Optical waveguide and AR glasses

Abstract

The invention discloses an optical waveguide and AR glasses, the optical waveguide comprises a transverse prism and a lateral waveguide, and the transverse prism is arranged behind the lateral waveguide; the lateral waveguide is of a butterfly-shaped structure, a coupling-in grating area is arranged on the end side of the upper portion of the lateral waveguide, and two turning grating areas and two coupling-out grating areas are symmetrically arranged below the coupling-in grating area along the central axis of the lateral waveguide. Incident light is coupled into the coupling grating area and then enters the transverse prism, and after multiple times of total internal reflection in the transverse prism, when the light is propagated to the joint of the transverse prism and the lateral waveguide, a light beam is divided into two paths: the light enters the transverse prism to be continuously propagated or enters the lateral waveguide. A light beam enters from the end side of the lateral waveguide, the structure is more friendly, and a single-light-machine binocular scheme can be realized; and a split structure of the transverse prism and the lateral waveguide is adopted, so that processing and manufacturing are easier.

Description

Technical Field

[0001] This invention relates to the field of AR display technology, and in particular to an optical waveguide and AR glasses. Background Technology

[0002] The optical module of AR is mainly divided into two parts. The first part is the micro-display module, including micro-displays (LCD screen, LCOS / DLP display panel, uLED / uOLED, and other micro-projectors). The second part is the waveguide that enters the eye, including prism waveguides (prism method, mainly by Epson and NEDJ), array waveguides (a beam splitter device made of multiple grating sheets bonded together, mainly by Shanghai Lipace and Longjing Optoelectronics), diffraction waveguides (nanoscale micro-stripes are transferred onto silicon-based glass by nanoimprinting, and light propagates through diffraction), and other waveguide solutions.

[0003] While existing waveguide models and AR glasses can achieve dual-lens display with a single optical engine in the middle, their biggest drawback is that in actual use, the optical engine in the middle makes the glasses very thick at the bridge of the nose (the thickness of the optical engine), which seriously affects the aesthetics of wearing them. At the same time, because the optical engine is on the side of the bridge of the nose, the weight of the optical engine is on the bridge of the nose, which makes the nose bear a lot of weight and affects the comfort of wearing them.

[0004] In summary, there is a lack of readily usable optical waveguides and AR glasses in the current technology.

[0005] It should be noted that the information disclosed in the background section above is only for understanding the background of this application, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0006] This invention provides an optical waveguide and AR glasses, which can solve at least one of the problems in the background art.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: An optical waveguide includes a transverse prism and a lateral waveguide. The transverse prism is disposed behind the lateral waveguide. The lateral waveguide has a butterfly-shaped structure with a coupling grating region at its upper end. Below the coupling grating region, two deflection grating regions and two output grating regions are symmetrically arranged along the central axis of the lateral waveguide. Incident light couples into the coupling grating region and then enters the transverse prism. After multiple total internal reflections inside the transverse prism, when the light propagates to the junction of the transverse prism and the lateral waveguide, the light beam splits into two paths: either entering the transverse prism to continue propagating or entering the interior of the lateral waveguide. The light entering the interior of the lateral waveguide is sequentially transmitted to the deflection grating region and the output grating region.

[0008] Preferably, the transverse prism is a prism that has been polished at the top, bottom, front, and back, and the left and right sides are not propagation surfaces.

[0009] Preferably, the grating period of the coupled-in grating region is d101; the transition grating region includes a first transition grating and a first extended grating, with grating periods of d201 and d203 respectively; the coupled-out grating region includes a first coupled-out grating and a second coupled-out grating, with grating periods of d202 and d204 respectively; in K-space, the grating period d101 of the optical waveguide coupled-in region, the grating periods d201 / d203 of the first transition grating and the first extended grating, and the grating periods d202 / d204 of the first coupled-out grating and the second coupled-out grating realize K-space closed loop.

[0010] Preferably, the grating period d101 of the optical waveguide coupling region, the grating periods d201 / d203 of the first turning grating and the first extended grating, and the grating periods d202 / d204 of the first coupling grating and the second coupling grating form an equilateral triangle in K-space, and the three gratings have the same grating period except for the grating angle.

[0011] Preferably, the angle between the grating period d101 of the optical waveguide coupling region and the horizontal is 10°~50°, and the direction is upward or downward; the angle between the grating periods d201 / d203 of the first turning grating and the first extended grating and the horizontal is 10°~50°, and the direction is upward or downward; the grating periods d202 / d204 of the first coupling grating and the second coupling grating are in the vertical direction, and the direction is upward or downward.

