GB2625731A

GB2625731A - Actuator assembly

Info

Publication number: GB2625731A
Application number: GB2219495.5A
Authority: GB
Inventors: Armstrong Samuel; Heijne Nicolas; Hart Oliver; Lam Andrew
Original assignee: Cambridge Mechatronics Ltd
Current assignee: Cambridge Mechatronics Ltd
Priority date: 2022-12-22
Filing date: 2022-12-22
Publication date: 2024-07-03
Also published as: GB202219495D0

Abstract

An assembly comprises a support structure; a movable component 4, an actuator 20 configured to drive movement of the movable component relative to the support structure; and a bearing component 6a, 6b configured to guide movement of the movable component 4. The assembly further comprises a further component 8a, 8b which is also engaged with the bearing component to align the further component with the one or more other components. The bearing component may be pins 6a, 6b, and the further component 8 may be an intermediate actuator component.

Description

SMA ACTUATOR ASSEMBLY

Field

The present disclosure relates to actuator assemblies.

Background

It is known to use an actuator, for example a shape memory alloy, SMA, element, to drive translational movement of a movable element with respect to a support structure. SMA has particular advantages in miniature devices and may be applied in a variety of devices including handheld devices, such as cameras and mobile phones. Such SMA elements may be used for example in an optical device such as a camera for driving translational movement of a camera lens element along its optical axis, for example to effect focussing (autofocus, AF), zoom and/or to account for thermal variations in the device.

Some examples of an SMA actuation apparatuses which are cameras of this type are disclosed in WO 2007/113478 41. Herein, the movable element is a camera lens element supported on a support structure by a helical bearing arrangement comprising flexures that guide translational movement along the optical axis. In one example described herein, the SMA element is a piece of SMA wire connected at its ends to a support structure and hooked over a hook on a camera lens element for driving the translational movement. The straight SMA wires formed by the portions of the piece of SMA wire on either side of the hook extend at an acute angle of greater than 0 degrees to the movement direction parallel to the optical axis. Angling the SMA wires in this way increases the amount of movement compared to an SMA wire extending along the movement direction and also reduces the extent of the actuator in the movement direction. In this way, a relatively higher stroke is achieved.

It is desirable in some circumstances to drive the movable element to make relatively small movements and to accurately control the position of the movable component.

Summary

According to an aspect of the present disclosure there is provided an actuator assembly comprising: a support structure; a movable component which is movable relative to the support structure; an intermediate component configured to engage with the movable component; and an SMA element connected between the support structure and the intermediate component.

The SMA element is configured, on contraction, to drive movement of the intermediate component relative to the support structure and thereby drive, as a result of the engagement of the intermediate component with the movable component, movement of the movable component along a movement direction. The actuator assembly is configured such that on contraction of the SMA element by a first amount, the movable component moves by a distance along the movement direction which is less than the first amount. The support structure may define a primary axis and the actuator assembly may be configured such that on contraction of the SMA element by a first amount, the movable component moves by a distance along the primary axis which is less than the first amount An advantage of this gearing down effect (i.e. movement of the movable component by less than an amount by which the SMA element contracts) is that greater positional accuracy is provided. For a given contraction length of the SMA, the movable component moves by a relatively smaller distance and so the position of the movable component can be more precisely controlled. A further advantage of the arrangement described above is that the SMA element is connected between the intermediate component and the support structure, as opposed to between the movable component and the support structure. This may simplify the manufacture process. For example, in cases where the movable component comprises a lens, the process of integrating the lens into the assembly may be simplified when no SMA is connected to the movable component. A lack of SMA elements connected to the movable component may also be beneficial when the device is dropped as the SMA is connected to a component (the intermediate component) which is much lighter than the potentially relatively heavy movable component (for example if it comprises a lens). There is thus less chance of the SMA element(s) being damaged. A further advantage of the gearing down effect is increased force imparted by the SMA on the intermediate component. This is beneficial in overcoming friction and/or moving large masses.

The movable component may comprise any element to be moved. For example, the movable component may comprise one or more of: an image sensor, a valve or component of a valve, a shaft for a motor, a lens and a light source (e.g. a laser).

In an embodiment, the movable component or the support structure (or both) comprises a lens and the movement direction is parallel (or is colinear with) the optical axis of the lens. Accordingly, there is provided an actuator assembly comprising: - a support structure; - a movable component which is movable relative to the support structure; an intermediate component configured to engage with the movable component; and - an SMA element connected between the support structure and the intermediate component.

The movable component and/or the support structure comprises a lens. The SMA element is configured, on contraction, to drive movement of the intermediate component relative to the support structure and thereby drive, as a result of the engagement of the intermediate component with the movable component, movement of the movable component along an optical axis of the lens. The actuator assembly is configured such that on contraction of the SMA element by a first amount, the movable component moves by a distance along the optical axis of the lens which is less than the first amount. In other words, the motion of the movable component is geared down such that the amount by which the movable component moves is less than the stroke of the SMA element. The first amount may be a distance.

Optionally, movement of the movable component along directions other than the optical axis of the lens may be constrained. For example, the support structure may comprise a bearing component which bears the movement of the movable component and prevents movement of the movable component along directions other than the optical axis. Optionally, the actuator assembly may comprise a biasing arrangement which is configured to bias the movable component onto such a bearing component. The biasing arrangement could comprise one or more resilient elements such as springs, for example, and/or one or more magnets and/or one or more SMA elements. Optionally, the one or more SMA elements may bias the movable component onto a bearing component as well as driving movement of a component of the assembly (e.g. the intermediate component).

Optionally, the bearing component may engage with a total of five surfaces of the movable component.

Optionally, the intermediate component may comprise a single, integral element. Alternatively, the intermediate component may comprise multiple, separate parts which move together as one. For example, the intermediate component may comprise a first intermediate sub-component and a second intermediate component which are connected together via a connecting component such that when the first sub-component moves, the second sub-component moves with it in the same direction and vice versa. Such a connection component may be a rigid body such as a rod or strip and/or may comprise a spring. Alternatively, no connecting component may be present and instead the assembly may be configured such that movement of one intermediate sub-component drives movement of the other intermediate sub-component with it.

Whether the intermediate component is a single, integral component or made up of multiple, separate sub-components, the intermediate component may comprise multiple, separate features (e.g. surfaces) which respectively engage with multiple, separate features (e.g. surfaces) on the movable component. For example, the intermediate component may comprise two separate surfaces which each engage with a respective surface or feature of the movable component. The intermediate component may also engage with the support structure.

Optionally, the actuator assembly may comprise control circuitry configured to send a signal to the SMA element to drive movement of the movable component along the optical axis of the lens to compensate for thermal variations in the actuator assembly, e.g. thermal variations in the lens itself, and/or thermal variations in a device on which the actuator assembly is disposed. Such a process may be referred to as athermalisation. The actuator assembly may comprise a thermistor or other means for detecting an ambient temperature.

The actuator assembly may be configured to move the movable component along an optical axis of a lens for purposes other than athermalisation, for example zoom or focusing (e.g. autofocusing).

Optionally, the intermediate component is configured to move in a direction which is non-parallel (e.g. perpendicular) to the optical axis. For example, the intermediate component may be driven to translate along a direction which is non-parallel (e.g. perpendicular) to the optical axis or to rotate in a plane which is non-parallel (e.g. perpendicular) to the optical axis. For example, the intermediate component may rotate about the optical axis.

