Dynamic information storage or retrieval – Control of storage or retrieval operation by a control... – Control of information signal processing channel
Reexamination Certificate
2000-08-29
2003-07-01
Psitos, Aristotelis M. (Department: 2653)
Dynamic information storage or retrieval
Control of storage or retrieval operation by a control...
Control of information signal processing channel
C369S013020, C369S053340
Reexamination Certificate
active
06587410
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a signal recording/reproduction method and apparatus that optimizes the laser beam intensity, magnetic field intensity, phase difference between a laser beam and a magnetic field, and an equalizer coefficient according to a reproduced signal in recording and/or reproducing a signal to and/or from a magneto recording medium to record and/or reproduce a signal to and/from a magneto-optical recording medium according to the optimized results.
2. Description of the Background Art
Attention is focused on a magneto-optical recording medium as a rewritable and reliable recording medium of large storage capacity. Magneto-optical recording media are now being adapted to practical use as a computer memory or the like. Standardization of a magneto-optical recording medium having a recording capacity of 6.0 Gbytes is in progress for practical applications. Reproduction of a signal from such a magneto-optical recording medium of high density is carried out by the MSR (magnetically induced super resolution) method in which a magnetic domain of a recording layer in a magneto-optical recording medium is transferred to a region of a reproduction layer exceeding a predetermined temperature by projecting a laser beam, and detecting the transferred magnetic domain.
In recording a signal on a magneto-optical recording medium using a pulsed laser beam (referred to as “pulse beam” hereinafter) and a magnetic domain modulated by a recording signal, the phase difference between the pulse beam and the magnetic field must be optimized. There was a problem that a signal cannot be recorded properly when a magnetic field is applied at a timing where the magnetic film of the magneto-optical recording medium is not increased to the temperature that can alter the direction of magnetization by an external magnetic field.
From the standpoint of recording a signal at high density to a magneto-optical recording medium, there was a problem that a small magnetic domain cannot be formed if the intensity of the pulse beam projected on the magneto-optical recording medium is too strong since a region wider than the desired region will attain a temperature exceeding the predetermined temperature.
In the case where the intensity of the pulse beam projected on the magneto-optical recording medium is too strong during signal recording in the land/groove scheme, an adjacent land or groove will also attain a temperature higher than the predetermined temperature so that a signal already recorded will be erased.
If the intensity of the magnetic field applied on the magneto-optical recording medium during signal recording is too weak, it will be difficult to form a magnetic domain having the desired direction of magnetization in the magnetic layer. There was problem that a signal cannot be recorded properly.
Various problems are also encountered in reproducing a signal from a magneto-optical recording medium. If the intensity of the laser beam projected onto the magneto-optical recording medium is too weak, the intensity of the reproduced signal is reduced to degrade the S/N. If the intensity of the laser beam is too strong, a signal will be reproduced also from an adjacent land or groove to cause crosstalk.
There is also the case where waveform interference occurs in the magneto-optical signal reproduced by a laser beam. Since the amplitude of a magneto-optical signal with waveform interference is small, it is necessary to remove the waveform interference.
SUMMARY OF THE INVENTION
In view of the foregoing, an object of the present invention is to provide a signal recording/reproduction method and apparatus to record and/or reproduce a signal properly to and/or from a magneto-optical recording medium by optimizing the phase difference between the pulse beam and the magnetic field, the intensity of the pulse beam, and the intensity of the magnetic field in recording a signal, and also the intensity of the laser beam and the equalizer coefficient to remove waveform interference in reproducing a signal, and recording and/or reproducing a signal to and/or from a magneto-optical recording medium according to the optimized results.
According to an aspect of the present invention, a recording/reproduction apparatus recording and/or reproducing a signal to and/or from a magneto-optical recording medium includes an optical head projecting laser beam onto a magneto-optical recording medium and detecting reflected light thereof, a laser drive circuit driving a semiconductor laser in the optical head, a magnetic head applying a magnetic field to the magneto-optical recording medium, a magnetic head drive circuit driving the magnetic head, and a control circuit.
The control circuit generates a first driving signal for the magnetic head to generate a magnetic field of a predetermined intensity modulated by a recording signal. The generated first driving signal is provided to the magnetic head drive circuit.
The control circuit generates a second driving signal for the optical head to emit a pulse beam of a predetermined intensity with the phase difference from the first driving signal altered. The generated second driving signal is provided to the laser drive circuit.
The optimum phase difference between the first and second driving signals is determined according to a magneto-optical signal reproduced by the optical head corresponding to a signal recorded on the magneto-optical recording medium with the phase difference between the first and second driving signals altered according to the first and second driving signals.
According to the recording/reproduction apparatus of the present aspect, a first driving signal to apply a magnetic field is generated, in addition to a second driving signal to generate a pulse beam with the phase difference from the first driving signal altered. A predetermined signal is recorded on the magneto-optical recording medium according to the first and second driving signals. The optimum phase difference between the first and second driving signals is determined according to a magneto-optical signal which is a reproduced version of that recorded signal.
According to the invention of the present aspect, the correct phase difference can be determined to allow proper signal recording since a signal is actually recorded on a magneto-optical recording medium and the phase difference is determined according to a reproduced signal thereof.
According to another aspect of the present invention, a recording/reproduction apparatus recording and/or reproducing a signal to and/or from a magneto-optical recording medium includes an optical head projecting laser beam onto a magneto-optical recording medium and detecting reflected light thereof, a laser drive circuit driving a semiconductor laser in the optical head, a magnetic head applying a magnetic field to the magneto-optical recording medium, a magnetic head drive circuit driving the magnetic head, and a control circuit.
The control circuit generates a first driving signal for the magnetic head to generate a magnetic field of a predetermined intensity modulated by a recording signal. The first driving signal is provided to the magnetic head drive circuit.
The control circuit generates a second driving signal for the optical head to emit a pulse beam of a predetermined intensity. The second driving signal has an optimum phase difference from the first driving signal. The second driving signal is provided to the laser drive circuit.
After a signal is recorded on the magneto-optical recording medium by the first and second driving signals, the control circuit generates a third driving signal that alters the intensity of the laser beam to reproduce the recorded signal. The generated third driving signal is provided to the laser drive circuit.
The control circuit determines a provisional optimum laser beam intensity for the optical head to reproduce a signal according to a magneto-optical signal reproduced from the magneto-optical recording medium according to the third driving signal, an
Suzuki Yoshihisa
Tanaka Sayoko
Armstrong Westerman & Hattori, LLP
Psitos Aristotelis M.
Sanyo Electric Company Ltd.
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