A diffractive optical structure, an optical system, and a near-eye display device

Abstract

Embodiments of the present application provide a diffractive optical structure, an optical system, and a near-eye display device; wherein, the diffractive optical structure is characterized by comprising a main waveguide and an pupil-expanding waveguide; the main waveguide includes an input grating and an output grating, and the vector directions of the input grating and the output grating are the same and both are the first direction; the pupil-expanding waveguide is stacked on one side of the input grating of the main waveguide; the pupil-expanding waveguide includes a pupil-expanding grating, the vector direction of the pupil-expanding grating is the second direction, and the second direction is different from the first direction; in the thickness direction of the diffractive optical structure, at least a partial area of the pupil-expanding grating and the input grating are correspondingly arranged.

Description

Technical Field

[0001] Embodiments of the present application relate to the field of optical display technologies, and more specifically, to a diffractive optical structure, an optical system, and a near-eye display device. Background Art

[0002] Augmented reality technology (AR technology) combines virtual information with the real world and is widely used in multiple industries. In AR devices, the optical waveguide solution is regarded as one of the best optical display solutions due to its good optical effects and low process difficulty. Currently, the optical waveguide solution is divided into a geometric waveguide solution, a relief grating waveguide solution, and a volume holographic waveguide solution. Among them, the relief grating waveguide solution has become the focus of research due to its superior comprehensive performance.

[0003] However, traditional relief grating waveguide solutions often have poor pupil expansion effects when dealing with users with different interpupillary distances, which limits the applicability and user experience of AR devices.

[0004] Therefore, how to achieve a two-dimensional pupil expansion solution with a simple structure and significant effects while ensuring optical efficiency has become an urgent problem to be solved in the current field of augmented reality technology. Summary of the Invention

[0005] The purpose of the present application is to provide a new technical solution for a diffractive optical structure, an optical system, and a near-eye display device.

[0006] In a first aspect, the present application provides a diffractive optical structure. The diffractive optical structure includes a main waveguide and a pupil expansion waveguide;

[0007] The main waveguide includes an input grating and an output grating, and the vector directions of the input grating and the output grating are the same and are both the first direction;

[0008] The pupil expansion waveguide is stacked on one side of the input grating of the main waveguide;

[0009] The pupil expansion waveguide includes a pupil expansion grating, the vector direction of the pupil expansion grating is the second direction, and the second direction is different from the first direction;

[0010] In the thickness direction of the diffractive optical structure, at least a partial area of the pupil expansion grating and the input grating are correspondingly arranged.

[0011] Optionally, an included angle is formed between the second direction and the first direction θ , 80° ≤ θ ≤ 100°.

[0012] Optionally, the second direction is perpendicular to the first direction.

[0013] Optionally, the light source range emitted by the optical engine of the peripheral device has an overlapping area with the coupling grating and the pupil expansion grating in a direction perpendicular to the main waveguide and the pupil expansion waveguide.

[0014] Optionally, the orthographic projection of the coupling grating on the pupil expansion waveguide is located within the pupil expansion grating.

[0015] Optionally, the coupling grating is used to couple external light into the main waveguide, and the coupling-out grating is used to expand the pupil of the light propagating in the main waveguide along the first direction and couple it out;

[0016] The pupil expansion grating is used to couple the light that sequentially transmits through the coupling grating and the main waveguide into the pupil expansion waveguide, and couple the light out to the coupling grating after the light is expanded along the second direction within the pupil expansion waveguide.

[0017] Optionally, there is an air gap between the main waveguide and the pupil expansion waveguide.

[0018] Optionally, the shape and size of the pupil expansion grating match those of the coupling grating.

[0019] Optionally, the pupil expansion waveguide includes a substrate, and the substrate includes two opposite surfaces;

[0020] The pupil expansion grating is disposed on one surface of the substrate;

[0021] The size of the substrate is larger than the size of the pupil expansion grating.

[0022] Optionally, the coupling grating is a trapezoidal structure that gradually increases from the middle to both sides;

[0023] The middle part of the coupling grating is the entrance pupil area, and the size of the entrance pupil area matches the size of the exit pupil area of the optical engine of the peripheral device.

[0024] Optionally, the main waveguide includes a substrate, and the substrate includes two opposite surfaces;

[0025] The coupling grating and the coupling-out grating are disposed on at least one surface of the substrate.

[0026] Optionally, the coupling grating and the coupling-out grating are one-dimensional gratings;

[0027] The pupil expansion grating is a one-dimensional grating or a two-dimensional grating.

[0028] Optionally, the coupling grating, the coupling-out grating, and the pupil expansion grating are surface relief gratings or volume gratings.

[0029] In a second aspect, an embodiment of the present application provides an optical system. The optical system includes:

[0030] The diffractive optical structure as described in the first aspect; and

[0031] An optical engine configured to project light onto the diffractive optical structure.

[0032] Optionally, the pupil-expanding waveguide and the optical engine are located on the same side of the main waveguide;

[0033] Or,[[]]

[0034] the pupil-expanding waveguide and the optical engine are respectively disposed on two sides of the main waveguide.

