CN219799828U - Optical waveguide and near-to-eye display module based on asymmetric optical structure - Google Patents

Abstract

The embodiment of the utility model discloses an optical waveguide based on an asymmetric optical structure and a near-to-eye display module, which enable light energy transmitted in a grating and output to human eyes to be distributed more uniformly by arranging an optical structure with a specific closed curve structure in a coupling-out area of the waveguide, and effectively improve brightness uniformity, thereby improving the imaging effect of the optical waveguide.

Description

Optical waveguide and near-to-eye display module based on asymmetric optical structure

Technical Field

The utility model relates to the technical field of scanning display, in particular to an optical waveguide based on an asymmetric optical structure and a near-to-eye display module.

Background

In some Augmented Reality (AR) devices, diffractive waveguides utilize diffraction of gratings to deflect and expand light. In some diffractive waveguides employing gratings (particularly two-dimensional gratings), the light energy transmitted in the grating and output to the human eye is unevenly distributed, manifesting as poor brightness uniformity, which severely affects the viewing experience of the user.

Disclosure of Invention

Based on the above, the present utility model provides an optical waveguide and a near-eye display module based on an asymmetric optical structure, which are used for solving the problem of brightness uniformity of the existing optical waveguide.

According to an aspect of the present utility model, an embodiment of the present utility model provides an optical waveguide based on an asymmetric optical structure, the optical waveguide including a waveguide substrate, at least one coupling-in region, and at least one coupling-out region; wherein, a two-dimensional grating is arranged in the coupling-out area; the two-dimensional grating comprises a plurality of optical structures which are arranged periodically on the optical waveguide plane, wherein the optical structures are in a closed curve graph, the optical structures comprise at least one vertex in a first direction, and the optical structures have vertices in a second direction; the optical structure is an asymmetric structure in the first direction, and the slope of the closed curve graph is continuous;

the optical structures are used as diffractive optical elements, each of the optical structures receiving light from a set input direction and transmitting light toward a set output direction on a plane in which the optical structures are arranged; some or all of the optical structures transmit light in a direction out of the plane in which the optical structures are arranged.

Optionally, the optical structure comprises two vertices distributed at both ends of the optical structure in the first direction.

Optionally, the optical structure includes an apex at one end of the optical structure in the first direction, and the other end of the optical structure in the first direction is a smoothly transitioned curve.

Optionally, a tangent to the optical structure at an apex in a first direction is 90 degrees from the first direction.

Optionally, the optical structure includes an axis of symmetry parallel to the first direction such that the optical structure is symmetrical in the second direction.

Optionally, the optical structure comprises at least two vertices distributed on both sides of the symmetry axis in the second direction; and at least two connecting lines between vertexes distributed on two sides of the symmetry axis in the second direction are perpendicular to the first direction.

Optionally, the optical structure comprises at least two vertices distributed on the same side of the symmetry axis in a second direction; and the curve line type distributed between the adjacent vertexes on the same side of the symmetry axis is an inward bending curve.

Optionally, in the second direction of the optical structure, the distance between any two mutually symmetrical vertices is not the same.

Optionally, the maximum distance of the optical structure in the first direction is greater than the maximum distance of the optical structure in the second direction.

The embodiment of the utility model provides a near-to-eye display module, which comprises an image projection device and the optical waveguide, wherein the image projection device is used for generating image light and projecting the image light to a corresponding coupling-in area on the optical waveguide, and diffracting and outputting the image light through the coupling-out area after the image light is transmitted through the optical waveguide.

It should be noted that, the optical waveguide may be designed by a corresponding design method, where the design method includes:

determining the period size of a grating unit in a two-dimensional grating in the optical waveguide;

dividing the grating units in a set direction according to the period sizes of the grating units to obtain a specified number of control points;

and performing curve fitting by adopting a preset curve fitting constraint condition and a set fitting method based on each control point, constructing a continuous closed curve graph, and taking the continuous closed curve graph as the optical structure of the two-dimensional grating.

