WO2020120998A2

WO2020120998A2 - Techniques for controlling the motion of sma actuators

Info

Publication number: WO2020120998A2
Application number: PCT/GB2019/053568
Authority: WO
Inventors: Matthew John Reynolds; Daniel John BURBRIDGE; Robert LANGHORNE; Samuel ARMSTRONG; Nicolas HEIJNE; James Howarth
Original assignee: Cambridge Mechatronics Limited
Priority date: 2018-12-14
Filing date: 2019-12-16
Publication date: 2020-06-18
Also published as: GB2594015A; GB201905771D0; GB2594015B; GB201820457D0; WO2020120998A3; GB202109540D0; CN113195891A

Abstract

Broadly speaking, embodiments of the present techniques provide techniques for improving the operation of a shape memory alloy (SMA) actuator by using at least one damping element to reduce undesired movement of the actuator.

Description

Techniques for Controlling the Motion of SMA Actuators

The present application generally relates to techniques for improving the operation of a shape memory alloy (SMA) actuator, and in particular to the use of viscous materials to reduce undesirable movement of the actuator.

A shape memory alloy (SMA) actuator assembly for actuating movement of a movable element in two dimensions perpendicular to a primary axis is described in International Patent Publications WO2013/175197 and

WO2014/083318. Such actuators may be used for Optical Image Stabilization (OIS) in miniature cameras. These actuators comprise four SMA wires connected between a movable element and a fixed support. Each wire is connected at one of its ends to the movable element at a crimp (the moving crimp) and at its other end to the support structure (the static crimp).

An SMA actuator assembly for providing positional control of a moveable component with multiple degrees of freedom is described in International Patent Publication No. W02011/104518 and in International Patent Application No. PCT/GB2018/052302. Such actuators comprise eight SMA actuator wires which may be independently driven or driven in groups. The eight SMA actuator wires may be driven to move the moveable component with all the following degrees of freedom : movement along the primary axis (e.g. an optical axis when the actuator is used in a camera), movement in any arbitrary direction laterally of the primary axis, and tilting in any arbitrary direction. Accordingly, such eight- wire SMA actuators may be used to provide both auto-focus (AF) and optical image stabilisation (OIS) in cameras/miniature cameras. In these actuators, a moveable component is supported on a support structure by the eight SMA actuator wires. Each wire is connected at one of its ends to the moveable component and at its other end to the support structure.

The present applicant has identified the need for an SMA actuator in which undesired motion of the actuator is reduced or prevented.

In a first approach of the present techniques, there is provided a shape shape memory alloy (SMA) actuation apparatus comprising : a support structure comprising : a base plate, and a static crimp plate comprising static wire attach structures; a moveable component supported on the support structure in a manner allowing movement of the moveable component relative to the support structure in two orthogonal directions perpendicular to a notional primary axis extending through the moveable component, the moveable component comprising : a spring plate comprising moveable wire attach structures; at least two shape memory alloy (SMA) actuator wires connected between the moveable component and the support structure and arranged to, on contraction, move the moveable component; and a viscous material provided in at least one location in the SMA actuation apparatus and arranged to reduce undesirable motion of the moveable component.

In a second approach of the present techniques, there is provided a shape memory alloy (SMA) actuation apparatus comprising: a support structure; a moveable component supported on the support structure in a manner allowing movement of the moveable component relative to the support structure; eight SMA actuator wires inclined with respect to a notional primary axis with two SMA actuator wires on each of four sides around the primary axis, the SMA actuators being connected between the moveable component with a component in opposite directions along the primary axis, the SMA actuator wires of each group being arranged with two-fold rotational symmetry about the primary axis; and at least one damping element arranged to reduce undesirable motion of the moveable component.

In a third approach of the present techniques, there is provided an apparatus comprising an SMA actuation apparatus of the types described herein.

The apparatus may be any one of: a smartphone, a protective cover or case for a smartphone, a functional cover or case for a smartphone or electronic device, a camera, a foldable smartphone, a foldable image capture device, a foldable smartphone camera, a foldable image capture device, a foldable consumer electronics device, an image capture device, a camera with folded optics, an array camera, a periscope camera, a 3D sensing device or system, a consumer electronics device (including domestic appliances such as vacuum cleaners, washing machines and lawnmowers), a mobile or portable computing device, a mobile or portable electronic device, a laptop, a tablet computing device, an e-reader (also known as an e-book reader or e-book device), a computing accessory or computing peripheral device (e.g. mouse, keyboard, headphones, earphones, earbuds, etc.), an audio device (e.g. headphones, headset, earphones, etc.), a security system, a medical device (e.g. an endoscope), a gaming system, a gaming accessory (e.g. controller, headset, a wearable controller, joystick, etc.), a robot or robotics device, a medical device (e.g. an endoscope), a robot or robotics device, an augmented reality system, an augmented reality device, a virtual reality system, a virtual reality device, a haptics device, a wearable device (e.g. a watch, a smartwatch, a fitness tracker, etc.), a drone (aerial, water, underwater, etc.), an autonomous vehicle (e.g. a driverless car), a vehicle (e.g. an aircraft, a spacecraft, a submersible vessel, a car, etc.), a tool, a surgical tool, a remote controller (e.g. for a drone or a consumer electronics device), clothing (e.g. a garment, shoes, etc.), a switch, dial or button (e.g. a light switch, a thermostat dial, etc.), a sensor, a display screen, a touchscreen, a flexible surface, and wireless communication devices (e.g. a near-field communication (NFC) device). It will be understood that this is a non-exhaustive list of example apparatus.

The SMA actuation apparatus described herein may be used in

devices/systems suitable for, for example, image capture, 3D sensing, depth mapping, aerial surveying, terrestrial surveying, surveying in or from space, hydrographic surveying, underwater surveying, scene detection, collision warning, security, medical imaging, facial recognition, augmented and/or virtual reality, advanced driver-assistance systems in vehicles, autonomous vehicles, gaming, gesture control/recognition, haptics, robotic devices, robotic device control, touchless technology, home automation, and medical devices.

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 the typical location of a damper in an SMA actuator; Figure 2 shows a first arrangement of a damper in a first SMA actuator;

Figures 3A and 3B show a second arrangement of a damper in a first SMA actuator;

Figure 4 shows a third arrangement of a damper in a first SMA actuator;

Figure 5 shows a fourth arrangement of a damper in a first SMA actuator;

Figure 6 shows a fifth arrangement of a damper in a first SMA actuator;

Figure 7 shows a sixth arrangement of a damper in a first SMA actuator;

Figure 8 shows a seventh arrangement of a damper in a first SMA actuator;

Figure 9A shows a camera lens assembly and Figures 9B to 9D shows three arrangements of dampers within the camera lens assembly for reducing audible noise;

Figure 10A shows a camera lens assembly that uses an 8-wire SMA actuator;

Figure 10B shows a side view of a camera lens assembly that uses an 8- wire SMA actuator;

Figure 11A shows a location in a second SMA actuator where a damper may be provided, and Figures 10B to 10D show how the damper may be arranged in that location;

Figure 12 shows a side view of a camera lens assembly and illustrates possible locations of a damper;

Figures 13A and 13B show two ways the screening can of the second SMA actuator may be modified to interact with a damper; Figures 14A to 14G show schematic diagrams of various modifications to the second SMA actuator to incorporate a damper;

Figures 15A and 15B show schematic diagrams of two modifications to the second SMA actuator to incorporate a damper;

Figure 16 shows a schematic diagram of an actuator comprising a formed sheet as a damper;

Figure 17A shows a diagram of the second actuator comprising a damper;

Figure 17B shows a schematic diagram of the second actuator comprising a damper; and

Figures 18A to 18C show schematic diagrams of how a well or recess may enable movement of a damper.