Optionally, the SMA element is a first SMA element which is configured to drive the intermediate component in a first direction and the actuator assembly further comprises a second SMA element connected between the intermediate component and the support structure and which is configured to drive the intermediate component in a second direction which is opposite to the first direction. In other words, the actuator assembly comprises one SMA element which drives movement of the intermediate component in a first direction and another SMA element which drives movement in a second, opposite direction. The first SMA element may be parallel to the second SMA element.

Optionally, the actuator assembly is configured such that movement of the intermediate component in the first direction drives movement of the movable component in a third direction, along the optical axis, and movement of the intermediate component in the second direction drives movement of the movable component in a fourth direction which is opposite to the third direction. The first and second directions may refer to rotation of the intermediate component in opposite directions about the optical axis or to translation in opposite directions along an axis which is nonparallel to the optical axis.

Optionally: - one of the intermediate component and the movable component comprises a first surface which is at a non-zero, acute angle to the optical axis (optionally greater than 45 degrees); -the other of the intermediate component and the movable component comprises a first feature which directly or indirectly engages with the first surface; and - the actuator assembly comprises a biasing arrangement to bias the first feature against the first surface, such that movement of the intermediate component in a direction which is non-parallel to the optical axis induces movement of the movable component along the optical axis.

Accordingly, in some embodiments, the engagement between the intermediate component and the movable component involves a surface which is angled with respect to the optical axis (specifically at a non-zero, acute angle, optionally greater than 45 degrees, to the optical axis when viewed along a direction perpendicular to the optical axis). Such a surface may be provided on one or both of the movable and intermediate components. In some cases the intermediate component may comprise the angled surface and the feature on the movable component that engages with the angled surface could comprise a projection (e.g. a cylindrical projection) which moves over the angled surface. Alternatively, the movable component may comprise the angled surface and the intermediate component may comprise the projection.

In some embodiments, both the intermediate component and the movable component may comprise a respective surface which is at a non-zero, acute angle to the optical axis. This angle may be greater than 45 degrees. Accordingly, the first feature (referred to above) may comprise a surface, which may also be at a non-zero, acute angle to the optical axis. The surface may conform to and/or be parallel to the first surface. In an embodiment, the intermediate comprises a first angled surface and a second angled surface which are spaced apart from each other along a direction perpendicular to the optical axis but overlap along the optical axis. The movable component also comprises a first angled surface and a second angled surface which are spaced apart from each other along a direction perpendicular to the optical axis (but overlap along the optical axis). The first respective angled surfaces engage with each other and the second respective angled surfaces engage with each other.

As mentioned above, the first surface may be configured such that the intermediate component moves in a direction which is perpendicular to the optical axis, for example in a straight line. In some embodiments, the first surface may be a helical surface. The helical axis may be parallel (or colinear) to the optical axis. In this case, the intermediate component may move along the optical axis and also rotate about the optical axis.

The first feature either engages directly or indirectly with the first surface. In embodiments in which there is direct engagement, the first feature may be in contact with the first surface. In embodiments in which there is indirect engagement, there may be an intervening component such as a ball bearing between the first surface and the first feature.

In some embodiments, the actuator assembly comprises a bearing component comprising a bearing surface. The bearing surface is configured to guide movement of the movable component along the optical axis of the lens relative to the support structure. The bearing surface may be parallel to the optical axis.

Optionally, the bearing component is in contact with one or more additional components of the actuator assembly (or the device in which the actuator assembly is disposed) for aligning the one or more additional components with each other and/or with the movable component. For example, the assembly may comprise one or more arrays which need to be precisely aligned with the movable component, which may itself comprise a lens, for example. The bearing component thus may have a dual purpose of providing a bearing surface and also aligning components of the assembly with each other. A benefit of such an arrangement is that the movable component and the additional components are precisely located (because their positions are defined with respect to the same component, namely the bearing component and specifically the bearing surface).

In some embodiments the bearing component comprises an elongate component, for example a pin or rod. The elongate component may be parallel to the optical axis of the lens. In some embodiments, the elongate component may be or comprise a ground pin and/or a lapped pin. An advantage of using a ground pin or a lapped pin is that the surface of such a pin (which corresponds to the bearing surface) can be made to be very straight and smooth. The bearing surface is thus very well-defined and smoother movement of the movable component is provided as well as better alignment between the movable component and the additional components (including better alignment between the additional components themselves). The term 'ground pin' refers to a pin which has been manufactured using a grinding process. The term 'lapped pin' refers to a pin which has been manufactured using a lapping process.

As mentioned above, the bearing component may comprise an elongate component which is parallel to the optical axis of the lens. A further advantage of such a vertical bearing is that the bearing component can be positioned on one side of the assembly and so the footprint of the assembly (in a plane perpendicular to the optical axis) can be reduced.

Alternatively, the bearing component could comprise moulded tracks, folded metal tracks or insert moulded sheet metal tracks. Such tracks could be an elongate body with a square or rectangular cross-section, which could be made by moulding, by folding sheet metal or by insert moulding.

In some embodiments, the first surface and the first feature are configured such that, when the intermediate component moves relative to the support structure, the movable component moves along the optical axis and a normal force between the movable component and the bearing surface is reduced, thus reducing a frictional force between the movable component and the bearing surface. An advantage of this is that the frictional force between the movable component and the bearing surface is reduced upon movement of the movable component. This results in better performance in terms of accuracy and also in speed of movement.

As mentioned above, the first feature may also be a surface and both surfaces (on the intermediate component and movable component respectively) may be angled such that a normal force between the movable component and the support structure may be reduced on movement of the intermediate component (e.g. on contraction of the SMA). For example, the bearing surface may be parallel to the optical axis and the two surfaces may be angled such that when the intermediate component moves it exerts a force on the movable component which has a component along the optical axis and a component in a direction perpendicular to the optical axis, away from the bearing component.

In some embodiments, the actuator assembly comprises a first friction surface and a first friction feature which moves across the first friction surface as a result of movement of the intermediate component relative to the support structure. The actuator assembly comprises a biasing arrangement for biasing the first friction surface and the first friction feature together so as to generate a frictional force therebetween for retaining the first friction feature in position on the first friction surface when no power is supplied to the SMA element. An advantage of this arrangement is that when the SMA element(s) is/are unpowered (and hence not contracted), frictional forces are high enough to retain the first friction feature in place on the first friction surface. Accordingly, the movable component is held in position with respect to the support structure when no power is supplied to the SMA element(s). Power consumption of the assembly is thus reduced as compared to an assembly in which SMA element(s) (or another powered actuator) are used to hold the movable component in a given position.

In some embodiments, the first friction surface is provided on one of the movable component and the support structure and the first friction feature is provided on the other of the movable component and the support structure. The first friction surface may correspond to the bearing surface and the first friction feature may correspond to a feature on the movable component. In this way, the frictional forces between the movable component and the bearing surface may be sufficient to retain the movable component in position with respect to the support structure when the SMA element is unpowered.

In some embodiments, the SMA element extends in a direction which is perpendicular to the optical axis of the lens. In the case when more than one SMA element is present, each SMA element may extend in a direction which is perpendicular to the optical axis.

