Diffractive optical waveguide device and method therefor

Abstract

A diffractive optical waveguide device, method, and apparatus are disclosed. The diffractive optical waveguide device includes an optical waveguide substrate, a first grating structure, a second grating structure, and a third grating structure. The optical waveguide substrate has a first region, a second region, and a third region, with the second region located between the first and third regions. The first grating structure is formed in the first region of the optical waveguide substrate for coupling image light from the first region of the optical waveguide substrate to the second region within the optical waveguide substrate. The second grating structure is formed in the second region of the optical waveguide substrate for splitting the coupled light into diffracted light of different diffraction orders to propagate from the second region to different positions in the third region within the optical waveguide substrate along different propagation directions. The third grating structure is formed in the third region for coupling image light out of the third region.

Description

Technical Field

[0001] This invention relates to the field of augmented reality technology, and in particular to diffractive waveguide devices and methods thereof. Background Technology

[0002] Augmented reality (AR) is a technology that seamlessly integrates information from the virtual world with information from the real world. It projects pixels from a micro-projector onto a human eye through an optical display screen, allowing the user to simultaneously see the real world through the optical display screen. In other words, it overlays the virtual content provided by the micro-projector with the real environment in real time onto the same screen or space, allowing users to experience a fusion of virtual and reality.

[0003] To achieve augmented reality display solutions, optical waveguide technology is commonly used. This technology allows light to undergo total internal reflection within the waveguide when the refractive index of the transmission medium is greater than that of the surrounding medium and the angle of incidence in the waveguide is greater than the critical angle for total internal reflection, enabling leakage-free transmission. In this way, image light from a projector is coupled into the waveguide and continues to propagate without loss until it is coupled out by subsequent structures. Currently, waveguides on the market are generally divided into geometric array waveguides and diffractive waveguides. Diffractive waveguides are further divided into volume holographic waveguides and surface relief grating waveguides. Although all diffractive waveguides essentially couple incident light into or out of the waveguide using gratings, surface relief grating waveguides have significant advantages over other solutions due to their extremely high design freedom and mass production capabilities brought about by nanoimprint processing.

[0004] Specifically, in augmented reality waveguides (hereinafter referred to as AR waveguides), their technical parameters mainly include field of view (FOV), eye relief, and eyebox size. The FOV is usually expressed as a diagonal angle, such as 40°, which corresponds to approximately 35°(H) * 20°(V) for a 16:9 aspect ratio screen. The eye relief is typically around 20-25mm, which generally meets the wearing needs of most users, including those wearing nearsighted or farsighted glasses. The eyebox size determines the range of free eye movement for the user; a larger size reduces the likelihood of image loss, thus offering wider adaptability. The horizontal size of the eyebox needs to accommodate the range of exit pupil distances of the human eye and provide sufficient margin for different horizontal wearing references. The vertical size of the eyebox needs to match the user's vertical wearing reference; generally, an eyebox size of 15mm(H) * 10mm(V) is considered sufficient to meet basic user experience requirements. AR waveguides are optimized for high efficiency and good uniformity. High efficiency aims to achieve high brightness output under the same micro-projection input, so that the image seen by the human eye is bright enough. Uniformity includes FOV uniformity, which means that the image seen by the human eye has good brightness and color uniformity across the entire field of view, and eyebox uniformity, which means that the brightness difference received by the human eye at different positions of the eyebox (or when users with different interpupillary distances or nose bridge heights wear the device) should be minimized, and it is expected that there should be good FOV uniformity at different positions.

[0005] To simplify the design of diffractive waveguides and increase optical energy utilization, a common optical waveguide device employs a system structure with one-dimensional grating coupling in and two-dimensional grating pupil expansion coupling out, such as... Figure 1A As shown. The light rays diffracted from the insertion region 11P enter the expanding pupil extraction region 12P directly below and then expand to both sides (i.e., the +1st order rays and the -1st order rays). Adding this to the original 0th order ray, there are a total of three propagation directions; that is, the light propagates and couples out in these three directions simultaneously. However, due to... Figure 1A As shown, light cannot reach the two apex corners of the pupil-expanding coupling region 12P, meaning no light escapes from these points. Therefore, the human eye will observe a certain visual field loss at these locations, known as vignetting. It can be imagined that at other visual angles, such as... Figure 1B As shown, due to the symmetry of light diffraction, there will always be at least one corner of the expanded pupil coupling region 12P where a dark corner of the field of view will appear, which seriously affects the uniformity and integrity of the optical waveguide display image.

[0006] To address the aforementioned problems, another existing optical waveguide device expands the coupled light beam before it enters the two-dimensional coupling grating, allowing the pre-expanded light to reach the left and right apex corners of the grating. For example, as... Figure 2As shown, light coupled through a one-dimensional coupling grating 21P is laterally transmitted to a one-dimensional pupil-expanding grating 22P, where it is expanded into multiple beams. These expanded beams then propagate to a lower one-dimensional coupling-out grating 23P for coupling and viewing. However, this waveguide architecture only utilizes the +1st order light diffracted through the pupil-expanding grating 22P, while the -0th order light diffracted through it is lost because it does not reach the coupling-out grating. In particular, since the intensity of the lost -0th order light is often greater than that of the diffracted +1st order light, the energy utilization rate of this waveguide architecture is low, making it difficult to meet the requirements of AR products for image contrast and brightness. Summary of the Invention

[0007] One advantage of this invention is that it provides a diffractive waveguide device and method that can solve the vignetting problem while ensuring high optical efficiency.

[0008] Another advantage of the present invention is that it provides a diffractive waveguide device and method thereof. In one embodiment of the present invention, the diffractive waveguide device can simultaneously utilize different diffraction orders of coupled light, which helps to solve the problem of dark corners in the field of view, while also improving light efficiency and display uniformity.

[0009] Another advantage of the present invention is that it provides a diffractive waveguide device and method thereof, wherein, in one embodiment of the present invention, the diffractive waveguide device can achieve good energy distribution uniformity at the entrance pupil of the human eye, which helps to alleviate the problem of image vignetting caused by uneven field of view.

[0010] Another advantage of the present invention is that it provides a diffractive waveguide device and method thereof. In one embodiment of the present invention, the diffractive waveguide device can increase the uniformity of the distribution of the coupled light rays at the exit pupil and improve the problem of the lack of field of view at the exit pupil by reasonably designing the light beam expansion region of the second region and the parameters of the gratings of each region.

