Rainbow reduction in augmented reality displays using filled anisotropic gratings

Abstract

An optical element includes a substrate and a periodic relief structure formed on a surface of the substrate. The relief structure includes a series of alternating ridges and valleys where the ridges are formed from a first optically anisotropic material and the valleys are filled with an optically isotropic material. The ridges have a pitch defined by a distance between adjacent ridges is configured to diffract light incident on the relief structure.

Description

RAINBOW REDUCTION IN AUGMENTED REALITY DISPLAYS USING FILLEDANISOTROPIC GRATINGSCROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of priority under 35 U.S.C. §119(e) of U.S. Provisional Application No. 63 / 572,888, filed April 1, 2024, the contents of which are incorporated herein by reference in their entirety.BRIEF DESCRIPTION OF THE DRAWINGS

[0002] The accompanying drawings illustrate a number of exemplary embodiments and are a part of the specification. Together with the following description, these drawings demonstrate and explain various principles of the present disclosure.

[0003] FIG. 1 is an illustration of a waveguide display system according to some embodiments.

[0004] FIG. 2 is an illustration of an exemplary filled anisotropic grating according to various embodiments.

[0005] FIG. 3 is an illustration of the interaction of s-polarized light with the filled anisotropic grating of FIG. 2 according to certain embodiments.

[0006] FIG. 4 is an illustration of the interaction of p-polarized light with the filled anisotropic grating of FIG. 2 according to certain embodiments.

[0007] FIG. 5 is an illustration of exemplary augmented-reality glasses that may be used in connection with embodiments of this disclosure.

[0008] FIG. 6 is an illustration of an exemplary virtual-reality headset that may be used in connection with embodiments of this disclosure.

[0009] Throughout the drawings, identical reference characters and descriptions indicate similar, but not necessarily identical, elements. While the exemplary embodiments described herein are susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and will be described in detail herein. However, the exemplary embodiments described herein are not intended to be limited to the particular forms disclosed. Rather, the present disclosure covers all modifications, equivalents, and alternatives falling within the scope of the appended claims.DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

[0010] Mixed reality (MR) and augmented reality (AR) eyewear devices orheadsets may enable users to experience events, such as interactions with people in a computer-generated simulation of a three-dimensional world or viewing data superimposed on a real-world view. By way of example, superimposing information onto a field of view may be achieved through an optical head-mounted display (OHMD) or by using embedded wireless glasses with a transparent heads-up display (HUD) or augmented reality (AR) overlay. MR / AR eyewear devices and headsets may be used for a variety of purposes. For example, governments may use such devices for military training, medical professionals may use such devices to simulate surgery, and engineers may use such devices as design visualization aids.

[0011] A waveguide display system for MR and AR applications may include a micro-display module and waveguide optics for directing a display image to a user. The microdisplay module may include a light source, such as a light emitting diode (LED). The waveguide optics may include input-coupling and output-coupling elements such as surface relief gratings that are configured to couple light into and out of the waveguide. Example grating structures may have a one-dimensional or two-dimensional periodicity, and may include a binary, slanted, or blazed architecture. In some embodiments, a vertical grating coupler, for instance, may be configured to change an out-of-plane wave-vector direction of light to an inplane waveguide direction, or vice versa, and accordingly direct the passage of light through the waveguide display. An input-coupling grating may determine the angular uniformity and coupling efficiency of image light.

[0012] In exemplary systems, the waveguide optics may be advantageously configured to create illuminance uniformity and a wide field of view (FOV). The FOV relates to the angular range of an image observable by a user, whereas illuminance uniformity may include both the uniformity of image light over an expanded exit pupil (exit pupil uniformity) and the uniformity of image light over the FOV (angular uniformity). In various waveguide configurations, the supported field of view (FOV) is directly proportional to the refractive index of the waveguide material.

[0013] A variety of large refractive index materials may be used to form waveguide components. Organic solid crystals, for example, include organic compounds that form solid crystalline structures. The molecular structure of the organic solids allows for flexibility, facile modification, and a broad range of potential functionalities and applications. Organic solid crystals possess a range of properties that make them attractive for use in varioustechnologies.

[0014] One characteristic of organic solid crystals is their electrical properties. Many organic crystals are semiconductors. This makes them suitable for use in electronic devices such as transistors, sensors, and memory storage systems. Another important attribute of organic solid crystals is their optical properties. These materials may have a large refractive index (n>1.5) and often exhibit fluorescence and absorption in the visible and infrared spectrums, allowing them to be used in light-emitting devices, displays, and photo detectors. Their ability to emit light efficiently makes them valuable in applications such as organic light-emitting diodes.

[0015] In addition, organic crystals are often more mechanically compliant than inorganic materials, which opens up possibilities forflexible electronics and wearable devices. Their low density also contributes to their lightweight nature making them ideal for portable and wearable technologies.

[0016] The properties of organic solid crystals may be tunable. By adjusting the molecular structure of these materials, their electronic and optical characteristics can be preset or modified in real time to meet specific needs, allowing for greater customization in various applications.

