The present invention relates to actuator assemblies, particularly those in which wobulation or 3D imaging is provided.

The present invention is concerned with an actuator assembly that exhibits reduced frictional forces between a movable assembly and a support structure, while maintaining adequate heat transfer between the movable assembly and the support structure. The present invention is also concerned with providing an improved actuator assembly for the purpose of applications requiring accurate positional control, such as wobulation (e.g. the projection or display of a super-resolution image), or 3D imaging.

According to the present invention, there is provided an actuator assembly comprising a support structure; a movable assembly comprising a display, an emitter or a part thereof, wherein a primary axis is defined with reference to the movable assembly, wherein the movable assembly has a first side from which, in use, radiation is emitted by the display or emitter and wherein the movable assembly is supported on the support structure such that a gap is formed between the movable assembly and the support structure on a side of the movable assembly which is opposite the first side; and a region of heat transfer material arranged in the gap, wherein the heat transfer material is arranged to transfer heat between the movable assembly and the support structure, and wherein the heat transfer material is configured to deform so as to allow movement of the movable assembly relative to the support structure.

Provision of the gap reduces the friction between the movable assembly and the support structure. This may ultimately allow more accurate positioning of the movable assembly with respect to the support structure, for example for the purpose of wobulation or 3D imaging. The heat transfer material in the gap improves the transfer of heat away from the display or emitter (or part thereof) and to the support structure. The support structure may thus act as a heat sink for the display or emitter. The deformability of the heat transfer material ensures that the movable assembly remains movable, as for example required for wobulation and/or 3D sensing.

As mentioned above, the movable assembly may be moved to achieve wobulation, for example for the display of a super-resolution image (i.e. an image having a resolution higher than that of the intrinsic resolution of the emitter or display). In this case, a high- resolution image is displayed (or projected) by displaying a number of lower-resolution images at different positions in rapid succession. The image displayed at each position is a lower-resolution image formed of a subset of pixels of the high-resolution image. The movable assembly may be moved between the positions in a repeated pattern at a high frequency, for example greater than 30 Hz, preferably greater than 60 Hz, further preferably greater than 120 Hz. The succession of lower-resolution images is thus perceived by the human eye as one high-resolution image. According to the invention, there is further provided an actuator assembly comprising: a support structure; a movable assembly, wherein a primary axis is defined with reference to the movable assembly; plural SMA actuator components in an arrangement capable, on selective driving thereof, of moving the movable assembly relative to the support structure in any direction perpendicular to the primary axis, and a control circuit configured to drive the SMA actuator components so as to controllably move the movable assembly to two or more positions, wherein: the movable assembly comprises a display comprising a plurality of pixels and wherein the two or more positions are offset from each other in a direction perpendicular to the primary axis by a distance that is less than a pitch of the pixels of the display, or the movable assembly comprises an emitter for projecting an image, the emitter comprising an array of illumination sources, and wherein the two or more positions are offset from each other in a direction perpendicular to the primary axis by a distance that is less than a distance between the centres of two adjacent illumination sources.

For example, such an emitter may be a VCSEL (vertical-cavity surface-emitting laser) array and the two or more positions may be offset from each other in a direction perpendicular to the primary axis by a distance that is less than a distance between the centres of two adjacent cavities of the VCSEL.

Due to their high actuation forces, SMA actuator components (which each may comprise one or more SMA wires) enable particularly accurate control of the movement and positioning of the movable assembly relative to the support structure. Controllable movement by sub-pixel distances (or by distances less than a distance between illumination sources of an emitter comprising an array of illumination sources, such as a VCSEL array) enables use of the actuator assembly in applications such as wobulation. Positional accuracy may further be improved by reducing the frictional forces between the movable assembly and the support structure, for example by providing the gap between the movable assembly and the support structure. The gap may be formed by supporting the movable assembly on the support structure using a roller bearing or a flexure arrangement. A region of heat transfer material may be provided in the gap to increase the transfer of heat between the movable assembly and the support structure. The actuator may further comprise one or more optical elements which may be fixed relative to the support structure. Alternatively, the one or more optical elements may be supported on the support structure so as to be movable with respect to the support structure. The one or more optical elements may comprise a lens, for example a collimation lens, and in driving movement of the movable assembly to the two or more positions, the movable assembly may be moved relative to the one or more optical elements (e.g. a lens). In embodiments in which the movable assembly comprises an emitter, the movable assembly may be driven to the two or more positions in order to move an illumination pattern across a scene, for example for the purposes of 3D imaging. The movable assembly (and hence the emitter) may be moved relative to a lens, e.g. a collimation lens. The emitter may emit the same illumination at each of the two or more positions such that an illumination pattern is moved across a scene by virtue of the movement of the emitter relative to the lens.

According to the invention, there is further provided an actuator assembly comprising: a support structure; a moving part supported on the support structure, wherein one of the support structure and the moving part comprises a display, an emitter or a part thereof; and a bearing arrangement configured to support the moving part on the support structure, wherein the bearing arrangement is configured to allow movement of the moving part relative to the support structure; wherein at least one of the support structure and the moving part comprises at least one plate provided with a hole extending at least partly through the plate for accommodating the bearing arrangement.

The hole accommodates the bearing. This can help to reduce the height of the actuator assembly, i.e. reduce the dimension in the thickness direction of the plates that form the actuator assembly.

According to the invention, there is further provided an actuator assembly comprising: a support structure; a movable assembly comprising a display, an emitter or a part thereof, wherein the movable assembly is supported on the support structure; one or more bearings configured to support the movable assembly on the support structure, the one or more bearings being configured to allow movement of the movable assembly relative to the support structure; and a bearing shock protection structure comprising cantilever structures comprised in the support structure or the movable assembly, the one or more bearings resting on the free ends of the cantilever structures.

According to the invention, there is further provided an actuator assembly comprising: a support structure; a moving part supported on the support structure, wherein one of the support structure and the moving part comprises a display, an emitter or a part thereof; one or more bearings configured to support the moving part on the support structure, the one or more bearings being configured to allow movement of the moving part relative to the support structure; and a bearing shock protection structure comprising cantilever structures comprised in the moving part, the one or more bearings resting on the free ends of the cantilever structures.

Generally, in normal operation, the bearings enable movement of the movable assembly perpendicular to the primary axis. In shock conditions the cantilevers deflect, thereby absorbing energy and protecting the bearings and/or bearing surfaces.

According to the invention, there is further provided an actuator assembly comprising: a support structure; a movable assembly comprising a display, an emitter or a part thereof, wherein the movable assembly is supported on the support structure and a primary axis is defined with reference to the movable assembly; and a flexure arrangement configured to support the movable assembly on the support structure in a manner allowing movement of the movable assembly relative to the support structure in any direction perpendicular to the primary axis and/or in a manner allowing rotation of the movable assembly about any axis parallel to the primary axis.

The flexure arrangement comprises one or more flexures. Generally, the movable assembly is supported on the support structure by only the flexure arrangement, e.g. without any additional (plain or ball) bearings. Generally, in normal operation, the flexure arrangement constrains movement of the movable assembly parallel to the primary axis.

According to the invention, there is further provided an actuator assembly comprising: a support structure; a moving part supported on the support structure, wherein one of the support structure and the moving part comprises a display, an emitter or a part thereof, and a primary axis is defined with reference to the movable assembly; and a flexure arrangement configured to support the moving part on the support structure in a manner allowing movement of the moving part relative to the support structure in any direction perpendicular to the primary axis and/or in a manner allowing rotation of the moving part about any axis parallel to the primary axis, wherein the flexure arrangement comprises three or more beams that extend between the moving part and the support structure in a direction parallel to the primary axis, wherein each beam comprises first and second portions that are parallel to each other and each extend in a direction parallel to the primary axis, wherein the first portion is connected at one end to the moving part and the second portion is connected at one end to the support structure, and wherein the other ends of the first and second portions are connected to each other.

Generally, the moving part is supported on the support structure by only the flexure arrangement, e.g. without any additional (plain or ball) bearings. Generally, in normal operation, the flexure arrangement constrains movement of the moving part parallel to the primary axis. The flexure arrangement may help to reduce the friction between the moving part and the support structure.

According to the invention, there is further provided an actuator assembly comprising: a support structure defining a primary plane; a moving part configured to receive a display, an emitter or a part thereof; plural SMA wires in an arrangement capable of moving the moving part relative to the support structure in any direction parallel to the primary plane and/or rotating the moving part about any axis orthogonal to the primary plane; and one or more endstops configured to limit the movement of the moving part relative to the support structure, wherein each end stop comprises a surface region comprised in the support structure and a surface region comprised in the moving part.

The actuator assembly need not comprise a display, an emitter or part thereof or any other component that is incorporated after the display or emitter in the normal order of assembly. Hence, the actuator assembly (including the endstops) can be tested before attaching the display or emitter.

