Volume holographic optical waveguide and near-to-eye display equipment

Abstract

The utility model provides a volume holographic optical waveguide and near-to-eye display equipment, and relates to the technical field of augmented reality. The volume holographic optical waveguide comprises a waveguide substrate and a volume holographic grating. The volume holographic grating comprises a first coupling-in grating, a first turning grating, a first coupling-out grating and a second coupling-in grating, the areas where the second turning grating and the second coupling-out grating are located coincide, the areas where the two turning gratings are located coincide, the included angle between the first coupling-in grating and the first direction is a preset positive included angle, and the included angle between the first coupling-in grating and the second direction is a preset negative included angle. The included angle between the first turning grating and the first direction is a preset positive included angle plus 45 degrees, the included angle between the second coupling-in grating and the first direction is a preset negative included angle, the included angle between the second turning grating and the first direction is a preset negative included angle plus 45 degrees, and the preset positive included angle is smaller than the angle bandwidth of the volume holographic grating. The absolute value of the preset negative included angle is smaller than the angular bandwidth of the volume holographic grating. According to the volume holographic optical waveguide, the eye box is enlarged through superposition of the two transmission channels.

Description

Technical Field

[0001] This application relates to the field of augmented reality technology, and more specifically, to a volume holographic waveguide and near-eye display device. Background Technology

[0002] There are two main types of existing volume holographic two-dimensional pupil-expanding waveguides: L-shaped and dual-channel. The L-shaped waveguide includes an input grating, a bend grating, and an output grating, all of which are one-dimensional. The input grating can be placed on the upper right or upper left side of the waveguide lens, conforming to the user's eyeglass wearing habits. The upper left or upper right side corresponds to the position of the temple (left or right eye) of AR (Augmented Reality) glasses, used to house the projection optical engine. The dual-channel waveguide includes an input grating and an output grating. The input grating is one-dimensional, and the output grating is two-dimensional. The dual-channel waveguide can have a larger eyebox size and field of view, but it is only suitable for structures with input from the top and output from the bottom, making it unsuitable for AR glasses.

[0003] Increasing the size of the coupling grating can increase the size of the eyepiece, but for an L-shaped volume holographic two-dimensional pupil-expanding waveguide, the length of the deflection grating must be greater than the width of the coupling grating to ensure that light from different viewing angles can pass through the deflection grating and enter the coupling grating while ensuring that the eyepiece can see the complete field of view. Therefore, if a larger coupling grating width is required, a longer deflection grating is needed, increasing manufacturing difficulty. Moreover, due to the bandwidth limitation of the deflection grating, the field of view is also reduced, resulting in a smaller field of view for the L-shaped volume holographic two-dimensional pupil-expanding waveguide. Utility Model Content

[0004] The purpose of this application is to address the shortcomings of the prior art by providing a volume holographic waveguide and near-eye display device that can increase the size of the eye box.

[0005] To achieve the above objectives, the technical solutions adopted in the embodiments of this application are as follows:

[0006] One aspect of this application provides a volume holographic waveguide, comprising: a waveguide substrate and a volume holographic grating disposed on the surface of the waveguide substrate; the volume holographic grating includes: a first coupling grating, a first bend grating, and a first coupling grating forming a first transmission channel for light, and a second coupling grating, a second bend grating, and a second coupling grating forming a second transmission channel for light; the region where the first coupling grating is located coincides with the region where the second coupling grating is located, the region where the first bend grating is located coincides with the region where the second bend grating is located, the angle between the first coupling grating and a first direction is a preset positive angle, the angle between the first bend grating and the first direction is a preset positive angle plus 45°, the angle between the second coupling grating and the first direction is a preset negative angle, and the angle between the second bend grating and the first direction is a preset negative angle plus 45°, the preset positive angle is less than the angular bandwidth of the volume holographic grating, and the absolute value of the preset negative angle is less than the angular bandwidth of the volume holographic grating.

[0007] Optionally, the absolute value of the preset negative angle is equal to the preset positive angle.

