Display structure, display device, and vehicle

Abstract

A display structure (1000), a display device, and a vehicle are disclosed, the display structure (1000) comprising a waveguide plate (1100), an incoupling structure (1200) configured to incouple incoupling beams (1021), a diffractive exit pupil extension structure (1300) configured to receive and diffract the incoupling beams (1021) to form a first guided beam group (1031) and a second guided beam group (1032), and a diffractive outcoupling structure (1400) configured to receive a first diffracted beam group (1041) and a second diffracted beam group (1042) from the exit pupil extension structure (1300) and outcouple light from the first diffracted beam group (1041) and the second diffracted beam group (1042).

Description

[Technical field]

[0001] The present disclosure relates to a display device, and more particularly to a waveguide-based display structure, a display device including such a display structure, and a vehicle including such a display device. [Background technology]

[0002] In general, small form factors are very important for various portable and vehicular displays, which can be realized using waveguide-based structures that guide the light from the optical engine of such displays to the user's eye.

[0003] Because the images produced by typical optical engines are relatively small, conventional waveguide-based displays typically use an exit pupil expansion method based on pupil replication to increase the size of the output image. In conventional exit pupil expansion methods, a light beam is coupled into a waveguide to propagate in a first direction through an exit pupil expansion structure, such as a diffraction grating or multiple successive beam splitters, which forms multiple light beams propagating in a second direction perpendicular to the first direction. Light from such multiple light beams is then coupled out of the waveguide to form the output image.

[0004] While such conventional methods have been successfully used to generate a variety of portable and vehicle displays, the light losses caused by typical exit pupil extension structures can be significant. Such losses can be mitigated to some extent by increasing the efficiency with which the exit pupil extension structure reflects or diffracts the incoupled light. However, simply increasing the efficiency of the exit pupil extension structure can result in brightness non-uniformities in the output image.

[0005] In light of this, it would be desirable to develop new solutions for display devices. Summary of the Invention [Means for solving the problem]

[0006] This Summary is provided to introduce in a simplified form selected concepts that are further described below in the Detailed Description. This Summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.

[0007] In a first aspect, a display structure is provided comprising a waveguide, an incoupling structure configured to couple input beams into the waveguide as incoupling beams corresponding to a group of incoupling k-vectors defining a first region in k-space of an annular waveguide propagation region associated with the waveguide, and a diffractive exit pupil extension structure configured to receive the incoupling beams and diffract the incoupling beams to form a first group of guided beams corresponding to the first group of k-vectors present in the first region and a second group of guided beams corresponding to a second group of k-vectors present in a second region separate from the first region. The display structure further comprises a diffractive outcoupling structure configured to receive from the exit pupil extension structure a first group of diffracted beams corresponding to the first group of diffracted k-vectors present in the first region and a second group of diffracted beams corresponding to the second group of diffracted k-vectors present in the second region, the outcoupling structure configured to couple light from the first group of diffracted beams and light from the second group of diffracted beams out of the waveguide.

[0008] In a second aspect, there is provided a display device comprising a display structure according to the first aspect.

[0009] In a third aspect, there is provided a vehicle comprising a vehicle display device according to the second aspect.

[0010] The present disclosure will be better understood from the following detailed description when read in light of the accompanying drawings. [Brief description of the drawings]

[0011] [Figure 1] FIG. 2 shows a partial orthogonal top view of the display structure. [Diagram 2] 2 shows a normalized k-vector diagram 2000 illustrating the working principle of the display structure. [Diagram 3] 1 shows multiple k-vector diagrams illustrating the effect of various diffraction events associated with the operation of the display structure. [Figure 4] A display device is shown. [Diagram 5] Shows the vehicle. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Unless specifically noted otherwise, any of the above-described drawing figures may not be drawn to scale, such that any element in that drawing may be drawn inaccurately sized relative to other elements in that drawing to emphasize certain structural aspects of the embodiments of that drawing.

[0013] Furthermore, corresponding elements in the embodiments of any two of the above drawings may be out of proportion to one another in size in the two drawings to emphasize certain structural aspects of the embodiments of the two drawings.

[0014] With respect to the display structures and display devices discussed in the detailed description below, please note the following.

[0015] As used herein, a "display device" may refer to an output device, e.g., an electronic device, operable to visually display images and / or data. A display device may generally include any components or elements necessary or useful for visually displaying images and / or data, such as a power supply unit, an optical engine, a combiner optical unit, e.g., a waveguide-based combiner optical unit, an eye tracking unit, a head tracking unit, a gesture detection unit, and / or a depth mapping unit. A display device may or may not be implemented as a see-through display device and / or as a portable display device and / or a vehicular display device.

[0016] As used herein, a "see-through display device" or "transparent display device" may refer to a display device that allows a user to see images and / or data presented on the display device as well as see through the display device.

[0017] As used herein, "portable display device" may refer to a display device that is configured to be easily transportable and / or configured to be carried and / or worn.

[0018] Further, a "vehicle display device" may refer to a display device configured for use within a vehicle, such as while operating the vehicle. Additionally or alternatively, a vehicle display device may refer to a display device configured to display images and / or data associated with the vehicle and / or operation of the vehicle. In general, a vehicle display device may or may not be implemented as a vehicle-mounted display device fixed to the vehicle.

[0019] Throughout this disclosure, a "display structure" may refer to at least a portion of an operational display device. Additionally or alternatively, a display structure may refer to a structure suitable for use within a display device.

