Optics for mitigating dark band issues in augmented reality devices

Abstract

An optical device for an augmented reality (AR) device is provided that mitigates dark band issues. The optical device includes a waveguide, a first in-coupling element to receive light and couple a first portion of the light into the waveguide and toward an expansion element. A second portion of the light is not coupled into the waveguide. The expansion element directs the first portion to an out-coupling element. Further, a re-coupling element receives a third portion of the light and directs the third portion of the light to a second in-coupling element, where the third portion includes some or all of the second portion. The second in-coupling element couples a fourth portion of the light into the waveguide and toward the out-coupling element, where the fourth portion includes some or all of the third portion. The out-coupling element receives the first portion and the fourth portion and couples the light out of the waveguide.

Description

TECHNICAL FIELD

[0001] The present invention relates to the field of Augmented Reality (AR). Specifically, the present invention provides an optical device for an AR device that is capable of mitigating the dark band problem in the AR device. In addition, the present invention provides an AR device and a method of implementing AR using the optical device. BACKGROUND

[0002] AR applies virtual content to the real world using a digital platform. The virtual content is usually in the form of video, text or images. AR aims to enhance the user experience by bringing the digital closer to human senses. Users can use a mobile phone, tablet or headset to view the world with the help of AR.

[0003] A Head Mounted Display (HMD) is one such example of an AR device that projects virtual images onto the user's retina without affecting the user's view of the real world. Such HMDs usually use Figure 9 a display screen as shown, Figure 9 a schematic diagram of an HMD that uses micro-nano structures (gratings) to expand and redirect virtual content to the user's eyes is shown.

[0004] Specifically, micro-nano structures (gratings) are used to couple and direct the light produced by a light engine (e.g., a light projector) into a waveguide A (e.g., located in or formed by a display screen as shown). Figure 9 Waveguide A contains one or more gratings that are responsible for coupling light from waveguide A to the user's eyes and for expanding the light beam so that the user can see the AR image even when moving the eyes.

[0005] However, a problem arises when the following two conditions are met. The first condition is met when all gratings are located on the same surface of waveguide A (this is usually because it is easier to manufacture and align this way). For example, as shown in the example optical device in Figure 10 , the grating forming and coupling-in element 111 and the coupling-out element 115 can be located on the same surface of waveguide A. In addition, the expanding element 113 (see Figure 11 ) can also be located on the surface of waveguide A. As shown in the example optical device in Figure 11 , the second condition is met when the coupling-out element 115 is axially located vertically below the coupling-in element 111.

[0006] The gratings in the in-coupling element 111 are typically 1D gratings, which are responsible for diffracting the incoming virtual light in one direction. Thus, the in-coupling element 111 is not able to direct light vertically downwards to the out-coupling element 115 and only after the light has reached the out-coupling element 115 from the in-coupling element 111, the in-coupling element 111 first interacts with the expansion element 113. As Figure 11 indicated, the grating lines in the expansion element 113 are typically slanted to ensure simultaneous lateral and downward propagation of light.

[0007] Thus, the user will see "dark bands" on the AR image. This shadowing effect is a direct result of the geometry and thus additional such optical elements are needed to redirect light to fill the dark bands. There are many conventional ways to do this.

[0008] In one conventional approach, the dark band problem is solved by introducing an additional set of gratings. However, the use of additional gratings reduces the overall image brightness. In another conventional approach, the dark band problem is solved by cross gratings in the in-coupling element. However, this also reduces the brightness. In another conventional approach, the dark band problem is solved by using an exit pupil grating at the back of the display screen. However, this approach increases the manufacturing complexity due to the eye pupil expansion (e.g. expansion element 113) alignment with respect to the in-coupling element (they are on opposite sides). SUMMARY

[0009] In view of the problems and drawbacks of the above conventional approaches, embodiments of the present invention aim to provide an improved optical device for an AR device. It is an object of the present invention to overcome the above dark band problem of the optical device. Thus, the optical device should not affect the overall image brightness. Furthermore, the manufacturing complexity of the optical device should not be too high.

