Diffractive optical structure and near-to-eye display equipment

Abstract

The embodiment of the invention provides a diffractive optical structure and near-to-eye display equipment. The diffractive optical structure comprises a waveguide substrate, a grating area and a non-grating area, wherein the grating area and the non-grating area are formed on the waveguide substrate. Wherein a transition structure is arranged at the boundary of at least part of the grating area and the non-grating area; the transition structure is configured in such a manner that the optical characteristics of the transition structure continuously change along the width direction of the transition structure, so that smooth transition of the phase or the phase and the amplitude of the light beam is realized when the light beam passes through the boundary, thereby suppressing diffraction stray light generated by sudden change of the optical characteristics.

Description

Technical Field

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

[0002] Augmented reality (AR) near-eye display devices overlay virtual information onto the real-world field of vision, finding wide applications in consumer electronics, industry, and medicine. Among these, the diffractive waveguide-based technology has become the mainstream solution due to its thin and light design, large eye movement range, and ease of mass production. This technology uses a coupling grating to guide the imaging beam emitted by the optical engine into the waveguide substrate. After internal total internal reflection, the beam is guided by a deflection grating and finally projected into the eye through an output grating.

[0003] However, diffractive waveguides are typically composed of both grating and non-grating regions. When a beam propagates within the waveguide to the boundary between these two regions, a significant boundary diffraction effect occurs due to abrupt changes in optical properties: in the non-grating region, the beam undergoes only a phase change after total internal reflection, while the amplitude remains essentially unchanged; whereas in the grating region, the zero-order reflected light of the beam experiences both phase and amplitude changes. This abrupt change at the microscopic scale results in directionally propagating stray light.

[0004] When stray light overlaps with the main imaging beam, it causes image trailing, ghosting, and fogging, severely impacting contrast and visual experience. Existing technologies such as TW202514187A reduce phase breakage by controlling the etching depth, or TW202509547A uses a gradient phase region for smooth transition. However, these methods often focus on optimizing the performance of the grating region itself and do not fundamentally solve the inherent abrupt change problem at the "grating-non-grating" boundary. Boundary diffraction remains a key bottleneck restricting image quality.

[0005] Therefore, there is an urgent need in this field for a diffractive optical structure that can effectively suppress boundary diffraction stray light and improve image quality. Summary of the Invention

[0006] The purpose of this application is to provide a new technology solution for a diffractive optical structure and a near-eye display device, so as to solve the problem of diffractive stray light generated at the boundary between the grating region and the non-grating region of existing diffractive waveguides due to abrupt changes in optical properties.

[0007] In a first aspect, embodiments of this application provide a diffractive optical structure, the diffractive optical structure including a waveguide substrate and a grating region and a non-grating region formed on the waveguide substrate; A transition structure is provided at the boundary between at least a portion of the grating region and the non-grating region; The transition structure is configured such that its optical properties change continuously along its own width direction, so that when the light beam passes through the boundary, its phase or phase and amplitude achieve a smooth transition, thereby suppressing diffraction stray light caused by abrupt changes in optical properties.

[0008] Optionally, the width of the transition structure is 1% to 10% of the beam spot width incident on the diffractive optical structure.

[0009] Optionally, the width of the transition structure is from 20 μm to 400 μm.

[0010] Optionally, the transition structure is a membrane structure disposed at the boundary; the membrane structure is a single-layer or multi-layer structure, and its thickness varies continuously along the width direction of the transition structure.

[0011] Optionally, the material of the film structure has an absorption rate of less than a first threshold for the light beam, so that the transition structure is used to achieve a smooth transition of the optical phase difference.

[0012] Optionally, the material of the film structure has an absorption rate of more than a second threshold for the light beam, so that the transition structure can simultaneously achieve a smooth transition of the optical phase difference and amplitude difference; wherein, the material of the film structure includes a metallic material or an amorphous silicon material.

[0013] Optionally, the transition structure is an auxiliary grating structure formed on the waveguide substrate, wherein the grating depth or duty cycle of the auxiliary grating structure varies continuously along the width direction of the transition structure.

[0014] Optionally, the period of the auxiliary grating structure is less than the grating period of the grating region, so that the transition structure is used to achieve a smooth transition of the optical phase difference.

