GB2629390A

GB2629390A - Camera assembly

Info

Publication number: GB2629390A
Application number: GB2306154.2A
Authority: GB
Inventors: Carr Joshua; Foote Will; matthew bunting Stephen; Benjamin Simpson Brown Andrew; Webber Dominic; Holdaway David
Original assignee: Cambridge Mechatronics Ltd
Current assignee: Cambridge Mechatronics Ltd
Priority date: 2023-04-26
Filing date: 2023-04-26
Publication date: 2024-10-30
Also published as: WO2024224069A1; GB202306154D0

Abstract

Optical image stabilisation (OIS) of a camera where one or more Shape Memory Alloys (SMA) actuator elements 1 are controlled 12 to rotate (tilt) a lens 11 relative to an image sensor 20, about an axis which is orthogonal to a primary/optical axis. The camera assembly has a support structure 30, which defines a primary axis, wherein the one or more SMA elements are connected between the support structure and the lens. The controller 12 may drive translational/lateral movement of the lens in a direction perpendicular to the primary axis. Preferably there are 4 or 8 SMA elements. The camera assembly maybe a hand-held device, e.g. a mobile telephone or tablet computer. Also, a camera assembly wherein the actuator SMA elements moves the lens in a translational (lateral) direction relative to the image sensor or where the SMA elements act to move the image sensor in a lateral direction relative to the lens.

Description

CAMERA ASSEMBLY

Field

The present application relates to camera assemblies.

Background

It is known to move various optical components of a camera. For example, a lens assembly and/or an image sensor of a camera can be moved to achieve optical image stabilisation (i.e. to counteract user handshake in order to stabilise an image on the image sensor). One or more lenses of a lens assembly may also be moved along the optical axis to focus an image on the image sensor.

The present disclosure relates to camera assemblies for achieving photographic effects.

Summary

According to an aspect of the present invention, there is provided a camera assembly comprising a support structure defining a primary axis; a first component; a movable component which is movable relative to the first component; an actuator arrangement comprising one or more SMA elements connected between the support structure and the movable component, and a controller arranged to control the actuator arrangement to drive rotation of the movable component relative to the first component about an axis of rotation which is perpendicular to the primary axis. The first component comprises an image sensor and the movable component comprises a lens or the first component comprises a lens and the movable component comprises an image sensor.

According to another aspect of the present invention, there is provided a camera assembly comprising: a support structure defining a primary axis; a first component; a movable component which is movable relative to the first component; an actuator arrangement comprising one or more SMA elements connected between the support structure and the movable component, and a controller arranged to control the actuator arrangement to drive translational movement of the movable component relative to the first component in a direction perpendicular to the primary axis. The first component comprises an image sensor and the movable component comprises a lens or the first component comprises a lens and the movable component comprises an image sensor. The controller is arranged to: - determine information identifying one or more objects, part of which are in a field of view of the camera assembly; and control the translational movement of the movable component based on the information such that the movable component moves from a first position to a second position relative to the first component.

A greater proportion of the one or more objects are in the field of view of the camera assembly in the second position as compared to the first position.

According to another aspect of the present invention, there is provided a device comprising any camera assembly as described herein.

In this way, relative tilt and/or translational movement between the lens and the image sensor is provided for, which facilitates or corrects for a number of photographic effects, including the following: (1) The Scheimpflug principle Generally, in capturing images with a camera a lens is maintained parallel to an image sensor to keep the image in focus. However, by tilting the lens and/or the image sensor relative to one another such that the focal plane is at an angle to the image plane, an object which is not parallel to the image plane can be photographed in focus. Alternatively, a series of objects which are at different distances from the image sensor can be photographed simultaneously, with each of the objects in focus.

(2) The Model Village effect Relative tilt between a lens and an image sensor can also be used to achieve a photographic effect referred to as the 'model village' effect. In this effect, the focal plane is again non-parallel to the image sensor such that a first portion of the image is in focus and one or more second portions of the image are blurred. This can give rise to an effect in which the brain misinterprets the scale of the image and the image appears to be on a miniature scale (i.e. 'model village').

