DISPLAY STRUCTURE AND DISPLAY DEVICE
FIELD OF TECHNOLOGY
[0001] This disclosure concerns display devices. In particular, some embodiments concern waveguide-based display devices with one or more diffraction gratings, and structures therefor.
BACKGROUND[0002] Waveguide-based display device, such as aug- mented reality (AR) headsets, or smart glasses, may use diffraction arating(s) to couple light into a waveguide and/or out of the waveguide to project a virtual image onto a user's eye.
[0003] A challenge with such waveguide-based display device is to produce a color-balanced virtual image.
SUMMARY[0004] This summary is provided to introduce a selec- tion of concepts in a simplified form that are further described below in the detailed description. This sum- mary is not intended to identify key features or essen- n tial features of the claimed subject matter, nor is it
N
S intended to be used to limit the scope of the claimed
N subject matter.
D [0005] It is an object to provide a display structure
E 20 and a display device producing a color-balanced virtual
N image. The foregoing and other objects are achieved by
O
3 the features of the independent claims. Further imple-
O
N mentation forms are apparent from the dependent claims,
N the description and the figures.
[0006] According to a first aspect, a display struc- ture comprises a waveguide, and a diffraction structure, the diffraction structure comprising: a diffraction grating arranged on a face of the waveguide, a first coating layer of transparent dielectric material, the first coating layer at least partially covering the dif- fraction grating and configured to shift a resonance band of the diffraction grating, and a second coating layer at least partially covering the first coating layer.
[0007] According to a second aspect, a display de- vice comprises a display structure according to the first aspect.
[0008] Many of the attendant features will be more readily appreciated as they become better understood by reference to the following detailed description consid- ered in connection with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS[0009] The present disclosure will be better under- stood from the following detailed description read in light of the accompanying drawings, wherein:
[0010] FIG. 1 shows a planar view of a display struc-
S ture according to an example embodiment,
N [0011] FIG. 2 shows a cross-sectional view of a dis- o play structure according to an example embodiment, = 25 [0012] FIG. 3 shows a cross-sectional view of a ridge - of a display structure according to an example embodi- 8 ment,
N
&
[0013] FIG. 4 shows a cross-sectional view of a ridge of a display structure according to another example em- bodiment,
[0014] FIG. 5A shows a spectral response of a baseline display structure,
[0015] FIG. 5B shows a spectral response of a display structure according to an example embodiment for a var- ying thickness of the coating laver,
[0016] FIG. 5C shows a spectral diffraction effi- ciency of a baseline display structure,
[0017] FIG. 5D shows a spectral diffraction effi- ciency of a display structure according to an example embodiment,
[0018] FIG. 5E shows a spectral diffraction effi- ciency of a display structure according to an example embodiment without an additional underlayer,
[0019] FIG. 5F shows a spectral diffraction effi- ciency of a display structure according to an example embodiment with an additional underlayer,
[0020] FIG. 6 illustrates a display device according to an example embodiment.
[0021] Unless specifically stated to the contrary, any
JN drawing of the aforementioned drawings may be not drawn
S to scale such that any element in said drawing may be
N 25 drawn with inaccurate proportions with respect to other o elements in said drawing in order to emphasize certain
I structural aspects of the embodiment of said drawing. q [0022] Moreover, corresponding elements in the embod- 2 iments of any two drawings of the aforementioned draw- & 30 ings may be disproportionate to each other in said two
N drawings in order to emphasize certain structural as- pects of the embodiments of said two drawings.
DETAILED DESCRIPTION[0023] FIG. 1 depict a planar view of a display struc- ture 1000 according to an example embodiment. The dis- play structure 1000 may be part of a display device.
[0024] In this specification, a "display device” may refer to an operable output device, e.g., electronic device, for visual presentation of images and/or data.
