Patent ID: 6870285

Claim:
A voice coil actuator comprising a first magnet having a length; a second magnet having a length; a first soft magnetic pole piece having a length greater than the length of the first magnet and the length of the second magnet, wherein the first and second magnets are positioned at different ends of the first soft magnetic pole piece and magnetized in opposite directions; a coil having a length less than the length of the first soft magnetic pole piece and positioned for travel along an axis common to the first soft magnetic pole piece and first and second magnets; and a structure which provides a magnetic path between free ends of the first and second magnets, and wherein the lengths of the first and second magnets and the first soft magnetic pole piece are selected to provide a force versus stroke characteristic in which a force is provided which is greater at one end of a stroke of the voice coil actuator and decreases to a lowest level at an other end of the stroke.