Background

The present application generally relates to a method of controlling an actuator assembly and an actuator assembly.

Background

Actuators are used in electronic apparatus for effecting motion in a variety of movable parts, in order to achieve desired functionalities. However, in some actuators, the movable parts may undesirably experience a degree of free movement when the electronic apparatus is switched off. As an example, W02011/104518A discloses a Shape Memory Alloy (SMA) apparatus for controlling a lens carriage in a smartphone camera with the use of eight SMA wires. Upon energising, the SMA wires are selectively contracted and cause movement in the movable element in the direction of contraction. Upon ceasing power supply the SMA wires cool and may no longer be in tension. Since the lens carriage is suspended entirely by the SMA wires, the slack in the SMA wire may cause a degree of free movement in the lens carriage. Such free movement in the lens carriage may lead to collision with other components. This may not only generate audible noise, in some cases it may even result in damage to the components, as well as to the SMA wires.

Summary

The present invention provides an actuator assembly for an electronic apparatus, and various means for counteracting acceleration in the electronic apparatus during a standby mode or when the electronic apparatus is switched off, such as those caused by sudden movements, knocks and vibration. In order words, the present invention may stabilise the various movable parts relative to the electronic apparatus even when a key function or the entire electronic apparatus is disabled. Thus, the present invention may eliminate, or at least minimise, the likelihood of collision between different components of the electronic apparatus, and it may advantageously reduce audible noise resulting from such collision, as well as prolonging the lifetime of the electronics apparatus. According to a first aspect of the present invention, there is provided a method of controlling an actuator assembly of an electronic apparatus, the actuator assembly comprising a support structure and a movable part movable relative to the support structure, the electronic apparatus being operable in a standby mode during which at least one key function of the electronic apparatus is disabled, the method comprising driving, during or upon entering the standby mode, the movable part to counteract acceleration of the electronic apparatus.

In contrast with an active mode, where the electronic apparatus is fully functional, the standby mode generally refers to a state where some of the (main) components of the electronic apparatus are unpowered, or unutilised. Therefore, in a standby mode the electronic apparatus may have one or more of its key (or main) functions disabled, or at least in a state where there is no control of the said function. More specifically, the key function may refer to the function for which the electrical apparatus is primarily used.

For example, the electronic apparatus may be a haptic assembly, wherein the movable element may comprise a button movable with respect to a support structure for providing a haptic feedback in response to a user press or other forms of input, and wherein during the standby mode the said haptic feedback is disabled, e.g. no haptic feedback is provided during the user press or other forms of input. In this case, the actuator may continue to function during the standby mode in order to counteract movement in the haptic assembly. Advantageously, such an arrangement may limit or eliminate free movements in the button, thus minimising the amount of audible noise and damage to the button and the support structure resulting from a collision therebetween. In addition, by maintaining the relative position between the button and the support structure of the electronic apparatus, it may advantageously allow the button to be always positioned at a desirable location. In other examples, the electronic apparatus may be a vibration motor, an audio speak, a display, a user interface, or an actuatable mirror assembly.

Alternatively, the electronic apparatus may be a camera assembly, wherein the movable element may comprise a lens carriage or an image sensor. The lens carriage having at least one lens for focusing an image onto an image sensor provided on the support structure, and wherein during the standby mode the image sensor is disabled, or at least in a state where there is no control of the image sensor. In this example, at least the image sensor is disabled in the standby mode, but the actuator may continue to function during the standby mode in order to counteract movement in the camera assembly. This is particularly advantageous because an image sensor, or a lens carriage with lens installed, are relatively heavy and thus the present invention minimises or eliminates physical damage to the lens and/or the image sensor, as well as damage to the SMA wires or other actuator components. Moreover, by reducing the free movement in the lens carriage, the lens may be maintained at its preferred focal position in the standby mode.

In contrast, once the electronic apparatus is switched off, the actuator may not activate until the electronic apparatus is powered up again, e.g. by powering up through receiving a user input or an electrical means such as signal from a timer or a remote control. Therefore, upon switching off, the actuator may put the movable element in a "safe" position before deactivating so as to counteract acceleration in the electronic apparatus.

The actuator may be a micro-actuator for a camera or a mobile phone. In some embodiments, the actuator comprises a voice coil motor (VCM). In some other embodiments, the actuator may be a shape memory alloy (SMA) actuator comprising one or more SMA wires connecting the support structure and the movable part, the one or each SMA wire being configured to, on contraction, effect movement of the movable part, e.g. a lens carriage, along multiple axes. Such an arrangement enables at least autofocus (AF) and optical image stabilisation (OIS) to be performed upon actuating some or all of the SMA wires during the active mode. The SMA wires may extend in different directions and in close proximity to each other. For example, each SMA wire may preferably be an SMA wire, or it may be a strip, or a rod formed from SMA material.

