Actuator assembly

Abstract

An actuator assembly comprises a first part (10), a second part (20) that is movable relative to the first part (10), and a plurality of actuating units (30, 31) each configured to apply an actuating force to the second part (20) capable of moving the second part (20) relative to the first part (10). The actuator assembly has a primary axis z extending through the actuator assembly. The plurality of actuating units comprise a first set of actuating units (30a-d) each configured to apply an actuating force in a direction that lies in a plane substantially perpendicular to the primary axis z, and a second set of actuating units (31a-d) each configured to apply an actuating force substantially parallel to the primary axis z.

Description

[0001] ACTUATOR ASSEMBLY

[0002] Field

[0003] The present application relates to an actuator assembly with at least one actuating unit including a shape memory alloy (SMA) element.

[0004] Background

[0005] SMA actuator assemblies may be used in a variety of applications for moving a movable part relative to a support structure.

[0006] For example, WO 2011 / 104518 Al describes an actuator assembly having eight SMA wires capable of effecting positional control of a movable element with multiple degrees of freedom. Such an actuator assembly may be referred to as an "8-wire actuator assembly". The movable element may include a lens and may be moved relative to an image sensor in a plane that is perpendicular to the optical axis of the lens, thereby enabling lens-shift optical image stabilization (OIS), and may also be moved relative to the image sensor in a direction parallel to the optical axis, thereby enabling autofocus (AF). Alternatively, the movable element may include a camera module and may be rotated about two or three perpendicular axes, thereby enabling two-axis or three-axis module-tilt OIS.

[0007] Typically, the range of movement (also known as "stroke") of such SMA actuator assemblies is limited by the maximum contraction of the SMA wires, and the actuating force is limited by the maximum force that can be generated by the SMA wires. To increase the movement range or the actuating force, longer or thicker SMA wires can be used, but this may be at the expense of increased cost, size and / or power, which may not be practical in miniature applications.

[0008] WO 2022 / 084699 Al discloses an actuator assembly comprising at least one actuating unit (incorporating an SMA wire) that, on actuation, moves a movable part relative to the support structure. The actuating unit may be configured to increase the stroke or the actuating force and / or to re-direct the force applied by the SMA wire. WO 2022 / 118048 Al discloses an 8-wire actuator assembly with actuating units as disclosed in WO 2022 / 084699 Al.

[0009] Summary

[0010] According to a first aspect of the present disclosure, there is provided an actuator assembly comprising a first part, a second part that is movable relative to the first part and a plurality of actuating units each configured to apply an actuating force to the second part capable of moving the second part relative to the first part. At least one of the actuating units comprises a body portion, an SMA element connected between the body portion and one of the first and second parts, and configured, on actuation, to apply an input force to the body portion, a force-modifying element connected between the body portion and the one of the first and second parts and configured to modify the input force so as to give rise to the actuating force, and a coupling link connected between the body portion and the other of the first and second parts, wherein the coupling link is configured to transmit the actuating force from the body portion to the other of the first and second parts, and wherein the coupling link is compliant in a direction perpendicular to the actuating force. The actuator assembly has a primary axis extending through the actuator assembly, and the plurality of actuating units comprise a first set of actuating units each configured to apply an actuating force in a direction that lies in a plane substantially perpendicular to the primary axis, and a second set of actuating units each configured to apply an actuating force substantially parallel to the primary axis.

[0011] The arrangement of the first set of actuating units configured to apply an actuating force in a direction that lies in a plane substantially perpendicular to the primary axis, and a second set of actuating units each configured to apply an actuating force substantially parallel to the primary axis can be referred to as a "decoupled arrangement". A decoupled arrangement of actuating units may be advantageous because it allows translational movement of the movable part in the z direction (parallel to the primary axis) to be decoupled from movement in the x or y direction (or in any lateral direction lying in a plane perpendicular to the primary axis). Alternatively or additionally, a decoupled arrangement of actuating unit may allow tilting / rotation of the movable part about a lateral axis (perpendicular to the primary axis) to be decoupled from rotation about the primary axis or an axis parallel thereto. That these movements are "decoupled" means, for example, that actuation of one or more of a first SMA elements substantially produces one type of movement (e.g. Tx and Ty) and actuation of one or more of a second, disjoint set of SMA elements substantially produces the other type of movement (e.g. Tz). Thus, compared to the prior art, the first aspect of the present disclosure provides an actuator assembly with alternative movement characteristics which is advantageous in some circumstances.

[0012] On particular improvement which may be provided by the decoupled arrangement of actuating units is a larger and / or more usefully shaped movement operating window (shown in Figure 9) compared to that of known 8-wire actuator assemblies. Figure 8 illustrates an operating stroke window for actuator assemblies such as those provided in the prior art, which can be seen to be approximately diamond shaped for such known 8-wire actuator assemblies. This means lateral movement is limited when the movable part is away from a central position along the z axis and especially so when the movable part is at or near its positional extent in the z direction. However, by decoupling lateral movement from movement parallel to the primary axis (vertical movement), it is possible to achieve a generally rectangular movement operating window with a more constant range of lateral movement and, especially, a greater range of lateral movement when the movable part is at or near its positional extent in the z direction. Figure 9 illustrates such a generally rectangular movement operating window of a decoupled actuator arrangement according to the first aspect of the present disclosure.

[0013] An additional advantage of decoupling lateral movement of the movable part from vertical movement may be that OIS functionality (which requires lateral movement) can be decoupled from AF / zoom functionality (which requires vertical movement). The first set of actuating units enable OIS whilst the separate, second set of actuating units enable AF. This may simplify and / or improve control of the actuating units and, for example, may reduce AF-OIS crosstalk. Furthermore, the decoupled arrangement of actuating units may enable the actuator assembly to operate in a low-power AF-only mode (using only the actuating units that produce vertical movement) or, possibly, a low-power OIS- only mode (using only the actuating units that produce lateral movement).

[0014] It will be appreciated that a reference to a component being "connected between" two other components means, for example, that the component is directly or indirectly connected to each of the other components. Such an indirect connection may involve a connection via further component(s) (e.g. a connector) with fixed position(s) relative to one of the other components. Such an indirect connection may involve a connection via further component(s) which is / are movable relative to the other components. For example, an SMA element may be connected to the one of the first and second parts via a further flexure, e.g. as described in WO 2022 / 144541 (which is herein incorporated by reference).

[0015] In some embodiments, each of the first and second sets of actuating units is directly connected between the first and second parts. That is, there may not be any intermediate movable parts in between the actuating units and the first part or the second part, where some of the actuating units could be connected between the first part and the intermediate part, and others of the actuating units could be connected between the intermediate part and the second part. Hence the actuator assembly is distinct from, for example, a conventional lens-shift OIS actuator assembly with a conventional AF actuator assembly mounted thereon.

[0016] In some embodiments, only the second set of actuating units are flexure-amplified. That is, only the second set of actuating units comprise the body portion, force-modifying element and coupling link. In these embodiments, the first set of actuating units only comprise an SMA element connected directly between the first part and second part. In such actuating units, the force produced by the SMA element (which is called the input force in the above-described actuating units) acts directly on the second part (i.e. is equivalent to the actuating force).

[0017] Reference is made herein to lateral axes, for example the x and y axes, that are perpendicular to the primary axis. Any lateral direction or axis mentioned herein that is perpendicular to the primary axis is not necessarily directly crossing the primary axis, but may lie in any plane that is perpendicular to the primary axis.

[0018] In some embodiments, the first set of actuating units comprises four actuating units. In some embodiments, the actuator assembly comprises four sides arranged around the primary axis, and each actuating unit of the first set of actuating units is arranged along a different respective one of the four sides. Adjacent sides may be substantially perpendicular such that the four sides form a quadrilateral shape when viewed along the primary axis.

[0019] In some embodiments, wherein the second set of actuating units comprises four actuating units. Each actuating unit of the second set of actuating units may be arranged along a different respective one of the four sides.

[0020] In some embodiments, the first set of actuating units may be configured to be capable of causing a translation of the second part relative to the first part in any direction that is substantially perpendicular to the primary axis, and / or causing a rotation of the second part relative to the first part (in both senses) about an axis that is substantially parallel to the primary axis. Any direction substantially perpendicular to the primary axis means any direction within a movement plane that is substantially perpendicular to the primary axis.

[0021] The first set of actuating units may comprise a first actuating unit configured to apply an actuating force in first direction substantially parallel to a first lateral axis, wherein the first lateral axis is perpendicular to the primary axis, a second actuating unit configured to apply an actuating force in second direction, substantially opposite the first direction, parallel to the first lateral axis; a third actuating unit configured to apply an actuating force in a first direction substantially parallel to a second lateral axis, wherein the second lateral axis is perpendicular to the primary axis and the first lateral axis, and a fourth actuating unit configured to apply an actuating force in a second direction, substantially opposite the first direction, parallel to the second lateral axis.

[0022] In some embodiments, the first and second actuating units are arranged along opposite sides of the actuator assembly, and wherein the third and fourth actuating units are arranged along opposite sides that are adjacent to the sides along which the first and second actuating units are arranged.

[0023] In some embodiments, the second set of actuating units may be configured to be capable of causing a translation of the second part relative to the first part (in both directions) along a line that is substantially parallel to the primary axis; and / or causing a rotation of the second part relative to the first part (in both senses) about any axis substantially perpendicular to the primary axis.

[0024] The second set of actuating units may comprise at least one actuating unit, optionally a first pair of actuating units, configured to apply an actuating force in a first direction substantially parallel to the primary axis, and at least one actuating unit, optionally a second pair of actuating units, configured to apply an actuating force in a second direction, opposite to the first direction, substantially parallel to the primary axis.

[0025] In some embodiments, the actuating units of each of the first and second pair are arranged diametrically opposite to one another with respect to the primary axis. This embodiment is particularly advantageous as it allows the actuating forces parallel to the primary axis to be balanced and equally spaced around the primary axis to provide tilt of the second part about any lateral axis.

[0026] In some embodiments, at least one of the second set of actuating units comprises a coupling link formed of at least two elements connected by a substantially 180-degree bend. The coupling link may be a coupling flexure that is compliant in a direction perpendicular to the actuating force. A first one of the at least two elements of the least one coupling link may be configured to transmit an actuating force through compression of the first element, and a second one of the at least two element may be configured to transmit an actuating force through tension in the second element.

[0027] In some embodiments, the at least one coupling link comprises two elements configured to transmit an actuating force through compression of the respective elements, the two elements being connected by respective substantially 180-degree bends to opposite ends of an element configured to transmit an actuating force through tension in the element. In other embodiments, the at least one coupling link comprises two elements configured to transmit an actuating force through tension, the two elements being connected by respective substantially 180-degree bends to opposite ends of an element configured to transmit an actuating force through compression.

[0028] In some embodiments, the length of each element configured to transmit an actuating force through compression is less than the length of each element configured to transmit an actuating force through tension.

[0029] In some embodiments, one end of the at least one coupling link is not offset from the other end of the coupling link in a direction perpendicular to the primary axis, meaning that a notional line drawn between the two ends of the coupling link would be substantially parallel to the primary axis. In some embodiments, the at least one element comprises at least one chicane comprising a first bend in the element in a first direction and a second bend in the element in an opposite direction, wherein the first and second bend are adjacent and have substantially the same radius and angle.

[0030] In some embodiments, in at least one of the actuating units, the coupling link is a flexure.