[0011] Another advantage of the present invention is that it provides a diffractive waveguide device and method thereof, wherein, in one embodiment of the present invention, the diffractive waveguide device can more effectively utilize the diffracted 0th order light, and the light rays can almost all reach the coupling grating and be coupled out after beam expansion, which helps to maximize the utilization of light energy.

[0012] Another advantage of the present invention is that it provides a diffractive waveguide device and method thereof, wherein, in one embodiment of the present invention, the diffractive waveguide device enables different light beams to compensate for each other, which helps to improve the uniformity of the coupled light.

[0013] Another advantage of the present invention is that it provides a diffractive waveguide device and method thereof. In one embodiment of the present invention, the coupling grating in the first region of the diffractive waveguide device can be combined with the temple of the mirror, which facilitates the placement of the optical engine inside the temple and helps to make the whole device lighter and more aesthetically pleasing to the user.

[0014] Another advantage of this invention is that it provides a diffractive optical waveguide device and method, wherein, to achieve the aforementioned objectives, expensive materials or complex structures are not required. Therefore, this invention successfully and effectively provides a solution that not only provides a diffractive optical waveguide device and method, but also increases the practicality and reliability of the diffractive optical waveguide device and method.

[0015] To achieve at least one of the above advantages or other advantages and objectives, the present invention provides a diffractive optical waveguide device, comprising:

[0016] An optical waveguide substrate, wherein the optical waveguide substrate has a first region, a second region and a third region, and the second region is located between the first region and the third region;

[0017] A first grating structure, wherein the first grating structure is formed in the first region of the optical waveguide substrate for coupling image light from the first region of the optical waveguide substrate to transmit from the first region to the second region within the optical waveguide substrate;

[0018] A second grating structure, wherein the second grating structure is formed in the second region of the optical waveguide substrate, for splitting the coupled light into diffracted light of different diffraction orders, so as to transmit the light from the second region to different positions in the third region along different propagation directions within the optical waveguide substrate; and

[0019] A third grating structure, wherein the third grating structure is formed in the third region of the optical waveguide substrate for coupling image light out from the third region of the optical waveguide substrate.

[0020] According to one embodiment of this application, the first region, the second region, and the third region are arranged axially symmetrically on the surface of the optical waveguide substrate.

[0021] According to one embodiment of this application, the second grating structure is implemented as a two-dimensional relief grating disposed in the second region or as a plurality of one-dimensional relief gratings superimposed on the second region.

[0022] According to one embodiment of this application, the second grating structure includes two or more one-dimensional relief gratings, wherein the one-dimensional relief gratings are arranged longitudinally side by side in the second region of the optical waveguide substrate, so as to be located between the first region and the third region in sequence, and the grating directions of the one-dimensional relief gratings are different from each other.

[0023] According to one embodiment of this application, the second grating structure includes a two-dimensional relief grating and two one-dimensional relief gratings, wherein the two one-dimensional relief gratings and the two-dimensional relief gratings are arranged laterally side by side in the second region of the optical waveguide substrate, and the two one-dimensional relief gratings are respectively located on the left and right sides of the two-dimensional relief grating.

[0024] According to one embodiment of this application, the second grating structure includes three one-dimensional relief gratings, wherein the three one-dimensional relief gratings are arranged side by side laterally in the second region of the optical waveguide substrate, and the grating directions of the one-dimensional relief gratings located on the left and right sides are different from each other.

[0025] According to one embodiment of this application, the second grating structure includes a two-dimensional relief grating and two one-dimensional relief gratings, wherein the one-dimensional relief gratings and the two-dimensional relief gratings are arranged side by side longitudinally in the second region of the optical waveguide substrate, and the two one-dimensional relief gratings are arranged side by side laterally in the second region of the optical waveguide substrate to form a triangular beam expansion region.

[0026] According to one embodiment of this application, the second grating structure includes two one-dimensional relief gratings, wherein the two one-dimensional relief gratings are arranged laterally side by side in the second region of the optical waveguide substrate, and the two one-dimensional relief gratings are respectively arranged around the first region by rotating at a certain angle.

[0027] According to one embodiment of this application, the first region, the second region, and the third region are arranged asymmetrically on the surface of the optical waveguide substrate, and the first region is located on the upper side of the optical waveguide substrate.

[0028] According to one embodiment of this application, the second grating structure includes two one-dimensional relief gratings, wherein the two one-dimensional relief gratings are arranged side by side longitudinally in the second region of the optical waveguide substrate, and the one-dimensional relief grating located above is used to split the coupled light corresponding to the positive field of view into 0th order diffraction light and -1st order diffraction light, and the one-dimensional relief grating located below is used to split the coupled light corresponding to the negative field of view into 0th order diffraction light and +1st order diffraction light.

[0029] According to one embodiment of this application, the first region of the optical waveguide substrate is configured as a circular shape to form a circular coupling region on the optical waveguide substrate, wherein the first grating structure is implemented as a one-dimensional relief grating or a two-dimensional relief grating disposed in the first region.

[0030] According to one embodiment of this application, the third region of the optical waveguide substrate is configured as a rectangular shape to form a rectangular coupling region on the optical waveguide substrate, wherein the third grating structure is implemented as a two-dimensional relief grating disposed in the third region.

[0031] According to one embodiment of this application, the grating depth of the third grating structure gradually increases along the direction away from the second region.

[0032] According to another aspect of this application, one embodiment of this application further provides a method for optimizing vignetting in the field of view, including the steps of:

[0033] Image light is coupled into the optical waveguide substrate via diffraction by a first grating structure disposed in a first region of the optical waveguide substrate, so that the coupled light is transmitted to a second region of the optical waveguide substrate.

[0034] The coupled light is expanded into diffracted light of different orders by the diffraction of the second grating structure disposed in the second region, so that the diffracted light is transmitted to different positions in the third region of the optical waveguide substrate through different propagation directions; and

[0035] Image light is coupled out of the optical waveguide substrate via diffraction by the third grating structure disposed in the third region, so that the coupled light is uniformly distributed throughout the third region.

[0036] According to one embodiment of this application, the diffracted light of different diffraction orders includes 0th order diffracted light and at least one ±1st order diffracted light, and the diffracted light of different diffraction orders are all effective order light in the optical waveguide substrate so that they can all reach the third region for utilization.

[0037] According to one embodiment of this application, the first region, the second region, and the third region are arranged axially symmetrically on the surface of the optical waveguide substrate.

[0038] According to one embodiment of this application, the second grating structure includes two or more one-dimensional relief gratings, wherein the one-dimensional relief gratings are arranged longitudinally side by side in the second region of the optical waveguide substrate, so as to be located between the first region and the third region in sequence, and the grating directions of the one-dimensional relief gratings are different from each other.