The term 'shape memory alloy (SMA) wire' may refer to any element comprising SMA. The SMA wire may have any shape that is suitable for the purposes described herein. 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 pliant or, in other words, flexible. In some examples, when connected in a straight line between two elements, the SMA wire can apply only a tensile force which urges the two elements together. In other examples, the SMA wire may be bent around an element and can apply a force to the element as the SMA wire tends to straighten under tension. The SMA wire may be beam-like or rigid and may be able to apply different (e.g. non-tensile) forces to elements. The SMA wire may or may not include material(s) and/or component(s) that are not SMA. For example, the SMA wire may comprise a core of SMA and a coating of non-SMA material. Unless the context requires otherwise, the term 'SMA wire' may refer to any configuration of SMA wire acting as a single actuating element which, for example, can be individually controlled to produce a force on an element. For example, the SMA wire may comprise two or more portions of SMA wire that are arranged mechanically in parallel and/or in series. In some arrangements, the SMA wire may be part of a larger piece of SMA wire. Such a larger piece of SMA wire might comprise two or more parts that are individually controllable, thereby forming two or more SMA wires.

The SMA actuator wires may be formed of any suitable shape memory alloy material, typically a nickel-titanium alloy (e.g. Nitinol), but they may also contain tertiary components such as copper. The SMA actuator wires may have any cross- sectional profile and diameter suitable for the application. For example, the SMA wires may have a cross section diameter of 25p.m capable of generating a maximum force of between 120mN to 200mN whilst maintaining the strain in the SMA wire within safe limits (e.g. 2-3% reduction in length over original length). Increasing the diameter of each SMA wire from 25p.m to 35p.m approximately doubles the cross-sectional area of the SMA wire and thus approximately doubles the force provided by each SMA wire. Preferably, the SMA wire may be capable of delivering a high force, e.g. between 1.2 to 3N, more preferably between 1.2 to ION, whilst maintaining the strain in the SMA wire within safe limits (e.g. 2-3% reduction in length over original length). The force may be dependent on the target displacement required. In an unenergized state, the SMA wires may have a degree of slack, wherein upon energising the unenergized SMA wires may contract and thereby eliminate the slack therein. More specifically, an unenergized SMA wire, as well as the lens carriage or the image sensor it is connected to, may have a degree of free movement when the actuator is powered off. Thus, when the device is in motion or encountering sudden movements or acceleration, e.g. during transit, the SMA wires may experience a substantial amount of wear over time due to abrasion with other components and/or other wires. In some serious cases, the SMA wires may break due to the momentum of the lens carriage or image sensor. Such issues may be prominent in actuators where the lens carriage is solely supported or suspended by the SMA wires, e.g. such as the embodiments as disclosed in W02011/104518A.

In the standby mode, the actuator may actively counteract the movement in the actuator assembly, continuously or as required. That is, the actuator may actively apply a force on the movable element in order to act against the acceleration in the electronic apparatus. In some embodiments, during the standby mode, the actuator is configured to activate only to counteract acceleration in the electronic assembly. For example, in the case of a camera assembly, the actuator may not activate to drive or move the lens carriage or the image sensor for other functions such as aligning an image onto the image sensor during said standby mode.

Optionally, the method comprises receiving, during the standby mode, a signal indicating acceleration and/or onset of acceleration in the electronics apparatus; activating, upon receiving the said signal, the actuator to counteract against said acceleration. For example, the signal may be generated from an accelerometer and/or a gyroscope configured to detect one or more of a direction, magnitude and frequency of the movement in the electronic device. Thus, the method may further comprise detecting, by an accelerometer and/or a gyroscope, one or more of a direction, magnitude and frequency of the acceleration in the electronic device; and generating the signal.

The accelerometer and/or the gyroscope may be a component of the actuator assembly, e.g. it may be the same accelerometer and/or gyroscope applicable for performing OIS. Alternatively, or in addition, the accelerometer may be a component of the electronic apparatus comprising the actuator assembly, or a device comprising the electronic apparatus. That is, the accelerometer may output a signal applicable for other components of the apparatus. In use, the accelerometer may produce a signal upon detecting movement in the device, and upon receiving such signal a controller may produce a drive signal to drive movement in the actuator.

Alternatively, or in addition, the method further comprises generating a signal for activating an auxiliary actuator, wherein the motion of the auxiliary actuator causes acceleration in the electronic device; the auxiliary actuator comprises one or more of a vibration motor, a haptic driver, and a speaker. For example, the signal may comprise a drive signal generated by a controller. The auxiliary actuator may be an actuator independent of the actuator assembly. That is, the vibration motor may be a component provided in the electronic apparatus configured to generate a vibrating or haptic motion in the electronic apparatus, in order to alert the user an incoming message or phone call, or to indicate a user input. The said vibration or haptic motion may cause the lens carriage or image sensor to vibrate, or in some cases resonate. In this case, upon sending a control signal to the vibration motor, the controller may also send the drive signal (in the same or a different form) to the actuator to counteract the vibrating motion.

Optionally, the method further comprises driving and/or retaining the movable part to a predetermined position to counteract acceleration in the electronic apparatus wherein, at the said predetermined position, the risk of collision between the movement part and other components of the actuator assembly and/or electronic apparatus is reduced. In some embodiments, the movable part may be moved to one of a plurality of predetermined positions depending on one or more of: the position of the movable part prior to performing the counteracting; or the characteristic of the movement in the electronic apparatus (e.g. magnitude, frequency and/or direction of the movement). In the standby mode, the movable part may be moved to and maintained at the predetermined position until the acceleration in the electronic device ceases. Alternatively, or in addition, upon entering the standby mode or upon switching off the electronic apparatus, the movable part may be moved to and maintained at the predetermined position regardless of the presence of an acceleration in the electronic apparatus, e.g. the actuator is put into a "safe" position.

