The present application generally relates to a tuneable fluid lens, and in particular to a fluid lens which is controllable using an actuator comprising at least one shape memory alloy (SMA) actuator wire to provide autofocus and/or optical image stabilisation.

In a first approach of the present techniques, there is provided a tuneable optical device comprising:

a first component and a second component, wherein the first component is moveable relative to the second component;

a deformable lens provided between the first component and the second component; and

a first actuator comprising:

at least one shape memory alloy (SMA) actuator wire coupled to the first component and arranged to, on contraction, drive movement of the first component whereby the deformable lens is deformed to provide (in particular, to enable the provision of) autofocus and/or optical image stabilisation.

Optionally, the first component is a movable component and the second component is a static component, and wherein the deformable lens is deformed to provide (in particular, to enable the provision of) at least optical image stabilisation.

Optionally, the first component is coupled to the second component.

Optionally, the tuneable optical device comprises:

a body relative to which each of the first and second components are movable: and

a second actuator comprising :

at least one SMA actuator wire coupled to the second component and arranged to, on contraction, drive movement of the second component, whereby the deformable lens is deformed and/or displaced by the movement of the first and second components. Optionally, the deformable lens is configured to be deformed and displaced by the movement of first and second components to enable the provision of optical zoom.

Optionally, the at least one SMA actuator wire of the second actuator is also coupled to the first component.

Optionally, the first and/or second actuators each comprises a plurality of SMA actuator wires arranged at an acute angle to an optical axis of the device.

Optionally, on contraction, the or each plurality of SMA actuator wires apply a force in the same direction to the component to which they are coupled.

Optionally, on contraction, the or each plurality of SMA actuator wires comprises two groups of SMA actuator wires of the actuator that apply a force in opposite directions to the component to which they are coupled.

Optionally, the tuneable optical device comprises:

control circuitry configured to supply a drive signal to at least one of the SMA actuator wires to tilt the component to which it is coupled relative to the other component to provide optical image stabilisation.

Optionally, the first and/or second actuators each comprise eight lengths of SMA actuator wire inclined with respect to an optical axis of the device, with a pair of lengths of SMA actuator wire provided on each of four sides of the component to which they are coupled, where each pair of lengths comprises a first length that is coupled to a first corner of a side of the component and second length that is coupled to a second corner of the side of the component.

Optionally, in a given actuator, two lengths of SMA actuator wire are coupled to each corner and provided on adjacent sides of the component, and are electrically connected together. Optionally, in a given actuator, on contraction, the eight lengths of SMA actuator wire apply a force to the component in the same direction along the optical axis. Optionally, in a given actuator, on contraction, two groups of four lengths of SMA actuator wire apply a force to the component in opposite directions along the optical axis.

Optionally, the tuneable optical device comprises:

control circuitry configured to supply a drive signal to at least the two lengths of SMA actuator wire coupled to one of the four corners of the first and/or second component to tilt the component relative to the other component and provide optical image stabilisation. Optionally, the tuneable optical device comprises:

control circuitry configured to supply drive signals to at least the two lengths of SMA actuator wire coupled to one of the four corners of the first and/or second component to move the component. Optionally, the control circuitry is configured to supply drive signals to at least one group of four lengths of SMA actuator wire to move the first and/or second component.

Optionally, the first and/or second components each comprises a set of through-holes, through each of which at least one of the plurality of wires coupled to the other component passes.

Optionally, the first actuator is configured to move the first component in directions perpendicular to the optical axis to move at least a portion of the deformable lens to enable the provision of optical image stabilisation; and

the second actuator is configured to move the second component along the optical axis to distort the deformable lens to enable the provision of autofocus.

Optionally, the first actuator comprises: four SMA actuator wires, each wire coupled to a corner of the first component and arranged substantially parallel to a side of the first component and substantially perpendicular to the optical axis of the device.

Optionally, each of the first and/or second components comprises a rigid portion and a flexible portion that flexes when the deformable lens is deformed, thereby changing at least a focal length of the device.

Optionally, the flexible portion of each of the first and/or second component extends across an aperture in the rigid portion, through which the deformable lens is configured to protrude when it is deformed.

Optionally, each of the first and/or second components are plates.

Optionally, one or more of the first component, second component and deformable lens is transparent.

