Optical waveguide structure

Abstract

The application provides an optical waveguide structure, comprising: a first layer waveguide and a second layer waveguide arranged in parallel; the first layer waveguide comprises a first in-coupling area and a first out-coupling area; the second layer waveguide comprises a second in-coupling area and a second out-coupling area; the first in-coupling area is used for coupling image light beams emitted by an optical machine into the first layer waveguide; the first out-coupling area is used for coupling the image light beams transmitted in the first layer waveguide out of the first layer waveguide; the second in-coupling area is used for coupling the image light beams coupled out of the first out-coupling area into the second layer waveguide; and the second out-coupling area is used for coupling the image light beams transmitted in the second layer waveguide out of the second layer waveguide to enter a human eye; and the first layer waveguide restricts the propagation of the image light beams towards a first direction by reflection.

Description

Technical Field

[0001] This invention relates to the field of AR technology, and more particularly to an optical waveguide structure. Background Technology

[0002] Augmented reality (AR) is a technology that blends the real world with virtual information. An AR display system typically includes a micro-projector and an optical display screen. The micro-projector provides virtual content for the AR display system, which is then projected onto the viewer's eyes through the optical display screen. The optical display screen is usually a transparent optical component, allowing the user to see the real world through it at the same time.

[0003] Optical waveguides are one implementation path for optical displays. When the refractive index of the transmission medium is greater than that of the surrounding medium and the angle of incidence in the waveguide is greater than the critical angle for total internal reflection, light can propagate without leakage within the waveguide, resulting in total internal reflection. After the beam of virtual content from the projector is coupled into the waveguide, the beam can continue to propagate without loss within the waveguide to transmit the virtual content until it is coupled out by subsequent optical structures. Currently, optical waveguides on the market are generally divided into geometric array waveguides and diffractive waveguides. Diffractive waveguides are further divided into volume holographic waveguides and surface relief grating waveguides. The essence of diffractive waveguides is to couple the incident beam into the waveguide through grating diffraction. Surface relief grating waveguides have significant advantages among many solutions due to their extremely high design freedom and the mass production capability brought by nanoimprint processing.

[0004] Generally, a diffractive waveguide typically consists of three parts: coupling in, pupil expansion, and coupling out. A schematic diagram of a traditional one-dimensional grating architecture using a side-projection waveguide structure is shown below. Figure 1 To avoid image loss, especially when the field of view (FOV) is large, the pupil expansion area is large, resulting in a larger required waveguide size. Summary of the Invention

[0005] This invention provides an optical waveguide structure to solve the problem of excessively large area of ​​waveguide pupil gratings in the prior art.

[0006] To solve the above-mentioned technical problems, the present invention is achieved through the following technical solution:

[0007] This invention provides an optical waveguide structure, comprising: a first waveguide layer and a second waveguide layer;

[0008] The first waveguide layer and the second waveguide layer are stacked in parallel.

[0009] The first waveguide includes: a first coupling-in region and a first coupling-out region; the first coupling-in region is used to couple an image beam emitted by an optomechanical device into the first waveguide; the first coupling-out region is used to couple an image beam transmitted in the first waveguide out of the first waveguide.

[0010] The second waveguide includes a second coupling-in region and a second coupling-out region; the position of the second coupling-in region corresponds to the position of the first coupling-out region, so as to couple the image beam coupled out of the first coupling-out region into the second waveguide; the second coupling-out region is used to couple the image beam transmitted in the second waveguide out of the second waveguide so as to enter the human eye;

[0011] The image beam emitted by the optomechanical system is obliquely incident into the first coupling region, and the first waveguide constrains the image beam to propagate in a first direction by reflection; the first direction is from the first coupling region to the first coupling region, and the reflection includes reflection on four surfaces of the first waveguide that are parallel to the first direction.

[0012] Preferably, the first coupling region is further used to expand the exit pupil in the first direction; the second coupling region is further used to expand the exit pupil in a second direction different from the first direction.

[0013] Preferably, the first waveguide includes at least one strip waveguide;

[0014] The four surfaces include a first surface and a second surface that are parallel to each other, and a third surface and a fourth surface that are parallel to each other.

[0015] The first and second surfaces constrain the image beam to propagate in the strip waveguide toward the first direction by total internal reflection of the image beam, and the third and fourth surfaces constrain the image beam to propagate in the first direction by reflection of the image beam.

[0016] Preferably, the first coupling region is used to couple an image beam transmitted in the strip waveguide, which has an even number of reflections on the third and fourth surfaces, out of the second waveguide to enter the human eye.

[0017] Preferably, the parallelism between the third surface and the fourth surface is less than a preset parallelism value; and the roughness of the third surface and the fourth surface is less than a preset roughness value.

[0018] Preferably, the outer surfaces of the third surface and the fourth surface are provided with a reflective film layer.

[0019] Preferably, when the number of strip waveguides is at least two, the at least two strip waveguides are distributed sequentially along a third direction perpendicular to the first direction; wherein, there is an air gap between adjacent strip waveguides.

[0020] Preferably, at least two of the said strip waveguides are connected at one end and separated at the other end; or,

[0021] At least two of the strip waveguides are independent of each other and parallel to each other.

[0022] Preferably, when at least two of the strip waveguides are connected at one end and separated at the other end, the thickness and / or width of the strip waveguides are modulated such that the density of the image beams coupled out of the different strip waveguides tends to be consistent.

[0023] Different strip waveguides propagate image beams with different reflection angles and / or different wavelengths.

