Dynamic information storage or retrieval – With servo positioning of transducer assembly over track... – Optical servo system
Reexamination Certificate
2001-01-26
2004-06-29
To, Doris H. (Department: 2655)
Dynamic information storage or retrieval
With servo positioning of transducer assembly over track...
Optical servo system
C369S030130, C369S053290
Reexamination Certificate
active
06757226
ABSTRACT:
This application incorporates by reference Taiwanese application Serial No. 89101716, filed Feb. 1
st
, 2000.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates in general to a method for reducing the turn-back of the track-seeking control in an optical storage device and an apparatus thereof.
2. Description of the Related Art
FIG. 1
is a block diagram illustrating the structure of an optical storage device. The optical storage device indicated here includes at least a CD-ROM drive and a Digital Versatile Disk (DVD) drive.
Referring to
FIG. 1
, a spindle motor
100
is used to drive an optical disk
101
to the required rotation speed. A sled motor
102
is used to drive the sled
105
which is equipped with an optical pickup head
104
for rough tracking and seeking operations. The tracking operation is used to drive the optical pickup head
104
to a certain track on the optical disk
101
for reading data.
Fine-tuning operations include focusing and tracking operations. The focusing operation involves the objective lens
120
running in a vertical direction in order to accurately read data on the optical disk
101
whereas the tracking operation involves the objective lens
120
running in a horizontal direction to find the desired track.
When a laser is focused on the optical disk
101
, the reflected light is received by the optical sensor on the optical pickup head
104
. Optical pickup head
104
outputs the signals corresponding to data stored in the optical disk
101
as well as signals for various servo controls.
The signals outputted from the optical pickup head
104
are transformed by a preamplifier
106
into radio frequency (RF) signals and other signals for various servo controls such as tracking error (TE) signal, RFRP signal, and RFCT signal. These signals are then inputted to the control integrated circuit (control IC) for processing. Included in the control IC
108
are, for example, a digital signal processor (DSP) in addition to other analog or digital circuitry. The control IC
108
obtains an output data by performing the demodulation and error correction of the received RF signals and sends out the output data to the decoder
112
and then the host computer
114
for further processing. Meanwhile, the control IC
108
processes the servo signals with necessary compensations and outputs to power amplifiers
116
and
118
to drive the spindle motor
100
, the sled motor
102
, the focusing actuator and the tracking actuator.
The microprocessor
122
is responsible for the overall operation of the disk as well as the user interfaces such as controlling the opening of the disk tray.
Next, signals obtained by the optical pickup head
104
is inputted to the preamplifier
106
which outputs the RF signal, and other signals for various servo controls, for example, the TE signal, the RFRP signal, and the RFCT signal. Then, these signals are processed by the control IC
108
such as a digital signal processor, DSP, or other digital or analog circuits. The control IC
108
processes the RF signal with error correction and outputs data to the decoder
112
. Then, the output of the decoder
112
is inputted to the main computer
114
for further processing. On the other hand, the control IC
108
outputs the servo signals to the power amplifiers
116
and
118
for driving the spindle motor
100
, the sled motor
102
, the focusing actuator and the tracking actuator of the objective lens
120
in the optical pickup head
104
.
Moreover, the microprocessor
122
controls the whole process and the user interface of the optical storage device, for example, the opening the tray of the optical storage device.
Referring to
FIG. 2
, the flow chart of the track-seeking control is illustrated. Before the track-seeking control starts, in step
200
, the target is set up. The target is a position of an optical disk for reading data. For a CD-ROM, the target is a data block number, and, for a DVD-ROM, the target is a data sector number.
In step
202
, the current position is read. In step
204
, whether the current position is the target is determined. If the current position is the target, the track-seeking control is ended. On the other hand, if the current position is not the target, in step
206
, the direction and the number of tracks needed for the track-seeking control is calculated from the difference between the target and the current positions.
Next, step
208
is executed whereby the tracking operation ends and the track-seeking control starts. Then, in step
210
, whether the number of traversed tracks is equal to the number of tracks needed for the track-seeking control is determined. If not, step
208
is repeated. If yes, in step
212
, the track-seeking control is ended and the tracking operation is started and step
202
is repeated.
Generally, there is a phenomenon called eccentricity for the optical disk
101
. The eccentricity is formed due to the fact that the center of the optical disk
101
's circular hole is not located exactly in the center. Moreover, sometimes, when the optical disk
101
is spinning, there are vertical and horizontal vibrations. As a result, when the optical pickup head
104
is in seeking control, the turn-back occurs under some circumstances. For example, because of the serious eccentricity of optical disk
101
or noises when in low-speed track-seeking control or actuator's inertia when the sled motor is speeding up or slowing down, the turn-back of the optical pickup head occurs.
FIG. 3
is a block diagram illustrating the track-seeking control of the optical storage device. The RF signals reflected from the optical disk
101
are received by an optical pickup head
300
, and amplified by the preamplifier
302
. After the procession of the track-seeking processor
304
and the frequency compensation of the compensators
306
and
308
, the RF signals are inputted to power amplifiers
310
and
312
for fine tuning of the objective lens actuator
314
and rough tuning of the sled motor
316
, respectively. Then, the whole process is repeated until the target track is found, that is, the purpose of the track-seeking control is achieved.
Here, the track-seeking processor
304
and compensators
306
and
308
are in the control IC
108
shown in FIG.
1
. The track-seeking processor
304
is used to reduce the turn-back of the track-seeking control of the optical storage device according to the invention.
Referring to
FIG. 4
, a diagram of the target speed and the actual speed of the track-seeking control is illustrated. In
FIG. 4
, the unbroken line
40
represents the target speed and the dotted line
42
represented actual speed. Considering the target speed first, it is assumed that the pickup head is to jump over 200 tracks. Speed of track-seeking control is kept at 20 kHz at the beginning. Then, when residual track number is 100, speed of track-seeking control slows down. The reasons that the target speed is set in this way are illustrated below. Because there are many tracks for seeking at the beginning, the target speed can be set in a higher speed. Then, when the target track is approached, the speed of track-seeking needs to slow down for preventing that the target track cannot be locked correctly because of inertia of the pickup head.
The actual speed of the pickup head starts from zero and responsive to the target speed until the target track is approached.
The difference between the target speed and the actual speed is called speed error. The speed error feeds back to the track-seeking processor
304
for controlling the spinning speed of the optical disk
101
. When the actual speed is smaller than the target speed, the speed error is positive. Then, when the speed error is fed back to the compensator, the actual speed is increased. On the other hand, when the actual speed is greater than the target speed, the speed error is negative. Then, when the speed error is fed back to the compensator, the actual speed is decreased.
Referring to FIG.
5
and
FIG. 6
,
FIG. 5
is a bloc
Criado Jorge Ortiz
Rabin & Berdo P.C.
To Doris H.
Via Technologies Inc.
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