Dynamic information storage or retrieval – Storage or retrieval by simultaneous application of diverse... – Magnetic field and light beam
Patent
1990-05-21
1992-11-17
Levy, Stuart S.
Dynamic information storage or retrieval
Storage or retrieval by simultaneous application of diverse...
Magnetic field and light beam
360114, 360 66, G11B 1304, G11B 1112
Patent
active
051649250
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to an over-write opto-magnetic recording apparatus which is capable of over-writing information by light-intensity modulation alone without requiring modulation of direction of the recording magnetic field Hb.
BACKGROUND ART
In recent years, efforts have been directed toward development of an opto-magnetic recording/reproducing method which would satisfy various requirements such as higher recording density, greater storage capacity, higher access speed and higher recording/reproducing speed, as well as toward development of recording apparatus, reproducing apparatus and recording medium which would be used in carrying out such an opto-magnetic recording/reproducing method.
Among a variety of optical recording/reproducing methods, opto-magnetic recording/reproducing is most promising because its allow for erasion of recorded information and recording of new information after erasion, which enables repeated use of the recording medium.
However, when a recording medium is to be re-used, it is generally necessary that (i) the medium is initialized by an initializing device, (ii) that a recording apparatus is provided with an erase head similar to that of the recording head or (iii) that erasing operation is conducted as a preparatory step by a recording device or an erasion device.
Such requirements tend to make opto-magnetic recording impractical for over-writing of information, i.e., recording of new information regardless of whether the recording medium has information recorded thereon.
Over-writing could also be achieved if the direction of the recording magnetic field Hb could be freely modulated between a "direction A" (e.g., an upward direction) and a "direction counter to A" (e.g., a downward direction). However, it is impossible as a practical matter to modulate the direction of the recording magnetic field Hb at sufficiently high speed. For instance, when the recording magnetic field Hb is provided by a permanent magnet, it would be necessary to mechanically invert the orientation of the magnet at a high speed. This is practically impossible. A similar problem is encountered also when the recording magnetic field Hb is provided by a solenoid, because it is practically impossible to modulate the direction of the large current at such a high speed.
As a result of recent progress in the art, there has been developed an opto-magnetic recording method which enables over-writing solely by modulating the intensity of recording light in accordance with the binary information to be recorded, without requiring the magnetic field Hb to be turned on and off or direction-modulated, as well as an over-writable recording medium and recording apparatus which enables such over-writing, as disclosed in Japanese Patent Unexamined Publication No. 62-175948.
One of the features of this known technique resides in the use of an opto-magnetic recording medium made of a laminated vertical magnetization film of two-layered structure composed of a recording layer (first layer) and an auxiliary recording layer (second layer). The information is recorded in the first layer and also in the second layer as required, with a bit having "A direction" and a bit having "counter A direction".
This known over-writing method has the following steps: magnetization of the second layer in the "A direction" while maintaining the magnetization of the first layer unchanged until the recording is conducted; binary information to be recorded; magnetic field to the irradiated portion of the recording medium; and bit having the "A direction" and a bit having the "counter A direction", while forming the other bit when the level of intensity of the pulse beam is low.
The recording with this opto-magnetic recording method is carried out by using, for example, an over-writable opto-magnetic recording apparatus having the following features:
means for moving an opto-magnetic recording medium;
means for applying an initial auxiliary magnetic field Hini;
a laser beam source;
modulation means for pulse-mod
REFERENCES:
patent: 4855975 (1989-08-01), Akasaka et al.
patent: 4908809 (1990-03-01), Tadokoro et al.
patent: 4910622 (1990-03-01), Saito et al.
"Simple Nikon Technique Permits Erase and Write in One Pass", Electronic, Apr. 16, 1987, p. 33.
Swartz et al., "Stabilized Biasing of Semiconductor Lasers", The Bell System Technical Journal, Sep. 1983, vol. 62, No. 7, Part 1, pp. 1923-1936.
U.S. Ser. No. 453,255 filed Dec. 20, 1989 for "Over Write Capable Magnetooptical Recording Method, and Magnetooptical Recording Apparatus and Medium Used Therefor"--Sato et al.
Kawai Toshihiko
Sato Masatoshi
Levy Stuart S.
Nguyen Hoa
Nikon Corporation
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