[0017] Due to their optical and mechanical properties, organic solid crystals may enable high-performance devices, and may be incorporated into passive or active optics, including AR / MR headsets, and may replace comparative material systems such as polymers, inorganic materials, and liquid crystals. In certain aspects, organic solid crystals may have optical properties that rival those of inorganic crystals while exhibiting the processability and electrical response of liquid crystals.

[0018] Organic solid crystal (OSC) materials with high refractive index and birefringence can be used for various optical components, including surface relief gratings, meta-surfaces, waveguides, beam splitting, photonic elements such as photonic integrated circuits, and polarization selective elements. For instance, an augmented reality display may include an OSC-based waveguide.

[0019] Structurally, the disclosed organic materials may be glassy, polycrystalline, or single crystal. Organic solid crystals may include closely packed structures (e.g., organic molecules) that exhibit desirable optical properties such as a high and tunable refractive index, and high birefringence. Anisotropic organic solid materials may include a preferredpacking of molecules, i.e., a preferred orientation or alignment of molecules. Example devices may include a waveguide substrate and / or a grating structure formed from an optically anisotropic material.

[0020] Organic solid crystals with high refractive index and birefringence have a unique value proposition for use in diffractive optical elements, such as a planar diffractive waveguide. An example waveguide includes a longitudinally extending high-index optical medium, which is transversely encased by low-index media or cladding. During use, a guided optical wave propagates in the waveguide through the high-index core along the longitudinal direction by total internal reflection. Such a construction may beneficially impact one or more of the display field of view, uniformity, efficiency, and cost of manufacture.

[0021] According to various embodiments, the waveguide substrate includes or is formed from an organic solid crystal material. The OSC material may be single crystal or polycrystalline and may include an amorphous organic phase. In some examples, the substrate may include a single phase OSC material. In some examples, the substrate may include a single organic solid crystal layer or an OSC multilayer. Each OSC layer or other optically anisotropic layer may be characterized by three principal refractive indices, where ni * nz ns, ni= nz* n3, or ni* nz = n3. The characteristic refractive indices (ni, nz, ns) may be aligned or askew with respect to the principal dimensions of the substrate. The waveguide substrate may include an OSC material with either a fixed optical axis or a spatially varying optical axis.

[0022] The organic crystalline phase may be characterized by a refractive index along at least one principal axis of at least approximately 1.5 at 589 nm. By way of example, the refractive index of the organic crystalline phase at 589 nm and along at least one principal axis may be at least approximately 1.5, at least approximately 1.6, at least approximately 1.7, at least approximately 1.8, at least approximately 1.9, at least approximately 2, at least approximately 2.1, at least approximately 2.2, at least approximately 2.3, at least approximately 2.4, at least approximately 2.5, or at least approximately 2.6, including ranges between any of the foregoing values.

[0023] Particular example organic and optically anisotropic materials include polycene, triazole, thiophene, anthracene, as well as derivatives thereof. As alternatives to OSC materials, example inorganic optically anisotropic materials include SiOz, TiOz, GazOs, LiNbOs, SiC, and ZnS. As used herein, an optically anisotropic material may be characterizedby a refractive index difference between at least one pair of principal axes of at least approximately 0.1, e.g., 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, or 0.9, including ranges between any of the foregoing values. An optically isotropic material, on the other hand, may be characterized by a refractive index difference between each respective pair of principal axes of less than approximately 0.05, e.g., 0.05, 0.02, 0.01, 0.005, 0.002, 0.001, or 0, including ranges between any of the foregoing values. In particular examples, the principal refractive indices of an optically isotropic material may be equivalent or substantially equivalent.

[0024] Although not limited, example optically isotropic materials include various glass compositions (e.g., soda lime glasses, borosilicate glasses, etc.), polymers (e.g., polyethylene, polystyrene, polymethyl methacrylate, etc.), and oxides (e.g., amorphous aluminum oxide).

[0025] A coupling element, such as a grating, may overlie a waveguide substrate through which an electromagnetic wave may propagate. The grating may include a plurality of raised structures and may constitute a surface relief grating, for example. Example gratings may be configured with a polar angle (9) and an azimuthal angle (<p), where 0 < 9 < TC and 0 < q> < 7t. As used herein, a grating is an optical element having a periodic structure that is configured to disperse or diffract light into plural component beams. The direction or diffraction angles of the diffracted light may depend on the wavelength of the light incident on the grating, the orientation of the incident light with respect to a grating surface, and the refractive index and spacing between adjacent diffracting elements. In certain embodiments, grating architectures may be tunable along one, two, or three dimensions.

