JPH10269643A - Method and device for recording and reproducing magneto-optical recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the deterioration of a reproduced signal and to increase the ratio of a carrier wave to noise. SOLUTION: In the method for recording and reproducing a magneto-optical recording medium for reading recording information by using an aperture are 16' held between an area 14' that is equal to or lower than a 1st temp. and an area 18' that is equal to or higher than a 2nd temp. which is higher than the 1st temp. in a temp. rising area by a light beams 12, the rotating direction of the magneto-optical recording medium is reversed between the recording time and the reproducing time in order to conform a shape of an effectively operating area for reproducing in the aperture area 16' with a shape of a recording domain 10, and the medium is irradiated with a 1st beam for raising the temp. of the medium at the time of reproducing and a 2nd beam for obtaining a regenerative signal. The center of the 2nd light beam is positioned in the rear of the center of the 1st beam. After initializing the recording area to arrange its magnetization in one direction, information is recorded in order to make a recording domain width narrower than a track width by a magnetic field modulation system.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a recording / reproducing method and a recording / reproducing apparatus for a magneto-optical recording medium, and more particularly to a so-called double-mask type magneto-optical recording medium for forming a front mask and a rear mask for super-resolution. The present invention relates to a method and an apparatus for recording and reproducing.

[0002]

2. Description of the Related Art The magneto-optical recording / reproducing method is a method of performing recording and reproduction by utilizing a temperature rise (thermomagnetic writing) of a medium by a laser beam and rotation of a polarization plane (magneto-optical effect). This method has a higher recording density due to the use of an optical head and a non-contact between the head and the medium, compared to a magnetic recording method using a magnetic head, such as a hard disk or a floppy disk. Attention and research began because of its high reliability and great merit of being removable. At present, it has already been put to practical use for computer memory and music data recording and has been widely used, and it has entered the stage of further increasing the density in anticipation of next-generation use.

As a technique for increasing the density, magnetic super-resolution (MS)
R) technology. Since the intensity of the laser light changes in a shape called a Gaussian distribution, a temperature distribution occurs in the film irradiated with the laser light. Using this phenomenon, a mask is created for a region where the film temperature is equal to or higher than a certain value, or conversely, is equal to or lower than a certain value, thereby enabling reproduction of a signal smaller than the spot diameter of the laser beam, thereby achieving high density. You. Currently, the principle of this super-resolution technology is mainly FAD (F
Ron Aperture Detection),
RAD (Rear Aperture Detective)
on) and CAD (Center Architecture)
(Detection). These have advantages and disadvantages, such as recording density, film configuration, and the necessity of applying a magnetic field during reproduction. By combining these super-resolution techniques, a double-mask type magneto-optical recording medium that masks both a region where the film temperature is equal to or lower than a certain value and a region where the film temperature is equal to or higher than a certain value has been studied. A recording / reproducing method using such a medium is promising as a technique for reproducing a minute domain.

[0004]

The principle of super-resolution is that a window (aperture) for displaying information of a recording layer in a rear portion where the temperature is increased by a laser beam or in a reverse portion where the temperature is not increased. Is to generate The FAD method uses a high-temperature portion as a mask and has a simple film configuration and device, but does not change the density in the track direction. Meanwhile, RA
On the other hand, in the D method, a high-density portion in the track direction can be expected because a low-temperature portion is used as a mask and a window is formed in a high-temperature portion in the rear. Inevitable. The CAD method has both features that the window shape is the same as that of the RAD medium, that high density in the track direction can be expected, and that an initialization magnetic field is unnecessary.

[0005] A magneto-optical recording medium called a double mask type is one in which a fine window can be formed by combining these super-resolution techniques and forming a mask in both a low-temperature portion and a high-temperature portion. Since the intensity of the light spot shows a Gaussian distribution, the window shape of the double mask type shows a ring shape. The front end of the ring is formed at the center of the spot, while the rear end is formed at the rear of the spot or outside the spot according to the reproduction speed. for that reason,
The shape of the window at the tip of the ring becomes important during super-resolution reproduction. On the other hand, the recording domain shape is
In contrast to the arc shape protruding at both the end and the end of the domain, in the case of magnetic field modulation recording, the shape is like an arrow blade protruding in a direction opposite to the traveling direction. Therefore, the modulation method at the time of recording and the double mask type medium have compatibility for sufficiently exhibiting the performance. Until now, a method combining a double-mask type super-resolution medium and magnetic field modulation recording has not been able to obtain a sufficient effect.

