Detachable light engine for optical devices

Abstract

The present disclosure provides a device that includes a substrate having a first face and a second face. The first face of the substrate includes a waveguide. The waveguide includes an input coupling grating, a pupil expansion grating, and an output coupling grating. An interposer is aligned with the input coupling grating and is coupled to the second face of the substrate using a reversible adhesive including a plurality of microstructures. A light engine is aligned with the input coupling grating and is coupled to the interposer.

Description

DETACHABLE LIGHT ENGINE FOR OPTICAL DEVICESBACKGROUNDField

[0001] Embodiments of the present disclosure generally relate to waveguides. More specifically, embodiments described herein relate to detachable light engines for waveguide devices, and related apparatus and methods.Description of the Related Art

[0002] Virtual reality is generally considered to be 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 display lenses 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. As an emerging technology, there are many challenges and design constraints with augmented reality.

[0004] Waveguides, such as augmented reality waveguides, are used to assist in overlaying images in a device. Generated light of the device is propagated through a waveguide until the light exits the waveguide and is overlaid on the ambient environment. One challenge with using waveguides is the need to replace components of the waveguide such as the light engine which generates the light.

[0005] Accordingly, what is needed in the art are devices that facilitate recycling of individual device components.SUMMARY

[0006] In an embodiment, the present disclosure provides a device that includes a substrate having a first face and a second face. The first face of the substrate includes a waveguide. The waveguide includes an input coupling grating, a pupil expansion grating, and an output coupling grating. An interposer is aligned with the input coupling grating and is coupled to the second face of the substrate using a reversible adhesive including a plurality of microstructures. A light engine is aligned with the input coupling grating and is coupled to the interposer.

[0007] In another embodiment, the present disclosure provides a device that includes a substrate having a first face and a second face. The first face of the substrate includes a waveguide. The waveguide includes an input coupling grating, a pupil expansion grating, and an output coupling grating. A lens is disposed over the first face. A gap is formed between the lens and the first face using an adhesive. A second lens is disposed over the second face. A second gap is formed between the second lens and the second face using the adhesive. A light engine is aligned with the input coupling grating and is coupled to the second lens using a reversible adhesive. The reversible adhesive includes a plurality of microstructures.

[0008] In another embodiment, the present disclosure provides a device that includes a substrate having a first face and a second face. The first face of the substrate includes a waveguide. The waveguide includes an input coupling grating, a pupil expansion grating, and an output coupling grating. A light engine is aligned with the input coupling grating and is coupled to the second face of the substrate using a reversible adhesive. The reversible adhesive includes a plurality of microstructures.BRIEF DESCRIPTION OF THE DRAWINGS

[0009] 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 of the disclosure and are therefore not to be considered limiting of its scope, as the disclosure may admit to other equally effective embodiments.

[0010] Figure 1 is a schematic, top view of a waveguide, according to one or more embodiments.

[0011] Figure 2 is a schematic, cross-sectional view of the waveguide shown in Figure 1 , according to one or more embodiments.

[0012] Figure 3 is a schematic, perspective view of a device, according to one or more embodiments.

[0013] Figures 4A and 4B are schematic, frontal and side views of an interposer shown in Figure 3, according to one or more embodiments.

[0014] Figure 5 is a flow diagram of a method of fabricating a device, according to one or more embodiments.

[0015] Figures 6A-6C are schematic, cross-sectional views of a substrate during fabrication of the device, according to one or more embodiments.

[0016] Figure 7 is a graphical representation of a pull-off stress, according to one or more embodiments.

[0017] Figure 8 is a graphical representation of a specific adhesion force, according to one or more embodiments.

[0018] Figure 9A is a schematic, top view of a waveguide including an interposer with a gap, according to one or more embodiments.

[0019] Figure 9B is a schematic, cross-sectional view of a waveguide including a reflective layer disposed between an interposer and a second surface of the waveguide, according to one or more embodiments.

[0020] Figure 9C is a schematic, cross-sectional view of a waveguide including a reflective coating disposed under a portion of an interposer, according to one or more embodiments.

[0021] To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It iscontemplated that elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation.DETAILED DESCRIPTION

[0022] Embodiments described herein relate to detachable light engines for waveguide devices, and related apparatus and methods. The detachable light engines allow for recycling of device components (e.g., waveguides, interposers, and / or light engines) using reversible adhesives, in which no reconditioning of the waveguide device occurs. Moreover, the reversible adhesives may allow for replacing substrates, such as a prescription lens of the waveguide devices, with reduced complexity compared to conventional waveguide devices. Additionally, due to the use of the improved reversible adhesives described herein, manufacturing of the waveguide devices may be reduced due to the reduction of curing requirements and reduction of assembly costs.

