Display device

Abstract

According to an embodiment, a display device (100) comprises: a waveguide (101); a projector (102) configured to transmit a set of input beams (103) representing an image; an in-coupling and out-coupling structure (104) on the wave-guide (101) configured to: receive the set of input beams (103) in a first angle with respect to the waveguide (101); couple a first part of the set of input beams (103) into the waveguide (101) as a set of in-coupled beams (105); diffract a second part of the set of input beams (103) in a second angle with respect to the waveguide (101), different from the first angle; and out-couple the set of in-coupled beams (105) out of the wave-guide (101) as a set of out-coupled beams (106) in the second angle

Description

DISPLAY DEVICETECHNICAL FIELD

[0001] The present disclosure relates to the field of diffractive optics, and more particularly to a display device .BACKGROUND

[0002] Diffraction gratings can be utilized in various optical applications, such as in augmented reality (AR) applications. For example, diffraction gratings can be used to couple light into a waveguide, manipulate light coupled into a waveguide, and couple light out of a waveguide. When designing diffraction gratings for AR applications, for example, various challenges may arise, such as how to maximize the optical efficiency of the device .SUMMARY

[0003] This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.

[0004] It is an object to provide a display device. The foregoing and other objects are achieved by thefeatures of the independent claims . Further implementation forms are apparent from the dependent claims , the description and the figures .

[0005] According to a first aspect , a display device comprises : a waveguide ; a proj ector configured to transmit a set o f input beams representing an image ; an incoupling and out-coupling structure on the waveguide configured to : receive the set of input beams in a first angle with respect to the waveguide ; couple a first part of the set of input beams into the waveguide as a set of in-coupled beams ; di f fract a second part of the set of input beams in a second angle with respect to the waveguide, di f ferent from the first angle ; and out-cou- ple the set of in-coupled beams out of the waveguide as a set of out-coupled beams in the second angle .

[0006] In an implementation form of the first aspect , the set of in-coupled beams is associated with a set of in-coupled k-vectors in an annular guided propagation domain associated with the waveguide , the set of out- coupled beams is associated with a set of out-coupled k-vectors lying in an inner segment of a coupling domain associated with the waveguide, and the set of input beams is associated with a set of input k-vectors lying in the coupling domain outside the inner segment of the coupling domain .

[0007] In another implementation form of the first aspect , the inner segment of the coupling domain corresponds to an output field of view of the display device .

[0008] In another implementation form of the first aspect, the projector is arranged to transmit the set of input beams towards the in-coupling and out-coupling structure in the first angle.

[0009] In another implementation form of the first aspect, the projector further comprises a diffraction grating configured to diffract the set of input beams towards the in-coupling and out-coupling structure in the first angle.

[0010] In another implementation form of the first aspect, the in-coupling and out-coupling structure comprises a two-dimensional diffraction grating.

[0011] In another implementation form of the first aspect, the two-dimensional diffraction grating is configured to: couple the first part of the set of input beams into the waveguide as the set of in-coupled beams according to a first grating vector of the two-dimensional diffraction grating; diffract the set of in- coupled beams according to a second grating vector of the two-dimensional diffraction grating, thus producing a set of diffracted beams; and out-couple the set of diffracted beams out of the waveguide as the set of out- coupled beams in the second angle according to the first grating vector of the two-dimensional diffraction grating .

[0012] In another implementation form of the first aspect, the display device is further configured to perform exit pupil expansion via total internal reflection of the set of in-coupled beams inside the waveguide anddi f fraction of the set o f in-coupled beams caused by the in-coupling and out-coupling structure .

[0013] In another implementation form of the first aspect , the second angle is substantially zero with respect to a normal direction of the waveguide .

[0014] In another implementation form of the first aspect , the in-coupling and out-coupling structure causes a distortion to the set of out-coupled beams and the proj ector is configured to compensate for the distortion by performing a manipulation on the image and transmitting the manipulated image in the set of input beams .

[0015] In another implementation form of the first aspect , the proj ector i s a first proj ector , the set of input beams is a first set o f input beams compri sing a first wavelength range , and the display device further comprises : a second proj ector configured to transmit a second set of input beams comprising a second wavelength range ; and a third proj ector configured to transmit a third set of input beams comprising a third wavelength range ; wherein the in-coupling and out-coupling structure is further configured to : receive the second set of input beams in a third angle with respect to the waveguide and receive the third set of input beams in a fourth angle with respect to the waveguide ; couple a first part of the second set of input beams into the waveguide as a second set of in-coupled beams and couple a first part of the third set o f input beams into the waveguide as a third set o f in-coupled beams ; di f fracta second part of the second set o f input beams in the second angle and di ffract a second part of the third set of input beams in the second angle ; and out-couple the second set of in-coupled beams out of the waveguide as a second set of out-coupled beams in the second angle and out-couple the third set of in-coupled beams out of the waveguide as a third set of out-coupled beams in the second angle .

[0016] In another implementation form of the first aspect , the proj ector i s a first proj ector , the set of input beams is a first set o f input beams compri sing a first part of an image , wherein the display device further comprises : a second proj ector configured to transmit a second set of input beams compri sing second part of the image ; wherein the in-coupling and out-coupling structure is further configured to : receive the second set of input beams in a third angle with respect to the waveguide ; couple a first part of the second set of input beams into the waveguide as a second set of incoupled beams ; di f fract a second part of the second set of input beams in a fourth angle with respect to the waveguide, di f ferent from the third angle ; and out-cou- ple the second set of in-coupled beams out of the waveguide as a second set of out-coupled beams in the fourth angle .

[0017] In another implementation form of the first aspect , the display device is implemented as a head-mounted display device and the display device is arranged to direct the set of out-coupled beams towards an eye of a user of the head-mounted display device .