SUMMARY OF THE INVENTION It is an object of the present invention to prevent a reproduction signal from lowering and increase a carrier-to-noise ratio (C / N) in a system combining a double-mask type super-resolution medium and magnetic field modulation recording. It is an object of the present invention to provide a recording / reproducing method and a recording / reproducing apparatus which can perform the recording / reproducing.

[0007]

According to the present invention, an aperture region sandwiched between a region having a first temperature or lower and a region having a second temperature or higher which is higher than the first temperature in a temperature rising region by a light beam is provided. Provided is a recording and reproducing method for a magneto-optical recording medium used for reading recorded information.

In the first invention, information is recorded on a magneto-optical recording medium rotated in a first direction by a magnetic field modulation method, and the light is rotated in a second direction opposite to the first direction. Recorded information is read from an aperture area formed by irradiating the magnetic recording medium with a light beam for raising the temperature. Upon reproduction by this method, the order of the read data signals can be reversed.

In the second invention, information is recorded on a magneto-optical recording medium by a magnetic field modulation method, and when reproducing the recorded information, a first light beam for raising the temperature of the medium and a reproduction signal are obtained. Are respectively radiated to the medium. The second light beam does not substantially affect the temperature rise of the medium by the first light beam. The center of the second light beam is located behind the center of the first light beam in the direction in which the first light beam moves relative to the medium. In this method, the ratio of the peak intensity of the second light beam to the peak intensity of the first light beam is preferably less than 0.6.

According to a third aspect of the invention, after performing initialization for aligning the magnetization of the recording area in the magneto-optical recording medium in one direction,
Information is recorded by a magnetic field modulation method so that the recording domain width becomes smaller than the track width. The recorded information is read from an aperture area formed by irradiating a light beam for raising the temperature.

According to a fourth aspect of the present invention, an aperture area sandwiched between an area lower than a first temperature and an area higher than a first temperature and higher than a second temperature is read out of recorded information. And a recording / reproducing apparatus for a magneto-optical recording medium used for the above. This device includes a light source for heating a magneto-optical recording medium for recording and reproducing information, a collimator for converting light from the light source into a parallel light beam, and shields a central portion of the light from the collimator. And a means for selectively detecting light obtained by reflecting the side lobe light generated by blocking the central part of the light from the collimator to the medium. In this device,
At the time of recording, the light shielding means is released, and at the time of reproduction, the light shielding means is operated. As the light shielding means, for example, a liquid crystal device can be used.

The domain shape recorded by the magnetic field modulation recording and the reproduction window shape formed in the double mask type medium both have a dependence on the traveling direction. Even if the width is reduced, it is not possible to reproduce a micro domain. In the present invention, as described in more detail below,
In order to avoid a drop in the playback signal due to the mismatch between the recording domain and the playback window shape, the shape of the playback signal is increased by matching each shape or defining the curvature of the shape to increase the area of the area effective for playback. Is increasing. Further, in the present invention, by keeping the recording domain width narrower than the track width, a region where magnetization reversal does not occur during recording is provided, and recording is performed in a state where the magnetic domains of the entire film are in non-equilibrium.
As described later, according to such a recording method, information can be efficiently transferred from the recording layer to the reproduction layer, and the number of reproduction signals can be increased. Hereinafter, the present invention will be described in more detail with reference to specific examples.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A magneto-optical recording medium used in the present invention has, for example, a structure as shown in FIG.
On a substrate 1, a base layer 2, a reproducing layer 3, an intermediate magnetic layer 4, a recording layer 5, and a protective layer 6, which are dielectric films, are sequentially formed. The reproducing layer 3 is an in-plane magnetized film at room temperature,
When the temperature exceeds a predetermined temperature (first temperature), the intermediate magnetic layer 4
A perpendicular magnetization film can be formed by the exchange coupling force acting between the reproducing layer 3 and the recording layer 5 through the layer. On the other hand, the intermediate magnetic layer 4 functions to break the exchange coupling between the reproducing layer 3 and the recording layer 5 when the temperature reaches a predetermined temperature (second temperature) higher than the first temperature. As a result, a mask is formed in a region below the first temperature and in a region above the second temperature, and an aperture region is formed between the first temperature and the second temperature.

