CN115079334A

CN115079334A - Diffractive optical waveguide device and method therefor

Info

Publication number: CN115079334A
Application number: CN202110271898.6A
Authority: CN
Inventors: 黄鹏; 张雅琴; 黄河; 楼歆晔; 林涛
Original assignee: Shanghai Kunyou Technology Co ltd
Current assignee: Shanghai Kunyou Technology Co ltd
Priority date: 2021-03-12
Filing date: 2021-03-12
Publication date: 2022-09-20

Abstract

A diffractive light waveguide apparatus and method and apparatus therefor. The diffraction light waveguide device comprises 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, and the second region is located between the first region and the third region. The first grating structure is formed at the first region of the optical waveguide substrate for coupling in image light from the first region of the optical waveguide substrate to be transmitted from the first region to the second region within the optical waveguide substrate. The second grating structure is formed in the second area of the optical waveguide substrate for splitting the coupled-in light into diffracted light of different diffraction orders for transmission from the second area to different positions of the third area along different propagation directions within the optical waveguide substrate. The third grating structure is formed in the third region for coupling out image light from the third region.

Description

Diffractive optical waveguide device and method therefor

Technical Field

The present invention relates to the field of augmented reality technology, and more particularly to a diffractive light waveguide apparatus and method.

Background

Augmented reality is a technology for seamlessly integrating virtual world information and real world information, and the pixels on a micro projector are projected to human eyes through an optical display screen and see the real world through the optical display screen at the same time, namely, virtual content provided by the micro projector and a real environment are overlaid to the same picture or space in real time to exist at the same time, so that a user obtains the experience of fusion of virtual and reality.

In order to realize an augmented reality display scheme, currently, an optical waveguide technology is generally used, that is, when a refractive index of a transmission medium is greater than that of a surrounding medium and an incident angle in a waveguide is greater than a total reflection critical angle, light may be totally reflected within the waveguide to be transmitted without leakage. Thus, after image light from the projector is coupled into the waveguide, the image light continues to propagate within the waveguide without loss until it is coupled out by a subsequent structure. Currently, waveguides on the market are generally classified into geometric array waveguides and diffractive optical waveguides, wherein the diffractive optical waveguides are further classified into volume holographic waveguides and surface relief grating waveguides. While the nature of diffractive optical waveguides is to couple incident light into or out of the waveguide through the grating, surface relief grating waveguides offer significant advantages in many scenarios due to the extremely high degree of design freedom and the mass producibility afforded by nanoimprint processing.

Specifically, technical parameters of an optical waveguide (hereinafter referred to as an AR waveguide) in augmented reality mainly include a field angle FOV, a viewing distance eye relief, an eye box size eye box, and the like. The field of view is typically expressed in terms of a diagonal angle, e.g., 40 °, corresponding to a field of view of about 35 ° (H) 20 ° (V) for a 16:9 scale frame; the visual range is usually about 20-25mm, and the wearing requirements of most users can be basically met, including the users wearing myopia or hyperopia glasses; the orbit size determines the range of free movement of the user's eyes, and larger sizes are less likely to lose images, and are therefore more adaptable. The horizontal size of the orbit needs to be capable of adapting to the range of the exit pupil distance of human eyes and leave sufficient margin for different horizontal wearing references of users, the vertical size of the orbit needs to be adapted to the vertical wearing reference of users, and the orbit size of 15mm (h) 10mm (v) is generally considered to meet the basic requirements of user experience. The AR waveguide takes high efficiency and good uniformity as optimization targets, and the high efficiency aims to realize higher brightness output under the same micro-projection input, so that the picture seen by human eyes is bright enough; the uniformity includes FOV uniformity, i.e., the full-field picture seen by human eyes has better brightness and color uniformity, and eyebox uniformity, i.e., the brightness difference received by human eyes at different positions of the eyebox (or when worn by users with different interpupillary distances and different nose bridge heights) is as small as possible, and the different positions are expected to have better FOV uniformity.

In order to simplify the design of the diffractive optical waveguide and increase the utilization rate of optical energy, an optical waveguide device in the prior art generally adopts a system structure of one-dimensional grating coupling-in and two-dimensional grating pupil-expanding coupling-out, as shown in fig. 1A. The light diffracted from the coupling-in region 11P enters the pupil coupling-out region 12P right below and expands to both sides (i.e., light in the +1 st order direction and light in the-1 st order direction), and in addition to the original light in the 0 th order direction, there are a total of three propagation directions, i.e., the light is coupled out while propagating in these three directions. However, since light does not reach the right and left corners of the pupil-expanding coupling-out region 12P as shown in fig. 1A, i.e., no light is coupled out, the human eye observes a certain lack of viewing angle, i.e., a so-called dark angle of field. It is contemplated that at other viewing angles, as shown in figure 1B, at least one corner of the pupil-expanding coupling-out area 12P will always have a dark viewing angle due to the symmetry of light diffraction, which significantly affects the uniformity and integrity of the displayed image on the lightguide.

In order to solve the above problem, another conventional optical waveguide device expands the coupled light before entering the two-dimensional coupling grating, so that the light expanded in advance can reach the left and right vertex angles of the two-dimensional grating. For example, as shown in fig. 2, the light rays coupled in by the one-dimensional in-coupling grating 21P are transmitted transversely to the one-dimensional pupil expanding grating 22P to expand one coupled-in light ray into a plurality of light rays by the one-dimensional pupil expanding grating 22P, and the expanded light rays are propagated to the one-dimensional out-coupling grating 23P therebelow to be coupled out and viewed. However, the optical waveguide in this configuration utilizes only +1 order light diffracted by the one-dimensional pupil grating 22P, and 0 order light diffracted by the one-dimensional pupil grating is lost without reaching the outcoupling grating. In particular, the intensity of the 0-order light that is lost is often greater than the intensity of the + 1-order light that is diffracted, so the energy utilization efficiency of the optical waveguide under this architecture is low, and it is difficult to meet the requirements of AR products for image contrast, brightness, and the like.

Disclosure of Invention

An advantage of the present invention is to provide a diffractive optical waveguide device and a method thereof, which can solve a dark angle problem of a field of view while ensuring high optical efficiency.

Another advantage of the present invention is to provide a diffractive optical waveguide device and a method thereof, wherein in an embodiment of the present invention, the diffractive optical waveguide device can simultaneously utilize different diffraction orders of the coupled-in light, which helps to solve the dark angle problem of the field of view and simultaneously improve the light efficiency and the display uniformity.

Another advantage of the present invention is to provide a diffractive optical waveguide device and a method thereof, wherein in an embodiment of the present invention, the diffractive optical waveguide device can achieve good energy distribution uniformity at the entrance pupil of the human eye, which helps to reduce the image dark angle problem caused by the non-uniform field angle.