[0023] Figure 1 is a schematic, frontal view of a device 100, according to one or more embodiments. It is to be understood that the device 100 described herein is an exemplary waveguide and that other waveguides may be used with or modified to accomplish aspects of the present disclosure. The device 100 includes a plurality of structures 111. The structures 111 may be disposed over, under, or on a first face 102 of a substrate 101 , or disposed in the substrate 101. The structures 111 are nanostructures and have a sub-micron critical dimension, e.g., a width less than 1 micrometer. Regions of the structures 111 correspond to one or more gratings 104. In one or more embodiments, the device 100 includes at least a first grating 104a corresponding to an input coupling grating and a third grating 104c corresponding to an output coupling grating. In one or more embodiments, the device 100 further includes a second grating 104b. The second grating 104b corresponds to a pupil expansion grating or a fold grating.

[0024] The substrate 101 may also be selected to transmit a suitable amount of light of a desired wavelength or wavelength range, such as one or more wavelengths from about 100 to about 3000 nanometers. Without limitation, in one or more embodiments, the substrate 101 is configured such that the substrate 101 transmits greater than or equal to about 50% to about 100%, of an infrared to ultraviolet region of the lightspectrum. The substrate 101 may be formed from any suitable material, provided that the substrate 101 can adequately transmit light in a desired wavelength or wavelength range and can serve as an adequate support for the device 100 described herein. Substrate selection may include optical device 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 substrate 101 includes a transparent material. In one or more embodiments, the substrate 101 is transparent with an absorption coefficient smaller than 0.001. Suitable examples may include silicon (Si), silicon dioxide (SiC>2), fused silica, quartz, silicon carbide (SiC), germanium (Ge), silicon germanium (SiGe), indium phosphide (InP), gallium arsenide (GaAs), gallium nitride (GaN), sapphire, lithium tantalate (LiTaOs), lithium niobate (LiNbOs), or combinations thereof. In one or more embodiments, the substrate 101 has a substrate refractive index greater than 1.4, such as greater than 1 .6, such as about 1 .8, or about 2.0.

[0025] In one or more embodiments, the structures 111 are disposed in the substrate 101. In one or more embodiments, the structures 111 are disposed on or over the substrate 101. The structures 111 include a device material. The device material includes, but is not limited to, silicon carbide (SiC), silicon oxycarbide (SiOC), titanium dioxide (TiC ), silicon dioxide (SiC>2), vanadium (IV) oxide (VOx), aluminum oxide (AI2O3), aluminum-doped zinc oxide (AZO), indium tin oxide (ITO), tin dioxide (SnO2), zinc oxide (ZnO), tantalum pentoxide (Ta2Os), silicon nitride (SisN4), zirconium dioxide (ZrO2), niobium oxide (Nb20s), cadmium stannate (Cd2SnO4), silicon mononitride (SiN), silicon oxynitride (SiON), barium titanate (BaTiOs), diamond like carbon (DLC), hafnium(IV) oxide (HfO2), lithium niobate (LiNbOs), silicon carbon-nitride (SiCN), or combinations thereof.

[0026] In operation of the device 100 a virtual image is projected from a near-eye display, such as a microdisplay, to the first grating 104a. The structures 111 of the first grating 104a in-couple the incident beams of light of the virtual image and diffract the incident beams to the second grating 104b. The diffracted beams undergo total- internal-reflection (TIR) through the device 100 until the diffracted beams come in contact with structures 111 of the second grating 104b. The diffracted beams from thefirst grating 104a incident on the second grating 104b are split into a first portion beams refracted back or lost in the device 100, a second portion beams that undergo TIR in the second grating 104b until the second portion beams contact another structure of the plurality of structures 111 of the second grating 104b, and a third portion of beams that are coupled through the device 100 to the third grating 104c. The beams of the second portion of beams that undergo TIR in the second grating 104b continue to contact structures of the plurality of structures until either the intensity of the second portion of beams coupled through the device 100 to the second grating 104b is depleted, or remaining second portion of beams propagating through the second grating 104b reach the end of the second grating 104b.

