Hydraulic actuator

Abstract

A head-mounted device may have a lens module with a tunable lens. The tunable lens may include a lens element and one or more actuators that control the shape of the lens element. Each actuator may be a hydraulic actuator. The hydraulic actuator may have an actuation pump between first and second fluid-filled chambers and a brake pump between third and fourth fluid-filled chambers. The actuation pump may control displacement of the tunable lens. The brake pump may fix a position of the tunable lens. The position of the tunable lens may be fixed when the brake pump and actuation pump are turned off A single flexible membrane may have a first portion that bulges to displace the tunable lens, a. second portion that bulges to engage the brake, and a third, portion that selves as a pressure release for the actuation pump.

Description

Hydraulic Actuator This application claims priority to U.S. provisional patent application No. 63 / 674,628, filed July 23, 2024, which is hereby incorporated by reference herein in its entirety. Background

[0001] This relates to wearable electronic device systems. Head-mounted devices sometimes include lenses with fixed shapes and properties. It may be difficult to adjust these types of lenses to optimally present content to each user of the head-mounted device. Summary

[0002] An actuator may include a first fluid-filled chamber, a second fluid-filled chamber, a first pump configured to selectively transfer a first fluid from the first fluid-filled chamber to the second fluid-filled chamber, a third fluid-filled chamber, a fourth fluid-filled chamber, a second pump configured to selectively transfer a second fluid from the third fluid-filled chamber to the fourth fluid-filled chamber, and a flexible membrane having a first portion aligned with a component and a second portion that defines at least part of the fourth fluid- filled chamber. Positions of the first portion and the component may be fixed when the second pump is off and the positions of the first portion and the component may be changed when the first pump transfers, while the second pump is on, the first fluid from the first fluid- filled chamber to the second fluid-filled chamber.

[0003] A tunable lens may include a lens element, a ring-shaped lens shaping element that is attached to the lens element, and an actuator that is attached to the ring-shaped lens shaping element. The actuator may be configured to linearly displace the ring-shaped lens shaping element. The actuator may include a brake pump that is configured to fix a position of the ring-shaped lens shaping element and an actuation pump that is configured to adjust the position of the ring-shaped lens shaping element while the brake pump is turned on. The position of the ring-shaped lens shaping element may be fixed when the brake pump is turned off and the position of the ring-shaped lens shaping element may be adjustable when the brake pump is turned on.

[0004] An actuator may be configured to displace a component. The actuator may include a first outer housing structure, a second outer housing structure that is parallel to the firstouter housing structure, a pump housing structure having at least first and second openings, a first pump in the first opening, and a second pump in the second opening. The first pump may be interposed between the first and second outer housing structures, the first pump may have first and second opposing sides, the second pump may be interposed between the first and second outer housing structures, and the second pump may have first and second opposing sides. The actuator may also include a first fluid that is on both the first and second sides of the first pump, a second fluid that is on both the first and second sides of the second pump, and a flexible membrane that is parallel to the first and second outer housing structures. The flexible membrane may be interposed between the first and second pumps and the second outer housing structure. Brief Description of the Drawings

[0005] FIG. 1 is a schematic diagram of an illustrative electronic device such as a head- mounted device in accordance with some embodiments.

[0006] FIG. 2 is a top view of an illustrative head-mounted device in accordance with some embodiments.

[0007] FIG. 3 is a cross-sectional side view of an illustrative lens module with first and second lens elements in accordance with some embodiments.

[0008] FIGS. 4 and 5 are cross-sectional side views of an illustrative fluid-filled lens element in accordance with some embodiments.

[0009] FIG. 6 is a top view of an illustrative tunable lens with a lens shaping structure in accordance with some embodiments.

[0010] FIGS. 7A-7C are cross-sectional side views of an illustrative hydraulic actuator in accordance with some embodiments.

[0011] FIG. 8 is an exploded view of the illustrative hydraulic actuator of FIGS. 7A-7C in accordance with some embodiments.

[0012] FIG. 9 is a cross-sectional side view of an illustrative hydraulic actuator with a flexible membrane attached directly to a lens shaping structure in accordance with some embodiments.

[0013] FIGS. 10A and 10B are cross-sectional side views of an illustrative hydraulic actuator with one or more flexures to control the shape of a bulge in a flexible membrane in accordance with some embodiments.

[0014] FIG. 11 is a top view of an illustrative flexible membrane with varying stiffness in accordance with some embodiments.

[0015] FIGS. 12A-12D are cross-sectional side views of an illustrative hydraulic actuator with a multi-stage piston in accordance with some embodiments.

[0016] FIG. 13 is a cross-sectional side view of an illustrative hydraulic actuator with a brake pump having side-by-side reservoirs in accordance with some embodiments.

[0017] FIG. 14 is a top view of an illustrative hydraulic actuator with a curved footprint in accordance with some embodiments.

[0018] FIG. 15 is a top view showing an illustrative method for forming multiple hydraulic actuators in a lens housing in accordance with some embodiments. Detailed Description

[0019] Electronic devices include displays and other components for presenting content. The electronic devices may be wearable electronic devices. A wearable electronic device such as a head-mounted device (HMD) may have head-mounted support structures that allow the HMD to be worn on a user’s head.

[0020] An HMD may contain a display formed from one or more display panels (displays) for displaying visual content to a user. A lens system may be used to allow the user to focus on the display and view the visual content. The lens system may have a left lens module that is aligned with a user’s left eye and a right lens module that is aligned with a user’s right eye.

[0021] In some cases, the user may wish to view real-world content rather than a display. The user may require different optical prescriptions depending on the distance to an object, the degree to which the user’s eyes are verging (which may be predictable based on the distance to the object viewed), lighting conditions, and / or other factors. The HMD may contain lenses disposed in such a way as the real-world content is viewable through the lens system.

[0022] The lens modules in the HMD may include lenses that are adjustable. For example, fluid-filled adjustable lenses may be adjusted for specific viewers.

[0023] A schematic diagram of an illustrative system having an electronic device with a lens module is shown in FIG. 1. As shown in FIG. 1, system 8 may include one or more electronic devices such as electronic device 10. The electronic devices of system 8 may include computers, cellular telephones, HMDs, wristwatch devices, and other electronicdevices. Configurations in which electronic device 10 is an HMD are sometimes described herein as an example.

[0024] Device 10 may include input-output devices 22. Input-output devices 22 may be used to allow a user to provide device 10 with user input. Input-output devices 22 may also be used to gather information on the environment in which device 10 is operating. Output components in devices 22 may allow device 10 to provide a user with output and may be used to communicate with external electrical equipment.

[0025] As shown in FIG. 1, electronic devices such as electronic device 10 may have control circuitry 12. Control circuitry 12 may include storage and processing circuitry for controlling the operation of device 10. Circuitry 12 may include storage such as hard disk drive storage, nonvolatile memory (e.g., electrically-programmable-read-only memory configured to form a solid-state drive), volatile memory (e.g., static or dynamic random- access-memory), etc. Processing circuitry in control circuitry 12 may be based on one or more microprocessors, microcontrollers, digital signal processors, baseband processors, power management units, audio chips, graphics processing units, application specific integrated circuits, and other integrated circuits. Software code may be stored on storage in circuitry 12 and run on processing circuitry in circuitry 12 to implement control operations for device 10 (e.g., data gathering operations, operations involved in processing three- dimensional facial image data, operations involving the adjustment of components using control signals, etc.). Control circuitry 12 may include wired and wireless communications circuitry. For example, control circuitry 12 may include radio-frequency transceiver circuitry such as cellular telephone transceiver circuitry, wireless local area network (WiFi®) transceiver circuitry, millimeter wave transceiver circuitry, and / or other wireless communications circuitry.

[0026] During operation, the communications circuitry of the devices in system 8 (e.g., the communications circuitry of control circuitry 12 of device 10), may be used to support communication between the electronic devices. For example, one electronic device may transmit video and / or audio data to another electronic device in system 8. Electronic devices in system 8 may use wired and / or wireless communications circuitry to communicate through one or more communications networks (e.g., the internet, local area networks, etc.). The communications circuitry may be used to allow data to be received by device 10 from external equipment (e.g., a tethered computer, a portable device such as a handheld device orlaptop computer, online computing equipment such as a remote server or other remote computing equipment, or other electrical equipment) and / or to provide data to external equipment.