Another advantage of the present invention is to provide a diffractive optical waveguide device and a method thereof, wherein in an embodiment of the present invention, the diffractive optical waveguide device can increase the uniformity of the distribution of the coupled-out light at the exit pupil and improve the problem of the missing field angle at the exit pupil by reasonably designing the parameters of the light beam expanding region and the gratings of the respective regions of the second region.

Another advantage of the present invention is to provide a diffractive optical waveguide device and a method thereof, wherein in an embodiment of the present invention, the diffractive optical waveguide device can more effectively utilize diffracted 0 th-order light, and the light almost reaches the coupling grating after being expanded, so as to be coupled out, which facilitates the maximum efficient utilization of light energy.

Another advantage of the present invention is to provide a diffractive optical waveguide device and a method thereof, wherein in an embodiment of the present invention, the diffractive optical waveguide device can compensate different light beams with each other, which can help to improve uniformity of the coupled-out light.

Another advantage of the present invention is to provide a diffractive optical waveguide apparatus and a method thereof, wherein, in an embodiment of the present invention, the in-coupling grating in the first region of the diffractive optical waveguide apparatus can be combined with the temple, which facilitates the placement of the optical engine in the temple, which helps to make the entire apparatus lighter and more aesthetically pleasing to the user.

It is another advantage of the present invention to provide a diffractive optical waveguide apparatus and method thereof wherein expensive materials or complex structures are not required in the present invention in order to achieve the above objects. The present invention, therefore, successfully and effectively provides a solution that not only provides a diffractive optical waveguide apparatus and method therefor, but also increases the practicality and reliability of the diffractive optical waveguide apparatus and method therefor.

To achieve at least one of the above advantages or other advantages and objects, the present invention provides a diffractive light waveguide apparatus, including:

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;

a first grating structure, wherein the first grating structure is formed in the first region of the optical waveguide substrate for coupling in image light from the first region of the optical waveguide substrate for transmission from the first region to the second region within the optical waveguide substrate;

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 for transmission along different propagation directions within the optical waveguide substrate from the second region to different locations of the third region; and

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

According to an embodiment of the present application, the first region, the second region, and the third region are arranged axisymmetrically on the surface of the optical waveguide substrate.

According to an embodiment of the application, the second grating structure is implemented as a two-dimensional relief grating arranged in the second region or as a plurality of one-dimensional relief gratings arranged in superposition in the second region.

According to an embodiment of the present application, the second grating structure includes two or more one-dimensional embossed gratings, where the one-dimensional embossed gratings are longitudinally arranged in the second region of the optical waveguide substrate side by side to be sequentially located between the first region and the third region, and grating directions of the one-dimensional embossed gratings are different from each other.

According to an embodiment of the present application, the second grating structure includes a two-dimensional relief grating and two one-dimensional relief gratings, where the two one-dimensional relief gratings and the two one-dimensional relief grating are transversely arranged side by side in the second region of the optical waveguide substrate, and the two one-dimensional relief gratings are respectively located on left and right sides of the two-dimensional relief grating.

According to an embodiment of the application, the second grating structure includes three one-dimensional embossed gratings, where the three one-dimensional embossed gratings are transversely arranged side by side in the second region of the optical waveguide substrate, and grating directions of the one-dimensional embossed gratings on the left and right sides are different from each other.

According to an embodiment of the present application, the second grating structure includes one two-dimensional relief grating and two one-dimensional relief gratings, wherein the one-dimensional relief grating and the two-dimensional relief grating are longitudinally arranged side by side in the second region of the optical waveguide substrate, and two the one-dimensional relief grating is transversely arranged side by side in the second region of the optical waveguide substrate to form a delta-shaped beam expanding region.

According to an embodiment of the application, the second grating structure comprises two one-dimensional relief gratings, wherein the two one-dimensional relief gratings are laterally arranged side by side in the second region of the optical waveguide substrate, and the two one-dimensional relief gratings are respectively arranged with a certain angle of rotation around the first region.

According to an embodiment of the present application, the first region, the second region, and the third region are asymmetrically arranged on a surface of the optical waveguide substrate, and the first region is located at a side upper portion of the optical waveguide substrate.

According to an embodiment of the present application, the second grating structure includes two one-dimensional relief gratings, two of the one-dimensional relief gratings are longitudinally disposed side by side in the second region of the optical waveguide substrate, and the one-dimensional relief grating located above is configured to split the coupled light corresponding to the positive field angle into 0-order diffracted light and-1-order diffracted light, and the one-dimensional relief grating located below is configured to split the coupled light corresponding to the negative field angle into 0-order diffracted light and + 1-order diffracted light.

According to an embodiment of the application, the first region of the optical waveguide substrate is arranged in a circular shape to form a circular coupling-in 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 arranged in the first region.

According to an embodiment of the application, the third region of the optical waveguide substrate is arranged in a rectangular shape to form a rectangular coupling-out region on the optical waveguide substrate, wherein the third grating structure is implemented as a two-dimensional relief grating arranged in the third region.

According to an embodiment of the application, the grating depth of the third grating structure gradually increases along a direction away from the second region.

According to another aspect of the present application, an embodiment of the present application further provides a method for optimizing vignetting of a field of view, comprising the steps of:

coupling in image light into the optical waveguide substrate through diffraction of a first grating structure disposed at a first region of the optical waveguide substrate so that the coupled light is transmitted to a second region of the optical waveguide substrate;

expanding the coupled light into diffracted light of different diffraction orders through diffraction of a second grating structure arranged in the second area, so that the diffracted light is transmitted to different positions of a third area of the optical waveguide substrate through different propagation directions; and

image light is coupled out of the optical waveguide substrate by diffraction of a third grating structure disposed in the third region, so that the coupled-out light is uniformly distributed in the entire third region.

According to an embodiment of the present application, the diffracted lights of different diffraction orders include 0 th order diffracted light and at least one ± 1 st order diffracted light, and the diffracted lights of different diffraction orders are all effective orders of light in the optical waveguide substrate to all reach the third area to be utilized.

According to an embodiment of the present application, the second grating structure includes two or more one-dimensional embossed gratings, where the one-dimensional embossed gratings are longitudinally arranged side by side in the second region of the optical waveguide substrate to be sequentially located between the first region and the third region, and grating directions of the one-dimensional embossed gratings are different from each other.

According to an embodiment of the application, the second grating structure includes a two-dimensional relief grating and two one-dimensional relief gratings, where the two one-dimensional relief gratings and the two one-dimensional relief grating are transversely arranged in the second region of the optical waveguide substrate side by side, and the two one-dimensional relief gratings are respectively located at left and right sides of the two-dimensional relief grating.

