Dynamic information storage or retrieval – Information location or remote operator actuated control – Selective addressing of storage medium
Reexamination Certificate
2002-10-24
2004-12-21
Dinh, Tan (Department: 2653)
Dynamic information storage or retrieval
Information location or remote operator actuated control
Selective addressing of storage medium
Reexamination Certificate
active
06834028
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an optical disk device and, more particularly, to an optical disk device that reduces a seek time.
BACKGROUND OF THE INVENTION
Conventional optical disk devices prevent swings of a lens of a pickup at seeking, under position control and speed control, to perform high-speed seeking.
Here, a conventional optical disk device will be described with reference to FIG.
14
.
FIG. 14
is a block diagram illustrating a structure of a conventional optical disk device.
In
FIG. 14
, reference numeral
1
denotes an optical disk in which information is recorded on spiral tracks. A lens
2
focuses laser light on the optical disk
1
, and is driven in axial and radial directions of the optical disk
1
by means of an actuator (not shown) provided on an upper part of the main body of an optical pickup
3
. The optical pickup
3
applies laser light to the lens
2
, and receives reflected light from the optical disk
1
to generate a signal that detects track crossing of the laser light on the optical disk
1
(hereinafter, abbreviated as a “track crossing signal”), a signal that detects deviation of the lens
2
from the center position on the optical pickup
3
(hereinafter, abbreviated as a “position detection signal”), a signal that indicates defocusing of the laser light on the optical disk
1
(hereinafter, abbreviated as a “focus error signal”), and a signal that indicates deviation of the laser light from the center of the track (hereinafter, abbreviated as a “tracking error signal”). A traverse driving means
4
drives the optical pickup
3
in the radial direction of the optical disk
1
. A speed control means
5
measures a movement speed of the lens
2
on the basis of the track crossing signal that is generated by the optical pickup
3
, and controls an actuator driving means
8
such that the movement speed of the lens
2
follows a target movement speed. A position control means
6
controls the actuator driving means
8
on the basis of the tracking error signal generated by the optical pickup
3
such that a midpoint of the lens
2
follows the center position of the optical pickup
3
. A switching means
7
switches between outputs of the speed control means
5
and the position control means
6
, to decide control input to the actuator driving means
8
. The actuator driving means
8
controls the actuator provided on the optical pickup
3
to drive the lens
2
in the axial and radial directions of the optical disk
1
. A system control means
9
reads information about a target speed of the optical pickup
3
, which is previously set in a table corresponding to a speed profile
10
, and controls the traverse driving means
4
and the actuator driving means
8
on the basis of the read information. The speed profile
10
is a table in which driving speed increasing/decreasing patterns for promptly moving the optical pickup
3
to a target track are described. A track lead-in means
30
guides the optical pickup
3
to the center position of the track on the optical pickup
1
on the basis of the tracking error signal, and it can make the optical pickup
3
follow the center of the track of the optical disk
1
.
FIG. 15
is a diagram for explaining the speed control means
5
. In this figure, the ordinate represents the movement speed of the lens
2
and the movement speed of the optical disk
1
varying due to eccentricity, and the abscissa represents the time.
When the traverse driving means
4
receives a command instructing a seek operation from the system control means
9
, it moves the optical pickup
3
to a predetermined position, in accordance with a target speed that is previously set in the speed profile
10
. At this time, the lens
2
that is provided on the optical pickup
3
via the actuator is moved while swinging as the optical pickup
3
is moved. Thus, the speed control means
5
performs the speed control such that the lens
2
has a fixed movement speed, thereby preventing swings of the lens
2
at the seek time, and realizing a prompt lead-in to the target track.
Actually, however, the optical disk
1
is also off-centered (radially swinging) while rotating, and there exists changes in the speed like SIN waves as shown in FIG.
15
. Accordingly, the speed control means
5
controls the actuator driving means
8
for making the lens
2
follow the disk eccentricity shown by a broken line, and keeping a relative speed between the movement speed of the lens
2
and the movement speed of the optical disk
1
at a constant value. Therefore, the speed control means
5
that operates so as to make the movement speed of the lens
2
follow the changes in the speed of the optical disk
1
due to the eccentricity before leading into the target track immediately before the end of the seek operation, and to make the relative speed between the lens
2
and the optical disk
1
0 (zero) is effective.
On the other hand, as the speed control means
5
drives the traverse driving means
4
through the system control means
9
, particularly when the traverse driving means
4
is sensitive to control inputs of a stepping motor and the like, the traverse driving means
4
sometimes responds too much to changes in the speed due to interference such as eccentricity or swings of the optical disk
1
, so that step-out occurs at high-speed rotation, and the seek time is unfavorably delayed greatly.
FIG. 16
is a diagram for explaining the position control means
6
(lens midpoint control). In this figure, the ordinate represents the actuator sensitivity of the lens
2
at the seek time of the optical pickup
3
, and the abscissa represents the amount of swings of the lens
2
(lens shift). This figure shows the state where the actuator sensitivity of the lens
2
varies according to the lens shift.
As shown in
FIG. 16
, a state in which the lens shift amount is zero, indicating that the lens
2
is located at the center of the optical pickup
3
, is a state in which the actuator sensitivity is the highest. At this time, the response speed of the actuator to the control input from the actuator driving means
8
is the highest. Therefore, the lens
2
swings hard at the seek time when the optical pickup
3
is moving at high speeds, and thus, the position control means
6
that controls the lens
2
for being positioned at the center of the optical pickup
3
is effective. There are also merits that the position control means
6
controls only the actuator driving means
8
, and the traverse driving means
4
can be controlled by the speed profile
10
independently.
On the other hand, the position control means
6
cannot control the movement speed of the lens
2
for following the movement speed of the optical disk
1
due to the eccentricity. Accordingly, there are some cases where the leading into the target track is delayed in the case of the optical disk
1
having larger eccentricity.
An operation of the conventional optical disk device that is constructed as described above will be described with reference to FIG.
17
.
FIG. 17
is a diagram showing the operation of the conventional optical disk device immediately before an end of seeking. In this figure, the ordinate represents the sensitivity and movement speed of the lens
2
, and the abscissa represents the seek time.
Initially, at high-speed movements of the lens
2
and the optical pickup
3
from when the seek operation is started until the optical pickup
3
reaches the vicinity of the target track, the switching means
7
is connected to the position control means
6
to control the lens shift, thereby keeping the lens in a high sensitivity state.
Then, when the optical pickup
3
reaches the vicinity of the target track, the switching means
7
is switched from the position control means
6
to the speed control means
5
, and the lens
2
and the optical pickup
3
are moved at low speeds by the actuator driving means
6
and the traverse driving means
4
, respectively, thereby enabling the movement speed of the lens
2
to follow the movement speed
Itoh Fumihiro
Kikuchi Jun
Dinh Tan
Parkhurst & Wendel L.L.P.
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