Dynamic information storage or retrieval – Storage or retrieval by simultaneous application of diverse... – Magnetic field and light beam
Reexamination Certificate
1999-11-26
2002-11-05
Dinh, Tan (Department: 2653)
Dynamic information storage or retrieval
Storage or retrieval by simultaneous application of diverse...
Magnetic field and light beam
C369S013130, C369S013150
Reexamination Certificate
active
06477118
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an information-recording medium on which information is reproduced by transferring magnetization information recorded in a recording layer to a reproducing layer. The present invention also relates to a recording and reproducing method to be performed on the information-recording medium, and a recording and reproducing apparatus to be used for the information-recording medium. In particular, the present invention relates to an information-recording medium in which minute recording magnetic domains are easily formed. The present invention also relates to a method for recording information and a method for reproducing information by applying a recording magnetic field and a reproducing magnetic field by means of a novel magnetic field-applying method respectively. Further, the present invention relates to a recording apparatus and a reproducing apparatus to be preferably used for the above as well.
2. Description of the Related Art
The optical recording medium such as a magneto-optical recording medium is known as an external memory for the computer or the like. The magneto-optical recording medium can deal with a large capacity of data such as animation image and voice data, and hence it is frequently used as a recording medium suitable for the multimedia age. In general, the recording on the magneto-optical recording medium is performed by utilizing the temperature characteristic of the coercive force of a magnetic material which constitutes a recording layer. That is, a recording magnetic field, which has a direction opposite to a direction in the initial state, is applied to the magneto-optical recording medium in which the direction of magnetization in the recording layer is aligned in the certain direction in the initial state. Simultaneously, a recording light beam is radiated to locally heat the recording layer. Accordingly, the coercive force is lowered in a heated area of the recording layer to cause inversion into the direction of the recording magnetic field. After that, the magnetization of the recording layer is settled in a stable state while maintaining the inversion in the cooling process to form the recording magnetic domain. Thus, the information is recorded as magnetization information in the recording layer.
In recent years, it is demanded to further increase the storage capacity of the magneto-optical recording medium. Those suggested to realize such a demand include, for example, the mark edge recording system and the light pulse magnetic field modulation system. In the mark edge recording system, only one piece of information is not given to one recording mark in the recording layer, but pieces of information are given to a leading edge and a trailing edge of one recording mark, respectively. That is, the recording density in the linear direction is improved by giving two pieces of information to one recording mark. According to this method, it is possible to achieve a high density of about 1.5-fold, even in consideration of the separation limit of the reproducing light beam during reproduction.
On the other hand, the light pulse magnetic field modulation system resides in a method in which a recording magnetic field having a polarity corresponding to a recording signal is applied while radiating a pulsed recording light beam in synchronization with a recording clock. According to this method, it is possible to form a minute recording magnetic domain in a recording layer, and the recording density is improved.
When it is intended to further advance the realization of the high density of the magneto-optical recording medium, it is considered to be extremely important to control the recording magnetic field and the recording light beam, for example, in the case of the light pulse magnetic field modulation system. That is, in order to form a minute recording magnetic domain in the recording layer, it is necessary to strictly control the power of the recording light beam which determines the size of the recording magnetic domain, and the power of the recording magnetic field which is used to invert such a recording magnetic domain respectively. Therefore, the power margin (write power margin) is narrowed for the recording light beam and the recording magnetic field. For this reason, it has been strongly demanded to realize a novel recording method in which the high density recording can be performed with ease.
On the other hand, a problem also arises when it is intended to reproduce the minute recording magnetic domain formed in the recording layer. In general, the spot diameter of the reproducing light beam is restricted by the limit of NA of a lens carried on an optical head, and it cannot be decreased to be smaller than the above. For this reason, it is impossible to individually reproduce a plurality of minute magnetic domains existing within the spot of the reproducing light beam. That is, the individual minute magnetic domains cannot be reproduced, because of the shortage of resolution of the reproducing light beam. Therefore, it has been required to reproduce the minute magnetic domain by using the reproducing spot diameter having a certain size in the present circumstances.
The magnetically induced super resolution technique (MSR) has been suggested as a method for dissolving the foregoing problem, as described, for example, in
Journal of Magnetic Society of Japan,
Vol. 17 Supplement No. S1, pp. 201 (1993). In this technique, even when two recording magnetic domains are present within the reproducing light beam spot, one of the magnetic domains is masked to disappear so that the effective field of vision is narrowed. Thus, the other recording magnetic domain can be reproduced. The use of this technique makes it possible to improve the reproducing resolution without actually reducing the diameter of the reproducing light beam spot. However, even when the magnetically induced super resolution technique is used, the reproduced signal intensity obtained from each magnetic domain is not changed. Therefore, C/N of the reproduced signal is still low.
The present inventors have disclosed, in a patent document of International Publication No. WO98/02878, a magneto-optical recording medium comprising a magnetically magnifying reproducing layer and a recording layer on a substrate, in which a minute magnetic domain in the recording layer is individually transferred to the reproducing layer during reproduction, a reproducing magnetic field is applied, and thus the magnetic domain transferred to the reproducing layer can be magnified and reproduced. When the magneto-optical recording medium is used, the reproduced signal intensity is remarkably increased, because the magnetic domain transferred to the magnetically magnifying reproducing layer is magnified to have a size which is approximate to the light spot size. This technique is called “MAMMOS” (Magnetic Amplifying Magneto-Optical System), which dissolves the foregoing problem of the magnetically induced super resolution technique concerning the reproducing C/N of the minute magnetic domain.
In MSR and MAMMOS as described above, the reproducing magnetic field is applied perpendicularly to the medium, and the recording magnetic domain, which is located in the high temperature area of the recording layer heated by being irradiated with the reproducing light beam, is transferred to the reproducing layer to read the information. However, when the reproduction is performed on an information-recording medium which is subjected to the super high density recording, it is feared that any reproduced signal is detected as a result of inversion of a magnetic domain in the reproducing layer in the recording direction effected by a large reproducing magnetic field, although no recording magnetic domain exists in the high temperature area of the recording layer heated by being irradiated with the reproducing light beam. On the other hand, in order to ensure that a magnetic domain in the reproducing layer in the recording direction is inv
Awano Hiroyuki
Ido Hiroshi
Sekine Masaki
Tani Manabu
Yoshihiro Masafumi
LandOfFree
METHOD AND APPARATUS FOR RECORDING AND REPRODUCING... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with METHOD AND APPARATUS FOR RECORDING AND REPRODUCING..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and METHOD AND APPARATUS FOR RECORDING AND REPRODUCING... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2923459