Field

The present application relates to an actuator assembly, particularly an actuator assembly comprising a plurality of lengths of shape memory alloy (SMA) wire.

Background

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

WO 2019/086855 Al 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 and a second part moveable in a first plane relative to the first part. The actuator assembly also includes a first set of one or more shape memory alloy wires configured to move the second part relative to the first part in the first plane. The first set of shape memory alloy wires are arranged such that movements of the second part are amplified relative to corresponding length changes of the first set of shape memory alloy wires. The actuator assembly also includes a third part moveable in a second plane relative to the second part. The second plane is parallel to, or coplanar with, the first plane. The actuator assembly also includes a second set of one or more shape memory alloy wires configured to move the third part relative to the second part in the second plane. The second set of shape memory alloy wires are arranged such that movements of the third part are amplified relative to corresponding length changes of the second set of shape memory alloy wires.

So, movement of the third part relative to the first part is a combination of movement of the second part relative to the first part and movement of the third part relative to the second part. The second part may be coupled to the first part via the first set of memory alloy wires and the third part may be coupled to the second part via the second set of shape memory alloy wires.

The second part may be constrained to movements within the first plane. The second part may be moveable parallel to a first axis and a second, non-parallel axis within the first plane. The first and second axes may be orthogonal directions within the first plane. The third part may be constrained to movements within the second plane. The third part may be moveable in a pair of orthogonal directions within the second plane.

The actuator assembly may include a first bearing arrangement between the first part and the second part. The first bearing arrangement may be configured to constrain movement of the second part relative to the first part to the first plane. The actuator assembly may include a second bearing arrangement between the third part and the second part. Alternatively, the actuator assembly may include a second bearing arrangement between the third part and the first part. In either case, the second bearing arrangement may be configured to constrain movement of the third part relative to the second part and/or relative to the first part to the second plane.

Movements of a second/third part may be amplified relative to corresponding length changes of a shape memory alloy wire of the respective first/second set by constraining the respective second/third part such that it cannot move directly in a contraction direction of that shape memory alloy wire. Constraint leading to amplification may be provided by one or more other shape memory alloy wires of the respective first/second set. Constraint leading to amplification may be provided by one or more resilient elements. Resilient elements may include, or take the form of, springs. Resilient elements may include, or take the form of, flexures. Constraint leading to amplification may be provided by one or more bearings. Constraint leading to amplification may be provided by a combination of two or more of other shape memory alloy wires of the respective first/second set, one or more resilient elements, one or more springs, one or more flexures, and one or more bearings.

The second part may be moveable in the first plane parallel to a first axis and a second, different axis, relative to the first part. These first and second axes may be orthogonal. Movements of the second part parallel to the first axis may be amplified by a larger factor than movements of the second part parallel to the second axis. So, the first set of shape memory alloy wires may provide asymmetric stroke amplification within the first plane, such that movement of the second part parallel to the first axis is amplified by a larger factor than movement of the second part parallel to the second axis. This allows the first set of shape memory alloy wires to preferentially move the second part along the first axis.

The third part may be moveable in the second plane parallel to the first axis and the second axis, relative to the second part. Movements of the third part parallel to the second axis may be amplified by a larger factor than movements of the third part parallel to the first axis. So, the second set of shape memory alloy wires may provide asymmetric stroke amplification within the second plane, such that movement of the third part parallel to the second axis is amplified by a larger factor than movement of the third part parallel to the first axis. This allows the second set of shape memory alloy wires to preferentially move the third part along the second axis.

So, the first set of shape memory alloy wires may be arranged for preferential amplification along the first axis and the second set of shape memory alloy wires may be arranged for preferential amplification along the second axis.

Alternatively, the third part may be movable parallel to third and fourth non-parallel axes in the second plane relative to the second part. The third and fourth axes may be non-parallel with either of the first and second axes. Movements of the third part parallel to the third axis may be amplified by a larger factor than movements of the third part parallel to the fourth axis.

The actuator assembly may also include a controller configured to control selective contraction of the shape memory alloy wires of the first and second sets so as to move the third part relative to the first part by a first component parallel to the first axis and a second component parallel to the second axis. In particular, the controller may control drive signals supplied to the shape memory alloy wires of the first and second sets.

Control of movement of the second part relative to the first part may be implemented by controlling drive signals supplied to the first set of shape memory alloy wires. Control of movement of the third part relative to the second part may be implemented by controlling drive signals supplied to the second set of shape memory alloy wires. Drive signals may be current controlled. Drive signals may be voltage controlled. The controller may be configured (at least in a first mode) such that the first component corresponds to movement of the second part relative to the first part and the second component corresponds to movement of the third part relative to the second part.

The first component may be provided by controlling selective contraction of the first set of shape memory alloy wires so as to cause the second part to move along the first axis in the first plane relative to the first part. The second component may be provided by controlling selective contraction of the second set of shape memory alloy wires so as to cause the third part to move along the second axis in the second plane relative to the second part. So, movement of the third part along the first axis may be entirely controlled using the first set of shape memory allow wires, and movement of the third part along the second axis may be entirely controlled using the second set of shape memory allow wires. The controller may be configured (at least in the first mode) to control contraction of the shape memory alloy wires such that the second part does not or only negligibly move parallel to the second axis relative to the first part, and such that the third part does not or only negligibly move parallel to the first axis relative to the second part.

Alternatively or additionally, the controller may be configured (at least in a second mode), such that within a first movement envelope the first component corresponds to movement of the second part relative to the first part and the second component corresponds to movement of the third part relative to the second part. The controller may further be configured (at least in the second mode), such that outside the first movement envelope and within a second movement envelope, the first component and/or the second component corresponds to a movement of the second part relative to the first part combined with a movement of the third part relative to the second part.

In other words, the first movement envelope is enclosed within the second movement envelope. A movement envelope corresponds to a locus of points to which, relative to the first part, the second part may be moved using the first and second sets of shape memory alloy wires.

Within the first movement envelope, the first component may correspond exclusively to movement of the second part relative to the first part. Within the first movement envelope, the second component may correspond exclusively to movement of the third part relative to the second part. In other words, within the first locus, the controller may isolate movements of the second and third parts so that the second part and the first set of shape memory alloy wires provide movement along the first axis, whilst the third part and the second set of shape memory alloy wires provide movement along the second axis.

Outside the first movement envelope and within the second movement envelope, the first component may correspond to a superposition of movement of the second part relative to the first part and movement of the third part relative to the second part. Outside the first movement envelope and within the second movement envelope, the second component may correspond to a superposition of movement of the second part relative to the first part and movement of the third part relative to the second part. In other words, the drive circuit may be configured to extend the range of motion of the third part (relative to the first part) beyond the first movement envelope by combining movements of both second and third parts along the same axes.

For example, the first set of shape memory alloy wires may be configured to move the second part (relative to the first part) parallel to first (x) and second (y) axes. The first set of shape memory alloy wires may be configured to amplify movements of the second part parallel to the x-axis more than movements parallel to the y-axis. The second set of shape memory alloy wires may also be configured to move the third part (relative to the second part) parallel to the x- and y-axes.

However, the second set of shape memory alloy wires may be configured to amplify movements of the third part parallel to the y-axis more than movements parallel to the x-axis. In such an example, the first movement envelope may correspond to positions to which the third part can be moved by moving the second part only parallel to the x-axis and moving the third part only parallel to the y- axis. The second movement envelope may correspond to the additional movement obtainable by adding the range of motion of the third part parallel to the x-axis (due to the second set of shape memory alloy wires) to the range of motion of the second part parallel to the x-axis, and adding the range of motion of the second part parallel to the y-axis (due to the first set of shape memory alloy wires) to the range of motion of the third part parallel to the y-axis.

Additionally or alternatively, the controller may be configured (at least in a third mode) such that the first component includes or is selectively one of i) a first movement of the second part relative to the first part parallel to the first axis, and ii) a second movement, smaller than the first movement, of the third part relative to the second part parallel to the first axis. The controller may further be configured (at least in the third mode), such that the second component includes or is selectively one of i) a third movement of the third part relative to the second part parallel to the second axis, and ii) a fourth movement, smaller than the third movement, of the second part relative to the first part parallel to the second axis.

In this way, the controller may move the third part to a position relative to the first part using the most amplified movements of the second and third parts respectively to provide relatively coarse movements, and the less amplified movements of the second and third parts respectively to provide relatively fine movements. The controller may use both of the most amplified and less amplified movements in combination, for example to allow both high stroke movement (with the most amplified movement) and fine control/accurate movement.

Alternatively or additionally, the controller may selectively use either one of the most amplified and less amplified movements, for example depending whether relatively large or relatively small movement is required. The controller may control the first component either by controlling the first set of shape memory alloy wires when relatively large movement along the first axis is required or by controlling the second set of shape memory alloy wires when relatively small movement along the first axis is required. Similarly, the controller may control the second component either by controlling the first set of shape memory alloy wires when relatively small movement along the second axis is required or by controlling the second set of shape memory alloy wires when relatively large movement along the second axis is required.

The controller may be configured to be switchable between at least two of the first, second and third modes.

