Display structure
By designing a display structure including waveguide, input coupling, exit pupil expansion and output coupling structure in augmented reality applications, the problem of insufficient image uniformity in AR applications is solved, and higher image perception quality is achieved.
Patent Information
- Application Number
- CN202380071299.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2022-10-13
- Filing Date
- 2023-09-28
- Publication Date
- 2025-05-13
AI Technical Summary
In augmented reality (AR) applications, it is difficult for the prior art to effectively improve image uniformity in the eye box and affect the perceived quality of the image.
By designing a display structure, the structure includes a waveguide, an input coupling structure, an exit pupil expansion structure and an output coupling structure, the input beam group is coupled, diffraction and output, ensuring uniformity of the image in the output beam group.
This technology significantly improves image perception quality in augmented reality applications by improving image uniformity of output beam groups.
Smart Images
Figure CN119998711A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the field of diffractive optics, and in particular to a display structure and a display device. Background Art
[0002] In augmented reality (AR) applications (e.g., AR glasses), waveguides with properly designed input- and output-coupling structures can be used to create multiple replicas of the exit pupil of a microprojector in front of the user's eyes to form an eyebox. Image uniformity within the eyebox is one of the main factors in perceived image quality in such applications. Summary of the invention
[0003] This summary introduces some concepts in a simplified form that are further described in the detailed description below. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to limit the scope of the claimed subject matter.
[0004] The object of the present invention is to provide a display structure and a display device. The above and other objects are achieved by the features of the independent claims. Further embodiments are obvious from the dependent claims, the description and the drawings.
[0005] According to a first aspect, a display structure includes: a waveguide; an input coupling structure configured to couple an input light beam group into the waveguide as an input coupled light beam group; an exit pupil expansion structure located on a first side of the waveguide and configured to receive the input coupled light beam group and diffract the input coupled light beam group in a plurality of directions to generate a diffracted light beam group; and an output coupling structure located on a second side of the waveguide opposite to the first side and configured to receive at least the diffracted light beam group from the exit pupil expansion structure to output couple at least the diffracted light beam group from the waveguide as an output light beam group and not output couple the input coupled light beam group. The display structure can improve, for example, image uniformity of an image represented by the output light beam group.
[0006] According to a second aspect, a display device includes the display structure according to the first aspect.
[0007] Many of the accompanying features will be more readily understood by reference to the following detailed description taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS
[0008] The embodiments will be described in more detail below with reference to the accompanying drawings, in which:
[0009] Figure 1 A schematic diagram showing a display structure according to an embodiment is shown;
[0010] Figure 2shows a cross-sectional view of a display structure according to an embodiment;
[0011] Figure 3 shows a cross-sectional view of a display structure according to an embodiment;
[0012] Figure 4 shows a cross-sectional view of a display structure according to an embodiment;
[0013] Figure 5 shows a k-space representation of a beam diffracted by a display structure according to an embodiment;
[0014] Figure 6 shows a k-space representation of a beam diffracted by a display structure according to an embodiment;
[0015] Figure 7 shows a k-space representation of a beam diffracted by a display structure according to an embodiment;
[0016] Figure 8 shows a k-space representation of a beam diffracted by a display structure according to an embodiment;
[0017] Fig. 9 shows a k-space representation of a beam diffracted by a display structure according to an embodiment;
[0018] Fig.10 A schematic diagram showing a beam path according to an example; and
[0019] Fig.11 A schematic diagram showing the corresponding relationship between the input beam group and the output beam group.
[0020] In the following, identical reference signs refer to similar or at least functionally equivalent features. DETAILED DESCRIPTION
[0021] In the following description, reference is made to the accompanying drawings, which form a part of the present invention and show the specific contents of the present invention in an illustrative manner in the drawings. It should be understood that other embodiments may be utilized and structural or logical changes may be made without departing from the scope of the present invention. Therefore, the following detailed description should not be regarded as limiting, because the scope of the present invention is defined by the appended claims.
[0022] For example, it should be understood that the disclosure related to the described method may also apply to a corresponding device or system configured to perform the method, and vice versa. For example, if a specific method step is described, the corresponding device may include a unit for performing the described method step, even if such a unit is not explicitly described or shown in the drawings. On the other hand, for example, if a specific instrument is described based on a functional unit, the corresponding method may include steps for performing the described function, even if such steps are not explicitly described or shown in the drawings. In addition, it should be understood that the features of the various example aspects described herein may be combined with each other unless otherwise specifically noted.
[0023] Figure 1 A schematic diagram of a display structure according to an embodiment is shown.
[0024] According to an embodiment, the display structure 100 includes a waveguide 101 .
[0025] The waveguide 101 may include, for example, a substantially planar waveguide. Alternatively or additionally, the waveguide 101 may also include a curved portion. For example, the waveguide 101 may correspond to a lens of augmented reality (AR) glasses.
[0026] The display structure 100 may further include an in-coupling (IC) structure 102 configured to input-couple the input light beam group 110 into the waveguide 101 as an input-coupled light beam group 111 .
[0027] The input light beam set 110 may be generated by, for example, a scanner-based optical engine. The input light beam set 110 may represent an image generated by, for example, such an optical engine. Therefore, the input light beam set 110 may also be referred to as, for example, image-bearing rays / beams, image-bearing rays / beams, and / or the like.