In some embodiments, the SMA element extends at an acute, non-zero angle to the optical axis of the lens. In the case when more than one SMA element is present, each SMA element may extend at an acute, non-zero angle to the optical axis of the lens. An advantage of such an angled SMA element is that, in the case of an SMA wire for example, a longer length of wire may be able to be used within a given space. A longer length of wire provides a greater level of accuracy in controlling the length of the SMA. Angling the SMA element in this way, however, may provide a gearing up effect (i.e. the intermediate component would move by an amount which is greater than the contraction of the SMA element). However, as described above an overall gearing down effect is desired to afford greater positional control over a movable component. Accordingly, in the case where such angled SMA elements are used, other aspects of the assembly (e.g. the angle of the first feature with respect to the optical axis) may be selected in order to over-compensate for the gearing up to achieve an overall gearing-down effect. In some embodiments, the SMA element is at an angle to the optical axis which is less than 45 degrees. In other embodiments, the angle may be greater than 45 degrees.

In some embodiments the assembly comprises a de-amplification flexure connected between the support structure and the intermediate component. The de-amplification flexure is configured to convert contraction of the SMA element by a first amount into translation of the movable component along the optical axis of the lens by an amount which is less than the first amount. The de-amplification flexure may comprise one or more flexure arms which are configured to bend in one or more directions perpendicular to their length but do not flex in directions parallel to their length.

Optionally, the de-amplification flexure is configured to convert rotation of the intermediate component into translation of the movable component along the optical axis. Specifically, the de-amplification flexure is configured such that the movable component moves along the optical axis but an amount less than a contraction amount of the SMA element(s) which drives rotation of the intermediate component.

Optionally, the assembly further comprises an anti-rotation flexure connected between the movable component and the support structure, wherein the anti-rotation flexure is configured to prevent rotation of the movable component about the optical axis.

According to a further aspect of the present disclosure there is provided an assembly comprising: - a support structure; - a movable component; - an actuator configured to drive movement of the movable component relative to the support structure; - a bearing component configured to guide movement of the movable component, wherein the bearing component comprises a bearing surface which is engaged with the movable component; and a further component to be aligned with one or more other components of the assembly, wherein the bearing component is engaged with the further component to align the further component with the one or more other components.

The bearing component thus has a dual function: it provides a bearing surface to guide movement of the movable component and also engages with a further component to align it with other parts of the assembly (for example the movable component or another component of the assembly). Advantageously, very precise alignment is provided. Accordingly, active alignment methods (involving the use of motors to move components in order to align them) may be avoided or at least partially dispensed with.

The actuator may be configured to drive movement of the movable component over a range of motion. The movable component may be in contact with the bearing surface over the full range of motion of the movable component. The bearing component may extend beyond the range of motion of the movable component and, outside of the range of motion, be in contact with a further component which is to be aligned with one or more other components of the assembly.

The further component may be or comprise a light source, e.g. a pixel array (or LED array). A pixel array or LED array may include a micro LED array or a 3-LED array. The one or more other components of the assembly (i.e. the one or more components to be aligned with the further component) may comprise one or more of the movable component and an LED array or pixel array.

In some embodiments, the assembly may be configured to allow movement of the movable component in one degree of freedom only and movement in the other degrees of freedom may be constrained.

In some embodiments, the movable component is in contact with the bearing surface and the movable component is configured to slide across the bearing component In this sense, the bearing is a plain bearing.

In some embodiments, the movable component may comprise a rolling element, such as a ball bearing, which rolls across the bearing component as the movable component moves.

In some embodiments, the bearing component is elongate. The bearing component may be a rod or pin, for example. In some embodiments the bearing component comprises a bearing pin. Optionally, the bearing component comprises two or more bearing pins. In some embodiments, the bearing component may comprise a total of two bearing pins.

In some embodiments the bearing pin comprises a ground pin or a lapped pin. A ground pin or lapped pin is particularly advantageous as they can be manufactured to high precision which facilitates accurate alignment of the various components to be aligned and also smooth movement of the movable component.

Additionally or alternatively, the bearing component may comprise moulded tracks, folded metal tracks and/or insert-moulded sheet tracks. Such tracks could be an elongate body with a square or rectangular cross-section, which could be made by moulding, by folding sheet metal or by insert moulding.

As mentioned above, in some embodiments the movable component comprises a lens and the actuator is configured to drive movement of the lens along an optical axis of the lens.

Optionally, the assembly comprises control circuitry configured to send a signal to the actuator to drive movement of the lens along the optical axis of the lens to compensate for thermal variations in the assembly and/or a device on which the assembly is disposed.

In some embodiments the assembly is configured such that a frictional force between the bearing surface and the movable component is sufficient to maintain the position of the movable component with respect to the support structure when the actuator is unpowered. An advantage of this arrangement is that the actuator is unpowered (i.e. turned off), frictional forces are high enough to retain movable component in place with respect to the support structure. Power consumption of the assembly is thus reduced as compared to an assembly in which it is required to continuously supply power to the actuator hold the movable component in a given position.

In some embodiments the actuator comprises one or more shape memory alloy elements. Additionally or alternatively the actuator may comprise any suitable actuator, for example one or more voice coil motors (VCM), a piezo actuator, a MEMS (microelectromechanical system) drive system and/or shape memory polymer.

In some embodiments the bearing component is received within an aperture in the movable component, an aperture within the further component or both. In other words, the bearing component (which may be a pin or rod, for example) may extend through one or more of the movable component and the further component.

In some embodiments the assembly further comprises an additional assembly (e.g. such as an assembly described above) and an alignment component for aligning the two assemblies relative to one another. The bearing components of the two assemblies may be received in respective apertures in the alignment component. For example, the alignment component may comprise a sheet or planar structure comprising a plurality of apertures through which respective bearing components of the assemblies are received. The alignment component could be made from a moulding and the bearing components (e.g. bearing pins) may be insert moulded into the alignment component.

Brief description of the drawings

Figures 1A-D are schematic views of an actuator assembly; Figure 2A is a schematic view of a variation on the assembly illustrated in Figures 1A-D; Figure 2B is a further view of the assembly of Figure 2A; Figures 3A and 3B are schematic views of a further actuator assembly; Figures 4A-C are schematic views of a further actuator assembly; Figures SA-C are schematic views of an actuator assembly comprising a de-amplification flexure; Figures 6A and 6B are schematic views of an actuator assembly comprising a helical bearing arrangement; Figure 7 is a schematic view of an assembling comprising bearing pins; and Figure 8 is a schematic view of multiple assemblies aligned by an alignment component.

Detailed description

Figures 1A-D are schematic views of an SMA actuator assembly 1. Figures 1A and 1B are perspective views, Figure 1C is a front view and figure 1D is a plan view. The actuator assembly 1 comprises a support structure 2 and a movable component 4. The movable component 4 comprises one or more lenses (not shown) and is configured to move relative to the support structure 2 along an optical axis 0 of the one or more lenses. The support structure 2 comprises two bearing pins 6a and 6b which bear the movement of the movable component 4. The bearing pins 6a and 6b constrain movement of the movable component. As seen in Figure 1D a portion of the movable component 4 has a cross-section having a V-shaped surface. This portion engages with a first bearing pin 6a at two surfaces (one on each side of the V). A further V-shaped portion is provided underneath the one seen in Figure 10D (such that the two V-shaped portions are separated from each other along the optical axis 0). In this way, the first bearing pin 6a contacts the movable component 4 at four surfaces.

A second bearing pin 6b engages with a single surface (specifically a flat face) of the movable component 4. Accordingly, a total of five surfaces of the movable component 4 contact the bearing pins. These multiple contact surfaces ensure that the movable component 4 moves along the bearing pins smoothly. A greater number of contact surfaces could over-constrain the movable component and lead to less-smooth motion.

