Dynamic information storage or retrieval – With servo positioning of transducer assembly over track... – Optical servo system
Reexamination Certificate
2003-01-29
2004-04-06
Huber, Phil W. (Department: 2653)
Dynamic information storage or retrieval
With servo positioning of transducer assembly over track...
Optical servo system
C369S053120
Reexamination Certificate
active
06717894
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a recording method for recording data on an optical disc and a recording and/or reproducing apparatus for recording and/or reproducing data on or from an optical disc.
2. Description of Related Art
Heretofore, an optical disc called a DVD (digital versatile disc) is furnished as an optical disc convenient for multi-media usage. In this optical disc, the recording capacity is appreciably increased due to the small pitch of the recording track or the data compression technique.
This optical disc copes with a wide field of application encompassing video data, audio data or computer data. This optical disc is used as a replay-only data recording medium in which data is formed as pits. This optical disc is called a DVD-ROM.
There has also been furnished an interchangeable recordable optical disc which can be reproduced on a reproducing apparatus adapted to cope with this optical disc. Specifically, the formats for a DVD+RW (DVD+Rewritable), DVD−RW (DVD-Rewritable) and DVD-R (DVD-Recordable) on which data can be recorded only once.
In recording and/or reproducing these optical discs, tracking error signals indicating the deviation from the recording track of a converging point of the laser light are generated to follow the recording tracks or row of pits carrying the recorded data.
The tracking error signals are generated in accordance with the three spot system, differential push-pull PPP system or the differential phase detection DPD system. Specifically, the tracking error signals are generated based on detection signals obtained by a light receiving section
101
shown in FIG.
1
.
The light receiving section
101
is made up of four split areas S
A
, S
B
, S
C
and S
D
and two areas each split into two, namely areas S
E
, S
F
, S
G
and S
H
.
The light receiving section
101
is provided on an optical pickup facing the signal recording surface of the optical disc, and is fed with the reflected laser light from the optical disc. From the respective areas S
A
, S
B
, S
C
, S
D
, S
E
, S
F
, S
G
and S
H
of the light receiving section
101
are output RF signals A, B, C, D, E, F, G and H associated with the received light quantities.
In the three-spot system, the laser light is split using a diffraction grating to generate three spots along a recording track formed on a signal recording surface of the optical disc. The tracking error signals TE
3SP
of the three spot system are generated by operational processing of
TE
3SP
=(
E+F
)−(
G+H
).
In the DPP system, the laser light illuminated on an optical disc is split using a diffraction grating to generate three spots along the recording track formed on the signal recording surface of the optical disc. In the DPP system, tracking error signals TE
DPP
are generated by a circuit shown in FIG.
2
. In this circuit, the tracking error signals TE
DPP
are generated by operational processing:
TE
DPP
={(
A+D
)−(
B+C
)}−{(
F+H
)−(
E+G
)}.
That is, the result of an operation (F+H)−(E+G) is calculated from the signals E, F, G and H in a first difference taking unit
102
, whilst the result of an operation (A+D)−(B+C) is calculated from the signals A, B, C and D in a second difference taking unit
104
. The aforementioned tracking error signals TE
DPP
is calculated from the results of the above operational processing.
In the DPD system, the tracking error signals are generated on reception of the laser light radiated towards and reflected back from the pits on the optical disc.
In the DPD system, the tracking error signals TE
DPD
are generated by a circuit shown in FIG.
3
. In this circuit, the signals A, B, C and D from the light receiving section
101
are filtered by filters
105
a
,
105
b
,
105
c
and
105
d
and made into a bi-level signal on level comparison to a reference potential V
C
in comparators
106
a
,
106
b
,
106
c
and
106
d.
The results of comparison in the level comparators
106
a
,
106
b
are phase-compared in a phase comparator
107
a
, whilst the results of comparison in the level comparators
106
c
,
106
d
are phase-compared in a phase comparator
107
b
. The results of comparison in these phase comparators
107
a
,
107
b
are integrated by an integrating circuit
108
to give the tracking error signals TE
DPD
.
The filters
105
a
,
105
b
.
105
c
and
105
d
are made up of a high-pass filter HP
109
for cutting off dc components and two band-pass filters
110
,
111
for amplifying EFM signal components.
The outputs of the band-pass filters
110
,
111
are of different frequency response, as shown in FIG.
5
. An output selection switch SW
DPD
switches between these outputs.
In capturing data from the optical disc, tracking error signals by the DPD system are used. The DPD system has been selected as giving the best signal in consideration of the offset or tilt of the optical disc and the lens movement.
Meanwhile, a recording apparatus adapted for coping with a recordable optical disc, such as DVD+RW, DVD−RW or DVD-R, data are recorded so that the data will be reproduced by a reproducing apparatus adapted for coping with a replay-only optical disc, such as DVD-ROM.
This recording apparatus applies the servo, such as tracking servo or focussing servo to the recordable optical disc, in its non-recorded state, to generate the timing for recording. Since no pits are formed in an optical disc in which no data has been recorded, the aforementioned recording apparatus controls the servo in a manner different from the aforementioned reproducing apparatus, that is with the use of a method for generating tracking error signals using a recording track. Moreover, the recording apparatus generates the timing for recording the data using signals not detectable by the aforementioned reproducing apparatus, such as wobbling of the grooves formed as recording tracks.
The aforementioned reproducing apparatus generates tracking error signals in accordance with the DPD system of detecting the reflected light from the pits recorded on the replay-only optical disc. From the reproduced data, synchronization signals are detected by the PLL (phase-locked loop) to generate the timing signals pertinent to reproduction.
On the other hand, the recording apparatus generates tracking error signals from the recording track in accordance with the DPP system. The data write timing is acquired using an ADIP (address in pre-groove) signal, recorded by modulating the groove of the recording track at a low speed, followed by wobbling, and also using fine clock marks, obtained on high-speed modulation. Meanwhile, this timing can be used not only during recording but also during reproduction.
In light of the above, it may be an occurrence that a recordable optical disc, on which data has been recorded by the above-described recording apparatus, cannot be reproduced by the above-mentioned reproducing apparatus adapted for coping with the replay-only optical disc. For example, assume that there is portion of the recordable optical disc, if small, in which pits have not been recorded appropriately. With the aforementioned recording apparatus, there is raised no particular problem if the unreadable portion is in a range of possible error correction, even though the portion cannot be read correctly. However, there may be an occasion where tracking error signals are generated by the DPP method by the presence of the groove, but the generation of the tracking error signals by the DPD method becomes difficult to disable the servo control and the readout of such portion.
The same applies for the timing. That is, in the aforementioned recording apparatus, timing compensation becomes possible by the timing generated by ADIP or ATIP even though timing generation cannot be made by the signal from the pits recorded and/or reproduced, whereas, in the aforementioned reproducing apparatus, such compensation is not possible, thus aga
Frommer William S.
Frommer & Lawrence & Haug LLP
Huber Phil W.
Polito Bruno
Sony Corporation
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