[0035] In a third aspect, an embodiment of the present application provides a near-eye display device. The near-eye display device includes:

[0036] A housing; and

[0037] The optical system as described in the second aspect, the optical system being disposed in the housing.

[0038] The beneficial effects of the present application are as follows:

[0039] The diffractive optical structure of the embodiment of the present application includes a main waveguide and a pupil-expanding waveguide. The main waveguide is equipped with an input grating and an output grating for coupling light in and out and one-dimensional pupil expansion; while the pupil-expanding waveguide is stacked on one side of the input grating of the main waveguide and realizes pupil expansion in the second direction through a pupil-expanding grating, thereby realizing two-dimensional pupil expansion of light; the present application avoids the complexity of traditional light turning pupil expansion, simplifies the optical path directly through the stacking structure, not only greatly reduces optical loss, but also ensures stable transmission and final clear presentation of light.

[0040] Through the following detailed description of the exemplary embodiments of the present specification with reference to the accompanying drawings, other features and advantages of the present specification will become clear. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The drawings incorporated in the specification and constituting a part of the specification illustrate embodiments of the present specification and, together with the description, are used to explain the principles of the present specification.

[0042] Figure 1 A top view of the main waveguide of the diffractive optical structure provided by the embodiment of the present application;

[0043] Figure 2 A top view of the pupil-expanding waveguide of the diffractive optical structure provided by the embodiment of the present application;

[0044] Figure 3 A side view of the diffractive optical structure provided by the embodiment of the present application;

[0045] Figure 4The front view of the diffractive optical structure provided by the embodiment of the present application;

[0046] Figure 5 The K-space diagram of the light propagation of the diffractive optical structure provided by the embodiment of the present application.

[0047] Explanation of reference numerals:

[0048] 1. Main waveguide; 11. Coupling grating; 111. Entrance pupil region; 12. Output coupling grating; 13. Substrate; 2. Beam expander waveguide; 21. Beam expander grating; 22. Substrate; 3. Opto-mechanics; 01. Human eye. Detailed implementation manners

[0049] Now, various exemplary embodiments of the present application will be described in detail with reference to the accompanying drawings. It should be noted that: Unless otherwise specifically stated, the relative arrangements, numerical expressions, and numerical values of the components and steps set forth in these embodiments do not limit the scope of the present application.

[0050] The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way a limitation on the present application, its application, or its use.

[0051] Techniques and devices known to those of ordinary skill in the relevant art may not be discussed in detail, but where appropriate, such techniques and devices should be regarded as part of the specification.

[0052] In all the examples shown and discussed herein, any specific value should be construed as merely exemplary and not as a limitation. Thus, other examples of the exemplary embodiments may have different values.

[0053] It should be noted that: Similar reference numerals and letters denote similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further discussed in subsequent drawings.

[0054] Next, with reference to the accompanying drawings, the diffractive optical structure, optical system, and near-eye display device provided by the embodiments of the present application will be described in detail.

[0055] According to an embodiment of the present application, a diffractive optical structure is provided. Refer to Figures 1 to 4, the diffractive optical structure includes a main waveguide 1 and an pupil-expanding waveguide 2; the main waveguide 1 includes an input grating 11 and an output grating 12, and the vector directions of the input grating 11 and the output grating 12 are the same and both are the first direction; the pupil-expanding waveguide 2 is stacked on one side of the input grating 11 of the main waveguide 1; the pupil-expanding waveguide 2 includes a pupil-expanding grating 21, and the vector direction of the pupil-expanding grating 21 is the second direction, and the second direction is different from the first direction; in the thickness direction of the diffractive optical structure, at least part of the pupil-expanding grating 21 and the input grating 11 are correspondingly arranged.

[0056] The diffractive optical structure provided by the embodiment of the present application mainly consists of the following parts:

[0057] Main waveguide 1: It is the main channel for carrying the transmission of imaging light. An input grating 11 and an output grating 12 are arranged thereon. The vector directions of these two gratings are the same and are both defined as the first direction, which is used to realize the transmission, pupil expansion and output of imaging light in the main waveguide 1. For example, the vector directions of the input grating 11 and the output grating 12 are both horizontal directions.

[0058] Input grating 11: It is located at the input end of the main waveguide 1 and is responsible for coupling light from an external optical machine into the main waveguide 1 for total reflection propagation.

[0059] Output grating 12: It is located at the output end of the main waveguide 1 and is responsible for coupling and outputting light from the main waveguide 1 to the human eye 01 or subsequent optical elements, see Figure 4 .

[0060] Pupil-expanding waveguide 2: It is integrally stacked on one side of the input grating 11 of the main waveguide 1. A pupil-expanding grating 21 is arranged on the pupil-expanding waveguide 2, and its vector direction is the second direction different from that of the input grating and the output grating, which is used to realize the pupil expansion of light along the second direction.