[0024] Preferably, in any two of the at least two strip waveguides, the reflection angle of the image beam propagated by the strip waveguide with the larger thickness or width is smaller than the reflection angle of the image beam propagated by the strip waveguide with the smaller thickness or width, or the wavelength of the image beam propagated by the strip waveguide with the larger thickness or width is smaller than the wavelength of the image beam propagated by the strip waveguide with the smaller thickness or width.

[0025] Preferably, when at least two of the strip waveguides are independent of each other and parallel to each other, each strip waveguide corresponds to a first coupling region; the grating parameters of the first coupling regions of different strip waveguides are different, so as to couple image beams of different wavelengths into different strip waveguides.

[0026] Preferably, the first coupling region is a partitioned first coupling region; the partitioned first coupling region is configured to make the coupling energy of the first coupling regions of different partitions relatively uniform; and / or,

[0027] The second coupling region is a partitioned second coupling region; the partitioned second coupling region is configured to make the coupling energy of the second coupling regions of different partitions relatively uniform.

[0028] Preferably, the image beam is coupled into the second waveguide by refraction or reflection in the second coupling region; the image beam is coupled out of the second waveguide by refraction or reflection in the second coupling region; or, the image beam is coupled into the second waveguide by diffraction in the second coupling region; the image beam is coupled out of the second waveguide by diffraction in the second coupling region.

[0029] Preferably, the second coupling region and the second coupling out region are connected, and the grating structures of the second coupling region and the second coupling out region have the same period and direction.

[0030] Preferably, the size of the second coupling region is greater than or equal to the size of the first coupling region.

[0031] Preferably, it further includes: a correction element disposed in the beam coupling direction of the second coupling region, used to modulate the direction of the coupled beam in the second coupling region to achieve coupled beam imaging correction.

[0032] The optical waveguide structure provided by this invention uses a two-layer waveguide design: a first waveguide and a second waveguide. The first waveguide constrains the image beam to propagate in a first direction by reflection, which greatly reduces the area of ​​the pupil expansion region compared with the prior art, thereby reducing the size of the waveguide.

[0033] The optical waveguide structure provided by this invention has a first waveguide and a second waveguide stacked in parallel. The design in which the opposite surfaces of the first waveguide and the second waveguide are parallel to each other occupies less space than a design with a certain angle, which can further reduce the size of the waveguide and thus reduce the thickness of the AR device that carries the AR optical waveguide structure.

[0034] In an optional embodiment of the present invention, the first waveguide is designed as a strip waveguide to achieve constrained propagation of the image beam, and the strip waveguide is configured such that the image beam that interacts with the side an odd number of times cannot be coupled out, that is, the first waveguide has a unidirectional coupling characteristic. This characteristic can ensure that the coupled light rays are all in the same direction and there will be no two opposite light rays coupled out, thereby ensuring the consistency of the direction of the coupled image.

[0035] In one optional embodiment of the present invention, the first waveguide includes at least two strip waveguides distributed sequentially along a third direction perpendicular to the first direction. Compared with the case of only one waveguide, this increases the density of coupled light, that is, it increases the coupling efficiency of the waveguide. The higher the efficiency, the higher the brightness of the image. In addition, multiple strip waveguides can transmit light of different wavelengths respectively, thereby enabling color coupling.

[0036] In an optional embodiment of the present invention, when the first waveguide includes at least two strip waveguides, the thickness and / or width of the different strip waveguides can be different. By adjusting the thickness and / or width, the output light density of each strip waveguide can be balanced, thereby further improving the output efficiency of the waveguide and also making the FOV uniformity better.

[0037] In one optional embodiment of the present invention, the first coupling region is partitioned, i.e., the first coupling region is a partitioned first coupling region. This can make the coupling efficiency and / or energy relatively uniform at various positions in the first coupling region, thereby improving the quality of the image beam coupled from the first waveguide. And / or, the second coupling region is partitioned, i.e., the second coupling region is a partitioned second coupling region. This can make the coupling efficiency and / or energy relatively uniform at various positions in the second coupling region, thereby improving the quality of the image beam coupled from the second waveguide.

[0038] In an optional embodiment of the present invention, the first waveguide and the second waveguide are arranged in parallel and stacked, and the size of the first waveguide and the second waveguide is small. This creates a space that can be used for extended functions, such as setting a correction element in this space. The direction of the coupled beam in the second coupled region is modulated by the correction element to the desired direction, that is, the direction of the coupled light is controlled, which facilitates imaging and further improves the light utilization rate. Attached Figure Description

[0039] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0040] Figure 1 This is a schematic diagram of the grating structure distribution in a diffractive waveguide in the prior art.

[0041] Figure 2 This is a perspective view of an optical waveguide structure according to an embodiment of the present invention;

[0042] Figure 3 This is a schematic diagram of the first waveguide according to an embodiment of the present invention;

[0043] Figure 4 This is a schematic diagram of the second waveguide according to an embodiment of the present invention;

[0044] Figure 5 This is a front view of an optical waveguide structure according to an embodiment of the present invention;

[0045] Figure 6 This is a three-dimensional schematic diagram of beam propagation in an optical waveguide structure according to an embodiment of the present invention;

[0046] Figure 7 This is a schematic diagram of beam propagation from a perspective of an optical waveguide structure according to an embodiment of the present invention.

[0047] Figure 8 This is a schematic diagram comparing an optical waveguide structure according to an embodiment of the present invention with a conventional optical waveguide;

[0048] Figure 9 For a certain field of view (FOV) of an embodiment of the present invention i A spatial schematic diagram of the beam propagating in the first waveguide layer;

[0049] Figure 10 For FOV i The image shows a top view of the beam propagating in the first waveguide.