Optionally, the set fitting method includes one fitting method of B-spline, bessel, polynomial.

Optionally, the curve fitting constraint includes: if the control point positions obtained based on the first direction are fitted with the curve, the tangential angles at the head and tail control point positions of the curve are 90 degrees with the first direction;

if the control point positions obtained based on the second direction are fitted to the curve, the tangential angles at the head and tail control point positions of the curve are 90 degrees with the second direction.

Optionally, after the division to obtain the specified number of control points, the method further includes: and determining variable parameters corresponding to the control points.

Optionally, the method further comprises: optimizing the curve graph according to the single coupling efficiency of the target by using an optimization variable comprising the variable parameter to obtain and return to the optimized target value; and optimizing the variable parameters by adopting one of optimization algorithms such as a simulated annealing algorithm, a genetic algorithm or a least square algorithm.

Optionally, based on each control point location, performing curve fitting by adopting a preset curve fitting constraint condition and a set fitting method to obtain a continuous closed curve graph, which specifically comprises:

on one side of a direction axis, fitting and generating a curve according to a set fitting method based on each control point, wherein the tangential angle of the head and the tail of the curve is perpendicular to the direction axis, so that the tangential angles of the head and the tail connecting points are continuous;

and turning over the curve by taking the direction shaft as a rotating shaft, and constructing a curve at the other side of the direction shaft to form a closed curve graph.

Optionally, based on each control point location, performing curve fitting by adopting a preset curve fitting constraint condition and a set fitting method to obtain a continuous closed curve graph, which specifically comprises:

and fitting and generating a curve according to a set fitting method on the two sides of the direction axis based on the control points respectively, wherein the tangential angles of the head and the tail of the curve are perpendicular to the direction axis.

Additional features and advantages of the utility model will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the utility model. The objectives and other advantages of the utility model may be realized and attained by the structure and/or process particularly pointed out in the written description and claims hereof as well as the appended drawings.

Drawings

Other features, objects and advantages of the present utility model will become more apparent upon reading of the detailed description of non-limiting embodiments, made with reference to the accompanying drawings in which:

FIG. 1a is a schematic view of a waveguide structure according to an embodiment of the present utility model;

FIG. 1b is a schematic view of a partial structure of the two-dimensional grating in the coupling-out region of FIG. 1 a;

FIG. 1c is a schematic diagram of an optical structure included in the two-dimensional grating of FIG. 1 b;

FIG. 2a is a schematic diagram of an optical path for diffraction-extended transmission of light within a waveguide according to an embodiment of the present utility model;

FIG. 2b is a schematic view of light coupled out to the human eye based on the mydriatic position shown in FIG. 2 a;

fig. 3 is a schematic diagram of light spot distribution formed by light received by a human eye under a certain view field according to an embodiment of the present utility model;

FIG. 4 is a schematic view of another optical structure provided by an embodiment of the present utility model;

FIG. 5a is a schematic diagram of a grating unit according to an embodiment of the present utility model;

FIG. 5b is a schematic diagram of a raster vector relationship;

FIG. 5c is a schematic diagram of a partial structure of a grating corresponding to a grating vector;

FIG. 5d is a schematic diagram of a periodically arranged two-dimensional grating structure obtained by superimposing the grating partial structures shown in FIG. 5 c;

fig. 5e is a schematic diagram of two control points in the raster unit 400 according to an embodiment of the present utility model;

fig. 5f is a schematic diagram of an optical structure constructed based on control points according to an embodiment of the present utility model.

Detailed Description

The utility model is described in further detail below with reference to the drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the utility model and are not limiting of the utility model. It should be noted that, for convenience of description, only the portions related to the present utility model are shown in the drawings.