[0061] Pupil-expanding grating 21: It is located on the pupil-expanding waveguide 2 and is responsible for coupling the light transmitted from the main waveguide 1 into the pupil-expanding waveguide 2 for pupil expansion processing, and then coupling the pupil-expanded light back into the main waveguide 1 for propagation. It cooperates with the output grating 12 to realize the two-dimensional pupil expansion of light.

[0062] In the diffractive optical structure provided by the embodiment of the present application, by introducing the pupil-expanding waveguide 2, the pupil-expanding grating 21 thereon cooperates with the output grating 12 on the main waveguide 1 to realize the two-dimensional pupil expansion effect of light. This not only improves the flexibility of light transmission, but also significantly enhances the ability to adapt to users with different interpupillary distances.

[0063] Compared with directly setting a turning and pupil-expanding grating on a traditional optical waveguide, the present application can expand light in two directions, namely the first direction (such as the horizontal direction) and the second direction (such as the vertical direction), making the diffractive optical structure more suitable for diverse usage scenarios and user requirements.

[0064] Regarding directly setting a turning and pupil-expanding grating on a traditional optical waveguide, it has the following obvious defects:

[0065] (1) Directly setting a turning and pupil-expanding grating on the optical waveguide results in a large loss of light during the turning process, thus affecting the overall optical efficiency.

[0066] (2) Directly setting a turning and pupil-expanding grating on the optical waveguide may require more complex manufacturing processes and higher costs, increasing the complexity of the product and the production difficulty.

[0067] In contrast, the technical solution provided by the embodiments of the present application effectively solves the above-mentioned problems existing in the traditional method by introducing an additional pupil-expanding waveguide 2 outside the main waveguide 1, improving the optical efficiency of the diffractive optical structure while reducing the manufacturing complexity and cost of the diffractive optical structure.

[0068] The technical solution provided by the embodiments of the present application can provide sufficient adaptability for people with different interpupillary distances, mainly due to its unique two-dimensional pupil-expanding architecture. Specifically: by introducing the pupil-expanding waveguide 2 in the embodiments of the present application, the pupil-expanding grating 21 thereon cooperates with the coupling-out grating 12 on the main waveguide 1 to achieve a two-dimensional pupil-expanding effect of light. This two-dimensional pupil-expanding ability provides a larger adaptation space for users with different interpupillary distances because the pupil-expanding range and angle can be adjusted according to needs to better match the visual needs of users.

[0069] In order to balance the optical efficiency of the two paths for light transmission between the main waveguide 1 and the pupil-expanding waveguide 2, in the present application, partition parameter modulation can be selected for components such as the coupling-in grating 11, the pupil-expanding grating 21, and the coupling-out grating 12. These parameters include the depth, tilt angle, duty cycle, etc. of the grating, and they can be optimized and adjusted according to the needs of users with different interpupillary distances. Through this modulation, it can be ensured that the loss of light during transmission is minimized while providing the best visual effect for different users.

[0070] The diffractive optical structure of the embodiment of the present application includes a main waveguide 1 and an pupil-expanding waveguide 2. The main waveguide 1 is equipped with an input grating 11 and an output grating 12 for coupling light in and out and one-dimensional pupil expansion. The pupil-expanding waveguide 2 is stacked on one side of the input grating 11 of the main waveguide 1 and realizes pupil expansion in the second direction through a pupil-expanding grating 21, thereby realizing two-dimensional pupil expansion of light. The present application avoids the complexity of traditional light turning pupil expansion, simplifies the optical path directly through the stacked structure, not only greatly reduces optical loss, but also ensures stable transmission and final clear presentation of light.

[0071] The technical solution proposed in the present application realizes two-dimensional pupil expansion of light without involving light turning, bringing beneficial effects such as improving optical efficiency, simplifying the structure, reducing costs, and enhancing applicability, which is of great significance to the development and application of augmented reality technology.

[0072] In some examples of the present application, an included angle is formed between the second direction and the first direction θ , 80° ≤ θ ≤ 100°.

[0073] Wherein, the vector directions of the input grating 11 and the output grating 12 are the first direction, and the vector direction of the pupil-expanding grating 21 is the second direction.

[0074] By setting the vector direction of the pupil-expanding grating 21 to be almost perpendicular to the vector directions of the input grating 11 and the output grating 12 (i.e., the first direction) (i.e., the included angle θ is between 80° and 100°), this example of the present application realizes a better two-dimensional pupil expansion effect on light. This design ensures that while light can be expanded in one direction (i.e., the first direction, such as the horizontal direction) of the main waveguide 1, it can also be effectively expanded in another direction (i.e., the second direction) of the pupil-expanding waveguide, thereby significantly improving the field of view angle and light adaptability of the entire diffractive optical structure.

[0075] When the included angle between the vector direction of the pupil-expanding grating 21 on the pupil-expanding waveguide 2 and the vector direction of the input / output grating on the main waveguide 1 θ is between 80° and 100°, the crosstalk phenomenon of light between different gratings can also be reduced. This helps to maintain the purity and transmission efficiency of light and improve the imaging quality.

