Dynamic information storage or retrieval – Storage or retrieval by simultaneous application of diverse... – Magnetic field and light beam
Reexamination Certificate
2001-09-13
2003-04-22
Dinh, Tan (Department: 2653)
Dynamic information storage or retrieval
Storage or retrieval by simultaneous application of diverse...
Magnetic field and light beam
C369S013330
Reexamination Certificate
active
06552966
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an information recording apparatus of an optical magnetic recording system for recording information on a recording medium based on both operations of light and magnetism, a recording head employed in this information recording apparatus, and a method of manufacturing this recording head.
BACKGROUND ART
In recent years, a recording medium and an information recording apparatus of an optical magnetic recording system have been widely distributed. In this optical magnetic recording system, a further high-density recording has been required, like in other information recording system.
In order to satisfy this requirement, focus has been placed on a magnetic field modulation system for modulating a magnetic field, in addition to an optical modulation system for modulating light.
FIG. 15
is a schematic diagram showing one conventional example of an optical magnetic recording system that employs both the optical modulation system and the magnetic field modulation system.
A recording medium
10
shown in the drawing is formed with a recording layer
12
for having information recorded on the surface of a light-transmissive substrate
11
. A transparent protection layer
13
is formed on the surface of the recording layer
12
for protecting this recording layer.
A magnetic head
20
is disposed at a position close to the protection layer
12
(for example, with a gap of about 2 to 4 &mgr;m from the surface of the protection layer
12
). The protection layer
13
has a thickness of about 5 to 10 &mgr;m. Therefore, the magnetic head
20
is disposed at a position of about 10 &mgr;m to 100 &mgr;m from the recording layer
12
.
A magnetic coil
21
of this magnetic head
20
is input with a modulation signal S as shown in the drawing, and a modulation magnetic field is formed.
For carrying out a magnetic field modulation, it is necessary to dispose the magnetic head
20
at a position extremely close to the recording layer
12
like about 10 &mgr;m as described above. Therefore, an objective lens
31
for guiding a laser beam
30
to the recording layer
12
is disposed at a substrate
11
side. The laser beam
30
is irradiated from the substrate
11
side to the recording layer
12
. In this example, the laser beam
30
is also modulated in recording information on the recording medium
10
. This is called a laser pulse light-emission magnetic field modulation recording, which further improves the density of the tracks. Information is recorded on the recording layer
12
based on both operations of the magnetic field generated by the magnetic head
20
and the heating generated by the irradiation of the laser beam
30
.
In order to achieve a high-density recording on the recording medium, it is necessary to increase the NA of the objective lens
31
and to form an extremely small light spot on the recording layer
12
.
FIG. 16
is a schematic diagram showing one conventional example of forming an extremely small light spot on the recording medium.
As the objective lens, there are disposed a condensation lens
32
that is similar to the objective lens
31
shown in
FIG. 15
, and a semi-spherical lens
33
, for example, that is called a solid immersion lens (SIL). Based on the use of the SIL
33
, a laser beam
30
a
leaked from the SIL
33
to a position extremely near the SIL
33
is used as a light for recording on the recording medium
10
. With this arrangement, it is possible to realize a certain level of high NA. From the viewpoint of only the light spot, it is considered possible to achieve a certain level of high-density recording.
However, this SIL
33
has a short depth of focus like a few &mgr;n to 100 nm or below. Therefore, when it is tried to apply the system shown in
FIG. 15
to the magnetic field modulation system, it is necessary to dispose the objective lens and the magnetic coil including this SIL
33
at the same side of the recording medium. For this purpose, it is necessary to dispose a magnetic coil
34
on the bottom surface
33
a
of the SIL
33
. Consequently, it becomes necessary to use a coil without a core for allowing the laser beam
30
to pass through. This has a problem that it is difficult to obtain a magnetic field that has strength necessary for the high-speed modulation.
DISCLOSURE OF THE INVENTION
In the light of the above situation, it is an object of the present invention to provide an information recording apparatus capable of realizing a high-density recording based on both operations of light and a magnetic field, a recording head that is suitable for use in this information recording apparatus, and a method of manufacturing this recording head.
In order to achieve the above object, according to the present invention, there is provided a recording head disposed between a light source and a recording medium. This recording head comprising: a magnetic head for generating a magnetic field toward the recording medium; and a light guide disposed on an optical path at the downstream of the magnetic head, for condensing an optical beam guided from the upstream of the magnetic head, and emitting this optical beam to the recording medium.
In the recording head of the present invention, it is preferable that the light guide comprising: a light guiding layer disposed on the optical path at the downstream of the magnetic head, for being incident with an optical beam guided from the upstream of the magnetic head; and a sharp-headed light guide disposed on the optical path at the downstream of the light guide, having a sharp head toward an aperture of the front end of the recording medium, for condensing an optical beam guided from the light guiding layer, and emitting the optical beam to the recording medium via the aperture.
In this case, it is preferable that the light guiding layer has a diffraction grating for guiding the optical beam to the optical-beam incident surface.
Further, according to the present invention, there is provided a recording head comprising: a light-transmissive substrate having a magnetic head made up of an embedded magnetic core, and a magnetic coil formed on an area surrounding the magnetic core on the surface facing the recording medium; a sharp-headed light guide with a sharp head toward the front end facing the recording medium, having a light-incident aperture for receiving an incidence of a light at a position with a predetermined distance from the front surface of the magnetic head that faces the recording medium, for condensing a light incident from the light-incident hole, and emitting the condensed light toward the recording medium from a light-emitting hole formed at the front end facing the recording medium; and a light guiding layer having the front surface facing the recording medium in contact with the light-incident hole, with the rear surface spread in contact with the front surface of the light-transmissive substrate, having an incident-light guide diffraction grating in the area in contact with the front surface of the light-transmissive substrate, and having a light-emission diffraction grating in the area in contact with the light-incident aperture, for introducing a light incident from the rear surface of the light-transmissive substrate via the incident-light guide diffraction grating, condensing the introduced light toward the light-incident hole, and emitting the condensed light toward the sharp-headed light guide via the light-emission diffraction grating.
The recording head has the above-described structure, and both the objective optical system and the magnetic coil are disposed at the same one side of the recording medium. Even when a light irradiated onto a portion of the magnetic head has been shielded by the magnetic head, only a small portion of the total optical beam is shielded. Therefore, it is possible to focus a light with sufficient intensity into an extremely small optical spot, and irradiate this focused beam onto the recording medium.
Moreover, based on the formation of the diffraction grating, it is possible to efficiently introduce the
Aoyama Nobuhide
Hasegawa Shin-ya
Odajima Wataru
Tawa Fumihiro
Dinh Tan
Fujitsu Limited
Greer Burns & Crain Ltd.
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