Embedded fold grating for ar waveguide

Abstract

Embodiments of the present disclosure include a waveguide. The waveguide includes a substrate, the substrate having a substrate thickness, a first surface opposing a second surface, and at least one sidewall coupled to the first surface and the second surface. The waveguide includes an input-coupler disposed over the first surface. The waveguide includes an output-coupler disposed over the first surface; and a fold grating disposed in the substrate, where the fold grating is operable to split reflected beams into transmitted beams that transmit to the output-coupler and subsequent reflected beams to the second surface.

Description

EMBEDDED FOLD GRATING FOR AR WAVEGUIDEBACKGROUNDField

[0001] Embodiments of the present disclosure generally relate to augmented reality waveguides. More specifically, embodiments described herein a waveguide having an embedded fold grating.Description of the Related Art

[0002] Virtual reality is generally considered a computer generated simulated environment in which a user has an apparent physical presence. A virtual reality experience can be generated in 3D and viewed with a head-mounted display (HMD), such as glasses or other wearable display devices that have near-eye display panels as lenses to display a virtual reality environment that replaces an actual environment.

[0003] Augmented reality, however, enables an experience in which a user can still see through the near-eye display panels of the glasses or other HMD device to view the surrounding environment, yet also see images of virtual objects that are generated for display and appear as part of the environment. Augmented reality can include any type of input, such as audio and haptic inputs, as well as virtual images, graphics, and video that enhances or augments the environment that the user experiences.

[0004] As an emerging technology, there are many challenges and design constraints with augmented reality. Accordingly, what is needed in the art is a waveguide having an embedded fold grating.SUMMARY

[0005] In one embodiment, a waveguide is provided. The waveguide includes a substrate, the substrate having a substrate thickness, a first surface opposing a second surface, and at least one sidewall coupled to the first surface and the second surface. The waveguide includes an input-coupler disposed over the first surface. The waveguide includes an output-coupler disposed over the first surface; and a fold grating disposed in the substrate, where the fold grating is operable to split reflected beams into transmitted beams that transmit to the output-coupler and subsequent reflected beams to the second surface.

[0006] In another embodiment, a waveguide is provided. The waveguide includes a substrate, the substrate having a first surface opposing a second surface, and at least one sidewall coupled to the first surface and the second surface, where the substrate has a substrate thickness of about 0.1 millimeters (mm) to about 3 mm. The waveguide includes an input-coupler disposed over the first surface. The waveguide includes an output-coupler disposed over the first surface; and a fold grating disposed in the substrate, where the fold grating is operable to split reflected beams into transmitted beams that transmit to the output-coupler and subsequent reflected beams to the second surface.

[0007] In yet another embodiment, a waveguide is provided. The waveguide includes a substrate, the substrate having a first surface opposing a second surface separated by a substrate thickness, and at least one sidewall coupled to the first surface and the second surface. The waveguide includes an input-coupler disposed over the first surface. The waveguide includes an output-coupler disposed over the first surface; and a fold grating disposed in the substrate at about a midpoint of the substrate thickness, where the fold grating is operable to split reflected beams into transmitted beams that transmit to the output-coupler and subsequent reflected beams to the second surface.BRIEF DESCRIPTION OF THE DRAWINGS

[0008] So that the manner in which the above recited features of the present disclosure can be understood in detail, a more particular description of the disclosure, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only exemplary embodiments and are therefore not to be considered limiting of its scope, and may admit to other equally effective embodiments.

[0009] FIG. 1 is a perspective view of a waveguide according to embodiments described herein.

[0010] FIGS. 2A-2B are cross-sectional views of a fold grating according to embodiments described herein.10011] FIGS. 3A-3C are graphs of in-coupling efficiency according to embodiments described herein.

[0012] To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation.DETAILED DESCRIPTION

[0013] Embodiments of the present disclosure generally relate to augmented reality waveguides. More specifically, embodiments described herein a waveguide having an embedded fold grating.