(3) The Keystone effect Typically, when photographing a large object (e.g. a tall building), a camera must be tilted manually by a user in order to fit the whole of the object into the frame of view. Accordingly, a base of the object is closer to the image sensor than a top of the object and so the object converges towards a central axis ('A') of the image, as illustrated in Figure 1A. By shifting and optionally tilting a lens relative to an image sensor of a camera (or an image sensor relative to a lens), the whole (or more of) an image can be captured within the field of view without the convergence effect (as illustrated in Figure 1B).

In some embodiments, the actuator arrangement may comprise a total of eight SMA elements. The SMA elements may be inclined with respect to the primary axis with two SMA elements on each of four sides around the primary axis. The SMA elements may be connected between the movable component and the support structure so that on contraction two groups of four SMA elements provide a force on the movable component with a component in opposite directions along the primary axis.

The eight SMA actuator wires may have electrical connections that allow each of the SMA actuator wires to receive an independent drive signal. On each side, the two SMA actuator wires may be parallel to one another or may be inclined in opposite senses with respect to each other and cross. In some embodiments, the movable component may be supported on the support structure solely by the SMA actuator wires.

As mentioned above, the movable part may comprise one or more lenses. The lens or lenses may have a diameter of at most 20mm, preferably at most 15mm, preferably at most 10mm.

The image sensor may be any one of: a light sensor, an image sensor, a photodetector, a complementary metal-oxide-semiconductor (CMOS) image sensor, an active pixel sensor and a charge-coupled device (CCD).

In some embodiments, the controller may be configured to drive the actuator arrangement to: move the movable component to a primary position (e.g. the lens to a tilted position in order to focus on the faces of two people at different distances from the camera assembly), - then further drive the actuator arrangement (or a different actuator arrangement) to move one or more components of the camera assembly or device (for example the movable component, the first component or another component) to effect OIS.

For example, in embodiments in which the movable component comprises the lens, the lens may be tilted or shifted about the primary position to counteract user handshake. Alternatively or additionally, the image sensor may be shifted (e.g. by a second, separate actuator arrangement) in order to stabilize the image.

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 1A is a schematic view of a demonstration of the Keystone effect; Figure 1B is a schematic view of the object of Figure 1A in which the Keystone effect has been corrected; Figure 1C is a schematic side view of an SMA actuation arrangement; Fig. 2 is a perspective view of a first configuration of the SMA actuation arrangement; Fig. 3 is an axial view of a second configuration of the SMA actuation arrangement; and Fig. 4 shows a controller for controlling a camera assembly.

Detailed description

Camera assembly and actuator arrangements In the following description, the movable component comprises the lens and it is thus the lens that is moved relative to the image sensor. It will be appreciated that the movable component could instead comprise the image sensor and the image sensor is moved by the actuator arrangement relative to the lens. In this way, the following description equally applies to movement of the image sensor. Movement of both the lens and the image sensor could also be effected in order to achieve the desired relative movement between them.

Fig. 1C illustrates an SMA actuation arrangement 1 for a camera. The SMA actuation arrangement 1 comprises a support structure 30 having an image sensor 20 mounted thereon. A camera lens element 10 is suspended on the support structure 30 and is arranged to focus an image on the image sensor 20.

The camera lens element comprises one or more lenses 11, a single lens being illustrated in Fig. 1C for clarity. The camera is a miniature camera in which the or each lens 11 has a diameter of no more than 20mm.

As stated above, the SMA actuation arrangement 1 is for a miniature camera in which the camera lens element 10 is the movable component. The image sensor 20 is mounted on the support structure 30.

The image sensor may be held stationary with respect to the support structure or may be movable with respect to the support structure 30, the image sensor being driven by a separate, second actuator arrangement, for example comprising one or more SMA elements and/or voice coil motors (VCM).

