Facebook Patent | Fluid lens with reduced bubble formation

Patent: Fluid lens with reduced bubble formation

Drawings: Click to check drawins

Publication Number: 20210132266

Publication Date: 20210506

Applicant: Facebook

Abstract

Disclosed devices may include a fluid lens that includes a membrane, optionally a substrate, and a fluid located within an enclosure that may be at least partially defined by the substrate and the membrane. A coating may be disposed on at least a portion of the interior surface of the enclosure. The coating may have a coating surface in contact with the fluid. The coating may significantly reduce bubble formation within the fluid (e.g., compared with an uncoated surface). Example devices include adjustable fluid lenses that may be adjusted to a plano-concave configuration. Various other methods, systems, and computer-readable media are also disclosed.

Claims

1. A device including a fluid lens, wherein the fluid lens comprises: a membrane; a substrate; a fluid located within an enclosure formed at least in part by the membrane and the substrate, the enclosure having an enclosure surface; and a coating disposed on at least a portion of the enclosure surface, the coating having a coating surface adjacent the fluid, wherein: the membrane is an elastic membrane; the coating and the membrane have different compositions; and the coating significantly reduces bubble formation within the fluid.

2. The device of claim 1, wherein the membrane has a membrane curvature, and the fluid lens further includes a support structure configured to: retain the membrane under tension; and allow adjustment of the membrane curvature to modify an optical property of the fluid lens.

3. The device of claim 2, wherein the membrane curvature is adjustable to a negative value.

4. The device of claim 2, wherein the optical property is an optical power of the fluid lens, and the optical power is adjustable to a negative value.

5. The device of claim 1, wherein the substrate is a rigid substrate, and the coating is deposited directly on the enclosure surface.

6. The device of claim 1, wherein: the coating surface has a coating surface roughness; the enclosure surface has an enclosure surface roughness; and the coating surface roughness is significantly less than the enclosure surface roughness.

7. The device of claim 1, wherein the coating includes a polymer.

8. The device of claim 7, wherein the polymer includes at least one of an acrylate polymer, a silicone polymer, an epoxy polymer, or a urethane polymer.

9. The device of claim 7, wherein the coating comprises a fluoropolymer.

10. The device of claim 1, wherein the device includes a frame, the frame enclosing the fluid lens.

11. The device of claim 1, wherein the device is a head-mounted device.

12. The device of claim 11, wherein the device is an ophthalmic device configured to be used as eyewear.

13. The device of claim 1, wherein the fluid is a liquid, the device is an adjustable liquid lens, and the coating significantly reduces gas bubble formation within the liquid.

14. The device of claim 13, wherein the liquid includes a silicone oil.

15. A method, comprising: assembling a fluid lens assembly including a substrate and an elastic membrane, the fluid lens assembly having an enclosure at least partially enclosed by the substrate and the elastic membrane, the enclosure having an interior surface; forming a coating on at least a portion of the interior surface of the enclosure; and introducing a lens fluid into the enclosure to form a fluid lens, wherein the coating is configured to reduce bubble formation within the lens fluid during operation of the fluid lens.

16. The method of claim 15, wherein forming the coating includes: introducing a coating material into the enclosure; and depositing the coating material onto the interior surface.

17. The method of claim 16, wherein depositing the coating material onto the interior surface includes ultrasonic agitation of the fluid lens assembly.

18. The method of claim 16, wherein the coating material is introduced into the enclosure before introducing the lens fluid into the enclosure.

19. The method of claim 16, further including polymerizing the coating material to form the coating on the interior surface.

20. The method of claim 15, wherein the method is a method of fabricating an ophthalmic device including the fluid lens.

Description

CROSS REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of U.S. Provisional Application No. 62/930,790, filed Nov. 5, 2019, the disclosure of which is incorporated, in its entirety, by this reference.

BRIEF DESCRIPTION OF THE DRAWINGS

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

[0003] FIGS. 1A-1C illustrate example fluid lenses.

[0004] FIGS. 2A-2G illustrate example fluid lenses, and adjustment of the optical power of the fluid lenses.

[0005] FIG. 3 illustrates an example ophthalmic device.

[0006] FIGS. 4A-4B illustrate a fluid lens having a membrane assembly including a support ring.

[0007] FIG. 5 illustrates deformation of a non-circular fluid lens.

[0008] FIGS. 6A-6C illustrate a fluid lens having a concave configuration.

[0009] FIGS. 7A-7C illustrate bubble formation in a fluid lens.

[0010] FIG. 7D illustrates avoidance of bubble formation using an interior coating, according to embodiments of this disclosure.

[0011] FIGS. 8A-81 illustrate fabrication of a fluid lens having an interior coating, according to embodiments of this disclosure.

[0012] FIG. 9 illustrates a method of fabricating a fluid lens having an interior coating, according to embodiments of this disclosure.

[0013] FIG. 10 illustrates a method of fabricating a fluid lens having an interior coating, according to embodiments of this disclosure.

[0014] FIG. 11 is an illustration of an exemplary artificial-reality headband that may be used in connection with embodiments of this disclosure.

[0015] FIG. 12 is an illustration of exemplary augmented-reality glasses that may be used in connection with embodiments of this disclosure.

[0016] FIG. 13 is an illustration of an exemplary virtual-reality headset that may be used in connection with embodiments of this disclosure.

[0017] FIG. 14 is an illustration of exemplary haptic devices that may be used in connection with embodiments of this disclosure.

[0018] FIG. 15 is an illustration of an exemplary virtual-reality environment according to embodiments of this disclosure.

[0019] FIG. 16 is an illustration of an exemplary augmented-reality environment according to embodiments of this disclosure.

[0020] 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 are described in detail herein. However, the exemplary embodiments described herein are not intended to be limited to the particular forms disclosed. Rather, the present disclosure covers all modifications, equivalents, and alternatives falling within the scope of the appended claims.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

[0021] Formation of bubbles in the lens fluid of a fluid lens may degrade the appearance and the optical performance of the fluid lens. It would be useful to reduce, or substantially eliminate, the formation of bubbles.

[0022] The present disclosure is generally directed to fluid lenses, which include liquid lenses, such as adjustable liquid lenses. As is explained in greater detail herein, embodiments of the present disclosure include fluid lenses, membranes used in fluid lenses, membrane assemblies, and improved devices using fluid lenses, such as ophthalmic devices, augmented reality devices, virtual reality devices, and the like.

[0023] Adjustable fluid lenses are useful for ophthalmic, virtual reality (VR), and augmented reality (AR) devices. In some example ophthalmic devices, fluid lenses may be used for vision correction, including correction of presbyopia. In some example AR and/or VR devices, fluid lenses may be used for the correction of what is commonly known as the vergence accommodation conflict (VAC). Examples described herein may include such devices, including fluid lenses for the correction of VAC.