[0027] As shown in FIG. 1, input-output devices 22 may include one or more displays such as display 14. Displays in device 10 such as display 14 may be organic light-emitting diode displays or other displays based on arrays of light-emitting diodes, liquid crystal displays, liquid-crystal-on-silicon displays, projectors or displays based on projecting light beams on a surface directly or indirectly through specialized optics (e.g., digital micromirror devices), electrophoretic displays, plasma displays, electrowetting displays, or any other suitable displays.

[0028] Display 14 may be used to display images for a user of HMD 10. Display 14 may be a transparent or translucent display so that a user may observe physical objects through the display while computer-generated content is overlaid on top of the physical objects by presenting computer-generated images on the display. A transparent or translucent display may be formed from a transparent or translucent pixel array (e.g., a transparent organic light- emitting diode display panel) or may be formed by a display device that provides images to a user through a transparent structure such as a beam splitter, holographic coupler, or other optical coupler (e.g., a display device such as a liquid crystal on silicon display).

[0029] Alternatively, display 14 may be an opaque display that blocks light from physical objects when a user operates HMD 10. In this type of arrangement, a pass-through camera may be used to display physical objects to the user. The pass-through camera may capture images of the physical environment and the physical environment images may be displayed on the display for viewing by the user. Additional computer-generated content (e.g., text, game-content, other visual content, etc.) may optionally be overlaid over the physical environment images to provide an extended reality environment for the user. When display 14 is opaque, the display may also optionally display entirely computer-generated content (e.g., without displaying images of the physical environment).

[0030] Display 14 may include one or more optical systems (e.g., lenses) (sometimes referred to as optical assemblies) that allow a viewer to view images on display(s) 14. A single display 14 may produce images for both eyes or a pair of displays 14 may be used to display images. In configurations with multiple displays (e.g., left and right eye displays), the focal length and positions of the lenses may be selected so that any gap present betweenthe displays will not be visible to a user (e.g., so that the images of the left and right displays overlap or merge seamlessly). Display modules (sometimes referred to as display assemblies) that generate different images for the left and right eyes of the user may be referred to as stereoscopic displays. The stereoscopic displays may be capable of presenting two-dimensional content (e.g., a user notification with text) and three-dimensional content (e.g., a simulation of a physical object such as a cube).

[0031] The example of device 10 including a display is merely illustrative and display(s) 14 may be omitted from device 10 if desired. Device 10 may include an optical pass-through area where real-world content is viewable to the user either directly or through a tunable lens.

[0032] Input-output circuitry 22 may include sensors 16. Sensors 16 may include proximity sensors (e.g., capacitive proximity sensors, light-based (optical) proximity sensors, ultrasonic proximity sensors, and / or other proximity sensors). Proximity sensors may, for example, be used to sense relative positions between a user’s nose and lens modules in device 10.

[0033] Sensors 16 may include, for example, touch sensors, buttons, force sensors, sensors such as contact sensors based on switches, gas sensors, pressure sensors, moisture sensors, magnetic sensors, audio sensors (microphones), ambient light sensors, microphones for gathering voice commands and other audio input, three-dimensional sensors (e.g., three- dimensional image sensors such as structured light sensors that emit beams of light and that use two-dimensional digital image sensors to gather image data for three-dimensional images from light spots that are produced when a target is illuminated by the beams of light, binocular three-dimensional image sensors that gather three-dimensional images using two or more cameras in a binocular imaging arrangement, three-dimensional lidar (light detection and ranging) sensors, three-dimensional radio-frequency sensors, or other sensors that gather three-dimensional image data), cameras (e.g., infrared and / or visible digital image sensors), gaze tracking sensors (e.g., a gaze tracking system based on an image sensor and, if desired, a light source that emits one or more beams of light that are tracked using the image sensor after reflecting from a user’s eyes), sensors that are configured to gather information on motion, position, and / or orientation (e.g., accelerometers, gyroscopes, compasses, and / or inertial measurement units that include all of these sensors or a subset of one or two of these sensors), fingerprint sensors and other biometric sensors, optical position sensors (optical encoders), and / or other position sensors such as linear position sensors, and / or other sensors.

[0034] User input and other information may be gathered using sensors and other inputdevices in input-output devices 22. If desired, input-output devices 22 may include other devices 24 such as haptic output devices (e.g., vibrating components), light-emitting diodes and other light sources, speakers such as ear speakers for producing audio output, and other electrical components. Device 10 may include circuits for receiving wireless power, circuits for transmitting power wirelessly to other devices, batteries and other energy storage devices (e.g., capacitors), joysticks, buttons, and / or other components.

[0035] Electronic device 10 may have housing structures (e.g., housing walls, straps, etc.), as shown by illustrative support structures 26 of FIG. 1. In configurations in which electronic device 10 is an HMD (e.g., a pair of glasses, goggles, a helmet, a hat, etc.), support structures 26 may include head-mounted support structures (e.g., a helmet housing, head straps, temples in a pair of eyeglasses, goggle housing structures, and / or other head-mounted structures). The head-mounted support structures may be configured to be worn on a head of a user during operation of device 10 and may support display(s) 14, sensors 16, other components 24, other input-output devices 22, and control circuitry 12.

[0036] FIG.2 is a top view of electronic device 10 in an illustrative configuration in which electronic device 10 is an HMD. As shown in FIG. 2, electronic device 10 may include support structures (see, e.g., support structures 26 of FIG. 1) that are used in housing the components of device 10 and mounting device 10 onto a user’s head. These support structures may include, for example, structures that form housing walls and other structures for main unit 26-2 (e.g., exterior housing walls, lens module structures, etc.) and straps or other supplemental support structures such as structures 26-1 that help to hold main unit 26-2 on a user’s face.

[0037] The electronic device may include optical modules such as optical module 70. The electronic device may include left and right optical modules that correspond respectively to a user’s left eye and right eye. An optical module corresponding to the user’s left eye is shown in FIG. 2.

[0038] Each optical module 70 includes a corresponding lens module 72 (sometimes referred to as lens stack-up 72, lens 72, or adjustable lens 72). Lens 72 may include one or more lens elements (sometimes referred to as lenses) arranged along a common axis. Each lens may have any desired shape and may be formed from any desired material (e.g., with any desired refractive index). The lenses may have unique shapes and refractive indices that, in combination, focus light (e.g., from a display or from the physical environment) in adesired manner. Each lens of lens module 72 may be formed from any desired material (e.g., glass, a polymer material such as polycarbonate or acrylic, a crystal such as sapphire, etc.).

[0039] Modules 70 may optionally be individually positioned relative to the user’s eyes and relative to some of the housing wall structures of main unit 26-2 using positioning circuitry such as positioner 58. Positioner 58 may include stepper motors, piezoelectric actuators, motors, linear electromagnetic actuators, shape memory alloys (SMAs), and / or other electronic components for adjusting the position of displays, the optical modules 70, and / or lens modules 72. Positioners 58 may be controlled by control circuitry 12 during operation of device 10. For example, positioners 58 may be used to adjust the spacing between modules 70 (and therefore the lens-to-lens spacing between the left and right lenses of modules 70) to match the interpupillary distance IPD of a user’s eyes. In another example, the lens module may include an adjustable lens. The curvature of the adjustable lens may be adjusted in real time by positioner(s) 58 to compensate for a user’s eyesight and / or viewing conditions.

[0040] Each optical module may optionally include a display such as display 14 in FIG. 2. As previously mentioned, the displays may be omitted from device 10 if desired. In this type of arrangement, the device may still include one or more lens modules 72 (e.g., through which the user views the real world). In this type of arrangement, real-world content may be selectively focused for a user.

