阅读说明：本技术 光学透明的致动器 (Optically transparent actuator ) 是由 凯瑟琳·玛丽·史密斯 斯宾塞·艾伦·威尔斯 安德鲁·约翰·欧德柯克 于 2020-05-20 设计创作，主要内容包括：可以被并入到透明光学元件中的电活性陶瓷具有小于200nm的平均晶粒尺寸、至少99％的相对密度和在可见光谱内的至少50％的透射率,同时保持至少20pC/N的d-(33)值。电活性陶瓷层的包括透射率、雾度和净度的光学性质在光学元件通过电压施加的致动期间可以基本上不变。(The electroactive ceramics that can be incorporated into the transparent optical element have an average grain size of less than 200nm, a relative density of at least 99%, and a transmission of at least 50% in the visible spectrum while maintaining a d of at least 20pC/N 33 The value is obtained. The optical properties of the electroactive ceramic layer, including transmittance, haze, and clarity, may be substantially unchanged during actuation of the optical element by application of a voltage.)

1. An electroactive ceramic that lacks crystal inversion centers in its unit cells, and further comprising:

an average grain size of less than about 200 nm;

a relative density of at least 99%;

a transmission of at least 50% in the visible spectrum.

2. The electroactive ceramic of claim 1, further comprising a haze of less than 10%.

3. The electroactive ceramic of claim 1, wherein the transmittance in the visible spectrum is at least 75%.

4. The electroactive ceramic of claim 1, comprising at least one of the following when exposed to an applied field of from about-2 MV/m to about 2MV/m, or when exposed to an applied field equal to at least 50% of its breakdown strength, or when exposed to an applied field equal to at least 50% of its coercive field:

a change in transmission of less than 50%;

a change in haze of less than 50%, an

Less than 50% change in cleanliness.

5. The electroactive ceramic of claim 1, further comprising at least one compound selected from the group consisting of: lead titanate, lead zirconate titanate, lead magnesium niobate, lead zincate niobate, lead indium niobate, lead magnesium tantalate, lead indium tantalate, barium titanate, lithium niobate, potassium sodium niobate, bismuth sodium titanate, and bismuth ferrite.

6. The electroactive ceramic of claim 1, further comprising a solid solution of two or more of: lead titanate, lead zirconate titanate, lead magnesium niobate, lead zincate niobate, lead indium niobate, lead magnesium tantalate, lead indium tantalate, barium titanate, lithium niobate, potassium sodium niobate, bismuth sodium titanate, and bismuth ferrite.

7. The electroactive ceramic of claim 1, further comprising at least one dopant selected from the group consisting of: niobium, potassium, sodium, calcium, gallium, indium, bismuth, aluminum, strontium, barium, samarium, dysprosium, magnesium, iron, tantalum, yttrium, lanthanum, europium, neodymium, scandium, and erbium.

8. The electroactive ceramic of claim 1, further comprising an RMS surface roughness of less than about 50 nm.

9. The electroactive ceramic of claim 1, consisting essentially of a perovskite ceramic.

10. An optical element, comprising:

a primary electrode;

a secondary electrode overlapping at least a portion of the primary electrode; and

an electroactive layer disposed between and abutting the primary electrode and the secondary electrode, wherein the electroactive layer comprises:

an average grain size of less than 200 nm;

a relative density of at least 99%; and

a transmission of at least 50% in the visible spectrum.

11. The optical element of claim 10, wherein the electroactive layer comprises an RMS surface roughness of less than about 50 nm.

12. The optical element of claim 10, wherein the electroactive layer comprises a perovskite ceramic; and/or

Wherein the electroactive layer comprises less than a 50% change in each of transparency, haze, and clarity when a voltage is applied to the primary electrode.

13. A head-mounted display comprising the optical element of claim 10.

14. A method, comprising:

forming a powder mixture; and

sintering the powder mixture to form an electroactive ceramic, wherein the electroactive ceramic comprises:

an average grain size of less than 200nm,

a relative density of at least 99%, and

a transmission of at least 50% in the visible spectrum.

15. The method of claim 14, wherein forming the powder mixture comprises:

forming a partial powder mixture, wherein the partial powder mixture is lead-free;

calcining the partial powder mixture; and

adding lead oxide to the calcined portion of the powder mixture to form the powder mixture; and/or

Wherein the method further comprises forming a transparent electrode on the electroactive ceramic.

SUMMARY

According to one aspect of the present disclosure, there is provided an electroactive ceramic that lacks crystal inversion centers (crystallitic centers of inversion) in its unit cell, and further comprises an average grain size of less than about 200nm, a relative density of at least 99%, and a transmittance of at least 50% in the visible spectrum.

In some embodiments, the electroactive ceramic may further comprise a haze of less than 10%. The transmission in the visible spectrum may be at least 75%. When exposed to an applied field from about-2 MV/m to about 2MV/m, the electroactive ceramic may comprise at least one of: a change in transmission of less than 50%, a change in haze of less than 50%, and a change in clarity (clarity) of less than 50%. When exposed to an applied field from about-2 MV/m to about 2MV/m, the electroactive ceramic may comprise: a change in transmission of less than 50%, a change in haze of less than 50%, and a change in clarity of less than 50%. The electroactive ceramic may comprise at least one of the following when exposed to an applied field equal to at least 50% of its breakdown strength: a change in transmission of less than 50%, a change in haze of less than 50%, and a change in clarity of less than 50%. The electroactive ceramic may comprise at least one of the following when exposed to an applied field equal to at least 50% of its coercive field: a change in transmission of less than 50%, a change in haze of less than 50%, and a change in clarity of less than 50%.

In some embodiments, the electroactive ceramic may further comprise at least one compound selected from the group consisting of: lead titanate, lead zirconate titanate, lead magnesium niobate, lead zincate niobate, lead indium niobate, lead magnesium tantalate, lead indium tantalate, barium titanate, lithium niobate, potassium sodium niobate, bismuth sodium titanate, and bismuth ferrite. The electroactive ceramic may also include a solid solution of two or more of the following: lead titanate, lead zirconate titanate, lead magnesium niobate, lead zincate niobate, lead indium niobate, lead magnesium tantalate, lead indium tantalate, barium titanate, lithium niobate, potassium sodium niobate, bismuth sodium titanate, and bismuth ferrite. The electroactive ceramic may further comprise at least one dopant selected from the group consisting of: niobium, potassium, sodium, calcium, gallium, indium, bismuth, aluminum, strontium, barium, samarium, dysprosium, magnesium, iron, tantalum, yttrium, lanthanum, europium, neodymium, scandium, and erbium.

In some embodiments, the electroactive ceramic may further comprise an RMS surface roughness of less than about 50 nm. The electroactive ceramic may also consist essentially of a perovskite ceramic.

According to a second aspect of the present disclosure, there is provided an optical element comprising: the device includes a primary electrode, a secondary electrode overlapping at least a portion of the primary electrode, and an electroactive layer disposed between and abutting the primary and secondary electrodes. The electroactive layer includes: an average grain size of less than 200nm, a relative density of at least 99%, and a transmittance of at least 50% in the visible spectrum.

In some embodiments, the electroactive layer comprises an RMS surface roughness of less than about 50 nm. The electroactive layer may comprise a perovskite ceramic. The electroactive layer can include a change in each of transparency, haze, and clarity of less than 50% when a voltage is applied to the primary electrode.

According to a third aspect of the present disclosure, there is provided a head mounted display comprising the optical element of the second aspect.

According to a fourth aspect of the present disclosure, there is provided a method comprising: forming a powder mixture and sintering the powder mixture to form the electroactive ceramic. The electroactive ceramic includes: an average grain size of less than 200nm, a relative density of at least 99%, and a transmittance of at least 50% in the visible spectrum.

In some embodiments, forming the powder mixture may include: forming a portion of the powder mixture, wherein the portion of the powder mixture is lead-free; the portion of the powder mixture is calcined and lead oxide is added to the calcined portion of the powder mixture to form a powder mixture. The method may further include forming a transparent electrode on the electroactive ceramic.

Brief Description of Drawings

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.

Fig. 1 is a schematic diagram of an exemplary optically transparent bimorph actuator (bimorph activator), according to some embodiments.

Fig. 2 illustrates optical scattering from discrete domains (discrete domains) located within an exemplary electroactive ceramic, according to some embodiments.

Fig. 3 is a graph illustrating the effect of particle size of an exemplary electroactive ceramic layer on reflection of blue incident light, according to some embodiments.

