ENHANCED GRIN LC LENS RESPONSE TIME USING TEMPERATURE CONTROL

A system includes (a) an optical device having a GRIN LC lens, the GRIN LC lens including a liquid crystal layer, (b) a sensor configured to assess an attribute of the liquid crystal layer, (c) a heat source, and (d) a controller configured to mediate heat flow between the heat source and the liquid crystal layer based on a signal provided by the sensor.

BRIEF DESCRIPTION OF DRAWINGS

FIG.1illustrates a portion of an example GRIN LC lens stack having a liquid crystal layer disposed between a patterned electrode and a ground electrode according to some embodiments.

FIG.2is a cross-sectional view of a GRIN LC lens stack including an array of spacer elements disposed between first and second optical substrates and a metallization architecture for applying an electric field across a liquid crystal layer located between the substrates according to some embodiments.

FIG.3shows a cross-sectional view of an optical system having a thermally monitored and temperature controlled liquid crystal layer according to some embodiments.

FIG.4is a plot showing the temperature effects on refractive index and viscosity for a representative liquid crystal composition according to various embodiments.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Across various optical engineering applications including eyeglasses, contact lenses, and vision correction elements in augmented reality (AR) and virtual reality (VR) systems, liquid crystal (LC) lenses may provide a number of advantages due to their electrically tunable focusing capability, where the associated optical mechanism is based on a spatially localized modulation of light speed resulting from LC molecular orientations driven by an applied electric field.

In such context, and as will be appreciated, the realization of a continuous distribution of phase retardation across larger aperture (>10 mm) LC lenses may be challenged by the limited birefringence (<0.4) of LC materials as well as their mechanically compliant nature. In some embodiments, a gradient-index configuration may be used to provide tunability of focus quality.

Gradient refractive index (GRIN) optics refers to a branch of optics where optical effects are produced by a spatial gradient in the refractive index of a material. A gradual refractive index variation may be used to manufacture lenses having planar surfaces, for example, or to reduce aberrations in imaging applications. In an LC lens having an axial gradient configuration, the refractive index may vary along the optical axis of an inhomogeneous medium such that surfaces of constant index are planes that are oriented perpendicular to the optical axis. In a radial/cylindrical refractive index gradient configuration, on the other hand, the index profile may vary continuously from a centerline of the optical axis to the periphery along the transverse direction in such a way that surfaces of constant index are concentric cylinders located about the optical axis. Hybrid GRIN LC lenses having both an axial and a radial/cylindrical refractive index gradient configuration are also contemplated.

A gradient refractive index lens utilizes a spatially-defined refractive index gradient across the viewing aperture of the lens to impart an optical phase profile at a selected design wavelength. In particular examples, a GRIN lens may have a planar form factor, such as a disk shape, and lensing performance that may be improved relative to lenses formed from a material having a single, spatially-invariant index, such as comparative lenses made from glass or quartz.

GRIN-type varifocal LC lenses may be configured to exhibit a gradient distribution of refractive index in response to a spatially inhomogeneous electric field that is applied across the LC layer(s). As such, the lens power of a GRIN-type LC lens may also be continuously tunable. In some instantiations, there may be a continuous variation of the refractive index within the lens material. An LC lens may be configured in both planar and non-planar (e.g., concave or convex) geometries.

In some systems, a tunable architecture may include a plurality of discrete, ring electrodes formed over the LC layer(s) within the optical aperture of the lens. During operation, a different voltage may be applied to each electrode, which may be used to locally tune the refractive index of the LC material. The patterning of multiple electrodes, however, may create manufacturing challenges and also induce performance liabilities, including a loss of transmission, a decrease in focal power, and/or the generation of optical artifacts such as haze and/or ghosting due to angular diffraction arising from sub-critical electrode dimensions or the gap between neighboring electrodes. In some embodiments, the inter-electrode gaps across the viewing aperture of a varifocal GRIN LC lens may be greater than approximately 1 micrometer.

As used herein, the terms “haze” and “clarity” may refer to optical phenomena associated with the transmission of light through a material, and may be attributed, for example, to the refraction of light within the material, e.g., due to secondary phases or porosity and/or the reflection of light from one or more surfaces of the material. As will be appreciated by those skilled in the art, haze may be associated with an amount of light that is subject to wide angle scattering (i.e., at an angle greater than 2.5° from normal) and a corresponding loss of transmissive contrast, whereas clarity may relate to an amount of light that is subject to narrow angle scattering (i.e., at an angle less than 2.5° from normal) and an attendant loss of optical sharpness or “see through quality.”

