JPH11162033A - Magneto-optical recording/reproducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reproduce a magnetic pit smaller than a laser spot by bisecting incident luminous flux of linear polarization onto a disk in the track direction, specifying the phase difference between bisected two luminous flux and forming twin spots on the disk surface in the track direction. SOLUTION: Outgoing light rays from a laser light source 21 are made into parallel light rays by a collimate lens 22. The parallel light rays are bisected by phase change means (1/2 wavelength plates) 25a, 25b arranged between a beam splitter 24 and an objective lens 23 in the track direction of the disk. That is, a half of linear polarization luminous flux is nearly 90 deg. rotated clockwise, and a remained half of linear polarization luminous flux is nearly 90 deg. rotated counterclockwise. The parallel light rays become laser luminous flux that the phase difference of two luminous flux is nearly 180 deg. inverted, and respective luminous flux transmit through the objective lens 23, and are converged on an information recording surface 20a of a magneto-optical disk 20 to be emitted. A two peaks spot distribution having minimum independent peaks on left-right around an optical axis related to a disk rotational direction is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a magneto-optical data recording / reproducing apparatus capable of magneto-optically recording and reproducing data on a magneto-optical recording medium.

[0002]

2. Description of the Related Art At present, as a method of recording information in a magneto-optical disk device, for example, a laser beam modulated by a code data signal to be recorded is condensed on a disk surface by a lens, and a magnetic recording medium such as TeFeCo, Gd-Tb-
Amorphous rare earth (R) such as Fe and transition metal (TM)
Alloy, that is, the temperature of the (R-TM) alloy film is set to 150 to
Raise to about 200 ° C. When the temperature of the medium becomes equal to or higher than the Curie temperature (Tc) due to the heating of the laser beam, the magnetization is lost. In this case, if a DC bias magnetic field is applied in one direction by a magnet, the heated portion returns to room temperature. The magnetization reversal occurs, and the magnetic domain 32 is magnetized and recorded in the direction perpendicular to the disk surface.

On the other hand, a magneto-optical recording / reproducing apparatus for reproducing code data recorded on a disk in this way is a method of forming a laser spot obtained by condensing a linearly polarized laser beam on a recording surface of a magneto-optical disk with a lens. Irradiation is performed, and the information recorded as the magnetization direction on the recording surface is detected by changing the rotation of the polarization plane by the electro-optic Kerr effect or the Faraday effect, which is the interaction between light and magnetization. That is, the information of the magnetization on the disk can be read out by optically detecting the change in the polarization state of the reflected light.

[0004] The technology described above is already 3.5 inches,
Alternatively, a practically used 5.25 inch magneto-optical disk drive is used. However, the diameter D of the focused laser spot is theoretically determined by the wavelength λ of light and the numerical aperture NA of the lens.
D = 0.5λ / NA, for example, the wavelength λ of the semiconductor laser light = 0.68 μm, the lens numerical aperture NA = 0.5
If it is 5, D = 0.62 microns, and it becomes difficult to read out even smaller magnetic pits.

In recent years, a method called magnetic super-resolution has been studied as a method for reading out magnetic pits d (<D) smaller than the laser spot diameter D. For example, JP-A-3-93
No. 056, or Journal of the Japan Society of Applied Magnetics, 15-5, 8
38-844 (1991) In a "super-resolution magneto-optical disk", a laser beam is scanned on the disk with a power larger than a normal reproduction output, and a temperature distribution in a magnetic film in a central region and an external region in an irradiation laser spot is obtained. Utilizing what happens,
“Magnetic super-resolution (MSR)” that reads out magnetic pit information smaller than the laser spot, for example, FAD (Fron
A method called “t Aperture Detection” has been proposed. However, this FAD method has problems such as the necessity of a magnetic field during data reproduction.