Fig. 4 is a graph illustrating the effect of particle size of an exemplary electroactive ceramic layer on scattering of blue incident light, according to some embodiments.

Fig. 5 is a graph of haze versus particle size for an exemplary electroactive ceramic layer exposed to incident blue light, according to some embodiments.

Fig. 6 is a graph illustrating the effect of particle size of an exemplary electroactive ceramic layer on the reflection of red incident light, according to some embodiments.

Fig. 7 is a graph illustrating the effect of particle size of an exemplary electroactive ceramic layer on scattering of red incident light, according to some embodiments.

Fig. 8 is a graph of haze versus particle size for exemplary electroactive ceramic layers exposed to incident red light, according to some embodiments.

Fig. 9 is a graph illustrating the effect of aperture size of an exemplary electroactive ceramic layer on reflection of blue incident light, according to some embodiments.

Fig. 10 is an illustration of an exemplary artificial reality headband that can be used in connection with embodiments of the present disclosure.

Fig. 11 is an illustration of exemplary augmented reality glasses that can be used in conjunction with embodiments of the present disclosure.

Fig. 12 is an illustration of an example virtual reality headset that may be used in conjunction with embodiments of the present disclosure.

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 disclosure covers all modifications, equivalents, and alternatives falling within the scope of the appended claims.

Detailed description of illustrative embodiments

Ceramic materials and other dielectric materials can be incorporated into a variety of optical and electro-optical device architectures, including active and passive optical devices and electroactive devices. Electroactive materials, including piezoceramic materials and electrostrictive ceramic materials, can change their shape under the influence of an electric field. Electroactive materials have been investigated for use in a variety of technologies, including actuation, sensing, and/or energy harvesting. Lightweight and conformable electroactive ceramics can be incorporated into wearable devices, such as haptic devices, and are attractive candidates for emerging technologies, including virtual reality/augmented reality devices, where a comfortable, adjustable form factor is desired.

Virtual reality and augmented reality glasses devices (eyewear devices) or head-mounted devices may enable a user to experience events such as interactions with a person in a computer-generated three-dimensional world simulation or viewing data superimposed on a real-world view. The virtual reality/augmented reality eyewear devices and head-mounted devices may also be used for purposes other than entertainment. 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.

These and other applications may utilize one or more characteristics of an electro-active material, including the piezoelectric effect, to produce lateral deformation (e.g., lateral expansion or contraction) in response to compression between conductive electrodes. Exemplary virtual reality/augmented reality components that include an electroactive layer may include deformable optics (deformable optics), such as mirrors, lenses, or adaptive optics (adaptive optics). Deformation of the electroactive ceramic may be used to actuate an optical element, such as a lens system, in an optical assembly.

While many thin layers of electroactive piezoelectric ceramics may be inherently transparent, with respect to their incorporation into optical components or optical devices, variations in refractive index between such materials and adjacent layers, such as air, may result in optical scattering and a corresponding degradation in optical quality or performance. In a similar manner (in a related field), the ferroelectric material can be spontaneously polarized (polarize) in different directions, forming domains and associated birefringent boundaries (birefringent boundaries) that scatter light. Additional sources of optical scattering include porosity (porosity), domain walls, and grain boundaries. Thus, despite recent developments, it would be advantageous to provide ceramic or other dielectric materials with improved actuation characteristics, including controllable and robust deformation response in optically transparent packaging.

As will be described in greater detail below, the present disclosure relates to actuatable and transparent optical elements and methods for forming such optical elements. The optical element may comprise a layer of electroactive material sandwiched between conductive electrodes. The electroactive layer may be capacitively actuated to deform the optical element and thereby change its optical properties. By configuring the electroactive ceramic to have small domains and/or grain sizes, the probability of scattering events may be reduced, thereby improving optical quality. In certain embodiments, the optical element may be located within a transparent aperture of an optical device, such as a liquid lens, although the present disclosure is not particularly limited and may be applied in a broader context. For example, the optical element may be incorporated into an active grating, a tunable lens, an adaptive optical element (adaptive optical element), or adaptive optics, and the like. According to various embodiments, the optical element may be optically transparent.

As used herein, a "transparent" or "optically transparent" material or element can have, for example, a transmission of at least about 50%, such as about 50%, 60%, 70%, 80%, 90%, 95%, 97%, 98%, 99%, or 99.5% in the visible spectrum, including ranges between any of the foregoing values; and a haze of less than about 80%, such as a haze of about 1%, 2%, 5%, 10%, 20%, 30%, 40%, 50%, 60%, or 70%, including ranges between any of the foregoing values. According to some embodiments, a "fully transparent" material or element may have a transmission (i.e., optical transmission) of at least about 75% within the visible spectrum, such as a transmission of about 75%, 80%, 90%, 95%, 97%, 98%, 99%, or 99.5%, including ranges between any of the foregoing values; and a haze of less than about 10%, such as a haze of about 0%, 1%, 2%, 4%, 6%, or 8%, including ranges between any of the foregoing values. Transparent materials and fully transparent materials will generally exhibit very low light absorption and minimal optical scattering.

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 due to, for example, refraction of light within the material, for example, due to a secondary phase or porosity, and/or reflection of light from one or more surfaces of the material. As will be understood by those skilled in the art, haze may be associated with the amount of light that undergoes wide angle scattering (i.e., at an angle greater than 2.5 ° from normal) and the corresponding loss of transmission contrast (transmissive contrast), while net degree may be associated with the amount of light that undergoes narrow angle scattering (i.e., at an angle less than 2.5 ° from normal) and the accompanying loss of optical sharpness or "quality of penetration".

Referring to fig. 1, according to various embodiments, an optical element 100 may include a primary electrode 111, a secondary electrode 112 overlapping at least a portion of the primary electrode, and a first electroactive layer 121 disposed between the primary electrode 111 and the secondary electrode 112 and adjacent to the primary electrode 111 and the secondary electrode 112, wherein the optical element 100 is optically transparent. In the illustrated embodiment, the disclosed bimorph architecture can further include a second electroactive layer 122 disposed on the secondary electrode 112, and a third electrode 113 disposed on the second electroactive layer 122, i.e., opposite and overlapping at least a portion of the secondary electrode 112.

As used herein, in some examples, an "electroactive material" may refer to a material that exhibits a change in size or shape when stimulated by an electric field. In the presence of an electrostatic field (E-field), electroactive materials can deform (e.g., compress, elongate, bend, etc.) depending on the magnitude and direction of the applied field. Such field generation may be achieved, for example, by placing an electroactive material between two electrodes, a primary electrode and a secondary electrode, each at a different electrical potential. As the potential difference (i.e., voltage difference) between the electrodes increases (e.g., increases from zero potential), the amount of distortion may also increase, primarily along the electric field lines. This deformation may reach saturation when a certain electrostatic field strength has been reached. In the absence of an electrostatic field, the electroactive material may be in its relaxed state, undergo no induced deformation, or equivalently, no internal or external induced strain.

In some cases, the physical origin of the compressive properties of an electroactive material, which is the force generated between opposing charges, in the presence of an electrostatic field (E-field), is the physical origin of Maxwell stress (Maxwell stress), which is mathematically expressed in Maxwell stress tensor. The level of strain or deformation induced by a given E-field depends on the square of the E-field strength, as well as the dielectric constant and elastic compliance (elastic compliance) of the electroactive material. In this case, compliance is the change in strain with respect to stress, or similarly, more practically, displacement with respect to force. In some embodiments, the electroactive layer may be pre-strained (or pre-stressed) to change the stiffness of the optical element, and thereby change its actuation characteristics.

In some embodiments, the physical origin of electromechanical strain (electromechanical strain) of an electroactive material in the presence of an E-field, i.e., the physical origin of electrically induced strain in crystalline materials lacking inversion symmetry, results from the inverse piezoelectric effect, which is mathematically expressed in terms of a piezoelectric tensor.

The electroactive layers can include, for example, a ceramic material, and each electrode can include one or more layers of any suitable conductive material, such as a transparent conductive oxide (e.g., a TCO such as ITO), graphene, and the like. In some embodiments, the ceramic layer may comprise a transparent polycrystalline ceramic or a transparent single crystal ceramic. In some embodiments, a polycrystalline ceramic lacking crystal inversion centers in its unit cells may have an average grain size of less than 200nm and a relative density of at least 99%. Such ceramics may exhibit a piezoelectric coefficient (d) of at least 20pC/N when exposed to an applied field of from about-2 MV/m to about 2MV/m₃₃)。

Exemplary electroactive ceramics may include one or more electroactive ceramics, piezoelectric ceramics, antiferroelectric ceramics, relaxor ceramics (ferroelectric ceramics) or ferroelectric ceramics, such as perovskite ceramics, including lead titanate, lead zirconate titanate, lead magnesium niobate, lead zinc niobate, lead indium niobate, lead magnesium tantalate, lead indium tantalate, barium titanate, lithium niobate, potassium sodium niobate, sodium bismuth titanate, and bismuth ferrite, and solid solutions or mixtures thereof. Exemplary non-perovskite piezoelectric ceramics include quartz and gallium nitride.