[0050] Figure 11 For FOV i The image shows the front view of the beam propagating in the first waveguide;

[0051] Figure 12 This is a wave vector diagram of ray propagation in the first waveguide of an embodiment of the present invention;

[0052] Figure 13 This is a top view of the first waveguide according to an embodiment of the present invention;

[0053] Figure 14 This is a top view of the first waveguide according to an embodiment of the present invention;

[0054] Figure 15 This is a schematic diagram showing the relationship between the total internal reflection angle and the incident angle within the waveguide.

[0055] Figure 16 The light density coupled from multiple strip waveguides of the first layer waveguide in an embodiment of the present invention and the total internal reflection angle θ dif Relationship diagram;

[0056] Figure 17 The light density and total internal reflection angle φ of the multiple strip waveguides coupled from the first layer waveguide in an embodiment of the present invention dif Relationship diagram;

[0057] Figure 18 This is a schematic diagram of the width modulation of the strip waveguide of the first layer waveguide according to an embodiment of the present invention;

[0058] Figure 19 This is a schematic diagram of light propagation when the first waveguide of an embodiment of the present invention includes a strip waveguide;

[0059] Figure 20 This is a schematic diagram of light propagation when the first waveguide of an embodiment of the present invention includes three strip waveguides;

[0060] Figure 21 This is a front view of a coupled beam direction modulation element according to an embodiment of the present invention;

[0061] Explanation of reference numerals in the attached figures:

[0062] 1-First waveguide layer,

[0063] 11-First coupling region,

[0064] 12-First coupling region;

[0065] 2-Second waveguide,

[0066] 21-Second coupling region,

[0067] 22-Second coupling region;

[0068] 3-Optics;

[0069] 4-Corrective elements. Detailed Implementation

[0070] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0071] In the description of this invention, it should be understood that the terms "upper part", "lower part", "upper end", "lower end", "lower surface", "upper surface", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the 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, and therefore should not be construed as a limitation of the invention.

[0072] In the description of this invention, 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 indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature.

[0073] In the description of this invention, "a plurality of" means multiple, such as two, three, four, etc., unless otherwise explicitly specified.

[0074] In the description of this invention, unless otherwise explicitly specified and limited, the term "connection" and other such terms should be interpreted broadly. For example, it can refer to a fixed connection, a detachable connection, or an integral connection; it can refer to a mechanical connection, an electrical connection, or a connection that allows communication between the components; it can refer to a direct connection or an indirect connection through an intermediate medium; it can refer to the internal communication between two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0075] The technical solution of the present invention will be described in detail below with reference to specific embodiments. These specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments.

[0076] This application provides an optical waveguide structure, which includes: a first waveguide 1 and a second waveguide 2, as shown in the reference. Figure 2 , Figure 3 , Figure 4 , Figure 5 , Figure 6 , Figure 7 The first waveguide 1 and the second waveguide 2 are stacked in parallel. Please refer to [reference needed]. Figure 2 The first waveguide 1 includes a first coupling-in region 11 and a first coupling-out region 12, as referenced. Figure 3 The second waveguide 2 includes a second coupling-in region 21 and a second coupling-out region 22. Please refer to [reference needed]. Figure 4 . refer to Figure 6 , Figure 7 The first coupling region 11 is used to couple the image beam emitted by the optomechanical 3 into the first waveguide 1; the first coupling region 12 is used to couple the image beam transmitted in the first waveguide 1 out of the first waveguide 1 and incident it into the second waveguide 2. (Reference) Figure 6 The position of the second coupling-in region 21 corresponds to the position of the first coupling-out region 12. The second coupling-in region 21 is used to couple the image beam coupled out of the first coupling-out region 12 into the second waveguide 2; the second coupling-out region 22 is used to couple the image beam propagating in the second waveguide 2 out of the second waveguide 2. It should be noted that in Figure 2 , 5 In the figure, since the second waveguide 2 is located below the first waveguide 1, the second coupling region 21 corresponds to the position of the first coupling region 12. Therefore, the second coupling region 21 is blocked by the first coupling region 12, which is not shown in the figure.

[0077] The first waveguide layer constrains the image beam to propagate in a first direction via reflection; the first direction is from the first coupling region to the first coupling region, as referenced. Figure 5 It should be noted that the reflection here includes reflections on the four surfaces of the first waveguide that are parallel to the first direction, as shown in the reference. Figure 5 The four surfaces include a surface parallel to the XY plane and a surface parallel to the XZ plane.

[0078] The first waveguide 1 and the second waveguide 2 are stacked in parallel, meaning the plane containing the first coupling region is parallel to the plane containing the second coupling region, and there is no angle between the opposing surfaces of the first and second waveguides. (Refer to...) Figure 5The plane containing the first coupling-out region and the plane containing the second coupling-in region are XY planes. Of course, in other embodiments, the faces of the first waveguide 1 and the second waveguide 1 can also have an angle. Compared to a design where the two waveguides have an angle, a design where the two waveguides are parallel occupies less volume, especially when the dimension of the first waveguide in the direction of the angle is larger, the volume reduction is more significant.

[0079] In this design, the image beam emitted by the optical engine is incident obliquely into the first coupling region. It should be noted that the propagation of the image beam along the four surfaces of the first waveguide parallel to the first direction can cause a mirrored beam. By adjusting the beam exit direction of the optical engine, the image beam emitted by the optical engine is incident obliquely into the first coupling region, preventing the mirrored beam from coupling out of the first waveguide. Inclining the image beam emitted by the optical engine into the first coupling region also avoids ghosting caused by the image beam reflecting back to the optical engine.