[0027] The beams pass through the device 100 to the third grating 104c and undergo TIR in the device 100 until the beams contact a structure of the plurality of gratings 104 of the third grating 104c where the beams are split into beams that are refracted back or lost in the device 100, beams that undergo TIR in the third grating 104c until the beams contact another structure of the plurality of gratings 104, or beams that are out-coupled from the device 100 to the user’s eye. The beams that undergo TIR in the third grating 104c continue to contact structures of the plurality of gratings 104 until either the intensity of the beams passing through the device 100 to the third grating 104c is depleted, or remaining beams propagating through the third grating 104c have reached the end of the third grating 104c. The beams of the virtual image are propagated from the third grating 104c to overlay the virtual image over the ambient environment.

[0028] The device 100 includes the substrate 101 having the first face 102, a second face 103, and an outer edge 105, as shown in Figure 2. The first face 102 of the substrate 101 includes the waveguide. The device 100 includes a lens 112 coupled to the substrate 101 using an adhesive 116. The waveguide is disposed radially inward of the adhesive 116. In one or more embodiments, the adhesive 116 includes a pressure sensitive adhesive, a heat-activated adhesive, and / or a glue. The present disclosure contemplates that other adhesives may be used. A gap 114 is between the substrate 101 and the lens 112, and the waveguide is disposed in the gap 114. A size of the gap 114 can be defined at least partially by a thickness of the adhesive 116. The composition of the gap 114 can include air having a refractive index of less than1.4 (such as 1.0) and an absorption coefficient of 0. A coating, such as a mirror coating, can be disposed on the first face 102 of the substrate 101. The gap 114 between the lens 112 and the substrate 101 can have a height of less than or equal to 0.1 mm, such as less than 0.050 mm, such as about 0.1 mm, such as about 0.030 mm, about 0.020 mm or about 0.0025.

[0029] A light engine 140, as shown in Figure 2, is disposed over a grating of the device, e.g., the first grating 104a. The light engine 140 is operable to project light. In some embodiments, which can be combined with other embodiments described herein, the light engine 140 projects a pattern to the first grating 104a. The light engine can include a light source. The light source can include any suitable type of light source, such as a light-emitting diode (LED), a laser, or a lamp. The light source can include adjustable parameters such as the light intensity and the timing of the light pulses.

[0030] Optionally, a second lens 120 is disposed over the second face 103 of the substrate 101 to produce a second gap 122. The second lens 120 can include a cover glass, a push-pull material, a prescription lens, and / or a dimming module. For example, the second lens 120 is a prescription lens. The second lens 120 can include a plastic material and / or a glass material. For example, the second lens 120 can include a UV-curable acrylate, a UV-curable epoxy, a UV-curable silicone, a UV- curable thiolene, or combinations thereof. The second lens 120 is disposed over the second face 103 of the substrate 101 . The second gap 122 is defined by the second lens 120 and the second face 103 of the substrate 101 .

[0031] In one or more embodiments, the lens 112 is a world-side lens and the second lens 120 is an eye-side lens. For example, the lens 112 faces a world side of the resulting AR display, i.e. , the side away from the user. The second lens 120 faces the eye side of the resulting AR display, i.e., the side facing the user’s eye.

[0032] The second gap 122 includes air. The second gap 122 optically isolates the substrate 101 from the second lens 120. The optical isolation of the substrate 101 and the second lens 120 is caused by the second gap 122 having a lower refractive index compared to the substrate 101 and the second lens 120.

[0033] The light engine 140 is coupled to the second lens 120 using a reversible adhesive 142. The reversible adhesive 142 includes a plurality of microstructures. Each microstructure of the plurality of microstructures can include a diameter of about 10 pm to about 1000 pm, e.g., about 10 pm to about 300 pm.

[0034] Each microstructure of the plurality of microstructures includes an aspect ratio of about 0.5 to about 4, in which the aspect ratio is a ratio of the diameter of each microstructure of the plurality of microstructures relative to the depth of each microstructure of the plurality of microstructures. In an aspect, the microstructure can include an inclined thin beam microstructure.

[0035] Each microstructure of the plurality of microstructures can include a mushroomshape, e.g., a stem having a circular section and / or an ellipsoidal section, and a cap, e.g., a substantially planar surface disposed over the stem. Without being bound by theory, the stem can provide an anisotropic response to lateral loads, e.g., the stem can resist forces in one direction while it detaches in the perpendicular direction.

