TECHNICAL FIELD

The present disclosure relates in general to actuators for mobile cameras, in particular to actuators for producing a rotary movement. The rotary movement may specifically be used to move one or more optical elements of a lens of a mobile camera. To this end, the present disclosure provides an actuator assembly, which is based on a shape memory alloy (SMA) element.

BACKGROUND

Cameras are widely integrated into an increasing number of electronic devices, in particular into handheld devices such as mobile terminals and action cameras. The cameras may incorporate telephoto lenses and/or multiple lens groups in a single device. Therefore, advanced optomechanics structures, including long-range tele-centric lenses and optical zoom architectures, are employed. For integrating these advanced optomechanics structures inside the electronic devices, optical element manipulation on a very small scale, for instance, from a few to several millimeters is required.

Moreover, the size of the cameras is an important factor due to limited space inside those electronic devices. In this regard, tunable lenses (e.g., lenses known as gel or liquid based lenses) may be used. These tunable lenses have the advantage that they are thin and compact.

SUMMARY

In a conventional approach, stepper motors are used to manipulate optical elements such as lenses. The stepper motors can generate a high-speed and low-torque rotational motion, which is converted into a translational movement by using different transmission elements such as leadscrews, racks and pinions, and planetary gearboxes. In another conventional approach, a voice coil motor (VCM) is used to move optical elements inside a camera module. The VCM utilizes a magnet and yoke in conjunction with a coil that surrounds the lens and generates a VCM force in proportion to an input current. Positions of the optical elements can be adjusted by using the generated VCM force.

In another conventional approach, piezoelectric ultrasonic actuators (also known as piezo actuators) are used. Piezo actuators can generate ultrasonic vibrations with micrometerscale amplitude in a controlled manner, to move lenses inside a camera module. In particular, a Smooth Impact Drive Mechanism (SIDM) based piezo actuator uses a rapidly expanding/contracting piezo element, which is attached to a shaft having a compressional gripper mounted. Fast expansion and slow contraction (or vice versa) of the piezo element causes the gripper to move using slip-stick principle. Optical elements can be attached onto the gripper.

However, those conventional approaches do not meet the need of being thin and compact for integration into small electronic devices. In particular, quite a large space consumption is required for those conventional approaches. For example, stepper motors and VMCs both have a specific cylindrical form factor, length and diameter, which cannot be shrunk further to be accommodated into a more compact electronic device. Further, piezo actuators can cause severe, resonating noise demerits inside its mechanical camera package, which is normally a hollow, plastic casing structure. Further, for operating zoom lenses in one electronic device, more than one independent actuator may be needed, which requires an even larger space consumption and results in even worse noise demerits. Further, the piezo actuators are not suitable for operating tunable lenses. This is due to the fact that high forces, such as 200-300 mN or more, are typically needed.

In view of the above-mentioned problems and disadvantages of the conventional approaches, embodiments of the present disclosure aim to provide an improved actuator assembly for one or more camera lenses, with the objective to make the actuator assembly thin and compact for easy integration into even small electronic devices. In particular, the actuator assembly should exhibit a wire-free, flat shaped actuation architecture. The actuator assembly should be suitable for operating optical elements in a miniature (narrow and thin form factor) imaging system. Another goal is to reduce noise and cost of the actuator assembly. One aim is also to reduce assembly difficulties in manufacturing the actuator assembly.

These and other objectives are achieved by the embodiments of the disclosure as described in the enclosed independent claims. Further implementations of the embodiments of the disclosure are further defined in the dependent claims.

A concept underlying embodiments of the disclosure is to implement a core actuation element as a sequentially driven and sheet-based SMA, element, which may produce a reasonable torque on a connected drive shaft without additional mechanical torque converters or audible noises.

A first aspect of the disclosure provides an actuator assembly, in which the actuator assembly comprises a support structure, a drive shaft, and a sheet-based shape memory alloy, SMA, element. The SMA element comprises an actuation section, at least three energy supply sections each adapted to provide an electric potential, wherein the energy supply sections are arranged around the actuation section and are stationary with the support structure, and at least three arms each connecting one of the energy supply sections to the actuation section. The SMA element is configured such that a sequence of electric potentials provided clockwise or counterclockwise one by one to the energy supply sections arranged around the actuation section causes a loop-shaped movement of the actuation section. The drive shaft is coupled such to the actuation section that the loop-shaped movement of the actuation section is transformed into an axial rotation of the drive shaft.

In particular, the sheet-based SMA element may be a piece of a SMA sheet, i.e., of an SMA element having a sheet shape. Thereby, the sheet-based SMA element may be molded or cut from an SMA sheet, in order to form its shape, in particular, in order to form the actuation section, the energy supply sections, and the arms. Further, the actuation section may be located in a center area of the SMA element. The arms and the energy supply sections may be regularly (i.e. evenly or uniformly) arranged around the actuation section. The actuation section and the arms may be moveable relative to the support structure.