FIG. 2 shows how a so-called double-mask type magneto-optical recording medium is reproduced by irradiating it with a laser beam. The recording domain 10 formed on the track 8 of the medium has a shape like an arrow protruding in the moving direction of the medium indicated by an arrow. As for the direction in which the laser spot 12 moves relative to the medium, the recording domain 10 has a shape protruding backward. The laser spot 12 causes the inside of the region 1 above the second temperature
8 are formed. On the other hand, a region 14 having a temperature equal to or lower than the first temperature is formed according to the temperature distribution, and an aperture region (window region) 16 between the first temperature and the second temperature is formed between the region 14 and the region 18. It is formed. In the conventional method, the laser spot 12 in the aperture area 16 shown by hatching is used.
The portion near the center of the laser spot inside is used for reproduction. Therefore, the shape of this part is
It has a shape like an arrow protruding in the traveling direction of the laser spot 12. That is, the direction in which the recording domain protrudes is opposite to the direction in which the portion used for reproduction protrudes, and their shapes are symmetric. Laser spot 12
The portion where the aperture region 16 and the recording domain 10 in the area overlap is the portion effective for reproduction, but if the shapes are different in this way, the area of the region effective for reproduction is reduced, The reproduction signal is reduced.

Therefore, in the present invention, first, by reversing the traveling direction of the medium at the time of recording and the traveling direction of the medium at the time of reproduction, the above-described shape mismatch is overcome, and the area effective for reproduction is defined. The area is increasing. As shown in FIG.
If the medium is moved in the direction of the arrow at the time of reproduction, an area 14 ′ formed by the laser spot 12 and having a temperature equal to or lower than the first temperature is formed.
An aperture region 16 'as shown by oblique lines is formed between the region 18' and the region 18 'having the second temperature or higher. The portion of the aperture area 16 ′ near the center of the laser spot 12 has a shape protruding in the direction in which the laser spot 12 moves relative to the medium. Direction. Therefore, the aperture area in the laser spot 12 is well overlapped with the recording domain 10, and the effective area for reproduction is increased. As a result, the playback signal increases,
C / N is improved.

