Method and system for integration of diffractive eyepiece waveguide display with refractive optics

Abstract

The present invention relates generally to methods and systems for waveguide displays.SOLUTION: An eyepiece waveguide, comprising: a set of waveguide layers having a world side and a user side; a first cover plate having a first optical power and disposed adjacent the world side of the set of waveguide layers; and a second cover plate having a second optical power and disposed adjacent the user side of the set of waveguide layers.SELECTED DRAWING: Figure 1B

Description

[Technical Field]

[0001] This application claims priority to U.S. Provisional Patent Application No. 63 / 025,069, filed May 14, 2020, and entitled "Method and System for Integration of Refractive Optics with a Diffractive Eyepiece Waveguide Display," the disclosure of which is incorporated herein by reference in its entirety for all purposes. [Background technology]

[0002] Modern computing and display technology has facilitated the development of systems for so-called "virtual reality" or "augmented reality" experiences, in which digitally reproduced images, or portions thereof, are presented to a viewer in a manner that makes them appear or be perceived as real. Virtual reality, or "VR," scenarios typically involve the presentation of digital or virtual image information without transparency to other actual, real-world visual input. Augmented reality, or "AR," scenarios typically involve the presentation of digital or virtual image information as an extension to the viewer's visualization of the real world around them.

[0003] Despite the advances made in these display technologies, there remains a need in the art for improved methods and systems relating to augmented reality systems, and in particular display systems. Summary of the Invention [Means for solving the problem]

[0004] The present invention relates generally to methods and systems for waveguide displays. More specifically, embodiments of the present invention provide methods and systems that integrate refractive optics with a diffractive eyepiece waveguide display, also referred to as a waveguide display. The present invention is applicable to a variety of applications in computer vision and image display systems.

[0005] As described herein, embodiments of the present invention relate to methods and systems for fabricating laminated lenses and optical elements having optical power that can be utilized with a diffractive eyepiece waveguide forming part of an augmented reality display device. As described herein, methods of lens integration with a waveguide optical combiner for a mixed reality display are provided. In certain embodiments, a pair of lenses is utilized to create a virtual image depth plane while preserving the depth plane of a real-world object. The pair of lenses is integrated with the waveguide layer to provide a very thin, compact, wearable form factor and an improved user experience, including high optical transmittance, by reducing the distance between the lenses in the pair while compensating for lens effects for the world view.

[0006] According to an embodiment of the present invention, there is provided a method of fabricating an optical element, the method including the steps of providing a substrate, forming a castable material bonded to the substrate, and casting the castable material using a mold, the method also including the steps of hardening the castable material and removing the mold.

[0007] According to another embodiment of the present invention, a method of fabricating an optical element is provided. The method includes the steps of providing a mold set having mold plates and placing a moldable material between the mold plates. The method also includes the steps of joining the mold plates, curing the moldable material to form the optical element, and removing the optical element from the mold set.

[0008] According to a specific embodiment of the present invention, an eyepiece waveguide is provided. The eyepiece waveguide includes a set of waveguide layers having a world side and a user side. The eyepiece waveguide also includes a first cover plate having a first optical power and positioned adjacent to the world side of the set of waveguide layers, and a second cover plate having a second optical power and positioned adjacent to the user side of the set of waveguide layers.

[0009] Numerous benefits are achieved by the methods of the present invention over conventional techniques. For example, embodiments of the present invention provide methods and systems that provide a compact eyepiece waveguide system with an integrated stacked lens or optical element that functions as both a cover plate and a lens. Furthermore, embodiments of the present invention allow paired lenses integrated with the eyepiece waveguide to be positioned closer to each other, thereby reducing optical aberrations compared to conventional techniques. These and other embodiments of the invention, along with many of their advantages and features, are described in further detail in the following text and in conjunction with the accompanying figures. [Brief explanation of the drawings]

[0010] [Figure 1A] FIG. 1A is a simplified cross-sectional view illustrating a viewing optics assembly including an eyepiece waveguide and a stacked lens pair, according to one embodiment of the present invention.

[0011] [Figure 1B] FIG. 1B is a simplified cross-sectional view illustrating a viewing optics assembly including an eyepiece waveguide with optical power and a set of cover plates according to one embodiment of the present invention.

[0012] [Figure 2A] 2A-2C are simplified cross-sectional views illustrating a process for fabricating a laminated lens according to one embodiment of the present invention. [Figure 2B]2A-2C are simplified cross-sectional views illustrating a process for fabricating a laminated lens according to one embodiment of the present invention. [Figure 2C] 2A-2C are simplified cross-sectional views illustrating a process for fabricating a laminated lens according to one embodiment of the present invention.

[0013] [Figure 2D] FIG. 2D is a simplified cross-sectional view illustrating a process for fabricating a laminated lens according to another embodiment of the present invention.

[0014] [Figure 3A] 3A-3D are simplified cross-sectional views illustrating a process for fabricating a laminated lens using a master, according to one embodiment of the present invention. [Figure 3B] 3A-3D are simplified cross-sectional views illustrating a process for fabricating a laminated lens using a master, according to one embodiment of the present invention. [Figure 3C] 3A-3D are simplified cross-sectional views illustrating a process for fabricating a laminated lens using a master, according to one embodiment of the present invention. [Figure 3D] 3A-3D are simplified cross-sectional views illustrating a process for fabricating a laminated lens using a master, according to one embodiment of the present invention.

[0015] [Figure 4] FIG. 4 is a simplified cross-sectional view of a laminated lens according to one embodiment of the present invention.

[0016] [Figure 5] FIG. 5 is a simplified plan view of a laminated lens overlying elements of an eyepiece waveguide, according to one embodiment of the present invention.

[0017] [Figure 6]6A-6C are simplified cross-sectional views illustrating a process for fabricating a laminated lens with positive optical power according to one embodiment of the present invention.

[0018] [Figure 7] 7A-7C are simplified cross-sectional views illustrating a process for fabricating a laminated lens with positive optical power according to another embodiment of the present invention.

[0019] [Figure 8] FIG. 8 is a simplified perspective view of a system for forming multiple laminated lenses according to one embodiment of the present invention.

[0020] [Figure 9A] 9A-9D are simplified cross-sectional views illustrating a process for fabricating an optical element according to one embodiment of the present invention. [Figure 9B] 9A-9D are simplified cross-sectional views illustrating a process for fabricating an optical element according to one embodiment of the present invention. [Figure 9C] 9A-9D are simplified cross-sectional views illustrating a process for fabricating an optical element according to one embodiment of the present invention. [Figure 9D] 9A-9D are simplified cross-sectional views illustrating a process for fabricating an optical element according to one embodiment of the present invention.

[0021] [Figure 10] FIG. 10 is a simplified cross-sectional view illustrating a mold with an anti-stick coating, according to one embodiment of the present invention.

[0022] [Figure 11A] FIG. 11A is a simplified cross-sectional view illustrating an optical element with nano-features fabricated on the planar side of the optical element, according to one embodiment of the present invention.

[0023] [Figure 11B]FIG. 11B is a simplified cross-sectional view illustrating an optical element with nanofeatures fabricated on the curved side of the optical element, according to an embodiment of the present invention.

[0024] [Figure 11C] FIG. 11C is a simplified cross-sectional view illustrating an optical element with nanofeatures fabricated on both the planar and curved sides of the optical element, according to an embodiment of the present invention.

[0025] [Figure 12] FIG. 12 is a simplified cross-sectional view illustrating a VOA including an eyepiece waveguide and a set of optical elements according to one embodiment of the present invention.

[0026] [Figure 13A] FIG. 13A is a simplified cross-sectional view illustrating a biconvex stacked lens according to one embodiment of the present invention.

[0027] [Figure 13B] FIG. 13B is a simplified cross-sectional view illustrating a convex meniscus lens according to one embodiment of the present invention.

[0028] [Figure 13C] FIG. 13C is a simplified cross-sectional view illustrating an achromatic lens stack according to one embodiment of the present invention.

[0029] [Figure 13D] FIG. 13D is a simplified cross-sectional view illustrating an apochromatic stack lens according to one embodiment of the present invention.

[0030] [Figure 14A] FIG. 14A is a simplified perspective view illustrating a first mold according to an embodiment of the present invention.

[0031] [Figure 14B]FIG. 14B is a simplified perspective view illustrating a first molding according to an embodiment of the present invention.

[0032] [Figure 14C] FIG. 14C is a simplified side view of a portion of a molding before and after a release layer coating process, according to an embodiment of the present invention.

[0033] [Figure 14D] FIG. 14D is a perspective view illustrating a coated first molding according to an embodiment of the present invention.