[0015] Optionally, the period of the auxiliary grating structure is equal to the grating period of the grating region, so that the transition structure is used to simultaneously achieve a smooth transition of the optical phase difference and amplitude difference.

[0016] Optionally, the transition structure is disposed at the straight edge boundary of the grating region and at least partially surrounds the contour of the grating region.

[0017] Optionally, the grating region includes an input grating, a folding grating, and an output grating.

[0018] Optionally, the transition structure is disposed at one, more, or all of the straight edge boundaries of at least one of the folding grating and the coupling grating.

[0019] Optionally, the shape of the coupling grating is non-circular, and the transition structure is disposed at one, more, or all of the straight edge boundaries of the coupling grating.

[0020] 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 diffractive optical structure as described in the first aspect is configured to receive and conduct the imaging beam.

[0021] The beneficial effects of this application are as follows: The diffractive optical structure provided in this application provides a transition structure with continuously changing optical properties at the boundary between the grating region and the non-grating region. This allows the phase distribution, or phase and amplitude distribution, of the light beam to smoothly and gradually change as it passes through the boundary, rather than the abrupt change seen in existing technologies. This design effectively eliminates stray diffraction light caused by discontinuities in the boundary optical properties, thereby significantly improving the purity, contrast, and detail of the image, and enhancing the overall visual experience.

[0022] 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

[0023] 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.

[0024] Figure 1 This is one of the structural schematic diagrams of the diffraction optical structure provided in the embodiments of this application; Figure 2 A schematic diagram comparing the phase distribution and amplitude distribution of the beam within the light spot at the boundary before and after the addition of the transition structure to the diffractive optical structure of this application. Figure 3 The diffraction intensity distribution diagram of the existing diffraction optical structure (without the addition of a transition structure); Figure 4 A diffraction intensity distribution diagram of the diffraction optical structure provided in the embodiments of this application; Figure 5 This is the second schematic diagram of the diffractive optical structure provided in the embodiments of this application; Figure 6 This is the third schematic diagram of the diffraction optical structure provided in the embodiments of this application; Figure 7 Fourth schematic diagram of the diffractive optical structure provided in the embodiments of this application; Figure 8 Fifth schematic diagram of the diffractive optical structure provided in the embodiments of this application; Figure 9Sixth schematic diagram of the diffractive optical structure provided in the embodiments of this application; Figure 10 Seventh schematic diagram of the diffractive optical structure provided in the embodiments of this application; Figure 11 Eighth schematic diagram of the diffractive optical structure provided in the embodiments of this application; Figure 12 One of the top views of the diffractive optical structure provided in the embodiments of this application; Figure 13 This is a second top view of the diffractive optical structure provided in an embodiment of this application.

[0025] Explanation of reference numerals in the attached figures: 1. Waveguide substrate; 2. Non-grating region; 3. Grating region; 4. Transition structure; 31. Coupled-in grating; 32. Tilting grating; 33. Coupled-out grating. Detailed Implementation

[0026] 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.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] The diffractive optical structure and near-eye display device provided in the embodiments of this application will be described in detail below with reference to the accompanying drawings.

[0032] According to one embodiment of this application, a diffractive optical structure is provided, see [link to relevant documentation]. Figure 1The diffractive optical structure includes a waveguide substrate 1 and a grating region 3 and a non-grating region 2 formed on the waveguide substrate 1; wherein a transition structure 4 is provided at at least part of the boundary between the grating region 3 and the non-grating region 2; the transition structure 4 is configured such that its optical properties change continuously along its own width direction, so that when the light beam passes through the boundary, its phase or phase and amplitude achieve a smooth transition, thereby suppressing diffractive stray light caused by abrupt changes in optical properties.

[0033] This application provides a diffractive optical structure, the specific implementation of which can be found in [reference needed]. Figure 1 As shown. This diffractive optical structure is suitable for waveguide-type near-eye display devices with strict requirements for image quality, and has significant application value, especially in near-eye display systems such as augmented reality (AR) and mixed reality (MR). In practical applications, abrupt changes in optical properties often occur at the boundary between the grating region 3 and the non-grating region 2 on the diffractive optical structure (e.g., a diffractive waveguide device). This abrupt change leads to significant directional stray light, thus affecting image quality. The embodiments of this application effectively solve this technical problem by setting a special transition structure 4 at the aforementioned boundary.