[0080] Generally, a diffractive waveguide typically consists of three parts: coupling in, pupil expansion, and coupling out. Existing technologies use a single-layer waveguide grating structure. A schematic diagram of the existing one-dimensional grating structure when employing a front-projection waveguide architecture is shown below. Figure 1 To avoid image loss, especially with a large field of view (FOV), the pupil expansion area is larger, resulting in a larger required waveguide size. When optical waveguides are used in AR glasses, the waveguide size cannot be increased indefinitely to meet user wearing requirements and glasses size standards. This inevitably leads to the waveguide exceeding the bounds of the waveguide shape, especially with a large FOV, affecting the AR glasses' design. Furthermore, the grating structure layout of a single-layer waveguide, especially with a large field of view, requires a large exit pupil expander (EPE), such as... Figure 1 The larger the field of view (FOV) of the pupil, the greater the angle of pupil dilation, which poses a significant challenge to the design of eyeglasses.

[0081] The optical waveguide structure of this invention, through a two-layer waveguide design, significantly reduces the area of ​​the pupil expansion region. Please refer to [link / reference needed] for details. Figure 8 The existing single-layer grating structure layout is: input 1 + pupil expander (2+3+4) + output 5. The double-layer waveguide layout provided by this invention is: first layer waveguide: input 1 + output 2; second layer waveguide: input 2' (directly below 2) + output 5'. Figure 8As can be seen from the above, compared with the prior art, the present invention has the following advantages: (1) The first waveguide constrains the image beam to propagate in the first direction by reflection. The reflection effect of the sidewall reflects the light that originally propagated in region 3 and region 4 into region 2 and propagates it. The first waveguide is coupled out by the structure in region 2. That is to say, only region 2 is set as the pupil expansion region, which can cover the entire field of view. The positions of region 3 and region 4 are saved, so that the area of ​​the pupil expansion region is reduced; (2) Since the position of region 4 is saved, the distance between coupling in 2' and coupling out 5' is reduced, which also increases the design freedom of the size and position of coupling out 5'.

[0082] In the embodiments provided in this application, the first coupling region is further used for exit pupil expansion in a first direction; the second coupling region is further used for exit pupil expansion in a second direction different from the first direction. That is, the exit pupil expansion directions of the first waveguide and the second waveguide are different, which can realize two-dimensional pupil expansion. (Reference) Figure 5 The direction from the first coupling-in region to the first coupling-out region is the first direction, which realizes the expansion of the exit pupil in the first direction. The direction from the second coupling-in region to the second coupling-out region is the second direction, which realizes the expansion of the exit pupil in the second direction.

[0083] Furthermore, the first and second waveguide layers of the optical waveguide structure provided in this application can be directly stacked, and the process is mature and stable. (Refer to...) Figure 7 For example, an adhesive can be used for lamination.

[0084] The first waveguide layer is described in detail below.

[0085] In one embodiment, the first waveguide is implemented as a strip waveguide. For example, the strip waveguide can be implemented as a square strip waveguide. Along the propagation direction of the image beam, the four faces of the square strip waveguide are: a first surface and a second surface that are parallel to each other, and a third surface and a fourth surface that are parallel to each other. All four faces are working surfaces. The first and second surfaces perform total internal reflection of the image beam, and the third and fourth surfaces reflect the image beam, thus confining the image beam within the strip waveguide to propagate in the first direction.

[0086] Specifically, after the image beam is coupled into the first optical waveguide, it propagates by total internal reflection along the beam propagation direction on the first and second surfaces of the first waveguide. The first and / or second surfaces of the first waveguide have a first coupling-out region. Thus, as the image beam propagates by total internal reflection between the first and second surfaces, it continuously couples out from the first coupling-out region, expanding the circular or rectangular coupled-in light spot emitted by the optomechanical system into a striped light spot. Simultaneously, when the image beam propagates to the third and fourth surfaces of the first waveguide, these surfaces reflect the image beam, confining it within the first waveguide to continue propagating. This increases the number of times the image beam interacts with the first coupling-out region, thereby increasing the light density of the beam coupled out from the first coupling-out region.

[0087] It should be noted that this application provides a first-layer waveguide implemented as a strip waveguide. The image beam is constrained and transmitted within the first-layer waveguide by the reflection of the third and fourth surfaces of the first-layer waveguide. However, the image beam is a mirror image before and after reflection at the third or fourth surface. If both mirror images are coupled out of the first-layer waveguide, two images with opposite directions will appear. To ensure the consistency of the coupled image direction and prevent two images with opposite directions, this application designs the first-layer waveguide to have unidirectional coupling characteristics. Only specific light rays can be coupled out; that is, only image beams that are reflected an even number of times at the third and fourth surfaces can be coupled out from the first coupling region.

[0088] Specifically, this application sets a coupling grating in the first coupling region to couple the image beam into the first waveguide, and sets a coupling grating in the first coupling region to couple the image beam out of the first waveguide. Then, by designing the output direction of the image beam emitted by the optomechanic towards the first coupling region and / or the period and direction of the coupling grating and the coupling grating, the mirror beam is prevented from coupling out of the first waveguide.

[0089] The working principle of the first-layer waveguide with unidirectional coupling characteristics is described in detail below.