Optionally, the predetermined position comprises a centred position, wherein at the centred position the movable part is positioned substantially at a midpoint of its movement range along one or more axes. The movement range may be defined as movement stroke along the one or more axes. Optionally at the centred position the movable part is positioned substantially at a midpoint of its movement range along all the axes where movement is permitted. For example, at the centred position the movable part may be positioned at the mid-point of its movement range along the X, Y and Z axes. Such an arrangement may advantageously ensure the movable part is positioned furthest away from other components of the actuator assembly (e.g. the support structure and a screening can attached to the support structure) along at least one of the axes.

Optionally, at the predetermined position, the movable part is positioned furthest away from at least one surface of the support structure along one or more axes. For example, the movable part may be at a position furthest away from a given surface of the support structure. This may advantageously allow maximum clearance to be provided between the lens carriage and said portion of the support structure, where said given surface may be particularly susceptible to noise or damage caused by collision and/or contact with the lens carriage, e.g. conductive tracks and electrical terminals.

Alternatively, at the predetermined position, the movable part is positioned immediately adjacent to a surface of the support structure. For example, the movable part may be arranged to be in contact with and/or being held against the support structure at the predetermined position. As the electronic apparatus experiences acceleration, the movable part may continue to stay in contact with the support structure, and therefore such an arrangement may prevent collision therebetween. In other embodiments, in particular in the case of sudden and abrupt movement in the electronic apparatus, the movable element may experience a degree of jittering. However, since the movable part is in close proximity to the support structure, the noise, as well as the risk of damage resulting from collision is much reduced. Optionally, the method further comprises retaining, by a retaining means, the movable element at the predetermined position to counteract acceleration in the electronic apparatus. For example, a retaining means may be provided for preventing slippage between the movable part and the surface of the support structure. The retaining means may comprise one or more of a protrusion, a recess, a high friction surface having a higher surface roughness than other surfaces on the support structure or the movable element, a clamp and a bayonet mount. The use of a retaining means may be particularly advantageous as it may aid retaining the movable part on the surface of the support structure, thus counteracting the acceleration in the electronic apparatus.

The high friction surface may have a surface roughness of at least 0.1mm, 0.2mm, or at least 0.5mm. For example, when the lens carriage is in contact with a roughened surface of the support structure or the lens carriage, the increase in friction at the roughened surface may prevent lateral movement, or slippage, between the lens carriage and the support structure. Alternatively, or in addition, the retaining means may be a protrusion (e.g. ridges) or recess (e.g. dimples or grooves) that corresponds to the surface profile of the lens carriage. Alternatively, or in addition, the retaining means may comprise a magnetic attachment which comprises one or more magnets provided on the support structure and/or movable part for preventing movement in the movable part.

Optionally, the method further comprises applying, by an or the actuator or a physical input, a force on the retaining means to drive and/or retain the movable part to a predetermined position. For example, a clamp may be provided to hold the lens carriage against the surface of the support structure, wherein the actuator may be configured to force the lens carriage into the predetermined position by the clamp. In other words, the actuator may engage the clamp to lock the lens carriage in the predetermined position. Advantageously, such an arrangement may allow the lens carriage to be retained at the predetermined position even if the actuator is unenergized, e.g. when the electronic apparatus is switched off. The actuator may be the same actuator that effects motion in the movable element, or it may be a different actuator separate to the said actuator. In some embodiments, the clamp may be physically engaged by the user. Alternatively, or in addition, the retaining means may be a bayonet fitting, e.g. a pin movable in a guide slot. For example, the actuator may, during or upon entering the standby mode or upon switching off the electronics apparatus, manipulate the lens carriage into a locking position in the bayonet fitting. The lens carriage may be released, by the actuator, from the locking position when the electronic apparatus is put into an active mode.

Optionally, the actuator may apply a biasing force on the movable part against the said surface of the support structure. .That is, the biasing force may act in a direction normal to the surface of the support structure. The biasing force may increase the friction between the movable part and the support structure, thereby reducing the amount of free movement in the movable part. In some embodiments, the biasing force may be based on the magnitude, direction and/or frequency of the movement in the electronic apparatus. More specifically, the biasing force may react to the characteristic of the movement, thereby it may allow the movable part to be retained on the support surface more effectively.

Alternatively, or in addition, the method further comprises attracting or repelling, by one or more magnets, the movable part towards or away from the said surface of the support structure. The one or more magnets may be provided on the movable part or the support structure. A single magnet may be used when one of the movable part and the support structure is formed from a ferromagnetic material. Alternatively, at least one pair of magnets may be provided for effecting magnetic attraction. The attraction force by the magnet may aid the biasing force for reducing free movement in the movable part. In some cases, the magnet may provide the biasing force in lieu of that effected by the actuator. That is, such an arrangement may allow the movable part to be retained in place when the actuator is not energised, e.g. once the actuator has moved the movable part into the proximity of the magnet. Advantageously, such an arrangement may allow the movable part to be locked in place until the actuator is put into the active mode. During normal operation, e.g. in an active mode, the magnetic attraction/repulsion may not affect the movement of the movable part because the latter operates at a position unaffected by the magnetic field. Alternatively, or in addition, the method further comprises biasing, by a biasing means, the movable part against said surface of the support structure. The biasing means may be a spring plate, a coil spring, an elastic element or any other suitable means. Similar to the magnetic arrangement, the biasing means may provide the biasing force in lieu of that effected by the actuator. This may allow the movable part to be retained in place when the actuator is no longer energised. Advantageously, such an arrangement may allow the movable part to be locked in place until the actuator is put into the active mode. During normal operation, e.g. in an active mode, the biasing means may be released and therefore it may not affect the movement of the movable part.

