Title:
OBJECTIVE LENS
Document Type and Number:
Japanese Patent JP2015053107
Kind Code:
A
Abstract:
PROBLEM TO BE SOLVED: To provide an objective lens suitably configured to suppress variation in spherical aberration caused by changes in temperature.SOLUTION: A single objective lens 10 having an NA larger than 0.8 and made of a resin converges light emitted by a light source 1 onto recording surfaces M1 to M3 in a multilayer structure of an optical disk D. An annular zone structure having the first order of diffraction is provided on a first surface 10a of the objective lens; and the objective lens is configured to satisfy predetermined conditions relating to a focal length of the objective lens, a sum of absolute values of heights in steps of the annular zone, an imaging magnification produced by a coupling lens 3 and the objective lens, the number of steps in the annular zone within an effective beam diameter of the objective lens, a moving amount of the coupling lens necessary for correcting a spherical aberration caused by a difference in an optical distance from a surface of a protective layer to the recording surface of the optical disc, and the like.
Inventors:
YAMAGATA NAOKI
INOUE SATOSHI
TAKEUCHI SHUICHI
INOUE SATOSHI
TAKEUCHI SHUICHI
Application Number:
JP2014235528A
Publication Date:
March 19, 2015
Filing Date:
November 20, 2014
Export Citation:
Assignee:
HOYA CORP
International Classes:
G11B7/135
Attorney, Agent or Firm:
Shuhei Matsuoka
Oyama 栄啓
Oyama 栄啓
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