[0076] For users with different interpupillary distances, this almost perpendicular two-dimensional pupil expansion design can provide a large adjustment space. By finely tuning the included angle θ and other parameters of the grating (such as depth, tilt angle, duty cycle, etc.), the propagation path and pupil expansion effect of light can be optimized to meet the visual needs of different users.

[0077] Within the range of the included angle provided by this example of the present application θ , the optical efficiency of light passing through the two paths of the main waveguide 1 and the pupil expansion waveguide 2 can be better balanced. This helps to ensure that under different eye separation conditions, users can obtain visual effects with sufficient brightness and contrast.

[0078] In a preferred example of the present application, the second direction is perpendicular to the first direction.

[0079] As a preferred example of the present application, setting the vector direction (i.e., the second direction) of the pupil expansion grating 21 perpendicular to the vector directions (i.e., the first direction) of the coupling grating 11 and the output coupling grating 12 brings significant technical effects:

[0080] (1) Optimal two-dimensional pupil expansion effect: When the second direction is perpendicular to the first direction, after light propagates along one dimension in the main waveguide 1, the pupil can be maximally expanded in the other perpendicular dimension through the pupil expansion grating 21. This orthogonal layout ensures that light can be effectively expanded in two mutually perpendicular directions, thus maximizing the field of view angle of the optical waveguide and providing a wider and clearer visual experience.

[0081] (2) Facilitating the reduction of optical crosstalk and cross influence: The perpendicular layout reduces the crosstalk and cross influence of light between different gratings. Since light propagates and expands in two almost perpendicular planes, the interference between them is minimized, ensuring the purity and transmission efficiency of light.

[0082] (3) Improving optical efficiency: By optimizing the layout and parameter design of the gratings, the optical efficiency can be improved while ensuring the pupil expansion effect of light. The perpendicular layout makes the transmission path of light in the waveguide more clear and efficient, reducing unnecessary losses and attenuations.

[0083] (4) Enhancing the adaptability to users with different eye separations: The perpendicular layout makes the pupil expansion effect more uniform and stable, capable of meeting the needs of users with different eye separations. By fine-tuning the grating parameters, the propagation path and pupil expansion effect of light can be further optimized, enabling each user to obtain the best visual effect.

[0084] In addition, the design of the perpendicular layout is relatively simple, which helps to simplify the design complexity of the gratings and the waveguide. At the same time, this layout is also convenient for precise control and adjustment during the manufacturing process, improving production efficiency and product quality.

[0085] As a preferred example of the present application, the vector direction of the pupil expansion grating 21 is set perpendicular to the vector directions of the input grating 11 and the output grating 12, achieving a maximized two-dimensional pupil expansion effect, reducing optical crosstalk and cross influence, improving optical efficiency, simplifying the design, and optimizing the manufacturing process, and enhancing the adaptability to users with different interpupillary distances. This design choice fully demonstrates the innovation and practicality of the technical solution of the present application in the waveguide pupil expansion architecture.

[0086] In some examples of the present application, the light source range emitted by the external opto-mechanics has an overlapping region with the input grating 11 and the pupil expansion grating 21 in a direction perpendicular to the main waveguide 1 and the pupil expansion waveguide 2.

[0087] According to the design in this example of the present application, it is beneficial to improve the optical coupling efficiency. Specifically:

[0088] The opto-mechanics is used to provide imaging information. The overlapping of the light source range emitted by the opto-mechanics with the input grating 11 and the pupil expansion grating 21 ensures that light can be more accurately coupled into the waveguide structure. When the light source emitted by the opto-mechanics is aligned with the input grating 11 and the pupil expansion grating 21, the light can be maximally captured by the grating and guided into different waveguides, reducing light loss, thereby improving the optical coupling efficiency.

[0089] By restricting the light source range emitted by the opto-mechanics to the region overlapping with the above two gratings, stray light in non-target directions can be reduced from entering the waveguide, improving the imaging quality. The reduction of stray light helps to enhance the clarity of the image.

[0090] This design in this example of the present application enables the diffractive optical structure to better adapt to different types of opto-mechanics. As long as the light source range of the opto-mechanics can have an overlapping region with the grating, efficient optical coupling can be achieved.

[0091] In some examples of the present application, see Figure 3 , the orthographic projection of the input grating 11 on the pupil expansion waveguide 2 is located within the pupil expansion grating 21.

[0092] In this example of the present application, the situation where the orthographic projection of the input grating 11 on the pupil expansion waveguide 2 is located within the pupil expansion grating 21 is described. This design means that the size of the input grating 11 (or more accurately, its projection size perpendicular to the waveguide surface) is smaller than the size of the pupil expansion grating 21. This design has advantages in terms of the flexibility of the light incident angle, and the specific analysis is as follows:

[0093] Both normal incidence and oblique incidence are applicable: Since the projection of the coupling grating 11 is completely within the pupil expansion grating 21, this allows the light rays emitted by the external optical engine to not only be normally incident, but also be obliquely incident within a certain range, and still be effectively captured by the coupling grating 11 and the pupil expansion grating 21 as much as possible. This design significantly improves the tolerance to the light incident angle, enabling the diffractive optical structure to more flexibly adapt to different optical layouts.