[0018] Many of the attendant features wi ll be more readily appreciated as they become better understood by reference to the following detailed description considered in connection with the accompanying drawings .DESCRIPTION OF THE DRAWINGS

[0019] In the following, embodiments are described in more detail with re ference to the attached f igures and drawings , in which :

[0020] Fig . 1 illustrates a schematic representation of a display device according to an embodiment ;

[0021] Fig . 2 illustrates a k-space representation of di f fraction according to an embodiment ;

[0022] Fig . 3 illustrates a schematic representation of out-couped beams according to an embodiment ;

[0023] Fig . 4 illustrates a schematic representation of out-couped beams according to another embodiment ;

[0024] Fig . 5 illustrates a schematic representation of a display device according to another embodiment ;

[0025] Fig . 6 illustrates a schematic representation of a display device according to another embodiment ;

[0026] Fig . 7 illustrates a k-space representation of di f fraction according to another embodiment ;

[0027] Fig . 8 illustrates a schematic representation of a display device according to another embodiment ;

[0028] Fig . 9 illustrates a k-space representation of di f fraction according to another embodiment ;

[0029] Fig . 10 illustrates a k-space representation of di f fraction according to another embodiment ;

[0030] Fig . 11 illustrates a schematic representation of a display device according to another embodiment ; and

[0031] Fig . 12 illustrates a schematic representation of a display device according to another embodiment .

[0032] In the following, identical reference signs refer to similar or at least functionally equivalent features .DETAILED DESCRIPTION

[0033] In the following description, reference is made to the accompanying drawings , which form part of the disclosure , and in which are shown, by way of illustration, speci fic aspects in which the present disclosure may be placed . I t i s understood that other aspects may be utilised, and structural or logical changes may be made without departing from the scope of the present disclosure . The following detailed description, therefore , is not to be taken in a limiting sense , as the scope of the present disclosure i s defined by the appended claims .

[0034] For instance , it is understood that a disclosure in connection with a described method may also hold true for a corresponding device or system configured to perform the method and vice versa . For example , i f aspeci fic method step is described, a corresponding device may include a unit to perform the described method step, even i f such unit i s not expl icitly described or illustrated in the figures . On the other hand, for example , i f a speci fic apparatus is described based on functional units , a corresponding method may include a step performing the described functionality, even i f such step is not explicitly described or illustrated in the figures . Further, it is understood that the features of the various example aspects described herein may be combined with each other, unless speci fically noted otherwise .

[0035] Fig . 1 illustrates a schematic representation of a display device according to an embodiment .

[0036] According to an embodiment , a display device 100 comprises a waveguide 101 .

[0037] The waveguide 101 may comprise, for example , a planar waveguide . The waveguide 101 may comprise substantially planar sections . Alternatively or additionally, the waveguide 101 may also comprise curved sections . For example , the waveguide 101 may correspond to a lens or a layer of a lens of augmented reality (AR) glasses .

[0038] The display device 100 may further comprise a proj ector 102 configured to transmit a set of input beams 103 representing an image .

[0039] Herein, a beam may also be referred to as a ray, a light beam, a light ray, or similar .

[0040] For example, in the embodiment of Fig. 1, three beams, corresponding to a leftmost beam 111, a rightmost beam 113, and a central beam 112, of the set of input beams 103 are illustrated. These beams are only illustrated to describe the functionality of the display device 100. In practical applications, the set of input beams 103 may comprise any number of beams.

[0041] The set of input beams 103 may also be referred to as, for example, image-bearing light rays / beams, image-carrying light rays / beams, or similar.

[0042] The display device 100 may further comprise an in-coupling and out-coupling structure 104 on the waveguide 101 configured to receive the set of input beams 103 in a first angle with respect to the waveguide.

[0043] The set of input beams 103 may propagate in a range of angles. The first angle may refer to the cen- tral / average angle of the set of input beams 103.

[0044] For example, in the embodiment of Fig. 1, the leftmost beam 111 and the rightmost beam 113 define the edges of the set of input beams 103. Thus, the first angle of the set of input beams 103 may be considered the central / average angle of the angles of the leftmost beam 111 and of the rightmost beam 113.

[0045] The in-coupling and out-coupling structure 104 may comprise, for example, a monolithic diffraction grating .

[0046] The in-coupling and out-coupling structure 104 may be further configured to couple a first part of theset of input beams into the waveguide 101 as a set of in-coupled beams 105.

[0047] For example, in the embodiment of Fig. 1, the in-coupling and out-coupling structure 104 can couple the leftmost beam 111 and the rightmost beam 113 into the waveguide 101 as the set of in-coupled beams 105. This is only an illustrative example. In practical implementations, various parts of the set of input beams 103 can be coupled into the waveguide 103 as a set of in-coupled beams 105.

[0048] The in-coupling and out-coupling structure 104 may be further configured to diffract a second part of the set of input beams in a second angle with respect to the waveguide, different from the first angle.

[0049] For example, in the embodiment of Fig. 1, the in-coupling and out-coupling structure 104 can diffract the central beam 112 in a second angle with respect to the waveguide 101.

[0050] The in-coupling and out-coupling structure 104 may be further configured to out-couple the set of incoupled beams 105 out of the waveguide as a set of out- coupled beams 106 in the second angle.

[0051] The set of out-coupled beams 106 may propagate in a range of angles. The second angle may refer to the central / average angle of the set of out-coupled beams 106. The set of out-coupled beams 106 can arrive to an eye 120 of a user in various angles and thus represent different parts of the image.

[0052] For example , in the embodiment o f Fig . 1 , the set of in-coupled beams 105 are out-coupled from the waveguide 101 as the set of out-coupled beams 106 .

[0053] According to an embodiment , the proj ector is arranged to transmit the set of input beams towards the in-coupling and out-coupling structure in the first angle .

[0054] The in-coupling and out-coupling structure 104 may comprise , for example , an in-coupling and out-coupling dif fraction grating . The in-coupling and out-coupling structure 104 may be configured to couple the set of input beams 103 into the waveguide 101 as the set of in-coupled beams 105 via di f fraction .

[0055] Herein, a di f fraction grating may refer to a grating that has a spatial periodicity of the same order of magnitude or greater than the smallest wavelength of the set of input beams 103 . Alternatively or additionally, a di f fraction grating may refer to a grating that has a spatial periodicity o f the same order of magnitude or greater than the smallest wavelength of visible light , such as greater than 380 nanometres (nm) .