[0036] Each microstructure of the plurality of microstructures includes a substantially planar surface. In some embodiments, the substantially planar surface can allow for each microstructure of the plurality of microstructures to bond to the second lens 120 and / or the substrate 101 according to Van Der Waals forces. In some embodiments, the plurality of microstructures can provide a specific adhesion of about 5 centinewtons per millimeter squared (cN / mm2) to about 50 cN / mm2. Without being bound by theory, the plurality of microstructures can allow for a reversible coupling which can be released by individual detachment of each microstructure of the plurality of microstructures. Moreover, advantageously the plurality of microstructures can be recoupled following detachment due to the use of Van Der Waals forces.

[0037] In some embodiments, the reversible adhesive is composed of a polymer, e.g., a polyurethane polymer. While Figure 2 depicts the light engine 140 coupled to the second lens 120 using the reversible adhesive 142, the light engine 140 can be coupled directly to the substrate 101 .

[0038] In some embodiments, an interposer 302 can be disposed between the light engine 140 and the substrate 101 , as shown in Figure 3. While Figure 3 depicts the interposer 302 disposed between the light engine 140 and the substrate 101 , theinterposer 302 can be disposed between the second lens 120 and the light engine 140. In some embodiments, the interposer 302 is aligned with the light engine 140. For example, the interposer 302 can be aligned over a grating of the device, e.g., the first grating 104a.

[0039] The interposer 302 includes an interposer substrate 402, as shown in Figures 4A and 4B. The interposer substrate 402 can be composed of amorphous dielectrics, non-amorphous dielectrics, crystalline dielectrics, polymers, metallic materials, or combinations thereof. For example, the interposer substrate 402 can include a metal material including a foil. The interposer substrate 402 can include a rigid substrate or a flexible substrate. The interposer substrate 402 can include a mechanical resistance that is greater than the force, e.g., bond, exerted by the microstructure. In some embodiments, which can be combined with other embodiments, the interposer substrate 402 can include an absorption material. The absorption material can include one or more blacking inks, one or more siloxane-containing resins, one or more dyes, one or more pigments, a polymer mix of one or more binders, or a combination thereof. In an embodiment, the absorption material can include one or more types of particles, at least one of one or more dyes or one or more pigments, or a polymer matrix of one or more binders embedded in the interposer substrate 402. In some embodiments, the one or more types of particles, one or more dyes, and / or one or more pigments can include a particle size of about 5 nm to about 500 pm. In some embodiments, the absorption material includes one or more filler dispersions, one or more photoinitiators, one or more epoxy resins, one or more additives, one or more silanes, one or more isocyanates, one or more acids, one or more phosphine oxides, or combinations thereof. Examples of the filler dispersions include acrylates or methacrylates. Examples of the additives include amines or amides. Examples of the dyes include organic dyes. The one or more pigments include, but are not limited to, carbon black, carbon nanotubes, iron oxide black, black pigments, or combinations thereof. The one or more binders are operable to be cured by radiation, to form a polymer matrix. The one or more types of particles are disposed in the polymer matrix. The one or more binders include, but are not limited to, a UV curable binder, a LED curable binder, a thermal curable binder, an infrared curable binder, or combinations thereof.

[0040] The one or more types of particles include, but are not limited to, titanium, titanium oxide (TiC ), chromium, Si, zirconium oxide (ZrC ), zinc oxide (ZnO), ferrosoferric oxide (FesCM), germanium (Ge), SiC, diamond, dopants thereof, or any combination thereof. The one or more types of particles includes at least one of nanoparticles or microparticles. Each nanoparticle (NP) or microparticle (MP) can be a coated particle, such as one, two, or more shells disposed around a core. In some examples, the NPs or MPs can contain one or more types of ligands coupled to the outer surface of the NPs or MPs (e.g., ligated NPs or stabilized NPs). The NPs or MPs can have one or more different shapes or geometries, such as spherical, oval, rod, cubical, wire, cylindrical, rectangular, or combinations thereof. The NPs can have a size or a diameter of about 2 nm to about 1000 nm. The MPs can have a size or a diameter of about 1 pm to about 500 pm.

[0041] The interposer 302 includes at least an aperture, d, as shown in Figure 4B. The aperture, d, includes a diameter of about 2 mm to about 8 mm. In some embodiments, the aperture, d, aligns with the light source of the light engine 140 such that the light emitted by the light source of the light engine 140 may be emitted through the aperture, d. While the aperture, d, is depicted as a circular shape, the aperture can be implemented as any suitable shape to allow light from the light engine 140 to progress to the substrate 101 and / or the second lens 120. For example, the aperture, d, can include a triangular shape, polygonal shape, square shape, rectangular shape, oval shape, rhomboid shape, or a combination thereof.