The present disclosure is generally directed to a GRIN LC lens having rapidly switchable operation, and more particularly to a system including a GRIN LC lens where a temperature of the liquid crystal material is monitored and controlled in a manner effective to tune the switching speed and/or refractive index of the liquid crystal. A heat source suitable for supplying heat to an LC layer may include an element that is indigenous to the system, such as a power supply, display element, or projector.

According to some embodiments, a GRIN LC lens may include a first optical substrate, a second optical substrate overlying and spaced away from at least a portion of the first optical substrate, a liquid crystal layer disposed between the first optical substrate and the second optical substrate, a first electrode layer disposed between the liquid crystal layer and the first optical substrate, and a second electrode layer disposed between the liquid crystal layer and the second optical substrate. The optical substrates may include high transmissivity and low haze glass substrates, for example.

The first and second optical substrates may be transparent and may define an optical aperture of a GRIN LC lens. As used herein, an “optical” substrate may be characterized by a transmissivity within the visible light spectrum of at least approximately 80%, e.g., 80, 90, 95, 97, or 99%, including ranges between any of the foregoing values, and less than approximately 10% bulk haze, e.g., 0, 1, 2, 4, 6, or 8% bulk haze, including ranges between any of the foregoing values.

The first and second electrode layers may each independently include one or more transparent conductive oxide (TCO) such as indium oxide, tin oxide, indium tin oxide (ITO), indium gallium zinc oxide (IGZO), and the like. In some examples, the electrodes (e.g., a first patterned electrode layer and a second patterned electrode layer) may have a thickness of approximately 1 nm to approximately 1000 nm, with an example thickness of approximately 10 nm to approximately 50 nm.

In some embodiments, a GRIN LC lens may further include a layer of a dielectric or insulating material located between each electrode and the LC layer. The presence or absence of a dielectric or insulating layer may be used to locally vary the magnitude or direction of an electric field applied to the liquid crystal, and correspondingly tune the LC layer's refractive index and/or birefringence. Example dielectric layers may include organic materials such as polyimide or inorganic materials such as silicon dioxide.

Liquid crystals may exhibit optical anisotropy or birefringence (Δn). Birefringence, the average refractive index, and the temperature gradients of refractive indices of various liquid crystals may be determined experimentally or empirically. When light propagates through an anisotropic medium such as a liquid crystal, it will be divided into two rays that travel through the material at different velocities. Thus, the material may be characterized by different refractive indices, the ordinary index (no), and extraordinary index (ne), where the difference is defined as birefringence or double refraction (Δn=ne−no). Depending on the values of neand no, birefringence can be positive or negative.

Example liquid crystal compositions include nematic liquid crystals, including ordinary nematic phase liquid crystals and twisted nematic phase (cholesteric) liquid crystals, although further classifications are contemplated. A liquid crystal is typically transparent or translucent and may be configured to cause the polarization of light waves that pass through the liquid to change. The extent of the change in polarization may be a function of the intensity of an applied electric field.

Liquid crystals may be used in electro-optic elements and devices (e.g., switchable lenses) due to their anisotropic refractive indices and the ability to reorient in response to an applied voltage. A liquid crystal layer can provide a variable lens element using a variety of different approaches to change the optical path length through a lens. Example LC lens platforms include a concave or convex solid LC lens, an LC diffractive zone plate, where lensing is induced when the LC is switched to create a phase grating, a Fresnel shaped LC lens, and an electrode patterned LC lens.

Some lens designs (such as a solid LC lens) may be characterized by slower switching times due to greater LC cell gaps. Faster times for switching the lens ON can generally be achieved by increasing the applied voltage. Additionally or alternatively, a dual frequency LC may be used where changing the frequency of the applied field changes the response of the LC.

Without wishing to be bound by theory, temperature may play a fundamental role in affecting the refractive indices of liquid crystals. As the temperature increases, ordinary (no) and extraordinary (ne) refractive indices of LCs typically behave differently from each other. Moreover, an increasing temperature may decrease the viscosity of a liquid crystal material, which may result in faster switching speeds in certain applications.