[0006]

Problems of the prior art The problems of the prior art will be described with reference to FIGS. 11, 12, 13, 14, and 15 by taking a magneto-optical disk recording / reproducing method by laser pulse irradiation and magnetic field modulation as an example.

In FIG. 15, a laser light source 1 forms pulsed light 2 by a laser driving circuit 9, and a laser spot 4 is condensed and irradiated on a magneto-optical recording medium 8 by an objective lens 3. On the disk, the numerical aperture of the objective lens 3 is NA,
Assuming that the wavelength of the laser beam 1 is λ, a spot diameter of D = 0.5λ / NA is focused on the disk. On the other hand, when the pulse of the clock 10 is increased while the magnetic field modulation 7 is applied to the disk surface by the data signal generator 6 using the magnetic head 5 set near the disk and pulse irradiation is performed, the heated portion is reduced. When the temperature returns to room temperature, magnetization reversal occurs, and the magnetic domains 11 having a mark length smaller than the laser spot diameter D are sequentially overwritten in the direction perpendicular to the disk surface, and magnetization recording is performed. This recording method is described in JP-A-1-292603.
This is a known technique. For example, wavelength λ = 0.68
If the micron and the numerical aperture of the lens NA are 0.55, the converged laser spot 4 has a diameter D = 0.62 micron. However, by shortening the pulse irradiation interval, the shortest mark length d = 0.1. Recording of .about.0.2 microns is possible. Now, for a disc with a diameter of 120 mm, the track pitch p
= 0.6 microns and the shortest mark length d = 0.26 microns, information with a capacity C of 7 to 10 GB (gigabytes) can be recorded.

FIG. 14 is a view perpendicular to the disk surface of FIG.
1 is a perspective view showing a configuration of a magneto-optical recording / reproducing apparatus for reproducing magneto-optical data 32 recorded on a recording surface 20a of a magneto-optical disk 20 by a method shown in FIG. Indicates the direction of linearly polarized light.

Referring to FIG. 14, this magneto-optical recording / reproducing apparatus includes a laser light source 21, a collimator lens 22 for collimating the light emitted from the laser light source 21, and a magneto-optical disk 20 for condensing the parallel light. And a beam splitter (BS) 24 disposed between the collimator lens 22 and the objective lens 23 for separating the light reflected on the recording surface 20a of the magneto-optical disk 20. A half-wave plate 26 for rotating the polarization plane by 45 degrees, a condenser lens 28, a polarization beam splitter (PBS) 27 for separating the S-wave component and the P-wave component, and each of the P and S polarization components. Detectors 29a and 29b for detecting
It is composed of

In FIG. 14, a laser light source 21 is constituted by, for example, a semiconductor laser. The laser light source 21 outputs, for example, a P-wave whose polarization plane (oscillation direction) is parallel to the P-axis. The P-wave is parallelized by the collimator lens 22 and passes through the transmittance of the P-wave, for example, the beam splitter 24 with Tp = 80%, to the recording surface 20a of the magneto-optical disk 20 in a polarized state of linear P-polarized light via the objective lens 23. The spot is irradiated. The optical path of the light reflected by the disk surface 20a is reversed. At this time, the polarization plane is rotated by an angle + θk by the electro-optical Kerr effect by the recording data magnetic domain 32 magnetized in the direction perpendicular to the disk surface. This reflected light is reflected by a beam splitter (BS) 24 (for example, P-polarized component reflectance Rp = 20%, S-polarized component reflectance Rs = 1)
The light flux reflected by the half-wave plate 26 is further rotated by 45 degrees by the half-wave plate 26, and the luminous flux condensed by the lens 28 is converted into an S-wave component and a P-wave by a polarization beam splitter (PBS) 27. The components are separated and received by the detectors 29a and 29b. An MO signal is detected from a difference signal between the output signals of the respective detectors. However, in such a reproducing method, a laser spot irradiated on the recording surface 20a (D = λ / 2NA)
There is a problem that even if smaller magneto-optical data 32 exists on the recording surface 20a, it cannot be resolved.