[0031] In some embodiments, at least one of the second set of actuating units comprises a coupling link in the form of a sliding or rolling bearing configured to transmit the actuating force in a direction substantially parallel to the primary axis and configured to allow relative movement in any direction substantially perpendicular to the primary axis.

[0032] In some embodiments, the input force applied by each SMA element of each actuating unit of the first set and / or second set is in a direction that lies in a plane that is substantially perpendicular to the primary axis.

[0033] In some embodiments, in each actuating unit of the second set of actuating units, the input force applied by the SMA element is substantially perpendicular to the corresponding actuating force applied by the actuating unit.

[0034] In some embodiments, in each actuating unit of the first set of actuating units, the input force applied by the SMA element is substantially parallel to the corresponding actuating force applied by the actuating unit.

[0035] In some embodiments, the input force applied by each SMA element of each actuating unit of the first set and / or the second set has a first component that is in a direction that lies in a plane substantially perpendicular to the primary axis and a second component that is parallel to the primary axis. Such SMA elements may therefore be arranged at an angle along a side of the actuator assembly, meaning that the length of the SMA element may be maximised to increase the stroke or force of the corresponding actuating unit.

[0036] In some embodiments, the SMA elements of each of the second set of actuating units are longer than the SMA elements of each of the first set of actuating units. In such embodiments, the second actuating units, which provide AF functionality, may have less amplification (i.e. be configured to produce less movement of the second part per unit change in length of the SMA element) compared to the first set of actuating units which provide OIS functionality. This may be advantageous because, in general, AF requires a higher degree of precision and accuracy compared to OIS which can be more easily achieved with a longer SMA element with less amplification.

[0037] In some embodiments, the first set of actuating units are configured such that the respective actuating forces lie in a common plane that is substantially perpendicular to the primary axis.

[0038] In some embodiments, the body portions, SMA elements, and force-modifying elements of each of the first set of actuator units are arranged along one or more surfaces each facing generally in a direction perpendicular to the primary axis. In some embodiments, the angular extent of the actuating unit of the first set along a given side overlaps at least partly with the angular extent of the actuating unit of the second set along the same side. Alternatively, there may be substantially no angular overlap between actuating units.

[0039] In some embodiments, the actuating units are actuated so as to cause rotation of the second part relative to the first part (in both senses) about any axis substantially perpendicular to the primary axis and optionally about the primary axis. Such embodiments may enable 2-axis or 3-axis module-tilt OIS. In such embodiments, the actuator assembly may comprise a bearing arrangement between the first and second parts. The bearing arrangement may be configured to allow rotation of the second part relative to the first part about any axis substantially perpendicular to the primary axis and optionally about the primary axis. Such a bearing arrangement may restrict other types of movement such as translational movement of the second part relative to the first part, and therefore may help improve performance of the actuator assembly. The bearing arrangement may include, for example, one or more gimbals. According to a second aspect of the present disclosure, there is provided an actuator assembly comprising a first part, a second part that is movable relative to the first part; and a plurality of actuating units each configured to apply an actuating force to one of the first and second parts capable of moving the second part relative to the first part. Each actuating unit comprises an SMA element. The actuator assembly has a primary axis extending through the actuator assembly. The plurality of actuating units comprise a first set of actuating units each configured to apply an actuating force in a direction that lies in a plane substantially perpendicular to the primary axis, and a second set of actuating units each configured to apply an actuating force substantially parallel to the primary axis. The SMA element of each actuating unit may be directly connected between the first part and the second part, and may be configured, on actuation, to apply the actuating force to the second part.

[0040] According to a third aspect of the present disclosure, there is provided a camera assembly comprising an actuator assembly according to any one of the embodiments or aspects disclosed herein, one or more lenses comprised in one of the first and second parts of the actuator assembly, and an image sensor comprised in the other of the first and second parts of the actuator assembly. The actuator assembly is configured to move the one or more lenses and the image sensor relative to each other with three translational degrees of freedom and / or with two or three rotational degrees of freedom.

[0041] According to a fourth aspect of the present disclosure, there is provided a camera assembly comprising an actuator assembly according to any one of the embodiments or aspects disclosed herein, a support structure comprising one of the first and second parts of the actuator assembly, and a module comprised in the other of the first and second parts of the actuator assembly. The module comprises one or more lenses and an image sensor. The actuator assembly is configured to rotate the module relative to the support structure with at least two or three rotational degrees of freedom.

[0042] Brief description of the drawings

[0043] Certain embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings in which:

[0044] Figures 1A-E are schematic cross-sectional views of different variations of a camera module incorporating an actuator assembly;

[0045] Figure 2 is a schematic perspective view of the actuator assembly; Figures 3A and 3B are perspective and plan views of an actuating unit forming part of the actuator assembly, and Figure 3C is a plan view of another such actuating unit;

[0046] Figure 4A is a perspective view of an actuator assembly according to the present disclosure;

[0047] Figure 4B is a perspective view of the actuating forces provided by an actuator assembly according to the present disclosure;

[0048] Figures 4C and 4D are side views of the actuator assembly of Figure 4A;

[0049] Figures 5A and 5B illustrate a coupling link according to some embodiments of the present disclosure;

[0050] Figures 5C and 5D illustrate side views of an actuator assembly according to some embodiments the present disclosure;

[0051] Figures 6A and 6B are side views of an alternative actuator assembly according to some embodiments of the present disclosure;

[0052] Figures 7A is a perspective view of another alternative actuator assembly according to some embodiments of the present disclosure;

[0053] Figure 7B is a side view of the actuation assembly of Figure 7A;

[0054] Figure 8 shows a movement operating region for an actuator assembly known in the prior art; and

[0055] Figure 9 shows a movement operating region for an actuator assembly according to the present disclosure.

[0056] Detailed description

[0057] Camera assembly

[0058] Figures 1A-E schematically show different variations of an apparatus 1 incorporating an actuator assembly 2. The apparatus 1 is, for example, a camera assembly 1. Generally, the apparatus 1 is to be incorporated in a portable electronic device such as a smartphone. Thus, miniaturisation can be an important design criterion.

[0059] Figure 2 schematically shows the actuator assembly 2. The actuator assembly 2 includes a support structure 10 and a movable part 20. The movable part 20 is movable relative to the support structure 10. When the actuator assembly 2 is included e.g. in the apparatus 1, the support structure 10 may be fixed relative to the main body of the apparatus 1. However, in general, the support structure 10 need not be stationary and may be movable relative to or within the apparatus 1. The actuator assembly 2 includes one or more actuating units 30. Each actuating unit 30 is configured to apply an actuating force to the movable part 20 capable of moving the movable part 20 relative to the support structure 10.

[0060] The movable part 20 may be supported (i.e. suspended) on the support structure 10 exclusively by the actuating units 30. Alternatively, the actuator assembly 2 may include a bearing arrangement 40 that supports the movable part 20 on the support structure 10. The actuating units 30 and the bearing arrangement 40 may together support the movable part 20 on the support structure 10. The bearing arrangement 40 may have any suitable form for allowing movement of the movable part 20 with respect to the support structure 10 with one or more degrees of freedom (DOFs). The actuating units 30 and / or the bearing arrangement 40 may constrain, i.e. reduce or prevent, other DOFs of movement of the movable part 20 relative to the support structure 10. For this purpose, the bearing arrangement 40 may, for example, include one or more of the following bearings: a rolling bearing (such as a ball bearing), a flexure bearing (i.e. an arrangement of flexures or other resilient elements that guide movement), or a plain (i.e. sliding contact) bearing.

[0061] A primary axis P can be defined with reference to the actuator assembly 2 and / or the support structure 10. The primary axis P may extend through the actuator assembly 2, e.g. through the centre of the actuator assembly 2. In some examples, the actuator assembly 2, the support structure 10 and / or the movable part 20 extends predominantly in a direction perpendicular to the primary axis P. In other words, the extent of the actuator assembly 2, the support structure 10 and / or the movable part 20 along the primary axis P is less than the extent thereof along any direction perpendicular to the primary axis P. The primary axis P may be the longitudinal axis of the actuator assembly 2 and / or the support structure 10. Alternatively or additionally, the support structure 10 and / or movable part 20 may include a planar component that extends perpendicularly to the primary axis P. Alternatively or additionally, in examples in which the apparatus 1 includes an optical element (such as a lens assembly 3) with an optical axis, or an imaging element (such as an imager sensor 4) with an imaging axis, the primary axis P may be parallel to such an axis and / or may coincide with such an axis when the movable part 20 is in a central position or orientation (for example, see Figure 1A).

[0062] In general, the movable part 20 may be movable relative to the support structure 10 with up to six degrees of freedom (DOFs). In the context of describing the DOFs of movement, the primary axis P may also be referred to as the z axis, and two further axes that are perpendicular to the primary axis P and to each other may be referred to as the x and y axes. The movable part 20 may be movable relative to the support structure 10 in all or in any subset (including only one) of the following DOFs:

[0063] Tx and Ty: Translational movement in the x-y plane. In other words, the movable part 20 may be independently movable along the x and y axes. The movable part 20 may be movable to any position in the x-y plane within a range of movement. Instead of such planar movement, the movable part 20 may be movable linearly, e.g. along the x or y axis.

[0064] Rx and Ry: Rotational movement (or simply rotation or tilting) about the x and y axes. In other words, the movable part 20 may be rotated about any line perpendicular to the primary axis P. The movable part 20 may be rotatable to any rotational position (i.e. to any orientation) within a range of movement. Instead of such two-axis rotation, the movable part 20 may be rotatable about a single axis, e.g. about the x or y axis.

[0065] Tz: Translational movement along the z axis. The movable part 20 may be movable to any translational position along the z axis within a range of movement.

[0066] Rz: Rotational movement (or simply rotation) about the z axis. The movable part 20 may be rotatable to any rotational position (i.e. to any orientation) within a range of movement. In some examples, the movable part 20 may be supported, e.g. by the bearing arrangement 40, so as to allow translational movement in the x-y plane (Tx, Ty) and / or rotational movement about the z axis (Rz). Translational movement along the z axis (Tz) and rotational movement about the x and y axes (Rx, Ry) may be constrained. Such support may be provided, for example, with a bearing arrangement 40 with a suitable arrangement of ball bearings or plain bearings which produce bearing forces in the +z direction and a biasing arrangement which produces a biasing force in the -z direction. Examples of actuator assemblies with such a bearing arrangement are disclosed in WO 2013 / 175197 Al and WO 2017 / 072525 Al, each of which is herein incorporated by reference.

[0067] In some examples, the movable part 20 may be supported so as to allow tilting about the x and y axes (Rx, Ry) and optionally rotation about the z axis (Rz). The other DOFs of movement (i.e. Tx, Ty, Tz, Rz, or Tx, Ty, Tz) may be constrained. Such support may be provided by the bearing arrangement 40, for example in the form of a gimbal. Examples of such a bearing arrangement 40 are disclosed in WO 2021 / 209770 Al, which is herein incorporated by reference. Alternatively, such support may be provided exclusively by the actuating units 30, similarly to WO 2011 / 104518 Al which discloses an actuator assembly with 8 SMA wires connected between the support structure 10 and the movable part 20. WO 2011 / 104518 Al is herein incorporated by reference.

