Inclined auxiliary double-sided display structure

Abstract

The invention relates to a tilt-assisted double-sided display structure. The tilt-assisted double-sided display structure includes an optical waveguide substrate, a coupling-in grating, a coupling-out grating, and an expansion grating. The optical waveguide substrate has a first surface and a second surface, and the first surface and the second surface face each other. The coupling-in grating is arranged on the first face. The out-coupling grating is arranged on the first surface. The expansion grating is arranged on the second face, and a part of the expansion grating is overlapped with the coupling-out grating. According to the inclined auxiliary double-sided display structure, when the optical waveguide substrate is inclined or the incident angle of the incident light irradiated to the coupled-in grating is inclined, unexpected diffraction of the coupled-out light can be avoided through the expansion grating, image pixel missing is avoided, and signals are prevented from being leaked to a free space.

Description

TECHNICAL FIELD

[0001] The present application relates to a dual display structure, in particular to an inclined auxiliary dual display structure. BACKGROUND

[0002] An augmented reality (AR) glass is a kind of display. The AR glass uses augmented reality technology, so that the user can have an immersive experience. The AR glass guides light into the human eye through the microstructure on the surface of the lens. Specifically, the image (light) sent by the image device is projected to the AR glass, and then guided to the human eye from the lens of the AR glass, so that the user can see the image provided by the image device, and at the same time, the user can also see the real world scene, and the image and the real world scene are overlaid to realize the function of augmented reality.

[0003] A diffractive optical waveguide is one of the main ways to realize the AR glass, which enables the user to see the real world while also seeing the virtual image provided by the device, i.e., the virtual information is superimposed in the real world, thereby providing the user with an "augmented" display effect. At present, the diffractive optical waveguide technology is commonly used to realize the augmented reality display scheme. In a transmission medium (e.g., an optical waveguide substrate) with a refractive index greater than the surrounding medium, light can be totally reflected in the transmission medium for non-leakage transmission.

[0004] Figure 1 A conventional single-surface grating optical waveguide structure is shown. Figure 1 The single-surface grating optical waveguide structure 10 includes an optical waveguide substrate 11, a coupling-in grating 12, and a coupling-out grating 13. The coupling-in grating 12 and the coupling-out grating 13 are disposed on the same surface of the optical waveguide substrate 11. The coupling-in grating 12 is a one-dimensional grating, and the coupling-out grating 13 is a two-dimensional grating. The coupling-in grating 12 has a grating direction (not shown in the figure), and the coupling-out grating 13 has two grating directions (not shown in the figure), which can also be referred to as grating vectors. The grating directions of the coupling-in grating 12 and the coupling-out grating 13 form a closed loop. The incident light Lin (image) sent by an image device (not shown in the figure) is coupled into the optical waveguide substrate 11 by the coupling-in grating 12. After passing through the coupling-in grating 12, the incident light Lin forms light Lg that propagates inside the optical waveguide substrate 11 by total reflection. When the light Lg is diffracted by the coupling-out grating 13, a part of the light Lg is coupled out of the optical waveguide substrate 11 to form the coupling-out light Lout. The coupling-out light Lout enters the user's eye (not shown in the figure), so that the user can see the image provided by the image device.

[0005] With the increasing demand for visual quality, the single grating structure has been difficult to meet the needs of people, so the development of double grating structure becomes a trend. Double grating structure can also be called double display structure. Double grating structure refers to the same optical waveguide substrate on both sides of the diffraction (diffraction) optical element, including grating.