[0034] The innovation of the transition structure 4 lies in the continuous variation of its optical properties along the width direction. This design allows for a smooth transition in phase characteristics when the light beam passes through the boundary region, or, when necessary, a smooth transition in both phase and amplitude. This smooth transition mechanism fundamentally eliminates the diffraction stray light problem caused by abrupt changes in optical properties in traditional structures.

[0035] Through this structural design, the embodiments of this application can improve the imaging performance of the diffractive optical structure, specifically by increasing image contrast and eliminating image ghosting. This technical solution is particularly suitable for display devices that require high-definition, high-contrast visual experiences, including applications such as AR glasses.

[0036] The diffraction optical structure provided in the embodiments of this application will be described in detail below with reference to the accompanying drawings. See also Figure 1 As shown, this diffractive optical structure is, for example, a diffractive waveguide device. Its basic components include a waveguide substrate 1, and grating regions 3 and non-grating regions 2 with different optical functions formed on the waveguide substrate 1. This structural design forms the basis for realizing efficient optical waveguide transmission and control, where the specific arrangement and optical characteristics of each region provide the necessary physical basis for subsequent beam management and stray light suppression.

[0037] According to the diffraction optical structure provided in the embodiments of this application, see [link to relevant documentation]. Figure 1The diffractive optical structure comprises three basic components: a waveguide substrate 1 serving as the light transmission carrier, a grating region 3 formed on the surface of the waveguide substrate 1, and a non-grating region 2 located between the different grating regions. These regions together constitute the optical functional basis of the diffractive waveguide device.

[0038] In this design, a functional transition structure 4 is provided at the boundary between the selected grating region 3 and the non-grating region 2. It should be noted that this transition structure 4 is not a simple physical separation layer or a single type of structural element, but rather refers to a specially designed optical structure system capable of achieving specific optical control functions. Its core function is to actively control the optical behavior of the light beam at the boundary, rather than merely serving a physical separation purpose.

[0039] The key technical feature of the transition structure 4 lies in its optical properties along a specific direction parallel to the surface of the waveguide substrate (i.e., the width direction of the transition structure, see reference). Figure 1 The distribution (horizontal direction shown in the figure) exhibits a continuous, gradual distribution characteristic. This gradual characteristic of the design enables a smooth optical transition when the light beam propagates in the waveguide substrate 1 in the form of total internal reflection to the boundary between the grating region 3 and the non-grating region 2, rather than the abrupt change in the traditional structure.

[0040] In this application, the transition structure 4 achieves two key functions through its continuously varying optical properties: first, it can transform the phase abrupt changes that may occur in the beam at the boundary into a gradual phase distribution; second, when needed, it can also simultaneously achieve a smooth transition of amplitude characteristics. This modulation mechanism effectively reconstructs the wavefront characteristics of the beam in the boundary region.

[0041] The design of this application fundamentally changes the light propagation behavior in traditional diffractive waveguides. By transforming the original step optical abrupt change that caused strong diffraction stray light into a gradual optical transition that produces almost no stray light, the embodiments of this application effectively solve the technical problem of boundary diffraction.

[0042] Ultimately, through this structural optimization, the embodiments of this application can significantly suppress directional diffraction stray light caused by abrupt changes in boundary optical properties, thereby improving the imaging quality of the diffractive optical structure at the system level, including but not limited to improving image contrast, reducing image ghosting, and improving optical performance indicators such as signal-to-noise ratio.

[0043] In some examples of this application, the width of the transition structure 4 is 1% to 10% of the beam spot width incident on the diffractive optical structure.

[0044] In this example of the application, the key dimension of the transition structure 4—namely, its width—was optimized. Specifically, the width of the transition structure 4 was designed to be between 1% and 10% of the incident beam spot width. This specific range was determined based on the results of optical simulation and experimental verification of the system: when the width of the transition region is less than 1% of the spot size, its smoothing effect on phase and amplitude jumps at the boundary is weak, making it difficult to effectively suppress diffraction stray light; conversely, when the width of the transition region exceeds 10%, although the stray light suppression effect is improved, it will cause significant angular dispersion, leading to spatial separation of the RGB three colors, thereby degrading the modulation transfer function (MTF) of the system and affecting the final image sharpness.