[0039] According to one embodiment of this application, the second grating structure includes a two-dimensional relief grating and two one-dimensional relief gratings, wherein the two one-dimensional relief gratings and the two-dimensional relief gratings are arranged laterally side by side in the second region of the optical waveguide substrate, and the two one-dimensional relief gratings are respectively located on the left and right sides of the two-dimensional relief grating.

[0040] According to one embodiment of this application, the second grating structure includes three one-dimensional relief gratings, wherein the three one-dimensional relief gratings are arranged side by side laterally in the second region of the optical waveguide substrate, and the grating directions of the one-dimensional relief gratings located on the left and right sides are different from each other.

[0041] According to one embodiment of this application, the second grating structure includes a two-dimensional relief grating and two one-dimensional relief gratings, wherein the one-dimensional relief gratings and the two-dimensional relief gratings are arranged side by side longitudinally in the second region of the optical waveguide substrate, and the two one-dimensional relief gratings are arranged side by side laterally in the second region of the optical waveguide substrate to form a triangular beam expansion region.

[0042] According to one embodiment of this application, the second grating structure includes two one-dimensional relief gratings, wherein the two one-dimensional relief gratings are arranged laterally side by side in the second region of the optical waveguide substrate, and the two one-dimensional relief gratings are respectively arranged around the first region by rotating at a certain angle.

[0043] According to one embodiment of this application, the first region, the second region, and the third region are arranged asymmetrically on the surface of the optical waveguide substrate, and the first region is located on the upper side of the optical waveguide substrate.

[0044] According to another aspect of this application, one embodiment of this application further provides a method for manufacturing a diffractive optical waveguide device, including the steps of:

[0045] Fabricating a master plate, wherein the master plate has grating structures to be transferred corresponding to the first grating structure, the second grating structure, and the third grating structure; and

[0046] The first grating structure, the second grating structure, and the third grating structure are formed on the surface of an optical waveguide substrate using a nanoimprinting process. The first grating structure is formed in a first region of the optical waveguide substrate to couple image light from the first region to a second region of the optical waveguide substrate. The second grating structure is formed in the second region to split the coupled light into diffracted light of different diffraction orders, so that it can be transmitted along different propagation directions to different positions in the third region of the optical waveguide substrate. The third grating structure is formed in the third region to couple image light out from the third region.

[0047] The further objects and advantages of the invention will become fully apparent from the following description and accompanying drawings.

[0048] These and other objects, features and advantages of the present invention will be fully realized through the following detailed description, drawings and claims. Attached Figure Description

[0049] Figure 1A and Figure 1B Two schematic diagrams of optical paths for an existing optical waveguide device are shown respectively.

[0050] Figure 2 A schematic diagram of the optical path of another existing optical waveguide device is shown.

[0051] Figure 3 This is a schematic diagram of a diffractive waveguide device according to an embodiment of the present invention.

[0052] Figure 4 A schematic diagram of the optical path of the diffractive waveguide device according to the above embodiment of the present invention is shown.

[0053] Figure 5A A schematic diagram of the K-domain of the 0th order diffracted light beam generated by beam splitting in the diffractive waveguide device according to the above embodiments of this application is shown.

[0054] Figure 5B A schematic diagram of the K-domain of the +1st order diffracted beam generated by beam splitting in the diffractive waveguide device according to the above embodiment of this application is shown.

[0055] Figure 5C A schematic diagram of the K-domain of the -1st order diffracted beam generated by beam splitting in the diffractive waveguide device according to the above embodiments of this application is shown.

[0056] Figure 6 A first modified embodiment of the second grating structure in the diffractive waveguide device according to the above embodiments of the present invention is shown.

[0057] Figure 7A A second modified embodiment of the second grating structure according to the above-described embodiment of the present invention is shown.

[0058] Figure 7B A third modified embodiment of the second grating structure according to the above-described embodiment of the present invention is shown.

[0059] Figure 7C A fourth modified embodiment of the second grating structure according to the above-described embodiment of the present invention is shown.

[0060] Figure 7DA fifth modified embodiment of the second grating structure according to the above-described embodiment of the present invention is shown.

[0061] Figure 8 A schematic diagram of a near-eye display device according to an embodiment of this application is shown, which is configured with the diffractive waveguide device according to the above embodiment of this application.

[0062] Figure 9 A modified embodiment of the diffractive waveguide device according to the above-described embodiment of the present invention is shown.

[0063] Figure 10A A schematic diagram of the optical path of the diffractive waveguide device according to the above-described modified embodiment of this application for light rays at the normal field of view is shown.

[0064] Figure 10B A schematic diagram of the optical path for negative field-angle rays is shown in the diffractive waveguide device according to the above-described modified embodiment of this application.

[0065] Figure 11A A schematic diagram of the K-domain of the 0th-order diffracted light beam generated by beam splitting in the diffractive waveguide device according to the above-described modified embodiment of this application is shown.

[0066] Figure 11B A schematic diagram of the K-domain of the +1st order diffracted ray generated in the diffractive waveguide device according to the above-described modified embodiment of this application is shown.

[0067] Figure 11C A schematic diagram of the K-domain of the -1st order diffracted beam generated by beam splitting in the diffractive waveguide device according to the above-described modified embodiment of this application is shown.

[0068] Figure 12 A schematic diagram of another near-eye display device according to an embodiment of this application is shown, which is configured with the diffractive waveguide device according to the above-described modified embodiment of this application.

[0069] Figure 13 This is a flowchart illustrating a method for optimizing vignetting according to an embodiment of this application.

[0070] Figure 14 This is a schematic flowchart of a method for manufacturing an integrated optical waveguide device according to an embodiment of this application. Detailed Implementation

[0071] The following description is intended to disclose the present invention and enable those skilled in the art to implement it. The preferred embodiments described below are merely examples, and other obvious variations will occur to those skilled in the art. The basic principles of the invention defined in the following description can be applied to other embodiments, modifications, improvements, equivalents, and other technical solutions that do not depart from the spirit and scope of the invention.

[0072] Those skilled in the art should understand that, in the disclosure of this invention, the terms "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, 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, the above terms should not be construed as limiting this invention.

[0073] In this invention, the term "a" in the claims and specification should be understood as "one or more," that is, in one embodiment, the number of an element can be one, while in another embodiment, the number of the element can be multiple. Unless explicitly indicated in the disclosure of this invention that the number of the element is only one, the term "a" should not be construed as unique or single, and the term "a" should not be construed as a limitation on the quantity.