[0012] Preferably, the angle between the grating period d101 of the optical waveguide coupling region and the horizontal is 30°; the angle between the grating periods d201 / d203 of the first folding grating and the first extended grating and the horizontal is 30°.

[0013] Preferably, the grating period of the coupled-in grating region is d101; the turning grating region includes two sets of longitudinal gratings, the first set of longitudinal turning gratings includes a second turning grating and a second extended grating, with grating periods of d201a and d202a respectively; the second set of longitudinal turning gratings includes a third turning grating and a third extended grating, with grating periods of d203a and d204a respectively; the coupled-out grating region includes a third coupled-out grating and a fourth coupled-out grating, with grating periods of d205a and d206a respectively; in K-space, the grating period d101 of the optical waveguide coupled-in region, the grating periods d201a / d203a of the second turning grating / the third turning grating, the grating periods d202a / d204a of the second extended grating / the third extended grating, and the d205a / d206a of the third coupled-out grating and the fourth coupled-out grating realize K-space closed loop.

[0014] Preferably, the grating period d101 of the optical waveguide coupling region, the grating periods d201a / d203a of the second transition grating / third transition grating, the grating periods d202a / d204a of the second extended grating / third extended grating, and the third and fourth coupling gratings d205a / d206a form a quadrilateral grating.

[0015] The present invention also provides an optical waveguide, including a transverse prism and a lateral waveguide, wherein the transverse prism is disposed behind the lateral waveguide; a coupling grating region is disposed on the transverse prism; the lateral waveguide is a butterfly structure, with two folding grating regions and two coupling out grating regions symmetrically arranged along the central axis; the incident light is coupled into the coupling grating region and then enters the transverse prism, and after multiple total internal reflections inside the transverse prism, it is sequentially transmitted to the folding grating region and the coupling out grating region.

[0016] The present invention further provides an optical waveguide, comprising a transverse prism and a lateral waveguide, wherein the transverse prism is disposed in front of the lateral waveguide; a coupling grating region is disposed on the transverse prism; the lateral waveguide is a butterfly structure, with two folding grating regions and two coupling out grating regions symmetrically arranged along the central axis; incident light is coupled into the coupling grating region and then enters the transverse prism, and after multiple total internal reflections inside the transverse prism, it is sequentially transmitted to the folding grating region and the coupling out grating region.

[0017] The present invention further provides an AR glasses, including any of the optical waveguides described above.

[0018] The present invention has the following beneficial effects: The optical waveguide of the present invention provides a lateral propagation optical waveguide structure, in which the light beam enters from the side of the lateral waveguide rather than from the center, making the structure more user-friendly and enabling a single-optical-mechanical binocular scheme; furthermore, the optical waveguide of the present invention adopts a separate structure of transverse prism and lateral waveguide, which is easier to process and manufacture. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of an optical waveguide according to an embodiment of the present invention.

[0020] Figure 2 This is a schematic diagram of optical transmission in an optical waveguide according to an embodiment of the present invention.

[0021] Figure 3 This is a schematic diagram of optical transmission in another optical waveguide according to an embodiment of the present invention.

[0022] Figure 4 This is a schematic diagram of the K-space of an optical waveguide according to an embodiment of the present invention.

[0023] Figure 5 This is another K-space schematic diagram of an optical waveguide according to an embodiment of the present invention.

[0024] Figure 6 This is another K-space schematic diagram of an optical waveguide according to an embodiment of the present invention.

[0025] Figure 7 This is a schematic diagram of optical transmission in another optical waveguide according to an embodiment of the present invention.

[0026] Figure 8 This is a schematic diagram of optical transmission in another optical waveguide according to an embodiment of the present invention.

[0027] Figure 9 This is a schematic diagram of an optical waveguide according to an embodiment of the present invention.

[0028] Figure 10 This is another K-space schematic diagram of an optical waveguide according to an embodiment of the present invention.

[0029] Figure 11 This is a schematic diagram of an optical waveguide according to an embodiment of the present invention.

[0030] Figure 12 This is a schematic diagram of optical transmission in another optical waveguide according to an embodiment of the present invention.

