Dynamic information storage or retrieval – Storage medium structure – Optical track structure
Reexamination Certificate
2001-08-10
2004-04-27
Dinh, Tan (Department: 2653)
Dynamic information storage or retrieval
Storage medium structure
Optical track structure
C428S064400
Reexamination Certificate
active
06728197
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a recording format of a large-capacity recordable type optical disk; and, more specifically, the invention relates to a multilayer large-capacity optical disk that is capable of performing random recording and which has more than one information recording layer.
One example of the track configuration of a conventional optical disk will be described with reference to
FIG. 11. A
plurality of groove tracks
11
and land tracks
12
are arranged alternately in a radial direction of a disk-shaped recording medium. Each track is wobbled in a radial direction by a relatively small amount. Further, each track is divided into a plurality of arc sectors aligned in a radial direction; and, at a beginning end of each arc sector, a header
6
containing address information is arranged, whereby a recorded region in the arc sector is identified. Therefore, the headers
6
are aligned in a radial direction, that is, they are arranged on plural radials. In this example, the width of each track is approximately 0.6 &mgr;m and the groove depth of the groove is approximately 60 nm. In this example, the length of the sector is approximately 6 mm, which corresponds to a user capacity of 2048 bytes. The groove and the land are wobbled in a radial direction by an amplitude of approximately 20 nm. The wobble period is set to 1/232 times the sector length, namely approximately 25 &mgr;m. This ratio of 1:232 is chosen so as to fulfil the need for a wobble period to be an integer multiple of the length of the recorded data (channel bit length). The reason for this is to make it possible to generate a recording clock from the wobble easily.
FIG. 11
is a view showing details of the header part at the top end of the track, namely an ID or address data part. In
FIG. 11
, pieces of the ID or address data are arranged so as to be aligned in a radial direction at a first location
631
and at a second location
632
. A track and its neighboring tracks are connected in such a way that the track on the groove
11
connects to such and the track on the land
12
connects to such. In the example of this figure, each ID or address data shown in the figure corresponds to the recorded region that is located on the right side thereof. Further, the ID or address data corresponding to a groove information track
3
on the right side of the figure is arranged at the first location
631
; the ID or address data corresponding to a land information track
4
is arranged at the second location
632
. That is, the arrangement is such that, for adjacent tracks, locations of the ID or address data are different from each other in a direction along the information track, and for adjacent-but-one tracks, locations of the ID or address data agree with each other in that direction. That is, looking at the configuration on a boundary line between a land track and a groove track, the configuration is such that the location for the ID or address data is divided into first and second regions, and either the first or second ID or address data region is arranged alternately, the same ID or address data region for every other track.
By virtue of this configuration, for example, when the light spot
21
scans the groove
11
, either pits of the first or second ID or address data are reproduced and there isn't a fear that crosstalk from the adjacent tracks would be generated. Therefore, it becomes possible to reproduce the address data allocated in prepits excellently without generating crosstalk. In this example, the address information of the prepits is recorded by means of the 8/16 modulation code (channel bit length: 0.14 &mgr;m).
The ID or address data of the header part is formed with small hollows (pits), and these are formed as an unevenness of the substrate or other features together with the groove etc. during the manufacture of the disk.
A phase change type recording layer (GeSbTe) is used as the recording layer, and the recorded mark is formed in the form of a non-crystalline region.
Regarding the foregoing conventional examples, for example, JP-C-2856390 gives a detailed description.
With an arrangement of the ID or address data are provided in the above-mentioned conventional example, the effect of crosstalk arising from the ID or address data of the adjacent tracks can be eliminated. However, there is a problem in that, when the data is reproduced, for example, under a condition such that the ID or address data of a certain track and that of an adjacent-but-one track are both covered with a single light spot, there occurs the effect of crosstalk to a large degree. For example, as shown in
FIG. 12
, when the light spot is focused on one layer
16
of two recording layers in an optical disk having two layers therein and the reproducing is performed there, a condition may occur as a result of the light spot intercepting the other layer
15
. The reason for this is that, since the light spot is not focused on the layer
15
, the light spot is out of focus and becomes considerably large; and, therefore, the reading operation is affected by the plural tracks simultaneously. In this case, the ID or address data part aligned in a radial direction will come under a single light spot simultaneously and the effect of the ID or address part data becomes extremely large. Therefore, the extension of the technology to a two-layer recording medium has been substantially impossible.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a recording format for an optical disk that solves the above-mentioned problem and that can easily be applied to a two-layer recording medium.
The following means (or configurations) are used to achieve the object of this invention.
(1) An optical disk having at least one or more information recording layers therein is configured in such a way that there are provided at least a plurality of spiral information tracks each corresponding to one rotation of the disk on the information recording layer, a plurality of information recording units are arranged on the said plurality of tracks, any two of the information recording units that are arranged on all the tracks located in a doughnut region demarcated by two concentric circles with a spacing of 5 &mgr;m in a radial direction are arranged such that their top ends are separated by at least 5 &mgr;m or more in the circumferential direction. In this configuration, the information tracks, each specified as being wobbled in a radial direction with an almost constant frequency, are used and the amplitude of the wobble is specified to be constant in a radial direction. More preferably, the wobble and the recording unit are arranged in synchronization with each other.
Thanks to this format, even when the recorded region and unrecorded region exist together on the recording layer, any recording units existing in the tracks located in the doughnut region demarcated by the concentric circles with a spacing of 5 &mgr;m do not come into alignment to each other in the circumferential direction; and, therefore, when the defocussed light spot moves in the circumferential direction, the light spot will not move from the recorded regions to non-recorded regions or vice versa over a plurality of tracks simultaneously. Therefore, the reproduced signal and the servo signal, which are obtained by the reflected light of the light spot, do not suffer abrupt changes.
In an optical disk having therein a plurality of recording layers that can be accessed from one side of the disk, when one of the layers (a first layer) is being recorded/reproduced, the light spot is defocused (out of focus) on the second layer (with a recording format according to the present invention) to a degree corresponding to the amount of the layer spacing. The size of this defocused light spot is proportional to the layer spacing, and it is common that the size is set to be, for example, 10 times the spot size (0.5-1 &mgr;m) that was focused to the diffraction limit of light or more, in consideration of the effect of the
Ariyoshi Tetsuo
Kurokawa Takahiro
Maeda Takeshi
Miyamoto Harukazu
Shintani Toshimichi
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