Field

The present application relates to an actuator assembly, particularly an actuator assembly comprising four shape-memory alloy (SMA) wires.

Background

Such an actuator assembly may be used, for example, in a camera to move a lens assembly in directions perpendicular to an optical axis so as to provide optical image stabilization (OIS), and to move the lens assembly along the optical axis to provide automatic focussing (AF). Where such a camera is to be incorporated into a portable electronic device such as a mobile telephone, miniaturization can be important.

WO 2013/175197 A1 describes an SMA actuation apparatus which moves a movable element relative to a support structure in two orthogonal directions using a total of four SMA actuator wires each connected at its ends between the movable element and the support structure and extending perpendicular to the primary axis. None of the SMA actuator wires are collinear, but the SMA actuator wires have an arrangement in which they are capable of being selectively driven to move the movable element relative to the support structure to any position in said range of movement without applying any net torque to the movable element in the plane of the two orthogonal directions around the primary axis.

WO 2019/243849 A1 describes a shape memory alloy actuation apparatus which comprises a support structure and a movable element. A helical bearing arrangement supported on the movable element on the support structure guides helical movement of the movable element with respect to the support structure around a helical axis. At least one shape memory alloy actuator wire is connected between the support structure and the movable element in, or at an acute angle to, a plane normal to the helical axis, so as to drive rotation of the movable element around the helical axis which the helical bearing arrangement converts into said helical movement. WO 2019/086855 A1 describes a camera with an actuator assembly including a support platform, a moving platform that supports a lens assembly, SMA wires connected to the support platform and the moving platform, bearings to bear the moving platform on the support platform, and two arms extending between the support platform and the moving platform.

Summary

According to a first aspect of the present invention, there is provided an actuator assembly including a first part, a second part and a bearing arrangement mechanically coupling the first part to the second part. The actuator assembly also includes a drive arrangement including four lengths of shape memory alloy wire. Each length of shape memory alloy wire is connected between the first part and the second part. The drive arrangement and the bearing arrangement are configured such that the first part is movable towards or away from the second part along a primary axis passing through the actuator assembly. The drive arrangement and the bearing arrangement are configured such that the first part is tiltable relative to the second part about first and/or second axes which are not parallel, and which are perpendicular to the primary axis.

The movement of the first part towards or away from the second part along the primary axis, the tilting of the first part relative to the second part about the first axis and the tilting of the first part relative to the second part about the second axis may be substantially independent from one another. The movement of the first part towards or away from the second part along the primary axis may be controllable substantially independently from the tilting of the first part relative to the second part about the first axis and/or the second axis.

The drive arrangement may include a total of four lengths of shape memory alloy wire. Neither the actuator assembly nor the drive arrangement may include any further lengths of shape memory alloy wire or other driving means. The actuator assembly includes a maximum of four lengths of shape memory alloy wire. The drive arrangement includes a maximum of four lengths of shape memory alloy wire. The first axis and/or the second axis may be perpendicular to the primary axis. The first axis may be perpendicular to the second axis. The first and second axes may pass through a pivot point. The pivot point may be offset from the first part and/or the second part along the primary axis.

Each of the four lengths of shape memory alloy wire corresponds to a section of shape memory alloy wire over which a drive current may be controlled independently. For example, a pair of lengths of shape memory alloy wire may be provided by a single physical wire having a first current source connected to one end, a second current source connected to the other end and a current return connection at a point between the two ends.

The bearing arrangement may be configured to guide movement of the first part relative to the second part along the primary axis, and to guide tilting of the first part relative to the second part about the first axis and/or the second axis.

The bearing arrangement may be configured to constrain movement of the first part relative to the second part along the first axis and/or the second axis. The bearing arrangement may be configured to constrain rotation of the first part relative to the second part about the primary axis.

The bearing arrangement may include a first bearing. The first bearing may include a first pair of flexures, each extending substantially parallel to the first axis and coupling the first part to the second part. The first pair of flexures may be spaced apart parallel to the second axis to bracket the first part. The first bearing may include a second pair of flexures, each extending substantially parallel to the second axis and coupling the first part to the second part. The second pair of flexures may be spaced apart parallel to the first axis to bracket the first part. Each flexure of the first pair and the second pair may be configured to be compliant in a direction corresponding to movement of the first part relative to the second part along the primary axis.

The first bearing may take the form of a simple flexure. The term substantially parallel may mean within ±5 degrees, or within ±10 degrees. The first part may be flat. The first part may be generally circular (i.e., a disc), elliptical (i.e., an elliptical disc or plate) or polygonal (i.e., a polygonal plate), for example, rectangular (i.e., a rectangular plate), in particular square (i.e., a square plate). The first part may be rigid or more rigid than the flexures.

One or more, or all of the first and/or second pair of flexures may be flat. One or more, or all of the first and/or second pair of flexures may include at least one bend (or "turn" or "elbow"). One or more, or all of the first and/or second pair of flexures may comprise a respective arm which may include at least one bend. One or more, or all of the arms may include a first portion extending away from the platform and a second portion running along a respective side of the platform. The first and second portions may be straight.

The first and second pairs of flexures be co-planar when the flexures are unflexed. The first and second pairs of flexures may be co-planar in a plane perpendicular to the primary axis when the flexures are unflexed. Any two of the first and/or second pairs of flexures may be formed as a single piece. The first and second pairs of flexures may be formed as single piece. The first and second pairs of flexures may be attached or bonded to the first part. The first and second pairs of flexures may be integrally formed with the first part.

The first bearing may include a flexure arrangement. The flexure arrangement may include a first pair of flexures extending from the first part and constraining movement of the first part along the first axis. The flexure arrangement may include a second pair of flexures extending from the first part and constraining movement of the first part along the second axis.

The bearing arrangement may include a second bearing configured to generate, in response to a torque applied about the primary axis by the drive arrangement, movement of the first part towards or away from the second part along the primary axis.

The second bearing may guide helical movement about and along the primary axis. The second bearing may mechanically couple a rotation about the primary axis to a translation along the primary axis.

The second bearing may be configured such that a movement of the first part relative to the second part along the first axis is coupled to a tilting of the first part relative to the second part about the first axis, and wherein a movement of the first part relative to the second part along the second axis is coupled to a tilting of the first part relative to the second part about the second axis.

The second bearing may take the form of a helical flexure. A helical flexure may take the form of a flat ring and at least three flexures extending from the flat ring. There may be four or more flexures extending from the flat ring. The flexures may be attached at equally-spaced angles around the flat ring. The flat ring and flexures may be a single-piece.

The second bearing may include a first set of helical flexures configured to be compliant in directions corresponding to movement of the first part relative to the second part along the primary axis and/or the first axis. The second bearing may include a second set of helical flexures configured to be compliant in directions corresponding to movement of the first part relative to the second part along the primary axis and/or the second axis.

The second bearing may include a first set of four ramps arranged in a loop about the primary axis and coupled to the first part. The second bearing may include a second set of four ramps arranged in a loop about the primary axis and coupled to the second part. The first and second sets of ramps may be arranged to oppose one another such that a sloped surface of each ramp of the first set of ramps engages a sloped surface of a corresponding ramp of the second set of ramps.

The second bearing may take the form of an under-constrained helical bearing.

A sloped surface of a ramp of the first or second sets makes an angle of more than zero and less than ninety degrees with a plane containing the first and second axes. The actuator may include one or more resilient biasing means configured to urge the first set of ramps towards the second set of ramps along the primary axis.

Each of the four lengths of shape memory wire may not be perpendicular to the primary axis.

The drive arrangement may be configured to provide a force having a component along the primary axis. First and second lengths of shape memory alloy wire may be oriented at respective angles to the primary axis and may lie substantially in planes parallel to the primary and first axes. Third and fourth lengths of shape memory alloy wire may be oriented at respective angles to the primary axis and may lie substantially in planes parallel to the primary and second axes. The four lengths of shape memory alloy wire oriented at respective angles to the primary axis may be configured to apply a net force along the first axis in combination with a torque about the first axis, a net force along the second axis in combination with a torque about the second axis, and/or a net force along the primary axis in combination with a torque about the primary axis.

The four lengths of shape memory alloy wire may be substantially co-planar within a plane parallel to the first and second axes. The substantially co-planar lengths of shape memory alloy wire may be configured to apply a net force along first and/or second axes, and/or a torque about the primary axis. The four lengths of shape memory alloy wire of the drive arrangement may be substantially co-planar with a top or bottom of the first bearing along the primary axis.

A camera may include the actuator assembly, an image sensor supported by one of the first part and the second part, and a lens supported by the other of the first part and the second part.