Broadly speaking, embodiments of the present techniques provide techniques for improving the operation of a shape memory alloy (SMA) actuator by using at least one damper to reduce undesired movement of the actuator.

The at least one damper provides mechanical damping in the SMA actuator which may reduce undesired motion, thereby improving accuracy of positional control and reducing non-linear oscillation. Thus, the positional accuracy of the SMA actuator may be improved by the present techniques. While the present techniques are described with reference to both an AF and OIS SMA actuator and an OIS SMA actuator, it will be understood that the present techniques may be used for any SMA actuator.

Damping materials may be used to provide mechanical damping. Damping gels of appropriate viscosity may improve AF and/or OIS actuator performance by reducing the severity of undesired motions of the actuator, as mentioned above. However, a problem with damping materials such as gels/oils is that they can migrate from the location where the damping material is provided within the actuator during the actuator manufacturing process, or during use of the actuator.

Generally speaking, more viscous oils/gels are less likely to migrate from their original location within the actuator but if the viscosity is too high then the AF and/or OIS performance will be degraded. Migration of the damping material within the actuator is problematic, as it may reduce the damping function which it is supposed to provide and the material may contaminate other areas within the actuator or within a device/apparatus in which the actuator is provided, and interfere with the correct operation of the actuator/device.

Figure 1 shows the typical location of a damper in an SMA actuation apparatus 100. In Figure 1, the right image is a plan view of the SMA actuation apparatus 100, and the left image is a zoomed-in cross-sectional view of a portion of the SMA actuation apparatus taken along section line A-A. In the right image, the spring plate 106 is partly transparent/opaque in order to show the location of other components of the SMA actuation apparatus.

The SMA actuation apparatus 100 comprises a support structure which comprises a base plate 102 and a static crimp plate 104. The static crimp plate4 comprises static wire attach structures 114. The static wire attach structures 114 may be crimps. The SMA actuation apparatus 100 comprises a moveable component which is supported on the support structure in a manner that allows movement of the moveable component relative to the support structure in two orthogonal directions perpendicular to a notional primary axis P extending through the moveable component. The moveable component comprises a spring plate 106 which comprises moveable wire attach structures 112. The moveable wire attach structures 112 may be crimps. The spring plate 106 may comprise flexure arms 110 which extend from the spring plate and are connected to the static crimp plate 104. The SMA actuation apparatus 100 may comprise at least one bearing 108 which bears the spring plate of the moveable component on the support structure, allowing movement of the spring plate relative to the support structure orthogonal to the primary axis P. The SMA actuation apparatus 100 comprises at least two shape memory alloy (SMA) actuator wires 118 connected between the moveable component and the support structure, and arranged to, on contraction, move the moveable component. Each SMA actuator wire 118 may be coupled to a moveable wire attach structure 112 at one end and to a static wire attach structure 114 at another end. In Figure 1, the SMA actuation apparatus 100 has four SMA actuator wires 118, but it will be understood that this is only one particular arrangement.

Figure 1 shows a typical placement of a damping material 116, which may be a damping gel. The damping material 116 is provided between the static crimp plate 104 and the spring plate 106. In some arrangements, a small gap (e.g. 0.05mm) may exist between the static crimp plate 104 and the spring plate 106, and the damping material 116 is provided in this gap.

However, due to the small height of the gap between the static crimp plate 104 (of the support structure) and the spring plate 106 (of the moveable component), use of more viscous damping materials, which are less likely to migrate from their intended location, may not be possible as they can degrade OIS performance. This is due to shear stress within the damping material increasing with the reduction of the gap height and thus the resistive force exerted by the damping material on the spring 106 movement becoming intolerably high.

The present applicant has identified new techniques for providing a damper in an SMA actuator, which work in one of the following three ways (or a combination of these) :

1. Use a less viscous material to reduce the shear in the material to an optimal level, while designing an environment which prevents migration.

2. Increase the gap size between the moving and static components to reduce shear stress in the damping material. This allows for good actuator performance with use of a more viscous/stiffer damping gel which will not migrate from its intended position within the actuator. 3. Change the way the components interact with the damping material. So instead of the gel acting between two flat plates, one of the interacting components can consist of a protrusion of different shape and reduced contact area. This enables deformation of a smaller volume of damping material which reduces resistive force and enables use of a more viscous damping material that does not migrate from its intended position within the actuator.

Embodiments of these techniques are now described with reference to Figures 2 to 8. In each of the embodiments, the shape memory alloy (SMA) actuation apparatus comprises: a support structure comprising: a base plate, and a static crimp plate comprising static wire attach structures; a moveable component supported on the support structure in a manner allowing movement of the moveable component relative to the support structure in two orthogonal directions perpendicular to a notional primary axis extending through the moveable component, the moveable component comprising : a spring plate comprising moveable wire attach structures; at least two shape memory alloy (SMA) actuator wires connected between the moveable component and the support structure and arranged to, on contraction, move the moveable component; and a viscous material provided in at least one location in the SMA actuation apparatus and arranged to reduce undesirable motion of the moveable component. For the sake of simplicity, in the following description, like reference numerals are used to denote the same or similar features.

The viscous material provided in the at least one location in the SMA actuation apparatus may be a damper. Figures 2 to 8 show possible locations where the damper may be provided.

The term "damping" is used herein to mean a technique for reducing the height of a resonant peak. In the case of an SMA actuator, damping may allow a higher control loop gain to be used without oscillation.

The term "damper" is used herein to mean any material which can be used to reduce the height of the resonant peak. The term "damper" is also used interchangeably herein with the terms "damping material", "damping gel", "gel", "damping oil", "oil", "damping fluid" and "fluid".

Damping Material in a Small Gap

In Figures 2 to 4, a damper is provided in one or more locations in the SMA actuation apparatus where there is a small gap between components, or where a small gap may be formed.

Figure 2 shows a first arrangement of a damper in an SMA actuation apparatus 200. In Figure 2, the top left image is a plan view of the SMA actuation apparatus 200, the top right image is a plan view of the spring plate6 of the SMA actuation apparatus, and the bottom image is a zoomed-in cross- sectional view of a portion of the SMA actuation apparatus taken along section line A-A. In the top left image, the spring plate 106 is partly transparent/opaque in order to show the location of other components of the SMA actuation apparatus.

Here, the spring plate 106 further comprises at least one well 124 in a side/face/surface of the spring plate 106 that contacts the static crimp plate 104, and the at least one damper 120 is provided in the at least one well 124. The arrangement is similar to that shown in Figure 1 except that the at least one well 124 provides a way to contain the damping material in position. The at least one well 124 may be formed by etching or partially-etching the spring plate6 using any suitable etching technique (such as laser etching or chemical etching). Alternatively, the at least one well 124 may be formed using a metal forming technique, such as coining or stamping.

The pocket or well 124 increases the distance between the static crimp plate 104 of the support structure and the spring plate 106 of the moveable component by up to 2.5 times relative to Figure 1, and this may reduce resistive force of a more viscous damping material making it acceptable for OIS

performance (or something similar). The depth of the pocket 124 may be adjusted during manufacture to tune the performance of the damping material. Additionally or alternatively, the static crimp plate 104 may further comprise at least one well in a face of the static crimp plate 104 that contacts the spring plate 106, and the damper 120 may be provided in the at least one well. In other words, the static crimp plate may be formed (e.g. by partial- etching) to comprise one or more wells. In embodiments, both the static crimp plate 104 and the spring plate 106 may comprise one or more wells at different locations.

Figure 3 shows a second arrangement of a damper in an SMA actuation apparatus 300, which is similar to the first arrangement shown in Figure 2. In Figure 3, the top left image is a plan view of the SMA actuation apparatus 300, the top right image is a plan view of the spring plate 106 of the SMA actuation apparatus, and the bottom image is a zoomed-in cross-sectional view of a portion of the SMA actuation apparatus taken along section line A-A. In the top left image, the spring plate 106 is partly transparent/opaque in order to show the location of other components of the SMA actuation apparatus.