Plural SMA actuator wires 50 are connected in tension between the support structure 30 and the camera lens element 10. The camera lens element 10 may be suspended on the support structure 30 exclusively by the SMA actuator wires 50. Alternatively, the camera lens element 10 may be suspended on the support structure 30 by a suspension system (not shown) that may have any suitable form for allowing movement of the camera lens element 10 with respect to the support structure 30 with the desired degrees of freedom, for example formed by flexures to allow movement in three dimensions, or formed by ball bearings or sliding bearings to allow movement in two dimensions while constraining movement in a third dimension, or constraining movement within a particular range of movement.

The SMA actuator wires 50 are in an arrangement in which the SMA actuator wires 50 are capable of driving movement of the camera lens element 10 with respect to the support structure 30 (and hence the image sensor) with plural degrees of freedom on selective contraction of the SMA actuator wires 50. The SMA actuator wires 50 may be configured to drive such movement as shown in Fig. 2 or Fig. 3 which show first and second configurations of the SMA actuation arrangement 1, or in general may have other configurations.

The first and second configurations of the SMA actuation arrangement 1 will now be described. For ease of reference, the z axis is taken to be the optical axis of the camera lens element 10 (when in a neutral position) and the x and y axes are perpendicular thereto. In a neutral orientation of the camera lens element 10, the optical axis of the camera lens element 10 is perpendicular to the image sensor 20 and the x and y axes are lateral to the image sensor 20.

Fig. 2 illustrates a first configuration for the SMA actuator arrangement 1 in which eight SMA actuator wires 50 are provided. In the first configuration, the SMA actuation arrangement 1 may have a construction as described in further detail in any of WO-2011/104518, WO-2012/066285 or WO 2014/076463, to which reference is made and which are each incorporated herein in their entireties. However, an overview of the arrangement of SMA actuator wires 50 is as follows.

Two SMA actuator wires 50 are provided on each of four sides of the camera lens element. Each SMA actuator wire 50 extends perpendicular to a line radial of the optical axis of the camera lens element 10, that is substantially perpendicular to the x axis or to the y axis. However, the SMA actuator wires 50 are inclined with respect the optical axis of the camera lens element 10, so that they each provide a component of force along the z axis and a component of force primarily along the x axis or primarily along the y axis.

Each SMA actuator wire 50 is connected at one end to the support structure 30 and at the other end to the camera lens element 10, selected so that in combination with the inclination of the SMA actuator wires 50, different SMA actuator wires 50 provide components of force in different directions along the z axis and different directions along the x axis or along the y axis. In particular, the pair of SMA actuator wires 50 on any given side of the camera lens element 10 are connected to provide components of force in opposite directions along the z axis, but in the same direction along the x axis or along the y axis. The two pairs of SMA actuator wires SO on opposite sides of the camera lens element 10 are connected to provide components of force in opposite directions along the x axis or along the y axis.

Thus, the SMA actuator wires 50 are capable, on selective contraction, of driving movement of the camera lens element 10 with respect to the support structure 30 in translational movement with three degrees of freedom (i.e. along the x, y and z axes) and also rotational movement with three degrees of freedom (i.e. around the x, y and z axes). Movement with each of the degrees of freedom is driven by contraction of different combinations of SMA actuator wires 50. As the movements add linearly, movement to any translational and/or rotational position within the six degrees of freedom is driven by a linear combination of contractions of the SMA actuator wires 50. Thus, the translational and rotational position of the camera lens element 50 is controlled by controlling the drive signals applied to each SMA actuator wire 50.

Movement of the lens may be performed for a number of reasons, including the photographic effects 1- 3 listed above. In addition, translational movement along the optical axis of the camera lens element 10 (i.e. along the z axis) may be used to change the focus of an image formed by the camera lens element 10 and translational movement laterally of the optical axis of the camera lens element 10 (i.e. along the x and y axes) may be used to provide 015.