A display device may generally comprise any part(s) or element(s) necessary or beneficial for visual presenta- tion of images and/or data, for example, a power unit; an optical engine; a combiner optics unit, such as a waveguide-based combiner optics unit; an eye tracking unit; a head tracking unit; a gesture sensing unit; and/or a depth mapping unit. A display device may or may not be a portable display device, for example, a head- mounted display device, such as an augmented reality (AR) headset, and/or a see-through display device, such as smart glasses or head-up display.
[0025] Herein, a "head-mounted display device” may refer to a display device configured to be worn on the 2 head, as part of a piece of headgear, and/or on or over
N the eyes.
N
T [0026] Further, a "see-through display device” or 2 25 “transparent display device” may refer to a display de-
E vice allowing its user to see the images and/or data 5 shown on the display device as well as to see through 3 the display device.
N [0027] Throughout this disclosure, a "display struc- ture” may refer to at least part of an operable display device. Additionally of alternatively, a display struc- ture may refer to a structure suitable for use in a display device.
[0028] According to an embodiment, a display structure 5 1000 comprises a waveguide 101. The waveguide 101 may comprise, for example, a substantially planar waveguide.
Alternatively, or additionally, the waveguide 101 may also comprise curved sections. For example, the wave- guide 101 may correspond to a lens of an augmented re- ality (AR) headset, or smart glasses.
[0029] The display structure 1000 may further comprise an in-coupling (IC) structure 102 configured to couple light into the waveguide 101.
[0030] The light may be generated by, for example, a scanner-based optical engine. The light may represent an image generated by, for example, such an optical engine. Thus, the image may be referred to as, for ex- ample, virtual image or AR image.
[0031] The in-coupling structure 102 may comprise a diffraction grating on a face of the waveguide 101. The in-coupling structure 102 may couple the light into the waveguide 101 via diffraction. The in-coupling diffrac- tion grating may be arranged on either face of the wave- = guide 101. The in-coupling diffraction grating may be
N 25 configured to function as a reflection-type diffraction = grating or as a transmission-type diffraction grating. > The side from which the in-coupling diffraction grating = is configured to in-couple the visible light does not 5 depend on which side of the waveguide 101 the in-cou-
O 30 pling diffraction grating is positioned.
O [0032] The display structure 1000 may further comprise an exit pupil expansion (EPE) structure 103 arranged on a face of the waveguide 101 and configured to perform exit pupil expansion e.g., by pupil replication. The EPE structure 103 may comprise a diffraction grating on ei- ther one of the faces of the waveguide 101.
[0033] “Exit pupil expansion” may refer to a process of distributing light within a waveguide in a controlled manner so as to expand a portion of said waveguide where out-coupling of light occurs. Further, “pupil replica- tion” may refer to an exit pupil expansion process, wherein a plurality of exit sub-pupils are formed in an imaging system. The EPE structure 103 may be configured to perform exit pupil expansion along one or more other directions perpendicular to a thickness direction of the waveguide.
[0034] The display structure 1000 may further comprise an out-coupling (OC) structure 104 arranged on a face of the waveguide 101 and configured to out-couple light from the waveguide.
[0035] The out-coupling structure 104 may comprise a diffraction grating on a face of the waveguide 101. The out-coupling structure 104 may couple the light out of the waveguide 101 via diffraction. The out-coupling dif- fraction grating may be arranged on either face of the
Q waveguide 101. The out-coupling diffraction grating may
N 25 be configured to function as a reflection-type diffrac- = tion grating or as a transmission-type diffraction grat- > ing. The side from which the out-coupling diffraction
E grating is configured to out-couple the light does not 5 depend on which side of the waveguide 101 the out-cou-
O 30 pling diffraction grating is positioned.
O [0036] The diffractive out-coupling structure 104 may be configured to perform exit pupil expansion. Both the
EPE structure 103 and the diffractive out-coupling structure 104 can be configured to expand the image. For example, the EPE structure 103 may expand the image in one direction and the diffractive out-coupling structure 104 can expand the image in a perpendicular direction.