[0026] In some embodiments, the substrate and the grating may be formed from an isotropic material and the grating may be backfilled with an anisotropic material such as an organic solid crystal or a liquid crystal. The anisotropic material may be aligned crystallographically with respect to the grating structure, where the extraordinary refractive index of the anisotropic material is matched to the extraordinary refractive index of the grating and an ordinary refractive index of the anisotropic material is less than the ordinary refractive index of the grating. By way of example, a backfilled OSC layer may be crystallized in situ on grating surfaces by controlled cooling from a melt phase or by controlled crystallization from solution. An imposed temperature gradient during cooling or solvent evaporation may be used to control the kinetics of nucleation and growth and the formation of a backfilled OSC layer have a desired crystalline orientation. In further embodiments, theorientation of a backfilled liquid crystal layer may be controlled using an engineered thermal profile during crystallization, optionally in conjunction with the formation of an alignment layer over the grating structure prior to backfilling with the liquid crystal material.

[0027] During operation of an AR or MR display, diffractive gratings configured to decouple image light from a waveguide substrate can also diffract ambient external light, which may create optical artifacts including rainbow-like streaks within a user's field of view. Notwithstanding recent developments, it would be advantageous to configure a display such that artificial reality content is superimposed on a real world view that is unaffected by the diffractive gratings.

[0028] As disclosed herein, a diffractive grating is configured as a backfilled dual solid phase construction. An example grating includes an array of first grating elements interspersed with a complementary array of second grating elements, where the first grating elements include an optically anisotropic material, and the second grating elements include an optically isotropic material. Such a two solid phase construction may be arranged as the output grating to a diffractive waveguide, for example. According to particular embodiments, the first and second grating elements in such a grating are partially index matched. That is, one or two pairs of corresponding refractive indices amongst the first and second grating elements are matched in a manner effective to provide a non-diffractive grating for selected polarizations of incident light.

[0029] In some embodiments, the pitch of the relief structure may range from 100 nm to 10 pm, e.g., 100, 200, 500, 1000, 2000, 5000, or 10000 nm, including ranges between any of the foregoing values.

[0030] Where provided, the index mismatch between anisotropic grating elements and isotropic grating elements may be at least approximately 0.1, but at most approximately 1, e.g., 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 or 1, including ranges between any of the foregoing values. Such a composite grating may act as a polarization selective structure enabling higher efficiency diffraction orders for one polarization over another. Moreover, the polarization-selective grating response may be tuned by configuring the refractive index differential along principal axes between the first (anisotropic) and second (isotropic) grating elements.

[0031] In some embodiments, to account for optical dispersion, in some embodiments, the refractive indices of the anisotropic grating elements and the isotropicgrating elements may match or substantially match for a given wavelength, e.g., green light, and differ by less than 0.1, e.g., 0.1, 0.05, or 0.02, including ranges between any of the foregoing values, for wavelengths different than the given wavelength, e.g., red light and / or blue light.

[0032] By way of example, for index matching along in-plane directions (e.g., nxand / or ny), external s-polarized light will encounter a homogenous grating and pass undiffracted into the user's eye. For external p-polarized light, the effective contrast between grating elements is reduced resulting in weak diffraction. For index matching along a through thickness direction of the grating (e.g., nz), p-polarized external light may pass un-diffracted. Beyond the Brewster angle of the grating material, light may propagate through the grating and into the user's eye without diffracting.

[0033] The following will provide, with reference to FIGS. 1-6, detailed descriptions of augmented reality (AR) and mixed reality (MR) displays having filled anisotropic gratings for rainbow effect mitigation. The discussion associated with FIG. 1 includes a description of example light paths through an example display. The discussion associated with FIG. 2 includes a description of an example filled anisotropic grating. The discussion associated with FIGS. 3 and 4 includes a description of the interaction of polarized light with filled anisotropic gratings. The discussion associated with FIGS. 5 and 6 relates to exemplary augmented reality and mixed reality devices that may include one or more filled anisotropic gratings as disclosed herein.

[0034] Referring to FIG. 1, illustrated schematically are the interactions of both virtual and real world image light with input and folding / output diffractive gratings. As will be appreciated, the interaction of real world image light with the output grating of the waveguide display may create undesired rainbow artifacts visible to the user.

[0035] The structure of a diffractive waveguide including a filled anisotropic grating is shown in FIG. 2. The grating includes first grating elements 210 formed from an optically anisotropic material and second grating elements 220 formed from an optically isotropic material. In the illustrated architecture, openings (e.g., trenches) between anisotropic grating elements are backfilled with an index-matching isotropic material. Matching indices may be aligned with a polarization direction of image light. In an example embodiment, anisotropic grating elements 210 may have in-plane refractive indices ni=1.6, n2=1.6, and an out-of-plane index n3=2.4, where complementary second grating elements 220(i.e., complementary backfill material) may have refractive indices ni=1.6, n2=1.6, n3=1.6.

[0036] As shown in FIG. 3, such a diffractive grating may be essentially invisible to incident s-polarized light, where the grating presents a homogeneous (isotropic) structure along both the x and y directions. That is, s-polarized light is not diffracted by the grating of FIG. 3. On the other hand, referring to FIG. 4, p-polarized light may interact with the grating architecture along the x and z direction and therefore may be diffracted. However, such interactions may dominate only for low angles of incidence. Without wishing to be bound by theory, p-polarized light that is incident on the grating at high angles may pass through the grating essentially un-diffracted and therefore not contribute appreciably to rainbow formation.Example Embodiments

[0037] Example 1: An optical element includes a substrate and a periodic relief structure formed on a surface of the substrate, where the relief structure includes a series of ridges and valleys, the ridges are formed from a first optically anisotropic material, the valleys are filled with an optically isotropic material, the relief structure has a pitch defined by a distance between adjacent ridges, and the relief structure is configured to diffract light incident thereon.