[0068] In some examples, the movable part 20 may be supported so as to allow three-dimensional translational movement (Tx, Ty, Tz), while rotational movement (Rx, Ry, Rz) may be constrained. Such support may be provided by the bearing arrangement 40, for example in the form of nested linear bearings. Examples of such a bearing arrangement 40 are disclosed in WO 2021 / 209769 Al, which is herein incorporated by reference. Alternatively, such support may be provided exclusively by the actuating units 30, similarly to WO 2011 / 104518 Al.

[0069] The movable part 20 may, alternatively or additionally, move in other DOFs. The movable part 20 may move in DOFs that are a combination of any two or more of Tx, Ty, Tx, Rx, Ry and Rz. For example, the movable part 20 may move along a helical path (i.e. move helically) about the z axis, and so concurrently move along the z axis and rotate about the z axis. In other words, Tz and Rz movement may be coupled. An example of such a helical actuator assembly is disclosed in WO 2019 / 243849 Al, which is herein incorporated by reference.

[0070] The actuating units 30 are connected between the support structure 10 and the movable part 20. The actuating units 30 are arranged to apply actuating forces F (see e.g. Figs. 5) between the movable part 20 and the support structure 10. Selectively varying the actuating forces F may cause the movable part 20 to move relative to the support structure 10, for example within the DOFs allowed by the bearing arrangement 40. The actuating units 30 are thus capable of driving movement of the movable part 20 relative to the support structure 10.

[0071] The bearing arrangement 40 may cause the movable part 20 to move in directions which differ from the directions of the actuating forces F. In simple examples of this, one component of each actuating force F causes the movement of the movable part 20, and another component of each actuating force F acts against the bearing forces produced by the bearing arrangement 40. Referring back to Figure 1, the camera assembly 1 also includes a lens assembly 3 and an image sensor 4. The lens assembly 3 includes one or more lenses configured to focus an image on the image sensor 4. The lens assembly 3 defines an optical axis O. The lens assembly 3 may include a lens carrier, for example in the form of a cylindrical body, supporting the one or more lenses. The image sensor 4 captures an image and may be of any suitable type, for example a charge coupled device (CCD) or a complementary metal-oxide-semiconductor (CMOS) device. The camera assembly 1 may be a compact camera module in which each lens has a diameter of 20mm or less, for example of 12mm or less.

[0072] In the ("sensor-shift") variation of the camera assembly 1 shown in Figure 1A, the movable part 20 includes the image sensor 4. The lens assembly 3 may be fixed relative to the support structure 10, or may be movable relative to the support structure 10 along the optical axis O, as described below.

[0073] In the ("lens-shift") variation shown in Figure IB, the image sensor 4 is fixed relative to the support structure 10 and the movable part 20 includes the lens assembly 3. The lens assembly 3 may be movable relative to the movable part 20 along the optical axis O, as described below.

[0074] In both of these variations, the actuator assembly 2 is configured to move the lens assembly 3 relative to the image sensor 4 in any direction in the plane perpendicular to the primary axis P and hence the optical axis O. Such movement has the effect of moving the image on the image sensor 4 and enables optical image stabilisation (OIS) to be implemented in the camera assembly 1. In the sensor-shift variation, the movable part 20 may also be rotatable about the primary axis P so as to also enable compensation for roll.

[0075] In the ("module-tilt") variation shown in Figure 1C, the movable part 20 includes both the lens assembly 3 and the image sensor 4. Again, the lens assembly 3 may be movable relative to the movable part 20 along the optical axis O, as described below. The actuator assembly 2 is configured to tilt the movable part 20 about two axes perpendicular to the primary axis P and to each other, and optionally rotate the movable part 20 about the primary axis P, enabling OIS to be implemented in the camera assembly 1.

[0076] In the ("autofocus") variation shown in Figure ID, the movable part 20 includes the lens assembly 3, and the actuator assembly 2 moves the movable part 20 relative to the support structure 10 along the primary axis P and hence the optical axis O. Such movement has the effect of adjusting the focus of the image on the image sensor 4. So, auto-focus (AF) or zoom functionality can be implemented in the camera assembly 1.

[0077] In some examples (not shown), the camera assembly 1 may include a first actuator assembly for providing OIS as illustrated in Figures 1A-C, and a second actuator assembly for providing AF as illustrated in Figure ID. One or both of the first and second actuator assemblies may correspond to actuator assemblies 2 as described herein. One of the first and second actuator assemblies may be another type of SMA actuator assembly or may be a non-SMA actuator assembly, e.g. a voice-coil motor (VCM) actuator assembly. As will be appreciated, in the lens-shift and module-tilt variations, the support structure 10 of the second actuator assembly 2 is fixed to (or corresponds to) the movable part 20 of the first actuator assembly 2.

[0078] In the ("AF+OIS") variation shown in Figure IE, the movable part 20 includes the lens assembly 3, and the actuator assembly 2 produces three-dimensional translational movement of the movable part 20 relative to the support structure 10, enabling both AF and OIS to be implemented using one actuator assembly 2.

[0079] Other variations are also possible. For example, in the autofocus variation or the AF+OIS variation, the movable part 20 may include the image sensor 4 rather than the lens assembly 3. The camera assembly 1 may include combinations of the above-described features, e.g. (a) lens shift and sensor shift, (b) module tilt and lens shift or sensor shift and autofocus, or (c) module tilt and AF+OIS.

[0080] The camera assembly 1 also includes a controller 8. The controller 8 may be implemented in an integrated circuit (IC) chip. The controller 8 generates drive signals for the actuating units 30, in particular for SMA wires 34 forming part of the actuating units 30. SMA material has the property that, on heating, it undergoes a solid-state phase change that causes the SMA material to contract. Thus, applying drive signals to the SMA wires 34, thereby heating the SMA wires 34 by causing an electric current to flow, will cause the SMA wires 34 to contract and thus actuate the actuating unit 30 so as to move the movable part 20. The drive signals are chosen to drive movement of the movable part 20 in a desired manner, for example so as to achieve OIS by stabilizing the image sensed by the image sensor 4 or to achieve AF / zoom by adjusting the focus of the image sensed by the image sensor 4. The controller 8 supplies the generated drive signals to the SMA wires 34.

[0081] Optionally, the camera assembly 1 also includes a motion sensor (not shown), which may include a 3- axis gyroscope and a 3-axis accelerometer. The motion sensor can generate signals representative of the motion (specifically vibrations or "shake") of the camera assembly 1, which can be processed so as to produce signals representative of the required movement of the movable part 20 to compensate for such shake. The controller 8 receives such signals and can generate the drive signals for the SMA wires 34 to achieve OIS.

[0082] Although the actuator assembly 2 is described in connection with a camera assembly 1, it will be appreciated that the actuator assembly 2 may be used in any device in which movement of a movable part 20 relative to a support structure 10 is desired, e.g. to provide haptic feedback in a haptic feedback device or to move a projector or display in an augmented reality (AR) or virtual reality (VR) device.

[0083] Actuating unit

[0084] Figure 3A shows a perspective view of an example of the actuating unit 30. Figure 3B shows part of the actuating unit 30 in plan view.

[0085] A single actuating unit 30 is shown in Figures 3A and 3B, but it will be appreciated that the actuator assembly 2 generally has multiple actuating units 30, each of which may include the same components described with reference to Figures 3A and 3B.

[0086] The actuating unit 30 includes a body portion 37 to which several other components of the actuating unit 30 are connected as described below. Typically, the body portion 37 is relatively rigid compared to the other components of the actuating unit, and does not deform significantly on actuation of the actuating unit 30. In some examples, the body portion 37 is not a distinct part of the actuating unit 30. For example, the body portion 37 may be defined as part of one of the other components of the actuating unit 30 or simply as a connection point between other components of the actuating unit 30. The actuating unit 30 also includes a force-modifying flexure 32, also known as a force modifying element. The force-modifying flexure 32 is connected between the body portion 37 and the support structure 10. One end of the force-modifying flexure 32 is connected to the body portion 37. The other end of the force-modifying flexure 32 is connected to the support structure 10, e.g. via a foot portion 36. The foot portion 36 is fixed relative to the support structure 10. The force-modifying flexure 32 allows the body portion 37 to pivot relative to the support structure 10 about an effective pivot point P. Although the effective pivot point P is shown in Figure 3B as being positioned in the middle of forcemodifying flexure 32, the effective pivot point P may have a different position and also need not lie on the force-modifying flexure 32. Such pivotal movement of the body portion 37 relative to the support structure 10 is initially in a direction that is substantially perpendicular to the force-modifying flexure 32.

[0087] The actuating unit 30 also includes an SMA element 34. In this example, the SMA element 34 is an SMA wire 34. The SMA wire 34 is connected between the body portion 37 and the support structure 10. One end of the SMA wire 34 is connected to the support structure 10, e.g. by a crimp 15. The other end of the SMA wire 34 is connected to the body portion 37, e.g. by a crimp 35.

[0088] The actuating unit 30 also includes a coupling link 33. In this example, the coupling link 33 is a coupling flexure 33. The coupling flexure 33 is connected between the body portion 37 and the movable part 20. One end of the coupling flexure 33 is connected to the body portion 37. The other end of the coupling flexure 33 is connected to the movable part 20. The coupling link 33 transfers or transmits an actuating force F from the body portion 37 to the movable part 20. The coupling link 33 is compliant (i.e. deformable) in a direction (or in multiple directions) perpendicular to the actuating force F. This allows the movable part 20 to move in directions other than the direction of the coupling flexure 33 and actuating force F. This can be needed, for example, where different actuating units 30 cause the movable part 20 to move in different directions.

[0089] In this example, the body portion 37, the force-modifying flexure 32, the coupling flexure 33 and the foot portion 36 are integrally formed, for example from a single sheet of material (such as metal). In other examples, one or more of these features, if present, may be formed from different parts or materials.

[0090] The SMA wire 34 is arranged, on contraction, to apply an input force Fi on the body portion 37. The input force Fi acts parallel to the length of the SMA wire 34. The force-modifying flexure 32 and the body portion 37 are arranged to modify the input force Fi so as to give rise to the actuating force F, which is transmitted from the body portion 37 to the movable part 20 by the coupling flexure 33. In particular, the input force Fi deforms the force-modifying flexure 32, thereby causing the body portion 37 to pivot about the effective pivot point P. In simple terms, the force-modifying flexure 32 and the body portion 37 act like a lever. The force-modifying flexure 32 and the body portion 37 may modify the direction and / or the magnitude of the input force Fi so as to give rise to the actuating force F.

[0091] In the example illustrated in Figures 3A and 3B, the coupling flexure 33 is at an angle of ~90° relative to the SMA wire 34. Also, in this example, the force-modifying flexure 32 is arranged at an angle a of ~30° relative to the SMA wire 34, and the force-modifying flexure 32 is placed in tension on contraction of the SMA wire 34. Hence, on contraction of the SMA wire 34 and on resulting deformation of the forcemodifying flexure 32, the body portion 37 initially moves at an angle of ~60° (90°-a) relative to the length of the SMA wire 34. Thus, it will be appreciated that, in this example, the force is de-amplified and the stroke is amplified, while the direction of the forces / movements is changed by an angle of ~90°. In more detail, a de-amplification of force means that the magnitude of the actuating force is less than that the magnitude of the input force that causes the actuating force. The amplification of stroke means that the amount of movement of the coupling link along the length of the coupling link is greater than the amount of contraction of the SMA wire that causes the movement of the coupling link. In other examples, the input force may be amplified (meaning that the actuating force is greater than the input force) whilst stroke may be de-amplified (the amount of movement of the coupling link is less than the amount of contraction of the SMA wire).