The camera may also include a controller configured to control the actuator assembly to implement an auto-focus function using the movement of the first part towards or away from the second part along the primary axis. The controller may also be configured to implement an optical image stabilisation function using the tilting of the first part relative to the second part about the first axis and/or the second axis.

According to a second aspect of the invention, there is provided a method including using the actuator assembly to implement an optical image stabilisation function and/or an automatic focussing function of a camera. Brief Description of the Drawings

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

Figure 1 schematically illustrates a camera;

Figure 2 illustrates possible translations and rotations of a lens assembly for a camera as shown in Figure 1;

Figure 3 schematically illustrates a first drive arrangement using four shape memory alloy (SMA) wires;

Figure 4 is a projection view of a flat actuator assembly;

Figures 5A to 5C schematically illustrate a second drive arrangement using four shape memory alloy (SMA) wires;

Figure 6 schematically illustrates a two-bar link bearing;

Figure 7A is a plan view of a simple flexure bearing, Figure 7B is a side view of a deformed state of the simple flexure bearing;

Figure 8 is a plan view of a second simple flexure bearing;

Figure 9 is an exploded projection view of a z-flexure bearing;

Figure 10A is a side view of a first planar bearing, Figure 10B is an exploded projection view of the first planar bearing;

Figure 11 is a side view of a second planar bearing;

Figure 12 is a projection view of a helical flexure bearing;

Figure 13 is a projection view of an under-constrained helical bearing;

Figure 14 is an exploded projection view of a first combined OIS and AF actuator assembly;

Figure 15 is a projection view of the first combined OIS and AF actuator assembly;

Figure 16 is a top view of the first combined OIS and AF actuator assembly; Figure 17 is a side view of the first combined OIS and AF actuator assembly; Figure 18 schematically illustrates the first combined OIS and AF actuator assembly;

Figure 19 is an exploded projection view of a second combined OIS and AF actuator assembly;

Figure 20 is a projection view of the second combined OIS and AF actuator assembly; and

Figure 21 schematically illustrates the first combined OIS and AF actuator assembly. Detailed Description

In the following, like parts are denoted by like reference numerals.

Camera

Referring to Figure 1, a camera 1 incorporating an SMA actuator assembly 2 (herein also referred to as an "SMA actuator" or simply an "actuator") is shown.

The camera 1 includes a first part in the form of a lens assembly 3 suspended on a second part in the form of a support structure 4 by the SMA actuator assembly 2. The SMA actuator assembly 2 supports the lens assembly 3 in a manner allowing one or more movements (or degrees-of-freedom) of the lens assembly 3 relative to the support structure 4. The lens assembly 3 has an optical axis O.

The second part in the form of the support structure 4 includes a base 5. An image sensor 6 is mounted on a front side of the base 5. On a rear side of the base 5 (i.e. the base 5 is interposed between the lens assembly 3 and the rear side), there is mounted an integrated circuit (IC) 7 in which a control circuit is implemented, and also a gyroscope sensor (not shown). The support structure 4 also includes a can 8 which protrudes forwardly from the base 5 to encase and protect the other components of the camera 1.

The first part in the form of the lens assembly 3 includes a lens carriage 9 in the form of a cylindrical body supporting two lenses 10 arranged along the optical axis O. In general, any number of lenses 10 may be included. Preferably, each lens 10 has a diameter of up to about 30 mm. The camera 1 can therefore be referred to as a miniature camera.

The lens assembly 3 is arranged to focus an image onto the image sensor 6.

The image sensor 6 captures the image and may be of any suitable type, for example, a charge-coupled device (CCD) or a complementary metal-oxide- semiconductor (CMOS) device.

The lenses 10 are supported on the lens carriage 9 and the lens carriage 9 is supported by the SMA actuator assembly 2 such that the lens assembly 3 is movable along the optical axis 0 relative to the support structure 4, for example to provide focussing or zoom. Although all the lenses 10 are fixed to the lens carriage 9 in this example, in general, one or more of the lenses 10 may be mounted to a component other than the lens carriage 9, and may be fixed in place relative to the image sensor 6, leaving at least one of the lenses 10 attached to the lens carriage and movable along the optical axis O relative to the image sensor 6.

In general, the lens assembly 3 may be moved orthogonally to the optical axis O in use, relative to the image sensor 6, with the effect that the image on the image sensor 6 is moved. For example, if a set of right-handed orthogonal axes x, y, z is aligned so that a third, primary axis z is oriented substantially parallel to the optical axis O, then the lens assembly 3 may be moveable in a direction parallel to the first x axis and/or in a direction parallel to the second y axis. This is used to provide optical image stabilization (OIS), compensating for movement of the camera 1, which may be caused by hand shake etc. The movement providing OIS need not be constrained to the x-y plane. Additionally or alternatively, OIS functionality may be provided by tilting the lens assembly 3, or both the lens assembly 3 and the image sensor 6, about an axis parallel to the first axis x and/or about an axis parallel to the second y axis. Additionally, the lens assembly 3, or at least one lens 10 thereof, may be moved parallel to the optical axis O (along/parallel to the primary axis z) to provide focussing of an image formed on the image sensor 6, for example as part of an automatic focussing (AF) function.

This specification is concerned with examples of SMA actuator assemblies 2 which provide a combination of automatic focussing (AF) and optical image stabilisation (OIS) that is based on tilting at least one lens 10 of the lens assembly 3 relative to the image sensor 6.

Referring also to Figure 2, possible types of movement (or degrees-of-freedom) which may be provided by an SMA actuator assembly 2 are illustrated.

A first degree-of-freedom (DOF) Tx corresponds to movement parallel to (along) the first axis x. A second DOF Ty corresponds to movement parallel to (along) the second axis y. A third DOF Tz corresponds to movement parallel to (along) the primary axis z, which is oriented substantially parallel to the optical axis O. The third DOF Tz corresponds to movement of the lens assembly 3 towards or away from the image sensor 6. The first, second and primary axes x, y, z form a right-handed Cartesian coordinate system. A fourth DOF Rx corresponds to rotation about an axis parallel to the first axis x. A fifth DOF Ry corresponds to rotation about an axis parallel to the second axis y. A sixth DOF Rz corresponds to rotation about an axis parallel to the primary axis z. In some examples, one or more of the axes may be attached to (and move and/or rotate/tilt with) a first part, a second part, or any other elements of an SMA actuator assembly 2 or camera 1. For example, an origin may be an element of the camera 1 such as the image sensor 6 or a lens 10 of the lens assembly 3.

Motions of the lens assembly 3 relative to the support structure 4 may be broken down into components of any or all of the first to sixth DOF (movements) Tx, Ty, Tz, Rx, Ry, Rz. Although described as degrees-of-freedom, in some cases translations and rotations may be linked. For example, a given translation Tz along the primary axis z may be tied to a corresponding rotation Rz so that motion of the lens assembly 3 is helical. Such linked motions may be referred to using a pair enclosed in square brackets to avoid confusion with more independent motions, for example [Tz, Rz] will denote a helical motion as described hereinafter.

This specification concerns SMA actuator assemblies 2 which provide relative movement Tz of the first part relative to the second part along (or parallel to) the primary axis z, and/or rotation Rx, Ry of the first part relative to the second part about axes parallel to the first and/or second axes x, y. Relative movement of the first part towards or away from the second part along the primary axis z may be a simple translation, or may be in the form of a helical motion linking translation along the primary axis z to rotation about the primary axis z. The rotations Rx, Ry provide the OIS functionality herein, whilst motions along Tz, or along and about [Tz, Rz], the primary axis z provide AF functionality. Other motions are constrained by the SMA actuator assemblies 2 described herein. Shape-memory alloy drive assemblies

Referring also to Figure 3, a first type of drive arrangement 11 (first drive arrangement) which may be included in SMA actuator assemblies 2 is shown schematically.

The first drive arrangement 11 includes a first structure 12 and a second structure 13. The second structure 13 is generally supported within a boundary defined by the first structure 12, for example using one or more bearings as described hereinafter. The second structure 12 generally need not provide a complete or uninterrupted boundary. The first and second structures 12, 13 may take the form of respective patterned sheets of metal, e.g., etched or machined stainless steel, and may be coated with an electrically-insulating dielectric material.

