Actuator assembly

Abstract

An actuator assembly is disclosed. The actuator assembly comprises: a support structure (2); a first movable part (10); a second movable part (12); actuator means configured to drive rotation of the first movable portion relative to the support structure about a main axis (O); first support means (20, 21) configured to convert said rotation of the first movable part into a helical movement of the first movable part relative to the support structure about the main axis; a rotation control means capable of limiting rotation of the second movable part about the main axis relative to the support structure; and second support means (30, 31) configured such that when the first movable part experiences said helical movement and the second movable part experiences said rotational restriction, the second movable part experiences a translational movement along the main axis relative to the support structure and / or the first movable part.

Description

Technical Field

[0001] The present application relates to an actuator assembly. background

[0002] It is known to use actuators, such as shape memory alloy (SMA) wires, to drive translational movement of a movable element relative to a support structure. SMA actuator wires have particular advantages in micro devices and can be applied in a variety of devices including handheld devices such as cameras and mobile phones. For example, such SMA actuator wires can be used in optical devices such as cameras to drive translational movement of a camera lens element along its optical axis, for example to achieve focusing (autofocus, AF) or zooming.

[0003] Some examples of SMA actuators for cameras of this type are disclosed in WO-2007 / 113478. Here, the movable element is a camera lens element supported on a support structure by a helical bearing arrangement, the helical bearing arrangement including a flexure that guides translational movement along the optical axis. In one example described in this document, the SMA actuator wire is a piece of SMA wire connected at its ends to the support structure and hooked on a hook on the camera lens element for driving the translational movement. The straight SMA actuator wire formed by the portions of the SMA wire on either side of the hook extends at an acute angle greater than 0 degrees relative to a direction of movement parallel to the optical axis. Angling the SMA actuator wire in this way increases the amount of movement compared to an SMA actuator wire extending in the direction of movement and also reduces the range of the actuator in the direction of movement.

[0004] WO 2019 / 243849 A1 discloses an SMA device comprising a helical support device that converts a rotation about a helical axis into a helical movement.

[0005] It is desirable for the actuator to have a higher stroke, ie to increase the range of movement along the screw axis. More specifically, it is desirable to increase the stroke without unduly reducing the accuracy and repeatability of the movement. SUMMARY OF THE INVENTION

[0006] According to an aspect of the present invention, an actuator assembly is provided, which includes: a support structure; a first movable part; a second movable part; an actuator device, which is configured to (when actuated) drive the first movable part to rotate relative to the support structure (and relative to the second movable part) around a main axis; a first support device (supporting the first movable part on the support structure), which is configured to convert the rotation of the first movable part into a spiral movement of the first movable part relative to the support structure (and relative to the second movable part) around the main axis; a rotation control device, which is capable of limiting the rotation of the second movable part relative to the support structure around the main axis; and a second support device, which is configured so that when the first movable part undergoes the spiral movement and the second movable part undergoes the rotation restriction, the second movable part undergoes a (non-rotational) translational movement along the main axis relative to the support structure and / or the first movable part.

[0007] By providing a second movable part and a second support means, the stroke of the actuator assembly can be increased without unduly increasing the normal force on the first support means. The second movable part can move a greater distance along the axis for a given level of actuation of the actuator means than the first movable part. The stroke and / or gain of the actuator assembly can be increased without unduly reducing the accuracy of the movement.

[0008] Optionally, the rotation control arrangement is an anti-rotation arrangement configured to prevent rotation of the second movable part relative to the support structure about the primary axis.

[0009] By providing an anti-rotation device, the second movable part may be prevented from rotating. This may allow the actuator assembly to be used in mechanisms where the rotational position of the movable part needs to remain constant (eg, non-rotationally symmetric optical elements).

[0010] Optionally, the anti-rotation means comprises third bearing means (eg comprising a linear bearing) configured to provide said rotation prevention.

[0011] By providing the third supporting means, the second movable part can be moved more stably and reliably.

[0012] Optionally, the rotation control means comprises further actuator means configured to (when actuated) drive the second moveable part in rotation about the primary axis relative to the first moveable part and / or the support structure so as to provide said rotational limitation.

[0013] By providing further actuator means, the rotational position of the second movable part may be controlled more accurately.

[0014] Optionally, the first bearing means comprises a helical bearing configured to guide relative helical movement between the first movable part and the support structure about the primary axis.

[0015] By providing a helical bearing, a rotation of the first movable part can be converted into a helical movement comprising a movement along the main axis in a simple and energy efficient manner.

[0016] Optionally, the second bearing means comprises a helical bearing configured to guide relative helical movement between the first movable part and the second movable part about the main axis.

[0017] Optionally, the helical support of the first support device is at a positive angle relative to a plane orthogonal to the main axis, and the helical support of the second support device is at a negative angle relative to the plane orthogonal to the main axis. In other words, the helical support of the first support device has a positive slope / gradient relative to the plane orthogonal to the main axis, and the second support device has a negative slope / gradient relative to the plane orthogonal to the main axis.

[0018] By providing helical bearings with opposite angles, when the first movable part undergoes said helical movement and the second movable part undergoes said rotational restriction, the second bearing means will undergo a (non-rotational) translational movement along the main axis relative to the first movable part.

[0019] Optionally, the actuator arrangement comprises one or more shape memory alloy (SMA) elements (eg SMA wires) configured to (upon contraction) drive the first movable part to rotate in the first direction.

[0020] By providing an SMA element, the rotation of the first movable part can be controlled in a particularly accurate and simple manner.

[0021] Optionally, the actuator arrangement comprises one or more SMA elements configured to (when contracted) drive the first movable part to rotate in a second direction opposite to the first direction.

[0022] By providing SMA elements driving rotation in opposite directions, the rotation of the first moveable part may be more accurately controlled.

[0023] The opposite SMA element is optional. After actuation, the actuator assembly can be "reset" by manually moving the first movable part and / or the second movable part back to the retracted / retracted position. Alternatively, the actuator assembly can have a biasing arrangement configured to bias the first movable part and / or the second movable part back to the retracted / retracted position, for example, a biasing arrangement configured to oppose the helical movement of the first movable part and / or the translational movement of the second movable part driven by the actuator arrangement. In other words, the actuator assembly can have a biasing arrangement (e.g., including one or more springs and / or magnets) that is configured to oppose rotation of the first movable part in a first direction.

[0024] Optionally, the one or more SMA elements configured to drive the first movable part to rotate in the first direction include: SMA elements coupled to the support structure and the first movable part, and / or SMA elements coupled to the first movable part and the second movable part.

[0025] Optionally, the one or more SMA elements configured to drive the first movable part to rotate in the second direction include: SMA elements coupled to the support structure and the first movable part, and / or SMA elements coupled to the first movable part and the second movable part.

[0026] Optionally, one or more SMA elements configured to drive the first movable part to rotate in the first direction extend in a plane orthogonal to the main axis and / or extend at an acute angle relative to the plane orthogonal to the main axis (when the first movable part is in an intermediate / mid-position between the retracted / retracted position and the extended / pop-up position).