[0020] Throughout this specification, a "k-vector" or "wave vector" may refer to a vector in k-space. Additionally or alternatively, a k-vector may represent a light beam, i.e., a ray, having a particular propagation direction. In general, a k-vector associated with a light beam propagating through a medium is given by:

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[0021] As used herein, "k-space" or "angle space" can refer to a framework that relates k-vectors to geometric points using spatial frequency space analysis. Additionally or alternatively, k-space can refer to a two-dimensional projection space associated with a waveguide. In k-space, any diffraction events that occur as light propagates through a waveguide can be represented as translations. Using the k-space formalism, the behavior of a display structure can be described by how input k-vectors are moved through k-space by the display structure.

[0022] In general, in a homogeneous infinite medium, all directions of propagation are allowed, and all k-vectors for a particular wavelength have the same magnitude. Thus, the allowed k-vectors for a particular wavelength in a homogeneous infinite medium define a hollow sphere in k-space whose radius is determined by the common wavenumber of the k-vectors. Since the common wavenumber of the k-vectors is proportional to the refractive index of the medium, the radius of the hollow sphere is also proportional to the refractive index of the medium.

[0023] However, in a homogeneous waveguide stretched along a plane, the allowed k-vectors for a particular wavelength are usually represented by a dense disk whose radius is defined by the common wave number of the k-vectors. Such a representation can be seen as a projection of the hollow sphere mentioned above onto a plane in k-space corresponding to the plane along which the waveguide stretches. Every point within the boundary of the dense disk corresponds to two allowed k-vectors with opposing components perpendicular to the plane. For example, if a homogeneous waveguide stretches along the xy plane, then the out-of-plane component k of the k-vector for wave number k is z teeth,

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[0024] Typically, not all k-vectors allowed in a waveguide are guided in the waveguide. A waveguide is typically surrounded by a medium whose refractive index is smaller than that of the waveguide. In general, a separate dense disk can be defined to represent the k-vectors allowed in such a medium. Since the refractive index of the surrounding medium is smaller than that of the waveguide, the dense disk associated with the surrounding medium has a smaller radius than the dense disk associated with the waveguide.

[0025] In general, an annular region in k-space defined by the difference set of such a small dense disk in such a large dense disk, i.e., the difference between the large dense disk and the small dense disk, can be called a "waveguiding propagation region" associated with the waveguide. Any k-vector whose in-plane component lies in such a waveguiding propagation region of the waveguide can propagate in the waveguide in a guided manner.

[0026] As mentioned above, a small dense disk represents the k-vectors allowed in the medium surrounding the waveguide. Since light to be coupled into or out of the waveguide must be able to propagate in such a surrounding medium, only k-vectors whose in-plane components lie within such a small dense disk can be coupled into or out of the waveguide. Thus, a small dense disk representing the k-vectors allowed in the medium surrounding the waveguide can be referred to as the "coupling region" associated with that waveguide.

[0027] In light of the above, the k-vectors allowed in a waveguide can be depicted in k-space using a two-dimensional k-vector diagram. As used herein, a "k-vector diagram" can refer to a diagram of k-space in which the guided propagation angle of a light beam propagating in a waveguide is represented by an annular guided propagation region associated with the waveguide. Additionally or alternatively, a k-vector diagram can refer to a diagram of k-space in which the non-guided propagation angle of a light beam propagating in a waveguide is represented by a coupling region associated with the waveguide.

[0028] In general, the outer radius of a waveguide propagation region may be inversely proportional to the wavelength of light, with shorter wavelengths of light corresponding to wider waveguide propagation regions. Although the width of the waveguide propagation region can affect the range of k-vectors that can be guided in the waveguide, even non-dispersive waveguides may not be able to accommodate the wider field of view that occurs with shorter wavelengths. This may be because the angular range of the field of view is inversely proportional to the wavelength. With this in mind, k-vector diagrams are usually normalized to plot a dense disk of unit radius that corresponds to propagation in a vacuum, i.e., each k-vector is expressed as its vacuum wavenumber (k0), i.e.

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[0029] Figure 1 shows a partial orthogonal top view of a display structure 1000 according to one embodiment, Figure 2 shows a normalized k-vector diagram 2000 illustrating the principle of operation of the display structure 1000, and Figure 3 shows a number of k-vector diagrams 3000 further illustrating the effect of various diffraction events associated with the operation of the display structure 1000. In other embodiments, the display structure may be the same as, similar to, or different from the display structure 1000 of the embodiment of Figures 1-3.

[0030] In the embodiment of figures 1 to 3, the display structure 1000 comprises a waveguide 1100. In figure 1, the waveguide 1100 extends parallel to the plane of the figure.

[0031] In this disclosure, a "waveguide" can refer to an optical waveguide plate. Additionally or alternatively, a waveguide plate can refer to a two-dimensional waveguide plate in which light may be confined along the thickness of the waveguide plate. Additionally or alternatively, a waveguide plate can refer to a two-dimensional waveguide plate in which light may be confined between opposing faces of the waveguide plate by total internal reflection.

[0032] In the embodiment of FIGS. 1-3, the display structure 1000 comprises an incoupling structure 1200 .

[0033] Throughout this disclosure, an "incoupling structure" may refer to a structure configured to couple input beams into a waveguide for guided propagation therein. In general, an incoupling structure may comprise, for example, one or more diffractive optical elements, such as a diffraction grating, and / or one or more reflective optical elements, such as a mirror, and / or one or more refractive optical elements, such as a prism.

[0034] 1-3, the waveguide 1100 may have a refractive index of about 2 across the visible spectrum. In other embodiments, the waveguide may have any suitable refractive index with any suitable dispersion characteristics.