[0094] In some examples of the present application, referring to Figures 1 to 4 , the coupling grating 11 is used to couple external light rays into the main waveguide 1, and the coupling-out grating 12 is used to expand the pupil of the light rays propagating in the main waveguide 1 along the first direction and couple them out; the pupil expansion grating 21 is used to couple the light rays that sequentially pass through the coupling grating 11 and the main waveguide 1 into the pupil expansion waveguide 2, and couple the light rays out to the coupling grating 11 after the light rays complete pupil expansion along the second direction within the pupil expansion waveguide 2.

[0095] Among them, the main function of the coupling grating 11 is to couple external light rays (such as light rays from an optical engine or a light source) into the main waveguide 1. This step is the basis for realizing the optical waveguide display technology, which ensures that the light rays can stably propagate within the main waveguide 1. The coupling-out grating 12 is responsible for expanding the pupil of the light rays propagating along the first direction in the main waveguide 1 and coupling them out of the main waveguide, and finally guiding them to the human eye 01, referring to Figure 4 . This process not only expands the field of view angle of the light rays, but also improves the utilization efficiency of the light rays, making the AR display clearer and wider.

[0096] Among them, the pupil expansion waveguide 2 is one of the cores of the innovation points of the present application. Referring to Figure 3 , the pupil expansion grating 21 on the pupil expansion waveguide 2 first receives the light rays that pass through the coupling grating 11 and the main waveguide 1, and then couples these light rays into the pupil expansion waveguide 2. Inside the pupil expansion waveguide 2, the light rays are subjected to pupil expansion processing along the second direction, and then the pupil-expanded light rays are coupled back into the main waveguide 1 by the pupil expansion grating 21 and finally coupled out to the human eye 01 through the coupling-out grating 12. This process realizes the two-dimensional pupil expansion of the light rays, significantly enhancing the visual experience of the AR display.

[0097] By additionally introducing the pupil expansion waveguide 2, the pupil expansion grating 21 thereon is paired with the coupling-out grating 12 on the main waveguide 1, and the present application realizes the two-dimensional pupil expansion of the light rays. This design significantly expands the field of view angle of the AR display, allowing users to see clear virtual images within a wider range, thereby enhancing the practicality and immersion of the AR device.

[0098] In this application, the combined action of the input grating 11, the output grating 12, and the pupil-expanding grating 21 ensures the efficient transmission and pupil-expanding processing of light in the main waveguide 1 and the pupil-expanding waveguide 2. Additionally, by finely adjusting the grating parameters, the transmission path of light and the pupil-expanding effect can be further optimized, improving the optical efficiency and reducing energy loss.

[0099] In some examples of this application, referring to Figure 3 and Figure 4 , there is an air gap between the main waveguide 1 and the pupil-expanding waveguide 2.

[0100] The introduction of the air gap can reduce the optical coupling and mutual interference between the main waveguide 1 and the pupil-expanding waveguide 2, making the transmission of light in each waveguide clearer and more stable. This design helps to improve the overall optical performance of the diffractive optical structure, including the light transmittance, reflectivity, and diffraction efficiency, etc. Moreover, the existence of the air gap provides more freedom for the pupil-expanding grating 21, making the pupil-expanding process of light in the pupil-expanding waveguide 2 more sufficient and effective, which helps to improve the pupil-expanding effect, making the two-dimensional pupil expansion of light more uniform and consistent, and thus enhancing the user's visual experience.

[0101] Optionally, the air gap between the main waveguide 1 and the pupil-expanding waveguide 2 can be controlled, for example, within 50um to 200um.

[0102] The size of the air gap can be adjusted and optimized according to actual requirements. Within the above range of 50um to 200um, by finely tuning the size of the air gap, the optical performance of the diffractive optical structure can be further improved to make it more adaptable to different usage scenarios and user needs.

[0103] To a certain extent, due to the existence of the air gap, excessive mechanical stress will not be generated between the main waveguide 1 and the pupil-expanding waveguide 2 due to direct contact, thus helping to protect the integrity and durability of the diffractive optical structure.

[0104] In some examples of this application, referring to Figure 1 and Figure 2 , the shape and size of the pupil-expanding grating 21 match those of the input grating 11.

[0105] The pupil-expanding grating 21 is located on the additionally introduced pupil-expanding waveguide 2, and it is separately arranged from the main waveguide 1. The input grating 11 and the output grating 12 are arranged on the main waveguide 1. In this example of this application, the shape and size of the pupil-expanding grating 21 match those of the input grating 11, which can ensure a more efficient and stable coupling process of light between the two.

[0106] Specifically, when light rays are emitted from the light engine of the peripheral device and enter the main waveguide 1 through the input grating 11, their coupling efficiency is affected by the shape and size of the grating. Similarly, when light rays are coupled out from the pupil expansion waveguide 2 through the pupil expansion grating 21 and enter the main waveguide 1 again, the matching between the pupil expansion grating 21 and the input grating 11 also directly affects the coupling efficiency. Therefore, this design helps to improve the optical coupling efficiency of the entire diffractive optical structure.

