Two-dimensional coupling-out grating structure, diffraction optical waveguide and augmented reality display equipment

Abstract

The invention provides a two-dimensional coupling-out grating structure, a diffraction optical waveguide and an augmented reality display device.The two-dimensional coupling-out grating structure comprises a plurality of coupling-out grating units, each coupling-out grating unit comprises a basic structure and at least one additional structure, and the basic structures in the coupling-out grating units are the same; wherein the structures of the at least two coupling-out grating units are different, so that different phase changes are generated when image light rays respectively pass through the at least two coupling-out grating units; the different structures comprise at least one of different relative positions of the basic structures and the additional structures, different numbers of the additional structures and different sizes of the additional structures. According to the diffraction optical waveguide, the additional structure is randomly added in the coupling-out grating unit, so that the random coupling-out grating unit adds random phase movement to the image light, the unexpected interference effect can be improved or even eliminated, and the display effect of the diffraction optical waveguide is improved.

Description

Technical Field

[0001] This application relates to the field of optical technologies, and particularly to a two-dimensional output grating structure, a diffractive optical waveguide, and an augmented reality display device. Background Art

[0002] Augmented reality is a technology that combines the real world and virtual information. An augmented reality display system typically includes a micro projector and an optical display screen. The micro projector provides virtual display content for the augmented reality display system, which is projected into the human eye through the optical display screen. The optical display screen is usually a transparent optical component, so that the user can also see the real world through the optical display screen at the same time.

[0003] A diffractive optical waveguide is an implementation of an optical display screen. Usually, a grating structure is used for pupil expansion. When realizing pupil expansion, there are multiple expansion paths, and then there will be a very large number of light rays with equal optical path differences traveling in the same direction. These light rays will undergo constructive interference or destructive interference when coupled out to the human eye, resulting in bright and dark stripes in the display screen, which greatly affects the display effect. Summary of the Invention

[0004] Embodiments of this application provide a diffractive optical waveguide and an augmented reality display device, which can improve or even eliminate undesired interference effects, thereby enhancing the display effect of the diffractive optical waveguide.

[0005] A two-dimensional output grating structure includes a plurality of output grating units. Each output grating unit includes a basic structure and at least one additional structure, and the basic structures in each output grating unit are the same; wherein, the structures of at least two output grating units are different, so that image light rays generate different phase changes when passing through the at least two output grating units respectively. The different structures include at least one of different relative positions of the basic structure and the additional structure, different numbers of the additional structures, and different sizes of the additional structures.

[0006] Implementably, the cross-sectional shape of the output grating unit is the union of the cross-sectional shape of the basic structure and the cross-sectional shape of the additional structure; or, the cross-sectional shape of the output grating unit is the union of the cross-sectional shape of the basic structure or the cross-sectional shapes of the additional structures.

[0007] Implementably, the additional structures in the output grating unit appear in pairs, and the geometric centers of each pair of additional structures coincide with the geometric center of the basic structure; or, the additional structures are randomly distributed in terms of quantity and position on the side surface of the basic structure.

[0008] Implementably, the infrastructure is a first elliptical structure; the additional structure is the difference set between a second elliptical structure and the first elliptical structure; the centers of the first elliptical structure and the second elliptical structure coincide, and the included angle range between the major axis of the first elliptical structure and the major axis of the second elliptical structure is (0°, 180°).

[0009] Implementably, the size range of the major axis of the second elliptical structure is (0, 0.6*T), and the size range of the minor axis of the second elliptical structure is (0, 0.3*T), where T is the grating period of the two-dimensional output grating structure.

[0010] Implementably, the maximum size of the additional structure protruding from the outer contour of the infrastructure is less than 50 nm.

[0011] Implementably, the diffraction efficiency is the same when the image light passes through the at least two output grating units and undergoes diffraction.

[0012] Implementably, the phase differences are not equal when the image light propagating along every two different paths in the two-dimensional output grating structure converges.

[0013] A diffractive optical waveguide includes: a waveguide substrate, an input grating, and the two-dimensional output grating structure as described in any one of the foregoing items, and the input grating and the two-dimensional output grating structure are disposed on the surface of the waveguide substrate.