A temperature of the liquid crystal material may be monitored and controlled in a manner effective to tune its viscosity and hence the switching speed of the lens. With low voltage operation, economical fabrication, and relatively high switching speed, such lenses and lens systems may be applied in many modern optical and photonic devices.

In accordance with various embodiments, an optical device may include a lens having a liquid crystal layer disposed between a pair of optical substrates, a sensor configured to assess at least one attribute of the liquid crystal layer, a heat source, and a controller configured to mediate heat flow between the heat source and the liquid crystal layer based on a signal provided by the sensor. Example sensors may include thermometers and refractometers.

According to still further embodiments, an optical device may include a liquid crystal lens including (a) a first optical substrate, (b) a second optical substrate overlying and spaced away from the first optical substrate, (c) a liquid crystal (LC) layer disposed between the first and second optical substrate, (d) a first electrode structure between the LC layer and the first optical substrate, and (e) a second electrode structure between the LC layer and the second optical substrate, a sensor configured to assess at least one attribute of the liquid crystal layer, a heat source, and a controller configured to mediate heat flow between the heat source and the liquid crystal layer based on a signal provided by the sensor.

A controller may be configured to mediate the heat flow in an amount effective to increase a temperature of the liquid crystal layer by as much as approximately 20° C., while changing a refractive index of the liquid crystal layer by less than approximately 0.1. In particular embodiments, the controller may be configured to mediate heat flow in an amount effective to decrease a response time of the lens by at least approximately 1 ms.

Re-directed heat from the heat source may increase a temperature of the liquid crystal layer and correspondingly decrease its viscosity. For instance, a temperature of the liquid crystal layer may be increased to a value less than a clearing point (Tc) of the liquid crystal, and the viscosity of the liquid crystal layer may be decreased by at least 1%, e.g., 1, 2, 4, 10, 20, 30, or 40%, including ranges between any of the foregoing values.

A method may include forming an optical device having (a) a lens including a liquid crystal layer disposed between optical substrates, (b) a sensor configured to assess an attribute of the liquid crystal layer, (c) a heat source, and (d) a controller configured to mediate heat flow between the heat source and the liquid crystal layer based on a signal provided by the sensor, and directing heat from the heat source to the liquid crystal layer in an amount effective to change the attribute of the liquid crystal layer.

In accordance with various embodiments, a GRIN LC lens may be incorporated into an optical element such as AR eyeglasses or a VR headset. A temperature sensing element and a control element may be used to respectively detect a temperature of the liquid crystal material and adjust the flow of heat into or out of the LC layer. According to particular embodiments, other components within the optical element, such as power supplies or projectors, may be configured also as a heat source to heat the LC material.

The following will provide, with reference toFIGS.1-6, a detailed description of graded refractive index (GRIN) liquid crystal lenses. The discussion associated withFIGS.1-3relates to exemplary GRIN LC lens architectures using temperature control. The discussion associated withFIG.4includes a description of the influence of temperature on the refractive index and viscosity of a liquid crystal material. The discussion associated withFIGS.5and6relates to exemplary virtual reality and augmented reality devices that may include one or more GRIN LC lenses as disclosed herein.

Referring toFIG.1, shown is a schematic cross-sectional illustration of a portion of a GRIN LC lens. GRIN LC lens100includes a first optical substrate110, a second optical substrate170overlying and spaced away from at least a portion of the first optical substrate110, a liquid crystal layer140disposed between the first optical substrate and the second optical substrate, a patterned electrode layer120disposed between the liquid crystal layer140and the first optical substrate110, and a grounded electrode layer160disposed between the liquid crystal layer140and the second optical substrate170. Optional insulating layers130,150may be disposed between the patterned electrode120and the liquid crystal layer140and between the liquid crystal layer140and the grounded electrode160, respectively. Insulating layers130,150may include an optical quality polymer, such as polyimide, and may be configured to mediate the magnitude of the electric field applied to the liquid crystal layer.

Turning toFIG.2, shown is a cross-sectional view of a segment of an example GRIN LC lens200having an optical aperture202. The GRIN LC lens includes a pair of optical substrates212,214defining a liquid crystal-filled cell gap220located between the substrates. The substrates212,214may be formed from glass or another optically transparent and insulating material and may each have a thickness ranging from approximately 100 to 300 micrometers, e.g., 100, 150, 200, 250, or 300 micrometers, including ranges between any of the foregoing values.