[0074] In the description of this invention, it should be understood that terms such as "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance. In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, terms such as "connected" or "linked" should be interpreted broadly. For example, it can refer to a fixed connection, a detachable connection, or an integral connection; it can refer to a mechanical connection or an electrical connection; it can refer to a direct connection or an indirect connection through a medium. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0075] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0076] In recent years, with the rapid development of augmented reality technology, devices and apparatuses capable of realizing augmented reality have become increasingly popular and widely used. However, such as Figure 1A , Figure 1B as well as Figure 2 As shown, existing optical waveguide devices either improve light energy utilization but suffer from vignetting, or eliminate vignetting but have lower light energy utilization, making it difficult to meet the image contrast and brightness requirements of AR products. Therefore, to solve the above problems, refer to the appendix... Figures 3 to 5C As shown, one embodiment of the present invention provides a diffractive waveguide device that can solve the vignetting problem while ensuring high optical efficiency.

[0077] Specifically, such as Figure 3 and Figure 4 As shown, the diffractive waveguide device 1 may include an optical waveguide substrate 10, a first grating structure 20, a second grating structure 30, and a third grating structure 40. The optical waveguide substrate 10 has a first region 11, a second region 12, and a third region 13, and the second region 12 is located between the first region 11 and the second region 13.

[0078] The first grating structure 20 is formed in the first region 11 of the optical waveguide substrate 10 to couple image light from the first region 11 of the optical waveguide substrate 10, so as to transmit the image light from the first region 11 to the second region 12 within the optical waveguide substrate 10. The second grating structure 30 is formed in the second region 12 of the optical waveguide substrate 10 to split the coupled light into diffracted light of different diffraction orders, so as to transmit the image light from the second region 12 to different positions in the third region 13 along different propagation directions within the optical waveguide substrate 10, thereby facilitating coverage of the entire third region 13. The third grating structure 40 is formed in the third region 13 of the optical waveguide substrate 10 to couple image light out of the third region 13 of the optical waveguide substrate 10, so as to facilitate reception by the human eye and the viewing of the corresponding image.

[0079] It is worth noting that the multiple diffracted beams generated by the second grating structure 30 can include, but are not limited to, 0th-order diffracted beams and at least one ±1st-order diffracted beam. The at least one ±1st-order diffracted beam can be one beam of +1st-order diffracted beam or -1st-order diffracted beam, or it can be both +1st-order diffracted beam and -1st-order diffracted beam.

[0080] Before the image light coupled to the first grating structure 20 is transmitted to the third region 13, the diffractive waveguide device 1 of this application first splits the coupled image light into the 0th order diffraction light and the at least one ±1st order diffraction light with different propagation directions via the second grating structure 30, so that the diffraction light in different directions can be transmitted to the third region 13 of the waveguide substrate 10 to cover the entire third region 13, and then coupled out of the waveguide substrate 10 by the third grating structure 40 and viewed by the user. Therefore, the diffractive waveguide device 1 of this application can not only improve the light energy utilization rate of the image light, but also solve the problem of dark angle in the field of view caused by the lack of light. Meanwhile, the third grating structure 40 of the diffractive waveguide device 1 of this application can further split the light in the waveguide while coupling out the diffractive light, so that the diffractive light energy in different coupling regions can compensate each other to improve the uniformity of the coupled light, that is, increase the uniformity of the energy distribution of the coupled light at the entrance pupil of the human eye, so as to improve the problem of image vignetting caused by uneven energy at the field of view.

[0081] In particular, compared to Figure 2The existing optical waveguide devices shown, compared with the diffractive optical waveguide device 1 of this application, can fully utilize the 0th order diffracted light. Since the 0th order diffracted light is the highest energy diffracted light, and almost all the diffracted light formed after the image light is split by diffraction can reach the third region 13 for coupling, the diffractive optical waveguide device 1 of this application utilizes light energy more effectively, improving the overall light energy utilization efficiency. In other words, the diffracted light of different diffraction orders (including the 0th order diffracted light and at least one ±1st order diffracted light) are all effective order light in the optical waveguide substrate 10, so that they can all reach the third region and be utilized.

[0082] More specifically, in the above embodiments of this application, the optical waveguide substrate 10 of the diffractive optical waveguide device 1 may, but is not limited to, be made of glass material, so that while the diffracted light is transmitted within the optical waveguide substrate 10 by total internal reflection, ambient light is also allowed to pass through the optical waveguide substrate 10 and be seen by the human eye, thus providing the user with an augmented reality experience. Of course, in other examples of this application, the optical waveguide substrate 10 of the diffractive optical waveguide device 1 may, but is not limited to, be made of light-transmitting resin material or light-transmitting polymer material, etc.

[0083] The types of the first grating structure 20, the second grating structure 30, and the third grating structure 40 can be adjusted according to specific needs. For example, they can be implemented as surface relief gratings, to be processed and formed on the surface of the optical waveguide substrate 10 by techniques such as nanoimprinting. Of course, in other examples of this application, the first grating structure 20, the second grating structure 30, and the third grating structure 40 can also be implemented as holographic gratings, to form periodic bright and dark stripes in the material through holographic exposure.

[0084] Preferably, the optical waveguide substrate 10 is implemented as a transparent parallel waveguide with a certain thickness, having a front surface 101 and a rear surface 102, wherein the first grating structure 20, the second grating structure 30 and the third grating structure 40 can be respectively formed on the front surface 101 and / or the rear surface 102 of the optical waveguide substrate 10.

[0085] More preferably, the first region 11, the second region 12 and the third region 13 of the optical waveguide substrate 10 are coaxially symmetrically distributed on the surface of the optical waveguide substrate 10, that is, the first region 11, the second region 12 and the third region 13 of the optical waveguide substrate 10 have mutually overlapping central axes.

[0086] Thus, when the diffractive waveguide device 1 is working, the image light emitted by the optomechanical system illuminates the first region 11 of the waveguide substrate 10, and after being diffracted by the first grating structure 20, it is coupled into the interior of the waveguide substrate 10. At this time, the propagation direction of the coupled light is determined by the following formula:

[0087]

[0088] In the formula: n0 is the refractive index of air, usually taken as 1; n is the refractive index of the optical waveguide substrate 10; i is the incident angle; θ is the diffraction angle; constant k = 0, ±1, ±2...; λ is the wavelength of light; d is the grating period.