[0107] Since the shape and size of the pupil expansion grating 21 match those of the input grating 11, the manufacturer can use the same process parameters and molds to manufacture these two gratings during the manufacturing process. This helps to simplify the manufacturing process, reduce production costs, and improve production efficiency.

[0108] In some examples of the present application, referring to Figures 2 to 4 , the pupil expansion waveguide 2 includes a substrate 22, and the substrate 22 includes two opposite surfaces; the pupil expansion grating 21 is disposed on one surface of the substrate 22; the size of the substrate 22 is larger than that of the pupil expansion grating 21.

[0109] Among them, the substrate 22 serves as a support structure for the pupil expansion waveguide 2, and its larger size provides better mechanical stability and stiffness. Thus, the overall stability and reliability of the diffractive optical structure are ensured.

[0110] The pupil expansion grating 21 is disposed on one surface of the substrate 22, and the size of the substrate 22 is larger than that of the grating, which provides a stable and large working environment for the grating. The larger working environment helps to reduce the optical interference and scattering effects around the grating, and improve the coupling efficiency and optical performance of the grating.

[0111] Since the size of the substrate 22 is larger than that of the pupil expansion grating 21, the grating can perform pupil expansion processing on light rays in a larger space. This helps to increase the pupil expansion range and efficiency of the light rays, enabling more light rays to be effectively coupled and transmitted to the user's eyes, thereby improving the display effect and user experience of the AR device.

[0112] Although the manufacturing of the substrate 22 may be relatively complex, the larger size helps to simplify the subsequent manufacturing and processing process of the pupil expansion grating 21. The manufacturer can more easily and precisely etch or deposit the grating structure on the substrate, thereby improving production efficiency and reducing manufacturing costs.

[0113] In some examples of the present application, referring to Figure 1 , the input grating 11 is a trapezoidal structure that gradually increases from the middle to both sides; the middle part of the input grating 11 is the entrance pupil region 111, and the size of the entrance pupil region 111 matches the size of the exit pupil region of the light engine of the peripheral device.

[0114] The shape of the coupling grating 11 provided in the embodiments of the present application is designed such that, referring to Figure 1 , the coupling grating 11 is composed of, for example, two isosceles trapezoids, and the size of the middle region is smaller. This designed coupling grating 11 enables light to be more effectively coupled when entering the main waveguide 1 from the pupil region of the optical engine. Since the pupil region 111 matches the size of the pupil region of the optical engine, the loss of light during transmission is reduced, thereby improving the optical coupling efficiency. This efficient coupling helps ensure that more light enters the diffractive optical structure, providing sufficient light sources for subsequent pupil expansion and imaging display.

[0115] The structure of the coupling grating 11 provided in this example of the present application is such that, referring to Figure 1 , the shape is relatively simple and is easy to manufacture and process. Manufacturers can precisely adjust the size of the pupil region 111 by controlling parameters such as the etching depth, angle, and width of the grating, thereby meeting the matching requirements with the pupil region of the optical engine. This simple manufacturing process helps reduce production costs and improve production efficiency.

[0116] In some examples of the present application, referring to Figure 1 , Figure 3 and Figure 4 , the main waveguide 1 includes a substrate 13, and the substrate 13 includes two opposite surfaces; the coupling grating 11 and the coupling-out grating 12 are disposed on at least one surface of the substrate 13.

[0117] The diffractive optical structure provided in the embodiments of the present application offers a high degree of flexibility in layout.

[0118] For the main waveguide 1, the coupling grating 11 and the coupling-out grating 12 can be disposed on the same surface of the substrate 13 of the main waveguide 1. For example, the coupling grating 11 and the coupling-out grating 12 can be disposed together on the upper surface or the lower surface of the substrate 13.

[0119] Of course, the coupling grating 11 and the coupling-out grating 12 can also be separately disposed on two surfaces of the substrate 13 of the main waveguide 1. For example, the coupling grating 11 is disposed on the upper surface of the substrate 13, and the coupling-out grating 12 is disposed on the lower surface of the substrate 13, and vice versa.

[0120] In some examples of the present application, the coupling grating 11 and the coupling-out grating 12 are one-dimensional gratings; the pupil-expanding grating 21 is a one-dimensional grating or a two-dimensional grating.

[0121] In this application, the input grating 11, the output grating 12, and the pupil-expanding grating 21 can all be one-dimensional gratings. This makes their manufacturing relatively simple and the cost relatively low. One-dimensional gratings couple and diffract light in a specific direction, and can effectively control the propagation direction of light, thereby improving the optical efficiency.

[0122] Of course, the pupil-expanding grating 21 can also be a two-dimensional grating. When the pupil-expanding grating 21 is designed as a two-dimensional grating, it can perform pupil expansion of light in two directions. This design increases the flexibility of the diffractive optical structure, and the direction and range of pupil expansion can be adjusted according to actual needs, so as to meet a wider range of application scenarios.

