Patent Application
20250199232
A waveguide-based optical combiner (“waveguide combiner”) often is used in augmented reality (AR)-based near-eye displays for providing a view of the real world overlayed with static imagery or video (recorded or rendered). Typically, such optical combiners employ an input coupler (IC) to receive display light, an optional exit pupil expander (EPE) to increase the size of the display exit pupil, and an output coupler (OC) to direct the resulting display light toward a user's eye. Conventional waveguide combiners typically implement a monolithic plastic substrate implementing an IC, EPE, and OC using the same base material.
Large-scale production of diffractive waveguides often relies on the use of nanoparticle-infused nano imprint lithography (NIL) resin. For example, in an ultraviolet (UV)-NIL process, diffractive optical elements are formed by applying a liquid NIL resin onto a substrate, which is then patterned and imprinted using a stamp, followed by UV curing. Substrates with high refractive indices (RI) may be associated with expanded field-of-view (FOV) and improved image quality. It typically is advantageous for the NIL resins to match the refractive index of the substrate to prevent Fresnel reflections at the interface between the resin and glass. Glass substrates may possess refractive indices exceeding 1.8. While many suitable NIL resins with high refractive indices, such as n>1.8, may include titanium dioxide nanoparticles and a polymeric binder, titanium dioxide is highly photoactive. Consequently, high RI NIL materials containing titanium dioxide nanoparticles exhibit poor light stability, particularly towards UV. Exposure to short-wavelength light such as UV and blue light may lead to undesirable effects such as transmission loss, changes in spectral transmission, increased haze, alterations in refractive index, and/or modifications in film thickness, to name a few. Many of these factors may adversely impact the functionality of the waveguide.
The present disclosure may be better understood, and its numerous features and advantages made apparent to those skilled in the art, by referencing the accompanying drawings. The use of the same reference symbols in different drawings indicates similar or identical items.
The disclosed systems and methods of utilizing core-shell nanoparticle-based NIL materials in diffractive structures of a waveguide further includes incorporating a polymer resin containing core-shell nanoparticles to withstand light-induced aging. This light may encompass one or both of environmental lighting (e.g., solar radiation or artificially-generated external lighting) or emitted light from a light source such as a light engine. The nanoparticles in NIL materials may include, but not be limited to, a metal core, for instance, titanium dioxide, along with ligands that facilitate their solubility and stability. In certain instances, the metal core may be doped with another metal such as aluminum. In an embodiment, a thin layer of a metal, such as zirconium dioxide, may be disposed as a shell overlapping and/or covering the metal core, thus influencing the properties of the nanoparticle. The use of core-shell nanoparticles may be applicable to various combinations of metal-core and metal-shell embodiments. The core provides specific optical properties, while the shell adds additional functionality and maintains stability of the nanoparticle.
A waveguide component of AR devices, such as smart glasses, headsets, and smartphone applications utilize the device's camera and screen to deliver augmented experiences. These devices find applications in fields including gaming, education, navigation, and various industries for tasks such as remote assistance, training, and visualization to name a few. The layers, structures, and materials constituting optical components like the IC, EPE, and OC may experience degradation when exposed to high-intensity light. This degradation often arises from phenomena such as photochemical reactions, thermal effects, and alterations in material properties induced by photon absorption. For instance, the IC, tasked with coupling light into the waveguide, may undergo changes in its optical characteristics due to prolonged exposure to intense light. Similarly, the EPE, designed to expand the light beam, and the OC, responsible for extracting light from the waveguide, may encounter issues related to thermal stress and optical degradation under intense illumination.
The nanoparticle-infused NIL material layer 102 can serve one or more purposes. For example, the nanoparticle-infused NIL material layer 102 may act as a barrier against photochemical reactions, enhance thermal stability, modify the optical properties of the surface, and the like. The nanoparticles, integrated into the coating, may contribute to the durability of the optical components by absorbing and/or dispersing incident light, thereby reducing the impact of photon-induced processes. This NIL layer strategy, with its nanoparticle characteristics and nanoimprint lithography application, serves as a solution to mitigate the detrimental effects of light exposure, to facilitate the longevity and performance of optical elements in various applications. Some of these nanoparticles are described in detail below.
Turning now to
The stabilization and enhanced solubility of nanoparticles by the ligands 204, as described in
Furthermore, the ligands 204 contribute to facilitate the solubility of nanoparticles in the surrounding medium. The chemical nature of the ligands 204 and their interactions with the medium influence the dispersion behavior of nanoparticles. Ligands 204 may alter the surface properties of nanoparticles, making them more compatible with the surrounding medium, which is exploited in the context of the NIL polymer resin layer. This enhanced solubility facilitates the dispersion of nanoparticles in the material. The ligands function as molecular stabilizers by creating a protective layer around the nanoparticles, preventing undesirable interactions that could compromise their stability. The chemical nature of the ligands 204 and their attachment to the metal core 202 contribute to the solubility enhancement of nanoparticles and their dispersion in the nanoparticle-infused NIL material layer 102 of the waveguide.
