Dynamic information storage or retrieval – Storage or retrieval by simultaneous application of diverse... – Magnetic field and light beam
Reexamination Certificate
2001-11-19
2003-01-21
Neyzari, Ali (Department: 2653)
Dynamic information storage or retrieval
Storage or retrieval by simultaneous application of diverse...
Magnetic field and light beam
C369S013170, C360S234700
Reexamination Certificate
active
06510109
ABSTRACT:
TECHNICAL FIELD
This invention relates to a magnetic head, and a magnetic head and a magneto-optical disc recording device used for recording on a recording medium. Particularly, this invention relates to a magnetic head for supplying a magnetic field when recording an information signal onto a recording medium, and a magnetic head and a magneto-optical disc recording device used for recording on a recording medium.
BACKGROUND ART
There have been used magnetic recording media such as a magnetic disk and a magnetic tape on which an information signal is magnetically recorded and reproduced, and magneto-optical recording media such as a magneto-optical disc on which an information signal is recorded and reproduced by using the magneto-optical effect of a recording film.
On a magnetic recording medium such as a magnetic disk or a magnetic tape, an external magnetic field is applied to change the local direction of magnetization of the magnetic recording medium by using a magnetic head, thus writing an information signal.
On the other hand, on a magneto-optical recording medium such as a magneto-optical disc, while a condensed laser beam is cast onto a recording film, an external vertical magnetic field modulated in accordance with an information signal is applied by using a magnetic head to a portion which is locally heated to the Curie temperature or higher, thus writing the information signal. That is, in the portion heated to the Curie temperature or higher of the recording film of the recording medium, the coercive force is lost and the direction of magnetization is changed in accordance with the external magnetic field. On the magneto-optical recording medium, a laser beam which is weaker than in recording is cast onto the recording film and the rotation of the plane of polarization of the laser beam corresponding to the direction of magnetization due to a Kerr effect is detected, thus reading out the information signal.
An example of the magnetic head used for the magneto-optical recording medium will now be described with reference to
FIG. 1. A
magnetic head
200
shown in
FIG. 1
has a magnetic core member
202
on which a coil
201
for magnetic modulation is wound. The magnetic core member
202
is made of a material having a high magnetic permeability and has a substantially prism-shaped base
203
, substantially prism-shaped yokes
204
a
,
204
b
provided to protrude upward from both ends of the base
203
, and a substantially prism-shaped magnetic core
205
provided to stand upward from the base
203
at a position between the yokes
204
a
,
204
b
, as shown in FIG.
2
. On outer circumferential surface of the magnetic core
205
of the magnetic core member
202
, the coil
201
is wound as shown in FIG.
1
.
When a current corresponding to an information signal is supplied to the coil
201
, the magnetic head
200
generates a magnetically modulated vertical magnetic field from a distal end portion
205
a
of the magnetic core
205
on which the coil
201
. is wound. In the magnetic head
200
, the distal end portion
205
a
of the magnetic core
205
is cause to closely contact or slide in contact with the magneto-optical recording medium, and the vertical magnetic field generated from the distal end portion
205
a
of the magnetic core
205
is applied to the recording film of the magneto-optical recording medium, thus writing the information signal to the magneto-optical recording medium.
For a magneto-optical recording medium, a recording/reproducing device for the purpose of recording and reproducing music data is practically used. With such a recording/reproducing device for carrying out recording and reproduction on a magneto-optical disc, though a sufficient transfer rate is achieved in the case of recording and reproducing ordinary music data, a higher transfer rate is desired in the case of recording and reproducing image data in a computer or the like. As for music data, too, a higher transfer rate is desired in the case where duplication or shift is carried out.
To realize such a higher transfer rate, power saving and improvement in the magnetic field inversion band are made in the recording/reproducing device. Specifically, the inductance of the magnetic head
200
is reduced and miniaturization of the magnetic head
200
is done. Particularly, since the magnetic field is narrowed down and concentrated at the distal end portion
205
a
of the magnetic core
205
, improvement in the generation efficiency of the magnetic field due to a so-called edge effect can be realized by narrowing the distal end portion
205
a.
In the magnetic head
200
shown in
FIG. 1
, narrowing the distal end portion
205
a
of the magnetic core
205
causes reduction in the cross-sectional area of the distal end portion
205
a
. Therefore, the range where an effective magnetic field is obtained is narrowed and it is difficult to carry out appropriate write operation onto the magneto-optical recording medium. That is, if the area of the distal end portion
205
a
of the magnetic core
205
is reduced, the intensity of an effective magnetic field applied to a predetermined recording track on the magneto-optical recording medium is insufficient for a positional deviation that is generated when an actuator for driving an objective lens within the recording/reproducing device into a focusing direction and a tracking direction makes a fine adjustment of the position of the objective lens, a positional deviation that is generated when the magneto-optical recording medium is loaded on the recording/reproducing device, and a positional deviation that is generated by the fluctuation of the magnetic head in the direction of height due to the wavering of the magneto-optical recording medium. Therefore, it is very difficult to carry out stable write operation of the information signal onto the magneto-optical recording medium.
If the distal end portion
205
a
of the magnetic core
205
is narrowed, the heat generated in the magnetic core member
202
concentrates at the magnetic core
205
and the magnetic core
205
is deteriorated by a high temperature. Therefore, a sufficient magnetic field cannot be generated.
Generally, in the magnetic head
200
, when a current corresponding to an information signal is supplied to the coil
201
, a magnetic field modulated by the information signal to be recorded is generated from the distal end portion
205
a
of the magnetic core
205
on which the coil
201
is wound. In this case, electric losses proportionate to the number of inversions of the magnetic field are generated. The electric losses mainly include a hysteresis loss due to the delay in the change of the direction of magnetization within the magnetic core member
202
from the change of the magnetic field by the coil
201
, and an eddy-current loss due to the flow of an eddy current induced by the inversion of the magnetic field within the magnetic core member
202
. All these losses are consumed as heat.
In the case where recording of music data is to be carried out as in the conventional technique, the calorific value due to the above-described electric losses is relatively small because of a low data transfer rate. Moreover, since the distal end portion.
205
a
of the magnetic core
205
has a large cross-sectional area and can efficiently release the generated heat toward the base
203
and the yokes
204
a
,
204
b
of the magnetic core member
202
, the influence of such heating is not problematical.
However, in the case where the data transfer rate is high, the number of inversions of the external vertical magnetic field applied to the magneto-optical recording medium increases and therefore the calorific value due to the above-described electric losses increases, too. If the distal end portion
205
a
of the magnetic core
205
is narrowed, the generated heat cannot be efficiently released toward the base
203
and the yokes
204
a
,
204
b
of the magnetic core member
202
and the generated heat concentrates at the magnetic core
205
, thus causing an abrupt increase i
LandOfFree
Magnetic head including stepped core and magneto-optical... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Magnetic head including stepped core and magneto-optical..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Magnetic head including stepped core and magneto-optical... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3057032