[0041] FIG. 3 is a cross-sectional side view of an illustrative lens module with multiple lenses. As shown, lens module 72 includes a first lens 72-1 and a second lens 72-2. Each surface of the lenses may have any desired curvature. For example, each surface may be a convex surface (e.g., a spherically convex surface, a cylindrically convex surface, or an aspherically convex surface), a concave surface (e.g., a spherically concave surface, a cylindrically concave surface, or an aspherically concave surface), or a freeform surface. A cylindrical surface may only be curved about one axis instead of about multiple axes as with the spherical surface. A spherically curved surface (e.g., a spherically convex or spherically concave surface) may have a constant radius of curvature across the surface. In contrast, an aspherically curved surface (e.g., an aspheric concave surface or an aspheric convex surface) may have a varying radius of curvature across the surface. In some cases, one of the lens surfaces may have an aspheric surface that changes from being convex (e.g., at the center) to concave (e.g., at the edges) at different positions on the surface. This type of surface may be referred to as an aspheric surface, a primarily convex (e.g., the majority of the surface isconvex and / or the surface is convex at its center) aspheric surface, a freeform surface, and / or a primarily convex (e.g., the majority of the surface is convex and / or the surface is convex at its center) freeform surface. A freeform surface may include both convex and concave portions. Alternatively, a freeform surface may have varying convex curvatures or varying concave curvatures (e.g., different portions with different radii of curvature, portions with curvature in one direction and different portions with curvature in two directions, etc.). Herein, a freeform surface that is primarily convex (e.g., the majority of the surface is convex and / or the surface is convex at its center) may sometimes still be referred to as a convex surface and a freeform surface that is primarily concave (e.g., the majority of the surface is concave and / or the surface is concave at its center) may sometimes still be referred to as a concave surface. In one example, shown in FIG. 3, lens 72-1 has a convex surface that faces display 14 and an opposing concave surface. Lens 72-2 has a convex surface that faces lens 72-1 and an opposing concave surface.

[0042] The example of lens module 72 including two lenses is merely illustrative. In general, lens module 72 may include any desired number of lenses (e.g., one, two, three, four, more than four, etc.). Any subset or all of the lenses may optionally be adjustable. Any of the adjustable lenses in the lens module may optionally be fluid-filled adjustable lenses. Lens module 72 may also include any desired additional optical layers (e.g., partially reflective mirrors that reflect 50% of incident light, linear polarizers, retarders such as quarter wave plates, reflective polarizers, circular polarizers, reflective circular polarizers, etc.) to manipulate light that passes through lens module.

[0043] One or both of lenses 72-1 and 72-2 may be adjustable. In one example, lens 72-1 is a fixed (e.g., non-adjustable) lens whereas lens 72-2 is an adjustable lens. The adjustable lens 72-2 may be used to accommodate a user’s eyeglass prescription, for example. The shape of lens 72-2 may be adjusted if a user’s eyeglass prescription changes (without needing to replace any of the other components within device 10). As another possible use case, a first user with a first eyeglass prescription (or no eyeglass prescription) may use device 10 with lens 72-2 having a first shape and a second, different user with a second eyeglass prescription may use device 10 with lens 72-2 having a second shape that is different than the first shape. Lens 72-2 may have varying lens power and / or may provide varying amount of astigmatism correction to provide prescription correction for the user.

[0044] One or more of the adjustable lenses may be a fluid-filled lens. An example isdescribed herein where lens 72-2 from FIG. 3 is a fluid-filled lens. When lens 72-2 is a fluid- filled lens, the lens may include one or more components that define the surfaces of lens 72- 2. These elements may also be referred to a lenses. In other words, adjustable lens 72-2 (sometimes referred to as adjustable lens module 72-2) may be formed by multiple respective lenses.

[0045] FIG. 4 is a cross-sectional side view of adjustable fluid-filled lens 72-2. As shown, fluid-filled chamber 82 (sometimes referred to as chamber 82 or fluid chamber 82) that includes fluid 92 is interposed between lenses 84 and 86. Fluid 92 may be a liquid, gel, or gas with a pre-determined index of refraction (and may therefore sometimes be referred to as liquid 92, gel 92, or gas 92). The fluid may sometimes be referred to as an index-matching oil, an optical oil, an optical fluid, an index-matching material, an index-matching liquid, etc. Lenses 84 and 86 may have the same index of refraction or may have different indices of refraction. Fluid 92 that fills chamber 82 between lenses 84 and 86 may have an index of refraction that is the same as the index of refraction of lens 84 but different from the index of refraction of lens 86, may have an index of refraction that is the same as the index of refraction of lens 86 but different from the index of refraction of lens 84, may have an index of refraction that is the same as the index of refraction of lens 84 and lens 86, or may have an index of refraction that is different from the index of refraction of lens 84 and lens 86. Lenses 84 and 86 may have a circular footprint, may have an elliptical footprint, may have or may have a footprint any another desired shape (e.g., an irregular footprint).

[0046] The amount of fluid 92 in chamber 82 may have a constant volume or an adjustable volume. If the amount of fluid is adjustable, the lens module may also include a fluid reservoir and a fluid controlling component (e.g., a pump, stepper motor, piezoelectric actuator, motor, linear electromagnetic actuator, and / or other electronic component that applies a force to the fluid in the fluid reservoir) for selectively transferring fluid between the fluid reservoir and the chamber.

[0047] Lenses 84 and 86 may be transparent lenses formed from any desired material (e.g., glass, a polymer material such as polycarbonate or acrylic, a crystal such as sapphire, etc.). Each one of lenses 84 and 86 may be elastomeric, semi-rigid, or rigid. Rigid lenses may be formed from glass, a polymer material such as polycarbonate or acrylic, a crystal such as sapphire, etc. In general, the rigid lenses may not deform when pressure is applied to the lenses within the lens module. In other words, the shape and position of the rigid lenses maybe fixed. Each surface of a rigid lens may be planar, concave (e.g., spherically, aspherically, or cylindrically concave), or convex (e.g., spherically, aspherically, or cylindrically convex). Rigid lenses may be formed from a material having a Young’s modulus that is greater than greater than 25 GPa, greater than 30 GPa, greater than 40 GPa, greater than 50 GPa, etc.

[0048] Semi-rigid lenses may be formed from a semi-rigid material that is stiff and solid, but not inflexible. A semi-rigid lens may, for example, be formed from a thin layer of polymer or glass. Semi-rigid lenses may be formed from a material having a Young’s modulus that is greater than 1 Gpa, greater than 2 GPa, greater than 3 GPa, greater than 10 GPa, greater than 25 GPa, etc. Semi-rigid lenses may be formed from polycarbonate, polyethylene terephthalate (PET), polymethylmethacrylate (PMMA), acrylic, glass, or any other desired material. The properties of semi-rigid lenses may result in the lens becoming rigid along a first axis when the lens is curved along a second axis perpendicular to the first axis or, more generally, for the product of the curvature along its two principal axes of curvature to remain roughly constant as it flexes. This is in contrast to an elastomeric lens, which remains flexible along a first axis even when the lens is curved along a second axis perpendicular to the first axis. The properties of semi-rigid lenses may allow the semi-rigid lenses to form a cylindrical lens with tunable lens power and a tunable axis.

[0049] Elastomeric lenses may be formed from a natural or synthetic polymer that has a low Young’s modulus for high flexibility. For example the elastomeric membrane may be formed from a material having a Young’s modulus of less than 1 GPa, less than 0.5 GPa, less than 0.1 GPa, etc.

[0050] One or more structures such as a lens housing 101 (sometimes referred to as housing 101, lens chassis 101, chassis 101, support structure 101, etc.) may also define the fluid chamber 82 of lens 72-2.

[0051] FIG. 5 is a cross-sectional side view of lens 72-2 showing an illustrative adjustment of the shape of lens 72-2. As shown, during adjustments of lens 72-2, lens 84 may be biased in direction 94 at multiple points along its periphery (e.g., a point force is applied in direction 94 at multiple points). In this way, the curvature of the lens 84 (and accordingly, the lens power of lens 72-2) may be adjusted.

[0052] FIG. 6 is a top view of an illustrative lens shaping element 88. As shown, lens shaping element 88 may have an annular or ring shape with the lens shaping element surrounding a central opening. The lens shaping element may have any desired shape. Forexample, the lens shaping element may be circular, elliptical, or have an irregular shape. In the example of FIG. 6, the lens shaping element has an elliptical shape (e.g., a non-uniform radius around the ring shape). For example, a first distance 96 (e.g., a minimum distance) from the center of the central opening to the edge of the lens shaping element may be smaller than a second distance 98 (e.g., a maximum distance) from the center of the central opening to the edge of the lens shaping element. Distance 96 and 98 may be less than 100 millimeters, less than 60 millimeters, less than 40 millimeters, less than 30 millimeters, greater than 10 millimeters, greater than 20 millimeters, between 10 and 50 millimeters, etc.