The bearings pins are made of a magnetic material (e.g. magnetic steel) and a two magnets are disposed on or in the movable component 4, each magnet opposite a respective bearing pin. The magnetic force between the magnets and the bearing pins keeps the movable component in contact with the bearing pins.

The actuator assembly 1 further comprises first and second intermediate components 8a and 8b. The first intermediate component Sa comprises a first angled surface 12a, which is at an acute, nonzero angle to the optical axis 0 of the one or more lenses. The second intermediate component 8b comprises a second angled surface 12b, which is at an acute, non-zero angle (which is greater than 45 degrees) to the optical axis 0.

The movable component comprises an engagement feature 14, which comprises a first engagement surface 14a and a second engagement surface 14b. The first angled surface 12a of the first intermediate component 8a engages with the first engagement surface 14a of the movable component 4 and the second angled surface 12b of the second intermediate component 8b engages with the second engagement surface 14b of the movable component 4. First and second springs 16a and 16b are each connected between the first and second intermediate components 8a and 8b and act to bias the intermediate components against the engagement feature 14 of the movable component 4 along the x direction (labelled in Figure 1A). The first and second springs 8a and Share rigid enough to ensure that the first and second intermediate components 8a and 8b move along the x direction together as a single unit. The springs may be referred to as a connection component.

A third spring 18 is connected to the support structure 2 and acts to bias the intermediate components 8a and 8b in a direction parallel to the optical axis 0. This third spring 18 pushes the intermediate components 8a and 8b and the movable component (specifically the engagement feature 14) down onto the support structure 2.

The third spring 18 also acts as a bearing surface to support movement of the intermediate components 8a and 8b along the x direction, perpendicular to the optical axis. Specifically, the first intermediate component 8a comprises bearing features 21a and 21b which are in contact with and slide over the third spring 18 as the first and second intermediate components 8a and 8b move along the x direction.

The actuator assembly further comprises a first SMA wire 10a and a second SMA wire 10b to drive movement of the intermediate components 8a and 8b along the x direction. The SMA wires are shown in Figure 1C but are omitted from Figure 1A for clarity of other features of the assembly.

The first SMA wire 10a is connected between the support structure 2 and the first intermediate component 8a and the second SMA wire 10b is connected between the support structure 2 and the second intermediate component 8b. The SMA wires 10a and 10b are connected to the respective intermediate components and the support structure 2 by crimps 20a, 20b, 20c and 20d. It will be appreciated that any suitable connection element that provides both a mechanical and electrical connection could be used. Each SMA wire is connected to a power source which is in turn connected to control circuitry which controls the power supplied to each SMA wire.

During use, power is supplied to each SMA wire to cause resistive heating of the wire which in turn causes the SMA wire to contract. With reference to Figure 1C, when the first SMA wire 10a contracts, the first intermediate component 10a (and hence also the second intermediate component 10b and the first and second springs 16a and 16b due to the rigidity of the springs 16a and 16b) is moved in the negative x direction as labelled in Figure 1C (i.e. to the left). As a result of the engagement between the intermediate components 8a and 8b and the engagement portion 14 of the movable component 4 and specifically the angled surfaces 12a, 12b, 14a and 14b, when the first and second intermediate components 8a and 8b move in the negative X direction, the movable component 4 moves in the negative Z direction, labelled in Figure 1C, which is parallel to the optical axis 0 of the one or more lenses (i.e. downwards).

Contraction of the first SMA wire 10a causes expansion of the second SMA wire 10b. Conversely, contraction of the second SMA wire 10b causes expansion of the first SMA wire 10a. When the second SMA wire 10b is caused to contract, the first and second intermediate components 8a and 8b (and the springs 16a and 16b) moved in the positive X direction (i.e. right in Figure 1C) and as a result, the movable component moves in the positive Z direction (i.e. upwards). In this way, opposing wires can be used to move the movable component in both directions along the optical axis 0. As a result of the angled surfaces 12a, 126, 14a and 14b, when one of the SMA wires contracts by a first amount AX, the amount by which the movable component moves along the optical axis, AZ will be less. It can be seen that for an angle a between the surface 12a (for example) and a normal to the optical axis, AZ = AX tan a. Therefore for a <45 degrees, the movable component 4 will move by an amount along the optical axis which is less than an amount by which the respective SMA wire contracts. In other words, the motion of the movable component is geared down.

It will be appreciated that it is not necessary that both the intermediate component and the movable component comprise a surface angled in the way shown in Figures 1A and 1C and described above. For example, the engagement feature 14 may comprise a different shape (for example a cylindrical or otherwise shaped notch or projection) which engages with an angled surface on one or both of the first and second intermediate components. Similarly, the engagement feature 14 of the movable component may comprise one or more angled surfaces and one or both of the intermediate components may comprise a different shaped surface or feature which engages with the angled surface(s) of the engagement feature of the movable component 4. For example, the movable component could comprise a projection which moves in an angled slot on the intermediate component (or vice versa).

The embodiment shown in Figures 1A-D is a wire vs. wire arrangement (i.e. a first SMA wire contracting causes expansion of a second wire and vice versa). Alternatively, the actuator assembly 1 may instead comprise a single SMA wire which acts to move the intermediate components Sa and 8b in a first direction along the x axis and a biasing arrangement which acts to bias the intermediate components along the x axis in a second direction. Such a biasing arrangement could comprise a resilient element such as a spring or a magnet, for example.

The assembly comprises a number of plain bearings (e.g. between the movable component and the bearing pins and between the intermediate component 8a and the spring 18). One or more of these plain bearings could be replaced with another bearing arrangement, such as a roller bearing. This may advantageously reduce friction in the assembly (at interfaces where that is desired) but may also add to the manufacturing cost and complexity.

With reference to Figures 2A and 2B, a particular configuration of the engagement feature 14 of the movable component 4 and the angled surfaces 12a and 126 of the first and second intermediate components respectively is described. Figure 2A is a perspective view of the engagement feature 14, which is an alternative configuration to that shown in Figures 1A and 1C. Only the differences between the Figure 2 embodiment and the Figure 1 embodiment are described here. Figure 2B shows a plan view of the actuator assembly in which Figure 2A is disposed.

It may be desirable to reduce the power consumption of the actuator assembly. One way of achieving this is to reduce the amount of time during which power must be supplied to the SMA wire(s). The configuration of the actuator assembly described with reference to Figures 2A and 2B has the result that a normal force between the movable component 4 and the bearing pins 6a and 6b is reduced when the movable component is in motion and is increased when the movable component 4 is stationary. In this way, frictional forces between the bearing pins 6a and 6b and the movable component 4 are lower during motion of the movable component and higher when the movable component 4 is stationary. The actuator assembly can be thus configured such that when no power is supplied to the SMA wires the movable component 4 remains stationary with respect to the support structure 2.

As shown in Figure 2A, the engagement feature 14 comprises two engagement surfaces 14a and 14b. A difference between the embodiment in Figures 2A and 2B and the embodiment of Figures 1A-D is that the two engagement surfaces 14a and 14b are not parallel to each other. Similarly, the first and second angled surfaces 12a and 12b of the first and second intermediate components 8a and 8b respectively are also not parallel. However, the first angled surface 12a is parallel to the first engagement surface 14a and the second angled surface 12b is parallel to the second engagement surface 14b. Specifically, as compared to the first engagement surface 14a in the Figures 1A-D embodiment, the first engagement surface 14a in the Figure 2 embodiment is rotated by a non-zero acute angle about an axis lying within the plane of the first engagement surface. The same is true of the second engagement surface 14b (although the rotation is in an opposite direction).