Alternatively, the EPE structure 103 may be configured to expand the image in two perpendicular directions and the diffractive out-coupling structure 104 may be con- figured to out-couple the light from the waveguide 101.
[0037] It should be understood that the geometry of the display structure 1000 illustrated in the embodiment of Fig. 1 is only exemplary and the display structure 1000 may be implemented in various other ways. For ex- ample, the waveguide 101, the in-coupling structure 102, the EPE structure 103, and/or the out-coupling structure 104 can be of different sizes and/or shapes than what is illustrated in the embodiment of Fig. 1.
[0038] FIG. 2 shows a cross-sectional view of a dis- play structure (e.g., display structure 1000 of FIG. 1) according to an example embodiment. The example embod- iment of FIG. 2 may be in accordance with any of the example embodiments disclosed with reference to and/or in conjunction with FIG. 1. Additionally, or alterna- @ tively, although not explicitly shown in FIG. 2, the & 25 example embodiment of FIG. 2 or any part thereof may
N generally comprise any features and/or elements of the > example embodiments of FIG. 1 which are omitted from
E FIG. 2. 5 [0039] The display structure 1000 comprises a wave-
O 30 guide 101 and at least one diffraction structure 200.
O The diffraction structure 200 may be an in-coupling structure 102, an EPE structure 103, an out-coupling structure 104, or any combination thereof.
[0040] In this disclosure, a “waveguide” may refer to an optical waveguide. Additionally, or alternatively, a waveguide may refer to a two-dimensional waveguide, wherein light may be confined along a thickness direc- tion of said waveguide. The waveguide may be made of transparent dielectric material.
[0041] The waveguide 101 may comprise a first face 201 and a second face 202 for confining light in the wave- guide by total internal reflection. In this disclosure, “total internal reflection” may refer to total or sub- stantially total internal reflection. The second face is arranged opposite the first face 101 and towards a thickness direction therefrom.
[0042] In this disclosure, a “face” of a waveguide may refer to a part of a surface of said waveguide viewable from or facing a certain viewing direction. Addition- ally, or alternatively, faces of a waveguide may refer to surfaces suitable for or configured to confine light in said waveguide by total internal reflection.
[0043] The diffraction structure 200 comprises a dif- fraction grating 210. The “diffraction grating” may re- = fer to an optical grating the operation of which is
N 25 based on diffraction of light. Generally, a diffraction — grating may comprise one or more structural features > with at least one dimension of the order of the wave-
E lengths of visible light, for example, at least one 5 dimension less than one micrometer. Generally, a dif-
O 30 fraction grating may be implemented as a single-region
O diffraction grating or as a multi-region diffraction grating. Diffraction gratings may generally be imple- mented, at least, as surface relief diffraction gratings or volume holographic diffraction gratings, and they may be configured to function as transmission- and/or re- flection-type diffraction gratings.
[0044] The waveguide 101 and diffraction structure 200 form a resonant waveguide grating structure also called grating coupler. For specific light freguencies (within a resonance band), the diffraction structure 200 couples light in/out of a guided mode of the waveguide. If the diffraction structure 200 is used as an in-coupling structure, the resonant light is coupled into a guided mode of the waveguide. If the diffraction structure 200 is used as an out -coupling structure, the resonant light is coupled out of a guided mode of the waveguide. Off- resonance light incident on the diffraction structure 200 remains in the guided mode of the waveguide.
[0045] For a specific light frequency, the larger the diffraction efficiency of the diffraction structure 200, the larger percent of light is coupled in/out. As il- lustrated by FIG. 5A, the diffraction efficiency of the diffraction structure 200 may vary along the visible spectrum. In the example of FIG. 5A, there is a heavy @ loss of red color wavelengths while green wavelengths & 25 are dominant. As a result, the virtual image may not be
N color balanced. The color balance of the virtual image 2 may be affected by the in-coupling structure 102, the
E EPE structure 103, and/or the out-coupling structure
K 104. 1
O 30 [0046] The diffraction grating 210 may be a surface
O relief grating. In particular, the diffraction grating
210 may comprise an alternance of depressions and ele- vations. The elevations may be ridges 211. In FIG. 2, the ridges 211 extend longitudinally perpendicular to the plane of the drawing. The ridges 211 may have a rectangular cross-sectional shape as illustrated on FIG. 2, or any other suitable cross-sectional shape.