[0028] The input coupling structure 102 may include, for example, a diffraction grating on the surface of the waveguide 101. The input coupling structure 102 may couple the input light beam set 110 into the waveguide 101 via diffraction.
[0029] The display structure 100 may further include an exit pupil expansion (EPE) structure 103 located at a first side of the waveguide 101 and configured to receive the input coupled light beam group 111 and diffract the input coupled light beam group 111 in multiple directions to generate a diffracted light beam group 112 .
[0030] It should be understood that Figure 1The diffracted beam group 112 shown in the embodiment is only illustrative. In actual embodiments, the EPE structure 103 can diffract the input coupling beam group 111 in multiple directions in a more complex manner, and the diffracted beam group 112 as disclosed in this specification can interact with the EPE structure 103 multiple times.
[0031] The display structure 100 may further include an out-coupling (OC) structure 104, which is located on a second side of the waveguide 101 opposite to the first side and is configured to receive at least the diffraction beam group 112 from the exit pupil expansion structure 103, to output-couple at least the diffraction beam group 112 from the waveguide 101 as an output beam group 113, and not output-couple the input coupling beam group 111.
[0032] The output coupling structure 104 may comprise, for example, a diffraction grating on a surface of the waveguide 101. The output coupling structure 104 may couple the diffracted light beam set 112 out of the waveguide 101 via diffraction.
[0033] When the OC structure 104 is configured to not out-couple the set of in-coupled light beams 111 , the OC structure 104 may be configured to not out-couple the set of in-coupled light beams 111 via zero-order or first-order diffraction.
[0034] Output beam set 113 may represent, for example, an expanded version of the image formed by input beam set 110 .
[0035] The in-coupled beam group 111 and the diffracted beam group 112 may be guided inside the waveguide via total internal reflection (TIR).
[0036] The diffracted group beam 112 may interact with the EPE structure 103 and / or the OC structure 104 multiple times before the diffracted group beam 112 is output coupled from the waveguide 101 as the output group beam 113 .
[0037] In this article, a beam of light may also be a ray, a beam of light, a ray of light, etc.
[0038] Since the OC structure 104 does not output-couple the input coupling beam group 111, the EPE structure 103 and / or the OC structure 104 can be positioned in a flexible manner. For example, the input coupling beam group 111 from the IC structure 102 can be directly directed to the OC structure 104 and / or the EPE structure 103 without reducing the imaging uniformity of the output coupling image due to the output coupling of the input coupling beam group 111 by the OC structure 104.
[0039] Due to the overlying EPE structure 103, the display structure 100 can allow additional control over the diffraction efficiency and phase over the area of the OC structure 104, which can help improve image uniformity over the eye box. In addition, due to the interaction between the EPE structure 103 and the OC structure 104, the light can take multiple paths within the waveguide 101, so possible interference effects can be reduced. The multiple paths that the light can take can result in an averaging of any phase differences, so interference effects can be reduced.
[0040] According to an embodiment, the input coupling structure 102 comprises a one-dimensional input coupling diffraction grating and the output coupling structure 104 comprises a one-dimensional output coupling diffraction grating.
[0041] According to an embodiment, the exit pupil expansion structure 103 comprises a two-dimensional diffraction grating.
[0042] According to an embodiment, the exit pupil expansion structure 103 includes a two-dimensional hexagonal diffraction grating or a two-dimensional rectangular diffraction grating.
[0043] In this article, the diffraction grating may also be referred to as a surface relief grating, a grating, a diffraction grating, etc.
[0044] According to an embodiment, the exit pupil expansion structure 103 is configured to diffract the in-coupled beam set via zeroth and first order diffraction.
[0045] According to an embodiment, IC structure 102 is configured to diffract input light beam set 110 via zeroth and first order diffraction.
[0046] According to an embodiment, the OC structure 104 is configured to diffract the set of diffracted beams 112 via zeroth and first order diffraction.
[0047] It should be understood that Figure 1 The geometric shape of the display structure 100 shown in the embodiment is merely exemplary, and the display structure 100 may be implemented in various other ways.
[0048] According to an embodiment, a display device includes a display structure 100 .
[0049] The display device may include a scanner based optical engine, such as a laser scanning optical engine, for directing the set of input light beams to the input coupling structure 102. Other types of optical engines may also be used.
[0050] The display device may be implemented as, for example, a see-through display device.
[0051] The display device may be implemented as, for example, a head-mounted display device.
[0052] Figure 2 A cross-sectional view showing a display structure according to an embodiment is shown.
[0053] According to an embodiment, the exit pupil expansion structure 103 covers a first portion of the waveguide 101, the output coupling structure 104 covers a second portion of the waveguide 101, and the first portion and the second portion at least partially overlap.
[0054] Herein, a portion of the waveguide 101 may refer to any portion of the waveguide 101 in the plane of the waveguide 101, such as a subsection of the waveguide 101. Thus, a portion may include both the first side 201 and the second side 202 of the waveguide 101.
[0055] In this context, overlap may refer to overlap in a dimension along the plane of the waveguide 101 .
[0056] For example, in Figure 2 In some embodiments, the first portion and the second portion are substantially identical. In other embodiments, the first portion and the second portion may only partially overlap. Figure 2 Compared to the embodiments of the present invention, the first portion and / or the second portion may be offset, and / or the second portion may be smaller than the first portion.