[0038] Example 2: The optical element of Example 1, where the substrate is polycrystalline.

[0039] Example 3: The optical element of Example 1, where the substrate is a single crystal.

[0040] Example 4: The optical element of any of Examples 1-3, where the substrate includes a second optically anisotropic material.

[0041] Example 5: The optical element of Example 4, where the second optically anisotropic material includes an organic solid crystal.

[0042] Example 6: The optical element of any of Examples 1-5, where the first optically anisotropic material has refractive indices (ni, n2, ns), the optically isotropic material has a refractive index (n), and n is equal to at least one of ni, m, and ns.

[0043] Example 7: The optical element of any of Examples 1-6, where the first optically anisotropic material includes an organic solid crystal.

[0044] Example 8: The optical element of any of Examples 1-5, where a refractive index of the first optically anisotropic material is at least 1.5.

[0045] Example 9: The optical element of any of Examples 1-8, where the first optically anisotropic material has refractive indices (ni, n?, ns), where ni > 1.5, ns > 1.5, and n3> 1.5.

[0046] Example 10: The optical element of any of Examples 1-9, where a birefringence of the first optically anisotropic material is at least 0.1.

[0047] Example 11: The optical element of any of Examples 1-10, where the valleys are entirely filled with the optically isotropic material.

[0048] Example 12: The optical element of any of Examples 1-11, where top surfaces of the ridges and top surfaces of the filled valleys are co-planar.

[0049] Example 13: The optical element of any of Examples 1-12, where the pitch of the relief structure ranges from 100 nm to 10 .m.

[0050] Example 14: An optical element includes a substrate and a periodic relief structure including a series of alternating ridges and valleys disposed over a surface of the substrate, where the ridges include an optically anisotropic material, and the valleys are filled with an optically isotropic material.

[0051] Example 15: The optical element of Example 14, where the optically anisotropic material has refractive indices (ni, n3, n3), the optically isotropic material has a refractive index (n), and n is equal to at least one of ni, n3, and n3.

[0052] Example 16: The optical element of any of Examples 14 and 15, where the optically anisotropic material includes an organic solid crystal.

[0053] Example 17: The optical element of any of Examples 14-16, where a refractive index of the optically anisotropic material is at least 1.5.

[0054] Example 18: The optical element of any of Examples 14-17, where the optically anisotropic material has refractive indices (ni, n2, n3), with ni > 1.5, n2 > 1.5, and n3> 1.5.

[0055] Example 19: The optical element of any of Examples 14-18, where a birefringence of the optically anisotropic material is at least 0.1.

[0056] Example 20: An optical element includes a periodic relief structure including a series of alternating ridges and valleys disposed over a surface of a substrate, where the ridges include an optically anisotropic material having refractive indices (ni, n2, n3) with ni > 1.5, n2 > 1.5, and n3> 1.5, the valleys are filled with an optically isotropic material having a refractive index (n), and n is equal to at least one of ni, n3, and n3.

[0057] E mbodiments of the present disclosure may include or be implemented in conjunction with various types of artificial-reality systems. Artificial reality is a form of reality that has been adjusted in some manner before presentation to a user, which may include, for example, a virtual reality, an augmented reality, a mixed reality, a hybrid reality, or some combination and / or derivative thereof. Artificial-reality content may include completely computer-generated content or computer-generated content combined with captured (e.g., real-world) content. The artificial-reality content may include video, audio, haptic feedback, or some combination thereof, any of which may be presented in a single channel or in multiple channels (such as stereo video that produces a three-dimensional (3D) effect to the viewer). Additionally, in some embodiments, artificial reality may also be associated with applications, products, accessories, services, or some combination thereof, that are used to, for example, create content in an artificial reality and / or are otherwise used in (e.g., to perform activities in) an artificial reality.

[0058] Artificial-reality systems may be implemented in a variety of different form factors and configurations. Some artificial-reality systems may be designed to work without near-eye displays (NEDs). Other artificial-reality systems may include an NED that also provides visibility into the real world (e.g., augmented-reality system 500 in FIG. 5) or that visually immerses a user in an artificial reality (e.g., virtual-reality system 600 in FIG. 6). While some artificial-reality devices may be self-contained systems, other artificial-reality devices may communicate and / or coordinate with external devices to provide an artificial-reality experience to a user. Examples of such external devices include handheld controllers, mobile devices, desktop computers, devices worn by a user, devices worn by one or more other users, and / or any other suitable external system.

[0059] Turning to FIG. 5, augmented-reality system 500 may include an eyewear device 502 with a frame 510 configured to hold a left display device 515(A) and a right display device 515(B) in front of a user's eyes. Display devices 515(A) and 515(B) may act together or independently to present an image or series of images to a user. While augmented-reality system 500 includes two displays, embodiments of this disclosure may be implemented in augmented-reality systems with a single NED or more than two NEDs.

