Dynamic information storage or retrieval – Storage or retrieval by simultaneous application of diverse...
Reexamination Certificate
1998-09-25
2001-08-21
Psitos, Aristotelis M. (Department: 2651)
Dynamic information storage or retrieval
Storage or retrieval by simultaneous application of diverse...
C369S112010
Reexamination Certificate
active
06278666
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a magneto-optical disk recording and reproducing device using a disk type magneto-optical media. More specifically, it relates to an optical head and a magnetic head of the magneto-optical disk recording and reproducing device.
BACKGROUND OF THE INVENTION
Recently, disk recording and reproducing devices have been used for various applications, for example, DVD, MD, CD, CD-ROM, etc., and devices having a high density, small size, high performance, high quality, and high added value have been demanded. In particular, in the magneto-optical disk recording and reproducing device using a magneto-optical media capable of recording, the demands of devices for data and devices for image-recording tend to greatly increase. Consequently devices having a small size, thin shape, high performance and high recording density have been increasingly demanded.
Hitherto, a great deal of investigations concerning the techniques of an optical head and magnetic head for a magneto-optical disk has been reported.
Hereinafter, a conventional magneto-optical head and magnetic head for magneto-optical disk will be described with reference to the drawings.
FIG. 8
is a schematic view showing a light path of a conventional magneto-optical disk recording and reproducing device.
As shown in
FIG. 8
, the light beam irradiated from a semiconductor laser
1
is converted into a parallel light beam by a collimator lens
2
and is separated into a plurality of different parallel light fluxes by a diffraction grating
3
. A plurality of different parallel light fluxes pass through a beam splitter
4
a
of a composite element
4
and are converged on an information recording medium
6
having a magneto-optical effect as a main beam. The main beam has a diameter of about 1 &mgr;m by means of an object lens
5
incorporated in an object lens holder
33
(see FIG.
10
). At the same time, a preceding beam and a following beam as sub-beams are produced at constant intervals in front of and behind the main beam on the same track as that of the main beam by so-called three-beam method.
Moreover, a parallel light flux reflected from the beam splitter
4
a
of the composite element
4
is incident on a light receiving element
7
for monitoring, and thereby the driving current of the semiconductor laser
1
is controlled.
The light beam reflected from the information recording medium
6
travels in the opposite direction, is reflected from and splitted by the beam splitter
4
a
of the composite element
4
and then is incident on a polarization separating element
4
b
of the composite element
4
. The semiconductor laser
1
is provided in such a way that the polarization direction of the laser beam is parallel with respect to the paper. The polarization direction of the incident light beam is rotated by 45°, and then the incident light beam is separated into three different fluxes having two polarization components crossing at right angles by the polarization separating element
4
b,
and then reflected from a mirror
4
c
of the composite element
4
.
The reflected light beam that passes through the composite element
4
is incident on a cylindrical-shaped convex lens
8
to form a convergent light beam. Then, the convergent light beam is incident on a concave cylindrical lens
9
. Herein, the concave cylindrical lens
9
is provided in such a way that the lens effect is exhibited in the direction of approximately 45° with respect to the image of the recording track of the information recording medium
6
that is present in the direction of W
1
in a plane being parallel to the paper.
The light beam that passes through the concave cylindrical lens
9
generates astigmatism, which is an error signal detected by a focus error signal detecting means. The light beam being incident on a plane that does not have the lens effect of the concave cylindrical lens
9
passes through an optical path shown by solid lines and is converged in a focal point
12
. On the other hand, the light beam being incident on a plane that has the lens effect of the concave cylindrical lens
9
passes through an optical path shown by broken lines and is converged in a focal point
13
.
A multi-divided photo-detector
10
is located in such a way that its light receiving face is approximately midway between the focal point
12
and the focal point
13
.
The magnetic head is located above the information recording medium
6
. The electric current is applied to the coil
26
from the current applying means
29
, and thereby the magnetic field is generated.
FIG. 9
is a schematic view showing a multi-divided photo-detector and a signal detecting circuit.
As shown in
FIG. 9
, the multi-divided photo-detector
10
comprises a quadrant region
19
of receiving light beam, a region
20
of receiving preceding beam, a region
21
of receiving following beam, and regions
22
a
and
22
b
of receiving information signals. These light receiving regions are connected to a subtractor
23
and an adder
24
. Herein, the quadrant region
19
of receiving light beam receives a light spot
16
of the main beam (P+S polarization), the region
22
a
of receiving information signals receives a light spot
15
of the main beam (S polarization), the region
22
b
of receiving information signals receives a light spot
14
of the main beam (P polarization), the region
20
of receiving preceding beam receives a light spot
17
of the preceding beam of the sub-beams, and the region
21
of receiving following beam receives a light spot
18
of the following beam of the sub-beams, respectively.
The focus error signal is detected by so-called astigmatism method. In the astigmatism method, the sums of electric signals generated at two diagonals of the quadrant region
19
of receiving light beam of the central part are calculated, and then the difference thereof is calculated. The tracking error detection signal is detected by so-called three-beam method. In the three-beam method, the difference between the light spot
17
of the preceding beam and the light spot
18
of the following beam is calculated. Furthermore, the magneto-optical disk information signal can be detected by the differential detection method. In the differential detection method, the difference between the main beam
14
comprising P polarization and the main beam
15
comprising S polarization is calculated. Furthermore, by calculating the sums thereof, a prepit signal also can be detected.
FIG. 10
is a schematic view showing a configuration of a conventional disk recording and reproducing device.
As shown in
FIG. 10
, the object lens
5
located below the information recording medium
6
is held by the object lens holder
33
. The object lens holder
33
is fixed to an optical housing
11
using an object lens driving device
32
. On the other hand, a coil
26
, a yoke
27
and a slider
30
that are located above the information recording medium
6
are precisely fixed to the optical housing
11
using a suspension
28
and a suspension holder
31
. The optical housing
11
can be moved in the radial direction of the information recording medium
6
by means of a carrying means
34
such as a ball screw. Moreover, the information recording medium
6
can be rotated by a spindle motor
25
.
When signals are recorded on the information recording medium
6
, the coil
26
and yoke
27
are held at a predetermined distance from the surface of the information recording medium
6
by the spring pressure of the suspension
28
. Subsequently, in a state where the temperature on the information recording medium
6
is increased by light spot, electric current is applied to the coil
26
by a current applying means
29
(see FIG.
8
). Thus, the vertical magnetic field is generated in accordance with the direction of the applied current and the vertical magnetic field is provided to the information recording medium
6
by the magnetic circuit comprising the yoke
27
. Thus, the signals are recorded on the information recording medium
6
.
Howev
Aikoh Hideki
Miyamori Kenichi
Murakami Yutaka
Nakata Hideki
Matsushita Electric - Industrial Co., Ltd.
Psitos Aristotelis M.
Rosenthal & Osha L.L.P.
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