Fig. 3 illustrates a second configuration for the SMA actuator arrangement 1 in which only four SMA actuator wires 50 are provided. The second configuration is capable of translating the movable component in directions perpendicular to the primary axis of the assembly (i.e. in or parallel to the x/y plane, as shown in Figure 3) and rotating the movable component about the primary axis. In the second configuration, the SMA actuation arrangement 1 may have a construction as described in further detail in any of W0-2013/175197 or W0-2014/083318, to which reference is made and which are each incorporated herein in their entireties. However, an overview of the arrangement of SMA actuator wires 50 is as follows.

In the second configuration, movement of the camera lens element 10 with respect to the support structure 30 along the optical axis (i.e. along the z axis) is constrained mechanically, for example by a suspension system which supports the camera lens element 10 on the support structure 30, which may comprise beams as disclosed in WO-2013/175197, ball bearings as disclosed in WO-2014/083318, or a sliding bearing. Thus fewer SMA actuator wires 50 are provided with a simpler arrangement as it is not necessary to drive movement along the optical axis.

One SMA actuator wire 50 is provided on each of four sides of the camera lens element. Each SMA actuator wire 50 extends substantially perpendicular to a line radial of the optical axis of the camera lens element 10, that is substantially perpendicular to the x axis or to the y axis and thus provides a component of force primarily along the x axis or primarily along the y axis. Each SMA actuator wire 50 is connected at one end to the support structure 30 and at the other end to the camera lens element 10.

The ends at which the SMA actuator wires 50 are connected to the support structure 30 alternate on successive sides around the z axis. As a result, the pairs of SMA actuator wires 50 on opposing sides provide a component of force in opposite directions along the x axis or in opposite directions along the y axis. However, the torques applied by two pairs of SMA actuator wires 50 are in opposite directions around optical axis (z axis).

Thus, the SMA actuator wires 50 are capable, on selective contraction, of driving movement of the camera lens element 10 with respect to the support structure 30 to translational movement with two degrees of freedom (i.e. along the x and y axes) and also rotational movement with one degrees of freedom (i.e. around the z axis). Movement with each of the degrees of freedom is driven by contraction of different combinations of SMA actuator wires 50. As the movements add linearly, movement to any translational and/or rotational position within the three degrees of freedom is driven by a linear combination of contractions of the SMA actuator wires 50. Thus, the translational and rotational position of the camera lens element 10 is controlled by controlling the drive signals applied to each SMA actuator wire 50.

Fig. 4 shows a schematic arrangement of a control circuit 12 for controlling a camera assembly. The control circuit 12 includes a processor 41 and a memory device 42. The processor receives inputs from sensors 40 which are physically coupled to the camera assembly and detects the vibrations experienced by the camera assembly. The sensor 40 may be a vibration sensor such as a gyroscope sensor which detects the angular velocity of the camera assembly in three dimensions or an accelerometer which detects motion allowing the orientation and/or position to be inferred. The control circuit monitors these inputs and determines any shake of the camera assembly when capturing an image. The processor also optionally receives inputs from a user input device 90, such as a touchscreen or one or more buttons.

The control circuit sends actuation signals to actuators 44 (such as SMA actuator wires) to cause the lens element of the camera assembly to move relative to the image sensor (or vice versa) according to the techniques described above to achieve the desired photographic effect and optionally correct or compensate for detected shake. The memory device 42 may store predetermined algorithms for moving the movable component which the processor 41 uses to drive the actuators 44.

Photographic effects Various actuator arrangements have been described above which facilitate translation and/or rotational movement of a movable component. Such movement can be used to achieve one or more photographic effects which are now described in more detail.

Scheimpflug effect The actuator arrangements described above (or any other suitable actuator arrangement) may be used to tilt the lens to achieve one or more photographic effects. By tilting the lens, the focal plane is angled relative to the image sensor, specifically to the light-sensitive region of the image sensor (generally the focal plane is parallel to the light-sensitive region instead). In this way, a plurality of objects (or a plurality of parts of a single object) which are at different distances from the camera assembly can be imaged, whilst maintaining each of the objects in focus. This is because the focal plane is tilted to intersect each of the objects. For example, a number of people at different distances from the camera assembly could be imaged, with the focal plane intersecting each of their faces.