[0034] [Figure 14E] FIG. 14E is a simplified perspective view illustrating a second molding according to an embodiment of the present invention.

[0035] [Figure 14F] FIG. 14F is a perspective view illustrating a coated second molding according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0036] Detailed Description The present invention relates generally to methods and systems relating to wearable displays. More specifically, embodiments of the present invention provide methods and systems that integrate refractive optics with a diffractive eyepiece waveguide display, also referred to as a waveguide display. The present invention is applicable to a variety of applications in computer vision and image display systems.

[0037] FIG. 1A is a simplified cross-sectional view illustrating a viewing optics assembly including an eyepiece waveguide and a stacked lens pair according to one embodiment of the present invention. As shown in FIG. 1A, viewing optics assembly (VOA) 100 includes eyepiece waveguide 110, first stacked lens 112, and second stacked lens 114. In one embodiment, eyepiece waveguide 110 is designed to generate a virtual image that appears to occur at infinite distance. To allow a user to perceive the virtual image as occurring at a non-infinite depth plane, first stacked lens 112, which has negative optical power, is utilized to diverge the light rays generated by eyepiece waveguide 110, causing the virtual image generated by eyepiece waveguide 110 to appear to occur from the depth plane at a predetermined distance (e.g., 1 meter or 0.3 meters) from the user. In some implementations, the first lens stack 112 is referred to as the inner lens or user-side lens because it is positioned on the side of the eyepiece waveguide that faces the user.

[0038] The second stack lens 114 is utilized to compensate for the optical power of the first stack lens 112 so that light incident on the VOA 100 from the world side of the VOA can emerge at specific distances associated with various objects in the world. Thus, as illustrated in FIG. 1A , the second stack lens 114 has a positive optical power that is equal to and opposite to the negative optical power of the first stack lens 112. In some implementations, the second stack lens 114 is referred to as an outer lens or world-side lens because it is positioned on the side of the eyepiece waveguide that faces the world. As will be apparent to those skilled in the art, the ability to position the first stack lens 112 and the second stack lens 114 closer together allows for improvements in the ability of these lenses to form a compensating pair. By fabricating the lenses as stack lenses, the spacing between the refractive elements and the cover plate is eliminated because the refractive elements are formed on the cover plate. Furthermore, the thickness of the laminated lens is reduced compared to conventional lenses, which is advantageous for AR wearable devices.

[0039] 1B is a simplified cross-sectional view illustrating a viewing optics assembly including an eyepiece waveguide and a set of optical elements according to one embodiment of the present invention. As described more fully herein, the optical elements may be referred to as cover plates or cover glasses with optical power. These optical elements or cover plates may be fabricated from a variety of materials, including glass or organic materials, such as, but not limited to, polymers such as polycarbonate, polyethylene terephthalate, cycloolefin polymers, or the like.

[0040] Referring to FIG. 1B , VOA 150 includes eyepiece waveguide 160, first optical element 162, and second optical element 164. Because the optical elements provide both a mechanical function (i.e., protecting the waveguide layer) and an optical function (i.e., focusing or defocusing incident light), they can be referred to as cover plates with optical power. In one embodiment, eyepiece waveguide 160 is designed to generate a virtual image that appears to occur at infinite distance. To allow a user to perceive the virtual image as occurring at a non-infinite depth plane, first optical element 162, which has negative optical power, is utilized to diverge the light rays generated by eyepiece waveguide 160, causing the virtual image generated by eyepiece waveguide 160 to appear to occur from the depth plane at a predetermined distance from the user (e.g., 1 meter or 0.3 meters). In some implementations, the first optical element 162 is referred to as an inner cover plate or user-side cover plate because it is positioned on the side of the eyepiece waveguide that faces the user.

[0041] A second optical element 164 is utilized to compensate for the optical power of the first optical element 162 so that light incident on the VOA 150 from the world side of the VOA can emerge at specific distances associated with various objects in the world. Thus, as illustrated in FIG. 1B , the second optical element 164 has a positive optical power that is equal to and opposite to the negative optical power of the first optical element 162. In some implementations, the second optical element 164 is referred to as an outer cover plate or world-side cover plate because it is positioned on the side of the eyepiece waveguide that faces the world. As will be apparent to one skilled in the art, the ability to position the first optical element 162 and the second optical element 164 closer together allows for improvements in the ability of these cover plates with optical power to form a compensation pair.

[0042] In contrast to conventional designs that typically utilize separate and independent inner and outer lenses with a minimum thickness of about 2 mm to 3 mm to maintain their mechanical rigidity, thereby resulting in a VOA that is approximately 7 mm thick, the stacked lenses and cover plates with optical power described herein have a very thin thickness, e.g., about <1 mm, e.g., about 600 μm, and in some cases can be thinned from 7 mm to <3 mm, reducing the thickness of the VOA and thus resulting in a lighter and smaller VOA than achievable using conventional approaches. Furthermore, because the optical elements are positioned closely together, as measured along a longitudinal axis perpendicular to the VOA, embodiments of the present invention feature higher optical quality for the user because the compensation provided by the set of lenses or cover plates with optical power is improved over systems using conventional approaches.

[0043] 2A-2C are simplified cross-sectional views illustrating a process for fabricating a laminated lens according to some embodiments of the present invention. Referring to FIG. 2A, a substrate 210 is provided along with a mold 220. In some embodiments, a glass substrate is utilized as the substrate 210, although this is not required for the present invention. In other embodiments, other substrates with suitable mechanical rigidity, optical transparency, and the like are utilized as the substrate 210, including plastic substrates, polymer substrates, molded photoresist substrates, combinations thereof, or the like. The substrate 210 is a planar substrate suitable for forming a molded film having at least one planar surface; however, as described in connection with FIG. 2D, a curved substrate can be utilized according to some embodiments of the present invention. The substrate 210 can be cleaned using a substrate cleaning process such as an acidic or basic piranha solution, an acidic, basic, or neutral water-based ultrasonic treatment process, a water spin-rinse-dry method, or similar processes. The substrate 210 with a clean surface onto which the mold replica will be cast / cured can be treated with a thin adhesive intermediate crosslinking layer (e.g., <10 nm), which can be coated using coating processes such as, but not limited to, vapor treatment, slot die, spraying, spin coating, inkjet, screen coating, etc. Such an adhesive coating allows the molding material to form a chemical, heat, or physical bond with the intermediate adhesive layer, allowing the molded lens to be free of breakage or peel defects after replication, ensuring reliability of the molded part over time and with use of the wearable.

[0044] Substrate 210 can also be mechanically restrained to a planar surface, for example, on a vacuum chuck to prevent mechanical changes in curvature during the lens molding process. As an example, mold 220 can be fabricated to have a predetermined curvature, which may have a bias built in to account for, for example, approximately 10% material volume shrinkage, to fabricate a molded film with a matching or desired predetermined curvature, i.e., a mold with a radius of curvature of R = 0.5665 m and a molded film with a radius of curvature of R = -0.515 m. For a refractive index of n = 1.53, the molded lens would therefore have a depth of focus of -1,000 mm. In the embodiment illustrated in FIG. 2A, mold 220 is a convex mold used to form a plano-concave molded film, although other curvatures are utilized in other implementations. The castable material or curable resin 212 is deposited in an unreacted or semi-reacted form, for example, dispensed as a low-to-high viscosity (10 cP-1,000 cP) liquid onto the substrate 210 or onto a mold (as described below). The castable material 212 can be a resin, i.e., a UV-curable resin, a UV-curable photoresist, or the like, that is cured using ultraviolet (UV) radiation to provide a cast film with a fixed geometry and high optical transparency. Deposition processes for dispensing the castable material or curable resin 212 can include, but are not limited to, micro-jet positive displacement systems, such as syringe pumps, pipetting, or the like.

[0045] As shown in FIG. 2B , mold 220 is brought into close proximity with substrate 210, and castable material 212 is compressed between the mold and substrate, thereby forming the surface of the castable material facing the mold to a matching predetermined curvature. In the illustrated example, mold 220 has a convex curvature, thereby creating a concave curvature for the surface of castable material 212 facing mold 220. Because substrate 210 is planar in the embodiment illustrated in FIGS. 2A-2C , the surface of castable material 212 facing substrate 210 is planar. As will be apparent to one skilled in the art, shaping of the castable material is performed in a manner such that the surface of the castable material, after hardening, has a curvature appropriate for the optical effect (e.g., a predetermined focal length) desired for the laminated lens.