In an embodiment, when employing core-shell nanoparticles, featuring for example, a titanium-dioxide core, encased by a thin layer of zirconium dioxide along with a plurality of ligands, extending therefrom, for solubilization and stabilization, diffractive waveguides may exhibit enhanced light stability. This translates to the preservation, for example, during and post light exposure. Notably, these improvements may manifest as reduced color-shifting, diminished transmission loss, mitigated haze increase, limited refractive index alterations, and/or controlled film thickness adjustments, all of which are factors that may otherwise compromise waveguide performance.
In some embodiments, each nanoparticle of the plurality of nanoparticles has a size of about 50 nanometers (nm) to about 700 nm. In some embodiments, each nanoparticle of the plurality of nanoparticles having a size of about 2 nanometers (nm) to about 50 nm. In some embodiments, the plurality of nanoparticles comprising a metal core composed of a first metal material and plurality of ligands disposed on at least a portion of the metal core.
Referring now to
In an example CVD process, the substrate, potentially the surface of the waveguide, is prepared for deposition. The precursor chemicals for the polymer resin and core-shell nanoparticles are introduced into the reaction chamber, and the deposition takes place in a controlled environment. During the deposition, the precursor molecules undergo chemical reactions on the substrate's surface. The polymer resin is formed as a thin film, and the core-shell nanoparticles become integrated into this growing film. The controlled reaction conditions, such as temperature and pressure, ensure the precise formation of the desired coating. The core-shell nanoparticles, with their metal core and ligand shell, are incorporated into the polymer matrix during the deposition process. The uniformity and thickness of the coating are regulated by the deposition parameters and may be monitored in real-time. After the deposition is complete, the coated substrate may undergo additional processing steps, such as curing or annealing, to enhance the stability and optical properties of the coating.
In another example, the implementation of nanoparticles in a NIL layer involves nanoparticles chosen based on specific properties aligned with the coating's desired characteristics, considering factors like optical, thermal, or mechanical performance. These nanoparticles undergo synthesis through precise methods, ensuring controlled size, shape, and composition. The coating material, typically a polymer or substance for nanoimprint lithography, is then prepared. The synthesized nanoparticles are uniformly dispersed within this material, utilizing techniques such as ultrasonication or mechanical mixing for even distribution. Surface treatments or functionalization may be applied to stabilize the dispersion, preventing nanoparticle agglomeration, and to facilitate stability. Integration into the nanoimprint lithography process follows, involving the application of the nanoparticle-infused coating onto the substrate through methods like spin coating or dip coating. Nanoimprint lithography is then employed to imprint nanoscale patterns onto the coated material using a template. Subsequent curing or solidification fixes the nanoparticle-infused NIL layer onto the substrate, ensuring stability and integrity. The final step involves thorough characterization to verify the desired nanoparticle distribution and properties. The process, from nanoparticle selection to nanoimprint lithography optimization, is conducted to tailor the coating for one or both sides of the waveguide. This implementation enhances the waveguide's durability and performance under optical conditions through the integration of nanoparticles into the nanoimprint lithography coating.
At block 415, one or more other NIL processes are employed to form various optical features in, at, and/or above the NIL material layer 412, resulting in a waveguide workpiece 414. Such NIL processes may include, for example, a step-and-flash imprint lithography technique. In this process, a template or mold, containing the desired nanoscale patterns for the optical features, is brought into contact with the NIL material layer 412. The template is often a transparent material with relief patterns on its surface corresponding to the optical structures required in the waveguide. The contact is carefully controlled to ensure proper alignment and uniformity. Upon contact, the NIL material layer 412 undergoes deformation and replicates the nanoscale patterns from the template. This step is often referred to as the “imprint” step. UV-light in this step cures the material and the hardened material takes the shape of the template, forming the desired optical structures. Following the imprint step, the template is separated from the NIL material layer 412, leaving behind the imprinted patterns. This separation, or “demolding” step, needs to be carefully executed to avoid damaging the newly formed optical features. The result is a waveguide workpiece 414 with optical structures in, at, and/or above the NIL material layer 412 which may be advantageous for the fabrication of waveguides where nanoscale optical features are configured to guide and manipulate light.
Some optical features formed may include, for example, diffractive features forming one or more of an IC, an EPE, an OC, and the like. For example, a set 416 of diffractive gratings may be formed during an NIL process so as to form an IC for the waveguide workpiece 414, and a different set 418 of diffractive gratings may be formed during the same or different NIL process so as to form an OC for the waveguide workpiece 414.
At block 515, one or more other NIL processes are employed to form various optical features in, at, and/or above the NIL material layer 512, resulting in a waveguide workpiece 414. Such NIL processes may include, for example, a step-and-flash imprint lithography technique. In this process, a template or mold, containing the desired nanoscale patterns for the optical features, is brought into contact with the NIL material layer 512. The template is often a transparent material with relief patterns on its surface corresponding to the optical structures required in the waveguide. The contact is carefully controlled to ensure proper alignment and uniformity. Upon contact, the NIL material layer 512 undergoes deformation and replicates the nanoscale patterns from the template. This step is often referred to as the “imprint” step. UV-light in this step cures the material and the hardened material takes the shape of the template, forming the desired optical structures. Following the imprint step, the template is separated from the NIL material layer 512, leaving behind the imprinted patterns. This separation, or “demolding” step, needs to be carefully executed to avoid damaging the newly formed optical features. The result is a waveguide workpiece 514 with optical structures in, at, and/or above the NIL material layer 512 which may be advantageous for the fabrication of waveguides where nanoscale optical features are configured to guide and manipulate light.
