Objective lens driving device for tracking and focus corrections

Claim 1

In an objective lens driving device for correcting a relative positional error, i.e., a tracking error, between an information track recorded spirally or concentrically on a record medium and a reading-out light spot projected onto the record medium by means of the objective lens by moving the objective lens in a direction perpendicular to the optical axis of said objective lens and information track, the improvement which comprises: at least one set of objective lens driving means, each set including: an elongated movable member comprising a magnetic body movable together with the objective lens or a holding frame therefor; a stationary yoke extending in a direction which is substantially parallel with the moving direction of said movable member and spaced apart from and opposed to said movable member at both end portions to provide interposing gaps; a magnetic field generation means for producing a closed loop magnetic field passing through said movable member and stationary yoke via said gaps; a coil wound around at least one end portion of said stationary yoke such that at least one portion of said coil is exposed to the magnetic field produced by said magnetic field generation means in at least one said gap; and objective lens supporting means for movably supporting said objective lens in said direction perpendicular to the optical axis of said objective lens and information track; said coil being supplied with an electric current corresponding to a tracking error signal representing said relative positional error so as to displace said movable member comprising the magnetic body and hence said objective lens in said direction perpendicular to the optical axis of said objective lens and information track to correct the tracking error.