Here, instead of having one or more wells etched into the spring plate, the spring plate 106 comprises at least one ring-shaped well 126 in a

side/face/surface of the spring plate 106 that contacts the static crimp plate4. The damper 120 is provided in the centre of the or each ring-shaped well 126. The at least one ring-shaped well 126 may be formed by etching or partially- etching the spring plate 106 using any suitable etching technique (such as laser etching or chemical etching). Alternatively the at least one ring-shaped well 126 may be formed using a metal forming technique, such as coining or stamping.

As mentioned above with respect to Figure 1, a low viscosity damping gel provides good actuator performance when placed in the small 0.05mm gap between the static crimp plate 104 and the spring plate 106, but the damping gel tends to move/migrate from the original position during the

assembly/manufacturing process or during use. The second arrangement shown in Figure 5 is therefore advantageous because the ring-shaped well 126 in the underside of the spring plate 106 could prevent the low viscosity material from migrating from its original location. Low viscosity fluids tend to move into small gaps through capillary action. The ring-shaped well 126 which surrounds the damper 120 expands the cross-sectional area, which may help to prevent the motion of the damping material through capillary action, whilst still allowing use of the low viscosity gel.

Additionally or alternatively, the static crimp plate 104 may further comprise at least one ring-shaped well in a face of the static crimp plate that contacts the spring plate, and the damper is provided in the centre of the ring- shaped well. In other words, the static crimp plate 104 may be formed (e.g. by partial-etching) to comprise one or more ring-shaped wells. In embodiments, both the static crimp plate 104 and the spring plate 106 may comprise one or more ring-shaped wells at different locations.

Figure 4 shows a third arrangement of a damper in an SMA actuation apparatus 400, which is similar to the first arrangement shown in Figure 2. In Figure 4, the top image is a plan view of the SMA actuation apparatus 400, and the bottom image is a plan view of the spring plate 106 of the SMA actuation apparatus. In the top image, the spring plate 106 is partly transparent/opaque in order to show the location of other components of the SMA actuation apparatus.

Here, the spring plate 106 further comprises at one area comprising a plurality of dimples 130, and the damper is provided in this area over the dimples 130. In Figure 4, two areas of the spring plate 106 comprise a plurality of dimples 130. As shown, each area comprising the dimples 130 may have an area similar to the area of the well 124 in Figure 2. Each dimple is an

indentation in surface of the spring plate 106. Thus, each dimple is like a very small well. The dimples in each area are clustered together, such that they form a surface texture on the surface of the spring plate 106. In other words, the spring plate 106 further comprises at least one cluster of dimples 130. The or each cluster of dimples 130 may be formed by etching or partially-etching the spring plate 106 using any suitable etching technique (such as laser etching or chemical etching). In alternative embodiments, the cluster of dimples may be replaced by a cluster of bumps or small protrusions. However, this may be more difficult or expensive to manufacture using etching (due to the amount of material that needs to be removed and the spacing between each

bump/protrusions).

The cluster of dimples 130 may increase the distance between the static crimp plate 104 of the support structure and the spring plate 106 of the moveable component by up to 2.5 times relative to Figure 1, and this may reduce the resistive force of a more viscous damping material, making it acceptable for OIS performance (or something similar).

Additionally or alternatively, the static crimp plate 104 may further comprise at least one area comprising a plurality of dimples, and the damper is provided over the dimples. In other words, the static crimp plate 104 may be formed (e.g. by partial-etching) to comprise the cluster(s) of dimples 130. In embodiments, both the static crimp plate 104 and the spring plate 106 may comprise one or more cluster of dimples 130 in different locations.

In each of the first, second and third arrangements, the depth or height of the at least one well 124, at least one ring-shaped well 126, and each dimple of the plurality of dimples 130 may be adjusted during manufacture to tune and optimise the performance of the damper.

Damping Material in Alternative Locations

In Figures 5 to 8, a damper is provided in one or more locations in the SMA actuation apparatus where there is a larger gap between components (relative to the small gaps of Figures 2 to 4), or where a larger gap may be formed.

Figure 5 shows a fourth arrangement of a damper in an SMA actuation apparatus 500. In Figure 5, the top left image is a plan view of the SMA actuation apparatus 500, the top right image is a plan view of the spring plate6 of the SMA actuation apparatus, and the bottom image is a zoomed-in cross- sectional view of a portion of the SMA actuation apparatus taken along section line A-A. In the top left image, the spring plate 106 is partly transparent/opaque in order to show the location of other components of the SMA actuation apparatus.

Here, the at least one damper 120 is disposed between the static crimp plate 104 and at least one projection 128 extending from the spring plate 106. A though-hole may be etched into the spring plate 106 while leaving the projection 128, where the projection 128 extends from the perimeter of the hole to its centre, as shown in Figure 5. The radial projection 128 interacts with the damper 120 which would be provided at the centre of the hole.

The fourth arrangement is advantageous because a more viscous damping material could be used, and the interaction of the projection 128 with the damper 120 will be different to the interaction of the spring plate 106 with the damper 120 (as per Figures 4 and 5). It is likely that the resistive forces will be much lower due to this interaction and therefore, the actuator performance may be improved.

Figure 6 shows a fifth arrangement of a damper in an SMA actuation apparatus 600. In Figure 6, the top image is a plan view of the SMA actuation apparatus 600, and the bottom image is a zoomed-in cross-sectional view of a portion of the SMA actuation apparatus taken along section line A-A. In the top image, the spring plate 106 is partly transparent/opaque in order to show the location of other components of the SMA actuation apparatus. As mentioned earlier, the spring plate 106 comprises flexure arms 110 extending from the spring plate 106 and connected to the static crimp plate 104. In this

arrangement, the at least one damper 120 is provided between the flexure arms 110 and the static wire attach structures 114. Advantageously, a more viscous damping material could be used between the flexure arm 110 and the static wire attach structures 114. The interaction of the flexure arm 110 with the damper 120 will be different to the interaction of the spring plate 106 with the damper 120 (as per Figures 2 to 4). It is likely that the shear forces will be much lower due to this interaction and therefore, the actuator performance may be

improved. Figure 7 shows a sixth arrangement of a damper in an SMA actuation apparatus 700. The top left image is a plan view of the SMA actuation apparatus 700, the top right image is a cross-sectional view of the SMA actuation

apparatus taken through the section line A-A, and the bottom image is zoomed- in cross-sectional view of a portion of the SMA actuation apparatus. In the top left image, the spring plate 106 is partly transparent/opaque in order to show the location of other components of the SMA actuation apparatus.

The SMA actuation apparatus 700 comprises at least one damper 120 disposed between the base plate 102 of the support structure and the moveable wire attach structures 112 of the moveable component. The at least one damper 120 may be a damping gel. The damping gel may be more viscous than that used in the arrangement of Figure 1. The damper 120 may be provided in one or more corners of the SMA actuation apparatus 700, between the base plate 102 and the moveable wire attach structures 112. The distance between the moveable wire attach structures 112 and the base plate 102 may be about 0.3mm. This is six times larger than the typical location of a damping material, as shown in Figure 1 (and also shown in Figure 2 for reference), and consequently, may reduce the shear stress in the more viscous damping material 120 and thus resistive force on the spring 106 significantly. The damper 120 may be a silicone gel or a damping oil. A further advantage of this

arrangement is that the location of the damper 120 also allows full access for UV curing, which is a necessary process step for many viscous damping materials.

