Optical waveguide and display device
By introducing coupling gratings, coupling gratings and brightness suppression gratings into the optical waveguide, the cyclic transmission and multi-level reflection of image light are realized, solving the problem of uneven brightness of the optical waveguide image, and improving the uniformity of image display and user experience.
Patent Information
- Application Number
- CN202422242764.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-11
- Publication Date
- 2025-07-22
- Estimated Expiration
- 2034-09-11
AI Technical Summary
In the augmented reality technology, the image brightness distribution of existing diffraction light waveguides affects the display effect and user experience.
A coupling grating, coupling grating and a brightness suppression grating are introduced into the optical waveguide. The image light is transmitted in the optical waveguide in a cyclic manner of partially coupled, partially reflected, partially coupled, and partially reflected. The brightness suppression grating has multiple preset working levels to reflect image light to improve brightness uniformity.
The brightness uniformity of the optical waveguide output image is significantly improved, and the image quality and user experience of the display device are improved.
Smart Images
Figure CN223139892U_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of augmented reality technology, and more particularly, to an optical waveguide and a display device. Background Art
[0002] Currently, diffraction waveguides (DWGs) are widely used in augmented reality (AR) technology to confine light therein and perform total internal reflection transmission. Generally, diffraction waveguides use grating structures to achieve light coupling in and out. Affected by the diffraction characteristics of the gratings, the finally output image will exhibit an uneven brightness distribution.
[0003] Therefore, how to improve the image brightness uniformity of diffraction waveguides is an urgent problem to be solved. Summary of the Utility Model
[0004] This application proposes an optical waveguide and a display device to improve the above-mentioned defects.
[0005] In a first aspect, an embodiment of this application provides an optical waveguide, which includes an input grating and an output grating. Image light is coupled in through the input grating and then coupled out through the output grating. After the image light is transmitted to the output grating area in the optical waveguide, it is transmitted along the working order direction of the input grating in a cyclic manner of partial coupling out, partial reflection, then partial coupling out, and then partial reflection on the output grating to achieve pupil expansion. The optical waveguide further includes at least one brightness suppression grating, which is disposed back-to-back with the output grating on the surface of the optical waveguide. The brightness suppression grating has multiple preset working orders, and is used to receive the image light reflected by the output grating and reflect the image light back to the output grating along the multiple preset working order directions, where the preset working order direction includes the working order direction of the input grating.
[0006] Optionally, the grating parameters of the brightness suppression grating are set based on the grating parameters of the input grating. The grating parameters of the brightness suppression grating are set such that the image light transmitted along the working order direction of the input grating is reflected on the brightness suppression grating, and the propagation direction after reflection is the multiple preset working order directions. The grating parameters of the output grating are set based on the grating parameters of the brightness suppression grating and the grating parameters of the input grating. The grating parameters of the output grating are set such that the image light transmitted along the working order direction of the input grating is partially coupled out and partially reflected on the output grating. The grating parameters of the output grating are further set such that the image light reflected by the brightness suppression grating along the preset working order direction is coupled out on the output grating.
[0007] Optionally, the brightness suppression grating has an incident grating vector, and the output grating has an output grating vector; wherein, the incident grating vector is the same as at least one of the output grating vectors, or the incident grating vector is the same as the superposition result of any two of the output grating vectors.
[0008] Optionally, the area of the brightness suppression grating is greater than or equal to a first minimum coverage area, and the first minimum coverage area is the area of a first light ray coverage area formed on the output grating area when the image light propagates along the working order direction of the incident grating.
[0009] Optionally, the incident grating is a one-dimensional grating, the output grating is a two-dimensional grating, the incident grating is disposed outside the output grating, and the working order direction of the incident grating points from the incident grating to the output grating.
[0010] Optionally, the brightness suppression grating includes a plurality of sub-grating structures, and each sub-grating structure is a one-dimensional grating. The sub-grating structure is configured to propagate the incident image light in the optical waveguide along different preset working order directions; wherein, the grating vector of the sub-grating structure is the same as at least one of the grating vectors of the output grating, or the grating vector of the sub-grating structure is the same as the superposition result of any two of the grating vectors of the output grating; wherein, the grating vectors of each sub-grating structure are different from each other.
[0011] Optionally, the optical waveguide includes a plurality of brightness suppression gratings, the incident grating is a two-dimensional grating, the output grating is a two-dimensional grating, and the incident grating is disposed inside the output grating; wherein, the incident grating has a plurality of the working order directions, and different working order directions point from the incident grating to the output grating along different directions; wherein, each brightness suppression grating corresponds to one of the working order directions and is disposed on the optical waveguide along the corresponding working order direction.
[0012] Optionally, the grating vector of each brightness suppression grating is the same as the grating vector of the output grating.
[0013] Optionally, the area of each brightness suppression grating is greater than or equal to a second minimum coverage area;
[0014] Wherein, when the image light propagates in the optical waveguide along each of the working order directions, a corresponding second light ray coverage area is formed on the output grating, and the second minimum coverage area is the area of the second light ray coverage area corresponding to the working order direction.
[0015] In a second aspect, an embodiment of the present application further provides a display device, including an image source and the optical waveguide as described above. The image source is configured to emit the image light, and the light is propagated by the optical waveguide, coupled out, and then projected onto an observation area.