[0010] This object is achieved by the embodiments of the present invention described in the attached independent claims. Advantageous implementations of embodiments of the present invention are further defined in the dependent claims.

[0011] The basic concept of embodiments of the present invention is to recollect light that would otherwise be lost in the in-coupling element and to redirect the recollected light using additional optical elements so that they are able to fill the dark bands. The redirection can be done by directing the light to a second in-coupling element, which can be directly aligned with the out-coupling element so that the dark bands are at least filled in the part view direction where they appear. There can be various ways to direct the recollected light to the second in-coupling element.

[0012] The first aspect of the present application provides an optical device for an AR device, the optical device comprising: a waveguide; a first in-coupling element for receiving light and coupling a first portion of the received light into the waveguide and towards an expansion element, the first in-coupling element not coupling a second portion of the received light into the waveguide; the expansion element for receiving the first portion of the light and directing the received first portion of the light in the waveguide to an out-coupling element; a re-coupling element for receiving a third portion of the light and directing the received third portion of the light to a second in-coupling element, wherein the third portion of the light comprises part or all of the second portion of the light; the second in-coupling element for coupling a fourth portion of the received light into the waveguide and towards the out-coupling element, wherein the fourth portion of the light comprises part or all of the third portion of the light; the out-coupling element for receiving the first portion of the light from the expansion element and the fourth portion of the light from the re-coupling element and coupling the received light out of the waveguide.

[0013] By the re-coupling element and the second in-coupling element, light that would otherwise be lost can be recollected and directed to the out-coupling element. At the out-coupling element, the light (the fourth portion of the light) can at least partially fill the dark band. The optical device according to the first aspect does not affect the overall image brightness and can be manufactured with low complexity.

[0014] In an implementation form of the first aspect, a central region of the second in-coupling element, a central region of the first in-coupling element and a central region of the out-coupling element are arranged along a first axis.

[0015] This can efficiently solve the dark band problem, as the fourth portion of the light provided from the second in-coupling element to the out-coupling element can be output by the out-coupling element at the correct position to alleviate the dark band problem.

[0016] In an implementation form of the first aspect, the central region of the first in-coupling element and a central region of the expansion element are arranged along a second axis.

[0017] In an implementation form of the first aspect, the first in-coupling element is configured to direct the first portion of the received light along the second axis; and / or the second axis is perpendicular to the first axis.

[0018] In an implementation form of the first aspect, the second in-coupling element directs part or all of the fourth portion of the light to the out-coupling element, which part or all of the fourth portion of the light passes and / or passes through the first in-coupling element.

[0019] Thus, in particular, the fourth portion of the light is guided along a path, which the first in-coupling element is not able to guide the received light directly along. Thus, the dark band problem is at least partially mitigated.

[0020] In an implementation form of the first aspect, the first in-coupling element and / or the second in-coupling element and / or the expansion element and / or the out-coupling element comprises a grating.

[0021] In an implementation form of the first aspect, the grating lines of the grating of the first in-coupling element have a crossing direction with respect to the grating lines of the grating of the second in-coupling element.

[0022] The first in-coupling element can interfere with the fourth portion of the light and can deliver a nominal amount of light towards the out-coupling element.

[0023] In an implementation form of the first aspect, the first portion of the received light is non-zero order light; and / or the second portion of the received light is zero order light.

[0024] In an implementation form of the first aspect, the re-coupling element comprises a wedge element for directing the received third portion of the light to the second in-coupling element by total internal reflection.

[0025] In an implementation form of the first aspect, the re-coupling element comprises a pair of first and second retro-reflectors arranged on opposite sides of the waveguide; the first retro-reflector is configured to receive the third portion of the light and direct it to the second retro-reflector; the second retro-reflector is configured to further direct the received third portion of the light to the second in-coupling element.