[0014] An augmented reality display device includes: a projection optical machine and the diffractive optical waveguide as described in the foregoing, and the projection optical machine is configured to emit the image light.

[0015] The two-dimensional output grating structure provided by the present application adds an additional structure to the infrastructure of the output grating unit, and brings random phase shifts to the image light by the differences in the additional structure itself or the relative relationship between the additional structure and the infrastructure among different output grating units, so as to modulate the phase differences between different interfering lights. When the phase differences change, the interference effects between different lights are averaged or even eliminated, thereby improving the display effect of the diffractive optical waveguide. Further, when the relative relationship between the additional structure itself or the additional structure and the infrastructure among different output grating units is different, it will not cause a change in the diffraction efficiency, and thus will not introduce additional negative performance impacts.

[0016] The diffractive optical waveguide provided by the present application includes the foregoing two-dimensional output grating structure, and thus has the advantages of the foregoing two-dimensional output grating structure. The augmented reality display device provided by the present application includes the foregoing diffractive optical waveguide, and thus has the advantages of the foregoing diffractive optical waveguide. Description of the Drawings

[0017] To more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the accompanying drawings required for the description of the embodiments. Obviously, the accompanying drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can also be obtained based on these drawings.

[0018] Figure 1 Schematic diagram of a diffractive optical waveguide provided by the prior art;

[0019] Figure 2 Schematic diagram of an output grating unit provided by an embodiment of the present application;

[0020] Figure 3 Schematic diagram of an output grating unit provided by another embodiment of the present application;

[0021] Figure 4 Schematic diagram of an output grating unit provided by another embodiment of the present application;

[0022] Figure 5 Schematic diagram of the phase change of image light rays when the additional structure of the output grating unit provided by an embodiment of the present application changes;

[0023] Figure 6 Schematic diagram of a two-dimensional output grating structure provided by an embodiment of the present application;

[0024] Figure 7 Scanning electron micrograph of a two-dimensional output grating structure provided by an embodiment of the present application;

[0025] Figure 8 Schematic diagram of the change in diffraction efficiency when the additional structure of the output grating unit provided by an embodiment of the present application changes.

[0026] Reference signs in the drawings:

[0027] 100: Input structure;

[0028] 200: Two-dimensional output grating structure;

[0029] 210: Output grating unit;

[0030] 211: Basic structure;

[0031] 212: Additional structure. Detailed implementation manners

[0032] To enable those skilled in the art to better understand the solution of this application, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of this application. Obviously, the described embodiments are only a part of the embodiments of this application, rather than all the embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of this application.

[0033] It should be noted that the terms "first", "second", etc. in the description and claims of this application and the above-mentioned drawings are used to distinguish similar objects, and do not necessarily need to describe a specific order or sequence. It should be understood that such data can be interchanged under appropriate circumstances so that the embodiments of this application described here can be implemented in an order different from those illustrated or described here. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products, or devices.

[0034] A diffractive optical waveguide provided by the prior art, refer to Figure 1 , includes an input coupling structure 100 and a two-dimensional output grating structure 200. After the image light rays emitted by the projection optical machine are diffracted by the input coupling structure 100, they are totally reflected and transmitted towards the two-dimensional output grating structure 200. Since the two-dimensional output grating structure 200 has 6 basic diffraction orders, the image light rays can be diffracted and transmitted in different directions, and then coupled out into the human eye. This will cause the image light rays transmitted through multiple optical paths to converge at the same position. The image light rays of these optical paths have the same optical path difference, and constructive interference or destructive interference will occur when they are coupled out into the human eye, resulting in bright and dark stripes appearing in the display screen, which greatly affects the display effect.

[0035] According to one aspect of this application, refer to Figures 2 to 5 , the embodiments of this application provide a two-dimensional output grating structure, which includes a plurality of output grating units. Each output grating unit includes a basic structure and at least one additional structure, and the basic structures in each output grating unit are the same; among them, the structures of at least two output grating units are different, so that the image light rays generate different phase changes when passing through at least two output grating units respectively. The different structures include at least one of the relative positions of the basic structure and the additional structure being different, the number of additional structures being different, and the size of the additional structure being different.

