Title:
OBJECTIVE LENS AND OPTICAL PICKUP
Document Type and Number:
WIPO Patent Application WO/2005/119668
Kind Code:
A1
Abstract:
An object lens for an optical pickup performing at least reproduction of information from a first optical disc and reproduction and/or recording of information from/to second and third optical discs. A diffraction structure, divided into a plurality of ring zones, centering around the optical axis and having a sawtooth-like cross-section is formed in the common use region of the objective lens. A relation 57≤&Verbar (nd2-nd1)/(&lgr 2-&lgr 1) ≤90 is satisfied by the difference nd1 in refractive index for a light beam having a wavelength &lgr 1 between medium A on the light source side of an optical plane wherethe diffraction structure is formed and medium B on the optical disc side of the optical plane, and by the difference nd2 in refractive index for a light beam having a wavelength &lgr 2 between the medium A and medium B. When &agr is defined by expression &agr ==C0×&Verbar nd1/&lgr 1&Verbar using an approximation coefficient C0 where Pearson’s correlation coefficient R becomes 0.99998≤R when the depth parallel with the optical axis and the vertical distance from the optical axis in the level difference between the plurality of zones are approximated by a method of least squares, &agr of the objective lens falls within a predetermined range.
Inventors:
IKENAKA KIYONO (JP)
Application Number:
PCT/JP2005/009403
Publication Date:
December 15, 2005
Filing Date:
May 24, 2005
Export Citation:
Assignee:
KONICA MINOLTA OPTO INC (JP)
IKENAKA KIYONO (JP)
IKENAKA KIYONO (JP)
International Classes:
G02B5/18; G02B13/00; G02B13/18; G02B27/44; G11B7/135; G11B7/00; G11B7/125; (IPC1-7): G11B7/135; G02B5/18; G02B13/00; G02B13/18
Foreign References:
| JP2004062971A | 2004-02-26 | |||
| JP2004071134A | 2004-03-04 | |||
| JP2004030724A | 2004-01-29 |
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