[0123] In some examples of this application, one-dimensional gratings are used for the input and output processes to ensure the effective transmission of light in the main waveguide 1; while two-dimensional gratings are used for the pupil expansion process, and uniform distribution of light can be achieved within a wider field of view. This combined design helps to improve the overall optical performance.

[0124] In some examples of this application, the input grating 11, the output grating 12, and the pupil-expanding grating 21 are surface relief gratings or volume gratings.

[0125] In this application, the surface relief grating can be one or more of a straight grating, a tilted grating, a blazed grating, a stepped grating, and a quadrilateral grating.

[0126] The surface relief grating is formed by etching a periodic structure on the substrate surface of the waveguide. Its manufacturing process is relatively simple and the cost is relatively low. This type of grating is suitable for occasions that require high-precision and high-efficiency coupling.

[0127] The volume grating forms a periodic structure inside the waveguide, and its depth control is more flexible. The volume grating can achieve the coupling and diffraction of light within a wider wavelength range and is suitable for occasions with high requirements for spectral performance.

[0128] According to different application scenarios and requirements, a suitable grating type can be selected to optimize the performance of the diffractive optical structure. For example, in the case of requiring high coupling efficiency, a surface relief grating can be used; while in the case of requiring wide spectral response, a volume grating can be selected.

[0129] See Figure 5 , Figure 5 is the K-space diagram of the light propagation of the diffractive optical structure provided by the embodiment of this application. Here Figure 5Among them, TIR represents the total internal reflection phenomenon. K1, as the K vector of the coupling grating 11, marks the starting point where light officially enters the diffractive optical structure. And K3, as the K vector of the output grating 12, represents the end point where light leaves the structure after completing its transmission task. Between K1 and K3, K2 and K2' play important roles: K2 represents the input vector of the pupil expansion grating 21, which guides light into the pupil expansion process, enabling more light to pass through. And K2' represents the output vector of the pupil expansion grating 21, which marks the new path of light after the pupil expansion. The existence of these two vectors fully demonstrates the fine control ability of the diffractive optical structure over light.

[0130] Through the elaborate design of K1, K2, K2' and K3, and the ingenious utilization of the TIR phenomenon, Figure 5 it demonstrates the complete process of light from coupling to pupil expansion and output in the diffractive optical structure of this application. This process ensures that the diffractive optical structure can maintain an efficient and stable working state under different lighting conditions.

[0131] According to the diffractive optical structure provided by the embodiment of this application, an absorbing coating can be provided on the side wall of the pupil expansion waveguide 2. This is because, during the process of transmitting light, the pupil expansion waveguide 2 may generate some unexpected stray light due to internal reflection, scattering, etc. If these stray lights are not processed, they may affect the imaging quality and reduce the image clarity. By providing an absorbing coating on the inner wall of the pupil expansion waveguide 2, these stray lights can be effectively absorbed, reducing their interference with the imaging quality.

[0132] In addition, the absorbing coating can reduce the light loss inside the pupil expansion waveguide 2, enabling more effective light to be transmitted along the pupil expansion waveguide 2 and finally reach the human eye 01. This can improve the optical efficiency of the entire diffractive optical structure, making the image brighter and clearer.

[0133] Of course, an absorbing coating can also be provided on the inner wall of the main waveguide 1.

[0134] According to another embodiment of this application, an optical system is provided. The optical system includes: the diffractive optical structure as described above and an opto-mechanical device; wherein, the opto-mechanical device is used to project light onto the coupling grating 11 of the diffractive optical structure.

[0135] The optical system provided by the embodiment of this application mainly consists of two parts: one is the diffractive optical structure described in all the above embodiments, and the other is an external opto-mechanical device. These two parts work together to jointly achieve the functions of efficient and high-quality light processing and projection.

[0136] Among them, the diffractive optical structure, as the core part of the optical system, is responsible for effectively guiding the light emitted by the optomechanics so that the light can enter the human eye for imaging.

[0137] Among them, the optomechanics is another important component in the optical system. Its main function is to project light onto the diffractive optical structure and provide a stable and high-quality light source for the diffractive optical structure.

[0138] In some examples of this application, referring to Figure 3 , the pupil-expanding waveguide 2 and the optomechanics 3 are located on the same side of the main waveguide 1; or, referring to Figure 4 , the pupil-expanding waveguide 2 and the optomechanics 3 are respectively arranged on both sides of the main waveguide 1.

[0139] The diffractive optical structure provided by the embodiments of this application provides a high degree of flexibility in layout.

[0140] Among them, the position of the pupil-expanding waveguide 2 relative to the main waveguide 1 and the optomechanics 3 is also variable. Specifically, relative to the main waveguide 1, the pupil-expanding waveguide 2 can be on the same side as the optomechanics 3 (referring to Figure 3 ), or it can be on the opposite side of the optomechanics 3 (referring to Figure 4 ).