[0042] The interposer 302 includes a width, m. The width, m, is about 2 mm to about 20 mm. The interposer 302 includes a height, n. The height, n, is about 2 mm to about 20 mm. While the interposer 302 is depicted as a rectangular and / or square shape, any shape and / or orientation of the interposer can be implemented when disposing the light engine over the substrate 101 and / or the second lens 120. For example, the interposer 302 can include a triangular shape, polygonal shape, circular shape, oval shape, rhomboid shape, or a combination thereof. An interface area is defined by the width and the height of the interposer minus the aperture area. For example, an interposer having a width of about 12 mm, a height of about 12 mm, and an aperture having a diameter of about 6 mm may have an interface area of 115 mm2. In some embodiments, which can be combined with other embodiments, an interface area ofabout 10 mm2to about 1000 mm2can provide a bond strength that is about 500 times to about 1000 times the weight of the light engine 140.

[0043] Optionally, the interposer 302 can include a tab (not shown). The tab can be included where the interposer substrate 402 is a flexible substrate, e.g., a foil. The tab can include an area of the interposer that does not include a reversible adhesive and / or a bonding layer disposed on the interposer substrate. The tab can include a section that is not configured to adhere and / or couple the light engine to the substrate. Without being bound by theory, the tab can be used to detach the interposer from the substrate, the second lens, and / or the light engine, such that the reversible adhesive remains intact during detachment.

[0044] The interposer 302 includes a bonding layer 404 on a first side of the interposer substrate 402, as shown in Figure 4A. The bonding layer 404 can include a pressure sensitive adhesive, a heat-activated adhesive, and / or a glue. The bonding layer 404 couples the light engine 140 to the interposer 302. The interposer 302 includes the reversible adhesive 142 on a second side of the interposer substrate 402. The second side of the interposer substrate is parallel and opposite the first side of the interposer substrate 402.

[0045] The bonding layer 404 may comprise a plurality of microstructures. The plurality of microstructures function as an adhesive as described above. The bonding layer 404 may be positioned between the interposer substrate 402 and the substrate 101 . The bonding layer 404 positioned between the interposer substrate 402 and the substrate 101 allows the interposer 302 to be removed from the device. This may be advantageous if the device needs to be repaired or replaced, or if the interposer 302 and / or light engine need to be repaired or replaced.

[0046] The bonding layer 404 may also be positioned between the interposer substrate 402 and the light engine 140. The bonding layer 404 positioned between the interposer substrate 402 and the light engine 140 allows the interposer 302 to be removed from the light engine 140. This is advantageous if the light engine 140 needs to be repaired or needs to be replaced.

[0047] Figure 5 is a flow diagram of a method 500 of fabricating a device, according to one or more embodiments. Figures 6A-6C are schematic, cross-sectional views of a substrate during fabrication of the device, according to one or more embodiments.

[0048] At operation 502, the reversible adhesive 142 is deposited over the interposer substrate 402. The reversible adhesive 142 may be deposited over a first side of an interposer substrate 402, in which a bonding layer 404 is deposited over a second side of the interposer substrate 402, the first side parallel and opposite the second side, as best shown in Figure 4. Optionally, in embodiments without an interposer 302, the reversible adhesive 142 may be deposited over the light engine 140. In embodiments with an interposer 302, the light engine 140 is attached to the interposer 302. The light engine 140 may be attached to the interposer 302 using an additional reversible adhesive similar to the reversible adhesive 142. This allows the interposer 302 to be detached from the light engine 140.

[0049] The reversible adhesive 142 may be deposited over the light engine 140 or interposer substrate 402 according to one or more in-molding and / or spin-coating processes followed by etching. For example, the in-molding processes can be performed by forming each microstructure of the plurality of microstructures on a surface of the light engine. As a further example, the spin-coating process can include producing a sheet of microstructures, which can be cut to shape and glued to the light engine. In one or more embodiments, the reversible adhesive 142 is pre-fabricated (e.g., as a pre-form) into a microstructure having a tapered outer surface such that the outer surface includes a greater surface area than an inner surface. For example, the reversible adhesive 142 can include a plurality of microstructures, in which each microstructure includes a tapered outer surface such that the outer surface includes a diameter greater than the diameter of a column of the microstructure.