[0053] Lens shaping element 88 has a plurality of tabs 88E that extend from the main portion of the lens shaping element. The tabs 88E (sometimes referred to as extensions 88E, actuator points 88E, etc.) may each be coupled to a respective actuator 90. Each actuator may selectively move its respective extension 88E up and down (e.g., in the Z-direction) to control the position of tab 88E in the Z-direction. In other words, actuator 90 is a linear actuator.

[0054] FIG. 6 shows how a plurality of tabs 88E (and corresponding actuators) may be distributed around the perimeter of lens shaping element 88. Tabs 88E may be distributed around lens shaping element 88 in a uniform manner (e.g., with equal spacing between each pair of adjacent tabs 88E) or in a non-uniform manner (e.g., with unequal spacing between at least two of the adjacent tabs 88E).

[0055] Between each pair of adjacent tabs 88E, there is a lens shaper segment 88S. In the example of FIG. 6, there are 8 tabs 88E and 8 actuators 90 around the perimeter of lens shaping element 88. This example is merely illustrative. In general, more tabs (and corresponding actuators) allow for greater control of the shape of the lens element (e.g., lens element 84) to which lens shaping element 88 is coupled. Any desired number of tabs and actuators (e.g., one, two, three, four, more than four, more than six, more than eight, more than ten, more than twelve, more than twenty, less than twenty, less than ten, between four and twelve, etc.) may be used depending upon the specific target shapes for the lens element, the target cost / complexity of the lens module, etc.

[0056] Lens shaping element 88 may be elastomeric (e.g., a natural or synthetic polymer that has a low Young’s modulus for high flexibility, as discussed above in greater detail) or semi-rigid (e.g., formed from a semi-rigid material that is stiff and solid, but not inflexible, as discussed above in greater detail). A semi-rigid lens shaping element may, for example, beformed from a thin layer of polymer, glass, metal, etc. Because lens shaping element 88 is formed in a ring around the lens module, lens shaping element 88 does not need to be transparent (and therefore may be formed from an opaque material such as metal). The rigidity of lens shaping element 88 may be selected such that the lens shaping element assumes desired target shapes when manipulated by the actuators around its perimeter.

[0057] One or more structures such as a lens housing 101 (sometimes referred to as housing 101, lens chassis 101, chassis 101, support structure 101, etc.) may also be included in tunable lens element 72-2. Actuators 90 may be positioned within lens housing 101. Lens housing 101 may optionally define a portion of the fluid-filled chamber 82.

[0058] Lens housing 101 may have a width 103. Each actuator 90 may have a width 105. In some devices, it may be desirable for the magnitude of width 103 to be small (e.g., to achieve a thin bezel with a target aesthetic appearance). However, the magnitude of width 103 need to be greater than or equal to the magnitude of width 105 (of actuators 90) to accommodate actuators 90. In other words, the width of the actuators may be a limiting factor in the width of the lens housing.

[0059] To mitigate the width 105 of actuator 90, the actuator may be a hydraulic actuator. The hydraulic actuator may have a compact arrangement with integrated reservoir(s), valve(s), pump(s), and / or bladder(s). With this type of arrangement (shown in FIGS. 7A-7C), the maximum width 105 of the actuator may be less than 3 millimeters, less than 2 millimeters, etc. The maximum height of the actuator (in the Z-direction) may be less than 3 millimeters, less than 2 millimeters, etc.

[0060] FIGS. 7A-7C are cross-sectional side views of an illustrative hydraulic actuator. FIG. 8 is an exploded view of the illustrative hydraulic actuator of FIGS. 7A-7C. As shown in FIGS. 7 and 8, actuator 90 includes a first outer housing structure 102, a first flexible membrane 104, a first inner housing structure 106, a pump housing structure 108, a second inner housing structure 110, a second flexible membrane 112, a second outer housing structure 114, a piston 116, a brake pump 118, and an actuation pump 120.

[0061] First and second outer housing structures 102 and 114 (sometimes referred to as housing walls, structural members, plastic pieces, etc.) may be formed from polymethyl methacrylate (PMMA) or any other desired material. One or both of outer housing structures 102 and 114 may optionally be formed from a rigid structure in adjustable lens 72-2. As examples, rigid lens element 86 in tunable lens 72-2 and / or lens housing 101 of tunable lens72-2 may be used to form outer housing structure 102 and / or outer housing structure 114.

[0062] First and second inner housing structures 106 and 110 (sometimes referred to as structural members, plastic pieces, etc.) may be formed from polymethyl methacrylate (PMMA) or any other desired material.

[0063] Pump housing structure 108 (sometimes referred to as an inner housing structure, a structural member, an overmolded plastic piece, etc.) may be formed from a polymer (e.g., PMMA or another desired material) that is overmolded around pump 118, pump 120, and / or piston 116. Pump housing structure 108 may therefore conform to and directly contact pump 118, pump 120, and / or piston 116.

[0064] First and second flexible membranes 104 and 112 (sometimes referred to as elastomeric membranes) may be formed from rubber, silicone, polymer, or any other desired material. As an example, membranes 104 and 112 may be formed from a natural or synthetic polymer that has a low Young’s modulus for high flexibility. Membranes 104 and 112 may be formed from a material having a Young’s modulus of less than 1 GPa, less than 0.5 GPa, less than 0.1 GPa, etc.

[0065] Piston 116 may be attached to a tab 88E of lens shaping element 88 (e.g., as shown in FIG. 6). Actuator 90 may displace piston 116 along the Z-axis, thereby adjusting the position of tab 88E along the Z-axis. This example is merely illustrative and in general actuator 90 may displace any desired component(s) along the Z-axis. In one example, tabs 88E may be omitted from lens shaping element 88 and each piston may be attached directly to the ring-shaped portion of lens shaping element 88. Omitting the tabs from lens shaping element 88 may reduce the bezel width of tunable lens 72-2.

[0066] Pumps 118 and 120 may be electroosmotic pumps comprising active ceramic elements. An electroosmotic pump (EOP) generates flow or pressure by use of an electric field. This example is merely illustrative and in general each pump may be any desired type of pump. The pumps may include glass fiber active elements if desired.

[0067] Actuator 90 comprises four discrete fluid-filled chambers (sometimes referred to as reservoirs). Pump 120 is interposed between fluid-filled chamber 122 and fluid-filled chamber 124. Fluid-filled chambers 122 and 124 may be filled with a fluid 130. When power is applied to pump 120, fluid 130 may be moved from fluid-filled chamber 122 (on a first side of pump 120) to fluid-filled chamber 124 (on a second, opposing side of pump 120).

[0068] Pump 118 is interposed between fluid-filled chamber 126 and fluid-filled chamber128. Fluid-filled chambers 126 and 128 may be filled with a fluid 132. When power is applied to pump 118, fluid 132 may be moved from fluid-filled chamber 128 (on a first side of pump 118) to fluid-filled chamber 126 (on a second, opposing side of pump 118). Fluids 130 and 132 may be the same material or may be different materials. The example of pump 118 moving fluid from fluid-filled chamber 128 to fluid-filled chamber 126 is merely illustrative and pump 118 may instead move fluid from fluid-filled chamber 126 to fluid- filled chamber 128 when power is applied to pump 118.

[0069] Flexible membrane 104 has a portion 104-P1 that at least partially defines fluid- filled chamber 126. Chamber 126 is defined by pump 118, pump housing structure 108, internal housing structure 106, and flexible membrane portion 104-P1.

[0070] Flexible membrane 112 has different portions that perform different functions within actuator 90. A portion 112-P1 of membrane 112 is aligned with a component such as piston 116 (and is used to displace the component). A portion 112-P2 of membrane 112 at least partially defines fluid-filled chamber 128 (and is used as a brake). Chamber 128 is defined by pump 118, pump housing structure 108, internal housing structure 110, and flexible membrane portion 112-P2. A portion 112-P3 of membrane 112 at least partially defines fluid-filled chamber 122 (and may serve as a pressure release for chamber 122). Chamber 122 is defined by pump 120, pump housing structure 108, internal housing structures 106 and 110, flexible membrane 104, and flexible membrane portion 112-P3.

