Dynamic information storage or retrieval – With servo positioning of transducer assembly over track... – Optical servo system
Patent
1997-11-06
2000-09-26
Tran, Thang V.
Dynamic information storage or retrieval
With servo positioning of transducer assembly over track...
Optical servo system
369 4441, 369112, 369 4429, G11B 709
Patent
active
061250872
ABSTRACT:
Disclosed is an optical pickup and an optical disc device using the same, each including a laser diode, a photo-detector having a region divided into at least six photo-detection areas, and a diffraction grating disposed between the laser diode and the photo-detector and having a region divided into four areas by cross-shaped division lines. The diffraction grating divides a light beam reflected from an optical disc into four diffracted light beams. A focus error signal in accordance with a knife edge method and two kinds of tracking error signals in accordance with a push-pull method and a differential phase detection method are detected by irradiating the light beams diffracted at the areas of the diffraction grating on the detection areas of the photo-detector and/or at boundary lines therebetween, and arithmetically operating light intensity signals obtained from the detection areas of the photo-detector. As a result, there can be realized an optical pickup and an optical disc device, each of which can be matched with various optical discs different in structure by detecting a tracking error signal in accordance with the push-pull method and a tracking error signal suitable for a read only disc using only one photo-detector. Further, in the present invention, a holographic element can be used as the diffraction grating.
REFERENCES:
patent: 5570333 (1996-10-01), Katayama
patent: 5737296 (1998-04-01), Komma et al.
patent: 5757754 (1998-05-01), Yamamoto et al.
patent: 5859819 (1999-01-01), Miyabe et al.
Fukui Yukio
Inoue Masayuki
Nakao Takeshi
Ohnishi Kunikazu
Sasaki Tohru
Hitachi , Ltd.
Tran Thang V.
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