Referring to fig. 1a, a waveguide 100 according to an embodiment of the present utility model includes: the waveguide substrate 101, the coupling-in region 102 and the coupling-out region 103 are provided with grating structures in the coupling-in region 102 and the coupling-out region 103, and the grating structures can be realized by adopting technologies such as imprinting, coating, etching and the like, and are not limited herein. In general, the grating structure provided in the coupling-in region 102 may be referred to as: the specific grating type of the coupling grating can be a one-dimensional grating or a two-dimensional diffraction grating; the grating structure provided in the outcoupling region 103 may be referred to as: the coupling-out grating may be a two-dimensional diffraction grating. In the following description, the two-dimensional diffraction grating may be simply referred to as a two-dimensional grating.

Of course, the profile topography, relative position of the coupling-in region 102, the coupling-out region 103 shown in fig. 1a are exemplary, and in practical applications, the coupling-in region 102 may not be a circular profile as shown in fig. 1a, may be a rounded rectangle, trapezoid, etc.; similarly, the profile of the out-coupling region 103 may also be trapezoidal, rounded rectangular. The relative positions of the in-coupling region 102 and the out-coupling region 103 may be distributed over each other instead of being distributed right and left in the current view of fig. 1 a. The in-coupling region 102 and the out-coupling region 103 shown in fig. 1a should not be construed as limiting the utility model.

In practical applications, the waveguide 100 is generally used to output image light to eyes (left or right) of an observer, and if it is to be used as binocular AR glasses, a structure of at least two waveguides 100 is required to correspond to both eyes of the observer, respectively; in other cases, the lateral (x-axis) dimension of the out-coupling region 103 is sufficient to cover both eyes of the viewer, and only one waveguide 100 structure may be required for use as binocular AR glasses.

Fig. 1a shows the view angle of the waveguide 100 with the side out of which the light is coupled towards the eye of the observer, which is also the view angle the user's eye looks at when he/she wears the AR glasses normally, the xy coordinate system is shown (wherein the direction parallel to the x-axis is also referred to as the first direction in the present utility model; the direction parallel to the y-axis is also referred to as the second direction in the present utility model), in the present embodiment the direction perpendicular to the xy-plane can be considered as the positive z-axis direction (the z-axis is not shown in fig. 1; the direction parallel to the z-axis is also referred to as the third direction in the present utility model). In the following embodiments, the coordinate system and the viewing angle will be used, and the description of the corresponding direction names will be applied throughout, unless otherwise specified. It should be understood by those skilled in the art that, in the practical use process, there may be a certain deviation in the viewing angle relationship between the human eye and the waveguide, such as an angle deviation caused by wearing, so that the coordinate system and the corresponding viewing angle described in the scheme of the present utility model are ideal, and allow a small amount of deviation in the practical use.

Referring to fig. 1b, a two-dimensional grating 2 disposed in a coupling-out region 103 according to an embodiment of the present utility model includes a plurality of optical structures 20 (only a portion of the optical structures 20 are shown in fig. 1 b), which are arranged periodically, and each optical structure 20 has the same shape. Typically, the individual optical structures 20 lie in the same plane, and in some embodiments of the utility model, portions of the optical structures 20 may lie in different planes, such as: the degree of protrusion in the grating from left to right optical structure 20 in the positive Z-axis direction increases gradually so that optical structure 20 lies in different planes. Of course, this should not be construed as limiting the utility model.

With continued reference to FIG. 1c, in this example, an xoy coordinate system is established with the center o of the optical structure 20 as the origin, the x, y coordinate values being in nm. The optical structure 20 is a left-right asymmetric closed curve structure (in the description of the embodiment of the present utility model, a curve graph, a curve profile, etc. are also used, and these descriptions have similar meanings and should not be construed as limiting the present utility model), and includes a plurality of vertices: including a left vertex 20a in the x-axis (i.e., first direction); the optical structure 20 further includes an upper vertex 20c and an upper vertex 20d on the positive y-axis side, and a lower vertex 20e and a lower vertex 20f on the negative y-axis side. Upper vertex 20c and upper vertex 20d have a curved line 230 therebetween that curves inwardly (toward the x-axis); similarly, there is also an inwardly curved curve 240 between lower apex 20e and lower apex 20f. The right side profile of the optical structure 20 forms a smooth curved profile around the x-axis.