Optionally, said counteracting comprises driving the movable part against detected movement in the electronic apparatus, thereby avoiding collision between the movable part and other components of the actuator assembly. Said driving comprises applying a force on the lens carriage against the detected movement in the electronic apparatus, said movement being detectable by the accelerometer and/or gyroscope. The force may be strong enough to maintain the relative position between the movable part and the support structure, or it may merely be sufficient to dampen a portion of the movement in the electronic apparatus, such that the risk of collision between the lens carriage and the support structure and/or other parts of the electronic apparatus may be reduced. Optionally, the counteracting comprises driving the movable part based on one or more of a direction, magnitude and frequency of detected movement in the electronic component.

According to a second aspect of the present invention, there is provided an actuator assembly according to the first aspect, wherein the actuator comprises a voice coil motor (VCM), or a shape memory alloy (SMA) actuator having one or more SMA wires connecting the support structure and the movable part, the or each SMA wire is configured to, on contraction, effect acceleration in the movable part or to at least counteract acceleration of the electronic apparatus.

The actuator assembly may comprise one or more of: an accelerometer, a gyroscope, an auxiliary actuator, a controller, one or more magnets, a biasing means and a retaining means having one or more of a protrusion, a recess, a high friction surface having a higher surface roughness or elasticity than other surfaces on the support structure or the movable element, a clamp and a bayonet mount.

Optionally, the electronic apparatus is a camera assembly, wherein the movable element comprises a lens carriage having at least a lens for focusing an image onto an image sensor provided on the support structure, and wherein during the standby mode the image sensor is disabled.

Alternatively, the electronic apparatus being a camera assembly, and wherein the movable part supports thereon an image sensor, and wherein during the standby mode the image sensor is disabled.

Alternatively, the electronic apparatus is a haptic assembly, wherein the haptic assembly comprises a button movable to the support structure for providing a haptic feedback in response to a user press, and wherein during the standby mode the haptic feedback is disabled.

According to a third embodiment of the present invention, there is provided an actuator assembly for an electronic apparatus, comprising: a support structure; a movable part movable relative to the support structure; a shape memory alloy (SMA) actuator having at least SMA wire connected between the movable part and the support structure, wherein the at least one SMA wire is configured to, on contraction, drive movement of the movable part; and a shock absorber provided in and/or connecting between adjacent surfaces on the movable part and the support structure, wherein the shock absorber is configured to suppress an impact between the said adjacent surfaces.

The shock absorber may absorb, suppress shock resulting from an impact, or it may prevent the impact altogether. Therefore advantageously, the provision of a shock absorber may reduce audible noise during sudden acceleration, as well as prolonging the life of the actuator assembly. Optionally, the shock absorber is formed on the surface of the movable part and/or the support structure, wherein the shock absorber comprises one or more of a deformable element, a resilient element, a viscous fluid and a gel. The shock absorber may stand proud of the said surface such that during an impact the adjacent surfaces of the movable part and the support structure do not come into contact.

Optionally, the shock absorber comprises a resilient member connected between the movable part and/or support structure, and wherein the resilient member is configured to exert a substantial biasing force against the movement of the movable part once the movable part has moved outside a predetermined movement range. The predetermined movement range may be the range of movement in the movable part that is achievable by the actuator, wherein when the electronic apparatus experiences sudden acceleration the movable part may be forced outside the said range of movement. Thus, the resilient member may bias, and maintain, the movable part within the said range of movement. In some embodiments, the resilient member is a flexure. The flexure may have a U-shaped profile resembling a hairpin.

Optionally, the resilient member extends radially from the movable part, and wherein the resilient member is configured to bias the movable part towards a predetermined position. For example, the resilient member may be one or more fixtures or resilient beams bridging between the movable part and the support structure. In some embodiments, the resilient member may be a diaphragm radially extending between the movable part and the support structure.

According to a third aspect of the present invention, there is provided an actuator assembly for an electronic apparatus, comprising: a support structure; a movable part movable relative to the support structure; a shape memory alloy (SMA) actuator having at least one SMA wire connected between the movable part and the support structure, wherein the at least one SMA wire is configured to, on contraction, drive movement of the movable part; and a retaining means for retaining the movable part at the predetermined position to counteract acceleration in the electronic apparatus when the at least one SMA wire is not energised.

Optionally, the retaining means comprises one or more of a protrusion, a recess, a magnetic attachment, a high friction surface having a higher surface roughness or elasticity than other surfaces on the support structure or the movable part, a clamp and a bayonet mount.

According to a fourth aspect of the present invention, there is provided an actuator assembly for an electronic apparatus, comprising: a support structure; a movable part movable relative to the support structure, the movable part comprises a main body and an endstop resiliently connected to an end of the main body; and a shape memory alloy (SMA) actuator having at least one SMA wire connected between the end stop of the movable part and the support structure, wherein the at least one SMA wire is configured to, on contraction, drive movement in the movable part; wherein, upon ceasing energy supply to the SMA actuator, the end stop is configured to bias against the support structure by the resilient connection, so as to reduce movement in the movable part and, upon contraction, the SMA wire draws the end stop towards the main body and thereby allows movement in the movable part.