[0071] Pump 120 may be used to control displacement of piston 116 (and, correspondingly, tab 88E of the lens shaping element). FIGS. 7A and 7B illustrate how pump 120 may displace piston 116 and tab 88E. In FIG. 7A, pump 120 may be turned off (sometimes referred to as powered off or simply off) and there may be a first amount of fluid in chamber 122 and a second amount of fluid in chamber 124. With this arrangement, flexible membrane 112 may be planar across the footprint of the actuator.

[0072] In FIG. 7B, pump 120 is turned on (sometimes referred to as powered on, powered, or on) to transfer some of the fluid from chamber 122 to chamber 124 (as indicated by arrow 134 across pump 120). The increased volume of fluid in chamber 124 increases the pressure on portion 112-P1 of flexible membrane 112. The increased pressure on portion 112-P1 causes portion 112-P1 to bulge in direction 136 (e.g., the positive Z-direction). The bulge in direction 136 displaces piston 116 in the positive Z-direction. The more fluid transferred from chamber 122 to chamber 124 across pump 120, the greater the displacement of piston116 in the Z-direction. The example of pump 120 moving fluid from fluid-filled chamber 122 to fluid-filled chamber 124 is merely illustrative and pump 120 may instead move fluid from fluid-filled chamber 124 to fluid-filled chamber 122 when power is applied to pump 120.

[0073] In FIG.7B, the decreased volume of fluid in chamber 122 caused by pump 120 shifting fluid from chamber 122 to chamber 124 decreases the pressure on portion 112-P3 of flexible membrane 112. The decreased pressure on portion 112-P3 causes portion 112-P3 to bulge in direction 138 (e.g., the positive Z-direction). Portion 112-P3 effectively serves as a pressure release.

[0074] FIGS. 7A and 7B therefore illustrate how actuation pump 120 may control the displacement of piston 116 by selectively transferring fluid from chamber 122 to chamber 124.

[0075] Power may be required for pump 120 to transfer fluid from chamber 122 to chamber 124. When no power is applied to pump 120, the actuator may revert to the arrangement of FIG. 7A (with portion 112-P1 being planar). However, it may be desirable to fix piston 116 in a position with positive displacement in the Z-direction (as in FIG. 7B). Pump 120 may be constantly powered to fix piston 116 in a position with positive displacement in the Z- direction (as in FIG. 7B). However, this may cause the power consumption of actuator 90 to be higher than desired. Instead of constantly powering pump 120, actuator 90 includes a brake pump 118 as shown in FIGS. 7 and 8.

[0076] Brake pump 118 and flexible membrane portion 112-P2 form a valve that may be used to enable and disable a brake for the displacement of piston 116. Brake pump 118 is capable of fixing the position of piston 116 without consuming power. When no power is applied to brake pump 118, actuator 90 has the arrangement of FIG. 7C. As shown in FIG. 7C, pump 118 is off and there may be a first amount of fluid in chamber 126 and a second amount of fluid in chamber 128. With this arrangement, portion 104-P1 of flexible membrane 104 has a bulge and portion 112-P2 of flexible membrane 112 has a bulge. When pump 118 is off, the bulge of portion 112-P2 is sufficiently large to contact outer housing structure 114 and form a seal with a channel in outer housing structure 114. The bulge forms a seal between a first portion of chamber 124 (that includes portion 112-P1 of membrane 112 aligned with piston 116) and a second portion of chamber 124 (that includes pump 120). The seal created by portion 112-P2 of membrane 112 effectively locks the position of piston 116.

[0077] In FIG. 7B, pump 118 is turned on (powered) to transfer some of the fluid from chamber 128 to chamber 126 (as indicated by arrow 140 across pump 118). The decreased volume of fluid in chamber 128 decreases the pressure on portion 112-P2 of flexible membrane 112. The decreased pressure on portion 112-P2 causes the bulge from FIG. 7C to be removed, thus breaking the seal between different portions of chamber 124. While pump 118 is turned on and there is no seal between different portions of chamber 124 in FIG. 7C, pump 120 is free to control the displacement of piston 116 by selectively pumping fluid into chamber 124.

[0078] It is noted that the bulge of portion 104-P1 is greater when pump 118 is turned on (as in FIG. 7A and 7B) than when pump 118 is turned off (as in FIG. 7C).

[0079] Therefore, when pump 118 is turned off, the position of piston 116 is braked and does not move (regardless of the state of pump 120). This allows for the position of piston 116 to be fixed without pumps 118 and 120 consuming any power.

[0080] As an example, actuator 90 may start with portion 112-P1 of flexible membrane being planar at a first time. This state may be defined as a zero displacement state for piston 116. At the first time, pumps 118 and 120 are both off. Because pump 118 is off, there is a seal between different portions of chamber 124 and the brake preventing displacement of piston 116 is engaged. Next, at a second time, pump 118 may be turned on to disable (disengage) the brake. The state of actuator 90 at the second time is shown in FIG. 7A. As shown in FIG. 7A, there is no seal between different portions of chamber 124 and piston 116 is free to be displaced by actuation pump 120. Next, at a third time, while brake pump 118 remains turned on, actuation pump 120 may be turned on to displace piston 116 by a target amount. The more fluid transferred to chamber 124 by pump 120 while the pump is powered on, the greater the displacement of piston 116. The state of actuator 90 at the third time is shown in FIG. 7B. Finally, at a fourth time, brake pump 118 may be turned off to create a seal between different portions of chamber 124 and fix the location of piston 116. While the brake pump 118 is turned off (and the brake is engaged), pump 120 cannot cause further displacement of piston 116. Pump 120 may also be turned off to conserve power while the piston remains in the fixed position. The state of actuator 90 at the fourth time is shown in FIG. 7C.

[0081] The example in FIGS. 7A-7C of membrane 112 having a portion 112-P1 aligned with piston 116 is merely illustrative. In another possible arrangement, portion 112-P1 ofmembrane 112 may have (or may be replaced with a rigid structure that has) an optional outlet 112-O1. The outlet may be connected to a fluid-filled bladder that is connected to tab 88E. Fluid may be pumped into the fluid-filled bladder to increase the height of the fluid- filled bladder. Said another way, structure 116 connected between membrane 112 and tab 88E in FIG. 7A may be a fluid-filled bladder defined by one or more flexible membranes (instead of the piston previously described). Structure 116 may therefore sometimes be referred to as fluid-filled bladder 116. Fluid-filled bladder 116 may have an opening that is aligned with optional outlet 112-O1 to allow fluid to flow freely in and out of the fluid-filled bladder.

[0082] Another illustrative position for an outlet is shown by outlet 112-O1’ in FIG. 7A. In this example, the outlet is positioned within outer housing structure 114 opposite brake pump 118 and portion 112-P2 of flexible membrane 112. Brake pump 118 may selectively press portion 112-P2 of flexible membrane 112 into outlet 112-O1’ to block the outlet.

[0083] As shown in the exploded view of FIG. 8, outer housing structure 102 has a first opening 102-O1 that extends completely through the thickness of the outer housing structure. Opening 102-O1 is aligned with piston 116 in actuator 90. Outer housing structure 102 has a second opening 102-O2 that extends completely through the thickness of the outer housing structure. Opening 102-O2 is aligned with brake pump 118 and portion 104-P1 of flexible membrane 104 in actuator 90.

[0084] As shown in the exploded view of FIG. 8, flexible membrane 104 has a first opening 104-O1 that extends completely through the thickness of the flexible membrane. Opening 104-O1 is aligned with piston 116 in actuator 90. Flexible membrane 104 has a first portion 104-P1 that is aligned with brake pump 118 and opening 102-O2 of outer housing structure 102.

[0085] As shown in the exploded view of FIG. 8, inner housing structure 106 has a first opening 106-O1 that extends completely through the thickness of the inner housing structure. Opening 106-O1 is aligned with piston 116 in actuator 90. Inner housing structure 106 has a second opening 106-O2 that extends completely through the thickness of the outer housing structure. Opening 106-O2 is aligned with brake pump 118 and portion 104-P1 of flexible membrane 104 in actuator 90. Inner housing structure 106 has a third opening 106-O3 that extends completely through the thickness of the inner housing structure. A first portion of opening 106-O3 is aligned with actuation pump 120 in actuator 90. A second portion ofopening 106-O3 is aligned with openings 108-O4 and 110-O4.