[0045] This design achieves an optimal balance between optical performance and system constraints, ensuring sufficient stray light suppression while avoiding dispersion problems caused by an excessively wide transition region. Through optimized control of this proportional range, the performance of the waveguide display is systematically optimized.

[0046] In some examples of this application, the width of the transition structure 4 is 20 μm to 400 μm.

[0047] In this example of the application, the width of the transition structure 4 is further defined as a size range of 20 μm to 400 μm. This specific numerical range is determined based on typical scenarios in practical engineering applications: in most near-eye display devices, the output spot size of the imaging optical engine is typically 2 mm to 4 mm. Applying the previously determined relative proportion of 1% to 10% to this actual spot size range yields the specific width parameter of 20 μm to 400 μm.

[0048] The effectiveness of this size range was fully verified through system optical simulations. For example... Figures 2 to 4 The simulation results show that when the incident light spot diameter is 3 mm, the stray light diffusion angle can be significantly suppressed from the original greater than 2° to less than 1° by using a transition structure with a width of 30 μm (corresponding to a 1% ratio); while the transition structure with a width of 300 μm (corresponding to a 10% ratio) can achieve a better suppression effect, further reducing the stray light diffusion angle to less than 0.5°, which is close to the theoretical diffraction limit of the system.

[0049] The proposed size range in this example provides clear design guidance for engineering implementation, ensuring both the fabrication feasibility of the transition structure 4 and its ability to achieve optimal stray light suppression in typical application scenarios.

[0050] It should be noted that the relative proportion limit and the specific size limit are interrelated technical features. The relative proportion limit (1%~10%) ensures the adaptability of this design to different optical architectures, allowing it to automatically adjust according to the actual spot size; while the specific size limit (20μm~400μm) provides a clear engineering benchmark for specific process implementation, particularly suitable for typical near-eye display systems with spot sizes of 2~4mm. These two limiting dimensions together constitute a complete protection system for the critical dimensions of the transition structure, ensuring both the universality of the technical solution and the operability of specific implementation.

[0051] See some examples in this application. Figures 5 to 7 The transition structure 4 is a membrane structure disposed at the boundary; the membrane structure is a single-layer or multi-layer structure, and its thickness varies continuously along the width direction of the transition structure 4.

[0052] In this example of the application, the transition structure 4 is implemented in the form of a membrane structure, the specific structure of which can be found in [reference needed]. Figures 5 to 7 The film structure is disposed at the boundary between the grating region 3 and the non-grating region 2, and achieves the required optical control function through its specific geometric configuration.

[0053] From a structural perspective, the membrane structure can be a single-layer membrane design or a multi-layer composite membrane structure. Regardless of the type of layered structure used, its core characteristic is that the physical thickness of the membrane structure exhibits a continuous and gradually changing distribution along the width direction of the transition structure 4.

[0054] This continuously varying thickness film structure can effectively modulate the characteristics of a beam passing through it. As the beam passes through this gradually thickened film structure, it experiences a corresponding phase delay change, thus achieving a smooth phase transition. In some embodiments, by selecting a suitable film material, the structure can also simultaneously achieve beam amplitude modulation.

[0055] It should be noted that the material selection for the film structure is quite flexible. It can use the same material as the grating region to ensure process compatibility, or it can use materials with different refractive indices to enhance optical controllability. This design freedom allows the implementation scheme of the film structure to adapt well to different process conditions and performance requirements.

[0056] Through this film-structure-based implementation scheme, this application can effectively achieve optically smooth transitions at the boundaries without significantly increasing process complexity, providing a practical technical path for suppressing diffraction stray light.

[0057] In one specific embodiment of this application, see [reference needed]. Figure 5The transition structure 4 employs a single-layer film design. This film is directly disposed at the boundary between the grating region 3 and the non-grating region 2, and its physical thickness exhibits a continuous and gradually varying distribution along the width direction parallel to the surface of the waveguide substrate 1. This simple single-layer structure achieves continuous control of the beam phase through thickness gradient, providing a fundamental and effective solution for a smooth optical transition at the boundary.