The actuator assembly may be arranged such that contraction of each shape memory alloy wire of the first set is opposed by one or more other shape memory alloy wires of the first set, and/or contraction of each shape memory alloy wire of the second set is opposed by one or more other shape memory alloy wires of the second set. The controller may control the tension in the shape memory alloy wires of the first and/or second sets. This allows for more accurate and reliably movement control compared to arrangements in which springs or other resilient elements oppose the shape memory alloy wires.

Alternatively, contraction of each shape memory alloy wire of the first set may be opposed by one or more resilient elements, such as springs coupling the first part to the second part. Contraction of each shape memory alloy wire of the second set may be opposed by one or more resilient elements, such as springs coupling the third part to the second part. A resilient element (opposing any SMA wire) may take the form of a coil spring, a flat spring, a leaf spring, a flexure, an element formed of elastomeric material, and so forth.

The first set of shape memory alloy wires may include four shape memory alloy wires in an arrangement in which none of the shape memory alloy wires are collinear. The second set of shape memory alloy wires may include four shape memory alloy wires in an arrangement in which none of the shape memory alloy wires are collinear.

The first set of shape memory alloy wires may include four shape memory alloy wires arranged in a loop. A shape memory alloy wire of the first set may make a different angle to each of a pair of adjoining (around the loop) shape memory alloy wires of the first set. The second set of shape memory alloy wires may include four shape memory alloy wires arranged in a loop. A shape memory alloy wire of the second set may make a different angle to each of a pair of adjoining (around the loop) shape memory alloy wires of the second set. The angle between adjoining (around the loop) shape memory alloys wires may not be 90 degrees. The angle between adjoining (around the loop) shape memory alloys wires may, for example, be between 10 degrees and 80 degrees or between 100 degrees and 170 degrees. Optionally, the angle between adjoining (around the loop) shape memory alloys wires may, for example, be between 20 degrees and 70 degrees or between 110 degrees and 160 degrees.

The four shape memory alloy wires of the first set may be arranged so as to correspond to edges of a diamond shape. The four shape memory alloy wires of the second set may be arranged so as to correspond to edges of a diamond shape. The four shape memory alloy wires of the first set may correspond to edges of a kite shape. The four shape memory alloy wires of the second set may correspond to edges of a kite shape.

The first and second sets of shape memory alloy wires may consist of two pairs of shape memory alloy wires, wherein the shape memory alloy wires within each pair are arranged parallel to each other. However, this is not essential and the first set of shape memory alloy wires may include four shape memory alloy wires in an arrangement in which none of the shape memory alloy wires are parallel. The second set of shape memory alloy wires may include four shape memory alloy wires in an arrangement in which none of the shape memory alloy wires are parallel. Each shape memory alloy wire in the first set may make an angle greater than 0° with each other shape memory alloy wire in the first set. Each shape memory alloy wire in the second set may make an angle greater than 0° with each other shape memory alloy wire in the second set.

The first set of shape memory alloy wires may include four shape memory alloy wires in an arrangement capable of applying a torque about a vertical axis perpendicular to the first plane. The second set of shape memory alloy wires may include four shape memory alloy wires in an arrangement capable of applying a torque about the vertical axis. This allows rotation of the second and/or third part (relative to the first and/or second part) about the vertical axis to be controlled by the first and/or second sets of shape memory alloy wires.

The first set of shape memory alloy wires may include shape memory alloy wires which cross over when viewed along the vertical axis. The second set of shape memory alloy wires may include shape memory alloy wires which cross over when viewed along the vertical axis. This may allow the shape memory alloy wires to be made longer compared to a situation in which such cross over is not allowed. Longer shape memory alloy wires enable larger stroke.

The first set of shape memory alloy wires may include a pair of shape memory alloy wires which have mirror symmetry when viewed along the vertical axis. The second set of shape memory alloy wires may include a pair of shape memory alloy wires which have mirror symmetry when viewed along the vertical axis.

The first set of shape memory alloy wires may include a shape memory alloy wire arranged at an angle between 20° and 80° to the first axis. Each shape memory alloy wire of the first set may be arranged at an angle between 20° and 80° to the first axis. The second set of shape memory alloy wires may include a shape memory alloy wire arranged at an angle between 45° and 77° to the second axis. Each shape memory alloy wire of the second set may be arranged at an angle between 45° and 77° to the second axis.

Edges of the first part, or an envelope encompassing the first part, may be substantially parallel to the first or second axes. Edges of the second part, or an envelope encompassing the second part, may be substantially parallel to the first or second axes. Edges of the third part, or an envelope encompassing the third part, may be substantially parallel to the first or second axes. The first set of shape memory alloy wires may comprise first, second, third and fourth shape memory alloy wires, and may be configured such that, relative to the first part:

• Actuation of the first and second shape memory alloy wires urges the second part in a negative direction along the first axis (e.g. x);

• Actuation of the third and fourth shape memory alloy wires urges the second part in a positive direction along the first axis (e.g. x);

• Actuation of the first and fourth shape memory alloy wires urges the second part in a negative direction along the second axis (e.g. y) perpendicular to the first axis (e.g. x);

• Actuation of the second and third shape memory alloy wires urges the second part in a positive direction along the second axis (e.g. y);

• Actuation of the first and third shape memory alloy wires urges the second part to rotate anti-clockwise; and

• Actuation of the second and fourth shape memory alloy wires urges the second part to rotate clockwise.

The second set of shape memory alloy wires may comprise first, second, third and fourth shape memory alloy wires, and may be configured such that, relative to the second part:

• Actuation of the first and second shape memory alloy wires urges the third part in a negative direction along the second axis (e.g. y);

• Actuation of the third and fourth shape memory alloy wires urges the third part in a positive direction along the second axis (e.g. y);

• Actuation of the first and fourth shape memory alloy wires urges the third part in a positive direction along a first axis (e.g. x);

• Actuation of the second and third shape memory alloy wires urges the third part in a negative direction along the first axis (e.g. x);

• Actuation of the first and third shape memory alloy wires urges the third part to rotate anticlockwise; and

• Actuation of the second and fourth shape memory alloy wires urges the third part to rotate clockwise.

The first and second planes may be co-planar. The second part may surround the third part.

The first and second planes may be parallel. The first part, the second part and the third part may be stacked in order along a vertical direction perpendicular to the first and second planes. The third part may include a central aperture. The central aperture may be suitable to allow a light path to pass through, for example via one or more lenses that can be arranged in the central aperture. No shape memory alloy wires may cross the central aperture. No shape memory alloy wires belonging to the first set may cross the central aperture. No shape memory alloy wires belonging to the second set may cross the central aperture. Shape memory alloy wires of the first set may be arranged to form a loop surrounding the central aperture. Shape memory alloy wires of the second set may be arranged to form a loop surrounding the central aperture.

The third part may have first and second surfaces. The second surface may oppose the first part across a gap. Shape memory alloy wires belonging to the first set may be routed through the gap. Shape memory alloy wires belonging to the second set may be routed through the gap. The separation of the second surface and the first part across the gap may be parallel to the vertical axis.

The first set of shape memory alloy wires may include one or more actuation pairs. The second set of shape memory alloy wires may include one or more actuation pairs. Each actuation pair may include a long wire arranged such that movements of the respective part are amplified relative to corresponding length changes of the long wire. Each actuation pair may include a short wire having a length less than the long wire and arranged to oppose contraction of the long wire.

The actuator assembly may include two or more actuation pairs. The short wire of one first actuation pair may be electrically connected in series or parallel with the short wire of a different actuation pair.

The first set of shape memory alloy wires may be further configured to rotate the second part relative to the first part in the first plane. The second set of shape memory alloy wires may be further configured to rotate the third part relative to the second part in the second plane.

The controller may be configured to control selective contraction of the first set of shape memory alloy wires so as to rotate the second part about the vertical axis in the first plane relative to the first part. The controller may be configured to control selective contraction of the second set of shape memory alloy wires so as to rotate the third part about the vertical axis in the second plane relative to the second part. The actuator assembly may also include a fourth part moveable in a third plane relative to the third part. The third plane parallel to, or coplanar with, the second plane. The actuator assembly may also include a third set of one or more shape memory alloy wires configured to move the fourth part relative to the third part in the third plane. The third set of shape memory alloy wires may be arranged such that movements of the fourth part are amplified relative to corresponding length changes of the third set of shape memory alloy wires.

So, movement of the fourth part relative to the first part is a combination of movement of the second part relative to the first part, movement of the third part relative to the second part and movement of the fourth part relative to the third part. The fourth part may be coupled to the third part via the third set of shape memory alloy wires.

Alternatively, the fourth part may be movable parallel to the third and fourth axes.

The fourth part may include features corresponding to any features of the second part and/or the third part. The third set of shape memory alloy wires may include features corresponding to any features of the first and/or second sets of shape memory alloy wires. The mechanical coupling between the fourth part and the third part may include features corresponding to any features of the mechanical coupling between the third part and the second part, and/or between the second part and the first part.