In other words, the resiliently loaded end stop may serve as a retaining means. For example, when the SMA actuator is unenergized, e.g. when the SMA wire has a degree of slack, the resilient connection between the end stop and the main body of the movable part is configured to exert a biasing force against the support structure to retain it in place. Upon energising, the SMA wire may configure to tension and thereby overcome the biasing force of the resilient connection to move both the end stop and the main body in unison.

Advantageously, such an arrangement may allow the retaining means to engage automatically, e.g., the movable element may be supported by an energised SMA wire during contraction, or it may be suspended by the end stop when the SMA wire is not energised.

Optionally, the end stop is integrally formed with the main body and configured to pivot about the resilient connection. Advantageously, such an arrangement may simplify the manufacturing process. In some other cases, the endstop and the main body may be discretely formed and bridged by a resilient element. Advantageously, such an arrangement may allow the resilience of the resilient element to be fine-tuned and thus does not have to possess the same elastic properties as the main body and the endstop.

Features from any aspect of the present invention may be combined with features from any other aspects.

Brief Description of the Drawings

Certain embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 is an exploded view of SMA actuator wire arrangements in a camera according to a reference embodiment;

Figures 2A and 2B are flow diagrams illustrating methods of controlling an SMA actuator assembly according to embodiments of the present invention;

Figures 3A and 3B are respective plan and side sectional views of an SMA actuator according to a first embodiment of the present invention;

Figures 4A and 4B are respective plan and side sectional views of an SMA actuator according to a second embodiment of the present invention;

Figures 5A and 5B are respective plan and side sectional views of an SMA actuator according to a third embodiment of the present invention;

Figures 6A and 6B are respective plan and side sectional views of an SMA actuator according to a fourth embodiment of the present invention; Figures 7A and 7B are respective plan and side sectional views of an SMA actuator according to a fifth embodiment of the present invention;

Figures 7C and 7D are respective side sectional views of an SMA actuator in a first position and second position according to a sixth embodiment of the present invention;

Figures 7E and 7F are respective side sectional views of an SMA actuator in a first position and second position according to a seventh embodiment of the present invention;

Figures 8A and 8B are respective side sectional views of an SMA actuator in a first position and second position according to an eighth embodiment of the present invention;

Figures 9A and 9B are respective side sectional views of an SMA actuator in a first position and second position according to a ninth embodiment of the present invention;

Figures 10A and 10B are respective plan and side sectional views of an SMA actuator according to a tenth embodiment of the present invention;

Figures 10C and 10D are respective plan and side sectional views of an SMA actuator according to an eleventh embodiment of the present invention;

Figures 11A and 11B are respective plan and side sectional views of an SMA actuator according to a twelfth embodiment of the present invention;

Figures 12A and 12B are respective plan and side sectional views of an SMA actuator according to a thirteenth embodiment of the present invention;

Figures 13A and 13B are respective plan and side sectional views of an SMA actuator according to a fourteenth embodiment of the present invention; Figure 14A is a plan sectional view of an SMA actuator of a fifteenth embodiment of the present invention; and

Figures 14B and 14C are respective side sectional views of the SMA actuator of Fig. 14A in a first position and a second position.

Detailed Description

Figure 1 shows an exploded view of a shape memory alloy (SMA) actuator wire arrangement 10 or actuator apparatus in a miniature camera according to a reference embodiment. The SMA actuator arrangement 10 includes a support structure 5, that comprises a base 11 that is an integrated chassis and sensor bracket for mounting an image sensor, and a screening can 12 attached to the base 11. The SMA actuator arrangement 10 includes a movable part 6, that is a camera lens assembly comprising a lens carriage 13 carrying at least one lens (not shown).

In this example, the actuator 10 includes eight SMA wires 2 each attached between the support structure 5 and the movable part 6. A pair of SMA wires 2 that cross each other are provided on each of four sides of the SMA actuator arrangement 10 as viewed along an optical axis, along a first direction. The SMA wires 2 are attached to the static part 5 and the moving part 6 in such a configuration that upon heating, they contract and thereby provide relative movement of the moving part 5 with multiple degrees of freedom. Such an arrangement enables a miniature camera to provide both autofocus (AF) and optical image stabilisation (OIS) during an active mode, i.e. when the image sensor of the miniature camera is enabled.

Thus, in respect of each pair of SMA wires 2, the SMA wires 2 are attached at one end to two static mount portions 15, which are themselves mounted to the static part 5 for attaching the SMA wires 2 to the static part 5. The static mount portions 15 are adjacent one another but are separated to allow them to be at different electrical potentials. Similarly, in respect of each pair of SMA wires 2, the SMA wires 2 are attached at one end to a moving mount portion 16 which is itself mounted to the moving part 6 for attaching the SMA wires 2 to the moving part 6. The moving part 6 further comprises a conductive ring 17 connected to each of the moving mount portions 16 for electrically connecting the SMA wires 2 together at the moving part 6.

