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1. WO1997024717 - DEVICE FOR SCANNING AN OPTICALLY READABLE RECORD CARRIER

Publication Number WO/1997/024717
Publication Date 10.07.1997
International Application No. PCT/IB1996/001359
International Filing Date 05.12.1996
IPC
G11B 7/00 2006.01
GPHYSICS
11INFORMATION STORAGE
BINFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
7Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation, reproducing using an optical beam at lower power; Record carriers therefor
G11B 7/09 2006.01
GPHYSICS
11INFORMATION STORAGE
BINFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
7Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation, reproducing using an optical beam at lower power; Record carriers therefor
08Disposition or mounting of heads or light sources relatively to record carriers
09with provision for moving the light beam or focus plane for the purpose of maintaining alignment of the light beam relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following
CPC
G11B 2007/0006
GPHYSICS
11INFORMATION STORAGE
BINFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
7Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation ; by modifying optical properties or the physical structure; , reproducing using an optical beam at lower power ; by sensing optical properties; Record carriers therefor
0003Recording, reproducing or erasing systems characterised by the structure or type of the carrier
0006adapted for scanning different types of carrier, e.g. CD & DVD
G11B 2007/0013
GPHYSICS
11INFORMATION STORAGE
BINFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
7Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation ; by modifying optical properties or the physical structure; , reproducing using an optical beam at lower power ; by sensing optical properties; Record carriers therefor
0003Recording, reproducing or erasing systems characterised by the structure or type of the carrier
0009for carriers having data stored in three dimensions, e.g. volume storage
0013for carriers having multiple discrete layers
G11B 7/0908
GPHYSICS
11INFORMATION STORAGE
BINFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
7Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation ; by modifying optical properties or the physical structure; , reproducing using an optical beam at lower power ; by sensing optical properties; Record carriers therefor
08Disposition or mounting of heads or light sources relatively to record carriers
09with provision for moving the light beam or focus plane for the purpose of maintaining alignment of the light beam relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following
0908for focusing only
G11B 7/0909
GPHYSICS
11INFORMATION STORAGE
BINFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
7Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation ; by modifying optical properties or the physical structure; , reproducing using an optical beam at lower power ; by sensing optical properties; Record carriers therefor
08Disposition or mounting of heads or light sources relatively to record carriers
09with provision for moving the light beam or focus plane for the purpose of maintaining alignment of the light beam relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following
0908for focusing only
0909by astigmatic methods
G11B 7/0912
GPHYSICS
11INFORMATION STORAGE
BINFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
7Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation ; by modifying optical properties or the physical structure; , reproducing using an optical beam at lower power ; by sensing optical properties; Record carriers therefor
08Disposition or mounting of heads or light sources relatively to record carriers
09with provision for moving the light beam or focus plane for the purpose of maintaining alignment of the light beam relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following
0908for focusing only
0912by push-pull method
G11B 7/094
GPHYSICS
11INFORMATION STORAGE
BINFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
7Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation ; by modifying optical properties or the physical structure; , reproducing using an optical beam at lower power ; by sensing optical properties; Record carriers therefor
08Disposition or mounting of heads or light sources relatively to record carriers
09with provision for moving the light beam or focus plane for the purpose of maintaining alignment of the light beam relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following
094Methods and circuits for servo offset compensation
Applicants
  • PHILIPS ELECTRONICS N.V. [NL]/[NL]
  • PHILIPS NORDEN AB [SE]/[SE] (SE)
Inventors
  • BRAAT, Josephus, Johannes, Maria
Agents
  • VISSER, Derk
Priority Data
95203643.227.12.1995EP
Publication Language English (EN)
Filing Language English (EN)
Designated States
Title
(EN) DEVICE FOR SCANNING AN OPTICALLY READABLE RECORD CARRIER
(FR) DISPOSITIF SERVANT A SCANNER UN SUPPORT D'ENREGISTREMENT A LECTURE OPTIQUE
Abstract
(EN)
A device is described for optically scanning an information layer (2') by means of a focused radiation beam (5). Radiation reflected from the information layer is made astigmatic by an oblique plane parallel plate (50) and subsequently detected by a detection system (51). An electronic circuit (26) derives two focus error signals, each representing the distance between the focal point (7) of the radiation beam (5) and the information plane (2'). The first focus error signal is formed from the high-frequency components in the electrical detector signals, the second focus error signal is formed from the low-frequency components in the same detector signals. A second electronic circuit (27) combines the two focus error signals to a combined focus error signal to control a focus servo loop. The circuit changes the control gradually from one focus error signal to another.
(FR)
L'invention concerne un dispositif servant à scanner optiquement une couche d'information (2') au moyen d'un faisceau de rayonnement focalisé (5). Le rayonnement réfléchi par la couche d'information est rendu astigmate par une plaque parallèle à plan oblique (50) et détecté ensuite par un système de détection (51). Un circuit électronique (26) calcule deux signaux d'erreur de focalisation, représentant chacun la distance entre le point focal (7) du faisceau de rayonnement et la couche d'information (2'). Le premier signal d'erreur de focalisation est constitué à partir des composantes haute fréquence des signaux de détection électriques, le deuxième signal d'erreur de focalisation étant constitué à partir des composantes haute fréquence des mêmes signaux de détection. Un deuxième circuit électronique (27) combine les deux signaux d'erreur de focalisation, afin d'obtenir un signal combiné d'erreur de focalisation, de manière à commander une boucle asservie de focalisation. Le circuit modifie graduellement la commande depuis un signal d'erreur de focalisation vers l'autre
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