[0089] At the same time, the diffraction angle θ in the above equation also needs to satisfy the total internal reflection condition, that is...

[0090] Subsequently, when the image light coupled from the first region 11 is transmitted through continuous total internal reflection within the optical waveguide substrate 10 to reach the second region 12, the coupled light is diffracted by the second grating structure 20 to split into 0th order diffracted light and ±1st order diffracted light. The +1st order diffracted light and the -1st order diffracted light are deflected to change their propagation direction, while the propagation direction of the 0th order diffracted light remains unchanged, so that the light is split from one beam into three beams, thereby achieving beam expansion. Specifically, the 0th-order diffracted light and the ±1st-order diffracted light, split into beams, continue to propagate along their respective propagation directions and can both reach the third region 13. Furthermore, each order of diffracted light satisfies the coupling condition in the third region 13, that is, the 0th-order diffracted light and the ±1st-order diffracted light are respectively diffracted by the third grating structure 40 to form the 0th-order diffracted light and the ±1st-order diffracted light again. The +1st-order diffracted light or the -1st-order diffracted light is coupled out to enter the human eye and be observed. The 0th-order diffracted light can continue to propagate within the optical waveguide substrate 10 to reach the third grating structure 40 again after total internal reflection, and then be diffracted out again. This process is repeated sequentially to cover the entire third region 13.

[0091] It is worth noting that the thickness of the optical waveguide substrate 10 described in this application may be, but is not limited to, 0.2 mm to 3 mm, and its refractive index may be, but is not limited to, 1.4 to 2.5.

[0092] According to the above embodiments of this application, the first region 11 of the optical waveguide substrate 10 of the diffractive waveguide device 1 may, but is not limited to, be configured as a circular shape to form a circular coupling region on the optical waveguide substrate 10. Of course, in other examples of this application, the first region 11 of the optical waveguide substrate 10 may also be configured as a regular shape such as a rectangle, triangle, polygon, or ellipse, or it may be configured as an irregular shape.

[0093] Preferably, the first grating structure 20 can be implemented as an embossed grating for diffracting image light to couple incoming light. It is worth noting that the first grating structure 20 can be implemented as a one-dimensional embossed grating; for example, the one-dimensional embossed grating can be, but is not limited to, a rectangular grating, a serrated grating, or a sawtooth grating, etc.; of course, the first grating structure 20 can also be implemented as a two-dimensional embossed grating. It is understood that each of the two-dimensional embossed gratings in this application can be replaced by multiple one-dimensional embossed gratings stacked together.

[0094] In the above embodiments of this application, the second region 12 of the optical waveguide substrate 10 of the diffractive waveguide device 1 may, but is not limited to, be configured as a rectangular shape to form a rectangular beam-expanding region on the optical waveguide substrate 10. Of course, in other examples of this application, the second region 12 of the optical waveguide substrate 10 may also be configured as other shapes that are conducive to controlling the optical path, such as a polygonal shape.

[0095] Preferably, the second grating structure 30 can be implemented as one or more relief gratings for diffraction and coupling of incident light, thereby splitting the light beam. It is worth noting that the second grating structure 30 can be implemented as one or more two-dimensional relief gratings, or one or more one-dimensional relief gratings stacked together; it can also be implemented as one or more one-dimensional relief gratings; or it can be implemented as a combination of one-dimensional and two-dimensional relief gratings.

[0096] In the above embodiments of this application, the third region 13 of the optical waveguide substrate 10 of the diffractive waveguide device 1 may, but is not limited to, be implemented in a rectangular shape to form a rectangular coupling region on the optical waveguide substrate 10. Of course, in other examples of this application, the third region 12 of the optical waveguide substrate 10 may also be implemented in a shape such as a circle to meet the exit pupil size requirements, which will not be elaborated further in this application.

[0097] Preferably, the third grating structure 40 can be implemented as a two-dimensional relief grating for diffracting multiple beams of diffracted light, so as to serve as a beam splitter and a beam coupling device.

[0098] More preferably, the grating depth of the third grating structure 40 is between 50nm and 300nm to meet the light quantity requirements for coupling out light and realizing image display.

[0099] Most preferably, the grating depth of the third grating structure 40 gradually increases along the direction away from the second region 12 to improve the uniformity of the distribution of the coupled rays at the exit pupil. It is understood that, within a certain range, the greater the grating depth of the third grating structure 40, the greater the diffraction efficiency of the grating. In this application, the grating depth of the third grating structure 40 away from the second region 12 is greater than the grating depth of the third grating structure 40 adjacent to the second region 12, which helps to ensure that the energy of the coupled rays at various locations on the third grating structure 40 is substantially the same, thereby improving the uniformity of the distribution of the coupled rays at the exit pupil.

[0100] For example, such as Figure 4 As shown in one example of this application, the first region 11, the second region 12, and the third region 13 are sequentially located at the upper, middle, and lower parts of the optical waveguide substrate 10 (i.e., the first region 11 and the third region 13 are located above and below the second region 12, respectively). The first region 11 is implemented as a circular coupling region, the second region 12 as a rectangular beam-expanding region, and the third region 13 as a rectangular coupling region. The first grating structure 20 is implemented as a one-dimensional relief grating 51 disposed in the first region 11, and the second grating structure 30 and the third grating structure 40 are respectively implemented as two-dimensional relief gratings 52 disposed in the second region 12 and the third region 13.

[0101] Thus, firstly, the image light emitted by the optical engine is diffracted by the one-dimensional relief grating 51 disposed in the first region 11 and coupled into the optical waveguide substrate 10, so as to propagate to the second region 12 through total internal reflection; then, the two-dimensional relief grating 52 disposed in the second region 12 diffracts the coupled light into three beams, namely the 0th order diffracted light, the +1st order diffracted light, and the -1st order diffracted light, wherein the +1st order diffracted light and the -1st order diffracted light propagate towards the upper left corner and the upper right corner of the third region 13, respectively, and the propagation direction of the 0th order diffracted light is consistent with the propagation direction of the coupled light and remains unchanged; finally, the two-dimensional relief grating 52 disposed in the third region 13 diffracts the three diffracted beams, which continue to propagate downwards while continuously coupling out light, so that light reaches and couples out at every position (including the corners) of the third region 13, which helps to improve the vignetting problem of the image. At the same time, the energy of the three diffracted beams can compensate for each other within the third region 13, which helps to improve the energy uniformity of the coupled beams.