[0035] Waveguide 1100 may be surrounded by air, which has a refractive index of approximately 1 across the visible spectrum. Thus, light may be guided in waveguide 1100 between opposing air-glass interfaces. In other embodiments, light may be guided in the waveguide between any suitable interfaces, for example, air-glass interfaces.

[0036] As shown diagrammatically in FIG. 1, the incoupling structure 1200 of the embodiment of FIGS. 1-3 is configured to couple input beams 1020 into a waveguide 1100 as incoupling beams 1021 .

[0037] As used herein, "input beams" may refer to light beams that are directed to an incoupling structure and correspond to an input image. Additionally or alternatively, input beams may refer to light beams that propagate toward an incoupling structure of a display structure at a solid angle that defines a field of view of the display structure. Additionally or alternatively, input beams may refer to light beams that correspond to input k-vectors that are present in a coupling region associated with a waveguide.

[0038] Additionally, "incoupling beams" can refer to light beams coupled into a waveguide by an incoupling structure. Additionally or alternatively, incoupling beams can refer to light beams that correspond to an image and propagate in a guided manner in a waveguide. Additionally or alternatively, incoupling beams can refer to light beams associated with incoupling k-vectors that are present in a guided propagation region associated with the waveguide.

[0039] Additionally or alternatively, the incoupling beams and / or the input beams may correspond to a field of view of an image. The image may include, for example, an image that is displayed to a user.

[0040] The input beam group 1020 and the incoupling beam group 1021 in the embodiment of FIGS. 1 to 3 correspond to an input k-vector group 3020 and an incoupling k-vector group 3021, respectively.

[0041] In the multiple k vector diagrams 3000 of Figure 3, the input k vector group 3020 is diagrammatically shown as a group of points in the first k vector diagram 3100, the incoupling k vector group 3021 is diagrammatically shown as a group of points in the second k vector diagram 3200, and the coupling of the input beam group 1020 into the waveguide 1100 as the incoupling beam group 1021 is diagrammatically represented as an arrow extending from the first k vector diagram 3100 to the second k vector diagram 3200.

[0042] 2 and 3, the input k-vector group 3020 and the incoupling k-vector group 3021 are present in the incoupling region 2100 and the first region 2310, respectively. The first region 2310 is located in an annular waveguide propagation region 2001 associated with the waveguide plate 1100, while the incoupling region 2100 is present in a coupling region 2002 surrounded by the waveguide propagation region 2001.

[0043] 1-3, the in-coupling region 2100 is located centrally in the coupling region 2002. In other embodiments, the in-coupling region may be located in any suitable manner within the coupling region, such as centrally or off-center.

[0044] As used herein, a "first region" may refer to a region in k-space located within a guided-wave propagation region associated with a waveguide. Additionally or alternatively, a first region may refer to a region in k-space defined by a set of incoupling k-vectors coupled into the waveguide by an incoupling structure. As used herein, a "region in k-space defined by a set of incoupling k-vectors" may refer to a minimal non-empty connected open set within a guided-wave propagation region associated with a waveguide that includes each of the points representing the set of incoupling k-vectors.

[0045] In the embodiment of FIGS. 1-3, the display structure 1000 further comprises a diffractive exit pupil extension structure 1300.

[0046] Herein, a "diffractive" structure may refer to a structure that comprises a diffractive optical element. Herein, a "diffractive optical element" may refer to an optical element whose operation is based on the diffraction of light. In general, a diffractive optical element may comprise structural features with at least one dimension on the order of a visible light wavelength, e.g., at least one dimension smaller than 1 micrometer. Exemplary diffractive optical elements include gratings, such as one-dimensional and two-dimensional gratings, which may be implemented as single-domain or multi-domain gratings. Diffraction gratings may generally be implemented as at least a surface relief type grating or a volume hologram type grating, and may be configured to function as a transmission type grating and / or a reflection type grating.

[0047] Furthermore, "exit pupil expansion" or "EPE" can refer to the process of distributing light in a waveguide in a controlled manner and expanding the portion of the waveguide where light outcoupling occurs. In general, exit pupil expansion can be performed in waveguide-based display structures using a so-called "pupil duplication" approach, where multiple exit sub-pupils are formed in the imaging system. Thus, an "exit pupil expansion structure" can refer to a structure that is suitable or configured for exit pupil expansion, e.g., by pupil duplication.

[0048] As shown diagrammatically in FIG. 1, the exit pupil extension structure 1300 of the embodiment of FIGS. 1-3 is configured to receive an incoupling beam group 1021 and diffract the incoupling beam group 1021 to form a first guided beam group 1031 and a second guided beam group 1032.

[0049] If the incoupling beam group and / or the input beam group correspond to a field of view of an image, the first guided beam group 1031 and the second guided beam group 1032 may also correspond to a field of view of the image. Thus, the exit pupil extension structure 1300 may generate a copy of the full field of view of the image. This allows the first guided beam group 1031 and the second guided beam group 1032 to comprise a copy of the full field of view of the image.

[0050] 1-3, the first guided beam group 1031 is associated with the first k-vector group 3031, and the second guided beam group 1032 is associated with the second k-vector group 3032. In the multiple k-vector diagrams 3000 of FIG. 3, the first k-vector group 3031 and the second k-vector group 3032 are depicted as groups of points in the third k-vector diagram 3300, and the diffraction of the incoupling beam group 1021 by the exit pupil extension structure 1300 to form the first guided beam group 1031 and the second guided beam group 1032 is represented diagrammatically as an arrow extending from the second k-vector diagram 3200 to the third k-vector diagram 3300. As shown in Figures 2 and 3, the first k-vector group 3031 exists in a first region 2310, and the second k-vector group 3032 exists in a second region 2320 separated from the first region 2310, and is disposed within the waveguide propagation region 2001.

