Dynamic information storage or retrieval – Storage or retrieval by simultaneous application of diverse...
Reexamination Certificate
1994-12-12
2001-04-03
Korzuch, William R. (Department: 2652)
Dynamic information storage or retrieval
Storage or retrieval by simultaneous application of diverse...
Reexamination Certificate
active
06212136
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an apparatus for magneto-optical disc.
2. Description of the Prior Art
Research and development of various magneto-optical discs have achieved remarkable results these days and a wide variety of magneto-optical discs are now commercially available on the market. According to the ISO (international organization for standardization), a magnetic field applied to a magneto-optical disc by a magneto-optical disc apparatus is limited to 600 Oe (oersted). A magneto-optical recording apparatus capable of recording a writable magneto-optical disc disclosed in Japanese laid-open patent publication No. 62-175948 or a magneto-optical reproducing method capable of reproducing a magneto-optical disc of an ultra-high resolution disclosed in Japanese laid-open patent publication No. 3-88156 needs plural kinds of external magnetic fields. In this case, when a recording, e.g., overwrite is effected or a reproduction is effected, a strong external magnetic field different from a recording magnetic field or a reproducing magnetic field generated from a portion in which an optical pickup is disposed is applied to a magneto-optical disc in order to initialize a predetermined magnetic layer of, for example, a multi-layer magnetic film constructing a magnetic film.
FIG. 1
of the accompanying drawing shows a schematic plan view of a main portion of a conventional magneto-optical disc apparatus and
FIG. 2
is a schematic side view thereof. As shown in
FIGS. 1 and 2
, when a magneto-optical recording apparatus is realized, a recording magnet
3
for generating a recording magnetic field is disposed on an optical axis of an optical pickup
2
that irradiates a magneto-optical disc
1
across the optical pickup
2
that records and reproduces the magneto-optical disc
1
in an opposing relation to the magneto-optical disc
1
. An initialization magnet
4
is disposed at a different position in an opposing relation to the magneto-optical disc
1
.
The initialization magnet
4
is used to generate a strong initialization magnetic field Hini of several kilooersteds as described above. Therefore, it is inappropriate that the magneto-optical disc, based on the restriction of the ISO (under which it is inhibited from being applied with a magnetic field of larger than 600 Oe) and the magneto-optical disc capable of overwrite or magneto-optical disc having special functions such as reproduction of ultra-high high solution or the like are applied to a common drive apparatus, i.e., common magneto-optical disc apparatus.
However, when the optical disc is recorded and reproduced, it is very disadvantageous for the user to properly use the magneto-optical disc based on the ISO and the special magneto-optical disc that needs the application of plural kinds of magnetic fields including a strong magnetic field on the common drive apparatus.
OBJECTS AND SUMMARY OF THE INVENTION
Therefore, it is an object of the present invention to provide an improved magneto-optical disc apparatus in which the aforesaid shortcomings and disadvantages encountered with the prior art can be eliminated.
More specifically, it is an object of the present invention to provide a magneto-optical disc apparatus which can record, reproduce and erase with a compatibility both a magneto-optical disc requiring plural kinds of different magnetic fields, such as a special magneto-optical disc, i.e., overwritable magneto-optical disc on which a recording can be effected by a light intensity modulation or a magneto-optical disc in which a reproduction with ultra-high resolution can be effected and a magneto-optical disc based on the ISO.
According to an aspect of the present invention, there is provided a magneto-optical disc apparatus which comprises a magnetic field generating source for applying a magnetic field to a magneto-optical disc, the magnetic field generating source being made freely rotatable about an axis substantially extended along a surface of the magneto-optical disc and a device for changing a distance of a rotation central axis of the magnetic field generating source relative to the magneto-optical disc.
The above and other objects, features, and advantages of the present invention will become apparent from the following detailed description of an illustrative embodiment thereof to be read in conjunction with the accompanying drawings, in which like reference numerals are used to identify the same or similar parts in the several views.
REFERENCES:
patent: 4748606 (1988-05-01), Naito et al.
patent: 4837758 (1989-06-01), Motoyama et al.
patent: 4993009 (1991-02-01), Shiho
patent: 5179544 (1993-01-01), Hezemans et al.
patent: 5202863 (1993-04-01), Miyatake et al.
Patent Abstracts of Japan, vol. 15, No. 492, Dec. 12, 1991,Magnetic Field Application Device, Akira et al.
Patent Abstracts of Japan, vol. 8, No. 208, Sep. 21, 1991,Photo-Magnetic Recorder, Akira et al.
Maeda Fumisada
Matsumoto Yoshinori
Korzuch William R.
Sonnenschein Nath & Rosenthal
Sony Corporation
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