[0006] Figure 2 A known double grating structure is shown. Figure 3 A known double grating structure is shown. Figure 2 The top view of the in-coupling grating 22 and the out-coupling grating 23, and the bottom view of the in-coupling grating 24 and the out-coupling grating 25 are shown. Figure 2 The double grating structure 20 includes an optical waveguide substrate 21, an in-coupling grating 22 and an out-coupling grating 23, an in-coupling grating 24 and an out-coupling grating 25. The in-coupling grating 22 and the out-coupling grating 23 are arranged on the upper surface of the optical waveguide substrate 21, and the in-coupling grating 24 and the out-coupling grating 25 are arranged on the lower surface of the optical waveguide substrate 21. The in-coupling gratings 22 and 24 are used to couple the light (image) emitted by the image device (not shown) into the optical waveguide substrate 21. The out-coupling gratings 23 and 25 are used to couple the light out of the optical waveguide substrate 21. The in-coupling grating 22, the out-coupling grating 23, the in-coupling grating 24 and the out-coupling grating 25 are all one-dimensional gratings. As shown in Figure 3 The in-coupling grating 22 includes a plurality of parallel grating lines 221, the out-coupling grating 23 includes a plurality of parallel grating lines 231, the in-coupling grating 24 includes a plurality of parallel grating lines 241, and the out-coupling grating 25 includes a plurality of parallel grating lines 251. The grating direction (or grating vector) D1 of the in-coupling grating 22 is parallel to the grating direction D2 of the out-coupling grating 23. The grating direction D3 of the in-coupling grating 24 is parallel to the grating direction D4 of the out-coupling grating 25. The grating direction D1 of the in-coupling grating 22 and the grating direction D3 of the in-coupling grating 24 have an angle, for example, 60 degrees. The in-coupling grating 22, the out-coupling grating 23, the in-coupling grating 24 and the out-coupling grating 25 have the same grating period T. The grating directions D1, D2, D3 and D4 of the in-coupling grating 22, the out-coupling grating 23, the in-coupling grating 24 and the out-coupling grating 25 form a closed loop, as shown in Figure 4

[0007] ​More specific structure and operation principle of the double-sided grating light guide structure can refer to Chinese patent publication No. CN118759631A. The double-sided grating light guide structure helps to reduce the overall volume of the optical display and expand the eyebox. The eyebox refers to the effective observation area in which the image can be projected to the user's eyes. The double-sided grating light guide structure can achieve excellent results when the projected image (light) is coupled into and out of the light guide substrate at a normal incidence angle or an approximately normal angle. However, the known double-sided grating light guide structure has the disadvantage that when the light guide substrate or the incidence angle of the image (light) is tilted, for example, by more than 30 degrees, the configuration of the wave vectors in the K-space is often destroyed, causing the light to propagate in an unintended manner, for example, resulting in signal loss (image pixel missing) or causing signal leakage to the free space.

[0008] Figure 5 Wave vectors in the K-space when the incidence angle of the light guide substrate or the image (light) is not tilted. Figure 6 Wave vectors in the K-space when the incidence angle of the light guide substrate or the image (light) is tilted. Refer to Figure 2 and Figure 5 When the incidence angle of the light guide substrate 21 or the image (light) is not tilted, the light coupled out by the out-coupling gratings 23 and 25 (such as the red color light R, the green color light G and the blue color light B shown in Figure 4 ) are all located within the circular ring in the K-space, i.e., within the area with a radius of 1.0-1.9. Refer to Figure 2 and Figure 6 When the incidence angle of the light guide substrate 21 or the image (light) is tilted, part of the red color light R, the green color light G and the blue color light B coupled out by the out-coupling gratings 23 and 25 will exceed the area of the circular ring, thus resulting in signal loss (image pixel missing) or causing signal leakage to the free space. As shown in Figure 6 When part of the red color light R, the green color light G and the blue color light B fall into the middle circular area, i.e., fall into the area with a radius less than 1.0, this will result in signal leakage to the free space. When part of the red color light R, the green color light G and the blue color light B exceed the area of the circular ring, i.e., exceed the area with a radius of 1.9, this will result in signal loss (image pixel missing).