As mentioned above, a primary axis may be defined with reference to the movable assembly. Optionally, the primary axis may be aligned with a general direction in which radiation is emitted by a display or emitter disposed on the movable assembly. Alternatively or additionally, the primary axis may be perpendicular to a plane defined by the movable assembly. In the case that the movable assembly comprises a display, the primary axis may be aligned with a general direction in which light is emitted from the display. The display may define a plane and the primary axis may be perpendicular to the plane defined by the display. In the case that the movable assembly comprises an emitter, the primary axis may be aligned with a general direction in which radiation is emitted by the emitter. The emitter may define a plane and the primary axis may be perpendicular to the plane defined by the emitter. For example, the emitter may comprise a VCSEL array and the primary axis may be perpendicular to the plane defined by the VCSEL array.

To allow better understanding, an embodiment of the present invention will now be described by way of non-limitative example with reference to the accompanying drawings, in which:

Fig. l is a schematic cross-sectional view of an apparatus including an actuator assembly;

Fig. 2 is a cross-sectional view of the actuator assembly comprising a roller bearing;

Fig. 3 is a perspective view of a moving plate of a carrier of the actuator assembly;

Fig. 4 is a plan view of the actuator assembly from above;

Fig. 5 is a cross-sectional view of the actuator assembly comprising another roller bearing;

Fig. 6 is a cross-sectional view of the actuator assembly comprising another roller bearing;

Fig. 7 is a perspective view of the actuator assembly comprising a flexure arrangement;

Fig. 8 is a perspective view of another flexure arrangement;

Fig. 9 is a perspective view of another flexure arrangement;

Fig. 10 is a perspective view of another flexure arrangement;

Figs. 10a and 10b schematically depict examples of moving the movable assembly using the flexure arrangement of Fig. 10;

Fig. 11 is a cross-sectional view of part of the actuator assembly, illustrating the gap and the heat transfer material;

Figs. 12 and 13 are plan views of the region of heat transfer material arranged in the gap and on the support structure;

Fig. 14 is a cross-sectional view of part of the actuator assembly, illustrating another arrangement of the gap and the heat transfer material;

Figs. 15 to 17 are cross-sectional views of alternative actuator assemblies;

Fig. 18 is another cross-sectional view of the actuator assembly of Fig. 15;

Fig. 19 is a perspective view of a bearing shock protection structure;

Fig. 20 is a perspective view of part of a movable assembly with accommodated bearings; and

Fig. 21 is a cross-sectional view of the apparatus shown in Fig. 20.

An apparatus 1 that incorporates an actuator assembly 2 in accordance with the present invention is shown in Fig. 1, which is a cross-sectional view taken along a primary axis O. The apparatus 1 may correspond to (part of) an illumination source which may be for use in a 3-dimensional (3D) sensing system such as that described in W02020/030916 (which in incorporated herein by reference) or in an augmented reality (AR) display system. The apparatus 1 is to be incorporated in a portable electronic device. Thus, miniaturisation is an important design criterion. The actuator assembly 2 is shown in detail in Figs. 2 to 4, Fig. 2 being a side view of the actuator assembly 2, Fig. 3 being a perspective view of a moving plate 9 of a carrier 8 of the actuator assembly 2; and Fig. 4 being a plan view of the actuator assembly 2. For clarity, Figs. 2 and 4 omit the flexures 67 described below. The actuator assembly 2 may be manufactured first and then assembled with the other components of the apparatus 1.

The actuator assembly 2 comprises a support structure 4. On the support structure 4 is supported a movable assembly 12. The movable assembly 12 comprises an emitter 7 and generally further comprises a printed circuit board (PCB) on which the emitter 7 is mounted. When incorporated into the apparatus 1, the emitter 7 is aligned with the primary axis O and perpendicular to the primary axis O. The emitter 7 may be for example a VCSEL (vertical -cavity surface-emitting laser) array.

Optionally, the movable assembly 12 comprises a carrier 8 that comprises a moving plate 9. The emitter 7 may be mounted on the carrier 8, in particular on the moving plate 9. The moving plate 9 may be formed from sheet material, which may be a metal for example steel such as stainless steel. The moving plate 9 is shown in isolation in Fig. 3 and includes flexures 67 that are described in more detail below.

Although the carrier 8 comprises a single moving plate 9 in this example, optionally the carrier 8 may comprise other layers which may be attached to or laminated with the moving plate 9.

Optionally, the support structure 4 comprises a support plate 5 which may be formed from sheet material, which may be a metal for example steel such as stainless steel.

Although the support structure 4 comprises a single support plate 5 in this example, optionally the support structure 4 may comprise other layers which may be attached to or laminated with the support plate 5.

The support structure 4 further comprises a rim portion 10 fixed to the front side of the support plate 5 and extending around the support plate 5. The rim portion 10 has a central aperture 11.

The apparatus 1, and/or the device in which the apparatus 1 is integrated, comprises integrated circuit (IC) chips 30 and 31 which, in the illustrated example, are fixed on the rear side of the support plate 5.

The movable assembly 12 is supported on the support structure 4 in a manner allowing movement of the movable assembly 12 relative to the support structure 4 in any direction perpendicular to the primary axis O. So, the movable assembly 12 may be supported in a manner supressing movement of the movable assembly 12 in a direction parallel to the primary axis O. The movable assembly 12 is further supported on the support structure 4 in a manner allowing rotation of the movable assembly about any axis parallel to the primary axis O. So, the movable assembly 12 may be supported in a manner supressing tilt or rotation of the movable assembly about any axis perpendicular to the primary axis O.

WO-2017/072525 (which is incorporated herein by reference) discloses use of a plain bearing for supporting a movable assembly, specifically an image sensor assembly, on a support structure in a manner allowing the above-described movement. Such a plain bearing comprises two bearing surfaces that bear on each other, permitting relative sliding motion. Such a plain bearing may be compact and facilitate heat transfer between the image sensor assembly and the support structure. However, in certain applications it may be desirable to reduce friction between such a movable assembly and a support structure compared to an arrangement in which a plain bearing is provided. Such applications include, for example, the use of the movable assembly for wobulation or 3D imaging.

In the illustrated embodiments, the movable assembly 12 is supported on the support structure 4 such that a gap 104 is formed between the movable assembly 12 and the support structure 4. The gap 104 is formed on a side of the movable assembly 12 facing away from the side of the movable assembly from which radiation (e.g. light) is emitted by the emitter 7, in particular in a direction parallel to the primary axis O. The gap 104 is formed, in particular, between the moving plate 9 and the support plate 5. Provision of the gap 104 reduces the friction between the movable assembly 12 and the support structure 4. This enables more accurate movement and positioning of the movable assembly 12 relative to the support structure 4.

The actuator assembly 2 further comprises a region of heat transfer material 103 arranged in the gap 104. The heat transfer material 103 transfers heat between the movable assembly 12 and the support structure 4. Heat conductance between the movable assembly 12 and the support structure 4 is increased compared to a situation in which the heat transfer material 103 is not provided. The heat transfer material 103 spans the gap 104 in a direction parallel to the primary axis O. So, the heat transfer material 103 is in direct contact with a surface of the support structure 4 facing the gap 104 and a surface of the movable assembly 12 facing the gap 104.

The region of heat transfer material 103 may have a thermal conductance greater than 0.02 W/K, preferably greater than 0.1 W7K, further preferably greater than 0.2 W/K. For this purpose, the heat transfer material 103 may have a thermal conductivity greater than 0.02 W/m»K, preferably greater than 0.1 W/m»K, further preferably greater than 0.2 W/m»K. The heat transfer material 103 may comprise thermally conductive particles, for example metal particles. Such thermally conductive particles may increase the thermal conductivity of the heat transfer material 103.

The heat transfer material 103 deforms so as to allow movement of the movable assembly 12 relative to the support structure 4. In particular, the heat transfer material 103 undergoes shear deformation when the movable assembly 12 moves relative to the support structure 4. Sliding between the heat transfer material 103, the movable assembly 12 and/or the support structure 4 may be avoided, thereby avoiding or reducing friction between the moveable and static components of the actuator assembly 2. The heat transfer material 103 may have a shear modulus, in the direction parallel to the emitter 7, of less than 100 kPa, preferably less than 10 kPa, further preferably less than 1 kPa. For example, the heat transfer material 103 may comprise one or more of silicone rubber or any other rubber, a gel (such as a hydrogel or an organogel) and a liquid. The liquid may be a shear thinning liquid, for example a liquid for which the viscosity reduces by more than a factor of 1000 under shear.

The region of heat transfer material 103 may fill the gap 104, as for example shown in Fig. 2. The area of contact between the heat transfer material 103 and the movable assembly 12 may thus be equal to or greater than the area of the emitter 7, optionally equal to or greater than the area of the emitter over which radiation (e.g. light) is emitted. Alternatively, the region of heat transfer material 103 may partially fill the gap 104, and so the area of contact between the heat transfer material 103 and the movable assembly 12 may be less than the area of the emitter 7, optionally less than the area of the emitter over which radiation (e.g. light) is emitted. In general, the heat transfer material 103 has a total area of contact with the movable assembly 12 that is at least 0.1 times, preferably in the range from 0.2 times to 4 times, further preferably 1 times to 4 times, the area of the emitter 7, optionally the area of the emitter over which radiation (e.g. light) is emitted.