[0092] More generally, the change in direction of the force depends on the angle between the SMA wire 34 and the coupling flexure 33. Also more generally, the change in magnitude of the force is dependent on the ratio of i) the distance Ds from the effective pivot point P to the line on which the SMA wire 34 lies and ii) the distance De from the effective pivot point P to the line on which the coupling flexure 33 lies, where Ds is the shortest distance from the pivot point to the line along which the SMA lies, and De is the shortest distance from the pivot point to the line along which the coupling link lies. In particular, F / Fi is proportional to Ds / Dc. If the SMA wire 34 lies on a line that is closer to the effective pivot point P than the line on which the coupling flexure 33 lies, then the input force Fi is de-amplified. At the same time, the movement of the movable part 20 is amplified, i.e. increased relative to a change in length of the SMA wire 34. Alternatively, if the SMA wire 34 lies on a line that is further away from the effective pivot point P than the line on which the coupling flexure 33 lies, then the input force Fi is amplified. At the same time, the movement of the movable part 20 is de-amplified, i.e. decreased relative to a change in length of the SMA wire 34. The actuating unit 30 can thus be configured to amplify movement or to amplify force due to contraction of the SMA wire 34. The actuating unit 30 can also be configured to change the direction of the input force Fi. In some examples, the actuating unit 30 is configured to change the direction of the input force Fi without changing the magnitude of the force or movement.

[0093] The ratio Ds / Dc is dependent on the location of the end of the SMA wire 34 that is connected to the body portion 37, and on the location of the end of the coupling flexure 33 that is connected to the body portion 37. By way of example, the distance De could be increased by connecting the coupling flexure 33 further to the left of body portion 37 shown in Figure 3B, thereby decreasing Ds / Dc and so increasing the amount of stroke amplification. The ratio Ds / Dc is also dependent on the orientation of the SMA wire 34, and on the orientation of the coupling flexure 33. Such orientations can be defined with reference to the forcemodifying flexure 32 (as above) or any suitable reference line. By way of example, the distance Ds could be decreased by angling the SMA wire 34 shown in Figure 3B so that it passes closer to the effective pivot point P, thereby decreasing Ds / Dc and so increasing the amount of stroke amplification. In summary, the amount by which the force-modifying flexure 32 amplifies or de-amplifies the force / stroke of the SMA wire 34 may be tailored by: adjusting the orientation of the SMA wire 34 (and thus of the input force Fi); adjusting the location of the connection point between the SMA wire 34 and the body portion 37 (and thus the location at which the input force Fi acts on the body portion 37); adjusting the orientation of the coupling flexure 33 (and thus of the actuating force F); and / or adjusting the location of the connection point between the coupling flexure 33 and the body portion 37 (and thus the location from which the body portion 37 applies the actuating force F). In some examples, at least one actuating unit 30 (preferably each actuating unit 30) is configured such that the force-modifying flexure 32 and the body portion 37 amplifies an amount of contraction of the SMA wire 34. Such amplification, for example, may be by a factor greater than 1.5, preferably greater than 2, further preferably greater than 3. For this purpose, in the example illustrated in Figures 3A and 3B, the angle a between the SMA wire 34 and the force-modifying flexure 32 may be in the range from 0 to 45 degrees, preferably from 13 to 40 degrees. However, in general, the angle a may have other values and the connection points of the SMA wire 34 and / or coupling flexure 33 to the body portion 37 may be adjusted to achieve a desired amount of amplification.

[0094] As described above, in the example illustrated in Figures 3A and 3B, the coupling flexure 33 is at an angle of about 90 degrees relative to the SMA wire 34. This allows the actuating unit 30 to fold around a corner of the movable part 20 in a compact manner. The angle between the coupling flexure 33 and the SMA wire 34 may be in the range from 70 to 110 degrees, preferably from 80 to 100 degrees. However, in general, the angle between coupling flexure 33 and SMA wire 34 may be outside these ranges.

[0095] For instance, in the actuating unit 30 illustrated in Figure 3C, the force-modifying flexure 32, the coupling flexure 33 and the SMA wire 34 are substantially parallel to one another.

[0096] In the above-described examples, the actuating unit 30 is arranged in a plane. In particular, the SMA wire 34, the coupling flexure 33 and the force-modifying flexure 32 are arranged so as to substantially extend in a common plane, at least when the actuator assembly 2 is in an initial configuration. This allows for a compact configuration of the actuating unit 30. The body portion 37, when embodied by a plate, may further be arranged to extend in the plane. However, in general, the components of the actuating unit 30 need not be arranged in a common plane. The SMA wire 34 and / or the coupling flexure 33 may be angled relative to the plane, for example.

[0097] In the above-described examples, the force-modifying flexure 32 is placed in tension on contraction of the SMA wire 34. This reduces the risk of buckling of the force-modifying flexure 32, reducing the risk of damage to the actuator assembly 2 and making the actuator assembly 2 more reliable. However, the force-modifying flexure 32 could instead be arranged so as to be placed under compression on contraction of the SMA wire 34. With reference to Figure 3B, for example, the force-modifying flexure 32 could extend to the bottom-right from the connection point between the body portion 37 and the force-modifying flexure 32, and so be placed under compression on contraction of the SMA wire 34. An arrangement in which the force-modifying flexure 32 is placed under compression is disclosed in WO 2022 / 084699 Al, which is herein incorporated by reference.

[0098] In the above-described examples, the force-modifying flexure 32 and the SMA wire 34 connect at one end to the support structure 10, and the coupling flexure 33 connects at one end to the movable part 20. In general, this arrangement may also be reversed, with the force-modifying flexure 32 and the SMA wire 34 connecting at one end to the movable part 20, and the coupling flexure 33 connecting at one end to the support structure 10.

[0099] In the above-described examples, the actuating unit 30 includes a coupling link 33 in the form of a coupling flexure 33. The purpose of the coupling link 33 is to allow movement of the movable part 20 in directions perpendicular to the actuating force F. In general, however, the actuating unit 30 need not include a coupling link 33, e.g. in examples in which there is no movement of the movable part 20 in directions perpendicular to the actuating force F. Furthermore, the coupling link 33 may be embodied by components other than the coupling flexure 33, for example by a ball bearing or plain bearing configured to transmit the actuating force F to the movable part 20 while allowing movement of the movable part 20 in directions perpendicular to the actuating force F. Such alternative examples of the coupling link 33 are disclosed in WO 2022 / 084699 Al. The coupling link 33 may be formed by an SMA wire, which may (or may not) be integral with the SMA wire 34 and may (or may not) be driven together with the SMA wire 34.

[0100] Furthermore, instead of the force-modifying flexure 32, the actuator assembly may include a different type of force-modifying element configured to enable the above-described movement of the body portion 37 relative to the support structure 10. Such a force-modifying element may include, for instance, a rigid member with one end connected to the support structure 10 via a suitable pivoting connection (e.g. a pin joint) and the other end connected to the body portion 37.

[0101] The coupling link 33 may (or may not) be formed by an SMA wire, which may (or may not) be integral with the SMA wire 34 and may (or may not) be driven together with the SMA wire 34.

[0102] Furthermore, instead of the force-modifying flexure 32, the actuator assembly may include a different type of force-modifying element configured to enable the above-described movement of the body portion 37 relative to the support structure 10. Such a force-modifying element may include, for instance, a rigid member with one end connected to the support structure 10 via a suitable pivoting connection (e.g. a pin joint) and the other end connected to the body portion 37.

[0103] An arrangement of actuating units

[0104] Figures 4a - 4d illustrate an actuator assembly 2 according to an embodiment of the present disclosure. Figure 4a shows a perspective view of the actuator assembly 2, comprising a plurality of actuating units connected to a support structure 10 and movable part 20, whilst Figure 4b schematically illustrates the directions of the actuating forces F provided by each actuating unit of the actuator assembly, and Figure 4c and 4d shows side views of the actuator assembly. In more detail, Figure 4a depicts the specific arrangement of actuating units along two of the four sides of the actuator assembly according to this embodiment. Sides "A" and "C" of the actuator unit can be seen in the particular perspective view of Figure 4a. Although not seen in the figure, the actuating unit arrangement along side "B" is identical to or at least similar to that of side "A" (when viewed looking towards the primary axis), whilst the actuating unit arrangement of side "D" is identical or at least similar to that of side "C" (when viewed looking towards the primary axis).

[0105] In this embodiment, the actuator assembly 2 comprises two sets of actuating units: a first set of four actuating units 30a-d and a second set of four actuating units 31a-d. It will however be appreciated that at least some of the functionality of the actuator assembly (described below) can be achieved with more or fewer actuating units in each set. The first and second sets of actuating units are configured apply actuating forces F between a support 10 and a movable part 20. As discussed in more detail below, the first set and second set of actuating units are capable of causing movement of the movable part 10 relative to the support structure in three translational degrees of freedom (Tx, Ty, Tz) (see Figure 2) or in two or three rotational degrees of freedom (Rx + Ry, or Rx + Ry + Rz) (see Figure 2). Generally speaking, and as discussed in more detail below, the specific arrangement of actuating units shown in Figure 4 enables translational movement of the movable part relative to the support structure in any lateral direction (in a plane that lies perpendicular to the primary axis P, e.g., Tx, Ty) to be decoupled from translational movement along the z axis (Tz, parallel to the primary axis P). Similarly, rotational movement of the movable part relative to the support structure about any lateral axis (perpendicular to the primary axis, e.g., Rx, Ry) is decoupled from rotational movement about the z axis (Rz) by means of the specific arrangement of actuating units.

[0106] As can be seen from Figure 4a, each actuating unit 30a-d and 31a-d of the actuator assembly 2 is similar to the actuating units 30 described above with reference to Figures 3A-C. In particular, each actuating unit of the actuator assembly 2 depicted in Figures 4a comprises a body portion, SMA element connected between the body portion and the support structure, a force-modifying element (e.g. a force modifying flexure) connected between the body portion and the support structure, and a coupling link (e.g. a coupling flexure) connected between the body portion and the movable part. A more detailed view of sides A and C of the actuator assembly showing the components of the actuating units is provided in Figures 4c and 4d, which are discussed below. Each actuating unit is connected to the support structure at the distal end of the force-modifying flexure (in particular via the foot portion 36). Additionally, each actuating unit is connected to the support structure at the distal end of the SMA element (in particular via the crimp 15). Each actuating unit is further connected to the movable part via the distal end of the coupling link (in particular via the connection portion 21a). The components of each actuating unit are shown in more detail in Figures 4c, which illustrates, among other things, the forcemodifying flexure 32, coupling flexure 33, SMA element 34 and body portion 37 of each of the units 30a, 31a.

[0107] It is generally described herein that the force modifying flexure 32 and SMA element 34 are connected to the support structure 10, whilst the coupling link (e.g. coupling flexure 33) is connected to the movable part 20. However, in some embodiments, some of the actuating units may be connected in the opposite sense between the support structure and the movable part. In other words, in at least some of the actuating units, the SMA element 34 and the force-modifying flexure 32 may be connected to the movable part 20, and the coupling link / flexure 34 may be connected to the support structure 10. For instance, some or all of the first set of actuating units may be connected in the opposite sense and / or some or all of the second set of actuating units may be connected in the opposite sense.

