Title:
OBJECTIVE LENS FOR OPTICAL PICK-UP APPARATUS AND OPTICAL PICK-UP APPRATUS
Document Type and Number:
WIPO Patent Application WO/2010/073826
Kind Code:
A1
Abstract:
Provided is an objective lens for an optical pick-up apparatus and an optical pick-up apparatus capable of recording/reproducing information appropriately with respect to a multi-layer disk.
An objective lens (OBJ) has a diffraction structure on an optical surface thereof. When a light flux having a wavelength λ is made incident on the diffraction structure, the diffraction structure generates m-th order diffraction light having the highest diffraction efficiency and n-th order diffraction light whose diffraction efficiency is the next highest relative to the m-th order diffraction light. Information is recorded/reproduced using the m-th order diffraction light converged on an information recording layer of an optical disk. A distance (L) between the paraxial light convergence position of the m-th order diffraction light and the paraxial light convergence position of the n-th order diffraction light, and a gap (d), on the optical disk, between the information recording layer closest to the objective lens (OBJ) and the information recording layer farthest from the objective lens (OBJ) satisfy:
L/d ≥ 1.5 (1).
Because the paraxial light convergence position of the n-th order diffraction light is distant from the information recording layers which are not the information recording layer on and from which information is to be recorded and reproduced, the noise in the signals output from an optical detector (PD) can be decreased.
Inventors:
SHINDO HIROYUKI (JP)
Application Number:
PCT/JP2009/068971
Publication Date:
July 01, 2010
Filing Date:
November 06, 2009
Export Citation:
Assignee:
KONICA MINOLTA OPTO INC (JP)
SHINDO HIROYUKI (JP)
SHINDO HIROYUKI (JP)
International Classes:
G02B5/18; G02B13/00; G02B13/18; G11B7/135
Foreign References:
| JPH09179020A | 1997-07-11 | |||
| JP2008047177A | 2008-02-28 |
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