In this example, the x-axis is the symmetry axis of optical structure 20, the overall topography of optical structure 20 is mirror symmetric with respect to the x-axis, upper vertex 20c and upper vertex 20d are asymmetric with respect to the y-axis, and lower vertex 20e and lower vertex 20f are asymmetric with respect to the y-axis; upper vertex 20c and lower vertex 20e are symmetrical with respect to the x-axis, and upper vertex 20d and lower vertex 20f are symmetrical with respect to the x-axis. So that the overall morphology of the optical structure 20 is large and small. In the optical structure 20, the left profile formed by the upper vertex 20c, the lower vertex 20e, and the left vertex 20a extends to a greater extent to the left and narrows in profile compared to the right profile formed by the upper vertex 20d, the lower vertex 20f, and the right profile.

The vertex positions of the optical structure 20 are smooth and have no sharp points.

Applicants have found that in general, the light entering the waveguide coupling-in region 102 propagates in the optical path between the coupling-in region 102 and the coupling-out region 103 as shown in fig. 2a, and that light 300 is transmitted from the coupling-in region 102 to the coupling-out region 103 and diffracted by the coupling-out grating in the coupling-out region 103, thereby expanding the transmission, resulting in light transmitted in different directions, comprising: light 301 continuing in the direction of light 300, a series of light 302 traveling obliquely upward, a series of light 303 traveling obliquely downward, and light coupled out toward the human eye (not shown in fig. 2 a).

The positions where the light rays exit the coupling-out grating outwards can also be referred to as pupil expansion positions (e.g. three circular shadow positions a, b and c as shown in fig. 2 a), and the light rays transmitted in the coupling-out grating will be coupled out from a series of pupil expansion positions towards the human eye, forming light rays with different field angles. Referring to fig. 2b, for the human eye, the light spots formed by the plurality of outcoupled light rays exiting the waveguide outcoupling area will be received at the same time. Because of a certain exit pupil distance, a certain degree of superposition exists between light spots formed after the coupled light rays are incident to human eyes. The lateral intermediate region of the coupling-out region 103 is distributed with a series of mydriatic positions (a series of laterally distributed mydriatic positions including mydriatic position a but not shown in the figure), which is laterally intermediateThe region is mainly coupled out by the light (such as light 301) which expands transversely to form a corresponding coupled-out light (such as light 301 a), and the coupling-out efficiency is denoted as eta ₁ . The upper and lower regions (a series of pupil expansion positions including pupil expansion positions b and c) of the coupling-out region 103 except the middle region are mainly coupled out by lateral light rays (such as light rays 302 and 303) generated by diffraction of light rays based on lateral expansion, so as to form corresponding coupling-out light rays (such as light rays 302b and 303 c), and the actual coupling-out efficiency of the light rays is also related to diffraction efficiency: the diffraction efficiency of the lateral rays is denoted herein as η ₂ The coupling-out efficiency is marked as eta ₃ Then, the actual outcoupling efficiency of the outcoupled light formed by the lateral light with respect to the laterally expanded light can be characterized as η ₂ *η ₃ 。

Referring to fig. 3, there is shown a case where spots are superimposed under the same field of view of the human eye, a part of the field of view receives the spot 3n formed by the coupled-out light in the central region, and a part of the field of view receives the spot 3m formed by the coupled-out light in the lateral region. On the basis, if the ratio of the coupling-out efficiencies of the coupling-out lights of the two areas is too large, namely eta ₁ /(η ₂ *η ₃ ) Far greater than 1 or far less than 1, the light spots 3n or 3m can be too bright or too dark to form bright stripes or dark stripes, so that the imaging brightness is uneven, and the viewing experience of a user is seriously affected.