Optionally, the deformable lens comprises any one of: a liquid, a soft silicone material, a soft polymer, and a gel.

Optionally, there is provided an apparatus comprising a tuneable optical device of the type described herein. The apparatus may be any one of: a smartphone, a camera, binoculars, spectacles, a foldable smartphone, a foldable tablet computing device, a foldable communications device, a foldable phablet, a foldable image capture device, 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 consumer electronic device, a mobile or portable computing device, a mobile or portable electronic device, a laptop, a tablet computing device, a phablet, a security system, a gaming system, a gaming accessory, an augmented reality system or device, a virtual reality system or device, a wearable device, a drone (aerial, water, underwater, etc.), an aircraft, a spacecraft, a submersible vessel, a vehicle, and an autonomous vehicle. It will be understood that this is a non-exhaustive list of example apparatus. Implementations of the present techniques will now be described, by way of example only, with reference to the accompanying drawings, in which :

Figure 1 shows a perspective view of a tuneable optical device comprising four SMA actuator wires;

Figure 2 shows a perspective view of a tuneable optical device comprising eight lengths of SMA actuator wire;

Figure 3 shows a perspective view of a tuneable optical device comprising opposing SMA actuator wires;

Figure 4 shows a perspective view of a tuneable optical device comprising an alternative arrangement of eight lengths of SMA actuator wire;

Figure 5 shows an exploded perspective view of a tuneable optical device comprising two sets of eight lengths of SMA actuator wire;

Figure 6 shows a perspective view of another tuneable optical device; and

Figure 7 shows how a deformable lens may be moved or deformed to achieve different types of optical effect.

Broadly speaking, embodiments of the present techniques provide an optical device comprising a lens (e.g. a fluid lens or deformable lens) in which one or more SMA actuator wires may be used for tuning the focal length of the lens and/or for adjusting the light beam direction through the lens to shift the image and achieve optical image stabilisation. Meanwhile, one or more SMA actuator wires may be used for also displacing the lens e.g. to achieve optical zoom.

A liquid or fluid lens uses one or more fluids to create an infinitely-variable lens. Fluid lenses can be adjusted to adjust their focus. Fluid lenses can also be used for optical image stabilisation (OIS). Fluid lenses offer a number of advantages over conventional glass, plastic or hybrid lenses, including a compact design, lower weight, lower power consumption (because they are lower weight), a completely sealed system (which does not allow dirt or dust ingress), and a low sensitivity to manufacturing tolerances. Fluid lenses could, therefore, replace conventional lenses in a variety of applications, such as in mobile phone cameras. Fluid lenses require an actuator to provide them with focussing and image stabilisation functionality. Accordingly, the present techniques use an SMA-based actuator to actuate a deformable lens/fluid lens.

An advantage of using an SMA-based actuator is that it is a low power actuator which is particularly suitable for use in size-constrained devices, such as cameras in smartphones.

The term "fluid lens" is used herein to mean any type of deformable lens, which may or may not comprise any liquid. Generally, the fluid lens comprises a deformable material, such as a liquid, a soft silicone material, a soft polymer, or a gel. It will be understood that this is a non-exhaustive and non-limiting list of example deformable materials. Thus, the term "fluid lens" is used interchangeably herein with the terms "lens", "deformable lens", "deformable material" and "liquid lens".

Generally speaking, a fluid lens that can achieve OIS may be constructed by providing a fluid or a deformable material between a moving plate and a static plate, where both plates may be rigid or may comprise rigid portions. The light may be steered through the fluid lens onto an image sensor by tilting the moving plate. Thus, the present techniques may provide a tuneable optical device comprising: a lens comprising : a static component; a moveable component coupled to the static component and moveable relative to the static component; and a deformable material provided between the static component and the moveable component; and an actuator comprising: at least one shape memory alloy (SMA) actuator wire coupled to the moveable component and arranged to, on contraction, drive movement of the moveable component whereby the deformable material is deformed such that the lens is adjusted to provide autofocus and/or optical image stabilisation. The optical device may further comprise control circuitry electrically connected to the at least one SMA actuator wire and for supplying drive signals to the at least one SMA actuator wire.