[0102] Preferably, the depth of the two-dimensional relief grating 52 in the third region 13 (i.e., the grating depth of the third grating structure 40) gradually increases from top to bottom, for example, from 80nm to 150nm, so as to modulate the output light efficiency of the third grating structure 40 and further increase the energy uniformity of the output light.

[0103] Specifically, the K-domain diagram of the 0th-order diffracted light split into 30 beams by the second grating structure is as follows: Figure 5A As shown, the K-domain diagram of the +1st order diffracted light split into 30 beams by the second grating structure is as follows. Figure 5B As shown, the K-domain diagram of the -1st order diffracted light split into 30 beams by the second grating structure is as follows. Figure 5C As shown, this is to ensure, through the K-domain diagram, that all three diffracted beams can be effectively transmitted within the optical waveguide substrate 10 and can be coupled out by the third grating structure 40 to maintain a constant field of view when entering the human eye.

[0104] It is worth mentioning that, such as Figure 6 As shown, compared to the embodiments described above according to this application, the difference between the second grating structure 30 in the first modified embodiment of this application and the second grating structure 30 is that the second grating structure 30 may include two one-dimensional relief gratings 51a and 51b, wherein the two one-dimensional relief gratings 51a and 51b are arranged longitudinally side by side in the second region 12, located sequentially between the first region 11 and the third region 13, and the grating directions of the two one-dimensional relief gratings 51a and 51b are different from each other. Of course, in other examples of this application, the second grating structure 30 may also include more than two one-dimensional relief gratings 51.

[0105] Thus, firstly, the image light emitted by the optical engine, after being diffracted by the one-dimensional relief grating 51 disposed in the first region 11, is coupled into the optical waveguide substrate 10 and propagates to the second region 12 via total internal reflection. Next, the one-dimensional relief grating 51a disposed in the second region 12 diffracts the coupled light into two beams, namely, a 0th-order diffracted beam and a +1st-order diffracted beam. The +1st-order diffracted beam propagates towards the upper left corner of the third region 13, and the propagation direction of the 0th-order diffracted beam remains consistent with the propagation direction of the coupled light. Then, the one-dimensional relief grating 51b disposed in the second region 12 diffracts the +1st-order diffracted beam into two beams. The diffracted light is divided into two beams: the 0th-order diffracted light and the -1st-order diffracted light. The -1st-order diffracted light propagates towards the upper right corner of the third region 13, and the propagation direction of the 0th-order diffracted light remains unchanged, consistent with the propagation direction of the 0th-order diffracted light. Finally, the two-dimensional relief grating 52 disposed in the third region 13 diffracts the three beams of diffracted light (+1st-order diffracted light, 0th-order diffracted light, and -1st-order diffracted light), continuously propagating downwards while simultaneously coupling out light rays. This ensures that light reaches and couples out at every location (including the corners) in the third region 13, helping to improve the vignetting problem in the image. Simultaneously, the energy of the three diffracted beams can compensate for each other within the third region 13, helping to improve the energy uniformity of the coupled light rays.

[0106] It is understood that although the one-dimensional relief grating 51a and the one-dimensional relief grating 51b are located between the first region 11 and the third region 13 in the first modified embodiment of this application, in another example of this application, the positions of the one-dimensional relief grating 51a and the one-dimensional relief grating 51b can be interchanged to split the light into +1st order diffraction light, 0th order diffraction light, and -1st order diffraction light; of course, in other examples of this application, more one-dimensional gratings can be set in the second region 12 and presented in the form of rotation or superposition.

[0107] Furthermore, compared to the above embodiments of this application, the diffractive waveguide device 1 in the first modified embodiment of this application replaces the two-dimensional relief grating 52 disposed in the second region 12 with two one-dimensional relief gratings 51 arranged side by side. On the one hand, it can reduce the loss of light diffraction and ensure that a higher light energy enters the third region 13. On the other hand, it can also significantly reduce the processing cost and time cost because one-dimensional gratings are easy to process.

[0108] It is worth noting that the second grating structure 30 of the diffractive waveguide device 1 described in this application can also have other modified embodiments, mainly focusing on the grating type and grating position arrangement of the second grating structure 30. For example:

[0109] Figure 7A A second modified embodiment of the second grating structure 30 according to the above embodiments of this application is shown, wherein the second grating structure 30 may include a two-dimensional relief grating 52 and two one-dimensional relief gratings 51a, 51b disposed in the second region 12, wherein the one-dimensional relief gratings 51a, 51b and the two-dimensional relief grating 52 are arranged side by side laterally, and the two one-dimensional relief gratings 51a, 51b are respectively located on the left and right sides of the two-dimensional relief grating 52.

[0110] Figure 7B A third modified embodiment of the second grating structure 30 according to the above-described embodiment of this application is shown, wherein the second grating structure 30 may be implemented as three one-dimensional relief gratings 51a, 51b, and 51c disposed in the second region 12, wherein the one-dimensional relief gratings 51a, 51b, and 51c are arranged laterally side by side, and two of the one-dimensional relief gratings 51a and 51b are respectively located on the left and right sides of the one-dimensional relief grating 51c. It is understood that the grating direction of the one-dimensional relief grating 51c may be the same as or different from one of the two one-dimensional relief gratings 51a and 51b.

[0111] Figure 7C A fourth modified embodiment of the second grating structure 30 according to the above embodiments of this application is shown, wherein the second grating structure 30 may be implemented as a two-dimensional relief grating 52 and two one-dimensional relief gratings 51a, 51b disposed in the second region 12, wherein the one-dimensional relief gratings 51a, 51b and the two-dimensional relief grating 52 are arranged longitudinally side by side, and the two one-dimensional relief gratings 51a, 51b are arranged laterally side by side to form a triangular beam expansion region.

[0112] Figure 7D A fifth modified embodiment of the second grating structure 30 according to the above-described embodiments of this application is shown. The second grating structure 30 can be implemented as two one-dimensional relief gratings 51a and 51b disposed in the second region 12. The one-dimensional relief gratings 51a and 51b are arranged laterally side-by-side, and each one-dimensional relief grating 51a and 51b extends outwardly obliquely around the first region 11, such that the incident light, after diffraction by the one-dimensional relief gratings 51a and 51b, can sufficiently reach the corner regions of the third region 13, thereby better covering the entire third region 13. It is worth noting that the two one-dimensional relief gratings 51a and 51b can be arranged alternately or partially overlapping, and the area or shape of the two one-dimensional relief gratings 51a and 51b can be the same or different; this application will not elaborate further on this.

