Optical image stabilization comprising shape memory alloy actuators
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.
1. A camera apparatus comprising:
a support structure;
a camera unit comprising an image sensor and a lens system for focussing an image on the image sensor;
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 around two notional axes that are perpendicular to each other and to the optical axis of the lens system on deflection of the flexure elements; and
a plurality of SMA actuator wires each connected between the camera unit and the support structure and arranged on contraction to drive tilting of the camera unit.
2. A camera apparatus according to claim 1 , wherein the SMA actuator wires each comprise a piece of SMA wire fixed at both ends to one of the camera unit and the support structure and intermediate its ends hooked over a portion of a respective flexure element that is connected to the other one of the camera unit and the support structure, the SMA actuator wires being arranged on contraction to drive tilting of the camera unit, the resultant deflection of the flexure elements providing a biassing force reacting against the SMA actuator wire.
3. An apparatus according to claim 1 , wherein said resultant deflection of the flexure elements provides the sole biassing force reacting against the SMA actuator wire.
4. An apparatus according to claim 2 , wherein said one of the camera unit and the support structure is the support structure and said other one of the camera unit and the support structure is the camera unit.
5. A camera apparatus according to claim 1 , further comprising a biassing element, separate from the suspension system, that provides a biassing force reacting against the SMA actuator wire on contraction of the SMA actuator wire.
6. An apparatus according to claim 5 , wherein the SMA actuator wires are arranged at different positions spaced evenly around the optical axis.
7. An apparatus according to claim 6 comprising four SMA actuator wires.
8. An apparatus according to claim 2 , wherein the flexure elements each comprise a pair of flexure beams extending from an intermediate portion that is connected to said other one of the camera unit and the support structure to portions that are connected to said one of the camera unit and the support structure, the pieces of SMA wire being hooked over the intermediate portion.
9. An apparatus according to claim 8 , wherein the intermediate portion protrudes away from the flexure beams along the optical axis.
10. An apparatus according to claim 8 , wherein the flexure elements are formed integrally.
11. An apparatus according to claim 8 , wherein the flexure elements are each a shaped sheet of material.
12. An apparatus according to claim 2 , wherein each piece of SMA wire extends between the one of the camera unit and the support structure and portion of a respective flexure element that is connected to the other one of the camera unit and the support structure perpendicular to a notional line radial of the optical axis.
13. An apparatus according to claim 12 , wherein the piece of SMA wire extends at a non-zero angle to the optical axis.
14. An apparatus according to claim 2 , further comprising a biassing element, separate from the suspension system, that provides a biassing force reacting against the SMA actuator wire on contraction of the SMA actuator wire.