[0057] The overlap of the EPE structure 103 and the OC structure 103 can allow additional control over the intensity and phase distribution of light reaching the OC structure 104, because the diffraction efficiency and phase can be adjusted relative to the position at the EPE structure 103 (and the OC structure 104). The diffraction efficiency and phase can be adjusted relative to the position by, for example, adjusting the local characteristics of the diffraction grating of the EPE structure 103 and / or the diffraction grating of the OC structure 104.
[0058] exist Figure 2 In the embodiment of FIG. 1 , the IC structure 102 is located on the first side 201 of the waveguide 101 .
[0059] Figure 3 A cross-sectional view of a display structure according to an embodiment is shown.
[0060] exist Figure 3 In the embodiment of FIG. 1 , the IC structure 102 is located on the second side 202 of the waveguide 101 .
[0061] In any of the embodiments disclosed herein, the OC structure 104 can be configured to couple the diffracted light beam group 112 out of the waveguide 101 as the output light beam group 113 to the first side 201 or the second side 202. Therefore, the side at which the OC structure 104 is configured to couple the diffracted light beam group 112 out of the waveguide 101 does not depend on which side of the waveguide 101 the OC structure 104 is located.
[0062] In any of the embodiments disclosed herein, the IC structure 102 can be configured to input-couple the input light beam group 110 into the waveguide 101 as the input-coupled light beam group 111 from the first side 201 or the second side 202 of the waveguide 101. Thus, the side of the waveguide 101 on which the IC structure 102 is configured to input-couple the input light beam group 110 does not depend on which side of the waveguide 101 the IC structure 102 is located.
[0063] In any embodiments disclosed herein, the IC structure 102 and / or the OC structure 104 may include a reflective or transmissive diffraction grating. The side of the OC structure 104 configured to output-couple a diffracted light beam group 112 from the waveguide 101 may be the same side or the opposite side as the side of the IC structure 102 configured to input-couple the input light beam group 110. Therefore, a projector generating an image corresponding to the input light beam group 110 may be located on the same side or the opposite side as the eyes of a user viewing the image corresponding to the input light beam group 113.
[0064] Figure 4 A cross-sectional view of a display structure according to an embodiment is shown.
[0065] According to an embodiment, the first portion surrounds the second portion.
[0066] When the first portion surrounds the second portion, the EPE structure 103 may be configured to extend the image corresponding to the input light beam group 110 to the entire area of the OC structure 104 .
[0067] When the first part does not surround the second part, the EPE structure 103 can still extend the image corresponding to the input beam group 110 to the entire area of the OC structure 104 because the EPE structure 103 can extend the image to at least some areas outside the first part, such as areas close to the edge of the first part.
[0068] In some embodiments, the first portion corresponds to the second portion. Thus, the EPE structure 103 and the OC structure 104 may have the same shape and position.
[0069] According to an embodiment, the input coupling structure 102 is located at the second side 202 of the waveguide 101 and covers a third portion of the waveguide 101 , and the first portion also surrounds the third portion.
[0070] For example, in Figure 4 In an embodiment, the first portion surrounds the second portion and the third portion.
[0071] In some embodiments, the first portion may cover the entire waveguide 101. In some embodiments, the first portion may cover a smaller area.
[0072] Figure 5A k-space representation of grating vectors and transitions in a waveguide is shown according to an embodiment.
[0073] According to one embodiment, the input coupling structure 102 includes a first one-dimensional diffraction grating having a first grating vector 501, the output coupling structure includes a second one-dimensional diffraction grating having a second grating vector 502, and the exit pupil expansion structure includes a two-dimensional hexagonal diffraction grating having a third grating vector 503, the angle between the first grating vector 501 and the third grating vector 503 is substantially 30 degrees or substantially 90 degrees, and the length of the third grating vector 503 is substantially 1.7 times the length of the first grating vector 501.
[0074] For example, in Figure 5 In the embodiment of FIG. 5 , two grating vectors are shown that can correspond to the third grating vector 503. The angle between the two vectors is substantially 60 degrees and their lengths are substantially equal. Therefore, they form a hexagonal lattice.
[0075] Additionally or alternatively, the length of the third grating vector 503 may be substantially the same as the length of the first grating vector 501. For example, the length of the third grating vector 503 may be substantially 1.5-1.9, 1.6-1.8, 1.65-1.75 or 1.675-1.725 times the length of the first grating vector 501.
[0076] The angle between the first grating vector 501 and the third grating vector 503 may be, for example, substantially 29.5-30.5 degrees or substantially 89.5-90.5 degrees.
[0077] According to one embodiment, the angle between the first grating vector 501 and the second grating vector 502 is substantially 60 degrees.
[0078] The angle between the first grating vector 501 and the second grating vector 502 may be, for example, substantially 59.5-60.5 degrees.
[0079] According to an embodiment, the length of the first grating vector 501 is substantially equal to the length of the second grating vector 502 .