The height (i.e. the extent in the direction parallel to the primary axis O) of the gap 104, or in particular of the heat transfer material 103 in the gap 104, may be chosen to control the heat transfer between the movable assembly 12 and the support structure 4. In general, the minimum height of the gap 104 may be sufficiently large to avoid contact between the movable assembly 12 and the support structure 12 in the gap 103 during movement of the movable assembly 12. The minimum height of the gap 104 is thus greater than the surface flatness of the surfaces of the movable assembly 12 and/or the support structure 4 facing the gap 104. The minimum height of the gap 104 may be greater than 10 pm, preferably greater than 20 pm, further preferably greater than 50pm. The height of the gap 104 may be sufficiently small to ensure adequate heat transfer between the movable assembly 12 and the support structure 4. A smaller gap 104 also ensures that the actuator assembly 2 remains compact. The height of the gap 104, or of the heat transfer material 103, may be smaller than 1mm, preferably smaller than 300pm, further preferably smaller than 200pm, most preferably smaller than 100pm.

The minimum height of the heat transfer material 103 may be sufficiently large to allow movement of the movable assembly 12 relative to the support structure 4 within a range of movement required for the relevant application, for example within a range of movement of at least 100pm, preferably at least 200pm. The minimum height of the heat transfer material 103 may thus depend on the flexibility of the heat transfer material 103. Typically, the height of the heat transfer material may be in the range from 20pm to 300pm, preferably from 50pm to 150pm.

The gap may have a substantially uniform height, as shown in Fig. 11. Alternatively, as shown in Fig. 14, the support structure 4 may comprise depressions on a surface facing the gap 104. Additionally or alternatively, the movable assembly 12 may comprise depressions on a surface facing the gap 104 (not shown). Fig. 14 shows the gap 104 having a stepwise variable height, but in general the height of the gap 104 may vary in any other manner. The region of heat transfer material 103 may be provided within the depressions, i.e. in the regions of the gap 104 having a greater height. This allows the height of the heat transfer material 103 to be increased, thereby increasing the flexibility of the region of heat transfer material 103 and the range of movement of the movable assembly. At the same time, the minimum height of the gap 104 remains small, thus increasing heat transfer across the gap 104 in regions in which no heat transfer material 103 is provided.

The region of heat transfer material 103 may be patterned. For example, the region of heat transfer material 103 may be provided in a plurality of separated regions. Fig. 12 shows, in plan view, the region of heat transfer material 103 formed as five dots. Fig. 13 shows an alternative pattern of the heat transfer material 103, in which the region of heat transfer material 103 is formed in a star shape. Patterning the region of heat transfer material may reduce the lateral extent of the heat transfer material 103, thus improving compliance of the heat transfer material 103. This may help prevent damage to (e.g. tearing of) the heat transfer material 103 due to impacts, for example when a device in which the actuator assembly 2 is incorporated is dropped.

In the illustrated embodiments, the actuator assembly 2 further comprises a bearing arrangement 110, 120, 130. The bearing arrangement 110, 120, 130 supports the movable assembly 12 on the support structure 4 so as to form the gap 104. The bearing arrangement 110, 120, 130 allows movement of the movable assembly 12 relative to the support structure 4, for example in a manner allowing movement of the movable assembly 12 relative to the support structure 4 in any direction perpendicular to the primary axis O 7 and/or in a manner allowing rotation of the movable assembly 12 about any axis parallel to the primary axis O.

As shown in Figs. 2, 5 and 6, the bearing arrangement may comprise a rolling bearing 110. The rolling bearing 110 may, for example, be a ball bearing, a roller bearing or a rocker bearing. The rolling bearing 110 comprising a rolling element, for example a ball, a roller or a rocking element. The rolling element may be spherical or may in general be any rotary element with curved surfaces that bear against the movable assembly 12 and the support structure 4 and are able to roll back and forth and around in operation.

The rolling element is disposed between the movable assembly 12 and the support structure 4. The movable assembly 12 is thus supported on the support structure 4 by the rolling element. The rolling bearing 110 may comprise plural rolling elements, for example three rolling elements. Although in general any number of rolling elements could be provided, it is preferable to provide at least three rolling elements to prevent relative tilting of the movable assembly 12 and the support structure 4. Three rolling elements are sufficient to support the movable assembly 12 without tilting, and the provision of three rolling elements has the advantage of easing the tolerances required to maintain point contact with each rolling element in a common plane.

In the embodiments of Figs. 2 and 6, the rolling bearing 110 is disposed on the same side of the movable assembly 12 as the gap 104, as shown in Figs. 2 and 6. This may ensure that the height of the gap 104 remains constant even when large forces act upon the movable assembly 12. The rolling bearing 110 may be arranged outside the gap 104, for example laterally to the gap 104, as shown in Fig. 2. The extent of the rolling element may thus be larger than the extent of the gap 104 in the direction parallel to the primary axis O. This may allow the height of the gap 104 to be reduced compared to a situation in which the rolling element is arranged in the gap 104.

Alternatively, as shown in Fig. 6, the rolling bearing 110 may be arranged in the gap 104. This may reduce the lateral extent of the bearing arrangement 110. The rolling element may be incorporated into the heat transfer material 103, or else may be arranged in regions of the gap 104 in which no heat transfer material 103 is provided.

In an alternative embodiment, the rolling bearing 110 is disposed on the side of the movable assembly 12 that is opposite to the gap 104. The rolling bearing 110 is disposed on the same side of the movable assembly 12 as the emitter 7, in particular laterally to the emitter 7. This is schematically depicted in Fig. 5. In such an embodiment, the heat transfer material 103 that is arranged in the gap 104 may bias, or contribute to biasing, the movable assembly 12 against the rolling bearing 110.

The bearing arrangement 110, 120, 130 may, alternatively or additionally, comprise a flexure arrangement 120, 130. Examples of the flexure arrangement 120, 130 are schematically depicted in Figs. 7, 8, 9 and 10. The flexure arrangement 120, 130 is disposed between the movable assembly 12 and the support structure 4. The movable assembly 12 is thus supported on the support structure 4 by the flexure arrangement 120, 130. The flexure arrangement 120, 130 comprises a fixed portion 121, 131 that is fixed relative to the support structure 4 and a movable portion 122, 132 that is fixed relative to the movable assembly 12. The flexure arrangement 120, 130 further comprises a flexible element 123, 133 disposed between the fixed portion 121, 131 and the moveable portion 122, 132.

Generally, the movable assembly 12 is supported on the support structure 4 by only the flexure arrangement 120, 130, e.g. without any additional (plain or ball) bearings. Generally, in normal operation, the flexure arrangement 120, 130 constrains movement of the movable assembly 12 parallel to the primary axis O.

Fig. 7 schematically depicts an example of the flexure arrangement 120. The fixed portion 121 of the flexure arrangement is fixed to the support structure 4 or a component that is fixed relative to the support structure 4. The moveable portion 122 is fixed to the carrier 8, in particular to the moving plate 9. The flexible element 123 comprises beams 123 that are connected between the movable assembly 12 and the support structure. Fig. 7 shows four beams 123, although in general any number of beams 123 may be provided, for example three or more beams 123. The beams 123 extend parallel to each other and to the primary axis O, and therefore extend perpendicular to the orthogonal directions in which the emitter 7 moves. The beams 123 could extend at a non-perpendicular angle, provided that they are transverse to the orthogonal directions.

The beams 123 are fixed to each of the support structure 4 and the movable assembly 12 in a manner that the beams 123 cannot rotate, for example by being soldered. The beams 123 thereby support the movable assembly 12 on the support structure 4 in said manner allowing movement of the movable assembly 12 relative to the support structure 4 in two orthogonal directions perpendicular to the primary axis O simply by means of the beams 123 bending, in particular in an S-shape. Conversely, the beams 123 resist movement along the primary axis O. The beams 123 may have any construction that provides the desired compliance perpendicular to the primary axis O, typically being formed by wires, for example metal wires. The beams 123 may be mechanically connected to different comers of the movable assembly 12.

Fig. 8 schematically depicts an alternative example of the flexure arrangement 120. In the example of Fig. 8, the beams 123 comprise a first portion 123a and a second portion 123b. Each beam 123 is formed in a U-shape, with the first portion 123a corresponding to one arm of the U-shape and the second portion corresponding to another arm of the U- shape. The first and second portions 123a, 123b are parallel to each other and extend in a direction parallel to the primary axis O. The first and second portions 123a, 123b are not collinear. The first portion 123a comprises the moveable portion 122, and so the first portion 123a is connected at one end to the movable assembly 12. The second portion 123b comprises the fixed portion 121, and so is connected at one end to the support structure 4. The other ends of the first and second portions 123a, 123b are connected to each other.