[0031] Figure 13 This is a schematic diagram of optical transmission in another optical waveguide according to an embodiment of the present invention. Detailed Implementation

[0032] The embodiments of the present invention will be described in detail below. It should be emphasized that the following description is merely exemplary and not intended to limit the scope and application of the present invention. Unless otherwise specified, the embodiments and features in the embodiments of this application can be combined with each other.

[0033] It should be noted that when a component is referred to as "fixed to" or "set on" another component, it can be directly on or indirectly on that other component. When a component is referred to as "connected to" another component, it can be directly connected to or indirectly connected to that other component. Furthermore, a connection can be used for fixing, coupling, or communication.

[0034] It should be understood that the terms "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention.

[0035] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of embodiments of the present invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0036] See Figures 1-3 One embodiment of the present invention provides an optical waveguide, including a transverse prism 1 and a lateral waveguide 2, wherein the transverse prism 1 is disposed behind the lateral waveguide 2; The lateral waveguide 2 has a butterfly-shaped structure. A coupling grating region 101 is provided on the upper end side. Below the coupling grating region 101, two turning grating regions and two coupling out grating regions are symmetrically arranged along the central axis of the lateral waveguide 2; this can be understood as corresponding to a binocular setup. After the incident light is coupled into the coupling grating region 101, it enters the transverse prism 1. After multiple total internal reflections inside the transverse prism 1, when the light propagates to the junction of the transverse prism 1 and the lateral waveguide 2, the light beam splits into two paths: it enters the transverse prism 1 to continue propagating or it enters the interior of the lateral waveguide 2. The light entering the lateral waveguide 2 is sequentially transmitted to the turning grating region and the coupling grating region.

[0037] The optical waveguide of the present invention provides a lateral propagation optical waveguide structure, in which the light beam enters from the side of the lateral waveguide rather than from the center, making the structure more user-friendly and enabling a single-optical-mechanical binocular scheme; furthermore, the optical waveguide of the present invention adopts a separate structure of transverse prism and lateral waveguide, which is easier to process and manufacture.

[0038] In a specific embodiment of the present invention, the transverse prism 1 is a prism that has been polished at the top, bottom, front, and back, and the left and right sides are not propagation surfaces.

[0039] Understandable Figure 1 The coupling grating region 101 shown in the figure is located on the right side of the lateral waveguide 2, and can also be located on the left side.

[0040] In a specific embodiment of the present invention, the grating period d101 of the coupled-in grating region 101 has a size of 2mm to 10mm; the transition grating region includes a first transition grating 201 and a first extended grating 203, with grating periods of d201 and d203 respectively; the coupled-out grating region includes a first coupled-out grating 202 and a second coupled-out grating 204, with grating periods of d202 and d204 respectively; in the K-space, the grating period d101 of the waveguide coupled-in region, the grating periods d201 / d203 of the first transition grating 201 and the first extended grating 203, and the grating periods d202 / d204 of the first coupled-out grating 202 and the second coupled-out grating 204 realize the K-space closed loop.

[0041] like Figure 4 As shown, the grating period d101 of the optical waveguide coupling region, the grating periods d201 / d203 of the first transition grating 201 and the first extended grating 203, and the grating periods d202 / d204 of the first coupling grating 202 and the second coupling grating 204 form an equilateral triangle in K-space, and the three gratings have the same grating period except for the grating angle.

[0042] In one specific embodiment, the grating period d101 of the waveguide coupling region, the grating periods d201 / d203 of the first transition grating 201 and the first extended grating 203, and the grating periods d202 / d204 of the first output grating 202 and the second output grating 204 are 300nm~500nm, and the grating periods of the five regions are consistent. The grating direction of the waveguide coupling region forms a downward angle θ1=30° with the horizontal direction. The grating direction of the first transition grating and the first extended grating forms a downward angle θ2=30° with the horizontal direction, and the grating direction of the first output grating and the second output grating 202 / 204 is vertically upward, θ3=90°.

[0043] In the K-space structure, the grating period d101 of the optical waveguide coupling region, the grating periods d201 / d203 of the first turning grating 201 and the first extended grating 203, and the grating periods d202 / d204 of the first coupling grating 202 and the second coupling grating 204, and the sum of the grating vectors of the left eye and the right eye are 0, all of which are closed loops.

[0044] Here, BND1 and BND2 represent the first boundary used to satisfy the total internal reflection (TIR) ​​criterion in the optical waveguide, respectively; BND2 represents the second boundary for the maximum wave vector in the optical waveguide. The maximum wave vector can be determined by the refractive index of the optical waveguide and the incident angle.