[0009] Whether it is the single-sided grating light guide structure 10 of Figure 1 or the double-sided grating light guide structure 20 of Figure 2 , in order to ensure that the incident light Lin (image) provided to the in-coupling grating and the out-coupled light coupled out by the out-coupling grating are parallel or mirror-symmetric, the grating directions of all the gratings on the light guide substrate must form a closed loop, which is referred to as grating vector closure, thus avoiding signal loss (image pixel missing) or causing signal leakage to the free space. SUMMARY

[0010] One of the purposes of the present application is to provide a slanted auxiliary dual-sided display structure suitable for incident light having a slant angle.

[0011] One of the purposes of the present application is to provide a slanted auxiliary dual-sided display structure having an expansion grating.

[0012] The present application provides a slanted auxiliary dual-sided display structure, comprising a light waveguide substrate, a coupling-in grating, a coupling-out grating, and an expansion grating. The light waveguide substrate has a first surface and a second surface, the first surface and the second surface being opposite to each other. The coupling-in grating is disposed on the first surface. The coupling-out grating is disposed on the first surface. The expansion grating is disposed on the second surface, and a portion of the expansion grating overlaps with the coupling-out grating.

[0013] In an embodiment, the grating directions of the coupling-in grating, the coupling-out grating, and the expansion grating are the same.

[0014] In an embodiment, the coupling-in grating and the coupling-out grating have the same first grating period.

[0015] In an embodiment, the expansion grating has a second grating period, and the second grating period is half of the first grating period.

[0016] In an embodiment, the expansion grating comprises a sub-wavelength grating.

[0017] In an embodiment, a light ray diffracted by the coupling-out grating does not produce diffraction when passing through the expansion grating.

[0018] In an embodiment, the coupling-in grating is used to couple an incident light ray into the light waveguide substrate, and the incident light ray forms a first light ray by the coupling grating.

[0019] In an embodiment, the expansion grating is used to diffract the first light ray to generate a second light ray to the coupling-out grating.

[0020] In an embodiment, the coupling-out grating is used to diffract the second light ray to generate a third light ray to the expansion grating.

[0021] In an embodiment, a portion of the third light ray passes through the expansion grating, and another portion of the third light ray is diffracted by the expansion grating back to the coupling-out grating.

[0022] The tilt-assisted double-sided display structure of this application is a double-sided display structure employing diffraction optical elements, and using a subwavelength grating as the expanding grating. The second grating period of the expanding grating is half the first grating period of the coupling-in grating and the coupling-out grating, therefore the second-order diffraction of the coupling-in grating and the coupling-out grating can be matched with the first-order diffraction of the expanding grating. A subwavelength grating refers to a grating period smaller than the critical value at which diffraction occurs for a specific wavelength, thus it will not cause diffraction of light of that wavelength. In other words, the expanding grating ensures that the light coupled out of the optical waveguide substrate will not diffract.

[0023] Furthermore, compared to known technologies that require the use of gratings with different grating orientations to form a closed loop, the grating orientations of the coupling grating, coupling grating, and expansion grating used in the tilt-assisted double-sided display structure of this application are parallel to each other.

[0024] When the optical waveguide substrate is tilted or the incident angle of the incident light illuminating the coupled grating is tilted, the tilt-assisted double-sided display structure of this application can avoid unexpected diffraction of the light coupled out of the optical waveguide substrate by expanding the grating, thereby avoiding signal loss (image pixel loss) and preventing signal leakage into free space. Attached Figure Description

[0025] Figure 1 The traditional single-sided grating waveguide structure is shown.

[0026] Figure 2 A known double-sided grating waveguide structure is shown.

[0027] Figure 3 It shows Figure 2 Top view of the medium raster.

[0028] Figure 4 It shows Figure 3 The closed loop formed by the grating direction in the middle.

[0029] Figure 5 The wave vector in K-space is shown when the incident angle of the optical waveguide substrate or the image (light ray) is not tilted.

[0030] Figure 6 The wave vector in K-space is shown when the incident angle of an optical waveguide substrate or an image (light ray) is tilted.