[0047] In example embodiments, the diffraction grat- ing 210 may have a fill factor F in a range of 0 to 1, in a range of 0.01 to 0.99, in a range of 0.05 to 0.95, in a range of 0.1 to 0.9, or in a range of 0.2 to 0.8.
The fill factor F is the fraction of the grating period that is filled with the grating material.
[0048] The diffraction grating 210 may be formed at least partly using nanoimprint lithography. In other embodiments, any suitable fabrication method(s), for example, nanoimprint lithography and/or grayscale elec- tron-beam lithography, may be used.
[0049] FIG. 3 depicts a zoomed view of zone Z1 (as indicated on FIG. 2) around a ridge 211 of a diffraction structure 200 according to an example embodiment. The example embodiment of FIG. 3 may be in accordance with any of the example embodiments disclosed with reference to and/or in conjunction with FIG. 1 or 2. Additionally
Q or alternatively, although not explicitly shown in
N 25 FIG. 3, the example embodiment of FIG. 3 or any part = thereof may generally comprise any features and/or el- > ements of the example embodiments of FIG. 1 or 2 which
E are omitted from FIG. 3. 5 [0050] The diffractive structure 200 may comprise a
O 30 first coating layer 301 and a second coating layer 302.
O The first coating layer 301 covers partially, substan- tially completely, or completely the diffraction grating
210. The second coating layer 302 covers partially, sub- stantially completely, or completely the first coating layer 301.
[0051] The first coating layer 301 may be formed di- rectly on the diffraction grating 210. The second coat- ing layer 302 may be formed directly on the first coating layer 301. Alternatively, the diffractive structure 200 may comprise one or more additional layers between the first coating layer 301 and the second coating layer 302, and/or between the diffraction grating 210 and the first coating layer 301. The diffractive structure 200 may also comprise one or more additional layers on top of the second coating layer 302.
[0052] The first coating layer 301 may cover the el- evations of the diffraction grating 210 and optionally the depressions. In particular, the first coating layer 301 may cover at least some of the ridges 211, and more specifically an upper surface 212 of the ridge 211 and optionally side surfaces 213, 214 of the ridge 211.
[0053] In the case of a reflection-type diffraction grating, the second coating layer 302 may be a reflec- tive coating. In particular, the second coating layer 302 may comprise or consist of a metal such as Silver
S or Aluminum. Such a reflective coating can improve the
N 25 brightness efficiency of the display structure. = [0054] In any embodiment, the second coating layer 302 > may be a transparent coating. In particular, the second
E coating layer 302 may comprise or consist of a trans- 5 parent material such as silicon dioxide (Si0,), aluminum
O 30 oxide (Al0;), and/or magnesium fluoride (MgF.). Such a
O transparent coating can improve the brightness effi- ciency of the display structure.
[0055] The first coating layer 301 may be a transpar- ent dielectric coating.
[0056] The first coating layer 301 can shift the res- onance band of the diffractive grating 210 (e.g., along the visible spectrum). The first coating layer 301 can be configured (e.g., the material and/or thickness of the first coating layer 301 can be selected) to adjust the diffraction efficiency for at least one visible wavelength (e.g., a first visible wavelength) in rela- tion to at least another visible wavelength (e.g., a second visible wavelength), e.g., to improve the uni- formity of the diffraction efficiency across the visible spectrum. This can be used to adjust the intensities of the various colors (e.g., red, green, and blue) in the virtual image, e.g., to produce an evenly distributed white color in the virtual image.