[0045] The grating period d101 and the refractive index n of the waveguide coupling region 101 are adjusted to satisfy the total internal reflection condition within waveguide 1. θ is the incident angle of the beam, θ' is the diffraction angle within waveguide 1, λ is the wavelength of the incident light, and d is the grating period; according to the grating diffraction formula and the total internal reflection condition: 1 After transforming the above formula, we take the diffraction order as ±1 order to obtain the grating period d. By substituting different incident angles and refractive indices, we can obtain a suitable grating period.

[0046] like Figure 5 As shown, is Figure 4 The equivalent grating of the grating structure shown has an upward angle θ1=30° between the grating period d101 of the waveguide coupling region and the horizontal. The grating directions of the first turning grating 201 and the first extended grating 203 are downward angled θ2=30° with the horizontal. The grating directions of the first coupling grating 202 and the second coupling grating 204 are vertically downward, θ3=90°.

[0047] like Figure 6 As shown, in this invention, the grating period d101 of the waveguide coupling region, the grating periods d201 / d203 of the first transition grating 201 and the first extended grating 203, and the grating periods d202 / d204 of the first and second output gratings 202 and 204 form a triangular grating in K-space. The angle θ1 between the grating 101 of the waveguide coupling region and the horizontal is not 30°, but can be extended to 10°~50°. The direction of the grating 101 of the waveguide coupling region can be horizontally downward or horizontally upward. Similarly, the angle θ2 between the grating directions of the first transition grating and the first extended grating and the horizontal ranges from 10° to 50°, and the direction can be horizontally downward or horizontally upward. The grating directions of the first and second output gratings 202 / 204 are 10°~50°.

[0048] like Figure 7As shown, the coupled grating region 101 is located on the left side of the lateral waveguide 2. Its grating structure is as described above, except that the light incident direction is different, which will not be repeated here.

[0049] It is understandable that, in the scheme described above, the folding grating is positioned directly above the coupling grating, so the first folding grating 201 and the first extended grating 203 are upper-side light incident and then light emitted.

[0050] like Figure 8 and Figure 9 As shown, the present invention also provides an optical waveguide implementation. The transition grating region includes two sets of longitudinal gratings. The first set of longitudinal transition gratings includes a second transition grating 201a and a second extended grating 202a; the second set of longitudinal transition gratings includes a third transition grating 203a and a third extended grating 204a; the coupling grating region includes a third coupling grating 205a and a fourth coupling grating 206a. The light beam enters from the side of the second transition grating 201a and the third transition grating 203a, then enters the second extended grating 202a and the third extended grating 204a respectively, and exits from the third coupling grating 205a and the fourth coupling grating 206a. The coupling grating changes from a transverse grating to a longitudinal grating. The advantage of this longitudinal coupling waveguide is that it can reduce ambient light diffraction into the eye.

[0051] In one specific embodiment, the grating period of the coupling grating region of the optical waveguide is d101; the transition grating region includes two sets of longitudinal gratings, the first set of longitudinal transition gratings includes a second transition grating 201a and a second extended grating 202a, with grating periods of d201a and d202a respectively; the second set of longitudinal transition gratings includes a third transition grating 203a and a third extended grating 204a, with grating periods of d203a and d204a respectively; the coupling out grating region includes a third coupling grating region. The output grating 205a and the fourth output grating 206a have grating periods of d205a and d206a, respectively. In the K-space, the grating period d101 of the optical waveguide coupling region, the grating periods d201a / d203a of the second transition grating / third transition grating, the grating periods d202a / d204a of the second extended grating / third extended grating, and the third output grating and the fourth output grating d205a / d206a realize the K-space closed loop.

[0052] like Figure 10 As shown, the grating period d101 of the optical waveguide coupling region, the grating periods d201a / d203a of the second transition grating / third transition grating, the grating periods d202a / d204a of the second extended grating / third extended grating, and the third and fourth coupling gratings d205a / d206a form a quadrilateral grating.

[0053] The angle between the grating diffraction direction and the horizontal direction in the optical waveguide coupling region 101 is θ4, and the angle range of θ4 is 10°~50°.

[0054] The angle between the diffraction direction of the second grating 201a / the third grating 203a and the horizontal direction is θ5, and the angle range of θ5 is 10°~50°.

[0055] The angle between the diffraction direction of the second extended grating 202a / the third extended grating 204a and the horizontal direction is θ6, and the angle range of θ6 is 30°~70°.

