US Patent 7576931 Driving unit for optical pick-up including lens

A lens driving unit includes a lead screw, a nut having a projection, and a lens frame having a contact portion that is supported movably in the direction of an optical axis with respect to a base and that is brought into contact with the nut. The nut is held so that only an end face thereof in the direction of the optical axis comes into contact with the lens frame. The base has a guide groove that receives and guides the projection in the direction of the optical axis. The base or the lens frame has a regulatory wall that directs and guides the projection of the nut screwed to the lead screw toward the guide groove only during assembly.