[0080] When the IC structure 102 includes a one-dimensional diffraction grating, the OC structure 104 includes a one-dimensional diffraction grating, and the EPE structure 103 includes a two-dimensional hexagonal diffraction grating, the direct output coupling between the IC structure 102 and the OC structure 104 can be reduced or even blocked. This can allow the IC structure 102 to be positioned more flexibly relative to the OC structure 104. Therefore, the input coupling beam group 111 from the IC structure 102 can be directly pointed to the OC structure 104. In addition, the EPE structure 103 does not output couple the diffraction beam group 112. Therefore, for output coupling, the input coupling beam group 111 needs to interact with the EPE structure 103 at least once, and then the resulting diffraction beam group 112 needs to interact with the OC structure 104.
[0081] The interaction between the hexagonal EPE structure 103 and the one-dimensional OC structure 104 can allow the diffracted beam group 112 to take a greater number of paths. Figure 5 As can be seen in the embodiment of FIG. 1 , before the diffracted beam group 112 is output coupled by the OC structure 104 as the output beam group 113, the diffracted beam group 112 can interact with the EPE structure 103 and the OC structure 104 in various ways. This can reduce interference effects in the image formed by the output beam group 113.
[0082] Herein, the hexagonal diffraction grating may refer to a diffraction grating having a two-dimensional hexagonal lattice structure. The angle between grating vectors of the hexagonal lattice is 60°, and the grating vectors have the same length.
[0083] It should be understood that the manufacture of the lattice structure may be limited by the manufacturing method used. Therefore, any lattice having the aforementioned characteristics within the tolerance range of the manufacturing method used can be considered a hexagonal lattice.
[0084] The grating vector may represent the periodicity and orientation of the corresponding diffraction grating. For example, the diffraction grating may include ridges / grooves, and the grating vector may correspond to the spatial periodicity and orientation of these ridges / grooves. The structure of these ridges / grooves defines the diffraction caused by the diffraction grating. The length of the grating vector may be inversely proportional to the spatial period of the corresponding diffraction grating in the direction of the grating vector. Thus, the ridges / grooves of the diffraction grating may extend in a direction perpendicular to the grating vector.
[0085] It should be understood that the grating vector of a particular diffraction grating can be selected in various ways. For example, for a one-dimensional grating, there may be two possible grating vectors pointing in opposite directions that describe the same one-dimensional grating. Therefore, in some embodiments disclosed herein, the grating vectors may be shown as bidirectional arrows.
[0086] The two-dimensional hexagonal diffraction grating of the EPE structure 103 may include two grating vectors. One of the two grating vectors of the two-dimensional hexagonal diffraction grating may form an angle of 30 degrees with the first grating vector 501. The other of the two grating vectors of the two-dimensional hexagonal diffraction grating may form an angle of 90 degrees with the first grating vector 501. Therefore, the angle between the two grating vectors of the two-dimensional hexagonal diffraction grating may be 60 degrees.
[0087] Herein, the annular guided propagation domain 510 may refer to a portion of k-space where a light beam is guided inside the waveguide 101 . Figure 5 The embodiment of FIG. 5 shows an example of a ring-shaped guided propagation domain 510 .
[0088] Each k vector in the k-space can represent the propagation direction of the light beam in the waveguide 101. The magnitude of each k vector corresponds to the wave number k. The k vector can be expressed as where n is the refractive index of the medium of the waveguide 101, is a unit vector pointing in the direction of propagation of the k-vector. k can also be called the normalized k-vector.
[0089] The waveguide 101 can guide a light beam with a specific k-vector via total internal reflection (TIR). The coupling domain 511 corresponds to a k-vector that does not have sufficient x and / or y components to be guided within the waveguide 101 via TIR. Here, the x-axis and the y-axis are located in the plane of the waveguide 101, while the z-axis is along the thickness direction of the waveguide 101. For such a light beam, the angle between the light beam and the surface of the waveguide 101 is not sufficient to cause TIR as specified by Snell's law. The K-vector within the annular guided propagation domain 510 has sufficient x and / or y components to be guided within the waveguide 101 via TIR. The K-vector at the outer circumference of the annular guided propagation domain 510 corresponds to a light beam propagating along the plane of the waveguide 101, that is, such a light beam does not have any z-component. The radius of the coupling domain 511 can be 1 and the radius of the annular guided propagation domain 510 can be n.
[0090] The input beam group 110 may be associated with a corresponding k-vector 505. The input coupling structure 102 may couple the input beam group 110 into the waveguide 101 as an input coupled beam group 111. The input coupled beam group 111 may be associated with an input coupled k-vector group 506.
[0091] For example, in Figure 5In the embodiment of FIG. 5 , the k-vector 505 corresponding to the input beam group 110 is located in the coupling domain 511 of the k-space. The input coupling structure 102 can couple the input beam group 110 into the waveguide 101 as the input coupled beam group 111 associated with the input coupled k-vector group 506 .
[0092] The input coupling structure 101 may include, for example, a diffraction grating that can couple the input light beam group 110 into the waveguide 101. Figure 5 As shown in the embodiment, since the input coupling k-vector group 506 is located inside the annular guided propagation domain 510, the corresponding input coupling light beam group 111 is guided inside the waveguide 101 via TIR.
[0093] Different k-vectors in the input coupling k-vector set 506 can correspond to, for example, different colors and / or different portions of an image represented by the input beam set 110. For example, the input beam set 110 can include green, blue, and red channels. Since the wavelength of each such color channel is different, each color can occupy a different portion of k-space. For example, in Figure 5 In the embodiment of FIG. 5 , each of the three rectangles in the input coupling k-vector group 506 may correspond to a color channel of the image represented by the input beam group 110. Figure 5 In the embodiment of FIG. 1 , for the sake of clarity, only the possible transformation of one of the rectangles is illustrated.