[0056] Herein, when the spatial periodicity is of the same order of magnitude with the the smallest wavelength of the set o f input beams 103 , the spatial periodicity may be, for example, at least one third of the smallest wavelength of the set of input beams 103 . Thus , when the spatial periodicity is of the same order of magnitude with the smallest wavelength of the set o f input beams 103 , the spatial periodicity may be smaller than but ofthe same order of magnitude with the the smallest wavelength of the set of input beams 103 . For example , in some embodiments , the spatial periodicity may be 130 nm or greater .

[0057] According to an embodiment , the second angle is substantially zero with respect to a normal direction 110 of the waveguide 101 .

[0058] Herein, a normal direction 110 of waveguide 101 may refer to a normal direction of the waveguide 101 on the side of the waveguide 101 on which the in-coupling and out-coupling structure 104 is located . The normal direction 110 of waveguide 101 may also be referred to as a normal direction of the in-coupling and out-coupling structure 104 .

[0059] For example , in the embodiment of Fig . 1 , the second angle i s substantially zero with respect to the normal direction 110 of the waveguide 101 . Thus , the set of out-coupled beams 106 may be substantially parallel with the normal direction 110 of the waveguide 101 .

[0060] Herein, substantially parallel may mean that the angle between the substantially parallel directions is substantially 0 degrees , such as less than 5 degrees , less than 1 degrees , or less than 0 . 1 degrees .

[0061] In other embodiments , the first angle may be substantially zero with respect to a normal direction 110 of the waveguide . In such embodiments , the set o f input beams 103 may propagate substantially parallel with the normal direction 110 of the waveguide 101 whi lethe set of out-coupled beams 106 may propagate in some other direction .

[0062] In other embodiments , the first angle and the second angle may be non- zero with respect to a normal direction 110 of the waveguide . For example , in some embodiments , the first angle and / or the second angle may be 10 - 15 degrees . In other embodiments , the first angle and / or the second angle may be 3 - 5 degrees . In other embodiments , the second angle may be 13 - 20 degrees . The first angle may be , for example , 55 - 60 degrees .

[0063] According to an embodiment , the in-coupling and out-coupling structure 104 causes a distortion to the set of out-coupled beams 106 and the proj ector 102 i s configured to compensate for the distortion by performing a manipulation on the image and transmitting the manipulated image in the set of input beams 103 .

[0064] For example, the manipulation may be an inverse of the distortion caused by the in-coupling and out- coupling structure 104 .

[0065] The distortion may also be referred to as an optical distortion .

[0066] For example, the edges of the image transmitted by the in-coupling and out-coupling structure 104 may be less bright than the centre of the image . In such cases , the manipulation may comprise increasing the brightness of the image at the edges compared to the centre . In other embodiments , the distortion may comprise any other type of distortion .

[0067] Since the second angle is di f ferent from the first angle , the image transmitted in the second angle by the in-coupling and out-coupling structure may be referred to as a ghost image .

[0068] The di splay device 100 may be able to provide improved optical ef ficiency .

[0069] Since the display device 100 may reduce interactions between the light and the in-coupling and out- coupling structure 104 , the di splay device 100 may improve image quality, image sharpness , and / or colour balance .

[0070] Since the in-coupling and out-coupling structure 104 may perform both in-coupling and out-coupling of light , designing of the waveguide 101 may be made easier, since separate in-coupling and out-coupling structures are not needed . This can also reduce the required si ze of the waveguide 101 , since less surface area may be needed .

[0071] In some embodiments , the in-coupling and out- coupling structure 104 may be implemented as separate in-coupling structure and a separate out-coupling structure . The in-coupling structure may comprise, for example, an in-coupling di f fraction grating and / or the out- coupling structure may comprise , for example , an out- coupling di f fraction grating .

[0072] It should be understood that the geometry of the display device 100 illustrated in the embodiment of Fig . 1 is only exemplary and the display device 100 maybe implemented in various other ways . Further, the embodiment of Fig . 1 illustrates the display device 100 only in one plane .

[0073] Fig . 2 illustrates a k-space representation of di f fraction according to an embodiment .

[0074] Each k-vector in k-space can represent a propagation direction o f a light beam ins ide the waveguide 101 . The magnitude of each k-vector corresponds to a wavenumber k . A k-vector can be expressed as k = nv , where n is the refractive index of the medium of the waveguide 101 and v is a unit vector pointing towards the propagation direction of the k-vector . k may also be referred to as a normali zed k-vector .

[0075] An annular guided propagation domain 232 may refer to a part of the k-space in which beams are guided inside the waveguide 101 . An example of an annular guided propagation domain 232 is illustrated in the embodiment of Fig . 2 .

[0076] The waveguide 101 can guide beams having certain k-vectors via total internal reflection ( TIR) . A coupling domain 231 corresponds to k-vectors that do not have suf ficient x and / or y components to be guided inside the waveguide 101 via TIR . Here , the x and y axes are in the plane of the waveguide 101 while the z axis is along a thickness direction of the waveguide 101 . For such beams , the angle between the beam and the surface ( s ) of the waveguide 101 is not suf ficient to cause TIR as governed by Snell ' s law . K-vectors inside the annular guided propagation domain 232 have suf ficient xand / or y components to be guided inside the waveguide 101 via TIR . K-vectors at the outer circumference of the annular guided propagation domain 232 correspond to beams propagating along the plane of the waveguide 101 , i . e . such beams do not have any z component . Radius of the coupling domain 231 may be 1 and radius o f the annular guided propagation domain 232 may be n .

[0077] According to an embodiment, the set of in-coupled beams 105 is associated with a set of in-coupled k-vectors 201 in an annular guided propagation domain associated with the waveguide , the set of out-coupled beams 106 is associated with a set of out-coupled k- vectors 202 lying in an inner segment 230 of a coupling domain 231 associated with the waveguide 101 , and the set of input beams 103 is associated with a set of input k-vectors 203 lying in the coupling domain 231 outs ide the inner segment 230 of the coupling domain 231 .