Figure 7 shows generally how a deformable/liquid lens 12 can be moved or deformed to achieve different types of optical effects. In the leftmost image in Figure 7, no force is being applied to the liquid lens 12. As shown in the central image, if a force is applied to the liquid lens 12 in a direction parallel to the optical axis O using an actuator, then the shape of the liquid lens 12 can be altered, thereby altering its focal length (for autofocus, macro focus, etc.). In this example, the shape of the liquid lens 12 is altered by pushing a lens shaper 4 onto the liquid lens 12, but it will be understood that this is merely one example technique to illustrate the concept. In the rightmost image in Figure 7, the lens shaper 4 is tilted, such that it is forced closer to the liquid lens 12 on one side, and moved away from the liquid lens 12 on the other side. This may be achieved by applying a force to the lens shaper 4 with a component in a direction orthogonal to the optical axis O. The result is a shape adjustment of the liquid lens 12 which is asymmetrical, and this enables OIS as well as focussing to be achieved. Techniques for achieving OIS and/or focussing or beam steering using a liquid lens and SMA actuator wire are now described with respect to Figures 1 to 6. The liquid lens 12 may be used in conjunction with an assembly 14 of non-liquid lenses.

Figure 1 shows a perspective view of an example tuneable optical device 100 comprising four SMA actuator wires. The tuneable optical device 100 comprises a static component 102 and a moveable component 104, which are coupled together (e.g. their edges may be coupled together). The device 100 comprises a deformable material 106 which is provided between the static component 102 and the moveable component 104. At least in those cases where the deformable material 106 is able to flow (e.g. when it is a liquid), but possibly all arrangements, the static component 102 and the moveable component 104 may be sealed together along their edges such that the deformable material 106 is retained between them. Together, the static component 102, moveable component 104 and deformable material 106 form the fluid lens 110 of the optical device 100. Moving the moveable component 104 may cause the shape or area of the deformable material 106 to change. For example, if deformable material 106 is confined to a smaller area, the focal length of the optical device may be adjusted, whereas if deformable material 106 is squeezed to have a particular shape (e.g. prism-like shape), the optical device may be able to adjust the beam direction of incoming light so that it is directed to an image sensor.

In the embodiment shown in Figure 1, the static component 102 and/or the moveable component 104 may be completely or substantially rigid. Alternatively, the static component 102 and/or the moveable component 104 may comprise a rigid portion, and a flexible portion 112 that flexes when the deformable material is deformed, thereby enabling the focal length of the lens 110 to be changed. For instance, when the deformable material is deformed by squeezing it into a smaller area/space, the deformable material may cause the flexible portion 112 to expand or bulge, such that the lens shape moves from flat to convex. For example, the moveable component 104 may comprise a flexible portion 112 at its centre, while the rest of the moveable component 104 may be rigid. The flexible portion 112 may not be circular or provided at the centre of the moveable component 104 - the illustration is merely exemplary and non-limiting. The flexible portion 112 may be formed from a flexible membrane that is coupled to the rigid portion of the moveable component 104. Alternatively, the flexible portion 112 may be provided by a thin layer of the same material which is used to provide the rigid portion - when the material is thin, it may exhibit some flexibility/may be less stiff. The flexible portion 112 may function as a resilient biasing element or 'return spring'. For example, when the deformable material is forced to deform such that the flexible portion 112 is caused to stretch and expand/bulge, the stretched flexible portion 112 returns the lens to return to an equilibrium or rest state when the force applied to the deformable material is removed. Thus, the flexible portion 112 may be formed of an elastic or resilient material which is able to stretch when a force is applied to the deformable material, and relax when the force is removed and thereby return the lens to the equilibrium state.

The tuneable optical device 100 comprises an actuator comprising at least one shape memory alloy (SMA) actuator wire coupled to the moveable component 104 and arranged to, on contraction, drive movement of the moveable component 104 whereby the area or shape of the deformable material 106 is adjusted to provide autofocus and/or optical image stabilisation. In this example arrangement, the actuator comprises four SMA actuator wires 108a-d, where each wire is coupled to a corner of the moveable component 104 and is arranged at an acute angle to, or parallel (or substantially parallel) to, an optical axis O of the device. For example, each of the SMA actuator wires may extend at an angle of less than 60°, or less than 45°, or less than 30°, or less than 10°, or ~0° relative to the optical axis O. The moveable component 104 may be tilted to provide OIS by contracting one of the SMA actuator wires. The wire which is driven and contracted is chosen based on which way incoming light needs to be steered/directed. For example, if SMA actuator wire 108a is driven and caused to contract, the moveable component 104 tilts such that the corner of the moveable component 104 to which wire 108a is attached moves closer to the static component 102, and the corner to which wire 108c is attached moves away from the static component 102 as wire 108c extends/stretches. Thus, deformable material 106 is squeezed away from the corner to which wire 108a is attached and the resulting change in the shape of the fluid lens 110 may enable OIS. The moveable component 104 may be considered to move about a virtual pivot point. The virtual pivot may be at the centre of the fluid lens or otherwise.

