Dynamic information storage or retrieval – Storage or retrieval by simultaneous application of diverse... – Magnetic field and light beam
Patent
1997-12-16
1999-07-13
Neyzari, Ali
Dynamic information storage or retrieval
Storage or retrieval by simultaneous application of diverse...
Magnetic field and light beam
3692751, G11B 1100
Patent
active
059236256
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a magneto-optical recording medium and a method for recording and reproduction thereon. In particular, the present invention relates to a magneto-optical recording medium including a plurality of magnetic layers capable of multi-valued recording or multi-layered recording, and a method for recording and reproduction thereon.
BACKGROUND ART
Development in information processing technology in recent years involves the use of optical recording media as recording media having a small size and a large capacity. Such optical recording media are classified into recording media exclusively used for reproduction such as CD and CD-ROM, write-once type recording media on which information can be written only once, and rewritable type recording media on which information can be rewritten. Known rewritable recording media include magneto-optical recording media such as magneto-optical disks. Recording is performed on such a magneto-optical recording medium by applying an external magnetic field while irradiating a recording layer (magnetic layer) with a laser light beam so that the polarity of magnetization in the recording layer is inverted into a direction of the external magnetic field.
It is also one of important technical tasks for the magneto-optical recording medium to achieve a high recording density. A system for recording signals converted into multi-valued information has been hitherto known as a means for achieving a high density on a magneto-optical recording medium, as described in, for example, Proceedings of 13th Congress of Applied Magnetics Society (published in 1989, page 63) and Japanese Journal of Applied Physics, Vol. 28 (1989) Supplement 28-3, pp. 343-347.
In such a multi-valued recording system, a plurality of magnetic layers having mutually different coercive forces are stacked, and magnetization of a specified magnetic layer is selectively magnetically inverted by modulating, at multiple levels, the intensity of a magnetic field applied to the magnetic layers. It is described that four-valued (quaternary) signal recording can be achieved in accordance with this system by providing, in a recording medium, three magnetic layers having mutually different coercive forces
However, according to the multi-valued recording system applied to the magneto-optical recording medium as described above, in order to detect, upon reproduction, signals recorded as multi-valued signals, the multi-valued signals have been distinguished by slicing, at a plurality of levels, signals detected from the magneto-optical recording medium. Accordingly, it has been impossible to obtain a large difference in signal amplitude corresponding to each of multi-valued states, and it has been difficult to clearly distinguish two states with a close difference in signal amplitude therebetween. For this reason, a problem arises in that the S/N ratio is low with respect to reproduced multi-valued signals. Therefore, it has been demanded to realize a reproduction technique for obtaining reproduction signals at a high S/N ratio from a certain magneto-optical recording medium subjected to high density recording.
As for magneto-optical recording media each having a plurality of magnetic layers, a recording medium, in which information can be recorded and reproduced independently on each of magnetic layers, may serve as an extremely effective recording medium when various types of information are recorded on a single recording medium in a correlated manner, or when they are simultaneously recorded and reproduced in parallel together with a plurality pieces of channel information.
JP-A-4305841 discloses a method for reproducing a multilevel information which has been recorded by illuminating with a recording light a magneto-optical recording medium, which has a magneto-optical layer wherein a magnetization direction may be changed by means of a magnetic field and heat with the illumination of the light, and an enhanced layer wherein a refractive index with respect to a reproducing light
REFERENCES:
patent: 5442597 (1995-08-01), Spruit et al.
patent: 5461602 (1995-10-01), Moriya et al.
patent: 5708652 (1998-01-01), Ohki et al.
patent: 5732065 (1998-03-01), Braat et al.
Saito, et al; "Multi-valued Magneto-Optical Recording in TbFe Compositionally Modulated Films"; 1989; Digests of the 13th Annual Conference on Magnetics in Japan; Proceeding of 13th Congress of Applied Magnetics Society; p. 63.
Saito, et al; "Multi-valued Magneto-Optical Recording in TbFe/SiO Compositionally Modulated Films"; 1989; Proceedings of the International Symposium on Optical Memory; Japanese Journal of Applied Physics, vol. 28(1989) Suppl. 28-3; pp. 343-347.
Inoue Kazuko
Ito Akiyoshi
Nakagawa Katsuji
Ohta Norio
Shimazaki Katsusuke
Hitachi Maxell Ltd.
Neyzari Ali
LandOfFree
Magneto-optical recording medium and method for recording and re does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Magneto-optical recording medium and method for recording and re, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Magneto-optical recording medium and method for recording and re will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2283215