Dynamic information storage or retrieval – With servo positioning of transducer assembly over track... – Optical servo system
Patent
1989-12-18
1992-09-01
Richardson, Robert L.
Dynamic information storage or retrieval
With servo positioning of transducer assembly over track...
Optical servo system
369 4428, G11B 700
Patent
active
051446057
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The invention relates to an optical disk apparatus and the method for controlling the movement of its light spot, and is applied to, for example, an optical disk apparatus in which data recording or reproduction is performed on an optical disk on which sequences of cyclic identification signals are recorded in advance on its consecutive recording tracks.
BACKGROUND OF ART
Heretofore, in this type of optical disk apparatus, the optical head is moved as far as the desired recording track to bring about a just-tracking state, and the desired data or information is subsequently recorded or reproduced. At this time, movement of the optical head is terminated in a shorter time to make data recording or reproduction in a shorter time as a whole.
Thus, in the conventional optical disk apparatus, the optical head is driven so that, as shown in FIG. 1, it is accelerated promptly so that its speed of movement becomes zero on the recording track of destination, referred to hereinafter as the target track.
That is, the distance X traversed by a light spot, as shown by the following formula (1) recording track being scanned by the light spot emanating from the optical head as far as the target track and Tp the pitch of the recording tracks, and the target speed of movement proportionate to .times..sup.1/2 is set, for driving the optical head.
In addition, the number of tracks traversed by the light spot during movement of the optical head is counted (this counting is referred to hereinafter as traverse counting) and the traversed distance X is sequentially corrected to compensate for the target speed of movement of the optical head so that the speed of movement of the optical head becomes zero on the target track.
When the light spot has moved as far as the target track, the optical head is tracking-controlled on the basis of the track error signal S.sub.TE, as shown in FIG. 2, which is obtained by the medium of the optical head, in such a manner that the desired information may be positively recorded or reproduced with the light spot in the state of just-tracking of the target track.
Meanwhile, in this type of optical disk apparatus, if traverse counting can be made with a high degree of precision, the speed of movement of the optical head can be correctly controlled so as to be equal to zero on the target track, and hence the information can be recorded or reproduced within a correspondingly shorter time.
For this reason, there is proposed in the Japanese Patent application No. 207542/1987 or the like an arrangement in which, as shown for example in FIG. 3, sequentially circulating simple identification signals are recorded on consecutive recording tracks on the optical disk 1, so that, even when the light spot is moved across a given recording track, the position of the recording track may be discriminated.
The optical disk 1 shown in FIG. 3 is divided circumferentially into plural sectors at a predetermined angular interval, and a control recording area AR.sub.C is formed at the terminal part of each sector.
In a forward area AR.sub.S of the control recording region AR.sub.C, there are formed a pit Q.sub.B on a track center TRC of each recording track, and pits Q.sub.A and Q.sub.C, each with a predetermined offset from each track center TRC. Tracking error signals are obtained on the basis of these pits Q.sub.A, Q.sub.B and Q.sub.C.
On the other hand, in a forward zone of the control recording region AR.sub.C, there is formed a traverse area AR.sub.T, in which recording patterns sequentially circulated at a period of 16 tracks are formed using first pits Q.sub.E1 and second pits Q.sub.E2.
More specifically, the traverse area AR.sub.T is divided into eight parts at a predetermined interval D, and the first pits Q.sub.E1 are shifted at intervals of the four consecutive record tracks towards the rear by a distance equal to the interval D. On the other hand, the second pits Q.sub.E2 are shifted each by a distance equal to the interval D towards the rear or towards the front at periods of the four con
REFERENCES:
patent: 3919697 (1975-11-01), Walker
patent: 4977472 (1990-12-01), Volz et al.
Eguchi Naoya
Kobayashi Seiji
Nishida Norio
Yoshimura Shunji
Richardson Robert L.
Sony Corporation
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