[0046] The shaped castable material 212, disposed between the mold 220 and the substrate 210, is exposed to UV radiation 230 to cure the castable material into the shape impressing onto the castable material by the mold and substrate. UV curing can be carried out for times on the scale of, for example, tens of seconds, e.g., minutes to less than a minute, e.g., 30 seconds, for various UV-curable materials exposed under different wavelengths in the UV-Vis range. Curing lamps can be used, including metal halide lamps, mercury lamps, or banks of LEDs with the desired wavelength spectrum.

[0047] FIG. 2C illustrates the separation of mold 220 from cast film 214 once the castable material has hardened. Thus, using the process illustrated in FIGS. 2A-2C, a cast film 214 is provided that is attached to and supported by substrate 210. The curvature of cast film 214 can be fabricated as needed for a particular application, e.g., as an aspheric optical element, although this is not required; spherical surfaces can also be fabricated. Generally, the thickness of cast film 214, measured along its optical axis, also referred to as the longitudinal axis, aligned with the z-axis in FIG. 2A , and in this example of a plano-concave lens, ranges from zero or near zero, measured in the xy plane, to nanometer scales of, e.g., several microns at the center of cast film 214, to approximately 300 μm at its maximum lateral extent. Thus, utilizing embodiments of the present invention, extremely thin cast films that are mechanically supported by substrate 210 can be produced, enabling the creation of thinner lens structures than can be produced using conventional injection molding processes. This should be contrasted with conventional self-supporting lenses. For example, if a plano-concave lens were utilized, the thickness of the center of the plano-concave lens and its resulting mechanical stiffness as a function of thickness would limit the ability to reduce lens thickness. In contrast, embodiments of the present invention can utilize cast film thicknesses as thin as zero, including thicknesses of a few nanometers to a few microns, which can be considered to be approximately zero at the center of the cast film because the cast film is supported by the substrate. Thus, the thickness of a laminated lens is determined by the thickness of the substrate (e.g., about 1 mm or thinner) and the optical power, which affects the thickness of the cast film at the edges for plano-concave lenses and at the center (e.g., 600 μm) for plano-convex lenses.

[0048] In contrast to conventional lenses that mechanically support a lens and are machined to suitable dimensions to provide optical refractive power, embodiments of the present invention utilize a substrate to provide mechanical rigidity and support while utilizing a molded film to provide optical refractive power. Thus, by separating these two functions into two structures / materials, embodiments of the present invention are able to provide similar mechanical and optical functionality, particularly in terms of thickness along the optical or longitudinal axis, in a package that is a certain percentage of the size of a conventional lens. As an example, using a rigid glass substrate, a molded film that is much less rigid and not self-supporting is formed on the rigid glass substrate, achieving a thickness of the molded film of about 300 μm to 600 μm, which would not be possible if the lens was not machined from the material utilized as the molded film.

[0049] Although a single lens is processed using the process illustrated in FIGS. 2A - 2C, it should be understood that embodiments of the present invention are not limited to the processing of a single lens using the methods and systems described herein. Rather, the mold 220 is characterized by a plurality of regions of convex curvature, whereby multiple lenses can be formed using a multi-lens mold, either in parallel or simultaneously. Thus, for example, in FIGS. 2A - 2C and in other figures as well, illustrations showing the processing of a single lens using a single-lens mold are provided merely to facilitate the illustration and are not intended to limit embodiments of the present invention.

[0050] The inventors have determined that during curing of the resin material, mechanical and volumetric material shrinkage of the molded material, such as the lens geometry, occurs. However, this mechanical shrinkage is predictable and can be accounted for during the lens design process, eliminating undesired bowing / distortion in the substrate (if applicable), mechanically constraining the substrate with the mold curvature corrected for the desired curvature of the lens, avoiding undesired substrate or mold movement, and resulting in a lens featuring the desired curvature after molding and mechanical shrinkage have occurred. Furthermore, because different moldable materials featuring different refractive indices can be utilized in conjunction with the processes described herein, a single mold can be utilized to produce layered lenses with different focal lengths. The inventors have determined that by utilizing moldable materials with refractive indices ranging from about 1.5 to 1.75, focal lengths ranging from about 0.85F to about 1.1F can be produced (F is the focal length (e.g., 1 / 3.5 diopters)).

[0051] Figure 2D is a simplified cross-sectional view illustrating a process for fabricating a laminated lens according to another embodiment of the present invention. Figure 2D shares some similarities with Figure 2A, and the description provided in connection with Figure 2A is applicable to Figure 2D, where appropriate. As illustrated in Figure 2D, substrate 240 features a curved geometry, allowing for the fabrication of a cast film having two curved surfaces, in this case a convex lower surface 242 and a concave upper surface 244, thereby forming either a positive or negative lens, depending on the curvature of mold 220 and substrate 240.

[0052] Referring to Figure 2D, a process for molding refractive lenses onto a flexible plastic substrate (e.g., an organic material made, by way of example, of PC, PET, PEN, or the like) is illustrated. Such plastic substrates have an elastic modulus below 10 GPa, unlike, for example, thin glass substrates (e.g., soda lime, quartz glass, or the like), which have a higher elastic modulus. Plastic substrates may also come in rolls for use in web or sheet processes using such substrates, where the plastic substrate may have a predefined curvature with a uniform thickness, of which Figure 2D is an example cross-section provided for illustrative purposes.

[0053] Referring to FIG. 2D , a substrate 240 is provided along with the mold 220. In some embodiments, a glass substrate is utilized as the substrate 240, although this is not required for the present invention. In other embodiments, other substrates with suitable mechanical rigidity, optical transparency, and the like are utilized as the substrate 240, including plastic substrates, polymer substrates, molded photoresist substrates, combinations thereof, or the like. As an example, the mold 220 can be fabricated to have a predetermined curvature, which may have a bias built in to account for, for example, approximately 10% material volume shrinkage, to fabricate a matching or desired molded film with a predetermined curvature, i.e., a mold with a radius of curvature of R=0.5665 m and a molded film with a radius of curvature of R=−0.515 m. With a refractive index of n=1.53, the molded lens would therefore have a depth of focus of −1,000 mm. In the embodiment illustrated in FIG. 2D , mold 220 is a convex mold used to form a textured molded film, although other curvatures are utilized in other implementations. The castable material or curable resin 212 is deposited in an unreacted or semi-reacted form, dispensed as a low-to-high viscosity (10 cP-1,000 cP) liquid onto substrate 210 or onto a mold (as described below). The castable material 212 can be a resin, i.e., a UV-curable resin, a UV-curable photoresist, or the like, that is cured using ultraviolet (UV) radiation to provide the molded film with a fixed geometry and high optical transparency. Deposition processes for dispensing the castable material or curable resin 212 can include, but are not limited to, micro-jet positive displacement systems, such as syringe pumps, pipetting, or the like.

[0054] 2B and 2C, mold 220 is brought into proximity with substrate 240, and castable material 212 is compressed between the mold and substrate, thereby forming a predetermined curvature that conforms to the surface of the castable material facing the mold. The shaped castable material 212, disposed between mold 220 and substrate 240, is then exposed to UV radiation to cure the castable material into the shape impress upon the castable material by the mold and substrate. UV curing can be carried out in times on the scale of, for example, tens of seconds, e.g., several minutes to less than a minute, e.g., 30 seconds, for various UV-curable materials.

[0055] After curing, the mold 220 is separated from the cast film to produce a laminated lens with a curved substrate.

[0056] 3A-3D are simplified cross-sectional views illustrating a process for fabricating a laminated lens using a master, according to one embodiment of the present invention. In this process, an intermediate submaster of the opposite nature to the master mold is created. As explained below, the substrate 310 with the molding film 314 illustrated in FIG. 3C can be considered an intermediate mold or submaster used to create a lens of the same nature as the mold 320 used as the master. In other words, starting with the mold 320, a process is provided in which a castable material 334, illustrated in FIG. 3D, is molded to provide a molding film by using a submaster that is a fraction of the thickness of the mold 320. For example, referring to FIG. 3D, the molding film 314 and anti-stick coating 316 can have a combined thickness of less than 1 mm, compared to the thickness of the mold 320, which typically has a thickness of more than 2 mm.