[0090] like Figure 9 , 10 As shown in 11 and 12, Figure 9 This is a spatial schematic diagram of an image beam propagating in the first waveguide at a certain field of view (FOVi). Figure 10 This is a top view of the image beam propagating in the first waveguide layer of FOVi. Figure 11 This is a front view of the image beam propagating in the first waveguide of FOVi, according to... Figure 9 The beam propagation direction is defined in the diagram. The four surfaces along the beam propagation direction are: the first surface S1, the second surface S2, the third surface S3, and the fourth surface S4. The two surfaces perpendicular to the beam propagation direction are: the fifth surface S5 and the sixth surface S6. Figure 12 This is the K-domain graph of the image beam propagation.

[0091] refer to Figure 9 , 10 After the image beam from FOVi is incident on the coupling region of the first waveguide, it diffracts at position 102 of the first coupling region 11 on S2 and is coupled into the first waveguide. It then undergoes total internal reflection between S1 and S2 in the negative X-axis direction. After the first total internal reflection at position 103 on S1, it continues to propagate to S2, where diffraction occurs at position 104 of the first coupling region 12 on S2. At this point, the image beam does not produce a mirror image, allowing a portion of the beam to couple out of the first waveguide (not shown in the figure), while another portion continues to propagate through total internal reflection to S3. After reflection at position 105 on S3, it continues to propagate to S1. After total internal reflection at position 106 on S1, it continues to propagate to S2, where diffraction occurs at position 107 of the first coupling region 12 on S2. At this point, the image beam is optically and mechanically... The outgoing image beam is mirrored, and the beam is not allowed to couple out of the first waveguide. The beam continues to propagate through total internal reflection to S1. After total internal reflection occurs at position 108 in S1, it continues to propagate to S2. Diffraction occurs at position 109 in the first coupling region 12 on S2. At this time, no beam couples out, and part of the beam continues to propagate through total internal reflection to S4. After reflection occurs at position 110 in S4, it continues to propagate to S1. After total internal reflection occurs at position 111 in S1, it continues to propagate to S2. Diffraction occurs at position 112 in the first coupling region 12 on S2. Since the beam undergoes two reflections on the left and right sides and is mirrored twice, it aligns with the image beam emitted from the optomechanical system. Beam coupling is permitted, so a portion of the beam couples out of the first waveguide (not shown in the figure), while another portion continues total internal reflection to S1. After reflection at position 113 in S1, it continues to propagate to S2. Diffraction occurs again at position 114 in the first coupling region 12 on S2, resulting in another portion of the beam coupling out of the first waveguide (not shown in the figure). A third portion continues total internal reflection to S3, where reflection occurs at position 115. Diffraction then occurs at position 117 in the first coupling region 12 on S2. At this point, the image beam is a mirror image of the image beam emitted from the optomechanical system, and beam coupling out of the first waveguide is not permitted. The beam continues total internal reflection to S6.

[0092] It is understood that when the image beam interacts with the first coupling region after being reflected several times in planes S3 and S4, the beam is consistent with the image beam emitted by the optomechanical system. When the image beam interacts with the first coupling region after an odd number of reflections in planes S3 and S4, the beam is a mirror image of the image beam emitted by the optomechanical system. To avoid two images with opposite directions, the mirror image should be prevented from coupling out of the first waveguide. This application prevents the mirror image beam from coupling out of the first waveguide by designing the output direction of the image beam emitted by the optomechanical system towards the first coupling region and the period and direction of the coupling grating and the coupling grating. (Reference) Figure 12The wave vector of the image beam emitted from the optomechanical system can exist in a region Box0 of the wave vector space defined by the initial wave vectors kx and ky. When the optomechanical system emits vertically, Box0 is located at the center of the wave vector diagram. When the optomechanical system is tilted, the direction of the wave vector of the image beam changes, and the position of Box0 in the wave vector diagram shifts relative to the center position. After passing through the coupling grating, the beam enters the waveguide for total internal reflection propagation. The function of the coupling grating is represented by the arrow Kin. If the beam has already entered the coupling region before first reaching the side of the waveguide (the third or fourth surface), it will inevitably interact with the coupling grating and couple out. The function of the coupling grating at this time is represented by the arrow Kout. When the light beam first reaches the side of the waveguide, the light vector along the Y direction reverses, and this reflection process is represented by the arrow Kre. After one side reflection, the beam continues to propagate through total internal reflection and is incident on the coupling grating again. The effect of the coupling grating is represented by Kout. As shown in the K-domain diagram, there is no coupling order at this point, meaning that the light beam that has undergone one side reflection will not be coupled out in the coupling region. Furthermore, if the beam undergoes another side reflection, the light vector along the Y direction reverses again, and the reflection can be represented by Kre. At this point, the beam continues to propagate and is incident on the coupling grating, where it can be coupled out. Thus, it can be seen that beams that interact with the side of the waveguide an odd number of times cannot be coupled out, while beams that interact with the side an even number of times can be coupled out from the second waveguide to enter the human eye. This characteristic ensures that the direction of the coupled light rays is consistent, and there will not be two opposing light rays coupled out.

[0093] The degree and direction of the shift of the source image from the center dashed line to the upper right solid line are related to the optomechanical tilt angle. The effect of the coupling grating Kin is related to the period of the coupling grating, the effect of the coupling grating Kout is related to the period of the coupling grating, the direction of the effect of the coupling grating Kin is related to the direction of the coupling grating, and the direction of the effect of the coupling grating Kout is related to the direction of the coupling grating. By selecting parameters such as the optomechanical tilt angle, grating period, and direction, it is possible to ensure that beams acting on the waveguide side an odd number of times cannot be coupled out, while beams acting on the side an even number of times can be coupled out, thus ensuring the consistency of the direction of the coupled image.