The controller 12 may be arranged to control the image sensor to capture one or more images of the field of view of the camera assembly. The controller 12 may be arranged to determine (e.g. to receive or generate) information regarding one or more objects within the field of view and to drive movement of the movable component based on the determined information. Such information could be input by a user of the assembly. For example, the camera assembly may be part of a mobile telephone also comprising a touch screen. The user may select one or more objects in a field of view of the camera assembly e.g. via the touchscreen, and the controller 12 may be configured to tilt the lens relative to the image sensor based on that input, i.e. to tilt the focal plane in order to intersect each of the one or more objects. Alternatively or additionally, object recognition (e.g. facial recognition) could be used to identify one or more objects (e.g. faces) in the field of view and the controller 12 may then drive the actuator arrangement (e.g. SMA wires 50) to tilt the lens so that the focal plane intersects each of the objects such that they are in focus in the image.

In some embodiments the actuator arrangement 1 may be driven to tilt the movable component about an axis of rotation which is through the movable component (e.g. the lens), optionally through a centre of the movable component. In embodiments in which the movable component comprises the lens, the axis of rotation may be through the effective centre of the lens.

In some embodiments the actuator arrangement 1 may be configured to shift the movable component (i.e. translate the movable component) in a direction perpendicular to the primary axis as well as rotating the movable component about the primary axis.

Model village effect The focal plane may be tilted in the ways described above to achieve a 'model village effect' in which a first portion of the image is in focus and a second portion of the image is blurred. This second portion may cover (span) at least 50%, optionally at least 40%, optionally at least 30% of the area of the captured image.

The second, blurred, portion may comprise two sub-portions which may lie either side of the first (in-focus) portion. For example, a foreground section and background section of the image may be blurred, with a central portion of the image in focus.

Keystone effect When photographing a tall building (for example) the user may tilt the image capture device (e.g. a smartphone) relative to the building in order to fit it into the field of view of the device. This results in the image sensor being tilted relative to the building and in the resulting image, the sides of the building (as seen by the user) would converge towards a central axis of the image (e.g. as shown in Figure 1A). This is known as the Keystone effect.

To avoid (or reduce) this effect, the actuator arrangement may be driven to shift (i.e. translate) the movable component (e.g. the lens) in a direction perpendicular to the primary axis. In this way, there is a relative shift between the image sensor and the lens. By shifting in this way, all (or a greater proportion of) and object can be fit into the field of view of the camera assembly without having to tilt the focal plane (or with less tilt required). The convergence of the object in the resulting image (the Keystone effect) can thus be reduced or avoided.

In some embodiments the controller 12 is arranged to drive translational movement of the movable component (e.g. the lens) relative to the first component (e.g. the image sensor) in a direction perpendicular to the primary axis. There is thus lateral relative shift between the two components. The controller is further arranged to: - determine information identifying one or more objects, part of which are in a field of view of the camera assembly and control the translational movement of the movable component based on the information such that the movable component moves from a first position to a second position relative to the first component.

A greater proportion of the one or more objects are in the field of view of the camera assembly in the second position as compared to the first position. Taking the example of a tall building, the relative shift between the lens and image sensor facilitates a field of view with a greater angular extent and more of (or all) of the building can be photographed without the user needing to tilt the device (as much or at all) in order to fit the building into the field of view.

Determining information may comprise receiving and/or generating information. For example, the camera assembly may be part of a handheld device (e.g. a mobile telephone) also comprising a touch screen. The user may select one or more objects in a field of view of the camera assembly e.g. via the touchscreen, and the controller 12 may be configured to move the movable component (e.g. the lens) relative to the first component (e.g. the image sensor) based on that input. Alternatively or additionally, object recognition could be used to identify one or more objects (or parts of an object) in the field of view and the controller 12 may drive the actuator arrangement (e.g. SMA wires 50) to move the movable component accordingly.

In some embodiments, the controller may be configured to drive rotation of the movable component about an axis of rotation which is perpendicular to the primary axis (in addition to the translational movement). For example, some relative tilt between the image sensor and lens may be desired to increase the proportion of an object which can be photographed, whilst still reducing the Keystone effect with relative shift.