The static mount portions 15 and the moving mount portions 16 comprise crimp tabs 23 which may be formed into crimps and used to hold the SMA wires 2. The moving mount portions 16 may comprise electrical connection tabs 31 for providing electrical connection to the conductive ring 17. Thus, in the example shown in Figure 1, the crimp tabs 23 that are formed into crimps are integral parts of the static and moving portions of the actuator arrangement 10. Methods for forming the crimps and trapping the SMA wires within the crimp tabs 23 are described in International Patent Publication No. WO2016/189314.

In practice, when the SMA wires 2 are unenergized, i.e. when the SMA actuator 10 is powered off, they may no longer be under tension. In some cases, a degree of slack may be observed in the unenergized SMA wires 2. This may cause free movement in the SMA wires, and in some cases in the lens carriage. Such free movement causes the SMA wires to contact and rub over each other, leading to abrasion and wear of the wire.

The miniature camera is also operable in a standby mode. During the standby mode, a key function of the miniature camera, such as image sensing, is turned off. However, during the standby mode, the actuator assembly may remain functional, e.g. the SMA wires remain actuatable to apply a force on the lens carriage. As such, by actuating one or more of the SMA wires, the actuator is configured to actively counteract against movement in the camera during the standby mode.

Figure 2A shows a process flow diagram illustrating one of the methods for controlling an actuator assembly according to the present invention. In a standby mode, a controller of the camera receives a signal indicating movement in the electronic apparatus (100). The signal may be indicative of one or more of magnitude, direction and frequency of the said movement. The signal may be generated by a sensor such as an accelerometer and/or a gyroscope of the camera, e.g. the sensor may be used by other components of the camera. Or the accelerometer and/or the gyroscope may form part of the actuator assembly. Alternatively, the signal may be a signal indicating onset of movement in the camera. In this case, the signal may be a drive signal to activating an auxiliary actuator such as a haptic assembly, a vibration motor or a speaker.

In response to the signal, the controller generates a drive signal to cause contraction in one or more SMA wires (200). The degree of contraction in each of the SMA wires may be based on the characteristics of the detected movement (e.g. magnitude, direction and frequency) in the camera. This causes the lens carriage to move (300) in an opposite direction, at a magnitude and frequency matching, or at least similar to, the detected movement or acceleration. Therefore, such an arrangement actively counteracts the movement or acceleration in the camera by dampening or stabilising the lens carriage.

In some embodiments, the drive signal may not cause movement or acceleration in the lens carriage, it may merely tension up the SMA wires to remove the slack therein. This causes a significant reduction in free movement in the lens carriage. In particular, such tensioning may occur continuously when the camera is put into the standby mode.

Alternatively, the drive signal may cause the lens carriage to move and/or be retained at a predetermined position at which the lens carriage is less susceptible to collision with the support structure and/or other parts of the camera. The lens carriage may stay at the predetermined position after the movement or acceleration in the camera has subsided. As such, the lens carriage is said to be put into a "safe" position.

In particular, as illustrated in Figure 2B, the lens carriage may be driven to the "safe" position as soon as the miniature camera is put into a standby mode, or when the miniature camera is being switched off.

Figures 3A and 3B are respective plan view and side view of an SMA actuator 310 according to a first embodiment of the present invention. In the illustrated embodiment, the lens carriage 6 has been put into a predetermined position in response to a signal indicating movement in the device. The predetermined position is a centred position, at which the lens carriage 6 is positioned at substantially mid-points of movement range along the x, y and z axes. In this centred position the lens carriage is positioned furthest away from the support structure 5 and other parts of the actuator assembly, e.g. a screening can, thus providing significant clearance therebetween and reducing the risk of collision.

Figure 4A and 4B are respective plan view and side view of an SMA actuator 410 according to a second embodiment of the present invention. In this embodiment, the lens carriage 6 has been put into a predetermined position in response to a signal indicating movement in the device. In this position, the lens carriage 6 is at least contacting the side surface of the support structure 5. By putting the two parts in close proximity to each other, the energy imparted by a collision therebetween reduces significantly, and thereby the risk of damage resulting from collision reduces accordingly.

Figure 5A and 5B are respective plan view and side view of an SMA actuator 510 according to a third embodiment of the present invention. In this embodiment, the lens carriage 6 is contacting at least a base of the support structure 5 in the predetermined position. Since there exists minimal clearance between the two parts, the energy imparted by a collision therebetween reduces significantly, and thereby the risk of damage resulting from collision reduces accordingly.

In some other embodiments, the lens carriage 6 may contact both the sidewall and the base of the support structure 5 in the predetermined position. For example, the lens carriage 6 may recede into a corner of the support structure 5.

Figure 6A and 6B are respective plan and side views of an SMA actuator 610 according to a fourth embodiment of the present invention. In this embodiment, the lens carriage 6 is provided with a pair of magnets 50 in its peripheral regions. The magnets 50 are configured to cause the lens carriage 6 to be attracted onto a metallic portion of the support structure 5 when the two come into close proximity with each other, e.g. once lens carriage 6 has been put into the position by the actuator as shown in Figures 5A and 5B. In some cases, the actuator may not need to move the lens carriage 6 towards the magnets 50 to form the attachment. That is, the lens carriage 6 may fall into position by gravity. Alternatively, the magnets may be configured to cause the lens carriage 6 to be attracted onto a sidewall of support structure 5, e.g. once lens carriage 6 has been put into the position by the actuator as shown in Figures 4A and 4B. Advantageously, this allows the lens carriage 6 to be retained on the surface of the support structure more effectively. Furthermore, the attraction force may cause the lens carriage to be retained thereon even after the power supplied to the actuator has ceased. The attraction force may be overcome by the actuator once the camera is put into the active mode, e.g. the attractive force may not affect the movement of the lens carriage when the camera is operating in full functionality. Ideally the magnets are located on the lens carriage, thus during the active mode it does not cause magnetic interference to the image sensor. However, they can be placed onto other components in the camera, such as the support structure, or a screening/shielding can where the magnet may be configured to repel the lens carriage towards the support structure.