[0094] In this context, a transition in k-space may correspond to an interaction of a group of light beams with a diffraction grating. This interaction may cause the group of light beams to propagate in one or more directions different from before the interaction. The change in propagation direction may be observed as a translation along the transition in k-space.
[0095] In the embodiments disclosed herein, some transitions correspond to grating vectors and are therefore illustrated using grating vectors in k-space. Figure 5 In the embodiment of FIG. 5 , the grating vectors 501 , 502 , 503 also correspond to possible transitions in k-space.
[0096] The EPE structure 103 can receive the input coupled beam group 111 and diffract the input coupled beam group 111 in multiple directions, thereby producing a diffracted beam group 112. In terms of k-space representation, this can be shown as the input coupled k-vector 506 is transformed in k-space along the transitions 503, 523 corresponding to the diffraction caused by the EPE structure 103, thereby producing a diffracted k-vector 507.
[0097] The output coupling structure 104 can receive the diffracted beam group 112 from the EPE structure 103 and couple the diffracted beam group 112 out of the waveguide 101 as the output beam group 113. In terms of k-space representation, this can be shown as a transition from the propagation domain 510 to the coupling domain 511 along the second grating vector 502. For example, in Figure 5 In the embodiment of FIG. 5 , two possible diffraction k-vectors 507 in the propagation domain 510 from which the OC structure 104 may couple out the diffracted beam set 112 are shown.
[0098] When interacting with the OC structure 104, the diffracted beam set 112 is not always outcoupled. Figure 5 In the embodiment of FIG. 5 , transition 522 corresponds to diffraction caused by OC structure 104 that is not coupled out of diffracted beam set 112 .
[0099] According to one embodiment, the guided propagation domain 510 surrounds the coupling domain 511 .
[0100] Although in some embodiments disclosed herein, the k-vector 505 corresponding to the input beam group 110 is located at the origin of k-space, this may not be the case for all embodiments. For example, if the input beam group 110 is not perpendicular to the waveguide 101, the k-vector 505 corresponding to the input beam group 110 may be located in some other part of the coupling domain 511.
[0101] Figure 6 A k-space representation of grating vectors and transitions in a waveguide is shown according to an embodiment.
[0102] exist Figure 6 In the embodiment of the present invention, the IC structure 102 includes a one-dimensional diffraction grating, the OC structure 104 includes a one-dimensional diffraction grating, and the EPE structure 103 includes a two-dimensional rectangular diffraction grating.
[0103] According to one embodiment, the input coupling structure comprises a first one-dimensional diffraction grating having a first grating vector 601, the output coupling structure comprises a second one-dimensional diffraction grating having a second grating vector 602, the exit pupil expansion structure comprises a two-dimensional rectangular diffraction grating having a third grating vector 603 and a fourth grating vector 604, and the first grating vector and the second grating vector correspond to half diagonals of a rectangle defined by the third grating vector 603 and the fourth grating vector 604.
[0104] In this document, a half-diagonal may refer to half of the diagonal of a rectangle. Figure 6 The embodiment of FIG. 4 shows an example of a half-diagonal line, where the second grating vector 602 corresponds to the half-diagonal line of the rectangle formed by the third grating vector 603 and the fourth grating vector 604.
[0105] According to an embodiment, the length of the first grating vector 601 is substantially equal to the length of the second grating vector 602 .
[0106] When the IC structure 102 includes a first one-dimensional diffraction grating, the OC structure 104 includes a second one-dimensional diffraction grating, and the EPE structure 103 includes a two-dimensional rectangular diffraction grating, the light needs to interact with all three gratings before the light can be output coupled from the waveguide 101. Therefore, the OC structure 104 does not output couple the input coupling beam group 111. Since the input coupling beam group 111 can be directly pointed to the OC structure 104 without the OC structure 104 output coupling the input coupling beam group 111, this can allow the IC structure 102 to be flexibly positioned relative to the OC structure 104.
[0107] When the EPE structure 103 includes a two-dimensional rectangular diffraction grating, the EPE structure 103 can also output coupled light from the waveguide 101. For example, the input coupled light beam group 111 can first interact with the OC structure 104 and then interact with the EPE structure 103. Figure 6 As can be seen in , this results in the coupling-out of the diffracted beam set 112 .
[0108] In this document, a rectangular diffraction grating may refer to a diffraction grating having a two-dimensional rectangular lattice structure. The rectangular lattice includes substantially 90° angles between grating vectors, and the grating vectors may have different or identical lengths.
[0109] It should be understood that the manufacture of the lattice structure may be limited by the manufacturing method used. Therefore, any lattice having the aforementioned features within the tolerance range of the manufacturing method used can be considered a rectangular lattice.
[0110] Figure 6 An embodiment shows at least some possible transitions in the k-space of a display structure, which includes an IC structure 102, which includes a first one-dimensional diffraction grating with a first grating vector 601, an OC structure 104, which includes a second one-dimensional diffraction grating with a second grating vector 602, and an EPE structure 103, which includes a two-dimensional rectangular diffraction grating with a third grating vector 603 and a fourth grating vector 604.