In certain embodiments, the electroactive ceramics disclosed herein may be perovskite ceramics and may be substantially free of secondary phases, i.e., may comprise less than about 2% by volume of any secondary phase, including porosity, e.g., less than 2%, less than 1%, less than 0.5%, less than 0.2%, or less than 0.1%, including ranges between any of the foregoing values. In certain embodiments, the disclosed electroactive ceramics may be birefringent, which may be due to the material comprising different domains or regions having multiple varying polarizations of different refractive indices.

Ceramic electroactive materials, such as single crystal piezoelectric materials, can be formed, for example, using hydrothermal processing or by the czochralski method to produce oriented ingots (oriented ingot) that can be sliced along specified crystal planes to produce wafers having desired crystal orientations. Additional methods for forming single crystals include float zone (float zone), Bridgman, Stockbarger, chemical vapor deposition, physical vapor transport (physical vapor transport), solvothermal (solvothermal) techniques, and the like. The wafer may be thinned, for example, via grinding or lapping and/or polishing, and the transparent electrode may be formed directly on the wafer, for example, using a chemical vapor deposition or physical vapor deposition process such as sputtering or evaporation.

In addition to the foregoing, the polycrystalline piezoelectric material may be formed, for example, by powder processing. The densely packed network of high purity, ultra-fine polycrystalline particles may be highly transparent and may be more mechanically robust in thin layers than their single crystal counterparts. For example, have>Optical grade PLZT of 99.9% purity can use sub-micron (e.g.,<2 μm) of particles. In this regard, by using La²⁺And/or Ba²⁺Doping of the vacancies in the A and B positions with Pb²⁺Can be used to increase the transparency of perovskite ceramics such as PZN-PT, PZT and PMN-PT.

According to some embodiments, the ultrafine particle precursors may be manufactured by wet chemical methods, such as chemical co-precipitation, sol-gel, and gel combustion. Green bodies may be formed using tape casting, slip casting, or gel casting. For example, high pressure and high temperature sintering by techniques such as conventional sintering, cold sintering, hot pressing, High Pressure (HP) and hot isostatic pressing (hot isostatic pressing), spark plasma sintering (spark plasma sintering), rapid sintering (flash sintering), two-stage sintering, and microwave sintering may be used to improve the ceramic particle packing density. As will be appreciated by those skilled in the art, more than one of the foregoing techniques may be used in combination, for example, to achieve initial densification by one process and final densification by a second process while minimizing grain growth during sintering. The sintered ceramic may be cut to the desired final shape and thinning by grinding and/or polishing may be used to reduce the surface roughness to achieve a thin, highly optically transparent layer suitable for high displacement actuation (high displacement actuation). The electroactive ceramic may be polarized to achieve the desired dipole alignment.

As will be appreciated, the methods and systems shown and described herein may be used to form electroactive devices having single or multiple layers of electroactive material (e.g., several layers to tens, hundreds, or thousands of stacked layers). For example, an electroactive device can include a stack of from two electroactive elements and corresponding electrodes to thousands of electroactive elements (e.g., about 5, about 10, about 20, about 30, about 40, about 50, about 100, about 200, about 300, about 400, about 500, about 600, about 700, about 800, about 900, about 1000, about 2000, or greater than about 2000 electroactive elements, including ranges between any of the foregoing values). A high displacement output can be achieved using a large number of layers, where the overall device displacement can be expressed as the sum of the displacements for each layer. Such complex arrangements enable compression, extension, twisting and/or bending when operating the electroactive device.

In some embodiments, the optical element may comprise a pair of electrodes that allow generation of an electrostatic field that forces contraction of the electroactive layer. In some embodiments, "electrode" as used herein may refer to a conductive material, which may be in the form of a film or layer. The electrodes may comprise a relatively thin conductive metal or metal alloy and may have non-compliant (non-compliant) or compliant (compliant) properties.

The electrodes may include one or more conductive materials, such as metals, semiconductors (such as doped semiconductors), carbon nanotubes, graphene oxide, fluorinated graphene, hydrogenated graphene, other graphene derivatives, carbon black, transparent conductive oxides (TCOs, e.g., Indium Tin Oxide (ITO), zinc oxide (ZnO), etc.), or other conductive materials. In some embodiments, the electrodes may include metals such as aluminum, gold, silver, platinum, palladium, nickel, tantalum, tin, copper, indium, gallium, zinc, alloys thereof, and the like. Additional exemplary transparent conductive oxides include, but are not limited to, aluminum-doped zinc oxide, fluorine-doped tin oxide, indium-doped cadmium oxide, indium-zinc oxide, indium-gallium-tin oxide, indium-gallium-zinc-tin oxide, strontium vanadate, strontium niobate, strontium molybdate, calcium molybdate, and indium-zinc-tin oxide.

In some embodiments, the electrodes or electrode layers may be self-healing, such that damage due to local shorting of the circuit may be isolated. Suitable self-healing electrodes may include thin films of materials that irreversibly deform or oxidize upon joule heating, such as, for example, graphene.

In some embodiments, the primary electrode may overlap with at least a portion of the secondary electrode (e.g., overlap in a parallel direction). The primary and secondary electrodes may be substantially parallel and spaced apart, and separated by a layer of electroactive material. The third electrode may overlap with at least a portion of the primary or secondary electrode.

The optical element can include a first electroactive layer, which can be disposed between a first pair of electrodes (e.g., a primary electrode and a secondary electrode). The second optical element, if used, may comprise a second electroactive layer and may be disposed between a second pair of electrodes. In some embodiments, there may be electrodes that are common to both the first pair of electrodes and the second pair of electrodes.

In some embodiments, one or more electrodes may optionally be electrically interconnected with a common electrode, for example, through a contact layer or a schoopage layer. In some embodiments, the optical element may have a first common electrode connected to the first more than one electrode and a second common electrode connected to the second more than one electrode. In some embodiments, the electrodes (e.g., one of the first more than one electrode and one of the second more than one electrode) may be electrically insulated from each other using an insulator, such as a dielectric layer. The insulator may comprise a material that is not significantly conductive, and may comprise a dielectric material, such as, for example, an acrylate or silicone polymer.

In some embodiments, the common electrode may be electrically coupled (e.g., electrically contacted at an interface having a low contact resistance) to one or more other electrodes, such as a secondary electrode and a third electrode located on either side of the primary electrode.

In some embodiments, the electrodes may be flexible and/or elastic (resilient) and may, for example, elastically stretch when the optical element undergoes deformation. In this regard, the electrodes may include one or more Transparent Conductive Oxides (TCOs), such as indium oxide, tin oxide, Indium Tin Oxide (ITO), Indium Gallium Zinc Oxide (IGZO), and the like, graphene, carbon nanotubes, silver nanowires, and the like. In other embodiments, a relatively rigid electrode (e.g., an electrode comprising a metal such as aluminum) may be used.

In some embodiments, the electrodes (e.g., primary and secondary electrodes) may have a thickness of about 0.35nm to about 1000nm, e.g., a thickness of about 0.35nm, 0.5nm, 1nm, 2nm, 5nm, 10nm, 20nm, 50nm, 100nm, 200nm, 500nm, or 1000nm, including ranges between any of the foregoing values, with exemplary thicknesses being about 10nm to about 50 nm. In some embodiments, the common electrode may have a slanted shape, or may be a more complex shape (e.g., patterned or free-form). In some embodiments, the common electrode may be shaped to allow compression and expansion of the optical element or optical device during operation.

In certain embodiments, the electrode may have an optical transmittance of at least about 50%, for example, an optical transmittance of about 50%, about 60%, about 70%, about 80%, about 90%, about 95%, about 97%, about 98%, about 99%, or about 99.5%, including ranges between any of the foregoing values.