[0086] As shown in the exploded view of FIG. 8, pump housing structure 108 has a first opening 108-O1 that extends completely through the thickness of the pump housing structure. Opening 108-O1 is aligned with piston 116 in actuator 90. Pump housing structure 108 has a second opening 108-O2 that extends completely through the thickness of the pump housing structure. Opening 108-O2 is aligned with brake pump 118, portion 104-P1 of flexible membrane 104, and portion 112-P2 of flexible membrane 112 in actuator 90. Pump housing structure 108 has a third opening 108-O3 that extends completely through the thickness of the pump housing structure. Opening 108-O3 is aligned with actuation pump 120 in actuator 90. Pump housing structure 108 has a fourth opening 108-O4 that extends completely through the thickness of the pump housing structure. Opening 108-O4 is aligned with portion 112-P3 of flexible membrane 112 in actuator 90.

[0087] As shown in the exploded view of FIG. 8, inner housing structure 110 has a first opening 110-O1 that extends completely through the thickness of the inner housing structure. Opening 110-O1 is aligned with piston 116 in actuator 90. Inner housing structure 106 has a second opening 110-O2 that extends completely through the thickness of the outer housing structure. Opening 110-O2 is aligned with brake pump 118, portion 104-P1 of flexible membrane 104, and portion 112-P2 of flexible membrane 112 in actuator 90. Inner housing structure 110 has a third opening 110-O3 that extends completely through the thickness of the inner housing structure. Opening 110-O3 is aligned with actuation pump 120 in actuator 90. Inner housing structure 110 has a fourth opening 110-O4 that extends completely through the thickness of the inner housing structure. Opening 110-O4 is aligned with portion 112-P3 of flexible membrane 112 in actuator 90.

[0088] As shown in the exploded view of FIG. 8, flexible membrane 112 has a first opening 112-O3 that extends completely through the thickness of the flexible membrane. Opening 112-O3 is aligned with actuation pump 120 in actuator 90. Flexible membrane 112 has a first portion 112-P1 that is aligned with piston 116, a second portion 112-P2 that is aligned with brake pump 118 and opening 110-O2, and a third portion 112-P3 that is aligned with openings 108-O4 and 110-O4.

[0089] As shown in the exploded view of FIG. 8, outer housing structure 114 has a first recess 114-O1 that extends only partially through the thickness of the outer housing structure. Recess 114-O1 is aligned with piston 116, brake pump 118, and actuation pump 120 inactuator 90. Recess 114-O1 creates a channel that may be selectively sealed by brake pump 118, as discussed in detail in connection with FIGS. 7A-7C. Recess 114-O1 may have a complex shape (e.g., a chamfer, a curved cross-sectional profile, a spherical profile, etc.) in order to create a tight seal with portion 112-P2 of membrane 112 when the brake is engaged. Outer housing structure 114 has a second opening 114-O4 that extends completely through the thickness of the outer housing structure. Opening 114-O4 is aligned with portion 112-P3 of flexible membrane 112, opening 110-O4, and opening 108-O4.

[0090] To summarize, openings 102-O1, 104-O1, 106-O1, 108-O1, and 110-O1 may be vertically aligned (e.g., aligned in the Z-direction) and accommodate piston 116. The openings may constrict lateral movement of piston 116 within the XY-plane while enabling vertical movement of piston 116 along the Z-direction. Openings 102-O1, 104-O1, 106-O1, 108-O1, and 110-O1 are also vertically aligned with portion 112-P1 of flexible membrane 112.

[0091] Pump 118 is positioned within opening 108-O2 of pump housing structure 108. Opening 102-O2, portion 104-P1 of flexible membrane 104, opening 106-O2, opening 108- O2, pump 108, opening 110-O2, and portion 112-P2 of flexible membrane 112 may all be vertically aligned. FIG. 8 further shows how pump 118 has first and second conductive contacts 118-C (sometimes referred to as electrodes 118-C) that may be used to control pump 118. The contacts may be pins that are embedded within pump housing structure 108.

[0092] Pump 120 is positioned within opening 108-O3 of pump housing structure 108. FIG. 8 further shows how pump 120 has first and second conductive contacts 120-C (sometimes referred to as electrodes 120-C) that may be used to control pump 120. The contacts may be pins that are embedded within pump housing structure 108. A first portion of opening 106-O3, opening 108-O3, pump 120, opening 110-O3, opening 112-O3, and a portion of recess 114-O1 may all be vertically aligned. A second portion of opening 106-O3, opening 108-O4, opening 110-O4, portion 112-P3 of flexible membrane 112, and opening 114-O2 may all be vertically aligned.

[0093] The examples of electrodes 118-C and 120-C in FIG. 8 are merely illustrative. If desired, actuator 90 may include planar electrodes that electrically and mechanically contact pumps 118 and 120. The planar electrodes may comprise steel, platinum, gold, palladium, copper, conductive polymer, or any other desired material. The planar electrodes may be formed in place of (or as part of) inner housing structure 106 and / or inner housing structure108. In other words, the planar electrodes may be formed above and / or below pumps 118 and 120. The top and bottom electrodes may be each a single piece or may be cut such that there are four terminals, each addressing one side of one pump. Alternatively one side (e.g., the bottom) may be a single piece of conducting material that contacts one side of each pump and the other side (e.g., the top) may be cut to allow individual connection to the other side of each pump.

[0094] If desired, piston 116 may be omitted from actuator 90 and tab 88E may be attached directly to portion 112-1 of flexible membrane 112. However, if care is not taken, there is a risk of portion 112-P1 of flexible membrane 112 bulging in the transverse direction (perpendicular to the Z-axis). FIG. 9 shows how portion 112-P1 may bulge in the positive Z- direction to displace tab 88E. Ideally, portion 112-P1 will have no bulging in the transverse direction (as shown by the upper surface following profile P1). When the profile of the upper surface has no bulging in the transverse direction, the displacement 142-1 of tab 88E is at a maximum (for the pressure conditions associated with membrane 112). However, there is a risk of the upper surface of portion 112-P1 bulging in the transverse direction as shown by profile P2. Consequently, the displacement 142-2 of tab 88E associated with profile P2 is reduced relative to displacement 142-1 associated with profile P1.

[0095] To constrain the bulge of portion 112-P1 (e.g., to mitigate bulging out in the transverse direction), piston 116 may be included as shown in FIGS. 7A-7C. However, including piston 116 increases the total height required to accommodate actuator 90. To constrain bulging in the transverse direction while attaching tab 88E directly to flexible membrane 112, one or more flexures may be included in actuator 90.

[0096] FIGS. 10A and 10B show an illustrative actuator 90 with one or more flexures 144 to mitigate bulging of membrane portion 112-P1 in the transverse direction. The flexures may be formed from any desired material (e.g., plastic, a metal such as aluminum, etc.) and may sometimes be referred to as guide structures 144, biasing structures 144, etc. As shown in FIG. 10A, when portion 112-P1 is planar, one or more flexures 144 may rest on the upper surface of portion 112-P1. Flexure(s) 144 may be planar when portion 112-P1 is planar. In FIG. 10B, when portion 112-P1 bulges in the positive Z-direction, flexure(s) 144 may apply inward force from multiple directions to prevent bulging in the transverse direction while displacing tab 88E.

[0097] In another possible arrangement, flexure(s) 144 may be omitted and flexiblemembrane 112 may have non-uniform stiffness in portion 112-P1 to prevent bulging in the transverse direction when portion 112-P1 bulges to displace tab 88E. FIG. 11 is a top view of flexible membrane 112 with non-uniform stiffness in portion 112-P1. As shown in FIG. 11, portion 112-P1 has a first subset 146, a second subset 148, and a third subset 150. The second subset 148 may be stiffer than subsets 146 and 150. Subset 148 may be thicker than subsets 146 and 150. The Young’s modulus of subset 148 may be greater than subsets 146 and 150. Subset 148 may have a ring-shaped footprint and laterally surrounds subset 150. Subset 146 may have a ring-shaped footprint and laterally surrounds subsets 148 and 150. Subsets 146 and 148 may be concentric (with the center of subsets 146 and 148 aligned with subset 150).