[0024] Embodiments of the present disclosure include fluid lenses, including a substrate and a membrane, at least in part enclosing a lens enclosure. The lens enclosure may be referred to hereinafter as an “enclosure” for conciseness. The enclosure may receive a lens fluid, and the interior surface of the enclosure may be proximate the lens fluid. In some examples, at least part of the interior surface of the enclosure may have a coating that reduces, or substantially eliminates, formation of bubbles in the lens fluid. The coating may be located between the lens fluid and the interior surface of the enclosure (that may include interior surfaces of the membrane and/or substrate).

[0025] Examples disclosed herein may include fluid lenses, membrane assemblies (that may include a membrane and, e.g., a peripheral structure such as a support ring or a peripheral wire), and devices including one or more fluid lenses. Example devices include ophthalmic devices (e.g., spectacles), augmented reality devices, virtual reality devices, and the like. In some examples, a device may include a fluid lens configured as a primary lens of an optical device, for example, as the primary lens for light entering the user’s eye.

[0026] Features from any of the embodiments described herein may be used in combination with one another in accordance with the general principles described herein. These and other embodiments, features, and advantages will be more fully understood upon reading the detailed description in conjunction with the accompanying drawings and claims.

[0027] The following provides, with reference to FIGS. 1-16, detailed descriptions of fluid lenses, including fluid lenses having a reduced propensity for bubble formation. FIGS. 1-5 illustrate example fluid lenses. FIGS. 6A-6C show the configuration of an example plano-concave fluid lens. FIGS. 7A-7D illustrate bubble formation on an interior rough surface of a fluid lens, and an example approach to bubble formation reduction or prevention. FIGS. 8A-81 illustrate various possible approaches to fabrication of a fluid lens with a reduced propensity for bubble formation. FIGS. 9 and 10 illustrate example methods of fabricating a fluid lens having an interior coating. FIGS. 11-16 illustrate example augmented reality and/or virtual reality devices, that may include one or more fluid lenses.

[0028] In fluid lenses, the application of negative pressure (e.g., reduced pressure in the liquid enclosure) may increase the possibility of bubble formation on an interior surface of the lens enclosure. Bubble formation may be induced by nucleation on surface defects. Bubble formation may be reduced by having a lens fluid that is maintained above atmospheric pressure, so that it is energetically unfavorable for a bubble to form. However, this may restrict the adjustments that are available to a surface of the fluid lens, for example, to convex lens surfaces only. A greater range of optical powers may be achieved by applying a negative pressure to the lens fluid, which may induce a concave membrane profile. (In this context, the term “concave” may refer to the external surface of the membrane, with a concave lens tending to be narrower in the center of the lens.) However, any design requirement of elevated fluid pressure (relative to atmospheric pressure) may be in direct conflict with such device configurations. Bubble formation may also be reduced by fabricating relatively small diameter lenses (e.g., a smaller diameter than typically used for ophthalmic lenses) that may have relatively low tension membranes. However, the applications of such reduced diameter lenses may be correspondingly restricted.

[0029] In some examples, an adjustable fluid lens (such as a liquid lens) includes a pre-strained flexible membrane that at least partially encloses a fluid volume, a fluid enclosed within the fluid volume, a flexible edge seal that defines a periphery of the fluid volume, and an actuation system configured to control the edge of the membrane such that the optical power of the lens can be modified. In some examples, movement of an edge portion of the membrane, such as a control point, along a guide path provided by a support structure may result in no appreciable change in the elastic energy of the membrane. The membrane profile may be adjusted by movement of a plurality of control points along respective guide paths, and this may result in no appreciable change in the elastic energy of the membrane. The membrane may be an elastic membrane, and the membrane profile may be a curved profile providing a refractive surface of the fluid lens.

[0030] FIG. 1A depicts a cross-section through a fluid lens, according to some examples. The fluid lens 100 illustrated in this example includes a substrate 102 (which in this example is a generally rigid, planar substrate), a substrate coating 104, a membrane 106, a fluid 108 (denoted by dashed horizontal lines), an edge seal 110, a support structure 112 providing a guide surface 114, and a membrane attachment 116. In this example, the substrate 102 has a lower (as illustrated) outer surface, and an interior surface on which the substrate coating 104 is supported. The interior surface 120 of the substrate coating 104 is in contact with the fluid 108. The membrane 106 has an upper (as illustrated) outer surface and an interior surface 122 bounding the fluid 108. The substrate coating 104 may be optional.

[0031] The fluid 108 is enclosed within an enclosure 118, which is at least in part defined by the substrate 102 (along with the substrate coating 104), the membrane 106, and the edge seal 110, which here cooperatively define the enclosure 118 in which the fluid 108 is located. The edge seal 110 may extend around the periphery of the enclosure 118, and retain (in cooperation with the substrate and the membrane) the fluid within the enclosed fluid volume of the enclosure 118. In some examples, an enclosure may be referred to as a cavity or lens cavity.

[0032] In this example, the membrane 106 has a curved profile, so that the enclosure has a greater thickness in the center of the lens than at the periphery of the enclosure (e.g., adjacent the edge seal 110). In some examples, the fluid lens may be a plano-convex lens, with the planar surface being provided by the substrate 102 and the convex surface being provided by the membrane 106. A plano-convex lens may have a thicker layer of lens fluid around the center of the lens. In some examples, the exterior surface of a membrane may provide the convex surface, with the interior surface being substantially adjacent the lens fluid.

[0033] The support structure 112 (which in this example may include a guide slot through which the membrane attachment 116 may extend) may extend around the periphery (or within a peripheral region) of the substrate 102, and may attach the membrane to the substrate. The support structure may provide a guide path, in this example a guide surface 114 along which a membrane attachment 116 (e.g., located within an edge portion of the membrane) may slide. The membrane attachment may provide a control point for the membrane, so that the guide path for the membrane attachment may provide a corresponding guide path for a respective control point.

[0034] The fluid lens 100 may include one or more actuators (not shown in FIG. 1A) that may be located around the periphery of the lens and may be part of or mechanically coupled to the support structure 112. The actuators may exert a controllable force on the membrane at one or more control points, such as provided by membrane attachment 116, that may be used to adjust the curvature of the membrane surface and hence at least one optical property of the lens, such as focal length, astigmatism correction, surface curvature, cylindricity, or any other controllable optical property. In some examples, the membrane attachment may be attached to an edge portion of the membrane, or to a peripheral structure extending around the periphery of the membrane (such as a peripheral guide wire, or a guide ring), and may be used to control the curvature of the membrane.