In some embodiments, the electrodes described herein (e.g., primary electrodes, secondary electrodes, or any other electrode including any common electrode) may be fabricated using any suitable process. For example, the electrode may be fabricated using Physical Vapor Deposition (PVD), Chemical Vapor Deposition (CVD), Atomic Layer Deposition (ALD), evaporation, spray coating, spin coating, dip coating, screen printing, gravure printing, inkjet printing, aerosol jet printing (aerosol jet printing), knife coating (sector blanking), and the like. In further aspects, the electrodes can be fabricated using thermal evaporators, sputtering systems, stamping, and similar processes.

In some embodiments, the electroactive material layer may be deposited directly onto the electrode. In some embodiments, the electrodes may be deposited directly onto the electroactive material. In some embodiments, the electrodes may be prefabricated and attached to the electroactive material. In some embodiments, the electrodes may be deposited on a substrate, such as a glass substrate or a flexible polymer film. In some embodiments, the electroactive material layer may directly abut the electrode. In some embodiments, an insulating layer, such as a dielectric layer, may be present between the electroactive material layer and the electrode.

The electrodes may be used to affect large scale deformation, i.e. via full area coverage, or the electrodes may be patterned to provide a spatially localized stress/strain profile. In particular embodiments, the deformable optical element and the electroactive layer may be co-integrated, whereby the deformable optical element itself may be actuatable. In addition, various methods of forming optical elements are disclosed, including solution-based deposition techniques and solid-state deposition techniques.

According to certain embodiments, optical elements including electroactive layers disposed between transparent electrodes may be incorporated into a variety of device architectures where capacitive actuation and concomitant strain (i.e., lateral expansion and compression in the direction of an applied electric field) achieved in the electroactive layers may induce deformation in one or more adjacent active layers within the device and thus alter the optical properties of the active layers. The transverse deformation may be substantially one-dimensional, in the case of an anchored membrane, or two-dimensional. In some embodiments, engineered deformation of two or more electroactive layers alternately placed in expansion and compression by oppositely applied voltages may be used to induce bending or curvature changes in a device stack (device stack), which may be used to provide optical tuning, such as focus or aberration control.

In some applications, an optical element used in conjunction with the principles disclosed herein may include a primary electrode, a secondary electrode, and an electroactive layer disposed between the primary and secondary electrodes. According to various embodiments, the transparent electroactive layer may be formed by microstructural engineering.

In some embodiments, there may be one or more additional electrodes, and the common electrode may be electrically coupled to one or more of the additional electrodes. For example, the optical elements may be arranged in a stacked configuration, wherein a first common electrode is coupled to a first more than one electrode and a second common electrode is electrically connected to a second more than one electrode. The first more than one electrode and the second more than one electrode may alternate in a stacked configuration such that each optical element is located between one of the first more than one electrode and one of the second more than one electrode.

In some embodiments, the optical element (i.e., the electroactive ceramic disposed between and abutting one or more layers of the respective electrodes) can have a thickness of about 10nm to about 300 μm (e.g., about 10nm, about 20nm, about 30nm, about 40nm, about 50nm, about 60nm, about 70nm, about 80nm, about 90nm, about 100nm, about 200nm, about 300nm, about 400nm, about 500nm, about 600nm, about 700nm, about 800nm, about 900nm, about 1 μm, about 2 μm, about 3 μm, about 4 μm, about 5 μm, about 6 μm, about 7 μm, about 8 μm, about 9 μm, about 10 μm, about 20 μm, about 50 μm, about 100 μm, about 200 μm, or about 300 μm), with an exemplary thickness of about 200nm to about 500 nm.

Application of a voltage between the electrodes may result in compression or expansion of the intervening electroactive layer in the direction of the applied electric field, and associated expansion or contraction of the electroactive layer in one or more lateral dimensions. In some embodiments, the applied voltage (e.g., to the primary and/or secondary electrodes) can produce a strain in the electroactive element of at least about 0.02% in at least one direction (e.g., the x, y, or z direction relative to a defined coordinate system) (e.g., the amount of deformation in the direction of the applied force caused by the applied voltage divided by the initial dimension of the material).

In some embodiments, the electroactive response may include a mechanical response to an electrical input that varies over a spatial range of the device, wherein the electrical input is applied between the primary electrode and the secondary electrode. The mechanical response may be referred to as actuation, and the example device or optical element may be, or may include, an actuator.

The optical element may be deformed from an initial state to a deformed state when a first voltage is applied between the primary electrode and the secondary electrode, and may be further deformed to a second deformed state when a second voltage is applied between the primary electrode and the secondary electrode.

The electrical signal may comprise a potential difference, which may comprise a direct or alternating voltage. In some embodiments, the frequency may be higher than the highest mechanical response frequency of the device, such that deformation may occur in response to an applied RMS electric field, but without a significant oscillating mechanical response to the applied frequency. The applied electrical signal may generate a non-uniform contraction of the electroactive layer between the primary and secondary electrodes. The non-uniform electroactive response may include a curvature of a surface of the optical element, which in some embodiments may be a compound curvature.

In some embodiments, the optical element may have a maximum thickness in an undeformed state and a compressed thickness in a deformed state. In some embodiments, the optical element in the undeformed state may have a density that is about 90% or less of the density of the optical element in the deformed state. In some embodiments, the optical element may exhibit a strain of at least about 0.02% when a voltage is applied between the primary and secondary electrodes.

In some embodiments, the optical device may include one or more optical elements, and the optical elements may include one or more electroactive layers. In various embodiments, an optical element may include a primary electrode, a secondary electrode overlapping at least a portion of the primary electrode, and an electroactive layer disposed between the primary electrode and the secondary electrode.

In some embodiments, applying an electric field across the electroactive layer can produce substantially uniform deformation between the primary and secondary electrodes. In some embodiments, the primary and/or secondary electrodes may be patterned, which allows a local electric field to be applied to a portion of the optical element, e.g., to provide local deformation.

According to some embodiments, patterned electrodes (e.g., one or both of the primary and secondary electrodes) may be used to actuate one or more regions within the intervening electroactive layer, i.e., excluding adjacent regions within the same electroactive layer. For example, spatially localized actuation of an optical element comprising a ceramic electroactive layer can be used to adjust the birefringence of such a structure, where birefringence can be a function of local mechanical stress.

In some embodiments, such patterned electrodes may be independently actuatable. The patterned electrodes may be formed by selective deposition of an electrode layer or by blanket deposition of an electrode layer, followed by patterning and etching, for example using photolithographic techniques, as is known to those skilled in the art. For example, the patterned electrode may comprise a wire grid, or the wire grid may be incorporated into the optical element as a separate layer adjacent to the electrode layer. The discretely patterned electrodes may be individually addressable with different voltages, either simultaneously or sequentially.

The optical device may comprise more than one stacked element. For example, each element may comprise an electroactive layer disposed between a pair of electrodes. In some embodiments, electrodes may be shared between elements, e.g., a device may have alternating electrodes and electroactive layers located between adjacent pairs of electrodes. A variety of stacked configurations can be constructed in different geometries that vary the shape, alignment, and spacing between elements. Such complex arrangements enable compression, extension, twisting and/or bending when operating such actuators.

In some embodiments, the optical device may include additional elements interleaved between the electrodes, such as in a stacked configuration. For example, the electrodes may form an interdigitated stack of electrodes (interleaved stack) in which alternate electrodes are connected to a first common electrode and the remaining alternate electrodes are connected to a second common electrode. Further optical elements may be arranged on the other side of the primary electrode. The further optical element may overlap the first optical element. The further electrode may be arranged to abut a surface of any further optical element.

In some embodiments, the optical device may include more (e.g., two, three, or more) such additional electroactive layers and corresponding electrodes. For example, the optical device may comprise a stack of two or more optical elements and corresponding electrodes. For example, the optical device may include from 2 optical elements to about 5, about 10, about 20, about 30, about 40, about 50, about 100, about 200, about 300, about 400, about 500, about 600, about 700, about 800, about 900, about 1000, about 2000, or greater than about 2000 optical elements.

The present disclosure relates generally to electroactive ceramics and optical elements including electroactive ceramics. As will be explained in more detail below, exemplary electroactive ceramics may be characterized by: an average grain size of less than 200 nm; a relative density of at least 99%; a transmittance of at least about 50% in the visible spectrum, e.g., at least 50%, 60%, 70%, 80%, 90%, 95%, 97%, 98%, 99%, or 99.5%, including ranges between any of the foregoing values; and a piezoelectric coefficient (d) of at least 20pC/N when exposed to an applied field from about-2 MV/m to about 2MV/m₃₃) For example, 20pC/N, 30pC/N, 50pC/N, 100pC/N, 150pC/N, or 200pC/N, including ranges between any of the foregoing values. In particular embodiments, the optical properties of the disclosed electroactive ceramics, including transmittance, haze, and clarity, can be stable (i.e., substantially unchanged) in response to an applied voltage.