[0026] In an implementation form of the first aspect, the re-coupling element comprises a second waveguide; the second waveguide comprises a third in-coupling element for coupling the received third portion of the light into the second waveguide; and a second out-coupling element for coupling the received third portion of the light out of the second waveguide and towards the second in-coupling element.

[0027] In an implementation form of the first aspect, the first in-coupling element and / or the second in-coupling element and / or the expansion element and / or the out-coupling element are arranged on a surface of the waveguide.

[0028] In an implementation form of the first aspect, the first in-coupling element, the second in-coupling element, the expansion element and the out-coupling element are arranged on the same surface of the waveguide.

[0029] In an implementation form of the first aspect, the recoupling element is arranged next to the waveguide; a gap is formed between the recoupling element and the waveguide, the gap having a size of at least five times the wavelength of the light.

[0030] In an implementation form of the first aspect, the expansion element comprises a first portion and a second portion, wherein the first portion and the second portion are arranged on opposite sides of the first in-coupling element; the first in-coupling element is configured to split the received first portion of the light and direct the split first portions of the light to the first portion and the second portion of the expansion element, respectively.

[0031] In an implementation form of the first aspect, the expansion element is configured to distribute the received first portion of the light to different areas of the out-coupling element, in particular uniformly.

[0032] A second aspect of the present application provides an AR device, comprising: a light engine, in particular a light projector, configured to generate light; an eyebox; the optical device according to the first aspect or any one of its implementation forms; wherein the light generated by the light engine comprises the light received by the first in-coupling element, the light coupled out of the waveguide by the out-coupling element is directed to the eyebox.

[0033] A third aspect of the present application provides a method for implementing AR, the method comprising: generating light related to a virtual image; providing the generated light to a first in-coupling element of an optical device according to the first aspect or any one of its implementation forms; combining the light coupled out of the waveguide by an out-coupling element of the optical device and the light related to a real-world image.

[0034] It should be noted that all devices, elements, units and means described in the present application can be implemented in software or hardware elements or any combination thereof. All steps which are described in the present application to be performed by the various entities or any function described to be performed by the various entities are intended to mean that the respective entity is adapted to or configured to perform the respective steps and functions. Even if a specific functionality or step to be performed by an external entity is not reflected in the description of a specific detailed element of that entity performing that specific step or functionality, it should be clear for the skilled person that these methods and functionalities can be implemented in respective software or hardware elements, or in any kind of combination thereof. BRIEF DESCRIPTION OF DRAWINGS

[0035] The above aspects and implementation forms will be described in greater detail in the following specific embodiments, in connection with the attached drawings, in which:

[0036] Figure 1A side view (a) and a front view (b) of the optical device provided in an embodiment of the present invention are shown respectively;

[0037] Figure 2 A side view of the device provided in an embodiment of the present invention is shown;

[0038] Figure 3 The embodiments of the present invention are shown. Figure 2 The front view of the device shown;

[0039] Figure 4 A front view of the device provided in an embodiment of the present invention is shown;

[0040] Figure 5 A side view of the device provided in an embodiment of the present invention is shown;

[0041] Figure 6 A side view of the device provided in an embodiment of the present invention is shown;

[0042] Figure 7 The method provided by an embodiment of the present invention is illustrated;

[0043] Figure 8 An AR device provided in an embodiment of the present invention is shown;

[0044] Figure 9 An example of an HMD is shown;

[0045] Figure 10 A side view of an exemplary optical device is shown;

[0046] Figure 11 A front view of an exemplary optical device is shown. Detailed Implementation

[0047] The embodiments of the present invention are further based on Figure 10 and Figure 11 The following are relevant considerations for the exemplary optics shown. The layout of the optics resembles a dragonfly, wherein the head of the dragonfly is defined by a coupling element 111 for coupling virtual light from the optical engine to waveguide A within the incident angle and wavelength range. The wings of the dragonfly layout are defined by an EPE (i.e., extension element 113 as used herein), wherein the light beam is replicated in the x-direction while being guided downward in the negative y-direction. A rectangular area shows a coupling element 115 responsible for directing the light to the user while propagating the light downward.