[0035] In some examples, FIG. 1A may represent a cross-section through a circular lens, though examples fluid lenses may also include non-circular lenses, as discussed further below.

[0036] FIG. 1B shows a fluid lens, of which FIG. 1A may be a cross-section. The figure shows the fluid lens 100, including the substrate 102, the membrane 106, and the support structure 112. In this example, the fluid lens 100 may be a circular fluid lens. The figure shows the membrane attachment 116 as moveable along a guide path defined by the guide slot 130 and the profile of the guide surface 114 (shown in FIG. 1A). The dashed lines forming a cross are visual guides indicating a general exterior surface profile of the membrane 106. In this example, the membrane profile may correspond to a plano-convex lens.

[0037] FIG. 1C shows a non-circular lens 150 that may otherwise be similar to the fluid lens 100 of FIG. 1B and may have a similar configuration. The non-circular lens 150 includes substrate 152, membrane 156, and support structure 162. The lens has a similar configuration of the membrane attachment 166, movable along a guide path defined by the guide slot 180. The profile of a guide path may be defined by the surface profile of the support structure 162, through which the guide slot is formed. The cross-section of the lens may be analogous to that of FIG. 1A. The dashed lines forming a cross on the membrane 156 are visual guides indicating a general exterior surface profile of the membrane 156. In this example, the membrane profile may correspond to a plano-convex lens.

[0038] FIGS. 2A-2D illustrate an ophthalmic device 200 including a fluid lens 202, according to some examples. FIG. 2A shows a portion of an ophthalmic device 200, which includes a portion of a peripheral structure 210 (that may include a guide wire or a support ring) supporting a fluid lens 202.

[0039] In some examples, the lens may be supported by a frame. An ophthalmic device (e.g., spectacles, goggles, eye protectors, visors, and the like) may include a pair of fluid lenses, and the frame may include components configured to support the ophthalmic device on the head of a user, for example, using components that interact with (e.g., rest on) the nose and/or ears of the user.

[0040] FIG. 2B shows a cross-section through the ophthalmic device 200, along A-A’ as shown in FIG. 2A. The figure shows the peripheral structure 210 and the fluid lens 202. The fluid lens 202 includes a membrane 220, lens fluid 230, an edge seal 240, and a substrate 250. In this example, the substrate 250 includes a generally planar, rigid layer. The figure shows that the fluid lens may have a planar-planar configuration, which in some examples may be adjusted to a plano-concave and/or plano-convex lens configuration.

[0041] In some examples disclosed herein, one or both surfaces of the substrate may include a concave or convex surface, and in some examples the substrate may have a non-spherical surface such as a toroidal or freeform optical progressive or digressive surface. In various examples, the substrate may include a plano-concave, plano-convex, biconcave, biconvex, or concave-convex (meniscus) lens, or any other suitable optical element. In some examples, one or both surfaces of the substrate may be curved. For example, a fluid lens may be a meniscus lens having a substrate (e.g., a generally rigid substrate having a concave exterior substrate surface and a convex interior substrate surface), a lens fluid, and a convex membrane exterior profile. The interior surface of a substrate may be adjacent to the fluid, or adjacent to a coating layer in contact with the fluid.

[0042] FIG. 2C shows an exploded schematic of the device shown in FIG. 2B, in which corresponding elements have the same numbering as discussed above in relation to FIG. 2A. In this example, the edge seal is joined with a central seal portion 242 extending over the substrate 250.

[0043] In some examples, the central seal portion 242 and the edge seal 240 may be a unitary element. In other examples, the edge seal may be a separate element, and the central seal portion 242 may be omitted or replaced by a coating formed on the substrate. In some examples, a coating may be deposited on the interior surface of the seal portion and/or edge seal. In some examples, the lens fluid may be enclosed in a flexible enclosure (sometimes referred to as a bag) that may include an edge seal, a membrane, and a central seal portion. In some examples, the central seal portion may be adhered to a rigid substrate component and may be considered as part of the substrate. In some examples, the coating may be deposited on at least a portion of the enclosure surface (e.g., the interior surface of the enclosure). The enclosure may be provided, at least in part, by one or more of the following; a substrate, an edge seal, a membrane, a bag, or other lens component. The coating may be applied to at least a portion of the enclosure surface at any suitable stage of lens fabrication, for example, to one or more lens components (e.g., the interior surface of a substrate, membrane, edge seal, bag, or the like) before, during, or after lens assembly. For example, a coating may be formed before lens assembly (e.g., during or after fabrication of lens components); during lens assembly; after assembly of lens components but before introduction of the fluid to the enclosure; or by introduction of a fluid including a coating material into the enclosure. In some examples, a coating material (such as a coating precursor) may be included within the fluid introduced into the enclosure. The coating material may form a coating on at least a portion of the enclosure surface adjacent the fluid.

[0044] FIG. 2D shows adjustment of the device configuration, for example, by adjustment of forces on the membrane using actuators (not shown). As shown, the device may be configured in a planar-convex fluid lens configuration. In an example plano-convex lens configuration, the membrane 220 tends to extend away from the substrate 250 in a central portion.

[0045] In some examples, the lens may also be configured in a planar-concave configuration, in which the membrane tends to curve inwardly towards the substrate in a central portion.

[0046] FIG. 2E illustrates a similar device to FIG. 2B, and element numbering is similar. However, in this example, the substrate 250 of the example of FIG. 2B is replaced by a second membrane 221, and there is a second peripheral structure (such as a second support ring) 211. In some examples disclosed herein, the membrane 220 and/or the second membrane 221 may be integrated with the edge seal 240.

[0047] FIG. 2F shows the dual membrane fluid lens of FIG. 2E in a biconcave configuration. For example, application of negative pressure to the lens fluid 230 may be used to induce the biconcave configuration. In some examples, the membrane 220 and second membrane 221 may have similar properties, and the lens configuration may be generally symmetrical, for example, with the membrane and second membrane having similar radii of curvature (e.g., as a symmetric biconvex or biconcave lens). In some examples, the lens may have rotational symmetry about the optical axis of the lens, at least within a central portion of the membrane, or within a circular lens. In some examples, the properties of the two membranes may differ (e.g., in one or more of thickness, composition, membrane tension, or in any other relevant membrane parameter), and/or the radii of curvature may differ. In these examples, the membrane profiles have a negative curvature, that corresponds to a concave curvature. The membrane profile may relate to the external shape of the membrane. A negative curvature may have a central portion of the membrane closer to the optical center of the lens than a peripheral portion (e.g., as determined by radial distances from the center of the lens).

[0048] FIG. 2G shows the dual membrane fluid lens of FIG. 2E in a biconvex configuration, with corresponding element numbers.