[0078] The inner segment 230 may comprise a subsection of the coupling domain 231 . The inner segment 230 may be enclosed by the coupling domain 231 . For example , the coupling domain 231 may have a circular shape , the inner segment 230 may have a circular shape, the center of the coupling domain 231 and the center of the inner segment 230 may be located in the same point, and the radius of the inner segment 230 may be less than the radius of the coupling domain 231 . For example, the radius of the inner segment 230 may be les s than 95% , 90% , 85% , 80% , 70% , 65% , 55% , 50% , 45% , 40% , or 35% of the radius o f the coupling domain 231 .

[0079] Although the inner segment 230 is illustrated as circular in the embodiment of Fig . 2 , the inner segment 230 may also have various other shapes . For example , in some embodiments , the inner segment 230 may have a pillow-like shape .

[0080] In some embodiments , the location of the set of input k-vectors 203 and the location of the set of out-coupled k-vectors 202 may be swapped compared to what is illustrated in the embodiment of Fig 2 . In such embodiments , the set of input beams 103 may propagate substantially parallel with the normal direction 110 o f the waveguide 101 , thus the set o f input k-vectors 203 may be located substantially in the center o f the coupling domain 231 , while the set of out-coupled beams 106 may propagate in some other direction . In such embodiments , the inner segment 230 may not be located in the center of the coupling domain 231 .

[0081] A transition and / or a combination of transitions in k-space may correspond to an interaction of light with a di f fraction grating . Such an interaction can cause the light to propagate into a di f ferent direction or directions than before the interaction . The change in propagation direction can be observed as a translation in k-space along a transition .

[0082] The in-coupling and out-coupling structure 104 can couple the set of input beams 103 into the waveguide 101 as the set of in-coupled beams 105 . This corresponds to shi fting the set of input k-vectors 203 into the annular guided propagation domain 232 along transition211 . The in-coupling and out-coupling structure 104 can also couple the set of input beams 103 into the waveguide 101 as the set of in-coupled beams 105 in various other ways . For example , one such in-coupling can be illustrated with shi fting the set of input k-vectors 203 into the annular guided propagation domain 232 along transition 215 .

[0083] According to an embodiment , the inner segment 230 of the coupling domain 231 corresponds to an output field of view of the display device .

[0084] By having the set of input k-vectors 203 lying in the coupling domain 231 outside the inner segment 230 of the coupl ing domain, an unwanted ghost image due to the set of input beams 103 may not be visible to the user of the display device 100 .

[0085] Output definitions , such as the field of view, possible tilts etc . , together with eye-box definition can determine the si ze and shape of the in-coupling and out-coupling structure 104 . The corner-to-corner angles from the in-coupling and out-coupling structure 104 to eye-box to can be calculated to determine which light rays can exit from the in-coupling and out-coupling structure 104 and end up in eye-box . This angle area / space , corresponding to the inner segment 230 , should be forbidden for set of input k-vectors 203 and non-wanted ghost images i f these should not be seen by the user . The remaining area / space o f the coupling domain 231 is allowed for the set of input k-vectors 203 .

[0086] The different k-vectors in the set of in-coupled k-vectors 201, the set of out-coupled k-vectors 202, and the set of input k-vectors 203 illustrated by the rectangles in the embodiment of Fig. 2, may correspond to, for example, different parts of an image represented by the set of input beams 103. Different parts of the set of input beams 103 can arrive to the incoupling and out-coupling structure 104 at slightly different angles. Thus different parts of the set of input k-vectors 203 may be in slightly different locations of the k-space, thus producing the illustrated rectangles.

[0087] As the set of in-coupled beams 105 propagate in the area of the in-coupling and out-coupling structure 104, the corresponding light can interact with the in-coupling and out-coupling structure 104 each time the light hits the side of the waveguide 101 on which the in-coupling and out-coupling structure 104 is located. In the interaction, a part of the light can diffract from the in-coupling and out-coupling structure 104. Each diffraction from the in-coupling and out-coupling structure 104 can correspond to a transition in k-space.

[0088] According to an embodiment, the in-coupling and out-coupling structure 104 comprises a two-dimensional diffraction grating.

[0089] According to an embodiment, the two-dimensional diffraction grating is configured to: couple the first part of the set of input beams into the waveguide as the set of in-coupled beams according to a firstgrating vector of the two-dimensional di f fraction grating ; di f fract the set of in-coupled beams according to a second grating vector of the two-dimensional di ffraction grating, thus producing a set of dif fracted beams ; and out-couple the set o f di f fracted beams out of the waveguide as the set of out-coupled beams in the second angle according to the first grating vector of the two- dimensional di f fraction grating .

[0090] Each transition in k-space can correspond to a grating vector of the in-coupling and out-coupling structure 104 . For example , transition 211 can correspond to a first grating vector a of the in-coupling and out-coupling structure 104 .

[0091] The set o f in-coupled beams 105 can be guided inside the waveguide 101 via TIR . As the set of incoupled beams 105 propagate in the area of the in-coupling and out-coupling structure 104 , the corresponding light can interact with the in-coupling and out-coupling structure 104 each time the light hits the s ide of the waveguide 101 on which the in-coupling and out-coupling structure 104 is located . In the interaction, a part of the light can di f fract from the in-coupling and out- coupling structure 104 and a part can continue to propagate in the original direction in the xy plane whi le the z component can change direction due to TIR . This di f fraction can be illustrated with transition 212 in k-space corresponding to a second grating vector a2of the in-coupling and out-coupling structure 104 . The set of in-coupled beams 105 can be further di f fracted fromthe in-coupling and out-coupling structure 104. This can be illustrated with transition 213 in k-space corresponding to a negative version of the first grating vector — a of the in-coupling and out-coupling structure 104. Transition 211 may be referred to as 1st diffraction and transition 213 may be referred to as -1st order diffraction.