In embodiments, the four SMA actuator wires 108a-d may, on contraction, apply a force to the moveable component 104 in the same direction. Alternatively, two pairs of wires (e.g. a first pair formed of wires 108a and 108c, and a second pair formed of wires 108b and 108d) apply, on contraction, a force to the moveable component 104 in opposite directions (not illustrated). An opposing wire arrangement may provide finer control or movement of the moveable component 104, and thus finer adjustment of the lens 110, relative to a wire arrangement in which all the wires apply a force in the same direction. As mentioned above, the flexible portion 112 of the fluid lens may be formed of a resilient material and provide a return force when the SMA actuator wires are no longer being driven, such that the lens is able to return to its default, equilibrium state.

The optical device 100 may comprise control circuitry (not shown) which supplies a drive signal to one of the four SMA actuator wires to tilt the moveable component and provide optical image stabilisation. In embodiments, the control circuitry may supply drive signals to two or more of the four SMA actuator wires to move the moveable component.

Thus, an actuator comprising four SMA actuator wires may be used to provide a fluid lens that can perform OIS.

However, while the height of the fluid lens 110 may be low, the overall height of the device 100 is quite large. An alternative arrangement of the SMA actuator wires may enable the height of the device 100 to be reduced without loss of functionality. Example alternative arrangements are shown in Figure 2.

Figure 2 shows a perspective view of a tuneable optical device 200 comprising eight lengths of SMA actuator wire. The device 200 comprises a fluid lens formed of a static component, moveable component 204 and a deformable material. The deformable material and static component are not shown here for the sake of clarity. Here, the actuator comprises eight lengths of SMA actuator wire 208a-h which are inclined with respect to an optical axis O of the device 200. A pair of lengths of SMA actuator wire are provided on each of four sides of the moveable component 204, where each pair of lengths comprises a first length that is coupled to a first corner of a side of the moveable component 200 and second length that is coupled to a second corner of the side of the moveable component 200. Two lengths of SMA actuator wire are coupled to each corner and provided on adjacent sides of the moveable component. The two lengths of SMA actuator wire coupled to each corner are electrically connected together. Thus, wire lengths 208a, b are electrically connected together, wire lengths 208c, d are electrically connected together, wire lengths 208e,f are electrically connected together, and wire lengths 208g,h are electrically connected together. The angle by which the wire lengths 208a-h are inclined relative to the optical axis O may be the same, and may amplify the amount by which the moveable component 204 tilts as wires contract or stretch.

In this embodiment, when all the SMA actuator wires 208a-h are contracted and have the same tension, the resultant force from all the wires does not create a torque. Thus, if all the wires 208a-h are driven (e.g. simultaneously) and have the same resulting tension, the moveable component 204 may be moved in its entirety closer to the static component, which may cause the deformable material to be squeezed across a greater area, which may enable adjustment of the focal length of the fluid lens as described above. Similarly, driving the two lengths of wire coupled to a corner of the moveable component 204, such as lengths 208e and 208f, causes the moveable component 204 to tilt such that the corner of the moveable component 204 to which wire lengths 208e,f are attached moves closer to the static component, and the corner to which wire lengths 208a, b are attached moves away from the static component. Thus, the deformable material may be squeezed away from the corner to which wire lengths 208e,f are attached and the resulting change in the fluid lens enables OIS.

In embodiments, the eight lengths of SMA actuator wire may, on contraction, apply a force to the moveable component 204 in the same direction along the optical axis. Alternatively, two groups of four lengths of SMA actuator wire may, on contraction, apply a force to the moveable component in opposite directions along the optical axis. An opposing wire arrangement may provide finer control or movement of the moveable component 204, and thus finer adjustment of the lens, relative to a wire arrangement in which all the wires apply a force in the same direction. (See Figure 3 for an example opposing wire arrangement).