[0008] Optionally, the absolute values ​​of the preset positive angle and the preset negative angle are both less than 20°.

[0009] Optionally, the region where the first coupling grating is located completely overlaps with the region where the second coupling grating is located, and the region where the first bend grating is located completely overlaps with the region where the second bend grating is located.

[0010] Optionally, the periods of the first coupling grating and the second coupling grating are equal, the periods of the first folding grating and the second folding grating are equal, and the periods of the first coupling grating and the second coupling grating are equal.

[0011] Optionally, the center viewing angle of the first transmission channel is denoted as γ1, the center viewing angle of the second transmission channel is denoted as γ2, and the angular bandwidth of the volume holographic grating is denoted as Δγ. Then |γ 1- γ2|>Δγ.

[0012] Optionally, the refractive index of the waveguide substrate is equal to the refractive index of the volume holographic grating.

[0013] In another aspect of the embodiments of this application, a near-eye display device is provided, including an image source and a volume holographic waveguide as described above, wherein the image source is used to emit light rays into a first coupling grating and a second coupling grating of the volume holographic waveguide.

[0014] Optionally, the incident direction of the light is perpendicular to the surface of the waveguide substrate of the volume holographic waveguide.

[0015] Optionally, the first coupling grating, the first bend grating, the first output grating, the second coupling grating, the second bend grating, and the second output grating of the volume holographic waveguide are all disposed on the surface of the waveguide substrate away from or close to the eye box.

[0016] The beneficial effects of this application include:

[0017] This application provides a volume holographic waveguide, comprising: a waveguide substrate and a volume holographic grating disposed on the surface of the waveguide substrate; the volume holographic grating includes: a first coupling grating, a first bend grating, and a first coupling grating forming a first transmission channel for light, and a second coupling grating, a second bend grating, and a second coupling grating forming a second transmission channel for light; the region where the first coupling grating is located coincides with the region where the second coupling grating is located, the region where the first bend grating is located coincides with the region where the second bend grating is located, the angle between the first coupling grating and a first direction is a preset positive angle, the angle between the first bend grating and the first direction is a preset positive angle plus 45°, the angle between the second coupling grating and the first direction is a preset negative angle, and the angle between the second bend grating and the first direction is a preset negative angle plus 45°, the preset positive angle is less than the angular bandwidth of the volume holographic grating, and the absolute value of the preset negative angle is less than the angular bandwidth of the volume holographic grating.

[0018] The aforementioned volume holographic waveguide forms two light transmission channels by simultaneously setting a first coupling grating, a first bend grating, and a first output grating, as well as a second coupling grating, a second bend grating, and a second output grating on the same waveguide substrate. The superposition of these two light transmission channels increases the total coverage area of ​​the first and second output gratings, thus increasing the output area and consequently enlarging the eyepiece. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of an existing L-shaped volume holographic two-dimensional pupil-expanding optical waveguide.

[0021] Figure 2 for Figure 1 A schematic diagram of the transmission of the field of view of a medium-L-shaped volume holographic two-dimensional pupil-expanding optical waveguide in a vector circle;

[0022] Figure 3 This is a schematic diagram of the structure of the volume holographic waveguide provided in the embodiments of this application;

[0023] Figure 4 This is a schematic diagram of the structure of the first transmission channel in the volume holographic waveguide provided in an embodiment of this application;

[0024] Figure 5 for Figure 4 A schematic diagram of the transmission of the field of view of the first transmission channel in the vector circle;

[0025] Figure 6 This is a schematic diagram of the structure of the second transmission channel in the volume holographic waveguide provided in the embodiments of this application;

[0026] Figure 7 for Figure 6 A schematic diagram of the transmission of the field of view of the second transmission channel in the vector circle;

[0027] Figure 8 This is a schematic diagram of light transmission in a volume holographic waveguide provided in an embodiment of this application.