[0058] In another embodiment of this application, see Figure 6 The transition structure 4 employs a double-layer film stacking design. The first layer is formed directly on the surface of the waveguide substrate 1, and the second layer covers the first layer. This design is characterized by the fact that the thickness of the second layer continuously and gradually changes along the width direction of the transition structure 4, and this layer further extends into the adjacent non-grating region 2. This structure not only achieves continuous variation in optical properties through the thickness gradient of the upper film, but also enhances the coupling effect with adjacent optical regions through the extended design.

[0059] In yet another embodiment of this application, see [link to application]. Figure 7 The transition structure 4 also adopts a double-layer membrane design, but its configuration is similar to... Figure 6 The scheme shown is different. In this configuration, the second layer precisely covers the first layer, forming a localized area of ​​varying thickness, without extending into the non-grating region 2.

[0060] The above three implementation methods demonstrate the flexibility of film structure design. By using different layered configurations and thickness distribution schemes, the different requirements for optical performance and process implementation in various specific applications can be met.

[0061] In some examples of this application, the material of the film structure has an absorption rate of less than a first threshold for the light beam, so that the transition structure 4 is used to achieve a smooth transition of the optical phase difference.

[0062] In this example of the application, the film structure is made of a material with extremely low absorption in the operating wavelength band, ensuring negligible light energy loss. Such materials include, but are not limited to, optical dielectric materials such as silicon dioxide and silicon nitride. In this configuration, the transition structure 4 provides a corresponding gradual phase delay for the light beam passing through it through a continuous change in film thickness.

[0063] Specifically, when the beam wavefront passes through the transition structure 4, its phase distribution is readjusted, forming a smooth phase transition in the boundary region, thereby effectively eliminating diffraction stray light caused by phase abrupt changes. This scheme is suitable for scenarios where the amplitude difference between the reflected beams in the grating region 3 and the non-grating region 2 is small, achieving high-quality stray light suppression through pure phase modulation.

[0064] In some examples of this application, the material of the film structure has an absorption rate of more than a second threshold for the light beam, so that the transition structure 4 can simultaneously achieve a smooth transition of the optical phase difference and amplitude difference; wherein, the material of the film structure includes a metallic material or an amorphous silicon material.

[0065] In this example of the application, the film structure is made of a material with specific absorption properties, such as metallic materials (e.g., aluminum, silver) or semiconductor materials such as amorphous silicon.

[0066] In this configuration, the transition structure 4 optimizes optical performance through a unique dual modulation mechanism: (1) Phase modulation: by continuously changing the film thickness, a gradual phase delay is provided for the transmitted beam; (2) Amplitude modulation: by utilizing the absorption characteristics of the material itself, a gradual attenuation of the beam intensity is achieved. This synergistic control mechanism enables the phase distribution and amplitude intensity of the beam to transition smoothly when it passes through the boundary region, thereby simultaneously eliminating the diffraction stray light caused by phase jumps and amplitude jumps.

[0067] This implementation scheme is particularly suitable for application scenarios where the amplitude of the reflected beams in grating region 3 and non-grating region 2 differs significantly. Through more comprehensive optical parameter control, it achieves a more thorough stray light suppression effect, significantly improving the contrast and clarity of the image.

[0068] See some examples in this application. Figures 8 to 11 The transition structure 4 is an auxiliary grating structure formed on the waveguide substrate 1, and the grating depth or duty cycle of the auxiliary grating structure changes continuously along the width direction of the transition structure 4.

[0069] In this example of the application, the transition structure 4 is implemented in the form of an auxiliary grating structure. The auxiliary grating structure is formed on the surface of the waveguide substrate 1 and is located at the boundary between the grating region 3 and the non-grating region 2.

[0070] The key parameters of the auxiliary grating structure include the grating depth or duty cycle, and these key parameters are distributed continuously and gradually along the width direction of the transition structure 4. This gradual parameter design allows the optical properties of the auxiliary grating to transition smoothly in space.

[0071] By adjusting the grating depth parameter, the accumulated path difference of the light beam can be altered, thereby achieving gradual phase adjustment. Furthermore, by adjusting the duty cycle (i.e., the ratio of the grating groove width to the period), the diffraction efficiency of the light beam can be controlled, thus enabling continuous amplitude control.

[0072] This scheme, based on the gradual variation of grating parameters, provides an optical control method independent of material absorption characteristics, allowing the desired optical performance to be achieved through geometric design. Compared to the aforementioned film structure schemes, the scheme provided in this example offers better process compatibility and structural stability, making it suitable for applications requiring precise control of optical properties.