[0098] In another possible arrangement, a multi-stage piston 116’ may be included in actuator 90. FIG.12A is a side view of an actuator with multi-stage piston 116’ when there is no displacement of tab 88E. FIG. 12B is a side view of an actuator with multi-stage piston 116’ when there is a positive displacement of tab 88E in the Z-direction. As shown by FIGS. 12A and 12B, the multi-stage piston may be planar when no positive pressure is applied to the multi-stage piston (as in FIG. 12A). However, when positive pressure is applied to the multi-stage piston, the multi-stage piston may expand in the positive Z-direction (as in FIG. 12B). The multi-stage piston may have multiple concentric portions that are attached to portion 112-P1. FIG. 12B shows a multi-stage piston with three discrete portions (a central portion, a first ring-shaped portion that surrounds the central portion, and a second ring- shaped portion that surrounds the first ring-shaped portion and the central portion). Other arrangements may be used for the multi-stage piston if desired.

[0099] In the example of FIGS. 12A and 12B, the multi-stage piston includes membrane portion 112-P1 on one side of the concentric portions. In other possible embodiments, shown in FIGS. 12C and 12D, the multi-stage piston may have a membrane on both sides of the concentric portions. FIGS. 12C and 12D show examples where the multi-stage piston is interposed between membrane portion 112-P1 and supplemental membrane 162. The multi- stage piston 116’ may be interposed between tab 88E and membrane portion 112-P1 (as in FIGS. 12C and 12D) or membrane portion 112-P1 may be interposed between tab 88E and multi-stage piston 116’. In other words, the positions of membranes 112-P1 and 162 in FIGS. 12C and 12D may be switched if desired.

[0100] As shown in FIG. 12C, membranes 112-P1 and 162 may be planar when the multi-stage piston is in a flat position. Alternatively, as shown in FIG. 12D, membranes 112-P1 and 162 may include bulges at the seams between adjacent concentric portions of the multi- stage piston when the multi-stage piston is in a flat position. In both FIGS. 12C and 12D, the multi-stage piston may optionally include lubricant 164 between adjacent concentric portions of the multi-stage piston. The lubricant may fill the volume between stages and the volume defined by the bulges in the membranes of FIG.12D.

[0101] FIGS. 12C and 12D also show how the concentric portions of the multi-stage piston (which may be referred to as stages) may include overhang features 166 that prevent overextension of the stages of the piston. When the multi-stage piston is extended (as in FIG. 12B), an overhang feature in a first stage may mate with an overhang feature in a second, adjacent stage to prevent overextension.

[0102] In FIGS. 7 and 8, chambers 126 and 128 are arranged such that the chambers are vertically overlapping. Outer housing structure 102, flexible membrane 104, and inner housing structure 106 may have openings to accommodate the bulge of portion 104-P1 caused by fluid-filled chamber 126. This example is merely illustrative. If desired, chambers 126 and 128 may be arranged such that chambers 126 and 128 share common flexible membrane 112.

[0103] FIG. 13 is a cross-sectional side view of an illustrative actuator with a brake pump having chambers that share a common flexible membrane. As shown in FIG. 13, pump 118 is interposed between chambers 126 and 128 (similar to as in FIGS. 7 and 8). FIG. 13 shows the actuator when the brake pump is turned off (and the brake is enabled). As shown, when the pump is turned off (as indicated by the position of flexible membrane in FIG. 13), flexible membrane 112 has a portion 112-P2 that seals chamber 124 into first and second portions. When pump 118 is turned on, fluid 132 is shifted from chamber 128 to chamber 126. The decreased pressure in chamber 128 causes portion 112-P2 to become planar (as indicated by the dashed line profile in FIG. 13) and removes the seal between different portions of chamber 124. Conversely, the increased pressure in chamber 126 causes portion 112-P2’ of membrane 112 to bulge by a greater amount than when the pump is off (as indicated by the dashed line profile in FIG. 13). The channel in outer housing structure 114 may be deeper in a region aligned with portion 112-P2’ than in a region aligned with portion 112-P2 to avoid portion 112-P2’ unintentionally sealing chamber 124 while the brake is intended to be disengaged. Outer housing structure 114 may be thinner in a region vertically overlappingportion 112-P2’ than in a region vertically overlapping portion 112-P2 to create the deeper channel.

[0104] With the arrangement of FIG. 13, membrane 104 from FIGS. 7 and 8 may be omitted. Additionally, openings 102-O2 and 106-O2 may be omitted from housing structures 102 and 106, respectively.

[0105] Actuator 90 may have a rectangular footprint when viewed from the Z-direction. Alternatively, as shown in FIG. 14, actuator 90 may have a curved footprint when viewed from the Z-direction. The footprint has first and second curved edges. The curvature of actuator 90 may accommodate (match) the curvature of lens housing 101 in FIG. 6, for example.

[0106] Multiple actuators of the type shown in FIGS. 7-14 may optionally be manufactured in a single sheet. As shown in FIG. 15, actuators 90 may be formed in a single plane that includes material for lens housing 101. The actuators 90 may be formed simultaneously at target locations within the plane that are aligned with the final positions of the actuators within lens housing 101. The actuators may be formed by laminating layers on top of one another. The material for lens housing 101 may then be cut along scribe lines 152 (on the left side of FIG. 15) to create a lens housing 101 with multiple integrated actuators 90 (as show on the right side of FIG. 15). It is noted that outer housing structures 102 and 114 from FIGS. 7 and 8 may optionally serve as the lens housing if desired.

[0107] In accordance with an embodiment, an actuator includes a first fluid-filled chamber, a second fluid-filled chamber, a first pump configured to selectively transfer a first fluid between the first fluid-filled chamber and the second fluid-filled chamber, a third fluid-filled chamber, a fourth fluid-filled chamber, a second pump configured to selectively transfer a second fluid between the third fluid-filled chamber and the fourth fluid-filled chamber, and a flexible membrane that defines at least part of the fourth fluid-filled chamber, where a position of a component is fixed when the second pump is off and the position of the component is changed when the first pump transfers, while the second pump is on, the first fluid between the first fluid-filled chamber and the second fluid-filled chamber.

[0108] In accordance with another embodiment, the first and second pumps are optionally first and second electroosmotic pumps.

[0109] In accordance with another embodiment, the component is optionally a piston.

[0110] In accordance with another embodiment, the component is optionally a multi-stagepiston.

[0111] In accordance with another embodiment, the component is optionally a fluid-filled bladder.

[0112] In accordance with another embodiment, a first portion of the flexible membrane optionally defines at least part of the fourth fluid-filled chamber and the flexible membrane has a second portion that defines at least part of the first fluid-filled chamber.

[0113] In accordance with another embodiment, the flexible membrane optionally has a third portion that defines at least part of the third fluid-filled chamber.

[0114] In accordance with another embodiment, the actuator optionally includes an additional flexible membrane that defines at least part of the third fluid-filled chamber.

[0115] In accordance with another embodiment, the actuator optionally includes an additional flexible membrane that defines at least part of the first fluid-filled chamber.

[0116] In accordance with another embodiment, the actuator optionally includes a first outer housing structure, a first inner housing structure, a pump housing structure, where the first inner housing structure is interposed between the pump housing structure and the first outer housing structure, a second inner housing structure, and a second outer housing structure, the second inner housing structure is interposed between the pump housing structure and the second outer housing structure and the first outer housing structure, the first inner housing structure, the pump housing structure, the second inner housing structure, and the second outer housing structure are formed within respective parallel planes.

[0117] In accordance with another embodiment, the first outer housing structure, the first inner housing structure, the pump housing structure, and the second inner housing structure each optionally have respective first openings that are aligned and the first outer housing structure, the first inner housing structure, the pump housing structure, and the second inner housing structure each have respective second openings that are aligned with the second pump.

[0118] In accordance with another embodiment, a first portion of the flexible membrane optionally defines at least part of the fourth fluid-filled chamber and the flexible membrane has a second portion aligned with the component.

[0119] In accordance with another embodiment, the second portion of the flexible membrane optionally has a first subset and a second subset and the first subset is stiffer than the second subset.

[0120] In accordance with another embodiment, the first subset is optionally thicker than the second subset.

[0121] In accordance with another embodiment, the first subset is optionally ring-shaped and laterally surrounds the second subset.

[0122] In accordance with another embodiment, the actuator optionally includes one or more flexures that control a shape of a bulge in the second portion of the flexible membrane.

