Dynamic information storage or retrieval – Binary pulse train information signal – Binary signal level detecting using a reference signal
Reexamination Certificate
2001-09-20
2002-12-10
Edun, Muhammad (Department: 2653)
Dynamic information storage or retrieval
Binary pulse train information signal
Binary signal level detecting using a reference signal
C369S059100, C369S124150
Reexamination Certificate
active
06493306
ABSTRACT:
BACKGR
0
UND OF THE INVENTION
This invention relates to an optical disk in which signals are recorded both onto recording tracks in depressed portions formed by guide grooves and onto recording tracks on projecting portions between the guide grooves, and to an optical disk apparatus, and an optical disk tracking method.
As a data recording method for a large-capacity rewritable optical disk, a land/groove recording method in which data is recorded both in guide grooves (sometimes denoted by G) and on lands (sometimes denoted by L) to increase a recording density, has been proposed. When this method is used, the recording density can be increased because the recording track pitch can be halved compared to an optical disk having the same groove pitch but for which this method is not used. Grooves and lands may also be referred to as depressed portions and projecting portions, respectively.
As a conventional land/groove recording optical disk, there is provided an optical disk shown in
FIG. 13
, for example. It is described in Japanese Examined Patent Publication 63-57859. As shown in
FIG. 13
, grooves
94
and lands
95
are formed by means of guide grooves inscribed on the substrate of the disk, and a recording film
91
is formed thereon. Recording marks
92
are formed on the recording film
91
extending both on the grooves
94
and the lands
95
. The grooves
94
and the lands
95
form continuous data recording tracks, respectively. A light-focused spot
93
of an optical disk drive apparatus for performing data recording and reproduction onto this recording medium records or reproduces data while scanning either of the recording tracks. With a conventional land/groove recording format, guide grooves are continuous on a disk. Thus, each of the data recording tracks of the grooves
94
and the data recording tracks of the lands
95
form a single continuous recording spiral.
A single spiral land/groove format is described next.
FIG. 14
shows the configuration of an optical disk having a format in which each data recording track of grooves (hereinafter also referred to as a groove track)
94
having a length corresponding to a revolution of the disk and each data recording track of lands (hereinafter also referred to as a land track)
95
also having a length corresponding to a revolution of the disk are connected alternately to form a data recording spiral. An example of optical disks having the format shown in
FIG. 14
in which groove tracks
94
and land tracks
95
are connected alternately to form a data recording spiral, is described in Japanese Unexamined Patent Publication 4-38633 and Japanese Unexamined Patent Publication 6-274896. The format of such optical disks is herein referred to as the single spiral land/groove format or the SS-L/G format.
An SS-L/G format optical disk has continuous data recording tracks on the disk, so that it is suitable for continuous data recording and reproduction. When an optical disk is used as a video file, for example, continuous data recording and reproduction is essential. However, in a conventional land/groove recording optical disk shown in
FIG. 13
, the land tracks
95
and the groove tracks
94
form separate data recording spirals. Thus, when data recording or reproduction is performed continuously from the land tracks
95
to the groove tracks
94
, for example, it is interrupted at least at one portion of the disk due to an access between the land tracks
95
and the groove tracks
94
. The same interruption occurs when data recording or reproduction is performed continuously from the groove tracks
94
to the land tracks
95
. In order to avoid such an interruption in the data recording or reproduction, it is necessary to provide an additional buffer memory, which raises the cost. If optical disk is of a single spiral land/groove format, no such an additional buffer memory is necessary.
In an SS-L/G format optical disk, however, a tracking servo polarity must be switched at every revolution of the disk. Since the detection of this tracking servo polarity switching point is difficult, application of the tracking servo is also difficult. For this reason, the SS-L/G format optical disk has found few practical applications. Although formatting an SS-L/G format optical disk is disclosed in Japanese Unexamined Patent Publication 4-38633 and Japanese Unexamined Patent Publication 6-274896 mentioned above, nothing is disclosed about a specific method of detecting a tracking servo polarity switching point.
In order to apply a tracking servo to an SS-L/G format optical disk, it is necessary to accurately detect between alternating points between alternating groove tracks and land tracks, and to switch a tracking servo polarity to be set for tracking a groove track or a land track. Examples of methods of detecting connecting alternating points connecting groove tracks and land tracks are disclosed in Japanese Unexamined Patent Publication 6-290465 and Japanese Unexamined Patent Publication 7-57302.
In the method disclosed in Japanese Unexamined Patent Publication 6-290465, depressed portions and projecting portions of a constant frequency are provided at the connecting points between land tracks and groove tracks.
FIG. 15
shows the configuration of an optical disk recording medium described in the above-mentioned publication. Referring to
FIG. 15
, the connecting points are at A1, A2, A3, B1, B2, etc. Between the connecting points next to each other either a land or a groove continues, and positional data such as a track address is represented by wobbling grooves.
In the method disclosed in Japanese Unexamined Patent Publication 7-57302, a flat part having no grooves or a predetermined pattern of pits are provided at the connecting points between groove tracks and land tracks. FIG.
16
A and
FIG. 16B
show the configuration of an optical disk recording medium described in the above-mentioned publication.
FIG. 16A
shows an example of a flat part provided at a connecting point, while
FIG. 16B
shows an example of a predetermined pattern of pits. In this prior art example, nothing is disclosed about positional data such as a track address, and it can be regarded that either a groove or a land continues between the connecting points on a spiral.
Now, description is directed to a case where pit pattern data for detecting a connecting point is provided on an optical disk in which each of the data recording tracks is composed of a plurality of data recording sectors having their own identification data. In the method of providing identification data by wobbling grooves, no interrupting portion is present in the groove of a data recording part in one revolution except for a connecting point. Thus, the problem of erroneous detection of a connecting point will not arise. However, the function of recording data onto a sector is restricted. For instance, data recording or reproduction in units of short sectors is difficult.
In contrast with an optical disk of the above-mentioned configuration, in the case of an optical disk such as a conventional ISO magneto-optical disk having a format in which preformatted identification data parts representing addresses and data recording parts recording user data are arranged separately on data recording tracks, if identification data and a connecting point between a groove and a land are represented in the same recording form, the problem of erroneous detection of the connecting point will arise. In order to avoid such a problem, it is necessary to ensure discrimination between the pit pattern of identification data and the pit pattern for detecting a connecting point between a groove and a land. In the example disclosed in Japanese Unexamined Patent Publication 7-57302, since the pit sequence as shown in
FIG. 16B
is provided only at connecting points, the problem of erroneous detection of the connecting point will not occur. However, when identification data is preformatted with a pit pattern similar to that for detecting a connecting point and arranged in a data recording track, it is nece
Gotoh Kenji
Ishida Yoshinobu
Nagasawa Masato
Nakane Kazuhiko
Oohata Hiroyuki
Edun Muhammad
Mitsubishi Denki & Kabushiki Kaisha
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