SMA actuators for optical image stabilisation
Broadly speaking, embodiments of the present techniques provide shape memory alloy (SMA) actuation apparatus for moving a moveable component relative to a static component or support structure and along a notional primary axis. The SMA actuation apparatus may comprise a biasing element to resist motion of the moveable component in particular directions relative to the primary axis, or may comprise an arrangement of SMA actuator wires that provides the biasing function.
1 . A shape memory alloy (SMA) actuation apparatus comprising:
a support structure;
a moveable component moveable relative to the support structure;
at least four SMA actuator wires connected between the moveable component and the support structure and arranged to move the moveable component relative the support structure; and
a biasing element to resist translation of the moveable component in a plane perpendicular to a notional primary axis, wherein:
the SMA actuator wires are configured to only exert a force on the moveable component along an x axis and/or a y axis;
the x and y axes are perpendicular to the primary axis; and
the combination of the biasing element and the force exerted by the SMA actuator wires cause the moveable component to tilt about the x axis and/or the y axis.
2 . The SMA actuation apparatus as claimed in claim 1 , wherein the biasing element further resists rotation of the moveable component about the primary axis.
3 . The SMA actuation apparatus as claimed in claim 1 , wherein the moveable component is a camera lens, and wherein the primary axis is the optical axis of the camera lens.
4 . The SMA actuation apparatus as claimed in claim 3 , wherein the camera lens has a diameter of at most 20 mm.
5 . The SMA actuation apparatus as claimed in claim 3 , wherein the camera lens is a compound lens or a telephoto lens.
6 . The SMA actuation apparatus as claimed in claim 1 , wherein the moveable component is a camera unit comprising an image sensor and a camera lens arranged to focus light on the image sensor, and wherein the primary axis is the optical axis of the camera lens.
7 . The SMA actuation apparatus as claimed in claim 1 , wherein each SMA actuator wire is inclined with respect to the primary axis.
8 . The SMA actuation apparatus as claimed in claim 1 , wherein each SMA actuator wire is parallel to the plane perpendicular to the primary axis.
9 . The SMA actuation apparatus as claimed in claim 1 , wherein each SMA actuator wire is tangential to a side of the moveable component.
10 . The SMA actuation apparatus as claimed in claim 1 , wherein one SMA actuator wire of the at least four SMA actuator wires is provided on each side of the moveable component.
11 . The SMA actuation apparatus as claimed in claim 1 , wherein two SMA actuator wires are provided on two opposite sides of the moveable component, and optionally wherein, on each side, the two SMA actuator wires are parallel to one another or are inclined in opposite senses with respect to each other and cross.
12 . The SMA actuation apparatus as claimed in claim 1 , wherein the biasing element comprises at least one flexure.
13 . The SMA actuation apparatus as claimed in claim 12 , wherein:
the flexure is provided around the centre of the moveable component and is parallel to the plane perpendicular to the primary axis; or
the flexure is provided above or below the moveable component parallel to the plane perpendicular to the primary axis; or
the at least one flexure comprises a first flexure above the moveable component and a second flexure below the moveable component, where both the first and second flexures are parallel to the plane perpendicular to the primary axis, preferably wherein one of the first flexure and the second flexure is stiffer than the other of the first flexure and second flexure.
14 . The SMA actuation apparatus as claimed in claim 12 , wherein the flexure comprises one or more flexure arms.