[0092] Any diffraction from the in-coupling and out- coupling structure 104 can also occur via higher order diffractions. Such diffractions can be illustrated in k-space as linear combinations Aa1+Ba2of the first grating vector a and the second grating vector a2, where A and B are integers. For example, the in-coupling and out-coupling structure 104 can couple the set of input beams 103 into the waveguide 101 as the set of in-coupled beams 105 via such higher order diffractions. Thus the embodiments illustrated in the figures illustrate only some of the diffractions that may occur.

[0093] The in-coupling and out-coupling structure 104 can diffract the second part of the set of input beams in a second angle with respect to the waveguide, different from the first angle. This can be illustrated in k-space with transition 214.

[0094] It should be appreciated that the set of incoupled beams 105 can propagate inside the waveguide 101 and diffract from the in-coupling and out-coupling structure 104 in various other ways in addition to what is described above. For example, as is illustrated in the embodiment of Fig. 2, the set of input beams 103 canbe in-coupled according to transition 215 as the set of in-coupled beams 105 and the set of in-coupled beams 105 can be diffracted via transitions 216 and 217. Further, after transition 212, the light can be diffracted again according to the second grating vector a2, resulting in transition 218. This light can then be out-coupled from the waveguide 101 via transitions 219 and 220. Some out- coupling can occur after transition 219, which can produce an unwanted ghost image. Similarly, the set of input beams 103 can be in-coupled according to transition 215 as the set of in-coupled beams 105 and the set of in-coupled beams 105 can be diffracted via transitions 216, 221, 223, and 220. Further, light can also be diffracted via higher order diffractions. For example, the set of in-coupled beams 105 can be diffracted via 2nd order diffraction along the second grating vector. This can be illustrated in k-space with a transition 2a2. Further, the set of in-coupled beams 105 can be out-coupled from the waveguide 101 via various other paths in k-space that can be formed as linear combinations of the grating vectors a and a2.

[0095] It should be appreciated that any combination of transition in k-space illustrated herein may occur due to various different interactions with the in-coupling and out-coupling structure 104. For example, the combination of transition 211, 212, and 213 may occur, for example, by the set of input beams 103 being incoupled according to transition 211. The set of incoupled beams 105 can then be diffracted according totransition 212 during a first interaction with the incoupling and out-coupling structure 104 and the resulting light can then be di f fracted according to transition 213 , and thus be out-coupled, during a second interaction with the in-coupling and out-coupling structure 104 . Alternatively, the set o f input beams 103 can be in-coupled according to a linear combination of transition 211 and transition 212 . The resulting set of incoupled beams 105 can then be di f fracted according to transition 213 , and thus be out-coupled, during a first interaction with the in-coupling and out-coupling structure 104 . Alternatively, the set of input beams 103 can be in-coupled according to transition 211 . The resulting set of in-coupled beams 105 can then be di f fracted according to a linear combination of transition 212 and transition 213 , and thus be out-coupled, during a first interaction with the in-coupling and out-coupling structure 104 .

[0096] Fig . 3 illustrates a schematic representation of out-couped beams according to an embodiment .

[0097] The embodiment of Fig . 3 illustrates how the leftmost beam 111 illustrated in the embodiment of Fig . 1 can be manipulated by the in-coupling and out-coupling structure 104 as the corresponding light propagates inside the waveguide 101 and is di f fracted and out-coupled by the in-coupling and out-coupling structure 104 . It should be appreciated that the embodiment of Fig . 3 only illustrates the behaviour of the light in one plane .

[0098] The leftmost beam 111 can correspond to , for example , the left edge of the set of input k-vectors 203 illustrated in the embodiment of Fig . 2 . After trans itions 211 , 212 , and 213 , the leftmost beam can be out- coupled from the in-coupling and out-coupling structure 104 as the le ft edge o f the out-coupled k-vectors 202 . The leftmost beam 111 can arrive to the eye 120 of the user and represent the leftmost part of the image .

[0099] According to an embodiment, the display device 100 is further configured to perform exit pupi l expansion via total internal reflection of the set of incoupled beams 105 inside the waveguide 101 and di ffraction of the set of in-coupled beams 105 caused by the in-coupling and out-coupling structure 104 .

[0100] For example , in the embodiment of Fig . 3 , exit pupil expansion is illustrated in one direction . In embodiments , where the in-coupling and out-coupling structure 104 comprises a two-dimensional di f fraction grating, the in-coupling and out-coupling structure 104 may further perform exit pupil expansion in two directions as illustrated in, for example , the embodiment o f Fig .2 .

[0101] Fig . 4 illustrates a schematic representation of out-couped beams according to another embodiment .

[0102] The embodiment of Fig . 4 illustrates how the rightmost beam 113 illustrated in the embodiment of Fig . 1 can be manipulated by the in-coupling and out-coupling structure 104 as the corresponding light propagates inside the waveguide 101 and is di f fracted and out-coupledby the in-coupling and out-coupling structure 104. It should be appreciated that the embodiment of Fig. 4 only illustrates the behaviour of the light in one plane.

[0103] The rightmost beam 113 can correspond to, for example, the right edge of the set of input k-vectors 203 illustrated in the embodiment of Fig. 2. After transitions 211, 212, and 213, the rightmost beam can be out-coupled from the in-coupling and out-coupling structure 104 as the right edge of the out-coupled k-vectors 202. The rightmost beam 113 can arrive to the eye 120 of the user and represent the rightmost part of the image .

[0104] It should be appreciated that Figs. 3 and 4 only illustrate beams produced by the leftmost 111 and rightmost 113 beams. In other figures herein, only the beams arriving to the eye 120 of the user may be illustrated for clarity purposes although various other beams may also be produced in a similar fashion to what is illustrated in Figs. 3 and 4.

[0105] Fig. 5 illustrates a schematic representation of a display device according to another embodiment.

[0106] According to an embodiment, the projector 102 further comprises a diffraction grating 501 configured to diffract the set of input beams 103 towards the incoupling and out-coupling structure 104 in the first angle .

[0107] The diffraction grating 501 of the projector 102 can be configured to distribute the set of input beams 103 into different angles around the first angle.