The flexure arrangement 120 of Fig. 8 allows movement of the movable assembly 12 relative to the support structure 4 in a manner similar to the flexure arrangement 120 of Fig. 7. The flexure arrangement 120 of Fig. 8 is more compact, in that the extent of the flexure arrangement 120 in a direction along the axis O may be smaller in Fig. 8 than in Fig. 7. In Fig. 8, the connections between the flexure arrangement 120 and the support structure 4 may be in substantially the same plane as the connections between the flexure arrangement 120 and the movable assembly 12.

The flexure arrangement 120 of Fig. 8 may be integrally formed. For example, the flexure arrangement 120 may be formed from sheet metal. The beams 123 may be formed by etching and bending the sheet metal.

The flexure arrangements 120 of Figs 7 or 8 may further comprise drop protection elements. The drop protection elements may supress buckling and thus avoid damage to the beams 123 due to sudden impacts, for example when a device incorporating the actuator assembly 2 is dropped.

Generally, in normal operation, the flexure arrangement 120 constrains movement of the movable assembly 12 parallel to the primary axis O. Optionally, the flexure arrangement 120 is arranged to allow movement of the movable assembly 12 parallel to the primary axis O in the event of shock cause by, for example, a drop event. The flexure arrangement may help to reduce the friction between the moving part and the support structure. For example, the friction may be lower compared to when a plain bearing is used.

For example, the moveable portion 122 may be arranged as a drop protection element. In shock conditions, any vertical forces are at least partly taken up by bending of the moveable portion 122 (upwards or downwards in Fig. 8). The moveable portion 122 is compliant in the direction parallel to the primary axis O. By providing the drop protection element, the possibility of the flexure arrangement 120 being damaged in shock conditions is reduced.

Optionally, the actuator assembly 2 comprises one or more end stops (not shown) configured to limit movement of the movable assembly 12 in the direction parallel to the primary axis O. During shock conditions, the movable assembly 12 may move in the direction parallel to the primary axis O until the movable assembly 12 abuts against the one or more end stops.

The compliance of the moveable portion 122 may be controlled by selecting their thickness, length and material, for example. The distance between the end stops and the movable assembly 12 in normal conditions can be selected to control how far the movable assembly 12 can move in shock conditions. Optionally, the end stops and the drop protection elements such as the moveable portion 122 are arranged such that in shock conditions the movable assembly 12 is enabled to reach the one or more end stops. The possibility of the flexure arrangement 120 being over-stressed in shock conditions can be reduced.

Alternatively or additionally, at least one drop protection element may be provided by a portion that is similar to the moveable portion 122 illustrated in Fig. 8 (e.g. a horizontal portion of the beam 123) but is arranged between the fixed portion 121 of the beam 123 and the support structure 4.

Instead of extending at an angle of ~45° to the edges of the movable assembly 12 as illustrated in Fig. 8, the beams 123 may extend at different angles (when viewed in a direction along the primary axis O). For example, at least one beam 123 may extend in a direction parallel to an edge of the movable assembly 12 (when viewed in a direction along the primary axis O). There may be any number of beams 123.

The flexure arrangements 120 of Figs. 7 or 8 may be used to provide electrical connection. The purpose of the flexure arrangement 120 may thus be both to provide electrical connection and to provide a bearing arrangement that supports the movable assembly 12 on the support structure 4. The flexure arrangement 120 may be configured to provide drive signals (e.g. current) to the SMA actuator wires 40. The SMA actuator wires 40 may have a connection terminal at each end. Two or more of the SMA actuator wires 40 may share a common terminal. At least one terminal of each SMA actuator wire 40 is specific to the SMA actuator wire 40 (i.e. not common to the other wires). The flexure arrangement 120 may be configured to provide drive signals to one or more of the terminals (either specific or common). Where the flexure arrangement 120 is configured to provide drive signals to multiple terminals, the flexure arrangement 120 may be electrically subdivided into multiple sections, with each section including one or more beams 123 and being insulated from the other section(s). For example, each of the four beams 123 illustrated in Fig. 8 may form part of a different such section. This may be achieved by forming the flexure arrangement 120 from separate components that are mechanically but not electrically interconnected.

Figs. 9 and 10 schematically depict further examples of flexure arrangements 130. The flexure arrangements 130 comprise a flexible sheet 130. The flexible sheet 130 comprises two first arms 124. The flexible sheet further comprises one second arm 125 (as in Fig. 9) or two second arms 125 (as in Fig. 10). Each of the first and second arms 124, 125 extends in a direction parallel to the primary axis O. The first arms 124 are parallel and facing each other, and the second arms 125 are parallel and facing each other. The first arms 124 are perpendicular to the second arms 125. Each first arm 124 may comprise a rigid portion 124a, such as a rigid plate, that is fixedly connected to the movable assembly 12. Each first arm 124 may further comprise a flexible portion 124b, that extends from the rigid portion 124a to the respective connection with the one or two second arms 125. Each second arm 125 may comprise a rigid portion 125a, such as a rigid plate, that is fixedly connected to the support structure 4. Each second arm 125 may further comprise a flexible portion 125b, that extends from the rigid portion 125a to the respective connection with the two first arms 125. The connection between the first and second arms 124, 125 may be a rigid connection (such that the angle between the first and second arms 124, 125 is maintained) or a flexible connection, such as a hinge connection.

The flexure arrangement 130 of Fig. 9 is positioned to one side of the movable assembly 12. The flexure arrangement of Fig. 10 surrounds the movable assembly 12. The flexure arrangement of Fig. 10 may provide a more stable support of the movable assembly 12 on the support structure 4.

Figs. 10a and 10b schematically depict, in plan view, the movement allowed by the flexure arrangement 120 of Fig. 10. Although not shown, the movement allowed by the flexure arrangement 120 of Fig. 9 is similar. The dashed lines in Figs. 10a and 10b depict the position of the flexible sheet 120 prior to movement of the movable assembly 12, and the solid lines depict the position of the flexible sheet 120 after movement of the movable assembly 12 in the direction of the arrow in Fig. 10a and 10b. In particular, when moving the movable assembly 12 in a direction parallel to the first arms 124, the flexible portion 125b of the second arms 125 may deform. The first arms 124 may also deform if the joint between the first and second arms 124, 125 is rigid. If the joint between first and second arms 124, 125 is flexible (e.g. a hinge), the first arms may maintain their shape. Conversely, when moving the movable assembly 12 in a direction parallel to the second arms 124, the flexible portion 124b of the first arms 124 may deform so as to allow movement of the movable assembly 12. The second arms 125 may also deform if the joint between the first and second arms 124, 125 is rigid. If the joint between first and second arms 124, 125 is flexible (e.g. a hinge), the second arms 125 may maintain their shape.

The flexible sheet 120 may comprise at least two flexible printed circuits. The flexible printed circuits are electrically connected to the movable assembly. The purpose of the flexible sheet 120 may thus be both to provide electrical connection to the movable assembly and to provide a bearing arrangement that supports the movable assembly 12 on the support structure 4.

Optionally, the flexible sheet 120 may be configured to provide drive signals (e.g. current) to the SMA actuator wires 40. The flexible sheet 120 may be configured to transfer signals between the support structure 4 and the emitter 7. For example, the flexure arrangement 120 may transfer power and/or control signals to the emitter 7. The flexure arrangement 120 may transfer data from the emitter 7.

Alternatively or additionally, the bearing arrangement 110, 120, 130 may comprise the heat transfer material 103. The heat transfer material 103 may be selected so as to allow supporting the movable assembly 12 on the support structure. The heat transfer material 103 may be a silicone rubber or other rubber, for example. Some degree of tilt and/or movement along the primary axis O may be tolerable in certain situations, so that use of the above-described bearing arrangements 110, 120, 130 may not be required. Alternatively or additionally, the bearing arrangement 110, 120, 130 may comprise a plain bearing, such as a structured plain bearing. The plain bearing comprises a bearing surface on each of the movable assembly 12 and the support structure 4. The bearing surfaces may each be planar. The bearing surfaces bear on each other so as to support the movable assembly 12 on the support structure 4, permitting relative sliding motion. The plain bearing thus allows movement of the movable assembly 12 relative to the support structure 4, in particular in said manner allowing movement or rotation of the movable assembly 12 relative to the support structure 4 in any direction laterally to the emitter 7.

The plain bearing may be structured so as to reduce the contact area of the bearing surfaces, thus reducing friction between the movable assembly 12 and the support structure 4 and forming the gap 104. The plain bearing may be provided in select regions, and the gap 104 may be formed between the select region in which the plain bearing is provided. The total area of contact of the bearing surfaces that form the plain bearing may be less than 1, preferably less than 0.5, further preferably less than 0.2, particularly preferably less than 0.1, of the area of the emitter 7. With regard to reducing friction, the bearing surfaces may be designed to have a coefficient of friction of 0.2 or less.

