Objective lens device, optical pickup device, optical-disc driving device and driving method of objective lens

An optical pickup device comprising:

• a light source configured to emit a first laser beam including a first wavelength, a second laser beam including a second wavelength which is longer than said first wavelength, and a third laser beam including a third wavelength which is longer than said second wavelength;
• a first objective lens having a first numerical aperture, which can condense said first laser beam into a disc-shaped first optical recording medium including a first cover layer of first thickness;
• a second objective lens having a second numerical aperture which is smaller than said first numerical aperture, which can condense said second laser beam into a disc-shaped second optical recording medium including a second cover layer of second thickness which is thicker than said first thickness;
• a third objective lens having a third numerical aperture which is smaller than said second numerical aperture, which can condense said third laser beam into a disc-shaped third optical recording medium including a third cover layer of third thickness which is thicker than said second thickness;
• a lens holder configured to integrally hold said first, second, and third objective lenses;
• and
• an actuator configured to drive said lens holder,
• wherein when a mechanical vibration system including said first objective lens, second objective lens, third objective lens, and said lens holder resonates, said third objective lens is disposed at a position near the anti-node of vibration of the vibration system as compared with said first objective lens and said second objective lens.

An optical-disc driving device comprising:

• a rotational driving mechanism configured to rotationally drive a disc-shaped first optical recording medium including a first cover layer of first thickness, a disc-shaped second optical recording medium including a second cover layer of second thickness which is thicker than said first thickness, or a disc-shaped third optical recording medium including a third cover layer of third thickness which is thicker than said second thickness;
• a first objective lens including a first numerical aperture, which can condense light into said first optical medium;
• a second objective lens including a second numerical aperture which is smaller than said first numerical aperture, which can condense light into said second optical recording medium;
• a third objective lens including a third numerical aperture which is smaller than said second numerical aperture, which can condense light into said third optical recording medium;
• a lens holder configured to hold said first, second, and third objective lenses integrally;
• an actuator configured to drive said lens holder;
• and
• a recording/playback processing unit configured to record a signal in said first, second, or third optical recording medium which is rotationally driven by said rotational driving mechanism, or to play a signal recorded therefrom,
• wherein when a mechanical vibration system including said first objective lens, second objective lens, third objective lens, and said lens holder resonates, said third objective lens is disposed at a position near the anti-node of vibration of the vibration system as compared with said first objective lens and said second objective lens.

An objective lens driving method comprising the steps of:

• condensing light into a disc-shaped optical recording medium including a first cover layer of first thickness using a first objective lens including a first numerical aperture;
• condensing light into a disc-shaped second optical recording medium including a second cover layer of second thickness which is thicker than said first thickness, using a second objective lens including a second numerical aperture which is smaller than said first numerical aperture;
• condensing light into a disc-shaped third optical recording medium including a third cover layer of third thickness which is thicker than said second thickness using a third objective lens having a third numerical aperture which is smaller than said second numerical aperture;
• and
• driving a lens holder configured to integrally hold said first, second, and third objective lenses to record or play a signal,
• wherein when a mechanical vibration system including said first objective lens, second objective lens, third objective lens, and said lens holder resonates, said third objective lens is disposed at a position near the anti-node of vibration of the vibration system as compared with said first objective lens and said second objective lens.