[0028] Icons: 10-L-shaped volume holographic two-dimensional pupil-expanding optical waveguide; 11-waveguide substrate; 12-conventional coupling grating; 13-conventional bend grating; 14-conventional output grating; L-length of conventional bend grating; B-width of conventional output grating; 100-volume holographic optical waveguide; 110-waveguide substrate; 120-coupling grating; 121-first coupling grating; 122-second coupling grating; 130-bend grating; 131-first bend grating; 132-second bend grating; 140-output grating; 141-first output grating; 142-second output grating; - The grating vector of the first coupled grating; - The grating vector of the first angular grating; - The grating vector of the first coupled-out grating; - The grating vector of the second coupled grating; - The grating vector of the second folding grating; - The grating vector of the second coupled grating. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0030] Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. It should be noted that, unless otherwise specified, the various features in the embodiments of this application can be combined with each other, and the combined embodiments are still within the protection scope of this application.

[0031] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0032] In the description of this application, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this application is in use. They are only for the convenience of describing this application 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 on this application. In addition, the terms "first," "second," and "third," etc., are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0033] In the description of this application, it should also be noted that, unless otherwise expressly specified and limited, the terms "set up," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0034] There are two main types of existing volume holographic two-dimensional pupil-expanding waveguides: the L-shaped volume holographic two-dimensional pupil-expanding waveguide 10 and the dual-channel volume holographic two-dimensional pupil-expanding waveguide. Please refer to... Figure 1 The L-shaped volume holographic two-dimensional pupil-expanding optical waveguide 10 includes an optical waveguide substrate 11, a conventional coupling grating 12, a conventional transition grating 13, and a conventional output grating 14 disposed on the surface of the optical waveguide substrate 11. Please refer to the reference. Figure 2 , Figure 2 for Figure 1 A schematic diagram of the transmission of the field of view of the L-shaped volume holographic two-dimensional pupil-expanding optical waveguide 10 in a vector circle. Figure 2 The inner circle radius R1 = 1, the outer circle radius R2 = n, and n is the refractive index of the optical waveguide substrate 11. The grating vector of the conventional coupled grating 12, The grating vector of the traditional folding grating 13, The grating vector of the conventional output grating 14 is shown. The central square block represents the size of the field of view in the air. Through the conventional input grating 12, the field of view in the air is totally internally reflected into the optical waveguide substrate 11, and then transmitted to the conventional output grating 14 through the conventional deflection grating 13. Finally, it is coupled out into the air through the conventional output grating 14. The conventional input grating 12, the conventional deflection grating 13, and the conventional output grating 14 satisfy the condition of a closed vector triangle.

[0035] The L-shaped volume holographic two-dimensional pupil-expanding waveguide 10 is more suitable for use in AR glasses. However, the width B of the traditional output grating of the L-shaped volume holographic two-dimensional pupil-expanding waveguide 10 is difficult to exceed the length L of the traditional bend grating, which limits the size of the eye box. If the size of the eye box is to be increased, the width B of the traditional output grating needs to be increased. Correspondingly, a longer traditional bend grating 13 is required, which increases manufacturing difficulty and reduces the field of view, resulting in a smaller field of view for the L-shaped volume holographic two-dimensional pupil-expanding waveguide 10.

[0036] To address the aforementioned technical problems, one aspect of the embodiments of this application is described below. Figure 3 A volume holographic waveguide 100 is provided, comprising: a waveguide substrate 110 and a volume holographic grating disposed on the surface of the waveguide substrate 110.

[0037] Please refer to the reference. Figure 4 The volumetric holographic grating includes: a first coupling grating 121, a first turning grating 131, and a first coupling grating 141 forming a first transmission channel for light.