The surfaces 12a, 12b, 14a and 14b are angled such that when the first and second intermediate components 8a and 8b move along the x direction, the movable component is driven along the Z direction (parallel to the optical axis) as in the embodiment of Figures 1A-D but the force imparted by the intermediate components on the movable component also has a component along the Y direction (see figure 28). This has the effect that a normal force F (see Figure 28) and hence frictional forces between the movable component 4 and the bearing pins 6A and 6B are reduced. Force F is shown with respect to bearing pin 68 only for clarity but the frictional forces for both pins are reduced.

A further embodiment of an actuator assembly 1 is shown in Figure 3k The further embodiment shares a number of features in common with that described with reference to Figures 1A-D and the general principle of operation is the same. Accordingly, the differences will be focused on here.

In the embodiment shown in Figure 3A the biasing arrangement is different. The assembly 1 comprises a spring arrangement which comprises a frame 20, a central spring 22 and a wedge spring 24. The frame 20 is connected to (e.g. glued, welded, insert moulded or otherwise attached) and supports the central spring. The wedge spring is attached to and moves with the intermediate component 8. The actuator assembly 1 comprises a first SMA wire 102 and a second SMA wire 10b to drive movement of the intermediate component 8 back and forth along the x direction. The SMA wires drive movement in the same way as described for Figure 1C.

The frame 20 biases the intermediate component 8 and hence the movable component 4 downwards (in the negative Z direction) onto the support structure 2. The central spring 20 is glued (or otherwise attached) to the movable component and acts to pull the movable component 4 onto the bearings 6a and 6b (i.e. it imparts a force on the movable component 4 in the positive Y direction). The wedge spring 24 moves with the intermediate component 8 and biases the movable component 4 upwards (positive Z direction) onto the intermediate component 8.

The frame 20 also acts as a bearing surface and bears movement of the intermediate component 8 via a ball bearing 26. The assembly comprises further ball bearings 28 and 30 disposed between a lower surface of the intermediate component 8 and the support structure 2. Other bearing arrangements, such as a plain bearing, could be used instead.

The intermediate component 8 itself has a general rectangular frame shape and comprises an engagement feature 12 comprising a first angled surface 12a. The intermediate component 8 comprises a single component but could comprise multiple sub-components, as in the embodiment described with reference to Figures 1A-D.

The movable component 4 comprises an engagement feature 14 which itself comprises a first engagement surface 14a which engages with the first angled surface 12a.

As mentioned above, the wedge spring 24 biases the movable component 4 upwards. It also biases the movable component 4 to the right (as seen in Figure 34), onto the first angled surface 12a of the intermediate component 8. This is a result of the wedge shape of the wedge spring 24 and the angled face 24a which engages with a parallel angled face 4a of the movable component 4.

The embodiment shown in Figure 3A operates according to the same principles as previous embodiments. Taking the first SMA wire 10a as an example, when the first SMA wire 10a contracts, the intermediate component 8 is driven in the negative x direction (to the left in Figure 3a). The engagement between the intermediate component Sand the movable component (specifically at surfaces 12a and 14a) and the biasing effect of the wedge spring 24 means that the movable component 4 moves in the negative Z direction (downwards in Figure 3A). The movable component 4 is moved in the opposite direction by contracting the second SMA wire 10b.

A plan view of the actuator assembly 1 is shown in Figure 3B.

It will be appreciated that various features of the embodiments shown in Figures 1,2 and 3 (e.g. bearing arrangements, biasing arrangements etc.) could be combined in various combinations.

A further embodiment of an actuator assembly 1 is illustrated in Figures 4A-C. The actuator assembly operates using the same general principles as the embodiments described with reference to Figures 1A-D, 2A and 2B and 3A and 3B and has a number of features in common with them. Accordingly only the differences will be described here.

With reference to Figure 44, the actuator assembly 1 comprises a first intermediate sub-component 8a and a second intermediate sub-component 8b. A first SMA wire 10a is connected between the support structure 2 and the first intermediate sub-component 8a and is at a non-zero, acute angle al to the optical axis 0. The first SMA wire 10a is connected between a static crimp 20a (on the support structure 2) and a moving crimp 20b (on the first intermediate sub-component 8a). A second SMA wire 10b is connected between the support structure 2 and the second intermediate sub-component 8b and is at a non-zero, acute angle a2 to the optical axis 0. a1 may be equal to a2.

Angling the wire in the way described (as compared to arranging them to be perpendicular to the optical axis as in previous embodiments) means that more wire fit into the same space envelope. A longer length of wire results in a greater contraction amount. Accordingly, the contraction (and hence the position of the movable component 4) can be controlled more precisely.

The second SMA wire 10b is connected between a static crimp 20c (on the support structure 2) and a moving crimp 20d (on the second intermediate sub-component 8b).

The movable component 4 comprises an engagement feature 14 which comprises a first engagement surface 14a and a second engagement surface 14b (see figure 45) which are parallel to each other. The first intermediate sub-component 8a comprises a first angled surface 12a and the second intermediate sub-component 8b comprises a second angled surface 12b. The first and second angled surfaces are parallel to each other and to the first and second engagement surfaces 14a and 14b.

Two ball bearings 26 and 28 are respectively disposed between: the first engagement surface 14a and the first angled surface 12a and -the second engagement surface 14b and the second angled surface 12b.

In operation, taking the second SMA wire lob as an example, the second SMA wire lob is contracted. This moves the second intermediate sub-component 8b in Figure 45 to the right. The engagement between the second angled surface 12b and the second engagement surface 14b (via ball bearing 28) means that this movement causes translation of the movable component 4 upwards (in Figure 45) along the optical axis. Due to the engagement between the intermediate subcomponents 8a and 8b (via the ball bearings and the engagement feature 14), the first intermediate sub-component also moves to the right.

Movement of the movable component in the other direction (downward) along the optical axis is achieved by contracting the first SMA wire 10a.

As described above, the SMA wires 10a and 10b are angled with respect to the optical axis in order to fit a longer length of wire into the space. However, such angled wires leads to gearing-up of the movement of the intermediate sub-components 8a and 8b (i.e. they would move by an amount along the x axis which is greater than a contraction of the respective SMA wire). This is because the angle of the wires with respect to the optical axis is less than 45 degrees. Accordingly, this gearing-up must be over-compensated for by angling the angled and engagement surfaces (12a, 126, 14a and 14b) appropriately.