Movement of other components of the camera assembly or device

OLS

In any of the above embodiments in which the movable component is moved for any of the reasons given above, one or more components of the camera assembly may be moved to facilitate optical image stabilisation (01S). For example, the lens and/or the image sensor may be tilted and/or shifted relative to one another in order to counteract user handshake.

As illustrated in Figure 4, the assembly may comprise one or more vibration sensors 40 (e.g. gyroscopes, accelerometers). The amount or severity of the shake experienced by the camera assembly can be detected by the vibration sensors. The sensors 40 provide input to the processor which in turn drives the actuator arrangement based on that input to stabilize the image on the image sensor.

In some embodiments, the controller may drive the actuator arrangement to move the movable component to a primary position (e.g. the lens to a tilted position in order to focus on the faces of two people at different distances from the camera assembly). The controller may then further drive the actuator arrangement (or a different actuator arrangement) to move one or more components of the camera assembly or device (for example the movable component, the first component or another component) to effect OIS. For example, in embodiments in which the movable component comprises the lens, the lens may be tilted or shifted about the primary position to counteract user handshake.

Alternatively or additionally, the image sensor may be shifted (e.g. by a second, separate actuator arrangement) in order to stabilize the image.

Alignment of lens and image sensor The camera assembly may comprise a further actuator arrangement (e.g. such as that shown in Figure 2 or 3) configured to move the first component (e.g. the lens or image sensor). In some embodiments, the further actuator may be configured to translate the first component in directions perpendicular to the primary axis in order to align the image sensor and the lens. For example, if the lens is tilted relative to the image sensor, the image sensor may be shifted in order to capture the full image.

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

It will be appreciated that there may be many other variations of the above-described examples. For example, the above embodiments have been described with reference to image capture. It will be appreciated that the description applies to capture of a single or small number of images or to capture of video.

Specific embodiments have been described with reference to actuators comprising SMA elements. It will be appreciated that other actuator types (e.g. VCM) could be used.