Notably, surfaces of the actuation section, of the energy supply sections, and of the arms may be arranged in a common plane of the sheet-based SMA element. The electric potentials, e.g. based on voltages, provided to the energy supply sections may cause the loop-shaped movement of the actuation section within the common plane of the sheetbased SMA element.

In this way, the actuator assembly may be constructed particularly thin and compact. Moreover, the actuator assembly may be well suited for miniature cameras. Further, the axial rotation of the drive shaft may be transformed from the loop-shaped movement in a particular silent way, thereby reducing noise generated by the actuator assembly.

Moreover, components of the actuator assembly may be relatively simple components, in comparison to the conventional approaches. Thus, the cost for manufacturing the actuator assembly may be reduced.

Optionally, the support structure may be adapted to provide one or more mechanical coupling interfaces. In particular, the energy supply sections may be rigidly fixed to the support structure through some of the mechanical coupling interfaces. Further, the actuator assembly may interact with one or more transmission elements and/or optical elements through some of the mechanical coupling interfaces.

Further, the support structure may be adapted to provide one or more electrical interfaces, so that the actuator assembly can be controlled by the electric potentials and/or external signals that may be provided through the electrical interfaces.

Further, the support structure may be adapted to provide mechanical and/or electrical protections to the sheet-based SMA element and the drive shaft. That is to say, the support structure may be liquid resistant and waterproof, and/or antistatic. In particular, the support structure may comprise a unibody structure. In this way, the sheet-based SMA element and the drive shaft may be protected from one or more of shock, liquid, dust, electrostatic discharge, and the like.

In an implementation form of the first aspect, the sequence of the electric potentials provided to the energy supply sections causes the arms corresponding to the energy supply sections to contract one after the other, thereby causing the loop-shaped movement of the actuation section. Notably, the SMA material used for manufacturing the SMA element may have a two-way shape memory. That is, the sheet-based SMA element may be a two-way memory sheetbased SMA element.

In another implementation form of the first aspect, an electrical resistance of each arm may be larger than an electrical resistance of the corresponding energy supply section and of the actuation section.

In particular, the arms may have higher aspect ratio (i. e. , a ratio of a longer/longest side to a shorter/shortest side) than the actuation section and/or each energy supply section. Alternatively, the arms may have longer length in average and/or a shorter width in average than those of the actuation section and/or of each energy supply section.

Notably, the actuation section may be ground-connected.

When the electric potential is provided to each energy supply section, an electric current may be generated to flow from each energy supply section via each corresponding arm to the (e.g., ground-connected) actuation section. Each corresponding arm may thereby generate heat, in particular more heat than each of the energy supply sections and the actuation section, due to the larger electrical resistance.

In particular, the provided electrical potential may be controlled such that only each corresponding arm may be heated beyond a transformation temperature of the SMA material. As a result, only each corresponding arm may contract. By contracting the arms in a sequence, the loop-shaped movement of the actuation section can be achieved.

In another implementation form of the first aspect, the actuation section may be coupled to an end of the drive shaft at a location that is off-centered with respect to an axis of rotation of the drive shaft.

In this way, the loop-shaped movement of the actuation section may be transformed into the axial rotation of the drive shaft. In another implementation form of the first aspect, the actuation section is coupled to the drive shaft by a cam knob arranged on an end of the drive shaft off-centered with respect to the axis of rotation of the drive shaft.

In another implementation form of the first aspect, each arm may have a curved structure.

In particular, the curved structure may be a zigzag shape, or a meandering shape, or a winding shape, or a serpentine shape, or the like.

In this way, the electrical resistance of each arm can be increased. Moreover, the curved structure may facilitate a contraction of each arm, and thus of generating the loop-shaped movement of the actuation section.

In another implementation form of the first aspect, the SMA element may comprise four energy supply sections, which are regularly arranged around the actuation section.

Accordingly, the SMA element may further comprise four arms. The four arms may connect the four energy supply sections to the actuation section in a one-to-one correspondence.

Optionally, the four energy supply sections may be located at four comers of the support structure.

In another implementation form of the first aspect, the support structure may comprise a housing that houses the SMA element. A side wall of the housing may comprise a circuit board, which comprises a set of contact pads for providing the electric potentials to the energy supply sections.

Optionally, the circuit board may comprise a further contact pad that may be adapted to provide an electrical ground connection to the actuation section.

In particular, the circuit board may be a printed circuit board. In this way, no external circuit board may be needed to control the actuation assembly, and space consumption may be reduced.