Some optical features formed may include, for example, diffractive features forming one or more of an IC, an EPE, an OC, and the like. For example, a set 516 of diffractive gratings may be formed during an NIL process so as to form an IC for the waveguide workpiece 514, and a different set 518 of diffractive gratings may be formed during the same or different NIL process so as to form an OC for the waveguide workpiece 514.
In an embodiment, a UV light absorbing material 610, such as a UV light absorbing material may be disposed on and/or integrally formed within waveguide workpiece 602, first transparent body 606, and/or second transparent body 608 within an optical device 600 such as an augmented reality device. The UV light absorbing material 610 may be integrally formed within the nanoparticle-infused NIL material layer 604. In an embodiment, waveguide workpiece 602 has diffractive optical elements such as diffractive gratings that may be formed during an NIL process so as to form an IC 614 and a different set of diffractive gratings may be formed during the same or different NIL process so as to form an OC 616 on waveguide workpiece 602. In an embodiment, the employed in conjunction with UV light absorbing material 610 positioned on both sides of the waveguide workpiece 602. This configuration may enhance resilience of waveguide workpiece 602 against light-induced damage.
UV light-absorbing materials 610 may include a range of compounds designed to absorb ultraviolet radiation. For example, organic UV absorbers, such as benzotriazoles and benzophenones, have molecular structures capable of absorbing specific UV wavelengths. In another example, inorganic UV absorbers, such as zinc oxide and titanium dioxide, exhibit UV-blocking properties due to their electronic structures. Further, certain polymers inherently possess UV-absorbing capabilities; for instance, certain formulations of polyethylene or polypropylene may act as effective UV absorbers. Carbon-based materials, including carbon black and graphene, absorb UV radiation and dissipate the absorbed energy through various mechanisms. Dyes and pigments may be engineered to absorb UV light are employed in coatings and films. Nanoparticles, such as zinc oxide or cerium oxide nanoparticles, contribute to UV absorption when dispersed within materials. These UV light-absorbing materials may be selected based on factors such as the wavelength range of UV light to be absorbed, compatibility with the optical system, and the intended application for performance and protection in complex optical devices and systems.
In some embodiments, certain aspects of the techniques described above may be implemented by one or more processors of a processing system executing software. The software comprises one or more sets of executable instructions stored or otherwise tangibly embodied on a non-transitory computer readable storage medium. The software can include the instructions and certain data that, when executed by the one or more processors, manipulate the one or more processors to perform one or more aspects of the techniques described above. The non-transitory computer readable storage medium can include, for example, a magnetic or optical disk storage device, solid state storage devices such as Flash memory, a cache, random access memory (RAM) or other non-volatile memory device or devices, and the like. The executable instructions stored on the non-transitory computer readable storage medium may be in source code, assembly language code, object code, or other instruction format that is interpreted or otherwise executable by one or more processors.
A computer readable storage medium may include any storage medium, or combination of storage media, accessible by a computer system during use to provide instructions and/or data to the computer system. Such storage media can include, but is not limited to, optical media (e.g., compact disc (CD), digital versatile disc (DVD), Blu-Ray disc), magnetic media (e.g., floppy disc, magnetic tape, or magnetic hard drive), volatile memory (e.g., random access memory (RAM) or cache), non-volatile memory (e.g., read-only memory (ROM) or Flash memory), or microelectromechanical systems (MEMS)-based storage media. The computer readable storage medium may be embedded in the computing system (e.g., system RAM or ROM), fixedly attached to the computing system (e.g., a magnetic hard drive), removably attached to the computing system (e.g., an optical disc or Universal Serial Bus (USB)-based Flash memory), or coupled to the computer system via a wired or wireless network (e.g., network accessible storage (NAS)).
Note that not all of the activities or elements described above in the general description are required, that a portion of a specific activity or device may not be required, and that one or more further activities may be performed, or elements included, in addition to those described. Still further, the order in which activities are listed are not necessarily the order in which they are performed. Also, the concepts have been described with reference to specific embodiments. However, one of ordinary skill in the art appreciates that various modifications and changes can be made without departing from the scope of the present disclosure as set forth in the claims below. Accordingly, the specification and figures are to be regarded in an illustrative rather than a restrictive sense, and all such modifications are intended to be included within the scope of the present disclosure.
Benefits, other advantages, and solutions to problems have been described above with regard to specific embodiments. However, the benefits, advantages, solutions to problems, and any feature(s) that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as a critical, required, or essential feature of any or all the claims. Moreover, the particular embodiments disclosed above are illustrative only, as the disclosed subject matter may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. No limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular embodiments disclosed above may be altered or modified and all such variations are considered within the scope of the disclosed subject matter. Accordingly, the protection sought herein is as set forth in the claims below.