Claims

Claims 1. A camera assembly comprising: a support structure defining a primary axis; a first component; a movable component which is movable relative to the first component; an actuator arrangement comprising one or more SMA elements connected between the support structure and the movable component, and a controller arranged to control the actuator arrangement to drive rotation of the movable component relative to the first component about an axis of rotation which is perpendicular to the primary axis, wherein: the first component comprises an image sensor and the movable component comprises a lens, or wherein: the first component comprises a lens and the movable component comprises an image sensor.
2. A camera assembly according to claim 1 wherein the controller is arranged to control the actuator arrangement to drive translation of the movable component in a direction perpendicular to the primary axis.
3. A camera assembly according to claim 1 or claim 2 wherein the axis of rotation passes through the movable component.
4. A camera assembly according to claim 3 wherein the axis of rotation passes through the centre of the movable component.
5. A camera assembly according to any preceding claim wherein the controller is arranged to cause the image sensor to capture an image of a scene, wherein the scene comprises a plurality of objects or parts of an object which are at different distances from the camera assembly and wherein the focal plane of the camera assembly intersects each of the object or each of the parts of the object.
6. A camera assembly according to any preceding claim wherein the controller is arranged to cause the image sensor to capture an image of a scene, wherein a first portion of the image is in focus and a second portion of the image is blurred.
7. A camera assembly according to claim 6 wherein the second portion comprises two sub-portions and the first portion is between the two sub-portions in the image.
8. A camera assembly according to claim 6 or claim 7 wherein the second portion covers at least 30% of the area of the image, optionally at least 40%, optionally at least 50%.
9. A camera assembly according to any preceding claim wherein the controller is configured to determine information regarding a portion of the field of view and the controller is configured to drive movement of the movable component and capture an image such that the portion of the field of view is in focus in the image.
10. A camera assembly according to claim 9 wherein the information regarding a portion of the field of view is derived from user input.
11. A camara assembly according to any preceding claim wherein the controller is configured to: drive the actuator arrangement to rotate the movable component about the axis of rotation to a primary position and then further drive the actuator arrangement to move the movable component about the primary position to effect optical image stabilisation.
12. A camara assembly according to any preceding claim further comprising a second actuator arrangement for driving movement of the first component, wherein the controller is configured to: drive the actuator arrangement to rotate the movable component about the axis of rotation to a primary position and drive the second actuator arrangement to move the first component to effect optical image stabilization while the movable component is in the primary position.
13. A camera assembly comprising: a support structure defining a primary axis; a first component; a movable component which is movable relative to the first component; an actuator arrangement comprising one or more SMA elements connected between the support structure and the movable component, and a controller arranged to control the actuator arrangement to drive translational movement of the movable component relative to the first component in a direction perpendicular to the primary axis, wherein the first component comprises an image sensor and the movable component comprises a lens, or the first component comprises a lens and the movable component comprises an image sensor, wherein the controller is arranged to: determine information identifying one or more objects, part of which are in a field of view of the camera assembly; and control the translational movement of the movable component based on the information such that the movable component moves from a first position to a second position relative to the first component, wherein a greater proportion of the one or more objects are in the field of view of the camera assembly in the second position as compared to the first position.
14. A camera assembly according to claim 13 wherein the one or more objects comprises a surface, edge or longitudinal axis and wherein the controller is configured to move the movable component such that the focal plane is substantially parallel to the surface, edge or longitudinal axis.
15. A camera assembly according to claim 13 or 14 wherein the controller is arranged to control the actuator arrangement to drive rotation of the movable component relative to the first component about an axis of rotation which is perpendicular to the primary axis.
16. A camera assembly according to any preceding claim wherein the camera assembly comprises a second actuator arrangement for driving movement of the first component, optionally wherein the movement comprises translational movement in a direction perpendicular to the primary axis, optionally wherein the second actuator arrangement comprises one or more SMA elements.
17. A camera assembly according to any preceding claim wherein the lens has a diameter of at most 20mm, preferably at most 15mm, preferably at most 10mm.
18. A camera assembly according to any preceding claim wherein the actuator arrangement comprises eight SMA elements.
19. A camera assembly according to any preceding claim wherein the actuator arrangement comprises a total of eight SMA elements.
20. A camera assembly according to claim 19 wherein the SMA elements are inclined with respect to the primary axis with two SMA elements on each of four sides around the primary axis, optionally wherein the SMA elements are connected between the movable component and the support structure so that on contraction two groups of four SMA elements provide a force on the movable component with a component in opposite directions along the primary axis.
21. A camera assembly according to any of claims 1 to 17 wherein the actuator arrangement comprises four SMA elements.
22. A camera assembly according to any of claims 1 to 17 wherein the actuator arrangement comprises a total of four SMA elements.
23. A camera assembly according to claim 22 wherein the movable component is supported on the support structure in a manner allowing movement of the movable component relative to the support structure across a range of movement in two orthogonal directions perpendicular to the primary axis extending through the movable component; and a total of four SMA actuator wires connected between the movable component and the support structure in an arrangement wherein none of the SMA actuator wires are collinear, and wherein the SMA actuator wires are capable of being selectively driven to move the movable component relative to the first component to any position in said range of movement without applying any net torque to the movable component in the plane of the two orthogonal directions around the primary axis.
24. A camera assembly according to any of claims 13 to 23, wherein the controller is configured to: drive the actuator arrangement to translate the movable component to a primary position relative to the first component and then further drive the actuator arrangement to move the movable component about the primary position to effect optical image stabilisation.
25. A camara assembly according to any of claims 13 to 23 further comprising a second actuator arrangement for driving movement of the first component, wherein the controller is configured to: drive the actuator arrangement to translate the movable component to a primary position relative to the first component and drive the second actuator arrangement to move the first component to effect optical image stabilisation.
26. A device comprising the camera assembly according to any preceding claim, wherein the device is a hand-held device.
27. A device according to claim 23, wherein the device is a mobile telephone or tablet computer.