Figures 8A and 8B show a seventh arrangement of a damper in an SMA actuation apparatus, which is similar to the arrangement shown in Figure 7. In each of Figures 8A and 8B, the top image is a perspective view of a moveable wire attach structure of the SMA actuation apparatus, the middle image is a plan view of the SMA actuation apparatus, and the bottom image is a zoomed-in cross-sectional view of a portion of the SMA actuation apparatus. In the middle images, the spring plate 106 is partly transparent/opaque in order to show the location of other components of the SMA actuation apparatus. In both Figures 8A and 8B, the at least one damper 120 is disposed between the base plate 102 of the SMA actuation apparatus 800,810, and a projection 122 extending from each moveable wire attach structure 112. Thus, the arrangement is similar to that of Figure 7 as the gap between the projection 122 and the base plate 102 is large. The projection 122 may be used to manipulate the interaction with the damper 120. The projection 122 will reduce the contact area with the damper 120 compared to the arrangement of Figure 2, and therefore, may allow for further reduction of the resistive force of a more viscous damping material.

In Figure 8A, the projection 122 is parallel or substantially parallel to the base plate 102. The size of the projection 122 may be adjusted to optimise the interaction with the damper 120.

In Figure 8B, the projection 122 comprises a curved tip that extends into the damper 120. The amount by which the curved tip of the projection 122 extends into the damper 120 may be adjusted to optimise the interaction with the damper 120.

In each of the first to seventh arrangements, the damper 120 may be a viscoelastic material. The viscoelastic material may be a silicone gel or a damping oil.

In each of the first to seventh arrangements, the damper 120 may be cured using ultraviolet light.

Damping material for reducing audible noise

Figure 9A shows part of a first example of a camera lens assembly that uses an SMA actuation apparatus (not shown), which may be as described above or as described e.g. in WO 2013/175197 A1 (i.e. without damping gel). The moveable component of the SMA actuator apparatus supports a lens assembly, which may incorporate an actuator that provides autofocus. The lens assembly is at least partly contained within a housing (also referred to as an "AF yoke") 92. The camera lens assembly includes a further housing 91 (also referred to as a "screening can") within which the other components of the camera lens assembly are at least partly contained. During operation, the AF yoke 92 may move relative to the screening can 91 in three dimensions to provide AF and OIS.

The moveable component of the SMA actuator apparatus plate 106 is coupled to the static component via flexure arms (such as the flexure arms 110 described above with reference to Figure 1) or other suitable element providing a force (also referred to as "downforce") for generally maintaining the moveable component in contact with the static component via a bearing arrangement (such as the bearings 108 described above with reference to Figure 1). In some circumstances, the camera lens assembly may be subject to forces/accelerations that exceed the downforce, causing the moveable component to lift away from the bearing arrangement. This, in turn, may lead to (the top surface of) the AF yoke 92 striking (the inside top surface of) the screening can 91, generating audible noise. This is generally undesirable.

Dampers 93 comprising viscous damping material as described herein may be used to reduce the risk of such audible noise. Several arrangements of such dampers 93 will now be described. In each arrangement, the dampers 93 are arranged between the top surface of the AF yoke 92 and the inside top surface of the screening can 91. Moreover, in each arrangement, there are a set of (e.g. four or more or less) dampers 93 distributed around the central

("optical") axis of the camera lens assembly

Referring to Figure 9B, in a first arrangement, each damper 93 is located within a recess 92a in the top surface of the AF yoke 92. The damper 93 is adhered to the top surface of the AF yoke 92 and, when the movable element is in a normal position (i.e. in contact with the static component via the bearing arrangement), the damper 93 is spaced from the inside top surface of the screening can 91. If the moveable component lifts away from the bearing arrangement as described above, then the damper 93 contacts the inside top surface of the screening can 91 and prevents or reduces the audible noise associated with the AF yoke 92 striking the screening can 91. One purpose of the recess 92a is to enable a suitable size of damper 93 (e.g. a suitable amount of viscous damping material) to be accommodated (and located) between the AF yoke 92 and the screening can 91 without increasing the height of the camera lens assembly. Another purpose is to protect the damper by providing a volume that cannot be encroached upon in the event that very large forces causes the top surface of AF yoke 92 to come into close proximity with the inside top surface of the screening can 91.

Referring to Figure 9C, a second arrangement is equivalent to the first arrangement except that each damper 93 is located within a recess 91a in the inside top surface of the screening can 91, is adhered to the inside top surface of the screening can 91, and is normally spaced from the top surface of the AF yoke 92.

Referring to Figure 9D, a third arrangement is equivalent to the first arrangement except that each damper 93 extends between and is adhered to both the inside top surface of the screening can 91 and the top surface of the AF yoke 92. In this instance, one purpose of the recess 92a is to enable there to be a suitable height of damper 93 (without increasing the height of the camera lens assembly) such that the damper 93 has a suitably low shear strength and so has a suitably low effect on the OIS performance of the SMA actuator apparatus.

An equivalent fourth arrangement is equivalent to the third arrangement but with the recesses in the inside top surface of the screening can 91.

Lubricants

The viscous material provided in the at least one location in the SMA actuation apparatus may be a lubricant. As mentioned earlier with reference to Figure 1, the SMA actuation apparatus may comprise at least one bearing 108 which bears the spring plate 106 of the moveable component on the support structure. The lubricant may be provided between the at least one bearing 108 and the spring plate 106. The at least one bearing 108 may be a ball bearing, or may be a plain bearing (also known as a bearing surface). The lubricant may be any one of: a grease, a silicone grease, and an oil. It will be understood that the lubricant may be used in addition to the dampers described with reference to Figures 2 to 8. However, the lubricant may not be used in the locations where the damper is provided.

In any of the embodiments described herein, the SMA actuation apparatus may be a camera apparatus and may further comprise an image sensor fixed to the support structure. The moveable component may comprise a camera lens element comprising at least one lens arranged to focus an image on the image sensor, the primary axis being the optical axis of the camera lens element. The moveable component may be moved to provide optical image stabilisation.

In any of the embodiments described herein, the SMA actuation apparatus may comprise a total of four SMA actuator wires.

Damping an eight wire SMA actuator

The use of viscous materials to reduce undesirable movement of the actuator may be also used in other types of SMA actuator, such as an 8-wire SMA actuator of the type shown in International Patent Publications

W02011/104518 and W02019/034860, for example.

Figures 10A and 10B are taken from W02019/034860 and show a camera lens assembly that uses an 8-wire SMA actuator. The camera lens assembly 1 comprises a static portion 10 and a lens holder 20 holding a lens 21 (shown in dotted outline), or more generally any number of lenses, having an optical axis O. As described in more detail below, the lens holder 20 is supported on the static portion by eight SMA actuator wires 30, four of which are visible in Figure 10A. The lens holder 20 is capable of movement with respect to the static portion 10, driven by the SMA actuator wires 30, with six degrees of freedom, that is three orthogonal translational degrees of freedom and three orthogonal rotational degrees of freedom.

In this example, the lens holder 20 is supported solely by the SMA actuator wires 30, but as an alternative the lens holder 20 could additionally be supported by a suspension system which permits the movement with the six degrees of freedom, for example formed by one or more flexures.

The static portion 10 preferably also includes a screening can 15 (for clarity, not shown in Figure 10a and shown cut away in cross-section in Figure 10B) rigidly attached to the base plate 1 and extending around the lens holder 20 with enough clearance to allow full movement of the lens holder 20. Such a screening can 15 protects the camera lens assembly 1 against physical damage and the ingress of dust.

In more detail, the static portion 10 comprises a base plate 11 and two static posts 12 provided on opposite corners of the base plate 11. The static posts 12 which may be affixed to the base plate 11 or formed integrally with the base plate 11 as one piece. Two crimp assemblies 13 are affixed to each of the two static posts 12. The base plate 11 also rigidly mounts an image sensor 14 on which the lens 21 focuses an image.

The lens holder 20 includes two moving posts 22 aligned with the corners of the base plate 11 intermediate the static posts 12. Two crimp assemblies 23 are affixed to each of the moving posts 22.