[0050] At operation 504, the interposer substrate 402 is aligned with at least a portion of the substrate 101 , as shown in Figure 6A. The substrate 101 includes a first face 102, a second face 103 and a plurality of gratings 104 as seen in Figure 2. The interposer substrate 402 may be disposed over the second face 103 such that the light engine 140 coupled to the interposer substrate 402 is operable to project a light to the plurality of gratings 104, e.g., the first grating 104a.

[0047] At optional operation 506, as shown in Figure 6B, the interposer substrate 402 is disposed over at least a portion of the substrate 101 , as shown in Figure 6B. The interposer substrate 402 is disposed over the at least a portion of the substrate 101 by applying a pressure and / or force to couple the light engine 140 and the substrate 101 . Without being bound by theory, by applying a pressure or force, one or more Van Der Waals forces may be formed between the reversible adhesive 142 and the substrate 101 , thereby reversibly coupling the interposer substrate 402 to the substrate 101 . The reversible coupling may secure the interposer substrate 402 to the substrate 101 , in which a lateral force and / or an angular force, as described below, may remove the coupling between the interposer substrate 402 and the substrate 101. Optionally, the reversible coupling may secure the interposer substrate 402 to the substrate 101 , in which a lateral force may not remove the coupling between the interposer substrate 402 and the substrate 101 such that only an angular force may remove the coupling. Optionally, the interposer substrate 402 is disposed over the second lens 120, which aligns with the at least a portion of the substrate 101 , by applying a pressure and / or force to couple the interposer substrate 402 and the second lens 120. Without being bound by theory, by applying a pressure or force, one or more Van Der Waals forces may be formed between the reversible adhesive 142 and the second lens 120, thereby reversibly coupling the light engine 140 to the second lens 120.

[0048] Optionally, at operation 508, and as shown in Figure 6C, the interposer substrate 402 may be detached from the at least a portion of the substrate 101 . The interposer substrate 402 may be detached by applying a lateral force and / or an angular force to remove each microstructure of the plurality of microstructures. The lateral force and / or angular force may be a force greater than about 5 centi-newtons per millimetre squared (cN / mm2) to about 50 cN / mm2. Optionally, the interposer substrate 402 may be detached by applying only an angular force to remove each microstructure of the plurality of microstructures, in which the angular force is greater than about 5 cN / mm2The angular force may include applying a force at an angle 306. The angle 306 can include an angle of about 0.1 ° to about 45° relative to normal angle of the adhesive surface of the reversible adhesive 142. Without being bound by theory, by applying a lateral force and / or angular force each microstructure of the plurality of microstructure may be independently removed as the adhesion force ofeach individual microstructure is less than the adhesion force of the sum of the plurality of microstructures.

[0049] It should be appreciated that the method 500 may be used without an interposer 302 and instead applying the reversible adhesive 142 directly to the light engine 140 as described above.

[0050] As shown in Figure 7, two reversible adhesives were analyzed to determine the normal pull-off stress of a light engine weighing about 2.7 g from a substrate. The first reversible adhesive included microstructures having a diameter of about 700 pm, while the second adhesive included microstructures having a diameter of about 130 pm. The second reversible adhesive had a larger pull-off stress, indicating a stronger adhesion force between the light engine and the substrate. As shown in Figure 8, the smaller the diameter of the microstructures, the greater the adhesion force the reversible adhesive provided.

[0051] As shown in Figures 9A-9C, a device 100 is provided. The device 100 includes a substrate 101 having a first face 102 and a second face 103. The substrate 101 in Figures 9A-9C are a waveguide. The first face 102 of the waveguide includes an input coupling grating 104a, a pupil expansion grating 104b, and an output coupling grating 104c. The device 100 includes an interposer 302 aligned with the input coupling grating 104a. The interposer 302 is coupled to the second face 103 of the waveguide. The device 100 may include one or more of a gap 911 in the interposer substrate 402, a reflective layer 912, and / or a reflective coating 913 disposed under a portion of the interposer 302. The device 100 may include one or more of these elements to assist in maintaining total internal reflection (TIR). When the interposer 302 is positioned on the waveguide, the interposer substrate 402 may break TIR. When TIR fails, light may leak out of the device, contrast decreases, and overall efficiency of the device 100 decreases. Accordingly, one or more of the gap 911 , the reflective layer 912, and / or the reflective coating 913 may be used to maintain TIR.