According to an embodiment of the present application, the second grating structure includes a two-dimensional relief grating and two one-dimensional relief gratings, wherein the one-dimensional relief grating and the two-dimensional relief grating are longitudinally disposed side by side in the second region of the optical waveguide substrate, and the two one-dimensional relief gratings are transversely disposed side by side in the second region of the optical waveguide substrate to form a delta-shaped beam expanding region.

According to another aspect of the present application, an embodiment of the present application further provides a method of manufacturing a diffractive optical waveguide device, including the steps of:

manufacturing a mother board, wherein the mother board is provided with a grating structure to be transferred corresponding to the first grating structure, the second grating structure and the third grating structure; and

processing and forming the first grating structure, the second grating structure and the third grating structure on the surface of the optical waveguide substrate by utilizing the mother board in a nano-imprinting mode, wherein the first grating structure is formed in a first area of the optical waveguide substrate and is used for coupling image light from the first area to be transmitted to a second area of the optical waveguide substrate; wherein the second grating structure is formed in the second region for splitting the coupled-in light into diffracted lights of different diffraction orders to be transmitted to different positions of a third region of the optical waveguide substrate along different propagation directions within the optical waveguide substrate; wherein the third grating structure is formed in the third region for coupling out image light from the third region.

Further objects and advantages of the invention will be fully apparent from the ensuing description and drawings.

These and other objects, features and advantages of the present invention will become more fully apparent from the following detailed description, the accompanying drawings and the claims.

Drawings

Fig. 1A and 1B respectively show two optical path diagrams of a conventional optical waveguide device.

Fig. 2 is a schematic diagram showing an optical path of another conventional optical waveguide device.

Fig. 3 is a schematic structural diagram of a diffractive optical waveguide device according to an embodiment of the present invention.

Fig. 4 shows a schematic optical path diagram of the diffractive optical waveguide device according to the above embodiment of the present invention.

Fig. 5A shows a K-domain diagram view of 0-order diffracted light split in the diffractive light waveguide apparatus according to the above-described embodiment of the present application.

Fig. 5B shows a K-domain diagram view of +1 st order diffracted light rays split in the diffractive light waveguide apparatus according to the above-described embodiment of the present application.

Fig. 5C shows a K-domain diagram view of-1 st order diffracted light split in the diffractive light waveguide apparatus according to the above-described embodiment of the present application.

Fig. 6 shows a first modified embodiment of the second grating structure in the diffractive light waveguide apparatus according to the above-described embodiment of the present invention.

Fig. 7A shows a second variant implementation of the second grating structure according to the above-described embodiment of the invention.

Fig. 7B shows a third variant implementation of the second grating structure according to the above-described embodiment of the invention.

Fig. 7C shows a fourth variant implementation of the second grating structure according to the above-described embodiment of the invention.

Fig. 7D shows a fifth variant implementation of the second grating structure according to the above-described embodiment of the invention.

Fig. 8 shows a schematic structural diagram of a near-eye display device according to an embodiment of the present application, which is configured with the diffractive optical waveguide apparatus according to the above-described embodiment of the present application.

Fig. 9 shows a variant of the diffractive optical waveguide device according to the above-described embodiment of the present invention.

Fig. 10A is a schematic optical path diagram of the diffractive optical waveguide device according to the modified embodiment of the present application for a line of positive field angle.

Fig. 10B shows a schematic optical path diagram of the diffractive optical waveguide device according to the above-described modified embodiment of the present application for rays with a negative field angle.

Fig. 11A shows a K-domain diagram view of 0-order diffracted light split in the diffractive light waveguide device according to the above-described modified embodiment of the present application.

Fig. 11B shows a K-domain diagram view of +1 st order diffracted light rays split in the diffractive light waveguide device according to the above-described modified embodiment of the present application.

Fig. 11C shows a K-domain diagram view of-1 st order diffracted light split in the diffractive light waveguide apparatus according to the above-described modified embodiment of the present application.

Fig. 12 shows a schematic structural diagram of another near-eye display device according to an embodiment of the present application, which is configured with the diffractive optical waveguide apparatus according to the above-described modified embodiment of the present application.

FIG. 13 is a flow diagram illustrating a method for optimizing vignetting of a field of view according to an embodiment of the present application.

FIG. 14 is a schematic flow chart diagram of a method of fabricating an integrated optical waveguide device according to an embodiment of the present application.

Detailed Description

The following description is presented to disclose the invention so as to enable any person skilled in the art to practice the invention. The preferred embodiments in the following description are given by way of example only, and other obvious variations will occur to those skilled in the art. The basic principles of the invention, as defined in the following description, may be applied to other embodiments, variations, modifications, equivalents, and other technical solutions without departing from the spirit and scope of the invention.

It will be understood by those skilled in the art that in the present disclosure, the terms "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," and the like are used in an orientation or positional relationship indicated in the drawings for ease of description and simplicity of description, and do not indicate or imply that the referenced devices or components must be constructed and operated in a particular orientation and thus are not to be considered limiting.

In the present invention, the terms "a" and "an" are to be understood as meaning "one or more" in the claims and the description, that is, one element may be present in one embodiment, and another element may be present in plural in number. The terms "a" and "an" should not be construed as limiting the number unless the number of such elements is explicitly recited as one in the present disclosure, but rather the terms "a" and "an" should not be construed as being limited to only one of the number.

In the description of the present invention, it is to be understood that the terms "first," "second," and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance. In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "connected" and "connected" should be interpreted broadly, and may be, for example, a fixed connection, a detachable connection, or an integral connection; can be mechanically or electrically connected; they may be directly connected or indirectly connected through an intermediate. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.

In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.

In recent years, with the rapid development of augmented reality technology, devices or apparatuses capable of realizing augmented reality are becoming more popular and used. However, as shown in fig. 1A, 1B and 2, the conventional optical waveguide device either improves the light energy utilization efficiency, but has a dark angle of field; or the dark angle of the field of view is eliminated, but the light energy utilization rate is low, and the requirements of AR products on image contrast, brightness and the like are difficult to meet. Therefore, in order to solve the above problems, referring to fig. 3 to 5C, an embodiment of the present invention provides a diffractive light waveguide device that can solve the dark angle of field while ensuring high optical efficiency.

Specifically, as shown in fig. 3 and 4, the diffractive optical 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.

The first grating structure 20 is formed at the first region 11 of the optical waveguide substrate 10, and is used for coupling in image light from the first region 11 of the optical waveguide substrate 10 to be transmitted 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, and is configured to split the coupled light into diffracted lights of different diffraction orders, so as to transmit the coupled light from the second region 12 to different positions of the third region 13 along different propagation directions within the optical waveguide substrate 10, so as to cover the entire third region 13. The third grating structure 40 is formed on the third region 13 of the optical waveguide substrate 10, and is used for coupling out image light from the third region 13 of the optical waveguide substrate 10, so as to be received by human eyes to see a corresponding image.