[0108] As described in more detail above with reference to Figures 3A-C, the SMA element of each actuating unit 30a-d and 31a-d is configured, on actuation, to apply an input force Fi to the body portion. In turn, the force-modifying element is configured to modify the input force so as to give rise to the actuating force F through the coupling link. In other words, the force-modifying element is configured to amplify or de-amplify the input force / stroke of the SMA element according to the physical arrangement of the SMA element, force-modifying element, and the coupling link, which is described in more detail above with reference to Figures 3A=C. The coupling link is configured to transmit the actuating force from the body portion to the movable part in order to move the movable part relative to the support structure.

[0109] The actuator assembly 2 may have a square or rectangular (or more generally quadrilateral) footprint. In the particular example of Figures 4a-d, the actuator assembly has a square footprint, with four sides, corresponding to four sides of the support structure 10. The four sides are arranged around a primary axis P extending through the actuator assembly, similar to the primary axis depicted in Figures 1 and 2. It will be appreciated that in other examples, the actuator assembly may have a differently-shaped footprint, with a corresponding different number of sides. Moreover, the sides on which the actuating units 30, 31 are arranged need not correspond to sides of the support structure 10 or the movable part 20. In other words, the sides may be defined merely by the presence of the actuating units 30, 31. Furthermore, in some other embodiments, the sides on which the actuating units 30, 31 are arranged need not be parallel to the primary axis and / or need not all have the same extent along the primary axis. In general, the plurality of actuating units may be arranged in any suitable manner such that a first set of actuating units are configured to apply actuating forces in any direction in a plane substantially perpendicular to the primary axis, and a second set of actuating units are configured to apply actuating forces substantially parallel to the primary axis.

[0110] As mentioned above, the first set of actuating units comprises four actuating units 30a-d, with one actuating unit of the first set arranged along each of the four sides of the actuator assembly 2. Similarly, in this example, the second set of actuating units also comprises four actuating units 31a-d also arranged along each side of the actuator assembly 2. Thus, in this example each side of the actuator assembly comprises one of each of the first and second sets of actuating units. For instance, side "A" comprises actuating unit 30a of the first set and actuating unit 31a of the second set, side "B" comprises actuating unit 30b of the first set and 31b of the second set, side "C" comprises actuating unit 30c of the first set and 31c of the second set, and side "C" comprises actuating unit 30d of the first set and 31d of the second set,.

[0111] Reference is now made to Figure 4b, which schematically depicts the actuating forces F that can be applied by the actuating units 30a-d and 31a-d of the actuator assembly 2. The forces are described with reference to a Cartesian coordinate system (x, y, z) with a z axis corresponding to the primary axis P (and so the terms primary axis and z axis are used interchangeably herein) and with its origin towards the centre of the movable part 20 (the x, y, z axes are offset in some of the drawings for clarity).The perspective view of Figure 4b corresponds to Figure 4a. Figure 4b demonstrates that, in general, the actuating units of Figure 4 are arranged such that, for each direction along each axis of the Cartesian coordinate system (+x, -x, +y, -y, +z, -z), there is at least one actuating force F acting at least partly in that direction. This means that the arrangement of the first and second sets of actuating units is capable of moving the movable part relative to the support structure in three translational degrees of freedom (e.g. independent movement along each of the x, y and z axes) as well as rotation in three rotational degrees of freedom (e.g. independent rotation about each of the x, y and z axes), although, as will be appreciated, the movable part 20 may move with fewer degrees of freedom in specific examples because of the way in which the controller 8 controls the actuating units and / or because of constraints due to a bearing arrangement 40, etc. In this embodiment, there are actuating forces acting in lateral directions (e.g. +x, -x, +y, -y) provided by the first set of actuating units, and actuating forces acting in the +z or -z directions provided by the second set of actuating units. In other words, the actuator assembly comprises a first set of actuating units each configured to apply an actuating force substantially parallel to a plane (e.g. the xy plane) parallel to the z axis, and a second set of actuating units each configured to apply an actuating force substantially parallel to the z axis. Here, "substantially parallel" may mean, for example, at an angle of ~0° or <1° or <2.5° or <5° or <7.5° or <10°.

[0112] In more detail, and treating each actuating force as a vector in the cartesian coordinate system, Figure 4b demonstrates that each actuating force of the first set of actuating units acts in either a direction parallel to either the x or y axes (or more generally in any lateral direction that lies in a plane substantially perpendicular to the primary axis), and that each actuating force of the second set of actuating units acts in a direction that is substantially parallel to the z axis. In other words, given that the primary axis P extending through the actuator assembly is parallel to the z axis, each actuating force of the first set of actuating units has a substantially zero vector component parallel to the primary axis, meaning that these actuating forces (of the first set 30a-d) only have vector components that are substantially in a lateral direction. Contrastingly, each actuating force of the second set of actuating units has a substantially zero vector component in any lateral direction, meaning that these actuating forces (of the second set 31a-d) only have a vector component that is substantially parallel to the primary axis.

[0113] The first set of actuating units

[0114] In the example shown in Figure 4b, the first set of actuating units comprise four actuating units 30a-30d configured to apply actuating forces in each direction along each of the x and y axes. The x and y axes, or generally any axis orthogonal to the primary axis, may be referred to as a lateral axis. More generally, the actuating forces of the first set of actuating units act may be arranged such that, for each direction along each of the x and y axes (+x, -x, +y, -y), there is at least one actuating force acting at least partly in that direction. Hence, for example, the actuating forces of the first set of actuating units need not be parallel to perpendicular axes, need not be in pairs of oppositely directed actuating forces, etc. That said, the illustrated arrangement is generally advantageous as it can maximise the ability to move e.g. in any direction in the xy plane.

[0115] In more detail, the first set of actuating units comprises first and second actuating units 30a and 30b that are configured to apply actuating forces F in opposite directions parallel to a first lateral axis (e.g. the x axis). The other two actuating units of the first set, the third and fourth units 30c and 30d, are arranged to apply actuating forces F in opposite directions parallel to a second lateral axis (e.g. the y axis), perpendicular to the first lateral axis. By appropriately varying the difference in actuation amount between the opposing actuating units 30a and 30b, or 30c and 30d, the movable part 20 may thus be moved independently along the first and second axes. The opposing actuating forces F are not colinear, but offset from each other in a direction perpendicular to the actuating forces F. Providing opposing actuating units allows the tension in the SMA wires of the respective actuating units to be controlled, allowing for more accurate and reliable positioning of the movable part 20 compared to a situation in which actuating units do not oppose each other.

[0116] Preferably, the directions of the actuating forces applied by each actuating unit in the first set lie in a common plane that is substantially perpendicular to the primary axis (i.e. the normal of the common plane is parallel to the primary axis). This means that, when viewed side-on (e.g. viewed along the x or y axis), the coupling links of each of the first set of actuating units, which are all substantially parallel to the x or y axis, are all positioned at the same height on their respective side of the actuator assembly. In other words, the coupling links have the same coordinate in the z axis and therefore lie in the same x-y plane. This is particularly advantageous because this prevents unwanted torques about x or y axis (or in any lateral axis) arising due to an imbalance of actuating forces in the direction of the x or y axis. Instead, because the coupling links all lie substantially in the same x-y plane, the corresponding actuating forces do not induce torques about any lateral axis.

[0117] In some examples, none of the actuating forces F are collinear. This allows the arrangement of the first set of actuating units 30a-d to translationally move the movable part 20 without applying any net torque to the movable part 20. So, the movable part 20 can be moved translationally in a movement plane (i.e. the plane which lies parallel to both the first and second lateral axes) without rotating the movable part 20 in the movement plane. In general, the arrangement of the first set of actuating units 30a-d is capable of accurately controlling a torque or moment of the movable part 20 about the primary axis P. So, the first set of actuating units 30 are capable of rotating (or not rotating) the movable part 20 relative to the support structure about the primary axis P.

[0118] In particular, the first and second actuating units 30a and 30b are configured to apply actuating forces F so as to generate a torque or moment between the movable part 20 and the support structure 10 in a first sense (e.g. counter-clockwise) around the primary axis P. The third and fourth actuating units 30c and 30d are arranged to apply actuating forces F so as to generate a torque or moment between the movable part 20 and the support structure 2 in a second, opposite sense (e.g. clockwise) around the primary axis P. This allows the movable part 20 to be rotated about the z axis or an axis that is parallel to the z axis by simultaneously increasing or decreasing the tension of SMA wires in any of the two actuating units 30a-d. Preferably, this axis of rotation is the optical axis of the lens in the context of a camera assembly or lens assembly.

[0119] As shown, the first and third actuating units 30a and 30c may be arranged to apply actuating forces F in a corner of the actuator assembly 2 (e.g. the bottom corner as shown in Figure 4b). The other two actuating units, 30b and 30d, may be arranged to apply actuating forces F in another, opposite corner of the actuator assembly 2 (e.g. the top corner as shown in Figure 4b). As mentioned above, the actuator assembly 2, and in particular the movable part 20 and / or the support structure 10, may have a square or rectangular footprint. In some embodiments, each actuating unit 30a-30d of the first set may bend around a corner of the movable part 20 such that the SMA wire 34 and the coupling flexure 33 of each actuating unit 30a-30d extend along adjacent edges of the movable part 20.

[0120] Although the first set of actuating units is described here in the context of four actuating units 30a-30d, in general the first set of actuating units may include more or fewer actuating units. For example, the first set may include two actuating units 30a and 30c, e.g. the two actuating units depicted at the bottom corner of Figure 4b. The forces applied to the movable part 20 by the two actuating units 30a and 30c may be opposed by a biasing force of one or more resilient elements, such as springs. The two actuating units 30b and 30d in the top corner may be replaced with springs applying biasing forces along the corresponding depicted arrows, for example.

[0121] The second set of actuating units

[0122] In the example shown in Figure 4b, the second set of actuating units also comprises four actuating units 31a-31d configured to apply actuating forces in directions parallel to the z axis (i.e. the primary axis). In more detail, the second set of actuating units comprises a first pair of actuating units 31a and 31b that are configured to apply actuating forces in one direction parallel to the primary axis (e.g. the -z direction), and a second pair of actuating units 31c and 31d configured to apply actuating forces in the opposite direction (e.g. the +z direction). By appropriately varying the actuation amounts between the first and second pairs of actuating units within the second set of actuating units, the movable part may thus be translationally moved along the primary axis and / or rotated about any axis that is orthogonal to the primary axis.

[0123] For example, by varying the magnitude of the actuating forces applied by actuating units 31a and 31b, it is possible to generate a torque or moment between the movable part 20 and the support structure around the x axis, provided that there is no force differential between units 31c and 31d. For instance, if actuating units 31c and 31d are applying the same amount of actuating force (which may be zero) to the movable part, and the actuating force applied by unit 31b is greater than the actuating force applied by 31a, a torque or moment between the movable part and support structure will be generated in a first sense (e.g. clockwise) about the x axis. Alternatively, if the actuating force applied by unit 31a is greater than the actuating force applied by 31b, a torque or moment between the movable part and support structure will be generated in a second sense (e.g. counter-clockwise) about the x axis.

[0124] Considering tilt about the y axis, if actuating units 31a and 31b are applying the same amount of actuating force (which may be zero) to the movable part, and the actuating force applied by unit 31d is greater than the actuating force applied by 31c, a torque or moment between the movable part and support structure will be generated in a first sense (e.g. clockwise) about the y axis. Alternatively, if the actuating force applied by unit 31c is greater than the actuating force applied by 31d, a torque or moment between the movable part and support structure will be generated in a second sense (e.g. counter-clockwise) about the y axis.