If the fourth part is included, the controller may be configured to control selective contraction of the third set of shape memory alloy in any way described hereinbefore in relation to the first set of shape memory alloy wires and/or the second set of shape memory alloy wires.

When the fourth part is included, the controller may be configured to extend the range of motion of the fourth part (relative to the first part) beyond the second movement envelope by combining movements of the second, third and fourth parts along the same axes.

A camera may include the actuator assembly, an image sensor supported by one of the first part, the second part, and the third part, and one or more lenses. At least one lens of the one or more lenses may be supported by one of the first part, the second part and the third part. The one or more lenses may be supported by a different one of the first part, the second part, and the third part to the image sensor. Preferably, the image sensor may be supported by one of the first and third parts, and the at least one lens of the one or more lenses may be supported by the other of the first and third parts.

When the fourth part is included, the image sensor may be supported by one of the first part, the second part, the third part and the fourth part, whilst the at least one lens of the one or more lenses may be supported by a different one of the first part, the second part, the third part and the fourth part. When the fourth part is included, the image sensor may preferably be supported by one of the first and fourth parts, and the at least one lens of the one or more lenses may be supported by the other of the first and fourth parts.

In the camera, the first part may be fixed relative to the rest of the camera. In the camera, the second part may be fixed relative to the rest of the camera. Fixed relative to the camera may mean that the first or second part is mechanically fixed, and has no degrees of freedom relative to the rest of the camera. For example, whichever of the first and second parts is fixed may be rigidly attached to (or be integrally formed with) a screening can of the camera, a case of the camera, a frame of the camera, a package of the camera, and so forth.

According to a second aspect of the invention, there is provided a method of controlling the actuator assembly, or a camera incorporating the actuator assembly. The method includes controlling contraction of the shape memory alloy wires of the first and second sets so as to move the third part relative to the first part by a first component parallel to the first axis and a second component parallel to the second axis.

When the fourth part is included, the method may also include controlling the selective contraction of the third set of shape memory alloy wires so as to move the fourth part in the third plane relative to the third part.

The method according to the second aspect may include features corresponding to any features of the actuator assembly and/or a camera incorporating the actuator assembly. Definitions applicable to the actuator assembly and/or a camera incorporating the actuator assembly may be equally applicable to the method according to the second aspect. In particular, the method according to the second aspect may include features corresponding to one or more of the first, second and third modes described in relation to the controller of the actuator of the first aspect.

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 illustrates a camera;

Figure 2 is a plan view of a first actuator assembly;

Figures 3A and 3B illustrate a stroke amplification mechanism using shape memory alloy wires;

Figure 4 illustrates movement envelopes for a control mode of an actuator assembly;

Figure 5 is a plan view of a second actuator assembly;

Figure 6A is a projection view of a third actuator assembly;

Figure 6B is a plan view of the third actuator assembly;

Figure 7A is a plan view of a fourth actuator assembly;

Figure 7B is a side view of along a short axis of the fourth actuator assembly;

Figure 7C is a side view of along a long axis of the fourth actuator assembly;

Figure 8 is a plan view of a fifth actuator assembly;

Figure 9 schematically shows a first example of shape memory alloy wire electrical connections for the fifth actuator assembly;

Figure 10 schematically shows a second example of shape memory alloy wire electrical connections for the fifth actuator assembly;

Figure 11A is a plan view of a third part and a second set of shape memory alloy wires for a sixth actuator assembly;

Figure 11B is a plan view of a second part and a first set of shape memory alloy wires for the sixth actuator assembly;

Figure 11C is a side view of the sixth actuator assembly;

Figure 12A is a plan view of a second part and a first set of shape memory alloy wires for a seventh actuator assembly;

Figure 12B is a plan view of a third part and a second set of shape memory alloy wires for the seventh actuator assembly; and

Figure 12C is a side view of the seventh actuator assembly.

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

The camera 1 includes a lens assembly 3 suspended on a first part (or "support structure" 4 by an actuator assembly 2 that supports the lens assembly 3 in a manner allowing movement of the lens assembly 3 relative to the first part 4 in directions perpendicular to the optical axis O (on a first plane).

The first part 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, there is mounted a controller 7. For example, the controller 7 may take the form of an integrated circuit (IC) in which a control circuit is implemented. Optionally, for example when the camera 1 is configured with optical image stabilisation (OIS), a gyroscope sensor 8 may be mounted on the rear side of the base 5 and coupled to the controller 7. The precise locations of mounting the controller 7 (and optionally the gyroscope sensor 8 if present) relative to the actuator assembly 2 are not crucial, though it is preferred the arrangement be compact.

The first part 4 also includes a screening can (or "can") 9 which protrudes forwardly from the base 5 to encase and protect the other components of the camera 1.

The lens assembly 3 includes a lens carriage 10 in the form of a cylindrical body supporting two lenses 11 arranged along an optical axis O (parallel to the z-axis as illustrated). In general, any number of one or more lenses 11 may be included. Preferably, each lens 11 has a diameter of up to about 20 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 11 are supported on the lens carriage 10 such that the lenses 11 are movable along the optical axis O relative to the lens carriage 10, for example to provide focussing or zoom. In particular, the lenses 11 are fixed to a lens holder 12 which is movable along the optical axis O relative to the lens carriage 10. Although all the lenses 11 are fixed to the lens holder 12 in this example, in general, one or more of the lenses 11 may be fixed to the lens carriage 10 and so not movable along the optical axis O relative to the lens carriage 10, leaving at least one of the lenses 11 fixed to the lens holder 12.

An axial actuator assembly 13 provided between the lens carriage 10 and the lens holder 12 is arranged to drive movement of the lens holder 10 and the lenses 11 along the optical axis O relative to the lens carriage 10. The axial actuator arrangement 13 may be of any suitable type, for example, a voice coil motor (VCM) or an arrangement of SMA wires.

In operation, the lens assembly 3 is moved orthogonally to the optical axis O by the actuator assembly 2, relative to the image sensor 6, with the effect that the image on the image sensor 6 is moved. This is used to provide optical image stabilization (OIS), compensating for movement of the camera 1, which may be caused by hand shake etc.

First actuator assembly

Referring also to Figure 2, a first exemplary actuator assembly 14 is shown (hereinafter "first actuator assembly").

The first actuator assembly 14 may provide the actuator assembly 2 of a camera 1, but is not restricted to use in cameras 1. The first actuator assembly 14 includes a first part 4 (also referred to as a "support structure"), a second part 15 (also referred to as an "intermediate part") moveable in a first plane 16 (x-y as illustrated) relative to the first part 4, and a third part 17 (also referred to as a "moving part") moveable in a second plane 18 (x-y as illustrated) relative to the second part 15. The second plane 18 is coplanar with the first plane 16 in the first actuator assembly 14. However, in modifications of the first actuator assembly 14 the first and second planes 16, 18 need not be coplanar, and may be parallel to one another at different heights (z-axis as illustrated).

The first actuator assembly 14 includes a first set of shape memory alloy (SMA) wires 19 configured to move the second part 15 relative to the first part 4 in the first plane 16. In the first actuator assembly 14, the first set of shape memory alloy wires 19 includes first to fourth SMA wires 19i, 192, 19a, 194, arranged in a loop around the centre of the first actuator assembly 14. In general, the first set may include more or fewer SMA wires 19, though the minimum number is one (contraction of which should be opposed by a spring as described hereinafter). Each SMA wire 19 of the first set is fixed to the first part 4 by a respective first crimp 20 at one end, and at the other end is fixed to the second part 15 by a respective second crimp 21. The first actuator assembly 14 also includes a second set of shape memory alloy wires 22 configured to move the third part 17 relative to the second part 15 in the second plane 18. In the first actuator assembly 14, the second set of shape memory alloy wires 22 includes first to fourth SMA wires 22i, 222, 22a, 224, arranged in a loop around the centre of the first actuator assembly 14. In general, the second set may include more or fewer SMA wires 22, though the minimum number is one (contraction of which should be opposed by a spring as described hereinafter). Each SMA wire 22 of the second set is fixed to the second part 15 by a respective third crimp 23 at one end, and at the other end is fixed to the third part 17 by a respective fourth crimp 24.

In this way, the second part 15 is coupled to the first part 4 via the first set of memory alloy wires 19, and the third part 17 is coupled to the second 15 part via the second set of shape memory alloy wires 22. Consequently, movement of the third part 17 relative to the first part 4 is a combination of movement of the second part 15 relative to the first part 4 and movement of the third part 17 relative to the second part 15.

The SMA wires 19 of the first set and the SMA wires 20 of the second set may be caused to contract by resistive heating provided by electrical currents. Electrical connections between the first part 4 and the second part 15 are supported on (or provided by) first flexures 25 connecting the first part 4 and the second part 15. Each first flexure 25 may support one, two, or more separate electrical connections, for example insulated from one another. Similarly, electrical connections between the first part 4 and the third part 15 are supported on (or provided by) second flexures 26 connecting the first part 4 and the third part 17. Each second flexure 26 may support one, two, or more separate electrical connections, for example insulated from one another. The first and second flexures 25, 26 are designed to be highly compliant so as not to interfere with movements of the first actuator assembly 14. The first actuator assembly 14 includes a first pair of first flexures 25 and a pair of second flexures 26, though in general more or fewer first flexures 25 and/or second flexures 26 may be used to provide electrical connections to the SMA wires 19, 22. Alternative options for implementing electrical connections may include sliding sprung contacts, conductive ball-bearings, and so forth.