[0113] It is worth mentioning that, since the first region 11, the second region 12, and the third region 13 in the diffractive waveguide device 1 according to the above embodiments of this application are all arranged coaxially symmetrically, and the first region 11 is located at the center position (i.e., upper-middle part) of the upper part of the waveguide substrate 10, allowing image light to couple in from the center position of the upper part of the waveguide substrate 10, the diffractive waveguide device 1 can be configured as an upper-middle projection lens. For example, as Figure 8 As shown, the optical engine 71 that provides image light in the near-eye display device 7 is correspondingly disposed on the upper part of the optical waveguide substrate 10, so that the optical engine 71 is directly mounted to the crossbeam 72 of the near-eye display device 7, so that when the user wears the near-eye display device 7, the optical engine 71 is located near the user's forehead, which helps to reserve more installation space for the optical engine 71.

[0114] Of course, in other embodiments of this application, the first region 11, the second region 12, and the third region 13 may not be arranged symmetrically, that is, they may not be arranged with a straight line as the axis of symmetry. In other words, the first region 11, the second region 12, and the third region 13 may also be arranged asymmetrically. For example, Figures 9 to 10B A modified embodiment of the diffractive waveguide device 1 according to the above embodiments of this application is shown. Specifically, compared to the above embodiments of this application, the diffractive waveguide device 1 according to this modified embodiment differs in that: the first region 11 and the third region 13 are respectively located on the left and right sides of the second region 12, and the first region 11 is located in the upper corner of the waveguide substrate 10 (such as the upper right corner of the waveguide substrate 10). Meanwhile, the second grating structure 30 is implemented as two one-dimensional relief gratings 51a and 51b, and the two one-dimensional relief gratings 51a and 51b are arranged longitudinally side-by-side in the second region 12. It is understood that when the first region 11 is located on the right (or left) side of the second region 12, the third region 13 is located on the left (or right) side of the second region 12, and the distance between the first region 11 and the second region 12 in this modified embodiment is greater than the distance between the first region 11 and the second region 12 in the above embodiments.

[0115] Thus, as Figure 10A and Figure 10BAs shown, firstly, image light with a large field of view (e.g., ±20°) emitted by the optomechanic is diffracted by the one-dimensional relief grating 51 disposed in the first region 11 and coupled into the optical waveguide substrate 10, so as to propagate to the second region 12 by total internal reflection; then, the one-dimensional relief grating 51a disposed in the second region 12 and located above it diffracts the coupled light corresponding to the +20° field of view (i.e., the frontal field of view) into 0th order diffracted light and -1st order diffracted light, wherein the -1st order diffracted light propagates towards the lower right corner of the third region 13, and the propagation direction of the 0th order diffracted light is consistent with the propagation direction of the coupled light, remaining unchanged to propagate towards the upper right corner of the third region 13; at the same time, the one-dimensional relief grating 51a disposed in the first region 11 is coupled into the optical waveguide substrate 10 by the one-dimensional relief grating 51a disposed in the first region 11 and coupled into the optical waveguide substrate 10, so as to propagate towards the upper right corner of the third region 13; at the same time, the one-dimensional relief grating 51a disposed in the second region 12 and located above it will diffract the coupled light into the second region 12. The one-dimensional relief grating 51b located below the second region 12 diffracts the incident light corresponding to the -20° field of view (i.e., negative field of view) into 0th-order diffracted light and +1st-order diffracted light. The +1st-order diffracted light propagates towards the upper right corner of the third region 13, and the propagation direction of the 0th-order diffracted light is consistent with the propagation direction of the incident light, remaining unchanged to propagate towards the lower right corner of the third region 13. Finally, the two-dimensional relief grating 52 disposed in the third region 13 diffracts each beam of diffracted light, continuously propagating downwards while continuously escaping light, so that light reaches and escapes at every position (including corners) of the third region 13, which helps to improve the vignetting problem of the image.

[0116] It is worth noting that when the field of view of the image light is between ±20°, the corresponding incident light ray will be located between the incident light ray corresponding to the field of view angle +20° and the incident light ray corresponding to the field of view angle -20°. It can also be diffracted by the one-dimensional relief grating 51a or 51b located in the second region 12 to expand the beam. Therefore, the diffractive waveguide device 1 according to this modified embodiment of the present application can ensure that light reaches every position (including corners) in the third region 13 at every field of view angle (including larger field of view angles) and can be coupled out through the third grating structure 40, thereby significantly improving the vignetting problem of the image. At the same time, the energy of each diffracted beam can compensate for each other within the third region 13, which helps to improve the energy uniformity of the coupled light.

[0117] Specifically, the K-domain diagram of the 0th-order diffracted light split by the two one-dimensional relief gratings 51a and 51b in the second grating structure 30 is as follows: Figure 11A As shown, the K-domain diagram of the -1st order diffracted light split by the one-dimensional relief grating 51a in the second grating structure 30 is as follows. Figure 11B As shown, the K-domain diagram of the +1st order diffracted light split by the one-dimensional relief grating 51b in the second grating structure 30 is as follows. Figure 11CAs shown, this is to ensure that each diffracted beam can be effectively transmitted within the optical waveguide substrate 10 through the K-domain diagram, and can be coupled out by the third grating structure 40 to enter the human eye while maintaining a constant field of view.

[0118] It is worth mentioning that, since the first region 11 in the diffractive waveguide device 1 according to the above-described modified embodiment of this application is located at a slightly upper position (i.e., upper side) on the left or right side of the waveguide substrate 10, image light can be coupled in from the upper side of the waveguide substrate 10. Therefore, the diffractive waveguide device 1 can be configured as an upper side projection lens. For example, as Figure 12 As shown, the optical engine 71 that provides image light in the near-eye display device 7 is correspondingly disposed on the upper side of the optical waveguide substrate 10, so that the optical engine 71 is directly installed in the temple 73 of the near-eye display device 7, so that the optical engine 71 is hidden in the temple 73, which helps to make the whole device appear lighter and more in line with human aesthetics.

[0119] According to another aspect of this application, such as Figure 8 and Figure 12 As shown, this application further provides a near-eye display device 7, wherein the near-eye display device 7 may include at least one optical engine 71, a device body 70, and at least one of the aforementioned diffraction waveguide devices 1, wherein the optical engine 71 and the diffraction waveguide device 1 are correspondingly disposed on the device body 70, such that the image light provided by the optical engine 71 is coupled into the waveguide substrate 10 by the first grating structure 20, and after being expanded into multiple diffracted beams by the second grating structure 30, all of them are coupled out by the third grating structure 40 and received by the user's eye to see the corresponding image.