Four lengths of shape memory alloy (SMA) wire 14i, 142, 143, 144 (chained lines in Figure 3) form a loop around the second structure 13. For brevity, lengths of SMA wire shall hereinafter be referred to primarily as "SMA wires". First 14i and third 143 SMA wires extend substantially parallel to the first axis x and are spaced apart in a direction parallel to the second axis y. Contraction of the first SMA wire 14i will exert a force on the second structure 13 in the negative -x direction, whereas contraction of the third SMA wire 143 will exert a force on the second structure 13 in the positive +x direction. Second 142 and fourth 144 SMA wires extend substantially parallel to the second axis y and are spaced apart in a direction parallel to the first axis x. Contraction of the second SMA wire 142 will exert a force on the second structure 13 in the negative -y direction, whereas contraction of the fourth SMA wire 144 will exert a force on the second structure 13 in the positive +y direction.

Other examples configurations may be used, and further details are provided in WO 2017/055788 A1 and WO 2019/086855 Al, which are both incorporated herein in their entirety by this reference.

The position of the second structure 13 relative to the first structure 12 perpendicular to the optical axis O is controlled by selectively varying the temperatures of the SMA wires 14i, 142, 143, 144. This is achieved by passing selective drive signals through the SMA wires 14i, 142, 143, 144 that provide resistive heating. Heating is provided directly by the drive current. Cooling is provided by reducing or ceasing the drive current to allow the SMA wires 14i,

142, 143, 144 to cool by conduction, convection and radiation to its surroundings.

In operation, the SMA wires 14i, 142, 143, 144 are selectively driven to move the second structure 13 relative to the first structure 12 (or vice versa) in any lateral direction (i.e., a direction within a plane parallel to first and second axes x, y and perpendicular to the optical axis O and primary axis z).

Further details are also provided in WO 2013/175197 Al, which is incorporated herein by this reference.

Taking the example of the set of four SMA wires 14i, 142, 143, 144, the SMA wires 14i, 142, 143, 144 have an arrangement in a loop at different angular positions around the optical axis O (corresponding here to the primary axis z) to provide two pairs of opposed SMA wires 14i & 143, 142 & 144 that are substantially perpendicular to each other. Thus, each pair of opposed SMA wires 14i & 143, 142 & 144 is capable on selective driving of moving the second structure 13 in one of two perpendicular directions orthogonal to the optical axis O. As a result, the SMA wires 14i, 142, 143, 144 are capable of being selectively driven to move the second structure 13 relative to the first structure 12 to any position in a range of movement in a plane orthogonal to the optical axis O. Another way to view this movement is that contraction of any pair of adjacent SMA wires (e.g. SMA wires 143, 144) will move the second structure 13 in a direction bisecting the pair of SMA actuator wires (diagonally in Fig. 3). Another way to view this movement is that contraction of any pair of adjacent SMA wires (e.g. SMA wires 143, 144) will move the second structure 13 in a direction bisecting the pair of SMA actuator wires (diagonally in Fig. 3). Moreover, the SMA wires 14i, 142, 143, 144 are capable of being actuated to generate torque about an axis parallel to the primary axis z. In particular, contraction of one pair of opposite SMA wires (e.g. SMA wires 14i, 143) will produce a torque on the second structure 13 in one sense about an axis parallel to the primary axis z, and contraction of the other pair of opposite SMA wires (e.g. SMA wires 142, 144) will produce a torque in the other sense. The generation of torque and a resulting rotation may be substantially independent of the translations along directions parallel to the first and/or second axes x, y, at least over a part of the range of motion of the drive arrangement 11. The magnitude of the range of movement depends on the geometry and the range of contraction of the SMA wires 14i, 142, 143, 144 within their normal operating parameters.

On heating of one of the SMA wires 14i, 142, 143, 144, the stress in the SMA wire 14i, 142, 143, 144 increases and it contracts, causing movement of the second structure 13 relative to the first structure 12. A range of movement occurs as the temperature of the SMA increases over a range of temperature in which there occurs the transition of the SMA material from the Martensitic phase to the Austenitic phase. Conversely, on cooling of one of the SMA wires 14i, 142, 143, 144 so that the stress in the SMA wire 14i, 142, 143, 144 decreases, it expands under the force from opposing ones of the SMA wires 14i, 142, 143, 144 (and in some examples also biasing forces from one or more biasing means such as springs, armatures and so forth). This allows the second structure 13 to move in the opposite direction relative to the first structure 12.

The SMA wires 14i, 142, 143, 144 may be made of any suitable SMA material, for example Nitinol or another titanium-alloy SMA material.

The drive signals for the SMA wires 14i, 142, 143, 144 are generated and supplied by the control circuit implemented in the IC 7. For example, if the first structure 12 is fixed to (or part of) the support structure 4 and the second structure 13 is fixed to (or part or) the lens assembly 3, then the drive signals are generated by the control circuit in response to output signals of the gyroscope sensor (not shown) so as to drive movement of the lens assembly 3 to stabilise an image focused by the lens assembly 3 on the image sensor 6, thereby providing OIS. The drive signals may be generated using a resistance feedback control technique, for example as described in WO 2014/076463 Al, which is incorporated herein by this reference.

Each of the SMA wires 14i, 142, 143, 144 corresponds to a length of shape memory alloy wire over which a drive current may be controlled independently.

A pair of lengths of shape memory alloy wire may be provided by a single physical wire having a first current source connected to one end, a second current source connected to the other end and a current return connection at a point between the two ends. For example, in the first drive arrangement 11, the first and second SMA wires 14i, 142 may be provided by a single physical wire, with a current return provided through the second structure 13.

Referring also to Figure 4, an example of a "flat" SMA actuator assembly 15 implementing the first drive arrangement 11 is shown.

In the flat actuator assembly 15 the first structure 12 takes the form of a flat, annular plate 16 having a rectangular outer perimeter (or "outer edge") and a circular inner perimeter (or "inner edge"), whilst the second structure 13 takes the form of a flat, thin annular sheet 17 with a rectangular outer perimeter and a circular inner perimeter. The first structure 12 in the form of the plate 16 is supported on a base 5 in the form of a rectangular plate. The four SMA wires 14i, 142, 143, 144 are each attached at one end to respective first crimps 18i,

I82, I83, I84 (also referred to as "static" crimps) which are fixedly attached to (or formed as part of) the first structure 12, 16. The other end of each SMA wire 14i, 142, 143, 144 is attached to a respective second crimp 19i, 192, 193, 194 (also referred to as a "moving" crimp) which is fixedly attached to (or formed as part of) the second structure 13, 17.

The plate 16 and the sheet 17 may each take the form of respective patterned sheets of metal, e.g., etched or machined stainless steel, and may be coated with an electrically-insulating dielectric material. The plate 16 and the sheet 17 are each provided with a respective central aperture aligned with the optical axis O allowing the passage of light from a lens assembly 3 mounted to the sheet 17 to an image sensor 6 supported on the base 5.

The four SMA wires 14i, 142, 143, 144 may be perpendicular to the optical axis O or inclined at a small angle to a plane perpendicular to the optical axis O. Generally, in a set, the four SMA wires 14i, 142, 143, 144 are non-collinear.

The flat actuator assembly 15 includes a number of plain bearings (not shown in Figure 4) spaced around the optical axis O to bear the second structure 13, 17 on the first structure 12, 16. Preferably, at least three bearings are used in order to assist in providing stable support, although in general, a different number of bearings may be used. Each plain bearing (not shown in Figure 4) may take the form of a bearing member in the form of cylinder, and may be attached to, or formed as part of, the first structure 12. The plain bearings (not shown in Figure 4) may be made from a suitable metal or alloy such as phosphor bronze or stainless steel with a diamond-like carbon coating. The plain bearings (not shown in Fig. 4) may be made from, or may include an upper layer or coating of, a polymer such as Polyoxymethylene (POM, Acetal), Polytetrafluoroethylene (PTFE), or PTFE impregnated POM. The plain bearings (not shown in Fig. 4) may be made from, or may include an upper layer or coating of Stainless steel or phosphor bronze with coatings of Titanium Carbide, Tungsten Carbon Carbide, Diamond Like Coating (DLC), Chromium Carbide DLC. These bearing materials may interface with a second bearing surface formed of one of these bearing materials, which could be polished or stamped to reduce the effects of friction generated by surface texture.

The flat actuator assembly 15 will generally also include biasing means (not shown) such as one or more springs or flexure arms arranged and configured to maintain the first and second structures 12, 13 in contact (via the plain bearings) and/or to urge the first and second structures 12, 13 towards a neutral (for example central) relative position when the SMA wires 14i, 142, 143, 144 are not powered.

Details relevant to manufacturing actuator assemblies similar to the flat actuator assembly 15 can be found in WO 2016/189314 A1 which is incorporated herein in its entirety this reference.