On heating of one of the SMA wires 19, 22, the stress in the SMA wire 19, 22 increases and it contracts, providing a force urging the parts 4, 15, 17 that SMA wire 19, 22 connects between to be pulled toward one another (and to move if there is net force). A range of movement occurs as the temperature of the SMA material increases over the range of temperature in which there occurs the transition of the SMA material from the Martensite phase to the Austenite phase. Conversely, on cooling of one of the SMA wires 19, 22 so that the stress in the SMA wire 19, 22 decreases, it may extend under the force from opposing ones of the SMA wires 19, 22 (or springs, flexures and so forth). The SMA wires 19, 22 may be made of any suitable SMA material, for example Nitinol or another titanium-alloy SMA material.

The drive signals for the SMA wires 19, 22 are generated and supplied by a controller 7, for example a control circuit implemented in an IC as described hereinbefore. For example, the drive signals may be generated by the controller 7 in response to output signals of the gyroscope sensor 8) 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. Examples of first, second and third control modes in which the controller 7 may operate to control the first actuator assembly 14 are described hereinafter

In operation, the SMA wires 19, 22 are selectively driven to move the second part 15 and/or the third part 17 relative to the first part in any lateral direction in the planes 16, 18 (i.e., a direction perpendicular to the optical axis O). Further details of methods of driving SMA wires 19, 22 are also provided in WO 2013/175197 Al, which is incorporated herein by this reference.

The first actuator 14 is square with first to fourth sides 27i, 272, 27a, 274. The first and third sides 27i, 27a are parallel to one another and a first axis (x-axis as illustrated). The second and fourth sides 27a, 27 are parallel to one another and a second axis (y-axis as illustrated) perpendicular to the first axis x. In the first actuator 14, the sides 27 of the actuator 14 coincide with edges of the first part 4, which takes the form of a square plate. The first part 4 may provide the base 5 if used in a camera 1. Each of the second 15 and third 17 parts takes the form of a flat, thin annulus having square outer and inner edges, defining an aperture 28. When used in a camera 1, the aperture 28 allows passage of light focused by lenses 11 onto the image sensor 6 (for example mounted on the first part 4). For this reason, none of the SMA wires 19, 22 intersects the aperture 28 of the third part 17. The third part 17 is smaller than the second part 15, and is received within the aperture 28 of the second part 15 so that the second 15 and third 17 parts are substantially co-planar and the first and second planes 16, 18 coincide. The first 4, second 15 and third 17 parts are each generally perpendicular to a vertical axis (z-axis as illustrated). When used in a camera, the vertical axis z will lie parallel to the optic axis O.

The first part 4, second part 15 and third part 17 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. The dielectric material layer may include one or more windows (not shown) to allow electrical connections.

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

The first part 15 is constrained to move on the first plane 16, at least in part, using a first bearing arrangement (not shown) coupling the first part 15 to the first part 4. The first part 15 may be retained in contact with the first bearing arrangement (not shown) by one or more flexures, springs or similar devices (not shown) providing force along the vertical axis z towards the first part 4. Similarly, the second part 17 is constrained to move on the second plane 18 (coincident with the first plane 16 in this example), at least in part, using a second bearing arrangement (not shown) coupling the third part 17 to the first part 4. The first part 15 may be retained in contact with the second bearing arrangement (not shown) by one or more flexures, springs or similar devices (not shown) providing force along the vertical axis z towards the first part 4. The first and/or second bearing arrangement (not shown) may take the form or three or more plain bearings, three or more roller bearings, respective sets of flexures, and so forth.

SMA wire arrangement of the first actuator assembly

The first set of SMA wires 19 are arranged in a loop about the aperture 28, with the first and second SMA wires 19i, 192 of the first set opposing each other (in terms of contraction) along the second edge 272, and the third and fourth SMA wires 19a, 194 of the first set opposing each other along the fourth edge 27 . None of the first set of SMA wires 19 are collinear, although all make substantially the same angles to the first x and second y axes. The first set of SMA wires 19 make a smaller angle to the second axis y than to the first axis x.

Actuation of the first and second SMA wires 19i, 192 of the first set to contract urges the second part 15 in a negative direction parallel to the first axis x, relative to the first part 4. To urge the second part 15, relative to the first part, in the opposite direction (positive direction parallel to the first axis x), the third and fourth SMA wires 19a 194 of the first set are actuated to contract.

For movements of the second part 15 relative to the first part 4 parallel to the second axis y, the second part 15 may be urged in the negative y-direction by actuating the first and fourth SMA wires 19i, 19 of the first set to contract, and may be urged in the positive y-direction by actuating the second and third SMA wires 19a, 19a of the first set.

Clockwise moment on the second part 15 relative to the first part 4 may be obtained by actuating the second and fourth SMA wires 19a, 194 of the first set to contract together. Similarly, anticlockwise moment on the second part 15 relative to the first part 4 may be obtained by actuating the first and third SMA wires 19i, 19a of the first set to contract together.

If desired, one or more of the degrees of freedom of the second part 15 relative to the first part 4 may be constrained, for example using the first bearing arrangement (not shown). At least one degree of freedom should be retained for the second part 15 relative to the first part 4.

The second set of SMA wires 22 are also arranged in a loop about the aperture 28, with the first and second SMA wires 22i, 22a of the second set opposing each other (in terms of contraction) along the first edge 27i, and the third and fourth SMA wires 22a, 224 of the second set opposing each other along the third edge 27a. None of the second set of SMA wires 22 are collinear, although all make substantially the same angles to the first x and second y axes. The second set of SMA wires 22 make a smaller angle to the first axis x than to the second axis y.

For movements of the third part 17 relative to the second part 15 parallel to the second axis y, the second part 15 may be urged in the negative y-direction by actuating the first and second SMA wires 22i, 222 of the second set to contract, and may be urged in the positive y-direction by actuating the third and fourth SMA wires 22a, 224 of the second set.

For movements of the third part 17 relative to the second part 15 parallel to the first axis x, the second part 15 may be urged in the positive x-direction by actuating the first and fourth SMA wires 22i, 24 of the second set to contract, and may be urged in the negative y-direction by actuating the second and third SMA wires 222, 22a of the second set. Clockwise moment on the third part 17 relative to the second part 15 may be obtained by actuating the second and fourth SMA wires 222, 224 of the second set to contract together. Similarly, anticlockwise moment on the third part 17 relative to the second part 15 may be obtained by actuating the first and third SMA wires 22i, 22a of the second set to contract together.

If desired, one or more of the degrees of freedom of the third part 17 relative to the second part 15 may be constrained, for example using the second bearing arrangement (not shown). At least one degree of freedom should be retained for the third part 17 relative to the second part 15, and it should preferably be non-parallel with at least one degree of freedom of the second part 15 relative to the first part 4.

The total movement of the third part 17 relative to the first part 4 is the sum of the movement of the second part 15 relative to the first part 4 (from actuation of the first set of SMA wires 19), and the movement of the third part 17 relative to the second part 15 (from actuation of the second set of SMA wires 22). The total motion of the third part 17 relative to the first part 4 obtainable by combining actuation of the first 19 and second 22 sets of SMA wires is larger than would be obtainable using a single set of SMA wires 19, 22.

The first set of shape memory alloy wires 19 are arranged such that movements of the second part 15 relative to the first part 4 are amplified compared to corresponding length changes of the first set of shape memory alloy wires 19. Similarly, the second set of shape memory alloy wires 22 are arranged such that movements of the third part 17 relative to the second part 15 are amplified compared to corresponding length changes of the second set of shape memory alloy wires 22.

SMA wire amplification

Referring also to Figures 3A and 3B, the SMA wire 19, 22 amplification mechanism is illustrated.

Referring in particular to Figure 3A, an angled SMA wire 29 makes an angle 0 to the first axis x and an angle 90-i? to the second axis y. In the example shown in Figure 3A, i? = 45°.

The SMA wire 29 has an initial length L, having a component xo along the first axis x and a component yo along the second axis y. A first end 30 of the SMA wire 29 is fixed to the origin of the axes x-y drawn in Figure 3A. The SMA wire 29 is then actuated (by resistive heating using a drive current) and caused to contract by an amount 6L to a new length L-5L. The locus of points which a second end 31 of the SMA wire 29 can reach is a circle 32 of radius L-6L drawn for reference in Figure 3A. If the second end 31 of the SMA wire 29 is unconstrained, or constrained to move along the direction that the SMA wire 29 is lying (■& = 45°), then the total displacement of the second end 31 relative to the first end will simply be 6L to the point labelled Pl. This represents the unamplified displacement, and many SMA actuators operate in this way, directly pulling part of actuator along the length of an SMA wire 29. However, this limits the stroke of such actuator to the maximum length change 6L.