In Figure 6B, the SMA actuator 610 further comprises a plurality of ridges 52 on the supporting structure 5 each complementing a corresponding groove 52 provided on the base of the lens carriage 6. Thus, when the lens carriage 6 is magnetically biased toward the support structure 5, movement lateral to the optical axis is significantly limited, or is prevented altogether.

Figure 7A and 7B are respective plan and side views of an SMA actuator 710 according to a fifth embodiment of the present invention. In this embodiment, the support structure 5 comprises one or more recesses 54 in the form of grooves extending along its surface. The one or more recesses 54 may also be provided on the adjacent surfaces of the lens carriage 6. In some embodiments, one or more protrusions may be provided on the support structure in compliance with the surface profile of the lens carriage. Such an arrangement increases friction between the lens carriage 6 and the support structure 5, thereby reducing the amount of lateral movement in the lens carriage when it is put into a position as shown in Figures 7A and 7B. Figures 7C and 7D are side sectional views of an SMA actuator according to a sixth embodiment of the present invention in a first position and a second position, respectively. More specifically, in Figure 7C the lens carriage 6 is movable by the SMA actuator in an unrestricted manner, wherein in Figure 7D the lens carriage is being put into a predetermined position, e.g. the "safe" position, to counteract a lateral movement. As shown, the base of the lens carriage 6 comprises a dome shaped protrusion 55 which fits into a recess 54 on the support structure 5. This may allow the dome shaped protrusion 55 and the recess 7 to align more readily. In the second position, such dome shaped protrusion 54 forms the only contact point between the lens carriage 6 and the support structure 5. That is, the base of the lens carriage 6 is free from the support structure 5.

Figures 7E and 7F are side sectional views of an SMA actuator according to a seventh embodiment of the present invention in a first position and a second position, respectively. The SMA actuator is structurally and functionally similar to the sixth embodiment as shown in Figure 7C and 7D, the only difference being the protrusion 54 in Figures 7E and 7F is a rod-shaped protrusion. Such an arrangement may provide a stronger safeguard against slippage between the lens carriage 6 and the support structure 5.

Figures 8A and 8B are side sectional views of an SMA actuator 810 according to an eighth embodiment of the present invention in a first position and a second position, respectively. In this embodiment, a sprung clamp 56 extending underneath the lens carriage 6 is configured to bias the lens carriage 6 against the support structure 5, e.g. via a screen can. Therefore, once the power supply to the SMA actuator ceases and the SMA wires are no longer taut, the lens carriage 6 is pushed to and kept in place at the screen can by the sprung clamp 56. During the active mode, the contraction in the SMA wires overcomes the biasing force and thereby causes movement in the lens carriage 6.

Figures 9A and 9B are side sectional views of an SMA actuator 910 according to a ninth embodiment of the present invention in a first position and a second position, respectively. Similar to the embodiment as shown in Figures 8A and 8B, the SMA actuator 910 relies on a clamp 58 to drive and retain the lens carriage 6 at a predetermined position. More specifically, once the power supply to the SMA actuator ceases and the SMA wires are no longer taut, the lens carriage 6 is pushed to and kept in place at the screening can by the clamp 58. In this embodiment, the clamp 58 is actuated by an actuator, thus the clamp may engage or disengage by controlling the actuator. In some embodiments, such an actuator may have a second function, i.e. in addition to the clamping. For example, such an actuator may be for controlling a camera iris. In other embodiments, the clamp 58 may be spring loaded similar to the spring clamp 56 as shown in Figures 8A and 8B.

Figures 10A and 10B are respective plan and side sectional views of an SMA actuator 1010 according to a tenth embodiment of the present invention. In this embodiment, the base of the lens carriage 6 has a protruded portion at its peripheral region. As shown in Figures 10A and 10B, a shock absorbing coating 60 is provided on the surface of the support structure 5 adjacent to the top edge, side wall, and the protruded portion of the lens carriage 6. The shock absorbing coating 60 is formed from an elastic material, and is configured to absorb an impact between the support structure 5 and the protruded portion of the lens carriage 6. In some other embodiments, the shock absorbing coating may be formed from a deformable material such as a solid foam or a viscoelastic polymer. The shock absorbing coating may alternatively be provided on the lens carriage, as shown in the SMA actuator 1010 of Figures 10C and 10D, or on the adjacent surfaces on both the lens carriage 6 and the support structure 5.

Figures 11A and 11B are respective plan and side sectional views of an SMA actuator according to a twelfth embodiment of the present invention. In this embodiment, the lens carriage 6 is provided with a volume of damping gel 62 as a shock absorber. More specifically, a volume of damping gel 62a is provided in, and arranged to protrude from a recess along the top surface of the lens carriage 6 adjacent to the screening can 12. In addition, another volume of damping gel 62b is positioned between a protruding portion at the base of the lens carriage 6 and an adjacent recess on the support structure 5. The damping gel 62 may be a viscous fluid that deforms upon compression, thereby absorbing an impact between the lens carriage 6 and the support structure 5.