[0031] Figure 7 An embodiment of the tilt-assisted double-sided display structure of this application is shown.

[0032] Figure 8 It shows Figure 7 A schematic diagram of the structure of the input grating, output grating, and expanded grating.

[0033] Figure 9 The wave vector of K-space when the incident angle of the image (light) of the light waveguide substrate of the inclined auxiliary double-sided display structure of an embodiment of the present application is shown to be inclined.

[0034] Reference numerals: 10, single-sided grating light waveguide structure; 11, light waveguide substrate; 12, in-coupling grating;

[0035] 13, out-coupling grating; 20, double-sided grating light waveguide structure; 21, light waveguide substrate; 22, in-coupling grating; 221, grating line; 23, out-coupling grating; 231, grating line; 24, in-coupling grating; 241, grating line; 25, out-coupling grating; 251, grating line; 30, inclined auxiliary double-sided display structure; 31, light waveguide substrate; 311, first surface; 312, second surface; 32, in-coupling grating; 33, out-coupling grating; 34, expanding grating; 321, first grating line; 331, second grating line; 341, third grating line; B, blue color light; D, grating direction; D1, grating direction; D2, grating direction; D3, grating direction; D4, grating direction; G, green color light; L1, first light; L2, second light; L3, third light; Lg, light; Lin, incident light; Lout, out-coupled light; R, red color light; T, grating period; T1, first grating period; T2, second grating period. DETAILED DESCRIPTION

[0036] Certain terms are used throughout the description and following claims to refer to particular components. As one skilled in the art will appreciate, manufacturers can refer to a component by different names. This document does not intend to distinguish between components that differ in name but not in function. In the following description and in the claims, the terms "include" and "comprise" are used in an open-ended fashion, and thus should be interpreted to mean "including, but not limited to." Also, the term "couple" or "coupled" as used herein is intended to mean either an indirect or direct electrical connection. Thus, if a first device couples to a second device, that connection can be through some other intermediate device (indirect), or that connection can directly connect the first device to the second device. Either form can be referred to as a "coupled" relationship.

[0037] In order to make the above objectives, features and advantages of the present application more clear and understandable, the specific embodiments of the present application are described in detail below with reference to the accompanying drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present application. It will be apparent, however, to one skilled in the art, that the present application can be practiced without some or all of these specific details. In other instances, well known process steps have not been described in detail in order not to unnecessarily obscure the present application. The use of the same reference numerals in different figures indicates similar and / or like components.

[0038] In addition, the terms "first", "second", and the like, if any, are used herein for descriptive purposes only and should not be construed as indicating or implying relative importance or implicating the number of indicated technical features. Thus, a feature defined with "first", "second" may include at least one of the features, explicitly or implicitly. In the description of the present application, the term "plurality" means at least two, for example, two, three, etc., unless otherwise explicitly and specifically limited.

[0039] In the present application, unless otherwise explicitly specified and limited, if there is a description such as "on" or "under" or the like for the first feature to the second feature, it can mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, the first feature "above", "over" and "on" the second feature can be that the first feature is directly above or obliquely above the second feature, or only indicates that the first feature is higher in level than the second feature. The first feature "below", "under" and "under" the second feature can be that the first feature is directly below or obliquely below the second feature, or only indicates that the first feature is lower in level than the second feature.

[0040] It should be noted that if an element is referred to as being "fixed" or "set" to another element, it can be directly on the other element or there can be an intermediate element. If an element is considered to be "connected" to another element, it can be directly connected to the other element or there can be an intermediate element. If present, the terms "vertical", "horizontal", "up", "down", "left", "right", and similar expressions used herein are for illustrative purposes only and do not indicate the only implementation.