[0016] Therefore, for an optical waveguide and a display device provided by the present application, the optical waveguide includes an input grating, an output grating, and at least one brightness suppression grating. After the image light is transmitted in the optical waveguide to the output grating area, it is transmitted along the working order direction of the input grating in a cyclic manner of partial coupling out, partial reflection, then partial coupling out, and then partial reflection on the output grating. The brightness suppression grating has a plurality of preset working orders, and is configured to receive the image light reflected by the output grating and reflect the image light back to the output grating along the plurality of preset working order directions. Therefore, the image light diffracted by the brightness suppression grating will carry the energy in the working order direction of the input grating and leave the area where the brightness suppression grating is located, so that the energy of the finally coupled-out light on the optical waveguide within the projection range of the brightness suppression grating is significantly suppressed, and the energy outside the range is significantly increased, improving the brightness uniformity of the output image.
[0017] Other features and advantages of the embodiments of the present application will be described in the subsequent description. Moreover, some of them will become apparent from the description or be understood by implementing the embodiments of the present application. The objectives and other advantages of the embodiments of the present application can be achieved and obtained through the structures specifically pointed out in the written description, claims, and drawings. Description of the Drawings
[0018] To more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without creative efforts.
[0019] Figure 1 (1a - 1b) shows a schematic diagram of the light propagation of a diffractive waveguide and a schematic diagram of the brightness of the output image.
[0020] Figure 2 (2a - 2c) shows a schematic structural diagram of an optical waveguide proposed in an embodiment of the present application.
[0021] Figure 3 (3a - 3b) shows a schematic diagram of the grating vectors of an optical waveguide proposed in an embodiment of the present application.
[0022] Figure 4 (4a - 4b) shows a schematic structural diagram of another optical waveguide proposed in an embodiment of the present application.
[0023] Figure 5 (5a - 5b) shows a schematic structural diagram of another optical waveguide proposed in an embodiment of the present application.
[0024] Figure 6 (6a - 6b) shows a schematic diagram of the grating vector of another optical waveguide proposed in an embodiment of the present application.
[0025] Figure 7 (7a - 7b) shows a schematic structural diagram of yet another optical waveguide proposed in an embodiment of the present application.
[0026] Figure 8 (8a - 8c) shows a schematic diagram of the grating vector of yet another optical waveguide proposed in an embodiment of the present application. Detailed implementation manners
[0027] In order to enable those skilled in the art to better understand the solution of the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Usually, the components of the embodiments of the present application described and shown in the accompanying drawings here can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the present application to be protected, but only represents the selected embodiments of the present application. All other embodiments obtained by those skilled in the art based on the embodiments of the present application without creative efforts fall within the scope of protection of the present application.
[0028] It should be noted that: similar reference numerals and letters denote similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings. At the same time, in the description of the present application, the terms "first", "second", etc. are only used for differential description and cannot be understood as indicating or implying relative importance.
[0029] Please refer to Figure 1 , Figure 1 which shows a schematic diagram of the light propagation of a diffractive waveguide and a schematic diagram of the brightness of the output image. Among them, Figure 1 a shows a schematic diagram of the light propagation of the diffractive waveguide, Figure 1 b shows a schematic diagram of the brightness of the image output by the diffractive waveguide. Specifically, as Figure 1As shown in Fig. a, the diffractive waveguide 100 includes an input grating 101 and an output grating 102. Generally, to simultaneously achieve light coupling out and pupil expansion, the output grating 102 is set as a two-dimensional grating. When light is incident on the two-dimensional grating, multiple diffraction orders are generated, and the propagation directions of the light rays of different diffraction orders are different. Among them, most of the light energy is concentrated in the 0th order reflection order, and this part of the light rays will continue to propagate forward along the original propagation path incident on the two-dimensional grating. Thus, after the light is coupled into the diffractive waveguide 100 through the input grating 101, it propagates in the diffractive waveguide 100 to the output grating 102 and diffracts on the output grating 102. Further, the optical path with the strongest energy is the light propagation path L0 along the working order direction of the input grating, because most of the light energy is concentrated on the propagation path L0, and the light rays on the propagation path L0 always propagate in the form of 0th order reflection, with the least energy loss. Therefore, according to Figure 1 As shown in Fig. b, affected by the diffraction characteristics of the grating, the brightness of the image finally output by the diffractive waveguide 100 shows a distribution that gradually weakens from the main path to both sides, that is, the brightness distribution of the output image is very uneven, seriously affecting the image display effect and user experience.
[0030] Therefore, please refer to Figure 2 , Figure 2 which shows a structural diagram of an optical waveguide proposed in an embodiment of the present application. Among them, Figure 2 Fig. a shows a front view of the structure of the optical waveguide. The optical waveguide 200 includes an input grating 201, an output grating 202, and at least one brightness suppression grating 203. The brightness suppression grating 203 is disposed back-to-back with the output grating 202 on the surface of the optical waveguide 200. Among them, after the image light is transmitted to the area of the output grating 202, it is transmitted along the working order direction of the input grating 201 in a cyclic manner of partial coupling out, partial reflection, then partial coupling out, and then partial reflection on the output grating 202 to achieve pupil expansion. And the brightness suppression grating 203 has multiple preset working orders, which are used to receive the image light reflected by the output grating 202 and reflect the image light back to the output grating 202 along multiple preset working order directions, where the preset working order directions include the working order direction of the input grating.
[0031] As an implementation manner, the input grating 201 is disposed on the first surface S1 of the optical waveguide 200, the output grating 202 is also disposed on the first surface S1 of the optical waveguide 200, and the brightness suppression grating 203 is disposed on the second surface S2 of the optical waveguide 200, and the first surface S1 is opposite to the second surface S2. Further, Figure 2 Fig. b shows a top view of the structure of the optical waveguide along the first surface S1, Figure 2 Fig. c shows a top view of the structure of the optical waveguide along the second surface S2.