In the illustrated embodiment, a liquid crystal layer224is disposed within the cell gap220, and an array of spacers230extends across the cell gap220and is configured to maintain a uniform spacing between the substrates212,214. Further, an electrode architecture may be configured to apply an electrical bias across the cell gap220to tune the orientation of liquid crystal molecules226within the liquid crystal layer224.

Each substrate212,214may be metallized with a respective electrode242,244, and a further electrode layer243may be disposed adjacent to the liquid crystal layer224. Electrode layers242,243may be patterned, e.g., to overlie discrete portions of the liquid crystal layer224between the spacers230. Example electrode materials include transparent conductive oxides, such as indium tin oxide (ITO).

The electrode layers243,244are each insulated from the liquid crystal layer224by a respective cell gap-facing dielectric layer253,254, such as a polyimide layer. Opposing ends of the spacers230may directly contact each of the dielectric layers. The GRIN LC lens200may additionally include a metallization architecture260including a bus line262disposed between insulating layers264,266that is electrically connected to selected regions of the electrodes242,243, e.g., through conductive vias268for providing an electrical voltage to selected regions of the liquid crystal layer224. Relative to comparative GRIN LC lenses, the presently-disclosed lens architectures may exhibit improved optical performance, including decreased bulk haze and parallax, as well as improved manufacturability and cost.

Referring toFIG.3, shown is a schematic cross-sectional view of a VR headset that includes a GRIN LC lens according to some embodiments. The VR headset300has a front rigid body305that includes an optical block330that provides altered image light to an exit pupil350. The exit pupil350is positioned proximate to the position of an eye345of a user when the user is wearing headset300. For purposes of illustration,FIG.3shows a cross section associated with a single eye345, but another optical block, separate from the optical block330, may provide altered image light to a second eye of the user.

In the illustrated configuration, the optical block330includes an electronic display element335and an optics module315. The electronic display element335may include one or more electronic display panels (not separately shown). The electronic display panels may be, e.g., flat panels, cylindrically curved panels, or spherically curved panels. The electronic display panels may include a panel mounting surface and a panel display surface. The panel mounting surface may couple to the front rigid body305. The panel display surface may be adapted to emit image light.

According to various embodiments, the electronic display element335may emit image light toward the optics module315, which may be configured to magnify the image light, and in some embodiments, also correct for one or more additional optical aberrations (e.g., astigmatism, etc.). During operation, the optics module315directs the image light to the exit pupil350for presentation to the user.

The optics module315may include one or more optical elements (not individually shown). An optical element may include an aperture, a Fresnel lens, a GRIN LC lens, a convex lens, a concave lens, a filter, or any other suitable optical element that is configured to affect the image light emitted from the electronic display element335. In particular embodiments, optics module315may include a GRIN LC lens such as GRIN LC lens100or GRIN LC lens200, for example. Moreover, the optics module315may include combinations of different optical elements.

The optics module315may be configured to correct one or more types of optical aberration. Examples of optical aberration include: two dimensional optical aberrations, three dimensional optical aberrations, or some combination thereof. Two dimensional optical aberrations are errors that occur in two dimensions. Example types of two dimensional optical aberrations include: barrel distortion, pincushion distortion, longitudinal chromatic aberration, transverse chromatic aberration, or any other type of two-dimensional optical aberration. Three dimensional optical aberrations are errors that occur in three dimensions. Example types of three dimensional optical aberrations include spherical aberration, comatic aberration, field curvature, astigmatism, or any other type of three-dimensional optical aberration.

The VR headset300may additionally include a battery360for providing power to one or more headset components. In addition to providing power, a battery may constitute a heat source. A controller/sensor370may be configured to assess a property or state of one or more of the headset components, including the performance or one or more properties of a GRIN LC lens. In some embodiments, example processes may be integrated with a real-time feedback loop that is configured to assess one or more attributes of a GRIN LC lens, such as the viscosity, refractive index, and/or temperature of the LC medium, and accordingly adjust one or more operational variables, including the temperature of a heat source or an amount of heat conveyed from the heat source to the liquid crystal layer.