FIG. 13 illustrates an MO signal waveform obtained by reproducing magnetic data on the recording surface 20a of the disk 20 using the conventional magneto-optical recording and reproducing apparatus shown in FIG. In the conventional magneto-optical recording / reproducing apparatus, since the spot on the disk recording surface 20a has a Gaussian intensity distribution, the differential signal MO = 29 at the detectors 29a and 29b.
The MO reproduction signal according to a-29b is as shown in FIG.
The signal becomes maximum at the center of the magnetic data pit. For example, the signal does not come out at the domain wall which moves from the magnetic data pit in the upward arrow direction to the magnetic data pit in the downward arrow direction. Therefore, when the magnetic pit becomes small, the magneto-optical signal amplitude becomes small. . Therefore, the magnetic data 32 having the shortest mark length d = 0.1 to 0.2 μm recorded by the magnetic field modulation as shown in FIG.
Reproduction at 0.62 microns (= 0.5λ / NA) is extremely difficult.

FIG. 12 shows a FAD (FAD) in which magnetic pits smaller than the laser spot 4 are read out by a method called magnetic super-resolution.
This describes the method of “Ron Aperture Detection”, and is described in JP-A-3-93056 or the Journal of the Japan Society of Applied Magnetics, 15-5, 838-844 (1).
991) This is a known technique for a “super-resolution magneto-optical disk”. In FIG. 12A, the magneto-optical thin film 12 has three layers having different magnetic characteristics and temperature characteristics, that is, a recording layer 12-.
1, the reproducing layer 12-2, and the switching layer 12-3. When the laser spot 4 scans the data recording track 16 on the magnetic film surface 12 as shown in FIG. Absorbed by the magnetic medium, a temperature distribution occurs in the magnetic film in the laser spot 4. As a result, in the high temperature region 13-1, the switching layer 12-3 becomes close to the Curie temperature (Tc to 140 ° C.), and the recording layer 12
-1 and the reproducing layer 12-2 weaken, and when the reproducing magnetic field 14 is applied, the reproducing layer 12-2 having a small coercive force is applied.
Are aligned by the reproducing magnetic field 14. As a result, the magnetic pits 15-1 in the recording layer 12-1 in the high-temperature area 13-1 are masked in the laser spot 4, so that only the magnetic pits 15 in the low-temperature area 13-2 are transferred and readable. . However, this method can achieve a target signal level of 45 dB at a mark length of 0.4 μm, but 30 dB when the mark length is reduced to 0.3 μm.
Become. Furthermore, since the shape of the low-temperature region 13-2 is a crescent shape, if the track pitch is reduced, leakage of a reproduction signal from an adjacent track increases, and there is a problem that it is difficult to improve the track density. .

FIG. 11 shows a DWDD (Domain Wall) for reading out a magnetic pit smaller than the laser spot 4.
This is an explanation of the “Displacement Detection” method.
gh Density Magneto-Optica
l Recording with DomainWa
ll Displacement Detection
n "Tu-E-0438-39 (1997). FIG. 11A shows a structure of a magneto-optical thin film 12 of a DWDD system, in which a recording layer 12-1 and a reproducing layer (Displacement layer) are provided. 12-2-
1, a switching layer 12-3. This DW
The structure of the DD magnetic thin film 12 is similar to the above-mentioned FAD magneto-optical thin film structure, but a reproduction layer (Displacement layer) 12-2- of the DWDD type magneto-optical thin film 12 is used.
1 is a Displacement layer as described later.
The domain wall moves along the temperature gradient when the laser beam is irradiated, also called er.

