Dynamic information storage or retrieval – With servo positioning of transducer assembly over track... – Optical servo system
Reexamination Certificate
2001-11-26
2004-03-30
Patel, Gautan R. (Department: 2655)
Dynamic information storage or retrieval
With servo positioning of transducer assembly over track...
Optical servo system
C369S044350, C369S053140, C369S053300, C360S077030
Reexamination Certificate
active
06714492
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical disc player, and more particularly, to an optical disc player which compensates for eccentricity components regardless of the playback speed of an optical disc.
2. Description of the Related Art
Generally, compact disc players (CDP) or digital video disc players (DVDP) emit laser on the track of a disc, pick up a reflected ray and read information contained in the reflected ray that has been picked up. The disc has a plurality of spiral tracks, and pits having information data are contained in each track. The laser reads the information while following the spiral tracks.
Eccentricity may result in the event that the tracks are not manufactured in the structure of a concentric circle or if the central axis of a spindle motor rotating the disc is altered. A laser beam may deviate from the tracks when following the tracks to read information if the eccentricity deviates from the error tolerance range of an optical disc player.
FIG. 1
shows an example of a conventional optical disc player. Referring to
FIG. 1
, the conventional optical disc player includes an optical disc
10
, a pickup
20
, a radio frequency (RF) amplifier
50
, a focusing servo
60
, a tracking servo
70
, a spindle controller
80
and a compensating circuit
100
.
FIG. 2
shows another example of a conventional optical disc player. Referring to
FIG. 2
, the conventional optical disc player includes the optical disc
10
, the pickup
20
, the RF amplifier
50
, the focusing servo
60
, the tracking servo
70
, the spindle controller
80
and the compensating circuit
100
.
Eccentricity compensation in the conventional optical disc players is performed in accordance with the following. In
FIG. 1
, an eccentricity compensator
130
detects an eccentricity from the output signal of the tracking servo
70
, and an adder
120
combines the output signal of the tracking servo
70
with a signal which compensates for the detected eccentricity. The signal output from the adder
120
, i.e., the signal compensated for the eccentricity, controls a tracking actuator
40
in the pickup
20
.
In
FIG. 2
, the eccentricity compensator
130
extracts an eccentricity from the output signal of the RF amplifier
50
, and the output signal of the RF amplifier
50
is combined in the adder
120
with a signal from the eccentricity compensator
130
which compensates for the eccentricity. The signal output in the adder
120
, i.e., the signal compensated for the eccentricity, controls the tracking actuator
40
in the pickup
20
, via the tracking servo
70
.
The conventional optical disc players shown in
FIGS. 1 and 2
compensate for the eccentricity at the very place where the eccentricity is extracted, i.e., the output end of the tracking servo
70
(
FIG. 1
) and the output end of the RF amplifier
50
(FIG.
2
).
A tracking filter (not shown), which is one of the elements constituting the tracking servo
70
, outputs a signal having a phase delay. In the case of
FIG. 1
, the compensating circuit
100
has a disadvantage in that a phase delay included in an extracted eccentricity in the tracking filter must be considered. In
FIG. 2
, a signal, which is compensated in the compensating circuit
100
and then is transferred to the tracking actuator
40
via the tracking servo
70
, causes phase delay when passing through the tracking servo
70
, which results in incorrect eccentricity compensation.
FIG. 3
is a waveform diagram of signals related to eccentricity compensation in a conventional optical disc player. As can be seen in
FIG. 3
, a signal FG is the output signal of a disc rotation information detector
110
, a signal TE is an actual eccentricity which is input into the eccentricity compensator
130
from the tracking servo
70
or the RF amplifier
50
, a signal DE is an eccentricity extracted in accordance with the edge of the signal FG in the eccentricity compensator
130
and a signal EC which is compensated for eccentricity is the output signal of the adder
120
.
In
FIG. 3
, the eccentricity compensation rendered in a conventional optical disc player compensates for eccentricity during the subsequent rotation of an optical disc by extracting eccentricity included in the output of the RF amplifier
50
or the tracking servo
70
at the edge of the output signal FG of the disc rotation information detector
110
and storing the extracted eccentricity in a memory. However, with regard to the compensated signal EC (which is indicated as TRD in FIGS.
1
and
2
), the discontinuous points of an eccentricity, i.e., the portions corresponding to the edges of the signal FG, function as a high frequency component in the tracing servo
70
thereby preventing stable operation of the tracking actuator
40
.
FIG. 4
is a waveform diagram of signals related to eccentricity compensation when changing the playback speed of a disc in a conventional optical disc player. Referring to
FIG. 4
, the signal FG is the output signal of the disc rotation information detector
110
and a signal ECC is an eccentricity to be compensated for. An eccentricity to be extracted and compensated at 32-times speed is difficult to be correctly compensated at 24-times speed or an even slower section where the eccentricity is too large.
SUMMARY OF THE INVENTION
To solve the above problems, it is an objective of the present invention to provide an optical disc player that solves phase delay by making the positions where an eccentricity error is extracted and compensated for different from each other and includes a pulse signal generator to produce a plurality of pulse signals corresponding to a signal FG changing according to the change of the playback speed of a disc.
Accordingly, to achieve the above objective, there is provided an optical disc player according to the present invention including a spindle controller, a pickup, a radio frequency (RF) amplifier, a focusing servo, a tracking servo and an eccentricity compensator. The spindle controller rotates an optical disc. The pickup has a focusing actuator and a tracking actuator and reads information recorded on the optical disc. The RF amplifier detects and amplifies a focusing error signal and a tracking error signal from information on the optical disc obtained from the pickup. The focusing servo controls the focusing actuator in response to the amplified focusing error signal. The tracking servo outputs a tracking control signal in response to the amplified tracking error signal. The eccentricity compensator outputs a signal which compensates for the eccentricity of an optical disc in response to the output signal of the spindle controller, the amplified tracking error signal and the amplified tracking control signal. The eccentricity compensator detects the rotation period of the optical disc, produces a plurality of pulses using the detected rotation period, detects an eccentricity included in the amplified tracking error signal according to the plurality of generated pulses and generates a compensating signal for the detected eccentricity. Also, the compensating signal automatically changes in relation to the playback speed of the optical disc.
In one embodiment, the eccentricity compensator includes a disc rotation detector, a pulse signal generator, an eccentricity controller, an eccentricity compensator and an adder. The disc rotation detector outputs a series of digital pulses every rotation of the optical disc in response to the output signal of the spindle controller. The pulse signal generator outputs first and second pulse signals in response to the series of digital pulses. The eccentricity controller outputs an eccentricity control signal which indicates whether the eccentricity of the optical disc is to be compensated for. The eccentricity compensator outputs an eccentricity compensation signal in response to the eccentricity control signal, the first pulse signal, the second pulse signal and the amplified tracking error signal. The adder combines the eccentricity compensation
Mills & Onello LLP
Patel Gautan R.
Samsung Electronics Co,. Ltd.
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