Although not shown in Figure 4, the flat actuator assembly 15 may be provided with end stops to provide limits on lateral movement of the second structure 13 relative to the first structure 12. In this way, the SMA wires 14i, 142, 143, 144 can be protected from overextension resulting from, for example, impacts to which a device (not shown) incorporating the flat actuator assembly 15 may be subjected (for example being dropped). The first drive arrangement 11 can drive translations Tx, Ty along first and/or second axes x, y and rotations Rz about an axis parallel to the primary axis z (which is substantially parallel to the optical axis O). Each of these motions Tx, Ty, Rz is substantially independent of the others, at least over a part of a range of motion of the first drive arrangement. However, in order to provide translation Tz parallel to the primary axis z, the first drive arrangement 11 must be combined with at least one bearing capable of converting a torque applied about the optical axis O into a combination of rotation Rz and translation Tz (a helical movement [Tz, Rz] as described hereinafter).

Referring also to Figures 5A to 5C, a second type of drive arrangement 20 which may be included in SMA actuator assemblies 2 is shown schematically.

The second drive arrangement 20 is similar to the first drive arrangement 11 except that the first structure 12 includes a base 21 and a pair of first and second upstanding pillars 22i, 222, and that the SMA wires 14i, 142, 143, 144 are not substantially confined to a plane perpendicular to the primary axis z.

Figure 5A shows the second drive arrangement 20 viewed from above, along a direction parallel to the primary axis z.

Figure 5B shows the second drive arrangement 20 viewed from the side, along a direction parallel to the first axis x. Note that the fourth SMA wire 144 has been superimposed on Figure 5B for visual purposes, even though the fourth SMA wire 144 would be largely obscured behind the second structure 13.

Figure 5C shows the second drive arrangement 20 viewed from the side, along a direction parallel to the second axis y. Note that the first SMA wire 14i has been superimposed on Figure 5B for visual purposes, even though the first SMA wire 14i would be largely obscured behind the second structure 13.

The base 21 extends beyond the edges of the second structure 13 when viewed along the primary axis (Figure 5A), and in this example is rectangular (or square). The first pillar 22i is upstanding from a first corner of the base 21, and the second pillar 222 is upstanding from a second corner, diagonally opposite across the second structure 13.

The first SMA wire 14i connects from a lower portion (lower along the primary axis z) of the second structure 13 to an upper portion (higher along the primary axis z) of the first pillar 22i. The second SMA wire 142 connects from an upper portion of the second structure 13 to a lower portion of the second pillar 222.

The third SMA wire 143 connects from a lower portion of the second structure 13 to an upper portion of the second pillar 222. The fourth SMA wire 142 connects from an upper portion of the second structure 13 to a lower portion of the first pillar 22i.

In this way, the first SMA wire 14i opposes the third SMA wire 143 in a direction parallel to the first axis x, the second SMA wire 142 opposes the fourth SMA wire 144 in a direction parallel to the second axis y, and the first and third SMA wires 14i, 143 oppose the second and fourth SMA wires 142, 144 in a direction parallel to the primary axis z.

In this way, the second drive arrangement 20, using four angled (non-coplanar) SMA wires 14i, 142, 143, 144, may provide drive corresponding to Tx, Ty, Tz, Rx, Ry, Rz motions. The motions are not fully independent degrees of freedom, and in general translations will be linked to rotations, for example [Tx, Rx], [Ty, Ry] and [Tz, Rz], with the specific couplings depending on the angles of the SMA wires 14i, 142, 143, 144.

The SMA wires 14i, 142, 143, 144 are preferably inclined at an angle of between 10 and 25° relative to a plane perpendicular to the primary axis z.

Either or both of the first structure 12, 21 and the second structure 13 may include central apertures to permit light from a lens assembly 3 to form an image on an image sensor 6.

One of more of the motions driven by the first or second drive arrangements 11, 20 may be fully or partly constrained by mechanically coupling one or more bearings between the first and second structures 12, 13. Bearings

In general, a SMA actuator 2 according to this specification will include at least one of the first and second drive arrangements 11, 20 and also an arrangement of one or more mechanical bearings (also referred to as a "bearing arrangement") serving to support, constrain and/or convert the movements generated by the first or second drive arrangement 11, 20.

Referring also to Figure 6, a two-bar link bearing 1001 is shown.

The two-bar link bearing 1001 includes first and second rigid portions 1002i, 10022 connected by first and second beam portions 1003i, 10032 (also referred to as flexures) The rigid portions 1002i, 10022 are each elongated in a direction parallel to the first axis x, and are spaced apart from one another in a direction parallel to the second axis y. The beam portions 1003i, 10032 are each elongated in a direction parallel to the second axis y, and are spaced apart from one another in a direction parallel to the first axis x. The beam portions 1003i, 10032 are shown as being perpendicular to the rigid portions 1002i, 10022, however this is not essential and any angle will work provided that the beam portions 1003i, 10032 are parallel to one another. The beam portions 1003i, 10032 are unable to rotate about the joints with the rigid portions 1002i, 10022, for example the connections are not pin-jointed or similar.

The relative flexural rigidities of the beam portions 1003i, 10032 and the rigid portions 1002i, 10022 are selected (primarily using the dimensions and shapes of cross-sections) so that if the first rigid portion 1002i is clamped, the second rigid portion 10022 may move relative to the first rigid portion 1002i via bending of the beam portions 1003i, 10032 in the x-y and/or x-z planes. In this way, the two-bar link 1001 is able to provide for relative movements Tx, Tz, Rx and Ry between the first and second rigid portions 1002i, 10022. A deformed state in which the second rigid portion 10022 is displaced by a distance d parallel to the first axis is also shown in Figure 6 using dashed lines. The two-bar link bearing 1001 may be rotated 90 degrees to provide movement Ty parallel to the second axis y instead of Tx. The relative resistance to bending in x-y versus y-z planes may be controlled by using the cross-sectional shape of the beam portions 1003i, 10032 to select relative flexural rigidities.

Referring also to Figure 7A, a tiltable z-flexure in the form of a two-by-two parallel bar link bearing 1004 (also referred to as a simple flexure) is shown.

The simple flexure 1004 includes a central portion 1005 and two pairs of beam portions (or flexures) 1006i, IOO62, IOO63, IOO64. Each beam portion (or flexure) IOO61, IOO62, IOO63, IOO64 is rigidly connected to the central portion 1005 at one end, and has a second, free end 1007i, 10072, 10073, 10074. In some examples the central portion 1005 may also have a central aperture 1009 (Figure 8). The first and third beam portions (flexures) IOO61, IOO63 are elongated in a direction parallel to the first axis x, and are able to deform by beam bending in the x-z plane. Similarly, the second and fourth beam portions (flexures) IOO62, IOO64 are elongated in a direction parallel to the second axis y, and are able to deform e.g. by beam bending in the y-z plane. Deflection of beam portions (or flexures) IOO61, IOO62, IOO63, IOO64 laterally (perpendicular to the primary axis z) is constrained by the connection of all the beam portions (or flexures) IOO61, IOO62, IOO63, IOO64 to the central portion 1005 and/or by the cross-sectional shapes of the beam portions IOO61, IOO62, IOO63, IOO64.

In this way, if the free ends 1007 are clamped, the simple flexure 1004 is able to provide for relative movements Tz, Rx and/or Ry between the central portion 1005 and the clamped free ends 1007.

Referring also to Figure 7B, a deformed state 1004b of the simple flexure of Figure 7A is shown in which the central portion 1005 is displaced by a distance d parallel to the primary axis z.

Referring also to Figure 8, a second simple flexure (tiltable z-flexure) 1008 is shown.

The second simple flexure 1008 is the same as the simple flexure 1004, except that the central portion 1005 includes a central aperture 1009, that the ends of the beam portions 1006i, IOO62, IOO63, IOO64 not connected to the central portion 1005 are connected to an outer annulus 1010, and that the beam portions IOO61, IOO62, IOO63, IOO64 are curved instead of straight. The second simple flexure 1008 functions in substantially the same way as the simple flexure 1004. In particular, if the outer annulus is clamped, then the central portion 1005 may move in Tz, Rx and/or Ry.

The presence or absence of a central aperture 1009 in the second simple flexure 1008 or the simple flexure 1004 may depend on the position within a device, for example the camera 1. A simple flexure 1004, 1008 located below the image sensor 6 will not generally require a central aperture 1009, whereas a simple flexure 1004, 1008 located above the image sensor 6 will generally require a central aperture 1009.

Referring also to Figure 9, a z-flexure 1011 is shown.