The SMA actuator wires 30 are connected between the static portion 10 and the lens holder 20 by being crimped at one end to a crimp assembly 13 of the static portion and at the other end to a crimp assembly 23 of the lens holder 20. The crimp assemblies 13 and 23 provide both mechanical and electrical connection. The crimp assemblies 23 on the lens holder 20 at each corner may be electrically connected together, or may not be electrically connected together.

The SMA actuator wires 30 have the same configuration around the lens holder 20 as the SMA actuator wires in the camera apparatus described in W02011/104518. Specifically, two SMA actuator wires 30 are arranged on each of four sides around the optical axis O, and are inclined with respect to the optical axis (i.e. at an acute angle greater than 0 degrees) in opposite senses to each other and crossing each other, as viewed perpendicular to the optical axis O. Thus, in particular, each of the SMA actuator wires 30 is inclined with respect to the optical axis 0 of the lens element 20 and with respect to each other. Reference is made to WO2011/104518 for further details of the arrangement of the SMA actuator wires 30.

Selective contraction of the SMA actuator wires 30 drives movement of the lens holder 20 in any of the six degrees of freedom. Contraction and expansion of the SMA actuator wires 30 is generated by application of drive signals thereto. The SMA actuator wires 30 are resistively heated by the drive signals and cool by thermal conduction to the surroundings when the power of the drive signals is reduced.

Thus, the SMA actuator wires 30 may be used to provide both an AF function by translational movement of the lens holder 20 along the optical axis O and an OIS function by translational movement of the lens holder 20

perpendicular to the optical axis O.

As shown in Figure 10B (but omitted from Figure 10A for clarity), the static portion 10 also includes end-stops 16 having end-stop surfaces 17 which face the lens holder 20 and are arranged to limit the movement of the lens holder 20 by contacting it. There is an end-stop 16 corresponding to each SMA actuator wire 30. Figure 10b shows the two SMA actuator wires 30 and the two corresponding end-stops 16 on one side of the camera lens assembly 1, the other SMA actuator wires 30 on the other sides of the camera lens assembly 1 having corresponding end-stops 16 in the same configuration. Each end-stop surface 17 extends orthogonally to the direction along the corresponding SMA actuator wire 30. Thus, the end-stop surfaces 17 are inclined with respect to the optical axis O at a complementary angle to the angle at which the SMA actuator wires are inclined with respect to the optical axis O, the two end-stop surface 17 shown in Figure 10B being inclined in opposite senses to each other. It will be understood that the end-stops may not need to be angled and could be orthogonal. In other words, the angled end-stops shown in Figure 10B is non limiting. Thus, in the following description, where the damper is provided between end-stops, it will be understood that these may be any suitable end- stops (e.g. angled, not angled, orthogonal, etc.) Turning to Figures 11A to 17B, various techniques for reducing undesirable motion of the moveable component in an actuator of the type shown in Figures 10A and 10B are now described. Thus, embodiments of the present techniques provide a shape memory alloy (SMA) actuation apparatus

comprising: a support structure; a moveable component supported on the support structure in a manner allowing movement of the moveable component relative to the support structure; eight SMA actuator wires inclined with respect to a notional primary axis with two SMA actuator wires on each of four sides around the primary axis, the SMA actuators being connected between the moveable component with a component in opposite directions along the primary axis, the SMA actuator wires of each group being arranged with two-fold rotational symmetry about the primary axis; and at least one damping element arranged to reduce undesirable motion of the moveable component.

Figure 11A shows a location 1000 in an 8-wire SMA actuator where a damper may be provided, and Figures 11B to lid show how the damper may be arranged in that location 1000. Figure 11A is the same as Figure 10B, but has been annotated to show one possible location 1000 for the damper within the actuator. The possible damper location 1000 is indicated by a circle. In this embodiment, the damper is provided between a moveable component 1004 (which may be a lens holder, for example) and a static component 1002 and specifically, between the moveable component 1004 and the end-stops of the static component/support structure 1002. Figures 11B, 11C and 11D are zoom- in views of the possible damper location 1000.

In Figure 11B, a damper 1006 is provided between the support structure 1002 and the moveable component 1004. The damper 1006 may be held in position by viscous properties of the damper 1006 itself. In embodiments, the damper 1006 may have adhesive properties that enable the damper to remain in the required location 1000. As described above, the damper 1006 is arranged to reduce undesirable motion of the moveable component 1004. Thus, the damper 1006 may improve the autofocus (AF) and/or optical image stabilisation (OIS) performance of the actuator by reducing the severity of undesired motions of the actuator. However, as mentioned above, a problem with damping materials such as gels/oils is that they may migrate from the location where the damping material is provided within the actuator during the actuator manufacturing process, or during use of the actuator.

To mitigate this problem of migration, the embodiment shown in Figure llC comprises a well 1008, which may at least partly contain the damping material 1006. The well 1008 is illustrated as being formed in the support structure 1002. However, it will be understood that the well 1008 could alternatively be provided in the moveable component. In this arrangement, the damper 1006 may be held in position not only by viscous properties of the damper 1006 but also by the well 1008. Furthermore, the well 1008 provides an area for the damper 1006 to flow into when the moveable component 1004 exerts a force on the damper 1006. This may be advantageous as migration of the damper 1006 may be more controlled than in the arrangement of Figure 11B.

The well 1008 may be formed in a surface of the support structure 1002 (or in a surface of the moveable component 1004) by one of the following techniques: etching, partial-etching metal forming, coining and stamping. The well may be formed in an injection-moulded part of the support structure (or of the moveable component if the well is provided in the moveable component).

The skilled person will appreciate that one or more wells 1008 may be provided at different locations on the support structure 1002 (and/or on the moveable component 1004). The or each well 1008 may be the same size, shape or depth, or may be different. The depth of the or each well 1008 may depend on the actuator design and may be chosen to optimise the performance of the damper 1006. The well 1008 may have a cross-section or profile that has any shape, such as rectangular, circular, elliptical, triangular, trapezoidal, ring-shaped, or any other suitable shape which provides a way of containing the damping material 1006 in position.

Figure lid shows another mechanism to limit the migration of the damper 1006 from the desired position 1000. In this arrangement, one or more barriers or dykes 1010 are provided between the support structure 1002 and the moveable component 1004 in the location 1000 where the damper 1006 is to be provided. In this arrangement, the or each barrier 1010 may be arranged to prevent flow of the damper 1006 in a particular direction. Although Figure 11D shows the barriers 1010 being used in conjunction with well 1008 to contain the damper 1006, it will be understood that the barriers 1010 could be used without a well. The barrier(s) 1010 may be formed by any suitable structural element, such as a sharp angle change in the support structure 1002 and/or the moveable component 1004, by a step, or a wall.

In embodiments, the barriers 1010 may be formed from protrusions extending from the end-stops of the support structure 1002 and/or the

moveable component 1004. The protrusions may also increase the T surface area with which the damper 1006 interacts, which may help the damper 1006 to stay in position.

In the arrangements of Figures 11B to 11D, the damper 1006 may be any one of: a gel, silicone gel, glue, soft glue, oil, grease, silicone grease, damping oil, or any viscoelastic material of appropriate viscosity. Depending on the material used, the damper 1006 may be cured using ultraviolet light.

Figure 12 shows a side view of a camera lens assembly comprising an 8- wire SMA actuator. Figure 12 is the same as Figure 10B, but is annotated to show possible damper locations. For example, one location 1000 for a damper may be between the end-stops 16 and the end-stop surfaces 17 (as also shown in Figures 11A-D). Another location 1012 for a damper may be between a side of the support structure and a side of the moveable component. Another location 1014 for a damper may be over the crimp assemblies 13 and/or crimp

assemblies 23 of the actuator. Another location 1016 for a damper may be between the base of the moveable component and the support structure. It will be understood that the illustrated locations are non-limiting examples of possible damper locations, and the damper 1006 may be placed in any position (and in more than one position) within the actuator in order to minimise undesirable motion of the moveable component.

