Dynamic information storage or retrieval – Storage or retrieval by simultaneous application of diverse...
Reexamination Certificate
1999-08-25
2001-07-03
Dinh, Tan (Department: 2651)
Dynamic information storage or retrieval
Storage or retrieval by simultaneous application of diverse...
C369S275400
Reexamination Certificate
active
06256266
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to magneto-optical recording media, particularly to the structure of a magneto-optical recording medium including predetermined periodic discontinuous regions at the land or groove.
2. Description of the Background Art
Attention is focused on the magneto-optical recording medium as a rewritable and reliable recording medium of large storage capacity. The magneto-optical recording medium has began to be actually used as the computer memory and the like. Recently, the standard of AS-MO (Advanced Storaged Magnetic Optical) is in progress as a magneto-optical recording medium having the storage capacity of 6.0 Gbytes for practical usage. As shown in
FIG. 1
, the magneto-optical recording medium of such a high density has a plane structure in which a groove
40
and land
41
having the width of approximately 0.6 &mgr;m are formed alternately in the radial direction. Discontinuous regions are provided periodically at groove
40
and land
41
. More specifically, landed regions
42
are periodically formed at groove
40
. Also grooved regions
43
are formed periodically at land
41
.
In recording and/or reproducing a signal onto or from the magneto-optical recording medium, discontinuous regions
42
and
43
provided at groove
40
and land
41
are detected to generate a periodic fine clock signal from which a synchronizing signal is generated.
In the magneto-optical recording medium having a plane structure as shown in
FIG. 1
, further reduction of the width of groove
40
and land
41
for a higher density than the storage capacity of 6.0 Gbytes will result in a lower signal intensity for the detection of discontinuous regions
42
and
43
as shown in FIG.
2
. The discontinuous regions
42
and
43
cannot be detected properly. Thus, there is a problem that is difficult to generate an accurate synchronizing signal.
SUMMARY OF THE INVENTION
In view of the foregoing, an object of the present invention is to provide a magneto-optical recording medium that allows accurate detection of discontinuous regions and that allows generation of a stable synchronizing signal even when the width of the groove and land is narrowed for higher density.
According to an aspect of the present invention, a magneto-optical recording medium includes a substrate with grooves and lands. The lands and grooves are provided alternately forming a spiral or concentric track. The land has a plurality of first discontinuous regions formed periodically. The groove has a plurality of second discontinuous regions formed periodically. Each second discontinuous region is positioned corresponding to a region between two first discontinuous regions consecutive in one or the other land adjacent to that groove.
Therefore, a periodic fine clock signal of sufficient intensity can be obtained according to the discontinuous region even when the width of the land and groove is narrow.
Preferably, each second discontinuous region is positioned corresponding to a region at the center of the aforementioned two first discontinuous regions. This facilitates the cutting of the substrate.
According to another aspect of the present invention, a magneto-optical recording medium includes a substrate having grooves and lands. The grooves and lands are provided alternately forming a spiral or concentric track. One of the land and groove is continuous, and the other of the land and groove includes a plurality of discontinuous regions formed periodically.
Since discontinuous regions are to be formed only at the land or groove, fabrication of the magneto-optical recording medium is facilitated.
Preferably, each land and groove has a width equal to or smaller than 0.44 times the spot diameter of the laser beam directed onto the magneto-optical recording medium. Therefore, a periodic fine clock signal of sufficient intensity can be obtained according to the discontinuous region in the land and groove without being limited by the wavelength of the laser beam.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.
REFERENCES:
patent: 4744074 (1988-05-01), Imanaka et al.
patent: 4855991 (1989-08-01), Kaku et al.
patent: 4879707 (1989-11-01), Getreuer et al.
patent: 5084860 (1992-01-01), Maeda et al.
patent: 5444682 (1995-08-01), Yamada et al.
patent: 5539724 (1996-07-01), Ohtomo
patent: 6044049 (2000-03-01), Fujiune et al.
Armstrong Westerman Hattori McLeland & Naughton LLP
Dinh Tan
Sanyo Electric Co,. Ltd.
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