[0056] The angle between the diffraction direction of the third and fourth coupling gratings d205a / d206a and the horizontal direction ranges from 10° to 50°. Figure 10 As shown in the diagram, when the grating diffraction direction of the optical waveguide coupling region 101 is 30 degrees, the grating diffraction direction of the second bend grating 201a / third bend grating 203a is 30 degrees, the grating diffraction direction of the second extended grating 202a / third extended grating 204a is 45 degrees, and then the grating diffraction directions of the third coupling grating 205a and the fourth coupling grating 206a are horizontal.

[0057] like Figures 11-13 As shown, the present invention also provides an optical waveguide, and... Figure 1 The difference in the optical waveguides shown is that the coupling grating region 101 of the optical waveguide is set on the transverse prism 1 instead of the lateral waveguide 2. The advantage of this is that the external long transverse prism is easier to process with parallel sides, and the brightness of the binoculars can be adjusted according to the ratio of the thickness of the transverse prism waveguide to the thickness of the lens waveguide.

[0058] It is understandable that the upper side of optical waveguide 2 needs to be polished parallel to the surface, and the upper surface of the transverse prism 1 needs to be parallel to the upper surface of optical waveguide 2 when they are attached. Alternatively, if the upper side of optical waveguide 2 is not polished parallel, it needs to be blackened, in which case half of the energy is lost.

[0059] Furthermore, there are two bonding methods for the transverse prism 1 and the lateral waveguide 2. One method is that the transverse prism 11 is behind the lateral waveguide 2, and the coupling grating region 101 is bonded in the middle of the two waveguides. The other method is that the transverse prism 11 is in front of the lateral waveguide 2, and the coupling grating region 101 is not bonded in the middle of the two waveguides.

[0060] Specifically, the present invention provides an optical waveguide, including a transverse prism 1 and a lateral waveguide 2, wherein the transverse prism 1 is disposed behind the lateral waveguide 2; A coupling grating region 101 is provided on the transverse prism 1; The lateral waveguide 2 is a butterfly-shaped structure with two turning grating regions 201 / 203 and two coupling grating regions 202 / 204 symmetrically arranged along the central axis; After the incident light is coupled into the coupling grating region 101, it enters the transverse prism 1. After multiple total internal reflections inside the transverse prism 1, it is transmitted sequentially to the turning grating region and the coupling out grating region.

[0061] The present invention also provides an optical waveguide, including a transverse prism 1 and a lateral waveguide 2, wherein the transverse prism 1 is disposed in front of the lateral waveguide 2; A coupling grating region 101 is provided on the transverse prism 1; The lateral waveguide 2 is a butterfly-shaped structure with two turning grating regions 201 / 203 and two coupling grating regions 202 / 204 symmetrically arranged along the central axis; After the incident light is coupled into the coupling grating region 101, it enters the transverse prism 1. After multiple total internal reflections inside the transverse prism 1, it is transmitted sequentially to the turning grating region and the coupling out grating region.

[0062] It is understandable that after the light beam is diffracted by grating 101, it propagates through multiple total internal reflections inside the transverse prism 1. This propagation can directly and losslessly transmit the light from the coupling region to the distant waveguide side. This achieves lateral propagation of the optical waveguide. The grating structure for realizing the optical waveguide in the above scheme can be implemented using any of the forms described above, which will not be elaborated here.

[0063] The optical waveguide provided by this invention can be applied to AR glasses.

[0064] The above description provides a further detailed explanation of the present invention in conjunction with specific / preferred embodiments, and it should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various substitutions or modifications can be made to these described embodiments without departing from the concept of the present invention, and all such substitutions or modifications should be considered within the scope of protection of the present invention. In the description of this specification, the reference to terms such as "an embodiment," "some embodiments," "preferred embodiment," "example," "specific example," or "some examples," etc., indicates that the specific features, structures, materials, or characteristics described in connection with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in any suitable manner in one or more embodiments or examples. Without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification and the features of different embodiments or examples. Although the embodiments of the present invention and their advantages have been described in detail, it should be understood that various changes, substitutions, and modifications can be made herein without departing from the scope of protection of the patent application.

