Dynamic information storage or retrieval – With servo positioning of transducer assembly over track... – Optical servo system
Reexamination Certificate
1999-10-22
2004-02-10
Huber, Paul W. (Department: 2653)
Dynamic information storage or retrieval
With servo positioning of transducer assembly over track...
Optical servo system
C369S044340, C369S044260
Reexamination Certificate
active
06690629
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an apparatus for reproducing recording information data from a recording disc.
2. Related Background Art
Well known recording formats for recording information data onto a recording disc such as an optical recording medium include such systems as CAV (Constant Angular Velocity), CLV (Constant Linear Velocity), ZCAV (Zoned CAV), and ZCLV (Zoned CLV). In the ZCLV system, CAV zones and transition zones are concentrically alternately arranged in one recording disc. In the CAV zone, the recording and reproduction are performed by setting a rotational angular velocity of the disc to be constant, while in the transition zone, the recording and reproduction are performed with the rotational angular velocity of the disc changing.
Japanese patent Kokai No. 7-114733 (designated as “JPA '733 hereinafter) discloses a recording disc using both the sampled servo system and the ZCLV system.
FIG. 1
is a plan view showing a recording surface of the recording disc disclosed in JPA '733.
As shown in
FIG. 1
, the recording disc comprises an annular recording area
20
including a spiral (or a plurality of concentric) recording track(s)
10
with information signals including a sync signal. In the recording area
20
, a zone
21
as a CAV zone, and a boundary area
33
as a transition zone are concentrically alternately formed. A width of track pitch d
1
of the boundary area
33
is larger than a track pitch d
2
in the zone
21
. Servo areas
31
a
shown by circles in
FIG. 1
are intermittently formed on the recording track
10
so that a sampled servo tracking system applies a tracking servo. Further, as shown in
FIG. 1
, the servo areas
31
a
are formed in each zone
21
so as to be aligned in the same disc radial direction.
FIG. 2
is a diagram showing a recording format used in the servo area
31
a.
The servo area
31
a
comprises: a pair of wobble pits
50
for a tracking servo; a mirror surface portion
51
for synchronization and a focusing servo; and clock pits
52
for clock reproduction. Each pair of wobble pits is arranged so as to be deviated in the disc radial direction by an equal distance around the track center. The wobble pit pairs are arranged in a manner such that the wobble pit pair of the odd-number track and the wobble pit pair of the even-number track are deviated in the track direction, respectively. In the tracking servo of the sampled servo system, the position in the disc radial direction of the pickup is controlled so that levels of reproduction signals of the pair of wobble pits are equal.
In the recording disc, a recording density is increased by narrowing the track pitch d
2
. In the disc, since the wobble pit pair of the odd-number track and the wobble pit pair of the even-number track are arranged so as to be deviated in the track direction as mentioned above, an unnecessary interference by the wobble pits of the adjacent tracks does not occur, even if the track pitch d
2
is narrowed. Since the rotational angular velocity of the disc changes in the boundary area
33
, however, it is impossible to align the servo areas
31
a
in the same disc radial direction. If the track pitch d
1
is narrowed in a manner similar to d
2
, therefore, the reproduction signal is subjected to the unnecessary interference by the adjacent tracks. Therefore, the stable tracking servo is not performed. Thus, in the recording disc, the track pitch d
1
in the boundary area
33
is set to be larger than d
2
so as not to cause the unnecessary interference by the adjacent tracks.
The following problems arise when the recording information is reproduced from the recording disc. When the reproducing apparatus performs the searching operation after completion of the jumping operation of the pickup, the mirror surface portion
51
is first detected and the synchronization and focusing servo are established. Subsequently, the wobble pits are detected, the tracking servo is performed, the clock pits are detected, and the clock reproduction is performed. That is, it is necessary to first detect the mirror surface portion
51
to re-activate the reproducing apparatus after completion of the jumping operation of the pickup. If a jump destination of the pickup is the boundary area
33
, it is not guaranteed that the mirror surface portion
51
can be positively detected, since the servo areas
31
a
are not aligned. Since it takes more time to re-activate the reproducing apparatus than necessary or the re-activation fails, a case may occur where the searching operation becomes unstable. Even when the boundary area
33
is jumped and searched, in the case where the pickup jumps over a portion other than the servo areas
31
a
, a tracking error cannot be detected, so that the count number of the track jump is incorrect, and search time increases.
OBJECTS AND SUMMARY OF THE INVENTION
The invention is made in order to solve the above problems. An object of the invention is to provide a recording information reproducing apparatus which can perform a preferable searching operation.
One aspect of the invention features an apparatus for reproducing recording information data from a recording disc on which information data has been divided and recorded into a plurality of concentric zones, said apparatus comprising: reading means for reading recording information data from a recording disc; and tracking servo means for selecting one of a tracking servo control by a sampled servo system and a tracking servo control by a continuous servo system in accordance with a zone being read by said reading means to control the selected tracking servo system.
As described above, according to the invention, even if a track jump destination at the time of search is in a transition area, the control mode is switched to the tracking servo by the continuous servo system to perform the corresponding tracking servo control. Therefore, the preferable searching operation is performed.
REFERENCES:
patent: 5422760 (1995-06-01), Abbott et al.
patent: 7-114733 (1995-05-01), None
* Translation of Abstract only.
Huber Paul W.
Perman & Green LLP
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