It should be noted that the diffracted lights split by the second grating structure 30 can include, but are not limited to, 0 th order diffracted light and at least one ± 1 st order diffracted light, wherein the at least one ± 1 st order diffracted light can be one of +1 st order diffracted light and-1 st order diffracted light, and can also be two of +1 st order diffracted light and-1 st order diffracted light.

Since the diffractive optical waveguide device 1 of the present application splits the coupled image light into the 0 th order diffracted light and the at least one ± 1 st order diffracted light with different propagation directions through the second grating structure 30 before the coupled image light is transmitted to the third area 13 through the first grating structure 20, and then the diffracted lights with different directions can be transmitted to the third area 13 of the optical waveguide substrate 10, so as to cover the whole third area 13, and further the coupled image light is coupled out of the optical waveguide substrate 10 by the third grating structure 40 and viewed by the user, the diffractive optical waveguide device 1 of the present application can not only improve the light energy utilization rate of the image light, but also solve the dark angle problem of the field of view caused by light loss. Meanwhile, the third grating structure 40 of the diffractive optical waveguide device 1 of the present application can further split light in the waveguide while coupling out diffracted light, so that diffracted light energies of different coupling-out areas compensate each other, so as to improve uniformity of coupled-out light, that is, increase uniformity of energy distribution of coupled-out light at the entrance pupil of human eyes, and improve the problem of image dark angle caused by non-uniform energy of field angle.

In particular, compared to the conventional optical waveguide device shown in fig. 2, the diffractive optical waveguide device 1 of the present application can sufficiently utilize the 0 th order diffracted light, and the 0 th order diffracted light is the highest energy diffracted light, and almost all the diffracted light formed by the image light after being divided by the diffraction can reach the third region 13 to be coupled out, so that the diffractive optical waveguide device 1 of the present application can utilize the light energy more effectively, and the overall light energy utilization efficiency is improved. In other words, the diffracted lights of different diffraction orders (including the 0 th order diffracted light and the at least one ± 1 st order diffracted light) are all the effective orders of light in the optical waveguide substrate 10, so that the third region can be utilized.

More specifically, in the above-mentioned embodiments of the present application, the optical waveguide substrate 10 of the diffractive light waveguide device 1 may be, but is not limited to be, implemented to be made of a glass material to allow ambient light to be seen by human eyes through the optical waveguide substrate 10 while allowing diffracted light to be transmitted within the optical waveguide substrate 10 by total internal reflection, so that a user obtains an augmented reality experience. Of course, in other examples of the present application, the optical waveguide substrate 10 of the diffractive optical waveguide device 1 may also be, but is not limited to being, implemented to be made of a light-transmitting resin material, a light-transmitting polymer material, or the like.

The types of the first grating structure 20, the second grating structure 30 and the third grating structure 40 may be adjusted according to the needs of the specific situation, for example, but not limited to, the grating may be implemented as a surface relief grating, so as to be processed and formed on the surface of the optical waveguide substrate 10 by a nano-imprint technique or the like. Of course, in other examples of the present application, the first grating structure 20, the second grating structure 30 and the third grating structure 40 may also be implemented as holographic gratings, so as to form periodic alternating bright and dark stripes or the like in the material by holographic exposure.

Preferably, the optical waveguide substrate 10 is implemented as a transparent parallel waveguide having a thickness and a front surface 101 and a back surface 102, and the first grating structure 20, the second grating structure 30 and the third grating structure 40 may be formed on the front surface 101 and/or the back surface 102 of the optical waveguide substrate 10, respectively.

More preferably, the first region 11, the second region 12 and the third region 13 of the optical waveguide substrate 10 are distributed coaxially and symmetrically 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 central axes that coincide with each other.

Thus, when the diffractive optical waveguide device 1 is in operation, the image light emitted by the optical engine is irradiated to the first region 11 of the optical waveguide substrate 10 to be diffracted by the first grating structure 20 and then coupled into the optical waveguide substrate 10, and the propagation direction of the coupled light is determined by the following formula:

in the formula: n is ₀ Is the refractive index of air, typically taken as 1; n is the refractive index of the optical waveguide substrate 10; i is an incident angle; theta is a diffraction angle; the constant k is 0, ± 1, ± 2 … …; λ is the wavelength of light; d is the grating period.

At the same time, the diffraction angle θ in the above formula also needs to satisfy the total reflection condition, that is

Then, when the image light coupled in from the first region 11 is transmitted by the constant total reflection in the optical waveguide substrate 10 to reach the second region 12, the coupled-in light is diffracted by the second grating structure 20 to be split into 0 th order diffracted light and ± 1 st order diffracted light, wherein the +1 st order diffracted light and the-1 st order diffracted light are deflected to change the propagation direction, while the propagation direction of the 0 st order diffracted light is kept unchanged, so that the light is split into three light beams from the original one light beam, thereby realizing beam expansion. In particular, the 0 th order diffracted light and the ± 1 st order diffracted light that have been split can both reach the third region 13 by propagating continuously in their respective propagation directions; and each level of diffracted light satisfies the coupling-out condition in the third region 13, that is, the 0 th order diffracted light and the ± 1 st order diffracted light are respectively diffracted by the third grating structure 40 to form 0 th order diffracted light and ± 1 st order diffracted light again, wherein the +1 st order diffracted light or the-1 st order diffracted light is coupled out to enter human eyes to be observed, the 0 th order diffracted light can continue to propagate in the optical waveguide substrate 10 to reach the third grating structure 40 again after being totally reflected, and then the diffraction coupling is performed again, and the steps are repeated in sequence to cover the whole third region 13.

It is noted that the thickness of the optical waveguide substrate 10 of the present application may be implemented, but not limited to, 0.2mm to 3mm, and the refractive index thereof may be implemented, but not limited to, 1.4 to 2.5.

According to the above-described embodiments of the present application, the first region 11 of the optical waveguide substrate 10 of the diffractive optical waveguide device 1 may be, but is not limited to, be provided in a circular shape to form a circular coupling-in region on the optical waveguide substrate 10. Of course, in other examples of the present application, the first region 11 of the optical waveguide substrate 10 may also be provided in regular shapes such as a rectangular shape, a triangular shape, a polygonal shape, and an elliptical shape, or may also be provided in an irregular shape.

Preferably, the first grating structure 20 may be implemented as a relief grating for diffracting image light to function as incoupling light. It is noted that the first grating structure 20 may be implemented as a one-dimensional relief grating, for example, but not limited to, as a rectangular grating, a skewed tooth grating, a sawtooth grating, or the like; of course, the first grating structure 20 may also be implemented as a two-dimensional relief grating. It will be appreciated that each of the two-dimensional relief gratings described herein may be replaced by a plurality of the one-dimensional relief gratings described in the present application superimposed together.