[0049] In some examples, an ophthalmic device, such as an eyewear device, includes one or more fluid lenses. An example device includes at least one fluid lens supported by eyeglass frames. In some examples, an ophthalmic device may include an eyeglass frame, goggles, or any other frame or head-mounted structure to support one or more fluid lenses, such as a pair of fluid lenses.

[0050] FIG. 3 illustrates an ophthalmic device, in this example an eyewear device, including a pair of fluid lenses, according to some examples. The eyewear device 300 may include a pair of fluid lenses (306 and 308) supported by a frame 310 (which may also be referred to as an eyeglass frame). The pair of fluid lenses 306 and 308 may be referred to as left and right lenses, respectively (from the viewpoint of the user).

[0051] In some examples, an eyewear device (such as eyewear device 300 in FIG. 3) may include a pair of eyeglasses, a pair of smart glasses, an augmented reality device, a virtual reality headset, an augmented reality device, or the like. In some examples, a head-mounted device may be or include an eyewear device. An eyewear device may be or include an augmented reality headset, virtual reality headset, ophthalmic device (such as eyeglasses or spectacles), smart glasses, visor, goggles, other eyewear, or other device. An ophthalmic device may include fluid lenses that have an optical property (such as an optical power, astigmatism correction, cylindricity, or other optical property) corresponding to a prescription, for example, as determined by an eye examination. An optical property of the lens may be adjustable, for example, by a user or by an automated system. Adjustments to the optical property of a fluid lens may be based on the activity of a user, the distance to an observed article, or other parameter. In some examples, one or more optical properties of an eyewear device may be adjusted based on a user identity. For example, an optical property of one or more lenses within an AR and/or VR headset may be adjusted based on the identity of the user, which may be determined automatically (e.g., using a retinal scan) or by a user input.

[0052] In some examples, a device may include a frame (such as an eyeglass frame) that may include or otherwise support one or more of any of the following: a battery, a power supply or power supply connection, other refractive lenses (including additional fluid lenses), diffractive elements, displays, eye-tracking components and systems, motion tracking devices, gyroscopes, computing elements, health monitoring devices, cameras, and/or audio recording and/or playback devices (such as microphones and speakers). The frame may be configured to support the device on a head of the user.

[0053] FIG. 4A shows an example fluid lens 400 including a peripheral structure 410 that may generally surround a fluid lens 402. The peripheral structure 410 (in this example, a support ring) includes membrane attachments 412 that may correspond to the locations of control points for the membrane of the fluid lens 402. A membrane attachment may be an actuation point, where the lens may be actuated by displacement (e.g., by an actuator acting along the z-axis) or moved around a hinge point (e.g., where the position of the membrane attachment may be an approximately fixed distance “z” from the substrate). In some examples, the peripheral structure and hence the boundary of the membrane may flex freely between neighboring control points. Hinge points may be used in some examples to prevent bending of the peripheral structure (e.g., a support ring) into energetically favorable, but undesirable, shapes.

[0054] A rigid peripheral structure, such as a rigid support ring, may limit adjustment of the control points of the membrane. In some examples, such as a non-circular lens, a deformable or flexible peripheral structure, such as a guide wire or a flexible support ring, may be used.

[0055] FIG. 4B shows a cross-section of the example fluid lens 400 (e.g., along A-A’ as denoted in FIG. 4A). The fluid lens includes a membrane 420, fluid 430, edge seal 440, and substrate 450. In some examples, the peripheral structure 410 may surround and be attached to the membrane 420 of the fluid lens 402. The peripheral structure may include membrane attachments 412 that may provide the control points for the membrane. The position of the membrane attachments (e.g., relative to a frame, substrate, or each other) may be adjusted using one or more actuators, and used to adjust, for example, the optical power of the lens. A membrane attachment having a position adjusted by an actuator may also be referred to as an actuation point, or a control point.

[0056] In some examples, an actuator 460 may be attached to actuator support 462, and the actuator may be used to vary the distance between the membrane attachment and the substrate, for example, by urging the membrane attachment along an associated guide path. In some examples, the actuator may be located on the opposite side of the membrane attachment from the substrate. In some examples, an actuator may be located so as to exert a generally radial force on the membrane attachment and/or support structure, for example, exerting a force to urge the membrane attachment towards or away from the center of the lens.

[0057] In some examples, one or more actuators may be attached to respective actuator supports. In some examples, an actuator support may be attached to one or more actuators. For example, an actuator support may include an arcuate, circular, or other shaped member along which actuators are located at intervals. Actuator supports may be attached to the substrate, or, in some examples, to another device component such as a frame. In some examples, the actuator may be located between the membrane attachment and the substrate, or may be located at another suitable location. In some examples, the force exerted by the actuator may be generally directed along a direction normal to the substrate, or along another direction, such as along a direction at a non-normal direction relative to the substrate. In some examples, at least a component of the force may be generally parallel to the substrate. The path of the membrane attachment may be based on the guide path, and in some examples the force applied by the actuator may have at least an appreciable component directed along the guide path.

[0058] FIG. 5 shows an example fluid lens 500 including a peripheral structure 510, here in the form of the support ring including a plurality of membrane attachments 512, and extending around the periphery of a membrane 520. The membrane attachments may include or interact with one or more support structures that each provide a guide path for an associated control point of the membrane 520. Actuation of the fluid lens may adjust the location of one or more control points of the membrane, for example, along the guide paths provided by the support structures. Actuation may be applied at discrete points on the peripheral structure, for example, the membrane attachments shown. In some examples, the peripheral structure may be flexible, for example, so that the peripheral structure may not be constrained to lie within a single plane.

[0059] In some examples, a fluid lens includes a membrane, a support structure, a substrate, and an edge seal. The support structure may be configured to provide a guide path for an edge portion of the membrane (such as a control point provided by a membrane attachment). An example membrane attachment may function as an interface device, configured to mechanically interconnect the membrane and the support structure, and may allow the membrane to exert an elastic force on the support structure. A membrane attachment may be configured to allow the control point of the membrane (that may be located in an edge portion of the membrane) to move freely along the guide path.

[0060] An adjustable fluid lens may be configured so that adjustment of the membrane profile (e.g., an adjustment of the membrane curvature) may result in no appreciable change in the elastic energy of the membrane, while allowing modification of an optical property of the lens (e.g., a focal length adjustment). This configuration may be termed a “zero-strain” device configuration as, in some examples, adjustment of at least one membrane edge portion, such as at least one control point, along a respective guide path does not appreciably change the strain energy of the membrane. In some examples, a “zero-strain” device configuration may reduce the actuation force required by an order of magnitude when compared with a conventional support beam type configuration. A conventional fluid lens may, for example, require an actuation force that is greater than 1N for an actuation distance of 1 mm. Using a “zero-strain” device configuration, actuation forces may be 0.1N or less for an actuation of 1 mm, for quasi-static actuation. This substantial reduction of actuation forces may enable the use of smaller, more speed-efficient actuators in fluid lenses, resulting in a more compact and efficient form factor. In such examples, in a “zero-strain” device configuration, the membrane may actually be under appreciable strain, but the total strain energy in the membrane may not change appreciably as the lens is adjusted. This may advantageously greatly reduce the force used to adjust the fluid lens.