[0051] The first region 2310 and the second region 2320 in the embodiment of FIGS. 1 to 3 are k vectors in the k vector diagram 2000 in FIG. x / k0 axis. In other embodiments, the first and second regions may or may not be symmetrically disposed about a line extending through the origin of a k-vector diagram associated with the waveguide. For example, in some embodiments, one of the first and second regions may be disposed at a first radial distance from the origin of a k-vector diagram associated with the waveguide, and the other of the first and second regions may be disposed at a second radial distance from the origin that is different, i.e., greater or less than, the first radial distance.

[0052] The display structure 1000 of the embodiment of FIGS. 1-3 further comprises a diffractive outcoupling structure 1400.

[0053] In this disclosure, an "outcoupling structure" may refer to a structure configured to couple light out of a waveguide.

[0054] As shown diagrammatically in FIG. 1, the outcoupling structure 1400 of the embodiment of FIGS. 1 to 3 is configured to receive a first group of diffracted beams 1041 and a second group of diffracted beams 1042 from the exit pupil extension structure 1300.

[0055] Throughout this specification, "first diffracted beam group" and "second diffracted beam group" can refer to beam groups received by an outcoupling structure from an exit pupil expansion structure, where the first diffracted beam group can be mapped to a first diffracted k-vector group residing in a first region in k-space, and the second diffracted beam group can be mapped to a second k-vector group residing in a second region separate from the first region. Additionally or alternatively, "first diffracted beam group" can refer to beam groups including light from incoupling beam group and / or light from second incoupling beam group coupled into the waveguide by the incoupling structure.

[0056] The first diffracted beam group 1041 and the second diffracted beam group 1042 are respectively associated with the first diffracted k-vector group 3041 and the second diffracted k-vector group 3042. In the multiple k-vector diagrams 3000 of FIG. 3, the first diffracted k-vector group 3041 and the second diffracted k-vector group 3042 are depicted as groups of points in the fourth k-vector diagram 3400, and the propagation of the first diffracted beam group 1041 and the second diffracted beam group 1042 from the exit pupil extension structure 1300 to the outcoupling structure 1400 is represented diagrammatically as an arrow extending from the third k-vector diagram 3300 to the fourth k-vector diagram 3400. As shown in FIG. 2 and FIG. 3, the first diffracted k-vector group 3041 exists in the first region 2310, and the second diffracted k-vector group 3042 exists in the second region 2320.

[0057] 1-3, the outcoupling structure 1400 is further configured to couple light from the first diffracted beams 1041 and light from the second diffracted beams 1042 out of the waveguide 1100. In general, light losses associated with an exit pupil widening can be mitigated by the outcoupling structure being configured to outcouple light from both a first diffracted beams associated with a first diffracted k-vector group residing in a first region of k-space and a second diffracted beams associated with a second diffracted k-vector group residing in a second region separate from the first region.

[0058] In the multiple k vector diagrams 3000 of Figure 3, the k vectors corresponding to the light coupled out of the waveguide 1100 by the outcoupling structure 1400 are illustrated diagrammatically as a cloud of points in a fifth k vector diagram 3500, and the outcoupling of light is diagrammatically represented as an arrow extending from the fourth k vector diagram 3400 to the fifth k vector diagram 3500. As shown in Figures 2 and 3, the k vectors corresponding to the light coupled out of the waveguide 1100 by the outcoupling structure 1400 are in the outcoupling region 2200, which is disposed within the coupling region 2002.

[0059] 1-3, the outcoupling region 2200 is located centrally in the coupling region 2002. In other embodiments, the outcoupling region can be located in any suitable manner within the coupling region, such as centrally or off-center. In some embodiments, the outcoupling region can be aligned with the incoupling region.

[0060] In the normalized k-vector diagram 2000 of FIG. 2, the diffraction of the incoupling beam group 1021 by the exit pupil extension structure 1300 is expressed as a basic exit pupil extension grid k-vector extending from the first region 2310 to the second region 2320.

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[0061] As used herein, a "grating k-vector" may refer to a vector in k-space that represents the effect of a diffractive optical element on the propagation direction of a light beam represented by the k-vector. Additionally, or alternatively, a grating k-vector associated with a diffractive optical element may refer to a vector in k-space that may be added to an in-plane component of a k-vector associated with a light beam to represent the effect of the diffractive optical element on the propagation of the light beam.

[0062] In general, a diffractive optical element can be used to couple a light beam into and / or out of a waveguide and / or to change the propagation direction of the light beam in the waveguide. The magnitude and direction of the lattice k vector, which represents the effect of a diffractive optical element, are determined by the properties of the diffractive optical element. Specifically, an elementary lattice vector can be associated with each periodicity direction of a diffractive optical element, and the direction and magnitude of each elementary lattice vector are determined by the direction and pitch of the diffractive optical element in the periodicity direction to which it is associated. Then, the higher-order lattice vector of a diffractive optical element can be expressed as a linear combination of integers of the elementary lattice vectors of the diffractive optical element. For example, if a diffractive optical element has a first periodicity in a first direction and a second periodicity in a second direction, the first elementary lattice vector

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[0063] Throughout this specification, "Nth diffraction order", e.g., first or second diffraction order, can refer to positive Nth diffraction orders and / or negative Nth diffraction orders. Additionally or alternatively, a structure is configured to "diffract beams in an Nth diffraction order" if the structure is configured to diffract the beams in an Nth diffraction order by a grating k-vector

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[0064] In other embodiments, the exit pupil extension structure may or may not be configured to diffract the incoupling beams in a zeroth and first diffraction order to form the first and second waveguided beams. For example, in some embodiments, the exit pupil extension structure may be configured to diffract the incoupling beams in a zeroth diffraction order to form the first waveguided beams and in a second diffraction order to form the second waveguided beams. In such embodiments, the exit pupil extension structure may be configured to diffract the incoupling beams in a first diffraction order to form a third waveguided beam corresponding to a third group of k-vectors present in a third region separate from each of the first and second regions. In some such embodiments, the outcoupling structure may be configured to receive from the exit pupil extension structure a third group of diffracted beams corresponding to a third group of diffracted k-vectors present in the third region and to couple light out of the waveguide from the light from the third diffracted beams.