In FIG. 11A, when a track on which magnetic information is recorded is scanned while irradiating a laser beam,
The light energy is absorbed by the magnetic medium, and a temperature distribution as shown in FIG. As a result, in the high temperature region 13-1 (see FIG. 12), the switching layer 12-3 has a Curie temperature (Tc).
-140 ° C.), and the recording layer 12-1 and the moving reproduction layer (Displacement layer) 12-2-
1 is weakened and the regeneration layer (Displa)
The cement layer 12-2-1 is masked from the recording layer 12-1 by the switching layer 12-3.

Further, in FIG. 11B, a reproduction layer (Displacement layer) 12-2-
Since the gradient (differential) of the temperature distribution 1 theoretically corresponds to the force for moving the domain wall, when the laser beam is irradiated, the domain wall 36 on the higher temperature side is pulled in the direction of the larger temperature gradient, and the recording layer 12- The reproduction layer (Disp.) Corresponding to the minute magnetic domain 32 of FIG.
magnetic layer 3 of 12-2-1
The 2 * domain wall 36 is enlarged. As a result, the reproduction layer 12-2
The magnetic pit 32 * enlarged by -1 (Displacement layer) can be read using the magneto-optical recording / reproducing apparatus shown in FIG. The DWDD system can reproduce a finer magnetic domain than the FAD system, but has a disadvantage that the conventional magneto-optical recording and reproducing apparatus shown in FIG. 14 cannot accurately detect the edge position of the domain wall.

[0016]

SUMMARY OF THE INVENTION An object of the present invention is to provide a magneto-optical recording / reproducing apparatus capable of reproducing magnetic pits much smaller than a laser spot.

[0017]

According to the present invention, in a magneto-optical recording / reproducing apparatus, an incident light beam of linearly polarized light on a disk is divided into two in a track direction, and the phase difference between the two light beams is approximately 180. At the very least, it is proposed to have means for forming a twin spot in the track direction on the disk surface.

[0018]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a plan view of a magneto-optical recording / reproducing apparatus showing an embodiment of an optical data reproducing apparatus of a magneto-optical data apparatus according to one embodiment of the present invention. This magneto-optical recording / reproducing apparatus includes a laser light source 21, for example, a semiconductor laser, a collimator lens 22 that converts light emitted from the laser light source 21 into parallel light, and a beam splitter (BS) 24 that converts the parallel light from the collimator lens 22 into light. Through the disk surface (2
0a) is provided with an objective lens 23 for condensing and irradiating the beam onto the beam splitter, and a two-phase splitting means 25 (25a, 25b) disposed between the beam splitter (BS) 24 and the objective lens 23, and further comprising a magneto-optical device. 1/2 for separating the light reflected on the recording surface 20a of the disk 20 into a predetermined polarization component
Wave plate 26, condenser lens 28, polarizing beam splitter (PBS) 27, and two split photodetectors (29a, 29a).
29b) and (29c, 29d).

More specifically, the two-way phase changing means 25 (25a, 25b) rotates, for example, approximately 90 degrees clockwise about half (A) of the linearly polarized light beam and counterclockwise rotates the other half (B) of the linearly polarized light beam. Half-wave plate 2 for rotating the polarization by approximately 90 degrees
5a and 25b are laminated. Alternatively, one half of the phase plate 25 ′ a and the other half of the phase plate 25 ′
The phase plate is formed of the thick half and the thin half so that the linearly polarized light is delayed by approximately 180 degrees by b.

FIGS. 2 and 3 and FIGS. 4 and 5 are perspective views of the magneto-optical recording / reproducing apparatus according to the embodiment of the present invention illustrated in FIG. The light beam converted into parallel light by the collimator lens 22 is divided into laser light beams A and B passing through upper and lower optical paths. 2 and 3, and FIGS. 4 and 5, the condenser lens 28 is not shown for convenience of description, but this is not essential for the description of the present invention.

FIG. 2 shows the conversion of the plane of polarization of the light beam A, and FIG.
Indicates conversion of the polarization plane of the B light flux. 2 and 3, the direction of the arrow in the circle indicates the polarization direction of the polarized light.

