Dynamic information storage or retrieval – Control of storage or retrieval operation by a control... – Control of information signal processing channel
Reexamination Certificate
2001-03-21
2003-07-15
Huber, Paul W. (Department: 2653)
Dynamic information storage or retrieval
Control of storage or retrieval operation by a control...
Control of information signal processing channel
C369S053330, C369S124030
Reexamination Certificate
active
06594210
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a disc drive apparatus and a method for generating wobble information suitable for recording or reproduction of a disc recording medium on which recording tracks are formed, for example, in the form of grooves.
2. Description of the Related Art
A variety of discs, e.g., CDs-R (compact discs-recordable), CDs-RW (CDs-rewritable) and MDs (mini discs) have been developed and have spread as disc recording media.
In such CDS-R, CDs-RW and MDs, recording tracks are formed using grooves (guide grooves), and such grooves are wobbled to control the recording positions and the rotation of a spindle.
For example, such wobbles are formed based on frequency-modulated (FSK-modulated) signals according to information such as absolute addresses.
It is therefore possible to determine an address by extracting wobble information such as an absolute address from the groove.
For example, wobble information is extracted by an RF amplifier which generates necessary signals such as RF signals that are reproduction data, focus error signals FE and tracking error signals TE for servo control based on information of reflected light from spots of light projected upon a disc by a pickup.
The configuration of the RF amplifier depends on the method for controlling tracking of optical spots. For example, the well-known 3-spot method, push-pull system, DPP (differential push-pull) system and the like necessitate different configurations.
A method for generating wobble information in a conventional RF amplifier will now be described.
By way of example, a description will now be made on a method for generating wobble information in an RF amplifier which employs the DPP system as a tracking servo controlling system.
FIG. 9
shows a configuration of a DPP type RF processing circuit provided in a conventional disc drive apparatus.
In a disc drive apparatus in which tracking control is performed using a DPP system, a pickup generates a main spot for scanning a recording track and two side spots which are separate from the main spot.
Therefore, the pickup as a photo-detector
105
is provided with a main detector
151
that detects information of reflected light from the main spot and two side detectors
152
and
153
for detecting information of reflected light from the two side spots, respectively.
Referring to the actual locations of the detectors of the photo-detector
105
, the side detectors
152
and
153
are respectively provided in front of and behind the main detector
151
in the direction of a track. In
FIG. 9
, however, the side detectors
152
and
153
are shown side by side for better understanding of the circuit configuration.
The main detector
151
is divided by a division line in a direction orthogonal to a track formed on a disc and a division line in parallel with the track into four detection areas A, B, C and D, and information of reflected light from the recording track is detected by the detection areas A, B, C and D. Pieces of information on reflected light detected by the detection areas A through D are converted by respective photoelectric conversion portions
154
a,
154
b,
154
c
and
154
d
into electrical signals A, B, C and D depending on quantities of reflected light and are output to the RF processing circuit.
In the present specification, the electrical signals detected by the detection areas A through D and converted by the photoelectric conversion portions
154
a
through
154
d
are referred to as “detection signals A through D”, respectively.
The detection signals A through D from the respective photoelectric conversion portions
154
a
through
154
d
are output to an adder
131
and a main sample-and-hold circuit
132
provided in the RF processing circuit.
The adder
131
adds the detection signals A through D from the respective photoelectric conversion portions
154
a
through
154
d
and outputs a resultant sum signal (A+B+C+D) as an RF signal or reproduction data signal.
For example, the main sample-and-hold circuit
132
samples and holds the detection signals A through D based on sample pulses input thereto during data recording and allows the detection signals A through D to pass through as they are without sampling and holding them in any other occasion.
A main matrix calculation/amplification circuit (main matrix amplifier)
133
performs various arithmetic processes for obtaining, for example, tracking error signals TE, focus error signals FE, wobble information WOB and the like from the signals A through D output by the main sample-and-hold circuit
132
.
For example, it performs an arithmetic process (A+D)−(B+C) to obtain a tracking error signal TE and wobble information WOB before and during recording of data in a recording track and outputs the result of calculation as a main push-pull signal MPP.
Further, it performs an arithmetic process (A+C)−(B+D) to obtain a focus error signal FE.
For example, the main matrix amplifier
133
performs arithmetic processes (A+D) and (B+C) to obtain wobble information WOB after recording of data in a recording track and outputs the arithmetic outputs to AGC (automatic gain control) circuits
134
a
and
134
b,
respectively.
The AGC circuits
134
a
and
134
b
perform gain adjustment such that the amplitude levels of the arithmetic outputs (A+D) and (B+C) from the main matrix amplifier
133
become equal to each other and provides the output to a differential amplifier
135
.
The differential amplifier
135
outputs the difference between the output signal (A+D) from the AGC circuit
134
a
and the output signal (B+C) from the AGC circuit
134
b
as (A+D)−(B+C). Therefore, the differential amplifier
135
outputs a push-pull signal whose gain has been adjusted by the AGC circuits
134
a
and
134
b.
Switching of a switch
136
is controlled depending on the operating state of the disc drive apparatus.
For example, the switch is controlled such that it is switched between a position after recording of data and a position before and during recording of data, and the output of the differential amplifier
135
is output to a band-pass filter (BPF)
137
after recording of data. Before and during recording of data, the main push-pull signal MPP from the main matrix amplifier
133
is output to the BPF
137
.
The BPF
137
is a band-pass filter that allows wobble components having a central frequency of 22.05 kHz to pass through to eliminate other unnecessary frequency components. It extracts wobble components included in the push-pull signal input through the switch
136
to output wobble information WOB.
The side detectors
152
and
153
are divided into two detection areas E and F and G and H respectively by division lines in parallel with the track formed on the disc. Pieces of information of reflected light detected by the detection areas E through H are converted by photoelectric conversion portions
154
e,
154
f,
154
g
and
154
h
into respective output signals E, F, G and H which are in turn output to a side sample-and-hold circuit
138
of the RF amplifier.
In this case, the electrical signals detected by the detection areas E through H and converted by the photoelectric conversion portions
154
e
through
154
h
are referred to as “detection signals E through H”, respectively.
The side sample-and-hold circuit
138
receives the input of sample pulses similarly to the above-described main sample-and-hold circuit
132
. For example, it samples and holds the detection signals E through H based on the sample pulses during recording of data and allows the detection signals E through H to pass through without sampling and holding them in any other occasion.
A side matrix amplifier
139
performs an arithmetic process (F+H)−(E+G) to obtain a tracking error signal TE from the output signals E through H of the side sample-and-hold circuit
138
and outputs the arithmetic result to a differential amplifier
140
as a side push
Huber Paul W.
Kananen, Esq. Ronald P.
Rader & Fishman & Grauer, PLLC
Sony Corporation
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