[0027] Optionally, one or more SMA elements configured to drive the first movable part to rotate in the second direction extend in a plane orthogonal to the main axis and / or extend at an acute angle relative to the plane orthogonal to the main axis (when the first movable part is in an intermediate / mid-position between the retracted / retracted position and the extended / pop-up position).

[0028] Optionally, the actuator device comprises (for example, in total) four SMA elements configured to drive rotation of the first movable part; wherein the four SMA elements are arranged in a ring at different angular positions around the main axis; and wherein continuous SMA elements around the main axis are configured to (when contracted) apply force to the first movable part in alternating directions around the main axis. Optionally, each of the four SMA elements crosses at least one of the other SMA elements when viewed along the main axis.

[0029] Optionally, the support structure, the first movable part and the second movable part are stacked along the main axis. Optionally, the body / center / central part of the first movable part is configured to be positioned between the support structure and the second movable part along the main axis at any position within the possible range of movement of the first movable part.

[0030] Optionally, the actuator assembly is configured such that: when the actuator assembly is in a retracted / retracted state, the first movable part (e.g., its body / center / central portion) is nested within a space / opening / aperture / pocket defined / enclosed by the support structure; and when the actuator assembly is in an extended / pop-out state, the first movable part (e.g., its body / center / central portion) is positioned outside the space defined by the support structure. The second movable part may not be configured to be nested within the first movable part, i.e., the body / center / central portion of the second movable part may be configured to be positioned above the first movable part along the main axis at any position within the possible range of movement of the first movable part.

[0031] Optionally, the actuator assembly is configured such that: when the actuator assembly is in a retracted / retracted state (which corresponds to the retracted / retracted state mentioned in the previous paragraph), the second movable part (e.g., its body / center / central portion) is nested within the space / opening / aperture / recess defined / enclosed by the first movable part; and when the actuator assembly is in an extended / pop-out state (which corresponds to the extended / pop-out state mentioned in the previous paragraph), the second movable part (e.g., its body / center / central portion) is positioned outside the space defined by the first movable part. The space described in the previous paragraph (i.e., the space defined by the support structure) and the space described in this paragraph (i.e., the space defined by the first movable part) may overlap.

[0032] Optionally, in the retracted state, only the first movable part may be configured to nest.

[0033] Alternatively, in the retracted state, only the second moveable part may be configured to nest.

[0034] By nesting, the size of the actuator assembly in the direction along the main axis can be reduced.

[0035] Optionally, the actuator assembly is configured to maintain the second moveable part in position relative to the support structure when the actuator arrangement is not energized.

[0036] Optionally, the actuator assembly comprises a first friction surface and a second friction surface, wherein the first friction surface is configured to engage the second friction surface. The actuator assembly may include a biasing device configured to bias the first friction surface and the second friction surface against each other so as to generate a static friction force that constrains movement of the second movable part relative to the support structure at any position within the possible range of movement of the second movable part when the actuator device is not driving rotation of the first movable part (and / or when the actuator device is not powered).

[0037] Optionally, the first support device comprises a friction surface of the support structure, which friction surface is configured to engage the friction surface of the first movable part, and / or wherein the second support device comprises a friction surface of the first movable part, which friction surface is configured to engage the friction surface of the second movable part; and wherein the actuator assembly comprises a biasing device, which is configured to bias the friction surface of the first support device and / or the friction surface of the second support device against each other so as to generate a static friction force that constrains the movement of the first movable part relative to the support structure (and relative to the second movable part) at any position within the possible movement range of the first movable part when the actuator device does not drive the rotation of the first movable part.

[0038] By generating static friction forces, the position of the second movable part may be maintained with reduced power and / or energy requirements.

[0039] Providing a biasing arrangement configured to bias parts of the assembly together is optional, as for example a pin-in-slot bearing may be provided to hold the parts of the assembly together.

[0040] Optionally, the actuator assembly comprises holding means configured to releasably (ie temporarily) hold the first movable part in one or more positions within a range of possible positions to which the first movable part can be driven (eg by the actuator means).

[0041] By providing a retaining device, the position of the first movable part (and the second movable part) may be maintained with a greater resistance to external forces (eg due to inertial impacts).

[0042] Optionally, the actuator assembly includes a bistable device configured to cause the first movable part to have a first stable equilibrium position (at a first position about the main axis), a second stable equilibrium position (at a second position about the main axis), and an unstable equilibrium position between the first stable equilibrium position and the second stable equilibrium position (at a third intermediate position about the main axis). The first stable equilibrium position and the second stable equilibrium position may correspond to the boundaries of the possible range of movement of the first movable part relative to the support structure. For example, the bistable device may include a spring, a flexure, or one or more magnets configured to exert a force on the first movable part to provide such a bistable state.

[0043] Optionally, the actuator arrangement comprises two shape memory alloy (SMA) elements which cross each other when viewed along the main axis.

[0044] Optionally, the actuator device comprises a first pair of SMA elements and a second pair of SMA elements.When viewed along the main axis, each of the first pair of SMA elements crosses each of the second pair of SMA elements.

[0045] Optionally, in embodiments where the actuator assembly includes two or more SMA elements, each of the SMA elements is disposed within a footprint of one or both of the first movable portion and the second movable portion when viewed along the major axis (i.e., the SMA element is located within the footprint of the first movable portion and / or within the footprint of the second movable portion). Alternatively, one or more of the SMA elements may fully or partially overlap one or both of the first movable portion and the second movable portion when viewed along the major axis.

[0046] Optionally, the second moveable part comprises a display.In some embodiments the actuator arrangement is arranged on a first side of the display opposite to a second side of the display from which the light is emitted.

[0047] Optionally, the second movable part comprises an optical component or a part thereof.For example, the second movable part may comprise a lens or a reflector.

[0048] Optionally, the second movable part may comprise (or be engaged with) a deformable optical component, such as a deformable lens or a deformable mirror, or a portion thereof. Optionally, the second movable part comprises a portion of a lens, such as a surface or portion of a deformable lens. Optionally, the second movable part comprises a portion of a mirror, such as a surface or portion of a deformable mirror. Thus, movement of the second movable part along the principal axis may drive deformation of the deformable optical component. This may be done for the purpose of changing an optical property of the optical element, such as focal length or some other optical property.

[0049] Further details regarding the deformation of a deformable lens (e.g., a liquid lens) can be found in WO2020030915A1, which is incorporated herein by reference in its entirety.

[0050] Optionally, the actuator device is configured to apply a force to the first movable part at a first point to drive the rotation of the first movable part about the main axis relative to the support structure. The distance between the main axis and the first point may be less than the distance between the main axis and the first support device. For example, in an embodiment where the actuator device includes one or more SMA wires, the first point may correspond to a point where the SMA wire is attached (e.g., crimped) or hooked to the first movable part. The first support device may be a spiral support. The first support may include one or more contact points between the first movable part and the second movable part (or between the first movable part and an intermediate part such as a rolling part in the case where the first support device includes a rolling support). At least one (optionally all) of the one or more contact points may be further away from the main axis (the axis about which the first movable part rotates) than the first point. It should be understood that the actuator device may be arranged to apply a force to the first movable part at multiple points. One or more (or all) such points may be closer to the main axis than the first support device. One or more (or all) such points may be closer to the main axis than one or more contact points of the first bearing means. A technical effect of such an arrangement in which the bearing means is radially further from the axis of rotation (main axis) than the actuator means is that the helical bearing of the bearing means may be made less steep (compared to the case where the bearing means is closer to the axis of rotation). A more distant bearing surface facilitates a shallower angle. The advantages of such a shallower angle are: reducing the normal force on the bearing surface, and therefore reducing friction, and A more accurate placement of the first movable part (eg because tolerance errors in the position of the support surface have a smaller effect on the height of the surface and thus on the tilting of the first movable part).