The tuneable optical device 200 may comprise control circuity (not shown), which supplies a drive signal to the two lengths of SMA actuator wire coupled to one of the four corners of the moveable component to tilt the moveable component and provide optical image stabilisation. The control circuitry may supply drive signals to the two lengths of SMA actuator wire coupled to at least one of the four corners of the moveable component to move the moveable component. That is, the wires at one corner may be driven to tilt the moveable component 204 in one direction, or the wires at multiple corners may be driven. In embodiments, the control circuitry may supply drive signals to at least one group of four lengths of SMA actuator wire to move the moveable component

In embodiments, the eight lengths of SMA actuator wire 208a-h may be separate pieces of SMA wire. Additionally or alternatively, the two lengths of SMA actuator wire coupled to each corner may be portions of a single piece of SMA wire. In this case, the moveable component 204 may comprise a hook or protrusion (not shown) at each corner, and each piece of SMA wire may be hooked over the hook or protrusion such that one portion of the SMA wire is provided along one edge of the moveable component 204 and another portion of the SMA wire is provided along an adjacent edge of the moveable component 204. Thus, in embodiments, the device 200 may comprise four SMA actuator wires.

In the embodiment shown in Figure 2, the static component and/or the moveable component 204 may be completely or substantially rigid. Alternatively, the static component and/or moveable component 204 may comprise a rigid portion, and a flexible portion 212 that flexes when the area or shape of the deformable material is adjusted, thereby enabling the focal length of the lens to be changed. For instance, when the deformable material is deformed by squeezing it into a smaller area/space, the deformable material may cause the flexible portion 212 to expand or bulge, such that the lens shape moves from flat to convex. For example, as shown in Figure 2, the moveable component 204 may comprise a flexible portion 212 at its centre, while the rest of the moveable component 204 may be rigid. The flexible portion 212 may not be circular or provided at the centre of the moveable component 204 - the illustration is merely exemplary and non-limiting. The flexible portion 212 may be formed from a flexible membrane that is coupled to the rigid portion of the moveable component 204. Alternatively, the flexible portion 212 may be provided by a thin layer of the same material which is used to provide the rigid portion - when the material is thin, it may exhibit some flexibility/may be less stiff.

Figure 3 shows a perspective view of a tuneable optical device 300 comprising opposing SMA actuator wire. Many of the features or possible features of the optical device 300 are similar to those shown in Figure 2 and described above. Thus, the following only discusses the differences relative to Figure 2 for the sake of simplicity.

The device 300 comprises a fluid lens formed of a static component, moveable component 304 and a deformable material. The deformable material and static component are not shown here for the sake of clarity. Here, the actuator comprises eight lengths of SMA actuator wire 308a-h which are inclined with respect to an optical axis O of the device 300. A pair of lengths of SMA actuator wire are provided on each of four sides of the moveable component 304, where each pair of lengths comprises a first length that is coupled to a first corner of a side of the moveable component 300 and second length that is coupled to a second corner of the side of the moveable component 300. Two lengths of SMA actuator wire are coupled to each corner and provided on adjacent sides of the moveable component. The two lengths of SMA actuator wire coupled to each corner are electrically connected together. Thus, wire lengths 308a, b are electrically connected together, wire lengths 308c, d are electrically connected together, wire lengths 308e,f are electrically connected together, and wire lengths 308g,h are electrically connected together. Compared to Figure 2, here, two groups of four lengths of SMA actuator wire are arranged such that, on contraction, they apply a force to the moveable component 304 in opposite directions along the optical axis O. For example, a first group may be formed of wire lengths 308a, 308b, 308e and 308f, and a second group may be formed of wire lengths 308c, 308d, 308g and 308h. Thus, the first group of wire lengths are attached to two opposite corners of the moveable component 304, and the second group of wire lengths are attached to the remaining two opposite corners of the moveable component 304. This opposing wire arrangement may provide finer control or movement of the moveable component 304, and thus finer adjustment of the lens, relative to a wire arrangement in which all the wires apply a force in the same direction (e.g. Figure 2).