The z-flexure includes a pair of simple flexures 1004i, 10042 disposed perpendicular to the primary axis z (when not deformed), and spaced apart in a direction parallel to the primary axis z by a rigid structure 1012 sandwiched between the pair of simple flexures 1004i, 10042. The simple flexures 1004i, 10042 are fixed to opposed faces of the rigid structure 1012. The simple flexures 1004i, 10042 each include a central aperture 1009. The illustration in Figure 9 shows the rigid structure 1012 fixed to one of the simple flexures 1004i and detached from the other simple flexure 10042 for visual purposes, though in use both simple flexures 1004i, 10042 are fixed to the rigid structure 1012. Dashed lines in Figure 9 illustrate the projected outline of the rigid structure 1012.

In this way, each individual beam portion 1006 of each simple flexure 1004i, 10042 may deflect. However, the separation of the simple flexures 1004i, 10042 in a direction parallel to the primary axis z and the fixed connection via the rigid structure 1012 constrains movements Tx, Ty, Rx, Ry, Rz whilst guiding movement Tz in a direction parallel to the primary axis z. In this example the rigid structure 1012 is a hollow cylinder having an inner diameter equal to the diameter of the central apertures 1009. However, the rigid structure 1012 may have any shape suitable for spacing the simple flexures apart parallel to the primary axis z and compatible with an intended application of an actuator.

Referring also to Figures 10A and 10B, a first planar bearing 1064 (also referred to as a three-point bearing) is shown.

Figure 10A is a side view and Figure 10B is an exploded projection view.

The first planar bearing 1064 includes a first plate 1065 which slides in contact with a second plate 1066. The first plate 1065 supports at least three cylindrical protrusions 1067 including at least first 1067i, second 10672 and third 10673 cylindrical protrusions which are not co-linear, for example arranged at the points of a triangle. The second plate 1066 is urged into contact with the flat surfaces of the cylindrical protrusions 1067 by biasing means (not shown in Figures 10A and 10B), and is free to slide in a plane parallel to the first and second axes x, y, and to rotate about an axis parallel to the primary axis z. In this way, the relative motions between the first plate 1065 and the second plate 1066 correspond to Tx, Ty and/or Rz. Unless a biasing force urging the plates 1065, 1066 together is overcome, the movements Tz, Rx and Ry are constrained.

In the example shown in Figures 10A and 10B, both plates 1065, 1066 take the form of an annulus having a rectangular outer perimeter and a circular inner perimeter defining a central aperture 1009. However, the shape of the plates 1065, 1066 is not relevant to the function of the first planar bearing 1064, and any shapes of plate may be used instead. Although three cylindrical protrusions 1067i, 10672, 10673 are shown in Figures 10A and 10B, in general any number of cylindrical protrusions greater than or equal to three may be used. The flat actuator assembly 15 (Figure 4) is one example which includes an implementation of a first planar bearing 1064.

Referring also to Figure 11, a second planar bearing 1068 is shown. The second planar bearing 1068 is the same as the first planar bearing 1064, except that the cylindrical protrusions 67 are replaced by ball bearings 1030i, 10302, 10303. The first plate 1065 may also be replaced with a third plate 1069 including recesses 1070i, 10702, 10703, for example circular indents, for receiving corresponding ball bearings 1030i, 10302, 10303. The second planar bearing 1068 functions in the same way as the first planar bearing 1064, except that the second planar bearing 1068 is a rolling bearing instead of a plain bearing.

Referring also to Figure 12, an example of a helical flexure bearing 1090 is shown.

The helical flexure bearing 1090 includes a circular annulus 1091 having a central aperture 1009 and connected to three or more (preferably four or five) helical beam portions 1092. In the example shown in Figure 12, there are four helical beam portions 1092i, 10922, 10923, 10924. At the end not connected to the circular annulus, each helical beam portion 1092i, 10922, 10923, 10924 is connected to a pad 1093i, 10932, 10933, 10934, for example for connection to a layer or structure below (in relation to the primary axis z as drawn) the circular annulus 1091.

Each helical beam portion 1092i, 10922, 10923, 10924 is approximately tangential to the circular annulus 1091 (in the same sense) and its span includes both a first component parallel to the plane containing the first and second axes x, y and a second component parallel to the primary axis z. If the pads 1093i, 10932, 10933, 10934 are clamped and a force is exerted upwards (positive z direction) on the circular annulus 1091, then in response the helical beam portions 1092i, 10922, 10923, 10924 will deflect in the direction of that force. However, in doing so, the ends connected to the circular annulus are also deflected closer the respective pad 1093i, 10932, 10933, 10934, causing the circular annulus 1091 to rotate clockwise about an axis parallel to the primary axis z. Conversely, a force exerted downwards (negative z direction) on the circular annulus 1091 will result in both a downwards movement of the circular annulus 1091 and also an anti-clockwise (counter-clockwise) rotation of the circular annulus 1091.

In this way, the helical flexure bearing 1090 acts to convert a relative displacement parallel to the primary axis z into a rotation about the primary axis z and to convert a rotation about the primary axis z into a relative displacement parallel to the primary axis z. However, the movements are not independent of one another, and relative to clamped pads 1093i, 10932, 10933, 10934 the circular annulus 1091 is constrained to move along an approximately helical path. Since this does not reflect independent degrees-of-freedom, the motion will be denoted as [Tz, Rz] to highlight the relationship between translation Tz parallel to the primary axis z and rotation Rz about the primary axis z for this bearing type.

Although the helical beam portions 1092i, 10922, 10923, 10924 shown in Figure 12 are curving, in other examples of helical flexure bearings 1090 the helical beam portions 1091 may be straight. Further examples of helical flexure bearings 1090 are described in WO 2019/243849 Al, the contents of which are incorporated herein by reference in their entirety. Figures 19 to 22 of WO 2019/243849 Al and the accompanying description on page 22, line 23 to page 23, line 24 are particularly relevant to helical flexure bearings 1090. Additional examples of implementing helical flexure bearings 1090 are also shown and described hereinafter.

Referring also to Figure 13, an under-constrained helical bearing 1099 is shown. Occluded features are shown using dashed lines.

The unconstrained helical bearing 1099 includes a first plate 1100 supporting first to fourth ramps llOli, IIOI2,IIOI3,IIOI4, and a second plate 1102 supporting fifth to eight ramps IIOI5, 11016, IIOI7, llOls. The first plate 1100 takes the form of an annulus having a rectangular outer perimeter and a circular inner perimeter defining a central aperture 1009. The first to fourth ramps llOli, IIOI2,IIOI3,IIOI4 are arranged in a loop around the central aperture 1009. Similarly, the second plate 1102 takes the form of an annulus having a rectangular outer perimeter and a circular inner perimeter defining a central aperture 1009, and the fifth to eight ramps llOls, 11016, IIOI7, 1101s are arranged in a loop around the central aperture 1009.

Biasing means (not shown) urge the plates 1100, 1102 together so that a sloped surface of the first ramp llOli contacts a sloped surface of the fifth ramp llOls. Similarly, the second ramp IIOI2 contacts the sixth ramp 11016, the third ramp IIOI3 contacts the seventh ramp IIOI7 and the fourth ramp llO contacts the eighth ramp llOls. If the first and second plates 1100, 1102 are rotated Rz relative to one another about the primary axis z, then the ramps 1101 act to move Tz the first and second plates 1100, 1102 further apart along the primary axis z. In this way, the under-constrained helical bearing 1099 provides helical motion [Tz, Rz].

Additionally, a force urging the second plate 1102 parallel to the first axis x relative to the first plate 1100 will cause movement Tx parallel to the first axis x but also some rotation Rx about an axis parallel to the first direction x. For example, if the first plate 1100 is clamped, then translation in the positive x direction will cause the seventh and eighth ramps IIOI7, 1101s to be raised parallel to the third primary z whilst the fifth and sixth ramps llOls, 11016 are either lowered, or stay at the same level contacting the first plate 1100 (depending on ramp 1101 configurations). To denote the link between these motions, they will be denoted [Tx, Rx]. Similarly, linked motions [Ty, Ry] relative to the second axis y will result from a force urging the second plate 1102 parallel to the second axis y relative to the first plate 1100.

Although illustrated and described in particular orientations with respect to a set of right-handed Cartesian axes x, y, z for reference, any of the bearings described hereinbefore may be oriented at an arbitrary angle.