However, if the second end 31 is constrained to move along a path which is not parallel to the initial orientation of the SMA wire 29, amplification may be obtained. For example, if the second end 31 is constrained to move parallel to the second axis y, then the second end 31 is forced to the point P2 on the circle 32 intersecting the original component xo along the first axis x. The total displacement is then Ay = yo-yi > 6L. Alternatively, if the second end 31 is constrained to move parallel to the first axis x, then the second end 31 is forced to the point P3 on the circle 32 intersecting the original component yo along the second axis y. The total displacement is then Ax = xo-xi > 6L.

For the geometry shown in Figure 3A, with 0 = 45°, the amplification is the same when constrained to the first axis or the second axis, i.e. Ax = Ay, and the gain is Ax/5L ~ 1.5.

The gain may be increased for movements parallel to one axis x, y, at the expense of reduced gain for movements parallel to the other axis y, x, by changing the initial orientation angle i?.

Referring also to Figure 3B shows a configuration identical to Figure 3A, except that the angle is i? = 60° instead of i? = 45°. In the configuration of Figure 3B, when the second end 32 is constrained to move parallel to the first axis x to point P3, the gain is increased to Ax/5L ~ 2A. However, the when the second end 32 is constrained to move parallel to the second axis y to point P2, the gain is reduced (compared to -d = 45°) to Ay/6L ~ 1.2.

It will be appreciated that, since the shortest displacement corresponding to a length change 6L (zero amplification) will always be directly along the initial orientation of the SMA wire 29, constraining the second end 31 to any other path which is not parallel with 0 will lead to amplification. In other words, amplification does not require strict constraint to either the first axis x or second axis y. Referring again to Figure 2, the SMA wires 19 of the first set are angled closer to the second axis y, such that relative to the first part 4, movements of the second part 15 parallel to the first axis x are amplified by a larger factor (gain) than movements of the second part 15 parallel to the second axis y. In contrast, the SMA wires 22 of the second set are angled closer to the first axis x, such that relative to the second part 15, movements of the third part 17 parallel to the second axis y are amplified by a larger factor (gain) than movements of the third part 17 parallel to the first axis x.

In the first actuator assembly 14, the constraint of each SMA wire 19 of the first set leading to amplification is provided by opposing SMA wires 19 of the first set. Similarly, the constraint of each SMA wire 22 of the second set leading to amplification is provided by opposing SMA wires 22 of the second set. For example, to move the second part 15 in the negative direction parallel to the first axis x, both the first and second SMA wires 19i, 192 of the first set are caused to contract by the same amount 6L. The opposing directions of the first and second SMA wires 19i, 192 of the first set between the second part 15 and the first part 4 constrains the movement to be parallel to the first axis x, providing amplification of the movement of the second part 15 relative to the first part 4.

In general, to optimise amplification (gain) against the net component of force in the desired direction, SMA wires 19 of the first set are preferably arranged at angles between 20° and 80° to the first axis x. Similarly, SMA wires 22 of the second set are preferably arranged at angles between 45° and 77° to the second axis y.

The controller 7 is configured to control selective contraction of the shape memory alloy wires 19, 22 of the first and second sets so as to cause a desired overall movement of the third part 17 relative to the first part 4 by a first component Ax parallel to the first axis x and a second component Ay parallel to the second axis y. The controller 7 may be configured to operate in one of the first, second or third control modes described hereinafter. Alternatively, the controller 7 may be configured to operate in a pair, or all, of the first, second or third control modes described hereinafter, and to be switchable between the control modes depending on context. For example, when included in a camera 1, one control mode may be advantageous for capturing still images, whilst another may be advantageous for capturing video. The first, second and third control modes described hereinafter are merely exemplary, and many alternative control modes may be used with the first actuator assembly 14. Regardless of the particular control mode used, the controller 7 controls contraction of the SMA wires 19 of the first set and the SMA wires 22 of the second set by controlling drive signals supplied to the shape memory alloy wires 19, 22. Drive signals may be current controlled or voltage controlled. The drive signals may be generated using a resistance feedback control technique, for example, as described in WO 2014/076463 Al

First control mode

In a first control mode, the controller 7 is configured to isolate movements parallel to the first x and second y axes to be provided by a single set of SMA wires 19.

In particular, the controller 7 causes the first component Ax to correspond to controlling selective contraction of the first set of shape memory alloy wires 19 so as to move the second part 15 parallel to the first axis x in the first plane 16 relative to the first part 4. Specifically, the controller 7 either causes the first and second SMA wires 19i, 192 of the first set to contract as a pair to move in the negative x direction, or causes the third and fourth SMA wires 19a, 194 of the first set to contract as a pair to move in the positive x direction. This corresponds to the direction of maximum amplification (gain) for the first set of SMA wires 19.

Meanwhile, the controller 7 causes the second component Ay to correspond to controlling selective contraction of the second set of shape memory alloy wires 22 so as to move the third part 17 parallel to the second axis y in the second plane 18 (coincident with the first plane 16 in this example) relative to the second part 15. Specifically, the controller 7 either causes the first and second SMA wires 22i, 222 of the first set to contract as a pair to move in the negative y direction, or causes the third and fourth SMA wires 22a, 22 of the second set to contract as a pair to move in the positive y direction. This corresponds to the direction of maximum amplification (gain) for the second set of SMA wires 22.

In the first control mode, the movements (by Ax and Ay) of the third part 17 relative to the first part 4 are essentially isolated along the first axis x and the second axis y. This may simplify the drive signals required to control the first and second sets of SMA wires 19, 22. Primarily, the first mode helps to reduce cross-talk between intended movements parallel to the first x and second y axes. In other words, cross-talk is reduced between the two degrees of freedom of the third part 17 relative to the first part 4. Second control mode

Whilst in the first control mode good isolation is obtainable for the components Ax and y of movement of the third part 17 relative to the first part 4, the overall range of movement, or movement envelope, may be improved by additively combining the displacements of the second 15 and third 17 parts along one or both axes x, y.

Referring also to Figure 4, a second control mode will be described.

In the second control mode, the controller is configured such that, within a first movement envelope 33 (of the third part 17 relative to the first part 4), the first component Ax corresponds to movement of the second part 15 relative to the first part 4, whilst the second component Ay corresponds to movement of the third part 17 relative to the second part 15. In other words, within the first movement envelope 33, the second control mode is identical to the first control mode.

As shown in Figure 4, the first movement envelope 33 (or first locus) is generally square (assuming the SMA wires 19, 22 of the first and second sets have equal stroke lengths). The first movement envelope corresponds to the locus of all points to which the third part 17 may be moved, centred on an origin corresponding to an equilibrium relative position in relation to the first part 4. Thus, within the first movement envelope, the second control mode retains the advantages of the first control mode.

The second control mode differs from the first control mode in that the third part 17 may be moved outside the first movement envelope 33 by additively combining movements of the second 15 and third 17 parts parallel to the same axis. A second movement envelope (or second locus) 34 corresponds to the furthest that the third part 17 may be moved relative to the first part 4 along any given direction. The second movement envelope 34 shown in Figure 4 has the form of a regular octagon, and completely encompasses the first movement envelope 33. First to fourth regions 35i, 352, 35a, 354 correspond to points outside the first movement envelope 33 and within a second movement envelope 34.

Within the first to fourth regions 35i, 352, 35a, 35 , the controller 7 causes selective contraction of the first and second sets of SMA wires 19, 22 such that the first component Ax corresponds to a movement of the second part 15 relative to the first part 4 combined with a movement of the third part 17 relative to the second part 15, both parallel to the first axis x. Similarly for the second component Ay.

For example, the third part 17 may be moved from the origin to the edge of the first movement envelope 33 bordering the first region 35i by contracting the third and fourth SMA wires 19a, 194 of the first set (corresponding to maximum amplification). However, for the third part 17 to move further parallel to the first axis x and pass through the first region 35i up to the edge of the second movement envelope 34, the first and fourth SMA wires 22i, 22 of the second set are also caused to contract.

In this way, the controller 7 operating in the second mode may extend the range of motion of the third part 17 relative to the first part 15 beyond the first movement envelope 33, by combining movements of both second 15 and third 17 parts along the same axis.

Third control mode

In the first and second control modes, the controller 7 is configured, as much as possible, to isolate the first and second components Ax, Ay to be individually provided by the first and second sets of SMA wire 19, 22. This reduces cross-talk between the two degrees of freedom of the third part 17 relative to the first part 4. However, in some applications/uses of the first actuator 14, it may be advantageous to mix, across the entire second movement envelope 34, the contributions of the first and second sets of SMA wires 19, 22 to the first and second components Ax, Ay of movement of the third part 17 relative to the first part 4.

In the third mode, the controller is configured such that the first component Ax comprises a first movement 6xi and a second movement 6x2, Ax = 6x1 + 6x2. Similarly, the second component Ay comprises a third movement 6yi and a fourth movement 5/2, Ay = 6yi + 5/2.