[0065] As shown diagrammatically in FIG. 1, the exit pupil extension structure 1300 of the embodiment of FIGS. 1-3 is configured to diffract the first and second guided beam groups 1031, 1032 to further increase the number of diffracted beams. In general, the exit pupil extension structure is configured to diffract the first and second guided beam groups to further increase the number of diffracted beams, which facilitates reducing brightness variations in the aerial image across the outcoupling structure. In other embodiments, the exit pupil extension structure may or may not be configured to do so. For example, in some embodiments, the exit pupil extension structure may be configured to suppress diffraction of the second guided beam group by minimizing the diffraction efficiency for a particular diffraction order.

[0066] In the embodiment of Figures 1-3, the exit pupil extension structure 1300 comprises a one-dimensional exit pupil extension grating 1310 that diffracts the incoupling beam group 1021 to form the first guided beam group 1031 and the second guided beam group 1032. In general, the exit pupil extension structure may comprise a one-dimensional exit pupil extension grating to facilitate forming the exit pupil extension structure. Additionally or alternatively, the exit pupil extension structure may comprise a one-dimensional exit pupil extension grating to facilitate directing light from the incoupling beam group into specific diffraction orders to reduce light losses associated with the exit pupil extension.

[0067] In other embodiments, the exit pupil extension structure may or may not comprise a one-dimensional exit pupil extension grating. For example, in some embodiments, the exit pupil extension structure may comprise a two-dimensional diffractive exit pupil extension element. In some such embodiments, the exit pupil extension element may have a first order periodicity along a first order direction and a second order periodicity along a second order direction different from the first order direction that diffracts the incoupling beams to form the first and second guided beams. In some such embodiments, the second order periodicity may be defined by a pitch that prevents light received by the exit pupil extension structure from being diffracted along the second order direction.

[0068] In the embodiment of Figures 1-3, the first region 2310 defines a first light guiding direction 1001 and the second region 2320 defines a second light guiding direction 1002, with a minimum angle (α) between the first light guiding direction 1001 and the second light guiding direction 1002 being about 60°. In general, a smaller angle between the first light guiding direction and the second light guiding direction can reduce light losses due to light propagating through or within the outcoupling structure, while a larger angle between the first light guiding direction and the second light guiding direction can facilitate reducing the size of the exit pupil extension structure. In other embodiments, any suitable minimum angle may exist between the first light guiding direction and the second light guiding direction, for example a minimum angle of 45° or 55° or more and / or 65° or 75° or less.

[0069] As used herein, a region in k-space located within a waveguide propagation region associated with a waveguide "defines a light guiding direction" can mean that the waveguide extends laterally along a plane and that the region includes a characteristic point that defines the light guiding direction along the plane, such as the centroid of the region.

[0070] As shown diagrammatically in FIG. 1, the outcoupling structure 1400 of the embodiment of FIGS. 1 to 3 is configured to diffract the first diffracted beam group 1041 and the second diffracted beam group 1042 to form a first additional beam group 1043 and a second additional beam group 1044, respectively.

[0071] The first additional beam group 1043 and the second additional beam group 1044 are respectively associated with the first additional k vector group 3043 and the second additional k vector group 3044. In the multiple k vector diagrams 3000 in FIG. 3, the first additional k vector group 3043 and the second additional k vector group 3044 are depicted in the fourth k vector diagram 3400 as groups of points superimposed on groups of points indicating the second diffraction k vector group 3042 and the first diffraction k vector group 3041, respectively. As shown in FIG. 2 and FIG. 3, the first additional k vector group 3043 exists in the second region 2320, and the second additional k vector group 3044 exists in the first region 2310.

[0072] In general, the outcoupling structure may be configured to diffract the first and / or second diffracted beams to form first additional beams corresponding to the first additional k-vectors present in the second region and / or second additional beams corresponding to the second additional k-vectors present in the first region, respectively, to facilitate mitigating brightness variations in the aerial image across the outcoupling structure, although in other embodiments the outcoupling structure may or may not be so configured.

[0073] In the embodiment of Figures 1 to 3, the outcoupling structure 1400 comprises a two-dimensional outcoupling grating 1410 having a first periodicity for coupling light from a first diffractive beam group 1041 out of the waveguide 1100, a second periodicity for coupling light from a second diffractive beam group 1042 out of the waveguide 1100, and a third periodicity for forming a first additional beam group 1043 and a second additional beam group 1044.

[0074] In general, the outcoupling structure may comprise a two-dimensional outcoupling grating having a first periodicity for coupling light from a first group of diffracted beams out of the waveguide, a second periodicity for coupling light from a second group of diffracted beams out of the waveguide, and a third periodicity for forming the first additional beams and / or the second additional beams, thereby enabling the outcoupling structure to be formed in a single-sided process.