[0038] It should be noted that the first coupling grating 121, the first bend grating 131, and the first output grating 141 are disposed on the same surface of the waveguide substrate 110. Please refer to the reference. Figure 5 The first coupling grating 121 is used to couple light propagating in a first direction into the waveguide substrate 110. The first deflection grating 131 is used to expand the pupil of the light coupled into the waveguide substrate 110 by the first coupling grating 121 in a second direction. The first output grating 141 is used to receive the light after it has been expanded by the first deflection grating 131, expand the pupil of the light in a third direction, and then couple the light out of the waveguide substrate 110. The first direction is perpendicular to the surface of the waveguide substrate 110, and the second and third directions are perpendicular to the first direction. The grating vector of the first coupling grating... The grating vector of the first grating The grating vector of the first coupled grating A vector triangle is formed. The light emitted from the image source (such as a projection optical engine) is transmitted within the first transmission channel formed by the first coupling grating 121, the first deflection grating 131, and the first coupling out grating 141.

[0039] Please refer to Figure 3 and Figure 6 The volume holographic grating also includes: a second coupling grating 122, a second turning grating 132, and a second coupling grating 142 forming a second transmission channel for light.

[0040] It should be noted that the second coupling grating 122, the second bend grating 132, and the second output grating 142 are disposed on the same surface of the waveguide substrate 110. Please refer to the reference. Figure 7 The second coupling grating 122 is used to couple light propagating along the first direction into the waveguide substrate 110. The second deflection grating 132 is used to expand the pupil of the light coupled into the waveguide substrate 110 by the second coupling grating 122 in the second direction. The second coupling out grating 142 is used to receive the light after it has been expanded by the second deflection grating 132, expand the pupil of the light in the third direction, and then couple the light out of the waveguide substrate 110. The first direction is perpendicular to the surface of the waveguide substrate 110, and the second and third directions are perpendicular to the first direction. The grating vector of the second coupling grating... The grating vector of the second grating The grating vector of the second coupled grating A vector triangle is formed. The light emitted from the image source (such as a projection optical engine) propagates within the second transmission channel formed by the second coupling grating 122, the second deflection grating 132, and the second output grating 142. It should be noted that the light emitted from the image source propagates within both the first and second transmission channels.

[0041] Please refer to Figures 3 to 7 The regions containing the first coupling grating 121 and the second coupling grating 122 coincide, as do the regions containing the first bend grating 131 and the second bend grating 132. The angle between the grating vector of the first coupling grating and the third direction (positive x-axis) is a preset positive angle; the angle between the grating vector of the first bend grating 131 and the third direction is (preset positive angle + 45°); the angle between the grating vector of the second coupling grating 122 and the third direction is a preset negative angle; and the angle between the grating vector of the second bend grating 132 and the third direction is (preset negative angle + 45°). The preset positive angle is less than the angular bandwidth of the volume holographic grating, and the absolute value of the preset negative angle is less than the angular bandwidth of the volume holographic grating. In this way, the first transmission channel and the second transmission channel can be superimposed to obtain an L-shaped dual-channel volume holographic waveguide 100. By using different channels to expand the same image, the total coverage area of ​​the first coupling grating 141 and the second coupling grating 142 is increased, that is, the coupling area is increased, thereby increasing the size of the eye box.

[0042] It should be noted that the regions containing the first coupling grating 121 and the second coupling grating 122 may completely overlap or partially overlap. If they partially overlap, the overlapping area should be sufficient to ensure the reception of light for a complete image. Similarly, the regions containing the first bend grating 131 and the second bend grating 132 are also similar. The first direction refers to the transmission direction of light before it reaches the first coupling grating 121 and the second coupling grating 122.

[0043] The first coupling grating 121 and the second coupling grating 122 form the coupling grating 120 of the volume holographic waveguide 100, the first bend grating 131 and the second bend grating 132 form the bend grating 130 of the volume holographic waveguide 100, and the first output grating 141 and the second output grating 142 form the output grating 140 of the volume holographic waveguide 100.

[0044] The aforementioned volume holographic waveguide 100 forms two light transmission channels by simultaneously setting a first coupling grating 121, a first bend grating 131, and a first output grating 141, as well as a second coupling grating 122, a second bend grating 132, and a second output grating 142 on the same waveguide substrate 110. The superposition of these two light transmission channels increases the total coverage area of ​​the first output grating 141 and the second output grating 142, thus increasing the area of ​​the output grating 140 and consequently increasing the size of the eyepiece.

