Cambridge Mechatronics Limited

Richard Topliss

Andrew Benjamin David Brown

Thomas M Gregory

Anthony Hooley

Dominic George Webber

Robert John Leedham

David Charles William Richards

David Livingstone

Thomas Matthew Gregory

David Charles Wilson Richards

A camera apparatus capable of providing optical image stabilization comprises: a support structure; a camera unit comprising an image sensor and a lens system; a suspension system comprising a plurality of flexure elements supporting the camera unit on the support structure in a manner allowing the camera unit to tilt; and a plurality of SMA actuators. A sensor arrangement, whose output is used as the basis for generating drive signals, is mounted on the camera unit. A control circuit generates drive signals for the SMA actuators, by deriving closed-loop control signals representative of a desired degree of variation in the power of the drive signals from the output signals of the sensor arrangement without dependence on any measurement of the resistance of the SMA actuators, and generating the drive signals with powers that varies from a set-point power in correspondence with the closed-loop control signal.

Optical image stabilisation

A camera apparatus capable of providing optical image stabilization comprises: a support structure; a camera unit comprising an image sensor and a lens system; a suspension system comprising a plurality of flexure elements supporting the camera unit on the support structure in a manner allowing the camera unit to tilt; and a plurality of SMA actuators each formed as SMA wire connected between the camera unit and the support structure and arranged on contraction to drive tilting of the camera unit. The SMA wire may be fixed to the camera unit at its ends and hooked over an element of the support structure. A vibration sensor, whose output is used as the basis for generating drive signals, may be mounted on the camera unit.

Optical image stabilization comprising shape memory alloy actuators

An SMA actuation apparatus uses SMA actuator wires to move a movable element supported on a support structure, for example to provide optical image stabilization. Eight SMA actuator wires are arranged inclined with respect to a notional primary axis with a pair of the SMA actuator wires on each of four sides around the primary axis. The SMA actuators are connected so that on contraction two groups of four SMA actuator wires provide a force with a component in opposite directions along the primary axis, so that the groups are capable of providing movement along the primary axis. The SMA actuator wires of each group have 2-fold rotational symmetry about the primary axis, so that there are SMA actuator wires opposing each other that are capable of providing lateral movement or tilting.

SMA actuation apparatus

An SMA actuation apparatus comprises: an SMA actuator arranged to drive movement of a movable element; a current supply supplying a drive current; a detection circuit detecting a measure of the resistance of the SMA actuator; and a control unit operative to generate a closed-loop control signal supplied to current supply for controlling the power of the drive current to drive the resistance of the SMA actuator to a target value. The control unit derives: an estimate of a characteristic temperature of the SMA actuation apparatus on the basis of the supplied power, using a thermal model; and a resistance offset on the basis thereof. The closed-loop control signal is generated on the basis of the error between the measure of the resistance of the SMA actuator and the target value of the resistance of the SMA actuator, adjusted by the resistance offset to compensate for variations in resistance.

Control of a shape memory alloy actuation arrangement

An SMA actuation apparatus comprises a camera lens element supported on a support structure by a plurality of flexures. An SMA wire at an acute angle to the movement axis and a biasing element are connected between the support structure and the movable element. A component of the force applied by the SMA wire perpendicular to the movement axis compresses the flexures causing them to apply a force to the movable element having a component along the movement axis in the same direction as the SMA wire. An end-stop limits the movement of the movable element, and the moment applied by the end-stop to the movable element about the center of stiffness is equal to the moment applied by the SMA wire about the center of stiffness at the point when the movable element loses contact with the end-stop on contraction of the SMA wire.

Shape memory alloy actuation apparatus

A miniature camera lens actuation apparatus employs an SMA actuator comprising SMA wire to move a camera lens element. To provide autofocus, the SMA actuator is heated across its range of contraction and the resistance at which the focus is at an acceptable level is stored. To combat hysteresis, there is performed a flyback in which the SMA actuator is cooled, before heating the SMA actuator to the stored resistance. The stored resistance is adjusted to combat creep caused by non-linear heating of the SMA actuator. The SMA wire has conductive material extending along on a portion of the SMA wire which extends from a member connected to the SMA wire and being in electrical connection with the SMA wire in order to short out that portion of the SMA wire to reduce creep. Additional material is applied over the SMA wire and the member to reduce fatigue.

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Trumpington, United Kingdom

Richard Topliss