[0061] In some examples, a fluid lens may be configured to have one or both of the following features: in some examples, the strain energy in the membrane is approximately equal for all actuation states; and in some examples, the force reaction at membrane edge is normal to the guide path. Hence, in some examples, the strain energy of the membrane may be approximately independent of the optical power of the lens. In some examples, the force reaction at the membrane edge is normal to the guide path, for some or all locations on the guide path.

[0062] In some examples, movement of the edge portion of the membrane along the guide path may not result in an appreciable change in the elastic energy of the membrane. This configuration may be termed a “zero-strain” guide path as, in some examples, adjustment of the membrane edge portion along the guide path does not appreciably change the strain energy of the membrane.

[0063] FIG. 6A shows a fluid lens 600 according to some examples, as a view from the front of the fluid lens 600. The fluid lens 600 may include a membrane 620 that is held at its periphery by bendable support ring 610. The membrane 620 may be a tensioned distensible membrane.

[0064] FIG. 6B illustrates the fluid lens 600 in cross-section, for example, along line A-A’ denoted in FIG. 6A. The fluid lens 600 includes lens fluid 630 enclosed by the membrane 620 and an edge seal 640, and including a rigid substrate (that may be a rigid lens) 650. In some examples, the membrane 620, edge seal 640, and optionally an additional layer (not shown) may be interconnected to form a collapsible bag that may enclose the lens fluid. In some examples, the edge seal 640 and the membrane 620 may be joined to one another using ultrasonic welding, an adhesive, or other methods or combination of methods. The fluid lens 600 may be an adjustable liquid-filled lens.

[0065] FIG. 6C shows the example lens in a concave membrane configuration that may be effected by moving the bendable support ring 610 away from the substrate 650, for example, using an actuator (not shown). This may be used to provide a plano-concave lens configuration.

[0066] In some examples, a concave membrane surface may be achieved by reducing pressure on the lens fluid, and optionally by removing lens fluid from the enclosure. Reducing pressure on the lens fluid may reduce gas solubility within the fluid, and may lead to the formation of bubbles within the fluid. These may have negative effects on the lens quality, for example, by scattering light, and may degrade the appearance of a fluid lens.

[0067] FIGS. 7A-7D illustrate a possible mechanism for bubble formation in a fluid lens 700.

[0068] FIG. 7A shows a fluid lens 700 including a frame (or support ring) 710, membrane 720, fluid 730, edge seal 740, and substrate 750. As illustrated in this figure, fluid 730 may include bubbles, such as bubble 745.

[0069] The lower portion of FIG. 7A shows a more detailed representation of the surface roughness of the substrate 750. A bubble 735 may nucleate and grow within a recess 754 (e.g., a depression, indentation, or similar) within the interior surface 752 of the substrate 750. In some cases, the substrate surface in contact with (or more proximate to) the fluid may be referred to as the interior surface of the substrate. The recess 754 may include, for example, a scratch, a pit, or other surface imperfection of the interior surface 752 of the substrate 750.

[0070] The interior surface 752 of the substrate 750 may have a surface roughness, which may be represented illustratively by surface deviations from planarity, such as projections and recesses. These deviations from a mean surface profile may be generally referred to as surface defects.

[0071] The interior surfaces of the enclosure, such as the interior surfaces of the substrate, edge seal, or membrane, may each have an appreciable surface roughness, and may include surface defects that may act as nucleation sites for bubble formation during operation of the lens.

[0072] FIG. 7B shows the bubble 735 further growing in size.

[0073] FIG. 7C shows the bubble 748 floating away from the interior surface 752 and into the bulk of the fluid 730. Another bubble 738 may nucleate in the same (or different) location from the surface defect which nucleated the bubble 748.

[0074] FIG. 7D shows a fluid lens 760, according to some examples. The elements and corresponding element numbers are generally the same as discussed above in relation to FIGS. 7A-7C, and are not repeated. However, compared to the lens of FIG. 7A, fluid lens 760 further includes a coating 770, which in this example may be located adjacent the interior of the enclosure (e.g., located on the interior surface 752 of the substrate 750). The coating has an interior surface 765, where the interior surface is a fluid-facing surface. In some examples, the coating 770, when deposited on the interior surface 752 of the substrate 750, is self-leveling with respect to the surface on which the coating is deposited (e.g., an interior surface).

[0075] In some examples, coating 770 may be applied to interior surface 752 of the substrate 750 by introducing a liquid or a vapor into the enclosure. In some examples, the coating material may be polymerized or otherwise cured, after deposition of a coating material, before the fluid 730 is introduced to the lens enclosure. In some examples, the fluid 730 may be an optical fluid, such as an optical liquid. The coating material introduced into the enclosure may be or include a precursor to the final coating composition. For example, the coating material may include a monomer or other polymerizable material, and the coating may include a polymer formed by polymerizing the monomer or other polymerizable material.

[0076] In some examples, a coating material, such as a coating precursor, may be added to the fluid as a dissolved component, or in suspension, for example, as a component of an emulsion. A coating material may interact with the surface to form a coating. In some examples, the coating may be formed by a precursor coating, for example, by polymerization and/or cross-linking of a coating precursor.

[0077] In some examples, a coating material may be added to the fluid 730, and may be deposited on the interior surface of the enclosure from the fluid, when the fluid is introduced to the enclosure. The coating material may be a liquid, and in some examples may be immiscible with fluid 730. The coating material may deposit on, adhere to, or otherwise interact with the inside of the enclosure.

[0078] The interior surface 765 of the coating (that may be in contact with the lens fluid) may be relatively smooth, for example, relative to the surface on which the coating is deposited, and may provide essentially no, or a greatly reduced number of, nucleation sites, so that bubble formation may become negligible (e.g., vanishingly unlikely) in normal use of the fluid lens.