[0045] The principle of increased coupling area will be explained next using the trajectory of the image transmission in the central field of view. Figure 3 As shown, for the first transmission channel, OAB is a light transmission path. Vertically incident light in the air is coupled in by the first coupling grating 121 and propagates along the OAB path to the first deflection grating 131. A is the starting point of the transmission path at the first deflection grating 131, and B is the ending point of the transmission path at the first deflection grating 131. Due to the action of the first deflection grating 131, the light transmitted to point A propagates along ANA' to the first coupling grating 141, and is coupled out under the action of the first coupling grating 141 (not shown). The coupled light enters the human eye. Similarly, the light transmitted to point B propagates along BTB' to the first coupling grating 141, and is coupled out under the action of the first coupling grating 141 (not shown), and the coupled light enters the human eye. Therefore, the region where the first transmission channel transmits light to the first coupling grating 141 is the NA'B'T region.

[0046] Similarly, for the second transmission channel, OCD is a light transmission path. Perpendicularly incident light in the air is coupled in by the second coupling grating 122 and propagates along the OCD path to the second deflection grating 132. C is the starting point of the transmission path in the second deflection grating 132, and D is the ending point. Due to the action of the second deflection grating 132, the light transmitted to point C propagates along CMC' to the second coupling grating 142, and is coupled out under the action of the second coupling grating 142 (not shown). The coupled light enters the human eye. Likewise, the light transmitted to point D propagates along DSD' to the second coupling grating 142, and is coupled out under the action of the second coupling grating 142 (not shown), and the coupled light enters the human eye. Therefore, the region where the second emission channel transmits light to the second coupling grating 142 is the MC'D'S region.

[0047] Therefore, the total coverage area of ​​the first output grating 141 and the second output grating 142 is the combination of the areas where the first output grating 141 and the second output grating 142 are located, denoted as: L DO =NA'B'T∪MC'D'S. L DO This represents the coupling area of ​​the volume holographic waveguide 100. For ease of comparison, Figure 3 The paper also provides a schematic diagram of the area of ​​the existing L-shaped volume holographic two-dimensional pupil-expanding waveguide coupling grating, such as... Figure 3 Medium shadow L SO As shown, by Figure 3 It can be seen that L DO >L SO The specific angles of ray transmission along paths ANA', BTB', CMC', and DSD' can be obtained from the defined grating equations without further development. Image transmission from other viewpoints can be obtained through ray tracing simulations after setting the grating parameters. However, the conclusion we can reach regardless is: L DO >L SO The volume holographic waveguide 100 expands the area of ​​the coupling grating 140 by combining the coupling grating regions of the two transmission channels, thereby enabling a larger eyebox.

[0048] Optionally, the region where the first coupling grating 121 is located completely overlaps with the region where the second coupling grating 122 is located, and the region where the first bend grating 131 is located completely overlaps with the region where the second bend grating 132 is located, so as to improve the utilization rate of the waveguide substrate 110 surface and reduce the overall size of the volume holographic waveguide 100.

[0049] Optionally, the center viewing angle of the first transmission channel is denoted as γ1, the center viewing angle of the second transmission channel is denoted as γ2, and the angular bandwidth of the volume holographic grating is denoted as Δγ. Then |γ 1- γ2|>Δγ.

[0050] The volume holographic grating has angle selectivity; when the first and second transmission channels satisfy |γ 1- When γ2|>Δγ, the transmission of the two channels does not generate crosstalk between them.

[0051] Optionally, the absolute value of the preset negative angle is equal to the preset positive angle to simplify the fabrication process of the volume holographic waveguide 100.

[0052] The volume holographic grating is made of photopolymer material. The angular bandwidth of general photopolymer material is less than 20°. Therefore, optionally, the absolute values ​​of the preset positive angle and the preset negative angle are less than 20° respectively, so as to ensure that the light can be transmitted smoothly in the two transmission channels respectively.

