Optical waveguide structure and display device

Abstract

The utility model relates to a kind of optical waveguide structure and display equipment, belong to the field of optical display, it includes waveguide base body and entrance pupil grating, entrance pupil grating is set on the waveguide base body, for the image light beam emitted by light machine is coupled into the waveguide base body, the entrance pupil grating includes first area and second area, the first area and the second area about the middle axis of the waveguide base body symmetrically set, the first area and the second area all include multiple diffraction grating arranged along first direction, the utility model has promoted coupling-in efficiency, avoided the light loss caused by traditional grating structure design, and realize the optical symmetry of bilateral coupling-in structure, so that left eye and right eye are more consistent in light path, coupling-in angle and energy distribution, promote the effect of image brightness uniformity and image consistency.

Description

Technical Field

[0001] This utility model relates to the technical field of optical display, and in particular to an optical waveguide structure and display device. Background Technology

[0002] Optical waveguide technology, as a core component of augmented reality (AR), virtual reality (VR), and mixed reality (MR) near-eye display systems, is widely used in various head-mounted display devices due to its high resolution, thin and light form factor, and excellent imaging quality. With the development of AR technology, thin, light-weight, low-power, and high-efficiency display solutions have become crucial for the commercialization of AR glasses. Among these, diffractive waveguides have become one of the mainstream near-eye display optical solutions due to their advantages such as thinness, high transparency, and ease of integration. In a diffractive waveguide structure, the incident coupling grating is used to couple the image light from the optomechanism into the waveguide, and it is a key element affecting optical efficiency and display quality.

[0003] Current optical architectures include dual-optical-engine design or single-optical-engine binocular architecture. Dual-optical-engine design means that each eye is equipped with an independent optical engine, while single-optical-engine binocular architecture uses an optical engine to output image light, and then uses an optical path distribution system to guide the image into the optical waveguides of the left and right eyes respectively, thereby realizing binocular display. Although dual-optical-engine design has a simple optical path and is easy to adjust, it brings problems such as large device size, high power consumption, and high cost. On the other hand, single-optical-engine binocular architecture significantly reduces the number of hardware components and the overall size of the device, which helps to realize a lighter AR terminal, and therefore has become the mainstream architecture.

[0004] In a single-optical-mechanical binocular architecture, the image light needs to enter the left and right waveguides in two directions after being output from the optical engine. At this time, the entrance pupil grating needs to achieve efficient coupling in symmetrical directions. However, traditional entrance pupil gratings are usually just set as multiple identical rectangular gratings, which are difficult to adapt to the bidirectional high-efficiency coupling requirements at the same time. This can easily cause problems such as low coupling efficiency, uneven brightness, and poor image consistency, which limits the practical application performance of this architecture. Utility Model Content

[0005] In view of this, the purpose of this utility model is to provide an optical waveguide structure and display device to solve the technical problems in the prior art where the traditional entrance pupil grating is difficult to adapt to the bidirectional high-efficiency coupling requirements at the same time, which easily leads to low coupling efficiency, uneven brightness and poor image consistency.

[0006] This utility model provides an optical waveguide structure, comprising: Waveguide substrate; An entrance pupil grating is disposed on the waveguide substrate and is used to couple an image beam emitted by an optomechanical system into the waveguide substrate. The entrance pupil grating includes a first region and a second region, which are symmetrically arranged about the central axis of the waveguide substrate. Both the first region and the second region include multiple diffraction gratings arranged along the first direction.

[0007] Optionally, the surface of the diffraction grating is provided with a film layer, which is used to enhance the optical coupling efficiency of the diffraction grating.

[0008] Optionally, the diffraction grating is configured as an inclined grating, wherein the diffraction gratings of the first region and the second region are inclined from the end near the waveguide substrate toward the central axis away from the waveguide substrate.

[0009] Optionally, the diffraction grating is configured as a sawtooth grating, and the inclined surfaces of the diffraction gratings in the first region and the second region are both inclined toward the central axis of the waveguide substrate.

[0010] Optionally, the diffraction grating is configured as a rectangular grating, and the film layer includes a first part and a second part. The first part is disposed on the surface of the diffraction grating facing away from the waveguide substrate, and the second part is disposed on the surface of the diffraction grating facing or away from the central axis of the waveguide substrate. One end of the first part and one end of the second part are integrally formed.

[0011] Optionally, the film layer is configured as a reflective film, an antireflective film, or a refractive film.

[0012] Optionally, the diffraction gratings in the first region and the second region are both set as stepped types, with multiple steps on the diffraction gratings. The diffraction gratings in the first region and the diffraction gratings in the second region are symmetrically arranged about the central axis of the waveguide substrate.