In embodiments, the moveable component may be rigid. Alternatively, the moveable component may comprise a rigid portion and a flexible portion that flexes when the deformable material is deformed, thereby changing a focal length of the device.

In embodiments, the static component may be rigid. Alternatively, the static component may comprise a rigid portion and a flexible portion that flexes when the deformable material is deformed, thereby changing a focal length of the device.

In embodiments, the moveable component 104, 204 and static component 102 may be plates. In embodiments, the static component and moveable component may be transparent. In embodiments, only the portions of the static component and moveable component through which light passes may be transparent. For example, in some embodiments, on the flexible portion of the static component and/or moveable component may be transparent.

In embodiments, the deformable material may be transparent. The deformable material may be any one of: a liquid, a soft silicone material, a soft polymer, and a gel.

In each embodiment, the device may comprise an image sensor.

In the embodiments of Figures 1 to 3, the device comprises a moveable component and a static component. However, it may be useful for both components which sandwich the deformable material or lens to be moveable components. Figures 4 to 6 show embodiments where the device comprises two moveable components instead of a moveable and a static component. Thus, in these embodiments, the first component is a first moveable component and the second component is a second moveable component, and the actuator comprises: at least one SMA actuator wire coupled to the first moveable component; and at least one SMA actuator wire coupled to the second moveable component.

In these embodiments, the first moveable component and the second moveable component may be plates comprising an aperture. The deformable material or lens may protrude through each aperture. The first moveable component and the second moveable component may be rigid plates. Alternatively, one or both of the first moveable component and the second moveable component may be a plate which comprises a rigid portion and a flexible portion that flexes when the deformable material/lens is deformed.

Figure 4 shows a perspective view of an example tuneable optical device 400 comprising an alternative arrangement of eight lengths of SMA actuator wire to those shown in Figures 2 and 3. The tuneable optical device 400 comprises a first moveable component 402 and a second moveable component 404. The first and second moveable components may be coupled together (e.g. their edges may be coupled together). The device 400 comprises a deformable material or lens (not shown) which is provided between the first moveable component 402 and the second moveable component 404. That is, the deformable material/lens is sandwiched between the first and second moveable components. Each of the first moveable component 402 and second moveable component 404 comprises an aperture 414. Light is able to be enter through one aperture, pass through the deformable material/lens, and exit through another aperture. The deformable material/lens may extend or protrude through each aperture 414. Moving one or both of the first and second moveable components 402, 404 may cause the shape or area of the portion of the deformable lens which protrudes through the apertures 414 to change. For example, if the deformable lens is adjusted such that the lens bulges through one or both apertures 414, the focal length of the device 400 may be adjusted, whereas if the deformable material is squeezed to have a particular shape (e.g. prism-like shape or wedge), the optical device may be able to adjust the beam direction of incoming light so that it is directed to an image sensor (not shown).

The first moveable component 402 and the second moveable component 404 each comprise a through-hole 412 in each corner. As shown in Figure 4, the first moveable component 402 comprises four through-holes 412 in each corner, and the second moveable component 404 comprises four through-holes 412 in each corner.

The actuator of device 400 comprises a first set of four SMA actuator wires 406a-d arranged parallel to an optical axis O of the device 400. Each wire 406a- d in the first set passes through a through-hole 412 in a corner of the first moveable component 402 and is coupled to a corresponding (i.e. adjacent) corner of the second moveable component 404. The actuator of device 400 further comprises a second set of four SMA actuator wires 408a-d arranged parallel to the optical axis O of the device 400. Each wire 406a-d in the second set passes through a through-hole 412 in a corner of the second moveable component 404 and is coupled to a corresponding (i.e. adjacent) corner of the first moveable component 402. One or both of the moveable components 402, 404 may be tilted to provide OIS by contracting at least one of the SMA actuator wires which are coupled to that component. The wire which is driven and contracted is chosen based on which way incoming light needs to be steered/directed. For example, if SMA actuator wire 408a is driven and caused to contract, the second moveable component 404 tilts such that the corner of the first moveable component 402 to which wire 408a is attached moves towards the second moveable component 404, and the corner of the first moveable component 402 to which wire 408c is attached moves away from the second moveable component 404 as wire 408c extends/stretches. Thus, the deformable material/lens is squeezed away from the corner to which wire 408a is attached and the resulting change in the shape of the deformable lens may enable OIS. The moveable components 402, 404 may be considered to move about a virtual pivot point. The virtual pivot may be at the centre of the deformable lens or otherwise.