[0075] In other embodiments, the outcoupling structure may or may not comprise such a two-dimensional outcoupling grating.For example, in some embodiments, the outcoupling structure configured to diffract the first and / or the second diffracted beams to form the first and / or the second additional beams, respectively, may comprise at least two diffractive optical elements at least partially laterally overlapping each other, which couple light from both the first and the second diffracted beams out of the waveguide to form the first and / or the second additional beams.

[0076] In the normalized k-vector diagram 2000 of FIG. 2, coupling light from the first group of diffracted beams 1041 out of the waveguide 1100 is determined by a fundamental first order outcoupling grating k-vector extending from the first region 2310 to the outcoupling region 2200.

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[0077] Further, in the normalized k-vector diagram 2000 of FIG. 2, diffracting the first diffracted beam group 1041 to form the first additional beam group 1043 corresponds to a fundamental third-order outcoupling lattice k-vector extending from the first region 2310 to the second region 2320.

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[0078] 1, the incoupling structure 1200 is configured to couple input beams 1020 into the waveguide 1100 such that light from incoupling beams 1021 is guided to the outcoupling structure 1400 without undergoing non-zero order diffraction. In general, having the incoupling structure configured in this manner can further reduce light losses associated with the exit pupil expansion.

[0079] In other embodiments, the incoupling structure may or may not be configured to couple the input beams into a waveguide such that light from the incoupling beams is guided to the outcoupling structure without experiencing non-zero order diffraction. For example, in some embodiments, the incoupling structure may be configured to couple the input beams into a waveguide such that light from the incoupling beams is guided only by non-zero order diffraction and guided through the exit pupil extension structure. Such an arrangement may generally facilitate mitigating brightness variations in the aerial image across the outcoupling structure.

[0080] As shown diagrammatically in FIG. 1 by the dashed arrows extending from the incoupling structure 1200, the incoupling structure 1200 of the embodiment of FIGS. 1-3 can be configured to couple the input beam group 1020 into the waveguide 1100 as secondary incoupling beam group 1022.

[0081] The second order incoupling beam group 1022 in the embodiment of Figures 1-3 can be associated with a second order incoupling k-vector group 3022. In the multiple k-vector diagrams 3000 of Figure 3, the second order incoupling k-vector group 3022 is illustrated as a group of points in the sixth k-vector diagram 3600, and the coupling of the input beam group 1020 into the waveguide 1100 as the second order incoupling beam group 1022 is illustrated as a dashed arrow extending from the first k-vector diagram 3100 to the sixth k-vector diagram 3600. As shown in Figures 2 and 3, the second order incoupling k-vector group 3022 is present in the second region 2320.

[0082] In other embodiments, the incoupling structure may or may not be configured to couple the input beams into the waveguide as secondary incoupling beams corresponding to secondary incoupling k-vectors present in the second region.

[0083] In general, the display structure and / or any portion thereof may or may not be configured to control the propagation of light from the secondary incoupling beams in a manner corresponding to the manner in which it controls the propagation of light from the incoupling beams.

[0084] For example, as shown diagrammatically using dashed arrows in FIG. 1 , the diffractive exit pupil expansion structure 1300 can be configured to receive the secondary incoupling beam group 1022 and diffract the secondary incoupling beam group 1022 to form a first secondary guided beam group 1033 and a second secondary guided beam group 1034.

[0085] The first and second secondary guided beam groups 1033 and 1034 may be respectively associated with the first and second secondary k-vector groups 3033 and 3034. In the multiple k-vector diagrams 3000 of FIG. 3, the first and second secondary k-vector groups 3033 and 3034 are depicted as groups of points in the seventh k-vector diagram 3700, and the diffraction of the secondary incoupling beam group 1022 by the exit pupil extension structure 1300 to form the first and second secondary guided beam groups 1033 and 1034 is represented diagrammatically as a dashed arrow extending from the sixth k-vector diagram 3600 to the seventh k-vector diagram 3700.

[0086] In general, a diffractive exit pupil extension structure is configured to receive the secondary incoupling beams from the incoupling structure and diffract the secondary incoupling beams to form a first secondary guided beam group corresponding to a first secondary k-vector group present in a first region and a second secondary guided beam group corresponding to a second secondary k-vector group present in a second region, thereby facilitating mitigating brightness variations in the aerial image across the outcoupling structure.

[0087] In other embodiments where the incoupling structure is configured to couple the input beams into the waveguide as secondary incoupling beams corresponding to secondary incoupling k-vectors present in the second region, the exit pupil extension structure may or may not be configured to receive the secondary incoupling beams and diffract the secondary incoupling beams to form a first secondary guided beam group corresponding to a first secondary k-vector group present in the first region and a second secondary guided beam group corresponding to a second secondary k-vector group present in the second region.

[0088] In the normalized k-vector diagram 2000 of FIG. 2, the diffraction of the second incoupling beam group 1022 by the exit pupil extension structure 1300 is

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[0089] 1-3, the incoupling structure 1200 includes an incoupling grating 1210 that couples the input beams 1020 into the waveguide 1100. In other embodiments, the incoupling structure may or may not include such an incoupling grating. For example, in some embodiments, the incoupling structure may include, in addition to or instead of an incoupling grating, a reflective optical element, such as one or more mirrors, and / or a refractive optical element, such as one or more prisms.