[0060] In some embodiments, augmented-reality system 500 may include one or more sensors, such as sensor 540. Sensor 540 may generate measurement signals in response to motion of augmented-reality system 500 and may be located on substantially any portionof frame 510. Sensor 540 may represent a position sensor, an inertial measurement unit (IMU), a depth camera assembly, a structured light emitter and / or detector, or any combination thereof. In some embodiments, augmented-reality system 500 may or may not include sensor 540 or may include more than one sensor. In embodiments in which sensor 540 includes an IMU, the IMU may generate calibration data based on measurement signals from sensor 540. Examples of sensor 540 may include, without limitation, accelerometers, gyroscopes, magnetometers, other suitable types of sensors that detect motion, sensors used for error correction of the IMU, or some combination thereof.

[0061] Augmented-reality system 500 may also include a microphone array with a plurality of acoustic transducers 520(A)-520(J), referred to collectively as acoustic transducers 520. Acoustic transducers 520 may be transducers that detect air pressure variations induced by sound waves. Each acoustic transducer520 may be configured to detect sound and convert the detected sound into an electronic format (e.g., an analog or digital format). The microphone array in FIG. 5 may include, for example, ten acoustic transducers: 520(A) and 520(B), which may be designed to be placed inside a corresponding ear of the user, acoustic transducers 520(C), 520(D), 520(E), 520(F), 520(G), and 520(H), which may be positioned at various locations on frame 510, and / or acoustic transducers 520(1) and 520(J), which may be positioned on a corresponding neckband 505.

[0062] In some embodiments, one or more of acoustic transducers 520(A)-(F) may be used as output transducers (e.g., speakers). For example, acoustic transducers 520(A) and / or 520(B) may be earbuds or any other suitable type of headphone or speaker.

[0063] The configuration of acoustic transducers 520 of the microphone array may vary. While augmented-reality system 500 is shown in FIG. 5 as having ten acoustic transducers 520, the number of acoustic transducers 520 may be greater or less than ten. In some embodiments, using higher numbers of acoustic transducers 520 may increase the amount of audio information collected and / or the sensitivity and accuracy of the audio information. In contrast, using a lower number of acoustic transducers 520 may decrease the computing power required by an associated controller 550 to process the collected audio information. In addition, the position of each acoustic transducer 520 of the microphone array may vary. For example, the position of an acoustic transducer 520 may include a defined position on the user, a defined coordinate on frame 510, an orientation associated with each acoustic transducer 520, or some combination thereof.

[0064] Acoustic transducers 520(A) and 520(B) may be positioned on different parts of the user's ear, such as behind the pinna, behind the tragus, and / or within the auricle or fossa. Or, there may be additional acoustic transducers 520 on or surrounding the ear in addition to acoustic transducers 520 inside the ear canal. Having an acoustic transducer 520 positioned next to an ear canal of a user may enable the microphone array to collect information on how sounds arrive at the ear canal. By positioning at least two of acoustic transducers 520 on either side of a user's head (e.g., as binaural microphones), augmented- reality device 500 may simulate binaural hearing and capture a 3D stereo sound field around about a user's head. In some embodiments, acoustic transducers 520(A) and 520(B) may be connected to augmented-reality system 500 via a wired connection 530, and in other embodiments acoustic transducers 520(A) and 520(B) may be connected to augmented- reality system 500 via a wireless connection (e.g., a Bluetooth connection). In still other embodiments, acoustic transducers 520(A) and 520(B) may not be used at all in conjunction with augmented-reality system 500.

[0065] Acoustic transducers 520 on frame 510 may be positioned along the length of the temples, across the bridge, above or below display devices 515(A) and 515(B), or some combination thereof. Acoustic transducers 520 may be oriented such that the microphone array is able to detect sounds in a wide range of directions surrounding the user wearing the augmented-reality system 500. In some embodiments, an optimization process may be performed during manufacturing of augmented-reality system 500 to determine relative positioning of each acoustic transducer 520 in the microphone array.

[0066] In some examples, augmented-reality system 500 may include or be connected to an external device (e.g., a paired device), such as neckband 505. Neckband 505 generally represents any type or form of paired device. Thus, the following discussion of neckband 505 may also apply to various other paired devices, such as charging cases, smart watches, smart phones, wrist bands, other wearable devices, hand-held controllers, tablet computers, laptop computers, other external compute devices, etc.

[0067] As shown, neckband 505 may be coupled to eyewear device 502 via one or more connectors. The connectors may be wired or wireless and may include electrical and / or non-electrical (e.g., structural) components. In some cases, eyewear device 502 and neckband 505 may operate independently without any wired or wireless connection between them. While FIG. 5 illustrates the components of eyewear device 502 and neckband 505 in examplelocations on eyewear device 502 and neckband 505, the components may be located elsewhere and / or distributed differently on eyewear device 502 and / or neckband 505. In some embodiments, the components of eyewear device 502 and neckband 505 may be located on one or more additional peripheral devices paired with eyewear device 502, neckband 505, or some combination thereof.