[0073] It should be noted that the period of this auxiliary grating structure can be designed independently of grating region 3, providing additional degrees of freedom for optimizing its optical performance.

[0074] See some examples in this application. Figure 8 and Figure 9 The period of the auxiliary grating structure is less than the grating period of the grating region 3, so that the transition structure 4 is used to achieve a smooth transition of the optical phase difference.

[0075] In this example of the application, the period of the auxiliary grating structure is designed to be smaller than the grating period of the grating region 3. This small period design gives it special diffraction characteristics for the working wavelength beam: because the period size is smaller (or much smaller) than the diffraction conditions corresponding to the working wavelength, the auxiliary grating only produces zero-order diffracted light and does not excite effective propagating diffraction orders.

[0076] In this configuration, the transition structure 4 achieves gradual adjustment of the phase of the reflected beam by continuously changing the grating depth or duty cycle of the auxiliary grating structure along its width direction. This gradual grating parameter design allows the wavefront phase of the beam to transition smoothly as it passes through the transition region, rather than abruptly.

[0077] The advantage of the optical scheme in this example lies in its ability to compensate for phase jumps without altering the amplitude distribution. Through this pure phase modulation mechanism, the transition structure 4 effectively eliminates diffraction stray light caused by phase discontinuities. This design is suitable for applications where the amplitude difference between the reflected beams in the grating region and the non-grating region is small, providing an effective technical path for achieving high-quality stray light suppression.

[0078] See some examples in this application. Figure 10 and Figure 11 The period of the auxiliary grating structure is equal to the grating period of the grating region 3, so that the transition structure 4 is used to simultaneously achieve a smooth transition of the optical phase difference and amplitude difference.

[0079] In this example of the application, the period of the auxiliary grating structure is set to be equal to the grating period of the grating region 3. This equal-period design ensures that the auxiliary grating structure and the grating region 3 have completely identical diffraction characteristics.

[0080] In this configuration, the transition structure 4 achieves a dual control mechanism for the beam by continuously changing the grating depth or duty cycle of the auxiliary grating structure along its width direction: (1) Phase modulation: by continuously changing the grating depth, a gradual phase delay is provided for the reflected beam; (2) Amplitude modulation: by continuously changing the duty cycle, the diffraction efficiency is gradually controlled, thereby adjusting the amplitude intensity of the reflected beam.

[0081] This dual modulation mechanism enables a smooth, synchronous transition in phase distribution and amplitude intensity of the beam as it passes through the boundary region. Compared to the pure phase modulation scheme described above, the equal-period design can simultaneously eliminate stray diffraction light caused by phase and amplitude jumps.

[0082] The optical scheme in this example is particularly suitable for applications where the amplitude of the reflected beams in grating region 3 and non-grating region 2 differs significantly. Through coordinated modulation of phase and amplitude, a more comprehensive stray light suppression effect is achieved, providing a reliable technical guarantee for high-contrast imaging.

[0083] See some examples in this application. Figure 12 and Figure 13 The transition structure 4 is disposed at the straight edge boundary of the grating region 3 and at least partially surrounds the outline of the grating region 3.

[0084] In this example of the application, the transition structure 4 is configured at the straight edge boundary of the grating region 3 and may selectively partially or completely surround the contour of the grating region 3. This design choice is based on the principle of diffraction optics: compared to curved edges, straight edges produce the strongest directional diffraction effect. Specifically, a vertical straight edge will only induce a lateral diffraction spot, which has highly concentrated energy and a long diffraction propagation distance, appearing as a noticeable bright line or trail in visual observation, and significantly interfering with image quality.

[0085] In contrast, the diffraction energy generated by rounded or curved edges is dispersed in all directions, resulting in relatively low energy density and short diffraction length, thus having a relatively small impact on vision. Therefore, considering the priority and effectiveness of stray light suppression, the transition structure 4 is preferentially placed at straight edge boundaries to improve the system's visual performance with the highest efficiency.

[0086] In applications, this design can be implemented at the straight edges of various functional areas, including but not limited to: the straight edge boundaries of the square insertion grating (IG), the straight edge portions of the transition grating (FG), and the straight edge portions of the output grating (OG). By setting transition structures 4 at these key locations, the most interfering directional stray light can be suppressed to the maximum extent, thereby significantly improving the visual quality of the displayed image.