In the present embodiment, the profile curve of the optical structure 20 includes a plurality of control points, which can be adjusted to meet the requirements of various coupling-out efficiency distribution in the coupling-out region expansion transmission process. Therefore, the overall coupling-out efficiency distribution of the coupling-out region 103 of the waveguide 100 can be well controlled, so that the uniformity of the light coupled out from the coupling-out region 103 is better.

Of course, there are other various forms of profile shapes for the optical structures.

Referring to fig. 4, an optical structure 40 is shown in an embodiment of the present utility model. The curved profile of the optical structure 40 is likewise smooth and free of sharp points. Wherein the optical structure 40 comprises a plurality of vertices: a left vertex 40a and a right vertex 40b are included on the x-axis; an upper vertex 40c and an upper vertex 40d are included on the positive y-axis side, and a lower vertex 40e and a lower vertex 40f are included on the negative y-axis side. An inwardly curved curve 430 is provided between the upper apex 40c and the upper apex 40 d; similarly, there is also an inwardly curved curve 440 between lower apex 40e and lower apex 40f.

The overall topography of the optical structure 40 is asymmetric in the x-axis direction in the topographical features. Specifically, the upper and lower vertices 40c, 40d of the optical structure 40 are asymmetric with respect to the y-axis, and the lower and lower vertices 40e, 40f are asymmetric with respect to the y-axis. Distance h between upper vertex 40c and lower vertex 40e of optical structure 40 _ce Distance h between upper vertex 40d and lower vertex 40f _df ，h _ce >h _df 。

For both optical structures, the corresponding profile curves include a plurality of adjustable control points. The optical structure 40 is specifically described herein as an example.

Referring to fig. 5a, a grating unit 400 comprising an optical structure 40 is shown, wherein a boundary region having a diamond shape is provided outside the optical structure 40 (for convenience of description, the "diamond-shaped boundary region" may be abbreviated as "diamond shape" in the following). It should be noted here that if it is desired to ensure that the light is transmitted to the human eye uncompressed, the grating vector G of the grating is coupled in ₁ And a grating vector G coupled to the grating ₂ 、G ₃ The relationship shown in fig. 5b should be satisfied. That is, the light ray needs to pass through the grating vector G in the process of propagation ₂ G (G) ₃ In an embodiment of the present utility model, such a grating structure may be embodied as shown in fig. 5 c. On this basis, if the grating structures shown in fig. 5c are superimposed, the grating units with periodically arranged and diamond-shaped boundary morphology in the embodiment of the present utility model can be obtained, and referring to fig. 5d, the coupling-out grating 4 includes a plurality of grating units 400 that are periodically arranged. Of course, in various embodiments of the utility model, the described outcoupling grating also has such a grating unit or has a periodic distribution based on such a grating unit. In practical use, the grating prepared according to the scheme of the utility model, wherein the grating is a singleThe diamond-shaped outline of the element may not be significant or visible. In some embodiments, the sides of the diamond shape of the grating unit may have a certain relationship with the wavelength of the transmitted light, for example: the dimensions of the side length are in the range of 200nm to 650nm, although the dimensions of the diamond are not limited thereto, and are typically on the order of nanometers.

Returning to the example of fig. 5a, the curved profile of the optical structure 40 may be obtained by configuring the control points. The grating unit 400 has a transverse half-period size l and a longitudinal half-period size h. Based on this, in one embodiment of the present utility model, referring to fig. 5e, the abscissa values of the left and right vertex positions of the optical structure 40 can be first determined, and can be expressed as:

l ₀ ＝kl

l _n ＝k′l

wherein k and k' are adjustment coefficients, l ₀ Is the abscissa value of the left vertex position, l _n Is the abscissa value of the right vertex position. Correspondingly, the left vertex position has an abscissa of-l ₀ The abscissa of the right vertex position is l _n 。