In Figure 4, the two moveable components 402, 404 may be guided by bearings or flexures (not shown). In the simplest modification of the device 400, each moveable component 402, 404 may be actuated by a single SMA actuator wire, where each wire may pull a moveable component towards the other component, such that contracting one or both wires squashes the deformable lens, while contracting on wire while stretching the other wire may cause the deformable lens to move along the optical axis (i.e. to stretch/expand along the direction of the optical axis and form a thicker lens). It will be understood that any number of wires may be coupled to each moveable component in order to enable finer tuning of the shape of the deformable lens. For example, multiple wires may be coupled to each side of one or both of the moveable components 402, 404. It will be understood that in the arrangement shown in Figure 4, the wires coupled to each component need not be coupled to the corner of the component but could be coupled somewhere along an edge/side of the component.

Differential movement of both movable elements 402, 404 in the direction of the optical axis O can produce both displacement and distortion of the lens that achieves optical zoom. This optical zoom effect may be combined with a displacement and/or deformation of the lens to adjust the focus at the new zoom. In the arrangement shown in Figure 4, four wires pull on each of the moveable components 402, 404, and the tensions of the four wires act to compress the deformable lens. This arrangement may allow lens shape tuning to correct, or deliberately introduce, asymmetries about planes which include the optical axis. This may in turn enable distortion correction or beam steering.

The device 400 may comprise one or more resilient components such as flexures (not shown), which may provide a return force when the SMA actuator wires are no longer being drive, such that the deformable lens is able to return to its default, equilibrium state.

On contraction, the first set of four SMA actuator wires 406a-d may apply a force to the second moveable component 404 in a first direction, and the second set of four SMA actuator wires 408a-d may apply a force to the first moveable component 402 in a second, opposite direction.

The through-holes 412 of the first moveable component 402 are offset from the through-holes 412 of the second moveable component 404 as shown in Figure 4.

Figure 5 shows a perspective view of a tuneable optical device 500 comprising two sets of eight lengths of SMA actuator wire 508. The tuneable optical device 500 comprises a first moveable component 502 and a second moveable component 504. The device 500 comprises a deformable material or lens 506 which is provided between the first moveable component 502 and the second moveable component 504. That is, the deformable material/lens 506 is sandwiched between the first and second moveable components 502, 504. Each of the first moveable component 502 and second moveable component 504 comprises an aperture 514. Light is able to be enter through one aperture, pass through the deformable material/lens, and exit through another aperture. The deformable material/lens may extend or protrude through each aperture 514. Moving one or both of the first and second moveable components 502, 504 may cause the shape or area of the portion of the deformable lens which protrudes through the apertures 514 to change. For example, if the deformable lens is adjusted such that the lens bulges through one or both apertures 514, the focal length of the device 500 may be adjusted, whereas if the deformable material is squeezed to have a particular shape (e.g. prism-like shape or wedge), the optical device may be able to adjust the beam direction of incoming light so that it is directed to an image sensor (not shown).

The actuator of device 500 comprises: a first set of eight lengths of SMA actuator wire 508 inclined with respect to an optical axis O of the device 500, with a pair of lengths of SMA actuator wire 508 provided on each of four sides of the first moveable component, where each pair of lengths comprises a first length that is coupled to a first corner of a side of the first moveable component 502 and second length that is coupled to a second corner of the side of the first moveable component 504; and a second set of eight lengths of SMA actuator wire 508 inclined with respect to an optical axis of the device, with a pair of lengths of SMA actuator wire 508 provided on each of four sides of the second moveable component 504, where each pair of lengths comprises a first length that is coupled to a first corner of a side of the second moveable component 504 and second length that is coupled to a second corner of the side of the second moveable component 504. Thus, the wire arrangement is similar to that shown in Figure 2, except that here both moveable components 502, 504 are coupled to lengths of SMA actuator wire 508. For the sake of brevity, the movement of each moveable component 502, 504 is not described since the movement is similar to that described with respect to Figure 2. This arrangement may enable adjustable zoom and focus by combining changes in lens position along the optical axis O and lens deformation by squeezing the lens along the optical axis O. Distortion correction and OIS may be achieved by adjusting the relative tilts of the two moveable components 502, 504 in combination with motion of the deformable lens 506 perpendicular to the optical axis O.