Figures 13A and 13B show two ways the screening can of an actuator may be modified to interact with a damper. Specifically, Figures 13A and 13B each show a segment 1200 of the actuator where the screening can extend around and over the moveable component/lens holder. As shown in Figure 10B, an actuator, such as an 8-wire SMA actuator, may comprise a screening can 15 to protect the camera lens assembly against physical damage and ingress of dirt/dust that may impact the performance of the actuator or camera. Figures 13A and 13B show how the screening can may be modified to interact with a damping material 1206 that is provided on the moveable component 1204 (e.g. the lens holder/lens carriage). The moveable component 1204 may comprise at least one well 1208, where the or each well contains damping material 1206.

In Figure 13A, the screening can 1202 may comprise at least one projection 1210 which extends from the screening can 1202. The or each projection 1210 is arranged to partly extend into a well 1208 and interact with the damping material 1206 contained therein. It will be understood that one projection 1210 may interact with one well 1208, or multiple projections 1210 may interact with one well 1208. The concept is similar to that shown in Figure 5, and the advantages of this arrangement may also similar to those described above with respect to Figure 5. The projection 1210 may be formed by etching or forming the screening can 1202. Alternatively, the projection 1210 may be formed as a separate component to the screening can 1202 and subsequently attached to the screening can 1202 (e.g. using an adhesive, welding, or other suitable attachment technique).

In Figure 13B, the screening can 1202 may comprise at least one projection 1212 which extends from the screening can 1202. The projection 1212 is arranged to partly extend into a well 1208 and interact with the damping material 1206 contained therein. The concept is similar to that shown in Figure 5, and the advantages of this arrangement may also similar to those described above with respect to Figure 5. The projection 1212 may be formed by folding or otherwise forming the screening can 1202.

Modifications of the moveable component

Figures 14A to 14G show some ways the 8-wire actuator shown in

Figures 10A and 10B may be modified to interact with a damping element arranged to reduce undesirable motion of the moveable component. It may be possible to dampen undesirable motions in all six degrees of freedom of the 8- wire actuator by having multiple dampers in different locations or of different types that enable rotational motions to also be damped.

Figure 14A shows a schematic diagram (side view) of a first modification of the 8-wire actuator. Here, moveable component 1302 comprises at least one projection 1304 which extends from the moveable component 1302 towards a base 1300 of the support structure (not shown for clarity). A damping material 1308 is provided in at least one location on the base 1300 of the support structure. The at least one projection 1304 is arranged to extend into the damping material 1308. The at least one projection 1304 may not come into contact with the base 1300 of the support structure itself. In embodiments, the damping material 1308 may be provided in one or more wells in the base 1300 of the support structure. The or each projection 1304 may take the form of a rigid rod or cylinder. In the illustrated example, each projection 1304 may comprise a sphere 1306 at one end of the rod/cylinder, and at least the sphere 1306 interacts with the damping material 1308. The sphere 1306 increases the surface area of the projection 1304 that interacts with the damping material 1308. The arrangement shown in Figure 14A may be considered to be a three- dimensional damping arrangement. That is, the arrangement may be able to dampen undesirable motions in any of the three dimensions of movement of the moveable component 1302.

The top image in Figure 14B shows a schematic diagram (side view) of a second modification of a moveable component of the 8-wire actuator. As in Figure 14A, the moveable component 1302 comprises at least one projection 1304. Here, instead of the projection 1304 comprising a sphere/bail at one end, the or each projection 1304 comprises at least one paddle, stirrer blade or propeller blade. The at least one projection 1304 may not come into contact with the base 1300 of the support structure itself. The or each projection 1304 may have a single paddle 1310, or, as shown in the bottom image in Figure 14B, may have more than one paddle 1310. The embodiment shown in the bottom image in Figure 14B may be advantageous as it increases the surface area of the projection 1304 that interacts with the damping material 1308. The embodiment shown in Figure 14B may reduce displacement of the damping gel when the moveable component 1302 is moving along the primary axis P (which may be the optical axis if the actuator is being used to move an optical component such as a lens or lens stack). In cases where the damper 1308 is provided within a well rather than merely on a surface of the support structure (e.g. the base 1300), the paddle(s) may advantageously reduce the likelihood of the gel escaping the well.

Figure 14C shows a schematic diagram (side view) of a third modification of the 8-wire actuator. Here, the actuator comprises at least one arm 1312 which is coupled at one end to the moveable component 1302 and at another end to the base 1300 of the support structure. The at least one arm 1312 may be formed from a material which itself provides damping or shock absorption.

For example, the at least one arm 1312 may be formed from a foam, a urethane foam, a microcellular foam, a polyurethane foam, or PORON (RTM). In this embodiment, since the at least one arm 1312 is formed from a damping material itself, a liquid damper (e.g. a gel or oil) may not be required. Alternatively, the at least one damping arm 1312 may be used in conjunction with a liquid damping material.

Figure 14D shows a schematic diagram (side view) of a fourth

modification of the 8-wire actuator. Here, the actuator comprises a projection 1304 which extends from the moveable component 1302. The projection 1304 may take the form of a rigid rod or cylinder. Support structure 1301 is modified to comprise a well 1314. A fluid damping material may be provided in the well 1314. The projection 1304 extends into the damping material in the well 1314. A seal (not shown) may be provided over the well to reduce or prevent any flow of the fluid damping material out of the well 1314, and the projection 1304 may extend through this seal to interact with the damping material.

Figure 14E shows a schematic diagram (side view) of a fifth modification of the 8-wire actuator. Here, the actuator comprises one or more dashpots 1316. The or each dashpot 1316 comprises a piston 1318 which may be coupled at one end to the moveable component 1302 and which engages with a container 1320 containing a viscous fluid damping material (e.g. oil). The container containing viscous material is coupled to and extends from a base 1300 of the support structure (the whole support structure is not shown for clarity). The piston of the moveable component 1302 engages with the viscous fluid to provide damping.

Figure 14F shows a schematic diagram (side view) of a sixth modification of the 8-wire actuator. In Figure 14E, each dashpot 1316 is coupled to the top of the moveable component 1302 and is arranged to be substantially parallel to the primary axis of the actuator (e.g. the optical axis). In contrast, in Figure 14F, the or each dashpot 1316 may be coupled to the bottom of the moveable component 1302 and may be arranged at an angle to the primary axis.

Figure 14G shows a schematic diagram (plan view) of a seventh

modification of the 8-wire actuator. In this arrangement, the damping may be most effective when the damping material is in shear. The arrangement shown here is intended to give optimal damping along one specific axis of movement of the moveable component 1302. Here, the moveable component 1302 comprises a projection 1304 which extends from the side of the moveable component and interacts with a side or corner of the support structure 1301. The support structure 1301 may comprise a well 1314, and the well 1314 may contain damping material 1308. The projection 1304 is arranged to extend into the damping material 1308. The projection 1304 may take the form of a rigid rod or cylinder. In the illustrated example, the projection 1304 may comprise a sphere 1306 at one end of the rod/cylinder, and at least the sphere 1306 interacts with the damping material 1308. The sphere 1306 increases the surface area of the projection 1304 that interacts with the damping material 1308. Thus, this arrangement is similar to that shown in Figure 14A, except that the projection 1304 extends from the moveable component 1302 in a different direction and interacts with a different part of the support structure.