[0013] Optionally, the diffraction gratings in the first region and the diffraction gratings in the second region correspond one-to-one, and the diffraction gratings on the first region and the corresponding diffraction gratings on the second region are integrally formed into a grating unit.

[0014] Optionally, it also includes: An exit pupil grating is disposed on the waveguide substrate and is used to project an image beam from the waveguide substrate to the human eye. At least two exit pupil gratings are provided, and an entrance pupil grating is disposed between the two exit pupil gratings. A pupil grating is disposed on the waveguide substrate and receives light from the entrance pupil grating. The pupil grating and the exit pupil grating are disposed correspondingly. The image beam coupled into the waveguide substrate by the entrance pupil grating is transmitted to the corresponding exit pupil grating through the pupil grating.

[0015] This utility model also provides a display device, including the aforementioned optical waveguide structure, and further including an optical engine, the optical engine being used to emit an image beam, the optical engine being disposed at the entrance pupil grating and aligned with the entrance pupil grating.

[0016] The technical solution of this utility model has the following advantages: The optical waveguide structure provided by this utility model divides the entrance pupil grating into a first region and a second region, and the first and second regions are symmetrically arranged about the central axis of the waveguide substrate. The first and second regions are respectively responsible for the coupling of light rays from both sides, so that the energy of the light rays coupled into the first and second regions is higher, thereby improving the coupling efficiency of the image beam in the process of coupling into the waveguide substrate on both sides. This avoids the light loss caused by the traditional grating structure design, and realizes the optical symmetry of the dual-side coupling structure, making the light path, coupling angle and energy distribution of the left and right eyes more consistent, thus improving the brightness uniformity and image consistency of the image. Attached Figure Description

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

[0018] Figure 1 This is a schematic diagram of the overall structure of the optical waveguide structure in this utility model; Figure 2 This is a schematic diagram of the optical waveguide structure of the tilted grating in this utility model; Figure 3 This is a schematic diagram of the optical waveguide structure of the sawtooth grating in this utility model; Figure 4 This is a schematic diagram of the optical waveguide structure of the rectangular grating in this utility model; Figure 5 This is a schematic diagram of another embodiment of the optical waveguide structure of the rectangular grating in this utility model; Figure 6 This is a schematic diagram of the waveguide structure of the stepped grating in this utility model.

[0019] Explanation of reference numerals in the attached figures: 1. Waveguide substrate; 2. Entrance pupil grating; 21. First region; 22. Second region; 23. Diffraction grating; 3. Film layer; 31. First part; 32. Second part; 4. Exit pupil grating; 5. Dilation pupil grating. Detailed Implementation

[0020] The specific embodiments of this utility model will now be described in detail with reference to the accompanying drawings. Obviously, the described embodiments are merely some, not all, of the embodiments of this utility model. Based on the description of this utility model, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this utility model.

[0021] Unless otherwise explicitly specified and limited, the terms "setup," "installation," and "connection" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium. Those skilled in the art can understand the specific meaning of these terms based on the specific circumstances.

[0022] In the diagram, the direction indicated by arrow X is the first direction.

[0023] The term "central axis" refers to the symmetrical reference line running through the center of the waveguide substrate. The optical waveguide structure can be folded along the central axis so that the two sides can roughly coincide. The dashed line indicated by arrow Y in the figure is the central axis. The central axis in the figure is perpendicular to the first direction.

[0024] The terms “upper,” “lower,” “left,” “right,” “front,” “back,” “top,” “bottom,” “inner,” and “outer,” etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product is in use. They are used only for the convenience of description and simplification, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0025] The terms “first,” “second,” “third,” etc., are used merely to distinguish elements with similar properties, not to indicate or imply relative importance or a specific order.

[0026] The terms “include,” “comprising,” or any other variation thereof are intended to cover non-exclusive inclusion, which includes not only the elements listed but also other elements not expressly listed.

[0027] Example 1 Reference Figures 1-6As shown, this utility model provides an optical waveguide structure, including a waveguide substrate 1 and an entrance pupil grating 2. The waveguide substrate 1 is made of planar glass or resin, and the entrance pupil grating 2 is disposed on the waveguide substrate 1. The entrance pupil grating 2 can be fabricated on the waveguide substrate 1 by nanoimprinting, etching, or molding processes. An optomechanical system is aligned with the entrance pupil grating 2, which is used to couple the image beam emitted by the optomechanical system into the waveguide substrate 1. Specifically, the entrance pupil grating 2 includes a first region 21 and a second region 22, which are symmetrically arranged about the central axis of the waveguide substrate 1. Both the first region 21 and the second region 22 include a plurality of diffraction gratings 23 uniformly arranged along a first direction. A film layer 3 is disposed on the surface of the diffraction grating 23, which is used to enhance the optical coupling efficiency of the diffraction grating 23.