First, referring to FIG.
The linearly-polarized laser light, for example, the P-polarized light from the laser beam splitter 24 (for example, Tp = 80%, Rs = 100)
%), And when the light flux A of the upper half of the laser light flux passes through the half 25a of the divided half-wave plate 25 according to one embodiment of the present invention, the polarization plane is rotated clockwise by approximately 90 degrees. The rotated S-polarized light beam 33 is obtained. The light beam A ′ reflected by the disk and passed again through the other half 25 b of the half-wave plate 25 returns to the same polarization state as the original light beam A.

On the other hand, in FIG. 3, the light beam B in the lower half of the laser light beam is divided into half, which is one embodiment of the present invention.
When passing through the half 25b of the wave plate 25, the polarization plane
The s-polarized light flux 34 is rotated counterclockwise by degrees. The light beam B ′ reflected by the disk and re-passed through the other half 25a of the half-wave plate 25 returns to the same polarization state as the original light beam B. 2 and 3, the light beams 33 and 34 have a phase of approximately 180.
Laser light fluxes, each of which is transmitted through the objective lens 23 and each of which passes through the information recording surface 20 of the magneto-optical disk 20.
The light is condensed and radiated to a.

FIGS. 4 and 5 are perspective views of a magneto-optical recording / reproducing apparatus according to another embodiment of the present invention illustrated in FIG. Beam splitter 24 '(for example, Ts = 80
%, Rp = 100%), the S-polarized laser light is split into two phase plates 25 '(25') according to the embodiment of the present invention.
a, 25'b), the phase difference between the light beams A and B is approximately 18
It is formed from a thick portion and a thin portion so as to be shifted by 0 degrees. The state of S-polarized light does not change. The difference in wall thickness is d = λ / 2
(N-1) is preferred. λ is the wavelength of the laser beam, and n is the refractive index of the substrate. Further, according to the present invention, the optical system and the disk are arranged such that the polarization directions of the light beams 33 and 34 coincide with the disk track direction (θ). 4 and 5, the light beams 33 and 34 have a phase of approximately 180.
Laser light fluxes, each of which is transmitted through the objective lens 23 and each of which passes through the information recording surface 20 of the magneto-optical disk 20.
The light is condensed and radiated to a.

FIG. 6 is a plan view of a magneto-optical recording / reproducing apparatus according to another embodiment of the present invention. The phase difference between the light beams A and B shown in FIGS. 4 and 5 is shifted by about 180 degrees. The phase plate 25 '(25'a, 25'b) formed as described above is disposed between the collimator lens 22 and the beam splitter 24. When the laser light source 21 has enough power output, the collimator lens 22 can be omitted. In this case, the phase plate 25 ′ may be provided between the laser light source 21 and the beam splitter 24.

FIG. 7 is a diagram showing a two-part phase change means 25a, b and 25'a used in FIGS. 1, 2, 3, 4, 5 and 6, which are one embodiment of the present invention. , B. FIG. 7A shows a half-wave plate 25, for example.
FIG. 6 is a diagram showing a method of rotating half of the linearly polarized light beam by approximately 90 degrees to the right and setting the other half of the linearly polarized light beam to approximately 90 degrees by left-handed linear polarization by setting the crystal axes at different angles. The same effect can be obtained even if the phase changing means 25 is formed of an optical rotation plate or a liquid crystal plate. FIG. 7 (b) is formed of a thick portion and a thin portion so that the phase difference becomes approximately 180 degrees after passing through the phase plates 25'a and 25b divided into two. The thickness difference of the phase plate is preferably d = λ / 2 (n−1). The same effect can be obtained even if the phase changing means 25 'is formed of a liquid crystal plate. If this phase changing means 25 or 25 'is fixed to the surface on the side of the beam splitter (24) or the objective lens (23), it becomes very easy to construct an optical system.