[0057] The first coating layer 301 has a first thick- ness (ty). The second coating layer 302 has a second thickness (t,). Herein, a “thickness” of a coating layer may refer to a measure of the extent of said coating layer along a thickness direction of a waveguide. In particular, the “thickness” of a coating layer may be measured over the elevations of the diffraction grating & 210. In example embodiments, ti, may be greater than or equal to 5 nm and/or less than or equal to 40 nm. In a example embodiments, t, may be greater than or equal to = 100 nm and/or less than or equal to 250 nm. & [0058] The first coating layer 301 may comprise, con-
S sist essentially of, or consist of a first material 2 30 having a first refractive index (n,;) at a visible wave-
N length (Avis). The diffraction grating 210 (e.g., the ridges 211 forming the diffraction grating 210) may com- prise, consist essentially of, or consist of a second material having a second refractive index (n,).
[0059] In example embodiments, n, is greater than nj.
In example embodiments, n, is greater than or equal to 1.3, and/or less than or equal to 2.7. In example em- bodiments, n, is greater than or equal to 2.4 and/or less than or equal to 2.9. It should be appreciated that n, can depend on the wavelength of the light. For exam- ple, for short visible wavelengths (blue) n, may be large, such as close to 2.8, and for long visible wave- lengths (red) n, may be small, such as close to 2.4.
[0060] In example embodiments, the first material may be comprise one or a combination of the following mate- rials: Titanium nitride (TiN) (e.g., with a refractive index RI of approximately 2.7), Niobium pentoxide (Nb205) (e.g., RI ~2.24), Zirconium dioxide (Zr02) (RI ~2.11), Tantalum pentoxide (Ta205) (RI ~2.05), Silicon nitride (Si3N4) (RI ~1.98), Hafnium (IV) oxide (Hf02) (RI ~1.87), Aluminum oxide (AL203) (RI ~1.77), Silicon di- oxide (Si0;) (RI~1.45), or Magnesium fluoride (MgF2) (RI -1.38).
[0061] The first coating layer 301 may comprise a plu- & rality of sublayers of transparent dielectric material.
For example, the first coating layer 301 may comprise a (or consist of) a first sublayer of Magnesium fluoride (MgF2) and a second sublayer of Silicon dioxide (Si0,).
E MgF2 and Si02 can provide an advantageous wavelength-
S dependent resonance as a function of the fill factor. 2 30 [0062] In example embodiments, the second material may & be titanium dioxide (Ti0,) (e.g., with a RI of approxi- mately 2.45 at a wavelength of 520 nm).
[0063] The first coating layer 301 and/or the second coating layer 302 may be formed at least partly using evaporation or sputtering. In other embodiments, any suitable fabrication method(s) may be used.
[0064] FIG. 4 depicts a zoomed view of zone Z1 (as indicated on FIG. 2) around a ridge 211 of a diffraction structure 200 according to an example embodiment. The example embodiment of FIG. 4 may be in accordance with any of the example embodiments disclosed with reference to and/or in conjunction with FIG. 1 to 3. Additionally, or alternatively, although not explicitly shown in
FIG. 4, the example embodiment of FIG. 4 or any part thereof may generally comprise any features and/or el- ements of the example embodiments of FIG. 1 to 3 which are omitted from FIG. 3.
[0065] The diffractive structure 200 may further com- prise a first underlayer 401 and a second underlayer 402 between the waveguide 101 and the diffraction grating 210.
[0066] The first underlayer 401 covers partially, sub- stantially completely, or completely the waveguide 101.
The second underlayer 402 covers partially, substan- tially completely, or completely the first underlaver = 401. The diffraction grating 210 is arranged on the
N 25 second underlayer 402. The diffraction grating 210 co- = vers partially, substantially completely, or completely = the second underlayer 402.