[0053] Optionally, the periods of the first coupling grating 121 and the second coupling grating 122 are equal, the periods of the first transition grating 131 and the second transition grating 132 are equal, and the periods of the first coupling grating 141 and the second coupling grating 142 are equal, so as to simplify the fabrication process of the volume holographic waveguide 100.

[0054] Optionally, the refractive index of the waveguide substrate 110 is equal to the refractive index of the volume holographic grating.

[0055] If the refractive index of the waveguide substrate 110 is different from that of the volume holographic grating, the diffracted light passing through the grating will be deflected at a certain angle at the interface between the grating and the waveguide substrate 110, requiring additional calculations during the design process.

[0056] Please refer to Figure 3 and Figure 8 The following section designs the various parameters of the volume holographic waveguide 100, assuming the wavelength of the light is λ, the refractive index of the waveguide substrate 110 and the refractive index of the volume holographic grating are both n, and the total internal reflection angle of the light within the waveguide substrate 110 is θ. t The coupling grating 120, the deflection grating 130, and the output grating 140 are all located on the rear side (on the positive z-axis side) of the waveguide substrate 110. The incident light is incident from the negative z-axis direction to the positive z-axis direction, and the output light is output from the positive z-axis direction to the negative z-axis direction. Figure 8 The diagram shows the transmission of light rays in the central field of view of the volume holographic waveguide 100. The recording and reconstruction processes of the central field of view volume holographic grating are the same. Figure 8 In the middle, reference light When incident perpendicularly into the coupling grating 120, diffracted light S is generated. in Reverse propagation, with an angle θ between the vector and the normal. t θ t> θ C (θ C(This refers to the critical angle for total internal reflection), thus reflecting off the other surface of the waveguide substrate 110, and after one or more reflections (only one is shown as an example in the figure). Incident diffraction grating 130, the diffracted light is diverted and transmitted in the positive x-direction, using S t Let R represent the total internal reflection in the waveguide substrate 110 after several reflections (one example of total internal reflection in the figure), R o After incident on the coupling grating 140, diffracted light S is generated. o From the above analysis, it can be seen that... The parameters of the input grating 120 and the output grating 140 are the same, but the reproduction process is reversed.

[0057] The design method for the grating parameters of the volume holographic waveguide 100 is as follows:

[0058] First, the grating is calculated using a traditional L-shaped volume holographic two-dimensional expanding pupil optical waveguide 10. Then, the grating is rotated to obtain the grating parameters of the volume holographic optical waveguide 100 provided in this application embodiment.

[0059] For the coupled grating 120, the incident light R in and reference light S in The light vector can be represented as:

[0060]

[0061] in

[0062] The grating vector coupled into grating 120 for:

[0063]

[0064] For the folding grating 130, its reference light R t It is the reflection of the object light incident on the grating, and the light vector is represented as:

[0065]

[0066] object light S of 130 folding grating t The light vector can be represented as:

[0067]

[0068] Therefore, the grating vector of the angular grating 130 can be expressed as:

[0069]

[0070] The reference light R of the coupling grating 140 o The object beam from the grating 130 can be represented by the following light vector:

[0071]

[0072] The object light S of the coupling grating 140 o The outgoing light is incident perpendicularly in the opposite direction, and its light vector can be represented as:

[0073]

[0074] The grating vector of the coupled grating 140 can then be expressed as:

[0075]

[0076] The rotation matrix about the z-axis can be represented as:

[0077]

[0078] Where γ is the angle of rotation.

[0079] If γ = 15°, then the grating vectors of the first input grating 121, the first deflection grating 131, and the first output grating 141 of the first transmission channel can be expressed as:

[0080]

[0081] Similarly, setting γ = -15°, the grating vectors of the second input grating 122, the second deflection grating 132, and the second output grating 142 of the second transmission channel can be expressed as:

[0082]

[0083] At this point, we have constructed all the grating parameters. The exposure technique for the volume holographic waveguide 100 is existing technology and will not be described in detail here.