FIG. 8 shows an embodiment according to the present invention.
8A shows the polarization state of the condensed light beams 33 and 34 on the magneto-optical disk 20, and FIG. 8B shows the two-dimensional light intensity distribution of the condensed spot on the recording surface 20a of the magneto-optical disk 20 by rotating the disk. FIG. 3 is a cross-sectional view in the direction (θ) and the disk radial direction (R). According to the present invention, the focused laser beam 3
The polarization directions 3 and 34 are substantially opposite to each other in accordance with the disk rotation direction θ. When the laser beam having such a polarization state is condensed by the condenser lens 23, the disc recording surface 2
The two-dimensional distribution at 0a is a distribution as shown in FIG. That is, as shown by the dotted line, the disk rotation direction θ has a spot distribution of two peaks (P1, P2) having independent peaks on the left and right with the minimum intensity at the center of the optical axis (hereinafter referred to as twin spots). In the disk radial direction R, a Gaussian spot distribution having an optical axis peak is obtained as shown by a solid line.

Next, a twin laser spot as shown in FIG. 8 (b) is formed by a configuration as shown in FIG. 1, FIG. 2, FIG. 3, FIG. 4, FIG. so,
The reproduction of the spatial differential signal when scanning is performed in the disk rotation direction θ, that is, in the data recording direction, will be described with reference to FIG.

In FIG. 9, the vertical axis indicates the spatially differentiated MO signal output 31 obtained by scanning the magneto-optical recording medium using the twin spot according to one embodiment of the present invention. M
The O signal 31 includes a differential detection signal MO1 (29a-29c) corresponding to the twin spot P1 and a differential detection signal MO2 (29a) corresponding to the twin spot P2 in FIG.
b-29d) is a difference output. Since the positions of P1 and P2 are slightly shifted in the same spot, the signals MO1 and M
The O2 difference signal (MO1-MO2) 31 exerts a spatial differentiating action on the MO output signal. Therefore, a large signal is obtained when the center of the twin spot crosses the domain wall of the wall of the magnetic data pit, and the polarity of the output signal changes when the magnetic data pit moves from the magnetic data pit in the upward arrow direction to the magnetic data pit in the downward arrow direction. The polarity is reversed when the directional magnetic data pit moves to the upward arrow direction magnetic data pit. On the other hand, there is no signal when the signal moves from the magnetic data pit in the downward arrow direction to the magnetic data pit in the downward arrow direction or from the magnetic data pit in the upward arrow direction to the magnetic data pit in the upward arrow direction. The magneto-optical data recording / reproducing apparatus shown in FIG. 1 or FIG. 6, which is an embodiment according to the present invention, is suitable for reproducing minute magnetic pits because a large signal is obtained by the domain wall as shown in FIG. I have.

FIG. 10 explains the operation when the DWDD magneto-optical recording medium shown in FIG. 11 is reproduced using the twin spots shown in FIGS. 8 and 9.

In FIG. 10 (a), a magnetic film 12 on a magneto-optical recording medium is a magneto-optical film composed of three layers having different magneto-optical characteristics, and a recording layer 12-1, for example, TbFeC.
o, reproduction layer (Displacement layer)
12-2-1 For example, GdFe, and switching layer 1
2-3, for example, an example of a three-layer film of GdFeCo is shown, but the present invention is not limited to this example, and another known structure may be used. In FIG. 10, a vertical arrow 32 indicates a magnetization direction of data. When the laser beam converges on the twin spots shown in FIGS. 8 and 9 and scans the track, the light energy is absorbed by the magnetic medium and becomes heat, and the reproducing layer (Displacement layerer) is formed in the twin spots.
At 12-2-1, a temperature distribution having a large thermal gradient as shown in FIG. Since the gap between the twin spots P1 and P2 is very small, the temperature distribution is the same as the Gaussian spot shown in FIG. As a result, in the high temperature region 13-1 (see FIG. 12), the switching layer 12-
No. 3 is near the Curie temperature (Tc to 140 ° C.), and the recording layer 12-1 and the reproduction layer (Displacementlay)
er) The exchange coupling force with 12-2-1 is weakened, and the regeneration layer (Displacement layer) 12-2
-1 is masked by the switching layer 12-3.