In such a system, recording and reproduction can be performed by, for example, an apparatus configuration as shown in FIG. The disk 20, which is a magneto-optical recording medium, is rotated by a spindle motor 26 during recording and reproduction. A magnetic head 22 for recording is provided above the disk 20, and the magnetic head 22 is provided with a drive circuit 24.
The information is recorded on the recording layer on the disk 20 by the magnetic field modulation method. The optical head 3 is located below the disk 20.
0 is provided. The optical head includes a laser, an optical system, and a photodetector, as described later, and irradiates a laser beam to increase the temperature during recording and reproduction. Irradiation of laser light by the optical head 30 is controlled by a laser drive circuit 32. Tracking and focusing of the optical head are controlled by a servo circuit 28. The rotation speed and direction of the spindle motor 26 are also controlled by the servo circuit 28. Information read from the optical head 30 is sent to a data division circuit 38 via a reproduction signal amplification circuit 34 and an A / D conversion circuit 36. The error signal from the optical head is sent to the servo circuit 28 via the reproduction signal amplification circuit 34. The signal sent to the data division circuit 38 is taken out as reproduction data via the inversion circuit 40. When the recording mode or the reproduction mode is set, signals from the rotation direction control circuit 44 are sent to the servo circuit in different modes. For example, in the recording mode, the rotation direction control circuit 44 sends a signal to the servo circuit 28 to rotate the disk 20 clockwise. On the other hand, in the reproduction mode, the rotation direction control circuit 44 sends a signal to the servo circuit 28 so as to rotate the disk 20 in the counterclockwise direction, and sends a signal to the servo circuit 28 via the track jump control circuit 42, and The head 30 is caused to track in a predetermined mode. The data division circuit 38 receives a track jump timing signal from the track jump control circuit 42, and classifies data at each of these timings. Each of the divided data is sent to the inverting circuit 40, and its time series is inverted. By such a process, even if the rotation direction of the disc is reversed between recording and reproduction, it is possible to obtain reproduction information having the same time series as during recording. For example,
When tracks are formed on concentric circles on the disk, information for one round is read from point A as shown in FIG. 5, then track jump is performed to read information for one round from point B, and the timing of tracking is performed. If the respective data are divided, inverted, and connected in accordance with the information, it is possible to accurately reproduce the information in the same time series as at the time of recording. When tracks are spirally formed on the disc, for example, as shown in FIG. 6, one turn is read inward from point A ', and then two tracks are jumped inward from point A' for one turn inward from point B '. , And if the data is divided, inverted, and joined in accordance with the timing of tracking, the same time-series information as that at the time of recording can be reproduced.

FIG. 7 shows a specific example of the optical head of the apparatus shown in FIG. The optical head includes a semiconductor laser 50 as a light source, a photodetector 66, and a semiconductor laser 50.
An optical system for guiding the light from the disk 20 to the disk 20 and irradiating it with a spot of a predetermined size, and an optical system for guiding the laser light reflected by the disk 20 to the photodetector 66 are provided. Laser light emitted from the semiconductor laser 50 is converted into a parallel light beam by a collimator lens 52, and is condensed by an objective lens 56 through a half mirror 54. The disk 20 is irradiated with laser light at a spot of an appropriate size. The laser beam reflected by the disk 20 is turned by the half mirror 54 in the direction of the photodetector 66. The light reflected by the half mirror 54 is converted into three beams by the Wollaston prism 60. Each beam is directed to a respective section of the photodetector 66 via a condenser lens 62 and a cylindrical lens 64. The center beam of the three beams is used to generate an error signal for tracking and focusing. The remaining two beams are used to generate a reproduction signal.

On the other hand, an optical head as shown in FIG. 8 can be used in the present invention. In this optical head,
In the optical head shown in FIG. 7, a means for blocking light is provided between the collimator lens 52 and the half mirror 54, and a slit is provided between the cylindrical lens 64 and the photodetector 66. In the optical head shown in the figure, a liquid crystal element 71 having a structure in which a twisted nematic liquid crystal 70 is sandwiched between transparent electrode-attached glasses 72a and 72b, and a filter 78 are partially provided between the collimator lens 52 and the half mirror 54. 73 provided with a polarizing film 74 in a glass 76 covered with
Is provided. As shown in FIG. 9, the polarizing film 74 in the analyzer 73 is provided so as to cover the central portion of the light beam from the collimator lens. Therefore, the peripheral portion of the light beam having a ring shape does not hit the polarizing film 74. The liquid crystal element 71 includes a liquid crystal drive circuit 8
Controlled by 0. Note that, for example, a super twisted nematic liquid crystal may be used instead of the twisted nematic liquid crystal.