[0036] The two-dimensional output grating structure provided by the present application adds an additional structure to the basic structure of the output grating unit, and brings a random phase shift to the image light through the randomness brought by the relative relationship between the additional structures themselves or between the additional structure and the basic structure among different output grating units, so that different phase differences can be obtained through the random phase shifts brought by the units at different positions of the grating structure to the image light, avoiding the same phase when the image light reaches the same position through different paths, so that the image light propagating along different paths in the two-dimensional output grating structure experiences different phase shifts when converging, modulating the phase difference between different interfering lights. When the phase difference changes, the interference effect between different lights is averaged or even eliminated, thereby improving the display effect of the diffractive optical waveguide.

[0037] Implementably, the cross-sectional shape of the output grating unit is the union of the cross-sectional shape of the basic structure and the cross-sectional shape of the additional structure; or, the cross-sectional shape of the output grating unit is the union of the cross-sectional shape of the basic structure or the cross-sectional shapes of the additional structures.

[0038] Specifically, in the present application, the additional structure is a structure additionally attached to the surface of the basic structure. The two-dimensional output grating structure is a surface relief grating structure, and its basic structure includes a bottom surface, a top surface, and a side surface, and the bottom surface is the contact surface with the waveguide substrate. The additional structure can be attached to the side surface of the basic structure or the top surface of the basic structure. When the additional structure is on the side surface of the basic structure and has the same height as the basic structure, the cross-sectional shape of the output grating unit is the union of the cross-sectional shape of the basic structure and the cross-sectional shape of the additional structure, and the cross-section is the section obtained by intercepting the output grating unit with a plane parallel to the surface of the waveguide substrate. Refer to Figure 2 and 3 , Figure 2 and 3 The left figure in Figure 4 , Figure 4 is an example of the output grating unit. The additional structure is attached to the side surface of the basic structure. The output grating unit includes the basic structure 211 and the additional structure 212. The right figure is the cross-sectional shape of the output grating unit. When the height of the additional structure is not the same as that of the basic structure, with the different heights of the cross-section intercepted, the cross-sectional shape is different, which may be the cross-sectional shape of the basic structure, or the union of the cross-sectional shape of the basic structure and the cross-sectional shape of all or part of the additional structure, or may also be the union of the cross-sectional shapes of all or part of the additional structures, etc. When the additional structure is on the top surface of the basic structure, the cross-sectional shape of the output grating unit is the cross-sectional shape of the basic structure, or the union of the cross-sectional shapes of all or part of the additional structures. Refer to Figure 4 , Figure 4 The left figure in is an example of the output grating unit. The additional structure is attached to the top surface of the basic structure. The output grating unit includes the basic structure 211 and the additional structure 212. The right figure is the cross-sectional shape of the output grating unit.

[0039] In the above examples, a variety of ways to add additional structures to the basic structure to modulate the coupled-out grating unit to add a random phase shift to the image light are provided. Among them, the number of additional structures, the size of the additional structures, and the positional relationship between the additional structures and the basic structure can all affect the amount of phase shift of the image light, making the design of the two-dimensional coupled-out grating structure more flexible and having a higher degree of freedom.

[0040] Furthermore, it can be implemented that the additional structures in the coupled-out grating unit appear in pairs, and the geometric centers of each pair of additional structures coincide with the geometric center of the basic structure; or, the number and positions of the additional structures are randomly distributed on the side of the basic structure.

[0041] Specifically, the additional structure can be a randomly shaped structure or the difference set between a specific-shaped structure and the basic structure. The specific-shaped structure can be, for example, an elliptical structure, a rhombic structure, a square structure, etc. When the additional structure is the difference set between a specific-shaped structure and the basic structure, the relative position between the specific-shaped structure and the basic structure can be controlled so that the additional structures appear in pairs. At this time, the geometric center of each pair of additional structures is the geometric center of the specific-shaped structure, so as to control the relative position between the additional structure and the basic structure. When the additional structure is a randomly shaped structure, it can be randomly distributed in terms of quantity and position on the side of the basic structure to bring a random phase shift to the image light.

[0042] Exemplarily, referring to Figure 2 , the basic structure is a first elliptical structure; the additional structure is the difference set between a second elliptical structure and the first elliptical structure; the center of the first elliptical structure coincides with the center of the second elliptical structure, and the included angle range between the major axis of the first elliptical structure and the major axis of the second elliptical structure is (0°, 180°).