Figure 4C shows a side view of the actuator assembly 1. Portions of the intermediate subcomponents 8a and 8b are omitted so as to show the SMA wires 10a and 1013. The SMA wires 10a and 10b are angled outwards such that the end of each respective SMA wire which is connected to the respective intermediate sub-component (8a and 8b) is further from the optical axis (along the y direction) than the end which is connected to the support structure. Accordingly, taking the first SMA wire 10a as an example, when the first SMA wire 10a contracts, the force it applies on the first intermediate sub-component 8a has components along the X, Y and Z axes. The action of the components of force along the X and Z axes was described above. The component of force along the Y axis (which is in the negative Y direction, i.e. to the left in Figure 4C) acts to pull the first intermediate sub-component 8a along the negative V direction. This in turn reduces the normal force acting between the movable component 4 and the bearing pins 6a and 6b, along the negative Y direction (as the intermediate sub-component 8a and the movable component 4 are in engagement). This means that when the first SMA wire 10a is contracted, the normal force (and hence the frictional forces) between the movable component 4 and the bearing pins 6a and 6b is reduced. Friction is therefore lower during motion of the movable component and relatively higher when the movable component 4 is stationary. The assembly 1 can be configured such that when the movable component 4 is stationary the friction is high enough to hold it in position with respect to the support structure 2. Power therefore does not need to be supplied to the SMA wires to hold the movable component 4 still. The power consumption of the device is therefore reduced.

The second SMA wire 10b also acts in the same way to reduce the normal force of the movable component 4 on the bearing pins during motion.

Another benefit of angling the SMA wires so that they provide a component of force along the Y axis is that good contact is maintained between the intermediate sub-components and the movable component.

A further embodiment of an actuator assembly is illustrated in Figures SA-C. A first view of the actuator assembly is shown in Figure SA. A second view, in which the support structure is omitted but the movable component 4 is shown, is illustrated in Figure SB. Figure SC shows the movable component 4 and the anti-rotation flexure (which will be described below) and the engagement of the anti-rotation flexure with the movable component 4.

With reference to Figures 5A and 5B, the actuator assembly 1 comprises a support structure 2 (see Figure 5A) and a movable component 4 (see Figure 5B). The movable component 4 comprises one or more lenses (not shown) and is configured to move relative to the support structure 2 along an optical axis 0 of the one or more lenses. The assembly 1 comprises an intermediate component 8 which moves relative to the support structure 2 and engages with the movable component 4. Four SMA wires 10a, 10b, 10c and 10d are connected between the support structure 2 and the intermediate component 8. Specifically, wire 10a is connected between a first static crimp 20a (which forms part of the support structure 2) and a first moving crimp 20b (which is attached to the movable component 4). Wire 10b is connected between a second static crimp 20c (which also forms part of the support structure 2) and the first moving crimp 20b. Wire 10c is connected between the second static crimp 20c and a second moving crimp 20d (which is attached to the movable component 4). Wire 10d is connected between the first static crimp 20a and the second moving crimp 20d. The four SMA wires 10a,b,c and d drive rotation of the intermediate component 8 about the optical axis 0 of the lens. By causing contraction the wires 10a and 10c, the intermediate component 8 is driven to rotate anti-clockwise (as seen in Figure 5A) and by causing contraction the wires 10b and 10d, the intermediate component 8 is driven to rotate clockwise.

The assembly 1 further comprises a de-amplification flexure 32. With reference to Figure 5B, a first portion 32a of the flexure 32 is fixed (e.g. glued or otherwise attached) to the intermediate component S. The first portion is the inner annulus of the flexure 32. A second portion 32b is fixed with respect to the support structure 2 and so does not move relative to the support structure. The second portion corresponds to an outer portion of the flexure 32. The first and second portions 32a and 32b of the de-amplification flexure are connected by four flexure arms 32c, d, e and f (f not shown). In an unstressed state, the four flexure arms are flexible in directions perpendicular to their length but are not flexible in a direction parallel to their length.

The assembly 1 further comprises an anti-rotation flexure 34 (see Figure SC). The anti-rotation has an inner side (closer to the optical axis) and an outer side (further from the optical axis). On the inner side, the anti-rotation flexure 34 is fixed to the movable component 4. On the outer side, the anti-rotation flexure 34 is fixed to the support structure 2. The anti-rotation flexure 34 is configured to resist rotation about the optical axis 0 and because it is connected to both the movable component 4 and the support structure 2, the anti-rotation flexure 34 prevents rotation of the movable component about the optical axis. However, the anti-rotation flexure 34 is flexible in a direction parallel to the optical axis and so allows translation of the movable component 4 along the optical axis. In embodiments where the movable component 4 comprises a lens, an advantage of this is that the lens translates along the optical axis (facilitating e.g. focussing of an image or athermalisation) but does not rotate. It is preferable to avoid rotation of the lens so that imperfections in the lens do not alter the resulting image or optical effect as the lens moves.

Operation of the actuator assembly 1 will now be described. In order to translate the movable component 4 along the optical axis 0,a pair of the SMA wires are contracted. As described above, contracting the wires 10a and 10c causes the intermediate component 8 to rotate anti-clockwise (as seen in Figure SA) and contracting the wires 1013 and 10d causes the intermediate component 8 to rotate clockwise. Rotation of the intermediate component 8 about the optical axis imparts a torque about the optical axis on the de-amplification flexure 32. The structure of the de-amplification flexure and the fact that a portion of it is fixed with respect to the support structure 2 means that the flexure arms 32c,d,e and f flex and the intermediate component 8 (and the inner portion of the de-amplification flexure which is fixed to the intermediate component 8) is forced to follow a helical path (in the sense that it rotates about the optical axis 0 and simultaneously translates along the optical axis). The engagement between the intermediate component Sand the movable component means that the motion of the intermediate component 8 drives the movable component 4 to translate along the optical axis 0. Rotation of the movable component 4 about the optical axis is prevented by the anti-rotation flexure 34 as described above.

A further embodiment of an actuator assembly 1 is described with reference to Figure 6A and 6B. Figure 6A is an exploded view of the actuator assembly and Figure 6B is a cross-sectional view of the assembly when it is assembled.

The actuator assembly 1 comprises a support structure 2, an intermediate component 8 which is movable relative to the support structure 2 and a movable component 4 which also is movable relative to the support structure 2. As in previous embodiments, the intermediate component 8 engages with the movable component 4 and motion of the intermediate component 8 drives motion of the movable component 4.

Four SMA wires are connected between the intermediate component 4 and the support structure in an analogous way as that described with reference to Figures SA-C. Contraction of pairs of the four wires drives rotation of the intermediate component 8 about the optical 0 of the lens, as described with reference to Figures SA-C.

The support structure comprises a set of helical bearing surfaces 36a, 36b and 36c. The intermediate component 8 comprises corresponding helical bearing surfaces 38a, 38b and 38c which engage with and slide over the bearing surfaces on the support structure 2 as the intermediate component 8 rotates. The helical bearing surfaces (specifically the fact that they are each at an acute, non-zero angle, less than 45 degrees, to the plane perpendicular to the optical axis) means that for a given amount of contraction of the SMA wires, the movable component 4 moves along the optical axis 0 by a smaller amount (i.e. the helical surfaces have a de-amplifying effect).

During operation, a pair of the SMA wires is contracted and this drives rotation of the intermediate component 8 about the optical axis, either clockwise or anticlockwise depending on the pair of SMA wires. The helical bearing surfaces 38a, 38b and 38c of the intermediate component 8 slide over the helical bearing surfaces 36a, 36b and 36c of the support structure 2. As a result, the intermediate component 8 rotates about the optical axis and also moves along the optical axis. The engagement between the intermediate component Sand the movable component 4 results in the movable component 4 translating along the optical axis. Rotation of the movable component 4 about the optical axis is prevented by the anti-rotation flexure 34 in an analogous way to the embodiment described with reference to Figures 5A-C.

An assembly is described with reference to Figure 7. This assembly facilitates smooth motion of a movable component and also precise alignment of the movable component with respect to one or more other components of the assembly.