[0120] More specifically, such as Figure 8 and Figure 12 As shown, the main body 70 of the near-eye display device 7 may include a beam portion 72 and a pair of temple portions 73, wherein the temple portions 73 extend rearward from the left and right sides of the beam portion 72 respectively to form the main body 70 having an eyeglass frame structure. The diffractive waveguide device 1 is disposed below the beam portion 72 to serve as an eyeglass lens for near-eye display.

[0121] It is worth noting that, in one example of this application, such as Figure 8As shown, the first region 11 in the diffractive waveguide device 1 is located in the upper middle part of the waveguide substrate 10, corresponding to the crossbeam portion 72 of the device body 70; at this time, the optical engine 71 is adapted to be installed in the crossbeam portion 72 of the device body 70, so that when the user wears the near-eye display device 7, the optical engine 71 is located near the user's forehead, which helps to reserve more installation space for the optical engine 71.

[0122] In another example of this application, such as Figure 12 As shown, the first region 11 in the diffractive waveguide device 1 is located on the upper side of the waveguide substrate 10, corresponding to the temple portion 73 of the device body 70; at this time, the optical engine 71 is adapted to be hiddenly installed in the temple portion 73 of the device body 70, which helps to make the whole device appear lighter and more aesthetically pleasing.

[0123] According to another aspect of this application, such as Figure 13 As shown, one embodiment of this application further provides a method for optimizing vignetting, which may include the steps of:

[0124] S110: Image light is coupled into the optical waveguide substrate 10 via diffraction by the first grating structure 20 disposed in the first region 11 of the optical waveguide substrate 10, so that the coupled light is transmitted to the second region 12 of the optical waveguide substrate 10.

[0125] S120: Through diffraction by the second grating structure 30 disposed in the second region 12, the coupled light is expanded into diffracted light of different diffraction orders, so that multiple diffracted light beams are transmitted along different propagation directions to different positions in the third region 13 of the optical waveguide substrate 10; and

[0126] S130: The multiple diffracted beams are coupled out to the outside of the optical waveguide substrate 10 via the diffraction of the third grating structure 40 disposed in the third region 13, so that the image light is uniformly distributed throughout the entire third region 13.

[0127] It is worth noting that in step S120 of the method for optimizing the vignetting angle of the field of view in the above embodiments of this application: the multiple diffracted beams may include, but are not limited to, 0th order diffracted beams and ±1st order diffracted beams (i.e., +1st order diffracted beams and / or -1st order diffracted beams); they may also include 0th order diffracted beams and ±1st order diffracted beams (i.e., +1st order diffracted beams and / or -1st order diffracted beams), etc.

[0128] According to another aspect of this application, such as Figure 14 As shown, one embodiment of this application further provides a method for manufacturing a diffractive optical waveguide device, which may include the following steps:

[0129] S210: Fabricating a master plate, wherein the master plate has grating structures to be transferred corresponding to the first grating structure 20, the second grating structure 30, and the third grating structure 40; and

[0130] S220: Using a nanoimprinting method, the first grating structure 20, the second grating structure 30, and the third grating structure 40 are formed on the surface of the optical waveguide substrate 10 using the master plate. The first grating structure 20 is formed in a first region 11 of the optical waveguide substrate 10 to couple image light from the first region 11 to a second region 12 of the optical waveguide substrate 10. The second grating structure 30 is formed in the second region 12 to split the coupled light into diffracted light of different diffraction orders, so as to transmit the light along different propagation directions to different positions in the third region 13 of the optical waveguide substrate 10. The third grating structure 40 is formed in the third region 13 to couple image light out of the third region 13.

[0131] It is worth noting that, according to the above embodiments of this application, in step S210 of the manufacturing method of the diffractive waveguide device of this application, the mother plate can be fabricated by an etching process. For example, the etching process may include, but is not limited to, laser direct writing, electron beam direct writing, mask lithography, and two-beam interference exposure, etc.

[0132] Those skilled in the art should understand that the embodiments of the present invention described above and shown in the accompanying drawings are merely examples and do not limit the present invention. The objectives of the present invention have been fully and effectively achieved. The functions and structural principles of the present invention have been demonstrated and explained in the embodiments, and any variations or modifications may be made to the implementation of the present invention without departing from the stated principles.

Claims

1. A diffractive optical waveguide device, characterised in that, The application relates to an optical waveguide substrate, comprising: a first region, a second region and a third region, and the second region is located between the first region and the third region; a first grating structure formed in the first region of the optical waveguide substrate for coupling image light from the first region of the optical waveguide substrate to be transmitted in the optical waveguide substrate from the first region to the second region; a second grating structure formed in the second region of the optical waveguide substrate for splitting the coupled-in light into diffracted light of different diffraction orders to be transmitted in the optical waveguide substrate from the second region to different positions of the third region along different propagation directions; and a third grating structure formed in the third region of the optical waveguide substrate for coupling image light from the third region of the optical waveguide substrate out; wherein the first region, the second region and the third region are asymmetrically arranged on the surface of the optical waveguide substrate, and the first region is located on the upper side of the optical waveguide substrate; a one-dimensional relief grating arranged in the second region and located above diffracts and splits the coupled-in light corresponding to a +20-degree field of view into 0-order diffracted light and -1-order diffracted light, wherein the -1-order diffracted light propagates towards the lower right corner of the third region, and the propagation direction of the 0-order diffracted light is consistent with that of the coupled-in light and remains unchanged to propagate towards the upper right corner of the third region; a one-dimensional relief grating arranged in the second region and located below diffracts and splits the coupled-in light corresponding to a -20-degree field of view into 0-order diffracted light and +1-order diffracted light, wherein the +1-order diffracted light propagates towards the upper right corner of the third region, and the propagation direction of the 0-order diffracted light is consistent with that of the coupled-in light and remains unchanged to propagate towards the lower right corner of the third region.

2. The diffractive optical waveguide device of claim 1, wherein, The first region of the optical waveguide substrate is arranged in a circular shape to form a circular coupling-in area on the optical waveguide substrate, and the first grating structure is implemented as a one-dimensional relief grating or a two-dimensional relief grating arranged in the first region.

3. The diffractive optical waveguide device of claim 1, wherein, The third region of the optical waveguide substrate is arranged in a rectangular shape to form a rectangular coupling-out area on the optical waveguide substrate, and the third grating structure is implemented as a two-dimensional relief grating arranged in the third region.

4. The diffractive optical waveguide device of claim 3, wherein, The grating depth of the third grating structure gradually increases along the direction away from the second region.

Images