[0014] FIG. 1 is a perspective view of a waveguide 100. The waveguide 100 includes a substrate 102. The substrate 102 has a first surface 102T opposing a second surface 102B. At least one sidewall 102S is coupled to the first surface 102T and the second surface 102B. The substrate 102 has a substrate thickness 102H from the first surface 102T to the second surface 102B. In some embodiments, which can be combined with other embodiments described herein, the substrate 102 includes at least a second sidewall 102SS. For example, the substrate is a polyhedron including at least four sidewalls.

[0015] The substrate 102 may be formed from any suitable material, provided that the substrate 102 can adequately transmit light in a selected wavelength or wavelength range and can serve as an adequate support for the waveguide 100 described herein. Substrate selection may include substrates of any suitable material, including, but not limited to, amorphous dielectrics, non-amorphous dielectrics, crystalline dielectrics, silicon oxide, polymers, and combinations thereof. In some embodiments, which may be combined with other embodiments described herein, the waveguide substrate 102 includes glass, silicon (Si), silicon dioxide (SiC>2), germanium (Ge), silicon germanium (SiGe), indium phosphide (InP), gallium arsenide (GaAs), gallium nitride (GaN), fused silica, quartz, sapphire (AI2O3), silicon carbide (SiC), lithium niobate (LiNbOs), indium tin oxide (ITO), or combinations thereof. In other embodiments, which may be combined with other embodiments described herein, the substrate 102 includes high-refractive-index glass. The high-refractive-index glass includes greater than 2 percent by weight of lanthanide (Ln), titanium (Ti), tantalum (Ta), or combination thereof. In some embodiments, the substrate refractive index (Rl) of the substrate is about 1 .3 to about 4.0.

[0016] The waveguide 100 includes an input-coupler (IC) 110 disposed over the at least one sidewall 102S. The IC 110 includes one or more IC structures 112. The one or more IC structures 112 of the IC 110 form one or more IC grating patterns. In one embodiment, which may be combined with other embodiments, the one or more IC grating patterns is a periodic pattern. In some embodiments, which may be combined with other embodiments, the one or more IC grating patterns is an aperiodic pattern. In other embodiments, which may be combined with other embodiments, the one or more IC grating patterns is a combination of a periodic pattern and an aperiodic pattern. The one or more IC structures 112 of the one or more IC grating patterns may be binary gratings, or angled gratings. The one or more IC grating patterns may extend a partial distance, or an entire distance, of the at least the top surface 102T in the x- direction, y-direction, z-direction, or any combination thereof.

[0017] The one or more IC structures 112 include an input grating material having an IC refractive index. The input grating material includes, but is not limited to, amorphous dielectrics, non-amorphous dielectrics, crystalline dielectrics, metals, alloys, polymers, organic resist materials, nanoparticle doped resist materials, optical adhesives, silicon dioxide (SiO2), titanium monoxide (TiO), titanium dioxide (TiC ), niobium monoxide (NbO), niobium dioxide (NbC ), niobium pentoxide (Nb20s), hafnium dioxide (HfC ), tantalum pentoxide (Ta2Os), dilanthanum diitanium heptaoxide (La2Ti2O?), aluminum oxide (AI2O3), zirconium dioxide (ZrC ), magnesium difluoride (MgF2), cerium trifluoride (CeFs), silicon nitride (SisN4), or combinations thereof. In practice, the IC 110 is operable to receive incident beams of light 130. The incident beams of light 130 may include red light 130R, green light 130G, and blue light 130B. The IC 110 is operable to project the incident beams of light 130 to the substrate 102 as in-coupled beams 132 toward the first surface 102T, or the second surface 102B, where the in-coupled beams 132 then reflect off the first surface 102T, or the second surface 102B, as reflected beams 134.