In some embodiments, the lens carriage 6 may be biased, by a biasing element, towards a central position within its range of movement, in a manner similar to Figures 3A and 3B. This is illustrated in Figures 12A and 12B where respective plan and side sectional views of an SMA actuator 1210 according to a thirteenth embodiment of the present invention are shown. In this embodiment, a resilient diaphragm 64 overlays and extends between the lens carriage 6 and the support structure 5. The resilient diaphragm 64 may be a rubber skirt that resists movement away from the centred position. In some other embodiments, one or more resilient members may extend, in a direction orthogonal to the optical axis, between the lens carriage 6 and the support structure 5 in lieu of the resilient diaphragm 64.

Figures 13A and 13B are respective plan and side sectional views of an SMA actuator according to a fourteenth embodiment of the present invention. In this embodiment, a pair of opposing flexures 66 extends between adjacent sides of the lens carriage 6 and the support structure 5. The flexures 66, as illustrated, each having a U-shaped profile resembling a hairpin. Such design may allow the flexures 66 to exert a significant biasing force on the lens carriage 6 towards a centre position only when the lens carriage 6 extends beyond a normal operating window. That is, such an arrangement ensures that the lens carriage 66 can move freely in its normal operating envelope whilst stopping it moving before exceeding the allowable strain in the SMA wires or coming into contact with the support structure 5. In addition to restraining lateral movements of the lens carriage 6, the flexures 66 may also restrain the lens carriage 6 against the axial movement beyond the normal operating envelope.

Figure 14A is a plan sectional view of an SMA actuator 1410 according to a fifteenth embodiment of the present invention, and Figures 14A and 14B are side sectional views of this SMA actuator 1410 across the plane A in Figure 14A, with the SMA actuator 1410 in a first position and second position, respectively. The SMA actuator 1410 comprises a lens carriage 6 having a main body 6a resiliently connected to an end stop 6b by a bridge connection 6c. Thus, the end stop 6b is pivotable about the bridge connection 6c. The one or more lenses are positioned within the main body 6a.

As shown in Figures 14B and 14C, SMA wires 2 are arranged to extend between the stationary crimps 15 attached to the support structure 5 and the movable crimp 16 attached to the end stop 6b. Thus, on contraction, the SMA wires 2 rotate the ends stop 6b towards the main body 6a until the two components make contact at their respective edges 6d, as illustrated in Figure 14B. Further contraction in the SMA wires 2 causes both the end stop 6b and the main body 6a to move in unison, thus effecting a controlled movement in the lens carriage 6.

The biasing force exerted by the bridge connection 6c is configured not to interfere with the operation of the SMA wires 2. In other words, the biasing force is insignificant in comparison with the force resulting from the contraction in the SMA wires 2.

Upon ceasing energy supply the SMA wires 2 cool and relax, as shown in Figure 14C. In other words, the SMA wires 2 can no longer restrain the end stop 6b and thus the bridge connection 6c biases the end stop 6b away from the main body 6a and towards the support structure 5 and the screening can 12. Thus, when the SMA actuator 1410 is inactive, the end stop 6b is configured to spring out and contact the support structure 5 and the screening can 12 at locations 68. Since the cooling, or extension, in SMA wires is gradual, such an arrangement may reduce the impact during contact.

Further, the bridge connection 6c continues to exert a biasing force against the support structure 5 and the screening can 12 once they have made contact at location 68. This allows the lens carriage 6 to be stabilised against sudden acceleration in the camera. Advantageously, such an arrangement allows the pivoting end stop to engage in an automatic manner.

In the illustrated embodiment, the end stop 6b and the main body 6a are two discretely formed components, whereby the bridge connection 6c comprises a resilient element, e.g. an elastic member, connected on a first side of the main body 6a and the end stop 6b. In some other embodiments, the main body 6a and the end stop 6b are integrally formed, e.g. the separation between the main body 6a and the end stop 6b may be produced by injection moulding or by machining.

The above-described SMA actuator assemblies comprise an SMA wire. The term 'shape memory alloy (SMA) wire' may refer to any element comprising SMA. The SMA wire may have any shape that is suitable for the purposes described herein. 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 pliant or, in other words, flexible. In some examples, when connected in a straight line between two elements, the SMA wire can apply only a tensile force which urges the two elements together. In other examples, the SMA wire may be bent around an element and can apply a force to the element as the SMA wire tends to straighten under tension. The SMA wire may be beam-like or rigid and may be able to apply different (e.g. non-tensile) forces to elements. The SMA wire may or may not include material(s) and/or component(s) that are not SMA. For example, the SMA wire may comprise a core of SMA and a coating of non-SMA material. Unless the context requires otherwise, the term 'SMA wire' may refer to any configuration of SMA wire acting as a single actuating element which, for example, can be individually controlled to produce a force on an element. For example, the SMA wire may comprise two or more portions of SMA wire that are arranged mechanically in parallel and/or in series. In some arrangements, the SMA wire may be part of a larger piece of SMA wire. Such a larger piece of SMA wire might comprise two or more parts that are individually controllable, thereby forming two or more SMA wires.

It will be appreciated that there may be many other variations of the abovedescribed examples.