[0123] In accordance with another embodiment, the actuator optionally includes a housing structure that includes a channel, where the flexible membrane forms a seal with the channel and divides the second fluid-filled chamber into first and second isolated portions when the second pump is off.

[0124] In accordance with another embodiment, the flexible membrane optionally does not form the seal with the channel when the second pump is on.

[0125] In accordance with an embodiment, a tunable lens includes a lens element, a ring- shaped lens shaping element that is attached to the lens element, and an actuator that is attached to the ring-shaped lens shaping element, where the actuator is configured to linearly displace the ring-shaped lens shaping element and the actuator includes a brake pump that is configured to fix a position of the ring-shaped lens shaping element, the position of the ring- shaped lens shaping element is fixed when the brake pump is turned off and the position of the ring-shaped lens shaping element is adjustable when the brake pump is turned on, and an actuation pump that is configured to adjust the position of the ring-shaped lens shaping element while the brake pump is turned on.

[0126] In accordance with another embodiment, the actuator optionally includes a flexible membrane that optionally includes a first portion with a first bulge that is controlled by the actuation pump, where the first portion is configured to displace the ring-shaped lens shaping element, and a second portion with a second bulge that is controlled by the brake pump, the second portion is configured to fix the position of the ring-shaped lens shaping element.

[0127] In accordance with another embodiment, the flexible membrane optionally includes a third portion that serves as pressure release for the actuation pump.

[0128] In accordance with an embodiment, an actuator is configured to displace a component, the actuator optionally includes a first outer housing structure, a second outer housing structure that is parallel to the first outer housing structure, a pump housing structure having at least first and second openings, a first pump in the first opening, where the firstpump is interposed between the first and second outer housing structures and the first pump has first and second opposing sides, a second pump in the second opening, the second pump is interposed between the first and second outer housing structures and the second pump has first and second opposing sides, a first fluid that is on both the first and second sides of the first pump, a second fluid that is on both the first and second sides of the second pump, and a flexible membrane that is parallel to the first and second outer housing structures, the flexible membrane is interposed between the first and second pumps and the second outer housing structure.

[0129] In accordance with another embodiment, the flexible membrane optionally includes a first portion interposed between the component and the second outer housing structure, where the first fluid is interposed between the first portion of the flexible membrane and the second outer housing structure, a second portion interposed between the second pump and the second outer housing structure, the first fluid is interposed between the second portion of the flexible membrane and the second outer housing structure and the second fluid is interposed between the second portion of the flexible membrane and the second pump, and an opening that is aligned with the first pump, the opening is interposed between the first pump and the second outer housing structure.

[0130] The foregoing is merely illustrative and various modifications can be made to the described embodiments. The foregoing embodiments may be implemented individually or in any combination.

Claims

What is Claimed is:

1. An actuator comprising: a first fluid-filled chamber; a second fluid-filled chamber; a first pump configured to selectively transfer a first fluid between the first fluid-filled chamber and the second fluid-filled chamber; a third fluid-filled chamber; a fourth fluid-filled chamber; a second pump configured to selectively transfer a second fluid between the third fluid-filled chamber and the fourth fluid-filled chamber; and a flexible membrane that defines at least part of the fourth fluid-filled chamber, wherein a position of a component is fixed when the second pump is off and wherein the position of the component is changed when the first pump transfers, while the second pump is on, the first fluid between the first fluid-filled chamber and the second fluid- filled chamber.

2. The actuator defined in claim 1, wherein the first and second pumps are first and second electroosmotic pumps.

3. The actuator defined in claim 1, wherein the component is a piston.

4. The actuator defined in claim 1, wherein the component is a multi- stage piston.

5. The actuator defined in claim 1, wherein the component is a fluid-filled bladder.

6. The actuator defined in claim 1, wherein a first portion of the flexible membrane defines at least part of the fourth fluid-filled chamber and wherein the flexible membrane has a second portion that defines at least part of the first fluid-filled chamber.

7. The actuator defined in claim 6, wherein the flexible membrane has a third portion that defines at least part of the third fluid-filled chamber.

8. The actuator defined in claim 6, further comprising: an additional flexible membrane that defines at least part of the third fluid-filled chamber.

9. The actuator defined in claim 1, further comprising: an additional flexible membrane that defines at least part of the first fluid-filled chamber.

10. The actuator defined in claim 1, further comprising: a first outer housing structure; a first inner housing structure; a pump housing structure, wherein the first inner housing structure is interposed between the pump housing structure and the first outer housing structure; a second inner housing structure; and a second outer housing structure, wherein the second inner housing structure is interposed between the pump housing structure and the second outer housing structure and wherein the first outer housing structure, the first inner housing structure, the pump housing structure, the second inner housing structure, and the second outer housing structure are formed within respective parallel planes.

11. The actuator defined in claim 10, wherein the first outer housing structure, the first inner housing structure, the pump housing structure, and the second inner housing structure each have respective first openings that are aligned and wherein the first outer housing structure, the first inner housing structure, the pump housing structure, and the second inner housing structure each have respective second openings that are aligned with the second pump.

12. The actuator defined in claim 1, wherein a first portion of the flexible membrane defines at least part of the fourth fluid-filled chamber and wherein the flexiblemembrane has a second portion aligned with the component.

13. The actuator defined in claim 12, wherein the second portion of the flexible membrane has a first subset and a second subset and wherein the first subset is stiffer than the second subset.

14. The actuator defined in claim 13, wherein the first subset is thicker than the second subset.

15. The actuator defined in claim 13, wherein the first subset is ring- shaped and laterally surrounds the second subset.

16. The actuator defined in claim 12, further comprising: one or more flexures that control a shape of a bulge in the second portion of the flexible membrane.

17. The actuator defined in claim 1, further comprising: a housing structure that includes a channel, wherein the flexible membrane forms a seal with the channel and divides the second fluid-filled chamber into first and second isolated portions when the second pump is off.

18. The actuator defined in claim 17, wherein the flexible membrane does not form the seal with the channel when the second pump is on.

19. A tunable lens comprising: a lens element; a ring-shaped lens shaping element that is attached to the lens element; and an actuator that is attached to the ring-shaped lens shaping element, wherein the actuator is configured to linearly displace the ring-shaped lens shaping element and wherein the actuator comprises: a brake pump that is configured to fix a position of the ring-shaped lens shaping element, wherein the position of the ring-shaped lens shaping element is fixed when the brake pump is turned off and wherein the position of the ring-shaped lens shaping element is adjustable when the brake pump is turned on; and an actuation pump that is configured to adjust the position of the ring-shaped lens shaping element while the brake pump is turned on.

20. The tunable lens defined in claim 19, wherein the actuator further comprises: a flexible membrane that comprises: a first portion with a first bulge that is controlled by the actuation pump, wherein the first portion is configured to displace the ring-shaped lens shaping element; and a second portion with a second bulge that is controlled by the brake pump, wherein the second portion is configured to fix the position of the ring-shaped lens shaping element.

21. The tunable lens defined in claim 20, wherein the flexible membrane further comprises: a third portion that serves as pressure release for the actuation pump.

22. An actuator configured to displace a component, the actuator comprising: a first outer housing structure; a second outer housing structure that is parallel to the first outer housing structure; a pump housing structure having at least first and second openings; a first pump in the first opening, wherein the first pump is interposed between the first and second outer housing structures and wherein the first pump has first and second opposing sides; a second pump in the second opening, wherein the second pump is interposed between the first and second outer housing structures and wherein the second pump has first and second opposing sides;a first fluid that is on both the first and second sides of the first pump; a second fluid that is on both the first and second sides of the second pump; and a flexible membrane that is parallel to the first and second outer housing structures, wherein the flexible membrane is interposed between the first and second pumps and the second outer housing structure.

23. The actuator defined in claim 22, wherein the flexible membrane further comprises: a first portion interposed between the component and the second outer housing structure, wherein the first fluid is interposed between the first portion of the flexible membrane and the second outer housing structure; a second portion interposed between the second pump and the second outer housing structure, wherein the first fluid is interposed between the second portion of the flexible membrane and the second outer housing structure and wherein the second fluid is interposed between the second portion of the flexible membrane and the second pump; and an opening that is aligned with the first pump, wherein the opening is interposed between the first pump and the second outer housing structure.

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