[0125] As shown in the figure, it is preferable for the actuating units of each pair in the second set of actuating units to be arranged on opposite sides of the actuator assembly. In particular, actuating units 31a and 31b may be arranged on opposite sides and actuating units 31c and 31d may also be arranged on opposite sides, which may or may not be different to the sides on which the first pair of actuating units are arranged. For example, each actuating unit of the second set may be arranged on different respective sides of the actuator assembly. In other examples, two opposing sides of the actuator assembly may each comprise one of each of the first and second pairs of actuating units, whilst the remaining two sides do not have any actuating units arranged along them.

[0126] As can be seen in Figure 4b, the directions of the forces applied by the second set of actuating units alternate when viewed along the primary axis. In other words, the second set of actuating units are arranged around the primary axis and any two adjacent actuating units have actuating forces that act in opposite direction (i.e. one has an actuating force in the +z direction whilst the adjacent unit has an actuating force in the -z direction). This means that, when viewed along the primary axis (i.e. in a plan view of the actuator assembly), a notional line connecting the two actuating units that provide an actuating force in the +z direction crosses a notional line connecting the two actuating units that provide an actuating force in the -z direction.

[0127] The point at which the two notional lines cross may be referred to as a centre point of the second set of actuating units. Preferably, the actuating units are equally angularly spaced (i.e. 90 degrees) about this centre point when looking at the centre point in a direction parallel to the primary axis. This means adjacent actuating units subtend an angle of 90 degrees from the centre point. Assuming there are no other uneven external forces acting on the movable part, the equal spacing of the actuating units maximises the ability to control tilt of the movable part about any lateral axis that passes through the centre point. However, the skilled person will appreciate that it is still possible to control tilt about any lateral axis that passes through the centre point with an irregular spacing of the actuating units (for example if the four actuating units are arranged on two opposing sides as mentioned above). It may also be preferable that the coupling links of each of the second set of actuating units are arranged substantially in the centre of each side, as shown in Figures 4a-4d. In the context of a camera assembly or lens assembly, the centre point may lie on the optical axis (O) of the lens. This may be particularly advantageous as it allows the camera assembly or lens assembly to tilt about any lateral axis passing through the optical axis without causing any substantial translation of the movable part in the z direction (which, e.g. to minimise the z extent of the envelope of the movable part, may otherwise need to be compensated for with opposite z translational movement, thereby reduce the range of tilt achievable using the second set of actuating units). Similar considerations apply in different contexts.

[0128] If the centre point does lie on the optical axis of the lens, then the actuating units of a given pair (i.e. 31a and 31b, or 31c and 31d) are considered to be diametrically opposite to one another. This means that simultaneous actuating forces of the same magnitude applied by each unit within a given pair do not produce unwanted torque about any lateral axis.

[0129] Although the second set of actuating units is described here in the context of four actuating units 31a- 31d, in general the second set of actuating units may include more or fewer actuating units. For example, the second set may include only two actuating units 31a and 31c. In other words, the second set of actuating units may comprise a single actuating unit configured to apply an actuating force in each of the +z and -z directions. More generally, the second set of actuating units may include at least one actuating unit configured to apply an actuating force in a first direction substantially parallel to the primary axis (e.g. +z) and at least one actuating unit configured to apply an actuating force in a second direction, opposite to the first direction, substantially parallel to the primary axis (e.g. -z).

[0130] Further details of the actuating units

[0131] Referring now to Figures 4c, a side view of the actuator assembly illustrated in Figure 4a is shown. In particular, side "A" is shown. Figure 4d shows a schematic of the input forces Fi and the actuating forces F of the actuating units 30a and 31a arranged along side "A". The Figure shows side A as viewed side-on along the y axis. As such, the Figure lies in the x-z plane. The dashed line passing through the Figure indicates the direction of the primary axis. Figure 4d includes arrows that indicate the direction of the input forces Fi applied by the SMA elements of each actuating unit, as well as arrows indicating the direction of the actuation forces F applied to the movable part by the coupling link of each actuating unit.

[0132] As can be seen, in the embodiment depicted in Figures 4a-d, the input force Fi in the actuating unit 30a is in a direction that is substantially perpendicular to the primary axis, meaning that the input force Fi applied by the SMA element of actuating unit 30a and the actuating force F transmitted through the coupling link are substantially parallel (and in substantially opposite directions).

[0133] In general, the input force Fi in the actuating unit 31a is in a direction that is approximately perpendicular to the primary axis, meaning that the input force Fi and the actuating force F are approximately perpendicular to each other. Broadly speaking, this may be advantageous in the context of cameras and the like, in which the actuator assembly generally has a smaller dimension along the primary / optical / z axis and larger dimensions along the x and y axes. In particular, the configuration of the actuating unit 31a (and the other actuating units in the second set) allows the SMA element to be arranged along the longer (e.g. x or y) dimension and the actuating force to be applied in the direction of the shorter (e.g. z) dimension. In the illustrated embodiment, the input force applied by the SMA element of actuating unit 31a is not exactly perpendicular to the corresponding actuating force. Instead, the SMA element and corresponding input force of actuating unit 31a is angled with respect to the side, the actuating force, and the primary axis. In general, the input forces in any actuating unit on a given side (e.g. units 30a and 31a) may not necessarily be parallel to either the lateral axis or primary axis but may instead be at an oblique angle with respect to both the primary axes and the plane within which the lateral axes lie. More generally, the input force Fi applied by any SMA element of any of the actuating units of the first set and / or the second set may have a first component that is in a direction parallel to a lateral axis, and a second component that is parallel to the primary axis. Thus, the SMA element of these actuating units is angled with respect to the side on which it is arranged and with respect to the corresponding coupling link. Such embodiments are particularly advantageous is it allows for an increased movement range or force provided by the actuating unit. This is because, for any given length of the side of the actuator assembly, it may be possible to accommodate a longer SMA element that is arranged at an angle with respect to the side compared to an SMA element arranged substantially parallel to the side (i.e. parallel to the primary axis), due to the principles of geometry. Furthermore, such angling of one or both of the SMA elements can facilitate layout of the actuating units and, in particular, can allow longer lengths of SMA elements to be included on one side while keeping them apart from each other. In the illustrated embodiment, angling one of the SMA elements 34 facilitates a layout in which the "moving" crimps 35 are located at the same height (i.e. z coordinate) and in which the SMA elements 34 overlap in the (x) direction along the side.

[0134] As mentioned above (in the Summary), in the context of e.g. all-in-one AF and OIS actuators, it may be advantageous for the second set of actuating units to have longer SMA elements than the first set of actuating units. The second set of actuating units controls AF functionality, which generally requires a higher degree of precision and accuracy than OIS functionality. Since increasing the lengths of the SMA elements achieves increasing amounts of wire stroke, it is possible to decrease the amplification provided by the force-modifying element and the body portion, and therefore increase the precision and accuracy of the movement. In contrast, it may be preferable to minimise the lengths of the SMA elements of the first set of actuating elements (which do not have to achieve the same level of precision for OIS), while increasing the amplification, thereby minimising the OIS power requirements.

[0135] More generally, each of the input forces that can be applied by each of the first and second sets of actuating units may either be in a direction that lies in a plane that is substantially perpendicular to the primary axis (i.e. a lateral plane), or in a direction that lies at an oblique angle relative to the primary axis and a lateral plane. In some embodiments, such as that depicted in Figures 4a-d, the actuator assembly comprises both types of actuating units - those with input forces that lie in a lateral plane and those with input forces at an oblique angle.

[0136] Considering in more detail the relationship between the input forces and the actuating forces for each actuating unit, in general these may lie parallel to each other, perpendicular to each other, or at any oblique angle. The example shown in Figures 4c-d demonstrates that the actuating force applied by actuating unit 31b lies at an oblique angle relative to the corresponding input force, whilst the actuating force applied by actuating unit 30a lies substantially parallel to the corresponding input force. In other examples, the actuating force of a given actuating unit may be substantially perpendicular to the corresponding input force. In broad terms, the actuating unit 30a has some similarities to that described above with reference to Figures 3A and 3B, and the actuating unit 31a has some similarities to that described above with reference to Figure 3C. Referring in particular to Figure 4c, the actuating unit 31a is characterised by a relatively large body portion 37 that extends diagonally from the crimp 35 which is positioned towards the upper (+z) corner of the side to the coupling link 33 to which it is connected towards the centre of the lower (-z) edge of the side. The force-modifying flexure 32 extends from the opposite side of this body portion 37 to the SMA element 34 and coupling link 33 and so is under tension in operation.

[0137] Considering now the overlap of the actuating units 30a and 31a of Figure 4c-4d when viewed along the primary axis, it can be seen that in this particular embodiment, the angular extent of the actuating unit 30a about the primary axis overlaps with the angular extent of the actuating unit 31a about the primary axis. In other words, the actuating units 30a and 31a arranged along the same side of the actuator assembly are not spatially separated about the primary axis. More generally, any actuating units arranged along the same side of the actuator assembly may have overlapping angular extents. In a square arrangement, such as in the example depicted in the figures, the amount of overlap between the actuating units on the same side (e.g. 30a and 31a) i.e. the angle subtended by the overlapping portions of the pair of actuating units, is 90° or less due to the square geometry. If the actuating units extend along the full length of the side on which they are arranged, then the overlap between the actuating units is exactly 90°. However, typically, the actuating units may extend along less than the full length of the side on which they are arranged, meaning that the angle subtended by the overlapping portions of the actuating units when viewed along the primary axis is less than 90°. In contrast, the arrangement of actuating units along a side of the actuator assembly depicted in Figures 7a-7b do not have overlap when viewed along the primary axis. This alternative embodiment is discussed in more detail below.

[0138] Arranging the actuating units (e.g. 30a and 31a) along a side such that there is overlap about the primary axis may be advantageous as this allows a longer length of SMA element to be used, compared to embodiments where there is no overlap (see Figures 7a-b). For example, the length of the SMA element may be at least 50% of the length of the side, 90% of the length of the side, or may even be longer than the length of the side if the SMA element is arranged at an oblique angle. As described in more detail above, longer SMA element provides increased contraction of the SMA element, therefore providing greater stroke (greater range of movement).

[0139] In the illustrated embodiment, each of the SMA elements 34 on one side overlap with other features (e.g. the connecting portion 21a) of the actuating units 30, 31 (when viewed side-on). To facilitate such a layout, one or both of the crimps 15, 35 of each of the SMA elements 34 may be offset in a direction perpendicular to the side, e.g. in the +y direction in the case of side "A", from these other features (e.g. the connecting portion 21a) of the actuating units 30, 31.

[0140] As can be seen in the embodiment depicted in Figures 4c and 4d, each of the actuating units 30a and 31a are connected via the respective coupling links to a single connecting portion 21a. In particular, the coupling link of actuating unit 30a, which is parallel to the x axis in this example, is connected to a bottom of the connecting portion, and is configured to apply an actuating force in the +x direction to cause movement of the connecting portion 21a in the +x direction. The coupling link of actuating unit 31a, which is parallel to the z axis, is connected to a top of the connection portion 21a and is configured to apply an actuating force in the -z direction to cause movement of the connecting portion in the -z direction. In this example, the connecting portion 21a is centrally located relative to the long length of the side (e.g. the length along the x axis in the case of side "A").