[0068] Pairing external devices, such as neckband 505, with augmented-reality eyewear devices may enable the eyewear devices to achieve the form factor of a pair of glasses while still providing sufficient battery and computation power for expanded capabilities. Some or all of the battery power, computational resources, and / or additional features of augmented-reality system 500 may be provided by a paired device or shared between a paired device and an eyewear device, thus reducing the weight, heat profile, and form factor of the eyewear device overall while still retaining desired functionality. For example, neckband 505 may allow components that would otherwise be included on an eyewear device to be included in neckband 505 since users may tolerate a heavier weight load on their shoulders than they would tolerate on their heads. Neckband 505 may also have a larger surface area over which to diffuse and disperse heat to the ambient environment. Thus, neckband 505 may allow for greater battery and computation capacity than might otherwise have been possible on a stand-alone eyewear device. Since weight carried in neckband 505 may be less invasive to a user than weight carried in eyewear device 502, a user may tolerate wearing a lighter eyewear device and carrying or wearing the paired device for greater lengths of time than a user would tolerate wearing a heavy standalone eyewear device, thereby enabling users to more fully incorporate artificial-reality environments into their day-to-day activities.

[0069] Neckband 505 may be communicatively coupled with eyewear device 502 and / or to other devices. These other devices may provide certain functions (e.g., tracking, localizing, depth mapping, processing, storage, etc.) to augmented-reality system 500. In the embodiment of FIG. 5, neckband 505 may include two acoustic transducers (e.g., 520(1) and 520(J)) that are part of the microphone array (or potentially form their own microphone subarray). Neckband 505 may also include a controller 525 and a power source 535.

[0070] Acoustic transducers 520(1) and 520(J) of neckband 505 may be configured to detect sound and convert the detected sound into an electronic format (analog or digital). In the embodiment of FIG. 5, acoustic transducers 520(1) and 520(J) may be positioned onneckband 505, thereby increasing the distance between the neckband acoustic transducers 520(1) and 520(J) and other acoustic transducers 520 positioned on eyewear device 502. In some cases, increasing the distance between acoustic transducers 520 of the microphone array may improve the accuracy of beamforming performed via the microphone array. For example, if a sound is detected by acoustic transducers 520(C) and 520(D) and the distance between acoustic transducers 520(C) and 520(D) is greater than, e.g., the distance between acoustic transducers 520(D) and 520(E), the determined source location of the detected sound may be more accurate than if the sound had been detected by acoustic transducers 520(D) and 520(E).

[0071] Controller 525 of neckband 505 may process information generated by the sensors on neckband 505 and / or augmented-reality system 500. For example, controller 525 may process information from the microphone array that describes sounds detected by the microphone array. Foreach detected sound, controller525 may perform a direction-of-arrival (DOA) estimation to estimate a direction from which the detected sound arrived at the microphone array. As the microphone array detects sounds, controller 525 may populate an audio data set with the information. In embodiments in which augmented-reality system 500 includes an inertial measurement unit, controller 525 may compute all inertial and spatial calculations from the IMU located on eyewear device 502. A connector may convey information between augmented-reality system 500 and neckband 505 and between augmented-reality system 500 and controller 525. The information may be in the form of optical data, electrical data, wireless data, or any other transmittable data form. Moving the processing of information generated by augmented-reality system 500 to neckband 505 may reduce weight and heat in eyewear device 502, making it more comfortable to the user.

[0072] Power source 535 in neckband 505 may provide power to eyewear device 502 and / or to neckband 505. Power source 535 may include, without limitation, lithium ion batteries, lithium-polymer batteries, primary lithium batteries, alkaline batteries, or any other form of power storage. In some cases, power source 535 may be a wired power source. Including power source 535 on neckband 505 instead of on eyewear device 502 may help better distribute the weight and heat generated by power source 535.

[0073] As noted, some artificial-reality systems may, instead of blending an artificial reality with actual reality, substantially replace one or more of a user's sensory perceptions of the real world with a virtual experience. One example of this type of system isa head-worn display system, such as virtual-reality system 600 in FIG. 6, that mostly or completely covers a user's field of view. Virtual-reality system 600 may include a front rigid body 602 and a band 604 shaped to fit around a user's head. Virtual-reality system 600 may also include output audio transducers 606(A) and 606(B). Furthermore, while not shown in FIG. 6, front rigid body 602 may include one or more electronic elements, including one or more electronic displays, one or more inertial measurement units (IMUs), one or more tracking emitters or detectors, and / or any other suitable device or system for creating an artificial reality experience.