In the above-described embodiments of the present application, the second area 12 of the optical waveguide substrate 10 of the diffractive optical waveguide device 1 may be, but is not limited to, provided in a rectangular shape to form a rectangular expanded beam area on the optical waveguide substrate 10. Of course, in other examples of the present application, the second region 12 of the optical waveguide substrate 10 may also be provided in other shapes, such as a polygonal shape, which facilitates control of the optical path.

Preferably, the second grating structure 30 may be implemented as one or more relief gratings for diffracting the coupled-in light to act as a beam splitter. It is noted that the second grating structure 30 may be implemented as one or more two-dimensional relief gratings, or as one or more superimposed one-dimensional relief gratings; may also be implemented as one or more one-dimensional relief gratings; it can also be implemented as a combination of one-dimensional relief gratings and two-dimensional relief gratings.

In the above-described embodiments of the present application, the third region 13 of the optical waveguide substrate 10 of the diffractive optical waveguide device 1 may be, but is not limited to, implemented in a rectangular shape to form a rectangular coupling-out area on the optical waveguide substrate 10. Of course, in other examples of the present application, the third region 12 of the optical waveguide substrate 10 may also be implemented in a shape satisfying the requirement of exit pupil size, such as a circular shape, which is not described in detail herein.

Preferably, the third grating structure 40 may be implemented as a two-dimensional relief grating for diffracting a plurality of diffracted light beams to function as a beam splitter and a beam outcoupler.

More preferably, the grating depth of the third grating structure 40 is between 50nm and 300nm to satisfy the light quantity requirement for coupling out light and realizing image display.

Most preferably, the grating depth of the third grating structure 40 gradually increases in a direction away from the second region 12 to improve the uniformity of the distribution of the outcoupled light rays at the exit pupil. It will be appreciated that, in a certain range, the larger the grating depth of the third grating structure 40, the larger the diffraction efficiency of the grating, and the larger the grating depth of the third grating structure 40 away from the second region 12 in the present application, the larger the grating depth of the third grating structure 40 adjacent to the second region 12, which helps to make the energy of the coupled-out light substantially the same everywhere on the third grating structure 40, and improves the uniformity of the distribution of the coupled-out light at the exit pupil.

Exemplarily, as shown in fig. 4, in an example of the present application, the first region 11, the second region 12, and the third region 13 are sequentially located at an upper portion, a middle portion, and a lower portion of the optical waveguide substrate 10 (i.e., the first region 11 and the third region 13 are respectively located at an upper side and a lower side of the second region 12), and the first region 11 is implemented as a circular coupling-in region, the second region 12 is implemented as a rectangular beam-expanding region, and the third region 13 is implemented as a rectangular coupling-out region. The first grating structure 20 is implemented as a one-dimensional relief grating 51 arranged in the first region 11, and the second and third

grating structures

30, 40 are implemented as two-dimensional relief gratings 52 arranged in the second and

third regions

12, 13, respectively.

Thus, first, the image light emitted from the optical engine is diffracted by the one-dimensional relief grating 51 disposed in the first region 11 and then coupled into the optical waveguide substrate 10 to propagate to the second region 12 by total reflection; next, the two-dimensional relief grating 52 provided in the second region 12 diffracts the coupled light into three beams, i.e., 0 th order diffracted light, +1 st order diffracted light, and-1 st order diffracted light, wherein the +1 st order diffracted light and the-1 st order diffracted light propagate toward the upper left corner and the upper right corner of the third region 13, respectively, and the propagation direction of the 0 th order diffracted light coincides 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 lights, and continuously propagates downward while continuously coupling out the lights, so that the lights arrive and couple out at each position (including the corner) of the third region 13, which is helpful for improving the dark angle problem of the image. At the same time, the energy of the three diffracted lights can compensate each other in the third region 13, which helps to improve the energy uniformity of the outcoupled light.

Preferably, the depth of the two-dimensional relief grating 52 of the third region 13 (i.e. the grating depth of the third grating structure 40) is gradually increased from top to bottom, for example from 80nm to 150nm, so as to modulate the light outcoupling efficiency of the third grating structure 40, so as to further increase the energy uniformity of the outcoupled light.

Specifically, a K-domain diagram of the 0 < th > order diffractive light split by the second grating structure 30 is shown in fig. 5A, a K-domain diagram of the +1 < th > order diffractive light split by the second grating structure 30 is shown in fig. 5B, and a K-domain diagram of the-1 < st > order diffractive light split by the second grating structure 30 is shown in fig. 5C, so as to ensure that all three diffractive lights can be efficiently transmitted in the optical waveguide substrate 10 by the K-domain diagrams and can be coupled out by the third grating structure 40 to enter the human eye with a constant angle of view.

It is worth mentioning that, as shown in fig. 6, the second grating structure 30 according to the first variant embodiment of the present application differs from the above-described example according to the present application in that: the second grating structure 30 may include two one-

dimensional relief gratings

51a, 51b, wherein the two one-

dimensional relief gratings

51a, 51b are longitudinally arranged side by side in the second region 12 to be sequentially located between the first region 11 and the third region 13, and grating directions of the two one-

dimensional relief gratings

51a, 51b are different from each other. Of course, in other examples of the present application, the second grating structure 30 may also include more than two one-dimensional relief gratings 51.

Thus, first, the image light emitted from the optical engine is diffracted by the one-dimensional relief grating 51 disposed in the first region 11 and then coupled into the optical waveguide substrate 10 to propagate to the second region 12 by total reflection; next, the one-dimensional relief grating 51a provided in the second region 12 diffracts the coupled light into two beams, that is, 0-order diffracted light and + 1-order diffracted light, wherein the + 1-order diffracted light propagates toward the upper left corner of the third region 13, and the propagation direction of the 0-order diffracted light coincides with the propagation direction of the coupled light and remains unchanged; thereafter, the one-dimensional relief grating 51b provided in the second region 12 diffracts the 0 th order diffracted light into two beams, i.e., 0 th order diffracted light and-1 st order diffracted light, wherein the-1 st order diffracted light propagates toward the upper right corner of the third region 13, and the propagation direction of the 0 th order diffracted light coincides with the propagation direction of the 0 th order diffracted light, and remains unchanged; finally, the two-dimensional relief grating 52 provided in the third region 13 diffracts the three diffracted lights (+1 st order diffracted light, 0 th order diffracted light, and-1 st order diffracted light) and continuously emits light while continuously propagating downward, so that light arrives and emits at each position (including a corner) of the third region 13, which contributes to improvement of a dark angle problem of an image. At the same time, the energies of the three diffracted lights can compensate each other in the third region 13, which helps to improve the energy uniformity of the outcoupled light.