[0111] Figure 6 The transition 612 shown in the embodiment of FIG. 1 may occur due to diffraction caused by the OC structure 104 . Figure 6 The transition 613 shown in the embodiment of FIG. 6 may occur due to diffraction caused by the EPE structure 103. The grating vectors 601 to 604 also correspond to transitions that may occur due to diffraction caused by the corresponding diffraction grating.
[0112] Figure 7A k-space representation of grating vectors and transitions in a waveguide is shown according to an embodiment.
[0113] exist Figure 7 In the embodiment of , the IC structure 102 includes a two-dimensional diffraction grating having two grating vectors 701 , 705 , the OC structure 104 includes a one-dimensional diffraction grating having a grating vector 702 , and the EPE structure 103 includes a two-dimensional rectangular diffraction grating having two grating vectors 703 , 704 .
[0114] Figure 7 The transition 714 shown in the embodiment of FIG. 1 may occur due to diffraction induced at the IC structure 102 or the EPE structure 103 . Figure 7 The transition 715 shown in the embodiment of FIG. 1 may occur due to diffraction caused at the OC structure 104 , the IC structure 102 , or the EPE structure 103 . Figure 7 The transition 713 shown in the embodiment of FIG. 1 may occur due to diffraction caused by the IC structure 102 .
[0115] In the case of a diagonal transition in transitions 714 , 715 , the EPE structure 103 can only cause a transition corresponding to the entire diagonal, while the IC structure 102 and the OC structure 104 can cause a transition corresponding to a half diagonal.
[0116] Grating vectors 701 to 705 may also correspond to transitions that may occur due to diffraction caused by the corresponding diffraction gratings. The transition corresponding to grating vector 702 may also occur due to diffraction caused by IC structure 102. The transition corresponding to grating vector 705 may also occur due to diffraction caused by OC structure 104. The transitions corresponding to grating vector 703 and grating vector 704 may also occur due to diffraction caused by IC structure 102. Diffraction caused by EPE structure 103 may also result in a transition corresponding to the sum of grating vector 702 and grating vector 705, and a transition corresponding to the sum of transition 713 and grating vector 701.
[0117] Figure 8 A k-space representation of grating vectors and transitions in a waveguide is shown according to an embodiment.
[0118] exist Figure 8 In the embodiment of , the IC structure 102 includes a one-dimensional diffraction grating with a grating vector 801 , the OC structure 104 includes a two-dimensional diffraction grating with two grating vectors 802 , 805 , and the EPE structure 103 includes a two-dimensional rectangular diffraction grating with grating vectors 803 , 804 .
[0119] Figure 8 The transition 812 shown in the embodiment of FIG. 1 may occur due to diffraction caused by the OC structure 104 or the EPE structure 103 . Figure 8The transition 815 shown in the embodiment of FIG. 8 may occur due to diffraction caused by the OC structure 104 , the IC structure 102 , or the EPE structure 103 . Figure 8 The transitions 813 , 816 shown in the embodiment of FIG. 8 may occur by diffraction caused by the IC structure 102 or by the OC structure 104 .
[0120] In the case of a diagonal transition in transitions 815 , 812 , the EPE structure 103 can only cause a transition corresponding to the entire diagonal, while the IC structure 102 and the OC structure 104 can cause a transition corresponding to a half diagonal.
[0121] Grating vectors 801 to 805 may also cause transitions that correspond to diffraction caused by the corresponding diffraction gratings. The transition corresponding to grating vector 801 may also occur due to diffraction caused by OC structure 104. The transition corresponding to grating vector 805 may also occur due to diffraction caused by IC structure 102. EPE structure 103 may also cause transitions that correspond to the sum of transition 813 and grating vector 801, transitions that correspond to the sum of grating vector 805 and transition 816, and transitions that correspond to the sum of grating vectors 802 and 815.
[0122] Fig. 9 A k-space representation of grating vectors and transitions in a waveguide is shown according to an embodiment.
[0123] exist Fig. 9 In the embodiment, the IC structure 102 includes a two-dimensional diffraction grating having two grating vectors 901 , 906 , the OC structure 104 includes a two-dimensional diffraction grating having two grating vectors 902 , 905 , and the EPE structure 103 includes a two-dimensional rectangular diffraction grating having two grating vectors 903 , 904 .
[0124] Fig. 9 The transition 913 shown in the embodiment of FIG. 1 may occur due to diffraction caused by the EPE structure 103 , the OC structure 104 , or the IC structure 102 . The transitions 915 , 916 may occur due to diffraction caused by the IC structure 102 or the OC structure 104 .
[0125] In the case of a diagonal transition of transition 913 , the EPE structure 103 can only cause a transition corresponding to the entire diagonal, while the IC structure 102 and the OC structure 104 can cause a transition corresponding to a half diagonal.
[0126] Grating vectors 901 to 906 may also correspond to transitions that may occur due to diffraction caused by the corresponding diffraction gratings. Transitions corresponding to grating vectors 902, 905 may also occur due to diffraction caused by IC structure 102. Transitions corresponding to grating vectors 901, 906 may also occur due to diffraction caused by OC structure 104. Grating vectors 903, 904 may also occur due to diffraction caused by IC structure 102 or OC structure 104. EPE structure 103 may also cause a transition corresponding to the sum of transition 915 and grating vector 901 and a transition corresponding to the sum of grating vector 905 and transition 916.