A piezoelectric coefficient, synonymous herein with an inverse piezoelectric coefficient (d), may be used to quantify (a) strain when a piezoelectric material is subjected to an electric field, or (b) polarization in response to application of a stress. Typical units for the piezoelectric coefficient are coulombs/newtons or meters/volt.

For example, in response to an applied voltage, an electroactive ceramic disclosed herein can exhibit a change in transmittance of less than about 50%, e.g., 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, or 45%, including ranges between any of the foregoing values; a change in haze of less than about 50%, e.g., 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, or 45%, including ranges between any of the foregoing values; and/or less than about 50% net change, such as 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, or 45%, including ranges between any of the foregoing values. In various embodiments, the applied voltage can range from about-2 MV/m to 2MV/m, such as-2 MV/m, -1.5MV/m, -1MV/m, -0.5MV/m, 0MV/m, 0.5MV/m, 1MV/m, 1.5MV/m, or 2MV/m, including ranges between any of the foregoing values. In various embodiments, the applied voltage may be an electric field equal to at least about 50% of the breakdown strength of the electroactive ceramic, such as 50%, 60%, 70%, 80%, or 90% of the breakdown strength, including ranges between any of the foregoing values. In various embodiments, the applied voltage may be an electric field equal to at least about 50% of the coercive field of the electroactive ceramic, such as 50%, 75%, 100%, 125%, 150%, 175%, or 200% of the coercive field, including ranges between any of the foregoing values.

Features of any of the embodiments described herein may be used in combination with each other in accordance with the general principles described herein. These and other embodiments, features and advantages will be more fully understood when the following detailed description is read in conjunction with the accompanying drawings and claims.

Detailed descriptions of methods, systems, and apparatus for forming an actively tunable optical component including a transparent and voltage-stabilized electroactive ceramic layer will be provided below with reference to fig. 1-12. The discussion related to fig. 1 includes a description of an optical element according to some embodiments. The discussion related to fig. 2 includes a description of optical scattering of an electroactive ceramic material comprising ferroelectric domains. The discussion related to fig. 3-9 includes a description of modeled optical loss for an exemplary layer of electroactive ceramic material. The discussion related to fig. 10-12 relates to exemplary virtual reality and augmented reality device architectures that can include an optical element that includes an actuatable transparent electroactive ceramic layer.

In various approaches, the optical transmittance of electroactive materials, including piezoelectric materials, can be improved by domain engineering (domain engineering) or elimination of porosity. In such methods, reducing domain size or adding dopants to disrupt long range domain formation, degree of anisotropy, and/or birefringence have been used to form transparent compositions, albeit in the absence of an applied electric field. For many domain engineered materials, it has been observed that the application of an electric field, particularly an electric field greater than about 0.5MV/m, significantly reduces the transmittance when the domains grow and coalesce, or when the material undergoes distortion under an applied E-field, which can make it more birefringent.

Referring to fig. 2, the propagation of light through a domain engineered material may be modeled by calculating scattering using the full Mie scattering solution (full Mie scattering solution) of individual particles, where the electroactive material layer 200 may include an electroactive matrix 210 and a plurality of ferroelectric domains 220 dispersed throughout the matrix 210. The matrix 210 may have an index of refraction n1, and the domains 220 may have an index of refraction n 2.

For a 50 micron thick electroactive layer (n1 ═ 2.6; n2 ═ n1+ Δ n) in the case of incident light having a wavelength of 400nm, the optical losses (e.g., reflected light, scattered light, and haze) are plotted as a function of domain size in fig. 3-5, respectively, for different Δ n values. According to some embodiments, the amount of reflected (backscattered) light scattered from the particles is shown in fig. 3. Referring to fig. 4, for Δ n values of 0.1, 0.05, 0.025, 0.01 and 0.005, respectively, an electroactive layer having less than 10% optical scattering may be achieved with domain sizes of less than 20nm, 30nm, 70nm, 150nm or 1000 nm. Further, referring to fig. 5, the effect of domain size on haze is illustrated.

Further data similar to the data disclosed in fig. 3-5 are shown in fig. 6-8 for incident light having a wavelength of 700 nm. The results for incident light at 700nm are comparable to those for light at 400nm, noting that the curve maxima move consistently to larger particle sizes, indicating improved optical quality for a given domain size. As will be appreciated, the data in fig. 3-8 may be used to domain engineer an electroactive layer that exhibits a desired amount of reflected light, optical scattering, and/or haze.

According to various embodiments, the deleterious effects of domain growth and coalescence on the transparency of polycrystalline ceramic compositions may be mitigated by limiting their grain size. That is, applicants have shown that optically transparent and voltage stable electroactive ceramics can include submicron grains because grain boundaries inhibit the growth and coalescence of the interparticle domains.

Furthermore, as the grain size of the material decreases, the degree of tetragonality (and correspondingly the degree of anisotropy) also decreases, which may advantageously reduce the value of Δ n. Thus, for a given composition, a smaller grain size may be associated with less scattering at a given value of Δ n and a smaller value of Δ n.

According to some embodiments, a voltage stable electroactive ceramic having a transmittance of at least 50% within the visible spectrum comprises an average grain size of less than about 200nm, e.g., 2nm, 4nm, 10nm, 20nm, 50nm, 100nm, 150nm, or 200nm, including ranges between any of the foregoing values; and a relative density of at least about 99%, such as 99%, 99.5%, 99.9%, or 99.99% density, including ranges between any of the foregoing values. The combination of small grain size and high density, which is often difficult to achieve simultaneously due to grain growth prevalent in sintering, can limit both domain growth and scattering from the pores. The effect of porosity on the reflectivity of 400nm incident light for a variable density electroactive layer having a total thickness of 50 microns is shown in fig. 9.

Exemplary methods of forming a dense, optically transparent electroactive ceramic may include forming a ceramic powder, mixing, calcining, milling, green body formation, and high temperature sintering.

High purity raw materials for electroactive ceramic compositions may include PbO, Pb₃O₄、ZrO₂、TiO₂、MgO、Mg(OH)₂、MgCO₃、MnO₂、Nb₂O₅And LaO, and its corresponding hydrates. In some embodiments, the starting material may be at least about 99.9% pureDegrees, such as 99.9%, 99.95%, or 99.99% purity, including ranges between any of the foregoing values.

Precursor powders of suitable reactant compositions can be prepared by, for example, flame spray pyrolysis (flame spray pyrolysis), whereby an aerosol of a suitable metal salt, chelate, coordination compound, or the like can be sprayed into an oven and heated to a temperature sufficient to evaporate the solvent and form nanoscale particles. The precursor powder may also be synthesized by a hydrothermal process, a sol-gel process or a solvothermal process as known to those skilled in the art.

The precursor powder may be milled to produce the desired particle size before or after mixing. Exemplary milling processes include ball milling, such as planetary ball milling and stirred milling (attrition milling), although other milling processes are contemplated. During milling, the particles may be dried or mixed with a liquid such as ethanol. Exemplary precursor powders, i.e., prior to sintering, may have an average particle size of less than about 500nm, e.g., less than about 500nm, less than about 400nm, less than about 300nm, less than about 250nm, less than about 200nm, less than about 150nm, less than about 100nm, less than about 50nm, or less than about 25nm, including ranges between any of the foregoing values, although precursor powders having larger average particle sizes may be used.

In some embodiments, the milled powder may be calcined at a temperature in the range of from about 300 ℃ to about 1000 ℃, e.g., 300 ℃, 400 ℃, 500 ℃, 600 ℃, 700 ℃, 800 ℃, 900 ℃, or 1000 ℃ for a period of time of about 1h to about 24h, e.g., 1h, 2h, 4h, 10h, 15h, 20h, or 24h, including ranges between any of the foregoing values. For example, calcination may be performed in an oxidizing environment and may be used to remove unwanted impurities, including organic impurities such as carbon.

According to various embodiments, the powder mixture may be compacted into pellets or dispersed in a liquid and cast into a film to produce a desired form factor. For example, the powder mixture may be compacted by applying a uniaxial pressure of about 10MPa to about 500MPa, such as 10MPa, 15MPa, 20MPa, 25MPa, 30MPa, 50MPa, 100MPa, 200MPa, 300MPa, 400MPa, or 500MPa, including ranges between any of the foregoing values.