[0094] In different embodiments, the number of strip waveguides in the first layer waveguide can be one, as shown in the reference. Figure 10 , 11 The number of strip waveguides in the first layer can also be at least two; please refer to [reference needed]. Figure 2 There are two lines in the middle. Figure 13 There are four strips in the middle. When the first layer waveguide is implemented as at least two strip waveguides, these at least two strip waveguides are distributed sequentially along a third direction perpendicular to the first direction. Please refer to [reference needed]. Figure 2 , 35, 6, 13. Preferably, there is a certain air gap between adjacent strip waveguides. Multiple strip waveguides can be parallel to each other. The number of strip waveguides can be modulated according to actual needs.

[0095] In addition, the first coupling region can be a rectangular region or a circular region.

[0096] In practice, when the first waveguide layer is implemented as multiple strip waveguides, the multiple strip waveguides can share a single coupling region or each have its own separate coupling region; similarly, the multiple strip waveguides can share a single coupling region or each have its own separate coupling region. Preferably, when the multiple strip waveguides each correspond to a separate coupling region, the grating parameters of the first coupling region of different strip waveguides can be different, so that image beams of different wavelengths are coupled into different strip waveguides.

[0097] refer to Figure 2 , 3 Examples 5 and 6, taking the first-layer waveguide as an example, which includes two strip waveguides, with one end of the two strip waveguides connected and the other end separated. Preferably, the two strip waveguides are parallel to each other.

[0098] Figure 14 The image shown is a top view of the first waveguide in another case, taking the first waveguide as an example, which includes two strip waveguides, and the two strip waveguides are independent of each other and parallel to each other.

[0099] In one embodiment, since the sides of the strip waveguide can reflect light to increase the density of the coupled light, the sides of the strip waveguide (third and fourth surfaces) can be optimized to better utilize their reflectivity. Specifically, the sides of the strip waveguide (third and fourth surfaces) can have a certain degree of parallelism, i.e., the parallelism is less than a preset parallelism value; the sides of the strip waveguide can also have a small roughness, i.e., the roughness is less than a preset roughness value; a reflective film layer (which can be applied, plated, etc.) can be provided on the outer surfaces of the third and fourth surfaces of the strip waveguide. The outer surfaces of the third and fourth surfaces are the sides located outside the strip waveguide. The reflective film layer can be a metal film layer, such as aluminum or silver, and can include one layer or multiple layers. More preferably, the above three measures can be used in combination.

[0100] In one embodiment, to make the coupled energy of the first waveguide more uniform and improve image quality, the thickness and / or width of the strip waveguide can be modulated, or the first coupled region can be partitioned. More preferably, the two methods can be combined.

[0101] The two adjustment methods described above are described in detail below.

[0102] In one embodiment, more uniform coupled energy can be achieved by modulating the thickness and / or width of the strip waveguide. Specifically, the reflection angle of the image beam propagated by the strip waveguide with a larger thickness or width is smaller than that of the image beam propagated by the strip waveguide with a smaller thickness or width, or the wavelength of the image beam propagated by the strip waveguide with a larger thickness or width is smaller than that of the image beam propagated by the strip waveguide with a smaller thickness or width. This makes the density of the coupled beam more uniform, i.e., the coupled energy more uniform.

[0103] The density of the coupled beam from a single strip waveguide is mainly affected by the total internal reflection angle and the wavelength. These two main factors are described in detail below.

[0104] First, let's describe the angle of total internal reflection:

[0105] The image beam emitted by the optomechanical engine reflects at different angles in different waveguides, that is, the incident beam angle varies. Please refer to [reference needed]. Figure 15 Therefore, the light density coupled out of different strip waveguides is also different. Please refer to [reference needed]. Figure 16 , 17 Please refer to this. Figure 15 For light to propagate in three-dimensional space, two angles (θ and φ) are required for definition. The angle of incidence (θ) of light rays at the incident plane varies depending on the field of view. in φ in The diffraction angle (θ) after entering the waveguide is different. dif φ dif Therefore, the angle of total internal reflection of light within the waveguide is different. The angle of total internal reflection of light with different diffraction angles is the diffraction angle.

[0106] In a waveguide, the total internal reflection angle θ dif The larger the value of θ, the longer the optical path traveled in the X direction during a single total internal reflection, resulting in lower optical density and a smaller contrast transmission. dif A strip waveguide for light transmission with a large θ value. di For light-emitting waveguides, the thickness D of the waveguide needs to be reduced to increase the light density, so that the light density is relatively uniform among the waveguides, i.e., the coupled energy is relatively uniform. Please refer to [reference needed]. Figure 16 .

[0107] In a waveguide, the total internal reflection angle φ dif The smaller the value, the longer the span in the X direction between the two sides in one round trip, the lower the optical density, and the larger the contrast transmission φ. dif A strip waveguide for light transmission with a small φ difFor light-emitting waveguides, the width W needs to be reduced to increase the light density, so that the light density is relatively uniform among the waveguides, i.e., the coupled energy is relatively uniform. Please refer to [reference needed]. Figure 17 .

[0108] like Figure 18 This is a schematic diagram showing the width distribution of three strip waveguides as an example.

[0109] Secondly, the wavelength is described:

[0110] The diffraction angle depends not only on the incident angle, but also on the wavelength and the grating period.

[0111] d(n1sinθ dif +n2sinθ in )=mλ

[0112] Where d is the grating period, n1 is the refractive index of the waveguide substrate, n2 is the refractive index of the external medium of the waveguide substrate (the external medium of the waveguide substrate is usually air, i.e., n2 = 1), λ is the wavelength of the image beam, and m = 0, 1, 2...

