Dynamic information storage or retrieval – Condition indicating – monitoring – or testing – Including radiation storage or retrieval
Reexamination Certificate
2001-01-19
2004-04-27
To, Doris H. (Department: 2655)
Dynamic information storage or retrieval
Condition indicating, monitoring, or testing
Including radiation storage or retrieval
C369S044280, C369S124150
Reexamination Certificate
active
06728184
ABSTRACT:
This application incorporates by reference Taiwanese application Serial No. 89101714, Filed Feb. 1st, 2000.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates in general to a method and device of determining the slice level of a radio frequency ripple (RFRP) signal in an optical storage device, and more particularly to the method and device of using a radio frequency center (RFCT) signal, as the slice level of the RFRP signal when the optical storage device is on tracking.
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.
Generally, there is a phenomenon called run-out for the optical disk
101
. The run-out phenomenon occurs due to the fact that the circular hole of the optical disk
101
is not located precisely in the center. As a result, when the optical disk
101
is spinning, the slight offset of the center hole causes track being read to run-out of the range of the objective lens
120
. Moreover, vertical and horizontal vibrations sometimes occur when the optical disk
101
is spinning, and a misread of the track is caused. As can be seen, tracking is not a trivial pursuit and as a result, a tracking controller is needed.
FIG. 2
is a block diagram illustrating the tracking servo apparatus of a optical storage device. Referring to
FIG. 2
, the tracking process is illustrated as follows. The optical sensor
200
receives the reflected light from the disk, and then outputs the received signals to the preamplifier
202
. These signals are amplified by the preamplifier
202
and transmitted to the tracking controller
204
and then to the compensators
206
and
208
for the desired frequency response compensation of the system. The compensated signals are then amplified by the power amplifiers
210
and
212
to drive the objective lens actuator
214
and the sled motor
216
, respectively. Then a position of the objective lens is obtained, and the position of the objective lens is fed back along with a disk eccentricity and vibration until the optical sensor
200
has exactly tracked the track needed.
In the above description, the tracking controller
204
and the compensators
206
and
208
mentioned are located in the control IC
108
mentioned in FIG.
1
.
FIG. 3
illustrates various signals needed by the tracking controller
204
and the compensator
206
mentioned in FIG.
2
. The signals inputted to the tracking controller
204
are transmitted from the preamplifier
202
mentioned in FIG.
2
.
FIG. 4
is a timing diagram of various signals illustrated in FIG.
3
. Before time T
7
, the objective lens moves outward relative to the optical disk whereas after time T
7
, the objective lens moves inward relative to the optical disk. During the outward movement of the objective lens (i.e. before time T
7
), there are negative and positive feedback periods. In the negative feedback period, for example, between time T
1
and T
3
, the TE signal makes the objective lens move toward the track needed. On the other hand, in the positive feedback period, between time T
3
and T
5
, the TE signal makes the objective lens move away from the track needed.
Referring to
FIG. 4
, when the objective lens is moving outward, the TE signal is in the negative feedback period when the slope of the TE signal is positive and in the positive feedback period when the slope of the TE signal is negative. On the contrary, when the objective lens is moving inward, the TE signal is in the positive feedback period when the slope of the TE signal is positive and in the negative feedback period when the slope of the TE signal is negative.
The TE signal is an index of the tracking operation. For example, during time T
2
and T
6
, the amplitude of the TE signal is 0 which means that laser spot is on the track needed. However, when laser spot is located between two tracks, the amplitude of the TE signal is also 0. An example is time T
4
in which TE is zero during the positive feedback period. On the other hand, when laser spot is on the edge of a track, the amplitude of the TE signal is highest. For example, at time T
1
or T
3
.
The RFRP signal is derived from the RF signal which is the data signal read from the optical disk. When the laser spot is tracking on the desired track, the amplitude of the RF signal is highest; when the laser spot is between two tracks, the amplitude of the RF signal is lowest. The RFRP signal is obtained either by a difference value between the bottom envelope and the peak envelope of the RF signal or by a low-pass filtering of the RF signal.
When the laser spot is tracking on the track
103
in
FIG. 1
, the amplitude of the RFRP signal is highest while when the laser spot is between two tracks, the amplitude of the RFRP signal is lowest.
The relationship between the phases of the RFRP signal and the TE signal is illustrated as follows. When the objective lens is moving outward, that is, before time T
7
, the phase of the RFRP signal is ahead of the phase of the TE signal by 90 degrees. On the other hand, when the objective lens is moving inward, that is, after time T
7
, the phase of the RFRP signal is behind the phase of the TE signal by 90 degrees as shown in FIG.
4
.
In
FIG. 4
, a radio frequency zero crossing (RFZC) signal is derived from the RFRP signal. While tracking in the conventional technique, there is a fixed reference value, for example the DC level of the RFRP signal during tracking off period, for the slice level of the RFRP signal. When the RFRP signal is larger than the slice level, the RFZC signal is at high level while the RFRP signal is lower than the slice level, the RFZC signal is at low level. Moreover, the RFZC signal is the same as the positive or negative feedback periods of the TE signal. That is, when the RFZC signal is at high level, the TE signal
Ortiz-Criado Jorge
Rabin & Berdo P.C.
To Doris H.
Via Technologies Inc.
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