Title:
光ヘッド装置及び光学式情報記録再生装置
Document Type and Number:
Japanese Patent JP4086069
Kind Code:
B2
Abstract:
Light emitted from a semiconductor laser ( 1 ) is split by a diffractive optical element ( 3 a) into a main beam and sub-beams. The diffractive optical element ( 3 a) is divided into four regions by a straight line parallel to a tangential direction of a disc ( 7 ) and a straight line parallel to a radial direction of the disc ( 7 ). A phase of grating in two regions arranged diagonally and a phase of grating in the other two regions arranged diagonally are different from each other by pi. A focused spot of the main beam and focused spots of the sub-beams are located on the same track. A focusing error signal is detected by a differential astigmatism method, using the main beam and the sub-beams.
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Inventors:
Ryuichi Katayama
Application Number:
JP2005504477A
Publication Date:
May 14, 2008
Filing Date:
February 24, 2004
Export Citation:
Assignee:
NEC
International Classes:
G11B7/09; G11B7/00; G11B7/131; G11B7/135; G11B7/1353; G11B7/13
Domestic Patent References:
| JP200351130A | ||||
| JP2001250250A |
Attorney, Agent or Firm:
Masanori Fujimaki
Kimura Mitsuru
Kimura Mitsuru