[0052] Figure 9A illustrates a device 100 including an interposer 302 with a gap 911 in the interposer substrate 402. In Figure 9A, the interposer 302 is positioned over the input coupling grating 104a. The interposer 302 is aligned with the input coupling grating 104a, but does not have to be positioned directly above the input couplinggrating 104a. In one or more embodiments, the interposer 302 is aligned with the input coupling grating 104a and coupled to the second face 103 of the waveguide while the input coupling grating 104a is coupled to the first face 102 of the waveguide.

[0053] The gap 911 in the interposer 302 creates an opening for light to propagate from the input coupling grating 104a to the pupil expansion grating 104b. In embodiments which do not include a pupil expansion grating 104b, the gap 911 creates an opening for light to propagate from the input coupling grating 104a to the output coupling grating 104c. In either embodiment, the gap 911 creates an opening for light to propagate to prevent the interposer 302 from breaking TIR. To facilitate efficient transfer of light and to maintain TIR, the width of the gap 911 may be substantially equivalent to or greater than the width of the edge of the grating 104 that the gap 911 is opened towards. As shown in Figure 9A, the width of the gap 911 is substantially equivalent to the left edge of the pupil expansion grating 104b.

[0054] Figure 9B illustrates a device 100 including a reflective layer 912 disposed between the interposer 302 and the second face 103 of the waveguide. In one or more embodiments, the reflective layer 912 is disposed between the bonding layer 404 and the interposer substrate 402. In one or more embodiments, the reflective layer 912 is disposed between the bonding layer 404 and the second face 103 of the waveguide. The bonding layer 404 may include a plurality of microstructures. The plurality of microstructures include a diameter of between about 10 pm to about 700 pm.

[0055] The reflective layer 912 may be made of transparent conductive oxides such as indium tin oxide or titanium oxide or combinations thereof. The reflective layer 912 may be made of a material with a refractive index less than 1.1. The reflective layer 912 may be made of a material with a refractive index substantially similar to the refractive index of the second face 103 of the waveguide. In some embodiments, the reflective layer 912 may include a plurality of microstructures or a similar adhesive as described above to assist in bonding to other components of the device 100, such as the second face 103 of the waveguide.

[0056] Figure 9C illustrates a device 100 including a reflective coating 913 disposed under a portion of the interposer 302. The portion of the interposer 302 that thereflective coating 913 is disposed under is facing towards the direction in which light propagates from the input coupling grating 104a towards the pupil expansion grating 104b. In embodiments without a pupil expansion grating 104b, the reflective coating 913 is disposed under a portion of the interposer 302 facing towards the direction in which light propagates from the input coupling grating 104a towards the pupil expansion grating 104c. The reflective coating 913 may be made of the same material as the reflective layer 912 as discussed above.

[0057] Advantageously, the present disclosure provides detachable light engines for waveguide devices, and related apparatus and methods. The detachable light engines allow for recycling of device components, e.g., waveguides, interposers, and / or light engines, using reversible adhesives, in which no reconditioning of the waveguide device occurs. The reversible adhesives may allow for replacing substrates, such as prescription lens of the waveguide devices, with reduced complexity compared to conventional waveguide devices. Additionally, due to the use of the improved reversible adhesives described herein, manufacturing of the waveguide devices may be reduced due to the reduction of curing requirements and reduction of assembly costs

[0058] The preceding discussion is directed to various embodiments. However, one of ordinary skill in the art will understand that the examples disclosed herein have broad application, and that the discussion of any embodiment is meant only to be exemplary of that embodiment, and not intended to suggest that the scope of the disclosure, including the claims, is limited to that embodiment.

[0059] The drawing figures are not necessarily to scale. Certain features and components herein may be shown exaggerated in scale or in somewhat schematic form and some details of conventional elements may not be shown in interest of clarity and conciseness.

[0060] Any one or more components of the various embodiments disclosed herein may be integrally formed together, directly coupled together, and / or indirectly coupled together and are not limited to the specific arrangement of components illustrated in Figures 1 -9C. Any one or more of the components, embodiments, or steps of theembodiments disclosed herein may be combined in whole or part with any other components, embodiments, or steps of the embodiments disclosed herein.