[0051] As mentioned above, such devices need not be limited to devices having two movable parts. Thus, an actuator assembly is disclosed, the actuator assembly comprising: Support structure; Removable parts; an actuator arrangement configured to drive rotation of the moveable portion relative to the support structure about the primary axis; and A first supporting device is configured to convert the rotation of the movable part into a spiral movement of the movable part relative to the supporting structure around the main axis, wherein the actuator device is configured to apply a force to the movable part at a first point to drive the rotation of the movable part relative to the supporting structure around the main axis, wherein the distance between the main axis and the first point is smaller than the distance between the main axis and the first supporting device.

[0052] Optionally, the first point may correspond to a point at which the SMA wire is attached (e.g., crimped) or hooked onto the first movable part. The first support device may be a spiral support. The first support may include one or more contact points located between the movable part and the support structure (or, in the case where the first support device includes a rolling support, between the movable part and an intermediate component such as a rolling component). At least one (optionally all) of the one or more contact points may be farther away from the main axis (the axis about which the movable part rotates) than the first point. It should be understood that the actuator device may be arranged to apply a force to the movable part at multiple points. One or more (or all) such points may be closer to the main axis than the first support device. One or more (or all) such points may be closer to the main axis than one or more contact points of the first support device. Such a device may be combined with any other features disclosed herein.

[0053] According to another aspect of the present invention, an actuator assembly is provided, which includes: a supporting structure; a first movable part; a second movable part; a first spiral supporting device, which is configured to guide the first movable part to spirally move relative to the supporting structure around a spiral axis; an actuator device, which is configured to drive the first movable part to rotate relative to the supporting structure around the spiral axis when actuated, and the first spiral supporting device converts this rotation into the spiral movement of the first movable part; and a second supporting device, which is configured to guide the second movable part to rotate or spirally move relative to the first movable part around the spiral axis, so that when the first movable part moves spirally relative to the supporting structure and the second movable part moves rotationally or spirally relative to the first movable part, the second movable part can move translationally along the spiral axis relative to the supporting structure.

[0054] Actuator components can be used for AF, zoom, haptics, optical image stabilization (OIS), valves, augmented reality (AR) applications, and more. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Certain embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a schematic diagram of an actuator assembly having a screw support device; Figure 2 is a schematic diagram of an actuator assembly having a screw support device; Figure 3 is a schematic diagram of an actuator assembly having two helical support devices; Figure 4 is a schematic diagram of an actuator assembly having two helical support devices; Figure 5 is a schematic diagram of an actuator assembly having two helical support devices; Figure 6 is a schematic diagram of an actuator assembly having two helical support devices; Figure 7 is a schematic diagram of an actuator assembly having two helical support devices; Figure 8 is a schematic diagram of an actuator assembly having two helical support devices; Fig. 9 is a schematic diagram of an actuator assembly having two helical support devices; Fig.10 is a schematic diagram of an actuator assembly having two helical support devices; Fig.11 is a schematic diagram of an actuator device including an SMA element; Fig.12 is a schematic diagram of an actuator device including an SMA element; and Fig.13 is a schematic diagram of an actuator device including an SMA element; and Fig.14 is a schematic diagram of the actuator assembly. Detailed Description

[0056] Figure 1 Actuator assembly Figure 1 is a schematic diagram of an actuator assembly 1 having a single movable part 10 configured to move helically relative to a support structure 2 about a helical axis H. The actuator assembly 1 is primarily described herein in the context of the actuator assembly 1 being part of a miniature camera. However, the actuator assembly 1 need not be part of a camera and may be part of a different type of device.

[0057] The support structure 2 has one or more components fixed to (e.g. mounted on) the support structure 2. The support structure 2 has an image sensor 3 mounted on the support structure 2. The support structure 2 may take any suitable form, typically including a base 4 to which the image sensor 3 is fixed. The support structure 2 may also support an integrated circuit (IC) chip 5.

[0058] The first movable part 10 comprises a lens assembly 11 comprising one or more lenses (also referred to herein as lens elements) arranged to focus an image on the image sensor 3. The one or more lenses may have a diameter of at most 20 mm, preferably at most 15 mm, preferably at most 10 mm.

[0059] The actuator assembly 1 comprises a first support device 20 (at Figure 1 ), the first support device 20 supports the first movable part 10 on the support structure 2. The first support device 20 is a spiral support device, which is arranged to guide the spiral movement of the first movable part 10 relative to the support structure 2 around the spiral axis H. The spiral axis H coincides with the main axis O of the actuator assembly 1, the optical axis of one or more lenses of the lens assembly 11, and the longitudinal axis of the actuator assembly 1. The spiral movement Figure 1 , shown by arrow M. The spiral motion may be along a circular spiral, i.e. a spiral with a constant radius, but in general any spiral is possible. The pitch of the spiral may be constant, or vary along the spiral motion. The spiral movement may be only a fraction of a full turn of the spiral (e.g., equal to or less than a quarter, a half, or three quarters).

[0060] The spiral movement of the first movable part 10 guided by the first support device 20 includes a component of translational movement along the spiral axis H and a component of rotational movement about the spiral axis H. The translational movement along the spiral axis H is a desired movement of the first movable part 10, for example to change the focus of the image on the image sensor 3 and / or to change the magnification (zoom) of the image on the image sensor 3. In a pop-up camera (also called a retractable lens camera or a telescopic camera), the translational movement of the first movable part 10 along the spiral axis H may also be desired, for example, to drive the camera to move between a retracted / retracted state (for example, one or more of the lenses are configured so that they cannot focus an image on the image sensor 3) and an extended / pop-up state (for example, one or more of the lenses are configured so that they can focus an image on the image sensor 3; in other words, where the pop-up camera is in an operating state).

[0061] Figure 2 Actuator assembly Figure 2 is a schematic diagram of an actuator assembly 1, the actuator assembly 1 comprising Figure 1 The invention has all the features of the actuator assembly 1 and further includes a second movable part 12, a second supporting device 30 supporting the second movable part 12 on the first movable part 10, and a rotation control device arranged between the second movable part 12 and the support structure 2.

[0062] exist Figure 2 In the figure, the first support device 20 and the second support device 30 are each shown to include a plurality of supports 21, 31, however any number of supports may be provided. For example, each of the first support device 20 and the second support device 30 may be provided with only one support instead of two supports.