[0028] By dividing the entrance pupil grating 2 into a first region 21 and a second region 22, and symmetrically arranging the first region 21 and the second region 22 about the central axis of the waveguide substrate 1, the first region 21 and the second region 22 are respectively responsible for the coupling of light rays on both sides, i.e., the light rays on the left and right sides in the figure. This makes the energy of the light rays coupled into the first region 21 and the second region 22 higher, thereby improving the coupling efficiency of the image beam in the process of coupling into the waveguide substrate 1 on both sides. This avoids the light loss caused by the traditional grating structure design and achieves the optical symmetry of the dual-side coupling structure, making the light path, coupling angle and energy distribution of the left and right eyes more consistent, improving the brightness balance and image consistency of the image. Compared with the traditional structure, this structure improves the effective coupling efficiency by more than 60% in terms of the total energy of binocular coupling, while the light energy difference between the left and right eyes is reduced from the traditional 15% to less than 5%.

[0029] It also simplifies the design difficulty of the coupling structure under symmetrical optical path, realizes the structural light energy control without increasing the complexity of the optical path system, is compatible with the system integration requirements of single-optical-mechanical binocular structure, and adapts to the needs of lightweight and highly integrated AR glasses products.

[0030] In this embodiment, the first region 21 and the second region 22 are symmetrically arranged about the central axis of the waveguide substrate 1. Slight deviations are allowed, as long as it can ensure that the energy of the light coupled into the first region 21 and the second region 22 is higher, thereby improving the coupling efficiency of the image beam in the process of coupling into the waveguide substrate 1 on both sides.

[0031] Additionally, refer to Figure 1As shown, the optical waveguide structure also includes an exit pupil grating 4 and a pupil dilator grating 5. The exit pupil grating 4 is disposed on the waveguide substrate 1 and has a certain gap with the entrance pupil grating 2. The exit pupil grating 4 is used to couple out the image beam coupled into the waveguide substrate 1 by the entrance pupil grating 2 and project it into the human eye. Specifically, two exit pupil gratings 4 are provided in this embodiment. When two exit pupil gratings 4 are provided, the two exit pupil gratings 4 are respectively located on both sides of the entrance pupil grating 2, and the entrance pupil grating 2 is located between the two exit pupil gratings 4. The two exit pupil gratings 4 are symmetrically arranged along the central axis of the optical waveguide structure, and the entrance pupil grating 2 is located on the central axis, thereby realizing a binocular waveguide.

[0032] The pupil grating 5 is disposed on the waveguide substrate 1 and can receive light from the entrance pupil grating 2. When there are two exit pupil gratings 4, there are also two pupil gratings 5. The two pupil gratings 5 ​​and the exit pupil gratings 4 are arranged in a one-to-one correspondence. The image beam coupled into the waveguide substrate 1 by the entrance pupil grating 2 is first transmitted to the pupil grating 5 and then to the corresponding exit pupil grating 4. The pupil grating 5 can receive the image beam coupled into the waveguide substrate 1 by the optomechanical system at any position of the entrance pupil grating 2.

[0033] As one specific implementation method, refer to Figure 2 As shown, the diffraction grating 23 is configured as an inclined grating. Multiple diffraction gratings 23 in the first region 21 are inclined from the end closest to the waveguide substrate 1 towards the direction away from the central axis of the waveguide substrate 1. Similarly, multiple diffraction gratings 23 in the second region 22 are also inclined from the end closest to the waveguide substrate 1 towards the direction away from the central axis of the waveguide substrate 1. That is, the diffraction gratings 23 in the first region 21 are inclined to the left, and the diffraction gratings 23 in the second region 22 are inclined to the right. Through this specific directional inclination, after the image beam is diffracted through the entrance pupil, most of the light will concentrate towards the left. The light propagates in both directions on the right and the left, with only a fraction of the light becoming zero-order light projected out of the optical waveguide. This allows the diffraction grating 23 to obtain higher energy, thereby greatly improving the diffraction efficiency of the entrance pupil grating 2 and thus improving the overall efficiency of the waveguide. When the user wears the device, the left and right eyes receive image light from the same optical engine through independent waveguide channels. The image beams are coupled into the optical engine through the symmetrical first region 21 and second region 22 provided in this application, ensuring that the brightness and clarity of the images received by the user's eyes are balanced, significantly enhancing the immersive AR experience.