When light propagates through anisotropic media such as liquid crystals, it will be divided into rays that travel through the material at different velocities. Hence, such a material may be characterized by different refractive indices, including an ordinary index (no) and an extraordinary index (ne), where their difference is the birefringence (Δn=ne−no).

The refractive indices of liquid crystals are fundamentally governed by temperature. With increasing temperature, for instance, ordinary (no) and extraordinary (ne) refractive indices of LCs behave differently yet typically converge proximate to the clearing point (Tc), which corresponds to the phase transformation from the liquid crystal phase to an isotropic liquid.

Referring toFIG.4, a semi-quantitative plot shows the effects of temperature on the refractive index as well as the dynamic viscosity of a representative liquid crystal. In certain embodiments, a method may include increasing the temperature of the LC layer within a GRIN LC lens without undergoing the liquid crystal-to-liquid phase transformation. Referring still toFIG.4, for such a process, an operational temperature range may be depicted by bar401, which corresponds to temperatures for which both the indices of refraction (noand ne) and the dynamic viscosity (μ) vary approximately linearly with a change in temperature.

As disclosed herein, the response time of a gradient-index (GRIN) liquid crystal (LC) lens may be improved by controlling the temperature of the liquid crystal medium. In some embodiments, the viscoelasticity and hence the switching speed of the liquid crystal may be thermally tuned during operation, which may beneficially impact performance of the lens. Additionally, the refractive index of the liquid crystal medium may be controlled.

A suitable source of heat to affect thermal control may include indigenous lens components such as a power supply (e.g., battery), display element, or projector. An example GRIN LC lens may include a temperature sensing element and a related control system for monitoring the temperature of the LC medium and mediating the ingress and output of heat flow.

Example Embodiments

Example 1: An optical device includes a lens having a liquid crystal layer disposed between a pair of optical substrates, a sensor configured to assess at least one attribute of the liquid crystal layer, a heat source, and a controller configured to mediate heat flow between the heat source and the liquid crystal layer based on a signal provided by the sensor.

Example 2: The optical device of Example 1, where the sensor includes a refractometer.

Example 3: The optical device of any of Examples 1 and 2, where the sensor includes a thermometer.

Example 4: The optical device of any of Examples 1-3, where the at least one attribute of the liquid crystal layer is selected from viscosity, refractive index, and temperature.

Example 5: The optical device of any of Examples 1-4, where the heat source is selected from a power supply, a display element, and a projector.

Example 6: The optical device of any of Examples 1-5, where the controller is configured to mediate the heat flow in an amount effective to increase a temperature of the liquid crystal layer by up to approximately 20° C. and change a refractive index of the liquid crystal layer by less than approximately 0.1.

Example 7: The optical device of any of Examples 1-6, where the controller is configured to mediate the heat flow in an amount effective to decrease a response time of the lens by at least approximately 1 ms.

Example 8: An optical device includes a liquid crystal lens including (a) a first optical substrate, (b) a second optical substrate overlying and spaced away from the first optical substrate, (c) a liquid crystal (LC) layer disposed between the first and second optical substrate, (d) a first electrode structure between the LC layer and the first optical substrate, and (e) a second electrode structure between the LC layer and the second optical substrate, a sensor configured to assess at least one attribute of the liquid crystal layer, a heat source, and a controller configured to mediate heat flow between the heat source and the liquid crystal layer based on a signal provided by the sensor.

Example 9: The optical device of Example 8, further including a first dielectric layer disposed between the first electrode structure and the liquid crystal layer and a second dielectric layer disposed between the second electrode structure and the liquid crystal layer.

Example 10: The optical device of any of Examples 8 and 9, where the liquid crystal lens includes an optical aperture having mutually orthogonal lateral dimensions each measuring at least approximately 10 mm.

Example 11: The optical device of any of Examples 8-10, where the first optical substrate and the second optical substrate each have a thickness independently ranging from approximately 100 to 300 micrometers.

Example 12: The optical device of any of Examples 8-11, where the first electrode structure and the second electrode structure each include an optically transparent conductive layer.

Example 13: The optical device of any of Examples 8-12, where the first electrode structure and the second electrode structure are each disposed within an optical aperture of the liquid crystal lens.