With further reference to FIG. 5f, here will be [ -l [ - ] ₀ ，l _n ]Divided into n parts (8 parts in FIG. 5 f), the abscissa l of each point can be determined _m Expressed as:

after the abscissa of each point position is determined, the height h of the unit outline corresponding to each point position can be further determined _m Expressed as:

based on l _m And h _m The required control points can be determined, and the coordinates of each control point can be expressed as [ l ] _m ，k _m h _m ]Generally, k ₀ And k _m Set to 0, thusObtaining n+1 control points. Further, the control points are fitted into a curve by adopting a set fitting method, so that a curve profile of one side of the optical structure is formed, wherein the set fitting method comprises the following steps: b-splines, bessel, polynomials, etc.

It should be noted that, in the embodiment of the present utility model, the slope of the end-to-end of the curve needs to be constrained in the fitting process, that is, the tangential angle at the end-to-end of the curve forms 90 degrees with the x-axis. In FIG. 5f, the position at [ -l ] is shown ₀ ，l _n ]And under the condition that 7 control points (2 control points from the head to the tail of the left end and the right end are calculated, and 9 control points are calculated in total), fitting a side curve, and then longitudinally overturning to generate a continuous closed graph (namely, the curve outline of the optical structure 40), wherein the slope of the closed graph is continuous everywhere.

In another embodiment, the curves on both sides of the x-axis can be fitted separately, and then the two curves are fitted into a closed curve graph. For example: n-1 control points (of course, not actually shown in fig. 5 f) are configured for the lower half area of fig. 5f, and simultaneously, in combination with the front-to-rear control points, new curve fitting is completed under the same slope constraint condition, and finally, two curves are connected to generate a closed graph. In the fitting mode, the head-tail tangent angle can be not 90 degrees, but the same constraint condition is adopted when two curves are fitted.

Of course, in practical applications, it is also possible to construct a closed curve image based on the control points selected for the longitudinal half period of the raster unit 400, in a similar manner as described above. And will not be described in detail here.

After the closed graph is obtained by the method, the curve outline of the closed graph can be optimized, so that the requirement of coupling efficiency distribution is further met.

Specifically, the k value and the optical structure depth are taken as optimization variables to complete the optimization of the curve, and the objective function can be defined as follows:

wherein V is the target value of the objective function;

ω ₁ omega, omega ₂ Is a weight coefficient;

η ₁ 、η ₂ η ₃ Reference may be made to the foregoing definitions;

η is the target single-time coupling-out efficiency and is determined according to the actual pupil expansion times.

The above expression contains control over the center bright stripe and single pupil expansion efficiency. For the objective function, a preset optimization algorithm can be adopted to optimize the target value V to the minimum. The preset optimization algorithm comprises the following steps: simulated annealing algorithms, genetic algorithms, or least squares algorithms, etc. Through the optimization of the optimized variable to the curve, the optimization of various coupling-out efficiency distribution of the light in the coupling-out region expansion transmission process can be further realized, so that the overall coupling-out efficiency distribution of the waveguide coupling-out region can be well controlled, and the uniformity of the light coupled out from the coupling-out region is better.

In some embodiments, the diamond-shaped regions are raised structures (raised in the positive z-axis direction) while the dark-colored optical structures are recessed structures (recessed in the negative z-axis direction). In other embodiments, the diamond-shaped regions and the optical structures may be reversed, i.e., the diamond-shaped regions are concave structures and the dark optical structures are convex structures.

For the optical waveguide in the foregoing embodiments, the two-dimensional grating is disposed on the surface of the coupling-out region of the waveguide; in yet another embodiment, the out-coupling region is located in the optical waveguide, rather than at the surface, and correspondingly the aforementioned grating is also disposed in the optical waveguide.

Of course, the specific structure to be adopted will depend on the practical application, and the utility model is not limited herein.