[0034] Furthermore, the film layer 3 is disposed on the surface of the tilted diffraction grating 23 on the side facing away from the waveguide substrate 1. By disposing of the film layer 3, the coupling efficiency of the image beam during the process of coupling into the waveguide substrate 1 on both sides can be further improved.

[0035] As another implementation method, refer to Figure 3As shown, the diffraction grating 23 is configured as a sawtooth grating with an inclined surface. The inclined surface of the diffraction grating 23 in the first region 21 is inclined toward the central axis of the waveguide substrate 1, and the inclined surface of the diffraction grating 23 in the second region 22 is also inclined toward the central axis of the waveguide substrate 1. At this time, the film layer 3 covers the surface of all the diffraction gratings 23, and all the film layers 3 are integrally formed as a whole. The inclined surfaces of the diffraction gratings 23 in the first region 21 and the second region 22 are inclined in opposite directions, thereby realizing independent and efficient coupling of multi-directional image beams and improving coupling efficiency.

[0036] As another implementation method, refer to Figure 4 As shown, the diffraction grating 23 is a rectangular grating, and the film layer 3 disposed on the diffraction grating 23 is L-shaped. The film layer 3 includes a first part 31 and a second part 32, wherein the first part 31 is horizontally disposed, and the second part 32 is vertically disposed. The first part 31 is disposed on the surface of the diffraction grating 23 facing away from the waveguide substrate 1 and extends along a first direction. The second part 32 is disposed on the surface of the diffraction grating 23 facing away from the central axis of the waveguide substrate 1 and extends along a direction perpendicular to the first direction. The end of the first part 31 facing the second part 32 and the end of the second part 32 facing the first part 31 are integrally formed, so that the direction of the film layer 3 on the diffraction grating 23 in the first region 21 is opposite to that on the diffraction grating 23 in the second region 22, and the film layer 3 in the first region 21 and the film layer 3 in the second region 22 are symmetrically disposed about the central axis of the waveguide substrate 1. In another embodiment, refer to Figure 5 As shown, the second part 32 is disposed on the surface of the diffraction grating 23 facing the central axis of the waveguide substrate 1. Similarly, the film layer 3 on the diffraction grating 23 in the first region 21 is opposite in direction to the film layer 3 on the diffraction grating 23 in the second region 22. The film layer 3 in the first region 21 and the film layer 3 in the second region 22 can be symmetrically arranged about the central axis of the waveguide substrate 1.

[0037] In this embodiment, the diffraction grating 23 is a rectangular grating, and the entrance pupil grating 2 is a continuous micro-nano grating region. The grating fringes of the first region 21 and the second region 22 are aligned, and the period and depth parameters are the same. The structure of the diffraction grating 23 is not changed, but the structure of the film layer 3 is changed. By tilting the deposition method, the deposition direction of the film layer 3 on the first region 21 and the second region 22 is symmetrical about the central axis of the waveguide substrate 1, so that the direction of the film layer 3 and the diffraction grating 23 are symmetrically matched. This helps to improve the interference and coupling ability of the image beam at the interface of the film layer 3, thereby improving the coupling efficiency.

[0038] Specifically, film layer 3 can be configured as a reflective film, an antireflective film, or a refractive film, thereby improving coupling efficiency and ensuring directional consistency. Film layer 3 can be made of a high refractive index medium (oxides such as titanium dioxide, carbon dioxide, silicates, and fluorides) or a metal-reinforced film.

[0039] As an alternative implementation method, such as Figure 6 As shown, the diffraction gratings 23 of the first region 21 and the second region 22 are set as stepped types. Multiple steps are arranged sequentially along the first direction on the diffraction grating 23, and the distance between the multiple steps arranged along the first direction and the waveguide substrate 1 increases sequentially. The stepped diffraction gratings 23 of the first region 21 and the stepped diffraction gratings 23 of the second region 22 are symmetrically arranged about the central axis of the waveguide substrate 1. The film layer 3 covers the stepped surface of the stepped diffraction grating 23. When the image beam output by the optomechanical system is directed onto the first region 21 and the second region 22 respectively, the image beam will be incident on the surface of the stepped diffraction grating 23. Multiple diffraction paths are formed on the multiple steps, thereby effectively widening the incident angle tolerance range. Furthermore, the symmetrical arrangement allows the left and right incident light to produce diffraction behavior in their respective first region 21 and second region 22, thereby achieving efficient and balanced optical coupling.