[0057] Referring to FIG. 3A , a substrate 310 is provided along with a mold 320. In some embodiments, a glass substrate is utilized as the substrate 310, although this is not required for the present invention. In other embodiments, other substrates with suitable mechanical rigidity, optical transparency, and the like are utilized as the substrate 310, including plastic substrates, polymer substrates, molded photoresist substrates, combinations thereof, or the like. While the substrate 310 is a planar substrate suitable for forming a molded film having at least one planar surface, curved substrates can be utilized in accordance with some embodiments of the present invention. The mold 320 is fabricated to have a predetermined curvature to fabricate a molded film with a matching predetermined curvature, i.e., a mold with a radius of curvature of R=1 m and a molded film with a radius of curvature of R=−1 m. In the embodiment illustrated in FIG. 3A , the mold 320 is a convex mold used to form a plano-concave molded film, although other curvatures are utilized in other implementations. Moldable material 312 is deposited, for example, dispensed as a liquid, on substrate 310. Moldable material 312 can be a resin, i.e., a UV-curable resin, a UV-curable photoresist, or the like, that is cured using ultraviolet (UV) radiation to provide a cast film with a fixed geometry and high optical transparency.

[0058] As shown in FIG. 3B , mold 320 is brought into close proximity with substrate 310, and castable material 312 is compressed between the mold and substrate, thereby forming the surface of the castable material facing the mold to a matching predetermined curvature. In the illustrated example, mold 320 has a convex curvature, thereby creating a concave curvature for the surface of castable material 312 facing mold 320. Because substrate 310 is planar in the embodiment illustrated in FIGS. 3A-3C , the surface of castable material 312 facing substrate 310 is planar. As will be apparent to one skilled in the art, shaping of the castable material is performed in a manner such that the surface of the castable material, after hardening, has a curvature appropriate for the optical effect (e.g., a predetermined focal length) desired for the laminated lens.

[0059] The shaped castable material 312, disposed between the mold 320 and the substrate 310, is exposed to UV radiation 330 to cure the castable material into the shape impress upon the castable material by the mold and substrate. UV curing can be carried out in times on the scale of, for example, tens of seconds, e.g., several minutes to less than a minute, e.g., 30 seconds, for various UV-curable materials.

[0060] Figure 3C illustrates the separation of mold 320 from casting film 314 once the castable material has hardened. Thus, using the process illustrated in Figures 3A-3C, a casting film is provided that is attached to, and supported by, a substrate.

[0061] FIG. 3D illustrates a cast film 314 that has been coated with an anti-adhesion coating 316, thereby forming a submaster. As an example, the anti-adhesion coating 316 can be fabricated using an inorganic layer, such as an oxide or nitride, e.g., silicon dioxide or silicon nitride, and deposited using, for example, an atmospheric pressure plasma-enhanced chemical vapor deposition (APPECVD) process. Additionally, the anti-adhesion coating 316 can be fabricated using a metal layer or other organic fluoropolymer or silane-based polymer material that is suitable as a release surface. Inorganic coating materials can include, but are not limited to, SiO2, SiC, Al2O3, Si3N4, TiN, Cr, Ag, Au, Cu, Ir, Pt, Pd, etc. Semiconductor-based processes, such as CVD or PVD processes, such as plasma-enhanced low-pressure CVD, atomic layer deposition, evaporation, sputtering, etc., can be used to deposit such anti-adhesion coatings. Coating methods such as spraying (atomization), inkjet, knife-edge coating, low-pressure, or atmospheric vapor coating can be used to coat fluoropolymer, siloxane (silicone), or other polymer-based coatings. Accordingly, embodiments of the present invention can utilize a wide variety of anti-adhesion materials, also referred to as release layer materials, including inorganic materials, including metals such as Au, Al, or the like, or dielectric materials such as SiO, AlO, TiN, or the like. Additionally, embodiments of the present invention can utilize chemical treatment processes, such as fluorinated surface release chemistries, using, for example, trichloro(1H,1H,2H,2H-perfluorooctyl)silane, or the like.

[0062] The thickness of the anti-adhesion coating 316 is thick enough to prevent pinholes and provide mold release, but thin enough not to affect the radius of curvature of the molded film 314, and can be on the order of a few nanometers, e.g., 1 nm, 2 nm, 3 nm, or the like, or can be tens of nanometers, e.g., 10 nm, 20 nm, 30 nm, or the like, or even hundreds of nanometers, e.g., 100 nm, 200 nm, 300 nm, or the like.

[0063] Coating the casting film 314 with the anti-stick coating 316 provides the master with a predetermined curvature and the ability to be used to cast additional casting films made using the same material as the casting film 314. As will be apparent to one skilled in the art, if the casting film 314 is placed in direct contact with the castable material 334, the castable material 334 will bond to the casting film 314 after UV curing, assuming they are made from the same material. Thus, using the anti-stick coating 316 allows the casting film 314 to be used as a master during the processing of multiple casting films (e.g., castable materials made from the casting film 334). Furthermore, in some embodiments, UV curing may result in shrinkage of the castable material. In this case, the presence of the anti-stick coating provides a hydrophobic surface that allows the castable material to flow more easily, which can improve the results obtained using the UV casting process. Furthermore, the use of the anti-stick material facilitates delamination of the cured casting film from the mold after curing. Although anti-stick coating 316 is discussed in connection with fabricating a master and Figure 3D, it should be understood that anti-stick coatings can be utilized on the molds described herein, such as mold 220 illustrated in Figure 2A and mold 320 illustrated in Figure 3A. Those skilled in the art will recognize many variations, modifications, and alternatives.

[0064] 3D, the casting film 314 and anti-stick coating 316 form a concave master that can be used to form a plano-convex casting film 334 supported by a substrate 340. Thus, in this embodiment, the casting film formed using the process illustrated in FIGS. 3A-3C can be coated and then utilized as a master to form additional lenses with complementary curvatures.

[0065] FIG. 4 is a simplified cross-sectional view of a laminated lens according to one embodiment of the present invention. As illustrated in FIG. 4, laminated lens 400 includes a cover plate 405 and a molded film 410. In some exemplary embodiments, the thickness of laminated lens 400, measured along the z-axis, is <1 mm, with the thickness of cover plate 405 being approximately 0.3 μm to 0.4 μm and the thickness of molded film 410 being approximately 300 μm to 500 μm at the thickest portion of the molded film. In addition to the refractive properties that result in the curvature of surface 411, nanofeatures can be imprinted on surface 411, for example, in region 412, as discussed more fully in connection with FIGS. 11A-11C .

[0066] FIG. 5 is a simplified plan view of a laminated lens covering elements of an eyepiece waveguide, according to one embodiment of the present invention. Referring to FIG. 5, the laminated lens includes region 510, which covers a combined pupil expander (CPE) (not shown), which typically implements the functions performed by an orthogonal pupil expander (OPE) and an exit pupil expander (EPE). Region 510 can be compared to portion 915 in FIG. 9D or portion 1212 or portion 1222 in FIG. 12. The laminated lens may or may not include region 505, which covers an internal coupling grating (ICG) 502.

[0067] 6A-6C are simplified cross-sectional views illustrating a process for fabricating a laminated lens with positive optical power according to some embodiments of the present invention. Referring to FIG. 6A, a substrate 610 is provided along with a mold 620. In some embodiments, a glass substrate is utilized as the substrate 610, although this is not required for the present invention. In other embodiments, other substrates with suitable mechanical rigidity, optical transparency, and the like are utilized as the substrate 610, including plastic substrates, polymer substrates, molded photoresist substrates, combinations thereof, or the like. While the substrate 610 is a planar substrate suitable for forming a cast film having at least one planar surface, curved substrates can be utilized according to some embodiments of the present invention. The mold 620 is fabricated to have a predetermined curvature to fabricate a cast film with a matching predetermined curvature, i.e., a mold with a radius of curvature of R=-1m and a cast film with a radius of curvature of R=1m. 6A, mold 620 is a concave mold used to form a plano-convex molded film, although other curvatures are utilized in other implementations. Moldable material 612 is deposited onto substrate 610, for example, dispensed as a liquid. Moldable material 612 can be a resin, i.e., a UV-curable resin, a UV-curable photoresist, or the like, that is cured using ultraviolet (UV) radiation to provide the molded film with a fixed geometry and high optical transparency.

[0068] As shown in FIG. 6B , a mold 620 is brought into close proximity with a substrate 610, and the castable material 612 is compressed between the mold and the substrate, thereby forming the surface of the castable material facing the mold into a matching predetermined curvature. In the illustrated example, the mold 620 has a concave curvature, thereby creating a convex curvature for the surface of the castable material 612 facing the mold 620. Because the substrate 610 is planar in the embodiment illustrated in FIGS. 6A-6C , the surface of the castable material 612 facing the substrate 610 is planar. As will be apparent to one skilled in the art, the shaping of the castable material is performed in a manner such that the surface of the castable material, after hardening, has a curvature appropriate for the optical effect (e.g., a predetermined focal length) desired for the laminated lens.