[0087] In some examples of this application, the grating region 3 includes an input grating 31, a transition grating 32, and an output grating 33.

[0088] In this example of the present application, the grating region 3 is specifically configured to include an input grating 31, a transition grating 32, and an output grating 33. This design defines the diffractive optical structure of the present application as an optical architecture of a complete diffractive waveguide device.

[0089] In this configuration, each grating unit performs a different optical function: the coupling grating 31 is responsible for efficiently coupling the imaging beam emitted from the image source into the waveguide substrate 1, initiating the optical waveguide transmission process; the deflection grating 32 performs optical path control, guiding the beam in a predetermined direction through specific diffraction characteristics; and the coupling grating 33 finally couples the transmitted beam out of the waveguide substrate 1 and projects it onto the human eye imaging area.

[0090] This grating region design enables the diffractive waveguide device to achieve complete beam conduction, expansion, and projection functions. In particular, when the transition structure 4 is applied to the boundaries of these functional gratings, it can specifically suppress boundary diffraction effects in key regions, thereby improving the imaging quality of the entire waveguide device at the system level.

[0091] This embodiment demonstrates the completeness and practicality of the diffractive optical structure of this application in practical applications, showing that it not only solves the problem of local boundary diffraction, but can also be integrated into functional optical devices to achieve overall performance optimization and improvement.

[0092] It should be noted that, depending on the optical path design, some diffractive waveguide architectures may not include transition gratings. In this case, the diffractive optical structure can still achieve effective stray light suppression by setting transition structures 4 at the corresponding boundaries of the input and output gratings. This design flexibility demonstrates the adaptability of the technical solution of this application to different waveguide architectures.

[0093] See some examples in this application. Figure 13 The transition structure 4 is disposed at one, more or all of the straight edge boundaries of at least one of the turning grating 32 and the coupling grating 33.

[0094] In this example of the application, the transition structure 4 is configured at one, more, or all of the straight edge boundaries of at least one functional region of the transition grating 32 and the coupling grating 33. This design is based on the unique optical properties of the transition grating 32 and the coupling grating 33: due to the presence of -2nd order diffraction in these regions, the light beam will form a round-trip propagation path within the waveguide. Under these complex optical path conditions, any optical abrupt change at the boundary will be significantly amplified through multiple reflections and diffractions.

[0095] By setting the transition structure 4 on one or more key straight edges of the transition grating 32 and the coupling grating 33, the generation and propagation of stray light can be effectively blocked. In particular, when the transition structure 4 is set on all straight edge boundaries of these gratings, a complete stray light suppression network can be constructed, achieving all-round control over diffraction stray light. At the same time, this design can also effectively suppress reflected light interference caused by incomplete extinction at the waveguide edge, further improving the imaging quality of the system.

[0096] The preferred solution is, for example Figure 13 As shown, the transition structure 4 is disposed at all straight edge boundaries of the transition grating 32 and the coupling grating 33.

[0097] See some examples in this application. Figure 12 The coupling grating 31 is non-circular in shape, and the transition structure 4 is disposed at one, more or all of the straight edge boundaries of the coupling grating 31.

[0098] In this example of the application, the shape features of the coupling grating 31 have been optimized. When the shape of the coupling grating 31 is non-circular (such as a rectangle, polygon, or other shape with straight edges), see [reference needed]. Figure 12 The transition structure 4 is disposed at one, more or all of its straight edge boundaries.

[0099] This design solves the unique optical problem of non-circular coupling gratings: although the coupling region is usually circular and the boundary diffraction effect is small, when a non-circular design is used, its straight edge boundary will generate strong directional diffraction stray light. By setting a transition structure at the straight edge boundary of the coupling grating 31, the stray light interference introduced by the shape characteristics of these regions can be effectively eliminated.

[0100] The optical solution provided in this example demonstrates the adaptability of this application under different grating shape configurations. Through targeted boundary processing, it ensures excellent stray light suppression under various optical architectures.

[0101] A more preferred embodiment is that the coupling grating 31 is non-circular in shape, such as... Figure 12The square shown has the transition structure 4 disposed at all straight edge boundaries of the coupling grating 31.