[0032] Specifically, the input grating 201 is used to couple the image light L into the optical waveguide 200, and the input grating 201 has its corresponding working order direction. Specifically, when light is incident on the grating, multi-order diffraction occurs. Taking the light incident on the grating as monochromatic light (such as green light) as an example, after the green light is incident on the input grating, it will be diffracted into several lights in different directions (i.e., diffraction orders). Among them, a non-zero diffraction order (such as the +1 order) will meet the total reflection condition of the waveguide layer, and thus enter the waveguide layer for total reflection propagation. Then, this diffraction order is the working order of the input grating, and the working order direction of the input grating is the propagation direction of the light of this diffraction order in the waveguide layer. Further, by precisely controlling grating parameters such as period, duty cycle, groove depth, and sidewall inclination angle, most of the light energy can be concentrated on the working order of the diffractive optical waveguide.
[0033] Exemplarily, the input grating 201 is a grating structure. Further, it can be a one-dimensional grating or a two-dimensional grating. It should be understood that if the input grating 201 is a one-dimensional grating, it has only one working order direction, that is, the image light is coupled into the optical waveguide 200 along one direction. At this time, the image light propagates in the optical waveguide only along the working order direction of one input grating. If the input grating 201 is a two-dimensional grating, it has multiple working order directions and can couple the image light into the optical waveguide 200 along multiple directions. At this time, the image light can also propagate in the optical waveguide along multiple different working order directions of the input grating. In this embodiment, the input grating 201 is taken as a one-dimensional grating for illustration. It should be noted that Figure 2 only the case where the optical waveguide includes a brightness suppression grating 203 and the image light continues to propagate only along one working order direction L1 of the input grating after being coupled into the optical waveguide 200 (corresponding to the input grating 201 being a one-dimensional grating) is shown, and the specific implementation manners of the optical waveguide including multiple brightness suppression gratings and the image light propagating along multiple working order directions of the input grating after being coupled into the optical waveguide can refer to Figure 7 the embodiments shown.
[0034] As an implementation manner, please refer to Figure 3 , Figure 3 which shows a schematic diagram of the grating vector distribution of an optical waveguide proposed in an embodiment of the present application. Among them, Figure 3 a shows a schematic diagram of the grating vector distribution on the first surface of the optical waveguide (i.e., the grating vector distribution diagrams of the input grating and the output grating), Figure 3 b shows a schematic diagram of the grating vector distribution on the second surface of the optical waveguide (i.e., the grating vector distribution diagram of the brightness suppression grating).
[0035] Specifically, for Figure 3 a or Figure 3For the K-vector circle shown in b, the light rays with wave vectors in the inner region of the small ring will transmit through the optical waveguide surface, and only the light rays with wave vectors in the region between the small ring and the large ring will undergo total internal reflection propagation in the optical waveguide. Moreover, the wave vectors of the image light incident on the optical waveguide 200 form a wave vector distribution region A0, and the coupling grating 201 has a coupling grating vector , and the coupling grating vector is used to move the light rays in the wave vector distribution region A0 to the wave vector distribution region A1, that is, the coupling of the image light is realized. Further, the propagation direction of the image light in the optical waveguide 200 is related to the position of the wave vector distribution region in the K-vector circle. Specifically, the propagation direction of the image light in the optical waveguide 200 can be approximately equivalent to the direction from the wave vector distribution region A0 to the wave vector distribution region where it is located. For example, if the image light wave vector is located in the wave vector distribution region A1, then its propagation direction can be approximated as the direction from the wave vector distribution region A0 to the wave vector distribution region A1. Combining Figure 3 a and Figure 2 b, it can be seen that when the image light is coupled into the optical waveguide 200 from the coupling grating 201, the wave vector is moved from the wave vector distribution region A0 to the wave vector distribution region A1 by the coupling grating vector of the coupling grating 201, and the working order direction L1 of the coupling grating after the image light is coupled into the optical waveguide 200 is also approximately the same as the direction from the wave vector distribution region A0 to the wave vector distribution region A1. It should be understood that the image light has a certain field of view (Field of View, FOV) when incident on the optical waveguide, and the complete field of view of the image light can be understood as the wave vector distribution region in the K-vector circle. Any point in the wave vector distribution region corresponds to the light rays incident at a field of view angle. Therefore, the image light coupled into the optical waveguide will have an initial working order direction L1 of the coupling grating corresponding to the incident field of view angle. Exemplarily, in Figure 2 b, the range of the working order direction L1 of the coupling grating after the image light is coupled into the optical waveguide from the coupling grating 201 is shown. Among them, the included angle θ can be determined according to the grating characteristics during the design of the optical waveguide. Specifically, in combination with Figure 3 a, according to the connection line between the center point of the wave vector distribution region A0 before coupling and the boundary end point of the wave vector distribution region A1 after coupling, the size of the included angle θ can be determined, so as to determine the range of the working order direction of the coupling grating of the image light in the Figure 2 b optical waveguide structure.
[0036] Further, as an implementation manner, after determining the grating vector to be designed for a certain grating, the grating parameters including period, duty cycle, groove depth, sidewall inclination angle, etc. can be inversely deduced according to the grating vector, and the grating using the grating parameters has the grating vector that can achieve this effect.