[0041] The present application is described below based on examples, but the present application is not limited to only these examples. In the following detailed description of the present application, some specific details are described in detail. The present application can also be fully understood without the description of these details by those skilled in the art. In order to avoid confusion of the essence of the present application, well-known methods, processes, procedures, elements and circuits are not described in detail. In addition, those skilled in the art should understand that the drawings provided herein are for illustrative purposes only and the drawings are not necessarily drawn to scale.

[0042] Figure 7 The inclined auxiliary double-sided display structure of the present application is shown. Figure 7The inclined auxiliary dual-sided display structure 30 includes a light guide substrate 31, an in-coupling grating 32, an out-coupling grating 33, and an expansion grating 34. The light guide substrate 31 has a first surface 311 and a second surface 312, wherein the first surface 311 is opposite to the second surface 312, i.e., the first surface 311 is the upper surface of the light guide substrate 31, and the second surface 312 is the lower surface of the light guide substrate. The in-coupling grating 32 is disposed on the first surface 311 of the light guide substrate 31. The out-coupling grating 33 is disposed on the first surface 311 of the light guide substrate 31. The expansion grating 34 is disposed on the second surface 312 of the light guide substrate 31, and a portion of the expansion grating 34 overlaps with the out-coupling grating 33. The out-coupling grating 33 and the expansion grating 34 work together to simultaneously achieve the functions of light beam expansion and light beam out-coupling. The in-coupling grating 32 is used to couple incident light rays Lin (image) provided by an image device (not shown in the figure) into the light guide substrate 31, wherein the incident light rays Lin form first light rays L1 through the in-coupling grating 32. The expansion grating 34 diffracts the first light rays L1 to generate second light rays L2 to the out-coupling grating 33, i.e., to generate the second light rays L2 incident to the out-coupling grating 33. The out-coupling grating 33 diffracts the second light rays L2 to generate third light rays L3 to the expansion grating 34, i.e., to generate the third light rays L3 incident to the expansion grating 34. A portion of the third light rays L3 forms out-coupling light rays Lout through the expansion grating 34, and another portion of the third light rays L3 is diffracted back to the out-coupling grating 33 by the expansion grating 34. The out-coupling light rays Lout enter the eyes (not shown in the figure) of a user, so that the user can see the image provided by the image device, which is overlaid with the real-world scene to achieve the function of augmented reality.

[0043] Figure 8 Display Figure 7 top view of the gratings. In Figure 7 In an embodiment, the in-coupling grating 32, the out-coupling grating 33, and the expansion grating 34 can be, but are not limited to, surface-relief gratings. The in-coupling grating 32 and the out-coupling grating 33 can be regular gratings, and the expansion grating 34 can be a sub-wavelength grating. The grating directions D of the in-coupling grating 32, the out-coupling grating 33, and the expansion grating 34 are the same, as shown in Figure 8 The in-coupling grating 32 includes a plurality of parallel first grating lines 321, the out-coupling grating 33 includes a plurality of parallel second grating lines 331, and the expansion grating 34 includes a plurality of parallel third grating lines 341. The in-coupling grating 32 and the out-coupling grating 33 have the same first grating period T1, and the expansion grating 34 has a second grating period T2, wherein the second grating period T2 is half of the first grating period T1, as shown in Figure 8The first grating period T1 is equal to or approximately the wavelength of the incident light ray Lin. Since the second grating period T2 of the expansion grating 34 is half of the first grating period T1 of the in-coupling grating 32 and the out-coupling grating 33, the second order diffraction of the in-coupling grating 32 and the out-coupling grating 33 can be matched with the first order diffraction of the expansion grating 34. The expansion grating 34 is a sub-wavelength grating, which means that the grating period is smaller than the critical value of a specific wavelength to produce diffraction, so that the expansion grating 34 does not cause diffraction to the specific wavelength of the light ray. In other words, the light ray diffracted by the out-coupling grating 33 does not cause diffraction when passing through the expansion grating 34.