[0108] In some embodiments, a grating vector of the diffraction grating 105 of the projector can be equal to the second grating vector of the in-coupling and out- coupling structure 104. With such a configuration, the in-coupling and out-coupling structure 104 can receive the set of input beams 103 in the first angle and transmit the set of out-coupled beams 106 in the second angle.

[0109] Fig. 6 illustrates a schematic representation of a display device according to another embodiment.

[0110] According to an embodiment, the projector 102 is a first projector, the set of input beams 103 is a first set of input beams comprising a first wavelength range, and the display device 100 further comprises a second projector 601 configured to transmit a second set of input beams 611 comprising a second wavelength range and a third projector 602 configured to transmit a third set of input beams 612 comprising a third wavelength range .

[0111] The first wavelength range can be different from the second wavelength range. The first wavelength range can be different from the third wavelength range. The second wavelength range can be different from the third wavelength range. The first, second, and third wavelength range may be non-overlapping. The first and second wavelength range may be non-overlapping and contiguous. The second and third wavelength range may be non-overlapping and contiguous.

[0112] The in-coupling and out-coupling structure 104 may be further configured to: receive the second set ofinput beams 611 in a third angle with respect to the waveguide 101 and receive the third set of input beams 612 in a fourth angle with respect to the waveguide 101 ; couple a first part of the second set of input beams 611 into the waveguide 101 as a second set of in-coupled beams 621 and couple a first part of the third set o f input beams 612 into the waveguide 101 as a third set of in-coupled beams 622 ; di f fract a second part of the second set of input beams 611 in the second angle and di f fract a second part of the third set o f input beams 612 in the second angle ; and out-couple the second set of in-coupled beams 621 out of the waveguide 101 as a second set of out-coupled beams 631 in the second angle and out-couple the third set of in-coupled beams 622 out of the waveguide 101 as a third set of out-coupled beams 632 in the second angle .[01 1 3] The second set of input beams 611 may propagate in a range o f angles . The third angle may re fer to the central / average angle of the second set o f input beams 611 .

[0114] The third set of input beams 612 may propagate in a range of angles . The fourth angle may refer to the central / average angle of the third set of input beams 612 .[01 1 5] The second set of out-coupled beams 631 may propagate in a range of angles . The second angle may refer to the central / average angle of the second set of out-coupled beams 631 .

[0116] The third set of out-coupled beams 632 may propagate in a range of angles. The second angle may refer to the central / average angle of the third set of out-coupled beams 632.

[0117] In some embodiments, the first, second and third projector 102, 601, 602 may be implemented as physically separated projectors. In other embodiments, the first, second, and third projector 102, 601, 602 may be implemented as virtual projectors using a single physical projector. For example, the output of a single physical projector may comprise three areas, wherein each area correspond to one wavelength range of the first, second, and third wavelength range.

[0118] For example, the first, second, and third wavelength range may correspond to the red, green, and blue channels of an image.

[0119] Since the diffraction cause by the in-coupling and out-coupling structure 104 may be wavelength dependent, by receiving the different sets of input beams in different angles, the different angles can compensate for the wavelength dependence of the diffraction so that the sets of out-coupled beams can be out-coupled in the second angle.

[0120] Fig. 7 illustrates a k-space representation of diffraction according to another embodiment.

[0121] The embodiment of Fig. 7 illustrates how the first, second, and third set of input beams 103, 611, 612 comprising the first, second, and third wavelength range can behave in k-space.

[0122] Since the first , second, and third set of input beams 103 , 611 , 612 can arrive to the in-coupling and out-coupling structure 104 in di f ferent angles , the corresponding sets of input k-vectors 203 may be located at slightly di f ferent locations in k-space as illustrated in the embodiment of Fig . 7 . Since the di f fraction caused by the in-coupling and out-coupling structure 104 can be wavelength dependent , the sets of incoupled k-vectors 201 may be further spread out in k- space . After transitions 212 and 213 , the sets o f out- coupled k-vectors 202 can be in the coupling domain and thus the sets of in-coupled beams can be out-coupled from the waveguide 101 .

[0123] As discussed in relation not the embodiment of Fig . 2 , in addition to what is illustrated in the embodiment of Fig . 7 , the the sets of in-coupled beams can also be out-coupled from the waveguide 101 via various other paths in k-space , such as those illustrated in the embodiment of Fig . 2 and / or that can be formed as linear combinations of the grating vectors a and a2.

[0124] Fig . 8 illustrates a schematic representation of a display device according to another embodiment .

[0125] According to an embodiment , the proj ector 102 is a f irst proj ector and the set of input beams 103 is a first set of input beams comprising a first part of an image .

[0126] The display device 100 may further comprise a second proj ector 901 configured to transmit a second set of input beams 911 comprising second part of the image .

[0127] The in-coupling and out-coupling structure 104 may be further configured to: receive the second set of input beams 911 in a third angle with respect to the waveguide 101, couple a first part of the second set of input beams 911 into the waveguide as a second set of in-coupled beams 921, diffract a second part of the second set of input beams 911 in a fourth angle with respect to the waveguide, different from the third angle; and out-couple the second set of in-coupled beams 921 out of the waveguide 101 as a second set of out- coupled beams 931 in the fourth angle.

[0128] The first projector 102 and the second projector 901 can be used to increase the field of view of the display device 100, since the first projector 102 can be used to transmit the first part of the image and the second projector 901 can be used to transmit the second part of the image. The second angle can correspond to a first part of the field of view and the fourth angle can correspond to a second part of the field of view.

[0129] In other embodiments, the display device may comprise a greater number of projectors, such as four projectors, and each projector can be used to transmit a different part of the image in order to increase the field of view of the display device 100.

[0130] In other embodiments, the projector 102 may be a first projector, the set of input beams 103 may be a first set of input beams comprising the image. The display device may further comprise a second projector 901configured to transmit a second set of input beams 911 comprising the image .