The shaped body may be sintered. In some embodiments, the sintering temperature may range from about 750 ℃ to about 1400 ℃, such as 750 ℃, 800 ℃, 900 ℃, 1000 ℃, 1100 ℃, 1200 ℃, 1300 ℃, or 1400 ℃, including ranges between any of the foregoing values. In certain embodiments, the powder may be sintered in a controlled atmosphere, such as an oxidizing atmosphere, a reducing atmosphere, or under vacuum. In certain embodiments, pressure may be applied during sintering, such as uniaxial pressure. Exemplary sintering processes include conventional sintering, spark plasma sintering, rapid sintering, or sintering using microwaves.

According to some embodiments, the sintered ceramic may be heated, for example, under oxidizing conditions or reducing conditions, to adjust the oxygen stoichiometry. Such post-sintering annealing may be performed under vacuum or at about atmospheric pressure. In some embodiments, the ceramic may be annealed within the bed of precursor powder mixture during the post-sintering heating step, which may inhibit evaporation of lead. In various embodiments, the densified ceramic may be ground, lapped, and/or polished to obtain a smooth surface. In exemplary embodiments, the transparent electroactive ceramic may have a surface roughness of less than about 50nm and exhibit a haze of less than 10%.

In an exemplary method, the magnesium oxide and niobium oxide powders may be ball milled in ethanol and calcined at 300 ℃ to 1000 ℃ for 1 to 24 hours. To suppress the formation of non-perovskite phases, lead oxide and titanium oxide powders may be added after the foregoing calcination step, and then the mixture may be ball-milled in ethanol and calcined at 500 ℃ to 1200 ℃ for 0.5h to 12 h. After the second calcination step, the powder mixture may be ground, compacted under uniaxial pressure of 10MPa to 500MPa, and sintered by spark plasma sintering at 750 ℃ to 1150 ℃ while maintaining the applied pressure. In some embodiments, the sintered ceramic may be heated to 400 ℃ to 1400 ℃ for 2h to 24h in an oxidizing environment. After sintering, the lead zirconium magnesium titanate (lead zirconium magnesium titanate) ceramic composition may have a relative density greater than about 99% and an average grain size less than about 200 nm.

In another method, powders of lead oxide, zirconium oxide and titanium oxide may be mixed in a suitable ratio and milled to form a powder mixture having an average particle size of less than 500 nm. The powder mixture may be heated (calcined) at about 300-700 ℃ to remove excess carbon. The calcined powder can be sintered to form a dense, transparent ceramic having an average particle size of less than about 200 nm.

In some embodiments, the ceramic powder may be derived from a solution of one or more salts, chelates, and/or coordination complexes of, for example, lead, zirconium, and titanium, although additional or alternative metal compounds may be used. The solution can be distilled, evaporated and dried to form a compositionally homogeneous powder. The powder mixture may be milled to an average particle size of less than about 300nm, calcined to remove residual carbon, compacted and sintered to form a dense, transparent ceramic having an average grain size of less than about 200nm, a relative density of at least 99%, and a transmittance of at least 50% in the visible spectrum.

As disclosed herein, an optically transparent actuator can include a pair of electrodes and an electroactive ceramic layer disposed between the electrodes. The method of making the ceramic layer can result in a dense nanocrystalline structure having a robust set of optical properties. That is, the transmittance, optical clarity, and haze characteristics of the ceramic exhibit a high optical quality layer under an applied electric field without exhibiting any significant degradation of the aforementioned characteristics. For example, exemplary ceramic layers can maintain greater than 75% transmission and less than 10% haze at applied fields of 1MV/m and greater. In particular embodiments, optical scattering, which may be a significant detractor factor from optical transparency (detrector), can be controlled during fabrication by engineering microstructures with grain sizes less than 200nm and densities greater than 99%. In conventional ceramics, such high densities and small grain sizes may be difficult to achieve simultaneously, but may be obtained by, for example, powder processing, including powder modification (e.g., milling to achieve sub-micron particle sizes), calcination, green body formation, and high temperature sintering. The ceramic may comprise a ferroelectric composition, such as a lead zirconate titanate (PZT) based material, or another perovskite ceramic.

Exemplary embodiments

Example 1: an electroactive ceramic that lacks crystal inversion centers in its unit cells, and further comprises an average grain size of less than about 200nm, a relative density of at least 99%, and a transmittance of at least 50% in the visible spectrum.

Example 2: the electroactive ceramic of example 1, further exhibiting less than 10% haze.

Example 3: the electroactive ceramic of any of examples 1 and 2, wherein the transmittance within the visible spectrum is at least 75%.

Example 4: the electroactive ceramic of any of examples 1-3, wherein when exposed to an applied field from about-2 MV/m to about 2MV/m at least one of: (a) a change in transmission of less than 50%, (b) a change in haze of less than 50%, and (c) a change in clarity of less than 50%.

Example 5: the electroactive ceramic of any of examples 1-4, wherein when exposed to an applied field from about-2 MV/m to about 2 MV/m: (a) a change in transmission of less than 50%, (b) a change in haze of less than 50%, and (c) a change in clarity of less than 50%.

Example 6: an electroactive ceramic according to any of examples 1 to 3, wherein when exposed to an applied field equal to at least 50% of its breakdown strength: (a) a change in transmission of less than 50%, (b) a change in haze of less than 50%, and (c) a change in clarity of less than 50%.

Example 7: an electroactive ceramic according to any of examples 1 to 3, wherein when exposed to an applied field equal to at least 50% of its coercive field: (a) a change in transmission of less than 50%, (b) a change in haze of less than 50%, and (c) a change in clarity of less than 50%.

Example 8: the electroactive ceramic of any of examples 1-7, further comprising at least one compound selected from the group consisting of: lead titanate, lead zirconate titanate, lead magnesium niobate, lead zincate niobate, lead indium niobate, lead magnesium tantalate, lead indium tantalate, barium titanate, lithium niobate, potassium sodium niobate, bismuth sodium titanate, and bismuth ferrite.

Example 9: the electroactive ceramic of any of examples 1-8, further comprising a solid solution of two or more of: lead titanate, lead zirconate titanate, lead magnesium niobate, lead zincate niobate, lead indium niobate, lead magnesium tantalate, lead indium tantalate, barium titanate, lithium niobate, potassium sodium niobate, bismuth sodium titanate, and bismuth ferrite.

Example 10: the electroactive ceramic of any of examples 1-9, further comprising at least one dopant selected from the group consisting of: niobium, potassium, sodium, calcium, gallium, indium, bismuth, aluminum, strontium, barium, samarium, dysprosium, magnesium, iron, tantalum, yttrium, lanthanum, europium, neodymium, scandium, and erbium.

Example 11: the electroactive ceramic of any one of examples 1-10, having an RMS surface roughness of less than about 50 nm.

Example 12: the electroactive ceramic of any of examples 1-11, consisting essentially of a perovskite ceramic.

Example 13: an optical element comprising a primary electrode, a secondary electrode overlapping at least a portion of the primary electrode, and an electroactive layer disposed between and abutting the primary and secondary electrodes, wherein the electroactive layer comprises an average grain size of less than 200nm, a relative density of at least 99%, and a transmittance of at least 50% within the visible spectrum.

Example 14: the optical element of example 13, wherein the electroactive layer has an RMS surface roughness of less than about 50 nm.

Example 15: an optical element according to any one of examples 13 and 14, wherein the electroactive layer comprises a perovskite ceramic.

Example 16: the optical element of any one of examples 13-15, wherein the electroactive ceramic exhibits less than a 50% change in each of transparency, haze, and clarity when a voltage is applied to the primary electrode.

Example 17: a head-mounted display comprising the optical element of any one of examples 13-16.

Example 18: a method comprising forming a powder mixture and sintering the powder mixture to form an electroactive ceramic, wherein the electroactive ceramic comprises (a) an average grain size of less than 200nm, (b) a relative density of at least 99%, and (c) a transmittance of at least 50% within the visible spectrum.

Example 19: the method of example 18, wherein forming a powder mixture comprises: forming a partial powder mixture, wherein the partial powder mixture is lead-free; calcining the partial powder mixture and adding lead oxide to the calcined partial powder mixture to form the powder mixture.

Example 20: the method of any one of examples 18 and 19, further comprising forming a transparent electrode on the electroactive ceramic.

