Dynamic information storage or retrieval – Condition indicating – monitoring – or testing – Including radiation storage or retrieval
Reexamination Certificate
2001-08-13
2004-05-11
Huber, Paul W. (Department: 2653)
Dynamic information storage or retrieval
Condition indicating, monitoring, or testing
Including radiation storage or retrieval
C369S047280, C369S275300
Reexamination Certificate
active
06735158
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a multilayer optical disc having a plurality of recording reproduction surfaces, a method and a device for recording optical information in this multilayer optical disc.
BACKGROUND ART
A conventionally known multilayer optical disc capable of recording on and reproducing from a plurality of recording reproduction surfaces is described, for example, in JP 10(1998)-505188A.
In the following, the structure of a conventional multilayer optical disc will be explained by referring to the drawings.
FIG. 7
is a cross-sectional view showing a conventional optical disc
10
taken in the direction perpendicular to the track direction. In addition, for simplifying the explanation, an optical disc of a double layer structure will be used.
As shown in
FIG. 7
, a guiding groove
7
for tracking (alternatively, an address signal recorded in advance and formed as a pit) is formed on one surface side of a first substrate
1
, and further on this surface, a recording reproduction film for partially reflecting and partially transmitting an optical beam
8
entering the first substrate
1
, focused by an objective lens
9
, is formed to create a first recording reproduction surface
3
. Furthermore, a guiding groove
6
for tracking (alternatively, an address signal recorded in advance and formed as a pit) also is formed on the surface of a second substrate
2
, and a recording reproduction film for reflecting the optical beam
8
passing through the first recording reproduction surface
3
is formed to create a second recording reproduction surface
4
. Furthermore, a separating layer
5
is interposed to separate the first recording reproduction surface
3
and the second recording reproduction surface
4
and to bond them together.
However, the multilayer structure as mentioned above (double layer structure in the conventional example) suffers from the following problem when the bonded state in the cross-sectional view taken perpendicular to the aforementioned cross-sectional view, that is in the track direction, is as that shown in FIG.
8
.
In addition, for explanatory purposes,
FIG. 8
expresses the actual sector structure (shown in FIG.
9
(
b
)) of a multilayer optical disc, which is shown as a plan view in FIG.
9
(
a
), in the form of a schematic sector structure for each recording reproduction surface.
FIG.
9
(
b
) is, as shown in FIG.
9
(
a
), an enlarged view of the vicinity of an address area
92
in a certain track among a group of tracks
91
formed as concentric circles or spirally in the multilayer optical disc, and shows a part of a groove portion
93
in the (n−1)th sector, an address pit portion
941
corresponding to an address area of the nth sector to be described later, and a part of a groove portion
942
in the following nth sector
94
. This groove portion, expressed in the form of a schematic sector structure, is divided into a gap area and a data area to be described later.
Moreover, the constituent elements shown in
FIG. 7
, i.e. the first substrate
1
, the second substrate
2
and the separating layer
5
are omitted in
FIG. 8
for explanatory purposes.
In
FIG. 8
,
31
is a first recording reproduction surface, and
41
is a second recording reproduction surface.
311
,
312
and
313
respectively are an address area, a data area and a gap area for dividing the address area
311
and the data area
312
in the first recording reproduction surface
31
. Moreover,
411
,
412
and
413
respectively are an address area, a data area and a gap area for dividing the address area
411
and the data area
412
in the second recording reproduction surface
32
.
The gap areas
313
,
413
are provided to perform a signal processing, when a recording and a reproduction for a multilayer optical disc are performed by a drive, by clearly separating a reproduced address signal and a reproduced data signal of a data area, and by avoiding the gap areas
313
,
413
, the recording operation is performed respectively for the first recording reproduction surface
31
and the second recording reproduction surface
41
.
However, as shown in
FIG. 8
, when the heads of the address areas
311
and
411
, that is, the front positions of sectors are bonded together by a shift L
1
, and when this amount of shift L
1
is larger than a length G
1
of the gap areas
313
and
413
, an area &Dgr;
1
, which is an area at the rear end portion in the address area
311
of the first recording reproduction surface
31
, overlaps with an area &Dgr;
2
, which is an area at the front end portion in the data area
412
of the second recording reproduction surface
41
, in the irradiation direction of an optical beam
81
, that is, seen from above the surface. In addition, a length of the area &Dgr;
1
and that of the area &Dgr;
2
are equal to L
1
−G
1
.
Furthermore, the optical beam
81
passes through the area &Dgr;
1
of the first recording reproduction surface
31
and is emitted onto the area &Dgr;
2
of the second recording reproduction surface
41
to record information.
Here, when the two recording reproduction surfaces of this multilayer optical disc are made of phase change type recording reproduction films, a recording in a phase change type recording reproduction film is performed based on the principle of changing its crystal structure by irradiation of a high-power optical beam. Therefore, when the recording is preformed for the area &Dgr;
2
in the second recording reproduction surface
41
, that is, for the area at the front end portion in the data area
412
of the second recording reproduction surface
41
, the high-power optical beam
81
is emitted also onto the area &Dgr;
1
at the rear end portion in the address area
311
of the first recording reproduction surface
31
.
Therefore, the crystal structure of the recording reproduction film formed on one part in the address area
311
of the first recording reproduction surface
31
also is affected. As a result, when the address area
311
of the first recording reproduction surface
31
is to be reproduced after completing the recording operation for the second recording reproduction surface
41
, the S/N ratio of the reproduced signal is deteriorated, and the problem that the address information cannot be recognized correctly arises.
Furthermore, the example shown in
FIG. 8
was explained by referring to the case where the first recording reproduction surface
31
and the second recording reproduction surface
41
were bonded together in a state in which the front position in the sector of the first recording reproduction surface
31
is shifted to the right side of the surface relative to the second recording reproduction surface
41
. Similarly, also in the case where the front position in the sector of the first recording reproduction surface
31
is shifted to the left side of the surface relative to the second recording reproduction surface
41
and bonded together, the address area
411
of the second recording reproduction surface
41
is affected when a recording operation for the first recording reproduction surface
31
is performed. As a result, the S/N ratio of the reproduced signal from the address area
411
is deteriorated, and the problem that the address information cannot be recognized correctly arises.
Moreover, the conventional example was explained by referring to the case of having two recording reproduction surfaces, but also in the case of having three and more recording reproduction surfaces, a recording operation for an arbitrary recording reproduction surface affects address areas in other recording reproduction surfaces, so that the problem that this address information cannot be recognized correctly arises.
Furthermore, in the case where data are already recorded in the data areas of both recording reproduction surfaces, at the time when a recording operation is performed for one of the recording reproduction surfaces, also for the data area in the other recording reproduction surface, a high-power optical beam is emitted onto an
Futakuchi Ryutaro
Ohara Shunji
Huber Paul W.
Matsushita Electric - Industrial Co., Ltd.
Merchant & Gould P.C.
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