It is to be understood that, although the one-dimensional relief grating 51a and the one-dimensional relief grating 51b are sequentially located between the first region 11 and the third region 13 in the above-described first modified embodiment of the present application, in another example of the present application, positions between the one-dimensional relief grating 51a and the one-dimensional relief grating 51b may be interchanged to split into +1 order diffracted light, 0 order diffracted light, and-1 order diffracted light; of course, in other examples of the present application, more one-dimensional gratings may be disposed in the second region 12 and may be represented by rotation or superposition.

In addition, compared to the above-mentioned example of the present application, the diffractive optical waveguide device 1 in the first modified embodiment of the present 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, which can reduce the loss of light diffraction, ensure that high light energy enters the third region 13, and greatly reduce the processing cost and time cost due to the easy processing of the one-dimensional gratings.

It should be noted that there may be other modified embodiments of the second grating structure 30 of the diffractive optical waveguide device 1 of the present application, and mainly focuses on the grating type, the grating position arrangement, and the like of the second grating structure 30. For example:

fig. 7A shows a second variant implementation of the second grating structure 30 according to the above-described embodiment of the present application, wherein the second grating structure 30 may include one two-dimensional relief grating 52 and two one-

dimensional relief gratings

51a, 51b arranged in the second region 12, wherein the one-

dimensional relief gratings

51a, 51b and the two-dimensional relief grating 52 are arranged laterally side by side, and the two one-

dimensional relief gratings

51a, 51b are respectively located at the left and right sides of the two-dimensional relief grating 52.

Fig. 7B shows a third variant implementation of the second grating structure 30 according to the above-described embodiment of the present application, wherein the second grating structure 30 may be implemented as three one-

dimensional relief gratings

51a, 51B, 51c arranged in the second region 12, wherein the one-

dimensional relief gratings

51a, 51B, 51c are arranged laterally side by side, and two one-dimensional relief gratings 51a, 51B are respectively located at the left and right sides of the one-dimensional relief grating 51 c. It is understood that the grating direction of the one-dimensional relief grating 51c may be the same as one of the two one-

dimensional relief gratings

51a, 51b, or may be different.

Fig. 7C shows a fourth variant implementation of the second grating structure 30 according to the above-described embodiment of the present application, wherein the second grating structure 30 may be implemented as one two-dimensional relief grating 52 and two one-

dimensional relief gratings

51a, 51b arranged at the second region 12, wherein the one-

dimensional relief gratings

51a, 51b and the two-dimensional relief grating 52 are arranged side by side longitudinally and the two one-

dimensional relief gratings

51a, 51b are arranged side by side transversely to form a delta-shaped beam expansion region.

Fig. 7D shows a fifth variant implementation of the second grating structure 30 according to the above-mentioned embodiment of the present application, wherein the second grating structure 30 can be implemented as two one-

dimensional relief gratings

51a, 51b disposed in the second region 12, wherein the one-

dimensional relief gratings

51a, 51b are laterally disposed side by side, and the two one-

dimensional relief gratings

51a, 51b extend obliquely outward around the first region 11, respectively, so that the coupled-in light can reach the corner regions of the third region 13 sufficiently after being diffracted by the one-

dimensional relief gratings

51a, 51b, thereby better covering the entire third region 13. It should be noted that the two one-

dimensional relief gratings

51a and 51b are arranged at intervals, or may be arranged to overlap partially, and the areas or the shapes of the two one-

dimensional relief gratings

51a and 51b may be the same or different, which is not described herein again.

It is worth mentioning that, since the first region 11, the second region 12 and the third region 13 in the diffractive optical waveguide device 1 according to the above-described embodiment of the present application are all coaxially and symmetrically arranged, and the first region 11 is located at the center position (i.e., the middle upper portion) of the upper portion of the optical waveguide substrate 10 so that image light can be coupled in from the center position of the upper portion of the optical waveguide substrate 10, the diffractive optical waveguide device 1 may be provided in the form of an upper projection lens. For example, as shown in fig. 8, the optical engine 71 providing image light in the near-eye display device 7 is correspondingly disposed on the upper portion of the optical waveguide substrate 10 to directly mount the optical engine 71 to the beam portion 72 of the near-eye display device 7, so that when the near-eye display device 7 is worn by a user, the optical engine 71 is correspondingly located near the forehead of the user, which helps to reserve a larger mounting space for the optical engine 71.

Of course, in other embodiments of the present application, the first region 11, the second region 12, and the third region 13 may not be symmetrically arranged, that is, not arranged with a straight line as a symmetry axis, in other words, the first region 11, the second region 12, and the third region 13 may also be asymmetrically arranged. Exemplarily, fig. 9 to 10B show one modified embodiment of the diffractive optical waveguide device 1 according to the above-described embodiment of the present application. Specifically, the diffractive optical waveguide device 1 according to this modified embodiment of the present application is different from the above-described examples according to the present application in that: the first region 11 and the third region 13 are respectively located at the left and right sides of the second region 12, and the first region 11 is located at an upper corner of the optical waveguide substrate 10 (e.g., the upper right corner of the optical waveguide substrate 10). At the same time, the second grating structure 30 is implemented as two one-

dimensional relief gratings

51a, 51b, and the two one-

dimensional relief gratings

51a, 51b are arranged side by side longitudinally in the second region 12. It is understood that when the first region 11 is located on the right side (or left side) of the second region 12, the third region 13 is located on the left side (or right side) of the second region 12, and the distance between the first region 11 and the second region 12 in the present modified embodiment is larger than the distance between the first region 11 and the second region 12 in the above-described embodiment.

Thus, as shown in fig. 10A and 10B, first, image light having a large field angle (e.g., ± 20 °) emitted from an optical engine is coupled into the optical waveguide substrate 10 after being diffracted by the one-dimensional relief grating 51 provided in the first region 11 to propagate to the second region 12 by total reflection; next, the one-dimensional relief grating 51a disposed above the second region 12 diffracts the coupled light corresponding to the +20 ° field angle (i.e., the front field angle) into 0-order diffracted light and-1-order diffracted light, wherein the-1-order diffracted light propagates toward the lower right corner of the third region 13, and the propagation direction of the 0-order diffracted light coincides with the propagation direction of the coupled light and remains unchanged to propagate toward the upper right corner of the third region 13; meanwhile, the one-dimensional relief grating 51b disposed below the second region 12 diffracts the incoming light corresponding to the-20 ° field angle (i.e., the negative field angle) into 0 th order diffracted light and +1 st order diffracted light, wherein the +1 st order diffracted light propagates toward the upper right corner of the third region 13, and the propagation direction of the 0 th order diffracted light coincides with the propagation direction of the incoming light and remains unchanged to propagate toward the lower right corner of the third region 13; finally, the two-dimensional relief grating 52 disposed in the third region 13 diffracts the diffracted light beams and continuously emits the light beams while continuously propagating downward, so that the light beams arrive and emerge at each position (including a corner) of the third region 13, which helps to improve the dark angle problem of the image.