[0061] Certain embodiments and features have been described using a set of numerical upper limits and a set of numerical lower limits. It should be appreciated that ranges including the combination of any two values, e.g., the combination of any lower value with any upper value, the combination of any two lower values, and / or the combination of any two upper values are contemplated unless otherwise indicated. Certain lower limits, upper limits, and ranges appear in one or more claims below.

[0062] In the preceding discussion and in the claims, the terms “including” and “comprising” are used in an open-ended fashion, and thus should be interpreted to mean “including, but not limited to . . . .” Also, the term “couple” or “couples” is intended to mean either an indirect or direct connection. Thus, if a first device couples to a second device, that connection may be through a direct connection of the two devices, or through an indirect connection that is established via other devices, components, nodes, and connections.

[0063] Certain embodiments and features have been described using the term “about,” “generally,” “substantially,” and / or “generally.” When any of these terms are used in conjunction with a numerical value, it should be construed as indicating any numerical value within 10% of the stated numerical value.

[0064] While the foregoing is directed to embodiments of the present disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.

Claims

What is claimed is:

1. A device, comprising: a substrate having a first face and a second face, wherein the first face of the substrate includes a waveguide, wherein the waveguide includes an input coupling grating, a pupil expansion grating, and an output coupling grating; and a light engine aligned with the input coupling grating coupled to the second face of the substrate using a reversible adhesive, wherein the reversible adhesive comprises a plurality of microstructures.

2. The device of claim 1 , each microstructure of the plurality of microstructures comprises a diameter of about 10 pm to about 300 pm.

3. The device of claim 1 , each microstructure of the plurality of microstructures comprises a tapered outer surface.

4. The device of claim 1 , wherein the reversible adhesive comprises a specific adhesion of about 5 centi-newtons per millimeter squared (cN / mm2) to about 50 cN / mm2.

5. The device of claim 1 , further comprising an interposer disposed between the substrate and the light engine.

6. The device of claim 5, wherein the interposer comprises the reversible adhesive disposed on a first side and a bonding layer disposed on a second side, wherein the first side and the second side are opposite.

7. The device of claim 6, wherein the bonding layer is configured to couple the interposer to the light engine.

8. The device of claim 5, wherein the interposer comprises an aperture.

9. The device of claim 5, wherein the interposer comprises a tab.

10. A device, comprising: a substrate having a first face and a second face, wherein the first face of the substrate includes a waveguide, wherein the waveguide includes an input coupling grating, a pupil expansion grating, and an output coupling grating; a lens disposed over the first face, wherein a gap is formed between the lens and the first face using an adhesive; a second lens disposed over the second face, wherein a second gap is formed between the second lens and the second face using the adhesive; and a light engine aligned with the input coupling grating coupled to the second lens using a reversible adhesive, wherein the reversible adhesive comprises a plurality of microstructures.

11. The device of claim 10, each microstructure of the plurality of microstructures comprises a tapered outer surface.

12. The device of claim 10, wherein the reversible adhesive comprises a specific adhesion of about 5 centi-newtons per millimeter squared (cN / mm2) to about 50 cN / mm2.

13. The device of claim 10, further comprising an interposer disposed between the second lens and the light engine.

14. The device of claim 13, wherein the interposer comprises the reversible adhesive disposed on a first side and a bonding layer disposed on a second side, wherein the first side and the second side are opposite.

15. The device of claim 14, wherein the bonding layer is configured to couple the interposer to the light engine.

16. The device of claim 10, wherein each microstructure of the plurality of microstructures comprises a diameter of about 10 pm to about 700 pm.

17. A device, comprising:a waveguide having a first face and a second face, wherein the first face of the waveguide includes an input coupling grating, a pupil expansion grating, and an output coupling grating; an interposer aligned with the input coupling grating and coupled to the second face of the waveguide, the interposer comprising an interposer opening disposed within an interposer substrate of the input coupling grating and at least one of: a gap in the interposer substrate, the gap creating an opening for light to propagate from the input coupling grating towards the pupil expansion grating; a reflective layer disposed between the interposer and the second face of the waveguide; or a reflective coating disposed under a portion of the interposer, the portion facing a direction in which light propagates from the input coupling grating towards the pupil expansion grating; and a light engine aligned with the input coupling grating and coupled to the interposer.

18. The device of claim 17, wherein the bonding layer comprises a plurality of microstructures.

19. The device of claim 18, wherein the reflective layer is disposed between the bonding layer and the interposer substrate.

20. The device of claim 18, wherein the reflective layer is disposed between the bonding layer and the second face of the waveguide.

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