Dynamic information storage or retrieval – Information location or remote operator actuated control – Selective addressing of storage medium
Reexamination Certificate
2001-09-17
2004-02-17
Psitos, Aristotelis M. (Department: 2653)
Dynamic information storage or retrieval
Information location or remote operator actuated control
Selective addressing of storage medium
C369S013170
Reexamination Certificate
active
06693856
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a magneto-optical disk apparatus, which can accurately reproduce a signal by removing a magnetic influence applied from a magnet for servo-control of an objective lens for converging laser beams onto a magneto-optical record medium. The present invention also relates to a magnetic field intensity detecting method of detecting an intensity of an influence magnetic field applied from a magnet for servo-control.
2. Description of the Related Art
Magneto-optical record mediums have received widespread attention as record mediums, which are rewritable and have large storage capacities and high reliability, and are being used as computer memories and others. Recently, a magneto-optical record medium having a storage capacity of 6.0 Gbytes is standardized as AS-MO (Advanced Storage Magneto Optical disk) and practical use thereof is starting.
A signal is recorded on the magneto-optical record medium in such a manner that a magnetic head is initially in contact with a surface of a side of the magneto-optical record medium provided with a magnetic layer, and a magnetic field modulated with the record signal (i.e., signal to be recorded) is applied to the magnetic layer of the magneto-optical record medium while floating the magnetic head by rotating the magneto-optical record medium at a predetermined rotation speed. Laser beams are emitted to a side remote from the magnetic head for heating a predetermined region of the magnetic layer of the magneto-optical record medium to or above a predetermined temperature. Thereby, magnetic domains, which are magnetized in different directions in response to the record signal, are formed on the record layer of the magnetic layer to record the signal.
For reproducing the signal from the magneto-optical record medium, the magnetic domains on the regions, which are heated to or above the predetermined temperature by laser beam irradiation, are transferred onto the reproduction layer and the magnetic domains thus transferred are detected as a rotation angle of a plane of polarization of the laser beams. Thereby, the signals are reproduced from the magneto-optical record medium. In this case, the magnetic head is disposed on the side opposite to the side irradiated with the laser beams. When reproducing the signal, the magnetic head is not in contact with the magneto-optical record medium, and is spaced from the magneto-optical record medium.
When the signal recorded on the magneto-optical record medium is to be reproduced such a manner is employed for quick reproduction of the signal that the magnetic head is kept in contact with the magneto-optical record medium, and the side opposite to the magnetic head is irradiated with the laser beams for reproducing the signal.
When the signal is reproduced from the magneto-optical record medium while keeping the magnetic head in contact with the magneto-optical record medium, a magnetic force applied from a magnet, which is used for focus servo-control or tracking servo-control of an objective lens for converging the laser beams onto the magneto-optical record medium, concentrates on a core (made of a magnetic material such as ferrite) of the magnetic head, and thus exerts an adverse effect on the reproduced signal.
SUMMARY OF THE INVENTION
Accordingly, an object of the invention is to provide a magneto-optical disk apparatus, which can reproduce signals from a magneto-optical record medium while removing an influence of a magnetic field, which is concentratedly applied to a core of a magnetic head from a magnet performing focus servo-control or tracking servo-control of an object lens.
Another object of the invention is to provide a magnetic field intensity detecting method of detecting an intensity of a magnetic field, which is concentratedly applied to a core of a magnetic head from a magnet performing focus servo-control or tracking servo-control of an object lens.
The invention provides a magneto-optical disk apparatus for recording a signal on a magneto-optical record medium with a laser beam and a magnetic field, and reproducing the signal from the magneto-optical record medium with the laser beam including a magnetic head for applying a magnetic field to the magneto-optical record medium; a lowering device for lowering the magnetic head to a position in contact with the magneto-optical record medium; an optical head disposed on a side remote from the magnetic head with the magneto-optical record medium therebetween, and including an objective lens for converging the laser beam onto the magneto-optical record medium, a first magnet for performing tracking servo-control of the objective lens and a second magnet for performing focus servo-control of the objective lens; and a third magnet for cancelling a leaked magnetic field produced by at least one of the first and second magnets and convergently applied toward the magnetic head.
In the above magneto-optical disk apparatus according to the invention, the magnetic head is lowered by the lowering device, and comes into contact with the magneto-optical record medium. When the magneto-optical record medium turns, the magnetic head floats from the magneto-optical record medium. The third magnet cancels the magnetic influence, which may be exerted on the magneto-optical record medium by the first or second magnets included in the optical head for performing the tracking servo-control of the objective lens or the focus servo-control thereof. While floating the magnetic head from the magneto-optical record medium, recording and/or reproducing of the signal on the magneto-optical record medium are performed. According to the invention, therefore, the recording and/or reproducing of the signal on the magneto-optical record medium can be accurately performed while keeping the magnetic head in contact with the magneto-optical record medium.
Preferably, the third magnet emits the magnetic field of an intensity determined by a magnetic field intensity detecting method using a DC magnetic field, and the magnetic field intensity detecting method includes a first step of irradiating the magneto-optical record medium with the laser beam, and reproducing the signal from the magneto-optical record medium by applying a DC magnetic field in a first direction to a point irradiated with the laser beam while changing an intensity of the DC magnetic field, a second step of detecting the number of errors in the signal reproduced in the first step, a third step of reproducing the signal from the magneto-optical record medium by applying a DC magnetic field in a second direction opposite to the first direction onto the irradiation point, a fourth step of detecting the number of errors in the signal reproduced in the third step, and a fifth step of detecting an intensity of the magnetic field applied from the first or second magnet at the irradiation point based on a relationship between the error numbers detected in the second and fourth steps and the intensities of the DC magnetic fields.
The magnetic head is lowered by the lowering device to make contact with the magnetic-optical record medium. When the magneto-optical record medium turns, the magnetic head floats from the magneto-optical record medium. The third magnet cancels the magnetic influence, which is applied to the magneto-optical record medium by the first magnet for tracking servo-control of the objective lens included in the optical head or the second magnet for the focus servo-control of the objective lens. While keeping the magnetic head in a position floated from the magneto-optical record medium, recording and/or reproducing of the signal on the magneto-optical record medium are performed. The intensity of the magnetic field emitted from the third magnet is determined to be equal to the magnetic field intensity, which is detected based on the relationship between the number of errors in the signal reproduced by applying the DC magnetic field to the magneto-optical record medium and the intensity of the DC magnetic field. Accor
Kajiyama Seiji
Koyama Kanichi
Maeda Mitsuhiko
Shidochi Masaaki
Takahashi Seiichiro
Armstrong Kratz Quintos Hanson & Brooks, LLP
Psitos Aristotelis M.
Sanyo Electric Co,. Ltd.
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