Objective lens and optical pickup device

Patent metadata

Field	Value
Publication number	US-9190098-B2
Application number	US-201414555509-A
Country	US
Kind code	B2
Filing date	Nov 26, 2014
Priority date	Aug 25, 2011
Publication date	Nov 17, 2015
Grant date	Nov 17, 2015

Abstract

An objective lens capable of converging light of a used wavelength with a satisfactory aberration on a recording medium is provided. An objective lens for converging light of a predetermined wavelength λ on a recording medium satisfies the following condition: |CML|+|CMF|<0.03 λ, where CML is an amount of a generated third-order coma aberration per 1 degree of tilt of the objective lens, and CMF is an amount of a generated third-order coma aberration per 1 degree of tilt of off-axis light.

First claim

What is claimed is:

1. An objective lens for converging light of a predetermined wavelength λ on a recording medium, the objective lens satisfying the following condition:
| CMD|< 0.02 λ

0.02 λ<|CML|< 0.2 λ

where
CML is an amount of a generated third-order coma aberration per 1 degree of tilt of the objective lens, and
CMD is an amount of a generated third-order coma aberration per 1 degree of tilt of the recording medium.

2. The objective lens according to claim 1 , wherein a wavefront aberration has a minimum value when the tilt of the objective lens is in a range larger than 0 degree and smaller than 1 degree.

3. The objective lens according to claim 1 , wherein a third-order spherical aberration or a third-order astigmatism has a minimum value when the tilt of the objective lens is in a range larger than 0 degree and smaller than 1 degree.

4. The objective lens according to claim 3 , wherein the minimum value of the third-order spherical aberration or the third-order astigmatism is smaller than 1/10 of a value of an on-axis third-order spherical aberration or an on-axis third-order astigmatism.

5. The objective lens according to claim 1 , wherein the value of the on-axis third-order spherical aberration or the on-axis third-order astigmatism is larger than the half of a value of an on-axis wavefront aberration.

6. The objective lens according to claim 1 , wherein
the predetermined wavelength λ is 380 to 430 nm,
the objective lens has a numerical aperture of 0.8 or larger, and
the objective lens is a single lens having a focal length of 1.3 mm or shorter.

7. An optical pickup device including:
a light source for emitting light of a predetermined wavelength λ; and
an objective lens for converging the light on a recording medium, wherein:
the objective lens satisfies the following condition:
| CMD|< 0.02 λ

0.02 λ<|CML|< 0.2 λ

where
CML is an amount of a generated third-order coma aberration per 1 degree of tilt of the objective lens, and
CMD is an amount of a generated third-order coma aberration per 1 degree of tilt of the recording medium.

Assignees

• Panasonic Corp
• Panasonic Ip Man Co Ltd

Inventors

• Minami Kazuhiro
• Tanaka Yasuhiro

Classifications

• G11B7/13927

  during transducing, e.g. to correct for variation of the spherical aberration due to disc tilt or irregularities in the cover layer thickness · CPC title

• G11B7/0956

  to compensate for tilt, skew, warp or inclination of the disc, i.e. maintain the optical axis at right angles to the disc · CPC title

• G11B7/1374 Primary

  Objective lenses {(optical objectives per se G02B9/00)} · CPC title

• G02B13/00

  Optical objectives specially designed for the purposes specified below (with variable magnification {in general} G02B15/00) · CPC title

• G02B27/0025

  for optical correction, e.g. distorsion, aberration · CPC title