E [0067] The first underlayer 401 may be formed directly 5 on the waveguide 101. The second underlayer 402 may be
O 30 formed directly on the first underlayer 401. The dif-
O fraction grating 210 may be arranged directly on the second underlayer 402. Alternatively, the diffractive structure 200 may comprise one or more additional layers between the waveguide 101 and first underlayer 401, and/or between the first underlayer 401 and the second underlayer 402, and/or between the second underlayer 402 and the diffraction grating 210.
[0068] The first underlayer 401 and second underlayer 402 can be implemented in combination or independently of the first coating layer 301 and the second coating layer 302.
[0069] The first underlayer 401 may be a transparent dielectric layer. The second underlayer 402 may be a transparent dielectric layer.
[0070] The first 401 and second 402 underlayers can shift the resonance band of the diffractive grating 210 (e.g., along the visible spectrum). The second under- layer 402 can be configured (e.g., the material and/or thickness of the second underlayer 402 can be selected) to adjust the diffraction efficiency for at least one visible wavelength (e.g., a third visible wavelength) in relation to at least another visible wavelength (e.g., a fourth visible wavelength), e.g., to improve the uniformity of the diffraction efficiency across the visible spectrum. This can be used to adjust the inten-
S sities of the various colors (e.g., red, green, and
N 25 blue) in the virtual image, e.g., to produce an evenly = distributed white color in the virtual image. > [0071] The first 401 and second 402 underlayers maybe = used in combination with the first coating layer 301 to 5 adjust the diffraction efficiency for the same or for
O 30 different visible wavelengths.
O [0072] The first underlayer 401 has a third thickness (tz) . The second underlayer 402 has a fourth thickness
(ty) . Herein, a “thickness” of a layer may refer to a measure of the extent of said layer along a thickness direction of a waveguide. In example embodiments, ts may be greater than or equal to 20 nm and/or less than or equal to 60 nm. In example embodiments, t4 may be greater than or equal to 5 nm and/or less than or equal to 20 nm.
[0073] The first underlayer 401 may comprise, consist essentially of, or consist of a third material having a third refractive index (ns) at a visible wave- length (Avis). The second underlayer 402 may comprise, consist essentially of, or consist of a fourth material having a fourth refractive index (ng).
[0074] In example embodiments, na is greater than ng.
In example embodiments, ng is greater than or equal to 1.3, and/or less than or equal to 2.7. In example em- bodiments, na; is greater than or equal to 2.4 and/or less than or equal to 2.8. It should be appreciated that ns can depend on the wavelength of the light. For exam- ple, for short visible wavelengths (blue) ns may be large, such as close to 2.8, and for long visible wave- lengths (red) ns may be small, such as close to 2.4. n [0075] In example embodiments, the fourth material may
S be one or a combination of two or more of the following
N 25 materials: Titanium nitride (TiN) (e.g., with a refrac- o tive index RI of approximately 2.7), Niobium pentoxide z (Nb205) (e.g., RI 2.24), Zirconium dioxide (Zr02) (RI - ~2.11), Tantalum pentoxide (Ta205) (RI ~2.05), Silicon 8 nitride (Si3N4) (RI ~1.98), Hafnium (IV) oxide (Hf02) (RI
N
&
~1.87), Aluminum oxide (AL203) (RI ~1.67), Silicon di- oxide (Si0;) (RI~1.45), or Magnesium fluoride (MgF2) (RI -1.38).
[0076] In example embodiments, the third material may be titanium dioxide (Ti0,) (e.g., with a RI of approxi- mately 2.45 at a wavelength of 520 nm).
[0077] The fourth material may be the same as the first material. The third material may be the same as the second material.
[0078] The first underlayer 401 and/or the second un- derlayer 402 may be formed at least partly using evap- oration or sputtering. In other embodiments, any suit- able fabrication method(s) may be used.
[0079] In some example embodiments, the values of the refraction indexes (e.g., ny, MN, nz, nu) may be consid- ered at a A,;; of 500 nm. In other example embodiments, the values of the refraction indexes may be considered at any suitable visible wavelength, i.e., any wavelength within a spectral range extending from 380 nm to 760 nm.