Further, in FIG. 10 (b), a reproduction layer (Displacement layer) 12-2-
Since the gradient (derivative) of the temperature distribution of 1 theoretically corresponds to the force for moving the domain wall, when the laser beam is irradiated, the domain wall on the higher temperature side is pulled in the direction of the larger temperature gradient and moves, As a result, the reproducing layer (disp) corresponding to the minute magnetic domain 32 of the recording layer 12-1 in the low temperature region 13-2 (see FIG. 12).
magnetic layer 3 of 12-2-1
The 2 * domain wall 36 is enlarged. As a result, the reproduction layer 12-2
The magnetic pit 32 * enlarged by -1 (Displacement layer) is a small magnetic domain 3 of the recording layer 12-1.
2 and can be read using the reproducing apparatus shown in FIG. At this time, the MO detection signal as shown in FIG. 9 according to the embodiment of the present invention is obtained only at the moment when the domain wall 36 expands and passes the boundary between the twin spots P1 and P2. Further, if a deep groove is provided in an inter-track area where recording is performed so that domain wall movement of the reproducing layer is easily performed, the effect is large. Therefore, using the magneto-optical recording and reproducing apparatus of the present invention shown in FIG. 1 or FIG.
When the WDD magneto-optical medium is reproduced, the edge position of the domain wall can be accurately detected at the center of the twin spot.

Further, according to the present invention, the method of detecting the MO signal is obtained by differential detection of the magneto-optical signal MO1 and the magneto-optical signal MO2, and the differential detection signal 31 is obtained. Since the magnetic signal is canceled by the differential, the gain of the differential detection can be set large, and when the edge of the domain wall crosses the center of the twin spot, a very large detection output can be obtained. The feature is that a good signal-to-noise ratio can be obtained.

[0035]

As described above, according to the present invention, when the twin spot is irradiated on the magneto-optical disk and reproduced, the edge position of the domain wall can be accurately detected at the center of the twin spot.

Further, according to the present invention, the magneto-optical signal MO1
Since the differential detection signal is obtained by differential detection of the magneto-optical signal MO2 and the magneto-optical signal MO2, the magneto-optical signal in a portion other than the domain wall is canceled by the differential, so that the differential detection gain can be set large. Yes, when the edge of the domain wall crosses the center of the twin spot, it is possible to obtain a very large detection output, obtain a good signal-to-noise ratio, and stably reproduce high-density magnetic recording information. Become.

[Brief description of the drawings]

FIG. 1 is a plan view of a magneto-optical recording / reproducing apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a vector of a laser beam for explaining an operation principle of a magneto-optical recording / reproducing apparatus according to an embodiment of the present invention.

FIG. 3 is a diagram illustrating a vector of a laser beam for explaining an operation principle of a magneto-optical recording / reproducing apparatus according to an embodiment of the present invention.

FIG. 4 is a diagram illustrating a vector of a laser beam for explaining an operation principle of a magneto-optical recording / reproducing apparatus according to an embodiment of the present invention.

FIG. 5 is a diagram illustrating laser light vectors for explaining the operation principle of the magneto-optical recording / reproducing apparatus, which is one embodiment of the present invention.

FIG. 6 is a plan view of a magneto-optical recording / reproducing apparatus as one embodiment of the magneto-optical recording / reproducing apparatus of the present invention.

FIG. 7 is a diagram for explaining a phase change unit divided into two, which can be used in the present invention.

FIG. 8 is a diagram illustrating, two-dimensionally, a polarization state of a light beam condensed on the magneto-optical disk 20 and an intensity distribution of a condensed spot on the recording surface 20a according to the present invention.

