Dynamic information storage or retrieval – Storage or retrieval by simultaneous application of diverse...
Reexamination Certificate
2000-12-12
2003-03-18
Faber, Alan T. (Department: 2651)
Dynamic information storage or retrieval
Storage or retrieval by simultaneous application of diverse...
C360S059000, C360S049000, C369S275300
Reexamination Certificate
active
06535463
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a method and apparatus for recording data signals on a disk-shaped recording medium, and to a recording medium for recording data signals.
Hitherto provided is so-called “magnetically induced super resolution (MSR) technique.” The MSR technique uses a material-characterized mask the behavior of which changes in accordance with the heat applied to the material. The changes in the behavior of the mask is utilized to record data at high density on a magneto-optical disk, thereby to reproduce images of super resolution, that is to reproduce images having high resolution that cannot be attained by optical reproduction technique.
A switched-connection, multi-layer film is used to provide an MSR magneto-optical disk. First, the principle of MSR will be explained, with reference to two types of two-layer magnetic films.
MSR achieved by means of FAD (Front Aperture Detection) will be described, with reference to FIG.
1
.
FIG. 1
shows various directions in which the two-layer magnetic film formed on the recording surface of a magneto-optical disk may be magnetized. The magnetic film is composed of two layers
101
and
102
. The first layer
101
, or surface layer, is a reproducing layer. The second layer
102
, or a base layer, is a recording layer. This holds true in any description that follows.
As shown at A in
FIG. 1
, the reproducing layer
101
and the recording layer
102
are magnetized in the direction opposite to the direction of an external magnetic field. As shown at B in
FIG. 1
, the reproducing layer
101
and the recording layer
102
are magnetized in the direction identical to the direction of an external magnetic field. Also shown in
FIG. 1
is an interface magnetic wall
100
at which the magnetism of the reproducing layer
101
meets that of the recording layer
102
.
As shown at A in
FIG. 1
, the direction of magnetization of the reproducing layer
101
is inverted when the temperature of the layer
101
rises from room temperature. That is, the direction is inverted when the intensity of the external magnetic field surpasses the sum of the coercive force and exchange force of there producing layer
101
. When the temperature of the recording layer
101
falls to room temperature, the direction of magnetization of the layer
101
changes to become the same as the direction of magnetization of the recording layer
102
.
As shown at B in
FIG. 1
, the direction of magnetization of the reproducing layer
101
remains unchanged even if the temperature of the layer
101
rises from room temperature. In other words, the direction is the same as the direction of magnetization of the recording layer
102
.
MSR accomplished by RAD (Rear Aperture Detection) will be described, with reference to FIG.
2
.
As shown at A in
FIG. 2
, the magnetic field of the reproducing layer
101
extends in the direction opposite to the direction of the external magnetic field, whereas the magnetic field of the recording layer
102
extends in the same direction as the direction of the external magnetic field. As shown at B in
FIG. 2
, both the reproducing layer
101
and the recording layer
102
are magnetized in the direction identical to the direction of the external magnetic field.
Namely, in the initial state, or at room temperature, the reproducing layer
101
is magnetized in a specific direction, irrespective of the direction of magnetization of the recording layer
102
. When the temperature of the reproducing layer
101
rises from room temperature, the direction of magnetization of the reproducing layer
101
changes, becoming the same as that of the recording layer
102
.
As shown at A in
FIG. 2
, the direction of magnetization of the reproducing layer
101
is inverted when the intensity of the external magnetic field surpasses the sum of the coercive force and exchange force of the layer
101
. As shown at B in
FIG. 2
, the reproducing layer
101
remains magnetized as long as the sum of its coercive force and exchange force surpasses intensity of the external magnetic field.
It suffices to impart a proper intensity to the external magnetic field in order to maintain this relationship. Nonetheless, it is necessary to impart a large coercive force to the recording layer
102
. Once the temperature of the reproducing layer
101
falls to room temperature, the reproducing layer
101
is magnetized in the same direction as the recording layer
102
. Therefore, only the reproducing layer
101
is initialized and magnetized in the direction opposite to the direction of magnetization of the recording layer
102
. Thus, one cycle of operation is terminated.
In summary, the reproducing layer
101
is magnetized in a certain direction when FAD shown in
FIG. 1
is carried out. When the RAD shown in
FIG. 2
is performed, the reproducing layer
101
is magnetized in the same direction as the recording layer
102
.
Assume that the magnetized state of the recording layer
102
corresponds to a signal recorded on it. Then, in the process of reading data from the reproducing layer
101
, a mark will disappear when FAD (
FIG. 1
) is effected and will appear when RAD (
FIG. 2
) is performed.
What is important is a temperature rise during the reproduction of data. The magneto-optical disk is rotating at all times. From this it can be understood that any part of the disk that follows the laser-beam spot formed on the disk will be heated to high temperature.
This fact may be taken into account when the magnetic layers are adjusted to cause the inversion shown in
FIG. 1 and 2
at the high temperature to which that part of the disk has been heated. Then, two recording media illustrated in
FIG. 3
may be designed.
Either recording medium shown in
FIG. 3
comprises a reproducing layer
101
, a recording layer
102
and a base layer
104
. The base layer
104
has lands and grooves at the upper surface. The recording layer
102
is provided on the base layer
104
, and the reproducing layer
101
is provided on the recording layer
102
. Marks
112
at which signals are recorded are provided on each land.
As shown in
FIG. 3
, two marks
112
are irradiated with the laser-beam spot
113
.
In
FIG. 3
, each dot indicates a mark that is appearing, or a part of the recording layer
102
which is seen through the reproducing layer
101
because the reproducing layer
101
is magnetized in the same direction as the recording layer
102
.
Each circle shown in
FIG. 3
indicates a mark that has disappeared, or a part of the recording layer
102
which is not seen through the reproducing layer
101
because the reproducing layer
101
is magnetized in a direction different from the direction in which the recording layer
102
is magnetized.
The magnetic layers may be adjusted such that a mark disappears at the high-temperature part as is shown at A in FIG.
3
. In this case, the signal will be detected only at the part in front of the laser-beam spot
113
. This manner of signal detection is therefore called “FAD (Front Aperture Detection).”
Conversely, the magnetic layers may be adjusted such that a mark appears at the high-temperature part as is shown at B in FIG.
3
. If so, the signal will be detected only at the part at the rear of the laser-beam spot
113
. This signal detection is therefore called “RAD (Rear Aperture Detection).”
Both FAD and RAD can detect a signal from only a part of the laser-beam spot
113
. Advantage attained by using a pinhole can be achieved, whichever signal detection, FAD or RAD, is carried out.
MSR can be accomplished not only by FAD and RAD, but also by another method recently proposed. This is made possible thanks to the re-designing of the magnetic layers. The concept of the new method will be described, along with RAD and RAD, with reference to FIG.
4
.
FIG. 4
shows thee lands
111
. Marks
112
, some seen and others not seen, are provided on each land
111
. A laser-beam spot
113
moves on the land
111
, toward the left. A high-temperature part
114
follows the laser-beam spot
113
. In
FIG. 4
Horigome Junichi
Nishino Masatoshi
Faber Alan T.
Frommer William S.
Frommer & Lawrence & Haug LLP
Sony Corporation
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