Example 14: A method includes forming an optical device having (a) a lens including a liquid crystal layer disposed between optical substrates, (b) a sensor configured to assess an attribute of the liquid crystal layer, (c) a heat source, and (d) a controller configured to mediate heat flow between the heat source and the liquid crystal layer based on a signal provided by the sensor, and directing heat from the heat source to the liquid crystal layer in an amount effective to change the attribute of the liquid crystal layer.

Example 15: The method of Example 14, where directing heat from the heat source to the liquid crystal layer increases a temperature of the liquid crystal layer by up to approximately 20° C.

Example 16: The method of any of Examples 14 and 15, where directing heat from the heat source to the liquid crystal layer increases a temperature of the liquid crystal layer to a value less than a clearing point (T a) of the liquid crystal.

Example 17: The method of any of Examples 14-16, where directing heat from the heat source to the liquid crystal layer decreases a viscosity of the liquid crystal layer by an amount of from approximately 1% to approximately 40%.

Example 18: The method of any of Examples 14-17, where directing heat from the heat source to the liquid crystal layer changes a refractive index of the liquid crystal layer by less than approximately 0.1.

Example 19: The method of any of Examples 14-18, where directing heat from the heat source to the liquid crystal layer decreases a response time of the lens by at least approximately 1 ms.

Example 20: The method of any of Examples 14-19, where directing heat from the heat source to the liquid crystal layer decreases a response time of the lens to less than approximately 100 ms.

Turning toFIG.5, augmented-reality system500may include an eyewear device502with a frame510configured to hold a left display device515(A) and a right display device515(B) in front of a user's eyes. Display devices515(A) and515(B) may act together or independently to present an image or series of images to a user. While augmented-reality system500includes two displays, embodiments of this disclosure may be implemented in augmented-reality systems with a single NED or more than two NEDs.

In some embodiments, augmented-reality system500may include one or more sensors, such as sensor540. Sensor540may generate measurement signals in response to motion of augmented-reality system500and may be located on substantially any portion of frame510. Sensor540may represent one or more of a variety of different sensing mechanisms, such as 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 system500may or may not include sensor540or may include more than one sensor. In embodiments in which sensor540includes an IMU, the IMU may generate calibration data based on measurement signals from sensor540. Examples of sensor540may 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.

In some examples, augmented-reality system500may also include a microphone array with a plurality of acoustic transducers520(A)-520(J), referred to collectively as acoustic transducers520. Acoustic transducers520may represent transducers that detect air pressure variations induced by sound waves. Each acoustic transducer520may be configured to detect sound and convert the detected sound into an electronic format (e.g., an analog or digital format). The microphone array inFIG.5may include, for example, ten acoustic transducers:520(A) and520(B), which may be designed to be placed inside a corresponding ear of the user, acoustic transducers520(C),520(D),520(E),520(F),520(G), and520(H), which may be positioned at various locations on frame510, and/or acoustic transducers520(1) and520(J), which may be positioned on a corresponding neckband505.

In some embodiments, one or more of acoustic transducers520(A)-(J) may be used as output transducers (e.g., speakers). For example, acoustic transducers520(A) and/or520(B) may be earbuds or any other suitable type of headphone or speaker.

The configuration of acoustic transducers520of the microphone array may vary. While augmented-reality system500is shown inFIG.5as having ten acoustic transducers520, the number of acoustic transducers520may be greater or less than ten. In some embodiments, using higher numbers of acoustic transducers520may 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 transducers520may decrease the computing power required by an associated controller550to process the collected audio information. In addition, the position of each acoustic transducer520of the microphone array may vary. For example, the position of an acoustic transducer520may include a defined position on the user, a defined coordinate on frame510, an orientation associated with each acoustic transducer520, or some combination thereof.

Acoustic transducers520(A) and520(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 transducers520on or surrounding the ear in addition to acoustic transducers520inside the ear canal. Having an acoustic transducer520positioned 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 transducers520on either side of a user's head (e.g., as binaural microphones), augmented-reality device500may simulate binaural hearing and capture a 3D stereo sound field around about a user's head. In some embodiments, acoustic transducers520(A) and520(B) may be connected to augmented-reality system500via a wired connection530, and in other embodiments acoustic transducers520(A) and520(B) may be connected to augmented-reality system500via a wireless connection (e.g., a BLUETOOTH connection). In still other embodiments, acoustic transducers520(A) and520(B) may not be used at all in conjunction with augmented-reality system500.