[0079] In some examples, the coating 770 may include a liquid coating. A liquid coating may include a liquid component that is immiscible with the lens fluid. A liquid coating may have the further property that the liquid coating scavenges particulate contaminants in the optical fluid, which may further reduce nucleation site availability for the lens fluid. In some examples, a liquid coating does not cavitate when under negative pressure, under normal operating conditions. A liquid coating may have a low vapor pressure, and may have a low gas solubility. In some examples, a liquid coating may be retained against the surface by hydrophobic or hydrophilic interactions with the surface. In some examples, a liquid coating may include polar molecules that may interact with polar groups on the substrate surface (or any other surface to be coated). For example, the substrate surface may include one or more species of polar groups. For example, a glass substrate surface may include silanol groups. A polar liquid may be introduced as a film between, for example, a hydrophobic lens fluid and a polar surface, and may be retained as a polar liquid layer adjacent the polar substrate surface by polar interactions, such as van der Waals interactions, and the like. In some examples, a substrate surface may be coated with a monolayer, such as a self-assembling monolayer. In some examples, the monolayer may include long flexible groups, such as long aliphatic chains (e.g., C10-C30 aliphatic chains, such as alkyl groups) that may tend in aggregate to smooth out the surface roughness of the substrate surface.

[0080] FIGS. 8A-81 show various aspects of example approaches to preparing a fluid lens. FIGS. 8A-8B show an example fluid lens, with FIG. 8A being an exploded view not showing the lens fluid. The fluid lens 800 includes a peripheral structure 810, a membrane 820, an edge seal 840, and a substrate 850. The fluid lens 800 may include a fill port 841 and a vent port 842 that may be included as a component of the edge seal 840. Lens components, such as the edge seal 840, may be molded, thermoformed from a film, or manufactured by other means as appropriate. The edge seal may be elastomeric or compliant, and may deform during lens actuation.

[0081] FIG. 8C shows the coating material 835 introduced to the enclosure through the fill port 841. The figure shows an injection method including a syringe and needle 836, but any suitable pump may be used. In some examples, the coating material 835 may be a liquid as shown here.

[0082] FIG. 8D shows that ultrasonic agitation may be used to spread the coating material over interior surfaces of the enclosure, forming a coating 860 on the interior surface of the membrane, and a coating 870 on the interior surface of the substrate.

[0083] Alternatively, the coating material 835 may be injected into the enclosure as a vapor that condenses on the interior surfaces. In some examples, the vapor material may include an aerosol. When an even coating of the interior surfaces has been achieved, the coating may be polymerized (e.g., cured) using one or more of ultraviolet radiation, catalysis, or other suitable approach.

[0084] FIG. 8E shows the use of UV (ultraviolet) radiation to polymerize the coatings 860 and 870.

[0085] FIG. 8F shows the lens enclosure being filled with lens fluid 830 using a syringe and needle. Injection may be achieved using a syringe and needle 836, or other suitable pump. Once the lens enclosure is filled with lens fluid, the fill port 841 and vent port 842 (shown in FIG. 8B) may be sealed.

[0086] FIGS. 8G and 8H show elevation and perspective views, respectively, of the edge seal 840, and example locations of fill port 841 and vent port 842.

[0087] FIG. 81 illustrates a method of sealing the lens using an anvil (including anvil base 880 and anvil component 875). An ultrasonic horn may be used to seal components and ports closed. Other sealing approaches, such as bungs or plugs, or liquid adhesive, may be used.

[0088] FIG. 9 illustrates an example method 900 of fabricating a fluid lens. The method includes introducing a coating material into the interior enclosure of a fluid lens (910), agitating the coating material to deposit the coating material onto one or more interior surfaces (920), polymerizing the coating material to form a coating (930), and introducing a lens fluid into the enclosure to form the fluid lens (940).

[0089] FIG. 10 illustrates an example method 1000 of fabricating a fluid lens. The method includes introducing a lens fluid into the interior enclosure of a fluid lens (1010), forming a coating on one or more interior surfaces of the enclosure using a coating material component of the lens fluid (1020), and polymerizing the coating to form the fluid lens (1030).

[0090] Examples described herein include a fluid lens, such as a liquid lens, having a relatively low-nucleating enclosure (e.g., using a coating to reduce the number of bubble nucleation sites). In some examples, a fluid lens may have an effectively non-nucleating lens enclosure. In this context, a low-nucleating lens enclosure may be a lens enclosure having a reduced propensity for formation of bubbles in the enclosed fluid, with the reduction being due to the coating. A non-nucleating lens enclosure may be a lens enclosure having no appreciable propensity for formation of bubbles in the enclosed fluid.

[0091] In some examples, the surface of a fluid lens enclosure (which may be referred to herein as the “fluid volume” or the “enclosure”) has a coating disposed between one or more interior surfaces of the enclosure and the enclosed fluid. The coating may substantially eliminate, or otherwise reduce, the number of nucleation sites for gas bubbles to form within the enclosure fluid. The coating may significantly reduce the probability of bubble formation within the enclosure, for example, by reducing the number of bubbles formed in the lens fluid for a given device condition (e.g., for a given temperature and/or optical parameter) by a factor of 2 or more, for example, when comparing a coated substrate with an uncoated substrate. The reduction in bubble formation may be particularly advantageous when the lens has a negative gage pressure (e.g., for a concave membrane). For example, a lens with an uncoated substrate may be prone to bubble formation on the substrate when the gage pressure is negative, and the lens is in, for example, a plano-concave state. However, a coating on the substrate surface may appreciably reduce or substantially eliminate bubble formation.

[0092] In some examples, the coating may include a solid, especially a low modulus solid, a gel, or an immiscible fluid such as a colloid, suspension, emulsion, hydrogel, or other fluid. In some examples, a low modulus solid may have a Young’s modulus at least one order of magnitude less than that of the substrate. In some examples, a low modulus solid may include a low modulus polymer, such as a polymer having a Young’s modulus at least one order of magnitude less than that of the substrate. In this context, a low modulus polymer may include an elastomer, a polymer having a low degree of polymerization (e.g., compared to that of a polymer substrate), or a polymer used to form a coating on a rigid glass substrate. In some examples, a polymer coating on the substrate surface may swell slightly on absorbing molecules of the lens fluid, that may reduce surface roughness (e.g., by helping to fill in surface depressions).

[0093] In some examples, a fluid lens, such as a liquid lens, includes an elastic membrane, a substrate, and a liquid filling an enclosure at least partially defined by the elastic membrane and the substrate. A coating may be applied to at least a portion of the enclosure surfaces, such as the membrane and/or substrate interior surfaces that define the enclosure and are in contact with the fluid when the enclosure is filled with the fluid. The enclosure surface may be an interior surface of the enclosure, proximate or adjacent the fluid. In some examples, the coating may be located between the enclosure surface and the fluid, and the coating surface roughness may be appreciably less than that of a corresponding uncoated enclosure surface.