[0040] Furthermore, in the embodiment of the stepped diffraction grating 23, the diffraction grating 23 in the first region 21 and the diffraction grating 23 in the second region correspond one-to-one, and the diffraction grating 23 on the first region 21 and the corresponding diffraction grating 23 on the second region 22 are integrally formed into a grating unit. Specifically, the grating unit has 2n+1 steps, with n steps on the left side, one step in the middle, and n steps on the right side, so that the steps on the left and right sides of the grating unit are symmetrical about the middle step. Through simulation modeling and optical testing of the stepped diffraction grating 23 structure, in the visible light band, the single-sided coupling efficiency of the traditional tilted grating structure is about 32%, while the symmetrical stepped diffraction grating 23 structure, through the superposition of multi-order reflection interference effects, can achieve a coupling efficiency of about 47%-52%, further improving the coupling efficiency.

[0041] Example 2 Reference Figure 3 and Figure 5As shown, this embodiment provides a display device, including the optical waveguide structure of Embodiment 1, and an optical engine for emitting an image beam. The optical engine is disposed at the entrance pupil grating 2 and aligned with the entrance pupil grating 2. By dividing the entrance pupil grating 2 into a first region 21 and a second region 22, and symmetrically arranging the first region 21 and the second region 22 about the central axis of the waveguide substrate 1, the first region 21 and the second region 22 are respectively responsible for the coupling of light rays from both sides, i.e., the left and right light rays in the figure. This results in higher energy coupling of light rays from the first region 21 and the second region 22, thereby improving the coupling efficiency of the image beam in the process of coupling into the waveguide substrate 1 on both sides. This avoids the light loss caused by the traditional grating structure design and achieves the optical symmetry of the dual-side coupling structure, making the light path, coupling angle and energy distribution of the left and right eyes more consistent, thus improving the brightness uniformity and image consistency of the image.

[0042] It should be noted that the various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0043] The above description is only a specific embodiment of this utility model, but the protection scope of this utility model is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this utility model should be included within the protection scope of this utility model.

Claims

1. An optical waveguide structure, characterized in that, include: Waveguide substrate; An entrance pupil grating is disposed on the waveguide substrate and is used to couple an image beam emitted by an optomechanical system into the waveguide substrate. The entrance pupil grating includes a first region and a second region, which are symmetrically arranged about the central axis of the waveguide substrate. Both the first region and the second region include multiple diffraction gratings arranged along the first direction.

2. The optical waveguide structure as described in claim 1, characterized in that, The surface of each diffraction grating is provided with a film layer, which is used to enhance the optical coupling efficiency of the diffraction grating.

3. The optical waveguide structure as described in claim 1, characterized in that, The diffraction grating is configured as an inclined grating, and the diffraction gratings in the first region and the second region are inclined from the end closest to the waveguide substrate toward the central axis away from the waveguide substrate.

4. The optical waveguide structure as described in claim 1, characterized in that, The diffraction grating is configured as a sawtooth grating, and the inclined surfaces of the diffraction gratings in the first and second regions are both inclined toward the central axis of the waveguide substrate.

5. The optical waveguide structure as described in claim 2, characterized in that, The diffraction grating is configured as a rectangular grating, and the film layer includes a first part and a second part. The first part is disposed on the surface of the diffraction grating facing away from the waveguide substrate, and the second part is disposed on the surface of the diffraction grating facing or away from the central axis of the waveguide substrate. One end of the first part and one end of the second part are integrally formed.

6. The optical waveguide structure as described in claim 2, characterized in that, The film layer is configured as a reflective film, an antireflective film, or a refractive film.

7. The optical waveguide structure as described in claim 1, characterized in that, Both the first and second regions have stepped diffraction gratings, with multiple steps on each grating. The diffraction gratings in the first and second regions are symmetrically arranged about the central axis of the waveguide substrate.

8. The optical waveguide structure as described in claim 7, characterized in that, The diffraction gratings in the first region and the diffraction gratings in the second region correspond one-to-one, and the diffraction gratings on the first region and the corresponding diffraction gratings on the second region are integrally formed into a grating unit.

9. The optical waveguide structure as described in claim 1, characterized in that, Also includes: An exit pupil grating is disposed on the waveguide substrate and is used to project an image beam from the waveguide substrate to the human eye. At least two exit pupil gratings are provided, and an entrance pupil grating is disposed between the two exit pupil gratings. A pupil grating is disposed on the waveguide substrate and receives light from the entrance pupil grating. The pupil grating and the exit pupil grating are disposed correspondingly. The image beam coupled into the waveguide substrate by the entrance pupil grating is transmitted to the corresponding exit pupil grating through the pupil grating.

10. A display device, characterized in that, The optical waveguide structure includes any one of claims 1-9, and further includes an optical engine for emitting an image beam, the optical engine being disposed at the entrance pupil grating and aligned with the entrance pupil grating.

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