The assembly 1 comprises a support structure 2 and a movable component 4 which is movable relative to the support structure 2. The assembly comprises a bearing component which comprises a first bearing pin 6a and a second bearing pin 6b. The bearing pins 6a and 6b are ground pins and so have a particularly well-defined, smooth surface. Five surfaces of the movable component 4 engage with the bearing pins 6a and 613, as shown in and described with reference to Figure 1D, and slide over the bearing pins as the movable component 4 moves along the bearing pins. The assembly further comprises an actuator which is configured to drive movement of the movable component 4 along the bearing pins (i.e. in direction D labelled in Figure 7. The actuator is not shown in Figure 7 but any suitable actuator could be used. For example, the actuator may comprise one or more SMA elements. Any of the arrangements shown in Figure 1C, 3A and 4A could be used, for example. Alternatively, any other suitable actuator could be used, such as voice coil motors (VCM), a piezo actuator, a MEMS (microelectromechanical system) drive system and/or shape memory polymer.

The bearings pin 6a and 6b have a second function, which is to align the movable component 4 with one or more further components of the assembly (or of a device on which the assembly is disposed). The one or more further components are indicated schematically by dashed lines and labelled with reference numeral 200. For example, the actuator assembly 1 may be part of a projector system and the movable component 4 may comprise a lens which is moved along the optical axis of the lens to account for thermal variations in the projector (i.e. to carry out athermalisation). The lens may be stacked on top of multiple multi-pixel arrays (otherwise referred to as pixel arrays or LED arrays), each of which provide a different colour for the pixels of an RGB image. The lens requires precise alignment with the arrays and the arrays themselves require precise alignment with each other. To achieve this, the bearing pins 6a and 6b extend beyond the extent (along the optical axis) of the movement range of the movable component. The multiple arrays are positioned so as to engage with the bearing pins 6a and 6b. Accordingly, the bearing pins 6a and 6b act as both a bearing component for the movable component 4 and also as a surface against which further components of the assembly are placed so as to align them with each other and with the movable component 4. The bearing pins 6a and 6b are received in respective apertures in the support structure 2.

It will be appreciated that the bearing pins 6a and 6b could be used to align only one component (e.g. an array) with the movable component or to align two components (e.g. two arrays) with each other, without aligning them with the movable component.

As mentioned above, the movable component 4 slides over the bearing pins 6a and 6b. One or more surfaces of the movable component 4 and/or the surface of the bearing pins 6a and 6b may be configured such that a frictional force between the bearing pins 6a and 6b and the movable component 4 is great enough to hold the movable component in position with respect to the support structure 2 when the actuator no longer applies a force to the movable component. In the case of an SMA actuator, for example, the frictional force holds the movable component 4 in position when the SMA element(s) is/are unpowered (and hence not contracted). A mechanism by which frictional forces are reduced during motion of the movable component 4 and are increased again when movement is ceased may be employed, for example that described with reference to Figure 2A or angled wires as shown in Figure 4C.

In addition to aligning components within an assembly, the bearing component may also align the assembly as a whole with respect to a further assembly. With respect to Figure 8, a system 40 comprises a first assembly 1, a second assembly 42 and a third assembly 44. Each assembly comprises a lens 46, a multi-pixel array 48 and two bearing pins 6a and 6b. The system 40 further comprises an alignment component 50, which is a rigid sheet of material. The bearing pins of each assembly are received in respective apertures in the alignment component 50. Accordingly, the alignment component 50 defines the positions of the assemblies 1,42 and 44 with respect to one another. As mentioned above, the alignment component could be made by insert moulding the bearing pins into the alignment component.

If the alignment component is a sheet, a step of active alignment (using a motor to move one or more components of the assembly) may be required to remove any tilt between the movable component and the array (or between multiple arrays themselves). Specifically, the bearing pins may be moved by a small angle to remove tilt.

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

Other variations It will be appreciated that there may be many other variations of the above-described examples. In particular, many features have been described with reference to embodiments in which the support structure or movable component comprise a lens. Any of the features described herein may be applied to any movable component and any support structure, whether or not a lens is present in the assembly or in the device as a whole.

Also disclosed is: 1. An actuator assembly comprising: a support structure defining a primary axis; a movable component which is movable relative to the support structure; an intermediate component configured to engage with the movable component; and an SMA element connected between the support structure and the intermediate component; wherein the SMA element is configured, on contraction, to drive movement of the intermediate component relative to the support structure and thereby drive, as a result of the engagement of the intermediate component with the movable component, movement of the movable component along the primary axis.

2. The actuator assembly according to item 1, further comprising control circuitry configured to send a signal to the SMA element to drive movement of the movable component along the primary axis to compensate for thermal variations in the actuator assembly and/or a device on which the actuator assembly is disposed.

3. The actuator assembly according to item 1 or item 2, wherein the intermediate component is configured to move in a direction perpendicular to the primary axis.

4. The actuator assembly according to any preceding item, wherein the SMA element is a first SMA element which is configured to drive the intermediate component in a first direction and the actuator assembly further comprises a second SMA element connected between the intermediate component and the support structure and which is configured to drive the intermediate component in a second direction opposite to the first direction.

The actuator assembly according to item 4, wherein the actuator assembly is configured such that movement of the intermediate component in the first direction drives movement of the movable component in a third direction, along the primary axis, and movement of the intermediate component in the second direction drives movement of the movable component in a fourth direction opposite to the third direction.

6. The actuator assembly according to any preceding item, wherein: one of the intermediate component and the movable component comprises a first surface which is at a non-zero, acute angle to the primary axis; the other of the intermediate component and the movable component comprises a first feature which directly or indirectly engages with the first surface, and the actuator assembly comprises a biasing arrangement to bias the first feature against the first surface, such that movement of the intermediate component in a direction which is non-parallel to the primary axis induces movement of the movable component along the primary axis.

7. The actuator assembly according to item 6, wherein the first feature is a surface.

8. The actuator assembly according to any preceding item further comprising a bearing component comprising a bearing surface, wherein the bearing surface is configured to guide movement of the movable component along the primary axis relative to the support structure.

9 The actuator assembly according to item 8 when dependent on item 6 or 7, wherein the first surface and the first feature are configured such that, when the intermediate component moves relative to the support structure, the movable component moves along the primary axis and a normal force between the movable component and the bearing surface is reduced, thus reducing a frictional force between the movable component and the bearing surface.

10. The actuator assembly according to item 8 or 9 wherein the bearing surface is parallel to the primary axis.

11. The actuator assembly according to any of items 8 to 10, wherein the bearing component is in contact with one or more additional components for aligning the one or more additional components with each other and/or with the movable component.

12. The actuator assembly according to any of items 8 to 11, wherein the bearing component comprises a ground pin and/or a lapped pin.

13 The actuator assembly according to any preceding item, wherein the actuator assembly comprises a first friction surface and a first friction feature which moves across the first friction surface as a result of movement of the intermediate component relative to the support structure; and wherein the actuator assembly comprises a biasing arrangement for biasing the first friction surface and the first friction feature together so as to generate frictional forces therebetween for retaining the first friction feature in position on the first friction surface when no power is supplied to the SMA element.

14. The actuator assembly according to item 13, wherein the first friction surface is provided on one of the movable component and the support structure and the first friction feature is provided on the other of the movable component and the support structure.

15. The actuator assembly of any preceding item, wherein the SMA element extends in a direction which is perpendicular to the primary axis.