[0090] The incoupling grating 1210 of the embodiment of Figures 1-3 may be implemented as a two-dimensional grating configured to couple the input beams 1020 into the waveguide 1100 as incoupling beams 1021 and second order incoupling beams 1022. In general, by having the incoupling structure comprise a two-dimensional incoupling grating that couples the input beams into the waveguide as incoupling beams and second order incoupling beams, brightness variations in the aerial image across the outcoupling structure may be facilitated to be mitigated. In other embodiments where the incoupling structure is configured to couple the input beams into the waveguide as second order incoupling beams that correspond to second order incoupling k-vectors present in a second region, the incoupling structure may or may not comprise a two-dimensional incoupling grating. For example, in some embodiments, the incoupling structure may comprise a first incoupling element, e.g., a diffractive, reflective or refractive optical element, that couples input beams into the waveguide as incoupling beams, and a second incoupling element, e.g., a diffractive, reflective or refractive optical element, that couples the input beams into the waveguide as secondary incoupling beams. In such embodiments, the first incoupling element and the second incoupling element may or may not be arranged to at least partially laterally overlap each other.

[0091] In the normalized k-vector diagram 2000 of FIG. 2, the coupling of the input beam group 1020 into the waveguide 1100 as incoupling beam group 1021 is represented by a fundamental first-order incoupling lattice k-vector extending from the incoupling region 2100 to the first region 2310.

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[0092] 1-3, the incoupling grating 1210, the exit pupil extension grating 1310 and the outcoupling grating 1410 are arranged symmetrically with respect to an imaginary cross-section 1003 extending along the thickness direction of the waveguide 1100. In FIG. 1, the cross-section 1003 extends perpendicular to the plane of the drawing. In other embodiments, the incoupling grating, the exit pupil extension grating and the outcoupling grating may or may not be arranged symmetrically with respect to a cross-section extending along the thickness direction of the waveguide.

[0093] Any diffractive optical elements in the display structure 1000, including the incoupling grating 1210, the exit pupil expansion grating 1310 and the outcoupling grating 1410, may be formed at least in part using nanoimprint lithography. In other embodiments, any suitable fabrication method may be used, such as nanoimprint lithography and / or electron beam lithography.

[0094] It should be understood that the embodiments of the first aspect described above can be used in combination with each other. Some embodiments can be combined to form further embodiments.

[0095] Above, features related mainly to the display structure are discussed. Below, more emphasis is placed on aspects related to the display device. All implementation methods, definitions, details and advantages mentioned above apply mutatis mutandis to the display device discussed below, and vice versa.

[0096] Figure 4 illustrates a display device 4000 according to one embodiment. The embodiment of Figure 4 may be based on any of the embodiments disclosed with reference to or in conjunction with any of Figures 1-3. Additionally or alternatively, although not explicitly shown in Figure 4, the embodiment of Figure 4 or any part thereof may generally include any feature and / or element of the embodiments of Figures 1-3.

[0097] In the embodiment of Fig. 4, the display device 4000 is implemented as a head-mounted see-through display device, more specifically, as glasses with a see-through display. In other embodiments, the display device can be implemented in any suitable manner, for example as a portable display device and / or a vehicle display device, which may or may not be further implemented as a see-through display device. In some embodiments, the display device can be specifically implemented as a head-mounted display device.

[0098] As used herein, a "head mounted display device" can refer to a portable display device configured to be worn on the head as part of a piece of headgear and / or on or floating above the eye. In general, a head mounted display device may or may not be implemented as a see-through display device and / or as a vehicular display device.

[0099] In the embodiment of Figure 4, the display device 4000 comprises a frame 4100 and a display structure 4200 according to the first aspect supported by the frame 4100. The display structure 4200 comprises a waveguide 4210, an in-coupling structure 4220, an exit pupil extension structure 4230 and an out-coupling structure 4240. In other embodiments, the display device may or may not comprise a frame supporting the display structure.

[0100] 4, the display device 4000 further comprises an optical engine 4250 configured to direct light 4251 to be coupled into the waveguide 4210 to an in-coupling structure 4220. In other embodiments, the display device may or may not comprise such an optical engine.

[0101] FIG. 5 illustrates a schematic of a vehicle 5000 according to one embodiment. In the embodiment of FIG. 5, the vehicle 5000 is implemented as a passenger vehicle. In other embodiments, the vehicle may or may not be implemented as a passenger vehicle. For example, in some embodiments, the vehicle may be implemented as a passenger car, a motor vehicle such as a truck, a motorcycle or a bus, a rail vehicle such as a train or a tram, heavy machinery such as a tractor or a harvester, a watercraft such as a ship or a boat, an aircraft such as a plane or a helicopter, or a spacecraft such as a space capsule or a spaceplane.

[0102] In the embodiment of Figure 5, a vehicle 5000 is provided with a vehicle display device 5100 according to the second aspect. Although not explicitly shown in Figure 5, the embodiment of Figure 5, or any part thereof, may generally include any feature and / or element disclosed with reference to or in conjunction with any of Figures 1-4.

[0103] The vehicle display device 5100 of the embodiment of Figure 5 comprises a display structure 5110 according to the first aspect and an optical engine 5120. The display structure 5110 comprises a waveguide 5111, an in-coupling structure 5112, an exit pupil expansion structure 5113 and an out-coupling structure 5114. In other embodiments, the vehicle display device may or may not comprise an optical engine.

[0104] The vehicle display device 5100 of the embodiment of Figure 5 is implemented as a head-up display device. In other embodiments, the display device may or may not be implemented as a head-up display device.

[0105] As used herein, a "head-up display device" may refer to a see-through vehicular display device configured to display images and / or data to an operator of a vehicle, e.g., a driver or pilot, without requiring the operator to look away from a normal viewpoint. In general, a head-up display device may or may not be implemented as a vehicle-mounted display device.

