Dynamic information storage or retrieval – With servo positioning of transducer assembly over track... – Optical servo system
Patent
1998-04-15
2000-11-07
Huber, Paul W.
Dynamic information storage or retrieval
With servo positioning of transducer assembly over track...
Optical servo system
3692753, G11B 700
Patent
active
061446246
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a method and device for controlling the tracking of an optical memory card. In particular it relates to a method and device for controlling the tracking of an optical memory card, which is capable of not only speeding up the operations of recording and reproducing in an optical memory card, but also capable of ensuring prevention of overwriting and similar operational errors resulting from mistakes in track holding.
BACKGROUND ART
Generally speaking, optical memory cards are plastic cards of a stipulated size configured in such a manner that their recording area may be recorded on to and reproduced with the aid of a laser beam.
FIG. 10 shows the recording area 102 of a conventional optical memory card 101. As may be seen from the enlarged drawing, the recording area 102 has data recording tracks 1 and guide tracks 2 arranged alternately on it. The data recording tracks 1 are the parts which serve to record data, while the guide tracks 2 are formed at a specified interval, which is required for the purpose of tracking control whereby the irradiation position of the laser beam used for recording and reproducing is stabilized.
Here, the reflection factors of the data recording tracks 1 and the guide tracks 2 differ, and a comparison between the two shows that of the data recording tracks 1 is high, while that of the guide tracks 2 is low.
The recording pits 3 are sections with low reflection factors which are formed by a laser beam within the recording tracks 1 at the time of recording. The presence or absence of these recording pits 3 corresponds to the digital codes 0 and 1.
FIG. 11 is a diagram illustrating the configuration of the optical system which records and reproduces information for the optical memory card 101.
In FIG. 11, a laser beam emitted from a laser diode 103 is rendered into a parallel beam by a collimator lens 104, is incident upon a diffraction grating 105, and is split into innumerable light rays.
The light rays which have been split with the aid of the diffraction grating 105 are directed on to a beam splitter 106, the zero-order beam being used as the main beam for recording and reproducing data, while the .+-.-order beam is used as a sub-beam for tracking control.
Part of the rays which are incident upon the beam splitter 106 are reflected in a 90.degree. direction and directed on to a power monitor 114 which monitors the strength of the light source. The remaining rays pass through the beam splitter 106 and proceed straight ahead by way of a reflecting mirror 107 and objective lens 108 to converge as three spots on the recording area 102 of the optical memory card 101.
Reflected off the recording area 102, the rays are rendered into a parallel beam once more by the objective lens 108, pass through the reflecting mirror 107, and are reflected in a 90.degree. direction by the beam splitter 106. They then proceed by way of a collimator lens 109 and concave lens 110 to assume a long focal length and be directed on to an edge mirror 111.
This edge mirror 111 is a reflecting mirror which is located so as to screen half the rays, so that they are divided into half the main beam along with the +-order light of the sub-beam on the one hand, and the remaining half of the main beam along with the --order light of the sub-beam on the other.
Having been divided by means of the edge mirror 111, the half of the main beam and the +-order light of the sub-beam proceed straight ahead to form an image on an photosensor 112, while the remaining half of the main beam and the --order light of the sub-beam are reflected in a 90.degree. direction to form an image on an photosensor 113.
The rays which form images on the photosensors 112 and 113 are here converted into electric signals.
It should be noted that the main beam (0-order light) 7 and the sub-beams (.+-.-order light) 8a, 8b, having passed through the objective lens 108, are directed on to the recording area 102 as illustrated in FIG. 10. The recording pits 3 are formed by this main beam 7 in the
REFERENCES:
patent: 5142519 (1992-08-01), Horie
Ohta Michihiro
Yoshida Hiroaki
Huber Paul W.
Kabushiki Kaisha Nippon Conlux
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