In another implementation form of the first aspect, the side wall of the housing may comprise an opening and a flexible printed circuit (FPC) arranged in the opening. The FPC may be connected to the SMA element to provide the electrical ground connection for the SMA element. The FPC may be moveable in the opening to allow the loop-shaped movement of the actuation section.

In particular, the FPC may be connected to the actuation section, so that the actuation section is ground-connected.

In another implementation form of the first aspect, the support structure may comprise a plurality of first rivets adapted to fix the energy supply sections to the housing and to connect the energy supply sections to the contact pads of the circuit board; and/or a second rivet adapted to connect the FPC to the actuation section.

In particular, the first rivets may be used to electrically connect the circuit board to the energy supply sections. Further, the first rivets may be electrically connected with the set of contact pads of the circuit board. The second rivet may be used to electrically connect the circuit board to the actuation section. Further, the second rivet may connected with the FPC and may be further connected to the further contact pad that provides the electrical ground connection.

In this way, no wire connection may be needed to provide electrical connections between the circuit board and the SMA element and thus, space consumption of the actuator assembly can be further reduced.

In another implementation form of the first aspect, the drive shaft may penetrate at least one side wall of the housing.

In this way, a penetrated end of the drive shaft may be adapted to provide connections to the one or more transmission elements and/or optical elements. Thus, the actuator assembly may be flexible for various application scenarios. In another implementation form of the first aspect, the loop-shaped movement is an elliptic, and in particular circular, movement.

Notably, the loop-shaped movement of the actuation section may be a substantially elliptic movement, and in particular, a substantially circular movement.

In another implementation form of the first aspect, the actuator assembly may comprise a first gear element and a first rack element. The first gear element may be mounted on the drive shaft and may be coupled to the first rack element. The first gear element may be adapted to convert the axial rotation of the drive shaft into a linear movement of the first rack element.

In particular, the first gear element may be rigidly mounted on the drive shaft so that no relative movement may exist between the drive shaft and the first gear element.

In another implementation form of the first aspect, the first gear element may comprise at least two sections, wherein the at least two sections have different tooth pitches.

In this way, an axial rotation with a fixed rotation velocity may be transformed into a linear movement with a variable velocity. Thus, a performance of a camera with the actuator assembly integrated may be enhanced. In particular, a focusing speed of the camera may be increased. Further, a speed of adjusting a focal length may also be increased.

In another implementation form of the first aspect, the actuator assembly may comprise one or more second gear elements and one or more second rack elements. The one or more second gear elements may be mounted on the drive shaft. Each of the second gear elements may be coupled to one of the second rack elements, and each second gear element may have one or more gear properties different than the first gear element.

In this way, the actuator assembly may support moving multiple lenses or multiple lens groups with a single actuator structure. In another implementation form of the first aspect, the actuator assembly may comprise a rotating screw and a nut. The rotating screw may be mounted on the drive shaft. The nut may be coupled to the rotating screw such that the nut and the rotating screw may be rotatable relative to another. The rotating screw may be adapted to convert the axial rotation of the drive shaft into a linear movement of the nut.

In particular, the rotating screw may be rigidly mounted onto the drive shaft. The support structure may comprise a stopping structure configured to stop the nut from rotating relative to the support structure. Thus, when the rotating screw rotates along with the axial rotation of the drive shaft, the coupled nut may be moved linearly along the axis of rotation of the drive shaft.

In this way, the linearly moving nut may be used to pump liquid inside a container via a rubber membrane or to deform an elastic optical element. Thus, the actuator assembly may be well suited for operating tunable lenses.

Moreover, a particularly thin and compact form factor of the actuator assembly may benefit in a lens integration and results in flat and compact camera module.

In another implementation form of the first aspect, the actuator assembly may comprise a bevel gear and a bevel gear wheel. The bevel gear may be mounted on the drive shaft. The bevel gear and the bevel gear wheel may be coupled to another, and the bevel gear may be adapted to convert the axial rotation of the drive shaft into a rotation of the bevel gear wheel.

In this way, the actuator assembly may support telescopically protruding camera optics.

A second aspect of the disclosure provides a camera module comprising a movable lens, and an actuator assembly according to the first aspect, or any of its implementation forms, in which the movable lens is movable by the axial rotation of the drive shaft of the actuator assembly.

A third aspect of the disclosure provides a method for operating an actuator assembly, in which the actuator assembly comprises a support structure, a drive shaft, and a sheet-based SMA element. The SMA element comprises an actuation section, at least three energy supply sections arranged around the actuation section and stationary with the support structure, and at least three arms each connecting one of the energy supply sections to the actuation section. The method comprises providing a sequence of electric potentials clockwise or counterclockwise one by one to the energy supply sections arranged around the actuation section, to cause a loop-shaped movement of the actuation section. The loopshaped movement of the actuation section is transformed into an axial rotation of the drive shaft.