[0141] Referring to Figure 3 , the optomechanics 3 and the human eye 01 can be located on the same side of the main waveguide 1. Of course, the optomechanics 3 and the human eye 01 can be located on the opposite sides of the main waveguide 1.

[0142] This design flexibility in this application enables the solution of this application to be customized according to the needs of users with different interpupillary distances, thereby providing a more fitting visual effect.

[0143] According to another embodiment of this application, a near-eye display device is provided. The near-eye display device includes a housing and the optical system as described above, wherein the optical system is disposed in the housing.

[0144] The near-eye display device provided by the embodiments of this application is, for example, an AR display device. The form of the AR display device is, for example, an AR smart glasses or an AR smart helmet, etc. This application does not limit this.

[0145] The specific implementation manners of the optical system and the near-eye display device of the embodiments of this application can refer to the respective embodiments of the above diffractive optical structure. Therefore, it has at least all the beneficial effects brought by the technical solutions of the above embodiments, and will not be elaborated one by one here.

[0146] In the above embodiments, the differences between the various embodiments are mainly described. As long as the different optimization features between the various embodiments are not contradictory, they can be combined to form a more optimal embodiment. For the sake of brevity of the text, they will not be elaborated here.

[0147] Although some specific embodiments of the present 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 not for limiting the scope of the present application. Those skilled in the art should understand that the above embodiments can be modified without departing from the scope and spirit of the present application. The scope of the present application is defined by the appended claims.

Claims

1. A diffractive optical structure, characterized in that: It includes a main waveguide (1) and a pupil expansion waveguide (2); The main waveguide (1) comprises an in-coupling grating (11) and an out-coupling grating (12), wherein the vector directions of the in-coupling grating (11) and the out-coupling grating (12) are the same and are both in a first direction; The pupil expansion waveguide (2) is stacked on one side of the main waveguide (1), the pupil expansion waveguide (2) comprises a pupil expansion grating (21), the vector direction of the pupil expansion grating (21) is a second direction, and the second direction is different from the first direction; The pupil expansion waveguide (2) comprises a substrate (22), wherein the substrate (22) comprises two opposite surfaces; the pupil expansion grating (21) is arranged on one surface of the substrate (22); the size of the substrate (22) is larger than the size of the pupil expansion grating (21); In the thickness direction of the diffractive optical structure, at least partial areas of the pupil expansion grating (21) and the coupling grating (11) are arranged correspondingly; The coupling-in grating (11) is used to couple external light into the main waveguide (1), and the coupling-out grating (12) is used to expand the pupil of the light propagating in the main waveguide (1) along the first direction and couple it out; The pupil expansion grating (21) is used to couple the light that sequentially transmits the coupling grating (11) and the main waveguide (1) into the pupil expansion waveguide (2), and to couple the light out to the coupling grating (11) after the light has completed pupil expansion along the second direction in the pupil expansion waveguide (2); An air gap is provided between the main waveguide (1) and the pupil expansion waveguide (2); The range of the light source emitted by the external optical machine (3) has an overlapping area with the coupling grating (11) and the pupil expansion grating (21) in a direction perpendicular to the main waveguide (1) and the pupil expansion waveguide (2); Relative to the main waveguide (1), the pupil expansion waveguide (2) and the optical machine (3) are arranged on opposite sides; The orthographic projection of the coupling grating (11) on the pupil expansion waveguide (2) is located within the pupil expansion grating (21); The coupling grating (11) is a trapezoidal structure that gradually increases from the middle to both sides; The middle part of the coupling grating (11) is an entrance pupil area (111), and the size of the entrance pupil area (111) matches the size of the exit pupil area of ​​the external optical machine (3).

2. The diffractive optical structure according to claim 1, characterized in that: The second direction forms an angle with the first direction θ , 80°≤ θ ≤100°.

3. The diffractive optical structure according to claim 2, characterized in that: The second direction is perpendicular to the first direction.

4. The diffractive optical structure according to claim 1, characterized in that: The pupil expansion grating (21) matches the shape and size of the coupling-in grating (11).

5. The diffractive optical structure according to claim 1, characterized in that: The main waveguide (1) comprises a substrate (13), wherein the substrate (13) comprises two opposite surfaces; The coupling-in grating (11) and the coupling-out grating (12) are arranged on at least one surface of the substrate (13).

6. The diffractive optical structure according to any one of claims 1 to 5, characterized in that: The coupling-in grating (11) and the coupling-out grating (12) are one-dimensional gratings; The pupil expansion grating (21) is a one-dimensional grating or a two-dimensional grating.

7. The diffractive optical structure according to claim 6, characterized in that: The coupling-in grating (11), the coupling-out grating (12) and the pupil expansion grating (21) are surface relief gratings or volume gratings.

8. An optical system, characterized in that: include: The diffractive optical structure according to any one of claims 1 to 7; and An optical machine (3), the optical machine (3) being used to project light onto the diffractive optical structure.

9. A near-eye display device, characterized in that: include: shell; and The optical system according to claim 8, wherein the optical system is disposed in the housing.

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