It should be noted that when the field angle of the image light is within ± 20 °, the corresponding incoming light is located between the incoming light corresponding to the field angle +20 ° and the incoming light corresponding to the field angle-20 °, and can also be diffracted by the one-dimensional relief grating 51a or 51b disposed in the second region 12 for expanding the beam, so that the diffractive optical waveguide device 1 according to this variant embodiment of the present application can ensure that light arrives at each position (including a corner) in the third region 13 at each field angle (including a larger field angle), and can realize the outcoupling through the third grating structure 40, thereby greatly improving the dark angle problem of the image. At the same time, the energy of the diffracted light beams can compensate each other in the third region 13, which contributes to improving the energy uniformity of the outcoupled light.

Specifically, a K-domain diagram of 0-order diffracted light split by two one-dimensional relief gratings 51A and 51B in the second grating structure 30 is shown in fig. 11A, a K-domain diagram of-1-order diffracted light split by the one-dimensional relief grating 51A in the second grating structure 30 is shown in fig. 11B, and a K-domain diagram of + 1-order diffracted light split by the one-dimensional relief grating 51B in the second grating structure 30 is shown in fig. 11C, so that it is ensured by the K-domain diagram that each diffracted light can be efficiently transmitted within the optical waveguide substrate 10 and can be coupled out by the third grating structure 40 to enter the human eye with a constant field angle.

It is worth mentioning that since the first region 11 in the diffractive optical waveguide device 1 according to the above-described modified embodiment of the present application is located at an upper position (i.e., upper side portion) on the left or right side of the optical waveguide substrate 10 so that image light can be coupled in from the upper side position of the optical waveguide substrate 10, the diffractive optical waveguide device 1 may be provided in the form of an upper side projection lens. For example, as shown in fig. 12, the optical engine 71 providing image light in the near-eye display device 7 is correspondingly disposed at a position on the side of the optical waveguide substrate 10 to directly mount the optical engine 71 into the temple portion 73 of the near-eye display device 7, so that the optical engine 71 is hidden in the temple portion 73, which helps to make the whole device appear lighter and more aesthetically pleasing.

According to another aspect of the present application, as shown in fig. 8 and 12, the present 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 diffractive optical waveguide device 1 as described above, wherein the optical engine 71 and the diffractive optical 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 optical waveguide substrate 10 by the first grating structure 20, and after expanded into a plurality of beams of diffracted light by the second grating structure 30, both are coupled out by the third grating structure 40 to be received by the eyes of the user to see the corresponding images.

More specifically, as shown in fig. 8 and 12, the equipment main body 70 of the near-eye display equipment 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 equipment main body 70 having a spectacle frame structure. The diffractive optical waveguide device 1 is provided below the beam portion 72 as a spectacle lens for near-eye display.

Note that, in an example of the present application, as shown in fig. 8, the first region 11 in the diffractive optical waveguide device 1 is located at an upper middle portion of the optical waveguide substrate 10 so as to correspond to the beam portion 72 of the apparatus body 70; at this time, the optical engine 71 is adapted to be mounted to the beam portion 72 of the device main body 70, so that when the user wears the near-eye display device 7, the optical engine 71 is correspondingly located near the forehead of the user, which helps to reserve a larger mounting space for the optical engine 71.

In another example of the present application, as shown in fig. 12, the first region 11 in the diffractive optical waveguide device 1 is located at a side upper portion of the optical waveguide substrate 10 so as to correspond to the mirror leg portion 73 of the apparatus body 70; at this time, the optical engine 71 is adapted to be mounted to the temple portion 73 of the apparatus main body 70 in a concealed manner, which contributes to making the entire apparatus more lightweight and more aesthetically pleasing.

According to another aspect of the present application, as shown in fig. 13, an embodiment of the present application further provides a method for optimizing a vignetting angle of a field of view, which may include the steps of:

s110: coupling in image light into the optical waveguide substrate 10 through diffraction of the first grating structure 20 disposed at the first region 11 of the optical waveguide substrate 10, so that the coupled-in light is transmitted to the second region 12 of the optical waveguide substrate 10;

s120: expanding the coupled light into diffracted light of different diffraction orders by diffraction of the second grating structure 30 disposed in the second region 12, so that a plurality of diffracted lights are transmitted to different positions of the third region 13 of the optical waveguide substrate 10 along different propagation directions; and

s130: the plurality of diffracted lights are coupled out of the optical waveguide substrate 10 by diffraction of the third grating structure 40 disposed in the third region 13, so that the image light is uniformly distributed throughout the third region 13.

It is noted that, in the step S120 of the method for optimizing the vignetting of the field of view according to the above embodiment of the present application: the plurality of diffracted light beams may include, but is not limited to, 0 th order diffracted light and +1 st order diffracted light (i.e., +1 st order diffracted light and/or-1 st order diffracted light); and may also include 0 th order diffracted light and ± 1 st order diffracted light (i.e., +1 st order diffracted light and/or-1 st order diffracted light), and the like.

According to another aspect of the present application, as shown in fig. 14, an embodiment of the present application further provides a method for manufacturing a diffractive optical waveguide device, which may include the steps of:

s210: manufacturing a mother board, wherein the mother board is provided with grating structures to be transferred corresponding to the first grating structure 20, the second grating structure 30 and the third grating structure 40; and

s220: processing and forming the first grating structure 20, the second grating structure 30 and the third grating structure 40 on the surface of the optical waveguide substrate 10 by using the master through a nanoimprint method, wherein the first grating structure 20 is formed in the first region 11 of the optical waveguide substrate 10, and is used for coupling in image light from the first region 11 to be transmitted to the second region 12 of the optical waveguide substrate 10; wherein the second grating structure 30 is formed in the second region 12 for splitting the coupled-in light into diffracted light of different diffraction orders for transmission along different propagation directions within the optical waveguide substrate 10 to different locations of the third region 13 of the optical waveguide substrate 10; wherein the third grating structure 40 is formed at the third region 13 for coupling out image light from the third region 13.

It is to be noted that, according to the above-mentioned embodiments of the present application, in the step S210 of the method for manufacturing a diffractive optical waveguide device of the present application, the motherboard may be manufactured by using an etching method. 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, among others.

It will be appreciated by persons skilled in the art that the embodiments of the invention described above and shown in the drawings are given by way of example only and are not limiting of the invention. The objects of the invention have been fully and effectively accomplished. The functional and structural principles of the present invention have been shown and described in the examples, and any variations or modifications of the embodiments of the present invention may be made without departing from the principles.