A fourth aspect of the disclosure provides a method for actuating a camera module comprising a movable lens and an actuator assembly. The method comprises moving the movable lens by an axial rotation of the drive shaft caused by performing the method according to the third aspect with the actuator assembly.

BRIEF DESCRIPTION OF DRAWINGS

The above described aspects and implementation forms will be explained in the following description of specific embodiments in relation to the enclosed drawings.

FIG. 1 shows an exploded view illustrating an actuator assembly according to an embodiment of the disclosure.

FIG. 2A shows a schematic view of an actuator assembly according to an embodiment of the disclosure.

FIG. 2B shows a schematic view of a drive shaft according to an embodiment of the disclosure.

FIG. 3A-3D show a loop-shaped movement of an actuation section according to an embodiment of the disclosure.

FIG. 4 shows a schematic view of a SMA element according to an embodiment of the disclosure. FIG. 5 shows an exploded view illustrating an actuator assembly according to an embodiment of the disclosure.

FIG. 6A-6C show schematic views of an actuator assembly according to an embodiment of the disclosure.

FIG. 7A-7C show schematic views of an actuator assembly according to an embodiment of the disclosure.

FIG. 8A-8B show schematic views of an actuator assembly according to an embodiment of the disclosure.

FIG. 9A-9B show schematic views of an actuator assembly according to an embodiment of the disclosure applied to lens groups.

FIG. 10 shows a schematic view of a gear element and a rack element according to an embodiment of the disclosure.

FIG. 11 shows a schematic view of an actuator assembly according to an embodiment of the disclosure applied to lens groups.

FIG. 12A shows a schematic view of an actuator assembly according to an embodiment of the disclosure.

FIG. 12B shows a cutaway view of an actuator assembly according to an embodiment of the disclosure.

FIG. 13 shows a schematic view of an actuator assembly according to an embodiment of the disclosure applied to a tunable lens.

FIG. 14 shows a schematic view of an actuator assembly according to an embodiment of the disclosure.

FIG. 15 shows a method according to an embodiment of the disclosure. DETAILED DESCRIPTION OF EMBODIMENTS

Embodiments of the disclosure provide solutions to support a camera module that has a narrow and thin form factor. To this end, this disclosure proposes a wire-free, flat shaped actuation architecture for operating optical elements on miniature imaging systems. The proposed actuation architecture may further support moving two or more lenses or lens groups by a single drive shaft.

To this end, FIG. 1 schematically shows an exploded view illustrating an actuator assembly 1000 according to an embodiment of the disclosure. The actuator assembly 1000 is schematically shown in a (Cartesian) coordinate system formed by perpendicular x-, y-, and z-axes, as displayed in FIG. 1.

It is noted that units, components, assemblies, modules and/or devices of the disclosure depicted in the drawings (FIG. 1-14) are schematically shown in each (Cartesian) coordinate system formed by the perpendicular x-, and/or y-, and/or z-axes, as displayed in each drawing where applicable.

The actuator assembly 1000 comprises a support structure (not shown in FIG. 1), a drive shaft 1200, and a sheet-based SMA element 1100. The SMA element 1100 comprises an actuation section 1103, at least three energy supply sections 1101 (as an example four energy supply sections lOOla-d are shown in FIG. 1), and at least three arms 1102 (as an example four arms 1102a-d are shown in FIG. 1). Each energy supply section 1101 is adapted to provide an electric potential. The energy supply sections 1101 are arranged around the actuation section 1103 and are stationary with the support structure. Each arm

1102 is adapted to connect one of the energy supply sections 1101 to the actuation section

1103 (i.e., each energy supply section 1101 corresponds to one arm 1102). The SMA element 1100 is configured such that a sequence of electric potentials provided clockwise or counterclockwise one by one to the energy supply sections 1101 arranged around the actuation section 1103 causes a loop-shaped movement of the actuation section 1103.

Optionally, the sheet-based SMA element 1100 may be a piece (e.g., cut-out) of a SMA element having a sheet shape. In particular, the sheet-based SMA element 1100 may have a thin form factor. Further, the actuation section 1103, the energy supply sections 1101, and the arms 1102 of the SMA element 1100 may be formed by molding, erosion, cutting, 3D printing, or any other suitable means in the art to produce a SMA with a particular shape.

