Dynamic information storage or retrieval – Condition indicating – monitoring – or testing – Including radiation storage or retrieval
Patent
1993-07-09
1997-06-24
Young, W. R.
Dynamic information storage or retrieval
Condition indicating, monitoring, or testing
Including radiation storage or retrieval
369 59, 369116, G11B 700
Patent
active
056423438
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a magnetooptic recording control method which can perform high density optical recording, and also relates to its apparatus.
BACKGROUND ART
In association with the progress of the recent advanced information society, the need for a file memory of large capacity and high density is continually increasing. Attention is paid to optical recording as a means which can satisfy the above need. The memories of the read only type, write-once type, and rewritable type have sequentially been put into practical use and have already been used in applications in which their inherent features can be effectively used. Among them, particularly, the rewritable magnetooptic recording memory has recently been put into practical use.
At present, studies and developments are progressing in many research facilities in order to realize products of mangetooptic recording memories of the next generation. As one of the main studies to realize such products, superhigh density recording can be mentioned. As a method of realizing superhigh density recording, there have been proposed various methods such that a track pitch is reduced, a recording magnetic domain interval is reduced, light of a short wavelength is used, information is recorded in the edge portion of the recording medium magnetic domain, and the like. It is considered to be effective to use a combination of these methods.
An optical disc apparatus is one of the means for recording a digital signal onto a recording medium. According to the optical disc apparatus, a laser beam is converged onto the recording surface by a lens, the intensity of the laser beam is changed in accordance with the information to be recorded, and the reflectance of the region of the recording film to which the laser beam is irradiated or the magnetizing direction in the case of magnetooptic recording is changed by the external magnetization or the like, thereby recording information. In reproducing the recorded information, a laser beam of an intensity which is weaker than the intensity of the recording laser beam is irradiated. A change in light amount is detected from the reflected light from the recording film, or the rotation of the polarization plane due to a difference of the magnetizing direction is detected, thereby reproducing the recorded information. A recording density is mainly determined by the size of the spot of the laser beam which is converged onto the recording surface. Since the spot size is presently as small as about 1 .mu.m, recording of a density which is about ten times as high as that of the magnetic disk can be realized.
On the other hand, a mark length recording method of expressing information at the positions on the front and rear sides of the recording mark, recorded by modulating the irradiation light power, is effective to realize a high recording density because two or more pieces of data are recorded in one recording mark.
In the mark length recording method for recording and/or reproducing information onto/from the optical disc at a high density, various kinds of signal processes are executed upon recording and reproducing of data to realize a highly reliable information.
For example, in general, when the irradiation light power upon recording is small, the shape of the recording mark easily becomes unstable. When the recording linear velocity differs, the heat amount which is applied to a unit area and the heat distribution differ, so that the recording mark shape differs. Therefore, as disclosed in "Application of Pit Edge Recording on PbTbSe Thin Film", The General National Conference of the 70th Anniversary of the founding of The Institute of Television Engineering of Japan, the collection of lectures and papers, page 4 to 176, since a stable recording mark shape is formed and the recording and reproduction are executed, there is executed an adjustment such that the recording irradiation light pulse is slightly largely set and the laser pulse length is set to a short value upon recording so that the mark l
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"Application of Pit Edge Recording on PbTeSe Thin Films", 70th Anniversary National Conference of Institute of Television Engineering of Japan, pp. 4-176.
Ide Hiroshi
Kaku Toshimitsu
Kirino Fumiyoshi
Maeda Takeshi
Mita Seiichi
Hitachi , Ltd.
Young W. R.
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