The bearings described hereinbefore may be formed of any suitable materials and using any suitable fabrication methods. For example, plate- or sheet-like components may be fabricated from metal sheets, for example stainless steel, with patterning provided by chemical or laser etching. Milling or stamping could be used provided that this does not unacceptably introduce residual strains causing distortion of parts. After patterning, such parts may be bent or pre- deformed as needed. Complex three-dimensional parts may be built up by attaching parts to plates, sheets or other parts, for example using adhesive, welding, brazing, soldering and so forth. Alternatively, complex three- dimensional parts may be formed by, for example, sintering or die-casting of metals, or by injection moulding of polymers. Any bearing surfaces may be made from, or may include an upper layer or coating of, a polymer such as Polyoxymethylene (POM, Acetal), Polytetrafluoroethylene (PTFE), or PTFE impregnated POM. Any bearing surfaces may be made from, or may include an upper layer or coating of Stainless steel or phosphor bronze with coatings of Titanium Carbide, Tungsten Carbon Carbide, Diamond Like Coating (DLC), Chromium Carbide DLC. These bearing materials may interface with a second bearing surface formed of one of these bearing materials, which could be polished or stamped to reduce the effects of friction generated by surface texture.

First combined OIS and AF actuator assembly

Referring also to Figures 14 to 18, a first combined OIS and AF actuator assembly 23 (hereinafter the first actuator assembly) is shown.

Figure 14 shows an exploded projection view of the first actuator assembly 23, Figure 15 shows a projection view, Figure 16 is a top view, Figure 17 is a side view, and Figure 18 is a schematic.

Referring in particular to Figure 18, the first actuator assembly 23 includes a first part 24 and a second part 25. A bearing arrangement 26 mechanically couples the first part 24 to the second part 25. The first actuator assembly 23 also includes a drive arrangement 11, 20 including a total of four shape memory alloy wires 14i, 142, 143, 144, connecting (or coupling) the second part 25 to the first part 24. In the example shown in Figures 14 to 17, the second drive arrangement 20 is used. However, depending on the configuration of the bearing arrangement 26, the first drive arrangement 11 could also be used (Figures 19 and 20).

The drive arrangement 11, 20 and the bearing arrangement 26 are configured such that the first part 24 is movable Tz towards or away from the second part 25 along a primary axis z passing through the first actuator assembly 23, and such that the first part 24 is tiltable (rotatable) Rx, Ry relative to the second part 25 (or vice versa) about first and/or second axes x, y which are not parallel, and which are perpendicular to the primary axis z. The first and second axes x, y may pass through a pivot point. Depending on the specific configuration, the pivot point may be coincident with the first part 24, the second part 25, or offset from both along the primary axis z. A tilt Rx, Ry may refer to small rotation, for example a rotation of less than or equal to 10 degrees, 5 degrees, or 1 degree about the respective axis x, y.

The bearing arrangement 26 is configured to guide movement Tz of the first part 24 relative to the second part 25 along the primary axis z, and to guide tilting of the first part 24 relative to the second part 25 (or vice versa) about the first axis x and/or the second axis y. The bearing arrangement 26 is also configured to constrain movement Tx, Ty of the first part 24 relative to the second part 25 along the first axis x and/or the second axis y, and to constrain rotation Rz of the first part 24 relative to the second part 25 about the primary axis z.

Referring in particular to Figures 14 to 17, one example implementation of the first actuator assembly 23 is shown in greater detail.

The first actuator assembly 23 includes a second part 25 in the form of a rectangular plate 27. First and second pillars 28i, 282 extend upwards (relative to the primary axis z) from diagonally opposed corners of the plate 27. The plate 27 and pillars 28i, 282 may correspond to the base 21 and pillars 22i, 222 of a second drive arrangement 20. Each pillar 28i, 283 has a cross-section in the form of a rectangle with one corner truncated (or bevelled). Each pillar 28i, 282 has a first face 29 substantially perpendicular to the second axis y and a second face 30 substantially perpendicular to the x axis. As shown in Figures 16 and 17, an image sensor 6 may be mounted to the centre of the rectangular plate 27 (second part 25).

In this example, the bearing arrangement 26 includes a first bearing 31 in the form of a modified simple flexure. Similar to the simple flexure 1004 and the second simple flexure 1008, the first bearing 31 includes four beam portions IOObi, 10062, 10063, 10064. The first beam portion 1006i extends substantially parallel to the first axis x (in a positive direction +x) from the second face 30i of the first pillar 28i. The second beam portion IOO62 extends substantially parallel to the second axis y (in a positive direction +y) from the first face 292 of the second pillar 282. The distal ends of the first and second beam portions IOO61,

10062 are connected by a first elbow joint 32i.

The third beam portion IOO63 extends substantially parallel to the first axis x (in a negative direction -x) from the second face 302 of the second pillar 282. The fourth beam portion IOO64 extends substantially parallel to the second axis y (in a negative direction -y) from the first face 29i of the first pillar 28i. The distal ends of the third and fourth beam portions IOO63, IOO64 are connected by a second elbow joint 322.

The first part 24 takes the form of an annular sheet 33 having a circular inner perimeter defining a central aperture 1009 and an outer perimeter having the general shape of a rectangle with truncated (or bevelled) corners. The annular sheet 33 could alternatively be described as having an (irregular) octagonal outer perimeter. The annular sheet 33 provides a lens carriage 9 for mounting one or more lenses 10. The annular sheet 33 is fixed to the elbow joints 32i,

322 of the first bearing 31, for example by welding, adhesive, or other suitable attachment methods. When assembled, the first and third beam portions IOO61,

10063 bracket the annular sheet 33 along the second axis y, whilst the second and fourth beam portions IOO62, IOO64 bracket the annular sheet 33 along the first axis x.

First and second wire coupling structures 34i, 342 extend from diagonally opposed corners of the annular sheet 33 (first part 24). When the first actuator assembly 23 is assembled, the wire coupling structures 34i, 342 will corresponding to corners not occupied by the pillars 28i, 282. Each wire coupling structure 34i, 342 takes the form of a pillar extending both above and below (relative to the primary axis z) the annular sheet 33. The wire coupling structures 34i, 342 take the form of a trapezoidal prisms oriented with the trapezoidal cross sections perpendicular to the primary axis z. Each wire coupling structure 34i, 342 includes an inner face 35 corresponding to the shorter of the parallel trapezium sides, a first face 36 corresponding to an angled side substantially perpendicular to the second axis y, and a second face 37 corresponding to an angled side substantially perpendicular to the first axis x. Other shapes of wire coupling structures 34i, 342 providing the same functions may be used instead of the illustrated trapezoidal prisms. Note that dashed lines outlining structures occluded by the first pillar 34i are shown in Figure 14 for visual purposes.

Once the annular sheet 33 has been fixed to the elbow joints 32i, 322, the first SMA wire 14i is connected from an upper region (relative to the primary axis z) of the second face 37i of the first wire coupling structure 34i to a lower region (relative to the primary axis z) of the second face 30i of the first pillar 28i. The second SMA wire 142 is connected from a lower region (relative to the primary axis z) of the first face 36i of the first wire coupling structure 34i to an upper region (relative to the primary axis z) of the first face 292 of the second pillar 282. The third SMA wire 143 is connected from an upper region (relative to the primary axis z) of the second face 372 of the second wire coupling structure 342 to a lower region (relative to the primary axis z) of the second face 302 of the second pillar 282. The fourth SMA wire 144 is connected from a lower region (relative to the primary axis z) of the first face 362 of the second wire coupling structure 342 to an upper region (relative to the primary axis z) of the first face 29i of the first pillar 28i. This arrangement corresponds to an implementation of the second drive arrangement 20.

The second drive arrangement 20 may cause movement Tz of the first part 24 towards the second part 25 along the primary axis z by contracting the first and third SMA wires 14i, 143 to provide a net downward force. Similarly, the second drive arrangement 20 may cause movement Tz of the first part 24 away from the second part 25 along the primary axis z by contracting the second and fourth SMA wires 142, 144 to provide a net upward force. In either case, a torque about the primary axis z is also generated, but a rotation Rz about the primary axis z is constrained by the rigid connection of the beam portions IOO61, IOO62, IOO63, IOO64 to the annular sheet 33. Such combinations of contractions do not apply net torque about the first or second axes x, y. The second drive arrangement 20 may cause tilting Rx', Ry' about first and/or second rotated axes x', y'. The rotated axes x', y', z are rotated 45 degrees anti-clockwise (counter-clockwise) about the primary axis z compared to the axes x, y, z referred to when describing the geometry of the first actuator assembly 1023.

The first and second SMA wires 14i, 142 may be contracted to cause clockwise tilting Rx' of the first part 24 relative to the second part 25 about the rotated first axis x'. Similarly, the third and fourth SMA wires 143, 144 may be contracted to cause anti-clockwise tilting Rx' of the first part 24 relative to the second part 25 about the rotated first axis x'. In either case, there is no net force along the primary axis z.