[0069] The shaped castable material 612, disposed between the mold 620 and the substrate 610, is exposed to UV radiation 630 to cure the castable material into the shape impress upon the castable material by the mold and substrate. UV curing can be carried out in times on the scale of, for example, tens of seconds, e.g., several minutes to less than a minute, e.g., 30 seconds, for various UV-curable materials.

[0070] Figure 6C illustrates the separation of mold 620 from cast film 214 once the moldable material has hardened. Thus, using the process illustrated in Figures 6A-6C, a cast film is provided that is attached to and supported by a substrate. The curvature of cast film 614 can be fabricated as needed for a particular application, for example, as an aspherical optical element, although this is not required and spherical surfaces can also be fabricated.

[0071] 7A-7C are simplified cross-sectional views illustrating a process for fabricating a laminated lens with positive optical power according to another embodiment of the present invention. Referring to FIG. 7A, a mold 710 is provided along with a substrate 720. In some embodiments, a glass substrate is utilized as the substrate 720, although this is not required for the present invention. In other embodiments, other substrates with suitable mechanical rigidity, optical transparency, and the like are also utilized as the substrate 720, including plastic substrates, polymer substrates, molded photoresist substrates, combinations thereof, or the like. While the substrate 720 is a planar substrate suitable for forming a molded film having at least one planar surface, curved substrates can be utilized according to some embodiments of the present invention.

[0072] Mold 710 is machined to have a predetermined curvature to machine a molded film with a matching predetermined curvature, i.e., a mold with a radius of curvature of R=-1m and a molded film with a radius of curvature of R=1m. In the embodiment illustrated in FIG. 7A, mold 710 is a concave mold used to form a plano-convex molded film, although other curvatures are utilized in other implementations. Moldable material 712 is deposited on mold 710, for example, dispensed as a liquid. Moldable material 712 can be a resin, i.e., a UV-curable resin, a UV-curable photoresist, or the like, that is cured using ultraviolet (UV) radiation to provide the molded film with a fixed geometry and high optical transparency.

[0073] As shown in FIG. 7B , substrate 720 is brought into proximity with mold 710, and castable material 712 is compressed between the substrate and mold, thereby forming the surface of the castable material facing the substrate into a planar surface with infinite curvature. In the illustrated example, mold 710 has a concave curvature, thereby creating a concave curvature for the surface of castable material 712 disposed within mold 710. Because substrate 720 is planar in the embodiment illustrated in FIGS. 7A-7C , the surface of castable material 712 facing substrate 710 is planar. As will be apparent to one skilled in the art, the shaping of the castable material is performed in a manner such that the surface of the castable material, after hardening, has a curvature appropriate for the optical effect (e.g., a predetermined focal length) desired for the laminated lens.

[0074] The shaped castable material 712, disposed between the mold 710 and the substrate 720, is exposed to UV radiation 730 to cure the castable material into the shape impress upon the castable material by the mold and substrate. UV curing can be carried out in times on the scale of, for example, tens of seconds, e.g., several minutes to less than a minute, e.g., 30 seconds, for various UV-curable materials.

[0075] Figure 7C illustrates the separation of mold 710 from casting film 714 once the castable material has hardened. Thus, using the process illustrated in Figures 7A-7C, a casting film is provided that is attached to, and supported by, a substrate.

[0076] FIG. 8 is a simplified perspective view of a system for forming multiple laminated lenses according to an embodiment of the present invention. As illustrated in FIG. 8, a sheet or web of cover plate material, from which the cover plate may be formed, is fed from right to left. A resin dispenser is positioned to dispense moldable material onto the sheet or web. The dispense volume and geometry can be selected as needed for a particular application. While top and bottom molds are utilized in the embodiment illustrated in FIG. 8, in some embodiments, only a top mold is utilized, with mechanical support applied to the bottom of the sheet or web. Using UV curing, with optional heating, the moldable material is formed into a mold film having the desired shape. After UV curing, the mold film can be separated from the sheet or web for assembly into a VOA.

[0077] 9A-9D are simplified cross-sectional views illustrating a process for fabricating optical elements according to one embodiment of the present invention. In the embodiment illustrated in FIGS. 9A-9D, rather than molding / casting a film deposited on a substrate, a cover glass utilized with an eyepiece waveguide is machined to include optical power. Referring to FIG. 9A, a first mold 910 and a second mold 920 are illustrated. In the embodiment illustrated in FIG. 9A, the first mold 910 is machined to provide a planar molding surface, and the second mold 920 is machined to have a predetermined curvature over a first portion of the molding surface and a planar molding surface over a second portion of the molding surface. Thus, the second mold 920 includes a first portion 922 having a finite curvature, e.g., an aspherical curvature, and a second portion 924 that is planar.

[0078] 9B, a moldable material 912 is deposited, for example, dispensed as a liquid, on the mold 910. The moldable material 912 can be a resin that is cured using UV radiation, i.e., a UV-curable resin, or the like.

[0079] 9C , the first mold 910 is brought into proximity with the second mold 920, and the castable material 912 is compressed between the first and second molds, thereby forming the surface of the castable material facing the molds into a matching predetermined surface curvature and planar characteristics, if necessary. In the illustrated example, the first portion 922 of the second mold 920 has a convex curvature, thereby creating a concave curvature for the surface of the castable material 912 facing the first portion 922 of the second mold 920. Because the first mold 910 and the second portion 924 of the second mold 920 are planar in the embodiment illustrated in FIGS. 9A-9D , the surfaces of the castable material 912 facing the first mold 910 and the second portion 924 of the second mold 920 are planar. As will be apparent to one skilled in the art, the shaping of the castable material is carried out in such a manner that the surface of the castable material, after hardening, has a curvature appropriate for the optical effect desired for the optical element (e.g., a predetermined focal length or flatness).

[0080] The shaped castable material 912, disposed between the first mold 910 and the second mold 920, is exposed to UV radiation 930 to cure the castable material into the shape impress upon the castable material by the mold. UV curing can be performed for a time period of, for example, about 30 seconds for various UV-curable materials.

[0081] As illustrated in FIG. 9D , separation of the first mold 910 from the second mold 920 once the castable material has hardened results in the release of the optical element 914 from the mold. Thus, using the process illustrated in FIGS. 9A-9D , optical elements having both flat and curved surfaces are produced. In some embodiments, the flat region 916 is utilized to provide a mechanical attachment region so that the optical element 914 can be mechanically coupled to an eyepiece waveguide, as illustrated in FIG. 12 . The curved region 915 is utilized to provide a refractive effect, as described herein. Referring to FIG. 5 , in some implementations, the flat region 916, which does not have optical refractive power, can be positioned so that light incident on the ICG 502 is not focused as it passes through the optical element 914. Thus, in addition to its use in mechanical attachment, the flat region 916 can be utilized to achieve optical effects as well.

[0082] The optical element 914 also includes a curved region 915, which can be utilized to diverge light rays in a plano-concave design as shown in FIG. 9D to create a virtual depth plane at a predetermined distance from the user, as discussed in connection with FIG. 1B . Thus, the curvature of the curved region 915 can be fabricated as needed for a particular application, e.g., as an aspheric optical element, although this is not required; a sphere can also be fabricated. Generally, the thickness of the optical element 914, measured along the optical axis, which is aligned with the z-axis in FIG. 9A , in this example of a plano-concave curved region 915, ranges from a few microns over a base thickness of 300 μm at the center of the curved region 915 to approximately 300 μm at its maximum lateral extent, which is approximately 600 μm, including the base thickness, as measured in the xy plane.

[0083] As an example, some eyepiece waveguides include a waveguide layer fabricated using a polymer material. This type of eyepiece waveguide is suitable for use with a cover layer fabricated using a polymer material and directly molded / cast to form an optical element that can provide both the cover layer and the lens function. Thus, utilizing both a polymer eyepiece waveguide and a polymer optical element, a compact and mechanically rigid sandwich structure (e.g., with consistent thermal properties) can be fabricated, with the waveguide layer providing mechanical support to the optical element, which does not need to be mechanically strong enough to support itself independently of the waveguide layer. The gap between the surface of the eyepiece waveguide facing the optical element and the optical element can be about 100 μm or less.

[0084] Furthermore, because different castable materials characterized by different refractive indices can be utilized in conjunction with the processes described herein, a single mold can be utilized to produce laminated lenses with different focal lengths. The inventors have determined that by utilizing castable materials with refractive indices that vary from approximately 1.5 to 1.75, focal lengths ranging from + / - 1 m to 0.690 m can be produced for an exemplary radius of curvature of 0.515 m.