[0037] Therefore, according to the above analysis, when designing the grating parameters of the coupling grating 201 based on the above principle so that the coupling grating 201 has a grating vector as shown in Figure 3 a, the coupling grating 201 can couple in the image light, and the image light has the working order direction L1 of the initial coupling grating. The image light can propagate in the optical waveguide 200 along the working order direction L1 of the coupling grating and be incident on the output coupling grating 202 and the brightness suppression grating 203.
[0038] Furthermore, the image light L coupled in by the coupling grating 201 propagates in the optical waveguide 200 and is incident on the output coupling grating 202 and the brightness suppression grating 203. Among them, the output coupling grating 202 is used to couple out part of the incident image light, reflect part of it, then couple out part of it again, and then reflect part of it again, and continue to propagate in the optical waveguide 200 along the working order direction L1 of the coupling grating. The brightness suppression grating 203 is used to reflect the incident image light on it along at least one preset working order direction L2 to the output coupling grating 202 for coupling out.
[0039] As an implementation manner, the grating parameters of the brightness suppression grating 203 are set based on the grating parameters of the coupling grating 201. The grating parameters of the brightness suppression grating 203 are set so that the image light propagating along the working order direction of the coupling grating 201 is reflected on the brightness suppression grating 203, and the propagation direction after reflection is multiple preset working order directions; the grating parameters of the output coupling grating 202 are set based on the grating parameters of the brightness suppression grating 203 and the grating parameters of the coupling grating 201. The grating parameters of the output coupling grating 202 are set so that the image light propagating along the working order direction of the coupling grating 201 is partially coupled out and partially reflected on the output coupling grating 202. The grating parameters of the output coupling grating 202 are also set so that the image light reflected by the brightness suppression grating 203 along the preset working order direction is coupled out on the output coupling grating 202. According to the above analysis, by setting the grating parameters of the brightness suppression grating 203 and the output coupling grating 202, it is possible to form a closed loop of its grating vector in the K vector circle, that is, to ensure that during the propagation process of the light after being reflected by the brightness suppression grating 203 along multiple preset working orders, it will definitely return to the output coupling grating 202 and be coupled out by the output coupling grating 202.
[0040] As an implementation manner, the output coupling grating 202 is a two-dimensional grating. Please continue to refer to Figure 3 a, the output coupling grating 202 can have as shown in Figure 3The output grating vector K2 shown in a. Further, the output grating vector K2 may include an output grating vector for output and an output grating vector for diffraction. Among them, the grating vector K2 for diffraction is used to move the light rays in the wave vector distribution regions A1 - A6 to other adjacent wave vector distribution regions A1 - A6. For example, Figure 3 One of the grating vectors K2 for diffraction identified in a can move the light rays in the wave vector distribution region A1 to the wave vector distribution region A5. The same applies to the grating vectors not identified in other figures and will not be elaborated here. According to the above analysis of the propagation direction of light rays in the optical waveguide, the light rays in the wave vector distribution regions A1 - A6 will undergo total internal reflection propagation in the optical waveguide 200. And according to the different wave vector distribution regions where the light rays are located, their propagation directions are also different (approximately the direction from the wave vector distribution region A0 to the wave vector distribution region where the light ray is located). That is, the preset working order direction L2 of the light rays in the wave vector distribution regions A2 - A6 is different from the working order direction L1 of the input grating of the light rays in the wave vector distribution region A1, and the preset working order directions L2 of the light rays in the wave vector distribution regions A2 - A6 are all different from each other. Moreover, the output grating 202 may also have an output grating vector K2 for output. The output grating vector K2 for output is used to move the light rays in the wave vector distribution regions A1 - A6 to the wave vector distribution region A0. According to the above analysis, the light rays in the wave vector distribution region A0 will undergo transmission on the surface of the optical waveguide 200, that is, the output of the image light is realized. It should be noted that, Figure 2 The dashed arrows shown in a are used to represent the preset working order direction L2.
[0041] Therefore, according to the above analysis, when designing the grating parameters of the output grating 202 based on the above principle so that the output grating 202 has an output grating vector K2 as shown in Figure 3 a, it can enable the output grating 202 to couple out a part of the incident image light from the optical waveguide 200, and the other part continues to propagate in the optical waveguide 200 along multiple preset working order directions L2 different from the working order direction L1 of the input grating. However, the main function of the output grating 202 is to couple out light rays. That is to say, the coupling - out efficiency of the image light on the output grating 202 is relatively high, and the diffraction efficiency is relatively low compared to the coupling - out efficiency. That is, most of the light rays with energy propagate along the working order direction L1 of the input grating to the output grating 202 and are then coupled out, and a small amount of light rays with energy are propagated in other directions along the preset working order direction L2, resulting in a higher energy of the light rays coupled out along the working order direction L1 of the input grating, and there is an obvious problem of partition in the brightness distribution of the displayed image.
[0042] As an implementation, the brightness suppression grating 203 can be a one-dimensional grating, a two-dimensional grating, or a partitioned modulation grating structure provided with a plurality of sub-region gratings. For example, the entire brightness suppression grating is divided into a plurality of sub-regions, and each sub-region can be either a one-dimensional grating or a two-dimensional grating, and the grating vectors of each sub-region are different.
