| US 7,567,495 B2 | ||
| Optical pickup apparatus and optical disc apparatus using same | ||
| Toshimasa Kamisada, Yokohama (Japan); Yasuo Kitada, Odawara (Japan); Kazuyoshi Yamazaki, Kawasaki (Japan); Tomoto Kawamura, Tokyo (Japan); and Yoshiro Konishi, Yokohama (Japan) | ||
| Assigned to Hitachi Media Electronics Co., Ltd., Iwate (Japan) | ||
| Filed on Mar. 01, 2007, as Appl. No. 11/680,705. | ||
| Claims priority of application No. 2006-283245 (JP), filed on Oct. 18, 2006; and application No. 2006-283248 (JP), filed on Oct. 18, 2006. | ||
| Prior Publication US 2008/0094948 A1, Apr. 24, 2008 | ||
| Int. Cl. G11B 7/135 (2006.01) | ||
| U.S. Cl. 369—112.12 | 3 Claims |
| 1. An optical pickup apparatus for irradiating a light flux onto an optical disc having a plurality of information recording
layers which are laminated at a predetermined interval with each other to detect the light flux reflected from said optical
disc, the apparatus comprising:
a light source;
an objective lens for focusing a light flux emitted from said light source on said optical disc;
a dividing element for dividing the light flux reflected from the optical disc into a plurality of light fluxes;
a condenser lens for condensing the plurality of light fluxes from the dividing element; and
a light detector for receiving the plurality of light fluxes condensed by the condenser lens by a plurality of light receiving
parts thereof and converting the received light fluxes to electrical signals,
wherein said dividing element having:
a first divided region disposed almost in the center;
a second divided region comprising four regions which are divided by a first dividing line and are disposed along the direction
of the first dividing line to sandwich said first divided region; and
a third divided region comprising four regions which are divided by a second dividing line perpendicular to said first dividing
line and are disposed along the direction of said second dividing line to sandwich said first divided region,
wherein said second and third divided regions are each structured such that when a target information recording layer of said
optical disc is brought into focus, a reflected light flux from said target information recording layer is focused on the
light receiving part of said light detector and the light flux reflected from a recording layer other than said target recording
layer is not irradiated onto said light receiving parts of said light detector;
wherein a diffraction grating is formed in each region of said dividing element;
wherein said light detector detects a signal for focus error according to a knife edge method by a minus first-order diffracted
light which is diffracted in said second divided region;
wherein said light detector detects a signal for tracking error using plus first-order diffracted lights which are diffracted
in said second and third divided regions and using a minus first-order diffracted light which is diffracted in said third
divided region; and
wherein said light detector detects a signal for reproduction using a sum of the plus first-order diffracted lights which
are diffracted in said second and third divided regions.
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