Optionally, the actuation section 1103 may be located in a center area of the SMA element 1100. The energy supply sections 1101 and the arms 1102 may be regularly (i.e. evenly or uniformly) arranged around the actuation section 1103. The actuation section 1103 and the arms 1102 may be moveable relative to the support structure. In particular, surfaces of the actuation section 1103, the energy supply sections 1101, and the arms 1102 may form a common plane of the sheet-based SMA element 1100. As depicted in FIG. 1, the common plane may be a plane formed by the perpendicular x- and y- axes. The electric potentials, i.e., voltages, provided to the energy supply sections 1101 may cause the loop-shaped movement of the actuation section 1103 within the common plane of the sheet-based SMA element.

Optionally, the actuation section 1103 may be ground-connected. Alternatively, the actuation section 1103 may comprise a ground connector 1104. As a result, when the electric potentials are provided to the energy supply sections 1101, electric currents are generated flowing along a path from the energy supply sections 1101, via the arms 1102, to the actuation section 1103.

In an embodiment of the disclosure, an electrical resistance of each arm 1102 may be larger than an electrical resistance of the corresponding energy supply section 1101 and of the actuation section 1103.

Optionally, each arm 1102 may have a higher aspect ratio (i.e., a ratio of a longer/longest side to a shorter/shortest side) than the corresponding energy supply section 1101 and the actuation section 1103 within the common plane of the sheet-based SMA element.

Optionally or alternatively, each arm 1102 may have a smaller thickness than the corresponding energy supply section 1101 and the actuation section 1103.

Optionally or alternatively, the arms 1102 may be produced by using a second SMA material, which is different from a first SMA material used to produce the energy supply sections 1101 and the actuation section 1103. The second SMA material may have a lower transformation temperature than that of the first SMA material. In this case, the energy supply sections 1101, the arms 1102, and the actuation section 1103 may be welded together correspondingly, in order to form the sheet-based SMA element 1100.

It is noted that holes depicted in the energy supply sections 1101 of the SMA element 1100 may be used to fix to the support structure. Further, the holes may be adapted to connect to electric components, from which the electric potentials are provided.

It is further noted that although a number of four energy supply sections 1 lOla-d and four arms 1102a-d are shown exemplarily in FIG. 1, this is not intended to limit the disclosure to the number of four energy supply sections and arms. The skilled person in the art understands that a minimum of three energy supply sections 1101 and three arms 1102 may be sufficient to cause the loop-shape movement of the actuation section 1103. The same applies to all other drawings where four energy supply sections HOla-d and four arms 1102a-d are also exemplarily depicted.

FIG. 2A shows an actuator assembly according to an embodiment of the disclosure. The actuator assembly 1000 builds on the actuator assembly 1000 shown in FIG. 1. Same elements in FIG. 1 and FIG. 2 share the same reference signs and functions likewise. The drive shaft 1200 is coupled such to the actuation section 1103 of the SMA element 1100 that the loop-shaped movement of the actuation section 1103 is transformed into an axial rotation of the drive shaft 1200.

In this way, the actuator assembly 1000 may have a thin form factor that is beneficial for a compact camera module, in particular, a miniature camera.

Optionally, a length of the drive shaft 1200 may be configurable. The length of the drive shaft 1200 may be adjusted based on transmission element(s) that is (are) attached onto the drive shaft 1200, which is described later in FIG. 7-14.

In an embodiment of the disclosure, preferably, the actuation section 1103 may be coupled to an end of the drive shaft 1200 at a location that is off-centered with respect to an axis of rotation of the drive shaft 1200. FIG. 2B shows the drive shaft 1200 of FIG. 1 from another point of view. The drive shaft 1200 may comprise a cam knob 1201 arranged on an end of the drive shaft 1200. The cam knob 1201 may be off-centered with respect to the axis of rotation of the drive shaft 1200.

In particular, the actuation section 1103 may be clamped onto the drive shaft 1200 by the cam knob 1201, as shown in FIG. 2 A.

FIG. 3A-3D shows the SMA element 1100 of the actuator assembly 1000 according to an embodiment of the disclosure. In particular, the sequence of FIG. 3A - 3B - 3C - 3D illustrates the generation of the loop-shaped movement of the actuation section 1103. Same elements in FIG. 3 and FIG. 1-2 share the same reference signs and functions likewise. In FIG. 3A-3D, the sequence of the electric potentials provided to the energy supply sections 1101 may cause the arms 1102 corresponding to the energy supply sections 1101 to contract one after the other, thereby causing the loop-shaped movement of the actuation section 1103.

It is noted that FIG. 3A-3D depict only the SMA element 1100 of the actuator assembly 1000 for the sake of simplicity and clarity. Furthermore, due to the point of view marked by the x- and y- axes in FIG. 3A-3D, the drive shaft 1200 may not be visible.