The first movement 6x1 is a movement of the second part 15 relative to the first part 4 parallel to the first axis x. The second movement 6x2 corresponds to movement of the third part 17 relative to the second part 15 parallel to the first axis x. The second movement 6x2 is smaller than the first movement, 5x2< 6x1, corresponding to the greater amplification for movement of the second part 15 relative to the first part 4 parallel to the first axis x. The third movement 6yi is a movement of the third part 17 relative to the second part 15 parallel to the second axis y. The fourth movement 5/2 corresponds to movement of the second part 15 relative to the first part 4 parallel to the second axis y. The fourth movement /2 is smaller than the third movement, 5/2< 6yi, corresponding to the greater amplification for movement of the third part 17 relative to the second part 15 parallel to the second axis /.

In this way, the controller 7 may move the third part 17 to a position relative to the first part 4 within the second movement envelope 34 using the most amplified movements of the second 15 and third 17 parts to provide relatively coarse movements, and the less amplified movements of the second 15 and third parts 17 to provide relatively fine movements. This may enable more precise positioning, since greater amplification of intended movements also leads to greater amplification of errors.

Any of the first, second and third control modes may optionally be combined with rotations of the second 15 and/or third parts 17 (about the vertical axis z).

For example, the controller 7 may be configured to control selective contraction of the first set of shape memory alloy wires 19 so as to rotate the second part 15 relative to the first part 4 about the vertical axis z perpendicular to the first plane 16. Contraction of any individual SMA wire 19 of the first set will generate a net moment about the vertical axis z, however it is preferable to cause contraction of the second and fourth SMA wires 192, 194 of the first set to rotate the second part 15 clockwise, and to cause contraction of the first and third SMA wires 19i, 19a of the first set to rotate the second part 15 anti-clockwise.

Similarly, the controller 7 may be configured to control selective contraction of the second set of shape memory alloy wires 22 so as to rotate the third part 17 relative to the second part 15 about the vertical axis z perpendicular to the second plane 18 (coincident with the first plane 16 in the first actuator assembly 14). Contraction of any individual SMA wire 22 of the second set will generate a net moment about the vertical axis z, however it is preferable to cause contraction of the second and fourth SMA wires 222, 22 of the second set to rotate the third part 17 clockwise, and to cause contraction of the first and third SMA wires 22i, 22a of the second set to rotate the third part 17 anti-clockwise. In this way, rotations generated by the first and second sets of SMA wires 19, 22 may also be additively combined, allowing for an increased maximum rotation of the third part 17 relative to the first part 4 compared to either set of SMA wires 19, 22 alone.

Incorporation into a camera

The first actuator assembly 14 may be incorporated into a camera in a number of different ways.

For example, the first actuator assembly 14 may be incorporated into the camera 1 shown in Figure 1, with the image sensor 6 supported on the first part 4 and the lens carriage 10 supported on the third part 17. The first part 4 is connected to the can 9, and functions as the fixed reference point relative to the camera 1.

However, the first actuator 14 may be incorporated into a camera in other ways. For example, another camera (not shown) may be similar to the camera 1, except that the second part 15 is fixed relative to the camera (not shown), e.g. to the can 9. In this way, the image sensor 6 supported on the first part 4 and the lens carriage 10 supported on the third part 17 may be moved independently relative to the optic axis O.

In general, for incorporation into a camera, any one of the first part 4, the second part 15 or third part 17 may support the image sensor 6, whilst one of the remaining pair of parts 4, 15, 17 supports at least one lens 11. In general, any one of the first part 4, the second part 15 or the third part 17 may be fixed relative to the camera. Fixed relative to the camera mean that the part 4, 15, 17 in question is mechanically fixed, and has no degrees of freedom relative to the rest of the camera. For example, whichever of the parts 4, 15, 17 is fixed may be rigidly attached to (or be integrally formed with) a can 9, a case (not shown), a frame (not shown) or a package of the camera.

Whilst the first actuator assembly 14 has been described with none of the shape memory alloy wires 19 of the first set being collinear, and none of the shape memory alloy wires 22 of the second set being collinear, this is not essential. In other examples, one or more SMA wires 19 of the first set may be arranged to be collinear, and/or one or more SMA wires 22 of the second set may be arranged to be collinear.

The first actuator assembly 14 has been described with shape memory alloy wires 19 of the first set arranged in a loop forming a bow-tie shape such that each SMA wire 19 of the first set makes the same angle with the pair of adjoining (about the loop) SMA wires 19 of the first set. For example, the first SMA wire 19i of the first set is oriented at the same angle relative to the second and fourth SMA wires 192, 194 of the first set. Moreover, the first and third SMA wires 19i, 19a of the first set are parallel, as are the second and fourth SMA wires 192, 19 of the first set. The SMA wires 22 of the second set are similarly configured, except rotated by 90° and forming a loop with slightly smaller dimensions.

However, it is not essential for the SMA wires 19, 22 of the first and/or second sets to be configured this way, and instead the SMA wires 19, 22 of the first and/or second sets may be arranged to form a loop corresponding to a quadrilateral shape such as a square, rectangle, diamond, kite, and so forth. Alternatively, the SMA wires 19, 22 of the first and/or second sets may be arranged such that none of the SMA wires 19, 22 in a given set are parallel to one another.

The first actuator assembly 14 has been described in which the first set of SMA wires 19 are capable of applying a net moment (torque) about the vertical axis z, and in which the second set of SMA wires 22 are capable of applying a net moment about the vertical axis z. However, in other examples the first and/or second sets of SMA wires 19, 22 may be arranged such that a net moment is not provided and/or may be small.

The first actuator assembly 14 has been described in which the first set of SMA wires 19 and the second set of SMA wires 22 each includes multiple pairs of SMA wires which have mirror symmetry when viewed along the vertical axis z. However, this is not essential, and in other examples, the first and/or second sets of SMA wires 19, 22 may include fewer, or even no, pairs of SMA wires 19, 22 having mirror symmetry when viewed along the vertical axis z.

The first actuator assembly 14 has been described relative to first x and second y axes which are orthogonal. However, this is not essential, and in other examples the first and second axes may be arranged at any non-parallel angle to one another, for example, any angle between 10° and 80°.

Additionally, the first actuator assembly 14 has been described having movements of the third part 17 relative to the second part 15 along the same axes as movements of the second part 15 relative to the first part 4. Alternatively, the third part 17 may be movable in the second plane 18 relative to the second part 15 along third and fourth non-parallel axes (not shown), which need not have any orientational relationship with the first or second axes. Movements of the third part 17 parallel to the third axis may be amplified by a larger factor than movements of the third part 17 parallel to the fourth axis.

The first actuator assembly 14 has been described with the constraint of the SMA wires 19, 22 leading to amplification provided by opposing SMA wires 19, 22 belonging to the same set. However, in other examples, constraint of SMA wires 19, 22 leading to amplification may be provided by one or more resilient elements such as, for example, springs, flexures and so forth. Alternatively, constraint of SMA wires 19, 22 leading to amplification may be provided by one or more bearings. In further examples, constraint of SMA wires 19, 22 leading to amplification may be provided by a combination of two or more of opposing shape memory alloy wires of the respective first/second set, one or more resilient elements, one or more springs, one or more flexures, and one or more bearings.

The sides 27 of the first actuator assembly 14 form a square shape, however, this is not essential. In other examples, the sides of an actuator assembly may form other shapes such as, for example, rectangular, diamond, kite, or any other regular or irregular quadrilateral. In still other examples, an actuator assembly may have more or fewer than four sides, for example three, five, six or eight sides.

In the first actuator assembly 14, the third part 17 is substantially coplanar with, and received within, the second part 15. However, in other examples, the third part 17 may be stacked above (along the vertical axis z), and substantially co-extensive with, the second part 15 (see for example Figures 6, 9 and 12).

Second exemplary actuator assembly

Referring also to Figure 5, a second exemplary actuator assembly 36 is shown (hereinafter "second actuator assembly").

The second actuator assembly 36 is the same as the first actuator assembly 14, except that each of the SMA wires 19 of the first set has increased length, and each of the SMA wires 22 of the second set has increased length. Preferably, each SMA wire 19 of the first set has a length extending along as much as possible of the side 27 length of the second part 15 whilst still connecting the first 4 and second 15 parts. For example, when projected onto the second axis y, a projected length of each SMA wire 19 of the first set may preferably be at least 80% of a side 27 length (also projected onto the second axis y) of the second part 15.

Preferably, each SMA wire 22 of the second set has a length extending along as much as possible of the side 27 length of the third part 15 whilst still connecting the second 15 and third 17 parts. For example, when projected onto the first axis x, a projected length of each SMA wire 22 of the second set may preferably be at least 80% of a side 27 length (also projected onto the first axis x) of the third part 17.

As illustrated in Figure 5, the extended lengths of the SMA wires 19 of the first set causes SMA wires 19 of the first set to cross over one another when viewed along the vertical axis z. Similarly, the SMA wires 22 of the second set cross over one another when viewed along the vertical axis z. SMA wires 19, 22 which cross each other when viewed along the vertical axis z will be slightly offset along the vertical axis z so that they do not contact each other and cause a short circuit.