[0141] The connecting portion may be integral to the actuating units 30a and 31a. That is, at least the coupling links 33, body portions 31, foot portions 36, and flexures of each of units 30a and 31a may be integrally formed with the connecting portion 21a, meaning that these components (optionally together with the crimps 15) may be made from a single piece of material. In some examples, these components of the actuating units and the connecting portion are integrally formed by etching from a thin sheet of metal or any other suitable manufacturing technique apparent to the skilled person.

[0142] As described above in relation to Figures 3A and 3B, the SMA elements 34 of the units may be connected to the respective body portions via a crimp (e.g. crimp 35).

[0143] The connecting portion 21a is configured to be rigidly fixed to the movable part such that the actuating forces are transmitted through the connecting portion 21a to the movable part. In this way, the actuating units are configured to cause movement of the movable part via the connecting portion 21a. The connection portion may be fixed to the movable part by welding (if the movable part (or a portion thereof) and the connection portion are metallic), or any other suitable means for providing a rigid connection. The single point of connection between the actuating units and the movable part (via the connecting portion) may be particularly beneficial from a manufacturing perspective, since it allows the movable part to be connected to all of the first and second sets of actuating units in a total of four places (one connection point per side). In comparison, some known actuator assemblies require a separate connection to the movable for each of eight different actuating units, resulting in increased complexity and cost.

[0144] As mentioned above, the configuration of actuating units 30b, 31b on side "B" may be the same as that on side "A". The configuration of actuating units 30c, 30d, 31c, 31d on each of sides "C" and "D" may be the same as that on each of sides "A" and "B" except that the configuration is mirrored about the xy plane (or a plane parallel to the xy plane extending through the centre of the side) such that, for instance, features towards the top (+z edge) of the side are towards the bottom (-z edge) of the side and vice versa.

[0145] Alternative designs of coupling link

[0146] Turning now to Figures 5A and 5B, a coupling link 53 according to some embodiments of the present disclosure is illustrated. Figure 5C shows the coupling link according to Figure 5A in arrangement with the other components of the actuating unit 31a (or more generally any one of the second sets of actuating units). In the previous embodiments the coupling link of each of the second sets of actuating units is a straight flexure that is compliant (i.e. deformable) in directions perpendicular to the actuating force F. Such coupling links are arranged such that an actuating force is transmitted to the movable part by the coupling link being placed in tension between the body portion of the actuating unit and the movable part. Since the coupling link is compliant in directions perpendicular to the actuating force, it is generally preferred to transmit the actuating force through a tension in the coupling link rather than a compression in the coupling link, since a compressive force is more likely to lead to a buckling of the coupling link. One possible problem with straight coupling links such as those depicted in Figures 4C and 4D is that their length is limited by the dimensions of the actuator assembly, meaning that the coupling links may have limited perpendicular compliance that restricts the range of movement of the movable part. For example, a translational movement of the movable part relative to the support structure in the +x direction would require the coupling links of each of the second set of actuating units to bend in the +x direction. If compliance of these coupling links in the x direction is limited by their length, then the range of movement in the +x direction is also limited accordingly. The same problem may arise for any type of lateral movement or rotation of the movable part about the primary axis, for example.

[0147] As will be appreciated by the skilled person, a shorter coupling link would be stiffer and therefore less compliant in a perpendicular direction in comparison to a longer coupling link. Therefore, this problem may particularly be relevant for the coupling links of each of the second set of actuating units, which lie parallel to the z axis and which are typically shorter than the coupling links of each of the first set of actuating units (which lie perpendicular to the z axis and are typically longer).

[0148] To prevent the range of movement of the movable part being limited by the compliance of short coupling links, an alternative design of coupling link 53 is provided as shown in Figures 5A and 5B. In these examples, the coupling link comprises two hairpin (i.e. substantially 180 degree) bends at opposite ends of the coupling link, which separate 3 different portions of the coupling link. In more detail, the coupling link comprises two compressive portions 531 and 533 and one tensile portion 532 that are all substantially parallel. Situated at either end of the tensile portion 532 is a hairpin bend to which each of the compressive portions 531 and 533 are connected.

[0149] Figure 5C illustrates the coupling link 53 as part of one of the second set of actuating units, e.g. 31a. As shown in this figure, one of the compressive portions 531 is connected to the body portion 56 of the actuating unit, whilst the other compressive portion is connected to the movable part 20 (optionally via a connecting portion 21a).

[0150] When the actuating unit 31a is actuated, the actuating force acting in the -z direction (indicated by arrow F) is transmitted through the coupling link to the movable part 20. In transmitting the actuating force to the movable part, the compressive portions 531 and 533 are placed in compression whilst the tensile portion is placed in tension. Therefore, unlike straight coupling links as described above with reference to Figures 3A - 4D which are only placed in tension, the coupling link according to the embodiment of Figure 5A-5B has at least one portion placed in compression as well as one portion placed in tension when the actuating force is applied to the coupling link. This particular arrangement of the one or more portions in compression connected by a hairpin bend to one or more portions in tension enables a longer coupling link to be used to transmit actuating forces in the + / - z direction compared to straight coupling links, therefore improving the compliance of the coupling link in the x or y (or any lateral) direction and reducing stress on the coupling link when it is in a deflected (bent) state.

[0151] As shown in Figure 5A, in some embodiments the tensile portion 532 has one or more, optionally two, chicane-type bends 534 which each consist of a first bend of connected to a complementary and opposite second bend, where the first and second bends have the same radius and angle. Each bend may have an acute angle or a substantially right angle. Such embodiments may be preferable since the chicane bends enable the compressive portions to be substantially aligned in the z direction (i.e. the short portions are substantially colinear), which helps to ensure the actuating force transmitted through the coupling link does not have any substantial lateral component (i.e. the actuating force is substantially parallel to the z axis). In contrast, compressive portions 531 and 533 in Figure 5B are not aligned since there are no chicane-type bends in the tensile portion 532.

[0152] Preferably, the tensile portion is longer than each of the compressive portions individually. Generally speaking, it is preferable that the compressive portions are not too long so as to minimise the risk of these portions buckling under the compressive actuating force. It is also preferable that the spatial separation between the compressive portion and the adjacent tensile portion (i.e. the width of the hairpin bend) is minimised so as to minimise compliance in the z direction. In order words, it is preferable that the coupling link is compliant (i.e. deformable) in the x or y direction, by is non- compliant (i.e. rigid) in the z direction. By minimising compliance, i.e. deformability, in the z direction, the actuating force can be transferred through the coupling link with high efficiency, i.e. minimal loss.

[0153] In the embodiments described in detail herein, the coupling link is a flexure.

[0154] In other embodiments, instead of a flexure, the actuating units may have a coupling link in the form of a sliding or rolling bearing configured to transmit the actuating force in a direction substantially parallel to the primary axis and configured to allow relative movement in any direction substantially perpendicular to the primary axis. Such a bearing may include, for example, a ball positioned between two bearing surfaces which are oriented perpendicularly to the primary axis, with features to retain the ball in the bearing.

[0155] Other arrangements of the actuating units

[0156] Referring to Figure 6a and 6b, a side view of an actuator assembly according to another embodiment of the present disclosure is shown, along with a corresponding force diagram indicating the directions of the input and actuating forces of each actuating unit. In this embodiment, actuating unit 30a of the first set of actuating units and actuating unit 31a of the second set of actuating units is provided in a different arrangement to that shown in Figures 4a-4d. In this example, the actuating units 30a and 31a overlap along the primary axis in a similar manner to the actuating units shown in Figures 4c and 4d.

[0157] In the embodiment shown in Figures 6a and 6b, the input force Fi applied by the SMA element of actuating unit 30a is not parallel to the corresponding actuating force (contrasting the arrangement of Figure 4c and 4d in which the input force and actuating force for unit 30a are parallel). Instead, the SMA element and corresponding input force of actuating unit 30a is angled with respect to the side, the actuating force, and the primary axis. With respect to actuating unit 31a, the input force Fi lies in a plane that is substantially perpendicular to the primary axis and is therefore substantially perpendicular to the actuating force Fi (which is parallel to the primary axis).

[0158] In contrast to the embodiment described above with respect to Figures 4a-4d, in which the coupling link of each of the second set of actuating units is arranged in the centre of the respective side, the embodiment of Figure 6a and 6b shows the coupling link (and therefore the actuating force) of actuating unit 31a arranged towards one longitudinal end of the side. In general, the coupling link of the actuating unit of the second set may be located at any position along the respective side(provided that there exists a centre point between each of the second set of actuating units as described above). Turning now to Figures 7a and 7b, an actuator assembly according to another alternative embodiment of the present disclosure is shown. In this embodiment, it can be seen that there is no overlap of the actuating units 30a and 31a when viewed along the primary axis. In particular, the actuating units 30a and 31a arranged along the same side of the actuator assembly are spatially separated about the primary axis, meaning that the angular extent of the actuating unit 30a about the primary axis does not overlap with the angular extent of the actuating unit 31a. More generally, in this embodiment, there is no overlap of the angular extent of any two of the actuating units along any of the sides.

[0159] It can also be seen in the embodiment of Figure 7a and 7b that the input force Fi of each actuating unit lies in a direction perpendicular to the primary axis. This means that the input force Fi of actuating unit 31a is perpendicular to the corresponding actuating force (which is parallel to the primary axis), and the input force Fi of actuating unit 30a is parallel to the corresponding actuating force (which lies in a plane perpendicular to the primary axis).

[0160] Considering Figure 7a in more detail, it can be seen that the coupling link of each actuating unit has a respective different connecting portion that is arranged to be coupled to the movable part 20 (not shown in the figure). This means that for any given side of the actuator assembly, the actuating units along that side (e.g. 30a and 31a) may be connected to the movable part 20 in separate places. This is in contrast to other embodiments, such as that described above with respect to Figures 4a-4d in which the actuating units along a given side (e.g. 30a and 31a) have a common connecting portion 21a, capable of being connected to the movable part in a single place, through which the respect coupling links can transmit the actuating force to the movable part.

[0161] In alternative embodiments to those shown in the figures, each of the first and second set of actuating units may comprise an SMA element connected directly between the support structure and movable part of the actuator assembly. This is instead of using the disclosed flexure-amplified actuating units that comprise an SMA element connected between the support structure and a body portion, and a coupling link connected between the body portion and the movable part. In such alternative embodiments, the input force applied by each SMA element is also the actuating force applied to the movable part, since the SMA element is connected directly between the support structure and the movable part and therefore directly transmits the input force to the movable part. In order to achieve this, actuating units of any of the embodiments described above may each be replaced with an SMA element that is positioned in place of the coupling link, and that is connected at a first end (corresponding to the end of the coupling link connected to the body portion) to the support structure and connected at the other end to the movable part. Thus, it will be appreciated that in such alternative embodiments, the arrangement of actuating forces applied to the movable part are the same as those described above in relation to the other embodiments. In particular, there is still a first set of actuating units each configured to apply an actuating force in a direction that is substantially perpendicular to the primary axis, and a second set of actuating units each configured to apply an actuating force substantially parallel to the primary axis.

[0162] In one particular alternative embodiment, each of the first set of actuating units configured to apply an actuating force in a direction that is substantially perpendicular to the primary axis may comprise an SMA element directly connected between the support structure and the movable part, whilst the second set of actuating units may comprise components as described above with reference to Figures 3A-3C. This embodiment may be particularly advantageous in actuator assemblies having aspect ratios as described above since it uses the simpler (and lower-cost) option of simply an SMA element for each of the first set of actuating units, where the SMA elements can be oriented (laterally) such that they are aligned with (a) the required actuating forces and (b) the longer dimensions of the actuator assembly. In contrast, in the second set of actuating units, the SMA elements cannot be oriented in this way and so "flexure amplification" components are required to amplify the movement and / or re-direct the forces.