FIG. 9 is a diagram showing a signal waveform reproduced by the magneto-optical recording / reproducing apparatus according to the present invention.

FIG. 10 is a view for explaining a method of reproducing magnetic pits recorded using twin spots by the DWDD method according to the present invention.

FIG. 11 is a view for explaining a method of reproducing recorded magnetic pits by a DWDD method using a conventional laser spot having a Gaussian distribution.

FIG. 12 is a view for explaining a method of performing magnetic super-resolution reproduction of recorded magnetic pits by the FAD method.

FIG. 13 is a diagram showing a signal waveform when a magnetic pit is reproduced by a conventional magneto-optical recording / reproducing apparatus.

FIG. 14 is a diagram showing a configuration of a conventional magneto-optical recording / reproducing apparatus.

FIG. 15 is a view for explaining a method of irradiating a pulse with laser light, modulating data with a magnetic field, and recording the data.

[Explanation of symbols]

Reference Signs List 1 laser light source 2 emission pulse waveform 3 objective lens 4 laser spot 5 magnetic head 6 data signal generator 7 modulation magnetic field 8 magneto-optical recording medium 9 laser driver 10 clock 11 magnetic pit 12 magneto-optical thin film 13 temperature region 14 reproducing magnetic field 15 magnetism Pit 16 Recording track 20 Magneto-optical disk 20a Recording surface 21 Laser light source 22 Collimator lens 23 Objective lens 24 Beam splitter (BS) 25 (25a, 25b) Phase changing means (1/2 wavelength plate, optical rotation plate) 25 '(25') a, 25'b) Phase changing means 26 1/2 wavelength plate 27 Polarizing beam splitter (PBS) 28 Condensing lens 29a, b, b, c, d Photodetector 30 Differential amplifier 31 Differential signal 32 Recording magnetic domain 32 * Reproduction Magnetic domain 33 Focused beam of beam A Beam 3 Condensed beam flux 35 enlarged magnetic domain 36 enlarged and gradually domain wall of the light beam B

Claims (5)

[Claims] Claims: 1. An optical device (1) disposed along an optical axis (O-O '),
A laser light source (21), a beam splitter (24),
Having an objective lens (23) and a photodetector (29);
An output light from the laser light source;
Of the reflected light from the recording surface of the magneto-optical recording medium is separated by a polarization beam splitter (27) into the photodetector (29). In the magneto-optical recording / reproducing apparatus, the light beam of linearly polarized light incident on the disk is divided into two in the track direction, the phase difference between the divided two light beams is made approximately 180 degrees, and a twin spot is formed on the disk surface in the track direction. A magneto-optical recording / reproducing apparatus having means for forming. 2. The method according to claim 1, wherein the phase difference is 180 degrees.
2. The magneto-optical recording / reproducing apparatus according to claim 1, further comprising a divided liquid crystal plate or a phase plate having different thicknesses. 3. A half-wave plate for rotating substantially 90-degree polarized lights in directions opposite to each other to make the phase difference 180 degrees,
2. The magneto-optical recording / reproducing apparatus according to claim 1, further comprising an optical rotation plate and a liquid crystal plate. 4. The photodetector (29) is configured as two split detectors (29a, b) and (29c, d),
MO signals from twin spots (MO1 = 29a
−29c, MO2 = 29b−29d) (= MO
2. The magneto-optical recording / reproducing apparatus according to claim 1, further comprising means for forming (1-MO2). 5. When reproducing data pits recorded on a magneto-optical recording medium comprising a recording layer, a switching layer and a reproducing layer, a laser or a laser light source (21) is applied to the disk recording surface (20a). 2. The magneto-optical recording / reproducing apparatus according to claim 1, further comprising means for irradiating and heating in a pulsed manner to move a domain wall of the data pit in the reproducing layer and to perform edge detection and reproduction of the data pit.