[0018] The waveguide 100 includes an output-coupler (OC) 120 disposed over the first surface 102T. The OC 120 includes one or more OC structures 122. The one ormore OC structures 122 of the OC 120 form one or more OC grating patterns. In one embodiment, which may be combined with other embodiments, the one or more OC grating patterns is a periodic pattern. In some embodiments, which may be combined with other embodiments, the one or more OC grating patterns is an aperiodic pattern. In other embodiments, which may be combined with other embodiments, the one or more OC grating patterns is a combination of a periodic pattern and an aperiodic pattern. The one or more OC structures 122 of the one or more OC grating patterns may be binary gratings, or angled gratings. The one or more OC grating patterns may extend a partial distance, or an entire distance, of the first surface 102T in the x- direction, y-direction, z-direction, or any combination thereof.

[0019] The one or more OC structures 122 include an output grating material having an OC refractive index. The output grating material includes, but is not limited to, amorphous dielectrics, non-amorphous dielectrics, crystalline dielectrics, metals, alloys, polymers, organic resist materials, nanoparticle doped resist materials, optical adhesives, silicon dioxide (SiO2), titanium monoxide (TiO), titanium dioxide (TiO2), niobium monoxide (NbO), niobium dioxide (NbO2), niobium pentoxide (Nb20s), hafnium dioxide (HfO2), tantalum pentoxide (Ta2Os), dilanthanum diitanium heptaoxide (La2Ti2O?), aluminum oxide (AI2O3), zirconium dioxide (ZrC ), magnesium difluoride (MgF2), cerium trifluoride (CeFs), silicon nitride (SisN4), or combinations thereof. In practice, the OC 120 is operable to receive transmitted beams 136 from the fold grating and project the transmitted beams 136 as output beams 138 to the first surface 102T.

[0020] The waveguide 100 includes a fold grating 104 disposed in the substrate 102. The fold grating 104 is disposed between the first surface 102T and the second surface 102B. The fold grating 104 is disposed at a depth 102M of the substrate thickness 102H between the first surface 102T and the second surface 102B. In some embodiments, which can be combined with other embodiments described herein, the depth 102M, as shown in FIG. 1 , is at about a midpoint of the substrate thickness 102H. In other embodiments, which can be combined with other embodiments described herein, as shown in FIG. 2A the depth 102M is above, or below, about a midpoint of the substrate thickness 102H. The fold grating 104 is positioned relative to the IC 110 and OC 120.

[0021] The fold grating 104 has a fold grating width 104W. The fold grating width 104W is less than a width of the substrate width 102W. In some embodiments, which may be combined with other embodiments, the fold grating width 104W is substantially equal to the substrate width 102W. The fold grating 104 has a fold grating length 104L. The fold grating length 104L is less than a length of the substrate length 102L. In some embodiments, which may be combined with other embodiments, the fold grating length 104L is substantially equal to the substrate length 102L.

[0022] The fold grating 104 includes fold grating material having a fold grating refractive index (Rl). The fold grating Rl is about 1.3 to about 4.0. The fold grating material includes, but is not limited to, glass, dielectric metals, photopolymers, or any combination thereof. In some embodiments, which may be combined with other embodiments, the fold grating material is part of an embedded film layer. In other embodiments, which may be combined with other embodiments, the fold grating 104 described herein may include one or more embedded film layers including the fold grating material. In other embodiments, which may be combined with other embodiments, as described below in FIG. 2B, the fold grating 104 may include a plurality of fold grating structures including the fold grating material.

[0023] The fold grating 104 described herein is operable to receive the reflected beams 134 from the second surface 102B, and split the reflected beams 134 into transmitted beams 136 and subsequent reflected beams 135. The fold grating 104 transmits the transmitted beams 136 to the OC 120, and transmits the subsequent reflected beams 135 to the second surface 102B.

[0024] The fold grating 104 described herein is operable to receive the reflected beams 134 from the first surface 102T, and split the reflected beams 134 into transmitted beams 136 and subsequent reflected beams 135. The fold grating 104 transmits the transmitted beams 136 to the OC 120, and transmits the subsequent reflected beams 135 to the first surface 102T.

[0025] Embodiments of the fold grating 104 described herein allow for improved control of light propagation and pathing, which allow for additional freedom in the substrate thickness 102H. For example, the substrate thickness 102H is about 0.1 mm to about 3mm. As described below in FIGS. 3A-3C, an increase in substrate thickness 102H correlates to an increase in in-coupling efficiency.