[0084] This embodiment also provides a near-eye display device, including an image source and a volume holographic waveguide 100 as described above, wherein the image source is used to emit light into the first coupling grating 121 and the second coupling grating 122 of the volume holographic waveguide 100.

[0085] This near-eye display device includes the same structure and beneficial effects as the volume holographic waveguide 100 in the foregoing embodiments. The structure and beneficial effects of the volume holographic waveguide 100 have been described in detail in the foregoing embodiments and will not be repeated here.

[0086] When the near-eye display device is AR glasses, it can be adapted to more users without having to consider differences in interpupillary distance. When the near-eye display device is a heads-up display device, it provides a larger vertical eye box to meet the needs of users of different heights to view images.

[0087] Optionally, the incident direction of the light is perpendicular to the surface of the waveguide substrate 110 of the volume holographic waveguide 100.

[0088] Light rays are incident perpendicularly on the first coupling grating 121 and the second coupling grating 122 of the waveguide substrate 11 to be smoothly coupled into the waveguide substrate 110.

[0089] Optionally, the first coupling grating 121, the first bend grating 131, the first output grating 141, the second coupling grating 122, the second bend grating 132, and the second output grating 142 of the volume holographic waveguide 100 are all disposed on the surface of the waveguide substrate 110 facing away from or close to the surface of the eye box. In this way, when light is coupled out, it can be directly directed to the location of the eye box.

[0090] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A volume holographic optical waveguide, characterized in that, include: A waveguide substrate and a volume holographic grating disposed on the surface of the waveguide substrate; the volume holographic grating includes: a first coupling grating, a first bend grating and a first coupling grating forming a first transmission channel for light rays, and a second coupling grating, a second bend grating and a second coupling grating forming a second transmission channel for light rays; The region where the first coupling grating is located coincides with the region where the second coupling grating is located, and the region where the first turning grating is located coincides with the region where the second turning grating is located. The angle between the first coupling grating and the first direction is a preset positive angle, the angle between the first turning grating and the first direction is the preset positive angle plus 45°, the angle between the second coupling grating and the first direction is a preset negative angle, and the angle between the second turning grating and the first direction is the preset negative angle plus 45°. The preset positive angle is less than the angular bandwidth of the volume holographic grating, and the absolute value of the preset negative angle is less than the angular bandwidth of the volume holographic grating.

2. The volume holographic waveguide as described in claim 1, characterized in that, The absolute value of the preset negative angle is equal to the preset positive angle.

3. The volume holographic waveguide as described in claim 1, characterized in that, The absolute values ​​of the preset positive angle and the preset negative angle are both less than 20°.

4. The volume holographic waveguide as described in claim 1, characterized in that, The region where the first coupling grating is located completely overlaps with the region where the second coupling grating is located, and the region where the first bend grating is located completely overlaps with the region where the second bend grating is located.

5. The volume holographic waveguide as described in claim 1, characterized in that, The periods of the first coupling grating and the second coupling grating are equal, the periods of the first bend grating and the second bend grating are equal, and the periods of the first coupling grating and the second coupling grating are equal.

6. The volume holographic waveguide as described in claim 1, characterized in that, Let γ1 be the center viewing angle of the first transmission channel, γ2 be the center viewing angle of the second transmission channel, and Δγ be the angular bandwidth of the volume holographic grating. Then |γ 1- γ2|>Δγ.

7. A near-eye display device, characterized in that, It includes an image source and a volume holographic waveguide as described in any one of claims 1 to 6, wherein the image source is used to emit light into a first coupling grating and a second coupling grating of the volume holographic waveguide.

8. The near-eye display device as described in claim 7, characterized in that, The incident direction of the light is perpendicular to the surface of the waveguide substrate of the volume holographic waveguide.

9. The near-eye display device as described in claim 7, characterized in that, The first coupling grating, the first bend grating, the first output grating, the second coupling grating, the second bend grating, and the second output grating of the volume holographic waveguide are all disposed on the surface of the waveguide substrate away from or close to the surface of the eye box.

Images