Claims

1. A diffractive light waveguide apparatus, comprising:

2. The diffractive optical waveguide apparatus according to claim 1, wherein said first region, said second region, and said third region are arranged axisymmetrically on the surface of said optical waveguide substrate.

3. The diffractive optical waveguide apparatus according to claim 2, wherein said second grating structure is implemented as a two-dimensional relief grating provided to said second area or a plurality of one-dimensional relief gratings provided to said second area in superposition.

4. The diffractive optical waveguide apparatus according to claim 2, wherein the second grating structure includes two or more one-dimensional embossed gratings, wherein the one-dimensional embossed gratings are longitudinally arranged side by side in the second region of the optical waveguide substrate so as to be located in sequence between the first region and the third region, and the grating directions of the one-dimensional embossed gratings are different from each other.

5. The diffractive optical waveguide apparatus according to claim 2, wherein said second grating structure includes one two-dimensional relief grating and two one-dimensional relief gratings, wherein said two one-dimensional relief gratings and said two one-dimensional relief grating are disposed laterally side by side in said second region of said optical waveguide substrate, and said two one-dimensional relief gratings are disposed on the left and right sides of said two-dimensional relief grating, respectively.

6. The diffractive optical waveguide apparatus according to claim 2, wherein said second grating structure includes three one-dimensional relief gratings, three of which are disposed laterally side by side in said second region of said optical waveguide substrate, and the grating directions of said one-dimensional relief gratings on the left and right sides are different from each other.

7. The diffractive optical waveguide apparatus according to claim 2, wherein said second grating structure includes one two-dimensional relief grating and two one-dimensional relief gratings, wherein said one-dimensional relief grating and said two-dimensional relief grating are disposed longitudinally side by side in said second region of said optical waveguide substrate, and two of said one-dimensional relief gratings are disposed transversely side by side in said second region of said optical waveguide substrate to form a delta-shaped beam expanding area.

8. The diffractive optical waveguide apparatus according to claim 2, wherein said second grating structure comprises two one-dimensional relief gratings, two of which are disposed laterally side by side at said second region of said optical waveguide substrate and two of which are disposed respectively at an angle rotated around said first region.

9. The diffractive light waveguide device according to claim 1, wherein the first area, the second area, and the third area are asymmetrically arranged on the surface of the optical waveguide substrate, and the first area is located on a side upper portion of the optical waveguide substrate.

10. The diffractive optical waveguide apparatus according to claim 9, wherein the second grating structure includes two one-dimensional relief gratings, two of which are disposed side by side longitudinally in the second region of the optical waveguide substrate, and the one-dimensional relief grating located above is for splitting the incoming light corresponding to a positive field angle into 0 order diffracted light and-1 order diffracted light, and the one-dimensional relief grating located below is for splitting the incoming light corresponding to a negative field angle into 0 order diffracted light and +1 order diffracted light.

11. The diffractive optical waveguide apparatus according to any one of claims 1 to 10, wherein the first area of the optical waveguide substrate is provided in a circular shape to form a circular coupling-in area on the optical waveguide substrate, wherein the first grating structure is implemented as a one-dimensional relief grating or a two-dimensional relief grating provided to the first area.

12. The diffractive optical waveguide device according to any one of claims 1 to 10, wherein the third area of the optical waveguide substrate is provided in a rectangular shape to form a rectangular coupling-out area on the optical waveguide substrate, wherein the third grating structure is implemented as a two-dimensional relief grating provided to the third area.

13. The diffractive light waveguide apparatus of claim 12 wherein the grating depth of the third grating structure progressively increases in a direction away from the second region.

14. A method for optimizing field vignetting, comprising the steps of:

15. The method of claim 14, wherein the diffracted light of different orders of diffraction comprises 0 th order diffracted light and at least one ± 1 st order diffracted light, and the diffracted light of different orders of diffraction is all of the effective orders of light in the optical waveguide substrate, so as to all reach the third area to be utilized.

16. The method of optimizing vignetting of a field of view of claim 14, wherein said first region, said second region, and said third region are arranged axisymmetrically on a surface of said optical waveguide substrate.

17. The method for optimizing the vignetting of a field of view of claim 16, wherein said second grating structure comprises two or more one-dimensional embossed gratings, wherein said one-dimensional embossed gratings are longitudinally arranged side by side in said second region of said optical waveguide substrate to be sequentially located between said first region and said third region, and the grating directions of said one-dimensional embossed gratings are different from each other.

18. The method of optimizing vignetting of a field of view of claim 16, wherein said second grating structure comprises a two-dimensional relief grating and two one-dimensional relief gratings, wherein said two one-dimensional relief gratings and said two-dimensional relief gratings are disposed laterally side-by-side in said second region of said optical waveguide substrate, and said two one-dimensional relief gratings are disposed on respective left and right sides of said two-dimensional relief gratings.

19. The method for optimizing vignetting of a field of view of claim 16, wherein said second grating structure comprises three one-dimensional relief gratings, wherein three of said one-dimensional relief gratings are disposed laterally side by side in said second region of said optical waveguide substrate, and the grating directions of said one-dimensional relief gratings on the left and right sides are different from each other.

20. The method for optimizing viewing field vignetting according to claim 16, wherein the second grating structure comprises a two-dimensional relief grating and two one-dimensional relief gratings, wherein the one-dimensional relief grating and the two-dimensional relief grating are longitudinally disposed side-by-side in the second region of the optical waveguide substrate, and the two one-dimensional relief gratings are laterally disposed side-by-side in the second region of the optical waveguide substrate to form a delta-shaped expanded beam region.

21. The method of optimizing vignetting of a field of view of claim 16, wherein said second grating structure comprises two one-dimensional relief gratings, wherein two of said one-dimensional relief gratings are disposed laterally side-by-side in said second region of said optical waveguide substrate and two of said one-dimensional relief gratings are disposed angularly rotated about said first region, respectively.

22. The method of optimizing dark angle of field according to claim 14, wherein the first, second and third regions are asymmetrically arranged on the surface of the optical waveguide substrate, and the first region is located at a laterally upper portion of the optical waveguide substrate.

23. A method of manufacturing a diffractive optical waveguide device, comprising the steps of:

processing and forming the first grating structure, the second grating structure and the third grating structure on the surface of the optical waveguide substrate by utilizing the mother board in a nano-imprinting mode, wherein the first grating structure is formed in a first area of the optical waveguide substrate and is used for coupling image light from the first area to be transmitted to a second area of the optical waveguide substrate; wherein the second grating structure is formed in the second area for splitting the coupled-in light into diffracted light of different diffraction orders to be transmitted to different positions of the third area of the optical waveguide substrate along different propagation directions within the optical waveguide substrate; wherein the third grating structure is formed in the third region for coupling out image light from the third region.