Based on the optical waveguide described in the foregoing, the embodiment of the present utility model further provides a near-eye display module, where the near-eye display module may be applied to AR glasses, and the near-eye display module includes: the image projection device is used for generating image light and projecting the image light to a corresponding coupling-in area on the optical waveguide, so that the image light can be transmitted in the waveguide and coupled out through the coupling-out area.

Based on the above, in the optical waveguide of the embodiment of the present utility model, the grating unit of the two-dimensional diffraction grating has an optical structure with a specific curve pattern, and the curve pattern of the optical structure is continuous and has no sharp points, so that the optical waveguide has good workability. In addition, in the embodiment of the utility model, the period size of the grating unit, the curve line type of the optical structure in the grating unit, the size of the optical structure, the overall geometric morphology and the like can be changed by adjusting the parameters, so that the curve pattern of the optical structure has extremely high design freedom, and the optical structure can be used for better regulating and controlling the coupling-out efficiency distribution of the optical waveguide coupling-out area, thereby being beneficial to realizing the improvement of the uniformity of light in the coupling-out area diffraction coupling-out process.

The terms "first," "second," "the first," or "the second," as used in various embodiments of the present disclosure, may modify various components without regard to order and/or importance, but these terms do not limit the corresponding components. The above description is only configured for the purpose of distinguishing an element from other elements.

The above description is only illustrative of the preferred embodiments of the present utility model and of the principles of the technology employed. It will be appreciated by persons skilled in the art that the scope of the utility model referred to in the present utility model is not limited to the specific combinations of the technical features described above, but also covers other technical features formed by any combination of the technical features described above or their equivalents without departing from the inventive concept described above. Such as the above-mentioned features and the technical features disclosed in the present utility model (but not limited to) having similar functions are replaced with each other.

Claims (10)

1. An optical waveguide based on an asymmetric optical structure, wherein the optical waveguide comprises a waveguide substrate, at least one coupling-in region and at least one coupling-out region; wherein, a two-dimensional grating is arranged in the coupling-out area; the two-dimensional grating comprises a plurality of optical structures which are arranged periodically on the optical waveguide plane, wherein the optical structures are in a closed curve graph, the optical structures comprise at least one vertex in a first direction, and the optical structures have vertices in a second direction; the optical structure is an asymmetric structure in the first direction, and the slope of the closed curve graph is continuous.

2. The optical waveguide of claim 1 wherein the optical structure comprises two apices distributed across the optical structure in the first direction.

3. The optical waveguide of claim 1 wherein the optical structure comprises an apex at one end of the optical structure in the first direction and the other end of the optical structure in the first direction is a smoothly transitioned curve.

4. The optical waveguide of claim 2 or 3 wherein a tangent to the optical structure at an apex in a first direction is at 90 degrees to the first direction.

5. The optical waveguide of any of claims 1-3 wherein the optical structure comprises an axis of symmetry parallel to the first direction such that the optical structure is symmetrical in the second direction.

6. The optical waveguide of claim 5 wherein the optical structure comprises at least two vertices in the second direction that are disposed on opposite sides of the axis of symmetry; and at least two connecting lines between vertexes distributed on two sides of the symmetry axis in the second direction are perpendicular to the first direction.

7. The optical waveguide of claim 5 wherein the optical structure comprises at least two vertices in the second direction that are disposed on the same side of the axis of symmetry; and the curve line type distributed between the adjacent vertexes on the same side of the symmetry axis is an inward bending curve.

8. The optical waveguide of claim 6 wherein the distance between any two mutually symmetrical vertices in the second direction of the optical structure is not the same.

9. The optical waveguide of claim 1 wherein the maximum distance of the optical structure in the first direction is greater than the maximum distance of the optical structure in the second direction.

10. A near-to-eye display module comprising an image projection device and the optical waveguide of any one of claims 1-9, wherein the image projection device is configured to generate image light and project the image light onto a corresponding coupling-in region on the optical waveguide, and to diffract the image light through the coupling-out region after the image light is transmitted through the optical waveguide.