Embodiments 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 way prior to presentation to a user, and may include, for example, virtual reality, augmented reality, mixed reality (mixed reality), hybrid reality (hybrid reality), or some combination and/or derivative thereof. The artificial reality content may include fully generated content or content generated in combination 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 (e.g., stereoscopic video that produces a three-dimensional effect to a viewer). Further, in some embodiments, the artificial reality may also be associated with an application, product, accessory, service, or some combination thereof, that is used, for example, to create content in the artificial reality and/or otherwise use in the artificial reality (e.g., to perform an activity in the artificial reality).

Artificial reality systems can be implemented in many different forms and configurations. Some artificial reality systems may be designed to operate without a near-eye display (NED), an example of which is the augmented reality system 1000 in fig. 10. Other artificial reality systems may include NED's that also provide visibility into the real world (e.g., augmented reality system 1100 in fig. 11), or NED's that visually immerse the user in artificial reality (e.g., virtual reality system 1200 in fig. 12). While some artificial reality devices may be stand-alone systems, other artificial reality devices may communicate and/or coordinate with external devices to provide an artificial reality experience to the user. Examples of such external devices include a handheld controller, a mobile device, a desktop computer, a device worn by a user, a device worn by one or more other users, and/or any other suitable external system.

Turning to fig. 10, augmented reality system 1000 generally represents a wearable device sized to fit a body part (e.g., head) of a user. As shown in fig. 10, the system 1000 may include a frame 1002 and a camera assembly 1004, the camera assembly 1004 being coupled to the frame 1002 and configured to gather information about the local environment by observing the local environment. Augmented reality system 1000 may also include one or more audio devices, such as output audio transducers 1008(a) and 1008(B) and input audio transducer 1010. The output audio transducers 1008(a) and 1008(B) may provide audio feedback and/or content to the user, and the input audio transducer 1010 may capture audio in the user's environment.

As shown, the augmented reality system 1000 may not necessarily include a NED positioned in front of the user's eyes. Augmented reality systems without NED may take a variety of forms, such as a headband, hat, hair band, belt, watch, wrist band, ankle band, ring, neck band, necklace, chest band, spectacle frame, and/or any other suitable type or form of device. Although the augmented reality system 1000 may not include a NED, the augmented reality system 1000 may include other types of screens or visual feedback devices (e.g., a display screen integrated into one side of the frame 1002).

Embodiments discussed in this disclosure may also be implemented in an augmented reality system that includes one or more NED's. For example, as shown in fig. 11, the augmented reality system 1100 may include an eyeglass device 1102 having a frame 1110, the frame 1110 configured to hold a left display device 1115(a) and a right display device 1115(B) in front of the user's eyes. The display devices 1115(a) and 1115(B) may function together or independently to present an image or series of images to a user. Although augmented reality system 1100 includes two displays, embodiments of the present disclosure may be implemented in augmented reality systems having a single NED or more than two NED.

In some embodiments, augmented reality system 1100 may include one or more sensors, such as sensor 1140. The sensors 1140 may generate measurement signals in response to movement of the augmented reality system 1100 and may be located on substantially any portion of the frame 1110. The sensors 1140 may represent positioning sensors, Inertial Measurement Units (IMUs), depth camera components, or any combination thereof. In some embodiments, augmented reality system 1100 may or may not include sensor 1140, or may include more than one sensor. In embodiments where the sensor 1140 comprises an IMU, the IMU may generate calibration data based on the measurement signals from the sensor 1140. Examples of sensors 1140 may include, but are not limited to, accelerometers, gyroscopes, magnetometers, other suitable types of sensors that detect motion, sensors for error correction of the IMU, or some combination thereof.

Augmented reality system 1100 may also include a microphone array having more than one acoustic transducer 1120(a) -1120(J), which are collectively referred to as acoustic transducers 1120. Acoustic transducer 1120 may be a transducer that detects changes in air pressure caused by acoustic waves. Each acoustic transducer 1120 may be configured to detect sound and convert the detected sound into an electronic format (e.g., analog or digital format). The microphone array in fig. 11 may include, for example, ten sound transducers: 1120(a) and 1120(B), which may be designed to be placed within the corresponding ears of a user; acoustic transducers 1120(C), 1120(D), 1120(E), 1120(F), 1120(G), and 1120(H), which may be positioned at a plurality of locations on frame 1110; and/or acoustic transducers 1120(I) and 1120(J) that may be positioned on corresponding neck straps 1105.

In some embodiments, one or more of the acoustic transducers 1120(a) -1120(F) may be used as output transducers (e.g., speakers). For example, acoustic transducers 1120(a) and/or 1120(B) may be ear buds or any other suitable type of earpiece or speaker.

The configuration of the acoustic transducers 1120 of the microphone array may vary. Although the augmented reality system 1100 is shown in fig. 11 as having ten acoustic transducers 1120, the number of acoustic transducers 1120 may be greater or less than ten. In some embodiments, using a greater number of acoustic transducers 1120 may increase the amount of audio information collected and/or the sensitivity and accuracy of the audio information. Conversely, using a lower number of acoustic transducers 1120 may reduce the computational power required by the controller 1150 to process the collected audio information. Further, the location of each acoustic transducer 1120 of the microphone array may vary. For example, the locations of acoustic transducers 1120 may include defined locations on a user, defined coordinates on frame 1110, an orientation associated with each acoustic transducer, or some combination thereof.

The acoustic transducers 1120(a) and 1120(B) may be positioned in different parts of the user's ears, such as behind the pinna (pinna) or within the pinna (auricle) or fossa. Alternatively, there may be additional acoustic transducers on or around the ear in addition to acoustic transducer 1120 within the ear canal. Positioning the acoustic transducer near the ear canal of the user may enable the microphone array to collect information about how sound reaches the ear canal. By positioning at least two of the sound transducers 1120 on either side of the user's head (e.g., as binaural microphones), the augmented reality device 1100 can simulate binaural hearing and capture a 3D stereo sound field around the user's head. In some embodiments, acoustic transducers 1120(a) and 1120(B) may be connected to augmented reality system 1100 via a wired connection 1130, and in other embodiments, acoustic transducers 1120(a) and 1120(B) may be connected to augmented reality system 1100 via a wireless connection (e.g., a bluetooth connection). In still other embodiments, acoustic transducers 1120(a) and 1120(B) may not be used in conjunction with augmented reality system 1100 at all.

The acoustic transducers 1120 on the frame 1110 may be positioned along the length of the temple, across the bridge, above or below the display devices 1115(a) and 1115(B), or some combination thereof. The acoustic transducer 1120 may be oriented such that the microphone array is capable of detecting sound in a wide range of directions around a user wearing the augmented reality system 1100. In some embodiments, an optimization process may be performed during the manufacture of the augmented reality system 1100 to determine the relative positioning of each acoustic transducer 1120 in the microphone array.

In some examples, augmented reality system 1100 may include or may be connected to an external device (e.g., a paired device), such as neck strap 1105. Neck strap 1105 generally represents any type or form of mating device. Thus, the following discussion of the neck strap 1105 may also be applicable to a variety of other paired devices, such as charging boxes, smart watches, smart phones, wristbands, other wearable devices, handheld controllers, tablets, laptops, and other external computing devices, and the like.

As shown, the neck strap 1105 may be coupled to the eyewear apparatus 1102 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, the eyeglass apparatus 1102 and the neck strap 1105 can operate independently without any wired or wireless connection between them. Although fig. 11 illustrates components of the eyeglass apparatus 1102 and the napestrap 1105 in exemplary locations on the eyeglass apparatus 1102 and the napestrap 1105, the components may be located elsewhere on the eyeglass apparatus 1102 and/or the napestrap 1105 and/or distributed differently on the eyeglass apparatus 1102 and/or the napestrap 1105. In some embodiments, the components of the eyewear device 1102 and the neck band 1105 may be located on one or more additional peripheral devices that are paired with the eyewear device 1102, the neck band 1105, or some combination thereof.