[0063] The second movable part 12 may comprise a lens assembly comprising one or more lenses arranged to focus an image on the image sensor 3. In this case, the first movable part 10 may not comprise the lens assembly 11. The one or more lenses of the second movable part 12 may have a diameter of at most 20 mm, preferably at most 15 mm, preferably at most 10 mm.

[0064] The second bearing device 30 is arranged between the first movable part 10 and the second movable part 12. The bearing 31 may be, for example, a plain bearing and / or a ball bearing. In contrast to the first bearing device 20, the bearing 31 of the second bearing device 30 is not a helical bearing. In other words, the bearing 31 is a non-helical bearing and the second bearing device 30 is a non-helical bearing.

[0065] The rotation control means are able to limit the rotation of the second movable part 12 relative to the support structure 2 about the axis O, ie the main axis. Figure 2 The rotation control device includes an anti-rotation device 13 (i.e., a third support device) configured to prevent the second movable part 12 from rotating relative to the support structure 2 around the axis O. In other words, the anti-rotation device 13 is configured to limit the movement of the second movable part 12 to a linear direction along the axis O. The anti-rotation device 13 is a linear support device including, for example, a slider support and / or a ball support. The anti-rotation device 13 is configured to guide the second movable part 12 to move relative to the support structure 2 only along the direction of the axis O.

[0066] The actuator assembly 1 also includes an actuator device ( Figure 2), the actuator device is configured to drive the rotation of the first movable part 10 relative to the support structure 2 around the main axis O. When the actuator device drives such rotation, the first support device 20 converts the rotation of the first movable part 10 into a spiral movement of the first movable part 10 relative to the support structure 2 around the main axis O.

[0067] Figure 2 The second bearing means 30 are configured so that when the first movable part 10 undergoes a helical movement and the second movable part 12 undergoes a rotational restriction, the second movable part 12 undergoes a non-rotational translational movement along the main axis O relative to the support structure 2 and not relative to the first movable part 10. In this way, when the actuator means drives the first movable part 10 to rotate about the main axis O relative to the support structure 2, the bearing 31 causes the second movable part 12 to undergo a purely non-rotational translational movement along the main axis O relative to the support structure (but not relative to the first movable part 10).

[0068] The translational movement of the first movable part 10 and the second movable part 12 can be used, for example, to change the focus of the image on the image sensor 3 and / or to change the magnification (zoom) of the image on the image sensor 3. The translational movement can also be used in a pop-up camera to drive the camera to move between a retracted / retracted state and an extended / pop-up state. For example, in the case where the parts of the second movable part 12 are not rotationally symmetrical, or in the case where the second movable part 12 is connected to a component that is not designed to rotate around the axis O or ideally does not rotate around the axis O, it may be beneficial to prevent the second movable part 12 from rotating around the axis O.

[0069] Figure 3 Actuator assembly Figure 3 is a schematic diagram of an actuator assembly 1, the actuator assembly 1 comprising Figure 2 All the features of the actuator assembly 1 of , but wherein the second support means 30 comprises a helical support 32 instead of a non-helical support 31 .

[0070] exist Figure 3 In the embodiment, the second support device 30 includes a spiral support 32 (hereinafter referred to as the second spiral support device 30), and the second support device 30 is shown as including two spiral supports 32, but any number of supports may be provided. For example, the second support device 30 may be provided with only one spiral support.

[0071] The second helical bearing means 30 is arranged to guide a helical movement of the second movable part 12 relative to the first movable part 10 about the axis O. The helical movement may be along a circular helix, i.e. a helix with a constant radius, but generally any helix is ​​possible. The pitch of the helix may be constant or vary along the helical movement. The helical movement may be only a portion of a full turn of the helix (e.g. equal to or less than a quarter, a half or three quarters).

[0072] The helical bearing 32 is inclined in a direction opposite to the direction in which the helical bearing 21 is inclined. The helical bearing 21 is at a positive angle relative to a plane orthogonal to the axis O, and the helical bearing 32 is at a negative angle relative to a plane orthogonal to the axis O. In other words, the helical bearing 21 has a positive slope / gradient relative to a plane orthogonal to the axis O, and the helical bearing 32 has a negative slope / gradient relative to a plane orthogonal to the axis O. Both the first bearing device 20 and the second helical bearing device 30 are configured to guide a helical movement about a common axis O.

[0073] Since the anti-rotation device 13 is configured to prevent the second movable part 12 from rotating relative to the support structure about the axis O, when the actuator device (also not in Figure 3 When the first movable part 10 is driven to rotate relative to the support structure 2 about the axis O, the second spiral support device 30 converts the rotation of the first movable part 10 into a spiral movement of the second movable part 12 relative to the first movable part 10 about the axis O. The spiral movement of the second movable part 12 includes a component of translational movement along the axis O and a component of rotational movement about the axis O.

[0074] Rotation of the first movable part 10 about the axis O in a first direction causes the first movable part 10 to move in translation upward along the axis O relative to the support structure 2, and simultaneously causes the second movable part 12 to move in translation upward along the axis O relative to the first movable part 10 (without rotation). Rotation of the first movable part 10 about the axis O in a second, opposite direction causes the first movable part 10 to move in translation downward along the axis O relative to the support structure 2, and simultaneously causes the second movable part 12 to move in translation downward along the axis O relative to the first movable part 10 (without rotation).

[0075] The distance that the second movable part 12 moves along the axis O is greater than the distance that the first movable part 10 moves in that direction. For example, when the spiral bearings 30 of the first and second bearing devices have the same design (except in opposite directions), the distance that the second movable part 12 moves along the axis O may be twice the distance that the first movable part 10 moves in the direction along the axis O.

[0076] The total linear movement of the second movable part 12 along the axis O relative to the support structure 2 is equal to the sum of (i) the movement of the first movable part 10 along the axis O relative to the support structure 2 and (ii) the movement of the second movable part 12 along the axis O relative to the first movable part 10.

[0077] and Figure 2 Compared with the device Figure 3 In other words, for a given level of actuation of the actuator device, the second movable part 12 moves a greater distance along the main axis O.

[0078] SMA Components Figure 4 is a schematic diagram of an actuator assembly 1, the actuator assembly 1 comprising Figure 3 The invention relates to an actuator assembly 1 of claim 1, wherein the actuator device comprises two SMA elements 41, 42, which are configured to drive the rotation of the first movable part 10 relative to the support structure 2 around the axis O. The SMA elements 41, 42 may be SMA wires, for example. The first support device 20 is located between the SMA elements 41, 42 and the second support device.

[0079] The first SMA element 41 is configured to drive rotation of the first movable part 10 about the axis O in a first direction when contracted (e.g., drive rotation of the first movable part 10 in a clockwise direction when the actuator assembly 1 is viewed along the axis O). The first SMA element 41 is coupled to the support structure 2 and the first movable part 10 .

[0080] The second SMA element 42 is configured to drive rotation of the first movable part 10 about the axis O in a second, opposite direction when contracted (e.g., drive rotation of the first movable part 10 in a counterclockwise direction when the actuator assembly 1 is viewed along the axis O). The second SMA element 42 is coupled to the support structure 2 and the first movable part 10 .