16. The actuator assembly according to any preceding item, wherein the SMA element extends at an acute, non-zero angle to the primary axis.

17. The actuator assembly according to any preceding item, wherein the assembly comprises a de-amplification flexure connected between the support structure and the intermediate component.

18. The actuator assembly according to item 17, wherein the de-amplification flexure is configured to convert rotation of the intermediate component into translation of the movable component along the primary axis.

19. The actuator assembly according to item 17 or 18 further comprises an anti-rotation flexure connected between the movable component and the support structure, wherein the anti-rotation flexure is configured to prevent rotation of the movable component about the primary axis.

20. The actuator assembly according to any preceding item wherein the movable component or the support structure comprises a lens and wherein the primary axis is parallel to or colinear with the optical axis of the lens.

21. The actuator assembly according to any preceding item wherein the actuator assembly is configured such that on contraction of the SMA element by a first amount, the movable component moves by a distance along the primary axis which is less than the first amount 22 An actuator assembly comprising: a support structure; a movable component which is movable relative to the support structure; an intermediate component configured to engage with the movable component; and a shape memory alloy, SMA, element connected between the support structure and the intermediate component; wherein the movable component or the support structure comprises a lens; wherein the SMA element is configured, on contraction, to drive movement of the intermediate component relative to the support structure and thereby drive, as a result of the engagement of the intermediate component with the movable component, movement of the movable component along an optical axis of the lens; and wherein the actuator assembly is configured such that on contraction of the SMA element by a first amount, the movable component moves by a distance along the optical axis of the lens which is less than the first amount.

23. The actuator assembly according to item 22, further comprising control circuitry configured to send a signal to the SMA element to drive movement of the movable component along the optical axis of the lens to compensate for thermal variations in the actuator assembly and/or a device on which the actuator assembly is disposed.

24. The actuator assembly according to item 22 or item 23, wherein the intermediate component is configured to move in a direction perpendicular to the optical axis of the lens.

The actuator assembly according to any of items 22 to 24, wherein the SMA element is a first SMA element which is configured to drive the intermediate component in a first direction and the actuator assembly further comprises a second SMA element connected between the intermediate component and the support structure and which is configured to drive the intermediate component in a second direction opposite to the first direction.

26. The actuator assembly according to item 25, wherein the actuator assembly is configured such that movement of the intermediate component in the first direction drives movement of the movable component in a third direction, along the optical axis, and movement of the intermediate component in the second direction drives movement of the movable component in a fourth direction opposite to the third direction.

27. The actuator assembly according to any of items 22 to 26, wherein: one of the intermediate component and the movable component comprises a first surface which is at a non-zero, acute angle to the optical axis; the other of the intermediate component and the movable component comprises a first feature which directly or indirectly engages with the first surface, and the actuator assembly comprises a biasing arrangement to bias the first feature against the first surface, such that movement of the intermediate component in a direction which is non-parallel to the optical axis induces movement of the movable component along the optical axis.

28. The actuator assembly according to item 27, wherein the first feature is a surface.

29. The actuator assembly according to any of items 22 to 28 further comprising a bearing component comprising a bearing surface, wherein the bearing surface is configured to guide movement of the movable component along the optical axis of the lens relative to the support structure.

30. The actuator assembly according to item 29 when dependent on item 27 or 28, wherein the first surface and the first feature are configured such that, when the intermediate component moves relative to the support structure, the movable component moves along the optical axis and a normal force between the movable component and the bearing surface is reduced, thus reducing a frictional force between the movable component and the bearing surface.

31. The actuator assembly according to item 29 or 30 wherein the bearing surface is parallel to the optical axis.

32. The actuator assembly according to any of items 29 to 31, wherein the bearing component is in contact with one or more additional components for aligning the one or more additional components with each other and/or with the movable component.

33. The actuator assembly according to any of items 29 to 32, wherein the bearing component comprises a ground pin and/or a lapped pin.

34. The actuator assembly according to any of items 22 to 33, wherein the actuator assembly comprises a first friction surface and a first friction feature which moves across the first friction surface as a result of movement of the intermediate component relative to the support structure; and wherein the actuator assembly comprises a biasing arrangement for biasing the first friction surface and the first friction feature together so as to generate frictional forces therebetween for retaining the first friction feature in position on the first friction surface when no power is supplied to the SMA element.

35. The actuator assembly according to item 34, wherein the first friction surface is provided on one of the movable component and the support structure and the first friction feature is provided on the other of the movable component and the support structure.

36. The actuator assembly of any of items 22 to 35, wherein the SMA element extends in a direction which is perpendicular to the optical axis of the lens.

37. The actuator assembly according to any of items 22 to 36, wherein the SMA element extends at an acute, non-zero angle to the optical axis of the lens.

38. The actuator assembly according to any of any of items 22 to 37, wherein the assembly comprises a de-amplification flexure connected between the support structure and the intermediate component.

39. The actuator assembly according to item 38, wherein the de-amplification flexure is configured to convert rotation of the intermediate component into translation of the movable component along the optical axis.

The actuator assembly according to item 38 or 39 further comprises an anti-rotation flexure connected between the movable component and the support structure, wherein the anti-rotation flexure is configured to prevent rotation of the movable component about the optical axis.

Claims

CLAIMS1. An assembly comprising: a support structure; a movable component; an actuator configured to drive movement of the movable component relative to the support structure; a bearing component configured to guide movement of the movable component, wherein the bearing component comprises a bearing surface which is engaged with the movable component; and a further component to be aligned with one or more other components of the assembly, wherein the bearing component is engaged with the further component to align the further component with the one or more other components.
2. The assembly according to claim 1, wherein the movable component is in contact with the bearing surface and the movable component is configured to slide across the bearing surface.
3 The assembly according to claim 1 or claim 2, wherein the bearing component is elongate.
4. The assembly according to claim 1 or 2, wherein the bearing component comprises a bearing pin.
5. The assembly according to claim 3, wherein the bearing component comprises two or more bearing pins.
6 The assembly according to claim 3 or 4, wherein the bearing pin comprises a ground pin or a lapped pin
7 The assembly according to any preceding claim, wherein the movable component comprises a lens and the actuator is configured to drive movement of the lens along an optical axis of the lens.
8 The assembly according to claim 7 further comprising control circuitry configured to send a signal to the actuator to drive movement of the lens along the optical axis of the lens to compensate for thermal variations in the assembly.
9. The assembly according to any preceding claim, wherein the further component is a light source, optionally wherein the further component is a pixel array.
10. The assembly according to any preceding claim, wherein the one or more other components of the assembly comprises one or more of: the movable component; and a light source, optionally a pixel array.
11. The assembly according to any preceding claim, wherein a frictional force between the bearing surface and the movable component is sufficient to maintain the position of the movable component with respect to the support structure when the actuator is unpowered.
12. The assembly according to any preceding claim wherein the actuator comprises one or more shape memory alloy, SMA, elements.
13. The assembly according to any preceding claim wherein the bearing component is received within an aperture in the movable component, an aperture within the further component or both.
14. The assembly according to any preceding claim further comprising an additional assembly according to any preceding claim and an alignment component for aligning the two assemblies relative to one another.
15. The assembly according to claim 14, wherein the bearing components of the two assemblies are received in respective apertures in the alignment component.
16 The assembly according to any preceding claim, wherein the support structure comprises a lens and the actuator is configured to drive movement of the movable component along an optical axis of the lens.