Figures 15A and 15B show schematic diagrams of two modifications to the 8-wire actuator to incorporate a damper. In Figure 15A, moveable component 1402 of the 8-wire actuator comprises end stops 1404 which interact with a surface of support structure 1400. The moveable component 1402 may comprise a protrusion 1410. The support structure 1400 may comprise a recess or well 1406. The protrusion 1410 of the moveable component 1402 may interact with the recess 1406 when the end stops 1404 come into contact with the surface of the support structure 1400. The recess 1406 may contain damping material 1408. Thus, the protrusion 1410 of the moveable component interacts with the damping material 1408 when the end stops 1404 contact the support structure 1400. In Figure 15B, the moveable component 1402 comprises protrusions 1410 which themselves form the end stops of the actuator. Thus, in Figure 15B, the protrusions 1410 contact the surface of the support structure 1400. A damping material 1408 may be provided between the end stops 1408 and the support structure 1400.

It will be understood that although Figures 15A and 15B show the protrusions being on the moveable component and the recess/well being on the support structure, the protrusions could be on the support structure and the recess/well could be on the moveable component.

Figure 16 shows a schematic diagram of an actuator comprising a formed sheet as a damper. Here, a formed sheet 1504 is coupled at one end to the moveable component 1502 and at another end to the support structure 1500. The formed sheet 1504 comprises two bends 1506 and may be able to flex about the bends 1506. The sheet 1504 may be arranged such that the moveable component 1502 is able to move in the required directions, but prevents movement of the moveable component 1502 in other directions. In this way, the sheet 1504 may function as a damper.

Figure 17A shows a diagram of the second actuator comprising a damper. The actuator comprises a common spring component 1602 which is located between the support structure 1600 and the moveable component (not shown here for clarity). The common spring 1602 may be modified to comprise a protrusion 1604 which is arranged to interact with a damping material 1606. The damping material 1606 may be provided on the support structure 1600, e.g. on a surface of the support structure or in a well in the support structure.

Figure 17B shows a schematic diagram of the second actuator comprising a damper. In this arrangement, the damping material 1606 may be provided on the common spring 1602 (i.e. between the moveable component 1608 and the common spring 1602), below the common spring 1602 (i.e. between the support structure 1600 and the common spring 1602), or both. The damping material 1606 may be provided in discrete locations on/below the common spring, or may cover the common spring 1602. The damping material may be provided on the mid-points on the common spring, which may gear down the movements.

Figures 18A to 18C show schematic diagrams of how a well or recess may enable movement of a damper. Here, a damper 1706 is provided between a surface of the moveable component 1700 and a well 1704 located in the support structure 1702. (It will be understood that the well could equally be located in the moveable component 1700 instead). The well 1704 prevents squashing or compression of the damper 1706 when the moveable component 1700 and support structure 1702 come into contact - significant compression of the damper may limit the material's ability to damp unwanted motions. Thus, the damper is able to function when the moveable component is separated from the support structure (Figure 18A), when the moveable component 1700 is in close contact with the support structure 1702 such that the damper 1706 move into the well 1704 (Figure 18B), and when the moveable component is moving in parallel/along the surface of the support structure (Figure 18C).

In the embodiments shown in Figures 11A to 14B, 14D to 15B and 17A to 17B, the at least one damping element may be a viscous material provided in at least one location in the SMA actuation apparatus. The viscous material may be a lubricant. The lubricant may be any one of: a grease, a silicone grease, and an oil. Alternatively, the at least one damping element may be a viscoelastic material provided in at least one location in the SMA actuation apparatus. The viscoelastic material may be a silicone gel or a damping oil, which may be cured using ultraviolet light.

The at least one damping element may be provided between the support structure and the moveable component.

The at least one damping element may be provided on a surface of the support structure, and the moveable component may comprise at least one projection that extends into the at least one damping element. The support structure may comprise at least one well and the damping element is provided within the at least one well. The at least one well may be provided in a base or a side of the support structure.

The at least one damping element may be provided on a surface of the moveable component, and the support structure may comprise at least one projection that extends into the at least one damping element. The moveable component may comprise at least one well and the damping element is provided within the at least one well. The at least one well may be provided in a base or a side of the moveable component.

The at least one projection may be a rod and an end of the rod may extend into the at least one damping element. Alternatively, the at least one projection may comprise a rod coupled at one end to a sphere/bail, and the sphere/bail may extend into the at least one damping element. Alternatively, the at least one projection may comprise a rod coupled at one end to at least one paddle, and the at least one paddle may extend into the at least one damping element. The at least one paddle may be able to flex or rotate about the rod.

The support structure may further comprise a screening can, and the screening can may comprise at least one projection arranged to extend into the at least one damping element. In this case, the moveable component may comprise at least one well wherein the damping element is provided within the at least one well.

In embodiments, the apparatus may comprise at least one dashpot coupled between the moveable component and the support structure, wherein the at least one dashpot contains the at least one damping element.

In embodiments, the apparatus may comprise a common spring coupled to the moveable component and the support structure, wherein the common spring comprises at least one projection arranged to extend into the at least one damping element. Alternatively, the at least one damping element may be provided between the support structure and the common spring and/or between the common spring and the moveable component. In embodiments, such as the example shown in Figure 14C, the at least one damping element may be an arm coupled at one end to the moveable component and at another end to the support structure. The arm may be formed from any one of: a foam, a urethane foam, a microcellular foam, a polyurethane foam, and PORON.

In embodiments, such as the example shown in Figure 16, the at least one damping element may be a formed sheet coupled at one end to the moveable component and at another end to the support structure. The formed sheet may be formed from any one of: a metal, a metal alloy, a metallic material, and an electrically-insulative material.

In any of the embodiments described with reference to Figures 11A to 17B, the SMA actuation apparatus may be a camera apparatus and may further comprise an image sensor fixed to the support structure. The moveable component may comprise a camera lens element comprising at least one lens arranged to focus an image on the image sensor, the primary axis being the optical axis of the camera lens element. The moveable component may be moved to provide autofocus and/or optical image stabilisation.

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 shape memory alloy (SMA) actuation apparatus comprising :

a support structure comprising:

a base plate, and

a static crimp plate comprising static wire attach structures;

a moveable component supported on the support structure in a manner allowing movement of the moveable component relative to the support structure in two orthogonal directions perpendicular to a notional primary axis extending through the moveable component, the moveable component comprising :

a spring plate comprising moveable wire attach structures;

at least two shape memory alloy (SMA) actuator wires connected between the moveable component and the support structure and arranged to, on contraction, move the moveable component; and

a viscous material provided in at least one location in the SMA actuation apparatus and arranged to reduce undesirable motion of the moveable component.

2. The SMA actuation apparatus as claimed in claim 1 wherein the viscous material provided in at least one location is a damper.

3. The SMA actuation apparatus as claimed in claim 2 wherein the spring plate further comprises at least one well in a face of the spring plate that contacts the static crimp plate, and the damper is provided in the at least one well.

4. The SMA actuation apparatus as claimed in claim 2 wherein the static crimp plate further comprises at least one well in a face of the static crimp plate that contacts the spring plate, and the damper is provided in the at least one well.

5. The SMA actuation apparatus as claimed in claim 2 wherein the spring plate further comprises at least one ring-shaped weli in a face of the spring plate that contacts the static crimp plate, and the damper is provided in the centre of the ring-shaped well.

6. The SMA actuation apparatus as claimed in claim 2 wherein the static crimp plate further comprises at least one ring-shaped well In a face of the static crimp plate that contacts the spring plate, and the damper is provided in the centre of the ring-shaped well.

7. The SMA actuation apparatus as claimed in any one of claims 3 to 6 wherein the at least one well or at least one ring-shaped well is formed by any one of the following techniques: etching, partial-etching, metal forming, coining and stamping.

8. The SMA actuation apparatus as claimed in claim 2 wherein the spring plate comprises at least one area comprising a plurality of dimples, and the damper is provided over the dimples.

9. The SMA actuation apparatus as claimed in claim 2 wherein the static crimp plate comprises at least one area comprising a plurality of dimples, and the damper is provided over the dimples.