[0085] FIG. 10 is a simplified cross-sectional view illustrating a mold with an anti-stick coating, according to one embodiment of the present invention. As illustrated in FIG. 10, mold 920 is coated with anti-stick coating 1012 in an inverted position. As discussed in connection with FIG. 3D, various materials can be utilized, either alone or in combination, to form anti-stick coating 1012. For example, anti-stick coating 1012 can include SiO, SiN, TiN, AlO, Al, Ag, Ni, combinations thereof, or fluoro- or siloxane-based polymers, or the like, can be used. As will be apparent to one skilled in the art, the anti-stick coating illustrated in FIG. 10 is also suitable for use with anti-stick coating 316 in FIG. 3D.

[0086] In some embodiments, nanofeatures, including those formed using nanometer-scale imprinting techniques, can be formed on the surfaces of the laminated lenses or optical elements described herein to provide additional optical functionality (i.e., diffractive optical effects) in addition to the refractive properties associated with the curvature of the material surface. As an example, in addition to the refraction associated with a plano-concave or plano-convex lens profile, an anti-reflection effect can be created using nanofeatures formed on the material surface. In addition to the anti-reflection effect, other diffractive optical effects can also be achieved. Those skilled in the art will recognize many variations, modifications, and alternatives.

[0087] 11A is a simplified cross-sectional view illustrating an optical element with nanofeatures fabricated on the planar surface of the optical element, according to one embodiment of the present invention. As illustrated in FIG. 11A, nanofeatures 1116, e.g., a diffraction grating, metasurface, or the like, can be formed on the planar surface 1114 of the optical element 1110. Thus, as light, as illustrated by light beam 1120, is incident on the optical element 1110, the light is defocused (i.e., a refractive effect) as it passes through the concave surface 1112 and experiences reduced reflection at the planar surface 1114 created by the presence of the nanofeatures 1116 (i.e., an anti-reflection effect created by a diffraction effect). Thus, in addition to refractive focusing as a result of the curvature characterized by the concave surface 1112, the light also experiences a diffraction effect as it passes through the planar surface 1114, including the nanofeatures 1116.

[0088] Nanofeatures can be birefringent or non-birefringent, depending on the particular design of the nanofeature being utilized. As an example, nanostructures that are non-birefringent and provide reduced reflection at the lens interface can be fabricated using pillars arranged at a pitch of 100 nm to 140 nm and a height of approximately 100 nm. Alternatively, holes can be formed in the optical element with a similar pitch and depth.

[0089] 9A-9D, embodiments of the present invention utilize a mold that includes both surface curvature and nanopatterning to form curved surfaces, such as illustrated by curved region 915 of optical element 914 (corresponding to concave surface 1112 in FIG. 11A) and nanofeatures, such as illustrated by nanofeature 1116 in FIG. 11A, respectively. Thus, while first portion 922 of second mold 920 illustrated in FIG. 9A is illustrated as having only convex curvature, it should be understood that first portion 922 can also include nanopatterning, which may be capable of forming, for example, the nanofeatures illustrated in FIGS. 11A-11C. Thus, in the single fabrication process illustrated in FIGS. 9A-9D, optical elements that produce both refractive and diffractive optical effects can be fabricated in a single process flow. This can also be applied to a curved surface molded onto a substrate (e.g., glass or plastic) as shown in Figures 2C, 3C, 3D, 4, 6C, 7C, 13A, 13B, 13C, 13D, 14A, 14B, 14D, 14E, and 14F. As an example, a cover plate with both optical power and anti-reflective properties can be fabricated in a single process flow without the need for subsequent coatings to achieve the anti-reflective properties.

[0090] FIG. 11B is a simplified cross-sectional view illustrating an optical element with nanofeatures fabricated on a curved surface of the optical element, according to an embodiment of the present invention. In addition to forming nanofeatures on planar surfaces, nanofeatures can be formed on curved surfaces, according to embodiments of the present invention. As illustrated in FIG. 11B, nanofeatures 1134, e.g., metasurfaces, can be formed on the curved surface of the optical element. Thus, as light, as illustrated by light beam 1140, is incident on optical element 1130, the light is both defocused as it passes through concave surface 1132 (i.e., a refractive effect) and suffers reduced reflection at concave surface 1132, which is created by the presence of nanofeatures 1134 (i.e., an anti-reflection effect, which is created by a diffraction effect). Thus, both the refractive and diffractive effects can be achieved by forming nanofeatures on one surface of optical element 1130.

[0091] 11C is a simplified cross-sectional view illustrating an optical element with nanofeatures fabricated on both the planar and curved surfaces of the optical element, according to an embodiment of the present invention. As an extension of the design illustrated in FIGS. 11A and 11B, nanofeatures 1156 and 1158, e.g., metasurfaces, can be formed on both the curved and planar surfaces of the optical element. Thus, as light, as illustrated by light beam 1160, is incident on optical element 1150, the light is both defocused as it passes through concave surface 1152 (i.e., a refractive effect) and experiences reduced reflection at concave surface 1152, which is created by the presence of nanofeatures 1156 (i.e., an anti-reflection effect, created by a diffraction effect). Furthermore, the light can experience additional reductions in reflection as a result of the same or additional diffraction effects, e.g., nanofeatures 1158 fabricated on planar surface 1154 of optical element 1150.

[0092] Figure 12 is a simplified cross-sectional view illustrating a VOA including an eyepiece waveguide and a set of optical elements, according to one embodiment of the present invention. In Figure 12, VOA 1200 includes eyepiece waveguide 1230, a pair of optical elements, world-side optical element 1220, and user-side optical element 1210. As described in connection with Figure 1B, the optical element provides both a mechanical function (i.e., protecting the waveguide layer) and an optical function (i.e., focusing or defocusing incident light), so the optical element can be referred to as a cover plate with optical power.

[0093] As discussed in connection with FIG. 1B , the eyepiece waveguide 1200 can be designed to generate a virtual image that appears to occur at infinite distance. To allow the user to perceive the virtual image as occurring at a non-infinite depth plane, a first optical element 1210 having negative optical power in portion 1212 is utilized to diverge the light rays generated by the eyepiece waveguide 1230, causing the virtual image generated by the eyepiece waveguide 1230 to appear to occur from the depth plane at a predetermined distance from the user (e.g., 1 meter or 0.3 meters). In some implementations, the first optical element 1210 is referred to as an inner cover plate or a user-side cover plate because it is positioned on the side of the eyepiece waveguide that faces the user. In addition to the portion 1212 having negative optical power, the first optical element 1210 also includes a planar portion 1214. In an exemplary implementation, portion 1214 may be outside the user's viewing area, and although the lateral dimensions of portions 1212 and 1214 are illustrated similarly to FIG. 12 , this is not required by the present invention, and portion 1214 may have a lateral size that is a percentage of the lateral size of portion 1212. Thus, portion 1214 is provided to allow mechanical mounting of first optical element 1210 to eyepiece waveguide 1230 without affecting the clear field associated with the user's viewing area. Additionally, depending on the optical design of the eyepiece waveguide, the ICG may be positioned on eyepiece waveguide 1230 so as to laterally overlap portion 1214, allowing light to be incident from the projector onto the ICG without being focused by curved surfaces within portion 1212. 5, portion 1214 can laterally overlap ICG 502 of eyepiece waveguide 1230, and portion 1212 can laterally overlap CPE of eyepiece waveguide 1230. While portion 1214 is illustrated as planar in this design, this is not required by the present invention, and portion 1214 may include indents and / or protrusions, or the like, used for mechanical alignment. Those skilled in the art will recognize many variations, modifications, and alternatives.

[0094] The second optical element 1220 is utilized to compensate for the optical power of the first optical element 1210 so that light incident on the VOA 1200 from the world side of the VOA can emerge at specific distances associated with various objects in the world. Thus, as illustrated in FIG. 12 , the second optical element 1220 has a positive optical power that is equal to and opposite to the negative optical power of the first optical element 1210. In some implementations, the second optical element 1220 is referred to as an outer cover plate or world-side cover plate because it is positioned on the side of the eyepiece waveguide that faces the world. As will be apparent to one skilled in the art, the ability to position the first optical element 1210 and the second optical element 1220 closer together allows for improvements in the ability of these cover plates with optical power to form a compensation pair.

[0095] In addition to portion 1222 having positive optical power, second optical element 1220 also includes planar portion 1224. In a typical implementation, portion 1224 may be outside the user's viewing area, and although the lateral dimensions of portions 1222 and 1224 are illustrated similarly to FIG. 12 , this is not required by the present invention, and portion 1224 may have a lateral size that is a percentage of the lateral size of portion 1222. Thus, portion 1224 is provided to allow mechanical mounting of second optical element 1220 to eyepiece waveguide 1230 without affecting the clear field associated with the user's viewing area. While portion 1224 is illustrated as planar in this design, this is not required by the present invention, and portion 1224 may include indents and / or protrusions, or the like, used for mechanical alignment. Those skilled in the art will recognize many variations, modifications, and alternatives.

