Dynamic information storage or retrieval – Storage or retrieval by simultaneous application of diverse... – Magnetic field and light beam
Reexamination Certificate
2000-08-29
2002-10-15
Dinh, Tan (Department: 2651)
Dynamic information storage or retrieval
Storage or retrieval by simultaneous application of diverse...
Magnetic field and light beam
Reexamination Certificate
active
06466523
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a magneto-optical recording head comprising a magnetic head and an optical head placed in opposition; the magnetic head having a magnetic field-generating portion for applying a magnetic field locally to a magneto-optical recording medium, and the optical head having a condenser lens for focusing a light beam on a magnetic recording layer to form a light spot in a region where the magnetic field is applied. The present invention relates also to a magneto-optical recording apparatus employing the magneto-optical recording head for recording information signals.
2. Related Background Art
Magneto-optical recording apparatus are known which record information signals by applying a magnetic field modulated by the information signals onto a magneto-optical recording medium and projecting thereto a light beam for recording.
FIG. 4
is a schematic side view of constitution of an example of the conventional magneto-optical recording apparatus. In
FIG. 4
, magneto-optical recording medium
21
is constituted of substrate
22
made of a transparent material like glass or a resin, and a magnetic recording layer
23
formed thereon, and is housed in cartridge
24
. Magnetic recording layer
23
has a spiral-shaped recording track for recordation of information signals. Magneto-optical recording medium
21
is connected to a spindle motor (not shown in the drawing). Cartridge
24
has apertures. Magnetic head
25
is placed at the aperture on the upper face side (on the side of magnetic recording layer
23
) of magneto-optical recording medium
21
and optical head
26
at the other aperture on the lower side thereof in opposition and with interposition of magneto-optical recording medium
21
.
Magnetic head
25
comprises core
28
which is composed of a magnetic material like ferrite and has protruding columnar magnetic pole P, coil
291
surrounding the magnetic pole P, slider
30
composed of a material like a lubricative resin or ceramic, and first supporter
31
in a flat plate shape composed of an elastic material like phosphor bronze or a beryllium copper. Core
28
together with coil
29
are mounted on slider
30
such that the end face of magnetic pole P for magnetic field generation opposes magneto-optical recording medium
21
. Slider
30
is fixed at the tip end of first supporter
31
and is pressed to the surface of magneto-optical recording medium
21
by the elasticity of first supporter
31
.
Optical head
26
comprises laser light source
32
like a semiconductor laser, condenser lens
33
, lens holder
34
for holding the condenser lens
33
, second supporter
35
constituted of an elastic material like phosphor bronze or beryllium copper in a straight line shape, actuator
36
placed around lens holder
34
, and basement
37
for holding these constituting members. Lens holder
34
is fixed to the tip end of second supporter
35
. The base end of second supporter
35
is fixed to basement
37
which is fixed to connecting member
27
. Actuator
36
is constituted of a coil and a permanent magnet which are not shown in the drawing, and drives lens holder
34
electromagnetically.
On recording the information signals, slider
30
of magnetic head
25
is pressed against the surface of magneto-optical recording medium
21
, and on loading or unloading of cartridge
24
, slider
30
is withdrawn upward so as not to collide with cartridge
24
. Therefore, the base end of first supporter
31
is fixed to connecting member
27
at a position higher than the upper face of cartridge
24
. Thus, when slider
30
is pressed against the surface of magneto-optical recording medium
21
, first supporter
31
is tilted at a certain angle relative to magneto-optical recording medium
21
.
Coil
29
of magnetic head
25
is connected to a magnetic head driving circuit (not shown in the drawing), and laser light source
32
of optical head
26
is connected to a laser driving circuit (not shown in the drawing), respectively.
In recordation of information signals on magneto-optical recording medium
21
, firstly, magneto-optical recording medium
21
is rotated by the spindle motor. In the rotation, slider
30
of magnetic head
25
is allowed to slide on or above magneto-optical recording medium
21
. Since slider
30
is pressed against the surface of magneto-optical recording medium
21
, magnetic pole P of core
28
set on slider
30
can follow the displacement in the Z direction (direction perpendicular to the surface of magneto-optical recording medium
21
) of the surface of the magneto-optical recording medium
21
caused by irregularity or variation in the thickness, or swing of the face of magneto-optical recording medium
21
. Thereby, the interspace is kept constant between the end face of magnetic pole P of core
28
and magnetic recording layer
23
of magneto-optical recording medium
21
. An electric current is applied from the magnetic head driving circuit to coil
29
of magnetic head
25
to generate a magnetic field modulated by information signals to be recorded at the end face of magnetic pole P of magnetic head
25
. This magnetic field is applied virtually perpendicularly to magnetic recording layer
23
of magneto-optical recording medium
21
opposing the end face of magnetic pole P. Simultaneously, electric current is applied from the laser driving circuit to laser light source
32
of optical head
26
, whereby laser light source
32
emits a light beam for recording. The emitted light beam for recording is focused by condenser lens
33
to form fine light spot S in a region of magnetic recording layer
23
of magneto-optical recording medium
21
where the magnetic field is locally applied. In the spot formation, the focusing and tracking are controlled by driving of lens holder
34
by actuator
36
so that light spot S formed by condenser lens
33
follows the displacement of magnetic recording layer
23
in the Z direction and the displacement of the recording track in the Y direction caused by the decentering of the recording medium (perpendicular to the recording track and parallel to the surface of magneto-optical recording medium
21
).
Light spot S locally heats magnetic recording layer
23
to lower the coercivity at spot S to form a magnetized region in correspondence with the direction of the applied magnetic field. Thereby, information signals are recorded on the magnetic recording layer by change of the magnetization direction.
As described above, in a conventional magneto-optical recording apparatus, the surface of magneto-optical recording medium
21
deviates positionally from the prescribed level in the Z direction (direction perpendicular to the surface of magneto-optical recording medium
21
) owing to irregularity or variation of the thickness, swing and so forth of the face of magneto-optical recording medium
21
. The positional deviation is within the range of about ±300 &mgr;m. Magnetic pole P of magnetic head
25
and light spot S of the recording light beam of optical head
26
are both displaced following the displacement of magneto-optical recording medium
21
in the Z direction.
In magnetic head
25
, slider
30
is held at the tip of first supporter
31
which is tilted at a certain angle relative to magneto-optical recording medium
21
. Therefore, with the displacement in the Z direction, magnetic pole P of core
28
is also displaced in the X direction (parallel to the recording track within the plane parallel to the surface of magneto-optical recording medium
21
). Similarly, since condenser lens
33
is held at the tip of second supporter
35
in optical head
26
, light spot S of the light beam for recording is also displaced in the X direction with its displacement in the Z direction. Accordingly, with the displacement in the Z direction, the relative position of magnetic pole P to light spot S is changed in the X direction.
Since a sufficient intensity of the magnetic field for the recording is applied only in the limited r
Canon Kabushiki Kaisha
Dinh Tan
Fitzpatrick ,Cella, Harper & Scinto
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