10. The SMA actuation apparatus as claimed in any one of claims 3 to 9 wherein a depth of the at least one well, a depth of the at least one ring-shaped well, and the depth of each dimple of the plurality of dimples is adjustable, during a manufacturing process, to optimise the performance of the damper.

11. The SMA actuation apparatus as claimed in claim 2 wherein the damper is disposed between the base plate and the moveable wire attach structures.

12. The SMA actuation apparatus as claimed in claim 2 wherein the damper is disposed between the base plate and a projection extending from each moveable wire attach structure.

13. The SMA actuation apparatus as claimed in claim 12 wherein the projection is parallel to the base plate.

14. The SMA actuation apparatus as claimed in claim 12 wherein the projection comprises a curved tip that extends into the damper.

15. The SMA actuation apparatus as claimed in claim 2 wherein the damper is disposed between the static crimp plate and at least one projection extending from the spring plate.

16. The SMA actuation apparatus as claimed in claim 2 wherein the spring plate comprises flexure arms extending from the spring plate and connected to the static crimp plate, and the damper is provided between the flexure arms and the static wire attach structures.

17. The SMA actuation apparatus as claimed in any one of claims 2 to 15 wherein the damper is a viscoelastic material.

18. The SMA actuation apparatus as claimed in claim 16 wherein the viscoelastic material is a silicone gel or a damping oil.

19. The SMA actuation apparatus as claimed in any one of claims 2 to 18 wherein the damper is cured using ultraviolet light.

20. The SMA actuation apparatus as claimed in claim 1 wherein the viscous material provided in at least one location is a lubricant.

21. The SMA actuation apparatus as claimed in claim 20 further comprising at least one bearing which bears the spring plate of the moveable component on the support structure, wherein the lubricant is provided between the at least one bearing and the spring plate.

22. The SMA actuation apparatus as claimed in claim 20 or 21 wherein the lubricant is any one of: a grease, a silicone grease, and an oil.

23. The SMA actuation apparatus as claimed in any preceding claim wherein the SMA actuation apparatus is a camera apparatus and further comprises an image sensor fixed to the support structure, and the moveable component comprises a camera lens element comprising at least one lens arranged to focus an image on the image sensor, the primary axis being the optical axis of the camera lens element.

24. The SMA actuation apparatus as claimed in claim 23 wherein the moveable component is moved to provide optical image stabilisation.

25. The SMA actuation apparatus as claimed in any preceding claim comprising a total of four SMA actuator wires.

26. The SMA actuation apparatus as claimed in any preceding claim, further comprising :

a lens element supported on the spring plate; and

an outer enclosure;

wherein the viscous material is provided between surfaces of the lens element and the outer enclosure so as to prevent or reduce audible noise caused by contact therebetween when the SMA actuation apparatus is subject to forces that cause the moveable component to at least partly separate from the support structure.

27. The SMA actuation apparatus as claimed in claim 26, wherein the viscous material is provided within recesses in the lens element and/or in the outer enclosure.

28. A shape memory alloy (SMA) actuation apparatus comprising: a support structure; a moveable component supported on the support structure in a manner allowing movement of the moveable component relative to the support structure;

eight SMA actuator wires inclined with respect to a notional primary axis with two SMA actuator wires on each of four sides around the primary axis, the SMA actuators being connected between the moveable component with a component in opposite directions along the primary axis, the SMA actuator wires of each group being arranged with two-fold rotational symmetry about the primary axis; and

at least one damping element arranged to reduce undesirable motion of the moveable component.

29. The SMA actuation apparatus as claimed in claim 28 wherein the at least one damping element is a viscous material provided in at least one location in the SMA actuation apparatus.

30. The SMA actuation apparatus as claimed in claim 29 wherein the viscous material is a lubricant.

31. The SMA actuation apparatus as claimed in claim 30 wherein the lubricant is any one of: a grease, a silicone grease, and an oil.

32. The SMA actuation apparatus as claimed in claim 28 wherein the at least one damping element is a viscoelastic material provided in at least one location in the SMA actuation apparatus.

33. The SMA actuation apparatus as claimed in claim 29 wherein the viscoelastic material is a silicone gel or a damping oil.

34. The SMA actuation apparatus as claimed in claim 33 wherein the viscoelastic material is cured using ultraviolet light.

35. The SMA actuation apparatus as claimed in one of claims 29 to 34 wherein the at least one damping element is provided between the support structure and the moveable component.

36. The SMA actuation apparatus as claimed in any one of claims 29 to 34 wherein the at least one damping element is provided on a surface of the support structure, and the moveable component comprises at least one projection that extends into the at least one damping element.

37. The SMA actuation apparatus as claimed in any one of claims 29 to 34 wherein the at least one damping element is provided on a surface of the moveable component, and the support structure comprises at least one projection that extends into the at least one damping element.

38. The SMA actuation apparatus as claimed in any one of claims 29 to 37 wherein the moveable component or the support structure comprises at least one well and the damping element is provided within the at least one well.

39. The SMA actuation apparatus as claimed in claim 38 wherein the at least one well is provided in a base or a side of the support structure or the moveable component.

40. The SMA actuation apparatus as claimed in claim 36, 37, 38 or 39 wherein the at least one projection is a rod and an end of the rod extends into the at least one damping element.

41. The SMA actuation apparatus as claimed in claim 36, 37, 38 or 39 wherein the at least one projection comprises a rod coupled at one end to a sphere, and the sphere extends into the at least one damping element.

42. The SMA actuation apparatus as claimed in claim 36, 37, 38 or 39 wherein the at least one projection comprises a rod coupled at one end to at least one paddle, and the at least one paddle extends into the at least one damping element.

43. The SMA actuation apparatus as claimed in any one of claims 29 to 35 wherein the support structure further comprises a screening can, and the screening can comprises at least one projection arranged to extend into the at least one damping element.

44. The SMA actuation apparatus as claimed in claim 43 wherein the moveable component comprises at least one well wherein the damping element is provided within the at least one well.

45. The SMA actuation apparatus as claimed in any one of claims 29 to 34 further comprising at least one dashpot coupled between the moveable component and the support structure, wherein the at least one dashpot contains the at least one damping element.

46. The SMA actuation apparatus as ciaimed in any one of claims 29 to 35 and 38 to 39 further comprising a common spring coupled to the moveable

component and the support structure, wherein the common spring comprises at least one projection arranged to extend into the at least one damping element.

47. The SMA actuation apparatus as claimed in any one of claims 29 to 35 and 38 to 39 further comprising a common spring coupled to the moveable

component and the support structure, wherein the at least one damping element is provided between the support structure and the common spring and/or between the common spring and the moveable component.

48. The SMA actuation apparatus as claimed in claim 28 wherein the at least one damping element is an arm coupled at one end to the moveable component and at another end to the support structure.

49. The SMA actuation apparatus as claimed in claim 48 wherein the arm is formed from any one of: a foam, a urethane foam, a microce!iu!ar foam, a polyurethane foam, and PORON.

50. The SMA actuation apparatus as ciaimed in claim 28 wherein the at least one damping element is a formed sheet coupled at one end to the moveable component and at another end to the support structure.

51. The SMA actuation apparatus as ciaimed in claim 50 wherein the formed sheet is formed from any one of: a metal, a metal alloy, a metallic material, and an electrically-insuiative material.

52. The SMA actuation apparatus as claimed in any of claims 28 to 51 wherein the SMA actuation apparatus is a camera apparatus and further comprises an image sensor fixed to the support structure, and the moveable component comprises a camera lens element comprising at least one lens arranged to focus an image on the image sensor, the primary axis being the optical axis of the camera lens element.

53. The SMA actuation apparatus as claimed in claim 52 wherein the moveable component Is moved to provide autofocus and/or optical image stabilisation.