In the optical head shown in FIG. 8, when a voltage is applied to the liquid crystal through the liquid crystal driving circuit 80, the major axis of the liquid crystal molecules rearranges in parallel with the direction of the electric field, so that the linearly polarized light incident on the liquid crystal Passes as it is. If an analyzer that transmits linearly polarized light as it is and blocks circularly polarized light is used as the polarizing film, the disk 20 is entirely irradiated with the laser beam through the half mirror 54 and the objective lens 56 when a voltage is applied. . On the other hand, when no voltage is applied to the liquid crystal, the light beam that has exited the collimator lens 52 is partially blocked by the light shielding film 74 as shown in FIG. That is, the central portion of the light beam is shielded, and a ring-shaped light beam is generated. In such a control system, a ring-shaped luminous flux can be generated without applying a voltage during reproduction, while applying a voltage of the liquid crystal during recording and irradiating the entire surface with laser light. Note that, by a combination of a liquid crystal and a polarizing film, it is also possible to partially block a light beam when a voltage is applied and to irradiate the light beam entirely when no voltage is applied. Instead of using a liquid crystal and a polarizing film to shield light, a light-shielding plate may simply be placed on the optical path. For example, as shown in FIG. 11, a light-shielding plate 94 that shields the central part of the light beam in a band shape may be provided between the half mirror 54 and the collimator lens 52. In this case, the light shielding plate is provided movably so that it can be inserted into the optical path as needed.

As shown in FIG. 10, when the center of the light beam is blocked, a spot profile as shown in FIG. 12, for example, is obtained. As described above, when the parallel light beam is partially shielded and condensed, side lobes 90 a and 90 b are formed at both ends of the main spot 92. That is, a plurality of spots having different peak intensities are provided on the disc at predetermined intervals. FIG. 13 shows how these spots are provided on the disk. Side spots 110a and 110b are provided before and after the main spot 102 in the track direction on the disc. In this case, the side spot 110 having a low intensity is used.
a and 110b do not substantially affect the heating effect by the main spot 102. By raising the temperature of the main spot 102, for example, an aperture region 106 shown by oblique lines in the figure is formed. In the present invention, information is read from the rear portion of the aperture region 106 using the side spot 110a. Aperture area 106
At the portion 106 'in the side spot 110a.
Has a shape protruding backward with respect to the traveling direction of the main spot 102 with respect to the medium. This shape
It overlaps well with the shape of the recording domain 10. Therefore,
By obtaining a reproduction signal from the side spot 110a located behind the main spot 102, the area of a region effective for reproduction can be increased as compared with the related art, and C / N can be improved. In the case of such a method, the ratio Is / Im of the peak intensity Is of the side lobe to the peak intensity Im of the main spot 92 as shown in FIG. 12 is preferably less than 0.6. With such a ratio, a reproduced signal can be obtained from the side spot without significantly affecting the temperature rise by the main spot.

As shown in FIG. 10, the light reflected by the disk 20 is reflected by the half mirror 54 and is divided into three by the Wollaston prism 60. The three beams are respectively condensed lens 62 and cylindrical lens 64
Irradiates each section of the photodetector 66 via the. Slits 82a and 82b are provided between the cylindrical lens 64 and the photodetector 66 so as to partially block beams on both sides of the three divided beams. As shown in FIG. 14, these slits are provided so as to pass only side lobe light involved in the reproduction of information as described above. That is, as shown in the figure, the slits 82a and 82b are provided so as to pass only one side lobe light of each beam. Thereby, the side lobe light is used for generating the reproduction signal.

FIG. 15 shows the configuration of a recording / reproducing system using the side lobe light described above. The disk 20 is driven to rotate by a spindle motor 26. The spindle motor 26 is controlled by a servo circuit 28. A magnetic head 22 controlled by a magnetic head drive circuit 24 is provided above the disk 20. Disc 20
Below this, an optical head 30 having an optical system as shown in FIGS. 8 and 10 is provided. Optical head 30
The tracking and focusing are controlled by the servo circuit 28. The light source of the optical head is controlled by the laser drive circuit 32 according to the recording mode and the reproduction mode. Information from the optical head is taken out as reproduction data via a reproduction signal amplifier circuit 34 and a low-pass circuit 35. The error signal from the optical head is sent to the servo circuit 28 via the reproduction signal amplification circuit 34, and is used for tracking and focusing.