As in Figure 2, in device 500, two lengths of SMA actuator wire 508 may be coupled to each corner and provided on adjacent sides of the first moveable component 502, and may be electrically connected together, and two lengths of SMA actuator wire 508 may be coupled to each corner and provided on adjacent sides of the second moveable component 504, and may be electrically connected together. In this example, the lengths of SMA actuator wire 508 apply a force to each of the moveable components 502, 504 in a direction towards the deformable lens 506. These forces are opposed by the resilience of the deformable lens 506. In other examples, each of the moveable components 502, 504 may be coupled to an arrangement of opposing SMA actuator wires similar to that described above with reference to Figure 3.

Figure 6 shows a perspective view of another example of a tuneable optical device 600. The tuneable optical device 600 comprises a first moveable component 602 and a second moveable component 604. The first and second moveable components may be coupled together (e.g. their edges may be coupled together). The device 600 comprises a deformable material or lens 606 which is provided between the first moveable component 602 and the second moveable component 604. That is, the deformable material/lens is sandwiched between the first and second moveable components. At least the first moveable component 602, but possibly also the second moveable component 604, comprises an aperture 614. (If the second moveable component 604 does not have an aperture, it may be formed of a transparent material). The deformable material/lens 606 may extend or protrude through each aperture 614.

The actuator of device 600 comprises four SMA actuator wires 608a-d, each wire coupled to a corner of the first moveable component 602 and arranged parallel to a side of the first moveable component 602 and perpendicular to the optical axis O of the device 600. The SMA actuator wires 608a-d may be used to move the first moveable component 602 laterally, i.e. in a plane perpendicular to the optical axis O.

The actuator also comprises a SMA actuation mechanism (not shown) similar to that illustrated in Figures 1 to 3 for moving the second moveable component 604 vertically, i.e. along the optical axis O.

Control circuitry (not shown) may supply drive signals to the four SMA actuator wires 608a-d to laterally move the first moveable component 602. The detailed arrangement of the four SMA actuator wires 608a-d and techniques for driving these wires may be as described in WO 2013/175197 Al, which is incorporated herein by this reference. Control circuitry may supply a drive signal to the SMA actuation mechanism for moving the second moveable component 604 vertically. The deformable lens 606 may have a dome-shaped upper portion (as shown) whose shape is at least substantially unaffected by the lateral movement of the first moveable component 602 relative to the second moveable component 604. The lateral movement of this upper portion of the deformable lens 606 can be used to achieve optical image stabilisation (as explained in WO 2013/175197 Al). A compliant lower portion of the deformable lens 606 accommodates the relative lateral movement of the first and second moveable component 602, 604.

In this example, the vertical movement of the second moveable component 604 causes the shape (or area) of the upper portion of the deformable lens 606 to change in such a way that its focal length is adjusted, e.g. for autofocus. In particular, the force from the second moveable component 604 may be transmitted via the lower portion to the upper portion of the deformable lens 606 and may change the extent to which the deformable lens 606 protrudes through the aperture 614.

In other examples, the second moveable component 604 may have an aperture and the movement of the second moveable component 604 may alternatively or additionally affect the extent to which the deformable lens 606 protrudes through this aperture.

The device 600 may comprise bearing pads 610 which bear over a static portion of the device such as a housing/body (not shown). In each of Figures 4 to 6, the deformable lens may comprise any one of: a liquid, a soft silicone material, a soft polymer, and a gel.

5/8 The deformable lens need not be a simple, single element, but could be a structured deformable lens such as, for example, a two-stage liquid lens designed to reduce or eliminate chromatic aberration. The device may further comprise an image sensor (not shown).

Those skilled in the art will appreciate that while the foregoing has described what is considered to be the best mode and where appropriate other modes of performing present techniques, the present techniques should not be limited to the specific configurations and methods disclosed in this description of the preferred embodiment. Those skilled in the art will recognise that present techniques have a broad range of applications, and that the embodiments may take a wide range of modifications without departing from any inventive concept as defined in the appended claims.

For example, at least some of the SMA wires may be coupled between the first and/or second components and a (static) body of the device and/or may be coupled between the first and second components.