GB2576173A

GB2576173A - Tuneable fluid lens

Info

Publication number: GB2576173A
Application number: GB1812809.0A
Authority: GB
Inventors: Benjamin Simpson Brown Andrew
Original assignee: Cambridge Mechatronics Ltd
Current assignee: Cambridge Mechatronics Ltd
Priority date: 2018-08-07
Filing date: 2018-08-07
Publication date: 2020-02-12
Also published as: GB201812809D0; GB202103203D0; CN112823305A; WO2020030915A1; GB2591646B; GB2591646A

Abstract

A tuneable optical device 100 has a static component 102, a moveable component 104 coupled to the static component and moveable relative to the static component; and a deformable material 106 provided between the static component and the moveable component. An actuator has at least one shape memory alloy (SMA) actuator wire 108 a-d coupled to the moveable component and arranged to, on contraction, drive movement of the moveable component whereby the deformable material is deformed and the lens is adjusted to provide autofocus and/or optical image stabilisation. The deformable material may be a liquid, a soft silicone material, a soft polymer or a gel. An image sensor may also be used and the optical device may be used in devices such as smartphones, cameras, laptops etc.

Description

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 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 and the lens is adjusted to provide autofocus and/or optical image stabilisation.

In a second approach of the present techniques, 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 image capture device, a foldable smartphone camera, an image capture device, a consumer electronic device, a mobile computing device, a laptop, a tablet computing device, a security system, a gaming system, an augmented reality system, a virtual reality system, 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.

Preferred features are set out in the appended dependent claims.

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; and

Figure 3 shows a perspective view of a tuneable optical device comprising opposing SMA actuator wire.

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 achieve optical image stabilisation.

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, 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 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 108-d, where each wire is coupled to a corner of the moveable component 104 and is arranged parallel or substantially parallel to an optical axis 0 of the device. 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 [primary?] 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 [primary?] 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.

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.

Claims

1. A tuneable optical device 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 and the lens is adjusted to provide autofocus and/or optical image stabilisation.

2. The tuneable optical device as claimed in claim 1 further comprising 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.

3. The tuneable optical device as claimed in claim 1 or 2 wherein the actuator comprises four SMA actuator wires, each wire coupled to a corner of the moveable component and arranged parallel to an optical axis of the device.

4. The tuneable optical device as claimed in claim 3 wherein, on contraction, the four SMA actuator wires apply a force to the moveable component in the same direction.

5. The tuneable optical device as claimed in claim 3 wherein, on contraction, two pairs of wires apply a force to the moveable component in opposite directions.

6. The tuneable optical device as claimed in any one of claims 3, 4 or 5 wherein the control circuitry:

supplies a drive signal to one of the four SMA actuator wires to tilt the moveable component and provide optical image stabilisation.

7. The tuneable optical device as claimed in any one of claims 3, 4 or 5 wherein the control circuitry:

supplies drive signals to two or more of the four SMA actuator wires to move the moveable component.

8. The tuneable optical device as claimed in claim 1 or 2 wherein the actuator comprises 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 moveable component, where each pair of lengths comprises a first length that is coupled to a first corner of a side of the moveable component and second length that is coupled to a second corner of the side of the moveable component.

9. The tuneable optical device as claimed in claim 8 wherein two lengths of SMA actuator wire are coupled to each corner and provided on adjacent sides of the moveable component, and are electrically connected together.

10. The tuneable optical device as claimed in claim 9 wherein, on contraction, the eight lengths of SMA actuator wire apply a force to the moveable component in the same direction along the optical axis.

11. The tuneable optical device as claimed in claim 9 wherein, on contraction, two groups of four lengths of SMA actuator wire apply a force to the moveable component in opposite directions along the optical axis.

12. The tuneable optical device as claimed in any of claims 9, 10 or 11 wherein the control circuitry:

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.

13. The tuneable optical device as claimed in any of claims 9, 10 or 11 wherein the control circuitry:

supplies 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.

14. The tuneable optical device as claimed in claim 11 wherein the control circuitry:

supplies drive signals to at least one group of four lengths of SMA actuator wire to move the moveable component.

15. The tuneable optical device as claimed in any one of claims 9 to 14 wherein the two lengths of SMA actuator wire coupled to each corner are portions of a single piece of SMA wire.

16. The tuneable optical device as claimed in any one of claims 1 to 15 wherein the moveable component is rigid.

17. The tuneable optical device as claimed in any one of claims 1 to 15 wherein the moveable component comprises a rigid portion and a flexible portion that flexes when the deformable material is deformed, thereby changing a focal length of the device.

18. The tuneable optical device as claimed in any one of claims 1 to 16 wherein the static component is rigid.

19. The tuneable optical device as claimed in any one of claims 1 to 16 wherein the static component comprises a rigid portion and a flexible portion that flexes when the deformable material is deformed, thereby changing a focal length of the device.

20. The tuneable optical device as claimed in any preceding claim wherein the moveable component and static component are plates.

21. The tuneable optical device as claimed in any preceding claim wherein one or more of the static component, moveable component and deformable material is transparent.

22. The tuneable optical device as claimed in any preceding claim wherein the deformable material is any one of: a liquid, a soft silicone material, a soft polymer, and a gel.

23. The tuneable optical device as claimed in any preceding claim further comprising an image sensor.

24. An apparatus comprising a tuneable optical device according to claims 1 to io 23.

25. The apparatus as claimed in claim 24 wherein the apparatus is any one of: a smartphone, a camera, binoculars, spectacles, a foldable smartphone, a foldable image capture device, a foldable smartphone camera, an image capture device, a

15 consumer electronic device, a mobile computing device, a laptop, a tablet computing device, a security system, a gaming system, an augmented reality system, a virtual reality system, a wearable device, a drone, an aircraft, a spacecraft, a submersible vessel, a vehicle, and an autonomous vehicle.