[0113] In one embodiment, at least two strip waveguides correspond to at least two first coupling regions; the grating parameters of the at least two first coupling regions are different, so that different wavelength beams are coupled into the different strip waveguides.

[0114] For example, two strip waveguides have different grating periods (depth, duty cycle, serration angle, etc.), one is 360nm and the other is 460nm. Due to the wavelength selectivity of the diffraction waveguide, light of different wavelengths propagates in the two strip waveguides and is coupled out at the coupling position, and the two do not interfere with each other.

[0115] Energy is related to wavelength. Different wavelengths of light beams have different reflection angles in the first waveguide, so the light density coupled out of the first waveguide is also different. The modulation of width and / or thickness is also applicable to the optimization of light beams of different wavelengths. For example, for light with low density, the waveguide width and / or thickness can be increased to make the outgoing light density of each waveguide comparable, that is, the energy comparable.

[0116] In one embodiment, more uniform coupling energy can also be achieved by partitioning the first coupling region. The energy of the light decreases with each coupling; assuming the initial energy is E0 and the coupling efficiency is η... i Then the energy coupled out each time is: E i =E0(1-η1)...(1-η i-1 )η i To ensure uniform coupling energy, then η i It should increase with continuous coupling, with higher energy and smaller η in the early stage.i If the energy level is low in the later stages, a larger η is required. i .

[0117] Specifically, different partitions can have different grating parameters, which can be one or more of the following: depth, duty cycle, and helical tooth tilt angle. For example, the depth of the coupling-out grating can be gradually increased along the direction away from the coupling in. Of course, other grating parameters can also be changed, as long as η can be optimized. i It can be increased as it continues to couple out.

[0118] In one embodiment, the density of light emitted from the first waveguide layer can be controlled by adjusting the number of strip waveguides. Please refer to [reference needed]. Figure 19 This is a schematic diagram showing the density of the coupled rays when the first waveguide layer includes a strip waveguide. Figure 20 This is a schematic diagram illustrating the density of the coupled rays when the first waveguide layer comprises three strip waveguides. From... Figure 19 , Figure 20 As can be seen, the more strip waveguides there are, the higher the density of the coupled light rays. Therefore, an appropriate number of strip waveguides can be selected according to the density requirements of the coupled light rays.

[0119] The second waveguide is described in detail below.

[0120] In one embodiment, the second waveguide includes a lens-shaped waveguide.

[0121] like Figure 4 The diagram shows a top view of the second waveguide. The upper strip-shaped region is the second coupling-in region 21, corresponding to the coupling-out region of the first waveguide, and the lower rectangular region is the second coupling-out region 22. The strip-shaped light spot obtained by the first waveguide extending in one direction couples into the second waveguide from the second coupling-in region 21, propagates in the second waveguide, reaches the second coupling-out region, and then propagates by total internal reflection and diffraction, expanding the pupil in another direction. Thus, it works in conjunction with the first waveguide to achieve two-dimensional pupil expansion.

[0122] In one embodiment, the coupling optical element in the second coupling region can be a prism, and the corresponding emitting optical element in the second coupling region can be a prism or an array of emitting surfaces. Both the coupling optical element in the second coupling region and the emitting optical element in the second coupling region can be gratings.

[0123] In one embodiment, the image beam is coupled into the second waveguide by refraction or reflection within the second coupling region; the image beam is coupled out of the second waveguide by refraction or reflection within the second coupling region. Alternatively, the image beam is coupled into the second waveguide by diffraction within the second coupling region; the image beam is coupled out of the second waveguide by diffraction within the second coupling region.

[0124] In one embodiment, the second coupling-in region and the second coupling-out region are connected, and the grating structures of the second coupling-in region and the second coupling-out region have the same period and direction.

[0125] The second coupling region corresponds to the first coupling region. The size of the second coupling region can be larger than that of the first coupling region, which ensures that all light rays can be received.

[0126] In one embodiment, the second coupling region can be a one-dimensional grating or a two-dimensional grating, preferably a one-dimensional grating.

[0127] In one embodiment, the input and output gratings of the second waveguide can be made into a single large-area grating.

[0128] In one embodiment, the second coupling region can be partitioned to achieve more uniform coupling energy.

[0129] Specifically, different partitions can have different grating parameters, which can be one or more of the following: depth, duty cycle, and helical tooth tilt angle. For example, the depth of the coupling-out grating can be gradually increased along the direction away from the coupling in. Of course, other grating parameters can also be changed, as long as η can be optimized. i It can be increased as it continues to couple out.

[0130] In one embodiment, to further improve light energy utilization, a reflective film layer can be provided on the surface of the first waveguide and / or the second waveguide. Specifically, in the optical waveguide structure provided in this application, when the first coupling region is located on the surface of the first waveguide away from the human eye, a reflective film layer is provided on the surface of the first waveguide near the human eye, corresponding to the area of ​​the first coupling region; when the first coupling region is located on the surface of the first waveguide near the human eye, a reflective film layer is provided on the surface of the coupling structure in the first coupling region; when the second coupling region is located on the surface of the second waveguide near the human eye, a reflective film layer is provided on the surface of the second waveguide away from the human eye, corresponding to the area of ​​the second coupling region; when the second coupling region is located on the surface of the second waveguide away from the human eye, a reflective film layer is provided on the surface of the coupling structure in the second coupling region. This allows some of the light beam leaking from the optical waveguide structure to be reflected back into the optical waveguide structure for reuse through the reflective film layer.