Using FIG. 3A as an illustration: at a first time slot, an electric potential may be provided to a first energy supply section 1101a. An electric current may be generated along a path from the first energy supply section 1101a, via a first arm 1102a, to the actuation section 1103. The first arm 1102a may generate heat, due to the electric current and it having a larger (or the largest) electrical resistance among the current path. The heat may activate the SMA material of the first arm 1102a and the SMA material may change from an austenite state to a martensite state in a form of contraction. That is to say, the first arm 1102a may be heated and thereby contract. Notably, although the electric current and the heat may also be generated on the first energy supply section 1101a and the actuation section 1103, the transformation temperature may not be reached for the first energy supply section 1101a and for the actuation section 1103 due to their smaller electrical resistances. In this way, the heated and contracted first arm 1102a may drag or pull the actuation section 1103 towards the first energy supply section 1101a, since the first energy supply section 1101a is stationary with the support structure.

Similarly, at a second time slot depicted in FIG. 3B, an electric potential may be only provided to the second energy supply section 1101b, so the first arm 1102a may cool down and restore to its original austenite state. In the meantime, a second arm 1102b may contract, and may drag or pull the actuation section 1103 towards a second energy supply section 1101b. Likewise, at a third time slot depicted in FIG. 3C, a third arm 1102c may drag or pull the actuation section 1103 towards a third energy supply section 1101c. At a fourth time slot depicted in FIG. 3D, a fourth arm 1102d may drag or pull the actuation section 1103 towards a fourth energy supply section 1 lOld.

Notably, the electric potentials may be provided repeatedly and consecutively according to the sequence described above. That is to say, an indefinite round of providing electrical potentials as depicted in FIG. 3A-3D may be achieved.

As such, a clockwise sequence of electric potentials provided one by one to the energy supply sections 1101 may cause a clockwise axial rotation of the drive shaft 1200. Similarly, a counterclockwise sequence of electric potentials provided one by one to the energy supply sections 1101 may cause a counterclockwise axial rotation of the drive shaft 1200. For example, a sequence of FIG. 3D - 3C- 3B - 3A forms one round of the counterclockwise sequence.

In an embodiment of the disclosure, the loop-shaped movement may be an elliptic, and in particular circular, movement.

In this way, the actuator assembly 1000 may be adapted to transform contractions of the SMA element 1100, in particular, the arms 1102, into the axial rotation of the drive shaft 1200 in a silent way. Therefore, noises generated by the actuator assembly may be reduced.

FIG. 4 shows a SMA element of an actuator assembly according to an embodiment of the disclosure. Same elements in FIG. 4 and FIG. 1-3 share the same reference signs and functions likewise.

Each arm 1102 may have a curved structure as depicted in FIG. 4. That is to say, each arm may be non-straight. In particular, the curved structure may be a structure with more abrupt changes or with smoother changes.

In particular, the curved structure may be a zigzag shape as depicted in FIG. 1, or may be a meandering shape, or may be a winding shape, or may be a serpentine shape as depicted in FIG. 4, or the like.

FIG. 5 shows an exploded view illustrating an actuator assembly according to an embodiment of the disclosure. Same elements in FIG. 5 and FIG. 1-4 share the same reference signs and functions likewise.

In this embodiment of the disclosure, the support structure may comprise a housing 1300 that houses the SMA element 1100. A side wall of the housing 1300 may comprise a circuit board 1301, which comprises a set of contact pads 1304 for providing the electric potentials to the energy supply sections. Moreover, the circuit may comprise a further contact pad adapted provide an electric ground connection. This further contact pad may be arranged along with the set of contact pads on the circuit board 1301.

Further, the side wall of the housing 1300 may comprises an opening 1302 and a flexible printed circuit (FPC) 1303 arranged in the opening 1302. The FPC 1303 may be connected to the SMA element 1100, in particular to the actuation section 1103, to provide an electrical ground connection. The FPC 1303 may be moveable in the opening to allow the loop-shaped movement of the actuation section.

Optionally, the FPC 1301 may be connected to the ground connector 1104 of the actuation section 1103.

Optionally, the actuator assembly may comprise a plurality of first rivets 1305. The first rivets 1305 may be adapted to fix the energy supply sections 1101 to the housing 1300. Further, the first rivets 1305 may be connected to a corresponding number of the contact pads 1304 in order to provide the electric potentials to the energy supply sections 1101. In particular, the first rivets 1305 may be connected to the circuit board 1301, and the circuit board 1301 may be adapted to provide electrical connections from the first rivets 1305 to the contact pads 1304. The corresponding number of the contact pads may be the same as a number of the energy supply sections 1101.

Optionally, the actuator assembly 1000 may comprise a second rivet 1306. The second rivet 1306 may be adapted to connect the FPC 1303 to the actuation section 1103. Further, the second rivet 1306 may be connected to one of the contact pads 1304 in order to provide the ground connection.