[0048] The period of the coupled element 111 can be selected such that at least one diffraction order exists in the positive x-direction and / or negative x-direction, and the diffraction angle of the first order is higher than the critical angle of the substrate guided by total internal reflection along the waveguide surface. However, there is also a non-diffractive light that conforms to Snell's law, referred to herein as zero-order light. Zero-order light leaves the waveguide A along the positive z-direction without further interaction.

[0049] Given the layout shown (where the centers of the coupling element 111 and the coupling element 115 are located on a common axis (i.e., a constant x-axis), and considering the configuration of the coupling element 111, geometric shadows or dark bands are unavoidable because no light propagates directly downwards from the coupling element 111. This results in no light reaching the user's eyes, thus creating dark bands in the user's vision (e.g., ...). Figure 11 (As shown by the rectangular dashed area in the image).

[0050] This invention provides a scheme for filling the dark band by reusing vanished light (especially vanished zero-order light). In this process, the vanished zero-order light from waveguide A can be recovered through different mechanisms and can be recoupled to the same waveguide A.

[0051] Specifically, for this reason Figure 1 An optical device 10 according to an embodiment of the present invention is shown. The optical device 10 is used in an AR device 100 (e.g., as shown in the image). Figure 10 (as shown). (a) shows a side view of the optical device 10 along the x direction, and (b) shows a front view of the optical device 10 along the z direction, wherein the vertical x, y and z directions form a (Cartesian) coordinate system.

[0052] The optical device 10 includes a waveguide A, which can be located at... Figure 11 The optical device 10 is incorporated in or formed from a display screen (e.g., an HMD display screen). Furthermore, the optical device 10 includes a first coupling element 1, an extension element 3, a recoupling element 4, a second coupling element 2, and a coupling element 5. The first coupling element 1 and the second coupling element 2 and / or the extension element 3 and / or the coupling element 5 may each include one or more gratings.

[0053] The coupling element 1 is used to receive light 11, for example, light from a light-generating engine such as a projector. Furthermore, the coupling element 1 is used to couple a first portion 12 of the received light 11 into the waveguide A and towards the extension element 3. The first coupling element 1 does not couple a second portion 13 of the received light 11 into the waveguide A; for example, the second portion 13 of the received light 11 can pass through the waveguide A. The light typically disappears and can be zero-order light.

[0054] The expansion element 3 is configured to receive the first portion 12 of the light 11 and to direct (at least partially) the received first portion 12 of the light 11 in the waveguide A to the out-coupling element 5.

[0055] The re-coupling element 4 is configured to receive a third portion 14 of the light 11, the third portion 14 of the light 11 comprising part or all of the second portion 13 of the light 11, i.e. light which is not coupled into the waveguide A and would be lost without the re-coupling element 4. Further, the re-coupling element 4 is configured to direct the received third portion 14 of the light 11 to the second in-coupling element 2.

[0056] The second in-coupling element 2 is configured to couple a received fourth portion 15 of the light 11 into the waveguide A and towards the out-coupling element 5. The fourth portion 15 of the light 11 comprises part or all of the third portion 14 of the light 11.

[0057] The out-coupling element 5 is then configured to receive the first portion 12 of the light 11 from the expansion element 3 and the fourth portion 15 of the light 11 from the second in-coupling element 2 and to out-couple the received light (12, 15) from the waveguide A, e.g. to an eyebox. By using the fourth portion 15 of the light 11, the dark band problem can be solved or at least mitigated.

[0058] In the optical device 10, the first in-coupling element 1 and / or the second in-coupling element 2 and / or the expansion element 3 and / or the out-coupling element 5 are arranged on a surface of the waveguide A, e.g. as gratings. In particular, the first in-coupling element 1, the second in-coupling element 2, the expansion element 3 and the out-coupling element 5 can be arranged on the same surface of the waveguide (A).