Pairing an external device, such as a neckband 1105, with an augmented reality eyewear device may enable the eyewear device to achieve the form factor of a pair of eyeglasses while still providing sufficient battery and computing power for extended capabilities. Some or all of the battery power, computing resources, and/or additional features of the augmented reality system 1100 may be provided by or shared between the paired device and the eyeglass device, thus reducing the weight, thermal profile, and form factor of the eyeglass device as a whole while still maintaining the desired functionality. For example, the neck strap 1105 may allow components that would otherwise be included on the eyewear apparatus to be included in the neck strap 1105 as the user may tolerate a heavier weight load on their shoulders than they would tolerate on their head. The neck strap 1105 may also have a larger surface area over which heat is spread and dispersed into the surrounding environment. Thus, the neck strap 1105 may allow for a greater battery and computing capacity than would otherwise be possible on a standalone eyewear device. Because the weight carried in the napestrap 1105 may be less intrusive to the user than the weight carried in the eyeglass device 1102, the user may tolerate wearing a lighter eyeglass device and carrying or wearing a paired device for a longer period of time than the user would tolerate wearing a heavier independent eyeglass device, thereby enabling the user to more fully incorporate the artificial reality environment into their daily activities.

The neck strap 1105 can be communicatively coupled with the eyeglass device 1102 and/or other devices. These other devices may provide certain functionality (e.g., tracking, positioning, depth mapping, processing, storage, etc.) to the augmented reality system 1100. In the embodiment of fig. 11, the neck strap 1105 may include two acoustic transducers (e.g., 1120(I) and 1120(J)) that are part of a microphone array (or potentially form their own microphone sub-array). The neck band 1105 may also include a controller 1125 and a power source 1135.

The acoustic transducers 1120(I) and 1120(J) of the neck strap 1105 may be configured to detect sound and convert the detected sound into an electronic format (analog or digital). In the embodiment of fig. 11, the acoustic transducers 1120(I) and 1120(J) may be positioned on the napestrap 1105, thereby increasing the distance between the napestrap acoustic transducers 1120(I) and 1120(J) and other acoustic transducers 1120 positioned on the eyeglass device 1102. In some cases, increasing the distance between the acoustic transducers 1120 of the microphone array may improve the accuracy of the beamforming performed via the microphone array. For example, if sound is detected by acoustic transducers 1120(C) and 1120(D), and the distance between acoustic transducers 1120(C) and 1120(D) is greater than, for example, the distance between acoustic transducers 1120(D) and 1120(E), the determined source location of the detected sound may be more accurate than if sound had been detected by acoustic transducers 1120(D) and 1120 (E).

The controller 1125 of the neck band 1105 may process information generated by the neck band 1105 and/or sensors on the augmented reality system 1100. For example, the controller 1125 may process information from the microphone array that describes the sound detected by the microphone array. For each detected sound, the controller 1125 may perform direction of arrival (DOA) estimation to estimate a direction in which the detected sound reaches the microphone array. When the microphone array detects sound, the controller 1125 may populate the audio data set with this information. In embodiments where the augmented reality system 1100 includes an inertial measurement unit, the controller 1125 may calculate all inertial and spatial calculations from the IMU located on the eyewear apparatus 1102. The connectors may communicate information between the augmented reality system 1100 and the napestrap 1105 and between the augmented reality system 1100 and the controller 1125. The information may be in the form of optical data, electrical data, wireless data, or any other form of transmittable data. Moving the processing of information generated by the augmented reality system 1100 to the neckband 1105 may reduce the weight and heat in the eyeglass apparatus 1102, making it more comfortable for the user.

A power source 1135 in the neck strap 1105 can provide power to the eyeglass apparatus 1102 and/or the neck strap 1105. Power source 1135 may include, but is not limited to, a lithium ion battery, a lithium-polymer battery, a primary lithium battery, an alkaline battery, or any other form of power storage device. In some cases, power supply 1135 may be a wired power supply. The inclusion of the power source 1135 on the neck strap 1105, rather than on the eyeglass apparatus 1102, can help better distribute the weight and heat generated by the power source 1135.

As mentioned, some artificial reality systems may substantially replace one or more sensory perceptions of the user to the real world with a virtual experience, rather than blending artificial reality with actual reality. One example of this type of system is a head mounted display system, such as virtual reality system 1200 in fig. 12, that covers most or all of the user's field of view. The virtual reality system 1200 may include a front rigid body 1202 and a band 1204 shaped to fit around the head of a user. Virtual reality system 1200 may also include output audio transducers 1206(a) and 1206 (B). Further, although not shown in fig. 12, the front rigid body 1202 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.

Artificial reality systems may include various types of visual feedback mechanisms. For example, the display devices in augmented reality system 1100 and/or virtual reality system 1200 may include one or more Liquid Crystal Displays (LCDs), Light Emitting Diode (LED) displays, organic LED (oled) displays, and/or any other suitable type of display screen. The artificial reality system may include a single display screen for both eyes, or a display screen may be provided for each eye, which may allow additional flexibility for zoom adjustment or for correcting refractive errors of the user. Some artificial reality systems may also include an optical subsystem having one or more lenses (e.g., conventional concave or convex lenses, fresnel lenses, adjustable liquid lenses, etc.) through which a user may view the display screen.

Some artificial reality systems may include one or more projection systems in addition to or instead of using a display screen. For example, a display device in augmented reality system 1100 and/or virtual reality system 1200 may include a micro LED projector that projects light (using, for example, a waveguide) into the display device, such as a transparent combination lens that allows ambient light to pass through. The display device may refract the projected light toward the pupil of the user and may enable the user to view both artificial reality content and the real world at the same time. The artificial reality system may also be configured with any other suitable type or form of image projection system.

The artificial reality system may also include various types of computer vision components and subsystems. For example, augmented reality system 1000, augmented reality system 1100, and/or virtual reality system 1200 may include one or more optical sensors, such as two-dimensional (2D) or three-dimensional (3D) cameras, time-of-flight depth sensors, single-beam or scanning laser rangefinders, 3D LiDAR sensors, and/or any other suitable type or form of optical sensor. The artificial reality system may process data from one or more of these sensors to identify the user's location, to map the real world, to provide the user with context about the real world surroundings, and/or to perform a variety of other functions.

The artificial reality system may also include one or more input and/or output audio transducers. In the examples shown in fig. 10 and 12, the output audio transducers 1008(a), 1008(B), 1206(a), and 1206(B) may include voice coil speakers, ribbon speakers, electrostatic speakers, piezoelectric speakers, bone conduction transducers, cartilage conduction transducers, and/or any other suitable type or form of audio transducer. Similarly, the input audio transducer 1010 may include a condenser microphone, an electrodynamic microphone (dynamic microphone), a ribbon microphone, 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.

Although not shown in fig. 10-12, the artificial reality system may include a haptic (i.e., tactile) feedback system that may be incorporated into headwear, gloves, bodysuits, handheld controllers, environmental devices (e.g., chairs, floor mats, etc.), and/or any other type of device or system. The haptic feedback system may provide various types of skin feedback including vibration, force, traction, texture, and/or temperature. The haptic feedback system may also provide various types of kinesthetic feedback, such as motion and compliance. The haptic feedback may be implemented using motors, piezoelectric actuators, fluidic systems, and/or a variety of other types of feedback mechanisms. The haptic feedback system may be implemented independently of, within, and/or in conjunction with other artificial reality devices.

By providing haptic sensations, audible content, and/or visual content, the artificial reality system can create an overall virtual experience or enhance a user's real-world experience in a variety of contexts and environments. For example, the artificial reality system may assist or augment a user's perception, memory, or cognition within a particular environment. Some systems may enhance user interaction with others in the real world, or may enable more immersive interaction with others in the 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, commercial enterprises, etc.), entertainment purposes (e.g., for playing video games, listening to music, viewing video content, etc.), and/or for accessibility purposes (e.g., as hearing aids, vision aids, etc.). Embodiments disclosed herein may implement or enhance a user's artificial reality experience in one or more of these contexts and environments and/or in other contexts and environments.

The process parameters and the sequence of steps described and/or illustrated herein are given by way of example only and may 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 need not necessarily be performed in the order illustrated or discussed. Various exemplary methods described and/or illustrated herein may also omit one or more steps described or illustrated herein, or may include additional steps in addition to those disclosed.

The preceding description has been provided to enable others skilled in the art to best utilize various aspects of the exemplary embodiments disclosed herein. The 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 disclosure. The embodiments disclosed herein are to be considered in all respects as illustrative and not restrictive. In determining the scope of the present disclosure, reference should be made to the appended claims and their equivalents.

Unless otherwise indicated, the terms "connected to" and "coupled to" (and derivatives thereof) as used in the specification and claims are to be construed to allow both direct and indirect (i.e., through other elements or components) connection. Furthermore, the terms "a" or "an" as used in the specification and claims should be interpreted to mean at least one of. Finally, for convenience in use, the terms "including" and "having" (and derivatives thereof) as used in the specification and claims may be interchanged with the word "comprising" and have the same meaning as the word "comprising".