[0043] Among them, the elliptical structure is a columnar structure with an elliptical cross-section. In another embodiment, the basic structure can also be a circular structure, a rhombic structure, a square structure, etc., that is, a columnar structure with a circular, square, rhombic, etc. cross-section. The present application does not limit the structural shape of the basic structure.

[0044] Specifically, the major axis size and minor axis size of the first elliptical structure, the major axis size, minor axis size, and quantity of the second elliptical structure, and the included angle between the major axis of the first elliptical structure and the major axis of the second elliptical structure are all adjustable to adjust the phase shift amount of the coupled-out grating unit for the image light.

[0045] Exemplarily, the size range of the major axis of the second elliptical structure is (0, 0.6*T), and the size range of the minor axis of the second elliptical structure is (0, 0.3*T). Among them, T is the grating period of the two-dimensional coupled-out grating structure. The two-dimensional coupled-out grating structure has grating periods in multiple directions, and T can be any one of them.

[0046] Exemplarily, referring to Figure 3 , the basic structure is an elliptical structure, and the additional structure is a random-shaped structure. Exemplarily, referring to Figure 4 , the basic structure is a first elliptical structure, and the additional structure is a second elliptical structure, and the first elliptical structure and the second elliptical structure are stacked.

[0047] Implementably, the maximum dimension by which the additional structure protrudes beyond the outer contour of the basic structure is less than 50 nm. This can avoid the additional negative performance impacts that may be brought about by an overly large size of the additional structure.

[0048] In the above embodiments, since adding the additional structure to the basic structure is mainly used to add a random phase shift to the image light, the additional structure can also be referred to as an additional phase structure.

[0049] Referring to Figure 5 , this figure shows the phase of the image light after passing through the output grating unit under various combinations of additional phase structure parameters. It can be seen that under different combinations of additional phase structure parameters, the phase shift added by the output grating unit to the image light is different. In this way, it can be applied to the design of the output grating unit 210 in the two-dimensional output grating structure 200 to disrupt the optical path difference of multiple paths of image light and destroy the coherence condition by adding a random phase shift to the image light. Among them, the combination of additional phase structure parameters includes at least one of the number of additional phase structures, the size of the additional phase structures, and the relative position between the additional phase structures and the basic structure.

[0050] Referring to Figure 6 , the output grating unit 210 in the two-dimensional output grating structure shown in this figure adopts the type of output grating unit shown in Figure 2 . By randomly adding additional phase structures to the entire two-dimensional output grating structure 200 and randomly varying the number, size, or positional relationship with the basic structure of the additional phase structures, a random phase shift can be added to the image light, disrupting the optical path difference of multiple paths of image light and destroying the coherence condition, so as to achieve the purpose of eliminating the bright and dark fringes in the display screen and improving the display effect. Figure 6 The output grating unit in the two-dimensional output grating structure in Figure 3 and Figure 4 can also be selected to adopt the types of output grating units shown in

[0051] Referring to Figure 7, this figure is a scanning electron microscope image of a two-dimensional output grating structure. The output grating units 210 in the two-dimensional output grating structure 200 shown in this figure adopt Figure 3 the type of output grating unit shown.

[0052] Implementably, when image light diffracts through at least two output grating units respectively, the diffraction efficiencies are the same and the phase changes are different. Refer to Figure 8 , this figure shows the diffraction efficiencies of image light after passing through the output grating units under various additional phase structure parameter combinations. It can be seen that when changing the additional phase structure parameter combinations, the diffraction efficiency hardly changes. In this way, the phase of the image light diffracted by it can be changed to a certain extent while keeping the diffraction efficiency of the grating structure almost unchanged, improving the display effect of the diffractive optical waveguide without causing negative performance impacts. For example, it does not have an adverse impact on uniformity and efficiency, etc.

[0053] Specifically implementably, the phase differences between the image lights propagating along every two different paths in the two-dimensional output grating structure are not equal when they converge. It can be understood that the image lights propagating along different paths will interfere when they converge. When the phase difference between the interfering image lights is a non-negative integer multiple of π, constructive interference or destructive interference will occur, resulting in the phenomenon of bright or dark stripes. In this application, by designing the additional structures of the output grating units in the two-dimensional output grating structure, the phase differences between any two beams of image lights propagating along different paths are disrupted, so that the interference effects between different image lights are averaged or even eliminated, thereby improving the display effect of the diffractive optical waveguide.