For example, in some example embodiments, the relevant visible wavelength may be selected from the group con- sisting of 450 nm, 460 nm, 470 nm, 480 nm, 490 nm, 500 nm, 510 nm, 520 nm, 530 nm, 540 nm, 550 nm, 560 nm, & 570 nm, 580 nm, 590 nm, 600 nm, 610 nm, 620 nm, 630 nm, 640 nm, and 650 nm. a [0080] FIG. 5B shows a spectral response of a display = structure according to an example embodiment for a o thickness of the first coating layer varying from 5 nm
S to 40 nm. FIG. 5B shows that the diffraction efficiency 2 30 varies with the thickness of the first coating layer.
N [0081] FIG. 5C shows a spectral diffraction effi- ciency of a baseline display structure without the first coating layer. FIG. 5D shows a spectral diffraction ef- ficiency of a display structure according to an example embodiment with the first coating layer. FIGs 5C and 5D show that the first coating layer shifts the resonance band of the diffractive grating along the visible spec- trum, thereby adjusting the diffraction efficiency of the various visible wavelengths.
[0082] FIG. 5E shows a spectral diffraction effi- ciency of a display structure according to an example embodiment with no underlayer. FIG. 5F shows a spectral diffraction efficiency of a display structure according to an example embodiment with a first and a second un- derlayer. FIGs 5E and 5F show that the first and second underlayer shift the resonance band of the diffractive grating along the visible spectrum, thereby adjusting the diffraction efficiency of the various visible wave- lengths.
[0083] FIG. 6 depicts a display device 6000 according to an example embodiment. The example embodiment of
FIG. 6 may be in accordance with any of the example embodiments disclosed with reference to and/or in con- junction with any of FIGs 1 to 4. Additionally, or al- ternatively, although not explicitly shown in FIG. 6, @ the example embodiment of FIG. 6 or any part thereof may
R 25 generally comprise any features and/or elements of any
N of the example embodiments of FIGs 1 to 4 which are > omitted from FIG. 6.
E [0084] In the example embodiment of FIG. 6, the dis- 5 play device 6000 is implemented as a see-through head-
O 30 mounted display device, more specifically, as spectacles
O comprising a see-through display. In other embodiments, a display device may be implemented in any suitable manner, for example, as a see-through and/or as a head- mounted display device.
[0085] In the example embodiment of FIG. 6, the dis- play device 6000 comprises a frame 601 and a display structure 1000 supported by the frame 601. In other em- bodiments, a display device may or may not comprise such frame.
[0086] In the example embodiment of FIG. 6, the dis- play structure 6200 comprises a waveguide 101, an in- coupling structure 102 for coupling light into the wave- guide 101, an EPE structure 103 configured to receive light from the in-coupling structure 102, and a reflec- tion-type out-coupling structure 104 configured to re- ceive light from the EPE structure 103. In other embod- iments, a display structure may or may not comprise such
EPE structure. In other embodiments, the out-coupling structure 104 may be transmission-type.
[0087] As shown in FIG. 6, the display device 6000 further comprises an optical engine 140 configured to direct light into the waveguide 101 for propagation in the waveguide 101 by total internal reflection. In other embodiments, a display device may or may not comprise such optical engine. = [0088] It is obvious to a person skilled in the art
N 25 that with the advancement of technology, the basic idea — of the invention may be implemented in various ways. The > invention and its embodiments are thus not limited to z the examples described above, instead they may vary 5 within the scope of the claims.
O 30 [0089] It will be understood that any benefits and
O 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 of the stated problems or those that have any or all of the stated benefits and advantages.
[0090] The term “comprising” is used in this specifi- cation to mean including the feature(s) or act (s) fol- lowed thereafter, without excluding the presence of one or more additional features or acts. It will further be understood that reference to 'an' item refers to one or more of those items.
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