[0074] Artificial-reality systems may include a variety of types of visual feedback mechanisms. For example, display devices in augmented-reality system 500 and / or virtual- reality system 600 may include one or more liquid crystal displays (LCDs), light emitting diode (LED) displays, organic LED (OLED) displays, digital light project (DLP) micro-displays, liquid crystal on silicon (LCoS) micro-displays, and / or any other suitable type of display screen. Artificial-reality systems may include a single display screen for both eyes or may provide a display screen for each eye, which may allow for additional flexibility for varifocal adjustments or for correcting a user's refractive error. Some artificial-reality systems may also include optical subsystems having one or more lenses (e.g., conventional concave or convex lenses, Fresnel lenses, adjustable liquid lenses, etc.) through which a user may view a display screen. These optical subsystems may serve a variety of purposes, including to collimate (e.g., make an object appear at a greater distance than its physical distance), to magnify (e.g., make an object appear larger than its actual size), and / or to relay (to, e.g., the viewer's eyes) light. These optical subsystems may be used in a non-pupil-forming architecture (such as a single lens configuration that directly collimates light but results in so-called pincushion distortion) and / or a pupil-forming architecture (such as a multi-lens configuration that produces so- called barrel distortion to nullify pincushion distortion).

[0075] In addition to or instead of using display screens, some artificial-reality systems may include one or more projection systems. For example, display devices in augmented-reality system 500 and / or virtual-reality system 600 may include micro-LED projectors that project light (using, e.g., a waveguide) into display devices, such as clear combiner lenses that allow ambient light to pass through. The display devices may refract the projected light toward a user's pupil and may enable a user to simultaneously view both artificial-reality content and the real world. The display devices may accomplish this using anyof a variety of different optical components, including waveguide components (e.g., holographic, planar, diffractive, polarized, and / or reflective waveguide elements), lightmanipulation surfaces and elements (such as diffractive, reflective, and refractive elements and gratings), coupling elements, etc. Artificial-reality systems may also be configured with any other suitable type or form of image projection system, such as retinal projectors used in virtual retina displays.

[0076] Artificial-reality systems may also include various types of computer vision components and subsystems. For example, augmented-reality system 500 and / or virtual- reality system 600 may include one or more optical sensors, such as two-dimensional (2D) or 3D cameras, structured light transmitters and detectors, time-of-f light depth sensors, singlebeam or sweeping laser rangefinders, 3D LiDAR sensors, and / or any other suitable type or form of optical sensor. An artificial-reality system may process data from one or more of these sensors to identify a location of a user, to map the real world, to provide a user with context about real-world surroundings, and / or to perform a variety of other functions.

[0077] Artificial-reality systems may also include one or more input and / or output audio transducers. In the examples shown in FIG. 6, output audio transducers 606(A) and 606(B) may include voice coil speakers, ribbon speakers, electrostatic speakers, piezoelectric speakers, bone conduction transducers, cartilage conduction transducers, tragus-vibration transducers, and / or any other suitable type or form of audio transducer. Similarly, input audio transducers may include condenser microphones, dynamic microphones, ribbon microphones, and / or any other type or form of input transducer. In some embodiments, a single transducer may be used for both audio input and audio output.

[0078] While not shown in FIG. 5, artificial-reality systems may include tactile (i.e., haptic) feedback systems, which may be incorporated into headwear, gloves, body suits, handheld controllers, environmental devices (e.g., chairs, floormats, etc.), and / or any other type of device or system. Haptic feedback systems may provide various types of cutaneous feedback, including vibration, force, traction, texture, and / or temperature. Haptic feedback systems may also provide various types of kinesthetic feedback, such as motion and compliance. Haptic feedback may be implemented using motors, piezoelectric actuators, fluidic systems, and / or a variety of other types of feedback mechanisms. Haptic feedback systems may be implemented independent of other artificial-reality devices, within other artificial-reality devices, and / or in conjunction with other artificial-reality devices.

[0079] By providing haptic sensations, audible content, and / or visual content, artificial-reality systems may create an entire virtual experience or enhance a user's real- world experience in a variety of contexts and environments. For instance, artificial-reality systems may assist or extend a user's perception, memory, or cognition within a particular environment. Some systems may enhance a user's interactions with other people in the real world or may enable more immersive interactions with other people in a virtual world. Artificial-reality systems may also be used for educational purposes (e.g., for teaching or training in schools, hospitals, government organizations, military organizations, business enterprises, etc.), entertainment purposes (e.g., for playing video games, listening to music, watching video content, etc.), and / or for accessibility purposes (e.g., as hearing aids, visual aids, etc.). The embodiments disclosed herein may enable or enhance a user's artificial-reality experience in one or more of these contexts and environments and / or in other contexts and environments.

[0080] The process parameters and sequence of the steps described and / or illustrated herein are given by way of example only and can be varied as desired. For example, while the steps illustrated and / or described herein may be shown or discussed in a particular order, these steps do not necessarily need to be performed in the order illustrated or discussed. The various exemplary methods described and / or illustrated herein may also omit one or more of the steps described or illustrated herein or include additional steps in addition to those disclosed.

[0081] The preceding description has been provided to enable others skilled in the art to best utilize various aspects of the exemplary embodiments disclosed herein. This exemplary description is not intended to be exhaustive or to be limited to any precise form disclosed. Many modifications and variations are possible without departing from the spirit and scope of the present disclosure. The embodiments disclosed herein should be considered in all respects illustrative and not restrictive. Reference should be made to the appended claims and their equivalents in determining the scope of the present disclosure.