Acoustic transducers520on frame510may be positioned in a variety of different ways, including along the length of the temples, across the bridge, above or below display devices515(A) and515(B), or some combination thereof. Acoustic transducers520may also 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 system500. In some embodiments, an optimization process may be performed during manufacturing of augmented-reality system500to determine relative positioning of each acoustic transducer520in the microphone array.

In some examples, augmented-reality system500may include or be connected to an external device (e.g., a paired device), such as neckband505. Neckband505generally represents any type or form of paired device. Thus, the following discussion of neckband505may 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.

As shown, neckband505may be coupled to eyewear device502via 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 device502and neckband505may operate independently without any wired or wireless connection between them. WhileFIG.5illustrates the components of eyewear device502and neckband505in example locations on eyewear device502and neckband505, the components may be located elsewhere and/or distributed differently on eyewear device502and/or neckband505. In some embodiments, the components of eyewear device502and neckband505may be located on one or more additional peripheral devices paired with eyewear device502, neckband505, or some combination thereof.

Pairing external devices, such as neckband505, 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 system500may 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, neckband505may allow components that would otherwise be included on an eyewear device to be included in neckband505since users may tolerate a heavier weight load on their shoulders than they would tolerate on their heads. Neckband505may also have a larger surface area over which to diffuse and disperse heat to the ambient environment. Thus, neckband505may allow for greater battery and computation capacity than might otherwise have been possible on a stand-alone eyewear device. Since weight carried in neckband505may be less invasive to a user than weight carried in eyewear device502, 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.

Neckband505may be communicatively coupled with eyewear device502and/or to other devices. These other devices may provide certain functions (e.g., tracking, localizing, depth mapping, processing, storage, etc.) to augmented-reality system500. In the embodiment ofFIG.5, neckband505may include two acoustic transducers (e.g.,520(1) and520(J)) that are part of the microphone array (or potentially form their own microphone subarray). Neckband505may also include a controller525and a power source535.

Acoustic transducers520(1) and520(J) of neckband505may be configured to detect sound and convert the detected sound into an electronic format (analog or digital). In the embodiment ofFIG.5, acoustic transducers520(1) and520(J) may be positioned on neckband505, thereby increasing the distance between the neckband acoustic transducers520(1) and520(J) and other acoustic transducers520positioned on eyewear device502. In some cases, increasing the distance between acoustic transducers520of the microphone array may improve the accuracy of beamforming performed via the microphone array. For example, if a sound is detected by acoustic transducers520(C) and520(D) and the distance between acoustic transducers520(C) and520(D) is greater than, e.g., the distance between acoustic transducers520(D) and520(E), the determined source location of the detected sound may be more accurate than if the sound had been detected by acoustic transducers520(D) and520(E).

Controller525of neckband505may process information generated by the sensors on neckband505and/or augmented-reality system500. For example, controller525may process information from the microphone array that describes sounds detected by the microphone array. For each detected sound, controller525may 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, controller525may populate an audio data set with the information. In embodiments in which augmented-reality system500includes an inertial measurement unit, controller525may compute all inertial and spatial calculations from the IMU located on eyewear device502. A connector may convey information between augmented-reality system500and neckband505and between augmented-reality system500and controller525. 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 system500to neckband505may reduce weight and heat in eyewear device502, making it more comfortable to the user.

Power source535in neckband505may provide power to eyewear device502and/or to neckband505. Power source535may 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 source535may be a wired power source. Including power source535on neckband505instead of on eyewear device502may help better distribute the weight and heat generated by power source535.

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 is a head-worn display system, such as virtual-reality system600inFIG.6, that mostly or completely covers a user's field of view. Virtual-reality system600may include a front rigid body602and a band604shaped to fit around a user's head. Virtual-reality system600may also include output audio transducers606(A) and606(B). Furthermore, while not shown inFIG.6, front rigid body602may 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.

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.

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.

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.

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 liquid crystal material that comprises a cyanobiphenyl compound include embodiments where a liquid crystal material consists essentially of a cyanobiphenyl compound and embodiments where a liquid crystal material consists of a cyanobiphenyl compound.