Optionally, the FPC 1301 may be connected to the ground connector 1104 of the actuation section 1103 by using the second rivet 1306.

In another implementation form, the drive shaft 1200 may penetrate at least one side wall of the housing 1300, in order to provide connections to various transmission movement elements.

FIG. 6A-6C show schematic views of an actuator assembly according to an embodiment of the disclosure from different points of view. Same elements in FIG. 6A-6C and FIG. 1- 5 share the same reference signs and functions likewise.

It is noted that a size of the actuator assembly 1000 may be configurable. The size of the actuator assembly 1000 may be determined based on a size of a camera module where the actuator assembly is assembled. Alternatively, the size of the actuator assembly may be determined based on a required torque that is generated by the actuator assembly 1000.

FIG. 7A-7C show schematic views of an actuator assembly according to an embodiment of the disclosure. Same elements in FIG. 7A-7C and FIG. 1-6 share the same reference signs and functions likewise.

In this embodiment of the disclosure, the actuator assembly 1000 may comprise a first gear element 1400 and a first rack element 1500 (only shown in FIG. 7C). The first gear element 1400 and the first rack element 1500 may be coupled to another. The first gear element 1400 may be rigidly mounted on the drive shaft 1200 and may be adapted to convert the axial rotation of the drive shaft 1200 into a linear movement of the first rack element 1500.

In particular, the first gear element may be a pinion gear. It is noted that for clearly showing the first rack element 1500, the SMA element is not displayed in FIG. 7C.

FIG. 8A-8B show schematic views of an actuator assembly according to an embodiment of the disclosure from different points of view. Same elements in FIG. 8A-8B and FIG. 1- 7 share the same reference signs and functions likewise.

In this embodiment of the disclosure, the SMA element 1100 may be housed inside the housing 1300. The drive shaft 1200 may penetrate a side wall of the housing 1300 and may be connected to the first gear element 1400 outside of the housing 1300. The first gear element 1400 may be further coupled to the first rack element 1500 (not shown in FIG. 8A- 8C).

FIG. 9A-9B show schematic views of an actuator assembly according to an embodiment of the disclosure applied to a camera module. Same elements in FIG. 9A-9B and FIG. 1-8 share the same reference signs and functions likewise.

In this exemplary embodiment of the disclosure, the camera module 2000 comprises a first lens group 2001a and a second lens group 2001b. A light path may be formed from the first lens group 2001a, via a second lens group 2001b, to an image sensor 2002. Each of the first lens group 2001a and the second lens group 2001b may be moved by each actuator assembly 1000.

It can be seen, in particular from FIG. 9B, that the actuator assembly 1000 is particularly thin and compact, so that the camera module 2000 may achieve a smaller size.

FIG. 10 shows a schematic view of a gear element and a rack element according to an embodiment of the disclosure.

In this embodiment of the disclosure, a variable-speed gear element 1600 that may be attached to the actuator assembly 1000 like the first gear element 1400. The variable-speed gear element may comprise at least two sections. Each section has different tooth pitches. As shown exemplarily in FIG. 10, the variable-speed gear element 1600 comprises three sections 1601, 1602 and 1603. A first section 1601 may comprise fine tooth pitches, i.e., with the smallest pitch length and/or tooth thickness among all tooth pitches of the three sections. A second section 1602 may comprise medium-fine tooth pitches. A third section 1603 may comprise coarse tooth pitches, i.e., with the largest pitch length and/or tooth thickness.

Further, a variable-speed rack element 1700 may be coupled to the variable-speed gear element 1600 and may be applied to the actuator assembly 1000 like the first rack element 1500.

In this way, the rotation of the drive shaft 1200 with a fixed rotational velocity may be transformed into a linear movement of the variable-speed rack element 1700 with a variable velocity.

FIG. 11 shows a schematic view of an actuator assembly according to an embodiment of the disclosure applied to a camera module. Same elements in FIG. 11 and FIG. 1-10 share the same reference signs and functions likewise.

In this embodiment of the disclosure, one or more second gear elements may be attached onto the drive shaft 1200. The one or more second gear elements may be coupled to one or more second rack elements in a one-to-one correspondence. The second gear elements may have different gear properties than the first gear element 1400 and/or between each other. In particular, the different gear properties may comprise different tip diameters, and/or different pitch diameters, and/or different tooth depths, and/or different numbers of gear teeth, and/or different center distances.

As shown exemplarily in FIG. 11, the actuator assembly 1000 is attached with two gear elements on the drive shaft 1200. The two gear elements and their corresponding rack elements may be adapted to move two lens groups 2001b, 2001c respectively. Optionally, the two gear elements may have different gear properties to move the two lens groups 2001b, 2001c at different speeds.

