Patent ID: 7203951

Claim:
An optical head device comprising: a lens holder including an objective lens mounted thereon, the lens including an optical axis; a first driving force generating unit including: a first coil unit held on of a first side surface of the lens holder, and a first magnet facing the first coil unit, and configured to generate a first driving force and either (1) a second driving force different from the first driving force or (2) a first moment based on the second driving force; and a second driving force generating unit including: a second coil unit held on a second side surface of the lens holder opposing the first side surface, and a second magnet facing the second coil unit and configured to generate a third driving force and either (1) a fourth driving force or (2) a second moment for canceling the second driving force or the moment generated by the first driving force generating unit, wherein the first and second magnets are multi-polarized and magnetic poles of at least one of the first and second magnets are asymmetrical about a plane taken at a midpoint of the at least one magnet, orthogonal to the optical axis, and which pierces multiple poles of the at least one magnet, and wherein each of the first and second coil units includes at least one focus coil and at least two tracking coils arranged such that the focus coil and the at least two tracking coils in the first coil unit are symmetrically disposed in relation to the focus coil and the at least two tracking coils in the second coil unit, respectively, about a plane including the optical axis and orthogonal to an axis of one of the focus coils.