[0081] In other words, the first SMA element 41 and the second SMA element 42 are configured to drive relative rotation between the first movable part 10 and the support structure 2 about the axis O in opposite directions when contracted.

[0082] The first movable part 10 includes one or more protrusions 14 extending parallel to the main axis O. The protrusions 14 are located radially outside the first support device 20 (e.g., the spiral support 21 of the first support device 20). A first SMA element 41 is coupled to the protrusion 14 of the first movable part 10. A second SMA element 42 is coupled to the protrusion 14 of the first movable part 10. The SMA elements 41, 42 extend in a plane orthogonal to the main axis O. The protrusions 14 are configured to provide locations for the SMA elements 41, 42 to be attached to the first movable part 10. The SMA elements 41, 42 can be coupled to the support structure 2 and / or the first movable part 10 by crimping.

[0083] Of course, during use of the actuator assembly 1, the position of the first movable part 10 relative to the support structure 2 along the main axis O changes. This affects the angle of the SMA elements 41, 42 coupled between the support structure 2 and the first movable part 10. When the first movable part 10 is in an intermediate / mid-position between the retracted / retracted position and the extended / pop-out position, the SMA elements 41, 42 extend in a plane orthogonal to the main axis O. The SMA elements 41, 42 may extend at an angle (e.g., an acute angle) relative to the plane orthogonal to the main axis O when the first movable part is in the retracted / retracted position and when the first movable part 10 is in the extended / pop-out position.

[0084] like Figure 5 As shown, the first movable part 10 does not necessarily have to include the protrusion 14 .

[0085] Figure 5 is a schematic diagram of an actuator assembly 1, the actuator assembly 1 comprising Figure 4 The support structure 2 has all the features of the actuator assembly 1 of , but without the protrusion 14 and with the SMA elements 41 , 42 located between the first support means 20 and the second support means 30. Instead of the protrusion 14, the support structure 2 comprises a protrusion 15 on the opposite side of the main axis O. The protrusion 15 provides a location where the SMA elements 41 , 42 can be attached to the support structure 2.

[0086] like Figure 6 As shown, the SMA element 40 does not necessarily extend in a plane orthogonal to the major axis O.

[0087] Figure 6 is a schematic diagram of an actuator assembly 1, the actuator assembly 1 comprising Figure 5 All the features of the actuator assembly 1 of , but wherein the SMA elements 41 , 42 extend at an acute angle relative to a plane orthogonal to the main axis O (when the first movable part 1 is in the intermediate / mid position). Figure 6In FIG. 4 , both the first SMA element 41 and the second SMA element 42 are at a positive angle relative to a plane normal to the axis O, however, one or both of the SMA elements 41 , 42 may alternatively be at a negative angle relative to the plane normal to the axis O.

[0088] Figure 7 is a schematic diagram of an actuator assembly 1, the actuator assembly 1 comprising Figure 4 The invention relates to an actuator assembly 1 of the present invention, but with an additional actuator device comprising two SMA elements 43, 44 (also referred to herein as third and fourth SMA elements 43, 44). The second helical bearing device 30 is located between the first movable part 10 and the third and fourth SMA elements 43, 44.

[0089] The further actuator arrangement is configured to drive a relative rotation about the main axis O between the second movable part 12 and the first movable part 10 .

[0090] The third and fourth SMA elements 43 and 44 are configured to drive relative rotation between the second and first movable parts 12 and 10 about the main axis O in opposite directions about the axis O when contracted. The third and fourth SMA elements 43 and 44 are coupled to the support structure 2 and the first movable part 10 .

[0091] Providing the further actuator means makes it possible to reduce the forces transmitted by the third bearing means 13, or even to completely dispense with the need to provide the third bearing means 13, since the further actuator means can be used as a rotation control means. In other words, the further actuator means can be considered as part of the rotation control means, since it is able to limit (and even completely prevent) the rotation of the second movable part 12 relative to the support structure 2 about the axis O.

[0092] The third SMA element 43 is coupled to the protrusion 14 of the first movable part 10. The fourth SMA element 44 is coupled to the protrusion 14 of the first movable part 10. The third SMA element 43 and the fourth SMA element 44 extend in a plane orthogonal to the main axis O. The protrusion 14 is configured to provide a location for the third SMA element 43 and the fourth SMA element 44 to be attached to the first movable part 10. The SMA elements 41, 42 may be coupled to the support structure 2 and / or the first movable part 10 by crimping.

[0093] Of course, during use of the actuator assembly 1, the position of the first movable part 10 relative to the support structure 2 along the main axis O changes. This affects the angles of the third SMA element 43 and the fourth SMA element 44 coupled between the support structure 2 and the first movable part 10. When the first movable part 10 is in an intermediate / mid-position between the retracted / retracted position and the extended / pop-out position, the SMA elements 43, 44 extend in a plane orthogonal to the main axis O. The SMA elements 43, 44 may extend at an angle (e.g., an acute angle) relative to the plane orthogonal to the main axis O when the first movable part is in the retracted / retracted position and when the first movable part 10 is in the extended / pop-out position.

[0094] like Figure 8 As shown, the SMA elements 43 , 44 do not necessarily extend in a plane orthogonal to the main axis O.

[0095] Figure 8 is a schematic diagram of an actuator assembly 1, the actuator assembly 1 comprising Figure 7 but wherein the SMA elements 41 , 42 , 43 , 44 extend at an acute angle relative to a plane orthogonal to the main axis O (when the first movable part 1 is in the intermediate / mid position) and without the protrusion 14 .

[0096] In place of the protrusion 14, the support structure 2 includes a protrusion 15 extending upwardly parallel to the main axis O, and the second movable part 12 includes a protrusion 16 extending downwardly parallel to the main axis O. The protrusion 15 of the support structure 2 provides a location where the first SMA element 41 can be attached to the support structure 2. The protrusion 16 of the second movable part 12 provides a location where the third SMA element 43 can be attached to the support structure 2.

[0097] Both the first SMA element 41 and the second SMA element 42 are at a positive angle relative to a plane normal to the axis O, however, one or both of these SMA elements 41, 42 may alternatively be at a negative angle relative to the plane normal to the axis O. Both the third SMA element 43 and the fourth SMA element 44 are at a negative angle relative to a plane normal to the axis O, however, one or both of these SMA elements 43, 44 may alternatively be at a positive angle relative to the plane normal to the axis O.

[0098] Fig. 9 is a schematic diagram of an actuator assembly 1, the actuator assembly 1 comprising Figure 5 All features of the actuator assembly 1 of FIG. 1 , but with two hooked SMA elements 45, 46 instead of Figure 5 The SMA elements 41 and 42 are provided.

[0099] The first hooking SMA element 45 is hooked around a first feature 47 of the first movable part 10. For example, the feature 47 of the first movable part 10 may be a pulley or a post. The feature 47 may be an integral part of the first movable part 10. Alternatively, the feature 47 may be fixedly connected to the body of the first movable part 10.

[0100] The second hooked SMA element 46 is hooked around a second feature 48 of the first movable part 10. For example, the feature 48 of the first movable part 10 can be a pulley or a post. The feature 48 can be an integral part of the first movable part 10. Alternatively, the feature 48 can be fixedly connected to the body of the first movable part 10.