[0127] When the IC structure 102 and / or the OC structure 104 include a two-dimensional diffraction grating, the input-coupled light beam group 111 may also not interact with the EPE structure 103 during outcoupling of the input-coupled light beam group 111 .
[0128] exist Figures 7 to 9 In the embodiment of the present invention, only the transformation caused by the first-order diffraction is described. Higher-order diffraction may also cause transformations not described in the embodiment.
[0129] Fig.10 A schematic diagram of a beam path according to an example is shown.
[0130] Fig.10 The examples of FIG. 1 show various paths that the input coupled beam group 111 and the diffracted beam group 112 can take that result in the beams returning to the IC structure 102. This can reduce the optical efficiency of the display structure 100. Fig.10 In the embodiment of the present invention, the EPE structure 103 includes a two-dimensional hexagonal diffraction grating.
[0131] The first path 951 corresponds to a group of light beams that first interact with the IC structure 102 , then interact with the EPE structure 103 , then interact with the EPE structure 103 again, and then interact with the OC structure 104 .
[0132] The second path 952 corresponds to a group of light beams that first interact with the IC structure 102, then interact with the OC structure 104, then interact with the EPE structure 103, and then interact with the EPE structure 103 again.
[0133] The first path 951 and the second path 952 may be blocked if the OC structure 104 is not along the initial path of the in-coupled beam group 111. However, such a solution limits the design options available for the display structure 100.
[0134] The third path 953 corresponds to a group of light beams that first interact with the IC structure 102, then interact with the EPE structure 103, then interact with the OC structure 104 via second order diffraction, and then interact with the EPE structure 103.
[0135] The third path 953 cannot be blocked, but due to the second order diffraction, the third path 953 should be weakened.
[0136] The fourth path 954 corresponds to a group of light beams that first interact with the IC structure 102, then interact with the EPE structure 103, then interact with the EPE structure 103 again, then interact with the OC structure 104, then interact with the EPE structure 103, and then interact with the EPE structure 103 again.
[0137] But the fourth path 954 may not be blocked.
[0138] There may be various other paths, such as longer paths, that also result in the beam group returning to the IC structure 102. For example, the diffracted beam group 112 may interact with the EPE structure 103 and / or the OC structure 104 multiple times before returning to the IC structure 102.
[0139] Portions of the beam paths 951 to 954 may be blocked by appropriately designing the geometry of the display structure 100. For example, if the OC structure 104 is not along the initial path of the input coupled beam group 111, the first path 951 and the second path 952 may be blocked. However, the EPE structure 103 should be along a path that allows the EPE structure 103 to receive the input coupled beam group 111. Furthermore, it may be desirable that the EPE structure 103 and the OC structure 104 at least partially overlap.
[0140] At least some embodiments disclosed herein can block beam paths 951 to 954 even when OC structure 104 is along the initial path of input coupled beam group 111. In addition, for some embodiments, direct output coupling between IC structure 102 and OC structure 104 can be blocked, since light from IC structure 102 can be directed directly to OC structure 104, thereby allowing flexible positioning of IC structure 102 relative to OC structure 104.
[0141] Fig.11 A schematic representation of the correspondence between the input light beam group and the output light beam group is shown.
[0142] The output coupling structure 104 may outcouple light from the waveguide 101 whenever the light interacts with the output coupling structure 104. Thus, an image may be expanded and outcoupled by the output coupling structure 104.
[0143] The light beam 910 in the input light beam group 110 corresponding to the middle portion of the image may be converted into corresponding output light beams 920 in the output light beam group 113 that are aligned with an optical axis that may be perpendicular to an exit pupil region / area 940 of the waveguide 101 .
[0144] Light beams 911 in input light beam group 110 corresponding to the right side of the image may be transformed into corresponding output light beams 921 in output light beam group 113 that exit waveguide 101 at an angle such that they appear to originate from locations in the right portion of the field of view of user 941. Similarly, light beams 912 in input light beam group 110 corresponding to the left side of the image may be transformed into corresponding output light beams 922 in output light beam group 113 that exit waveguide 101 at an angle such that they appear to originate from locations in the left portion of the field of view of user 941.
[0145] Although the beams 920, 921, 922 corresponding to different parts of the image in the output beam group 113 are shown as being output from a singular point from the waveguide 101, this is for illustration purposes only. In practice, each beam 920, 921, 922 may be output from a different part of the waveguide 101.
[0146] The output beams in the output beam group 113 corresponding to a particular point of the image may include beams propagating along parallel paths (e.g. Fig.11 In the former case, the image is projected so as to appear to originate from optical infinity, while in the latter case the image is projected so as to appear to originate from some finite distance.
[0147] Thus, the display structure 100 can input couple the input beam group 110 and direct them to form an exit pupil region / area 940 that is larger than the entrance pupil region / area 930. The display structure 100 can convert a given input beam at a specific angle in the input beam group 110 into a number of corresponding beams that output the specific input beam at an angle associated with the exit pupil region / area 940 in the output beam group 113.