[0043] Exemplarily, taking the brightness suppression grating as a two-dimensional grating for illustration, please refer to Figure 3 FIG. b. The brightness suppression grating 203 can have a coupling-in grating vector K1 as shown in Figure 3 FIG. b. The coupling-in grating vector K1 is used to move the light rays in the wave vector distribution region A1 to other wave vector distribution regions A3 - A6 that are different from it. Further, Figure 3 FIG. b shows a partial schematic of the possible coupling-in grating vector K1 of the brightness suppression grating 203. It should be noted that according to the different grating structures of the brightness suppression grating 203, the coupling-in grating vector K1 it has is also correspondingly different. Possibly, the coupling-in grating vector K1 can be at least the same as one coupling-out grating vector K2 (for example, Figure 3 in FIG. b, the coupling-in grating vector K1 pointing from the wave vector distribution region A1 to the wave vector distribution region A5 is the same as Figure 3 the coupling-out grating vector K2 pointing from the wave vector distribution region A1 to the wave vector distribution region A5 in FIG. a), and the coupling-in grating vector K1 can also be at least the same as the superposition result of any two coupling-out grating vectors K2 (for example, Figure 3 in FIG. b, the coupling-in grating vector K1 pointing from the wave vector distribution region A1 to the wave vector distribution region A6 is the same as Figure 3 the superposition result of the coupling-out grating vector K2 pointing from the wave vector distribution region A1 to the wave vector distribution region A5 and the coupling-out grating vector K2 pointing from the wave vector distribution region A5 to the wave vector distribution region A6 in FIG. a). More detailed implementation manners can refer to the relevant descriptions of the following embodiments. Here, an example is given with the brightness suppression grating 203 having the Figure 3 coupling-in grating vector K1 shown in FIG. b for illustration. It should be noted that no matter how the grating vectors of the brightness suppression grating are designed, it should be ensured that the grating vectors on the second surface are included in the grating vectors on the first surface, that is, it should be ensured that the grating vectors of the brightness suppression grating are changed from the grating vectors of the coupling-out grating to ensure the clarity and contrast of the output image.
[0044] Furthermore, according to the above analysis of the propagation direction of light in the optical waveguide, it can be known that when the coupling grating vector moves the light to the wave vector distribution regions A3 - A6, the image light will still undergo total internal reflection propagation in the optical waveguide 200. And according to the different wave vector distribution regions where the light is located, its propagation direction is also different (approximately the direction from the wave vector distribution region A0 to the wave vector distribution region where the light is located). That is, the light in the wave vector distribution regions A3 - A6 can still continue to propagate in the optical waveguide 200 along the corresponding preset working order direction L2, and return to the output coupling grating 202 during the propagation process to be output from the optical waveguide on the output coupling grating 202. That is to say, the brightness suppression grating can propagate the incident image light in the optical waveguide 200 along at least one preset working order direction L2, so that the image light is propagated to the output coupling grating 202 for output.
[0045] Therefore, it can be understood that when designing the grating parameters of the brightness suppression grating 203 based on the above principle, so that the brightness suppression grating 203 has a grating vector as shown in Figure 3 b, it can be ensured that the brightness suppression grating 203 can propagate the incident image light in the optical waveguide 200 along at least one preset working order direction L2, so that the image light is propagated to the output coupling grating 202 for output.
[0046] Therefore, combining the above analysis, in this embodiment, by setting a brightness suppression grating on the second surface of the optical waveguide opposite to the first surface, and enabling the brightness suppression grating to propagate the image light incident thereon along the original working order direction of the input coupling grating along at least one preset working order direction different from the working order direction of the input coupling grating in the optical waveguide, so as to be propagated to the output coupling grating for output. That is to say, the image light diffracted by the brightness suppression grating will carry a part of the light energy in the working order direction of the input coupling grating and leave the area surrounded by the brightness suppression grating, so that the output energy of the light finally output on the optical waveguide within the projection range of the brightness suppression grating is significantly suppressed, and the output energy of the light finally output on the optical waveguide outside the projection range of the brightness suppression grating is significantly increased, thereby effectively improving the brightness uniformity of the image output by the optical waveguide.
[0047] As an implementation manner, the shape and area size of the brightness suppression grating 203 on the second surface S2 can be set arbitrarily, as long as it is ensured that the brightness suppression grating 203 can cover the working order direction L1 range of the input coupling grating of the image light. It can be understood that since the brightness suppression grating is set separately and has a small area, when modulating the partition parameters of the brightness suppression grating, it can, to a certain extent, reduce the pressure on design and process caused by the partition modulation of the grating parameters.
[0048] Further, the area of the brightness suppression grating 203 on the second surface S2 is greater than or equal to the first minimum coverage area S3, where the first coverage area S3 is the area of the first light ray coverage region formed by the image light on the output grating 202 when the image light propagates in the optical waveguide 200 along the working order direction L1 of the input grating. Specifically, please refer to Figure 4 , Figure 4 which shows a schematic structural diagram of another optical waveguide proposed in the embodiment of the present application, where Figure 4 a shows a top view of the structure of the optical waveguide along the second surface S2, Figure 4 and b shows a top view of the structure of the optical waveguide along the first surface S1. According to the analysis of the previous embodiments, it can be known that the propagation direction of the light ray after being coupled into the optical waveguide is related to the field of view angle at the time of incidence. Therefore, the working order direction L1 of the input grating of the image light in this embodiment after being coupled into the optical waveguide 200 has a certain range, and the included angle θ can be determined according to the grating characteristics during the design of the optical waveguide. Specifically, it can be combined with Figure 3 a to determine the size of the included angle θ according to the connection line between the center point of the wave vector distribution region A0 before coupling and the boundary end point of the wave vector distribution region A1 after coupling, so as to determine the size of the region that can be enclosed on the output grating 202 when the image light propagates along the working order direction L1 of the input grating in the Figure 4 optical waveguide structure of b, that is, Figure 4 the region enclosed by the working order direction L1 of the input grating and the output grating 202 in b is used as the first light ray coverage region.