[0101] The first hooked SMA element 45 and the second hooked SMA element 46 are configured to drive relative rotation between the first movable part 10 and the support structure 2 about the main axis O when retracted, and to drive relative rotation between the second movable part 12 and the first movable part 10 about the main axis O. Both the first hooked SMA element 45 and the second hooked SMA element 46 are coupled at their ends to the support structure 2 and the second movable part 12. The first hooked SMA element 45 and the second hooked SMA element 46 are configured to drive the first movable part 10 to rotate in opposite directions about the axis O when retracted.

[0102] Fig.10 is a schematic diagram of an actuator assembly 1, the actuator assembly 1 comprising Fig. 9 The invention also has all the features of the actuator assembly 1 of , but wherein both hooked SMA elements 45 , 46 are coupled to the support structure 2 at their ends, rather than being coupled to the support structure 2 and the second movable part 12 at their ends.

[0103] Fig.11 is a plan view of the first movable part 10 of the actuator assembly 1 . Fig.11 The first movable part 10 may be Figure 1 , Figure 2 or Figure 3 The first movable part 10 of the actuator assembly 1.

[0104] Fig.11 The actuator arrangement comprises four SMA elements 40. The SMA elements 40 are configured to drive the rotation of the first movable part 10. The actuator arrangement comprises a total of (ie only) four SMA elements 40. Alternatively, additional SMA elements may be provided.

[0105] Four SMA elements 40 are arranged in a ring at different angular positions about the main axis O. Successive SMA elements 40 about the main axis O are configured to apply forces to the first movable part 10 in alternating directions about the main axis O. The first SMA element 40 shown horizontally at the top of the figure is configured to apply a force to rotate the first movable part 10 clockwise. Fig.11 The next SMA element 40 shown at the right hand side of FIG. 18 is configured to apply a force to the first movable part 10 in the opposite direction, i.e., to rotate the movable part 10 counterclockwise relative to the support structure 2. The next SMA element 40 shown at the bottom of FIG. 18 is configured to apply a force to rotate the first movable part 10 clockwise relative to the support structure 2 (i.e., in a clockwise direction relative to the support structure 2). Fig.11 40 is shown at the top of the SMA element 40). Fig.11 The last SMA element 40 shown on the left hand side of FIG. 1 (about the main axis O) is arranged to rotate the first movable part 10 counterclockwise (ie, in relation to the rotation of the first movable part 10). Fig.11 4.) The SMA element 40 may be configured to apply a force to the first movable portion 10 when the SMA element 40 contracts.

[0106] exist Fig.11 18 , the support structure 2 and the second movable part 12 are not shown. It should be understood that the SMA elements 40 can be coupled between the first movable part 10 and the support structure 2. Alternatively, the SMA elements 40 shown in FIG. 18 can be coupled between the first movable part 10 and the second movable part 12. As another alternative, at least one of the SMA elements 40 can be coupled between the first movable part and the support structure 2, while at least another of the SMA elements 40 is coupled between the first movable part and the second movable part 12.

[0107] Fig.12 yes Fig.11 A schematic diagram of a modified version of the apparatus shown. Fig.12 As shown, the SMA elements 40 on each side of the first movable part 10 are hooked to the first movable part 10, for example similar to Fig. 9 and Fig.10 As another alternative, instead of providing a hooking SMA element 40 , a plurality of (eg two) SMA elements 40 may be provided on each side of the first movable part 10 .

[0108] like Fig.12 As shown, the SMA element 40 is coupled to the first movable portion 10. The ends of the SMA element 40 are Fig.12However, in practice, the ends of the SMA element 40 are attached to the second movable part 12 and / or the support structure 2 .

[0109] Fig.13 An alternative arrangement of SMA elements is shown in Fig.11 and Fig.12 In an embodiment of the present invention, the actuator device includes four SMA elements. The four SMA elements 40a, 40b, 40c and 40d are configured to drive the rotation of the first movable part 10 (not shown). The SMA element is connected to the support structure at one end by a crimp (or some other connecting element) 50, and is connected to the first movable part at the other end by a crimp (or some other connecting element) 60. Alternatively, the SMA element in this arrangement can be attached to one of the support structure or the first movable part at both ends and hooked on the other of the support structure and the first movable part. Alternatively, the SMA element can be connected between the first movable part and the second movable part (rather than between the first movable part and the support structure).

[0110] When viewed along the major axis, each of the SMA elements 40a - 40d intersects with adjacent SMA elements (moving about the major axis).

[0111] The SMA elements 40a-40d include a first pair of SMA elements 40a and 40b and a second pair of SMA elements, wherein the first pair of SMA elements 40a and 40b are used to drive the first movable part to rotate in a first direction, and the second pair of SMA elements are used to drive the first movable part to rotate in a second direction opposite to the first direction. Fig.13 The cross in the center indicates that when observed, each of the first pair overlaps with each of the second pair.

[0112] The actuator assembly can be arranged such that each of the four SMA elements 40a-40d completely overlaps the first movable portion and / or the second movable portion when viewed along the main axis. In other words, each of the four SMA elements 40a-40d can be located within the footprint of the first movable portion and / or the second movable portion when viewed along the main axis. The footprint of the first movable portion and / or the second movable portion is determined by Fig.13 Indicated by the dashed line 100 in FIG. In some embodiments, the SMA element may only partially overlap the footprint of the first movable portion and / or the second movable portion when viewed along the major axis.

[0113] Fig.13The arrangement of the SMA elements shown has a number of advantages. First, the arrangement saves space (in a plane perpendicular to the major axis) compared to a situation where the SMA elements are outside the footprint of other components of the assembly. Second, the point at which the SMA elements are coupled (e.g., crimped or hooked) to the first movable portion is located in a manner consistent with the arrangement of the first movable portion. Fig.11 and Fig.12 The arrangement shown in FIG. 1 is closer to the main axis than the arrangement shown in FIG. 2 , which means that a greater amount of rotation of the first movable part can be achieved. Since the connection point is closer to the axis of rotation, the first movable part will be driven to rotate by a greater amount per unit contraction of the SMA element (compared to the case where the connection point is further away from the axis of rotation).

