Objective lens and optical pick-up device using the same
AssigneesSanyo Optec Design Co., Ltd., Sanyo Electric Co., Ltd.
InventorMitsuru Ito
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Abstract
Provided is an objective lens that allows securing of a long working distance for a laser beam with a long wavelength and has a predetermined thickness or larger, and an optical pickup apparatus including the objective lens. In an objective lens of the present invention, a first region that focuses laser beams of a BD, DVD, and CD standards, a second region that focuses the laser beams of the DVD and CD standards, and a third region that focuses the laser beams of the BD and the DVD standards are provided in this order from a center portion of the objective lens. An optical super resolution with the laser beam of the BD standard is achieved by preventing a portion of the laser beam of the BD standard transmitted through the second region from contributing to spot formation.
Claims8
An objective lens configured to
- focus a first laser beam having a first wavelength on an information recording layer of a first optical disc,
- focus a second laser beam having a second wavelength longer than the first wavelength on an information recording layer of a second optical disc, and
- focus a third laser beam having a third wavelength longer than the first and second wavelengths on an information recording layer of a third optical disc,
- the objective lens comprising a plurality of shared regions each configured to focus plural ones of the first laser beam, the second laser beam, and the third laser beam on the information recording layers of the corresponding optical discs, wherein
- a first invalid region is provided between the plurality of shared regions and is configured to prevent any one of the first laser beam, the second laser beam, and the third laser beam from contributing to spot formation on the information recording layer of the corresponding optical disc.
Dependencies are inferred from the claim text.