Claims

1. An optical waveguide, characterized in that, It includes a transverse prism and a lateral waveguide, wherein the transverse prism is disposed behind the lateral waveguide; The lateral waveguide has a butterfly-shaped structure, with a coupling grating region on the upper end side, and two turning grating regions and two coupling out grating regions symmetrically arranged along the central axis of the lateral waveguide below the coupling grating region. After the incident light is coupled into the coupling grating region, it enters the transverse prism. After multiple total internal reflections inside the transverse prism, when the light propagates to the junction of the transverse prism and the lateral waveguide, the light beam splits into two paths: it enters the transverse prism to continue propagating or it enters the interior of the lateral waveguide. Light entering the lateral waveguide is sequentially transmitted to the transition grating region and the coupling grating region.

2. The optical waveguide as described in claim 1, characterized in that, The transverse prism is a prism that has been polished at the top, bottom, front, and back, and its left and right sides are not propagation surfaces.

3. The optical waveguide as described in claim 2, characterized in that, The grating period d101 of the coupled grating region; The transition grating region includes a first transition grating and a first extended grating, with grating periods of d201 and d203, respectively; The coupled-out grating region includes a first coupled-out grating and a second coupled-out grating, with grating periods of d202 and d204 respectively; In the K-space, the grating period d101 of the optical waveguide coupling region, the grating periods d201 / d203 of the first transition grating and the first extended grating, and the grating periods d202 / d204 of the first coupling grating and the second coupling grating realize the K-space closed loop.

4. The optical waveguide as described in claim 3, characterized in that, The grating period d101 of the optical waveguide coupling region, the grating periods d201 / d203 of the first turning grating and the first extended grating, and the grating periods d202 / d204 of the first coupling grating and the second coupling grating form an equilateral triangle in K-space, and the three gratings have the same grating period except for the grating angle.

5. The grating structure as described in claim 4, characterized in that, The angle between the grating period d101 of the optical waveguide coupling region and the horizontal is 10°~50°, and the direction is upward or downward. The angle between the grating period d201 / d203 of the first folding grating and the horizontal is 10°~50°, and the direction is upward or downward; The grating periods d202 / d204 of the first and second coupled gratings are in the vertical direction, either upward or downward.

6. The grating structure as described in claim 5, characterized in that, The angle between the grating period d101 of the optical waveguide coupling region and the horizontal is 30°; the angle between the grating periods d201 / d203 of the first folding grating and the first extended grating and the horizontal is 30°.

7. The optical waveguide as described in claim 2, characterized in that, The grating period d101 of the coupled grating region; The transition grating region includes two sets of longitudinal gratings. The first set of longitudinal transition gratings includes a second transition grating and a second extended grating, with grating periods of d201a and d202a, respectively. The second set of longitudinal transition gratings includes a third transition grating and a third extended grating, with grating periods of d203a and d204a, respectively. The coupled-out grating region includes a third coupled-out grating and a fourth coupled-out grating, with grating periods of d205a and d206a respectively; In the K-space, the grating period d101 of the optical waveguide coupling region, the grating periods d201a / d203a of the second transition grating / the third transition grating, the grating periods d202a / d204a of the second extended grating / the third extended grating, and the third and fourth coupling gratings d205a / d206a realize the K-space closed loop.

8. The optical waveguide as described in claim 2, characterized in that, The grating period d101 of the optical waveguide coupling region, the grating periods d201a / d203a of the second transition grating / third transition grating, the grating periods d202a / d204a of the second extended grating / third extended grating, and the third coupling grating and the fourth coupling grating d205a / d206a form a quadrilateral grating.

9. An optical waveguide, characterized in that, It includes a transverse prism and a lateral waveguide, wherein the transverse prism is disposed behind the lateral waveguide; The transverse prism is provided with a coupling grating area; The lateral waveguide has a butterfly-shaped structure with two bend grating regions and two coupling grating regions symmetrically arranged along the central axis. After the incident light is coupled into the coupling grating region, it enters the transverse prism and, after multiple total internal reflections inside the transverse prism, is transmitted sequentially to the turning grating region and the coupling grating region.

10. An optical waveguide, characterized in that, It includes a transverse prism and a lateral waveguide, wherein the transverse prism is disposed in front of the lateral waveguide; The transverse prism is provided with a coupling grating area; The lateral waveguide has a butterfly-shaped structure with two bend grating regions and two coupling grating regions symmetrically arranged along the central axis. After the incident light is coupled into the coupling grating region, it enters the transverse prism and, after multiple total internal reflections inside the transverse prism, is transmitted sequentially to the turning grating region and the coupling grating region.

11. An AR glasses, characterized in that, Includes the optical waveguide as described in any one of claims 1-10.

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