[0131] The in-coupling and out-coupling structure 104 may be further configured to : receive the second set of input beams 911 in a third angle with respect to the waveguide 101 wherein the first angle and the third angle have opposite signs when measured with respect to a normal direction of the waveguide 101 , couple a first part of the second set of input beams 911 into the waveguide as a second set of in-coupled beams 921 , di ffract a second part of the second set of input beams 911 in the second angle ; and out-couple the second set o f in-coupled beams 921 out of the waveguide 101 as a second set of out-coupled beams 931 in the second angle .

[0132] In some embodiments , an absolute value of the first angle can be substantially equal to an absolute value of the third angle .

[0133] Since the first angle and the third angle have opposite signs when measured with respect to a normal direction of the waveguide 101 , the first proj ector 102 and the second proj ector 901 can transmit the same image from di f ferent sides of sets of out-coupled beams 106 , 931 as is illustrated in the embodiment of Fig . 8 . In such embodiments , the di f fraction experienced by the light transmitted by the second proj ector 901 can be illustrated in a similar fashion as what is illustrated in the embodiment of Fig . 2 but the set of input k- vectors of the second set of input beams 911 can be located on the opposite side of the y axis from the setof input k-vectors 203 of the first set of input beams 103 and at least some of the illustrated transitions may occur in the opposite direction from what is illustrated in the embodiment of Fig. 2.

[0134] In other embodiments, the in-coupling and out- coupling structure 104 may be further configured to receive the second set of input beams 911 in a third angle with respect to the waveguide 101 wherein the first angle and the third angle have opposite signs when measured with respect to the second angle.

[0135] Fig. 9 illustrates a k-space representation of diffraction according to another embodiment.

[0136] The embodiment of Fig. 9 illustrates a k-space representation of using the first projector 102 and the second projector 901 to increase the field of view of the display device 100. The embodiment of Fig. 9 illustrates the diffraction experienced by the first set of in-coupled beams 105.

[0137] In the embodiment of Fig. 9, the inner segment 230 has a pillow-like shape. This is only exemplary and the inner segment 230 may have any shape in any embodiment disclosed herein.

[0138] As discussed in relation to the embodiment of Fig. 2, the first set of in-coupled beams 105 can propagate inside the waveguide 101 and diffract from the incoupling and out-coupling structure 104 in various other ways in addition to what is illustrated in Fig. 9.

[0139] Fig. 10 illustrates a k-space representation of diffraction according to another embodiment.

[0140] The embodiment of Fig. 10 illustrates a k-space representation of using the first projector 102 and the second projector 901 to increase the field of view of the display device 100. The embodiment of Fig. 10 illustrates the diffraction experienced by the second set of input beams 911 corresponding to a second set of input k-vectors 1001.

[0141] The second set of input beams 911 can be incoupled to the waveguide 101 by the in-coupling and out- coupling structure 104, corresponding to transition1002, producing the second set of in-coupled beams 921 corresponding to a second set of in-coupled k-vectors1003. The second set of in-coupled beams 921 can be diffracted again by the in-coupling and out-coupling structure 104, corresponding to transition 1004, thus producing a second set of diffracted beams. The second set of diffracted beams can be out-coupled from the waveguide 101 by the in-coupling and out-coupling structure 104, corresponding to transition 1005.

[0142] As discussed in relation to the embodiment of Fig. 2, the second set of in-coupled beams 921 can also propagate inside the waveguide 101 and diffract from the in-coupling and out-coupling structure 104 in various other ways in addition to what is illustrated in Fig. 10.

[0143] Fig. 11 illustrates a schematic representation of a display device according to another embodiment.

[0144] According to an embodiment, set of input beams 103 is located on a different side of the waveguide from the set of out-coupled beams 106.

[0145] According to an embodiment, the projector 102 is located on a different side of the waveguide from the set of out-coupled beams 106.

[0146] According to an embodiment, the projector 102 is located on a different side of the waveguide from the in-coupling and out-coupling structure 104.

[0147] In some embodiments, the in-coupling and out- coupling structure 104 may be located on a different side of the waveguide 101 from the set of out-coupled beams 106.

[0148] The opposite side of the waveguide 101 from the set of out-coupled beams 106 may also be referred to as the world side, while the side of the waveguide 101 with the set of out-coupled beams 106 may be referred to as the image side or as the eye side. In practical implementations, out-coupling of light may occur to both sides of the waveguide 101.

[0149] Fig. 12 illustrates a schematic representation of a display device according to another embodiment.

[0150] According to an embodiment, the display device 100 is implemented as a head-mounted display device and the display device 100 is arranged to direct the set of out-coupled beams 106 towards an eye of a user of the head-mounted display device.

[0151] The display device 100 may comprise a near-eye display .

[0152] According to an embodiment, the projector 102 comprises a scanner-based optical engine and / or a laserscanning optical engine.

[0153] A laser-scanning optical engine may comprise, for example, a laser beam scanning (LBS) optical engine.

[0154] In some embodiments, the optical engine may comprise a liquid crystal on silicon (LCOS) based optical engine, a digital light processing (DLP) based optical engine, and / or a microLED based optical engine.

[0155] According to an embodiment, the display device 100 is implemented as a see-through display device.

[0156] For example, in the embodiment of Fig. 12, the display device 100 is implemented as smart glasses. The waveguide 101 can correspond to a lens or a layer of a lens of such smart glasses. Such smart glasses may be used to, for example, implement augmented reality (AR) , virtual reality (VR) , and / or extended reality (XR) functionality.

[0157] In the embodiment of Fig. 12, the display device 100 can direct the set of out-coupled beams 106, representing the image generated by the projector 102, into the eye of a user.

[0158] Any range or device value given herein may be extended or altered without losing the effect sought. Also any embodiment may be combined with another embodiment unless explicitly disallowed.

[0159] Although the subject matter has been described in language specific to structural features and / or acts, it is to be understood that the subject matter definedin the appended claims i s not necessarily limited to the speci fic features or acts described above . Rather, the speci fic features and acts described above are disclosed as examples of implementing the claims and other equivalent features and acts are intended to be within the scope of the claims .