[0094] In some examples, a device includes one or more fluid lenses. A fluid lens may include an enclosure including a fluid. The enclosure may be defined, at least in part, by lens components such as a membrane, a substrate (and/or a second substrate), and an optional edge seal. An example lens component may have an interior surface that may be substantially adjacent the enclosure. The interior surface may have a coating configured to appreciably reduce bubble formation on the interior surface during use of the fluid lens. Appreciable reduction may include a decrease in bubble numbers of approximately 25% or more under one or more particular operating conditions, such as approximately 50% or more, and may include substantial elimination of bubble formation. Appreciable reduction may be determined using a comparison of similar lenses having coated and uncoated interior surfaces under similar operating conditions, that may include application of a negative pressure to the fluid. In some examples, a lens may include a substrate, such as a transparent substrate, such as a rigid transparent substrate. In this context, a rigid substrate may show a relatively small mechanical deformation as the fluid pressure and/or volume is adjusted (e.g., as compared to the membrane). A relatively small mechanical deformation may be one that results in a relatively small change in an optical property of the lens, such as one that would not normally be perceptible to a human user during routine use of the device.

[0095] In some examples, a coating may be located between the substrate and the fluid. In some examples, the coating may be covalently bonded to a surface of the substrate. In some examples, the coating may be retained by the substrate by ionic or polar interactions. For example, the substrate may include a polar material, the bulk of the fluid may be non-polar, and a layer (e.g., a liquid coating) including a polar material, such as a polar liquid, may be located adjacent the substrate. In some examples, the layer may provide the coating. In some examples, the layer may be a precursor layer (a precursor coating) that may be further processed (e.g., polymerized) to form the coating.

[0096] In some examples, a substrate may include glass, such as a silicate glass, such as a borosilicate glass. A coating may interact with, or bond to, a glass surface, for example, using silicon-oxygen bonds, or other bonds. A coating may include a silicone polymer. A coating may include a polysiloxane having side-groups, such as hydrocarbon chains that may help reduce surface roughness. In some examples, a coating may include a self-assembled multilayer (SAM).

[0097] In some examples, a fluid lens component includes a polymer. A coating may include chemical groups that may form bonds to the polymer. For example, a substrate may include an acrylate polymer, and a coating material may include an acrylate material, that may, for example, be polymerized to form an acrylate polymer coating and that may also form bonds to unpolymerized or end groups within the polymer. In some examples, a fluid lens component and a coating may include polymers formed from chemically-related polymerizable materials (e.g., both substrate and coating may include an acrylate, urethane, and/or other particular polymer). In some examples, a substrate may be cross-linked, and the cross-linking process may both further stabilize the coating and introduce bonds between the coating and the substrate.

[0098] In some examples, the coating may include a polymer (e.g., an acrylate, silicone, epoxy, urethane, or other polymer, or co-polymers or blends thereof). In some examples, the coating may have a limited solubility in the fluid, and may, in some examples, have no significant solubility in the fluid.

[0099] In some examples, the coating may include a fluoropolymer, such as a polyfluoroethylene, such as polytetrafluorethylene.

[0100] In some examples, a method (e.g., a method of fabricating a fluid lens) includes preparing a fluid mixture, such as a liquid mixture, including a coating material, and filling the enclosure of a fluid lens with the fluid mixture. A coating may then form on the enclosure surface of the fluid lens. The coating may include or be formed from the coating material. In some examples, the coating material may be or include a coating precursor that may be used to form the coating. A coating precursor may include a polymerizable material (e.g., used to form a coating including a polymer), or a material that may otherwise react (e.g., with one or more of the substrate, other similar material, or other coating material component) to form the coating. Example methods may include a method of fabricating a fluid lens, or device including one or more fluid lenses. Example methods may include a method of applying a coating (such as a low-nucleation coating, that reduces the number of bubble nucleation sites) to the interior surface of the enclosure of a fluid lens. In some examples, a liquid mixture may be introduced to the enclosure, and may separate when in the enclosure of the fluid lens. For example, a non-polar component may form the lens fluid, and a polar component (or portion thereof) may interact with the enclosure surface to form the coating. A coating, such as a low-nucleation coating, may be formed from a mixture component including the coating material. In some examples, the mixture may include an emulsion of the coating material, for example, an emulsion of the coating material in a liquid (such as a high refractive index liquid). In some examples, the coating material and the fluid may be miscible. In some examples, the lens enclosure may be filled by the mixture at an elevated temperature.

[0101] In some examples, a method of fabricating a fluid lens includes introducing a lens fluid and a coating material (e.g., as a mixture, suspension, emulsion, solution, or other form) into the enclosure of a fluid lens that may be defined, at least in part, by a flexible membrane and a substrate. At least some of the coating material may form a layer on the interior surfaces of the enclosure, and the coating may then be formed from the layer of the coating material. Forming the coating may include polymerization of coating precursor (e.g., a precursor component of the coating material), such as photopolymerization of a monomer. In some examples, the substrate may be omitted and the enclosure formed by one or more membranes, such as two or more membranes, or a membrane assembly providing both exterior surfaces of the lens.

[0102] In some examples, formation of the coating may include a processing step such as polymerizing one or more precursor components of the coating material. In this context, a precursor may include a material that undergoes a further transformation (such as one or more of polymerization, cross-linking, adhesion to and/or reaction with a surface, or other process) as part of formation of the coating. For example, a precursor may be a monomer that may be polymerized to form a polymer component of the coating. The lens fluid of the fabricated lens may include one or more components originating from the coating material that do not become part of the coating, though the concentration may be sufficiently low as to not have an appreciable effect on the refractive index of the fluid.

[0103] In some examples, the coating material may include one or more polymerizable materials, such as one or more monomer molecular species. In some examples, the polymerizable material (such as a monomer) is polymerized after the fluid lens is filled with the mixture. Example coating materials (e.g., a coating precursor) may include one or more monomer molecular species, such as an epoxy, an acrylate (e.g., ethyl acrylate), a silicone (e.g., an alkylsiloxane, such as a dialkylsiloxane, such as dimethylsiloxane), or other suitable monomer. A polymerizable material, such as a monomer, may be polymerized (e.g., thermally polymerized, photopolymerized, or otherwise polymerized) and polymerization may optionally be promoted by addition of a catalyst or an initiator. In some examples, a polymerizable material may be polymerized using actinic radiation, such as UV and/or visible electromagnetic radiation, or an electron beam. A coating material may include one or more precursors, such as one or more polymerizable materials, and an additional processing step (such as polymerization) may be used to form the coating.