Optionally, the one or more second gear elements may comprise the variable-speed gear element 1600. In this way, the actuator assembly may use a single drive shaft, i.e., the drive shaft 1200, to drive multiple lens groups, as well as other additional optical elements such as a shutter, and/or a lens Iris. Thus, space consumption of the actuator assembly 1000 may be further reduced.

FIG. 12A shows a schematic of an actuator assembly according to an embodiment of the disclosure. FIG. 12B shows a cutaway view of the actuator assembly accordingly. Same elements in FIG. 12A-12B and FIG. 1-11 share the same reference signs and functions likewise.

In this embodiment of the disclosure, the actuator assembly 1000 may comprise a rotating screw 1701 and a nut 1702. The rotating screw 1701 may be mounted on the drive shaft 1200 as depicted in FIG. 12B. The nut 1702 may be coupled to the rotating screw 1701 such that the nut 1702 and the rotating screw 1701 may be rotatable relative to another. The rotating screw 1701 may be adapted to convert the axial rotation of the drive shaft into a linear movement of the nut 1702.

In particular, the rotating screw 1701 may be rigidly mounted onto the drive shaft 1200 so that the rotating screw 1701 and the drive shaft 1200 may not rotate relatively. The support structure may comprise a stopping structure 1307 adapted to stop the nut 1702 from rotating relative to the support structure. Thus, when the rotating screw 1701 rotates together with the axial rotation of the drive shaft 1200 relative to the support structure, the coupled nut 1702 may be screwed forwards or backwards along the rotating screw 1701, thereby resulting in a linear movement in a direction along the axis of rotation of the drive shaft 1200, as depicted in FIG. 12B.

FIG. 13 shows a schematic view of an actuator assembly according to an embodiment of the disclosure applied to a tunable lens. Same elements in FIG. 13 and FIG. 1-12 share the same reference signs and functions likewise.

In this embodiment of the disclosure, the actuator assembly 1000 with the rotating screw 1701 and the nut 1702 may be adapted to drive atunable lens 3000. The tunable lens 3000, e.g., a gel lens or a liquid lens, may be drilled with a hole on a top side and a bottom side, i.e., a top-side hole and a bottom-side hole. Each hole may be sealed with an elastic membrane 3001. A liquid may be injected into an inner chamber 3001 of the tunable lens 3000. When no pressure is applied to the elastic membrane 3001 on the top-side hole, an incident light may pass through the tunable lens 3000a unfocused from the bottom sidehole. When the nut 1702 is moved linearly by the actuator assembly 1000, the nut 1702 may apply an external pressure to the elastic membrane 3001 on the top-side hole and may cause the liquid to swell outward from the bottom-side hole. Thus, the elastic membrane sealed on the bottom side may deform and cause the incident light to focus from the bottomside hole.

In particular, variable rotation velocity of the drive shaft 1200 may produce various degrees of pressure on the tunable lens 3000, thereby achieving variable focusing results of the tunable lens 3000.

FIG. 14 shows a schematic view of an actuator assembly according to an embodiment of the disclosure.

In this embodiment of the disclosure, the actuator assembly 1000 may comprise a bevel gear 1800 and a bevel gear wheel 1900. The bevel gear and the bevel gear wheel may be coupled to another. The bevel gear 1800 may be mounted on the drive shaft 1200 may be adapted to convert the axial rotation of the drive shaft 1200 into a rotation of the bevel gear wheel 1800.

In this way, the actuator assembly 1000 may be suitable for operating telephoto lenses, such as optical elements of a telescopically protruding camera.

FIG. 15 shows a method 100 according to an embodiment of the disclosure. The method 100 is for operating the actuator assembly 1000. The method 100 comprises a step 101 of providing a sequence of electric potentials clockwise or counterclockwise one by one to the energy supply sections arranged around the actuation section, to cause a loop-shaped movement of the actuation section, in which the loop-shaped movement of the actuation section is transformed into an axial rotation of the drive shaft as a step 102.

It is noted that the steps of the method 100 may share the same functions and details from the perspective of the actuator assembly 1000 described above. Therefore, the corresponding method implementations 100 are not described again at this point.

The present disclosure has been described in conjunction with various embodiments as examples as well as implementations. However, other variations can be understood and effected by those persons skilled in the art and practicing the claimed disclosure, from the studies of the drawings, this disclosure and the independent claims. In the claims as well as in the description the word “comprising” does not exclude other elements or steps and the indefinite article “a” or “an” does not exclude a plurality. A single element or other unit may fulfill the functions of several entities or items recited in the claims. The mere fact that certain measures are recited in the mutual different dependent claims does not indicate that a combination of these measures cannot be used in an advantageous implementation.