In addition, the actuator assembly 2 may comprise a biasing arrangement. The biasing arrangement may provide a biasing force that biases the movable assembly 12 towards the bearing arrangement 110. An example of a biasing arrangement is schematically depicted in Fig. 3. Fig. 3 shows two flexures 67 connected between the support structure 4 and the carrier 8/moving plate 9 to act as a biasing arrangement, as well as providing an electrical connection to the movable assembly 12. In this example, the flexures 67 are formed integrally with the moving plate 9 at one end 68 thereof and are mounted to the support plate 5 of the support structure 4 at the other end 69 thereof. Alternatively, the flexures 67 could be formed integrally with a plate of the support structure 4 and mounted to the carrier 8, or else could be separate elements mounted to each of the support structure 4 and the carrier 8. In any of these examples, the mounting of the flexures 67 may be achieved e.g. by soldering which provides both mechanical and electrical connection.

The flexures 67 are arranged as follows to provide their mechanical function. Each flexure 67 is an elongate beam connected between the support structure 4 and carrier 8. The flexures 67, due to their intrinsic resilience, bias the support structure 4 and the movable assembly 12 together, the biasing force being applied parallel to the primary axis O. This may maintain the bearing arrangement 110, for example the bearing arrangement of Figs. 2, 5 or 6. At the same time, the flexures 67 may be laterally deflected to permit lateral movement and rotation of the movable assembly 12 relative to the support structure 4.

The flexures 67, again due to their intrinsic resilience, also provide a lateral biasing force that biases the movable assembly 12 towards a central position aligned with the primary axis O from any direction around that central position. As a result, in the absence of driving of the SMA wires 40, the movable assembly 12 will tend towards the central position. This ensures that the apparatus 1 remains functional, even in the absence of driving of the SMA wires 40.

The flexures 67 are designed as follows to provide a suitable retaining force along the primary axis O for the bearing arrangement 110, and also to permit lateral movement with a lateral biasing force. The magnitude of the lateral biasing force is kept low enough as not to hinder lateral movement, whilst being high enough to centre the movable assembly 12 in the absence of driving. Each flexure 67 has a cross-section with an average width orthogonal to the primary axis O is that is greater than its average thickness parallel to the primary axis O. Each flexure 67 extends in an L-shape around the primary axis O, it in general being desirable that the angular extent is at least 90° as measured between the ends of the flexure 67.

In the assembled state of the actuator assembly 2, the flexures 67 are deflected from their relaxed state to provide a pre-loading force that biases the support structure 4 and the movable assembly 12 together.

The flexures 67 are made of a suitable material that provides the desired mechanical properties and is electrically conductive. Typically, the material is a metal having a relatively high yield, for example steel such as stainless steel.

Alternatively or additionally, the biasing arrangement may comprise the heat transfer material 103. The heat transfer material 103 may be selected such that it is capable of applying a biasing force to the movable assembly 12, for example when used in combination with the bearing arrangement 110 of Fig. 5. The heat transfer material 103 may also provide or contribute to the lateral biasing force that biases the movable assembly 12 towards a central position.

Movement of the movable assembly 12 relative to the support structure 4 is driven by a lateral actuator arrangement that is arranged as follows, and seen most easily in Fig. 4. Particular advantage is achieved in the case that the actuator arrangement comprises plural SMA wires 40, as SMA provides a high actuation force compared to other forms of actuator. This may assist in accurate positioning of the movable assembly 12 relative to the support structure 4. In general, however, the actuator arrangement may comprise plural actuator components other than SMA wires 40.

The lateral actuator arrangement shown in Fig. 4 is formed by a total of four SMA wires 40 connected between the support structure 4 and the carrier 8. For attaching the SMA wires 40, the carrier 8 comprises crimp portions 41 fixed to the moving plate 9 and the support structure 4 comprises crimp portions 42 fixed to the rim portion 10. The crimp portions 41 and 42 crimp the four SMA wires 40 so as to connect them to the support structure 4 and the carrier 8. The crimp portions 41 fixed to the moving plate 9 are formed integrally from a sheet of metal so as to electrically connect the SMA wires 40 together at the carrier 8.

Although in this example the crimp portions 41 and 42 are separate elements fixed to the moving plate 9 and the rim portion 10, as an alternative the crimp portions 41 could be formed integrally with the moving plate 9 and/or the crimp portions 42 could be formed integrally with the support plate 5.

Fig. 15 is a cross-sectional view of an actuator assembly 2. The actuator assembly 2 comprises a movable assembly 12, which is movable relative to a support structure 4. The movable assembly comprises a moving plate 9 (which may also be referred to as an endstop plate, as described in more detail below) and an emitter 7. The support structure 4 comprises a can 15, a base plate 51 and a conductor layer 52. The can 15 may comprise a support plate 5.

The movable assembly 12 is supported on the support structure 4 such that a gap 104 is formed between the movable assembly 12 and the support structure 4. The gap 104 is formed on a side of the movable assembly 12 opposite to a side on which radiation (e.g. light) is emitted by the emitter 7, in particular in a direction parallel to the primary axis O. The gap 104 is formed, in particular, between the moving plate 9 and the support plate 5, which may be part of the can 15.

The actuator assembly 2 comprises a bearing 110, which may be a rolling bearing or a plain bearing for example. The bearing 110 is disposed on the side of the movable assembly 12 that is opposite to the gap 104. The bearing 110 is disposed on the same side of the movable assembly 12 as the emitter 7, in particular laterally to the emitter 7.

As shown in Fig. 15, optionally the support structure 4 comprises a support layer 51 (which may also be referred to as a subbase). The support layer 51 is configured to provide mechanical support to the actuator assembly 2. The support layer 51 may surround a hole that allows radiation to be emitted by the emitter 7. The support layer 51 may be shaped as a rim forming the top edge of the support structure 4. The support layer 51 may comprise a stiff material such as a metal. The support layer 51 may be formed as a separate component from the rest of the can 15 and subsequently attached (e.g. glued or welded) to the rest of the can 15. Alternatively the support layer 51 may be integral to the can 15.

As shown in Fig. 15, optionally the support structure 4 comprises a conductor layer 52. The conductor layer 52 comprises one or more electrical tracks configured to transport signals to and/or from the actuator. For example, the conductor layer 52 may comprise tracks for transferring electrical power and/or control signals to drive the SMA actuator wires. The conductor layer 52 may comprise one or more tracks from transferring data about the SMA actuator wires to a controller of the actuator assembly 2 or camera apparatus 1.

As shown in Fig. 15, optionally the conductor layer 52 is fixed relative to the can 15. For example, the conductor layer 52 may be attached to the support layer 51. The conductor layer 52 may be located between the support layer 51 and the movable assembly 12. The conductor layer 52 is arranged so as not to add to the depth of the actuator assembly 2. The conductor layer 52 may surround a hole that allows radiation to be emitted by the emitter 7. The conductor layer 52 may be shaped as a rim at the underside of the support layer 51 of the support structure 4.

As shown in Fig. 15, optionally one end 68 of the flexure 67 is fixed (e.g. glued or welded) to the moving plate 9. Alternatively, the end 68 of the flexure 67 may be integral to the moving plate 9. The other end 69 (not shown in Fig. 15) of the flexure 67 is attached to the support structure 4. As shown in Fig. 15, the end 68 of the flexure 67 may be located between the conductor layer 52 or the support layer 51 and the moving plate 9.

As shown in Fig. 15, optionally the bearing 110 is located between the conductor layer 52 and the end 68 of the flexure 67. The bearing 110 may run on the end 68 of the flexure 67 and the conductor layer 52. The bearing 110 abuts a surface of the conductor layer 52. The bearing abuts a surface of the end 68 of the flexure 67.

The diameter of the bearing 110 may be at least 30% and optionally at least 40% of the height of the actuator assembly 2. The height of the actuator assembly is the distance in the vertical direction shown in Fig. 15 between the top side of the support layer 51 and the bottom side of the support plate 5 of the can 15. It is desirable to reduce the height of the actuator assembly 2.

A gap 55 is provided between the parts of the actuator assembly 2 that move relative to each other. The gap 55 may be defined between the end 68 of the flexure 67 and the conductor layer 52 (or an enclosure 56 shown in Fig. 18 and described below). The gap may be at least 20pm, optionally at least 50pm and optionally at least 100pm. The gap 55 may be large enough to account for a small amount of bowing of the plates of the actuator assembly 2. The gap 55 reduces the possibility of components that are intended to move relative to each other touching each other. Any such contact can undesirably produce mechanical interference and potentially electrical short-circuiting.