[0104] In some examples, a method (e.g., a method of applying a low-nucleating coating) includes forming a coating on the interior surfaces of the fluid lens enclosure, and filling the fluid lens enclosure with a fluid (such as a high refractive index fluid, such as a silicone oil). In some examples, the coating is further processed before filling the lens with a fluid. For example, the initially deposited coating may be subject to one or more of the following: drying (including vapor removal), heat treatment, polymerization, cross-linking, further chemical treatment, further coating deposition, and the like. In some examples, the coating may undergo further processes after the enclosure is filled with a fluid. In some examples, the coating may be dried after filling with a fluid, where, for example, any fluid components of the coating (such as a solvent) may evaporate through the membrane, or other lens component. In some examples, a polymerizable component of the coating may be polymerized after the enclosure is filled with a lens fluid.

[0105] In some examples, fluid lenses may have a coating formed on at least part of the enclosure surface to reduce (e.g., substantially eliminate) bubble formation in the fluid lens. In some examples, gas solubility in the lens fluid may also be reduced. In some examples, a lens fluid may be used that has a reduced propensity for bubble formation.

[0106] Reducing bubble formation allows negative pressures to be applied to the lens fluid of a fluid lens, allowing a greater range of focal lengths and/or optical powers to be achieved by a fluid lens. In some examples, a fluid lens may have a membrane that may be adjusted from a generally convex configuration, through a generally planar configuration, to a generally concave configuration, and vice versa. This allows the fabrication of thinner and/or lighter lens configurations. The availability of concave configurations also allows a greater range of optical powers to be achieved. In some examples, the substrate may have a curved exterior and/or interior surface profile, and may contribute to the optical power of the fluidic lens.

[0107] In some examples, a coating may include a liquid or other fluid, such as a gel or mucus, that may immiscible with the lens fluid and that preferentially adheres to the inside of the enclosure. In some examples, a coating may interact with the coated surface through one or more of chemical bonds, hydrogen bonds, or dipolar interactions.

[0108] In some examples, one or more lens components (such as a substrate, edge seal, or membrane) may be imparted with a coating (e.g., using a similar method to those described herein) before, during, or after assembly of the fluid lens.

[0109] In some examples, the interior surface of the enclosure may be further processed to reduce nucleation sites. For example, the membrane or substrate may be locally heated to assist in providing a smooth surface. A membrane or substrate may be heated, or otherwise processed, before, during, or after assembly of the fluid lens. In some examples, a portion of an interior surface, with or without a coating, may be exposed to IR radiation to induce local heating of the surface, and reduction of nucleation sites.

[0110] In some applications, a fluid lens may show gravity sag, which is a typically undesired variation of optical power with height due to a hydrostatic pressure gradient in the fluid lens. Gravity sag may be expressed as change in optical power with height (e.g., 0.25 D in 20 mm). In some examples, a coating may also modify the elastic properties of a membrane in such a way that gravity sag is reduced or substantially eliminated.

[0111] In some examples, a membrane may be subject to a surface treatment, such as a coating, that may be provided before or after fluid lens assembly. In some examples, a polymer may be applied to the membrane, such as a polymer coating, for example, a fluoropolymer coating. A fluoropolymer coating may include one or more fluoropolymers, such as polytetrafluoroethylene, or its analogs, blends, or derivatives.

[0112] In some examples of an improved fluid lens, these inside surfaces may be treated to reduce or substantially eliminate bubble formation within the fluid of a fluid lens. The number of nucleation sites for bubble formation may be reduced using a surface coating and/or other treatment. The surface coating may be formed on the interior surface of the enclosure before filling the enclosure with the fluid, and in some examples may occur after filing using components added to the fluid. For example, the surfaces may be coated with a polymer layer (e.g., by polymerizing a precursor layer, such as surface monomer layer), or with a fluid, gel, or emulsion layer that is immiscible with the lens liquid. A coating may include one or more of various materials, such as an acrylate polymer, a silicone polymer, an epoxy-based polymer, or a fluoropolymer. In some examples, a coating may include a fluoroacrylate polymer, such as perfluoroheptylacrylate, or other fluoroalkylated acrylate polymer.

[0113] Reducing the number of nucleation sites may prevent or lower the number of bubbles that may form within a fluid lens, particularly when the fluid within the lens is subject to negative pressure (e.g., pressure below ambient pressure). Allowing reduced pressures to be applied to the fluid, with appreciably reduced bubble formation, may increase (e.g., double) the optical power range of an adjustable lens, for example, by enabling lens adjustment from a convex to a concave lens.

[0114] In some examples, a device includes at least one fluid lens. One or more of the fluid lenses may include: a membrane; a substrate, such as a rigid substrate, having a substrate surface; a fluid located within an enclosure defined at least in part by the membrane and the substrate; and a coating disposed on at least a portion of the substrate surface. The coating may have a coating surface adjacent the fluid, and may be deposited on at least part of an interior surface of the enclosure, such as on the substrate. After formation of the coating, the coating may then provide an interior surface of the enclosure having fewer nucleation points for bubbles within the lens fluid than the original uncoated interior surface. The membrane may be an elastic membrane. In some examples, the coating and the membrane may have different compositions. The coating may significantly reduce bubble formation within the fluid, for example, by reducing the number of bubble nucleation points relative to the number of bubble nucleation points that would be provided by the original uncoated interior surface of the enclosure, under similar conditions. For example, the number of bubbles formed on the coating may be 50%, 25%, or, in some examples, 10%, or less, than the number of bubbles formed on an uncoated enclosure surface under similar conditions (e.g., for a similar device configuration and optical power, and similar ambient conditions such as temperature). In some examples, the coating may at least halve, substantially eliminate, or eliminate bubble nucleation points within the coated portion of the interior surface of the enclosure.

[0115] In some examples, the coating may be formed directly on a substrate, membrane, at least a portion of the enclosure surface, and/or on any another lens component. For example, a coating may be deposited by one or more deposition techniques, such as dipping, spin-coating, vapor deposition, mist deposition, pulsed electron deposition, sputtering, vacuum deposition, or any other suitable deposition technique. In some examples, the coating may not be removable as an intact film from the substrate. In some examples, the coating thickness may be in the range 0.1 microns-100 microns. In some examples, a coating precursor may be deposited to form a coating precursor layer, and the coating precursor layer may be further processed (e.g., in situ) to form the coating. For example, a coating precursor layer may include a polymerizable material (e.g., a monomer), that may then be polymerized to form a coating including a polymer. In some examples, the coating (or a coating precursor) may be deposited as a liquid. In some examples, the coating may include a liquid, and may be retained near, for example, the substrate or other coated surface by interactions such as one or more of dipole interactions, bonding (e.g., hydrogen bonding), surface energy related forces, or other interaction. For example, a coating including a polar liquid may be retained near a polar substrate, located between the polar substrate and the hydrophobic lens fluid such as a hydrophobic oil. In some examples, a coating may modify the surface energy of a corresponding uncoated enclosure surface by at least 50%.

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