Dynamic information storage or retrieval – Storage or retrieval by simultaneous application of diverse... – Magnetic field and light beam
Reexamination Certificate
2000-07-28
2004-11-30
Psitos, Aristotelis M. (Department: 2653)
Dynamic information storage or retrieval
Storage or retrieval by simultaneous application of diverse...
Magnetic field and light beam
C369S013220, C360S059000
Reexamination Certificate
active
06826129
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method and an apparatus for magnet-optical recording. More specifically, the present invention relates to a method and an apparatus for magnet-optical recording, in which magnetized marks are recorded on a magnet-optical recording medium by using a pulsed magnetic field and by irradiating a pulsed light beam.
2. Description of the Prior Art
A magnet-optical recording apparatus (a magnet-optical disk drive), especially a magnetic field modulation type magnet-optical recording apparatus has a high recording density and enables high speed data transmission, so it is expected to be a main stream of recording media in a computerized society. However, it is important to improve the magnetic inversion speed of a magnetic head in order to take advantage of the high transmission speed.
In general, an optical head for irradiating a laser beam to a magnet-optical recording medium and a magnetic head for applying a magnetic field are disposed at the opposite sides with respect to the magnet-optical recording medium. Therefore, it is difficult to position the laser beam spot and the magnetic head precisely because of a registration error and an eccentricity. Accordingly, the magnetic head is usually made larger (e.g., approximately 200 &mgr;m×200 &mgr;m) so that the effective area of the magnetic field applied by the magnetic head can cover the movable area of the laser beam spot.
As a result, an inductance of the magnetic head increases, and the magnetic inversion speed becomes slow. In order to avoid an imprecise edge of the magnetized mark due to the slow magnetic inversion speed, a method is invented in which a pulsed laser beam is used for writing a magnetized mark when the magnetic field is large (see Japanese patent publication No. 7-21892, for example).
In addition, a front illumination method as shown in
FIG. 1
is invented for further improving the data transmission. In this method, a small magnetic head is arranged at the laser beam irradiation side of the magnet-optical recording medium. Namely, as shown in
FIG. 1
, the magnet-optical recording medium
11
is irradiated by the laser beam
12
not at the transparent substrate
11
a
side but at the recording layer
11
b
side above which the magnetic head
13
is disposed. The magnetic head
13
includes a magnetic head coil
14
made of a thin film pattern. The laser beam
12
that was concentrated by a focus lens
15
passes through an opening formed in the middle portion of the magnetic head coil
14
and is irradiated onto the recording layer
11
b
of the magnet-optical recording medium
11
.
The above-mentioned front illumination method enables the optical head including the focus lens
15
and the magnetic head
13
to be mounted on a common slider, so that the irradiation spot of the laser beam
12
and the position of the magnetic head
13
can be aligned precisely. Therefore, the effective area of the magnetic field applied by the magnetic head
13
can be small (less than 50 &mgr;m×50 &mgr;m, for example), so that an inductance of the magnetic head coil
14
can be decreased. As a result, the magnetic inversion speed can be improved.
However, since the magnetic head coil
14
is formed by a thin film technology so as to make the magnetic head
13
light and low profile, a resistance of the magnetic head coil
14
increases. A large resistance generates heat that may cause the detrimental effects such as fusing of the magnetic head coil
14
, deformation of the focus lens
15
and an excessive heat of the magnet-optical recording medium
11
.
In order to avoid the above-mentioned detrimental effects, a method is proposed in which a pulsed magnetic field is generated for applying the magnetic field to the magnet-optical recording medium as disclosed in Japanese Patent No. 2803841, for example. This method can suppress the heat of the magnetic head coil
14
by exciting the magnetic head coil
14
not continuously but intermittently for necessity.
However, the control of the heat of the magnetic head coil is not sufficient by the above-mentioned method. More effective method for decreasing the heat has been desired. In the conventional method, the magnetic field is required to be applied continuously from the irradiation of the pulsed light until the temperature of the recording layer of the magnet-optical recording medium becomes below the Curie point (Tc). Therefore, the heat reducing effect by the pulse driving of the magnetic head coil has a limitation.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a method and an apparatus for magnet-optical recording that utilize a novel concept for reducing a heat in the pulse driving of the magnetic head coil.
According to a first aspect of the present invention, a magnet-optical recording method is provided, in which magnetized marks are recorded on a magnet-optical recording medium by irradiating a pulsed light beam onto the recording medium and by applying a pulsed magnetic field to the recording medium. This method utilizes a reverse magnetic field generated by the magnetized mark that was recorded just before the present mark so as to reduce the exciting energy of the magnetic field to be applied when the present mark is recorded in the polarity that is opposite to the polarity of the magnetized mark that was recorded just before the present mark.
When the magnetic recording film is heated above the Curie point (Tc), the heated spot can be magnetized in the polarity opposite to that of the present magnetized mark due to the influence of the magnetic field generated by the surrounding magnetized marks without application of the external magnetic field. This phenomenon is known as a reverse magnetic field phenomenon and is utilized in a so-called overwrite type magnet-optical recording medium as disclosed in Japanese patent publication No. 6-79391, Japanese unexamined patent publication No. 3-127347 or Japanese Patent No. 2630976, for example.
The above-mentioned first magnet-optical recording method of the present invention utilizes the reverse magnetic field explained above so as to reduce the exciting energy of the applied magnetic field when recording a magnetized mark having a polarity opposite to that of the magnetized mark that was recorded just before the present mark. Thus, the total heat of the magnetic head coil can be reduced.
In an embodiment of the method for reducing the exciting energy of the applied magnetic field, an exciting current that is supplied to a magnetic head coil for generating the magnetic field is reduced. In another embodiment, an exciting period of a magnetic head coil for generating the magnetic field is reduced. It is also possible that an exciting current is not supplied to a magnetic head coil for generating the magnetic field when the present mark is recorded in the polarity that is opposite to the polarity of the magnetized mark that was recorded just before the present mark.
According to a second aspect of the present invention, the magnet-optical recording method uses a magnet-optical recording medium having a recording layer and an auxiliary recording layer, and magnetized marks are recorded on the magnet-optical recording medium by applying a pulsed magnetic field to the recording medium and by irradiating a pulsed light beam onto the recording medium. The method includes the steps of recording a magnetized mark on the auxiliary recording layer by applying the magnetic field in a short pulse form in accordance with data to be recorded, and transferring the magnetized mark recorded on the auxiliary recording layer to the recording layer by irradiating a pulsed light beam.
The magnet-optical recording medium that has a recording layer and an auxiliary recording layer has been used as an optical modulation overwrite type magnet-optical recording medium as disclosed in Japanese unexamined patent publication No. 6-44630 or No. 6-203418, for example. In this magnet-optical recording medium, a magnetic field th
Fujitsu Limited
Greer Burns & Crain Ltd.
Psitos Aristotelis M.
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