[0026] In some embodiments, which may be combined with other embodiments the properties of the fold grating 104 may be selected to perform double-pupil replication of the in-coupled beams 132. Double-pupil replication may be performed as the fold grating 104 is disposed within the substrate 102. This allows the fold grating 104 to both simultaneously reflect light and transmit light. In contrast, grating structures disposed on the substrate 102 surface may only reflect or pass light.

[0027] FIGS. 2A-2B are cross-sectional views of a fold grating according to embodiments described herein. FIG. 2A is a cross-sectional schematic view of a portion of a waveguide 200 according to a third embodiment. The illustrated portion of the waveguide 200 includes the substrate 102 as described above, and the fold grating 104 as described above.

[0028] In FIG. 2A, the fold grating 104 is disposed at a depth 102M of the substrate thickness 102H between the first surface 102T and the second surface 102B. In some embodiments, which can be combined with other embodiments described herein, the depth 102M, as shown in FIG. 2A is above a midpoint of the substrate thickness 102H. In some embodiments, which can be combined with other embodiments described herein, the depth 102M is below a midpoint of the substrate thickness 102H.

[0029] FIG. 2B is a cross-sectional schematic view of a portion of a waveguide 225 according to an embodiment. The illustrated portion of the waveguide 225 includes the substrate 102 as described above.

[0030] In one embodiment the fold grating 204 may include a plurality of fold grating structures 206 including a fold grating structure material. The fold grating structure material may include the fold grating material, the input grating material, the output grating material, or any combination thereof. In other embodiments, fold grating 204 described herein may additionally include one or more embedded film layers including fold grating material, the first input grating material, the output grating material, or any combination thereof. The plurality of fold grating structures 206 includes one or more fold grating structure patterns 207. In one embodiment, which may be combined with other embodiments, the one or more fold grating structure patterns 207 is a periodic pattern. In some embodiments, which may be combined with other embodiments, the one or more fold grating structure patterns 207 is an aperiodic pattern. In other embodiments, which may be combined with otherembodiments, the one or more fold grating structure patterns 207 is a combination of a periodic pattern and an aperiodic pattern. The plurality of fold grating structures 206 of the one or more fold grating structure patterns 207 may be binary gratings, or angled gratings. The operation of the plurality of fold grating structures mirrors the operation of the fold grating 104 described above.

[0031] FIGS. 3A-3C are graphs of in-coupling efficiency according to embodiments described herein. The graph 300, shown in FIG. 3A, includes a vertical axis 302, and a horizontal axis 304. The vertical axis 302 plots in-coupling efficiency. The horizontal axis 304 plots waveguide thickness. Plot line 306 depicts red light 130R. As shown in plot line 306, red light 130R in-coupling efficiency increases as substrate thickness 102H increases. As the fold grating 104 allows for increased thickness, the waveguide 100 has improved in-coupling efficiency.

[0032] Graph 325, shown in FIG. 3B, includes a vertical axis 302, and a horizontal axis 304. The vertical axis 302 plots an improvement in-coupling efficiency, with efficiency increasing from bottom to top. The horizontal axis 304 plots waveguide thickness, with the thickness increasing from left to right. Plot line 308 depicts green light 130G. As shown in plot line 308, green light 130G in-coupling efficiency increases as substrate thickness 102H increases. As the fold grating 104 allows for increased thickness, the waveguide 100 has improved in-coupling efficiency.

[0033] Graph 350, shown in FIG. 3C includes a vertical axis 302, and a horizontal axis 304. The vertical axis 302 plots an improvement in-coupling efficiency, with efficiency increasing from bottom to top. The horizontal axis 304 plots waveguide thickness, with the thickness increasing from left to right. Plot line 310 depicts blue light 130B. As shown in plot line 310, blue light 130B in-coupling efficiency increases as substrate thickness 102H increases. As the fold grating 104 allows for increased thickness, the waveguide 100 has improved in-coupling efficiency.