Conventionally, in recording by the magnetic field modulation method, FIG.
As shown in FIG. 6A, the width of the recording domain 122 was equal to the width of the track 120. In the present invention, FIG.
As shown in (b), a recording domain 122 'having a width smaller than the width of the track 120 is formed. Such a recording domain, without changing the size of the beam spot,
The laser beam can be formed by setting the laser power low and setting the temperature distribution in the beam spot low. Also, as shown in FIG. 17 (a), a magnetic field in a fixed direction is applied to the recording area 120 during recording to perform initialization, and then, as shown in FIG. 7 (b), has a width smaller than the track width. A recording domain 132 can be formed. In this case, the recording domain whose magnetization direction is reversed is
It is surrounded by a portion in which the direction of magnetization is made constant by initialization. Such recording domains are more easily identified in the track.

In conventional magnetic field modulation recording, since recording is performed over the entire width of a land or groove, the upward magnetization and the downward magnetization have substantially the same area. Therefore, conventionally, the magnetization characteristics of each domain are almost the same. In a medium recorded by the optical modulation method, the area in the erased state and the area in the recorded state are clearly separated, and there is a difference in the magnetization characteristics between the upward and downward magnetization because the areas and shapes thereof are different. Occurs.
According to the present invention, in magnetic field modulation recording, after the entire surface of the medium is first magnetized (initialized) in one direction and then the domain is recorded with a width smaller than the track, the recording is always unaffected at the time of recording. The existence of a region that maintains the magnetization state at the time exists, and a state is created in which the area having the upward and downward magnetizations becomes non-equilibrium as in the light modulation recording.
As shown in FIG. 17C, when the medium on which recording has been performed in this way is reproduced by the double mask method, the sign of the reproducing magnetic field depends on the sign. For example, assuming that the direction of the initialized magnetic field is − and the direction of the magnetic field recorded in a domain having a narrow width is +, the reproduction is performed by applying a magnetic field in the − direction, ie, the initialization direction, as the reproducing magnetic field. Efficient transfer was performed, leading to an increase in reproduced signals.

[0025]

EXAMPLE First, a magneto-optical recording medium having a structure as shown in FIG. 1 was prepared. The recording film is formed by an RF bipolar magnetron sputtering method, and a 5 inch diameter Tb
Each target of FeCo and GdFeCo was used. The ultimate degree of vacuum of the chamber is 2 × 10 ⁻⁷ Torr or less, the Ar flow rate during film formation is 25 sccm, and the Ar pressure is 7.5 mTo.
rr. Slide glass and 12cmφ on substrate
Was used. The thickness and composition of each formed layer were confirmed using a fluorescent X-ray analyzer. In the structure shown in FIG. 1, a SiN dielectric layer was formed on a substrate at 700 °, a GdFeCo reproducing layer was formed at 1000 °, and TbF
eCo intermediate layer 500 °, TbFeCo recording layer 500
Å, a SiN protective layer was formed in the order of 800Å. The Curie temperature of the recording layer is about 280 ° C., and its compensation temperature is set to approximately room temperature. The coercive force of the recording layer is 10 kOe or more at room temperature. The Curie temperature of the TbFeCo intermediate layer is 150 ° C. Both the recording layer and the intermediate layer are perpendicular magnetization films from room temperature to the Curie temperature. The reproducing layer is an in-plane magnetic film at room temperature, but is a perpendicular magnetic film at 120 ° C. or higher. In this medium, the reproducing magnetic field is 3
By adding 00 Oe, in a region of 150 ° C. or higher where the exchange coupling between the reproducing layer and the recording layer is broken, the magnetization of the reproducing layer is oriented in the direction of the magnetic field.
A mask is formed in the above regions. The aperture region formed by such a double mask is as shown in FIG.

In the configuration of the apparatus shown in FIGS. 4 and 7, recording and reproduction were performed in a 0.35 μm continuous domain using a recording and reproduction apparatus having a wavelength of 680 nm and a numerical aperture of 0.55. Reproduction speed is 2 m / s, reproduction laser power is 2.2 m
W. When the disc is rotated and played in the same direction as the disc during recording,
In playback performed by rotating the disc in the opposite direction, 3d
B increased C / N.