In this way, the total lengths L of SMA wires 19, 22 are increased. Since the maximum change of length 6L obtainable from phase changes is proportional to the length L, the size of the movement envelope(s) 33, 34 of the second actuator assembly 36 is increased compared to the first actuator assembly 14. When rotational movements are optionally supported, rotational stroke will also be increased.

Variations and/or modifications described in relation to the first actuator assembly 14 are equally applicable to the second actuator assembly 36.

Third exemplary actuator assembly

Referring also to Figures 6A and 6B, a third exemplary actuator assembly 37 is shown (hereinafter "third actuator assembly"). First 25 and second 26 flexures are omitted for visual clarity.

Figure 6A is a projection view with the third part 17 offset along the vertical axis z for visual clarity. Figure 6B is a rear view along the positive z-direction.

The third actuator assembly 37 is the same as the second actuator assembly 36, except that the first 4, second 15 and third 17 parts are stacked in order along the vertical direction z, and in that the first 4, second 15 and third 17 parts have different shapes to the second actuator assembly 36. In terms of relative motions and the associated contractions of the SMA wires, 19, 22, the third actuator assembly 37 functions the same as the second actuator assembly 36.

The first 4 and second 15 parts each take the form of a flat, thin annulus having rectangular outer and inner edges, defining an aperture 28. The third part 17 takes the form of a flat, thin square plate. The first 4, second 15 and third 17 parts are stacked in order along the negative direction of the vertical axis z. When used in a camera 2, the apertures 28 allows passage of light focused by lenses 11 onto the image sensor 6 mounted on the third part 4. For this reason, none of the SMA wires 19 of the first set intersects the portions of aperture 28 which correspond to the area of the third part 17, whilst the SMA wires 22 of the second set are routed below (relative to the vertical axis z) the third part 17.

The first 16 and second 18 planes remain parallel, but in the third actuator assembly 37 the first 16 and second 18 planes are offset from one another along the vertical axis z.

The third actuator 37 may be particularly suitable for a camera utilising a periscope lens configuration.

Although illustrated with rectangular first 4 and second 15 parts, and a square third part 17, these shapes are not essential for the third actuator 37. In other examples, the first 4, second 15 and/or third 17 parts (one or which may provide sides 27 of an actuator assembly) may have other shapes such as, for example, rectangular, diamond, kite, or any other regular or irregular quadrilateral, or may have more or fewer than four sides.

Variations and/or modifications described in relation to the first 14 and/or second 36 actuator assemblies are equally applicable to the third actuator assembly 37.

Fourth exemplary actuator assembly

Referring also to Figures 7A to 7C, a fourth exemplary actuator assembly 38 is shown (hereinafter "fourth actuator assembly"). First 25 and second 26 flexures are omitted for visual clarity.

Figure 7A is a rear view along the vertical axis z, Figure 7B is a side view along the second axis y, and Figure 7C is a side view along the first axis x. The fourth actuator assembly 38 operates according to the same principles as the first 14, second 36 and/or third 37 actuator assembles, differing principally in that the fourth actuator assembly 38 further includes a fourth part 39 and a third set of SMA wires 40, and in that the shapes and stacking order of the first 4, second 15 and third 17 parts are different.

The first 4, second 15, third 17 and fourth 39 parts are stacked in order along the vertical direction z. The first 4, second 15 and third 17 parts each take the form of a flat, thin annulus having rectangular outer and inner edges, defining an aperture. The apertures of first 4 and third 17 parts are empty, whilst the aperture of the second part 15 is bisected by a crossbar 41 aligned parallel with the first axis x. The crossbar 41 serves as an attachment point for the first 19 and second 22 sets of SMA wires. As for the first 14, second 36 and/or third 37 actuator assembles, the first set of SMA wires 19 couples the first part 4 to the second part 15 and the second set of SMA wires 22 couples the second part 15 to the third part 17. However, unlike the first 14, second 36 and/or third 37 actuator assembles, the first 19 and second 22 sets of SMA wires are both arranged to provide maximum amplification for movements parallel to the first axis x.

The fourth part 39 takes the form of a thin square plate, and may be formed in any way and/or using any material(s) described hereinbefore in relation to the first 4, second 15 and/or third 17 parts. The fourth part 39 is moveable in a third plane 41 relative to the third part 17. The third plane 41 is parallel to, but offset along the vertical axis z from, the first 16 and second 18 planes. The third set of SMA wires 40 are configured to move the fourth part 39 relative to the third part 17 in the third plane 41. SMA wires 40 of the third set are arranged such that movements of the fourth part 39 are amplified relative to corresponding length changes of the third set of SMA wires 40. The third set of SMA wires 40 are arranged to provide maximum amplification for movements parallel to the second axis y.

In this way, movement of the fourth part 39 relative to the first part 4 is a combination of movement of the second part 15 relative to the first part 4, movement of the third part 17 relative to the second part 15 and movement of the fourth part 39 relative to the third part 17.

The fourth part 39 may include features corresponding to any features described herein in connection with the second part 15 and/or the third part 17. Similarly, third set of SMA wires 40 may include features corresponding to any features described herein in connection with the first 19 and/or second 22 sets of SMA wires. Similarly, the mechanical coupling between the fourth part 39 and the third part 17 may include features, for example bearings, corresponding to any features described herein in connection with the mechanical coupling between any pair of the first 4, second 15 and third 17 parts.

The controller may be configured to control selective contraction of the third set of SMA wires 40 within the framework of any of the control modes described herein in relation to the first set of SMA wires 19 and/or the second set of SMA wires 22. For example, the controller may be configured to extend the range of motion of the fourth part 39 relative to the first part 4 beyond the second movement envelope 34 by combining movements of the second 15, third 17 and fourth 39 parts along the same axes x, y. When rotational movements are optionally supported, rotational stroke will also be increased.

When the fourth actuator assembly 38 is incorporated into a camera 1, the image sensor 6 is supported on the fourth part 39, whilst lenses 11 are held fixed relative to the first part 4.

Although in the fourth actuator assembly 38 the first 4, second 15, third 17 and fourth 39 parts are stacked along the vertical direction z, in other examples, two, three or all of the first 4, second 15, third 17 and fourth 39 parts may be configured to be substantially co-planar, for example by inserting a fourth part 39 within the aperture 28 of the third part 17 in the first 14 and/or second 36 actuator assemblies.

In the fourth actuator assembly 38 as shown, the image sensor 6 would be supported on the fourth part 39 for incorporation into a camera. However, in other examples in which one or more of the first 4, second 15, third 17 and fourth 39 parts is differently shaped, an image sensor 6 may be coupled to any one of the first 4, second 15, third 17 and fourth 39 parts. At least one lens 11 of the lens assembly 3 would then be supported by a different one of the first 4, second 15, third 17 and fourth 39 parts.

Variations and/or modifications described in relation to the first 14, second 36 and/or third 37 actuator assemblies are equally applicable to the fourth actuator assembly 38.

Fifth actuator assembly

Referring also to Figure 8, a fifth exemplary actuator assembly 42 is shown (hereinafter "fifth actuator assembly"). First 25 and second 26 flexures are omitted for visual clarity. The fifth actuator assembly 36 is similar to the first actuator assembly 14 and/or the second actuator assembly 36, except that each of the first 19 and second 22 sets of SMA wires includes two actuation pairs. Each actuation pair includes a long wire arranged such that movements of the respective part 15, 17 are amplified relative to corresponding length changes of the long wire, and a short wire having a length less than the long wire and arranged to oppose contraction of the long wire. In the first set of SMA wires 19, a first actuation pair includes the first SMA wire 19i as short wire and the second SMA wire 192 as long wire, and a second actuation pair includes the third SMA wire 19a as short wire and the fourth SMA wire 194 as long wire. Similarly, in the second set of SMA wires 22, a first actuation pair includes the first SMA wire 22i as short wire and the second SMA wire 222 as long wire, and a second actuation pair includes the third SMA wire 22a as short wire and the fourth SMA wire 22 as long wire.

The second part 15 includes a pair of protrusions 43i, 432 corresponding to the second Th and fourth 274 sides, allowing the short SMA wires 19i, 19a of the first set to lie substantially parallel to the second axis y in a neutral (or central) position of the second part 15 relative to the first part 4. Similarly, the third part 17 includes a pair of protrusions 44i, 442 corresponding to the first 27i and third 27a sides, allowing the short SMA wires 22i, 22a of the second set to lie substantially parallel to the first axis x in a neutral (or central) position of the third part 17 relative to the second part 15. The second part 15 includes a pair of cut-outs 45i, 452 which receive the protrusions to avoid unwanted interference in relative movements of the second 15 and third 17 parts.

The SMA wire 19, 22 configuration of the fifth actuator assembly 42 permits the natural length of the long wires 192, 194, 222, 24 to be extended to increase the maximum obtainable amplified stroke (displacement), whilst avoiding the need for SMA wires 19, 22 to cross over one another. This may have beneficial effects including simplified design and manufacture, reduced total height along the vertical axis z and/or reduced risk of SMA wire 19, 22 entanglements.