[0096] Referring again to FIG. 12, the dimensions of various elements of VOA 1200 are illustrated. As illustrated in FIG. 12, the spacing D between the optical elements and the eyepiece waveguide is on the order of tens of microns, e.g., about 100 μm to about 1 μm, thereby providing a very small gap while still providing an air gap between the eyepiece waveguide and the cover plate with optical power. As will be apparent to those skilled in the art, preserving the air gap allows light to propagate by total internal reflection (TIR) ​​inside the waveguide layer. Various techniques can be utilized to maintain the spacing D between the optical elements and the eyepiece waveguide, including adhesives, microspheres, or other suitable spacers, adhesive tape with a predetermined thickness, or the like. Utilizing a cover plate with optical power that may have a thickness (measured along the vertical dimension) of less than 1 mm, e.g., about 600 μm, and an eyepiece waveguide with a thickness of about 2 mm, the total thickness of the VOA can be about 3 mm, which is about half the thickness of a VOA fabricated using conventional designs.

[0097] Figure 13A is a simplified cross-sectional view illustrating a biconvex laminate lens according to one embodiment of the present invention. As illustrated in Figure 13A, a cover plate 1310 provides mechanical support for a molded film 1312 on a first side of the cover plate and a molded film 1314 on the opposite side of the cover plate. Thus, in addition to plano-concave laminate lenses as illustrated in Figure 3C, embodiments of the present invention can be utilized to fabricate biconvex laminate lenses. Note that in addition to biconvex laminate lenses, biconcave laminate lenses can be provided by forming a concave molded film on the cover plate 1310.

[0098] FIG. 13B is a simplified cross-sectional view illustrating a convex meniscus lens according to one embodiment of the present invention. As illustrated in FIG. 13B, a cover plate 1320 provides mechanical support for a molded film 1322 on a first side of the cover plate and a molded film 1324 covering the molded film 1322. By utilizing two different molded films with different refractive indices, a convex meniscus lens is formed in a stacked lens format. The materials and thicknesses of the molded films 1322 and 1324 can be selected depending on the particular application. Note that in addition to a convex meniscus lens in a stacked lens format, a concave meniscus lens can be provided by forming a concave molded film on the cover plate 1320.

[0099] FIG. 13C is a simplified cross-sectional view illustrating an achromatic stack lens according to an embodiment of the present invention. As illustrated in FIG. 13C, a cover plate 1340 provides mechanical support for a molded film 1342 on a first side of the cover plate and a molded film 1344 covering the molded film 1342. In this embodiment, the molded film 1342 is a refractive material with a low refractive index, and the molded film 1344 is a refractive material with a high refractive index (compared to the molded film 1342), thereby forming an achromatic lens. Thus, by utilizing two different molded films with different refractive indices, an achromatic lens is formed in a stacked lens format. The materials and thicknesses of the molded films 1342 and 1344 can be selected depending on the particular application. Note that in addition to a convex achromatic lens in a stacked lens format, a concave achromatic lens can be provided by forming a concave molded film on the cover plate 1340.

[0100] FIG. 13D is a simplified cross-sectional view illustrating an apochromatic laminate lens according to one embodiment of the present invention. As illustrated in FIG. 13D, cover plate 1350 provides mechanical support for molded film 1352 on a first side of the cover plate, molded film 1354 covering molded film 1352, and molded film 1356 covering molded film 1354. In this embodiment, molded film 1354 is a refractive material with a lower index of refraction compared to molded films 1352 and 1356, thereby forming a triple layer. Thus, by utilizing three different molded films, with a molded film with a higher index of refraction on either side of a molded film with a lower index of refraction, an apochromatic lens is formed in a laminated lens format. The materials and thicknesses of molded films 1352, 1354, and 1356 can be selected depending on the particular application. It should be noted that in addition to convex apochromatic lenses in a stacked lens format, concave apochromatic lenses can be provided by forming a concave molded film on the cover plate 1350 .

[0101] FIG. 14A is a simplified perspective view illustrating a first mold according to an embodiment of the present invention. As illustrated in FIG. 14A, the first mold 1410 is a multi-lens mold, suitable for use in fabricating multiple lenses in parallel or simultaneously. It should be understood that other molds described herein may be implemented as multi-lens molds, and the illustration showing fabrication of a single lens using a single-lens mold is provided merely for ease of illustration and is not intended to limit embodiments of the present invention. In other embodiments, the first mold 1410 is implemented as a single-lens mold. Those skilled in the art will recognize many variations, modifications, and alternatives. As illustrated in FIG. 14A, the first mold 1410 includes a plurality of planar-concave recesses 1412 distributed across the surface of the first mold 1410. Although planar-concave recesses 1412 are illustrated in FIG. 14A, embodiments of the present invention are not limited to this particular optical format, and convex features can be formed on the top surface of the first mold 1410 in other embodiments. Additionally, combinations of one or more planar concave recesses and one or more convex features can be implemented using first mold 1410 as needed for a particular application.

[0102] A variety of materials, including glass, plastic, metal, or the like, can be utilized in the first mold 1410. Any suitable material, including combinations of materials, characterized by mechanical rigidity and resistance to degradation by UV radiation can be utilized.

[0103] Figure 14B is a simplified perspective view illustrating a first mold according to one embodiment of the present invention. The first mold 1420 illustrated in Figure 14B is formed by a process similar to that discussed in connection with Figures 2A-2C, but utilizing a concave first mold 1410 rather than the convex mold discussed in connection with Figures 2A-2C. Thus, the first mold 1420 is formed using a castable material or curable resin that is deposited in an unreacted or semi-reacted form into the first mold 1410, formed into the desired lens shape, and brought into proximity with a substrate (not shown) to be UV-cured to form the first mold 1420.

[0104] The first mold 1420 can be utilized as a plano-convex lens as described herein, for example, in a viewing optics assembly, or can be utilized as a flexible mold suitable for use as a mold during the molding of additional molds, this latter use being illustrated in connection with FIG.

[0105] As illustrated in Figure 14B, the first molded product 1420 has plano-convex features 1422 that substantially match the plano-concave recesses 1412 shown in Figure 14A. As discussed above, mechanical and volumetric material shrinkage of the molded material may occur during UV curing, but this mechanical shrinkage is predictable and can be accounted for during the lens design process, with the curvature of the plano-convex features 1422 being modified relative to the curvature of the plano-concave recesses 1412 as a result of the mechanical and volumetric material shrinkage. Thus, the plano-convex features 1422 will feature the desired curvature after molding and mechanical and volumetric shrinkage has occurred.

[0106] FIG. 14C is a simplified side view of a portion of a molded article before and after a release layer coating process, according to an embodiment of the present invention. The release layer coating process illustrated in FIG. 14C is suitable for use in forming an anti-adhesion coating, as described more fully throughout this specification. Referring to FIG. 14C, a molded article 1430 is provided, and a deposition process is utilized to form an anti-adhesion coating 1432, also referred to as a release layer coating, on the molded article 1430. Referring to FIG. 14B, an anti-adhesion coating is deposited on a first molded article 1420 to form a plurality of convex features coated with the anti-adhesion coating, which can allow subsequent materials to be released after use of the coated molded article as a mold.

[0107] The anti-adsorption coating 1432 can be fabricated using an inorganic layer such as an oxide or nitride, e.g., silicon dioxide, silicon nitride, or other dielectric, and can be deposited using, for example, an atmospheric pressure plasma-enhanced chemical vapor deposition (APPECVD) process. Additionally, the anti-adsorption coating 1432 can be fabricated using a metal layer or other organic fluoropolymer or silane-based polymer material suitable as a release surface. Organic treatment processes can be used, including fluorinated surface release chemistry using, for example, trichloro(1H,1H,2H,2H-perfluorooctyl)silane or equivalents. Inorganic coating materials can include, but are not limited to, SiO2, SiC, Al2O3, Si3N4, TiN, Cr, Ag, Au, Al, Cu, Ir, Pt, Pd, etc. Semiconductor-based processes, such as CVD or PVD processes, such as plasma-enhanced low-pressure CVD, atomic layer deposition, physical vapor deposition, evaporation, sputtering, etc., can be used to deposit such anti-adsorption coatings. Coating methods such as spray (atomization), ink jet, knife edge coating, low pressure, or atmospheric vapor coating can be used to coat fluoropolymer, siloxane (silicone), or other polymer-based coatings.