[0049] It can be understood that since most of the light rays with energy in the image light coupled into the optical waveguide 200 propagate along the working order direction L1 of the input grating into the output grating 203, that is to say, the third input region 203 should at least cover the coverage range of the output grating 203 when the image light propagates along the working order direction L1 of the input grating, so as to ensure that this part of the light rays with stronger energy are diffracted to other regions, reduce the brightness of the high-energy light ray region and increase the brightness of the low-energy light ray region.
[0050] As an implementation manner, the area of the brightness suppression grating 203 is equal to the first minimum coverage area, and the position of the brightness suppression grating 203 on the second surface S2 corresponds to the position of the output grating 202 on the first surface S1, which ensures that the brightness suppression grating can diffract all the high-energy light rays incident along the working order direction L1 of the input grating to other directions. At the same time, using the brightness suppression grating with the smallest possible area is also beneficial to reducing the design difficulty of the brightness suppression grating, reducing the cost and improving the waveguide efficiency.
[0051] As an implementation manner, please refer to Figure 5 , Figure 5The figure shows a schematic structural diagram of another optical waveguide proposed in the embodiments of the present application. Specifically, the optical waveguide 300 includes an input grating 301, an output grating 302, and at least one brightness suppression grating 303. The input grating 301 is disposed on the first surface S1 of the optical waveguide 300, the output grating 302 is also disposed on the first surface S1 of the optical waveguide 300, and the brightness suppression grating 303 is disposed on the second surface S2 of the optical waveguide 300. The first surface S1 is opposite to the second surface S2. Among them, Figure 5 a shows a top view of the structure of the optical waveguide along the first surface S1, Figure 5 b shows a top view of the structure of the optical waveguide along the second surface S2.
[0052] Specifically, the input grating 301 is a one-dimensional grating, the output grating 302 is a two-dimensional grating, and the input grating 301 is disposed outside the output grating 302. The working order direction L1 of the input grating of the image light after being coupled into the optical waveguide 300 by the input grating 301 points from the input grating 301 to the output grating 302. Further, please refer to Figure 6 , Figure 6 The figure shows a schematic diagram of the grating vector of another optical waveguide proposed in the embodiments of the present application. Among them, Figure 6 a shows a schematic diagram of the grating vector distribution on the first surface of the optical waveguide, that is, the grating vector distribution diagrams of the input grating 301 and the output grating 302. According to Figure 6 a and the description of the above embodiments, the grating vector of the input grating 301 is used to move the light rays in the wave vector distribution region A0 to the wave vector distribution region A1 to realize the coupling of the image light. The grating vector K2 of the output grating 302 is used to move the light rays in the wave vector distribution regions A1 - A6 to other adjacent wave vector distribution regions A1 - A6 to realize the diffractive propagation of the image light incident on the output grating 302 in the optical waveguide, and the grating vector K2 of the output grating 302 is also used to move the light rays in the wave vector distribution regions A1 - A6 to the wave vector distribution region A0 to realize the coupling out of the image light incident on the output grating 302. Therefore, after the image light is coupled into the optical waveguide 300 by the input grating 301, it can propagate along the working order direction L1 of the input grating to the output grating 302 and the brightness suppression grating 303. A part of the image light incident on the output grating 302 is coupled out of the optical waveguide, and the other part continues to propagate in the optical waveguide 300 along multiple preset working order directions L2 different from the working order direction of the input grating.
[0053] Further, the brightness suppression grating 303 includes a plurality of sub-grating structures, and the sub-grating structures are all one-dimensional gratings. Exemplarily, such as Figure 5As shown in Fig. b, the brightness suppression grating 303 may include sub-grating structures 313, 314, 315, and 316. The grating vectors of the sub-grating structures 313, 314, 315, and 316 are the same as the grating vector of at least one output grating 302, or the grating vectors of the sub-grating structures 313, 314, 315, and 316 are the same as the superposition result of the grating vectors of any two output gratings 302, and the grating vectors of the sub-grating structures 313, 314, 315, and 316 are different from each other. Thus, the sub-grating structures 313, 314, 315, and 316 can be used to propagate the image light incident thereon along the working order direction L1 of the input grating in different preset working order directions L2.
[0054] Please refer to Figure 6 Fig. b, Figure 6 Fig. b shows a schematic diagram of the grating vector distribution on the second surface of the optical waveguide, that is, a schematic diagram of the grating vector distribution of the brightness suppression grating 303. Among them, the sub-grating structure 313 has a grating vector K3, the sub-grating structure 314 has a grating vector K4 pointing from the wave vector distribution region A1 to the wave vector distribution region A4, the sub-grating structure 315 has a grating vector K5 pointing from the wave vector distribution region A1 to the wave vector distribution region A5, and the sub-grating structure 316 has a grating vector K6 pointing from the wave vector distribution region A1 to the wave vector distribution region A6. Combining Figure 6 with Fig. a, it is easy to obtain that the grating vector K3 of the sub-grating structure 313 is the same as the grating vector of the output grating 302 pointing from the wave vector distribution region A1 to the wave vector distribution region A3, the grating vector K3 of the sub-grating structure 313 is the same as the grating vector of the output grating 302 pointing from the wave vector distribution region A1 to the wave vector distribution region A3, the grating vector K4 of the sub-grating structure 314 is the same as the superposition result of the grating vector of the output grating 302 pointing from the wave vector distribution region A1 to the wave vector distribution region A3 and the grating vector pointing from the wave vector distribution region A3 to the wave vector distribution region A4, and the grating vector K6 of the sub-grating structure 316 is the same as the superposition result of the grating vector of the output grating 302 pointing from the wave vector distribution region A1 to the wave vector distribution region A5 and the grating vector pointing from the wave vector distribution region A5 to the wave vector distribution region A6. Further, according to the above relevant descriptions of the grating vector and the propagation direction, as Figure 5 shown in Fig. b, the preset working order directions of the image light that can be diffracted and propagated by each sub-grating region are different from each other.