[0034] While the foregoing is directed to embodiments of the present disclosure, these should not be construed as limitations on the scope of what may be claimed, but rather as descriptions of features that may be specific to particular embodiments. Certain features that are described in this specification in the context of separate embodiments may also be implemented, in combination, in a single embodiment. Conversely, various features that are described in the context of single embodimentsmay also be implemented in multiple embodiments, separately, or in any suitable subcombination. Moreover, although previously described features may be described as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination may, in some cases, be excised from the combination, and the claimed combination may be directed to a sub-combination or variation of a sub-combination.

[0035] Particular embodiments of the subject matter have been described. Other embodiments, alterations, and permutations of the described embodiments are within the scope of the following claims as will be apparent to those skilled in the art.

Claims

What is claimed is:

1. A waveguide, comprising: a substrate, the substrate having a substrate thickness, a first surface opposing a second surface, and at least one sidewall coupled to the first surface and the second surface; an input-coupler disposed over the first surface; an output-coupler disposed over the first surface; and a fold grating disposed in the substrate, wherein the fold grating is operable to split reflected beams into transmitted beams that transmit to the output-coupler and subsequent reflected beams to the second surface.

2. The waveguide of claim 1 , wherein the input-coupler is operable to: receive incident beams of light; and project in-coupled beams toward the second surface.

3. The waveguide of claim 1 , wherein the output-coupler is operable to: receive the transmitted beams from the fold grating; and project the transmitted beams as output beams.

4. The waveguide of claim 1 , wherein the substrate has a substrate thickness of about 0.1 millimeters (mm) to about 3 mm.

5. The waveguide of claim 1 , wherein the fold grating is disposed about a midpoint of the substrate thickness.

6. The waveguide of claim 1 , wherein the fold grating is disposed above a midpoint of the substrate thickness.

7. The waveguide of claim 1 , wherein the fold grating is disposed below a midpoint of the substrate thickness.

8. The waveguide of claim 1 , wherein the substrate has a substrate width.

9. The waveguide of claim 8, wherein the fold grating has a fold grating width less than the substrate width.

10. The waveguide of claim 8, wherein the fold grating has a fold grating width substantially equal to the substrate width.11 . The waveguide of claim 1 , wherein the substrate has a substrate length.

12. The waveguide of claim 11 , wherein the fold grating has a fold grating length less than the substrate length.

13. The waveguide of claim 11 , wherein the fold grating has a fold grating length substantially equal to the substrate length.

14. The waveguide of claim 1 , wherein the substrate has a substrate refractive index of about 1 .3 to about 4.0.

15. The waveguide of claim 1 , wherein the fold grating has a fold grating refractive index (Rl), wherein the fold grating Rl of about 1 .3 to about 4.0.

16. The waveguide of claim 1 , wherein the fold grating has one or more fold grating structures.

17. The waveguide of claim 1 , wherein the fold grating is operable to perform double-pupil replication of in-coupled beams.

18. The waveguide of claim 1 , wherein the fold grating is comprised of a fold grating material, wherein the fold grating material includes, glass, dielectric metals, photopolymers, or any combination thereof.

19. A waveguide, comprising: a substrate, the substrate having a first surface opposing a second surface, and at least one sidewall coupled to the first surface and the secondsurface, wherein the substrate has a substrate thickness of about 0.1 millimeters (mm) to about 3 mm; an input-coupler disposed over the first surface; an output-coupler disposed over the first surface; and a fold grating disposed in the substrate, wherein the fold grating is operable to split reflected beams into transmitted beams that transmit to the output-coupler and subsequent reflected beams to the second surface.

20. A waveguide, comprising: a substrate, the substrate having a first surface opposing a second surface separated by a substrate thickness, and at least one sidewall coupled to the first surface and the second surface; an input-coupler disposed over the first surface; an output-coupler disposed over the first surface; and a fold grating disposed in the substrate at about a midpoint of the substrate thickness, wherein the fold grating is operable to split reflected beams into transmitted beams that transmit to the output-coupler and subsequent reflected beams to the second surface.

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