Dynamic information storage or retrieval – Information location or remote operator actuated control – Selective addressing of storage medium
Reexamination Certificate
2001-05-17
2002-12-31
Psitos, Aristotelis M. (Department: 2653)
Dynamic information storage or retrieval
Information location or remote operator actuated control
Selective addressing of storage medium
C369S030100, C369S044280
Reexamination Certificate
active
06501709
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a disk player for reproducing date recorded on an optical disk.
Many types of optical disks, e.g., CD, CD-ROM, CD-R, CD-RW, DVD-ROM, are employed to record data. Disk players having optical pickups have been used to read the data recorded on the optical disks.
The disk player includes a servo mechanism for driving a motor, which moves the optical pickup, and another servo mechanism for making the optical pickup trace tracks of the optical disk. The disk player controls the servo mechanisms to read data from the optical disk.
Action of the optical pickup of the conventional disk player will be explained.
To read assigned data, the optical pickup must be moved from a current track to an object track, in which the assigned date is recorded.
To move the optical pickup to the object track, the disk player calculate number of tracks between the current track and the object track, then the optical pickup is moved by two manners, which are selected on the basis of the number of the tracks there between. If the number of the tracks is less than a prescribed number, the pickup is moved by a manner called “short jump”; if the number of the tracks is equal to the prescribed number or more, the pickup is moved by a manner called “long jump”.
In the manner of “short jump”, the pickup is moved to trace the tracks with counting number of tracks until reaching the object track.
On the other hand, the manner of “long jump” is employed in the case that the number of the tracks between the current track and the object track is equal to the prescribe number or more. Namely, it takes a long time, by the manner of “short jump”, to move the optical pickup to the object track. In the manner of “long jump”, revolution number of the motor is counted without counting the number of the tracks while the optical pickup is moved. A distance to the object track is calculated on the basis of the revolution number of the motor, so that the optical pickup can be moved to the object track.
Moving accuracy of the long jump is low. To correctly move the optical pickup, the optical pickup is firstly move to a track near the object track by the long jump, then the optical pickup is further moved by the short jump, so that the optical pickup can be correctly moved to the object track.
FIGS. 4 and 5
show relationships between the optical pickup and an object lens of the optical pickup.
In
FIG. 4
, the optical pickup
10
has been moved to the track near the object track by the long jump. When the optical pickup
10
reaches the track
11
near the object track by the long jump, the tracking servo mechanism (not shown) drives the object lens
12
to lock the track
11
.
When the object lens
12
locks the track
11
by the servo mechanism, reading track can be executed from the track
11
. The optical pickup
10
is further moved from the track
11
to the object track by the short jump. While the short jump, the optical pickup
10
traces the tracks with driving the both servo mechanisms.
Revolutional speed of the motor during the long jump is faster than that of the motor during ordinary reproduction, so that the optical pickup
10
is moved faster during the long jump. By the fast motion, even if the long jump is finished, the optical pickup
10
cannot be stopped at a position, at which the object lens
12
locks the track
11
, by inertia. Namely, the position of the optical pickup
10
is sometimes slightly shifted in the moving direction thereof as shown in FIG.
5
.
If the optical pickup
10
is not completely stopped after the long jump and is shifted as described above, the object lens
12
, which has locked the track
11
, is shifted in the optical pickup
10
. Since the object lens
12
can be moved in focusing and tracking directions, the shift of the object lens
12
occurs in the optical pickup
10
.
After the long jump is finished, if the optical pickup
10
reads the track in the state of shifting the object lens
12
, difference between clock signals and reproduced signals are increased and level of tracking error signals are made lower, so that the track cannot be correctly read and the reading action is stopped.
SUMMARY OF THE INVENTION
The disk player of the present invention is invented to solve the problems of the conventional disk player.
An object of the present invention is to provide a disk player capable of preventing a shift of an object lens in an optical pickup, which occurs after the optical pickup is moved, and a poor action caused by the shift.
Namely, the disk player of the present invention comprises:
a first servo mechanism for driving a motor, which moves an optical pickup in a radial direction of a disk;
a second servo mechanism for moving an object lens in a radial direction in the optical pickup so as to trace tracks of the disk; and
a control unit controlling the first servo mechanism and the second servo mechanism so as to make the optical pickup jump over a plurality of the tracks to move the optical pickup from a current track to an object track,
wherein the control unit moves the optical pickup from the current track to the object track by the steps of:
driving the motor without driving the second servo mechanism so as to move the optical pickup to a track near the object track;
driving the second servo mechanism after the optical pickup reaches near the object track;
stopping the second servo mechanism; and
driving the first servo mechanism and the second servo mechanism after the laps of a prescribed time so as to move the optical pickup to the object track.
In the disk player of the present invention, the second servo mechanism is once driven after the optical pickup reaches near the object track, then the second servo mechanism is immediately stopped. The object lens locks the track while the second servo mechanism is firstly driven. By immediately stopping the second servo mechanism, the shift of the optical pickup caused by the inertia is braked. And, the object lens can be returned to a center of the optical pickup while the second servo mechanism is stopped. Further, the shift of the optical pickup caused by the inertia is stopped while the second servo mechanism is stopped. Therefore, the object lens is not shifted when the second servo mechanism is driven again, so that the tracks can be correctly read and poor action, e.g., read error, can be prevented after the optical pickup reaches the object track.
REFERENCES:
patent: 5216650 (1993-06-01), Noguchi
patent: 5442604 (1995-08-01), Osada
patent: 5577009 (1996-11-01), Takamine
Birch & Stewart Kolasch & Birch, LLP
Psitos Aristotelis M.
Shinano Kenshi Kabushiki Kaisha
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