Patent ID: 7065008
Filing Date: 2006-06-20
Classification: G11B

Abstract:
1. An objective lens unit comprising: an actuator base; a lens holder for supporting an objective lens, the lens holder having a shaft hole penetrating therethrough, an actuator base opposing face and a cover opposing face; a shaft disposed on the actuator base and fitted to the shaft hole, the shaft having a top face; a cover attached to the actuator base so as to cover the lens holder in such a manner that the cover comes into contact with or comes close to the top face of the shaft; protrusions disposed on the actuator base opposing face and the cover opposing face of the lens holder in such a manner that the protrusions do not contact the shaft; an annular blade section formed on the actuator base opposing face and the cover opposing face of the lens holder in such a manner that the annular blade section surrounds the shaft hole, the annular blade section having substantially triangular section and a protruding length smaller than that of the protrusions; a focusing coil disposed on the lens holder; and a tracking coil disposed on the lens holder, wherein the lens holder is capable of sliding in a focusing direction along the shaft by an excitation of the focusing coil and also capable of oscillating around the shaft in a tracking direction by an excitation of the tracking coil, and when the protrusions contact the actuator base and the cover, a predetermined gap is formed between the lens holder and the actuator base and between the lens holder and the cover, the gap is communicated with a space in the cover through the side of the protrusions.