With the configuration of the apparatus as shown in FIGS. 8, 10 and 15, recording and reproduction were performed on the magneto-optical recording medium prepared as described above. Recording was performed by a magnetic field modulation method under the conditions of a linear velocity of 2.0 m / s and a recording power of 4 mW. Next, at the time of reproduction, the power of the main beam was set to 1.8 mW, and the power of a side lobe formed behind the main beam was set to 1.0 mW. By the main beam,
Although the ring-shaped aperture region is formed in the double-mask type medium as described above, the side lobe at the rear plays almost no function for forming the aperture region. However, the shape of the aperture area in the rear spot matches the shape of the recording domain, and the use of this portion increases the effective area for reproduction. By using the rear spot for signal detection, it was possible to reproduce a minute domain.

FIG. 18 shows the light shielding ratio (%) of the light beam shielded by the polarizing film 74 in the optical system shown in FIGS. 8 and 10 (the ratio of the light-shielded portion in the cross section of the light beam).
3 shows the relationship between the spot diameter ratio and the intensity ratio with respect to. The ratio of the main spot diameter to the light blocking ratio is indicated by a dotted line A. The ratio of the peak intensity of the side lobe to the peak intensity of the main beam is indicated by a solid line B. It was desirable that the ratio Is / Im between the peak intensity Im of the main beam and the peak intensity Is of the following side beam be less than 0.6. Therefore, even when different light sources are used for the preceding beam and the following beam, if the wavelengths are different, it is desirable that the ratio of the power density at the center of each spot is less than 0.6.

FIG. 19 shows the relationship between the necessary distance between spots and the linear velocity of the disk, taking the preceding laser power as a parameter. The distance between the spots means the distance between the center of the main spot and the center of the side spot. FIG. 19 shows that the preceding laser power is 2.
2, 1.8, and 1.4 mW, respectively. When the linear velocity was 2.0 m / s, the distance between the spots was 1 μm at a laser power of 1.8 mW. However, when the linear velocity increased, the distance between the spots had to be increased. When the intensity of the laser beam is increased, the distance between the spots needs to be increased. Compared with the case where a single spot is generated with a laser power of 2.2 mW without using a light shielding means and reproduced, the C / N of the embodiment of the present invention in which the main spot and the side spot are formed increases by 3 dB. Was.

[0030]

As described above, in reproducing a minute domain recorded by a magnetic field modulation method using a medium for forming a double mask, the technique of the present invention is used for the reproduction window. The effective area increased, leading to an increase in the reproduced signal.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing the structure of a magneto-optical recording medium used in an embodiment of the present invention.

FIG. 2 is a schematic diagram showing the shape of a recording domain and the shape of an aperture region formed on a double-mask type medium.

FIG. 3 is a schematic diagram showing that the shape of a recording domain matches the shape of an area effective for reproduction when the direction of movement of a medium during reproduction is reversed according to the present invention;

FIG. 4 is a block diagram showing a configuration of an apparatus used for a recording / reproducing method according to the present invention.

FIG. 5 is a schematic diagram showing a specific example of tracking in the recording / reproducing method of the present invention.

FIG. 6 is a schematic diagram showing another specific example of tracking in the recording / reproducing method according to the present invention.

FIG. 7 is a schematic diagram showing a specific example of an optical head used in the recording / reproducing method of the present invention.

FIG. 8 is a schematic diagram showing another specific example of the optical head in the recording / reproducing apparatus according to the present invention.

FIG. 9 is a schematic diagram showing the light shielding unit shown in FIG. 8 from another angle.

FIG. 10 is a schematic diagram showing a state of light when no voltage is applied to the liquid crystal in the optical system shown in FIG.

FIG. 11 is a schematic diagram showing a specific example of a light shielding unit used in the recording / reproducing apparatus according to the present invention.

FIG. 12 is a diagram showing a spot profile of a laser beam generated in the recording / reproducing apparatus according to the present invention.

FIG. 13 is a schematic view showing that each beam having a spot profile as shown in FIG. 12 is irradiated on a double mask type medium.