[0114] The term "shape memory alloy (SMA) element" may refer to any element including SMA. The SMA element may be described as an SMA wire. The SMA element may have any shape suitable for the purposes described herein. The SMA element may be elongated and may have a circular cross section or a cross section of any other shape. The cross section may vary along the length of the SMA element. The SMA element may have a relatively complex shape, such as a spiral spring shape. It is also possible that the length of the SMA element (however defined) may be similar to one or more of the other dimensions of the SMA element. The SMA element may be sheet-like, and such a sheet may be planar or non-planar. The SMA element may be flexible, or in other words, the SMA element may be flexible. In some examples, when connected in a straight line between two components, the SMA element can only apply a tensile force that forces the two components together. In other examples, the SMA element may be bent around the component, and when the SMA element tends to straighten in a tensile state, the SMA element may apply a force to the component. The SMA element may be beam-like or rigid, and may be able to apply different forces (e.g., non-tensile forces) to the element. SMA elements may or may not include non-SMA materials and / or components. For example, an SMA element may include a core of SMA and a coating of non-SMA material. Unless the context requires otherwise, the term "SMA element" may refer to any configuration of SMA material that acts as a single actuating element, for example, the single actuating element can be individually controlled to generate a force acting on the element. For example, an SMA element may include two or more parts of SMA material that are mechanically arranged in parallel and / or in series. In some arrangements, an SMA element may be part of a larger SMA element. Such a larger SMA element may include two or more parts that can be individually controlled, thereby forming two or more SMA elements. An SMA element may include any other configuration of an SMA wire, an SMA foil, an SMA film, or an SMA material. An SMA element may be manufactured using any suitable method, such as by methods involving drawing, rolling, or deposition and / or other forming processes. An SMA element may exhibit any shape memory effect, such as a thermal shape memory effect or a magnetic shape memory effect, and may be controlled in any suitable manner (e.g., by Joule heating, another heating technique, or by applying a magnetic field).

[0115] Stacking and / or nesting Figures 2 to 10The first movable part 10 and the second movable part 12 are shown stacked in the direction of the screw axis H. The body of the first movable part 10 is configured to be positioned between the support structure 2 and the second movable part 12 along the main axis O at any position within the possible movement range of the first movable part 10. The body of the first movable part 10 includes the center of the first movable part 10. The body of the first movable part 10 includes the central part of the first movable part 10. The support structure 2, the first movable part 10 and the second movable part 12 are stacked along the main axis O.

[0116] Alternatively, the actuator assembly 1 may be configured such that when the actuator assembly 1 is in a retracted / retracted state, the first movable portion 10 (e.g., a body or a center or central portion of the first movable portion 10) is nested within a space (e.g., an opening, an aperture, or a recess) defined (or enclosed) by the support structure 2. And when the actuator assembly 1 is in an extended / popped-out state, the first movable portion 10 is positioned outside of the space defined by the support structure 2.

[0117] The actuator assembly 1 may also be configured such that when the actuator assembly 1 is in the retracted / retracted state, the second movable part 12 (e.g., the body of the second movable part 12) is nested within the space defined by the first movable part 10. Alternatively, when the actuator assembly 1 is in the extended state, the second movable part 12 is positioned outside the space defined by the first movable part 10. The above-mentioned space defined by the first movable part 10 may overlap with the space defined by the support structure 2.

[0118] Zero holding power Optionally, the first support means 20 and / or the second support means 30 (or some other part of the assembly 1, as described below) are arranged to have sufficient friction when loaded so that the first movable part 10 and / or the second movable part 12 remain in place over a continuous range of positions when the actuator component is not driving rotation of the first movable part 10. This may allow the first movable part 10 to be controlled to maintain any arbitrary helical position relative to the support structure 2. The friction within the support means may allow the first movable part 10 to remain at any of the continuous range of positions.

[0119] Optionally, the biasing means is arranged to load the first support means 20 and / or the second support means 30 so as to generate a friction force therein which, when the actuator member is not actuated, constrains the movement of the first movable part 10 at any position within the range of movement relative to the support structure 2. The constraint of the first movable part 10 may enable the first movable part 10 to maintain a helical position relative to the support structure 2.

[0120] Optionally, the first bearing means 20 comprises a friction surface of the support structure 2, which is configured to engage a friction surface of the first movable part 10. Additionally or alternatively, the second bearing means comprises a friction surface of the first movable part 10, which is configured to engage a friction surface of the second movable part 12.

[0121] Optionally, friction may (additionally or alternatively) be provided elsewhere in the actuator assembly 1. Optionally, sufficient friction may be present in the bearing between the second movable part 12 and the support structure 2. For example, Figure 2-Figure 10 The third support means 13 in any of the embodiments may be a planar support having sufficient friction when loaded so that the first movable part 10 and / or the second movable part 12 remain in position in a continuous sequence of positions when the actuator component is not driving the rotation of the first movable part 10. Such a third support means 13 may or may not form part of the rotation control means. For example, the rotation control may alternatively be provided by another actuator means (e.g., one or more SMA elements), for example as described in reference Figure 7 as described.

[0122] Alternatively, friction may (alternatively or additionally) be provided at a location other than the support. For example, the actuator assembly may include a friction component such as a spring arm. Fig.14 , the actuator assembly 1 comprises a spring arm 102 which is connected to the first movable part 10 at a first end and contacts the support structure 2 at a second end. The spring arm 102 is elastic and exerts a normal force on the support structure 2 which causes a friction force between the spring arm 102 and the support structure 2. Fig.14 As shown, the support structure 2 can be shaped to provide a surface for engaging with the spring arm 102. Alternatively, the spring arm 102 can be connected to the support structure and in contact with the first movable part. Alternatively, the spring can be arranged between the second movable part and the support structure (e.g., connected to one of the support structure and the second movable part and in contact with the other).

[0123] Optionally, the actuator assembly 1 comprises a biasing device configured to bias the friction surface of the first support device 20 and / or the friction surface of the second support device against each other. Alternatively, the biasing device may be referred to as a loading device. The biasing device is configured to generate a static friction force that constrains the movement of the first movable part 10 relative to the support structure 2 (and relative to the second movable part 12) at any position within the possible range of movement of the first movable part 10 when the actuator device is not driving the rotation of the first movable part 10.

[0124] Optionally, the actuator assembly 1 includes a retaining device configured to releasably (e.g., temporarily) retain the first movable part 10 at one or more positions within a range of possible positions to which the first movable part 10 can be driven (e.g., by the actuator device). The retaining device may include a mechanism including a protrusion configured to engage a recess. For example, the protrusion may be a spring-loaded protrusion. This may help to lock the position of the second movable part 12 along the main axis O. This may be desirable when it is desired to maintain the position of the second movable part 12. Additionally or alternatively, the retaining device may include a magnetic device.

[0125] Bistable device Optionally, the actuator assembly 1 includes a bistable device (not shown) configured to cause the first movable part 10 to have a first stable equilibrium position (at a first position around the main axis), a second stable equilibrium position (at a second position around the main axis), and an unstable equilibrium position between the first stable equilibrium position and the second stable equilibrium position (at a third intermediate position around the main axis). The first stable equilibrium position and the second stable equilibrium position may correspond to the ends of the possible range of movement of the first movable part 10 relative to the support structure 2. The bistable device may include, for example, a spring, a flexure, or one or more magnets configured to exert a force on the first movable part 10 in order to provide such a bistable state.

[0126] Other variants It will be appreciated that many other variations of the above examples are possible.

[0127] Figures 4 to 10 The actuator device includes an SMA element configured to drive the first movable part 10 to rotate in opposite directions. However, the actuator device does not have to include an SMA element configured to drive the first movable part 10 to rotate in opposite directions. For example, the actuator device may only include one or more SMA elements configured to drive the first movable part 10 to rotate in only one direction. For example, the rotation of the first movable part 10 in opposite directions can be achieved by an elastic element. The elastic element can be arranged to provide a biasing force to bias the rotational position of the first movable part 10 relative to the support structure 2.