[0055] As an implementation manner, the brightness suppression grating 303 can also be a two-dimensional grating structure. Similarly, the grating vector of the brightness suppression grating 303 can be at least the same as that of one of the output gratings 302, and the grating vector of the brightness suppression grating 303 can also be at least the same as the superposition result of the grating vectors of any two output gratings 302. For the specific implementation manner, reference can be made to Figure 3 the relevant description of the grating vector schematic diagram in
[0056] and details are not elaborated here.
[0057] As an implementation manner, please refer to Figure 7 , Figure 7 which shows a schematic structural diagram of another optical waveguide proposed in the embodiment of the present application. Specifically, the optical waveguide 400 includes an input grating 401, an output grating 402, and a plurality of brightness suppression gratings 403. The input grating 401 is disposed on the first surface S1 of the optical waveguide 400, the output grating 402 is also disposed on the first surface S1 of the optical waveguide 400, and the brightness suppression grating 403 is disposed on the second surface S2 of the optical waveguide 400, and the first surface S1 is opposite to the second surface S2. Among them, Figure 7 Fig. a shows a top view of the structure of the optical waveguide along the first surface S1, Figure 7 and Fig. b shows a top view of the structure of the optical waveguide along the second surface S2.
[0058] Specifically, the input grating 401 is a two-dimensional grating, the output grating 402 is also a two-dimensional grating, and the input grating 401 is disposed inside the output grating 402. The working order direction L1 of the input grating of the image light after being coupled into the optical waveguide 400 by the input grating 401 points from the input grating 301 to the output grating 402. Further, reference can be made to Figure 8 , Figure 8 which shows a schematic diagram of the grating vectors of another optical waveguide proposed in the embodiment of the present application. Among them, Figure 8 Fig. a shows a schematic diagram of the grating vector distribution of the input grating 401 of the optical waveguide. According to Figure 8 Fig. a and the description of the above embodiment, it can be known that since the input grating 401 is a two-dimensional grating, the input grating 401 has a plurality of grating vectors ( Figure 8The dashed arrows in (a) are used to move the light rays in the wave vector distribution region A0 to any one of the wave vector distribution regions A1 - A6 to achieve the coupling-in of the image light. That is to say, the image light coupled into the optical waveguide 400 will have multiple working order directions L1 of the coupling grating, and the working order directions L1 of the coupling grating point from the coupling grating 401 to the output grating 402 in different directions. Figure 8 Figure b shows a schematic diagram of the grating vector distribution of the output grating 402. According to Figure 8 Figure b and the description of the above embodiment, the grating vector K2 of the output grating 402 is used to move the light rays in the wave vector distribution regions A1 - A6 to other wave vector distribution regions A1 - A6 to achieve the diffractive propagation of the image light incident on the output grating 402 in the optical waveguide, and the grating vector K2 of the output grating 402 is also used to move the light rays in the wave vector distribution regions A1 - A6 to the wave vector distribution region A0 to achieve the coupling-out of the image light incident on the output grating 402. Therefore, after the image light is coupled into the optical waveguide 400 through the coupling grating 401, it can propagate along multiple working order directions L1 of the coupling grating to the output grating 402 and the brightness suppression grating 403. A part of the image light incident on the output grating 402 is coupled out of the optical waveguide, and the other part continues to propagate in the optical waveguide 400 along multiple preset working order directions L2 different from the working order directions of the coupling grating.
[0059] Furthermore, referring to Figure 7 Figure b, each brightness suppression grating 403 corresponds to a working order direction L1 of a coupling grating and is disposed on the second surface S2 of the optical waveguide 400 along the working order direction L1 of the coupling grating. As an implementation manner, the area of each brightness suppression grating 403 on the second surface S2 is greater than or equal to the second minimum coverage area, where a second light coverage region is formed on the output grating 402 when the image light propagates in the optical waveguide 400 along each working order direction L1 of the coupling grating, and the second minimum coverage area is the second light coverage region corresponding to the working order direction of the coupling grating. In this embodiment, the relevant description of the second light coverage region can refer to the content about the first light coverage region in the above embodiment. Similarly, the area of each brightness suppression grating 403 on the second surface S2 is equal to the second minimum coverage area, and the position of the brightness suppression grating 403 on the second surface S2 corresponds to the position of the output grating 402 on the first surface S1. Thus, it is ensured that the brightness suppression grating can diffract and propagate all the high-energy light rays incident along the working order direction L1 of the coupling grating to other directions. At the same time, using a brightness suppression grating with as small an area as possible is also beneficial to reducing the design difficulty of the brightness suppression grating, reducing costs, and improving the waveguide efficiency.