[0054] In summary, the core of this application is to change the phase of the image light after diffraction while not significantly changing the diffraction efficiency of the grating structure, so as to achieve the purpose of adding a random phase shift to the image light, thereby disrupting the optical path differences of multiple paths of image lights, destroying the coherence conditions, and achieving the purpose of eliminating the stripes in the display screen and improving the display effect. Moreover, under colored light, the color reality effect can also be improved.

[0055] According to one aspect of this application, a diffractive optical waveguide is also provided, including: a waveguide substrate, an input grating, and the two-dimensional output grating structure as described in any one of the foregoing. The input grating and the two-dimensional output grating structure are disposed on the surface of the waveguide substrate. The augmented reality display device provided by this application includes the foregoing diffractive optical waveguide, and thus has the advantages of the foregoing diffractive optical waveguide.

[0056] According to one aspect of the present application, an augmented reality display device is further provided, including: a projection optical machine and the diffraction optical waveguide as described above. The projection optical machine is used to emit image light rays. The augmented reality display device can be specifically implemented as augmented reality glasses or an augmented reality helmet, etc. The augmented reality display device provided by the present application includes the aforementioned diffraction optical waveguide, and thus has the advantages of the aforementioned diffraction optical waveguide.

[0057] The above specific implementation manners do not constitute a limitation on the protection scope of the present application. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principle of the present application shall be included within the protection scope of the present application.

Claims

1. A two-dimensional output grating structure, characterized in that, It includes a number of output grating units, each of which includes a basic structure and at least one additional structure, and the basic structures in each output grating unit are the same; among them, the structures of at least two output grating units are different, so that different phase changes occur when image light passes through the at least two output grating units respectively, and the different structures include at least one of different relative positions of the basic structure and the additional structure, different numbers of the additional structures, and different sizes of the additional structures.

2. The two-dimensional output grating structure according to claim 1, wherein The cross-sectional shape of the output grating unit is the union of the cross-sectional shape of the basic structure and the cross-sectional shape of the additional structure; or, the cross-sectional shape of the output grating unit is the cross-sectional shape of the basic structure or the union of the cross-sectional shapes of the additional structures.

3. The two-dimensional output grating structure according to claim 2, wherein The additional structures in the output grating unit appear in pairs, and the geometric centers of each pair of additional structures coincide with the geometric center of the basic structure; Alternatively, the additional structures are randomly distributed in terms of quantity and position on the side of the basic structure.

4. The two-dimensional output grating structure according to claim 3, wherein The basic structure is a first elliptical structure; the additional structure is the difference set between a second elliptical structure and the first elliptical structure; The center of the first elliptical structure coincides with the center of the second elliptical structure, and the included angle range between the major axis of the first elliptical structure and the major axis of the second elliptical structure is (0°, 180°).

5. The two-dimensional output grating structure according to claim 4, characterized in that, The size range of the major axis of the second elliptical structure is (0, 0.6*T), and the size range of the minor axis of the second elliptical structure is (0, 0.3*T), where T is the grating period of the two-dimensional output grating structure.

6. The two-dimensional output grating structure according to claim 3, characterized in that, The maximum size of the additional structure protruding from the outer contour of the basic structure is less than 50 nm.

7. The two-dimensional output grating structure according to claim 1, wherein The diffraction efficiencies are the same when the image light passes through the at least two output grating units and undergoes diffraction respectively.

8. The two-dimensional output grating structure according to claim 1, wherein, The phase differences are not equal when the image light propagating along every two different paths in the two-dimensional output grating structure converge.

9. A diffractive optical waveguide, characterized in that, It includes: A waveguide substrate, an input grating, and the two-dimensional output grating structure according to any one of claims 1-8, and the input grating and the two-dimensional output grating structure are arranged on the surface of the waveguide substrate.

10. An augmented reality display device, characterized in that, The augmented reality display device includes: a projection optical machine and the diffractive optical waveguide according to claim 9, and the projection optical machine is used to emit the image light.

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