Dynamic information storage or retrieval – Storage or retrieval by simultaneous application of diverse... – Magnetic field and light beam
Reexamination Certificate
1999-09-22
2002-05-14
Dinh, Tan (Department: 2651)
Dynamic information storage or retrieval
Storage or retrieval by simultaneous application of diverse...
Magnetic field and light beam
C369S013260
Reexamination Certificate
active
06388955
ABSTRACT:
TECHNICAL FIELD
This invention relates to a reproducing method with a magneto-optical recording medium and, more particularly to a reproducing method with a magneto-optical recording medium including, for example, recording and reproducing layers so that the microscopic domain can be recorded into the recording layer during recording and the recorded magnetic domain of the recording layer be expanded and transferred into the reproducing layer during reproduction.
Furthermore, the invention is concerned with a reproducing method and magneto-optical disk apparatus which reproduces a signal by optimally setting a laser light power level during expanding and reproducing the magnetic domain, wherein the magneto-optical disk apparatus performs signal recording and/or reproducing by using laser light and magnetic field applied to the magneto-optical recording medium.
Prior Art
Attentions have being drawn to magneto-optical recording mediums as rewritable recording mediums that are high in memory capacity and reliability. They have being put into practical use as computer memories, etc. Meanwhile, standardization has being put forward for magneto-optical recording mediums having a recording capacity of 6.0 G bytes toward a standard of AS-MO (Advanced Storage Magneto-Optical disk). It has been a practice to reproduce a signal from a high-density magneto-optical recording medium as mentioned above by an MSR (Magnetically Induced Super Resolution) method that irradiates laser light form a detection window in the reproducing layer of the magneto-optical recording medium so that a magnetic domain is transferred from the recording layer into the formed detection window, thereby carrying out signal reproduction.
Meanwhile, a technology of expanding and reproducing a magnetic domain has been developed, wherein alternating magnetic field is applied during reproducing signals from a magneto-optical recording medium so that the magnetic domain present in the recording layer can be expanded and transferred to the reproducing layer by the applications of laser light and alternating magnetic field, thus reproducing signals. There has been an proposal on a magneto-optical recording medium utilizing this technology to record and/or reproduce a signal of 14-G bytes.
The recording/reproducing apparatuses for a magneto-optical recording medium of this kind have been disclosed, for example, in Japanese Laid-open No. H
6
-295479 (Oct. 21, 1994) [G11B 11/10], Japanese Laid-open No. H8-7350 (Jan. 12, 1996) [G11B 11/10] and so on.
The magneto-optical recording medium
10
, as shown in
FIG. 1
, includes a recording layer
14
and reproducing layer
16
formed by respective magnetic layers on a substrate
12
. An intermediate layer
18
is formed between the recording layer
14
and the reproducing layer
16
while a protection layer
20
is formed on the recording layer
14
. Incidentally, although the intermediate layer
18
herein is formed by a non-magnetic layer, it may be made by a magnetic layer. Also, the recording layer
14
and reproducing layer
16
can be formed of arbitrary known magnetic materials.
Referring to
FIG. 2
, microscopic record magnetic domains are recorded within the recording layer
14
of the magneto-optical recording medium
10
through the use of a magnetic head (not shown). During reproduction, the record magnetic domain
22
of the recording layer
14
is transferred into the reproducing layer
16
by illuminating laser light
24
, as shown in FIG.
3
.
Specifically, laser light
24
provides a temperature profile to the magneto-optical recording medium
10
as shown in FIG.
3
. The temperature is highest at around a spot center but gradually decreased toward an outward thereof. It should be noted that, where the magneto-optical recording medium is for example a disk, the temperature profile is different in slant between forward and backward with respect to a moving direction of the magneto-optical recording medium. The temperature gradient is steeply slanted in a region of the disk entering into the laser spot as compared to that of a region exiting therefrom. By utilizing such a temperature profile, the magneto-optical recording medium
10
is increased in temperature up to a desired point.
Referring back to FIG.
2
(A), if laser light
24
is illuminated onto the magneto-optical recording medium
10
, the magneto-optical recording medium
10
is raised in temperature in accordance with the temperature profile as shown in FIG.
3
. The reproducing layer
16
herein is formed by a magnetic layer that, at from room temperature to the Curie temperature Tc, is enriched in transition metal and assumes a perpendicular magnetic anisotropy film. Consequently, if laser light
24
is illuminated, the reproducing layer
16
is increased in temperature, being decreased in coercivity. Due to this, the record magnetic domain
22
within the recording layer
14
is transferred into the reproducing layer
16
through the intermediate layer
18
due to static magnetic coupling. Thus, a transferred magnetic domain
26
is formed within the reproducing layer
16
. The transferred magnetic domain
26
is formed in a position corresponding to the record magnetic domain
22
.
After forming a transferred magnetic domain
26
in the reproducing layer
16
, an external magnetic field Hex as shown in FIG.
2
(B) is applied through a not-shown magnetic head. This external magnetic field Hex is of an alternating magnetic field. This alternating magnetic field is applied for at lease 1 period, preferably 2-4 periods while one magnetic domain is passing through a hot spot
24
a
formed due to the laser light
24
. The alternating magnetic field, or external magnetic field, if applied in the same direction (same polarity) as that of the transferred magnetic domain
26
, causes the transferred magnetic domain
26
to expand in its diameter, thus forming expanded magnetic domains
26
a
and
26
b
. This results in transfer and expansion of the record magnetic domain
22
. The transferred magnetic domain
26
with the expanded magnetic domains
26
a
and
26
b
are irradiated by laser light for reproduction through the optical head (not shown). Thus, a state is reproduced of magnetization within the reproducing layer
16
, i.e. record signal.
In this manner, in the conventional magneto-optical recording medium recording/reproducing apparatus, irradiation of laser light is with an intensity that can cause transfer of a magnetic domain from the record layer into the reproducing layer.
For such a case, according to the experiments conducted by the present inventors, when only laser light was illuminated for reproduction without applying an alternating magnetic field Hex, a reproduced signal obtained had a waveform as shown in FIG.
4
(A). In this state, when an alternating magnetic field was applied, a reproduced signal obtained had a waveform as shown in FIG.
4
(B). However, the reproduced signal of FIG.
4
(B) is not satisfactorily high in level. Thus, there has encountered a limitation in reproducing a signal when the record density is to be tried to increase.
SUMMARY OF THE INVENTION
It is therefore a primary object of the present invention to provide a novel apparatus and method for reproducing with a magneto-optical recording medium.
Another object of the invention is to provide a apparatus and method for reproducing with a magneto-optical recording medium which is capable of increasing the intensity of a reproduced signal.
Still another object of the invention is to provide a method for reproducing with a magneto-optical recording medium and magneto-optical disk apparatus which can optimally set a power level of laser light.
A reproducing apparatus according to the present invention is a reproducing apparatus for a magneto-optical recording medium to transfer, during reproduction, a magnetic domain recorded within a recording layer into a reproducing layer, characterized in that a magnetic domain is transferred with expansion from the recording layer to the reproducing layer by app
Mitani Kenichiro
Takagi Naoyuki
Yamaguchi Atsushi
Armstrong Westerman & Hattori, LLP
Dinh Tan
Sanyo Electric Co,. Ltd.
LandOfFree
Reproducing method for magneto-optic recording medium, and... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Reproducing method for magneto-optic recording medium, and..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Reproducing method for magneto-optic recording medium, and... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2844701