[0082] Uni ess otherwise noted, the terms "connected to" and "coupled to" (and their derivatives), as used in the specification and claims, are to be construed as permitting both direct and indirect (i.e., via other elements or components) connection. In addition, the terms "a" or "an," as used in the specification and claims, are to be construed as meaning "at least one of." Finally, for ease of use, the terms "including" and "having" (and theirderivatives), as used in the specification and claims, are interchangeable with and have the same meaning as the word "comprising."

[0083] It will be understood that when an element such as a layer or a region is referred to as being formed on, deposited on, or disposed "on" or "over" another element, it may be located directly on at least a portion of the other element, or one or more intervening elements may also be present. In contrast, when an element is referred to as being "directly on" or "directly over" another element, it may be located on at least a portion of the other element, with no intervening elements present.

[0084] As used herein, the term "approximately" in reference to a particular numeric value or range of values may, in certain embodiments, mean and include the stated value as well as all values within 10% of the stated value. Thus, by way of example, reference to the numeric value "50" as "approximately 50" may, in certain embodiments, include values equal to 50±5, i.e., values within the range 45 to 55.

[0085] As used herein, the term "substantially" in reference to a given parameter, property, or condition may mean and include to a degree that one of ordinary skill in the art would understand that the given parameter, property, or condition is met with a small degree of variance, such as within acceptable manufacturing tolerances. By way of example, depending on the particular parameter, property, or condition that is substantially met, the parameter, property, or condition may be at least approximately 90% met, at least approximately 95% met, or even at least approximately 99% met.

[0086] While various features, elements or steps of particular embodiments may be disclosed using the transitional phrase "comprising," it is to be understood that alternative embodiments, including those that may be described using the transitional phrases "consisting of" or "consisting essentially of," are implied. Thus, for example, implied alternative embodiments to a lens that comprises or includes polycarbonate include embodiments where a lens consists essentially of polycarbonate and embodiments where a lens consists of polycarbonate.

Claims

What is claimed is:

1. An optical element comprising: a substrate; and a periodic relief structure formed on a surface of the substrate, wherein: the relief structure comprises a series of ridges and valleys; the ridges are formed from a first optically anisotropic material; the valleys are filled with an optically isotropic material; the relief structure has a pitch defined by a distance between adjacent ridges; and the relief structure is configured to diffract light incident thereon.

2. The optical element of claim 1, wherein the substrate is polycrystalline.

3. The optical element of claim 1, wherein the substrate is a single crystal.

4. The optical element of claim 1, wherein the substrate comprises a second optically anisotropic material.

5. The optical element of claim 4, wherein the second optically anisotropic material comprises an organic solid crystal.

6. The optical element of claim 1, wherein: the first optically anisotropic material has refractive indices (ni, ns, ns); the optically isotropic material has a refractive index (n); and n is equal to at least one of ni, ns, and ns.

7. The optical element of claim 1, wherein the first optically anisotropic material comprises an organic solid crystal.

8. The optical element of claim 1, wherein a refractive index of the first optically anisotropic material is at least 1.5.

9. The optical element of claim 1, wherein the first optically anisotropic material has refractive indices (m, ns, ns), where ni > 1.5, ns > 1.5, and ns > 1.5.

10. The optical element of claim 1, wherein a birefringence of the first optically anisotropic material is at least 0.1.

11. The optical element of claim 1, wherein the valleys are entirely filled with the optically isotropic material.

12. The optical element of claim 1, wherein top surfaces of the ridges and top surfaces of the filled valleys are co-planar.

13. The optical element of claim 1, wherein the pitch of the relief structure ranges from 100 nm to 10 .m.

14. An optical element comprising: a substrate; and a periodic relief structure including a series of alternating ridges and valleys disposed over a surface of the substrate, wherein: the ridges comprise an optically anisotropic material, and the valleys are filled with an optically isotropic material.

15. The optical element of claim 14, wherein: the optically anisotropic material has refractive indices (ni, nz, ns); the optically isotropic material has a refractive index (n); and n is equal to at least one of m, nz, and ns.

16. The optical element of claim 14, wherein the optically anisotropic material comprises an organic solid crystal.

17. The optical element of claim 14, wherein a refractive index of the optically anisotropic material is at least 1.5.

18. The optical element of claim 14, wherein the optically anisotropic material has refractive indices (ni, nz, ns), with ni > 1.5, nz > 1.5, and ns > 1.5.

19. The optical element of claim 14, wherein a birefringence of the optically anisotropic material is at least 0.1.

20. An optical element comprising: a periodic relief structure including a series of alternating ridges and valleys disposed over a surface of a substrate, wherein: the ridges comprise an optically anisotropic material having refractive indices (ni, nz, ns) with ni > 1.5, nz > 1.5, and ns > 1.5, the valleys are filled with an optically isotropic material having a refractive index (n), and n is equal to at least one of ni, nz, and ns.

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