[0059] Figure 2 and Figure 3 An optical device 10 according to an embodiment of the present application is shown, which is based on Figure 1 the embodiment shown. In particular, Figure 2 a side view of the optical device 10 is shown, Figure 3 a front view of the optical device 10 is shown. Likewise, Figure 1 and Figure 2 the same elements in the figures have the same reference signs and function.

[0060] It is considered that Figure 2In the illustrated side view, virtual light 11 (e.g., from a light engine) is incident on the grating surface of the in-coupling element 1. Herein, the light 11 can be split in three directions (+1 order, -1 order and 0 order). In other words, the second portion 13 of the received light 11 can be zero order light and the first portion 12 of the received light 11 can be generally non-zero order light. The missing zero order light (i.e., the second portion 13 of the light 11 that is not coupled into the waveguide A) can be retrieved by the first side 41 of the wedge recoupling element 4. The slope of the side faces (41, 43) of the recoupling element 4 can be set in a Total Internal Reflection (TIR) configuration, for example 30° with respect to the base 42 of the wedge recoupling element 4. The material index of the recoupling element 4 can be any plastic or low molecular weight polymer, in particular a plastic or low molecular weight polymer with a refractive index of about 1.5. From the other side face 43 of the wedge recoupling element 4, the third portion 13 of the light 11 is redirected to the second in-coupling element 2.

[0061] It is considered that Figure 3 In the illustrated front view, the center of the in-coupling element 2 can lie on the same line containing the center of the in-coupling element 1 and the center of the out-coupling element 5. Furthermore, the grating vector of the second in-coupling element 2 can lie in the negative y direction, which is responsible for redirecting the third portion 14 of the feedback coupling of the light 11 as the fourth portion 15 of the light 11 to the first in-coupling element 1. Since the grating lines of the first in-coupling element 1 can have a cross direction with respect to the grating lines of the second in-coupling element 2, the fourth portion 15 of the light 11 continues to propagate towards the out-coupling element 5, while the out-coupling from the first in-coupling element 1 is relatively small or zero.

[0062] Figure 4 The beam expansion in the optical device 10 is illustrated, in particular the beam expansion achieved by the expansion element 3. In diffractive optics, a series of microstructures of the same shape placed next to each other in a periodic manner is called a grating. The grating can be used to control the phase, amplitude and propagation direction of light. The repetition period in which these structures are placed determines the propagation direction and the number of its corresponding directions. In the optical device 10, a pupil image (i.e., the beam size of the light 11 from a light engine) is replicated in the x-y plane, commonly referred to as 2D pupil expansion. Ideally, the light is distributed uniformly and brightly in the x-y plane.

[0063] These phenomena can be achieved by using the grating. In particular, in the optical device 10, the first in-coupling element 1 and / or the second in-coupling element 2 and / or the expansion element 3 and / or the out-coupling element 5 comprise a grating.

[0064] Figure 4 It is shown how the received light 11 (k in ) is redirected as a first portion 12 to the expansion element 3, wherein the light portion 12 is replicated and directed downwards to the out-coupling element 5. Thus, the light portion 12 is expanded in the x-y plane and is output together with the light portion 15 through the out-coupling element 5 (k out ).

[0065] Figure 5 It is shown an optical device 10 according to an embodiment of the application, which is based on the embodiment shown in Figure 1 . In particular, Figure 5 a side view of the optical device 10 is shown. Likewise, Figure 1 the same elements in Figure 5 have the same reference signs and function. Figure 5 The difference between the optical device 10 shown in Figure 2 lies in the implementation of the out-coupling element 4.

[0066] In particular, Figure 5 another embodiment of the light recoupling element 4 using a pair of retro-reflectors 4a and 4b is shown. Instead of the wedge-shaped recoupling element 4 shown in Figure 2 , the pair of retro-reflectors is used to reflect the zero-order light back into the waveguide A.