[0163] In some embodiments of the present disclosure, the actuating units of the first and second sets may be arranged along one or more surfaces of the support structure and / or the movable part of the actuator assembly that face generally in a lateral direction (i.e. perpendicular to the primary axis). These surfaces along which the actuating units are arranged may generally be aligned with the x and y axes. In other words, the one or more surfaces of the support structure and / or the movable part may be planar, and the normal to each of those surfaces may point generally in a direction orthogonal to the primary axis, or may at least have a larger component in a direction orthogonal to the primary axis than in a direction parallel to the primary axis.

[0164] Alternatively, in other embodiments, at least the actuating units of the first set may be arranged on one or more surfaces of the support structure and / or the movable part that face generally parallel to the primary axis. In other words, these one or more surfaces may be planar, and the normal to each of those surfaces may point generally in a direction parallel to the primary axis, or may at least have a larger component in a direction parallel to the primary axis than in any lateral direction. In such embodiments, each actuating unit of the first set may extends along two adjacent sides of the actuator assembly. In particular, each actuating unit may have its SMA element arranged along a first one of the four sides, and its coupling link arranged along a second side that is adjacent to the first side. In other words, each actuating unit of the first set may be arranged such that it bends around a corner of the actuator assembly so that the SMA element and the coupling link of each actuating unit 30 extend along adjacent sides of the actuator assembly. With respect to the input and actuation forces of each actuating unit, this means that, in some examples, input force applied by the SMA element of each actuating unit may be generally perpendicular to the respective actuating force, when the actuator assembly is viewed along the primary axis.

[0165] Bearing arrangement

[0166] The embodiments described above, e.g. the embodiment of Figures 4a-d can be used, amongst other things, to enable 2-axis or 3-axis module-tilt OIS. In such embodiments, the actuating units 30, 31 are actuated so as to cause rotation of the movable part 20 relative to the support structure 10 about any axis substantially perpendicular to the primary axis P and optionally about the primary axis P. In such embodiments, the movable part 20 may be supported on the support structure 10 exclusively by the actuating units 30, 31. However, such embodiments may also have a bearing arrangement 40 between the support structure 10 and the movable part 20 (as shown schematically in Figure 2). The bearing arrangement 40 may be configured to allow rotation of the movable part 20 relative to the support structure 10 about any axis substantially perpendicular to the primary axis P and optionally about the primary axis P. The bearing arrangement 40 may restrict other types of movement such as translational movement of the movable part 20 relative to the support structure 10, and therefore may help improve performance of the actuator assembly. The bearing arrangement 40 may include, for example, one or more gimbals. The bearing arrangement 40 may include, for example, bearing arrangements 40 equivalent to those described in WO 2021 / 209770 Al (which is herein incorporated by reference) with reference to e.g. Figures 16 or 17 thereof.

[0167] Other variations

[0168] It will be appreciated that there may be many other variations of the above-described examples.

[0169] For example, the actuator assembly may include different types of actuating units to those described above. Examples of such actuating units include a folded SMA wire arrangement as disclosed in WO 2021 / 111131 Al, a V-shaped SMA wire with a compliant connector as disclosed in

[0170] WO 2013 / 121225 Al, a scissor jack arrangement as disclosed in WO 2021 / 156458 Al, a two-stage arrangement as disclosed in WO 2021 / 111181 Al, or simply an SMA wire connected between the support structure 10 and the movable part 20. The documents referred to in the preceding sentence are each herein incorporated by reference. The actuator assembly may have any number of different types of actuating units, and may have any suitable number of actuating units of each type.

[0171] SMA

[0172] The above-described SMA actuator assemblies comprise at least one SMA element. The term 'shape memory alloy (SMA) element' may refer to any element comprising SMA. The SMA element may be described as an SMA wire. The SMA element may have any shape that is suitable for the purposes described herein. The SMA element may be elongate and may have a round cross section or any other shape cross section. The cross section may vary along the length of the SMA element. The SMA element might have a relatively complex shape such as a helical spring. It is also possible that the length of the SMA element (however defined) may be similar to one or more of its other dimensions. The SMA element may be sheet-like, and such a sheet may be planar or non-planar. The SMA element may be pliant or, in other words, flexible. In some examples, when connected in a straight line between two components, the SMA element can apply only a tensile force which urges the two components together. In other examples, the SMA element may be bent around a component and can apply a force to the component as the SMA element tends to straighten under tension. The SMA element may be beam-like or rigid and may be able to apply different (e.g. non-tensile) forces to elements. The SMA element may or may not include material(s) and / or component(s) that are not SMA. For example, the SMA element may comprise 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 acting as a single actuating element which, for example, can be individually controlled to produce a force on an element. For example, the SMA element may comprise two or more portions of SMA material that are arranged mechanically in parallel and / or in series. In some arrangements, the SMA element may be part of a larger SMA element. Such a larger SMA element might comprise two or more parts that are individually controllable, thereby forming two or more SMA elements. The SMA element may comprise an SMA wire, SMA foil, SMA film or any other configuration of SMA material. The SMA element may be manufactured using any suitable method, for example by a method involving drawing, rolling, deposition, sintering or powder fusion. The SMA element may exhibit any shape memory effect, e.g. a thermal shape memory effect or a magnetic shape memory effect, and may be controlled in any suitable way, e.g. by Joule heating, another heating technique or by applying a magnetic field.

Claims

Claims1. An actuator assembly comprising: a first part; a second part that is movable relative to the first part; a plurality of actuating units each configured to apply an actuating force to the second part capable of moving the second part relative to the first part, wherein at least one of the actuating units comprises: a body portion an SMA element connected between the body portion and one of the first and second parts, and configured, on actuation, to apply an input force to the body portion; and a force-modifying element connected between the body portion and the one of the first and second parts and configured to modify the input force so as to give rise to the actuating force; and a coupling link connected between the body portion and the other of the first and second parts, wherein the coupling link is configured to transmit the actuating force from the body portion to the other of the first and second parts, and wherein the coupling link is compliant in a direction perpendicular to the actuating force; wherein the actuator assembly has a primary axis extending through the actuator assembly, and wherein the plurality of actuating units comprise: a first set of actuating units each configured to apply an actuating force in a direction that lies in a plane substantially perpendicular to the primary axis, and a second set of actuating units each configured to apply an actuating force substantially parallel to the primary axis.

2. The actuator assembly of claim 1, wherein the first set of actuating units comprises four actuating units.

3. The actuator assembly of claim 2, wherein the actuator assembly comprises four sides arranged around the primary axis, and wherein each actuating unit of the first set of actuating units is arranged along a different respective one of the four sides, optionally wherein adjacent sides are substantially perpendicular such that the four sides form a quadrilateral shape when viewed along the primary axis.

4. The actuator assembly of any preceding claim, wherein the second set of actuating units comprises four actuating units.

5. The actuator assembly of claim 4 when dependent on claim 3, wherein each actuating unit of the second set of actuating units is arranged along a different respective one of the four sides.

6. The actuator assembly of any preceding claim, wherein the first set of actuating units are configured to be capable of: causing a translation of the second part relative to the first part in any direction that is substantially perpendicular to the primary axis; and / or causing a rotation of the second part relative to the first part in both senses about an axis that is substantially parallel to the primary axis.

7. The actuator assembly of any preceding claim, wherein the first set comprises: a first actuating unit configured to apply an actuating force in first direction substantially parallel to a first lateral axis, wherein the first lateral axis is perpendicular to the primary axis; a second actuating unit configured to apply an actuating force in second direction, substantially opposite the first direction, parallel to the first lateral axis; a third actuating unit configured to apply an actuating force in a first direction substantially parallel to a second lateral axis, wherein the second lateral axis is perpendicular to the primary axis and the first lateral axis; and a fourth actuating unit configured to apply an actuating force in a second direction, substantially opposite the first direction, parallel to the second lateral axis.

8. The actuator assembly of any preceding claim, wherein the second set of actuating units are configured to be capable of: causing a translation of the second part relative to the first part in both directions along a line that is substantially parallel to the primary axis; and / or causing a rotation of the second part relative to the first part about any axis substantially perpendicular to the primary axis.

9. The actuator assembly of any preceding claim, wherein the second set of actuating units comprises: at least one actuating unit configured to apply an actuating force in a first direction substantially parallel to the primary axis; at least one actuating unit configured to apply an actuating force in a second direction, opposite to the first direction, substantially parallel to the primary axis.

10. The actuator assembly of claim 9, comprising: a first pair of actuating units configured to apply an actuating force in the first direction substantially parallel to the primary axis; and a second pair of actuating units configured to apply an actuating force in the second direction, opposite to the first direction, substantially parallel to the primary axis.

11. The actuator assembly of claim 10, wherein the actuating units of each of the first and second pair are arranged diametrically opposite to one another with respect to the primary axis.

12. The actuator assembly of any preceding claim, wherein at least one of the second set of actuating units comprises a coupling link formed of at least two elements connected by a substantially 180-degree bend.

13. The actuator assembly of claim 12, wherein a first one of the at least two elements of the least one coupling link is configured to transmit an actuating force through compression of the first element, and wherein a second one of the at least two element is configured to transmit an actuating force through tension in the second element, optionally wherein the length of the first element is less than the length of the second element.

14. The actuator assembly of any preceding claim, wherein the SMA elements of each of the second set of actuating units are longer than the SMA elements of each of the first set of actuating units.

15. The actuator assembly of any of claims 4 to 14 when dependent on claim 3, wherein each actuating unit of the second set of actuating units is arranged along a different respective one of the four sides.

16. The actuator assembly of claim 15, wherein the angular extent of the actuating unit of the first set along a given side overlaps at least partly with the angular extent of the actuating unit of the second set along the same side.

17. An actuator assembly comprising: a first part; a second part that is movable relative to the first part; and a plurality of actuating units each configured to apply an actuating force to one of the first and second parts capable of moving the second part relative to the first part, wherein each actuating unit comprises an SMA element; wherein the actuator assembly has a primary axis extending through the actuator assembly, and wherein the plurality of actuating units comprise: a first set of actuating units each configured to apply an actuating force in a direction that lies in a plane substantially perpendicular to the primary axis, and a second set of actuating units each configured to apply an actuating force substantially parallel to the primary axis.

18. The actuator assembly of claim 17, wherein the SMA element of each actuating unit is directly connected between the first part and the second part, and wherein the SMA element is configured, on actuation, to apply the actuating force to the second part.

19. A camera assembly comprising: an actuator assembly according to any one of claims 1 to 18; one or more lenses comprised in one of the first and second parts of the actuator assembly; and an image sensor comprised in the other of the first and second parts of the actuator assembly; wherein the actuator assembly is configured to move the one or more lenses and the image sensor relative to each other with three translational degrees of freedom.

20. A camera assembly comprising: an actuator assembly according to any one of claims 1 to 18; and a support structure comprising one of the first and second parts of the actuator assembly; a module comprised in the other of the first and second parts of the actuator assembly, wherein the module comprises one or more lenses and an image sensor; wherein the actuator assembly is configured to rotate the module relative to the support structure with at least two or three rotational degrees of freedom.

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