[0102] 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 diffractive optical structure as described above; wherein, the image source is configured to generate an imaging beam carrying image information; and the diffractive optical structure is configured to receive and conduct the imaging beam.

[0103] 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.

[0104] The diffractive optical structure described above 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.

[0105] The application of the diffractive optical structure of this application brings the following significant advantages to near-eye display devices: By eliminating phase / amplitude abrupt changes at the grating boundary, diffraction stray light is suppressed, effectively solving image ghosting, haze, and image blurring problems, and significantly improving contrast and visual clarity.

[0106] While effectively suppressing stray light, by controlling the width of the transition region (20μm~400μm), dispersion problems caused by an excessively wide transition region are avoided, ensuring that the modulation transfer function (MTF) is not damaged and achieving a balance in the overall system performance.

[0107] In summary, the diffractive optical structure of this application provides a reliable core optical solution for high-quality, thin and light AR / MR near-eye display devices through boundary optical design.

[0108] The specific implementation of the near-eye display device in this application can refer to the various embodiments of the diffractive optical structure 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.

[0109] 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.

[0110] 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 optical structure, characterized in that, It includes a waveguide substrate (1) and a grating region (3) and a non-grating region (2) formed on the waveguide substrate (1). A transition structure (4) is provided at the boundary between at least a portion of the grating region (3) and the non-grating region (2). The transition structure (4) is configured such that its optical properties change continuously along its own width direction, so that when the light beam passes through the boundary, its phase or phase and amplitude achieve a smooth transition, thereby suppressing the diffraction stray light caused by abrupt changes in optical properties.

2. The diffractive optical structure according to claim 1, characterized in that, The width of the transition structure (4) is 1% to 10% of the beam spot width incident on the diffractive optical structure.

3. The diffractive optical structure according to claim 1 or 2, characterized in that, The width of the transition structure (4) is 20 μm to 400 μm.

4. The diffractive optical structure according to claim 1, characterized in that, The transition structure (4) is a membrane structure disposed at the boundary; the membrane structure is a single layer or a multi-layer structure, and its thickness varies continuously along the width direction of the transition structure (4).

5. The diffractive optical structure according to claim 4, characterized in that, The material of the film structure has an absorption rate of less than a first threshold for the light beam, so that the transition structure (4) is used to achieve a smooth transition of the optical phase difference.

6. The diffractive optical structure according to claim 4, characterized in that, The absorption rate of the material of the film structure to the light beam is greater than the second threshold, so that the transition structure (4) can simultaneously achieve a smooth transition of the optical phase difference and amplitude difference; wherein, the material of the film structure includes a metallic material or an amorphous silicon material.

7. The diffractive optical structure according to claim 1, characterized in that, The transition structure (4) is an auxiliary grating structure formed on the waveguide substrate (1), and the grating depth or duty cycle of the auxiliary grating structure changes continuously along the width direction of the transition structure (4).

8. The diffractive optical structure according to claim 7, characterized in that, The period of the auxiliary grating structure is less than the grating period of the grating region (3), so that the transition structure (4) is used to achieve a smooth transition of the optical phase difference.

9. The diffractive optical structure according to claim 7, characterized in that, The period of the auxiliary grating structure is equal to the grating period of the grating region (3), so that the transition structure (4) is used to simultaneously achieve a smooth transition of the optical phase difference and amplitude difference.

10. The diffractive optical structure according to claim 1, characterized in that, The transition structure (4) is disposed at the straight edge boundary of the grating region (3) and is disposed at least partially around the outline of the grating region (3).

11. The diffractive optical structure according to claim 10, characterized in that, The grating region (3) includes an input grating (31), a folding grating (32), and an output grating (33).

12. The diffractive optical structure according to claim 11, characterized in that, The transition structure (4) is disposed at one, more or all of the straight edge boundaries of at least one of the transition grating (32) and the coupling grating (33).

13. The diffractive optical structure according to claim 11, characterized in that, The shape of the coupling grating (31) is non-circular, and the transition structure (4) is disposed at one, more or all of the straight edge boundaries of the coupling grating (31).

14. A near-eye display device, characterized in that, include: An image source is used to generate an imaging beam that carries image information. as well as, The diffractive optical structure as described in any one of claims 1-13 is configured to receive and conduct the imaging beam.

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