[0106] In the embodiment of FIG. 5, the vehicle 5000 further comprises a laminated window 5200, with the waveguide 5111 extending into the window 5200. In other embodiments, the one or more waveguides may be arranged in any suitable manner. In some embodiments, the waveguide may extend inside the laminated window, such as the windshield. In some embodiments, the vehicle may comprise a vehicle display device comprising a waveguide located away from the window.

[0107] It is obvious to those skilled in the art that the basic idea of ​​the present invention can be implemented in various ways according to the advancement of technology. Therefore, the present invention and its embodiments are not limited to the above examples, but can be modified within the scope of the claims.

[0108] It will be understood that any of the benefits and advantages described above may relate to one embodiment or may relate to several embodiments, and the embodiments are not limited to embodiments that solve any or all of the stated problems or have any or all of the stated benefits and advantages.

[0109] The term "comprising" is used herein to mean the inclusion of the features or acts preceding the term without excluding the presence of one or more additional features or acts. Further, by reference to "the singular" item, it will be understood to refer to one or more of that item. [Explanation of symbols]

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Claims

1. a waveguide (1100), an incoupling structure (1200) configured to couple input beams (1020) into said waveguide (1100) as incoupling beams (1021) associated with incoupling k-vectors (3021) defining a first region (2310) in k-space within an annular waveguide propagation region (2001) associated with said waveguide (1100); a diffractive exit pupil extension structure (1300) configured to receive the incoupling beams (1021) and diffract the incoupling beams (1021) to form a first guided beam group (1031) associated with a first k-vector group (3031) present in the first region (2310) and a second guided beam group (1032) associated with a second k-vector group (3032) present in a second region (2320) separate from the first region (2310); A display structure (1000) comprising: the display structure (1000) further comprises a diffractive outcoupling structure (1400) configured to receive from the exit pupil extension structure (1300) a first group of diffracted beams (1041) corresponding to a first group of diffracted k-vectors (3041) present in the first region (2310) and a second group of diffracted beams (1042) corresponding to a second group of diffracted k-vectors (3042) present in the second region (2320); A display structure (1000) wherein the outcoupling structure (1400) is configured to couple light from the first group of diffraction beams (1041) and light from the second group of diffraction beams (1042) out of the waveguide plate (1100).

2. 2. The display structure (1000) of claim 1, wherein the exit pupil expansion structure (1300) is configured to diffract the incoupling beam group (1021) in zeroth and first diffraction orders to form the first guided beam group (1031) and the second guided beam group (1032).

3. 3. A display structure (1000) as described in claim 1 or 2, wherein the exit pupil expansion structure (1300) is configured to further increase the number of diffracted beams by diffracting the first group of guided beams (1031) and the second group of guided beams (1032).

4. 2. The display structure (1000) of claim 1, wherein the exit pupil extension structure (1300) comprises a one-dimensional exit pupil extension grating (1310) that diffracts the incoupling beam group (1021) to form the first guided beam group (1031) and the second guided beam group (1032).

5. 2. The display structure (1000) of claim 1, wherein the first region (2310) defines a first light guiding direction (1001) and the second region (2320) defines a second light guiding direction (1002), and the minimum angle α between the first light guiding direction (1001) and the second light guiding direction (1002) is greater than or equal to 45° or 55° and / or less than or equal to 65° or 75°.

6. 2. The display structure (1000) of claim 1, further configured to diffract the first diffraction beam group (1041) and / or the second diffraction beam group (1042) to form a first additional beam group (1043) corresponding to a first additional k-vector group (3043) present in the second region (2320) and / or a second additional beam group (1044) corresponding to a second additional k-vector group (3044) present in the first region (2310), respectively.

7. 7. The display structure (1000) of claim 6, wherein the outcoupling structure (1400) comprises a two-dimensional outcoupling grating (1410) having a first periodicity for coupling light from the first diffraction beam group (1041) out of the waveguide plate (1100), a second periodicity for coupling light from the second diffraction beam group (1042) out of the waveguide plate (1100), and a third periodicity for forming the first additional beam group (1043) and / or the second additional beam group (1044).

8. 2. The display structure (1000) of claim 1, wherein the incoupling structure (1200) is configured to couple the input beam group (1020) into the waveguide plate (1100) so that light from the incoupling beam group (1021) is guided to the outcoupling structure (1400) without undergoing non-zero order diffraction.

9. the incoupling structure (1200) is further configured to couple the input beams (1020) into the waveguide (1100) as second-order incoupling beams (1022) associated with second-order incoupling k-vectors (3022) present in the second region (2320); 2. The display structure (1000) of claim 1, wherein the exit pupil extension structure (1300) is configured to receive the second-order incoupling beam group (1022) and diffract the second-order incoupling beam group (1022) to form a first second-order guided beam group (1033) corresponding to a first second-order k-vector group (3033) present in the first region (2310), and a second second-order guided beam group (1034) corresponding to a second second-order k-vector group (3034) present in the second region (2320).

10. 10. The display structure (1000) of claim 9, wherein the incoupling structure (1200) comprises a two-dimensional incoupling grating (1210) that couples the input beam group (1020) into the waveguide plate (1100) as the incoupling beam group (1021) and the secondary incoupling beam group (1022).

11. A display device (4000) comprising a display structure (1000) according to claim 1.

12. 12. The display device (4000) of claim 11 implemented as a see-through display device.

13. 12. The display device (4000) of claim 11 implemented as a portable display device.

14. The display device (4000) of claim 11 implemented as a vehicle display device.

15. A vehicle (5000) comprising a vehicle display device (5100) according to claim 14.

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