The second and third SMA wires 142, 143 may be contracted to cause clockwise tilting Ry' of the first part 24 relative to the second part 25 about the rotated second axis y'. Similarly, the first and fourth SMA wires 14i, 144 may be contracted to cause anti-clockwise tilting Ry' of the first part 24 relative to the second part 25 about the rotated second axis y'. In either case, there is no net force along the primary axis z.

The tilting Rx', Ry' is about an implied pivot point at the centre of the beam portions 1006i, IOO62, IOO63, IOO64. A general motion may be broken down in components Rx', Ry', Tz of these motions.

In this way, the first actuator assembly 23 may provide an OIS function based on tilting Rx' and/or Ry', and an AF function based on the translation Tz along the primary axis z, using a drive arrangement 20 including a total of 4 SMA wires 14i, 142, 143, 144. The two functions may be substantially independent, across at least part of a range of motion.

Although explained with reference to the specific example shown in Figures 14 to 17, the first actuator assembly 23 may be varied through a large number of permutations to provide the same functionality. Although the first actuator assembly 23 has been explained with the plate 27 (second part 25) corresponding to a support structure 4 of a camera and the annular sheet 33 (first part 24) corresponding to a lens carriage 9 of a lens assembly 3, the roles may be reversed so that the second part 25 corresponds to a lens carriage 9 and the first part 24 provides a support structure 4. Equally, the first actuator assembly 23 need not be restricted to use in a camera 1, and the first and second parts 24, 25 may be any parts requiring the relative motions Rx, Ry and/or Tz.

The plate 27 and the sheet 33 may each take the form of respective patterned sheets of metal, e.g., etched or machined stainless steel, and may be coated with an electrically-insulating dielectric material. Either or both of the plate 27 and the sheet 33 may be provided with a respective central aperture 1009.

Although shown in Figures 14 to 17 using a particular first bearing 31, in general the first bearing 31 may include a first pair of flexures, and a second pair of flexures. Each flexure of the first pair may extend in a direction substantially parallel to the first axis x and couple the second part 25 to the first part 24, with the first pair of flexures being spaced apart in a direction parallel to the second axis y to bracket the first part 24. Each flexure of the second pair may extend in a direction substantially parallel to the second axis and couple the second part 25 to the first part 24, with the second pair of flexures being spaced apart in a direction parallel to the first axis x to bracket the first part 24. Each flexure of the first pair and the second pair should be configured to be compliant in a direction corresponding to movement Tz of the first part 24 relative to the second part 25 along the primary axis z.

One or more, or all of the first and/or second pair of flexures may be flat. One or more, or all of the first and/or second pair of flexures may include at least one bend (or "turn" or "elbow"). One or more, or all of the first and/or second pair of flexures may include a respective arm which may include at least one bend. One or more, or all of the arms may include a first portion extending away from the second part 25 and a second portion running along a respective side of the second part 25. The first and second portions may be straight. The first and second pairs of flexures be co-planar when the flexures are unflexed. The first and second pairs of flexures may be co-planar in a plane perpendicular to the primary axis when the flexures are unflexed. Any two of the first and/or second pairs of flexures may be formed as a single piece. The first and second pairs of flexures may be formed as single piece. The first and second pairs of flexures may be attached or bonded to the first part and/or the second part. The first and second pairs of flexures may be integrally formed with the first part or the second part. The illustrated first bearing 31 is one suitable example, with the first and third beam portions 1006i, IOO63 corresponding to the first pair of flexures and the second and fourth beam portion IOO62, IOO64 corresponding to the second pair of flexures.

Providing the OIS and AF functions using a single drive arrangements 20 including a total of four SMA wires 14i, 142, 143, 144, and requiring no fifth or further SMA wires may advantageously reduce the complexity and/or power consumption of a SMA actuator 2 for a camera 1. Moreover, a second drive arrangement, whether based on SMA wires or other technologies, is neither included nor necessary. Combined AF and OIS may reduce costs of parts, assembly and/or testing. The robustness of the bond/coupling between OIS and AF functions may also be improved. Furthermore, moving electrical connections between a static part and a separate AF drive system moving with the OIS actuation are not required.

Each of the four shape memory alloy wires 14i, 142, 143, 144, corresponds to a section of SMA wire over which a drive current may be controlled independently. For example, a pair of SMA wires (e.g. 14i, 142) may be provided by a single physical wire having a first current source (not shown) connected to one end, a second current source (not shown) connected to the other end and a current return connection (not shown) at a point between the two ends.

As additional advantage of the combined AF and OIS is that the first actuator assembly 23 could potentially be controlled from the output of a single three- axis hall sensor. Such a sensor may be mounted on a static section of the first actuator assembly 23 (either the first or second part 24, 25 depending on the configuration) to avoid potential hysteresis in rotation restraining lens carriage rotation. For example, a magnet (not shown) could be mounted to the first part 24 and a three-axis hall sensor (not shown) could be mounted to the second part 25 in the example shown in Figures 15 to 17.

An advantage of using a first bearing 31 in the form of a simple flexure is that the beam portions 1006 may provide their own restoring forces to urge the first and second parts 24, 25 towards an equilibrium or neutral position when the SMA wires 14 are unpowered. This may avoid the need for separate springs, magnets or other biasing means.

Second combined OIS and AF actuator assembly

Referring also to Figures 19 to 21, a second combined OIS and AF actuator assembly 40 (hereinafter the second actuator assembly) is shown.

Figure 19 shows an exploded projection view of the second actuator assembly 40, Figure 20 shows a projection view, and Figure 21 is a schematic.

Referring in particular to Figure 21, similarly to the first actuator assembly 23, the second actuator assembly 40 includes a first part 24 and a second part 25, coupled together by a bearing arrangement 26 connected in parallel with a drive arrangement 11, 20. The second actuator assembly 40 differs from the first actuator assembly 23 in that either of the first and second drive arrangements 11, 20 may be used, and in that the first bearing 31 is replaced with a second bearing 41.

The second bearing 41 is configured to generate, in response to a torque applied about the primary axis z by the drive arrangement 11, 20, movement of the first part 24 towards or away from the second part 25 along the primary axis z. The second bearing 41 provides this function by guiding helical movement [Tz, Rz] about and along the primary axis z. In other words, the second bearing may mechanically couple a rotation Rz about the primary axis z to a translation Tz along the primary axis z along a helical path [Tz, Rz].

The second bearing 41 is also configured such that a movement Tx of the first part 24 relative to the second part 25 along the first axis x is coupled to a tilting Rx of the first part 24 relative to the second part 25 about the first axis x, and such that a movement Ty of the first part 24 relative to the second part 25 along the second axis y is coupled to a tilting Ry of the first part 24 relative to the second part 25 about the second axis y.

Referring in particular to Figures 19 and 20, the second actuator assembly 40 includes a second part 25 in the form of a flat annular plate 42 having a rectangular outer perimeter and a circular inner perimeter defining a central aperture 1009. The flat annular plate 42 (second part 25) may be supported on a base 5 of a camera 1. First and second pillars 43i 432 are fixed to (or integrated with) diagonally opposed corners of the annular plate 42. The first and second pillars 43i 432 extend in a direction substantially along the primary axis z. The first pillar 43i supports first and fourth static crimps 18i, 184, and the second pillar 432 supports second and third static crimps I82, I83.

The first part 24 takes the form of a flat, thin annular sheet 44 having the same shape as the sheet 17 of the flat actuator arrangement 15. First and second moving crimps 19i, 192 are fixed to one corner of the annular sheet 44, and third and fourth moving crimps 193, 194 are fixed to a diagonally opposite corner. When assembled, the moving crimps 19 are arranged at corners which are not occupied by the pillars 43i, 432. The annular sheet 44 may correspond to, or support, a lens carriage 9 for attachment of one of more lenses 10.

An implementation of the first drive arrangement 11 is completed by connecting first to fourth SMA wires 14i, 142, 143, 144 between respective static crimps I81, I82, I83, I84 and moving crimps 19i, 192, 193, 194.

The second bearing arrangement 41 takes the form of the helical flexure bearing

1090 as described hereinbefore. When assembled, each pad 1093i, 10932, 10933, 10934 is fixed to the plate 42 (second part 25), and the circular annulus

1091 is fixed to the annular sheet 44 (first part 24). Other types of helical flexure may be used as described hereinbefore in relation to the helical flexure bearing 1090 (in relation to Figure 12. Helical flexures typically include an annulus and at least three flexures extending therefrom. Assembly may be completed by fixing a can 8 (screening can) over the second actuator assembly 40 to protect the component parts. An image sensor 6 is mounted on a base 5 to which the plate 42 (second part 25) is fixed, aligned with the central apertures 1009 of the plate 42 and sheet 44.