In addition, because the short wires 19i, 19a, 22i, 22a may be used primarily to oppose and constrain contraction of the paired long wires 192, 194, 222, 224 (through appropriate modification of any control mode described herein), the electrical connections of the SMA wires 19, 22 of the fifth actuator assembly 42 may also be simplified. In general, a short wire of one actuation pair may be electrically connected in series, or in parallel, with the short wire of a different actuation pair belonging to the same set, or to a different set. For example, referring also to Figure 9, short wires in the same set may be connected in series. For example, short wires 19i and 19a of the first set being connected in series, whilst short wires 22i and 22a of the second set are connected in series.

Alternatively, referring also to Figure 10, short wires may be connected in series across the first and second sets. For example, short wire 19i of the first set being connected in series with short wire 22i of the second set, whilst short wire 19a of the first set is connected in series with short wire 22a of the second set.

Although in the fifth actuator assembly 42 the first set of SMA wires 19 includes two actuation pairs and the second set of SMA wires 22 also includes two actuation pairs, configurations are not limited thereto. In other examples, any of the first to fourth actuator assemblies 14, 36, 37, 38 may be modified such that the first set of SMA wires 19 includes one or more actuation pairs and/or the second set of SMA wires 22 includes one or more actuation pairs.

The fifth actuator assembly 42 may be modified to include a fourth part 29 in the same way as the fourth actuator assembly 38.

Variations and/or modifications described in relation to the first 14, second 36, third 37 and/or fourth 38 actuator assemblies are equally applicable to the fifth actuator assembly 42.

Sixth actuator assembly

Whilst actuator pairs configured as in the fifth actuator assembly 42 avoid the need for SMA wires 19, 22 to cross over one another, in other examples, actuator pairs of SMA wires 19, 22 may be arranged to cross over.

Referring also to Figures 11A to 11C, a sixth exemplary actuator assembly 46 is shown (hereinafter "sixth actuator assembly").

Figure 11A shows the third part 17 and the second set of SMA wires 22 viewed from below along the vertical axis z. Figure 11B shows the second part 15 and the first set of SMA wires 19 viewed from below along the vertical axis z. Figure 11C shows the sixth actuator assembly 46 viewed from the side along the second axis y. First 25 and second flexures 26 are omitted for visual clarity. The sixth actuator assembly 46 is similar to the fifth actuator assembly 42, except that the first 4, second 15 and third 17 parts are stacked along the vertical axis z and have different shapes, and in that the long and short wires of each actuation pair cross over each other when viewed along the vertical axis z (but do not physically touch). The first 16 and second 18 planes remain parallel, but are offset from one another along the vertical axis z.

The first part 4 takes the form of a flat, thin plate. Each of the second 15 and third 17 parts takes the form of a flat, thin annulus having a rectangular outer edge and a circular inner edge, defining an aperture 28. The second part 15 slides relative to the first part 4 on first plain bearings 47. Similarly, the third part 17 slides relative to the second part 15 on second plain bearings 48. The first crimps 20 are supported on an upper surface of the first part 4. The second part 15 supports the second crimps 21 on a lower surface and the third crimps 23 on an upper surface. The third part 17 supports the fourth crimps 24 on a lower surface.

When used in a camera 2, the image sensor 6 is supported on the first part 4 and at least one lens 11 of lens assembly 3 is coupled to the third part 17. The apertures 28 allows passage of light focused onto the image sensor 6. For this reason, none of the SMA wires 19, 22 intersect the apertures 28. Any one of the first 4, second 15 and third 17 parts may be fixed relative to the rest of the camera 1 structure, for example the can 9.

Although illustrated with particular shapes of the first 4, second 15 and third 17 parts, these shapes are not essential for the sixth actuator assembly 46. In other examples, the first 4, second 15 and/or third 17 parts (one or which may provide sides 27 of an actuator assembly) may have other inner and/or outer edges shaped as, for example, rectangles, diamonds, kites, or any other regular or irregular quadrilateral, or may have more or fewer than four sides.

Although the sixth actuator assembly 46 includes plain bearings 47, 48, any or all of these bearing may be replaced by other suitable bearings such as, for example, roller bearings, flexures and so forth.

Variations and/or modifications described in relation to any of the first 14 to fifth 42 actuator assemblies are equally applicable to the sixth actuator assembly 46. Seventh actuator assembly

In the first to sixth actuator assemblies 14, 36, 37, 38, 42, 46, the sides 27 are substantially parallel to the first x and second y axes, whilst first 19 and second 22 sets of SMA wires are configured to provide maximum amplification for movements constrained to be parallel to the first x and/or second y axes. However, this is not essential, and in other examples, first 19 and second 22 sets of SMA wires may be configured to provide maximum amplification for movements constrained to be parallel to axes oriented to be angled other than parallel/perpendicular to sides 27 of an actuator assembly.

Referring also to Figures 12A to 12C, a seventh exemplary actuator assembly 49 is shown (hereinafter "seventh actuator assembly").

Figure 12A shows the second part 15 and the first set of SMA wires 19 viewed from below along the vertical axis z. Figure 12B shows the third part 17 and the second set of SMA wires 22 viewed from below along the vertical axis z. Figure 12C shows the seventh actuator assembly 49 viewed from the side along the second axis y. SMA wires 19, 22 are omitted from Figure 12C for visual clarity.

The seventh actuator assembly 49 has a similar stacked structure to the sixth actuator assembly 46, except that the second 15 and third parts 17 both take the form of thin, flat square plates without apertures 28. In the seventh actuator assembly 49, the second flexures 26 connect the third part 17 to the second part 15, and electrical connections are then routed onward to the first part 4 via one or more first flexures 25.

The seventh actuator assembly 49 has an SMA wire crossing configuration similar to the second actuator assembly 36, except rotated such that the first set of SMA wires 19 provides maximum amplification along a rotated first axis 50 parallel to the line y = x. The second set of SMA wires 22 provides maximum amplification along a rotated second axis 51 parallel to the line y = -x.

In this way, the SMA wires 19, 22 may be oriented more diagonally relative to the sides 27, allowing for further increases in total length, and hence improved maximum stroke (displacement). When rotational movements are optionally supported, rotational stroke will also be increased.

The third part 17 has an upper (first) surface 52 and a lower (second) surface 53. The second surface 52 opposes the first part 4 across a gap/space (which in this example includes the second part 15. SMA wires 19, 22 belonging to the first and second sets are routed through the gap separating the first part 4 from the lower surface 53 of the third part 17, and pass close to the centre of the seventh actuator assembly 49 (when viewed along the vertical axis z). Consequently, when included in a camera 1, the image sensor 6 is mounted on the upper surface 52 of the third part 17, whilst the lens assembly 3 is fixed relative to the first part 4, for example via the can 9 (see Figure 1).

Variations and/or modifications described in relation to any of the first 14 to sixth 46 actuator assemblies are equally applicable to the seventh actuator assembly 49.

Other variations

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

The first 14 to seventh 49 actuator assemblies include four SMA wires 19, 22 in each of the first and second sets. However, more or fewer SMA wires 19, 22 may be used in one, some or all of the first, second and optionally third sets.

Instead of opposed pairs of SMA wires, contraction of each SMA wire 19 of the first set may be opposed by one or more springs (not shown) coupling the first part 4 to the second part 15. For example, the second and third SMA wires 192, 19a of the first set may be replaced by springs such that the first set includes two SMA wires 19. Additionally or alternatively, contraction of each SMA wire 22 of the second set may be opposed by one or more springs (not shown) coupling the third part 17 to the second part 15. For example, the second and third SMA wires 222, 22a of the second set may be replaced by springs such that the second set includes two SMA wires 22.

At a minimum, the first set of SMA wires 19 may include a single SMA wire 19, and the second set of SMA wires 22 may include a single SMA wire 22, each opposed by one or more corresponding springs (not shown). Such a configuration is best suited for operation in the first control mode, with movements parallel to first and second directions isolated to the first and second SMA wires 19, 22. When used, a spring (opposing any SMA wire) may take the form of a coil spring, a flat spring, a leaf spring, a flexure, an element formed of elastomeric material, and so forth.

One or more of the first plane 16, the second plane 18, and if included the third plane 41, need not be parallel to one or both other planes. One or more of the first plane 16, the second plane 18, and if included the third plane 41, need not be perpendicular to the vertical axis z. The actuator assemblies 2, 14, 36, 37, 38, 42, 46, 49, or parts 4, 15, 17, 39 thereof, need not be configured to support a lens assembly and, for example, may be configured to support another type of optical element, an image sensor, etc. The parts 4, 15, 17, 39 may, or may not, include apertures 28.

The actuator assemblies 2, 14, 36, 37, 38, 42, 46, 49 need not be used in a camera.

The vertical axis z need not correspond to an optical axis O. The vertical axis z may correspond to a line that is perpendicular to a plane defined by planar surfaces of the first 4, second 15, third 17 and/or fourth 39 parts. The vertical axis z may correspond to a line that is perpendicular to a plane defined by the directions of movement of the second 15, third 17 and/or fourth 39 parts.

The actuator assemblies 2, 14, 36, 37, 38, 42, 46, 49 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.