[0067] The pair of first and second retro-reflectors 4a and 4b is arranged at opposite sides of the waveguide A. The first retro-reflector 4a is used to receive the third portion 14 of the light 11 and direct it to the second retro-reflector 4b. The second retro-reflector 4b is used to further direct the received third portion 14 of the light 11 to the second in-coupling element 2.

[0068] Figure 6 It is shown an optical device 10 according to an embodiment of the application, which is based on the embodiment shown in Figure 1 . In particular, Figure 6 a side view of the optical device 10 is shown. Likewise, Figure 1 the same elements in Figure 6 have the same reference signs and function. Figure 6 The difference between the optical device 10 shown in Figure 2 lies in the implementation of the out-coupling element 4.

[0069] In particular, Figure 6Another embodiment is shown using a second waveguide B (low molecular weight polymer or plastic). In other words, the recoupling element 4 comprises a second waveguide B which can comprise a third in-coupling element 4c for in-coupling the received third portion 14 of the light 11 into the second waveguide B and a second out-coupling element 4d for out-coupling the received third portion 13 of the light 11 out of the second waveguide B and towards the second in-coupling element 2. The third in-coupling element 4c and the second out-coupling element 4d can comprise gratings.

[0070] Figure 7 A method 700 according to an embodiment of the application is shown, which employs an optical device 10. The method 700 is used for implementing AR. The method 700 comprises a step 701 of generating light 11 related to a virtual image and a step 702 of providing the generated light 11 to a first in-coupling element 1 of the optical device 10. In a third step 703, an out-coupling element 5 of the optical device 10 out-couples light (12, 15) of a waveguide A and light related to a real-world image in combination.

[0071] The application has been described in relation to various embodiments and implementations as examples. However, other variations can be understood and effected by persons of ordinary skill in the art from the figures, the description and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. A single element or other unit can fulfil the functions of several entities or items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

Claims

1. An optical device (10) for an augmented reality (AR) device (100), characterized in that The optical device (10) comprises: a waveguide (A); a first in-coupling element (1) for receiving light (11) and for coupling a first portion (12) of the received light (11) into the waveguide (A) and towards an expansion element (3), wherein the first in-coupling element (1) does not couple a second portion (13) of the received light (11) into the waveguide (A); the expansion element (3) for receiving the first portion (12) of the light and for directing the received first portion (12) of the light (11) in the waveguide (A) to an out-coupling element (5); a re-coupling element (4) for receiving a third portion (14) of the light (11) and for directing the received third portion (14) of the light (11) to a second in-coupling element (2), wherein the third portion (14) of the light (11) comprises part or all of the second portion (13) of the light (11); the second in-coupling element (2) for coupling a fourth portion (15) of the received light (11) into the waveguide (A) and towards the out-coupling element (5), wherein the fourth portion (15) of the light (11) comprises part or all of the third portion (14) of the light (11); the out-coupling element (5) for receiving the first portion (12) of the light (11) from the expansion element (3) and the fourth portion (15) of the light (11) from the re-coupling element (4) and for coupling the received light (12, 15) out of the waveguide (A); wherein a central region of the second in-coupling element (2), a central region of the first in-coupling element (1) and a central region of the out-coupling element (5) are arranged along a first axis (31), the central region of the first in-coupling element (1) and a central region of the expansion element (3) are arranged along a second axis (32), the second axis (32) being perpendicular to the first axis (31).

2. The optical device (10) according to claim 1, wherein: the first in-coupling element (1) is configured to direct the first portion (12) of the received light along the second axis (32).

3. The optical device (10) according to claim 1 or 2, wherein: the second in-coupling element (2) directs part or all of the fourth portion (15) of the light (11) to the out-coupling element (5), which part or all of the fourth portion (15) of the light (11) passes and / or passes through the first in-coupling element (1).

