate ink) is applied to the surface of the micro / nano structure region 2 using processes such as spraying or spin coating, forming a structure-material composite functional unit. The light-absorbing layer 3 not only inherits the light-absorbing function of traditional solutions, but more importantly, it forms a complementary and synergistic system with the micro / nano structure region 2.

[0098] Finally, the total internal reflection condition is disrupted by the micro / nano structure region 2, achieving stray light extraction and absorption. When stray light propagating within the waveguide substrate 1 reaches the edge region 101, the micro / nano structure region 2 actively modulates the propagation direction of the light wave through the diffraction and scattering effects of its subwavelength structure, disrupting the phase-matching condition required for total internal reflection at the smooth interface. This mechanism forces the stray light to change its propagation path, effectively leaking or extracting it from the waveguide substrate 1. Subsequently, these extracted rays are absorbed by the covering light-absorbing layer 3, thereby achieving the final elimination of stray light.

[0099] The specific implementation of the near-eye display device in this application can refer to the various embodiments of the diffractive waveguide device described above. Therefore, it has at least all the beneficial effects brought about by the technical solutions of the above embodiments, and will not be described in detail here.

[0100] The above embodiments mainly describe the differences between the various embodiments. As long as the different optimization features between the various embodiments are not contradictory, they can be combined to form a better embodiment. For the sake of brevity, they will not be elaborated here.

[0101] While specific embodiments of this application have been described in detail by way of examples, those skilled in the art should understand that the above examples are for illustrative purposes only and are not intended to limit the scope of this application. Those skilled in the art should understand that modifications can be made to the above embodiments without departing from the scope and spirit of this application. The scope of this application is defined by the appended claims.

Claims

1. A diffractive waveguide device, characterized by The application relates to a diffraction waveguide device, comprising: a waveguide substrate (1) having a main area for transmitting image light and an edge area (101) surrounding the main area; a micro-nano structure area (2) arranged on the edge area (101); and a light-absorbing layer (3) covering at least the micro-nano structure area (2); wherein the micro-nano structure area (2) is configured to break the total reflection condition at the interface between the waveguide substrate (1) and the light-absorbing layer (3) so as to guide stray light transmitted to the edge area (101) out and absorb the stray light by the light-absorbing layer (3).

2. The diffractive waveguide device of claim 1, wherein, The edge area (101) comprises a sidewall of the waveguide substrate (1) and a part of the upper surface (11) and the lower surface (12) of the waveguide substrate (1) adjacent to the sidewall; The micro-nano structure area (2) is formed on at least one of the upper surface (11), the lower surface (12) and the sidewall; The light-absorbing layer (3) covers the micro-nano structure area (2) and the sidewall not covered by the micro-nano structure area.

3. A diffractive waveguide device according to claim 1 or 2, characterised in that, The main area is provided with an in-coupling grating (a) and an out-coupling grating (b); The micro-nano structure area (2) has no overlap with the in-coupling grating (a) and the out-coupling grating (b) in orthographic projection.

4. A diffractive waveguide device according to claim 1 or 2, characterised in that, The micro-nano structure area (2) forms a belt-shaped area arranged around the periphery of the main area, and the width of the belt-shaped area is 0.5mm-2mm.

5. The diffractive waveguide device of claim 3, wherein, The micro-nano structure area (2) comprises a plurality of micro-nano structure units arranged periodically, and the period of the micro-nano structure area (2) is greater than 1 / 2 of the period of the out-coupling grating (b).

6. A diffractive waveguide device according to claim 5, wherein, The period of the micro-nano structure area (2) is greater than or equal to the period of the out-coupling grating (b).

7. The diffractive waveguide device of claim 1, wherein, For stray light transmitted to the edge area (101) in the waveguide substrate (1) at an incident angle greater than 25 degrees, the micro-nano structure area (2) reduces the light reflectivity at the interface between the waveguide substrate (1) and the light-absorbing layer (3) by at least 50% compared with the same waveguide substrate without the micro-nano structure area.

8. The diffractive waveguide device of claim 2, wherein, The light-absorbing layer (3) is an ink layer; The thickness of the light-absorbing layer (3) on the waveguide substrate (1) is greater than 2um; and / or An overflow part is formed outside the micro-nano structure area (2) of the light-absorbing layer (3), and the thickness of the overflow part is greater than 2um.

9. A diffractive waveguide device according to claim 8, wherein, An overflow part is formed outside the micro-nano structure area (2) of the light-absorbing layer (3); The width of the overflow part is w, the thickness of the waveguide substrate (1) is d, the reflection angle of the imaging light in the waveguide substrate (1) is a, and d=w*tan(a) is satisfied, wherein w<2mm.

10. The diffractive waveguide device of claim 2, wherein, The sum of the normal angles of the upper surface (11) and the sidewall of the waveguide substrate (1) is 90 degrees, and the sum of the normal angles of the lower surface (12) and the sidewall is 90 degrees.

11. A near-eye display device, comprising: The application relates to a diffraction waveguide device, comprising: an image source for generating an imaging light beam carrying image information; and a diffraction waveguide device according to any one of claims 1-10, configured to receive and conduct the imaging light beam.

12. A method for stray light suppression for a diffractive waveguide device, characterized by, The application relates to a diffraction waveguide device, comprising: an image source for generating an imaging light beam carrying image information; and a diffraction waveguide device according to any one of claims 1-10, configured to receive and conduct the imaging light beam. A micro-nano structure area (2) is arranged at the edge area of the waveguide substrate (1); An optical absorption layer (3) is covered on the micro-nano structure area (2); The stray light transmitted to the edge area (101) in the waveguide substrate (1) is broken through the micro-nano structure area (2) and the total reflection condition of the waveguide substrate (1) and the optical absorption layer (3) interface, so as to guide the stray light out of the waveguide substrate (1) and be absorbed by the optical absorption layer (3).

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