[0044] Unlike the prior art which needs to use different grating directions of the gratings to form a closed loop, the grating directions D of the in-coupling grating 32, the out-coupling grating 33 and the expansion grating 34 of the tilt-assisted dual-sided display structure 30 of the present application are parallel to each other, i.e. the grating directions D of the in-coupling grating 32, the out-coupling grating 33 and the expansion grating 34 are the same, as shown in Figure 8

[0045] When the optical waveguide substrate 31 of the tilt-assisted dual-sided display structure 30 of the present application is tilted or the incident angle of the incident light ray Lin to the in-coupling grating is tilted, for example, by 30 degrees, the tilt-assisted dual-sided display structure 30 of the present application can avoid the out-coupling light ray Lout coupled out of the optical waveguide substrate 31 from being diffracted unexpectedly by the expansion grating 34, thereby avoiding signal loss (image pixel missing) and preventing signal leakage to the free space.

[0046] Figure 9 The wave vectors of the K-space when the optical waveguide substrate or the incident angle of the image (light ray) of the tilt-assisted dual-sided display structure of the present application is tilted are shown. Figure 9 is the normalized wave vector of the K-space when the optical waveguide substrate 31 of the tilt-assisted dual-sided display structure of the present application is tilted by 30 degrees or the incident angle of the incident light ray Lin is 30 degrees. As shown in Figure 9 When the optical waveguide substrate 31 or the incident angle of the incident light ray Lin of the tilt-assisted dual-sided display structure 30 of the present application is tilted, the red color light R, the green color light G and the blue color light B are all located within the circular ring with a radius of 1.0-1.9 in the K-space. Therefore, the tilt-assisted dual-sided display structure 30 of the present application can indeed avoid signal loss (image pixel missing) and prevent signal leakage to the free space.

[0047] ​The above merely describes the embodiments of the present application, and does not limit the present application in any form. Although the present application has been disclosed as the above embodiments, the present application is not limited by the above embodiments. Any person skilled in the art can make some changes or modifications to the above disclosed technical contents to obtain equivalent embodiments with equivalent changes, as long as the changes or modifications do not depart from the technical solutions of the present application. Any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present application still belong to the scope of the technical solutions of the present application.

Claims

1. A tilt assist dual-sided display structure, comprising: Comprising: an optical waveguide substrate having a first surface and a second surface, wherein the first surface is opposite to the second surface; an in-coupling grating disposed on the first surface; an out-coupling grating disposed on the first surface; and an expansion grating disposed on the second surface; wherein a portion of the expansion grating overlaps with the out-coupling grating. The in-coupling grating, the out-coupling grating and the expansion grating have the same grating direction.

2. The tilt-assisted dual-sided display structure of claim 1, wherein, The in-coupling grating and the out-coupling grating have the same first grating period.

3. The tilt-assisted dual-sided display structure of claim 1, wherein, The expansion grating has a second grating period, which is half of the first grating period.

4. The tilt-assisted dual-sided display structure of claim 3, wherein, The expansion grating comprises a sub-wavelength grating.

5. The tilt-assisted dual-sided display structure of claim 1, wherein, Light rays diffracted by the out-coupling grating do not diffract when passing through the expansion grating.

6. The tilt-assisted dual-sided display structure of claim 1, wherein, The in-coupling grating is configured to couple an incident light ray into the optical waveguide substrate, the incident light ray forming a first light ray by the in-coupling grating.

7. The tilt-assisted dual-sided display structure of claim 1, wherein, The expansion grating is configured to diffract the first light ray to generate a second light ray to the out-coupling grating.

8. The tilt-assisted dual-sided display structure of claim 7, wherein, The out-coupling grating is configured to diffract the second light ray to generate a third light ray to the expansion grating.

9. The tilt-assisted dual-sided display structure of claim 8, wherein, A portion of the third light ray passes through the expansion grating, and another portion of the third light ray is diffracted by the expansion grating back to the out-coupling grating.

10. The tilt-assisted dual-sided display structure of claim 9, wherein, ​

Images