Fig. 16 is a cross-sectional view of an actuator assembly 2. The actuator assembly 2 shown in Fig. 16 has a smaller height than the actuator assembly 2 shown in Fig. 15. Features that are in common between the actuator assembly 2 of Fig. 16 and the actuator assembly 2 of Fig. 15 are not described in detail below. Instead, the description focuses on the differences between the actuator assembly 2 of Fig. 16 and the actuator assembly 2 shown in Fig. 15.

As shown in Fig. 16, optionally the components can be brought closer (relative to the actuator assembly 2 shown in Fig. 15) by having the bearings 110 running on the support layer 51 and the moving plate 9. As shown in Fig. 16, optionally a hole is provided in the conductor layer 52 to accommodate each bearing 110. The bearing 110 is located in the hole such that the bearing 110 abuts the support layer 51. By providing the hole (which may also be referred to as a cut-out) the height of the actuator assembly 2 is reduced by the thickness of the conductor layer 52. The thickness of the conductor layer 52 may be at least 50pm and optionally at least 100pm. The thickness of the conductor layer 52 may be at most 200pm and optionally at most 100pm.

As shown in Fig. 16, optionally a hole is provided in the end 68 of the flexure 67 that is fixed to the moving plate 9 to accommodate each bearing 110. The bearing 110 is located in the hole such that the bearing 110 abuts the moving plate 9. By providing the hole (which may also be referred to as a cut-out) the height of the actuator assembly 2 is reduced by the thickness of the material from which the flexure 67 is formed. The thickness of the material from which the flexure 67 is formed may be at least 50pm and optionally at least 100pm. The thickness of the material from which the flexure 67 is formed may be at most 200pm and optionally at most 150pm.

By providing the hole in the end 68 of the flexure 67, the flexure 67 extends over a shorter distance in the height direction. The distance between the two ends 68, 69 of the flexure 67 in the direction parallel to the primary axis O is decreased. This may reduce the force that the flexure 67 imparts between the support structure 4 and the movable assembly 12. Optionally, the flexure 67 may be shaped during manufacture of the actuator assembly 2 so as to provide an additional biasing force to compensate for the reduced distance. Optionally the flexure 67 is formed into a particular shape before the actuator assembly 2 is assembled (i.e. before the movable assembly 12 is assembled with the support plate 5). For example, the flexures 67 may comprise a jog.

The actuator assembly 2 shown in Fig. 16 has holes in both the conductor layer 52 and the end 68 of the flexure 67. Alternatively, such holes may be provided in only one of the conductor layer 52 and the end 68 of the flexure 67.

Fig. 17 is a cross-sectional view of an actuator assembly 2. The actuator assembly 2 shown in Fig. 17 has a smaller height than the actuator assembly 2 shown in Fig. 15 or the actuator assembly 2 shown in Fig. 16. Features that are in common between the actuator assembly 2 of Fig. 17 and the actuator assembly 2 of Fig. 15 are not described in detail below. Instead the description focuses on the differences between the actuator assembly 2 of Fig. 17 and the actuator assembly 2 shown in Fig. 15.

As shown in Fig. 17, holes are provided in both the conductor layer 52 and the end 68 of the flexure 67 to accommodate the bearing 110. As shown in Fig. 17, optionally the moving plate 9 can be split into two plates consisting of a bearing plate 53 (which may also be referred to as a cradle) for the bearings 110 to run on and an accommodating plate 54 for accommodating the bearings 110. Alternatively, a half etched single plate could be used as the moving plate 9 (i.e. the bearing plate 53 and the accommodating plate 54 may be integral).

As shown in Fig. 17, optionally a hole is provided in the accommodating plate 54 to accommodate each bearing 110. The bearing 110 is located in the hole such that the bearing 110 abuts the bearing plate 53. This can help to reduce the height of the actuator assembly 2 by a fraction of the thickness of the moving plate 9.

The thickness of the moving plate 9 may be at least 50pm and optionally at least 100pm. The thickness of the moving plate 9 may be at most 200pm and optionally at most 150pm. The height of the actuator assembly 2 may be reduced (relative to the height of the actuator assembly 2 shown in Fig. 16) by the difference between the thickness of the moving plate 9 and the thickness of the bearing plate 53. The thickness of the bearing plate 53 may be at least 20pm and optionally at least 50pm. The thickness of the bearing plate 53 may be at most 100pm and optionally at most 50pm. The difference between the thickness of the moving plate 9 and the thickness of the bearing plate 53 may be at least 50pm and optionally at least 100pm.

The actuator assembly 2 shown in Fig. 17 has holes in both the conductor layer 52 in addition to holes in the end 68 of the flexure 67 and the accommodating plate 53. Alternatively, such holes may be provided in the end 68 of the flexure 67 and the accommodating plate 53 but not in the conductor layer 52.

Although not shown in the drawings, the principle described above applied to the moving plate 9 may additionally or alternatively be applied to the support layer 51. Optionally, the support layer 51 can be split into two plates consisting of a bearing plate for the bearings 110 to run on and an accommodating plate for accommodating the bearings 110. Alternatively, a half etched single plate could be used as the support layer 51 (i.e. the bearing plate and the accommodating plate may be integral).

Optionally a hole is provided in the accommodating plate of the support layer 51 to accommodate each bearing 110. The bearing 110 is located in the hole such that the bearing 110 abuts the bearing plate of the support layer 51. This can help to reduce the height of the actuator assembly 2 by a fraction of the thickness of the support layer 51.

The thickness of the support layer 51 may be at least 50pm and optionally at least 100pm. The thickness of the support layer 51 may be at most 200pm and optionally at most 150pm. The height of the actuator assembly 2 may be reduced (relative to the height of the actuator assembly 2 shown in Fig. 16 or Fig. 17) by the difference between the thickness of the support layer 51 and the thickness of the bearing plate of the support layer 51. The thickness of the bearing plate of the support layer 51 may be at least 20pm and optionally at least 50pm. The thickness of the bearing plate of the support layer 51 may be at most 100pm and optionally at most 50pm. The difference between the thickness of the support layer 51 and the thickness of the bearing plate of the support layer 51 may be at least 50pm and optionally at least 100pm.

Fig. 18 is another cross-sectional view of the actuator assembly 2 of Fig. 15. Fig. 18 shows further details particularly relating to the crimp portion 41 and the function of the moving plate 9 as an endstop. Fig. 18 is a cross-sectional view taken along a different line of the actuator assembly 2. The cross-section shown in Fig. 15 (and also in Fig. 16 and Fig. 17) extends across the full width of the actuator assembly and passes through the emitter 7 but does not pass through any crimp portion 41, 42. The cross-section shown in Fig. 18 extends only partly across the actuator assembly 2 and passes through the crimp portion 41 fixed to the movable assembly 12 and the arm of the flexure 67.

The features shown and described in relation to Fig. 18 may equally apply to the actuator assembly 2 shown in Fig. 16 or the actuator assembly 2 shown in Fig. 17. As shown in Fig. 18, optionally the actuator assembly 2 comprises an enclosure 56. The enclosure 56 is configured to accommodate the bearing 110. The enclosure 56 is configured to constrain the movements of the bearing 110. The enclosure 56 may be shaped as a plate provided with a hole to accommodate the bearing 110. The enclosure 56 may be part of the support structure 4. The enclosure 56 may be fixed (e.g. glued or welded) to the conductor layer 52. Such an enclosure 56 may be provided in the actuator assembly 2 shown in Fig. 16, albeit with a smaller thickness (because of there being less available space and the hole in the conductor layer 52 effectively functioning similarly to the enclosure 56). It is not essential to provide an enclosure 56. For example a hole in the conductor layer 52 may sufficiently constrain the bearing 110.

As shown in Fig. 18, optionally the actuator assembly 2 comprises a crimp spacer 57. The crimp spacer 57 is arranged to connect the crimp portion 41 to the moving plate 9. The crimp spacer may be fixed (e.g. welded) onto the end 68 of the flexure 67. The crimp spacer 57 may connect the crimp portion 41 to the end 68 of the flexure 67. It is not essential to provide the crimp spacer 57. Alternatively, the crimp portion 41 may be connected directly to the end 68 of the flexure 67 or the moving plate 9. As shown in Fig. 18 optionally a hole is provided in the moving plate to accommodate each crimp spacer 57.

Each hole that accommodates the bearing 110 may be dimensioned such that the diameter of the bearing 110 is at least half, optionally at least 80% and optionally at least 90% of the diameter of the hole.