[0060] As an implementation manner, the grating vectors of each brightness suppression grating 403 are the same as those of the output grating 402. Specifically, reference can be made to Figure 8 c, Figure 8 Figure c shows a schematic diagram of the grating vector distribution of any one of the brightness suppression gratings 403. According to Figure 8 Figure c and the description of the above embodiments, it can be known that the grating vector K7 of the brightness suppression grating 403 is used to move the light rays in the wave vector distribution regions A1 - A6 to other wave vector distribution regions A1 - A6, so as to realize the diffraction propagation of the image light incident on the brightness suppression grating 403 in the optical waveguide. Therefore, after the image light is coupled into the optical waveguide 400 through the input grating 401, it propagates along the working order direction L1 of multiple input gratings to the brightness suppression grating 403, and the image light incident on the brightness suppression grating 403 can continue to propagate in the optical waveguide 400 along multiple preset working order directions L2 different from the working order direction of the input grating.
[0061] Therefore, for the optical waveguide provided in this implementation manner, the input grating is also set as a two-dimensional grating, so that the image light can be coupled into the optical waveguide along multiple propagation directions, which improves the brightness uniformity to a certain extent. Moreover, by setting the brightness suppression grating, the image light diffracted by the brightness suppression grating can carry the light energy in the working order direction of the input grating and leave the area surrounded by the brightness suppression grating along different directions. This not only significantly suppresses the coupled-out energy of the light finally coupled out from the optical waveguide within the projection range of the brightness suppression grating, but also improves the uniformity of the light coupled out from the optical waveguide outside the projection range of the brightness suppression grating, and further improves the brightness uniformity of the image output by the optical waveguide to a greater extent.
[0062] As an implementation manner, the present application also provides a display device. The display device includes an image source and the optical waveguide as described above. The image source is used to emit image light, and the image light is propagated and coupled out by the optical waveguide and then projected onto the viewing area. Thus, the brightness uniformity of the image output by the display device is significantly improved, enhancing the user experience.
[0063] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, and are not intended to limit them. Although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present application.
Claims
1. An optical waveguide, which includes an input grating and an output grating. Image light is coupled into the optical waveguide through the input grating and then coupled out through the output grating. After the image light is transmitted in the optical waveguide to the output grating region, it is transmitted along the working order direction of the input grating in a cyclic manner of partial coupling out, partial reflection, then partial coupling out, and then partial reflection on the output grating to achieve pupil expansion. It is characterized in that the optical waveguide further includes at least one brightness suppression grating, which is disposed back-to-back with the output grating on the surface of the optical waveguide. The brightness suppression grating has a plurality of preset working orders, and is used to receive the image light reflected by the output grating and reflect the image light back to the output grating along the plurality of preset working order directions. Among them, the preset working order direction includes the working order direction of the input grating.
2. The optical waveguide according to claim 1, wherein The grating parameters of the brightness suppression grating are set based on the grating parameters of the input grating, and the grating parameters of the brightness suppression grating are set so that the image light transmitted along the working order direction of the input grating is reflected on the brightness suppression grating, and the propagation direction after reflection is the plurality of preset working order directions; The grating parameters of the output grating are set based on the grating parameters of the brightness suppression grating and the grating parameters of the input grating. The grating parameters of the output grating are set so that the image light transmitted along the working order direction of the input grating is partially coupled out and partially reflected on the output grating. The grating parameters of the output grating are further set so that the image light reflected by the brightness suppression grating along the preset working order direction is coupled out on the output grating.
3. The optical waveguide according to claim 2, characterized in that, The brightness suppression grating has an input grating vector, and the output grating has an output grating vector; Among them, the input grating vector is the same as at least one of the output grating vectors, or the input grating vector is the same as the superposition result of any two of the output grating vectors.
4. The optical waveguide according to claim 1, characterized in that, The area of the brightness suppression grating is greater than or equal to the first minimum coverage area, and the first minimum coverage area is the area of the first light coverage region formed on the output grating region when the image light propagates along the working order direction of the input grating.
5. The optical waveguide according to claim 1, wherein The input grating is a one-dimensional grating, the output grating is a two-dimensional grating, the input grating is disposed outside the output grating, and the working order direction of the input grating points from the input grating to the output grating.
6. The optical waveguide according to claim 5, characterized in that, The brightness suppression grating includes a plurality of sub-grating structures, and each sub-grating structure is a one-dimensional grating. The sub-grating structure is used to propagate the incident image light in the optical waveguide along different preset working order directions; Among them, the grating vector of the sub-grating structure is the same as at least one of the output grating vectors, or the grating vector of the sub-grating structure is the same as the superposition result of any two of the output grating vectors; Among them, the grating vectors of each sub-grating structure are different from each other.
7. The optical waveguide according to claim 1, characterized in that, The optical waveguide includes a plurality of brightness suppression gratings, the input grating is a two-dimensional grating, the output grating is a two-dimensional grating, and the input grating is disposed inside the output grating; Among them, the coupled-in grating has a plurality of the working order directions, and different working order directions point from the coupled-in grating to the coupled-out grating along different directions; Among them, each brightness suppression grating corresponds to one of the working order directions and is disposed on the optical waveguide along the corresponding working order direction.
8. The optical waveguide according to claim 7, wherein The grating vector of each brightness suppression grating is the same as the grating vector of the coupled-out grating.
9. The optical waveguide according to claim 8, characterized in that, The area of each brightness suppression grating is greater than or equal to the second minimum coverage area; Among them, when the image light propagates in the optical waveguide along each working order direction, a corresponding second light ray coverage area is formed on the coupled-out grating, and the second minimum coverage area is the area of the second light ray coverage area corresponding to the working order direction.
10. A display device, characterized in that, It includes an image source and an optical waveguide as described in any one of claims 1-9, the image source is used to emit the image light, and the image light is propagated by the optical waveguide and then projected onto the observation area.