[0128] The actuator arrangement may for example be a voice coil motor (VCM) actuator arrangement or a piezoelectric actuator arrangement instead of an SMA actuator arrangement.

[0129] For example, the actuator assembly 1 may comprise a mixture of sliding and rolling bearings. As a further alternative, the bearing means may comprise flexure means.

[0130] Actuator assemblies can be used for AF, zoom, haptics, OIS, valves, AR applications, etc.

Claims

1. An actuator assembly, comprising: Support structure; a first movable portion; a second movable portion; an actuator arrangement configured to drive rotation of the first movable part relative to the support structure about a primary axis; a first support arrangement configured to convert the rotation of the first movable part into a helical movement of the first movable part relative to the support structure about the main axis; a rotation control device capable of limiting rotation of the second movable part relative to the support structure about the main axis; and A second bearing arrangement is configured such that, when the first movable part undergoes the helical movement and the second movable part undergoes the rotational restriction, the second movable part undergoes a translational movement along the main axis relative to the support structure and / or the first movable part.

2. The actuator assembly according to claim 1, wherein: The rotation control device is an anti-rotation device configured to prevent a rotation of the second movable part relative to the support structure about the main axis.

3. The actuator assembly according to claim 2, wherein: The anti-rotation arrangement comprises a third bearing arrangement configured to provide said rotation prevention.

4. An actuator assembly according to any one of the preceding claims, wherein: The rotation control means comprises further actuator means configured to drive rotation of the second movable part relative to the first movable part and / or the support structure about the main axis so as to provide the rotation limitation.

5. An actuator assembly according to any one of the preceding claims, wherein: The first bearing arrangement comprises a helical bearing configured to guide relative helical movement between the first movable part and the support structure about the primary axis.

6. An actuator assembly according to any one of the preceding claims, wherein: The second support arrangement comprises a helical support, the helical support of the second support arrangement being configured to guide relative helical movement between the first movable part and the second movable part about the main axis.

7. An actuator assembly according to claim 6 when dependent on claim 5, wherein: The helical support of the first support means is at a positive angle relative to a plane normal to the main axis, and the helical support of the second support means is at a negative angle relative to a plane normal to the main axis.

8. An actuator assembly according to any one of the preceding claims, wherein: The actuator arrangement includes one or more shape memory alloy (SMA) elements configured to drive the first movable portion to rotate in a first direction.

9. The actuator assembly of claim 8, wherein: The actuator arrangement includes one or more SMA elements configured to drive the first movable part to rotate in a second direction opposite to the first direction.

10. An actuator assembly according to claim 8 or 9, wherein: The one or more SMA elements configured to drive the first movable portion to rotate in the first direction include: an SMA element coupled to the support structure and the first movable portion, and / or An SMA element is coupled to the first movable portion and the second movable portion.

11. An actuator assembly according to claim 9 or claim 10 when dependent on claim 9, wherein: The one or more SMA elements configured to drive the first movable portion to rotate in the second direction include: an SMA element coupled to the support structure and the first movable portion, and / or An SMA element is coupled to the first movable portion and the second movable portion.

12. An actuator assembly according to any one of claims 8 to 11, wherein: The one or more SMA elements configured to drive the first movable part to rotate in the first direction extend in a plane orthogonal to the main axis and / or extend at an acute angle relative to the plane orthogonal to the main axis.

13. An actuator assembly according to claim 9 or any one of claims 10 to 12 when dependent on claim 9, wherein: The one or more SMA elements configured to drive the first movable part to rotate in the second direction extend in a plane orthogonal to the main axis and / or extend at an acute angle relative to the plane orthogonal to the main axis.

14. An actuator assembly according to any one of the preceding claims, wherein: The actuator device comprises four SMA elements, which are configured to drive rotation of the first movable part; wherein the four SMA elements are arranged in a ring at different angular positions around the main axis; and wherein continuous SMA elements around the main axis are configured to apply force to the first movable part in alternating directions around the main axis.

15. An actuator assembly according to any one of the preceding claims, wherein: The support structure, the first movable part and the second movable part are stacked along the main axis.

16. An actuator assembly according to any one of the preceding claims, wherein: The body of the first movable part is configured to be positioned between the support structure and the second movable part along the main axis at any position within the range of possible movement of the first movable part.

17. An actuator assembly according to any one of claims 1 to 14, wherein: The actuator assembly is configured such that: When the actuator assembly is in a retracted state, the first movable portion is nested within a space defined by the support structure; and When the actuator assembly is in the extended state, the first movable portion is positioned outside the space defined by the support structure.

18. An actuator assembly according to any one of claims 1 to 14 and claim 17, wherein: The actuator assembly is configured such that: When the actuator assembly is in a retracted state, the second movable portion is nested in a space defined by the first movable portion; and When the actuator assembly is in the extended state, the second movable portion is positioned outside the space defined by the first movable portion.

19. An actuator assembly according to any preceding claim, configured to maintain the second moveable part in position relative to the support structure when the actuator device is not energised.

20. An actuator assembly according to claim 19, comprising a first friction surface and a second friction surface, wherein the first friction surface is configured to engage the second friction surface; and wherein the actuator assembly comprises a biasing device, the biasing device being configured to bias the first friction surface and the second friction surface against each other so as to generate a static friction force that constrains the movement of the second movable part relative to the support structure at any position within the possible range of movement of the second movable part when the actuator device is not driving the rotation of the first movable part.

21. An actuator assembly according to any one of the preceding claims, wherein: The actuator assembly comprises a retaining arrangement configured to releasably retain the first movable part at one or more positions within a range of possible positions to which the first movable part can be driven.

22. An actuator assembly according to any one of the preceding claims, comprising a bistable device, the bistable device being configured to cause the first movable part to have a first stable equilibrium position, a second stable equilibrium position and an unstable equilibrium position between the first stable equilibrium position and the second stable equilibrium position.

23. An actuator assembly according to any one of the preceding claims, wherein: The actuator device comprises two shape memory alloy (SMA) elements which cross each other when viewed along the main axis.

24. An actuator assembly according to any one of the preceding claims, wherein: The actuator device includes a first pair of SMA elements and a second pair of SMA elements, wherein each of the first pair of SMA elements crosses each of the second pair of SMA elements when viewed along the primary axis.

25. The actuator assembly of claim 14, wherein: Each of the four SMA elements crosses at least one of the other SMA elements when viewed along the major axis.

26. An actuator assembly according to any one of claims 23 to 25, wherein: Each of the SMA elements is disposed within a footprint of one or both of the first movable portion and the second movable portion when viewed along the major axis.

27. An actuator assembly according to any one of the preceding claims, wherein: The second movable part includes a display.

28. An actuator assembly according to any one of the preceding claims, wherein: The second movable part comprises an optical component or a part of an optical component.

29. An actuator assembly according to any one of the preceding claims, wherein: The actuator arrangement is configured to apply a force to the first movable part at a first point to drive the first movable part to rotate about the main axis relative to the support structure, wherein the distance between the main axis and the first point is smaller than the distance between the main axis and the first bearing arrangement.

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