[0108] The thickness of the anti-adhesion coating 1432 is thick enough to prevent pinholes and provide mold release, but thin enough not to affect the radius of curvature of the resulting molded film, and can be on the order of a few nanometers, e.g., 1 nm, 2 nm, 3 nm, or the like, or can be tens of nanometers, e.g., 10 nm, 20 nm, 30 nm, or the like, or even hundreds of nanometers, e.g., 100 nm, 200 nm, 300 nm, or the like.

[0109] Figure 14D is a perspective view illustrating a coated first molding according to an embodiment of the present invention. Accordingly, the materials and processes discussed in connection with Figure 14C have been used to coat first molding 1420, resulting in the fabrication of coated first molding 1440. Coated first molding 1440 can be utilized as a mold, e.g., a flexible mold, and can be referred to as a first daughter mold because the mold features are based on the mold features present on first molding 1410. As illustrated in Figure 14D, coated first molding 1440 has plano-convex features 1442 that substantially match plano-convex features 1422 shown in Figure 14B and is coated with an anti-stick or release layer coating.

[0110] Figure 14E is a simplified perspective view illustrating a second molded article according to one embodiment of the present invention. The second molded article 1450 is processed in a manner similar to that discussed with respect to the first molded article 1420 illustrated in Figure 14B. Accordingly, the second molded article 1450 illustrated in Figure 14E is formed using a castable material or curable resin that is deposited in an unreacted or semi-reacted form on a substrate (not shown), forms the desired lens shape, and is then placed in close proximity to the coated first molded article 1440 for UV curing in a manner similar to that illustrated in Figures 2A-2C to form the second molded article 1450. The presence of an anti-stick coating on the coated first molded article 1440 allows the second molded article 1450 to be removed from the coated first molded article 1440 after processing.

[0111] The second mold 1450 can be utilized as a plano-concave lens as described herein, for example, in a viewing optics assembly, or can be utilized as a flexible mold suitable for use as a mold during the molding of additional molded objects, this latter use being illustrated in connection with FIG.

[0112] As discussed above in connection with the curvature of the plano-convex feature 1422, the second molded product 1450 has a plano-concave recess 1452 that substantially matches the plano-convex feature 1442 shown in FIG. 14D. As discussed above, mechanical and volumetric material shrinkage of the molded material may occur during UV curing, but this mechanical shrinkage is predictable and can be accounted for during the lens design process, with the curvature of the plano-concave recess 1452 being modified relative to the curvature of the plano-convex feature 1442 as a result of the mechanical and volumetric material shrinkage. Thus, the plano-concave recess 1452 will feature the desired curvature after molding and mechanical and volumetric shrinkage has occurred.

[0113] 14B and 14E, two sets of complementary molded articles are provided in accordance with an embodiment of the present invention, each having optical elements that can be used as positive or negative lenses. The surface features associated with the surfaces of the molded articles can be controlled to provide spherical or aspherical lenses of a predetermined curvature. Furthermore, each of these complementary molded articles can be utilized to fabricate an additive mold, as discussed in connection with FIG. 14D above or FIG. 14F below.

[0114] Figure 14F is a perspective view illustrating a coated second molding according to an embodiment of the present invention. Referring to Figure 14F, the materials and processes discussed in connection with Figure 14C are used to coat second molding 1450, resulting in the fabrication of coated second molding 1460. Coated second molding 1460 can be utilized as a mold, e.g., a flexible mold, and can be referred to as a second daughter mold because the mold features are based on the mold features present on second molding 1450. As illustrated in Figure 14F, coated second molding 1460 has plano-concave features 1462 that substantially match plano-concave features 1452 shown in Figure 14E and is coated with an anti-stick or release layer coating.

[0115] 14D and 14F, two complementary molds, i.e., coated molded articles, are provided according to an embodiment of the present invention, having mold features that can be used during the fabrication of negative or positive lenses, respectively. The surface features associated with the mold surfaces can be controlled to provide the mold with a spherical or aspherical lens of a predetermined curvature. Given the mechanical and volumetric material shrinkage associated with the fabrication of the coated first molded article 1430 and the coated second molded article 1460, two complementary molds of opposite curvature features can be utilized during the fabrication of the lens, effectively replicating the surface features characteristic of the first mold 1410, thereby extending the useful life of the first mold 1410.

[0116] It is also understood that the examples and embodiments described herein are for illustrative purposes only, and that various modifications or changes in light thereof will be suggested to those skilled in the art and are to be included within the spirit and scope of the present application and the appended claims.

Claims

1. An eyepiece waveguide, comprising: a set of waveguide layers having a world side and a user side; a first cover plate having a first optical power and positioned adjacent the world side of the set of waveguide layers; a second cover plate having a second optical power and positioned adjacent the user side of the set of waveguide layers; and An eyepiece waveguide comprising:

2. The eyepiece waveguide of claim 1 , wherein the set of waveguide layers comprises three waveguide layers, each of the three waveguide layers being associated with a red, green, or blue wavelength.

3. 2. The eyepiece waveguide of claim 1, wherein the first optical power is positive and the second optical power is negative.

4. 4. The eyepiece waveguide of claim 3, wherein the absolute values ​​of the first optical power and the second optical power are equal.

5. The eyepiece waveguide of claim 1 , wherein at least one of the first cover plate or the second cover plate comprises nanofeatures.

6. The eyepiece waveguide of claim 5 , wherein the nano-features comprise anti-reflective structures.

7. The eyepiece waveguide of claim 6 , wherein the anti-reflection structure is disposed on a planar surface of the first cover plate or the second cover plate.

8. The eyepiece waveguide of claim 1 , wherein the first optical power is associated with an aperture, and the first cover plate comprises a planar area adjacent the aperture.

9. 9. The eyepiece waveguide of claim 8, wherein the second optical power is associated with the aperture, and the second cover plate comprises the planar area adjacent the aperture.

10. 2. The eyepiece waveguide of claim 1, wherein the first cover plate is separated from the world side of the set of waveguide layers by a distance of 1 μm to 1 mm, and the second cover plate is separated from the user side of the set of waveguide layers by a distance of 1 μm to 1 mm.

11. 2. The eyepiece waveguide of claim 1, wherein the first cover plate has a maximum thickness of less than 1 mm and the second cover plate has a maximum thickness of less than 1 mm.

12. 12. The eyepiece waveguide of claim 11, wherein the first cover plate comprises a first substrate and a first molded film bonded to the first substrate and characterized by a minimum thickness of 5 nm to 600 nm, and the second cover plate comprises a second substrate and a second molded film bonded to the second substrate and characterized by a minimum thickness of 5 nm to 600 nm.

13. 1. A method of fabricating an optical element, the method comprising: Providing a substrate; forming a moldable material bonded to the substrate; casting the castable material using a mold; hardening the castable material; and removing the mold; A method comprising:

14. The method of claim 13 , wherein the substrate comprises a cover glass.

15. The method of claim 14 , wherein the cover glass is planar.

16. The method of claim 13 , wherein the substrate comprises a planar polymer structure.

17. The method of claim 13 , wherein the moldable material comprises a UV-curable resin.

18. The method of claim 13 , wherein the mold comprises an anti-stick coating.

19. 20. The method of claim 18, wherein the anti-adsorption coating is hydrophobic.

20. 20. The method of claim 18, wherein the anti-adhesion coating comprises silicon oxide or silicon nitride.

21. The method of claim 13 , wherein casting the moldable material comprises forming nanofeatures in the moldable material.

22. 22. The method of claim 21, wherein the nanofeatures are diffractive features that reduce reflections at interfaces of the moldable material.

23. 1. A method of fabricating an optical element, the method comprising: providing a mold set having a mold plate; placing a moldable material between said mold plates; joining the mold plates; curing the moldable material to form the optical element; removing the optical element from the mold set; A method comprising:

24. 24. The method of claim 23, wherein the optical element is characterized by negative optical power.

25. 24. The method of claim 23, wherein the optical element is characterized by a positive optical power.

26. The method of claim 23 , wherein one of the mold plates is characterized by a planar surface.

27. 24. The method of claim 23, wherein the moldable material comprises a UV curable resin.

28. The method of claim 23 , wherein at least one of the mold plates comprises nanofeatures.

29. 24. The method of claim 23, wherein the optical element comprises a planar region and an aperture adjacent the planar region and characterized by optical power.

30. 24. The method of claim 23, wherein the mold comprises an anti-stick coating.

31. 31. The method of claim 30, wherein the anti-adsorption coating is hydrophobic.

32. 31. The method of claim 30, wherein the anti-adhesion coating comprises silicon oxide or silicon nitride.

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