FIG. 14 is a schematic diagram for explaining a function of a slit for extracting side lobe light.

FIG. 15 is a block diagram showing another specific example of an apparatus used for the recording / reproducing method according to the present invention.

FIG. 16 is a schematic diagram showing recording domains formed on a track.

FIG. 17 is a schematic diagram for explaining steps of forming a recording domain and reproducing the recording domain according to the present invention.

FIG. 18 is a diagram showing a relationship between a light shielding ratio by a light shielding unit, a spot diameter, and an intensity ratio in the recording / reproducing apparatus according to the present invention.

FIG. 19 is a diagram showing the relationship between the linear velocity of a disk and the distance between spots in the apparatus according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Underlayer 3 Reproducing layer 4 Intermediate magnetic layer 5 Recording layer 6 Protective layer 8 Track 10 Recording domain 12 Light spot 14 Area below 1st temperature 16 Aperture area 18 Area above 2nd temperature

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Satoshi Sumi 2-5-5 Keihanhondori, Moriguchi City, Osaka Prefecture Inside Sanyo Electric Co., Ltd. (72) Inventor Shigeki Hori 2-chome Keihanhondori, Moriguchi City, Osaka Prefecture No. 5 Sanyo Electric Co., Ltd.

Claims (7)

[Claims] An aperture area sandwiched between an area lower than a first temperature and an area higher than a first temperature and higher than a first temperature in a temperature rising area by a light beam for reading recorded information. A recording / reproducing method for a magneto-optical recording medium to be used, wherein information is recorded on the magneto-optical recording medium rotated in a first direction by a magnetic field modulation method, and a second direction opposite to the first direction is provided. Recording / reproducing a magneto-optical recording medium, characterized in that recording information is read from the aperture region formed by irradiating the magneto-optical recording medium rotated with a light beam for raising the temperature. 2. The recording / reproducing method according to claim 1, wherein the order of the read data signal is reversed during reproduction. 3. An aperture region sandwiched between a region having a first temperature or lower and a region having a second temperature or higher which is higher than the first temperature in a temperature rising region by a light beam for reading recorded information. A method for recording / reproducing a magneto-optical recording medium to be used, wherein information is recorded on the magneto-optical recording medium by a magnetic field modulation method, and a first light for heating the medium when reproducing the recorded information. Irradiating the medium with a beam and a second light beam for obtaining a reproduction signal, wherein the second light beam substantially affects the temperature rise of the medium by the first light beam. And the center of the second light beam is the first light beam relative to the direction in which the first light beam moves relative to the medium.
Characterized by being located behind the center of the light beam of
A recording / reproducing method for a magneto-optical recording medium. 4. The recording / reproducing method according to claim 3, wherein a ratio of a peak intensity of the second light beam to a peak intensity of the first light beam is less than 0.6. 5. An aperture area sandwiched between an area lower than a first temperature and an area higher than a first temperature and higher than a first temperature in a temperature rising area by a light beam for reading recorded information. A recording / reproducing method for a magneto-optical recording medium to be used, comprising: performing initialization for aligning the magnetization of a recording region in the medium in one direction, and then recording information by a magnetic field modulation method so that a recording domain width is smaller than a track width. And reading the recorded information from the aperture region formed by irradiating a light beam for raising the temperature. 6. An aperture area sandwiched between an area lower than a first temperature and an area higher than a first temperature and higher than a second temperature in a temperature rising area by a light beam for reading recorded information. A recording / reproducing apparatus for a magneto-optical recording medium to be used, comprising: a light source for raising the temperature of the medium for recording and reproducing information; a collimator for converting light from the light source into a parallel light beam; and the collimator. Means for blocking the central part of the light from the light source; and for selectively detecting light obtained by reflecting the side lobe light generated by shielding the central part of the light from the collimator to the medium. A recording and reproducing apparatus for a magneto-optical recording medium, wherein the light shielding means is released during recording and the light shielding means is operated during reproduction. 7. The recording / reproducing apparatus according to claim 6, wherein said light shielding means includes a liquid crystal device.