As shown in Fig. 18, optionally the moving plate 9 is arranged such that there is a gap 58 between the edge of the moving plate 9 and the inner surface of the can 15. During use of the actuator assembly 2 the moving plate 9 moves relative to the can 15. The movement causes the gap 58 to increase or decrease in size. Optionally, the moving plate 9 is configured to function as an endstop. When the moving plate 9 moves such that the gap 58 becomes zero and the moving plate 9 abuts the can 15, further movement in that direction of the movable assembly 12 relative to the support structure 4 is prevented. This can help to reduce the possibility of the SMA actuator wires becoming damaged as a result of the movable assembly 12 moving too far relative to the support structure 4 in a particular direction. That the endstops are provided within the actuator assembly 2 can also facilitate testing of the actuator before the emitter 7 is incorporated into the actuator assembly 2. In turn, this can help reduce the possibility of an emitter being discarded with an actuator that does not pass the testing process, thereby reducing the average cost of manufacturing the actuator assembly 2. This is contrast to, for example, a comparative example in which such endstops involve a separate component, e.g. a can, which must be incorporated after the emitter 7. The same principle may apply in relation to endstops (not shown) that limit movement in other directions, e.g. along the primary axis O.

In Figs. 15-18, the bearing 110 is disposed on a side of the movable assembly 12 that is opposite to the gap 104. Alternatively, the bearing 110 may be disposed on a same side of the movable assembly 12 as the gap 104.

Fig. 19 is a perspective view of a bearing shock protection structure 60. The bearing shock protection structure 60 may be incorporated as part of any of the arrangements of the actuator assembly 2 described elsewhere in this document. Fig. 19 shows the carrier 8 of the actuator assembly 2 comprising a bearing shock protection structure 60. The bearing shock protection structure 60 may be comprised in the movable assembly 12 which moves relative to the support structure 4.

Shock protection is provided by cantilevers 61 cut into a plate. In the arrangement shown in Fig. 19, the cantilevers 61 are cut into a plate of the carrier 8. The plate of the carrier 8 comprising the cantilevers 61 may be formed of a metal sheet. One or more shaped cuts 62 form cantilevers 61 in portions of the plate. Fig. 19 shows three such cantilevers 61, but there could be more, for example four, cantilevers 61. Each cantilever 61 supports a bearing 110, which may be ball bearing, at its free end 63. The one or more bearings 110 in Fig. 19 are shown in exploded view for clarity, the dotted lines indicating where they locate.

In normal operation, the bearing 110 is free to move laterally over the area at the free end 63 of the cantilever 61. In shock conditions, any vertical forces are taken up by bending of the free end 63 of the cantilever 61 (downwards in Fig. 19). The bearing shock protection structure 60 may be formed as a single part of cut metal, which is easy to manufacture and assemble to other components.

The plate in which the cantilevers 61 are provided may be the plate that forms the surface with which the bearing 110 comes into contact. For example, the cantilevers 61 may be provided in the peripheral part of the moving plate 9 shown in Fig. 2 lateral to the gap 104. The cantilevers 61 may be provided in the moving plate 9 shown in any of Figs. 5 to 8. The cantilevers 61 may be provided in the end 68 of the flexure 67 shown in Fig. 15. A hole may be provided in the moving plate 9 adjacent to each cantilever 61 so as to allow the cantilevers 61 to flex away from the bearing 110 into the hole. The cantilevers 61 may be provided in the moving plate 9 shown in Fig. 16. The cantilevers 61 may be provided in the bearing plate 53 shown in Fig. 17.

As mentioned above, alternatively the cantilevers 61 may be provided in a plate of the support structure 4. For example, the cantilevers 61 may be provided in the support plate 5 shown in Fig. 2. The cantilevers 61 may be provided in the support structure 4 of any of the arrangements shown in Figs. 5 to 8. The cantilevers 61 may be provided in the conductor layer 52 shown in Fig. 15. A hole may be provided in the support layer 51 adjacent to each cantilever 61 so as to allow the cantilevers 61 to flex away from the bearing 110 into the hole. The cantilevers 61 may be provided in the support layer 51 shown in Figs. 16 or 17.

The cantilevers 61 are arranged to deflect during a drop event, for example. The bearing shock protection structure 60 is configured to reduce the possibility of the bearings 110 and/or the bearing surface from being damaged. The deflection of the cantilevers 61 dissipates energy, thereby reducing the energy that could otherwise damage the actuator assembly 2 during a drop event.

Fig. 20 is a perspective view of part of a movable assembly 12 with accommodated bearings 110. Fig. 20 shows a sub-assembly including the bearing shock protection structure 60 of Fig. 19. In Fig. 20, the cantilevers 61 are provided in a moving plate 9 of a movable assembly 12 of an actuator. In Fig. 20, a bearing retaining structure 64 is shown assembled on top of the moving plate 9 which incorporates the cantilevers 61. The bearing retaining structure 64 is shown as a relatively thick plate with holes 65 for locating the bearings 110.

Also shown in Fig. 20 is a further shock protection structure in the form of end stops 66. Four end stops 66 are shown, but there may be more or fewer. For example, three end stops 66 may be used. Each endstop 66 may be a pad of material raised above the main body but lower in height than the bearings 110. The relative heights of the bearings 110, the end stops 66 and the main body of the bearing retaining structure 64 is shown in Fig. 21. Fig. 21 is a cross-sectional view of the sub-assembly shown in Fig. 20.

In normal operation, the end stops 66 play no role, but in shock conditions they prevent the bearing surface of the support structure 4 (which is not shown, but which normally resides at the level of the top of the bearings 110) from moving further down than the top of the end stops 66. Thus, under a vertical shock force, the cantilevers 61 take up part of the downward movement by deflecting and the end stops 66 limit further movement. The end stops 66 may be arranged to limit vertical movement of support structure 4 with respect to the carrier 8. The end stops 66 may be simple pads of material and are easily assembled or mounted on to the top of the bearing retaining structure 64.

In the arrangement shown in Fig. 20, the end stops 66 are comprised in the moving part of the actuator assembly 2. The end stops 66 protrude towards the support structure 4 and are arranged to abut the support structure 4 only during a drop event, for example. Alternatively, the end stops 66 may be comprised in the support structure 4 and may protrude towards the movable assembly 12. The end stops 66 may be arranged with a gap between the end stops 66 and the movable assembly 12. The end stops 66 may be arranged to abut the movable assembly 12 only during a drop event, for example.

It is not essential for the bearing retaining structure 64 to be provided. As an alternative, the end stops 66 may protrude from the moving plate 9 towards the support structure 4. Alternatively, the end stops 66 may protrude from the end 68 of the flexures 67 towards the support structure 4, or from the conductor layer 52 towards the movable assembly 12, or from the support layer 51 towards the movable assembly 12, or from the enclosure 56 towards the movable assembly 12. In other examples, instead of being formed by cuts in a particular plate, the cantilevers 61 may be formed as a separate element and attached to the plate.

The SMA wires 40 are arranged as follows so that they are capable, on selective driving, of moving the movable assembly 12 relative to the support structure 4 in any direction perpendicular to the primary axis O and also of rotating the movable assembly 12 about an axis parallel to the primary axis O.

Each of the SMA wires 40 is held in tension, thereby applying a force between the support structure 4 and the carrier 8.

The SMA wires 40 may be perpendicular to the primary axis O so that the force applied to the carrier 8 is lateral to the emitter 7. Alternatively, the SMA wires 40 may be inclined at a small angle to the emitter 7 so that the force applied to the carrier 8 includes a component lateral to the emitter 7 and a component along the primary axis O that acts as a biasing force that biases the movable assembly 12 against the bearing arrangement 110. So, the SMA wires 40 may act as the biasing arrangement. The biasing arrangement may comprise plural actuator components that are inclined relative to the emitter 7 for applying a biasing force that biases movable assembly 12 towards the bearing arrangement 110, 120, 130.

The overall arrangement of the SMA wires 40 will now be described, being similar to that described in WO-2014/083318 (which is incorporated herein by reference), except that the SMA wires move the movable assembly 12, not the lens assembly 20.

SMA material has the property that on heating it undergoes a solid-state phase change which causes the SMA material to contract. At low temperatures, the SMA material enters the Martensite phase. At high temperatures, the SMA enters the Austenite phase which induces a deformation causing the SMA material to contract. The phase change occurs over a range of temperature due to the statistical spread of transition temperature in the SMA crystal structure. Thus heating of the SMA wires 40 causes them to decrease in length.

The SMA wires 40 may be made of any suitable SMA material, for example Nitinol or another Titanium-alloy SMA material. Advantageously, the material composition and pre-treatment of the SMA wires 40 is chosen to provide phase change over a range of temperature that is above the expected ambient temperature during normal operation and as wide as possible to maximise the degree of positional control.

On heating of one of the SMA wires 40, the stress therein increases and it contracts, causing movement of the movable assembly 12. A range of movement occurs as the temperature of the SMA increases over the range of temperature in which there occurs the transition of the SMA material from the Martensite phase to the Austenite phase. Conversely, on cooling of one of the SMA wires 40 so that the stress therein decreases, it expands under the force from opposing ones of the SMA wires 40. This causes the movable assembly 12 to move in the opposite direction.

The carrier 8 and the movable assembly 12 are positioned axially within the aperture 11 of the rim portion 10 of the support structure 4. The four SMA wires 40 are arranged on four sides of the movable assembly 12. The SMA wires 40 are of the same length and have a rotationally symmetrical arrangement.