[0131] In one embodiment, the optical waveguide structure may further include: a correction element 4, please refer to... Figure 21 The correction element 4 is positioned in the beam coupling direction of the second coupling region to modulate the direction of the coupled beam from the second coupling region. When the optomechanical system is obliquely incident, the direction of the coupled beam from the second coupling region may deviate from the expected direction, and the correction element can modulate it back to the expected direction.

[0132] In one embodiment, the corrective element 4 can be a prism.

[0133] In addition, the corrective element 4 can also have refractive power to achieve the function of vision correction.

[0134] This application also provides an augmented reality device, which includes a device body, an optical engine, and the optical waveguide structure provided in this application. The optical engine and the optical waveguide structure are disposed within the device body. Specifically, the augmented reality device can also be implemented as a near-eye display device or a vehicle-mounted head-up display device, such as AR glasses, AR helmets, or AR-HUDs.

[0135] In the description of this specification, the references to terms such as "an embodiment," "an example," "a specific implementation process," and "an example" indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0136] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An optical waveguide structure, characterized by include: First waveguide, second waveguide; The first waveguide layer and the second waveguide layer are stacked in parallel. The first waveguide includes a first coupling-in region and a first coupling-out region; the first coupling-in region is used to couple an image beam emitted by an optomechanical system into the first waveguide; the first coupling-out region is used to couple an image beam transmitted in the first waveguide out of the first waveguide; the second waveguide includes a second coupling-in region and a second coupling-out region; the position of the second coupling-in region corresponds to the position of the first coupling-out region, so as to couple an image beam coupled out of the first coupling-out region into the second waveguide; the second coupling-out region is used to couple an image beam transmitted in the second waveguide out of the second waveguide to enter the human eye; The image beam emitted by the optomechanical system is obliquely incident into the first coupling region, and the first waveguide layer constrains the image beam to propagate in a first direction by reflection; the first direction is from the first coupling region to the first coupling region, and the reflection includes reflection on four surfaces of the first waveguide layer that are parallel to the first direction. The first waveguide layer includes at least one strip waveguide; the four surfaces include a first surface and a second surface that are parallel to each other, and a third surface and a fourth surface that are parallel to each other. The first and second surfaces constrain the image beam to propagate in the strip waveguide toward the first direction by total internal reflection of the image beam, and the third and fourth surfaces constrain the image beam to propagate in the first direction by reflection of the image beam. The first coupling region is used to couple the image beam transmitted in the strip waveguide, which has an even number of reflections on the third and fourth surfaces, out of the first waveguide layer.

2. The optical waveguide structure of claim 1, wherein, The first coupling region is further used to expand the exit pupil in the first direction; the second coupling region is further used to expand the exit pupil in a second direction different from the first direction.

3. The optical waveguide structure of claim 1, wherein, The outer surfaces of the third and fourth surfaces are provided with reflective film layers.

4. The optical waveguide structure of claim 1, wherein, When the number of strip waveguides is at least two, the at least two strip waveguides are distributed sequentially along a third direction perpendicular to the first direction; wherein, there is an air gap between two adjacent strip waveguides.

5. The optical waveguide structure of claim 4, wherein, At least two of the said strip waveguides are connected at one end and separated at the other end; or, At least two of the strip waveguides are independent of each other and parallel to each other.

6. The optical waveguide structure according to claim 5, characterized in that, When at least two of the strip waveguides are connected at one end and separated at the other end, the thickness and / or width of the strip waveguides are modulated such that the density of the image beams coupled out of the different strip waveguides tends to be consistent. Different strip waveguides propagate image beams with different reflection angles and / or different wavelengths.

7. The optical waveguide structure according to claim 6, characterized in that, In at least two of the strip waveguides, the reflection angle of the image beam propagated by the strip waveguide with the larger thickness or width is smaller than the reflection angle of the image beam propagated by the strip waveguide with the smaller thickness or width, or the wavelength of the image beam propagated by the strip waveguide with the larger thickness or width is smaller than the wavelength of the image beam propagated by the strip waveguide with the smaller thickness or width.

8. The optical waveguide structure according to claim 5, characterized in that, When at least two of the strip waveguides are independent of each other and parallel to each other, each strip waveguide corresponds to a first coupling region; the grating parameters of the first coupling regions of different strip waveguides are different, so as to couple image beams of different wavelengths into different strip waveguides.

9. The optical waveguide structure according to claim 1, characterized in that, The first coupling region is a partitioned first coupling region; the partitioned first coupling region is configured to make the coupling energy of the first coupling regions of different partitions relatively uniform. And / or, The second coupling region is the second coupling region of the partition; The second coupling region of the partition is configured to make the coupling energy of the second coupling regions of different partitions relatively uniform.

10. The optical waveguide structure according to claim 1, characterized in that, The image beam is coupled into the second waveguide by refraction or reflection within the second coupling region; the image beam is coupled out of the second waveguide by refraction or reflection within the second coupling region; or, the image beam is coupled into the second waveguide by diffraction within the second coupling region; the image beam is coupled out of the second waveguide by diffraction within the second coupling region.

11. The optical waveguide structure according to claim 10, characterized in that, The second coupling-in region and the second coupling-out region are connected, and the grating structures of the second coupling-in region and the second coupling-out region have the same period and direction.

12. The optical waveguide structure according to claim 1, characterized in that, Also includes: A correction element is disposed in the beam coupling direction of the second coupling region to modulate the direction of the coupled beam in the second coupling region to achieve coupled beam imaging correction.

Images