It may be observed that the second bearing arrangement 41 is in many ways similar to the flat actuator arrangement 15, with the separation along the primary axis z increased and the planar bearing replaced with the second bearing 41.

If the first driving arrangement 11 applies clockwise torque about the primary axis z, each of the helical beam portions 1092 will be deflected upwards (relative to the primary axis z) away from the plate 42 (second part 25), whilst the circular annulus 1091 and attached sheet 44 (first part 24) are moved away from the plate 42 (second part 25) along a helical path [Tz, Rz]. Similarly, an applied anti-clockwise (counter-clockwise) torque will cause the sheet 44 (first part 24) to move towards the plate 42 (second part 25) along the helical path [Tz, Rz] about and along the primary axis z.

If the first driving arrangement 11 applies a net force along the first axis x (in a positive direction +X), then the helical beam portions 1092 will be deflected along the first axis x. For the second and fourth helical beam portions 10922, 10924 this deflection is perpendicular to their extension in a direction of relatively easy compliance. However, deflection of the first helical beam portion 1092i along the first axis is also deflection downwards (relative to the primary axis z), and similarly deflection of the third helical beam portion 10923 along the first axis is also deflection upwards (relative to the primary axis z).

Consequently, the circular annulus 1019 and attached sheet 44 (first part 24) tilt Rx about the first axis x, in addition to a movement Tx along the first axis x.

In an analogous manner, if the first driving arrangement 11 applies a net force along the second axis y, then the sheet 44 (first part 24) tilts Ry about the second axis y, in addition to a movement Ty along the second axis y. The effective pivot point is offset below (relative to the primary axis z) the circular annulus 1091 along the primary axis z. In this way, the second actuator assembly 40 may provide an OIS function based on tilting Rx and/or Ry, and an AF function based on the translation Tz along the primary axis z, using a drive arrangement 11 including a total of 4 SMA wires 14i, 142, 143, 144. The OIS and AF functions may be substantially independent, across at least part of a range of motion.

Although explained with reference to the specific example shown in Figures 19 and 20, the second actuator assembly 40 may be varied through a large number of permutations to provide the same functionality.

Although the second actuator assembly 40 has been explained with the plate 42 (second part 25) corresponding to a support structure 4 of a camera 1 and the sheet 44 (first part 24) corresponding to a lens carriage 9 of a lens assembly 3, the roles may be reversed so that the second part 25 corresponds to a lens carriage 9 and the first part 24 provides a support structure 4. Equally, the second actuator assembly 40 need not be restricted to use in a camera 1, and the first and second parts 24, 25 may be any parts requiring the relative motions Rx, Ry and/or[Tz, Rz].

The plate 42 and the sheet 44 may each take the form of respective patterned sheets of metal, e.g., etched or machined stainless steel, and may be coated with an electrically-insulating dielectric material. Either or both of the plate 42 and the sheet 44 may be provided with a respective central aperture 1009.

Although the example shown in Figures 26 and 27 uses an implementation of the first (flat) drive arrangement 11, the second (angled) drive arrangement 20 may be used instead. The angled drive arrangement 20 may apply a force along the primary axis z in combination with a torque about the primary axis z, which may help with smoother helical movement [Tz, Rz] of the first bearing 28.

Although shown in Figures 19 and 20 with the second bearing 41 in the form of a helical flexure bearing 1090, other types of helical bearings which are partially unconstrained in lateral (perpendicular to the primary axis z) directions may be used. For example, the under-constrained helical bearing 1099 (see Figure 13) may provide the second bearing 41.

Providing the OIS and AF functions using a single drive arrangement 11, 20 including a total of four SMA wires 14i, 142, 143, 144, and requiring no fifth or further SMA wires may advantageously reduce the complexity and/or power consumption of a SMA actuator 2 for a camera 1. Moreover, a second drive arrangement, whether based on SMA wires or other technologies, is neither included nor necessary. Combined AF and OIS may reduce costs of parts, assembly and/or testing. The robustness of the bond/coupling between OIS and AF functions may also be improved. Furthermore, moving electrical connections between a static part and a separate AF drive system moving with the OIS actuation are not required.

Each of the four shape memory alloy wires 14i, 142, 143, 144, corresponds to a section of SMA wire over which a drive current may be controlled independently. For example, a pair of SMA wires (e.g. 14i, 142) may be provided by a single physical wire having a first current source (not shown) connected to one end, a second current source (not shown) connected to the other end and a current return connection (not shown) at a point between the two ends.

As additional advantage of the combined AF and OIS is that the first actuator assembly 23 could potentially be controlled from the output of a single three- axis hall sensor. Such a sensor may be mounted on a static section of the first actuator assembly 23 (either the first or second part 24, 25 depending on the configuration) to avoid potential hysteresis in rotation restraining lens carriage rotation. For example, a magnet (not shown) could be mounted to the first part 24 and a three-axis hall sensor (not shown) could be mounted to the second part 24 in the example shown in Figures 19 and 20.

An advantage of using a second bearing 41 in the form of a flexure is that the helical beam portions 1092 provide their own restoring forces to urge the first and second parts 24, 25 towards an equilibrium or neutral position when the SMA wires 14 are unpowered. This avoids the need for separate springs, magnets or other biasing means. When the second bearing 41 is an under-constrained helical bearing 1099, sloped surfaces of ramp 1101 make an angle of more than zero and less than ninety degrees with a plane parallel to the first and second axes x, y. In such examples, the second actuator 40 will also include one or more biasing means configured to urge the first set of ramps towards the second set of ramps along the primary axis z.

It will be appreciated that there may be many other variations of the above- described embodiments.

In the description hereinbefore, parts have been described as rectangular, and this should be interpreted as encompassing square shapes. In the description hereinbefore, parts have been described as circular, and this should be interpreted as encompassing elliptical shapes.

The first to fourth SMA wires 14i, 142, 143, 144 have been described and shown as directly connecting the first and second parts 24, 25. However, in some examples the first to fourth SMA wires 14i, 142, 143, 144 may indirectly connect the first and second parts 24, 25, for example via one or more intermediate structures (not shown). Intermediate structures (not shown) may be configured to help extend the stroke of one or more SMA wires 14i, 142, 143, 144.

The actuator assembly may be any type of assembly that comprises a first part which is movable with respect to the first part. The actuator assembly may be, or may be provided in, any one of the following devices: a smartphone, a protective cover or case for a smartphone, a functional cover or case for a smartphone or electronic device, a camera, a foldable smartphone, a foldable smartphone camera, a foldable consumer electronics device, a camera with folded optics, an image capture device, an array camera, a 3D sensing device or system, a servomotor, a consumer electronic device, a mobile or portable computing device, a mobile or portable electronic device, a laptop, a tablet computing device, an e-reader, a computing accessory or computing peripheral device, an audio device, a security system, a gaming system, a gaming accessory, a robot or robotics device, a medical device, an augmented reality system, an augmented reality device, a virtual reality system, a virtual reality device, a wearable device, a drone, an aircraft, a spacecraft, a submersible vessel, a vehicle, and an autonomous vehicle, a tool, a surgical tool, a remote controller, clothing, a switch, dial or button, a display screen, a touchscreen, a flexible surface, and a wireless communication device. It will be understood that this is a non-exhaustive list of example devices.

The term 'shape memory alloy (SMA) wire', or length of SMA wire, may refer to any element comprising SMA. The SMA wire may have any shape that is suitable for the purposes described herein. The SMA wire 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 wire. It is also possible that the length of the SMA wire (however defined) may be similar to one or more of its other dimensions. The SMA wire may be pliant or, in other words, flexible. In some examples, when connected in a straight line between two elements, the SMA wire can apply only a tensile force which urges the two elements together. In other examples, the SMA wire may be bent around an element and can apply a force to the element as the SMA wire tends to straighten under tension. The SMA wire may be beam-like or rigid and may be able to apply different (e.g. non-tensile) forces to elements. The SMA wire may or may not include material(s) and/or component(s) that are not SMA. For example, the SMA wire may comprise a core of SMA and a coating of non-SMA material. Unless the context requires otherwise, the term 'SMA wire' may refer to any configuration of SMA wire acting as a single actuating element which, for example, can be individually controlled to produce a force on an element. For example, the SMA wire may comprise two or more portions of SMA wire that are arranged mechanically in parallel and/or in series. In some arrangements, the SMA wire may be part of a larger piece of SMA wire. Such a larger piece of SMA wire might comprise two or more parts that are individually controllable, thereby forming two or more SMA wires.