As viewed axially, a first pair of the SMA wires 40 extend parallel to a first axis (vertical in Fig. 4) that is lateral to the emitter 7. However, the first pair of the SMA wires 40 are oppositely connected to the support structure 4 and the carrier 8 so that they apply forces in opposite directions along the first axis (vertically up and down in Fig. 4). The forces applied by the SMA wires 40 of the first pair balance in the event that the tension in each SMA wire 40 is equal. This means that the first pair of the SMA wires 40 apply a first torque to the movable assembly 12 (anti-clockwise in Fig. 4).

As viewed axially, a second pair of SMA wires 40 extend parallel to a second axis (horizontal in Fig. 4) that is lateral to the emitter 7. However, the second pair of SMA wires 40 are oppositely connected to the support structure 4 and the carrier 8 so that they apply forces in opposite directions along the second axis (horizontally left and right in Fig. 4). The forces applied by the SMA wires 40 of the second pair balance in the event that the tension in each SMA wire 40 is equal. This means that the second pair of the SMA wires 40 apply a second torque (clockwise in Fig. 4) to the movable assembly 12 that is arranged to be in an opposite sense to the first torque. Thus, the first and second torques balance in the event that tension in each SMA wire 40 is the same.

As a result, the SMA wires 40 may be selectively driven to move the movable assembly 12 in any direction laterally and to rotate the movable assembly 12 about an axis parallel to the primary axis O. That is:

• movement of the movable assembly 12 in either direction along the first axis may be achieved by driving the first pair of SMA wires 40 to contract differentially, due to them applying forces in opposite directions;

• movement of the movable assembly 12 in either direction along the second axis may be achieved by driving the second pair of SMA wires 40 to contract differentially, due to them applying forces in opposite directions; and

• rotation of the movable assembly 12 may be achieved by driving the first pair of SMA wires 40 and the second pair of SMA wires 40 to contract differentially, due to the first and second torques being in opposite senses.

The magnitude of the range of movement and rotation depends on the geometry and the range of contraction of the SMA wires 40 within their normal operating parameters.

This particular arrangement of the SMA wires 40 is advantageous because it can drive the desired lateral movement and rotation with a minimum number of SMA wires. However, other arrangements of SMA wires 40 could be applied. To provide three degrees of motion (two degrees of lateral motion and one degree of rotational motion), then a minimum of four SMA wires 40 are provided. Other arrangements could apply a different number of SMA wires 40. Less SMA wires 40 could be provided for lateral motion, but not rotation. Arrangements with more than four SMA wires 40 are also possible, and may have advantages in allowing additional parameters to be controlled in addition to motion, for example the degree of stress in the SMA wires 40.

The lateral position and orientation of the movable assembly 12 relative to the support structure 4 is controlled by selectively varying the temperature of the SMA wires 40. This driving of the SMA wires 40 is achieved by passing selective drive signals through the SMA wires 40 to provide resistive heating. Heating is provided directly by the current of the drive signals. Cooling is provided by reducing or ceasing the current of the drive signals to allow the SMA wire 40 to cool by conduction, convection and radiation to its surroundings.

The apparatus 1 may comprise a lens assembly 20 that is assembled with the actuator assembly 2 by being mounted to the support structure 4, in particular to the rim portion 10.

As discussed above, in operation the SMA wires 40 are selectively driven to move the movable assembly 12 in any direction perpendicular to the primary axis O and/or to rotate the movable assembly 12 about an axis parallel to the primary axis O. Where the apparatus 1 is part of a 3D sensing system, this is used to provide increased range/resolution, for example. Where the apparatus 1 is part of an augmented reality (AR) display system, this is used to provide wobulation, for example.

The SMA wires 40 are driven by the control circuit implemented in the IC chips 30 and 31. In particular, the control circuit generates drive signals for each of the SMA wires 40 and supplies the drive signals to the SMA wires 40.

The drive signals are generated by the control circuit in response to the desired position of the movable assembly. The drive signals may be generated using a resistance feedback control technique for example as disclosed in any of WO-2013/175197, WO- 2014/076463, WO-2012/066285, WO-2012/020212, WO-2011/104518, WO-2012/038703, WO-2010/089529 or WO-2010/029316, each of which is incorporated herein by reference.

The apparatus 1 may be incorporated into a portable electronic device. There is thus provided a portable electronic device comprising the apparatus 1. The portable electronic device may comprise a processor. The device may provide wobulation, e.g. for the display of a super-resolution image or may be used for 3D sensing.

For the purpose of wobulation, the movable assembly is controllably moved between two or more positions such that the emitter 7 is moved between the two or more positions. The emitter 7 comprises an array of illumination sources. For example, the emitter 7 may be a VCSEL array. The VCSELs are separated by a cavity pitch (which is the distance between the centre of two adjacent VCSEL cavities in a direction perpendicular to the primary axis). The two or more positions are offset from each other, in a direction perpendicular to the primary axis O, by a distance which is less than the cavity pitch.

The movable assembly may be controllably moved to a positional accuracy of 0.5pm or smaller. Particular advantage is achieved in the case that the actuator arrangement comprises plural SMA wires, as SMA provides a high actuation force compared to other forms of actuator. This may assist in accurate positioning of the movable assembly relative to the support structure.

The two or more positions may be stationary positions, so the movable assembly may stop at each of the two or more positions before moving on to the next of the two or more positions.

An image is projected at each of the two or more positions using the emitter 7. A controller may control the emitter 7 to project the images. The controller may be implemented as part of the control circuit on the IC chips 30 and 31 or as part of another circuit on the IC chips 30 and 31. Alternatively, the controller may be implemented as part of another IC that forms part of the apparatus 1. Further alternatively, the controller may be implemented as part of the processor that forms part of the portable electronic device.

By projecting different images at different positions (e.g. those described above) in rapid succession, a super-resolution image is displayed. The super-resolution image has a resolution that is greater than the intrinsic resolution of the emitter 7.

Whilst embodiments shown in the figures have been described with reference to the movable assembly comprising an emitter 7, the movable assembly may instead (or additionally) comprise a display, for example a display panel, for displaying an image. In any of the embodiments described above, the emitter 7 may be replaced by a display, for example a display panel. For wobulation in the case of moving a display, the movable assembly is controllably moved between two or more positions such that the display is moved between the two or more positions. The display comprises a plurality of pixels and may be oriented perpendicular to the primary axis O. The two or more positions are offset from each other, in a direction perpendicular to the primary axis O, by a distance which is less than the pixel pitch (i.e. less than a distance between the centres of two adjacent pixels).

It will be appreciated that there may be many other variations of the abovedescribed embodiments. For example, the bearing arrangement 110, 120, 130 may comprise any combination of the above-described bearing arrangements 110, 120, 130. The roller bearing 110 may comprise rolling elements on both sides of the movable assembly 12 in a direction parallel to the primary axis O, so the rolling elements shown in Fig. 5 and the rolling elements shown in Fig. 2 or Fig. 6. The bearing arrangement 110, 120, 130 may comprise one or more rolling bearings of Figs. 2, 5 and 6 and one or more of the flexure arrangements of Figs. 7 to 10.

Any of the above-described bearing arrangements 110, 120, 130 may be combined with any of the above-described arrangements of the gap 104 and/or the region of heat transfer material 103.

The display (e.g. projection) of super-resolution images or 3D imaging may be achieved using an actuator assembly with any bearing arrangement, including a bearing arrangement comprising a continuous plain bearing without provision of the gap 104. The high actuation force of SMA wires 40 may allow accurate positioning by overcoming any frictional forces that are due to such a continuous plain bearing.

As described above, a movable assembly as described herein may comprise a display, an emitter or a part thereof. The display may be a display panel, for example a LCOS (liquid crystal on silicon) display, a MicroLED display, a digital micromirror device (DMD) or a laser beam scanning (LBS) system. The emitter is configured to emit radiation (visible light or non-visible radiation, e.g. near infrared (NIR) light, short-wave infrared (SWIR) light). The emitter may comprise one or more LEDs or lasers, for example VCSELs (vertical-cavity surface-emitting lasers) or edge-emitting lasers. The emitter may comprise a VCSEL array. The emitter may otherwise be referred to as an illumination source or a light source and/or may comprise an image projector. The emitter is described above as projecting an image. An image may comprise any sort of illumination pattern (and may otherwise be referred to as an illumination pattern).

The term SMA wire may refer to any suitably-shaped element comprising SMA. The SMA wire 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 wire. It is also possible that the length of the SMA wire (however defined) may be similar to one or more of its other dimensions. The SMA wire may be flexible. Accordingly, when connected between two elements, the SMA wire may only be able to apply a force that urges the two elements together, this force being applied when the SMA wire is in tension. Alternatively, the wire may be beam-like or rigid. The SMA wire may or may not include material(s) and/or component(s) that are not SMA.