[0148] Both the EPE structure 103 and the output coupling structure 104 can be configured to expand the image. For example, the EPE structure 103 can expand the image in one direction, and the output coupling structure 104 can expand the image in a perpendicular direction. Alternatively, the EPE structure 103 can be configured to expand the image in two perpendicular directions, and the output coupling structure 104 can be configured to output couple light from the waveguide 101.
[0149] Any range or device value given herein may be expanded or changed without losing the effect sought. In addition, unless explicitly not permitted, any embodiment may be combined with another embodiment.
[0150] Although the subject matter of the present invention has been described in language specific to structural features and / or behaviors, it should be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or actions described above. On the contrary, the specific features and actions described above are disclosed as examples of implementing the claims, and other equivalent features and actions also fall within the scope of the claims.
[0151] It is understood that the benefits and advantages described above may relate to one embodiment or to multiple embodiments. The embodiments of the present invention are not limited to those embodiments that solve any or all of the problems described, nor are they limited to those embodiments that have any or all of the benefits and advantages described. It is also understood that the reference to "one" item may refer to one or more items.
[0152] Any aspect of the above-described embodiments may be combined with any aspect of the other described embodiments to form further embodiments without losing the effects sought.
[0153] The term "comprising" is used herein to mean including the identified methods, blocks or elements, but such blocks or elements do not include an exclusive list and the method or apparatus may contain additional blocks or elements.
[0154] It should be understood that the above description is given as an example only, and various modifications may be made by those skilled in the art. The above description, examples and data provide a complete description of the structure and use of the exemplary embodiments. Although various embodiments have been described to a certain extent above, or one or more separate embodiments have been mentioned, various modifications may be made to the disclosed embodiments by those skilled in the art without departing from the spirit or scope of this specification.
Claims
1. A display structure (100), comprising: Waveguide (101); An input coupling structure (102) configured to couple the input beam group into the waveguide as an input coupled beam group; An exit pupil expansion structure (103) located on a first side (201) of the waveguide (101) and configured to receive an input coupled light beam group and diffract the input coupled light beam group in a plurality of directions to generate a diffracted light beam group; as well as an output coupling structure (104) located on a second side (202) of the waveguide (101) opposite to the first side (201) and configured to receive at least the diffracted light beam group from the exit pupil expansion structure (103), to output couple at least the diffracted light beam group from the waveguide (101) as an output light beam group, and not to output couple the input coupled light beam group; Wherein the output coupling structure (104) is further configured to diffract the input coupled light beam group.
2. The display structure (100) according to claim 1, wherein: The input coupling structure (102) comprises a one-dimensional input coupling diffraction grating, and the output coupling structure (104) comprises a one-dimensional output coupling diffraction grating.
3. The display structure (100) according to claim 1 or 2, wherein: The exit pupil expansion structure (103) includes a two-dimensional hexagonal diffraction grating or a two-dimensional rectangular diffraction grating.
4. The display structure (100) according to any one of the preceding claims, wherein: The exit pupil expansion structure (103) covers a first portion of the waveguide (101), and the output coupling structure (104) covers a second portion of the waveguide (101), and the first portion and the second portion at least partially overlap.
5. The display structure (100) according to claim 4, wherein: The first part surrounds the second part.
6. The display structure (100) according to claim 5, wherein: The input coupling structure (102) is located at the second side (202) of the waveguide (101) and covers a third portion of the waveguide, and wherein the first portion also surrounds the third portion.
7. The display structure (100) according to any one of the preceding claims, wherein: The input coupling structure (102) comprises a first one-dimensional diffraction grating having a first grating vector (501), the output coupling structure (104) comprises a second one-dimensional diffraction grating having a second grating vector (502), the exit pupil expansion structure (103) comprises a two-dimensional hexagonal diffraction grating having a third grating vector (503), the angle between the first grating vector (501) and the third grating vector (503) is substantially 30 degrees or substantially 90 degrees, and the length of the third grating vector (503) is substantially 1.7 times the length of the first grating vector (501).
8. The display structure (100) according to claim 7, wherein: The angle between the first grating vector (501) and the second grating vector (502) is substantially 60 degrees.
9. The display structure (100) according to any one of claims 1 to 6, wherein: The input coupling structure (102) comprises a first one-dimensional diffraction grating having a first grating vector (601), the output coupling structure (104) comprises a second one-dimensional diffraction grating having a second grating vector (602), the exit pupil expansion structure (103) comprises a two-dimensional rectangular diffraction grating having a third grating vector (603) and a fourth grating vector (604), and the first grating vector (601) and the second grating vector (602) correspond to half diagonals of a rectangle defined by the third grating vector (603) and the fourth grating vector (604).
10. The display structure (100) according to any one of claims 7 to 9, wherein: The length of the first grating vector (501, 601) is substantially equal to the length of the second grating vector (502, 602).
11. The display structure (100) according to any one of the preceding claims, wherein: The exit pupil expansion structure (103) is configured to diffract the in-coupled beam set (111) via zero-order and first-order diffraction.
12. A display device comprising the display structure (100) according to any one of the preceding claims.
13. A display device according to claim 12, comprising a scanner based optical engine, such as a laser scanning optical engine, for directing the set of input light beams to the input coupling structure.
14. The display device according to claim 12 or 13, which is implemented as a see-through display device.
15. The display device according to any one of claims 12 to 14, which is implemented as a head-mounted display device.