[0160] It will be understood that the benefits and advantages described above may relate to one embodiment or may relate to several embodiments . The embodiments are not limited to those that solve any or all o f the stated problems or those that have any or all of the stated benefits and advantages . I t wil l further be understood that reference to ' an ' item may refer to one or more of those items .

[0161] Aspects of any of the embodiments described above may be combined with aspects of any of the other embodiments described to form further embodiments without losing the ef fect sought .

[0162] The term ' comprising ' is used herein to mean including the method, blocks or elements identi fied, but that such blocks or elements do not comprise an exclusive list and a method or apparatus may contain additional blocks or elements .

[0163] It will be understood that the above description is given by way of example only and that various modi fications may be made by those ski lled in the art . The above speci fication, examples and data provide a complete description of the structure and use of exemplary embodiments . Although various embodiments havebeen described above with a certain degree of particularity, or with reference to one or more individual embodiments , those skilled in the art could make numerous alterations to the disclosed embodiments without departing from the spirit or scope of this speci fication .

Claims

CLAIMS :

1. A display device (100) , comprising: a waveguide (101) ; a projector (102) configured to transmit a set of input beams (103) representing an image; an in-coupling and out-coupling structure (104) on the waveguide (101) configured to: receive the set of input beams (103) in a first angle with respect to the waveguide (101) ; couple a first part of the set of input beams (103) into the waveguide (101) as a set of in-coupled beams (105) ; diffract a second part of the set of input beams (103) in a second angle with respect to the waveguide (101) , different from the first angle; and out-couple the set of in-coupled beams (105) out of the waveguide (101) as a set of out-coupled beams (106) in the second angle.

2. The display device (100) according to claim 1, wherein the set of in-coupled beams (105) is associated with a set of in-coupled k-vectors (201) in an annular guided propagation domain (232) associated with the waveguide (101) , the set of out-coupled beams (106) is associated with a set of out-coupled k-vectors (202) lying in an inner segment (230) of a coupling domain (231) associated with the waveguide (101) , and the set of input beams (103) is associated with a set of inputk-vectors (203) lying in the coupling domain (231) outside the inner segment (230) of the coupling domain (231) .

3. The display device (100) according to claim 2, wherein the inner segment (230) of the coupling domain (231) corresponds to an output field of view of the display device (100) .

4. The display device (100) according to any preceding claim, wherein the projector (102) is arranged to transmit the set of input beams (103) towards the incoupling and out-coupling structure (104) in the first angle .

5. The display device (100) according to any of claims 1 - 3, wherein the projector (102) further comprises a diffraction grating (501) configured to diffract the set of input beams (103) towards the in-coupling and out-coupling structure (104) in the first angle .

6. The display device (100) according to any preceding claim, wherein the in-coupling and out-coupling structure (104) comprises a two-dimensional diffraction grating .

7. The display device (100) according to claim 6, wherein the two-dimensional diffraction grating is configured to:couple the first part of the set of input beams (103) into the waveguide (101) as the set of incoupled beams (105) according to a first grating vector of the two-dimensional diffraction grating; diffract the set of in-coupled beams (105) according to a second grating vector of the two-dimensional diffraction grating, thus producing a set of diffracted beams; and out-couple the set of diffracted beams out of the waveguide as the set of out-coupled beams (106) in the second angle according to the first grating vector of the two-dimensional diffraction grating.

8. The display device (100) according to any preceding claim, wherein the display device (100) is further configured to perform exit pupil expansion via total internal reflection of the set of in-coupled beams (105) inside the waveguide (101) and diffraction of the set of in-coupled beams (105) caused by the in-coupling and out-coupling structure (104) .

9. The display device (100) according to any preceding claim, wherein the second angle is substantially zero with respect to a normal direction of the waveguide (101) .

10. The display device (101) according to any preceding claim, wherein the in-coupling and out-coupling structure (104) causes a distortion to the set of out-coupled beams (106) and the projector (102) is configured to compensate for the distortion by performing a manipulation on the image and transmitting the manipulated image in the set of input beams (103) .

11. The display device (100) according to any preceding claim, wherein the projector (102) is a first projector, the set of input beams (103) is a first set of input beams comprising a first wavelength range, and the display device further comprises: a second projector (601) configured to transmit a second set of input beams (611) comprising a second wavelength range; and a third projector (602) configured to transmit a third set of input beams (612) comprising a third wavelength range; wherein the in-coupling and out-coupling structure (104) is further configured to: receive the second set of input beams (611) in a third angle with respect to the waveguide (101) and receive the third set of input beams (612) in a fourth angle with respect to the waveguide (101) ; couple a first part of the second set of input beams (611) into the waveguide (101) as a second set of in-coupled beams (621) and couple a first part of the third set of input beams (612) into the waveguide as a third set of in-coupled beams (622) ; diffract a second part of the second set of input beams (611) in the second angle and diffract asecond part of the third set of input beams (612) in the second angle; and out-couple the second set of in-coupled beams out of the waveguide as a second set of out-coupled beams (631) in the second angle and out-couple the third set of in-coupled beams out of the waveguide as a third set of out-coupled beams (632) in the second angle.

12. The display device (100) according to any of claims 1 - 10, wherein the projector (102) is a first projector, the set of input beams (103) is a first set of input beams comprising a first part of an image, wherein the display device further comprises: a second projector (901) configured to transmit a second set of input beams (911) comprising second part of the image; wherein the in-coupling and out-coupling structure (104) is further configured to: receive the second set of input beams (911) in a third angle with respect to the waveguide (101) ; couple a first part of the second set of input beams (911) into the waveguide as a second set of incoupled beams (921) ; diffract a second part of the second set of input beams (911) in a fourth angle with respect to the waveguide, different from the third angle; and out-couple the second set of in-coupled beams (901) out of the waveguide (101) as a second set of out- coupled beams (922) in the fourth angle.

13. The display device (100) according to any preceding claim, wherein the display device (100) is implemented as a head-mounted display device and the display device is arranged to direct the set of out-coupled beams (106) towards an eye of a user of the head-mounted display device (100) .

Images