4. The optical device (10) according to claim 1 or 2, wherein: the first in-coupling element (1) and / or the second in-coupling element (2) and / or the expansion element (3) and / or the out-coupling element (5) comprise a grating.

5. The optical device (10) according to claim 4, wherein: The grating lines of the grating of the first in-coupling element (1) have a crossing direction with respect to the grating lines of the grating of the second in-coupling element (2).

6. The optical device (10) according to claim 1 or 2, characterized in that: the first portion (12) of the received light (11) is non-zero order light; and / or the second portion (13) of the received light (11) is zero order light.

7. The optical device (10) according to claim 1 or 2, characterized in that: the re-coupling element (4) comprises a wedge-shaped element for directing the received third portion (14) of the light (11) to the second in-coupling element (2) by total internal reflection.

8. The optical device (10) according to claim 1 or 2, characterized in that: the re-coupling element (4) comprises a pair of a first retro-reflector (4a) and a second retro-reflector (4b), the pair of a first retro-reflector (4a) and a second retro-reflector (4b) being arranged on opposite sides of the waveguide (A); the first retro-reflector (4a) is configured to receive the third portion (14) of the light (11) and direct it to the second retro-reflector (4b); the second retro-reflector (4b) is configured to further direct the received third portion (14) of the light (11) to the second in-coupling element (2).

9. The optical device (10) according to claim 1 or 2, characterized in that: the re-coupling element (4) comprises a second waveguide (B); the second waveguide (B) comprises a third in-coupling element (4c) for coupling the received third portion (14) of the light (11) into the second waveguide (B) and a second out-coupling element (4d) for coupling the received third portion (14) of the light (11) out of the second waveguide (B) and towards the second in-coupling element (2).

10. The optical device (10) according to claim 1 or 2, characterized in that: the first in-coupling element (1) and / or the second in-coupling element (2) and / or the expansion element (3) and / or the out-coupling element (5) are arranged on a surface of the waveguide (A).

11. The optical device (10) according to claim 10, characterized in that: the first in-coupling element (1), the second in-coupling element (2), the expansion element (3) and the out-coupling element (5) are arranged on the same surface of the waveguide (A).

12. The optical device (10) according to claim 1 or 2, characterized in that: the re-coupling element (4) is arranged next to the waveguide (A); a gap is formed between the re-coupling element (4) and the waveguide (A), the gap has a size of at least five times the wavelength of the light (11).

13. The optical device (10) according to claim 1 or 2, characterized in that: the expansion element (3) comprises a first portion (3a) and a second portion (3b), wherein the first portion (3a) and the second portion (3b) are arranged on opposite sides of the first in-coupling element (1); The first in-coupling element (1) is configured to split the received light (11) of the first portion (12) and direct the split first portion (12) of the light (11) to the first portion (3a) and the second portion (3b) of the expansion element (3), respectively.

14. The optical device (10) according to claim 1 or 2, characterized in that: The expansion element (3) is configured to distribute the received first portion (12) of the light (11) evenly to different areas of the out-coupling element (5).

15. An augmented reality (AR) device (100), characterized by, Comprising: a light engine (101) configured to generate light (11), wherein the light engine (101) is a light projector; an eyebox (102); the optical device (10) according to any one of claims 1 to 14; wherein the light (11) generated by the light engine (101) comprises light (11) received by the first in-coupling element (1), and light (12, 15) out-coupled by the out-coupling element (5) from the waveguide (A) is directed to the eyebox (102).

16. A method (700) for implementing augmented reality (AR), the method (700) comprising: The method (700) comprises: (701) generating light (11) associated with a virtual image; (702) providing the generated light (11) to a first in-coupling element (1) of an optical device (10) according to any one of claims 1 to 14; (703) combining light (12, 15) out-coupled by an out-coupling element (5) of the optical device (10) from a waveguide (A) and light associated with a real-world image.

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